Polishing method and polishing device

Abstract

To provide a polishing method that enables fluid to flow out through an upper surface of a wafer and enables a polishing head to apply proper force to the wafer.SOLUTION: A polishing method for a wafer W, which uses a polishing head 1 having a plurality of pressure chambers formed of elastic films 34, performs steps of: forming positive pressure in the first pressure chamber and forming negative pressure in the second pressure chamber positioned outside the first pressure chamber; forming positive pressure in the second pressure chamber and forming negative pressure in a third pressure chamber positioned outside the second pressure chamber, after moving fluid Q existing between an upper surface of the wafer W and the first pressure chamber to the outside; and polishing a lower surface of the wafer W while making the elastic films 34 press the lower surface of the wafer W against a polishing surface 2a, after moving the fluid Q existing between the upper surface of the wafer W and the second pressure chamber to the outside, forming positive pressure in the pressure chamber positioned at the outermost side, of the plurality of pressure chambers, and flowing out the fluid Q through the upper surface of the wafer W.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a technique for polishing a wafer by causing a fluid to flow over the top surface 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 a polishing surface while supplying a polishing fluid onto the surface and sliding the wafer against the polishing surface in the presence of the polishing fluid. During wafer polishing, the wafer is pressed against the polishing surface by a polishing head. The wafer surface is planarized by the chemical action of the polishing fluid and the mechanical action of the abrasive grains contained in the polishing fluid and / or the polishing pad.

[0003] 12 is a cross-sectional view showing a schematic diagram of the polishing head 100. The polishing head 100 has an elastic membrane 110 that contacts the upper surface of the wafer W1. The elastic membrane 110 has a shape that forms a plurality of pressure chambers 101-104, and the pressure in each of the pressure chambers 101-104 can be adjusted independently. Therefore, the polishing head 100 can press a plurality of regions of the wafer W1 corresponding to these pressure chambers 101-104 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. 13, the next wafer W2 is transported by the transport device to a transfer position below the polishing head 100. At the same time, the polishing head 100 is washed with a liquid (e.g., pure water) supplied from the cleaning nozzle 115, and the polishing liquid and polishing debris are removed from the polishing head 100. Then, the next wafer W2 is held by the polishing head 100 and transported by the polishing head 100 to a position above the polishing surface. The wafer W2 is pressed against the polishing surface by the polishing head 100 and polished in the presence of the polishing liquid. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-131414 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, as shown in FIG. 14, a fluid Q such as a liquid used for cleaning the polishing head 100 or air may exist between the upper surface of the wafer W2 and the elastic membrane 110 of the polishing head 100. If the fluid Q exists between the upper surface of the wafer W2 and the polishing head 100, the polishing head 100 cannot apply a force appropriately to the multiple regions of the wafer W2 corresponding to the pressure chambers 101 to 104. For example, if the fluid Q spreads across multiple pressure chambers, the pressure in the adjacent pressure chamber is transmitted to the fluid Q, and an unintended force is applied to the wafer W2. In the example shown in FIG. 14, even though the pressure in the central pressure chamber 101 is lowered to lower the polishing rate of the center of the wafer W2, the pressure of the adjacent pressure chamber 102 is applied to the center of the wafer W2 through the fluid Q. As a result, the polishing rate of the center of the wafer W cannot be lowered. In this way, the fluid Q existing between the wafer W2 and the polishing head 100 prevents the polishing head 100 from applying an appropriate force to the wafer W2.

[0007] Therefore, the present invention provides a polishing method and polishing apparatus that allows a fluid to flow from the top surface of the wafer, enabling 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 plurality of pressure chambers formed by an elastic membrane, the plurality of pressure chambers including a first pressure chamber, a second pressure chamber located outside the first pressure chamber, and a third pressure chamber located outside the second pressure chamber, the method including forming a positive pressure in the first pressure chamber and a negative pressure in the second pressure chamber to move a fluid present between an upper surface of the wafer and the first pressure chamber outward, then forming a positive pressure in the second pressure chamber and a negative pressure in the third pressure chamber to move the fluid present between the upper surface of the wafer and the second pressure chamber outward, forming a positive pressure in a pressure chamber located at the outermost position among the plurality of pressure chambers to move the fluid present between the upper surface of the wafer and the pressure chamber located at the outermost position outward, causing the fluid to flow out from the upper surface of the wafer, and then pressing the lower surface of the wafer against a polishing surface with the elastic membrane to polish the lower surface of the wafer.

[0009] In one embodiment, the timing at which the formation of the positive pressure in the first pressure chamber starts and the timing at which the formation of the negative pressure in the second pressure chamber starts are the same, and the timing at which the formation of the positive pressure in the second pressure chamber starts and the timing at which the formation of the negative pressure in the third pressure chamber starts are the same. In one embodiment, forming the negative pressure in the second pressure chamber includes reducing the pressure in the second pressure chamber to a negative pressure set value and then opening the second pressure chamber to the atmosphere, and forming the negative pressure in the third pressure chamber includes reducing the pressure in the third pressure chamber to a negative pressure set value and then opening the third pressure chamber to the atmosphere.

[0010] In one embodiment, the timing at which the generation of the negative pressure in the second pressure chamber begins is before the timing at which the generation of the positive pressure in the first pressure chamber begins, and the timing at which the generation of the negative pressure in the third pressure chamber begins is before the timing at which the generation of the positive pressure in the second pressure chamber begins. In one embodiment, forming the negative pressure in the second pressure chamber includes lowering the pressure in the second pressure chamber to a negative pressure set value and then eliminating the negative pressure in the second pressure chamber, forming the positive pressure in the first pressure chamber is performed while the negative pressure in the second pressure chamber is being eliminated, forming the negative pressure in the third pressure chamber includes lowering the pressure in the third pressure chamber to a negative pressure set value and then eliminating the negative pressure in the third pressure chamber, and forming the positive pressure in the second pressure chamber is performed while the negative pressure in the third pressure chamber is being eliminated.

[0011] In one embodiment, the first pressure chamber is located in a center portion of the elastic membrane. In one embodiment, forming the positive pressure in the first pressure chamber includes increasing the pressure in the first pressure chamber to a first positive pressure set value and then maintaining the pressure in the first pressure chamber at the first positive pressure set value, and forming the positive pressure in the second pressure chamber includes increasing the pressure in the second pressure chamber to a second positive pressure set value and then maintaining the pressure in the second pressure chamber at the second positive pressure set value.

[0012] In one aspect, a polishing apparatus for polishing a substrate includes a polishing head having a plurality of pressure chambers formed by an elastic membrane, the plurality of pressure chambers pressing the substrate against a polishing surface, and an operation control unit for controlling an operation of the polishing apparatus, the plurality of pressure chambers including a first pressure chamber, a second pressure chamber positioned outside the first pressure chamber, and a third pressure chamber positioned outside the second pressure chamber, the operation control unit forming a positive pressure in the first pressure chamber and a negative pressure in the second pressure chamber to move a fluid present between an upper surface of the wafer and the first pressure chamber to the outside, and then forming a negative pressure in the second pressure chamber to move a fluid present between the upper surface of the wafer and the first pressure chamber to the outside, a positive pressure formed in the third pressure chamber and a negative pressure formed in the third pressure chamber to move the fluid present between the upper surface of the wafer and the second pressure chamber outward, a positive pressure formed in the outermost pressure chamber of the plurality of pressure chambers to move the fluid present between the upper surface of the wafer and the outermost pressure chamber outward to cause the fluid to flow out from the upper surface of the wafer, and then, the elastic membrane is used to press the lower surface of the wafer against a polishing surface, thereby operating the polishing apparatus to polish the lower surface of the wafer.

