POLISHING METHOD AND POLISHING DEVICE

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefits of Japanese application no. 2024-106659, filed on Jul. 2, 2024. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to a polishing method and polishing device for polishing substrates such as wafers.

Related Art

In semiconductor device manufacturing processes, planarization technology for semiconductor device surfaces is becoming increasingly important. Among these planarization technologies, the most important technology is chemical mechanical polishing (CMP). This chemical mechanical polishing uses a polishing device to supply polishing liquid containing abrasive grains such as silica (SiO2) onto the polishing surface of a polishing pad, while pressing a substrate such as a wafer against the polishing surface with a polishing head to perform polishing.

In polishing devices that perform such CMP, during substrate polishing, monitor signals related to film thickness on the substrate are measured for a plurality of areas on the substrate, and the film thickness profile (film thickness distribution) of the substrate being polished is monitored based on the measured monitor signals. Patent Document 1 discloses a polishing device that controls the pressure in a plurality of pressure chambers of a polishing head such that monitor signals acquired in other areas converge to a reference signal, which is a monitor signal acquired in a reference area on the substrate.

CITATION LIST

Patent Document

[Patent Document 1] Japanese Patent Application Laid-Open Publication No. 2008-503356

In the polishing device described in Patent Document 1, polishing endpoints of a plurality of areas on the substrate are uniformly determined based on the polishing endpoint of the reference area. However, due to differences in surface structure and underlying structure of the plurality of areas, the polishing endpoint of the reference area and the polishing endpoints of other areas (i.e. time points at which the target film thickness is reached) may occur at different time points. Thus, in the case of uniformly ending polishing at the time point at which the polishing endpoint of the reference area is reached, over-polishing and under-polishing may occur in other areas.

Thus, the disclosure provides a polishing method and polishing device capable of preventing under-polishing and over-polishing of substrates.

SUMMARY

In one aspect, a polishing method is provided, which includes: a polishing table that supports a polishing pad is rotated; a substrate is pressed against a polishing surface of the polishing pad by a first pressure chamber and a second pressure chamber of a polishing head to polish the substrate; a film thickness monitoring signal in accordance to a film thickness of the substrate is output by a sensor during polishing of the substrate; based on the film thickness monitoring signal in each of a first region and a second region on the substrate corresponding to the first pressure chamber and the second pressure chamber, a first polishing endpoint in the first region and a second polishing endpoint in the second region are determined, in which the second polishing endpoint is a polishing endpoint later than the first polishing endpoint; progress of polishing in the first region is stopped by reducing pressure in the first pressure chamber in response to the first polishing endpoint being reached; and progress of polishing in the second region is stopped by reducing pressure in the second pressure chamber in response to the second polishing endpoint being reached.

In one aspect, a polishing device is provided, which includes: a polishing table supporting a polishing pad; a table motor rotating the polishing table; a polishing head having a first pressure chamber and a second pressure chamber and pressing a substrate against a polishing surface of the polishing pad; a first pressure regulator adjusting pressure in the first pressure chamber; a second pressure regulator adjusting pressure in the second pressure chamber; a sensor outputting a film thickness monitoring signal in accordance to a film thickness of the substrate; and an operation control part controlling operations of the first pressure regulator and the second pressure regulator. The operation control part is configured to: determine, based on the film thickness monitoring signal in each of a first region and a second region on the substrate corresponding to the first pressure chamber and the second pressure chamber, a first polishing endpoint in the first region and a second polishing endpoint in the second region, in which the second polishing endpoint is a polishing endpoint later than the first polishing endpoint; issue a command to the first pressure regulator to stop progress of polishing in the first region by reducing the pressure in the first pressure chamber in response to the first polishing endpoint being reached; and issue a command to the second pressure regulator to stop progress of polishing in the second region by reducing the pressure in the second pressure chamber in response to the second polishing endpoint being reached.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating one embodiment of a polishing device.

FIG. 2 is a cross-sectional diagram illustrating one embodiment of a polishing head.

FIG. 3 is a schematic diagram illustrating one example of a plurality of measurement points on a surface of a substrate.

FIG. 4 is a cross-sectional diagram illustrating one example of a laminated structure of a substrate to be polished.

FIG. 5 is a graph illustrating one example of a relationship between output values of film thickness monitoring signals and polishing time in a plurality of regions of a substrate.

FIG. 6 is a graph illustrating one example of a relationship between output values of film thickness monitoring signals and polishing time in a plurality of regions of a substrate according to another embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating one embodiment of a polishing device 1. The polishing device 1 illustrated in FIG. 1 is a device for chemically mechanically polishing a substrate W such as a wafer. The polishing device 1 includes a polishing pad 2, a polishing table 3 that supports the polishing pad 2, a table motor 6 that rotates the polishing table 3, a polishing head 10 that presses the substrate W against the polishing pad 2, and a polishing liquid supply nozzle 20 that supplies polishing liquid (for example, slurry containing abrasive grains) onto the polishing pad 2.

