JP6082682B2 - How to format a table - Google Patents

Description

  The present invention relates to a table shaping method for shaping a chuck table for holding a wafer in a grinding apparatus for grinding a wafer to form a circular recess.

  Technology that makes it easy to handle the wafer and reduces the risk of breakage during transport by grinding only the central part of the wafer to form a circular concave part and leaving the outer peripheral part unground to form an annular convex part Has been proposed.

  In the grinding apparatus used in this case, the wafer is ground using a grinding wheel having a grinding wheel having an outer diameter of the outermost periphery of the rotating track that is substantially equal to the radius of the circular recess (hereinafter, the rotating track of the grinding wheel is rotated). The diameter of the outermost periphery is simply referred to as “the outer diameter of the grinding wheel”). When grinding the wafer, the grinding wheel rotation axis is slightly tilted with respect to the chuck table rotation axis in order to prevent the wafer from being burnt and to prevent the formation of damped grinding marks on the wafer. ing. For this reason, the recesses of the wafer are ground relatively shallowly near the center and near the outer periphery, and relatively deeply ground near the center in the radial direction. On the other hand, if the holding surface of the chuck table is formed in a flat shape, the thickness of the concave portion of the wafer is not uniform, so the holding surface of the chuck table is previously set so that the finished thickness of the concave portion of the wafer is uniform. Is ground and shaped so as to be parallel to the surface of the concave portion of the wafer after grinding (see, for example, Patent Document 1).

JP 2008-60470 A

  However, the diameter of the chuck table is larger than the diameter of the concave portion of the wafer, so if the holding surface is ground using a grinding wheel having the same diameter as that of the grinding wheel for forming the concave portion, the area that is not ground on the outer periphery of the holding surface Remains. On the other hand, if the holding surface is ground using a grinding wheel having a diameter larger than that of the grinding wheel for forming the recess so as not to leave an unground area on the outer periphery of the holding surface, the thickness of the recess can be made uniform on the holding surface. It is difficult to shape the shape with high accuracy.

  The present invention has been considered in view of such problems, and the shape of the holding surface is shaped with high accuracy into a shape that can make the thickness of the concave portion of the wafer uniform without leaving an unground area on the outer periphery of the holding surface. The purpose is to do.

The present invention has a chuck table that holds and rotates a disk-shaped wafer mounted on a circular holding surface, and a grinding wheel in which grinding wheels are arranged in an annular shape, and is attached to the tip. The grinding wheel is rotated about a rotation axis inclined at a desired angle with respect to the wafer, and the grinding wheel is brought into contact with the central portion of the wafer held by the chuck table to form a circular recess in the central portion, Grinding means for forming an annular convex portion on the outer peripheral side of the circular concave portion, and radial moving means for relatively moving the grinding means and the chuck table in a direction parallel to the radial direction of the chuck table. A table shaping method for grinding and shaping the holding surface of the chuck table using a grinding apparatus, the grinding wheel for grinding the wafer to form the circular recess and the grinding wheel A holding surface grinding wheel having the same outer diameter is attached to the grinding means, the grinding means and the chuck table are positioned at the same position as when the wafer is ground by the radial movement means, and the chuck table is rotated. And forming a concave surface formed by grinding a predetermined amount of the central portion of the holding surface by the grinding means and a convex portion having a step between the concave surface and having a convex surface on the outer peripheral portion of the holding surface. The grinding means and the chuck table are positioned at a position where the rotation axis of the grinding means and the rotation axis of the chuck table are separated from each other by the grinding step and the radial movement means than in the first grinding step. A second grinding step of rotating so as to eliminate a step between the concave surface and the convex surface of the holding surface.
In this table shaping method, the grinding apparatus is provided with a height measuring means for measuring the height of the holding surface, and in the first grinding step, the holding surface in the central portion of the holding surface is measured by the height measuring means. The center portion is ground by the grinding means while measuring the height of the holding surface, and in the second grinding step, the height measuring means measures the height of the holding surface in the outer peripheral portion of the holding surface. It is desirable to grind the outer peripheral portion by the grinding means.

