JP2023092276A - Wafer grinding method - Google Patents

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

The present invention relates to a wafer grinding method.

A wafer grinding method for grinding a wafer held on a holding surface of a chuck table with a grinding wheel measures the holding surface height and the wafer top surface height, as disclosed in Patent Document 1, and calculates the two measured values. The difference is calculated, and grinding is performed until the calculated value (wafer thickness) reaches a predetermined thickness.

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

JP 2008-073785 A JP 2013-188813 A JP 2019-181634 A

Conventionally, however, fragments generated by grinding collide with the height gauge for measuring the height of the holding surface, making it difficult to measure the height of the holding surface.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to prevent a height gauge for measuring the height of a holding surface from being hit by a fragment and making it difficult to measure the thickness.

In the wafer grinding method (this grinding method) of the present invention, a wafer held on a holding surface of a chuck table is ground by a grinding wheel until it reaches a predetermined thickness while being measured by a thickness measuring device. In the grinding method of 1, the wafer is provided with a ring-shaped recessed trimming portion that does not reach the other surface on the outer peripheral portion of one surface side, and the thickness measuring device is attached to the frame surface surrounding the holding surface. A holding surface height gauge that contacts and measures the height of the holding surface, an upper surface height gauge that contacts the upper surface of the wafer held on the holding surface and measures the height of the upper surface of the wafer, and the measured value of the holding surface height gauge. and a calculating unit that calculates the difference between the measured value of the top surface height gauge, a holding step of holding one surface side of the wafer with the other surface of the wafer facing up, and at least the holding Without measuring the height of the holding surface with a surface height gauge, the other surface of the wafer is ground with the grinding wheel to expose the trimmed portion on the other surface, and the scrap material separated from the wafer is a first grinding step to be removed; after the first grinding step, measurement of the height of the holding surface by the holding surface height gauge, measurement of the height of the upper surface of the wafer by the upper surface height gauge, and calculation by the calculating unit and a second grinding step of grinding the other surface of the wafer until the value calculated by the calculation unit reaches a predetermined thickness while performing the above.

In this grinding method, in the first grinding step, when the offcuts are separated from the wafer and removed, the height of the holding surface is not measured by the holding surface height gauge. ing. Therefore, even if the offcuts are thrown off the wafer by the rotating grinding wheel, the offcuts collide with the holding surface height gauge that is being measured, making it difficult for the holding surface height gauge to measure the height of the holding surface. Also, deterioration of the measurement accuracy of the holding surface height gauge can be prevented. Also, it is possible to prevent damage to the holding surface height gauge.

It is a perspective view which shows the structure of a grinding apparatus. It is explanatory drawing which shows a holding process and a 1st grinding process. It is explanatory drawing which shows a 1st grinding process. It is explanatory drawing which shows a 1st grinding process. It is explanatory drawing which shows a 2nd grinding process. It is explanatory drawing which shows a holding process and a 1st grinding process. It is explanatory drawing which shows a 1st grinding process. It is explanatory drawing which shows a 1st grinding process. It is explanatory drawing which shows a 2nd grinding process.

As shown in FIG. 1, a grinding apparatus 1 according to this embodiment is an apparatus for grinding a wafer 100. As shown in FIG. A wafer 100 is, for example, a circular plate-like workpiece and has a front surface 101 and a back surface 102 . A back surface 102 of the wafer 100 is a surface to be ground.

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

A first cassette stage 160 and a second cassette stage 162 are provided on the -Y direction side of the first device base 10 . A first cassette 161 containing wafers 100 before processing is mounted on the first cassette stage 160 . A second cassette 163 that accommodates the processed wafers 100 is mounted on the second cassette stage 162 .

The first cassette 161 and the second cassette 163 are internally provided with a plurality of shelves, each containing one wafer 100 . That is, the first cassette 161 and the second cassette 163 accommodate a plurality of wafers 100 like shelves.

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

The temporary placement mechanism 152 is used to temporarily place the wafers 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 alignment pins are moved toward the center in the radial direction of the temporary placement table 154 , thereby reducing the diameter of the circle connecting the alignment pins. As a result, the wafer 100 placed on the temporary placement table 154 is aligned (centered) at a predetermined position.

