A preparation method of β-Ga2O3 film and β-Ga2O3 film

Abstract

The present invention discloses a method for preparing a β-Ga2O3 thin film and a β-Ga2O3 thin film. The method comprises: selecting an off-angle substrate with a certain off-angle range; annealing the off-angle substrate; epitaxially growing a first β-Ga2O3 layer on the off-angle substrate; and epitaxially growing a second β-Ga2O3 layer on the first β-Ga2O3 layer using a pulsed growth method to obtain the β-Ga2O3 thin film. The present invention improves the flatness of the epitaxial film by using the off-angle substrate; and simultaneously, by using the pulsed growth method, significantly reduces the surface roughness of the film, thereby improving the quality of the β-Ga2O3 film.

Description

Technical Field

[0001] The invention belongs to the field of microelectronics technology, and in particular relates to a preparation method of a β-Ga2O3 film and the β-Ga2O3 film. Background Art

[0002] With the development of microelectronics technology and the widespread application of high-breakdown, high-power devices, traditional narrow-bandgap semiconductor materials such as silicon have encountered many challenges. Among them, breakdown voltage has gradually become a key factor in measuring device performance. As a third-generation semiconductor material, β-Ga2O3 has a bandgap of approximately 5eV and a breakdown field strength more than twice that of SiC and GaN. The Baliga figure of merit of β-Ga2O3 is also much greater than that of Si, SiC, and GaN materials. Therefore, β-Ga2O3 has great potential in the application of high-power, high-breakdown devices and solar-blind detectors.

[0003] In recent years, research on the growth of β-Ga2O3 thin films has primarily focused on heterogeneous and homogeneous substrate epitaxy. Sapphire substrates are the preferred choice for heterogeneous epitaxy due to their low cost and high compatibility with β-Ga2O3 thin films.

[0004] However, existing heteroepitaxial β-Ga2O3 films suffer from numerous defects and generally exhibit high surface roughness, making them unsuitable for use in electronic devices. Homoepitaxial growth is also subject to numerous experimental growth parameters, making it difficult to find optimal growth conditions, which in turn affects film flatness. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing a β-Ga2O3 thin film and a β-Ga2O3 thin film. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] A method for preparing a β-Ga2O3 thin film, comprising:

[0007] Select an off-angle substrate with a certain off-angle range;

[0008] performing annealing on the off-angle substrate;

[0009] epitaxially growing a first β-Ga2O3 layer on the off-angle substrate;

[0010] A second β-Ga2O3 layer is epitaxially grown on the first β-Ga2O3 layer by adopting a pulsed growth method to obtain a β-Ga2O3 thin film.

[0011] In one embodiment of the present invention, the material of the off-angle substrate is Ga2O3 or sapphire.

[0012] In one embodiment of the present invention, the off-angle angle of the off-angle substrate is in the range of 1.5-6°.

[0013] In one embodiment of the present invention, annealing the off-angle substrate includes:

[0014] The off-angle substrate is placed in a low-pressure MOCVD reaction chamber, and the oxygen flow rate is set to 1000-1500 sccm, the temperature is set to 900-950° C., and the reaction chamber pressure is set to 35-45 Torr;

[0015] The off-angle substrate is thermally annealed in the above oxygen atmosphere for 20-30 minutes.

[0016] In one embodiment of the present invention, epitaxially growing a first β-Ga2O3 layer on the off-angle substrate comprises:

[0017] After annealing the β-Ga2O3 substrate, the reaction chamber temperature is lowered to 700-850°C and the pressure in the reaction chamber is maintained at 35-45 Torr.

[0018] Open the Ga source and O2 gas lines at the same time, and adjust the Ga source flow rate to 35-40 sccm and the O2 flow rate to 1800-2100 sccm;

[0019] Under the above process conditions, a β-Ga2O3 thin film is epitaxially grown on the off-angle substrate to form a first β-Ga2O3 layer; wherein the growth time is 50-60 minutes.

[0020] In one embodiment of the present invention, the thickness of the first β-Ga2O3 layer is 500-600 nm.

[0021] In one embodiment of the present invention, epitaxially growing a second β-Ga2O3 layer on the first β-Ga2O3 layer using a pulse method comprises:

[0022] Keeping other growth parameters unchanged, switch the film growth method to the pulse method and adjust the pulse time ratio of Ga source and O2 to 1:1-1:3;

[0023] Under the above conditions, 30-50 cycles of growth are performed to form a second β-Ga2O3 layer on the first β-Ga2O3 layer.

