阅读说明：本技术 一种三氧化钨气敏薄膜的制备方法 (Preparation method of tungsten trioxide gas-sensitive film ) 是由 刘皓 徐瑶华 张晓� 赵文瑞 明安杰 于 2020-12-02 设计创作，主要内容包括：本发明公开了一种高灵敏度三氧化钨气敏薄膜的制备方法,涉及气敏薄膜制备技术领域。本发明将带有氧化层的硅基片置于氟化铵、氢氟酸及去离子水的混合溶液中静置一段时间,之后再采用射频掠射角磁控溅射在处理后的硅基片表面沉积三氧化钨薄膜并进行热处理。本发明能够提高在硅基体上沉积的三氧化钨气敏薄膜对二氧化氮的灵敏度,且制备工艺简单,与目前微型气体传感器的制备工艺兼容性高,便于实现硅基集成,适合于工业大规模生产。(The invention discloses a preparation method of a high-sensitivity tungsten trioxide gas-sensitive film, and relates to the technical field of gas-sensitive film preparation. The silicon substrate with the oxide layer is placed in a mixed solution of ammonium fluoride, hydrofluoric acid and deionized water to stand for a period of time, and then a tungsten trioxide film is deposited on the surface of the treated silicon substrate by adopting radio frequency glancing angle magnetron sputtering and is subjected to heat treatment. The method can improve the sensitivity of the tungsten trioxide gas-sensitive film deposited on the silicon substrate to nitrogen dioxide, has simple preparation process, high compatibility with the preparation process of the existing micro gas sensor, is convenient for realizing silicon-based integration, and is suitable for industrial large-scale production.)

1. A preparation method of a tungsten trioxide gas-sensitive film is characterized by comprising the following steps:

(1) placing the silicon substrate with the oxide layer in a mixed solution of ammonium fluoride, hydrofluoric acid and deionized water for standing for a period of time, ultrasonically cleaning the silicon substrate after standing in the deionized water, and then drying by using nitrogen;

(2) depositing a tungsten trioxide film on the surface of the silicon substrate obtained in the step (1) by adopting a grazing angle magnetron sputtering by taking tungsten trioxide as a target material and argon as a working gas;

(3) and (3) placing the tungsten trioxide film obtained in the step (2) in a muffle furnace for heat treatment.

2. The production method according to claim 1, wherein the oxide layer thickness of the silicon substrate in the step (1) is 500nm to 2000 nm.

3. The preparation method according to claim 1, wherein the mass percent of the ammonium fluoride in the mixed solution in the step (1) is 15 to 20%, and the mass percent of the hydrofluoric acid is 1 to 3%.

4. The preparation method according to claim 1, wherein the standing time in the step (1) is 5-10 min, the temperature of the mixed solution is 5-15 ℃ during standing, and the ultrasonic cleaning time is 10-15 min.

5. The preparation method according to claim 1, wherein in the step (2), a grazing angle formed between the normal of the silicon substrate plane and the normal of the target plane is 75-85 °, a sputtering pressure is 0.1-0.5 Pa, a sputtering power is 50-200W, and a sputtering time is 10-60 min.

6. The preparation method according to claim 1, wherein the heat treatment temperature in the step (3) is 400-500 ℃ and the heat treatment time is 1-4 h.

Technical Field

The invention relates to a preparation method of a gas-sensitive film, in particular to a preparation method of a high-sensitivity tungsten trioxide gas-sensitive film.

Background

Nitrogen dioxide is a common atmospheric pollutant, is one of main substances forming acid rain and photochemical smog, and can cause great damage to human bodies after being exposed to nitrogen dioxide environment with the concentration of 0.1ppm or even lower for a long time. With the development of modern industry, nitrogen dioxide emitted during the combustion of various fossil fuels and industrial production processes gradually becomes the key point of environmental governance, and nitrogen dioxide gas sensors become more important. Therefore, the method has important significance and development prospect for the research of the nitrogen dioxide gas-sensitive material.