The polishing pad 2 is attached to an upper surface of the polishing table 3. A surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the substrate W. The polishing table 3 is connected to the table motor 6 via a table shaft 5. The table motor 6 is configured to rotate the polishing table 3 in a direction indicated by an arrow in FIG. 1. The polishing table 3 is rotated around its axis by the table motor 6. The polishing pad 2 rotates integrally with the polishing table 3.

The polishing head 10 is connected to a lower end of a polishing head shaft 12. The polishing head 10 is configured to be able to hold the substrate W on a lower surface by vacuum suction. The polishing head 10 is connected to a polishing head motor (not illustrated) via the polishing head shaft 12. The polishing head motor is configured to rotate the polishing head 10 in a direction indicated by an arrow in FIG. 1. The polishing head 10 is rotated around its axis by the polishing head motor. The polishing head 10 rotates integrally with the polishing head shaft 12.

The polishing head 10 is connected to a polishing head lifting mechanism (not illustrated) via the polishing head shaft 12. The polishing head lifting mechanism is configured to lift and lower (move up and down) the polishing head 10. The polishing head 10 moves up and down relative to the polishing pad 2 by the polishing head lifting mechanism. The polishing head 10 moves up and down integrally with the polishing head shaft 12. The polishing head lifting mechanism brings a surface of the substrate W (in other words, a surface to be polished) into contact with the polishing surface 2a of the polishing pad 2 by lowering the polishing head 10 holding the substrate W toward the polishing pad 2.

The polishing device 1 further includes an operation control part 50 that controls operation of each component of the polishing device 1. The operation control part 50 includes a memory device 50a in which a program is stored, and a calculation device 50b that executes calculations according to instructions included in the program. The operation control part 50 is composed of at least one computer. The memory device 50a includes a main memory device such as random access memory (RAM), and an auxiliary memory device such as a hard disk drive (HDD) and a solid-state drive (SSD). Examples of the calculation device 50b include a CPU (central processing unit) and a GPU (graphics processing unit). However, the specific configuration of the operation control part 50 is not limited to these examples.

Polishing of the substrate W is performed as follows. The polishing head 10 holds the substrate W in a state where a surface of the substrate W (surface to be polished) faces the polishing pad 2. While the polishing table 3 is rotated by the table motor 6, polishing liquid is supplied from the polishing liquid supply nozzle 20 onto the polishing surface 2a of the polishing pad 2. In this state, the polishing head 10 is lowered by the polishing head lifting mechanism while being rotated by the polishing head motor. As a result, the surface of the substrate W contacts the polishing surface 2a of the polishing pad 2. Furthermore, the polishing head 10 presses the substrate W toward the polishing pad 2. The surface of the substrate W is polished by chemical action of the polishing liquid and mechanical action of abrasive grains included in the polishing liquid and/or the polishing surface 2a.

Next, details of the polishing head 10 will be described. FIG. 2 is a cross-sectional diagram illustrating one embodiment of the polishing head 10. The polishing head 10 includes a carrier 41 fixed to an end part of the polishing head shaft 12, an elastic film 44 attached to a lower part of the carrier 41, and a retainer ring 42 disposed below the carrier 41. The retainer ring 42 is disposed around the elastic film 44. This retainer ring 42 is an annular structure that holds the substrate W to prevent the substrate W from flying out from the polishing head 10 during polishing of the substrate W.

The elastic film 44 includes a contact part 45 having a contact surface 45a capable of contacting an upper surface of the substrate W, and inner wall parts 46a, 46b, 46c and an outer wall part 46d connected to the contact part 45. The contact part 45 has substantially the same size and the same shape as the upper surface of the substrate W. The inner wall parts 46a, 46b, 46c and the outer wall part 46d are endless walls arranged concentrically. The outer wall part 46d is positioned outside the inner wall parts 46a, 46b, 46c and is disposed so as to surround the inner wall parts 46a, 46b, 46c. In the embodiment, three inner wall parts 46a, 46b, 46c are provided, but the number of inner wall parts is not limited to the embodiment. In one embodiment, one or two inner wall parts may be provided, or four or more inner wall parts may be provided.

Between the elastic film 44 and the carrier 41, a plurality of (four in the embodiment) pressure chambers 40A, 40B, 40C, 40D are provided. The pressure chambers 40A, 40B, 40C, 40D are formed by the contact part 45, the inner wall parts 46a, 46b, 46c, and the outer wall part 46d of the elastic film 44. That is, the pressure chamber 40A is positioned within the inner wall part 46a, the pressure chamber 40B is positioned between the inner wall part 46a and the inner wall part 46b, the pressure chamber 40C is positioned between the inner wall part 46b and the inner wall part 46c, and the pressure chamber 40D is positioned between the inner wall part 46c and the outer wall part 46d. The sizes of the pressure chambers 40A, 40B, 40C, 40D, that is, the distances from a center of the elastic film 44 to the inner wall parts 46a, 46b, 46c and the outer wall part 46d, are not particularly limited. For example, the inner wall parts 46a, 46b, 46c and the outer wall part 46d may be disposed at different intervals from the center of the elastic film 44, or may be disposed at equal intervals.

