PROCESSING APPARATUS AND POLISHING SURFACE SHAPING METHOD

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a processing apparatus for shaping, i.e., dressing, a polishing surface of a polishing pad that polishes a workpiece, and a polishing surface shaping method.

Description of the Related Art

According to a process of manufacturing device chips, wafers each having devices constructed in respective areas demarcated on face sides thereof by a grid of streets or projected dicing lines are processed, e.g., ground and polished, by a processing apparatus. Each of the processed wafers is then divided into device chips that include the respective devices along the streets. The device chips thus fabricated will be incorporated into various types of electronic equipment such as cellular phones and personal computers.

If wafers from which to manufacture device chips have face sides that are not flat but contain minute surface irregularities such as faults or scratches, they tend to give rise to bending strength reductions and dimensional errors, for example, of the device chips, possibly resulting in a poor device chip quality. To avoid these deficiencies, it has been customary in the art to polish wafers with use of a polishing apparatus before the wafers are divided into device chips.

The polishing apparatus includes a chuck table for holding a workpiece, e.g., a wafer, thereon and a polishing unit for polishing the workpiece on the chuck table. The polishing unit houses a spindle therein, and a disk-shaped polishing pad is mounted on the distal end of the spindle that faces the chuck table. In operation, the workpiece is held on the chuck table, and while the chuck table and the polishing pad are being rotated about their own axes independently of each other, the polishing pad is moved toward the workpiece, bringing its polishing surface into abrasive contact with a surface to be polished, i.e., a face side, of the workpiece, thereby polishing the workpiece. By polishing the workpiece, the polishing pad removes minute surface irregularities from the face side of the workpiece, planarizing the face side of the workpiece.

If a workpiece to be polished has in-plane thickness variations, then the workpiece cannot be polished uniformly by the polishing pad and is liable to leave the thickness variations unremoved even when the workpiece is polished. In view of this drawback, there has been proposed a processing apparatus that measures a thickness distribution of a workpiece and shapes the polishing surface of a polishing pad on the basis of the measured thickness distribution of the workpiece (see JP 2015-223636A). The proposed processing apparatus makes it possible to press the polishing pad uniformly against a workpiece that contains thickness variations, so that the thickness variations of the workpiece can be reduced after it has been polished.

SUMMARY OF THE INVENTION

When a workpiece is polished on a processing apparatus, the workpiece is held on a holding surface of a chuck table. However, the holding surface of the chuck table may not have been formed flatwise because of the specifications of the processing apparatus. In this case, even though the workpiece itself has a uniform thickness, the workpiece held on the chuck table is deformed to match the shape of the holding surface and fails to keep its face side at a constant height. As a result, the force, i.e., the polishing pressure, applied to the workpiece when the polishing pad is pressed against the face side of the workpiece tends to become irregular, with the result that the polished workpiece is likely to have thickness variations.

The present invention has been made in view of the above problems. It is an object of the present invention to provide a processing apparatus and a polishing surface shaping method that are capable of reducing thickness variations of a processed workpiece.

In accordance with an aspect of the present invention, there is provided a processing apparatus including a chuck table having a holding surface for holding a workpiece thereon, a chuck table rotary actuator for rotating the chuck table about an axis extending across the holding surface, a polishing unit on which a polishing pad having a polishing surface for polishing the workpiece is mounted, a polishing pad rotary actuator for rotating the polishing pad about an axis extending across the polishing surface, a polishing moving mechanism for moving the chuck table and the polishing pad relatively to each other along a first direction across the holding surface and the polishing surface, a shape measuring instrument for measuring a shape of the holding surface, a shaping mechanism for shaping the polishing surface while in contact therewith, a shaping moving mechanism for moving the polishing pad and the shaping mechanism relatively to each other along a second direction across the first direction, and a controller for controlling shaping of the polishing surface with the shaping mechanism depending on the shape of the holding surface that has been measured by the shape measuring instrument, thereby to make the polishing surface complementary in shape to the holding surface.

Preferably, a diameter of the polishing pad is at least twice a diameter of the workpiece. Preferably, the shaping mechanism has a shaping member for shaping the polishing surface while in contact therewith and a displacement measuring instrument for measuring an amount of displacement of the shaping member in the first direction, and the controller specifies a shape of the polishing surface on the basis of the amount of displacement of the shaping member that has been measured by the displacement measuring instrument when the shaping member has contacted the polishing surface at a plurality of positions.

In accordance with another aspect of the present invention, there is provided a polishing surface shaping method including measuring a shape of a holding surface of a chuck table for holding a workpiece thereon, and shaping a polishing surface of a polishing pad for polishing the workpiece by bringing a shaping member for shaping the polishing surface into contact with the polishing surface depending on the shape of the holding surface that has been measured in the measuring of the holding surface, thereby to make the polishing surface complementary in shape to the holding surface.

Preferably, the polishing surface shaping method further includes specifying a shape of the polishing surface on the basis of an amount of displacement of the shaping member when the shaping member has contacted the polishing surface shaped in the shaping at a plurality of positions. Preferably, the holding surface of the chuck table is of a conical shape, and in the shaping, the polishing surface of the polishing pad is shaped to form in the polishing surface an annular recess that is complementary in shape to the holding surface.

The processing apparatus and the polishing surface shaping method according to the aspects of the present invention measure the shape of the holding surface of the chuck table and shape the polishing surface of the polishing pad depending on the measured shape of the holding surface. It is thus possible to make the shape of the polishing surface of the polishing pad complementary in shape to the holding surface of the chuck table. Therefore, at the time the workpiece is held on the chuck table and polished by the polishing pad, thickness variations of the workpiece are reduced.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a processing apparatus according to a first embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view of a chuck table of the processing apparatus;

FIG. 3 is a side elevational view, partly in cross-section of a grinding unit of the processing apparatus;

FIG. 4 is a side elevational view, partly in cross-section, of a polishing unit of the processing apparatus;

FIG. 5 is a flowchart of a sequence of a polishing surface shaping method;

FIG. 6 is a side elevational view, partly in cross-section and partly in block form, of the processing apparatus in a holding surface measuring step of the polishing surface shaping method;

FIG. 7 is a plan view of the chuck table and a shape measuring instrument;

FIG. 8 is a side elevational view, partly in cross-section and partly in block form, of the processing apparatus in a shaping step of the polishing surface shaping method;

FIG. 9 is a side elevational view, partly in cross-section and partly in block form, of the processing apparatus in a polishing surface shape specifying step of the polishing surface shaping method;

FIG. 10 is a side elevational view, partly in cross-section, illustrating the manner in which the processing apparatus polishes a workpiece; and

FIG. 11 is a perspective view of a processing apparatus according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A first embodiment of the present invention will be described below with reference to the accompanying drawings. First, a structural example of a processing apparatus according to the first embodiment will be described below. FIG. 1 illustrates in perspective the processing apparatus, i.e., a grinding and polishing apparatus, denoted by 2, that is capable of grinding and polishing a workpiece 11. In FIG. 1, the processing apparatus 2 is illustrated in reference to a three-dimensional coordinate system having an X-axis, a Y-axis, and a Z-axis. The X-axis and the Y-axis extend perpendicularly to each other, and the Z-axis extends perpendicularly to the X-axis and the Y-axis. The X-axis refers to an axis along which first horizontal directions or leftward and rightward directions are defined, and the Y-axis refers to an axis along which second horizontal directions or forward and rearward directions are defined. The Z-axis refers to an axis along which vertical directions, heightwise directions, or upward and downward directions are defined.

The workpiece 11 includes, for example, a disk-shaped wafer made of a semiconductor material such as monocrystalline silicon, for example, and has a face side, i.e., a first surface, 11a and a reverse side, i.e., a second surface, 11b that lie opposite each other and that extend generally parallel to each other. The workpiece 11 has a plurality of rectangular areas demarcated by a grid of streets or projected dicing lines established thereon. Devices, not depicted, such as integrated circuits (ICs), large-scale-integration (LSI) circuits, light-emitting diodes (LEDs), or microelectromechanical-systems (MEMS) devices, for example, are constructed respectively in the demarcated rectangular areas on the face side 11a.

When the workpiece 11 is divided along the streets, a plurality of device chips including the respective devices are fabricated from the workpiece 11. The workpiece 11 is divided by a processing apparatus such as a cutting apparatus for cutting the workpiece 11 with an annular cutting blade or a laser processing apparatus for processing the workpiece 11 with a laser beam applied thereto, for example. The processing apparatus 2 grinds and polishes the reverse side 11b of the workpiece 11 before the workpiece 11 is divided. When the reverse side 11b of the workpiece 11 is ground and polished, the workpiece 11 is thinned down, and the reverse side 11b of the workpiece 11 is planarized.

The workpiece 11 is not limited to any particular kinds, materials, sizes, shapes, and structures. For example, the workpiece 11 may include a substrate or wafer made of a semiconductor other than silicon, e.g., GaAs, InP, GaN, SiC, or sapphire, glass, ceramic, resin, or metal, for example. The devices are not limited to any particular kinds, numbers, shapes, structures, sizes, and layouts, for example. The workpiece 11 may even be free of the devices.

According to the present embodiment, the reverse side 11b of the workpiece 11 will be described by way of example as a processed surface, i.e., a ground surface and polished surface, that is ground and polished by the processing apparatus 2. While the reverse side 11b of the workpiece 11 is being processed, a protective member may be attached to the face side 11a of the workpiece 11. For example, a film-shaped protective sheet made of resin is affixed as the protective member to the face side 11a of the workpiece 11, thereby protecting the face side 11a of the workpiece 11.

The processing apparatus 2 includes a foundation base 4 supporting and/or housing various components of the processing apparatus 2. The foundation base 4 has an opening 4a defined in an upper surface of a front end portion thereof. The opening 4a houses therein a delivery unit, i.e., a delivery mechanism, 6 for delivering the workpiece 11. For example, the delivery unit 6 includes a delivery robot having a robot hand, i.e., an end effector, for capable of holding the workpiece 11.

