JP7413103B2 - Wafer grinding method - Google Patents

Description

The present invention relates to a grinding method for grinding semiconductor wafers and the like.

A grinding device for grinding semiconductor wafers consists of a chuck table that holds the wafer on a holding surface and rotates around the center of the holding surface, and a grinding wheel that rotates around the center of an annular grindstone to grind the wafer held on the holding surface. and a grinding means for doing so. The holding surface is formed into an extremely gentle conical slope that cannot be seen with the naked eye and has its apex at the center. Then, the holding surface, which is a very gentle conical slope, is tilted so that it is parallel to the bottom surface of the grinding wheel using the inclination adjustment means, and the grinding wheel that is being ground passes through the center of the holding surface and is held in the rotation trajectory of the grinding wheel. The wafer is ground from the outer periphery to the center of the surface.

For example, by moving a vitrified bond grindstone with air holes in the direction approaching the holding surface at a predetermined grinding feed rate, the grinding wheel is pressed against the wafer held on the holding surface, and the wafer to be ground is polished while applying a load of, for example, 60N. The top surface is ground. Therefore, when the grinding wheel passes through the center of the wafer held on the holding surface during grinding, it is compressed by the drag force from the wafer resisting the grinding load before the center, and after passing the center, the grinding wheel It expands because the drag from it disappears. As a result, the center of the wafer in the rotation locus area of the grindstone comes into contact with the grindstone more often, and is ground more than other parts, resulting in the formation of a depression, which is a cylindrical space with a diameter of 2 mm to 4 mm.

Therefore, there is an invention, for example, as disclosed in Patent Document 1, in which the upper surface of the chuck table is ground to form an appropriate holding surface that prevents the formation of cylindrical depressions on the wafer (self-grinding).

JP 2019-136806 Publication

However, forming an appropriate holding surface by self-grinding the upper surface of the chuck table as described above has a problem in that it takes time because the shape of the desired holding surface is complex.
Therefore, in the wafer grinding method in which the wafer held on the holding surface is ground with a grindstone, the process of forming the holding surface by self-grinding does not take much time, and the wafer is ground while being held on the holding surface. There is a problem in preventing the formation of a cylindrical depression at the center of the subsequent wafer.

In order to solve the above problems, the present invention includes a holding means that holds a wafer on a conical sloped holding surface having an apex at the center and is rotatable about the center of the holding surface, and a holding means that is rotatable about the center of the holding surface, and an annular grinding wheel whose center is an axis. a grinding means for rotatably mounting the grinding wheel and using the grinding wheel to grind a wafer held on the holding surface; and a grinding means for moving the holding means and the grinding means relative to each other in a horizontal direction parallel to the lower surface of the grinding wheel. parallel to the lower surface of the grinding wheel using a grinding device equipped with a horizontal moving means for moving the holding means and the grinding means relative to each other in a direction perpendicular to the holding surface. A wafer grinding method for grinding a wafer in a radial area of the holding surface, the holding step of aligning the center of the holding surface with the center of the wafer and holding the wafer on the holding surface, and the horizontal moving means. a first positioning step of positioning the wafer with respect to the grinding wheel so that the rotation locus of the grinding wheel, which is defined by the radial blade width of the grinding wheel, passes through the center of the holding surface; After that, a first grinding step in which the grinding wheel is moved in a direction approaching the holding surface by the grinding feeding means and the wafer is ground to a thickness that is thicker by a preset value (1 μm to 3 μm) than a preset finishing thickness; , After the first grinding step, use the horizontal moving means to locate a position where the inner circumference of the rotation locus of the grinding wheel and the outer circumference of the cylindrical recess formed in the center of the wafer in the first grinding step are in contact with each other, or a second positioning step of positioning the wafer with respect to the grinding wheel at a position where the outer periphery of the rotation locus and the outer periphery of the cylindrical recess are in contact with each other, and after the second positioning step, the grinding wheel is moved by the grinding feeding means A second grinding step of moving the wafer in a direction approaching the holding surface and grinding the wafer to the preset finishing thickness.

