CN113035689A - Method for manufacturing gallium nitride single crystal substrate - Google Patents

Abstract

The invention relates to the technical field of semiconductors, in particular to a method for manufacturing a gallium nitride single crystal substrate, which aims to solve the problem of crystal defects in the gallium nitride single crystal substrate manufactured by the prior art and comprises the following steps: s1, selecting scandium aluminate magnesite (ScAlMgO)₄) As a substrate; s2, growing a GaN-based buffer layer on the substrate by MOCVD metal organic chemical vapor phase growth method; s3, epitaxially growing a GaN single crystal layer on the GaN-based buffer layer by an HVPE vapor phase growth method; s4, slicing the GaN single crystal layer to form a GaN single crystal substrate; s5, grinding and polishing; and S6, washing. In the present invention, the lattice constant and thermal expansion coefficient of the GaN substrate are the same as those of ScAlMgO₄The substrates are substantially uniform, so that the MOCVD method is usedScAlMgO₄A GaN-based buffer layer is grown on a substrate at a low temperature, and a GaN single crystal layer is grown on the GaN-based buffer layer grown as a second stage at a high temperature by an HVPE method, thereby realizing the production of a high-quality GaN crystal free from dislocation and crystal defects.

Description

Method for manufacturing gallium nitride single crystal substrate

Technical Field

The invention relates to the technical field of semiconductors, in particular to a method for manufacturing a gallium nitride single crystal substrate.

Background

GaN is a typical representative of third-generation wide bandgap semiconductors, has been widely used in semiconductor illumination, microwave power devices, power electronic devices, and the like, and shows great application prospects. The most ideal substrate for gallium nitride growth is naturally gallium nitride single crystal material, and such homoepitaxy (i.e. the epitaxial layer and the substrate are the same material) can greatly improve the crystal quality of the epitaxial film, reduce the dislocation density, prolong the service life of the device, improve the luminous efficiency and improve the working current density of the device.

However, the gallium nitride single crystal growth is difficult and expensive, and large-scale homoepitaxial growth is not possible at present. Therefore, the current gallium nitride single crystal production still uses heteroepitaxy, such as sapphire (α Al)₂O₃) Silicon carbide (SiC), gallium arsenide (GaAs), scandium aluminate magnesite (ScAlMgO)₄) For example, a composite substrate in which GaN layers are laminated is produced by a Hydride Vapor Phase Epitaxy (HVPE) method, or the laminated GaN layers are separated or sliced from a substrate of a different material and used as a GaN independent substrate. When a GaN crystal is grown on a substrate made of these materials, because of the difference between the lattice constant and the thermal expansion coefficient between the grown crystal and the substrate, stress is generated inside the grown GaN, and crystal defects are broken even, and the influence of residual stress inside the GaN causes warpage of the wafer as a whole. In addition, scandium aluminate magnesite has a lattice constant of 1.01 times and a thermal expansion coefficient of 1.1 times, which are almost equal to those of gallium nitride, but if it is used as a substrate for GaN crystal growth, in a general HVPE method, aluminum aluminate magnesite is damaged during GaN crystal growthThe scandium substrate, like the above method, is not able to avoid the occurrence of crystal defects, which is not significantly improved in comparison.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a method for manufacturing a gallium nitride single crystal substrate, which solves the problem of crystal defects in the conventional method for manufacturing a gallium nitride single crystal substrate.

The technical purpose of the invention is realized by the following technical scheme:

a method for manufacturing a gallium nitride single crystal substrate, comprising the steps of:

s1, selecting scandium aluminate magnesite (ScAlMgO)₄) As a substrate;

s2, growing a GaN-based buffer layer on the substrate by MOCVD metal organic chemical vapor phase growth method;

s3, epitaxially growing a GaN single crystal layer on the GaN-based buffer layer by an HVPE vapor phase growth method;

s4, slicing the GaN single crystal layer to form a GaN single crystal substrate;

s5, grinding and polishing;

and S6, washing.

Optionally, in the step S2, the substrate is heat-treated in the MOCVD reaction chamber at a temperature of 800-.

Optionally, in the step S3, the epitaxial growth of the GaN single crystal layer is promoted by the HVPE vapor phase growth method under the high temperature reaction condition of 800-1050 ℃, and the thickness of the GaN single crystal layer is controlled to be 0.2-1.5 times of the thickness of the substrate.

Optionally, in step S4, the GaN single crystal layer is sliced by using an inner circular saw cutter, wherein the slicing direction is perpendicular to the central axis direction of the GaN single crystal layer.

Alternatively, in the step S4, the GaN single crystal substrate has a thickness of 500 μm.

Alternatively, in step S5, the surface of the GaN single crystal substrate is polished by chemical mechanical polishing using colloidal silica.

Alternatively, in step S6, the substrate is cleaned by moving a brush in a direction parallel to the surface of the GaN single crystal substrate using an alkaline aqueous solution and a polymer material having a hardness lower than that of the GaN single crystal substrate and absorbing the alkaline aqueous solution.

Alternatively, in step S6, the alkali aqueous solution is selected from the group consisting of potassium hydroxide and sodium hydroxide, and the alkali concentration is 0.05 to 0.5 mass%, and the polymer material is composed of a melamine-foam resin, a porous polyvinyl alcohol resin, a fibrous polyester resin, or a nylon resin.

The invention has the beneficial effects that:

the lattice constant and the thermal expansion coefficient of the GaN substrate are the same as those of ScAlMgO₄The substrates are substantially uniform, so that the MOCVD method is used to form ScAlMgO₄And growing a GaN-based buffer layer on the substrate at a low temperature, growing a GaN single crystal layer on the GaN-based buffer layer grown as the second stage at a high temperature by an HVPE method, and slicing, grinding, polishing and cleaning to manufacture the high-quality GaN crystal substrate without dislocation and crystal defects.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic view showing a process for producing a gallium nitride single crystal substrate according to one embodiment of the present invention.