A pair of cassette support tables 8A and 8B are mounted on a front end of the foundation base 4 forwardly of the opening 4a. The cassette support tables 8A and 8B support box-shaped cassettes 10A and 10B respectively thereon. Each of the cassettes 10A and 10B includes a receptacle capable of storing a plurality of workpieces 11 to be processed by the processing apparatus 2. For processing workpieces 11 on the processing apparatus 2, the cassettes 10A and 10B with the workpieces 11 stored therein are set on the respective cassette support tables 8A and 8B.

An alignment mechanism, i.e., a positioning mechanism, 12 for positioning a workpiece 11 supplied thereto is disposed on the foundation base 4 obliquely rearwardly of the opening 4a. The alignment mechanism 12 includes, for example, a temporary rest table for supporting the workpiece 11 temporarily placed thereon and a circular array of radially movable pins for contacting the outer circumferential edge of the workpiece 11 placed on the temporary rest table and gripping the workpiece 11. The workpieces 11 stored in the cassettes 10A and 10B are delivered one at a time to the alignment mechanism 12 by the delivery unit 6. The alignment mechanism 12 holds the delivered workpiece 11 on the temporary rest table and grips the workpiece 11 with the plurality of movable pins, thereby bringing the workpiece 11 into a predetermined position on the temporary rest table.

In the vicinity of the alignment mechanism 12, there are disposed a delivery unit, i.e., a delivery mechanism or a loading arm, 14 and a delivery unit, i.e., a delivery mechanism or an unloading arm, 16, each for holding and turning a workpiece 11 supplied thereto. The delivery units 14 and 16 are positioned behind the opening 4a. Each of the delivery units 14 and 16 includes one or more suction pads for attracting the upper surface of the workpiece 11 under suction and delivering the attracted workpiece 11.

A moving mechanism 18 is disposed on the foundation base 4 behind the alignment mechanism 12 and the delivery units 14 and 16. The moving mechanism 18 includes a disk-shaped turntable, for example, and a rotary actuator, not depicted, such as an electric motor, coupled to the turntable for rotating the turntable about a vertical axis extending generally parallel to the Z-axis.

A plurality of chuck tables, i.e., holding tables, 20 each for holding a workpiece 11 are mounted on the moving mechanism 18. Each of the chuck tables 20 has an upper surface acting as a holding surface for holding a workpiece 11 thereon. The chuck tables 20 include four chuck tables 20, for example, angularly spaced at substantially equal intervals, i.e., 90° intervals, along circumferential directions of the moving mechanism 18. While the moving mechanism 18 is in operation, the rotary actuator intermittently rotates the turntable about the vertical axis counterclockwise as viewed in plan in the direction indicated by the arrow x, positioning each of the chuck tables 20 successively in a delivery zone A, a grinding zone B, i.e., a first grinding zone or a coarsely grinding zone, a grinding zone C, i.e., a second grinding zone or a finishingly grinding zone, a polishing zone D, and back in the delivery zone A.

The delivery unit 14 holds a workpiece 11 that has been positioned by the alignment mechanism 12 and moves the workpiece 11 rearwardly, thereby delivering the workpiece 11 from the alignment mechanism 12 to a chuck table 20 positioned in the delivery zone A. The delivery unit 16 holds a workpiece 11 held on a chuck table 20 that has been positioned in the delivery zone A and moves the workpiece 11 forwardly, thereby delivering the workpiece 11 from the chuck table 20 in the delivery zone A to a cleaning unit 98 to be described later.

FIG. 2 illustrates one of the chuck tables 20 in cross section. All the chuck tables 20 are structurally identical to each other. The chuck table 20 includes a cylindrical frame body or main body 22 made of a metal material such as stainless steel (SUS), glass, ceramic, or resin, for example. The frame body 22 has an annular upper surface 22a extending circumferentially therealong and an upwardly open, hollow cylindrical recess 22b defined therein that is concentrically encircled by the annular upper surface 22a. A disk-shaped holding member 24 made of a porous material such as porous ceramic is fitted in the recess 22b. The holding member 24 contains a multiplicity of pores defined therein that are interconnected from upper to lower surfaces of the holding member 24. When the chuck table 20 holds a workpiece 11 on the holding member 24, the upper surface of the holding member 24 acts as a circular suction surface 24a that attracts the workpiece 11 under suction.

The upper surface 22a of the frame body 22 and the suction surface 24a of the holding member 24 jointly make up a holding surface 20a of the chuck table 20. The holding surface 20a is fluidly connected to a suction source, not depicted, such as an ejector, via the pores contained in the holding member 24, a fluid channel 22c defined in the frame body 22, and a valve, not depicted. With the workpiece 11 placed on the holding surface 20a of the chuck table 20, the suction source is actuated to generate and apply a suction force, i.e., a negative pressure via the valve, the fluid channel 22c, and the pores in the holding member 24 to the holding surface 20a, whereupon the workpiece 11 is held under suction on the chuck table 20.

The holding surface 20a of the chuck table 20 is of an upwardly protruding conical shape whose apex is aligned with the center of the holding surface 20a. Therefore, the holding surface 20a is slightly inclined to a diametrical plane that lies perpendicularly to the central axis of the chuck table 20. In FIG. 2 and some other figures, the inclination of the holding surface 20a is illustrated as exaggerated for a better understanding of the present embodiment. Actually, however, the holding surface 20a is inclined to a much smaller extent. For example, in case the holding surface 20a has a diameter ranging approximately from 290 mm to 310 mm, the difference between the heights of the center of the holding surface 20a and its outer circumferential edge, i.e., the height of the conical shape, is approximately in the range from 20 to 40 μm.

A rotary actuator, i.e., a chuck table rotary actuator, 26 for rotating the chuck table 20 is coupled to the chuck table 20. The rotary actuator 26 includes an electric motor, for example, for rotating the chuck table 20 about a rotation axis, i.e., a chuck table axis, 28 that is aligned with the central axis of the chuck table 20 and extends across the holding surface 20a. For example, the rotation axis 28 extends perpendicularly to the diametrical plane, referred to above, and extends across the holding surface 20a through the center thereof.

A tilt adjusting mechanism, not depicted, for adjusting tilt of the chuck table 20 is operatively coupled to the chuck table 20. The tilt adjusting mechanism is actuated to adjust the tilt of the chuck table 20 to switch between a vertical position in which the rotation axis 28 extends along the Z-axis and a tilted position in which the rotation axis 28 is tilted from the Z-axis.

For grinding a workpiece 11 held on the chuck table 20, the tilt adjusting mechanism is actuated to adjust the tilt of the chuck table 20 such that the rotation axis 28 is slightly tilted from the Z-axis (see FIG. 3). At this time, a grinding holding region 20b that is part of the holding surface 20a and extends from the center of the holding surface 20a radially outwardly to an outer circumferential edge thereof lies generally parallel to a horizontal plane, i.e., an XY plane, along the X-axis and the Y-axis. Then, the workpiece 11 is placed and held on the holding surface 20a of the chuck table 20, and a region of the reverse side 11b of the workpiece 11 that is held on the grinding holding region 20b and close regions thereto is ground by grinding units 42A and 42B to be described later. In FIG. 3, the region of the reverse side 11b of the workpiece 11 is illustrated as being ground by the grinding unit 42A. For polishing a workpiece 11 held on the chuck table 20, the tilt adjusting mechanism is actuated to adjust the tilt of the chuck table 20 such that the rotation axis 28 extends generally parallel to the Z-axis (see FIG. 4). The workpiece 11 is placed and held on the holding surface 20a of the chuck table 20, and the reverse side 11b of the workpiece 11 is polished in its entirety by a polishing unit 80 to be described later.

As illustrated in FIG. 1, the processing apparatus 2 includes a pair of support structures 30A and 30B mounted on a rear end portion of the foundation base 4 behind the moving mechanism 18 and the chuck tables 20 thereon. The support structures 30A and 30B, each in the shape of a rectangular parallelepiped, protrude upwardly from the upper surface of the foundation base 4. Also, the support structures 30A and 30B have respective face sides, i.e., front surfaces, lying generally parallel to a vertical plane, i.e., an XZ plane along the X-axis and the Z-axis. The support structures 30A and 30B are disposed adjacent to each other, i.e., spaced from each other, along the X-axis.

A moving mechanism, i.e., a grinding moving mechanism, 32A for moving the grinding unit 42A along the Z-axis is mounted on the face side of the support structure 30A. A moving mechanism, i.e., a grinding moving mechanism, 32B for moving the grinding unit 42B along the Z-axis is mounted on the face side of the support structure 30B.

The moving mechanisms 32A and 32B have respective pairs of guide rails 34 extending along the Z-axis and mounted respectively on the face sides of the support structures 30A and 30B. A movable plate 36 shaped as a flat plate is slidably mounted on the guide rails 34 in each pair for sliding movement along the guide rails 34. A nut, not depicted, is fixedly disposed on a reverse side, i.e., a rear surface, of the movable plate 36 and operatively threaded over a ball screw 38 that is disposed between the guide rails 34 and extends along the Z-axis. The ball screw 38 has an upper end to which a stepping motor 40 is coupled for rotating the ball screw 38 about its central axis. When the stepping motor 40 is energized, it rotates the ball screw 38 about its central axis, causing the nut to move the movable plate 36 along the Z-axis along the guide rails 34.

The grinding unit 42A for coarsely grinding a workpiece 11 on the chuck table 20 in the grinding zone B is fixedly mounted on a face side, i.e., a front surface, of the movable plate 36 of the moving mechanism 32A. The grinding unit 42B for finishingly grinding a workpiece 11 on the chuck table 20 in the grinding zone C is fixedly mounted on a face side, i.e., a front surface, of the movable plate 36 of the moving mechanism 32B. The grinding unit 42A is positioned above the grinding zone B, whereas the grinding unit 42B is positioned above the grinding zone C.

