JP7316639B2 - Substrate separation method - Google Patents

Description

The present disclosure relates to a method of separating substrate material.

In general, when manufacturing a brittle wafer represented by a silicon (Si) wafer, a cylindrical ingot solidified from a silicon melt melted in a quartz crucible (not shown) is placed in a block of an appropriate length. and grind the periphery to the target diameter. After that, the blocked ingot (substrate) is sliced with a wire saw to manufacture a brittle wafer. In this case, since a cutting allowance larger than the thickness of the wire saw is required for cutting, it is extremely difficult to produce a thin brittle wafer with a thickness of 0.1 mm or less, and the yield rate does not improve. be. Therefore, by aligning the focal point of the laser beam with the inside of the brittle material with a condenser lens and relatively scanning the brittle material with the laser beam, a planar processing area is created inside the brittle material by multiphoton absorption. A wafer manufacturing method and a wafer manufacturing apparatus are disclosed in which a part of a brittle material is peeled off as a wafer by using the processed region as a peeling surface. This technology has been developed not only for silicon (Si) but also for silicon carbide (SiC) and gallium nitride (GaN).

Further, in the method for producing a wafer described in Patent Document 1, a laser beam is incident on a condenser lens, a modified layer is formed inside a hexagonal single crystal ingot, and cracks extending from the modified layer are formed and separated. In this method, a starting point is formed and ultrasonic waves are applied to the ingot to separate the wafer.

JP 2016-124015 A

However, with the above-described conventional structure, there is a problem that cracks propagate in unintended directions from the starting point due to the application of ultrasonic vibration, particularly in materials having cleavability, leading to cracking.

Accordingly, an object of the present disclosure is to provide a substrate separation method with high separation performance.

The substrate separation method of the present disclosure includes a formation step of forming a modified layer inside a substrate of a workpiece by condensed irradiation of a laser beam;
a melting step of melting the modified layer by immersing the substrate of the processed material in a liquid having a temperature lower than the melting point of the processed material and higher than or equal to the melting point of the substance contained in the modified layer;
A separation step of separating the substrate of the work material with the melted modified layer as a boundary;
including.

According to the substrate separation method according to the present disclosure, substrate separation with high separation can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows an example of a structure of the laser processing apparatus which concerns on Embodiment 1 of this indication. 1 is a schematic plan view showing a laser beam scanning method 1 by a laser processing apparatus according to Embodiment 1 of the present disclosure; FIG. FIG. 4 is a schematic plan view showing a laser beam scanning method 2 by the laser processing apparatus according to the first embodiment of the present disclosure; FIG. 3 shows a laser beam scanning method 3 by a laser processing apparatus according to an embodiment of the present disclosure; FIG. 4 is a diagram showing a formation state of a modified layer in a substrate material after laser processing according to an embodiment of the present disclosure; Schematic diagram of an apparatus for separating a brittle material on which a modified layer is formed in a substrate separation method according to Embodiment 1 of the present disclosure.

A substrate separation method according to a first aspect includes a modified layer forming step of forming a modified layer inside a substrate of a workpiece by focused irradiation of a laser beam;
a melting step of melting the modified layer by immersing the substrate of the processed material in a liquid having a temperature lower than the melting point of the processed material and higher than or equal to the melting point of the substance contained in the modified layer;
A separation step of separating the substrate of the work material with the melted modified layer as a boundary;
including.

In the substrate separating method according to the second aspect, in the first aspect, in the forming step, the laser light may be scanned continuously over one surface of the inside of the substrate of the workpiece.

A substrate separation method according to a third aspect is, in the first or second aspect, in the melting step, after the substrate of the work material is immersed, the temperature of the liquid is set to be less than the melting point of the modified layer. to a temperature lower than the melting point of the material to be processed and higher than or equal to the melting point of the modified layer.

A substrate separating method according to a fourth aspect, in any one of the first to third aspects, may reduce the pressure in a liquid tank containing the liquid in the melting step.

