POLISHING HEAD AND POLISHING SYSTEM

CROSS REFERENCE TO RELATED APPLICATION

This document claims priority to Japanese Patent Application No. 2023-089989 filed May 31, 2023, the entire contents of which are hereby incorporated by reference.

BACKGROUND

A precision required for each process in a manufacturing of recent semiconductor devices has already reached an order of several nm, and a chemical mechanical polishing (CMP) is no exception. In addition, with an increasing integration density of semiconductor integrated circuits, miniaturization and multi-layering are accelerating.

Therefore, in order to realize such miniaturization and multi-layering, it is necessary to limit a variation in film thickness after CMP polishing to the order of several nm over the entire surface of the wafer.

In order to achieve the above-described requirements, a polishing method capable of controlling a film thickness profile with a resolution at a chip-size level is required. The process of forming a film on a wafer is performed using various film formation techniques such as plating, chemical vapor deposition (CVD), and physical vapor deposition (PVD).

These film formation techniques may not form the film uniformly across the entire surface of the wafer. For example, there may be variations in film thickness along the circumference of the wafer. Conventional polishing head can also independently vary the pressure along a radius of the wafer, so it is possible to control the film thickness profile along the radius of the wafer.

However, since pressure chambers are arranged concentrically, it is not possible to control a pressing force along a circumferential direction of the wafer, and therefore it is not possible to control the film thickness profile in the circumferential direction. To address this issue, a method of dividing the pressure chambers in the circumferential direction is conceivable, but there are substantial limitations to dimensions of the pressure chambers and the number of compressed gas supply lines to each pressure chamber. Therefore, it is difficult to control the film thickness profile with chip-size level resolution.

In recent years, a polishing head that controls partial pressure by means of actuators such as chip-sized piezoelectric elements have been developed as a means of solving the above problem. However, in the case of a method in which pressure is applied using an actuator with a small expansion and contraction rate, stroke errors may occur due to a surface accuracy, inclination, and installation errors of a portion where the actuator is attached.

In this case, the actuator is expanded and contracted to correct the stroke error, and then the actuator is expanded and contracted by the necessary pressure. Therefore, the amount of expansion and contraction of the actuator may be insufficient. In this case, it may not be possible to apply a sufficient pressing force to the wafer, and it may not be possible to accurately control the film thickness profile of the wafer.

SUMMARY

Therefore, there is provided a polishing head and a polishing system that are capable of controlling the film thickness profile of the wafer with high precision.

Embodiments described below relate to a polishing head and a polishing system.

In an embodiment, there is provided a polishing head, comprising: a plurality of pressure actuators configured to independently press a specific portion of a substrate; an actuator operation controller configured to control an operation of each of the pressure actuators, the actuator operation controller being mounted on a head main body; the head main body comprising an actuator support portion configured to support the pressure actuators; and an elastic holder configured to hold the actuator support portion.

In an embodiment, the pressure actuators are arranged along a radial direction and a circumferential direction of the actuator support portion.

In an embodiment, the elastic holder comprises a bag-shaped airbag.

In an embodiment, the airbag comprises a plurality of pressurized chambers arranged concentrically.

In an embodiment, the elastic holder comprises an elastic sheet fixed to the head main body.

In an embodiment, the polishing head comprises a linear guide member configured to restrict a movement direction of the actuator support portion to a direction along a pressing direction of the pressing actuator.

In an embodiment, the actuator operation controller is mounted on the actuator support portion.

In an embodiment, the actuator operation controller is mounted on a flange portion of the head main body.

In an embodiment, the head main body has a space formed between the elastic holder and a flange portion of the head main body, and the actuator operation controller is arranged in the space.

In an embodiment, there is provided a polishing head, comprising: a plurality of pressure actuators configured to independently press a specific portion of a substrate; a head main body comprising an actuator support portion configured to support the pressure actuators; an elastic holder configured to hold the actuator support portion; and an elastic cover configured to cover the pressure actuators.

In an embodiment, the elastic cover is configured to form a suction space of the elastic cover between the pressure actuators adjacent to each other among the pressure actuators by forming a vacuum inside the elastic cover, thereby adsorbing the substrate.

In an embodiment, the pressure actuators are arranged along a radial direction and a circumferential direction of the actuator support portion.

In an embodiment, the elastic holder comprises a bag-shaped airbag.

In an embodiment, the airbag comprises a plurality of pressurized chambers arranged concentrically.

In an embodiment, the elastic holder comprises an elastic sheet fixed to the head main body.

In an embodiment, the polishing head comprises an actuator operation controller configured to control an operation of each of the pressure actuators, and the actuator operation controller is mounted on the head main body.

In an embodiment, there is provided a polishing system, comprising: forming a suction space of an elastic cover between pressure actuators adjacent to each other among the pressure actuators by forming a vacuum inside the elastic cover covering the pressure actuators, thereby adsorbing a substrate, the pressure actuators being configured to independently press a specific portion of the substrate; transporting the substrate above a polishing surface of a polishing pad while the substrate is adsorbed; supplying a pressurized fluid to an elastic holder, the elastic holder holding an actuator support portion supporting the pressure actuators, to bring the pressure actuators together with the actuator support portion into close proximity to the polishing surface; and operating at least one of the pressure actuators through an actuator operation controller mounted on the actuator support portion to press the substrate against the polishing surface.

