JP2009224496A - Wafer edge grinding method, wafer edge grinding unit, and wafer rear-face grinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer edge grinding method for highly accurately grinding an outer periphery at the outer peripheral part of a wafer, a wafer edge grinding unit, and a wafer rear-face grinder. <P>SOLUTION: The wafer edge grinding method is used for grinding the edge of the wafer in which a BG tape 13 is stuck to its surface having a circuit pattern. The method includes a step of holding a wafer 10 to a table 5 so as to make the wafer surface face upward, a step of arranging a cup grinding wheel 8, having a rotary shaft G in a vertical direction or in a direction that is inclined at a prescribed angle with respect to the vertical direction around the wafer 10, and a step of grinding the outer periphery at the outer peripheral part of the wafer 10 by bringing the cup grinding wheel 8 into contact with the outer peripheral part of the wafer 10 while rotating the cup grinding wheel so as to form a step 14 along the outer peripheral part exposed from the BG tape 13 of the wafer 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wafer edge grinding method, a wafer edge grinding unit, and a pre-wafer backside apparatus that are performed in a pre-process of wafer backside grinding.

  As a processing method for reducing the thickness of the semiconductor wafer, there is a method of grinding the back surface of the semiconductor wafer. This processing method is a method for processing a semiconductor wafer to a predetermined thickness by a relative rotational movement between the semiconductor wafer and the grindstone. A semiconductor wafer may be processed to be thinner than 100 μm. However, as the thickness of the semiconductor wafer becomes thinner, the outer peripheral portion becomes a sharp edge (knife edge), so that there is a problem that the outer peripheral portion of the wafer is likely to be chipped or chipped.

  FIG. 8 shows the semiconductor wafer 40 after back-grinding, which is held on the table 50 with the front side to which the film (tape) protecting the circuit pattern 41 is bonded facing down. As shown in the drawing, the edge 43 at the outer peripheral portion of the wafer becomes sharper as the chamfered portion 42 such as roundness is formed on the outer peripheral portion of the wafer 40 before the back surface grinding, and exhibits a so-called sharp edge aspect. Become. The round chamfered portion 42 formed on the outer peripheral portion of the wafer 40 is formed to prevent chipping or cracking or cracks from occurring on the outer peripheral portion of the wafer 40. This facilitates chipping of the wafer that has been removed.

  One example of a conventional method for preventing chipping at the outer peripheral portion of the wafer is disclosed in Patent Document 1. This method is a method of cutting the outer peripheral portion of the wafer using high-pressure water. Paragraph No. [0009] of Patent Document 1 states that “in the peripheral portion cutting step, the peripheral portion of the semiconductor wafer is aligned along the circumferential direction. Cut to form a vertical cut surface that is substantially perpendicular to the back surface, or an inclined cut surface that is inclined outward from the back surface side to the front surface side. The back surface of the semiconductor wafer is subjected to surface grinding while leaving a vertical cut surface or an inclined cut surface ".

  Similarly, paragraph number [0011] of Patent Document 1 states that “in the peripheral edge cutting step, all or part of the peripheral edge of the semiconductor wafer having an R shape is cut off by chamfering, and the rear surface of the semiconductor wafer is cut. The edge angle of the peripheral edge on the side can be set to at least 90 °, that is, a portion that can become an acute angle shape during back grinding is removed in advance, and the back side of the semiconductor wafer is chamfered for back grinding. For this reason, in the back grinding process, even if the back grinding progresses and the semiconductor wafer becomes thin, the load accompanying grinding can be received at an edge having a substantially right angle or an obtuse angle, so that it occurs at the peripheral edge on the back side. Chipping and cracking of the semiconductor wafer can be suppressed ”.

  As another example, there is a method of cutting a wafer outer peripheral portion having a chamfered portion with a dicing blade. In this method, the outer peripheral portion of the wafer is peripherally ground in a state where the wafer is held on the table so that the surface side of the wafer to which the protective film is bonded is directed upward.

JP-A-2005-150200

  In the method using high-pressure water disclosed in Patent Document 1 or the method of grinding using a dicing blade, vibration is induced in the outer peripheral portion of the wafer during cutting or grinding, and cutting or grinding is performed with high accuracy. I was worried that I couldn't.

  An object of this invention is to provide the wafer edge grinding method, wafer edge grinding unit, and wafer back surface grinding apparatus which can grind the outer peripheral part of a wafer with high precision in view of an above-described point.

