Gallium oxide film hetero-epitaxially grown on a diamond surface and a method for preparing the same

Abstract

The application provides a gallium oxide film hetero-epitaxially grown on a diamond surface and a preparation method thereof, and belongs to the technical field of semiconductor materials. The gallium oxide film is prepared by adopting an atomic layer deposition technology, first preparing an oxygen terminal diamond substrate surface, and then depositing gallium oxide on the oxygen terminal diamond substrate surface to obtain the gallium oxide film. The gallium oxide film obtained by the application has excellent thickness uniformity and extremely precise composition control. Meanwhile, the atomic layer deposition method is carried out under low temperature conditions, so that the adhesion of the gallium oxide at the interface with the diamond is very good and is not affected by the large material property difference between the diamond and the gallium oxide.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor materials, and particularly relates to a gallium oxide film hetero-epitaxially grown on a diamond surface and a preparation method thereof. BACKGROUND

[0002] As a new material, gallium oxide (Ga2O3) has attracted much attention from researchers at home and abroad due to its ultra-wide band gap and ultra-high Baliga figure of merit, and is considered to be one of the semiconductor materials with great application potential after SiC and GaN. The most expected application of gallium oxide is in power electronic devices, especially in high-power application scenarios. In recent years, with the continuous innovation of technology, the size of gallium oxide single crystal is increasing, and the defect density is also decreasing. Like silicon carbide, the single crystal substrate has many structural defects, and directly making a device will accelerate the degradation of its performance and even cause the device to fail prematurely. Therefore, a high-quality and low-defect-density gallium oxide film is often obtained by epitaxial growth, and then a device is made. However, due to the current price of gallium oxide single crystal and the process conditions of homo-epitaxy, the single crystal substrate and homo-epitaxial growth are not suitable for the current situation, and the relatively cheap substrate and flexible process conditions of hetero-epitaxy are better. Therefore, the growth of gallium oxide in this way has developed rapidly in recent years, and many studies on growing gallium oxide films on different substrates by various deposition methods have been reported at home and abroad, including physical vapor deposition (PVD), chemical vapor deposition (CVD), and atomic layer deposition (ALD) deposition techniques.

[0003] Gallium oxide material has many advantages in various aspects, and its growth and preparation are becoming more and more mature. However, gallium oxide material also has a natural deficiency, that is, very low thermal conductivity (11-27 W / m·K), which makes the heat accumulated in the device cannot be quickly dispersed in the application of Ga2O3-based power devices, especially in high-power scenarios, thereby inducing the reliability problem of the device. Therefore, the bottleneck problem to be solved for the application and promotion of gallium oxide is its poor thermal conductivity. At present, the international cutting-edge innovative method is to rely on heterogeneous integration with high thermal conductivity materials to achieve the thermal management of gallium oxide-based devices. Diamond, as the material with the highest thermal conductivity in nature (2000-2200 W / m·K), is an excellent choice for gallium oxide heat sink. So far, the existing reported technologies have integrated gallium oxide and diamond through mechanical exfoliation and ionic bonding. The gallium oxide / diamond heterostructure obtained by this method can be combined very compactly through certain process treatment. However, this method is only suitable for the research stage, and it is difficult to play a role in future industrial production. There are also reports that chemical vapor deposition (CVD) and magnetron sputtering method are used to heteroepitaxially grow gallium oxide film on diamond. However, the interface bonding force, surface microstructure and morphology of the gallium oxide film prepared by the two methods still need to be improved. Therefore, a new preparation method is needed, which not only meets the good heterogeneous bonding ability, but also considers the future industrialization, and also has excellent gallium oxide film microstructure and morphology characteristics. SUMMARY

[0004] Therefore, the present application aims to provide a gallium oxide film heteroepitaxially grown on the surface of diamond and a preparation method thereof. The gallium oxide film provided by the present application has excellent thickness uniformity and extremely precise composition control, and the adhesion at the interface between gallium oxide and diamond is very good and is not affected by the large difference in material properties between diamond and gallium oxide.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solution: a preparation method of gallium oxide film heteroepitaxially grown on the surface of diamond, comprising the following steps:

[0006] (1) The surface of diamond is pretreated, and is placed into the reaction chamber of atomic layer deposition;

[0007] (2) The oxygen source reaction precursor is introduced into the reaction chamber to react with the diamond to form an oxygen-terminated diamond surface;

[0008] (3) The gallium source precursor is introduced into the reaction chamber to grow gallium oxide on the oxygen-terminated diamond surface to obtain a gallium oxide film.

