Edge trimming method and edge trimming device for laminated wafer

Abstract

To prevent a wafer from being damaged in trimming processing for removing a chamfered part of one of wafers constituting a laminated wafer.SOLUTION: An edge trimming method comprises: a holding step of causing a chuck table to hold the other of wafers constituting a laminated wafer 9; a first grinding step of rotating a disc grindstone 212 in a rotation direction B opposite to a rotation direction A of the rotating laminated wafer 9, and grinding, by using the disc grindstone 212, an outer peripheral portion 913 of one wafer 91 until a thickness thereof becomes a preset thickness; and a second grinding step of rotating the disc grindstone 222 in a rotation direction C opposite to the rotation direction B in the first grinding step, and removing, in a ring shape by using the disc grindstone 222, the outer peripheral portion 913.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an edge trimming method for removing an outer peripheral portion of one wafer constituting a bonded wafer in a ring shape, and an edge trimming apparatus used for carrying out this edge trimming method.

Background Art

[0002] When grinding one surface of a wafer whose outer peripheral edge is chamfered, since the outer peripheral edge may be formed into an acute angle and cracks or chips may occur, trimming is performed to process the outer peripheral edge of the wafer in a ring shape and remove the chamfered portion of the outer peripheral edge of the wafer (see, for example, Patent Document 1). As shown in Patent Document 1, such trimming is performed by rotating a disk-shaped grindstone (disk grindstone) and bringing the outer surface of the rotating disk grindstone into contact with the rotating wafer. At this time, in order to efficiently remove the chamfered portion of the wafer, the rotation direction of the disk grindstone is set to be opposite to the rotation direction of the wafer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When trimming the chamfered portion of one wafer constituting a bonded wafer, when the thickness of the ground portion becomes thin, the portion being trimmed by the rotation of the disk grindstone is lifted, and there is a problem that the portion being trimmed cracks.

[0005] The present invention has been conceived in view of such problems, and has a problem to be solved of preventing a wafer from being damaged in a trimming process of removing a chamfered portion of one of the wafers constituting a bonded wafer.

Means for Solving the Problems

[0006] This edge trimming method is an edge trimming method of a bonded wafer in which an outer peripheral portion of one of the wafers constituting a bonded wafer formed by bonding at least two wafers is ground with an outer surface of a disk-shaped grindstone and removed in a ring shape, and includes a holding step of holding the other wafer constituting the bonded wafer on a chuck table, and a first grinding step of rotating the disk-shaped grindstone in a direction opposite to the rotation direction of the rotating wafer by rotating the chuck table, and grinding the outer peripheral portion of the one wafer until a preset thickness is reached using the disk-shaped grindstone, and a second grinding step of removing the outer peripheral portion in a ring shape using a disk-shaped grindstone rotating in a direction opposite to the rotation direction in the first grinding step. This edge trimming method of a bonded wafer may use a first disk-shaped grindstone for performing the first grinding step and a second disk-shaped grindstone for performing the second grinding step, and perform the second grinding step with the second disk-shaped grindstone on the downstream side in the rotation direction of the chuck table from the processing point where the first grinding step is performed by the first disk-shaped grindstone. Furthermore, the present edge trimming device is an edge trimming device for performing edge trimming on a bonded wafer obtained by bonding at least two wafers together, and includes a chuck table for holding the bonded wafer, a table rotation mechanism for rotating the chuck table about the center of the chuck table, a first grinding mechanism for mounting and rotating a first disk grindstone at the tip of a first spindle, a second grinding mechanism for mounting and rotating a second disk grindstone at the tip of a second spindle, and a thickness measurement mechanism for measuring the thickness of the bonded wafer. The first spindle rotates the first disk grindstone in a direction opposite to the rotation direction of the chuck table, the second spindle rotates the second disk grindstone in the same direction as the rotation direction of the chuck table, and when the thickness of the portion being ground by the first disk grindstone is measured by the thickness measurement mechanism and the measured thickness reaches a predetermined thickness, a control unit starts the grinding process using the second disk grindstone.