  In order to achieve the above object, the wafer edge grinding method according to claim 1 is a wafer edge grinding method for grinding an edge of a wafer having a protective film attached to a surface on which a circuit pattern is formed, The wafer is held on the table so that the surface of the wafer faces upward, and a cup grindstone having a rotation axis in the vertical direction or in a direction inclined at a predetermined angle with respect to the vertical direction is arranged around the wafer. And rotating the cup grindstone to contact the outer peripheral portion of the wafer so as to form a step portion along the outer peripheral portion of the wafer exposed from the protective film, and peripherally grinding the outer peripheral portion of the wafer. It is characterized by providing.

  Further, the invention according to claim 2 is the wafer edge grinding method according to claim 1, wherein in the peripheral grinding, the height of the stepped portion is equal to or larger than the target thickness after the back surface grinding of the wafer. It is characterized by dimensions.

  The invention according to claim 3 is the wafer edge grinding method according to claim 1 or 2, wherein in the outer periphery grinding, an inclined surface having a reverse taper shape is formed on the outer periphery of the wafer.

  Further, the invention according to claim 4 is the wafer edge grinding method according to claim 3, wherein the cup grinding wheel is rotated around the rotation axis inclined at a predetermined angle with respect to the vertical direction, and the outer periphery is ground. The inclined surface is formed.

  The invention according to claim 5 is the wafer edge grinding method according to any one of claims 1 to 3, wherein the wafer and the cup grindstone are rotated in the same direction in the peripheral grinding. And

  The invention according to claim 6 is the wafer edge grinding method according to claim 1, wherein the outer peripheral portion of the wafer exposed from the protective film cuts the protective film along the outer periphery of the wafer. It is formed by this.

  Further, the wafer edge grinding unit according to claim 7 is tilted by a predetermined angle with respect to the vertical direction or the vertical direction with the table holding the wafer so that the surface of the wafer to which the protective film is bonded faces upward. A cup grindstone having a rotating shaft in the direction and grinding the outer peripheral portion of the wafer exposed from the protective film, while rotating so as to form a step portion along the outer peripheral portion of the wafer And a cup grindstone for contacting and grinding the outer periphery of the wafer.

  The invention according to claim 8 is the wafer edge grinding unit according to claim 7, wherein the cup grindstone includes a cup-shaped base metal, and a grindstone portion disposed annularly on a tip end surface of the base metal. In the grindstone portion, the inner peripheral side abrasive grains are finer than the outer peripheral side abrasive grains.

  The invention according to claim 9 is the wafer edge grinding unit according to claim 7 or 8, wherein the protective film is cut along an outer periphery of the wafer so that an outer peripheral portion of the wafer is exposed. It is characterized by.

  The wafer back surface grinding apparatus according to claim 10 is a wafer back surface grinding apparatus for grinding a back surface of a wafer having a circuit pattern formed on the surface thereof, and the wafer according to any one of claims 7 to 9. An edge grinding unit is provided.

  As described above, by performing peripheral grinding of the wafer with the cup grindstone, it is possible to grind the peripheral portion of the wafer while rotating the cup grindstone around the rotation axis in a stable state. Therefore, the grinding resistance is lowered, the occurrence of vibration during grinding is avoided, and the outer peripheral portion of the wafer can be ground with high accuracy.

  Further, since the reverse tapered inclined surface formed on the outer peripheral portion of the wafer remains as an obtuse chamfer after the back surface of the wafer is ground, the outer peripheral portion of the wafer can be strengthened. Thereby, the chip | tip of a wafer outer peripheral part, etc. can be prevented effectively.

  Moreover, the wafer can be processed by an in-feed grinding method by rotating the wafer and the cup grindstone in the same direction. Thereby, the biting and detachment of the cup grindstone with respect to the wafer can be performed smoothly, and chipping at the outer peripheral portion of the wafer can be effectively prevented.

  Also, in the grinding wheel part of the cup grindstone, the inner peripheral side abrasive grains are finer than the outer peripheral side abrasive grains, so that from roughing to finishing with one cup grindstone without using multiple grinding grindstones as in the past It can be carried out. For this reason, the processing efficiency can be increased and the processing cost can be reduced.

  Hereinafter, preferred embodiments of a wafer edge grinding method, a wafer edge grinding unit, and a wafer back grinding apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view used for explaining an embodiment of a wafer back grinding apparatus according to the present invention.

