JP2017191825A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a corner of a device from being caused a chip, or a calf near the corner from being meandered.SOLUTION: A processing method of a wafer, includes: a first modified layer forming step and a second modified layer forming step. In the first modified layer forming step or the second modified layer forming step, or both of the first modified layer forming step and the second modified layer forming step, a modified layer M formed in an inner part of a wafer W is formed in a complex manner by at least one or more induction modified layer Mi that inducts the growth of a crack from a modified layer M to a front surface Wa of the wafer W in each one division scheduled line and at least one or more adjustment modified layer Ma that adjusts the growth of the crack from the modified layer M to the front surface Wa of the wafer W. Therefore, since the crack generated by the induction modified layer Mi from the modified layer M is inducted to the front surface Wa side of the wafer W and the growth level of the crack to the front surface Wa by the adjustment modified layer Ma, the wafer W can be preferably divided into an individual device.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wafer dividing method for dividing a wafer into individual chips.

  In the process of forming a modified layer inside the wafer, and then grinding into device chips at the same time as grinding, there is a problem that the separated devices move during grinding and the devices come into contact with each other to cause chipping at the corners of the device. there were. This problem is due to the fact that the device moves when it is singulated. Therefore, in order to adjust the timing of singulation by adjusting the growth of cracks from the modified layer to the surface, a processing method of irradiating the inside of the wafer with a laser beam for forming the modified layer in a broken line shape (For example, see Patent Document 1 below).

JP 2014-33163 A

  However, in recent years, silicon wafers and the like whose crystal orientation is at an angle of 45 ° with respect to the line to be divided have been used in order to improve electrical characteristics, and the silicon wafer is modified by irradiating it with a laser beam. If the material layer is formed in a broken line shape, the kerf will meander near the corner of the device. This is presumably because cracks from the modified layer to the surface could not grow smoothly along the planned dividing line because the modified layer was formed in a broken line shape.

  The present invention has been made in view of the above circumstances, and in the process of forming a modified layer and then grinding and dividing into individual devices, chipping occurs in the corners of the device, and the kerf near the corners meanders. The purpose is to prevent it.

  In the present invention, a plurality of divisions defined on the surface by a plurality of first division lines extending in a predetermined direction and a plurality of second division lines formed intersecting with the plurality of first division lines. A method of processing a wafer in which a wafer having a device formed in the region is divided along the first scheduled dividing line and the second scheduled dividing line, and a protective member is attached to the surface side of the wafer. After the protective member attaching step and the protective member attaching step, the protective member side is held, and a laser beam having a wavelength that is transparent to the wafer is positioned from the back side of the wafer to the focusing point inside the wafer. A first modified layer forming step of irradiating the wafer along the first planned division line and forming a first modified layer along the first planned division line inside the wafer; Of wavelength with transparency The laser beam is irradiated from the back surface side of the wafer at the condensing point inside the wafer and irradiated along the second planned dividing line, and the second modification is performed inside the wafer along the second planned dividing line. After performing the second modified layer forming step for forming the layer, the first modified layer forming step, and the second modified layer forming step, the protective member side is held and the wafer is separated from the back surface of the wafer. Dividing by dividing the wafer into individual devices by grinding by means of grinding and thinning to the finished thickness, and by the grinding operation, cracks reaching the surface of the wafer starting from the modified layer are grown along the planned dividing line. A step, in the first modified layer forming step, in the second modified layer forming step, or in both the first modified layer forming step and the second modified layer forming step. The modified layer is divided into one segment At least one induction modified layer for inducing the growth of cracks from the modified layer to the surface of the wafer, and at least for adjusting the growth of cracks from the modified layer to the surface of the wafer. It is characterized in that it is formed in combination with one or more adjustment / modification layers.

  The adjustment modified layer has a non-modified layer region at a predetermined interval inside the wafer by stopping irradiation of the laser beam at least once with respect to one side of each device with a predetermined interval. It is characterized by that.

