TW201543560A - Wafer processing method - Google Patents

Abstract

The purpose of this invention is to provide a wafer processing method capable of preventing notches from being generated at the corners of a chip. The solution comprises: a protective member arrangement step which arranges a protective member on the surface of a wafer; a modified layer formation step which emits a laser beam of the wavelength having permeability to the wafer to form a modified layer in the wafer; a holding step which holds the wafer by a holding means via the protective member; and a polishing step for polishing the wafer by a polishing means containing a polishing stone to thin the wafer to a predetermined thickness and for forming a plurality of chips divided along the modified layer. In the modified layer formation step, the modified layer is formed along cutting grooves, and the modified layer formed in the intersected area of the cutting grooves has a rectangular shape from the view of a plane, thereby forming cutting parts without corners on the plurality of chips.

Description

Wafer processing method Field of invention

The present invention relates to a method of processing a wafer that divides a wafer to form a plurality of wafers.

Background of the invention

In recent years, in order to realize a small and lightweight component, a wafer made of a material such as silicon is required to be ground to be thinned. What is used in the grinding is a grinding wheel including, for example, a working chuck for attracting and holding the wafer, and a rock disposed above the working chuck and having a vermiculite (grinding vermiculite) fixed on the lower surface thereof. Grinding device.

The wafer can be ground and thinned by rotating the working chuck and the grinding wheel to each other and lowering the grinding wheel to press the grinding vermiculite against the surface to be processed of the wafer. However, in order to divide the wafer whose rigidity has been reduced as the thickness is reduced into a plurality of wafers, when cutting with a cutter or the like, problems such as cracks (notches) and cracks (cracks) are likely to occur.

Therefore, in recent years, a laser beam having a wavelength at which a wafer is difficult to absorb (having a penetrating power) is condensed inside the wafer to form a modified region (modified layer) as a starting point of the division, and then the crystal is ground. The processing method of the circle has been put into practical use (see, for example, Patent Document 1). In this processing method, since it is utilized The external force applied during the grinding thins the wafer to be divided into a plurality of wafers, so that it is not necessary to cut the wafer having reduced rigidity.

Prior technical literature Patent literature

Patent Document 1: International Publication No. 03/077295

Summary of invention

However, in the above-described processing method, a plurality of wafers formed by division are brought close to each other, and thus the formed wafers are in contact with each other during grinding, resulting in a high possibility of occurrence of a notch particularly at the corners of the wafer. . When the corners of the wafer are notched, cracks are generated starting from the gap, causing component damage.

The present invention has been made in view of the above problems, and an object thereof is to provide a method of processing a wafer which can prevent a chip from being chipped at a corner.

The method for processing a wafer according to the present invention is a method for processing a wafer in which an element is formed in each of a front surface divided by a plurality of streets, characterized in that the method for processing the wafer includes : a protective member disposing step, a reforming layer forming step, a holding step, and a grinding step. The protective member is disposed by disposing a protective member on a front surface of the wafer; the reforming layer forming step is to irradiate a laser beam having a wavelength penetrating the wafer before or after the step of performing the protective member In-wafer Forming a reforming layer; the holding step is, after performing the protective member disposing step and the modifying layer forming step, holding the wafer through the protective member by holding means; the grinding step is after performing the holding step, The wafer is ground by a grinding method with a grinding vermiculite to thin the wafer to a predetermined thickness, and a plurality of wafers divided along the modified layer are formed. Wherein, in the reforming layer forming step, a modified layer along the scribe line is formed, and each apex has been positioned on the scribe line and is a rectangular modified layer in plan view, or in a plan view A circular reforming layer is formed in the intersection of the dicing streets, whereby a cut-out portion that cuts the corners is formed on the plurality of wafers formed in the grinding step.

In the method for processing a wafer of the present invention, since the modified layer is formed along the scribe line of the wafer, and the intersection of the vertices on the scribe line is formed in the intersection area of the scribe line to be rectangular in plan view. Since the material layer or the modified layer is circular in plan view, a plurality of wafers having the cut-out portions with the corners removed can be formed by dividing the wafer along the modified layer.

That is, as long as the rectangular or circular modified layer for forming the cut-out portion is provided in advance, the corners are cut off during the grinding of the wafer, so that even if adjacent wafers are in contact with each other, there is no wafer. The corner of the corner creates a gap. As described above, according to the present invention, it is possible to provide a method of processing a wafer which can prevent the corners of the wafer from being chipped.

