WO2020130053A1 - Laser machining method, semiconductor member manufacturing method, and laser machining device - Google Patents

Abstract

A laser machining method for cutting a semiconductor target along a virtual plane that is inside the semiconductor target and faces the surface of the semiconductor target, said method comprising: a first step for preparing the semiconductor target; and a second step for forming a plurality of modified spots along the virtual plane by causing laser light to enter into the semiconductor target from the surface thereof. At the second step, the laser light is made incident such that the implantation energy per unit area in a first region among the virtual plane is greater than the implantation energy per unit area in a second region among the virtual plane.

Description

Laser processing method, semiconductor member manufacturing method, and laser processing apparatus

The present disclosure 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 a laser beam, a modified region is formed inside the semiconductor object, and a crack extending from the modified region is propagated, so that the semiconductor object is a semiconductor such as a semiconductor wafer. A processing method for cutting out a member is known (see, for example, Patent Documents 1 and 2).

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

In the processing method as described above, the method of forming the modified region greatly affects the state of the obtained semiconductor member.

The present disclosure has an object to provide a laser processing method, a semiconductor member manufacturing method, and a laser processing apparatus that enable acquisition of a suitable semiconductor member.

A laser processing method according to one aspect of the present disclosure is a laser processing method for cutting a semiconductor object inside a semiconductor object along a virtual surface that faces a surface of the semiconductor object. A first step of preparing and a second step of forming a plurality of modified spots along a virtual surface by injecting laser light into the inside of the semiconductor object from the surface are provided. In the second step, The laser light is made incident such that the implantation energy per unit area in the first region of the virtual surface is larger than the implantation energy per unit area in the second region of the virtual surface.

In this laser processing method, the laser light is made incident so that the implantation energy per unit area in the first region is larger than the implantation energy per unit area in the second region, so that a plurality of modifications are made along the virtual plane. Form quality spots. As a result, when a plurality of cracks respectively extending from the plurality of modified spots are connected to each other and a crack extending over the virtual surface is formed, the crack progresses so that the crack propagates from the first region to the second region. Can be controlled, and as a result, it is possible to accurately form a crack across the virtual surface along the virtual surface. Therefore, according to this laser processing method, it is possible to obtain a suitable semiconductor member by obtaining the semiconductor member from the semiconductor object with the crack across the virtual surface as the boundary.

In the laser processing method according to the one aspect of the present disclosure, in the second step, the peripheral area that prevents the development of the plurality of cracks extending from the plurality of modified spots may be set so as to surround the virtual surface. According to this, since the growth of a plurality of cracks to the outside of the virtual surface surrounded by the peripheral region is blocked, for example, when gas is generated in the plurality of cracks, the gas is prevented from escaping to the outside of the virtual surface. can do. Therefore, the crack (internal pressure) of the gas can be utilized to easily form a crack over the virtual surface.

In the laser processing method according to one aspect of the present disclosure, in the second step, the pulse energy of laser light per one condensing point in the first region is changed to the pulse energy of laser light per one converging point in the second region. May be larger than. According to this, it is possible to appropriately realize a state in which the implantation energy per unit area in the first region is larger than the implantation energy per unit area in the second region.

In the laser processing method according to one aspect of the present disclosure, the pulse pitch of the laser light in the first region may be smaller than the pulse pitch of the laser light in the second region in the second step. According to this, it is possible to appropriately realize a state in which the implantation energy per unit area in the first region is larger than the implantation energy per unit area in the second region.

In the laser processing method according to the one aspect of the present disclosure, in the second step, the condensing point of the laser light is moved along each of the plurality of rows on the virtual surface, and the inter-row pitch of the laser light in the first region is set to the first row. It may be smaller than the inter-row pitch of the laser light in the two regions. According to this, it is possible to appropriately realize a state in which the implantation energy per unit area in the first region is larger than the implantation energy per unit area in the second region.

In the laser processing method according to one aspect of the present disclosure, the first region may be the outer edge region of the virtual surface. According to this, the progress of the crack can be controlled so that the crack propagates inward from the outer edge region.

In the laser processing method according to one aspect of the present disclosure, the second area may be an outer edge area of the virtual surface. According to this, the progress of the crack can be controlled so that the crack propagates from the inner side to the outer edge region.

In the laser processing method according to one aspect of the present disclosure, the virtual surface has a rectangular shape, and the first area may be a plurality of corner areas of the virtual surface. According to this, the progress of the crack can be controlled so that the crack propagates inward from the plurality of corner regions.

In the laser processing method according to one aspect of the present disclosure, the virtual surface may have a rectangular shape, and the second area may be a plurality of corner areas of the virtual surface. According to this, the progress of the crack can be controlled so that the crack propagates from the inner side to the plurality of corner regions.

In the laser processing method according to one aspect of the present disclosure, the material of the semiconductor object may include gallium nitride. In this case, when gallium nitride is decomposed by the irradiation of laser light, nitrogen gas is generated in a plurality of cracks extending from the plurality of modified spots. Therefore, the pressure (internal pressure) of the nitrogen gas can be used to easily form a crack over the virtual surface.

A semiconductor member manufacturing method according to one aspect of the present disclosure includes a first step and a second step included in the above-described laser processing method, and a plurality of cracks respectively extending from a plurality of modified spots, which are connected to each other to form a crack across a virtual surface. And a fourth step of obtaining a semiconductor member from a semiconductor object with a crack across a virtual surface as a boundary.

According to this semiconductor member manufacturing method, in the third step, it is possible to accurately form a crack extending over the virtual surface along the virtual surface, and thus it is possible to obtain a suitable semiconductor member.

In the semiconductor member manufacturing method according to the one aspect of the present disclosure, the semiconductor object may be heated in the third step. According to this, for example, when gas is generated in a plurality of cracks respectively extending from the plurality of reforming spots, the gas can be expanded. Therefore, the crack (internal pressure) of the gas can be utilized to easily form a crack over the virtual surface.

In the semiconductor member manufacturing method according to one aspect of the present disclosure, a plurality of virtual surfaces may be set so as to be aligned in a direction facing the surface. According to this, a plurality of semiconductor members can be obtained from one semiconductor object.

In the method for manufacturing a semiconductor member according to one aspect of the present disclosure, the semiconductor object may be a semiconductor ingot, and the semiconductor member may be a semiconductor wafer. According to this, a plurality of suitable semiconductor wafers can be obtained.

In the semiconductor member manufacturing method according to one aspect of the present disclosure, a plurality of virtual surfaces may be set so as to be arranged in the direction in which the surface extends. According to this, a plurality of semiconductor members can be obtained from one semiconductor object.

In the semiconductor member manufacturing method according to one aspect of the present disclosure, the semiconductor object may be a semiconductor wafer, and the semiconductor member may be a semiconductor device. According to this, a plurality of suitable semiconductor devices can be obtained.

A laser processing apparatus according to one aspect of the present disclosure is a laser processing apparatus for cutting a semiconductor object inside a semiconductor object along a virtual surface that faces a surface of the semiconductor object. The laser irradiation unit includes a supporting stage and a laser irradiation unit that forms a plurality of modified spots along the virtual surface by making a laser beam enter the inside of the semiconductor object from the surface. The laser light is made incident so that the implantation energy per unit area in the first region is larger than the implantation energy per unit area in the second region of the virtual surface.

With this laser processing apparatus, it is possible to accurately form a crack across a virtual surface along the virtual surface, and thus it is possible to obtain a suitable semiconductor member.

According to the present disclosure, it is possible to provide a laser processing method, a semiconductor member manufacturing method, and a laser processing apparatus capable of obtaining a suitable semiconductor member.

