POLISHING APPARATUS, AND METHOD FOR POLISHING SiC WAFERS

Abstract

A polishing apparatus for polishing SiC wafers includes at least two chuck tables configured to hold the SiC wafers; a turntable, on which the at least two chuck tables are arranged; a polishing assembly configured to polish a surface of one of the SiC wafers held on one of the at least two chuck tables located at a polishing position with a polishing pad; and a C-surface polishing assembly configured to, while the surface of the one of SiC wafers held on the one of the at least two chuck tables located at the polishing position in the polishing assembly is being polish-processed, polish a C surface of another SiC wafer held on another of the at least two chuck tables not located at the polishing position with a C-surface polishing pad. The polishing assembly and the C-surface polishing assembly polish the respective surfaces of each of the SiC wafers.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2024-015377 filed on Feb. 5, 2024; the entire contents of which are incorporated herein by reference.FIELD

[0002] The present disclosure relates to a polishing apparatus and a method for polishing SiC wafers.BACKGROUND

[0003] SiC wafers made of silicon carbide (SiC) are increasingly used in a field of semiconductor devices and other fields due to their superior properties such as current capacity and heat resistance. As disclosed in, for example, Japanese Patent Laid-Open Publications No. 2020-027895, No. 2022-028362, and No. 2023-071254, in a process for manufacturing SiC wafers, surfaces on both sides of a plate-shaped wafer sliced from an ingot may be ground and then the both surfaces may be polished. The SiC wafers may be formed to have a Si surface terminated with Si atoms being exposed on one side and a C surface terminated with C atoms being exposed on the other side.SUMMARY

[0004] The Sic wafers may require a long time in a process to be polish-processed due to hardness and chemical stability thereof. Moreover, mechanical and chemical properties of the Si and C surfaces of the SiC wafers may differ largely, and the time required to polish the Si surface may tend to be longer than the time required to polish the C surface. For example, polishing of the Si surface may require approximately three times longer than polishing of the C surface. Therefore, during the polishing process, when a Si surface of a SiC wafer is being polished, a length of time for a next SiC wafer to wait to be polish-processed may increase, and such waiting time may include a margin to be reduced in order to improve productivity.

[0005] Therefore, a polishing apparatus that may polish surfaces on both sides of the SiC wafer is required to reduce a total processing time by effectively utilizing the time when the next SiC wafer is waiting.

[0006] According to an aspect of the present disclosure, a polishing apparatus configured to polish SiC wafers includes at least two chuck tables configured to hold the SiC wafers; a turntable, on which the at least two chuck tables are arranged; a polishing assembly configured to polish a surface of one of the SiC wafers held on one of the at least two chuck tables located at a polishing position with a polishing pad, the one of the at least two chuck tables being located at the polishing position by rotation of the turntable; and a C-surface polishing assembly configured to, while the surface of the one of SiC wafers held on the one of the at least two chuck tables located at the polishing position in the polishing assembly is being polish-processed, polish a C surface of another SiC wafer held on another of the at least two chuck tables not located at the polishing position with a C-surface polishing pad. The polishing assembly and the C-surface polishing assembly polish the respective surfaces of each of the SiC wafers.

[0007] Optionally, the polishing apparatus may further include a conveyer assembly configured to load and unload the at least two chuck tables with the SiC wafers. Optionally, the polishing apparatus may further include an inverting assembly configured to invert the another SiC wafer held on the another of the at least two chuck tables not located at the polishing position vertically.

[0008] According to another aspect of the present disclosure, a method for polishing surfaces on both sides of each of a plurality of SiC wafers, while a Si surface of a first SiC wafer being one of the plurality of SiC wafers held on one of at least two chuck tables arranged on a turntable is being polished with a polishing pad, includes a cycle of at least a first holding process for causing a second SiC wafer being another one of the plurality of SiC wafers to be held on another of the at least two chuck tables with a C surface thereof facing upward, a C-surface polishing process for polishing the C surface of the second SiC wafer with a C-surface polishing pad; and a second holding process for separating the second SiC wafer from the another of the at least two chuck tables, inverting the second SiC wafer, and causing the second SiC wafer to be held on the another of the at least two chuck tables with a Si surface of the second SiC wafer facing upward.

[0009] Optionally, the method further includes an unloading process for, before the first holding process, unloading another one of the plurality of SiC wafers, which is the second SiC wafer in a previous cycle, from the another of the at least two chuck tables.

[0010] According to the polishing apparatus in the present disclosure, while the polishing assembly polishes-processes the Si surface of the wafer, the C-surface polishing assembly may polish-process the C surface of the next wafer, thereby a time required to polish the Si surface may be effectively used, and a total processing time to process the plurality of wafers may be reduced.

[0011] According to the method for polishing SiC wafers in the present disclosure, while the Si surface of the first SiC wafer is being polished with the polishing pad, the second SiC wafer is held on the another of the at least two chuck tables with the C surface thereof facing upward, polished with the C-surface polishing pad, and inverted to have the Si surface thereof ready to be polished next, thereby the time required to polish the Si surface may be effectively used, and the total processing time to process the plurality of wafers may be reduced. As such, by polishing the Si surface of the first SiC wafer and polishing the C surface of the second SiC wafer in parallel, the surfaces on both sides of each of the plurality of SiC wafers may be polished efficiently.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a perspective view of the polishing apparatus.

[0013] FIG. 2 illustrates a configuration and an operation of the polishing assembly.

[0014] FIG. 3 illustrates a configuration and an operation of the C-surface polishing assembly.

[0015] FIG. 4 illustrates a configuration and an operation of a wafer upper-surface cleaner device.

[0016] FIG. 5 illustrates a configuration and an operation of a conveyer assembly.

[0017] FIG. 6 illustrates a configuration and an operation of a cleaner device.

[0018] FIG. 7 illustrates a configuration and an operation of a conveyer robot.

[0019] FIG. 8 illustrates a configuration and an operation of a conveyer robot.

[0020] FIG. 9A illustrates steps and sequence of operations of the polishing apparatus.

[0021] FIG. 9B illustrates steps and sequence of operations of the polishing apparatus.

[0022] FIG. 10 is a perspective view of the polishing apparatus according to another embodiment.DESCRIPTION OF EMBODIMENTS

[0023] Hereinbelow, a polishing apparatus and a method for polishing according to an embodiment of the present disclosure will be described with reference to the accompanying drawings. An X-axis direction, a Y-axis direction, and a Z-axis direction indicated in each drawing are orthogonal to one another. The X-axis direction and the Y-axis direction are substantially horizontal directions, and the Z-axis direction is a vertical direction.

[0024] A wafer W to be polished using the polishing apparatus 10 is a SiC (silicon carbide) wafer, one side of which is a Si surface terminated with Si atoms and the other side of which is a C surface terminated with C atoms. The wafer W may be formed by, for example, grinding a sliced wafer, sliced from a SiC ingot with use of, for example, laser irradiation, to a predetermined thickness to remove traces or unevenness caused by the process of slicing. The wafers W having been through the grinding process are stored in a cassette 11 and conveyed to the polishing apparatus 10. Inside the cassette 11, a plurality of wafer storages partitioned in the Z-axis direction are formed so that a single cassette 11 may store a plurality of wafers W.

[0025] FIG. 1 shows an overall structure of the polishing apparatus 10 that may polish to process surfaces on both sides of the wafer W. The polishing apparatus 10 is a processing apparatus that may perform CMP (Chemical Mechanical Polishing) acting mechanically and chemically on the both surfaces of each wafer W that has been processed through grinding. In the following description concerning the structure of the polishing apparatus 10, further to FIG. 1 showing the overall structure, with reference to, FIGS. 2-8, detailed structures of parts of the polishing apparatus 10 will be explained.

[0026] At an end of a base 12 of the polishing apparatus 10 on a −Y direction side, two cassette stages 13 are located at different positions in the X-axis direction. On one of the cassette stages 13, a cassette 11 containing the wafers W before polish-processing is placed. On the other of the cassette stages 13, a cassette 11 containing the wafers W after polish-processing is placed. The number of the cassette stages 13 is not necessarily limited to two. For example, three or more cassette stages 13 may be provided. Alternatively, solely one cassette stage 13 may be provided to store the wafers W before and after polish-processing therein.

[0027] The polishing apparatus 10 includes a controller 14 composed of devices including a processor that may execute various processes and a memory storing programs. The polishing apparatus 10 is configured to automatically perform a series of operations such as a loading process, polish-processing, a cleaning process, and an unloading process of the wafers W, according to the programs stored in the memory of the controller 14 and control signals transmitted by the controller 14 to the other components therein. Details of these series of operations will be described later.

[0028] In proximity to the two cassette stages 13, a conveyer robot 15 to convey the wafers W is provided. Within a range where the conveyer robot 15 may convey the wafers W from one to another of the cassettes 11, a temporary placement table 16 and a cleaner device 17 are provided. The temporary placement table 16 and the cleaner device 17 are located at different positions in the X-axis direction, where the temporary placement table 16 is located on a +X direction side and the cleaner device 17 is located on a-X direction side. The conveyer robot 15 may unload or load the cassette 11 with the wafers W and may convey the wafers W between the cassette 11 and the temporary placement table 16, and between the cassette 11 and the cleaner device 17.

[0029] The conveyer robot 15 includes a robot hand 18 at an end of a movable arm composed of multi-joint links. The robot hand 18 is in a form of a plate and may suction and hold a surface of the wafer W on one side by suctioning air through a plurality of suction holes formed on a holder surface thereof (see FIGS. 7 and 8). The robot hand 18 is attachable to and detachable from the movable arm, and any robot hand 18 may be selected to be attached from several types of robot hands 18 with different shapes and sizes of holder surfaces. The robot hand 18 shown in FIG. 1 is a C-shaped robot hand with a gutter-shaped opening formed inward from an outer edge of a disk-shaped body toward a center.

[0030] The conveyer robot 15 may convey the wafer W by rotating the multiple links that compose the movable arm relatively and thereby changing a position of the robot hand 18. In particular, the conveyer robot 15 may perform an operation to pick up a wafer W before polish-processing from the cassette 11 and place the wafer W on the temporary placement table 16, and an operation to unload the wafer W having been polish-processed and cleaned from the cleaner device 17 and store the wafer W in the cassette 11.

[0031] The conveyer robot 15 further includes a rotating device 19, which may rotate the robot hand 18 on an axis extending in the horizontal direction. As shown in FIGS. 7 and 8, with the robot hand 18 holding the wafer W, when the rotating device 19 rotates the robot hand 18 by 180 degrees, the waver W is inverted upside-down. As such, the conveyer robot 15 is, not only configured to convey the wafer W, but also composes an inverting assembly that may invert the wafer W vertically (switch the vertical orientations of the Si surface and the C surface).

[0032] The temporary placement table 16 is a table for temporarily placing the wafer W before polish-processing and has a holder surface, on which the wafer W is placed and held. Around the temporary placement table 16, a plurality of positioning pins 20 that are movable in a radial direction of the temporary placement table 16 are arranged. With the wafer W held on the holder surface of the temporary placement table 16, a center of the temporary placement table 16 and a center of the wafer W are aligned, and the wafer W is set to a position by moving the plurality of positioning pins 20 to respectively contact an outer circumference of the wafer W.

[0033] The cleaner device 17 may clean wafer W having been polish-processed. As shown in FIG. 6, the cleaner device 17 has a spinner cleaning table 21 to hold the wafer W and a cleaner nozzle 22 through which cleaning water and air may be jetted at the wafer W on the spinner cleaning table 21.

[0034] An upper surface of the spinner cleaning table 21 is a holder surface, on which the wafer W is placed and held. By a suction source 23 suctioning the air on the holder surface of the spinner cleaning table 21, the wafer W may be suctioned and held against the upper surface of the spinner cleaning table 21. The spinner cleaning table 21 may be rotated on an axis extending in the Z-axis direction by a rotating operation of a rotating assembly 24 which includes a motor.

