CN105862131B - A kind of introducing method of molybdenum when preparing molybdenum carbide crystal using MPCVD - Google Patents

Abstract

The invention belongs to the field of two-dimensional crystal preparation. A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals is characterized in that it comprises the following steps: the first step, first carrying out ultrasonic cleaning of the silicon chip, then putting the cleaned silicon chip on the substrate stage, and the substrate stage Located in the cavity, vacuumize the cavity; the second step is to introduce hydrogen and methane into the cavity, adjust the gas flow, microwave power and air pressure, so that the gas absorbs microwave energy to generate plasma; the third step is to turn on the pulse power supply and adjust The voltage between the molybdenum electrode and the substrate stage in the cavity causes an arc discharge between the molybdenum electrode and the substrate stage, and the time of the pulse is adjusted to control the generation time of the arc; the fourth step, after the reaction is completed, turn off the pulse power supply, After the chamber inside the cavity is cooled, the sample is taken out to obtain molybdenum carbide crystals. The method solves the problem that molybdenum is difficult to introduce in microwave plasma chemical vapor deposition (MPCVD), and can better control the intake of molybdenum, and obtain relatively pure molybdenum carbide crystals.

Description

A method for introducing molybdenum when preparing molybdenum carbide crystals by MPCVD

technical field

The invention belongs to the field of two-dimensional crystal preparation, and in particular relates to a method for introducing molybdenum when preparing molybdenum carbide crystals by microwave plasma chemical vapor deposition (MPCVD).

Background technique

Transition metal carbides (TMCs), consisting of carbon atoms bonded to metal atoms in a metal lattice, are a class of materials that combine the properties of metals and ceramics. On the one hand, TMCs exhibit extremely high strength and hardness, high melting point and stability, acid and alkali corrosion resistance, high electrical and thermal conductivity, and low chemical reactivity; on the other hand, TMCs exhibit noble metal-like catalytic activity. In addition, molybdenum carbide (Mo ₂ C), tungsten carbide (W ₂ C), tantalum carbide (TaC) and the like exhibit low-temperature superconducting properties.

At present, the introduction methods of molybdenum when preparing molybdenum carbide crystals are mainly divided into three categories: the first category is to obtain molybdenum carbide powder by reducing the oxide of molybdenum. This method has simple process, low cost, and easy control of the reaction process, but the obtained product There are carbon-containing components in it, and the carbon-containing components will greatly affect the performance of molybdenum carbide; the second type uses molybdenum salts such as phosphomolybdic acid, ammonium molybdate, and molybdenum chloride. This method is mostly used to prepare molybdenum carbide and other materials. compound; the third type uses organic molybdenum sources, such as molybdenum hexacarbonyl. Through the above molybdenum introduction method, molybdenum carbide powder and crystals can be prepared, but the obtained molybdenum carbide has many disadvantages, such as: the influence of carbon-containing components, small grain size, difficult to peel off the film, agglomeration of molybdenum carbide powder, etc. question. Therefore, it is necessary to provide a method for introducing molybdenum. By controlling the intake of molybdenum in the reaction system, the combination of molybdenum and carbon-containing groups is realized, thereby preparing high-quality molybdenum carbide single crystals and powders.

Contents of the invention

In order to overcome the deficiencies in the prior art, the object of the present invention is to provide a method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, which solves the difficult problem of molybdenum introduction in microwave plasma chemical vapor deposition (MPCVD) problems, and can better control the intake of molybdenum to obtain purer molybdenum carbide crystals.

In order to achieve the above object, the technical scheme adopted in the present invention: a method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, is characterized in that comprising the steps:

In the first step, the silicon wafer is ultrasonically cleaned, and then the cleaned silicon wafer is placed on the substrate stage. The substrate stage is located in the cavity (the silicon wafer is also located in the cavity of the cavity), and the cavity is evacuated to The vacuum degree is 0.1-10Pa;

The second step is to feed hydrogen and methane into the chamber (the volume ratio of hydrogen and methane is 30:1-200:1), adjust the gas flow, microwave power and air pressure, so that the gas (hydrogen and methane) absorbs microwave energy to generate Plasma (microwave plasma);

The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc (intermittent type) ;Molybdenum was introduced on the silicon wafer;

In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals.

The ultrasonic cleaning in the first step is ultrasonic cleaning with acetone or ethanol solvent (ultrasonic power is 50W, frequency is 40KHz).

