WO2021258820A1 - Composite substrate based on an aluminium nitride ceramic material, and preparation method and application therefor - Google Patents

Abstract

Provided in the present invention is a composite substrate based on aluminium nitride ceramic material, comprising: (a) an aluminium nitride ceramic substrate; (b) a graphical structure layer comprising a graphical structure positioned on the aluminium nitride ceramic substrate, the graphical structure being distributed on the aluminium nitride ceramic substrate at periodic intervals; and (c) a polycrystalline film coating layer, the polycrystalline film coating layer being a continuous layer covering the graphical structure layer and the aluminium nitride ceramic substrate not covered by the graphical structure. The composite substrate based on AlN ceramic material provided in the present invention is used for growing GaN or AlN single crystal material, reducing the cost of the substrate material whilst avoiding thermal mismatch dislocations.

Description

Composite substrate based on aluminum nitride ceramic material and preparation method and application thereof Technical field

The invention belongs to the field of semiconductor material preparation, and specifically relates to a composite substrate based on aluminum nitride (AlN) ceramic material, and a preparation method and application thereof.

Background technique

With the development of the gallium nitride (GaN) material system, the application of GaN material system devices has become more and more extensive. Except for the widely used GaN-based LED devices, GaN-based radio frequency devices have been widely used in 5G and other fields. At the same time, GaN-based power devices, such as high electron mobility transistor (HEMT) devices, have also been developed very rapidly in the fields of electric vehicles and fast charging. At the same time, aluminum nitride (AlN) single crystal materials have also been extensively developed. application. Some application areas where third-generation semiconductors gradually replace the first and second-generation semiconductors have become a reality.

In the development of GaN material devices, the substrate material has always been the basis for the development of the entire GaN material system. At present, the substrate material widely used in LED devices is the sapphire substrate material. For light-emitting devices such as LEDs, the sapphire substrate and its graphic substrate system have accumulated incomparable advantages in the fields of GaN-based LED devices due to its excellent price advantage and long-term technology accumulation.

For power devices such as GaN-based radio frequency devices and HEMT devices that have been developed in recent years for use in 5G or electronic power, due to their pursuit of high power and high mobility, GaN grown on sapphire materials has a high dislocation density and sapphire Due to poor heat dissipation and other reasons, the sapphire substrate cannot become the mainstream substrate for GaN-based radio frequency devices and HEMT devices. At present, the mainstream substrates used in this application field are SiC substrates or Si substrates. SiC substrate has become the first choice due to its higher thermal conductivity and lower misfit dislocations during material growth; while Si substrate is mainly because of its low price.

In fact, for GaN system materials, the best substrate is a homoepitaxial substrate, that is, a GaN single crystal substrate or an AlN single crystal substrate. Using a homoepitaxial substrate can greatly reduce the thermal misfit dislocations during the growth process and the application process. Thermal misfit dislocations mean that under high-temperature growth conditions (such as the epitaxial growth temperature of GaN or AlN single crystal materials are above 1000 ℃), the substrate material and the epitaxial material have different thermal expansion coefficients, resulting in thermal expansion. The difference is that when the temperature is lowered to room temperature after the growth, the shrinkage ratio of the two is significantly different, which causes the epitaxial material and the substrate material to accumulate a large amount of stress and dislocations due to thermal mismatch. However, the GaN single crystal substrate or AlN single crystal substrate and the epitaxially grown GaN or AlN are homogeneous materials, and there is basically no such thermal mismatch problem, so the quality of the grown material can be significantly improved. This advantage is even It is not available for SiC substrates.

However, GaN single crystal substrates are very expensive, and the preparation process is complex, and the global Ga resources are not sufficient, which severely limits its application in power devices and other fields; while the AlN single crystal substrate is because the preparation process is very difficult. The complexity and difficulty are very high, which also leads to very expensive prices and also cannot be popularized. Therefore, how to maximize the use of homogeneous materials, that is, GaN or AlN, while reducing its cost, has become the key to solving the problem.

Compared with the AlN single crystal substrate, the cost advantage of the AlN ceramic substrate is very large. The cost of the AlN single crystal and AlN ceramic of the same size is dozens of times different. However, it is generally believed in the industry that although AlN ceramic materials are homogeneous materials with GaN or AlN materials, because AlN ceramics are amorphous or polycrystalline materials, it is impossible to achieve epitaxial growth of single crystal materials on their surface, so it is impossible to use them. AlN ceramic materials are used as substrates for growing GaN or AlN single crystals.

Summary of the invention

The purpose of the present invention is to provide a composite substrate based on an AlN ceramic material for growing GaN or AlN single crystal material, and a preparation method and application thereof, which can reduce the cost of the substrate material while avoiding thermal misfit dislocations.

Since AlN ceramic materials are amorphous or polycrystalline materials, how to achieve GaN or AlN single crystal epitaxy is a huge technological gap, and it is also the key to which no one has tried in the world. Due to his technical experience covering ALN ceramic substrates, as well as GaN material substrates and epitaxial technology research, the inventor of the present invention is proficient in the properties of ALN ceramic substrates and the generation and storage characteristics of sapphire substrates. After a lot of experimental research, he unexpectedly developed a composite The structured AlN ceramic substrate can solve the problem of single crystal growth and obtain high-quality GaN and AlN epitaxial single crystal materials, which greatly reduces the cost of substrate materials while avoiding thermal misfit dislocations, and becomes the entire GaN and AlN The material system is a huge breakthrough in the application of power devices.

The present invention provides a composite substrate based on aluminum nitride ceramic material, including:

(a) Aluminum nitride ceramic substrate;

(b) A patterned structure layer, the patterned structure layer comprising patterned structures distributed on the aluminum nitride ceramic substrate at periodic intervals; and

(c) A polycrystalline coating layer, which is a continuous layer covering the pattern structure layer and the aluminum nitride ceramic substrate not covered by the pattern structure.

