阅读说明：本技术 研磨方法及研磨装置 (Polishing method and polishing apparatus ) 是由 石井遊 户川哲二 吉田笃史 于 2020-10-23 设计创作，主要内容包括：本发明提供能够正确确定基板的研磨终点的研磨方法及研磨装置。本方法为,使支承研磨垫(2)的研磨台(3)旋转,由研磨头(10)将基板(W)向研磨垫(2)的研磨面(2a)按压而对基板(W)进行研磨,对基板(W)进行研磨的工序包括一面使研磨头(10)沿着研磨面(2a)摆动一面对基板(W)进行研磨的摆动研磨工序,和在使研磨头(10)的摆动停止的状态下对基板(W)进行研磨的静止研磨工序,静止研磨工序在摆动研磨工序后进行,静止研磨工序包括确定静止研磨终点的工序,该静止研磨终点是用来使研磨台(3)旋转的转矩的变化的比例达到变化比例阈值的时间点。(The invention provides a polishing method and a polishing apparatus capable of accurately determining a polishing end point of a substrate. The method is characterized in that a polishing table (3) supporting a polishing pad (2) is rotated, a substrate (W) is pressed against a polishing surface (2a) of the polishing pad (2) by a polishing head (10) to polish the substrate (W), the step of polishing the substrate (W) includes a swing polishing step of polishing the substrate (W) while swinging the polishing head (10) along the polishing surface (2a), and a stationary polishing step of polishing the substrate (W) in a state in which the swinging of the polishing head (10) is stopped, the stationary polishing step is performed after the swing polishing step, and the stationary polishing step includes a step of determining a stationary polishing end point, which is a time point at which a change ratio of a torque for rotating the polishing table (3) reaches a change ratio threshold value.)

1. A method of polishing a substrate,

the polishing table supporting the polishing pad is rotated,

the substrate is pressed against the polishing surface of the polishing pad by a polishing head to polish the substrate,

the step of polishing the substrate includes:

a swing polishing step of polishing the substrate while swinging the polishing head along the polishing surface; and

a stationary polishing step of polishing the substrate while stopping the oscillation of the polishing head,

the stationary polishing step is performed after the swing polishing step,

the static polishing step includes a step of determining a static polishing end point, which is a time point at which a change rate of the torque for rotating the polishing table reaches a change rate threshold value.

2. The method of polishing a substrate according to claim 1, wherein the step of polishing the substrate includes a swing stop operation of stopping the swing of the polishing head after the torque reaches a preset torque threshold or after a preset swing polishing time elapses for a current polishing time.

3. The method of polishing a substrate according to claim 2, wherein the oscillation stopping operation includes an operation of stopping oscillation of the polishing head when the polishing head is at a predetermined stop position above the polishing table.

4. A method of polishing a substrate according to any one of claims 1 to 3, wherein the step of determining the stationary polishing end point is a step of determining the stationary polishing end point as a time point at which the change rate decreases and reaches the change rate threshold value.

5. A method of polishing a substrate according to any one of claims 1 to 3, wherein the step of determining the stationary polishing end point is a step of determining the stationary polishing end point as a time point at which the rate of change increases and reaches the change rate threshold value.

6. A method of polishing a substrate according to any one of claims 1 to 3, wherein the step of polishing the substrate further comprises a finish polishing step performed after the stationary polishing step,

the finish grinding process includes a process of determining a finish grinding end point, which is a point of time when a finish grinding time determined from the stationary grinding end point has elapsed.

7. The method of claim 6, wherein the finish polishing step includes a step of polishing the substrate while swinging the polishing head along the polishing surface.

8. A method of polishing a substrate as recited in any of claims 1-3, wherein the polishing head is on the axis of the polishing table during the oscillation of the polishing head.

9. A method of polishing a substrate,

the polishing table supporting the polishing pad is rotated,

polishing the substrate by pressing the substrate against the polishing surface of the polishing pad with the polishing head while swinging the polishing head along the polishing surface,

a process of polishing the substrate, comprising:

measuring a torque for rotating the polishing table while polishing the substrate;

determining a plurality of representative values of the torque based on the plurality of measured values of the torque;

generating a relational expression indicating a relationship between a plurality of representative values of the torque and the polishing time; and

and a step of determining a first polishing end point, which is a point of time at which the predicted value of the torque calculated based on the relational expression reaches a torque threshold value.

10. The method of claim 9, wherein the plurality of representative values of the torque are a plurality of minimum values of the torque, a plurality of maximum values of the torque, or a plurality of moving averages of the torque.

11. A method of polishing a substrate according to claim 9 or 10, wherein the step of polishing the substrate includes a step of determining a second polishing end point, which is a point in time when a finish polishing time determined based on the first polishing end point has elapsed.

12. A method of polishing a substrate as recited in claim 9 or 10, wherein the polishing head is on the axis of the polishing table during the oscillation of the polishing head.

13. A polishing apparatus for polishing a substrate, comprising:

a polishing table supporting a polishing pad;

a polishing table motor that rotates the polishing table;

a torque measuring device for measuring a torque for rotating the polishing table;

a polishing head for pressing a substrate against a polishing surface of the polishing pad to polish the substrate;

a polishing head swing arm connected to the polishing head;

a swing motor connected to the polishing head swing arm and configured to swing the polishing head along the polishing surface; and

an operation control unit for controlling the operation of the polishing apparatus,

the operation control unit is configured to:

causing the polishing apparatus to perform a swing polishing step of polishing the substrate while rotating the polishing table and swinging the polishing head along the polishing surface,

after the swing polishing step, causing the polishing apparatus to perform a stationary polishing step of polishing the substrate while stopping the swing of the polishing head while rotating the polishing table,

in the static polishing step, a static polishing end point is determined, and the static polishing end point is a time point when a change rate of the torque for rotating the polishing table reaches a change rate threshold value.

14. The polishing apparatus as set forth in claim 13, wherein the operation control unit is configured to instruct the swing motor to stop the swing of the polishing head after the torque reaches a preset torque threshold or after a preset swing polishing time elapses from a current polishing time.