The process parameters of microwave plasma generation in the second step are as follows: hydrogen flow: 100-400 sccm, methane flow: 0.5-10 sccm, microwave power: 800-1200W, working pressure: 10-25kPa.

The process parameters of arc discharge in the third step are as follows: the voltage between the molybdenum electrode and the substrate table: 300-600V, the time for generating arc is 0.1-10s, the time for not generating arc is 1-10s, the total time 6h (intermittent).

The present invention adopts the microwave plasma chemical vapor deposition method (MPCVD) for the first time. The MPCVD method uses microwaves as the energy source. This method has the advantages of strong microwave energy and high power density, so that the gas phase components can obtain higher energy and increase gas ionization. However, the preparation of molybdenum carbide by MPCVD must require a liquid or gaseous molybdenum source, and there are fewer liquid or gaseous molybdenum sources when consulting relevant information, which limits the preparation of molybdenum carbide by MPCVD. The invention introduces molybdenum by applying high-voltage direct current pulse to the molybdenum target to generate arc discharge. On the one hand, the arc discharge provides a higher temperature for the evaporation of atoms on the surface of the molybdenum target; on the other hand, the charged particles in the plasma also bombard the molybdenum target, which further promotes the introduction of molybdenum.

The present invention has the following beneficial effects: the present invention generates arc discharge between two electrodes to heat molybdenum to evaporate, and the evaporated molybdenum reacts with carbon-containing groups in microwave plasma to form molybdenum carbide, and the present invention solves the problem of preparing molybdenum carbide by MPCVD There are few problems in liquid molybdenum source or gaseous molybdenum source. The prepared molybdenum carbide crystals have high purity (mass purity ≥ 96%).

Description of drawings

Fig. 1 is a schematic diagram of the device for preparing molybdenum carbide crystals according to the present invention.

Fig. 2 is the XRD spectrogram of the molybdenum carbide crystal prepared by the present invention.

Fig. 3 is a low-temperature superconducting magnetic test curve of the molybdenum carbide crystal prepared in the present invention.

In Figure 1: 1-molybdenum electrode; 2-substrate platform; 3-silicon wafer; 4-cavity; 5-pulse power supply; 6-microwave plasma; Metal flange; 10-rubber sealing ring, 11-compression rectangular waveguide.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the content of the present invention is not limited only to the following embodiments.

As shown in Figure 1, the device for preparing molybdenum carbide crystals adopted in the following embodiments of the present invention includes a cavity 4, a molybdenum electrode 1, a substrate stage 2, a pulse generator, a microwave generator, a molybdenum electrode 1 and a substrate The chip stage 2 is located in the cavity of the cavity 4, and the molybdenum electrode 1 is located above the substrate stage 2. The molybdenum electrode 1 and the substrate stage 2 are respectively connected to the output end of the pulse generator by wires, and the cavity 4 is connected by an upper metal flange. 8. The lower metal flange 9 is connected to the compressed rectangular waveguide, and the compressed rectangular waveguide 11 is connected to the microwave generator; the cavity 4 is provided with an air inlet and a suction inlet.

The cavity 4 includes a quartz glass tube, an upper metal flange 8, and a lower metal flange 9 (constituting a chamber). The upper metal flange 8 is located at the upper end of the quartz glass tube, and a Rubber sealing ring 10, the lower metal flange 9 is located at the lower end of the quartz glass tube, a rubber sealing ring 10 is arranged between the lower metal flange 9 and the quartz glass tube, and the molybdenum electrode 1 is fixed on the upper metal flange 8 (the molybdenum electrode 1 Take it away together with the upper metal flange, and then put silicon on the substrate stage 2).

Example 1

A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, comprising the steps:

The first step is to prepare the device for preparing molybdenum carbide crystals; first, the silicon wafer is ultrasonically cleaned (ultrasonic cleaning with acetone or ethanol solvent) to remove oil stains; then the cleaned silicon wafer is placed on the substrate stage, and the substrate stage is located on the In the cavity (the silicon chip is also located in the cavity of the cavity), the cavity is evacuated (to a vacuum degree of 0.1-10Pa);

The second step is to feed hydrogen and methane into the chamber (the volume ratio of hydrogen and methane is 30:1-200:1), adjust the gas flow, microwave power and air pressure, so that the gas (hydrogen and methane) absorbs microwave energy to generate Plasma (microwave plasma);

The process parameters for microwave plasma generation are as follows: hydrogen flow: 150 sccm, methane flow: 1 sccm, microwave power: 800W, working pressure: 11kPa.