According to the composite substrate based on aluminum nitride ceramic material provided by the present invention, the thickness of the aluminum nitride ceramic substrate may be 100-1000 μm, preferably 200-700 μm. In order to realize the growth of GaN single crystal or AlN single crystal material, the AlN ceramic substrate used in the present invention is a substrate material with a highly polished surface, and the surface roughness can be 0.01-100 nm, preferably 0.01-50 nm.

According to the composite substrate based on aluminum nitride ceramic material provided by the present invention, the thickness of the pattern structure layer may be 0.01-5 μm, preferably 0.1-3.5 μm. The pattern structure layer may be composed of a homogeneous material, a heterogeneous material, or a combination of a homogeneous material and a heterogeneous material of an aluminum nitride ceramic substrate. When the pattern structure layer is composed of a combination of the homogenous material and the heterogeneous material of the aluminum nitride ceramic substrate, the homogenous material is located at the bottom of the pattern structure layer, close to the aluminum nitride ceramic substrate. The thickness of the heterogeneous material and the thickness of the homogeneous material can be any ratio. In some preferred embodiments, the ratio of the thickness of the heterogeneous material to the thickness of the homogeneous material is (0.05-0.99):(0.01-0.95), preferably (0.8-0.99):(0.01-0.2), more preferably It is (0.9-0.99):(0.01-0.1), for example, 0.95:0.05.

The heterogeneous material constituting the pattern structure layer may be a substrate material other than AlN commonly used in the art, for example, may be selected from _{one or more of SiO 2} , Si ₃ N ₄ , SiC, Si, ZnO, and GaAs .

The present invention does not particularly limit the shape of the graphic structure, and it may be a convex structure or a concave structure. For example, the convex structure can be selected from a cone, a cylinder, a trapezoidal truncated cone, a triangular cone, a square cone, a square column, a triangular square cone, a trapezoidal square cone, a pentagonal cone, a pentagonal column, and a trapezoid with five sides. One or more of polygonal cone, polygonal column and trapezoidal polygonal pyramid such as truncated cone, hexagonal pyramid, hexagonal pillar, trapezoidal hexagonal pyramid, 12-sided pyramid, 12-sided pillar, trapezoidal 12-sided pyramid, etc. . The recessed structure can be selected from conical pits, cylindrical pits, trapezoidal round truncated pits, triangular pyramidal pits, triangular truncated trellis pits, square cone pits, square cylindrical pits, trapezoidal square truncated pits, pentagonal cone pits, and pentagonal pits. Cylindrical pit, trapezoidal pentagonal pit, hexagonal pentagonal pit, hexagonal cylindrical pit, trapezoidal hexagonal pedestal pit, 12-sided cone pit, 12-sided cylindrical pit, trapezoidal 12-sided pedestal pit, etc. , One or more of polygonal columnar pits and trapezoidal polygonal pedestal pits.

The period of the pattern structure (that is, the distance between the central axes of two adjacent pattern structures, represented by the letter A) may be 0.1-50 μm, preferably 0.2-10 μm. The diameter of the bottom surface of the graphic structure (indicated by the letter W) may be 0.02-50 μm, preferably 0.1-9 μm. The height of the graphic structure (indicated by the letter d) can be 0.01-5 micrometers, preferably 0.1-3.5 micrometers. Fig. 1 exemplarily shows the period and size of the graphic structure of the present invention.

According to the composite substrate based on aluminum nitride ceramic material provided by the present invention, the polycrystalline coating layer can be selected from AlN polycrystalline film, graphene polycrystalline film, GaN polycrystalline film, SiC polycrystalline film, GaAs polycrystalline film, and GaAs polycrystalline film. One or more of crystalline film and ZnO polycrystalline film. The polycrystalline coating layer is conducive to the nucleation of GaN single crystal or AlN single crystal during epitaxial growth. The preferred polycrystalline coating layer is an AlN polycrystalline film and/or a graphene polycrystalline film. Wherein, the thickness of the polycrystalline coating layer may be 0.01-2000 nm, preferably 1-500 nm.

According to the composite substrate based on aluminum nitride ceramic material provided in the present invention, the composite substrate may further include:

(d) A single crystal film layer, the single crystal film layer being an aluminum nitride single crystal layer or a gallium nitride single crystal layer covering the polycrystalline coating layer.

In this embodiment, the single crystal film layer is an AlN or GaN single crystal layer grown on the surface of the polycrystalline coating layer by side epitaxial technology. The thickness of the single crystal film layer can vary within a wide range, for example, it can be 0.01-1000 μm, preferably 0.05-100 μm.

According to the composite substrate based on aluminum nitride ceramic material provided by the present invention, in order to further reduce the dislocation density and improve the crystal quality, the composite substrate may further include:

(e) A second pattern structure layer, the second pattern structure layer includes a second pattern structure on the single crystal film layer, and the second pattern structure is periodically spaced on the single crystal film layer ; And optional

(f) A second polycrystalline coating layer, the second polycrystalline coating layer being a continuous layer covering the second pattern structure layer and the single crystal film layer not covered by the second pattern structure; and any Chosen

(g) A second single crystal film layer, the second single crystal film layer being an aluminum nitride single crystal layer or a gallium nitride single crystal layer covering the second polycrystalline coating layer.

Wherein, the definitions of the second graphic structure layer, the second graphic structure, the second polycrystalline coating layer and the second single crystal film layer are respectively the same as those of the graphic structure layer, the graphic structure, the polycrystalline coating layer and the single crystal film described above. The definition of layers is the same.

