TW201539562A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To divide a wafer with annular convex portion formed on the rear surface outer periphery into individual devices without degrading the quality. SOLUTION: A processing method of this invention, which grinds only the backside corresponding to the device formation area, so as to divide a wafer formed with reinforcing annular convex portion at the backside corresponding to the peripheral remaining area surrounding the device formation area, comprising: in a state of keeping the protective tape adhered on the front surface of the wafer, forming a dividing groove at the intersection of the annular convex portion of the wafer and the recess; adhering a cutting tape on the backside of the wafer, while removing the protective tape and the annular convex portion from the front surface of the wafer; dividing the device formation area of the wafer into individual devices.

Description

Wafer processing method Field of invention

The present invention relates to a method of processing a wafer in which a wafer having an annular convex portion formed on the outer periphery of a wafer is divided into individual elements.

Background of the invention

In recent years, in order to achieve weight reduction and miniaturization of a motor device, it is required to make the thickness of the wafer thinner, for example, 50 μm or less. The wafer which is formed in such a thin manner is not only reduced in rigidity but also warped, so that handling processing becomes difficult, and damage may occur in transportation or the like. Then, by grinding only the back surface corresponding to the element forming region in which the wafer is formed with the element, the annular convex portion for reinforcing is formed on the back surface corresponding to the remaining portion of the outer circumference surrounding the element forming region. A grinding method is proposed (refer to, for example, Patent Document 1).

As a method of dividing such a wafer along a predetermined dividing line, a method of removing the annular convex portion before dividing the wafer has been proposed (see, for example, Patent Document 2). In this method, the dicing tape is adhered along the back surface of the wafer protruding with the annular projection, and the back side of the wafer is supported on the working gantry through the dicing tape. On the working chuck, the porous portion protruding from the top surface of the table is engaged into the concave portion of the wafer, and is cut from the wafer by the cutting blade. The front side cuts off the annular projection. Thereafter, the wafer is cut from the front side by the cutting insert to be divided into individual components.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2007-173487

Patent Document 2: Japanese Patent Laid-Open Publication No. 2010-186971

Summary of invention

In the method described in Patent Document 2, since the annular convex portion and the concave portion are formed on the back surface of the wafer, if the dicing tape is adhered along the back surface of the wafer, there is a corner of the concave portion of the wafer. The bubbles remain. When the annular projection is cut away from the wafer, when the cutting insert is cut from the front side of the wafer toward the back surface on which the concave portion is formed, the cutting blade may be shaken due to the bubble or the cutting debris may enter the bubble. Therefore, it has a bad influence on the wafer. Therefore, there is a problem that the quality of the element on the outer peripheral side of the wafer deteriorates on the wafer on which the annular convex portion has been removed.

The present invention has been made in view of such a problem, and an object thereof is to provide a wafer in which a wafer having an annular convex portion formed on the outer periphery of the back surface can be divided into individual components without deteriorating the quality thereof. processing methods.

The method for processing a wafer of the present invention has a substantially circular element forming region in which a plurality of elements are formed by dividing a predetermined line on the front side, and processing of a wafer surrounding a remaining area of the periphery of the element forming region. The method is composed of the following steps: a recess forming step of adhering a protective tape on the front side of the wafer, and grinding only a region on the back side corresponding to the element forming region of the wafer to a predetermined thickness to form the member. The region is thinned to a desired thickness, and a concave portion is formed on the back surface, and an annular convex portion protruding from the back surface side is formed in the outer peripheral portion; the annular convex portion dividing step is performed in the annular portion after the concave portion forming step is performed a circular dividing groove is formed at a boundary between the convex portion and the concave portion, and the annular convex portion and the concave portion are divided; and a transferring step is performed on the back surface of the wafer after the step of dividing the annular convex portion The dicing tape is adhered to the entire inner side, and the protective tape is peeled off, and the annular convex portion is removed; and the element forming region dividing step is performed, and after the transferring step, the dividing is performed along the dividing line of the element forming region.

