# US 10,870,169 B2 · Laser processing apparatus and wafer producing method

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- Number: US 10,870,169 B2
- Document ID: US10870169B2
- Status: Granted
- Kind: B2
- Application number: 15/601,321
- Filed: 2017-05-22
- Published: 2017-11-30
- Granted: 2020-12-22
- Earliest claimed: 2016-05-30
- Assignees: Disco Corporation
- Applicants: Disco Corporation
- Inventors: Kazuya Hirata; Yasuyoshi Yubira
- Web page: https://patentgrep.com/patent/US10870169B2

## CPC

- B23K 26/0622: by shaping pulses
- B23K 26/0006: {taking account of the properties of the material involved (B23K26/32, B23K26/40 take precedence)}
- B23K 26/032: {using optical means}
- B23K 26/035: Aligning the laser beam (automatically B23K26/042)
- B23K 26/0823: {Devices involving rotation of the workpiece}
- B23K 26/0853: {Devices involving movement of the workpiece in at least two axial directions, e.g. in a plane}
- B23K 26/10: using a fixed support {, i.e. involving moving the laser beam}
- B23K 26/364: for making a groove or trench, e.g. for scribing a break initiation groove
- B23K 26/38: by boring or cutting
- B23K 26/40: taking account of the properties of the material involved
- B23K 26/53: for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
- C30B 29/406: {Gallium nitride}
- C30B 33/06: Joining of crystals
- H01S 3/1003: {tunable optical elements, e.g. acousto-optic filters, tunable gratings}
- H10P 90/00: Preparation of wafers not covered by a single main group of this subclass, e.g. wafer reinforcement
- B23K 2101/40: Semiconductor devices
- B23K 2103/50: {Inorganic materials other than metals or composite materials}
- H01S 3/0085: {Modulating the output, i.e. the laser beam is modulated outside the laser cavity}
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A laser processing apparatus for producing a GaN wafer from a GaN ingot includes a laser beam irradiating unit configured to apply a laser beam having a wavelength capable of passing through the GaN ingot held by a chuck table. The laser beam irradiating unit includes a laser oscillator configured to oscillate the laser beam. The laser oscillator includes a seeder configured to oscillate a high-frequency pulsed laser, a thinning-out unit configured to thin out high-frequency pulses oscillated by the seeder at a predetermined repetition frequency, and generate one burst pulse with a plurality of high-frequency pulses as sub-pulses, and an amplifier configured to amplify the generated burst pulse.

## Claims

### Claim 1

A laser processing apparatus suitable for producing a GaN wafer from a GaN ingot, the laser processing apparatus comprising:
a chuck table configured to hold the ingot;
laser beam irradiating means for applying a laser beam having a wavelength capable of passing through the GaN ingot held by the chuck table,
the laser beam irradiating means including
a laser oscillator configured to oscillate the laser beam, and
a condenser configured to form a destruction layer in an interface at a depth corresponding to a thickness of the GaN wafer to be produced, by applying the laser beam oscillated by the laser oscillator while positioning a focusing point of the laser beam within the GaN ingot,
the laser oscillator including:
a seeder configured to oscillate a high-frequency pulsed laser,
a thinning-out unit configured to thin out high-frequency pulses oscillated by the seeder at a predetermined repetition frequency, and generate one burst pulse with a plurality of high-frequency pulses as sub-pulses, and
an amplifier configured to amplify the generated burst pulse; and
peeling means including a suction piece with vibration applying means said suction piece configured to hold the ingot and said vibration applying means applies vibration to the ingot while said suction piece moves to separate the GaN wafer from the ingot.

### Claim 2 (depends on 1)

The laser processing apparatus according to claim 1, wherein the thinning-out unit thins out the high-frequency pulses so as to generate the burst pulse in which, of two to ten as numbers of sub-pulses constituting one burst pulse, the number of sub-pulses that cause the destruction layer to extend longest at a position of the interface at which the focusing point is positioned is set.

### Claim 3 (depends on 2)

The laser processing apparatus according to claim 2, wherein the number of sub-pulses that cause the destruction layer to extend longest is three.

### Claim 4 (depends on 1)

The laser processing apparatus according to claim 1, wherein said laser beam irradiating means applies the laser beam to the ingot and rotates the chuck table to form a laser processing trace gradually inward in a spiral shape on the ingot.

### Claim 5 (depends on 1)

The laser processing apparatus according to claim 1, wherein said laser beam irradiating means applies the laser beam to a center of the ingot and rotates the chuck table to form a laser processing trace gradually outward in a spiral shape on the ingot.

### Claim 6 (depends on 1)

The laser processing apparatus according to claim 1, wherein said laser beam irradiating means applies the laser beam to the ingot while moving the chuck table in the X and Y directions.

### Claim 7

A GaN wafer producing method for producing a GaN wafer from a GaN ingot, the GaN wafer producing method comprising:
a holding step of holding the GaN ingot by a chuck table;
a laser beam irradiating step of using a condenser configured for forming a destruction layer in an interface at a depth corresponding to a thickness of the GaN wafer to be produced, by applying a laser beam having a wavelength capable of passing through the GaN ingot held by the chuck table while positioning a focusing point of the laser beam within the GaN ingot; and
a wafer peeling step of holding the GaN ingot using a suction piece and applying vibration to the ingot using vibration applying means while moving said suction piece to peel off the GaN wafer from the GaN ingot;
oscillating the laser beam using a laser oscillator including a seeder configured to oscillate a high-frequency pulsed laser, a thinning-out unit configured to thin out high-frequency pulses oscillated by the seeder at a predetermined repetition frequency, and generate one burst pulse with a plurality of high-frequency pulses as sub-pulses, and an amplifier configured to amplify the generated burst pulse.

### Claim 8 (depends on 7)

The GaN wafer producing method according to claim 7, wherein the thinning-out unit thins out the high-frequency pulses so as to generate the burst pulse in which, of two to ten as numbers of sub-pulses constituting one burst pulse, the number of sub-pulses that cause the destruction layer to extend longest at a position of the interface at which the focusing point is positioned is set.

### Claim 9 (depends on 8)

The GaN wafer producing method according to claim 8, wherein the number of sub-pulses that cause the destruction layer to extend longest is three.

### Claim 10 (depends on 8)

The GaN wafer producing method according to claim 8, wherein said laser beam irradiating step includes applying the laser beam to a center of the ingot while rotating the chuck table to form a laser processing trace gradually outward in a spiral shape on the ingot.

### Claim 11 (depends on 8)

The GaN wafer producing method according to claim 8, wherein said laser beam irradiating step includes applying the laser beam to the ingot while rotating the chuck table to form a laser processing trace gradually inward in a spiral shape on the ingot.

### Claim 12 (depends on 8)

The GaN wafer producing method according to claim 8, wherein said laser beam irradiating step includes applying the laser beam to the ingot while moving the chuck table in the X and Y directions.