In some embodiments of the present invention, in order to further reduce the dislocation density and improve the crystal quality, the composite substrate may further include: a third pattern structure layer, and an optional third polycrystalline coating layer and an optional second Three single crystal film layers. In some embodiments of the present invention, the composite substrate may further include: a fourth pattern structure layer, and an optional fourth polycrystalline coating layer and an optional fourth single crystal film layer; ...; Graphic structure layer, and optional Nth polycrystalline coating layer and optional Nth single crystal film layer (N is any integer greater than 4). That is to say, after the substrate of the present invention has a basic structure of "aluminum nitride ceramic substrate-pattern structure layer-polycrystalline coating layer-single crystal film layer", the pattern structure layer and polycrystalline film layer can be cyclically stacked as needed. The coating layer and the single crystal film layer, and the surface layer of the final substrate can be any one of a pattern structure layer, a polycrystalline coating layer and a single crystal film layer.

In the present invention, the setting of the single crystal film layer, as well as the selective and cyclically superimposed setting of the pattern structure layer, the polycrystalline coating layer and the single crystal film layer are all ways to improve the crystal quality by using the side epitaxial technology. The inventor unexpectedly discovered that with this method, with each additional layer, the epitaxially grown AlN or GaN can be significantly improved in crystal quality. However, the present invention does not limit that the substrate must be provided with a single crystal film layer or the cyclic superposition of each layer. Whether these layers are provided depends on the requirements of the epitaxial GaN single crystal or AlN single crystal crystal quality of the substrate application scene. For areas with low crystal quality requirements, there is no need to set up a single crystal film layer or cycle stacking of each layer; for applications with high crystal quality requirements, the single crystal film layer or even the cycle of each layer can be set as needed Overlay.

The present invention also provides a method for preparing a composite substrate based on aluminum nitride ceramic material. The method includes the following steps:

(1) Polish the aluminum nitride ceramic substrate to a surface roughness of 0.01-100nm;

(2) Using coating technology to prepare a heterogeneous film on the surface of the polished aluminum nitride ceramic substrate;

(3) Coating photoresist on the surface of the heterogeneous film, exposing the photoresist into a pattern using a photolithography process, and then etching the heterogeneous film using an etching process to form a pattern structure layer, so The pattern structure layer includes pattern structures distributed on the aluminum nitride ceramic substrate at periodic intervals;

(4) A polycrystalline coating layer is formed on the pattern structure layer using coating technology.

In a preferred embodiment, the preparation method may further include:

(5) Using an epitaxial growth device to grow an aluminum nitride single crystal layer or a gallium nitride single crystal layer on the surface of the polycrystalline coating layer to form a single crystal film layer.

According to the preparation method provided by the present invention, the step (1) may include: selecting a high-quality AlN ceramic substrate, and using CMP (Chemical Mechanical Polishing) technology or other polishing techniques to polish the surface of the AlN ceramic substrate to the surface There is no obvious step, and the roughness meets the requirements. Wherein, the thickness of the aluminum nitride ceramic substrate may be 100-1000 μm, preferably 200-700 μm. In order to facilitate the growth of GaN single crystal or AlN single crystal material, the AlN ceramic substrate used in the present invention is a substrate material with a high-precision polished surface, and the roughness is preferably 0.01-50 nm.

According to the preparation method provided by the present invention, the step (2) may include: using PECVD (plasma enhanced chemical vapor deposition), CVD (chemical vapor deposition), PLD (pulse laser deposition) and other coating techniques, in A heterogeneous thin film is prepared on the surface of the AlN ceramic substrate. The heterogeneous film may be SiO ₂ , Si ₃ N ₄ , SiC, Si, ZnO, GaAs and other materials. Preferably, the thickness of the heterogeneous film is the same as or slightly larger than the thickness of the second pattern structure layer described above. For example, in some embodiments of the present invention, the thickness of the heterogeneous membrane may be 0.01-5 μm, preferably 0.1-3.5 μm.

According to the preparation method provided by the present invention, in the step (3), a glue coating process can be used to coat photoresist on the surface of the heterogeneous film. The thickness of the coated photoresist depends on the height of the required etching pattern and the etching selection ratio between the heterogeneous material and the photoresist. The present invention does not specifically limit the thickness of the photoresist. Then, use a photolithography process to expose the photoresist to a desired pattern, such as the cylinder, cone, cylinder, trapezoidal truncated cone, triangular pyramid, square pyramid, square pillar, triangular square pyramid, etc., as described above. shape. The photolithography process can use a traditional photolithography machine, a distributed exposure machine, or a nanoimprint process. Next, an etching process is used to etch the heterogeneous material on the AlN ceramic surface and/or part of the AlN ceramic substrate into the pattern structure. The etching process may use dry etching or wet etching. Dry etching can use ICP (Inductively Coupled Plasma Etching Technology), RIE (Reactive Ion Etching Technology) and other etching processes. Wet etching can use chemical etching methods, such as acid-base reagents or organic Reagents and other methods.

According to the preparation method provided by the present invention, in the step (4), a homogenous or heterogeneous polycrystalline film is plated on the pattern structure layer formed in the step (3) using a coating technology, and the polycrystalline film may be AlN polycrystalline. One or more of crystal film, graphene polycrystalline film, GaN polycrystalline film, SiC polycrystalline film, GaAs polycrystalline film, and ZnO polycrystalline film. The coating process can be selected from one of PVD (physical vapor deposition), MOCVD (metal organic vapor deposition), HVPE (hydride vapor deposition), MBE (molecular beam epitaxy), and PLD (pulse laser deposition). Kind or more.

According to the preparation method provided by the present invention, in the step (5), an epitaxial growth device is used to epitaxially grow a GaN or AlN single crystal thin film on the surface side of the polycrystalline coating layer. Various growth methods such as MOCVD, HVPE, PLD and PVD can be used for epitaxial growth, and MOCVD and HVPE methods are preferred. The growth technology can refer to the well-known GaN or AlN single crystal epitaxial growth technology.