The pressure chamber 40A positioned at the center of the elastic film 44 is circular, and the other pressure chambers 40B, 40C, 40D are annular. The pressure chambers 40A, 40B, 40C, 40D are arranged concentrically. The pressure chamber 40B is positioned outside the pressure chamber 40A, the pressure chamber 40C is positioned outside the pressure chamber 40B, and the pressure chamber 40D is positioned outside the pressure chamber 40C. In the embodiment, the elastic film 44 forms four pressure chambers 40A to 40D, but in one embodiment, the elastic film 44 may form two or three pressure chambers, or may form five or more pressure chambers.

An annular membrane (rolling diaphragm) 47 is disposed between the carrier 41 and the retainer ring 42, and a pressure chamber 40E is formed inside the membrane 47. Gas transfer lines F1, F2, F3, F4, F5 are respectively connected to the pressure chambers 40A, 40B, 40C, 40D, 40E. The gas transfer lines F1, F2, F3, F4, F5 extend via a rotary joint 15 attached to the polishing head shaft 12.

The gas transfer lines F1, F2, F3, F4, F5 are respectively connected to gas supply lines La1, La2, La3, La4, La5 on the upstream side of the rotary joint 15. The gas supply lines La1, La2, La3, La4, La5 are connected to a compressed gas supply source (not illustrated) as a utility supply source provided in a factory where the polishing device 1 is installed. Compressed gas such as compressed air etc. is configured to be respectively supplied from the gas supply lines La1, La2, La3, La4, La5 to the pressure chambers 40A, 40B, 40C, 40D, 40E through the gas transfer lines F1, F2, F3, F4, F5.

Gas supply valves Va1, Va2, Va3, Va4, Va5 and pressure regulators Ra1, Ra2, Ra3, Ra4, Ra5 are respectively attached to the gas supply lines La1, La2, La3, La4, La5. The gas supply valves Va1, Va2, Va3, Va4, Va5 are actuator driven valves such as, for example, electromagnetic valves, electric valves, or air operated valves. In one embodiment, the gas supply valves Va1 to Va5 may be manual. In response to the gas supply valves Va1 to Va5 being opened, compressed gas from the compressed gas supply source is independently supplied into the pressure chambers 40A to 40E respectively through the pressure regulators Ra1 to Ra5. The pressure regulators Ra1 to Ra5 are configured to adjust the pressure of the compressed gas in the pressure chambers 40A to 40E.

The gas supply valves Va1 to Va5 and the pressure regulators Ra1 to Ra5 are connected to the operation control part 50. The operations of the gas supply valves Va1 to Va5 and the pressure regulators Ra1 to Ra5 are controlled by the operation control part 50. The operation control part 50 sends respective target pressure values of the pressure chambers 40A to 40E to the pressure regulators Ra1 to Ra5, and the pressure regulators Ra1 to Ra5 operate such that the pressures in the pressure chambers 40A to 40E are maintained at the corresponding target pressure values.

The pressure regulators Ra1 to Ra5 are capable of changing internal pressures of the pressure chambers 40A to 40E independently of each other. Thus, the polishing head 10 is capable of independently adjusting polishing pressures for the corresponding four regions of the substrate W, namely, a central part, an inner intermediate part, an outer intermediate part, and an edge part, and a pressing force of the retainer ring 42 against the polishing surface 2a of the polishing pad 2. For example, the polishing head 10 is capable of pressing different regions of the surface of the substrate W against the polishing surface 2a of the polishing pad 2 with different polishing pressures. Thus, the polishing device 1 is capable of polishing different regions of the surface of the substrate W at different polishing rates.

Furthermore, the gas transfer lines F1, F2, F3, F4, F5 are respectively connected to vacuum lines Lb1, Lb2, Lb3, Lb4, Lb5 on an upstream side of the rotary joint 15. Compressed gas such as compressed air etc. is respectively supplied from the gas supply lines La1, La2, La3, La4, La5 to the pressure chambers 40A, 40B, 40C, 40D, 40E through the gas transfer lines F1, F2, F3, F4, F5. Vacuum valves Vb1, Vb2, Vb3, Vb4, Vb5 and vacuum regulators Rb1, Rb2, Rb3, Rb4, Rb5 are respectively attached to the vacuum lines Lb1, Lb2, Lb3, Lb4, Lb5. The vacuum valves Vb1, Vb2, Vb3, Vb4, Vb5 are actuator driven valves such as electromagnetic valves, electric valves, or air operated valves. In one embodiment, the vacuum valves Vb1 to Vb5 may be manual.

In response to the vacuum valves Vb1 to Vb5 being opened, the compressed gas in the pressure chambers 40A to 40E is respectively independently discharged from inside the pressure chambers 40A to 40E to the outside through the gas transfer lines F1 to F5 and the vacuum lines Lb1 to Lb5, and negative pressure is formed in the pressure chambers 40A to 40E. The vacuum regulators Rb1 to Rb5 are configured to adjust the vacuum pressure in the pressure chambers 40A to 40E.