Each of the grinding units 42A and 42B includes a tubular housing 44 and a cylindrical spindle 46 extending along the Z-axis and rotatably disposed in the housing 44 for rotation around the Z-axis. The spindle 46 has a lower distal end portion protruding downwardly from the lower end of the housing 44. A disk-shaped mount 48 made of metal, for example, is fixed to a lower distal end of the spindle 46.

The mount 48 of the grinding unit 42A has a lower surface on which a grinding wheel 50A for coarsely grinding a workpiece 11 is mounted. The mount 48 of the grinding unit 42B has a lower surface on which a grinding wheel 50B for finishingly grinding a workpiece 11 is mounted. The grinding wheels 50A and 50B are detachably fastened to the respective mounts 48 by fasteners such as bolts.

FIG. 3 illustrates the grinding unit 42A in side elevation, partly in cross-section. As illustrated in FIG. 3, the grinding wheel 50A includes an annular wheel base 52 made of a metal material such as aluminum alloy, for example, and a plurality of grindstones 54 fixed to a lower surface of the wheel base 52. The grindstones 54 have respective lower surfaces collectively acting as a grinding surface 54a for grinding the workpiece 11 in abrasive contact therewith. Each of the grindstones 54 is made of abrasive grains of diamond and cubic boron nitride (cBN), for example, fixedly bound together by a binder or a bonding material such as a metal bond, a resin bond, or a vitrified bond. The grindstones 54, each shaped as a rectangular parallelepiped, for example, are arranged in an annular array at substantially equal spaced intervals along the outer circumferential edge of the wheel base 52.

The spindle 46 has an upper proximal end that is coupled to a rotary actuator, i.e., a grinding wheel rotary actuator, 56 for rotating the grinding wheel 50A. The rotary actuator 56 includes an electric motor, for example, that rotates the spindle 46 about a rotation axis, i.e., a grinding wheel axis, 58 that extends perpendicularly to the grinding surface 54a. For example, the rotation axis 58 extends generally parallel to the Z-axis. When the rotary actuator 56 is energized, it rotates the spindle 46, the mount 48, and the grinding wheel 50A about the rotation axis 58, turning the grindstones 54 along an annular turn path generally parallel to the horizontal plane, i.e., the XY plane.

The grinding unit 42B and the grinding wheel 50B (see FIG. 1) are similar in structure and function to the grinding unit 42A and the grinding wheel 50A, respectively. However, the abrasive grains contained in the grindstones 54 of the grinding wheel 50B are smaller in average grain size than the abrasive grains contained in the grindstones 54 of the grinding wheel 50A.

A workpiece 11 is ground successively by the grinding units 42A and 42B as follows. The workpiece 11 is delivered to the chuck table 20 positioned in the delivery zone A (see FIG. 1) and held on the chuck table 20. Specifically, the workpiece 11 is placed on the chuck table 20 such that the reverse side 11b, i.e., the processed surface, is exposed upwardly and the face side 11a faces the holding surface 20a. When the suction force from the suction source is then applied to act on the holding surface 20a, the workpiece 11 is held under suction on the chuck table 20. In case the protective member is attached to the face side 11a of the workpiece 11, the workpiece 11 is held under suction on the chuck table 20 through the protective member interposed therebetween.

As described above, the holding surface 20a of the chuck table 20 is of an upwardly protruding conical shape. When the workpiece 11 is held under suction on the chuck table 20, the workpiece 11 is slightly flexibly deformed along the conical holding surface 20a. The region of the reverse side 11b of the workpiece 11 that is held on the grinding holding region 20b and close regions thereto are disposed generally parallel to the horizontal plane, i.e., the XY plane.

Then, the moving mechanism 18 (see FIG. 1) is actuated to move and position the chuck table 20 that is holding the workpiece 11 in the grinding zone B. The workpiece 11 that is held on the chuck table 20 is positioned beneath the grinding wheel 50A. At this time, the chuck table 20 is positioned such that the center of the workpiece 11 and the annular turn path along which the grindstones 54 will turn overlap each other along the Z-axis.

The chuck table rotary actuator 26 rotates the chuck table 20 about the rotation axis 28, and the grinding wheel rotary actuator 56 rotates the grinding wheel 50A about the rotation axis 58. At the same time, the moving mechanism 32A (see FIG. 1) lowers the grinding wheel 50A to bring the grinding surface 54a of the grindstones 54 into abrasive contact with the reverse side 11b of the workpiece 11. The grinding surface 54a of the grindstones 54 now grinds the reverse side 11b of the workpiece 11 in its entirety, thereby coarsely grinding and hence thinning down the workpiece 11. When the workpiece 11 has been thinned down to a predetermined thickness, the moving mechanism 32A stops lowering the grinding wheel 50A. The process of coarsely grinding the workpiece 11 on the grinding unit 42A is now completed.

Then, the moving mechanism 18 (see FIG. 1) is actuated to move and position the chuck table 20 that is holding the workpiece 11 in the grinding zone C. The workpiece 11 that is held on the chuck table 20 is positioned beneath the grinding wheel 50B. The grinding wheel 50B now finishingly grinds the reverse side 11b of the workpiece 11 in its entirety. The grinding wheel 50B grinds the workpiece 11 in essentially the same manner as the grinding wheel 50A grinds the workpiece 11.

A nozzle, not depicted, for supplying a grinding liquid such as pure water, for example, is provided in or near each of the grinding units 42A and 42B. While each of the grinding units 42A and 42B is grinding the workpiece 11, the nozzle continuously supplies the workpiece 11 and the grindstones 54 with the grinding liquid. The grinding liquid thus supplied cools the workpiece 11 and the grindstones 54 and washes away debris or swarf produced while the grindstones 54 grind the workpiece 11.

The workpiece 11 has now been coarsely and finishingly ground by the grinding wheels 50A and 50B. When the grindstones 54 grind the reverse side 11b of the workpiece 11, they tend to leave arcuate saw marks on the reverse side 11b along the turn path followed by the grindstones 54.

As illustrated in FIG. 1, the processing apparatus 2 further includes a support structure 60 mounted on a side wall of the foundation base 4 alongside of the polishing zone D, i.e., the moving mechanism 18. The support structure 60 is in the shape of a rectangular parallelepiped and has a face side facing the moving mechanism 18 and lying generally parallel to a vertical plane, i.e., a YZ plane along the Y-axis and the Z-axis. A moving mechanism, i.e., a polishing moving mechanism, 62 for moving the polishing unit 80 along the Y-axis and the Z-axis is mounted on the face side of the support structure 60.

The moving mechanism 62 has a pair of Y-axis guide rails 64 extending along the Y-axis and mounted on the face side of the support structure 60. A Y-axis movable plate 66 shaped as a flat plate is slidably mounted on the Y-axis guide rails 64 for sliding movement along the Y-axis guide rails 64. A nut, not depicted, is fixedly disposed on a reverse side, i.e., a rear surface, of the Y-axis movable plate 66 and operatively threaded over a Y-axis ball screw 68 that is disposed between the Y-axis guide rails 64 and extends along the Y-axis. The Y-axis ball screw 68 has an end to which a Y-axis stepping motor 70 is coupled for rotating the Y-axis ball screw 68 about its central axis. When the Y-axis stepping motor 70 is energized, it rotates the Y-axis ball screw 68 about its central axis, causing the nut to move the Y-axis movable plate 66 along the Y-axis along the Y-axis guide rails 64.

A pair of Z-axis guide rails 72 extending along the Z-axis are mounted on a face side of the Y-axis movable plate 66 that faces the moving mechanism 18. A Z-axis movable plate 74 shaped as a flat plate is slidably mounted on the Z-axis guide rails 72 for sliding movement along the Z-axis guide rails 72. A nut, not depicted, is fixedly disposed on a reverse side, i.e., a rear surface, of the Z-axis movable plate 74 and operatively threaded over a Z-axis ball screw 76 that is disposed between the Z-axis guide rails 72 and extends along the Z-axis. The Z-axis ball screw 76 has an upper end to which a Z-axis stepping motor 78 is coupled for rotating the Z-axis ball screw 76 about its central axis. When the Z-axis stepping motor 78 is energized, it rotates the Z-axis ball screw 76 about its central axis, causing the nut to move the Z-axis movable plate 74 along the Z-axis along the Z-axis guide rails 72.

The polishing unit 80 for polishing a workpiece 11 on the chuck table 20 in the polishing zone D is fixedly mounted on a face side of the Z-axis movable plate 74 that faces the moving mechanism 18. The polishing unit 80 is positioned above the polishing zone D. The moving mechanism 62 controls the movement of the polishing unit 80 along the Y-axis and the Z-axis. However, in case it is possible for the moving mechanism 18 to adjust the positional relation of the chuck table 20 and the polishing unit 80 along the Y-axis, the moving mechanism 62 may be free of the mechanism for moving the polishing unit 80 along the Y-axis, i.e., the Y-axis guide rails 64, the Y-axis movable plate 66, the Y-axis ball screw 68, and the Y-axis stepping motor 70.

The polishing unit 80 includes a tubular housing 82 and a cylindrical spindle 84 extending along the Z-axis and rotatably disposed in the housing 82 for rotation around the Z-axis. The spindle 84 has a lower distal end portion protruding downwardly from the lower end of the housing 82. A disk-shaped mount 86 made of metal, for example, is fixed to a lower distal end of the spindle 84. The mount 86 has a lower surface on which a polishing pad 88 for polishing the workpiece 11 is mounted. The polishing pad 88 is detachably fastened to the mount 86 by fasteners such as bolts.