The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc (intermittent); Molybdenum is introduced on the silicon wafer;

The process parameters for generating arc discharge are as follows: the voltage between the molybdenum electrode and the substrate stage: 350V, the time for generating arc is 1s, the time for not generating arc is 5s, and the total time is 6h (intermittent).

In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals.

Fig. 2 is the XRD spectrum of the molybdenum carbide crystal prepared in this example, and the phase structure of the material is confirmed to be an α-phase molybdenum carbide crystal by comparing with the standard X-ray diffraction data. The prepared molybdenum carbide crystals have high purity (mass purity is 97.4%).

Example 2

A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, comprising the steps:

The first step is to prepare the device for preparing molybdenum carbide crystals; first, the silicon wafer is ultrasonically cleaned (ultrasonic cleaning with acetone or ethanol solvent) to remove oil stains; then the cleaned silicon wafer is placed on the substrate stage, and the substrate stage is located on the In the cavity (the silicon chip is also located in the cavity of the cavity), the cavity is evacuated (to a vacuum degree of 0.1-10Pa);

The second step is to feed hydrogen and methane into the chamber (the volume ratio of hydrogen and methane is 30:1-200:1), adjust the gas flow, microwave power and air pressure, so that the gas (hydrogen and methane) absorbs microwave energy to generate Plasma (microwave plasma);

The process parameters of microwave plasma generation are as follows: hydrogen flow: 150 sccm, methane flow: 5 sccm, microwave power: 800W, working pressure: 11kPa.

The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc; introduced molybdenum;

The process parameters for generating arc discharge are as follows: the voltage between the molybdenum electrode and the substrate stage: 450V, the time for generating arc is 5s, the time for not generating arc is 5s, and the total time is 6h (intermittent).

In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals.

Fig. 3 is the low-temperature superconducting magnetic test curve of the molybdenum carbide crystal prepared in this example, and the superconducting transition occurs around 6.83K, which is close to the superconducting transition occurring at 7K in related reports. It shows that the molybdenum carbide crystal prepared by this method has certain superconducting properties. The prepared molybdenum carbide crystals have high purity (mass purity is 98.5%).

Example 3

A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, comprising the steps:

The first step is to prepare the device for preparing molybdenum carbide crystals; first, the silicon wafer is ultrasonically cleaned (ultrasonic cleaning with acetone or ethanol solvent) to remove oil stains; then the cleaned silicon wafer is placed on the substrate stage, and the substrate stage is located on the In the cavity (the silicon chip is also located in the cavity of the cavity), the cavity is evacuated (to a vacuum degree of 0.1-10Pa);

The second step is to feed hydrogen and methane into the chamber (the volume ratio of hydrogen and methane is 30:1-200:1), adjust the gas flow, microwave power and air pressure, so that the gas (hydrogen and methane) absorbs microwave energy to generate Plasma (microwave plasma);

The process parameters for microwave plasma generation are as follows: hydrogen flow: 150 sccm, methane flow: 5 sccm, microwave power: 1000W, working pressure: 11kPa.

The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc; introduced molybdenum;

The process parameters for generating arc discharge are as follows: the voltage between the molybdenum electrode and the substrate stage: 450V, the time for generating arc is 1s, the time for not generating arc is 5s, and the total time is 6h.

In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals. The prepared molybdenum carbide crystals have high purity (mass purity is 98%).

Example 4

A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, comprising the steps:

The first step is to prepare the device for preparing molybdenum carbide crystals; first, the silicon wafer is ultrasonically cleaned (ultrasonic cleaning with acetone or ethanol solvent) to remove oil stains; then the cleaned silicon wafer is placed on the substrate stage, and the substrate stage is located on the In the cavity (the silicon chip is also located in the cavity of the cavity), the cavity is evacuated (to a vacuum degree of 0.1-10Pa);

The second step is to feed hydrogen and methane into the chamber (the volume ratio of hydrogen and methane is 30:1-200:1), adjust the gas flow, microwave power and air pressure, so that the gas (hydrogen and methane) absorbs microwave energy to generate Plasma (microwave plasma);

The process parameters for microwave plasma generation are as follows: hydrogen flow: 100 sccm, methane flow: 0.5 sccm, microwave power: 800W, working pressure: 10kPa.