[0013] In one embodiment, the operation control unit is configured to operate the polishing apparatus so that the timing at which the operation control unit starts to form the positive pressure in the first pressure chamber is the same as the timing at which the operation control unit starts to form the negative pressure in the second pressure chamber, and to operate the polishing apparatus so that the timing at which the operation control unit starts to form the positive pressure in the second pressure chamber is the same as the timing at which the operation control unit starts to form the negative pressure in the third pressure chamber. In one embodiment, the operation control unit is configured to operate the polishing apparatus such that forming the negative pressure in the second pressure chamber includes lowering the pressure in the second pressure chamber to a negative pressure set value and then opening the second pressure chamber to the atmosphere, and to operate the polishing apparatus such that forming the negative pressure in the third pressure chamber includes lowering the pressure in the third pressure chamber to a negative pressure set value and then opening the third pressure chamber to the atmosphere.

[0014] In one embodiment, the operation control unit is configured to operate the polishing apparatus so that the timing at which the formation of the negative pressure in the second pressure chamber begins is before the timing at which the formation of the positive pressure in the first pressure chamber begins, and the operation control unit is configured to operate the polishing apparatus so that the timing at which the formation of the negative pressure in the third pressure chamber begins is before the timing at which the formation of the positive pressure in the second pressure chamber begins. In one embodiment, the operation control unit is configured to operate the polishing apparatus such that forming the negative pressure in the second pressure chamber includes lowering the pressure in the second pressure chamber to a negative pressure set value and then eliminating the negative pressure in the second pressure chamber, and forming the positive pressure in the first pressure chamber while the negative pressure in the second pressure chamber is being eliminated, and forming the negative pressure in the third pressure chamber includes lowering the pressure in the third pressure chamber to a negative pressure set value and then eliminating the negative pressure in the third pressure chamber, and forming the positive pressure in the second pressure chamber while the negative pressure in the third pressure chamber is being eliminated.

[0015] In one embodiment, the first pressure chamber is located in a center portion of the elastic membrane. In one embodiment, the operation control unit is configured to operate the polishing apparatus such that forming the positive pressure in the first pressure chamber includes increasing the pressure in the first pressure chamber to a first positive pressure set value and then maintaining the pressure in the first pressure chamber at the first positive pressure set value, and to operate the polishing apparatus such that forming the positive pressure in the second pressure chamber includes increasing the pressure in the second pressure chamber to a second positive pressure set value and then maintaining the pressure in the second pressure chamber at the second positive pressure set value. Effect of the Invention

[0016] According to the present invention, in a polishing head having a plurality of pressure chambers, a positive pressure is created in an inner pressure chamber among the adjacent pressure chambers, and a negative pressure is created in an outer pressure chamber, thereby moving fluid present on the upper surface of the wafer outward. This operation is performed sequentially in the adjacent pressure chambers on the outer side, thereby moving fluid present on the upper surface of the wafer outward. Furthermore, by creating a positive pressure in the outermost pressure chamber, fluid can be caused to flow out from the upper surface of the wafer. As a result, the elastic membrane forming the pressure chamber can apply the intended force to the wafer. [Brief description of the drawings]

[0017] [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 one embodiment of 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 a state in which a fluid is present on the upper surface of a wafer. [Diagram 5] 1 is a schematic diagram showing how an elastic membrane of a polishing head moves fluid present on the upper surface of a wafer outward. [Figure 6] 1 is a schematic diagram showing how the elastic membrane of the polishing head moves the fluid present on the upper surface of the wafer further outward. [Figure 7] 1 is a schematic diagram showing how the elastic membrane of the polishing head moves the fluid present on the upper surface of the wafer further outward. [Figure 8] 1 is a schematic diagram showing how an elastic membrane of a polishing head causes fluid present on the upper surface of a wafer to flow out. [Figure 9] 13 is a graph showing the relationship between pressure and time in a plurality of pressure chambers. [Figure 10] 11 is a graph showing pressure versus time within multiple pressure chambers according to another embodiment of a method for flushing fluid from an upper surface of a wafer. [Figure 11]13 is a graph illustrating pressure versus time within multiple pressure chambers according to yet another embodiment of a method for draining fluid from an upper surface of a wafer. [Figure 12] FIG. 2 is a cross-sectional view illustrating a polishing head. [Figure 13] FIG. 13 is a diagram illustrating a state in which the polishing head is being cleaned. [Figure 14] 1A-1C are diagrams illustrating problems caused by fluid being present between the top surface of the wafer and the elastic membrane of the polishing head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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 workpiece, against the polishing pad 2, a table motor 6 that rotates the polishing table 3, and a polishing liquid supply nozzle 5 for supplying a polishing liquid (e.g., a slurry containing abrasive grains) onto the polishing pad 2. The surface of the polishing pad 2 constitutes a polishing surface 2a that polishes the wafer W.

[0019] 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, which is rotatably supported by a head arm 15. The head arm 15 is rotatably supported by a support shaft 16. The polishing head shaft 11 is connected to a vertical movement mechanism 18 disposed within the head arm 15. The vertical movement mechanism 18 is configured to move the polishing head shaft 11 up and down in its axial direction. By the vertical movement of the polishing head shaft 11 by the vertical movement mechanism 18, the wafer W held by the polishing head 1 can be moved close to or away from the polishing pad 2 on the polishing table 3.

[0020] The polishing apparatus further includes an operation control unit 9 that controls the operation of each component of the polishing apparatus. The operation control unit 9 is electrically connected to the polishing head 1, the polishing table 3, the polishing liquid supply nozzle 5, and the vertical movement mechanism 18, and controls the operations of the polishing head 1, the polishing table 3, the polishing liquid supply nozzle 5, and the vertical movement mechanism 18. The operation control unit 9 includes a storage device 9a in which a program is stored, and a calculation device 9b that executes calculations according to instructions included in the program. The operation control unit 9 includes at least one computer. The storage device 9a includes a main storage device such as a random access memory (RAM), and an auxiliary storage device such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the calculation device 9b include a CPU (central processing unit) and a GPU (graphic processing unit). However, the specific configuration of the operation control unit 9 is not limited to these examples.

[0021] The wafer W is polished as follows. The operation control unit 9 issues commands to the polishing table 3, polishing head 1, and polishing liquid supply nozzle 5 to rotate the polishing table 3 and polishing head 1 in the directions indicated by the arrows in FIG. 1 while supplying a polishing liquid from the polishing liquid supply nozzle 5 to the polishing surface 2a of the polishing pad 2 on the polishing table 3. While being 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 the polishing liquid present between the polishing pad 2 and the wafer W. The surface of the wafer W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad.

[0022] Next, the polishing head 1 will be described. Fig. 2 is a cross-sectional view showing one embodiment of 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.

[0023] 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, two inner wall portions may be provided, or four or more inner wall portions may be provided.

[0024] A plurality of pressure chambers 25A, 25B, 25C, and 25D (four in this embodiment) 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 sizes of the pressure chambers 25A, 25B, 25C, and 25D, that is, the distances from the center of the elastic membrane 34 to the inner wall portions 36a, 36b, and 36c, and the outer wall portion 36d, are not particularly limited. For example, the inner wall portions 36a, 36b, 36c and the outer wall portion 36d may be disposed at equal intervals from the center of the elastic membrane 34, or may be disposed at different intervals.

[0025] The pressure chamber 25A located at the center of the elastic membrane 34 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. In this embodiment, the elastic membrane 34 forms four pressure chambers 25A to 25D, but in one embodiment, the elastic membrane 34 may form three pressure chambers, or may form five or more pressure chambers.

[0026] An annular membrane (rolling diaphragm) 37 is disposed between the carrier 31 and the retainer ring 32, and a pressure chamber 25E is formed inside the membrane 37. Gas transfer lines F1, F2, F3, F4, and F5 are connected to the pressure chambers 25A, 25B, 25C, 25D, and 25E, respectively. The gas transfer lines F1, F2, F3, F4, and F5 extend via a rotary joint 40 attached to the polishing head shaft 11.

[0027] The gas transfer lines F1, F2, F3, F4, and F5 are connected to the gas supply lines La1, La2, La3, La4, and La5, respectively, on the upstream side of the rotary joint 40. The gas supply lines La1, La2, La3, La4, and La5 are 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 configured to be supplied from the gas supply lines La1, La2, La3, La4, and La5 through the gas transfer lines F1, F2, F3, F4, and F5 to the pressure chambers 25A, 25B, 25C, 25D, and 25E, respectively.

