JP6817761B2 - How to divide the wafer - Google Patents

Description

The present invention relates to a method for dividing a wafer, which divides the wafer into individual chips.

As a method of dividing the wafer into individual chips, for example, a modified layer serving as a division starting point is formed by irradiating the inside of the wafer with a laser beam along a planned division line, and then the back surface of the wafer is ground. Therefore, there is a division method in which a crack is generated on the surface side of the modified layer as a division starting point to divide the wafer into individual chips (see, for example, Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2013-171846

However, in the above-mentioned division method, there is a problem that the wafer may be warped due to cracks, and the warped wafer cannot be satisfactorily conveyed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable satisfactorily transporting a wafer after laser beam irradiation to a predetermined transport destination.

The present invention is a method for dividing a wafer whose surface is divided by a planned division line along the planned division line, and comprises a bonding step of attaching a protective member to the surface of the wafer and the attachment. After performing the step, the protective member side is held by the holding means, and a laser beam having a wavelength that is transparent to the wafer is irradiated from the back surface of the wafer along the planned division line to the planned division line. After performing the division starting point modifying layer forming step for forming the dividing starting point modified layer which is the division starting point of a predetermined thickness from the surface inside the wafer and the dividing starting point modifying layer forming step, from the back surface of the wafer. By irradiating the wafer with a laser beam having a wavelength having transparency, the divided starting point modified layer is formed in a region between the back surface of the wafer and the divided starting point modified layer where the divided starting point modified layer is not formed. While adsorbing the wafer by a transport means having a straightening modified layer forming step for forming a straightening modified layer having a stress for correcting the stress warp caused by the wafer and a suction surface smaller than the wafer after performing the straightening modified layer forming step. The transfer step and the protective member side are held by the holding means and ground from the back surface of the wafer by the grinding means to reduce the thickness to the finished thickness, and the wafer is transferred from the divided starting point modified layer as a starting point by the grinding operation. A grinding step for dividing along a scheduled division line is provided, and the straightening / modifying layer forming step is characterized in that the straightening / modifying layer is formed only in a region corresponding to the adsorption surface of the conveying means. ..

The method for dividing the wafer according to the present invention includes a sticking step of sticking a protective member on the surface of the wafer and a laser having a wavelength that is transparent to the wafer from the back surface of the wafer by holding the protective member side with a holding means. A step of forming a dividing starting point modifying layer, which irradiates a beam along a scheduled dividing line to form a dividing starting point modifying layer having a predetermined thickness from the surface inside the wafer along the scheduled dividing line, and a wafer. By irradiating a laser beam having a wavelength that is transparent to the wafer from the back surface of the wafer, the partition starting point modified layer is formed in the region between the back surface of the wafer and the dividing starting point modified layer where the dividing origin modified layer is not formed. After performing the straightening and modifying layer forming step of forming the straightening and modifying layer having the stress to correct the stress warp caused by the wafer, and the conveying means having an adsorption surface smaller than the wafer after performing the correcting and modifying layer forming step, the wafer is conveyed while being adsorbed. The transfer step to be performed and the protective member side are held by the holding means, and the back surface of the wafer is ground by the grinding means to reduce the thickness to the finished thickness, and the wafer is divided into the planned division line starting from the divided starting point modified layer by the grinding operation. A grinding step that divides along the wafer is provided, and in the straightening / modifying layer forming step, the straightening / modifying layer is formed at least in the region corresponding to the suction surface of the conveying means, so that the region may be warped. It can be reduced. As a result, when the transfer step is carried out, the transfer means attracts the region, and the wafer can be satisfactorily transferred to a predetermined transfer destination such as a grinding device. As a result, the processing time of the wafer can be shortened as compared with the conventional case.

