Fluorine-doped metal oxide film and preparation method and application thereof

Abstract

The invention relates to a fluorine-doped metal oxide film and a preparation method and application thereof, and belongs to the technical field of materials. The method comprises the steps that a cleaned substrate and a cleaned metal wire are fixed in a cavity of a hot filament chemical vapor deposition (CVD) device, the metal wire is located below the substrate in the cavity, and after the cavity is vacuumized, the metal wire is electrified and preheated; the preheated metal wire is continuously electrified and heated, meanwhile, mixed gas is continuously introduced into the cavity, a layer of fluorine-doped metal oxide film is deposited on the surface of the substrate, and the mixed gas comprises fluorine-containing gas and oxygen. According to the method, the safety and feasibility of fluorine doping can be greatly improved while the original low-temperature performance of the material is not influenced.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a fluorine-doped metal oxide film and a preparation method and application thereof. Background Art

[0002] As functional materials, metal oxides have been widely used in the fields of solar cells, electrolytic materials, catalysts, etc. Fluorine doping modification of metal oxides is one of the current research hotspots. Existing technologies usually use high-temperature solid-phase method and spray pyrolysis method to prepare fluorine-doped metal oxides, but these methods require high temperatures and are not suitable for fluorine doping modification of metal oxides that are not resistant to high temperatures or are easily denatured at high temperatures. For example, at high temperatures, the work function of molybdenum oxide will decrease, the oxygen vacancy content will increase, etc. Directly using fluorine gas doping at low temperatures has great safety risks.

[0003] Therefore, it is very necessary to improve the preparation method of fluorine-doped metal oxide films. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a fluorine-doped metal oxide film and a preparation method and application thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides a method for preparing a fluorine-doped metal oxide thin film, comprising the following steps:

[0007] S1, cleaning the substrate;

[0008] S2, fixing the cleaned substrate and the metal wire in the chamber of a hot wire CVD device respectively, wherein the metal wire is located below the substrate in the chamber, evacuating the chamber, and then energizing the metal wire for preheating;

[0009] S3, continuing to electrically heat the preheated metal wire, and continuously introducing a mixed gas into the chamber to deposit a fluorine-doped metal oxide film on the surface of the substrate, wherein the mixed gas includes a fluorine-containing gas and oxygen.

[0010] In the present invention, a mixed gas is introduced during the process of heating the metal wire by electricity, oxygen in the mixed gas undergoes an oxidation-reduction reaction with the metal wire to generate metal oxide, carbon tetrafluoride in the mixed gas undergoes a cracking reaction at high temperature to release fluorine, and the released fluorine is doped into the generated metal oxide and sublimates and deposits on the substrate together with the metal oxide to form a fluorine-doped metal oxide film. The method of the present invention can greatly improve the safety and feasibility of fluorine doping without affecting the original low-temperature performance of the material.

[0011] Preferably, in step S1, the substrate is a silicon wafer.

[0012] Preferably, in step S2, the metal wire includes any one of tungsten wire, molybdenum wire and tantalum wire, and the diameter of the metal wire is 1 to 5 mm.

[0013] Preferably, in step S2, the pressure of the chamber after evacuation is no more than 0.1 Pa, and the temperature of the metal wire after being powered on and preheated is 900-1000°C.

[0014] Preferably, in step S3, the electrical heating includes: heating the preheated metal wire to 1000-1500° C. within 5-20 minutes and then keeping the temperature.

[0015] The present invention controls the temperature of the metal wire in step S3 within the range of 1000-1500° C., which can prevent the metal wire from melting and ensure that the generated metal oxide can sublime quickly.

[0016] Preferably, in step S3, the partial pressure of the oxygen is P1, the partial pressure of the fluorine-containing gas is P2, the total pressure of the mixed gas is P, and P1, P2 and P satisfy the following conditions:

[0017] (1)0.4≤P1 / P≤0.7; (2)0.1≤P2 / P≤0.4; (3)0.5≤(P1+P2) / P≤1.

[0018] Further preferably, P1, P2 and P satisfy the following conditions:

[0019] (1) 0.6≤P1 / P≤0.7; (2) 0.2≤P2 / P≤0.3.