FIG. 4 illustrates the polishing unit 80 in side elevation, partly in cross-section. As illustrated in FIG. 4, the polishing pad 88 includes a disk-shaped base 90 and a polishing layer 92 fixed to the base 90. The base 90 is made of a metal material such as aluminum alloy, for example, and is substantially equal in diameter to the mount 86. The polishing layer 92 is of a disk shape that is substantially equal in diameter to the base 90, and is secured to the lower surface of the base 90 by way of adhesive bonding, for example.

The polishing layer 92 is made of a non-woven fabric such as felt or resin such as polyurethane, for example, and contains abrasive grains, i.e., bound abrasive grains. For example, particles of silica or alumina having an average gain size ranging from 0.2 to 0.5 μm are retained in the polishing layer 92. The abrasive grains may be made of a material and may have a grain size that are appropriately selected depending on the material of the workpiece 11, and the like. The polishing layer 92 has a lower surface acting as a polishing surface 88a for polishing the workpiece 11 in abrasive contact therewith.

The spindle 84 has an upper proximal end that is coupled to a rotary actuator, i.e., a polishing pad rotary actuator, 94 for rotating the polishing pad 88. The rotary actuator 94 includes an electric motor, for example, that rotates the spindle 84 about a rotation axis, i.e., a polishing pad axis, 96 that extends across the polishing surface 88a. For example, the rotation axis 96 extends generally parallel to the Z-axis. When the rotary actuator 94 is energized, it rotates the spindle 84, the mount 86, and the polishing pad 88 about the rotation axis 96.

When the moving mechanism 62 (see FIG. 1) moves the polishing unit 80 along the Z-axis, the chuck table 20 and the polishing pad 88 move relatively to each other in a first direction along the Z-axis across the holding surface 20a and the polishing surface 88a. When the moving mechanism 18 (see FIG. 1) moves the chuck table 20 or the moving mechanism 62 (see FIG. 1) moves the polishing unit 80 along the Y-axis, the chuck table 20 and the polishing pad 88 move relatively to each other in a second direction along the XY plane across the first direction along the Z-axis. A lifting and lowering mechanism, not depicted, for lifting and lowering the chuck table 20 along the Z-axis may be coupled to the chuck table 20. The lifting and lowering mechanism functions as a polishing moving mechanism for moving the chuck table 20 and the polishing pad 88 relatively to each other in the first direction along the Z-axis.

When the grinding of the workpiece 11 (see FIG. 3) is completed, the moving mechanism 18 (see FIG. 1) is actuated to bring the chuck table 20 that is holding the ground workpiece 11 to the polishing zone D where the workpiece 11 is positioned beneath the polishing pad 88. The moving mechanism 62 (see FIG. 1) then adjusts the position of the polishing pad 88 along the Y-axis to position the polishing layer 92 of the polishing pad 88 over the entire reverse side 11b, i.e., the processed surface, of the workpiece 11.

The tilt of the chuck table 20 is adjusted to make the rotation axis 28 generally parallel to the Z-axis. The rotation axis 28 of the chuck table 20 and the rotation axis 96 of the polishing pad 88 now lie generally parallel to each other. Then, the chuck table 20 is rotated about the rotation axis 28, whereas the polishing pad 88 is rotated about the rotation axis 96. The moving mechanism 62 (see FIG. 1) lowers the polishing pad 88 to move the workpiece 11 and the polishing pad 88 relatively to each other, bringing the workpiece 11 and the polishing pad 88 toward each other along the Z-axis. The process of moving the workpiece 11 and the polishing pad 88 toward each other along the Z-axis is also referred to as a processing feed process. The polishing surface 88a of the polishing pad 88 now abrasively contacts the reverse side 11b of the workpiece 11, starting to polish the reverse side 11b.

While the workpiece 11 is being polished by the polishing pad 88, the workpiece 11 and the polishing pad 88 are supplied with a polishing liquid. The polishing liquid includes, for example, a liquid or chemical solution for performing a chemical surface treatment on the workpiece 11. The polishing liquid may be made of a material appropriately selected depending on the material of the workpiece 11, the purpose for which the workpiece 11 is polished, and processing conditions in which the workpiece 11 is polished, for example. Examples of the polishing liquid include an acidic solution in which permanganate is dissolved and an alkaline solution in which sodium hydroxide or potassium hydroxide is dissolved. In case the polishing layer 92 of the polishing pad 88 contains bound abrasive grains, the polishing solution contains no abrasive grains.

When the polishing liquid is supplied to an area of contact between the reverse side 11b of the workpiece 11 and the polishing surface 88a of the polishing pad 88, the polishing liquid acts on the reverse side 11b of the workpiece 11, thereby performing chemical mechanical polishing (CMP) on the reverse side 11b of the workpiece 11. The polishing layer 92 of the polishing pad 88 may not contain abrasive grains. In case the polishing layer 92 is free of abrasive grains, the polishing liquid contains free abrasive grains that are supplied together with the polishing liquid to the area of contact between the workpiece 11 and the polishing pad 88.

When the reverse side 11b of the workpiece 11 is thus polished by the polishing unit 80, minute surface irregularities remaining on the reverse side 11b are removed, with the result that the reverse side 11b is planarized. For example, if saw marks remain unremoved on the reverse side 11b after the workpiece 11 has been ground, the saw marks are polished off when the reverse side 11b is polished. After the workpiece 11 has been continuously polished until its thickness reaches a predetermined thickness, the processing feed process is brought to a stop, and the polishing of the workpiece 11 is completed.

As illustrated in FIG. 1, the processing apparatus 2 further includes a cleaning unit 98 for cleaning the polished workpiece 11. The cleaning unit 98 is positioned on the foundation base 4 forwardly of the moving mechanism 18 and the chuck tables 20 thereon. The cleaning unit 98 includes a spinner table that rotates about its vertical axis while holding the workpiece 11 thereon and a nozzle for supplying a cleaning liquid such as pure water to the workpiece 11. In operation, the workpiece 11 is held on the spinner table, and then the spinner table is rotated about its vertical axis while the cleaning liquid is being supplied from the nozzle to the workpiece 11. The workpiece 11 is thus cleaned with remaining debris or swarf washed away therefrom by the cleaning liquid and under centrifugal forces generated by the rotating spinner table.

When the polishing of the workpiece 11 by the polishing unit 80 is completed, the moving mechanism 18 rotates the turntable to move the chuck table 20 that is holding the polished workpiece 11 from the polishing zone D back to the delivery zone A. The workpiece 11 is then delivered by the delivery unit 16 from the chuck table 20 to the cleaning unit 98, and cleaned by the cleaning unit 98. The workpiece 11 that has been cleaned is stored back into the cassette 10A or the cassette 10B by the delivery unit 6.

The processing apparatus 2 includes a controller, also referred to as a control unit, a control section, or a control device, 100 for controlling the processing apparatus 2. The controller 100 is electrically connected to various components of the processing apparatus 2 that include the delivery unit 6, the alignment mechanism 12, the delivery units 14 and 16, the moving mechanism 18, the chuck tables 20, the rotary actuator 26, the moving mechanisms 32A and 32B, the grinding units 42A and 42B, the rotary actuator 56, the moving mechanism 62, the polishing unit 80, the rotary actuator 94, and the cleaning unit 98 among others. The controller 100 controls the processing apparatus 2 in its operation by outputting control signals to the components of the processing apparatus 2. For example, the controller 100 is constituted by a computer and includes a processing unit for performing processing operations such as arithmetic operations required to operate the processing apparatus 2 and a storage unit for storing various pieces of information, i.e., data and programs, used to operate the processing apparatus 2. The processing unit includes a processor such as a central processing unit (CPU). The storage unit also includes memories such as a read only memory (ROM) and a random access memory (RAM).

For processing a workpiece 11 on the processing apparatus 2, the holding surface 20a of each of the chuck tables 20 is of an upwardly protruding conical shape (see FIG. 3). When the workpiece 11 is held on each chuck table 20, the workpiece 11 is deformed to match the conical shape of the holding surface 20a. At a time at which the workpiece 11 that is held on the chuck table 20 is polished (see FIG. 4) as described above, the processed surface of the workpiece 11 is conical in shape and does not have a constant height, and as a result, lies out of parallel with the polishing surface 88a of the polishing pad 88 that lies flatwise along the XY plane. If the polishing pad 88 were pressed against the conical workpiece 11 in this state, then the polishing pad 88 would be pressed strongly against the center of the workpiece 11 in particular, and the force, i.e., the polishing pressure, applied from the polishing pad 88 to the workpiece 11 would tend to become irregular within the plane of the workpiece 11, with the result that the polished workpiece 11 would be likely to have thickness variations.

According to the present embodiment, the processing apparatus 2 shapes the polishing surface 88a of the polishing pad 88 to a shape matching the shape of the holding surface 20a of the chuck table 20, thereby making the polishing surface 88a complementary in shape to the holding surface 20a. With the polishing surface 88a being thus shaped, even though the holding surface 20a of the chuck table 20 is not flat, it is possible for the polishing surface 88a to apply a uniform polishing pressure to the workpiece 11 held on the chuck table 20, thereby reducing thickness variations of the polished workpiece 11.

Specifically, as illustrated in FIG. 4, the processing apparatus 2 includes a shape measuring instrument 110 for measuring the shape of the holding surface 20a of the chuck table 20 and a shaping mechanism (dressing mechanism) 120 for contacting and shaping, i.e., dressing, the polishing surface 88a of the polishing pad 88.