[0035] To the cleaner nozzle 22, a cleaning-water supplying source 25 and an air supplying source 26 are connected. By operating an open / close valve, the cleaner nozzle 22 may be switched between a state, in which the cleaning water supplied from the cleaning-water supplying source 25 is jetted therefrom, and a state, in which air supplied from the air supplying source 26 is jetted therefrom. The cleaner nozzle 22 may rotate (pivot) on an axis extending in the Z-axis direction.

[0036] In the cleaner device 17, with the wafer W held on the holder surface of the spinner cleaning table 21, the spinner cleaning table 21 is rotated, and the cleaning water is jetted from the cleaner nozzle 22 onto the wafer W on the spinner cleaning table 21, and thereby the wafer W is cleaned. After cleaning, air is jetted from the cleaner nozzle 22 at the wafer W to dry the wafer W. By rotating the spinner cleaning table 21 and pivoting the cleaner nozzle 22 while rotating the spinner cleaning table 21, the cleaning water and the air may be jetted at the upper surface of the wafer W entirely.

[0037] As shown in FIG. 1, the spinner cleaning table 21 is located inside a recess formed on an upper side the base 12. The cleaner device 17 is provided with a cover that may be lifted or lowered and surrounds the recess. The structure with these may prevent the cleaning water from splashing around the cleaner device 17 when the wafer W is cleaned in the cleaner device 17.

[0038] The polishing apparatus 10 has a turntable 30 on a +Y direction side with respect to the temporary placement table 16 and the cleaner device 17, and a first chuck table 31 and a second chuck table 32 are arranged on the turntable 30. The turntable 30 is in a shape of a disk and is rotatable on an axis extending in the Z-axis direction. The turntable 30 may be rotated by being driven by a motor of a turntable rotating assembly (not shown).

[0039] In the present embodiment, two chuck tables 31 and 32 are arranged on the turntable 30; however, optionally, three or more chuck tables may be arranged on the turntable. In other words, the polishing apparatus to which the present disclosure is applied should satisfy a requirement of being equipped with a turntable with only at least two chuck tables being arranged thereon.

[0040] The first chuck table 31 and the second chuck table 32 have the same configuration. Items that are common between the first chuck table 31 and the second chuck table 32 will be referred to by the same reference signs.

[0041] As shown in FIGS. 2 and 3, the first chuck table 31 and the second chuck table 32 each have a frame 35 fixed on a table base 34 and a disk-shaped porous sheet 36 mounted in a recess formed on an upper side of the frame 35. The porous sheet 36 is made of a porous material such as ceramics and has minute pores formed throughout. The porous sheet 36 is connected to a suction source 37 via a suction path. By driving the suction source 37 and opening an open / close valve 38, air in the porous sheet 36 is suctioned, and a negative pressure produced acts on a holder surface and an upper surface of the porous sheet 36, thereby enabling the wafer W to be suction and held thereon.

[0042] The first chuck table 31 and the second chuck table 32 are each supported on the turntable 30 to rotate on an axis extending in the Z-axis direction. By driving a motor of a chuck table rotating assembly 39, the first chuck table 31 and the second chuck table 32 may rotate respectively.

[0043] The first chuck table 31 and the second chuck table 32 are located symmetrically with respect to a rotation center of the turntable 30 (a center of the first chuck table 31 and a center of the second chuck table 32 are apart from each other by 180 degrees in a rotating direction of the turntable 30). The first chuck table 31 or the second chuck table 32 may be located at a polishing position, which is on a +Y direction side and a-X direction side with respect to the rotation center of the turntable 30, or a C-surface polishing position, which is on the +X direction side and the −Y direction side with respect to the rotation center of the turntable 30. The polishing position is a position where a polishing assembly 40, which will be described later, may polish the Si surface of the wafer W. The C-surface polishing position is a position where a C-surface polishing assembly 50, which will be described later, may polish the C surface of the wafer W. Further, the C-surface polishing position is a position where a conveyer assembly 70, which will be described later, may load or unload the first chuck table 31 or the second chuck table 32 with the wafer W.

[0044] The controller 14 controls operations of the turntable rotating assembly to rotate the turntable 30 by 180 degrees increments. FIG. 1 shows the first chuck table 31 at the polishing position and the second chuck table 32 at the C-surface polishing position. When the turntable 30 is rotated by 180 degrees from the state shown in FIG. 1, the second chuck table 32 shifts to be located at the polishing position, and the first chuck table 31 shifts to be located at the C-surface polishing position. In other words, by rotating the turntable 30 by 180 degrees increments, the positions of the first chuck table 31 and the second chuck table 32 are swapped between the polishing position and the C-surface polishing position.

[0045] Above the turntable 30, the polishing assembly 40 and the C-surface polishing assembly 50 are provided. The polishing assembly 40 may polish-process the Si surface of the wafer W held on the first chuck table 31 or the second chuck table 32 located at the polishing position. The C-surface polishing assembly 50 may polish-process the C surface of the wafer W held on the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position.

[0046] FIG. 2 illustrates a configuration and an operation of the polishing assembly 40. The polishing assembly 40 may be lifted or lowered in the Z-axis direction by a lift / lower assembly 41. The lift / lower assembly 41 is attached to a column 411 erecting from the upper surface of the base 12, and the column 411 is located on the-X direction side of the turntable 30.

[0047] As shown in FIGS. 1 and 2, the lift / lower assembly 41 includes a pair of guide rails 412 located on a surface of the column 411 on the +X-direction side and extending in the Z-axis direction, a lift / lower table 413 supported by the column 411 via the pair of guide rails 412 movably in the Z-axis direction, a ball screw 415 extending in the Z-axis direction and screwed to a screw thread 414 in the lift / lower table 413, and a motor 416 that may rotate the ball screw 415. When the ball screw 415 is driven by the motor 416 to rotate, the lift / lower table 413 moves in the Z-axis direction. The polishing assembly 40 is attached to the lift / lower table 413 via a housing 42 and may move up or down in the Z-axis direction together with the lift / lower table 413.

[0048] The polishing assembly 40 includes a spindle unit 43. The spindle unit 43 may be, for example, an air spindle, which supports a spindle shaft 44 rotatably via high-pressurized air inside a casing. The spindle shaft 44 is a shaft extending in the Z-axis direction. A mount 45 is connected to a lower end of the spindle shaft 44, and a polishing wheel 46 is attached to a lower surface of the mount 45. On a lower surface of the polishing wheel 46, a polishing pad 47 is provided. As a motor provided in the spindle unit 43 drives the spindle shaft 44 to rotate, the polishing pad 47 on the polishing wheel 46 rotates. The polishing assembly 40 has a slurry supplying source 48 to supply slurry containing abrasives. The slurry fed from the slurry supplying source 48 is supplied to a lower surface of the polishing pad 47 through a path in the spindle shaft 44.

[0049] The polishing assembly 40 may polish an upper surface (Si surface) of the wafer W by CMP polishing, which includes a mechanical act caused by contacting with the polishing pad 47 and a chemical effect caused by the components in the slurry supplied from the slurry supplying source 48. As shown in FIG. 2, the controller 14 drives the spindle shaft 44 to rotate and operates the polishing pad 47 to rotate while lowering the polishing pad 47 with the lift / lower assembly 41 to cause the polishing pad 47 to contact the upper surface (Si surface) of the wafer W held on the first chuck table 31 or the second chuck table 32 located at the polishing position. Moreover, the controller 14 causes the slurry to be supplied from the slurry supplying source 48 to a point where the polishing pad 47 contacts the wafer W. Furthermore, the controller 14 operates the chuck table rotating assembly 39 to rotate the first chuck table 31 or the second chuck table 32 located at the polishing position.

[0050] As such, for polish-processing the wafer W using the polishing assembly 40, the polishing assembly 40 supplies the slurry to the polishing pad 47 and the wafer W, while rotating the polishing pad 47 and the wafer W relatively, and urges the polishing pad 47 against the wafer W by a predetermined intensity of force to polish the Si surface.

[0051] FIG. 3 illustrates a configuration and an operation of the C-surface polishing assembly 50. The C-surface polishing assembly 50 may move horizontally in the Y-axis direction by a Y-axis movable assembly 51 and may move up or down in the Z-axis direction by a lift / lower assembly 52. The Y-axis movable assembly 51 and the lift / lower assembly 52 are located on the +X direction side of the turntable 30.

[0052] As shown in FIGS. 1 and 3, the Y-axis movable assembly 51 includes a pair of guide rails 511 located on the upper surface of the base 12 and extending in the Y-axis direction, a Y-axis movable table 512 supported by the base 12 via the pair of guide rails 511 movably in the Y-axis direction, a ball screw 514 extending in the Y-axis direction and screwed to a screw thread 513 in the Y-axis movable table 512, and a motor 515 that may rotate the ball screw 514. When the ball screw 514 is driven by the motor 515 to rotate, the Y-axis movable table 512 moves in the Y-axis direction. The C-surface polishing assembly 50 is supported by the Y-axis movable table 512 via the lift / lower assembly 52, and the C-surface polishing assembly 50 may move in the Y-axis direction together with the Y-axis movable table 512.

[0053] The lift / lower assembly 52 is provided to a column 521 that projects upward from the Y-axis movable table 512. As shown in FIGS. 1 and 3, the lift / lower assembly 52 includes a pair of guide rails 522 located on a surface of the column 521 on the-X direction side and extending in the Z-axis direction, a lift / lower table 523 supported by the column 521 via the pair of guide rails 522 movably in the Z-axis direction, a ball screw 525 extending in the Z-axis direction and screwed to a screw thread 524 in the lift / lower table 523, and a motor 526 that may rotate the ball screw 525. When the ball screw 525 is driven by the motor 526 to rotate, the lift / lower table 523 moves in the Z-axis direction. The C-surface polishing assembly 50 is attached to the lift / lower table 523 via a housing 53 and may move up or down in the Z-axis direction together with the lift / lower table 523.

[0054] The C-surface polishing assembly 50 includes a spindle unit 54. The spindle unit 54 may be, for example, an air spindle, which supports a spindle shaft 55 rotatably via high-pressurized air inside a casing. The spindle shaft 55 is a shaft extending in the Z-axis direction. A mount 56 is connected to a lower end of the spindle shaft 55, and a polishing wheel 57 is attached to a lower surface of the mount 56. On a lower surface of the polishing wheel 57, a C-surface polishing pad 58 is provided. As a motor provided in the spindle unit 54 drives the spindle shaft 55 to rotate, the C-surface polishing pad 58 on the polishing wheel 57 rotates. The C-surface polishing assembly 50 has a slurry supplying source 59 to supply slurry containing abrasives. The slurry fed from the slurry supplying source 59 is supplied to a lower surface of the C-surface polishing pad 58 through a path in the spindle shaft 55.

[0055] The C-surface polishing assembly 50 may polish an upper surface (C surface) of the wafer W by CMP polishing, which includes a mechanical act caused by contacting with the C-surface polishing pad 58 and a chemical effect caused by the components in the slurry supplied from the slurry supplying source 59. As shown in FIG. 3, the controller 14 drives the spindle shaft 55 to rotate and operates the C-surface polishing pad 58 to rotate while lowering the C-surface polishing pad 58 with the lift / lower assembly 52 to cause the C-surface polishing pad 58 to contact the upper surface (C surface) of the wafer W held on the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. Moreover, the controller 14 causes the slurry to be supplied from the slurry supplying source 59 to a point where the C-surface polishing pad 58 contacts the wafer W. Furthermore, the controller 14 operates the chuck table rotating assembly 39 to rotate the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position.

[0056] As such, for polish-processing the wafer W using the C-surface polishing assembly 50, the C-surface polishing assembly 50 supplies the slurry to the C-surface polishing pad 58 and the wafer W, while rotating the C-surface polishing pad 58 and the wafer W relatively, and urges the C-surface polishing pad 58 against the wafer W by a predetermined intensity of force to polish the C surface.

[0057] As shown in FIG. 1, above the turntable 30, further, a wafer upper-surface cleaner device 60 and a holder-surface cleaner nozzle 61 are provided. The wafer upper-surface cleaner device 60 is located on the-X direction side of the C-surface polishing assembly 50. The holder-surface cleaner nozzle 61 is located on the −Y direction side of the wafer upper-surface cleaner device 60.

