JP5959193B2 - Wafer grinding method and wafer grinding apparatus - Google Patents

Description

  The present invention relates to a wafer grinding method for grinding a wafer, in particular, a wafer including a chamfered portion located on the outer periphery and a flat portion located inward of the chamfered portion, and a wafer grinding apparatus for performing such a method. .

  In the semiconductor manufacturing field, wafers tend to increase in size year by year, and the wafers are becoming thinner to increase the mounting density. In order to reduce the thickness of the wafer, so-called back grinding is performed to grind the back surface of the wafer.

  As is well known, a chamfered portion is formed on the outer periphery of the wafer to prevent dust generation, and the cross section at the wafer edge is narrower toward the tip. In recent years, since it is required to perform a large back surface grinding, the back surface grinding may be performed in excess of half the thickness of the wafer. In such a case, a tapered portion that is thinner than the thickness of the wafer after back grinding is formed on the outer periphery of the wafer.

  Since this thin taper portion has a sharp edge and is vulnerable to the cutting of the grindstone, cracks are likely to occur in the taper portion. And a crack may spread to the inside of a wafer. That is, the crack propagates to the inside of the wafer because the action of bringing the outer peripheral crack into the inner periphery increases as the grinding wheel velocity vector from the outer peripheral edge of the wafer toward the inner periphery increases. . Therefore, in order to suppress the formation and progress of cracks, edge trimming is performed to remove the chamfered portion of the wafer before the wafer is ground so that the wafer edge does not become a sharp edge.

  Patent Document 1 discloses edge chamfering of a wafer by a rotating blade. In Patent Document 1, after edge trimming of a chamfered portion of a wafer, the turntable is rotated to move the wafer to a grinding unit, and the flat portion of the wafer is ground by the grinding unit.

JP 2007-165802 A

  However, in the method of Patent Document 1, a rotating blade for removing the chamfered portion and a motor for driving the rotating blade are required. In Patent Document 1, since the wafer is moved by the turntable, the position of the wafer cannot be finely adjusted.

Instead of finely adjusting the position of the wafer, Patent Document 1 requires a separate positioning mechanism unit for positioning the rotating blade. That is, in Patent Document 1, a rotating blade, a motor for the rotating blade, and a positioning mechanism are required. Therefore, in patent document 1, there existed a problem that the whole apparatus enlarged.
Further, when cutting is performed on the outer peripheral edge of the substrate from the back surface to the front surface, the depth at which the cutting is performed becomes delicate. That is, even when the substrate is completely separated, if the rotating blade is inserted a little too deep, it reaches the chuck and damages the chuck. If the wafer cannot be completely cut, it may break from the portion left thin without being cut.

  The present invention has been made in view of such circumstances, and performs wafer grinding for performing both removal of a chamfered portion of a wafer and grinding of a flat portion of a wafer without requiring a rotating blade and related members. It is an object to provide a method and a wafer grinding apparatus for carrying out such a method.

According to the first aspect of the present invention, in the wafer grinding apparatus for grinding a wafer including a chamfered portion located on the outer periphery and a flat portion located inward of the chamfered portion, the chamfered portion of the wafer is ground. A cup-type grinding wheel including a chamfered grinding part and a flat grinding part for grinding a flat part of the wafer, and the chamfered grinding part is disposed on an outer peripheral side of the flat grinding part, The wafer is positioned relative to the cup grinding wheel so that the chamfered portion or the flat portion of the wafer is positioned at a position corresponding to the chamfered grinding portion and the flat grinding portion of the cup grinding wheel. And a chamfer grinding by positioning the chamfered portion of the wafer at a position corresponding to the chamfered grinding portion of the cup-type grinding wheel by the moving mechanism portion. Part After removing the chamfered portion of the wafer, the moving mechanism portion positions the flat portion of the wafer at a position corresponding to the flat grinding portion in the cup-type grinding wheel. A wafer grinding apparatus is provided that grinds the flat portion of the wafer.
According to a second aspect, in the first aspect , the chamfering grinding part and the flat grinding part are arranged coaxially with each other in the cup-type grinding wheel.
According to the third invention, in the first or second invention, the chamfered grinding part and the flat grinding part are formed to have a step.
According to a fourth invention , in any one of the first to third inventions , the wafer is attached to a base substrate.
According to a fifth aspect, in the fourth aspect , the base substrate is another wafer having the same dimensions as the wafer.

