Method for removing liquid from the top surface of a wafer being 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 upper surface of a wafer before or during wafer polishing.

Background Art

[0002] Chemical mechanical polishing (CMP) is a technique for polishing the surface of a wafer by pressing the wafer against a polishing surface while supplying slurry onto the polishing surface and causing the wafer to slide in contact with 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] FIG. 28 is a cross-sectional view schematically showing a polishing head. The polishing head 600 has an elastic film 610 that contacts the upper surface of the wafer W1. This elastic film 610 has a shape that forms a plurality of pressure chambers 601 to 604, and the pressure in each of the pressure chambers 601 to 604 can be independently adjusted. Therefore, the polishing head 600 can press a plurality of regions of the wafer W1 corresponding to these pressure chambers 601 to 604 with different forces, and a desired film thickness profile of the wafer W1 can be achieved.

[0004] When the polishing of the wafer W1 is completed, the polished wafer W1 is transported to the next process by a transfer device. As shown in FIG. 29, the next wafer W2 is carried to a delivery position below the polishing head 600 by the transfer device. At the same time, the polishing head 600 is cleaned with a liquid (for example, pure water), and the slurry and polishing debris are removed from the polishing head 600. Then, the next wafer W2 is held by the polishing head 600 and transported to a position above the polishing surface by the polishing head 600. 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] Japanese Patent Publication No. 2003-11056 [Patent Document 2] Japanese Patent Publication No. 2005-313312 [Patent Document 3] Japanese Patent Publication No. 2007-242655 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, as shown in Figure 30, liquid Q used to clean the polishing head 600 may be present between the top surface of the wafer W2 and the elastic film 610 of the polishing head 600. If this liquid Q spreads across multiple pressure chambers, the pressure in adjacent pressure chambers is transmitted to the liquid Q, resulting in unintended forces being applied to the wafer W2. In the example shown in Figure 30, even though the pressure in the central pressure chamber 601 is reduced to lower the polishing rate of the central part of the wafer W2, the pressure in the adjacent pressure chamber 602 is applied to the central part of the wafer W2 via liquid Q. As a result, the polishing rate of the central part of the wafer W cannot be reduced. Thus, the liquid Q present between the wafer W2 and the polishing head 600 prevents the polishing head 600 from applying the appropriate force to the wafer W2.

[0007] Therefore, the present invention provides a method for removing liquid from the upper surface of a wafer to be polished, enabling the polishing head to apply appropriate force to the wafer. [Means for solving the problem]

[0008] In one embodiment, a method for polishing a wafer is provided using a polishing head having a central pressure chamber and an outer pressure chamber formed by an elastic film, wherein the elastic film 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 the liquid present on the upper surface of the wafer outwards, and then the lower surface of the wafer is pressed against the polishing surface with the elastic film to remove the liquid from the upper surface of the wafer, and the lower surface of the wafer is polished by sliding the polishing head against the polishing surface.

[0009] In one embodiment, compressed gas is supplied to the central pressure chamber and the outer pressure chamber in that order, thereby pressing the lower surface of the wafer against the polishing surface with the elastic film and 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, the liquid present on the upper surface of the wafer is moved to the outside.

[0010] In one embodiment, a method for polishing a wafer using a polishing head is provided, comprising removing liquid from the 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 embodiment, 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 tilting the wafer with the transport device. In one embodiment, 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 shaking the wafer with the transport device. In one embodiment, 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 sending a jet of gas to the upper surface of the wafer on the transport device.

[0012] In one embodiment, a method for polishing a wafer is provided using a polishing head having a central pressure chamber and an outer pressure chamber formed by an elastic film, wherein the central part of the elastic film is brought into contact with the central part of the upper surface of the wafer, and then the outer peripheral part of the elastic film is brought into contact with the outer peripheral part of the upper surface of the wafer to remove liquid from the upper surface of the wafer, and the lower surface of the wafer is polished by pressing the lower surface of the wafer against a polishing surface with the elastic film. In one embodiment, the central part of the elastic film is brought into contact with the central part of the upper surface of the wafer while the pressure in the central pressure chamber is higher than the pressure in the outer pressure chamber. In one embodiment, the central pressure chamber is in communication with an air cylinder, and a weight is placed on the piston of the air cylinder.

