JP2022050976A - Grinding method for wafer - Google Patents

Abstract

To flatly grind a wafer without forming a recess around the center thereof and without taking time for formation of a holding surface, when the wafer is ground.SOLUTION: A method for grinding a wafer in a radial region of a holding surface 302 parallel to a lower surface of a grind stone 1644 by using a grinding device 1 including: holding means 3 capable of rotating a chuck table 30 about a center of the conical inclined holding surface 302 as an axis; means 16 that rotates the annular grind stone 1644 and grinds the wafer, the grinding means 16 including a rotary shaft 160 that uses a center of the grind stone 1644 as an axis and a motor 162 that rotates the rotary axis 160; and a rotation control unit 90 that controls a rotation speed of the motor 162, includes: a first grinding step of grind-feeding the grind stone 1644 rotating the wafer at a first rotational speed and grinding the wafer by a predetermined amount of removal; and a second grinding step of, after the first grinding step, grinding the wafer without grind-feeding the grind stone 1644 rotated at a second rotational speed higher than the first rotational speed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a grinding method for grinding a semiconductor wafer or the like.

The method of grinding a wafer that grinds a workpiece such as a semiconductor wafer held on the holding surface of a chuck table with an annular grinding wheel is parallel to the holding surface so that the rotation trajectory of the grinding wheel passes through the center of the holding surface. The grinding wheel and the chuck table are arranged in the horizontal direction. The holding surface is a conical slope having its center as an apex, and the wafer is ground by the rotation locus in which the lower surface of the grinding wheel and the conical slope are parallel to each other.

When the upper surface of the wafer is ground, a dent is formed in the center of the wafer. Therefore, as disclosed in Patent Document 1, the upper surface of the chuck table is self-grinded to form a holding surface in which the apex portion of the conical slope is flattened in advance, and the wafer is held and ground by the holding surface. A dent is not formed in the center of the table.

Japanese Unexamined Patent Publication No. 2019-136806

However, in order to self-grind the upper surface of the chuck table as described above to form an appropriate holding surface, there is a problem that it takes a lot of time because the shape of the holding surface to be formed is complicated.
Therefore, in the grinding method for grinding a wafer, there is a problem that the wafer held by the holding surface is ground flat so as not to form a dent without taking time for forming the holding surface.

The present invention for solving the above problems is a holding means capable of rotating a chuck table holding a wafer on a holding surface of a conical slope having a center as an apex about the center of the holding surface, and a center of an annular grinding wheel. A grinding means for rotating the grinding wheel around the axis to grind the wafer held on the holding surface, and a grinding feeding means for moving the holding means and the grinding means relatively in a direction perpendicular to the holding surface. , The grinding means includes a rotating shaft about the center of the grinding wheel, a motor for rotating the rotating shaft, and a grinding device including a rotation control unit for controlling the rotation speed of the motor. A method for grinding a wafer in a radial region of the holding surface parallel to the lower surface of the grinding wheel, wherein the holding step of holding the wafer on the holding surface and the wafer held in the holding step are used. A first grinding step in which the grinding grindstone rotating at a preset first rotation speed is fed and ground by a preset removal amount, and a second rotation speed higher than the first rotation speed after the first grinding step. A method for grinding a wafer, comprising a second grinding step of rotating the grinding wheel at a rotational speed and grinding the wafer without feeding the grinding wheel.

In the method for grinding a wafer according to the present invention, for example, the grinding wheel is a grinding wheel in which a vitrified bond grindstone having pores is continuously arranged.

The wafer grinding method according to the present invention is a wafer grinding method for grinding a wafer in a radial region of a holding surface parallel to the lower surface of the grinding wheel, and is held in a holding step of holding the wafer on the holding surface and a holding step. A first grinding step in which a grinding wheel that rotates a wafer at a preset first rotation speed is fed to grind a preset removal amount, and a second rotation speed higher than the first rotation speed after the first grinding step. By providing a second grinding step of rotating the grinding wheel at a rotation speed and grinding the wafer without feeding the grinding wheel, the time for forming the holding surface (self-grinding time) is not required. It is possible to grind the wafer flat without forming a dent of a predetermined depth or more in the center of the wafer held by the holding surface.

It is a perspective view which shows an example of a grinding apparatus. It is sectional drawing explaining the state which grinds and feeds a grinding wheel which rotates a wafer at a preset first rotation speed, and grinds by a preset removal amount. It is a top view explaining the state which grinds and feeds a grinding wheel which rotates a wafer at a preset first rotation speed, and grinds only a preset removal amount. It is sectional drawing explaining the state which grinds a wafer by rotating a grinding wheel at a second rotation speed, and grinding and feeding a grinding wheel.

