Wafer processing method

Abstract

To propose a new technique for restraining chipping at a boundary portion between an annular convex portion and a circular concave portion from remaining as foreign matter on an adhesive tape in a processing method for removing an annular convex portion of a wafer.SOLUTION: A method for processing a wafer in which an annular convex portion is formed on an outer peripheral portion of the back side and a circular concave portion is formed in an area surrounded by the annular convex portion includes a bonding step of bonding the back side of the wafer to an adhesive tape, a holding step of holding the back side of the wafer via the adhesive tape, a groove forming step of forming a dividing groove at the boundary between the circular concave portion and the annular convex portion on the held wafer, and a removal step of removing the annular convex portion separated by the dividing groove from the adhesive tape. In the bonding step, an unbonded area to which the adhesive tape is not bonded is formed by a step at the boundary portion, and in the groove forming step, the dividing groove is formed so as to straddle a bonded area to which the adhesive tape is bonded and the unbonded area in the circular concave portion.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for processing a wafer having an annular convex portion formed on the outer periphery of the back surface side and a circular concave portion formed in an area surrounded by the annular convex portion, and more particularly to a method for removing the annular convex portion. [Background technology]

[0002] A wafer having IC, LSI, and other devices formed on its front surface along planned dividing lines is ground on its back surface to a predetermined thickness, and then divided into individual device chips by a cutting device or the like for use in electrical devices such as mobile phones, personal computers, etc. Since a wafer that has been ground and thinned loses rigidity and is prone to cracking, a method is known in which, for example, a region of the back surface of the wafer corresponding to a device region in which multiple devices are formed is ground with a grinding wheel to form a circular recess, and then an annular protrusion is formed surrounding the periphery of the circular recess.

[0003] On the other hand, when dividing such a wafer into individual chips, the annular convex portion is known to be an obstacle to division, and therefore the annular convex portion is removed in advance. For example, Patent Document 1 describes a method in which an adhesive tape is attached to the back surface of the wafer so as to conform to the circular concave portion and the annular convex portion, the wafer is held by a holding table via the adhesive tape, a dividing groove is formed in the held wafer, and the annular convex portion is removed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-061137 A Summary of the Invention [Problem to be solved by the invention]

[0005] When removing the annular convex portion, it is ideal to remove only the annular convex portion from the wafer by dividing it at the boundary between the annular convex portion and the circular concave portion. However, it is difficult to divide it exactly at the boundary, and in most cases, the division is performed so that part of the circular concave portion is included inside the annular convex portion after division.

[0006] Here, when removing the annular protrusion after the cutting, there is a concern that a part of the circular recess inside the annular protrusion may be chipped off, and the chipped part may remain on the adhesive tape as a foreign body. Since the circular recess remaining inside the annular protrusion after the cutting is thin, chipping is likely to occur.

[0007] Furthermore, foreign matter remaining on the adhesive tape may fall onto the surface of the wafer or into the processing equipment during the process of transporting the wafer or dividing it into device chips, and may cause contamination.

[0008] The present invention has been made in consideration of the above problems, and proposes a new technology for preventing chipping at the boundary between the annular convexity and the circular concaveity from remaining on the adhesive tape as foreign matter in a processing method for removing annular convexities from a wafer. [Means for solving the problem]

[0009] The problem to be solved by the present invention has been described above, and the means for solving this problem will now be described.

[0010] According to one aspect of the present invention, there is provided a method for processing a wafer having an annular convex portion formed on the outer periphery of the back side and a circular recess portion formed in an area surrounded by the annular convex portion, the method comprising: an adhering step of adhering the back side of the wafer to an adhesive tape; a holding step of holding the back side of the wafer via the adhesive tape; a groove forming step of forming a dividing groove at the boundary between the circular recess portion and the annular convex portion in the held wafer; and a removing step of removing the annular convex portion separated by the dividing groove from the adhesive tape, wherein in the adhering step, a non-adhered area to which the adhesive tape is not adhered is formed by a step at the boundary portion, and in the groove forming step, the dividing groove is formed in the circular recess portion so as to straddle the adhered area to which the adhesive tape is adhered and the non-adhered area.

