Grinding surface shaping method

Abstract

To quickly shape the polishing surface of a polishing pad and efficiently obtain a wafer of the desired shape through polishing. [Solution] The polishing surface shaping method for shaping the polishing pad 25 of the polishing device 1 includes a shaping step in which the dressing portion 51 is brought into contact with the polishing surface 25a of the polishing pad 25, and the dressing portion 61 is moved horizontally (second direction) to shape the polishing surface 25a; a polishing surface shape measuring step in which the shape of the polishing surface 25a is measured from the vertical displacement (first direction) and the horizontal movement position of the dressing portion 51; and a determination step in which the quality of the shape of the polishing surface 25a is determined. In the determination step, if the shape of the polishing surface 25a is determined to be "good", the process proceeds to the polishing step. If the shape of the polishing surface 25a is determined to be "bad", a condition changing step is performed to change the contact conditions of the dressing portion 51 with the polishing surface 25a in the shaping step, and the shaping step is performed based on the contact conditions changed in the condition changing step.

Description

Technical Field

[0001] The present invention relates to a method for dressing a polishing surface of a polishing pad for polishing a workpiece such as a wafer.

Background Art

[0002] For example, in the manufacturing process of semiconductor devices such as ICs and LSIs, in order to miniaturize and reduce the weight of the semiconductor devices, the back surface of the wafer is ground and the wafer is thinned to a predetermined thickness. This grinding of the wafer is performed by pressing a grinding wheel against the back surface of the wafer (the upper surface in the processing state) while rotating the grinding wheel at high speed. When the back surface of the wafer is ground by such a grinding method, grinding marks remain on the back surface (grinding surface) of the wafer, and these grinding marks cause a decrease in the fracture strength of the wafer.

[0003] Therefore, the back surface (grinding surface) of the wafer is polished with a polishing pad by a polishing device to remove the grinding marks. Here, as the polishing device, for example, a chemical mechanical polishing (CMP) device that supplies slurry, which is a polishing liquid, to the polishing area between a rotating polishing pad and a wafer, and presses a polishing pad having a larger diameter than the wafer against the wafer to polish the wafer is known. In such a polishing device, the rotating polishing pad is pressed against the entire upper surface of the wafer with a predetermined force in a state where the rotation axis of the polishing pad and the rotation axis of the wafer are shifted in a direction parallel to the polishing surface of the polishing pad, so as to polish the entire upper surface of the wafer.

[0004] In such wafer polishing, the polishing surface of the polishing pad is shaped (dressed) periodically by a dressing mechanism, for example. However, if there is variation in the thickness of the wafer ground by the grinding process performed before the polishing process, it is difficult to make the thickness of the wafer uniform even if the wafer with such thickness variation is polished by the subsequent polishing process.

[0005] Therefore, Patent Document 1 proposes a grinding and polishing apparatus that measures the radial thickness distribution of a workpiece, such as a wafer, using a thickness measuring instrument before polishing, and adjusts the amount of polishing pad dressed by a dressing mechanism according to the measured radial thickness distribution of the workpiece, thereby polishing the workpiece to a uniform thickness. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-223636 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the grinding and polishing apparatus proposed in Patent Document 1 does not measure the shape of the polishing surface of the polishing pad, but rather changes the shaping conditions of the polishing surface based only on the thickness distribution of the workpiece. This leads to problems such as excessive removal of material from the polishing surface and inability to fully correct the shape of the polishing surface through shaping (dressing). Furthermore, since it is necessary to measure the radial thickness distribution of the workpiece before shaping (dressing) the polishing surface of the polishing pad, there is a problem of wasted time before shaping the polishing surface of the polishing pad.

[0008] By the way, when the workpiece is a wafer, various shapes are required for the wafer after polishing when applying epitaxial films or other coatings to the wafer surface. In wafer polishing, the entire surface of the polishing pad is in contact with the wafer, so it is necessary to change the shape of the polishing surface of the polishing pad according to the required wafer shape.

[0009] Conventionally, a surface pressure measuring device is pressed against the polishing surface of a polishing pad to measure the shape of the polished surface after shaping, and the wafer is polished to the desired shape by shaping the polished surface based on the measured shape.

[0010] However, the conventional shaping method described above has the problem of being time-consuming and inefficient because it is necessary to measure the shape of the polishing surface of the polishing pad using a surface pressure measuring instrument before shaping the polishing surface.

[0011] The present invention has been made in view of the above problems, and its object is to provide a polishing surface shaping method that can efficiently obtain a wafer of a desired shape by polishing by shaping the polishing surface of a polishing pad in a short time. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a polishing surface shaping method for a polishing apparatus comprising: a rotatable holding table for holding a workpiece; a rotatable polishing pad having a polishing surface provided facing the holding surface of the holding table; a dressing mechanism for shaping the polishing surface by contacting the polishing surface; a first direction movement mechanism for moving the dressing portion of the dressing mechanism in a first direction perpendicular to the polishing surface; a second direction movement mechanism for moving at least one of the dressing portion and the polishing pad in a second direction parallel to the polishing surface; and a displacement measuring unit for measuring the amount of displacement of the dressing portion in the first direction, wherein the polishing surface of the polishing pad is shaped by the dressing portion while the dressing portion is in contact with the polishing surface by the first direction movement mechanism, and the dressing portion is moved by the second direction movement mechanism The device comprises a shaping step of moving a dressing portion along the polishing surface to shape the polishing surface; a polishing surface shape measuring step of measuring the shape of the polishing surface from the displacement of the dressing portion in the first direction and the position of movement in the second direction when the dressing portion contacts the polishing surface; and a determination step of determining whether the shape of the polishing surface measured in the polishing surface shape measuring step is good or bad. In the determination step, if the shape of the polishing surface is determined to be "good", the device proceeds to a polishing step of polishing the polishing surface with the polishing pad; if the shape of the polishing surface is determined to be "bad", the device proceeds to a condition changing step of changing the contact conditions of the dressing portion to the polishing surface in the shaping step; and the device executes the shaping step based on the contact conditions changed in the condition changing step. [Effects of the Invention]

