CN108315823A - A method of utilizing laser treatment substrate growth low stress Free-standing GaN monocrystalline - Google Patents

Abstract

A method for growing a low-stress self-supporting GaN single crystal using a laser treatment substrate, comprising the following steps: (1) epitaxially growing a layer of GaN film on a sapphire substrate to obtain an MGA substrate; (2) making the obtained MGA substrate (3) Put the cleaned MGA substrate into the thermostatic chamber, with the sapphire surface facing the laser exit window of the laser, and perpendicular to the beam; (4) Set the temperature of the thermostatic chamber; (5) Set Laser parameters, including laser wavelength and laser output energy; (6) set the laser scanning step, and scan the sapphire surface of the MGA substrate point by point, and form a hole-shaped weak connection structure at the junction of sapphire and GaN; (7) set the constant temperature Cool down to room temperature; a low-stress MGA substrate is obtained. Under the premise of ensuring the integrity of the surface structure, the present invention effectively reduces the stress of the substrate, thereby reducing the residual stress of GaN single crystal grown by HVPE, improving the quality of GaN single crystal, and has the advantages of simplicity, speed, low cost and strong practicability specialty.

Description

A method for growing low-stress self-supporting GaN single crystals using laser-treated substrates

technical field

The invention relates to a method for processing MOCVD-GaN/sapphire substrate growth crystals by using laser technology, and belongs to the field of crystal growth.

Background technique

Gallium nitride (GaN), as a representative of the third-generation semiconductor materials, has a large band gap, high breakdown voltage (3.4eV at 25°C), high electron mobility, high temperature stability, acid resistance, alkali resistance, and Corrosion and other excellent properties. This makes it have very broad application prospects in LED, semiconductor laser, solid-state optical storage, microelectronic devices, microwave devices, high-power devices, high-frequency high-power devices, etc. At present, GaN has become a hot research topic in the world. However, due to the lack of homogeneous substrates, GaN is mostly grown on heterogeneous substrates. In order to be more conducive to nucleation, a layer of GaN film (hereinafter referred to as MGA) will be grown heteroepitaxially by MOCVD, but Due to the lattice mismatch and thermal mismatch, there is a large stress in the MGA, which affects further growth, leads to cracking, and greatly reduces the performance and service life of the device. Therefore, a low-stress MGA substrate is very necessary to improve the quality of GaN crystals.

At present, there are mainly the following methods for preparing low-stress substrates: one is to use a porous substrate prepared by a patterned substrate; The porous structure of TiN nano-grid is generated to achieve the purpose of preparing porous substrate; the third is to use the method of two-dimensional material blocking layer to coat a layer of graphene on the surface of MGA to form a dislocation blocking layer. These methods can effectively reduce the dislocation density in GaN single crystals, but they do not do enough to reduce stress, and are not conducive to large-scale promotion and use.

Contents of the invention

Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a simple, direct and easy-to-operate method for growing low-stress self-supporting GaN single crystals by using laser processing substrates, which can reduce substrate stress and ensure substrate stress The bottom surface structure is complete, and a low-stress substrate is obtained for HVPE (Hydride Vapor Phase Epitaxy) growth of GaN single crystal, so as to achieve the purpose of reducing the residual stress in the single crystal while reducing the dislocation density in the GaN single crystal.

The method for growing a low-stress self-supporting GaN single crystal by using a laser treatment substrate of the present invention is to use laser treatment on an MGA substrate to prepare a low-stress substrate for HVPE growth of a GaN single crystal, specifically comprising the following steps:

(1) Epitaxially grow a layer of GaN film on the sapphire substrate to obtain the MGA substrate;

(2) cleaning and drying the obtained MGA substrate;

(3) Put the cleaned MGA substrate into the thermostatic chamber, with the sapphire face facing the laser exit window of the laser and perpendicular to the beam;

(4) Set the temperature of the thermostatic chamber;

(5) Set laser parameters, including laser wavelength and laser output energy;

(6) Set the laser scanning step, and scan the sapphire surface of the MGA substrate point by point, forming a hole-like weak connection structure at the junction of sapphire and GaN;

(7) Decrease the temperature of the thermostatic chamber to room temperature; obtain a low-stress MGA substrate.

The obtained low-stress MGA substrate was used for HVPE growth to further obtain a self-supporting GaN single crystal.

The thickness of the GaN thin film in the step (1) is 2-6 μm.