[0013] In one embodiment, a method is provided for polishing a wafer using a polishing head having an elastic film, wherein the elastic film is brought into contact with the upper surface of the wafer, and liquid present on the upper surface of the wafer is allowed to flow into a liquid channel formed in the elastic film to remove the liquid from the upper surface of the wafer, and then the lower surface of the wafer is pressed against a polishing surface with the elastic film to polish the lower surface of the wafer.

[0014] In one embodiment, the elastic film has a contact surface that contacts the upper surface of the wafer, and the liquid channel has an opening that opens at the contact surface and a transverse hole connected to the opening and extending within the elastic film, the transverse hole opening on the outer surface of the elastic film. In one embodiment, the step of introducing liquid present on the upper surface of the wafer into the liquid channel is a step of sucking the liquid present on the upper surface of the wafer through the liquid channel, and the liquid channel is in communication with a suction line connected to the elastic membrane. In one embodiment, the elastic film has a contact surface that contacts the upper surface of the wafer, and the liquid channel is a groove formed in the contact surface. In one embodiment, the width of the groove inside the elastic membrane is greater than the width of the groove on the contact surface.

[0015] In one embodiment, an elastic film is provided for pressing a wafer against a polishing surface, comprising a contact portion having a contact surface that can contact the wafer, and an outer wall portion connected to the contact portion, wherein the contact portion has an opening that opens at the contact surface and a transverse hole connected to the opening and extending within the contact portion. In one embodiment, the transverse hole opens on the outer surface of the elastic membrane. In one embodiment, the lateral hole opens on the side of the contact portion opposite to the contact surface.

[0016] In one embodiment, an elastic film is provided for pressing a wafer against a polishing surface, comprising a contact portion having a contact surface that can contact the wafer, and an outer wall portion connected to the contact portion, wherein the contact portion has grooves formed on the contact surface. In one embodiment, the width of the groove inside the contact portion is greater than the width of the groove on the contact surface. [Effects of the Invention]

[0017] According to the present invention, liquid is removed from the upper surface of the wafer before polishing or immediately after polishing begins. As a result, the elastic film forming the pressure chamber can apply the intended force to the wafer, thereby achieving the desired film thickness profile of the wafer. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram showing one embodiment of a polishing apparatus. [Figure 2] It is a cross-sectional view showing a polishing head. [Figure 3] It is a top view of a transfer device for transferring a wafer to the polishing head shown in FIG. 1. [Figure 4] It is a schematic diagram showing a polishing head when removing liquid from the upper surface of a wafer. [Figure 5] It is a schematic diagram showing a state where the elastic film of the polishing head extrudes the liquid existing on the upper surface of the wafer to the outside. [Figure 6] It is a schematic diagram showing a state where the elastic film of the polishing head further extrudes the liquid existing on the upper surface of the wafer to the outside. [Figure 7] It is a diagram for explaining an embodiment in which a combination of an air cylinder and a weight is used to inflate the central portion of the elastic film instead of a pressure regulator. [Figure 8] It is a schematic diagram showing another embodiment of the elastic film. [Figure 9] It is a schematic diagram showing still another embodiment of the elastic film. [Figure 10] It is a diagram for explaining another embodiment of a method for removing liquid from the upper surface of a wafer. [Figure 11] It is a diagram for further explaining the embodiment shown in FIG. 10. [Figure 12] It is a diagram for further explaining the embodiment shown in FIG. 10. [Figure 13] It is a diagram for further explaining the embodiment shown in FIG. 10. [Figure 14] It is a diagram for explaining still another embodiment of a method for removing liquid from the upper surface of a wafer. [Figure 15] It is a diagram for further explaining the embodiment shown in FIG. 14. [Figure 16] It is a diagram for further explaining the embodiment shown in FIG. 14. [Figure 17] It is a diagram for explaining still another embodiment of a method for removing liquid from the upper surface of a wafer. [Figure 18] It is a diagram for further explaining the embodiment shown in FIG. 17. [Figure 19]This figure illustrates yet another embodiment of a method for removing liquid from the top surface of a wafer. [Figure 20] This figure further illustrates the embodiment shown in Figure 19. [Figure 21] This is a cross-sectional view showing one embodiment of an elastic film that can remove liquid from the upper surface of a wafer. [Figure 22] Figure 21 is a schematic diagram showing how the elastic film removes liquid from the top surface of the wafer. [Figure 23] This is a cross-sectional view showing another embodiment of an elastic film that can remove liquid from the top surface of a wafer. [Figure 24] Figure 23 is a schematic diagram showing how the elastic film removes liquid from the top surface of the wafer. [Figure 25] This is a cross-sectional view showing yet another embodiment of an elastic film that can remove liquid from the top surface of a wafer. [Figure 26] Figure 25 is a bottom view of the elastic membrane. [Figure 27] Figure 25 is a schematic diagram showing how the elastic film removes liquid from the top surface of the wafer. [Figure 28] This is a schematic cross-sectional view of the polishing head. [Figure 29] This diagram illustrates the cleaning process of the polishing head. [Figure 30] This diagram illustrates a problem caused by the liquid present between the top surface of the wafer and the elastic film of the polishing head. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram showing one embodiment of a polishing apparatus. As shown in Figure 1, the polishing apparatus comprises 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 for supplying slurry onto the polishing pad 2. The surface of the polishing pad 2 constitutes a polishing surface 2a for polishing 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 the end of the 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 pivot 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 arrows in Figure 1, slurry is supplied from the slurry supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. As the wafer W is rotated by the polishing head 1, the wafer W is pressed against the polishing surface 2a of the polishing pad 2 by the polishing head 1 with 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 operation of the polishing head 1, the polishing table 3, and the slurry supply nozzle 5. The operation control unit 9 consists of at least one computer.

