JP5770436B2 - Laser processing apparatus and laser processing method - Google Patents

Description

  The present invention relates to a laser processing apparatus and a laser processing method for forming a modified layer inside a workpiece by irradiating a workpiece such as an optical device wafer with a transparent laser beam.

  As a method of dividing a workpiece such as a semiconductor wafer or an optical device wafer along a planned dividing line formed on the workpiece, a pulse laser beam having transparency to the workpiece is used, and a condensing point is formed inside the region to be divided. Attempts have been made to use a laser processing method in which a pulsed laser beam is irradiated. The dividing method using this laser processing method is to irradiate a work with a pulse laser beam having a wavelength that is transmissive to the work, aligning the condensing point inside the work, and modifying the layer along the line to be divided inside the work. Are formed continuously. A workpiece | work is divided | segmented along a division | segmentation scheduled line by intensity | strength falling in the part in which the modified layer was formed, and external force being added (for example, refer patent document 1).

Japanese Patent No. 3408805

  By the way, when the optical device wafer is divided along the modified layer, if the depth (thickness) of the modified layer is insufficient with respect to the wafer thickness, a large force is required to divide the wafer. Cause chipping and oblique cracking. In order to improve the division property, it is necessary to form a modified layer having a sufficient depth inside the wafer by increasing the output of the pulse laser beam or by repeatedly irradiating the pulse laser beam. However, at the same time, damage to the light emitting device formed on the surface of the wafer also increases, and the electrical characteristics of the light emitting device may deteriorate.

  This invention is made in view of this point, and provides the laser processing apparatus and laser processing method which can achieve simultaneously the improvement of the division property of an optical device wafer, and suppression of the fall of the electrical property of a light emitting device. Objective.

The laser processing apparatus of the present invention includes a holding unit that holds a surface side of a sapphire wafer on which a plurality of light emitting devices partitioned by a division line is formed, and the division of the sapphire wafer held by the holding unit Pulse laser irradiation means for irradiating a pulse laser having a wavelength that passes through the sapphire wafer along a predetermined line, the pulse laser irradiation means comprising: an oscillator for oscillating a pulse laser; and a pulse laser oscillated by the oscillator And a condenser for irradiating the exposed surface of the sapphire wafer held by the holding means, and the condenser uses a pulse laser oscillated from the oscillator. Two condensing points displaced in the thickness direction of the sapphire wafer held by the holding means The pulse laser that is configured to focus and is focused on the far side from the exposed surface of the sapphire wafer is linearly polarized light whose vibration direction is parallel to the processing progress direction, and the exposure of the sapphire wafer The pulsed laser focused on the side closer to the surface is linearly polarized light whose vibration direction is orthogonal to the machining progress direction, and two types of modification with different splitting characteristics of the pulsed laser focused at two focused points The modified layer formed at the light condensing point far from the exposed surface has a low splitting characteristic, whereas the modified layer formed at the light condensing point near the exposed surface is It is characterized by high splitting characteristics .

Further, the laser processing method of the present invention holds the surface side of the sapphire wafer formed on the surface with a plurality of light-emitting devices partitioned by the division line, and along the division line of the held sapphire wafer The laser processing method of irradiating the sapphire wafer with a pulse laser having a wavelength that transmits the sapphire wafer, wherein the pulse laser is displaced in the thickness direction of the sapphire wafer and collected at two condensing points. The pulsed laser that is irradiated and focused on the side far from the exposed surface of the sapphire wafer is linearly polarized light whose vibration direction is parallel to the processing progress direction, and is focused on the side closer to the exposed surface of the sapphire wafer. The pulse laser is linearly polarized light whose vibration direction is orthogonal to the processing progress direction, and is focused on two condensing points. Two different types of modified layer formed divisions characteristics pulsed laser, the modified layer formed on the focal point remote from the exposed surface whereas breaking property is low, a side closer to the exposed surface The modified layer formed at the light condensing point is characterized by high splitting characteristics .