[0058] As shown in FIG. 1, the wafer upper-surface cleaner device 60 and the holder-surface cleaner nozzle 61 are supported by the base 12 via a supporting block 63 provided on the upper surface of the base 12. The supporting block 63 is located between the temporary placement table 16 and the cleaner device 17 in the X-axis direction, connected to the upper surface of the base 12, and extends in the Y-axis direction. The supporting block 63 is supported on the base 12 in a cantilevered structure spaced above from the turntable 30.

[0059] As shown in FIG. 4, the wafer upper-surface cleaner device 60 has a cleaning brush 62 and a cleaning-water nozzle 67. The cleaning brush 62 is attached to a lower end of a brush supporting shaft 64 extending in the Z-axis direction, and the brush supporting shaft 64 is drivable by a brush rotating assembly 65 having a motor to rotate. The brush supporting shaft 64 is supported by a lift / lower cylinder 66 shown in FIG. 1, which is movable up or down in the Z-axis direction. The lift / lower cylinder 66 is attached to a surface of the supporting block 63 on the +X-direction side.

[0060] As shown in FIG. 4, the cleaning-water nozzle 67 is located in proximity to the cleaning brush 62. The cleaning-water nozzle 67 is connected to a cleaning-water supplying source 68, and cleaning water supplied from the cleaning-water supplying source 68 may be jetted from the cleaning-water nozzle 67.

[0061] At the C-surface polishing position, either the first chuck table 31 or the second chuck table 32 shown in FIG. 4 may be located, and the wafer upper-surface cleaner device 60 may clean the upper surface of the wafer W held on the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. For cleaning the upper surface of the wafer W using the wafer upper-surface cleaner device 60, the controller 14 operates the brush rotating assembly 65 to rotate the cleaning brush 62 and the lift / lower cylinder 66 to lower the cleaning brush 62 to contact the upper surface of the wafer W. Moreover, the controller 14 operates the chuck table rotating assembly 39 to rotate the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. Furthermore, the controller 14 controls the cleaning water to be jetted at a position where the cleaning brush 62 contacts the wafer W.

[0062] As shown in FIG. 1, the holder-surface cleaner nozzle 61 is connected to an air-water supplying source 69. From the air-water supplying source 69, air and the cleaning water may be supplied to the holder-surface cleaner nozzle 61. The holder-surface cleaner nozzle 61 may jet a mixed fluid (two-fluid) mixing the air and the cleaning water at the holder surface of the first chuck table 31 or second chuck table 32 located at the C-surface polishing position.

[0063] The mixed fluid jetted from the holder-surface cleaner nozzle 61 may clean the holder surface of the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. For cleaning the holder surface with the mixed fluid jetted from the holder-surface cleaner nozzle 61, the controller 14 operates the chuck table rotating assembly 39 to rotate the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. Thereby, the entire holder surface of the first chuck table 31 or the entire holder surface of the second chuck table 32 may be cleaned.

[0064] The polishing apparatus 1 includes a conveyer assembly 70 that may load the first chuck table 31 or the second chuck table 32 with the wafer W and unload the wafer W from the first chuck table 31 or the second chuck table 32. The conveyer assembly 70 may convey the wafer W among the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position, the temporary placement table 16, and the cleaner device 17. In other words, the C-surface polishing position on the turntable 30 is a loading / unloading position where the wafer W may be conveyed to and from the chuck table 31 or 32 using the conveyer assembly 70.

[0065] As shown in FIG. 5, the conveyer assembly 70 has a conveyer pad 71 that may suction and hold the upper surface of the wafer W. On a lower side of the conveyer pad 71, a porous sheet 72 formed of a porous material is provided. By a suction source 73 suctioning air in the porous sheet 72, a suction force may be generated to act on the lower surface of the porous sheet 72.

[0066] As shown in FIGS. 1 and 5, the conveyer assembly 70 further includes a rotating device 74 that may rotate (pivot) the conveyer pad 71 around an axis extending in the Z-axis direction, a lift / lower assembly 75 supporting the conveyer pad 71 movably up or down in the Z-axis direction, and a Y-axis movable assembly 76 to move the conveyer pad 71 in the Y-axis direction. The rotating device 74 is supported by the lift / lower assembly 75, and the lift / lower assembly 75 is supported by a Y-axis movable device 762 in the Y-axis movable assembly 76. The conveyer pad 71 is supported at an end of an arm 77 extending in the horizontal direction from a lower end of the rotating device 74. The rotating device 74 and the lift / lower assembly 75 are driven by driving forces from motors and actuators, which are not shown, to move the arm 77 rotationally and vertically, respectively.

[0067] The Y-axis movable assembly 76 includes a pair of guide rails 761 located on a surface of the supporting block 63 on the +X direction side and extending in the Y-axis direction, a Y-axis movable device 762 supported by the supporting block 63 via the pair of guide rails 761 movably in the Y-axis direction, a ball screw 763 extending in the Y-axis direction and screwed to a screw thread (not shown) in the Y-axis movable device 762, and a motor 764 that may rotate the ball screw 763. When the ball screw 763 is driven by the motor 764 to rotate, the Y-axis movable device 762 moves in the Y-axis direction. As the Y-axis movable device 762 moves in the Y-axis direction, the arm 77 supported by the Y-axis movable device 762 through the rotating device 74 and the lift / lower assembly 75 moves in the Y-axis direction, and a result, the position of the conveyer pad 71 changes in the Y-axis direction.

[0068] The conveyer assembly 70 may move the conveyer pad 71 horizontally using the rotational movement by the rotating device 74 and the Y-axis movement by the Y-axis movable assembly 76. Moreover, the conveyer assembly 70 may move the conveyer pad 71 up or down in the Z-axis direction using the lifting or lowering movement by the lift / lower assembly 75. Through these movements, the wafer W may be conveyed among the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position, the temporary placement table 16, and the cleaner device 17.

[0069] For loading or unloading the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position with the wafer W using the conveyer assembly 70, the controller 14 operates the Y-axis movable assembly 51 to retract the C-surface polishing assembly 50 toward the +Y direction side. Moreover, the controller 14 operates the lift / lower cylinder 66 to retract the cleaning brush 62 upward. By the retracting movements of the C-surface polishing assembly 50 and the cleaning brush 62, the conveyer assembly 70 is enabled to move the conveyer pad 71 to reach the first chuck table 31 or the second chuck table 32 without being interfered by the C-surface polishing assembly 50 or the cleaning brush 62.

[0070] On the other hand, for polish-processing or cleaning the wafer W on the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position with the C-surface polishing assembly 50 or the cleaning brush 62, the controller 14 operates the Y-axis movable assembly 76 to retract the conveyer pad 71 of the conveyer assembly 70 toward the −Y direction side. By the retracting movement of the conveyer pad 71, the C-surface polishing assembly 50 and the cleaning brush 62 are enabled to polish-process or clean the wafer W located at the C-surface polishing position without being interfered by the conveyer pad 71.

[0071] The holder-surface cleaner nozzle 61 is not located straight above the first chuck table 31 or second chuck table 32 located at the C-surface grinding position but is located at a position distanced toward the −X direction side, and the holder-surface cleaner nozzle 61 may jet the mixed fluid at the holder surface of the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position diagonally from the upper position. As such, the holder-surface cleaner nozzle 61 does not interfere with the operation of the C-surface polishing assembly 50 or the conveyer assembly 70.

[0072] In the polishing apparatus 10 configured as above, while the polishing assembly 40 polishes to process the Si surface of the wafer W, the C-surface polishing assembly 50 may polish-process the C surface of the next wafer W, thereby reducing the total processing time to process the multiple wafers W through the efficiently preferable operation. In addition to the configuration of the polishing apparatus 10 shown in FIGS. 1 through 8, a series of operations of the polishing apparatus 10 and the polishing method using the polishing apparatus 10 for polish-processing the surfaces on both sides of each of the wafers W, which are SiC wafers, will be described with reference to a time chart shown in FIGS. 9A through 9B.

[0073] FIGS. 9A and 9B are time charts showing operations for polish-processing any three (nth, n+1th, n+2th) wafers W continuously, with a horizontal axis representing progression of time. FIGS. 9A and 9B form one continuous time chart but is divided at a middle, and the time Ta indicated in FIG. 9A coincides with the time Ta indicated in FIG. 9B. In the following description, an nth wafer W that is to be polished first is called wafer Wa, an n+1th wafer W that is to be polished next is called wafer Wb, and an n+2th wafer W that is to be polished last is called wafer Wc. The nth wafer W may be a first wafer W to be fed to the polishing apparatus 10 with no preceding wafer W polish-processed being provided ahead thereof (no wafer W is set on either the first chuck table 31 or the second chuck table 32), or it may be a second or subsequent wafer W to be polish-processed following another wafer W that is polish-processed precedingly. In the present embodiment, a case where the nth wafer W is the first wafer W will be explained. Operations of each component described below are controlled and executed by the controller 14. In a case where no explicit entity is specified as a subject to control the operation, it is assumed that the operation is performed under the control of the controller 14.

[0074] Prior to explaining the flow of polish-processing for the three wafers W (Wa, Wb, Wc), a loading operation to load the first chuck table 31 or the second chuck table 32 with one of unpolished wafers W, which are stored in the cassette 11 and provided to the polishing apparatus 10, to be held on the first chuck table 31 or second chuck table 32, is explained.

[0075] The unpolished wafers W are stored in the cassette 11 to be conveyed to the polishing apparatus 10. For example, the cassette 11 containing the unpolished wafers may be placed on one of the two cassette stages 13 on the +X direction side.

[0076] The controller 14 operates the robot hand 18 to suction and hold one of the unpolished wafers W stored in the cassette 11, draws out of the cassette 11, and conveys to the temporary placement table 16 through the operation of the conveyer robot 15. Once the conveyer robot 15 places the wafer W on the temporary placement table 16, the controller 14 performs a positioning operation, in which the plurality of positioning pins 20 arranged around the temporary placement table 16 are moved toward the center of the temporary placement table 16 to contact the outer edge of the wafer W. Thereby, the center of the wafer W aligns with the center of the temporary placement table 16.

[0077] Next, the controller 14 operates the conveyer assembly 70 to convey the wafer W from the temporary placement table 16 to the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. In particular, first, the conveyer pad 71 is located above the wafer W on the temporary placement table 16 by the Y-axis movable assembly 76 moving toward the −Y direction side and rotation of the rotating device 74. The suction source 73 applying the suction force to the lower surface of the porous sheet 72 and the lift / lower assembly 75 lowering the conveyer pad 71 cause the porous sheet 72 to suction and hold the upper surface of the wafer W. Once the porous sheet 72 suctions and holds the upper surface of the wafer W, the conveyer pad 71 is lifted by the lift / lower assembly 75, and the conveyer pad 71 is, by being moved toward the +Y direction side by the Y-axis movable assembly 76 and rotated by the rotating device 74, conveyed to the position above the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. Meanwhile, the C-surface polishing assembly 50 is retracted off from the C-surface polishing position toward the +Y direction side by the Y-axis movable assembly 51. Moreover, the cleaning brush 62 is retracted upward by the lift / lower cylinder 66. As such, the conveyer pad 71 is prevented from interfering with the C-surface polishing assembly 50 or the cleaning brush 62.

[0078] The controller 14 operates the lift / lower assembly 75 to lower the conveyer pad 71 and sets the lower surface of the wafer W on the holder surface of the first chuck table 31 or the second chuck table 32 located at the C-surface polishing position. At this point, the suction force from the suction source 37 is being applied to the holder surface of the first chuck table 31 or the second chuck table 32. By discontinuing applying of the suction force from the suction source 73 to the porous sheet 72 and releasing the upper surface of the wafer W from the suctioning and holding act of the conveyer pad 71, the wafer W is shifted to a state where the wafer W is suctioned and held on the holder surface of the first chuck table 31 or the second chuck table 32.

