A method for preparing a p-type gallium oxide thin film

Abstract

The application belongs to the field of semiconductors, and discloses a preparation method of a p-type gallium oxide film, which comprises the following steps: S1, growing a pretreatment layer on a substrate; S2, placing the substrate after the pretreatment layer is grown in a protective gas atmosphere, and heating and warming to a treatment temperature; S3, irradiating the substrate with a one-dimensional linear laser in a nitrogen plasma atmosphere; and S4, performing annealing treatment in the protective gas atmosphere.The nitrogen-metal co-doping of the gallium oxide film is realized through nitrogen plasma and laser, so that the p-type gallium oxide film with high quality is prepared; the preparation process is simple, the production cost is low, and the application is conducive to the popularization and application of the gallium oxide device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a preparation method of p-type gallium oxide film. BACKGROUND

[0002] As a new type of ultra-wide bandgap semiconductor material, gallium oxide has an ultra-wide bandgap width (4.9 eV), a high breakdown field strength (8 MV·cm -1 ), and a Baliga figure of merit more than ten times that of silicon carbide and gallium nitride. Therefore, gallium oxide-based power devices can theoretically have higher breakdown voltage and lower on-resistance, and have broad application prospects in the fields of rail transit, high-voltage power transmission, new energy vehicles, aerospace, etc.

[0003] Homogeneous p-n junctions and bipolar transistors have better power characteristics, so realizing n-type and p-type is crucial for high-power device applications. At present, n-type gallium oxide has been controllably prepared by doping elements such as tin and silicon. However, due to the low solubility of the doping elements, the hole self-trapping effect and the background electron self-compensation effect, the preparation of p-type gallium oxide still faces great challenges. This directly limits the development of gallium oxide-based power devices, making their breakdown voltage and on-resistance much lower than the theoretical values.

[0004] In recent years, people have considered that nitrogen has a similar atomic size to oxygen and that the nitrogen element has a shallow acceptor impurity level in gallium oxide, and believe that nitrogen is the most potential element to realize p-type doping of gallium oxide. However, nitrogen in gallium oxide faces problems such as poor stability and low solubility, making it difficult to prepare nitrogen-doped p-type gallium oxide films and poor stability. Metal elements such as magnesium, iron, and zinc, which have a large ionization energy, are deep-level acceptor impurity defects, and are difficult to ionize at room temperature, making it impossible to form effective p-type doping.

[0005] To solve the above problems, multiple element co-doping is currently used, among which nitrogen and metal co-doping is considered a potential solution to realize p-type gallium oxide. For example, Chinese patent documents CN 119092385A and CN 119920683A disclose an ultraviolet photocathode based on gallium oxide and a preparation method thereof, and a p-type gallium oxide film co-doped with nitrogen and metal and a preparation method thereof, respectively. The former sample has a hole carrier concentration of 6.2×10 15 ~1.1×10 18 cm -3 , and the latter sample has a hole concentration of 1×10 11 cm~1×10 19 cm -3Both of them have achieved good p-type doping effect, but the former method needs a higher temperature of 700-800℃ for film growth, and the annealing treatment needs to take out the sample and takes a long time of 1.5h; the latter method is to firstly obtain nitrogen-doped gallium oxide through high-temperature annealing, then to place or spin a layer of metal on the surface of the sample after taking it out, and to obtain nitrogen and metal co-doped gallium oxide film through high-temperature annealing again, which needs to go through two high-temperature processes and the steps are relatively complicated. Both of the two methods are not conducive to industrial production. SUMMARY

[0006] The present application aims to provide a preparation method of p-type gallium oxide film to solve the problems in the background art.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method of p-type gallium oxide film, characterized in that it comprises the following steps:

[0008] S1, growing a pretreatment layer on a substrate;

[0009] S2, placing the substrate after growing the pretreatment layer in a protective gas atmosphere and heating to a treatment temperature;

[0010] S3, irradiating the substrate in a nitrogen plasma atmosphere with a one-dimensional linear laser;

[0011] S4, annealing the substrate after laser irradiation treatment in a protective gas atmosphere.

[0012] Preferably, in step S1, the substrate is silicon or sapphire.

[0013] Preferably, in step S1, the substrate is sapphire.

[0014] Preferably, in step S1, the pretreatment layer is a multilayer film structure of gallium oxide film and M film alternately arranged, wherein the M film is one of zinc film, copper film, magnesium film, zinc oxide film, copper oxide film and magnesium oxide film.