  According to these configurations, the linearly polarized pulse laser whose vibration direction is parallel to the processing progress direction is improved on the side far from the exposed surface of the sapphire wafer (the side closer to the light emitting device) with low splitting characteristics and small damage. A quality layer is formed. In addition, a linearly polarized pulsed laser whose vibration direction is orthogonal to the processing progress direction forms a modified layer with high splitting characteristics and high damage on the side close to the exposed surface of the sapphire wafer (the side far from the light emitting device). The Therefore, it is possible to simultaneously achieve improvement of the splitting property of the optical device wafer and suppression of deterioration of the electrical characteristics of the light emitting device.

  ADVANTAGE OF THE INVENTION According to this invention, the laser processing apparatus and laser processing method which can achieve simultaneously the improvement of the division | segmentation property of an optical device wafer, and suppression of the fall of the electrical property of a light-emitting device can be provided.

1 is a perspective view of a laser processing apparatus according to an embodiment of the present invention. It is a schematic diagram of the optical system of the laser processing apparatus which concerns on embodiment of this invention. It is explanatory drawing of the relationship between the polarization direction of the laser beam and the damage given to a wafer in the laser processing apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the relationship between the process advancing direction by the laser processing apparatus which concerns on embodiment of this invention, and a polarization direction. It is a schematic diagram of the optical system of the laser processing apparatus which concerns on the modification of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The configuration of the laser processing apparatus will be described with reference to FIG. FIG. 1 is a perspective view of a laser processing apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the laser processing apparatus 1 relatively moves a laser processing unit (pulse laser irradiation means) 26 that irradiates a wafer W with a laser beam and a holding table (holding means) 20 that holds the wafer W. The wafer W is configured to be processed. The wafer W is formed in a substantially disk shape, and is divided into a plurality of regions by dividing lines 64 arranged in a lattice pattern on the surface of the sapphire (Al ₂ O ₃ ) substrate. In the partitioned region, light emitting devices such as a light emitting diode (LED) and a laser diode (LD) are formed from a gallium nitride compound semiconductor or the like. The wafer W is supported by the annular frame 32 via the adhesive tape 31 with the device formation surface side on which the light emitting device is formed facing downward, and is carried into and out of the laser processing apparatus 1.

  In the present embodiment, a sapphire substrate will be described as an example of a single crystal substrate serving as a base of the wafer W, but the present invention is not limited to this configuration. As the wafer W, a GaAs (gallium arsenide) substrate, a SiC (silicon carbide) substrate, or the like may be used as a single crystal substrate. Further, as the wafer W, a single crystal substrate on which a gallium nitride compound semiconductor or the like is not stacked may be used.

  The laser processing apparatus 1 includes a rectangular parallelepiped processing table 10 and a support column 24 erected on the rear side of the upper surface of the processing table 10. An arm portion 25 protruding forward is provided on the front surface of the column portion 24, and a processing head 27 of the laser processing unit 26 is provided on the distal end side of the arm portion 25. A pair of guide rails 11 a and 11 b extending in the Y-axis direction are provided on the upper surface of the processing table 10. A motor-driven Y-axis table 12 supported so as to be movable in the Y-axis direction, which is the machining feed direction, is disposed on the pair of guide rails 11a and 11b.

  A pair of guide rails 15 a and 15 b extending in the X-axis direction are provided on the upper surface of the Y-axis table 12. A pair of guide rails 15a and 15b is provided with a motor-driven X-axis table 16 supported so as to be movable in the X-axis direction, which is the indexing feed direction. A holding table 20 is provided on the upper surface of the X-axis table 16. Further, nut portions (not shown) are formed on the back sides of the Y-axis table 12 and the X-axis table 16, respectively, and ball screws 13 and 17 are screwed to the nut portions, respectively. Drive motors 14 and 18 are connected to one end portions of the ball screws 13 and 17, and the ball screws 13 and 17 are rotationally driven by the drive motors 14 and 18.

  The holding table 20 includes a θ table 21 that can rotate around the Z-axis on the upper surface of the X-axis table 16, and a work holding unit 22 that is provided on the θ table 21 and holds the wafer W by suction. The work holding portion 22 has a disk shape having a predetermined thickness, and an adsorption surface is formed of a porous ceramic material at the center portion of the upper surface. The suction surface is a surface that sucks the wafer W through the sticking tape 31 by negative pressure, and is connected to a suction source through a pipe inside the θ table 21.