15. The polishing apparatus as recited in claim 14, wherein the operation control unit is configured to instruct the swing motor to stop the swing of the polishing head when the polishing head is at a predetermined stop position above the polishing table.

16. The polishing apparatus according to any one of claims 13 to 15, wherein the operation control section is configured to,

after the stationary polishing step, causing the polishing apparatus to perform a finish polishing step of polishing the substrate while rotating the polishing table,

in the finish polishing step, a finish polishing end point is determined, and the finish polishing end point is a time point when a finish polishing time determined from the stationary polishing end point has elapsed.

17. The polishing apparatus as recited in any one of claims 13 to 15, wherein the polishing head is disposed on an axis of the polishing table.

18. A polishing apparatus is characterized by comprising:

a polishing table supporting a polishing pad;

a polishing table motor that rotates the polishing table;

a torque measuring device for measuring a torque for rotating the polishing table;

a polishing head for pressing the substrate against a polishing surface of the polishing pad;

a polishing head swing arm connected to the polishing head;

a swing motor connected to the polishing head swing arm and configured to swing the polishing head along the polishing surface; and

an operation control part for controlling the operation of the motor,

the operation control unit is configured to acquire a plurality of measured values of the torque from the torque measurement device, specify a plurality of representative values of the torque based on the plurality of measured values of the torque, generate a relational expression indicating a relationship between the plurality of representative values of the torque and a polishing time, and specify a first polishing end point at which a predicted value of the torque calculated based on the relational expression reaches a torque threshold value.

19. The abrading apparatus of claim 18, wherein the plurality of representative values of the torque are a plurality of minimum values of the torque, a plurality of maximum values of the torque, or a plurality of moving averages of the torque.

20. The polishing apparatus according to claim 18 or 19, wherein the operation control unit is configured to determine a second polishing end point, which is a time point when a finish polishing time determined from the first polishing end point has elapsed.

21. The polishing apparatus of claim 18 or 19, wherein the polishing head is on an axis of the polishing table.

Technical Field

The present invention relates to a polishing method and a polishing apparatus for polishing a substrate such as a wafer, and more particularly to a method and an apparatus for polishing a substrate by pressing the substrate against a polishing pad on a polishing table by a polishing head while swinging the polishing head.

Background

In recent years, with the high integration and high density of semiconductor devices, the wiring of circuits has become finer and the number of layers of multilayer wiring has increased. When a multilayer wiring is to be realized while the miniaturization of a circuit is required, the step is made larger in accordance with the surface unevenness of the lower layer, and thus, as the number of wiring layers increases, the film coverage (step coverage (japanese: ステップカバレッジ)) for the step shape in the thin film formation is deteriorated. Therefore, in order to perform multilayer wiring, it is necessary to improve the step coverage and perform planarization processing in an appropriate process. Further, since the depth of focus is reduced along with the miniaturization of photolithography, it is necessary to planarize the surface of the semiconductor device so as to reduce the difference in height between the irregularities on the surface of the semiconductor device to the depth of focus or less.

Therefore, in the manufacturing process of semiconductor devices, planarization of the surface of the semiconductor device becomes increasingly important. The most important technique in the planarization of this surface is Chemical Mechanical Polishing (CMP). This chemical mechanical polishing (hereinafter referred to as CMP) is performed by supplying a polishing liquid containing abrasive grains such as silica (SiO2) onto a polishing surface of a polishing pad and bringing a substrate such as a wafer into sliding contact with the polishing surface. As a substrate to be polished, there are not only a circular substrate such as a wafer but also a rectangular substrate such as a Printed Circuit Board (PCB) having an insulator or a wiring on a surface thereof.

A polishing apparatus for performing CMP includes a polishing table for supporting a polishing pad having a polishing surface, and a polishing head for holding a substrate. Such a polishing apparatus is configured such that a polishing table and a polishing head are relatively moved, and a substrate is pressed against a polishing surface of the polishing pad by the polishing head while supplying a polishing liquid such as slurry onto the polishing surface of the polishing pad. The surface of the substrate is in sliding contact with the polishing surface in the presence of the polishing liquid, and the surface of the substrate is polished flat and mirror-finished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid.

The substrate such as a wafer has a laminated structure made of different materials such as a semiconductor, a conductor, and an insulator. The frictional force acting between the substrate and the polishing pad changes depending on the material of the surface to be polished of the substrate. As a method for determining the polishing end point, there has been a method for detecting a change in frictional force caused by a transition of a material of a surface to be polished of a substrate to a different material, and determining the polishing end point based on a time point at which the frictional force has changed. Since the frictional force acts at a position away from the rotation center (axial center) of the polishing table, a change in the frictional force can be detected as a change in torque for rotating the polishing table. In the case where the member for rotationally driving the polishing table is a motor, the torque may be measured as a current flowing through the motor.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 8-197417

Patent document 2: japanese patent laid-open No. 2008-110471

Problems to be solved by the invention

In the polishing apparatus, the substrate may be polished while the polishing head is oscillated (reciprocated) along the polishing surface of the polishing pad, from the viewpoint of improving polishing performance, productivity, and the like. Fig. 9 is a diagram showing changes in torque for rotating the polishing table when polishing a substrate without swinging the polishing head. In the example shown in fig. 9, as the polishing of the substrate progresses, the torque for rotating the polishing table gradually decreases, and the torque becomes constant from around 80 seconds (point a in the figure). This indicates that the material of the surface to be polished changed in the vicinity of 80 seconds. Therefore, the polishing end point can be determined from the point of time (point a of the graph) at which the torque becomes constant.

Fig. 10 is a diagram showing changes in torque for rotating the polishing table when polishing a substrate similar to the substrate of fig. 9 while swinging the polishing head along the polishing surface of the polishing pad. When the polishing head is oscillated along the polishing surface of the polishing pad, the position on the polishing pad where the frictional force acts changes. The torque required to rotate the polishing table at a constant speed varies depending on the distance from the axial center of the polishing table to the position where the frictional force acts (the position of the polishing head). Therefore, as shown in fig. 10, when the polishing head is oscillated during the polishing of the substrate, the torque may be greatly changed, and the polishing end point may not be accurately determined.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a polishing method and a polishing apparatus capable of accurately determining a polishing end point of a substrate including a step of oscillating a polishing head along a polishing surface of a polishing pad.

