JP2021122041A - Laser processing method, semiconductor member manufacturing method, and laser processing apparatus - Google Patents

Abstract

To provide a laser processing method, a semiconductor member manufacturing method, and a laser processing apparatus that can obtain, from a semiconductor target object, a semiconductor member having a shape different from that of the semiconductor object.SOLUTION: The laser processing method includes a first step and a second step. In the first step, a GaN wafer 20 is irradiated with first laser light L1 along lines A1 and A2, thereby forming modified regions M1 and M2 extending linearly along the lines A1 and A2 when viewed in a Z-axis direction intersecting a first surface 20a. In the second step, second laser light L2 is caused to be incident to the GaN wafer 20 from the first surface 20a, and a focusing point C2 of the second laser light L2 is moved within a virtual surface 15 so as to pass through the modified regions M1 and M2 when viewed in the Z-axis direction, thereby forming a plurality of modified spots 13 arranged in the form of a plane in the virtual surface 15.SELECTED DRAWING: Figure 15

Description

The present invention relates to a laser processing method, a semiconductor member manufacturing method, and a laser processing apparatus.

By irradiating a semiconductor object such as a semiconductor ingot with laser light, a modified region is formed inside the semiconductor object, and cracks extending from the modified region are developed to develop a semiconductor such as a semiconductor wafer from the semiconductor object. A processing method for cutting out a member is known (see, for example, Patent Documents 1 and 2).

JP-A-2017-183600 JP-A-2017-057103

In the processing method described above, a semiconductor member having the same shape as the semiconductor object is cut out when viewed from the direction intersecting the laser beam incident surface of the semiconductor object. On the other hand, in the future, as in the case of cutting out a semiconductor chip from a semiconductor wafer, it may be required to cut out a semiconductor member in a unit smaller than the original semiconductor object (that is, a shape different from the semiconductor object).

An object of the present invention is to provide a laser processing method, a semiconductor member manufacturing method, and a laser processing apparatus capable of obtaining a semiconductor member having a shape different from that of the semiconductor object from the semiconductor object.

The laser processing method according to the present invention is for cutting a semiconductor object along a virtual surface facing the first surface of the semiconductor object and a line extending along the first surface inside the semiconductor object. In a laser processing method, by irradiating a semiconductor object with a first laser beam along a line, a modified region extending linearly along the line when viewed from a first direction intersecting the first surface is formed. After the first step and the first step, the second laser beam is incident on the semiconductor object from the first surface, and the condensing point of the second laser beam passes through the modified region when viewed from the first direction. A second step of forming a plurality of modified spots arranged in a plane in the virtual plane by moving the light into the virtual plane is provided. In the first step, the light is viewed from a second direction along the first surface. , At least from the first surface to the virtual surface to form a modified region.

In this method, in the second step, the second laser beam is incident on the semiconductor object from the first surface of the semiconductor object, and the condensing point of the second laser beam is virtual facing the first surface of the semiconductor object. It is moved in the plane to form a plurality of modified spots arranged in a plane in the virtual plane. Therefore, it is possible to cut the semiconductor object with the crack extending from the modified spot and extending over the virtual surface as a boundary. In particular, in this method, prior to the second step, in the first step, the first laser beam is irradiated along the line along the first surface of the semiconductor object to form a linear shape along the line. Form a modified region. This modified region is formed from at least the first surface of the semiconductor object to the virtual surface. Therefore, after the second step, in addition to the cutting with the crack over the virtual surface as the boundary, the cutting with the modified region as the boundary becomes possible. Therefore, according to this method, it is possible to obtain a semiconductor member having a shape (smaller unit) different from that of the original semiconductor object.

When the focusing point of the second laser beam passes through the modified region when viewed from the first direction, the modified region affects the condensed state of the second laser light, and as a result, a modified spot is formed. It is hard to be done. Therefore, a region in which no modification spot is formed is likely to be formed around the modification region. This region has the function of preventing the growth of cracks extending from the modified spot. Therefore, according to this method, it is possible to prevent cracks extending from the modified spot from reaching the cut surface of the member obtained by cutting the modified region at the boundary.

In the laser processing method according to the present invention, a plurality of virtual surfaces are set so as to be arranged in the first direction, and in the first step, at least the virtual surface farthest from the first surface is set. A modified region may be formed across. In this case, a plurality of semiconductor members can be obtained by cutting the semiconductor object with a plurality of virtual surfaces (cracks across the virtual surfaces) arranged in the first direction as boundaries.

In the laser processing method according to the present invention, the semiconductor object has a second surface which is a surface opposite to the first surface and faces the virtual surface, and in the first step, the first surface to the first surface. The modified region may be formed over the two surfaces. In this case, in addition to the portion on the first surface side of the semiconductor object, the portion on the second surface side of the semiconductor object is also cut with the modified region as a boundary, so that a plurality of semiconductor members can be obtained.

In the laser processing method according to the present invention, in the second step, a peripheral region including the peripheral edge of the semiconductor object when viewed from the first direction and in which a modified spot is not formed may be formed. In this case, the peripheral region can prevent cracks extending from the modified spot from reaching the outer edge of the semiconductor object.

In the laser processing method according to the present invention, in the second step, the focusing point of the second laser beam is moved from the outside of the semiconductor object to the inside of the semiconductor object when viewed from the first direction. Peripheral regions may be formed by allowing them to form a peripheral region. In this way, by moving the condensing point of the second laser beam from the outside to the inside of the semiconductor object through the periphery, the change in the condensing state at the periphery (inhibition of condensing) is utilized. Peripheral regions where modified spots are not formed can be easily formed.

In the laser processing method according to the present invention, the material of the semiconductor object may contain gallium. In this case, when gallium is deposited in a plurality of cracks extending from the plurality of modified spots by irradiation with the laser beam, the gallium is in a state where the laser beam is easily absorbed. Therefore, it is possible to form a crack over the virtual surface with a smaller output.

In the laser processing method according to the present invention, the material of the semiconductor object may include gallium nitride. In this case, when gallium nitride is decomposed by irradiation with laser light, nitrogen gas is generated in the cracks. Therefore, it is possible to easily form a crack over the virtual surface by utilizing the pressure (internal pressure) of the nitrogen gas.

The semiconductor member manufacturing method according to the present invention includes the first step and the second step provided in the above laser processing method, and after the second step, a crack extending from the modification spot and extending over the virtual surface, a modification region, and the like. A third step of acquiring a semiconductor member from a semiconductor object with the above as a boundary is provided. In this manufacturing method, the first step and the second step of the above-mentioned laser processing method are carried out. Therefore, for the same reason, it is possible to obtain a semiconductor member having a shape (smaller unit) different from that of the original semiconductor object.

In the method for manufacturing a semiconductor member according to the present invention, the semiconductor object may be a semiconductor ingot, and the semiconductor member may be a semiconductor wafer. In this case, it is possible to obtain a semiconductor wafer having a shape different from that of the semiconductor ingot.

In the semiconductor manufacturing method according to the present invention, the semiconductor object may be a semiconductor wafer, and the semiconductor member may be a semiconductor chip. In this case, it is possible to obtain a semiconductor chip having a shape different from that of the semiconductor wafer.

The laser processing apparatus according to the present invention is for cutting a semiconductor object along a virtual surface facing the first surface of the semiconductor object and a line extending along the first surface inside the semiconductor object. A laser processing device that includes a stage that supports a semiconductor object, a laser irradiation unit that irradiates the semiconductor object supported by the stage with laser light, and at least a control unit that controls the laser irradiation unit. By irradiating the semiconductor object with the first laser beam along the line, the control unit forms a modified region extending linearly along the line when viewed from the first direction intersecting the first surface. After the first treatment and the first treatment, the second laser beam is incident on the semiconductor object from the first surface, and the condensing point of the second laser beam is virtual so as to pass through the modified region when viewed from the first direction. The second process of forming a plurality of modified spots arranged in a plane in the virtual surface by moving the laser surface is executed, and in the first process, when viewed from the second direction along the first surface. , At least from the first surface to the virtual surface to form a modified region.

