An apparatus and a preparation method for realizing high-efficiency phosphorus-doped diamond thin film

Abstract

The utility model provides a device for realizing high -efficient phosphorus doped diamond film preparation, including reaction chamber and gas input system, be equipped with for doped growth's sample support and diamond substrate in reaction chamber, the sample support is inclined, and be equipped with the recess of containing diamond substrate on sample support, gas input system includes first pipeline and second pipeline, first pipeline is located in the top of reaction chamber, second pipeline is located in sample support one side, second pipeline can be located in the bottom center of sample support, and it is round hole structure, the reaction chamber and gas input system provided by the utility model can effectively improve the problem of low phosphorus doped diamond efficiency and MPCVD chamber impurity contamination, and the utility model discloses high doping efficiency, good repeatability, high quality, fast growth speed, and the uniformity of the phosphorus doped diamond film is improved by the design of the inclined sample support, which is of great significance for n-type doping of diamond.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diamond thin film, and particularly relates to a device for realizing high-efficiency phosphorus-doped diamond thin film and a preparation method. BACKGROUND

[0002] Semiconductor diamond materials are expected to be potential materials for high-performance electronic devices, such as high-sensitivity ultraviolet (UV) light detectors, UV light-emitting diodes and high-efficiency electron emitters, due to their physical properties such as super-wide band gap, high carrier mobility and high breakdown voltage.

[0003] However, there are a series of challenges in the application of diamond in active electronic devices, one of the most limiting factors being the lack of n-type shallow donor doping in diamond.

[0004] CN2018101803848 A method and device for removing hydrogen impurities in the preparation process of n-type phosphorus-doped diamond thin film. A femtosecond laser and a temperature field are applied simultaneously in the preparation process of n-type phosphorus-doped diamond thin film. The femtosecond laser only excites the phosphorus-hydrogen bond valence electron in the n-type phosphorus-doped diamond thin film to the excited state. The temperature field only breaks the phosphorus-hydrogen bond whose valence electron is excited to the excited state. Thus, the hydrogen element in the thin film is removed. By applying a femtosecond laser and a temperature field in the preparation process of n-type phosphorus-doped diamond thin film, the phosphorus-hydrogen bond in the n-type phosphorus-doped diamond thin film is broken, and the hydrogen element in the thin film is removed, thereby improving the electrical properties of the n-type phosphorus-doped diamond. The efficiency of growth and doping needs to be increased.

[0005] CN2015101512637 An n-type nano-diamond thin film / p-type monocrystalline silicon heterojunction pn junction prototype device and a preparation method thereof. A nano-diamond thin film is prepared on a p-type (100) monocrystalline silicon substrate by a hot-wire chemical vapor deposition method. Phosphorus ions are injected into the nano-diamond thin film by an ion implantation method. The obtained heterojunction is annealed at a temperature of 800-1000℃ for 10-50 minutes under a low-pressure environment. Then, a titanium / gold electrode is deposited on one side of the nano-diamond thin film and vacuum annealed. An indium electrode is made on the other side of the p-type monocrystalline silicon, thereby obtaining the n-type nano-diamond thin film / p-type monocrystalline silicon heterojunction pn junction prototype device.

[0006] In recent years, researchers have mainly focused on the doping of nitrogen, phosphorus and sulfur, among which phosphorus-doped diamond has been reported to show n-type. However, due to the fact that the radius of phosphorus atom is larger than that of carbon atom, it is difficult for phosphorus to be integrated into the diamond lattice, and the doping efficiency of phosphorus-doped diamond is low, about 0.1%-3%, and the ionization energy is 0.6eV, which makes it difficult to be applied at room temperature. In addition, the internal structure of the traditional MPCVD system, the limitation of the gas flow transportation and other equipment, such as the excessive decomposition of the doping gas by high-temperature plasma, will also lead to low utilization rate of the doping gas. The present application further improves the reaction chamber and the gas input system to improve the efficiency and quality of phosphorus-doped diamond on the basis of the application of double-gas pipeline (a high-efficiency doping HFCVD device based on double-gas flow, CN 2022114279749) for the growth of gas by the inventors' research group. SUMMARY

[0007] In view of the problems existing in the prior art, the present application provides a device and a preparation method for realizing high-efficiency phosphorus-doped diamond thin film, which solves the problem of low efficiency of phosphorus-doped diamond in traditional MPCVD (microwave plasma chemical vapor deposition method) by designing the reaction chamber and the gas input system and improving the preparation method.

