阅读说明：本技术 一种衬底的预处理方法和金刚石膜的制备方法 (Substrate pretreatment method and diamond film preparation method ) 是由 冯曙光 于金凤 李光存 于 2021-09-10 设计创作，主要内容包括：本发明属于金刚石膜制备领域,公开了一种衬底的预处理方法和金刚石膜的制备方法,包括以下步骤：S1.清洗衬底,然后干燥；S2.将步骤S1所得衬底进行酸液湿法刻蚀；S3.制备金刚石微粉浆料,将金刚石微粉浆料均匀地旋涂在步骤S2刻蚀后的衬底上,得旋涂后的衬底；S4.低温烘干步骤S3旋涂后的衬底；S5.将步骤S4低温烘干后的衬底进行等离子体干法刻蚀,得预处理后的衬底,最后使用上述衬底的预处理方法所得预处理后的衬底沉积金刚石。本发明所述方法提高了金刚石形核的速率、密度与质量,克服了机械研磨和普通超声接种的缺点,有利于高品质金刚石膜的制备。(The invention belongs to the field of preparation of diamond films, and discloses a pretreatment method of a substrate and a preparation method of a diamond film, which comprise the following steps: s1, cleaning a substrate, and then drying; s2, carrying out acid liquor wet etching on the substrate obtained in the step S1; s3, preparing diamond micro powder slurry, and uniformly spin-coating the diamond micro powder slurry on the substrate etched in the step S2 to obtain the spin-coated substrate; s4, drying the spin-coated substrate in the step S3 at a low temperature; and S5, carrying out plasma dry etching on the substrate dried at the low temperature in the step S4 to obtain a pretreated substrate, and finally depositing diamond on the pretreated substrate obtained by the pretreatment method of the substrate. The method of the invention improves the nucleation rate, density and quality of diamond, overcomes the defects of mechanical grinding and common ultrasonic inoculation, and is beneficial to the preparation of high-quality diamond films.)

1. A method of pre-processing a substrate, comprising the steps of:

s1, cleaning a substrate, and then drying;

s2, carrying out acid liquor wet etching on the substrate obtained in the step S1;

s3, preparing diamond micro powder slurry, and uniformly spin-coating the diamond micro powder slurry on the substrate etched in the step S2 to obtain the spin-coated substrate;

s4, drying the spin-coated substrate in the step S3 at a low temperature;

and S5, carrying out plasma dry etching on the substrate dried at the low temperature in the step S4 to obtain a pretreated substrate for later use.

2. The method for pretreating a substrate according to claim 1, wherein the substrate is selected from the group consisting of silicon, silicon dioxide, and titanium.

3. The method for pretreating a substrate according to claim 1 or 2, wherein in step S2, after acid wet etching, the surface roughness of the substrate obtained is less than 100 nm.

4. The method for pretreating a substrate according to claim 3, wherein in step S2, the acid solution is one or more of hydrofluoric acid, nitric acid and hydrochloric acid, and is etched at 40-150 ℃ for 2-30 min; preferably, the pH value of the acid solution is 2-5.

5. The method for pretreating a substrate according to claim 1, wherein in step S3, the thickness of the diamond micro powder gel on the surface of the spin-coated substrate is 1-500 um; the preferable specific parameters of the spin coating process are as follows: 800-20000 r/min, and the spin coating time is 10-120 s.

6. The method for pretreating a substrate according to claim 1 or 5, wherein in step S3,

in the diamond micro powder slurry, the mass fraction of diamond micro powder is 10-50%.

7. The method for pretreating a substrate according to claim 1, wherein in step S4, the low-temperature baking process comprises: and (4) performing drying treatment at 40-100 ℃ for 40-80 min.

8. The method for pretreating a substrate according to claim 1, wherein in step S5, the plasma dry etching process comprises performing oxygen plasma dry etching and hydrogen plasma dry etching on the substrate dried at low temperature in step S4 in sequence;

preferably, the specific steps are as follows:

s51, dry etching of oxygen plasma: the pressure is 10-16 kPa, the temperature is 200-600 ℃, and the etching time is 8-60 min;

s52, etching by using a hydrogen plasma dry method: the pressure is 10-16 kPa, the temperature is 200-900 ℃, and the etching time is 8-80 min.

9. A method for producing a diamond film, characterized by depositing diamond on a pretreated substrate obtained by the method for pretreating a substrate according to any one of claims 1 to 8.

10. The method of claim 9, wherein the deposition atmosphere comprises hydrogen and methane, and the volume ratio of hydrogen to methane is 100: 1.5-5.5, the deposition pressure is 9-21 kPa, and the deposition temperature is 800-920 ℃.