When performing the first grinding step, the second positioning step, and the second grinding step, the grinding feed means is controlled so as not to separate the grinding wheel from the surface to be ground of the wafer held on the holding surface. Then it is preferable.

For example, in the wafer grinding method according to the present invention, the grinding wheel is a grinding wheel in which vitrified bond grinding wheels having pores are arranged in a continuous manner.

The wafer grinding method according to the present invention uses a grinding device to grind a wafer in a radial area of a holding surface that is parallel to the lower surface of a grinding wheel. a holding step of holding the wafer; and a first positioning step of positioning the wafer with respect to the grinding wheel using a horizontal moving means so that the rotation locus of the grinding wheel, which consists of the radial blade width of the grinding wheel, passes through the center of the holding surface; After the first positioning process, a first grinding process in which the grinding wheel is moved in the direction approaching the holding surface using the grinding feed means and the wafer is ground to a thickness that is a preset value (1 μm to 3 μm) thicker than the preset finishing thickness. By performing these steps, the proportion of contact between the expanded grinding wheel released from compression at the center of the wafer increases, and a cylindrical recess, which is a cylindrical space, is formed in the center of the wafer after the first grinding process. Ru. After the first grinding process, the horizontal moving means is used to locate the position where the inner periphery of the rotation trajectory of the grinding wheel and the outer periphery of the cylindrical recess formed in the center of the wafer in the first grinding process touch, or the outer periphery of the rotation trajectory. A second positioning step of positioning the wafer with respect to the grinding wheel at a position where the wafer and the outer circumference of the cylindrical recess are in contact with each other, that is, a position where the grinding wheel does not hit the entire cylindrical recess; and after the second positioning step, the wafer is ground. By performing a second grinding process in which the grinding wheel is moved in a direction approaching the holding surface using a feeding means and the wafer is ground to a preset finishing thickness, a concave portion is formed around the wafer after the second grinding process. This makes it possible to create wafers with a uniform thickness, which is not possible before.

It is a perspective view showing an example of a grinding device. It is a sectional view for explaining a holding process, a 1st positioning process, and a 1st grinding process. It is a top view for explaining a holding process, a 1st positioning process, and a 1st grinding process. It is a graph showing the relationship between grinding time and height of a grinding means in the wafer grinding method according to the present invention. It is a sectional view for explaining a 2nd positioning process and a 2nd grinding process. It is a top view for demonstrating a 2nd positioning process and a 2nd grinding process. FIG. 7 is a cross-sectional view illustrating a case where the wafer is positioned with respect to the grinding wheel at a position where the outer periphery of the rotation locus and the outer periphery of the cylindrical recess are in contact with each other in the second positioning step. FIG. 7 is a plan view illustrating a case where the wafer is positioned with respect to the grinding wheel at a position where the outer periphery of the rotation locus and the outer periphery of the cylindrical recess are in contact with each other in the second positioning step.

The grinding device 1 shown in FIG. 1 is a device that uses a grinding device 16 to grind a wafer 80 that is suction-held on a holding device 30 such as a chuck table. side) is an attachment/detachment area where the wafer 80 is attached/detached to/from the holding means 30, and the rear (+Y direction side) on the apparatus base 10 is an attachment/detachment area where the wafer 80 held on the holding means 30 by the grinding means 16 is attached/detached. This is a processing area where grinding is performed.
Note that the grinding apparatus according to the present invention is not limited to a grinding apparatus in which the grinding means 16 is uniaxial like the grinding apparatus 1, but is equipped with a rough grinding means and a finishing grinding means, and the wafer is processed by a rotating turntable. A two-axis grinding device or the like may be used in which the grinding device 80 can be positioned below the rough grinding means or the finish grinding means.

The wafer 80 shown in FIG. 1 is, for example, a circular as-sliced wafer formed by cutting a cylindrical silicon ingot into thin pieces using a wire saw or the like. The surface of the wafer 80 facing downward in FIG. 1 is defined as a surface 801, and the surface opposite to the surface 801 in the Z-axis direction (vertical direction) is defined as a surface to be ground 802. For example, the surface 801 may be protected by attaching a protective member (not shown).
Note that the wafer 80 is not limited to an as-sliced wafer.

