Method for removing liquid from upper surface of wafer to be polished

Abstract

To provide a method for removing liquid from an upper surface of a wafer to be polished and allowing a polishing head to apply appropriate force to the wafer.SOLUTION: In a method, an elastic film 34 is brought into contact with an upper surface of a wafer W, and then a vacuum is formed in an outer pressure chamber and a center side pressure chamber in order of the outer pressure chamber and the center side pressure chamber which are formed by the elastic film 34 to move the liquid present on the upper surface of the wafer W outward, and then a lower surface of the wafer W is pressed against a polishing surface 2a by the elastic film 34 to remove the liquid from the upper surface of the wafer W, and the lower surface of the wafer W is brought into sliding contact with the polishing surface 2a by the polishing head 1 to polish the lower surface of the wafer W.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a technique for removing liquid from the top surface of a wafer before or during polishing of the wafer. [Background technology]

[0002] Chemical mechanical polishing (CMP) is a technique for polishing the surface of a wafer by pressing the wafer against the polishing surface while supplying a slurry onto the surface, and sliding the wafer against the polishing surface in the presence of the slurry. During wafer polishing, the wafer is pressed against the polishing surface by a polishing head. The surface of the wafer is planarized by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0003] 28 is a cross-sectional view showing a polishing head. The polishing head 600 has an elastic membrane 610 that contacts the upper surface of the wafer W1. This elastic membrane 610 has a shape that forms a plurality of pressure chambers 601-604, and the pressure in each of the pressure chambers 601-604 can be adjusted independently. Therefore, the polishing head 600 can press a plurality of regions of the wafer W1 corresponding to these pressure chambers 601-604 with different forces, and can achieve a desired film thickness profile of the wafer W1.

[0004] When polishing of the wafer W1 is completed, the polished wafer W1 is transported to the next process by the transport device. As shown in Fig. 29, the next wafer W2 is transported by the transport device to a transfer position below the polishing head 600. At the same time, the polishing head 600 is washed with liquid (e.g., pure water) to remove slurry and polishing debris from the polishing head 600. Then, the next wafer W2 is held by the polishing head 600 and transported by the polishing head 600 to a position above the polishing surface. The wafer W2 is pressed against the polishing surface by the polishing head 600 and polished in the presence of the slurry. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2003-11056 A [Patent Document 2] JP 2005-313312 A [Patent Document 3] JP 2007-242655 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, as shown in FIG. 30, the liquid Q used for cleaning the polishing head 600 may be present between the upper surface of the wafer W2 and the elastic membrane 610 of the polishing head 600. If the liquid Q spreads across multiple pressure chambers, the pressure in the adjacent pressure chamber is transmitted to the liquid Q, and an unintended force is applied to the wafer W2. In the example shown in FIG. 30, even though the pressure in the central pressure chamber 601 is lowered to reduce the polishing rate of the center of the wafer W2, the pressure of the adjacent pressure chamber 602 is applied to the center of the wafer W2 through the liquid Q. As a result, the polishing rate of the center of the wafer W cannot be reduced. In this way, the liquid Q present between the wafer W2 and the polishing head 600 prevents the polishing head 600 from applying an appropriate force to the wafer W2.

[0007] Thus, the present invention provides a method for removing liquid from the top surface of the wafer being polished, allowing the polishing head to apply an appropriate force to the wafer. [Means for solving the problem]

[0008] In one aspect, there is provided a method for polishing a wafer using a polishing head having a central pressure chamber and an outer pressure chamber formed by an elastic membrane, in which the elastic membrane is brought into contact with the upper surface of the wafer, and then a vacuum is formed in the outer pressure chamber and the central pressure chamber, in that order, to move liquid present on the upper surface of the wafer outward, and then the elastic membrane is used to press the underside of the wafer against a polishing surface to remove liquid from the upper surface of the wafer, and the polishing head is used to slide the underside of the wafer against the polishing surface, thereby polishing the underside of the wafer.

[0009] In one aspect, compressed gas is supplied into the central pressure chamber and then the outer pressure chamber, causing the elastic membrane to press the underside of the wafer against the polishing surface, thereby removing liquid from the upper surface of the wafer. In one embodiment, the outer pressure chamber and the central pressure chamber include at least a first pressure chamber, a second pressure chamber, and a third pressure chamber, the second pressure chamber being located outside the first pressure chamber and the third pressure chamber being located outside the second pressure chamber, and by forming a vacuum in the third pressure chamber, the second pressure chamber, and the first pressure chamber in that order, liquid present on the upper surface of the wafer is moved outward.

[0010] In one aspect, a method is provided for polishing a wafer using a polishing head, comprising removing liquid from an upper surface of the wafer on a transport device, then holding the wafer on the transport device with the polishing head and pressing the lower surface of the wafer against a polishing surface with the polishing head to polish the lower surface of the wafer.

[0011] In one aspect, the step of removing liquid from the top surface of the wafer on the transport device is a step of removing liquid from the top surface of the wafer by tilting the wafer using the transport device. In one aspect, the step of removing liquid from the upper surface of the wafer on the transport device is a step of removing liquid from the upper surface of the wafer by rocking the wafer with the transport device. In one aspect, the step of removing liquid from the top surface of the wafer on the transport device is a step of removing liquid from the top surface of the wafer by directing a jet of gas onto the top surface of the wafer on the transport device.

[0012] In one aspect, there is provided a method for polishing a wafer using a polishing head having a central pressure chamber and an outer pressure chamber formed by an elastic membrane, in which a central portion of the elastic membrane is brought into contact with a central portion of an upper surface of the wafer, and then an outer periphery of the elastic membrane is brought into contact with an outer periphery of the upper surface of the wafer to remove liquid from the upper surface of the wafer, and the underside of the wafer is polished by pressing the underside of the wafer against a polishing surface with the elastic membrane. In one embodiment, the central portion of the elastic membrane is brought into contact with the central portion of the upper surface of the wafer while the pressure in the central pressure chamber is set higher than the pressure in the outer pressure chamber. In one embodiment, the central pressure chamber communicates with an air cylinder, and a weight is placed on a piston of the air cylinder.