In this apparatus, in the second process, the second laser beam is incident on the semiconductor object from the first surface of the semiconductor object, and the focusing point of the second laser beam is set to face the first surface of the semiconductor object. It is moved in the plane to form a plurality of modified spots arranged in a plane in the virtual plane. Therefore, it is possible to cut the semiconductor object with the crack extending from the modified spot and extending over the virtual surface as a boundary. In particular, in this apparatus, prior to the second treatment, in the first treatment, the first laser beam is irradiated along the line along the first surface of the semiconductor object to form a linear shape along the line. Form a modified region. This modified region is formed from at least the first surface of the semiconductor object to the virtual surface. Therefore, after the second treatment, in addition to the cutting with the crack over the virtual surface as the boundary, the cutting with the modified region as the boundary becomes possible. Therefore, according to this apparatus, it is possible to obtain a semiconductor member having a shape (smaller unit) different from that of the original semiconductor object.

When the focusing point of the second laser beam passes through the modified region when viewed from the first direction, the modified region affects the focusing of the second laser light, and as a result, a modified spot is formed. Hateful. Therefore, a region in which no modification spot is formed is likely to be formed around the modification region. This region has the function of preventing the growth of cracks extending from the modified spot. Therefore, according to this apparatus, it is possible to prevent cracks extending from the reforming spot from reaching the cut surface of the member obtained by cutting the reformed region at the boundary.

According to the present invention, it is possible to provide a laser processing method, a semiconductor member manufacturing method, and a laser processing apparatus capable of obtaining a semiconductor member having a shape different from that of the semiconductor object from the semiconductor object.

It is a schematic diagram which shows the laser processing apparatus which concerns on one Embodiment. It is a top view which shows the GaN wafer as the object shown in FIG. It is sectional drawing of the GaN wafer shown in FIG. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a figure which shows the main process of the laser processing method and the semiconductor member manufacturing method. It is a top view (photograph) of a GaN wafer showing a state in which cracks are formed over a virtual surface. It is a figure which shows the main process of the semiconductor member manufacturing method. It is an image of the peeling surface of the GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of one example. It is a height profile of the peeling surface shown in FIG. It is an image of the peeling surface of the GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of another example. It is a height profile of the peeling surface shown in FIG. It is a schematic diagram for demonstrating the formation principle of the peeling surface by an example laser processing method and the semiconductor member manufacturing method. It is a schematic diagram for demonstrating the formation principle of the peeling surface by the laser processing method and the semiconductor member manufacturing method of another example. It is an image of a crack formed in the middle of an example of a laser processing method and a semiconductor member manufacturing method. It is an image of a crack formed in the middle of the laser processing method and the semiconductor member manufacturing method of another example. It is an image of the modified spot and the crack formed by the laser processing method and the semiconductor member manufacturing method of the comparative example. It is an image of a modified spot and a crack formed by the laser processing method and the semiconductor member manufacturing method of the first embodiment. It is an image of a modified spot and a crack formed by the laser processing method and the semiconductor member manufacturing method of the second embodiment and the third embodiment. It is a figure which shows the modification. It is a figure which shows the modification.

Hereinafter, one embodiment will be described in detail with reference to the drawings. In the description of each figure, the same or corresponding elements may be designated by the same reference numerals, and duplicate description may be omitted. In addition, each figure may show a Cartesian coordinate system defined by the X-axis, the Y-axis, and the Z-axis.
[Construction of laser processing equipment]

As shown in FIG. 1, the laser processing apparatus 1 includes a stage 2, a light source 3, a spatial light modulator 4, a condenser lens 5, and a control unit 6. The laser processing device 1 is a device that forms a modified region 12 on the object 11 by irradiating the object 11 with the laser beam L. Hereinafter, the first horizontal direction is referred to as an X-axis direction, and the second horizontal direction perpendicular to the first horizontal direction is referred to as a Y-axis direction. Further, the vertical direction is referred to as a Z-axis direction.

The stage 2 supports the object 11 by, for example, adsorbing a film attached to the object 11. In this embodiment, the stage 2 can move along the X-axis direction and the Y-axis direction, respectively. Further, the stage 2 can rotate about an axis parallel to the Z-axis direction as a center line.

The light source 3 outputs a laser beam L having transparency to the object 11 by, for example, a pulse oscillation method. The spatial light modulator 4 modulates the laser beam L output from the light source 3. The spatial light modulator 4 is, for example, a spatial light modulator (SLM) of a reflective liquid crystal display (LCOS: Liquid Crystal on Silicon). The condenser lens 5 collects the laser light L modulated by the spatial light modulator 4. In the present embodiment, the spatial light modulator 4 and the condenser lens 5 can move along the Z-axis direction as a laser irradiation unit.

When the laser beam L is focused inside the object 11 supported by the stage 2, the laser beam L is particularly absorbed at the portion of the laser beam L corresponding to the focusing point C, and is modified inside the object 11. The quality region 12 is formed. The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding non-modified region. The modified region 12 includes, for example, a melting treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and the like.

As an example, when the stage 2 is moved along the X-axis direction and the focusing point C is moved relative to the object 11 along the X-axis direction, a plurality of reforming spots 13 are moved in the X-axis direction. It is formed so as to line up in a row along the line. One modification spot 13 is formed by irradiation with one pulse of laser light L. The modified region 12 in one row is a set of a plurality of modified spots 13 arranged in one row. Adjacent modified spots 13 may be connected to each other or separated from each other depending on the relative moving speed of the focusing point C with respect to the object 11 and the repetition frequency of the laser beam L.

The control unit 6 controls the stage 2, the light source 3, the spatial light modulator 4, and the condenser lens 5 (that is, the laser irradiation unit). The control unit 6 is configured as a computer device including a processor, a memory, a storage, a communication device, and the like. In the control unit 6, software (program) read into the memory or the like is executed by the processor, and reading and writing of data in the memory and storage, and communication by the communication device are controlled by the processor. As a result, the control unit 6 realizes various functions.
[One Embodiment of Laser Machining Method and Semiconductor Member Manufacturing Method]

As shown in FIGS. 2 and 3, the object 11 of the laser processing method and the semiconductor member manufacturing method according to the present embodiment is a GaN wafer (semiconductor wafer, for example, formed in the shape of a rectangular plate by gallium nitride (GaN). Semiconductor object) 20. The size of the GaN wafer 20 is, for example, about 50 mm × 50 mm (for example, when the GaN wafer 20 has a disk shape, it is about φ2 inch).

The GaN wafer 20 has a first surface 20a and a second surface 20b opposite to the first surface 20a. Here, the first surface 20a and the second surface 20b are parallel to each other. Further, a virtual surface 15 and lines A1 and A2 are set on the GaN wafer 20. The virtual surface 15 is a surface inside the GaN wafer 20 that faces the first surface 20a and the second surface 20b of the GaN wafer 20. Here, the virtual surface 15 is a surface parallel to the first surface 20a, and has a rectangular shape, for example. The line A1 is a virtual line along the first surface 20a. The line A2 is a line along the first surface 20a and intersecting (orthogonal) with the line A1.

