Method and apparatus for grinding wafers

Abstract

To finish a wafer so as to have a uniform thickness after grinding, in grinding wafers with an upwardly warped outer peripheral side.SOLUTION: In a first grinding step, a wafer 10 is ground while an outer peripheral part is supported by an elastic member 217 and force of warping up the wafer 10 is weakened. In a subsequent second holding step, the entire lower surface of the wafer 10 can be sucked and held. In a second grinding step, grinding is performed while the entire lower surface of the wafer 10 is sucked and held, so that the entire surface including the outer peripheral part of the wafer 10 can be finished flat. Accordingly, a risk that a device 12 formed near the outer periphery of the wafer 10 becomes defective can be reduced.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for grinding a warped wafer.

Background Art

[0002] As a chuck table for holding a wafer having an element with the outer peripheral side warping upward, there is a configuration including a suction surface for sucking the lower surface of the central portion of the wafer and an annular elastic member (such as a sponge, a rubber plate, a rubber tube, etc.) that contacts the lower surface of the outer peripheral portion of the wafer. When the wafer held on this chuck table is ground with a grinding wheel, since the elastic member is crushed by the grinding load, leakage of the suction force can be prevented and the wafer can be securely sucked and held (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the elastic member is crushed during grinding, a thick portion is formed in the portion of the wafer supported by the elastic member, so that there is a problem that a thick portion is formed annularly and the outer peripheral edge is formed thin.

[0005] The present invention has been conceived in view of such problems, and an object thereof is to finish a wafer with an upward warped outer peripheral side to a uniform thickness.

Means for Solving the Problems

[0006] The present invention relates to a wafer grinding method comprising holding a wafer with a curved outer edge by suction along the suction surface of a chuck table and grinding the wafer with a grinding wheel, The device comprises a suction member having a first suction surface for sucking the lower surface of a wafer, and a frame that supports the suction member from the outer periphery and below, wherein the upper surface of the frame has a ring-shaped recess with a ring-shaped opening, and an elastic member formed in the shape of a rubber plate is housed in the recess and protrudes upward from the upper surface of the frame. With the elastic member in contact with the lower surface of the outer periphery of the warped wafer, A first holding step of holding the wafer by suction on the first suction surface, and the wafer held by suction on the first suction surface The grinding wheel is brought into contact with the upper surface, and the grinding load applied by the grinding wheel pressing the wafer causes the elastic member to sink into the recess, while the wafer with its lower surface entering the recess is The material is ground down to a thickness that does not reach the final thickness using a grinding wheel. A ring-shaped, thicker section is formed on the outer circumference. Wafer warping The force that tries to A first grinding step to weaken the first suction surface suction The process comprises: a transport step of transporting the held wafer to the second suction surface of a second chuck table equipped with a porous member having a second suction surface that sucks the entire lower surface of the wafer; a second holding step of suctioning and holding the wafer, which has been ground to a thickness not reaching the finish thickness, on the second suction surface; and a second grinding step of grinding the wafer held by suction on the second suction surface to the finish thickness using a grinding wheel. In this wafer grinding method, it is preferable to use a coarse grinding wheel in the first grinding step and a finish grinding wheel in the second grinding step. Furthermore, the present invention relates to a grinding apparatus for grinding a wafer whose outer periphery is curved upward using a grinding wheel, comprising: a suction member having a first suction surface for sucking the lower surface of the wafer; a frame supporting the suction member from the outer periphery and below; the upper surface of the frame having a ring-shaped recess formed by a ring-shaped opening; and an elastic member formed in the shape of a rubber plate housed in the recess and protruding upward from the upper surface of the frame, the elastic member being brought into contact with the lower surface of the outer periphery of the curved wafer, and a first chuck table for sucking and holding the wafer at the first suction surface; and the wafer held at the first suction surface The grinding wheel is brought into contact with the upper surface, and the grinding load applied by the grinding wheel to the wafer causes the elastic member to sink into the recess, while the wafer, with its lower surface entering the recess, Grinding with a grinding wheel Furthermore, a ring-shaped, thicker portion is formed on the outer edge to weaken the force that causes the wafer to warp upwards.A first grinding mechanism, a second chuck table equipped with a porous member having a second suction surface that sucks the entire lower surface of a wafer, and a second grinding mechanism that grinds the wafer held by suction on the second suction surface with the grinding wheel, The wafer, which is held on the first suction surface and has a ring-shaped thick portion formed on its outer circumference, The system includes a conveying mechanism that transports from the first suction surface to the second suction surface. [Effects of the Invention]