FIG. 1 is a configuration diagram of a laser processing apparatus according to an embodiment. FIG. 2 is a side view of a GaN ingot which is an object of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 3 is a plan view of the GaN ingot shown in FIG. FIG. 4 is a vertical cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 5 is a cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 6 is a vertical cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 7 is a cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 8 is a vertical cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 9 is a cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 10 is a vertical cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 11 is a cross-sectional view of a part of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 12 is a side view of the GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 13 is a side view of a GaN wafer in one step of the laser processing method and semiconductor member manufacturing method of the first embodiment. FIG. 14 is an image of a separated surface of a GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of an example. FIG. 15 is a height profile of the peeled surface shown in FIG. FIG. 16 is an image of the separated surface of the GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of another example. FIG. 17 is a height profile of the peeled surface shown in FIG. FIG. 18 is a schematic diagram for explaining the principle of forming a peeled surface by an example laser processing method and semiconductor member manufacturing method. FIG. 19 is a schematic view for explaining the principle of forming a peeled surface by a laser processing method and a semiconductor member manufacturing method of another example. FIG. 20 is an image of a crack formed in the course of an example laser processing method and semiconductor member manufacturing method. FIG. 21 is an image of a crack formed during the laser processing method and the semiconductor member manufacturing method of another example. FIG. 22 is an image of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the comparative example. FIG. 23 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. 24 is an image of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the second and third embodiments. FIG. 25 is a plan view of a GaN wafer which is an object of the laser processing method and the semiconductor member manufacturing method of the second embodiment. FIG. 26 is a plan view of the virtual surface shown in FIG. FIG. 27 is a side view of a part of the GaN wafer in one step of the laser processing method and the semiconductor member manufacturing method of the second embodiment. FIG. 28 is a side view of a part of the GaN wafer in one step of the laser processing method and the semiconductor member manufacturing method of the second embodiment. FIG. 29 is a side view of the semiconductor device in one step of the laser processing method and the semiconductor member manufacturing method of the second embodiment. FIG. 30 is an image of cracks in the SiC wafer formed by the laser processing method and the semiconductor member manufacturing method of the comparative example. FIG. 31 is an image of a crack of a SiC wafer formed by the laser processing method and the semiconductor member manufacturing method of the example. FIG. 32 is an image of the separated surface of the SiC wafer formed by the laser processing method and the semiconductor member manufacturing method of the example. 33 is a height profile of the peeled surface shown in FIG. 32. FIG. 34 is a plan view of a GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the modified example. FIG. 35 is a plan view of a GaN ingot in one step of the laser processing method and the semiconductor member manufacturing method of the modified example. FIG. 36 is a plan view of a modified GaN ingot. FIG. 37 is a plan view of a virtual surface of the modified example.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the same reference symbols and redundant description will be omitted.
[Configuration 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 apparatus 1 is an apparatus that forms a modified region 12 on the object 11 by irradiating the object 11 with a laser beam L. Hereinafter, the first horizontal direction will be referred to as the X direction, and the second horizontal direction perpendicular to the first horizontal direction will be referred to as the Y direction. The vertical direction is called the Z direction.

The stage 2 supports the target object 11 by, for example, adsorbing a film attached to the target object 11. In the present embodiment, the stage 2 is movable along each of the X direction and the Y direction. Further, the stage 2 can rotate about an axis parallel to the Z direction as a center line.

The light source 3 outputs a laser beam L that is transparent to the object 11 by using, for example, a pulse oscillation method. The spatial light modulator 4 modulates the laser light L output from the light source 3. The spatial light modulator 4 is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). The condenser lens 5 condenses the laser light L modulated by the spatial light modulator 4. In this embodiment, the spatial light modulator 4 and the condenser lens 5 are movable as a laser irradiation unit along the Z direction.

When the laser light L is condensed inside the target object 11 supported by the stage 2, the laser light L is particularly absorbed at a portion corresponding to the condensing point C of the laser light L, and the inside of the target object 11 is modified. A quality region 12 is formed. The modified region 12 is a region in which density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding unmodified region. The modified region 12 includes, for example, a melt-processed region, a crack region, a dielectric breakdown region, and a refractive index change region.

As an example, when the stage 2 is moved along the X direction and the condensing point C is moved relative to the target object 11 along the X direction, a plurality of modified spots 13 are moved along the X direction by 1. It is formed so as to line up in a row. One modified spot 13 is formed by irradiation with one pulse of laser light L. The one-row reforming region 12 is a set of a plurality of reforming spots 13 arranged in one row. The adjacent modified spots 13 may be connected to each other or may be separated from each other depending on the relative moving speed of the condensing point C with respect to the object 11 and the repetition frequency of the laser light L.

The control unit 6 controls the stage 2, the light source 3, the spatial light modulator 4, and the condenser lens 5. 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, the software (program) read into the memory or the like is executed by the processor, and the reading and writing of data in the memory and the storage and the communication by the communication device are controlled by the processor. Thereby, the control unit 6 realizes various functions.
[Laser Processing Method and Semiconductor Member Manufacturing Method of First Embodiment]

The object 11 of the laser processing method and the semiconductor member manufacturing method of the first embodiment is, as shown in FIGS. 2 and 3, a GaN ingot (semiconductor ingot, formed of gallium nitride (GaN), for example, in a disk shape. Semiconductor object) 20. As an example, the GaN ingot 20 has a diameter of 2 inches and the GaN ingot 20 has a thickness of 2 mm. The laser processing method and the semiconductor member manufacturing method of the first embodiment are performed to cut out a plurality of GaN wafers (semiconductor wafers, semiconductor members) 30 from the GaN ingot 20. As an example, the GaN wafer 30 has a diameter of 2 inches and the GaN wafer 30 has a thickness of 100 μm.

First, a GaN ingot 20 is prepared (first step), and the laser processing apparatus 1 described above forms a plurality of modified spots 13 along each of a plurality of virtual surfaces 15. Each of the plurality of virtual surfaces 15 is a surface facing the surface 20a of the GaN ingot 20, and is set so as to be aligned in a direction facing the surface 20a. In the present embodiment, each of the plurality of virtual planes 15 is a plane parallel to the surface 20a inside the GaN ingot 20, and has, for example, a circular shape. Each of the plurality of virtual surfaces 15 is set so as to overlap each other when viewed from the front surface 20a side. Each of the plurality of virtual surfaces 15 includes a first region R1 and a second region R2. The second region R2 is an outer edge region along the outer edge of the virtual surface 15. The first region R1 is a region surrounded by the second region R2. In the present embodiment, the first region R1 has, for example, a circular shape, and the second region R2 has, for example, an annular shape. A plurality of peripheral regions 16 are set in the GaN ingot 20 so as to surround each of the plurality of virtual surfaces 15. That is, each of the plurality of virtual surfaces 15 does not reach the side surface 20b of the GaN ingot 20. As an example, the distance between the adjacent virtual surfaces 15 is 100 μm, and the width of the peripheral region 16 (in the present embodiment, the distance between the outer edge of the virtual surface 15 and the side surface 20b) is 30 μm or more.

The formation of the plurality of modified spots 13 is sequentially performed for each one virtual surface 15 from the side opposite to the surface 20a by the irradiation of the laser light L having a wavelength of 532 nm, for example. Since the formation of the plurality of modified spots 13 is the same on each of the plurality of virtual surfaces 15, the formation of the plurality of modified spots 13 along the virtual surface 15 closest to the surface 20a will be described below with reference to FIGS. This will be described in detail with reference to 11. In addition, in FIG. 5, FIG. 7, FIG. 9, and FIG. 11, the arrow indicates the locus of the condensing point C of the laser light L. Further, the modified spots 13a, 13b, 13c, 13d described later may be collectively referred to as the modified spot 13, and the cracks 14a, 14b, 14c, 14d described later may be collectively referred to as the crack 14.

First, as shown in FIGS. 4 and 5, the laser processing apparatus 1 causes the laser light L to enter the inside of the GaN ingot 20 from the front surface 20 a, so that the laser light L is incident along the virtual surface 15 (for example, in the virtual surface 15). A plurality of modified spots 13a are formed (two-dimensionally arranged along the whole) (second step). At this time, the laser processing apparatus 1 forms the plurality of modified spots 13a so that the plurality of cracks 14a extending from the plurality of modified spots 13a are not connected to each other. Further, the laser processing apparatus 1 forms the modified spots 13a in a plurality of rows by moving the condensing point C of the pulsed laser light L along the virtual surface 15. Further, the laser processing apparatus 1 makes the laser light L enter such that the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2. In the present embodiment, the laser processing apparatus 1 determines the pulse energy of the laser light L per one focus point C in the first region R1 as the pulse energy of the laser light L per one focus point C in the second region R2. Bigger than. 4 and 5, the modified spot 13a is shown in white (no hatching), and the range in which the crack 14a extends is shown by broken lines (the same applies to FIGS. 6 to 11).