Further, in the GaN wafer 20, a portion corresponding to a peripheral edge region 16 described later is set so as to surround the virtual surface 15 when viewed from the first direction (here, the Z-axis direction) intersecting (orthogonal) with the first surface 20a. ing. That is, the virtual surface 15 does not reach the outer edge of the GaN wafer 20 when viewed from the Z-axis direction. The peripheral region 16 is, for example, a rectangular ring when viewed from the Z-axis direction. The width of the peripheral edge region 16 (here, the distance between the outer edge of the virtual surface 15 and the outer edge of the GaN wafer 20 when viewed from the Z-axis direction) is, for example, 30 μm or more.

In the laser processing method and the semiconductor member manufacturing method according to the present embodiment, a plurality of chips (semiconductor chips, semiconductors) are formed from the GaN wafer 20 by cutting the GaN wafer 20 along the virtual surface 15 and the lines A1 and A2. Member) 30A is carried out to cut out. The portion of the GaN wafer 20 corresponding to the chip 30A is bounded by the virtual surface 15 when viewed from the second direction (here, the X-axis direction or the Y-axis direction) along the first surface 20a, and is viewed from the Z-axis direction. It is a part whose boundary is lines A1 and A2. Here, eight chips 30A are set for one GaN wafer 20. The size of the chip 30A is, for example, about 25 mm × 25 mm.

In this laser processing method and the semiconductor member manufacturing method, first, as shown in FIGS. 4, 5, and 6, the above-mentioned laser processing apparatus 1 first lasers the GaN wafer 20 along the lines A1 and A2. By irradiating light L1 (for example, having a wavelength of 532 nm), modified regions M1 and M2 (machining marks) extending linearly along the lines A1 and A2 when viewed from the Z-axis direction are formed (first step). .. The first step will be described more specifically.

In the first step, first, the GaN wafer 20 as the object 11 is arranged on the stage 2. At this time, as an example, the first surface 20a is directed toward the laser irradiation unit (condensing lens 5). Subsequently, the laser processing apparatus 1 controls the stage 2 and the like so that the condensing point C1 of the first laser beam L1 is located inside the GaN wafer 20. Then, the laser processing apparatus 1 controls the stage 2 and the laser irradiation unit so that the condensing point C1 of the first laser beam L1 moves relative to the line A1 (on the line A1) when viewed from the Z-axis direction. .. Here, as an example, the line A1 is arranged along the X-axis direction, and the stage 2 is along the X-axis direction while the laser irradiation unit is irradiating the GaN wafer 20 with the first laser beam L1. By being moved, the focusing point C1 is moved along the line A1.

Irradiation along the line A1 of the first laser beam L1 is performed from a position farther from the first surface 20a in the Z-axis direction (that is, a deeper processing position of the GaN wafer 20) to the first surface 20a in the Z-axis direction. The process is repeated until a closer position (that is, a shallower processing position of the GaN wafer 20) is reached. At this time, the focusing point C1 may be located on the first surface 20a and the second surface 20b in the Z-axis direction. As a result, the modified region M1 extending from the first surface 20a to the second surface 20b is formed when viewed from the X-axis direction or the Y-axis direction.

Subsequently, in the first step, in a state where the condensing point C1 of the first laser beam L1 is positioned inside the GaN wafer 20, the laser processing apparatus 1 has the condensing point C1 as the line A2 when viewed from the Z-axis direction. The stage 2 and the laser irradiation unit are controlled so as to move relative to each other (on the line A2). Here, as an example, the arrangement of the GaN wafer 20 is changed so that the line A2 is along the X-axis direction due to the rotation of the stage 2, and in that state, the laser irradiation unit transfers the first laser beam L1 to the GaN wafer 20. The light collection point C1 is moved along the line A2 by moving the stage 2 along the X-axis direction while irradiating the light.

Irradiation along the line A2 of the first laser beam L1 is performed from a position farther from the first surface 20a in the Z-axis direction (that is, a deeper processing position of the GaN wafer 20) to the first surface 20a in the Z-axis direction. The process is repeated until a closer position (that is, a shallower processing position of the GaN wafer 20) is reached. At this time, the focusing point C1 may be located on the first surface 20a and the second surface 20b in the Z-axis direction. As a result, the modified region M2 extending from the first surface 20a to the second surface 20b is formed when viewed from the X-axis direction or the Y-axis direction. FIG. 6 shows the state after the first step.

The above first step is performed under the control of the control unit 6 of the laser processing apparatus 1. That is, the control unit 6 irradiates the GaN wafer 20 with the first laser beam L1 along the lines A1 and A2, so that the first surface 20a extends linearly along the lines A1 and A2 when viewed from the Z-axis direction. The first treatment for forming the modified regions M1 and M2 is executed. In particular, in the first treatment, the modified regions M1 and M2 are formed from at least the first surface 20a to the virtual surface 15 when viewed from the X-axis direction or the Y-axis direction along the first surface 20a.

The modified regions M1 and M2 here include cracks extending from the modified spots in addition to the plurality of modified spots. Therefore, when the modified regions M1 and M2 are formed from one first position to another second position, the modified spots are continuously formed between the first position and the second position. In some cases, cracks and modified spots are alternately formed between the first position and the second position. In the latter case, further, the crack extending from one modified spot and the crack extending from another modified spot adjacent to the modified spot may not be connected to each other. Therefore, what is present at the first position or the second position may be a modified spot, a crack, or a portion between cracks.

The peripheral regions 16 described later do not form modified regions M1 and M2 (at least modified spots) (cracks extending from the modified spots may be formed). That is, in the first step, the modified regions M1 and M2 are formed only at the portion where the virtual surface 15 and the lines A1 and A2 overlap when viewed from the Z-axis direction. As a method for that purpose, a method using a mask that covers the peripheral edge (edge) of the GaN wafer 20 or a method of turning off the first laser beam L1 when the condensing point C1 passes through the peripheral edge of the GaN wafer 20 is used. You may. Alternatively, by moving the focusing point C1 from the outside of the GaN wafer 20 through the periphery to the inside of the GaN wafer 20 while the first laser beam L1 is on, the first laser beam C1 is moved on the periphery of the GaN wafer 20. The peripheral region 16 in which the modified regions M1 and M2 are not formed may be formed by utilizing the fact that the condensing state of the laser beam L1 changes (condensing is hindered).

In the subsequent steps of the laser processing method and the semiconductor member manufacturing method according to the present embodiment, the GaN wafer 20 is irradiated with a second laser beam L2 having a wavelength of, for example, 532 nm along the virtual surface 15, and a plurality of modified spots are formed. Form (second step).

The second step will be described in detail with reference to FIGS. 7 to 14. In the following, the arrow indicates the locus of the focusing point C2 of the second laser beam L2. Further, the modified spots 13a, 13b, 13c, 13d described later may be collectively referred to as a modified spot 13, and the cracks 14a, 14b, 14c, 14d described later may be collectively referred to as a crack 14.

First, as shown in FIGS. 7 and 8, the laser processing apparatus 1 causes the second laser beam L2 to be incident on the inside of the GaN wafer 20 from the first surface 20a along the virtual surface 15 (for example, for example. A plurality of modified spots 13a are formed (so as to be arranged two-dimensionally along the entire virtual surface 15). At this time, the laser machining apparatus 1 forms a plurality of reforming spots 13a so that the plurality of cracks 14a extending from the plurality of reforming spots 13a are not connected to each other. Further, the laser processing apparatus 1 forms a plurality of rows of reforming spots 13a (first reforming spots) by moving the focusing point C2 of the pulse-oscillated second laser beam L2 along the virtual surface 15. do. In addition, in FIGS. 7 and 8, the modified spot 13a is shown in white (without hatching), and the range in which the crack 14a extends is shown by a broken line (the same applies to other figures).