[0007] In the wafer grinding method according to the present invention, in the first grinding step, the wafer is ground while its outer periphery is supported by an elastic member, thereby weakening the force that causes the wafer to warp upward. This makes it possible to hold the entire surface of the wafer by suction in the subsequent second holding step. Furthermore, in the second grinding step, grinding is performed while the entire lower surface of the wafer is held by suction, so the entire surface of the wafer, including the outer periphery, can be finished flat. Therefore, the risk of defects in devices formed near the outer periphery of the wafer is reduced. Furthermore, the grinding apparatus according to the present invention includes an annular elastic member that contacts the lower surface of the outer periphery of the wafer with the first chuck table and a first suction surface that sucks the lower surface of the wafer inside the first chuck table, a second suction surface that sucks the entire lower surface of the wafer with the second chuck table, and a transport mechanism that transports the wafer from the first suction surface to the second suction surface. Therefore, it is suitable for carrying out the above wafer grinding method and makes it possible to automate a series of processes until the entire surface of the wafer is finished flat. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing an example of a grinding machine. [Figure 2] This is a schematic cross-sectional view showing a chuck table and a warped wafer. [Figure 3] This is a schematic cross-sectional view showing the first grinding process. [Figure 4] This is a schematic cross-sectional view showing the second grinding process. [Modes for carrying out the invention]

[0009] The grinding apparatus 1 shown in Figure 1 is used for wafers. 10 The system includes a first chuck table 21 and a second chuck table 22 for suction and holding the wafer, a first grinding mechanism 3 for grinding the wafer 10 held on the first chuck table 21, and a second grinding mechanism 4 for grinding the wafer 10 held on the second chuck table 22.

[0010] The front of the grinding apparatus 1 is provided with cassette mounting areas 61 and 62 on which cassettes 610 and 620 for housing wafers 10 are placed. For example, wafers 10 before grinding are stored in cassette 610, and wafers 10 after grinding are stored in cassette 620.

[0011] A robot 63 is positioned behind the cassette mounting area (+Y side) to load and unload wafers 10 into and out of cassettes 610 and 620. The robot 63 comprises a hand 631 for suction and holding the wafers 10, a reversing drive unit 632 for reversing the front and back of the hand 631, and an arm 633 connected to the reversing drive unit 632 for rotating and raising / lowering the hand 631.

[0012] A temporary placement mechanism 64 is provided within the range of motion of the hand 631 for temporarily placing the wafer 10 before grinding. The temporary placement mechanism 64 includes a mounting table 641 on which the wafer 10 is placed, and a plurality of positioning pins 642 arranged in an arc shape and movable radially toward the center of the mounting table 641. With the wafer 10 placed on the mounting table 641, the plurality of positioning pins 642 move toward each other, thereby aligning the wafer 10 to a predetermined position.

[0013] Within the range of motion of the hand 631, a cleaning mechanism 65 for cleaning the ground wafer 10 is positioned in the same direction as the temporary placement mechanism 64 in the X-axis direction. The cleaning mechanism 65 includes a spinner table 651 for suction-holding the ground wafer 10 and a nozzle 652 for spraying cleaning fluid onto the wafer 10 held on the spinner table 651.

[0014] The first chuck table 21 and the second chuck table 22 are driven by a horizontal movement mechanism (not shown) and are movable in the Y-axis direction. A transfer mechanism 7 for transferring the wafer 10 is disposed between the movement paths of the first chuck table 21 and the second chuck table 22 in the Y-axis direction. This transfer mechanism 7 is disposed at the position 70 in FIG. 1.

[0015] The transfer mechanism 7 includes a portal-shaped wall portion 71, a ball screw 72 disposed on one surface side of the wall portion 71 and having an axis in the Y-axis direction, a pair of guide rails 73 disposed in parallel with the ball screw 72, a motor 74 connected to one end of the ball screw 72 for rotating the ball screw 72, and a slide portion 75 having a nut screwed onto the ball screw 72 inside and having its side portion slidably contacting the guide rail 73. When the motor 74 rotates the ball screw 72, the slide portion 75 is guided by the guide rail 73 and moves in the Y-axis direction.

