Wafer grinding method

Abstract

To prevent a situation where an end material collides with a holding surface height gauge, making it difficult to gauge a thickness.SOLUTION: When end materials 105 are separated from a wafer 100 in a first grinding step, a holding surface height gauge 81 does not perform height measurement of a holding surface 22 and the holding surface height gauge 81 separates from a frame body surface 24, which can avoid the end materials 105 from colliding with the holding surface height gauge 81, even if the end materials 105 are flicked out by a grinding stone 77 which is rotating. This can prevent situations where the colliding of the end materials 105 makes it difficult for the holding surface height gauge 81 to measure a height of the holding surface and the holding surface height gauge 81 deteriorates in measurement accuracy, and further can prevent the holding surface height gauge 81 from being damaged.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for grinding a wafer.

Background Art

[0002] As disclosed in Patent Document 1, in a method for grinding a wafer in which a wafer held on a holding surface of a chuck table is ground with a grinding wheel, the height of the holding surface and the height of the upper surface of the wafer are measured, the difference between the two measured values is calculated, and grinding is performed until the calculated value (wafer thickness) reaches a predetermined thickness.

[0003] Also, as disclosed in Patent Document 2, when grinding a wafer whose outer peripheral portion has been trimmed, arc-shaped fragments are formed. Further, in the technique disclosed in Patent Document 3, a chuck table having a measurement surface formed lower than the holding surface may be used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventionally, fragments generated during grinding may hit a height gauge that measures the height of the holding surface, making it difficult to measure the height of the holding surface.

[0006] Therefore, an object of the present invention is to prevent fragments from hitting a height gauge that measures the height of the holding surface and making it difficult to measure the thickness.

Means for Solving the Problems

[0007] The wafer grinding method (this grinding method) of the present invention is a wafer grinding method for grinding a wafer held on the holding surface of a chuck table with a grinding wheel until a predetermined thickness is reached while performing measurement with a thickness measuring device. The wafer has a ring-shaped recessed trimming portion on the outer peripheral portion on one surface side that does not reach the other surface. The thickness measuring device includes a holding surface height gauge that contacts a frame surface surrounding the holding surface to measure the height of the holding surface, an upper surface height gauge that contacts the upper surface of the wafer held on the holding surface to measure the upper surface height of the wafer, and a calculation unit that calculates the difference between the measurement value of the holding surface height gauge and the measurement value of the upper surface height gauge. The method includes a holding step of holding one surface side of the wafer with the holding surface with the other surface of the wafer facing up, a first grinding step of grinding the other surface of the wafer with the grinding wheel in a state where at least the height of the holding surface is not measured by the holding surface height gauge to expose the trimming portion on the other surface, and removing the end material separated from the wafer. After the first grinding step, while performing the height measurement of the holding surface by the holding surface height gauge, the height measurement of the upper surface of the wafer by the upper surface height gauge, and the calculation by the calculation unit, the other surface of the wafer is ground until the value calculated by the calculation unit reaches a predetermined thickness set in advance, including a second grinding step.

Advantages of the Invention

[0008] In this grinding method, in the first grinding step, when the end material is separated from and removed from the wafer, the height measurement of the holding surface by the holding surface height gauge is not performed. For example, the holding surface height gauge is separated from the frame surface. Therefore, even when the end material is bounced off the wafer by the rotating grinding wheel, it is possible to prevent the end material from colliding with the holding surface height gauge during measurement, making it difficult for the holding surface height gauge to measure the height of the holding surface, or deteriorating the measurement accuracy of the holding surface height gauge. Also, damage to the holding surface height gauge can be prevented.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0010] As shown in FIG. 1, the grinding device 1 according to the present embodiment is a device for grinding the wafer 100. The wafer 100 is, for example, a circular plate-shaped workpiece and has a front surface 101 and a back surface 102. The back surface 102 of the wafer 100 is the surface to be machined where grinding is performed.

[0011] The grinding device 1 has a first device base 10 and a second device base 11 disposed behind the first device base 10 (on the +Y direction side).

[0012] On the -Y direction side of the first device base 10, a first cassette stage 160 and a second cassette stage 162 are provided. A first cassette 161 in which the wafer 100 before processing is accommodated is placed on the first cassette stage 160. A second cassette 163 in which the wafer 100 after processing is accommodated is placed on the second cassette stage 162.