Advantages of the Invention

[0007] In the present edge trimming method, in the first grinding step, the outer peripheral portion is ground in a ring shape using a disk grindstone that rotates in a direction opposite to the rotation direction of the wafer, and in the second grinding step, the remaining portion ground in the first grinding step is ground and removed in a ring shape using a disk grindstone that rotates in a direction opposite to the rotation direction of the disk grindstone in the first grinding step. Therefore, in the first grinding step, grinding can be performed efficiently, and in the second grinding step, since the disk grindstone rotates in the same direction as the wafer to be ground, it is possible to avoid the resistance being small and the portion to be trimmed being lifted by the rotation of the grindstone. Thus, edge trimming can be performed without reducing the productivity of trimming and without damaging the wafer. In the first grinding step, the first disk grindstone is used, and in the second grinding step, the second disk grindstone is used. By performing the second grinding step with the second disk grindstone behind the processing point where the first grinding step is performed by the first disk grindstone in the rotation direction of the chuck table, the portion ground by the first disk grindstone can be immediately ground by the second disk grindstone, and since the first grinding step and the second grinding step can be performed in parallel, the productivity can be increased. This edge trimming device includes a chuck table for holding a bonded wafer, a first disk grinding wheel mounted on a first spindle, a second disk grinding wheel mounted on a second spindle, and a thickness measurement mechanism for measuring the thickness of the bonded wafer. The first disk grinding wheel is rotated in the direction opposite to the rotation direction of the chuck table for grinding, and the thickness of the portion being ground by the first disk grinding wheel is measured by the thickness measuring device. When the measured thickness reaches a predetermined thickness, the second disk grinding wheel is rotated in the forward direction with respect to the rotation direction of the chuck table to start grinding. Therefore, grinding using the first disk grinding wheel can be performed efficiently, and in grinding using the second disk grinding wheel, it is possible to avoid the resistance being small and the portion to be trimmed being lifted by the rotation of the grinding wheel. Thus, edge trimming can be performed without reducing the productivity of trimming and without damaging the wafer.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0009] 1 First Embodiment The edge trimming device 1 shown in FIG. 1 includes a base 7 and a gantry column 8 that stands upright from the base 7 and has an opening 80. A chuck table 10 for holding the bonded wafer 9 is horizontally movable in the X-axis direction through the opening 80 of the gantry column 8. Further, a first grinding mechanism 21 and a second grinding mechanism 22 for grinding the bonded wafer 9 are movable in the Y-axis direction and the Z-axis direction along the side surface of the gantry column 8.

[0010] As shown in FIG. 2, the bonded wafer 9 held on the chuck table 10 is composed of a wafer to be ground 91 which is one wafer and a support wafer 92 which is the other wafer, and is formed by bonding the lower surface 912 of the wafer to be ground 91 and the upper surface 921 of the support wafer 92. The upper surface of the wafer to be ground 91 is the surface to be ground by the first grinding mechanism 21 and the second grinding mechanism 22, and the lower surface 922 of the support wafer 92 is the surface held by the chuck table 10. The outer peripheral portion 913 of the wafer to be ground 91 is chamfered. Note that there is also a bonded wafer in which three or more wafers are bonded. In that case as well, the uppermost wafer becomes the wafer to be ground.

[0011] The chuck table 10 is driven by an X-direction movement mechanism 31 and is movable in the X-axis direction. The X-direction movement mechanism 31 includes a ball screw 311 extending in the X-axis direction which is the horizontal movement direction of the chuck table 10, a pair of guide rails 312 arranged in parallel with the ball screw 311, a slider 313 in which a nut member (not shown) protruding at the lower part is screwed onto the ball screw 311 and the lower end of which is in sliding contact with the guide rail 312, and a motor 314 connected to one end of the ball screw 311 for rotating the ball screw 311 forward and backward. When the motor 314 rotates the ball screw 311, the slider 313 is guided by the guide rail 312 and moves in the X-axis direction.

[0012] On the upper surface of the slider 313, a table rotation mechanism 32 for rotating the chuck table 10 about a vertical rotation axis (Z-axis direction) passing through the center of the chuck table 10 is arranged. The table rotation mechanism 32 includes a servo motor and an encoder for detecting the rotation direction, rotation angle, rotation speed, etc. of the servo motor. When the motor 314 constituting the X-direction movement mechanism 31 rotates the ball screw 311 and the slider 313 moves in the X-axis direction, the chuck table 10 and the table rotation mechanism 32 also move in the X-axis direction.

[0013] As shown in FIG. 3, the first grinding mechanism 21 includes a first spindle 211 extending in the Y-axis direction orthogonal to the X-axis direction in the horizontal direction, a first disk grindstone 212 mounted at the tip of the first spindle 211, a first spindle housing 213 rotatably supporting the first spindle 211, and a motor (not shown) provided in the first spindle housing 213. The first spindle housing 213 is supported by a first lifting mechanism 41 so as to be movable up and down. The first disk grindstone 212 is formed in a disk shape having a predetermined thickness and is, for example, a #400 grindstone.