[0013] In one aspect, a method is provided for polishing a wafer using a polishing head having an elastic membrane, the method comprising contacting the elastic membrane with an upper surface of the wafer, causing liquid present on the upper surface of the wafer to flow into a liquid flow path formed in the elastic membrane, thereby removing liquid from the upper surface of the wafer, and then using the elastic membrane to press the underside of the wafer against a polishing surface, thereby polishing the underside of the wafer.

[0014] In one aspect, the elastic membrane has a contact surface that contacts the upper surface of the wafer, and the liquid flow path has an opening that opens at the contact surface and a horizontal hole that is connected to the opening and extends through the elastic membrane, and the horizontal hole opens at the outer surface of the elastic membrane. In one aspect, the step of flowing liquid present on the upper surface of the wafer into the liquid flow path is a step of sucking the liquid present on the upper surface of the wafer through the liquid flow path, and the liquid flow path is connected to a suction line connected to the elastic membrane. In one aspect, the elastic membrane has a contact surface that contacts the upper surface of the wafer, and the liquid flow path is a groove formed in the contact surface. In one embodiment, the width of the groove within the elastic membrane is greater than the width of the groove at the contact surface.

[0015] In one aspect, an elastic membrane for pressing a wafer against a polishing surface is provided, the elastic membrane comprising a contact portion having a contact surface capable of contacting the wafer and an outer wall portion connected to the contact portion, the contact portion having an opening that opens at the contact surface and a transverse hole that is connected to the opening and extends within the contact portion. In one embodiment, the cross hole opens at an outer surface of the elastic membrane. In one embodiment, the horizontal hole opens on a surface of the contact portion opposite the contact surface.

[0016] In one aspect, an elastic membrane for pressing a wafer against a polishing surface is provided, the elastic membrane comprising a contact portion having a contact surface capable of contacting the wafer and an outer wall portion connected to the contact portion, the contact portion having a groove formed in the contact surface. In one embodiment, the width of the groove within the contact portion is greater than the width of the groove at the contact surface. Effect of the Invention

[0017] According to the present invention, liquid is removed from the top surface of the wafer before or immediately after polishing of the wafer is started, so that the elastic membrane forming the pressure chamber can apply a desired force to the wafer, thereby realizing a desired film thickness profile of the wafer. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a polishing apparatus. [Diagram 2] FIG. 2 is a cross-sectional view showing a polishing head. [Diagram 3] 2 is a top view of a transfer device that transfers a wafer to the polishing head shown in FIG. 1. [Figure 4] FIG. 2 is a schematic diagram showing the polishing head when removing liquid from the top surface of the wafer. [Diagram 5] 1 is a schematic diagram showing how the elastic membrane of the polishing head pushes liquid present on the upper surface of the wafer outward. [Figure 6] 1 is a schematic diagram showing how the elastic membrane of the polishing head further pushes the liquid present on the upper surface of the wafer outward. [Figure 7] 13A and 13B are diagrams illustrating an embodiment in which a combination of an air cylinder and a weight is used to inflate the center of the elastic membrane instead of the pressure regulator. [Figure 8] 13A and 13B are schematic diagrams illustrating another embodiment of the elastic membrane. [Figure 9] 13A and 13B are schematic diagrams showing still another embodiment of the elastic membrane. [Figure 10] 10A-10C illustrate another embodiment of a method for removing liquid from the top surface of a wafer. [Figure 11] 11A and 11B are diagrams further illustrating the embodiment shown in FIG. [Figure 12] 11A and 11B are diagrams further illustrating the embodiment shown in FIG. [Figure 13] 11A and 11B are diagrams further illustrating the embodiment shown in FIG. [Figure 14] 11A-11D illustrate yet another embodiment of a method for removing liquid from the top surface of a wafer. [Figure 15] 15A and 15B are diagrams further illustrating the embodiment shown in FIG. 14. [Figure 16] 15A and 15B are diagrams further illustrating the embodiment shown in FIG. 14. [Figure 17] 11A-11D illustrate yet another embodiment of a method for removing liquid from the top surface of a wafer. [Figure 18] 18A to 18C are diagrams further illustrating the embodiment shown in FIG. 17. [Figure 19]11A-11D illustrate yet another embodiment of a method for removing liquid from the top surface of a wafer. [Figure 20] FIG. 20 is a diagram further illustrating the embodiment shown in FIG. 19. [Figure 21] 1 is a cross-sectional view illustrating one embodiment of an elastic membrane capable of removing liquid from the top surface of a wafer. [Figure 22] 22 is a schematic diagram showing the elastic membrane shown in FIG. 21 removing liquid from the upper surface of the wafer. FIG. [Diagram 23] 11A-11C are cross-sectional views illustrating other embodiments of elastic membranes capable of removing liquid from the top surface of a wafer. [Figure 24] 24 is a schematic diagram showing the elastic membrane shown in FIG. 23 removing liquid from the upper surface of the wafer. [Diagram 25] 11 is a cross-sectional view illustrating yet another embodiment of an elastic membrane capable of removing liquid from the top surface of a wafer. [Figure 26] FIG. 26 is a bottom view of the elastic membrane shown in FIG. 25. [Figure 27] 26 is a schematic diagram showing the elastic membrane shown in FIG. 25 removing liquid from the upper surface of the wafer. [Figure 28] FIG. 2 is a cross-sectional view illustrating a polishing head. [Figure 29] FIG. 13 is a diagram illustrating a state in which the polishing head is being cleaned. [Diagram 30] 1A-1C are diagrams illustrating problems caused by liquid being present between the top surface of the wafer and the elastic membrane of the polishing head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing one embodiment of a polishing apparatus. As shown in Fig. 1, the polishing apparatus includes a polishing table 3 that supports a polishing pad 2, a polishing head 1 that presses a wafer W, which is an example of a substrate, against the polishing pad 2, a table motor 6 that rotates the polishing table 3, and a slurry supply nozzle 5 that supplies slurry onto the polishing pad 2. The surface of the polishing pad 2 constitutes a polishing surface 2a that polishes the wafer W.