It is a perspective view which shows the structure of an example of a laser processing apparatus. (A) is a perspective view showing an example of a wafer. (B) is a cross-sectional view showing a sticking step. (A) to (d) are cross-sectional views showing the steps of forming a modified layer at a division starting point. (A) to (d) are sectional views which show the straightening modification layer formation step. (A) is a plan view which shows the wafer in which the circular correction modification layer was formed. (B) is a plan view showing a transport step. (A) is a cross-sectional view showing a grinding step. (B) is a cross-sectional view showing a state in which a wafer is divided into chips having individual devices by a grinding step. (A) is a plan view showing a wafer in which a U-shaped straightening and modifying layer is formed. (B) is a plan view showing a second example of the transport step. (A) is a plan view which shows the wafer in which the rectangular correction modification layer was formed. (B) is a plan view showing a third example of the transport step.

1 Laser Machining Device The laser machining device 10 shown in FIG. 1 has a base 11, and a column 12 extending in the Z-axis direction is erected on the rear side of the base 11 in the Y-axis direction. On the upper surface of the base 11, a chuck table 14 that functions as a holding means for holding the wafer, an X-axis direction feeding means 16 that moves the chuck table 14 in the X-axis direction, and a chuck table 14 that are orthogonal to the X-axis direction. A Y-axis direction feeding means 17 for index feeding in the Y-axis direction is provided.

For example, a porous member is provided inside the chuck table 14, and the upper surface of the porous member is a holding surface 14a. A suction source is connected to the holding surface 14a, and the wafer can be sucked and held by the holding surface 14a that has been subjected to the suction action of the suction source. The chuck table 14 is rotatably supported by a support base 15 arranged on the Y-axis direction feeding means 17.

The X-axis direction feeding means 16 includes a ball screw 160 extending in the X-axis direction, a motor 161 connected to one end of the ball screw 160, a pair of guide rails 162 extending in parallel with the ball screw 160, and the X-axis direction. It is equipped with a movable X-axis base 163. A chuck table 14 is supported on one surface of the X-axis base 163 via a Y-axis direction feeding means 17, and a pair of guide rails 162 are slidably contacted on the other surface of the X-axis base 163. A ball screw 160 is screwed into the nut formed in the central portion. Then, by rotating the ball screw 160 driven by the motor 161 the X-axis base 163 moves in the X-axis direction along the guide rail 162, and the chuck table 14 can be moved in the X-axis direction.

The Y-axis direction feeding means 17 includes a ball screw 170 extending in the Y-axis direction, a motor 171 connected to one end of the ball screw 170, a pair of guide rails 172 extending in parallel with the ball screw 170, and the Y-axis direction. It is equipped with a movable Y-axis base 173. A chuck table 14 supported by a support base 15 is rotatably supported on one surface of the Y-axis base 173, and a pair of guide rails 172 are slidably contacted on the other surface of the Y-axis base 173. A ball screw 170 is screwed into the nut formed in the central portion of the above. Then, by rotating the ball screw 170 driven by the motor 171, the Y-axis base 173 moves in the Y-axis direction along the guide rail 172, and the chuck table 14 can be index-fed in the Y-axis direction.

A casing 22 extending in the Y-axis direction is connected to the side portion of the column 12. The tip portion 22a of the casing 22 has a configuration extending to a position on the upper side of the movement path in the movement direction (X-axis direction) of the chuck table 14. The casing 22 can be moved up and down in the Z-axis direction by an elevating mechanism (not shown) arranged in the column 12. The tip portion 22a of the casing 22 has a laser beam irradiating means 20 having a laser head 21 for irradiating a laser beam having a wavelength transparent to the wafer downward, and an imaging means for imaging a region to be irradiated with the laser beam. 23 and 23 are arranged.

An oscillator 200 that oscillates a laser beam is housed inside the casing 22. A condensing lens for condensing the laser beam oscillated from the oscillator 200 is built in the laser head 21. The laser head 21 can move up and down as the casing 22 moves in the vertical direction to adjust the focusing position of the laser beam.

The imaging means 23 is not particularly limited, and is, for example, a CCD image sensor or a camera incorporating a CMOS image sensor. The imaging means 23 can detect the position where the laser beam of the wafer should be irradiated by imaging the wafer held on the chuck table 14 and performing image processing such as pattern matching.

