JP6600237B2 - Wafer dividing method and laser processing apparatus - Google Patents

Description

  The present invention relates to a method for dividing a wafer into individual devices and a laser processing apparatus used therefor.

  As a method of dividing a workpiece such as a semiconductor wafer into individual devices, for example, a condensing point of a laser beam having a wavelength that is transmissive to the workpiece is placed inside the workpiece corresponding to the planned division line. By positioning and relatively scanning the laser beam and the work piece, an altered layer is formed inside the wafer, and then an external force is applied along the planned dividing line where the strength is reduced to cover the altered layer as the starting point. There is a method of dividing a workpiece (for example, see Patent Document 1 below).

JP 2009-283753 A

  However, when the altered layer is formed using the above-described method, the laser beam overlaps the altered layer formed by condensing the laser beam, and the laser beam in the altered layer has a direction different from the focal point (laser beam). The light is scattered in a direction different from the direction in which the light is condensed, and is absorbed by the wiring of the device to damage the device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a laser beam from overlapping an altered layer formed inside a wafer so as not to damage the device.

The present invention is directed to irradiating a wafer having a device having a wavelength divided by a predetermined division line with a laser beam having a transparency, and condensing the wafer inside the wafer to cause an altered layer along the predetermined division line. Forming a wafer, and dividing the wafer along the planned dividing line, the holding step of holding the wafer with a holding table, and the dividing line of the wafer held in the holding step Is irradiated with two laser beams from two directions across the planned division line intersecting the beam, and is condensed inside the wafer, and the laser beam and the holding table are processed relatively parallel to the planned division line. Bei feed to the deteriorated layer forming step of forming the modified electrolyte layer, after the said alteration electrolyte layer formation step, a dividing step of dividing the modified protein layer as a starting point by applying an external force along the dividing lines, the In the modified electrolyte layer formation step, you irradiated from the rear side of the two laser beams relative to the processing-feed direction.

The present invention is a laser processing apparatus, which holds a wafer that is partitioned by lines to be divided and on which a device is formed, and irradiates a laser beam having a wavelength that is transparent to the wafer held by the holding table. Then, a laser processing means for forming a deteriorated layer along the scheduled dividing line inside the wafer, and a processing for processing and feeding the holding table and the laser processing means in a direction parallel to the upper surface of the wafer. and a feeding means, a laser machining apparatus for forming the modified protein layer inside the wafer, the laser machining means, said dividing intersecting the machining feed direction of the dividing line of the feeding means comprising a first and a laser processing unit and a second laser processing unit for matching the focal point from two directions across the lines by irradiating two laser beams to the inside of the wafer, and said Of the laser processing unit and a laser processing part of the second, irradiating the two laser beams from the rear side with respect to the processing-feed direction.

  The laser processing apparatus is transparent to the wafer in a direction perpendicular to the upper surface of the wafer at a condensing point where the laser beam irradiated by the first laser processing unit and the second laser processing unit is focused. A third laser processing unit that irradiates a laser beam having a wavelength having the above-described characteristics, and extending the altered layer from the condensing point toward the upper surface of the wafer by irradiation of the laser beam by the third laser processing unit. You can also.

  The method for dividing a wafer according to the present invention includes a deteriorated layer that forms a deteriorated layer by irradiating two laser beams from two directions intersecting with the wafer division planned line held in the holding step so as to be condensed inside the wafer. Since the forming step is provided, the two laser beams irradiated along the division planned lines are not irradiated so as to overlap the deteriorated layer formed by the laser beam irradiation. Therefore, it is possible to prevent the laser beam from being scattered in a different direction from the condensing point in the altered layer, and to prevent the device from being damaged.

