JP2017050404A - Wafer production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent warp in a wafer, which may affect conveyance, and occurrence of undivided area in the wafer.SOLUTION: The present invention comprises: a protective member bonding step in which a protective member 1 is bonded to the surface Wa of a wafer W; a hold step in which the surface Wa side of the wafer W is held by second means 2, and the rear Wb side of the wafer W is exposed; a modified layer formation step in which a modified layer 4 is formed by emitting a laser beam 32 of transmissive wavelength to the wafer W along a dividing line S from the rear Wb side of the wafer W; and a division step in which the wafer W is divided into individual devices D. In the modified layer formation step, a laser beam 32 the output of which is 1.1 to 2 times as intense as output for an outer peripheral area 11 surrounding a central area 10 is emitted to the central area 10 of 1/4 of a diameter from the center Wo of the wafer W. This prevents warp in the wafer W, which may affect conveyance, and also prevents occurrence of undivided area in the wafer W.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a wafer processing method for forming a modified layer inside a wafer by laser beam irradiation.

  As a method of dividing a wafer into individual devices, for example, a modified layer serving as a division starting point is formed by irradiating a laser beam along the street to the inside of the wafer, and the thickness of the wafer starts from the modified layer. There is a processing method in which a crack is generated toward the front surface side in a direction, and then the back surface of the wafer is ground and divided into individual devices (for example, see Patent Document 1 below).

Japanese Patent No. 3762409

  However, when a region where cracks reaching the surface of the wafer are formed is large, there is a problem that the wafer is warped and the wafer cannot be transported to a desired transport destination. Wafer warpage occurs because the modified layer portion thermally expands due to laser beam irradiation. In particular, in the case of small index processing, warpage of several millimeters occurs in the wafer surface due to accumulation of thermal expansion.

  In order to prevent the warpage of the wafer, it is conceivable to reduce the laser beam irradiation output. However, when the rear surface of the wafer is ground after forming a modified layer inside the wafer by irradiation with a low-power laser beam, There is a concern that undivided regions (mainly the central portion of the wafer) are generated. This is considered to be caused by the fact that the central portion of the wafer is less likely to move than the outer peripheral portion, and the wafer is not broken even by pressing of grinding.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the warpage of the wafer which hinders the conveyance of the wafer, and to prevent the undivided area from occurring on the wafer.

  The present invention is a wafer processing method in which a plurality of intersecting division lines are set on the surface, and a protective member attaching step for attaching a protective member to the surface of the wafer and the protective member attaching step are performed. After that, a holding step for holding the front side of the wafer with the holding member through the protective member and exposing the back side of the wafer, and a laser beam having a wavelength that is transparent to the wafer after performing the holding step A modified layer forming step of forming a modified layer by irradiating a laser beam from the back side of the wafer along the planned dividing line with the condensing point of the wafer positioned inside the wafer, and forming the modified layer A step of grinding the back surface of the wafer to reduce the thickness to a predetermined thickness, and dividing the wafer into individual devices. , The central region of the first range of quarter of the diameter from the center of the wafer, and irradiating a laser beam output two times from 1.1 times than the outer peripheral area surrounding the central area.

  Further, the present invention is a wafer processing method in which a plurality of intersecting division lines are set on the surface, a protective member attaching step for attaching a protective member to the surface of the wafer, and the protective member attaching step After holding, the holding step of holding the front side of the wafer with the holding means through the protective member and exposing the back side of the wafer, and after the holding step, the wavelength of the wavelength having transparency to the wafer A modified layer forming step for forming a modified layer by irradiating the laser beam along the planned dividing line from the back surface side of the wafer with the condensing point of the laser beam positioned inside the wafer, and the modification After the layer forming step is performed, the rear surface of the wafer is ground and thinned to a predetermined thickness, and the wafer is divided into individual devices. The flop, the central region of the first range of quarter of the diameter from the center of the wafer, and forming a number of the modified layer of the outer peripheral region surrounding the central region.

  The wafer processing method according to the present invention includes a protective member attaching step for attaching a protective member to the surface of the wafer, and holding the front side of the wafer with a holding means via the protective member to expose the back side of the wafer. A holding step, a modified layer forming step of forming a modified layer by irradiating a laser beam having a wavelength transparent to the wafer from the back side of the wafer along a division line, and dividing the wafer into individual devices. And the modified layer forming step includes 1.1 to 2 times the central region in the range of a quarter of the diameter from the center of the wafer as compared to the outer peripheral region surrounding the central region. Therefore, it is possible to prevent the wafer from being warped, which hinders the conveyance, and to form a desired modified layer in the central region. Therefore, it is possible to prevent the undivided area from occurring in the wafer when the dividing step is performed, and to reliably divide the wafer into individual devices.