In the present embodiment, the pulse-oscillated second laser beam L2 is modulated by the spatial light modulator 4 so as to be focused on a plurality of (for example, six) focusing points C2 arranged in the Y-axis direction. Then, the plurality of focusing points C2 are relatively moved on the virtual surface 15 along the X-axis direction. As an example, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, and the pulse pitch of the second laser beam L2 (that is, the relative moving speed of the plurality of focusing points C2 is determined by the second laser beam. The value divided by the repetition frequency of L2) is 10 μm. The pulse energy of the second laser beam L2 per one focusing point C2 (hereinafter, simply referred to as “pulse energy of the second laser beam L2”) is 0.33 μJ. In this case, the distance between the centers of the adjacent reforming spots 13a in the Y-axis direction is 8 μm, and the distance between the centers of the adjacent reforming spots 13a in the X-axis direction is 10 μm. Further, the plurality of cracks 14a extending from the plurality of modified spots 13a are not connected to each other.

Subsequently, as shown in FIGS. 9 and 10, the laser processing apparatus 1 causes the second laser beam L2 to be incident on the inside of the GaN wafer 20 from the first surface 20a along the virtual surface 15 (for example,). , A plurality of modified spots 13b (second modified spots) are formed so as to be arranged in two dimensions along the entire virtual surface 15. At this time, the laser machining apparatus 1 forms a plurality of modified spots 13b so as not to overlap the plurality of modified spots 13a and the plurality of cracks 14a. Further, the laser processing apparatus 1 modifies the plurality of rows of the second laser beam L2 by moving the condensing point C2 of the pulse-oscillated second laser beam L2 between the rows of the plurality of rows of the reforming spots 13a along the virtual surface 15. The spot 13b is formed. In this step, a plurality of cracks 14b extending from the plurality of modified spots 13b may be connected to the plurality of cracks 14a. In FIGS. 9 and 10, the modified spot 13b is indicated by dot hatching, and the range in which the crack 14b extends is indicated by a broken line (the same applies to other figures).

In the present embodiment, the pulse-oscillated second laser beam L2 is modulated by the spatial light modulator 4 so as to be focused on a plurality of (for example, six) focusing points C2 arranged in the Y-axis direction. Then, the plurality of focusing points C2 are relatively moved on the virtual surface 15 along the X-axis direction at the center between the rows of the plurality of rows of the modified spots 13a. As an example, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, and the pulse pitch of the second laser beam L2 is 10 μm. The pulse energy of the second laser beam L2 is 0.33 μJ. In this case, the distance between the centers of the modified spots 13b adjacent to each other in the Y-axis direction is 8 μm, and the distance between the centers of the modified spots 13b adjacent to each other in the X-axis direction is 10 μm.

Subsequently, as shown in FIGS. 11 and 12, the laser processing apparatus 1 causes the second laser beam L2 to be incident on the inside of the GaN wafer 20 from the first surface 20a along the virtual surface 15 (for example,). , A plurality of modified spots (third modified spots) 13c are formed so as to be arranged in two dimensions along the entire virtual surface 15. Further, as shown in FIGS. 13 and 14, the laser processing apparatus 1 causes the second laser beam L2 to be incident on the inside of the GaN wafer 20 from the first surface 20a along the virtual surface 15 (for example, for example. A plurality of modified spots (third modified spots) 13d are formed so as to be arranged two-dimensionally along the entire virtual surface 15. At this time, the laser machining apparatus 1 forms a plurality of modified spots 13c and 13d so as not to overlap the plurality of modified spots 13a and 13b.

Further, the laser processing apparatus 1 moves the pulse-oscillated second laser beam L2 focusing point C2 between the rows of the modified spots 13a and 13b in the plurality of rows along the virtual surface 15 to form a plurality of rows. The modified spots 13c and 13d are formed. In this step, the plurality of cracks 14c and 14d extending from the plurality of modified spots 13c and 13d, respectively, may be connected to the plurality of cracks 14a and 14b. In addition, in FIGS. 11 and 12, the modified spot 13c is shown by solid line hatching, and the range in which the crack 14c extends is shown by a broken line (the same applies to other figures). Further, in FIGS. 13 and 14, the modified spot 13d is indicated by solid line hatching (solid line hatching that is inclined in the opposite direction to the solid line hatching of the modified spot 13c), and the range in which the crack 14d extends is indicated by a broken line. There is.

In the present embodiment, the pulse-oscillated second laser beam L2 is modulated by the spatial light modulator 4 so as to be focused on a plurality of (for example, six) focusing points C2 arranged in the Y-axis direction. Then, the plurality of condensing points C2 are relatively moved on the virtual surface 15 along the X-axis direction at the center between the rows of the reformed spots 13a and 13b in the plurality of rows. As an example, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, and the pulse pitch of the second laser beam L2 is 5 μm. The pulse energy of the second laser beam L2 is 0.33 μJ. In this case, the distance between the centers of the adjacent reforming spots 13c in the Y-axis direction is 8 μm, and the distance between the centers of the adjacent reforming spots 13c in the X-axis direction is 5 μm. Further, the distance between the centers of the modified spots 13d adjacent to each other in the Y-axis direction is 8 μm, and the distance between the centers of the modified spots 13d adjacent to each other in the X-axis direction is 5 μm.

In this second step, as described above, the second laser beam L2 is incident on the GaN wafer 20 from the first surface 20a, and the condensing point C2 of the second laser beam L2 is moved into the virtual surface 15. A plurality of modified spots 13 arranged in a plane shape are formed in the virtual surface 15. In the second step, the condensing point C2 of the second laser beam L2 is moved into the virtual surface 15 so as to pass through the modified regions M1 and M2 when viewed from the Z-axis direction.

The above second step is performed under the control of the control unit 6 of the laser processing apparatus 1. That is, here, after the first processing, the control unit 6 causes the second laser beam L2 to enter the GaN wafer 20 from the first surface 20a, and sets the focusing point C2 of the second laser beam L2 in the Z-axis direction. The second process of forming a plurality of reforming spots 13 arranged in a plane shape in the virtual surface 15 is executed by moving the modification spots 13 into the virtual surface 15 so as to pass through the modification regions M1 and M2.

Further, in this second step, the peripheral region 16 in which the modified spot 13 is not formed (cracks extending from the modified spot may be formed) is formed. Therefore, in the present embodiment, the focusing point C2 is moved from the outside of the GaN wafer 20 to the inside of the GaN wafer 20 through the periphery (edge) of the GaN wafer 20 with the second laser beam L2 turned on. By making the GaN wafer 20, the condensing state of the second laser beam L2 changes (condensing is hindered) at the peripheral edge (edge) of the GaN wafer 20, and the peripheral region where the modified spot 13 is not formed is utilized. 16 is formed. However, the modification spot 13 is formed by a method using a mask that covers the peripheral edge of the GaN wafer 20 or a method of turning off the second laser beam L2 when the condensing point C2 passes through the peripheral edge of the GaN wafer 20. Peripheral regions 16 that are not formed may be formed.

Here, since the required modification region and the mode of cracking are different between the irradiation of the first laser beam L1 in the first step and the irradiation of the second laser beam L2 in the second step, the irradiation conditions are also different. There is. That is, in the first step, in order to cut the GaN wafer 20 vertically (at a plane orthogonal to the first surface 20a), the modified region and the crack (modified layer) are orthogonal to the vertical direction (orthogonal to the first surface 20a). It is necessary to extend in the direction (Z-axis direction). Therefore, in the first step, the first laser beam L1 is applied so as to form a vertically long modified region (melting / high internal pressure region) and a crack, and to align the vertically elongated modified region and the crack in the vertical direction. Irradiate.

Then, the adjacent cracks are pulled and extended in the vertical direction by the stress distribution due to the increase in the internal pressure. This makes it possible to cut the GaN wafer 20 vertically. At this time, the pulse width of the first laser beam L1 is relatively longer than the pulse width of the second laser beam L2, and the pulse energy and pulse pitch of the first laser beam L1 are the pulse widths of the second laser beam L2. It can be relatively large compared to the pulse energy and pulse pitch. As an example, the output of the first laser beam L1 is 10 μJ to 20 μJ, the pulse pitch is 10 μm, and the processing is relatively high output and sparse.

