A tin-doped amorphous gallium oxide film and a preparation method thereof

Abstract

The present application relates to the technical field of metal oxide thin film preparation, and particularly relates to a tin-doped amorphous gallium oxide thin film and a preparation method thereof. The method comprises the following steps: uniformly mixing nano SnO2 powder and common SnO2 powder, adding the mixture into an infrared ceramic mold to press a pre-sintering target block, sintering and cooling under an oxygen atmosphere to obtain a SnO2 dopant ceramic target material; placing a cleaned substrate and a target holder loaded with a Ga2O3 target material into a sputtering chamber; stacking N pieces of SnO2 dopant ceramic target materials at equal intervals on a ring-shaped sputtering area of the Ga2O3 target material to form a ring-shaped arrangement distribution, and vacuumizing; wherein N is greater than or equal to 1; introducing inert gas at room temperature, and performing magnetron sputtering to make the sputtering target material deposit on the surface of the substrate. The method has the advantages that the doping concentration is flexibly controlled, the preparation efficiency is high, the thin film quality is good, the defect concentration is low, the process is simple, the cost is low, and the device performance can be optimized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal oxide thin film preparation, and particularly relates to a tin-doped amorphous gallium oxide thin film and a preparation method thereof. BACKGROUND

[0002] Amorphous gallium oxide (a-Ga2O3) thin film has great application potential in the field of optoelectronic devices due to its excellent physical and chemical properties. Doping can effectively regulate its electrical properties, which is one of the key technologies to realize device application.

[0003] Magnetron sputtering method is an ideal method for preparing doped thin films due to its low cost, high yield and good controllability. Currently, there are mainly two processes for preparing doped a-Ga2O3 thin films by magnetron sputtering:

[0004] 1. Co-sputtering method: a composite target with a fixed doping concentration is prepared in advance and then sputtered. The advantage of this method is that the process is stable and it is easy to obtain a thin film with uniform quality. However, its disadvantages are also very obvious: first, the doping concentration of the thin film cannot be flexibly adjusted, and a target needs to be customized for each concentration, which is high in research and production cost; second, different sputtering process parameters need to be explored for different target concentrations, resulting in low production efficiency.

[0005] 2. Metal particle stacking method: metal particles (dopant source) are stacked on the surface of a conventional Ga2O3 target, and then sputtered. Although this method can flexibly adjust the doping concentration, it has serious defects: the metal particles are difficult to be completely ionized during sputtering, which will cause some metal atoms to directly enter the thin film, forming impurities and causing lattice distortion and a large number of defects. Although the defects can be repaired to some extent by introducing oxygen and heating, this not only significantly increases the complexity of the equipment and energy cost, but also puts high requirements on the accurate control of gas flow, and the introduction of oxygen also reduces the sputtering yield, affecting the production efficiency and stability of the thin film. In addition, the multi-target co-sputtering method usually requires a high-temperature annealing process, which will cause the crystallization of amorphous gallium oxide, so it is difficult to be used for preparing high-performance amorphous doped thin films.

[0006] Therefore, how to flexibly, efficiently and low-costly prepare high-quality amorphous gallium oxide thin films with different doping concentrations is a technical problem to be solved in the field. SUMMARY

[0007] The present application provides a tin-doped amorphous gallium oxide thin film and a preparation method thereof to solve the above problems.

[0008] The first object of the present application is to provide a preparation method of a tin-doped amorphous gallium oxide thin film, which specifically comprises the following steps:

[0009] S1. Mix the nano-sized SnO2 powder with the common SnO2 powder, add to the infrared ceramic mold to press the pre-sintering target block, and then sinter and cool under oxygen atmosphere to obtain the SnO2 dopant ceramic target material;

[0010] S2. Clean the substrate; place the cleaned substrate and the target holder loaded with the Ga2O3 target material into the sputtering chamber;

[0011] S3. Place the Ga2O3 target material at the center position of the sputtering chamber, and according to the required doping concentration, stack N pieces of SnO2 dopant ceramic target materials at equal intervals on the annular sputtering area of the Ga2O3 target material to form an annular arrangement distribution, and then vacuumize; wherein N≥1;

[0012] S4. At room temperature, introduce inert gas and adjust the sputtering pressure to 3-5 Pa; perform magnetron sputtering to deposit the sputtering target material on the surface of the substrate to obtain a tin-doped amorphous gallium oxide film.