In the first invention, the chamfered portion and the flat portion of the wafer can be positioned in correspondence with the chamfered grinding portion and the flat ground portion of the grindstone, respectively. It is possible to perform both removal of the surface and grinding of the flat portion. Thus, the need for a rotating blade and its associated members can be eliminated.
In addition, since the removal depth of the chamfered portion of the wafer and the grinding depth of the flat portion can be arbitrarily set using a grindstone attached to one shaft, for example, the removal depth of the chamfered portion is determined by a desired flat grinding amount. By setting a little deeper, it becomes possible to greatly reduce the influence of cracks from sharp edges during flat grinding.
Furthermore, by arranging the chamfered grinding portion on the outer peripheral side of the grindstone, not only the surface of the outer peripheral grindstone but also the outer peripheral surface can be used efficiently.
In the second invention, by arranging the chamfered grinding part and the flat grinding part coaxially, it is possible to remove the chamfered part and grind the flat part with one spindle shaft. The flat part can be continuously ground.
In the third aspect of the invention, the chamfered portion and the flat portion can be ground properly by providing a step on the inner and outer peripheries.
In the fourth invention, when removing the chamfered portion of the wafer, a part of the base substrate can be deleted together. For this reason, it is possible to avoid damage to the holding portion that holds the base substrate. The base substrate is preferably attached to the wafer with an adhesive or the like.
In the fifth aspect, a base substrate having the same dimensions as the wafer can be easily prepared.

1 is a schematic perspective view of a wafer grinding apparatus according to the present invention. It is a side view of the wafer grinding device based on this invention. FIG. 3 is a rear view of the wafer grinding apparatus shown in FIG. 2. FIG. 3 is a top view of the wafer grinding apparatus shown in FIG. 2. It is a figure which shows a wafer. It is a fragmentary sectional view showing an example of a cup type grinding wheel. (A) is a fragmentary sectional view of a wafer grinding device when a chamfer is removed, and (b) is a partial top view of the wafer grinding device shown in FIG. 7 (a). It is a partial side view of a wafer after chamfering part removal. It is a fragmentary sectional view of a wafer grinding device when grinding a flat part. It is a partial side view of a wafer after flat part grinding. It is a fragmentary sectional view showing the 1st other example of a cup type grinding wheel. It is a fragmentary sectional view showing the 2nd other example of a cup type grinding wheel.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following drawings, the same members are denoted by the same reference numerals. In order to facilitate understanding, the scales of these drawings are appropriately changed.
FIG. 1 is a schematic perspective view of a wafer grinding apparatus according to the present invention. As shown in FIG. 1, the wafer grinding apparatus 10 mainly includes an arch-type column unit 12 including a cup-type grinding wheel 36, and a transfer unit 11 as a moving mechanism unit disposed below the column unit 12. Is included.

  The wafer grinding apparatus 10 grinds a wafer 60, for example, a silicon wafer. As shown in the drawing, a single groove 13 is formed in one side surface 12 b of the column unit 12 in the vertical direction, and this groove 13 extends from the top surface 12 a of the main unit 12 to the lower passage 14. Further, the transfer unit 11 can position such a wafer 60 at two desired positions corresponding to the cup-type grinding wheel 36. Further, the transport unit 11 carries the wafer 60 into and out of the grinding unit.

  As can be seen from FIG. 1, two linear guides 32 and 33 are provided on the side surface 12 b, respectively, on both edges of the groove 13 or adjacent to each other. Further, a similar linear guide 31 is provided in parallel to the linear guides 32 and 33 at the bottom of the groove 13. These linear guides 31, 32, and 33 serve as guide rails that slide on a single saddle.

  2 is a side view of the wafer grinding apparatus according to the present invention, FIG. 3 is a front view of the wafer grinding apparatus shown in FIG. 2, and FIG. 4 is a top view of the wafer grinding apparatus shown in FIG. . As can be seen from these drawings, the transport unit 11 includes a transport base 21 on which two rails 22 parallel to each other are arranged. A chuck 29 for holding the wafer 60 is slidably disposed on the rail 22. The slider 25 coupled to the chuck 29 drives the ball screw 23 by the motor 26 via the belt / pulley mechanism 24. Thereby, the slider 25 comes to slide on the rail 22.