  According to the table shaping method according to the present invention, in the first grinding step, the grinding wheel for forming the recess of the wafer and the grinding wheel for the holding surface having the same outer diameter of the grinding wheel are used, and the rotation axis of the chuck table is used. Since the holding surface is ground by rotating the grinding wheel around the rotation axis inclined at the desired angle, the shape of the holding surface is shaped with high precision so that the thickness of the recess can be made uniform during subsequent wafer grinding. Can do. Moreover, since the convex part which cannot be ground in the 1st grinding process is ground in the 2nd grinding process, it can prevent that the outer peripheral part of a holding surface remains without being ground, and a wafer can be hold | maintained reliably.

The front view which shows a grinding device, side view sectional drawing, and a top view. The side view sectional drawing which shows a wafer grinding process, and the perspective view which shows the ground wafer. The flowchart which shows the table shaping method. Side surface sectional drawing which shows a 1st grinding process. Side surface sectional drawing which shows a 2nd grinding process.

  The grinding apparatus 20 shown in FIG. 1 grinds only the central part of a disk-shaped wafer to form a circular concave part in the central part, and leaves the outer peripheral part without grinding, thereby forming an annular convex on the outer peripheral side of the central part. It is an apparatus which can form a part. The grinding apparatus 20 includes a chuck table 21 that holds a wafer, a grinding unit 22 that grinds the wafer held by the chuck table 21, a grinding feed unit 26 that moves the grinding unit 22 in ± Z directions, a grinding unit 22, and a grinding unit. A radial moving means 23 for moving the feeding means 26 relative to the chuck table 21 in the ± Y direction, a height measuring means 24 for measuring the height of the holding surface 211 of the chuck table 21, and a height measuring means 24 are provided. Positioning means 25 for moving in the ± Y direction is provided.

  The chuck table 21 sucks and holds a wafer placed on a circular holding surface 211 parallel to the XY plane. The chuck table 21 can rotate around the rotating shaft 219 parallel to the Z-axis direction together with the held wafer.

  In the grinding means 22, a grinding wheel 30 is attached to the tip of the spindle. On the −Z side of the grinding wheel 30, a plurality of grinding wheels 31 are arranged in an annular shape around the rotation shaft 229. The outer diameter 317 of the grinding wheel 31 arranged in an annular shape is smaller than the radius of the wafer held on the chuck table 21. The grinding means 22 rotates the grinding wheel 30 about the rotation shaft 229. The rotating shaft 229 of the grinding means 22 is slightly inclined with respect to the Z axis in the XZ plane. Although exaggerated in the figure, the inclination angle 228 of the rotating shaft 229 is, for example, about 0.01 degrees.

  The grinding feed means 26 has, for example, a ball screw mechanism, and moves the grinding means 22 in the −Z direction to bring the grinding wheel 30 attached to the grinding means 22 closer to the holding surface 211 of the chuck table 21 and perform grinding. The grinding wheel 30 can be separated from the holding surface 211 by moving the means 22 in the + Z direction.

  The radial movement means 23 has, for example, a ball screw mechanism, and rotates the grinding means 22 by moving the grinding means 22 and the grinding feed means 26 in the radial direction of the chuck table 21 (direction parallel to the holding surface 211). The distance between the shaft 229 and the rotation shaft 219 of the chuck table 21 can be changed.

  The positioning means 25 moves the height measuring means 24 to change the distance between the position where the height measuring means 24 measures the height of the holding surface 211 and the rotating shaft 219 of the chuck table 21.

  When a circular recess is formed by grinding the central portion of the wafer using the grinding apparatus 20 and an annular protrusion is formed on the outer peripheral side of the circular recess, as shown in FIG. 2, a chuck table 21 holding the wafer is used. , And while the grinding means 22 rotates the grinding wheel 30, the grinding feed means 26 moves the grinding means 22 in the -Z direction and presses the grinding wheel 31 against the wafer to grind the wafer.