[0013] The first cassette 161 and the second cassette 163 each have a plurality of shelves inside, and each shelf accommodates one wafer 100. That is, the first cassette 161 and the second cassette 163 accommodate a plurality of wafers 100 in a shelf-like manner.

[0014] The openings (not shown) of the first cassette 161 and the second cassette 163 face the +Y direction side. A robot 155 is disposed on the +Y direction side of these openings. The robot 155 has a holding surface for holding the wafer 100. The robot 155 carries (stores) the processed wafer 100 into the second cassette 163. Also, the robot 155 takes out the wafer 100 before processing from the first cassette 161 and places it on the temporary placement table 154 of the temporary placement mechanism 152.

[0015] The temporary placement mechanism 152 is used to temporarily place the wafer 100 taken out from the first cassette 161 and is provided at a position adjacent to the robot 155. The temporary placement mechanism 152 has a temporary placement table 154 and an alignment member 153. The alignment member 153 includes a plurality of alignment pins arranged outside so as to surround the temporary placement table 154 and a slider for moving the alignment pins in the radial direction of the temporary placement table 154. In the alignment member 153, the circle connecting the plurality of alignment pins is reduced in diameter by moving the alignment pins toward the center in the radial direction of the temporary placement table 154. Thereby, the wafer 100 placed on the temporary placement table 154 is aligned (centered) at a predetermined position.

[0016] An input mechanism 170 is provided at a position adjacent to the temporary placement mechanism 152. The input mechanism 170 places the wafer 100 temporarily placed by the temporary placement mechanism 152 on the holding surface 22 of the chuck table 20.

[0017] An opening 13 is provided on the upper surface side of the second apparatus base 11. And a wafer holding mechanism 30 is disposed in the opening 13. The wafer holding mechanism 30 includes a chuck table 20 having a holding surface 22 for holding the wafer 100, a table support mechanism 26 for supporting the chuck table 20, a table rotation mechanism 25 for rotating the chuck table 20, and support columns 27 whose inclination of the chuck table 20 can be adjusted.

[0018] The chuck table 20 includes a porous member 21 and a frame 23 that houses the porous member 21 so that the upper surface of the porous member 21 is exposed. The upper surface of the porous member 21 is a holding surface 22 for sucking and holding the wafer 100. The holding surface 22 sucks and holds the wafer 100 by being communicated with a suction source (not shown). That is, the chuck table 20 holds the wafer 100 by the holding surface 22. Further, a frame surface 24 that is the upper surface of the frame 23 surrounds the holding surface 22 and is formed to be flush with the holding surface 22 (flush). Note that the frame surface 24 may be formed lower than the holding surface 22.

[0019] The table rotation mechanism 25 rotates the chuck table 20 about the center of the holding surface 22. That is, the chuck table 20 can rotate about a rotation axis passing through the center of the holding surface 22 while holding the wafer 100 by the holding surface 22 by the table rotation mechanism 25 provided below.

[0020] Around the chuck table 20, a cover plate 39 that moves along the Y-axis direction together with the chuck table 20 is provided. Further, a bellows cover 12 that expands and contracts in the Y-axis direction is connected to the cover plate 39. And below the wafer holding mechanism 30, a Y-axis direction movement mechanism 40 is disposed.

[0021] The Y-axis direction movement mechanism 40 relatively moves the chuck table 20 and the grinding mechanism 70 in the Y-axis direction parallel to the holding surface 22. In the present embodiment, the Y-axis direction movement mechanism 40 is configured to move the chuck table 20 in the Y-axis direction with respect to the grinding mechanism 70.

[0022] The Y-axis direction movement mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis direction, a Y-axis movement table 45 that slides on the Y-axis guide rails 42, a Y-axis ball screw 43 parallel to the Y-axis guide rails 42, a Y-axis motor 44 connected to the Y-axis ball screw 43, and a holding base 41 that holds these components.

[0023] The Y-axis movement table 45 is slidably installed on the Y-axis guide rails 42. A nut portion (not shown) is fixed to the Y-axis movement table 45. The Y-axis ball screw 43 is screwed into this nut portion. The Y-axis motor 44 is connected to one end of the Y-axis ball screw 43.

[0024] In the Y-axis direction movement mechanism 40, when the Y-axis motor 44 rotates the Y-axis ball screw 43, the Y-axis movement table 45 moves in the Y-axis direction along the Y-axis guide rails 42. A wafer holding mechanism 30 is placed on the Y-axis movement table 45. Therefore, as the Y-axis movement table 45 moves in the Y-axis direction, the wafer holding mechanism 30 including the chuck table 20 moves in the Y-axis direction.