  The chuck 29 is connected to a vacuum source (not shown) and holds the wafer 60 by suction or the like. Further, a motor 27 is disposed below the transfer table 21, and the chuck 29 rotates around the vertical axis while holding the wafer 60.

  Further, as can be seen from FIGS. 2 and 3, a saddle 34 is slidably attached to the linear guides 32, 33 of the main unit 12. The saddle 34 is also slidably attached to the linear guide 31 via a nut 39 of a ball screw 38. As shown in the figure, a cup type grinding wheel 36 is attached below the saddle 34, and the cup type grinding wheel 36 slides along the linear guides 31 to 33 integrally with the saddle 34. . The rotation axis of the cup-type grinding wheel 36 is arranged in parallel to the linear guides 31 to 33. When the motor 35 provided in the saddle 34 is driven, the cup-type grinding wheel 36 rotates around the rotation axis.

  As described above, the ball screw 38 is disposed between the saddle 34 and the linear guide 31. The ball screw 38 is driven by a motor 37 disposed above, and serves as a grinding feed section that additionally feeds the cup-type grinding wheel 36 toward the wafer 60 of the chuck 29. As can be seen from FIGS. 2 and 4, the edge of the cup-type grinding wheel 36 is located on or adjacent to the feeding direction in which the cup-type grinding wheel 36 is fed toward the wafer 60. .

  FIG. 5 is a view showing a wafer. As shown in FIG. 5, a plurality of circuit patterns C, for example, through electrodes are formed in a lattice pattern on the surface 61 of the wafer 60 in the previous step. As can be seen from FIG. 5, all the circuit patterns C are formed on the flat portion 67 of the wafer 60, and the outer peripheral portion of the wafer 60 positioned around the flat portion 67 is formed as a chamfered portion 68. Note that such a circuit pattern C is not formed on the back surface 62 of the wafer 60.

  In FIG. 5, the surface 21 of the wafer 60 is attached to the base substrate 70 with an adhesive or the like. It is assumed that such a wafer 60 is supplied to the wafer grinding apparatus 10 shown in FIG. 1 and the like so that the base substrate 70 is positioned below.

  As shown in FIG. 5, the base substrate 70 is a flat member having substantially the same shape as the wafer 60. It is preferable to use another wafer 60 as the base substrate 70. In such a case, the base substrate 70 can be easily prepared. However, the base substrate 70 having another shape may be used.

Next, FIG. 6 shows an example of a cup-type grinding wheel 36 used in the wafer grinding apparatus 10 shown in FIG.
The cup-type grinding wheel 36 includes a flat grinding portion 36 a that grinds the flat portion 67 of the wafer 60 described above, and a chamfering grinding portion 36 b that grinds a chamfered portion 68 in the outer peripheral portion around the flat portion 67. . The flat portion 67 and the chamfered portion 68 of the wafer 60 are ground by the flat grinding portion 36a and the chamfered grinding portion 36b, respectively.
The flat grinding portion 36a and the chamfering grinding portion 36b are provided coaxially with the rotation axis O of the rotating grindstone base 36v. In this case, the flat grinding portion 36a is disposed near the rotation axis O of the grindstone base 36v, and the chamfering grinding portion 36b is disposed outside the flat grinding portion 36a. Further, a level difference is set so that the grinding tip of the flat grinding portion 36a protrudes downward in the drawing compared to the chamfered grinding portion 36b. The flat grinding portion 36a and the chamfering grinding portion 36b may use grindstones with different particle sizes, or may use grindstones with the same particle size. For example, a metal bond (# 2000) grindstone can be used for both the flat grinding portion 36a and the chamfering grinding portion 36b.
Further, the flat grinding portion 36a and the chamfering grinding portion 36b may be integrally provided on the rotating grindstone base 36v, but may be individually removed. That is, the cup-type grinding wheel 36 may be divided into two parts and divided into a flat grinding part 36a, a chamfering grinding part 36b, and two grinding stones. The chamfered grinding portion 36 b is configured on the outer peripheral portion of the flat grinding portion 36 b, but is for applying a stress in a tangential direction to the wafer 60.
If a sharp edge is formed in the process of thinning by the surface grinding portion 36a, a crack occurs from the edge, and the crack enters the inside. The biggest factor that the crack enters inside and damages the inside of the wafer 60 is that, as described above, the grindstone to be ground relatively increases the velocity component in the radial direction toward the wafer 60 center side. Due to that. That is, the sharp edge rising on the outer peripheral portion vibrates slightly, and the crack enters inside in proportion to the velocity component of the grindstone relatively toward the center.
Therefore, in order to avoid such a situation, it is desirable that the chamfered grinding portion 36b is made to act on the wafer 60 only in the tangential direction as much as possible. In particular, it is preferable to increase the outer diameter of the chamfered grinding portion 36b because the grindstone acts in the tangential direction, and the velocity component in the radial direction in which the grindstone relatively moves toward the center of the wafer 60 becomes smaller.

