PROCESSING APPARATUS AND METHOD FOR MANUFACTURING A WAFER

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2024-210949 filed on Dec. 4, 2024; the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure relates to a processing apparatus for processing a wafer and a method for manufacturing a wafer.

BACKGROUND

For polishing a wafer, as disclosed in Japanese Patent Application Laid-Open Publications No. 2024-097550 and No. 2023-178694, a polishing pad may be operated to rotate and contact an entire upper surface of the wafer so that the upper surface of the wafer being rotated is polished. According to these publications, a rotation center of the polishing pad is offset from a rotation center of the wafer, and the polishing pad is pressed against the wafer with a predetermined load for polishing; therefore, a force to tilt may act on a spindle that rotates the polishing pad.

Accordingly, depending on conditions such as a rotation speed of the polishing pad, a rotation speed of a chuck table holding the wafer, a polishing load acting on the wafer through the polishing pad, and a roughness or a shape of a polishing surface of the polishing pad, a position of center of gravity in a polishing portion where the polishing pad contacts the wafer may move toward a center of the wafer. As a result, for example, a central portion of the wafer may be polished more, whereas a peripheral portion of the wafer may be polished less. In such a case, a problem may occur after polishing such that the central portion of the polished surface of the wafer is grind-burnt. For another example, a problem may occur such that an in-plane thickness of the wafer is not uniform, with the central portion of the wafer being polished more and the central portion being thinned.

When grinding a wafer, the wafer is in contact with a grindstone at a radial portion thereof. In other words, a part of the grindstone being in contact with the wafer grinds the wafer; therefore, a tilting degree of the grindstone differs between when grinding and when not grinding. Further, the tilting degree of the grindstone varies depending on conditions such as a grinder-feeding speed, a rotation speed of the grindstone, and presence of a film on a wafer surface.

As such, the tilting degree of the grindstone may vary; therefore, as disclosed in Japanese Patent Application Laid-Open Publications No. 2008-264913 and No. 2013-119123, before grinding a product wafer, a test wafer made of the same material as the product wafer may be ground for testing, and the tilt of the chuck table relative to the grindstone may be adjusted so that the wafer ground for testing has a uniform thickness. However, this operation of test grinding may take time.

In an earlier stage of grinding where the wafer is thicker, the wafer may be ground roughly with the grindstone being operated to approach the wafer in a faster grinder-feeding speed, and in a later stage of grinding where, once thinned approximately to a predetermined thickness, the wafer may be ground finely with the grindstone being operated in a slower grinder-feeding speed. Due to at least these two different grinder-feeding speeds, tilt of the grindstone and a position of the grinding load center of gravity relative to the chuck table holding the wafer are differed between the earlier stage and the latter stage. In fine grinding, damage marks caused on the wafer by rough grinding are removed. However, because the tilt of the grindstone and the grinding load center of gravity differ between rough grinding and fine grinding, a problem occurs such that fine grinding takes time.

Thus, in an operation of wafer polishing, there is a technical issue to overcome: a wafer after polishing should be in a state such that roughness of the polished surface is uniform and thickness of the wafer is uniform.

In an operation of wafer grinding, there is a technical issue to overcome: a grinding time should be shortened. Further, while grinding, due to, for example, glazing of a grinding surface of the grindstone, the tilt of the spindle and the position of the load center of gravity may vary, causing a problem such that the grindstone is disabled to grind correctly. Such problem needs to be overcome by detecting the incorrect grinding early and taking necessary measures such as temporarily stopping griding or dressing the grindstone to grind the wafer correctly.

These technical problems in the processes to polish and grind a wafer may be caused by the varied position of the load center of gravity on the rotating tools, i.e., the polishing pad and the grindstone, which are pressed against the wafer while the wafer is being processed. Therefore, suppressing the position of the load center of gravity from varying in a state where the processing tool is pressed against the wafer is a common technical issue for wafer processing including polishing and grinding.

SUMMARY

According to an aspect of the present disclosure, a processing apparatus includes a chuck table configured to hold a wafer on a holder surface thereof and rotate on a chuck shaft that extends along a center of the holder surface; a processing mechanism configured to rotate a spindle, to which an annular processing tool is attached, and process the wafer with a lower surface of the processing tool; a process-feeding mechanism configured to lift or lower the processing mechanism; at least three load sensors arranged at equal intervals along a circle centered on a rotation axis of the spindle or the chuck table and configured to measure a force pressing the processing tool against the wafer; and a controller configured to control pressing of the processing tool against the wafer such that a sum of values from the at least three load sensors corresponds to a set load which is set in advance and control a rotation speed of the spindle or a rotation speed of the chuck shaft such that a ratio of the values from the at least three load sensors is maintained at a set ratio which is set in advance.

According to another aspect of the present disclosure, a processing apparatus includes a chuck table configured to hold a wafer on a holder surface thereof and rotate on a chuck shaft that extends along a center of the holder surface; a processing mechanism configured to rotate a spindle, to which an annular processing tool is attached, and process the wafer with a lower surface of the processing tool; a process-feeding mechanism configured to lift or lower the processing mechanism; at least three load sensors arranged at equal intervals along a circle centered on a rotation axis of the spindle or the chuck table and configured to measure a force pressing the processing tool against the wafer; and a controller configured to control pressing of the processing tool against the wafer such that a sum of values from the at least three load sensors corresponds to a set load which is set in advance and control a rotation speed of the spindle or a rotation speed of the chuck shaft such that a value from at least one of the at least three load sensors is maintained within a set range which is set in advance.

Preferably, the processing apparatus may further include a rotation ratio setting device configured to set a ratio between the rotation speed of the spindle and the rotation speed of the chuck shaft. The controller may perform control including maintaining the rotation ratio set in the rotation ratio setting device.

The processing tool may be, for example, a polishing pad or a grindstone.

Optionally, the processing mechanism may include a grinding mechanism, to which a grindstone as the processing tool is attached, and a polishing mechanism, to which a polishing apparatus as the processing tool is attached. The processing apparatus may further include a turntable, on which at least two chuck tables each being the chuck table are arranged, and which is configured to locate one of the at least two chuck tables at a position corresponding to the grindstone or a position corresponding to the polishing pad.

According to another aspect of the present disclosure, a method for manufacturing a wafer by processing with the processing apparatus includes processing the wafer held on the holder surface of the chuck table with the processing tool by controlling pressing of the processing tool against the wafer such that the sum of values from the at least three load sensors corresponds to the set load which is set in advance; and controlling the rotation speed of the spindle or the rotation speed of the chuck shaft such that the ratio of the values from the at least three load sensors is maintained at the set ratio which is set in advance.

According to another aspect of the present disclosure, a method for manufacturing a wafer by processing with the processing apparatus includes processing the wafer held on the holder surface of the chuck table with the processing tool by controlling pressing of the processing tool against the wafer such that the sum of values from the at least three load sensors corresponds to the set load which is set in advance; and controlling the rotation speed of the spindle or the rotation speed of the chuck shaft such that the value from the at least one of the at least three load sensors is maintained within the set range which is set in advance.

Optionally, the spindle and the chuck shaft may be rotated in a same direction. Alternatively, the spindle and the chuck shaft may be rotated in opposite directions.

According to the above aspects, change in a position of a center of gravity of a force from the processing tool acting on the wafer may be prevented. In a case where the processing mechanism is a polishing mechanism, an effect of making uniformity in a state (roughness) and a thickness of a polished surface of the wafer may be achieved. In a case where the processing mechanism is a grinding mechanism, effects of shortening a grinding time and correct grinding of the wafer may be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a processing apparatus.

FIG. 2 is a cross-sectional view of a chuck table and a polishing mechanism.