By supplying the fluid to the elastic holder, the elastic holder brings the pressure actuators together with the actuator support portion close to the polishing surface of the polishing pad. Therefore, the pressure actuators can approach the polishing surface without stretching themselves, and an insufficient amount of expansion and contraction of the pressure actuators can be eliminated. As a result, the polishing head can accurately control the film thickness profile of the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an embodiment of a polishing apparatus;

FIG. 2 is a cross-sectional view of a polishing head;

FIGS. 3A to 3D are schematic views showing an example of an arrangement of pressure actuators;

FIG. 4A is a view showing the polishing head with a vacuum formed inside an elastic cover, and FIG. 4B is a view showing a depression in the elastic cover formed between adjacent pressure actuators;

FIG. 5 is a view showing a polishing flow of the polishing apparatus;

FIG. 6 is a view showing another embodiment of the polishing head;

FIG. 7 is a view showing another embodiment of the polishing head;

FIG. 8 is a view showing another embodiment of the polishing head;

FIG. 9 is a cross-sectional view taken along line A-A in FIG. 8;

FIG. 10 is a view showing other embodiment of the polishing head;

FIG. 11 is a view showing other embodiment of the polishing head;

FIG. 12 is a view showing other embodiment of the polishing head; and

FIG. 13 is a view showing other embodiment of the polishing head.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments will be described with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the multiple embodiments described below, the configuration of one embodiment that is not particularly described is the same as the other embodiments, so duplicated descriptions will be omitted.

FIG. 1 is a schematic view showing an embodiment of the polishing apparatus. As shown in FIG. 1, a polishing apparatus PA includes a polishing head PH that holds and rotates a wafer W, which is an example of a substrate, a polishing table 2 that supports a polishing pad 1, a polishing liquid supply nozzle 3 that supplies a polishing liquid (slurry) onto a polishing surface 1a of the polishing pad 1, and a dresser 41 that dresses the polishing surface 1a of the polishing pad 1.

The polishing head PH and the polishing table 2 rotate in the same direction, and in this state, the polishing head PH presses the wafer W against the polishing surface 1a of the polishing pad 1. The polishing liquid supply nozzle 3 supplies the polishing liquid onto the polishing surface 1a, and the wafer W is polished by sliding contact with the polishing pad 1 in the presence of the polishing liquid.

The polishing apparatus PA includes a head shaft 16 connected to the polishing head PH, a vertical movement mechanism 5 that moves the polishing head PH up and down via the head shaft 16, a rotation mechanism 6 that rotates the polishing head PH via the head shaft 16, and a swing arm 14 on which the vertical movement mechanism 5 and the rotation mechanism 6 are mounted.

The vertical movement mechanism 5 and the rotation mechanism 6 are supported by a support base 14a of the swing arm 14. The vertical movement mechanism 5 includes a vertical movement motor 30 and a coupling member 31 that couples the vertical movement motor 30 and the head shaft 16. The vertical movement motor 30 is a precision motor such as a servo motor. The vertical movement motor 30 is driven to move the head shaft 16 up and down via the coupling member 31. The polishing head PH moves up and down together with the head shaft 16.

The rotation mechanism 6 includes a rotation motor 22, a rotating cylinder 23 attached to the head shaft 16 via a key (not shown), and a timing belt 24 stretched between the rotation motor 22 and the rotating cylinder 23. The rotation motor 22 is, for example, a precision motor such as a servo motor.

The rotating cylinder 23 is rotatably supported by bearings 25A and 25B mounted on the support base 14a. The rotating motor 22 rotates the rotating cylinder 23 via the timing belt 24. The rotating cylinder 23 transmits a rotational force to the head shaft 16, causing the head shaft 16 to rotate. The polishing head PH rotates together with the head shaft 16.

The head shaft 16 is inserted into the rotating cylinder 23 so as to be movable up and down. Therefore, the rotational force acting on the rotating cylinder 23 is transmitted to the head shaft 16, while a vertical force acting on the head shaft 16 is not transmitted to the rotating cylinder 23. A rotary joint 32 is attached to an upper end of the head shaft 16.

The polishing apparatus PA includes a swing mechanism 7 that swings the swing arm 14. The swing mechanism 7 includes an arm shaft 12 that supports the swing arm 14, and a swing motor 20 that swings the swing arm 14 via the arm shaft 12. The swing motor 20 is, for example, a precision motor such as a servo motor. The swing motor 20 swings the swing arm 14 via the arm shaft 12 by driving the swing motor 20. In this manner, the swing arm 14 is configured to be rotatable around the arm shaft 12.

FIG. 2 is a cross-sectional view of the polishing head. As shown in FIG. 2, the polishing head PH includes a head main body 49. The head main body 49 includes a circular flange portion 53 connected to the head shaft 16, a retaining-ring mechanism 57 arranged to surround the wafer W, a retaining-ring pressing structure 56 arranged between the flange portion 53 and the retaining-ring mechanism 57, and an actuator support portion 52.