[0025] In this embodiment, the wafer holding mechanism 30 is moved in the Y-axis direction along the Y-axis by the Y-axis direction movement mechanism 40 between a -Y direction side work holding position for holding the wafer 100 on the holding surface 22 of the chuck table 20 and a +Y direction side grinding position where the wafer 100 held on the holding surface 22 is ground.

[0026] Also, a column 15 is erected on the +Y direction side of the second device base 11. A grinding mechanism 70 for grinding the wafer 100 and a grinding feed mechanism 60 are provided on the front surface of the column 15.

[0027] The grinding feed mechanism 60 relatively moves the chuck table 20 and the grinding wheel 77 of the grinding mechanism 70 in the Z-axis direction (grinding feed direction) perpendicular to the holding surface 22. In this embodiment, the grinding feed mechanism 60 is configured to move the grinding wheel 77 in the Z-axis direction with respect to the chuck table 20.

[0028] The grinding feed mechanism 60 includes a pair of Z-axis guide rails 61 parallel to the Z-axis direction, a Z-axis moving table 63 that slides on the Z-axis guide rails 61, a Z-axis ball screw 62 parallel to the Z-axis guide rails 61, a Z-axis motor 64, a Z-axis encoder 65 for detecting the rotation angle of the Z-axis ball screw 62, and a holder 66 attached to the Z-axis moving table 63. The holder 66 supports the grinding mechanism 70.

[0029] The Z-axis moving table 63 is slidably installed on the Z-axis guide rails 61. A nut portion (not shown) is fixed to the Z-axis moving table 63. The Z-axis ball screw 62 is screwed into this nut portion. The Z-axis motor 64 is connected to one end of the Z-axis ball screw 62.

[0030] In the grinding feed mechanism 60, when the Z-axis motor 64 rotates the Z-axis ball screw 62, the Z-axis moving table 63 moves in the Z-axis direction along the Z-axis guide rails 61. As a result, the holder 66 attached to the Z-axis moving table 63 and the grinding mechanism 70 supported by the holder 66 also move in the Z-axis direction together with the Z-axis moving table 63.

[0031] The Z-axis encoder 65 is rotated when the Z-axis motor 64 rotates the Z-axis ball screw 62, and can recognize the rotation angle of the Z-axis ball screw 62. Then, based on the recognition result, the Z-axis encoder 65 can detect the height position of the grinding wheel 77 of the grinding mechanism 70 that moves in the Z-axis direction.

[0032] The grinding mechanism 70 includes a spindle housing 71 fixed to the holder 66, a spindle 72 rotatably held in the spindle housing 71, a spindle motor 73 for rotationally driving the spindle 72, a wheel mount 74 attached to the lower end of the spindle 72, and a grinding wheel 75 supported by the wheel mount 74.

[0033] The spindle housing 71 is held by the holder 66 so as to extend in the Z-axis direction. The spindle 72 extends in the Z-axis direction so as to be orthogonal to the holding surface 22 of the chuck table 20, and is rotatably supported by the spindle housing 71.

[0034] The spindle motor 73 is connected to the upper end side of the spindle 72. By this spindle motor 73, the spindle 72 rotates about a rotation axis extending in the Z-axis direction.

[0035] The wheel mount 74 is formed in a disk shape and is fixed to the lower end (tip) of the spindle 72. The wheel mount 74 supports the grinding wheel 75.

[0036] The grinding wheel 75 is formed so that its outer diameter is substantially the same as the outer diameter of the wheel mount 74. The grinding wheel 75 includes an annular wheel base 76 formed of a metal material. A plurality of grinding wheels 77 arranged in an annular shape are fixed to the lower surface of the wheel base 76 over the entire circumference. The grinding wheels 77 are rotated by the spindle motor 73 together with the spindle 72 about its center as an axis, and grind the back surface 102 of the wafer 100 held by the chuck table 20.

[0037] Also, as shown in FIG. 1, a thickness measuring device 80 is disposed on the side portion of the opening 13 in the second apparatus base 11.