  Around the work holding part 22, four clamp parts 23 are provided via a pair of support arms extending radially outward from the four sides of the θ table 21. The four clamp parts 23 are driven by an air actuator to clamp and fix the annular frame 32 around the semiconductor wafer W from four directions.

  The laser processing unit 26 has a processing head 27 provided at the tip of the arm portion 25. The processing head 27 irradiates the wafer W with a laser beam that forms a modified layer inside the wafer W. An optical system (see FIG. 2) of the laser processing unit 26 is provided in the processing head 27, the arm portion 25, and the column portion 24. The optical system of the laser processing unit 26 is not limited to the configuration formed over the processing head 27, the arm portion 25, and the support column portion 24, and may be configured only in the processing head 27. .

  In this case, the laser beam is separated into two linearly polarized light in the optical system, and is adjusted so as to be condensed in two condensing points by being displaced in the thickness direction of the wafer W. One linearly polarized light is a vibration direction parallel to the processing progress direction and is condensed at a position close to the light emitting device, and the other linearly polarized light is a vibration direction orthogonal to the processing progress direction and a position away from the light emitting device. It is condensed with. In this way, two types of modified layers serving as division starting points are formed inside the wafer W. The modified layer refers to a region where the density, refractive index, mechanical strength, and other physical characteristics inside the wafer differ from those of the surroundings due to the irradiation of the laser beam, and the strength is lower than that of the surroundings. The modified layer is, for example, a melt treatment region, a crack region, a dielectric breakdown region, a refractive index change region, or the like, and may be a region in which these are mixed.

  Here, the optical system of the laser processing apparatus will be described in detail with reference to FIG. FIG. 2 is a schematic diagram of an optical system of the laser processing apparatus according to the embodiment of the present invention.

  As shown in FIG. 2, the optical system of the laser processing apparatus includes an oscillator 41 that oscillates a linearly polarized pulse laser beam that is transmissive to the wafer W, and a laser beam 47 that is oscillated by the oscillator 41. A condenser 44 that collects light is provided inside. On the optical path of the laser beam 47 oscillated from the oscillator 41, a λ / 2 wavelength plate 42, a mirror 43, and the condenser 44 described above are arranged. This concentrator 44 disperses the laser beam 47 oscillated from the oscillator 41 in the thickness direction of the wafer W and condenses it at two locations, and has a birefringent lens 45 and an objective lens 46. Composed. The objective lens 46 may be a single lens or a combination lens.

  The linearly polarized laser beam 47 emitted from the oscillator 41 has its linear polarization direction rotated by the rotation angle of the transmitting λ / 2 wavelength plate 42, and the ratio of the two orthogonal linearly polarized light components is adjusted. One of the two orthogonally polarized light components orthogonal to each other is a linearly polarized light component parallel to the processing progress direction, and the other is a linearly polarized light component orthogonal to the processing progress direction. The laser beam 47 transmitted through the λ / 2 wavelength plate 42 is reflected by the mirror 43 toward the birefringent lens 45. In addition, the ratio of two orthogonally polarized light components orthogonal to each other may be adjusted to 1: 1, and can be flexibly changed according to a processing target.

  The birefringent lens 45 is configured by combining a glass body 451 having a concave surface 451a and a crystal body 452 having a convex surface 452a. The birefringent lens 45 configured in this manner separates the laser beam 47 into separated light 47a indicated by a solid line and separated light 47b indicated by a one-dot chain line. The separated light 47a is linearly polarized light whose vibration direction is orthogonal to the machining progress direction, and the separated light 47b is linearly polarized light whose vibration direction is parallel to the machining progress direction. The birefringent lens 45 allows the separated light 47a to pass through without being refracted, and allows the separated light 47b to be refracted by the crystal body 452 to pass therethrough.

  The objective lens 46 condenses the separated light 47 a separated by the birefringent lens 45 on a condensing point 48 a inside the wafer W, and condenses the separated light 47 b on a condensing point 48 b inside the wafer W. Since the separated light 47b is refracted outward by the birefringent lens 45, the condensing point 48b is located at a position deeper than the condensing point 48a of the separated light 47a (position close to the device formation surface Wb), that is, from the objective lens 46. It is formed at a distant position.