[0011] According to another aspect of the present invention, in the holding step, the back surface side of the wafer is held in an area inside the non-adhered area.

[0012] According to one aspect of the present invention, the groove forming step is performed by cutting using a cutting blade, and a dividing groove having a width spanning the adhesive region and the non-adhesive region is formed by one or more cutting operations.

[0013] According to one aspect of the present invention, the groove formation step is performed by laser processing using a laser beam, and a dividing groove having a width spanning the adhered area and the non-adhered area is formed by one or more laser processing steps. Effect of the Invention

[0014] The present invention provides the following advantages. That is, according to one aspect of the present invention, it is possible to prevent the remaining portion of the annular convex portion on the dividing groove side from chipping off and remaining on the adhesive tape T as foreign matter, thereby eliminating a cause of contamination. [Brief description of the drawings]

[0015] [Figure 1] (A) is a diagram showing the front side of the wafer, and (B) is a diagram showing the back side of the wafer. [Diagram 2] FIG. 2 is a diagram showing an example of a processing device. [Diagram 3] (A) is a perspective view of the wafer unit, and (B) is a cross-sectional view of the wafer unit. [Figure 4] 1A is a diagram for explaining the holding step, and FIG. 1B is a diagram for explaining the state in which the wafer unit is held. [Diagram 5] 5A to 5C are diagrams illustrating a groove forming step. [Figure 6] FIG. 1A is a diagram for explaining a groove forming step using a thin cutting blade, and FIG. 1B is a diagram for explaining the state after a dividing groove is formed. [Figure 7] FIG. 1A is a diagram for explaining a groove forming step using a thick cutting blade, and FIG. 1B is a diagram for explaining a state in which a dividing groove has been formed. [Figure 8] 1A is a side view of the annular protrusion removal device, and FIG. 1B is a plan view of the annular protrusion removal device. [Figure 9] (A) is a diagram for explaining the process of lowering the annular protrusion removal device, (B) is a diagram for explaining the process of inserting the lower claw between the annular protrusion and the adhesive tape, and (C) is a diagram for explaining the process of removing the annular protrusion. [Figure 10] 1A is a diagram showing a comparative example of a dividing groove, and FIG. 1B is a diagram showing a state in which foreign matter remains in the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1(A) and (B) are diagrams showing one form of a wafer to be processed when implementing the present invention, where FIG. 1(A) shows the front side of the wafer and FIG. 1(B) shows the back side of the wafer.

[0017] As shown in Fig. 1(A), the wafer W is configured as a semiconductor wafer, and devices D are regularly formed on the surface Wa. Streets S (planned division lines) that are perpendicular to each other are set between each of the devices D, and cutting grooves are formed along the streets S to divide the devices into chips. It is noted that the devices D may not necessarily be formed.

[0018] On the front surface Wa of the wafer W, a region in which the devices D are formed is defined as a device formation region Da, and a region outside the device formation region Da is defined as a peripheral excess region Ga.

[0019] 1(B), a region corresponding to the device formation region Da on the back surface Wb of the wafer W is thinned to form a circular recess Wc. An annular protrusion Wk is formed on the outer periphery of the back surface Wb of the wafer W so as to surround the circular recess Wc. A step Wg is formed between the circular recess Wc and the annular protrusion Wk.

[0020] FIG. 2 shows an example of the configuration of a processing device used in the groove forming step described later. A holding table 20 is disposed on a base 4 of the processing device 2. A water cover 14 is disposed around the holding table 20, and a bellows 16 that covers an opening of the base 4 is connected to the water cover 14. Below the water cover 14 and the bellows 16, there are provided a moving mechanism (not shown) that moves the holding table 20 in the X-axis direction, and a rotating mechanism (not shown) that rotates the holding table 20 around the Z-axis.

[0021] The upper surface of the holding table 20 is configured as a holding surface 21 that is connected to a suction source (not shown). Around the periphery of the holding table 20, a plurality of clamp mechanisms 22 for holding the annular frame F of the wafer unit U are arranged.

