JP2019181634A - Chuck table and grinding apparatus - Google Patents

Abstract

To prevent grinding debris from adhering to a holding surface of a chuck table holding a wafer, thus preventing a lower surface of the wafer from staining, when grinding water is sprayed from an outer peripheral side of the wafer toward the center.SOLUTION: In a chuck table 2, a disc-shaped porous plate 21 having a holding surface 211, which has a diameter substantially equal to a diameter of a wafer, is supported on a base 22. An annular portion 23 surrounds a side surface of the porous plate 21. The annular portion 23 includes: a ring upper surface 234 which is ring-shaped and is flush with the holding surface 211; and an outside surface extending downward from an outer peripheral edge of the ring upper surface 234. The outside surface is formed of: a drooping surface 231 drooping from the outer peripheral edge of the ring upper surface; and a divergent surface 232 which connects a lower end of the drooping surface 231 to an upper surface 224 of the base 22, and in which a diameter increases from the lower end of the drooping surface 231 toward the upper surface 224 of the base 22.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a chuck table for holding a wafer and a grinding apparatus including the chuck table.

  In a grinding apparatus comprising: a chuck table having a holding surface for holding a wafer; and a grinding means for rotating a grinding wheel in which a grinding wheel is annularly arranged and grinding the wafer held by the chuck table by the grinding wheel. The upper surface of the wafer held by the holding surface is ground with the holding surface to be held parallel to the grinding surface of the grinding wheel.

  In the grinding apparatus configured as described above, the chuck table for holding the wafer is rotated, the grinding wheel is rotated, the grinding wheel of the grinding wheel enters the center from the outer peripheral side of the wafer, and the grinding water is supplied to the grinding wheel. While grinding the wafer. Since the grinding water also receives a centrifugal force due to the rotation of the grinding wheel, it is scattered from the outer periphery of the wafer toward the center (for example, see Patent Document 1).

JP 2012-121118 A

  However, since the grinding water from the outer periphery to the center of the wafer is sprayed on the side surface of the wafer, it is in the gap between the lower surface of the wafer (actually, the lower surface of the protective tape attached to the lower surface of the wafer) and the holding surface. Then, grinding water containing grinding waste enters. Therefore, grinding dust enters and adheres to the portion of the holding surface that holds the outer peripheral portion of the wafer. Further, when grinding scraps adhere to the portion of the holding surface, there is a problem that the lower surface of the outer peripheral portion held by the portion of the wafer is also soiled.

  Therefore, when grinding water is sprayed from the outer peripheral side of the wafer toward the center, it is required that the grinding debris does not adhere to the holding surface of the chuck table that holds the wafer and the lower surface of the wafer is not soiled. It has been.

A first invention is a chuck table which is mounted on a grinding apparatus for grinding a disk-shaped wafer by supplying grinding water to a grinding wheel and sucks and holds the wafer, and a holding surface having a diameter substantially the same as the surface of the wafer A disk-shaped porous plate, a base having an upper surface that supports a surface opposite to the holding surface, and a communication path that communicates the upper surface with a suction source; and the porous supported by the base An annular portion surrounding the side surface of the plate, and the annular portion includes a ring upper surface that is flush with the holding surface and formed in a ring shape, and an outer surface that extends downward from the outer peripheral edge of the ring upper surface. The outer surface connects a suspended surface that hangs down from the outer peripheral edge of the ring upper surface, a lower end of the suspended surface, and an upper surface of the base, and has a diameter from the lower end of the suspended surface toward the upper surface of the base. Is formed with a divergent surface that becomes larger.
A second invention is a grinding apparatus provided with the chuck table, wherein the height of the holding surface and the height of the diverging surface for measuring the diverging surface height are measured, and the wafer held by the holding surface is measured. Wafer upper surface height measuring means for measuring the height of the upper surface, and the height of the holding surface measured by the divergent surface height measuring means and of the divergent surface measured by the divergent surface height measuring means of the chuck table Among the storage means for storing the height difference with the height at a position away from the rotation center by a predetermined distance, the height of the wafer upper surface measured by the wafer upper surface height measuring means and the edge spread surface measured by the edge spread height measuring means A difference with a height at a position away from the rotation center of the chuck table by a predetermined distance is calculated, and further, the height difference stored in the storage means is subtracted from the difference, and the chuck table And a calculating means for calculating a thickness of the wafer holding ends the grinding When the thickness of the wafer thickness and the calculated output means of the wafer which is set in advance to calculate match.
3rd invention is a grinding device provided with the above-mentioned chuck table, and measures the height of the end spread surface height measuring means for measuring the height of the end spread surface, and the height of the upper surface of the wafer held by the holding surface. Wafer upper surface height measuring means and the height of the divergent surface measured by the divergent surface height measuring means at a position away from the rotation center of the chuck table by a predetermined distance and the holding surface measured by the wafer upper surface height measuring means A storage means for storing a difference in height from the height of the surface, and a center of rotation of the chuck table among the height of the upper surface of the wafer measured by the height measurement means of the wafer and the end spread surface measured by the height measurement means of the end spread surface The height difference at a position away from the predetermined distance from the height is calculated, and the height difference stored in the storage means is subtracted from the difference, and the wafer held by the chuck table is calculated. And a calculating means for calculating a thickness of the wafer, the grinding device and the thickness of the wafer thickness and the calculated output means of the wafer preset is calculated to terminate the grinding After match.