  When the separated light 47a of the laser beam 47 is condensed at the condensing point 48a, a modified layer is formed in the vicinity of the condensing point 48a. Similarly, when the separated light 47b of the laser beam 47 is condensed at the condensing point 48b, a modified layer is formed in the vicinity of the condensing point 48b. In this case, as will be described in detail later, the modified layer formed on the separation light 47a has excellent splitting characteristics, and damage to the wafer W is large. In addition, the modified layer formed in the separation light 47b has low splitting characteristics and little damage to the wafer W. Therefore, a modified layer having excellent splitting characteristics is formed at a position close to the exposed surface Wa of the wafer W, that is, a position away from the device forming surface Wb, and is formed at a position far from the exposed surface Wa of the wafer W, that is, the device forming surface Wb. A modified layer in which electrical characteristics are unlikely to deteriorate is formed at a close position.

  Then, the laser processing apparatus 1 feeds the holding table 20 to the processing head 27 along the scheduled division line 64 in the processing progress direction (Y-axis direction) indicated by the arrow D1, thereby bringing the holding table 20 into the wafer W. Upper and lower two rows of modified layers are formed. Thus, by forming the upper and lower two rows of modified layers inside the wafer W, a modified layer having a sufficient depth can be formed, and the division characteristics can be improved. Note that the modified layer may be formed continuously along the planned division line, or may be formed intermittently.

  With reference to FIG. 3, the relationship between the polarization direction of the separated light and the damage to the wafer will be described. FIG. 3 is an explanatory diagram of the relationship between the polarization direction of the laser beam and the damage given to the wafer in the laser processing apparatus according to the present embodiment. In FIG. 3A, B1 is a schematic plan view of the laser beam, B2 is a schematic side view of the laser beam viewed from the X-axis direction, and B3 is a schematic side view of the laser beam viewed from the Y-axis direction.

  FIG. 3B is an enlarged schematic diagram of the condensing point. In addition, the condensing point in FIG. 3 is shown in the annular | circular shape for convenience of explanation, and the tendency of the energy distribution of the separated light is indicated by hatching. A portion where the energy density of the condensing point tends to be high is indicated by dark hatching, and a portion where the energy density of the condensing point tends to be low is indicated by thin hatching.

  In the plan view indicated by B1 in FIG. 3A, the laser beam 47 is polarized in the Y-axis direction indicated by the arrow D2. The laser beam 47 is focused to a smaller spot diameter inside the wafer W. In this case, on the Y side view side indicated by B2, the laser beam 47 is oscillating parallel to the incident surface as indicated by an arrow D3. Therefore, the incident light on the wafer W of the laser beam 47 becomes p-polarized light parallel to the incident surface, so that it is difficult to be reflected by the reflecting surface Wa (exposed surface Wa) of the wafer W, and a lot of energy is condensed and modified. A layer is formed.

  On the other hand, on the X side view side indicated by B3, the laser beam 47 vibrates in a direction orthogonal to the incident surface as indicated by D4. Therefore, since the incident light of the laser beam 47 on the wafer W becomes s-polarized light orthogonal to the incident surface, it is easily reflected by the reflecting surface Wa (exposed surface Wa) of the wafer W, and a small amount of energy is collected to form the modified layer. It is formed.

  For this reason, as shown in FIG. 3B, the energy density of the condensing point 48 becomes high in the dark hatched portion 481 parallel to the polarization direction of the laser beam 47 and thin hatching perpendicular to the polarization direction of the laser beam 47. Lower at portion 482. Therefore, a modified layer having a strong internal stress in the Y-axis direction is formed on the wafer W by the laser beam 47 as indicated by an arrow D5. When the wafer W is irradiated with the laser beam 47 whose polarization direction is the X-axis direction, a modified layer having a strong internal stress in the X-axis direction is formed on the wafer W. That is, a modified layer having a strong internal stress in the same direction as the polarization direction of the laser beam 47 (linearly polarized light) is formed in the wafer W.