  The wafer processing method according to the present invention includes a protective member attaching step for attaching a protective member to the surface of the wafer, and holding the front side of the wafer with a holding means via the protective member, so that the back side of the wafer is A holding step for exposing, a modified layer forming step for forming a modified layer by irradiating a laser beam having a wavelength transparent to the wafer from the back surface side of the wafer along a predetermined division line, and a wafer for each device In the modified layer forming step, more modified layers are formed in the central region in the range of a quarter of the diameter from the center of the wafer than in the outer peripheral region surrounding the central region. Therefore, the central region is easily broken. Accordingly, it is possible to prevent the wafer from being warped and to prevent an undivided region from being generated on the wafer when the dividing step is performed.

It is a perspective view which shows an example of a wafer. It is a perspective view which shows a protection member sticking step. It is a perspective view which shows a holding step and a modified layer formation step. It is a top view which shows the center area | region of the range of 1/4 of the diameter of a wafer, and the outer peripheral area | region surrounding a center area | region. It is sectional drawing which shows the state which forms a modified layer in the inside of a wafer. It is a partially expanded sectional view for demonstrating the modification of a modified layer formation step. (A) is sectional drawing which shows a division | segmentation step. (B) is sectional drawing which shows the state by which the wafer was divided | segmented into each device by the division | segmentation step. (A) is sectional drawing which shows a tape expansion | extension step. (B) is sectional drawing which shows the state by which the space | interval of each device was expanded by the tape expansion | extension step. It is the top view which divided and divided the center area | region of the wafer into five ranges.

  The wafer W shown in FIG. 1 is an example of a circular plate-like workpiece, and a device D is formed in each of the regions partitioned by setting a plurality of division lines S that intersect the surface Wa. Yes. On the other hand, the surface on the opposite side of the front surface Wa of the wafer W is not particularly formed, and is, for example, a back surface Wb that is thinned by grinding. Below, the processing method of the wafer W is demonstrated, referring an accompanying drawing.

(1) Protection Member Adhesion Step As shown in FIG. 2, at least the protection member 1 having substantially the same diameter as the wafer W is adhered to the surface Wa of the wafer W. As a result, the entire surface Wa of the wafer W is covered with the protective member 1 and each device D is protected. In addition, the material etc. of the protection member 1 are not specifically limited, What is necessary is just to have adhesiveness at least.

(2) Holding Step After performing the protective member attaching step, the wafer W is held using the holding means 2 that holds the workpiece as shown in FIG. The upper surface of the holding means 2 is a holding surface 20 that sucks and holds the workpiece by receiving a suction action from a suction source (not shown). The holding means 2 is connected to a moving means (not shown) that moves in the X-axis direction (machining feed direction) and the Y-axis direction (index feed direction). The wafer W is transported onto the holding means 2. Specifically, after the surface Wa side of the wafer W is placed on the holding surface 20 of the holding means 2 via the protective member 1, the surface Wa side of the wafer W is sucked and held by the holding surface 20. The back surface Wb side is exposed upward.

(3) Modified layer forming step After carrying out the holding step, the laser beam irradiation means 3 disposed above the holding means 2 is used to irradiate a laser beam from the back surface Wb side of the wafer W for modification. Form a layer. The laser beam irradiation means 3 includes a laser oscillator 30 that oscillates a laser beam having a wavelength that is transmissive to the wafer W, a condenser 31 that condenses the laser beam, and an output that adjusts the output of the laser beam. And an output regulator that does not. The laser beam irradiation means 3 is movable in the vertical direction, and the condensing position of the laser beam can be adjusted by moving the condenser 31 up and down. As the processing conditions, for example, the following processing conditions 1 are used.