FIG. 3 is a plan view illustrating a relation between a wafer and a polishing pad in a polishing region of the processing apparatus.

FIG. 4 is a table showing values measured in three load sensors and ratios thereof in normal and abnormal conditions under control according to a first embodiment.

FIG. 5 is a table showing values measured in three load sensors and ratios thereof in normal and abnormal conditions under control according to a second embodiment.

FIG. 6 is a graph illustrating a method for controlling the processing apparatus so that values from the load sensors remain within a set range under the control according the second embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a processing apparatus and a method for manufacturing a wafer according to the present embodiment will be described with reference to the drawings. An X-axis direction, a Y-axis direction, and a Z-axis direction shown in the accompanying drawings are orthogonal to each other. The X-axis direction and the Y-axis direction are substantially horizontal directions, and the Z-axis direction is a vertical direction.

A processing apparatus 10 shown in FIG. 1 is an apparatus for grinding and polishing a wafer W, which is a workpiece to be processed. Grinding with the processing apparatus 10 includes rough grinding and finish grinding which are performed in this order, and is continued with polishing. The processing apparatus 10 is controlled by a controller 11 to automatically perform a series of processes including conveying, processing, and cleaning of the wafer W. The controller 11 includes a processor and a memory and performs the processes according to a program stored in the memory and controls respective parts of the processing apparatus 10. Operations of the processing apparatus 10 described below are performed under control of the controller 11.

On a base table 12 of the processing apparatus 10, a turntable 13 is provided rotatably about an axis in the Z-axis direction. On the turntable 13, four chuck tables 14 are supported at equal intervals in a rotational direction of the turntable 13. As shown in FIG. 2, a holder surface 141 of the chuck table 14 has a conical shape with an apex at a rotation center. An inclination angle of the holder surface 141 is substantially moderate that it is visually unrecognizable. The wafer W is held by suction on the holder surface 141 in a state fitted to the shape of the holder surface 141.

The four chuck tables 14 are sequentially moved to a loading/unloading region Ea, a rough grinding region Eb, a finish grinding region Ec, and a polishing region Ed by rotating the turntable 13 by 90 degrees increments with a turntable rotating mechanism 15 which includes a motor (not shown). Each chuck table 14 is rotatably supported by a chuck table supporting mechanism 32 shown in FIG. 2 to revolve around a rotation axis that extends through the center of the holder surface 141. Details of the chuck table supporting mechanism 32 will be described later.

The loading/unloading region Ea is a region where the chuck table 14 is loaded or unloaded with the wafer W. The rough grinding region Eb is a region where the wafer W held by the chuck table 14 is roughly ground by a rough grinding mechanism 16. The finish grinding region Ec is a region where the wafer W held on the chuck table 14 is ground for finishing by a finish grinding mechanism 17. The polishing region Ed is a region where the wafer W held on the chuck table 14 is polished by a polishing mechanism 18. The rough grinding mechanism 16, the finish grinding mechanism 17, and the polishing mechanism 18 compose a processing mechanism in the processing apparatus 10. A grindstone 163 provided in the rough grinding mechanism 16, a grindstone 173 provided in the finish grinding mechanism 17, and a polishing pad 183 provided in the polishing mechanism 18 compose annular processing tools in the processing apparatus 10.

Optionally, the processing apparatus 10 may have solely a single grinding mechanism rather than the separated rough grinding mechanism 16 and finish grinding mechanism 17. While the processing apparatus 10 has the four chuck tables 14 corresponding to the four regions Ea-Ed on the turntable 13 in order to improve efficiency of loading and unloading the chuck table 14 with the wafer W at the loading/unloading region Ea W between the processes, the number of the chuck tables is not necessarily limited to four.

On a −Y-direction side of the base table 12, two cassette stages 19 are provided at an end. On one of the cassette stages 19, a cassette 20 for storing unprocessed wafers W is placed, and on the other of the cassette stages 19, a cassette 20 for storing processed wafers W is placed. The number of the cassette stages 19 is not limited to two but may optionally be one, three, or more.

One of the unprocessed wafers W stored in the cassette 20 is taken out of the cassette 20 by a conveyer robot 21 and conveyed to a positioning mechanism 22. The conveyer robot 21 includes a robot hand 211 capable of holding the wafer W by suction, a robot arm 212 to which the robot hand 211 is attached, and an X-axis moving device 213 configured to move the robot arm 212 in the X-axis direction. The conveyer robot 21 conveys the wafer W through operations to the robot arm 212 and the X-axis moving device 213 to move the robot hand 211. The positioning mechanism 22 places the wafer W on a positioning table 221 and locates the wafer W so that a center of the wafer W matches a center of the chuck table 14.

A first conveyer mechanism 24 conveys the wafer W from the positioning mechanism 22 to the chuck table 14 at the loading/unloading region Ea. The first conveyer mechanism 24 includes a conveyer pad 241 configured to hold an upper surface of the wafer W by suction, a lifting device 242 configured to move the conveyer pad 241 in the Z-axis direction, and a Y-axis moving device 243 configured to move the conveyer pad 241 in the Y-axis direction. The first conveyer mechanism 24 holds the upper surface of the wafer W placed on the positioning table 221 by suction with the conveyer pad 241, lifts the conveyer pad 241 through the lifting device 242, moves the conveyer pad 241 in the +Y direction through the Y-axis moving device 243, and lowers the conveyer pad 241 through the lifting device 242, thereby placing the wafer W on the chuck table 14 in the loading/unloading region Ea.

As the unprocessed wafer W is held on the chuck table 14 in the loading/unloading region Ea, the turntable 13 is rotated by 90 degrees in a clockwise direction in FIG. 1. Accordingly, the chuck table 14 holding the unprocessed wafer W is located in the rough grinding region Eb. In the rough grinding region Eb, the rough grinding mechanism 16 is operated to roughly grind the upper surface of the wafer W held on the chuck table 14. The rough grinding mechanism 16 includes a grinding wheel 162 at a lower end of a spindle 161 that extends in the Z-axis direction, and a grindstone 163 is attached to a lower surface of the grinding wheel 162. The spindle 161 is rotated by a spindle motor. The grindstone 163 is annularly arranged on the lower surface along an outer edge of the grinding wheel 162. The rough grinding mechanism 16 moves up or down in the Z-axis direction by an operation of a process-feeding mechanism 25.

As shown in FIG. 1, the rough grinding mechanism 16 is arranged such that a position of a rotation axis Ca of the chuck table 14 located in the rough grinding region Eb, i.e., a rotation axis of the wafer W on the chuck table 14, is offset from a position of a rotation axis Da of the spindle 161, and the grindstone 163 passes above the rotation axis Ca of the chuck table 14. The chuck table supporting mechanism 32 (FIG. 2) rotates the chuck table 14, the spindle motor rotates the spindle 161 and the grinding wheel 162, and the process-feeding mechanism 25 lowers the grinding wheel 162. Accordingly, the wafer W rotates about the rotation axis Ca, the grindstone 163 rotates about the rotation axis Da, and the lower surface of the grindstone 163 is pressed against the upper surface of the wafer W, whereby the upper surface (a surface to be ground) of the wafer W is roughly ground with the grindstone 163. While grinding roughly, the wafer W on the chuck table 14 rotates in a rotation direction Rc shown in FIG. 1, and the grindstone 163 rotates in a rotation direction Rd shown in FIG. 1. Rotation directions of the wafer W on the chuck table 14 and the grindstone 163 are not limited to the rotation direction Rc and the rotation direction Rd but may optionally be directions opposite to these directions Rc, Rd, respectively. The controller 11 controls a process-feeding operation of the process-feeding mechanism 25 so that the grindstone 163 is pressed against the wafer W with a predetermined force.