The laser processing apparatus 10 includes at least a chuck table 14, an X-axis direction feeding means 16, a Y-axis direction feeding means 17, and a control means 18 for controlling each operation of the laser beam irradiating means 20. The control means 18 includes at least a storage element such as a CPU and a memory. When the imaging means 23 detects the region to be irradiated with the laser beam of the wafer, the detection data is sent to the control means 18. Then, the control means 18 can control the rotation operation of the chuck table 14 and the movement operation of the chuck table 14 by the X-axis direction feed means 16 and the Y-axis direction feed means 17 based on the detection data. The position of the laser head 21 and the position to be irradiated with the laser beam are aligned by index-feeding the chuck table 14 together with the Y-axis base 173 in the Y-axis direction by the Y-axis direction feeding means 17.

A base 13 is connected to the front side of the base 11 in the Y-axis direction, and a transport unit 30 for loading and unloading a wafer with respect to the chuck table 14 is provided on the upper surface of the base 13. The transport unit 30 is composed of a transport means 31 that sucks and holds the wafer and transports the wafer to a predetermined transport destination, and a Y-axis direction moving means 35 that horizontally moves the transport means 31 in the Y-axis direction. The transport means 31 is connected to a suction pad 32 having a suction surface for sucking and holding the wafer on the lower surface, an arm portion 33 having one end connected to the suction pad 32, and the other end of the arm portion 33 so as to be able to move up and down and rotate. It includes a shaft portion 34. By raising and lowering the shaft portion 34, the arm portion 33 can be raised and lowered in the Z-axis direction, and the suction pad 32 can be raised and lowered. Further, as the shaft portion 34 rotates, the arm portion 33 rotates horizontally, and the suction pad 32 can be rotated horizontally.

The suction surface of the suction pad 32 shown in the present embodiment is formed in a circular shape, and its area has a diameter at least smaller than that of the wafer to be transported. As a result, the area of contact between the suction pad 32 and the wafer can be reduced. A suction source is connected to the suction pad 32, and the suction force of the suction source acts on the suction surface of the suction pad 32, so that the suction pad 32 can suck the wafer.

The Y-axis direction moving means 35 includes a ball screw 350 extending in the Y-axis direction, a motor 351 connected to one end of the ball screw 350, a pair of guide rails 352 extending in parallel with the ball screw 350, and a conveying means 31. It has a moving base 353 to support. A shaft portion 34 is rotatably arranged on one surface of the moving base 353, and a pair of guide rails 352 are slidably contacted with the other surface of the moving base 353 to form a central portion of the moving base 353. A ball screw 350 is screwed into the nut. By rotating the ball screw 350 driven by the motor 351 the moving base 353 moves in the Y-axis direction along the guide rail 352, and the conveying means 31 can be moved horizontally in the Y-axis direction. In the transport unit 30, although not shown, the wafer before processing is transported from the cassette to the chuck table 14, the wafer after processing is accommodated in the cassette from the chuck table 14, or is transported to, for example, a grinding device. Can be done.

2 Wafer division method Next, a method for dividing the wafer W shown in FIG. 2A into individual chips will be described using the laser processing apparatus 10. The wafer W is an example of a workpiece, and has a circular plate-shaped substrate, and a device D is formed on a surface Wa of the wafer W in a plurality of regions partitioned by grid-like division schedule lines S. .. On the other hand, the back surface Wb on the opposite side of the front surface Wa of the wafer W is a surface to be machined to be irradiated with a laser beam or ground by a grinding wheel.

(1) Adhesion step As shown in FIG. 2B, the protective member 1 is attached to the surface Wa of the wafer W. The protective member 1 has adhesiveness and has an area covering the entire surface Wa of the wafer W. When the protective member 1 is attached to the surface Wa of the wafer W, the region where the device D shown in FIG. 2A is formed is covered by the protective member 1 to protect the device D. A plurality of wafers W before processing are housed in, for example, a cassette (not shown) set in the laser processing apparatus 10.