[0016] On the side surface of the slide portion 75, a lifting mechanism 8 for lifting and lowering a suction holding portion 89 for sucking and holding the upper surface of the wafer 10 is disposed. The lifting mechanism 8 includes a ball screw 81 having an axis in the Z-axis direction, a guide rail 82 disposed in parallel with the ball screw 81, a motor 83 connected to one end of the ball screw 81 for rotating the ball screw 81, and a lifting member 84 having a nut screwed onto the ball screw 81 inside and having its side portion slidably contacting the guide rail. When the motor 83 rotates the ball screw 81, the lifting member 84 is guided by the guide rail 82 and moves up and down in the Z-axis direction.

[0017] The lifting member 84 supports the swivel mechanism 85. The swivel mechanism 85 comprises a shaft portion 86 hanging down from the lifting member 84, a motor 87 connected to the upper end of the shaft portion 86, and an arm 88 connected to the lower end of the shaft portion 86, with a suction holding portion 89 connected to the tip of the arm 88. When the motor 87 rotates the shaft portion 86, the arm 88 swivels, causing the suction holding portion 89 to rotate around the shaft portion 86. The suction holding portion 89 can move between the front side (+X direction side) and the back side (-X direction side) of the wall portion 71 by rotating, and can move from the movement path of the first chuck table 21 to the movement path of the second chuck table 22. Furthermore, when the motor 74 rotates the ball screw 72, the slide portion 75 is guided by the guide rail 73 and moves in the Y-axis direction, causing the suction holding portion 89 to also move in the Y-axis direction. In addition, when the motor 83 rotates the ball screw 81, causing the lifting member 84 to move up and down in the Z-axis direction, the suction holding portion 89 also moves up and down in the Z-axis direction. The lower part of the suction holding unit 89 is equipped with a suction pad connected to a suction source (not shown).

[0018] The first grinding mechanism 3 comprises a spindle 30 having a rotation axis extending in the Z-axis direction, a spindle rotation mechanism 31 for rotating the spindle 30, a spindle housing 32 for rotatably supporting the spindle 30, a mount 33 connected to the lower end of the spindle 30, and a grinding wheel 34 mounted on the mount 33. When the spindle rotation mechanism 31 rotates the spindle 30, the grinding wheel 34 also rotates. The grinding wheel 34 consists of a base 340 fixed to an annular mount 33 having an opening in the center, and a plurality of grinding wheels 341 fixed in an annular shape to the lower surface of the base 340. The grinding wheels 341 are, for example, coarse grinding wheels with relatively large abrasive grain sizes.

[0019] The second grinding mechanism 4 is configured in the same way as the first grinding mechanism 3, except for the grinding wheel 342. The grinding wheel 342 is a finishing grinding wheel with a smaller abrasive particle size than the grinding wheel 341 of the first grinding mechanism 3. The parts other than the grinding wheel 342 are given the same reference numerals as the first grinding mechanism 3, and their descriptions are omitted.

[0020] The first grinding mechanism 3 and the second grinding mechanism 4 are each supported so as to be able to move up and down by a grinding feed mechanism 5 having the same structure. The grinding feed mechanism 5 includes a ball screw 50 having a rotation axis in the Z-axis direction, a motor 51 for rotating the ball screw 50, a pair of guide rails 52 arranged parallel to the ball screw 50, a lifting plate 53 whose side slides against the guide rails 52 and has a nut (not shown) inside that screws onto the ball screw 50, and a holder 54 connected to the lifting plate 53 and supporting the spindle housing 32. When the ball screw 50 rotates, the lifting plate 53 is guided by the guide rails 52 and moves in the Z-axis direction, and the first grinding mechanism 3 also moves in the Z-axis direction accordingly.