[0028] Gas supply valves Va1, Va2, Va3, Va4, Va5 and pressure regulators Ra1, Ra2, Ra3, Ra4, Ra5 are attached to the gas supply lines La1, La2, La3, La4, La5, respectively. The gas supply valves Va1, Va2, Va3, Va4, Va5 are actuator-driven valves such as solenoid valves, motorized valves, or air-operated valves. In one embodiment, the gas supply valves Va1 to Va5 may be manual. When the gas supply valves Va1 to Va5 are opened, the compressed gas from the compressed gas supply source is independently supplied into the pressure chambers 25A to 25E through the pressure regulators Ra1 to Ra5. The pressure regulators Ra1 to Ra5 ​​are configured to adjust the pressure of the compressed gas in the pressure chambers 25A to 25E.

[0029] The gas supply valves Va1-Va5 and the pressure regulators Ra1-Ra5 are connected to an operation control unit 9. The operations of the gas supply valves Va1-Va5 and the pressure regulators Ra1-Ra5 are controlled by the operation control unit 9. The operation control unit 9 sends target pressure values ​​for each of the pressure chambers 25A-25E to the pressure regulators Ra1-Ra5, and the pressure regulators Ra1-Ra5 operate so as to maintain the pressures in the pressure chambers 25A-25E at the corresponding target pressure values.

[0030] The pressure regulators Ra1 to Ra5 ​​can change the internal pressures of the pressure chambers 25A to 25E independently of each other. Therefore, the polishing head 1 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 surface 2a of the polishing pad 2. 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. Therefore, the polishing head 1 can control the film thickness profile of the wafer W to achieve a target film thickness profile.

[0031] Furthermore, the gas transfer lines F1, F2, F3, F4, and F5 are connected to the vacuum lines Lb1, Lb2, Lb3, Lb4, and Lb5, respectively, on the upstream side of the rotary joint 40. Compressed gas such as compressed air is supplied from the gas supply lines La1, La2, La3, La4, and La5 through the gas transfer lines F1, F2, F3, F4, and F5 to the pressure chambers 25A, 25B, 25C, 25D, and 25E, respectively. The vacuum lines Lb1, Lb2, Lb3, Lb4, and Lb5 are respectively equipped with vacuum valves Vb1, Vb2, Vb3, Vb4, and Vb5 and vacuum regulators Rb1, Rb2, Rb3, Rb4, and Rb5. The vacuum valves Vb1, Vb2, Vb3, Vb4, and Vb5 are actuator-driven valves such as solenoid valves, motor-operated valves, and air-operated valves. In one embodiment, the vacuum valves Vb1 to Vb5 may be manual.

[0032] When the vacuum valves Vb1 to Vb5 are opened, the compressed gas in the pressure chambers 25A to 25E is discharged independently from the pressure chambers 25A to 25E to the outside through the gas transfer lines F1 to F5 and the vacuum lines Lb1 to Lb5, respectively, and a negative pressure is created in the pressure chambers 25A to 25E. The vacuum regulators Rb1 to Rb5 are configured to adjust the vacuum pressure in the pressure chambers 25A to 25E.

[0033] The vacuum valves Vb1 to Vb5 and the vacuum regulators Rb1 to Rb5 are connected to the operation control unit 9. The operation of the vacuum valves Vb1 to Vb5 and the vacuum regulators Rb1 to Rb5 is controlled by the operation control unit 9. When the polishing head 1 holds the wafer W, the vacuum valves Vb1, Vb2, and Vb3 are opened with the contact portion 35 of the elastic film 34 in contact with the wafer W, and a vacuum is formed in the pressure chambers 25A, 25B, and 25C. The contact portion 35 forming the pressure chambers 25A, 25B, and 25C is recessed upward, and the polishing head 1 can suction the wafer W by the suction effect of the elastic film 34. When the suction effect is released by supplying compressed gas to the pressure chambers 25A, 25B, and 25C, the polishing head 1 can release the wafer W.

[0034] Furthermore, the gas transfer lines F1, F2, F3, F4, and F5 are connected to the atmosphere release lines Lc1, Lc2, Lc3, Lc4, and Lc5, respectively, on the upstream side of the rotary joint 40. The atmosphere release lines Lc1, Lc2, Lc3, Lc4, and Lc5 are respectively attached with the atmosphere release valves Vc1, Vc2, Vc3, Vc4, and Vc5. The atmosphere release valves Vc1, Vc2, Vc3, Vc4, and Vc5 are actuator-driven valves such as solenoid valves, motorized valves, and air-operated valves. In one embodiment, the atmosphere release valves Vc1 to Vc5 may be manual. When the atmosphere release valves Vc1 to Vc5 are opened, the pressure chambers 25A to 25E are independently opened to the atmosphere. The atmosphere release valves Vc1 to Vc5 are connected to the operation control unit 9. The operation of the atmosphere release valves Vc1 to Vc5 is controlled by the operation control unit 9. In one embodiment, the atmosphere release lines Lc1 to Lc5 and the atmosphere release valves Vc1 to Vc5 do not necessarily have to be provided.

[0035] In this embodiment, the gas supply valves Va1-Va5, the vacuum valves Vb1-Vb5, and the air release valves Vc1-Vc5 are attached to the gas supply lines La1-La5, the vacuum lines Lb1-Lb5, and the air release lines Lc1-Lc5, which are connected to the pressure chambers 25A-25E via the gas transfer lines F1-F5, respectively. In one embodiment, instead of the gas supply valves Va1-Va5, the vacuum valves Vb1-Vb5, and the air release valves Vc1-Vc5, three-way valves may be attached to the gas transfer lines F1-F5, respectively. In this case, by operating the three-way valves, the lines connected to the pressure chambers 25A-25E via the gas transfer lines F1-F5 may be switched to any one of the gas supply lines La1-La5, the vacuum lines Lb1-Lb5, and the air release lines Lc1-Lc5.

[0036] 3 is a top view of a transport device 44 that transports a wafer W to the polishing head 1 shown in FIG. 1. As shown in FIG. 3, the wafer W is transported to the polishing head 1 by the 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.

[0037] 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.

[0038] The polishing liquid supply nozzle 5 supplies the polishing liquid 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 bottom surface of the wafer W is polished by the chemical action of the polishing liquid and the mechanical action of the abrasive grains contained in the polishing liquid and / or the polishing pad.

[0039] After polishing the wafer W, the polishing head 1 moves to the transfer position P2 together with the wafer W. Then, the polishing head 1 transfers the polished wafer W 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.

[0040] 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.

[0041] 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. 14. 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.

[0042] Furthermore, when the polishing head 1 holds the next wafer by adsorbing the wafer using the suction effect of the elastic film 34 described above, gas such as air may be present between the upper surface of the wafer and the elastic film 34 of the polishing head 1. Gas present on the upper surface of the wafer also prevents the polishing head 1 from applying an appropriate force to the wafer, as described with reference to FIG.

[0043] Therefore, in this embodiment, the fluid is discharged from the upper surface of the wafer as follows. FIG. 4 is a schematic diagram showing a state where the fluid Q exists on the upper surface of the wafer W. In FIG. 4, the detailed configuration of the polishing head 1 is omitted. The polishing head 1 holding the wafer W to be polished is touched down on the polishing surface 2a of the polishing pad 2 by the vertical movement mechanism 18. When the polishing head 1 is touched down on the polishing surface 2a, the negative pressure formed in the pressure chambers 25A, 25B, and 25C for adsorbing the wafer W is eliminated. FIG. 4 shows a state where the negative pressure formed in the pressure chambers 25A, 25B, and 25C of the polishing head 1 is eliminated and the fluid Q exists on the upper surface of the wafer W, i.e., between the wafer W and the elastic film 34.