[0023] Next, the polishing head 1 will be described. Figure 2 is a cross-sectional view showing the polishing head 1. The polishing head 1 comprises 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 positioned below the carrier 31. The retainer ring 32 is positioned around the elastic membrane 34. This retainer ring 32 is an annular structure that holds the wafer W to prevent the wafer W from flying out of the polishing head 1 during polishing.

[0024] The elastic film 34 comprises a contact portion 35 having a contact surface 35a that can contact the upper surface of the wafer W, and inner wall portions 36a, 36b, 36c and 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 outer wall portion 36d are concentrically arranged endless walls. The outer wall portion 36d is located outside the inner wall portions 36a, 36b, 36c and is arranged 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, inner wall portions 36a, 36b, and 36c, and outer wall portion 36d of the elastic membrane 34. Specifically, pressure chamber 25A is located within inner wall portion 36a, pressure chamber 25B is located between inner wall portions 36a and 36b, pressure chamber 25C is located between inner wall portions 36b and 36c, and pressure chamber 25D is located between inner wall portion 36c and outer wall portion 36d. The central pressure chamber 25A is circular, while the other pressure chambers 25B, 25C, and 25D are annular. These pressure chambers 25A, 25B, 25C, and 25D are arranged concentrically. Pressure chamber 25B is located outside pressure chamber 25A, pressure chamber 25C is located outside pressure chamber 25B, and pressure chamber 25D is located outside pressure chamber 25C.

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

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

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

[0029] Pressure regulators R1 to R5 can independently change the internal pressure of pressure chambers 25A to 25E, thereby independently adjusting the polishing pressure on the four corresponding regions of the wafer W, namely the central portion, the inner intermediate portion, the outer intermediate portion, and the edge portion, and the pressing force of the retainer ring 32 on the polishing pad 2. Gas transfer lines F1, F2, F3, F4, and F5 are also connected to atmospheric release valves (not shown), respectively, making it possible to release the pressure chambers 25A to 25E 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 than four or more pressure chambers.

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

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

[0032] Vacuum lines L1, L2, L3, L4, and L5 are connected to gas transfer lines F1, F2, F3, F4, and F5, respectively. Vacuum valves V1, V2, V3, V4, and V5 are installed on vacuum lines L1, L2, L3, L4, and L5, respectively. Vacuum valves V1, V2, V3, V4, and V5 are actuator-driven valves such as solenoid valves, electric valves, or air-operated valves. Vacuum valves V1 to V5 are connected to the operation control unit 9, and the operation of vacuum valves V1 to V5 is controlled by the operation control unit 9. When 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 contact portion 35 of the elastic film 34 is in contact with the wafer W, and the vacuum valves V2, V3, and V4 are opened to create a vacuum in the pressure chambers 25B, 25C, and 25D. The portion of the contact portion 35 that forms these pressure chambers 25B, 25C, and 25D is recessed upward, and the polishing head 1 can attract the wafer W due to the suction effect of the elastic film 34. Furthermore, by supplying compressed gas to these pressure chambers 25B, 25C, and 25D to release the suction effect, the polishing head 1 can release the wafer W.