  The induction modified layer has a predetermined interval inside the wafer by stopping the irradiation of the laser beam at least once with respect to one side of each device by providing a predetermined interval shorter than the non-modified layer region. And having a non-modified layer region smaller than the non-modified layer region.

  In the wafer processing method according to the present invention, a protective member adhering step for adhering a protective member to the front surface side of the wafer, and a first modified layer is formed along the first division line inside the wafer. The first modified layer forming step, the second modified layer forming step for forming the second modified layer along the second division line inside the wafer, and the modified layer as a starting point by the grinding operation In the first modified layer forming step or in the second modified layer forming step, and the step of growing the cracks reaching the surface of the wafer along the planned dividing line and dividing the wafer into individual devices. Alternatively, in both the first modified layer forming step and the second modified layer forming step, the modified layer formed inside the wafer is transferred from the modified layer to the surface of the wafer for each division line. Induces crack growth Since at least one induction modified layer and at least one adjustment modified layer for adjusting the growth of cracks from the modified layer to the surface of the wafer are formed in combination, the induction modified layer is formed. Cracks generated from the modified layer are guided to the surface side of the wafer by the quality layer, and the growth of cracks reaching the surface is adjusted by the modified layer, so that when dividing the wafer into individual devices It is possible to prevent chipping at the corner of the chip and meandering at the kerf near the corner.

  The adjustment modified layer has a non-modified layer region at a predetermined interval inside the wafer by stopping irradiation of the laser beam at least once with respect to one side of each device with a predetermined interval. Therefore, when the wafer is divided, cracks do not occur in the non-modified layer region, and the timing of device separation is adjusted so that adjacent devices do not come into contact with each other. It is possible to effectively prevent the nearby kerf from meandering.

  The induction modified layer has a predetermined interval inside the wafer by stopping the irradiation of the laser beam at least once with respect to one side of each device by providing a predetermined interval shorter than the non-modified layer region. Since the non-modified layer region is smaller than the non-modified layer region, cracks are not induced from the small non-modified layer region, and the movement of the device is limited at the corner of the device by dividing the wafer. It is possible to more effectively prevent the chipping and the kerf near the corner from meandering.

It is a perspective view which shows a protection member sticking process. It is a partially expanded sectional view which shows a modified layer formation process. It is a partially expanded sectional view which shows the state in which one or more induction | guidance | derivation modification layers and one or more adjustment modification layers were formed in the inside of a wafer by the modification layer formation process. It is a partially expanded sectional view which shows a division | segmentation process. (A) is sectional drawing which shows the state before implementation of an expanding process. (B) is sectional drawing which shows the state by which the space | interval of each device was expanded by the expanding process. It is a partially expanded sectional view which shows the 1st modification of a modified layer formation process. It is a partially expanded sectional view which shows the 2nd modification of a modified layer formation process.

  A wafer W shown in FIG. 1 is an example of a workpiece having a circular plate-like substrate. On the surface Wa of the wafer W, for example, a plurality of first division lines S1 extending in the first direction as a predetermined direction and a plurality of second areas extending in the second direction intersecting the plurality of first division lines S1. A device D is formed in a plurality of regions partitioned by the planned division line S2. On the other hand, the surface on the side opposite to the front surface Wa of the wafer W is a back surface Wb on which grinding is performed. The wafer W is, for example, a silicon wafer having a crystal orientation formed at an angle of 45 ° with respect to the extending direction of the first planned division line S1 and the second planned division line S2, and is formed on the outer periphery thereof. Has a notch N oriented in a direction of 45 ° with respect to the crystal orientation. Hereinafter, a wafer processing method for dividing the wafer W into the individual devices D will be described.

(1) Protection member sticking process As shown in Drawing 1, protection member 1 is stuck on the surface Wa side of wafer W. The protection member 1 is formed at least approximately the same diameter as the wafer W. When the entire surface Wa of the wafer W is covered with the protection member 1, each device D is protected. The material of the protective member 1 is not particularly limited as long as it has at least adhesiveness.