[0044] In this embodiment, before polishing the wafer W, the pressures in the multiple pressure chambers 25A to 25D formed by the elastic film 34 of the polishing head 1 are sequentially changed to move the fluid Q present on the upper surface of the wafer W outward, and the fluid Q flows out from the upper surface of the wafer W. FIGS. 5 to 8 are schematic diagrams showing how the elastic film 34 of the polishing head 1 moves the fluid Q present on the upper surface of the wafer W outward, and flows out the fluid Q present on the upper surface of the wafer W. FIG. 9 is a graph showing the relationship between the pressure and time in the multiple pressure chambers 25A to 25D in this embodiment. In FIG. 9, the solid line indicates the change over time in the pressure in the pressure chamber 25A, the thick line indicates the change over time in the pressure in the pressure chamber 25B, the dashed line indicates the change over time in the pressure in the pressure chamber 25C, and the dashed line indicates the change over time in the pressure in the pressure chamber 25D.

[0045] First, as shown in FIG. 5, a positive pressure is formed in the pressure chamber 25A located at the center of the polishing head 1, and a negative pressure is formed in the pressure chamber 25B located outside the pressure chamber 25A. The pressure chamber 25B is adjacent to the pressure chamber 25A. The formation of the positive pressure in the pressure chamber 25A and the formation of the negative pressure in the pressure chamber 25B are performed during a time T1 shown in FIG. 9. As shown in FIG. 9, the timing of starting the formation of the positive pressure in the pressure chamber 25A and the timing of starting the formation of the negative pressure in the pressure chamber 25B are the same. During the time T1, the pressure in the pressure chamber 25A is increased to a positive pressure setting value PS1, and then the pressure in the pressure chamber 25A is maintained at the positive pressure setting value PS1. During the time T1, the pressure in the pressure chamber 25B is decreased to a negative pressure setting value NS1, and then the negative pressure in the pressure chamber 25B is eliminated.

[0046] More specifically, during time T1, the operation control unit 9 issues a command to the gas supply valve Va1 (see FIG. 2) to open the gas supply valve Va1, communicate the gas supply line La1 with the pressure chamber 25A via the gas transfer line F1, and issues a command to the pressure regulator Ra1 (see FIG. 2) to supply compressed gas into the pressure chamber 25A, increasing the pressure in the pressure chamber 25A to the positive pressure set value PS1. Thereafter, the pressure in the pressure chamber 25A is maintained at the positive pressure set value PS1. During time T1, the operation control unit 9 issues a command to the vacuum valve Vb2 (see FIG. 2) to open the vacuum valve Vb2, communicate the vacuum line Lb2 with the pressure chamber 25B via the gas transfer line F2, and issues a command to the vacuum regulator Rb2 (see FIG. 2) to reduce the pressure in the pressure chamber 25B to the negative pressure set value NS1. Thereafter, the operation control unit 9 issues a command to the vacuum valve Vb2 to close the vacuum valve Vb2. Furthermore, the operation control unit 9 issues a command to the gas supply valve Va2 (see FIG. 2) to open the gas supply valve Va2, connects the gas supply line La2 to the pressure chamber 25B via the gas transfer line F2, and issues a command to the pressure regulator Ra2 (see FIG. 2) to supply compressed gas into the pressure chamber 25B, raising the pressure in the pressure chamber 25B to atmospheric pressure and eliminating the negative pressure.

[0047] As shown in FIG. 5, by forming a positive pressure in the pressure chamber 25A, the center of the elastic film 34 forming the pressure chamber 25A contacts the center of the upper surface of the wafer W. By forming a negative pressure in the pressure chamber 25B, the part of the elastic film 34 forming the pressure chamber 25B is pulled upward, and a gap is formed between the upper surface of the wafer W and the pressure chamber 25B. In particular, as the negative pressure is formed in the pressure chamber 25B, the inner wall part 36a between the pressure chamber 25A and the pressure chamber 25B is lifted upward, and the fluid Q present between the upper surface of the wafer W and the pressure chamber 25A can flow outward. In this way, by forming a positive pressure in the pressure chamber 25A and forming a negative pressure in the pressure chamber 25B during the time T1, the center of the elastic film 34 pushes outward the fluid Q present between the upper surface of the wafer W and the pressure chamber 25A, and moves it to the gap between the upper surface of the wafer W and the pressure chamber 25B. Since the positive pressure in the pressure chamber 25A is maintained, the fluid Q that has moved outward does not return toward the pressure chamber 25A, but remains between the upper surface of the wafer W and the pressure chamber 25B. The fluid Q may move further outward or may flow out from the upper surface of the wafer W.

[0048] Next, as shown in FIG. 6, while a positive pressure is formed in the pressure chamber 25A of the polishing head 1, a positive pressure is formed in the pressure chamber 25B, and a negative pressure is formed in the pressure chamber 25C located outside the pressure chamber 25B. The pressure chamber 25C is adjacent to the pressure chamber 25B. The formation of the positive pressure in the pressure chamber 25B and the formation of the negative pressure in the pressure chamber 25C are performed during a time T2 shown in FIG. 9. As shown in FIG. 9, the timing of starting the formation of the positive pressure in the pressure chamber 25B and the timing of starting the formation of the negative pressure in the pressure chamber 25C are the same. During the time T2, the pressure in the pressure chamber 25B is increased to a positive pressure setting value PS2, and then the pressure in the pressure chamber 25B is maintained at the positive pressure setting value PS2. During the time T2, the pressure in the pressure chamber 25C is decreased to a negative pressure setting value NS2, and then the negative pressure in the pressure chamber 25C is eliminated.

[0049] More specifically, during time T2, the operation control unit 9 issues a command to the pressure regulator Ra2 to supply compressed gas into the pressure chamber 25B and increase the pressure in the pressure chamber 25B to the positive pressure set value PS2. Thereafter, the pressure in the pressure chamber 25B is maintained at the positive pressure set value PS2. During time T2, the operation control unit 9 issues a command to the vacuum valve Vb3 (see FIG. 2) to open the vacuum valve Vb3 and communicate the vacuum line Lb3 and the pressure chamber 25C via the gas transfer line F3, and issues a command to the vacuum regulator Rb3 (see FIG. 2) to reduce the pressure in the pressure chamber 25C to the negative pressure set value NS2. Thereafter, the operation control unit 9 issues a command to the vacuum valve Vb3 to close the vacuum valve Vb3. Furthermore, the operation control unit 9 issues a command to the gas supply valve Va3 (see Figure 2) to open the gas supply valve Va3, connects the gas supply line La3 to the pressure chamber 25C via the gas transfer line F3, and issues a command to the pressure regulator Ra3 (see Figure 2) to supply compressed gas into the pressure chamber 25C, raising the pressure in the pressure chamber 25C to atmospheric pressure and eliminating the negative pressure.

[0050] As shown in FIG. 6, by forming a positive pressure in the pressure chamber 25B, the portion of the elastic film 34 that forms the pressure chamber 25B comes into contact with the upper surface of the wafer W. By forming a negative pressure in the pressure chamber 25C, the portion of the elastic film 34 that forms the pressure chamber 25C is pulled upward, and a gap is formed between the upper surface of the wafer W and the pressure chamber 25C. In particular, as the negative pressure is formed in the pressure chamber 25C, the inner wall portion 36b between the pressure chamber 25B and the pressure chamber 25C is lifted upward, and the fluid Q present between the upper surface of the wafer W and the pressure chamber 25B can flow outward. In this way, by forming a positive pressure in the pressure chamber 25B and forming a negative pressure in the pressure chamber 25C during the time T2, the portion of the elastic film 34 that forms the pressure chamber 25B pushes outward the fluid Q present between the upper surface of the wafer W and the pressure chamber 25B, and moves it to the gap between the upper surface of the wafer W and the pressure chamber 25C. Since the positive pressure in the pressure chamber 25B is maintained, the fluid Q that has moved outward does not return toward the pressure chamber 25B, but remains between the upper surface of the wafer W and the pressure chamber 25C. The fluid Q may move further outward or may flow out from the upper surface of the wafer W.