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

[0035] The transport device 44 includes a transport stage 45 on which the wafer W is placed, a lifting device 47 that moves the transport stage 45 up and down, and a horizontal moving device 49 that moves the transport stage 45 and the lifting device 47 together horizontally. The wafer W to be polished is placed on the transport stage 45 and moved to the transfer position P2 together with the transport stage 45 by the horizontal moving device 49. When the polishing head 1 is at the transfer position P2, the lifting device 47 raises the transport stage 45. The polishing head 1 holds the wafer W on the transport 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, causing the wafer W to slide against the polishing surface 2a. The underside 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 with the wafer W to the transfer position P2. The polished wafer W is then transferred to the transport stage 45. The transport stage 45 moves the wafer W to the next process. A cleaning nozzle 53 is located at the transfer position P2 to supply liquid (such as a rinsing solution like pure water) to the polishing head 1 for cleaning. The cleaning nozzle 53 is facing the polishing head 1. After releasing the wafer W, the polishing head 1 is cleaned by 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 transport stage 45 to a receiving position P2 below the polishing head 1. When the polishing head 1 is cleaned, the lifting device 47 raises the transport stage 45 on which the next wafer is placed. The cleaned polishing head 1 then holds the next wafer and moves to the polishing position P1. In this way, multiple wafers are polished continuously.

[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 present on the top surface of the wafer prevents the polishing head 1 from applying the appropriate force to the wafer, as explained with reference to Figure 30. One solution is to move the next wafer to the receiving position P2 only after the cleaning of the polishing head 1 is complete. However, such an operation reduces the throughput of the polishing apparatus.

[0040] Therefore, in this embodiment, the liquid is removed from the top surface of the wafer as follows. Figure 4 is a schematic diagram showing the polishing head 1 when the liquid is removed from the top surface of the wafer. In Figure 4, the detailed configuration of the polishing head 1 is omitted. Before holding the wafer W to be polished, the pressure in the central pressure chambers 25A, 25B, and 25C 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 commands to the pressure regulators R1, R2, and R3 (see Figure 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 create a vacuum in the pressure chamber 25D.

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

[0042] The pressure difference between pressure chambers 25A, 25B, and 25C and pressure chamber 25D causes the central part of the contact portion 35 of the elastic film 34 to bulge, causing the central part of the contact portion 35 to protrude toward the wafer W. With the central part of the contact portion 35 protruding, the polishing head 1 descends toward the wafer W, bringing the elastic film 34 into contact with the upper surface of the wafer W. As shown in Figure 5, the central part of the elastic film 34, i.e., the central part of the contact portion 35, first comes into contact with the central part 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 outwards.

[0043] Furthermore, the polishing head 1 is lowered so that most of the contact portion 35 comes into contact with the upper surface of the wafer W. More specifically, as shown in Figure 6, with the central part of the elastic film 34 in contact with the central part 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, comes 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, removing the liquid Q from the upper surface of the wafer W. Subsequently, the elastic film 34 of the polishing head 1 slides against the polishing surface 2a in the presence of slurry on the polishing surface 2a, and polishes the wafer W through the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0044] In this way, the liquid Q present on the upper surface of the wafer W is moved to the outside of the wafer W by the elastic film 34 with a protruding central portion and removed from the upper surface of the wafer W. Therefore, the polishing head 1 can hold the wafer W with substantially no liquid Q between the elastic film 34 and the upper surface of the wafer W. As a result, the elastic film 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 the desired film thickness profile of the wafer W.