According to this configuration, in a state in which the protective tape is adhered to the front side of the wafer, a circular dividing groove is formed at the boundary between the annular convex portion and the concave portion on the wafer back side. Therefore, when the dicing tape is adhered to the back side of the wafer, the air between the back surface of the wafer and the dicing tape can be made to flow into the dividing groove. Therefore, the dicing tape can be attached by removing the air bubbles on the entire back surface of the wafer, and the protective tape is peeled off from the front surface of the wafer, and the annular convex portion is removed from the wafer. Transfer well from the protective tape to the cutting tape. Further, since the wafer is divided without leaving air bubbles on the back surface of the wafer, there is no possibility that the quality of the element is lowered due to the influence of the air bubbles.

According to the present invention, by forming a dividing groove at the boundary between the annular convex portion and the concave portion before attaching the dicing tape to the back surface of the wafer, the wafer having the annular convex portion formed on the outer periphery of the back surface can be When the quality is deteriorated, it is divided into individual components.

11‧‧‧ Wafer front

12‧‧‧ Back of wafer

13, 19‧‧‧ outer edge

14‧‧‧ gap

15‧‧‧ recess

16‧‧‧ annular convex

17‧‧‧dividing trench

18‧‧‧ dividing line

21‧‧‧ grinding device

22, 32‧‧‧Working table

23‧‧‧ grinding wheel

26‧‧‧ cuttings

31‧‧‧ cutting device

33‧‧‧Cutting inserts

34‧‧‧Clamping Department

A1‧‧‧Component formation area

A2‧‧‧ remaining area of the periphery

D‧‧‧ components

F‧‧‧Ring frame

T1‧‧‧Protective tape

T2‧‧‧ cutting tape

W‧‧‧ wafer

X, Y, Z‧‧ Direction

Fig. 1 is a perspective view of a wafer of the embodiment.

Fig. 2 is a view showing an example of a step of forming a concave portion in the embodiment.

Fig. 3 is a view showing an example of the step of dividing the annular convex portion in the embodiment.

4A to 4C are views showing an example of the transfer procedure of the embodiment.

Fig. 5 is a view showing an example of the step of dividing the element formation region in the embodiment.

6A to 6C are explanatory views of a method of processing a wafer of a comparative example.

Form for implementing the invention

The wafer processing method of the present embodiment is a so-called TAIKO wafer in which only the outer peripheral portion of the wafer back surface is retained and only the inner side thereof is ground. In the case where the wafer is divided into individual components, when only the center of the back surface of the wafer is thinned into a concave shape, the back side of the wafer cannot be formed by the outer peripheral portion protruding from the back side of the wafer. Keep on the work table. Therefore, the wafer is usually divided into individual wafers after the outer peripheral portion of the wafer is removed to planarize the back surface of the wafer.

At this time, although the dicing tape must be adhered to the back side of the wafer, Since the peripheral portion protrudes from the back side of the wafer, air bubbles remain between the back surface of the wafer and the dicing tape. Therefore, in the wafer processing method of the present embodiment, before the dicing tape is pasted to the back surface of the wafer, a dividing groove which becomes a discharge path of the bubble is formed at the boundary between the concave portion and the outer peripheral portion of the wafer. . Thereby, even if the outer peripheral portion of the wafer is formed to protrude, it becomes possible to adhere the dicing tape to the entire back surface of the wafer without any gap.

Hereinafter, a method of processing a wafer according to the present embodiment will be described in detail with reference to additional drawings. Fig. 1 is a perspective view of a wafer of the embodiment. Fig. 2 is a view showing an example of a step of forming a concave portion in the embodiment. Fig. 3 is a view showing an example of the step of dividing the annular convex portion in the embodiment. Fig. 4 is a view showing an example of a transition procedure of the embodiment. Fig. 5 is a view showing an example of the step of dividing the element formation region in the embodiment.