[Processing condition 1]
Light source: YAG pulse laser or YVO ₄ pulse laser wavelength: 1342 nm
Output: 0.9W ~ 1.4W
Processing feed rate: 700mm / sec

  In the modified layer forming step, the laser beam is not radiated at a constant output to the entire area of the wafer W (the entire area of the back surface Wb), but the output is changed for each predetermined area set in advance on the wafer W. Irradiate with a laser beam. As shown in FIG. 4, the predetermined area of the wafer W includes a central area 10 having a diameter that is a quarter of the diameter of the wafer W from the center Wo of the wafer W, and an outer peripheral area 11 that surrounds the central area 10. Is set. Here, when the output difference between the laser beams applied to the central region 10 and the outer peripheral region 11 is less than 1.1 times or more than twice, warpage generated in the wafer W and undivided regions can be prevented at the same time. Since this is not possible, the central region 10 is irradiated with a laser beam with an output adjusted to 1.1 to 2 times that of the outer peripheral region 11. The range of the central region 10 is not limited to a range of a quarter of the diameter of the wafer W, but this range is the most preferable one that does not warp the wafer W or generate undivided regions. This will be described in Example 1 described later.

  Based on the processing condition 1, a modified layer is formed inside the wafer W. As shown in FIG. 3, the wafer W sucked and held by the holding means 2 is moved below the laser beam irradiation means 3. Subsequently, as shown in FIG. 5, while the holding means 2 is processed and fed in the X-axis direction, for example, at a predetermined processing feed speed (700 mm / second), the concentrator 31 has transparency to the wafer W. By irradiating the laser beam 32 along the planned division line S shown in FIG. 1 from the back surface Wb side of the wafer W with the condensing point of the laser beam 32 having a wavelength (1342 nm) positioned inside the wafer W. The modified layer 4 is formed. Switching of the division planned lines S to be irradiated with the laser beam 32 is performed by indexing and feeding the holding means 2 shown in FIG. 3 in the Y-axis direction.

  Here, when irradiating the laser beam 32 to the central region 10 of the wafer W shown in FIG. 4, the laser irradiation means 3 adjusts the output to be higher than the output of the laser beam 32 irradiated to the outer peripheral region 11. For example, when the laser irradiation unit 3 irradiates the outer peripheral region 11 with the laser beam 32 with an output of 0.9 w, the central region 10 is irradiated with the laser beam 32 with an output adjusted to 1.4 w. Thereby, the modified layer 4 shown in FIG. 5 is formed. Thereby, the center area | region 10 becomes easy to break in the division | segmentation step mentioned later. In this way, while adjusting the output of the laser beam irradiated to the central region 10 and the outer peripheral region 11 of the wafer W, the laser beam 32 is irradiated along all the scheduled division lines S shown in FIG. The modified layer 4 is formed inside W.

  As a modified example of the modified layer forming step, as shown in FIG. 6, the number of times of irradiation of the laser beam to the central region 10 of the wafer W is increased so that more modified layers than the modified layer formed in the outer peripheral region 11 are formed. May be formed in the central region 10. As a processing condition in this case, for example, the following processing condition 2 is used.

[Processing condition 2]
Light source: YAG pulse laser or YVO ₄ pulse laser wavelength: 1342 nm
Output: 0.9W ~ 1.4W
Processing feed rate: 700 mm / second Irradiation count (center area): 3 irradiation counts (outer peripheral area): 2 times

  As shown in FIG. 6A, when the laser beam irradiation means 3 irradiates the central region 10 of the wafer W with the laser beam 32, the position of the condenser 31 is shifted and the laser beam 32 is further moved to the surface Wa side. The condensing point is positioned and irradiated with the laser beam 32 to form the modified layer 4a. Next, as shown in FIG. 6B, the laser beam irradiation means 3 shifts the position of the condenser 31 upward, and the laser beam 32 is spaced evenly from the front surface Wa side to the back surface Wb side. Are gradually formed to form the modified layers 4b and 4c sequentially. As a result, the center region 10 is easily broken when performing the division step described later.

  On the other hand, the laser beam irradiation means 3 irradiates the outer peripheral region 11 shown in FIG. 4 with the laser beam 32 twice stepwise to form a plurality of modified layers 4. In this way, the laser beam 32 is irradiated along all the division lines S shown in FIG. 1 while switching the number of times the laser beam is irradiated to the central region 10 and the outer peripheral region 11 of the wafer W. Three modified layers are formed in the central region 10 of W, and two modified layers are formed in the outer peripheral region 11.