Tungsten trioxide is often used as a sensitive material of a nitrogen dioxide semiconductor sensor due to its high sensitivity to nitrogen dioxide. The traditional industrial production generally adopts a chemical synthesis process to prepare a powdery gas-sensitive material, but with the development of a gas sensor to the field of Micro Electro Mechanical Systems (MEMS), the disadvantage of poor compatibility of the preparation of the gas-sensitive powder and the MEMS process is more obvious. At present, the MEMS gas sensor chip generally adopts a silicon substrate with an oxide layer on the surface, and adopts methods such as magnetron sputtering and the like to grow a tungsten trioxide film in situ on the silicon substrate, so that the problem of process compatibility can be solved, and the defect of higher working temperature of gas-sensitive powder can be overcome more easily, thereby having great research value. However, the film prepared on the silicon substrate by adopting the conventional magnetron sputtering is compact and is difficult to meet the characteristics of porosity and large specific surface area of the gas sensitive material, so that the gas sensitive performance such as sensitivity is low, and the prepared gas sensitive film has excellent performance, but the process is complex, the cost is high and the method is not suitable for industrial large-scale production by adopting auxiliary methods such as anodic oxidation and the like disclosed in CN 105803502B. Therefore, how to prepare the tungsten trioxide gas-sensitive film with high sensitivity by adopting magnetron sputtering compatible with the MEMS process still needs further research.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the preparation method of the high-sensitivity tungsten trioxide gas-sensitive film, which is convenient for realizing silicon-based integration and is suitable for industrial large-scale production.

The invention is realized by the following technical scheme.

A preparation method of a tungsten trioxide gas-sensitive film is characterized by comprising the following steps:

(1) placing the silicon substrate with the oxide layer in a mixed solution of ammonium fluoride, hydrofluoric acid and deionized water for standing for a period of time, ultrasonically cleaning the silicon substrate after standing in the deionized water, and then drying by using nitrogen;

(2) depositing a tungsten trioxide film on the surface of the silicon substrate obtained in the step (1) by adopting a grazing angle magnetron sputtering by taking tungsten trioxide as a target material and argon as a working gas;

(3) and (3) placing the tungsten trioxide film obtained in the step (2) in a muffle furnace for heat treatment.

Preferably, the thickness of the oxide layer (which is silicon oxide) of the silicon substrate in the step (1) is 500nm to 2000 nm.

Preferably, the mass percent of the ammonium fluoride in the mixed solution in the step (1) is 15-20%, and the mass percent of the hydrofluoric acid is 1-3%.

Preferably, the standing time in the step (1) is 5-10 min, the temperature of the mixed solution is 5-15 ℃ during standing, and the ultrasonic cleaning time is 10-15 min.

Preferably, in the step (2), a grazing angle formed between the normal of the silicon substrate plane and the normal of the target plane is 75-85 degrees, the sputtering pressure is 0.1-0.5 Pa, the sputtering power is 50-200W, and the sputtering time is 10-60 min.

Preferably, the heat treatment temperature in the step (3) is 400-500 ℃, and the heat treatment time is 1-4 h.

The invention has the beneficial technical effects that:

(1) according to the invention, the silicon substrate is pretreated to increase the surface roughness, so that the surface roughness of the tungsten trioxide gas-sensitive film deposited on the silicon substrate can be improved, and the sensitivity of the tungsten trioxide gas-sensitive film to nitrogen dioxide is enhanced.

(2) According to the invention, the tungsten trioxide gas-sensitive film is prepared by adopting glancing angle magnetron sputtering, the specific surface area of tungsten trioxide is further improved by the shadow effect in the glancing angle deposition process, and the sensitivity of the tungsten trioxide gas-sensitive film to nitrogen dioxide is enhanced.

(3) The preparation method of the gas-sensitive film adopted by the invention has simple process and high compatibility with the MEMS process, is convenient for realizing silicon-based integration, and is suitable for industrial large-scale production.

Drawings

FIG. 1 shows WO prepared in example 1 and comparative example₃Response curve of the film to 1ppm nitrogen dioxide at 150 ℃. Wherein #1 is WO prepared in example 1₃Film, #2 WO prepared in comparative example₃A film.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example 1

(1) Placing a silicon substrate with the thickness of 1000nm in a mixed solution of ammonium fluoride, hydrofluoric acid and deionized water, standing for a period of time, wherein the mass percent of the ammonium fluoride in the mixed solution is 17%, the mass percent of the hydrofluoric acid is 1.5%, the standing time is 8min, the temperature of the mixed solution is 10 ℃ during standing, ultrasonically cleaning the silicon substrate after standing in the deionized water for 10min, and then drying by using nitrogen;

(2) taking tungsten trioxide with the mass purity of 99.95% as a target material, taking argon with the mass purity of 99.999% as a working gas, and adopting a grazing angle magnetron sputtering to deposit a tungsten trioxide thin film on the surface of the processed silicon substrate, wherein the grazing angle is 82 degrees, the sputtering pressure is 0.2Pa, the sputtering power is 100W, and the sputtering time is 30 min;

(3) and (3) placing the prepared tungsten trioxide thin film in a muffle furnace for heat treatment at the temperature of 500 ℃ for 1h, and naturally cooling to room temperature after the heat treatment is finished to obtain the high-sensitivity tungsten trioxide gas-sensitive thin film with the number of # 1.