A loading mechanism 170 is provided at a position adjacent to the temporary placement mechanism 152 . The loading mechanism 170 places the wafer 100 temporarily placed on the temporary placement mechanism 152 on the holding surface 22 of the chuck table 20 .

An opening 13 is provided on the upper surface side of the second device base 11 . A wafer holding mechanism 30 is arranged in the opening 13 .
The wafer holding mechanism 30 includes a chuck table 20 having a holding surface 22 that holds the wafer 100, a table support mechanism 26 that supports the chuck table 20, a table rotation mechanism 25 that rotates the chuck table 20, and an inclination of the chuck table 20. includes a support post 27 with adjustable .

The chuck table 20 includes a porous member 21 and a frame 23 that accommodates 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 that holds the wafer 100 by suction. The holding surface 22 sucks and holds the wafer 100 by communicating with a suction source (not shown). That is, the chuck table 20 holds the wafer 100 with the holding surface 22 . A frame body surface 24 that is an upper surface of the frame body 23 surrounds the holding surface 22 and is formed to be flush with the holding surface 22 . Note that the frame body surface 24 may be formed lower than the holding surface 22 .

The table rotation mechanism 25 rotates the chuck table 20 around the center of the holding surface 22 . That is, the chuck table 20 is rotatable about a rotation axis passing through the center of the holding surface 22 with the wafer 100 held by the holding surface 22 by the table rotating mechanism 25 provided below.

A cover plate 39 is provided around the chuck table 20 to move along the Y-axis direction together with the chuck table 20 . A bellows cover 12 that expands and contracts in the Y-axis direction is connected to the cover plate 39 . A Y-axis direction moving mechanism 40 is arranged below the wafer holding mechanism 30 .

The Y-axis direction moving 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 this embodiment, the Y-axis direction moving mechanism 40 is configured to move the chuck table 20 in the Y-axis direction with respect to the grinding mechanism 70 .

The Y-axis movement mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis direction, a Y-axis movement table 45 sliding on the Y-axis guide rails 42, and a Y-axis ball screw 43 parallel to the Y-axis guide rails 42. , a Y-axis motor 44 connected to a Y-axis ball screw 43, and a holding base 41 for holding them.

The Y-axis moving table 45 is slidably installed on the Y-axis guide rail 42 . A nut portion (not shown) is fixed to the Y-axis moving table 45 . A 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 .

In the Y-axis direction moving mechanism 40 , the Y-axis motor 44 rotates the Y-axis ball screw 43 to move the Y-axis moving table 45 along the Y-axis guide rail 42 in the Y-axis direction. A wafer holding mechanism 30 is mounted on the Y-axis moving table 45 . Accordingly, as the Y-axis moving table 45 moves in the Y-axis direction, the wafer holding mechanism 30 including the chuck table 20 moves in the Y-axis direction.

In this embodiment, the wafer holding mechanism 30 has a work holding position on the -Y direction side for holding the wafer 100 on the holding surface 22 of the chuck table 20, and the wafer 100 held on the holding surface 22 is ground. It is moved along the Y-axis direction by the Y-axis direction moving mechanism 40 between the grinding positions on the +Y direction side.

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 .

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 .

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 sliding on the Z-axis guide rails 61, a Z-axis ball screw 62 parallel to the Z-axis guide rails 61, a Z Equipped with a shaft 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 . Holder 66 supports grinding mechanism 70 .

The Z-axis moving table 63 is slidably installed on the Z-axis guide rail 61 . A nut portion (not shown) is fixed to the Z-axis moving table 63 . A 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 .

In the grinding feed mechanism 60 , the Z-axis motor 64 rotates the Z-axis ball screw 62 to move the Z-axis moving table 63 along the Z-axis guide rail 61 in the Z-axis direction. 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 together with the Z-axis moving table 63 in the Z-axis direction.

The Z-axis encoder 65 is rotated by the Z-axis motor 64 rotating the Z-axis ball screw 62 and can recognize the rotation angle of the Z-axis ball screw 62 . 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 is moved in the Z-axis direction.