[0014] As shown in Fig. 3, the second grinding mechanism 22 includes a second spindle 221 extending in the Y-axis direction perpendicular to the X-axis direction in the horizontal direction, a second disk grinding wheel 222 mounted at the tip of the second spindle 221 and facing the first disk grinding wheel 212, a second spindle housing 223 that rotatably supports the second spindle 221, and a motor (not shown) provided in the first spindle housing 213. The second spindle housing 223 is supported by the second lifting mechanism 42 so as to be liftable. The second disk grinding wheel 222 is formed in a disk shape having the same thickness as the first disk grinding wheel 212, and is, for example, a #1500 grinding wheel with a smaller abrasive grain size than the first disk grinding wheel 212.

[0015] As shown in Fig. 1, the first lifting mechanism 41 includes a ball screw 411 extending in the Z-axis direction, a pair of guide rails 412 arranged in parallel with the ball screw 411, a lifting member 413 in which a nut member (not shown) protruding from the side is screwed onto the ball screw 411 and the side surface is in sliding contact with the guide rail 412, and a motor 414 connected to the upper end of the ball screw 411 for rotating the ball screw 411 forward and backward. When the motor 414 rotates the ball screw 411, the lifting member 413 is guided by the guide rail 412 and moves up and down in the Z-axis direction. The lifting member 413 supports the first spindle housing 213 that constitutes the first grinding mechanism 21 at its lower end. As the lifting member 413 moves up and down, the first grinding mechanism 21 also moves up and down.

[0016] Since the second lifting mechanism 42 is configured in the same manner as the first lifting mechanism 41 except that the object to be lifted is the second grinding mechanism 22, the same reference numerals as those of the first lifting mechanism 41 are given to the respective parts constituting the second lifting mechanism 42, and the description thereof is omitted.

[0017] As shown in Fig. 1, the first grinding mechanism 21 and the first lifting mechanism 41 are driven by the first feed mechanism 51 and are movable in the Y-axis direction. The first feed mechanism 51 includes a ball screw 511 extending in the Y-axis direction, a pair of guide rails 512 arranged in parallel with the ball screw 511, a slide member 513 having a nut member (not shown) protruding from a side portion screwed onto the ball screw 511 and having a side surface slidably contacting the guide rail 512, and a motor 514 connected to one end of the ball screw 511 for rotating the ball screw 511 forward and backward. When the motor 514 rotates the ball screw 511, the slide member 513 is guided by the guide rail 512 and moves in the Y-axis direction. The slide member 513 supports the first lifting mechanism 41 on its side surface. As the slide member 513 moves in the Y-axis direction, the first lifting mechanism 41 and the first grinding mechanism 21 also move in the Y-axis direction.

[0018] The second grinding mechanism 22 and the second lifting mechanism 42 are driven by the second feed mechanism 52 and are movable in the Y-axis direction. Since the second feed mechanism 52 is configured in the same manner as the first feed mechanism 51 except that the objects to be fed in the Y-axis direction are the second grinding mechanism 22 and the second lifting mechanism 42, the same reference numerals as those of the first feed mechanism 51 are given to the respective parts constituting the second feed mechanism 52, and the description thereof is omitted.

[0019] Above the position where grinding is performed on the wafer 91 to be ground in the movement path of the chuck table 10, a non-contact thickness measurement mechanism 61 for measuring the thickness of the portion of the bonded wafer 9 being ground is provided. The thickness measurement mechanism 61 may be movable in any one to three of the X-axis direction, Y-axis direction, and Z-axis direction.

[0020] The table rotation mechanism 32, the motors (not shown) of the first grinding mechanism 21, the motors (not shown) of the second grinding mechanism 22, the motor 414 of the first lifting mechanism 41, the motor 414 of the second lifting mechanism 42, the motor 514 of the first feed mechanism 51, the motor 514 of the second feed mechanism 52, and the thickness measurement mechanism 61 are electrically connected to the control unit 62, and the control unit 62 controls them. The control unit 62 includes storage elements such as a CPU and a memory.

[0021] Hereinafter, a method for trimming the outer peripheral portion 913 of the wafer to be ground 91 that constitutes the bonded wafer 9 using the edge trimming device 1 will be described.

[0022] (1) Holding step As shown in FIG. 2, on the chuck table 10, the lower surface 922 of the support wafer 92 that constitutes the bonded wafer 9 is sucked and held, and the upper surface 911 of the wafer to be ground 91 is exposed upward.

[0023] (2) First grinding step After the holding step is completed, as shown in FIG. 3, under the control of the control unit 62, a motor (not shown) rotationally drives the first spindle 211 to rotate the first disk grindstone 212. The rotation direction of the first disk grindstone 212 at this time is the B direction that is opposite to the A direction, which is the rotation direction of the chuck table 10. Also, under the control of the control unit 62, a motor (not shown) rotationally drives the second spindle 221 to rotate the second disk grindstone 222 as shown in FIG. 3. The rotation direction of the second disk grindstone 222 at this time is the C direction that is opposite to the B direction, which is the rotation direction of the first disk grindstone 212, and this C direction is the forward direction with respect to the A direction, which is the rotation direction of the chuck table 10.