The vacuum valves Vb1 to Vb5 and the vacuum regulators Rb1 to Rb5 are connected to the operation control part 50. The operations of the vacuum valves Vb1 to Vb5 and the vacuum regulators Rb1 to Rb5 are controlled by the operation control part 50. In response to the polishing head 10 holding the substrate W, with the contact part 45 of the elastic film 44 in contact with the substrate W, the vacuum valves Vb1, Vb2, Vb3 are opened to form vacuum in the pressure chambers 40A, 40B, 40C. The portions of the contact part 45 that form the pressure chambers 40A, 40B, 40C are recessed upward, and the polishing head 10 is capable of attracting the substrate W by suction cup effect of the elastic film 44. Furthermore, in response to compressed gas being supplied to the pressure chambers 40A, 40B, 40C to release the suction cup effect, the polishing head 10 is capable of releasing the substrate W.

Furthermore, the gas transfer lines F1, F2, F3, F4, F5 are respectively connected to atmospheric release lines Lc1, Lc2, Lc3, Lc4, Lc5 on the upstream side of the rotary joint 15. Atmospheric release valves Vc1, Vc2, Vc3, Vc4, Vc5 are respectively attached to the atmospheric release lines Lc1, Lc2, Lc3, Lc4, Lc5. The atmospheric release valves Vc1, Vc2, Vc3, Vc4, Vc5 are actuator driven valves such as electromagnetic valves, electric valves, or air operated valves. In one embodiment, the atmospheric release valves Vc1 to Vc5 may be manual. In response to the atmospheric release valves Vc1 to Vc5 being opened, the pressure chambers 40A to 40E are respectively independently released to atmosphere. The atmospheric release valves Vc1 to Vc5 are connected to the operation control part 50. The operations of the atmospheric release valves Vc1 to Vc5 are controlled by the operation control part 50. In one embodiment, the atmospheric release lines Lc1 to Lc5 and the atmospheric release valves Vc1 to Vc5 may not necessarily be provided.

In the embodiment, the gas supply valves Va1 to Va5, the vacuum valves Vb1 to Vb5, and the atmospheric release valves Vc1 to Vc5 are respectively attached to gas supply lines La1 to La5, vacuum lines Lb1 to Lb5, and atmospheric release lines Lc1 to Lc5 that communicate with pressure chambers 40A to 40E via the gas transfer lines F1 to F5. In one embodiment, instead of the gas supply valves Va1 to Va5, vacuum valves Vb1 to Vb5, and atmospheric release valves Vc1 to Vc5, three-way valves may be respectively attached to the gas transfer lines F1 to F5. In this case, by operating the three-way valves, the lines that communicate with the pressure chambers 40A to 40E via the gas transfer lines F1 to F5 may be switched to any of the gas supply lines La1 to La5, the vacuum lines Lb1 to Lb5, or the atmospheric release lines Lc1 to Lc5.

As illustrated in FIG. 1, the polishing device 1 further includes a sensor 30 that outputs a film thickness monitoring signal in accordance to a film thickness of the substrate W. The film thickness monitoring signal is a signal that directly or indirectly indicates the film thickness of the substrate W, and the output value of the film thickness monitoring signal changes according to the film thickness of the substrate W. The output value of the film thickness monitoring signal may be a value that represents the film thickness of the substrate W itself, or may be a physical quantity or signal value before being converted to film thickness.

Examples of the sensor 30 include an optical film thickness sensor and an eddy current sensor. The optical film thickness sensor is configured to irradiate light onto the surface of the substrate W and output a film thickness monitoring signal that directly or indirectly indicates the film thickness of the substrate W from the spectrum of reflected light from the substrate W. For example, the optical film thickness sensor determines a reference spectrum having a shape closest to the spectrum of the reflected light from a reference spectrum library, and outputs a film thickness monitoring signal indicating the film thickness associated with the determined reference spectrum. In another example, the optical film thickness sensor performs Fourier transform on the spectrum of the reflected light and outputs a film thickness monitoring signal indicating the film thickness calculated from the obtained frequency spectrum. In yet another example, the optical film thickness sensor outputs a film thickness monitoring signal indicating a relative change amount of the spectrum of the reflected light.

The eddy current sensor is configured to induce eddy currents in a conductive film formed on the substrate W and output a film thickness monitoring signal that changes according to an impedance of an electrical circuit including the conductive film and a coil of the eddy current sensor. Known devices may be configured for the optical film thickness sensor and the eddy current sensor.

The sensor 30 is installed within the polishing table 3 and rotates integrally with the polishing table 3. The sensor 30 is disposed at a predetermined distance from a center of the polishing table 3 in the radial direction of the polishing table 3. The sensor 30 is configured to output film thickness monitoring signals at a plurality of measurement points of the substrate W while crossing the substrate W on the polishing surface 2a each time the polishing table 3 makes one rotation. The sensor 30 is electrically connected to the operation control part 50, and the film thickness monitoring signal output by the sensor 30 is sent to the operation control part 50.