  7A is a partial cross-sectional view of the wafer grinding apparatus when the chamfered portion is removed, and FIG. 7B is a partial top view of the wafer grinding apparatus shown in FIG. 7A. . The removal operation of the chamfered portion 68 by the wafer grinding apparatus 10 according to the present invention will be described below with reference to these drawings.

  First, the wafer 60 is placed on the chuck 29. After the chuck 29 holds the wafer 60 in vacuum, the motor 26 in the transport unit 11 is driven. As a result, the chuck 29 slides along the rail 22 and the screw 23 together with the slider 25. As shown in FIGS. 7A and 7B, the chuck 29 has a position where the grinding tip of the chamfered grinding portion 36 b of the cup-type grinding wheel 36 corresponds to the chamfered portion 68 of the wafer 60. Is positioned.

Next, the motor 35 is driven to rotate the grindstone base 36v of the cup-type grinding wheel 36 about the rotation axis O, and the motor 27 is driven to rotate the chuck 29 about the rotation axis. Further, the motor 37 is driven to feed the cup-type grinding wheel 36 toward the wafer 60 of the chuck 29. As a result, the grinding tip of the chamfered grinding part 36 b in the cup-type grinding wheel 36 grinds only the chamfered part 68 of the wafer 60.
As a chamfering grinding method, the grinding tip of the chamfering grinding part 36 b of the cup-type grinding wheel 36 is first lowered to a predetermined processing depth with respect to the wafer 60. Next, the chuck 29 that holds the wafer 60 in this state is driven along the rail 22 and the screw 23 together with the slider 25 by driving the motor 26 in the transport unit 11, so that the grinding tip of the chamfered grinding part 36 b is moved. Next, the chamfered portion 68 of the wafer 60 is brought close.
In that case, the speed component in the radial direction of the cup-type grinding wheel 36 described above, which is relatively toward the center of the wafer 60, may cause cracks to propagate to the inner peripheral portion. In the transfer unit 11, it is required that the cup-type grinding wheel 36 is relatively sent to the center side of the wafer 60 by moving the chuck 29 at a continuously and precisely controlled relative speed. In this case, the relative feed speed between the cup-type grinding wheel 36 and the chuck 29 depends on the number of rotations of the wheel and the count.
Further, as a chamfering grinding method, depending on the grindstone shape of the chamfering grinding part 36b, the chamfering grinding part 36b of the cup-type grinding grindstone 36 is first inserted into the predetermined wafer outer periphery removing part, and then, Only the outer peripheral portion may be thinned to a predetermined depth by cutting in order from the upper side of the wafer 60.

  When the cup-type grinding wheel 36 is fed in an amount sufficient to remove the chamfered portion 68 of the wafer 60, the motor 37 is rotated in reverse to separate the cup-type grinding wheel 36 from the wafer 60. FIG. 8 is a partial side view of the wafer after removing the chamfered portion. As shown in FIG. 8, the chamfered grinding part 36 b of the cup-type grinding wheel 36 removes the chamfered part 68 of the wafer 60 and a part of the base substrate 70 corresponding thereto. As can be seen from FIG. 8, the base substrate 70 serves to prevent the chuck 29 from being damaged when the chamfered portion 68 is removed. It is also possible to remove the chamfered portion 68 by removing the base substrate 70 and holding the wafer 60 directly on the chuck 29.