The holding means 30, which has a circular outer shape in a plan view, includes a suction section 300 that is made of, for example, a porous member and that suctions the wafer 80, and a frame 301 that supports the suction section 300. The suction part 300 of the holding means 30 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 is applied to the exposed surface of the suction part 300. By being transmitted to the holding surface 302 composed of the upper surface of the frame body 301 and the upper surface of the frame body 301, the holding means 30 can suction-hold the wafer 80 on the holding surface 302.
The holding surface 302 has an extremely gentle conical slope with the rotation center 3022 of the holding means 30 as its apex, which cannot be determined with the naked eye.

The holding means 30 is surrounded by the cover 39 and is rotatable about a rotation axis whose axial direction is the Z-axis direction (vertical direction) and passes through the center 3022 of the holding surface 302. The device base 10 can be reciprocated in the Y-axis direction by the horizontal movement means 13 disposed below the connected bellows cover 390 that expands and contracts in the Y-axis direction.

The horizontal moving means 13 that relatively moves the holding means 30 and the grinding means 16 in the horizontal direction (Y-axis direction) parallel to the lower surface of the grinding wheel 1644 of the grinding means 16 is a ball screw 130 having an axis in the Y-axis direction. a pair of guide rails 131 arranged parallel to the ball screw 130; a motor 132 connected to one end of the ball screw 130 to rotate the ball screw 130; When the motor 132 rotates the ball screw 130, the movable plate 133 is guided by the guide rail 131 and moves directly in the Y-axis direction. The holding means 30 provided via the table base 35 can be moved in the Y-axis direction.
Note that the horizontal moving means 13 may be a turntable.

The holding means 30 is arranged on the movable plate 133 via the table base 35. 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 holding means 30, and by adjusting the inclination of the table base 35, The inclination of the holding surface 302 of the holding means 30 with respect to the lower surface of the grinding wheel 1644 of the grinding means 16 can be adjusted.
In this embodiment, the inclination adjusting means 34 includes, for example, two elevating parts 340 disposed at intervals of 120 degrees in the circumferential direction of the holding means 30, and two elevating parts 340 disposed at intervals of 120 degrees in the circumferential direction from the elevating part 340. A fixed column portion 341 is provided. The two elevating parts 340 are, for example, electric cylinders, air cylinders, etc. that can move up and down in the Z-axis direction.

A column 11 is erected in the processing area, and a holding means 30 and a grinding means 16 are mounted on the front surface of the column 11 in the −Y direction relative to each other in a direction perpendicular to the holding surface 302 (Z-axis direction). Grinding feed means 17 for moving is provided. 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 parallel to the ball screw 170, and a lifting motor 172 connected to the upper end of the ball screw 170 and rotating the ball screw 170. and an elevating plate 173 whose internal nut is screwed onto a ball screw 170 and whose side part slides into guide rail 171. When the elevating motor 172 rotates the ball screw 170, the elevating plate 173 moves as a guide. The grinding means 16 is guided by the rail 171 and reciprocated in the Z-axis direction, and the grinding means 16 fixed to the elevating plate 173 is sent for grinding in the Z-axis direction.

For example, the grinding device 1 includes a height position detection means 12 that detects the height position of the grinding means 16 that is moved up and down by the grinding feed means 17. The height position detection means 12 is fixed to a scale 120 extending in the Z-axis direction along a pair of guide rails 171 and an elevating plate 173, moves along the scale 120 together with the elevating plate 173, and optically detects the graduations of the scale 120. and a reading section 123 that reads the data using the formula.

The grinding means 16 that grinds the wafer 80 held on the holding surface 302 of the holding means 30 includes a rotating shaft 160 whose axial direction is the Z-axis direction, a housing 161 that rotatably supports the rotating shaft 160, and a rotating shaft. A motor 162 that rotationally drives the housing 160 , an annular mount 163 connected to the lower end of the rotating shaft 160 , a grinding wheel 164 removably attached to the lower surface of the mount 163 , and a grinding feed means 17 that supports the housing 161 and a holder 165 fixed to the elevating plate 173 of.