In any one of the first to fourth aspects, a substrate separation method according to a fifth aspect may be such that the laser beam has a pulse width of 100 ps or less.

In the substrate separating method according to a sixth aspect, in any one of the first to fifth aspects, in the forming step, the workpiece may be chemically decomposed by irradiation with the laser beam.

A substrate separation method according to a seventh aspect may be such that, in any one of the first to sixth aspects, the workpiece is gallium nitride.

A substrate separation method according to an embodiment of the present disclosure will be described below with reference to the accompanying drawings. In the drawings, substantially the same members are given the same reference numerals.

(Embodiment 1)
<Substrate separation method>
The substrate separation method according to the first embodiment includes a modified layer forming step of forming a modified layer inside a substrate of a workpiece, and a modified layer is melted by immersing the substrate of the workpiece in a liquid. and a separation step of separating the substrate of the workpiece with the molten modified layer as a boundary. The temperature of the liquid is lower than the melting point of the material to be processed and higher than or equal to the melting point of the substance contained in the modified layer.
As a result, the substance contained in the modified layer dissolves into the liquid, and the substrate can be separated with the modified layer as a boundary. In this case, even if the substrate is made of a material having cleavability, the substrate can be separated while suppressing cleavage, cracking, and the like.

The modified layer forming process included in this substrate separation method, the laser processing apparatus 20 (FIG. 1) used therein, the melting process and separation process, and the substrate separation apparatus 30 (FIG. 4) used therefor are described below. will be explained in order.

(Configuration of laser processing device)
FIG. 1 is a schematic diagram of a laser processing apparatus 20 used in a modified layer forming step included in a substrate separation method according to Embodiment 1 of the present disclosure.
The laser processing apparatus 20 includes a laser oscillator 2 that oscillates a laser beam, a phase modulation unit 11 that splits the laser beam into a plurality of beams or changes the shape and waveform of the beam, a mirror 4 that reflects the laser beam, and a laser beam. A condenser lens 5 for condensing and irradiating the substrate material 1, an XY stage 6, a Z stage 7, and a rotating stage 8 for driving the substrate material 1, a fixture 9 for fixing the substrate material 1, a laser and a control unit 10 that controls the processing device 20 .

<Substrate material>
The substrate material 1 illustrated in FIG. 1 is made of a brittle material. Substrate material 1 is, for example, a GaN ingot. The GaN ingot is preferably mirror-finished in advance.

<Laser oscillator>
The laser oscillator 2 is a device that oscillates (emits) laser light. Efficient laser processing is possible by selecting a laser wavelength in consideration of the transmittance of the substrate material 1 to be processed.
<Mirror>
The mirror 4 reflects the laser beam emitted from the laser oscillator 2 and has a reflectance of 90% or more with respect to the wavelength of the laser.
<Condensing lens>
The condenser lens 5 is for condensing the laser beam reflected by the mirror 4 and irradiating it into the substrate material 1 . The condenser lens 5 preferably has a numerical aperture (NA) of 0.1 or more and 0.95 or less with respect to the wavelength of the laser light, and more preferably has a large working distance.
Further, it is desirable that the condenser lens 5 has an aberration correction function. The aberration correction function is a function capable of suppressing the extension of the condensing point Q in the irradiation direction of the laser beam due to the spherical aberration of the lens. Therefore, the energy density of the laser beam at the focal point Q can be increased. The aberration correction method is not particularly limited and may be a method using the condenser lens 5 with a correction ring or a method using a phase modulation element.