[0015] Preferably, in step S1, the pretreatment layer is a single layer of metal-doped gallium oxide film, wherein the metal is one of copper, zinc and magnesium.

[0016] Preferably, in step S1, the total thickness of the pretreatment layer is 100-1000nm.

[0017] Preferably, in steps S2 and S4, the protective gas is nitrogen or argon.

[0018] Preferably, in step S2, the treatment temperature is 200-500℃.

[0019] Preferably, in step S3, the nitrogen plasma is a nitrogen-hydrogen mixed gas or an ammonia-argon mixed gas; when the protective gas is nitrogen, the nitrogen plasma is a nitrogen-hydrogen mixed gas, which is mixed from nitrogen and hydrogen according to a gas flow ratio of 4:1-10:1; when the protective gas is argon, the nitrogen plasma is an ammonia-argon mixed gas, which is mixed from argon and ammonia according to a gas flow ratio of 2:1-10:1.

[0020] Preferably, in step S3, the one-dimensional linear laser is a continuous Nd:YAG laser, the power of the laser is 300W-800W, and the scanning speed of the laser is 2mm / s-10mm / s.

[0021] Preferably, in step S4, the temperature of the annealing treatment is 650℃-1000℃, and the time of the annealing treatment is 20min-60min.

[0022] From the above description of the structure of the present application, compared with the prior art, the present application has the following advantages:

[0023] The present application provides a preparation method of a p-type gallium oxide film. First, a gallium oxide film containing metal is prepared on a cheap substrate (such as a silicon wafer, sapphire, etc.). The film is melted by using the laser heat effect. The melting process of the film promotes the metal to be doped into the gallium oxide film. Since the film is simultaneously in a nitrogen plasma atmosphere, nitrogen elements are also doped into the gallium oxide film, thereby realizing a nitrogen-metal co-doped gallium oxide film. Finally, the film is converted from an amorphous state to a crystalline state through high-temperature annealing treatment, and the nitrogen-metal impurities doped into the film are also activated, greatly improving the hole carrier concentration of the film and making the film become p-type. The prepared film can be grown at room temperature, and only one high-temperature annealing is needed, and the annealing time is relatively short, which simplifies the process flow and is convenient for industrial production. After laser treatment, the substrate does not need to be taken out, and the in-situ annealing process greatly reduces the risk of introducing other impurities, thereby obtaining high-quality p-type gallium oxide material. By adjusting the pretreatment layer, laser parameters and annealing conditions, the injection of effective holes is controlled, thereby realizing the preparation of a p-type gallium oxide film with controllable hole carrier concentration. The prepared p-type gallium oxide film is helpful for the popularization and application of gallium oxide-based devices. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments illustrated in the drawings are provided to explain the present application and are not intended to limit the present application unduly. In the drawings:

[0025] Figure 1 The flowchart of the present application is shown in the figure;

[0026] Figure 2 Figure 5 is a graph showing the Hall hole carrier concentration of the sample after treatment of Example 5 of the present application as a function of test temperature.

[0027] In the figure: 1, substrate; 2, pretreatment layer; 3, Nd:YAG continuous laser; 4, nitrogen plasma; 5, p-type gallium oxide film. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0029] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0030] Example 1

[0031] The present embodiment provides a method for preparing a p-type gallium oxide film, which specifically comprises the following contents:

[0032] (1) A 30 nm gallium oxide film and a 30 nm magnesium oxide film were sequentially deposited on the surface of a cleaned silicon wafer by a magnetron sputtering method, and the alternating cycle growth was performed 5 times to obtain a total thickness of 300 nm of the film as a pretreatment layer;

[0033] (2) The sample after deposition of the pretreatment layer was placed in an argon atmosphere and heated to 400°C;

[0034] (3) Argon and ammonia were introduced, the gas flow ratio was 4:1, the plasma radio frequency power source was turned on, one-dimensional linear Nd:YAG continuous laser was used to irradiate one side of the sample after deposition of the pretreatment layer, the laser power was selected to be 450 W, the scanning speed of the laser was 3 mm / s, and the laser reciprocating irradiated the sample for 6 times;

[0035] (4) The plasma radio frequency power source and ammonia were turned off, the temperature was heated to 850°C, and annealing treatment was performed in an argon atmosphere for 30 minutes.