11‧‧‧ wafer

11a, 21a‧‧‧ positive

11b, 21b‧‧‧ back

11c‧‧‧out week

12‧‧‧ grinding device

13‧‧‧Component area

14‧‧‧Working table (holding means)

15‧‧‧The remaining areas of the periphery

16‧‧‧ shaft

17‧‧‧Cut Road (cutting line)

18‧‧‧ wheel seat

19‧‧‧ components

2‧‧‧ Laser processing equipment

20‧‧‧ grinding wheel

21‧‧‧Protection components

22‧‧‧Roller abutment

23, 23a, 23b, 23c, 23d, 23e, 23f‧‧ ‧ modified layer

23f‧‧‧Modified layer

24‧‧‧ grinding diamonds

25‧‧‧ crack layer

27‧‧‧ wafer

27a, 27b‧‧‧cutting department

4‧‧‧ Laser processing head

L‧‧‧Laser beam

Fig. 1(A) is a schematic perspective view showing a configuration example of a wafer, and Fig. 1(B) is a view A schematic perspective view of the protective member arrangement step.

2(A) is a partial cross-sectional side view schematically showing the reforming layer forming step, and FIG. 2(B) is a plan view schematically showing the modified layer formed on the wafer.

Figure 3 is a schematic perspective view of the holding step and the grinding step.

Figure 4 is a schematic plan view of the shape of the formed wafer.

Fig. 5(A) is a schematic plan view showing a modified layer formed on a wafer in a first modification, and Fig. 5(B) is a schematic plan view showing a modified layer formed on a wafer in a second modification.

Fig. 6 is a schematic plan view showing the shape of a wafer formed in the first modification.

Form for implementing the invention

Embodiments of the present invention will be described with reference to the accompanying drawings. The method for processing a wafer according to the present embodiment includes a protective member disposing step (Fig. 1(B)), a modified layer forming step (Fig. 2(A), Fig. 2(B)), and a holding step (Fig. 3). And grinding steps (Figure 3, Figure 4).

In the protective member disposing step, a protective member is disposed on the front side of the wafer. In the reforming layer forming step, a laser beam having a wavelength (having a penetrating wavelength) that is hard to be absorbed by the wafer is irradiated to form a modified layer inside the wafer. In the reforming layer forming step, a modified layer which is linear in plan view is formed along the dicing street, and a rectangular shape is formed in a plane of intersection (in the vicinity of the intersection) in a plane view. Quality layer.

In the holding step, the front side of the wafer is attracted and kept As a clamping table (holding means). In the grinding step, the back side is ground to thin the wafer, and the wafer is divided along the modified layer to form a plurality of wafers. Hereinafter, a method of processing a wafer according to the present embodiment will be described in detail.

FIG. 1(A) shows the processing method of the wafer according to the embodiment. A schematic perspective view of a configuration example of a wafer. As shown in FIG. 1(A), the wafer 11 is a disk-shaped semiconductor wafer made of a material such as silicon, and the front surface 11a is divided into a central element region 13, and the element region 13 is surrounded. The remaining area of the periphery is 15.

The element region 13 is arranged in a grid-like cutting path (cutting pre-cut The alignment line 17 is further divided into a plurality of regions, and elements 19 such as ICs are formed in each region. The outer periphery 11c of the wafer 11 is chamfered and has a circular arc shape in cross section.

In the method of processing a wafer of the present embodiment, first, implementation is performed In the protective member disposing step, a protective member is disposed on the front surface 11a side of the wafer 11. Fig. 1(B) is a perspective view schematically showing a step of disposing a protective member. As shown in FIG. 1(B), the protective member 21 is formed in a disk shape having substantially the same shape as the wafer 11. As the protective member 21, for example, a resin substrate, an adhesive tape, a semiconductor wafer, or the like can be used.

In the protective member disposing step, the front surface 11a of the wafer 11 is made The side faces the front surface 21a side of the protective member 21, and the wafer 11 and the protective member 21 are overlapped. At this time, an adhesive or the like is interposed between the front surface 11a of the wafer 11 and the front surface 21a of the protective member 21. Thereby, the protective member 21 can be fixed to the front surface 11a side of the wafer 11 through an adhesive or the like.