[0013] According to the present invention, in the shaping step, the dressing portion that contacts the polishing surface of the polishing pad is moved horizontally to shape the polishing surface, and at the same time, in the polishing surface shape step, the shape of the polishing surface is measured from the displacement of the dressing portion in a first direction and the movement position in a second direction, which are measured by a displacement measuring unit. In other words, the shaping and shape measurement of the polishing surface of the polishing pad are performed simultaneously, thus shortening the time required to determine whether the shape of the polishing surface after shaping is good or bad.

[0014] Furthermore, if the shape of the polishing surface of the shaped polishing pad is "good," the next step, wafer polishing, is performed using the polishing pad with the shaped surface, thus efficiently obtaining a wafer of the desired shape through polishing. Also, if the shape of the polishing surface of the shaped polishing pad is "bad," the measured shape of the polishing surface of the polishing pad is fed back, and the contact conditions between the dressing part of the dressing mechanism and the polishing pad are changed based on the fed-back shape of the polishing surface to reshape the polishing surface of the polishing pad, thereby obtaining a wafer of the desired shape by polishing the wafer with the reshaped polishing pad. [Brief explanation of the drawing]

[0015] [Figure 1] This is a broken side view of the main part of a polishing apparatus showing the shaping step and the polishing surface shape measurement step of the polishing surface shaping method according to the present invention. [Figure 2] This is a cross-sectional side view of the main part of a polishing apparatus showing the polishing step of the polishing surface shaping method according to the present invention. [Figure 3] This flowchart shows the flow of each step in the polishing surface shaping method according to the present invention. [Figure 4] This flowchart shows the processing procedure for the polishing surface shaping method according to the present invention. [Figure 5]It is a diagram showing three patterns of the shape of a polishing pad and the shape of a wafer after polishing when the shape of the wafer before polishing is flat in the polishing surface shaping method according to the present invention. [Figure 6] It is a diagram showing three patterns of the shape of a polishing pad and the shape of a wafer after polishing when the shape of the wafer before polishing is convex in the polishing surface shaping method according to the present invention. [Figure 7] It is a diagram showing three patterns of the shape of a polishing pad and the shape of a wafer after polishing when the shape of the wafer before polishing is concave in the polishing surface shaping method according to the present invention.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

[0017] [Configuration of Polishing Apparatus] First, the configuration of a polishing apparatus 1 for carrying out the polishing surface shaping method according to the present invention will be described. In the following description, the X-axis direction (the second direction parallel to the polishing surface 25a of a polishing pad 25 described later) indicated by an arrow in FIGS. 1 and 2 is referred to as the "horizontal direction", and the Z-axis direction (the first direction perpendicular to the polishing surface 25a of the polishing pad 25 described later) is referred to as the "vertical direction".

[0018] The polishing apparatus 1 shown in FIGS. 1 and 2 is an apparatus for polishing the upper surface of a thin disk-shaped wafer W (see FIG. 2) which is a workpiece. It includes a holding table 10 for holding the wafer W, a polishing unit 20 for polishing the wafer W held on the holding table 10, a lifting mechanism 30 which is a first-direction moving mechanism for moving the polishing unit 20 up and down along the vertical direction (first direction), a slurry supply means 40 for supplying slurry toward the space between the polishing pad 25 of the polishing unit 20 and the wafer W, a dressing mechanism 50 (see FIG. 1) for dressing (shaping) the polishing surface 25a of the polishing pad 25, a horizontal moving mechanism 60 which is a second-direction moving mechanism for moving the dressing mechanism 50 along the horizontal direction (second direction), a displacement measurement unit 70 for measuring the displacement in the vertical direction (first direction) of the dressing part 51 (see FIG. 1) of the dressing mechanism 50, and a control unit 80 for controlling each component as the main components.

[0019] Here, the wafer W is made of a single-crystal silicon base material. On the surface facing downward in the state shown in FIG. 2, a plurality of devices (not shown) are formed. These devices are protected by a protective tape (not shown) adhered to the surface of the wafer W. And the wafer W is held on the holding table 10 with its surface (the lower surface in FIG. 2), and its back surface (the upper surface in FIG. 2) is polished by the polishing unit 20. Note that as the material of the wafer W, gallium arsenide (GaAs), silicon carbide (SiC), ceramic, etc. other than silicon (Si) are used.

[0020] Next, the configurations of the holding table 10, the polishing unit 20, the lifting mechanism 30, the slurry supply means 40, the dressing mechanism 50, the horizontal moving mechanism 60, the displacement measurement unit 70, and the control unit 80, which are the main components constituting the polishing apparatus 1, will be sequentially described below.

[0021] (Holding Table) As shown in Figure 2, the holding table 10 is constructed by connecting and integrating upper and lower disc-shaped frames 10A and a base 10B, both made of stainless steel (SUS), and by incorporating a disc-shaped porous member 11 into a circular recess 10a formed in the center of the frame 10A. Here, the porous member 11 is made of porous ceramic or the like, and its upper surface exposed to the frame 10A constitutes a holding surface 11a that sucks and holds the disc-shaped wafer W. The porous member 11 is selectively connected to a suction source (not shown), such as a vacuum pump or ejector.