The grinding device 1 shown in FIG. 1 is a device for grinding a wafer 80 sucked and held on a holding means 3 provided with a chuck table 30 by the grinding means 16, and is a front (-Y) on the device base 10 of the grinding device 1. The direction side) is an attachment / detachment region where the wafer 80 is attached / detached to / from the holding means 3, and the rear side (+ Y direction side) on the apparatus base 10 is the wafer 80 held on the holding means 3 by the grinding means 16. This is the processing area where the grinding process is performed.
The grinding device used in the method for grinding the wafer 80 according to the present invention is not limited to a single-axis grinding device such as the grinding device 1, but includes a rough grinding means and a finish grinding means. It may be a biaxial grinding device or the like capable of positioning the wafer 80 below the rough grinding means or the finish grinding means with a rotating turntable.

The wafer 80 shown in FIG. 1 is, for example, a circular asslice wafer formed by thinly cutting a cylindrical silicon ingot with a wire saw or the like. In FIG. 1 of the wafer 80, the surface facing downward is the surface 801 and the surface opposite to the surface 801 in the Z-axis direction (vertical direction) is the surface to be ground 802. For example, the surface 801 may be protected by attaching a protective member (not shown).
The wafer 80 is not limited to the asslice wafer.
A silicon wafer in which a device is formed on the surface 801 may be used.

The chuck table 30 having a circular shape in a plan view constituting the holding means 3 includes, for example, a suction portion 300 which is made of a porous member or the like and sucks the wafer 80, and a frame body 301 which supports the suction portion 300. The suction unit 300 communicates with a suction source 37 (see FIG. 2) such as an ejector mechanism or a vacuum generator, and the suction force generated by the suction source 37 sucks the exposed surface of the suction unit 300 and the frame 301. The chuck table 30 can suck and hold the wafer 80 on the holding surface 302 by being transmitted to the holding surface 302 composed of the upper surface of the surface.
The holding surface 302 has an extremely gentle conical slope with the rotation center 3022 of the chuck table 30 as the apex and cannot be judged by the naked eye.

As shown in FIG. 1, the chuck table 30 is surrounded by a cover 39 from the surroundings, and has a Z-axis direction (vertical direction) and can rotate about a rotation shaft 33 passing through the center 3022 of the holding surface 302. The horizontal moving means 13 is arranged below the cover 39 and the bellows cover 390 which is connected to the cover 39 and expands and contracts in the Y-axis direction, so that the device base 10 can be reciprocated in the Y-axis direction.

The horizontal moving means 13 for moving the chuck table 30 in the horizontal direction (Y-axis direction) parallel to the lower surface of the grinding wheel 1644 of the grinding means 16 is arranged with a ball screw 130 having an axial center in the Y-axis direction and parallel to the ball screw 130. A pair of guide rails 131 provided, a motor 132 connected to one end of the ball screw 130 to rotate the ball screw 130, and a movable plate 133 in which an internal nut is screwed into the ball screw 130 and the bottom slides into the guide rail 131. When the motor 132 rotates the ball screw 130, the movable plate 133 is guided by the guide rail 131 and moves linearly in the Y-axis direction, and is arranged on the movable plate 133 via the table base 35. The chuck table 30 can be moved in the Y-axis direction.
The horizontal moving means 13 may be a turntable in which a plurality of chuck tables 30 are arranged on the upper surface.

The chuck table 30 is arranged on the movable plate 133 via a table base 35 having a circular shape in a plan view. Further, the inclination of the table base 35 can be adjusted by a plurality of inclination adjusting means 34 arranged at equal intervals in the circumferential direction of the chuck table 30, and the inclination of the table base 35 is adjusted by adjusting the inclination of the table base 35. The inclination of the holding surface 302 of the chuck table 30 integrated with the table base 35 with respect to the lower surface of the grinding grindstone 1644 of the grinding means 16 can be adjusted.
In the present embodiment, the tilt adjusting means 34 is arranged, for example, two elevating portions 340 arranged at intervals of 120 degrees in the circumferential direction of the chuck table 30 and 120 degrees apart from the elevating portion 340 in the circumferential direction. It is provided with a fixed pillar portion 341. The two elevating portions 340 are, for example, electric actuators that can move a part of the table base 35 up and down in the Z-axis direction.