[0020] The present invention controls the deposition rate of the fluorine-doped metal oxide film and the fluorine content in the fluorine-doped metal oxide film by controlling the flow rate of the fluorine-containing gas, the partial pressure ratio of each gas in the mixed gas and other parameters, thereby controlling the contact resistance between the fluorine-doped metal oxide film and the substrate and the resistivity of the fluorine-doped metal oxide film, which is beneficial to expanding the application scope of the fluorine-doped metal oxide film, so that the fluorine-doped metal oxide film can be used as a hole transport layer, a sacrificial layer or an insulating layer in solar cells, can also be used as an electrode material in ion batteries, and can also be used as a catalyst material in catalytic reaction processes.

[0021] The inventors have found that by controlling P1 / P within the range of 0.4 to 0.7, P2 / P within the range of 0.1 to 0.4, and (P1+P2) / P within the range of 0.5 to 1, the passivation level of the fluorine-doped metal oxide film can be improved while ensuring the deposition rate of the film. If P1 / P>0.7, the oxygen content in the mixed gas is continuously increased, resulting in a significantly greater risk of the chemical reaction process in the chamber, while the passivation level of the fluorine-doped metal oxide film does not change significantly.

[0022] Preferably, the flow rate of the mixed gas is 20 to 300 sccm, more preferably 80 to 150 sccm.

[0023] The inventors have found that when the content of each gas in the mixed gas (i.e., the partial pressure ratio) is fixed, controlling the flow rate of the mixed gas to 80-150 sccm can improve the passivation level of the fluorine-doped metal oxide film while ensuring the deposition rate of the fluorine-doped metal oxide film.

[0024] Preferably, in step S3, the fluorine-containing gas includes at least one of carbon tetrafluoride, trifluoromethane and tetrafluoroethane.

[0025] Preferably, in step S3, the mixed gas further includes an inert gas, and the inert gas includes at least one of argon and nitrogen.

[0026] Preferably, in step S3, the air pressure of the chamber is 10-20Pa.

[0027] Preferably, in step S3, the substrate is rotated at a speed of 5 to 20 rad / min while the mixed gas is introduced. Rotating the substrate during the sublimation deposition process can improve the thickness uniformity of the fluorine-doped metal oxide film.

[0028] In a second aspect, the present invention provides a fluorine-doped metal oxide film, which is prepared by the preparation method described in the first aspect.

[0029] In a third aspect, the present invention provides a use of the fluorine-doped metal oxide film as described in the second aspect as a hole transport layer in the preparation of a solar cell.

[0030] In a fourth aspect, the present invention provides a use of the fluorine-doped metal oxide film as described in the second aspect as an electrode material in the preparation of an ion battery.

[0031] In a fifth aspect, the present invention provides a use of the fluorine-doped metal oxide film as described in the second aspect in preparing a catalyst.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] In the present invention, a mixed gas is introduced during the process of heating the metal wire by electricity, oxygen in the mixed gas undergoes an oxidation-reduction reaction with the metal wire to generate metal oxide, carbon tetrafluoride in the mixed gas undergoes a cracking reaction at high temperature to release fluorine, and the released fluorine is doped into the generated metal oxide and sublimates and deposits on a substrate together with the oxide to form a fluorine-doped metal oxide film. The method of the present invention can achieve fluorine doping without affecting the original low-temperature performance of the material, thereby greatly improving the safety and feasibility of fluorine doping. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the preparation principle of the fluorine-doped metal oxide provided by the present invention;

[0035] Figure 2 This is a diagram showing the SEM morphology, EDS spectrum analysis, and element content analysis results of the fluorine-doped metal oxide film provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0037] The temperature of the molybdenum wire in the following examples is measured by contacting the edge of the molybdenum wire with a thermocouple.

[0038] A fluorine-doped metal oxide film with a thickness of 50 nm was formed on a silicon wafer using the following examples and comparative examples, and then tested:

[0039] (1) Perform SEM morphology test, EDS spectrum analysis and element content analysis on each fluorine-doped metal oxide film;

[0040] (2) Passivation level: The Sinton minority carrier lifetime tester is used for testing. The implicit open circuit voltage level represents the passivation level of the film layer.