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

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 perpendicular to the holding surface 22 of the chuck table 20 and is rotatably supported by the spindle housing 71 .

The spindle motor 73 is connected to the upper end side of the spindle 72 . The spindle motor 73 rotates the spindle 72 around a rotation axis extending in the Z-axis direction.

The wheel mount 74 is disc-shaped and fixed to the lower end (tip) of the spindle 72 . A wheel mount 74 supports a grinding wheel 75 .

The grinding wheel 75 is formed to have an outer diameter approximately the same as the outer diameter of the wheel mount 74 . Grinding wheel 75 includes an annular wheel base 76 formed from a metallic 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 wheel 77 is rotated about its center by the spindle motor 73 together with the spindle 72 to grind the back surface 102 of the wafer 100 held on the chuck table 20 .

Further, as shown in FIG. 1, a thickness measuring device 80 is arranged on the side of the opening 13 in the second device base 11 .

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

Note that 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 measurement value of the holding surface height gauge 81 and the measurement value of the upper surface height gauge 82 as Calculate as thickness.
In some cases, the wafer 100 is held on the holding surface 22 of the chuck table 20 via a supporting member whose thickness is known in advance, such as a substrate or tape, which will be described later. In this case, the calculator 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 .

The wafer 100 after grinding is unloaded by the unloading mechanism 172 . The unloading mechanism 172 conveys the wafer 100 held on the chuck table 20 to the spinner table 157 of the single-wafer spinner cleaning mechanism 156 .

A spinner cleaning mechanism 156 is a spinner cleaning unit that cleans the wafer 100 . The spinner cleaning mechanism 156 has a spinner table 157 that holds the wafer 100 and a nozzle 158 that sprays cleaning water and dry air toward the spinner table 157 .

In the spinner cleaning mechanism 156, a spinner table 157 holding the wafer 100 rotates, and cleaning water is sprayed toward the wafer 100 to clean the wafer 100 with the spinner. Dry air is then blown onto the wafer 100 to dry the wafer 100 .

The wafers 100 cleaned by the spinner cleaning mechanism 156 are transferred to the second cassette 163 on the second cassette stage 162 by the robot 155 .

The grinding device 1 also has a control unit 7 for controlling the grinding device 1 therein. The control unit 7 includes a CPU that performs arithmetic processing according to a control program, a storage medium such as a memory, and the like. The control unit 7 executes various processes and centrally controls each component of the grinding apparatus 1 .

For example, the control unit 7 controls the above-described members of the grinding device 1 to grind the wafer 100 .

A method of grinding the wafer 100 in the grinding apparatus 1 controlled by the controller 7 will be described below. This grinding method is a method in which the wafer 100 held on the holding surface 22 of the chuck table 20 is ground by the grinding wheel 77 until it reaches a predetermined target thickness while being measured by the thickness measuring device 80 .

[Holding step]
First, the back surface 102 of the wafer 100 is turned upward, and the front surface 101 of the wafer 100 is held by the holding surface 22 of the chuck table 20 .

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 places the wafer 100 at a predetermined position. Align.

Further, the control unit 7 controls the Y-axis direction moving mechanism 40 to place the wafer holding mechanism 30 including the chuck table 20 at the work 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. do.

As shown in FIG. 2, in this embodiment, the wafer 100 is provided with a first trimming portion 103 recessed in a ring shape not reaching the back surface 102 at the outer peripheral portion on the front surface 101 side. The first trimming portion 103 is a recessed stepped portion formed on the outer peripheral edge of the front surface 101 of the wafer 100 . Due to this first trimming portion 103 , the diameter of the front surface 101 of the wafer 100 is smaller than the diameter of the back surface 102 .

In this embodiment, a substrate 110 having substantially the same diameter as the back surface 102 of the wafer 100 is bonded to the front surface 101 of the wafer 100 by bonding using an adhesive, direct bonding, or the like. In this embodiment, by handling the wafer 100 and the substrate 110 as an integrated workpiece, it is possible to improve the handleability of the wafer 100 and to prevent warping and breakage of the wafer 100 during processing. ing.