The grindstone 163 contacts the wafer W, which is held on the chuck table 14 and fitted to the holder surface 141, along an arc-shaped processing line Qa on a radial portion between a contact start point Pa on a periphery of the wafer W and the rotation axis Ca of the chuck table 14, and roughly grinds the wafer W. When the wafer W is ground roughly to a desired thickness, the process-feeding mechanism 25 lifts the grinding wheel 162 to separate the grindstone 163 from the upper surface of the wafer W, thereby completing the rough grinding. As shown in FIG. 1, when the wafer W is roughly ground, saw marks M1, which are radial grinding marks along the processing lines Qa, are formed.

When rough grinding of the wafer W in the rough grinding region Eb is completed, the turntable 13 is rotated by 90 degrees in the clockwise direction in FIG. 1. This locates the chuck table 14 holding the roughly processed wafer W in the finish grinding region Ec. In the finish grinding region Ec, the finish grinding mechanism 17 is operated to finish by grinding the upper surface of the wafer W held on the chuck table 14. Similarly to the rough grinding mechanism 16, the finish grinding mechanism 17 includes a grinding wheel 172 at a lower end of a spindle 171 that extends in the Z-axis direction, and a grindstone 173 is attached to a lower surface of the grinding wheel 172. The spindle 171 is rotated by a spindle motor. The grindstone 173 is annularly arranged on the lower surface along an outer edge of the grinding wheel 172. A grit size of abrasive grains in the grindstone 173 is smaller than a grit size of abrasive grains in the grindstone 163. The finish grinding mechanism 17 moves up or down in the Z-axis direction by an operation of a process-feeding mechanism 26.

As shown in FIG. 1, the finish grinding mechanism 17 is arranged such that a position of a rotation axis Cb of the chuck table 14 located in the finish grinding region Ec, i.e., the rotation axis of the wafer W on the chuck table 14, is offset from a position of a rotation axis Db of the spindle 171, and the grindstone 173 passes above the rotation axis Cb of the chuck table 14. The chuck table supporting mechanism 32 (FIG. 2) rotates the chuck table 14, the spindle motor rotates the spindle 171 and the grinding wheel 172, and the process-feeding mechanism 26 lowers the grinding wheel 172. Accordingly, the wafer W rotates about the rotation axis Cb, the grindstone 173 rotates about the rotation axis Db, and the lower surface of the grindstone 173 is pressed against the upper surface of the wafer W, whereby the upper surface (the surface to be ground) of the wafer W is ground for finish with the grindstone 173. While grinding for finish, the wafer W on the chuck table 14 rotates in a rotation direction Re shown in FIG. 1, and the grindstone 173 rotates in a rotation direction Rf shown in FIG. 1. Rotation directions of the wafer W on the chuck table 14 and the grindstone 173 are not limited to the rotation direction Re and the rotation direction Rf but may optionally be directions opposite to these directions Re, Rf, respectively. The controller 11 controls a process-feeding operation of the process-feeding mechanism 26 so that the grindstone 173 is pressed against the wafer W with a predetermined force.

The grindstone 173 contacts the wafer W, which is held on the chuck table 14 and fitted to the holder surface 141, along an arc-shaped processing line Qb on a radial portion between a contact start point Pb on a periphery of the wafer W and the rotation axis Cb of the chuck table 14, and grinds to finish the wafer W. When the wafer W is ground and finished to a desired thickness, the process-feeding mechanism 26 lifts the grinding wheel 172 to separate the grindstone 173 from the upper surface of the wafer W, thereby completing the finish grinding. As shown in FIG. 1, when the wafer W is ground and finished, saw marks M2, which are radial grinding marks along the processing line Qb, are formed.

When grinding to finish the wafer W in the finish grinding region Ec is completed, the turntable 13 is rotated by 90 degrees in the clockwise direction in FIG. 1. This locates the chuck table 14 holding the finish-ground wafer W in a polishing region Ed. In the polishing region Ed, the polishing mechanism 18 is operated to polish the upper surface of the wafer W held on the chuck table 14.

For polishing with the polishing mechanism 18, the wafer W having been ground is thinned to a desired thickness and the saw marks M2 formed on the upper surface (a surface to be polished) of the wafer W are removed.

As shown in FIG. 2, the polishing mechanism 18 includes a polishing wheel 182 at a lower end of a spindle 181 that extends in the Z-axis direction, and an annular polishing pad 183 is attached to a lower surface of the polishing wheel 182. At a center of the polishing pad 183, a circular opening 184 is formed. The spindle 181 is rotated by a spindle motor 185. The polishing mechanism 18 has a slurry supply source 186 configured to supply a slurry containing an abrasive to a polishing location. The slurry delivered from the slurry supply source 186 is supplied to a lower side of the polishing wheel 182 through a flow path 187 inside the spindle 181 and flows toward the wafer W through the opening 184.

The polishing mechanism 18 moves up or down in the Z-axis direction by an operation of a process-feeding mechanism 27. The process-feeding mechanism 27 includes a guide rail 271 and a ball screw 272 that extend in the Z-axis direction, and a process-feeding motor 273 configured to rotate the ball screw 272. An up-down movable device 274, to which a housing 188 of the polishing mechanism 18 is attached, is movably supported by the guide rail 271 to move in the Z-axis direction, and the ball screw 272 is screwed into a threaded portion 275 in the up-down movable device 274. As the ball screw 272 rotates by being driven by the process-feeding motor 273, the up-down movable device 274 moves in the Z-axis direction together with the polishing mechanism 18.

The process-feeding mechanism 25 to move the rough grinding mechanism 16 in the Z-axis direction and the process-feeding mechanism 26 to move the finish grinding mechanism 17 in the Z-axis direction are each formed of, similarly to the process-feeding mechanism 27 shown in FIG. 2, a ball screw mechanism that rotates a ball screw with a motor to move the rough grinding mechanism 16 or the finish grinding mechanism 17 in the Z-axis direction.

As shown in FIG. 1, the polishing mechanism 18 is arranged such that a position of a rotation axis Cc of the chuck table 14 located in the polishing region Ed, i.e., the rotation axis of the wafer W on the chuck table 14, is offset from a position of a rotation axis Dc of the spindle 181. The chuck table supporting mechanism 32 (FIG. 2) rotates the chuck table 14, the spindle motor 185 rotates the spindle 181 and the polishing wheel 182, and the process-feeding mechanism 27 lowers the polishing wheel 182. Accordingly, while the wafer W and the polishing pad 183 rotate respectively, a lower surface of the polishing pad 183 is pressed against the upper surface of the wafer W. For example, the wafer W on the chuck table 14 rotates in a rotation direction Ra shown in FIGS. 1 and 3, and the polishing pad 183 rotates in a rotation direction Rb shown in FIGS. 1 and 3. The controller 11 controls a process-feeding operation of the process-feeding mechanism 27 so that the polishing pad 183 is pressed against the wafer W with a predetermined force. Further, a slurry is supplied from the slurry supply source 186 toward a position where the polishing pad 183 contacts the wafer W. The polishing mechanism 18 polishes the upper surface (the surface to be polished) of the wafer W by a CMP (Chemical Mechanical Polishing) method using mechanical action caused by contact of the polishing pad 183 and chemical action caused by components contained in the slurry supplied from the slurry supply source 186. Processing by the polishing mechanism 18 may be dry polishing, without using a slurry, solely due to mechanical action caused by contact of the polishing pad.