After the protective member is disposed, the implementation is performed inside the wafer 11 The reforming layer forming step of the modified layer. 2(A) is a partial cross-sectional side view schematically showing a step of forming a modified layer, and FIG. 2(B) is a plan view schematically showing a modified layer formed on the wafer 11. The reforming layer forming step can be carried out using, for example, the laser processing apparatus 2 shown in Fig. 2(A).

The laser processing apparatus 2 is provided to attract and hold the wafer 11 Clipping table (not shown). The work chuck is coupled to a rotating mechanism (not shown) such as a motor, and rotates around a rotating shaft extending in the vertical direction. Further, a moving mechanism (not shown) is provided below the working table, and the working table is moved in the horizontal direction by the moving mechanism.

The upper surface of the working chuck is used to attract and hold the wafer 11 A holding surface on the front surface 11a side (the back surface 21b side of the protective member 21). On the holding surface, the suction force of the suction source acts by the passage formed in the inside of the work chuck, and the suction force of the suction wafer 11 is generated. A laser processing head 4 is disposed above the working chuck.

The laser processing head 4 can oscillate the laser oscillator (not shown) The emitted laser beam L is condensed on the inside of the wafer 11 which is held by the work chuck. The laser oscillator is a laser beam L that is configured to oscillate a wavelength (having a penetrating wavelength) that is difficult to be absorbed by the wafer 11. For example, in the case where a modified layer is formed on the wafer 11 made of ruthenium, as a laser oscillator, a YAG or YVO4 pulsed laser oscillator which can oscillate a laser beam L having a wavelength of 1064 nm is used. good.

In the reforming layer forming step, first, the front side of the wafer 11 is made The 11a side (the back surface 21b side of the protective member 21) is in contact with the holding surface of the work chuck, And the negative pressure of the suction source acts. Thereby, the wafer 11 is sucked and held on the work chuck in a state where the back surface 11b side is exposed upward.

Next, the work chuck is moved and rotated, and the laser processing head 4 is aligned with the cutting path 17 of the processing object. After the alignment, the laser beam L is irradiated from the laser processing head 4 toward the back surface 11b of the wafer 11, and the work chuck is moved in the first direction parallel to the cutting path 17 to be processed (machining feed). That is, the wafer 11 and the laser processing head 4 are relatively moved in parallel with respect to the dicing street 17 of the object to be processed.

Here, the condensed light of the laser beam L is spotted inside the wafer 11, and is positioned at a position where the distance from the front surface 11a is made larger than the final processed thickness of the wafer 11. Further, the power of the laser beam L is set to be slightly higher in advance so as to be cracked (cracked) toward the front surface 11a of the wafer 11 from the vicinity of the light collecting point. As described above, the wavelength of the laser beam L is a wavelength (wavelength having transparency) that is difficult to be absorbed by the wafer 11. However, the irradiation conditions of the laser beam L are not necessarily limited as a result.

When such a laser beam L is condensed inside the wafer 11, the wafer 11 can be modified by multiphoton absorption generated in the vicinity of the condensed spot. Therefore, by causing the laser beam L to relatively move and irradiate as described above, as shown in FIG. 2(B), a modified layer which is linear in plan view can be formed along the dicing street 17 to be processed. 23a. Further, since the power of the laser beam L is set slightly higher, as shown in Fig. 2(A), a crack layer 25 is formed between the reforming layer 23a and the front surface 11a.

After forming the reforming layer 23a along the cutting path 17 of the processing object, the irradiation of the laser beam L is stopped, and the work is clamped on the cutting object. The track 17 moves vertically in the second direction (index feed). That is, the wafer 11 and the laser processing head 4 are relatively vertically moved with respect to the dicing street 17 to be processed. Thereby, the laser processing head 4 can be aligned with the adjacent cutting lanes 17.

After the alignment is performed, phases are formed along adjacent scribe lines 17. The same modified layer 23a. Repeating this action, after forming the reforming layer 23a along all the cutting lanes 17 extending in the first direction, the working clamping table is rotated by 90° around the rotating shaft extending in the vertical direction to form along the cutting path 17 The modified layer 23a, wherein the scribe line 17 extends in a second direction perpendicular to the first direction.

After the reforming layer 23a along all the dicing streets 17 is formed, The irradiation of the laser beam L is stopped to position the laser processing head 4 above the intersection region (near the intersection) where the scribe lines 17 intersect. That is, the working chuck is moved relative to the laser processing head 4 to position the laser processing head 4 to the reforming layer 23a extending in the first direction and the modifying layer 23a extending in the second direction. Above the intersection area.