[0051] Next, as shown in FIG. 7, while positive pressure is being formed in the pressure chambers 25A and 25B of the polishing head 1, positive pressure is formed in the pressure chamber 25C, and negative pressure is formed in the pressure chamber 25D located outside the pressure chamber 25C. The pressure chamber 25D is adjacent to the pressure chamber 25C. The formation of the positive pressure in the pressure chamber 25C and the formation of the negative pressure in the pressure chamber 25D are performed during the time T3 shown in FIG. 9. As shown in FIG. 9, the timing of starting the formation of the positive pressure in the pressure chamber 25C and the timing of starting the formation of the negative pressure in the pressure chamber 25D are the same. During the time T3, the pressure in the pressure chamber 25C is increased to a positive pressure setting value PS3, and then the pressure in the pressure chamber 25C is maintained at the positive pressure setting value PS3. During the time T3, the pressure in the pressure chamber 25D is decreased to a negative pressure setting value NS3, and then the negative pressure in the pressure chamber 25D is eliminated.

[0052] More specifically, during time T3, the operation control unit 9 issues a command to the pressure regulator Ra3 to supply compressed gas into the pressure chamber 25C and increase the pressure in the pressure chamber 25C to the positive pressure set value PS3. Thereafter, the pressure in the pressure chamber 25C is maintained at the positive pressure set value PS3. During time T3, the operation control unit 9 issues a command to the vacuum valve Vb4 (see FIG. 2) to open the vacuum valve Vb4, communicate the vacuum line Lb4 with the pressure chamber 25D via the gas transfer line F4, and issues a command to the vacuum regulator Rb4 (see FIG. 2) to reduce the pressure in the pressure chamber 25D to the negative pressure set value NS3. Thereafter, the operation control unit 9 issues a command to the vacuum valve Vb4 to close the vacuum valve Vb4. Furthermore, the operation control unit 9 issues a command to the gas supply valve Va4 (see Figure 2) to open the gas supply valve Va4, connects the gas supply line La4 to the pressure chamber 25D via the gas transfer line F4, and issues a command to the pressure regulator Ra4 (see Figure 2) to supply compressed gas into the pressure chamber 25D, raising the pressure in the pressure chamber 25D to atmospheric pressure and eliminating the negative pressure.

[0053] As shown in FIG. 7, by forming a positive pressure in the pressure chamber 25C, the portion of the elastic film 34 that forms the pressure chamber 25C comes into contact with the upper surface of the wafer W. By forming a negative pressure in the pressure chamber 25D, the portion of the elastic film 34 that forms the pressure chamber 25D is pulled upward, and a gap is formed between the upper surface of the wafer W and the pressure chamber 25D. In particular, as the negative pressure is formed in the pressure chamber 25D, the inner wall portion 36c between the pressure chamber 25C and the pressure chamber 25D is lifted upward, and the fluid Q present between the upper surface of the wafer W and the pressure chamber 25C can flow outward. In this way, by forming a positive pressure in the pressure chamber 25C and forming a negative pressure in the pressure chamber 25D during the time T3, the portion of the elastic film 34 that forms the pressure chamber 25C pushes outward the fluid Q present between the upper surface of the wafer W and the pressure chamber 25C, and moves it between the upper surface of the wafer W and the pressure chamber 25D. Since the positive pressure in the pressure chamber 25C is maintained, the fluid Q that has moved outward does not return toward the pressure chamber 25C, but remains between the upper surface of the wafer W and the pressure chamber 25D. The fluid Q may move further outward or may flow out from the upper surface of the wafer W.

[0054] Next, as shown in FIG. 8, while the positive pressure is formed in the pressure chambers 25A, 25B, and 25C of the polishing head 1, the positive pressure is formed in the pressure chamber 25D. The formation of the positive pressure in the pressure chamber 25D is performed during a time T4 shown in FIG. 9. As shown in FIG. 9, during the time T4, the pressure in the pressure chamber 25D is increased to a positive pressure set value PS4, and then the pressure in the pressure chamber 25D is maintained at the positive pressure set value PS4. More specifically, during the time T4, the operation control unit 9 issues a command to the pressure regulator Ra4 to supply compressed gas into the pressure chamber 25D, and the pressure in the pressure chamber 25D is increased to the positive pressure set value PS4. Then, the pressure in the pressure chamber 25D is maintained at the positive pressure set value PS4.

[0055] 8, by generating a positive pressure in pressure chamber 25D, which is the outermost pressure chamber, the portion of elastic film 34 that forms pressure chamber 25D comes into contact with the upper surface of wafer W. Therefore, during time T4, the portion of elastic film 34 that forms pressure chamber 25D pushes fluid Q present between the upper surface of wafer W and pressure chamber 25D outward, causing fluid Q to flow out from the upper surface of wafer W.

[0056] In this embodiment, by forming a positive pressure in the inner pressure chamber 25A of the adjacent pressure chambers 25A, 25B and forming a negative pressure in the outer pressure chamber 25B, it is possible to move the fluid Q present on the upper surface of the wafer W outward. By sequentially performing this operation in the adjacent pressure chambers 25B, 25C on the further outer side and the adjacent pressure chambers 25C, 25D on the further outer side, the fluid Q present on the upper surface of the wafer W is moved further outward. Furthermore, by forming a positive pressure in the pressure chamber 25D located on the outermost side, it is possible to cause the fluid to flow out from the upper surface of the wafer W.

[0057] According to this embodiment, the polishing head 1 can hold the wafer W in a state where the fluid Q is not substantially present between the elastic film 34 and the upper surface of the wafer W. Thereafter, the lower surface of the wafer W is pressed against the polishing surface 2a by the elastic film 34 of the polishing head 1 while controlling the pressure in the pressure chambers 25A to 25D according to the polishing conditions of the wafer W, thereby polishing the lower surface of the wafer W. In a state where the fluid Q is not substantially present between the elastic film 34 and the upper surface of the wafer W, the elastic film 34 presses the lower surface of the wafer W against the polishing surface 2a, thereby applying an intended force to the wafer W. As a result, the polishing head 1 can achieve a desired film thickness profile of the wafer W. The state where the fluid Q is not substantially present between the elastic film 34 and the upper surface of the wafer W includes not only a state where the fluid Q is not present at all, but also a state where the fluid Q has flowed out to an extent that the pressure chambers 25A to 25D of the polishing head 1 can apply an appropriate force to the corresponding multiple regions of the wafer W.

[0058] In this embodiment, the positive pressure set values ​​PS1, PS2, PS3, and PS4 are the same pressure value, but the positive pressure set values ​​PS1, PS2, PS3, and PS4 may be different positive pressure values. In this embodiment, the negative pressure set values ​​NS1, NS2, and NS3 are the same pressure value, but the negative pressure set values ​​NS1, NS2, and NS3 may be different negative pressure values.

[0059] In this embodiment, the lengths of times T1 to T4 are the same, but the lengths of times T1, T2, T3, and T4 are not limited to this embodiment as long as the fluid Q present on the upper surface of the wafer W can be moved outward and the fluid can be discharged from the upper surface of the wafer W. The lengths of times T1, T2, T3, and T4 may be adjusted based on the volumes in the pressure chambers 25A to 25D, the flow rates of the compressed gas supplied from the gas supply lines La1 to La4, the flow rates of the compressed gas discharged to the vacuum lines Lb1 to Lb4, and the like.

[0060] In this embodiment, first, a positive pressure is formed in the inner pressure chamber 25A of the adjacent pressure chambers 25A and a negative pressure is formed in the outer pressure chamber 25B, thereby moving the fluid Q present on the upper surface of the wafer W outward, but the two adjacent pressure chambers that start this operation are not limited to the pressure chambers 25A and 25B. In one embodiment, when the fluid Q does not exist between the upper surface of the wafer W and the pressure chamber 25A, but exists between the upper surface of the wafer W and the pressure chamber 25B, first, a positive pressure may be formed in the inner pressure chamber 25B of the adjacent pressure chambers 25B and 25C, and a negative pressure may be formed in the outer pressure chamber 25C, thereby moving the fluid Q present between the upper surface of the wafer W and the pressure chamber 25B outward. In this case, a positive pressure is formed in the pressure chamber 25A in advance. This operation is sequentially performed in the adjacent pressure chambers 25C and 25D on the outer side to move the fluid Q present on the upper surface of the wafer W further outward. Furthermore, by forming a positive pressure in the outermost pressure chamber 25D, it is possible to cause the fluid to flow out from the upper surface of the wafer W. In this manner, the two adjacent pressure chambers that start the operation may be appropriately changed depending on the position of the fluid Q present on the upper surface of the wafer W.