In the present embodiment, the pulsed laser light L is modulated by the spatial light modulator 4 so as to be condensed at a plurality of (for example, six) condensing points C arranged in the Y direction. Then, the plurality of condensing points C are relatively moved on the virtual surface 15 along the X direction. As an example, the distance between the condensing points C adjacent to each other in the Y direction is 8 μm, and the pulse pitch of the laser light L (that is, the relative moving speed of the plurality of condensing points C is determined by the repetition frequency of the laser light L). The divided value) is 10 μm. In addition, the pulse energy of the laser light L per one condensing point C (hereinafter, simply referred to as “pulse energy of the laser light L”) is 0.4 μJ in the first region R1, and is 0.4 μJ in the second region R2. It is 33 μJ. In this case, the center-to-center distance between adjacent modified spots 13a in the Y direction is 8 μm, and the center-to-center distance between adjacent modified spots 13a in the X direction is 10 μm. Further, the cracks 14a extending from the modified spots 13a are not connected to each other.

Then, the laser processing apparatus 1 causes the laser light L to enter the inside of the GaN ingot 20 from the surface 20a as shown in FIGS. 6 and 7, and along the virtual plane 15 (for example, the virtual plane 15). A plurality of modified spots 13b are formed so as to be two-dimensionally arranged along the entire area (second step). At this time, the laser processing apparatus 1 forms the plurality of modified spots 13b so as not to overlap the plurality of modified spots 13a and the plurality of cracks 14a. Moreover, the laser processing apparatus 1 moves the condensing point C of the pulsed laser light L along the virtual plane 15 between the rows of the reforming spots 13a of the plurality of rows to thereby form the reforming spots 13b of the plurality of rows. To form. Further, the laser processing apparatus 1 makes the laser light L enter such that the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2. In the present embodiment, the laser processing apparatus 1 makes the pulse energy of the laser light L in the first region R1 larger than the pulse energy of the laser light L in the second region R2. In this step, the cracks 14b extending from the modified spots 13b may be connected to the cracks 14a. 6 and 7, the modified spot 13b is shown by dot hatching, and the range in which the crack 14b extends is shown by broken lines (the same applies to FIGS. 8 to 11).

In the present embodiment, the pulsed laser light L is modulated by the spatial light modulator 4 so as to be condensed at a plurality of (for example, six) condensing points C arranged in the Y direction. Then, the plurality of condensing points C are relatively moved on the virtual surface 15 along the X direction at the centers between the rows of the reformed spots 13a. As an example, the distance between the condensing points C adjacent to each other in the Y direction is 8 μm, and the pulse pitch of the laser light L is 10 μm. The pulse energy of the laser light L is 0.4 μJ in the first region R1 and 0.33 μJ in the second region R2. In this case, the center-to-center distance between adjacent modified spots 13b in the Y direction is 8 μm, and the center-to-center distance between adjacent modified spots 13b in the X direction is 10 μm.

Then, the laser processing apparatus 1 causes the laser light L to enter the inside of the GaN ingot 20 from the surface 20a as shown in FIGS. A plurality of modified spots 13c are formed so as to be arranged two-dimensionally along the entire area (second step). Further, as shown in FIGS. 10 and 11, the laser processing apparatus 1 causes the laser light L to enter the inside of the GaN ingot 20 from the surface 20 a, so that the laser light L is incident along the virtual surface 15 (for example, the virtual surface 15 A plurality of modified spots 13d are formed so as to be two-dimensionally arranged along the whole (second step). At this time, the laser processing apparatus 1 forms the 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 condensing point C of the pulsed laser light L along the virtual plane 15 between the rows of the reforming spots 13a and 13b of the plurality of rows, thereby reforming the plurality of rows. The spots 13c and 13d are formed. Further, the laser processing apparatus 1 makes the laser light L enter such that the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2. In the present embodiment, the laser processing apparatus 1 makes the pulse energy of the laser light L in the first region R1 larger than the pulse energy of the laser light L in the second region R2. In this step, the cracks 14c and 14d extending from the modified spots 13c and 13d may be connected to the cracks 14a and 14b. 8 and 9, the modified spot 13c is shown by solid line hatching, and the range in which the crack 14c extends is shown by broken lines (also in FIGS. 10 and 11). 10 and 11, the modified spot 13d is shown by solid line hatching (solid line hatching that is the reverse of the solid line hatching of the modified spot 13c), and the range in which the crack 14d extends is shown by broken lines. There is.

In the present embodiment, the pulsed laser light L is modulated by the spatial light modulator 4 so as to be condensed at a plurality of (for example, six) condensing points C arranged in the Y direction. Then, the plurality of converging points C are relatively moved on the virtual surface 15 along the X direction at the center between the rows of the reformed spots 13a and 13b of the plurality of rows. As an example, the distance between the condensing points C adjacent to each other in the Y direction is 8 μm, and the pulse pitch of the laser light L is 5 μm. The pulse energy of the laser light L is 0.33 μJ in the first region R1 and the second region R2. In this case, the center-to-center distance between adjacent modified spots 13c in the Y direction is 8 μm, and the center-to-center distance between adjacent modified spots 13c in the X direction is 5 μm. Further, the center-to-center distance between the modified spots 13d adjacent to each other in the Y direction is 8 μm, and the center-to-center distance between the modified spots 13d adjacent to each other in the X-direction is 5 μm.

Subsequently, a heating device including a heater or the like heats the GaN ingot 20 to connect the plurality of cracks 14 extending from the plurality of modified spots 13 to each other on each of the plurality of virtual planes 15, thereby being shown in FIG. As described above, in each of the plurality of virtual planes 15, the crack 17 (hereinafter, simply referred to as “crack 17”) across the virtual plane 15 is formed (third step). In FIG. 12, a range in which the plurality of modified spots 13, the plurality of cracks 14, and the crack 17 are formed is shown by a broken line. The cracks 17 may be formed by connecting the plurality of cracks 14 to each other by applying some force to the GaN ingot 20 by a method other than heating. Further, by forming the plurality of modified spots 13 along the virtual surface 15, the plurality of cracks 14 may be connected to each other to form the crack 17.

Here, in the GaN ingot 20, nitrogen gas is generated in a plurality of cracks 14 extending from the plurality of modified spots 13, respectively. Therefore, by heating the GaN ingot 20 and expanding the nitrogen gas, the crack 17 can be formed by utilizing the pressure (internal pressure) of the nitrogen gas. Moreover, since the peripheral region 16 prevents the cracks 14 from propagating to the outside of the virtual surface 15 surrounded by the peripheral region 16 (for example, the side surface 20b of the GaN ingot 20), nitrogen generated in the cracks 14 is prevented. It is possible to prevent the gas from escaping to the outside of the virtual surface 15. That is, the peripheral area 16 is a non-modified area that does not include the modified spot 13, and when the crack 17 is formed on the virtual surface 15 surrounded by the peripheral area 16, the virtual surface 15 surrounded by the peripheral area 16 is formed. It is a region that prevents the plurality of cracks 14 from propagating to the outside. Therefore, the width of the peripheral region 16 is preferably 30 μm or more. Furthermore, by irradiating the laser light L so that the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2, a plurality of modifications are performed along the virtual surface 15. A quality spot 13 is formed. Thereby, when the plurality of cracks 14 respectively extending from the plurality of modified spots 13 are connected to each other, a crack (a crack that connects the plurality of cracks 14 to each other and finally becomes a crack 17) is generated from the first region R1 to the second region. Propagation of the crack is controlled so as to propagate to R2.

Then, the grinding device grinds (polishs) the portions of the GaN ingot 20 corresponding to the plurality of peripheral regions 16 and the plurality of virtual surfaces 15, respectively, so that a plurality of cracks 17 are formed as shown in FIG. A plurality of GaN wafers 30 are obtained from the GaN ingot 20 with each of them as a boundary (fourth step). In this way, the GaN ingot 20 is cut along each of the virtual surfaces 15. In this step, portions of the GaN ingot 20 corresponding to the plurality of peripheral regions 16 may be removed by mechanical processing other than grinding, laser processing, or the like.