[0009] After the deposition of Ga2O3 thin film is completed, the Ga2O3 / diamond sample is placed in a N2 box for protection to prevent the sample surface from being contaminated or attached by pollutants or particles in the air.

[0010] Preferably, the pretreatment in step (1) comprises cleaning and drying; the cleaning comprises cleaning with an organic solvent and deionized water; and the drying is drying the diamond in a N2-filled drying cabinet.

[0011] Further preferably, the organic solvent is acetone and alcohol solution; in the present application, the cleaning specifically comprises cleaning the diamond substrate in an ultrasonic cleaner with acetone and alcohol solution for 5-10 min, and then cleaning the surface of the diamond substrate according to a standard RCA cleaning process, mainly to remove chemical contaminants and particle impurities on the surface of the diamond substrate, and then rinsing the diamond substrate with high-purity deionized water to remove the chemical solution remaining from the previous process.

[0012] Preferably, the oxygen source reaction precursor in step (2) is selected from oxygen, ozone or oxygen plasma; and the purity of the oxygen is greater than 99.995%.

[0013] Preferably, the oxygen source reaction precursor is introduced into the reaction chamber in an O2 plasma pulse mode, the chamber pressure is 1-10 mbar, the O2 plasma activation power is 100-500 W, and 1-500 pulses are used, each pulse lasting 1-50 s.

[0014] Preferably, inert gas pulses are introduced in steps (2) and (3) to flush the reaction by-products and excess precursor gas.

[0015] Preferably, step (3) further comprises a step of determining the growth parameters of the gallium oxide thin film.

[0016] Further preferably, the step of determining the growth parameters of the gallium oxide thin film specifically comprises:

[0017] S1. selecting an ALD growth temperature window of Ga2O3 thin film, fixing the pulse time of trimethyl gallium and O2 plasma, depositing gallium oxide thin films with the same cycle number at 50-300℃, respectively, measuring the film thickness by ellipsometer combined with XRR, and calculating the growth rate to find the ALD temperature window;

[0018] S2. Select a temperature in the temperature window as the growth temperature, then change the pulse time of the trimethyl gallium precursor, and fix the pulse time of the O2 plasma, to explore the saturation curve of the gallium source, and select the optimal pulse time of the precursor;

[0019] S3. Select a temperature in the temperature window as the growth temperature, then change the duration of the O2 plasma, and fix the pulse time of the trimethyl gallium, to explore the saturation curve of the O2 plasma, and select the optimal duration of the O2 plasma;

[0020] S4. The optimal temperature and precursor pulse time obtained in the above steps are used as process parameters to grow Ga2O3 films of different cycle periods, and the thickness test is used to verify whether they have a linear increase with the number of growth cycles, and the growth process parameters are fine-tuned according to the results to find the optimal process parameters.

[0021] Further preferably, the duration of the pulse time of the trimethyl gallium precursor in step S2 is 10-100 ms.

[0022] Further preferably, the duration of the O2 plasma in step S3 is 1-30 s.

[0023] Further preferably, the cycle period in step S4 is 100-5000 cycles.

[0024] Further preferably, the optimal process parameters are that the ALD growth temperature of the Ga2O3 film is 150-250 DEG C, the optimal duration of the O2 plasma is 10-20 s, and the TMGa inlet time is 20-40 ms.

[0025] The application also provides a hetero-epitaxial gallium oxide film on a diamond surface prepared by the preparation method.