The shape measuring instrument 110 includes, for example, a laser displacement meter for measuring the heightwise position, i.e., the position along the Z-axis, of the holding surface 20a of the chuck table 20 in a contactless manner. The laser displacement meter as the shape measuring instrument 110 operates as follows: The laser displacement meter applies a laser beam to the holding surface 20a and detects a laser beam reflected from the holding surface 20a. Then, the laser displacement meter specifies the heightwise position of the holding surface 20a on the basis of an amount of displacement of the detected spot of the laser beam. The shape measuring instrument 110 is not limited to the laser displacement meter, but may be of any of other types as long as it is capable of measuring the heightwise position of the holding surface 20a.

The shape measuring instrument 110 is coupled to a moving mechanism that moves the shape measuring instrument 110 along the horizontal plane, i.e., the XY plane. For example, as illustrated in FIG. 4, the shape measuring instrument 110 is mounted on the lower surface of an outer circumferential edge of the mount 86 of the polishing unit 80. The positions of the shape measuring instrument 110 along the Y-axis and the Z-axis can be adjusted by the moving mechanism 62 (see FIG. 1). When the rotary actuator 94 is energized, the shape measuring instrument 110 turns along an annular turn path generally parallel to the horizontal plane, i.e., the XY plane, about the rotation axis 96. When the shape measuring instrument 110 has reached a desired position on the annular turn path, the rotary actuator 94 is de-energized.

The shape measuring instrument 110 may be installed in any of other positions. For example, the shape measuring instrument 110 may be mounted on the mount 48 (see FIG. 1) of one of the grinding units 42A and 42B. The shape measuring instrument 110 mounted on the mount 48 may have its position adjusted along the Z-axis by the corresponding one of the moving mechanisms 32A and 32B (FIG. 1). In addition, when the rotary actuator 56 (see FIG. 3) is energized, it turns the shape measuring instrument 110 along an annular turn path generally parallel to the horizontal plane, i.e., the XY plane, about the rotation axis 58. Alternatively, the shape measuring instrument 110 may be coupled to a moving mechanism such as a swing arm provided separately from the grinding units 42A and 42B and the polishing unit 80.

For measuring the shape of the holding surface 20a of the chuck table 20, the shape measuring instrument 110 is positioned in overlapping relation to the holding surface 20a along the Z-axis. Then, while the chuck table 20 and the shape measuring instrument 110 are being horizontally moved relatively to each other, the shape measuring instrument 110 continuously or intermittently measures the heightwise position of the holding surface 20a. In this manner, the shape of the holding surface 20a is measured. The positional relation between the chuck table 20 and the shape measuring instrument 110 may be adjusted by moving the chuck table 20 with the moving mechanism 18 (see FIG. 1). In this case, the shape measuring instrument 110 may not necessarily be coupled to the mounts 48 and 86 or a dedicated moving mechanism. Details of a process of measuring the shape of the holding surface 20a with the shape measuring instrument 110 will be described later.

As illustrated in FIG. 4, the shaping mechanism 120 includes a shaping member (dressing member) 122 for contacting and shaping the polishing surface 88a of the polishing pad 88. The shaping member 122 includes, for example, a plate-shaped or columnar grindstone including a base of metal and abrasive grains of diamond, for example, electrodeposited on the base. The shaping member 122 has an upper surface acting as a shaping surface 122a for contacting the polishing surface 88a of the polishing pad 88, with abrasive grains exposed to an appropriate extent from the shaping surface 122a. The shaping mechanism 120 shapes the polishing surface 88a of the polishing pad 88 with the shaping surface 122a by moving and rotating the shaping member 122.

The shaping mechanism 120 includes a support base 124 that supports thereon various components of the shaping mechanism 120. The components of the shaping mechanism 120 will be described in detail below. The support base 124 supports directly thereon a lifting and lowering mechanism 126 for moving the shaping member 122 in first directions along the Z-axis, i.e., lifting and lowering the shaping member 122 along the Z-axis, across the holding surface 20a and the polishing surface 88a. The lifting and lowering mechanism 126 includes, for example, an air cylinder including a tubular cylinder 128 and a rod 130 telescopically housed in the cylinder 128. The rod 130 has an upper distal end portion protruding upwardly from the upper end of the cylinder 128 and fixed to a support member 132. The rod 130 has a lower end fixed to a piston, not depicted, that is movably fitted in the cylinder 128 and divides the inner space of the cylinder 128 into a first compartment and a second compartment. A pressure regulator, not depicted, and the like, controls the pressure of air supplied to the first compartment and the second compartment to move the rod 130 upwardly in a direction to protrude out of the cylinder 128 or downwardly in a direction to retract into the cylinder 128, thereby lifting or lowering the rod 130 and the support member 132 along the Z-axis.

A rotating mechanism 134 for rotating the shaping member 122 is mounted on the support member 132. The rotating mechanism 134 includes, for example, a cylindrical spindle 136 and a rotary actuator 138 such as an electric motor, for example, connected to the lower proximal end of the spindle 136. The shaping member 122 is supported on a base 140 fixed to the upper distal end of the spindle 136. The shaping member 122 supported on the base 140 has its shaping surface 122a exposed upwardly. When the rotary actuator 138 is energized, it rotates the shaping member 122, the spindle 136, and the base 140 about an axis generally parallel to the Z-axis.

The shaping mechanism 120 includes a displacement measuring instrument 142 for measuring an amount of displacement of the shaping member 122. The displacement measuring instrument 142 directly or indirectly measures an amount of displacement, i.e., an amount of positional change, of the shaping member 122 in the first directions along the Z-axis across the holding surface 20a and the polishing surface 88a. For example, the displacement measuring instrument 142 includes a laser displacement meter mounted on the support base 124. The shaping mechanism 120 also includes a reference element 144 that functions as a reference with respect to displacement of the shaping member 122. The reference element 144 is made of a material that reflects light, i.e., a laser beam, emitted from the displacement measuring instrument 142. The reference element 144 is fixed to one of the components of the shaping mechanism 120 that is lifted or lowered in unison with the shaping member 122 and positioned in overlapping relation to the displacement measuring instrument 142 along the Z-axis. In FIG. 4, the reference element 144 is illustrated as being fixed to the support member 132.

When the shaping member 122 is lifted or lowered along the Z-axis by the lifting and lowering mechanism 126 or an external force applied thereto, the reference element 144 is also lifted or lowered in unison with the shaping member 122. In other words, an amount of displacement of the shaping member 122 and an amount of displacement of the reference element 144 are equal to each other. The displacement measuring instrument 142 detects light reflected by a lower surface of the reference element 144 and measures the amount of displacement of the reference element 144 along the Z-axis on the basis of the detected light. In this fashion, the displacement of the shaping member 122 is indirectly measured by the displacement measuring instrument 142.

To the shaping mechanism 120, there is connected a moving mechanism, i.e., a shaping moving mechanism 146, for moving the shaping mechanism 120 in second directions, i.e., horizontal directions or along the XY plane, across the first directions along the Z-axis. The moving mechanism 146 includes, for example, a ball-screw-type moving mechanism including a ball screw, not depicted, extending along the X-axis or the Y-axis and a stepping motor, not depicted, for rotating the ball screw about its central axis. Specific structural details of the ball-screw-type moving mechanism are similar to those of the moving mechanisms 32A and 32B and the moving mechanism 62 (see FIG. 1). The moving mechanism 146 is coupled to the support base 124 of the shaping mechanism 120. When the moving mechanism 146 is actuated, it moves the support base 124 and the components supported thereon in the second or horizontal directions. The moving mechanism 146 is thus able to control the relative positional relation in the horizontal directions between the polishing pad 88 and the shaping member 122.

The shaping mechanism 120 and the moving mechanism 146 may be structurally modified as long as they remain capable of moving and rotating the shaping member 122. For example, the shaping mechanism 120 may further include a tilt adjusting mechanism for adjusting a tilt angle of the shaping member 122, and the like.

A specific example of a polishing surface shaping method for shaping the polishing surface 88a of the polishing pad 88 on the processing apparatus 2 will be described below. FIG. 5 is a flowchart of a sequence of a polishing surface shaping method according to the present embodiment. The polishing surface shaping method according to the present embodiment includes a holding surface measuring step S1 that measures the shape of the holding surface 20a of the chuck table 20 and a shaping step S2 that shapes the polishing surface 88a of the polishing pad 88 to a shape matching the holding surface 20a of the chuck table 20, thereby making the polishing surface 88a complementary in shape to the holding surface 20a. The polishing surface shaping method according to the present embodiment may additionally include a polishing surface shape specifying step S3 that specifies the shape of the shaped polishing surface 88a on the basis of the amount of displacement of the shaping member 122.

FIG. 6 illustrates, in side elevation, partly in cross-section and partly in block form, the processing apparatus 2 in the holding surface measuring step S1. FIG. 6 illustrates in functional block form the controller 100 including its functions, as well as the chuck table 20, the polishing unit 80, the polishing pad 88, the rotary actuator 94, and the shape measuring instrument 110. As illustrated in FIG. 6, the controller 100 includes a processing unit 150 for performing processing operations required to shape the polishing surface 88a of the polishing pad 88 and a storage unit, i.e., memories, 160 for storing various pieces of information, i.e., data and programs, used to shape the polishing surface 88a of the polishing pad 88.

The processing unit 150 includes a holding surface shape specifying section 152, a shaping condition setting section 154, and a polishing surface shape specifying section 156. The holding surface shape specifying section 152 specifies the shape of the holding surface 20a of the chuck table 20 and stores information regarding the shape of the holding surface 20a, i.e., holding surface shape information, in a holding surface shape storing section 162 included in the storage unit 160. The shaping condition setting section 154 sets shaping conditions for shaping the polishing surface 88a of the polishing pad 88 to a predetermined shape and stores information regarding the shaping conditions, i.e., shaping condition information, in a shaping condition storing section 164 included in the storage unit 160. The polishing surface shape specifying section 156 specifies the shape of the shaped polishing surface 88a and stores information regarding the shape of the shaped polishing surface 88a, i.e., polishing surface shape information, in a polishing surface shape storing section 166 included in the storage unit 160.