[0079] As described above, the three wafers W (Wa, Wb, Wc) are conveyed from the cassette 11 to the first chuck table 31 or the second chuck table 32 via the temporary placement table 16 using the conveyer robot 15 and the conveyer assembly 70 one by one. In the following description of operations, loading of the second chuck table 32 with the wafer Wb in Step 103 shown in FIG. 9A and loading of the first chuck table 31 with the wafer Wc in Step 118 in FIG. 9B are performed in the same manner as described above.

[0080] The time chart in FIG. 9A starts from Step 100, which is a process to load the first chuck table 31 with the wafer Wa in preparation to polish-process the Si surface of the nth wafer Wa. By the time of Step 100, polish-processing of the C surface of the wafer Wa has already been completed.

[0081] A process to be performed with the wafer Wa prior to Step 100 will be briefly explained. The controller 14 operates the conveyer robot 15 and the conveyer assembly 70 to convey the unpolished wafer Wa stored in the cassette 11 via the temporary placement table 16 to the first chuck table 31 located at the C-surface polishing position. The wafer Wa is conveyed in an orientation, in which the Si surface faces downward and the C surface faces upward, and is suctioned and held with the Si surface placed on the holder surface of the first chuck table 31. Next, the controller 14 operates the C-surface polishing assembly 50 to polish the C-surface being the upper surface of the wafer Wa (see FIG. 3). As polishing of the C-surface is completed, the conveyer assembly 70 suctions and holds the upper surface (C surface) of the wafer Wa with the conveyer pad 71 and conveys the wafer Wa from the first chuck table 31 to the cleaner device 17. In the cleaner device 17, the spinner cleaning table 21 holds the wafer Wa, and the wafer Wa is cleaned thereat.

[0082] As cleaning of the wafer Wa in cleaner device 17 is completed, the controller 14 operates the conveyer robot 15 to suction and hold the lower surface (Si surface) of the wafer Wa held on the spinner cleaning table 21 in the cleaner device 17 with the robot hand 18, as shown in FIG. 7. Next, the controller 14 operates the conveyer robot 15 to lift the wafer Wa above the spinner cleaning table 21 and separate the wafer Wa from the holder surface of the spinner cleaning table 21, and operates the rotating device 19 to invert the robot hand 18 vertically. By this inverting act, the wafer Wa is shifted to an orientation in which the C surface faces downward and the Si surface faces upward. After inverting the wafer Wa, the controller 14 operates the conveyer robot 15 to return the wafer Wa to the cleaner device 17 and set the lower surface (C surface) of the wafer Wa not suctioned or held by the robot hand 18 to be placed on the spinner cleaning table 21, as shown in FIG. 8. Thereafter, the controller 14 operates the robot hand 18 to release the wafer Wa from the suctioning and holding force and retract the robot hand 18 from the cleaner device 17. The operation up to this point is the operation to be performed prior to Sep 100, and from this state, a process to convey the wafer Wa back to the first chuck table 31 using the conveyer assembly 70 is performed in Step 100.Step 100: Load the First Chuck Table 31 With the Wafer Wa

[0083] In Step 100, the rotational position of the turntable 30 is set to a location where the first chuck table 31 is located at the C-surface polishing position and the second chuck table 32 is located at the polishing position. The controller 14 operates the conveyer assembly 70 to locate the conveyer pad 71 above the wafer Wa held on the spinner cleaning table 21. The suction force from the suction source 73 is applied to the porous sheet 72, and the conveyer pad 71 is lowered by the lift / lower assembly 75, so that the conveyer pad 71 suctions and holds the Si surface being the upper surface of the wafer Wa. Next, the conveyer assembly 70 is operated to convey the conveyer pad 71, which is suctioning and holding the wafer Wa, from the cleaner device 17 to the first chuck table 31 located at the C-surface polishing position. There, the conveyer pad 71 is lowered to place the C-surface being the lower surface of the wafer Wa on the holder surface of the first chuck table 31. The controller 14 operates the suction source 37 and opens the open / close valve 38 to apply the suction force to the holder surface of the first chuck table 31 to suction and hold the C surface of the wafer Wa. Accordingly, the wafer Wa, which is fed to the first chuck table 31 using the conveyer assembly 70, is suctioned and held on the holder surface of the first chuck table 31 with the Si surface facing up and the C surface facing down.Step 101: Rotate the Turntable 30

[0084] Following Step 100, in Step 101, the controller 14 operates the turntable 30 to rotate by 180 degrees to locate the first chuck table 31 at the polishing position. Since earlier Step 100, the wafer Wa has been held on the first chuck table 31, and by the rotation of the turntable 30 in Step 101, the polishing assembly 40 is located above the wafer Wa. Moreover, according to the rotation of the turntable 30, the second chuck table 32 not holding a wafer W is located at the C-surface polishing position.Step 102: Polish the Si Surface of the Wafer Wa

[0085] Next, the controller 14 operates the polishing assembly 40 to polish-process the Si surface of the wafer Wa (see FIG. 2). Since Step 100, the first chuck table 31 has been loaded with the wafer Wa with the C surface facing downward; therefore, in the state where the first chuck table 31 suctioning and holding the wafer Wa is located at the polishing position, the Si surface of the wafer Wa faces upward.

[0086] The polishing assembly 40 operates the spindle unit 43 to rotate the spindle shaft 44 and the lift / lower assembly 41 to lower the mount 45 and the polishing wheel 46. In other words, the polishing pad 47 arranged on the lower side of the polishing wheel 46 rotates and approaches the Si surface of the wafer Wa. Moreover, the first chuck table 31 holding the wafer Wa is rotated by the chuck table rotating assembly 39. The polishing pad 47 contacts the Si surface of the wafer Wa and polish-processes the Si surface. While the Si surface is being polish-processed, the slurry is supplied from the slurry suppling source 48. As such, in parallel to Step 102 where the Si surface of the wafer Wa is being polish-processed, each of Steps 103 through 110 will be performed.Step 103: Load the Second Chuck Table 32 With the Wafer Wb

[0087] After rotating the turntable 30 in Step 101, at a timing equal to the time when the polish-processing to the Si surface of the wafer Wa starts in Step 102, the controller 14 executes a process in Step 103. In Step 103, the second chuck table 32 located at the C-surface polishing position is loaded with the wafer Wb being the n+1th wafer W to hold the wafer Wb. The loading operation to the second chuck table 32 with the wafer Wb is performed in the state where the C-surface polishing assembly 50 is retracted by the Y-axis movable assembly 51 toward the +Y direction side.

[0088] In the example shown in FIG. 9A, Step 102 and Step 103 start simultaneously, but Step 103 may be performed at any time after the turntable 30 is rotated in Step 101, and Step 102 and Step 103 may start at different timings. However, since Step 103 is the beginning of the process related to polishing of the C surface of the wafer Wb, if Step 103 is started too late, the series of processes related to the wafer Wb (Steps 104 through Step 110), which are performed in parallel to Step 102, may end later than the end of the polish-processing of the Si surface of the wafer Wa in Step 102, and the efficiency to use the time period required for polish-processing of the Si surface of the wafer Wa may be undesirably lowered. Therefore, it is desirable that Step 103 is started as soon as possible after Step 102 is started, so that at least Step 110 ends earlier than the end of Step 102. For the same reason, each of the Steps described below should also be executed once a preceding and related step ends and as soon as possible without delay when the step is ready to be performed.

[0089] In Step 103, the conveyer robot 15 and conveyer assembly 70 are operated to convey the wafer Wb from the cassette 11 to the second chuck table 32 via the temporary placement table 16. While the wafer Wb is being conveyed, the controller 14 sets the orientation of the wafer Wb such that the second chuck table 32 holds the wafer Wb with the C surface facing upward and the Si surface facing downward. Thereafter, the controller 14 operates the suction source 37 and opens the open / close valve 38 to apply the suction force to the holder surface of the second chuck table 32 to suction and hold the Si surface of the wafer Wb.

[0090] The conveyer robot 15 functions as an inverting assembly that may invert the vertical orientation of the robot hand 18 using the rotating device 19; therefore, regardless of the vertical orientation of the Si and C surfaces of the wafers W stored in the cassette 11, the vertical orientation of each wafer W to be fed to the first chuck table 31 or the second chuck table 32 may be set as desired. For example, in Step 103, at the time when the wafer Wb drawn out from the cassette 11 is placed on the temporary placement table 16, the conveyer robot 15 is controlled so that the Si surface of the wafer Wb faces downward. Meanwhile, the conveyer assembly 70 conveys the wafer Wb without changing the vertical orientation of the upper and lower surfaces of the wafer Wb; therefore, the wafer Wb conveyed from the temporary placement table 16 to the second chuck table 32 by the conveyer assembly 70 is in the orientation where the C surface facing upward and the Si surface facing downward.

[0091] The operation by the conveyer robot 15 from drawing the wafer Wb out of the cassette 11 to placing the wafer Wb to be held on the temporary placement table 16 may be performed regardless of the position of the second chuck table 32. Therefore, the conveyer robot 15 may be operated to place the wafer Wb to be held on the temporary placement table 16 before the rotation of the turntable 30 in Step 101 is completed. As such, as long as Step 103 at least includes the operation by the conveyer assembly 70 to convey the wafer Wb from the temporary placement table 16 to the second chuck table 32, the part of the operation by the conveyer robot 15 to place the wafer Wb on the temporary placement table 16 may be performed at any time (prior to Step 103) different from Step 103 shown in FIG. 9A.

[0092] As the feeding of the wafer Wb to the second chuck table 32 is completed in Step 103, the controller 14 operates the Y-axis movable assembly 76 to retract the conveyer pad 71 toward the −Y direction side. The retracting movement of the conveyer pad 71 toward the −Y direction side enables the C-surface polishing assembly 50 to polish-process the C surface of the wafer Wb without interfering with the conveyer assembly 70 in the next Step 104.Step 104: Polish the C Surface of the Wafer Wb

[0093] Next, in Step 104, the controller 14 operates the C-surface polishing assembly 50 to polish-process the C-surface of the wafer Wb (see FIG. 3). For polish-processing the C surface of the wafer Wb with the C-surface polishing assembly 50, the C-surface polishing assembly 50 having been retracted toward the +Y direction side in the previous Step 103 is moved toward the −Y direction side by the Y-axis movable assembly 51, and the polishing wheel 57 is located above the second chuck table 32 located at the C-surface polishing position. The wafer Wb is, at the time of Step 103 when the wafer Wb is conveyed from the temporary placement table 16 to the second chuck table 32, in the orientation where the Si surface faces downward and the C surface faces upward.

[0094] The C-surface polishing assembly 50 operates the spindle unit 54 to rotate the spindle shaft 55 and the lift / lower assembly 52 to lower the mount 56 and the polishing wheel 57. In other words, the C-surface polishing pad 58 arranged on the lower side of the polishing wheel 57 rotates and approaches the C surface of the wafer Wb. The C-surface polishing pad 58 contacts the C surface of the wafer Wb and polish-processes the C surface. While the C surface is being polish-processed, the slurry is supplied from the slurry suppling source 59.

[0095] As shown in FIG. 9A, a polishing time required to polish the Si surface of the wafer Wa in Step 102 is considerably longer than a polishing time required to polish the C surface of the wafer Wb in Step 104. Therefore, even combined with the time required to load the second chuck table 32 with the wafer Wb in Step 103, the polishing time in Step 104 to polish the C surface of the wafer Wb ends before the Si surface of the wafer Wa is polished completely.

[0096] As polishing of the C surface of the wafer Wb is completed, the controller 14 finishes the polish-processing operation with the C-surface polishing assembly 50. In particular, the lift / lower assembly 52 is operated to lift the polishing wheel 57 to separate the C-surface polishing pad 58 from the C surface of the wafer Wb, and supplying of the slurry from the slurry supplying source 59 is discontinued. Moreover, the Y-axis movable assembly 51 is operated to retract the C-surface polishing assembly 50 toward the +Y direction side. In the meantime, in the same manner as Step 104, the second chuck table 32 will be rotated also in Step 105; therefore, while shifting from Step 104 to Step 105, optionally, the chuck table rotating assembly 39 may continuously rotate the second chuck table 32. Alternatively, at the end of Step 104, the chuck table rotating assembly 39 may temporarily stop rotation of the second chuck table 32.Step 105: Clean the C Surface of the Wafer Wb

[0097] After polishing of the C surface of the wafer Wb is completed, in Step 105, the wafer upper-surface cleaner device 60 is operated to clean the C surface of the wafer Wb held on the second chuck table 32 (see FIG. 4).