[0013] Preferably, step S1 comprises the following sub-steps:

[0014] S101. Mix the nano-sized SnO2 powder with the 250-350 mesh common SnO2 powder at a mass ratio of 1:8-10, add a small amount of alcohol for grinding, and mix thoroughly;

[0015] S102. Add the mixed powder to the infrared ceramic mold, apply a pressure of 8-10 MPa, and after pressure maintaining for 0.5-2 minutes, demold to obtain a pre-sintering target block with a thickness of 1-2 mm;

[0016] S103. Sinter the pre-sintering target block at 1000-1200℃ under oxygen atmosphere for 1.5-2.5 hours to make it completely dense and ceramic, and then cool to obtain the SnO2 dopant ceramic target material.

[0017] Preferably, the particle diameter of the nano-sized SnO2 powder is less than 100 nm; and the mass ratio of the nano-sized SnO2 powder to the common SnO2 powder is 1:9.

[0018] Preferably, the pressure maintaining time in step S102 is 1 minute.

[0019] Preferably, the sintering in step S103 is performed in a tube furnace, the sintering temperature is 1100℃, and the sintering time is 2 hours.

[0020] Preferably, the particle diameter of the nano-sized SnO2 powder is less than 100 nm; and the substrate is selected as an Al2O3 (0001) double-polished sapphire substrate.

[0021] Preferably, N=3 in step S3.

[0022] Preferably, the inert gas in step S4 is pure argon; the sputtering pressure is adjusted to 4 Pa; the power of the magnetron sputtering is 100-150 W, and the sputtering time is 20-40 minutes.

[0023] Preferably, the power of the magnetron sputtering is 120 W; the thickness of the tin-doped amorphous gallium oxide film is 300-350 nm.

[0024] The second object of the present application is to provide a tin-doped amorphous gallium oxide film prepared by the preparation method of the tin-doped amorphous gallium oxide film.

[0025] Compared with the prior art, the present application can achieve the following beneficial effects:

[0026] (1) Flexible doping concentration control and high preparation efficiency: By simply increasing or decreasing the number of dopant ceramic targets stacked on the main target material, the doping concentration in the film can be quickly and conveniently controlled without the need to replace the entire main target material, greatly improving the research and production efficiency of preparing films with different doping concentrations.

[0027] (2) Good film quality and low defect concentration: The present application uses an oxide ceramic target of a doping element (such as SnO2) as a doping source. During sputtering, the target can not only ionize doping element ions (such as Sn 4+ ), but also release oxygen ions simultaneously; these oxygen ions can effectively supplement the oxygen lost due to sputtering, thereby significantly reducing the oxygen vacancy defects in the film and avoiding lattice distortion caused by direct metal atom doping. Experiments show that by optimizing the doping concentration, the oxygen vacancy concentration can be reduced from more than 36% to within 10%.

[0028] (3) Simple process and low cost: The preparation method of the present application does not require additional oxygen to be introduced during sputtering, simplifying the process control and reducing the requirements for gas flow control equipment. At the same time, since high-quality amorphous films can be obtained without high-temperature annealing, energy consumption is also reduced, making the entire preparation process have very low requirements for equipment and energy, and the cost advantage is obvious.

[0029] (4) Device performance optimization: The preparation method of the present application can easily perform gradient doping experiments and accurately find the "optimal process window" with the least defects (such as oxygen vacancies) and the best electrical properties (such as carrier concentration), providing a reliable basis for preparing high-performance devices. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of the arrangement and distribution of SnO2 dopant ceramic targets on the ring-shaped sputtering area of a Ga2O3 target according to an embodiment of the present application.