In the chuck table according to the present invention, the width of the upper surface of the ring is formed narrow by forming the drooping surface and the divergent portion on the outer surface of the annular portion, so that the grinding water containing the grinding dust adheres to the ring upper surface. Hateful. Therefore, it becomes difficult for the grinding water to enter between the holding surface and the lower surface of the wafer, and the possibility that the lower surface of the wafer becomes dirty is reduced. Further, most of the scattered grinding water hits the drooping surface of the annular portion, and the grinding water hitting the drooping surface flows down along the diverging surface. Therefore, it is possible to prevent grinding defects from being caused by accumulation of grinding scraps along the outer surface of the wafer and adhesion of the grinding scraps to the upper surface of the wafer.
In the grinding device according to the present invention, the height of the ring upper surface is measured even when the height of the ring upper surface cannot be measured by the height measuring means because the width of the ring upper surface is narrow. Thus, it becomes possible to measure the thickness of the wafer.

It is a perspective view which shows the example of a grinding device. It is a disassembled perspective view which shows the example of a chuck table. It is a perspective view which shows the example of a chuck table. It is a longitudinal cross-sectional view which shows the example of a chuck table. It is sectional drawing which shows the state which a wafer upper surface height measurement means measures the height of a holding surface while a diverging surface height measurement means measures the height of an end diverging surface. It is sectional drawing which shows the state in which a divergent surface height measuring means measures the height of a divergent surface, and a divergent surface height measuring means measures the height of a holding surface. It is sectional drawing which shows the state which grinds a wafer. It is a top view which shows the relationship between the wafer at the time of grinding a wafer, and a grinding wheel. It is sectional drawing which shows another example of the state which grinds a wafer.

  A grinding apparatus 1 shown in FIG. 1 includes a chuck table 2 that holds a disk-shaped wafer, grinding means 3 that grinds the wafer held on the chuck table 2, and a direction approaching and separating from the wafer. And a grinding feed means 4 for moving the grinding means 3.

  The grinding means 3 includes a spindle 31 having a vertical axis, a housing 32 that rotatably supports the spindle 31, a mount 33 attached to the lower end of the spindle 31, and a grinding wheel 34 attached to the mount 33. A motor 35 for rotating the spindle 31 and a grinding water inflow portion 36 for allowing grinding water to flow into the spindle 31 are provided. The grinding wheel 34 includes a base 341 that is fixed to the mount 33 and a plurality of grinding wheels 342 that are fixed to the lower surface of the base 341 in an annular shape.

  The grinding feed means 4 includes a ball screw 41 having an axis parallel to the spindle 31, a pair of guide rails 42 arranged in parallel to the ball screw 41, a pulse motor 43 that rotates the ball screw 41, and a ball screw 41. An elevating part 44 having a nut to be screwed therein and having a side part slidably contacting the guide rail 42 and a holder 45 fixed to the elevating part 44 and holding the housing 32 are provided.

  The chuck table 2 is movable in the horizontal direction, and includes a disc-shaped porous plate 21 having a holding surface 211 having substantially the same area as a wafer to be ground, and a base 22 that supports the porous plate from below. Yes. The holding surface 211 is formed with substantially the same diameter as the surface of the wafer.