Thus, in this embodiment, the wafer 100 is placed on the holding surface 22 of the chuck table 20 with the back surface 102 facing up, with the substrate 110 interposed therebetween. After that, the controller 7 causes the holding surface 22 to communicate with a suction source (not shown). Thereby, the holding surface 22 sucks and holds the front surface 101 side of the wafer 100 via the substrate 110 . The wafer 100 is thus held by the chuck table 20 .

After that, the control unit 7 controls the Y-axis direction moving mechanism 40 (see FIG. 1) to place the wafer holding mechanism 30 including the chuck table 20 at the grinding position on the +Y direction side below the grinding mechanism 70 . .

[First Grinding Step]
The controller 7 then rotates the grinding wheel 75 of the grinding mechanism 70 as indicated by arrow 301 in FIG. 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. 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).

As a result, the grinding wheel 77 of the rotating grinding wheel 75 contacts the back surface 102 of the wafer 100 held on the rotating chuck table 20 and grinds the back surface 102 .

In the grinding in this first grinding step, the back surface 102 of the wafer 100 is ground 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 100 by the top surface height gauge 82. The first trimming portion 103 is exposed on the rear surface 102 by grinding with the grindstone 77, and offcuts separated from the wafer 100 are removed.

That is, in the first grinding step, the control unit 7 measures the height of the upper surface of the back surface 102 of the wafer 100 held by the holding surface 22 with the upper surface height gauge 82, and then, as shown in FIG. A holding surface height gauge 81 that moves in the vertical direction is raised to a height position sufficiently separated from the frame surface 24 of the frame 23 on the chuck table 20 and the wafer 100 , and a top surface height gauge 82 is positioned on the back surface of the wafer 100 . It is raised to a height position sufficiently separated from 102 and arranged.

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 includes the grinding wheel 77 at a high speed in the immediate vicinity where the lower surface of the grinding wheel 77 does not contact the back surface 102. After grinding and feeding the grinding mechanism 70 in the -Z direction, the grinding mechanism 70 including the grinding wheel 77 is ground and 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. Grind with a whetstone 77 . As a result, as shown in FIG. 3, the bottom portion of the first trimming portion 103 on the wafer 100 becomes thinner, and the scrap material 105 remains.

As the grinding by the grinding wheel 77 progresses further, the portion connecting the wafer 100 and the scrap 105 becomes thinner, and the impact caused by the contact of the grinding wheel 77 cracks the connecting portion. 4, the first trimming portion 103 is exposed on the back surface 102, and the offcuts 105 are separated from the wafer 100 as, for example, arcuate fragments and removed. This completes the first grinding step.

In addition, in the first grinding process, the control unit 7 acquires the timing of completion of the first grinding process, for example, as follows. That is, the control unit 7 determines the thickness of the substrate 110 obtained in advance, the thickness of the wafer 100 before grinding, the depth of the first trimming portion 103, and the like, so that the first trimming portion 103 is the back surface. A height position (target position) of the grinding wheel 77 that is exposed at 102 is obtained in advance. When the grinding wheel 77 is fed in the -Z direction, the control unit 7 confirms the height position of the grinding wheel 77 with the Z-axis encoder 65 of the grinding feed mechanism 60 shown in FIG. Then, when the height position of the grinding wheel 77 reaches the target position, the control section 7 determines that the first trimming section 103 is exposed on the back surface 102, and recognizes that the first grinding process is completed. .
Note that the control unit 7 measures the height of the back surface 102 of the wafer 100 with the top surface height gauge 82, and determines that the first trimming unit 103 is exposed on the back surface 102 based on the amount of change in the height of the back surface 102. good.
The scrap 105 separated from the wafer 100 scatters outside the chuck table 20 as the chuck table 20 rotates.

[Second Grinding Step]
After the first grinding process, the control unit 7 subsequently performs the second grinding process. In this second grinding process, the height of the holding surface 22 is measured by the holding surface height gauge 81, the height of the rear surface 102 of the wafer 100 is measured by the upper surface height gauge 82, and the measured value of the holding surface height gauge 81 and the upper surface are measured by the calculating unit 83. While calculating the difference from the measured value of the height gauge 82, the back surface 102 of the wafer 100 is ground until the value calculated by the calculator 83 reaches a predetermined thickness.