For example, the grinding apparatus 1 includes, for example, three load sensors 36 that measure the load applied to the wafer 80 when grinding the wafer 80 held by the chuck table 30. In the present embodiment, the three load sensors 36 are arranged so as to be sandwiched from above and below by two elevating portions 340, one fixed pillar portion 341, and a movable plate 133, respectively, and the circumference of the chuck table 30. They are located at intervals of 120 degrees in the direction, that is, at the vertices of virtual equilateral triangles in the horizontal plane. The load sensor 36 supports the chuck table 30 via the elevating portion 340 or the fixed pillar portion 341 and the table base 35, and the load applied from the + Z direction to the chuck table 30 that sucks and holds the wafer 80. That is, the load applied to the wafer 80 is received and detected. The load sensor 36 is composed of, for example, a thin force sensor manufactured by Kistler Co., Ltd. using a piezoelectric element such as lead zirconate titanate (PZT).

A column 11 is erected in the machined area, and the holding means 3 and the grinding means 16 are placed on the front surface of the column 11 on the −Y direction side in the direction perpendicular to the holding surface 302 (Z-axis direction). A grinding feed means 17 for moving is arranged. The grinding feed means 17 includes a ball screw 170 whose axial direction is the Z-axis direction, a pair of guide rails 171 arranged in parallel with the ball screw 170, and an elevating motor 172 connected to the upper end of the ball screw 170 to rotate the ball screw 170. And an elevating plate 173 in which the internal nut is screwed into the ball screw 170 and the side portion is in sliding contact with the guide rail 171. When the elevating motor 172 rotates the ball screw 170, the elevating plate 173 guides the ball screw 170. Guided by the rail 171 and reciprocates in the Z-axis direction, the grinding means 16 fixed to the elevating plate 173 is grounded and fed in the Z-axis direction.

For example, the grinding device 1 includes a height position detecting means 12 that detects the height position of the grinding means 16 that moves up and down by the grinding feed means 17. The height position detecting means 12 is fixed to the elevating plate 173 and moves together with the elevating plate 173 along the elevating plate 173 and the scale 120 extending in the Z-axis direction along the pair of guide rails 171 to optically illuminate the scale of the scale 120. A reading unit 123 for reading by an equation is provided.

The grinding means 16 for grinding the wafer 80 held on the holding surface 302 of the holding means 3 includes, for example, a rotary shaft 160 whose axial direction is the Z-axis direction and whose axis is the center of the grinding wheel 1644, and a rotary shaft 160. A housing 161 that rotatably supports, a motor 162 that rotationally drives the rotary shaft 160, an annular mount 163 connected to the lower end of the rotary shaft 160, and a grinding wheel 164 that is detachably mounted on the lower surface of the mount 163. A holder 165 that supports the housing 161 and is fixed to the elevating plate 173 of the grinding feed means 17, and a rotary encoder 166 that detects the rotational speed of the motor 162 are provided.

The grinding wheel 164 includes a wheel base 1643 and a grinding wheel 1644 arranged in an annular shape on the bottom surface of the wheel base 1643. In the present embodiment, the grinding wheel 1644 is, for example, a continuously arranged vitrified bond grindstone formed into one annular ring in which diamond abrasive grains or the like are fixed by a vitrified bond having pores. The blade width of the annular grinding wheel 1644 is set to, for example, 3 mm. The grinding wheel may be a segmented grindstone in which a plurality of grinding wheel tips having a substantially rectangular parallelepiped shape are arranged in an annular shape with a predetermined interval between the grinding wheel tips on the lower surface of the wheel base 1643. The bond for fixing the grindstone is not limited to the vitrified bond, and may be a resin bond or the like.

Inside the rotating shaft 160, a flow path (not shown) that communicates with the grinding water supply source and serves as a passage for the grinding water is provided so as to penetrate in the axial direction (Z-axis direction) of the rotating shaft 160, which is not shown. The flow path further passes through the mount 163 and is open at the bottom surface of the wheel base 1643 so that the grinding water can be ejected toward the grinding wheel 1644.

At a position adjacent to the grinding means 16 in a state of being lowered to the grinding position, for example, a thickness measuring means 38 for measuring the thickness of the wafer 80 by a contact method is arranged. The thickness measuring means 38 may be a non-contact type or may not be arranged in the grinding device 1.