  In the modified layer forming step, as described above, the output of the laser beam to the central region 10 is made higher than that of the outer peripheral region 11, and the number of times of irradiation of the laser beam to the central region 10 is increased compared to the outer peripheral region 11. The machining feed rate of the holding means 2 in the central region 10 may be set faster than the machining feed rate in the outer peripheral region 11. Thereby, since the power of the laser beam irradiated to the center area | region 10 can be increased, it can prevent that the curvature and the undivided area | region generate | occur | produce in the wafer W.

(4) Dividing Step After performing the modified layer forming step (after performing the modified example of the modified layer forming step), as shown in FIG. 7, the grinding disposed above the holding means 2a The back surface Wb of the wafer W is ground to a predetermined thickness using the means 5, and the wafer W is divided into the individual devices D shown in FIG.

  As shown in FIG. 7A, the grinding means 5 includes a spindle 50 having a vertical axis, a grinding wheel 52 mounted on the lower part of the spindle 50 via a mounter 51, and a lower part of the grinding wheel 52. A grinding wheel 53 fixed in an annular shape is provided, and the entire structure can be raised and lowered while rotating the grinding wheel 52.

  When the wafer W is divided, as shown in FIG. 7A, the protective member 1 side is held by the holding means 2a, the back surface Wb of the wafer W is exposed upward, and the holding means 2a is moved in the direction of arrow A, for example. Rotate to Next, the grinding means 5 lowers the grinding wheel 53 until it abuts against the back surface Wb of the wafer W while rotating the grinding wheel 52 in the direction of arrow A, for example. Subsequently, as shown in FIG. 7 (b), the grinding wheel 53 is pressed to the back surface Wb of the wafer W while being ground until it reaches a predetermined thickness and thinned, thereby improving the modification shown in FIGS. A crack 7 shown in FIG. 7A starting from the layers 4 and 4a to 4c is formed, and the wafer 7 is divided into individual devices D with the crack 7 being the starting point of the crack. At this time, even in the central region 10 shown in FIG. 4, since the crack 7 is reliably cracked from the starting point, all the devices D can be acquired from the wafer W.

(5) Tape Expansion Step After performing the division step, the interval between the divided individual devices D is expanded by the tape expansion means 6 as shown in FIG. As shown in FIG. 8A, the tape extending means 6 includes a holding table 60 that holds the wafer W, a frame mounting table 61 that is disposed on the outer peripheral side of the holding table 60 and on which the annular frame F is mounted, A clamp portion 62 that clamps the annular frame F placed on the frame placing table 61 and an elevating means 63 that is connected to the lower part of the frame placing table 61 and moves the frame placing table 61 up and down. The elevating means 63 includes a cylinder 63a and a piston 63b that is driven to move up and down by the cylinder 63a, and the frame placing table 61 can be raised and lowered by moving the piston 63b up and down.

  When expanding the wafer W, first, the protective tape T is attached to the lower part of the annular frame F, and the protective tape T is attached to the entire surface of the protective member 1 attached to the wafer W. Subsequently, the protective member 1 side is placed on the holding table 60 and the frame F is placed on the frame placing table 61. Then, the clamp part 62 presses and fixes the upper part of the flame | frame F so that it may not move.

  Next, as shown in FIG. 8B, the piston 63 b moves downward to lower the frame mounting table 61 and lower the frame mounting table 61 relative to the holding table 60. Thereby, the protective tape T and the protective member 1 are radially expanded, an external force in the radial direction is applied to the wafer W, the distance between the devices D is expanded, and a gap 8 is formed between the devices D. Thereby, the pick-up of each device D can be made easy.

  As described above, in the wafer processing method according to the present invention, when the modified layer forming step is performed after the protective member attaching step and the holding step, a quarter of the diameter from the center Wo of the wafer W is obtained. Compared with the outer peripheral region 11 surrounding the central region 10, the laser beam 32 is irradiated to the central region 10 having a diameter in the range of 1.1 to 2 times higher than the outer peripheral region 11, and the modified layer is irradiated with the laser beam 32. 4 is formed, it is possible to prevent the wafer W from being warped and to prevent the wafer W from being hindered. And since the crack 7 used as the division | segmentation starting point is generated not only from the outer periphery area | region 11 but from the modification | reformation layer 4 formed in the center area | region 10, when performing a division | segmentation step, an undivided area | region generate | occur | produces in the wafer W. Absent.