[0020] The polishing table 3 is connected to a table motor 6, and is configured to rotate the polishing table 3 and the polishing pad 2 together. The polishing head 1 is fixed to an end of a polishing head shaft 11, and the polishing head shaft 11 is rotatably supported by a head arm 15. The head arm 15 is rotatably supported by a support shaft 16.

[0021] The wafer W is polished as follows. While the polishing table 3 and polishing head 1 are rotated in the direction indicated by the arrow in Fig. 1, slurry is supplied from a slurry supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. While the wafer W is rotated by the polishing head 1, the polishing head 1 presses the wafer W against the polishing surface 2a of the polishing pad 2 with the slurry present between the polishing pad 2 and the wafer W. The surface of the wafer W is polished by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0022] The polishing apparatus further includes an operation control unit 9 that controls the operations of the polishing head 1, the polishing table 3, and the slurry supply nozzle 5. The operation control unit 9 is composed of at least one computer.

[0023] Next, the polishing head 1 will be described. Fig. 2 is a cross-sectional view showing the polishing head 1. The polishing head 1 includes a carrier 31 fixed to the end of the polishing head shaft 11, an elastic membrane 34 attached to the lower part of the carrier 31, and a retainer ring 32 arranged below the carrier 31. The retainer ring 32 is arranged around the elastic membrane 34. The retainer ring 32 is an annular structure that holds the wafer W to prevent the wafer W from jumping out of the polishing head 1 during polishing of the wafer W.

[0024] The elastic membrane 34 includes a contact portion 35 having a contact surface 35a capable of contacting the upper surface of the wafer W, and inner wall portions 36a, 36b, 36c and an outer wall portion 36d connected to the contact portion 35. The contact portion 35 has substantially the same size and shape as the upper surface of the wafer W. The inner wall portions 36a, 36b, 36c and the outer wall portion 36d are endless walls arranged concentrically. The outer wall portion 36d is located outside the inner wall portions 36a, 36b, 36c and is arranged so as to surround the inner wall portions 36a, 36b, 36c. In this embodiment, three inner wall portions 36a, 36b, 36c are provided, but the present invention is not limited to this embodiment. In one embodiment, only one or two inner wall portions may be provided, or four or more inner wall portions may be provided.

[0025] Four pressure chambers 25A, 25B, 25C, and 25D are provided between the elastic membrane 34 and the carrier 31. The pressure chambers 25A, 25B, 25C, and 25D are formed by the contact portion 35 of the elastic membrane 34, the inner wall portions 36a, 36b, and 36c, and the outer wall portion 36d. That is, the pressure chamber 25A is located within the inner wall portion 36a, the pressure chamber 25B is located between the inner wall portion 36a and the inner wall portion 36b, the pressure chamber 25C is located between the inner wall portion 36b and the inner wall portion 36c, and the pressure chamber 25D is located between the inner wall portion 36c and the outer wall portion 36d. The central pressure chamber 25A is circular, and the other pressure chambers 25B, 25C, and 25D are annular. These pressure chambers 25A, 25B, 25C, and 25D are arranged concentrically. The pressure chamber 25B is located outside the pressure chamber 25A, the pressure chamber 25C is located outside the pressure chamber 25B, and the pressure chamber 25D is located outside the pressure chamber 25C.

[0026] Gas transfer lines F1, F2, F3, and F4 are connected to the pressure chambers 25A, 25B, 25C, and 25D, respectively. One end of the gas transfer lines F1, F2, F3, and F4 is connected to a compressed gas supply source (not shown) as a utility supply source provided in a factory in which the polishing apparatus is installed. Compressed gas such as compressed air is supplied to the pressure chambers 25A, 25B, 25C, and 25D through the gas transfer lines F1, F2, F3, and F4, respectively.

[0027] An annular membrane (rolling diaphragm) 37 is disposed between the carrier 31 and the retaining ring 32, and a pressure chamber 25E is formed inside the membrane 37. The pressure chamber 25E is connected to the compressed gas supply source via a gas transfer line F5. The compressed gas is supplied into the pressure chamber 25E through the gas transfer line F5, and the pressure chamber 25E presses the retaining ring 32 against the polishing surface 2a of the polishing pad 2.

[0028] The gas transfer lines F1, F2, F3, F4, and F5 extend via a rotary joint 40 attached to the polishing head shaft 11. The gas transfer lines F1, F2, F3, F4, and F5 communicating with the pressure chambers 25A, 25B, 25C, 25D, and 25E are provided with pressure regulators R1, R2, R3, R4, and R5, respectively. Compressed gas from a compressed gas supply source is supplied independently into the pressure chambers 25A to 25E through the pressure regulators R1 to R5. The pressure regulators R1 to R5 are configured to adjust the pressure of the compressed gas in the pressure chambers 25A to 25E.

[0029] The pressure regulators R1 to R5 can change the internal pressures of the pressure chambers 25A to 25E independently of each other, and thus can independently adjust the polishing pressures for the four corresponding regions of the wafer W, i.e., the center, the inner middle, the outer middle, and the edge, and the pressing force of the retainer ring 32 against the polishing pad 2. The gas transfer lines F1, F2, F3, F4, and F5 are also connected to air release valves (not shown), respectively, and the pressure chambers 25A to 25E can also be opened to the atmosphere. In this embodiment, the elastic membrane 34 forms four pressure chambers 25A to 25D, but in one embodiment, the elastic membrane 34 may form fewer or more than four pressure chambers.