In some embodiments of the present invention, in order to further reduce the dislocation density and improve the crystal quality, the preparation may further include: repeating one or more steps of steps (2) to (5) after step (5) Operation, further forming a second pattern structure layer, and an optional second polycrystalline coating layer and an optional second single crystal film layer; further optional third pattern structure layer, a third polycrystalline coating layer and a third Single crystal film layer; further optional fourth pattern structure layer, fourth polycrystalline coating layer and fourth single crystal film layer; ...; and optional Nth pattern structure layer, Nth polycrystalline coating layer and first N single crystal film layer (N is any integer greater than 4). That is to say, after the substrate of the present invention has a basic structure of "aluminum nitride ceramic substrate-pattern structure layer-polycrystalline coating layer-single crystal film layer", the pattern structure layer and polycrystalline film layer can be cyclically stacked as needed. The coating layer and the single crystal film layer, and the surface layer of the final substrate can be any one of a pattern structure layer, a polycrystalline coating layer and a single crystal film layer.

The present invention also provides the application of the AlN ceramic material-based composite substrate or the AlN ceramic material-based composite substrate prepared according to the method of the present invention in the epitaxial growth of GaN or AlN single crystal materials.

The beneficial effects and technological breakthroughs of the present invention over the prior art are:

(1) The use of the first three-layer structure solves the biggest technical problem of growing GaN or AlN single crystal on an amorphous substrate such as an AlN ceramic substrate. The existence of the second layer structure and the third layer structure solves the problem of epitaxial growth of single crystal GaN or AlN on a non-single crystal AlN ceramic substrate. Using the method provided by the present invention, an unexpected extension effect is obtained, which breaks through the original concept. The original thinking and experimental law believed that it is impossible to break through the growth of single crystal structure on non-single crystal substrate. The invention breaks through the inherent thinking and successfully realizes the growth of GaN or AlN single crystal material on the AlN ceramic substrate.

(2) Compared with the existing SiC substrate, the substrate of the present invention has obvious advantages. The cost of the SiC substrate of the same size and the substrate of the present invention can be 10 times different; the substrate of the present invention is compared with Si The advantage of the substrate is that the use of homogeneous epitaxy significantly reduces the dislocation density and at the same time reduces the growth difficulty, and the thermal conductivity has obvious advantages. First, the present invention utilizes the high heat dissipation performance of the AlN ceramic substrate. The theoretical thermal conductivity of the AlN ceramic substrate can reach 320W/mk, and most of the current AlN ceramic substrates can achieve more than 180W/mk, which is significantly improved compared to the thermal conductivity of 100W/mk of the Si substrate. The thermal conductivity of the upper SiC substrate is mostly between 120-150W/mk. The composite substrate of the present invention has obvious advantages, and can meet the current heat dissipation requirements of GaN or AlN power devices such as 5G or HEMT. Second, the AlN ceramic composite substrate of the present invention and the epitaxially grown AlN single crystal or GaN single crystal belong to the same material, and there is almost no thermal mismatch between the two, which is significant for the crystal quality improvement of epitaxial GaN or AlN. Advantage. Third, the fourth layer of the composite substrate of the present invention is a GaN or AlN single crystal layer. Such a composite substrate undergoes GaN or AlN epitaxy and basically achieves homogeneous epitaxy. Compared with SiC substrate or Si substrate The advantage is huge.

(3) In the preferred embodiment of the present invention, the crystal quality is further improved by arranging the AlN or GaN single crystal film layer of the fourth layer, so that the composite substrate of the present invention can achieve homoepitaxial growth of high quality GaN single crystal or AlN single crystal.

(4) Compared with a GaN single crystal substrate or an AlN single crystal substrate, the composite substrate of the present invention has a simple preparation process and an obvious price advantage. The cost of a GaN single crystal substrate or an AlN single crystal substrate of the same size is more than 10 to 20 times that of the substrate of the present invention.

Brief description of the drawings

Figure 1 is a schematic diagram of the period and size of the pattern structure of the composite substrate of the present invention;

2 is an SEM image of the pattern structure layer formed in step (3) of Example 1 of the present invention;

FIG. 3 is an SEM photograph of a GaN surface with a thickness of 2 microns grown by MOCVD in step (5) of Embodiment 1 of the present invention; FIG.

4 is an SEM photograph of a GaN surface with a thickness of 4 microns grown by MOCVD in step (5) of Example 1 of the present invention;

5 is an XRD pattern of the GaN single crystal layer on the surface of the composite substrate prepared in Example 1 of the present invention;

6 is an XRD pattern of the GaN single crystal layer on the surface of the composite substrate prepared in Example 2 of the present invention;

7 is a SEM image of the surface of the composite substrate prepared in Example 3 of the present invention;

8 is a SEM image of the surface of the composite substrate prepared in Example 4 of the present invention;

9 is a SEM image of the surface of the composite substrate prepared in Example 5 of the present invention;

10 is a cross-sectional SEM image of a GaN single crystal grown on the surface of the composite substrate prepared in Example 6 of the present invention;

11 is a SEM image of the surface of the composite substrate prepared in Example 7 of the present invention;

Fig. 12 is a photograph of the back surface of the substrate prepared in Comparative Example 1 viewed through a high-power microscope.

The best way to implement the invention

The present invention will be further described in conjunction with the following examples. The examples are only illustrative and in no way mean that they limit the scope of the present invention in any way.