(2) Tape Affixing Step As shown in FIG. 2, the expandable tape T is affixed to the lower part of the annular frame F and the tape T is affixed to the entire surface of the protective member 1 affixed to the wafer W. . Thereby, the wafer W is formed integrally with the frame F with the back surface Wb side exposed upward.

(3) Modified layer forming step The modified layer forming step is divided into a first modified layer forming step and a second modified layer forming step. In the present embodiment, a case will be described in which the second modified layer forming step is performed after the first modified layer forming step is performed. In addition, you may implement a 1st modified layer formation process after implementing a 2nd modified layer formation process.

(3-1) 1st modified layer formation process After implementing a protection member sticking process and a tape sticking process, the protection member 1 side is hold | maintained with the holding table 10 which can rotate, and the upper side of the holding table 10 The modified layer M (first modified layer m1) is formed in the wafer W along the first scheduled division line S1 using the laser beam irradiation means 20 arranged. The upper surface of the holding table 10 is a holding surface 11 that sucks and holds the wafer W by receiving a suction action from a suction source. Although not shown in the figure, the holding table 10 has moving means for relatively moving the holding table 10 and the laser beam irradiation means 20 in the horizontal direction (X-axis direction and Y-axis direction) perpendicular to the vertical direction (Z-axis direction). It is connected.

  The laser beam irradiation means 20 includes an oscillator 21 that oscillates a laser beam LB having a wavelength that is transmissive to the wafer W, a condenser 22 that collects the laser beam LB, and an output adjustment that adjusts the output of the laser beam. At least. The laser beam irradiation means 20 is movable in the Z-axis direction, and the condensing position of the laser beam LB can be adjusted by moving the condenser 22 in the Z-axis direction.

  When the first modified layer m1 is formed inside the wafer W, the wafer W is placed on the holding surface 11 of the holding table 10 with the tape T facing downward, and the back surface Wb of the wafer W is faced upward. The protective member 1 side is sucked and held by the holding surface 11 of the holding table 10 by the suction force of the suction source. The laser beam application means 20 lowers the condenser 22 in the Z-axis direction approaching the wafer W, and adjusts the condensing point P of the laser beam LB to a desired position. Subsequently, for example, by moving the holding table 10 in the X-axis direction by a moving means, the laser beam irradiation means 20 and the holding table 10 are relatively parallel to the back surface Wb of the wafer W (X-axis direction). While moving, the laser beam LB having a wavelength that is transmissive to the wafer W from the oscillator 21 is irradiated from the back surface Wb side of the wafer W in a broken line shape along the first divisional line S1 to enter the inside of the wafer W. A first modified layer m1 is formed. When the first modified layer m1 is formed by irradiating the laser beam LB along all the first division planned lines S1, the first modified layer forming step is completed.

(3-2) Second Modified Layer Formation Step Next, the modified layer M (second modified layer m2) is formed inside the wafer W using the laser beam irradiation means 20 along the second scheduled division line S2. Form. Specifically, the holding table 10 is rotated, and the wafer W shown in FIG. 1 is rotated by 90 °, whereby the second scheduled division line S2 facing in the second direction is directed in the X-axis direction, for example. The laser beam application means 20 lowers the condenser 22 in the Z-axis direction approaching the wafer W, and adjusts the condensing point P of the laser beam LB to a desired position. Subsequently, for example, by moving the holding table 10 in the X-axis direction, the laser beam irradiation means 20 and the holding table 10 are relatively moved in a direction parallel to the back surface Wb of the wafer W (X-axis direction). The laser beam irradiating means 20 irradiates a laser beam LB having a wavelength that is transmissive to the wafer W from the back surface Wb side of the wafer W along the second division line S2 in a broken line shape. Two modified layers m2 are formed. When the second modified layer m2 is formed by irradiating the laser beam LB along all the second scheduled division lines S2, the second modified layer forming step is completed.