[0021] As shown in Figure 2, the first chuck table 21 consists of a suction member 211 made of porous material and a frame 212 that supports the suction member 211 from the outer periphery and below. The first suction surface 213, which is the surface of the suction member 211, sucks the lower surface 101 of the warped wafer 10. The first suction surface 213 is formed to be smaller in diameter than the warped wafer 10. The first suction surface 213 is also formed flush with the upper surface 214 of the frame 212. An annular recess 215 is formed on the outer periphery of the first suction surface 213, i.e., the outer periphery of the upper surface 214 of the frame 212. A space 216 is formed in the recess 215, extending from the bottom of the space toward the center of the first chuck table 21. An elastic member 217 is housed in the recess 215, with one end fixed in the space 216 and the other end protruding above the upper surface 214. The elastic member 217 is formed in an annular shape from, for example, a sponge or a rubber sheet, and has a bent portion 218 that bends upward from the portion housed in the space 216. When a warped wafer 10 is held by suction on the first suction surface 213, the bent portion 218 bends and the elastic member 217 comes into contact with the outer circumference of the lower surface 101 of the wafer 10. The outer circumference of the wafer 10 also comes into contact with the upper surface 214 of the frame 212. The upper surface of the recess 215 is then closed by the lower surface 101 of the wafer 10.

[0022] The upper end of the rotating shaft 231 is connected to the lower part of the frame 212. The lower end of the rotating shaft 231 is rotatably supported by a support part 232. A driven pulley 233 is arranged around the rotating shaft 231, and a drive pulley 234 is arranged to the side of the driven pulley 233. The drive pulley 234 is driven by a motor 235. A belt 236 is wound around the drive pulley 234 and the driven pulley 233. When the drive pulley 234 is driven by the motor 235 and rotates, the rotational force is transmitted to the driven pulley 233 by the belt 236, causing the rotating shaft 231 to rotate and the first chuck table 21 to rotate.

[0023] A fluid passage 241 is formed through the frame 212, the rotating shaft 231, and the support portion 232. One end of the fluid passage 241 opens onto the upper surface of the frame 212 and communicates with the suction member 211. The other end of the fluid passage 241 branches into three paths, each of which is connected to a suction source 245, an air supply source 246, and a water supply source 247 via valves 242, 243, and 244. A pressure gauge 248 is connected to the fluid passage 241 to measure the pressure within the fluid passage 241.

[0024] As shown in Figure 1, the second chuck table 22 comprises a porous member 221 and a frame 222 that supports the porous member 221. The second suction surface 223, which is the surface of the porous member 221, sucks the entire lower surface of the wafer 10. The second suction surface 223 is formed flush with the upper surface 224 of the frame 222. The second chuck table 22 is rotatable by a rotational drive mechanism (not shown) similar to that of the first chuck table 21 shown in Figure 2. Furthermore, the frame 222 of the second chuck table 22 and its lower surface are provided with a flow path 241 connected to a suction source 245, an air supply source 246, and a water supply source 247 via valves 242, 243, and 244, as shown in Figure 2, similar to the first chuck table 21.

[0025] A thickness measuring device 25 is positioned to the side of the movement path of the first chuck table 21 to measure the thickness of the wafer 10 held by the first chuck table 21. The thickness measuring device 25 includes a first measuring unit 251 that measures the height of the upper surface 214 of the frame 212, and a second measuring unit 252 that measures the height of the upper surface 100 of the wafer 10 held by the first suction surface 213. The thickness of the wafer 10 is calculated based on the difference between the measurement value of the first measuring unit 251 and the measurement value of the second measuring unit 252.

[0026] A thickness measuring device 26 is positioned to the side of the movement path of the second chuck table 22 to measure the thickness of the wafer 10 held by the second chuck table 22. The thickness measuring device 26 has a first measuring section that measures the height of the upper surface 224 of the frame 222. 261 And, 2 Suction surface 2 2 The second measuring unit 2 measures the height of the upper surface 100 of the wafer 10 which is held in place by suction 3. 6 The system comprises a first measuring unit 2 6 Measurement value 1 and second measurement unit 2 6 The thickness of wafer 10 is calculated based on the difference with the measurement value in 2.

[0027] Next, the operation of the grinding apparatus 1 when grinding the warped wafer 10 shown in Figure 2 will be described. This wafer 10 is constructed by forming a device 12 on a substrate 11, and the device 12 is sealed with resin 13, and has elements that cause it to warp due to the shrinkage of the resin 13, etc.