Means for solving the problems

In one mode, there is provided a method of polishing a substrate, wherein the step of polishing the substrate by rotating a polishing table supporting a polishing pad and pressing the substrate against a polishing surface of the polishing pad by a polishing head includes: a swing polishing step of polishing the substrate while swinging the polishing head along the polishing surface; and a stationary polishing step of polishing the substrate while stopping the oscillation of the polishing head, the stationary polishing step being performed after the oscillation polishing step, the stationary polishing step including a step of determining a stationary polishing end point, which is a time point at which a change rate of a torque for rotating the polishing table reaches a change rate threshold value.

In one mode, the step of polishing the substrate includes a swing stop operation of stopping the swing of the polishing head after the torque reaches a preset torque threshold or after a preset swing polishing time elapses for a current polishing time.

In one mode, the oscillation stopping operation includes an operation of stopping oscillation of the polishing head when the polishing head is at a predetermined stop position above the polishing table.

In one mode, the step of determining the stationary polishing end point is a step of determining the stationary polishing end point as a time point when the rate of change decreases and reaches the change rate threshold value.

In one mode, the step of determining the stationary polishing end point is a step of determining the stationary polishing end point as a time point when the rate of change increases and reaches the change rate threshold value.

In one mode, the step of polishing the substrate further includes a finish polishing step performed after the stationary polishing step, and the finish polishing step includes a step of determining a finish polishing end point, which is a point in time when a finish polishing time determined based on the stationary polishing end point has elapsed.

In one mode, the finish polishing step includes a step of polishing the substrate while swinging the polishing head along the polishing surface.

In one mode, the polishing head is on an axis of the polishing table during the oscillation of the polishing head.

In one mode, there is provided a method of polishing a substrate by rotating a polishing table supporting a polishing pad and polishing the substrate by pressing the substrate against a polishing surface of the polishing pad by a polishing head while swinging the polishing head along the polishing surface, the method including: measuring a torque for rotating the polishing table while polishing the substrate; determining a plurality of representative values of the torque based on the plurality of measured values of the torque; generating a relational expression indicating a relationship between a plurality of representative values of the torque and the polishing time; and determining a first polishing end point, which is a point of time at which the predicted value of the torque calculated based on the relational expression reaches a torque threshold value.

In one mode, the representative values of the torques are minimum values of the torques, maximum values of the torques, or moving average values of the torques.

In one mode, the step of polishing the substrate includes a step of determining a second polishing end point, which is a point in time when a finish polishing time determined based on the first polishing end point has elapsed.

In one mode, the polishing head is on an axis of the polishing table during the oscillation of the polishing head.

In one mode, there is provided a polishing apparatus for polishing a substrate, including: a polishing table supporting a polishing pad; a polishing table motor that rotates the polishing table; a torque measuring device for measuring a torque for rotating the polishing table; a polishing head for pressing a substrate against a polishing surface of the polishing pad to polish the substrate; a polishing head swing arm connected to the polishing head; a swing motor connected to the polishing head swing arm and configured to swing the polishing head along the polishing surface; and an operation control unit that controls an operation of the polishing apparatus, the operation control unit being configured to: and a swing polishing step of rotating the polishing table and swinging the polishing head along the polishing surface to polish the substrate, wherein after the swing polishing step, the polishing apparatus is caused to perform a stationary polishing step of rotating the polishing table and polishing the substrate while stopping the swinging of the polishing head, and wherein a stationary polishing end point is determined in the stationary polishing step, the stationary polishing end point being a time point at which a change ratio of a torque for rotating the polishing table reaches a change ratio threshold value.

In one mode, the operation control unit is configured to instruct the swing motor to stop the swing of the polishing head after the torque reaches a preset torque threshold or after a preset swing polishing time elapses from a current polishing time.

In one mode, the operation control unit is configured to instruct the swing motor to stop the swing of the polishing head when the polishing head is at a predetermined stop position above the polishing table.

In one mode, the operation control unit is configured to cause the polishing apparatus to perform a finish polishing step of polishing the substrate while rotating the polishing table after the stationary polishing step, and to specify a finish polishing end point at a time point when a finish polishing time specified based on the stationary polishing end point has elapsed in the finish polishing step.

In one mode, the abrading head is on an axis of the abrading table.

In one mode, there is provided a polishing apparatus including: a polishing table supporting a polishing pad; a polishing table motor that rotates the polishing table; a torque measuring device for measuring a torque for rotating the polishing table; a polishing head for pressing the substrate against a polishing surface of the polishing pad; a polishing head swing arm connected to the polishing head; a swing motor connected to the polishing head swing arm and configured to swing the polishing head along the polishing surface; and an operation control unit configured to acquire a plurality of measurement values of the torque from the torque measurement device, determine a plurality of representative values of the torque based on the plurality of measurement values of the torque, generate a relational expression indicating a relationship between the plurality of representative values of the torque and a polishing time, and determine a first polishing end point at which a predicted value of the torque calculated based on the relational expression reaches a torque threshold value.

In one mode, the representative values of the torques are minimum values of the torques, maximum values of the torques, or moving average values of the torques.

In one mode, the operation control unit is configured to determine a second polishing end point at which the finish polishing time determined based on the first polishing end point has elapsed.

In one mode, the abrading head is on an axis of the abrading table.

Effects of the invention

According to the present invention, the polishing apparatus polishes the substrate while swinging the polishing head, and then stops swinging of the polishing head, and determines the stationary polishing end point which is a point of time when the rate of change of the torque used to rotate the polishing table reaches the change rate threshold while the substrate is polished while the swinging of the polishing head is stopped.

The polishing apparatus calculates a predicted value of the torque from a plurality of measured values of the torque, and determines a first polishing end point, which is a point of time when the predicted value reaches a torque threshold value, based on the predicted value.

As a result, the polishing end point can be correctly determined based on the stationary polishing end point or the first polishing end point.

Drawings

Fig. 1 is a schematic view showing one embodiment of a polishing apparatus.

Fig. 2 is a sectional view showing the polishing head shown in fig. 1.