[0098] For cleaning the C surface of the wafer Wb in Step 105, the controller 14 operates the brush rotating assembly 65 to rotate the brush supporting shaft 64 and the cleaning brush 62 and operates the lift / lower cylinder 66 to lower the brush supporting shaft 64 and the cleaning brush 62. Moreover, the chuck table rotating assembly 39 is operated to rotate the second chuck table 32 holding the wafer Wb. Furthermore, the cleaning water supplied from the cleaning-water supplying source 68 is jetted from the cleaning-water nozzle 67 at the C surface of the wafer Wb. As such, while the cleaning water is supplied from the cleaning-water nozzle 67, the cleaning brush 62 is moved to rotate and contact the C surface of the wafer Wb to clean the C surface. The slurry and polishing swarf that adhered to the C surface of the wafer Wb during the polish-processing in Step 104 may be removed by the cleaning operation in Step 105.

[0099] When cleaning of the C surface of the wafer Wb is completed, the controller 14 operates the lift / lower cylinder 66 to lift the cleaning brush 62 to separate from the C surface of the wafer Wb and operates the brush rotating assembly 65 to stop rotating the cleaning brush 62. Moreover, the controller 14 operates the chuck table rotating assembly 39 to stop rotating the second chuck table 32.Step 106: Unload the Wafer Wb From the Second Chuck Table 32

[0100] Next, in Step 106, the wafer Wb is unloaded from the second chuck table 32 and conveyed to the cleaner device 17. For unloading the wafer Wb from the second chuck table 32, the conveyer assembly 70 is operated. The controller 14 operates the Y-axis movable assembly 76 to move in the Y-axis direction and the rotating device 74 to rotate, thereby locating the conveyer pad 71 above the wafer Wb. By the suction source 73 applying the suction force to the lower surface of the porous sheet 72 and the lift / lower assembly 75 lowering the conveyer pad 71, the porous sheet 72 is enabled to suction and hold the C surface of the wafer Wb on the lower surface thereof.

[0101] In the preceding Step 105, the C surface of the wafer Wb has been cleaned using the wafer upper-surface cleaner device 60, and thereby dirt on the C surface has been reduced. As such, the wafer Wb may be securely suctioned and held by the conveyer pad 71, the conveyer pad 71 may be prevented from adherence of the dirt.

[0102] Meanwhile, the wafer Wb will be cleaned entirely in the next Step 107; therefore, in a case where the dirtiness of the wafer Wb is at an extent that does not particularly cause a problem in unloading of the wafer Wb from the second chuck table 32, optionally, cleaning of the C surface of the wafer Wb in Step 105 may be omitted.

[0103] The controller 14 operates the lift / lower assembly 75 to lift the conveyer pad 71, with the C surface of the wafer Wb being suctioned and held thereon (see FIG. 5). Further, the controller 14 operates the Y-axis movable assembly 76 to move toward the −Y direction side and the rotating device 74 to rotate, thereby locating the conveyer pad 71 and the wafer Wb above the spinner cleaning table 21. The lift / lower assembly 75 is operated to lower the conveyer pad 71 to place the Si surface of the wafer Wb on the spinner cleaning table 21. The suction source 23 is operated to apply the suction force to the holder surface of the spinner cleaning table 21 to suction and hold the wafer Wb, and the conveyer assembly 70 is operated to release the wafer Wb from the suctioning and holding force of the porous sheet 72. As such, the wafer Wb is passed from the conveyer pad 71 to the spinner cleaning table 21.Step 107: Clean the Wafer Wb

[0104] In Step 107, the controller 14 operates the cleaner device 17 to clean the wafer Wb, of which C surface has been polish-processed. As shown in FIG. 6, the controller 14 operates the rotating assembly 24 to rotate the spinner cleaning table 21, and the cleaning water supplied from the cleaning-water supplying source 25 is jetted at the wafer Wb from the cleaner nozzle 22. A diameter of the spinner cleaning table 21 is smaller than a diameter of the wafer W being polish-processed in the polishing apparatus 10, and the wafer Wb is held on the spinner cleaning table 21 in a state jutting outward from the spinner cleaning table 21. Therefore, the cleaner device 17 may clean not only the C surface being the upper surface of the wafer Wb but also the Si surface being the lower surface with the cleaning water spreading to reach the Si surface. After cleaning the wafer Wb with the cleaning water, air supplied from the air supplying source 26 is jetted from the cleaner nozzle 22 to dry the wafer Wb.Step 108: Clean the Holder Surface of the Second Chuck Table 32

[0105] In Step 108, the controller 14 performs an operation to clean the holder surface of the second chuck table 32 after unloaded with the wafer Wb. In particular, the controller 14 controls the mixed fluid mixed with the cleaning water and the air supplied from the air-water supplying source 69 to be jetted at the holder surface of the second chuck table 32 from the holder-surface cleaner nozzle 61 to clean the holder surface of the second chuck table 32. By this cleaning operation, the slurry or the grinding swarf caused in the preceding Step 104 when the C surface of the wafer Wb was polish-processed may be washed off from the holder surface of the second chuck table 32.

[0106] From a perspective of the time usage efficiency, it is preferable that cleaning of the wafer Wb by the cleaner device 17 in Step 107 and cleaning of the holder surface of the second chuck table 32 in Step 108 are performed simultaneously. The term “simultaneously” means that the two cleaning processes are performed at least partly in the same time period and does not necessarily mean that the two cleaning processes are started and finished at exactly the same time. For example, in the example of FIG. 9A, cleaning of the wafer Wb in Step 107 and cleaning of the holder surface of the second chuck table 32 in Step 108 are started substantially simultaneously, but cleaning of the holder surface of the second chuck table 32 ends earlier.

[0107] Optionally, in a case where, after polishing the C surface of the wafer Wb in Step 104, the holder surface of the second chuck table 32 suctioning and holding the Si surface of the wafer Wb is not substantially dirty, cleaning of the second holder surface of the second chuck table 32 in Step 108 may be omitted.Step 109: Invert the Wafer Wb

[0108] As cleaning of the wafer Wb by the cleaner device 17 in Step 107 is completed, the controller 14 operates the conveyer robot 15 to invert the wafer Wb in Step 109. Step 109 is executable as long as Step 107 is completed; therefore, even if completion of Step 108 is later than completion of Step 107, the controller 14 may execute Step 109 without awaiting the completion of Step 108. For inverting the wafer Wb, the spinner cleaning table 21 is operated to release the wafer Wb from the suctioning and holding force, and the robot hand 18 of the conveyer robot 15 is operated to suction and hold the wafer Wb.

[0109] In the example shown in FIG. 7, the controller 14 instructs the conveyer robot 15 to hold the lower surface (Si surface) of the wafer Wb on the spinner cleaning table 21 from below with the robot hand 18, i.e., in a form of a bottom pick-up. The robot hand 18 shown in FIG. 1 is a C-shaped robot hand with a gutter-shaped opening, of which width is larger than the diameter of the spinner cleaning table 21, and is capable of holding the lower surface of the wafer Wb from below without interfering with the spinner cleaning table 21.

[0110] Next, the controller 14 operates the movable arm of the conveyer robot 15 to move the wafer Wb to separate above the spinner cleaning table 21 while the wafer Wb is suctioned and held by the robot hand 18, and operates the rotating device 19 to invert the robot hand 18 upside-down. The inverting operation changes the vertical orientation of the wafer Wb so that the C surface faces downward and the Si surface faces upward. After inverting the wafer Wb, the controller 14 operates the conveyer robot 15 to return the wafer Wb to the spinner cleaning table 21 to place the C surface being the lower surface of the wafer Wb on the spinner cleaning table 21, as shown in FIG. 8.

[0111] In the polishing apparatus 10, conveyance of the wafer W on the chuck table 31 or 32 where the slurry or the ground swarf may adhere to the wafer W is performed by the conveyer assembly 70 while conveyance of the cleaned wafer W on the clean side, which should avoid adherence of the slurry or the ground swarf, is performed by the conveyer robot 15. In Step 109, the wafer Wb is inverted after being cleaned by the wafer upper-surface cleaner device 60 in Step 105 and by the cleaner device 17 in Step 107; therefore, in a case where the conveyer robot 15 is used as the inverting assembly, the conveyer robot 15 is prevented from being dirtied by the slurry or the swarf.Step 110: Load the Second Chuck Table 32 With the (Inverted) Wafer Wb

[0112] Next, in Step 110, the controller 14 moves the inverted wafer Wb from the spinner cleaning table 21 of the cleaner device 17 to load the second chuck table 32 located at the C-surface polishing position therewith. In particular, the controller 14 controls the conveyer assembly 70 to apply a suction force to the porous sheet 72 to suction and hold the Si surface of the wafer Wb on the spinner cleaning table 21, the lift / lower assembly 75 to lift the conveyer pad 71, and the Y-axis movable assembly 76 to move toward the +Y direction side and the rotating device 74 to rotate, thereby moving the conveyer pad 71 and the wafer Wb above the second chuck table 32. The lift / lower assembly 75 is operated to lower the conveyer pad 71 to place the lower surface (the C surface having been polish-processed) of the wafer Wb on the holder surface of the second chuck table 32. Thereafter, the controller 14 operates the suction source 37 and opens the open / close valve 38 to apply the suction force to the holder surface of the second chuck table 32 to suction and hold the C surface of the wafer Wb.

[0113] Optionally, as a modified example of the operations in Step 109 and Step 110, after inverting the wafer Wb in Step 109, the conveyer robot15 may be operated to place the wafer Wb on the temporary placement table 16 rather than placing back in the cleaner device 17 so that the inverted wafer Wb may be conveyed via the temporary placement table 16 to the second chuck table 32. In this arrangement, in Step 110, the conveyer assembly 70 is operated to convey the inverted wafer Wb from the temporary placement table 16 to the second chuck table 32 located at the C-surface polishing position. Since the conveyer robot 15 is in a configuration enabled to convey the wafer Wb from the cleaner device 17 to the temporary placement table 16, if no another wafer W (e.g., n+2th wafer Wc) is held on the temporary placement table 16 at the time of Step 109 or Step 110, the operation in this modified example may be performed optionally.

[0114] The series of operations and processes from Step 103 to Step 110 is performed while the Si surface of the wafer Wa is being polish-processed in Step 102. In other words, the long time period required to polish-process the Si surface of the nth wafer Wa is effectively used to perform the processes related to polish-processing of the C surface of the n+1th wafer Wb simultaneously.

[0115] More specifically, in parallel to the polish-processing of the Si surface of the wafer Wa (Step 102), processes of preparation for polish-processing of the wafer Wb (Step 103), polish-processing of the C surface of the wafer Wb (Step 104), post-processing after polish-processing of the C surface of the wafer Wb (Steps 105-108), and preparation including inverting of the wafer Wb for the Si surface of the wafer Wb to be polish-processed next (Steps 109-110) are performed. As such, as shown in FIG. 9A, before polish-processing of the Si surface of the wafer Wa (Step 102) is completed, final preparation (Step 110) for polish-processing of the Si surface of the next wafer Wb is completed.