As shown in FIG. 1, diameters of the polishing wheel 182 and the polishing pad 183 are larger than a diameter of the wafer W, and the polishing wheel 182 is located so as to cover the entire upper surface of the wafer W. The polishing pad 183 polishes the wafer W, which is held on the chuck table 14 and fitted with the holder surface 141, in an arrangement such that the lower surface of the polishing pad 183 (the surface to be polished) substantially in contact with the entire upper surface of the wafer W is pressed intensely against a processing region Fa, which extends radially from the rotation axis Cc of the wafer W. When the wafer W is polished to a desired thickness, the process-feeding mechanism 27 lifts the polishing wheel 182 to separate the polishing pad 183 from the upper surface of the wafer W.

When the wafer W in the polishing region Ed is completely polished, the turntable 13 is rotated by 90 degrees in the clockwise direction in FIG. 1, or the turntable 13 is rotated by 270 degrees in the counterclockwise direction. This locates the chuck table 14 holding the polished wafer W in the loading/unloading region Ea. That is, once the chuck table 14 in the loading/unloading region Ea is loaded with the unprocessed wafer W, the processes of grinding roughly, grinding for finish, and polishing of the wafer W are performed along with the rotation of the turntable 13, and the processed wafer W returns to the loading/unloading region Ea.

A second conveyer mechanism 28 unloads the processed wafer W from the chuck table 14 in the loading/unloading region Ea and conveys the wafer W to a spin cleaning mechanism 29. The second conveyer mechanism 28 includes a conveyer pad 281 configured to hold the upper surface of the wafer W by suction, a pivoting device 282 configured to pivot the conveyer pad 281 about an axis in the Z-axis direction, a lifting device 283 configured to move the conveyer pad 281 in the Z-axis direction, and a Y-axis moving device 284 configured to move the conveyer pad 281 in the Y-axis direction. The second conveyer mechanism 28 holds by suction the upper surface of the wafer W on the chuck table 14, which is located in the loading/unloading region Ea, through the conveyer pad 281, lifts the conveyer pad 281 with the lifting device 283, and separates the wafer W from the chuck table 14. The second conveyer mechanism 28 further operates the pivoting device 282 to pivot the conveyer pad 281, moves the conveyer pad 281 in the-Y direction with the Y-axis moving device 284, and lowers the conveyer pad 281 with the lifting device 283, thereby placing the wafer W on a spinner table 291 of the spin cleaning mechanism 29.

The spin cleaning mechanism 29 rotates a spinner table 291 that holds the wafer W by a motor and cleans the wafer W by jetting cleaning water from a cleaning nozzle 292 onto the wafer W. After cleaning, air is jetted from the cleaning nozzle 292 onto the wafer W to dry the wafer W.

The wafer W cleaned and dried by the spin cleaning mechanism 29 is held by suction on the conveyer pad 281 of the second conveyer mechanism 28 and conveyed from the spinner table 291 to the positioning table 221 of the positioning mechanism 22. The wafer W located on the positioning table 221 is held by the robot arm 212 of the conveyer robot 21 and is conveyed from the positioning table 221 to the cassette 20 by operations of the robot arm 212 and the X-axis moving device 213, and is stored in the cassette 20. Optionally, the wafer W may be conveyed from the spin cleaning mechanism 29 to the cassette 20, without being conveyed through the positioning mechanism 22, and stored in the cassette 20.

As above, the series of processes of rough grinding, finish grinding, polishing, and cleaning is performed with the wafer W in the processing apparatus 10. That is, the unprocessed wafer W taken out of the cassette 20 is processed through rough grinding, finish grinding, polishing, and cleaning, and thereafter stored in the cassette 20. This series of processes may be performed fully automatically under control of the controller 11. In the above paragraphs, a flow of processes to a single wafer W has been described. The processing apparatus 10 may perform at least two of rough grinding in the rough grinding region Eb, finish grinding in the finish grinding region Ec, and polishing in the polishing region Ed simultaneously to a plurality of wafers W, and may further perform, during these processes, loading/unloading the chuck table 14 in the loading/unloading region Ea with the wafer W and cleaning of the wafer W in the spin cleaning mechanism 29.

Next, a structure of the chuck table 14 and the chuck table supporting mechanism 32 will be described with reference to FIG. 2. FIG. 2 shows the chuck table 14 located in the polishing region Ed. Note that the chuck table 14 and the chuck table supporting mechanism 32 are in the same structures as those shown in FIG. 2 in each of the loading/unloading region Ea, the rough grinding region Eb, and the finish grinding region Ec as well.

The chuck table 14 includes a frame 30 and a disk-shaped porous plate 31 attached in a recess on an upper surface side of the frame 30. With the porous plate 31 set in the recess of the frame 30, an upper surface of the frame 30 and an upper surface of the porous plate 31 align on a plane, and the upper surface of the porous plate 31 forms the holder surface 141 for holding the wafer W.

The chuck table supporting mechanism 32 for rotatably supporting the chuck table 14 includes a chuck shaft 35, of which rotation axis extends through the center of the holder surface 141. The chuck shaft 35 is rotatably supported inside a supporting frame 34, which is supported on the turntable 13, via a bearing 36. The chuck shaft 35 is provided with a driven pulley 37 on an outer surface thereof and with a driving pulley 39 which is rotated by a table driving motor 38, and a transmission belt 40 being an endless belt is strained around the driven pulley 37 and the driving pulley 39. As the driving pulley 39 is rotated by the table driving motor 38, the rotation is transmitted to the driven pulley 37 via the transmission belt 40, and the chuck shaft 35 rotates. The frame 30 of the chuck table 14 is attachable to and detachable from a table base 41 provided at an upper end of the chuck shaft 35, and in a state where the chuck table 14 is attached to the table base 41, the chuck table 14 rotates together with the chuck shaft 35.

Inside the chuck table 14 and the chuck shaft 35, a flow path 42 is formed. The flow path 42 communicates with a bottom portion of the porous plate 31 and extends in the axial direction inside the chuck shaft 35 to a rotary joint 43 provided at a lower end of the chuck shaft 35. To the flow path 42 in the rotary joint 43, a suction source 44, an air supply source 45, and a water supply source 46 are connected via open/close valves 441, 451, and 461, respectively.

When the open/close valve 441 is opened and the suction source 44 is operated, air in the porous plate 31 is sucked through the flow path 42, a negative pressure acts on the holder surface 141, and the wafer W is held by suction on the holder surface 141. When the open/close valve 451 is opened and the air supply source 45 is operated, air supplied from the air supply source 45 is fed to the porous plate 31 via the flow path 42, and the air is jetted from the holder surface 141. When the open/close valve 461 is opened and the water supply source 46 is operated, water supplied from the water supply source 46 is fed to the porous plate 31 via the flow path 42, and the water is jetted from the holder surface 141. When the air supply source 45 and the water supply source 46 are operated simultaneously, a two-fluid mixture of air and water is jetted from the holder surface 141.

When a wafer W is conveyed to the chuck table 14 in the loading/unloading region Ea and held thereon, the suction source 44 is operated to apply a negative pressure to the holder surface 141 and hold the wafer W by suction. While the series of processes of rough grinding, finish grinding, and polishing is performed with the wafer W, the wafer W is maintained in the state of being held by suction on the holder surface 141. When the processes on the wafer W are completed and the wafer W is unloaded from the chuck table 14 in the loading/unloading region Ea, the wafer W held on the holder surface 141 is separated by jetting air, water, or a two-fluid mixture from the holder surface 141. Further, by jetting air, water, or a two-fluid mixture from the holder surface 141, foreign matter clogged in pores in the porous plate 31 may be pushed out and removed.

The processing apparatus 10 includes a notification device 47 (FIG. 1). The notification device 47 includes, for example, a display monitor provided on an outer face of the processing apparatus 10, a lamp that may glow or blink, and a speaker that may generate sound, to notify an operator of a state of the processing apparatus 10. Optionally, the notification device may be provided to an external device such as a personal computer or a tablet terminal that may communicate with the processing apparatus 10.