The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc; introduced molybdenum;

The process parameters for generating arc discharge are as follows: the voltage between the molybdenum electrode and the substrate stage: 300V, the time for generating arc is 0.1s, the time for not generating arc is 1s, and the total time is 6h (intermittent).

In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals. The prepared molybdenum carbide crystals have high purity (mass purity is 97.1%).

Example 5

A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals (that is, utilizing microwave plasma chemical vapor deposition to prepare molybdenum carbide crystals), comprising the steps:

The first step is to prepare the device for preparing molybdenum carbide crystals; first, the silicon wafer is ultrasonically cleaned (ultrasonic cleaning with acetone or ethanol solvent) to remove oil stains; then the cleaned silicon wafer is placed on the substrate stage, and the substrate stage is located on the In the cavity (the silicon chip is also located in the cavity of the cavity), the cavity is evacuated (to a vacuum degree of 0.1-10Pa);

The second step is to feed hydrogen and methane into the chamber (the volume ratio of hydrogen and methane is 30:1-200:1), adjust the gas flow, microwave power and air pressure, so that the gas (hydrogen and methane) absorbs microwave energy to generate Plasma (microwave plasma);

The process parameters for microwave plasma generation are as follows: hydrogen flow: 400 sccm, methane flow: 10 sccm, microwave power: 1200W, working pressure: 25kPa.

The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc; introduced molybdenum;

The process parameters for generating arc discharge are as follows: the voltage between the molybdenum electrode and the substrate stage: 600V, the time for generating arc is 10s, the time for not generating arc is 1-10s, and the total time is 6h (intermittent).

In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals. The purity of the prepared molybdenum carbide crystals is high (98.6%).

The upper and lower limits and interval values of each raw material of the present invention, and the upper and lower limits and interval values of process parameters (such as gas flow, microwave power, gas pressure, etc.) can realize the present invention, and the embodiments are not enumerated here one by one.

The embodiments selected in the present invention for the purpose of disclosing the present invention are currently considered suitable, but it should be understood that the present invention is intended to include all changes and improvements of the embodiments belonging to the concept and scope of the invention .

Claims (5)

1. a method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals, is characterized in that comprising the steps: In the first step, the silicon wafer is ultrasonically cleaned, and then the cleaned silicon wafer is placed on the substrate stage. The substrate stage is located in the cavity, and the cavity is evacuated to a vacuum degree of 0.1-10Pa; The second step is to feed hydrogen and methane into the cavity, adjust the gas flow, microwave power and air pressure, so that hydrogen and methane absorb microwave energy to generate plasma; The third step is to turn on the pulse power supply, adjust the voltage between the molybdenum electrode and the substrate stage in the cavity, so that an arc discharge is generated between the molybdenum electrode and the substrate stage, and adjust the time of the pulse to control the generation time of the arc; introduced molybdenum; In the fourth step, after the reaction is finished, turn off the pulse power supply, and after the chamber inside the cavity cools down, take out the sample to obtain molybdenum carbide crystals. 2. a kind of introduction method of molybdenum when utilizing MPCVD to prepare molybdenum carbide crystal according to claim 1 is characterized in that: in the first step, ultrasonic cleaning is to carry out ultrasonic cleaning with acetone or ethanol solvent, and the power of ultrasonic wave is 50W , The frequency is 40KHz. 3. A method for introducing molybdenum when utilizing MPCVD to prepare molybdenum carbide crystals according to claim 1, characterized in that: in the second step, the volume ratio of hydrogen and methane is 30:1-200:1. 4. a kind of introduction method of molybdenum when utilizing MPCVD to prepare molybdenum carbide crystal according to claim 1, is characterized in that: the process parameter that microwave plasma produces in the described second step is as follows: hydrogen flow rate is: 100-400sccm, The methane flow rate is: 0.5-10sccm, the microwave power is 800-1200W, and the working pressure is 10-25kPa. 5. a kind of introduction method of molybdenum when utilizing MPCVD to prepare molybdenum carbide crystal according to claim 1, is characterized in that: the process parameter that produces arc discharge in the described 3rd step is as follows: between molybdenum electrode and substrate platform The voltage is: 300-600V, the time of arc generation is 0.1-10s, the time of no arc generation is 1-10s, and the total time is 6h.