[0038] The thickness measuring device 80 has a holding surface height gauge 81, an upper surface height gauge 82, and a calculation unit 83. The holding surface height gauge 81 measures the height of the holding surface 22 by bringing the tip into contact with the frame surface 24 of the frame body 23 that is on the same surface as the holding surface 22 of the chuck table 20. Note that the frame surface 24 may be formed lower than the holding surface 22. The upper surface height gauge 82 measures the height of the back surface 102, which is the upper surface of the wafer 100 held by the holding surface 22, by bringing the tip into contact with the back surface 102. The calculation unit 83 calculates the difference between the measurement value of the holding surface height gauge 81 and the measurement value of the upper surface height gauge 82. Note that the holding surface height gauge 81 and the upper surface height gauge 82 move in a direction perpendicular to the holding surface 22.

[0039] In addition, when the wafer 100 is directly held on the holding surface 22 of the chuck table 20, the calculation unit 83 calculates the difference between the measured value of the holding surface height gauge 81 and the measured value of the upper surface height gauge 82 as the thickness of the wafer 100. Also, the wafer 100 may be held on the holding surface 22 of the chuck table 20 via a support member such as a substrate or a tape whose thickness is known in advance. In this case, the calculation unit 83 calculates the difference between the measured value of the holding surface height gauge 81 and the measured value of the upper surface height gauge 82 as the sum of the thickness of the support member and the thickness of the wafer 100.

[0040] The ground wafer 100 is carried out by the carry-out mechanism 172. The carry-out mechanism 172 conveys the wafer 100 held on the chuck table 20 to the spinner table 157 of the single-wafer type spinner cleaning mechanism 156.

[0041] The spinner cleaning mechanism 156 is a spinner cleaning unit for cleaning the wafer 100. The spinner cleaning mechanism 156 includes a spinner table 157 for holding the wafer 100 and a nozzle 158 for injecting cleaning water and drying air toward the spinner table 157.

[0042] In the spinner cleaning mechanism 156, the spinner table 157 holding the wafer 100 rotates, and cleaning water is injected toward the wafer 100, so that the wafer 100 is spinner-cleaned. Then, drying air is blown onto the wafer 100, and the wafer 100 is dried.

[0043] The wafer 100 cleaned by the spinner cleaning mechanism 156 is carried into the second cassette 163 on the second cassette stage 162 by the robot 155.

[0044] Further, the grinding device 1 has a control unit 7 inside for controlling the grinding device 1. The control unit 7 includes a CPU that performs arithmetic processing according to a control program, and a storage medium such as a memory. The control unit 7 executes various processes and comprehensively controls each component of the grinding device 1.

[0045] For example, the control unit 7 controls the above-described respective members of the grinding device 1 to perform a grinding process on the wafer 100.

[0046] Hereinafter, a method for grinding the wafer 100 in the grinding device 1, which is controlled by the control unit 7, will be described. This grinding method is a method of grinding the wafer 100 held on the holding surface 22 of the chuck table 20 with a grinding wheel 77 until a predetermined target thickness is reached while measuring with a thickness measuring device 80.

[0047] [Holding Step] First, with the back surface 102, which is the other surface of the wafer 100, facing upward, the surface 101 side, which is one surface of the wafer 100, is held by the holding surface 22 of the chuck table 20.

[0048] Specifically, the control unit 7 takes out the wafer 100 before processing from the first cassette 161 by the robot 155, places it on the temporary placement table 154 of the temporary placement mechanism 152, and aligns the wafer 100 to a predetermined position.

[0049] Furthermore, the control unit 7 controls the Y-axis direction movement mechanism 40 to arrange the wafer holding mechanism 30 including the chuck table 20 at the workpiece holding position on the -Y direction side. Then, the control unit 7 controls the loading mechanism 170 to hold the wafer 100 on the temporary placement mechanism 152, and as shown in FIG. 2, places the back surface 102 as the upper surface on the holding surface 22 of the chuck table 20.

[0050] As shown in FIG. 2, in this embodiment, the wafer 100 includes a first trimming portion 103 that is recessed in a ring shape on the outer peripheral portion on the surface 101 side and does not reach the back surface 102. This first trimming portion 103 is a portion that is recessed in a stepped shape formed on the outer peripheral edge of the surface 101 of the wafer 100. Due to this first trimming portion 103, in the wafer 100, the diameter of the surface 101 is smaller than the diameter of the back surface 102.