  In the present invention, by utilizing the property of this linearly polarized light, the internal stress is mutually applied to two different locations in the thickness direction of the wafer W by irradiation with two laser beams (separated beams 47a and 47b) whose polarization directions are orthogonal. A modified layer having an orthogonal orientation is formed. In this case, the polarization direction of one laser beam (separation light 47a) is set to a direction orthogonal to the processing progress direction, and the polarization direction of the other laser beam (separation light 47b) is set to a direction parallel to the processing progress direction. The

  Here, with reference to FIG. 4, the relationship between the polarization direction of the separated light and the processing progress direction will be described. FIG. 4 is an explanatory diagram showing the relationship between the processing progress direction and the polarization direction by the laser processing apparatus according to the embodiment of the present invention. 4A shows a state where the polarization direction of the separated light is parallel to the processing progress direction, and FIG. 4B shows a state where the polarization direction of the separated light is orthogonal to the processing progress direction.

  As shown in FIG. 4A, when the polarization direction of the laser beam 47 is parallel to the planned division line 64, the condensing point 48 has a high energy density in the direction parallel to the planned division line 64. Then, when the workpiece is fed along the scheduled division line 64 in the machining progress direction indicated by the arrow D1, the modified layer is continuously formed along the planned division line 64 by the laser beam 47 condensed at the condensing point 48. It is formed. At this time, the dark hatched portion 481 having a high energy density at the condensing point 48 has a small overlapping range, and damage to the wafer W is small.

  Therefore, by forming the modified layer in the vicinity of the light emitting device with the laser beam 47 having a polarization direction parallel to the processing progress direction, it is possible to suppress a decrease in electrical characteristics as the light emitting device. On the other hand, as described above, the direction of the internal stress of the modified layer is parallel to the polarization direction. That is, since the internal stress due to the formation of the modified layer acts in a direction perpendicular to the direction in which the chips are separated from each other, the force required for division is large and the division characteristics are low.

  As shown in FIG. 4B, when the polarization direction of the laser beam 47 is orthogonal to the planned division line 64, the energy density of the condensing point 48 increases in the direction orthogonal to the planned division line 64. Then, when the workpiece is fed along the scheduled division line 64 in the machining progress direction indicated by the arrow D1, the modified layer is continuously formed along the planned division line 64 by the laser beam 47 condensed at the condensing point 48. It is formed. At this time, there is a large range in which the dark hatched portion 481 having a high energy density at the condensing point 48 overlaps, and the damage to the wafer W is large.

  Therefore, when the modified layer near the light emitting device is formed by the laser beam 47 having the polarization direction orthogonal to the processing progress direction, the light emitting device is damaged, and the electrical characteristics as the light emitting device are deteriorated. On the other hand, as described above, the direction of the internal stress of the modified layer is parallel to the polarization direction. That is, since the internal stress due to the formation of the modified layer acts in a direction to separate the chips, the force required for division is small and the division characteristics are high.

  Returning to FIG. 2, laser processing by the laser processing apparatus will be described. As shown in FIG. 2, the laser processing apparatus 1 separates the laser beam 47 into separated light 47 a and 47 b and focuses them at two locations in the thickness direction of the wafer W. The separation light 47a is collected at a condensing point 48a far from the device formation surface Wb, and the separation light 47b is collected at a condensing point 48b near the device formation surface Wb. The separated light 47a is linearly polarized light orthogonal to the processing progress direction, and the separated light 47b is linearly polarized light parallel to the processing progress direction.

  Therefore, at a position far from the device formation surface Wb of the wafer W, linearly polarized light orthogonal to the processing progress direction is collected, so that the direction of internal stress works in the direction to separate the chips and the division property is improved. A quality layer is formed. Although this modified layer has a large damage to the wafer W, it is formed at a position far from the device formation surface Wb, and therefore has little influence on the light emitting device.

  In addition, at a position close to the device formation surface Wb of the wafer W, linearly polarized light parallel to the processing progress direction is collected, so that the direction of internal stress works in a direction perpendicular to the direction of separating the chips and splitting. A modified layer having low characteristics is formed. Since this modified layer has little damage to the wafer W, even if it is formed at a position close to the device forming surface Wb, the modified layer has little influence on the light emitting device.