[0041] (3) Contact resistance between fluorine-doped metal oxide film and silicon wafer: TLM method is used to test contact resistance, four-wire method is used to eliminate wire resistance, and KEITHLEY 2400 source meter is used to collect current and voltage information;

[0042] (4) Intrinsic resistivity of fluorine-doped metal oxide film, the test method is: using KEITHLEY 2400 source meter to collect current and voltage information, and testing the film resistance by two-wire method;

[0043] (5) Deposition rate: A crystal oscillator film thickness meter is used for testing. The thickness of the film layer is measured by the change in vibration frequency caused by the deposition of the film layer on the crystal oscillator. The deposition rate is calculated according to the following formula: Deposition rate = film thickness / deposition time.

[0044] Examples 1 to 11

[0045] The fluorine-doped metal oxide film and the preparation method thereof according to the present invention are prepared according to the principle of the fluorine-doped metal oxide. Figure 1 As shown, Figure 1 In the figure, 1 is a substrate, 2 is a molybdenum wire; the method for preparing the fluorine-doped metal oxide film comprises the following steps:

[0046] S1. Cleaning silicon wafer (i.e. substrate) using RCA process;

[0047] S2, respectively fixing the cleaned substrate and molybdenum wire in the chamber of a hot wire CVD device, wherein the diameter of the molybdenum wire is 2 mm, the molybdenum wire is located below the substrate in the chamber, the chamber is evacuated, and the molybdenum wire is powered on for preheating under the condition of a vacuum degree of 0.1 Pa until the temperature of the molybdenum wire reaches 900° C.;

[0048] S3, continuing to heat the preheated molybdenum wire with electricity, raising the temperature of the preheated metal wire to 1500° C. within 5 minutes and then keeping the temperature, while continuously introducing a mixed gas into the chamber from the bottom of the chamber to maintain the gas pressure in the chamber at 15 Pa, and depositing a layer of fluorine-doped metal oxide film on the surface of the substrate;

[0049] The mixed gas is a mixture of carbon tetrafluoride, oxygen and argon, the partial pressure of the oxygen is P1, the partial pressure of the carbon tetrafluoride is P2, and the partial pressure of the argon is P3;

[0050] In step S3, the substrate is rotated at a speed of 10 rad / min while the mixed gas is introduced.

[0051] The partial pressure ratio P1:P2:P3 and the flow rate of the mixed gas in Examples 1 to 11 are shown in Table 1.

[0052] The energy spectrum analysis results of the fluorine-doped metal oxide thin films obtained in Examples 1 to 11 show that the prepared thin films are fluorine-doped metal molybdenum oxide thin films, and no carbon impurity elements are introduced during the preparation process.

[0053] The test results of implicit open circuit voltage, contact resistance and intrinsic resistivity are shown in Table 1.

[0054] Table 1

[0055]

[0056] It can be seen from Table 1 that the contact resistance between the fluorine-doped metal oxide film and the silicon wafer in each embodiment is extremely small (less than 100 mΩ·cm 2), the intrinsic resistivity of the fluorine-doped metal oxide film of each embodiment is extremely large, and the influence of the change of the contact resistance and intrinsic resistivity of each embodiment on the performance of the solar cell is almost negligible.

[0057] It can be seen from Examples 1 to 4 that when the ratio of the partial pressure of oxygen to the total pressure of the mixed gas is 0.6 to 0.8, a higher deposition rate can be ensured and a higher implicit open circuit voltage can be obtained, and the passivation level of the fluorine-doped metal oxide film is higher.

[0058] It can be seen from Examples 3 and 5 to 8 that when the ratio between the partial pressure of the fluorine-containing gas and the total pressure of the mixed gas is 0.2 to 0.3, the measured implicit open circuit voltage is larger and the passivation level of the fluorine-doped metal oxide film is higher.

[0059] It can be seen from Examples 3 and 9 to 11 that the flow rate of the mixed gas is controlled at 80 to 150 sccm, which can not only ensure a higher deposition rate but also obtain a larger implicit open circuit voltage, and the passivation level of the fluorine-doped metal oxide film is higher.