[0024] The first feed mechanism 51 shown in FIG. 1 positions the first disk grindstone 212 above the end portion on the -Y direction side of the outer peripheral portion 913 of the wafer to be ground 91 as shown in FIG. 3. On the other hand, the second feed mechanism 52 positions the second disk grindstone 222 above the end portion on the +Y direction side of the outer peripheral portion 913 of the wafer to be ground 91. At this point, the first disk grindstone 212 and the second disk grindstone 222 are positioned at a height where they do not contact the wafer to be ground 91.

[0025] Further, by controlling the table rotation mechanism 32 by the control unit 62, the chuck table 10 is rotated about the center 100 of the chuck table 10 in the A direction, for example, counterclockwise in a plan view. Then, without changing the positions of the first disk grindstone 212 and the second disk grindstone 222 in the Y-axis direction, the first elevating mechanism 41 lowers the first grinding mechanism 21. Then, the outer surface of the first disk grindstone 212 rotating in the B direction comes into contact with the outer peripheral portion 913 of the upper surface 911 of the wafer 91 to be ground, and grinding is started. Then, with the first disk grindstone 212 positioned at a predetermined height, the outer peripheral portion 913 of the wafer 91 to be ground is ground in a ring shape by so-called up-cut, and the chamfered portion is removed along the outer peripheral portion 913.

[0026] During the grinding of the outer peripheral portion 913 by the first disk grindstone 212, the thickness measuring mechanism 61 is positioned above the outer peripheral portion 913, and the thickness of the outer peripheral portion 913 of the bonded wafer 9 is measured by the thickness measuring mechanism 61. The measured value is recognized by the control unit 62. Then, after the measured value reaches a predetermined thickness value, when the chuck table 10 is rotated 360 degrees in that state, the entire outer peripheral portion 913 is formed to have a predetermined set thickness. Therefore, the first grinding mechanism 21 is raised by the control of the control unit 62 to end the grinding by the first disk grindstone 212. In the first embodiment, since the thickness measuring mechanism 61 is located 90 degrees downstream in the rotation direction of the chuck table 10 from the first disk grindstone 212, the grinding by the first disk grindstone 212 may be ended when the chuck table 10 has rotated 270 degrees after the predetermined set thickness is measured by the thickness measuring mechanism 61. The predetermined set thickness is the thickness at which the remaining grinding portion 914 shown in FIG. 4 is formed on the wafer 91 to be ground, and is slightly thicker than the thickness of the support wafer 92. The value of the set thickness is stored in advance in the storage element of the control unit 62.

[0027] Also, as shown in FIG. 4, when the first grinding process is started, in order to be able to start the next second grinding process as soon as possible, the second elevating mechanism 42 lowers the second grinding mechanism 22 under the control of the control unit 62 to a height at which the second disk grindstone 222 does not contact the wafer 91 to be ground and as low as possible according to the measured value of the thickness measuring mechanism 61.

[0028] (3) Second grinding process The processing point where grinding is performed by the second disk grindstone 222 is located at a position where the chuck table 10 has rotated 90 degrees from the measurement position by the thickness measuring mechanism 61. Therefore, after the chuck table 10 has rotated 90 degrees since the thickness measuring mechanism 61 has measured the predetermined set thickness, the thickness measuring portion moves below the second disk grindstone 222. Thus, when the control unit 62 reads from the encoder of the table rotation mechanism 32 that the chuck table 10 has rotated 90 degrees since the thickness measuring mechanism 61 has measured the predetermined set thickness, the control unit 62 controls the motor 414 of the second elevating mechanism 42 to lower the second grinding mechanism 22, and the remaining grinding portion 914 is ground by the second disk grindstone 222 rotating in the C direction by so-called down-cut. That is, grinding by the second disk grindstone 222 is performed downstream in the rotation direction of the chuck table 10 from the processing point in the first grinding process. The height position of the second disk grindstone 222 at this time is a height at which the lower end of its outer surface coincides with the lower surface of the wafer 91 to be ground.

[0029] From the time when grinding by the second disk grindstone 222 is started until the chuck table 10 rotates 180 degrees, grinding by the first disk grindstone 212 and grinding by the second disk grindstone 222 proceed simultaneously. That is, during that time, the first grinding process and the second grinding process are carried out in parallel. Then, after the chuck table 10 has rotated 180 degrees since the start of grinding by the second disk grindstone 222, since all the portions ground by the first disk grindstone 212 have reached the predetermined set thickness, as shown in FIG. 5, the first elevating mechanism 41 raises the first grinding mechanism 21 to separate the first disk grindstone 212 from the wafer 91 to be ground, and the grinding by the first disk grindstone 212 is completed.