[0024] In one embodiment of the present invention, the pulse time of the Ga source is 0.1 min, and the pulse time of the O2 is 0.2 or 0.3 min.

[0025] In one embodiment of the present invention, the thickness of the second β-Ga2O3 layer is 20-30 nm.

[0026] Another embodiment of the present invention also provides a β-Ga2O3 film, which includes, from bottom to top, an off-angle substrate, a first β-Ga2O3 layer, and a second β-Ga2O3 layer, wherein the second β-Ga2O3 layer is prepared by a pulsed growth method, and the β-Ga2O3 film is prepared by the method described in the above embodiment.

[0027] Beneficial effects of the present invention:

[0028] The present invention adopts an off-angle substrate, so that during the subsequent epitaxial growth of the β-Ga2O3 film, the reaction atoms and the substrate sites combine to grow in a two-dimensional step flow pattern, which is beneficial to improving the flatness of the epitaxial film. At the same time, a pulsed growth method is adopted in the final stage of epitaxial growth. By staggering the reaction sources and adjusting the pulse time of each reaction source, the lateral migration length of atoms on the surface is increased, the two-dimensional growth pattern is further enhanced, the roughness of the film surface is greatly reduced, and the quality of the β-Ga2O3 film is improved.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of a method for preparing a β-Ga2O3 thin film provided in an embodiment of the present invention;

[0031] Figure 2a-2b 1 is a timing diagram of two growth modes of the pulse method provided by an embodiment of the present invention;

[0032] Figures 3a-3c This is a schematic diagram of the growth process of a β-Ga2O3 thin film provided by an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the β-Ga2O3 thin film structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0035] Example 1

[0036] See Figure 1 , Figure 1 Schematic diagram of a method for preparing a β-Ga2O3 thin film provided in an embodiment of the present invention, comprising the following steps:

[0037] S1: Select an off-angle substrate with a certain off-angle range.

[0038] In this embodiment, the off-angle substrate can be a β-Ga2O3 homogeneous substrate or a heterogeneous substrate. Preferably, the heterogeneous substrate is made of sapphire.

[0039] Generally speaking, zero-offset sapphire substrates can be divided into a-plane (11-20), c-plane (0001), m-plane (1-100), and r-plane (1102) substrates. Offset substrates are substrates that are not cut completely parallel to the corresponding crystal plane during the substrate processing and cutting process, but instead deviate slightly from the plane, with this small angle tilted toward another surface of the sapphire substrate. For example, a CA sapphire off-angle substrate is cut with the sapphire c-plane tilted toward the a-plane. There are also cm and cr off-angle substrates.

[0040] Off-angle substrates are often used to improve the crystallinity of epitaxial films because they are generally believed to enhance step flow growth and control domain structure in films. Atomic steps on the off-angle substrate surface serve as preferential binding sites for incoming adatoms, which can promote step flow growth.

[0041] Furthermore, the off-angle angle range of the off-angle substrate selected in this embodiment is 1.5-6°.

[0042] After the substrate is determined, it needs to be cleaned for subsequent operations. Specifically, the cleaning process is as follows:

[0043] First, the selected substrate was immersed in a 20% HF acid solution for 60 seconds, then cleaned with H2O2, alcohol and acetone in sequence, and finally rinsed with running deionized water for 60 seconds.

[0044] S2: Annealing the off-angle substrate.

[0045] Specifically, the cleaned off-angle substrate is first placed in a low-pressure MOCVD reaction chamber, and the oxygen flow rate is set to 1000-1500 sccm, the temperature is set to 900-950° C., and the reaction chamber pressure is set to 35-45 Torr.

[0046] The off-angle substrate is then thermally annealed in the above oxygen atmosphere for 20-30 minutes to expose the substrate atomic steps.

[0047] In this embodiment, by annealing the off-angle substrate, atomic steps are exposed on the substrate. This allows the reactive atoms to grow in a step-flow pattern during the subsequent epitaxial growth phase. This two-dimensional growth pattern is beneficial for improving the flatness of the epitaxial film.

[0048] S3: epitaxially growing a first β-Ga2O3 layer on the off-angle substrate.

[0049] Preferably, this embodiment adopts MOCVD process to prepare β-Ga2O3 thin film.

[0050] Specifically, after the β-Ga2O3 substrate is annealed, the temperature of the reaction chamber is lowered to 700-850°C, and the pressure in the reaction chamber is maintained at 35-45 Torr.