Among the above steps, up to the step of forming the plurality of modified spots 13 along each of the plurality of virtual surfaces 15 is the laser processing method of the first embodiment. Further, among the above steps, the steps up to the step of obtaining the plurality of GaN wafers 30 from the GaN ingot 20 with each of the plurality of cracks 17 as boundaries are the semiconductor member manufacturing method of the first embodiment.

As described above, in the laser processing method according to the first embodiment, the laser light L is irradiated so that the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2. By making it enter, a plurality of modified spots 13 are formed along each of the plurality of virtual surfaces 15. Thereby, in each of the plurality of virtual surfaces 15, when the plurality of cracks 14 extending from the plurality of modified spots 13 are connected to each other to form the crack 17, a crack (the plurality of cracks 14 are connected to each other and finally The crack can be controlled so that the crack 17 becomes a crack 17) from the first region R1 to the second region R2, and as a result, the crack 17 can be accurately aligned along each of the plurality of virtual planes 15. It becomes possible to form well. Therefore, according to the laser processing method of the first embodiment, a plurality of suitable GaN wafers 30 can be obtained by obtaining a plurality of GaN wafers 30 from the GaN ingot 20 with each of the plurality of cracks 17 as a boundary. Become.

Similarly, according to the laser processing apparatus 1 that implements the laser processing method of the first embodiment, it is possible to accurately form the crack 17 along each of the plurality of virtual surfaces 15, and thus it is possible to perform a plurality of preferable operations. The GaN wafer 30 can be acquired.

Further, in the laser processing method of the first embodiment, the peripheral region 16 that prevents the development of the cracks 14 extending from the modified spots 13 is set so as to surround each of the virtual surfaces 15. As a result, the growth of the plurality of cracks 14 to the outside of the virtual surface 15 surrounded by the peripheral region 16 is prevented, so that, for example, when gas is generated in the plurality of cracks 14, the gas escapes to the outside of the virtual surface 15. Can be suppressed. Therefore, the crack 17 can be easily formed by utilizing the pressure of the gas. In this embodiment, when gallium nitride contained in the material of the GaN ingot 20 is decomposed by the irradiation of the laser light L, nitrogen gas is generated in the cracks 14. Therefore, the crack 17 can be easily formed by utilizing the pressure of the nitrogen gas.

Further, in the laser processing method of the first embodiment, the laser light L is irradiated so that the pulse energy of the laser light L in the first region R1 is larger than the pulse energy of the laser light L in the second region R2. This makes it possible to appropriately realize a state in which the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2.

Further, in the laser processing method of the first embodiment, the second region R2 is the outer edge region of the virtual surface 15 in each of the virtual surfaces 15. Thereby, in each of the plurality of virtual surfaces 15, the progress of the crack is controlled so that the crack (the crack that connects the plurality of cracks 14 and finally becomes the crack 17) propagates from the inner side to the outer edge region. You can

Further, according to the semiconductor member manufacturing method of the first embodiment, it is possible to accurately form the crack 17 along each of the virtual surfaces 15 by the steps included in the laser processing method of the first embodiment. Therefore, it is possible to obtain a plurality of suitable GaN wafers 30.

Further, in the semiconductor member manufacturing method of the first embodiment, the GaN ingot 20 is heated to connect the plurality of cracks 14 to each other to form the crack 17. Thereby, for example, when gas is generated in the plurality of cracks 14 extending from the plurality of reforming spots 13, the gas can be expanded. Therefore, the crack 17 can be easily formed by utilizing the pressure of the gas. In this embodiment, when gallium nitride contained in the material of the GaN ingot 20 is decomposed by the irradiation of the laser light L, nitrogen gas is generated in the cracks 14. Therefore, the crack 17 can be easily formed by utilizing the pressure of the nitrogen gas. As described above, by controlling the progress of cracks (cracks in which a plurality of cracks 14 are connected to each other to finally become the cracks 17), it is expected that the heating time is shortened, the heating temperature is lowered, and the like. You can

Further, in the semiconductor member manufacturing method of the first embodiment, the plurality of virtual surfaces 15 are set so as to be arranged in a direction facing the surface 20 a of the GaN ingot 20. This makes it possible to obtain a plurality of GaN wafers 30 from one GaN ingot 20.

Here, an explanation will be given of an experimental result showing that the GaN wafer 30 formed by the laser processing method and the semiconductor member manufacturing method of the first embodiment has a smaller unevenness on the separated surface of the GaN wafer 30.

FIG. 14 is an image of a peeled surface of a GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of an example, and FIGS. 15A and 15B show the height of the peeled surface shown in FIG. It is a profile. In this example, laser light L having a wavelength of 532 nm is made incident on the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and one condensing point C is relatively moved on the virtual plane 15 along the X direction. By moving, a plurality of modified spots 13 were formed along the virtual surface 15. At this time, the distance between adjacent condensing points C in the Y direction was 10 μm, the pulse pitch of the laser light L was 1 μm, and the pulse energy of the laser light L was 1 μJ. In this case, as shown in (a) and (b) of FIG. 15, irregularities of about 25 μm appeared on the separated surface (surface formed by the crack 17) of the GaN wafer 30.

FIG. 16 is an image of a peeled surface of a GaN wafer formed by a laser processing method and a semiconductor member manufacturing method of another example, and FIGS. 17A and 17B show the peeled surface of FIG. It is a height profile. In this example, laser light L having a wavelength of 532 nm is made to enter the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment is performed. A plurality of modified spots 13 were formed along the virtual surface 15. When forming the plurality of modified spots 13a, the distance between the condensing points C adjacent to each other in the Y direction was 6 μm, the pulse pitch of the laser light L was 10 μm, and the pulse energy of the laser light L was 0.33 μJ. When forming the plurality of modified spots 13b, the distance between the condensing points C adjacent to each other in the Y direction was 6 μm, the pulse pitch of the laser light L was 10 μm, and the pulse energy of the laser light L was 0.33 μJ. When forming the plurality of modified spots 13c, the distance between the condensing points C adjacent to each other in the Y direction was 6 μm, the pulse pitch of the laser light L was 5 μm, and the pulse energy of the laser light L was 0.33 μJ. When forming the plurality of modified spots 13d, the distance between the condensing points C adjacent to each other in the Y direction was 6 μm, the pulse pitch of the laser light L was 5 μm, and the pulse energy of the laser light L was 0.33 μJ. In this case, as shown in FIGS. 17A and 17B, unevenness of about 5 μm appeared on the separated surface of the GaN wafer 30.

From the above experimental results, in the GaN wafer formed by the laser processing method and the semiconductor member manufacturing method of the first embodiment, the irregularities appearing on the separated surface of the GaN wafer 30 become small, that is, cracks occur along the virtual surface 15. It was found that 17 was accurately formed. It should be noted that if the irregularities appearing on the peeled surface of the GaN wafer 30 become small, the amount of grinding for flattening the peeled surface will be small. Therefore, it is advantageous in terms of material utilization efficiency and production efficiency that the irregularities appearing on the separated surface of the GaN wafer 30 become small.

Next, the principle that unevenness appears on the peeled surface of the GaN wafer 30 will be described.

For example, as shown in FIG. 18, a plurality of modified spots 13a are formed along a virtual surface 15, and the modified spots 13b are virtual so that the modified spots 13b overlap the cracks 14a extending from the modified spots 13a on one side. A plurality of modified spots 13b are formed along the surface 15. In this case, since the laser light L is easily absorbed by the gallium deposited in the plurality of cracks 14a, even if the condensing point C is located on the virtual surface 15, the laser is not applied to the modified spot 13a. The modified spot 13b is easily formed on the incident side of the light L. Then, 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. Also in this case, since the laser light L is easily absorbed by the gallium deposited in the plurality of cracks 14b, even if the condensing point C is located on the virtual surface 15, the laser is not applied to the modified spot 13b. The modified spot 13c is easily formed on the incident side of the light L. As described above, in this example, the plurality of modified spots 13b are formed on the incident side of the laser light L with respect to the plurality of modified spots 13a, and further, the plurality of modified spots 13c are formed into the plurality of modified spots 13b. On the other hand, it tends to be formed on the incident side of the laser light L.