On the other hand, in the second step, in order to cut the GaN wafer 20 laterally (on a plane parallel to the first surface 20a (virtual plane 15)), the modified region and cracks are cut laterally (parallel to the first surface 20a). It is necessary to extend in the direction (X-axis direction and Y-axis direction). Therefore, in the second step, the second laser beam L2 is irradiated so as to form the point-shaped modified region (melting / high internal pressure region) and the crack, and to align the modified region and the crack in the lateral direction. ..

Then, due to the stress distribution due to the increase in internal pressure, the cracks extending from each of the modified regions are laterally extended and connected to form lateral cracks. This makes it possible to cut the GaN wafer 20 laterally. At this time, the pulse width of the second laser beam L2 is relatively shorter than the pulse width of the first laser beam L1, and the pulse energy and pulse pitch of the second laser beam L2 are the pulse widths of the first laser beam L1. It can be relatively small compared to the pulse energy and pulse pitch. As an example, the output of the second laser beam L2 is 1.5 μJ to 2 μJ, the pulse pitch is 1 μm, and the processing is relatively low and dense. In this example, the output and pulse pitch of the second laser beam L2 are set to about 1/10 of the output and pulse pitch of the first laser beam L1.

In the laser processing method and the semiconductor member manufacturing method according to the present embodiment, a heating device provided with a heater or the like subsequently heats the GaN wafer 20 and connects a plurality of cracks 14 extending from the plurality of modification spots 13 to each other. As a result, as shown in FIG. 15, a crack 17 (hereinafter, simply referred to as “crack 17”) extending over the virtual surface 15 is formed. A plurality of cracks 14 may be connected to each other to form a crack 17 by applying some force to the GaN wafer 20 by a method other than heating. Further, by forming a plurality of modified spots 13 along the virtual surface 15, a plurality of cracks 14 may be connected to each other to form a crack 17.

Here, in the GaN wafer 20, nitrogen gas is generated in the plurality of cracks 14 extending from the plurality of reforming spots 13. Therefore, by heating the GaN wafer 20 to expand the nitrogen gas, the crack 17 can be formed by utilizing the pressure (internal pressure) of the nitrogen gas. Moreover, since the peripheral edge region 16 prevents the growth of the plurality of cracks 14 to the outside of the virtual surface 15 surrounded by the peripheral edge region 16 (for example, the outer edge (side surface) of the GaN wafer 20), it occurs in the plurality of cracks 14. It is possible to prevent the nitrogen gas from escaping to the outside of the virtual surface 15. That is, the peripheral region 16 is a non-modified region that does not include the modified spot 13, and when a crack 17 is formed in the virtual surface 15 surrounded by the peripheral region 16, the virtual surface 15 surrounded by the peripheral region 16 is formed. It is a region that hinders the growth of a plurality of cracks 14 to the outside. Therefore, the width of the peripheral region 16 is preferably 30 μm or more.

FIG. 16 is a plan view (photograph) of a GaN wafer showing a state in which cracks are formed over a virtual surface. Gallium (precipitate) is deposited in the crack 17 extending over the virtual surface 15 by irradiation with the second laser beam L2. As a result, as shown in FIG. 16, the crack 17 is observed as a portion darker (the transmittance of the observation light is reduced) than the other portions. Here, it is understood that cracks 17 extending over the virtual surface 15 are formed in the portions of the GaN wafer 20 corresponding to each of the chips 30A.

If the change in the condensing state at the peripheral edge of the GaN wafer 20 is used when forming the peripheral edge region 16, cracks extending from the modification spot 13 may be slightly included in the peripheral edge region 16. As a result, a portion 16a in which the crack 17 reaches the outer edge of the chip 30A (the outer edge of the GaN wafer 20) is formed with respect to the peripheral edge region 16. The portion 16a has a function of venting nitrogen gas generated in the crack 17. As a result, an excessive increase in internal pressure can be suppressed in each of the portions of the GaN wafer 20 corresponding to the chip 30A.

In the laser processing method and the semiconductor member manufacturing method according to the present embodiment, subsequently, as shown in FIGS. 15 and 17, the grinding apparatus grinds (polishs) the portion corresponding to the peripheral region 16 of the GaN wafer 20. By doing so, a plurality of chips 30A are obtained from the GaN wafer 20 with the crack 17 and the modified regions M1 and M2 as boundaries (third step). In this way, the GaN wafer 20 is cut along the virtual surface 15 and the lines A1 and A2. In this step, the portion corresponding to the peripheral region 16 of the GaN wafer 20 may be removed by machining other than grinding, laser machining, or the like.

Of the above steps, up to the step of forming a plurality of modified spots 13 along the virtual surface 15 is the laser machining method according to the present embodiment. Further, among the above steps, the step of acquiring a plurality of chips 30A from the GaN wafer 20 with the crack 17 and the modified regions M1 and M2 as boundaries is the semiconductor member manufacturing method of the present embodiment.

As described above, in the laser processing method according to the present embodiment, in the second step, the second laser beam L2 is incident on the GaN wafer 20 from the first surface 20a of the GaN wafer 20, and the second laser beam L2 is collected. The light spot C2 is moved into the virtual surface 15 facing the first surface 20a of the GaN wafer 20, and a plurality of modified spots 13 arranged in a plane shape are formed in the virtual surface 15. Therefore, the GaN wafer 20 can be cut with the crack 17 extending from the reforming spot 13 and extending to the virtual surface 15 as a boundary.

In particular, in the laser processing method according to the present embodiment, prior to the second step, the first laser beam L1 is irradiated along the lines A1 and A2 along the first surface 20a of the GaN wafer 20 in the first step. As a result, the modified regions M1 and M2 are formed linearly along the lines A1 and A2. The modified regions M1 and M2 are formed at least from the first surface 20a of the GaN wafer 20 to the virtual surface 15. Therefore, after the second step, in addition to cutting with the crack 17 extending over the virtual surface 15 as the boundary, cutting with the modified regions M1 and M2 as the boundary is possible. Therefore, according to this method, it is possible to obtain the chip 30A having a shape (smaller unit) different from that of the original GaN wafer 20.

When the condensing point C2 of the second laser beam L2 passes through the modified regions M1 and M2 when viewed from the Z-axis direction, the modified regions M1 and M2 affect the condensing state of the second laser beam L2. As a result, the modified spot 13 is unlikely to be formed. Therefore, a region in which the modification spot 13 is not formed is likely to be formed around the modification regions M1 and M2. This region has the function of preventing the growth of cracks extending from the modified spot. Therefore, according to the laser processing method according to the present embodiment, it is possible to prevent cracks extending from the modified spot from reaching the cut surface of the member obtained by cutting the modified regions M1 and M2 at the boundary.

Further, in the laser processing method according to the present embodiment, the GaN wafer 20 has a second surface 20b that is a surface opposite to the first surface 20a and faces the virtual surface 15. Then, in the first step, the modified regions M1 and M2 are formed from the first surface 20a to the second surface 20b. Therefore, in addition to the portion on the first surface 20a side of the GaN wafer 20, the portion on the second surface 20b side of the GaN wafer 20 is also cut with the modification regions M1 and M2 as boundaries, so that the plurality of chips 30A can be formed. It can be obtained.

Further, in the laser processing method according to the present embodiment, in the second step, a peripheral region 16 including the peripheral edge of the GaN wafer 20 when viewed from the Z-axis direction and in which the modification spot 13 is not formed is formed. Therefore, the peripheral region 16 can prevent cracks extending from the reforming spot 13 from reaching the outer edge of the GaN wafer 20.

