Method for raising a polishing head after polishing a workpiece, and polishing apparatus for a workpiece

Abstract

To provide a method for raising a polishing head, which can prevent bending of a workpiece caused by contact with a retainer ring and prevent generation of excessive stress in the workpiece when the polishing head is raised from a polishing pad after polishing of the workpiece.SOLUTION: This method presses a workpiece W to a polishing pad 2 to polish it while rotating a polishing head 7 and the polishing pad 2, stops the rotation of the polishing pad 2 and the polishing head 7, raises a retainer ring 48 of the polishing head 7 relative to the workpiece W to separate the retainer ring 48 from the polishing pad 2, moves the retainer ring 48 to a position higher than the workpiece W, and then raises the polishing head 7 in a state where the workpiece W is held on the polishing head 7.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a technique for reducing the stress of a workpiece after polishing the workpiece used in the manufacture of semiconductor devices such as wafers, substrates, and panels, and raising the polishing head together with the workpiece.

Background Art

[0002] Chemical Mechanical Polishing (CMP) is a technique for polishing a workpiece by bringing the workpiece into sliding contact with a polishing surface while supplying a polishing liquid containing abrasive grains such as silica (SiO 2 ) onto the polishing surface of a polishing pad. As shown in FIG. 13, a polishing apparatus for performing CMP includes a polishing table 501 that supports a polishing pad 500, a polishing head 505 that holds a workpiece W, and a polishing liquid nozzle 508 that supplies a polishing liquid to the polishing pad 500.

[0003] Polishing of the workpiece W using such a polishing apparatus is performed as follows. While rotating the polishing table 501 together with the polishing pad 500, a polishing liquid is supplied from the polishing liquid nozzle 508 onto the polishing pad 500. The polishing head 505 presses the workpiece W against the polishing pad 500 while rotating the workpiece W. The surface of the workpiece W is flattened by a combination of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and the polishing pad 500 while the workpiece W is in sliding contact with the polishing pad 500 in the presence of the polishing liquid.

[0004] During polishing of the workpiece W, since the surface of the workpiece W is in sliding contact with the rotating polishing pad 500, a frictional force acts on the workpiece W. Therefore, in order to prevent the workpiece W from coming off the polishing head 505 during polishing of the workpiece W, the polishing head 505 is provided with a retainer ring 510. This retainer ring 510 is arranged so as to surround the workpiece W, and during polishing of the workpiece W, the retainer ring 510 presses the polishing pad 500 outside the workpiece W while rotating.

[0005] FIG. 14 is a cross-sectional view showing a part of the polishing head 505 shown in FIG. 13. As shown in FIG. 14, the polishing head 505 has an annular elastic film 512 for pressing the retainer ring 510 against the polishing pad 500. A pressure chamber 513 is formed inside the elastic film 512. When pressurized gas (for example, pressurized air) is supplied into the pressure chamber 513, the elastic film 512 receiving the fluid pressure in the pressure chamber 513 presses the retainer ring 510 against the polishing pad 500. Therefore, during the polishing of the workpiece W, the retainer ring 510 can prevent the workpiece W from jumping out of the polishing head 505.

[0006] The polishing head 505 further has an elastic film 514 for pressing the workpiece W against the polishing pad 500. A pressure chamber 515 is formed inside the elastic film 514. When pressurized gas (for example, pressurized air) is supplied into the pressure chamber 515, the elastic film 514 receiving the fluid pressure in the pressure chamber 515 presses the workpiece W against the polishing pad 500. Therefore, the workpiece W is brought into sliding contact with the polishing pad 500 in a state where polishing liquid exists on the polishing pad 500.

[0007] Both the elastic film 512 and the elastic film 514 are fixed to the carrier 517 of the polishing head 505. The retainer ring 510 is configured to be vertically movable relative to the carrier 517 and the elastic film 514 in order to be able to press the polishing pad 500 independently of the workpiece W.

[0008] After polishing the workpiece W, as shown in Fig. 15, a negative pressure is formed in the pressure chamber 515 to adsorb the workpiece W to the elastic membrane 514. When the workpiece W is adsorbed to the elastic membrane 514, the workpiece W is slightly lifted. If the surface tension of the liquid existing between the workpiece W and the polishing pad 500 is large, the workpiece W may fail to be lifted from the polishing pad 500. Therefore, in order to reduce the surface tension acting between the workpiece W and the polishing pad 500, while rotating the polishing head 505 and the polishing pad 500 respectively, the workpiece W is adsorbed to the elastic membrane 514. Then, the polishing head 505 is lifted together with the workpiece W, and further the polishing head 505 is moved together with the workpiece W to a predetermined workpiece transfer position.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] Even when the polishing head 505 rises, in order to prevent the workpiece W on the rotating polishing pad 500 from jumping out of the polishing head 505, the retainer ring 510 is pressed against the polishing pad 500. For this reason, as shown in Fig. 16, while the carrier 517 of the polishing head 505 and the workpiece W rise and separate from the polishing pad 500, the lower surface of the retainer ring 510 remains in contact with the polishing pad 500.

[0011] However, if the workpiece W attempts to rise while remaining in contact with the inner surface of the retainer ring 510, the portion of the workpiece W in contact with the inner surface of the retainer ring 510 will tend to remain on the polishing pad 500, causing the workpiece W to bend downward and excessive stress may be generated in the workpiece W. If this stress is too large, the workpiece W may crack. In particular, as shown in FIG. 17, when wear grooves 510a are formed on the inner surface of the retainer ring 510 due to contact with the workpiece W, it becomes easier to get caught, so the workpiece W is likely to bend downward significantly, and as a result, the workpiece W is likely to crack.