[0031] Figure 2It is a schematic diagram of the principle of the stacked target radio frequency magnetron sputtering according to the embodiment of the present application.

[0032] Figure 3 It is a tin different doping concentration analysis statistical result graph according to the embodiment of the present application.

[0033] Figure 4 It is an XPS analysis spectrum of the tin doped amorphous gallium oxide (Sn:a-Ga2O3) film with different doping concentrations according to the embodiment of the present application; wherein: (a) is an XPS full spectrum graph of the sample; (b) is a three-dimensional spectrum of Sn 3d peak.

[0034] Figure 5 It is a chemical state and defect analysis result graph of the tin doped amorphous gallium oxide film with different doping concentrations according to the embodiment of the present application; wherein: (a) is a fine spectrum of Sn 3d peak of different samples; (b) is a fine spectrum of O 1s peak of different samples; (c) is a Sn 4+ ion proportion and lattice oxygen O L proportion statistical graph.

[0035] Figure 6 It is a relationship graph of the carrier concentration, resistivity and Sn doping concentration of the tin doped amorphous gallium oxide film according to the embodiment of the present application.

[0036] Reference signs:

[0037] 1. SnO2 dopant ceramic target material;

[0038] 2. Ga2O3 target material;

[0039] 3. annular sputtering area;

[0040] 4. substrate;

[0041] 5. magnetic field;

[0042] 6. copper target;

[0043] 7. cooling system. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0045] In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application.

[0046] The application provides a tin-doped amorphous gallium oxide (Sn:a-Ga2O3) film preparation method based on a stacked target radio frequency magnetron sputtering, and specifically comprises the following steps:

[0047] S1. Preparing a SnO2 dopant ceramic target (SnO2 small target): uniformly mixing nano SnO2 powder and common SnO2 powder, adding to an infrared ceramic mold to press a pre-sintering target block, sintering and cooling under an oxygen atmosphere to obtain the SnO2 dopant ceramic target; specifically comprising:

[0048] S101. Mixing nano SnO2 powder and 250-350 mesh common SnO2 powder at a mass ratio of 1:8-10, adding a small amount of alcohol for grinding, and fully mixing;

[0049] Preferably, the particle diameter of the nano SnO2 powder is less than 100 nm; the mass ratio of the nano SnO2 powder to the common SnO2 powder is 1:9;

[0050] S102. Adding the mixed powder to an infrared ceramic mold, applying a pressure of 8-10 MPa, and demolding after pressure maintaining for 0.5-2 minutes to obtain a pre-sintering target block with a thickness of 1-2 mm;

[0051] Preferably, 0.35 g of the mixed powder is weighed; the size of the infrared ceramic mold is determined according to the size of the effective sputtering area of the main target material, and in a specific embodiment, the radius of the infrared ceramic mold is 4 mm; the pressure maintaining time is 1 minute; and the pre-sintering target block has a thickness of 1.5 mm;

[0052] S103. Sintering the pre-sintering target block under an oxygen atmosphere at 1000-1200℃ for 1.5-2.5 hours to make it completely dense and ceramic, and obtaining the SnO2 dopant ceramic target after cooling;

[0053] Preferably, the sintering is performed in a tube furnace, the sintering temperature is 1100℃, and the sintering time is 2 hours.

[0054] S2. Cleaning a substrate by using a standard cleaning process, and placing the cleaned substrate and a target holder loaded with a Ga2O3 target into a sputtering chamber;

[0055] Specifically, an Al2O3 (0001) double-polished sapphire substrate is selected;

[0056] S3. Placing the Ga2O3 target at a central position of the sputtering chamber as a main target; according to a required doping concentration, stacking N pieces of SnO2 dopant ceramic targets at equal intervals on a ring-shaped sputtering area of the Ga2O3 target to form a ring-shaped arrangement distribution, and obtaining a sputtering target; vacuumizing; wherein N≥1;

[0057] Specifically, the vacuum degree of the sputtering chamber is extracted to 5*10 -4 Pa;