The grinding wheel 164 includes a wheel base 1643 and a grinding wheel 1644 arranged annularly on the bottom surface of the wheel base 1643. In this embodiment, the grinding wheel 1644 is, for example, a vitrified bonded grindstone in a continuous arrangement formed into a single annular ring by fixing diamond abrasive grains or the like with a vitrified bond having pores. The blade width of the annular grinding wheel 1644 is set to, for example, 3 mm. Note that the grinding wheel may be a segmented grinding wheel in which a plurality of approximately rectangular parallelepiped-shaped grinding wheel chips are arranged in a ring shape with a predetermined interval between the grinding wheel chips on the lower surface of the wheel base 1643, or The bond for fixing is not limited to vitrified bond, but may be resin bond.

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

At a position adjacent to the grinding means 16 that has been 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 disposed. Note that the thickness measuring means 38 may be of a non-contact type, or may not be provided in the grinding device 1.

The grinding device 1 includes a control means 9 that can control each component of the grinding device 1 described above. The control means 9 composed of a CPU, a storage element such as a memory, etc. is electrically connected to, for example, the grinding feed means 17, the grinding means 16, the horizontal movement means 13, etc., and is operated under the control of the control means 9. The grinding feed operation of the grinding means 16 by the grinding feed means 17, the rotation operation of the grinding wheel 164 in the grinding means 16, and the positioning operation of the holding means 30 with respect to the grinding wheel 164 by the horizontal moving means 13 are controlled.

The lifting motor 172 is, for example, a servo motor, and an encoder (not shown) of the lifting motor 172 is connected to the control means 9 which also functions as a servo amplifier. The rotating shaft 160 rotates when the operating signal is supplied, and the rotational speed detected by an encoder (not shown) is output as an encoder signal to the input interface of the control means 9. After receiving the encoder signal, the control means 9 can successively recognize the height of the grinding means 16 that is being fed by the grinding feeding means 17, and can feedback-control the grinding feeding speed of the grinding means 16.
Note that the control means 9 may be able to receive height position information of the grinding means 16 detected by the height position detection means 12 and sequentially recognize the height of the grinding means 16 based on the information.

The motor 132 of the horizontal movement means 13 is, for example, a servo motor, and an encoder (not shown) of the motor 132 is connected to the control means 9 which also functions as a servo amplifier, and the control means 9 operates the motor 132. When the signal is supplied, the ball screw 130 rotates, and the rotational speed detected by an encoder (not shown) is output to the control means 9 as an encoder signal. After receiving the encoder signal, the control means 9 successively recognizes the position in the Y-axis direction of the holding means 30 that is horizontally moved in the Y-axis direction by the horizontal movement means 13, and can control the positioning at a predetermined position. .

Each step in carrying out the method of grinding a wafer 80 according to the present invention using the grinding apparatus 1 shown in FIG. 1 will be described below.

(1) Holding process First, the wafer 80 is held with the surface to be ground 802 facing upward so that the center 3022 of the holding surface 302 of the holding means 30 positioned in the attachment/detachment area matches the center 808 of the wafer 80. It is 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 holding means 30. Further, the table base 35 is adjusted by the inclination adjustment means 34 shown in FIG. By adjusting the inclination of the holding means 30, the surface to be ground 802 of the wafer 80 that is suction-held along the holding surface 302, which is a conical slope, becomes approximately parallel to the lower surface of the grinding wheel 1644.

(2) First positioning step Next, the wafer 80 is positioned with respect to the grinding wheel 1644 using the horizontal moving means 13 so that the rotation locus of the grinding wheel 1644 passes through the center 3022 of the holding surface 302. Specifically, as shown in FIGS. 2 and 3, the holding means 30 holding the wafer 80 by suction is sent in the +Y direction by the horizontal moving means 13, so that the center of rotation of the grinding wheel 1644 is aligned with the holding surface of the holding means 30. 302 (i.e., the center 808 of the wafer 80) by a predetermined distance in the horizontal direction (+Y direction), and the rotation trajectory consisting of the radial blade width (for example, 3 mm) of the grinding wheel 1644 is the wafer 80. The rotation center 808 of the For example, the center 808 of the wafer 80 held on the holding surface 302 is aligned with the midpoint of the blade width of the grinding wheel 1644 in the Y-axis direction. In addition, in FIG. 2, FIG. 3, each structure of the grinding apparatus 1 is shown in a simplified manner.