[0030] On the other hand, even after the grinding by the first disk grindstone 212 is completed, the grinding by the second disk grindstone 222 continues. When the chuck table 10 further rotates 180 degrees from the end of the grinding by the first disk grindstone 212, all of the remaining grinding portion 914 is removed by the second disk grindstone 222. Then, the second elevating mechanism 42 raises the second grinding mechanism 22 to finish the grinding by the second disk grindstone 222.

[0031] As described above, in the first grinding step, the outer peripheral portion 913 is ground in a ring shape using the first disk grindstone 212 that rotates in the B direction opposite to the A direction which is the rotation direction of the bonded wafer 9, so that the outer peripheral portion 913 can be efficiently ground. On the other hand, in the second grinding step, the remaining grinding portion 914 of the outer peripheral portion 913 is ground in a ring shape using the second disk grindstone 222 that rotates in a direction opposite to the rotation direction of the first disk grindstone 212 in the first grinding step, so that the remaining grinding portion 914 can be removed with a small grinding resistance. Therefore, in the first grinding step, grinding can be performed efficiently, and in the second grinding step, it is possible to avoid the portion to be trimmed being lifted by the rotation of the second disk grindstone 222. Thus, edge trimming can be performed without reducing the productivity of trimming and without damaging the bonded wafer 9.

[0032] Also, in the first grinding step, the first disk grindstone 212 is used, and in the second grinding step, a second disk grindstone 222 different from the first disk grindstone 212 is used. The second grinding step is performed by the second disk grindstone 222 behind the machining point where the first grinding step is performed by the first disk grindstone 212 in the rotation direction of the chuck table 10. Thus, the portion ground by the first disk grindstone 212 can be immediately ground by the second disk grindstone 222, and since the first grinding step and the second grinding step can be performed in parallel, the productivity can be increased.

[0033] 2 Second Embodiment The edge trimming device 2 shown in Fig. 6 includes a chuck table 10 that holds the bonded wafer 9, a table rotation mechanism (not shown) that rotates the chuck table 10 about the center 100 of the chuck table 10, a first grinding mechanism 21, a second grinding mechanism 22, and a thickness measurement mechanism 61 that measures the thickness of the bonded wafer 9.

[0034] Since each of the first grinding mechanism 21 and the second grinding mechanism 22 is configured in the same manner as in the first embodiment, the same reference numerals as those in the first embodiment are given and the description thereof is omitted.

[0035] The rotation axis of the first spindle 211 that constitutes the first grinding mechanism 21 and the rotation axis of the second spindle 221 that constitutes the second grinding mechanism 22 form a predetermined angle. The predetermined angle is between 0 and 180 degrees. Also, the first grinding mechanism 21 and the second grinding mechanism 22 are separated from each other such that the members constituting the first grinding mechanism 21 and the members constituting the second grinding mechanism 22 do not contact each other. The first lifting mechanism 41 that raises and lowers the first grinding mechanism 21 is arranged on the side far from the second grinding mechanism 22, and the second lifting mechanism 42 that raises and lowers the second grinding mechanism 22 is arranged on the side far from the first grinding mechanism 21, and the structure is such that the first grinding mechanism 21 and the second grinding mechanism 22 can be easily brought closer to each other.

[0036] (1) Holding step As shown in Fig. 2, on the chuck table 10, the lower surface 922 of the support wafer 92 that constitutes the bonded wafer 9 is sucked and held, and the upper surface 911 of the wafer 91 to be ground is exposed upward.

[0037] (2) First grinding step After the completion of the holding step, as shown in Fig. 6, under the control of the control unit 62, a motor (not shown) rotationally drives the first spindle 211 to rotate the first disk grindstone 212. The rotation direction of the first disk grindstone 212 at this time is the B direction that opposes the A direction, which is the rotation direction of the chuck table 10.

[0038] Also, under the control of the control unit 62, a motor (not shown) rotationally drives the second spindle 221 to rotate the second disk grindstone 222 as shown in FIG. 6. At this time, the rotation direction of the second disk grindstone 222 is the C direction, which is opposite to the B direction, which is the rotation direction of the first disk grindstone 212.

[0039] Then, as shown in FIG. 6, a first feed mechanism (not shown) positions the first disk grindstone 212 above the -Y-direction side end of the outer peripheral portion 913 of the wafer 91 to be ground. On the other hand, a second feed mechanism (not shown) moves the second disk grindstone 222 to a position above the outer peripheral portion 913 of the wafer 91 to be ground and closer to the first disk grindstone 212, and at a position where it does not contact the first disk grindstone 212.