[0022] A motor 13 and an encoder 14 for detecting the rotation speed and direction of the motor 13 are connected to a rotation axis 12 that extends vertically downward from the center of the holding table 10. When the rotation axis 12 is driven to rotate by the motor 13 in the direction of the arrow shown in the figure, the holding table 10 and the wafers held therein rotate at a predetermined speed in the same direction around the vertical rotation axis CL1. The motor 13 and the encoder 14 are electrically connected to a control unit 80, and the control unit 80, which receives the detection signal detected by the encoder 14, controls the rotation of the motor 13 based on the received detection signal.

[0023] (Polishing unit) The polishing unit 20 includes a vertical spindle 22 that is driven to rotate at a predetermined speed in the direction of the arrow in the figure by a spindle motor 21, which is a rotational drive source; a disc-shaped platen 24 attached to the lower end of the spindle 22 via a cylindrical connecting member 23; and a disc-shaped polishing pad 25 that is detachably attached to the lower surface of the platen 24. Here, the platen 24 is made of an aluminum alloy or the like, and the polishing pad 25 attached to the platen 24 is made of a nonwoven fabric containing abrasive grains such as silica, diamond, or alumina, or polyurethane. The spindle motor 21 is equipped with an encoder 26 that detects the rotational speed of the spindle motor 21, and this encoder 26 is electrically connected to a control unit 80, which controls the rotation of the spindle motor 21 based on the detection signal transmitted from the encoder 26.

[0024] Here, as shown in Figure 2, the polishing pad 25 has an area that covers the wafer W held on the holding surface 11a of the holding table 10 from above. Specifically, the outer diameter of the polishing pad 25 is set to be larger than the outer diameter of the wafer W, and the polishing pad 25 is driven to rotate at a predetermined speed in the direction of the arrow shown in the figure, around a vertical rotation axis CL1 that is horizontally eccentric by ε from the center of the wafer W. The holding table 10 and the wafer W held thereon are also driven to rotate at a predetermined speed in the direction of the arrow shown in the figure (same direction as the rotation direction of the polishing pad 25) around a vertical rotation axis CL2 that is horizontally offset by ε from the rotation axis CL1 of the polishing pad 25.

[0025] (Lifting mechanism) The lifting mechanism 30 is a mechanism for moving the polishing unit 20 up and down along the vertical direction (first direction), and is composed of a known ball screw mechanism. Here, although not shown in the figures, the ball screw mechanism is composed of a vertically arranged rotatable ball screw, a motor which is a rotational drive source that rotates the ball screw in the forward and reverse directions, a nut member attached to a lifting plate that holds the polishing unit 20, and a vertical guide rail which guides the vertical movement of the lifting plate, and the ball screw is screwed into the nut member.

[0026] Therefore, when the motor is started and the ball screw is rotated forward and backward, the nut member that screws onto the ball screw moves up and down along the guide rail together with the lifting plate, causing the polishing unit 20 held by the lifting plate to move up and down in the vertical direction (first direction).

[0027] (Slurry supply means) The slurry supply means 40 supplies slurry to the contact area (polishing region) between the wafer W and the polishing pad 25 during the polishing of the wafer W, and includes a slurry supply source 41. Here, a pipe 42 extending from the slurry supply source 41 is connected to a circular hole-shaped supply passage 43 formed perpendicularly to the centers of the spindle 22, connecting member 23, platen 24, and polishing pad 25 of the polishing unit 20. An electromagnetic on / off valve V is provided in the pipe 42. The slurry used can be an acidic solution in which permanganate is dissolved, or an alkaline solution in which sodium hydroxide or potassium hydroxide is dissolved.

[0028] (Dress mechanism) As shown in Figure 1, the dressing mechanism 50 includes a disc-shaped dressing portion 51 that contacts the polishing surface 25a of the polishing pad 25 and rotates in the direction of the arrow shown in the figure. This dressing portion 51 is composed of a metal base 51a and a grinding wheel 51b containing abrasive grains such as diamond that are electroplated onto the base 51a.

[0029] Here, the dressing section 51 is attached to the upper end of an output shaft (motor shaft) 53a that extends vertically upward from a motor 53, which is a rotational drive source installed on a support plate 52. The motor 53 is equipped with an encoder 54 that detects the rotational speed and direction of the motor 53. The motor 53 and the encoder 54 are electrically connected to a dressing section rotation control unit 83, which will be described later and is provided in the control unit 80.

[0030] Furthermore, in the dressing mechanism 50, an air cylinder 56, which constitutes a lifting mechanism for raising and lowering the dressing section 51 in the vertical direction, is installed on a horizontal support base 55. A support plate 52 is attached to the upper end of a vertically movable piston rod 56a that extends vertically upward from the air cylinder 56, together with the motor 53, encoder 54, and dressing section 51.

[0031] Here, the air cylinder 56 is composed of a cylinder 56A, a piston (not shown) fitted inside the cylinder 56A so as to be vertically movable, and a piston rod 56a extending upward from the piston through the cylinder 56A. Compressed air is supplied to and discharged from an upper chamber (not shown) and a lower chamber (not shown) which are vertically divided by the piston inside the cylinder 56A, causing the piston (not shown) and the piston rod 56a to move up and down, and the dressing portion 51 also moves up and down in accordance with the vertical movement of the piston rod 56a. The lifting mechanism for raising and lowering the dressing portion 51 may be composed of a hydraulic cylinder or a ball screw mechanism, etc.