FIG. 3 is a schematic diagram illustrating one example of a plurality of measurement points MP1 to MP4 on the surface (surface to be polished) of the substrate W. As illustrated in FIG. 3, the sensor 30 outputs film thickness monitoring signals at the plurality of measurement points MP1 to MP4 each time it crosses the substrate W. A plurality of (four in the embodiment) regions C1 to C4 on the substrate W respectively correspond to the pressure chambers 40A to 40D of the polishing head 10 described above. That is, the region C1 is the central part of the substrate W, the region C2 is the inner intermediate part of the substrate W, the region C3 is the outer intermediate part of the substrate W, and the region C4 is the edge part of the substrate W.

The plurality of measurement points MP1 are located in the region C1, the plurality of measurement points MP2 are located in the region C2, the plurality of measurement points MP3 are located in the region C3, and the plurality of measurement points MP4 are located in the region C4. The positions of the plurality of measurement points MP1 to MP4 are determined based on a time interval at which the sensor 30 outputs the film thickness monitoring signal, a rotation speed of the polishing table 3, a position of the polishing head 10, and a rotation speed of the polishing head 10, etc. FIG. 3 illustrates an arrangement where the sensor 30 crosses a center CP of the substrate W as one example. That is, one of the plurality of measurement points MP1 located in the region C1 is positioned at the center CP of the substrate W. However, the arrangement of the sensor 30 is not limited to this example as long as the sensor 30 is capable of crossing below the substrate W.

The operation control part 50 associates measurement coordinates indicating the position of each measurement point with each of the film thickness monitoring signals at the measurement points MP1 to MP4. The measurement coordinates are coordinates (position coordinates) indicating positions on the surface of the substrate W. For example, the measurement coordinates are indicated as radial positions on the substrate W. The operation control part 50 associates the film thickness monitoring signal at each measurement point with the measurement coordinates each time the sensor 30 passes through the substrate W.

The measurement coordinates are determined as follows as one example. The operation control part 50 is electrically connected to the table motor 6. The operation control part 50 receives information regarding the rotation of the polishing table 3 from the table motor 6. The operation control part 50 determines that the sensor 30 is moving below the substrate W in the case of the polishing table 3 being within a predetermined rotation angle range set in advance. Based on the determination, the operation control part 50 causes the sensor 30 to output the film thickness monitoring signal at predetermined measurement intervals. Furthermore, based on the determination, the operation control part 50 detects the rotation speed (or angular velocity) of the polishing table 3 during the output of the film thickness monitoring signal. The operation control part 50 obtains the rotation angle at a predetermined time based on the detected rotation speed.

Thereby, the operation control part 50 determines the position of the sensor 30 at the predetermined time based on the rotation angle. Furthermore, the operation control part 50 obtains the position of the measurement point, that is, the measurement coordinates, based on the determined position of the sensor 30 and the measurement interval. In this manner, the operation control part 50 associates the measurement coordinates with the film thickness monitoring signal at the predetermined measurement point.

The range of the predetermined rotation angle for determining that the sensor 30 is passing below the substrate W may be set in advance based on the position and size of the substrate W. The measurement coordinates may be determined by methods other than those described above.

The operation control part 50 determines the regions C1 to C4 on the substrate W where the measurement points are located from the respective measurement coordinates of the measurement points MP1 to MP4. For example, the operation control part 50 determines that the region where the plurality of measurement points MP1 are located is C1 from the respective measurement coordinates of the plurality of measurement points MP1. In one embodiment, the operation control part 50 may calculate a signal average value which is an average value of output values of a plurality of film thickness monitoring signals at the plurality of measurement points MP1 located in the region C1. In this case, signal average values are similarly calculated for the plurality of measurement points MP2 located in the region C2, the plurality of measurement points MP3 located in the region C3, and the plurality of measurement points MP4 located in the region C4.

FIG. 4 is a cross-sectional diagram illustrating one example of a laminated structure of the substrate W to be polished. The substrate illustrated in FIG. 4 has a stopper layer 101 made of silicon nitride (Si3N4) formed on convex portions of a silicon (Si) layer 100 having uneven steps, and a polishing object film 102 having uneven steps is formed on the stopper layer 101. The polishing object film 102 of the embodiment is an insulating film made of silicon dioxide (SiO2). One example of the laminated structure illustrated in FIG. 4 includes shallow trench isolation (STI). In the embodiment, a polishing endpoint of the substrate W is a time point at which the film thickness of the substrate W becomes the target film thickness, and the substrate W is polished until the polishing of the polishing object film 102 progresses and the stopper layer 101 appears on the surface of the substrate W. However, the laminated structure of the substrate W is not limited to this example, and the substrate W may be polished until its film thickness reaches a predetermined target film thickness.

FIG. 5 is a graph illustrating one example of a relationship between output values of film thickness monitoring signals and polishing time in a plurality of regions C1 to C4 of the substrate W. In FIG. 5, the solid line represents the relationship between the output value of the film thickness monitoring signal and polishing time in region C1 on the substrate W, the dashed-dotted line represents the relationship between the output value of the film thickness monitoring signal and polishing time in the region C2 on the substrate W, the thick line represents the relationship between the output value of the film thickness monitoring signal and polishing time in the region C3 on the substrate W, and the broken line represents the relationship between the output value of the film thickness monitoring signal and polishing time in the region C4 on the substrate W.