FIG. 3 illustrates a load acting on the wafer W when the wafer W is polished using the polishing mechanism 18 in the processing apparatus 10. In a state where the polishing pad 183 is normally pressed against the wafer W, the polishing pad 183 intensely contacts the processing region Fa, of which center of gravity coincides with a polishing load center of gravity Ga, in the wafer W. The polishing load center of gravity Ga is located at approximately one half of a radius of the wafer W.

While being polished, positions of the rotation axis Cc of the chuck table 14 (i.e., the rotation axis Cc of the wafer W) and the rotation axis Dc of the spindle 181 (i.e., the rotation axis Dc of the polishing pad 183) are offset from each other, and the polishing pad 183 is pressed against the wafer W with a predetermined load, which acts to tilt the spindle 181 while the spindle 181 rotates the polishing pad 183. Accordingly, depending on factors such as a rotation speed of the spindle 181, a rotation speed of the chuck table 14, and a polishing load set in polishing conditions, the position of the load center of gravity may move from the polishing load center of gravity Ga toward the center of the wafer W. For example, the position of the load center of gravity of the polishing pad 183 contacting the wafer W may move to the polishing load center of gravity Gb toward the center of the wafer W. Further, a processing region where the polishing pad 183 intensely contacts the wafer W becomes a processing region Fb, of which center of gravity coincides with the polishing load center of gravity Gb. In this state, compared with a normal state, the wafer W is polished more at the central portion, and the peripheral portion is less likely to be polished. This ununiform polishing may cause a problem of polish-burn at the central portion of the polished wafer. Further, the central portion of the polished wafer W may be thinner, which may cause a problem such that an in-plane thickness of the wafer W becomes ununiform.

The processing apparatus 10 measures, with a load sensor including a piezoelectric element, a force that presses the processing tool against the wafer W, and the controller 11 controls the process-feeding mechanism so that a value measured by the load sensor becomes equal to a set polishing load, thereby preventing the above problems and enabling the wafer W to be processed accurately and efficiently. Details of the control will be described below.

The polishing mechanism 18 includes a load sensor 50 configured to measure a force that presses the polishing pad 183 against the wafer W. As shown in FIG. 2, the load sensor 50 is disposed between a flange 189 supporting a spindle unit 180 and the housing 188. As shown in FIG. 3, in particular, three load sensors 50 are arranged at equal intervals along a circle centered on the rotation axis Dc of the spindle 181. These three load sensors 50 are referred to as a first load sensor 501, a second load sensor 502, and a third load sensor 503, respectively. The first load sensor 501 and the second load sensor 502 are arranged, in a plan view shown in FIG. 3, at positions distributed on both sides of the wafer W such that distances from the rotation axis Cc of the chuck table 14 are approximately equal. The third load sensor 503 is disposed, in the plan view shown in FIG. 3, at a position farthest from the rotation axis Cc of the chuck table 14. Values measured by the respective load sensors 50 are transmitted to the controller 11.

The polishing mechanism 18 may at least include three load sensors 50 arranged at equal intervals along a circle centered on the rotation axis Dc of the spindle 181, and four or more load sensors 50 may be provided.

As a modified example regarding the arrangement of the load sensors, as shown in FIG. 3, at least three load sensors 51 may be arranged at equal intervals along a circle centered on the rotation axis Cc of the chuck table 14. These three load sensors 51 are herein referred to as a first load sensor 511, a second load sensor 512, and a third load sensor 513. The load sensors 51 are disposed, for example, between the frame 30 of the chuck table 14 and the table base 41 in the chuck table supporting mechanism 32. When the polishing pad 183 is pressed against the wafer W, a load acting on the wafer W on the holder surface 141 of the chuck table 14 may be measured by the load sensors 51. In the paragraphs below, a case where the load sensors 50 of the polishing mechanism 18 is described. In the description below, the load sensors 50, i.e., the first load sensor 501, the second load sensor 502, and the third load sensor 503, may be read as the load sensor 51, i.e., the first load sensor 511, the second load sensor 512, and the third load sensor 513, to apply the below case to the configuration where the load sensors 51 are provided on the chuck table 14 side.

In both a first embodiment and a second embodiment described below, when the polishing mechanism 18 polishes the wafer W, the controller 11 controls the pressing act of the polishing pad 183 by monitoring the values measured by the three load sensors 50 continuously and controlling the lifting/lowering speed and the lifting/lowering direction of the polishing mechanism 18 through the process-feeding mechanism 27 so that a sum of the values from the three load sensors 50 should stay within a set load range (e.g., 299N-301N) including a set load (e.g. 300N) which is set in advance. For example, in examples shown in tables in FIGS. 4 and 5, a sum of the values from the three load sensors 50 in a normal condition is 300.6N.

Although details will be described later, a rotation speed of the spindle 181 in the polishing mechanism 18 and a rotation speed of the chuck shaft 35 in the chuck table 14 affect the position of the load center of gravity that presses the polishing pad 183 against the wafer W. When the position of the load center of gravity changes, ratios of the values from the three load sensors 50 and values from the respective load sensors 50 change.

As described above, the position of the load center of gravity changes depending on the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35. Specifically, increasing the rotation speed of the chuck shaft 35 or decreasing the rotation speed of the spindle 181 changes the position of the load center of gravity in a direction to separate away from the center of the wafer W (the third load sensor 503). On the other hand, decreasing the rotation speed of the chuck shaft 35 or increasing the rotation speed of the spindle 181 changes the position of the load center of gravity in a direction to approach the center of the wafer W (the third load sensor 503).

A change (abnormality) in the position of the load center of gravity during a process of polishing is undesirable; therefore, monitoring the values from the three load sensors 50 is necessary to prevent such a change in the position of the load center of gravity. The polishing load center of gravity Gb under the abnormal condition shown in FIG. 3 is shifted to a position closer to the third load sensor 503 (a position closer to the rotation axis Cc of the wafer W) than the polishing load center of gravity Ga under the normal condition. Accordingly, by the controller 11 controlling the rotation speed of the chuck shaft 35 to increase or the rotation speed of the spindle 181 to decrease, the load center of gravity moves in the direction to separate away from the center of the wafer W (the third load sensor 503), and the polishing load center of gravity Gb under the abnormal condition moves to the normal polishing load center of gravity Ga.

Further, tilt of the spindle 181 is also related to a process-feeding speed of the polishing mechanism 18 by the process-feeding mechanism 27. That is, when the process-feeding speed of the polishing mechanism 18 by the process-feeding mechanism 27 changes, the position of the load center of gravity pressing the polishing pad 183 against the wafer W changes. When the process-feeding speed for lowering the polishing pad 183 increases, the position of the load center of gravity changes in the direction to separate away from the center of the wafer W (the third load sensor 503). When the process-feeding speed for lowering the polishing pad 183 decreases, the position of the load center of gravity changes in the direction to approach the center of the wafer W (the third load sensor 503).

In the first embodiment of adjusting the load center of gravity based on the operation principle as described above, the controller 11 controls the process-feeding mechanism 27 so that a sum of the load values measured by the three load sensors 50 should fall within the set load range, and controls a rotation speed of the spindle 181 or a rotation speed of the chuck shaft 35 so that a ratio of the load values measured by the three load sensors 50 should maintain a set ratio which is set in advance.

Table in FIG. 4 shows the load values measured by the first load sensor 501, the second load sensor 502, and the third load sensor 503 and ratios thereof under the control in the first embodiment. In a case of the polishing load center of gravity Ga under the normal condition, values from the first load sensor 501 and the second load sensor 502 are each 167.0N, a value from the third load sensor 503 is −33.4N, and a ratio of the values from these three load sensors 50 is 5:5:−1. A sum of the values from the three load sensors 50 is 300.6N. This ratio “5:5:−1” in the normal condition is stored in a memory of the controller 11 as the set ratio.