  A laser processing apparatus according to the present invention includes a holding table for holding a wafer, and a deteriorated layer along a predetermined division line inside the wafer by irradiating a laser beam having a wavelength that is transparent to the wafer held by the holding table. And a processing feed means for processing and feeding the holding table and the laser processing means in a direction relatively parallel to the upper surface of the wafer. The laser processing means is a processing feed of the processing feed means. In order to provide the first laser processing unit and the second laser processing unit that irradiate two laser beams from two directions intersecting the direction to make the condensing point coincide with each other inside the wafer, Even if two laser beams are irradiated along the planned dividing line from the first laser processing unit and the second laser processing unit while processing and feeding Laser beam by the formation of the damaged layer will not overlap. Therefore, it is possible to prevent the laser beam from being scattered in a different direction from the condensing point in the altered layer, and to prevent the device from being damaged.

  The laser processing apparatus is directed to the wafer in a direction perpendicular to the upper surface of the wafer, including a condensing point for condensing the laser beam irradiated by the first laser processing unit and the second laser processing unit. In the case of including a third laser processing unit that irradiates a laser beam having a wavelength having transparency, the first laser processing unit and the second laser processing unit irradiate the laser beam by the third laser processing unit. The altered layer can be extended from the condensing point of the two laser beams to the upper side toward the upper surface of the wafer. As a result, it is possible to form a deteriorated layer that facilitates division within the wafer without damaging the device.

It is a perspective view which shows an example of a laser processing apparatus. It is a perspective view which shows the wafer united with the flame | frame via the protective tape. It is sectional drawing which shows a part of structure of a laser processing means. It is a partially expanded plan view which shows the 1st example of a deteriorated layer formation process. It is a partially expanded sectional view which shows the 1st example of a deteriorated layer formation process. It is a partially expanded plan view which shows the 2nd example of a deteriorated layer formation process. It is a partially expanded sectional view which shows the 2nd example of a deteriorated layer formation process. It is a partially expanded plan view which shows the 3rd example of a deteriorated layer formation process. It is sectional drawing which shows a part of modification of a laser processing means.

  A laser processing apparatus 1 shown in FIG. 1 is a laser processing apparatus that forms a deteriorated layer inside a wafer W that is a workpiece. A wafer W shown in FIG. 2 is an example of a workpiece to be subjected to laser processing, and a device D is formed in each region partitioned by a grid-shaped division planned line S on the surface Wa. A back surface Wb opposite to the front surface Wa is an irradiated surface on which a laser beam is incident.

  The laser processing apparatus 1 has an apparatus base 2. The apparatus base 2 includes a holding table 3 having a holding surface 3a for holding the wafer W, an image pickup means 6 for picking up an area of the wafer W to be laser processed (division planned line S), and a wafer held by the holding table 3. A laser processing means 30 for irradiating a laser beam having a wavelength having transparency to W to form a deteriorated layer inside the wafer W; a processing feed means 10 for processing and feeding the holding table 3 in the X-axis direction; and a laser. Index feeding means 40 for indexing the processing means 30 and the imaging means 6 in the Y-axis direction, and an elevating means 50 for raising and lowering the laser processing means 30 and the imaging means 6 in the Z-axis direction are provided.

  The holding table 3 is fixed on the cover table 4, and a rotating means 5 is connected to the lower part of the cover table 4. The rotating means 5 can rotate the holding table 3 by a predetermined angle. A suction source (not shown) is connected to the holding table 3. The holding table 3 can suck and hold the wafer W on the holding surface 3a on which the suction force of the suction source acts.

  The processing feed means 10 includes a ball screw 11 extending in the X-axis direction, a motor 12 connected to one end of the ball screw 11, a pair of guide rails 13 extending parallel to the ball screw 11, and the other end of the ball screw 11. A bearing 14 that is rotatably supported and a moving base 15 that supports the holding table 3 are provided. One surface of the moving base 15 is in sliding contact with the pair of guide rails 13, and a ball screw 11 is screwed to a nut formed at the center of the moving base 15. When the motor 12 rotates the ball screw 11, the moving base 15 moves in the X-axis direction along the guide rail 13, and the holding table 3 can be moved in the same direction.