[0032] The air cylinder 56, which constitutes the lifting mechanism for raising and lowering the dressing section 51, is electrically connected to the dressing section pressing force control unit 85, which will be described later and is provided in the control unit 80. When the pressure in the upper or lower chamber formed in the cylinder 56A is detected by a pressure sensor (not shown) and the detection signal is transmitted to the dressing section pressing force control unit 85 of the control unit 80, the dressing section pressing force control unit 85 controls the pressure regulator (not shown) to adjust the pressure in the upper or lower chamber in the cylinder 56A and control the pressing force of the polishing pad 25 of the dressing section 51 against the polishing surface 25a.

[0033] (Horizontal movement mechanism) The horizontal movement mechanism 60 shown in Figure 1 constitutes the dressing mechanism 50, that is, the second-direction movement mechanism that moves the dressing section 51 in the horizontal direction (second direction), and is constructed by a ball screw mechanism, similar to the lifting mechanism 30. Specifically, although not shown, the ball screw mechanism that constitutes this horizontal movement mechanism 60 consists of a horizontally positioned rotatable ball screw, a motor which is a rotational drive source that rotates the ball screw in the forward and reverse directions, a nut member attached to the support base 55, and a horizontal guide rail that guides the horizontal movement of the dressing mechanism 50, with the ball screw screwed into the nut member.

[0034] Therefore, when the motor of the ball screw mechanism is started and the ball screw is rotated forward and backward, the nut member that screws onto the ball screw moves horizontally along the guide rail together with the dressing mechanism 50, causing the dressing portion 51 of the dressing mechanism 50 to move horizontally (second direction). The horizontal movement mechanism 60 is electrically connected to the dressing portion movement speed control unit 84, which will be described later and is provided in the control unit 80. An encoder (not shown) that detects the rotation speed and rotation direction of a motor (not shown) that is the drive source of the horizontal movement mechanism 60 is also electrically connected to the control unit 80. Therefore, the detection signal from the encoder is transmitted to the control unit 80, and the horizontal position of the dressing portion 51 of the dressing mechanism 50 is calculated by the control unit 80, and the calculated horizontal position of the dressing portion 51 is stored in the storage unit 81, which will be described later and is provided in the control unit 80.

[0035] (Displacement measurement unit) The displacement measuring unit 70 optically and non-contactively measures the amount of displacement of the dressing portion 51 of the dressing mechanism 50 in the vertical direction (first direction) when the dressing portion 51 of the dressing mechanism 50 is in contact with the polishing surface 25a of the polishing pad 25 and moving horizontally (second direction) while shaping (dressing) the polishing surface 25a. In this embodiment, it is configured as a laser displacement meter. The displacement measuring unit 70 is installed on the support base 55 of the dressing mechanism 50, and above it is an arm-shaped reference member 71 that extends horizontally from the support plate 52 of the dressing mechanism 50. The reference member 71 is made of a material with high light reflectivity.

[0036] The laser light emitted vertically upward from the displacement measuring unit 70 is reflected from the lower surface of the reference member 71 and returns to the displacement measuring unit 70, where it is received. The displacement measuring unit 70 measures the vertical displacement of the dressing portion 51 of the dressing mechanism 50 by spectrally analyzing the optical interference of the laser. The measured displacement of the dressing portion 51 is transmitted to the storage unit 81 of the control unit 80 and stored in the storage unit 81.

[0037] (Control Unit) The control unit 80 includes a CPU (Central Processing Unit) that performs calculations according to a control program, and a storage unit 81 such as ROM (Read Only Memory) and RAM (Random Access Memory).

[0038] Furthermore, in this embodiment, as described later, the contact conditions of the polishing pad 25 of the dressing portion 51 with the polishing surface 25a are changed in the condition change step, but in this embodiment, the parameters for changing the contact conditions are, 1) Rotation speed of polishing pad 25 2) Rotation speed of the dressing section 51 3) Movement speed of the dress section 51 4) Pressing force of the dressing part 51 I try to use it.

[0039] Therefore, the control unit 80 is equipped with a pad rotation control unit 82 that controls the rotational speed of the polishing pad 25, a dressing unit rotation control unit 83 that controls the rotational speed of the dressing unit 51, a dressing unit movement speed control unit 84 that controls the movement speed of the dressing unit, and a dressing unit pressing force control unit 85 that controls the pressing force of the dressing unit 51 against the polishing pad 25. Details of the control of the rotational speed of the polishing pad 25 by the pad rotation control unit 82, the control of the rotational speed of the dressing unit 51 by the dressing unit rotation control unit 83, the control of the movement speed of the dressing unit 51 by the dressing unit movement speed control unit 84, and the control of the pressing force of the dressing unit 51 against the polishing pad 25 by the dressing unit pressing force control unit 85 will be described later.

[0040] [Polished surface shaping method] Next, the polishing surface shaping method according to the present invention, which is performed in the polishing apparatus 1 configured as described above, will be explained below with reference to Figures 3 to 7.

[0041] The polishing surface shaping method according to the present invention will be outlined with reference to Figure 3. In this polishing surface shaping method, the shaping step and the polishing surface shape measurement step are performed simultaneously and in parallel.