[0058] S4. Pure argon (Ar) gas is introduced as a sputtering atmosphere at room temperature, and the sputtering pressure is adjusted to 3-5 Pa; a radio frequency power source is turned on for stacked target magnetron sputtering, so that the sputtering target material is deposited on the surface of the substrate to obtain a tin-doped amorphous gallium oxide film;

[0059] Preferably, the power of the magnetron sputtering is 100-150 W, and the sputtering time is 20-40 minutes; the thickness of the tin-doped amorphous gallium oxide film is 300-350 nm;

[0060] In specific embodiments, the parameters of the magnetron sputtering are as follows: the sputtering pressure is 4 Pa, the sputtering power is set to 120 W, and the sputtering time is 30 minutes.

[0061] Embodiment 1

[0062] Referring to Figures 1-2 , the embodiment provides a preparation method of a tin-doped amorphous gallium oxide film (Sn:a-Ga2O3) based on stacked target radio frequency magnetron sputtering, which specifically comprises the following steps:

[0063] S1. Preparation of SnO2 dopant ceramic target 1 (SnO2 small target):

[0064] S101. Mix nano-sized SnO2 powder with a particle diameter of less than 100 nm and 300-mesh ordinary SnO2 powder at a mass ratio of 1:9, add a small amount of alcohol for grinding, and mix thoroughly;

[0065] S102. Weigh 0.35 g of the mixed powder after mixing, add it to an infrared ceramic mold with a radius of 4 mm, apply a pressure of 8-10 MPa, and after 1 minute of pressure holding, demold to obtain a pre-sintered target block with a thickness of about 1.5 mm;

[0066] S103. Sinter the pre-sintered target block in an oxygen atmosphere at 1100°C for 2 hours to make it completely dense and ceramic, and after cooling, the SnO2 dopant ceramic target 1 is obtained.

[0067] S2. Clean the substrate 4 using a standard cleaning process, and place the cleaned substrate and a target holder loaded with a Ga2O3 target 2 into a sputtering chamber;

[0068] The substrate 4 is an Al2O3 (0001) double-polished sapphire substrate.

[0069] S3. Place the Ga2O3 target 2 at the center position of the sputtering chamber as the main target; stack 1 piece of SnO2 dopant ceramic target 1 on the ring-shaped sputtering area 3 of the Ga2O3 target 2 to obtain a sputtering target; and extract the vacuum degree to 5*10-4 Pa;

[0070] S4. At room temperature, pure argon (Ar) gas is introduced as the sputtering atmosphere, and the sputtering pressure is adjusted to 4 Pa; the RF power supply is turned on to perform magnetron sputtering, so that the sputtering target material is deposited on the substrate surface to obtain a tin-doped amorphous gallium oxide film with a thickness of 300~350 nm (doping concentration 1.96%); the magnetron sputtering parameters are: sputtering pressure of 4 Pa, sputtering power of 120 W, and sputtering time of 30 minutes.

[0071] according to Figure 2 The principle of stacked target magnetron sputtering is shown. The specific sputtering process is as follows: During the sputtering process, Ar gas is ionized to form Ar⁺ ions, which are accelerated towards the target material under the action of electric field E. The Ar⁺ ions bombard the target surface, causing the target atoms or molecules to be sputtered out and move towards the substrate 4, eventually forming a thin film on the substrate. Figure 2 The presence of magnetic field 5 is also shown, which helps to confine electron movement and improve sputtering efficiency; there is a cooling system 7 below the copper target 6 (cathode) to maintain the temperature of the target material during the sputtering process; this stacking method and sputtering process can be used to prepare tin-doped amorphous gallium oxide (Sn:a-Ga2O3) thin films with different doping concentrations.

[0072] Example 2

[0073] This embodiment provides a method for preparing tin-doped amorphous gallium oxide thin films based on stacked target radio frequency magnetron sputtering; wherein, in step S3, two SnO2 doped ceramic targets 1 are stacked at equal intervals on the annular sputtering region 3 of Ga2O3 target 2 to form an annular arrangement to obtain sputtering targets; the final tin-doped amorphous gallium oxide thin film has a doping concentration of 3.7%.