The flange portion 53, the retaining-ring mechanism 57, and the retaining-ring pressing structure 56 are configured to rotate integrally with a rotation of the head shaft 16. The retaining-ring mechanism 57 is configured to be movable up and down independently of the flange portion 53 by an operation of the retaining-ring pressing structure 56.

The retaining-ring mechanism 57 includes a drive ring 57a arranged below the retaining-ring pressing structure 56, and a retaining-ring 57b held by the drive ring 57a. The retaining-ring 57b is capable of contacting the polishing surface 1a of the polishing pad 1. The retaining-ring 57b is arranged so as to surround a peripheral portion of the wafer W, and prevents the wafer W from jumping out of the polishing head PH during polishing of the wafer W.

The retaining-ring pressing structure 56 includes an annular rolling diaphragm 56a and an accommodating ring 56b that accommodates the rolling diaphragm 56a. The rolling diaphragm 56a has a retaining-ring pressure chamber SP2 formed therein.

The retaining-ring pressure chamber SP2 communicates with a fluid line 60B. A fluid (e.g., air) is supplied to the retaining-ring pressure chamber SP2 through the fluid line 60B. When a pressurized fluid is supplied to the retaining-ring pressure chamber SP2, the rolling diaphragm 56a presses down the retaining-ring mechanism 57, pressing the retaining ring 57b against the polishing surface 1a of the polishing pad 1.

By forming a negative pressure in the retaining-ring pressure chamber SP2, the rolling diaphragm 56a lifts an entire retaining-ring mechanism 57. The retaining-ring pressure chamber SP2 is also connected to an atmosphere opening mechanism (not shown), so that the retaining-ring pressure chamber SP2 can be opened to the atmosphere.

As shown in FIG. 2, the polishing head PH includes a plurality of pressing actuators 50A that independently press specific portions of the wafer W, an actuator operation controller 55 that controls an operation of each pressing actuator 50A, and an elastic holder 58 that holds the actuator support portion 52.

The actuator support portion 52 is configured to support a plurality of pressure actuators 50 A. The actuator support portion 52 has a plate shape extending parallel to the flange portion 53, and is arranged in a space surrounded by the flange portion 53, the retaining-ring pressing structure 56, and the retaining-ring mechanism 57.

The pressure actuators 50A are supported on a lower surface of the actuator support portion 52, and are arranged along a radial direction and a circumferential direction of the actuator support portion 52. The polishing head PH including the pressure actuators 50A can eliminate film thickness variations in the radial and circumferential directions of the wafer W.

The pressure actuators 50A have the same structure. The pressure actuators 50A are configured to be able to press a plurality of regions of the wafer W against the polishing surface 1a with different pressure forces. In this embodiment, each pressure actuator 50A includes a piezoelectric element that applies a pressure force to the wafer W.

The pressing actuator 50A has a pressing surface 50a arranged on a rear side of the wafer W. When the polishing head PH is arranged on the polishing surface 1a of the polishing pad 1, the pressing surface 50a faces the polishing surface 1a.

The polishing head PH includes an actuator holder 59 that holds the pressure actuators 50A. The actuator holder 59 is fixed to a lower surface of the actuator support portion 52, and holds the pressure actuators 50A. A relative distance between the pressure actuators 50A held by the actuator holder 59 is fixed.

The actuator holder 59 is configured to absorb an impact that the pressure actuator 50A receives, and prevent breakdown of the pressure actuator 50A. The actuator holder 59 is made of, for example, a resin (such as PEEK (polyether ether ketone)).

FIGS. 3A to 3D are schematic views showing an example of an arrangement of the pressure actuators. In the example shown in FIG. 3A, the pressure actuators 50A are arranged in a honeycomb or staggered pattern, and the pressure surface 50a of each pressure actuator 50A has a regular hexagonal shape. In the example shown in FIG. 3B, the pressure actuators 50A are arranged in a lattice pattern, and the pressure surface 50a of each pressure actuator 50A has a circular shape.

In an example shown in FIG. 3C, the pressure actuators 50A are arranged concentrically, and the pressure surface 50a of each pressure actuator 50A has a sector shape. In an example shown in FIG. 3D, the pressure actuators 50A are arranged concentrically, and the pressure surface 50a of each pressure actuator 50A has a circular shape and a sector shape.

As shown in FIG. 2, the elastic holder 58 includes a bag-shaped airbag. The elastic holder 58 is made of a thin elastic member (e.g., a flexible rubber material having excellent strength and durability, such as ethylene propylene rubber (EPDM), polyurethane rubber, or silicone rubber). The elastic holder 58 has a thickness of, for example, 0.5 mm to 2.0 mm.

The elastic holder 58 serving as an airbag has an actuator pressure chamber SP1 formed therein. The actuator pressure chamber SP1 communicates with a fluid line 60A. A fluid (e.g., air) is supplied to the actuator pressure chamber SP1 through the fluid line 60A. When the pressurized fluid is supplied to the actuator pressure chamber SP1, the elastic holder 58 expands (deforms).