The response curve of the #1 gas-sensitive film prepared in example 1 to 1ppm nitrogen dioxide gas at the operating temperature of 150 ℃ is shown in fig. 1, and the sensitivity S to 1ppm nitrogen dioxide is 6.42.

Example 2

(1) Placing a silicon substrate with the thickness of 500nm in a mixed solution of ammonium fluoride, hydrofluoric acid and deionized water, standing for a period of time, wherein the mass percent of the ammonium fluoride in the mixed solution is 20%, the mass percent of the hydrofluoric acid is 1%, the standing time is 10min, the temperature of the mixed solution is 5 ℃ during standing, ultrasonically cleaning the silicon substrate after standing in the deionized water for 15min, and then drying by using nitrogen;

(2) taking tungsten trioxide with the mass purity of 99.95% as a target material, taking argon with the mass purity of 99.999% as a working gas, and adopting a grazing angle magnetron sputtering to deposit a tungsten trioxide thin film on the surface of the processed silicon substrate, wherein the grazing angle is 75 degrees, the sputtering pressure is 0.5Pa, the sputtering power is 200W, and the sputtering time is 10 min;

(3) and (3) placing the prepared tungsten trioxide thin film in a muffle furnace for heat treatment at 400 ℃ for 4h, and naturally cooling to room temperature after the heat treatment is finished to obtain the high-sensitivity tungsten trioxide gas-sensitive thin film with the number of # 2.

The response curve of the #2 gas-sensitive film prepared in example 2 to 1ppm nitrogen dioxide gas at the operating temperature of 150 c has a sensitivity S of 5.54 to 1ppm nitrogen dioxide.

Example 3

(1) Placing a silicon substrate with the thickness of 2000nm in a mixed solution of ammonium fluoride, hydrofluoric acid and deionized water, standing for a period of time, wherein the mass percent of the ammonium fluoride in the mixed solution is 15%, the mass percent of the hydrofluoric acid is 3%, the standing time is 5min, the temperature of the mixed solution is 15 ℃ during standing, ultrasonically cleaning the silicon substrate after standing in the deionized water for 12min, and then drying by using nitrogen;

(2) taking tungsten trioxide with the mass purity of 99.95% as a target material, taking argon with the mass purity of 99.999% as a working gas, and adopting a grazing angle magnetron sputtering to deposit a tungsten trioxide thin film on the surface of the processed silicon substrate, wherein the grazing angle is 85 degrees, the sputtering pressure is 0.4Pa, the sputtering power is 50W, and the sputtering time is 60 min;

(3) and (3) placing the prepared tungsten trioxide thin film in a muffle furnace for heat treatment at the temperature of 450 ℃ for 2h, and naturally cooling to room temperature after the heat treatment is finished to obtain the high-sensitivity tungsten trioxide gas-sensitive thin film with the number of # 3.

The response curve of the #3 gas sensitive film prepared in example 3 to 1ppm nitrogen dioxide gas at the operating temperature of 150 c has a sensitivity S of 3.27 to 1ppm nitrogen dioxide.

Comparative example 1

This comparative example differs from example 1 in that: preparing a tungsten trioxide gas-sensitive film with the number of #2 directly through the steps (2) and (3) without pretreating the silicon substrate through the step (1).

The response curve of the #2 gas-sensitive film prepared in comparative example 1 to 1ppm nitrogen dioxide gas at the operating temperature of 150 c is shown in fig. 1, and its sensitivity S to 1ppm nitrogen dioxide is 2.16.

As can be seen from the comparison of the sensitivity of the two gas-sensitive films in FIG. 1, the preparation method of the high-sensitivity tungsten trioxide gas-sensitive film provided by the invention can significantly improve the sensitivity of the tungsten trioxide film to nitrogen dioxide, and the process adopted by the invention is compatible with the MEMS process, so that the silicon-based integration is convenient to realize, and the method is suitable for industrial large-scale production.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention. It should be noted that other equivalent modifications can be made by those skilled in the art in light of the teachings of the present invention, and all such modifications can be made as are within the scope of the present invention.