<Laser light>
If the laser beam irradiated to the substrate material 1 has a wavelength of 1064 nm or less, a pulse width of 100 ps or less, a frequency of 10 MHz or less, and an NA of 0.95 or less, a modified layer is formed without causing cracks in the substrate material 1. be able to.
Moreover, the laser beam with which the substrate material 1 is irradiated is not limited as long as internal processing by induction of multiphoton absorption is possible. The modified layer 12 can be formed by internal processing by this multiphoton absorption. Furthermore, using this multiphoton absorption contributes to the chemical precipitation of Ga in the case of GaN, for example.
Considering productivity, the repetition frequency of the laser light irradiated to the substrate material 1 should be high, so it is preferable to apply a well-balanced one in the range of 1 Hz or more and 10 MHz or less.
Further, the laser light with which the substrate material 1 is irradiated has a wavelength in the range of 100 nm or more and 10000 nm or less, and is not limited as long as 30% or more of the laser light is transmitted through the substrate material 1 . A shorter wavelength is desirable because the spot diameter can be made smaller when the light is collected, and the heat effect can be reduced.

<XY stage>
The XY stage 6 is one of driving means used for processing the entire surface of the substrate material 1, and is for moving the fixture 9 in the X-axis direction or the Y-axis direction. The positioning accuracy is 1 μm, and the stroke is 200 mm in both the X and Y axis directions. Also, the scanning speed can be varied within the range of 0.1 mm/sec to 3 m/sec.
<Z stage>
The Z stage 7 is one of driving means used for processing the entire surface of the substrate material 1, and is for moving the fixture 9 in the Z-axis direction. The positioning accuracy is 1 μm and the stroke is 10 mm in the Z direction.
<Rotating stage>
The rotating stage 8 is one of driving means used for processing the entire surface of the substrate material 1, and is for rotating the fixing jig 9 in the normal direction or the reverse direction. The rotation speed can be varied within the range of 0.1 rpm or more and 5000 rpm or less.

<fixing jig>
A fixing jig 9 is a jig for fixing the substrate material 1 . As the fixing jig 9, for example, one having a function of clamping and fixing the side surface of the substrate material 1, one having a function of fixing the substrate material 1 by adhesion, and one having a function of fixing the substrate material 1 by vacuum suction. Things, etc. can be considered.

<Control section>
The control unit 10 is for controlling the laser processing device 20 . A computer, for example, can be used as the control unit 10 . The control unit 10 performs ON/OFF control of laser light oscillation of the laser oscillator 2 . The control unit 10 also controls the driving of the XY stage 6 , the Z stage 7 , and the rotary stage 8 . The laser oscillator 2, the XY stage 6, the Z stage 7, and the rotary stage 8 are synchronously controlled by the controller 10. FIG.

<Phase Modulator>
The phase modulating section 11 splits a passing or reflected laser beam into a plurality of beams and changes the shape and waveform of the beam. As the phase modulating section 11, for example, a diffraction grating can be used, but the present invention is not limited to this.

The modified layer 12 shown in FIG. 1 is a layer formed when the substrate material 1 is focused and irradiated with laser light. When the substrate material 1 is a GaN ingot, the modified layer 12 is formed by a reaction (2GaN→2Ga+N ₂ ) due to multiphoton absorption processing. The modified layer 12 is desirably formed continuously by a layer chemically decomposed by this reaction. A method for continuously forming a chemically decomposed layer will be described later. The thickness of the modified layer 12 can be selectively formed from several micrometers to several hundreds of micrometers depending on conditions by condensed laser light irradiation. In the later-described separation step, the greater the thickness of the modified layer 12, the better the separation. On the other hand, however, since enlarging the modified layer 12 leads to material loss, the thickness of the modified layer 12 is preferably 50 μm or less.

A plurality of modified layers 110 can be hierarchically formed by scanning the substrate material 1 while irradiating it with a focused laser beam from the front side to the back side of the substrate material 1 using the laser processing apparatus 20 having such a configuration. can be done.

(laser beam scanning method)
FIG. 2A is a diagram showing a laser beam scanning method 1 by a laser processing apparatus according to an embodiment of the present disclosure. Moreover, FIG. 2B is a diagram showing a laser beam scanning method 2 by the laser processing apparatus according to the embodiment of the present disclosure. Moreover, FIG. 2C is a diagram showing a laser beam scanning method 3 by the laser processing apparatus according to the embodiment of the present disclosure.