As shown in FIG. 1, the wafer W is formed in a substantially circular plate shape, and is divided into a plurality of regions by a lattice-shaped dividing line 18 arranged on the front surface 11. In the center of the wafer W, an element D is formed in each of the regions divided by the division planned line 18. The front surface 11 of the wafer W can be divided into an element formation region A1 in which a plurality of elements D are formed, and a peripheral remaining area A2 around the element formation region A1. Further, a notch 14 indicating a crystal orientation is formed on the outer edge 13 of the wafer W. The wafer W is carried into the grinding device 21 in a state in which the protective tape T1 is adhered to the front surface 11 (see FIG. 2).

As shown in Fig. 2, the recess forming step is first performed. In the recess forming step, the front surface 11 side of the wafer W is held by the protective tape T1 on the work chuck 22 of the grinding device 21. Then, while making the grinding device 21 The grinding wheel 23 rotates around the Z-axis while approaching the work chuck 22, and the wafer W is ground by the rotational contact between the grinding wheel 23 and the back surface 12 of the wafer W. At this time, in the back surface 12 of the wafer W, only the back side of the element forming region A1 of the front surface 11 is ground. Thereby, on the back surface 12 of the wafer W, the region corresponding to the element formation region A1 can be thinned to a desired thickness to form a circular recess 15 and the region corresponding to the peripheral remaining region A2 can be made of the wafer W. The back surface 12 side protrudes to form an annular convex portion 16.

As described above, only the central portion of the wafer W is thinned by the concave portion 15, and the rigidity of the wafer W can be increased by the annular convex portion 16 surrounding the concave portion 15. As a result, the element forming region A1 of the wafer W is thinned, and the warpage of the wafer W can be suppressed by the annular convex portion 16 to prevent breakage during transportation. Further, the wafer W may be a semiconductor wafer such as germanium or gallium arsenide, or may be a ceramic, glass or sapphire optical device wafer. The wafer W in which the concave portion 15 and the annular convex portion 16 are formed is carried into the cutting device 31 in a state in which the protective tape T1 is adhered (see FIG. 3).

As shown in FIG. 3, an annular convex portion dividing step is performed after the concave portion forming step. In the annular convex portion dividing step, the front surface 11 side of the wafer W is held by the protective tape T1 on the working chuck 32 of the cutting device 31. At this time, the position of the wafer W is aligned with respect to the work chuck 32 so that the center of the wafer W matches the rotation axis (Z axis) of the work chuck 32. Further, the cutting insert 33 is positioned at the boundary between the annular convex portion 16 and the concave portion 15 of the wafer W, and the cutting insert 33 that rotates at a high speed cuts the annular convex portion 16 and the concave portion 15 from the back surface 12 side of the wafer W. Junction.

And, when cutting with the cutting blade 33 into the half of the protective tape T1 At the mid-waist, the work chuck 32 is rotated to cut the wafer W into a circle by the cutting insert 33. Thereby, a circular dividing groove 17 can be formed between the concave portion 15 and the annular convex portion 16 along the outer circumference of the wafer W, and the annular convex portion 16 can be cut away from the wafer W. The wafer W on which the division grooves 17 are formed is carried into a transfer device (not shown). At this time, the element formation region A1 of the wafer W is conveyed in a state where the protective tape T1 is supported by the annular convex portion 16 . In other words, the annular convex portion 16 functions as an annular frame to suppress deflection of the element forming region A1 in which the wafer W is thinned.

Further, the step of dividing the annular convex portion is not limited to the dividing step of cutting (circle cut) by the cutting insert 33. The annular convex portion dividing step may be a configuration in which the dividing groove 17 is formed between the circular concave portion 15 and the annular convex portion 16 of the wafer W. For example, the wafer W may be used. The ablation process performed by the laser beam of the absorptive wavelength is carried out. The so-called ablation refers to the conversion of the solid surface to electronic, thermal, optical, and mechanical energy when the intensity of the laser beam is above a predetermined processing threshold. As a result, the neutral atom, Molecules, positive and negative ions, free radicals, clusters, electrons, and light are released violently, causing the solid surface to be etched.