The flange portion 53 fixed to the head shaft 16 is arranged above the elastic holder 58. Therefore, by supplying the pressurized fluid to the actuator pressure chamber SP1, the elastic holder 58 expands downward (i.e., toward the actuator support portion 52) and presses down the actuator support portion 52. In this manner, the actuator support portion 52 brings the pressing actuators 50A into close proximity with the polishing surface 1a of the polishing pad 1.

The elastic holder 58 can apply a uniform pressing-down force to the actuator support portion 52 by the pressure (base pressure) applied to the actuator pressure chamber SP1. When the elastic holder 58 presses down on the actuator support portion 52, the actuator support portion 52 can press down the pressure actuators 50A uniformly.

According to this embodiment, by applying the base pressure to the actuator pressure chamber SP1 of the elastic holder 58, the elastic holder 58 can press down the pressure actuators 50A together with the actuator support portion 52. Therefore, the pressure actuators 50A can approach the polishing surface 1a without stretching themselves.

The pressure actuator 50A can expand and contract while in close proximity to the polishing surface 1A, thus eliminating the lack of expansion and contraction of the pressure actuator 50A. As a result, the polishing head PH can operate each pressing actuator 50A to accurately control the film thickness profile of the wafer W.

By adjusting the base pressure of the actuator pressure chamber SP1, the pressing actuator 50A can utilize most of its expansion and contraction for the pressing force against the polishing surface 1a of the wafer W. Therefore, the expansion and contraction amount of the pressing actuator 50A can be reduced. As a result, a small pressing actuator having a small maximum stroke amount can be adopted as the pressing actuator 50A.

By adopting a small pressure actuator, it is possible to realize a miniaturized polishing head PH. For example, by adopting a small piezoelectric element as the pressure actuator 50A, it is possible to adjust the amount of expansion and contraction of the stroke in nanometer units at high speed.

As shown in FIG. 2, the polishing apparatus PA includes a power line 33A and a control line 33B connected to the actuator operation controller 55, a power supply source 35 connected to the power line 33A, and a pressure regulator 36 that adjusts the pressure in the actuator pressure chamber SP1 and the pressure in the retaining ring pressure chamber SP2.

The power supply source 35 is configured to supply power through the power line 33A to the actuator operation controller 55. The actuator operation control section 55 is configured to control the power supplied to each pressing actuator 50A.

The actuator operation controller 55 is configured to issue a command through the control line 33B to the pressure regulator 36. The pressure regulator 36 is configured to adjust the pressure of the fluid supplied to each of the actuator pressure chamber SP1 and the retaining-ring pressure chamber SP2 based on the command from the actuator operation controller 55.

As shown in FIG. 1, the rotary joint 32 has a slip ring structure 38 coupled to the power line 33A and the control line 33B. Therefore, even if the head shaft 16 rotates continuously, the power line 33A and the control line 33B can electrically connect the power supply source 35 and the pressure regulator 36 to the actuator operation controller 55 without being twisted.

As shown in FIG. 1, the power line 33A and the control line 33B extend inside the head shaft 16. Similarly, the fluid lines 60A, 60B extend inside the head shaft 16. Each of the fluid lines 60A, 60B extends to the rotary joint 32 and is connected inside the rotary joint 32 to a fluid port (not shown) coupled to the pressure regulator 36. The fluid whose pressure is regulated by the pressure regulator 36 is supplied to the pressure chambers SP1, SP2, respectively, through the fluid port and the fluid lines 60A, 60B.

The polishing apparatus PA includes a control device 10 that controls operations of components (e.g., the polishing table 2, the polishing head PH, the dresser 41, the polishing liquid supply nozzle 3, etc.) of the polishing apparatus PA (see FIG. 1). The control device 10 includes a storage unit 10a that stores a program, and a calculation unit 10b that executes calculations according to instructions included in the program.

The storage unit 10a includes a main storage device such as a RAM, and an auxiliary storage device such as a hard disk drive (HDD), a solid state drive (SSD), etc. An example of the calculation unit 10b includes a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit).

The control device 10 is composed of at least one computer. The computer may be one server or multiple servers. The control device 10 may be an edge server, a cloud server connected to a communication network such as the Internet or a local area network, or a fog computing device (gateway, fog server, router, etc.) installed in the network. The control device 10 may be multiple servers connected by a communication network such as the Internet or a local area network. For example, the control device 10 may be a combination of an edge server and a cloud server.

The control device 10 may be electrically connected to the actuator operation controller 55 and configured to issue commands to the actuator operation controller 55. In this case, the actuator operation controller 55 controls the operation of the power supply source 35 and the operation of the pressure regulator 36 based on commands from the control device 10.

In order to control the operation of each pressure actuator 50 A, it is necessary to connect wiring to each pressure actuator 50A. In particular, in order to control the film thickness profile with higher accuracy, it is necessary to arrange a large number of pressure actuators 50A, and the number of wirings increases according to the number of pressure actuators 50A.

In this case, if these wires are directly connected to the control device 10, the wiring mechanism becomes complicated, which may make it difficult to properly operate the polishing head PH. Therefore, in this embodiment, a large number of wires extending from the pressure actuator 50A are connected to the actuator operation controller 55.