  The reason why the rotating shaft 229 of the grinding means 22 is slightly tilted is to prevent the surface burn and the wrinkle-shaped streak from occurring on the wafer. As a result, the grinding wheel 31 rotates in a plane inclined by an inclination angle 228 with respect to the XY plane. For this reason, when the grinding wheel 31 is in the semicircular region on the −X direction side, it is in a floating state without contacting the wafer, and only when it is in the semicircular region on the + X direction side, the grinding wheel 31 comes into contact with the wafer. Grind. Since the grinding wheel 31 is positioned in the −Z direction as it is further away from the rotation axis 229 of the grinding means 22 in the + X direction, the wafer is ground most deeply at a position farthest from the rotation axis 229 in the + X direction. The grinding depth differs depending on the distance from the rotation shaft 219, and the difference depending on the grinding depth position is, for example, about 20 μm.

  In order to make the thickness in the circular concave portion of the ground wafer uniform, as shown in FIG. 2, the holding surface 211 may be provided with, for example, arc-shaped irregularities according to the depth to be ground. . That is, the holding surface 211 is lowered in the −Z direction at a deeply ground position, and the holding surface 211 is raised in the + Z direction at a shallowly ground position.

  In this way, the wafer 40 placed on the holding surface 211 is bent along the shape of the holding surface 211 by being sucked. In this state, the chuck table 21 is rotated about the rotation shaft 219, and the grinding means 22 moves the grinding device 22 in the -Z direction while the grinding device 22 rotates the grinding wheel 30 about the rotation shaft 229. The wafer 40 is ground by pressing the grinding surface (surface in the −Z direction) of the grinding wheel 31 against the surface to be ground (surface in the + Z direction) of the wafer 40. As a result, the central portion of the wafer 40 is ground to form the circular concave portion 42 having an inner diameter smaller than the outer diameter 417 of the wafer 40, and the annular convex portion 41 is formed to the outer peripheral portion remaining without being ground. Since the wafer 40 is ground in a state of being curved along the unevenness of the holding surface 211, the thickness of the circular recess 42 is uniform even though the grinding depth varies depending on the position.

  In this way, in order to make the thickness of the circular recess 42 of the wafer W uniform, in the table shaping method 10 shown in FIG. 3, the chuck table 21 of the grinding device 20 is shaped to match the grinding depth. The holding surface 211 is uneven. The table shaping method 10 includes a first grinding step 11 for grinding a central portion of the chuck table 21 and a second grinding step 12 for grinding an outer peripheral portion of the chuck table 21. Hereinafter, each step will be described in detail.

  As shown in FIG. 4, in the first grinding step 11, a holding surface grinding wheel 30 b for grinding the holding surface 211 is mounted on the grinding means 22. The holding surface grinding wheel 30b has an outer diameter 317 of the grinding wheel 31 equal to that of the wafer grinding wheel 30 for grinding a wafer.

  The radial direction moving means 23 positions the grinding means 22 and the grinding feed means 26 at the same position as when the wafer is ground. Then, the positioning means 25 positions the height measuring means 24 so that the height measuring means 24 can measure the height of the holding surface 211 at the position where the depth to be ground is deepest. In this state, the chuck table 21 is rotated around the rotation shaft 219, and the grinding means 22 rotates the holding surface grinding wheel 30b around the rotation shaft 229, while the grinding feed means 26 moves the grinding means 22 in the -Z direction. The holding surface 211 is ground by pressing the grinding wheel 31 against the chuck table 21. The grinding amount of the holding surface 211 is calculated based on the height of the holding surface 211 measured by the height measuring unit 24, and when the predetermined amount set in advance is reached, the grinding feed unit 26 moves the grinding unit 22 to + Z. It moves to the direction, it leaves | separates from the chuck table 21, and grinding is complete | finished.