[0061] In one embodiment, the elastic membrane 34 may form three pressure chambers 25A, 25B, and 25C, and the outermost pressure chamber may be the pressure chamber 25C. In this case, a positive pressure may be formed in the inner pressure chamber 25A of the adjacent pressure chambers 25A and a negative pressure may be formed in the outer pressure chamber 25B to move the fluid Q present on the upper surface of the wafer W outward, and then a positive pressure may be formed in the inner pressure chamber 25B of the adjacent pressure chambers 25B and 25C on the outer side to move the fluid Q present on the upper surface of the wafer W further outward, and further a positive pressure may be formed in the outermost pressure chamber 25C to cause the fluid to flow out from the upper surface of the wafer W.

[0062] 10 is a graph showing the relationship between the pressure in the pressure chambers 25A-25D and time according to another embodiment of the method for causing the fluid Q to flow out from the upper surface of the wafer W. Details of this embodiment that are not particularly described are similar to those of the above-mentioned embodiment, so duplicated descriptions will be omitted. In this embodiment, the pressure in the pressure chambers 25B, 25C, 25D is lowered to the negative pressure set values ​​NS1, NS2, NS3, and then the pressure chambers 25B, 25C, 25D are opened to the atmosphere, thereby eliminating the negative pressure in the pressure chambers 25B, 25C, 25D.

[0063] During time T1, a positive pressure is formed in the pressure chamber 25A, and the pressure in the pressure chamber 25B is lowered to a negative pressure setting value NS1, and then the pressure chamber 25B is opened to the atmosphere. The operation of forming a positive pressure in the pressure chamber 25A is the same as that of the embodiment described with reference to Figs. 5 to 9. More specifically, during time T1, the operation control unit 9 issues a command to the vacuum valve Vb2 to open the vacuum valve Vb2, communicates the vacuum line Lb2 with the pressure chamber 25B via the gas transfer line F2, and issues a command to the vacuum regulator Rb2 to lower the pressure in the pressure chamber 25B to the negative pressure setting value NS1. Thereafter, the operation control unit 9 issues a command to the vacuum valve Vb2 to close the vacuum valve Vb2. Furthermore, the operation control unit 9 issues a command to the atmosphere release valve Vc2 (see Fig. 2) to open the atmosphere release valve Vc2 to open the atmosphere to the pressure chamber 25B.

[0064] Furthermore, during time T2, a positive pressure is formed in the pressure chamber 25B, and the pressure in the pressure chamber 25C is lowered to the negative pressure setting value NS2, and then the pressure chamber 25C is opened to the atmosphere. The operation of forming a positive pressure in the pressure chamber 25B is the same as that of the embodiment described with reference to Figs. 5 to 9. More specifically, during time T2, the operation control unit 9 issues a command to the vacuum valve Vb3 to open the vacuum valve Vb3, communicates the vacuum line Lb3 with the pressure chamber 25C via the gas transfer line F3, and issues a command to the vacuum regulator Rb3 to lower the pressure in the pressure chamber 25C to the negative pressure setting value NS2. Thereafter, the operation control unit 9 issues a command to the vacuum valve Vb3 to close the vacuum valve Vb3. Furthermore, the operation control unit 9 issues a command to the atmosphere release valve Vc3 (see Fig. 2) to open the atmosphere release valve Vc3 to open the atmosphere.

[0065] Furthermore, during time T3, a positive pressure is formed in the pressure chamber 25C, and the pressure in the pressure chamber 25D is lowered to a negative pressure setting value NS3, and then the pressure chamber 25D is opened to the atmosphere. The operation of forming a positive pressure in the pressure chamber 25C is the same as that of the embodiment described with reference to Figs. 5 to 9. More specifically, during time T3, the operation control unit 9 issues a command to the vacuum valve Vb4 to open the vacuum valve Vb4, communicates the vacuum line Lb4 with the pressure chamber 25D via the gas transfer line F4, and issues a command to the vacuum regulator Rb4 to lower the pressure in the pressure chamber 25D to the negative pressure setting value NS3. Thereafter, the operation control unit 9 issues a command to the vacuum valve Vb4 to close the vacuum valve Vb4. Furthermore, the operation control unit 9 issues a command to the atmosphere release valve Vc4 (see Fig. 2) to open the atmosphere release valve Vc4 to open the atmosphere release valve Vc4.

[0066] Furthermore, a positive pressure is generated in the pressure chamber 25D during a time T4. The operation of generating a positive pressure in the pressure chamber 25D is similar to that of the embodiment described with reference to FIGS.

[0067] The elimination of the negative pressure in the pressure chambers 25B, 25C, and 25D by opening to the atmosphere can be accomplished in a shorter time than the elimination of the negative pressure in the pressure chambers 25B, 25C, and 25D by supplying compressed gas. In the above-described embodiment, as shown in Fig. 9, it takes time A1 to eliminate the negative pressure in the pressure chamber 25B by supplying compressed gas into the pressure chamber 25B. In contrast, in the present embodiment, as shown in Fig. 10, the elimination of the negative pressure in the pressure chamber 25B by opening the pressure chamber 25B to the atmosphere can be accomplished in time B1, which is shorter than time A1.

[0068] Similarly, in pressure chamber 25C, the time B2 (see FIG. 10) required to release pressure chamber 25C to the atmosphere and eliminate the negative pressure therein is shorter than the time A2 (see FIG. 9) required to supply compressed gas into pressure chamber 25C and eliminate the negative pressure therein. Similarly, in pressure chamber 25D, the time B3 (see FIG. 10) required to release pressure chamber 25D to the atmosphere and eliminate the negative pressure therein is shorter than the time A3 (see FIG. 9) required to supply compressed gas into pressure chamber 25D and eliminate the negative pressure therein.

[0069] According to this embodiment, the times A1, A2, and A3 required to eliminate the negative pressure in the pressure chamber 25C can be shortened to times B1, B2, and B3, thereby shortening the overall time required to cause the fluid Q to flow out from the upper surface of the wafer W.

[0070] 11 is a graph showing the relationship between pressure and time in a plurality of pressure chambers 25A-25D according to yet another embodiment of the method for causing a fluid Q to flow out from the upper surface of a wafer W. Details of this embodiment that are not particularly described are similar to those of the embodiment described with reference to FIGS. 5 to 9, and therefore redundant description will be omitted. In this embodiment, the timing at which negative pressure starts to be generated in the outer pressure chamber of the adjacent pressure chambers is before the timing at which positive pressure starts to be generated in the inner pressure chamber.

[0071] As shown in FIG. 11, in this embodiment, the timing at which negative pressure starts to be formed in the pressure chamber 25B is before the timing at which positive pressure starts to be formed in the pressure chamber 25A. Specifically, during time T0, the pressure in the pressure chamber 25B is lowered to a negative pressure set value NS1. Then, during time T1, the negative pressure in the pressure chamber 25B is eliminated, and the pressure in the pressure chamber 25A is increased to a positive pressure set value PS1. Then, the pressure in the pressure chamber 25A is maintained at the positive pressure set value PS1. Therefore, during time T1, a positive pressure is formed in the pressure chamber 25A located at the center of the polishing head 1, and a negative pressure is formed in the pressure chamber 25B located outside the pressure chamber 25A.