Under the abnormal condition shown in the table in FIG. 4 (in the case of, for example, the polishing load center of gravity Gb), values from the first load sensor 501 and the second load sensor 502 are each 165.0N, a value from the third load sensor 503 is −30.0N, and the ratio of these is 5.5:5.5:−1. A sum of the values from the three load sensors 50 is 300.0N. The ratio (5.5:5.5:−1) of the measured values from the three load sensors 50 differs from the set ratio (5:5:−1) stored in the memory of the controller 11; therefore, the controller 11 determines that the position of the load center of gravity is not normal. Specifically, based on a difference between the ratio of the values measured by the three load sensors 50 and the set ratio, the controller 11 determines that the load center of gravity has moved toward the center of the wafer W (i.e., toward the third load sensor 503) as compared with the normal condition and controls the rotation speed of the chuck shaft 35 to increase or the rotation speed of the spindle 181 to decrease. This causes the load center of gravity to move toward the periphery of the wafer W (i.e., in the direction to separate away from the third load sensor 503). The controller 11 determines that the load center is at the normal polishing load center of gravity Ga (approximately at one half of the radius of the wafer W) by detecting that the ratio of the load values from the three load sensors 50 reached the set ratio.

Optionally, when the ratio of the load values from the three load sensors 50 deviates from the set ratio, the controller 11 may notify an operator via the notification device 47. The notification device 47 may notify the operator by, for example, displaying information on the display monitor, glowing or blinking of the lamp, or generating a notification sound from the speaker. The operator notified of the abnormality by the notification may, as needed, inspect a state (roughness) of the surface of the wafer W to be polished, or inspect or review processing conditions in the polishing mechanism 18.

Thus, in the first embodiment of adjusting the load center of gravity, the controller 11 controls a rotation speed of the spindle 181 or a rotation speed of the chuck shaft 35 so that the ratio of load values measured by the three load sensors 50 maintains the set ratio which is set in advance. While polishing, by continuously controlling as above, displacement of the position of the load center of gravity may be suppressed, thereby preventing the problems such that the central portion of the wafer W is polished more and the peripheral portion is polished less and that the wafer W has uneven thickness.

Optionally, regarding the set ratio of the values from the three load sensors 50, a range with margins may be set for ratio of the values from the individual load sensors 50 such as, for example, (4.9 to 5.1): (4.9 to 5.1): (−1to −1.1).

As the second embodiment of adjusting the load center of gravity, the controller 11 controls a rotation speed of the spindle 181 or a rotation speed of the chuck shaft 35 so that a value from at least one load sensor 50 should remain within a set range which is set in advance. In this second embodiment, the controller 11 controls operations or monitors the value from the third load sensor 503, while controlling the process-feeding mechanism 27 so that a sum of the load values measured by the three load sensors 50 should fall within the set load range, so that the value from the third load sensor 503 should fall within a set range.

Table in FIG. 5 shows the load values measured by the first load sensor 501, the second load sensor 502, and the third load sensor 503 and a ratio thereof under the control in the second embodiment. In a case of the polishing load center of gravity Ga under the normal condition, values from the first load sensor 501 and the second load sensor 502 are each 167.0N, a value from the third load sensor 503 is −33.4N, and the ratio thereof is 5:5:−1. A sum of the values from the three load sensors 50 is 300.6N.

Graph in FIG. 6 shows a relation between a load value measured by the third load sensor 503 and a rotation speed of the spindle 181. A vertical axis in FIG. 6 indicates the value (load) of the third load sensor 503, and a horizontal axis indicates time passing. A range from −30.0N to −34.0N shown in the graph in FIG. 6 is a load control range of the third load sensor 503 in the normal condition, and this load control range “−30.0N to −34.0N” under the normal condition is stored in the memory of the controller 11 as the set range.

Under the abnormal condition shown in the table in FIG. 5 (in the case of, for example, the polishing load center of gravity Gb), load values from the first load sensor 501 and the second load sensor 502 are each 167.6N, a load value from the third load sensor 503 is −35.2N, and the ratio thereof is 5.0:5.0:−1.05. A sum of the values from the three load sensors 50 is 300.0N. The controller 11 monitors solely the load value from the third load sensor 503 among the three load sensors 50 and, when the load value deviates from the set range of −30.0N to −34.0N, determines that the position of the load center of gravity is not normal and that the tilt of the spindle 181 has changed. Specifically, as shown in the table in FIG. 5, when the load value −35.2N of the third load sensor 503 is below the set range (−30.0N to −34.0N), the controller 11 determines that the load center of gravity has moved toward the center of the wafer W (i.e., toward the third load sensor 503) as compared with the normal condition and controls the rotation speed of the chuck shaft 35 to increase or to the rotation speed of the spindle 181 to decrease. This reduces the tilt of the spindle 181 and moves the load center of gravity toward the periphery of the wafer W (i.e., in the direction to separate away from the third load sensor 503). As described above, when the value from the third load sensor 503 increases in the negative direction, the values from the first load sensor 501 and the second load sensor 502 increase in the positive direction to maintain the set polishing load of 300N. Therefore, the change is reflected largely in the value from the third load sensor 503; therefore, in the present embodiment, the value from the third load sensor 503 is monitored and the controller 11 may respond quickly to the change in the tilt of the spindle.

With reference to the graph in FIG. 6, details of controlling an operation to maintain the value from the third load sensor 503 within the set range which is set in advance will be described. Periods Ta through Te along the horizontal axis in the graph in FIG. 6 are time ranges segmented by changes in the rotation speed of the spindle 181. A start point Sa of the period Ta indicates a time point at which the polishing pad 183 starts pressing the upper surface (the surface to be polished) of the wafer W.

In the period Ta, a rotation speed of the spindle 181 is set to a set polishing rotation speed (e.g., 1500 rpm) which is set in advance, and the polishing pad 183 is pressed against the wafer W. By pressing the polishing pad 183 against the wafer W, the value from the third load sensor 503 gradually decreases from the start point Sa and falls in the set range (−30.0N to −34.0N), which is a target when polishing. As the polishing pad 183 continues polishing under this condition, the value approaches a first point Sb. When the value from the third load sensor 503 reaches the first point Sb, the rotation speed of the spindle 181 is increased to, for example, 1800 rpm (period Tb). Accordingly, values from the first load sensor 501 and the second load sensor 502 decrease, and a sum of the values from the three load sensors 50 also decreases. Therefore, the polishing mechanism 18 is lowered through the process-feeding mechanism 27 to maintain the sum of the values from the three load sensors 50 at 300N. As a result, the value from the third load sensor 503 turns to increase.

At a second point Sc, when the value from the third load sensor 503 reaches −30.0N, which is an upper limit of the set range, the controller 11 decreases the rotation speed of the spindle 181 to, for example, 1500 rpm (period Tc). In the period Tc, due to the decreased rotation speed of the spindle 181, the value from the third load sensor 503 turns to decrease, and the position of the load center of gravity moves to the position at one half of the radius of the wafer W. Optionally, when the decrease of the value from the third load sensor 503 is slow, or when the value from the third load sensor 503 needs be lowered quickly, the rotation speed of the spindle 181 may be further decreased (e.g., to 1200 rpm).