Further, in the laser processing method according to the present embodiment, in the second step, the condensing point C2 of the second laser beam L2 is viewed from the outside of the GaN wafer 20 in the Z-axis direction and passed through the peripheral edge to the inside of the GaN wafer 20. By moving it so as to reach, the peripheral region 16 is formed. In this way, by moving the condensing point C2 of the second laser beam L2 from the outside of the GaN wafer 20 through the periphery to the inside, the change in the condensing state at the periphery (inhibition of condensing) is utilized. Therefore, the peripheral region 16 in which the modified spot 13 is not formed can be easily formed.

Further, in the laser processing method according to the present embodiment, the material of the object 11 contains gallium. Therefore, when gallium is deposited in the plurality of cracks 14 extending from the plurality of modified spots 13 by the irradiation of the second laser beam L2, the second laser beam L2 is easily absorbed by the gallium. Therefore, it is possible to form a crack 17 over the virtual surface 15 with a smaller output.

Further, in the laser processing method according to the present embodiment, the material of the object 11 contains gallium nitride. Therefore, when gallium nitride is decomposed by irradiation with the second laser beam L2, nitrogen gas is generated in the crack 14. Therefore, the crack 17 extending over the virtual surface 15 can be easily formed by utilizing the pressure (internal pressure) of the nitrogen gas.

The semiconductor member manufacturing method according to the present embodiment includes the first step and the second step provided in the above laser processing method, the crack 17 extending over the virtual surface 15 after the second step, and the modified regions M1 and M2. A third step of acquiring the chip 30A from the GaN wafer 20 with the above as a boundary is provided. Therefore, for the same reason, it is possible to obtain the chip 30A having a shape (smaller unit) different from that of the original GaN wafer 20.

Further, in the laser processing apparatus 1 according to the present embodiment, in the second processing, the second laser beam L2 is incident on the GaN wafer 20 from the first surface 20a of the GaN wafer 20, and the condensing point C2 of the second laser beam L2. Is moved into the virtual surface 15 facing the first surface 20a of the GaN wafer 20, and a plurality of modified spots 13 arranged in a plane shape are formed in the virtual surface 15. Therefore, the GaN wafer 20 can be cut with the crack 17 extending from the reforming spot 13 and extending to the virtual surface 15 as a boundary. In particular, in the laser processing apparatus 1, the first laser beam L1 is irradiated along the lines A1 and A2 along the first surface 20a of the GaN wafer 20 in the first processing prior to the second processing. The modified regions M1 and M2 are linearly formed along the lines A1 and A2. The modified regions M1 and M2 are formed from the first surface 20a to the second surface 20b. Therefore, after the second treatment, in addition to the cutting with the crack 17 extending over the virtual surface 15 as the boundary, the cutting with the modified regions M1 and M2 as the boundary is possible. Therefore, according to the laser processing apparatus 1, it is possible to obtain the GaN wafer 20 in a shape (smaller unit) different from that of the original GaN wafer 20.

Here, an experimental result showing that the unevenness appearing on the peeled surface of the GaN wafer becomes smaller when the GaN wafer is formed by the laser processing method and the semiconductor member manufacturing method of the present embodiment will be described. In the following description, a case where a GaN ingot is used as the object 11 and a GaN wafer is formed by peeling along the virtual surface of the GaN ingot will be described. However, the chip is formed by peeling along the virtual surface 15 of the GaN wafer 20. The same applies to the case of forming 30A.

FIG. 18 is an image of a peeling surface of a GaN wafer formed by an example laser processing method and a semiconductor member manufacturing method, and FIGS. 19A and 19B are heights of the peeling surface shown in FIG. It is a profile. In this example, a second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and one focusing point C2 is placed on the virtual surface 15 along the X-axis direction. By moving them relative to each other, a plurality of modified spots 13 were formed along the virtual surface 15. At this time, the distance between adjacent condensing points C2 in the Y-axis direction was 10 μm, the pulse pitch of the second laser beam L2 was 1 μm, and the pulse energy of the second laser beam L2 was 1 μJ. In this case, as shown in FIGS. 19A and 19B, irregularities of about 25 μm appeared on the peeled surface (surface formed by the crack 17) of the GaN wafer.

FIG. 20 is an image of a peeling surface of a GaN wafer formed by another example of a laser processing method and a semiconductor member manufacturing method, and FIGS. 21A and 21B are images of the peeling surface shown in FIG. Height profile. In this example, the second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and the first step and the second step of the laser processing method and the semiconductor member manufacturing method of the present embodiment are performed. Similar to the step, a plurality of modified spots 13 were formed along the virtual surface 15.

When forming a plurality of modified spots 13a, the distance between adjacent condensing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0. It was set to .33 μJ. When forming a plurality of modified spots 13b, the distance between adjacent focusing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0. It was set to .33 μJ. When forming a plurality of modified spots 13c, the distance between adjacent condensing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0. It was set to .33 μJ. When forming a plurality of modified spots 13d, the distance between adjacent focusing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0. It was set to .33 μJ. In this case, as shown in FIGS. 21 (a) and 21 (b), irregularities of about 5 μm appeared on the peeled surface of the GaN wafer.

From the above experimental results, in the GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of the present embodiment, the unevenness appearing on the peeled surface of the GaN wafer is reduced, that is, the crack 17 is formed along the virtual surface 15. It was found that it was formed with high accuracy. When the unevenness appearing on the peeled surface of the GaN wafer becomes small, the amount of grinding for flattening the peeled surface can be reduced. Therefore, reducing the unevenness that appears on the peeled surface of the GaN wafer is advantageous in terms of material utilization efficiency and production efficiency.

Next, the principle that unevenness appears on the peeled surface of the GaN wafer will be described.

For example, as shown in FIG. 22, a plurality of modified spots 13a are formed along the virtual surface 15, and the modified spots 13b are virtual so as to overlap the cracks 14a extending from the modified spots 13a on one side thereof. A plurality of modified spots 13b are formed along the surface 15. In this case, since the second laser beam L2 is easily absorbed by the gallium deposited in the plurality of cracks 14a, even if the condensing point C2 is located on the virtual surface 15, the modified spot 13a is Therefore, the modified spot 13b is likely to be formed on the incident side of the second laser beam L2.

Subsequently, a plurality of modified spots 13c are formed along the virtual surface 15 so that the modified spots 13c overlap the cracks 14b extending from the modified spots 13b on one side thereof. In this case as well, since the second laser beam L2 is easily absorbed by the gallium deposited in the plurality of cracks 14b, even if the condensing point C2 is located on the virtual surface 15, the modified spot 13b can be seen. Therefore, the modified spot 13c is likely to be formed on the incident side of the second laser beam L2. As described above, in this example, a plurality of reforming spots 13b are formed on the incident side of the second laser beam L2 with respect to the plurality of reforming spots 13a, and further, the plurality of reforming spots 13c are a plurality of reforming spots. It is more likely to be formed on the incident side of the second laser beam L2 with respect to 13b.

On the other hand, for example, as shown in FIG. 23, a plurality of modified spots 13a are formed along the virtual surface 15 so that the modified spots 13b do not overlap the cracks 14a extending from the modified spots 13a on both sides thereof. , A plurality of modified spots 13b are formed along the virtual surface 15. In this case, although the second laser beam L2 is easily absorbed by the gallium deposited in the plurality of cracks 14a, the modified spots 13b do not overlap the cracks 14a, so that the modified spots 13b are also modified spots 13a. It is formed on the virtual surface 15 in the same manner as above.