[0012] Therefore, the present invention provides a method for raising a polishing head that can prevent the workpiece from bending by avoiding contact with the inner surface of the retainer ring when raising the polishing head from the polishing pad after polishing the workpiece, and prevent excessive stress from occurring in the workpiece. Further, the present invention provides a polishing apparatus for a workpiece that can execute such a method. It is.

Means for Solving the Problems

[0013] In one aspect, there is provided a method for raising a polishing head after polishing a workpiece, the method comprising pressing the workpiece against the polishing pad while rotating the polishing head and the polishing pad to polish the workpiece, stopping the rotation of the polishing pad and the polishing head, and raising the retainer ring of the polishing head relative to the workpiece to separate the retainer ring from the polishing pad and move the retainer ring to a position higher than the workpiece, and then raising the polishing head while the workpiece is held by the polishing head.

[0014] In one aspect, the method further includes holding the workpiece by the polishing head after polishing the workpiece and before raising the polishing head. In one aspect, the step of raising the retainer ring to a position higher than the workpiece is performed before or simultaneously with holding the workpiece by the polishing head. In one aspect, the step of holding the workpiece by the polishing head is performed while directly supplying fluid between the workpiece and the polishing pad. In one aspect, the polishing head has an elastic film forming a plurality of pressure chambers for pressing the workpiece against the polishing pad, and the step of holding the workpiece by the polishing head includes forming a negative pressure in the outer pressure chamber among the plurality of pressure chambers and then forming a negative pressure in the inner pressure chamber to hold the workpiece by the polishing head. In one aspect, the step of holding the workpiece by the polishing head is performed before stopping the rotation of the polishing pad and the polishing head. In one aspect, the step of raising the polishing head includes raising the polishing head at a first speed until the whole of the workpiece is separated from the polishing pad, and after the whole of the workpiece is separated from the polishing pad, raising the polishing head at a second speed higher than the first speed.

[0015] In one aspect, there is a polishing apparatus for a workpiece, comprising a polishing table for supporting a polishing pad, a polishing table rotating device for rotating the polishing table together with the polishing pad, a polishing head for pressing the workpiece against the polishing pad to polish the workpiece, a polishing head pressure control device for controlling the pressure within the polishing head, a polishing head rotating device for rotating the polishing head, a polishing head lifting device for moving the polishing head vertically relative to the polishing table, and an operation control unit for controlling the operations of the polishing table rotating device, the polishing head pressure control device, the polishing head rotating device, and the polishing head lifting device. The polishing head has a retainer ring surrounding the workpiece. After polishing the workpiece, the operation control unit gives commands to the polishing table rotating device and the polishing head rotating device to stop the rotation of the polishing pad and the polishing head, gives a command to the polishing head pressure control device to lift the retainer ring relative to the workpiece, thereby separating the retainer ring from the polishing pad and moving the retainer ring to a position higher than the workpiece, and then gives a command to the polishing head lifting device to lift the polishing head with the workpiece held by the polishing head. A polishing apparatus is provided which is configured as such.

[0016] In one aspect, the operation control unit is configured to give a command to the polishing head pressure control device to hold the workpiece by the polishing head after the workpiece has been polished and before the polishing head is lifted. In one aspect, the operation control unit is configured to give a command to the polishing head pressure control device to lift the retainer ring to a position higher than the workpiece before or simultaneously with holding the workpiece by the polishing head. In one aspect, the polishing apparatus further includes a fluid supply system that supplies fluid between the workpiece and the polishing pad, and the operation control unit gives an instruction to the fluid supply system to directly supply fluid between the workpiece and the polishing pad while the polishing head is configured to hold the workpiece. In one aspect, the polishing head has an elastic film that forms a plurality of pressure chambers for pressing the workpiece against the polishing pad, and the operation control unit gives an instruction to the polishing head pressure control device to form a negative pressure in the outer pressure chamber among the plurality of pressure chambers, and then form a negative pressure in the inner pressure chamber, so that the workpiece is configured to be held by the polishing head. In one aspect, the operation control unit gives an instruction to the polishing head pressure control device to configure the workpiece to be held by the polishing head before stopping the rotation of the polishing pad and the polishing head. In one aspect, the operation control unit gives an instruction to the polishing head lifting device to raise the polishing head at a first speed until the entire workpiece is separated from the polishing pad, and after the entire workpiece is separated from the polishing pad, raise the polishing head at a second speed higher than the first speed.

[0017] In one aspect, a computer-readable recording medium having a program recorded thereon for causing a computer to execute steps including: giving commands to a polishing head pressure control device, a polishing table rotation device, and a polishing head rotation device to polish a workpiece by pressing the workpiece against a polishing pad while rotating the polishing head and the polishing pad on the polishing table; after polishing the workpiece, giving commands to the polishing table rotation device and the polishing head rotation device to stop the rotation of the polishing pad and the polishing head; giving a command to the polishing head pressure control device to relatively raise the retainer ring with respect to the workpiece to separate the retainer ring from the polishing pad and move the retainer ring to a position higher than the workpiece; and giving a command to the polishing head lifting device to raise the polishing head while the workpiece is held by the polishing head.

Advantages of the Invention

[0018] According to the present invention, before the polishing head is lifted, the retainer ring is raised to a position higher than the workpiece. Therefore, when the polishing head is lifted, the workpiece does not come into contact with the retainer ring, and the workpiece is not bent downward by the retainer ring. As a result, excessive stress does not occur in the workpiece, and cracking of the workpiece can be prevented.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a polishing apparatus. The polishing apparatus is an apparatus for chemically and mechanically polishing a workpiece W used in the manufacture of semiconductor devices such as wafers, substrates (for example, circular substrates, square substrates), and panels. In the embodiment shown in FIG. 1, a wafer is used as the workpiece W.