[0030] The pressure regulators R1 to R5 are connected to the operation control unit 9. The operation control unit 9 sends target pressure values ​​for each of the pressure chambers 25A to 25E to the pressure regulators R1 to R5, and the pressure regulators R1 to R5 operate so as to maintain the pressures in the pressure chambers 25A to 25E at the corresponding target pressure values.

[0031] The polishing head 1 can apply independent polishing pressures to multiple regions of the wafer W. For example, the polishing head 1 can press different regions of the surface of the wafer W against the polishing surface 2a of the polishing pad 2 with different polishing pressures. Thus, the polishing head 1 can control the film thickness profile of the wafer W to achieve a target film thickness profile.

[0032] The vacuum lines L1, L2, L3, L4, and L5 are connected to the gas transfer lines F1, F2, F3, F4, and F5, respectively. The vacuum lines L1, L2, L3, L4, and L5 are respectively equipped with vacuum valves V1, V2, V3, V4, and V5. The vacuum valves V1, V2, V3, V4, and V5 are actuator-driven valves such as solenoid valves, motorized valves, or air-operated valves. The vacuum valves V1 to V5 are connected to an operation control unit 9, and the operation of the vacuum valves V1 to V5 is controlled by the operation control unit 9. When the vacuum lines L1, L2, L3, L4, and L5 are opened, a vacuum is formed in the corresponding pressure chambers 25A, 25B, 25C, 25D, and 25E.

[0033] When the polishing head 1 holds the wafer W, the vacuum valves V2, V3, and V4 are opened to form a vacuum in the pressure chambers 25B, 25C, and 25D with the contact portion 35 of the elastic membrane 34 in contact with the wafer W. The portions of the contact portion 35 that form the pressure chambers 25B, 25C, and 25D are recessed upward, and the polishing head 1 can suction the wafer W by the suction effect of the elastic membrane 34. When compressed gas is supplied to the pressure chambers 25B, 25C, and 25D to release the suction effect, the polishing head 1 can release the wafer W.

[0034] 3 is a top view of a transport device that transports a wafer to the polishing head 1 shown in FIG. 1. As shown in FIG. 3, a wafer W is transported to the polishing head 1 by a transport device 44. The polishing head 1 is movable between a polishing position P1 shown by a solid line in FIG. 3 and a transfer position P2 shown by a dotted line. More specifically, the head arm 15 rotates about a support shaft 16, so that the polishing head 1 can move between the polishing position P1 and the transfer position P2. The polishing position P1 is located above the polishing surface 2a of the polishing pad 2, and the transfer position P2 is located outside the polishing surface 2a.

[0035] The transfer device 44 includes a transfer stage 45 on which the wafer W is placed, a lifting device 47 for moving the transfer stage 45 up and down, and a horizontal movement device 49 for moving the transfer stage 45 and the lifting device 47 together in the horizontal direction. The wafer W to be polished is placed on the transfer stage 45, and is moved together with the transfer stage 45 to a transfer position P2 by the horizontal movement device 49. When the polishing head 1 is at the transfer position P2, the lifting device 47 raises the transfer stage 45. The polishing head 1 holds the wafer W on the transfer stage 45, and moves together with the wafer W to the polishing position P1.

[0036] The slurry supply nozzle 5 supplies slurry to the polishing surface 2a of the rotating polishing pad 2, while the polishing head 1 rotates the wafer W and presses the wafer W against the polishing surface 2a of the polishing pad 2, bringing the wafer W into sliding contact with the polishing surface 2a. The lower surface of the wafer W is polished by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0037] After polishing the wafer W, the polishing head 1 moves to the transfer position P2 together with the wafer W. Then, the polished wafer W is transferred to the transfer stage 45. The transfer stage 45 moves the wafer W to the next process. A cleaning nozzle 53 is disposed at the transfer position P2, which supplies liquid (e.g., a rinsing liquid such as pure water) to the polishing head 1 to clean the polishing head 1. The cleaning nozzle 53 faces the polishing head 1. After releasing the wafer W, the polishing head 1 is cleaned with the liquid supplied from the cleaning nozzle 53.

[0038] While the polishing head 1 is being cleaned, the next wafer to be polished is moved by the transfer stage 45 to a receiving position P2 below the polishing head 1. When cleaning of the polishing head 1 is completed, the lifting device 47 raises the transfer stage 45 on which the next wafer is placed. Then, the cleaned polishing head 1 holds the next wafer and moves to the polishing position P1. In this manner, multiple wafers are polished successively.

[0039] However, while the polishing head 1 is being cleaned, the next wafer to be polished is moved to the receiving position P2 below the polishing head 1, causing liquid to fall onto the top surface of the wafer. The liquid on the top surface of the wafer prevents the polishing head 1 from applying an appropriate force to the wafer, as described with reference to FIG. 30. One solution is to move the next wafer to the receiving position P2 after the polishing head 1 has finished cleaning. However, such an operation reduces the throughput of the polishing apparatus.

[0040] Therefore, in this embodiment, the liquid is removed from the upper surface of the wafer as follows. FIG. 4 is a schematic diagram showing the polishing head 1 when removing the liquid from the upper surface of the wafer. In FIG. 4, the detailed configuration of the polishing head 1 is omitted. Before holding the wafer W to be polished, the pressure in the pressure chambers 25A, 25B, and 25C on the center side of the polishing head 1 is made higher than the pressure in the outer pressure chamber 25D. More specifically, the operation control unit 9 issues a command to the pressure regulators R1, R2, and R3 (see FIG. 2) to supply compressed gas into the pressure chambers 25A, 25B, and 25C, while the operation control unit 9 opens the vacuum valve V4 to form a vacuum in the pressure chamber 25D.