  As a result, the holding surface 211 is ground in the same circular area as the area where the wafer 40 is ground and the circular recess 42 is formed, and the radius of the holding surface 211 is a concave surface 211a having an arc cross section (scheduled to be added to the figure). Formed. That is, the vicinity of the center of the holding surface 211 in the radial direction is the most depressed, and the height is increased by drawing an arc from the most depressed portion to the center and the outer periphery of the holding surface 211. Since the position of the grinding means 22 and the outer diameter 317 of the holding surface grinding wheel 30 b are the same as the position of the grinding means 22 and the outer diameter 317 of the grinding wheel 30 when grinding the wafer 40, it is formed on the wafer 40. A concave surface 211 a having the same cross-sectional shape as the circular concave portion 42 is formed on the holding surface 211. Thereby, the thickness of the circular recessed part 42 formed in the wafer 40 can be made uniform with high accuracy. Further, a convex portion having a convex surface 211b (planned to be added to the drawing) having a step between the concave surface 211a and the concave surface 211a is formed on the outer peripheral portion of the holding surface 211.

  However, in the first grinding step 11, the outer peripheral portion outside the range where the circular recess 42 is formed on the wafer 40 is not ground. Since the outer diameter 417 of the wafer 40 is larger than the inner diameter of the circular recess 42, the outer peripheral portion of the wafer 40 (the portion that becomes the annular convex portion 41) hits the outer peripheral portion of the holding surface 211 that remains without being ground. The wafer 40 cannot be curved along the unevenness formed on the holding surface 211. As a result, the wafer W cannot be held firmly, and the thickness of the circular recess 42 of the wafer 40 can be increased with high accuracy. It cannot be made uniform. In order to prevent this, the following second grinding step 12 is executed.

  As shown in FIG. 5, in the second grinding step 12, the radial movement means 23 moves the grinding means 22, and the rotation shaft 219 of the chuck table 21 and the rotation shaft 229 of the grinding means 22 are compared with those in the first grinding step. The grinding means 22 and the chuck table 21 are positioned at positions where the distance between them is increased. Further, the positioning means 25 positions the height measuring means 24 so that the height of the holding surface 211 in the outer peripheral portion remaining without being ground in the first grinding step 11 can be measured.

  In this state, the chuck table 21 is rotated around the rotation shaft 219, and the grinding means 22 rotates the holding surface grinding wheel 30b around the rotation shaft 229, while the grinding feed means 26 moves the grinding means 22 in the -Z direction. The holding surface 211 is ground by pressing the grinding wheel 31 against the chuck table 21. During grinding, the grinding amount of the holding surface 211 is calculated based on the height of the holding surface 211 measured by the height measuring means 24, and the grinding is terminated when a predetermined amount set in advance is reached. For example, when the height of the outer peripheral portion of the holding surface 211 is the same as the height of the holding surface 211 on the rotation shaft 219, the grinding feed means 26 moves the grinding means 22 in the + Z direction, and the chuck table 21. Grinding is finished after separating from.

  As a result, the outer peripheral portion of the holding surface 211 is ground to eliminate the level difference between the concave surface 211a and the convex surface 211b, and the height discontinuity between the central portion ground in the first grinding step 11 is removed. . Thereby, since the wafer can be curved along the unevenness formed on the holding surface 211, the wafer can be held firmly and the thickness of the circular concave portion of the wafer can be made uniform with high accuracy.

As described above, in the first grinding step 11, the wafer grinding wheel 30 for grinding the wafer 40 to form a circular recess is held using the holding surface grinding wheel 30 b having the same outer diameter of the grinding wheel 31. Since the central portion of the surface 211 is ground, unevenness having a shape that can make the thickness of the circular recess 42 of the wafer 40 uniform can be formed on the holding surface 211 with high accuracy.
In addition, since the outer peripheral portion of the holding surface 211 is ground in the second grinding step 12, when the wafer 40 is held by the holding surface 211, the wafer 40 is bent and held along the unevenness formed on the holding surface 211. The thickness of the circular recess 42 of the wafer 40 can be made uniform with high accuracy.

  The grinding feed means 26 may be any means as long as the grinding means 22 and the chuck table 21 are moved relative to each other in a direction perpendicular to the holding surface 211, and the grinding table 22 is not moved. The structure which moves 21 may be sufficient, and the structure which moves both the grinding means 22 and the chuck table 21 may be sufficient.