On the other hand, for example, as shown in FIG. 19, 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 laser light L is easily absorbed by the gallium deposited in the plurality of cracks 14a, the modified spot 13b does not overlap the crack 14a, so the modified spot 13b is similar to the modified spot 13a. Are formed on the virtual surface 15. 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 laser light L is easily absorbed by the gallium deposited on the plurality of cracks 14a and 14b, even if the condensing point C is located on the virtual surface 15, the modified spots 13a, The modified spots 13c and 13d are easily formed on the incident side of the laser light L with respect to 13b. As described above, in this example, the modified spots 13c and 13d are easily formed on the incident side of the laser light L with respect to the modified spots 13a and 13b.

From the above principle, in the laser processing method and the semiconductor member manufacturing method of the first embodiment, a plurality of modified spots 13a and a plurality of modified spots 13a are provided so as not to overlap the cracks 14a extending from the modified spots 13a. It can be seen that the formation of the quality spots 13b is extremely important in reducing the unevenness appearing on the separated surface of the GaN wafer 30.

Next, in the laser processing method and the semiconductor member manufacturing method according to the first embodiment, an experimental result showing that the crack 17 propagates along the virtual surface 15 with high accuracy will be described.

20A and 20B are images of cracks formed during the laser processing method and the semiconductor member manufacturing method of an example, and FIG. 20B is a rectangle in FIG. 20A. It is an enlarged image in the frame. In this example, laser light L having a wavelength of 532 nm is made to enter the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and the six condensing points C arranged in the Y direction are arranged on the virtual surface 15 along the X direction. Were relatively moved to form a plurality of modified spots 13 along the virtual surface 15. At this time, the distance between the condensing points C adjacent to each other in the Y direction was 6 μm, the pulse pitch of the laser light L was 1 μm, and the pulse energy of the laser light L was 1.33 μJ. Then, the laser processing was stopped in the middle of the virtual surface 15. In this case, as shown in (a) and (b) of FIG. 20, the crack that propagated from the processed region to the unprocessed region largely deviated from the virtual surface 15 in the unprocessed region.

21(a) and 21(b) are images of cracks formed during the laser processing method and the semiconductor member manufacturing method of another example, and FIG. 21(b) is FIG. 21(a). It is an enlarged image in the rectangular frame in. In this example, laser light L having a wavelength of 532 nm is made to enter the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and the six condensing points C arranged in the Y direction are arranged on the virtual surface 15 along the X direction. Were relatively moved to form a plurality of modified spots 13 along the virtual surface 15. Specifically, first, the processing area 1 and the processing area 2 are set such that the distance between the condensing points C adjacent to each other in the Y direction is 6 μm, the pulse pitch of the laser light L is 10 μm, and the pulse energy of the laser light L is 0.33 μJ. A plurality of rows of modified spots 13 were formed on the surface. Then, the distance between the condensing points C adjacent to each other in the Y direction is 6 μm, the pulse pitch of the laser light L is 10 μm, and the pulse energy of the laser light L is 0.33 μJ. A plurality of rows of modified spots 13 were formed such that each row was positioned in the center between the plurality of rows of modified spots 13. Then, the distance between the condensing points C adjacent to each other in the Y direction is 6 μm, the pulse pitch of the laser light L is 5 μm, and the pulse energy of the laser light L is 0.33 μJ. A plurality of rows of reforming spots 13 were formed such that each row was positioned at the center between the rows of reforming spots 13. In this case, as shown in (a) and (b) of FIG. 21, the crack propagated from the processing region 1 to the processing region 2 was not largely deviated from the virtual surface 15 in the processing region 2.

From the above experimental results, it was found that in the laser processing method and the semiconductor member manufacturing method of the first embodiment, the crack 17 propagates along the virtual surface 15 with high accuracy. It is assumed that this is because the plurality of modified spots 13 previously formed in the processed region 2 served as guides when the crack propagated.

Next, in the laser processing method and the semiconductor member manufacturing method of the first embodiment, an experimental result showing that the extension amount of the crack 14 extending from the modified spot 13 to the incident side of the laser light L and the opposite side thereof is suppressed. Will be described.

FIG. 22 is an image (side view image) 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 laser beam L having a wavelength of 532 nm is made incident on the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and one condensing point C is relatively moved on the virtual plane 15 along the X direction. The plurality of modified spots 13 were formed along the imaginary plane 15 by moving the modified spots 13 to. Specifically, the distance between the condensing points C adjacent to each other in the Y direction is 2 μm, the pulse pitch of the laser light L is 5 μm, and the pulse energy of the laser light L is 0.3 μJ. Quality spot 13 was formed. In this case, as shown in FIG. 22, the extension amount of the crack 14 extending from the modified spot 13 to the laser light L incident side and the opposite side was about 100 μm.

23A and 23B are images of modified spots and cracks formed by the laser processing method and the semiconductor member manufacturing method of the first embodiment. FIG. 23A is an image in plan view, and FIG. Is an image in side view. In the first embodiment, laser light L having a wavelength of 532 nm is made incident on the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and the six condensing points C arranged in the Y direction are virtual along the X direction. By relatively moving on the surface 15, a plurality of modified spots 13 were formed along the virtual surface 15. Specifically, first, the distance between the condensing points C adjacent to each other in the Y direction is 8 μm, the pulse pitch of the laser light L is 10 μm, and the pulse energy of the laser light L is 0.3 μJ. The modified spot 13a of No. 1 was formed. Then, with the six condensing points C aligned in the Y direction shifted from the previous state by +4 μm in the Y direction, the distance between the converging points C adjacent in the Y direction is 8 μm, and the pulse pitch of the laser light L is 10 μm. A plurality of modified spots 13b were formed along the virtual surface 15 by setting the pulse energy of the laser light L to 0.3 μJ. Then, with the six converging points C arranged in the Y direction shifted from the previous state by -4 μm in the Y direction, the distance between the converging points C adjacent to each other in the Y direction is 8 μm, and the pulse pitch of the laser light L is changed. A plurality of modified spots 13 were formed along the virtual surface 15 with the pulse energy of the laser beam L being 5 μm and 0.3 μJ. Subsequently, with the six condensing points C arranged in the Y direction shifted from the previous state by +4 μm in the Y direction, the distance between the converging points C adjacent in the Y direction is 8 μm, and the pulse pitch of the laser light L is 5 μm. A plurality of modified spots 13 were formed along the virtual surface 15 with the pulse energy of the laser light L set to 0.3 μJ. As a result, the first modified spot 13a and the third modified spot 13 overlap each other, and the second modified spot 13b and the fourth modified spot 13 overlap each other. It is assumed that In this case, as shown in (b) of FIG. 23, the extension amount of the crack 14 extending from the modified spot 13 to the incident side of the laser light L and the opposite side thereof was about 70 μm.

24A and 24B 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. 24A is a plan view. The image, (b) of FIG. 24, is an image in a side view. In this second example, a laser beam L having a wavelength of 532 nm is made incident on the inside of the GaN ingot 20 from the surface 20a of the GaN ingot 20, and the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment is performed. Similarly, a plurality of modified spots 13 were formed along the virtual surface 15. When forming the plurality of modified spots 13a, the distance between the condensing points C adjacent to each other in the Y direction was 8 μm, the pulse pitch of the laser light L was 10 μm, and the pulse energy of the laser light L was 0.3 μJ. When forming the plurality of modified spots 13b, the distance between the condensing points C adjacent to each other in the Y direction was 8 μm, the pulse pitch of the laser light L was 10 μm, and the pulse energy of the laser light L was 0.3 μJ. When forming the plurality of modified spots 13c, the distance between the condensing points C adjacent to each other in the Y direction was 8 μm, the pulse pitch of the laser light L was 5 μm, and the pulse energy of the laser light L was 0.3 μJ. When forming the plurality of modified spots 13d, the distance between the condensing points C adjacent to each other in the Y direction was 8 μm, the pulse pitch of the laser light L was 5 μm, and the pulse energy of the laser light L was 0.3 μJ. In this case, as shown in (b) of FIG. 24, the extension amount of the crack 14 extending from the modified spot 13 to the incident side of the laser light L and the opposite side thereof was about 50 μm.