In this embodiment, the actuator operation controller 55 is mounted on the actuator support portion 52 arranged adjacent to the pressure actuator 50A. More specifically, the actuator operation controller 55 is accommodated inside the actuator support portion 52. In one embodiment, the actuator operation controller 55 may be placed on the actuator support portion 52.

With this arrangement, the wirings extending from the pressing actuator 50A can be consolidated in the actuator operation controller 55, and the wirings can be shortened. The actuator operation controller 55 is electrically connected to the control device 10 through the power line 33A and the control line 33B. Therefore, the overall structure of the polishing head PH can be simplified.

As shown in FIG. 2, the polishing head PH includes a pressing force detector 54 that detects a signal (pressing signal) corresponding to the pressing force of each pressing actuator 50A. The number of pressing force detectors 54 corresponds to the number of pressing actuators 50A. Therefore, each pressing force detector 54 can individually detect the pressing signal of each pressing actuator 50A.

The pressing force detector 54 is arranged above the pressing actuator 50A, more specifically, between the actuator support portion 52 and the pressing actuator 50A. The pressing force detector 54 is, for example, a load cell coupled to the pressing actuator 50A.

When the pressing actuator 50A applies a pressing force to the wafer W, the pressing force detector 54 detects, through the pressing actuator 50A, a reaction force from the polishing pad 1 applied to the pressing actuator 50A. The reaction force from the polishing pad 1 corresponds to the pressing force of the pressing actuator 50A.

The actuator operation controller 55 is electrically connected to the pressing force detectors 54. Therefore, when each pressing force detector 54 detects a pressing signal, the pressing force detector 54 sends the pressing signal to the actuator operation controller 55.

The actuator operation controller 55 measures the pressing force of the pressing actuator 50A based on the pressing signals acquired from each pressing force detector 54. In one embodiment, the control device 10 electrically connected to the actuator operation controller 55 may measure the pressing force of the pressing actuator 50A.

As shown in FIG. 2, the polishing head PH includes an elastic cover 51 attached to the actuator support portion 52, which covers all the pressing actuators 50A (and the actuator holder 59).

The elastic cover 51 covers the pressure actuator 50A in a liquid-tight manner, and prevents the polishing liquid from coming into contact with the pressure actuator 50A. The elastic cover 51 is made of a thin elastic member (e.g., a flexible rubber material with excellent strength and durability, such as ethylene propylene rubber (EPDM), polyurethane rubber, or silicone rubber). The elastic cover 51 has a thickness of, for example, 0.5 mm to 2.0 mm.

FIG. 4A is a view showing the polishing head with a vacuum formed inside the elastic cover, and FIG. 4B is a view showing a depression in the elastic cover formed between adjacent pressure actuators.

As shown in FIGS. 4A and 4B, the polishing head PH is configured to hold the wafer W by forming a vacuum inside the elastic cover 51. An internal space V1 of the elastic cover 51 is connected to a vacuum line (not shown). The control device 10 is configured to control the operation of the vacuum line. When the control device 10 forms a vacuum in the internal space V1 of the elastic cover 51, the elastic cover 51 comes into close contact with the pressing surfaces 50a of the pressing actuators 50A.

A lower surface 59a of the actuator holder 59 is arranged above the pressing surface 50a of the pressing actuator 50A. Therefore, by forming the vacuum in the internal space V1, a suction space V2 is formed between the adjacent pressing actuators 50A (see FIG. 4B). In other words, the suction space V2 is a suction cup of the elastic cover 51. Therefore, the polishing head PH can hold the wafer W by forming the suction space V2 of the elastic cover 51.

FIG. 5 is a view showing a polishing flow of the polishing apparatus. When the control device 10 operates the swing motor 20 to rotate the swing arm 14, the polishing head PH moves between a polishing position above the polishing pad 1 and a load/unload position (not shown) outside the polishing pad 1.

The wafer W to be polished is attached to the polishing head PH by a robot hand (not shown) at a load/unload position. At this time, the polishing head PH forms the suction space V2 of the elastic cover 51 to hold the wafer W (see step S101). Thereafter, the polishing head PH moves to the polishing position while holding the wafer W.

The control device 10 is electrically connected to the vertical movement mechanism 5 and the rotation mechanism 6, and is configured to control the operation of the vertical movement mechanism 5 and the operation of the rotation mechanism 6. The control device 10 operates the vertical movement mechanism 5 to press the polishing head PH holding the wafer W against the polishing surface 1a of the polishing pad 1, and in this state, rotates the rotation mechanism 6 and the polishing table 2 to start polishing the wafer W (see step S102).

More specifically, the actuator operation controller 55 applies the base pressure to the actuator pressure chamber SP1 of the elastic holder 58 to press down all of the pressure actuators 50A together with the actuator support portion 52. Thereafter, the actuator operation controller 55 expands and contracts each pressure actuator 50A to correct the stroke error, and then expands and contracts each pressure actuator 50A by the required pressure amount.

When applying a uniform pressing force to the entire wafer W, the actuator operation controller 55 operates the pressure regulator 36 to supply the pressurized fluid to the actuator pressure chamber SP1 of the elastic holder 58.