  The radial direction moving means 23 moves the grinding means 22 and the chuck table 21 relative to each other in a direction parallel to the holding surface 211, and between the rotating shaft 229 of the grinding means 22 and the rotating shaft 219 of the chuck table 21. However, the grinding means 22 may be moved instead of moving the chuck table 21, or both the grinding means 22 and the chuck table 21 may be moved. There may be.

  The position where the height measuring unit 24 measures the height of the holding surface 211 in the first grinding step 11 is not limited to the position where the depth of grinding is the deepest, but is within the range where the holding surface 211 is ground (that is, the chuck). As long as the rotation axis 219 of the table 21 is the center, it may be within the range of a circular region having the same radius as the radius of the circular recess 42 formed in the wafer 40. Moreover, the structure which measures the grinding | polishing amount based on the feed amount of the grinding feed means 26 may be sufficient, and the height measurement means 24 does not need to measure the height of the holding surface 211 in that case.

  In the second grinding step 12, the holding surface 211 may be ground in a range wider than the outer diameter 417 of the wafer 40, and there may be a portion that remains on the outer peripheral portion of the chuck table 21 without being ground.

  Even if the first grinding step 11 is executed first, the second grinding step 12 is not executed later, but the first grinding step 11 is executed after the second grinding step 12 is executed first. Good.

  The positioning means 25 is moved relatively in a direction parallel to the holding surface 211 of the height measuring means 24 and the chuck table 21, and the height measuring means 24 measures the height of the holding surface 211. As long as the distance between the chuck table 21 and the rotation shaft 219 is changed, the chuck table 21 may be moved instead of moving the height measuring means 24. The structure which moves both the measurement means 24 and the chuck table 21 may be sufficient.

10 table shaping method, 11 first grinding step, 12 second grinding step,
20 grinding device, 21 chuck table, 211 holding surface,
217, 317, 417 outer diameter, 219, 229 rotating shaft,
22 grinding means, 228 inclination angle,
23 radial moving means, 24 height measuring means, 25 positioning means,
26 grinding feed means,
30, 30b grinding wheel, 31 grinding wheel,
40 wafer, 41 annular convex, 42 circular concave

Claims (2)

A chuck table capable of holding and rotating a disk-shaped wafer placed on a circular holding surface;
A wafer held on the chuck table by rotating a grinding wheel about a rotation axis inclined at a desired angle with respect to the rotation axis of the chuck table. Grinding means for bringing the grinding wheel into contact with the central portion of the substrate to form a circular concave portion in the central portion, and forming an annular convex portion on the outer peripheral side of the circular concave portion,
Radial movement means for relatively moving the grinding means and the chuck table in a direction parallel to the radial direction of the chuck table;
A table shaping method for grinding and shaping the holding surface of the chuck table using a grinding apparatus comprising:
When a grinding wheel for grinding the wafer to form the circular recess and a grinding wheel for holding surface having the same outer diameter of the grinding wheel are mounted on the grinding means, and the wafer is ground by the radial movement means The grinding means and the chuck table are positioned at the same position, and the chuck table is rotated, and the central portion of the holding surface is ground by a predetermined amount by the grinding means. A first grinding step comprising a step and a convex portion having a convex surface on the outer peripheral portion of the holding surface;
The grinding means and the chuck table are positioned at a position where the rotary shaft of the grinding means and the rotary shaft of the chuck table are separated from each other by the radial moving means than in the first grinding step, and the chuck table is rotated, A second grinding step of grinding so as to eliminate a step between the concave surface and the convex surface of the holding surface;
A table shaping method comprising: The grinding apparatus according to claim 1, further comprising height measuring means for measuring the height of the holding surface,
In the first grinding step, while measuring the height of the holding surface in the central portion of the holding surface by the height measuring means, the central portion is ground by the grinding means,
2. The table shaping method according to claim 1, wherein, in the second grinding step, the outer peripheral portion is ground by the grinding means while the height of the holding surface in the outer peripheral portion of the holding surface is measured by the height measuring means. .

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