  A wafer back grinding apparatus 1 shown in FIG. 1 includes an edge grinding unit 2 that performs peripheral grinding (edge grinding) on an outer peripheral portion of a wafer 10 using a cup grindstone 8 (FIG. 2), and a back surface that performs surface grinding on the back surface of the wafer 10. A grinding unit 3 and a polishing unit 4 for polishing the back surface of the wafer 10 are included. These units 2 to 4 are controlled by a control device (not shown).

  The back surface grinding apparatus 1 is provided with the wafer 10 before grinding accommodated in the wafer cassette 6A, and the wafer 10 after grinding is accommodated in the wafer cassette 6B and conveyed to the next process. A plurality of circuit patterns 12 (FIG. 4) are formed on the surface 11A of the wafer 10 before grinding, and a BG tape (protective film) 13 having a predetermined thickness for protecting the circuit patterns 12 is attached to the surface 11A. Yes. Since the BG tape 13 is elastic, it can absorb irregularities on the front surface 11A of the wafer 10, so-called bumps, thereby preventing the wafer 10 from cracking during back surface grinding.

  The wafers 10 are taken out from the wafer cassette 6A one by one by the robot arm 8A. The removed wafer 10 is placed on the table 5 with the front side (FIG. 2) facing upward, and is held by suction on the table 5 by a vacuum chuck.

  The edge grinding unit 2 includes a unit main body, a table 5 that holds the wafer 10 by suction, a cup grindstone 8 that edge grinds the outer peripheral portion of the wafer 10 exposed outside the BG tape 13, and the cup grindstone 8 in the vertical direction. A spindle head (not shown) that rotates around a rotation axis G (FIG. 2) in the (vertical direction). A vacuum chuck table can be applied to the table 5. The wafer 10 is attracted to the adsorption surface of the table 5 by using negative pressure and is held without being damaged. In this unit 2, since the rotation axis G is arranged in the vertical direction, the unit 2 has higher rigidity than the unit in which the rotation axis faces the horizontal direction, and the runout of the cup grindstone 8 can be reduced. For this reason, the outer peripheral part of the wafer 10 can be ground with high accuracy. A BG tape smaller than the wafer 10 may be attached to expose the outer peripheral portion of the wafer 10, or the outer periphery of the wafer 10 may be cut by cutting the BG tape 13 along the outer peripheral portion of the wafer 10 with a laser. The part may be exposed.

  The cup grindstone 8 is inscribed in the outer peripheral portion of the wafer 10 while being rotated so as to form a stepped portion 14 along the outer peripheral portion of the wafer 10 and edge grinding is performed. FIG. 2 shows a state in which a stepped portion 14 is formed on the outer peripheral portion of the wafer 10. The cup grindstone 8 has a cup-shaped base metal 9a and a grindstone portion 9b disposed in an annular shape on the front end surface of the base metal 9a. The grindstone portion 9b is composed of hard abrasive grains and a binder. The kind of hard abrasive and the kind of binder are arbitrary, but diamond abrasive is suitable for the hard abrasive, and resin bond having elasticity is suitable for the binder. A rotary ball spline that can simultaneously perform vertical movement and rotational movement can be applied to the spindle head.

  FIG. 3 shows a state in which edge grinding of the wafer 10 is performed in contact with the outer peripheral portion of the wafer 10 while the cup grindstone 8 rotates while the wafer 10 is disposed inside the cup grindstone 8. That is, the cup grindstone 8 is circularly moved in a horizontal plane orthogonal to the rotation axis G while rotating, so that the inner peripheral side of the grindstone portion 9b is in contact with the outer peripheral portion of the wafer 10 so that the edge grinding of the wafer 10 is performed. It has become. Accordingly, in FIG. 3, the rotation axis G of the cup grindstone 8 moves around the center axis W of the wafer 10 while drawing a circular orbit C, and the distance between the rotation axis G of the cup grindstone 8 and the center axis W of the wafer 10. Is kept in e.

  FIG. 2 shows the wafer 10 edge-ground by the edge grinding unit 2. A notch-shaped step portion 14 is formed along the outer periphery of the wafer 10 on the outer periphery of the wafer 10. The height t of the stepped portion 14 is the same as or larger than the target thickness after the back surface grinding of the wafer 10.