[0008] The present application adopts the following technical solution to solve the above technical problems: a device for realizing high-efficiency phosphorus-doped diamond thin film preparation, comprising a reaction chamber and a gas input system, prepared in an MPCVD system, wherein the reaction chamber is provided with a sample holder for doping growth and a diamond substrate, the sample holder is in an inclined shape, and the sample holder is provided with a groove for accommodating the diamond substrate, the gas input system comprises a first pipeline and a second pipeline, the first pipeline is located at the top of the reaction chamber, and the second pipeline is located at one side of the sample holder. The second pipeline can be located at the center of the bottom of the sample holder in a circular hole structure; the second pipeline is located at the center of the bottom of the sample holder, and the center of the sample holder is provided with a through hole for radiating doping gas to the periphery of the sample holder. In the MPCVD system, the microwave module is composed of a microwave source, a waveguide and a mode conversion antenna, the microwave source is used to form a 2.4GHz microwave required for reaction, the waveguide is used for microwave conduction to introduce the microwave into the reaction chamber, and the mode conversion antenna is used to convert the TM mode microwave generated by the microwave source into the TE mode microwave required for deposition reaction. MPCVD system refers to microwave plasma chemical vapor deposition.

[0009] The second pipeline can also be placed at the outer periphery of the sample holder in a circular ring structure, and radiate doping gas to the center of the sample holder. The cross-sectional structure of the reaction chamber is as shown in Figure 1

[0010] ​Further, the sample holder bottom is provided with a substrate support. The sample holder can be made of molybdenum or stainless steel, and the sample holder is cylindrical, and the thickness of the sample holder is not more than 7 mm, and the diameter is between 6 mm and 9 mm, so as to facilitate the control of the coupling and spatial distribution of the plasma ball, as shown in Figure 2 .

[0011] Further, the center of the sample holder is lower than the edge in the vertical height, and the plane of the center and the edge is inclined to the horizontal plane at an angle of 0-45 degrees, so as to facilitate the contact between the diamond substrate and the plasma ball, and realize the high doping and uniformity of the doping distribution of the diamond film.

[0012] Further, the diameter of the center through hole of the sample holder is less than 2 mm, so as to facilitate the realization of the jet delivery of the gas, thereby delivering the growth gas and the doping gas to the sample surface, and avoiding the influence of the excessive aperture on the plasma and the resulting gas dispersion.

[0013] Further, the shape of the surface groove of the sample holder can be square, triangular, rhombic, etc., and the area size and depth can be adjusted according to the actual diamond substrate size.

[0014] Further, the distance between the center through hole and the groove of the sample holder is between 0.5-2 mm, so as to ensure that the diamond substrate is within the range of the plasma coverage, thereby realizing the doping growth of the diamond.

[0015] Further, the first pipeline is located near the top of the reaction chamber, and the gas is uniformly transported to the diamond surface through the circular ring above the reaction chamber.

[0016] Further, the second pipeline is located at the center of the bottom of the sample holder, and is in a circular hole structure, and the reaction gas can be radiated from the center to the periphery, as shown in Figure 3

[0017] Further, the horizontal height of the second pipeline and the substrate support are basically consistent, and the height difference is within 0.5 cm, so as to facilitate the control of the spatial relationship between the reaction gas and the plasma ball, realize the uniform distribution of the gas on the diamond surface, and reasonably control the energy of the reaction group.