Next, FIG. 9 is a partial cross-sectional view of the wafer grinding apparatus when grinding a flat portion. The grinding operation of the flat portion 67 of the wafer 60 by the wafer grinding apparatus 10 according to the present invention will be described below with reference to FIG.
When the removal of the chamfered portion 68 is completed, the motor 26 is driven while the wafer 60 and the base substrate 70 are held by the chuck 29. As a result, the chuck 29 slides along the rail 22 and the screw 23 together with the slider 25. As shown in FIG. 9, the chuck 29 is positioned at a position where the grinding tip of the flat grinding portion 36 a of the cup-type grinding wheel 36 corresponds to the flat portion 67 of the wafer 60.

  Next, the motor 35 is driven to rotate the grindstone base 36v of the cup-type grinding wheel 36 about the rotation axis O, and the motor 27 is driven to rotate the chuck 29 about the rotation axis. Further, the motor 37 is driven to feed the grinding tip of the flat grinding portion 36 a toward the wafer 60 of the chuck 29 by a predetermined amount (smaller than the thickness of the wafer 60). As a result, the flat portion 67 of the wafer 60 is ground by the grinding tip of the flat grinding portion 36a.

  When the grinding tip of the flat grinding portion 36a in the cup-type grinding wheel 36 is fed by an amount that grinds the wafer 60 to a predetermined thickness, the motor 37 is rotated in the reverse direction so that the grinding tip of the flat grinding portion 36a is moved to the wafer 60. Separate from. FIG. 10 is a partial side view of the wafer after flat portion grinding. As shown in FIG. 10, when the thickness portion of the flat portion 67 is ground, the wafer 60 is thinned to a desired thickness. Thereafter, the holding of the chuck 29 is released, and the wafer 60 and the base substrate 70 are removed. Next, the wafer 60 is separated from the base substrate 70 using a predetermined jig (not shown) or the like. Thereby, the thinned wafer 60 can be obtained.

  As described above, in the present invention, the chamfered portion 68 and the flat portion 67 of the wafer 60 are caused to slide on the screw 23 by sliding the slider 25 on the chamfering grindstone 36b of the cup-type grinding wheel 36, respectively. The positioning can be performed in correspondence with the grinding tip of the flat grinding portion 36a. Accordingly, the cup-type grinding wheel 36 can remove the chamfered portion of the wafer by the chamfered grinding portion 36b and can grind the flat portion by the flat grinding portion 36a. In this case, since the flat grinding portion 36a and the chamfering grinding portion 36b of the cup-type grinding wheel 36 are arranged coaxially with the grinding wheel base 36v, the removal of the chamfering portion and the grinding of the flat portion with one spindle shaft. It is possible to perform a series of removal of the chamfered portion and grinding of the flat portion continuously.

Further, by disposing the chamfered grinding part 36b on the outer peripheral side of the grindstone base 36v, not only the surface of the outer peripheral grindstone but also the outer peripheral surface can be used efficiently.
It is advantageous that the diameter of the position where the chamfered grinding part 36b for grinding the chamfered part 68 is provided is larger than that of the flat grinding part 36a for grinding the flat part 67 of the wafer 60. The chamfered grinding part 36b enters from the radially outer side of the wafer 60 toward the inner side relatively. For this reason, the larger the diameter of the position where the chamfered grinding part 36b is provided, the more dominant the action of the chamfered grinding part 36b entering the wafer 60 from the tangential direction. Therefore, even at the edge of the thin wafer 60, the crack does not propagate toward the central axis side of the wafer 60, and it is possible to avoid the occurrence of the crack in the wafer 60 as much as possible.

  Further, since there is a step between the grinding tip of the chamfered grinding part 36b and the grinding tip of the flat grinding part 36a, grinding of the chamfered part and grinding of the flat part can be used properly.

  As described above, the cup-type grinding wheel 36 functions as both an edge trimming cutter for removing the chamfered portion 68 of the wafer 60 and a grinding member for grinding the back surface 62 of the wafer 60. For this reason, the present invention does not require a rotating blade and related members as in the prior art, and the entire apparatus can be downsized.