  The index feed means 40 includes a support portion 41 that supports the laser processing means 30, a ball screw 42 that extends in the Y-axis direction, a motor 43 that is connected to one end of the ball screw 42, and a pair that extends in parallel with the ball screw 42. The guide rail 44 is provided. The lower surface of the support portion 41 is in sliding contact with the pair of guide rails 44, and a ball screw 42 is screwed into a nut formed at the lower portion of the support portion 41. When the motor 43 rotates the ball screw 42, the support portion 41 is guided by the guide rail 44 and moves in the Y-axis direction, and the laser processing means 30 and the imaging means 6 can be moved in the same direction.

  The elevating means 50 includes at least a ball screw (not shown) extending in the Z-axis direction and a motor 51 connected to one end of the ball screw. The motor 51 rotates the ball screw, whereby the laser processing means 30 and the imaging means 6 are provided. Can be moved up and down in the Z-axis direction.

  The laser processing unit 30 irradiates two laser beams from two directions (Y-axis direction) intersecting with the processing feed unit 10 (X-axis direction) to make the condensing point coincide with the inside of the wafer W. The laser beam irradiated from the laser processing unit 31, the second laser processing unit 32, and the first laser processing unit 31 and the second laser processing unit 32 is perpendicular to the upper surface of the wafer W. And a third laser processing unit 33 that emits a laser beam in the direction.

  As shown in FIG. 3, the first laser processing unit 31 condenses the laser beam 310 that oscillates a laser beam having a wavelength that is transmissive to the wafer W, and the laser beam that is oscillated from the laser oscillator 310. A condensing lens 311 and a mirror 312 for guiding the laser beam condensed by the condensing lens 311 to a predetermined position (division planned line S) inside the wafer W are provided. Although not shown, the laser oscillator 310 includes an output adjusting unit that adjusts the output of the laser beam and a repetition frequency setting unit. The laser oscillator 310 can oscillate a pulsed laser beam having a wavelength that is transmissive to the wafer W. Similarly to the first laser processing unit 31, the second laser processing unit 32 also has a laser oscillator 320 that oscillates a pulsed laser beam having a wavelength that is transmissive to the wafer W, a condensing lens 321, and a mirror 322. And.

  In the first laser processing unit 31 and the second laser processing unit 32, the two laser beams oscillated from the laser oscillator 310 and the laser oscillator 320 have a condensing point inside the wafer W along the division line S. The mirror 312 and the mirror 322 are tilted so as to coincide with each other. Therefore, the two laser beams oscillated from the laser oscillator 310 and the laser oscillator 320 are reflected by the mirror 312 and the mirror 322 via the condenser lens 311 and the condenser lens 321, and the portion of the wafer W corresponding to the division line S is scheduled. Is introduced from the upper surface of the substrate, and is guided to a position where it does not overlap the deteriorated layer that has already been irradiated with the laser beam.

  As shown in FIG. 1, the third laser processing unit 33 is disposed between the first laser processing unit 31 and the second laser processing unit 32. The third laser processing unit 33 includes a laser oscillator 330 (illustrated in FIG. 6) that oscillates a laser beam having a wavelength that is transmissive to the wafer W. Although not shown, the laser oscillator 330 includes an output adjustment unit that adjusts the output of the laser beam and a repetition frequency setting unit. In the third laser processing unit 33, the condensing point of the two laser beams irradiated from the first laser processing unit 31 and the second laser processing unit 32 from above the division planned line S of the wafer W, A guiding pulse laser beam can be irradiated in a direction perpendicular to the upper surface of the wafer W, and the altered layer can be extended from the condensing point toward the upper surface of the wafer W.

  Next, a wafer dividing method for forming a deteriorated layer inside the wafer W using the laser processing apparatus 1 and dividing the wafer W into individual devices D starting from the deteriorated layer will be described. As shown in FIG. 2, the wafer W is integrated with the annular frame F in a state where the front surface Wa side is attached to the protective tape T attached to the annular frame F and the back surface Wb side is exposed upward. Formed.

(1) Holding process The wafer W is held by the holding table 3. Specifically, it is placed on the holding surface 3a of the holding table 3 from the protective tape T side, and the back surface Wb of the wafer W shown in FIG. 2 is exposed upward. Subsequently, the wafer W is sucked and held by the holding surface 3 a of the holding table 3 by a suction force of a suction source (not shown).