[0051] Then, open the Ga source and O2 gas lines at the same time, and adjust the Ga source flow rate to 35-40sccm and the O2 flow rate to 1800-2100sccm.

[0052] Under the above process conditions, a β-Ga2O3 thin film is epitaxially grown on an off-angle substrate to form a first β-Ga2O3 layer; wherein the growth time is 50-60 minutes.

[0053] It should be noted that the organic sources currently widely used for Ga sources mainly include TEGa and TMGa. TMGa needs to be stabilized in a water bath at a temperature near zero to maintain a suitable vapor pressure, while TEGa only needs to be kept in a water bath near room temperature. Furthermore, TEGa has a slower reaction rate than TMGa, which effectively reduces the pre-reaction of the organic source with O2 to the substrate surface, facilitates the migration of atoms on the substrate surface, and reduces the generation of by-products. Therefore, in this embodiment, TEGa is preferably used as the Ga source for growing β-Ga2O3 thin films.

[0054] By the above method, a first β-Ga2O3 layer with a thickness of 500-600 nm can be formed on the off-angle substrate.

[0055] S4: epitaxially growing a second β-Ga2O3 layer on the first β-Ga2O3 layer using a pulsed growth method to obtain a β-Ga2O3 thin film.

[0056] In this embodiment, in order to further promote the merging of the film surface, after the first β-Ga2O3 layer is grown, the film growth method is switched to the pulse growth method to continue growing β-Ga2O3, thereby obtaining a β-Ga2O3 film with better quality.

[0057] Specifically, after forming the first β-Ga2O3 layer in step S3, other growth parameters are kept unchanged, the thin film growth mode is switched to the pulse method, and the pulse time ratio of the Ga source and O2 is adjusted to 1:1-1:3.

[0058] More specifically, see Figure 2a-2b , Figure 2a-2b is a timing diagram of two growth modes of the pulse method provided by an embodiment of the present invention, wherein: Figure 2aThe pulse time of the Ga source is 0.1 min, and the pulse time of O2 is 0.2 min, that is, the pulse time ratio of the Ga source and O2 is 1:2; Figure 2b The pulse time of the Ga source is shown to be 0.1 min, and the pulse time of O2 is shown to be 0.3 min, that is, the pulse time ratio of the Ga source and O2 is 1:3.

[0059] Under the above conditions, 30-50 cycles of growth are performed to form a second β-Ga2O3 layer on the first β-Ga2O3 layer, wherein the thickness of the formed second β-Ga2O3 layer is 20-30 nm.

[0060] The present invention adopts an off-angle substrate, so that during the subsequent epitaxial growth of the β-Ga2O3 film, the reaction atoms and the substrate sites combine to grow in a two-dimensional step flow pattern, which is beneficial to improving the flatness of the epitaxial film. At the same time, a pulsed growth method is adopted in the final stage of epitaxial growth. By staggering the reaction sources and adjusting the pulse time of each reaction source, the lateral migration length of atoms on the surface is increased, the two-dimensional growth pattern is further enhanced, the roughness of the film surface is greatly reduced, and the quality of the β-Ga2O3 film is improved.

[0061] Example 2

[0062] The preparation method of the β-Ga2O3 thin film provided by the present invention is described in detail below through a detailed example.

[0063] See Figures 3a-3c , Figures 3a-3c Schematic diagram of a growth process of a β-Ga2O3 thin film provided by an embodiment of the present invention, comprising the following steps:

[0064] Step 1: Select β-Ga2O3 material with a bias angle of 3° as the substrate, such as Figure 3a shown.

[0065] Step 2: Soak the β-Ga2O3 substrate in a 20% HF acid solution for 60 seconds, then clean it with H2O2, alcohol, and acetone, and finally rinse it with running deionized water for 60 seconds.

[0066] Step 3: Place the cleaned substrate into a low-pressure MOCVD reaction chamber, set the oxygen flow rate to 1500 sccm, the temperature to 900°C, and the reaction chamber pressure to 40 Torr. Thermally anneal the substrate in an oxygen atmosphere for 30 minutes to expose the substrate atomic steps.

[0067] Step 4: After the thermal annealing is completed, the reaction chamber temperature is lowered to 800°C and the growth pressure is continued to be maintained at 40 Torr.