[0021] As shown in FIG. 1, this polishing apparatus includes a polishing table 5 that supports a polishing pad 2 having a polishing surface 2a, a polishing head 7 that presses the workpiece W against the polishing surface 2a, and a polishing liquid supply nozzle 8 that supplies a polishing liquid (for example, a slurry containing abrasive grains) to the polishing surface 2a. The polishing head 7 is configured to hold the workpiece W on its lower surface.

[0022] The polishing apparatus further includes a support shaft 14, a polishing head swing arm 16 connected to the upper end of the support shaft 14, a polishing head shaft 18 rotatably supported at the free end of the polishing head swing arm 16, and a polishing head rotation device 20 that rotates the polishing head shaft 18 and the polishing head 7. The polishing head 7 is fixed to the lower end of the polishing head shaft 18. The polishing head rotation device 20 is fixed to the polishing head swing arm 16. The polishing head rotation device 20 includes an electric motor, a torque transmission device, etc., but its configuration is not particularly limited. The polishing head rotation device 20 is connected to the polishing head shaft 18 and is configured to rotate the polishing head shaft 18 and the polishing head 7 in the direction indicated by the arrow. A rotary joint 22 is connected to the upper end of the polishing head shaft 18.

[0023] The polishing apparatus further includes a polishing head lifting device 25 that moves the polishing head 7 and the polishing head shaft 18 up and down relative to the polishing table 5 and the polishing head swing arm 16. The polishing head lifting device 25 has a combination of a ball screw mechanism and a servo motor, or an actuator such as an air cylinder, but its configuration is not particularly limited. When the polishing head lifting device 25 moves the polishing head shaft 18 up and down relative to the polishing head swing arm 16, the polishing head 7 moves up and down relative to the polishing head swing arm 16 and the polishing table 5 as shown by the arrow.

[0024] The polishing apparatus further includes a polishing table rotating device 30 that rotates the polishing pad 2 and the polishing table 5 about their axes. The polishing table rotating device 30 is disposed below the polishing table 5, and the polishing table 5 is connected to the polishing table rotating device 30 via a table shaft 5a. The polishing table rotating device 30 includes an actuator such as an electric motor, but its configuration is not particularly limited. The polishing table 5 and the polishing pad 2 are integrally rotated in the direction shown by the arrow about the table shaft 5a by the polishing table rotating device 30. The polishing pad 2 is attached to the upper surface of the polishing table 5. The exposed surface of the polishing pad 2 constitutes a polishing surface 2a for polishing a workpiece W such as a wafer.

[0025] The polishing apparatus further includes a polishing head pressure control device 33 that controls the pressure within the polishing head 7. This polishing head pressure control device 33 is configured to operate components of the polishing head 7 (for example, the retainer ring and the elastic film described later). In the present embodiment, the polishing head pressure control device 33 includes a pressure regulator (not shown) that adjusts the pressure of a gas (for example, air) as the operating fluid for operating the components of the polishing head 7. For example, by adjusting the pressure of the gas supplied to the polishing head 7 with the pressure regulator, the force with which the polishing head 7 presses the workpiece W against the polishing pad 2 can be adjusted. The polishing head pressure control device 33 is connected to the rotary joint 22 and supplies gas at a predetermined pressure to the polishing head 7 through the rotary joint 22.

[0026] The polishing apparatus further includes a polishing head moving device 37 that moves the polishing head 7 in a direction parallel to the polishing surface 2a of the polishing pad 2. This polishing head moving device 37 is fixed to the upper end of the support shaft 14 and is connected to the polishing head swing arm 16. The polishing head moving device 37 can move the polishing head 7 supported by the polishing head swing arm 16 in a direction parallel to the polishing surface 2a of the polishing pad 2 by rotating the polishing head swing arm 16 about the support shaft 14. However, the configuration of the polishing head moving device 37 is not limited to this embodiment. In one embodiment, the polishing head moving device 37 may be connected to the lower part of the support shaft 14 and configured to integrally rotate the support shaft 14 and the polishing head swing arm 16 about the support shaft 14.

[0027] The polishing apparatus further includes an operation control unit 40 that controls the overall operation of the polishing apparatus including the polishing head rotation device 20, the polishing head lifting device 25, the polishing table rotation device 30, the polishing head pressure control device 33, and the polishing head moving device 37. The operation control unit 40 includes at least one computer. The operation control unit 40 may include a plurality of computers. For example, the operation control unit 40 may be composed of a combination of an edge server and a cloud server.

[0028] The operation control unit 40 includes a storage device 40a and an arithmetic unit 40b. The arithmetic unit 40b includes a CPU (Central Processing Unit) or a GPU (Graphics Processing Module) that performs calculations according to instructions included in a program stored in the storage device 40a. The storage device 40a includes a main storage device (e.g., a random access memory) accessible by the arithmetic unit 40b and an auxiliary storage device (e.g., a hard disk drive or a solid state drive) that stores data and programs. However, the specific configuration of the operation control unit 40 is not limited to these examples.

