CN111809154B

CN111809154B - Method for preparing high-quality silicon-based aluminum nitride template

Info

Publication number: CN111809154B
Application number: CN202010583920.6A
Authority: CN
Inventors: 吴亮; 付丹扬; 王琦琨; 朱如忠; 龚建超; 刘欢
Original assignee: Aoti Photoelectric Technology Hangzhou Co ltd
Current assignee: Aoti Photoelectric Technology Hangzhou Co ltd
Priority date: 2020-06-23
Filing date: 2020-06-23
Publication date: 2021-07-23
Anticipated expiration: 2040-06-23
Also published as: CN111809154A

Abstract

The invention discloses a method for preparing a high-quality silicon-based aluminum nitride template, which aims to solve the problem that the quality of an epitaxial aluminum nitride layer is influenced by the poor surface quality and crystallization quality of a silicon-based buffer layer. The preparation method of the high-quality silicon-based aluminum nitride template comprises the following specific steps: 1) preparing a silicon single crystal substrate; 2) growing an initial buffer layer based on the silicon single crystal substrate; 3) reducing the surface roughness of the initial buffer layer by ion bombardment; 4) carrying out heat treatment on the buffer layer after ion bombardment; 5) and growing an aluminum nitride film based on the buffer layer after the heat treatment. A large number of tests are carried out based on the process, and detection results show that the performances of the aluminum nitride layer such as crystallization quality, roughness and the like are greatly improved, the template quality uniformity is high, and the method can be used for preparing large-batch high-quality silicon-based aluminum nitride templates and applying downstream devices.

Description

Method for preparing high-quality silicon-based aluminum nitride template

Technical Field

The invention relates to the technical field of aluminum nitride films, in particular to a method for preparing a high-quality silicon-based aluminum nitride template.

Background

The traditional semiconductor materials such as silicon-based and the like cannot meet the development requirements of the current electronic devices. Aluminum nitride (AlN), which is a typical representative of third/fourth generation semiconductor materials, has superior physicochemical properties such as an ultra-wide bandgap, high thermal conductivity, high breakdown field strength, high electron mobility, corrosion resistance, and radiation resistance. In addition, it has the largest piezoelectric response in group III-V nitrides, making it possible to achieve higher electromechanical coupling coefficients. The AlN thin film has very high sound wave transmission speed (about 6000-8000m/s) in the direction vertical to the c axis, and the transmission loss of AlN is relatively low, so that the thin film material is suitable for ultrahigh frequency and microwave devices.

For SAW devices in microwave frequency band, the substrate generally adopts an AlN/Diamond structure, and the structure requires that the Diamond is a nano Diamond with high elastic modulus and has higher cost; for the SAW/BAW device of ultra-high frequency band, the substrate can adopt an A1N/Si structure, so that the cost is low and the substrate is more compatible with the integrated circuit process. These properties make this material very suitable for applications in Surface Acoustic Wave (SAW) devices, Bulk Acoustic Wave (BAW) devices, MEMS filters, dielectric layers, optical sensors, etc.

The conventional AlN film manufacturing techniques include magnetron sputtering (Sputter), Metal Organic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), Atomic Layer Deposition (ALD), Pulsed Laser Deposition (PLD), and other film techniques. In various AlN film preparation technologies, the magnetron reactive sputtering method is suitable for large-area rapid growth and is beneficial to realizing industrialized production. However, in order to realize the wide application of the AlN thin film on a large scale, the quality of the aluminum nitride template must be improved.

At present, the preparation of a high-quality AlN template by using a Si substrate faces a plurality of challenges: (1) the lattice mismatch and thermal mismatch between Si and AlN are large, which causes a large amount of residual stress in the AlN thin film grown at high temperature, resulting in high-density defects and cracks; (2) the initial nucleation layer of AlN on the Si substrate has poor crystalline quality and surface quality, which have an extremely adverse effect on the subsequent sputtering process.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method for arranging the buffer layer on the Si substrate in the film growth process, and the buffer layer is optimized through two technologies of ion bombardment and heat treatment so as to improve the crystallization quality, reduce the surface roughness and release the stress, thereby reducing the adverse effects caused by lattice mismatch and thermal mismatch.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing a high-quality silicon-based aluminum nitride template comprises the following steps:

1) preparing a silicon single crystal substrate;

2) growing an initial buffer layer based on the silicon single crystal substrate;

3) reducing the surface roughness of the initial buffer layer by ion bombardment;

4) carrying out heat treatment on the buffer layer after ion bombardment;

5) and growing an aluminum nitride film based on the buffer layer after the heat treatment.

As an alternative embodiment, the initial buffer layer in step 2) includes, but is not limited to, a metal thin film, a compound semiconductor thin film, or a group III nitride semiconductor thin film material.

As an alternative embodiment, the preparation technique of the initial buffer layer in step 2) includes, but is not limited to, one or more of magnetron sputtering (Sputter), Metal Organic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), Atomic Layer Deposition (ALD), and Pulsed Laser Deposition (PLD).