  In a modified example of the modified layer forming step, the number of times of irradiation of the laser beam 32 is increased in the outer peripheral region 11 surrounding the central region 10 with respect to the central region 10 in the range of a quarter of the diameter from the center of the wafer W. Since more modified layers (for example, 4a, 4b, and 4c) can be formed than the modified layer 4 to be formed, the central region 10 is easily cracked, and the wafer W is not divided when the dividing step is performed. It is possible to prevent the area from occurring.

  Next, examples according to the present invention will be described. The wafer W shown in FIG. 9 shows the central region divided into five ranges. That is, a central region 10a having a diameter that is a half of the diameter of the wafer W and a central region 10b having a diameter that is a third of the diameter of the wafer W with respect to the center Wo of the wafer W. A central region 10c having a diameter of a quarter of the diameter of the wafer W, a central region 10d having a diameter of a fifth of the diameter of the wafer W, and a sixth of the diameter of the wafer W. The central region was divided into a central region 10e having a diameter of 1 as a diameter. Then, a modified layer was formed by irradiating each central region with a laser beam having a higher output than the region other than the central region, and it was confirmed which central region had the best processing result.

  If the modified layer is formed by irradiating the central region 10a and the central region 10b of the wafer W with high-power laser beams, respectively, the wafer W is warped, and the wafer W cannot be transported to a desired transport destination. Results were obtained. On the other hand, if the modified layer is formed by irradiating the central region 10d and the central region 10e of the wafer W with high-power laser beams, respectively, the wafer W is not warped and can be transported. However, an undivided area was generated on the wafer W. As described above, the warp of the wafer W is more likely to occur as the range of the central region irradiated with the high-power laser beam becomes wider, and the region of the central region irradiated with the high-power laser beam becomes less likely to be warped. It was confirmed that divided areas are likely to occur.

  Therefore, if the central layer 10c of the wafer W is irradiated with a high-power laser beam to form a modified layer, the wafer W is not warped, and there is no hindrance to the transfer of the wafer W, and the wafer W is not divided. Did not occur. As described above, it was confirmed that the best processing result is obtained when the central region 10c, which is the middle range among the five central regions, is irradiated with a laser beam having a higher output than the other regions. .

1: protective member 2, 2a: holding means 20: holding surface 3: laser beam irradiation means 30: laser oscillator 31: condenser 32: laser beams 4, 4a, 4b, 4c: modified layer 5: grinding means 50: Spindle 51: Mounter 52: Grinding wheel 53: Grinding wheel 6: Tape expanding means 60: Holding table 61: Frame mounting table 62: Clamping part 63: Lifting means 63a: Cylinder 63b: Piston 7: Crack 8: Clearance 10, 10a, 10b, 10c, 10d, 10e: central region 11: outer peripheral region

Claims (2)

A wafer processing method in which a plurality of intersecting division lines are set on the surface,
A protective member attaching step for attaching a protective member to the surface of the wafer;
After carrying out the protective member attaching step, a holding step for holding the front side of the wafer with a holding means through the protective member and exposing the back side of the wafer;
After carrying out the holding step, the laser beam is irradiated from the back side of the wafer along the planned division line with the condensing point of the laser beam having a wavelength transparent to the wafer positioned inside the wafer. And a modified layer forming step for forming a modified layer,
After performing the modified layer forming step, the back surface of the wafer is ground and thinned to a predetermined thickness, and the wafer is divided into individual devices.
In the modified layer forming step, a laser beam having an output that is 1.1 to 2 times higher than the outer peripheral region surrounding the central region is irradiated to the central region that is a quarter of the diameter from the center of the wafer. A method for processing a wafer. A wafer processing method in which a plurality of intersecting division lines are set on the surface,
A protective member attaching step for attaching a protective member to the surface of the wafer;
After carrying out the protective member attaching step, a holding step for holding the front side of the wafer with a holding means through the protective member and exposing the back side of the wafer;
After carrying out the holding step, the laser beam is irradiated from the back side of the wafer along the planned division line with the condensing point of the laser beam having a wavelength transparent to the wafer positioned inside the wafer. And a modified layer forming step for forming a modified layer,
After performing the modified layer forming step, the back surface of the wafer is ground and thinned to a predetermined thickness, and the wafer is divided into individual devices.
In the modified layer forming step, a modified layer is formed in a central region in the range of a quarter of the diameter from the center of the wafer as compared with the outer peripheral region surrounding the central region. Method.

Images