JP5312898B2 - Grinding method - Google Patents

Description

  The present invention relates to a method for grinding a wafer.

  In the manufacture of chips such as semiconductor wafers and optical device wafers, the wafers are thinned by a grinding device in the wafer state, and then divided into chips by a cutting device or the like. In the cutting apparatus, cutting is performed while supplying cutting water to a processing region by the cutting blade, thereby cooling the heat generated by the processing and discharging the cutting waste. In this way, the cutting water that contributes to cutting contains cutting waste, and the cutting water mixed with this cutting waste flows on the surface of the wafer, and the cutting waste adheres to the surface of the wafer to contaminate the wafer. There is a problem of doing. In particular, in the case of an optical device such as a CCD or a CMOS wafer, even a slight contamination of the image pickup device on the surface significantly reduces the quality.

  Therefore, for example, a CMOS device is covered with a transparent member such as a glass plate from a wafer state through a frame-shaped resin spacer surrounding each CMOS device to form a laminated wafer state, and the CMOS wafer is thinned in this laminated wafer state. In addition, there is one that minimizes contamination of the CMOS element on the surface side by performing singulation (see, for example, Patent Document 1).

JP 2006-80123 A

  However, the space between the CMOS wafer and the glass plate for the cover is hollow via a resin spacer, and when the back surface of the laminated wafer is thinned and ground, the hollow portion of the laminated wafer is damaged by a grinding wheel. There is a problem that it ends up.

  This point will be described with reference to FIGS. FIG. 8 is a schematic cross-sectional view exaggeratingly showing a configuration example of a CMOS laminated wafer, and FIG. 9 is a schematic plan view showing a state of saw marks formed by infeed processing. The wafer 100 forms, for example, a hollow rectangular region 105 in each CMOS device 101 portion by laminating a glass plate 104 via a resin spacer 103 on the surface side of a Si wafer 102 on which a plurality of CMOS devices 101 are formed. It becomes. Then, one end of an annular grinding wheel 111 attached to the grinding wheel 110 and having the same size as the wafer 100 is positioned so as to pass through the center of the wafer 100, and the grinding wheel 111 and the wafer 100 are rotated at high speed. By doing so, the surface layer of the wafer 100 (the back surface of the Si wafer 102) is ground by infeed processing. The saw marks (grinding marks) 106 formed on the Si wafer 102 by such infeed processing have a circular arc shape from the center of the wafer 100 toward the radial direction, as shown in FIG.

  Here, the hollow rectangular region 105 is formed in, for example, a rectangular shape in plan view, and as shown in A and B portions in FIG. 9, the long side of the grinding wheel 111 and the rectangular hollow rectangular region 105 When 105L is nearly parallel, the shear stress tends to work when the load of the grinding wheel 111 is applied to the Si wafer 102. Then, in this portion, the grinding process in the same saw mark state (and therefore the same load state) is repeatedly performed by the infeed process until the Si wafer 102 is thinned to a desired thickness. As a result, as shown in FIG. 8, the Si wafer 102 is bent in the hollow rectangular region 105, and the Si wafer 102 is damaged by cracking at the boundary of the hollow rectangular region 105. Since the thinner the Si wafer 102 is, the more easily it breaks. As a result, according to the conventional method, the Si wafer 102 cannot be made too thin for thinning.

  The present invention has been made in view of the above, and an object of the present invention is to provide a grinding method capable of performing thinning satisfactorily without causing the wafer to crack at the boundary of the hollow rectangular region.

In order to solve the above-described problems and achieve the object, a grinding method according to the present invention is a grinding method for thinning a wafer having a plurality of hollow rectangular regions therein by using an annular grinding wheel. A direction in which the grinding wheel rotating at high speed around a rotation axis having an axis in the vertical direction is not parallel to all the rectangular sides forming the hollow rectangular region with respect to the wafer held on the chuck table. The surface layer of the wafer is ground by a creep feed that is relatively moved horizontally to form a grinding mark curved in an arc shape on the wafer .

The grinding method according to the present invention is a grinding method for thinning a wafer having a plurality of rectangular hollow rectangular regions therein by using an annular grinding wheel, the wafer held on a chuck table. In contrast , a creep feed that relatively horizontally moves the grinding wheel that rotates at high speed around a rotation axis having an axis in the vertical direction in a direction parallel to the long side that forms the rectangular hollow rectangular region. According to the present invention, the surface layer of the wafer is ground to form a grinding mark curved in an arc shape on the wafer .