(laser beam scanning method 1)
FIG. 2A shows a scanning method for linearly scanning the substrate material 1 with laser light using the XY stage 6 . The width D in FIG. 2A indicates the pitch between the scanning lines when the laser light scans linearly. A start point S indicates a position where the laser beam starts to be irradiated, and an end point E indicates a position where the laser beam ends.

The laser beam irradiated onto the substrate material 1 first scans along the Y-axis as the fixing jig 9 is moved in the Y-axis direction by the XY stage 6 . Subsequently, the XY stage 6 moves the fixing jig 9 by the width D in the X-axis direction with respect to the previous scan.

Subsequently, by moving the XY stage 6 in the direction opposite to the previous scanning direction, the fixing jig 9 moves in the opposite direction to the previous scanning direction on the Y-axis. Therefore, the laser light scans the Y-axis in the opposite direction. Thereafter, by repeating this operation until the laser beam reaches the end point E, the entire surface of the substrate material 1 is subjected to laser processing. By irradiating the substrate material 1 with laser light in this manner, a linear modified layer 12 is formed on the inner surface of the substrate material 1 .

In laser processing, it is necessary to form a continuous modified layer 12 on the substrate material 1 in order to remove gas from the modified layer 12 formed on the outer edge of the substrate material 1 . In such a case, the formation amount of the modified layer 12 is changed by changing the width D and the interval between pulses, which change according to the scanning speed, laser power, and frequency of the laser light.

(Laser beam scanning method 2)
FIG. 2B shows a scanning method for circumferentially scanning the substrate material 1 with laser light using the rotary stage 8 and the XY stage 6 . In FIG. 2B, the start point S indicates the irradiation start position of the laser beam, and the end point E indicates the irradiation end position of the laser beam.

The laser beam irradiated onto the substrate material 1 moves from the start point S to the end point as the fixing jig 9 is rotated by the rotating stage 8 and the fixing jig 9 is moved in the X-axis direction/Y-axis direction by the XY stage 6. Scanning is performed toward E in the rotation direction of the fixture 9 . Therefore, the laser light is scanned spirally from the outer edge of the substrate material 1 toward the center.

When laser scanning is performed in this way, the control unit 10 moves the XY stage 6 while considering the rotation speed of the rotation stage 8 at the condensing point Q of this time. As a result, the scanning speed of the laser light is controlled, and the intervals of the helical paths of the irradiation of the laser light are controlled to be equal. It should be noted that scanning with the laser light from the outer edge of the substrate material 1 toward the center thereof is not limited to that described above. For example, the laser light may be scanned from the end point E to the start point S, that is, the laser light may be scanned from the center toward the outer edge. By irradiating the substrate material 1 with the laser in this manner, the modified layer 12 corresponding to the rotational position is formed in the substrate material 1 .

(Laser beam scanning method 3)
FIG. 2C shows scanning when laser light is scanned on the circumference using the rotary stage 8 and the XY stage 6 for each of a plurality of substrate materials 1a, 100b, 100c, ... arranged on the circumference. showing how. Note that the laser beam scanning method is the same as in FIG. 2B.

Rotational movement of the fixing jig 9 by the rotary stage 8 causes the rotational speed of the fixing jig 9 to approach infinity at the center of rotation. Therefore, in the scanning method of FIG. 2B, there is a possibility that excessive laser light irradiation occurs in the vicinity of the end point E, which is the center. Therefore, by arranging a plurality of substrate materials 1 as shown in FIG. 2C to avoid irradiation in the vicinity of the central portion, it is possible to prevent excessive laser light irradiation.

(Formation state of modified layer in substrate material after laser processing)
FIG. 3 is a diagram showing a formation state of a modified layer in a substrate material after laser processing according to an embodiment of the present disclosure.