[0040] Also, by the control unit 62 controlling a table rotation mechanism (not shown), the chuck table 10 is rotated in the A direction, which is, for example, counterclockwise in a plan view. Then, while maintaining the positional relationship between the first disk grindstone 212 and the second disk grindstone 222, and while maintaining the state where the first disk grindstone 212 is rotated in the B direction, when the first lifting mechanism 41 lowers the first grinding mechanism 21, the first disk grindstone 212 comes into contact with the outer peripheral portion 913 of the wafer 91 to be ground, and grinding starts. With the first disk grindstone 212 positioned at a predetermined height, the outer peripheral portion 913 of the wafer 91 to be ground is ground by so-called up-cut, and the chamfered portion is removed along the outer peripheral portion 913.

[0041] During the grinding of the outer peripheral portion 913 by the first disk grinding stone 212, the thickness measurement mechanism 61 is positioned above the outer peripheral portion 913, and the thickness of the outer peripheral portion 913 of the bonded wafer 9 is measured by the thickness measurement mechanism 61. In the example of FIG. 6, the thickness measurement mechanism 61 is positioned between the first disk grinding stone 212 and the second disk grinding stone 222. The measurement value by the thickness measurement mechanism 61 is recognized by the control unit 62. When the measurement value reaches a predetermined thickness value and the chuck table 10 is rotated 360 degrees in that state, the entire outer peripheral portion 913 is formed to have a predetermined thickness, and the first grinding mechanism 21 is raised under the control of the control unit 62 to end the grinding by the first disk grinding stone 212. The predetermined thickness is the thickness at which the grinding remaining portion 914 shown in FIG. 4 is formed on the wafer 91 to be ground, and is slightly thicker than the thickness of the support wafer 92.

[0042] When the first grinding process is started, in preparation for the next second grinding process, under the control of the control unit 62, the second lifting mechanism 42 lowers the second grinding mechanism 22 to a height such that the second disk grinding stone 222 does not contact the wafer 91 to be ground and as low as possible according to the measurement value of the thickness measurement mechanism 61. In the first grinding process, since the lower end of the outer surface of the first disk grinding stone 212 is positioned slightly above the lower surface 912 of the wafer 91 to be ground, the outer peripheral portion 913 of the wafer 91 to be ground forms the grinding remaining portion 914 shown in FIG. 4.

[0043] (3) Second grinding process When the thickness value of the outer peripheral portion 913 measured by the thickness measurement mechanism 61 reaches a predetermined value, the second elevating mechanism 42 lowers the second grinding mechanism 22 to align the height of the lower end of the outer surface of the second disk grindstone 222 with the height of the lower surface 912 of the wafer 91 to be ground. Since the thickness measurement mechanism 61 is downstream of the machining point in the rotational direction of the chuck table 10 from the machining point in the first grinding process and is located immediately adjacent to the machining point, the result of grinding by the first disk grindstone 212 is immediately reflected in the measurement value by the thickness measurement mechanism 61. Also, the second disk grindstone 222 is located downstream of the position of the thickness measurement mechanism 61 in the rotational direction of the chuck table 10 and immediately adjacent to the position of the thickness measurement mechanism 61. Therefore, immediately after the thickness value of the outer peripheral portion 913 measured by the thickness measurement mechanism 61 reaches the predetermined value, the second elevating mechanism 42 lowers the second grinding mechanism 22 to align the height of the lower end of the outer surface of the second disk grindstone 222 with the height of the lower surface 912 of the wafer 91 to be ground, so that the second grinding process can be started without wasting time. In the second grinding process, the remaining grinding portion 914 is ground by so-called down-cut.

[0044] Between the time when the thickness value of the outer peripheral portion 913 measured by the thickness measurement mechanism 61 reaches the predetermined set value and the time when the chuck table 10 rotates 360 degrees, the grinding by the first disk grindstone 212 and the grinding by the second disk grindstone 222 proceed in parallel. Then, after the chuck table 10 rotates 360 degrees from the start of grinding by the first disk grindstone 212, all of the outer peripheral portion 913 reaches the predetermined set thickness. Therefore, when the control unit 62 detects that the chuck table 10 has rotated 360 degrees from the encoder of the rotation mechanism that rotates the chuck table 10, the first elevating mechanism 41 raises the first grinding mechanism 21 to separate the first disk grindstone 212 from the wafer 91 to be ground, and ends the first grinding process.