(2) Altered Layer Formation Step After performing the holding step, the altered layer is formed at a predetermined position inside the wafer W using the laser processing means 30. Before starting the laser processing, the holding table 3 is positioned below the imaging unit 6 by the processing feeding unit 10, the wafer W is imaged by the imaging unit 6, and image processing such as pattern matching is performed. The alignment which detects the division | segmentation scheduled line S which should be laser-processed is performed.

  With reference to FIGS. 4 and 5, as a first example of the deteriorated layer forming step, a case where a deteriorated layer is formed inside the wafer W by the first laser processing unit 31 and the second laser processing unit 32 will be described. To do. After the alignment, as shown in FIG. 4, positions in two directions on the same axis line (Y-axis direction) intersecting the extending direction (X-axis direction) of the planned division line S (Y-axis direction) The first laser processing unit 31 and the second laser processing unit 32 positioned at the −Y-axis direction side and the + Y-axis direction side with respect to S as the center are two laser beams inside the wafer W. Irradiate.

  Specifically, the laser oscillator 310 of the first laser processing unit 31 oscillates a laser beam LB1 having a wavelength that is transmissive to the wafer W, and the laser oscillator 320 of the second laser processing unit 32 includes: A laser beam LB2 having a wavelength that is transparent to the wafer W is oscillated. Note that the outputs of the laser beam LB1 and the laser beam LB2 are adjusted to a lower output by the output adjusting unit (not shown) than when the altered layer is formed by irradiating a single laser beam.

  The laser beam LB1 oscillated from the laser oscillator 310 is condensed at the condensing point 7 on the division line S by the condenser lens 311 and the laser beam LB2 oscillated from the laser oscillator 320 is divided by the condenser lens 321. The light is condensed at the condensing point 7 on the planned line S. That is, the two laser beams LB1 and LB2 are irradiated with the converging points 7 coincident with each other at the scheduled division line S.

  The first laser processing unit 31 and the second laser processing unit 32 irradiate the laser beam LB1 and the laser beam LB2 along the planned division line S, and the holding table 3 and the first laser processing unit shown in FIG. The condensing point 7 is moved along the scheduled division line S by processing and feeding the 31 and the second laser processing unit 32 in a direction parallel to the back surface Wb of the wafer W (+ X axis direction). Then, as shown in the partially enlarged view, the deteriorated layer 8 having reduced strength is formed at a predetermined depth position inside the wafer W. At this time, the laser beam LB1 and the laser beam LB2 applied to the wafer W to be processed and fed do not overlap the altered layer 8 formed by the irradiation of the laser beam LB1 and the laser beam LB2. The laser beam is not scattered in a direction different from the direction in which the laser beam LB1 and the laser beam LB2 are condensed.

  Further, since the laser beam LB1 and the laser beam LB2 are incident on the back surface Wb of the wafer W obliquely (from the direction inclined with respect to the Z axis) from both side portions of the division planned line S, the laser beam LB1 and the laser beam. The heat of LB2 can be released upward. Then, when the deteriorated layer 8 is formed by irradiating the laser beam LB1 and the laser beam LB2 along all the division lines S of the wafer W, the deteriorated layer forming step is completed.

  Next, referring to FIGS. 6 and 7, as a second example of the deteriorated layer forming step, in addition to the first laser processing unit 31 and the second laser processing unit 32, a third laser processing unit 33 is provided. The case where the deteriorated layer is formed inside the wafer W will be described. Similar to the first example of the deteriorated layer forming step, after performing alignment, from two directions on the same axis in the direction (Y-axis direction) intersecting the extending direction (X-axis direction) of the planned division line S The first laser processing unit 31 and the second laser processing unit 32 irradiate the inside of the wafer W with two laser beams.