Fig. 3 is a view of a state in which the polishing head is swung along the polishing surface as viewed from above.

Fig. 4 is a flowchart showing an embodiment of a method for polishing a substrate and a method for determining a polishing end point of the substrate.

Fig. 5 is a flowchart showing an embodiment of a method for polishing a substrate and a method for determining a polishing end point of the substrate.

Fig. 6 is a diagram showing an example of a change in torque for rotating the polishing table in steps 1-1 to 1-12.

Fig. 7 is a flowchart showing another embodiment of a method for polishing a substrate and a method for determining a polishing end point of the substrate.

Fig. 8 is a diagram showing a relationship between a torque for rotating the polishing table and the first polishing end point.

Fig. 9 is a diagram showing changes in torque for rotating the polishing table when the substrate is polished without swinging the polishing head.

Fig. 10 is a diagram showing changes in torque for rotating the polishing table when a substrate similar to the substrate of fig. 9 is polished while swinging the polishing head along the polishing surface of the polishing pad.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a schematic view showing one embodiment of a polishing apparatus. The polishing apparatus 1 shown in fig. 1 is suitably used as a polishing apparatus for polishing a rectangular substrate.

As shown in fig. 1, the polishing apparatus 1 includes: a polishing head 10 for holding and rotating the substrate W, a polishing table 3 for supporting the polishing pad 2, a polishing table motor 8 for rotating the polishing table 3, a polishing head swing arm 16 connected to an upper end of the support shaft 14, a polishing head shaft 12 attached to a free end of the polishing head swing arm 16, and an operation control unit 7 for controlling operations of the respective components of the polishing apparatus 1. The polishing head swing arm 16 is disposed above the polishing table 3 and is disposed parallel to the polishing surface 2a of the polishing pad 2. The substrate W of the present embodiment is a substrate having a quadrangular shape such as a Printed Circuit Board (PCB) having an insulator or wiring formed on the surface thereof, and the polishing head 10 has a quadrangular shape. In one embodiment, the substrate W may be a circular wafer, and the polishing head 10 may have a circular shape. The polishing head 10 is coupled to a lower end of the polishing head shaft 12, and is configured to be capable of holding the substrate W on a lower surface thereof by vacuum suction. The polishing head swing arm 16 is connected to the polishing head 10 via the polishing head shaft 12, and the polishing head 10 is supported by the polishing head swing arm 16.

The operation control unit 7 is constituted by at least one computer. The operation control unit 7 includes a storage device 7a storing a program, and an arithmetic device 7b performing arithmetic operations in accordance with commands included in the program. The arithmetic device 7b includes a CPU (central processing unit) or a GPU (graphics processing unit) or the like that performs arithmetic operations in accordance with commands included in the program stored in the storage device 7 a. The storage device 7a includes a main storage device (e.g., a random access memory) capable of accessing the arithmetic device 7b, and an auxiliary storage device (e.g., a hard disk drive or a solid-state drive) storing data and programs.

The polishing apparatus 1 further includes a polishing head rotation motor 13 connected to the polishing head shaft 12. In the present embodiment, the polishing head rotation motor 13 is disposed inside the polishing head swing arm 16, but in one embodiment, the polishing head rotation motor 13 may be disposed outside the polishing head swing arm 16. Specifically, the polishing head rotation motor 13 may be disposed above the polishing head swing arm 16, and the rotation shaft of the polishing head rotation motor 13 may extend through the polishing head swing arm 16 and be connected to the polishing head shaft 12.

The polishing head shaft 12 is configured to be rotatable by a polishing head rotation motor 13. By this rotation of the polishing head shaft 12, the polishing head 10 rotates about the polishing head shaft 12 in the direction indicated by the arrow in the figure. The polishing head shaft 12 is connected to an elevator, not shown. The polishing head 10 is raised and lowered by a polishing head shaft 12 by a lifting device.

The polishing apparatus 1 further includes a swing motor 15 connected to the polishing head swing arm 16. In the present embodiment, the swing motor 15 is disposed inside the support shaft 14. The polishing head swing arm 16 is configured to be rotatable about the support shaft 14 by a swing motor 15. The polishing head 10 moves between a receiving position of the substrate W, not shown, and an upper position of the polishing table 3 by the turning of the polishing head swing arm 16. In one embodiment, the polishing head swing arm 16 may be fixed to the support shaft 14, and the swing motor 15 may be connected to the support shaft 14.

The polishing pad 2 is attached to the upper surface of the polishing table 3, and the polishing pad 2 and the polishing table 3 are configured to rotate integrally. The upper surface of the polishing pad 2 constitutes a polishing surface 2a for polishing the substrate W. The polishing table 3 is connected to a polishing table motor 8 disposed therebelow via a table shaft 3 a. The polishing table 3 is configured to be rotatable in a direction indicated by an arrow about a table shaft 3a by a polishing table motor 8. More specifically, the axis CP of the polishing table 3 coincides with the axis of the table shaft 3a, and the polishing table 3 rotates about the axis CP. As an example of the polishing table motor 8, a variable speed motor having an inverter is exemplified.

The polishing apparatus 1 further includes a torque measuring device 9 for measuring a torque for rotating the polishing table 3. The torque measuring device 9 is connected to the polishing table motor 8. In polishing the substrate W, the polishing table 3 is driven to rotate at a constant speed by a polishing table motor 8. Therefore, when the torque required to rotate the polishing table 3 at a constant speed is changed, the drive current of the polishing table motor 8 is changed.

The torque for rotating the polishing table 3 is a torque of a force for rotating the polishing table 3 about the axis CP thereof. The torque for rotating the polishing table 3 corresponds to the drive current of the polishing table motor 8. Therefore, in the present embodiment, the torque measuring device 9 is a current measuring instrument that measures the drive current of the polishing table motor 8. In one embodiment, the torque measuring device 9 may be configured by at least a part of a motor driver that drives the polishing table motor 8. In this case, the motor driver determines a current value required to rotate the polishing table 3 at a constant speed, and outputs the determined current value. The determined current value corresponds to the torque for rotating the polishing table 3. In one embodiment, the torque measuring device 9 may be a torque measuring device that directly measures the torque for rotating the polishing table 3 around the axial center CP thereof.