As shown in FIG. 4, the transfer step can be performed after the annular convex portion dividing step. In the transfer step, as shown in FIG. 4A, the dicing tape T2 is adhered along the back surface 12 of the wafer W. At this time, the wafer W is placed inside the annular frame F on a platform in the decompression space of the transfer device, for example, and the dicing tape T2 is pressed to the crystal with a circular plate corresponding to the concave portion 15 of the wafer W. The back side of the circle W is 12. Then, while the dicing tape T2 is stretched radially outward, The dicing tape T2 is adhered from the center of the back surface 12 of the wafer W toward the radially outer side.

When the dicing tape T2 is pasted, as shown in FIG. 4B, the air between the back surface 12 of the wafer W and the dicing tape T2 can be extruded radially outward so as to run to the annular convex portion 16 and the concave portion 15 In the dividing groove 17 at the junction. Therefore, there is no case where the air bubbles 25 (see FIG. 6) remain on the back surface 12 side of the wafer W, and the dicing tape T2 can be favorably adhered to the entire inner side of the dividing groove 17 of the back surface 12 of the wafer W. section. Next, as shown in FIG. 4C, the protective tape T1 is peeled off from the front surface 11 of the wafer W, and the annular convex portion 16 is further removed from the dicing tape T2. Thereby, the element forming region A1 of the wafer W can be retained on the dicing tape T2. The wafer W transferred to the dicing tape T2 is again carried into the cutting device 31 (see Fig. 5). Further, the peeling of the protective tape T1 and the removal of the annular convex portion 16 may be performed by a transfer device, or may be performed by an operator's manual work.

Further, in the present embodiment, the removal of the annular convex portion 16 is not performed in the cutting device 31 immediately after the completion of the annular convex portion dividing step, but is performed after the transfer device has been transferred. In the case where the removal of the annular convex portion 16 is performed in an automatic manner, for example, in the device shown in Japanese Laid-Open Patent Publication No. 2013-098246, a scraper is applied in a state where tension is applied to the tape. Since only the protective tape T1 of the same size is adhered to the wafer W after the annular convex portion dividing step, the annular convex portion 16 cannot be removed by the scraper before the dicing tape T2 is pasted in the transfer step. Therefore, it is difficult to automatically remove the annular convex portion 16 as long as the transfer step is not performed.

Also, by crystallizing at a stage before the recess forming step The configuration in which the circle W is held on the annular frame F to remove the annular convex portion 16 in the cutting device 31 can also be considered. However, in order to perform the concave portion forming step on the wafer W supported on the annular frame F in the grinding device 21, it is necessary to improve the grinding device 21 itself, which has a problem of increasing the cost. As described above, in the present embodiment, by transferring the wafer W to the transfer device, the transfer device transfers the wafer W from the protective tape T1 to the dicing tape T2, so that the annular convex portion can be implemented with a simple configuration. The removal of 16. Further, as described above, when the wafer W is transported to the transfer device, since the annular convex portion 16 functions as a ring-shaped frame, it is possible to prevent deflection of the element forming region A1 which is thinned by the wafer W. And the damage caused by damage.

As shown in FIG. 5, the element forming region dividing step can be performed after the transferring step. In the element formation region dividing step, the back surface 12 side of the wafer W is held on the work chuck 32 by the dicing tape T2, and the annular frame F around the wafer W is held by the clamp portion 34. The cutting insert 33 is positionally aligned with respect to the division planned line 18 on the radially outer side of the wafer W, and is lowered to a height at which it can be cut into the half mid-waist of the dicing tape T2. Then, by cutting the wafer W on the work chuck 32 with respect to the high speed rotating cutting insert 33 in the X-axis direction, the wafer W can be cut along the dividing line 18.