The processing unit 150 further includes a shaping controlling section 158 for controlling the shaping of the polishing surface 88a of the polishing pad 88. The shaping controlling section 158 is connected to those components of the processing apparatus 2 that are involved in shaping the polishing surface 88a. The shaping controlling section 158 outputs control signals to the components to control operation thereof for thereby enabling the processing apparatus 2 to shape the polishing surface 88a of the polishing pad 88.

In the holding surface measuring step S1, in a state in which no workpiece 11 is placed on the holding surface 20a of the chuck table 20, the angle of the chuck table 20 is adjusted to make the rotation axis 28 of the chuck table 20 generally parallel to the Z-axis. In addition, the positional relation between the chuck table 20 and the shape measuring instrument 110 is adjusted. For example, the shaping controlling section 158 outputs a control signal to the moving mechanism 18 and/or the moving mechanism 62 (see FIG. 1) to position the chuck table 20 and the polishing unit 80 such that the center, i.e., the rotation axis 28, of the holding surface 20a of the chuck table 20 and the turn path of the shape measuring instrument 110 overlap each other along the Z-axis.

Then, the shaping controlling section 158 outputs a control signal to the rotary actuator 94 and the shape measuring instrument 110. The shape measuring instrument 110 starts to operate to measure the heightwise position of the holding surface 20a. Moreover, the rotary actuator 94 is energized to rotate the spindle 84 about the rotation axis 96, causing the shape measuring instrument 110 to turn along its turn path while measuring the heightwise position of the holding surface 20a.

FIG. 7 illustrates in plan the chuck table 20 and the shape measuring instrument 110. For example, the shape measuring instrument 110 turns along an arcuate turn path 110a, which is part of the annular turn path thereof, while passing directly over the center, denoted by O, of the holding surface 20a of the chuck table 20. The shape measuring instrument 110 turns along the arcuate turn path 110a while being in operation, thereby measuring heightwise positions of the holding surface 20a at a plurality of points on the arcuate turn path 110a.

In case the holding surface 20a of the chuck table 20 is of an upwardly protruding conical shape, heightwise positions of the holding surface 20a are measured at two or more points that are spaced different distances from the center O of the holding surface 20a, and the gradient of the holding surface 20a may be calculated on the basis of the heightwise positions thus measured, so that the shape of the holding surface 20a can be specified. In the holding surface measuring step S1, therefore, the arcuate turn path 110a of the shape measuring instrument 110 is established to overlap the center O of the holding surface 20a and measuring points P₁ and P₂ that are positioned between the center O and the outer circumferential edge of the holding surface 20a. Then, heightwise positions of the holding surface 20a are measured at three points, i.e., the center O and the measuring points P₁ and P₂. Conditions for measuring the holding surface 20a with the shape measuring instrument 110 may be set appropriately depending on the specifications of the chuck table 20. For example, the shape measuring instrument 110 may measure heightwise positions of the holding surface 20a continuously along the arcuate turn path 110a. The positions of measuring points may also be adjusted by rotating the chuck table 20 with the rotary actuator 26 (see FIG. 6).

As illustrated in FIG. 6, information regarding the heightwise positions of the holding surface 20a as measured by the shape measuring instrument 110 is input to the holding surface shape specifying section 152 of the processing unit 150. On the basis of the information regarding the measured heightwise positions of the holding surface 20a with the shape measuring instrument 110, the holding surface shape specifying section 152 specifies the shape of the holding surface 20a and generates information regarding the shape of the holding surface 20a, i.e., the holding surface shape information. The holding surface shape information generated and acquired by the holding surface shape specifying section 152 is stored in the holding surface shape storing section 162.

The holding surface shape information is not limited to any particular types and kinds. For example, the holding surface shape specifying section 152 calculates an approximate surface that approximates the shape of the holding surface 20a from the heightwise positions of the holding surface 20a that have been measured by the shape measuring instrument 110, and stores the calculated approximate surface as holding surface shape information in the holding surface shape storing section 162. Specifically, in case heightwise positions of the holding surface 20a are measured at three points, i.e., the center O and the measuring points P₁ and P₂, as illustrated in FIG. 7, providing the holding surface 20a of the chuck table 20 is of an upwardly protruding conical shape, the holding surface shape specifying section 152 calculates a cone having an apex at the center O and including the measuring points P₁ and P₂ on its lateral area. The lateral area of the calculated cone corresponds to the approximate surface that approximates the holding surface 20a and is used as holding surface shape information.

However, the holding surface shape specifying section 152 may store the heightwise positions of the holding surface 20a that have been measured by the shape measuring instrument 110 directly as holding surface shape information in the holding surface shape storing section 162. For example, in case heightwise positions are continuously measured along a path from the center of the holding surface 20a to the outer circumferential edge thereof, the heightwise positions of the holding surface 20a that have been measured by the shape measuring instrument 110 directly correspond to the shape of the holding surface 20a. In this case, the set of the heightwise positions of the holding surface 20a that have been measured by the shape measuring instrument 110 may also be used as holding surface shape information.

Then, in the shaping step S2, the polishing surface 88a of the polishing pad 88 is shaped according to the shape of the holding surface 20a of the chuck table 20 that has been measured in the holding surface measuring step S1. FIG. 8 illustrates, in side elevation, partly in cross-section and partly in block form, the processing apparatus 2 in the shaping step S2.

In the shaping step S2, the shaping mechanism 120 shapes the polishing surface 88a of the polishing pad 88. Specifically, the shaping controlling section 158 outputs a control signal to the moving mechanism 62 (see FIG. 1) and/or the shaping moving mechanism 146 to adjust the positional relation between the polishing pad 88 and the shaping mechanism 120 such that the shaping mechanism 120 is positioned beneath the polishing pad 88.

Further, the shaping condition setting section 154 sets shaping conditions, i.e., processing conditions, for shaping the polishing surface 88a of the polishing pad 88 with the shaping mechanism 120. Specifically, the shaping condition setting section 154 selects shaping conditions for shaping the polishing surface 88a of the polishing pad 88 into a shape complementary in shape to the holding surface 20a of the chuck table 20, on the basis of the holding surface shape information stored in the holding surface shape storing section 162. More specifically, the shaping condition setting section 154 selects shaping conditions for forming a recess or slot 88b complementary in shape to the holding surface 20a of the chuck table 20 in the polishing surface 88a side of the polishing pad 88. Examples of the shaping conditions selected by the shaping condition setting section 154 include the speed at which the polishing pad 88 is to move, the distance that the polishing pad 88 is to move, the speed at which the polishing pad 88 is to rotate, the speed at which the shaping member 122 is to move, the distance that the shaping member 122 is to move, and the speed at which the shaping member 122 is to rotate. The shaping conditions set by the shaping condition setting section 154 is stored in the shaping condition storing section 164.

Then, the shaping controlling section 158 reads the shaping conditions stored in the shaping condition storing section 164 and controls the components of the processing apparatus 2 for shaping the polishing surface 88a of the polishing pad 88 according to the read shaping conditions. Specifically, the shaping controlling section 158 outputs a control signal to the lifting and lowering mechanism 126 of the shaping mechanism 120 to lift the shaping member 122 and secure the shaping member 122 in the lifted position. For example, in case the lifting and lowering mechanism 126 includes the air cylinder as described above, air is supplied under high pressure to the cylinder 128 to cause the rod 130 to protrude from the cylinder 128 and keep the rod 130 in the protruding position.

The shaping controlling section 158 then outputs a control signal to at least one of the components including the moving mechanism 62 (see FIG. 1), the rotary actuator 94, the rotary actuator 138, and the shaping moving mechanism 146 to enable the shaping mechanism 120 to shape the polishing surface 88a of the polishing pad 88 according to the shaping conditions set by the shaping condition setting section 154. Now, while the polishing pad 88 and the shaping member 122 are being rotated, the polishing surface 88a of the polishing pad 88 and the shaping surface 122a of the shaping member 122 are brought into contact with each other. As a result, the recess 88b complementary in shape to the holding surface 20a is formed in the polishing surface 88a side of the polishing pad 88.

The speed at which the polishing pad 88 and the shaping member 122 are moved relatively to each other and the distance that they are moved in horizontal directions along the XY plane are adjusted by controlling the moving mechanism 62 (see FIG. 1) and/or the shaping moving mechanism 146, for example. The shaping surface 122a can thus be brought into contact with the polishing surface 88a at a desired position thereon to form the recess 88b at a desired position and in a desired range in the polishing pad 88.

Moreover, the speed at which the polishing pad 88 and the shaping member 122 are moved relatively to each other and the distance that they are moved along the Z-axis are adjusted by controlling the moving mechanism 62 (see FIG. 1). Furthermore, the speed at which the polishing pad 88 is rotated and the speed at which the shaping member 122 is rotated are adjusted by controlling the rotary actuator 94 and the rotary actuator 138, respectively. The depth of the recess 88b is thus adjusted in the area of contact where the polishing surface 88a and the shaping surface 122a are held in contact with each other, so that the recess 88b can be formed to a desired depth in the polishing pad 88. While the polishing surface 88a is being shaped, the angle of the shaping member 122 may appropriately be adjusted depending on the shape of the recess 88b.

For shaping the polishing surface 88a of the polishing pad 88, the speed at which the polishing pad 88 and the shaping member 122 are moved relatively to each other along the Z-axis is adjusted to keep the pressure, i.e., a pressing force, that the shaping member 122 applies to the polishing surface 88a in a range from 100 N to 200 N, for example. However, the pressing force may be set to an appropriate level depending on the material of the polishing pad 88, for example.