[0029] The polishing of the workpiece W is performed as follows. The workpiece W is held by the polishing head 7 with its polished surface facing downward. While rotating the polishing head 7 and the polishing table 5 respectively, polishing liquid (e.g., slurry containing abrasive grains) is supplied from a polishing liquid supply nozzle 8 provided above the polishing table 5 onto the polishing surface 2a of the polishing pad 2. The polishing pad 2 rotates integrally with the polishing table 5 about its central axis. The polishing head 7 is lowered by a polishing head lifting device 25 to a predetermined polishing operation height. Further, with the polishing head 7 maintained at the above polishing operation height, the workpiece W is pressed against the polishing surface 2a of the polishing pad 2. The workpiece W rotates integrally with the polishing head 7. With the polishing liquid present on the polishing surface 2a of the polishing pad 2, the workpiece W is brought into sliding contact with the polishing surface 2a. The surface of the workpiece W is polished by a combination of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2.

[0030] Next, the details of the polishing head 7 will be described. FIG. 2 is a cross-sectional view showing an embodiment of the polishing head 7. The polishing head 7 includes a head body 45 and a retainer ring 48. The head body 45 includes a carrier 50 connected to a polishing head shaft 18 and a first elastic film 51 attached to the lower surface of the carrier 50.

[0031] The lower surface of the first elastic membrane 51 constitutes a pressing surface 51a for pressing the workpiece W against the polishing pad 2, and this pressing surface 51a is in contact with the upper surface of the workpiece W (the surface opposite to the surface to be polished). A plurality of first pressure chambers C1, C2, C3 are formed between the carrier 50 and the first elastic membrane 51. That is, a plurality of first pressure chambers C1, C2, C3 are formed inside the first elastic membrane 51. The central first pressure chamber C1 is circular, the first pressure chamber C2 outside the first pressure chamber C1 is annular, and the first pressure chamber C3 outside the first pressure chamber C2 is annular. These first pressure chambers C1, C2, C3 are arranged concentrically.

[0032] The first pressure chambers C1, C2, C3 are connected to the polishing head pressure control device 33 through the first fluid lines F1, F2, F3 and the rotary joint 22. The polishing head pressure control device 33 in this embodiment includes a pressure regulator (not shown) that supplies a gas at a predetermined pressure to the polishing head 7. When fluid (for example, a gas such as air) is supplied to the first pressure chambers C1, C2, C3, the pressing surface 51a of the first elastic membrane 51 receiving the fluid pressure in the first pressure chambers C1, C2, C3 presses the workpiece W against the polishing surface 2a of the polishing pad 2. The number of the first pressure chambers C1, C2, C3 is not limited to the embodiment shown in FIG. 2. In one embodiment, a single first pressure chamber may be provided between the carrier 50 and the first elastic membrane 51.

[0033] The retainer ring 48 is arranged so as to surround the workpiece W and the first elastic membrane 51. More specifically, the retainer ring 48 is arranged so as to surround the outer edge of the workpiece W and the pressing surface 51a of the first elastic membrane 51. The upper part of the retainer ring 48 is connected to an annular retainer ring pressing mechanism 60. This retainer ring pressing mechanism 60 is configured to apply a uniform downward load to the entire upper surface of the retainer ring 48 and press the lower surface of the retainer ring 48 against the polishing surface 2a of the polishing pad 2.

[0034] The retainer pressing mechanism 60 includes an annular second elastic membrane 62 attached to the carrier 50. A second pressure chamber 65 is formed inside the second elastic membrane 62. The second pressure chamber 65 is connected to the polishing head pressure control device 33 through the second fluid line F4 and the rotary joint 22. When fluid (for example, a gas such as air) is supplied to the second pressure chamber 65 through the second fluid line F4, the second elastic membrane 62 receiving the fluid pressure in the second pressure chamber 65 pushes down the entire retainer ring 48. In this way, the retainer pressing mechanism 60 presses the lower surface of the retainer ring 48 against the polishing surface 2a of the polishing pad 2.

[0035] When a negative pressure is formed in any one of the first pressure chambers C1, C2, C3 by the polishing head pressure control device 33, the workpiece W is held on the pressing surface 51a of the first elastic membrane 51 by vacuum suction. For example, as shown in FIG. 3, when a negative pressure is formed in the first pressure chambers C2 and C3, the pressing surface 51a of the first elastic membrane 51 is recessed upward, and the first elastic membrane 51 functions as a suction cup that attracts the workpiece W. When attracting the workpiece W to the first elastic membrane 51, a negative pressure may be formed in only one of the first pressure chambers C1, C2, C3, or a negative pressure may be formed in all of the first pressure chambers C1, C2, C3.

[0036] In one embodiment, the pressing surface 51a of the first elastic membrane 51 may have through holes (not shown) communicating with at least one of the first pressure chambers C1, C2, C3. In this case, when a negative pressure is formed in the first pressure chamber communicating with the through hole, a negative pressure is also formed in the through hole, and the workpiece W can be attracted to the pressing surface 51a of the first elastic membrane 51 by this negative pressure.

[0037] As shown in Fig. 4, when a negative pressure is formed in the second pressure chamber 65 by the polishing head pressure control device 33, the retainer ring 48 rises relative to the first elastic membrane 51, the carrier 50, and the workpiece W and moves away from the polishing pad 2. On the other hand, when the fluid pressurized in the second pressure chamber 65 is supplied by the polishing head pressure control device 33, as shown in Fig. 2, the retainer ring 48 descends relative to the first elastic membrane 51, the carrier 50, and the workpiece W and presses against the polishing pad 2. Thus, the polishing head pressure control device 33 can move the retainer ring 48 up and down by changing the pressure in the second pressure chamber 65.