(3) First Grinding Step Next, the grinding feed means 17 shown in FIG. 2 feeds the grinding means 16 at a predetermined grinding feed speed in the -Z direction, where the grinding wheel 1644 approaches the holding surface 302. Specifically, as shown in graph G in FIG. 4, the grinding means 16 located at, for example, the original height position descends at high speed. Further, the height position of the grinding means 16 that has started to descend from the original height position is always grasped by the control means 9 shown in FIG.
Then, as shown in graph G in FIG. 4, the grinding means 16 reaches the air cut start position Z1. In the graph G of FIG. 4, the horizontal axis shows the grinding time T, and the vertical axis shows the height position H of the grinding means 16.

When the grinding means 16 reaches the air cut start position Z1, the grinding feeding means 17 performs the air cut from the air cut start position Z1 until the grinding surface of the grinding means 16 contacts the ground surface 802 of the wafer 80 (see FIG. The air cut feed rate during air cut from time T1 to time T2 shown in graph G is lower than the descending speed before reaching the air cut start position Z1, for example, the same speed as the grinding feed rate during grinding. Control is performed under the control means 9. By performing the air cut, the grinding wheel 1644 is prevented from hitting the wafer 80 at a speed that would damage the wafer 80.

Thereafter, when the grinding means 16 is lowered to the height position Z2, the grinding surface of the grinding wheel 1644 rotated counterclockwise when viewed from the +Z direction side becomes the ground surface of the wafer 80, as shown in FIGS. 2 and 3, for example. 802, and grinding of the surface to be ground 802 is started. Further, as the holding means 30 rotates at a predetermined rotational speed, for example, counterclockwise when viewed from the +Z direction side, the wafer 80 held on the holding surface 302 also rotates, so that the grinding wheel 1644 rotates around the wafer 80. Grinding is performed on the entire surface 802 to be ground. Since the wafer 80 is suction-held along the holding surface 302, which is a gentle conical slope, of the holding means 30, as shown in FIG. When viewed from the holding surface 302 side, the grinding wheel 1644 contacts the wafer 80 within a radial region of the holding surface 302 that is parallel to the lower surface of the grinding wheel 1644, and performs grinding while applying a pressing load of, for example, 60 N to the wafer 80. During the grinding process, grinding water is supplied to the contact area between the grinding wheel 1644 and the surface to be ground 802 of the wafer 80 to cool and clean the contact area.

For example, the height position of the grinding means 16 is detected using the height position detection means 12 shown in FIG. By lowering the wafer 16 to the height position Z3 shown in graph G of FIG. 1st grinding from time T2 to time T3). After that, a so-called spark-out process is performed. Furthermore, due to the phenomenon explained in the background technology section, a cylindrical recess 807 shown in FIGS. 5 and 6 is formed at the center 808 of the wafer 80 which has been ground to a thickness 1 μm to 3 μm thicker than the finished thickness. be in a state of being For example, the diameter of the cylindrical recess 807 is approximately 2.6 mm.

In the spark-out from time T3 to time T4 shown in graph G in FIG. 4, the lowering of the grinding means 16 by the grinding feeding means 17 is stopped, and the height position of the grinding means 16 is maintained at the height position Z3 for a predetermined period of time. In this state, the rotating grinding wheel 1644 removes uncut portions of the surface to be ground 802 of the rotating wafer 80 and prepares the surface to be ground 802.
Note that in the first grinding step, the thickness of the wafer 80 may be measured by the thickness measuring means 38 shown in FIG.