  As shown in FIG. 2, the base 22 has an upper surface 221 that supports a surface 212 opposite to the holding surface 211 of the porous plate 21, a recess 223 that is lowered by one step from the upper surface 221, and a continuous opening that opens at the bottom surface of the recess 223. The passage 222 is composed of a ring-shaped upper surface 224. An annular portion 23 surrounding the porous plate 21 supported by the base 22 from the side surface side is formed above and on the inner peripheral side from the upper surface 224.

  The annular portion 23 is formed with a ring upper surface 234 that is flush with the holding surface 211 of the porous plate 21 and formed in a ring shape.

The outer surface extending downward from the outer peripheral end of the ring upper surface 234 includes a hanging surface 231 depending from the outer peripheral end of the ring upper surface 234 and a diverging surface whose diameter increases from the lower end of the hanging surface 231 toward the upper surface 224 of the base 22. 232 is formed. The drooping surface 231 is formed substantially perpendicular to the ring upper surface 234, but may not be completely perpendicular.
The drooping surface 231 and the divergent surface 232 may be formed of different materials. The hanging surface 231 does not have to expose the outer surface of the porous plate 21. For example, the drooping surface 231 may be formed by applying and curing a resin. The end spread surface 232 is formed of a material such as ceramics with a hardness that does not dent when the probe is touched so that the stylus-type end spread surface height measuring means 51 can measure.

  The lower end of the drooping surface 231 and the inner peripheral side of the upper surface 224 of the base 22 are connected by a diverging surface 232. In the illustrated example, the divergent surface 232 and the base 22 are connected via an annular vertical surface 233 perpendicular to the upper surface 224 of the base 22, but the divergent surface 232 and the annular vertical surface 233 are not connected. It is good also as a structure to which the base 22 is directly connected. By forming the drooping surface 231 and the diverging surface 232 in the annular portion 23, the ring upper surface 234 has a very narrow width.

  In addition, although the base 22 and the annular part 23 are integrally formed in the example of FIG. 2, the base 22 and the annular part 23 may be formed as separate members and connected to each other.

  As shown in FIG. 4, the communication path 222 formed in the base 22 communicates with the suction source 24, and suction force is applied to the holding surface 211 of the porous plate 21 by the suction force supplied from the suction source 24. The wafer can be held by acting.

As shown in FIG. 1, on the side of the movement path of the chuck table 2, a divergent surface height measuring means 51 for measuring the height of the divergent surface 232 of the chuck table 2, and the wafer held on the chuck table 2. A height measuring means 5 comprising a wafer upper surface height measuring means 52 for measuring the height of the upper surface is provided. The divergent surface height measuring means 51 and the wafer upper surface height measuring means 52 are stylus type, and recognize the height according to the position of the stylus when the lower end contacts the divergent surface 232 and the upper surface of the wafer. Further, the diverging surface height measuring means 51 and the wafer upper surface height measuring means 52 can measure the thickness of the wafer held on the holding surface 211 by measuring the height of the holding surface 211. .
The end spread surface height measuring means 51 and the wafer upper surface height measuring means 52 may be non-contact type.

(1) Preparatory Step In the grinding apparatus 1 configured as described above, before starting the grinding of the wafer, as shown in FIG. 5, the lower end of the divergent surface height measuring means 51 is brought into contact with the divergent surface 232, The height of the end spread surface 232 is measured. The measured height value is transferred to the calculation means 61 and stored in the storage means 62. Here, since the divergent surface 232 has a width and the height varies depending on the contact position, the height of the divergent surface 232 at a position away from the rotation center of the chuck table 2 is measured. This predetermined distance is stored in the storage means 62, for example.

  Further, the lower end of the wafer upper surface height measuring means 52 is brought into contact with the holding surface 211 to measure the height of the holding surface 211. The measured height value is transferred to the calculation means 61.

  Next, the calculating unit 61 holds the height of the end spread surface 232 measured by the end spread surface height measuring unit 51 at a position away from the rotation center of the chuck table 2 by a predetermined distance and the wafer upper surface height measuring unit 52 measured. The height difference 512 with respect to the height of the surface 211 is calculated, and the value of the height difference 512 is stored in the storage means 62.