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

[0046] Therefore, in one embodiment, as shown in Figure 7, instead of pressure regulators R1, R2, R3, a combination of an air cylinder 41 and a weight 42 is used to send compressed gas to pressure chambers 25A, 25B, and 25C. Pressure chambers 25A, 25B, and 25C are in communication with a common air cylinder 41 via gas transfer lines F1, F2, and F3. The air cylinder 41 is positioned vertically. Before the polishing head 1 holds the wafer W, the weight 42 is placed on the piston 41A of the air cylinder 41, pushing the piston 41A downward. The gas in the air cylinder 41 is sent into pressure chambers 25A, 25B, and 25C, causing the central part of the elastic membrane 34 to bulge. Similar to the embodiment shown in Figure 4, a vacuum is formed in the pressure chamber 25D. In one embodiment, the operation control unit 9 may open an atmospheric release valve (not shown) connected to the gas transfer line F4 to release the pressure chamber 25D into the atmosphere.

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

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

[0049] Figure 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 inner wall portions 36a, 36b, and 36c are fixed, and a second surface 31b to which an outer wall portion 36d is fixed. The first surface 31a is located lower than the second surface 31b. The lower ends of the inner wall portions 36a, 36b, and 36c are located lower than the lower end of the outer wall portion 36d. The difference in height between the first surface 31a and the second surface 31b of the carrier 31 causes the central part of the contact portion 35 of the elastic film 34 to protrude toward the wafer W.

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

[0051] Next, other embodiments of the method for removing liquid from the upper surface of wafer W will be described with reference to Figures 10 to 13. Details of these embodiments that are not specifically described are the same as those of the embodiments described above, so redundant explanations will be omitted.

[0052] As shown in Figure 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 Figure 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, some of the liquid Q spills off the upper surface of the wafer W.

[0053] As shown in Figure 12, vacuums are sequentially formed in pressure chambers 25D, 25C, and 25B in the order from the outer pressure chamber 25D to the central pressure chamber 25B (i.e., in the order of pressure chambers 25D, 25C, and 25B). The contact portions 35 that make up pressure chambers 25D, 25C, and 25B are recessed upward by the vacuum, and a space is 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, forming a flow of liquid Q toward the outside of the wafer W.

[0054] Subsequently, the polishing head 1 moves the wafer W to a position above the polishing pad 2, and as shown in Figure 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 central pressure chamber 25B to the outer pressure chamber 25D (i.e., in the order of pressure chambers 25B, 25C, and 25D). The liquid Q that was 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 and moves to the outside of the wafer W, and is removed from the upper surface of the wafer W.

[0055] Subsequently, the elastic film 34 of the polishing head 1 slides against the polishing surface 2a in the presence of slurry on the lower surface of the wafer W, and polishes it through the chemical action of the slurry and the mechanical action of the abrasive grains contained in the slurry.

[0056] Next, other embodiments 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 these embodiments that are not specifically described are the same as those of the embodiments described above, so redundant explanations will be omitted. Figure 14 is a schematic diagram showing a modified version of the transport device 44 shown in Figure 3. Details of these embodiments that are not specifically described are the same as those of the embodiment shown in Figure 3, so redundant explanations will be omitted.

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

[0058] The wafer W on the transport stage 45 is moved to the transfer position P2 by the horizontal movement device 49. The polishing head 1 is cleaned by the 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 transport stage 45. Figure 15 is a diagram of the transport device 44 viewed from the direction indicated by arrow A in Figure 14. As shown in Figure 15, liquid Q is present on the upper surface of the wafer W. Therefore, as shown in Figure 16, the tilting device 55 tilts the transport stage 45 and the wafer W together before the wafer W is held by the polishing head 1. The liquid Q spills off the tilted upper surface of the wafer W, thereby removing the liquid Q 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. The wafer W is then held by the polishing head 1. The polishing head 1 moves the wafer W to a polishing position P1 (see Figure 3) above the polishing pad 2, and the elastic film 34 presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2. The elastic film 34 of the polishing head 1 slides the lower surface of the wafer W against the polishing surface 2a in the presence of slurry on the polishing surface 2a, and polishes it through 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, there is no liquid Q between the upper surface of the wafer W and the elastic film 34 of the polishing head 1, the elastic film 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] Figures 17 and 18 are schematic diagrams illustrating yet another embodiment of a method for removing liquid from the top surface of wafer W. Details of this embodiment that are not specifically described are the same as those of the embodiment shown in Figure 3, so redundant explanations are omitted.