  The modified layer M (the first modified layer m1 and the second modified layer m2) is a region where the internal strength and physical characteristics of the wafer W are changed by the irradiation with the laser beam LB. As shown in the partially enlarged view of FIG. 2, the modified layer M is formed above the condensing point P, and the width t between the upper end and the lower end of the modified layer M is, for example, about 20 to 30 μm. It has become.

  Here, in performing the first modified layer forming step, the second modified layer forming step, or when performing both the first modified layer forming step and the second modified layer forming step, the wafer W As shown in FIG. 3, the modified layer M (the first modified layer m1 and the second modified layer m2) formed in the interior of the wafer is separated from the modified layer M to the wafer W with respect to one division planned line. At least one induction modified layer Mi for inducing the growth of cracks reaching the surface Wa of the wafer, and at least one adjustment for adjusting the growth of cracks from the modified layer M to the surface Wa of the wafer W. And a composite layer Ma. In the illustrated example, the modified layer M includes a single induction modified layer Mi formed at a position closest to the surface Wa side of the wafer W, and two layers of modified modified layers formed on the induced modified layer Mi. It is comprised by the quality layer Ma.

  When the induction modified layer Mi is formed inside the wafer W, the laser beam irradiation means 20 shifts the position of the condenser 22, and the laser beam LB in a state where the condensing point P of the laser beam LB is further positioned on the surface Wa side. It is good to form the induction | guidance | derivation modification layer Mi by irradiating. The number and thickness of the induction modification layers Mi are not particularly limited. Therefore, the number and thickness of the induction modified layers Mi may be set according to the thickness of the wafer W and the like. In the example of FIG. 3, the induction modification layer Mi is formed at a position closest to the surface Wa side of the wafer W, but is not limited to this position. However, as shown in the present embodiment, the modified layer M is preferably formed at a height position 6 that is ground and removed in a subsequent dividing step.

  Further, when the adjustment / modification layer Ma is formed inside the wafer W, the laser beam irradiation means 20 shifts the position of the condenser 22 further upward so that a uniform interval is provided from the front surface Wa side to the rear surface Wb side. Two layers of the modified layer Ma are formed by irradiating the laser beam LB stepwise. At this time, the laser beam irradiation means 20 is controlled so as to stop the irradiation of the laser beam LB at least once for one side of each device D shown in FIG. Specifically, the laser beam irradiation means 20 sets a predetermined interval H1 in the first division planned line S1, the second division planned line S2, or both the first division planned line S1 and the second division planned line S2. The laser beam LB is irradiated to a region other than the predetermined interval H1 without irradiating the provided portion with the laser beam LB. The adjustment modified layer Ma thus formed has the unmodified layer region 2 with a predetermined interval H1 inside the wafer W, and the intensity of the portion irradiated with the laser beam LB is reduced. The non-modified layer region 2 is a region where the internal strength of the wafer W is not lowered and cracks do not occur during subsequent division. There is no particular limitation on the number and thickness of the adjustment modified layers Ma.

(4) Dividing Step After performing the first modified layer forming step and the second modified layer forming step, as shown in FIG. 4, the protective member 1 side is held by a rotatable chuck table 40, Grinding from the back surface Wb of the wafer W by the grinding means 30 to reduce the finish thickness to 100, and growing a crack reaching the surface Wa of the wafer W from the modified layer M as a starting point by the grinding operation along the division line. The wafer W is divided into individual devices D. The chuck table 40 includes a holding portion 41 formed of, for example, a porous member, and an upper surface thereof serves as a holding surface 42 that sucks and holds the wafer W. A suction source (not shown) is connected to the holding surface 42. The grinding means 30 includes a spindle 31 having a vertical axis, a grinding wheel 32 attached to the lower part of the spindle 31, and a grinding wheel 33 fixed in a ring shape to the lower part of the grinding wheel 32. The whole can be moved up and down while rotating 32.