[0041] In one embodiment, the operation control unit 9 may open the atmosphere release valves (not shown) connected to the gas transfer lines F1, F2, and F3 to open the pressure chambers 25A, 25B, and 25C to the atmosphere, while the operation control unit 9 may open the vacuum valve V4 to create a vacuum in the pressure chamber 25D. Furthermore, in one embodiment, the operation control unit 9 may issue commands to the pressure regulators R1, R2, and R3 (see FIG. 2) to supply compressed gas into the pressure chambers 25A, 25B, and 25C, while the operation control unit 9 may open the atmosphere release valve (not shown) connected to the gas transfer line F4 to open the pressure chamber 25D to the atmosphere.

[0042] The difference between the pressures in the pressure chambers 25A, 25B, 25C and the pressure chamber 25D causes the center of the contact portion 35 of the elastic membrane 34 to expand, causing the center of the contact portion 35 to protrude toward the wafer W. With the center of the contact portion 35 protruding, the polishing head 1 descends toward the wafer W, causing the elastic membrane 34 to contact the upper surface of the wafer W. As shown in FIG. 5, the center of the elastic membrane 34, i.e., the center of the contact portion 35, first contacts the center of the upper surface of the wafer W. The elastic membrane 34 pushes the liquid Q present on the upper surface of the wafer W outward.

[0043] Further, the polishing head 1 is lowered to bring most of the contact portion 35 into contact with the upper surface of the wafer W. More specifically, as shown in FIG. 6, while the center portion of the elastic film 34 is in contact with the center portion of the upper surface of the wafer W, the outer periphery of the elastic film 34, i.e., the outer periphery of the contact portion 35, is brought into contact with the outer periphery of the upper surface of the wafer W. The elastic film 34 pushes the liquid Q present on the upper surface of the wafer W further outward, and removes the liquid Q from the upper surface of the wafer W. Thereafter, the elastic film 34 of the polishing head 1 brings the lower surface of the wafer W into sliding contact with the polishing surface 2a in the presence of the slurry on the polishing surface 2a, and polishes the wafer W by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0044] In this manner, the liquid Q present on the upper surface of the wafer W is moved to the outside of the wafer W by the elastic membrane 34 with the central protruding portion, and is removed from the upper surface of the wafer W. Therefore, the polishing head 1 can hold the wafer W in a state in which the liquid Q is substantially not present between the elastic membrane 34 and the upper surface of the wafer W. As a result, the elastic membrane 34 forming the pressure chambers 25A, 25B, 25C, and 25D can apply the intended force to the wafer W, and the polishing head 1 can achieve a desired film thickness profile of the wafer W.

[0045] Since the elastic membrane 34 is flexible, the elastic membrane 34 easily expands even when the pressure inside the pressure chambers 25A, 25B, 25C is low. If the elastic membrane 34 expands too much, there is a risk that an excessive load will be applied to the wafer W when the elastic membrane 34 presses against the wafer W. Although it is possible to maintain the pressure inside the pressure chambers 25A, 25B, 25C at a low pressure (for example, 25 hPa or less) by the pressure regulators R1, R2, R3, it takes a long time to lower the pressure to the target low pressure, and the pressure inside the pressure chambers 25A, 25B, 25C may not be stable.

[0046] Therefore, in one embodiment, as shown in FIG. 7, a combination of an air cylinder 41 and a weight 42 is used instead of the pressure regulators R1, R2, and R3 to send compressed gas to the pressure chambers 25A, 25B, and 25C. The pressure chambers 25A, 25B, and 25C are connected to a common air cylinder 41 via gas transfer lines F1, F2, and F3. The air cylinder 41 is arranged in a vertical position. Before the polishing head 1 holds the wafer W, the weight 42 is placed on the piston 41A of the air cylinder 41 and pushes the piston 41A downward. The gas in the air cylinder 41 is sent into the pressure chambers 25A, 25B, and 25C, so that the center of the elastic film 34 expands. As in the embodiment shown in FIG. 4, a vacuum is formed in the pressure chamber 25D. In one embodiment, the operation control unit 9 may open an atmosphere release valve (not shown) connected to the gas transfer line F4 to open the pressure chamber 25D to the atmosphere.

[0047] The expansion of elastic membrane 34 is adjusted by the diameter of air cylinder 41 and the stroke distance of piston 41A. If weight 42 is too light, elastic membrane 34 does not expand and piston 41A stops midway, so weight 42 that lowers piston 41A at an appropriate speed is used. According to this embodiment, the combination of air cylinder 41 and weight 42 can stably maintain low pressure in pressure chambers 25A, 25B, and 25C, and as a result, the expansion of elastic membrane 34 can be appropriately controlled.

[0048] 8 is a schematic diagram showing another embodiment of the elastic membrane 34. In this embodiment, the vertical length of the inner walls 36a, 36b, 36c is longer than the vertical length of the outer wall 36d, and the lower ends of the inner walls 36a, 36b, 36c are located lower than the lower end of the outer wall 36d. The difference in the vertical length between the inner walls 36a, 36b, 36c and the outer wall 36d causes the center of the contact portion 35 of the elastic membrane 34 to protrude toward the wafer W.

[0049] 9 is a schematic diagram showing another embodiment of the polishing head 1. In this embodiment, the lower part of the carrier 31 has a first surface 31a to which the inner walls 36a, 36b, and 36c are fixed, and a second surface 31b to which the outer wall 36d is fixed. The first surface 31a is located lower than the second surface 31b. The lower ends of the inner walls 36a, 36b, and 36c are located lower than the lower end of the outer wall 36d. The difference in height between the first surface 31a and the second surface 31b of the carrier 31 causes the center of the contact portion 35 of the elastic film 34 to protrude toward the wafer W.

[0050] 4 to 6, the elastic film 34 shown in Fig. 8 and Fig. 9 can push the liquid Q present on the upper surface of the wafer W outward when it comes into contact with the upper surface of the wafer W, and can remove the liquid Q from the upper surface of the wafer W. In the embodiment shown in Fig. 8 and Fig. 9, it is not necessary to provide a difference between the pressure in the pressure chambers 25A, 25B, 25C and the pressure in the pressure chamber 25D. Specifically, the pressure regulators R1, R2, R3, R4 may maintain the pressures of the compressed gas in the pressure chambers 25A, 25B, 25C, 25D at the same pressure.