[0051] Further, in this embodiment, a substrate 110 having substantially the same diameter as the back surface 102 of the wafer 100 is bonded to the surface 101 of the wafer 100 by bonding using an adhesive, direct bonding, or the like. In this embodiment, by treating the wafer 100 and the substrate 110 as an integral workpiece, it is possible to improve the handleability of the wafer 100 and prevent warping and breakage of the wafer 100 during processing.

[0052] Thus, in this embodiment, the wafer 100 is placed on the holding surface 22 of the chuck table 20 with the back surface 102 as the upper surface via the substrate 110. Thereafter, the control unit 7 communicates the holding surface 22 with a suction source (not shown). As a result, the holding surface 22 sucks and holds the surface 101 side of the wafer 100 via the substrate 110. In this way, the wafer 100 is held by the chuck table 20.

[0053] Thereafter, the control unit 7 controls the Y-axis direction movement mechanism 40 (see FIG. 1) to arrange the wafer holding mechanism 30 including the chuck table 20 at a grinding position on the +Y direction side below the grinding mechanism 70.

[0054] [First Grinding Step] Next, as indicated by arrow 301 in FIG. 2, the control unit 7 rotates the grinding wheel 75 of the grinding mechanism 70. Further, the control unit 7 controls the table rotation mechanism 25 (see FIG. 1) to rotate the chuck table 20 as indicated by arrow 302 in FIG. 2. Then, the control unit 7 feeds the grinding mechanism 70 including the grinding wheel 77 in the -Z direction by the grinding feed mechanism 60 (see FIG. 1).

[0055] Thereby, the grinding wheel 77 of the rotating grinding wheel 75 contacts the back surface 102 of the wafer 100 held by the rotating chuck table 20, and grinds this back surface 102.

[0056] In the grinding in this first grinding process, the back surface 102 of the wafer 100 is ground with the grinding wheel 77 without measuring the height of the holding surface 22 by the holding surface height gauge 81 and the height of the back surface 102 of the wafer 100 by the upper surface height gauge 82, so that the first trimming portion 103 is exposed on the back surface 102, and the end material separated from the wafer 100 is removed.

[0057] That is, in the first grinding process, after the control unit 7 measures the upper surface height of the back surface 102 of the wafer 100 held by the holding surface 22 by the upper surface height gauge 82, as shown in FIG. 2, the holding surface height gauge 81 that moves in a direction perpendicular to the holding surface is raised and arranged at a height position sufficiently away from the frame surface 24 of the frame body 23 in the chuck table 20 and the wafer 100, and the upper surface height gauge 82 is raised and arranged at a height position sufficiently away from the back surface 102 of the wafer 100.

[0058] In this state, the control unit 7 stores the height of the back surface 102 of the wafer 100 measured by the upper surface height gauge 82, and then quickly feeds the grinding mechanism 70 including the grinding wheel 77 in the -Z direction until the lower surface of the grinding wheel 77 does not contact the back surface 102. After that, the grinding mechanism 70 including the grinding wheel 77 is fed in the -Z direction at a predetermined grinding feed rate for grinding the wafer 100, thereby grinding the back surface 102 of the wafer 100 with the grinding wheel 77. As a result, as shown in FIG. 3, the bottom of the first trimming portion 103 in the wafer 100 becomes thinner, and the end material 105 remains in a residual state.

[0059] Then, as the grinding by the grinding wheel 77 further progresses, the portion connecting the wafer 100 and the end material 105 becomes thinner, and cracks enter the connecting portion due to the impact caused by the contact of the grinding wheel 77. As shown in FIG. 4, the first trimming portion 103 is exposed on the back surface 102, and the end material 105 is separated from the wafer 100 and removed as, for example, arc-shaped fragments. Thereby, the first grinding step is completed.

[0060] In addition, in the first grinding step, the control unit 7 acquires the timing of completion of the first grinding step as follows, for example. That is, the control unit 7 obtains in advance the height position (target position) of the grinding wheel 77 such that the first trimming portion 103 is exposed on the back surface 102 based on the thickness of the substrate 110 acquired in advance, the thickness of the wafer 100 before grinding, the depth of the first trimming portion 103, and the like. Further, when the control unit 7 feeds the grinding wheel 77 in the -Z direction, it confirms the height position of the grinding wheel 77 by the Z-axis encoder 65 of the grinding feed mechanism 60 shown in FIG. 1. Then, when the height position of the grinding wheel 77 reaches the target position, the control unit 7 determines that the first trimming portion 103 is exposed on the back surface 102 and recognizes that the first grinding step is completed. Note that the control unit 7 may measure the height of the back surface 102 of the wafer 100 with the upper surface height gauge 82 and determine that the first trimming portion 103 is exposed on the back surface 102 based on the change amount of the height of the back surface 102. Note that the end material 105 separated from the wafer 100 scatters outside the chuck table 20 due to the rotation of the chuck table 20.