Subsequently, a plurality of modified spots 13c are formed along the virtual surface 15 so that the modified spots 13c overlap the cracks 14a and 14b extending from the modified spots 13a and 13b on both sides thereof. Further, a plurality of modified spots 13d are formed along the virtual surface 15 so that the modified spots 13d overlap the cracks 14a and 14b extending from the modified spots 13a and 13b on both sides thereof. In these cases, since the second laser beam L2 is easily absorbed by the gallium deposited in the plurality of cracks 14a and 14b, even if the focusing point C2 is located on the virtual surface 15, the modified spot Modified spots 13c and 13d are likely to be formed on the incident side of the second laser beam L2 with respect to 13a and 13b. As described above, in this example, the plurality of modified spots 13c and 13d are only likely to be formed on the incident side of the second laser beam L2 with respect to the plurality of modified spots 13a and 13b.

Based on the above principle, in the laser processing method and the semiconductor member manufacturing method of the present embodiment, a plurality of modifications are made so as not to overlap the plurality of modification spots 13a and the plurality of cracks 14a extending from the plurality of modification spots 13a. It can be seen that forming the spot 13b is extremely important for reducing the unevenness appearing on the peeled surface of the GaN wafer.

Next, in the laser processing method and the semiconductor member manufacturing method of the present embodiment, experimental results showing that the crack 17 grows accurately along the virtual surface 15 will be described.

24 (a) and 24 (b) are images of cracks formed in the middle of the laser processing method and the semiconductor member manufacturing method of an example, and FIG. 24 (b) is a rectangle in FIG. 24 (a). It is an enlarged image in the frame. In this example, a second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and six focusing points C2 arranged in the Y-axis direction are formed along the X-axis direction. By relatively moving on the virtual surface 15, a plurality of modified spots 13 were formed along the virtual surface 15. At this time, the distance between adjacent condensing points C2 in the Y-axis direction was 6 μm, the pulse pitch of the second laser beam L2 was 1 μm, and the pulse energy of the second laser beam L2 was 1.33 μJ. Then, the laser machining was stopped in the middle of the virtual surface 15. In this case, as shown in FIGS. 24A and 24, the crack extending from the processed region to the unprocessed region largely deviated from the virtual surface 15 in the unprocessed region.

25 (a) and 25 (b) are images of cracks formed in the middle of the laser processing method and the semiconductor member manufacturing method of another example, and FIG. 25 (b) is the image of the crack formed in the middle of the laser processing method and the semiconductor member manufacturing method. It is an enlarged image in the rectangular frame in. In this example, a second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and six focusing points C2 arranged in the Y-axis direction are formed along the X-axis direction. By relatively moving on the virtual surface 15, a plurality of modified spots 13 were formed along the virtual surface 15. Specifically, first, the distance between adjacent focusing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0.33 μJ. A plurality of rows of modified spots 13 were formed in the processed region and the second processed region.

Subsequently, the distance between adjacent condensing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0.33 μJ. A plurality of rows of modified spots 13 were formed in the two processing regions so that each row was located at the center between the rows of the already formed plurality of rows of modified spots 13. Subsequently, the distance between adjacent condensing points C2 in the Y-axis direction is 6 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0.33 μJ. The plurality of rows of modified spots 13 were formed so that each row was located at the center between the rows of the plurality of rows of modified spots 13 that had already been formed. In this case, as shown in FIGS. 25 (a) and 25, the cracks extending from the first processed region to the second processed region did not deviate significantly from the virtual surface 15 in the second processed region.

From the above experimental results, it was found that in the laser processing method and the semiconductor member manufacturing method of the present embodiment, the crack 17 grows accurately along the virtual surface 15. It is presumed that this is because the plurality of modified spots 13 previously formed in the second processed region served as guides when the cracks grew.

Next, in the laser processing method and the semiconductor member manufacturing method of the present embodiment, an experiment showing that the amount of elongation of the crack 14 extending from the modified spot 13 to the incident side and the opposite side of the second laser beam L2 is suppressed. The result will be described.

FIG. 26 is an image (image in side view) of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the comparative example. In this comparative example, a second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and one focusing point C2 is placed on the virtual surface 15 along the X-axis direction. A plurality of modified spots 13 were formed along the virtual surface 15 by moving the light relative to each other. Specifically, the distance between adjacent condensing points C2 in the Y-axis direction is 2 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0.3 μJ, and the virtual surface 15 is formed. A plurality of modified spots 13 were formed along the line. In this case, as shown in FIG. 26, the amount of extension of the crack 14 extending from the modified spot 13 to the incident side of the second laser beam L2 and the opposite side thereof is about 100 μm.

27 is an image of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the first embodiment, FIG. 27 (a) is an image in a plan view, and FIG. 27 (b) is. Is a side view image. In this first embodiment, the second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and the six focusing points C2 arranged in the Y-axis direction are aligned in the X-axis direction. By relatively moving on the virtual surface 15 along the virtual surface 15, a plurality of modified spots 13 were formed along the virtual surface 15. Specifically, first, the distance between adjacent condensing points C2 in the Y-axis direction is 8 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0.3 μJ. A plurality of modified spots 13a were formed along the line 15.

Subsequently, with the six focusing points C2 arranged in the Y-axis direction shifted by +4 μm in the Y-axis direction from the previous state, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, and the second laser beam L2 A plurality of modified spots 13b were formed along the virtual surface 15 with a pulse pitch of 10 μm and a pulse energy of the second laser beam L2 of 0.3 μJ. Subsequently, with the six focusing points C2 arranged in the Y-axis direction shifted by -4 μm in the Y-axis direction from the previous state, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, and the second laser beam is emitted. A plurality of modified spots 13 were formed along the virtual surface 15 with the pulse pitch of L2 being 5 μm and the pulse energy of the second laser beam L2 being 0.3 μJ.

Subsequently, with the six focusing points C2 arranged in the Y-axis direction shifted by +4 μm in the Y-axis direction from the previous state, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, and the second laser beam L2 The pulse pitch of the second laser beam L2 was set to 5 μm, and the pulse energy of the second laser beam L2 was set to 0.3 μJ, and a plurality of modified spots 13 were formed along the virtual surface 15. As a result, the modified spot 13a formed the first time and the modified spot 13 formed the third time overlap each other, and the modified spot 13b formed the second time and the modified spot 13 formed the fourth time overlap each other. It is assumed that it is. In this case, as shown in FIG. 27 (b), the amount of extension of the crack 14 extending from the modified spot 13 to the incident side and the opposite side of the second laser beam L2 was about 70 μm.

(A) and (b) of FIG. 28 are images of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the second embodiment, and FIG. 28 (a) is a plan view. The image, FIG. 28 (b) is a side view image. In this second embodiment, the second laser beam L2 having a wavelength of 532 nm is incident on the inside of the GaN ingot from the first surface 20a of the GaN ingot, and the first step of the laser processing method and the semiconductor member manufacturing method of the present embodiment. And, similarly to the second step, a plurality of modified spots 13 were formed along the virtual surface 15. When forming a plurality of modified spots 13a, the distance between adjacent condensing points C2 in the Y-axis direction is 8 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0. It was set to 0.3 μJ.

When forming a plurality of modified spots 13b, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, the pulse pitch of the second laser beam L2 is 10 μm, and the pulse energy of the second laser beam L2 is 0. It was set to 0.3 μJ. When forming a plurality of modified spots 13c, the distance between adjacent condensing points C2 in the Y-axis direction is 8 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0. It was set to 0.3 μJ. When forming a plurality of modified spots 13d, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0. It was set to 0.3 μJ. In this case, as shown in FIG. 28 (b), the amount of extension of the crack 14 extending from the modified spot 13 to the incident side and the opposite side of the second laser beam L2 was about 50 μm.