[0038] Fig. 5 is a diagram for explaining the state of releasing the polished workpiece W from the polishing head 7. After the workpiece W is polished, the polishing head 7 is moved together with the workpiece W to the workpiece transfer position. At this workpiece transfer position, fluid (for example, a gas such as air) is supplied into the first pressure chambers C1, C2, C3, and the first elastic membrane 51 expands. Then, a jet of release fluid (for example, pure water or gas or a mixture thereof) is discharged from the release nozzle 71 to the contact portion between the workpiece W and the first elastic membrane 51, whereby the workpiece W is released from the polishing head 7. When the workpiece W is released, as shown in Fig. 5, the retainer ring 48 is at a position higher than the workpiece W. Therefore, the release fluid can reach the contact portion between the workpiece W and the first elastic membrane 51. The released workpiece W is received by a transfer device (not shown) and transferred for the next process.

[0039] Next, the operation of the polishing head 7 during and after the polishing of the workpiece W will be described with reference to Fig. 6. Fig. 6 is a flowchart for explaining an embodiment of the operation of the polishing head 7 during and after the polishing of the workpiece W.

[0040] In step 1, the operation control unit 40 gives commands to the polishing table rotation device 30 and the polishing head rotation device 20 to rotate the polishing pad 2 and the polishing head 7 at predetermined speeds respectively. The polishing liquid is supplied from the polishing liquid supply nozzle 8 onto the rotating polishing pad 2. The operation control unit 40 gives a command to the polishing head lifting device 25 to lower the polishing head 7 to a predetermined polishing operation height. The operation control unit 40 further gives a command to the polishing head pressure control device 33 to supply the fluid pressurized in the first pressure chambers C1, C2, C3 of the polishing head 7 and the second pressure chamber 65, and press the workpiece W and the retainer ring 48 against the polishing surface 2a of the polishing pad 2 (see Fig. 2). The workpiece W is brought into sliding contact with the polishing surface 2a of the polishing pad 2 in a state where the polishing liquid exists on the polishing pad 2.

[0041] The surface of the workpiece W is polished by the combined action of the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad 2. During the polishing of the workpiece W, the polishing pad 2 rotates integrally with the polishing table 5, and the workpiece W rotates integrally with the polishing head 7. During the polishing of the workpiece W, the polishing head 7 is maintained at the above-mentioned polishing operation height. The polishing operation height is the overall relative height of the polishing head 7 with respect to the polishing surface 2a of the polishing pad 2.

[0042] In step 2, after the polishing of the workpiece W is completed, the pressing of the workpiece W against the polishing pad 2 by the polishing head 7 is stopped. After the polishing of the workpiece W is completed, the supply of the polishing liquid to the polishing pad 2 is also stopped.

[0043] In step 3, the operation control unit 40 gives commands to the polishing table rotation device 30 and the polishing head rotation device 20 to stop the rotation of the polishing pad 2 and the polishing head 7. The polishing table rotation device 30 stops the rotation of the polishing table 5, thereby also stopping the rotation of the polishing pad 2.

[0044] In step 4, the operation control unit 40 gives an instruction to the polishing head pressure control device 33 to relatively raise the retainer ring 48 with respect to the workpiece W, thereby separating the retainer ring 48 from the polishing pad 2 and moving the retainer ring 48 to a position higher than the workpiece W (see Fig. 4). When the retainer ring 48 is relatively raised with respect to the workpiece W, the rotation of the polishing pad 2 and the polishing head 7 has already stopped. Therefore, the workpiece W does not jump out from the polishing head 7, and the relative position of the workpiece W with respect to the polishing head 7 does not change either. While the retainer ring 48 is relatively raised with respect to the workpiece W, the polishing head 7 is maintained at the above-mentioned polishing operation height, and the workpiece W is in contact with the polishing pad 2.

[0045] In step 5, the operation control unit 40 gives an instruction to the polishing head pressure control device 33 to cause the polishing head 7 to hold the workpiece W. More specifically, a negative pressure is formed in at least one of the first pressure chambers C1 to C3 of the polishing head 7, and the workpiece W is attracted to the pressing surface 51a of the first elastic film 51 by vacuum suction. At this time, at least a part of the workpiece W is slightly lifted from the polishing pad 2.

[0046] In step 6, the operation control unit 40 gives an instruction to the polishing head lifting device 25 to lift the entire polishing head 7 holding the workpiece W. The polishing head 7, together with the workpiece W, is lifted to a position higher than the above-mentioned polishing operation height. When the polishing head 7 and the workpiece W are being lifted, the rotation of the polishing pad 2 and the polishing head 7 has already stopped.

[0047] In step 7, the operation control unit 40 gives an instruction to the polishing head moving device 37 to rotate the polishing head swing arm 16 about the support shaft 14 and move the polishing head 7 and the workpiece W to a predetermined workpiece transfer position.

[0048] In step 8, at the workpiece transfer position, a jet of release fluid (for example, pure water or gas or a mixture thereof) is discharged from the release nozzle 71 to the contact portion between the workpiece W and the first elastic film 51 (see FIG. 5), whereby the workpiece W is released from the polishing head 7.

[0049] According to the embodiment shown in FIG. 6, before the polishing head 7 is lifted from the polishing pad 2, the retainer ring 48 is lifted to a position higher than the workpiece W (see FIG. 4). Therefore, when the polishing head 7 is lifted, the workpiece W does not come into contact with the retainer ring 48, and the workpiece W is not bent downward by the retainer ring 48. As a result, excessive stress does not occur in the workpiece W, and cracking of the workpiece W can be prevented.