After applying the base pressure to the actuator pressure chamber SP1 to press down all of the pressing actuators 50A together with the actuator support portions 52, the actuator operation controller 55 operates all of the pressing actuators 50A. Thereafter, the actuator operation controller 55 operates the pressing actuators 50A to apply the pressing force to the wafer W while monitoring the pressing force detectors 54.

When applying the pressing force to the specific portion of the wafer W, the actuator operation controller 55 applies the base pressure to the actuator pressure chamber SP1 to press down all the pressing actuators 50A together with the actuator support portion 52. Thereafter, the actuator operation controller 55 operates the pressing actuator 50A corresponding to the specific portion of the wafer W to apply a pressing force to the wafer W.

As shown in FIG. 1, the polishing apparatus PA includes a film thickness sensor 40 arranged below the polishing table 2. The film thickness sensor 40 is, for example, an optical sensor or an eddy current sensor, and is electrically connected to the control device 10. The control device 10 measures the film thickness of the wafer W based on a signal (film thickness signal) detected by the film thickness sensor 40. For example, the control device 10 determines an end point of polishing the wafer W based on the film thickness of the wafer W.

After starting polishing the wafer W, the control device 10 measures the film thickness of the wafer W by the film thickness sensor 40 during polishing of the wafer W (see step S103). The control device 10 determines whether the film thickness of the wafer W has reached a predetermined target film thickness (i.e., whether a polishing end point has been reached) (see step S104). For example, the control device 10 determines the polishing end point when a difference in film thickness between a thickest portion and a thinnest portion of the wafer W reaches within a predetermined range.

If the film thickness of the wafer W has not reached the predetermined target film thickness (see “NO” in step S104), the control device 10 continues polishing the wafer W. On the other hand, if the film thickness of the wafer W has reached the predetermined target film thickness (see “YES” in step S104), the control device 10 issues a command to the polishing head PH and the polishing table 2 to end polishing the wafer W (see step S105).

In this manner, the control device 10 that executes steps S101 to S105 and the components (e.g., the polishing head PH, the swing arm 14) operated by the control device 10 constitute a polishing system.

In particular, in the polishing system, the control device 10 forms the suction space V2 of the elastic cover 51 between adjacent pressure actuators 50A to suction the wafer W, and transports the wafer W above the polishing surface 1a while the wafer W is adsorbed. Furthermore, the control device 10 supplies the pressurized fluid to the elastic holder 58 to bring the pressure actuators 50A together with the actuator support portion 52 close to the polishing surface 1a, and operates at least one of the pressure actuators 50A through the actuator operation controller 55 to press the wafer W against the polishing surface 1a.

FIG. 6 is a view showing another embodiment of the polishing head. In the embodiment shown in FIG. 6, configurations that are not particularly described are the same as those in the above-described embodiment, so duplicated descriptions will be omitted.

In the embodiment shown in FIG. 6, the elastic holder 58 including a bag-shaped airbag includes a plurality of pressurized chambers arranged concentrically. More specifically, the elastic holder 58 has a plurality of annular peripheral walls 58a, 58b, 58c, 58d, and 58e arranged concentrically.

The peripheral walls 58a to 58e form a plurality of pressure chambers inside the elastic holder 58. More specifically, the elastic holder 58 has a central pressure chamber SP1a arranged in the central portion thereof, an annular pressure chamber SP1b surrounding the central pressure chamber SP1a, an annular pressure chamber SP1c surrounding the annular pressure chamber SP1b, an annular pressure chamber SP1d surrounding the annular pressure chamber SP1c, and an annular pressure chamber SP1e surrounding the annular pressure chamber SP1d.

In this embodiment, the elastic holder 58 includes an integrally configured airbag having the pressure chambers SP1a to SP1e, but in one embodiment, the elastic holder 58 may include a plurality of airbags each having a respective one of the pressure chambers SP1a to SP1e.

The central pressure chamber SP1a communicates with a first fluid line 60Aa, the annular pressure chamber SP1b communicates with a second fluid line 60Ab, the annular pressure chamber SP1c communicates with a third fluid line 60Ac, the annular pressure chamber SP1d communicates with a fourth fluid line 60Ad, and the annular pressure chamber SP1e communicates with a fifth fluid line 60Ae.

The first fluid line 60Aa to the fifth fluid line 60Ae are connected to the pressure regulator 36. Therefore, the actuator operation controller 55 can operate the pressure regulator 36 to independently control pressures of the pressure chambers SP1a to SP1e through the first fluid line 60Aa to the fifth fluid line 60Ae, respectively.

As shown in FIG. 6, the actuator support portion 52 includes a plurality of divided bodies 52a, 52b, 52c, 52d, and 52e. The number of divided bodies of the actuator support portion 52 corresponds to the number of pressure chambers of the elastic holder 58.

The divided bodies 52a to 52e are arranged below the pressure chambers SP1a to SP1e, respectively. The actuator operation controller 55 can individually press down the divided bodies 52a to 52e by adjusting the pressure in each of the pressure chambers SP1a to SP1e.

Also in the embodiment shown in FIG. 6, the actuator operation controller 55 is also mounted on the actuator support portion 52. More specifically, the actuator operation controller 55 has a control board 55A mounted on each of the divided bodies 52a to 52e. These control boards 55A are electrically connected to each other. In this embodiment, the control board 55A is mounted on all of the divided bodies 52a to 52e, but it may be mounted on at least one of the divided bodies.