[0116] As polish-processing of the Si surface of the wafer Wa in Step 102 is completed, the controller 14 finishes the polish-processing operation with the polishing assembly 40. In particular, the lift / lower assembly 41 is operated to lift the polishing wheel 46 to separate the polishing pad 47 from the Si surface of the wafer Wa, and supplying of the slurry from the slurry supplying source 48 is discontinued. Moreover, the chuck table rotating assembly 39 is operated to stop rotating the first chuck table 31.Step 111: Rotate the Turntable 30

[0117] After polishing of the Si surface of the wafer Wa is completed, in Step 111, the controller 14 operates the turntable 30 to rotate by 180 degrees. According to the rotation of the turntable 30, the first chuck table 31 holding the wafer Wa, of which Si surface has been polished, is located at the C-surface polishing position. In the meantime, the second chuck table 32 holding the wafer Wb with the C surface having been polished and being inverted is located at the polishing position.Step 112: Polish the Si Surface of the Wafer Wb

[0118] Next, the controller 14 operates the polishing assembly 40 to polish-process the Si surface of the wafer Wb (see FIG. 2). An operation to polish-process the Si surface of the wafer Wb is performed in the same manner as the operation to polish-process the Si surface of the wafer Wa in Step 102 described earlier; therefore, detailed description of the operation by the polishing assembly 40 is herein omitted. The second chuck table 32 suctioning and holding the wafer Wb thereon is rotated, and the rotating polishing pad 47 is lowered to contact the Si surface of the wafer Wb, thereby polish-processing the Si surface of the wafer Wb. While the Si surface is being polish-processed, the slurry is supplied from the slurry supplying source 48. As such, in parallel to Step 112 where the Si surface of the wafer Wb is being polish-processed, Steps 133 through 125 will be performed.Step 113: Clean the Si Surface of the Wafer Wa

[0119] At a timing equal to the time when the polish-processing to the Si surface of the wafer Wb starts in Step 112, the controller 14 operates the wafer upper-surface cleaner device 60 to clean the Si surface of the wafer Wa held on the first chuck table 31 (see FIG. 4).

[0120] Cleaning of the Si surface of the wafer Wa is performed in the same manner as the cleaning operation to clean the C surface of the wafer Wb in Step 105 described earlier. In other words, while the cleaning water supplied from the cleaning-water supplying source 68 is jetted at the Si surface of the wafer Wa from the cleaning-water nozzle 67, the brush rotating assembly 65 is operated to rotate the brush supporting shaft 64 and the cleaning brush 62, the lift / lower cylinder 66 is operated to lower the brush supporting shaft 64 and the cleaning brush 62, and the rotating cleaning brush 62 is moved to rotate and contact the Si surface of the wafer Wa, to clean the Si surface. The slurry and polishing swarf that adhered to the Si surface of the wafer Wa during the polish-processing in Step 102 may be removed by the cleaning operation in Step 113.Step 114: Unload the Wafer Wa from the First Chuck Table 31

[0121] After cleaning of the Si surface of the wafer Wa in Step 113 is completed, the controller 14 operates the conveyer assembly 70 to perform an unloading operation to move the wafer Wa from the first chuck table 31 located at the C-surface polishing position to the cleaner device 17. The unloading operation with the wafer Wa is similar to the unloading operation to convey the wafer Wb from the second chuck table 32 to the cleaner device 17; therefore, detailed description of the operation of the conveyer assembly 70 with the wafer Wa is herein omitted. The conveyer assembly 70 is operated to move the conveyer pad 71, with the porous sheet 72 suctioning and holding the Si surface of the wafer Wa, to convey the wafer Wa from the first chuck table 31 to the cleaner device 17 and pass the wafer Wa from the conveyer pad 71 to the spinner cleaning table 21. The wafer Wa is suctioned and held by the spinner cleaning table 21 with the C surface facing downward.

[0122] As the Si surface of the wafer Wa has been cleaned by the wafer upper-surface cleaner device 60 earlier in Step 113, the dirt on the Si surface has been reduced; therefore, in Step 114, the wafer Wa may be securely suctioned and held by the conveyer pad 71, and the conveyer pad 71 may be prevented from adherence of the dirt.

[0123] Meanwhile, the wafer Wa will be cleaned entirely in the next Step 115; therefore, in a case where the dirtiness of the wafer Wa is at an extent that does not particularly cause a problem in unloading of the wafer Wa from the first chuck table 31, optionally, cleaning of the Si surface of the wafer Wa in Step 113 may be omitted.Step 115: Clean the Wafer Wa

[0124] In Step 115, the controller 14 operates the cleaner device 17 to clean the wafer Wa, of which Si surface has been polish-processed. The cleaning operation to clean the wafer Wa is similar to the cleaning operation to clean the wafer Wb in Step 107; therefore, detailed description of the operation of the cleaner device 17 with the wafer Wa is herein omitted. The controller 14 operates the spinner cleaning table 21 suctioning and holding the wafer Wa to rotate and causes the cleaning water to be jetted from the cleaner nozzle 22 to clean the wafer Wa. After cleaning the wafer Wa, air is jetted from the cleaner nozzle 22 to dry the wafer Wa.Step 116: Store the Wafer Wa in the Cassette 11

[0125] After the cleaner device 17 finishes cleaning the wafer Wa, in Step 116, the controller 14 operates the conveyer robot 15 to convey the wafer Wa from the cleaner device 17 to the cassette 11 to store the wafer Wa in the cassette 11. For example, as shown in FIG. 7, the controller 14 instructs the conveyer robot 15 to operate the robot hand 18 to hold the lower surface (C surface) of the wafer Wa on the spinner cleaning table 21 from below. Thereafter, the robot hand 18 is moved upward to separate the wafer Wa from the spinner cleaning table 21 and convey the wafer Wa to the inside of the cassette 11 placed on the cassette stage 13.

[0126] While the wafer Wa is in a way to be conveyed to the cassette 11, optionally, the controller 14 may operate the conveyer robot 15 to invert the vertical orientation of the robot hand 18 through the rotating device 19. In this case where the wafer Wa is inverted, the wafer Wa is stored in the cassette 11 with the Si surface facing downward.

[0127] The manner to convey the wafer Wa to the cassette 11 is not necessarily limited to the one described above. For example, as shown in FIG. 8, the robot hand 18 may hold the upper surface (Si surface) of the wafer Wa on the spinner cleaning table 21 from above.

[0128] After processing through Step 116, the wafer Wa, of which both the Si surface and the C surface are completely polished, is stored in the cassette 11. In other words, the nth wafer Wa is completed with the series of processing and conveying that are to be performed by the polishing apparatus 10.Step 117: Clean the Holder Surface of the First Chuck Table 31

[0129] After the wafer Wa was conveyed from the first chuck table 31 to the cleaner device 17 in Step 114, the unloaded first chuck table 31 is open without holding any other wafer W. In Step 117 after the end of Step 114, the holder surface of the unloaded first chuck table 31 is cleaned. The controller 14 causes the mixed fluid supplied from the air-water supplying source 69 to be jetted at the holder surface of the first chuck table 31 from the holder-surface cleaner nozzle 61 to clean the holder surface of the first chuck table 31.

[0130] From a perspective of the time usage efficiency, it is preferable that cleaning of the wafer Wa by the cleaner device 17 in Step 115 and cleaning of the holder surface of the first chuck table 31 in Step 117 are performed simultaneously (the two cleaning processes are performed at least partly in the same time period), but the two cleaning processes may not necessarily be started and finished at exactly the same time.

[0131] Optionally, in a case where, after polishing the Si surface of the wafer Wa in Step 102, the holder surface of the first chuck table 31 suctioning and holding the C surface of the wafer Wa is not substantially dirty, cleaning of the holder surface of the first chuck table 31 in Step 117 may be omitted.Step 118: Load the First Chuck Table 31 With the Wafer Wc

[0132] Next, in Step 118, the wafer Wc being the n+2th wafer W is conveyed to be held by the first chuck table 31 located at the C-surface polishing position. The operation to convey the wafer Wc from the cassette 11 via the temporary placement table 16 to the first chuck table 31 is performed in the same manner as the operation to convey the wafer Wb to the second chuck table 32 in Step 103 described earlier; therefore, detailed description of the operation with the wafer Wc is herein omitted. In the same manner as the case of the wafer Wb, the wafer Wc is conveyed in the orientation with the Si surface facing downward and the C surface facing upward and is suctioned and held with the Si surface placed on the holder surface of the first chuck table 31.

[0133] In the example shown in FIG. 9B, Step 118 is performed earlier than Step 116. Step 116 is the operation to store the wafer Wa, of which both surfaces are polished, in the cassette 11, and is performed with the conveyer robot 15. Within the operation in Step 116, the part to convey the wafer Wc from the cassette 11 to the temporary placement table 16 is performed with use of the conveyer robot 15. Within the operation in Step 118, the part to convey the wafer Wc from the cassette 11 to the temporary placement table 16 is performed with use of the conveyer robot 15. Therefore, the time period for Step 116 and the time period for Step 118 are shifted from each other so that a waiting time in the operation of the conveyer robot 15 may not need to be reserved, and the operations may be conducted efficiently.

[0134] Meanwhile, a part of the operation in Step 118 with the conveyer robot 15 to draw the wafer Wc from the cassette 11 and place the wafer Wc to be held on the temporary placement table 16 may optionally be performed before cleaning of the holder surface of the first chuck table 31 in Step 117 is completed. As such, as long as Step 118 at least includes the operation with the conveyer assembly 70 to convey the wafer Wc from the temporary placement table 16 to the first chuck table 31, the part of the operation with the conveyer robot 15 to place the wafer Wc on the temporary placement table 16 may be performed any time (prior to Step 118) different from Step 118 shown in FIG. 9B.Step 119: Polish the C Surface of the Wafer Wc

[0135] Next, in Step 119, the controller 14 operates the C-surface polishing assembly 50 to polish-process the C surface of the wafer Wc (see FIG. 3). An operation for polish-processing the C surface of the wafer Wc is performed in the same manner as the operation to polish-process the C surface of the wafer Wb in Step 104 described earlier; therefore, detailed description of the operation by the polishing assembly 40 with the wafer Wc is herein omitted.

[0136] As shown in FIG. 9B, a polishing time required to polish the Si surface of the wafer Wb in Step 112 is considerably longer than a polishing time required to polish the C surface of the wafer Wc in Step 119. Therefore, even combined with the time required to load the first chuck table 31 with the wafer Wc in Step 118, the polishing time in Step 119 to polish the C surface of the wafer Wc ends before the Si surface of the wafer Wb is polished completely.

[0137] Moreover, in the example of FIG. 9B, polishing of the Si surface of the wafer Wb in Step 112, polishing of the C surface of the wafer Wc in Step 119, and cleaning and storing of the wafer Wa in the cassette 11 in Step 115 and Step 116 are performed in parallel. As such, a time period, in which the processes for all of the three wafers Wa, Wb, Wc are performed in parallel, is arranged, and thereby a total processing time in the polishing apparatus 10 may be reduced more efficiently.Step 120: Clean the C Surface of the Wafer Wc

[0138] After polishing of the C surface of the wafer Wc in Step 119 is completed, the controller 14 finishes the processing operation with the C-surface polishing assembly 50 and, in Step 120, operates the wafer upper-surface cleaner device 60 to clean the C surface of the wafer Wc held on the first chuck table 31 (see FIG. 4). An operation for cleaning the C surface of the wafer Wc with the wafer upper-surface cleaner device 60 is performed in the same manner as the operation to clean the C surface of the wafer Wb in Step 105 described earlier; therefore, detailed description of the operation with the wafer Wc is herein omitted.Step 121: Unload the Wafer Wc From the First Chuck Table 31

[0139] Next, in Step 121, the controller 14 operates the conveyer assembly 70 to unload the first chuck table 31 and move the wafer Wc to the cleaner device 17. Unloading of the wafer Wc with the conveyer assembly 70 is performed in the same manner as the operation to unload the wafer Wb from the second chuck table 32 in Step 106; therefore, detailed description of the operation with the wafer Wc is herein omitted.

[0140] As the C surface of the wafer Wc has been cleaned by the wafer upper-surface cleaner device 60 earlier in Step 120, the dirt on the C surface has been reduced; therefore, the wafer Wc may be securely suctioned and held by the conveyer pad 71, and the conveyer pad 71 may be prevented from adherence of the dirt.