[0042] In the shaping step, as shown in Figure 1, the dressing portion 51 of the dressing mechanism 50 is lowered by an air cylinder 56 and brought into contact with the polishing surface 25a of the polishing pad 25. Then, the dressing portion 51 is moved horizontally along the polishing surface 25a of the polishing pad 25 by a horizontal movement mechanism 60 to shape the polishing surface 25a with the dressing portion 51. The polishing surface shape measurement step measures the shape of the polishing surface 25a of the polishing pad 25 from the vertical displacement (first direction) and horizontal movement position of the dressing portion 51 when it comes into contact with the polishing surface 25a of the polishing pad 25 during the shaping step. The vertical displacement of the dressing portion 51 is measured optically and non-contact by a displacement measuring unit 70, and the horizontal position of the dressing portion 51 is calculated by detecting the rotation speed and rotation direction of a motor (not shown), which is the drive source of the horizontal movement mechanism 60, using an encoder (not shown).

[0043] In the shaping step described above, while the polishing surface 25a of the polishing pad 25 is shaped by the dressing portion 51 of the dressing mechanism 50, the shape of the polishing surface 25a of the shaped polishing pad 25 is measured in the polishing surface shape measurement step. Then, in the next determination step, the quality of the shape of the polishing surface 25a of the shaped polishing pad 25 ("good" or "bad (NG)") is determined in light of the desired shape of the wafer W after polishing.

[0044] In the above determination, if the shape of the polishing surface 25a of the shaped polishing pad 25 is "good", the process proceeds to the next polishing step, and the wafer W is polished using the polishing pad 25 whose shape and measurement have been performed. On the other hand, if the shape of the polishing surface 25a of the shaped polishing pad 25 is "bad (NG)", the shape of the polishing surface 25a of the polishing pad 25 measured in the polishing surface shape measurement step is fed back, and in the condition change step, the contact conditions of the dressing part 51 with the polishing surface 25a are changed based on the shape of the polishing surface 25a measured in the polishing surface shape step, and the (shaping step + polishing surface shape step) → (determination step) is repeated until the shape of the polishing surface 25a of the polishing pad 25 becomes "good", and the shaping and measurement of the shape of the polishing surface 25a of the polishing pad 25 are repeated. Details of changing the contact conditions of the dressing part 51 with the polishing surface 25a of the polishing pad 25 will be described later.

[0045] Next, the details of the processing procedure for the polishing surface shaping method according to the present invention will be described below based on the flowchart shown in Figure 4.

[0046] When shaping the polishing pad 25 using the dressing mechanism 50, the dressing mechanism 50 shown in Figure 1 moves horizontally (second direction) by the horizontal movement mechanism 60, and the dressing portion 51 of the dressing mechanism 50 moves to the position of the outer circumference of the polishing pad 25, which is the initial position shown by the solid line in Figure 1 (step S1 in Figure 4). Then, the air cylinder 56 of the dressing mechanism 50 is driven and the dressing portion 51 rises (step S2 in Figure 4), and it is determined whether or not the dressing portion 51 has come into contact with the polishing surface 25a of the polishing pad 25 (step S3 in Figure 4). Alternatively, the lifting mechanism 30 of the polishing unit 20 may be driven to lower the polishing pad 25, so that the polishing surface 25a of the polishing pad 25 comes into contact with the dressing portion 51 of the dressing mechanism 50.

[0047] When the dressing portion 51 of the dressing mechanism 50 comes into contact with the polishing surface 25a of the polishing pad 25 (Step S3: Yes), the shaping step (see Figure 3) is executed, and the polishing surface 25a of the polishing pad 25 is shaped by the dressing portion 51 of the dressing mechanism 50, and the polishing surface shape measurement step (see Figure 3) is executed to measure the shape of the polishing surface 25a (Step S4 in Figure 4). If the dressing portion 51 does not come into contact with the polishing surface 25a of the polishing pad 25 (Step S3: No), the process from Step S2 to S3 is repeated until the dressing portion 51 comes into contact with the polishing surface 25a of the polishing pad 25.

[0048] In the shaping step, as shown in Figure 1, the spindle motor 21 of the polishing unit 20 is activated, causing the polishing pad 25 to rotate at a predetermined speed in the direction of the arrow in the diagram, around the rotation axis CL1. At the same time, the motor 53 of the dressing mechanism 50 is activated, causing the dressing section 51 to rotate at a predetermined speed in the direction of the arrow (same direction as the rotation direction of the polishing pad 25) and move horizontally in the direction of the arrow (to the right in Figure 1) from the initial position shown by the solid line in Figure 1 to the position shown by the dashed line (the center position of the polishing pad 25) by the horizontal movement mechanism 60. As a result, the polishing surface 25a of the polishing pad 25 is shaped by the dressing section 51 of the dressing mechanism 50, and at the same time, the shape of the polishing surface 25a of the polishing pad 25 is measured, and the amount of dressing by the dressing section 51 of the polishing pad 25 is accumulated (step S4 in Figure 4).

[0049] In the polishing surface shape measurement step, the shape of the polishing surface 25a of the polishing pad 25 is measured by measuring the horizontal position (second direction) of the dressing portion 51 of the dressing mechanism 50 and the amount of vertical displacement (first direction) of the dressing portion 51 at that position using a displacement measuring unit 70. Here, the horizontal position of the dressing portion 51 is calculated by measuring the rotation speed of a motor (not shown) provided on the horizontal movement mechanism 60 using an encoder (not shown). The horizontal position of the dressing portion 51 and the amount of displacement at that position are transmitted to the storage unit 81 of the control unit 80 and sequentially stored in the storage unit 81.