[0018] Further, the second pipeline can also be located at the outer peripheral side of the sample holder, and is in a circular ring structure, which can be placed close to the sample holder and radiate the doping gas to the center of the sample holder, as shown in Figure 4

[0019] Further, a plurality of small holes are opened on the second pipeline, and the number is between 8 and 72, so as to obtain the uniform distribution of the reactants and dopants on the diamond substrate.

[0020] ​​The method for preparing the high-efficiency phosphorus-doped diamond film comprises the following steps: preparing in an MPCVD system, selecting a sample holder with a certain specification, placing a diamond substrate in a groove, and extracting vacuum in a reaction chamber; inputting a certain amount of H2 into a first pipeline to pretreat the diamond substrate; when the temperature of the diamond substrate is 600±30 DEG C, the time is 10-60 min; the temperature of the diamond substrate is adjusted by the power of the plasma ball and the H2 pressure;

[0021] During the process of phosphorus-doped diamond film, carbon-containing gas and doping gas are input from the second pipeline, and the H2 input of the first pipeline is maintained; during the process of phosphorus-doped diamond film, the hydrogen flow is generally controlled at 200 sccm to 5000 sccm, so as to ensure the ignition of plasma in the reaction chamber and the surface control effect in the diamond growth process;

[0022] During the process of phosphorus-doped diamond film, the flow of carbon-containing gas and doping gas is generally 1 sccm to 80 sccm; during the process of phosphorus-doped diamond film, the carbon-containing gas includes but is not limited to methane, ethane and acetylene, etc., the doping gas types include but are not limited to phosphine, nitrogen, hydrogen sulfide, borane, etc., and the doping gas is generally diluted in high-purity hydrogen or argon, and the dilution concentration is between 2 ppm and 3000 ppm; during the process of phosphorus-doped diamond film, the growth temperature of the diamond substrate is 750-1000 DEG C.

[0023] Compared with the prior art, the method has the advantages that the device and the preparation method for realizing high-efficiency phosphorus-doped diamond film can effectively deliver carbon-containing gas and doping gas to the surface of the diamond substrate, improve the growth rate and the doping efficiency of the film, realize high-efficiency phosphorus doping of the diamond film, and provide a preparation method for high-efficiency phosphorus-doped diamond, which utilizes the microwave plasma chemical vapor deposition technology, improves the original reaction chamber and the gas input mode in combination with the actual distribution structure of plasma in the reaction chamber, and realizes high-efficiency phosphorus-doped diamond film. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Figure of the sample holder geometry for the MPCVD reactor of the present invention;

[0025] Figure 2 Figure of the sample holder geometry for the MPCVD reactor of the present invention;

[0026] Figure 3 Figure of the structure of the second tube located at the center of the substrate holder;

[0027] Figure 4 Figure of the structure of the second tube located at the periphery of the substrate holder;

[0028] Figure 5 Figure of the secondary ion mass spectrum of the 0°, 15°, 30° phosphorus doped diamond film of the present invention;

[0029] Figure 6 Figure of the Raman scattering spectrum of the 0°, 15°, 30° phosphorus doped diamond film of the present invention. DETAILED DESCRIPTION

[0030] The embodiments of the present invention will be described in further detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments, and the described embodiments are only used to illustrate the present invention, rather than limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention.

[0031] In the figure: 1, sample holder; 2, through hole at the center of the sample holder; 3, groove; 4, diamond substrate; 5, substrate holder; 6, first tube; 7, plasma ball; 8, second tube. The microwave enters the sample holder in the reaction chamber through the quartz window.