  The back surface grinding unit 3 includes a subunit 20A that performs rough grinding and a subunit 20B that performs finish grinding. The configuration of each subunit 20A, 20B is substantially the same except that the type of diamond wheel used is different. FIG. 4 shows a wafer 10 in which the back surface 11B of the subunit 20A is ground by using a diamond wheel 18 having a rotation axis R in the vertical direction. In the back surface grinding, surface grinding is performed until the stepped portion 14 formed by edge grinding is completely removed. By forming the step portion 14 in the outer peripheral portion of the wafer 10 in advance, it is avoided that a sharp edge is formed in the outer peripheral portion even when the thickness of the wafer 10 is reduced.

  Next, a modified example of the wafer edge grinding method will be described with reference to FIG. This modification shows an example in which the outer peripheral portion of the wafer 10 is edge-ground while the rotation axis G of the cup grindstone 30 is inclined by the angle θ with respect to the vertical direction P. By tilting the cup grindstone 30 diagonally, the wall surface of the stepped portion 14A at the outer peripheral portion of the wafer can be formed into the reverse tapered inclined surface 15a. In the present embodiment, the inclination angle β of the inclined surface 15a is equal to the angle θ obtained by inclining the rotation axis G with respect to the vertical direction P. In FIG. 2, the step portion 14 has a vertical wall surface and a horizontal wall surface perpendicular to each other, whereas the step portion 14A of this modification has an inclined surface 15a and a horizontal wall surface 15b. . As shown in FIG. 6, the inclined surface 15 a remains as it is after grinding the back surface of the wafer 10, functions as an obtuse chamfered portion, and has an effect of strengthening the outer peripheral portion of the wafer. In this modification, it is important that the inclined surface 15a is inclined in a reverse taper shape, and the wall surface 15b intersecting the inclined surface 15a may not be horizontal.

  Moreover, the cup grindstone 30 of this modification is substantially the same as the cup grindstone 8 shown in FIG. 2 except the structure of the grindstone part 31b. In this modification, the grindstone portion 31b has a three-layer structure, and the abrasive grains of the grindstone portion 32a located inside are the abrasive grains of the grindstone portion 32b located in the middle and the abrasive grains of the grindstone portion 32c located outside. It is getting finer. Further, the abrasive grains of the grindstone portion 32b located in the middle are finer than the abrasive grains of the grindstone portion 32c located outside. As in this modified example, the abrasive grain size of the grindstone portion 31b is made fine on the inner peripheral side and roughened on the outer peripheral side, so that roughing and intermediate finishing are performed with one cup grindstone without using a plurality of cup grindstones. Finishing can be done at once. When the edge grinding of the wafer 10 is performed using the cup grindstone 30 of this embodiment, the outer grindstone portion 32c with coarse abrasive grains generates microcracks in the wafer 10, and the intermediate grindstone portion 32b develops microcracks. It is considered that the inner grindstone portion 32a removes the wafer material. For this reason, by using the cup grindstone 30, it is possible to perform from roughing to finishing at once, and it is possible to increase the grinding efficiency.

  In this modification, the stepped portion 14A having the inclined surface 15a is formed on the outer peripheral portion of the wafer 10 by inclining the cup grindstone 30, but as shown in FIG. 7, the stepped portion 14A is formed on the inner peripheral surface of the grindstone portion 35b. A similar stepped portion 14A can also be formed by using a cup grindstone 35 having a predetermined rake angle α.

  Next, after the back surface grinding of the wafer 10 is completed, the wafer 10 is transferred to the polishing unit 4 (FIG. 1) in the next process and polished by a lapping machine or the like in order to remove grinding marks and the like. In this way, the wafer 10 can be processed thinly to, for example, 100 μm or less without causing any chipping or the like in the outer peripheral portion. After the polishing is completed, the wafer 10 is stored in the wafer cassette 6B by the robot arm 8B and transferred to the next process.

  As described above, according to the present embodiment, the outer peripheral portion of the wafer is formed using the cup grindstones 8, 30, and 35 arranged in the direction in which the rotation axis G is inclined at an arbitrary angle with respect to the vertical direction or the vertical direction. By performing edge grinding, it is possible to suppress the whirling and vibration of the cup grindstones 8, 30, and 35 during grinding, and the outer peripheral portion of the wafer 10 can be precisely ground with high accuracy. In addition, the reverse tapered inclined surface 15a formed on the outer peripheral portion of the wafer 10 remains as an obtuse chamfered portion even after the back surface of the wafer 10 is ground, so that the outer peripheral portion of the wafer can be strengthened. It is possible to effectively prevent the lack of a part.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, it can deform | transform and implement variously. In this embodiment, the step portions 14 and 14A are formed on the outer peripheral portion of the wafer 10. However, the outer peripheral portion of the wafer 10 can be completely cut without forming the step portions 14 and 14A. Further, in edge grinding of the outer peripheral portion of the wafer, it is also possible to perform edge grinding by the in-feed grinding method while rotating the wafer 10 integrally with the table 5 in the same direction as the cup grindstone 8. According to this method, the cup grindstone 8 bites and detaches smoothly from the wafer 10, and chipping at the outer peripheral portion of the wafer can be effectively prevented.