N1 in FIG. 3 indicates the thickness of the modified layer 110a to the modified layer 110b. N2 indicates the thickness of the modified layer 110b to the modified layer 110c. N3 indicates the thickness of the surface 101 from the modified layer 110c. Also, Q1 indicates the depth of the focal point of the laser beam for generating the modified layer 110a. Q2 indicates the depth of the focal point of laser light for generating the modified layer 110b. Q3 indicates the depth of laser light for forming the modified layer 110c.

Referring to FIG. 3, modified layer 110a is a layer formed at the deepest position when viewed from surface 101 of substrate material 1 by laser processing. This modified layer 110a is the first layer to be formed.
The modified layer 110b is a layer formed after the modified layer 110a is formed by laser processing, and is a layer formed at the next deepest position after the modified layer 110a.
The modified layer 110 c is a layer formed after the modified layer 110 b is formed by laser processing, and is the layer formed at the shallowest position when viewed from the surface 101 of the substrate material 1 .

In this embodiment, the number of modified layers 110 formed on the substrate material 1 is three, but the number of layers is not limited to this. Moreover, the formation position, formation amount, and the like of the modified layer 110 are not limited.

(Method for forming multiple modified layers)
With continued reference to FIG. 3, a forming method for forming a plurality of modified layers within the substrate material 1 will be described.
As described above, in the present embodiment, the plurality of modified layers 110a, 110b, and 110c are hierarchically formed by scanning while irradiating the condensed laser light from the surface 101 of the substrate material 1 into the substrate material 1. to form.

When the modified layer 110 is formed, almost no laser light penetrates deeper than the modified layer 110 . Therefore, when a plurality of modified layers 110a, 110b, and 110c are hierarchically formed, first, the condensing point of the laser light is aligned with the deepest position from the surface 101 of the substrate material 1, and the lowest layer laser beam is scanned. process. This forms the deepest modified layer 110a. After that, laser processing is performed by sequentially scanning shallow positions Q2 and Q3 with the focal point of the laser beam aligned, thereby forming the modified layers 110b and 110c in sequence.

Moreover, when forming one modified layer 110 , it is preferable to form the modified layer 110 over the entire surface of the substrate material 1 . However, if there is a location where the modified layer 110 is not partially formed, the modified layer 110 can be formed later if the laser beam can be applied to the location later.

Steps 1 to 3 for forming the modified layers 110a, 110b, and 110c will be described.
Regarding process 1 (1-1) first, the control unit 10 controls the condenser lens 5 based on the condensing point data of the substrate material 1, and irradiates the surface 101 of the substrate material 1 with a laser beam substantially perpendicularly. to align the focal point with Q1 at the deepest position.
(1-2) Subsequently, laser processing is performed in substantially the same plane by scanning laser light using the above-described scanning method (step 1).
By this laser processing, first, the modified layer 110a is formed.

Regarding process 2 (2-1), the controller 10 then controls the condenser lens 5 based on the condensing point data of the substrate material 1 to irradiate the surface 101 of the substrate material 1 with laser light substantially perpendicularly. Then, the focal point is aligned with Q2, which is the next deepest position. Here, the condensing point Q2 is a value considering the thickness N1 that can sufficiently secure the thickness of the wafer.
(2-2) Subsequently, laser processing is performed in substantially the same plane by scanning with laser light using the above-described scanning method (step 2).
By this laser processing, the modified layer 110b is then formed.

Regarding process 3 (3-1), finally, the control unit 10 controls the condenser lens 5 based on the condensing point data of the substrate material 1 to direct the laser beam substantially perpendicularly to the surface 101 of the substrate material 1. Irradiate and align the focal point with the shallowest position Q3. Here, the condensing point Q3 is a value in consideration of the thickness N2 that can sufficiently secure the thickness of the wafer.
(3-2) Subsequently, laser processing is performed in substantially the same plane by scanning laser light using the above-described scanning method (step 3).
Finally, the modified layer 110c is formed by this laser processing.

It should be noted that the laser beam may be irradiated not from the front surface 101 side of the substrate material 1 but from the rear surface side (not shown). In such a case, the modified layers 110c, 110b, and 110a are formed in this order.