[0141] Meanwhile, the wafer Wc will be cleaned entirely in the next Step 122; therefore, in a case where the dirtiness of the wafer Wc is at an extent that does not particularly cause a problem in unloading of the wafer Wc from the first chuck table 31, optionally, cleaning of the C surface of the wafer Wc in Step 120 may be omitted.Step 122: Clean the Wafer Wc

[0142] In Step 122, the controller 14 operates the cleaner device 17 to clean the wafer Wc, of which C surface has been polish-processed. The cleaning operation to clean the wafer Wc is similar to the cleaning operations to clean the C surface of the wafer Wb in Step 107 and to clean the Si surface of the wafer Wa in Step 115 described earlier; therefore, detailed description of the operation with the wafer Wc is herein omitted.Step 123: Clean the Holder Surface of the First Chuck Table 31

[0143] In Step 123, the holder surface of the first chuck table 31 after unloading the wafer Wc is cleaned with the mixed fluid jetted from the holder-surface cleaner nozzle 61. An operation to clean the holder surface of the first chuck table 31 in Step 123 is performed in the same manner as the operation to clean the holder surface of the second chuck table 32 in Step 108 described earlier.

[0144] From a perspective of the time usage efficiency, it is preferable that cleaning of the wafer Wc by the cleaner device 17 in Step 122 and cleaning of the holder surface of the first chuck table 31 in Step 123 are performed simultaneously (the two cleaning processes are performed at least partly in the same time period), but the two cleaning processes may not necessarily be started and finished at exactly the same time.

[0145] Optionally, in a case where, after polishing the C surface of the wafer Wc in Step 119, the holder surface of the first chuck table 31 suctioning and holding the Si surface of the wafer Wc is not substantially dirty, cleaning of the holder surface of the first chuck table 31 in Step 123 may be omitted.Step 124: Invert the Wafer Wc

[0146] As cleaning of the wafer Wc by the cleaner device 17 in Step 123 is completed, the controller 14 operates the conveyer robot 15 to invert the wafer Wc in Step 124. An operation to invert the wafer Wc with the conveyer robot 15 is performed in the same manner as the operation to invert the wafer Wb in Step 109 described earlier; therefore, detailed description of the operation with the wafer Wc is herein omitted.

[0147] In Step 124, the wafer Wc is inverted after being cleaned by the wafer upper-surface cleaner device 60 in Step 120 and / or by the cleaner device 17 in Step 122; therefore, in a case where the conveyer robot 15 is used as the inverting assembly, the conveyer robot 15 may be prevented from being dirtied by the slurry or the swarf.Step 125: Load the First Chuck Table 31 With the (Inverted) Wafer Wc

[0148] Next, in Step 125, the controller 14 operates the conveyer assembly 70 to move the inverted wafer Wc from the cleaner device 17 and load the first chuck table 31 located at the C-surface polishing position with the wafer Wc. An operation to load the first chuck table 31 with the inverted wafer Wc is performed in the same manner as the operation to load the second chuck table 32 with the wafer Wb in Step 110 described earlier; therefore, detailed description of the operation with the wafer Wc is herein omitted.

[0149] The series of the operations and the processes from Step 113 to Step 125 is performed while the Si surface of the wafer Wb is being polish-processed in Step 112. In other words, the long time period required to polish-process the Si surface of the n+1th wafer Wb is effectively used to perform the process related to the nth wafer Wa of which both surfaces have been polished and the process related to polish-processing of the C surface of the n+2th wafer Wc simultaneously.

[0150] More specifically, in parallel to the polish-processing of the Si surface of the wafer Wb (Step 112), post-processing after polish-processing of the Si surface of the wafer Wa (Steps 113-117) including cleaning of the Si surface and unloading of the wafer Wa, preparation for polish-processing of the C surface of the wafer Wc (Step 118), polish-processing of the C surface of the wafer Wc (Step 119), post-processing after polish-processing of the C surface of the wafer Wc (steps 120-123), and a preparation operation including inverting of the wafer Wc for the Si surface of the wafer Wc to be polish-processed next (Steps 124-125) are performed. As such, as shown in FIG. 9B, before polish-processing of the Si surface of the wafer Wb (Step 112) is completed, final preparation (Step 125) for polish-processing of the Si surface of the next wafer Wc is completed.

[0151] The time chart shown in FIG. 9B ends at the point when the operation to polish-process the Si surface of the n+1th wafer Wb (Step 112) is finished. However, after completion of Step 112, a process to rotate the turntable 30 by 180 degrees and unload the wafer Wb, of which both surfaces are finished with polishing, to store in the cassette 11, and a process to polish the Si surface of the wafer Wc being the n+2th wafer are continued. The operations in these processes are performed in the same manner as the operations of conveying and storing the wafer Wa in the cassette 11 and polishing of the Si surface of the wafer Wb; therefore, detailed description of those is herein omitted.

[0152] Furthermore, after the n+2th wafer Wc, more wafers W such as an n+3th wafer W and an n+4th wafer W may be polish-processed. Operations and processes to these subsequent wafers W in the polishing apparatus 10 may be performed by repeating the same operations and the processes as those to the three wafers Wa, Wb, Wc described above. Therefore, description of those is herein omitted.

[0153] As described above, the polishing apparatus 10 in the present embodiment includes the polishing assembly 40 to polish the wafer W (SiC wafer) located at the polishing position with the polishing pad 47 and the C-surface polishing assembly 50 to polish the C surface of the wafer W held by chuck table 31 or 32 which is not located at the polishing position (but is located at the C-surface polishing position) with C-surface polishing pad 58; and the polishing assembly 40 and the C-surface polishing assembly 50 polish the respective surfaces (Si surface and C surface) of each of the wafers W. The polishing apparatus 10 configured as above may, while operating the polishing assembly 40 to polish-process the Si surface of the wafer W, operate the C-surface polishing assembly 50 to polish-process the C surface of another wafer W.

[0154] In other words, the polishing apparatus 10 may use the time, in which the Si surface of the preceding first wafer W is polish-processed (Steps 102 and 112), to polish-process the C surface of the following second wafer W (Steps 104 and 119). Accordingly, while the Si surface of the first wafer W being a SiC wafer is being polish-processed, the time in which the next second wafer W waits may be effectively utilized to shorten the total processing time, thereby improving the processing efficiency with the polishing apparatus 10.

[0155] The above series of operations explains an example, where three wafers Wa, Wb, Wc are polished consecutively as a single cycle, which are in a relationship such that the wafer Wb being the n+1th wafer is the reference wafer, and the wafers Wa, Wc are processed before and after the reference wafer. However, the effect of reducing the total processing time by using the polishing apparatus 10 is achievable when a number of the wafers S to be consecutively polish-processed is at least two. In other words, the number of the wafers W to be consecutively processed by the polishing apparatus 10 is not limited to three or more, but the effect is also achievable when the number of the wafers W is two. Moreover, the effect to reduce the total processing time may also be achievable when the number of the wafers W to be polish-processed continuously is four or more.

[0156] In consideration of the above as a description of a polishing method to be implemented by the polishing apparatus 10 for polishing at least two SiC wafers, the notable effect to reduce the total processing time is achievable by performing, while the Si surface of the first wafer W held on one of at least two chuck tables 31 or 32 arranged on the turntable 30 is being polished with the polishing pad 47, at least the first holding process (Step 103, Step 118), in which the second wafer W is held on another of the at least two chuck tables 31 or 32 with the C surface facing upward; the C-surface polishing process (Step 104, Step 119), in which the C-surface of the second wafer W is polished with the C-surface polishing pad 58; and the second holding process (Sep 109 and Step 110, Step 124 and Step 125), in which the second wafer W is separated from the another chuck table, inverted, and held on the another chuck table with the Si surface thereof facing upward.

[0157] For example, in a case where the first wafer is regarded as the wafer Wa being the nth wafer and the second wafer is regarded as the wafer Wb being the n+1th wafer, Step 103 is the first holding process, Step 104 is the C-surface polishing process, and Step 109 and step 110 are each the second holding process. Meanwhile, the one of the chuck tables corresponds to the first chuck table 31, and the another of the chuck tables corresponds to the second chuck table 32.

[0158] For another example, in a case where the first wafer is regarded as the wafer Wb being the n+1th wafer and the second wafer is considered as the wafer Wc being the n+2th wafer, Step 118 is the first holding process, Step 119 is the C-surface polishing process, and Step 124 and step 125 are each the second holding process. Meanwhile, the one of the chuck tables corresponds to the second chuck table 32, and the another of the chuck tables corresponds to the first chuck table 31.

[0159] Moreover, in a case where the second wafer is regarded as the wafer Wc, before the first holding process, Step 114 being the unloading process, in which the wafer Wa being the nth wafer (the second wafer in a previous cycle) is unloaded from the first chuck table 31 being the another one of the chuck tables, is performed. Thereby, the two chuck tables 31, 32 may be loaded or unloaded with three or more wafers W sequentially, and double-sided polishing may be consecutively performed and efficiently.

[0160] According to the polishing apparatus 10 and the polishing method of the present embodiment, various operations and processes are performed in addition to the polish-processing to the C surface of the subsequent second wafer W, using the time period for polish-processing to the Si surface of the preceding first wafer W, thereby improving the processing efficiency even more. In particular, the multiple processes to be performed usefully in the time period to polish-process the Si surface of the wafer W include loading the chuck table 31 or 32 located at the C-surface polishing position with the wafer W (Steps 103, 110, 118, 125), cleaning the upper surface of the polish-processed wafer W held on the chuck table 31 or 32 (Steps 105, 113, 120), unloading the wafer W from the chuck table 31 or 32 (Steps 106, 114, 121), cleaning the wafer W with the cleaner device 17 (Steps 107, 115, 122), cleaning the holder surface of the chuck table 31 or 32 from which the wafer W has been unloaded and conveyed to the cleaner device 17 (Steps 108, 117, 123), inverting the wafer W for switching the surface to be polished from the C surface to the Si surface (Step 109, 124), and storing the wafer W of which both surfaces have been polished in the cassette 11 (Step 116). Moreover, as shown in the time chart in FIGS. 9A and 9B, among these multiple processes, processes that may be performed in parallel at different locations in the polishing apparatus 10 are set to be performed in parallel to one another as many as possible, thereby improving the time usage efficiency.

[0161] The polishing apparatus 10 is configured such that the two chuck tables 31, 32 are arranged on the turntable 30, the Si surface of the wafer W held on one of the chuck tables 31, 32 located at the polishing position is polished by the polishing assembly 40, and the C surface of the wafer W held on another of the chuck tables 31, 32 located at the C surface polishing position is polished by the C-surface polishing assembly 50, which is a relatively simple configuration as a polishing apparatus of a type that may polish the surfaces of the wafer are polished by the different polishing assemblies (40, 50).

[0162] While the polishing assembly 40 polishes the Si surface of the wafer W, there is a restriction that the turntable 30 should not be rotated. Therefore, the polishing apparatus 10 of the present embodiment is configured such that the chuck table 31 or 32 located at the C-surface polishing position may be, without rotating the turntable 30, accessed by both the C-surface polishing assembly 50 and the conveyer assembly 70 without interfering with each other. In particular, the C-surface polishing assembly 50 is supported by the Y-axis movable assembly 51 so as to retract toward the +Y direction side, and the conveyer assembly 70 is supported by the Y-axis movable assembly 76 so as to retract toward the −Y direction side. According to this configuration, the operations of polish-processing with the C surface of the wafer W by the C-surface polishing assembly 50 and loading / unloading of the wafer W by the conveyer assembly 70 with the chuck table 31 or 32 located at the C-surface polishing position may be performed at any desirable timing. As a result, the processes that may be performed in parallel to the polishing of the Si surface of the wafer W by the polishing assembly 40 are not necessarily limited to the polish-processing of the C surface of the wafer W by the C-surface polishing assembly 50. As such, the various processes as described above are processible in parallel to one another.

[0163] Moreover, the wafer upper-surface cleaner device 60 and holder surface cleaner nozzles 61 are arranged also in the configuration not interfering with the operations of the C-surface polishing assembly 50 or the conveyer assembly 70. Therefore, while the Si surface of the wafer W is being polish-processed by the polishing assembly 40, the wafer upper-surface cleaner device 60 may clean the upper surface of the wafer W, or the holder surface of the chuck table 31 or 32 may be cleaned with the holder-surface cleaner nozzle 61, at any desired timing without rotating the turntable 30.