[0050] When the amount of dressing on the polishing surface 25a of the polishing pad 25 by the dressing unit 51 is accumulated, it is determined whether the accumulated amount of dressing is less than a predetermined set value (whether the accumulated amount of dressing has reached the endurance life of the polishing pad 25) (step S5 in Figure 4). If the accumulated amount of dressing is less than the set value (step S5: Yes), that is, if the polishing pad 25 has not reached its endurance life, it is determined whether the shaping of the polishing surface 25a of the polishing pad 25 is complete (step S6 in Figure 4). If the accumulated amount of dressing on the polishing pad 25 reaches the set value (step S5: No), it is determined that the polishing pad 25 has reached its endurance life, and an alarm is issued to that effect (step S11 in Figure 4), and the shaping of the polishing pad 25 and the measurement of the shape of the polishing surface 25a are completed (step S10 in Figure 4). In this case, the polishing pad 25 is replaced with a new one.

[0051] As the dressing mechanism 50's dressing section 51 moves by the horizontal movement mechanism 60 from the initial position shown by the solid line in Figure 1 to the final position shown by the dashed line (center position of the polishing pad 25) while shaping the polishing surface 25a of the polishing pad 25, the shaping and shape measurement of the polishing surface 25a of the polishing pad 25 is completed (Step S6: Yes). Then, the air cylinder 56 of the dressing mechanism 50 is driven, causing the dressing section 51 to descend and move away from the polishing surface 25a of the polishing pad 25 (Step 7 in Figure 4), and it is determined whether the shape of the shaped polishing surface 25a of the polishing pad 25 is good or not (Step S8 in Figure 4).

[0052] If the shape of the polishing surface 25a of the shaped polishing pad 25 is good (step S8 in Figure 4: Yes), the process moves to the polishing step (see Figure 3), and polishing is performed on the wafer W (step S9 in Figure 4).

[0053] In other words, during the polishing process of the wafer W, as shown in Figure 2, the wafer W is held by suction on the holding surface 11a of the holding table 10. Specifically, when the wafer W is placed on the holding surface 11a of the holding table 10, the porous member 11 of the holding table 10 is connected to a suction source (not shown). Then, the porous member 11 is evacuated by the suction source, generating negative pressure in the porous member 11, and the wafer W is held by suction on the holding surface 11a of the holding table 10 by this negative pressure. At this time, the vertical rotation axis CL2 CL2 passing through the center of the holding table 10 is offset by an amount ε shown in the figure in the horizontal direction (second direction) with respect to the vertical rotation axis CL1 passing through the center of the polishing pad 25.

[0054] As described above, when the wafer W is held by suction on the holding surface 11a of the holding table 10, the spindle motor 21 of the polishing unit 20 is activated and the polishing pad 25 is driven to rotate at a predetermined speed in the direction of the arrow in the figure, about the rotation axis CL1. In addition, the motor 13 is activated and the holding table 10 and the wafer W held therein are driven to rotate at a predetermined speed in the direction of the arrow in the figure (same direction as the rotation direction of the polishing pad 25) about the rotation axis CL2.

[0055] As described above, with the wafer W and polishing pad 25 rotating in the directions of the arrows shown, when the lifting mechanism 30 is driven to lower the polishing pad 25 in the -Z axis direction, the polishing surface 25a of the polishing pad 25 comes into contact with the entire upper surface (back surface) of the wafer W. At the same time, when the on / off valve V of the slurry supply means 40 is opened, slurry is supplied from the slurry supply source 41 to the contact area (polishing area) between the polishing pad 25 and the wafer W via the circular hole-shaped supply passage 43 formed perpendicular to the axis centers of the piping 42, spindle 22, connecting member 23, platen 24, and polishing pad 25. Therefore, the entire upper surface of the wafer W is chemically and mechanically polished by the polishing pad 25 while receiving the slurry supply, and grinding marks remaining on the upper surface of the wafer W are removed, thereby increasing the flexural strength of the wafer W. Thus, because the shape of the polishing surface 25a of the shaped polishing pad 25 is good (Step S8: Yes), the series of processes is completed when the upper surface of the wafer W is polished by the polishing pad 25 (Step S10 in Figure 4).

[0056] On the other hand, if the shape of the polishing surface 25a of the polishing pad 25 after shaping is "defective (NG)" (Step S8: No), the contact conditions of the dressing part 51 of the dressing mechanism 50 with the polishing pad 25 are changed (Step S12 in Figure 4). In this embodiment, as parameters for changing the contact conditions of the dressing part 51 with the polishing pad 25, as described above, four parameters are used: the rotation speed of the polishing pad 25, the rotation speed of the dressing part 51, the movement speed of the dressing part 51, and the pressing force of the dressing part 51. At least one of these parameters is controlled to change the contact conditions of the dressing part 51 with the polishing pad 25, and then the polishing surface 25a of the polishing pad 25 is reshaped (Steps S1 to S8 in Figure 4).

[0057] Here, the rotational speed of the polishing pad 25 is changed by the pad rotation control unit 82 provided in the control unit 80. That is, when the rotational speed of the spindle motor 21, i.e., the polishing pad 25, detected by the encoder 26 is transmitted to the pad rotation control unit 82 of the control unit 80, the pad rotation control unit 82 controls the rotational speed of the spindle motor 21 so that the rotational speed of the polishing pad 25 is set to an appropriate value. Specifically, the higher the rotational speed of the polishing pad 25, the greater the amount of material removed from the polishing surface 25a of the polishing pad 25.