In this embodiment, in order to prevent the grinding wheel 1644 from separating from the ground surface 802 of the wafer 80 held by the holding surface 302 when performing the first grinding step, the second positioning step, and the second grinding step, The control means 9 controls the grinding feed means 17. That is, after spark-out is performed, the grinding means 16 is escaped cut by the grinding feed means 17 (escape cut from time T4 to time T5 shown in graph G of FIG. 4). In the escape cut, the grinding means 16 slowly rises in order to suppress adverse effects on the surface to be ground 802 of the wafer 80. During the grinding process, a pressing load of, for example, 60 N is applied in the -Z direction from the grinding means 16 shown in FIG. When the grinding means 16 slowly rises, the wafer 80 and the like are released from the pressing load. As a result, a so-called springback phenomenon occurs and the surface to be ground 802 of the wafer 80 also rises, so that the surface to be ground 802 of the wafer 80 continues to be in contact with the lower surface of the grinding wheel 1644. Then, for example, while the surface to be ground 802 of the wafer 80 follows and contacts the lower surface of the rising grinding wheel 1644, the grinding means 16 rises to a predetermined height position Z4 and stops. This further suppresses the slippage of the lower surface of the grinding wheel 1644 against the ground surface 802 of the wafer 80 when the grinding means 16 is lowered again in the second grinding step.

(4) Second positioning step After the first grinding step, the holding means 30 is slightly moved in the +Y direction by the horizontal moving means 13 shown in FIG. The wafer 80 is positioned with respect to the grinding wheel 1644 at a position where the inner cutter on the circumferential side) contacts the outer periphery of the cylindrical recess 807 formed at the center of the wafer 80 in the first grinding process. For example, the horizontal distance from the midpoint of the blade width of the grinding wheel 1644 in the Y-axis direction of 3 mm to the center 808 of the wafer 80 is 2.8 mm. At this time, in the present embodiment, for example, as shown in graph G in FIG. 4, in the second positioning step performed from time T5 to time T6, the height position Z4 of the grinding means 16 is fixed, The grinding wheel 1644 is prevented from separating from the surface 802 of the wafer 80 to be ground.
Note that the grinding wheel 1644 may be separated from the ground surface 802 of the wafer 80 held by the holding surface 302 when performing the first grinding step, the second positioning step, and the second grinding step.

(5) Second grinding process Next, the grinding means 16 is fed at a predetermined grinding feed speed in the -Z direction until the grinding wheel 1644 approaches the holding surface 302 by the grinding feed means 17 shown in a simplified manner in FIG. go. The rotating grinding wheel 1644 contacts the surface to be ground 802 of the wafer 80, and the surface to be ground 802 is ground while avoiding the cylindrical recess 807, and the holding means 30 rotates at a predetermined rotational speed. Accordingly, the wafer 80 held on the holding surface 302 also rotates, and the grinding wheel 1644 grinds the entire surface of the surface to be ground 802 of the wafer 80 while supplying grinding water.

For example, the height position of the grinding means 16 is detected using the height position detection means 12 shown in FIG. After the wafer 80 is subjected to second grinding to the finishing thickness preset in the control means 9 from time T6 to time T7 shown in graph G of 4, spark-out occurs from time T7 to time T8 and escape cut occurs from time T8 to time T9. is performed, and further, the grinding means 16 is raised and retracted from the wafer 80, and the second grinding process is completed. The wafer 80 after the second grinding process was thinned while avoiding the grinding of the cylindrical recess 807 formed in the first grinding process, so that the grinding of the surface 802 to be ground other than the cylindrical recess 807 was faster than that of the cylindrical recess 807. Since the wafer 80 is ground to a large extent, the wafer 80 has a uniform thickness without a cylindrical recess formed in the center.
Further, since it is not necessary to carry out self-grinding in which the holding surface 302 has a complicated shape, self-grinding does not take much time.

It goes without saying that the wafer grinding method according to the present invention is not limited to the above embodiments, and may be implemented in various different forms within the scope of the technical idea. Further, the configuration of the grinding device 1 illustrated in the accompanying drawings is not limited to this, and can be changed as appropriate within the range where the effects of the present invention can be exhibited.