As described above, the polishing surface 88a of the polishing pad 88 is shaped under predetermined shaping conditions to form the recess 88b that has a desired shape in the polishing surface 88a, by the shaping mechanism 120. For example, the diameter of the polishing pad 88, i.e., the diameter of the polishing layer 92, is set to at least twice the diameter of the workpiece 11. While the polishing pad 88 and the shaping member 122 are being rotated, the polishing surface 88a and the shaping surface 122a are held in contact with each other and the polishing pad 88 and the shaping member 122 are moved relatively to each other. The speeds at which the polishing pad 88 and the shaping member 122 are rotated, the distances that the polishing pad 88 and the shaping member 122 are moved, the speeds at which the polishing pad 88 and the shaping member 122 are moved, and the like, at this time, are set on the basis of the shaping conditions selected by the shaping condition setting section 154. The recess 88b, which is of an annular shape, complementary in shape to the holding surface 20a of the chuck table 20 is now formed in the polishing surface 88a side of the polishing pad 88.

The annular recess 88b is concentric with the polishing surface 88a along circumferential directions of the polishing surface 88a. The recess 88b is of a triangular cross-sectional shape that is complementary in shape to the holding surface 20a of the chuck table 20. Consequently, the region of the polishing pad 88 between the center and the outer circumferential edge thereof is smaller in thickness than the center and the outer circumferential edge of the polishing pad 88. The shaping conditions are set such that the gradient of the side surface, i.e., the inner wall surface, of the recess 88b is equal to the gradient of the holding surface 20a of the chuck table 20. This makes the holding surface 20a and the recess 88b equal to each other in cross-sectional shape.

However, the cross-sectional shape of the holding surface 20a of the chuck table 20 and the cross-sectional shape of the shaped polishing surface 88a of the polishing pad 88, i.e., the cross-sectional shape of the recess 88b, may not necessarily be in full agreement with each other. For example, the bottom of the recess 88b that corresponds to the apex of the holding surface 20a may be of a round shape. Moreover, the side surface, i.e., the inner wall surface, of the recess 88b that is complementary in shape to the slanted holding surface 20a may be of a slightly curved shape. In this case, the side surface of the recess 88b may be in an upwardly protruding curved shape or a downwardly protruding curved shape.

As described above, when the shaping step S2 is carried out, the polishing surface 88a of the polishing pad 88 is shaped under the shaping conditions that correspond to the shape of the holding surface 20a of the chuck table 20, thereby forming the recess 88b that is complementary in shape to the holding surface 20a in the polishing surface 88a side. The recess 88b represents a slot capable of receiving the holding surface 20a fitted therein.

After the shaping step S2 has been carried out, the polishing surface shape specifying step S3 that specifies the shape of the shaped polishing surface 88a may be carried out. FIG. 9 illustrates in side elevation, partly in cross-section and partly in block form, the processing apparatus 2 in the polishing surface shape specifying step S3.

In the polishing surface shape specifying step S3, the shaping controlling section 158 outputs a control signal to the lifting and lowering mechanism 126 to cause the shaping member 122 to be lifted or lowered under an external force applied thereto. Specifically, the air supplied to the cylinder 128 is depressurized to the extent that the rod 130 is kept protruding from the cylinder 128. Then, when a downward external force is applied to the rod 130, the rod 130 is lowered in a direction to retract into the cylinder 128, and when the downward external force is removed, the rod 130 is lifted in a direction to protrude out of the cylinder 128. In other words, the rod 130 operates like a spring contracting under the external force applied thereto and expanding upon removal of the external force.

The shaping controlling section 158 outputs a control signal to the displacement measuring instrument 142 to energize the displacement measuring instrument 142. Now, the displacement measuring instrument 142 starts to monitor the amount of displacement of the shaping member 122 along the Z-axis. The displacement measuring instrument 142 indirectly monitors the amount of displacement of the shaping member 122 by continuously measuring the amount of displacement of the reference element 144 that is lifted and lowered in unison with the shaping member 122.

In a state in which the polishing pad 88 and the shaping member 122 are being kept rotating, the shaping controlling section 158 outputs control signals to the moving mechanism 62 (see FIG. 1) and the shaping moving mechanism 146 to adjust the positional relationship between the polishing pad 88 and the shaping mechanism 120 such that the shaping surface 122a of the shaping member 122 contacts the shaped polishing surface 88a. With the polishing surface 88a and the shaping surface 122a being held in contact with each other, the polishing pad 88 and the shaping member 122 are moved relatively to each other in horizontal directions.

For example, the moving mechanism 146 moves the shaping member 122 along a straight path interconnecting the center of the polishing surface 88a and the outer circumferential edge thereof. At this time, the rod 130 is lifted and lowered, i.e., contracted and expanded, depending on the depth of the recess 88b so as to keep the shaping member 122 and the polishing surface 88a in contact with each other. The shaping member 122 thus moves as it is lifted and lowered in tracing the polishing surface 88a, successively contacting a plurality of positions on the polishing surface 88a. The pressure, i.e., the pressing force, applied from the shaping member 122 to the polishing surface 88a is set to a level equal to or smaller than ⅕, preferably 1/10, or more preferably 1/20, of the pressing force applied when the polishing surface 88a is shaped in the shaping step S2. Typically, the pressure of the air supplied to the cylinder 128 is regulated to enable the shaping member 122 to apply a pressing force of approximately 10 N to the polishing surface 88a. However, the pressing force may be appropriately set depending on the material of the polishing pad 88, and the like. The rotation of the polishing pad 88 and the shaping member 122 may be decelerated or stopped to the extent that the shaping member 122 can be moved smoothly while being held in contact with the polishing surface 88a.

While the shaping member 122 is moving along the polishing surface 88a, the displacement measuring instrument 142 measures the amount of displacement of the shaping member 122, i.e., the reference element 144, along the Z-axis. The amount of displacement of the shaping member 122 at this time corresponds to the shape of the shaped polishing surface 88a. The amount of displacement of the shaping member 122 that has been measured by the displacement measuring instrument 142 is input to the polishing surface shape specifying section 156 of the controller 100.

The polishing surface shape specifying section 156 specifies the shape of the polishing surface 88a on the basis of the amount of displacement of the shaping member 122 that has been measured by the displacement measuring instrument 142 and generates information regarding the shape of the polishing surface 88a, i.e., polishing surface shape information. The polishing surface shape information generated and acquired by the polishing surface shape specifying section 156 is stored in the polishing surface shape storing section 166. The holding surface shape specifying section 152 may use the amount of displacement of the shaping member 122 that has been measured by the displacement measuring instrument 142 directly as the polishing surface shape information or may use information obtained by performing predetermined data processing on the amount of displacement of the shaping member 122 as the polishing surface shape information.

The amount of displacement of the reference element 144 has been described as being measured by the displacement measuring instrument 142. However, the displacement measuring instrument 142 may directly measure the heightwise position of the polishing surface 88a depending on the material of the polishing pad 88. In this case, the displacement measuring instrument 142 may directly measure the heightwise position of the polishing surface 88a and input the heightwise position of the polishing surface 88a to the polishing surface shape specifying section 156.

By carrying out the polishing surface shape specifying step S3 to specify the shape of the shaped polishing surface 88a as described above, it can be subsequently confirmed whether the polishing surface 88a has been shaped into a desired shape in the shaping step S2. After the polishing surface shape specifying step S3 has been carried out, the holding surface shape information, the shaping condition information, and the polishing surface shape information that have been stored respectively in the holding surface shape storing section 162, the shaping condition storing section 164, and the polishing surface shape storing section 166 are read and referred to for subsequently verifying the degree to which the shape of the holding surface 20a and the shape of the shaped polishing surface 88a have been in agreement with each other, the relation between the shape of the holding surface 20a and the shaping conditions, the relation between the shaping conditions and the shape of the shaped polishing surface 88a, and the like. This allows the shaping of the polishing surface 88a to be assessed and also allows the shaping conditions to be reviewed for an increase in the level of shaping accuracy.

There are no limitations on the timing of the holding surface measuring step S1, the shaping step S2, and the polishing surface shape specifying step S3. For example, the holding surface measuring step S1, the shaping step S2, and the polishing surface shape specifying step S3 may be carried out when the workpiece 11 is not ground and polished while the processing apparatus 2 is in operation, e.g., while the processing apparatus 2 is being set up, workpieces 11 are being delivered, and workpieces 11 are being cleaned. Moreover, the holding surface measuring step S1, the shaping step S2, and the polishing surface shape specifying step S3 may be carried out immediately after a chuck table 20 has been replaced or during maintenance of the processing apparatus 2.

After the shaping of the polishing surface 88a of the polishing pad 88 has been completed, a workpiece 11 is polished as described above. Specifically, the workpiece 11 is held on a chuck table 20 and then coarsely ground and finishingly ground in the respective grinding zones B and C (see FIG. 1). Thereafter, the chuck table 20 is positioned in the polishing zone D and then polished by the polishing pad 88 that has been shaped.

FIG. 10 illustrates in side elevation, partly in cross-section, the manner in which the processing apparatus 2 polishes a workpiece 11 held on a chuck table 20. For polishing the workpiece 11, the positional relation between the chuck table 20 and the polishing pad 88 is adjusted such that the reverse side 11b, i.e., the processed surface, of the workpiece 11 and the recess 88b in the polishing pad 88 overlap each other along the Z-axis. In a state in which the chuck table 20 is being rotated about the rotation axis 28 and the polishing pad 88 is being rotated about the rotation axis 96, the polishing pad 88 is lowered toward the workpiece 11 in the processing feed process such that the polishing pad 88 and the workpiece 11 become close to each other. The polishing pad 88 is continuously lowered to bring the polishing surface 88a into abrasive contact with the reverse side 11b of the workpiece 11, polishing the reverse side 11b.