(2) Separation origin modification layer forming step After performing the sticking step, the wafer W before processing is taken out from a cassette (not shown) by the transport unit 30 shown in FIG. 1, and the moving base 353 is moved by the Y-axis direction moving means 35. Moves in the + Y direction with. Then, the wafer W is placed on the holding surface 14a of the chuck table 14, the back surface Wb of the wafer W is turned upward, and the protective member 1 side is sucked and held by the holding surface 14a on which the suction force of the suction source is applied.

When the chuck table 14 is positioned directly under the imaging means 23 by the X-axis direction feeding means 16 and the imaging means 23 detects the position to irradiate the laser beam (scheduled division line S), the detection data is sent to the control means 18. .. The control means 18 controls the Y-axis direction feed means 17 based on the detection data, and index-feeds the chuck table 14 together with the Y-axis base 173 in the Y-axis direction to position the laser head 21 and the scheduled division line S. Matching is done. The laser beam irradiating means 20 shown in FIG. 3A lowers the laser head 21 in the −Z direction and adjusts the focusing point of the laser beam to a desired position (the position closest to the surface Wa side of the wafer W). .. After that, the X-axis direction feeding means 16 shown in FIG. 1 moves the chuck table 14 together with the X-axis base 163 in the −X direction, for example, and a laser beam having a wavelength that is transparent to the wafer W from the laser head 21. 24 is irradiated from the back surface Wb side of the wafer W along the planned division line S to form the division starting point modifying portion 2 inside the wafer W.

After forming the division starting point reforming portion 2 along the scheduled division line S facing the X-axis direction, the chuck table 14 is index-fed in the + Y direction by the Y-axis direction feeding means 17 shown in FIG. As shown in a), the laser head 21 is positioned above the adjacent planned division line S, and the laser head 21 is moved in the −X direction by the X-axis direction feeding means 16 in the same manner as described above. The laser beam 24 is irradiated from the back surface Wb side of the waha W along the planned division line S to form the division starting point modifying portion 2 inside the waha W.

After repeating the formation of the division starting point modifying section 2 and the index feed of the chuck table 14 in the Y-axis direction to form the dividing starting point modifying section 2 along all the planned division lines S facing the X-axis direction, the chuck table is formed. By rotating 14 by 90 °, the planned division line S, which is oriented in the Y-axis direction in which the division starting point modifying portion 2 is not formed, is directed in the X-axis direction, and the division starting point modifying portion 2 is formed in the same manner as described above. And the index feed in the Y-axis direction of the chuck table 14 are repeatedly performed to form the division starting point modifying portion 2 inside the wafer W. In this way, as shown in FIG. 3B, the first-stage division starting point modifying portion 2 is formed inside the wafer W along all the planned division lines S.

Next, the laser head 21 is raised in the + Z direction, and the focusing points of the laser beam are positioned above the first-stage division starting point modifying portion 2 at equal intervals from the front surface Wa side to the back surface Wb side. After that, as shown in FIG. 3C, the laser beam 24 is irradiated along all the scheduled division lines S in the X-axis direction and the Y-axis direction for each step to form the division starting point modifying portion 2. By stacking the division starting point modifying portions 2, the dividing starting point modifying layer 3 is formed. The formation of the division starting point modifying portion 2 is repeated until the division starting point modifying layer 3 exceeds the finishing thickness L with reference to the surface Wa of the wafer W, and as shown in FIG. 3D, the inside of the wafer W is formed. The division starting point modification layer 3 is formed along all the planned division lines S. The dividing starting point modifying layer 3 is formed on the Wa side of the surface of the wafer W, and the internal stress of the dividing starting point modifying layer 3 disrupts the stress balance between the front and back surfaces of the wafer W, so that the wafer W is likely to warp. There is.

The order in which the division starting point modification layer 3 is formed along the planned division line S is not limited to the case shown in the present embodiment. For example, after forming the division start point modification layer 3 composed of a plurality of stages of division start point modification portions 2 along all the division schedule line S in the X-axis direction, the division origin modification layer 3 is formed along all the division schedule line S in the Y axis direction. The division starting point modifying layer 3 composed of a plurality of stages of dividing starting point modifying portions 2 may be formed.