  The laser oscillator 330 of the third laser processing unit 33 oscillates a guiding laser beam LB3 having a wavelength that is transmissive to the wafer W. In the 3rd laser processing part 33, the condensing point 7 which the two laser beams irradiated from the 1st laser processing part 31 and the 2nd laser processing part 32 condense is included in the irradiation range of laser beam LB3. Thereby, the spot diameter of the laser beam LB3 is set larger than at least the spot diameters of the laser beam LB1 and the laser beam LB2. Based on this setting, the laser oscillator 330 irradiates a laser beam LB3 having an optical axis in the vertical direction with respect to the upper surface (back surface Wb) of the wafer W from above the planned division line S.

  The laser beam LB1 and the laser beam LB2 are irradiated along the planned division line S from the first laser processing unit 31 and the second laser processing unit 32, and the laser beam LB3 is divided from the third laser processing unit 33. While irradiating along S, the holding table 3 shown in FIG. 7 and the first laser processing unit 31, the second laser processing unit 32, and the third laser processing unit 33 are relatively placed on the back surface Wb of the wafer W. By processing and feeding in a parallel direction (+ X-axis direction), the condensing point 7 is moved along the scheduled division line S, and the altered layer 8a is formed at a predetermined depth position inside the wafer W. At this time, the altered layer 8a formed by the irradiation of the laser beam LB1 and the laser beam LB2 within the irradiation range of the laser beam LB3 may be extended from the condensing point 7 toward the upper surface (back surface Wb) of the wafer W. it can. That is, the deteriorated layer 8a is formed to be elongated from the position of the condensing point 7 upward as shown in the partial enlarged view. As a result, it is possible to form the altered layer 8a that facilitates the division inside the wafer W without damaging the device D shown in FIG. Further, the laser beam LB3 by the third laser processing unit 33 may be condensed. In the case of focusing, the focusing point is positioned so as to overlap the upper side of the wafer at the focusing point 7 of the laser beam LB1 and the laser beam LB2. Even in this way, the altered layer 8a can be extended from the condensing point 7 toward the upper surface (back surface Wb) of the wafer W.

  Next, referring to FIG. 8, as a third example of the deteriorated layer forming step, two laser beams are irradiated from the rear side in the processing feed direction (+ X axis direction) of the wafer W to enter the inside of the wafer W. The case where the altered layer is formed will be described. Specifically, the first laser processing unit 31 is disposed to be inclined to the rear side of the side portion side (−Y axis direction side) of the planned division line S, and the second laser processing unit 32 is arranged on the planned division line S. It is inclined and arranged at the rear position on the side part side (+ Y-axis direction side). By irradiating the laser beam LB1 and the laser beam LB2 along the planned division line S by the first laser processing unit 31 and the second laser processing unit 32 arranged in this way, the inside of the wafer W can be obtained. The altered layer 8 is formed. By irradiating the two laser beams LB1 and LB2 from the rear side with respect to the processing feed direction (+ X-axis direction) of the wafer W, it is possible to further prevent the laser beams from overlapping the altered layer 8. Also in this case, although not shown, the laser beam LB3 may be applied from above the planned division line S by the third laser processing unit 33.

(3) Dividing process After the altered layer forming process, an external force is applied along the scheduled division line S to divide the altered layer 8 as a starting point. The wafer W can be divided using, for example, a braking device including a pressing member. In this case, an external force is applied along the scheduled division line S by the pressing member, and the wafer W is divided into the individual devices D shown in FIG. Thereafter, the separated device D is picked up by a transport means (not shown) and transported to a desired transport destination.

  As described above, in the method for dividing a wafer according to the present invention, the deteriorated layer 8 is irradiated with two laser beams from two directions intersecting the planned division line S of the wafer W to be condensed inside the wafer W. The laser beam LB1 and the laser beam LB2 that are repeatedly irradiated to the wafer W from the first laser processing unit 31 and the second laser processing unit 32 have already been converted into the laser beam LB1 and There is no overlap with the deteriorated layer 8 formed by irradiation with the laser beam LB2. Therefore, in the altered layer 8, it is possible to suppress the laser beam from being scattered in a direction different from the direction in which the laser beam LB1 and the laser beam LB2 are condensed, and to prevent the device D from being damaged.