Specifically, following the first grinding step, the control unit 7 grinds the back surface 102 of the wafer 100 with the grinding wheel 77 by feeding the grinding mechanism 70 including the grinding wheel 77 in the −Z direction. At this time, 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 23 of the chuck table 20, as shown in FIG. Furthermore, the control unit 7 measures the height of the back surface 102 of the wafer 100 by bringing the top surface height gauge 82 into contact with the back surface 102 of the wafer 100 . Then, the calculator 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 .

Here, in this embodiment, the wafer 100 is held on the holding surface 22 of the chuck table 20 via the substrate 110 . Therefore, the calculator 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 100 and the thickness of the substrate 110 .

Then, the controller 7 grinds the wafer 100 by the grinding wheel 77 until the sum of the thickness of the wafer 100 and the thickness of the substrate 110 calculated by the calculator 83 reaches a predetermined thickness. Grinding of the back surface 102 of is performed.

Here, the predetermined thickness is, for example, the sum of the previously recognized thickness of the 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 reaches a predetermined thickness.

As described above, in the present embodiment, in the first grinding step, the rear surface 102 of the wafer 100 is ground to form the first trimming portion 103 without measuring the height of the holding surface 22 by the holding surface height gauge 81. The offcuts 105 exposed to 102 and separated from the wafer 100 are removed.

That is, in the present embodiment, when the scrap 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 used as the frame. away from the body surface 24; Therefore, even if the scrap 105 is flipped off by the rotating grinding wheel 77, it is possible to prevent the scrap 105 from colliding with the holding surface height gauge 81 being measured. Therefore, it is possible to prevent the holding surface height gauge 81 from making it difficult to measure the height of the holding surface and from deteriorating the measurement accuracy of the holding surface height gauge 81 due to the collision of the scrap material 105 . Moreover, damage to the holding surface height gauge 81 can be prevented.

In the above-described embodiment, the wafer 100 provided with the stepped first trimming portion 103 formed on the outer peripheral edge of the front surface 101 is shown as the wafer to be ground. In this regard, the wafer ground in this embodiment may be wafer 111 as shown in FIG.

This wafer 111 has a front surface 101 and a back surface 102 like the wafer 100 . In place of the first trimming portion 103, the wafer 111 has a second trimming portion 107 as shown in FIG. It has

The second trimming portion 107 is a groove-shaped concave portion formed inside the outer peripheral edge of the front surface 101 of the wafer 100 .

A tape 112 having approximately the same diameter as the wafer 100 is attached to the front surface 101 of the wafer 111 . By treating the wafer 100 and the tape 112 as a single workpiece, it is possible to protect, for example, the devices formed on the surface 101 of the wafer 100 .

A grinding method for grinding the wafer 111 including the second trimming portion 107 and the tape 112 will be described below.

[Holding step]
As in 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 includes the chuck table 20 at the grinding position on the +Y direction side below the grinding mechanism 70 . A wafer holding mechanism 30 is arranged.

[First Grinding Step]
Next, the control unit 7 rotates the grinding wheel 75 of the grinding mechanism 70 and rotates the chuck table 20 as indicated by arrows 301 and 302 in FIG. Then, the control unit 7 causes the grinding feed mechanism 60 (see FIG. 1) to grind and feed the grinding mechanism 70 including the grinding wheel 77 in the −Z direction, thereby grinding the back surface 102 of the wafer 111 with the grinding wheel 77. .

In the grinding in the first grinding step, similarly to the grinding of the wafer 100, 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 top surface height gauge 82 are not performed. , the back surface 102 of the wafer 111 is ground by the grinding wheel 77 to expose the second trimming portion 107 on the back surface 102, and the offcuts separated from the wafer 111 are removed.

That is, as shown in FIG. 6, the control unit 7 arranges the holding surface height gauge 81 at a height position sufficiently spaced upward from the frame surface 24 and the wafer 111, and moves the upper surface height gauge 82 from the rear surface 102 of the wafer 111. The back surface 102 of the wafer 111 is ground by the grindstone 77 while the wafer 111 is positioned at a sufficiently high height. As a result, as shown in FIG. 7, the bottom portion of the second trimming portion 107 on the wafer 111 becomes thinner, and the offcuts 108 outside the second trimming portion 107 remain.