Example 1

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Select a high-quality AlN ceramic substrate with a thickness of 500 microns (Zhongchuang Yanyuan Semiconductor Technology Co., Ltd., 180W/mk aluminum nitride ceramic substrate), use CMP polishing method to polish the surface of the AlN ceramic substrate, and the microscope display surface has no Obvious steps, the surface roughness is within 25nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 2.0 microns;

(3) Use a coating machine to _{coat photoresist with a thickness of 1.2 microns on the surface of the above SiO 2} and use nanoimprint technology to imprint the above photoresist into a base diameter of 2μm, a height of about 2.4μm, and a period of 3μm. Periodic cylinder; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a frustum-shaped pattern. The bottom diameter of the truncated cone pattern is 2.8μm, the height is 1.8μm, and the period is 3μm. It is uniformly arranged on the AlN ceramic surface. The upper part of the truncated cone pattern material is SiO ₂ , and the lower part is AlN ceramic. The _{height ratio of SiO 2} and AlN ceramic material is 0.95: 0.05. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns on the surface have no SiO ₂ , which exposes the surface of the AlN ceramic;

(4) Use PVD technology to coat the AlN polycrystalline film with a thickness of 15nm on the surface of the AlN ceramic patterned substrate to cover all patterns and areas without patterns;

(5) Using MOCVD technology to apply the above-mentioned AlN polycrystalline film-plated patterned AlN ceramic substrate to epitaxially grow a GaN film, and use side epitaxial technology to grow a single crystal GaN film with a thickness of 4 microns to obtain the present invention Composite substrate.

Figure 2 is an SEM image of the pattern structure layer formed in step (3) of this embodiment.

Figure 3 is a SEM photo of the GaN surface grown with a thickness of 2 microns using MOCVD in step (5) of this embodiment, and it can be seen that the pattern area is not completely closed; Figure 4 is a step (5) of this embodiment using MOCVD to grow a thickness of 4 microns The SEM photo of the GaN surface shows that the GaN surface is completely closed and the growth quality is high.

FIG. 5 is an XRD pattern of the GaN single crystal layer on the surface of the composite substrate prepared in this embodiment, and the pattern can reflect the quality of the GaN crystal of the composite substrate. According to the XRD test results, it is calculated that the dislocation density of the GaN crystal prepared by this embodiment reaches 7.3×10 ⁸ , and the crystal quality is very good. On the basis of this substrate, the crystal quality of the epitaxial GaN single crystal or AlN single crystal during the application process will not be lower than the quality of the GaN film grown in step (5), which can be perfectly applied in the application field.

Example 2

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Select a high-quality AlN ceramic substrate with a thickness of 500 microns (Zhongchuang Yanyuan Semiconductor Technology Co., Ltd. 180W/mk aluminum nitride ceramic substrate), use CMP polishing method to polish the surface of the AlN ceramic substrate, and the surface of the microscope display is not obvious Steps, the surface roughness reaches within 5nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 1.5 microns;

(3) Use a coating machine to _{coat photoresist with a thickness of 1.2 microns on the surface of the above SiO 2} and use nanoimprint technology to imprint the above photoresist into a base diameter of 2μm, a height of about 2.4μm, and a period of 3μm. Periodic cylinder; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a frustum-shaped pattern. The bottom diameter of the truncated cone pattern is 2.8μm, the height is 1.5μm, and the period is 3μm. It is uniformly arranged on the AlN ceramic surface. The upper part of the truncated cone pattern material is SiO ₂ , and the lower part is AlN ceramic. The _{height ratio of SiO 2} and AlN ceramic material is 0.8: 0.2. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns on the surface have no SiO ₂ , which exposes the surface of the AlN ceramic;

(4) Using PVD technology to plate an AlN polycrystalline film with a thickness of 40nm on the surface of the AlN ceramic patterned substrate to cover all patterns and areas without patterns;

(5) Using MOCVD technology to apply the above-mentioned AlN polycrystalline film-plated patterned AlN ceramic substrate to epitaxially grow a GaN film, and use side epitaxial technology to grow a single crystal GaN film with a film thickness of 2 microns.

_{(6) Using PECVD technology to grow an SiO 2} film on the surface of the GaN single crystal film that has been grown in step (5) above _{, the thickness of the SiO 2} film is 2.0 microns;

(7) In the above-coater using a SiO ₂ surface is coated with photoresist having a thickness of 1.2 microns, using a nanoimprint technique described resist imprinting a bottom diameter of 2 m, a height of about 2.4 m, the period 3μm Periodic cylinder; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a conical pattern. The bottom diameter of the cone pattern is 2.8μm, the height is 1.8μm, and the period is 3μm. They are evenly arranged on the surface of the GaN single crystal film. The upper part of the cone-shaped pattern material is SiO ₂ , and the lower part is GaN single crystal, SiO ₂ and GaN single crystal. The height ratio is 0.5:0.5. The area without a pattern on the surface of the GaN single crystal film is exposed by etching, that is, there is no SiO _{2 on the} surface of the area without a pattern, and the surface of the GaN single crystal film is exposed;

(8) Using PVD technology to coat the surface of the above-mentioned GaN single crystal film pattern substrate with an AlN polycrystalline film with a thickness of 20nm to cover all patterns and areas without patterns;

(9) Using HVPE technology to apply the above-mentioned AlN polycrystalline film-plated patterned AlN ceramic substrate to epitaxially grow a GaN film, and use side epitaxial technology to grow a single crystal GaN film with a film thickness of 40 microns to obtain the present invention Composite substrate.

FIG. 6 is an XRD pattern of the GaN single crystal layer on the surface of the composite substrate prepared in this embodiment. Through calculation, it can be obtained that after two cycles of pattern structure, the dislocation density of GaN single crystal is reduced to 5.1×10 ⁷ , and the crystal quality is significantly improved after the second lateral epitaxy. On the basis of this substrate, the crystal quality of the epitaxial GaN single crystal or AlN single crystal during the application process will not be lower than the quality of the GaN film grown in step (9), which can be perfect in power devices and other fields. application.