Next, the wafer 11 and the laser processing head 4 are relatively moved and irradiated The laser beam L is formed to form a reforming layer 23b which can cut off the corner of the rectangular region divided by the dicing street 17 (the reforming layer 23a). Specifically, as shown in FIG. 2(B), a modified layer 23b which is formed by positioning each vertex on the dicing street 17 (the reforming layer 23a) and having a rectangular shape in plan view is formed.

After the modified layer 23b is formed in the intersection region of the processed object, The laser processing head 4 is positioned in adjacent other intersection regions to form the same reforming layer 23b. This operation is repeated, and when the reforming layer 23b is formed in all the intersecting regions, the reforming layer forming step is ended. Furthermore, in this implementation In the embodiment, the rectangular reforming layer 23b is formed after all the linear modified layers 23a are formed, but the order in which the modified layers 23 (the modified layers 23a and 23b) are formed is not particularly limited.

After the reforming layer forming step, the front side of the wafer 11 is implemented The 11a side (the back surface 21b side of the protective member 21) sucks the holding step held by the working chuck (holding means) of the grinding device. Fig. 3 is a perspective view schematically showing the holding step and the grinding step performed after the holding step.

As shown in FIG. 3, the grinding device used in this embodiment 12 is provided with a work chuck (holding means) 14 for sucking and holding the wafer 11. The work chuck 14 is coupled to a rotating mechanism (not shown) such as a motor and rotates around a rotating shaft extending in the vertical direction.

The upper surface of the working chuck 14 serves to attract and hold the wafer 11 The holding surface of the front surface 11a side (the side of the back surface 21b of the protective member 21). On the holding surface, the suction force of the suction source is acted upon by the passage formed inside the working chuck 14 to generate an attractive force for attracting the wafer 11.

A grinding mechanism (grinding hand) is disposed above the work chuck 14 segment). The grinding mechanism is provided with a rotating shaft 16 rotatable about a rotating shaft extending in the vertical direction. The rotating shaft 16 is raised and lowered by a lifting mechanism (not shown). A disk-shaped wheel mount 18 is fixed to the lower end side of the rotating shaft 16.

The lower surface of the wheel base 18 is mounted substantially the same as the wheel base 18 The grinding wheel 20 of the diameter. The grinding wheel 20 is provided with a disk base 22 formed of a metal material such as stainless steel. A plurality of grinding vermiculite 24 are fixed along the entire circumference on the annular lower surface of the wheel base 22 .

In the holding step, first, the protection placed on the wafer 11 is made. The side of the back surface 21b of the member 21 is in contact with the holding surface of the work chuck 14, and the negative pressure of the suction source acts. Thereby, the wafer 11 is sucked and held on the work chuck 14 via the protective member 21. That is, in this state, the back surface 11b side of the wafer 11 is exposed above.

Grinding step after grinding step, grinding the back side 11b The wafer 11 is thinned on the side, and the wafer 11 is divided along the reforming layer 23 (the reforming layers 23a, 23b). In the grinding step, the work chuck 14 and the rotary shaft 16 are each rotated in a predetermined direction, and the rotary shaft 16 is lowered. As shown in FIG. 3, the grinding vermicia 24 is brought into contact with the back surface 11b side of the wafer 11. .

The rotating shaft 16 is any grinding suitable for grinding of the wafer 11. The feed rate is lowered. As described above, the reforming layer 23 as the starting point of the division is formed in the inside of the wafer 11. Therefore, by applying an external force to the wafer 11 by lowering the rotating shaft 16, the wafer 11 can be divided along the reforming layer 23, and a plurality of wafers corresponding to the respective elements 19 can be formed.

Figure 4 is a schematic view of the shape of the wafer formed in the grinding step Show the plan. The wafer 11 is divided along the modified layer 23a which is linear in plan view, and the modified layer 23b which is rectangular in plan view, and as shown in FIG. 4, a cut portion having the cut corners can be formed. A plurality of wafers 27 of 27a.

When the wafer 11 (wafer 27) is ground to the final processed thickness, End the grinding step. Furthermore, in the present embodiment, the condensed spot of the laser beam L is positioned such that the distance from the front surface 11a becomes larger than the final processed thickness of the wafer 11, thereby forming a modified layer. 23, so when the wafer 11 is ground to the final processed thickness, the modified layer 23 can be completely removed. Thereby, the bending strength of the wafer 27 can be improved.