[0072] More specifically, during time T0, the operation control unit 9 issues a command to the vacuum valve Vb2 to open the vacuum valve Vb2 and communicate the vacuum line Lb2 with the pressure chamber 25B via the gas transfer line F2, and issues a command to the vacuum regulator Rb2 to reduce the pressure in the pressure chamber 25B to the negative pressure set value NS1. Thereafter, during time T1, the operation control unit 9 issues a command to the vacuum valve Vb2 to close the vacuum valve Vb2. Furthermore, the operation control unit 9 issues a command to the gas supply valve Va2 to open the gas supply valve Va2 and communicate the gas supply line La2 with the pressure chamber 25B via the gas transfer line F2, and issues a command to the pressure regulator Ra2 to supply compressed gas into the pressure chamber 25B, thereby increasing the pressure in the pressure chamber 25B to atmospheric pressure and eliminating the negative pressure. During time T1, the operation control unit 9 issues a command to the gas supply valve Va1 to open the gas supply valve Va1, communicates the gas supply line La1 with the pressure chamber 25A via the gas transfer line F1, and issues a command to the pressure regulator Ra1 to supply compressed gas into the pressure chamber 25A and increase the pressure in the pressure chamber 25A to the positive pressure set value PS1. Thereafter, the pressure in the pressure chamber 25A is maintained at the positive pressure set value PS1.

[0073] In this embodiment, at time T1, while the negative pressure in pressure chamber 25B is being eliminated, a positive pressure is generated in pressure chamber 25A. Since the pressure chamber 25B is at a negative pressure even while the negative pressure in pressure chamber 25B is being eliminated, during time T1, the fluid Q present between the upper surface of the wafer W and pressure chamber 25A can be pushed outward and moved to the gap between the upper surface of the wafer W and pressure chamber 25B (see FIG. 5).

[0074] Furthermore, in this embodiment, the timing at which negative pressure starts to be formed in the pressure chamber 25C is earlier than the timing at which positive pressure starts to be formed in the pressure chamber 25B. Specifically, during time T1, the pressure in the pressure chamber 25C is lowered to a negative pressure set value NS2. Thereafter, during time T2, the negative pressure in the pressure chamber 25C is eliminated, and the pressure in the pressure chamber 25B is increased to a positive pressure set value PS2. Thereafter, the pressure in the pressure chamber 25B is maintained at the positive pressure set value PS2. Therefore, during time T2, a positive pressure is formed in the pressure chamber 25B, and a negative pressure is formed in the pressure chamber 25C located outside the pressure chamber 25B.

[0075] More specifically, during time T1, the operation control unit 9 issues a command to the vacuum valve Vb3 to open the vacuum valve Vb3 and communicate the vacuum line Lb3 with the pressure chamber 25C via the gas transfer line F3, and issues a command to the vacuum regulator Rb3 to reduce the pressure in the pressure chamber 25C to the negative pressure set value NS2. Thereafter, during time T2, the operation control unit 9 issues a command to the vacuum valve Vb3 to close the vacuum valve Vb3. Furthermore, the operation control unit 9 issues a command to the gas supply valve Va3 to open the gas supply valve Va3 and communicate the gas supply line La3 with the pressure chamber 25C via the gas transfer line F3, and issues a command to the pressure regulator Ra3 to supply compressed gas into the pressure chamber 25C, thereby increasing the pressure in the pressure chamber 25C to atmospheric pressure and eliminating the negative pressure. During time T2, the operation control unit 9 issues a command to the gas supply valve Va2 to open the gas supply valve Va2, communicates the gas supply line La2 with the pressure chamber 25B via the gas transfer line F2, and issues a command to the pressure regulator Ra2 to supply compressed gas into the pressure chamber 25B and increase the pressure in the pressure chamber 25B to the positive pressure set value PS2. Thereafter, the pressure in the pressure chamber 25B is maintained at the positive pressure set value PS2.

[0076] In this embodiment, at time T2, while the negative pressure in pressure chamber 25C is being released, a positive pressure is generated in pressure chamber 25B. Since the pressure chamber 25C is at a negative pressure even while the negative pressure in pressure chamber 25C is being released, during time T2, the fluid Q present between the upper surface of the wafer W and pressure chamber 25B can be pushed outward and moved to the gap between the upper surface of the wafer W and pressure chamber 25C (see FIG. 6).

[0077] Furthermore, in this embodiment, the timing at which negative pressure starts to be generated in the pressure chamber 25D is before the timing at which positive pressure starts to be generated in the pressure chamber 25C. Specifically, the pressure in the pressure chamber 25D is lowered to a negative pressure set value NS3 during a time T2. Thereafter, the negative pressure in the pressure chamber 25D is eliminated and the pressure in the pressure chamber 25C is increased to a positive pressure set value PS3 during a time T3. Thereafter, the pressure in the pressure chamber 25C is maintained at the positive pressure set value PS3. Therefore, during the time T3, a positive pressure is generated in the pressure chamber 25C, and a negative pressure is generated in the pressure chamber 25D located outside the pressure chamber 25C.

[0078] More specifically, during time T2, the operation control unit 9 issues a command to the vacuum valve Vb4 to open the vacuum valve Vb4 and communicate the vacuum line Lb4 with the pressure chamber 25D via the gas transfer line F4, and issues a command to the vacuum regulator Rb4 to reduce the pressure in the pressure chamber 25D to the negative pressure set value NS3. Thereafter, during time T3, the operation control unit 9 issues a command to the vacuum valve Vb4 to close the vacuum valve Vb4. Furthermore, the operation control unit 9 issues a command to the gas supply valve Va4 to open the gas supply valve Va4 and communicate the gas supply line La4 with the pressure chamber 25D via the gas transfer line F4, and issues a command to the pressure regulator Ra4 to supply compressed gas into the pressure chamber 25D, thereby increasing the pressure in the pressure chamber 25D to atmospheric pressure and eliminating the negative pressure. During time T3, the operation control unit 9 issues a command to the gas supply valve Va3 to open the gas supply valve Va3, communicates the gas supply line La3 with the pressure chamber 25C via the gas transfer line F3, and issues a command to the pressure regulator Ra3 to supply compressed gas into the pressure chamber 25C and increase the pressure in the pressure chamber 25C to the positive pressure set value PS3. Thereafter, the pressure in the pressure chamber 25C is maintained at the positive pressure set value PS3.

[0079] In this embodiment, at time T3, while the negative pressure in pressure chamber 25D is being eliminated, a positive pressure is generated in pressure chamber 25C. Since the pressure chamber 25D is at a negative pressure even while the negative pressure in pressure chamber 25D is being eliminated, during time T3, the fluid Q present between the upper surface of the wafer W and pressure chamber 25C can be pushed outward and moved to the gap between the upper surface of the wafer W and pressure chamber 25D (see FIG. 7).

[0080] Furthermore, in this embodiment, during time T4, the pressure in the pressure chamber 25D is increased to the positive pressure set value PS4. Thereafter, the pressure in the pressure chamber 25D is maintained at the positive pressure set value PS4. During time T4, the operation control unit 9 issues a command to the gas supply valve Va4 to open the gas supply valve Va4, communicates the gas supply line La4 with the pressure chamber 25D via the gas transfer line F4, and issues a command to the pressure regulator Ra4 to supply compressed gas into the pressure chamber 25D, thereby increasing the pressure in the pressure chamber 25D to the positive pressure set value PS4. Thereafter, the pressure in the pressure chamber 25D is maintained at the positive pressure set value PS4.

[0081] In this embodiment, at time T4, a positive pressure is created in the pressure chamber 25D, so that the fluid Q present between the upper surface of the wafer W and the pressure chamber 25D is pushed outward, causing the fluid Q to flow out from the upper surface of the wafer W (see FIG. 8).

[0082] According to this embodiment, the timing at which negative pressure begins to be generated in the outer pressure chamber of the adjacent pressure chambers is set before the timing at which positive pressure begins to be generated in the inner pressure chamber, thereby making it possible to shorten the overall time required to cause the fluid Q to flow out from the top surface of the wafer W more than in the embodiment described with reference to Figures 5 to 9.

[0083] In one embodiment, at time T0, lowering the pressure in the pressure chamber 25B to the negative pressure set value NS1 may be forming a negative pressure in the pressure chamber 25B to attract and hold the wafer W before the polishing head 1 touches down on the polishing surface 2a of the polishing pad 2. In this case, after the polishing head 1 touches down on the polishing surface 2a, as shown at time T1 in Fig. 11, formation of a positive pressure in the pressure chamber 25A may start, and release of the negative pressure in the pressure chamber 25B may start. This can further shorten the overall time required to cause the fluid Q to flow out from the upper surface of the wafer W.