[0036] Example 2

[0037] The present embodiment provides a method for preparing a p-type gallium oxide film, which specifically comprises the following contents:

[0038] (1) A zinc-doped gallium oxide film was deposited on the surface of a cleaned sapphire as a pretreatment layer by a magnetron sputtering method, and the thickness was 450 nm;

[0039] (2) The sample after deposition of the pretreatment layer was placed in a nitrogen atmosphere and heated to 350°C;

[0040] (3) nitrogen and hydrogen are introduced, the gas flow ratio is 8:1, the plasma radio frequency power source is turned on, one-dimensional linear Nd:YAG continuous laser is used to irradiate one side of the deposited pretreatment layer, the laser power is selected to be 500 W, the scanning speed of the laser is 2 mm / s, and the sample is reciprocally irradiated for 7 times;

[0041] (4) the plasma radio frequency power source and hydrogen are turned off, heating is performed to 700 DEG C, and annealing treatment is performed in a nitrogen atmosphere for 25 minutes.

[0042] Example 3

[0043] The embodiment provides a preparation method of a p-type gallium oxide film, and specifically comprises the following contents:

[0044] (1) a 25 nm gallium oxide film and a 25 nm copper film are sequentially deposited on a cleaned sapphire surface by a magnetron sputtering method, and the alternating cycle growth is performed 10 times, so that a film with a total thickness of 500 nm is obtained as a pretreatment layer;

[0045] (2) the sample after depositing the pretreatment layer is placed in a nitrogen atmosphere, and heating is performed to 400 DEG C;

[0046] (3) nitrogen and hydrogen are introduced, the gas flow ratio is 7:1, the plasma radio frequency power source is turned on, one-dimensional linear Nd:YAG continuous laser is used to irradiate one side of the deposited pretreatment layer, the laser power is selected to be 450 W, the scanning speed of the laser is 3 mm / s, and the sample is reciprocally irradiated for 8 times;

[0047] (4) the plasma radio frequency power source and ammonia are turned off, heating is performed to 800 DEG C, and annealing treatment is performed in an argon atmosphere for 30 minutes.

[0048] Example 4

[0049] The embodiment provides a preparation method of a p-type gallium oxide film, and specifically comprises the following contents:

[0050] (1) a magnesium-doped gallium oxide film is deposited on a cleaned silicon wafer surface by a magnetron sputtering method as a pretreatment layer, and the thickness is 600 nm;

[0051] (2) the sample after depositing the pretreatment layer is placed in an argon atmosphere, and heating is performed to 350 DEG C;

[0052] (3) argon and ammonia are introduced, the gas flow ratio is 6:1, the plasma radio frequency power source is turned on, one-dimensional linear Nd:YAG continuous laser is used to irradiate one side of the deposited pretreatment layer, the laser power is selected to be 600 W, the scanning speed of the laser is 2 mm / s, and the sample is reciprocally irradiated for 10 times;

[0053] (4) Turn off the plasma radio frequency power and ammonia, and heat to 750°C, and perform annealing treatment in an argon atmosphere for 35 minutes.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing a p-type gallium oxide film, which differs from Example 1 in that the laser treatment process and the annealing treatment process are omitted, and specifically includes the following contents:

[0056] (1) A 30 nm gallium oxide film and a 30 nm magnesium oxide film are sequentially deposited on the surface of a cleaned silicon wafer by a magnetron sputtering method, and alternately grown for 5 times, to obtain a total thickness of 300 nm of the film as a pretreatment layer;

[0057] (2) The sample after depositing the pretreatment layer is placed in an argon atmosphere, and heated to 400°C;

[0058] (3) Argon and ammonia are introduced, the gas flow ratio is 4:1, the plasma radio frequency power is turned on, and the plasma treatment time is the same as that in step (3) of Example 1.

[0059] Comparative Example 2

[0060] This comparative example provides a method for preparing a p-type gallium oxide film, which differs from Example 1 in that the nitrogen plasma environment and the annealing treatment process are omitted, and specifically includes the following contents:

[0061] (1) A 30 nm gallium oxide film and a 30 nm magnesium oxide film are sequentially deposited on the surface of a cleaned silicon wafer by a magnetron sputtering method, and alternately grown for 5 times, to obtain a total thickness of 300 nm of the film as a pretreatment layer;

[0062] (2) The sample after depositing the pretreatment layer is placed in an argon atmosphere, and heated to 400°C;

[0063] (3) One-dimensional linear Nd:YAG continuous laser is used to irradiate one side of the sample after depositing the pretreatment layer, the laser power is selected to be 450 W, the scanning speed of the laser is 3 mm / s, and the laser reciprocally irradiates the sample for 6 times.