As described above, the polishing surface 88a of the polishing pad 88 has been shaped in a manner to be complementary in shape to the holding surface 20a of the chuck table 20. Consequently, the reverse side 11b of the workpiece 11 held on the holding surface 20a of the chuck table 20 and the polishing surface 88a are complementary in shape to each other. When the polishing pad 88 is pressed against the workpiece 11, the reverse side 11b of the workpiece 11 enters the recess 88b and is entirely brought into contact with the side surface, i.e., the inner wall surface, of the recess 88b. The polishing pad 88 is thus uniformly pressed against the reverse side 11b of the workpiece 11. As a result, the workpiece 11 is less liable to be polished in local areas thereof, so that any thickness variations of the workpiece 11 after it has been polished are reduced.

When the polishing pad 88 is pressed against the reverse side 11b of the workpiece 11, the polishing layer 92 that is pliable is elastically deformed along the reverse side 11b of the workpiece 11. Therefore, even if the cross-sectional shape of the reverse side 11b and the cross-sectional shape of the recess 88b are not in full agreement with each other, the polishing layer 92 is elastically deformed to cause the polishing surface 88a to contact the reverse side 11b of the workpiece 11 in its entirety.

As described above, the processing apparatus 2 and the polishing surface shaping method according to the present embodiment measure the shape of the holding surface 20a of the chuck table 20 and shape the polishing surface 88a of the polishing pad 88 depending on the measured shape of the holding surface 20a. It is thus possible to make the polishing surface 88a complementary in shape to the holding surface 20a of the chuck table 20. At the time at which the workpiece 11 is held on the chuck table 20 and polished by the polishing pad 88, therefore, in-plane variations of the polishing rate, i.e., the amount of material polished off the workpiece 11 per unit time, are reduced, resulting in a reduction in thickness variations of the workpiece 11 that has been polished.

The polishing surface shaping method according to the present embodiment is performed by the controller 100 (see FIG. 6 and other drawings) when it executes programs. Specifically, the storage unit 160 of the controller 100 stores programs for operating the processing apparatus 2 to carry out the holding surface measuring step S1, the shaping step S2, and the polishing surface shape specifying step S3. The programs contain commands for enabling the controller 100 to generate control signals to be output to the components of the processing apparatus 2 for carrying out the holding surface measuring step S1, the shaping step S2, and the polishing surface shape specifying step S3. For shaping the polishing surface 88a of the polishing pad 88, the controller 100 reads the programs from the storage unit 160 and executes the read programs. In this manner, the controller 100 performs a sequence of processing operations representing the holding surface measuring step S1, the shaping step S2, and the polishing surface shape specifying step S3 and successively output control signals to the components of the processing apparatus 2. The polishing surface shaping method according to the present embodiment is thus carried out automatically.

Structural and methodical details according to the first embodiment may be changed or modified without departing from the scope of the invention.

Second Embodiment

The processing apparatus 2 (see FIG. 1) that is capable of grinding and polishing the workpiece 11 has been described according to the first embodiment. According to the present invention, a processing apparatus may be a dedicated processing apparatus for polishing the workpiece 11, i.e., a polishing apparatus. A structural example of the polishing apparatus to which the principles of the present invention are applicable will be described below as a processing apparatus according to a second embodiment.

FIG. 11 illustrates in perspective a processing apparatus, i.e., a polishing apparatus, 200 for polishing a workpiece 11. In FIG. 11, the processing apparatus 200 is illustrated in reference to a three-dimensional coordinate system having an X-axis, a Y-axis, and a Z-axis. The X-axis and the Y-axis extend perpendicularly to each other, and the Z-axis extends perpendicularly to the X-axis and the Y-axis. The X-axis refers to an axis along which first horizontal directions or leftward and rightward directions are defined, and the Y-axis refers to an axis along which second horizontal directions or forward and rearward directions are defined. The Z-axis refers to an axis along which vertical directions, heightwise directions or upward and downward directions are defined.

The processing apparatus 200 includes a foundation base 202 supporting and/or housing various components of the processing apparatus 200. The foundation base 202 has a rectangular opening 202a defined in the upper surface thereof and having a longitudinal axis extending along the Y-axis. A columnar support structure 204 is mounted on the upper surface of a rear end portion of the foundation base 202 and extends vertically along the Z-axis.

The opening 202a houses therein a chuck table, i.e., a holding table, 206 for holding the workpiece 11 thereon. The chuck table 206 has an upper surface lying generally parallel to a horizontal plane, i.e., an XY plane, along the X-axis and the Y-axis, and acting as a holding surface 206a for holding the workpiece 11 thereon. The holding surface 206a is porous in nature and fluidly connected to a suction source, not depicted, such as an ejector, for example, via a fluid channel, not depicted, defined in the chuck table 206 and a valve, not depicted.

The opening 202a also houses a moving mechanism 208 therein. The moving mechanism 208 is coupled to the chuck table 206 for moving the chuck table 206 along the Y-axis. The moving mechanism 208 includes a ball-screw-type moving mechanism, for example.

Specifically, the moving mechanism 208 includes a support base 210 that supports thereon various components of the moving mechanism 208. The moving mechanism 208 includes a pair of guide rails 212 mounted on the support base 210 and extending along the Y-axis and a movable table 214 slidably mounted on the guide rails 212 for movement along the guide rails 212. A nut, not depicted, is fixedly disposed on a lower surface, i.e., a reverse side, of the movable table 214. The nut is operatively threaded over a ball screw 216 disposed between the guide rails 212 and extending along the Y-axis. The ball screw 216 has an end coupled to a stepping motor 218 for rotating the ball screw 216 about its central axis. When the stepping motor 218 is energized, it rotates the ball screw 216 about its central axis, causing the nut to move the movable table 214 along the guide rails 212 along the Y-axis.

The chuck table 206 is mounted on the movable table 214. The chuck table 206 is surrounded by a table cover 220 shaped as a flat plate disposed in the opening 202a around the chuck table 206. Bellows-like dust-proof, drip-proof covers 222 that are expandable and contractible along the Y-axis are disposed in the opening 202a forwardly and rearwardly of the table cover 220. The table cover 220 and the dust-proof, drip-proof covers 222 close off the opening 202a in covering relation to the components of the moving mechanism 208.

When the moving mechanism 208 is actuated, it moves the chuck table 206 together with the table cover 220 along the Y-axis until the chuck table 206 is positioned at a front end portion of the opening 202a where a delivery position is defined or a rear end portion of the opening 202a where a processing position is defined. The chuck table 206 is coupled to a rotary actuator, not depicted, such as an electric motor for rotating the chuck table 206 about a vertical axis generally parallel to the Z-axis.

The support structure 204 has a face side, i.e., a front surface, lying along an XZ plane defined along the X-axis and the Z-axis. A moving mechanism 224 for moving a polishing unit 236, to be described later, along the Z-axis is mounted on the face side of the support structure 204. The moving mechanism 224 includes a ball-screw-type moving mechanism, for example.

Specifically, the moving mechanism 224 includes a pair of guide rails 226 mounted on face side of the support structure 204 and extending along the Z-axis and a movable table 228 shaped as a flat plate slidably mounted on the guide rails 226 for movement along the guide rails 226. A nut, not depicted, is fixedly disposed on a reverse side, i.e., a rear surface, of the movable table 228. The nut is operatively threaded over a ball screw 230 disposed between the guide rails 226 and extending along the Z-axis. The ball screw 230 has an upper end coupled to a stepping motor 232 for rotating the ball screw 230 about its central axis. When the stepping motor 232 is energized, it rotates the ball screw 230 about its central axis, causing the nut to move the movable table 228 along the guide rails 226 along the Z-axis, i.e., to lift and lower the movable table 228.

A support member 234 is fixedly mounted on a face side, i.e., a front surface, of the movable table 228. The support member 234 supports thereon the polishing unit 236 that polishes the workpiece 11. The polishing unit 236 is similar in structure and function to the polishing unit 80 (see FIG. 1 and other drawings) of the processing apparatus 2. Specifically, the polishing unit 236 includes a housing 238, a spindle 240, and a mount 242. The polishing pad 88 is detachably mounted on the lower surface of the mount 242.

The processing apparatus 200 includes a controller, also referred to as a control unit, a control section, or a control device, 244 for controlling the processing apparatus 200. The controller 244 is connected to various components of the processing apparatus 200 that include the chuck table 206, the moving mechanism 208, the moving mechanism 224, the polishing unit 236, and the like. The controller 244 is similar in structure and function to the controller 100 (see FIG. 1 and other drawings) of the processing apparatus 2.

The holding surface 206a of the chuck table 206 of the processing apparatus 200 may not be flat for various reasons. For example, the holding surface 206a may be inclined or curved or have surface irregularities depending on the kind of the workpiece 11, the specifications of the chuck table 206, and the like. Moreover, the planarity of the holding surface 206a may be low due to manufacturing errors of the chuck table 206. Therefore, as with the processing apparatus 2, the processing apparatus 200 incorporates the shape measuring instrument 110 and the shaping mechanism 120 (see FIG. 4). The controller 244 controls the moving mechanism 208, the moving mechanism 224, the undepicted rotary actuator for rotating the chuck table 206, the undepicted rotary actuator for rotating the polishing pad 88, the shape measuring instrument 110, and the shaping mechanism 120 to measure the holding surface 206a of the chuck table 206 with the shape measuring instrument 110 and shape the polishing surface 88a of the polishing pad 88 with the shaping mechanism 120. The polishing surface 88a is thus shaped into a shape complementary in shape to the holding surface 206a of the chuck table 206. Specific process details for shaping the polishing surface 88a of the polishing pad 88 are similar to those for shaping the polishing surface 88a with the processing apparatus 2 (see FIGS. 5 through 9).

The structural and methodical details according to the second embodiment may appropriately be changed or modified without departing from the scope of the invention. The description of the details of the first embodiment may appropriately be incorporated herein by way of reference with respect to the details of the second embodiment that have not been described above.

The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.