[0061] [Second grinding process] After the first grinding process, the control unit 7 subsequently performs the second grinding process. In this second grinding process, while measuring the height of the holding surface 22 with the holding surface height gauge 81, measuring the height of the back surface 102 of the wafer 100 with the upper surface height gauge 82, and calculating the difference between the measurement value of the holding surface height gauge 81 and the measurement value of the upper surface height gauge 82 by the calculation unit 83, the back surface 102 of the wafer 100 is ground by the grinding wheel 77 until the value calculated by the calculation unit 83 reaches a preset predetermined thickness.

[0062] Specifically, following the first grinding process, the control unit 7 grinds the back surface 102 of the wafer 100 with the grinding wheel 77 by grinding the grinding mechanism 70 including the grinding wheel 77 in the -Z direction. At this time, as shown in FIG. 5, the control unit 7 measures the height of the holding surface 22 by bringing the holding surface height gauge 81 into contact with the frame surface 24 of the frame body 23 on the chuck table 20. Further, the control unit 7 measures the height of the back surface 102 by bringing the upper surface height gauge 82 into contact with the back surface 102 of the wafer 100. Then, the calculation unit 83 calculates the difference between the measurement value of the holding surface height gauge 81 and the measurement value of the upper surface height gauge 82.

[0063] Here, in the present embodiment, the wafer 100 is held on the holding surface 22 of the chuck table 20 via the substrate 110. Therefore, the calculation unit 83 calculates the difference between the measurement value of the holding surface height gauge 81 and the measurement value of the upper surface height gauge 82 as the sum of the thickness of the wafer 100 and the thickness of the substrate 110.

[0064] Then, the control unit 7 performs grinding of the back surface 102 of the wafer 100 with the grinding wheel 77 until the value calculated by this calculation unit 83, that is, the sum of the thickness of the wafer 100 and the thickness of the substrate 110, reaches a preset predetermined thickness.

[0065] Here, the predetermined thickness is, for example, the sum of the thickness of the pre-recognized substrate 110 and the target thickness of the wafer 100. Therefore, the control unit 7 can grind the wafer 100 to the target thickness by performing grinding until the sum of the thickness of the wafer 100 and the thickness of the substrate 110 becomes the predetermined thickness.

[0066] As described above, in the present embodiment, in the first grinding step, the back surface 102 of the wafer 100 is ground to expose the first trimming portion 103 on the back surface 102 without measuring the height of the holding surface 22 by the holding surface height gauge 81, and the end material 105 separated from the wafer 100 is removed.

[0067] That is, in the present embodiment, when the end material 105 is separated from the wafer 100 (see FIG. 4), the height of the holding surface 22 is not measured by the holding surface height gauge 81, and the holding surface height gauge 81 is separated from the frame surface 24. For this reason, even when the end material 105 is bounced off by the rotating grinding wheel 77, it is possible to avoid the end material 105 from colliding with the holding surface height gauge 81 during measurement. Therefore, it is possible to prevent the holding surface height gauge 81 from having difficulty in measuring the height of the holding surface or the measurement accuracy of the holding surface height gauge 81 from deteriorating due to the collision of the end material 105. In addition, damage to the holding surface height gauge 81 can be prevented.

[0068] Note that in the above-described embodiment, the wafer 100 provided with the first trimming portion 103 that is recessed in a stepped shape formed on the outer peripheral edge of the front surface 101 is shown as the wafer to be ground. In this regard, the wafer to be ground in the present embodiment may be a wafer 111 as shown in FIG. 6.

[0069] This wafer 111 has a front surface 101 and a back surface 102, similar to wafer 100. And, instead of the first trimming portion 103, the wafer 111 is provided with a second trimming portion 107 as shown in FIG. 6, which is a ring-shaped recessed trimming portion formed on the outer peripheral portion on the front surface 101 side and does not reach the back surface 102.

[0070] This second trimming portion 107 is a groove-shaped recessed portion formed inside the outer peripheral edge of the front surface 101 in the wafer 100.