[0028] Multiple wafers 10 are housed inside the cassette 610 shown in Figure 1. Then, the hand 631 of the robot 63 enters the cassette 610 by the rotation and raising and lowering of the arm 633 and sucks and holds one wafer 10, and then the hand 631 retracts outside the cassette 610. Wafer 10 The wafer 10 is placed on the mounting table 641 of the temporary placement mechanism 64. Then, the positioning pins 642 move toward each other, and the wafer 10 is aligned to the predetermined position.

[0029] (1) First holding step Next, the transport mechanism 7 moves the suction holding unit 89 in the -Y direction, and the rotation mechanism 85 rotates the suction holding unit 89, thereby moving the suction holding unit 89 above the wafer 10 placed on the mounting table 641. Then, the lifting mechanism 8 lowers the suction holding unit 89, and holds the upper surface 100 of the wafer 10 by suction.

[0030] Next, the lifting mechanism 8 raises the suction holding unit 89, the transport mechanism 7 moves the suction holding unit 89 in the +Y direction, and the rotation mechanism 85 rotates the suction holding unit 89, moving the suction holding unit 89 that holds the wafer 10 above the first chuck table 21. Then, the lifting mechanism 8 lowers the suction holding unit 89 so that the lower surface 101 of the wafer 10 is placed on the first chuck table 21. Then, by opening the valve 242 shown in Figure 2 and connecting the suction member 211 of the first chuck table 21 with the suction source 245, a suction force is applied to the first suction surface 213 to hold the lower surface 101 of the wafer 10 by suction. At this time, because the wafer 10 is positioned in a predetermined position by the temporary placement mechanism 64, the center of the first suction surface 213 and the center of the wafer 10 coincide. After that, suction holding Department The suction force of 89 is released, and the lifting mechanism 8 is held in place by suction. Department Increase 89.

[0031] In this way, with the center of the first suction surface 213 and the center of the wafer 10 coincide, the lower surface 101 of the wafer 10, which is curved in accordance with the first suction surface 213, is held in place by suction. The outer circumference of the wafer 10 is curved upwards, and the first suction surface 213 is formed to be smaller in diameter than the wafer 10, so the curved outer circumference of the wafer 10 is not held in place by suction. That is, the lower surface 101 of the wafer 10 is held in place by suction on the inner circumference side of the elastic member 217.

[0032] (2) First grinding process Next, the first chuck table 21 is moved in the +Y direction to position the wafer 10 below the first grinding mechanism 3. Then, as shown in Figure 3, the motor 235 drives the first chuck table 21 to rotate, the spindle rotation mechanism 31 rotates the spindle 30 to rotate the grinding wheel 341, and the grinding feed mechanism 5 shown in Figure 1 lowers the first grinding mechanism 3, causing the rotating grinding wheel 341 to come into contact with the upper surface 100 of the wafer 10. As a result, the curved portion of the wafer 10 is pushed down, and the lower surface 101 comes into contact with the elastic member 217. As shown in an enlarged view in Figure 3, the outer circumference of the lower surface 101 pushes the elastic member 217 downward, preventing the suction force from leaking.

[0033] Then, the grinding feed mechanism 5 further lowers the first grinding mechanism 3 to roughly grind the upper surface 100 of the wafer 10. During grinding, the tip of the first measuring section 251 of the thickness measuring instrument 25 is brought into contact with the upper surface 214 of the frame 212, and the tip of the second measuring section 252 of the thickness measuring instrument 25 is brought into contact with the upper surface 100 of the wafer 10, and the thickness of the wafer 10 is calculated from the difference between the measurement value of the first measuring section 251 and the measurement value of the second measuring section 252. When the calculated value reaches a predetermined thickness, the grinding feed mechanism 5 raises the first grinding mechanism 3 to end the grinding. The predetermined thickness here is a value that does not reach the finish thickness.

[0034] As the resin 13 thins due to the grinding of the wafer 10 in the first grinding process, the element causing the wafer 10 to warp is weakened. In addition, in the first grinding process, the outer peripheral portion of the lower surface 101 of the wafer 10 is ground while supported by the elastic member 217. During grinding, as shown in the enlarged view of Figure 3, the elastic member 217 sinks slightly due to the grinding load that presses the grinding wheel 341 against the wafer 10, and the portion of the wafer 10 supported by the elastic member 217 is slightly recessed into the recess 215. As a result, the portion supported by the elastic member 217 is formed to be slightly thicker, while the outer peripheral portion is formed to be thinner.