The grinding device 1 includes a control means 9 capable of controlling each component of the grinding device 1 described above. The control means 9 composed of a storage element such as a CPU and a memory is electrically connected to, for example, a grinding feed means 17, a grinding means 16, a horizontal moving means 13, and the like, and is under the control of the control means 9. The grinding feed operation of the grinding means 16 by the grinding feed means 17 and the positioning operation of the chuck table 30 with respect to the grinding wheel 164 by the horizontal moving means 13 are controlled.

The elevating motor 172 shown in FIG. 1 is, for example, a servomotor, and a rotary encoder (not shown) of the elevating motor 172 is connected to a control means 9 which also has a function as a servo amplifier, and elevates from the output interface of the control means 9. When the operation signal is supplied to the motor 172, the ball screw 170 rotates, and the rotation speed detected by the rotary encoder (not shown) is output as an encoder signal to the input interface of the control means 9. Then, the control means 9 that has received the encoder signal can sequentially recognize the height of the grinding means 16 that is grounded by the grinding feed means 17, and can feedback control the grinding feed speed of the grinding means 16.
The control means 9 may receive the height position information of the grinding means 16 detected by the height position detecting means 12, and may be able to sequentially recognize the height of the grinding means 16 based on the information.

The motor 162 of the grinding means 16 is, for example, a servomotor, and the rotary encoder 166 connected to the motor 162 is connected to the rotation control unit 90 shown in FIG. 1 of the control means 9 which also has a function as a servo amplifier. When the operation signal is supplied from the rotation control unit 90 to the motor 162, the rotation shaft 160 rotates, and the rotation speed detected by the rotary encoder 166 is output to the rotation control unit 90 as an encoder signal. Then, the rotation control unit 90 that has received the encoder signal can continuously recognize the rotation speed of the grinding wheel 1644, maintain the desired rotation speed, and control the rotation speed to be changed to the desired rotation speed. ..

Hereinafter, each step when the method for grinding the wafer 80 according to the present invention is carried out using the grinding apparatus 1 shown in FIG. 1 will be described.

(1) Holding Step First, with the wafer 80 facing up with the surface to be ground 802 facing up so that the center 3022 of the holding surface 302 of the chuck table 30 positioned in the attachment / detachment region and the center 808 of the wafer 80 match. It was placed on the holding surface 302. Then, the suction force generated by the operation of the suction source 37 (see FIG. 2) is transmitted to the holding surface 302, so that the wafer 80 is held by the chuck table 30. Further, the table base 35 is provided by the tilt adjusting means 34 shown in FIG. 1 so that the holding surface 302, which is a gentle conical slope, is parallel to the grinding surface (lower surface) of the grinding wheel 1644 of the grinding means 16 shown in FIG. By adjusting the inclination of the chuck table 30, the surface to be ground 802 of the wafer 80, which is suction-held following the holding surface 302 which is a conical slope, is applied to the lower surface of the grinding wheel 1644 as shown in FIG. It was made almost parallel.

(2) First Grinding Step Next, a first grinding step was carried out in which the wafer 80 held in the holding step was grounded by a grinding wheel 1644 rotating at a preset first rotation speed to grind by a preset removal amount. ..
Specifically, as shown in FIGS. 2 and 3, the chuck table 30 that sucks and holds the wafer 80 is sent in the + Y direction by the horizontal moving means 13, and the center of rotation of the grinding wheel 1644 holds the chuck table 30. It is displaced horizontally (+ Y direction) by a predetermined distance with respect to the center 3022 of the surface 302 (that is, the center 808 of the surface to be ground 802 of the wafer 80), and the rotation locus of the grinding wheel 1644 passes through the rotation center 808 of the wafer 80. I went like that. In addition, in FIGS. 2 and 3, each configuration of the grinding apparatus 1 is shown in a simplified manner.

Next, the grinding feed means 17 shown in FIG. 2 was used to grind the grinding wheel 1644 in the −Z direction approaching the holding surface 302 at a predetermined grinding feed rate (0.3 μm in this example). .. Then, for example, as shown in FIGS. 2 and 3, the grinding surface of the grinding wheel 1644 rotated in the counterclockwise direction when viewed from the + Z direction side is brought into contact with the ground surface 802 of the wafer 80 to bring the ground surface 802 to the ground surface 802. Grinding was started. Further, as the chuck table 30 rotates at a predetermined rotation speed (185 rpm in this example), for example, in the counterclockwise direction when viewed from the + Z direction side, the wafer 80 held on the holding surface 302 also rotates. , The grinding wheel 1644 grinded the entire surface of the surface 802 to be ground of the wafer 80. Since the wafer 80 is suction-held following the holding surface 302 which is a gentle conical slope of the chuck table 30, as shown in FIG. 3, it is within the range indicated by the arrow R in the rotation locus of the grinding wheel 1644, that is, When viewed from the holding surface 302 side, the grinding wheel 1644 abuts on the wafer 80 and grinds the wafer 80 while applying a predetermined load within the radial region R of the holding surface 302 parallel to the lower surface of the grinding wheel 1644. During the grinding process, grinding water was supplied to the contact portion between the grinding wheel 1644 and the surface to be ground 802 of the wafer 80 to cool and clean the contact portion.