[0062] As shown in Figure 17, the wafer W on the transport stage 45 is moved to the transfer position P2 by the horizontal moving device 49. The polishing head 1 is cleaned by the 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 transport stage 45.

[0063] As shown in Figure 18, before the wafer W is held by the polishing head 1, the horizontal moving device 49 shakes the transport stage 45 and the wafer W in a horizontal direction. When the wafer W is shaken, the liquid Q spills off the top surface of the wafer W, thereby removing the liquid Q from the top surface of the wafer W. In one embodiment, the horizontal moving device 49 may shake the transport stage 45 and the wafer W in a horizontal direction while the transport stage 45 and the wafer W are tilted by a tilting device 55. Furthermore, in one embodiment, the tilting 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 moves the wafer W to a polishing position P1 (see Figure 3) above the polishing pad 2, and the elastic film 34 presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2. The elastic film 34 of the polishing head 1 slides the lower surface of the wafer W against the polishing surface 2a in the presence of the slurry on the polishing surface 2a, and polishes it through 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, there is no liquid Q between the upper surface of the wafer W and the elastic film 34 of the polishing head 1, the elastic film 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] Figure 19 is a schematic diagram illustrating yet another embodiment of a method for removing liquid from the top surface of wafer W. Details of this embodiment that are not specifically described are the same as those of the embodiment shown in Figure 3, so redundant explanations are omitted.

[0067] As shown in Figure 19, the polishing apparatus of this embodiment includes a gas jet nozzle 57 located at the transfer position P2. The gas jet nozzle 57 is inclined with respect to the horizontal direction and is positioned facing the upper part of the transport stage 45 at the transfer position P2, that is, facing the upper surface of the wafer W on the transport stage 45. The gas jet nozzle 57 is connected to a compressed gas supply source (not shown). In this embodiment, multiple 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 transport stage 45 is moved to the transfer position P2 by the horizontal moving device 49. The polishing head 1 is cleaned by the 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 transport stage 45. As shown in Figure 20, before the wafer W is held by the polishing head 1, the gas jet nozzle 57 delivers a jet of gas to the upper surface of the wafer W, removing 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 moves the wafer W to a polishing position P1 (see Figure 3) above the polishing pad 2, and the elastic film 34 presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2. The elastic film 34 of the polishing head 1 slides the lower surface of the wafer W against the polishing surface 2a in the presence of the slurry on the polishing surface 2a, and polishes it through 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, there is no liquid Q between the upper surface of the wafer W and the elastic film 34 of the polishing head 1, the elastic film 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] Figure 21 is a cross-sectional view showing one embodiment of an elastic film 34 capable of removing liquid from the upper surface of a wafer W. As shown in Figure 21, the elastic film 34 has liquid channels 60 formed inside it. More specifically, the contact portion 35 of the elastic film 34 has a plurality of openings 61 that open at the contact surface 35a and transverse holes 62 connected to the plurality of openings 61. The contact surface 35a of the elastic film 34 is one surface of the elastic film 34 that is in contact with the upper surface of the wafer W. The openings 61 are located below the central pressure chamber 25A and not below the other pressure chambers 25B to 25D. In one embodiment, the openings 61 may also be provided below the pressure chambers 25B to 25D. The transverse holes 62 extend within the contact portion 35, and the outer end of the transverse holes 62 opens at the outer surface 34a of the elastic film 34. Thus, the contact surface 35a and the outer surface 34a of the elastic film 34 are in communication by the liquid channels 60, which are composed of the openings 61 and the transverse holes 62.

[0072] As shown in Figure 22, compressed gas is supplied into pressure chambers 25A to 25D to inflate the elastic film 34, pressing the contact surface 35a of the elastic film 34 against the upper surface of the wafer W. Liquid Q (see Figure 21) present on the upper surface of the wafer W flows into the liquid channel 60 through the opening 61 and out of the elastic film 34 through the liquid channel 60. As a result, 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 moves the wafer W to a polishing position P1 (see Figure 3) above the polishing pad 2, and the elastic film 34 presses the lower surface of the wafer W against the polishing surface 2a of the polishing pad 2. The elastic film 34 of the polishing head 1 slides the lower surface of the wafer W against the polishing surface 2a in the presence of the slurry on the polishing surface 2a, and polishes it through 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 film 34 and the upper surface of the wafer W. As a result, the elastic film 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 the desired film thickness profile of the wafer W.