[0035] (3) Conveying process Next, the lifting mechanism 8 lowers the suction holding part 89 to hold the upper surface 100 of the roughly ground wafer 10 by suction. Then, the valve 242 is closed to release the suction force acting on the first suction surface 213 of the first chuck table 21, and the valve 243 is opened to eject air from the first suction surface 213. At this time, the valve 244 may also be opened to eject water along with the air from the first suction surface 213. With only air or air and water ejected from the first suction surface 213 in this state, the lifting mechanism 8 raises the suction holding part 89, thereby separating the wafer 10 from the first chuck table 21.

[0036] With the suction holding unit 89 in the raised position, the rotation mechanism 85 rotates the suction holding unit 89 to position it on the +X side relative to the wall 71. Then, the wafer 10 is positioned above the second chuck table 22, and the lifting mechanism 8 lowers the suction holding unit 89, placing the lower surface 101 of the roughly ground wafer 10 onto the second chuck table 22.

[0037] (4)Second holding process Next, the valve 242 shown in Figure 4 is opened to connect the suction source 245 and the second suction surface 223, and a suction force is applied to the second suction surface 223. After that, the suction force of the suction holding part 89 is released, and the lifting mechanism 8 raises the suction holding part 89, causing the suction holding part 89 to separate from the upper surface 100 of the wafer 10. In this way, the entire lower surface 101 of the wafer 10, which has been formed to a thickness not reaching the finish thickness by grinding in the first grinding process, is held by suction from the second suction surface 223 of the second chuck table 22. Because the warping of the wafer 10 is reduced in the first grinding process, the entire lower surface 101 of the wafer 10 can be held by suction from the second suction surface 223. Note that in the first grinding process, the outer periphery of the lower surface 101 of the wafer 10 was supported by the elastic member 217 and ground, so a convex portion 102 that is partially slightly thicker is formed in an annular shape on the wafer 10.

[0038] (5) Second grinding process Next, the roughly ground wafer 10 held on the second chuck table 22 is positioned below the second grinding mechanism 4. Then, as shown in Figure 4, the second chuck table 22 is rotated by the motor 235, and the spindle rotation mechanism 31 rotates the spindle 30 to rotate the grinding wheel 342. Furthermore, the grinding feed mechanism 5 shown in Figure 1 lowers the second grinding mechanism 4, bringing the rotating grinding wheel 342 into contact with the roughly ground upper surface 100. The grinding feed mechanism 5 then lowers the second grinding mechanism 4 further to finish grind the roughly ground upper surface 100 held by the suction of the second suction surface 223. During grinding, the tip of the first measuring section 261 of the thickness measuring instrument 26 is brought into contact with the upper surface 224 of the frame 222, and the tip of the second measuring section 262 of the thickness measuring instrument 26 is brought into contact with the upper surface 100 of the wafer 10. The thickness of the wafer 10 is calculated from the difference between the measurement value of the first measuring section 261 and the measurement value of the second measuring section 262. When the calculated value reaches a predetermined finished thickness, the grinding feed mechanism 5 raises the second grinding mechanism 4 to end the grinding.

[0039] In the second grinding process, grinding is performed while the entire lower surface 101 of the wafer 10 is held in place by suction, so that the convex portion 102 is removed and the entire surface can be finished flat. Therefore, the risk of defects in the device 12 formed near the outer edge of the wafer 10 is reduced. Note that grinding wheels 341 and 342 may be of the same type or of different types. [Explanation of Symbols]