[0060] Example 12

[0061] The embodiment of the fluorine-doped metal oxide film and the preparation method thereof of the present invention comprises the following steps:

[0062] S1. Cleaning silicon wafer (i.e. substrate) using RCA process;

[0063] S2, fix the cleaned substrate and tungsten wire in the chamber of the hot wire CVD device respectively, the diameter of the tungsten wire is 2 mm, the tungsten wire is located below the substrate in the chamber, the chamber is evacuated, and the tungsten wire is powered on for preheating under the condition of a vacuum degree of 0.1 Pa until the temperature of the tungsten wire reaches 1000° C.;

[0064] S3, continuing to electrically heat the preheated tungsten wire, raising the temperature of the preheated metal wire to 1300° C. within 5 minutes and then keeping the temperature, while continuously introducing a mixed gas into the chamber from the bottom of the chamber to maintain the gas pressure in the chamber at 10 Pa, and depositing a fluorine-doped metal oxide film on the surface of the substrate;

[0065] The mixed gas is a mixture of carbon tetrafluoride, oxygen and argon, the partial pressure of the oxygen is P1, the partial pressure of the carbon tetrafluoride is P2, the partial pressure of the argon is P3, the partial pressure ratio P1:P2:P3 and the flow rate of the mixed gas are the same as those in Example 3;

[0066] In step S3, the substrate is rotated at a speed of 5 rad / min while the mixed gas is introduced.

[0067] SEM images and energy spectrum analysis of fluorine-doped metal oxide films Figure 2 As shown, from Figure 2 It can be seen that the present embodiment can prepare a fluorine-doped metal tungsten oxide thin film, wherein the fluorine content is 9.41% and the carbon content is 0, which indicates that the method of the present invention does not introduce carbon impurity elements during the preparation process.

[0068] The implicit open circuit voltage test result is 650.2mV;

[0069] The contact resistance between the fluorine-doped metal oxide film obtained in this example and the silicon wafer is 59.7 mΩ·cm 2 ;

[0070] The intrinsic resistivity of the fluorine-doped metal oxide film obtained in this embodiment is 1.68*10 7 Ω·cm.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a fluorine-doped metal oxide thin film, characterized in that: The steps include: S1, cleaning the substrate; S2, fixing the cleaned substrate and the metal wire in the chamber of a hot wire CVD device respectively, wherein the metal wire is located below the substrate in the chamber, evacuating the chamber, and then energizing the metal wire for preheating; S3, continuing to electrically heat the preheated metal wire, and continuously introducing a mixed gas into the chamber to deposit a fluorine-doped metal oxide film on the surface of the substrate, wherein the mixed gas includes a fluorine-containing gas and oxygen.

2. The method for preparing a fluorine-doped metal oxide thin film according to claim 1, characterized in that: In step S2, the metal wire includes any one of tungsten wire, molybdenum wire and tantalum wire.

3. The method for preparing a fluorine-doped metal oxide thin film according to claim 1, characterized in that: In step S2, the pressure of the chamber after evacuation is no more than 0.1 Pa, and the temperature of the metal wire after being powered on and preheated is 900-1000°C.

4. The method for preparing a fluorine-doped metal oxide thin film according to claim 1, characterized in that: In step S3, the gas pressure of the chamber is 10-20 Pa; the partial pressure of the oxygen is P1, the partial pressure of the fluorine-containing gas is P2, the total pressure of the mixed gas is P, and P1, P2 and P satisfy the following conditions: (1)0.4≤P1 / P≤0.7; (2)0.1≤P2 / P≤0.4; (3)0.5≤(P1+P2) / P≤1.

5. The method for preparing a fluorine-doped metal oxide thin film according to claim 1, characterized in that: In step S3, the fluorine-containing gas includes at least one of carbon tetrafluoride, trifluoromethane, and tetrafluoroethane.

6. The method for preparing a fluorine-doped metal oxide thin film according to claim 1, characterized in that: In step S3, the substrate is rotated at a speed of 5-20 rad / min while the mixed gas is introduced.

7. A fluorine-doped metal oxide film, characterized in that: The fluorine-doped metal oxide film is prepared by the method for preparing the fluorine-doped metal oxide film as described in any one of claims 1 to 6.

8. Use of the fluorine-doped metal oxide film as claimed in any one of claims 7 as a hole transport layer, sacrificial layer or insulating layer in the preparation of solar cells.

9. Use of the fluorine-doped metal oxide film as claimed in any one of claim 7 as an electrode material in the preparation of an ion battery.

10. Use of the fluorine-doped metal oxide film as claimed in any one of claim 7 in preparing a catalyst.

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