JPS58100669A - Coating method - Google Patents

Abstract

PURPOSE:To permit uniform vapor deposition in an unevacuated state without using uneconomical halides as a starting raw material in chemical vapor deposition of layers of >=2 kinds among W, Mo, Re, by chlorinating these materials and reducing the materials on substrates. CONSTITUTION:A chemical vapor depositiing device is provided with a chlorinating furnace section 2 which extends in a quartz pipe 1 and is mounted at the left end of the pipe 1 and a reaction furnace 3 on the right side thereof. W chips 4 which is a starting raw materal put in an alumina boat are disposed in the section 2 and a substrate 5 is disposed on the susceptor 6 in the furnace 3. An inert gas is introudced into the section 2 and the furnace 3 through an inlet 7 and is heated with heaters 8, 9. Gaseous chlorine is introudced through an inlet 10 into the section 2, and the chips 4 are fed together with the above-described inert gas as a carrier gas and the gaseous H2 as a reducing gas through an inlet 12 in the form of WCl6 through an ejection port 11 into the furnace 3. As a result, the gaseous mixture of the gaseous WCl6 and the gaseous H2 reacts on the substrate 5 and the metallic film of W is formed on the substrate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method for producing refractory metal films of stainless steel, molybdenum, and rhenium, and alloy films thereof.

In general, chemical vapor deposition is a process in which vapor or gas of a volatile compound containing the element to be deposited or coated on a substrate is thermally decomposed or mixed with other vapors or gases on or near a heated substrate. This is a method in which a nonvolatile reaction product is precipitated from a gas phase and coated on a substrate by a chemical reaction.

Traditionally, when carrying out the chemical vapor deposition described above, a chemical reaction with another gas is used to generate a vapor or gas of a volatile compound containing the element to be coated. In particular, when considering the reduction reaction with hydrogen gas, chloride has a faster reduction reaction than fluoride, so chloride is often used as a starting material for chemical vapor deposition. There is a tendency.

On the other hand, when a film of a small number of metal elements such as tungsten, molybdenum, and rhenium among m-fusible metals is produced by chemical vapor deposition, fluoride is used as a starting material. This is because the boiling point of the exemplified refractory metal fluoride is low, gas transport is easy, and a uniform film is easily obtained. However, the use of fluoride as a starting material is very disadvantageous from an economic point of view, since the fluoride of the above-mentioned refractory metal is expensive.

It is also possible to use the chlorides of the refractory metals mentioned above as the starting material wire, but these chlorides are unstable and difficult to handle. However, using a halide of a refractory metal as a starting material is not a desirable method in terms of economy and film uniformity. Even when using
This is done under reduced pressure. In chemical vapor deposition under reduced pressure, the 9-surface reaction is the rate-determining process, so in order to form a uniform coating, it is necessary to carry out the 1-surface reaction in a constant reduced pressure atmosphere. However, in order to maintain a constant reduced pressure atmosphere, the gas supply unit, its control circuit,
Also, special measures must be taken for the reaction section.

It is an object of the present invention to provide an economical coating process that allows chemical vapor deposition to be carried out without using rhodan compounds as starting materials.

Another object of the present invention is to provide a coating method capable of producing a film of refractory metals such as tungsten, molybdenum, and reticulum having a uniform thickness without reducing the pressure.

Another object of the present invention is to provide a coating method capable of producing an alloy film of the above-mentioned refractory metal.

According to the invention, tungsten, molybdenum.

and a coating method comprising forming a layer of at least one material selected from the group of rhenium on a substrate.

While the selected material is placed under a given atmospheric pressure, it is chlorinated using chlorine gas, and the chloride produced by this chlorination is placed in the same reaction system at a pressure substantially equal to the given atmospheric pressure. A coating method is obtained in which a reducing gas is introduced onto a substrate held in a substrate, and a layer of the selected material is produced on the substrate by a reduction reaction between the chloride and the reducing gas.

In the present invention, a chemically stable pure metal is used as a starting material for the metal coating of tungsten, molybdenum, and rhenium, or an alloy coating thereof.

Pressure atmosphere 9 for easy operation, for example under atmospheric pressure.