[0071] Also, in the wafer 111, a tape 112 having substantially the same diameter as the wafer 100 is bonded to its front surface 101. By treating the wafer 100 and the tape 112 as an integral workpiece, for example, it is possible to protect the devices formed on the front surface 101 of the wafer 100.

[0072] Hereinafter, a grinding method for grinding the wafer 111 provided with such a second trimming portion 107 and tape 112 will be described.

[0073] [Holding step] Similar to the case of grinding the wafer 100, the control unit 7 holds the wafer 111 by the holding surface 22 of the chuck table 20 and arranges the wafer holding mechanism 30 including the chuck table 20 at the grinding position on the +Y direction side below the grinding mechanism 70.

[0074] [First grinding step] Next, as shown by the arrows 301 and 302 in FIG. 6, the control unit 7 rotates the grinding wheel 75 of the grinding mechanism 70 and rotates the chuck table 20. Then, the control unit 7 grinds the back surface 102 of the wafer 111 with the grinding wheel 77 by grinding and feeding the grinding mechanism 70 including the grinding wheel 77 in the -Z direction by the grinding feed mechanism 60 (see FIG. 1).

[0075] Even in the grinding process of this first grinding step, similar to the grinding of the wafer 100, without performing the height measurement of the holding surface 22 by the holding surface height gauge 81 and the height measurement of the back surface 102 of the wafer 111 by the upper surface height gauge 82, the back surface 102 of the wafer 111 is ground with the grinding wheel 77 to expose the second trimming portion 107 on the back surface 102, and the end material separated from the wafer 111 is removed.

[0076] That is, as shown in FIG. 6, the control unit 7 arranges the holding surface height gauge 81 at a height position sufficiently far above the frame surface 24 and the wafer 111, and arranges the upper surface height gauge 82 at a height position sufficiently far above the back surface 102 of the wafer 111, and then grinds the back surface 102 of the wafer 111 with the grinding wheel 77. As a result, as shown in FIG. 7, the bottom of the second trimming portion 107 in the wafer 111 becomes thinner, and the end material 108, which is a portion outside the second trimming portion 107, remains.

[0077] Then, as the grinding by the grinding wheel 77 further progresses, the second trimming portion 107 is exposed on the back surface 102, and as shown in FIG. 8, the end material 108 is separated from the wafer 111 and removed as, for example, an arc-shaped fragment. Note that the control unit 7 may perform the height measurement of the back surface 102 of the wafer 111 by the upper surface height gauge 82. The control unit 7 may determine that the end material 108 has been separated from the wafer 111 based on the change amount of the height of the back surface 102 measured by the upper surface height gauge 82.

[0078] [Second Grinding Step] Subsequently, the control unit 7, similar to the grinding of the wafer 100, performs the height measurement of the holding surface 22 by the holding surface height gauge 81, the height measurement of the back surface 102 of the wafer 111 by the upper surface height gauge 82, and the calculation of the difference between the measurement value of the holding surface height gauge 81 and the measurement value of the upper surface height gauge 82 by the calculation unit 83, and grinds the back surface 102 of the wafer 111 until the value calculated by the calculation unit 83 reaches a preset predetermined thickness.

[0079] That is, while the control unit 7 continues to grind the back surface 102 of the wafer 111 with the grinding wheel 77, as shown in FIG. 9, the control unit 7 measures the height of the holding surface 22 by bringing the holding surface height gauge 81 into contact with the frame surface 24 of the frame body 23 on the chuck table 20. Further, the control unit 7 measures the height of the back surface 102 by bringing the upper surface height gauge 82 into contact with the back surface 102 of the wafer 111. Then, the calculation unit 83 calculates the difference between the measured value of the holding surface height gauge 81 and the measured value of the upper surface height gauge 82.

[0080] Here, in the present embodiment, the wafer 111 is held on the holding surface 22 of the chuck table 20 via the tape 112. Therefore, the calculation unit 83 calculates the difference between the measured value of the holding surface height gauge 81 and the measured value of the upper surface height gauge 82 as the sum of the thickness of the wafer 111 and the thickness of the tape 112.

[0081] Then, the control unit 7 performs the grinding of the back surface 102 of the wafer 111 with the grinding wheel 77 until the value calculated by this calculation unit 83, that is, the sum of the thickness of the wafer 111 and the thickness of the tape 112 reaches a predetermined thickness set in advance.