The cleaning of the MGA substrate in the step (2) is carried out in sequence in ethanol, acetone and deionized water for ultrasonic cleaning for 10-30 minutes.

In the step (4), the temperature of the thermostatic chamber is controlled at 100 to 750°C;

The laser wavelength in the step (5) is 183nm-364nm.

In the step (5), the laser output energy is controlled to be 3-19mJ.

In the step (6), the laser scanning step is set as: S×L=0.5mm×0.5mm˜2mm×2mm, S is the perimeter, and L is the radius.

In the step (6), the occupancy rate of holes at the interface between sapphire and GaN is 1%-70%.

The present invention forms a hole-like weak connection structure at the junction of the GaN thin film and sapphire by means of laser treatment, thus effectively reducing the stress on the substrate while ensuring the integrity of the surface structure, thus reducing the cost of HVPE-grown GaN monolayers. The residual stress of the crystal can be improved to improve the quality of GaN single crystal, saving time and production cost. The utility model has the characteristics of simplicity, quickness, low cost and strong practicability.

Description of drawings

Figure 1 is a schematic diagram of laser processing to prepare a low-stress substrate.

Fig. 2 is a SEM image of the substrate surface treated with 3mJ laser energy.

Fig. 3 is a SEM image of a cross-section of a substrate treated with 3mJ laser energy.

Fig. 4 is a SEM image of the substrate surface treated with 5mJ laser energy.

Fig. 5 is an SEM image of a cross-section of a substrate treated with 5mJ laser energy.

Fig. 6 is a SEM image of the substrate surface treated with 7mJ laser energy.

Fig. 7 is a SEM image of a cross-section of a substrate treated with 7mJ laser energy.

Fig. 8 is a SEM image of the substrate surface treated with 19mJ laser energy.

Fig. 9 is an SEM image of a cross-section of a substrate treated with 19mJ laser energy.

Detailed ways

Example 1

As shown in Figure 1, a low-stress substrate for HVPE growth of GaN single crystals is prepared on an MGA substrate by laser treatment, and the specific steps are as follows.

(1) A 2-6 μm GaN thin film was grown on the sapphire substrate by MOCVD heteroepitaxial growth to obtain the MGA substrate.

(2) Put the obtained MGA into ethanol, acetone and deionized water in sequence for ultrasonic cleaning for 10-30 minutes, and dry.

(3) Put the cleaned MGA substrate into a thermostatic chamber, with the sapphire face facing the laser exit window and perpendicular to the light.

(4) Select a laser with a wavelength of 355nm, and heat the thermostatic chamber to 100°C;

(5) Set the laser parameters and adjust the output energy of the laser to 3mJ;

(6) Set the laser step to S0.5mm×L0.5mm, and scan the substrate point by point.

(7) The temperature of the thermostatic chamber is lowered to room temperature, and the substrate is taken out and cleaned;

Put the obtained substrate into the HVPE reaction chamber for HVPE growth to obtain GaN single crystal. Its surface and cross-section SEM, as shown in Figures 2 and 3, has less pore structure, and the pore occupancy rate is 5%. The Raman test results show that the stress is 1.076GPa.

Example 2

As described in Example 1, the difference is that the laser output energy is 5mJ in step (5), and the obtained MGA substrate surface and cross-section SEM are as shown in Figures 4 and 5; by calculating the hole occupancy rate of 20%, the Mann test results show that the magnitude of the stress is 0.767GPa.

Example 3

As described in Example 1, the difference is that the laser output energy is 7mJ in step (5), and the obtained MGA substrate surface and cross-section SEM, as shown in Figures 6 and 7, by calculating the hole occupancy rate of 40%, pull Mann test results indicated a stress of 0.372GPa.

Example 4

As described in Example 1, the difference is that the output energy of the laser in step (5) is 12mJ, and by calculation, the hole occupancy rate is 60%, and the stress is 0.298GPa.

Example 5

As described in Example 1, the difference is that the laser output energy in step (5) is 19mJ, and the obtained MGA substrate surface and cross-section SEM, as shown in Figures 8 and 9, the obtained MGA substrate is in the GaN thin film and sapphire A large area of peeling has occurred at the junction, and the pore occupancy rate reaches 70%.

Example 6

As described in Example 1, the difference is that the temperature of the thermostatic chamber in step (4) is 200°C. By calculating the pore occupancy rate of 8%, the Raman test results show that the stress is 0.957Gpa.