Technical Field

The invention belongs to the field of preparation of diamond films, and particularly relates to a pretreatment method of a substrate and a preparation method of a diamond film.

Background

The unique crystal structure of diamond determines that the diamond has a plurality of excellent physicochemical properties, such as extremely high hardness, excellent chemical stability, extremely low friction coefficient, extremely high elastic modulus and the like, is a typical multifunctional material, and has good application prospects in a plurality of high and new technical fields such as energy, catalysis, sensors, precision machining and the like. However, natural diamond is extremely low in storage amount and expensive in price, is mostly granular, and is commonly used in the luxury goods consumption field such as jewelry; the diamond prepared by the high-temperature and high-pressure method has more impurities, is difficult to dope, is mostly granular, is mainly used in the field of abrasive dies, and is difficult to meet the actual requirements of diamond in the high and new technology field.

The Chemical Vapor Deposition (CVD) method is an effective method for preparing high-quality diamond films, and especially the microwave CVD (MPCVD) method is the preferred solution for preparing high-quality diamond films by virtue of its advantages of high plasma density and no electrode contamination, however, it is not easy to prepare high-quality diamond films, and its quality is affected by many factors, especially the quality of nucleation directly determines the quality of diamond films. Pre-treatment of the substrate is the most common and important method to enhance nucleation density and quality.

The prior preparation method of the diamond film usually adopts processes such as mechanical grinding, ultrasonic treatment and the like to pre-treat the substrate, the randomness of the techniques is large, particularly the mechanical grinding is difficult to ensure the treatment consistency, so that the quality of the prepared diamond film has certain difference, and the mechanical grinding is easy to cause the substrate to break, thereby causing certain waste.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a substrate pretreatment method, which overcomes the defects of mechanical grinding and common ultrasonic inoculation, is beneficial to the preparation of high-quality diamond films, has simple process flow and is suitable for large-area industrial popularization.

The invention also aims to provide a preparation method of the diamond film.

In order to realize the purpose of the invention, the specific technical scheme is as follows:

a method of pre-processing a substrate, comprising the steps of:

s1, cleaning a substrate, and then drying;

s2, carrying out acid liquor wet etching on the substrate obtained in the step S1;

s3, preparing diamond micro powder slurry, and uniformly spin-coating the diamond micro powder slurry on the substrate etched in the step S2 to obtain the spin-coated substrate;

s4, drying the spin-coated substrate in the step S3 at a low temperature;

and S5, carrying out plasma dry etching on the substrate dried at the low temperature in the step S4 to obtain a pretreated substrate for later use.

In order to improve the high free energy position required by diamond nucleation, namely the defect, the invention creatively removes the material on the substrate by the reaction of the acid liquid and the substrate, controls the concentration of the acid and the reaction time, and realizes the control of the etching degree, thereby generating more uniform defects on the whole substrate and effectively improving the high free energy position required by diamond nucleation. And then carrying out gel spin coating, plasma etching and other treatments on the substrate with the surface defect, and carrying out inoculation, wherein the diamond micro powder can be uniformly spin-coated on the surface of the substrate by slurry spin coating, and the bonding force between carbon and a substrate material can be increased by removing the gel and the plasma etching.

Further, the substrate is selected from one of silicon, silicon dioxide, titanium and molybdenum, and is preferably silicon.

Further, in step S1, the cleaning method is ultrasonic cleaning, and the parameters of the ultrasonic cleaning are preferably set as follows: and ultrasonically cleaning for 3-10 min by sequentially adopting acetone, absolute ethyl alcohol and deionized water.

Further, in step S1, the substrate may be dried by blowing after cleaning.

Further, in step S2, after wet etching with an acid solution, the roughness of the surface of the substrate is less than 100 nm.

Preferably, in step S2, the acid solution is one or a mixture of hydrofluoric acid, nitric acid and hydrochloric acid, the etching temperature is 40 to 150 ℃, and the etching time is 2 to 30 min; preferably, the pH value of the acid solution is 2-5.

Preferably, the acid solution is a mixed solution of hydrofluoric acid and nitric acid, wherein the concentration of the nitric acid is 45-68%, the concentration of the hydrofluoric acid is 20-40%, and the volume ratio of the hydrofluoric acid to the nitric acid in the mixed solution is 1-5: 1.

Further, between the step S2 and the step S3, the substrate is cleaned and dried. Preferably, the cleaning mode is ultrasonic cleaning, and the parameters of the ultrasonic cleaning are set as follows: and ultrasonically cleaning for 3-10 min by sequentially adopting acetone, absolute ethyl alcohol and deionized water. The drying mode is blow drying.