[0058] Furthermore, the rotational speed of the dressing section 51 of the dressing mechanism 50 is changed by the dressing section rotation control unit 83 provided in the control unit 80. That is, when the rotational speed of the motor 53, i.e., the dressing section 51, detected by the encoder 54 is transmitted to the dressing section rotation control unit 83 of the control unit 80, the dressing section rotation control unit 83 controls the rotational speed of the motor 53 so that the rotational speed of the dressing section 51 becomes an appropriate value. Specifically, the higher the rotational speed of the dressing section 51, the greater the amount of dressing on the polishing surface 25a of the polishing pad 25.

[0059] Furthermore, the horizontal movement speed (second direction) of the dressing section 51 is changed by the dressing section movement speed control unit 84 provided in the control unit 80. That is, when the rotational speed of a motor (not shown) detected by an encoder (not shown) provided in the horizontal movement mechanism 60 is transmitted to the dressing section movement speed control unit 84 of the control unit 80, the dressing section movement speed control unit 84 controls the rotational speed of the motor so that the movement speed of the dressing section 51 is set to an appropriate value. Specifically, the higher the movement speed of the dressing section 51, the smaller the amount of dressing on the polishing surface 25a of the polishing pad 25, and conversely, the lower the movement speed of the dressing section 51, the larger the amount of dressing on the polishing surface 25a of the polishing pad 25.

[0060] Furthermore, the pressing force of the dressing section 51 is changed by a dressing section pressing force control unit 85 provided in the control unit 80. Specifically, the pressure in the lower chamber (not shown) of the air cylinder 56 of the dressing mechanism 50 is transmitted to the dressing section pressing force control unit 85 provided in the control unit 80, and when the dressing section pressing force control unit 85 calculates the pressing force of the dressing section 51 against the polishing pad 25, the dressing section pressing force control unit 85 controls the pressure in the lower chamber of the air cylinder 56 so that the pressing force of the dressing section 51 is at an appropriate value. In particular, the greater the pressing force of the dressing section 51, the greater the amount of dressing on the polishing surface 25a of the polishing pad 25, and conversely, the smaller the pressing force of the dressing section 51, the smaller the amount of dressing on the polishing surface 25a of the polishing pad 25.

[0061] Thus, by controlling at least one of the four parameters—the rotational speed of the polishing pad 25, the rotational speed of the dressing unit 51, the movement speed of the dressing unit 51, and the pressing force of the dressing unit 51—to change the contact conditions of the dressing unit 51 with the polishing pad 25 (step S12 in Figure 4), the processes in steps S1 to S8 in Figure 4 are repeated to reshape the polishing surface 25a of the polishing pad 25. This reshaping of the polishing surface 25a of the polishing pad 25 is repeated until the shape of the polishing surface 25a of the polishing pad 25 after shaping is "good".

[0062] Here, Figures 5, 6, and 7 show, as patterns 1 to 3, the shapes of the polishing surface 25a of the polishing pad 25 for various shapes required for the wafer W after polishing, in the following cases: 1) when the wafer W before polishing (after grinding) is straight (uniform thickness), 2) when it is convex with a thicker central part, and 3) when it is concave with a thinner central part. The shape of the wafer W before polishing (after grinding) is determined by measuring the thickness of the wafer W at multiple locations in the radial direction.

[0063] 1) If the shape of the wafer W before polishing is flat: As shown in Figure 5, when the shape of the wafer W before polishing is flat, and when the desired shape of the wafer W after polishing is a convex shape with a thicker central part, as shown in Pattern 1, the polishing surface 25a of the polishing pad 25 is shaped to be a convex shape with a thicker central part and a concave shape with a thinner radial middle section.

[0064] Furthermore, as shown in Pattern 2, if the required shape of the polished wafer W is flat, the polishing surface 25a of the polishing pad 25 is shaped to be a flat shape with a uniform thickness.

[0065] Furthermore, as shown in Pattern 3, if the required shape of the polished wafer W is a concave shape with a thin thickness in the center, the polishing surface 25a of the polishing pad 25 is shaped to be a concave shape with a thin thickness in the center and a convex shape with a thicker thickness in the radial middle.

[0066] 2) When the shape of the wafer W before polishing is convex: As shown in Figure 6, if the shape of the wafer W before polishing is convex, and the desired shape of the wafer W after polishing is a convex shape with a thicker central part, as shown in Pattern 1, then the polishing surface 25a of the polishing pad 25 is shaped to be a convex shape with a thicker central part and a concave shape with a thinner radial middle section.

[0067] Furthermore, as shown in Pattern 2, if the required shape of the polished wafer W is a gentler convex shape than the shape in Pattern 1, the polishing surface 25a of the polishing pad 25 is shaped to be a flat shape with a uniform thickness.

[0068] Furthermore, as shown in Pattern 3, if the required shape of the polished wafer W is flat, the polishing surface 25a of the polishing pad 25 is shaped to be a concave shape with a thin thickness in the center and a convex shape with a thicker thickness in the radial middle.

[0069] 3) When the shape of the wafer W before polishing is concave: As shown in Figure 7, if the shape of the wafer W before polishing is concave, and the desired shape of the wafer W after polishing is flat, as shown in Pattern 1, the polishing surface 25a of the polishing pad 25 is shaped to be convex in the center where the thickness is greater, and concave in the radial middle where the thickness is greater.

[0070] Furthermore, as shown in Pattern 2, if the required shape of the polished wafer W is concave, the polishing surface 25a of the polishing pad 25 is shaped to be a flat shape with a uniform thickness.