  As shown in FIG. 4, the tape T side is held by the chuck table 40, the back surface Wb of the wafer W is turned upward, and the chuck table 40 is rotated. The grinding means 30 lowers the grinding wheel 32 at a predetermined grinding feed speed while rotating the grinding wheel 32 in the direction of the arrow A, for example, and grinds to the predetermined finish thickness 100 while pressing the back surface Wb of the wafer W with the grinding wheel 33. Then, the wafer W is thinned. By this grinding operation, a crack reaching the surface Wa of the wafer W starting from the modified layer M is grown along the first scheduled division line S1 and the second scheduled division line S2. That is, when a crack is generated from the position where the modified layer M is formed, the crack is induced toward the surface Wa side by the induced modified layer Mi shown in FIG. Further, no cracks are generated from the non-modified layer region 2 of the adjusted modified layer Ma, the crack growth from the modified layer M to the surface Wa is adjusted, and the timing at which the device D is singulated is adjusted. The Therefore, when the wafer W is divided into individual devices D as the thickness is reduced, the adjacent devices D are prevented from coming into contact with each other and being damaged.

(5) Expanding Step After performing the dividing step, as shown in FIG. 5, the interval between the divided individual devices D is expanded by the tape expanding means 50. As shown in FIG. 5A, the tape extending means 50 includes a support table 51 that supports the wafer W, a frame mounting table 52 that is disposed on the outer peripheral side of the support table 51 and on which the frame F is mounted, A clamp unit 53 that clamps the frame F placed on the mounting table 52, and an elevating means 54 that is connected to the lower part of the frame mounting table 52 and moves the frame mounting table 52 up and down. The elevating means 54 includes a cylinder 54a and a piston 54b driven up and down by the cylinder 54a. The frame mounting table 52 can be raised and lowered by moving the piston 54b up and down.

  When extending the wafer W, the protective member 1 side is placed on the support table 51 and the frame F is placed on the frame placing table 52. Then, the clamp part 53 presses the upper part of the frame F and fixes it so as not to move. Next, as shown in FIG. 5B, the piston 54 b moves downward, lowers the frame mounting table 52, and lowers the frame mounting table 52 relative to the support table 51. As a result, the 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 5 is formed between the devices D. Then, each device D is picked up by a transport means or the like and transported to a desired transport destination.

  Thus, in the wafer processing method according to the present invention, in the first modified layer forming step or in the second modified layer forming step, or in the first modified layer forming step and the second modified layer. In both steps of the quality layer forming step, the modified layer M formed inside the wafer W has at least one that induces the growth of cracks from the modified layer M to the surface Wa of the wafer W with respect to one division planned line. Since the two or more induction-modified layers Mi and at least one adjustment-modified layer Ma for adjusting the growth of cracks from the modification layer M to the surface Wa of the wafer W are formed in a composite manner. The cracks generated from the modified layer M by the induction modified layer Mi are induced to the surface Wa side of the wafer W, and the growth of cracks reaching the surface Wa is adjusted by the adjustment modified layer Ma. The It is possible to prevent meandering kerf near the corner or caused lack of the device chip corner of that or generated upon the division into devices D. Further, since the adjustment modified layer Ma has the non-modified layer region 2 separated by a predetermined interval H1, when the dividing step is performed, the adjacent device D is placed by the non-modified layer region 2. Since the timing at which the device D is separated into pieces is adjusted so as not to contact, it is possible to effectively prevent the corner of the device D from being chipped or the kerf near the corner from meandering.

  The modified layer M1 (first modified layer m1 and second modified layer m2) shown in FIG. 6 is formed inside the wafer W1 by the first modification of the modified layer forming step. . Similarly to the above, the modified layer M1 is a single layer induction formed at a position closest to the surface Wa side of the wafer W1 by performing the first modified layer forming step and the second modified layer forming step. The modification layer Mi2 and the two adjustment modification layers Ma formed on the induction modification layer Mi2.