It is a top view which shows one Embodiment of the wafer back surface grinding apparatus which concerns on this invention. It is explanatory drawing which shows the state which edge-grinds a wafer outer peripheral part with an edge grinding unit. It is explanatory drawing which shows the state by which the wafer is arrange | positioned inside the cup grindstone. It is sectional drawing of the state which carried out the back surface grinding | polishing of the wafer ground by the edge by the back surface grinding unit. It is a modification of the edge grinding method, and is an explanatory view showing a method of grinding by tilting the rotation axis of the cup grindstone. It is sectional drawing of the state which carried out the back surface grinding | polishing of the wafer which carried out the edge grinding | polishing by the method of FIG. It is explanatory drawing which shows the example which rotates the cup grindstone around the rotation axis of a perpendicular direction, and performs edge grinding using the cup grindstone in which the rake angle was formed in the grindstone part, instead of tilting the rotation axis of the cup grindstone. is there. It is sectional drawing which shows an example of the conventional wafer of the back ground.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer back surface grinding apparatus 2 Edge grinding unit 3 Back surface grinding unit 8, 30, 35 Cup grindstone 9a Base metal 9b Grindstone part 10 Wafer 13 BG tape (protection film)
14,14A Step

Claims (10)

A wafer edge grinding method for grinding an edge of a wafer in which a protective film is attached to a surface on which a circuit pattern is formed,
Holding the wafer on a table so that the surface of the wafer faces up;
Disposing a cup grindstone having a rotation axis in a vertical direction or a direction inclined by a predetermined angle with respect to the vertical direction around the wafer;
The outer peripheral portion of the wafer is peripherally ground by contacting the outer peripheral portion of the wafer while rotating the cup grindstone so as to form a step portion along the outer peripheral portion of the wafer exposed from the protective film. When,
A wafer edge grinding method comprising:   2. The wafer edge grinding method according to claim 1, wherein in the outer peripheral grinding, the height of the stepped portion is set to a dimension that is approximately the same as or larger than a target thickness after the back surface grinding of the wafer.   The wafer edge grinding method according to claim 1, wherein in the outer peripheral grinding, an inclined surface having an inverse taper shape is formed on the stepped portion.   4. The wafer edge grinding method according to claim 3, wherein the inclined surface is formed by rotating the cup grindstone around the rotation axis inclined at a predetermined angle with respect to a vertical direction and grinding the outer periphery. 5.   The wafer edge grinding method according to any one of claims 1 to 3, wherein in the peripheral grinding, the wafer and the cup grindstone are rotated in the same direction.   The wafer edge grinding method according to claim 1, wherein the outer peripheral portion of the wafer exposed from the protective film is formed by cutting the protective film along the outer periphery of the wafer. A table for holding the wafer so that the surface of the wafer to which the protective film is bonded faces upward;
A cup grindstone that has a rotation axis in a vertical direction or a direction inclined at a predetermined angle with respect to the vertical direction, and that grinds the outer peripheral portion of the wafer exposed from the protective film, the outer peripheral portion of the wafer A wafer edge grinding unit comprising: a cup grindstone that contacts the outer peripheral portion of the wafer while rotating so as to form a step portion along the periphery.   The cup grindstone has a cup-shaped base metal and a grindstone part annularly arranged on the tip surface of the base metal, and the inner peripheral side abrasive grains are finer than the outer peripheral side abrasive grains in the grindstone part. The wafer edge grinding unit according to claim 7, which is configured as described above.   The wafer edge grinding unit according to claim 7 or 8, wherein the protective film is cut along an outer periphery of the wafer such that an outer peripheral portion of the wafer is exposed. A wafer back surface grinding device for grinding a back surface of a wafer having a circuit pattern formed on the front surface,
A wafer back grinding apparatus comprising the wafer edge grinding unit according to any one of claims 7 to 9.

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