[0064] Comparative Example 3

[0065] This comparative example provides a method for preparing a p-type gallium oxide film, which differs from Example 1 in that the laser treatment process in the nitrogen plasma environment is omitted, and specifically includes the following contents:

[0066] (1) A 30 nm gallium oxide film and a 30 nm magnesium oxide film are sequentially deposited on the surface of a cleaned silicon wafer by a magnetron sputtering method, and alternately grown for 5 times, to obtain a total thickness of 300 nm of the film as a pretreatment layer;

[0067] (2) The sample after depositing the pretreatment layer is placed in an argon atmosphere and heated to 400°C;

[0068] (3) The temperature is heated to 850°C, and annealing treatment is performed in an argon atmosphere for 30 minutes.

[0069] Table 1 - Properties of the gallium oxide thin film prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 (room temperature test)

[0070] Test item Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Conductivity type Strong p-type Weak n-type Weak n-type Weak p-type Carrier concentration (1 / cm2 3 ) 9.24 x 10 17 ]] 8.68 x 10 15 ]]> 2.11 x 10 16 ]] 4.51 x 10 16 ]]> Hall mobility (cm 2 / V.s) 19.13 443.05 210.51 86.54 Resistivity (Ω.cm) 3.04 1103.82 583.22 113.61

[0071] Comparative Example 1, Comparative Example 2 and Comparative Example 3 are comparative examples of Example 1. As can be seen from Table 1, the gallium oxide thin film prepared by the method of the present application, as in Example 1, exhibits strong p-type and low resistivity, meeting the requirements for gallium oxide device preparation. If only a nitrogen plasma environment treatment is performed, as in Comparative Example 1, or only a laser treatment is performed, as in Comparative Example 2, or only an annealing treatment is performed, as in Comparative Example 3, a good p-type gallium oxide thin film cannot be prepared, and even a weak n-type is exhibited.

[0072] Table 2 - Properties of the gallium oxide material prepared in Example 2, Example 3 and Example 4 (room temperature test)

[0073] Test item Example 2 Example 3 Example 4 Conductivity type Strong p-type Strong p-type Strong p-type hole carrier concentration (1 / cm 3 )]> 1.22 x 10 18 ]]> 3.38 x 10 17 ]] 9.72 x 10 17 ]] Hall mobility (cm 2 / V.s) 20.31 50.42 28.34 Resistivity (Ω.cm) 0.08 8.52 1.13

[0074] As can be seen from Table 2, the gallium oxide thin film prepared by the method of the present application exhibits strong p-type and low resistivity, meeting the requirements for gallium oxide device preparation.

[0075] The above description is merely preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall fall within the scope of the present application.

Claims

1. A method for preparing a p-type gallium oxide thin film, characterized in that, Includes the following steps: S1. A pretreatment layer is grown on the substrate; the pretreatment layer is a multilayer thin film structure consisting of alternating gallium oxide thin films and M thin films, wherein the M thin film is one of zinc thin film, copper thin film, magnesium thin film, zinc oxide thin film, copper oxide thin film, and magnesium oxide thin film; or the pretreatment layer is a metal-doped gallium oxide monolayer thin film, wherein the metal is one of copper, zinc, and magnesium. S2. Place the substrate after the growth of the pretreatment layer in a protective gas atmosphere and heat it to the processing temperature. S3. Irradiate the substrate with a one-dimensional linear laser in a nitrogen plasma atmosphere; S4. Anneal the laser-irradiated substrate in a protective gas atmosphere.

2. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In step S1, the substrate is silicon or sapphire.

3. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In step S1, the total thickness of the pretreatment layer is 100nm to 1000nm.

4. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In steps S2 and S4, the protective gas is nitrogen or argon.

5. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In step S2, the processing temperature is 200℃~500℃.

6. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In step S3, the nitrogen plasma is a nitrogen-hydrogen mixture or an ammonia-argon mixture. When the protective gas is nitrogen, the nitrogen plasma is a nitrogen-hydrogen mixture, which is formed by mixing nitrogen and hydrogen in a gas flow ratio of 4:1 to 10:

1. When the protective gas is argon, the nitrogen plasma is an ammonia-argon mixture, which is formed by mixing argon and ammonia in a gas flow ratio of 2:1 to 10:

1.

7. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In step S3, the one-dimensional linear laser is an Nd:YAG continuous laser with a power of 300W to 800W and a scanning rate of 2mm / s to 10mm / s.

8. The method for preparing a p-type gallium oxide thin film according to claim 1, characterized in that: In step S4, the annealing temperature is 650℃~1000℃, and the annealing time is 20min~60min.

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