Description of reference numerals:

21. a substrate; 22. a GaN-based buffer layer; 23. a GaN single crystal layer; 24. a GaN single crystal substrate.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the application described herein may be used. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In this application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. These terms are used primarily to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.

Moreover, some of the above terms may be used to indicate other meanings besides the orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of attachment or connection relationship in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate.

In addition, the term "plurality" shall mean two as well as more than two.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

A method for manufacturing a gallium nitride single crystal substrate, as shown in FIG. 1, comprises the steps of:

s1, selecting scandium aluminate magnesite (ScAlMgO)₄) As thesubstrate 21, the lattice constant and thermal expansion coefficient of the GaN substrate are the same as those of ScAlMgO₄The substrates are basically consistent, so that the crystal defects or wafer deformation caused by lattice bending and thermal expansion bending can be effectively inhibited, and the manufacturing of a GaN substrate with a larger diameter is facilitated;

s2, growingGaN buffer layer 22 onsubstrate 21 by MOCVD organometallic vapor phase growth;

the specific steps include performing heat treatment on thesubstrate 21 in the MOCVD reaction chamber at a temperature of 800-1300 ℃ for 300-2000s, then cooling, and promoting the growth of the GaN-basedbuffer layer 22 under the low-temperature reaction condition of less than 600 ℃ so that the thickness of the GaN-basedbuffer layer 22 is between 10 and 100 nm;

s3, epitaxially growing a GaN single crystal layer 23 on the GaN-basedbuffer layer 22 by HVPE vapor phase growth;

the specific steps include promoting the epitaxial growth of the GaN single crystal layer 23 under the high temperature reaction condition of 800-1050 ℃, and controlling the thickness of the GaN single crystal layer 23 to be 0.2-1.5 times of the thickness of thesubstrate 21;

s4, slicing the GaN single crystal layer 23 to form a GaNsingle crystal substrate 24, specifically, the GaNsingle crystal substrate 24 having a thickness of 500 μm;

due to ScAlMgO₄The substrate has the separable characteristic, and can easily realize the complete stripping of the GaN single crystal layer 23, so that in the embodiment of the invention, the GaN single crystal layer 23 is sliced by using an inner circular saw cutting machine, and the cutting direction is vertical to the central axis direction of the GaN single crystal layer 23;

s5, grinding and polishing, in this embodiment of the invention, the surface of the GaNsingle crystal substrate 24 is ground and polished by a chemical mechanical grinding and polishing method using colloidal silica;

s6, cleaning, in this embodiment of the invention, the GaNsingle crystal substrate 24 is cleaned by moving a brush in a direction parallel to the surface of the GaNsingle crystal substrate 24, using an alkaline aqueous solution, a polymer compound material having a hardness lower than that of the GaNsingle crystal substrate 24 and absorbing the alkaline aqueous solution;

wherein the alkaline aqueous solution is selected from the group consisting of potassium hydroxide and sodium hydroxide, the concentration of the alkali is 0.05-0.5 mass%, and the polymer material is composed of melamine foam resin, porous polyvinyl alcohol resin, fibrous polyester resin, or nylon resin.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (8)

1. A method for manufacturing a gallium nitride single crystal substrate, comprising the steps of:

s1, selecting scandium aluminate magnesite (ScAlMgO)₄) As a substrate (21);

s2, growing a GaN-based buffer layer (22) on the substrate (21) by MOCVD metal organic chemical vapor deposition;

s3, epitaxially growing a GaN single crystal layer (23) on the GaN-based buffer layer (22) by an HVPE vapor phase growth method;

s4, slicing the GaN single crystal layer (23) to form a GaN single crystal substrate (24);

s5, grinding and polishing;

and S6, washing.

2. The method as set forth in claim 1, wherein in step S2, the substrate (21) is heat-treated in the MOCVD reaction chamber at a temperature of 800-1300 ℃ for 300-2000S, and then cooled to promote the growth of the GaN-based buffer layer (22) under the low-temperature reaction condition of less than 600 ℃.

3. The method as set forth in claim 1, wherein in the step S3, the epitaxial growth of the GaN single crystal layer (23) is promoted by the HVPE vapor phase growth method under the high temperature reaction condition of 800-1050 ℃, and the thickness of the GaN single crystal layer (23) is controlled to be between 0.2-1.5 times the thickness of the substrate (21).

4. The method of claim 1, wherein in step S4, the GaN single crystal layer (23) is sliced by an inner circular saw cutting machine in a direction perpendicular to the central axis of the GaN single crystal layer (23).

5. The method of claim 4, wherein in step S4, the thickness of the GaN single crystal substrate (24) is 500 μm.

6. The method of claim 1, wherein in step S5, the surface of the GaN single crystal substrate (24) is polished by chemical mechanical polishing with colloidal silica.

7. The method of claim 1, wherein in step S6, the GaN single crystal substrate is cleaned by moving a brush in a direction parallel to the surface of the GaN single crystal substrate (24) using an alkaline aqueous solution, a polymer compound material that has a lower hardness than the GaN single crystal substrate (24) and absorbs the alkaline aqueous solution.

8. The method of claim 7, wherein in step S6, the aqueous alkaline solution is selected from the group consisting of potassium hydroxide and sodium hydroxide, the concentration of the alkali is 0.05 to 0.5% by mass, and the polymeric compound material is selected from the group consisting of a melamine foam resin, a porous polyvinyl alcohol resin, a fibrous polyester resin, and a nylon resin.

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