(3) Straightening and modifying layer forming step After performing the dividing starting point modifying layer forming step, as shown in FIG. 4A, the laser beam irradiating means 20 raises the laser head 21 in the + Z direction to further back the surface. The focusing point of the laser beam 25 is positioned on the Wb side. That is, the position of the focusing point of the laser beam 25 is adjusted to the region where the dividing starting point modifying layer 3 is not formed between the back surface Wb of the wafer W and the dividing starting point modifying layer 3. Further, in the straightening / modifying layer forming step, the laser beam irradiation means 20 is compared with the above-mentioned dividing starting point modified layer forming step so that the stress balance of the wafer W on which the dividing starting point modifying layer 3 is formed is adjusted. The laser output is small and the machining feed rate is set large. The X-axis direction feeding means 16 shown in FIG. 1 irradiates the laser beam 25 from the laser head 21 from the back surface Wb side of the wafer W while moving the chuck table 14 together with the X-axis base 163 in the X-axis direction. A straightening / modifying portion 4 is formed inside the Subsequently, the chuck table 14 is index-fed in, for example, the + Y direction by the Y-axis direction feeding means 17 shown in FIG. 1, and the straightening / modifying section 4 is sequentially formed in the region where the straightening / modifying section 4 is not formed. .. In this way, as shown in FIG. 4B, the first-stage straightening / modifying portion 4 concentric with the suction pad 32 shown in FIG. 1 is formed inside the wafer W.

Next, the laser head 21 is raised in the + Z direction, and the focusing point of the laser beam 25 is adjusted to the upper side of the first-stage straightening / modifying unit 4 at an even interval from the front surface Wa side to the back surface Wb side. After that, as shown in FIG. 4C, the straightening / reforming portion 4 is repeatedly formed and the index feed of the chuck table 14 in the Y-axis direction is repeatedly performed for each step to form the straightening / reforming portion 4 inside the wafer W. To do. The straightening / modifying layer 5 is formed by stacking the straightening / modifying portions 4. As shown in FIG. 4D, the straightening / modifying portion 4 is repeatedly formed until the straightening / modifying layer 5 reaches a predetermined thickness. The region forming the straightening / modifying layer 5 is a corresponding region corresponding to the suction surface of the suction pad 32 of the transport means 31 shown in FIG. 1 (a portion where the suction surface of the suction pad 32 and the back surface Wb of the wafer W are in contact with each other). This is set so as to be concentric with the suction pad 32. Since the stress balance inside the wafer W is adjusted by the straightening / modifying layer 5 formed in this way, the possibility of warping of the wafer W is reduced.

(4) Transfer Step After performing the straightening / modifying layer forming step, the wafer W is transported to a predetermined transport destination using the transport unit 30 shown in FIG. Specifically, the Y-axis direction moving means 35 moves the conveying means 31 together with the moving base 353 in the + Y direction along the guide rail 352, and the shaft portion 34 moves up and down and rotates to chuck the suction pad 32. Move it to a position directly above the table 14. Here, as shown in FIG. 5A, of the back surface Wb of the wafer W held on the chuck table 14, the portion where the suction pad 32 and the concentric straightening / modifying layer 5 are formed is shaded. It is given and illustrated. The inside of the portion where the straightening / modifying layer 5 is formed is a corresponding region corresponding to the suction surface of the suction pad 32. At least in the corresponding area, warpage is unlikely to occur.

Next, as shown in FIG. 5B, the suction pad 32 is brought into contact with the back surface Wb of the wafer W and held. Specifically, the suction pad 32 is brought into contact with the corresponding region of the back surface Wb of the wafer W, and the suction force of a suction source (not shown) is applied to the suction surface of the suction pad 32 to suck the back surface Wb of the wafer W. In this way, by sucking the corresponding region without warpage by the suction pad 32, the internal stress of the wafer W and the suction force acting on the suction pad 32 do not repel, and the wafer W is sucked and held by the suction pad 32. It becomes possible. Subsequently, the conveying means 31 raises the wafer W while adsorbing the wafer W on the suction pad 32, thereby carrying out the wafer W from the chuck table 14 shown in FIG. Then, the Y-axis direction moving means 35 moves the conveying means 31 together with the moving base 353 in the −Y direction along the guide rail 352, and conveys the wafer W to, for example, a grinding device.