[0022] A cassette mounting table 8 for mounting a cassette 7 thereon is provided at a front corner of the base 4. The cassette 7 accommodates a wafer unit U in which a wafer W is attached to an adhesive tape T and integrated with an annular frame F.

[0023] A gate-shaped column 9 is erected on the base 4, and a pair of guide rails 31 extending in the Y-axis direction are fixed to the column 9. A Y-axis moving block 33 is provided on the guide rails 31 so as to be movable in the Y-axis direction, and the Y-axis moving block 33 is guided by the guide rails 31 and moves in the Y-axis direction by a Y-axis moving mechanism 30 consisting of a ball screw 32 and a pulse motor 34.

[0024] A pair of guide rails 36 extending in the Z-axis direction are fixed to the Y-axis moving block 33. A Z-axis moving block 38 is provided so as to be movable in the Z-axis direction relative to the guide rails 36, and the Z-axis moving block 38 is guided by the guide rails 36 and moves in the Z-axis direction by a Z-axis moving mechanism 40 consisting of a ball screw 42 and a pulse motor 44.

[0025] The cutting unit 5 and the imaging unit 6 are attached to the Z-axis moving block 38. The cutting unit 5 is configured by removably mounting a cutting blade to the tip of a spindle that is rotationally driven by a motor (not shown).

[0026] A cleaning device 60 having a spinner table 62 is provided on the base 4, and the wafer W after cutting is sucked and held on the spinner table 62 for spin cleaning and spin drying.

[0027] Next, each step of the wafer processing method according to the present invention will be described in order. <Attachment steps> As shown in FIGS. 3(A) and 3(B), this is a step in which the back surface Wb side of the wafer W is attached to an adhesive tape T. Specifically, an adhesive layer is formed on the front surface Ta of the adhesive tape T, and the back surface Wb of the wafer W is adhered to the front surface Ta of the adhesive tape T. The circular recess Wc and the annular protrusion Wk on the back surface Wb of the wafer W are each adhered in close contact with the front surface Ta of the adhesive tape T. In addition, an annular frame F is adhered to the front surface Ta of the adhesive tape T so as to surround the wafer W, and a wafer unit U is formed by integrating the wafer W and the annular frame F.

[0028] 3(B), a step Wg is formed at the boundary portion We between the circular recess Wc and the annular protrusion Wk on the rear surface side of the wafer W. As a result, the front surface Ta of the adhesive tape T does not reach the corner of the step Wg, and a gap Ws is formed. This gap Ws forms a non-adhesive region Wh in the circular recess Wc, where the front surface Ta of the adhesive tape T is not attached. In the circular recess Wc, the region inside the non-adhesive region Wh becomes an attached region Wt that is attached to the front surface Ta of the adhesive tape T.

[0029] <Retention step> As shown in FIGS. 4(A) and 4(B), this is a step of holding the back side of the wafer W with an adhesive tape T. Specifically, the back surface Wb of the wafer W is suction-held on a holding surface 21 of the holding table 20 via an adhesive tape T. The holding table 20 has a porous plate 23 connected to a suction source (not shown), and the holding surface 21 is formed on the upper surface of the porous plate 23, generating negative pressure on the holding surface 21. A clamping mechanism 22 is disposed around the holding table 20, and clamps the annular frame F of the wafer unit U.

[0030] 4(A), the diameter 20D of the holding table 20 is smaller than and the back surface Wb side of the wafer W is held in an area inside the non-adhesive area Wh. This prevents the adhesive tape T from being pressed by the outer circumferential corners 20k of the holding table 20, and prevents the front surface Ta of the adhesive tape T from entering the step Wg and eliminating the non-adhesive area Wh. In other words, the adhesive tape T is prevented from being pressed by the outer circumferential corners 20k of the holding table 20, and thus prevents the non-adhesive area Wh from being eliminated.