24C and 24D 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. 24C is a plan view. An image, (d) of FIG. 24, is an image in a side view. In the third embodiment, further along the virtual plane 15 in the state shown in (a) and (b) of FIG. 24 (that is, the virtual plane 15 on which a plurality of rows of modified spots 13 have already been formed), A plurality of modified spots 13 were formed. Specifically, first, the distance between adjacent condensing points C in the Y direction is 8 μm, the pulse pitch of the laser light L is 5 μm, and the pulse energy of the laser light L is 0.1 μJ. A plurality of rows of reforming spots 13 were formed such that each row was positioned at the center between the rows of reforming spots 13. In this case, as shown in FIG. 24D, the extension amount of the crack 14 extending from the modified spot 13 to the incident side of the laser beam L and the opposite side thereof was about 60 μm.

From the above experimental results, if the modified spots 13b are formed along the virtual surface 15 so as not to overlap the modified spots 13a and the cracks 14a already formed along the virtual surface 15 (( 1st Example, 2nd Example, and 3rd Example), it turned out that the extension amount of the crack 14 extended from the modification spot 13 to the incident side of the laser beam L and the opposite side is suppressed. When forming a plurality of modified spots 13 along the virtual surface 15, the modified surface 13 is formed on the virtual surface 15 so as not to overlap the modified spots 13a and 13b already formed along the virtual surface 15. If a plurality of modified spots 13 are formed along the lines (second and third embodiments), it becomes easy to form a crack over the virtual surface 15.
[Laser Processing Method and Semiconductor Member Manufacturing Method of Second Embodiment]

The object 11 of the laser processing method and the semiconductor member manufacturing method of the second embodiment is, as shown in FIG. 25, a GaN wafer (semiconductor wafer, semiconductor object) 30 formed of GaN in a disk shape, for example. .. As an example, the GaN wafer 30 has a diameter of 2 inches and the GaN wafer 30 has a thickness of 100 μm. The laser processing method and the semiconductor member manufacturing method of the second embodiment are carried out to cut out a plurality of semiconductor devices (semiconductor members) 40 from the GaN wafer 30. As an example, the outer shape of the GaN substrate portion of the semiconductor device 40 is 1 mm×1 mm, and the thickness of the GaN substrate portion of the semiconductor device 40 is several tens μm.

First, a GaN wafer 30 is prepared (first step), and the laser processing apparatus 1 described above forms a plurality of modified spots 13 along each of a plurality of virtual surfaces 15. Each of the plurality of virtual surfaces 15 is a surface facing the surface 30a of the GaN wafer 30 inside the GaN wafer 30, and is set so as to be aligned in the direction in which the surface 30a extends. In the present embodiment, each of the plurality of virtual surfaces 15 is a surface parallel to the surface 30a and has, for example, a rectangular shape. Each of the plurality of virtual planes 15 is set to be arranged two-dimensionally in a direction parallel to the orientation flat 31 of the GaN wafer 30 and a direction perpendicular to the orientation flat 31. As shown in FIG. 26, each of the plurality of virtual surfaces 15 includes a first region R1 and a second region R2. The first region R1 is a plurality of corner regions of the virtual surface 15. The second region R2 is a region of the virtual surface 15 other than the first region R1. In the present embodiment, the first region R1 has, for example, a rectangular shape. As shown in FIG. 25, a plurality of peripheral regions 16 are set on the GaN wafer 30 so as to surround each of the plurality of virtual surfaces 15. That is, each of the plurality of virtual surfaces 15 does not reach the side surface 30b of the GaN wafer 30. As an example, the width of the peripheral region 16 corresponding to each of the plurality of virtual surfaces 15 (half the distance between the adjacent virtual surfaces 15 in the present embodiment) is 30 μm or more.

The formation of the plurality of modified spots 13 along each of the plurality of virtual surfaces 15 is performed in the same manner as the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. As a result, in the GaN wafer 30, as shown in FIG. 27, a plurality of modified spots 13 (that is, modified spots 13a, 13b, 13c, 13d) and a plurality of modified spots 13 are provided along each of the plurality of virtual planes 15. 14 (that is, the cracks 14a, 14b, 14c, 14d) are formed. In FIG. 27, the range in which the plurality of modified spots 13 and the plurality of cracks 14 are formed is indicated by broken lines.

Subsequently, the semiconductor manufacturing apparatus forms a plurality of functional elements 32 on the surface 30a of the GaN wafer 30, as shown in FIG. Each of the plurality of functional elements 32 is formed such that one functional element 32 is included in one virtual surface 15 when viewed from the thickness direction of the GaN wafer 30. The functional element 32 is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, a circuit element such as a memory, or the like.

In the present embodiment, the semiconductor manufacturing apparatus functions as a heating device when forming the plurality of functional elements 32 on the surface 30a. That is, when forming the plurality of functional elements 32 on the surface 30 a, the semiconductor manufacturing apparatus heats the GaN wafer 30, and the plurality of cracks 14 extending from the plurality of modified spots 13 on each of the plurality of virtual surfaces 15 are formed. Are connected to each other to form a crack 17 (that is, a crack 17 across the virtual surface 15) in each of the plurality of virtual surfaces 15 (third step). In FIG. 28, the range in which the plurality of modified spots 13, the plurality of cracks 14, and the crack 17 are formed is indicated by broken lines. A heating device different from the semiconductor manufacturing device may be used. The cracks 17 may be formed by connecting the plurality of cracks 14 to each other by applying some force to the GaN wafer 30 by a method other than heating. Further, by forming the plurality of modified spots 13 along the virtual surface 15, the plurality of cracks 14 may be connected to each other to form the crack 17.

Here, in the GaN wafer 30, nitrogen gas is generated in the cracks 14 extending from the modified spots 13, respectively. Therefore, by heating the GaN ingot 20 and expanding the nitrogen gas, the crack 17 can be formed by utilizing the pressure of the nitrogen gas. Moreover, since the peripheral region 16 prevents the plurality of cracks 14 from propagating to the outside of the virtual surface 15 surrounded by the peripheral region 16 (for example, the adjacent virtual surface 15 and the side surface 30b of the GaN wafer 30), the plurality of cracks is prevented. It is possible to prevent the nitrogen gas generated in 14 from escaping to the outside of the virtual surface 15. That is, the peripheral area 16 is a non-modified area that does not include the modified spot 13, and when the crack 17 is formed on the virtual surface 15 surrounded by the peripheral area 16, the virtual surface 15 surrounded by the peripheral area 16 is formed. It is a region that prevents the plurality of cracks 14 from propagating to the outside. Therefore, the width of the peripheral region 16 is preferably 30 μm or more. Furthermore, by irradiating the laser light L so that the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2, a plurality of modifications are performed along the virtual surface 15. A quality spot 13 is formed. Thereby, when the plurality of cracks 14 respectively extending from the plurality of modified spots 13 are connected to each other, a crack (a crack that connects the plurality of cracks 14 to each other and finally becomes a crack 17) is generated from the first region R1 to the second region. Propagation of the crack is controlled so as to propagate to R2.

Subsequently, the laser processing device cuts the GaN wafer 30 into each functional element 32, and the grinding device grinds the portions corresponding to each of the plurality of virtual planes 15, so that as shown in FIG. A plurality of semiconductor devices 40 are obtained from the GaN wafer 30 with each of the plurality of cracks 17 as a boundary (fourth step). In this way, the GaN wafer 30 is cut along each of the plurality of virtual planes 15. In this step, the GaN wafer 30 may be cut into each functional element 32 by mechanical processing (for example, blade dicing) other than laser processing.

Among the above steps, up to the step of forming a plurality of modified spots 13 along each of a plurality of virtual surfaces 15 is the laser processing method of the second embodiment. Further, among the above steps, the steps up to the step of obtaining the plurality of semiconductor devices 40 from the GaN wafer 30 with each of the plurality of cracks 17 as boundaries are the semiconductor member manufacturing method of the second embodiment.

