CN102828240A - Method for preparing GaN film material - Google Patents

Abstract

The invention relates to a method for preparing a GaN film material, which comprises the following steps: evaporating a metal nickel(Ni)film on a GaN/sapphire composite substrate, annealing to obtain the nano Ni paticles, then using an inductively coupled plasma etching (ICP) method to etch GaN on the GaN/sapphire composite substrate which is uncovered by Ni and forming the GaN/sapphire composite substrate with a nano structure. The hydride vapor phase epitaxy (HVPE) growth of GaN is carried out on the nano structure composite substrate to obtain the GaN film with low stress and high quality or the self-supporting GaN substrate material. The method of the invention can obtain the GaN film with low stress and high quality.

Description

A kind of method for preparing GaN thin film material

technical field

The invention relates to a method and process for reducing the stress in GaN thin film material grown by hydride vapor phase epitaxy (HVPE). Especially the method of high-quality low-stress GaN thin film.

Background technique

Group III-V nitride materials (also known as GaN-based materials) mainly composed of GaN, InGaN, and AlGaN alloy materials are new semiconductor materials that have attracted much attention in the world in recent years. GaN-based materials are direct bandgap wide bandgap semiconductor materials with continuously variable direct bandgap between 1.9-6.2eV, excellent physical and chemical stability, high saturation electron drift velocity, high breakdown field strength and high thermal conductivity It has important applications in the preparation of short-wavelength semiconductor optoelectronic devices and high-frequency, high-voltage, and high-temperature microelectronic devices. It is used to manufacture light-emitting devices and detectors such as blue, purple, and ultraviolet bands. High-field high-power devices, field emission devices, radiation-resistant devices, piezoelectric devices, etc.

There are many methods for the growth of GaN-based materials, such as metal-organic vapor phase epitaxy (MOCVD), high-temperature and high-pressure composite GaN single crystal, molecular beam epitaxy (MBE), sublimation method, and hydride vapor phase epitaxy (HVPE). Due to the limitations of the physical properties of GaN-based materials, the growth of GaN bulk single crystals is very difficult and has not been put into practical use. Hydride vapor phase epitaxy can be used for homoepitaxial growth of self-supporting GaN substrate due to its high growth rate and lateral-vertical epitaxy ratio, which has attracted extensive attention and research. In the early days, people mainly used hydride vapor phase epitaxy (HVPE) to directly grow GaN-based materials on sapphire substrates, and then separated them to obtain GaN substrate materials. The outstanding disadvantage of this method is that the dislocation density in the GaN epitaxial layer is very high, generally up to about 10 ¹⁰ cm ^-2 . The current main method is to use lateral epitaxy, hanging epitaxy and other methods, supplemented by HVPE high-speed epitaxy technology to grow thick films, and finally remove the original substrate to obtain a self-supporting GaN substrate material with low dislocation density. So far, the self-supporting GaN substrate grown by HVPE has a dislocation density lower than 10 ⁶ cm ^-2 and an area of 2 inches. But it is still far from meeting the needs of practical applications.

Since GaN can only grow on heterogeneous substrates such as sapphire and silicon, the lattice mismatch and thermal mismatch cause large stress inside the GaN film, making it difficult to improve the performance of GaN-based devices. In addition, the huge stress will cause GaN thick film and foreign substrate to break into fragments, so it cannot be applied. Therefore, reducing or eliminating the stress in the GaN thick film is an important solution to effectively exploit the potential of the GaN material. The invention provides a method and process for reducing the stress in the semiconductor material GaN film material grown by hydride vapor phase epitaxy (HVPE) and obtaining a self-supporting GaN substrate.

Contents of the invention

The purpose of the present invention is: because the existing GaN film is grown on a heterogeneous substrate such as sapphire, lattice mismatch and thermal mismatch will cause greater stress in the GaN film. The existence of stress will cause the performance reduction of GaN-based materials. The invention proposes a method for reducing the stress in the GaN thin film material grown by hydride vapor phase epitaxy (HVPE).

The technical scheme of the present invention is: a method for preparing high-quality and low-stress GaN thin film material, vapor-depositing metal nickel (Ni) thin film on GaN/sapphire composite substrate, nickel (Ni) thin film GaN/sapphire composite substrate in a high-temperature quartz furnace Perform high-temperature annealing treatment: temperature 600-1000°C, time 5-60 minutes; atmosphere is ammonia gas, flow rate 100-5000 ml/min; after annealing is completed, nitrogen gas is quickly introduced to exhaust ammonia gas, and the sample is taken out after cooling to room temperature ; high-temperature annealing to obtain nano-Ni particles on the GaN/sapphire composite substrate, and then use inductively coupled plasma etching (ICP) to etch the GaN on the GaN/sapphire composite substrate that is not covered by Ni to form a nanostructured GaN/sapphire composite substrate. Sapphire composite substrate;

Hydride vapor phase epitaxy (HVPE) growth of GaN on this nanostructure composite substrate can obtain a low-stress high-quality GaN film or a self-supporting GaN substrate material.

Annealing is carried out under the conditions of annealing atmosphere and temperature control to obtain Ni particles of different sizes.

The etch rate of Ni metal particles is slower than that of GaN, so that GaN nanostructures (nano-pillars or nano-dots) are etched.

The nanostructured GaN/sapphire composite substrate is placed in a HVPE growth system for lateral epitaxial growth to obtain a low-stress GaN film.