[0074] Example 3

[0075] This embodiment provides a method for preparing tin-doped amorphous gallium oxide thin films based on radio frequency magnetron sputtering using stacked targets; wherein, in step S3, three SnO2-doped ceramic targets 1 are stacked at equal intervals on the annular sputtering region 3 of Ga2O3 target 2 to form an annular arrangement to obtain sputtering targets; the final tin-doped amorphous gallium oxide thin film has a doping concentration of 5.45%.

[0076] Example 4

[0077] This embodiment provides a method for preparing tin-doped amorphous gallium oxide thin films based on radio frequency magnetron sputtering using stacked targets; wherein, in step S3, four SnO2-doped ceramic targets 1 are stacked at equal intervals on the annular sputtering region 3 of Ga2O3 target 2 to form an annular arrangement and obtain sputtering targets; the final tin-doped amorphous gallium oxide thin film has a doping concentration of 8.54%.

[0078] Example 5

[0079] The embodiment provides a tin-doped amorphous gallium oxide film preparation method based on a stacked target radio frequency magnetron sputtering; wherein, in step S3, 5 SnO2 dopant ceramic targets 1 are stacked at equal intervals on a ring-shaped sputtering area 3 of a Ga2O3 target 2 to form a ring-shaped arrangement distribution, so as to obtain a sputtering target; and finally, a tin-doped amorphous gallium oxide film with a doping concentration of 12.54% is obtained.

[0080] The tin-doped amorphous gallium oxide films prepared in Examples 1-5 are respectively marked as D1, D2, D3, D4 and D5 samples, and performance tests are performed on the samples D1-D5, and results are shown in Table 1. Figures 3-6

[0081] Figure 3 For the doping concentration analysis results: by changing the number of SnO2 targets, a series of thin films with Sn atomic concentrations (Sn / (Sn+Ga)) of 1.96% (D1), 3.70% (D2), 5.45% (D3), 8.54% (D4) and 12.54% (D5) are successfully prepared. The results show that by changing the number of SnO2 dopant ceramic targets, the Sn doping concentration in the thin film can be conveniently and accurately controlled.

[0082] Figure 4 XPS analysis spectra of the tin-doped amorphous gallium oxide films (D1-D5 samples) with different doping concentrations are shown.

[0083] Figure 5 Chemical state and defect analysis results of the D1-D5 samples. The results show that:

[0084] Sample D1 (1 target, 1.96% Sn): Sn 4+ ion ratio is only 43.89%, and the oxygen vacancy concentration is as high as 36.04%;

[0085] Sample D2 (2 targets, 3.70% Sn): with the increase of the SnO2 source, the O ions provided by the SnO2 source increase, the oxygen vacancy concentration decreases to 29.54%, and the Sn 4+ ion ratio increases to 56.41%;

[0086] Sample D3 (3 targets, 5.45% Sn): at this time, the O ions provided by the SnO2 effectively compensate the oxygen vacancies, so that the concentration of the oxygen vacancies sharply decreases to 8.66%; at the same time, the Sn 4+ ion ratio reaches a peak value of 91.34%, indicating that the Sn element realizes the highest efficient substitutional doping under this condition;

[0087] ​Sample D4 (4 targets, 8.54% Sn): The doping concentration is further increased, and the lattice distortion effect caused by the difference in ion radius between Sn and Ga begins to appear, and the oxygen vacancy concentration rises to 17.1%, Sn 4+ The proportion decreases to 78.83%;

[0088] Sample D5 (5 targets, 12.54% Sn): The lattice distortion effect caused by high concentration doping is more obvious, and the oxygen vacancy concentration rises to 19.08%, Sn 4+ The proportion decreases to 76.94%. This shows that under the fixed power of 120 W, too high a dopant flux exceeds the optimal process window.