[0045] On the other hand, when the chuck table 10 further rotates by a predetermined angle after the grinding by the first disk grindstone 212 is completed, all of the remaining grinding portion 914 is removed by the grinding by the second disk grindstone 222. Therefore, after the control unit 62 detects that the chuck table 10 has rotated by the predetermined angle, the second lifting mechanism 42 raises the second grinding mechanism 22 to end the grinding by the second disk grindstone 222. As described above, in the edge trimming device 2 of the second embodiment, the first disk grindstone 212 and the second disk grindstone 222 are positioned closer to each other, and the angle formed by the rotation axes of the first spindle 211 and the second spindle 221 is made smaller, so that the time from the start of the first grinding process to the start of the second grinding process can be made shorter, and thus more efficient operation can be achieved.

[0046] 3 Third Embodiment The edge trimming device 3 shown in FIG. 7 includes a chuck table 10 that holds the bonded wafer 9, a table rotation mechanism (not shown) that rotates the chuck table 10 about the center 100 of the chuck table 10, a first grinding mechanism 21, and a thickness measurement mechanism 61 that measures the thickness of the bonded wafer 9. That is, the edge trimming device 3 shown in FIG. 7 does not include a component corresponding to the second grinding mechanism 22 in the edge trimming device 1 of the first embodiment and the edge trimming device 2 of the second embodiment.

[0047] Since the first grinding mechanism 21 is configured in the same manner as in the first and second embodiments, the individual members are given the same reference numerals as in the first embodiment, and the description thereof is omitted.

[0048] (1) Holding Step As shown in FIG. 2, on the chuck table 10, the lower surface 922 of the support wafer 92 constituting the bonded wafer 9 is sucked and held, and the upper surface 911 of the wafer 91 to be ground is exposed upward.

[0049] (2) First Grinding Step As shown in FIG. 7, a motor (not shown) rotationally drives the first spindle 211 to rotate the first disk grinding wheel 212. At this time, the rotation direction of the first disk grinding wheel 212 is the B direction, which is opposite to the A direction, which is the rotation direction of the chuck table 10.

[0050] Then, as shown in FIG. 6, a first feed mechanism (not shown) positions the first disk grinding wheel 212 above the end portion on the -Y direction side of the outer peripheral portion 913 of the wafer 91 to be ground.

[0051] Further, the control unit 62 controls a table rotation mechanism (not shown) to rotate the chuck table 10 in the A direction, which is, for example, counterclockwise in a plan view. Then, while maintaining the state in which the first disk grinding wheel 212 is rotated in the B direction, when the first lifting mechanism 41 lowers the first grinding mechanism 21, the first disk grinding wheel 212 comes into contact with the outer peripheral portion 913 of the wafer 91 to be ground, and grinding is started. With the first disk grinding wheel 212 positioned at a predetermined height, the outer peripheral portion 913 of the wafer 91 to be ground is ground by so-called up-cut, and the chamfered portion is removed along the outer peripheral portion 913.

[0052] During the grinding of the outer peripheral portion 913 by the first disk grinding wheel 212, the thickness measurement mechanism 61 is positioned above the outer peripheral portion 913, and the thickness of the outer peripheral portion 913 of the bonded wafer 9 is measured by the thickness measurement mechanism 61. In the example of FIG. 7, the thickness measurement mechanism 61 is positioned 90 degrees downstream in the rotation direction of the chuck table 10 from the processing point by the first disk grinding wheel 212. The measurement value by the thickness measurement mechanism 61 is recognized by the control unit 62. Then, when the chuck table 10 is rotated 270 degrees from the time when the measurement value reaches a predetermined thickness value, the entire outer peripheral portion 913 is formed to have a predetermined thickness. In the first grinding step, as shown in FIG. 8, grinding is performed with the lower end of the outer surface of the first disk grinding wheel 212 positioned slightly above the lower surface 912 of the wafer 91 to be ground. Therefore, a grinding remaining portion 914 shown in FIG. 4 is formed on the outer peripheral portion 913 of the wafer 91 to be ground.

[0053] When the grinding residue portion 914 is formed in the entire outer peripheral portion 913, the first elevating mechanism 41 raises the first grinding mechanism 21, stops the rotation of the first spindle 211, and ends the first grinding process.

[0054] (3) Second grinding process Next, as shown in FIG. 9, a motor (not shown) rotates the first spindle 211 in a direction opposite to that in the first grinding process, that is, in the C direction. Then, the first elevating mechanism 41 lowers the first grinding mechanism 21 and brings it into contact with the grinding residue portion 914 of the rotating wafer 91 to be ground. Then, the height of the lower end of the outer surface of the first disk grindstone 212 is made to coincide with the lower surface 912 of the wafer 91 to be ground, and grinding is performed in this state.

[0055] During grinding by the first disk grindstone 212, the thickness measuring mechanism 61 measures the thickness of the outer peripheral portion 913 of the bonded wafer 9. When the measured value of the thickness of the outer peripheral portion 913 reaches a predetermined value, the chuck table 10 rotates 360 degrees from that point. Then, all of the grinding residue portion 914 is removed. Then, the first elevating mechanism 41 raises the first grinding mechanism 21, stops the rotation of the first spindle 211, and ends the second grinding process.