  The configuration of the laser processing means 30 is not limited to the above configuration. For example, a laser beam oscillated from one laser oscillator 34 may be split into two laser beams by a beam splitter 35 as in the laser processing means 30a shown in FIG. The beam splitter 35 is disposed on the optical path of the laser beam oscillated by the laser oscillator 34. On the optical path of the laser beam branched by the beam splitter 35, a mirror 36 for reflecting the laser beam toward the condenser lens 311 is disposed. Then, the reflected light oscillated from the laser oscillator 34 and reflected by the beam splitter 35 is irradiated onto the wafer W as the laser beam LB1 of the first laser processing unit 31, and is branched from the laser oscillator 34 and branched by the beam splitter 35. Is irradiated onto the wafer W as the laser beam LB2 of the second laser processing section 32. Note that the third laser processing unit 33 in this case is connected to an independent laser oscillator (not shown).

  As another configuration of the laser processing means 30, a laser beam oscillated from one laser oscillator is split by a beam splitter into a high-power laser beam and a low-power laser beam, and the high-power laser beam is half-cut. The laser beam may be split by a mirror and guided to the first laser processing unit 31 and the second laser processing unit 32, and a low-power laser beam may be guided to the third laser processing unit 33.

1: Laser processing device 2: Device base 3: Holding table 3a: Holding surface 4: Cover table 5: Rotating means 6: Imaging means 7: Condensing point 8: Altered layer 10: Processing feed means 11: Ball screw 12: Motor 13 : Guide rail 14: Bearing portion 15: Moving base 30, 30 a: Laser processing means 31: First laser processing portion 310: Laser oscillator 311: Condensing lens 312: Mirror 32: Second laser processing portion 320: Laser oscillator 321: Condensing lens 322: Mirror 33: Third laser processing part 330: Laser oscillator 34: Laser oscillator 35: Beam splitter 36: Mirror 40: Index feeding means 41: Support part 42: Ball screw 43: Motor 44: Guide rail 50: Lifting means 51: Motor

Claims (3)

Irradiating a laser beam having a wavelength having transparency with respect to the wafer partitioned by the planned dividing line and condensing inside the wafer to form a deteriorated layer in the interior along the planned dividing line, A method for dividing a wafer, wherein the wafer is divided along the planned division line with the altered layer as a starting point,
A holding step for holding the wafer on a holding table;
Two laser beams are irradiated from two directions sandwiching the planned division line that intersects the planned division line of the wafer held in the holding step to be condensed inside the wafer, and the laser beam, the holding table, A deteriorated layer forming step of forming the deteriorated layer by processing and relatively moving in parallel to the planned dividing line ;
After the deteriorated layer forming step, a dividing step of applying an external force along the planned division line and dividing the deteriorated layer as a starting point , and
In the modified electrolyte layer forming step, the wafer dividing method you irradiated from the rear side of the two laser beams relative to the processing-feed direction. A holding table for holding a wafer that is divided by a planned dividing line and on which a device is formed, and a laser beam having a wavelength that is transparent to the wafer held by the holding table is irradiated on the planned dividing line inside the wafer. Laser processing means for forming a deteriorated layer along the surface, and processing feed means for processing and feeding the holding table and the laser processing means in a direction parallel to the upper surface of the wafer. A laser processing apparatus for forming a deteriorated layer,
The laser machining means is a converging point within the illumination to a wafer processing feed direction of the dividing two laser beams from two directions across the dividing lines intersecting against the line of the feeding means A first laser processing unit and a second laser processing unit that are matched, and the first laser processing unit and the second laser processing unit transmit the two laser beams to the processing feed direction. Laser processing equipment that irradiates from the rear side . A laser beam having a wavelength that is transparent to the wafer in a direction perpendicular to the upper surface of the wafer at a condensing point where the laser beam irradiated by the first laser processing unit and the second laser processing unit is collected. A third laser processing unit for irradiating
3. The laser processing apparatus according to claim 2, wherein the deteriorated layer extends from the condensing point toward the upper surface of the wafer by irradiation with a laser beam from the third laser processing unit.

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