As a preferred embodiment, the conditions of the ion bombardment in step 3) are as follows: argon flow is 10-500sccm, power is 5-50W, bias voltage is 10-800V, and bombardment time is 0.1-5 min.

The compactness of the buffer layer interface can be increased and the roughness of the interface can be reduced by continuously bombarding the buffer layer interface by ions. Meanwhile, bombardment energy accumulation can enhance the activity and the migration capability of the adsorbed atoms, provide a high-quality growth surface for the next growth of the buffer layer or the aluminum nitride film, and the buffer layer or the aluminum nitride film is easy to orderly crystallize and have consistent crystal grains and reduced defect density.

As a preferred embodiment, the conditions of the heat treatment in step 4) are as follows: the substrate temperature is 100-₂、Ar、H₂Or a mixture of several gases.

The stress at the interface can be released through heat treatment, the crystallization quality of the buffer layer is improved through the recrystallization effect of crystal grains, the lattice parameter is optimized, the lattice adaptation and dislocation density between the aluminum nitride layer and the buffer layer are reduced, the crystallization quality of the buffer layer is improved, and a high-quality growth surface is provided for the next step of growing the buffer layer or the aluminum nitride film.

As a preferred embodiment, in step 5), an aluminum nitride film is grown on the optimized buffer layer by using a reactive magnetron sputtering technique, and the preparation conditions are as follows: the pressure of the reaction chamber is 0.1-5pa, the flow rate of nitrogen is 5-500sccm, the flow rate of argon is 5-500sccm, the sputtering power is 0.1-15KW, and the temperature is less than 1000 ℃.

By regulating and controlling different parameters, the aluminum nitride film material with high crystallization quality and low surface roughness can be grown on the basis of the buffer layer.

Compared with the prior art, the invention has the beneficial effects that:

the buffer layer is arranged in the film growth process, and the buffer layer is optimized through two technologies of ion bombardment and heat treatment, so that the crystallization quality of the buffer layer can be effectively improved, the surface roughness is reduced, the stress can be released, and the adverse effects caused by lattice mismatch and thermal mismatch are reduced.

The buffer layer is processed by adopting an ion bombardment technology, so that the compactness of the interface of the buffer layer is increased, the roughness of the interface is reduced, the bombardment energy is accumulated, the activity and the migration capability of the adsorbed atoms are enhanced, a high-quality growth surface is provided for the next step of growing the buffer layer or the aluminum nitride film, the buffer layer or the aluminum nitride film is easy to be orderly crystallized and consistent with crystal grains, and the defect density is reduced.

The buffer layer is processed by adopting a heat treatment technology, so that on one hand, the stress at the interface can be released, and a thicker (>1 mu m) crack-free aluminum nitride film can be obtained; on the other hand, through the recrystallization of the crystal grains, the crystallization quality and the surface quality of the buffer layer can be improved, the lattice parameter is optimized, and the adverse effects caused by lattice mismatch and thermal mismatch are further reduced, so that the high-quality aluminum nitride film is obtained.

The scheme of the invention is beneficial to obtaining the silicon substrate aluminum nitride film with higher quality, meets the requirements of downstream devices and improves the performance of the devices. Meanwhile, the reactive magnetron sputtering technology is adopted to grow the aluminum nitride film, so that the growth process is simple and feasible, large-scale mass production can be realized, and the requirement of the market on the yield of the aluminum nitride film with the silicon substrate is met. The technology provides an effective technical means for realizing the wide application of the silicon substrate aluminum nitride film in the fields of surface acoustic wave devices, piezoelectric films and the like.

Drawings

FIG. 1 is a schematic diagram of the process for preparing a high-quality silicon-based aluminum nitride template according to the present invention.

FIG. 2 is a schematic diagram of the preparation process of the high-quality silicon-based aluminum nitride template of the present invention.

FIG. 3 is a graph showing the relationship between the half-value width (0002) of the rocking curve of X-ray diffraction on the surface of a 500nm aluminum nitride template prepared by the method of the present invention and the detection position.

FIG. 4 is a graph showing the relationship between the surface roughness and the detection position of a 500nm aluminum nitride template prepared by the method of the present invention.

FIG. 5 is a graph (0002) showing the rocking X-ray diffraction pattern of a 500nm aluminum nitride template prepared by the method of the present invention at the schematic position in FIG. 4.

FIG. 6 is an atomic force microscope (5X 5 μm field of view) topographical view of a 500nm aluminum nitride template prepared by the method of the present invention at the schematic position in FIG. 5.

FIG. 7 is a FWHM variation graph and an atomic force microscopy topography of a 500nm aluminum nitride template prepared by a general method and a method of the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

Example 1

A method for preparing a high-quality silicon substrate aluminum nitride template comprises the following steps: the method mainly comprises the steps of preparing a base material 1, preparing and optimizing a buffer layer 4 and preparing an aluminum nitride template 5. Fig. 1 and 2 are a schematic view of a process for preparing an aluminum nitride template and a schematic view of a process for preparing an aluminum nitride template in this embodiment, respectively. The method for preparing the high-quality silicon substrate aluminum nitride template according to the present embodiment will be described in detail with reference to the accompanying drawings.