[0026] Beneficial technical effects: The application provides a gallium oxide film hetero-epitaxially grown on an oxygen-terminated diamond surface and a preparation method thereof. The application uses atomic layer deposition technology to first prepare an oxygen-terminated diamond substrate surface, and then deposit a gallium oxide film on the oxygen-terminated diamond substrate surface. The application first prepares an oxygen-terminated diamond substrate surface, which is conducive to better combination of the gallium oxide and the diamond substrate. In addition, the atomic layer deposition technology used is a continuous surface reaction with atomic-level control of the growth object. Due to its self-limiting and self-saturation, the gallium oxide can be stacked layer by layer on the diamond substrate surface. Therefore, the obtained gallium oxide film has excellent thickness uniformity and extremely precise composition control. At the same time, the atomic layer deposition is carried out under low temperature conditions, so that the adhesion of the gallium oxide at the interface with the diamond is very good and is not affected by the large material property difference between the diamond and the gallium oxide. DETAILED DESCRIPTION

[0027] In order to better understand the present application, the following further illustrates the content of the present application in conjunction with examples, but the content of the present application is not limited to the following examples only.

[0028] Example 1

[0029] Preparation of a hetero-epitaxial gallium oxide film on diamond

[0030] (1) The diamond is washed with acetone and alcohol solution in an ultrasonic cleaner for 5-10 minutes; then, the surface of the diamond substrate is cleaned according to the standard RCA cleaning process, and then the diamond substrate is rinsed with high-purity deionized water to remove the residual chemical solution in the previous process. Finally, the diamond substrate is placed in a dry cabinet filled with N2 for drying treatment, and then placed in an atomic layer deposition reaction chamber;

[0031] (2) 99.995% pure O2 is introduced into the reaction chamber using O2 plasma pulse mode, and the reaction chamber pressure is 1 mbar; the O2 plasma activation power is 200 W, 100 pulses are used, each pulse is 20 s, and O2 reacts with the diamond to form an oxygen-terminated diamond surface;

[0032] (3) Trimethyl gallium precursor is introduced into the reaction chamber, and the process parameters for growing the gallium oxide film are set as follows: the growth temperature is 200°C, the O2 plasma introduction time is 15 s, the TMGa introduction time is 30 ms, and 1000 cycles are cycled under the process parameters. The gallium oxide film thickness of the 2-inch diamond substrate is 90-100 nm, the uniformity is <2%, the roughness is <1 nm, the visible light transmittance is >80%, the refractive index is 1.85 (632.8 nm), and the band gap is 4.7 eV.

[0033] Example 2

[0034] Preparation of a hetero-epitaxial gallium oxide film on diamond

[0035] (1) The diamond is washed with acetone and alcohol solution in an ultrasonic cleaner for 5-10 minutes; then, the surface of the diamond substrate is cleaned according to the standard RCA cleaning process, and then the diamond substrate is rinsed with high-purity deionized water to remove the residual chemical solution in the previous process. Finally, the diamond substrate is placed in a dry cabinet filled with N2 for drying treatment, and then placed in an atomic layer deposition reaction chamber;

[0036] (2) The O2 with purity of 99.995% is introduced into the reaction cavity by O2 plasma pulse mode, the cavity chamber pressure is 10 mbar; the O2 plasma activation power is 500 W, 500 pulses are used, each pulse is 50 s, the O2 reacts with the diamond to form an oxygen-terminated diamond surface;

[0037] (3) The trimethyl gallium precursor is introduced into the reaction cavity, the process parameters for growing the gallium oxide film are set as follows: the growth temperature is 250 ℃, the O2 plasma introduction time is 20 s, the TMGa introduction time is 40 ms, under the process parameters, 1000 cycles are cycled, the gallium oxide film thickness of the 2-inch diamond substrate is 90-100 nm, the uniformity is <2%, the roughness is <1 nm, the visible light transmittance is >80%, the refractive index is 1.85 (632.8 nm), and the band gap is 4.7 eV.