According to this embodiment, the actuator operation controller 55 can change a pressing-down force of the actuator support portion 52 according to the radial direction of the actuator support portion 52 (in other words, the radial direction of the wafer W).

With this configuration, even if the film thickness profile before polishing of the wafer W is not uniform in the radial direction of the wafer W (for example, when the pressing force of the pressing actuator 50A must be changed in the radial direction of the wafer W), each pressing actuator 50A can approach the polishing surface 1a together with the divided body. Therefore, the actuator operation controller 55 can apply a sufficient pressing force of the pressing actuator 50A to the wafer W in the radial direction of the wafer W.

For example, when the film thickness profile of the wafer W before polishing is such that the film thickness is thin at the center of the wafer W and thick at the peripheral portion of the wafer W, the actuator operation controller 55 increases the pressure in the pressure chamber SP1e of the elastic holder 58 corresponding to the peripheral portion of the wafer W. As a result, the elastic holder 58 presses down the pressing actuator 50A arranged below the divided body 52e together with the divided body 52e.

FIG. 7 is a view showing another embodiment of the polishing head. In the embodiment shown in FIG. 7, configurations that are not particularly described are the same as those in the above-described embodiment, so duplicated descriptions will be omitted.

As shown in FIG. 7, the elastic holder 58 includes an elastic sheet made of a sheet-like elastic material fixed to the head main body 49 (in this embodiment, the flange portion 53). In the embodiment shown in FIG. 7, the head main body 49 has an actuator pressure chamber SP3 formed between the elastic holder 58 as an elastic sheet and the flange portion 53. In one embodiment, the elastic holder 58 as the elastic sheet may be fixed to the accommodating ring 56b and/or the drive ring 57a.

Also in the embodiment shown in FIG. 7, the actuator operation controller 55 is also mounted on the head main body 49. More specifically, the actuator operation controller 55 is not mounted on the actuator support portion 52, but is arranged in the actuator pressure chamber SP3 of the head main body 49.

According to this embodiment, the elastic holder 58 as the elastic sheet has excellent elasticity and is highly resilient to external forces. Therefore, the elastic holder 58 can improve a restoring force of the actuator support portion 52 held by the elastic holder 58.

In particular, the elastic holder 58 has a high restoring force against the twisting of the elastic holder 58. Therefore, even if a frictional force occurs between the wafer W and the polishing surface 1a when the polishing head PH presses the wafer W against the polishing surface 1a, the elastic holder 58 can prevent the pressing actuators 50A from moving downstream in the rotation direction of the polishing pad 1 due to the frictional force.

In this manner, in this embodiment, when the pressure actuator 50A presses the wafer W, the polishing head PH can reduce a positional deviation of the pressure actuator 50A caused by frictional force.

Furthermore, according to this embodiment, the head main body 49 can form the actuator pressure chamber SP3 by one sheet-like elastic holder 58. The polishing head PH having the actuator pressure chamber SP3 formed by such a simple structure can reduce its cost.

FIG. 8 is a view showing another embodiment of the polishing head. FIG. 9 is a cross-sectional view taken along line A-A in FIG. 8. In the embodiment shown in FIGS. 8 and 9, configurations that are not particularly described are the same as those in the above-described embodiment, and therefore redundant description thereof will be omitted. In FIG. 9, the actuator operation controller 55 is omitted from illustration.

In this embodiment, the polishing head PH includes a linear guide member 81 that restricts the movement direction of the actuator support portion 52 to a direction along a pressing direction of the pressing actuator 50A (i.e., the up-and-down movement direction of the polishing head PH, the vertical direction).

The linear guide member 81 is a rod-shaped protrusion that protrudes toward the inner periphery of the polishing head PH (that is, from the head main body 49 toward the actuator support portion 52) and extends in the pressing direction of the pressing actuator 50A.

The linear guide member 81 is attached to the head main body 49. The actuator support portion 52 has a recess 80 in which the linear guide member 81 is attached (see FIG. 9). The recess 80 is formed on an outer circumferential surface of the actuator support portion 52, and like the linear guide member 81, extends in the pressing direction of the pressing actuator 50A.

In the embodiment shown in FIG. 9, the linear guide members 81 are arranged at equal intervals along the circumferential direction of the polishing head PH. The number of recesses 80 corresponds to the number of linear guide members 81. In one embodiment, the number of linear guide members 81 is not limited to this embodiment as long as it can regulate the moving direction of the actuator support portion 52. At least two linear guide members 81 may be arranged.

According to this embodiment, the linear guide member 81 is configured to prevent the actuator support portion 52 from tilting when the actuator support portion 52 is pressed down. For example, when the specific portion of the wafer W is locally pressed, the actuator support portion 52 may be tilted as a whole due to the pressing force applied to the specific portion of the wafer W. In this case, due to the tilt of the actuator support portion 52, the pressing actuator 50A may not be able to press the wafer W with the necessary pressing force.