1) A silicon single crystal substrate 1 is prepared (S1). The silicon single crystal substrate 1 is a standard specification polished substrate wafer produced, the surface is an EPI-ready polished surface cleaned by RCA, the roughness is less than 0.3nm, the back surface is a grinding grade, and the roughness is 1 +/-0.2 mu m.

2) An initial buffer layer 2 is grown on the silicon substrate (S2). In this embodiment, the aluminum buffer layer is grown by magnetron sputtering (Sputter), and may be formed by using a thin film technique such as Metal Organic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), Atomic Layer Deposition (ALD), and Pulsed Laser Deposition (PLD), or by stacking several techniques. Preparation conditions of the buffer layer: the pressure in the reaction chamber is 0.5pa, the argon flow is 60sccm, the sputtering power is 2KW, the temperature is 400 ℃, and the thickness of the buffer layer is 20 nm.

3) The surface quality of the initial buffer layer 2 is improved using an ion bombardment technique to obtain an optimized buffer layer 3 (S3). The conditions of the ion bombardment technique are as follows: the argon flow is 180sccm, the power is 30W, the bias voltage is 600V, and the bombardment time is 1 min. The main purpose is that ions continuously bombard the interface of the buffer layer, so that the compactness of the interface of the buffer layer is increased, the roughness of the interface is reduced, bombarding energy is accumulated, and the activity and the migration capacity of adsorbed atoms are enhanced, thereby providing a high-quality growth surface for the next step of growing the buffer layer or the aluminum nitride film, the buffer layer or the aluminum nitride film is easy to be orderly crystallized and consistent with crystal grains, and the defect density is reduced.

4) The crystallization quality of the optimized buffer layer 3 is improved using a heat treatment technique to obtain the shaped buffer layer 4 (S4). The conditions of the heat treatment technique are as follows: the substrate temperature is 300 ℃, the reaction chamber pressure is 1atm, the time duration is 30min, and the atmosphere of the reaction chamber is Ar. The main purpose is to release the stress at the interface, improve the crystallization quality of the buffer layer, adjust the lattice parameter, correct the orientation of the crystal grains, further reduce the adverse effect caused by lattice mismatch and thermal mismatch, and provide a high-quality growth surface for the next growth of the buffer layer or the aluminum nitride film.

5) The aluminum nitride layer 5 is grown based on the optimized shape buffer layer 4 (S5). In this embodiment, a magnetron sputtering method (Sputter) is adopted, the pressure in the reaction chamber is 0.5pa, the flow rate of nitrogen is 150sccm, the flow rate of argon is 20sccm, the sputtering power is 4KW, the temperature is 500 ℃, and the thickness of the template is 500 nm.

In this embodiment, the crystal quality and the roughness uniformity of the surface of the 500nm aluminum nitride template with a silicon substrate prepared by the above method are further examined and analyzed (see fig. 3 and 4). The detection shows that the overall uniformity of the template is high, and the corresponding XRC and AFM spectra can be shown in figures 5 and 6. Further comparisons of FWHM-XRC and AFM patterns of 500nm aluminum nitride templates prepared using the general method and the method of the present invention were made (see FIG. 7). The detection result shows that the method greatly improves the performances of the aluminum nitride layer such as crystallization quality, roughness and the like, has high template quality uniformity, and can be used for preparing large-batch high-quality silicon-based aluminum nitride templates and applying downstream devices.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A method for preparing a high-quality silicon-based aluminum nitride template comprises the following steps:

1) preparing a silicon single crystal substrate;

2) growing an initial buffer layer based on the silicon single crystal substrate, wherein the initial buffer layer is made of a metal thin film material;

3) reducing the surface roughness of the initial buffer layer by ion bombardment; the conditions of ion bombardment were as follows: argon flow is 10-500sccm, power is 5-50W, bias voltage is 10-800V, and bombardment time is 0.1-5 min;

4) carrying out heat treatment on the buffer layer after ion bombardment; the conditions of the heat treatment were as follows: the substrate temperature is 100-₂、Ar、H₂Or a mixture of several gases;

2. The method of claim 1, wherein the technique for preparing the initial buffer layer in step 2) comprises one or more of magnetron sputtering, metal organic compound vapor phase epitaxy, molecular beam epitaxy, hydride vapor phase epitaxy, atomic layer deposition, or pulsed laser deposition.

3. The method as claimed in claim 1, wherein in step 5), an aluminum nitride film is grown on the optimized buffer layer by using a reactive magnetron sputtering technique under the following preparation conditions: the pressure of the reaction chamber is 0.1-5Pa, the flow rate of nitrogen is 5-500sccm, the flow rate of argon is 5-500sccm, the sputtering power is 0.1-15kW, and the temperature is less than 1000 ℃.