Example 7

As described in Example 1, the difference is that the temperature of the thermostatic chamber in step (4) is 300°C. By calculating the pore occupancy rate of 10%, the Raman test results show that the stress is 0.901Gpa.

Example 8

As described in Example 1, the difference is that the temperature of the thermostatic chamber in step (4) is 500°C. By calculating the pore occupancy rate of 14%, the Raman test results show that the stress is 0.856Gpa.

Example 9

As described in Example 1, the difference is that the temperature of the thermostatic chamber in step (4) is 750°C. By calculating the pore occupancy rate of 22%, the Raman test results show that the stress is 0.742Gpa.

Example 10

As described in Example 1, the difference is that the temperature of the thermostatic chamber in step (4) is 300° C.; the output energy of the laser in step (5) is 5 mJ. By calculating the pore occupancy rate of 25%, the Raman test results show that the stress is 0.601Gpa.

Example 11

As described in Embodiment 1, the difference lies in that the laser step is set to S1mm×L1mm in step (6). By calculating the pore occupancy rate of 2%, the stress size is 1.187Gpa.

Example 12

As described in Embodiment 1, the difference lies in that the laser step is set to S2mm×L2mm in step (6). By calculating the pore occupancy rate of 1%, the stress size is 1.256Gpa

Example 13

As described in Example 1, the difference is that the wavelength of step (4) is selected as 364 nm. By calculating the pore occupancy rate of 2%, the stress size is 1.179Gpa.

Example 14

As described in Example 1, the difference is that the wavelength of step (4) is selected as 300 nm. By calculating the pore occupancy rate of 7%, the stress size is 0.972Gpa.

Example 15

As described in Example 1, the difference is that the wavelength of step (4) is selected as 260 nm. By calculating the pore occupancy rate of 10%, the stress size is 0.998Gpa.

Example 16

As described in Example 1, the difference is that the wavelength of step (4) is selected as 183 nm. By calculating the pore occupancy rate of 20%, the stress size is 0.766Gpa.

Experimental research shows that this experiment successfully reduces the stress of the MGA substrate, effectively guarantees the integrity of the MGA substrate, and is more conducive to further HVPE growth. It has the advantages of simplicity, speed, and low cost, and is more conducive to further growth. .

Claims (8)

1. A method utilizing laser treatment substrate growth low stress self-supporting GaN single crystal, it is characterized in that, comprises the following steps: (1) Epitaxially grow a layer of GaN film on the sapphire substrate to obtain the MGA substrate; (2) cleaning and drying the obtained MGA substrate; (3) Put the cleaned MGA substrate into the thermostatic chamber, with the sapphire face facing the laser exit window of the laser and perpendicular to the beam; (4) Set the temperature of the thermostatic chamber; (5) Set laser parameters, including laser wavelength and laser output energy; (6) Set the laser scanning step, and scan the sapphire surface of the MGA substrate point by point, forming a hole-like weak connection structure at the junction of sapphire and GaN; (7) The temperature of the thermostatic chamber is lowered to room temperature to obtain a low-stress MGA substrate. 2 . The method for growing a low-stress self-supporting GaN single crystal by processing a substrate with laser according to claim 1 , wherein the thickness of the GaN thin film in the step (1) is 2-6 μm. 3. the method for utilizing laser processing substrate growth low-stress self-supporting GaN single crystal according to claim 1, it is characterized in that, the cleaning of MGA substrate among the described step (2) is to put into ethanol, acetone and remove successively Ultrasonic cleaning in deionized water for 10-30 minutes. 4. The method for growing a low-stress self-supporting GaN single crystal by processing a substrate with laser according to claim 1, characterized in that, in the step (4), the temperature of the thermostatic chamber is controlled at 100-750°C. 5 . The method for growing a low-stress self-supporting GaN single crystal by processing a substrate with laser according to claim 1 , wherein the wavelength of the laser in the step (5) is 183nm-364nm. 6 . The method for growing a low-stress self-supporting GaN single crystal by processing a substrate with laser according to claim 1 , wherein the output energy of the laser in the step (5) is 3-19 mJ. 7. The method for growing a low-stress self-supporting GaN single crystal by processing a substrate with laser according to claim 1, characterized in that, in the step (6), the laser scanning step is set as: S×L=0.5mm× 0.5mm～2mm×2mm, S is the circumference, L is the radius. 8. The method for growing a low-stress self-supporting GaN single crystal by using a laser treatment substrate according to claim 1, characterized in that, in the step (6), the pore occupancy at the junction of sapphire and GaN is 1% to 70% .