[0032] The MPCVD profile structure in the present invention is shown in the figure. Figure 1 The sample holder structure in the present invention is shown in the figure. Figure 2 The doping technology for realizing high-efficiency phosphorus doped diamond film includes a sample holder 1, the sample holder 1 is provided with different inclination angles, and a through hole 2 is arranged at the center of the sample holder 1, and a groove 3 is arranged on the surface of the sample holder 1. The first tube 6 is located at the top of the reaction chamber, and uniformly delivers the reaction gas into the reaction formula. The second tube 8 can be placed at the center of the holder 5, in a circular hole structure, as shown in the figure. Figure 3 The second tube 8 can also be placed at the periphery of the holder 5, in a circular ring structure, as shown in the figure. Figure 4

[0033] Example 1: Growth of phosphorus doped diamond film by using 0-degree inclined sample holder

[0034] ​Step 1: After cleaning, place the diamond substrate 4 (3mm×3mm×1mm) on the groove 3 of the sample holder 1 (0-degree tilt angle) and place the sample holder 1 on the substrate support 5.

[0035] Step two: The reaction chamber is evacuated using a mechanical pump and a molecular pump until the background vacuum level reaches 10. -4 At a pressure of 500 sccm, high-purity H2 is introduced into the reaction chamber through the first pipeline 6. The temperature of the diamond substrate is regulated by the power and pressure of the plasma ball 7. When the diamond substrate temperature is 600℃, the power is 3600W and the pressure is 18000Pa, and the diamond substrate is pretreated for 20 minutes.

[0036] Step 3: Continue to adjust the power and pressure of plasma ball 7. When the temperature is 850℃, simultaneously input 5 sccm CH4 and 5 sccm PH3 from the second pipe 8, and keep 500 sccm H2 input from the first pipe 6. The diamond film growth time is 1 hour.

[0037] According to this embodiment of the invention, the growth rate of phosphorus-doped diamond thin films grown using a 0-degree tilted sample holder is 3 μm / h, and the phosphorus doping concentration is 5.2 × 10⁻⁶. 15 cm -3 ,like Figure 5 As shown. Raman half-height width as Figure 6 As shown, the half-height width is 2.22cm. -1 The film is of very high quality.

[0038] Example 2: Growth of phosphorus-doped diamond thin films using a 15-degree tilted sample holder

[0039] The difference from Example 1 is that the sample holder in this example is tilted at a 15-degree angle for growing phosphorus-doped diamond films. In this example, the growth rate of the phosphorus-doped diamond film is 4 μm / h, and the phosphorus doping concentration is 5.4 × 10⁻⁶. 17 cm -3 ,like Figure 5 As shown. Compared with Example 1, the phosphorus doping concentration was significantly improved, by more than two orders of magnitude. Raman spectroscopy showed that the crystal quality of the sample prepared in this example was comparable to that of Example 1. However, under the conditions of this example, the film deposition rate was faster and the doping concentration was greatly increased.

[0040] Example 3: Growth of phosphorus-doped diamond thin films using a 30-degree tilted sample holder

[0041] The difference between this embodiment and Embodiments 1 and 2 is that the sample holder in this embodiment uses a larger tilt angle for the growth of phosphorus-doped diamond films, with a tilt angle of 30 degrees. In this embodiment, the growth rate of the phosphorus-doped diamond film reaches approximately 6 μm / h, which is twice the rate in Embodiment 1, while the phosphorus doping concentration is higher than 1.3 × 10⁻⁶. 18 cm -3 The phosphorus doping concentration was increased by 1 times compared to Example 2, such as Figure 5 As shown. The Raman full width at half maximum (FWHM) of a phosphorus-doped diamond film grown using a sample holder tilt angle of 30 degrees is shown in the figure. Figure 6 As shown, the half-height width is 2.77cm. -1 .pass Figure 6 It can be seen that the film quality is relatively poor. This indicates that while using a sample holder with a larger tilt angle to grow phosphorus-doped diamond films can improve doping efficiency and growth rate, an excessively fast growth rate may adversely affect the film quality. Therefore, it is necessary to comprehensively consider process conditions and equipment parameters to explore the optimal growth conditions.