For example, in the above embodiment, in the first grinding process and the second grinding process, the rotation direction of the grinding wheel 164 and the holding means 30 is the same, and the rotating grinding wheel 1644 enters from the outer periphery of the wafer 80 and moves toward the center 808. For example, in the first grinding process and the second grinding process, the rotating directions of the grinding wheel 164 and the holding means 30 are set to be opposite, so that the rotating grinding wheel 1644 is Internal and external grinding may be performed by starting from the center 808 of the blade 80 and grinding toward the outer periphery.

For example, in the second positioning process, as shown in FIGS. 7 and 8, the grinding wheel is positioned at a position where the outer periphery of the rotation locus of the grinding wheel 1644 (outer blade on the outer peripheral side of the grinding wheel 1644) and the outer periphery of the cylindrical recess 807 touch. The wafer 80 may be positioned relative to 1644. Thereafter, by performing the second grinding process as described above, the wafer 80 after the second grinding process is thinned while avoiding grinding of the cylindrical recess 807 that was formed in the first grinding process. Since the surface to be ground 802 other than the cylindrical recess 807 is ground more than the cylindrical recess 807, the wafer 80 has a uniform thickness without a cylindrical recess formed in the center.
In addition, since it is not necessary to perform self-grinding in which the holding surface 302 has a complicated shape, self-grinding does not take much time.

80: Wafer 802: Surface to be ground 801: Surface 807: Cylindrical recess 1: Grinding device 10: Device base 30: Holding means 300: Adsorption section 301: Frame body 302: Holding surface
35: Table base 34: Inclination adjusting means 340: Lifting section 341: Fixed column section 38: Thickness measuring means 37: Suction source 13: Horizontal moving means 130: Ball screw 132: Motor 133: Movable plate 11: Column 17: Grinding feeding means 170: Ball screw 172: Lifting motor 16: Grinding means 160: Rotating shaft 162: Motor 164: Grinding wheel 1643: Wheel base 1644: Grinding wheel 9: Control means

Claims (3)

A holding means that holds a wafer on a holding surface of a conical slope having an apex at the center and is rotatable about the center of the holding surface, and a holding means that is rotatable about the center of an annular grinding wheel and the holding means is rotatable about the center of the annular grinding wheel. A grinding means for grinding a wafer held on a surface with the grinding wheel, a horizontal moving means for relatively moving the holding means and the grinding means in a horizontal direction parallel to the lower surface of the grinding wheel, and the holding means and a grinding feeding means for relatively moving the grinding means in a direction perpendicular to the holding surface, and grinding the wafer in a radial area of the holding surface parallel to the lower surface of the grinding wheel. A wafer grinding method comprising:
a holding step of aligning the center of the holding surface with the center of the wafer and holding the wafer on the holding surface;
a first positioning step of positioning the wafer with respect to the grinding wheel using the horizontal movement means so that the rotation locus of the grinding wheel, which is defined by the radial blade width of the grinding wheel, passes through the center of the holding surface;
After the first positioning step, the grinding wheel is moved in a direction approaching the holding surface by the grinding feeding means, and the wafer is ground to a thickness that is a preset value (1 μm to 3 μm) thicker than the preset finishing thickness. 1 grinding process and
After the first grinding step, the horizontal moving means is used to move to a position where the inner periphery of the rotation locus of the grinding wheel and the outer periphery of the cylindrical recess formed in the center of the wafer in the first grinding step, or a second positioning step of positioning the wafer with respect to the grinding wheel at any position where the outer periphery of the rotation locus and the outer periphery of the cylindrical recess are in contact;
After the second positioning step, a second grinding step of moving the grinding wheel in a direction approaching the holding surface using the grinding feeding means to grind the wafer to the preset finishing thickness. . When performing the first grinding step, the second positioning step, and the second grinding step, the grinding feed means is controlled so as not to separate the grinding wheel from the surface to be ground of the wafer held on the holding surface. The method of grinding a wafer according to claim 1. 3. The method of grinding a wafer according to claim 1, wherein the grinding wheel is a vitrified bond grinding wheel having pores arranged in a continuous manner.

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