In the embodiments shown in FIGS. 8 and 9, the linear guide member 81 can prevent tilting of the actuator support portion 52. Therefore, even when locally pressing a specific portion of the wafer W, the pressing actuator 50A can reliably press the specific portion of the wafer W with the required pressing force.

Furthermore, the linear guide member 81 is configured to prevent rotation of the actuator support portion 52 during polishing of the wafer W. More specifically, the linear guide member 81 can prevent the pressing actuators 50A from moving downstream in the rotation direction of the polishing pad 1 due to the frictional force generated when the polishing head PH presses the wafer W against the polishing surface 1a. Therefore, when the pressing actuator 50A presses the wafer W, the polishing head PH can reduce a positional deviation of the pressing actuator 50A caused by the frictional force.

In the above-described embodiment, a plurality of embodiments of the polishing head PH have been described, but these embodiments may be appropriately combined. In the embodiment described with reference to FIGS. 1 to 5, the actuator support portion 52 is entirely held by a single clastic holder 58. Therefore, by supplying the pressurized fluid to the elastic holder 58, a uniform base pressure can be uniformly applied to all the pressing actuators 50A via the actuator support portion 52.

In the embodiment described with reference to FIG. 6, each of the elastic holder 58 and the actuator support portion 52 is divided concentrically. Thus, the elastic holder 58 can apply the base pressure to a particular pressure actuator 50A even when there is a large variation in the film thickness profile of the wafer W, especially in the radial direction of the wafer W.

In the embodiment described with reference to FIG. 7, the polishing head PH has a simple structure. Therefore, a cost of the polishing head PH can be reduced. Furthermore, the elastic holder 58 as an elastic sheet can prevent the rotation of the pressing actuators 50A around the actuator support portion 52 due to its high restoring force.

In the embodiment described with reference to FIGS. 8 and 9, the polishing head PH can regulate (limit) the moving direction of the actuator support portion 52. Therefore, the pressure actuator 50A can reliably press the specific portion of the wafer W with the required pressing force, even when pressing the specific portion of the wafer W locally.

In the above-described embodiment, the polishing head PH includes the elastic cover 51 that covers the pressing actuators 50A, but as long as all pressing actuators 50A have a structure that is liquid-resistant, the polishing head PH does not necessarily have to include the elastic cover 51.

In the embodiment described above, the polishing head PH includes the actuator support portion 52 on which the actuator operation controller 55 is mounted, but the actuator operation controller 55 does not necessarily have to be mounted on the actuator support portion 52. In one embodiment, the operation of the components of the polishing head PH may be controlled by the control device 10.

FIGS. 10 to 13 are views showing other embodiments of the polishing head. In the embodiment shown in FIG. 10, the polishing head PH has basically the same structure as the polishing head PH described with reference to FIG. 2, but the actuator operation controller 55 is not mounted on the actuator support portion 52 but on the flange portion 53 of the head main body 49.

The actuator operation controller 55 is electrically connected to the pressure actuators 50A through a large number of wirings 90. The wirings 90 pass through a space (i.e., a space between the flange portion 53 and the actuator support portion 52) outside the elastic holder 58.

In the embodiment shown in FIG. 11, the polishing head PH has basically the same structure as the polishing head PH described with reference to FIG. 6, but the actuator operation controller 55 includes the control boards 55A mounted on the flange portion 53. Each control substrate 55A is electrically connected to a plurality of pressure actuators 50A through a large number of wires 90.

In the embodiment shown in FIG. 12, the polishing head PH has basically the same structure as the polishing head PH described with reference to FIG. 7, but the actuator operation controller 55 is not arranged in the actuator pressure chamber SP3 but is mounted on the flange portion 53. The actuator operation controller 55 is electrically connected to the pressure actuators 50A through a large number of wires 90. The wire 90 penetrates the actuator pressure chamber SP3.

In the embodiment shown in FIG. 13, the polishing head PH has basically the same structure as the polishing head PH described with reference to FIG. 8, but the actuator operation controller 55 is not mounted on the actuator support portion 52, but on the flange portion 53. The actuator operation controller 55 is electrically connected to the pressure actuators 50A through a large number of wires 90. The wiring 90 penetrates the outer space of the elastic holder 58.

As described with reference to the above-described embodiments, the actuator operation controller 55 may be mounted on the actuator support portion 52 (see FIGS. 1 to 6, 8, and 9), may be mounted in the space between the elastic holder 58 and the flange portion 53 (i.e., the actuator pressure chamber SP3) (see FIG. 7), or may be mounted on the flange portion 53 (see FIGS. 10 to 13).

By mounting the actuator operation controller 55 on the actuator support portion 52, the actuator operation controller 55 is arranged adjacent to the pressure actuator 50A. This arrangement can shorten the wires 90 and improve maintenance efficiency.

By mounting the actuator operation controller 55 on the head main body 49 (e.g., the flange portion 53) other than the actuator support portion 52, the actuator operation controller 55 is arranged away from the pressing surface 50a of the pressing actuator 50A. With this arrangement, the actuator operation controller 55 is less susceptible to the effects of heat and vibrations generated by pressing the wafer W against the polishing surface 1a.

The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.

POLISHING HEAD AND POLISHING SYSTEM

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

International Classifications

Abstract

Description

Claims

Priority Claims (1)