In the example illustrated in FIG. 5, initial film thicknesses (that is, the film thicknesses of the substrate W before polishing) of the regions C1 to C4 are different. The magnitudes of the initial film thicknesses of the regions C1 to C4 are, in descending order, the initial film thickness of the region C4, the initial film thickness of the region C3, the initial film thickness of the region C2, and the initial film thickness of the region C1. However, the relationship of the magnitudes of the initial film thicknesses of the regions C1 to C4 illustrated in FIG. 5 is one example and the disclosure is not particularly limited to this example. The output values of the film thickness monitoring signals indicating the initial film thicknesses of regions C1, C2, C3, and C4 are Sini1, Sini2, Sini3, and Sini4, respectively. The relationship of the magnitudes of the output values Sini1 to Sini4 of the film thickness monitoring signals is Sini4 >Sini3 >Sini2 >Sini1.

In the example illustrated in FIG. 5, during polishing of the substrate W, the polishing rate in each of the plurality of regions C1 to C4 of the substrate W is constant. Thus, the output values of the film thickness monitoring signals in each of the plurality of regions C1 to C4 decrease linearly with polishing time. Polishing endpoints Tfin1 to Tfin4 in the plurality of regions C1 to C4 are the time points at which the output values of the film thickness monitoring signals of the regions C1 to C4 respectively reach the target signal value Sfin indicating the target film thickness. As illustrated in FIG. 5, the polishing endpoints Tfin1, Tfin2, Tfin3, and Tfin4 may be different time points. Thus, in the case of ending the polishing of the substrate W based on the polishing endpoint of any one region among the plurality of regions C1 to C4, over-polishing or under-polishing may occur in other regions.

In another example, the substrate W may be polished while adjusting the polishing rates in the plurality of regions C1 to C4 of the substrate W (while adjusting the pressures in the pressure chambers 40A to 40D corresponding to the regions C1 to C4) based on the film thickness monitoring signals acquired during polishing of the substrate W. However, due to differences in surface structures or underlying structures of the plurality of regions C1 to C4, it may be difficult to adjust the polishing rates in the plurality of regions C1 to C4 of the substrate W such that the polishing endpoints Tfin1, Tfin2, Tfin3, and Tfin4 occur at the same time point.

In the embodiment, the operation control part 50 is configured to respectively determine the polishing endpoints Tfin1 to Tfin4 in the regions C1 to C4 based on the film thickness monitoring signals in the regions C1 to C4 on the substrate W. Specifically, the operation control part 50 determines the polishing endpoint Tfin1, which is the time point at which the output value of the film thickness monitoring signal in the region Cl on the substrate W reaches the target signal value Sfin indicating the target film thickness; determines the polishing endpoint Tfin2, which is the time point at which the output value of the film thickness monitoring signal in the region C2 on the substrate W reaches the target signal value Sfin indicating the target film thickness; determines the polishing endpoint Tfin3, which is the time point at which the output value of the film thickness monitoring signal in the region C3 on the substrate W reaches the target signal value Sfin indicating the target film thickness; and determines the polishing endpoint Tfin4, which is the time point at which the output value of the film thickness monitoring signal in the region C4 on the substrate W reaches the target signal value Sfin indicating the target film thickness.

In one embodiment, the operation control part 50 may be configured to respectively calculate a plurality of signal average values in the regions C1 to C4 on the substrate W and respectively determine the polishing endpoints Tfin1 to Tfin4 in the regions C1 to C4 based on the plurality of signal average values respectively corresponding to the regions C to C4, as described with reference to FIG. 3. Specifically, the operation control part 50 may calculate the signal average value in the region C1 on the substrate W and determine the polishing endpoint Tfin1, which is the time point at which the signal average value in the region C1 reaches the target signal value Sfin. The determination of the polishing endpoint Tfin2 to the polishing endpoint Tfin4 in the regions C2 to C4 on the substrate W is similar.

In response to the polishing endpoint Tfin1 in the region C1 which is an initial polishing endpoint being reached, the operation control part 50 issues a command to the pressure regulator Ral that adjusts the pressure in the pressure chamber 40A corresponding to the region C1, and stops the progress of polishing in the region C1 by reducing the pressure in the pressure chamber 40A. Even after stopping the progress of polishing in the region C1, polishing in the regions C2 to C4 continues. The pressure value in the case of reducing the pressure in the pressure chamber 40A may be 0, or may be a pressure value to the extent that a minute positive pressure is formed in the pressure chamber 40A. In this specification, “stopping the progress of polishing” includes not only completely preventing polishing from progressing, but also allowing polishing to progress slightly to the extent that there is no problem with polishing quality.

In response to the polishing endpoint Tfin2 in the region C2 which is the polishing endpoint after (second) the polishing endpoint Tfin1 being reached, the operation control part 50 issues a command to the pressure regulator Ra2 that adjusts the pressure in the pressure chamber 40B corresponding to the region C2, and stops the progress of polishing in the region C2 by reducing the pressure in the pressure chamber 40B. Even after stopping the progress of polishing in the region C2, polishing in regions C3 and C4 continues.