[0051] Next, another embodiment of the method for removing liquid from the upper surface of the wafer W will be described with reference to Figures 10 to 13. Details of this embodiment that are not specifically described are the same as those of the above-mentioned embodiment, so duplicated descriptions will be omitted.

[0052] As shown in Fig. 10, the polishing head 1 is lowered toward the upper surface of the wafer W. Liquid Q is present on the upper surface of the wafer W. As shown in Fig. 11, the contact portion 35 of the elastic film 34 is brought into contact with the liquid Q on the upper surface of the wafer W, and the contact portion 35 of the elastic film 34 is further pressed against the upper surface of the wafer W. At this time, a part of the liquid Q spills down from the upper surface of the wafer W.

[0053] 12, vacuums are sequentially formed in the pressure chambers 25D, 25C, and 25B in the order from the pressure chamber 25D located on the outer side toward the pressure chamber 25B located on the central side (i.e., in the order of the pressure chambers 25D, 25C, and 25B). The contact portions 35 constituting the pressure chambers 25D, 25C, and 25B are recessed upward by the vacuum, and spaces are formed between the elastic film 34 and the upper surface of the wafer W. The liquid Q on the upper surface of the wafer W flows sequentially into these spaces, and a flow of the liquid Q toward the outside of the wafer W is formed.

[0054] Thereafter, the polishing head 1 carries the wafer W to a position above the polishing pad 2, and as shown in Fig. 13, the elastic film 34 presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2. At this time, the operation control unit 9 issues commands to the pressure regulators R2, R3, and R4 to supply compressed gas into the pressure chambers 25B, 25C, and 25D in the order from the pressure chamber 25B located on the central side toward the pressure chamber 25D located on the outer side (i.e., in the order of the pressure chambers 25B, 25C, and 25D). The liquid Q held in the space between the elastic film 34 and the upper surface of the wafer W is pushed by the contact portion 35 of the elastic film 34 to the outside of the wafer W, and is removed from the upper surface of the wafer W.

[0055] Thereafter, the elastic film 34 of the polishing head 1 brings the lower surface of the wafer W into sliding contact with the polishing surface 2a in the presence of the slurry on the polishing surface 2a, polishing the wafer W by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0056] Next, another embodiment of the method for removing liquid from the upper surface of the wafer W will be described with reference to Figures 14 to 16. Details of this embodiment that are not particularly described are the same as the embodiment described above, so duplicated descriptions will be omitted. Figure 14 is a schematic diagram showing a modified example of the transfer device 44 shown in Figure 3. Details of this embodiment that are not particularly described are the same as the embodiment shown in Figure 3, so duplicated descriptions will be omitted.

[0057] As shown in Fig. 14, the transport device 44 is provided with a tilting device 55 that tilts the transport stage 45. This tilting device 55 is held by the lifting device 47 and is moved up and down together with the transport stage 45. The tilting device 55 has a support shaft 55a that extends horizontally and a rotation device 55b that rotates the support shaft 55a. The support shaft 55a is connected to the transport stage 45, and the rotation device 55b is fixed to the lifting device 47. The rotation device 55b is configured to be able to rotate the support shaft 55a and the transport stage 45 by a predetermined angle. The rotation device 55b is provided with an actuator (not shown) such as a servo motor.

[0058] The wafer W on the transfer stage 45 is moved to the transfer position P2 by the horizontal movement device 49. The polishing head 1 is washed with liquid supplied from the cleaning nozzle 53. The liquid used to wash the polishing head 1 falls onto the upper surface of the wafer W on the transfer stage 45. FIG. 15 is a diagram of the transfer device 44 seen from the direction indicated by the arrow A in FIG. 14. As shown in FIG. 15, the liquid Q exists on the upper surface of the wafer W. Then, as shown in FIG. 16, the tilting device 55 tilts the transfer stage 45 and the wafer W together before the wafer W is held by the polishing head 1. The liquid Q spills down from the upper surface of the tilted wafer W, and the liquid Q is thereby removed from the upper surface of the wafer W.

[0059] After the liquid Q is removed from the upper surface of the wafer W, the tilting device 55 returns the wafer W to a horizontal position again. The wafer W is then held by the polishing head 1. The polishing head 1 carries the wafer W to the polishing position P1 (see FIG. 3) above the polishing pad 2, and presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2 with the elastic membrane 34. The elastic membrane 34 of the polishing head 1 brings the lower surface of the wafer W into sliding contact with the polishing surface 2a in the presence of slurry on the polishing surface 2a, and polishes the wafer W by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0060] According to this embodiment, after the liquid Q is removed from the upper surface of the wafer W, the wafer W is held by the polishing head 1. Therefore, the liquid Q does not exist between the upper surface of the wafer W and the elastic membrane 34 of the polishing head 1, the elastic membrane 34 can apply the intended force to the wafer W, and the polishing head 1 can achieve the desired film thickness profile of the wafer W.

[0061] 17 and 18 are schematic views for explaining still another embodiment of the method for removing liquid from the upper surface of a wafer W. Details of this embodiment that are not specifically explained are the same as those of the embodiment shown in FIG. 3, and therefore overlapping explanations will be omitted.

[0062] 17, the wafer W on the transfer stage 45 is moved to a transfer position P2 by the horizontal movement device 49. The polishing head 1 is cleaned with liquid supplied from the cleaning nozzle 53. The liquid used to clean the polishing head 1 falls on the upper surface of the wafer W on the transfer stage 45.