[0071] Furthermore, as shown in Pattern 3, if the required shape of the polished wafer W is a concave shape with a greater degree of concavity than the shape in Pattern 2, the polishing surface 25a of the polishing pad 25 is shaped to be a concave shape with a thin thickness in the center and a convex shape with a thicker thickness in the radial middle.

[0072] As is clear from the above description, according to the shaping method for the polishing pad 25 of this embodiment, in the shaping step, the dressing portion 51 that contacts the polishing surface 25a of the polishing pad 25 is moved horizontally to shape the polishing surface 25a, and at the same time, in the polishing surface shape measurement step, the shape of the polishing surface 25a is measured from the displacement in the vertical direction (first direction) and the movement position in the horizontal direction (second direction) of the dressing portion 51 measured by the displacement measuring unit 70. In other words, the shaping and shape measurement of the polishing surface 25a of the polishing pad 25 are performed simultaneously, thus shortening the time required to determine whether the shape of the polishing surface 25a after shaping is good or bad.

[0073] Furthermore, if the shape of the polishing surface 25a of the shaped polishing pad 25 is "good," the next step, polishing of the wafer W, is performed using the polishing pad 25 with the shaped polishing surface 25a, so that a wafer W of the desired shape can be efficiently obtained by polishing. Also, if the shape of the polishing surface 25a of the shaped polishing pad 25 is "bad," the measured shape of the polishing surface 25a of the polishing pad 25 is fed back, and the contact conditions of the dressing part 51 of the dressing mechanism 50 with the polishing pad 25 are changed based on the fed-back shape of the polishing surface 25a to reshape the polishing surface 25a of the polishing pad 25, so that a wafer W of the desired shape can be obtained by polishing the wafer W with the polishing pad 25 with the reshaped polishing surface 25a.

[0074] In the embodiments described above, the case where the workpiece is a wafer was explained as an example, but the present invention is similarly applicable to a method for shaping a polishing pad for polishing any workpiece other than a wafer.

[0075] Furthermore, in the above embodiments, the shaping of the polishing surface 25a of the polishing pad 25 in the shaping step is performed by moving the dressing portion 51 of the dressing mechanism 50 in the horizontal direction. However, a configuration may also be adopted in which the polishing surface 25a of the polishing pad 25 is shaped while moving either the polishing pad 25 or both the dressing portion 51 and the polishing pad 25.

[0076] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical idea described in the claims, specification, and drawings. [Explanation of Symbols]

[0077] 1: Polishing device, 10: Holding table, 10A: Frame, 10B: Base, 10a: Recess 11: Porous member, 11a: Holding surface, 12: Rotating shaft, 13: Motor, 14: Encoder, 20: Polishing unit, 21: Spindle motor, 22: Spindle, 23: Connecting member, 24: Platen, 25: Polishing pad, 25a: Polishing surface, 26: Encoder, 30: Lifting mechanism (first direction movement mechanism), 40: Slurry supply means, 41: Slurry supply source, 42: Piping, 43: Supply channel, 50: Dressing mechanism, 51: Dressing section, 52: Support plate, 53: Motor, 53a: Motor shaft, 54: Encoder, 55: Support base, 56: Air cylinder, 56A: Cylinder, 56a: Piston rod, 60: Horizontal movement mechanism (second direction movement mechanism), 70: Displacement measuring unit, 71: Reference member, 80: Control unit, 81: Memory unit, 82: Pad rotation speed control unit, 83: Dress section rotation speed control unit, 84: Dress section movement speed control unit, 85: Dressing part pressing force control unit, CL1: Rotation axis of polishing pad, CL2: Rotation axis of the holding table, V: On / off valve, W: Wafer (workpiece) ε: Offset amount of the rotation axis between the polishing pad and the holding table

Claims

1. A rotatable holding table for holding the workpiece, A rotatable polishing pad having a polishing surface provided facing the holding surface of the holding table, A dressing mechanism that contacts the polished surface and shapes the polished surface, A first direction movement mechanism moves the dressing portion of the dressing mechanism in a first direction perpendicular to the polishing surface, A second direction movement mechanism moves at least one of the dressing portion and the polishing pad in a second direction parallel to the polishing surface, A displacement measuring unit for measuring the amount of displacement of the dress portion in the first direction, A polishing surface shaping method for a polishing apparatus comprising the dressing portion, wherein the polishing surface of the polishing pad is shaped by the dressing portion, A shaping step in which, with the dressing portion in contact with the polishing surface by the first direction movement mechanism, the dressing portion is moved along the polishing surface by the second direction movement mechanism to shape the polishing surface, A polishing surface shape measurement step, which measures the shape of the polishing surface from the displacement of the dressing portion in the first direction and the position of movement of the dressing portion in the second direction when the dressing portion comes into contact with the polishing surface, A determination step for determining whether the shape of the polished surface measured by the polished surface shape measurement step is good or bad, Equipped with, A polishing surface shaping method characterized in that, if the shape of the polished surface is determined to be "good" in the determination step, the process moves to a polishing step in which the polished surface is polished with the polishing pad, and if the shape of the polished surface is determined to be "poor", a condition change step is performed to change the contact conditions of the dressed portion with the polished surface in the shaping step, and the shaping step is performed based on the contact conditions changed in the condition change step.

2. The polishing surface shaping method according to claim 1, characterized in that the contact condition is at least one of the rotational speed of at least one of the polishing surface and the dressing portion, the moving speed of the dressing portion, and the pressing force of the dressing portion against the polishing surface.

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