As described above, in the method of processing a wafer according to the embodiment, The reforming layer 23a is formed along the dicing street 17 of the wafer 11, and a plane for positioning the respective vertices on the dicing street 17 (the reforming layer 23a) is formed in the intersection region of the dicing street 17 (the reforming layer 23a). When the modified layer 23b is rectangular, the wafer 11 is ground along the modified layer 23 (the reforming layers 23a and 23b), and a plurality of cut portions 27a having the cut corners can be formed. Wafer 27.

That is, as long as the cutting portion 27a is formed in advance. The rectangular reforming layer 23b can cut off the corners of the wafer 27 during the grinding of the wafer 11, so that even if the adjacent wafers 27 are in contact with each other, there is no possibility that the corners of the wafer 27 are notched. As described above, according to the present embodiment, it is possible to provide a method of processing a wafer which prevents the corners of the wafer 27 from being chipped.

Furthermore, the present invention is not limited to the description of the above embodiment, and Implemented with various changes. For example, in the above-described embodiment, the modified layer 23b which is rectangular in plan view is formed in the intersection region of the dicing street 17, but the shape of the modified layer formed in the intersecting region is not limited thereto. FIG. 5(A) is a plan view schematically showing a modified layer formed on the wafer 11 in the first modification.

As shown in FIG. 5(A), in the first modification, it is along the cutting The track 17 forms a reforming layer 23c which is linear in plan view, and a reforming layer 23d which is circular in plan view is formed in the intersecting region of the scribe line 17 (the reforming layer 23c). FIG. 6 is a plan view schematically showing the shape of the wafer 27 formed in the first modification. As shown in FIG. 6, in the first modification, a plurality of wafers 27 including the cutout portions 27b having the corners removed may be formed.

Further, in the above-described embodiment and the first modification, although The modified layers 23a and 23c which are linear in appearance are also formed in the intersection area of the dicing street 17, but the present invention is not necessarily limited thereto. FIG. 5(B) is a plan view schematically showing a modified layer formed on the wafer 11 in the second modification. As shown in Fig. 5(B), it is also possible to form the modified layer 23e which is linear in plan view on the dicing street 17 except the intersection region, and to change the rectangle (or circle) in plan view. The layer 23f is formed in the intersection region of the scribe line 17.

Further, in the above embodiment, the reforming layer forming step is After the protective member is disposed, the reforming layer forming step may be performed before the protective member disposing step. Further, in the above embodiment, the reforming layer forming step is performed under the condition that the crack layer 25 is formed between the reforming layer 23 and the front surface 11a. However, the crack layer 25 may be modified without forming the crack layer 25. The layer formation step.

Further, in the above-described embodiment, the laser beam L is irradiated onto the side of the back surface 11b of the wafer 11 on which the element 19 is formed, but the laser beam L may be irradiated on the front surface 11a side of the wafer 11.

In addition, the configuration, the method, and the like of the above-described embodiments can be implemented by various appropriate modifications without departing from the scope of the invention.

11‧‧‧ wafer

11a, 21a‧‧‧ positive

11b, 21b‧‧‧ back

17‧‧‧Cut Road (cutting line)

19‧‧‧ components

2‧‧‧ Laser processing equipment

21‧‧‧Protection components

23, 23a, 23b‧‧‧ modified layer

25‧‧‧ crack layer

4‧‧‧ Laser processing head

L‧‧‧Laser beam

Claims (1)

A method for processing a wafer is a method for processing a wafer in which a component is formed in each of a front surface divided by a plurality of dicing streets, wherein the wafer processing method includes: a protective member arranging step, Providing a protective member on the front surface of the wafer; a reforming layer forming step of irradiating a laser beam having a wavelength that is transparent to the wafer to form a change inside the wafer before or after the step of performing the protective member is disposed a layer; a holding step of holding the wafer by the holding means by the protective member after performing the protective member disposing step and the reforming layer forming step; and a grinding step, after performing the holding step, to have a grinding The grinding means of the vermiculite grinds the wafer to thin the wafer to a predetermined thickness and form a plurality of wafers divided along the modified layer; in the reforming layer forming step, forming along the cutting The modified layer of the track, and the modified layer whose apex has been positioned on the scribe line and which is rectangular in plan view, or the modified layer which is circular in plan view is formed in the intersection of the scribe line , Whereby formed on a plurality of wafers in the grinding step, a cut portion of the cut corners.