[0050] In the embodiment shown in FIG. 6, the retainer ring 48 is lifted in step 4, and then the workpiece W is held by the polishing head 7 in step 5. However, in one embodiment, the lifting of the retainer ring 48 in step 4 and the holding of the workpiece W by the polishing head 7 in step 5 may be performed simultaneously. Further, in other embodiments, the workpiece W may be held by the polishing head 7 in step 4, and then the retainer ring 48 may be lifted in step 5. However, as described with reference to FIG. 17, when wear grooves are formed on the inner surface of the retainer ring 48 due to contact with the workpiece W, the order of steps 4 and 5 shown in FIG. 6 is preferable. This is because when the workpiece W is held by the polishing head 7, the first pressure chamber C3 is reduced by negative pressure and the workpiece W is slightly lifted, and there is a possibility that the outer edge of the workpiece W is caught by the wear groove and the workpiece W is bent.

[0051] FIG. 7 is a flowchart for explaining another embodiment of the operation of the polishing head 7 during and after polishing of the workpiece W. Since the specific operations of each step not specifically described are the same as those of each step described with reference to FIG. 6, the overlapping descriptions thereof are omitted.

[0052] As shown in FIG. 7, in this embodiment, in step 3, the polished workpiece W is held by the polishing head 7, and then, in step 4, the rotation of the polishing pad 2 and the polishing table 5 is stopped. Further, in step 5, the retainer ring 48 is raised to a position higher than the workpiece W. During steps 3 and 4, the retainer ring 48 remains in contact with the polishing pad 2.

[0053] In the embodiment shown in FIG. 7, when the workpiece W is held by the polishing head 7, since the polishing pad 2 and the polishing table 5 are rotating, the adhesion is reduced by the liquid or air that enters between the workpiece W and the polishing pad 2, and there is an advantage that the attracting operation of the workpiece W by the polishing head 7 to the pressing surface 51a can be ensured. On the other hand, when wear grooves are formed on the inner surface of the retainer ring 48 due to contact with the workpiece W, the embodiment shown in FIG. 6 is preferable for the reasons described above.

[0054] FIGS. 8 and 9 are schematic views showing an example of the operation of the polishing head 7 holding the workpiece W. In FIGS. 8 and 9, the polishing head 7 is drawn in a simplified manner, and the deformation of the workpiece W is drawn in an exaggerated manner. In the example shown in FIG. 8, among the plurality of first pressure chambers C1 to C3, negative pressures are formed in order from the outer pressure chamber. That is, first, a negative pressure is formed in the outer first pressure chamber C3, and then a negative pressure is formed in the inner first pressure chamber C2. By forming negative pressures in the first pressure chambers C3 and C2 in such an order, the outer portion of the workpiece W is slightly lifted by the first elastic film 51, and an open gap is formed between the outer portion of the workpiece W and the polishing pad 2.

[0055] In contrast, in the example shown in FIG. 9, among the plurality of first pressure chambers C1 to C3, negative pressures are formed in order from the inner pressure chamber. That is, first, a negative pressure is formed in the innermost first pressure chamber C1, and then a negative pressure is formed in the outer first pressure chamber C2. When negative pressures are formed in the first pressure chambers C1 and C2 in this order, the central portion of the workpiece W is slightly lifted by the first elastic film 51, and a closed space S is formed between the central portion of the workpiece W and the polishing pad 2. Since the inside of this closed space S becomes a negative pressure, the entire workpiece W functions as a suction cup, preventing the workpiece W from being held by the polishing head 7.

[0056] From the above, it is preferable to first form a negative pressure in the outer first pressure chamber C3 and then form a negative pressure in the inner first pressure chamber C2. By such a holding operation of the workpiece W, the polishing head 7 can hold the workpiece W smoothly.

[0057] In one embodiment, as shown in FIG. 10, when the polishing head 7 holds the workpiece W, fluid may be supplied between the workpiece W and the polishing pad 2. More specifically, the polishing apparatus includes a fluid supply system 80 that supplies fluid between the workpiece W and the polishing pad 2. The fluid supply system 80 includes a fluid line 81 that supplies fluid (for example, liquid, or gas, or a mixture thereof) to the polishing surface 2a of the polishing pad 2, and an actuator-driven valve 82 connected to the fluid line 81.

[0058] The fluid line 81 extends inside the polishing table 5, and the fluid flows out onto the polishing surface 2a of the polishing pad 2 through an opening 83 formed in the polishing pad 2. Examples of the actuator-driven valve 82 include an electric valve, a solenoid valve, and an air-operated valve. The actuator-driven valve 82 is electrically connected to the operation control unit 40, and the operation of the actuator-driven valve 82 is controlled by the operation control unit 40.

[0059] The operation control unit 40 gives an instruction to the polishing head pressure control device 33 to hold the workpiece W on the polishing head 7. On the other hand, the operation control unit 40 gives an instruction to the fluid supply system 80 to supply fluid between the workpiece W and the polishing pad 2. By such an operation, while fluid flows through the gap between the workpiece W and the polishing pad 2, the workpiece W is held by the polishing head 7. The flow of the fluid in the gap between the workpiece W and the polishing pad 2 reduces the surface tension of the liquid acting between the workpiece W and the polishing pad 2. As a result, the polishing head 7 can securely hold the workpiece W.

[0060] In one embodiment, while pulling up the polishing head 7 together with the workpiece W from the polishing pad 2, the operation control unit 40 may give an instruction to the fluid supply system 80 to supply fluid between the workpiece W and the polishing pad 2. The flow of the fluid in the gap between the workpiece W and the polishing pad 2 reduces the surface tension of the liquid acting between the workpiece W and the polishing pad 2. As a result, when the polishing head 7 rises, the polishing head 7 can smoothly separate the workpiece W from the polishing pad 2.