[0164] The configuration and the operations in the polishing apparatus 10 in the above embodiment is merely an example and is not limited to those as described in the above embodiment.

[0165] As a modified example, the polishing apparatus 10 of the above embodiment may be configured to have three or more chuck tables on the turntable. For example, three chuck tables may be arranged on the turntable, and three positions corresponding to the three chuck tables, including a third position being a load / unload position additionally to the polishing position and the C-surface polishing position, may be provided. The load / unload position is a position where the wafer is passed between the conveyer assembly and one of the chuck tables. In other words, the modified example is in a configuration such that one of the chuck tables located at the C-surface polishing position is not loaded or unloaded with the wafer.

[0166] However, according to the configuration of the modified example, loading and unloading of the chuck table with a wafer and polish-processing of the C surface of the wafer on the chuck table are performed at different positions on the turntable. Therefore, in order to load and unload the chuck table with the wafer before and after the C surface of the wafer is polish-processed, the turntable needs to be rotated. This causes the polish-processing operation with the Si surface of the wafer to be temporarily interrupted for the rotation of the turntable.

[0167] Therefore, from a perspective of processing efficiency to process other multiple operations without interrupting the polish-processing operation with the Si surface, it is preferable that the polishing apparatus is provided with two chuck tables 31, 32 that are located alternately at the polishing position and the C-surface polishing position, enabling both the polish-processing operation with the C surface and loading / unloading of the chuck table concentratively at the C-surface polishing position, as it is in the polishing apparatus 10 in the embodiment described above.

[0168] The polishing apparatus 10 in the above embodiment uses the conveyer robot 15 as the inverting assembly that may invert the wafer W upside-down to switch the surface to be polished from the C surface to the Si surface. The conveyer robot 15 is usable widely in operations such as loading and unloading the cassette 11 with wafers Wand is enabled to invert the robot hand 18 vertically by the rotating device 19. Therefore, by using the conveyer robot 15 to function as the inverting assembly, it is advantageous that the operations in the above embodiment are performable without requiring an additional new mechanism. However, the polishing apparatus may optionally be provided with an inverting assembly other than the conveyer robot 15.

[0169] As another modified example, the polishing apparatus 10 of the above embodiment may be configured to have a dedicated inverting assembly that may hold the wafer W on the chuck table 31 or 32 located at the C-surface polishing position directly, and lift and invert the wafer W. For another example, a conveyer assembly corresponding to the conveyer assembly 70 in the above embodiment may be provided with a function to invert the wafer W upside-down. In the cases of these modified examples, the operation to unload the wafer W, of which C surface has been polished, from the chuck table 31 or 32 and move to the cleaner device 17 may be omitted, and the wafer W may be placed back on the chuck table 31 or 32 immediately after being inverted to have the Si surface to be polished next.

[0170] The polishing apparatus 10 according to the above embodiment may, after polish-processing the upper surface of the wafer W, clean the upper surface of the wafer W being held on the chuck table 31 or 32 with the wafer upper-surface cleaner device 60 and, further, clean the holder surface of the chuck table 31 or 32 after unloading the wafer W with the mixed fluid jetted from the holder-surface cleaner nozzle 61. By cleaning the upper surface of the wafer W and chuck table 31 or 32 each time the polish-processing operation is completed, advantages such as improved holding ability of the conveyer pad 71 and the chuck tables 31, 32 to suction and hold the wafer W and improved processing accuracy to polish-process the next wafer W may be achieved. However, an option to not perform a part or an entirety of these cleaning operations as processes to be performed in parallel to the operation to polish-process the Si surface of the wafer W is also available.

[0171] For example, the upper surface of the wafer W on the chuck table 31 or 32 may be cleaned each time after polishing the Si surface and the C surface of each wafer W, while the holder surface of the chuck table 31 or 32 may be cleaned each time when a number of polish-processing operations with the upper surfaces of the wafers W reaches a predetermined number larger than or equal to two.

[0172] For another example, depending on differences in processing conditions such as the type of polishing pad and slurry used for polishing, an operation such that, in a case where cleaning after the polish-processing operation is considered to be particularly necessary, the controller 14 adds the process to clean the wafer W or the holder surface with the wafer upper-surface cleaner device 60 or the holder-surface cleaner nozzle 61 to the operation, but in the other cases, the controller 14 precludes the process to clean the wafer W or the holder surface with the wafer upper-surface cleaner device 60 or the holder-surface cleaner nozzle 61 from the operation, may be applicable.

[0173] For another example, depending on the configuration of the conveyer assembly to convey the wafer W between the chuck table 31 or 32 and the cleaner device 17, whether the wafer W is to be cleaned with the wafer upper-surface cleaner device 60 or not may be changed. For example, in a case where a conveyer assembly that may hold the wafer W partly at an outer peripheral edge of the wafer W to convey is used, compared to the conveyer assembly 70 in the above embodiment that has the conveyer pad 71 that may suction and hold the entire upper surface of the wafer W, the dirt on the upper surface of the wafer W may not directly affect the conveying ability of the conveyer assembly. Therefore, an option not to clean the wafer W with the wafer upper-surface cleaner device 60 may be applicable.

[0174] The polishing apparatus 10 according to the above embodiment is configured to clean the upper surface of the wafer W with the wafer upper-surface cleaner device 60 and clean the holder surfaces of the chuck tables 31, 32 with the mixed liquid jetted from the holder-surface cleaner nozzle 61. However, optionally, the upper surface of the wafer W and the holder surfaces of the chuck tables 31, 32 may be cleaned with a common cleaner device located in vicinity of the turntable 30.

[0175] In the above embodiment, the wafer W is conveyed to the chuck tables 31, 32 by the conveyer assembly 70; however, the wafer W may optionally be conveyed by a person (worker) to the chuck tables 31, 32. For another example, a person (worker) instead of the inverting assembly (conveyer robot 15) may invert the wafer W. FIG. 10 illustrates a polishing apparatus 80 of the type, in which wafer W may be conveyed to the chuck tables 31, 32 and inverted by a worker.

[0176] The polishing apparatus 80 has, similarly to the polishing apparatus 10 as above, two chuck tables 31, 32 arranged on the turntable 30 and is provided with the polishing assembly 40 and the C-surface polishing assembly 50. The configurations of the polishing assembly 40, the lift / lower assembly 41, the C-surface polishing assembly 50, the Y-axis movable assembly 51, and the lift / lower assembly 52 are the same as those of the above polishing apparatus 10. The polishing apparatus 80 is not equipped with the cassette stages 13, the conveyer robot 15, the temporary placement table 16, the cleaner device 17, the wafer upper-surface cleaner device 60, the holder-surface cleaner nozzle 61, or the conveyer assembly 70 that are provided in the above polishing apparatus 10.

[0177] For polishing the surfaces on both sides of the wafer W being a SiC wafer in the polishing apparatus 80, loading and unloading the chuck table 31 or 32 located at the C-surface polishing position with the wafer W (operations corresponding to Steps 100, 103, 106, 110, 114, 118, 121, 125 in FIGS. 9A and 9B) and inverting the wafer W of which C surface has been polished (operations corresponding to Steps 109 and 124) may be performed manually by the worker. More specifically, while the Si surface of the first wafer W held on one of the two chuck tables 31, 32 is being polished with the polishing pad 47, with regard to the first holding process (corresponding to Steps 103 and 118), in which the second wafer W is held on the other of the chuck tables 31, 32 with the C surface facing upward, an operation in the first holding process up to placing the second wafer W on the other of the chuck tables 31, 32, may be performed by the worker, and another operation in the first holding process to suction and hold the second wafer W placed on the other of the chuck tables 31, 32 may be performed under the control of the controller 14. After polishing the C surface, with regard to the second holding process (corresponding to Steps 109, 110, and Steps 124, 125), in which the second wafer W is separated from the other of the chuck tables 31, 32, inverted, and held on the other of the chuck tables 31, 32 with the Si surface facing upward, a part of the second process to separate the second wafer W from the other of the chuck tables 31, 32 and invert and place the second wafer W once again on the other of the chuck tables 3132 may be performed by the worker, and another part of the second holding process to release the second wafer W from the suctioning and holding force of the holder surface of the other of the chuck tables 31, 32 and to suction and hold the second wafer W once again may be performed under the control of the controller 14 in the polishing apparatus 80.

[0178] While the polishing apparatus 80 does not have the configuration to clean the wafer W or the chuck tables 31, 32, the steps related to cleaning of these items in the time chart shown in FIGS. 9A and 9B (Steps 105, 107, 108, 113, 115, 117, 120, 122, 123) are omitted.

[0179] According to the polishing apparatus 80 described above, while the Si surface of the first wafer W is being polished with the polishing pad 47 of the polishing assembly 40 (corresponding to Steps 102 and 112), the C surface of the second wafer W may be polished with the C-surface polishing pad 58 of the C-surface polishing assembly 50 (corresponding to Steps 104 and 119), and thereby the time required for polishing the both surfaces of the wafer W may be reduced. Moreover, while the first holding process and the second holding process that are performed before and after polishing of the C surface of the wafer W may be performed manually by the worker (conveying and inverting the wafer W) and by the automated operation of the polishing apparatus 80 (control to suction the wafer W on the holder surface of the chuck table 31, 32), these processes may be performed while the Si surface of the first wafer is being polished with the polishing pad 47 of the polishing assembly 40, and thereby the total processing time with the polishing apparatus 80 may be reduced.

[0180] Embodiment of the present disclosure may not necessarily be limited to the configuration described above and in the modified example but may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of the present disclosure. Furthermore, if the technical idea of the present disclosure may be realized in a different way due to technological progress or other derived technology, it may be implemented with use of the method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of the present disclosure.

[0181] As explained above, according to the polishing apparatus and the polishing method of the present disclosure, while the SiC wafer is being polish-processed, the time in which the next SiC wafer waits is utilized, and thereby the productivity of the SiC wafers may be improved, which contributes improvement of supply of the SiC wafers and reduction of the manufacturing costs.

Claims

1. A polishing apparatus configured to polish SiC wafers, comprising:at least two chuck tables configured to hold the SiC wafers;a turntable, on which the at least two chuck tables are arranged;a polishing assembly configured to polish a surface of one of the SiC wafers held on one of the at least two chuck tables located at a polishing position with a polishing pad, the one of the at least two chuck tables being located at the polishing position by rotation of the turntable; anda C-surface polishing assembly configured to, while the SiC wafer held on the one of the at least two chuck tables located at the polishing position in the polishing assembly is being polish-processed, polish a C surface of another SiC wafer held on another of the at least two chuck tables not located at the polishing position with a C-surface polishing pad,wherein the polishing assembly and the C-surface polishing assembly polish the respective surfaces of each of the SiC wafers.

2. The polishing apparatus according to claim 1, further comprising a conveyer assembly configured to load and unload the at least two chuck tables with the SiC wafers.

3. The polishing apparatus according to claim 1, further comprising an inverting assembly configured to invert the another SiC wafer held on the another of the at least two chuck tables not located at the polishing position vertically.

4. A method for polishing surfaces on both sides of each of a plurality of SiC wafers, while a Si surface of a first SiC wafer being one of the plurality of SiC wafers held on one of at least two chuck tables arranged on a turntable is being polished with a polishing pad, comprising a cycle of at least:a first holding process for causing a second SiC wafer being another one of the plurality of SiC wafers to be held on another of the at least two chuck tables with a C surface thereof facing upward;a C-surface polishing process for polishing the C surface of the second SiC wafer with a C-surface polishing pad; anda second holding process for separating the second SiC wafer from the another of the at least two chuck tables, inverting the second SiC wafer, and causing the second SiC wafer to be held on the another of the at least two chuck tables with a Si surface of the second SiC wafer facing upward.

5. The method according to claim 4, further comprising, an unloading process for, before the first holding process, unloading another one of the plurality of SiC wafers, which is the second SiC wafer in a previous cycle, from the another of the at least two chuck tables.

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