Example 3

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Select a high-quality AlN ceramic substrate with a thickness of 200 microns (Nippon Maruwa Co., Ltd. 180W/mk aluminum nitride ceramic substrate), and polish the surface of the AlN ceramic substrate by CMP polishing method. The microscope shows that the surface has no obvious steps and the surface is rough. The degree is within 0.01nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 1.5 microns;

(3) In the above-coater using a SiO ₂ surface is coated with photoresist having a thickness of 1.2 microns, using a nanoimprint technique described resist imprinting a bottom diameter of 2 m, a height of about 2.4 m, the period 3μm Periodic cylinder; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a frustum-shaped pattern. The bottom diameter of the truncated cone pattern is 2.8μm, the height is 1.5μm, and the period is 3μm. It is uniformly arranged on the AlN ceramic surface. The upper part of the truncated cone pattern material is SiO ₂ , and the lower part is AlN ceramic. The _{height ratio of SiO 2} and AlN ceramic material is 0.9: 0.1. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns have no SiO _{2 on the} surface, exposing the surface of the AlN ceramic;

(4) Using PVD technology to plate an AlN polycrystalline film with a thickness of 40nm on the surface of the AlN ceramic patterned substrate to cover all patterns and areas without patterns;

(5) Use MOCVD technology to apply the above-mentioned patterned AlN polycrystalline film to epitaxially grow a GaN film on a patterned AlN ceramic substrate, and use side epitaxial technology to grow a single crystal GaN film with a thickness of 4 microns.

_{(6) Using PECVD technology to grow an SiO 2} film on the surface of the GaN single crystal film that has been grown in step (5) above _{, the thickness of the SiO 2} film is 2.0 microns;

(7) In the above-coater using a SiO ₂ surface is coated with photoresist having a thickness of 1.2 microns, using a nanoimprint technique described resist imprinting a bottom diameter of 2 m, a height of about 2.4 m, the period 3μm Periodic cylinder; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a conical pattern. The bottom diameter of the conical pattern is 2.8μm, the height is 1.8μm, and the period is 3μm. It is evenly arranged on the surface of the GaN single crystal film. The upper part of the conical pattern material is SiO ₂ , and the lower part is GaN single crystal, SiO ₂ and GaN single crystal. The height ratio is 0.9:0.1. The area of the GaN single crystal film surface without a pattern is exposed by etching, that is, the surface of the area without a pattern does not have SiO ₂ , and the surface of the GaN single crystal film is exposed.

FIG. 7 is an SEM image of the surface of the composite substrate prepared in this embodiment, and a uniform pattern arrangement can be seen. According to the XRD test results, it is calculated that the dislocation density of the GaN single crystal grown on the composite substrate prepared in this embodiment is about ^{10 7.}

Example 4

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Choose a high-quality AlN ceramic substrate with a thickness of 1000 microns (Nippon Maruwa Co., Ltd. 180W/mk aluminum nitride ceramic substrate), and polish the surface of the AlN ceramic substrate by CMP polishing method. The microscope shows that the surface has no obvious steps and the surface is rough. The degree reaches within 50nm;

(2) Using PECVD technology to grow Si ₃ N ₄ film on the polished surface of the ceramic substrate, the _{thickness of the Si 3} N ₄ film is 1.5 microns;

(3) Use a coating machine to _{coat photoresist with a thickness of 1.2 microns on the surface of the above Si 3} N ₄ , and use nanoimprint technology to imprint the above photoresist to a base diameter of 2 μm, a height of about 2.4 μm, and a periodicity Periodic cylinders of 3 μm; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the Si ₃ N ₄ film on the surface of the ceramic substrate is etched into a conical pattern. The cone pattern has a bottom diameter of 2.8μm, a height of 1.5μm, and a period of 3μm. It is uniformly arranged on the surface of the AlN ceramic. The upper part of the cone pattern material is Si ₃ N ₄ , and the lower part is AlN ceramics, Si ₃ N ₄ and AlN ceramics. The material height ratio is 0.85:0.15. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns on the surface are free of Si ₃ N ₄ , exposing the surface of the AlN ceramic;

(4) Using PVD technology to plate an AlN polycrystalline film with a thickness of 100 nm on the surface of the AlN ceramic patterned substrate, and cover all patterns and areas without patterns to obtain the composite substrate of the present invention.

FIG. 8 is an SEM image of the surface of the composite substrate prepared in this embodiment, and a uniform pattern arrangement can be seen. According to XRD results, the calculated position of the GaN single crystal grown on a composite substrate prepared in Example dislocation density of about ¹⁰⁸ in the present.

Example 5

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Select a high-quality AlN ceramic substrate with a thickness of 650 microns (Zhongchuang Yanyuan Semiconductor Technology Co., Ltd. thermal conductivity 180W/mk ceramic substrate), use CMP polishing method to polish the surface of the AlN ceramic substrate, and the surface of the microscope display is not obvious Steps, the surface roughness is within 25nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 1.8 microns;

(3) Use a coating machine to _{coat photoresist with a thickness of 1.2 microns on the surface of the above SiO 2} and use nanoimprint technology to imprint the above photoresist into a base diameter of 2μm, a height of about 2.4μm, and a period of 3μm. Periodic cylinder; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a conical pattern. The bottom diameter of the cone pattern is 2.8μm, the height is 1.7μm, and the period is 3μm. It is evenly arranged on the AlN ceramic surface. The upper part of the cone pattern material is SiO ₂ and the lower part is AlN ceramic. The _{height ratio of SiO 2} and AlN ceramic material is 0.95: 0.05. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns have no SiO _{2 on the} surface, exposing the surface of the AlN ceramic;

(4) Using PVD technology to plate a graphene polycrystalline film with a thickness of 300 nm on the surface of the AlN ceramic patterned substrate, and cover all patterns and areas without patterns to obtain the composite substrate of the present invention.

FIG. 9 is an SEM image of the surface of the composite substrate prepared in this embodiment, and a uniform pattern arrangement can be seen. According to XRD results, the calculated position of the GaN single crystal grown on a composite substrate prepared in Example dislocation density of about ^108, in the present application needs.