[0082] Here, the predetermined thickness is, for example, the sum of the thickness of the tape 112 recognized in advance and the target thickness of the wafer 111. Therefore, the control unit 7 can grind the wafer 111 to the target thickness by performing the grinding until the sum of the thickness of the wafer 111 and the thickness of the tape 112 reaches the predetermined thickness.

[0083] Even in this case, when the scrap 108 is separated from the wafer 111, the height of the holding surface 22 is not measured by the holding surface height gauge 81, and the holding surface height gauge 81 is separated from the frame surface 24. This makes it possible to avoid the scrap 108 colliding with the holding surface height gauge 81 during measurement, thereby preventing the holding surface height gauge 81 from having difficulty measuring the height of the holding surface due to a collision of the scrap 108 and preventing the measurement accuracy of the holding surface height gauge 81 from deteriorating. In addition, damage to the holding surface height gauge 81 can be prevented.

[0084] Furthermore, in the above-described embodiment, in the first grinding step, the back surface 102 is ground by the grinding wheel 77 without measuring the height of the holding surface 22 with the holding surface height gauge 81 and without measuring the height of the back surface 102 of the wafer 100 (wafer 111) with the upper surface height gauge 82. In this regard, it is sufficient that the first grinding step is performed in a state where the height of the holding surface 22 is not measured with at least the holding surface height gauge 81. Therefore, in the first grinding step, the height of the back surface 102 may be measured with the upper surface height gauge 82. [Explanation of symbols]

[0085] 1: grinding device, 7: control unit, 10: first device base, 11: second device base, 12: bellows cover, 13: opening, 15: column, 20: chuck table, 21: porous member, 22: holding surface, 23: frame, 24: frame surface, 25: table rotation mechanism, 26: table support mechanism, 27: support column, 30: wafer holding mechanism, 39: cover plate, 40: Y-axis direction movement mechanism, 41: support table, 42: Y-axis guide rail, 43: Y-axis ball screw, 44: Y-axis motor, 45: Y-axis movement table, 60: Grinding feed mechanism, 61: Z-axis guide rail, 62: Z-axis ball screw, 63: Z-axis moving table, 64: Z-axis motor, 65: Z-axis encoder, 66: holder, 70: Grinding mechanism, 71: Spindle housing, 72: Spindle, 73: Spindle motor, 74: Wheel mount, 75: Grinding wheel, 76: Wheel base, 77: Grinding stone, 80: Thickness measuring device, 81: Holding surface height gauge, 82: Top surface height gauge, 83: Calculation unit, 100: Wafer, 101: Front surface, 102: Back surface, 103: First trimming section, 105: Edge material, 107: Second trimming section, 108: Edge material, 110: Substrate, 111: Wafer, 112: Tape, 152: Temporary placement mechanism, 153: Alignment member, 154: Temporary placement table, 155: Robot, 156: Spinner cleaning mechanism, 157: Spinner table, 158: Nozzle, 160: First cassette stage, 161: First cassette, 162: Second cassette stage, 163: Second cassette, 170: Loading mechanism, 172: Unloading mechanism

Claims

【Claim 1】 A method for grinding a wafer held on a holding surface of a chuck table until it reaches a predetermined thickness by a grinding wheel while performing measurement by a thickness measuring device, comprising: The wafer has, on the outer peripheral portion on one surface side, a trimming portion that is recessed in a ring shape and does not reach the other surface. The thickness measuring device includes a holding surface height gauge that contacts a frame surface surrounding the holding surface to measure the height of the holding surface, an upper surface height gauge that contacts the upper surface of the wafer held on the holding surface to measure the upper surface height of the wafer, and a calculation unit that calculates the difference between the measurement value of the holding surface height gauge and the measurement value of the upper surface height gauge. A holding step of holding one surface side of the wafer on the holding surface with the other surface of the wafer facing upward. A first grinding step of grinding the other surface of the wafer with the grinding wheel to expose the trimming portion on the other surface in a state where the height of the holding surface is not measured at least by the holding surface height gauge, and removing the end material separated from the wafer. After the first grinding step, while performing the height measurement of the holding surface by the holding surface height gauge, the height measurement of the upper surface of the wafer by the upper surface height gauge, and the calculation by the calculation unit, a second grinding step of grinding the other surface of the wafer until the value calculated by the calculation unit reaches a predetermined thickness set in advance. A method for grinding a wafer, including the above steps.

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