[0056] As described above, in the edge trimming method of the third embodiment, the grinding mechanism uses only one edge trimming device. In the first grinding process, the first disk grindstone 212 is rotated in the B direction for grinding, and in the second grinding process, the rotation direction of the first disk grindstone 212 is changed to the C direction for grinding. Therefore, even when using the edge trimming device 3 having only one grinding mechanism, the first grinding process and the second grinding process can be performed to remove the chamfered outer peripheral portion without damaging the wafer 91 to be ground.

[0057] In any of the first to third embodiments, the chuck table 10 may be rotated in the direction opposite to the A direction. In that case, in the first and second embodiments, the first disk grindstone 212 is rotated in the direction opposite to the B direction, and the second disk grindstone 222 is rotated in the direction opposite to the C direction. Further, in the third embodiment, in the first grinding step, the first disk grindstone 212 is rotated in the direction opposite to the B direction, and in the second grinding step, the first disk grindstone 212 is rotated in the direction opposite to the C direction.

[0058] In the third embodiment, the rotation direction of the first disk grindstone 212 is opposite between the first grinding step and the second grinding step. However, instead of changing the rotation direction of the first disk grindstone 212 between the first grinding step and the second grinding step, the rotation direction of the chuck table 10 may be made opposite. Further, after the first grinding step, the second grinding step may be performed without raising the first grinding mechanism 21.

Explanation of Reference Numerals

[0059] 1, 2, 3: Edge trimming device 7: Base 8: Gantry column 80: Opening 9: Bonded wafer 91: Wafer to be ground 911: Upper surface 912: Lower surface 913: Outer peripheral portion 914: Remaining grinding portion 92: Support wafer 921: Upper surface 922: Lower surface 10: Chuck table 100: Center 21: First grinding mechanism 211: First spindle 212: First disk grindstone 213: First spindle housing 22: Second grinding mechanism 221: Second spindle 222: Second disk grindstone 223: Second spindle housing 31: X-direction movement mechanism 311: Ball screw 312: Guide rail 313: Slider 314: Motor 32: Table rotation mechanism 41: First lifting mechanism 42: Second lifting mechanism 411: Ball screw 412: Guide rail 413: Lifting member 414: Motor 51: First feeding mechanism 52: Second feeding mechanism 511: Ball screw 512: Guide rail 513: Slide member 514: Motor 61: Thickness measurement mechanism 62: Control unit

Claims

1. An edge trimming method for a bonded wafer formed by bonding at least two wafers, the method comprising grinding an outer peripheral portion of one of the wafers constituting the bonded wafer with an outer surface of a disk-shaped grindstone and removing it in a ring shape, a holding step of holding the other wafer constituting the bonded wafer on a chuck table; a first grinding step of rotating the disk-shaped grindstone in a direction opposite to the rotation direction of the rotating bonded wafer by rotating the chuck table, and grinding the outer peripheral portion of the one wafer with the disk-shaped grindstone until a preset thickness is reached; a second grinding step of removing the portion ground in the first grinding step in a ring shape from the outer peripheral portion using a disk-shaped grindstone rotating in a direction opposite to the rotation direction in the first grinding step; The edge trimming method for a bonded wafer comprising the above steps.

2. using a first disk-shaped grindstone for performing the first grinding step and a second disk-shaped grindstone for performing the second grinding step, and performing the second grinding step with the second disk-shaped grindstone on the downstream side in the rotation direction of the chuck table from the processing point where the first grinding step is performed by the first disk-shaped grindstone. The edge trimming method for a bonded wafer according to Claim 1.

3. An edge trimming apparatus for performing edge trimming of a bonded wafer formed by bonding at least two wafers, the apparatus comprising: a chuck table for holding the bonded wafer; a table rotation mechanism for rotating the chuck table about the center of the chuck table; a first grinding mechanism for mounting and rotating a first disk-shaped grindstone at the tip of a first spindle; a second grinding mechanism for mounting and rotating a second disk-shaped grindstone at the tip of a second spindle; and a thickness measurement mechanism for measuring the thickness of the bonded wafer. The first spindle rotates the first disk-shaped grindstone in a direction opposite to the rotation direction of the chuck table. The second spindle rotates the second disk-shaped grindstone in a direction same as the rotation direction of the chuck table. A control unit that measures the thickness of the portion being ground with the first disk-shaped grindstone using the thickness measurement mechanism, and when the measured thickness reaches a predetermined thickness, starts the grinding process with the second disk-shaped grindstone. The edge trimming apparatus comprising the above components. ​

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