  As described above, the laser processing apparatus 1 according to the present embodiment enables the laser processing that improves the division characteristics of the wafer W and suppresses the deterioration of the electrical characteristics of the light emitting device. Note that when high-precision aberration correction is performed and the light condensing property is high, the Gaussian distribution of the separated light becomes dominant, and the energy density at the condensing point is not biased. Therefore, there is no change in laser processing due to the relationship between the polarization direction and the direction of internal stress (processing progress direction). However, since it is difficult to correct aberrations with high accuracy in practice, it is effective to form a modified layer in which the directions of internal stresses are orthogonal to each other at two locations in the thickness direction of the wafer W as in the present invention. .

  Here, the overall flow of the wafer dividing method will be described. First, when the wafer W is placed on the holding table 20, the holding table 20 is moved to a processing position facing the processing head 27. Next, the exit of the processing head 27 is aligned with the planned division line 64 of the wafer W, and the focus of the separated light 47a and 47b is adjusted to the inside of the semiconductor wafer W by the condenser 44, and laser processing is performed. Be started.

  In this case, the holding table 20 is processed and fed in the Y-axis direction while holding the wafer W, and two upper and lower rows of modified layers are formed along the scheduled division line 64. Subsequently, the holding table 20 is moved in the X-axis direction by several pitches, and the exit of the processing head 27 is aligned with the adjacent division planned line 64. Then, the holding table 20 is processed and fed in the Y-axis direction while holding the wafer W, and two upper and lower rows of modified layers are formed along the scheduled division line 64. This operation is repeated to form a modified layer along all the planned division lines 64 in the Y-axis direction of the wafer W. Next, the θ table 21 is rotated 90 degrees, and a modified layer is formed along all the division lines 64 in the X-axis direction of the semiconductor wafer W by the same operation.

  Next, when the laser processing is completed, the wafer W is removed from the holding table 20 and carried into a dividing device (not shown). Then, in the dividing device, an external force is applied to the modified layer formed along the planned dividing line 64 of the wafer W, whereby the chip is divided into individual chips.

  As described above, according to the laser processing apparatus 1 according to the embodiment, at a position away from the device formation surface Wb of the wafer W by the linearly polarized separated light 47a whose vibration direction is orthogonal to the processing progress direction, A modified layer having high splitting characteristics and high damage is formed. Further, the linearly polarized separated light 47b whose vibration direction is parallel to the processing progression direction forms a modified layer with low splitting characteristics and low damage at a position close to the device formation surface Wb of the wafer W. Therefore, it is possible to simultaneously achieve improvement of the splitting property of the optical device wafer and suppression of deterioration of the electrical characteristics of the light emitting device.

  In the above-described embodiment, the concentrator condenses the laser beam at two condensing points by the birefringent lens. However, the present invention is not limited to this configuration. The concentrator may be configured so that it is displaced in the thickness direction of the wafer and condensed at two condensing points. For example, a configuration using a polarization beam splitter as shown in FIG. FIG. 5 is a schematic diagram of an optical system of a laser processing apparatus according to a modification of the present invention. The optical system according to the modification is different only in the configuration of the condenser. Therefore, only the differences will be particularly described.

  As shown in FIG. 5, the condenser 51 includes polarization beam splitters 52 and 53, an objective lens 46, mirrors 55 and 56, and a variable beam expander 57. The objective lens 46 may be a single lens or a combination lens. The polarization beam splitter 52 separates the laser beam 47 incident through the λ / 2 wavelength plate 42 and the mirror 43 into separated light 47a indicated by a solid line and separated light 47b indicated by a one-dot chain line, and the separated light 47a is left as it is. The reflected light 47b is reflected and reflected toward the mirror 55.

  The separated light 47 a that has passed through the polarization beam splitter 52 also passes through the polarization beam splitter 53, and is collected by the objective lens 46 at a condensing point 48 a inside the wafer W. On the other hand, the separated light 47 b reflected by the polarization beam splitter 52 is reflected by the two mirrors 55 and 56 and enters the variable beam expander 57. The variable beam expander 57 includes two lenses (not shown), and widens the beam diameter of the separated light 47b by adjusting the distance between the two lenses.

  The separated light 47 b emitted from the variable beam expander 57 is reflected by the polarization beam splitter 53 and is collected by the objective lens 46 at a condensing point 48 b inside the wafer W. Thus, the focal length of the laser beam condensed on the wafer W can be changed by expanding the beam diameter of the separated light 47b by the variable beam expander 57. Therefore, the interval between the two condensing points can be adjusted, and the processing conditions can be selected in detail.