[0068] Step 5: Open the TEGa and O2 gas lines at the same time, adjust the TEGa flow rate to 40 sccm and the oxygen flow rate to 2000 sccm, and grow the β-Ga2O3 thin film epitaxial layer for 60 minutes to form the first β-Ga2O3 layer, as shown in FIG. Figure 3b shown.

[0069] Step 6: Keeping other growth parameters unchanged, switch the film growth mode to pulse method, adjust the TEGa pulse time to 0.1min, the oxygen pulse time to 0.2min, and grow 30-50 cycles of β-Ga2O3 layer to form the second β-Ga2O3 layer, such as Figure 3b shown.

[0070] At this point, the preparation of β-Ga2O3 thin film is completed.

[0071] Example 3

[0072] Based on the above embodiment 1, this embodiment provides a β-Ga2O3 film, which includes, from bottom to top, an off-angle substrate, a first β-Ga2O3 layer, and a second β-Ga2O3 layer, such as Figure 4 As shown, the second β-Ga2O3 layer is prepared by a pulsed growth method.

[0073] The β-Ga2O3 film provided in this embodiment adopts an off-angle substrate, so that the subsequent epitaxially grown β-Ga2O3 film has good flatness; at the same time, the pulsed growth method used in the final stage of epitaxial growth greatly reduces the roughness of the film surface and improves the quality of the β-Ga2O3 film.

[0074] The β-Ga2O3 thin film provided in this embodiment is prepared by the method provided in the above-mentioned embodiment 1. Since it has good surface flatness, it can be widely used in electronic devices.

[0075] It should be noted that although examples of parameters including specific values may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but rather are approximate to the corresponding values within an acceptable error tolerance or design constraint.

[0076] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a β-Ga2O3 thin film, characterized in that: include: Select an off-angle substrate with a certain off-angle range; performing annealing on the off-angle substrate; epitaxially growing a first β-Ga2O3 layer on the off-angle substrate; epitaxially growing a second β-Ga2O3 layer on the first β-Ga2O3 layer using a pulsed growth method to obtain a β-Ga2O3 thin film; The annealing treatment of the off-angle substrate includes: placing the off-angle substrate in a low-pressure MOCVD reaction chamber, wherein the oxygen atmosphere is set to an oxygen flow rate of 1000-1500 sccm, a temperature of 900-950° C., and a reaction chamber pressure of 35-45 Torr; and thermally annealing the off-angle substrate in the oxygen atmosphere for 20-30 minutes; Epitaxially growing a first β-Ga2O3 layer on the off-angle substrate comprises: after annealing the β-Ga2O3 substrate, setting process conditions as follows: lowering the reaction chamber temperature to 700-850° C. and maintaining the pressure in the reaction chamber at 35-45 Torr; simultaneously opening a Ga source and an O2 gas line, and adjusting the Ga source flow rate to 35-40 sccm and the O2 flow rate to 1800-2100 sccm; under the above process conditions, epitaxially growing a β-Ga2O3 thin film on the off-angle substrate to form the first β-Ga2O3 layer; wherein the growth time is 50-60 minutes; Epitaxially growing a second β-Ga2O3 layer on the first β-Ga2O3 layer using a pulsed growth method includes: keeping other growth parameters unchanged, switching the thin film growth mode to a pulsed method, and adjusting the pulse time ratio of the Ga source and O2 to 1:1-1:3; growing for 30-50 cycles to form the second β-Ga2O3 layer on the first β-Ga2O3 layer.

2. The method for preparing a β-Ga2O3 thin film according to claim 1, wherein: The material of the off-angle substrate is Ga2O3 or sapphire.

3. The method for preparing a β-Ga2O3 thin film according to claim 1, wherein: The deflection angle of the deflection substrate ranges from 1.5° to 6°.

4. The method for preparing a β-Ga2O3 thin film according to claim 1, wherein: The thickness of the first β-Ga2O3 layer is 500-600 nm.

5. The method for preparing a β-Ga2O3 thin film according to claim 1, wherein: The pulse time of the Ga source is 0.1 min, and the pulse time of the O2 is 0.2 or 0.3 min.

6. The method for preparing a β-Ga2O3 thin film according to claim 5, characterized in that: The thickness of the second β-Ga2O3 layer is 20-30 nm.

7. A β-Ga2O3 thin film, characterized in that From bottom to top, it includes: an off-angle substrate, a first β-Ga2O3 layer and a second β-Ga2O3 layer, wherein the second β-Ga2O3 layer is prepared by a pulsed growth method, and the β-Ga2O3 film is prepared by the method according to any one of claims 1 to 6.

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