(5) Grinding Step After performing the transport step, the wafer W is held by the chuck table 50 provided in the grinding apparatus as shown in FIG. 6A. The upper surface of the chuck table 50 is a holding surface 50a that sucks and holds the wafer W. A grinding means 40 is provided above the chuck table 50, and the grinding means 40 has a spindle 41 having an axial center in the vertical direction, a grinding wheel 42 mounted on the lower part of the spindle 41, and a lower part of the grinding wheel 42. A grinding wheel 43 fixed in a ring shape is provided, and the entire grinding wheel 42 can be raised and lowered while rotating.

As shown in FIG. 6A, the protective member 1 side is held by the chuck table 50 to expose the back surface Wb of the wafer W upward, and the chuck table 50 is rotated in the direction of arrow A, for example. The grinding means 40 lowers the grinding wheel 42 at a predetermined grinding feed speed while rotating it in the direction of arrow A, for example, and grinds the wafer W to a predetermined finish thickness while pressing the back surface Wb of the wafer W with the grinding wheel 43. To thin the wafer W. By such a grinding operation, a crack is generated toward the surface Wa side with the divided starting point modified layer 3 as the starting point, and as shown in FIG. 6B, the wafer W is formed along the scheduled division line S for each device D. Is divided into chips with.

As described above, the method of dividing the wafer according to the present invention includes a sticking step of sticking the protective member 1 to the front surface Wa of the wafer W and holding the protective member 1 side by the chuck table 14 from the back surface Wb of the wafer W. A laser beam 24 having a wavelength that is transparent to the wafer W is irradiated along the scheduled division line S, and the inside of the wafer W is divided along the scheduled division line S to be a division starting point of a predetermined thickness from the surface Wa. The division starting point for forming the starting point modifying layer 3 The modification starting point is irradiated from the back surface Wb of the wafer W to the laser beam 25 having a wavelength that is transparent to the wafer W, and the dividing starting point is formed from the back surface Wb of the wafer W. Dividing starting point between the modified layer 3 The straightening modified layer forming step of forming the straightening modified layer 5 having the stress to correct the stress warp by the dividing starting point modified layer 3 in the region where the modified layer 3 is not formed. After performing the straightening and modifying layer forming step, the wafer W is conveyed while being adsorbed by the conveying means 31 having an adsorption surface smaller than the wafer W, and the wafer W is held by holding the protective member 1 side with the chuck table 50. The back surface Wb of the wafer is ground by the grinding means 40 to reduce the thickness to the finished thickness, and the wafer W is divided along the planned division line S starting from the divided starting point modified layer 3 by the grinding operation. In the modified layer forming step, the straightening modified layer 5 is formed at least in the corresponding region corresponding to the suction surface of the suction pad 32 of the transport means 31, so that the possibility of warpage in the corresponding region can be reduced. it can. Therefore, when the transport step is performed, the suction pad 32 sucks the corresponding region, and the wafer W can be satisfactorily transported to a predetermined transport destination such as a grinding device. As a result, the processing time of the wafer W can be shortened as compared with the conventional case.

The shape of the straightening / modifying layer 5 formed inside the wafer W is not limited to the above-mentioned concentric circles, but may be formed at least in a region corresponding to the suction surface of the transport means. For example, as in the wafer W1 shown in FIG. 7A, a U-shaped straightening / modifying layer 5a may be formed inside the wafer W1. In this case, the wafer W1 may be conveyed by the conveying means 60 provided with the U-shaped suction pad 61 shown in FIG. 7B. Of the back surface Wb of the wafer W1, the inside of the portion where the straightening / modifying layer 5a is formed is a corresponding region corresponding to the adsorption surface of the adsorption pad 61. At least the corresponding area is in a state where warpage is unlikely to occur. When the wafer W1 is conveyed by the conveying means 60, the suction pad 61 is brought into contact with the corresponding region of the back surface Wb of the wafer W1 and the suction force of a suction source (not shown) is applied to the suction surface of the wafer W1 to act on the suction surface of the wafer W1. It is preferable to adsorb the back surface Wb of.