Further, in step S3, the thickness of the diamond micro powder gel on the surface of the spin-coated substrate is 1-500 um.

Further, the specific parameters of the spin coating process are preferably as follows: 800-20000 r/min, and the spin coating time is 10-120 s.

Further, in the step S3, the mass fraction of the diamond fine powder in the diamond fine powder slurry is 10 to 50%.

Further, in step S4, the low-temperature drying process includes: and (4) performing drying treatment at 40-100 ℃ for 40-80 min.

Further, in step S5, the plasma dry etching process includes performing oxygen plasma dry etching and hydrogen plasma dry etching on the substrate dried at low temperature in step S4 in sequence;

further preferably, the specific steps are as follows:

s51, dry etching of oxygen plasma: the pressure is 10-16 kPa, the temperature is 200-600 ℃, and the etching time is 8-60 min;

s52, etching by using a hydrogen plasma dry method: the pressure is 10-16 kPa, the temperature is 200-900 ℃, and the etching time is 8-80 min.

The significance of setting oxygen etching and hydrogen etching in plasma etching is as follows: the oxygen etching is to remove organic matters, and the hydrogen etching is to etch the diamond micro powder, so that the roughness of the whole plane is reduced, and the binding force of carbon and silicon is enhanced.

The invention also provides a preparation method of the diamond film, and the method uses the pretreated substrate obtained by the pretreatment method of the substrate to deposit diamond.

Further, the deposition atmosphere is hydrogen and methane, and the volume ratio of the hydrogen to the methane is 100: 1.5-5.5, the deposition pressure is 9-21 kPa, and the deposition temperature is 800-920 ℃.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention creatively combines the processes of equal acid etching, slurry spin coating, plasma etching and the like to pretreat the substrate, before the diamond deposition, the acid solution is used for carrying out wet etching on the substrate on which the diamond film is deposited, so that uniform defects are effectively etched on the surface of the substrate, particularly, a large amount of diamond micro powder can be embedded into the surface of the substrate and the defects in the later stage of slurry spin coating and plasma etching, according to the crystal nucleation theory, the embedded diamond micro powder can serve as the crystal nucleus of nucleation and high nucleation rate in the early stage of nucleation, and the large amount of defects etched on the substrate can provide high free energy positions required by the diamond nucleation, so that the nucleation position density is greatly improved.

(2) In the process of preparing the diamond film, the substrate pretreated by the method can be used as a nucleation crystal nucleus when nucleation is carried out on the substrate, diamond micro powder embedded in the treated substrate can be used as the nucleation crystal nucleus, the nucleation rate is improved, and the incubation period of the diamond film nucleation is shortened; and the etched defects of the substrate can provide high free energy positions required by diamond nucleation, so that the nucleation position density is greatly improved, and excellent nucleation quality provides good precondition for the growth of high-quality diamond film.

(3) The preparation method of the diamond film improves the nucleation rate, density and quality of diamond, overcomes the defects of mechanical grinding and common ultrasonic inoculation, and is beneficial to the preparation of high-quality diamond films. In the process of depositing the diamond film, the quality of the diamond film is further improved by adopting low carbon concentration.

(4) The invention has simple process flow and is suitable for large-area industrial popularization.

Drawings

FIG. 1 is a process flow diagram of an embodiment of the present invention.

FIG. 2 is a Raman diagram of a diamond film obtained in example 1 of the present invention.

Detailed Description

In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1

The embodiment provides a preparation method of a diamond film, which comprises the following steps:

s1, selecting monocrystalline silicon as a substrate, carrying out ultrasonic cleaning on the substrate by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s2, placing the silicon substrate cleaned and dried in the step S1 into a mixed solution of nitric acid and hydrofluoric acid for acid liquor wet etching, wherein the concentration of the nitric acid in the mixed solution is 40%, the concentration of the hydrofluoric acid in the mixed solution is 30%, and the volume ratio of the nitric acid to the hydrofluoric acid is 1: 1, setting the temperature of a water bath kettle to be 50 ℃, and etching by 10 mim;

s2-3, carrying out ultrasonic cleaning on the substrate after wet etching by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s3, preparing diamond micro powder slurry, weighing 2.5g w 0.25.25 g of diamond micro powder, putting the diamond micro powder into a mortar, gradually dropping 20g of terpineol and 5g of glycol into the mortar, grinding and dispersing for 5min, finally putting the mixture into a ball mill for further dispersion, wherein the rotating speed of the ball mill is 600r/min, the time is 30min, and the mixture is reserved after the dispersion is finished; uniformly spin-coating the diamond micro powder slurry on the substrate obtained in the step S2-3, wherein the process parameters in the spin-coating process are set to 10000r/min, the spin-coating time is 60S, and the spin-coating thickness is 20 um;