The polishing apparatus 1 further includes a dresser 30 for conditioning the polishing pad 2, a dressing liquid supply nozzle 5 for supplying a dressing liquid to the polishing pad 2, and an atomizer 33 for ejecting a liquid or a mixed fluid of a liquid and a gas to the polishing pad 2. An example of the finishing liquid is pure water. The liquid ejected from the atomizer 33 is, for example, pure water, and the gas ejected from the atomizer 33 is, for example, nitrogen gas.

The polishing table 3 and the table shaft 3a are provided with a polishing liquid supply path 39 for supplying a polishing liquid. The polishing liquid supply path 39 has one end communicating with the polishing liquid supply hole 36 formed in the surface of the polishing table 3, and the other end connected to a polishing liquid supply source, not shown. A polishing liquid supply hole 37 is formed in the polishing pad 2 at a position corresponding to the polishing liquid supply hole 36 of the polishing table 3. During polishing of the substrate W, the polishing liquid is supplied from the polishing liquid supply hole 37 to the polishing surface 2a of the polishing pad 2 through the polishing liquid supply path 39 and the polishing liquid supply hole 36. An example of the polishing liquid is slurry containing abrasive grains. Although fig. 1 shows a single set of polishing liquid supply holes 36 and 37, the polishing apparatus 1 may be provided with a plurality of sets of polishing liquid supply holes 36 and 37. The polishing liquid supply holes 36 and 37 are disposed on the axial center CP of the polishing table 3 or in the vicinity of the axial center CP.

Fig. 2 is a cross-sectional view of the polishing head 10 shown in fig. 1. The polishing head 10 includes an elastic film 45 for pressing the substrate W against the polishing surface 2a of the polishing pad 2, a polishing head body 11 holding the elastic film 45, and a retainer member 20 disposed below the polishing head body 11. The elastic membrane 45 is attached to the lower portion of the polishing head body 11. The polishing head body 11 is fixed to an end of the polishing head shaft 12, and the polishing head body 11, the elastic film 45, and the retainer member 20 are configured to rotate integrally by rotation of the polishing head shaft 12. The retainer ring member 20 is configured to be movable up and down relative to the polishing head body 11. The polishing head body 11 of the present embodiment has a quadrangular shape and is formed of a resin such as engineering plastic (for example, PEEK).

The lower surface of the elastic film 45 constitutes a substrate pressing surface 45a that presses the substrate W against the polishing surface 2a of the polishing pad 2. The retainer ring member 20 is disposed around the substrate pressing surface 45a, and the substrate W is surrounded by the retainer ring member 20. A pressure chamber (bladder) P1 is provided between the elastic membrane 45 and the polishing head body 11. The pressure chamber P1 is formed by the elastic membrane 45 and the polishing head body 11. A pressurized fluid such as pressurized air is supplied to the pressure chamber P1 through the fluid passage 46, or vacuum is drawn.

In the embodiment shown in fig. 2, the pressure chamber P1 is formed entirely over the upper surface of the substrate W. In one embodiment, a plurality of pressure chambers may be formed by the elastic membrane 45 and the polishing head body 11. When a plurality of pressure chambers are formed, a fluid passage communicating with each pressure chamber may be provided to independently control the pressure of each pressure chamber. The elastic membrane 45 is formed of a rubber material having excellent strength and durability, such as ethylene propylene rubber (EPDM), urethane rubber, and silicone rubber.

The retainer ring member 20 is disposed around the elastic film 45, and the retainer ring member 20 is in contact with the polishing surface 2a of the polishing pad 2 during polishing of the substrate W. The retaining ring member 20 is configured around the periphery of the substrate W to prevent the substrate W from escaping from the polishing head 10 during polishing of the substrate W. The retainer member 20 of the present embodiment has a rectangular ring shape corresponding to the rectangular substrate W, but the shape of the retainer member 20 is not limited to the shape of the present embodiment. The retainer ring member 20 may be formed of a resin material having high rigidity, ceramic, or the like.

An annular elastic bag 49 is disposed between the retainer ring member 20 and the polishing head body 11, and a pressure chamber Pr is formed inside the elastic bag 49. The retainer ring member 20 can move up and down relative to the grinding bit body 11 by the expansion/contraction of the elastic bladder 49. The elastic bag 49 presses the lower surface of the retainer ring member 20 against the polishing surface 2a of the polishing pad 2 by expansion.

The fluid passage 50 communicates with the pressure chamber Pr, and supplies a pressurized fluid such as pressurized air to the pressure chamber Pr through the fluid passage 50. The internal pressure of the pressure chamber Pr can be adjusted. Therefore, the pressing force of the retainer ring member 20 against the polishing pad 2 can be adjusted independently of the pressing force of the substrate W against the polishing pad 2. The elastic bag 49 of the present embodiment has a quadrangular ring shape corresponding to the quadrangular substrate W, but the shape of the elastic bag 49 is not limited to the shape of the present embodiment. In one embodiment, the polishing head 10 may also include a plurality of retainer ring members 20 and a plurality of elastomeric bladders 49. In this case, the pressing force of each retainer ring member 20 against the polishing pad 2 can be independently adjusted by each elastic bag 49. When the substrate W is polygonal, a plurality of retainer ring members 20 and a plurality of elastic bags 49 may be provided, which are independently adjusted for each side and/or each corner.

The above-described elevating device (not shown), polishing head rotation motor 13, swing motor 15, polishing table motor 8, and torque measuring device 9 are electrically connected to the operation control unit 7. The operations of the lifting device (not shown), the polishing head rotation motor 13, the swing motor 15, the polishing table motor 8, and the torque measuring device 9 are controlled by the operation control unit 7.

The polishing of the substrate W is performed as follows. While the polishing head 10 is rotated and the polishing table 3 and the polishing pad 2 are rotated integrally, a polishing liquid (slurry) is supplied onto the polishing surface 2a of the polishing pad 2 from the polishing liquid supply hole 37. The polishing head 10 is lowered to a predetermined position (polishing height) by an elevating device (not shown). When the compressed gas is supplied to the pressure chamber P1 of the polishing head 10 at the predetermined position (polishing height), the elastic film 45 is inflated, and the elastic film 45 presses the substrate W against the polishing surface 2a of the polishing pad 2. The compressed gas is also supplied into the pressure chamber Pr, and the elastic bag 49 presses the retainer member 20 against the polishing surface 2a of the polishing pad 2.