As in the wafer W2 shown in FIG. 8A, a rectangular straightening / modifying layer 5b may be formed inside the wafer W2. In this case, the wafer W2 may be conveyed by the conveying means 70 provided with the rectangular suction pad 71 shown in FIG. 8B. Of the back surface Wb of the wafer W2, the inside of the portion where the straightening / modifying layer 5b is formed is a corresponding region corresponding to the adsorption surface of the adsorption pad 71. At least the corresponding area is in a state where warpage is unlikely to occur. When the wafer W2 is conveyed by the conveying means 70, the suction pad 71 is brought into contact with the corresponding region of the back surface Wb of the wafer W2, and the suction force of a suction source (not shown) is applied to the suction surface of the wafer W2 to act on the suction surface of the wafer W2. It is preferable to adsorb the back surface Wb of.

Since the sizes of the straightening and modifying layers 5, 5a and 5b need only be adjusted so that the regions corresponding to the suction surfaces of the suction pads 32, 61 and 71 do not warp, the suction pads 32, 61 and 71 It may be the same as the size of the suction surface, or may be formed slightly larger than the outer edges of the suction pads 32, 61 and 71 as shown in this embodiment.

1: Protective member 2: Dividing starting point modifying part 3: Division starting point modifying layer 4: Straightening modifying part 5, 5a, 5b: Straightening modifying layer 10: Laser processing device 11: Base 12: Column 13: Base 14: Chuck table 14a: Holding surface 15: Support base 16: X-axis direction feed mechanism 160: Ball screw 161: Motor 162: Guide rail 163: X-axis base 17: Y-axis direction feed mechanism 170: Ball screw 171: Motor 172: Guide Rail 173: Y-axis base 18: Control means 20: Laser beam irradiation means 200: Oscillator 21: Laser head 22: Casing 23: Imaging means 24, 25: Laser beam 30: Conveying unit 31: Conveying means 32: Adsorption pad 33: Arm part 34: Shaft part 35: Y-axis direction moving means 350: Ball screw 351: Motor 352: Guide rail 353: Moving base 40: Grinding means 41: Spindle 42: Mount 43: Grinding wheel 44: Grinding grindstone 50: Chuck table 50a : Holding surface 60: Conveying means 61: Suction pad 70: Conveying means 71: Suction pad

Claims (1)

It is a method of dividing a wafer whose surface is divided by a planned division line and divides the wafer along the planned division line.
A sticking step to stick a protective member on the surface of the wafer,
After performing the bonding step, the protective member side is held by the holding means, and a laser beam having a wavelength that is transparent to the wafer is irradiated from the back surface of the wafer along the planned division line, and the division is performed. A step of forming a dividing starting point modifying layer, which is a dividing starting point of a predetermined thickness from the surface inside the wafer along a planned line, and a step of forming the dividing starting point modified layer.
After performing the division origin modification layer forming step, a laser beam having a wavelength that is transparent to the wafer is irradiated from the back surface of the wafer to the division from the back surface of the wafer to the division origin modification layer. A straightening modified layer forming step of forming a straightening modified layer having a stress for correcting stress warpage due to the divided starting point modified layer in a region where the starting modified layer is not formed,
After performing the straightening and modifying layer forming step, a transport step of transporting the wafer while adsorbing it by a transport means having a suction surface smaller than that of the wafer
The protective member side is held by the holding means and ground from the back surface of the wafer by the grinding means to reduce the thickness to the finished thickness, and the wafer is divided along the planned division line starting from the divided starting point modified layer by the grinding operation. With grinding steps to divide,
A method for dividing a wafer, which comprises forming the straightening / modifying layer only in a region corresponding to the adsorption surface of the transporting means in the straightening / modifying layer forming step.

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