  In addition, as shown in FIG. 6, you may measure the height of the holding surface 211 using the divergent surface height measuring means 51. FIG. In this case, the calculating means 61 includes the height of the end spread surface 232 measured by the end spread surface height measuring means 51 at a position away from the rotation center of the chuck table 2 by a predetermined distance and the holding measured by the end spread surface height measuring means 51. The height difference from the height of the surface 211 is calculated, and the value of the height difference 511 is stored in the storage means 62.

  The storage means 62 also stores the final finished thickness value of the wafer by an input from the operator.

(2) Grinding Step Next, as shown in FIG. 7, the wafer W is held on the chuck table 2. Here, in the example of FIG. 7, in order to prevent air leakage at the holding surface 211 of the porous plate 21, the diameter of the wafer W is slightly larger than the diameter of the porous plate 21. , Reaching the upper surface of the ring upper surface 234.

  Next, as shown in FIG. 8, the chuck table 2 is rotated in the B direction, for example, and the grinding feed means 4 shown in FIG. By doing so, the rotating grinding wheel 342 is brought into contact with the upper surface Wa of the wafer W for grinding. The grinding wheel 342 has a rotational trajectory that passes through the center of the wafer W and contacts at a radius portion of the wafer W. Further, the grinding wheel enters from the outer peripheral side of the wafer W toward the center.

  During grinding of the wafer W, the grinding water flows from the grinding water inflow portion 36 shown in FIG. 1, and the grinding water is discharged downward from the discharge port formed in the base 341 of the grinding wheel 34. Therefore, the grinding water is scattered in the direction from the outer periphery to the center of the wafer W by the centrifugal force acting on the grinding wheel 34 and is sprayed onto the outer surface Wc of the wafer W. This grinding water also contains grinding waste generated by grinding.

  However, since the ring upper surface 234 of the annular portion 23 is formed in a ring shape with a narrow width, the grinding water containing grinding scraps is difficult to adhere on the ring upper surface 234. In particular, in the example shown in FIG. 7, since the ring upper surface 234 is covered with the peripheral edge portion of the wafer W, the grinding water can be prevented from adhering to the ring upper surface 234. Therefore, it becomes difficult for the grinding water to enter between the holding surface 211 and the lower surface Wb of the wafer W, and the possibility that the lower surface of the wafer becomes dirty is reduced.

  Further, most of the grinding water hits the drooping surface 231, and the grinding water hitting the drooping surface 231 flows down along the end spreading surface 232. Therefore, it is possible to prevent grinding scraps from accumulating along the outer surface Wc of the wafer W and causing the grinding scraps to adhere to the upper surface Wa to cause poor grinding.

  During grinding of the wafer W, the height of the upper surface Wa of the wafer W is measured by the wafer upper surface height measuring means 52 as shown in FIG. Then, the calculating means 61 calculates the value of the height of the upper surface Wa of the wafer W measured by the wafer upper surface height measuring means 52 during grinding, and the end spread surface measured by the end spread surface height measuring means 51 stored in the storage means 62. By calculating a difference 513 from a value at a position a predetermined distance away from the center of rotation of the chuck table 2 in 232, and further subtracting the height difference 512 stored in the storage means 62 from the calculated difference 513, the chuck table The thickness of the wafer W held by 2 is calculated. When the thickness of the wafer W calculated by the calculation means 61 matches the finished thickness previously stored in the storage means 62, the grinding feed means 4 raises the grinding means 3 and finishes the grinding.

  In the preparation step, the height of the holding surface 211 is measured using the divergent surface height measuring unit 51, and a predetermined distance from the rotation center of the chuck table 2 in the divergent surface 232 measured by the divergent surface height measuring unit 51. Even in the case where the height difference 511 between the height at a position separated by a distance and the height of the holding surface 211 measured by the diverging surface height measurement means 51 is stored in the storage means 62, the calculation means 61 is capable of calculating the wafer upper surface during grinding. A predetermined distance R from the center of rotation of the chuck table 2 among the height value of the upper surface Wa of the wafer W measured by the height measuring unit 52 and the divergent surface height measuring unit 51 stored in the storage unit 62. A difference 513 from the height value at a position separated by a distance is calculated, and the difference 511 stored in the storage means 62 is subtracted from the calculated difference 513. It allows the chuck table 2 calculates the thickness of the wafer W held.