When the wafer W is cut along a predetermined dividing line 18, the cutting insert 33 can be aligned to the adjacent dividing line 18 for cutting. This action is repeated to cut the wafer W along all of the dividing lines 18 in one direction. After cutting along all the dividing lines 18 in one direction of the wafer W, the work chuck 32 can be rotated by 90 degrees and similarly performed. On the other hand, the wafer W is cut along the dividing line 18 which is orthogonal to the dividing line 18 in one direction. As a result, only the thinned element forming region A1 is completely cut along the dividing line 18, and the wafer W can be divided into a plurality of elements D.

As described above, in the method of processing the wafer W of the present embodiment, since the dicing tape T2 is favorably adhered to the entire back surface 12 of the element forming region A1 of the wafer W, it is not necessary to divide the element forming region A1. This causes a deterioration in the quality of the component D. That is, since a gap is not formed between the outer edge 19 of the element forming region A1 and the dicing tape T2 (refer to FIG. 6C), there is no case where chips enter the gap. According to this, the wafer W on which the annular convex portion 16 is formed can be divided into individual elements D without deteriorating the quality.

Further, the element forming region dividing step is not limited to the mechanical dicing dividing step by the cutting insert 33. The element forming region dividing step may be performed by dividing the element forming region A1 along the dividing line 18, for example, by ablation processing using a laser beam having a wavelength that absorbs the wafer W. Alternatively, it may be implemented by stealth dicing (registered trademark) using a laser beam having a wavelength that is transparent to the wafer W.

In the stealth dicing, the reforming layer is formed along the dividing line 18, and an external force is applied to the wafer W, and the element D is divided into individual elements starting from the modified layer. Furthermore, the modified layer refers to a state in which the density, the refractive index, the mechanical strength, and other physical properties of the inside of the wafer W become different from the surroundings by the irradiation of the laser beam, and the intensity is also lower than the surrounding. region. The modified layer may be, for example, a molten processed region, a cracked region, an insulating fractured region, or a refractive index change region, or a region obtained by mixing these.

Here, in order to compare with the present invention, a method of processing a wafer of a comparative example will be briefly described with reference to FIG. 6 is an explanatory view of a method of processing a wafer of a comparative example. In the wafer processing method of the comparative example, the method of processing the wafer of the present embodiment is different in that the embossed tape is adhered to the back surface of the wafer and the annular convex portion is cut away from the wafer. In addition, the configuration in which the annular convex portion and the concave portion are formed on the back surface of the wafer is the same as that of the present embodiment, and thus the description thereof will be omitted. In the comparative example, the same reference numerals are given to the same names for convenience of explanation.

As shown in FIG. 6A, in the method of processing the wafer W of the comparative example, the dicing tape T2 is adhered along the back surface 12 of the wafer W before the division groove 17 (see FIG. 6B) is formed. Therefore, in the case where there is no air discharge path between the back surface 12 of the wafer W and the dicing tape T2, the air bubbles 25 remain on the corners of the annular convex portion 16 and the concave portion 15 of the back surface 12 of the wafer W. Therefore, the dicing tape T2 cannot be adhered to the outer edge side of the element forming region A1 of the wafer W. When the wafer W is supported by the annular frame F (see FIG. 4) through the dicing tape T2, the protective tape T1 can be peeled off from the front surface 11 of the wafer W.

Next, as shown in FIG. 6B, a circular dividing groove 17 is formed by the cutting insert 33 at the boundary between the annular convex portion 16 of the wafer W and the concave portion 15. At this time, since the blade edge of the cutting insert 33 enters the bubble 25, the cutting blade 33 is shaken to deteriorate the processing quality, and the chip 26 enters the bubble 25 to cause contamination. When the dividing groove 17 is formed on the wafer W, the annular convex portion 16 of the wafer W can be removed from the dicing tape T2. Secondly, As shown in FIG. 6C, the wafer W is cut along the dividing line 18 (see FIG. 5) by the cutting insert 33, and the wafer W is divided into individual elements D. At this time, since the dicing tape T2 is not adhered to the outer edge 19 of the wafer W, the chips 26 enter the gap between the outer edge 19 of the wafer W and the dicing tape T2, resulting in deterioration of the quality of the element D.