[0031] <Groove formation step> As shown in FIG. 5 and FIGS. 6(A) and (B), this is a step of forming a dividing groove M in the boundary portion We between the circular recess Wc and the annular protrusion Wk in the held wafer W.

[0032] In this embodiment, in the device configuration of Fig. 2, a cutting blade 51 provided in a cutting unit 5 is rotated at high speed as shown in Fig. 5 to cut into the boundary portion We, and the wafer W is rotated 360 degrees to cut it. This processing is a so-called circle cut, and an annular dividing groove M is formed, dividing the circular recess Wc and the annular protrusion Wk.

[0033] 6(A), the cutting blade 51 reaches the surface Ta of the adhesive tape T and processes so as to completely separate the circular recess Wc and the annular protrusion Wk. Note that the position where the cutting blade 51 cuts is outside the device formation region Da, and does not cut into the device D (FIG. 1(A)).

[0034] 6(A) and (B), the dividing groove M is formed so as to straddle the adhesion region Wt where the adhesive tape is adhered in the circular recess Wc and the non-adhesive region Wh. In the example of Fig. 6(A) and (B), when a thin cutting blade 51 is used, a wide dividing groove M is formed by performing multiple circle cuts so that the dividing groove M straddles the adhesion region Wt and the non-adhesive region Wh.

[0035] 7(A), a thick cutting blade 52 may be used to perform a single circle cut to form a wide dividing groove M, so that the dividing groove M straddles the adhered region Wt and the non-adhesive region Wh. In this case, a dividing groove M of a predetermined width can be formed by a single circle cut, and therefore the processing time can be reduced.

[0036] 7(B), the dividing groove M is formed, so that the circular recess Wc and the annular protrusion Wk are completely separated. Since the dividing groove M is formed so as to straddle the non-adhesive region Wh, the remaining portion Wm of the annular protrusion Wk on the side of the dividing groove M does not come into contact with the adhesive tape T.

[0037] In addition, Figure 7 (B) shows an example in which the outer peripheral edge portion of the circular recess Wc becomes the remaining portion Wm and protrudes from the annular protrusion Wk, but the dividing groove M may be formed so that the remaining portion Wm is not formed.

[0038] In the above example, the cutting is performed by a cutting blade, and a dividing groove having a width spanning the adhered region and the non-adhesive region is formed by one or more cutting processes, but the dividing groove may be formed by laser processing (laser ablation processing). That is, the groove forming step is performed by laser processing using a laser beam, and a dividing groove having a width spanning the adhered region and the non-adhesive region may be formed by one or more laser processing processes.

[0039] <Removal Step> 8(A) and (B), this is a step of removing the annular convex portion Wk separated by the dividing groove M from the adhesive tape T. In this removing step, for example, an annular convex portion removing device 70 shown in FIGS.

[0040] 2, and after the groove forming step is completed, a removal step is performed on the wafer unit U that is still held on the holding table 20. Alternatively, the wafer unit U that has completed the groove forming step may be carried out and the removal step may be performed in the annular protrusion removing device 70 that is configured as a device separate from the processing device shown in FIG.

[0041] 8(A) and (B), annular protrusion removal device 70 is configured to include a disk-shaped base plate 71 that is driven to ascend and descend and rotate by a motor (not shown), an actuator 72 fixed to the upper surface of base plate 71, a moving arm 73 that is driven to move horizontally by actuator 72, a rotating shaft rod 74 that is suspended from the tip of moving arm 73 and located to the side of base plate 71, and a removal claw 75 that is rotatably provided at the lower end of the rotating shaft rod 74. The removal claws 75 are provided in three locations at 120 degree intervals, and a total of three removal claws 75 are configured to lift up and remove annular protrusion Wk.

[0042] The removal claw 75 inserts the lower claw 75b between the annular convex portion Wk and the adhesive tape T to peel the annular convex portion Wk from the adhesive tape T. The removal claw 75 has an upper claw 75a formed above the lower claw 75b, which prevents the annular convex portion Wk from jumping up when the annular convex portion Wk is peeled off forcefully.