[0089] The results of the electrical performance analysis Figure 6 . Figure 6 The change trend of the carrier concentration of the thin film with the doping concentration is highly consistent with the defect analysis results. From D1 to D3, with the improvement of the effective doping efficiency of Sn and the repair of defects, the carrier concentration continuously rises, reaching a peak (about 2.7x10 17 cm -3 ) at D3 (5.45% Sn); thereafter, with the rise of the defect concentration in D4 and D5, the carrier concentration begins to decrease. This clearly proves that the method can optimize the quality of the thin film by adjusting the doping concentration, thereby effectively regulating the electrical performance.

[0090] In summary, the stacked target magnetron sputtering method proposed in the present application can conveniently and quickly prepare amorphous gallium oxide thin films with different doping concentrations, and under suitable process parameters (such as a doping concentration of 5.45%, corresponding to a sputtering power of 120 W), can effectively reduce the defect concentration of the thin film and improve its electrical performance, having extremely high practical value and application prospect.

[0091] It should be understood that the various forms of the flow shown above can be reordered, added, or deleted steps. For example, the steps described in the present disclosure can be executed in parallel, in sequence, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, and the present disclosure does not limit this herein.

[0092] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing a tin-doped amorphous gallium oxide thin film, characterized by: Specifically comprising the following steps: S1. mixing nano-SnO2 powder with common SnO2 powder, adding to an infrared ceramic mold to press a pre-sintering target block, sintering and cooling in an oxygen atmosphere to obtain a SnO2 dopant ceramic target; comprising the following sub-steps: S101. mixing nano-SnO2 powder with 250-350 mesh common SnO2 powder at a mass ratio of 1:8-10, adding a small amount of alcohol for grinding, and thoroughly mixing; S102. adding the mixed powder to an infrared ceramic mold, applying a pressure of 8-10 MPa, and releasing the mold after pressure maintaining for 0.5-2 minutes to obtain a pre-sintering target block with a thickness of 1-2 mm; S103. sintering the pre-sintering target block at 1000-1200℃ in an oxygen atmosphere for 1.5-2.5 hours to make it completely dense and ceramic, and cooling to obtain a SnO2 dopant ceramic target; S2. cleaning the substrate and placing the cleaned substrate and a target holder loaded with a Ga2O3 target into a sputtering chamber; S3. placing the Ga2O3 target at the center of the sputtering chamber, stacking N pieces of SnO2 dopant ceramic targets at equal intervals on the ring-shaped sputtering area of the Ga2O3 target according to the required doping concentration to form a ring-shaped arrangement, and vacuumizing; wherein N≥1; S4. at room temperature, introducing an inert gas and adjusting the sputtering pressure to 3-5 Pa; performing magnetron sputtering to deposit the sputtering target on the surface of the substrate to obtain a tin-doped amorphous gallium oxide film.

2. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 1, characterized in that: The particle diameter of the nano-SnO2 powder is less than 100 nm; and the mass ratio of the nano-SnO2 powder to the common SnO2 powder is 1:

9.

3. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 1, characterized in that: The pressure maintaining time in the step S102 is 1 minute.

4. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 1, characterized in that: The sintering in the step S103 is performed in a tube furnace, the sintering temperature is 1100℃, and the sintering time is 2 hours.

5. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 1, characterized in that: The particle diameter of the nano-SnO2 powder is less than 100 nm; and the substrate is selected as an Al2O3 (0001) double-polished sapphire substrate.

6. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 1, characterized in that: N=3 in the step S3.

7. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 1, characterized in that: The inert gas in the step S4 is pure argon; the sputtering pressure is adjusted to 4 Pa; the power of the magnetron sputtering is 100-150 W, and the sputtering time is 20-40 minutes.

8. The method for preparing a tin-doped amorphous gallium oxide thin film according to claim 7, characterized in that: The power of the magnetron sputtering is 120 W; and the thickness of the tin-doped amorphous gallium oxide film is 300-350 nm.

9. A tin-doped amorphous gallium oxide thin film, characterized by: A tin-doped amorphous gallium oxide film is prepared by the preparation method of claim 1.

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