Inductively coupled plasma etching (ICP) chamber for plasma etching of samples. The ICP parameters are: the gas flow rate of Cl ₂ is 10-100 cm ³ /min; the gas flow rate of BCl ₃ is 1-50 cm ³ /min; the RF power and ICP power are 50-300W and 100-500W respectively, and the pressure is 1E- 09 Pa level; etching time 50-1000S.

The composite substrate of nano-GaN structure is placed in the HVPE reaction chamber for lateral epitaxial growth (for specific implementation, please refer to the patent: "Growing High-Quality Gallium Nitride Films by Lateral Epitaxy Technology", Patent No. ZL021113084.1), and high-quality Low stress GaN film.

Controlling the distribution and size of the nanostructured GaN obtained by ICP etching can also achieve self-separation between GaN thin films and sapphire, thereby obtaining low-stress self-supporting GaN substrate materials. After the temperature is lowered, the GaN thick film is separated from the sapphire, and a high-quality and low-stress GaN substrate material is obtained.

The beneficial effect of the invention is that it provides a method and process for reducing the stress in the GaN thin film material grown by hydride vapor phase epitaxy (HVPE).

Description of drawings

Fig. 1 is the photo schematic diagram of the embodiment of the present invention, the appearance of the nano-Ni particles formed after the annealing of the metal-plated Ni film. Ammonia atmosphere, 800 degrees, ammonia flow rate 800 ml/min.

Fig. 2 is a schematic diagram of a photograph of an embodiment of the present invention, which is the morphology of GaN nanostructures formed after ICP etching of the sample in Fig. 1 .

Detailed ways

The method and technique of the present invention comprise several parts: physical vapor deposition of metal Ni thin film on GaN/sapphire composite substrate; atmosphere annealing treatment of metal Ni thin film; Inductively coupled plasma etching GaN/sapphire composite substrate; GaN thin film HVPE regrowth.

The thickness of the metal Ni film and the size of the Ni particles after annealing depend on the length and size of the GaN nanostructure. Thicker Ni films and larger Ni particles help to obtain GaN nanostructures with longer and thicker vertical and lateral dimensions.

In one of the technical implementation modes of the present invention, preparing a low-stress GaN thin film includes the following steps:

1. Cleaning and processing of GaN/sapphire composite substrate.

2. The GaN/sapphire composite substrate is placed in the reaction chamber of the physical vapor deposition device, and the evaporation of the metal Ni film can be started under a certain reaction chamber pressure and metal source temperature. The deposition rate of the Ni film is set to be about 1-2 angstroms/second, and the thickness of the Ni nano film is 5-50 nm. the

3. Put the sample in step 2 into a high-temperature quartz furnace for high-temperature annealing. Parameters: temperature 600-1000°C, time 5-60 minutes; atmosphere is ammonia, flow rate 100-5000 ml/min. After the etching is completed, nitrogen gas is quickly introduced to exhaust the ammonia gas, and the sample is taken out after cooling down to room temperature.

4. After cleaning the sample in step 3, put it into an inductively coupled plasma etching (ICP) chamber to perform plasma etching on the sample. The ICP parameters are: the gas flow rate of Cl ₂ is 10-100 cm ³ /min; the gas flow rate of BCl ₃ is 1-50 cm ³ /min; the RF power and ICP power are 50-300W and 100-500W respectively, and the pressure is 1E- 09 Pa level; etching time 50-1000S.

5. After cleaning the sample in step 4, put it into the hydride vapor phase epitaxy equipment for HVPE lateral epitaxy growth of GaN. For specific parameters, please refer to the patent: ZL021113084.1 Lateral epitaxy technology to grow high-quality GaN thin films.

6. Take out the sample in step 5 to obtain high-quality and low-stress GaN thin film material.

7. Controlling the parameters in steps 2-5 can realize the separation between GaN film and sapphire, so as to obtain a self-supporting low-stress GaN substrate material.

Claims (4)

1. method for preparing the GaN thin-film material; It is characterized in that evaporation metal nickel (Ni) film on GaN/ sapphire compound substrate; Annealing obtains nanometer Ni particle; Adopt the etching of inductively coupled plasma etching (ICP) mode not by the GaN on the GaN/ sapphire compound substrate of Ni covering then, form the GaN/ sapphire compound substrate of nanostructure; Hydride gas-phase epitaxy (HVPE) growth of on this nanostructure compound substrate, carrying out GaN obtains low-stress high quality GaN film or self-supporting GaN substrate material.

2. the method for preparing the GaN thin-film material according to claim 1 when it is characterized in that metal Ni is annealed into nanometer Ni particle, is annealed under particular atmosphere, specified temp, obtains the Ni particle of different size size.

3. the method for preparing the GaN thin-film material according to claim 1; It is characterized in that in inductively coupled plasma (ICP) the etching GaN technology; Ni metallic particles etch rate is slower than GaN etch rate, thereby etches the GaN nanostructure of nano-pillar or nano dot.

4. according to the described method for preparing the GaN thin-film material of one of claim 1 to 3; It is characterized in that hydride gas phase epitaxial growth carries out in the technology of transversal epitaxial growth; The GaN/ sapphire compound substrate of nanostructure is placed on carries out transversal epitaxial growth in the HVPE growing system, obtain low-stress GaN film.

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