The substrate material 1 on which the modified layers 110a, 110b, and 110c are formed by such laser processing is separated by a separator (not shown) in a subsequent separation step, using the modified layers 110a, 110b, and 110c as separation surfaces. be. A plurality of substrates (here, three substrates) are produced by separating them with a separator.
In addition, since a residual modified layer remains on the remaining substrate material 1 by separating into the substrates, it is preferable to separate the next substrate after cleaning and polishing the separation surface.

(Configuration of substrate separation device)
FIG. 4 is a schematic diagram showing the configuration of a substrate separation device 30 for separating a brittle material having a modified layer formed thereon in the melting step and the separation step included in the substrate separation method according to Embodiment 1 of the present disclosure. .
This substrate separation device 30 includes a liquid tank 13 storing liquid 14, a temperature applying device 15 applying a temperature to the liquid 14, a decompression device 16 decompressing the inside of the liquid tank 13, and controlling temperature and pressure. and a control device 17 for performing.

<Liquid tank>
The liquid tank 13 stores a liquid such as water. The material of the liquid tank 13 is not particularly limited as long as it does not react with the liquid put therein and does not decompose.

<Liquid>
The liquid 14 is a liquid that can be stored in the liquid tank 13, such as water. Although the type of liquid is not particularly limited, it is preferable to select a substance that does not affect the liquid tank 13 and peripheral devices. In particular, it is preferable that the liquid is not a liquid that does not react with the material of the substrate material 1 or the molecules contained in the modified layer 12, that is, it is not a chemical liquid. For example, if a chemical solution that reacts with the modified layer 12 is used, there are concerns about safety concerns and increased costs. By using, for example, water with an elevated temperature as the liquid 14 as in the present method, the separation is performed only by melting, so that safety concerns and costs can be reduced. In addition, it is possible to further improve the cost by recovering the Ga that has melted and dispersed in the liquid 14 and reusing the metal.

<Temperature applying device>
The temperature application device 15 is a device that applies temperature to the liquid 14 . The temperature application device 15 is, for example, a heater, and the temperature application method is not particularly limited.
<Decompression device>
The decompression device 16 is a device capable of decompressing the pressure in the liquid tank 13 . By reducing the pressure in the liquid tank 13 , the liquid 14 enters the reformed layer 12 more quickly. This allows Ga to be more dispersed in the liquid 14 . Therefore, it is possible to shorten the time required for substrate separation.
<Control device>
The control device 17 is a device that controls temperature and pressure. For example, a computer can be used as the control device 17 . Control device 17 preferably controls temperature application device 15 based on the temperature of liquid 14 . Regarding the temperature measurement, for example, there is a method of grasping the temperature of the liquid using a thermocouple, a camera for temperature measurement, etc., but the method is not particularly limited.

(Method for separating substrate material)
A process of separating the substrate from the material in which the modified layer 12 is formed on the substrate material 1 will be described with reference to FIG.
When the substrate material 1 is a GaN ingot, the modified layer 12 formed by reaction due to multiphoton absorption processing contains metallic Ga. Here, the melting point of Ga is 29.7.degree.
Therefore, the substrate material 1 is immersed in the liquid 14 after making the temperature of the liquid 14 lower than the melting point of GaN and higher than the melting point of Ga using the temperature applying device 15 . This causes Ga to melt and disperse in liquid 14 . Then, a part of the modified layer 12 dissolves, so that the substrate is separated with the modified layer 12 as a boundary.

In order to further improve the separability, the substrate material 1 having the modified layer 12 formed thereon is immersed in a liquid 14 having a temperature lower than the melting point of Ga, and then the liquid 14 is immersed in the liquid 14 by using the temperature applying device 15. It is desirable to raise the temperature to a temperature below the melting point of Ga and above the melting point of Ga. As a result, when the temperature changes, the difference in thermal expansion coefficient between Ga contained in the substrate material 1 and Ga formed in the modified layer 12 further promotes separation.