  When the induction modified layer Mi2 is formed inside the wafer W1, the laser beam irradiation means 20 adjusts by shifting the position of the condenser 22 and positioning the condensing point P of the laser beam LB on the surface Wa side. Control is performed to stop irradiation of the laser beam LB at least once for one side of each device D by providing a predetermined interval H2 shorter than the non-modified layer region 2 of the modified layer Ma. Specifically, the laser beam irradiating means 20 is used in the first scheduled division line S1 or the second scheduled division line S2 shown in FIG. 1 or in both the first scheduled division line S1 and the second scheduled division line S2. The laser beam LB is irradiated to the area other than the predetermined interval H2 without irradiating the portion provided with the predetermined interval H2 with the laser beam LB. The induction modified layer Mi2 thus formed has a non-modified layer region 3 smaller than the non-modified layer region 2 with a predetermined interval H2 inside the wafer W1, and is a portion irradiated with the laser beam LB. The strength has decreased. The non-modified layer region 3 is a region where cracks do not occur when divided, as with the non-modified layer region 2.

  After carrying out the first modification of the modified layer forming process, the process proceeds to the same dividing process as described above, and cracks reaching the surface Wa of the wafer W1 from the modified layer M1 as a starting point by the grinding operation are processed in the first divided line S1. And it grows along 2nd division | segmentation scheduled line S2. That is, when a crack is generated from the position where the modified layer M1 is formed, the induced modified layer Mi2 induces the crack toward the surface Wa side. In addition, the device D is separated so that no cracks are generated from the non-modified layer region 2 of the adjustment modified layer Ma and the non-modified layer region 3 of the induction modified layer Mi2, and the adjacent devices D do not contact each other. The timing can be adjusted to divide the wafer W1 into individual devices D. As described above, in the modified layer M1, the induction modified layer Mi2 has the non-modified layer region 3 smaller than the non-modified layer region 2 of the adjustment modified layer Ma. Since cracks are not induced on the surface Wa of the wafer W1 from the modified layer region 3 as well, the movement of the device D to be separated can be restricted, and the corner of the device D may be chipped or the kerf near the corner may be generated. Can be more effectively prevented from meandering.

  The modified layer M2 (first modified layer m1 and second modified layer m2) shown in FIG. 7 is formed inside the wafer W2 by the second modification of the modified layer forming step. . Similarly to the above, the modified layer M2 is a single layer induction formed in the position closest to the surface Wa side of the wafer W2 by performing the first modified layer forming step and the second modified layer forming step. The reforming layer Mi2 and the two adjustment reforming layers Ma and Ma2 formed on the induction reforming layer Mi2 and having a predetermined interval are different. The configurations of the induction modification layer Mi2 and the adjustment modification layer Ma are the same as those in the first modified example.

  When forming the adjustment modified layer Ma2 inside the wafer W2, the laser beam irradiation means 20 is provided with a predetermined interval H3 longer than the non-modified layer region 3 and shorter than the non-modified layer region 2, Control is performed to stop the irradiation of the laser beam LB at least once for one side of the device D. Specifically, the laser beam irradiating means 20 is used in the first scheduled division line S1 or the second scheduled division line S2 shown in FIG. 1 or in both the first scheduled division line S1 and the second scheduled division line S2. The laser beam LB is irradiated to the region other than the predetermined interval H2 without irradiating the laser beam LB to the portion provided with the predetermined interval H3. The adjustment modified layer Ma2 has a non-modified layer region 4 that is larger than the non-modified layer region 3 and smaller than the non-modified layer region 2 with a predetermined interval H3 inside the wafer W2, and includes a laser beam. The intensity of the portion irradiated with LB is reduced.

  After carrying out the second modification of the modified layer forming process, the process proceeds to the same dividing process as described above, and cracks reaching the surface Wa of the wafer W2 from the modified layer M2 as a starting point by the grinding operation are divided into the first scheduled dividing line S1. And it grows along 2nd division | segmentation scheduled line S2. That is, when a crack is generated from the position where the modified layer M2 is formed, the crack is induced toward the surface Wa by the induction modified layer Mi2. Further, no cracks are generated from the non-modified layer regions 2, 3, and 4, and the timing at which the device D is separated is adjusted, so that the wafer W 2 can be divided into individual devices D. In this way, the modified layer M2 is divided into individual pieces because the region not irradiated with the laser beam LB from the back surface Wb to the front surface Wa of the wafer W2 is gradually reduced in the order of the non-modified layer regions 2, 4 and 3. The movement of the device D can be restricted, and the occurrence of chipping at the corner of the device D or the meandering of the chipped portion can be prevented.