[0061] In step 6 described with reference to FIGS. 6 and 7, with the retainer ring 48 at a position higher than the workpiece W, the polishing head 7 is raised together with the workpiece W. At this time, although the workpiece W is held by the polishing head 7, a part of the workpiece W may be in contact with the polishing pad 2. When the polishing head 7 is raised together with the workpiece W with a part of the workpiece W in contact with the polishing pad 2, due to the surface tension of the liquid existing between the workpiece W and the polishing pad 2, the workpiece W may be deformed and excessive stress may be generated in the workpiece W.

[0062] Therefore, in the embodiment described below, the polishing head 7 is raised at a first speed until the entire workpiece W is separated from the polishing pad 2, and after the entire workpiece W is separated from the polishing pad 2, the polishing head 7 is raised at a second speed higher than the first speed.

[0063] Figures 11(a) and 11(b) are schematic diagrams for explaining an embodiment in which the rising speed of the polishing head 7 is switched from a first speed to a second speed. In Figures 11(a) and 11(b), the polishing head 7 is drawn in a simplified manner. The polishing apparatus includes a workpiece detector 90 configured to detect the time when the workpiece W leaves the polishing pad 2. This workpiece detector 90 is disposed within the polishing table 5.

[0064] The configuration of the workpiece detector 90 is not particularly limited as long as it can detect the time when the workpiece W leaves the polishing pad 2, and the workpiece detector 90 may be a known sensor. For example, the workpiece detector 90 may be a displacement sensor that detects the displacement of the workpiece W, or a film thickness sensor that detects the thickness of the film of the workpiece W (e.g., an eddy current sensor or an optical film thickness sensor). In other examples, the workpiece detector 90 may be configured to detect the time when the workpiece W leaves the polishing pad 2 from a change in the pressure or flow rate of the fluid flowing between the polishing pad 2 and the workpiece W from the opening of the polishing pad 2.

[0065] As shown in Figure 11(a), the operation control unit 40 gives a command to the polishing head lifting device 25 (see Figure 1) to lift the polishing head 7 at a first speed until the entire workpiece W leaves the polishing pad 2. When the operation control unit 40 receives a signal from the workpiece detector 90 indicating that the entire workpiece W has left the polishing pad 2, as shown in Figure 11(b), the operation control unit 40 gives a command to the polishing head lifting device 25 (see Figure 1) to lift the polishing head 7 at a second speed higher than the first speed.

[0066] By such an operation, the stress on the workpiece W until the workpiece W leaves the polishing pad 2 can be reduced, and after the workpiece W leaves the polishing pad 2, the polishing head 7 can be quickly lifted to improve throughput.

[0067] FIG. 12(a) and FIG. 12(b) are plan views for explaining still another embodiment of the operation of the polishing head 7 after polishing the workpiece W. Since the specific operations of this embodiment not specifically described are the same as those of the embodiment described with reference to FIGS. 6 and 7, the overlapping explanations thereof are omitted.

[0068] In this embodiment, after polishing the workpiece W, the polishing head 7 is moved from the polishing position shown in FIG. 12(a) for polishing the workpiece W to the overhang position shown in FIG. 12(b) for raising the workpiece W. More specifically, after polishing the workpiece W, while the polishing pad 2 and the polishing head 7 are rotating, the operation control unit 40 gives a command to the polishing head moving device 37 to move the polishing head 7 from the polishing position shown in FIG. 12(a) to the overhang position shown in FIG. 12(b). The overhang position is a position where a part of the workpiece W held by the polishing head 7 protrudes radially outward from the polishing pad 2.

[0069] The operation of moving the polishing head 7 to the overhang position is performed after polishing the workpiece W and before the workpiece W is held by the polishing head 7. For example, in the flowchart shown in FIG. 6, the operation of moving the polishing head 7 to the overhang position is after stopping the pressing of the workpiece W against the polishing pad 2 in step 2 and before stopping the rotation of the polishing pad 2 and the polishing table 5 in step 3. In the flowchart shown in FIG. 7, the operation of moving the polishing head 7 to the overhang position is after stopping the pressing of the workpiece W against the polishing pad 2 in step 2 and before holding the workpiece W by the polishing head 7 in step 3.

[0070] At the overhang position, since a part of the workpiece W is located outside the polishing head 7, the surface tension of the liquid acting between the workpiece W and the polishing pad 2 is reduced. Therefore, the polishing head 7 can reliably hold the workpiece W.

[0071] After the polishing head 7 is lifted from the polishing pad 2 together with the workpiece W, the operation control unit 40 gives an instruction to the polishing head moving device 37 to move the polishing head 7 and the workpiece W to the workpiece transfer position TP shown in FIG. 12(b). At this workpiece transfer position TP, as described with reference to FIG. 5, a jet of release fluid (for example, pure water or gas or a mixture thereof) is discharged from the release nozzle 71 to the contact portion between the workpiece W and the polishing head 7, whereby the workpiece W is released from the polishing head 7.

[0072] The above-described embodiments are described for the purpose of enabling those having ordinary knowledge in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above embodiments can be naturally made by those skilled in the art, and the technical idea of the present invention can also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be construed in the broadest scope in accordance with the technical idea defined by the claims.