[0042] In summary, the apparatus and preparation method for achieving high-efficiency phosphorus-doped diamond thin films proposed in this invention can effectively improve the phosphorus doping concentration and growth rate of diamond thin films, thereby achieving high-efficiency phosphorus-doped diamond thin film growth.

[0043] For those skilled in the art, various corresponding changes and modifications can be made based on the technical solutions and concepts described in this invention, and all such changes and modifications fall within the protection scope of the claims of this invention.

Claims

1. A method for preparing highly efficient phosphorus-doped diamond thin films, characterized in that: The sample is prepared in an MPCVD system, which includes a reaction chamber and a gas input system. The reaction chamber is provided with a sample holder for doping growth and a diamond substrate. The sample holder is inclined and has a groove to accommodate the diamond substrate. The gas input system includes a first pipeline and a second pipeline. The first pipeline is located at the top of the reaction chamber and the second pipeline is located on one side of the sample holder. The second conduit can be located at the center of the bottom of the sample holder and has a circular hole structure; The second conduit is located at the center of the bottom of the sample holder, and the center of the sample holder is provided with a through hole that cooperates with the second conduit to radiate doped gas to the surrounding area of ​​the sample holder; The sample holder is positioned so that its center is lower than its edge in vertical height, and the plane between the center and the edge forms a 15-degree angle with the horizontal plane. This facilitates contact between the diamond substrate and the plasma sphere, thereby achieving high doping and uniform doping distribution in the diamond film. The preparation method is as follows: A sample holder is selected, and the diamond substrate is placed in the groove of the sample holder. The reaction chamber is then evacuated. A certain amount of H2 is introduced into the first pipeline to pretreat the diamond substrate. The diamond substrate temperature is 600±30℃ for 10-60 minutes. The temperature of the diamond substrate is adjusted by the power of the plasma ball and the H2 pressure. During the phosphorus-doped diamond film process, carbon-containing gas and dopant gas are introduced into the second pipeline while maintaining the H2 input in the first pipeline. The hydrogen flow rate is controlled between 200 sccm and 5000 sccm during the phosphorus-doped diamond film process to ensure the ignition of the plasma in the reaction chamber and the surface control effect during the diamond growth process. The flow rates of carbon-containing gas and dopant gas during the phosphorus-doped diamond film process range from 1 sccm to 80 sccm. The carbon-containing gas in the process includes methane, ethane, and acetylene, while the dopant gas includes phosphine, nitrogen, hydrogen sulfide, and borane. The dopant gas is diluted in high-purity hydrogen or argon, with a dilution concentration ranging from 2 ppm to 3000 ppm. The growth temperature of the diamond substrate during the phosphorus-doped diamond film process is 750-1000℃.

2. The preparation method according to claim 1, characterized in that: The second conduit can also be placed on the outer periphery of the sample holder, forming a circular structure, and located on the outer periphery of the sample holder, radiating doped gas towards the center of the sample holder.

3. The preparation method according to claim 1, characterized in that: The second conduit has a circular structure and is located on the outer periphery of the sample holder, radiating doped gas toward the center of the sample holder.

4. The preparation method according to claim 1, characterized in that: The sample holder has a substrate support at the bottom; the sample holder is made of molybdenum or stainless steel.

5. The preparation method according to claim 1, characterized in that: The sample holder is cylindrical, with a thickness not exceeding 7 mm and a diameter between 6 mm and 9 mm, to facilitate control of the coupling and spatial distribution of the plasma spheres.

6. The preparation method according to claim 2, characterized in that: The diameter of the through hole in the sample is less than 2 mm.

7. The preparation method according to claim 2, characterized in that: The distance between the sample support hole and the groove is between 0.5 and 2 mm.

8. The preparation method according to claim 1, characterized in that: Adjust the power and pressure of the plasma ball. When the temperature is 850℃, simultaneously input 5 sccm of CH4 and 5 sccm of PH3 from the second pipeline, and keep 500 sccm of H2 input from the first pipeline. The diamond film growth time is 1 hour.

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