  Usually, when measuring the thickness of the wafer W, the height of the ring upper surface 234 and the height of the upper surface Wa of the wafer W which are formed flush with the holding surface 211 during grinding of the wafer W are measured in real time. The value of the difference is set as the thickness of the wafer W. However, in the grinding apparatus 1, the height of the ring upper surface 234 cannot be measured by the height measuring unit 5 because the width of the ring upper surface 234 is narrow. However, the thickness of the wafer W can be measured by measuring the height of the predetermined position of the diverging surface 232.

  As shown in FIG. 9, during the grinding of the wafer W, the height of the end spread surface 232 at a predetermined position is not measured by the end spread surface height measurement unit 51, and the upper surface of the wafer W is measured by the wafer upper surface height measurement unit 52. Only the height of Wa may be measured, and the height of the predetermined position of the diverging surface 232 may be obtained by using the value measured in the preparation process and stored in the storage means 62.

1: Grinding device 2: Chuck table 21: Porous plate 211: Holding surface 212: Lower surface 22: Base 221: Upper surface 222: Communication path 223: Recessed portion 224: Upper surface 23: Annular portion 231: Hanging surface 232: End spreading surface 233: Annular vertical surface 234: Ring upper surface 24: Suction source 3: Grinding means 31: Spindle 32: Housing 33: Mount 34: Grinding wheel 341: Base 342: Grinding wheel 35: Motor 36: Grinding water inflow section 4: Grinding feed means 41: Ball screw 42: Guide rail 43: Pulse motor 44: Elevating part 45: Holder 5: Height measuring means 51: End spread surface height measuring means 52: Wafer upper surface height measuring means 61: Calculation means 62: Storage means W: Wafer Wa: Upper surface Wb: Lower surface

Claims (3)

A chuck table that is mounted on a grinding device for grinding a disk-shaped wafer by supplying grinding water to a grinding wheel, and sucking and holding the wafer,
A disc-shaped porous plate having a holding surface substantially the same diameter as the surface of the wafer;
A base including a communication path that has an upper surface that supports a surface opposite to the holding surface and communicates the upper surface with a suction source;
An annular portion surrounding the side surface of the porous plate supported by the base,
The annular portion includes a ring upper surface that is flush with the holding surface and is formed in a ring shape, and an outer surface that extends downward from an outer peripheral end of the ring upper surface.
The outer surface is
A drooping surface depending from the outer peripheral edge of the ring upper surface;
A chuck table formed by connecting a lower end of the drooping surface and an upper surface of the base, and a diverging surface whose diameter increases from the lower end of the drooping surface toward the upper surface of the base. A grinding apparatus comprising the chuck table according to claim 1,
A divergent surface height measuring means for measuring a height of the holding surface and a height of the divergent surface;
Wafer upper surface height measuring means for measuring the height of the upper surface of the wafer held by the holding surface;
The height difference between the height of the holding surface measured by the end spread surface height measuring means and the height of the end spread surface measured by the end spread surface height measuring means at a position away from the rotation center of the chuck table by a predetermined distance. Storage means for storing
Calculate the difference between the height of the wafer upper surface measured by the wafer upper surface height measuring means and the height at a position away from the center of rotation of the chuck table of the terminally expanded surface measured by the terminal spread height measuring means. And a calculating means for subtracting the height difference stored in the storage means from the difference and calculating a thickness of the wafer held by the chuck table,
A grinding apparatus that terminates grinding when a preset wafer thickness matches a wafer thickness calculated by the calculation means. A grinding apparatus comprising the chuck table according to claim 1,
A divergent surface height measuring means for measuring the height of the divergent surface;
Wafer upper surface height measuring means for measuring the height of the upper surface of the wafer held by the holding surface;
Difference in height between the height of the divergent surface measured by the divergent surface height measuring means at a position away from the center of rotation of the chuck table by a predetermined distance and the height of the holding surface measured by the wafer upper surface height measuring means. Storage means for storing
The difference between the height of the upper surface of the wafer measured by the wafer upper surface height measuring means and the height of the terminally expanded surface measured by the height of the divergent surface at a position away from the center of rotation of the chuck table is calculated. And a calculating means for subtracting the height difference stored in the storage means from the difference and calculating a thickness of the wafer held by the chuck table,
A grinding apparatus that terminates grinding when a preset wafer thickness matches a wafer thickness calculated by the calculation means.