Further, the grinding method according to the present invention is a grinding method for thinning a wafer having a plurality of hollow rectangular regions therein by using an annular grinding wheel, wherein the outer diameter is equivalent to the radius of the wafer. The grinding wheel is positioned such that one end of the grinding wheel passes through the center of the wafer, and the grinding wheel and the wafer are mutually rotated at high speed around a vertical axis, thereby the surface layer of the laminated wafer. A grinding mark curved in an arc shape is formed on the wafer .

  According to the grinding method of the present invention, there is an effect that the thinning can be performed satisfactorily without causing the wafer to break at the boundary of the hollow rectangular region.

  Hereinafter, a grinding method which is the best mode for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to the embodiment, and various modifications can be made without departing from the spirit of the present invention.

(Embodiment 1)
FIG. 1 is a schematic plan view showing a wafer to which the grinding method of the first embodiment is applied, and FIG. 2 is a schematic sectional view thereof. The wafer 1 is made of, for example, a glass plate through a resin spacer 4 arranged in a frame shape on the surface side of a plate-like wafer 3 made of Si wafer formed by aligning a plurality of CMOS devices 2 vertically and horizontally near the center. By laminating plate-like wafers 5, a plurality of hollow rectangular regions 6 are formed so that the periphery of each CMOS device 2 is partitioned in a hollow state. Here, each of the hollow rectangular regions 6 is formed in a rectangular shape corresponding to a rectangular device size of, for example, 3.6 mm × 4.2 mm in plan view. An orientation notch 7 that is a crystal orientation identification mark for identifying the crystal orientation of the plate-like wafer 3 is formed at a predetermined position on the outer periphery of the plate-like wafer 3. In addition, instead of the orientation notch 7, a linear orientation flat may be formed as a crystal orientation identification mark.

  FIG. 3 is a perspective view showing a grinding apparatus 10 for grinding the plate-like wafer 3 of such a wafer 1. The grinding apparatus 10 includes a chuck table 20 for holding a wafer 1 to be ground, a grinding means 30 for grinding the wafer 1 held on the chuck table 20, and a grinding feed means for grinding and feeding the grinding means 30 in a vertical direction. 40.

  The chuck table 20 holds the wafer 1 with the plate-like wafer 5 side down, and is rotatably supported by the base 21. The base 21 is provided so as to be movable in the horizontal direction by a table feed mechanism (not shown), and the chuck table 20 is also moved in the horizontal direction with respect to the grinding means 30 as the base 21 moves. The base 21 is connected to a bellows member 22 that expands and contracts with the horizontal movement of the base 21.

  The grinding means 30 includes a rotary shaft 31 having a vertical axis, a motor 32 that rotationally drives the rotary shaft 31, a wheel mount 33 formed at the lower end of the rotary shaft 31, and a grinding mounted on the wheel mount 33. Wheel 34. The grinding wheel 34 has a configuration in which a plurality of grinding wheels 35 are arranged in an annular shape on the lower surface of a ring-shaped base. When the rotating shaft 31 rotates at high speed when driven by a motor 32, the grinding wheel 35. Draws a circular orbit and rotates at high speed. The outer diameter of the grinding wheel 35 is set to be equal to or greater than the outer diameter of the wafer 1.

  The grinding feed means 40 includes a ball screw 41 disposed in the vertical direction, a pulse motor 42 coupled to the ball screw 41, a pair of guide rails 43 disposed in parallel to the ball screw 41, and an internal not shown. The nut is screwed into the ball screw 41, and the side portion is composed of an elevating portion 44 that slides against the guide rail 43 and supports the grinding means 30. Thus, the ball screw 41 is driven by the pulse motor 42 to rotate in both forward and reverse directions, whereby the elevating part 44 is guided by the guide rails 43 to elevate and the grinding means 30 is also elevated. As a result, the height position of the grinding wheel 35 and the load applied to the wafer 1 when the wafer 1 is ground with the grinding wheel 35 are adjusted.