At a third point Sd, when the value from the third load sensor 503 reaches −34.0N, which is a lower limit of the set range, the controller 11 increases the rotation speed of the spindle 181 (period Td). This prevents the value from the third load sensor 503 from deviating from the set range, such as to the abnormal load value −35.2N (in the case of the polishing load center of gravity Gb) shown in the table in FIG. 5. In the period Td, the controller 11 sets the rotation speed of the spindle 181 to 1800 rpm. As a result, the tilt of the spindle 181 reduces, the position of the load center of gravity moves to the position at one half of the radius of the wafer W, and the value from the third load sensor 503 turns to increase. When the value from the third load sensor 503 does not increase as shown in the period Td of FIG. 6, or when the period Td needs to be shortened, the controller 11 further increases the rotation speed of the spindle 181.

At a fourth point Se, when the value from the third load sensor 503 reaches −30.0N, which is the upper limit of the set range, the controller 11 reduces the rotation speed of the spindle 181 to 1500 rpm (period Te). Similarly to the period Tc described above, in the period Te, due to the decreased rotation speed of the spindle 181 (reaching the set rotation speed), the value from the third load sensor 503 turns to decrease. When the value from the third load sensor 503 does not decrease as shown in the period Te of FIG. 6, or when the period Te needs to be shortened, the controller 11 further decreases the rotation speed of the spindle 181.

At a fifth point Sf, when the value from the third load sensor 503 reaches −34.0N, which is the lower limit of the set range, the controller 11 controls to increase the rotation speed of the spindle 181 (period Tf). In the period Tf, the rotation speed of the spindle 181 is set to 1800 rpm. As a result, the value from the third load sensor 503 turns to increase.

As in the above embodiment, while the sum of the values from the three load sensors 50 is maintained at the set load of 300N, by managing the rotation speed of the spindle 181 so that the value from the third load sensor 503 falls within the set range, the load applied to the wafer W and the position of the load center of gravity may be controlled. It is noted that the change in the value from the third load sensor 503 as explained in the above embodiment means that the tilt of the spindle 181 is changing with respect to the rotation axis of the chuck table 14.

Optionally, when the value from the third load sensor 503 exceeds the set range, the controller 11 may notify the operator via the notification device 47. For example, in the period Tc, when the value from the third load sensor 503 exceeds the lower limit (−34.0N) of the set range, the controller 11 may operate the notification device 47 to notify the operator of the decrease. Notification by the notification device 47 may include, for example, information displayed on the display monitor, glowing or blinking of the lamp, or generating a notification sound from the speaker. The operator notified by the notification may, as needed, inspect a state (roughness) of the surface to be polished of the wafer W, or inspect or review processing conditions in the polishing mechanism 18.

Thus, in the second embodiment of adjusting the load center of gravity, the controller 11 controls, for example, the rotation speed of the spindle 181 so that the value from at least one load sensor 50, namely the third load sensor 503, remains within the set range which is set in advance. While polishing, by continuously controlling as above, the tilt of the spindle 181 is maintained at a predetermined degree, the position of the load center of gravity to press the polishing pad 183 against the wafer W is maintained at the position of the normal polishing load center of gravity Ga (approximately at one half of a radius of the wafer W), thereby preventing the problems such that the central portion of the wafer W is polished more and the peripheral portion is polished less and that the wafer W has uneven thickness.

As for the at least one load sensor 50 to be monitored so that the load value remains within the set range, it is preferable to select one, of which amount of change in the load value, when the center of gravity position of the load acting from the polishing pad 183 on the wafer W changes, is larger than that of the other load sensors 50. As shown in the table in FIG. 5, the third load sensor 503 exhibits a larger change in the load value when transitioning from the normal condition to the abnormal condition than the first load sensor 501 or the second load sensor 502. Therefore, by monitoring the third load sensor 503 and controlling as above, tilting of the spindle 181 and deviation of the load center of gravity may be manageably suppressed with high accuracy.

It is noted that although the graph in FIG. 6 illustrates an example of controlling the rotation speed of the spindle 181, the controller 11 may control the rotation speed of the chuck shaft 35 in order to maintain the value from the third load sensor 503 within the set range which is set in advance. Optionally, for controlling the value from the third load sensor 503 to maintain within the set range, the controller 11 may change both the rotation speed of the spindle 181 and the rotation speed of the chuck shaft 35.

In summary, the controller 11 may control adjustment of the processing condition of the polishing pad 183 to be pressed against the wafer W, in both the first embodiment and the second embodiment, by controlling the pressing act of the polishing pad 183 in the polishing mechanism 18 such that the sum of values from the three load sensors 50 stay within the set load which is set in advance while the polishing mechanism 18 polishes the wafer W. On that basis, in the first embodiment, the controller 11 controls the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35 so that the ratio of the load values measured by the three load sensors 50 stay within the set ratio which is set in advance. In the second embodiment, on the other hand, the controller 11 controls the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35 so that the value from at least one load sensor 50 (e.g., the third load sensor 503) stays within the set range which is set in advance.

In the embodiments described above, controlling of the rotation speed of the chuck shaft 35 or the spindle 181 based on the values from the load sensors 50 is applied to adjustment of the position of the load center of gravity in the state where the polishing pad 183 is pressed against the wafer W; however, the control may also be applied to management of the tilt of the spindle 181. For reducing the tilting degree of the spindle 181 from a larger tilting degree, for example, the controller 11 may control the rotation speed of the spindle 181 to increase or the rotation speed of the chuck shaft 35 to decrease.

On the other hand, when in need for increasing the tilting degree of the spindle 181, the controller 11 may control to the rotation speed of the spindle 181 to decrease or the rotation speed of the chuck shaft 35 to increase. For example, such control may be selectively applied in order to intentionally increase the polishing rate at the central portion of the wafer W, i.e., for a setting such as the polishing load center of gravity Gb as shown in FIG. 3.

Optionally, in either of the control in the first embodiment or the second embodiment, the controller 11 may operate the process-feeding mechanism 27 to change the process-feeding speed of the polishing mechanism 18 separately from the changes in the rotation speed of the spindle 181 or the rotation speed of the chuck shaft 35. Increasing the process-feeding speed to lower the polishing pad 183 provides an effect of reducing the tilting degree of the spindle 181. Therefore, when changing the polishing load center of gravity Gb under the abnormal condition to the normal polishing load center of gravity Ga, i.e., changing the position of the load center of gravity in the direction to separate away from the third load sensor 503, the control over the process-feeding mechanism 27 to increase the process-feeding speed may be applied. Moreover, for intentionally increasing the tilting degree of the spindle 181, the control over the process-feeding mechanism 27 to decrease the process-feeding speed may be applied.

In the exemplary operation shown in FIG. 3, the rotation direction Ra of the wafer W (the chuck shaft 35) and the rotation direction Rb of the polishing pad 183 (the spindle 181) are set to the same direction, i.e., the chuck shaft 35 and the spindle 181 rotate in the same direction. Unlike this exemplary operation, even in a case where the rotation direction of the wafer W (the chuck shaft 35) and the rotation direction of the polishing pad 183 (the spindle 181) are set to opposite directions, i.e., the chuck shaft 35 and the spindle 181 rotate in opposite directions, the above control according to the first embodiment and the control of the second embodiment may be applied.

The above examples are applicable to adjustment of the position of the load center of gravity and adjustment of the tilt of the spindle 181 when the polishing pad 183 of the polishing mechanism 18 polishes the wafer W. For another example, for adjusting the position of the load center of gravity and adjusting the tilt of the spindle 161 when the grindstone 163 of the rough grinding mechanism 16 roughly grinds the wafer W, or for adjusting the position of the load center of gravity and adjusting the tilt of the spindle 171 when the grindstone 173 of the finish grinding mechanism 17 finish by grinding the wafer W finely, the controller 11 may perform control similar to the first embodiment or the second embodiment described above. Details of the control to be applied to the rough grinding mechanism 16 and the finish grinding mechanism 17 are similar to those in the control of the polishing mechanism 18 described above; therefore, detailed description is omitted and it will be explained briefly herein.