Example 6

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Choose a high-quality AlN ceramic substrate with a thickness of 430 microns (Zhongchuang Yanyuan Semiconductor Technology Co., Ltd. 180W/mk aluminum nitride ceramic substrate), use CMP polishing method to polish the surface of the AlN ceramic substrate, and the surface of the microscope display is not obvious Steps, the surface roughness is within 5nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 200 nanometers;

(3) Use a glue _{applicator to coat photoresist with a thickness of 500 nanometers on the surface of the above SiO 2} and use nanoimprint technology to imprint the above photoresist with a base diameter of 400 nanometers, a height of about 700 nanometers, and a period of 500 nanometers. Nano periodic cylinder; using wet etching technology, specifically using BOE etching solution, 40 seconds at room temperature to soak the corrosion sample, then use acetone alcohol to remove the residual photoresist, and then use deionized water to clean the surface of the ceramic substrate SiO ₂ The thin film is wet-etched into a truncated cone-shaped pattern. The bottom diameter of the cone pattern is about 450 nanometers, the height is about 150 nanometers, and the period is 500 nanometers. They are evenly arranged on the surface of the AlN ceramic. The upper part of the cone-shaped pattern material is SiO ₂ , and the lower part is AlN ceramic, SiO ₂ and AlN ceramic materials. The height ratio is 0.8:0.2. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns on the surface are free of SiO ₂ and the AlN ceramic surface is exposed;

(4) Plating an AlN polycrystalline film with a thickness of 3 nm on the surface of the AlN ceramic patterned substrate using PVD technology to cover all patterns and areas without patterns to obtain the composite substrate of the present invention.

FIG. 10 is a cross-sectional SEM image of a GaN single crystal grown on the surface of the composite substrate prepared in this embodiment. It can be seen that the pattern period is about 500 nanometers and the height is about 150 nanometers. According to XRD results, the composite substrate of the present embodiment Preparation of growing GaN single crystals for good results, the crystal dislocation density can reach ^108.

Example 7

This embodiment is used to illustrate the composite substrate of the present invention and the preparation method thereof.

(1) Select a high-quality AlN ceramic substrate with a thickness of 500 microns (Nippon Maruwa Co., Ltd. 180W/mk aluminum nitride ceramic substrate), and polish the surface of the AlN ceramic substrate by CMP polishing method. The microscope shows that the surface has no obvious steps and the surface is rough. The degree is within 10nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 1 micron;

(3) Use a coating machine to _{coat photoresist with a thickness of 1.7 microns on the surface of the above SiO 2} and use nanoimprint technology to imprint the above photoresist with a base diameter of 2.5μm, a height of about 3.4μm, and a period of 5μm. Periodic triangular pillars; ICP etching technology is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a triangular pyramid pattern. The bottom diameter of the cone pattern is 2.8μm, the height is 3μm, and the period is 5μm. It is evenly arranged on the AlN ceramic surface. The upper part of the triangular pyramid pattern material is SiO ₂ and the lower part is AlN ceramic. The _{height ratio of SiO 2} and AlN ceramic material is 0.05: 0.95. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns on the surface have no SiO ₂ , which exposes the surface of the AlN ceramic;

(4) Using PVD technology to plate a graphene polycrystalline film with a thickness of 40 nm on the surface of the AlN ceramic patterned substrate, and cover all patterns and areas without patterns to obtain the composite substrate of the present invention.

FIG. 11 is an SEM image of the surface of the composite substrate prepared in this embodiment. According to the XRD test results, the composite substrate prepared in this embodiment has a good effect on growing GaN single crystals, and the crystal dislocation density can reach about 10 ⁹ .

The focus of the present invention is to break through the technical difficulties of growing GaN single crystal or AlN single crystal on amorphous or polycrystalline materials such as traditional AlN ceramic substrates.

In the previous patent application of the inventor of the present invention, a method for growing a GaN single crystal on a near-single crystal AlN ceramic substrate was disclosed. The present invention is clearly different from the previous invention.

The main types of AlN ceramic substrates are amorphous or polycrystalline material properties, and the preparation process of AlN ceramic substrates with similar c-axis orientations is very complicated, and the preparation cost is 3-5 higher than that of ordinary AlN ceramic substrates. Times.

In order to demonstrate the effectiveness of the pattern structure of the present invention for the growth of GaN or AlN single crystals on ordinary amorphous or polycrystalline AlN ceramic substrates, the following comparative examples were carried out.

Comparative example 1

The preparation steps are as follows:

(1) Choose a high-quality AlN ceramic substrate with a thickness of 500 microns (Zhongchuang Yanyuan Semiconductor Technology Co., Ltd. 180W/mk aluminum nitride ceramic substrate), use CMP polishing method to polish the surface of the AlN ceramic substrate, and the microscope display surface is not obvious Steps, the surface roughness is within 25nm;

(2) Using PECVD technology to grow SiO ₂ film on the _{polished surface of the ceramic substrate, the thickness of the SiO 2} film is 1.5 microns;

(3) Use a coating machine to _{coat photoresist with a thickness of 1.2 microns on the surface of the above SiO 2} and use nanoimprint technology to imprint the above photoresist into a base diameter of 2μm, a height of about 2.4μm, and a period of 3μm. Periodic cylinder

In this comparative example, the periodic cylindrical patterns are not uniformly distributed on the AlN ceramic surface, but form some areas with periodic patterns, and some areas without periodic patterns. The ICP etching technique is used to etch the imprinted AlN ceramic substrate, and the SiO ₂ film on the surface of the ceramic substrate is etched into a frustum-shaped pattern. The bottom diameter of the circular mesa pattern is 2.8 μm, the height is 1.5 μm, and the period is 3 μm.

The periodic frustum pattern is not uniformly distributed on the AlN ceramic surface, but forms some areas with periodic patterns, and some areas without periodic patterns. The upper part of the truncated cone-shaped pattern material is SiO ₂ , and the lower part is AlN ceramic, _{and the height ratio of SiO 2} and AlN ceramic material is 0.95:0.05. The areas without patterns on the AlN ceramic surface are exposed by etching, that is, the areas without patterns on the surface have no SiO ₂ , which exposes the surface of the AlN ceramic;

(4) Using PVD technology to plate an AlN polycrystalline film with a thickness of 15nm on the surface of the AlN ceramic patterned substrate to cover all patterns and areas without patterns;

(5) Use MOCVD technology to apply the above-mentioned patterned AlN polycrystalline film to epitaxially grow a GaN film on a patterned AlN ceramic substrate, and use side epitaxial technology to grow a single crystal GaN film with a thickness of 4 microns.