The rotation speed of the grinding wheel 1644 in the first grinding step is set in advance in the control means 9 under the feedback control of the motor 162 by the rotation control unit 90 of the control means 9 receiving the detection signal from the rotary encoder 166. The first rotation speed was used. The first rotation speed was, for example, 1785 rpm. Then, while the thickness of the wafer 80 is measured by the thickness measuring means 38 shown in FIG. 1, the wafer 80 is ground by a preset removal amount (20 μm in this example) by the grinding wheel 1644 rotating at 1785 rpm. By doing so, the first grinding process was completed.

(3) Second Grinding Step Next, after the first grinding step, the grinding wheel 1644 is rotated at a second rotation speed higher than the first rotation speed of 1785 rpm, and the wafer 80 is ground without feeding the grinding wheel 1644. The second grinding step of grinding was carried out. Specifically, under the control of the grinding feed means 17 of the control means 9, the lowering of the grinding means 16 by the grinding feed means 17 is stopped, and the height position of the grinding means 16 shown in FIG. 4 is the first grinding step. The grounded wafer 80 is to be ground by the rotating grinding wheel 1644 while being maintained at the height position (in this example, the height position where the wafer 80 is ground and removed by 20 μm from the input thickness of the wafer 80). The surface 802 was processed. The rotation speed of the grinding wheel 1644 in the second grinding step is higher than the first rotation speed of 1785 rpm under the feedback control of the motor 162 by the rotation control unit 90 of the control means 9 that receives the detection signal from the rotary encoder 166. The second rotation speed of. Here, the second rotation speed is preferably 2000 rpm to 4500 rpm, more preferably 3500 rpm to 4000 rpm, and most preferably 4000 rpm.
After finishing the first grinding step, under the control of the grinding feed means 17 of the control means 9, the grinding means 16 is raised to separate the lower surface of the grinding wheel 1644 from the wafer 80, and then the grinding means 16 is again used. The second grinding step may be carried out by lowering to the height position where the first grinding step is completed.

The surface to be ground 802 of the wafer 80 was ground for a predetermined time by the grinding wheel 1644 rotating at the second rotation speed in which the height position was fixed without feeding. In general, the more the wafer 80 is not properly ground by the grinding wheel 1644, the more difficult it is for the rotating shaft 160 to rotate the grinding wheel 1644. However, even in this case, the rotating shaft 160 is rotated at the second rotation speed. Since the motor 162 is feedback-controlled by the rotation control unit 90 so as to be caused, the load current value of the motor 162 increases. When the second rotation speed was set to 1500 rpm or the second rotation speed was set to 5000 rpm, the load current value of the motor 162 increased until it exceeded the permissible value, but the second rotation speed was set to 2000 rpm. In the case of 3500 rpm, 4000 rpm, and 4500 rpm, the load current value of the motor 162 could be kept below the permissible value.
That is, when the second rotation speed is 1500 rpm, the rotation is slow and the grinding wheel 1644 is consumed, so that a large amount of grinding and a small amount of grinding occur in the circumferential direction of the wafer 80, so that the thickness can be made uniform. Can not. Further, when the second rotation speed is 5000 rpm, the lower surface of the grinding wheel 1644 slides on the surface to be ground 802 of the wafer 80 because the rotation is fast, so that the grinding wheel 1644 causes blinding and grinds to a uniform thickness. I can't.
On the other hand, when the second rotation speed is 2000 rpm to 4500 rpm, the grinding wheel 1644 does not cause blinding, and until the load when the first grinding step is carried out disappears, that is, in the first grinding step. The wafer 80, the chuck table 30 and the like are released from the pressing load, and as a result, so-called springback occurs, and the surface to be ground 802 of the wafer 80 also rises toward the grinding wheel 1644 whose height position is fixed. By grinding the wafer 80 until the springback is eliminated, the grinding wheel 1644 is consumed, so that the grinding wheel can be ground to a uniform thickness.