The chloride gas produced by chlorination is directly introduced together with a reducing gas onto the substrate maintained in the above-mentioned pressure atmosphere. In this method, by selecting the method of introducing chlorine gas and reducing gas, the gas flow rate during introduction, and the geometrical arrangement of the chloride gas ejection end and the substrate, uniform, dense, and adhesive properties can be achieved. We were able to produce an excellent film.

Hereinafter, the present invention will be described in detail with reference to one drawing.

Embodiment 1 Below, referring to FIG. 9, a chemical vapor deposition apparatus used in an embodiment of the present invention extends inside a quartz tube 1.

It includes a chlorination furnace section 2 airtightly attached to the left end of a quartz tube 1, and a reaction furnace 3 positioned on the right side of the chlorination furnace section 2. In the chlorination furnace section 2, a tungsten chizo 4 placed in an alumina boat is placed, and in the reactor 3, a substrate 5 to be coated is placed on a graphite support 6. ing.

An inert gas such as argon is introduced into the chlorination furnace section 2 and the reaction furnace 3 through the introduction lower, and with the inert gas spread throughout the chlorination furnace section 2 and the reaction furnace 3, the heater 8 and 9 are driven, and the temperature of the chlorination furnace section 2 and the reactor 3 is set to 8.
00°C and 550°C, respectively.

Next, chlorine gas is introduced into the chlorination furnace section 2 from the inlet 10 provided at the left end of the chlorination furnace section 2 at a predetermined flow rate (for example, 30 Cφin). With this chlorine gas, the tungsten titanium 4 is chlorinated in the furnace section 2 and passed through the spout II provided at the right end of the chlorination furnace section 2 in the form of tungsten chloride (WCZ6).

It is guided into the reactor 3. Near the spout 11.

An inlet 12 is provided, and hydrogen gas is introduced as a reducing gas through the inlet 12.

Therefore, the chloride from the ejection port 11 is sent into the reactor 3 together with the inert gas as the carrier gas and the hydrogen gas as the reducing gas. As a result.

The mixed gas of tungsten chloride gas and hydrogen gas reacts on the substrate 5, and a tungsten metal coating is formed on the substrate 5.

As is clear from the figure, the pressure inside the 9-reactor 3 is maintained at the same pressure as the inside of the chlorination furnace section 2 (for example, atmospheric pressure).

Generally, in reactions by chemical vapor deposition under atmospheric pressure.

It is said that heterogeneous nucleation tends to occur in the gas phase, making it difficult to obtain a high-quality coating.Moreover, mass transport is the rate-limiting process in the gas phase, making it impossible to form a coating with a high growth rate. .

However, when the chemical vapor deposition apparatus described above was used, a tungsten metal film of good quality could be obtained quickly.

This is believed to be due to the selection of the geometry of the chemical vapor deposition apparatus and the flow rate of the gas introduced from each introduction lower, 10.12. More specifically, in the chemical vapor deposition apparatus shown in FIG. 1, the path for chlorine gas is separated from the path for inert gas (argon gas) as a carrier gas and the path for hydrogen gas. The gas inlet 12 is provided between the chloride gas outlet 11 and the base 5 . In this way, by separating the chlorine gas path,
Along with being able to promote chlorination.

Mixing of chloride gas and hydrogen gas can be improved. Furthermore, the chloride gas first comes into contact with the carrier gas near the ejection port 11, and then comes into contact with hydrogen gas near the base 5. Therefore, the chloride gas and hydrogen are mixed in the region adjacent to the substrate 5, and a rapid reduction reaction near the chloride spout 11 can be prevented.

Next, the distance between the chloride gas outlet 11 and the substrate 5 is shorter than the distance between the starting material and the substrate 5 in a chemical vapor deposition apparatus using a normal halogen compound as the starting material, and the gas reaches the substrate 5. This prevents the reduction reaction from proceeding.

The optimal length of the distance mentioned above depends on the size, shape, and size of the chemical reaction device.
Although it varies depending on the flow rate of gas from each inlet, the inventors' experiments have confirmed that it is sufficient to shorten the distance between the starting material and the substrate in conventional chemical vapor deposition equipment by about 60%. It was done. Incidentally, the size of the spout 11 was 25 mm.