The example of the cup-type grinding wheel 36 has been described above, and the edge trimming for removing the chamfered portion 68 of the wafer 60 by the wafer grinding apparatus 10 and the grinding process of the flat portion 67 of the wafer 60 have been described.
Of course, the cup-type grinding wheel 36 is not limited to this.
For example, FIG. 11 is a partial cross-sectional view showing a first other example of the cup-type grinding wheel. In FIG. 11, the chamfered grinding portion 36b and the flat grinding portion 36a of the cup-type grinding wheel 36 are coaxially adjacent to each other, and a step is provided at the grinding tip of the chamfering grinding portion 36b and the flat grinding portion 36a. I try not to be flat. In this case, the chamfered grinding part 36b and the flat grinding part 36a are used with different types of grindstones. Vitrified (porcelain) bond # 2000 is used for chamfered grinding portion 36b for edge trimming to remove chamfered portion 68, and metal bond # 2000 is used for flat grinding portion 36a for grinding the entire surface. . The chamfered grinding portion 36b is provided outside the flat grinding portion 36a, and # 2000 of vitrified (porcelain) bond is also used for the outer peripheral surface of the chamfered grinding portion 36b.

  FIG. 12 is a partial sectional view showing a second alternative example of the cup-type grinding wheel. The cup-type grinding wheel 36 can also be configured as shown in FIG. In this case, the grindstone can be used for both edge trimming and flat portion grinding by using a single grindstone (for example, vitrified bond: # 2000) on the grindstone base 36v. That is, the grindstone includes an edge trimming region I and a flat portion grinding region II. As can be seen from FIG. 12, the region I is a lower surface outer portion and an outer peripheral surface portion of the grindstone. Region II is the entire lower surface of the grindstone.

DESCRIPTION OF SYMBOLS 10 Wafer grinding device 11 Conveyance unit 12 Column unit 12a Top surface 12b Side surface 13 Groove 14 Lower channel | path 22 Rail 23 Ball screw (movement mechanism part)
24 Pulley mechanism 25 Slider (moving mechanism)
26 Motor 27 Motor 29 Chuck (holding part)
31-33 Linear guide 34 Saddle 35 Motor 36 Cup type grinding wheel 36a Flat grinding part 36b Chamfering grinding part 36v Grinding wheel base 37 Motor 38 Ball screw 39 Nut 60 Wafer 61 Front surface 62 Back surface 67 Flat part 68 Chamfering part 70 Base substrate C Circuit pattern

Claims (5)

In a wafer grinding apparatus for grinding a wafer including a chamfered portion located on the outer periphery and a flat portion located inward of the chamfered portion,
A cup-type grinding wheel including a chamfering grinding part for grinding the chamfering part of the wafer and a flat grinding part for grinding the flat part of the wafer, and the chamfering grinding part of the flat grinding part. It is arranged on the outer peripheral side,
further,
Relative to the cup-type grinding wheel so that the chamfered portion or the flat portion of the wafer is positioned at a position corresponding to the chamfered grinding portion and the flat grinding portion of the cup-type grinding wheel, respectively. A moving mechanism unit for moving the
After the chamfered portion of the wafer is removed by the chamfered grinding portion by positioning the chamfered portion of the wafer at a position corresponding to the chamfered grinding portion of the cup-type grinding wheel by the moving mechanism portion. Then, the flat portion of the wafer is positioned at a position corresponding to the flat grinding portion of the cup-type grinding wheel by the moving mechanism portion, and the flat portion of the wafer is ground by the flat grinding portion. , Wafer grinding equipment. 2. The wafer grinding apparatus according to claim 1 , wherein the cup-type grinding wheel has the chamfered grinding part and the flat grinding part arranged coaxially with each other. 3. The wafer grinding apparatus according to claim 1 , wherein the chamfered grinding part and the flat grinding part are formed to have a step. The wafer grinding apparatus according to any one of claims 1 to 3, wherein the wafer is attached to a base substrate. The wafer grinding apparatus according to claim 4 , wherein the base substrate is another wafer having the same dimensions as the wafer.

Images