[0038] Example 3

[0039] A method for preparing a hetero-epitaxial gallium oxide film on a diamond

[0040] (1) The diamond is washed in an ultrasonic cleaner with acetone and alcohol solution for 5-10 minutes; then, the diamond substrate surface is cleaned according to a standard RCA cleaning process, then the diamond substrate is rinsed with high-purity deionized water to remove the chemical solution remaining in the previous process, finally, the diamond substrate is placed in a dry cabinet filled with N2 for drying treatment, and then is placed into a reaction cavity of an atomic layer deposition;

[0041] (2) The O2 with purity of 99.995% is introduced into the reaction cavity by O2 plasma pulse mode, the cavity chamber pressure is 1 mbar; the O2 plasma activation power is 100 W, 100 pulses are used, each pulse is 10 s, the O2 reacts with the diamond to form an oxygen-terminated diamond surface;

[0042] (3) The trimethyl gallium precursor is introduced into the reaction cavity, the process parameters for growing the gallium oxide film are set as follows: the growth temperature is 150 ℃, the O2 plasma introduction time is 10 s, the TMGa introduction time is 20 ms, under the process parameters, 1000 cycles are cycled, the gallium oxide film thickness of the 2-inch diamond substrate is 90-100 nm, the uniformity is <2%, the roughness is <1 nm, the visible light transmittance is >80%, the refractive index is 1.85 (632.8 nm), and the band gap is 4.7 eV.

[0043] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a gallium oxide thin film hetero-epitaxially on a diamond surface, characterized by, The method comprises the following steps: (1) Pre-treating the diamond surface and putting it into an atomic layer deposition reaction chamber; (2) Passing an oxygen source reaction precursor into the reaction chamber to react with the diamond to form an oxygen-terminated diamond surface; (3) Passing a gallium source precursor into the reaction chamber to grow gallium oxide on the oxygen-terminated diamond surface to obtain a gallium oxide film; The method of introducing the oxygen source reaction precursor into the reaction chamber in step (2) is to use... Plasma is introduced via a pulsed method, and the pressure in the reaction chamber is 1–10 mbar; The plasma activation power is 100–500W, using 1–500 pulses, each pulse lasting 1–50 seconds.

2. The production method according to claim 1, characterized by, The oxygen source reaction precursor in step (2) is selected from oxygen, ozone or oxygen plasma; the purity of the oxygen is greater than 99.995%.

3. The preparation method according to claim 1, characterized in that, The gallium source precursor in step (3) is trimethyl gallium.

4. The method of claim 1, wherein, The step (3) further comprises a step of determining the process parameters for growing the gallium oxide film.

5. The preparation method according to claim 4, characterized in that, The step of determining the process parameters for growing the gallium oxide film specifically comprises: S1. Select ALD growth Temperature window of thin film, fixed trimethyl gallium and Pulse time of plasma, respectively depositing gallium oxide thin film with the same cycle number at 50-300℃, ellipsometer combined with XRR measurement to characterize the film thickness, and the growth rate is calculated to find the ALD temperature window; S2. Select a temperature within the temperature window as the growth temperature, then change the pulse time of the trimethylgallium precursor, and fix the pulse time of the plasma, to explore the saturation curve of the gallium source and select the optimal pulse time of the precursor; the pulse time of the plasma, to explore the saturation curve of the gallium source and select the optimal pulse time of the precursor; S3. Select the temperature within the temperature window as the growth temperature, and then change... The duration of plasma and the pulse duration of trimethylgallium were fixed to explore plasma saturation curve, select The optimal duration of plasma; S4. The best temperature and precursor pulse time obtained from the above steps are used as process parameters to grow different cycles of The thickness of the films is tested to verify whether it has a linear increase with the number of growth cycles, and the growth process parameters are fine-tuned according to the results to find the best process parameters.

6. The production method according to claim 5, wherein The duration of the pulse time of the trimethyl gallium precursor in step S2 is 10-100 ms.

7. The preparation method according to claim 5, characterized in that, The step S3 is described The duration of the plasma is 1 to 30 s.

8. The preparation method according to claim 5, characterized in that, The cycle period in step S4 is 100-5000 cycles.

9. A gallium oxide film hetero-epitaxially grown on a diamond surface prepared by the preparation method in any one of claims 1-8.