In response to the polishing endpoint Tfin3 in the region C3 which is the polishing endpoint after (third) the polishing endpoint Tfin2 being reached, the operation control part 50 issues a command to the pressure regulator Ra3 that adjusts the pressure in the pressure chamber 40C corresponding to the region C3, and stops the progress of polishing in the region C3 by reducing the pressure in the pressure chamber 40C. Even after stopping the progress of polishing in the region C3, polishing in the region C4 continues.

In response to Tfin4 in the region C4 which is the polishing endpoint after the polishing endpoint Tfin3 and is the final polishing endpoint being reached, the operation control part 50 issues a command to the pressure regulator Ra4 that adjusts the pressure in the pressure chamber 40D corresponding to the region C4, and stops the progress of polishing in the region C4 by reducing the pressure in the pressure chamber 40D. In this manner, polishing in all regions C1 to C4 on the substrate W is stopped. However, the order of reaching the polishing endpoints Tfin1 to Tfin4 illustrated in FIG. 5 is one example, and the disclosure is not particularly limited to this example.

In one embodiment, in response to the initial polishing endpoint Tfin1 being reached, the operation control part 50 may issue a command to the atmospheric release valve Vc1, which releases the pressure chamber 40A corresponding to the region Cl to atmosphere, instead of the pressure regulator Ra1 and stop the progress of polishing in the region C1 by releasing the pressure chamber 40A to atmosphere. Similarly, in response to the polishing endpoints Tfin2 to Tfin4 being reached, the operation control part 50 may issue commands to the atmospheric release valves Vc2 to Vc4 and stop the progress of polishing in the regions C2 to C4 respectively by releasing the pressure chambers 40B to 40D to atmosphere.

In one embodiment, the operation control part 50 may issue a command to the pressure regulator Ral after a predetermined time (for example, several seconds) has elapsed since the initial polishing endpoint Tfin1 is reached, and stop the progress of polishing in the region C1 by reducing the pressure in the pressure chamber 40A. Similarly, the operation control part 50 may issue commands to the pressure regulators Ra2 to Ra4 after a predetermined time (for example, several seconds) has elapsed since the polishing endpoints Tfin2 to Tfin4 are reached, and stop the progress of polishing in the regions C2 to C4 respectively by reducing the pressure in the pressure chambers 40B to 40D.

After polishing in all regions C1 to C4 on the substrate W is stopped, a polishing end operation of the substrate W is performed. In the polishing end operation of the substrate W, the operation control part 50 issues a command to the polishing liquid supply nozzle 20 to stop the supply of polishing liquid to the polishing surface 2a of the polishing pad 2, and issues a command to a pure water supply nozzle (not illustrated) to supply pure water to the polishing surface 2a and wash away the polishing liquid present on the polishing surface 2a. Furthermore, the operation control part 50 issues a command to a polishing head lifting mechanism to raise the polishing head 10 and separate the substrate W from the polishing surface 2a.

In one embodiment, after the last polishing endpoint Tfin4 is reached and the progress of polishing in the region C4 is stopped by reducing the pressure in the pressure chamber 40D, the polishing end operation of the substrate W may be performed after a predetermined time (for example, several seconds) has elapsed.

According to the embodiment, the polishing endpoints Tfin1 to Tfin4 in the plurality of regions C1 to C4 on the substrate W are determined, and in response to the polishing endpoint of each region being reached, the progress of polishing in each region is stopped by reducing the pressure in the corresponding pressure chamber. Thus, since it is possible to stop polishing at an appropriate polishing endpoint for each region on the substrate W, under-polishing and over-polishing of the substrate W can be prevented.

FIG. 6 is a graph illustrating one example of a relationship between output values of film thickness monitoring signals and polishing time in a plurality of regions C1 to C4 of the substrate W according to another embodiment. In the embodiment, the operation control part 50 is configured to: in response to the initial polishing endpoint Tfin1 being reached, stop the progress of polishing in the region C1 by reducing the pressure in the pressure chamber 40A corresponding to the region C1 on the substrate W and increase the polishing rate in the regions C2 to C4 by increasing the pressure in the pressure chambers 40B to 40D corresponding to the regions C2 to C4 on the substrate W.

Specifically, in response to the polishing endpoint Tfin1 in the region C1 on the substrate W which is the initial polishing endpoint being reached, the operation control part 50 calculates a correction pressure value in the pressure chamber 40B for increasing the polishing rate of the region C2 based on the output value S2 of the film thickness monitoring signal in accordance to the film thickness of the region C2 at the polishing endpoint Tfin1 and the target signal value Sfin indicating the target film thickness. The correction pressure value is higher than the current pressure in the pressure chamber 40B (the currently set target pressure value). The correction pressure value is calculated such that the larger the difference between the output value S2 of the film thickness monitoring signal and the target signal value Sfin, the larger the increase ratio of the correction pressure value relative to the current pressure in the pressure chamber 40B (the currently set target pressure value).