  Next, a grinding method according to the first embodiment using such a grinding apparatus 10 will be described. First, the target wafer 1 is held on the chuck table 20. Then, by moving the chuck table 20 holding the wafer 1 in the horizontal direction, the wafer 1 is positioned below the grinding means 30 as shown in FIG. Prior to this, the grinding table 35 is relatively horizontally moved in a direction that is not parallel to all the rectangular sides forming the hollow rectangular region 6 with respect to the wafer 1 by appropriately rotating the chuck table 20 in a horizontal plane. The direction of the wafer 1 is adjusted so that the In the first embodiment, the wafer 1 is horizontally moved relative to the fixed grinding wheel 35 to perform grinding by creep feed, and one diagonal line formed by the rectangular sides of the hollow rectangular region 6 ( For example, the orientation of the wafer 1 is adjusted so that the diagonal line that rises to the right in FIG. 5 horizontally moves in a direction substantially orthogonal to the grinding wheel 35. Such adjustment of the orientation of the wafer 1 may be performed with reference to the position of the orientation notch 7, for example.

  The grinding means 30 rotates the rotating shaft 31 while maintaining a predetermined height to rotate the grinding wheel 35 at a high speed, and horizontally moves the grinding table 30 toward the grinding means 30 without rotating the chuck table 20. The rotating grinding wheel 35 is brought into contact with the plate-like wafer 3 of the wafer 1 from the side, and the surface layer of the plate-like wafer 3 is ground by creep feed as shown in FIG.

  According to the grinding method of the first embodiment, the grinding wheel 35 is moved horizontally relative to the wafer 1 in a direction that is not parallel to all the rectangular sides forming the hollow rectangular region 6, and the plate is obtained by creep feed. Since the surface layer of the wafer 3 is ground, as shown in FIG. 5, there is a high probability that saw marks (grinding marks) 8 are formed so as to obliquely intersect the rectangular side forming the hollow rectangular region 6; Thinning can be performed satisfactorily without causing cracks in the plate-like wafer 3 at the boundary of the hollow rectangular region 6.

  At this time, since the grinding wheel 35 is formed in an annular shape, a part in which the saw mark (grinding mark) 8 is formed in a state close to being parallel to the long side 6L of the hollow rectangular region 6 may be generated. Unlike the conventional in-feed processing, even if the load is large, the wafer 1 moves sequentially with respect to the grinding wheel 35, and the grinding processing in which the load is concentrated due to the same saw mark state (and therefore the same load state) is repeated. Since it is not received, there is little damage and the crack of the plate-like wafer 3 does not occur in the said part. In addition, there is a portion where saw marks (grinding marks) 8 are formed in a state of being nearly parallel to the short side 6S of the hollow rectangular region 6, but originally such a portion where the grinding wheel 35 extends over the long side 6L is originally formed. Since bending is difficult to occur, the plate-like wafer 3 is not cracked at that portion. As described above, according to the grinding method of the first embodiment, it is possible to reduce the thickness of the plate-like wafer 3 to a desired thickness without causing any cracks.

  Although the first embodiment has been described as an application example in the case where the hollow rectangular region 6 is formed in a rectangular shape, the present invention is not limited to the rectangular shape and can be similarly applied to a square shape. Further, when the grinding wheel 35 is horizontally moved relative to the wafer 1 in a direction that is not parallel to all the rectangular sides forming the hollow rectangular region 6, one of the rectangular sides of the hollow rectangular region 6 is formed. Although the diagonal line is set in a substantially orthogonal direction, the movement direction may be set in a direction in which the formed saw mark (grinding mark) 8 is not substantially parallel to the short side 6S. . In the case of the first embodiment, as the outer diameter of the grinding wheel 35 is increased, it is easier to ensure that the formed saw mark (grinding mark) 8 is not parallel to the long side 6L, which is advantageous.

(Embodiment 2)
FIG. 6 is a schematic plan view of a wafer and a grinding wheel showing the grinding method of Embodiment 2 of the present invention. The second embodiment utilizes the fact that the hollow rectangular region 6 is formed in a rectangular shape, and a grinding wheel 35 that rotates at high speed relative to the wafer 1 held on the chuck table 20 is replaced with a rectangular hollow rectangular region. The surface layer of the plate-like wafer 3 is ground by creep feed that is relatively horizontally moved in a direction parallel to the long side 6L that forms 6. In this case, the orientation of the wafer 1 is also adjusted based on the position of the orientation notch 7, for example.

  According to the grinding method of the second embodiment, as shown in FIG. 6, there is a probability that saw marks (grinding marks) 8 are formed so as to obliquely intersect the rectangular side forming the hollow rectangular region 6. It can be thinned satisfactorily without causing cracks in the plate-like wafer 3 at the boundary of the hollow rectangular region 6. At this time, a part where saw marks (grinding marks) 8 are formed in a state of being almost parallel to the short side 6S of the hollow rectangular region 6 is also generated, but in such a part where the grinding stone 35 extends over the long side 6L. Since it is difficult to bend from the beginning, the plate-like wafer 3 is not cracked at this portion. In this way, according to the grinding method of the second embodiment, it is possible to reduce the thickness to a desired thickness without causing cracks in the plate-like wafer 3 as a whole.