[0063] 18, before the wafer W is held by the polishing head 1, the horizontal movement device 49 rocks the transfer stage 45 and the wafer W in the horizontal direction. When the wafer W is rocked, the liquid Q spills off the upper surface of the wafer W, and the liquid Q is thereby removed from the upper surface of the wafer W. In one embodiment, the horizontal movement device 49 may rock the transfer stage 45 and the wafer W in the horizontal direction while the transfer stage 45 and the wafer W are tilted by the tilt device 55. Furthermore, in one embodiment, the tilt device 55 may not be provided.

[0064] After the liquid Q is removed from the upper surface of the wafer W, the wafer W is held by the polishing head 1. The polishing head 1 carries the wafer W to a polishing position P1 (see FIG. 3) above the polishing pad 2, and presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2 with the elastic membrane 34. The elastic membrane 34 of the polishing head 1 brings the lower surface of the wafer W into sliding contact with the polishing surface 2a in the presence of slurry on the polishing surface 2a, and polishes the wafer W by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0065] According to this embodiment, after the liquid Q is removed from the upper surface of the wafer W, the wafer W is held by the polishing head 1. Therefore, the liquid Q does not exist between the upper surface of the wafer W and the elastic membrane 34 of the polishing head 1, the elastic membrane 34 can apply the intended force to the wafer W, and the polishing head 1 can achieve the desired film thickness profile of the wafer W.

[0066] Fig. 19 is a schematic diagram for explaining still another embodiment of the method for removing liquid from the upper surface of a wafer W. Details of this embodiment that are not specifically explained are the same as those of the embodiment shown in Fig. 3, and therefore overlapping explanations will be omitted.

[0067] 19, the polishing apparatus of this embodiment includes a gas jet nozzle 57 disposed at the transfer position P2. The gas jet nozzle 57 is inclined with respect to the horizontal direction and is disposed facing the upper part of the transfer stage 45 at the transfer position P2, i.e., facing the upper surface of the wafer W on the transfer stage 45. The gas jet nozzle 57 is connected to a compressed gas supply source (not shown). In this embodiment, a plurality of gas jet nozzles 57 are provided, but in one embodiment, only one gas jet nozzle 57 may be provided.

[0068] The wafer W on the transfer stage 45 is moved to the transfer position P2 by the horizontal movement device 49. The polishing head 1 is cleaned with liquid supplied from the cleaning nozzle 53. The liquid used to clean the polishing head 1 falls onto the upper surface of the wafer W on the transfer stage 45. As shown in FIG. 20, before the wafer W is held by the polishing head 1, the gas jet nozzle 57 sends a jet of gas to the upper surface of the wafer W to remove the liquid Q from the upper surface of the wafer W.

[0069] After the liquid Q is removed from the upper surface of the wafer W, the wafer W is held by the polishing head 1. The polishing head 1 carries the wafer W to a polishing position P1 (see FIG. 3) above the polishing pad 2, and presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2 with the elastic membrane 34. The elastic membrane 34 of the polishing head 1 brings the lower surface of the wafer W into sliding contact with the polishing surface 2a in the presence of slurry on the polishing surface 2a, and polishes the wafer W by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0070] According to this embodiment, after the liquid Q is removed from the upper surface of the wafer W, the wafer W is held by the polishing head 1. Therefore, the liquid Q does not exist between the upper surface of the wafer W and the elastic membrane 34 of the polishing head 1, the elastic membrane 34 can apply the intended force to the wafer W, and the polishing head 1 can achieve the desired film thickness profile of the wafer W.

[0071] FIG. 21 is a cross-sectional view showing an embodiment of an elastic membrane 34 capable of removing liquid from the upper surface of a wafer W. As shown in FIG. 21, the elastic membrane 34 has a liquid flow path 60 formed therein. More specifically, the contact portion 35 of the elastic membrane 34 has a plurality of openings 61 that open at the contact surface 35a, and a horizontal hole 62 that is connected to the plurality of openings 61. The contact surface 35a of the elastic membrane 34 is one surface of the elastic membrane 34 that contacts the upper surface of the wafer W. The opening 61 is provided below the pressure chamber 25A located on the center side, and is not provided below the other pressure chambers 25B to 25D. In one embodiment, the opening 61 may also be provided below the pressure chambers 25B to 25D. The horizontal hole 62 extends inside the contact portion 35, and the outer end of the horizontal hole 62 opens at the outer surface 34a of the elastic membrane 34. Therefore, the contact surface 35a and the outer surface 34a of the elastic membrane 34 are communicated with each other by the liquid flow path 60 that is composed of the openings 61 and the horizontal hole 62.

[0072] 22, compressed gas is supplied into the pressure chambers 25A to 25D to inflate the elastic membrane 34, and the contact surface 35a of the elastic membrane 34 is pressed against the upper surface of the wafer W. The liquid Q (see FIG. 21) present on the upper surface of the wafer W flows into the liquid flow path 60 from the opening 61, and flows out of the elastic membrane 34 through the liquid flow path 60. As a result, the liquid Q is removed from the upper surface of the wafer W.

[0073] After the liquid Q is removed from the upper surface of the wafer W, the wafer W is held by the polishing head 1. The polishing head 1 carries the wafer W to a polishing position P1 (see FIG. 3) above the polishing pad 2, and presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2 with the elastic membrane 34. The elastic membrane 34 of the polishing head 1 brings the lower surface of the wafer W into sliding contact with the polishing surface 2a in the presence of slurry on the polishing surface 2a, and polishes the wafer W by the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0074] According to this embodiment, the polishing head 1 can hold the wafer W in a state where there is substantially no liquid Q between the elastic membrane 34 and the upper surface of the wafer W. As a result, the elastic membrane 34 forming the pressure chambers 25A, 25B, 25C, and 25D can apply an intended force to the wafer W, and the polishing head 1 can achieve a desired film thickness profile of the wafer W.