Then, when 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. removed.
Note that the control unit 7 may measure the height of the back surface 102 of the wafer 111 using the top surface height gauge 82 . The control unit 7 may determine that the scrap 108 has been separated from the wafer 111 based on the amount of change in the height of the back surface 102 measured by the top surface height gauge 82 .

[Second Grinding Step]
Subsequently, the control unit 7 measures the height of the holding surface 22 by the holding surface height gauge 81, the height of the back surface 102 of the wafer 111 by the upper surface height gauge 82, and While calculating the difference between the measured value of the holding surface height gauge 81 and the measured value of the upper surface height gauge 82, the back surface 102 of the wafer 111 is moved until the value calculated by the calculator 83 reaches a predetermined thickness. Grind.

That is, the control unit 7 causes the holding surface height gauge 81 to come into contact with the frame surface 24 of the frame 23 of the chuck table 20 as shown in FIG. , the height measurement of the holding surface 22 is performed. Further, the control unit 7 measures the height of the back surface 102 of the wafer 111 by bringing the top surface height gauge 82 into contact with the back surface 102 of the wafer 111 . Then, the calculator 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 .

Here, in this embodiment, the wafer 111 is held on the holding surface 22 of the chuck table 20 via the tape 112 . Therefore, the calculator 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 .

Then, the control unit 7 causes the grinding wheel 77 to grind the wafer 111 until the sum of the thickness of the wafer 111 and the thickness of the tape 112 calculated by the calculation unit 83 reaches a predetermined thickness. Grinding of the back surface 102 is performed.

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

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 body surface 24. Therefore, it is possible to avoid the scraps 108 from colliding with the holding surface height gauge 81 being measured. Also, deterioration of the measurement accuracy of the holding surface height gauge 81 can be prevented. Moreover, damage to the holding surface height gauge 81 can be prevented.

In the above-described embodiment, in the first grinding step, 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 100 (wafer 111) by the top surface height gauge 82 are not performed. , the back surface 102 is ground by the grinding wheel 77 . In this regard, the first grinding step should be performed at least in a state in which the height of the holding surface 22 is not measured by the holding surface height gauge 81 . Therefore, in the first grinding step, the height of the back surface 102 may be measured using the top surface height gauge 82 .

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 movement mechanism, 41: Holder, 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 wheel, 80: Thickness measuring instrument,
81: holding surface height gauge, 82: upper surface height gauge, 83: calculator,
100: wafer, 101: front surface, 102: back surface, 103: first trimming unit,
105: End material, 107: Second trimming part, 108: End 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 (1)

A wafer grinding method for grinding a wafer held on a holding surface of a chuck table to a predetermined thickness with a grinding wheel while performing measurement with a thickness measuring device, the method comprising:
The wafer has a ring-shaped recessed trimming portion that does not reach the other surface on the outer peripheral portion of one surface side,
The thickness gauge includes a holding surface height gauge that contacts a frame surface surrounding the holding surface and measures the height of the holding surface, and a wafer upper surface height gauge that contacts the upper surface of the wafer held on the holding surface and measures the height of the wafer. a top surface height gauge that measures the height of the holding surface, and a calculator that calculates the difference between the measured value of the holding surface height gauge and the measured value of the top surface height gauge,
a holding step of holding one side of the wafer with the holding surface with the other side of the wafer facing up;
Grind the other surface of the wafer with the grinding wheel to expose the trimmed portion on the other surface while at least measuring the height of the holding surface with the holding surface height gauge, thereby separating from the wafer A first grinding step in which offcuts are removed;
After the first grinding step, while measuring the height of the holding surface by the holding surface height gauge, measuring the height of the upper surface of the wafer by the upper surface height gauge, and calculating by the calculating unit, the calculating unit A second grinding step of grinding the other surface of the wafer until the value calculated by reaches a preset predetermined thickness;
A method of grinding a wafer, comprising:

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