(Embodiment 3)
FIG. 7 is a schematic plan view of a wafer and a grinding wheel showing a grinding method according to Embodiment 3 of the present invention. In the third embodiment, first, a grinding wheel 35a having an outer diameter equal to the radius of the wafer 1 is used. Such a grinding wheel 35a is positioned so that one end of the grinding wheel 35a passes through the center of the plate-like wafer 3 (wafer 1), and the grinding wheel 35a and the wafer 1 are rotated at a high speed with respect to each other. The surface layer of No. 3 is ground.

  According to the grinding method of the third embodiment, since the grinding wheel 35a has a smaller diameter than the wafer 1 and the radius of curvature of the annular shape is small, the grinding wheel 35a is in any position where it is pressed against the plate-like wafer 3 during grinding. However, as shown in FIG. 7, the probability of forming saw marks (grinding marks) 8 that are parallel to the long side 6 </ b> L forming the hollow rectangular region 6 is extremely low. Therefore, the shearing force is dispersed and thinning can be performed satisfactorily without causing the crack of the plate-like wafer 3 at the boundary of the hollow rectangular region 6.

  In the case of the third embodiment, as in the case of the first embodiment, the hollow rectangular region 6 can be applied to a rectangular shape or a square shape. Further, the outer diameter of the grinding wheel 35a does not have to be exactly the same as the radius of the wafer 1, and may be formed slightly larger.

  In these embodiments, the device has been described as an application example in the case of the CMOS device 2. However, other optical devices such as a CCD may be used, and other than the optical device, for example, MEMS (Micro Electro Mechanical Systems). Even in the case of a wafer or the like having a hollow portion inside as described above, it can be similarly applied.

1 is a schematic plan view showing a wafer to which a grinding method according to Embodiment 1 of the present invention is applied. It is a schematic sectional drawing of FIG. It is a perspective view which shows the grinding device for grinding the plate-shaped wafer of a wafer. It is a schematic perspective view which shows the mode at the time of a grinding process start. 1 is a schematic plan view of a wafer and a grinding wheel showing a grinding method of a first embodiment. It is a schematic plan view of a wafer and a grinding wheel showing the grinding method of Embodiment 2 of the present invention. It is a schematic plan view of a wafer and a grinding wheel showing a grinding method of Embodiment 3 of the present invention. It is a schematic sectional drawing which exaggerates and shows the structural example of the conventional laminated wafer for CMOS. It is a schematic plan view which shows the mode of the saw mark formed by an infeed process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer 3, 5 Plate-shaped wafer 6 Hollow rectangular area 6L Long side 20 Chuck table 31 Rotating shaft 35, 35a Grinding wheel

Claims (3)

A grinding method for thinning a wafer having a plurality of hollow rectangular regions inside using an annular grinding wheel,
The grinding wheel that rotates at a high speed around a rotation axis having an axial center in the vertical direction with respect to the wafer held on the chuck table in a direction that is not parallel to all the rectangular sides that form the hollow rectangular region. A grinding method characterized in that a surface layer of the wafer is ground by a creep feed that is relatively horizontally moved to form a grinding mark curved in an arc shape on the wafer . A grinding method for thinning a wafer having a plurality of rectangular hollow rectangular regions inside using an annular grinding wheel,
With respect to the wafer held on the chuck table, the grinding wheel that rotates at a high speed around a rotation axis having an axis in the vertical direction is set in a direction parallel to the long side that forms the rectangular hollow rectangular region. A grinding method characterized in that a surface layer of the wafer is ground by a creep feed that is relatively horizontally moved to form a grinding mark curved in an arc shape on the wafer . A grinding method for thinning a wafer having a plurality of hollow rectangular regions inside using an annular grinding wheel,
The grinding wheel having an outer diameter equal to the radius of the wafer is positioned so that one end of the grinding wheel passes through the center of the wafer, and the grinding wheel and the wafer are mutually centered on a vertical axis. fast by rotating by grinding the surface of the wafer, grinding method being characterized in that so as to form a grinding traces curved in an arc shape to the wafer as.

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