[0075] 23 is a cross-sectional view showing another embodiment of the elastic membrane 34 capable of removing liquid from the upper surface of the wafer W. Details of this embodiment that are not particularly described are the same as those of the embodiment shown in FIG. 21 and FIG. 22, so that the overlapping description will be omitted. As shown in FIG. 23, the liquid flow path 60 communicates with the suction line 70 connected to the elastic membrane 34. More specifically, the horizontal hole 62 is connected to both the opening 61 and the suction line 70. One end of the horizontal hole 62 is connected to the opening 61, and the other end of the horizontal hole 62 opens on the upper surface 35b of the connection part 35 (the surface opposite to the contact surface 35a of the connection part 35).

[0076] The suction line 70 extends through the carrier 31, and an end of the suction line 70 is connected to the upper surface 35b of the contact portion 35. The suction line 70 communicates with the liquid flow path 60, but does not communicate with the pressure chamber 25A. Therefore, the suction line 70 can create a vacuum in the liquid flow path 60 without creating a vacuum in the pressure chamber 25A.

[0077] 24, compressed gas is supplied into the pressure chambers 25A to 25D to inflate the elastic membrane 34, and a vacuum is formed in the liquid flow path 60 by the suction line 70 while pressing the contact surface 35a of the elastic membrane 34 against the upper surface of the wafer W. The liquid Q (see FIG. 23) present on the upper surface of the wafer W is sucked into the liquid flow path 60 from the opening 61, and is removed from the upper surface of the wafer W.

[0078] Fig. 25 is a cross-sectional view showing yet another embodiment of the elastic membrane 34 capable of removing liquid from the upper surface of the wafer W. Details of this embodiment that are not specifically described are the same as those of the embodiment shown in Fig. 21 and Fig. 22, and therefore redundant description will be omitted. As shown in Fig. 25, the liquid flow path is composed of a plurality of grooves 75 formed in the contact surface 35a.

[0079] Fig. 26 is a bottom view of the elastic membrane 34 shown in Fig. 25. As shown in Fig. 26, the grooves 75 are annular grooves arranged concentrically. However, the shape of the grooves 75 is not limited to this embodiment. For example, the grooves 75 may be linear grooves arranged parallel to each other.

[0080] 27, compressed gas is supplied into the pressure chambers 25A to 25D to inflate the elastic membrane 34, and the contact surface 35a of the elastic membrane 34 is pressed against the upper surface of the wafer W. The liquid Q (see FIG. 25) present on the upper surface of the wafer W flows into the groove 75 serving as a liquid flow path. As a result, the liquid Q is removed from the upper surface of the wafer W.

[0081] In this embodiment, in order to prevent the liquid Q once flowing into the groove 75 from flowing out of the groove 75, the width of the groove 75 inside the contact portion 35 is greater than the width of the groove 75 at the contact surface 35a. That is, the entrance of the groove 75 is narrow and the inside of the groove 75 is wide. The groove 75 having such a cross-sectional shape is likely to hold the liquid Q therein. In order to remove the liquid that is irregularly present on the upper surface of the wafer W, the grooves 75 may be uniformly distributed over the entire contact surface 35a of the elastic membrane 34.

[0082] The elastic film 34 shown in FIGS. 21 to 27 can be produced using a 3D printer.

[0083] The above-mentioned embodiments can be combined as appropriate. For example, the embodiment shown in Figures 4 to 6 may be applied to the embodiment shown in Figures 14 to 16, or the embodiment shown in Figures 17 and 18, or the embodiment shown in Figures 19 and 20.

[0084] Although the polishing head 1 according to each of the above-described embodiments has four pressure chambers 25A, 25B, 25C, and 25D, the present invention is not limited to these embodiments. The above-described embodiments for removing liquid from the upper surface of the wafer can also be applied to polishing heads having fewer than four pressure chambers and polishing heads having more than four pressure chambers.

[0085] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0086] 1 Polishing head 2 Polishing Pads 2a Polished surface 3 Polishing table 5 Slurry supply nozzle 6 Table Motor 11 Grinding head shaft 15 Head Arm 25A, 25B, 25C, 25D, 25E ​​Pressure chamber 31 Career 32 Retainer ring 34 Elastic Membrane 35 Contact part 35a Contact surface 36a,36b,36c Inner wall 36d Exterior wall 37 Membrane (Rolling Diaphragm) 40 Rotary joint 41 Air Cylinder 42 Weight 44 Transport Equipment 45 Transport Stage 47 Lifting device 49 Horizontal movement device 53 Cleaning nozzle 55 Tilt device 57 Gas jet nozzle 60 Liquid flow path 61 Opening 62 Horizontal hole 70 Suction Line 75 Groove F1, F2, F3, F4, F5 Gas transfer lines R1, R2, R3, R4, R5 Pressure regulator L1, L2, L3, L4, L5 Vacuum lines V1, V2, V3, V4, V5 Vacuum valves

Claims

1. A method for polishing a wafer using a polishing head having a central pressure chamber and an outer pressure chamber formed by an elastic membrane, comprising: contacting the elastic membrane with the top surface of the wafer; and then A vacuum is formed in the outer pressure chamber and then in the central pressure chamber, thereby moving liquid present on the upper surface of the wafer outward, and then pressing the bottom surface of the wafer against a polishing surface with the elastic membrane to remove liquid from the top surface of the wafer; The method comprises the step of polishing the underside of the wafer by bringing the underside of the wafer into sliding contact with the polishing surface by the polishing head.

2. 2. The method according to claim 1, wherein compressed gas is supplied into the central pressure chamber and then the outer pressure chamber, thereby pressing the lower surface of the wafer against the polishing surface with the elastic membrane to remove liquid from the upper surface of the wafer.

3. the outer pressure chamber and the central pressure chamber include at least a first pressure chamber, a second pressure chamber, and a third pressure chamber, the second pressure chamber is located outside the first pressure chamber, and the third pressure chamber is located outside the second pressure chamber, 3. The method according to claim 1, further comprising forming a vacuum in the third pressure chamber, the second pressure chamber, and the first pressure chamber in that order, thereby moving liquid present on the upper surface of the wafer outward.

Images