For grinding the wafer W, the grindstones 163, 173 are operated to contact a radial portion of the wafer W (the processing line Qa and the processing line Qb shown in FIG. 1). As such, the grindstones 163, 173 partially contact the wafer W for grinding; therefore, the tilt of spindles 161, 171 that rotate the grindstones 163, 173 slightly changes between when grinding and when not grinding. Moreover, depending on conditions such as rotation speeds of the spindles 161, 171, a rotation speed of the chuck shaft 35, process-feeding speeds by the process-feeding mechanisms 25, 26, and the tilting degrees of the spindles 161, 171 relative to the chuck shaft 35 differ.

At least three load sensors are arranged at equal intervals along a circle centered on each of the rotational axes Da, Db of the spindles 161, 171, or on each of the rotation axes Ca, Cb of the chuck table 14, i.e., the rotation axis of the wafer W on the chuck table 14, and by these load sensors, forces that press the grindstones 163, 173 against the wafer W are measured.

In the first embodiment, the controller 11 controls the rotation speeds of the spindles 161, 171 or the rotation speed of the chuck shaft 35 while pressing the grindstones 163, 173 against the wafer W so that a sum of the values from the three load sensors stays within the set load which is set in advance and so that a ratio of the values from the three load sensors maintains the set ratio which is set in advance. Optionally, the controller 11 may further change process-feeding speeds for the process-feeding mechanisms 25, 26 to feed the grindstones 163, 173.

In the second embodiment, the controller 11 controls the rotation speeds of the spindles 161, 171 or the rotation speed of the chuck shaft 35 while pressing the grindstones 163, 173 against the wafer W so that a sum of the values from the three load sensors stays within the set load which is set in advance and so that a value from at least one load sensor remains within the set range which is set in advance. Optionally, the controller 11 may further change the process-feeding speeds for the process-feeding mechanisms 25, 26 to feed the grindstones 163, 173.

Conventionally, in order to preview grinding results, which may be changed depending on the change in the tilt of the grindstones 163, 173, before grinding a product wafer W, a test wafer in a similar form was ground and tilting degrees of the chuck table 14 relative to the grindstones 163, 173 were adjusted so that the ground wafer has a uniform thickness. In contrast, in the processing apparatus 10 according to the present disclosure, by the controller 11 performing the control according to the first or second embodiment described above, in other words, by controlling the rotation speeds of the spindles 161, 171 or the rotation speed of the chuck shaft 35 as above, the tilting degrees of the spindles 161, 171 (the grindstones 163, 173) are adjusted as needed so that the tinting degrees should not change while grinding. Accordingly, even without adjusting the tilting degree of the chuck table 14 preliminarily based on the test grinding, the wafer W may be ground to a uniform thickness. As a result, time required for the test grinding is omitted and grinding time may be shortened.

Further, when the thickness of the wafer W is large, the process-feeding speed for the grindstone to approach the wafer W is increased, and when the thickness of the wafer W becomes close to a finish thickness, the process-feeding speed may be decreased. Conventionally, due to at least these two different process-feeding speeds, the tilting degrees of the grindstones 163, 173 with respect to the chuck table 14 holding the wafer W and the positions of the grinding load center of gravity are differed, resulting in a problem such that finish grinding to remove damage marks produced by grinding at the higher process-feeding speed requires a long time. In contrast, in the processing apparatus 10 according to the present disclosure, by the controller 11 performing the control according to the first or second embodiment described above, in other words, by controlling the rotation speeds of the spindles 161, 171 or the rotation speed of the chuck shaft 35 as above, changes in the tilting degrees of the grindstones 163, 173 due to difference in the process-feeding speeds of the process-feeding mechanisms 25, 26 may be suppressed. Consequently, time required for the finish grinding to remove the damage marks may be shortened.

Meanwhile, due to, for example, glazing of the grinding surfaces (lower surfaces) of the grindstones 163, 173, the tilting degrees of the spindles 161, 171 and the positions of the grinding load center of gravity may change, resulting in an inability to grind correctly. In the processing apparatus 10 according to the present disclosure, in the control of the first embodiment when the ratio of the load values from the three load sensors deviates from the set ratio, or in the control of the second embodiment when the value from the at least one load sensor exceeds the set range, the controller 11 may notify an operator via the notification device 47. By being notified, the operator may detect the abnormality such as glazing on the grinding surfaces of the grindstones 163, 173 earlier, temporarily stop grinding to check the conditions of the grindstones 163, 173, or perform dressing to remove glazing of the grindstones 163, 173, thereby quickly returning to the condition in which the wafer W may be ground normally.

The controller 11 may include a rotation ratio setting device 111 (FIG. 1) configured to set a ratio between the rotation speed of spindles 161, 171 and the rotation speed of the chuck shaft 35, and for controlling as in the first embodiment or the second embodiment described above, the controller 11 may control the rotation speed of spindles 161, 171 and the rotation speed of the chuck shaft 35 so that the rotation ratio (ratio of the rotation speeds) is maintained at a rotation ratio (ratio of rotation speeds) set by the rotation ratio setting device 111. That is, when one of the rotation speed of the spindles 161, 171 or the rotation speed of the chuck shaft 35 is increased, the other rotation speed is also increased to maintain the rotation ratio, and when decreasing one of the rotation speed of the spindles 161, 171 or the rotation speed of the chuck shaft 35, the other rotation speed is also decreased to maintain the rotation ratio.

The shape and number of the saw marks M1, M2 (FIG. 1) as grinding marks generated when grinding a wafer W are determined by a ratio between the rotation speed of the spindles 161, 171 and the rotation speed of the chuck shaft 35. Changes in the shape and number of the saw marks M1, M2 may affect quality of devices (chips) formed on the wafer W. Therefore, maintaining the shape and number of the saw marks M1, M2 is required. By maintaining the ratio between the rotation speed of the spindles 161, 171 and the rotation speed of the chuck shaft 35 set in the rotation ratio setting device 111, controlling the spindles 161, 171 to prevent changes in the tilting degrees and the position of the center of gravity of the grinding load without changing the shape or number of the saw marks M1, M2 is possible.

The position of the grinding load center of gravity varies within a path of the grindstone along the processing line Qa where the rough grindstone (grindstone 163) contacts the wafer W and along the processing line Qb where the finish grindstone (grindstone 173) contacts the wafer W. Under normal conditions, the position of the grinding load center of gravity is in middle between the processing line Qa and the processing line Qb.

In the processing apparatus 10 according to the above embodiment, both rough grinding by the rough grinding mechanism 16 and finish grinding by the finish grinding mechanism 17 are performed; however, the present disclosure may also be applied to a processing apparatus that may grind a wafer using solely one type of grinding mechanism. Moreover, the technique according to the present disclosure may also be applied to a single-function processing apparatus that may perform only one of grinding or polishing. Furthermore, a mechanism for locating a chuck table with respect to a grindstone and a polishing pad is not limited to a turntable, but, for example, a linear slider may be used to locate the chuck table with respect to the grindstone and the polishing pad.

Embodiments of the present disclosure may not necessarily be limited to the configurations described above or in a modified example but may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of the present disclosure. Furthermore, if the technical idea of the present disclosure may be realized in a different way due to technological progress or other derived technology, it may be implemented with use of the method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of the present disclosure.

By applying the processing apparatus and the method for manufacturing a wafer according to the present disclosure, a position of a center of gravity of a force pressing a processing tool against a wafer is prevented from changing, thereby enabling, for example, improvement of processing results and reduction of processing time in polishing processing or grinding processing.