  Further, in the above-described embodiment, the pulse laser (separated light) focused on the side closer to the device forming surface of the wafer is linearly polarized light whose vibration direction is parallel to the processing progress direction. Parallel is not limited to being completely parallel. The direction of vibration of the pulse laser may be deviated from the direction parallel to the processing progressing direction so that a modified layer having low splitting characteristics and low damage is formed in the wafer.

  In the above-described embodiment, the pulse laser (separated light) focused on the side far from the device forming surface of the wafer is linearly polarized light whose vibration direction is orthogonal to the processing progress direction. The orthogonality is not limited to a case where the orthogonality is completely orthogonal. The vibration direction of the pulse laser may be deviated from the direction perpendicular to the processing progress direction so that a modified layer having high splitting characteristics and high damage is formed in the wafer.

  The present invention is not limited to the above-described embodiment, and can be implemented with various modifications. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  As described above, the present invention has an effect that it is possible to simultaneously achieve the improvement of the splitting property of the optical device wafer and the suppression of the deterioration of the electrical characteristics of the light emitting device. This is useful when a modified layer is formed inside a workpiece by irradiating a laser beam having a property.

1 Laser processing equipment 20 Holding table (holding means)
26 Laser processing unit (pulse laser irradiation means)
27 Processing Head 41 Oscillator 42 Wave Plate 44, 51 Condenser 45 Birefringence Lens 46 Objective Lens 47 Laser Beam (Pulse Laser)
47a Separated light (linearly polarized light whose vibration direction is orthogonal to the processing direction)
47b Separated light (linearly polarized light whose vibration direction is parallel to the processing direction)
48a Condensing point 48b Condensing point 52, 53 Polarizing beam splitter 57 Variable beam expander 64 Scheduled split line W wafer (sapphire wafer)
Wa Exposed surface Wb Device forming surface

Claims (2)

A holding means for holding the surface side of the sapphire wafer formed on the surface with a plurality of light emitting devices partitioned by the planned dividing line, and the sapphire wafer along the planned dividing line of the sapphire wafer held by the holding means And a pulse laser irradiation means for irradiating a pulse laser having a wavelength that passes through
The pulse laser irradiation means includes an oscillator that oscillates a pulse laser, and a condenser that condenses the pulse laser oscillated by the oscillator and irradiates the exposed surface of the sapphire wafer held by the holding means. A laser processing device,
The concentrator is configured to disperse the pulsed laser oscillated from the oscillator in the thickness direction of the sapphire wafer held by the holding means and to collect light at two condensing points.
The pulse laser focused on the far side from the exposed surface of the sapphire wafer is linearly polarized light whose vibration direction is parallel to the processing progress direction,
The pulse laser focused on the side closer to the exposed surface of the sapphire wafer is linearly polarized light whose vibration direction is orthogonal to the processing progress direction,
Two types of modified layers with different splitting characteristics are formed by a pulse laser focused on two focusing points, and the modified layer formed at the focusing point far from the exposed surface has low splitting characteristics. On the other hand, the modified layer formed at the light condensing point on the side closer to the exposed surface has high splitting characteristics . A plurality of light emitting devices partitioned by a predetermined division line is held on the surface side of the sapphire wafer formed on the surface, and a pulse having a wavelength transmitted through the sapphire wafer along the predetermined division line of the held sapphire wafer A laser processing method for irradiating the sapphire wafer with a laser,
The pulsed laser is displaced in the thickness direction of the sapphire wafer and focused on two focused points,
The pulse laser focused on the far side from the exposed surface of the sapphire wafer is linearly polarized light whose vibration direction is parallel to the processing progress direction,
The pulse laser focused on the side closer to the exposed surface of the sapphire wafer is linearly polarized light whose vibration direction is orthogonal to the processing progress direction,
Two types of modified layers with different splitting characteristics are formed by a pulse laser focused on two focusing points, and the modified layer formed at the focusing point far from the exposed surface has low splitting characteristics. On the other hand, the modified layer formed at the condensing point on the side closer to the exposed surface has high splitting characteristics .

Images