The polishing head 10 and the polishing table 3 (and the polishing pad 2) rotate in the same direction as indicated by an arrow in fig. 1, and in this state, the polishing head 10 presses the substrate W against the polishing surface 2a of the polishing pad 2. The substrate W is in sliding contact with the polishing surface 2a of the polishing pad 2 in a state where the slurry is present on the polishing surface 2a of the polishing pad 2. The surface of the substrate W is polished by a combination of chemical action based on the chemical components of the slurry and mechanical action of the abrasive grains contained in the slurry.

During polishing of the substrate W, the operation control unit 7 gives a command to the swing motor 15 to swing the polishing head 10 along the polishing surface 2 a. Fig. 3 is a view of the polishing head 10 in a state of being swung along the polishing surface 2a as viewed from above. The polishing head 10 shown in fig. 3 rotates about a polishing head axis 12. The operation controller 7 alternately rotates the swing motor 15 clockwise and counterclockwise by a predetermined angle, and the polishing head 10 is rotated and reciprocated about the support shaft 14 by the polishing head swing arm 16, whereby the polishing head 10 is swung along the polishing surface 2 a.

The polishing head 10 of the present embodiment is configured to be able to hold a relatively large-sized substrate. Therefore, as shown in fig. 3, the polishing head 10 has a relatively large size with respect to the polishing table 3, and during polishing, the polishing head 10 is disposed on the axial center CP of the polishing table 3. In this case, when the polishing liquid is supplied to the polishing surface 2a from above the polishing pad 2, the polishing liquid may not be supplied to the entire surface to be polished of the substrate W held by the polishing head 10. In this embodiment, the polishing liquid is supplied from the polishing liquid supply hole 37 on or near the axis CP in order to supply the polishing liquid to the entire surface to be polished of the substrate W. In order to uniformly supply the polishing liquid to the entire surface to be polished of the substrate W, the polishing apparatus 1 polishes the substrate W while swinging the polishing head 10 along the polishing surface 2 a. While the polishing head 10 is oscillating, the polishing head 10 and the substrate W are on the axis CP of the polishing table 3.

When the polishing of the substrate W is completed, the substrate W to be polished is detached from the polishing head 10 and transported to the next step. After polishing of the substrate W, the polishing surface 2a of the polishing pad 2 is dressed by the dresser 30. The dresser 30 shaves the polishing pad 2 slightly, thereby renewing the polishing surface 2 a. The polishing head 10 holds a new substrate, and the new substrate is polished in the same manner. Thus, the polishing of the substrate is repeated.

The polishing end point of the substrate is determined based on a change in torque for rotating the polishing table 3. As described above, in the present embodiment, the torque for rotating the polishing table 3 corresponds to the drive current of the polishing table motor 8, and the operation control unit 7 determines the polishing end point of the substrate based on the change in the drive current of the polishing table motor 8.

Hereinafter, a method of polishing a substrate and a method of determining a polishing end point of a substrate will be described in detail. Fig. 4 and 5 are flowcharts showing an embodiment of a method for polishing a substrate and a method for determining a polishing end point of a substrate.

In steps 1-1 to 1-4, the polishing apparatus 1 performs a swing polishing step. In the present specification, the swing polishing step is defined as a step of polishing a substrate while rotating the polishing table 3 and swinging the polishing head 10 along the polishing surface 2 a.

In step 1-1, the polishing apparatus 1 starts a swing polishing process. That is, the polishing table motor 8 rotates the polishing table 3 and the polishing pad 2 at a constant rotational speed integrally, and the polishing head 10 rotates the substrate W at a constant rotational speed. The swing motor 15 swings the polishing head 10 along the polishing surface 2a under a constant condition, and the polishing head 10 presses the substrate W against the polishing surface 2a of the polishing pad 2 under a constant condition, thereby polishing the substrate W. The retainer ring member 20 may be further pressed against the polishing surface 2a of the polishing pad 2 at the same time to polish the substrate W.

In step 1-2, the polishing head 10 polishes the substrate W on the polishing pad 2, and the torque measuring device 9 measures the torque for rotating the polishing table 3 (the drive current of the polishing table motor 8).

In step 1-3, the operation control unit 7 obtains the measured value of the torque from the torque measuring device 9, and compares the measured value of the torque with a preset torque threshold value. The measured value of the torque indicates a torque required to rotate the polishing table 3 at a constant speed. When the measured value of the torque does not reach the torque threshold value, the operation control section 7 causes the polishing apparatus 1 to continue the swing polishing step. When the measured value of the torque reaches the torque threshold value, the operation control section 7 gives a command to the swing motor 15 to stop the swing of the polishing head 10 (steps 1 to 4). Thereby, the polishing apparatus 1 ends the swing polishing process.

In the present embodiment, the substrate W to be polished has a structure in which the torque for rotating the polishing table 3 is reduced (the frictional force acting between the polishing pad 2 and the substrate W is reduced) as the polishing of the substrate W progresses. Therefore, in the present embodiment, when the measured value of the torque is larger than the torque threshold value, the operation control unit 7 causes the polishing apparatus 1 to continue the swing polishing step. When the measured value of the torque is equal to or smaller than the torque threshold value, the operation control unit 7 gives a command to the swing motor 15 to stop the swing of the polishing head 10.

In one embodiment, the substrate W to be polished may have a structure in which a torque for rotating the polishing table 3 is increased (a frictional force acting between the polishing pad 2 and the substrate W is increased) as the polishing of the substrate W is performed. In this case, when the measured value of the torque is smaller than the torque threshold value, the operation control section 7 causes the polishing apparatus 1 to continue the swing polishing step. When the measured value of the torque is equal to or greater than the torque threshold value, the operation control unit 7 gives a command to the swing motor 15 to stop the swing of the polishing head 10.