  Examples of the laser irradiation conditions used in the modified layer forming step shown in the present embodiment include a light source, a wavelength, an output, a feed rate of the holding table 10, and a width of a predetermined interval H1 to H3 where the laser beam LB is not irradiated. The predetermined intervals H <b> 1 to H <b> 3 set for each division-scheduled line may not be constant intervals. Since the central portion of the wafer W is less likely to move than the outer peripheral portion and an undivided region is likely to occur, for example, the width of the predetermined intervals H1 to H3 may be set narrow in the central portion region. Examples of the grinding conditions used in the dividing step include the type of grinding wheel 33, the grinding feed speed, the rotational speed of the chuck table 40, and the like. The laser irradiation conditions and the grinding conditions may be adjusted and combined as appropriate according to the thickness and material of the wafer W.

1: protective member 2, 3, 4: unmodified layer region 5: gap 6: height position 10: holding table 11: holding surface 20: laser beam irradiation means 21: oscillator 22: condenser 30: grinding means 31: Spindle 32: Grinding wheel 33: Grinding wheel 40: Chuck table 41: Holding part 42: Holding surface 50: Tape expanding means 51: Support table 52: Frame mounting table 53: Clamping part 54: Lifting means 54a: Cylinder 54b: Piston W , W1, W2: Wafer Wa: Front surface Wb: Back surface D: Device S1: First division planned line S2: Second division planned line M, M1, M2: Modified layer m1: First modified layer m2: Second modified layer Mi, Mi2: induction modified layer Ma, Ma2: adjusted modified layer H1, H2, H3: predetermined intervals

Claims (3)

Device in a plurality of regions defined by a plurality of first division lines extending in a predetermined direction on the surface and a plurality of second division lines formed intersecting with the plurality of first division lines Is a wafer processing method for dividing the wafer formed along the first division line and the second division line,
A protective member attaching step for attaching a protective member to the surface side of the wafer;
After the protective member attaching step, the first splitting schedule is performed by holding the protective member side and positioning a laser beam having a wavelength that is transmissive to the wafer from the back side of the wafer with the focusing point inside the wafer. A first modified layer forming step of irradiating along a line and forming a first modified layer along the first division line inside the wafer;
A laser beam having a wavelength that is transmissive to the wafer is irradiated from the back side of the wafer at the focal point inside the wafer along the second division line, and the second division is scheduled inside the wafer. A second modified layer forming step of forming a second modified layer along the line;
After carrying out the first modified layer forming step and the second modified layer forming step, the protective member side is held and ground from the back surface of the wafer by a grinding means to reduce to a finished thickness. A splitting step of growing a crack reaching the surface of the wafer from the modified layer as a starting point by a grinding operation along the planned dividing line, and dividing the wafer into individual devices, and
In the first modified layer forming step or in the second modified layer forming step or in both the first modified layer forming step and the second modified layer forming step,
The modified layer reaches at least one or more induction modified layers for inducing growth of cracks from the modified layer to the surface of the wafer, and from the modified layer to the surface of the wafer for each division line. A method of processing a wafer, wherein the wafer is formed in a composite manner with at least one modified layer for adjusting crack growth.   The adjustment modified layer has a non-modified layer region with a predetermined interval inside the wafer by stopping irradiation of the laser beam at least once with respect to one side of each device with a predetermined interval. The wafer processing method according to claim 1.   The induction modified layer has a predetermined interval shorter than that of the non-modified layer region, and stops irradiation of the laser beam at least once with respect to one side of each device. 3. The wafer processing method according to claim 2, further comprising a non-modified layer region that is smaller than the non-modified layer region with a gap therebetween.

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