[0075] Figure 23 is a cross-sectional view showing another embodiment of the elastic membrane 34 that can remove 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 embodiments shown in Figures 21 and 22, and therefore redundant descriptions are omitted. As shown in Figure 23, the liquid channel 60 communicates with a suction line 70 connected to the elastic membrane 34. More specifically, the lateral hole 62 is connected to both the opening 61 and the suction line 70. One end of the lateral hole 62 is connected to the opening 61, and the other end of the lateral hole 62 is open on the upper surface 35b of the connection portion 35 (the surface opposite to the contact surface 35a of the connection portion 35).

[0076] The suction line 70 extends through the carrier 31, and its end is connected to the upper surface 35b of the contact portion 35. The suction line 70 communicates with the liquid flow path 60 but not 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] As shown in Figure 24, compressed gas is supplied into pressure chambers 25A to 25D to inflate the elastic membrane 34, and a vacuum is formed in the liquid channel 60 by the suction line 70 while the contact surface 35a of the elastic membrane 34 is pressed against the upper surface of the wafer W. The liquid Q (see Figure 23) present on the upper surface of the wafer W is sucked into the liquid channel 60 through the opening 61 and removed from the upper surface of the wafer W.

[0078] Figure 25 is a cross-sectional view showing yet another embodiment of the elastic film 34 that can remove 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 embodiments shown in Figures 21 and 22, and therefore redundant descriptions are omitted. As shown in Figure 25, the liquid channel consists of a plurality of grooves 75 formed in the contact surface 35a.

[0079] Figure 26 is a bottom view of the elastic membrane 34 shown in Figure 25. As shown in Figure 26, the multiple 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 straight grooves arranged parallel to each other.

[0080] As shown in Figure 27, compressed gas is supplied into pressure chambers 25A to 25D to inflate the elastic film 34, pressing the contact surface 35a of the elastic film 34 against the upper surface of the wafer W. The liquid Q (see Figure 25) present on the upper surface of the wafer W flows into the groove 75, which acts as a liquid channel. 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 that has flowed 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 on the contact surface 35a. That is, the entrance to the groove 75 is narrow, and the inside of the groove 75 is wide. A groove 75 with such a cross-sectional shape is more likely to retain the liquid Q inside. In order to remove liquid that is irregularly present on the upper surface of the wafer W, the groove 75 may be uniformly distributed across the entire contact surface 35a of the elastic film 34.

[0082] The elastic membrane 34 shown in Figures 21 to 27 can be created using a 3D printer.

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

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

[0085] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense 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 motors 11 Polished Head Shaft 15 Head Arm 25A, 25B, 25C, 25D, 25E ​​Pressure Chambers 31 Careers 32 Retainer Rings 34 Elastic membrane 35 Contact area 35a Contact surface 36a,36b,36c Inner wall part 36d Exterior wall 37 Membrane (Rolling Diaphragm) 40 Rotary Joint 41 Air Cylinder 42 Weight 44 Conveying device 45 Conveyor Stages 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 lines 75 Groove F1, F2, F3, F4, F5 Gas Transfer Line R1, R2, R3, R4, R5 Pressure Regulators 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 film, The elastic film is brought into contact with the upper surface of the wafer, and then, By creating a vacuum in the outer pressure chamber and the central pressure chamber, in that order, the liquid present on the upper surface of the wafer is moved outwards, and then, By supplying compressed gas to the central pressure chamber and the outer pressure chamber in that order, the elastic film presses the lower surface of the wafer against the polishing surface, thereby removing liquid from the upper surface of the wafer. A method of polishing the lower surface of a wafer by sliding the lower surface of the wafer against the polishing surface using the polishing head.

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

3. The method according to claim 2, wherein after moving the liquid present on the upper surface of the wafer to the outside, compressed gas is supplied to the first pressure chamber, the second pressure chamber, and the third pressure chamber in that order, thereby pressing the lower surface of the wafer against the polishing surface with the elastic film and removing the liquid from the upper surface of the wafer.

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