(C) and (d) of FIG. 28 are images of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the third embodiment, and FIG. 28 (c) is a plan view. The image, FIG. 28D, is a side view image. In this third embodiment, further along the virtual surface 15 in the state shown in FIGS. 28 (a) and 28 (that is, the virtual surface 15 in which the modification spots 13 in a plurality of rows have already been formed). , A plurality of modified spots 13 were formed.

Specifically, first, the distance between adjacent focusing points C2 in the Y-axis direction is 8 μm, the pulse pitch of the second laser beam L2 is 5 μm, and the pulse energy of the second laser beam L2 is 0.1 μJ. A plurality of rows of modified spots 13 were formed so that each row was located at the center between the rows of the plurality of rows of modified spots 13. In this case, as shown in FIG. 28D, the amount of extension of the crack 14 extending from the modified spot 13 to the incident side and the opposite side of the second laser beam L2 was about 60 μm.

From the above experimental results, if a plurality of modified spots 13b are formed along the virtual surface 15 so as not to overlap the plurality of modified spots 13a and the plurality of cracks 14a already formed along the virtual surface 15 ( It was found that the amount of extension of the crack 14 extending from the modified spot 13 to the incident side and the opposite side of the second laser beam L2 from the first example, the second example and the third example) was suppressed. When a plurality of modified spots 13 are formed along the virtual surface 15, the virtual surface 15 is formed so as not to overlap the plurality of modified spots 13a and 13b already formed along the virtual surface 15. If a plurality of modified spots 13 are formed along the same (second embodiment and third embodiment), cracks extending over the virtual surface 15 are likely to be formed.

The above-described embodiment describes a laser processing method, a semiconductor member manufacturing method, and a mode of a laser processing apparatus according to the present invention. Therefore, the above-mentioned laser processing method, semiconductor member manufacturing method, and laser processing apparatus can be arbitrarily modified. Hereinafter, a modified example will be described.

In the above embodiment, in the first step, the modified regions M1 and M2 extending from the first surface 20a to the second surface 20b of the GaN wafer 20 when viewed from the Z-axis direction are formed. However, as shown in FIG. 29, in the first step, the modified regions M1 and M2 may be formed so as to extend from the first surface 20a to the virtual surface 15 when viewed from the Z-axis direction. In this case, the modified regions M1 and M2 are not interposed (formed) between the virtual surface 15 and the second surface 20b when viewed from the Z-axis direction. Therefore, by cutting the GaN wafer 20 at the boundary between the modified regions M1 and M2 and the crack 17, a plurality of chips 30A and a single chip 30B can be obtained as shown in FIG. .. The chip 30B has the same shape as the GaN wafer 20 when viewed from the Z-axis direction. That is, in this case, chips 30A and chips 30B having different shapes can be obtained from the GaN wafer 20.

Further, in the above embodiment, a single virtual surface 15 is set for the GaN wafer 20. However, a plurality of virtual surfaces 15 may be set so as to be arranged in the Z-axis direction. In this case, in the first step, the modified regions M1 and M2 are formed at least from the first surface 20a of the GaN wafer 20 to the virtual surface 15 farthest from the first surface 20a. As a result, the GaN wafer 20 is cut with the plurality of virtual surfaces 15 (cracks 17 extending over the virtual surface 15) arranged in the Z-axis direction as boundaries, so that more chips 30A and the like can be acquired.

Further, in the above embodiment, the GaN wafer 20 is exemplified as the object 11. However, the object 11 can be, for example, a GaN ingot (semiconductor ingot) or any other semiconductor object. When the object 11 is a GaN ingot, for example, a GaN wafer can be obtained as a semiconductor member. In this case, a GaN wafer having a shape different from that of the GaN ingot can be obtained.

Further, in the above embodiment, the line A1 and the line A2 intersecting the line A1 are set as the criteria (criteria for cutting) for forming the modified regions M1 and M2. However, the lines A1 and A2 can be set in any shape and relative relationship according to the required shape of the semiconductor members (chips 30A and 30B) and the number of acquisitions, and the lines A1 and A2 are not limited to the pair of lines A1 and A2. One line or three or more lines may be set.

1 ... Laser processing device, 2 ... Stage, 4 ... Spatial light modulator (laser irradiation unit), 5 ... Condensing lens (laser irradiation unit), 6 ... Control unit, 11 ... Object (semiconductor object), 13 ... Modification spot, 15 ... virtual surface, 16 ... peripheral region, 17 ... crack, 20 ... GaN wafer (semiconductor wafer, semiconductor object), 20a ... first surface, 20b ... second surface, 30A, 30B ... chip (semiconductor) Chip, semiconductor member), A1, A2 ... line, C, C1, C2 ... condensing point, L ... laser light, L1 ... first laser light, L2 ... second laser light, M1, M2 ... modified region.

Claims (11)

A laser machining method for cutting a semiconductor object along a virtual surface facing the first surface of the semiconductor object and a line extending along the first surface inside the semiconductor object. ,
A first step of irradiating the semiconductor object with a first laser beam along the line to form a modified region extending linearly along the line when viewed from the first direction intersecting the first surface. When,
After the first step, the second laser beam is incident on the semiconductor object from the first surface, and the condensing point of the second laser beam passes through the modified region when viewed from the first direction. A second step of forming a plurality of modified spots arranged in a plane in the virtual surface by moving the light into the virtual surface.
With
In the first step, the modified region is formed from at least the first surface to the virtual surface when viewed from the second direction along the first surface.
Laser processing method. A plurality of the virtual surfaces are set so as to be arranged in the first direction.
In the first step, the modified region is formed at least from the first surface to the virtual surface farthest from the first surface.
The laser processing method according to claim 1. The semiconductor object has a surface opposite to the first surface and has a second surface facing the virtual surface.
In the first step, the modified region is formed from the first surface to the second surface.
The laser processing method according to claim 1 or 2. In the second step, a peripheral region including the peripheral edge of the semiconductor object when viewed from the first direction and in which the modified spot is not formed is formed.
The laser processing method according to any one of claims 1 to 3. In the second step, the focusing point of the second laser beam is moved from the outside of the semiconductor object to the inside of the semiconductor object through the peripheral edge when viewed from the first direction. , Forming the peripheral region,
The laser processing method according to claim 4. The material of the semiconductor object contains gallium.
The laser processing method according to any one of claims 1 to 5. The material of the semiconductor object includes gallium nitride.
The laser processing method according to claim 6. The first step and the second step included in the laser processing method according to any one of claims 1 to 7.
After the second step, a third step of acquiring a semiconductor member from the semiconductor object with a crack extending from the reforming spot and extending over the virtual surface and the reforming region as a boundary.
A method for manufacturing a semiconductor member. The semiconductor object is a semiconductor ingot.
The semiconductor member is a semiconductor wafer.
The semiconductor member manufacturing method according to claim 8. The semiconductor object is a semiconductor wafer.
The semiconductor member is a semiconductor chip.
The semiconductor member manufacturing method according to claim 8. A laser processing device for cutting a semiconductor object along a virtual surface facing the first surface of the semiconductor object and a line extending along the first surface inside the semiconductor object. ,
A stage that supports the semiconductor object and
A laser irradiation unit for irradiating the semiconductor object supported by the stage with a laser beam,
At least a control unit that controls the laser irradiation unit and
With
By irradiating the semiconductor object with the first laser beam along the line, the control unit linearly extends the modified region along the line when viewed from the first direction intersecting the first surface. The first process to form and
After the first treatment, the second laser beam is incident on the semiconductor object from the first surface, and the condensing point of the second laser beam passes through the modified region when viewed from the first direction. A second process of forming a plurality of modified spots arranged in a plane in the virtual surface by moving the light into the virtual surface.
And
In the first treatment, the modified region is formed from at least the first surface to the virtual surface when viewed from the second direction along the first surface.
Laser processing equipment.

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