Further, the load value applied to the wafer 80 was measured by the load sensor 36 shown in FIG. When the second rotation speed is set to, for example, 1500 rpm, or when the second rotation speed is set to 5000 rpm, the load value applied to the wafer 80 may exceed a desired value or may be lower than the desired value. However, the load value applied to the wafer 80 is kept within the desired value regardless of whether the second rotation speed is 2000 rpm, 3500 rpm, 4000 rpm, or 4500 rpm. I was able to.

After completing the second grinding step, the grinding means 16 was escape-cut by the grinding feed means 17 under the control of the grinding feed means 17 by the control means 9. In the escape cut, the grinding means 16 was slowly raised (the rising speed was, for example, 0.2 μm / sec), and the lower surface of the grinding wheel 1644 was separated from the surface to be ground 802 of the wafer 80.

The thickness accuracy (Total Tickness Variation) of the wafer 80 after the second grinding step was measured, and it was observed whether or not a dent was formed in the center 808 of the wafer 80 after the grinding. When the second rotation speed is, for example, 1500 rpm, or when the second rotation speed is 5000 rpm, the TTV of the wafer 80 is contained in less than 1 μm, and the center 808 of the wafer 80 is recessed by a predetermined depth or more. We could not get the result that was not formed. On the other hand, when the second rotation speed is 2000 rpm, 3500 rpm, 4000 rpm, and 4500 rpm, the TTV of the wafer 80 is set to less than 1 μm, and the TTV of the wafer 80 is set to the center 808 of the wafer 80. We were able to obtain the result that no dents beyond the depth were formed. When the second rotation speed was 4000 rpm, the TTV could be made the best, and the dent in the center 808 of the wafer 80 could be alleviated most.

As described above, the method for grinding the wafer 80 according to the present invention is a method for grinding the wafer 80 in the radial region of the holding surface 302 parallel to the lower surface of the grinding wheel 1644, and is a method for grinding the wafer 80 on the holding surface 302. A holding step of holding the 80, a first grinding step of grinding and feeding a grinding wheel 1644 that rotates the wafer 80 held in the holding step at a preset first rotation speed, and grinding by a preset removal amount, and a first grinding. After the process, the holding surface is provided with a second grinding process in which the grinding wheel 1644 is rotated at a second rotation speed higher than the first rotation speed, and the wafer 80 is ground without feeding the grinding wheel 1644 by grinding. It is possible to grind the wafer 80 flat without forming a dent of a predetermined depth or more in the center of the wafer 80 held by the holding surface 302 without taking time for forming the 302 (self-grinding time). It becomes.

80: Wafer 802: Surface to be ground 801: Surface
1: Grinding device 10: Device base 3: Holding means 30: Chuck table 300: Suction part 301: Frame body 302: Holding surface
35: Table base 34: Tilt adjusting means 340: Elevating part 341: Fixed pillar part 36: Load sensor 38: Thickness measuring means 37: Suction source 39: Cover 13: Horizontal moving means 130: Ball screw 132: Motor 133: Movable plate 11: Column 17: Grinding feed means 170: Ball screw 172: Elevating motor 16: Grinding means 160: Rotating shaft 162: Motor 164: Grinding wheel 1643: Wheel base 1644: Grinding wheel 9: Control means 90: Rotation control unit

Claims (2)

A holding means that can rotate a chuck table that holds a wafer on a holding surface of a conical slope with the center as the apex around the center of the holding surface, and a holding means that rotates the grinding grind around the center of an annular grinding grind and holds the grinding grind. The grinding means includes a grinding means for grinding a wafer held on a surface, and a grinding feed means for moving the holding means and the grinding means relatively in a direction perpendicular to the holding surface, and the grinding means is the grinding. Using a grinding device provided with a rotation axis centered on the center of the grinding wheel, a motor for rotating the rotation axis, and a rotation control unit for controlling the rotation speed of the motor, the grinding device is parallel to the lower surface of the grinding wheel. A method for grinding a wafer in the radial region of the holding surface.
A holding step of holding the wafer on the holding surface and
In the first grinding step, the wafer held in the holding step is grounded at a preset first rotation speed, and the grinding wheel is fed to grind by a preset removal amount.
After the first grinding step, the wafer is provided with a second grinding step of rotating the grinding wheel at a second rotation speed having a rotation speed higher than the first rotation speed and grinding the wafer without feeding the grinding wheel. Grinding method. The method for grinding a wafer according to claim 1, wherein the grinding wheel is a vitrified bond grindstone having pores arranged continuously.

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