As described above, according to the laser processing method of the second embodiment, as in the laser processing method of the first embodiment, a plurality of cracks extending from the plurality of modified spots 13 are formed on each of the plurality of virtual surfaces 15. When 14 are connected to each other and a crack 17 is formed, the crack (a crack in which a plurality of cracks 14 are connected to each other to finally become the crack 17) propagates from the first region R1 to the second region R2. Can be controlled, and as a result, the crack 17 can be accurately formed along each of the virtual surfaces 15. Therefore, according to the laser processing method of the second embodiment, it is possible to obtain a plurality of suitable semiconductor devices 40 by obtaining a plurality of semiconductor devices 40 from the GaN wafer 30 with each of the plurality of cracks 17 as a boundary. Become. It is also possible to reuse the GaN wafer 30 after cutting out the plurality of semiconductor devices 40.

Similarly, according to the laser processing apparatus 1 that implements the laser processing method of the second embodiment, it is possible to accurately form the crack 17 along each of the plurality of virtual surfaces 15, and thus it is possible to perform a plurality of preferable operations. The semiconductor device 40 can be acquired.

Further, in the laser processing method of the second embodiment, the peripheral region 16 that prevents the development of the cracks 14 extending from the modified spots 13 is set so as to surround each of the virtual surfaces 15. As a result, the growth of the plurality of cracks 14 to the outside of the virtual surface 15 surrounded by the peripheral region 16 is prevented, so that, for example, when gas is generated in the plurality of cracks 14, the gas escapes to the outside of the virtual surface 15. Can be suppressed. Therefore, the crack 17 can be easily formed by utilizing the pressure of the gas. In this embodiment, when gallium nitride contained in the material of the GaN wafer 30 is decomposed by the irradiation of the laser light L, nitrogen gas is generated in the plurality of cracks 14. Therefore, the crack 17 can be easily formed by utilizing the pressure of the nitrogen gas.

Further, in the laser processing method of the second embodiment, the laser light L is applied so that the pulse energy of the laser light L in the first region R1 is larger than the pulse energy of the laser light L in the second region R2. This makes it possible to appropriately realize a state in which the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2.

Further, in the laser processing method of the second embodiment, each of the plurality of virtual surfaces 15 has a rectangular shape, and in each of the plurality of virtual surfaces 15, the first region R1 is a plurality of virtual surfaces 15. It is a corner area. Thereby, in each of the plurality of virtual planes 15, the progress of the crack is controlled so that the crack (the crack that connects the plurality of cracks 14 to each other and finally becomes the crack 17) propagates inward from the plurality of corner regions. can do.

Further, according to the semiconductor member manufacturing method of the second embodiment, it is possible to accurately form the crack 17 along each of the virtual surfaces 15 by the steps included in the laser processing method of the second embodiment. Therefore, it is possible to obtain a plurality of suitable semiconductor devices 40.

In the semiconductor member manufacturing method of the second embodiment, the GaN wafer 30 is heated to connect the plurality of cracks 14 to each other to form the crack 17. Thereby, for example, when gas is generated in the plurality of cracks 14 extending from the plurality of reforming spots 13, the gas can be expanded. Therefore, the crack 17 can be easily formed by utilizing the pressure of the gas. In this embodiment, when gallium nitride contained in the material of the GaN wafer 30 is decomposed by the irradiation of the laser light L, nitrogen gas is generated in the plurality of cracks 14. Therefore, the crack 17 can be easily formed by utilizing the pressure of the nitrogen gas. As described above, by controlling the progress of cracks (cracks in which a plurality of cracks 14 are connected to each other to finally become the cracks 17), it is expected that the heating time is shortened, the heating temperature is lowered, and the like. You can

Further, in the semiconductor member manufacturing method of the second embodiment, the plurality of virtual surfaces 15 are set to be aligned in the direction in which the surface 30a of the GaN wafer 30 extends. This makes it possible to obtain a plurality of semiconductor devices 40 from one GaN wafer 30.
[Modification]

The present disclosure is not limited to the above embodiments. For example, the various numerical values regarding the laser light L are not limited to those described above. However, in order to prevent the crack 14 from extending from the modified spot 13 to the incident side of the laser light L and the opposite side thereof, the pulse energy of the laser light L is 0.1 μJ to 1 μJ and the pulse of the laser light L is The width is preferably 200 fs to 1 ns.

The semiconductor object processed by the laser processing method and the semiconductor member manufacturing method according to the one aspect of the present disclosure is not limited to the GaN ingot 20 of the first embodiment and the GaN wafer 30 of the second embodiment. The semiconductor member manufactured by the semiconductor member manufacturing method according to the one aspect of the present disclosure is not limited to the GaN wafer 30 of the first embodiment and the semiconductor device 40 of the second embodiment. One virtual surface may be set for one semiconductor object.

As an example, the material of the semiconductor object may be SiC. Even in that case, if a plurality of modified spots 13 are formed stepwise as in the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment, as will be described below, cracks extending over an imaginary plane. Can be accurately formed along the virtual surface.

30A and 30B are images (images in side view) of cracks in the SiC wafer formed by the laser processing method and the semiconductor member manufacturing method of the comparative example, and FIG. 30 is an enlarged image in the rectangular frame in FIG. In this comparative example, laser light having a wavelength of 532 nm is made incident on the inside of the SiC wafer from the surface of the SiC wafer, and the six converging points arranged in the Y direction are relatively moved on the virtual surface along the X direction. By doing so, a plurality of modified spots were formed along the virtual surface. At this time, the distance between the condensing points C adjacent to each other in the Y direction was 2 μm, the pulse pitch of the laser light was 15 μm, and the pulse energy of the laser light was 4 μJ. In this case, as shown in (a) and (b) of FIG. 30, a crack extending in a direction inclined by 4° to 5° with respect to the imaginary plane occurred.

31A and 31B are images (images in side view) of cracks in the SiC wafer formed by the laser processing method and the semiconductor member manufacturing method of the example, and FIG. 31 is an enlarged image in the rectangular frame in FIG. In this example, laser light having a wavelength of 532 nm is made to enter the inside of the SiC wafer from the surface of the SiC wafer, and the virtual surface is formed on the virtual surface similarly to the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. A plurality of modified spots were formed along it. When forming a plurality of modified spots corresponding to each of the modified spots 13a, 13b, 13c, 13d, the distance between the condensing points C adjacent in the Y direction is 8 μm, and the pulse pitch of the laser light L is set. Was 15 μm, and the pulse energy of the laser beam L was 4 μJ. In this case, as shown in (a) and (b) of FIG. 31, the generation of cracks extending in the direction inclined by 4° to 5° with respect to the virtual plane was suppressed. 32A and 32B are images of the peeled surface of the SiC wafer formed by the laser processing method and the semiconductor member manufacturing method of the example, and FIGS. 33A and 33B show the height of the peeled surface shown in FIG. It is a profile. In this case, the unevenness appearing on the peeled surface of the SiC wafer was suppressed to about 2 μm.

From the above experimental results, even when the material of the semiconductor object is SiC, a plurality of modified spots 13 are formed stepwise as in the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment. Then, it was found that cracks were formed along the virtual surface with high precision. The SiC wafers used in the above-described comparative examples and examples are 4H-SiC wafers having an off angle of 4±0.5°, and the direction in which the focusing point of the laser light is moved is the m-axis direction. Is.

The method of forming the plurality of modified spots 13a, 13b, 13c, 13d is not limited to the above. The plurality of modified spots 13a may be formed such that the plurality of cracks 14a extending from the plurality of modified spots 13a are connected to each other. Further, the plurality of modified spots 13b may be formed so as not to overlap the plurality of modified spots 13a. Even if the plurality of reforming spots 13b overlap the plurality of cracks 14a extending from the plurality of reforming spots 13a, if the plurality of reforming spots 13b do not overlap the plurality of reforming spots 13a, the plurality of reforming spots 13b do not overlap. 13a and 13b are accurately formed along the virtual surface 15. Further, the method of forming the plurality of modified spots 13c and 13d is arbitrary, and the plurality of modified spots 13c and 13d may not be formed. Further, as shown in FIG. 34, for example, by rotating the GaN ingot 20, a plurality of condensing points arranged in the radial direction are relatively rotated (arrows indicated by a chain line), and a plurality of rows of modified spots are formed. 35, and further, as shown in FIG. 35, a plurality of condensing points arranged in the radial direction with each of the plurality of condensing points positioned between the rows of the modified spots 13 in a plurality of rows. May be relatively rotated (arrows indicated by alternate long and short dash lines) to form a plurality of rows of modified spots 13. The stepwise formation of the plurality of modified spots 13 as in the second step of the laser processing method and the semiconductor member manufacturing method of the first embodiment is performed by the laser processing method and the semiconductor member manufacturing method according to one aspect of the present disclosure. It is not essential in the method.