Fig. 12 is the experimental result of the above-mentioned comparative example. A detailed photo viewed through a high-power microscope from the back of the grown GaN sample. The circled area at the bottom left of the photo is an area with graphics, and the circled area at the top right of the photo is an area without graphics. From the detailed photo of the back of the grown GaN sample through a high-power microscope, it can be seen that in the patterned area, GaN grows continuously and forms a single crystal; while in the patterned area, GaN grows disorderly and is non-single crystal. This result fully proves the effectiveness of the present invention for epitaxial growth of GaN or AlN single crystals for ordinary AlN ceramic substrates overcoming the amorphous substrates or polycrystalline substrates. Make it independent of the crystal orientation structure of the substrate.

Claims (10)

1. A composite substrate based on aluminum nitride ceramic material, including:

   (a) Aluminum nitride ceramic substrate;

   (b) A patterned structure layer, the patterned structure layer comprising patterned structures distributed on the aluminum nitride ceramic substrate at periodic intervals; and

   (c) A polycrystalline coating layer, which is a continuous layer covering the pattern structure layer and the aluminum nitride ceramic substrate not covered by the pattern structure.
2. The aluminum nitride ceramic material-based composite substrate according to claim 1, wherein the thickness of the aluminum nitride ceramic substrate is 100-1000 μm, preferably 200-700 μm; preferably, the aluminum nitride ceramic substrate The surface roughness is 0.01-100nm, preferably 0.01-50nm.
3. The aluminum nitride ceramic material-based composite substrate according to claim 1 or 2, wherein the thickness of the pattern structure layer is 0.01-5 μm, preferably 0.1-3.5 μm; preferably, the pattern structure layer is composed of The aluminum nitride ceramic substrate is composed of homogeneous materials, heterogeneous materials, or a combination of homogeneous materials and heterogeneous materials; preferably, the pattern structure layer is composed of a combination of homogeneous materials and heterogeneous materials of the aluminum nitride ceramic substrate , The ratio of the thickness of the heterogeneous material to the thickness of the homogeneous material is (0.05-0.99): (0.01-0.95), preferably (0.8-0.99): (0.01-0.2), more preferably (0.9-0.99): (0.01-0.1).
4. The composite substrate based on aluminum nitride ceramic material according to claim 3, wherein the heterogeneous material is selected from _{one or more of SiO 2} , Si ₃ N ₄ , SiC, Si, ZnO, and GaAs.
5. The aluminum nitride ceramic material-based composite substrate according to any one of claims 1 to 4, wherein the period of the pattern structure is 0.1-50 μm, preferably 0.2-10 μm; the diameter of the bottom surface of the pattern structure It is 0.02-50 μm, preferably 0.1-9 μm; the height of the pattern structure is 0.01-5 μm, preferably 0.1-3.5 μm.
6. The composite substrate based on aluminum nitride ceramic material according to any one of claims 1 to 5, wherein the polycrystalline coating layer is selected from the group consisting of AlN polycrystalline film, graphene polycrystalline film, GaN polycrystalline film, One or more of SiC polycrystalline film, GaAs polycrystalline film and ZnO polycrystalline film, preferably AlN polycrystalline film and/or graphene polycrystalline film; preferably, the thickness of the polycrystalline coating layer is 0.01 -2000nm, preferably 1-500nm.
7. The composite substrate based on aluminum nitride ceramic material according to any one of claims 1 to 6, wherein the composite substrate further comprises:

   (d) A single crystal film layer, the single crystal film layer being an aluminum nitride single crystal layer or a gallium nitride single crystal layer covering the polycrystalline coating layer;

   Preferably, the thickness of the single crystal film layer is 0.01-1000 μm, preferably 0.05-100 μm.
8. The composite substrate based on aluminum nitride ceramic material according to any one of claims 1 to 7, wherein the composite substrate further comprises:

   (e) A second pattern structure layer, the second pattern structure layer includes a second pattern structure on the single crystal film layer, and the second pattern structure is periodically spaced on the single crystal film layer ; And optional

   (f) A second polycrystalline coating layer, the second polycrystalline coating layer being a continuous layer covering the second pattern structure layer and the single crystal film layer not covered by the second pattern structure; and any Chosen

   (g) A second single crystal film layer, the second single crystal film layer being an aluminum nitride single crystal layer or a gallium nitride single crystal layer covering the second polycrystalline coating layer.
9. A preparation method of a composite substrate based on aluminum nitride ceramic material, the preparation method comprising the following steps:

   (1) Polish the aluminum nitride ceramic substrate to a surface roughness of 0.01-100nm;

   (2) Using coating technology to prepare a heterogeneous film on the surface of the polished aluminum nitride ceramic substrate;

   (3) Coating photoresist on the surface of the heterogeneous film, exposing the photoresist into a pattern using a photolithography process, and then using an etching process to etch the heterogeneous film to form a pattern structure layer, so The pattern structure layer includes pattern structures distributed on the aluminum nitride ceramic substrate at periodic intervals;

   (4) Using coating technology to form a polycrystalline coating layer on the pattern structure layer,

   Preferably, the preparation method further includes:

   (5) Using an epitaxial growth device to grow an aluminum nitride single crystal layer or a gallium nitride single crystal layer on the surface of the polycrystalline coating layer to form a single crystal film layer.
10. The AlN ceramic material-based composite substrate according to any one of claims 1 to 8 or the AlN ceramic material-based composite substrate prepared according to the method of claim 9 is used in epitaxial growth of GaN or AlN single crystal materials Applications.

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