As described above, in the method of processing the wafer W of the comparative example, in particular, the quality of the element D on the outer peripheral side of the wafer W is deteriorated. On the other hand, in the method of processing the wafer W of the present embodiment, there is no residual bubble 25 between the back surface 12 of the wafer W and the dicing tape T2, such as the processing method of the wafer W of the comparative example. In this case, there is no possibility that the quality of the element D on the outer peripheral side of the wafer W is deteriorated due to the bubble 25.

As described above, according to the method of processing the wafer W of the present embodiment, the protective tape T1 is adhered to the front surface 11 side of the wafer W, and the annular convex portion 16 and the concave portion on the back surface 12 side of the wafer W are formed. A circular dividing groove 17 is formed at the junction of 15. Therefore, when the dicing tape T2 of the back surface 12 of the wafer W is pasted, the air between the back surface 12 of the wafer W and the dicing tape T2 can be made to flow to the dividing groove 17. Therefore, the dicing tape T2 can be pasted without leaving the air bubbles 25 on the entire back surface 12 of the wafer W, and the protective tape T1 can be peeled off from the front surface 11 of the wafer W, and the annular convex portion 16 can be removed. Thereby, the wafer W can be favorably transferred from the protective tape T1 to the dicing tape T2. In addition, since the wafer W is divided in a state where the air bubbles 25 remain on the back surface 12 of the wafer W, there is no possibility that the quality of the element W is lowered due to the influence of the air bubbles 25.

Furthermore, the present invention is not limited to the above embodiment, and can be Implemented with various changes. In the above-described embodiments, the size, shape, and the like shown in the drawings are not limited thereto, and may be appropriately changed within the scope of exerting the effects of the present invention. Further, any modification can be made without departing from the scope of the invention.

Further, in the above-described method of processing the wafer W, in the transfer step, the wafer W is transferred to the dicing tape T2 adhered to the annular frame F, but the configuration is not limited thereto. In the transfer step, the dicing tape T2 can be adhered to the back surface 12 of the wafer W, and the protective tape T1 can be peeled off from the front surface 11 of the wafer W, even if the wafer W is not supported by the annular frame through the dicing tape T2. F is also available.

Industrial availability

As described above, the present invention has an effect of being able to be divided into individual elements without deteriorating the quality thereof, and the wafer having the annular convex portion formed on the outer periphery of the back surface of the wafer is divided into individual elements. Wafer processing methods are useful.

11‧‧‧ Wafer front

12‧‧‧ Back of wafer

15‧‧‧ recess

16‧‧‧ annular convex

17‧‧‧dividing trench

A1‧‧‧Component formation area

A2‧‧‧ remaining area of the periphery

F‧‧‧Ring frame

T1‧‧‧Protective tape

T2‧‧‧ cutting tape

W‧‧‧ wafer

X, Y, Z‧‧ Direction

Claims (1)

A method for processing a wafer is a method of processing a wafer having a substantially circular element forming region in which a plurality of elements are formed by dividing a predetermined line, and a wafer surrounding a remaining portion of the periphery of the element forming region. It is composed of the following steps: a recess forming step of adhering a protective tape to the front side of the wafer, and grinding only a region on the back side corresponding to the element forming region of the wafer to a predetermined thickness to thin the element forming region a concave portion is formed on the back surface in a desired thickness, and an annular convex portion protruding from the back surface side is formed in the remaining portion of the outer circumference; an annular convex portion dividing step in which the annular convex portion and the annular convex portion are formed after the step of forming the concave portion a circular dividing groove is formed at the boundary of the concave portion, and the annular convex portion and the concave portion are divided; and the transferring step is performed on the inner side of the dividing groove on the back surface of the wafer after the annular convex portion dividing step is performed Pasting the dicing tape, peeling off the protective tape, and removing the annular convex portion; and an element forming region dividing step, along the element forming region after performing the transferring step Dividing the dividing lines.