s4, placing the substrate spin-coated in the step S3 into a drying oven, and preserving heat for 40min at 60 ℃;

s5, placing the substrate dried in the step S4 into a microwave plasma chemical vapor deposition system, firstly etching for 6min under the conditions of 100sccm of oxygen, 350 ℃ of etching temperature and 11kPa of pressure, stopping microwave and introducing oxygen after the oxygen etching is finished, introducing 200sccm of hydrogen after the pressure is changed to 0.01kPa, starting the microwave when the pressure is increased to 2kPa, and etching for 20min at 700 ℃ and 12kPa to obtain a pretreated substrate;

s6, after the step S5 is finished, stopping the introduction of the microwaves and the hydrogen, introducing 200sccm hydrogen after the pressure is changed to 0.01Pa, starting the microwaves when the pressure is increased to 2kPa, adjusting the power and the pressure to ensure that the temperature is indicated to be 850 ℃, the pressure is 14kPa, introducing 4sccm methane, and depositing for 20h to obtain the diamond film, wherein the Raman of the diamond film sample is shown in figure 2, and the Raman of the prepared sample is shown in figure 2cm^-1The diamond has sharp diamond characteristic peak D and no obvious amorphous carbon peak G, which shows that the prepared diamond has high quality.

Example 2

The embodiment provides a preparation method of a diamond film, which comprises the following steps:

s1, selecting monocrystalline silicon as a substrate, carrying out ultrasonic cleaning on the substrate by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s2, placing the silicon substrate cleaned and dried in the step S1 into a mixed solution of nitric acid and hydrofluoric acid for acid liquor wet etching, wherein the concentration of the nitric acid in the mixed solution is 40%, the concentration of the hydrofluoric acid in the mixed solution is 30%, and the volume ratio of the nitric acid to the hydrofluoric acid is 1: 1, setting the temperature of a water bath kettle to be 80 ℃, and etching by 10 mim;

s2-3, carrying out ultrasonic cleaning on the substrate after wet etching by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s3, preparing diamond micro powder slurry, weighing 2.5gw0.25 of diamond micro powder, putting the diamond micro powder into a mortar, gradually dropping 20g of terpineol and 5g of ethylene glycol into the mortar, grinding and dispersing for 5min, finally further dispersing in a ball mill, wherein the rotating speed of the ball mill is 600r/min, the time is 30min, and the diamond micro powder is reserved after the dispersion is finished; uniformly spin-coating the diamond micro powder slurry on the substrate obtained in the step S2-3, wherein the process parameters in the spin-coating process are set to 10000r/min, the spin-coating time is 60S, and the spin-coating thickness is 20 um;

s4, placing the substrate spin-coated in the step S3 into a drying oven, and preserving heat for 40min at 60 ℃;

s5, placing the substrate dried in the step S4 into a microwave plasma chemical vapor deposition system, firstly etching for 6min under the conditions of 100sccm of oxygen, 350 ℃ of etching temperature and 11kPa of pressure, stopping the microwave and introducing the oxygen after the oxygen etching is finished, introducing 200sccm of hydrogen after the pressure is changed to 0.01Pa, starting the microwave when the pressure is increased to 2kPa, and etching for 20min at 700 ℃ and 12kPa to obtain a pretreated substrate;

s6, after the step S5 is completed, stopping introducing the microwaves and the hydrogen, introducing 200sccm hydrogen after the pressure is changed to 0.01Pa, starting the microwaves when the pressure is increased to 2kPa, adjusting the power and the pressure to ensure that the temperature is indicated to be 850 ℃, the pressure is 14kPa, introducing 4sccm methane, and depositing for 20h to obtain the diamond film.

Comparative example 1

The comparative example provides a method of preparing a diamond film, comprising the steps of:

s1, selecting monocrystalline silicon as a substrate, carrying out ultrasonic cleaning on the substrate by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s2, placing the silicon substrate cleaned and dried in the step S1 into a mixed solution of nitric acid and hydrofluoric acid for acid liquor wet etching, wherein the concentration of the nitric acid in the mixed solution is 40%, the concentration of the hydrofluoric acid in the mixed solution is 30%, and the volume ratio of the nitric acid to the hydrofluoric acid is 1: 1, setting the temperature of a water bath kettle to be 10 ℃, and etching by 10 mim;