Furthermore, the flow rate of hydrogen gas was selected to be as low as 10 to 50 ccAnin, and the molar ratio of chlorine gas to hydrogen gas was set to 1.
: When set to 2, the growth rate of the tungsten metal film is 100
μrr1/1'1r, and this growth rate was almost the same as the growth rate in a conventional chemical vapor deposition apparatus in which a large amount of hydrogen gas is flowed under reduced pressure. From this, 9 in the chemical vapor deposition apparatus of the present invention.

It can be seen that the reduction reaction is carried out effectively.

The tungsten film obtained under the above conditions is dense and has excellent adhesion, and the crystal orientation is (1).
00) and (211).

Example 2 Tungsten was deposited using the chemical vapor deposition apparatus shown in FIG.
The case of forming a rhenium alloy film will be explained.

. In this case, after compacting 90wt tungsten powder and 10wt rhenium powder, the tungsten-rhenium alloy obtained by firing in a hydrogen stream was added to the tungsten-rhenium alloy as starting material 4 in the chlorination furnace section 2. Deploy. Next, heaters 8 and 9 are operated to maintain the temperatures of chlorination furnace section 2 and reaction furnace 3 at 700°C and 1000°C, respectively. In this state, chlorine gas is introduced into the chlorination furnace section 2 to chlorinate Ret to the 9 alloy, and tungsten chloride and rhenium chloride are ejected from the ejection port 11 in the form of gas.

The chloride gas from the ejection port 11 was sent onto the heated substrate 5 together with the argon gas from the introduction lower and the hydrogen gas from the introduction port 12, and a coating with metallic luster was obtained on the substrate 5. This film is a tungsten-rhenium alloy film containing 20% rhenium, and its growth rate is 50% rhenium.
Here, the chlorination rate of rhenium powder is 2.5 times higher than that of tungsten powder under the same temperature and same chlorine flow rate conditions. Taking this into consideration, by selecting the composition of the 9 alloy pellets and the flow rate of chlorine gas while keeping the chlorination temperature and substrate heating temperature constant, an alloy film with a stable composition ratio was obtained. In Example 2 described in 2, the case was described in which 1 alloy pellets were used as the starting material, but pellets or powders made of individual materials forming 1 alloy may be placed separately in the chlorination furnace section 2. O Example 3 In the above example, due to the hydrogen reduction reaction with hydrogen gas,
The case where a film is generated has been explained.

Films could also be produced by thermally decomposing chloride gas. Specifically, rhenium powder is placed in the chlorination furnace section 2 and heated to 850°C, and the base 5 is heated to 950°C. Next, chlorine gas is introduced into the chlorination furnace section 2 at a flow rate of 20 cc/fnjn to chlorinate the rhenium powder. The generated rhenium chloride was introduced onto the substrate 5 together with argon as a carrier gas. As a result, a rhenium film was formed at a growth rate of 20 ury'hr.

The present invention is applicable not only to the production of the above-mentioned single metal film or alloy film, but also to the replacement of starting materials.

It is also possible to form a multilayer film by repeating the above-mentioned operations.

The chemical vapor deposition method of the present invention is effective for forming a tungsten coating on a substrate such as graphite when manufacturing a tar'r'y for an X-ray tube.

[Brief explanation of the drawing]

The figure is a sectional view showing a chemical vapor deposition apparatus used in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Quartz tube, 2... Chlorination furnace part, 3... Reactor, 4... Starting raw material, 5... Substrate, 6... Support stand,
7...Carrier gas inlet, 8, 9...Heater, 1
0...Chlorine gas inlet, 11...Chloride gas outlet, 12...Hydrogen gas inlet 〇

Claims (1)

Claims: 1. A method for forming layers of at least two materials selected from the group of tungsten, molybdenum, and rhenium on a predetermined substrate. Chlorinating the selected material under a predetermined atmospheric pressure. The chloride produced by this chlorination is introduced onto a substrate in the same reaction system placed under substantially the same pressure as the predetermined pressure, and the chloride is reacted on the substrate. B. A coating method comprising forming a layer of the material on the substrate. 2. The coating method according to claim 1, characterized in that two or more types of materials are selected from the group as the material, and an alloy layer of these materials is formed as the layer of the material. 3. In claim 1 or 2. A coating method characterized in that a plurality of layers of material are formed on the substrate by carrying out the reaction with the chloride a plurality of times with respect to a material in the group.