In order to further improve the separability, it is desirable to immerse the substrate material 1 in the liquid 14 and then use the decompression device 16 to reduce the pressure inside the liquid tank 13 . This allows the liquid 14 to penetrate more into the modified layer 12 when the pressure changes, thereby promoting the dispersion of Ga in the liquid 14 .

It should be noted that combining the method using the temperature application device 15 and the method using the decompression device 16 as described above further improves the separability. Further, the chemically decomposed layers are continuously formed to form the modified layer 12, thereby further improving the separation.

Furthermore, it is conceivable that the substrates are difficult to separate naturally due to the surface tension of Ga. In this case, a method of assisting the separation by applying a force parallel to the surface of the substrate material 1 using a soft rubber material that can be lightly fixed without applying a large load to the substrate may be used.

Normally, when the substrate material is separated, for example, when the modified layer 12 is formed in multiple layers as shown in FIG. Therefore, when the substrate is separated from the position of the modified layer 12-B, in order to take out the substrate again, the metal Ga adhering to the modified layer 12-B is wiped off, and the surface on which the modified layer 12-B is formed is removed. It is necessary to introduce a step of separating the substrates after they can be re-fixed.

In this method, the substrate material 1 on which the modified layers 12-A, 12-B, and 12-C are formed is placed in a liquid 14, in which metallic Ga present in the modified layer 12 is dissolved. By doing so, even if the substrate material 1 is first separated at which position of the modified layer 12, it is possible to continuously separate the substrate thereafter.

Although the substrate material 1 is GaN, it is a material that can form a modified layer inside, and when decomposed by modification, it forms a low melting point material that has a lower melting point than the original substrate material. Any material can be applied.
Also, the pulse width is not limited as long as it is within the range of 100 ps or less and internal processing by multiphoton absorption is possible.

It should be noted that the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and each embodiment and / or The effects of the embodiment can be obtained.

The substrate separation method of the present disclosure is a substrate separation method that can generate a substrate by using a reformed layer as a separation surface from the entire surface and the brittle material during internal processing of the brittle material. As a result, it is possible to reduce the manufacturing cost of the brittle substrate by simplifying the substrate separation process and suppressing cracks during separation.

REFERENCE SIGNS LIST 1 substrate material 2 laser oscillator 4 mirror 5 condenser lens 6 XY stage 7 Z stage 8 rotation stage 9 fixture 10 control section 11 phase modulation section 12 modified layer 13 liquid tank 14 liquid 15 temperature application device 16 decompression device 17 control Apparatus 20 Laser processing apparatus 30 Substrate separation apparatus 100, 100a, 100b, 100c Substrate material 101 Surface 110, 110a, 110b, 110c Modified layer

Claims (6)

A modified layer forming step of forming a modified layer inside the gallium nitride substrate by focused irradiation of laser light;
a melting step of melting the modified layer by immersing the gallium nitride substrate in water having a temperature lower than the melting point of the gallium nitride and higher than or equal to the melting point of gallium contained in the modified layer;
a separating step of separating the gallium nitride substrate with the molten modified layer as a boundary;
including,
Substrate separation method. In the modified layer forming step, the laser light is scanned so as to be continuous over one surface inside the gallium nitride substrate.
2. The substrate separation method according to claim 1. In the melting step, after the gallium nitride substrate is immersed, the temperature of the water is raised from below the melting point of the modified layer to below the melting point of the gallium nitride and above the melting point of the modified layer.
3. The substrate separating method according to claim 1 or 2. reducing the pressure in the liquid tank containing the water in the melting step;
The substrate separating method according to any one of claims 1 to 3. The laser light has a pulse width of 100 ps or less,
The substrate separating method according to any one of claims 1 to 4. In the modified layer forming step, the gallium nitride is chemically decomposed by the irradiation of the laser light.
The substrate separating method according to any one of claims 1 to 5.

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