Explanation of Reference Numerals

[0073] 2 Polishing pad 2a Polishing surface 5 Polishing table 7 Polishing head 8 Polishing liquid supply nozzle 14 Support shaft 16 Polishing head swing arm 18 Polishing head shaft 20 Polishing head rotation device 22 Rotary joint 25 Polishing head lifting device 30 Polishing table rotation device 33 Polishing head pressure control device 37 Polishing head moving device 40 Operation control unit 40a Storage device 40b Arithmetic unit 45 Head body 48 Retainer ring 50 Carrier 51 First elastic membrane 51a Pressing surface 60 Retaining pressing mechanism 62 Second elastic membrane 65 Second pressure chamber 80 Fluid supply system 81 Fluid line 82 Actuator-driven valve 90 Workpiece detector W Workpiece C1, C2, C3 First pressure chamber F1, F2, F3 First fluid line F4 Second fluid line

Claims

1. A method for raising a polishing head after polishing a workpiece, comprising: while rotating the polishing head and the polishing pad, pressing the workpiece against the polishing pad to polish the workpiece; stopping the rotation of the polishing pad and the polishing head; raising the retainer ring of the polishing head relative to the workpiece to separate the retainer ring from the polishing pad and move the retainer ring to a position higher than the workpiece; after or simultaneously with raising the retainer ring to a position higher than the workpiece, holding the workpiece by the polishing head, and then raising the polishing head while the workpiece is held by the polishing head.

2. A method for raising a polishing head after polishing a workpiece, comprising: while rotating the polishing head and the polishing pad, pressing the workpiece against the polishing pad to polish the workpiece; stopping the rotation of the polishing pad and the polishing head; raising the retainer ring of the polishing head relative to the workpiece to separate the retainer ring from the polishing pad and move the retainer ring to a position higher than the workpiece; while directly supplying fluid between the workpiece and the polishing pad, holding the workpiece by the polishing head, and then raising the polishing head while the workpiece is held by the polishing head.

3. The polishing head has an elastic film forming a plurality of pressure chambers for pressing the workpiece against the polishing pad, The step of holding the workpiece by the polishing head forms a negative pressure in the outer pressure chamber among the plurality of pressure chambers, and then forms a negative pressure in the inner pressure chamber, so as to hold the workpiece by the polishing head. The method according to Claim 1 or 2.

4. The step of holding the workpiece by the polishing head is performed before stopping the rotation of the polishing pad and the polishing head. The method according to Claim 2.

5. The step of raising the polishing head includes raising the polishing head at a first speed until the entire workpiece is separated from the polishing pad, and after the entire workpiece is separated from the polishing pad, raising the polishing head at a second speed higher than the first speed. The method according to any one of claims 1 to 4.

6. A polishing apparatus for a workpiece, comprising: A polishing table for supporting a polishing pad; A polishing table rotating device for rotating the polishing table together with the polishing pad; A polishing head for pressing the workpiece against the polishing pad to polish the workpiece; A polishing head pressure control device for controlling the pressure inside the polishing head; A polishing head rotating device for rotating the polishing head; A polishing head lifting device for moving the polishing head up and down relative to the polishing table; An operation control unit for controlling the operations of the polishing table rotating device, the polishing head pressure control device, the polishing head rotating device, and the polishing head lifting device; The polishing head has a retainer ring surrounding the workpiece; The operation control unit: After polishing the workpiece, gives commands to the polishing table rotating device and the polishing head rotating device to stop the rotation of the polishing pad and the polishing head; Gives a command to the polishing head pressure control device to raise the retainer ring relative to the workpiece, thereby separating the retainer ring from the polishing pad and moving the retainer ring to a position higher than the workpiece; After or simultaneously with raising the retainer ring to a position higher than the workpiece, gives a command to the polishing head pressure control device to hold the workpiece by the polishing head, and then: Gives a command to the polishing head lifting device to raise the polishing head with the workpiece held by the polishing head. A polishing apparatus.

7. A polishing apparatus for a workpiece, comprising: A polishing table for supporting a polishing pad; A polishing table rotating device for rotating the polishing table together with the polishing pad; A polishing head for pressing the workpiece against the polishing pad to polish the workpiece; A polishing head pressure control device for controlling the pressure inside the polishing head; A polishing head rotating device for rotating the polishing head; A polishing head lifting device for relatively moving the polishing head up and down with respect to the polishing table; An operation control unit for controlling the operations of the polishing table rotating device, the polishing head pressure control device, the polishing head rotating device, and the polishing head lifting device; A fluid supply system for supplying fluid between the workpiece and the polishing pad; The polishing head has a retainer ring surrounding the workpiece; The operation control unit: After polishing the workpiece, gives commands to the polishing table rotating device and the polishing head rotating device to stop the rotation of the polishing pad and the polishing head; Gives a command to the polishing head pressure control device to raise the retainer ring relative to the workpiece, thereby separating the retainer ring from the polishing pad and moving the retainer ring to a position higher than the workpiece; Gives a command to the fluid supply system to supply fluid directly between the workpiece and the polishing pad, and the polishing head is configured to hold the workpiece. A polishing apparatus.

8. The polishing head has an elastic film forming a plurality of pressure chambers for pressing the workpiece against the polishing pad; The operation control unit gives a command to the polishing head pressure control device to form a negative pressure in the outer pressure chamber among the plurality of pressure chambers, and then form a negative pressure in the inner pressure chamber, so that the workpiece is held by the polishing head. The polishing apparatus according to claim 6 or 7.

9. The operation control unit is configured to give a command to the polishing head pressure control device to hold the workpiece by the polishing head before stopping the rotation of the polishing pad and the polishing head. The polishing apparatus according to claim 7.

10. The operation control unit gives a command to the polishing head lifting device to raise the polishing head at a first speed until the whole workpiece is separated from the polishing pad, and after the whole workpiece is separated from the polishing pad, raise the polishing head at a second speed higher than the first speed. The polishing apparatus according to any one of claims 6 to 9.

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