s2-3, carrying out ultrasonic cleaning on the substrate after wet etching by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s3, preparing diamond micro powder slurry, weighing 2.5g w 0.25.25 g of diamond micro powder, putting the diamond micro powder into a mortar, gradually dropping 20g of terpineol and 5g of ethylene glycol into the mortar, grinding and dispersing for 5min, finally further dispersing in a ball mill, wherein the rotating speed of the ball mill is 600r/min, the time is 30min, and the diamond micro powder is reserved after the dispersion is finished; uniformly spin-coating the diamond micro powder gel solution on the substrate obtained in the step S2-3, wherein the process parameters in the spin-coating process are set to 10000r/min, the spin-coating time is 60S, and the spin-coating thickness is 20 um;

s4, placing the substrate spin-coated in the step S3 into a drying oven, and preserving heat for 40min at 60 ℃;

s5, placing the substrate dried in the step S4 into a microwave plasma chemical vapor deposition system, firstly etching for 6min under the conditions of 100sccm of oxygen, 350 ℃ of etching temperature and 11kPa of pressure, stopping microwave and introducing oxygen after the oxygen etching is finished, introducing 200sccm of hydrogen after the pressure is changed to 0.01kPa, starting the microwave when the pressure is increased to 2kPa, and etching for 20min at 700 ℃ and 12kPa to obtain a pretreated substrate;

s6, after the step S5 is completed, stopping introducing the microwaves and the hydrogen, introducing 200sccm hydrogen after the pressure is changed to 0.01Pa, starting the microwaves when the pressure is increased to 2kPa, adjusting the power and the pressure to ensure that the temperature is indicated to be 850 ℃, the pressure is 14kPa, introducing 4sccm methane, and depositing for 20h to obtain the diamond film.

Comparative example 2

The comparative example provides a method of preparing a diamond film, comprising the steps of:

s1, selecting monocrystalline silicon as a substrate, carrying out ultrasonic cleaning on the substrate by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s2, placing the silicon substrate cleaned and dried in the step S1 into a mixed solution of nitric acid and hydrofluoric acid for acid liquor wet etching, wherein the concentration of the nitric acid in the mixed solution is 40%, the concentration of the hydrofluoric acid in the mixed solution is 30%, and the volume ratio of the nitric acid to the hydrofluoric acid is 1: 1, setting the temperature of a water bath kettle to be 80 ℃, and etching for 2 hours;

s2-3, carrying out ultrasonic cleaning on the substrate after wet etching by using acetone, absolute ethyl alcohol and deionized water in sequence, and then drying;

s3, preparing diamond micro powder slurry, weighing 2.5g w 0.25.25 g of diamond micro powder, putting the diamond micro powder into a mortar, gradually dropping 20g of terpineol and 5g of ethylene glycol into the mortar, grinding and dispersing for 5min, finally further dispersing in a ball mill, wherein the rotating speed of the ball mill is 600r/min, the time is 30min, and the diamond micro powder is reserved after the dispersion is finished; uniformly spin-coating the diamond micro powder gel solution on the substrate obtained in the step S2-3, wherein the process parameters in the spin-coating process are set to 10000r/min, the spin-coating time is 60S, and the spin-coating thickness is 20 um;

s4, placing the substrate spin-coated in the step S3 into a drying oven, and preserving heat for 40min at 60 ℃;

s5, placing the substrate dried in the step S4 into a microwave plasma chemical vapor deposition system, firstly etching for 6min under the conditions of 100sccm of oxygen, 350 ℃ of etching temperature and 11kPa of pressure, stopping the microwave and introducing the oxygen after the oxygen etching is finished, introducing 200sccm of hydrogen after the pressure is changed to 0.01Pa, starting the microwave when the pressure is increased to 2kPa, and etching for 20min at 700 ℃ and 12kPa to obtain a pretreated substrate;

s6, after the step S5 is completed, stopping introducing the microwaves and the hydrogen, introducing 200sccm hydrogen after the pressure is changed to 0.01Pa, starting the microwaves when the pressure is increased to 2kPa, adjusting the power and the pressure to ensure that the temperature is indicated to be 850 ℃, the pressure is 14kPa, introducing 4sccm methane, and depositing for 20h to obtain the diamond film.

Comparative example 3

The comparative example provides a method for preparing a diamond film, comprising the steps of selecting monocrystalline silicon as a substrate, carrying out direct deposition without pretreatment:

introducing 200sccm hydrogen, starting the microwave when the pressure is increased to 2kPa, adjusting the power and the pressure to make the temperature show as 850 ℃ and the pressure as 14kPa, introducing 4sccm methane, and depositing for 20h to obtain the diamond film.

Test examples

This example carried out tests on pretreated substrates and diamond films obtained in example 1/2 and comparative example 1/2/3, and the data obtained are shown in Table 1.

TABLE 1

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.