[0084] 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]

[0085] 1 Polishing head 2 Polishing Pads 2a Polished surface 3 Polishing table 5 Polishing fluid supply nozzle 6 Table Motor 9. Operation control section 9a Storage device 9b Arithmetic unit 11 Grinding head shaft 15 Head Arm 16 Spindle 18 Vertical movement mechanism 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 44 Transport Equipment 45 Transport Stage 47 Lifting device 49 Horizontal movement device 53 Cleaning nozzle F1, F2, F3, F4, F5 Gas transfer lines La1, La2, La3, La4, La5 gas supply lines Va1, Va2, Va3, Va4, Va5 gas supply valves Ra1,Ra2,Ra3,Ra4,Ra5 Pressure Regulators Lb1, Lb2, Lb3, Lb4, Lb5 Vacuum lines Vb1, Vb2, Vb3, Vb4, Vb5 Vacuum valves Rb1, Rb2, Rb3, Rb4, Rb5 Vacuum regulator Lc1, Lc2, Lc3, Lc4, Lc5 Atmospheric release line Vc1, Vc2, Vc3, Vc4, Vc5 Atmospheric release valve

Claims

1. A method for polishing a wafer using a polishing head having a plurality of pressure chambers formed by an elastic film, comprising: The plurality of pressure chambers include: a first pressure chamber; a second pressure chamber located outside the first pressure chamber; a third pressure chamber located outside the second pressure chamber, forming a positive pressure in the first pressure chamber and a negative pressure in the second pressure chamber to move the fluid existing between the upper surface of the wafer and the first pressure chamber outward; subsequently, forming a positive pressure in the second pressure chamber and a negative pressure in the third pressure chamber to move the fluid existing between the upper surface of the wafer and the second pressure chamber outward; forming a positive pressure in the pressure chamber located most outside among the plurality of pressure chambers to move the fluid existing between the upper surface of the wafer and the pressure chamber located most outside outward, and causing the fluid to flow out from the upper surface of the wafer; subsequently, pressing the lower surface of the wafer against the polishing surface with the elastic film to polish the lower surface of the wafer.

2. The timing of starting to form the positive pressure in the first pressure chamber is the same as the timing of starting to form the negative pressure in the second pressure chamber, The timing of starting to form the positive pressure in the second pressure chamber is the same as the timing of starting to form the negative pressure in the third pressure chamber. The polishing method according to claim 1.

3. Forming the negative pressure in the second pressure chamber includes reducing the pressure in the second pressure chamber to a negative pressure set value and then opening the second pressure chamber to the atmosphere, Forming the negative pressure in the third pressure chamber includes reducing the pressure in the third pressure chamber to a negative pressure set value and then opening the third pressure chamber to the atmosphere. The polishing method according to claim 2.

4. The timing of starting to form the negative pressure in the second pressure chamber is earlier than the timing of starting to form the positive pressure in the first pressure chamber, The timing of starting to form the negative pressure in the third pressure chamber is earlier than the timing of starting to form the positive pressure in the second pressure chamber. The polishing method according to claim 1.

5. Forming the negative pressure in the second pressure chamber includes reducing the pressure in the second pressure chamber to a negative pressure set value and then eliminating the negative pressure in the second pressure chamber. Forming the positive pressure in the first pressure chamber is performed while the negative pressure in the second pressure chamber is being eliminated. Forming the negative pressure in the third pressure chamber includes reducing the pressure in the third pressure chamber to a negative pressure set value and then eliminating the negative pressure in the third pressure chamber. Forming the positive pressure in the second pressure chamber is performed while the negative pressure in the third pressure chamber is being eliminated. The polishing method according to claim 4.

6. The first pressure chamber is located at the central portion of the elastic membrane. The polishing method according to claim 1.

7. Forming the positive pressure in the first pressure chamber includes increasing the pressure in the first pressure chamber to a first positive pressure set value and then maintaining the pressure in the first pressure chamber at the first positive pressure set value. Forming the positive pressure in the second pressure chamber includes increasing the pressure in the second pressure chamber to a second positive pressure set value and then maintaining the pressure in the second pressure chamber at the second positive pressure set value. The polishing method according to any one of claims 1 to 6.

8. A polishing apparatus for polishing a wafer, having a plurality of pressure chambers formed by an elastic membrane, and a polishing head that presses the wafer against a polishing surface with the plurality of pressure chambers; comprising an operation control unit that controls the operation of the polishing apparatus, wherein the plurality of pressure chambers include a first pressure chamber, a second pressure chamber located outside the first pressure chamber, and a third pressure chamber located outside the second pressure chamber, and the operation control unit forms a positive pressure in the first pressure chamber and a negative pressure in the second pressure chamber to move the fluid existing between the upper surface of the wafer and the first pressure chamber outward, then forms a positive pressure in the second pressure chamber and a negative pressure in the third pressure chamber to move the fluid existing between the upper surface of the wafer and the second pressure chamber outward, forms a positive pressure in the pressure chamber located outermost among the plurality of pressure chambers to move the fluid existing between the upper surface of the wafer and the outermost pressure chamber outward, and causes the fluid to flow out from the upper surface of the wafer, and then the polishing apparatus is configured to operate such that the lower surface of the wafer is pressed against the polishing surface by the elastic membrane to polish the lower surface of the wafer.

9. The operation control unit operates the polishing apparatus such that the timing at which the operation control unit starts forming the positive pressure in the first pressure chamber is the same as the timing at which the operation control unit starts forming the negative pressure in the second pressure chamber. The polishing apparatus according to claim 8, wherein the operation control unit is configured to operate the polishing apparatus such that the timing at which the positive pressure formation in the second pressure chamber starts and the timing at which the operation control unit starts the negative pressure formation in the third pressure chamber are the same.

10. The operation control unit forming the negative pressure in the second pressure chamber includes operating the polishing apparatus such that the pressure in the second pressure chamber is reduced to a negative pressure set value and then the second pressure chamber is opened to the atmosphere. The polishing apparatus according to claim 9, wherein forming the negative pressure in the third pressure chamber includes operating the polishing apparatus such that the pressure in the third pressure chamber is reduced to a negative pressure set value and then the third pressure chamber is opened to the atmosphere.

11. The operation control unit operates the polishing apparatus such that the timing at which the negative pressure formation in the second pressure chamber starts is earlier than the timing at which the positive pressure formation in the first pressure chamber starts. The polishing apparatus according to claim 8, wherein the operation control unit is configured to operate the polishing apparatus such that the timing at which the negative pressure formation in the third pressure chamber starts is earlier than the timing at which the positive pressure formation in the second pressure chamber starts.

12. The operation control unit forming the negative pressure in the second pressure chamber includes reducing the pressure in the second pressure chamber to a negative pressure set value and then eliminating the negative pressure in the second pressure chamber, and forming the positive pressure in the first pressure chamber while the negative pressure in the second pressure chamber is being eliminated. The polishing apparatus is operated accordingly. The polishing apparatus according to claim 11, wherein forming the negative pressure in the third pressure chamber includes reducing the pressure in the third pressure chamber to a negative pressure set value and then eliminating the negative pressure in the third pressure chamber, and forming the positive pressure in the second pressure chamber while the negative pressure in the third pressure chamber is being eliminated. The polishing apparatus is operated accordingly.

13. The first pressure chamber is located at the central portion of the elastic membrane in the polishing apparatus according to claim 8.

14. The operation control unit forming the positive pressure in the first pressure chamber includes operating the polishing apparatus such that the pressure in the first pressure chamber is increased to a first positive pressure set value and then the pressure in the first pressure chamber is maintained at the first positive pressure set value. Forming the positive pressure in the second pressure chamber includes raising the pressure in the second pressure chamber to a second positive pressure set value, and then maintaining the pressure in the second pressure chamber at the second positive pressure set value. The polishing apparatus according to any one of claims 8 to 13 is configured to operate the polishing apparatus as described above.

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