Hereinafter, in the present specification, the operation of stopping the oscillation of the polishing head 10 after the measured value of the torque reaches a preset torque threshold value is referred to as an oscillation stop operation. In the present embodiment, the swing stop operation is performed when the polishing head 10 is at a predetermined stop position above the polishing table 3. As described above, the torque required to rotate the polishing table 3 varies depending on the position of the polishing head 10 relative to the polishing pad 2. When the polishing head 10 for performing a stationary polishing step, which will be described later, is located at a different position for each substrate to be polished, a stationary polishing end point, which will be described later, is deviated. Therefore, by stopping the polishing head 10 at the same stop position, it is possible to prevent the stationary polishing end point from being deviated in the stationary polishing step.

In one embodiment, in step 1-3, the operation control unit 7 may compare the current polishing time with a preset oscillation polishing time instead of comparing the measured value of the torque with a preset torque threshold value. When the current polishing time does not pass through the swing polishing time, the operation control unit 7 causes the polishing apparatus 1 to continue the swing polishing process. After the elapse of the swing polishing time for the current polishing time, the operation control unit 7 instructs the swing motor 15 to stop the swing of the polishing head 10 (steps 1 to 4). In this case, the swing stopping operation is an operation of stopping the swing of the polishing head 10 after the current polishing time has elapsed from the swing polishing time.

In steps 1-5 to 1-9, after the swing stopping operation, the operation control section 7 causes the polishing apparatus 1 to perform a static polishing step. In the present specification, the stationary polishing step is defined as a step of polishing the substrate while stopping the oscillation of the polishing head 10 while rotating the polishing table 3.

In step 1-5, the polishing apparatus 1 starts a static polishing process. The stationary polishing step is different from the oscillating polishing step in that the polishing head 10 is not oscillated, and the other operations are the same as the oscillating polishing step. That is, the polishing head 10, which has stopped swinging by the swing stopping operation, presses the substrate W against the polishing surface 2a of the polishing pad 2 rotating together with the polishing table 3 while rotating the substrate W, thereby polishing the substrate W. The position of the polishing head 10 in the stationary polishing step is the above-described predetermined stop position. The oscillating grinding process and the stationary grinding process are performed substantially continuously.

In steps 1 to 6, the torque measuring device 9 measures the torque for rotating the polishing table 3 (the drive current of the polishing table motor 8) while the polishing head 10 polishes the substrate W.

In steps 1 to 7, the operation control unit 7 acquires a measured value of the torque from the torque measuring device 9, and calculates a rate of change of the torque with respect to the polishing time (i.e., a rate of change of the torque) from the measured value of the torque.

In steps 1 to 8, the operation control unit 7 compares the rate of change of the torque with a preset change rate threshold value. When the rate of change of the torque does not reach the change rate threshold value, the operation control unit 7 causes the polishing apparatus 1 to continue the static polishing step.

In steps 1 to 9, the operation control unit 7 determines a stationary polishing end point as a point of time when the rate of change of the torque reaches the change rate threshold value. Then, the operation control unit 7 causes the polishing apparatus 1 to end the static polishing step. In the stationary polishing step, since the oscillation of the polishing head 10 is stopped, the change in torque can be canceled according to the position of the polishing head 10, and the operation control unit 7 can accurately determine the stationary polishing end point.

In the present embodiment, the substrate W to be polished has a structure in which the rate of change in torque decreases as the static polishing step progresses. Therefore, in the present embodiment, when the rate of change of the torque is larger than the change rate threshold value, the operation control unit 7 causes the polishing apparatus 1 to continue the static polishing step. The operation control unit 7 specifies the stationary polishing end point as a point of time when the rate of change of the torque decreases and reaches the change rate threshold value.

In one embodiment, the substrate W to be polished may have a structure in which the rate of change in torque increases as the static polishing step progresses. In this case, when the rate of change of the torque is smaller than the change rate threshold value, the operation control unit 7 causes the polishing apparatus 1 to continue the static polishing step. The operation control unit 7 specifies the stationary polishing end point as a point of time when the rate of change of the torque increases and reaches the change rate threshold value.

In steps 1-10 to 1-12, after the static polishing step, the operation control unit 7 causes the polishing apparatus 1 to perform a finish polishing step. In polishing a substrate W having a structure in which the rate of change in torque decreases as the stationary polishing step progresses, the frictional force acting between the polishing pad 2 and the substrate W does not change greatly after the stationary polishing end point (that is, the torque for rotating the polishing table 3 does not change greatly). The stationary polishing end point indicates a point in time when the material of the surface to be polished of the substrate W changes. In polishing a substrate W having a structure in which the rate of change in torque increases as the static polishing step progresses, the static polishing end point also indicates the point in time when the material of the surface to be polished of the substrate W changes. After the stationary polishing end point, the flatness of the surface to be polished can be improved by further performing a finish polishing step of polishing the substrate W.

In step 1 to 10, the polishing apparatus 1 starts a finish polishing process. The finish polishing step is substantially the same operation as the swing polishing step. That is, the swing motor 15 swings the polishing head 10 along the polishing surface 2a, and the polishing head 10 rotates the substrate W and presses the substrate W against the polishing surface 2a of the polishing pad 2 rotating together with the polishing table 3 to polish the substrate W. In one embodiment, the finish polishing step may be performed with the polishing head 10 stopped from swinging. The stationary grinding step and the finish grinding step are carried out substantially continuously. In the finish polishing step, similarly to the stationary polishing step, the oscillation of the polishing head 10 may be stopped at all times or the oscillation of the polishing head 10 may be stopped discontinuously, but the flatness of the surface to be polished may be improved by oscillating the polishing head 10.

In steps 1 to 11, the operation control unit 7 compares the current polishing time with the finish polishing time. When the finish polishing time has not elapsed from the current polishing time, the operation control unit 7 causes the polishing apparatus 1 to continue the finish polishing process.