In one embodiment, the operation control part 50 may calculate the current polishing rate in the region C2 from the difference between the output value S2 of the film thickness monitoring signal and the output value Sini2 of the film thickness monitoring signal indicating the initial film thickness of the region C2, and the polishing time at the polishing endpoint Tfin1. In this case, the operation control part 50 calculates a correction pressure value in the pressure chamber 40B such that the polishing rate becomes larger than the current polishing rate in the region C2. The operation control part 50 calculates a correction pressure value in the pressure chamber 40B such that the larger the difference between the output value S2 of the film thickness monitoring signal and the target signal value Sfin, the larger the increase ratio of the polishing rate relative to the current polishing rate.

The operation control part 50 is configured to increase the polishing rate in the region C2 by issuing a command to the pressure regulator Ra2 that adjusts the pressure in the pressure chamber 40B corresponding to the region C2, and increasing the pressure in the pressure chamber 40B to the calculated correction pressure value. Thereafter, the operation control part 50 determines a polishing endpoint Tfin2′, which is the time point at which the output value of the film thickness monitoring signal in the region C2 on the substrate W reaches the target signal value Sfin. In response to the polishing endpoint Tfin2′ being reached, the operation control part 50 issues a command to the pressure regulator Ra2 to stop the progress of polishing in the region C2 by reducing the pressure in the pressure chamber 40B.

In the embodiment, similarly for the region C3, the operation control part 50 calculates a correction pressure value in the pressure chamber 40C corresponding to the region C3 based on the output value S3 of the film thickness monitoring signal in accordance to the film thickness of the region C3 at the polishing endpoint Tfin1 and the target signal value Sfin indicating the target film thickness. Similarly for the region C4, the operation control part 50 calculates a correction pressure value in the pressure chamber 40D corresponding to the region C4 based on the output value S4 of the film thickness monitoring signal in accordance to the film thickness of the region C4 at the polishing endpoint Tfin1 and the target signal value Sfin indicating the target film thickness. The operation control part 50 is configured to increase the polishing rates in the region C3 and the region C4 by issuing commands to the pressure regulator Ra3 that adjusts the pressure in the pressure chamber 40C and the pressure regulator Ra4 that adjusts the pressure in the pressure chamber 40D, and increasing the pressure in the pressure chamber 40C and the pressure in the pressure chamber 40D to the respectively calculated correction pressure values. Thereafter, the operation control part 50 respectively determines a polishing endpoint Tfin3′ and a polishing endpoint Tfin4′, which are the time points at which the output values of the film thickness monitoring signals in the region C3 and the region C4 on the substrate W reach the target signal value Sfin. In response to the polishing endpoint Tfin3′ being reached, the operation control part 50 issues a command to the pressure regulator Ra3 to stop the progress of polishing in the region C3 by reducing the pressure in the pressure chamber 40C. In response to the polishing endpoint Tfin4′ being reached, the operation control part 50 issues a command to the pressure regulator Ra4 to stop the progress of polishing in the region C4 by reducing the pressure in the pressure chamber 40D.

In the embodiment, the polishing endpoints Tfin2′, Tfin3′, and Tfin4′ are the same time point, but in one embodiment, the polishing endpoints Tfin2′, Tfin3′, and Tfin4′ may be different time points. In this case, in response to the second polishing endpoint (for example, polishing endpoint Tfin2′) being reached, the operation control part 50 may stop the progress of polishing in the region in which the polishing endpoint is reached second (for example, region C2) by reducing the pressure in the pressure chamber (for example, pressure chamber 40B) corresponding to that region (for example, region C2), and may further increase the polishing rates in the other regions (for example, regions C3, C4) by further increasing the pressure in the pressure chambers (for example, pressure chambers 40C, 40D) corresponding to the other regions (for example, regions C3, C4).

In one embodiment, in response to the initial polishing endpoint Tfin1 being reached, the operation control part 50 may increase the pressure in the pressure chamber corresponding to at least one region among the regions C2 to C4 on the substrate W. For example, in response to the initial polishing endpoint Tfin1 being reached, the operation control part 50 may increase only the pressure in the pressure chamber (pressure chamber 40D in the example of FIG. 6) corresponding to the region (region C4 in the example of FIG. 6) where the difference between the output value of the film thickness monitoring signal at the polishing endpoint Tfin1 and the target signal value Sfin is the largest, thereby increasing only the polishing rate in that region.

According to the embodiment, the overall polishing time of the substrate W can be shortened. Moreover, in the region where polishing was stopped first (region C1 in the example of FIG. 6), even after reducing the pressure in the corresponding pressure chamber (pressure chamber 40A in the example of FIG. 6), during polishing of the other regions (regions C2 to C4 in the example of FIG. 6), the contact part 45 (see FIG. 2) of the elastic film 44 may contact the region where polishing was stopped first (region C1 in the example of FIG. 6). In the case of such a state continuing for a long time, the region where polishing was stopped may be unintentionally polished. Thus, by minimizing the time difference between the earlier polishing endpoint and the polishing endpoint that comes after the earlier polishing endpoint as much as possible, over-polishing in the region where polishing was stopped first can be prevented.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the disclosure belongs to implement the disclosure. Various modification examples of the above embodiments may naturally be made by those skilled in the art, and the technical concept of the disclosure may be applied to other embodiments. Thus, the disclosure is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical concept defined by the claims.