Further, in the laser processing method and the semiconductor member manufacturing method of the first embodiment, the formation of the plurality of modified spots 13 may be sequentially performed for each of the plurality of virtual surfaces 15 from the side opposite to the surface 20a. Further, in the laser processing method and the semiconductor member manufacturing method of the first embodiment, the formation of the plurality of modified spots 13 is performed along the one or more virtual surfaces 15 on the surface 20a side, and the one or more GaN. After the wafer 30 is cut out, the surface 20 a of the GaN ingot 20 may be ground, and again, the plurality of modified spots 13 may be formed along the one or more virtual surfaces 15 on the surface 20 a side.

Further, in the laser processing method and the semiconductor member manufacturing method of the first and second embodiments, the peripheral region 16 may not be formed. In the case where the peripheral region 16 is not formed in the laser processing method and the semiconductor member manufacturing method of the first embodiment, for example, the GaN ingot 20 is formed after forming the modified spots 13 along each of the virtual surfaces 15. It is also possible to obtain a plurality of GaN wafers 30 by performing etching on.

Also, the method of adjusting the implantation energy per unit area in the first region R1 and the second region R2 is not limited to that described above. For example, the laser light L may be irradiated such that the pulse pitch of the laser light L in the first region R1 is smaller than the pulse pitch of the laser light L in the second region R2. Alternatively, the laser light L may be irradiated such that the inter-row pitch of the laser light L in the first region R1 is smaller than the inter-row pitch of the laser light L in the second region R2. In either case, it is possible to appropriately realize a state in which the implantation energy per unit area in the first region R1 is larger than the implantation energy per unit area in the second region R2. The inter-row pitch means the “distance between adjacent rows of the plurality of rows” when the condensing point C of the laser light L is moved along each of the plurality of rows on the virtual surface 15.

Further, as shown in FIG. 36, the first region R1 may be an outer edge region along the outer edge of the virtual surface 15, and the second region R2 may be a region surrounded by the first region R1. That is, the first region R1 may be the outer edge region of the virtual surface 15. Thereby, in the virtual surface 15, the progress of the crack can be controlled so that the crack (the crack that connects the plurality of cracks 14 to each other and finally becomes the crack 17) propagates inward from the outer edge region. In the example shown in FIG. 36, the virtual plane 15 further includes a third region R3 along the orientation flat 21 of the GaN ingot 20, and the implantation energy per unit area in the third region R3 is the first region R1 and The laser light L is irradiated so as to be larger than the implantation energy per unit area in the second region R2. Although it is difficult for a crack (a crack in which a plurality of cracks 14 are connected to each other to finally become a crack 17) to propagate in a region along the orientation flat 21, it is possible to reliably propagate the crack to the third region R3. You can

Further, as shown in FIG. 37, the rectangular virtual surface 15 has a rectangular annular second region R2 along the outer edge of the virtual surface 15 and a rectangular first region surrounded by the second region R2. R1 may be included. The rectangular virtual surface 15 includes a second area R2 that is a plurality of corner areas of the virtual surface 15 and a first area R1 that is an area other than the second area R2 of the virtual surface 15. You can leave. In that case, the progress of the cracks can be controlled so that the cracks (the cracks in which the plurality of cracks 14 are connected to each other and finally become the cracks 17) propagate from the inside to the plurality of corner regions.

Moreover, the laser processing apparatus 1 is not limited to the one having the above-described configuration. For example, the laser processing device 1 may not include the spatial light modulator 4.

Also, the materials and shapes described above are not limited to the materials and shapes described in the above embodiments, and various materials and shapes can be applied. Moreover, each configuration in the above-described one embodiment or modification can be arbitrarily applied to each configuration in the other embodiment or modification.

1... Laser processing device, 2... Stage, 4... Spatial light modulator (laser irradiation unit), 5... Condensing lens (laser irradiation unit), 13, 13a, 13b, 13d... Modification spot, 14, 14a, 14b. , 14c, 14d... Cracks, 15... Virtual plane, 16... Peripheral region, 17... Cracks extending over virtual plane, 20... GaN ingot (semiconductor ingot, semiconductor object), 20a... Surface, 30... GaN wafer (semiconductor wafer, Semiconductor member, semiconductor object), 30a... Surface, 40... Semiconductor device (semiconductor member), L... Laser light, R1... First region, R2... Second region.

Claims (17)

1. A laser processing method for cutting the semiconductor object along a virtual surface facing the surface of the semiconductor object inside the semiconductor object,
   A first step of preparing the semiconductor object;
   A second step of forming a plurality of modified spots along the virtual surface by making a laser beam enter the inside of the semiconductor object from the surface,
   In the second step, the laser beam is applied such that the implantation energy per unit area in the first region of the virtual surface is larger than the implantation energy per unit area in the second region of the virtual surface. Laser processing method.
2. The laser processing method according to claim 1, wherein, in the second step, a peripheral region that prevents the development of a plurality of cracks extending from the plurality of modified spots is set so as to surround the virtual surface.
3. In the second step, the pulse energy of the laser light per one condensing point in the first region is made larger than the pulse energy of the laser light per one converging point in the second region. Item 3. The laser processing method according to Item 1 or 2.
4. 4. The laser processing according to claim 1, wherein in the second step, a pulse pitch of the laser light in the first region is made smaller than a pulse pitch of the laser light in the second region. Method.
5. In the second step, the condensing point of the laser light is moved along each of a plurality of rows on the virtual surface, and the inter-row pitch of the laser light in the first area is set to the laser in the second area. The laser processing method according to any one of claims 1 to 4, wherein the pitch is smaller than the inter-row pitch of light.
6. The laser processing method according to any one of claims 1 to 5, wherein the first area is an outer edge area of the virtual surface.
7. The laser processing method according to any one of claims 1 to 5, wherein the second area is an outer edge area of the virtual surface.
8. The virtual surface has a rectangular shape,
   The laser processing method according to claim 1, wherein the first region is a plurality of corner regions of the virtual surface.
9. The virtual surface has a rectangular shape,
   The laser processing method according to claim 1, wherein the second region is a plurality of corner regions of the virtual surface.
10. The laser processing method according to any one of claims 1 to 9, wherein the material of the semiconductor object contains gallium nitride.
11. The first step and the second step, which are included in the laser processing method according to any one of claims 1 to 10,
    A third step of forming a crack across the virtual surface by connecting a plurality of cracks extending from the modified spots to each other,
    A fourth step of obtaining a semiconductor member from the semiconductor object with the crack extending over the virtual surface as a boundary.
12. The method for manufacturing a semiconductor member according to claim 11, wherein the semiconductor object is heated in the third step.
13. The semiconductor member manufacturing method according to claim 11 or 12, wherein a plurality of the virtual surfaces are set so as to be arranged in a direction facing the surface.
14. The semiconductor object is a semiconductor ingot,
    The semiconductor member manufacturing method according to claim 13, wherein the semiconductor member is a semiconductor wafer.
15. The semiconductor member manufacturing method according to claim 11 or 12, wherein a plurality of the virtual surfaces are set so as to be arranged in a direction in which the surface extends.
16. The semiconductor object is a semiconductor wafer,
    The semiconductor member manufacturing method according to claim 15, wherein the semiconductor member is a semiconductor device.
17. A laser processing apparatus for cutting the semiconductor object along a virtual surface facing the surface of the semiconductor object inside the semiconductor object,
    A stage for supporting the semiconductor object,
    A laser irradiation unit that forms a plurality of modified spots along the virtual surface by causing a laser beam to enter the inside of the semiconductor object from the surface,
    The laser irradiation unit emits the laser light so that the implantation energy per unit area in the first region of the virtual surface is larger than the implantation energy per unit area in the second region of the virtual surface. Laser processing equipment to make incident.

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