In steps 1 to 12, the operation control unit 7 specifies a finish polishing end point which is a point in time when the finish polishing time has elapsed since the current polishing time. The finish grinding time is determined according to the stationary grinding endpoint. Specifically, the operation control unit 7 determines the finish polishing time by adding the polishing time at the stationary polishing end point to a predetermined fixed time. The fixed time is determined by an experiment and a conventional polishing result. In another example, the operation control unit 7 may determine the finish polishing time by multiplying a predetermined coefficient by the polishing time at the stationary polishing end point. After the finish polishing end point is determined, the operation control unit 7 causes the polishing apparatus 1 to end the finish polishing process, thereby ending polishing of the substrate W. Fig. 6 shows an example of a change in torque for rotating the polishing table 3 in steps 1-1 to 1-12. Fig. 6 shows an example of the above-described torque change in the case of polishing the substrate in which the torque for rotating the polishing table 3 is reduced as the polishing progresses.

The torque threshold and the swing polishing time are determined by experiments and conventional polishing results, and are set in the vicinity of the stationary polishing end point. This makes it possible to accurately determine the stationary polishing end point while shortening the time required to stop the oscillation of the polishing head 10. As a result, the polishing apparatus 1 can accurately determine the polishing end points such as the stationary polishing end point and the finish polishing end point while maintaining the polishing performance. In order to reduce surface defects (scratches, etc.) of the substrate W, a water polishing step is performed at the end of the finish polishing step or continuously with the finish polishing step, in which pure water is supplied to the polishing surface 2a of the polishing pad 2 instead of the slurry, and the substrate W is brought into sliding contact with the polishing surface 2a of the polishing pad 2 while the pressing force of the polishing head 10 against the substrate W is reduced.

Next, another embodiment of a method for polishing a substrate and a method for determining a polishing end point of a substrate will be described. Fig. 7 is a flowchart showing another embodiment of a method for polishing a substrate and a method for determining a polishing end point of the substrate.

In step 2-1, the operation controller 7 causes the polishing apparatus 1 to perform polishing of the substrate W. The polishing of the present embodiment is performed as follows. That is, the polishing table motor 8 rotates the polishing table 3 and the polishing pad 2 at a constant rotational speed integrally, and the polishing head 10 rotates the substrate W at a constant rotational speed. The swing motor 15 swings the polishing head 10 along the polishing surface 2a under a constant condition, and the polishing head 10 presses the substrate W against the polishing surface 2a of the polishing pad 2 under a constant condition, thereby polishing the substrate W. Further, the retainer ring member 20 may be pressed against the polishing surface 2a of the polishing pad 2 at the same time to polish the substrate W. In the present embodiment, while the polishing head 10 is oscillating, the polishing head 10 and the substrate W are also on the axis CP of the polishing table 3.

In step 2-2, the polishing head 10 polishes the substrate W on the polishing pad 2, and the torque measuring device 9 measures the torque for rotating the polishing table 3 (the drive current of the polishing table motor 8).

In step 2-3, the operation control unit 7 acquires the measured value of the torque from the torque measuring device 9, and determines a plurality of representative values of the torque from the plurality of measured values of the torque. In the present embodiment, the plurality of representative values of the torque are a plurality of minimum values of the torque. In one embodiment, the plurality of representative values of the torque may be a plurality of local maximum values of the torque or a plurality of moving average values of the torque.

In step 2-4, the operation control unit 7 generates a relational expression indicating a relationship between a plurality of representative values of the torque and the polishing time.

In step 2-5, the operation control unit 7 determines a first polishing end point which is a point of time when the predicted value of the torque calculated from the relational expression reaches a preset torque threshold value. Fig. 8 is a diagram showing a relationship between a torque for rotating the polishing table 3 and the first polishing end point. The first polishing end point is a point of time predicted when the frictional force acting between the polishing pad 2 and the substrate W becomes constant. The torque threshold is determined by experiments and conventional grinding results.

In step 2-6, the operation control unit 7 compares the current polishing time with the finish polishing time. When the finish polishing time has not elapsed from the current polishing time, the operation control unit 7 causes the polishing apparatus 1 to continue polishing the substrate W.

In step 2-7, the operation control unit 7 specifies a finish polishing end point (second polishing end point) which is a point in time when the finish polishing time has elapsed since the current polishing time. The finish grinding time is determined according to the first grinding end point. Specifically, the operation control unit 7 determines the finish polishing time by adding the polishing time at the first polishing end point to a predetermined fixed time. The fixed time is determined by an experiment and a conventional polishing result. In another example, the operation control unit 7 may determine the finish polishing time by multiplying a predetermined coefficient by the polishing time at the first polishing end point. After the second polishing end point is determined, the operation control unit 7 causes the polishing apparatus 1 to end the finish polishing process, thereby ending the polishing of the substrate W. In order to reduce surface defects (scratches, etc.) of the substrate W, a water polishing step may be performed at the end of the finish polishing step or may be performed following the finish polishing step, in which pure water is supplied to the polishing surface 2a of the polishing pad 2 instead of the slurry, and the substrate W is brought into sliding contact with the polishing surface 2a of the polishing pad 2 while the pressing force of the polishing head 10 on the substrate W is reduced.

In the present embodiment, a predicted value of the torque is calculated from a plurality of measured values of the torque, and a first polishing end point is determined based on the predicted value. Therefore, in the present embodiment, the first polishing end point can be accurately determined while the polishing head 10 is oscillated. As a result, the polishing apparatus 1 can accurately determine the polishing end points such as the first polishing end point and the second polishing end point while maintaining the polishing performance.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the art to which the present invention pertains to practice the present invention. Various modifications of the above-described embodiments will be apparent to those skilled in the art, and the technical idea of the present invention is applicable to other embodiments. Therefore, the present invention is not limited to the embodiments described above, and can be interpreted as the broadest scope based on the technical idea defined by the scope of the claims.

Description of the symbols

1 grinding device

2 grinding pad

2a abrasive surface

3 grinding table

5 dressing liquid supply nozzle

7 operation control part

8 grinding table motor

9 Torque measuring device

10 grinding head

11 grinding head body

12 grinding head shaft

13 grinding head rotary motor

14 support shaft

15 swing motor

16 grinding head swing arm

20 baffle ring component

30 trimmer

33 sprayer

36 grinding liquid supply hole

37 grinding liquid supply hole

39 polishing liquid supply path

45 elastic film

46 fluid path

49 elastic bag

50 fluid path