[0040] 1: Grinding device 21: First Chuck Table 211: Suction member 212: Frame 213: First suction surface 214: Top surface 215: recess 216: space 217: elastic member 218: bent portion 22: Second Chuck Table 221: Porous member 222: Frame 223: Second suction surface 224: Top surface 231: Rotating shaft 232: Support part 233: Driven pulley 234: Drive pulley 235: Motor 236: Belt 241: Flow channel 242, 243, 244: Valves 245: Suction source 246: Air supply source 247: Water supply source 248: Pressure gauge 25: Thickness measuring instrument 251: First measuring section 252: Second measuring section 26: Thickness measuring instrument 261: First measuring section 262: Second measuring section 3: First grinding mechanism 4: Second grinding mechanism 30: Spindle 31: Spindle rotation mechanism 32: Spindle housing 33: Mount 34: Grinding Wheel 340: Base 341, 342: Grinding wheel 5: Grinding feed mechanism 50: Ball screw 51: Motor 52: Guide rail 53: Lifting plate 54: Holder 61, 62: Cassette mounting area 610: Cassette 620: Cassette 63: Robot 631: Hand 632: Reversing drive unit 633: Arm unit 64: Temporary placement mechanism 641: Mounting table 642: Positioning pin 65: Cleaning mechanism 651: Spinner table 652: Nozzle 7: Conveying mechanism 71: Wall section 72: Ball screw 73: Guide rail 74: Motor 75: Sliding section 8: Lifting mechanism 81: Ball screw 82: Guide rail 83: Motor 84: Lifting / lowering member 85: Swivel mechanism 86: Shaft 87: Motor 88: Arm 89: Suction holding part 10: Wafer 11: Substrate 12: Device 100: Top surface 101: Bottom surface 102: Convex part

Claims

1. A wafer grinding method comprising: holding a wafer with a curved outer edge by suction along the suction surface of a chuck table, and grinding the wafer with a grinding wheel, A suction member having a first suction surface for sucking the lower surface of a wafer, and a frame supporting the suction member from the outer periphery and below, wherein the upper surface of the frame has a ring-shaped recess with a ring-shaped opening, and an elastic member formed in the shape of a rubber plate is housed in the recess and protrudes upward from the upper surface of the frame, and the wafer is held in place by suction on the first suction surface with the elastic member in contact with the lower surface of the outer periphery of the warped wafer, A first grinding step in which the grinding wheel is brought into contact with the upper surface of the wafer held by suction on the first suction surface, the elastic member is pressed into the recess by the grinding load applied by the grinding wheel, the wafer with its lower surface entering the recess is ground to a thickness not reaching the finish thickness by the grinding wheel, a ring-shaped thicker portion is formed on the outer circumference, and the force that causes the wafer to warp is weakened. A conveying step of conveying the wafer, which is held by suction on the first suction surface, to the second suction surface of a second chuck table equipped with a porous member having a second suction surface that suctions the entire lower surface of the wafer, A second holding step involves suctioning and holding a wafer that has been ground to a thickness not reaching the finish thickness on the second suction surface, A second grinding step in which the wafer held by suction on the second suction surface is ground to the finished thickness using a grinding wheel, Consists of, A method for grinding wafers.

2. In the first grinding process, a coarse grinding wheel is used as the grinding wheel. In the second grinding process, a finishing grinding wheel is used for the grinding wheel. A method for grinding a wafer according to claim 1.

3. A grinding apparatus for grinding a wafer with a curved outer edge using a grinding wheel, A suction member having a first suction surface for sucking the lower surface of a wafer, and a frame supporting the suction member from the outer periphery and below, wherein the upper surface of the frame has a ring-shaped recess formed by a ring-shaped opening, and a first chuck table comprising an elastic member formed in the shape of a rubber plate that is housed in the recess and protrudes upward from the upper surface of the frame, wherein the elastic member is brought into contact with the lower surface of the outer periphery of the warped wafer, and the wafer is sucked and held by the first suction surface, A first grinding mechanism in which the grinding wheel is brought into contact with the upper surface of the wafer held by suction on the first suction surface, the grinding load applied by the grinding wheel to press the wafer into the recess causes the elastic member to sink into the recess, and the wafer, with its lower surface entering the recess, is ground by the grinding wheel, forming a ring-shaped thicker portion on the outer circumference, thereby weakening the force that causes the wafer to warp upward, A second chuck table equipped with a porous member having a second suction surface that sucks the entire bottom surface of the wafer, A second grinding mechanism for grinding a wafer held by suction on the second suction surface using the grinding wheel, A transport mechanism for transporting the wafer, which is held on the first suction surface and has a ring-shaped thick portion formed on its outer circumference, from the first suction surface to the second suction surface, A grinding device equipped with the following features.

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