[0043] In the above-mentioned device configuration, as shown in FIG. 8(A), the base plate 71 is lowered to position the lower claw 75b of the removal claw 75 to the side of the annular convex portion Wk, and then, as shown in FIG. 8(B), the lower claw 75b is inserted between the annular convex portion Wk and the adhesive tape T. Then, the entire base plate 71 is rotated to lift the lower surface of the annular convex portion Wk, and the annular convex portion Wk is peeled off from the adhesive tape T. Thereafter, as shown in FIG. 8(C), the base plate 71 is raised to pull up the annular convex portion Wk while it is supported by the lower claw 75b of the removal claw 75, and the annular convex portion Wk is removed from the adhesive tape T. The adhesive tape T is left with the portion corresponding to the circular concave portion Wc attached thereto, and is later processed, such as by dicing.

[0044] The configuration of the annular protrusion removing device 70 shown in FIGS. 8(A) to (C) is well known, and detailed description of the configuration and operation will be omitted.

[0045] Furthermore, as shown in Figures 7(B) and 9(B), when the annular convex portion Wk is peeled off and removed from the adhesive tape T, the remaining portion Wm on the dividing groove M side of the annular convex portion Wk is not in contact with the adhesive tape T, and therefore the remaining portion Wm is not chipped off and remains on the adhesive tape T as a foreign body.

[0046] 10(A) and 10(B) show comparative examples, if the remaining portion Wm of the annular convex portion Wk on the dividing groove Ma side is in contact with the adhesive tape T, the remaining portion Wm may break and chip due to stress generated when peeling off the annular convex portion Wk, and may remain on the adhesive tape T as foreign matter Z, causing contamination. The present invention prevents such problems from occurring.

[0047] The present invention can be implemented in the above manner. According to the present invention, as shown in Figures 9(A) and (B), it is possible to prevent the remaining portion Wm of the annular convex portion Wk on the dividing groove M side from chipping off and remaining as a foreign body on the adhesive tape T, thereby eliminating the cause of contamination. [Explanation of symbols]

[0048] 2 Processing equipment 20 Holding Table 20D diameter 20k outer corner 21 Holding surface 22 Clamping mechanism 70 Annular protrusion removal device 71 Base plate 72 Actuator 73 Moving Arm 74 Rotating shaft rod 75 Removal nail 75a Upper claw 75b Lower claw D Device Da device formation area F Annular frame Ga Surplus outer region M Dividing groove S Street T adhesive tape Ta surface U Wafer Unit W wafer Wa Surface Wb back side Wc Circular recess WD diameter We boundary part Wg Step Wh non-stick area Wk Circular convex part Wm remaining part Ws Gap Wt pasting area Z Foreign object

Claims

1. A method for processing a wafer having an annular convex portion formed on an outer periphery of a back surface side and a circular concave portion formed in an area surrounded by the annular convex portion, comprising the steps of: a bonding step of bonding the back side of the wafer to an adhesive tape; a holding step of holding the back side of the wafer via the adhesive tape; a groove forming step of forming a dividing groove at a boundary portion between the circular recess and the annular protrusion in the held wafer; a removing step of removing the annular convex portion separated by the dividing groove from the adhesive tape, In the adhering step, a non-adhered area to which the adhesive tape is not attached is formed by a step in the boundary portion, In the groove forming step, the dividing groove is formed so as to straddle an adhesion region, to which the adhesive tape is adhered, and a non-adhesive region in the circular recess. Wafer processing method.

2. 2. The wafer processing method according to claim 1, wherein in the holding step, the back surface side of the wafer is held in an area inside the non-adhered area.

3. The wafer processing method according to claim 1 or claim 2, characterized in that the groove forming step is performed by cutting using a cutting blade, and a dividing groove having a width spanning the adhesive region and the non-adhesive region is formed by one or more cutting processes.

4. The wafer processing method according to claim 1 or claim 2, characterized in that the groove forming step is performed by laser processing using a laser beam, and a dividing groove having a width spanning the adhesive region and the non-adhesive region is formed by one or more laser processing steps.

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