JPS63286574A - Vapor deposition method of tungsten by cvd method - Google Patents

Abstract

PURPOSE:To deposit metallic tungsten having a fine granular structure by accompanying the gaseous atmosphere with hydrocarbons or the like in the case of depositing metallic tungsten on the surface of a base material by means of halogenotungsten and hydrogen. CONSTITUTION:The pipe 1 (copper pipe) of a base material is heated at prescribed temp. in a heating furnace 2 and a vacuum pump 3 is operated and the exhaust amount is regulated by a valve 10 and exhausted. When the detection value of exhaust of the mass flow controllers 8, 9 is reached to the prescribed value, the prescribed amounts of WF6 and H2 are fed into the pipe 1 while controlling the feed amount with the valves 11, 12 and W is deposited on the inside of the pipe 1. At this time, WF6 and H2 are accompanied with substance being gas at the reaction temp. of at least one kind selected from among hydrocarbon (benzene or the like), metallic halide (FeCl3 or the like) and metallic carbonyl compd. [Cr(CO)6 or the like]. Thereby W having a fine granular structure can be deposited and the tungsten pipe good in mechanical strength is easily obtained by dissolving the pipe 1 with acid to remove it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing tungsten material that is suitably used for heater-related parts of vacuum furnaces, nuclear equipment parts, protection tubes for thermocouples, and the like.

[Conventional technology and problems]

Since tungsten has an extremely high melting point, it has been widely used in the form of iL rods and 1wA wires as a material constituting elements that require heat resistance. Recently, attempts have been made to use tungsten pipes as heat-resistant parts of laser oscillation parts.

However, since tungsten has poor workability, it is extremely difficult to produce parts with desired shapes (for example, elongated pipes) using methods other than powder metallurgy.

As a means to overcome this poor processability, attempts were made to manufacture pipes using the CVD method in the 1960s.

Some of them have been put into practical use. This method 1For example, OAK RIDGE NATIONAL LABOI in 1964
? As described in detail in the ATO11Y report 011NL-3662, this is a method for producing a W vibe by reducing WF with H.

and H2 under a predetermined reduced pressure (for example, 10 Torr).
) is introduced into the inside of a copper pipe heated to a predetermined temperature, and W is deposited inside the copper vibe by H2 reduction of WF. As a result, a pipe in which W is precipitated inside the copper pipe is obtained. Taking advantage of the fact that W does not dissolve in nitric acid, this laminated pipe is immersed in a nitric acid solution to dissolve 2 wt, thereby creating a W vibe. It's something you get.

It is known that in the CVD method in which WF is reduced and precipitated with H2, W forms a columnar crystal grain structure that grows vertically from the surface of the base material.

Therefore, since the W material obtained by such a method has columnar crystal grains, it has a problem that its mechanical strength is lower than that of the W material obtained by powder metallurgy.

For this reason, various methods have been attempted to overcome this problem. For example, a method has been developed in which the surface of deposited tungsten is mechanically rubbed with a tungsten brush. However, it is difficult to control, and it is extremely difficult to operate a pipe with a small diameter, so this is not a general solution.

[Purpose of the invention]

From the above, if a technology for refining tungsten crystal grains at the stage of depositing tungsten using the CVD method is established, it will be possible to manufacture tungsten parts of various shapes with good mechanical strength, and this field will can make a major contribution.

The present invention was made for the purpose of establishing this technology.

[Summary of the invention]

The present invention uses tungsten hagelonide and hydrogen as atmospheric gases in the CVD method, and when depositing metallic tungsten on the surface of a substrate, hydrocarbons, metal halides, metal carbonyl compounds, or organic metals are added to the five atmospheric gases. It is characterized by the entrainment of a small amount of compounds (both of which are gaseous substances at one reaction temperature).

The present inventors discovered that when a trace amount of a third compound is present in the atmosphere when tungsten hagelonide (WF6) is reduced at Hz to deposit metallic tungsten using the CVD method, the precipitated tungsten becomes columnar crystal grain-like. It was found that the structure did not become a fine grain structure, but a fine grain structure. Compounds that exhibit such a tungsten grain refinement effect include hydrocarbons such as benzene and toluene [HFeC]ff
+ Halogenated compounds such as TlC14+Cry3; Cr
Carbonyl compounds such as (Go)i, Rez(Co)to; Chromium acetylacetonate CCr (CHzC
There are organometallic compounds such as OC)IzCOCHs)x:l. In any case, these compounds need to be gaseous at the reaction temperature when tungsten is deposited by CVD.

[The above-mentioned third compound used in the detailed description of the invention is reduced by hydrogen in the atmosphere or thermally decomposed to precipitate its metal element or carbon together with tungsten, and by the precipitation of this metal or carbon. It is thought that this suppresses the growth of columnar crystal grains of tungsten. Therefore, the amount of the third compound introduced into one reaction zone is the amount necessary to obtain the effect of refining tungsten crystals, but if it is too large, the amount of the third metal element in the target tungsten material product will be reduced. Alternatively, the amount of carbon may increase, which may have beneficial effects on physical properties, but may also have the opposite effect, so it is necessary to determine the amount appropriately depending on the type of third compound used. be. As shown in the examples below, when hydrocarbons are used as the third compound, the amount of precipitated carbon is approximately 0.1% of tungsten and χ9, for example, 0.05.
It is preferable to set it in the range of ~0.5 匈t, χ. Furthermore, even if the third element that precipitates together with tungsten is a metal produced by reduction or decomposition of the compound, the range of 0.02 to Q, 5wt, and χ is recommended if alloying is not intended. Good.

In carrying out the method of the present invention, 1. As in the normal CVD method, a mixed gas of tungsten hexafluoride gas and hydrogen gas is reacted on the surface of the substrate, and at the same time, the above-mentioned metal or The gaseous compound of carbon is added in ml to the mixed gas and introduced into the reaction section, and this introduction may be carried out continuously into the mixed gas or intermittently at predetermined intervals. It is also possible to introduce If it is introduced intermittently, it will have a multilayer structure in which layers of fine tungsten crystal grains and layers of slightly larger tungsten crystal grains are alternately overlapped. Even in the case of this multilayer structure, the mechanical properties are significantly improved compared to the columnar crystal structure.

When introducing such a third compound into the reaction zone, any method may be used as long as the gas of the third compound is present in the reaction zone. When using Hensen as a compound to precipitate C, Hensen has a sufficiently high vapor pressure under low pressure (for example, 75 Torr), so by differentially pumping out the benzene container with a needle valve, a predetermined amount of benzene can be separated into H2 and W.
It can be introduced into a mixed gas of F. Also, FeCl:+
In the case of a compound with a high melting point, such as H!, it is melted in a heating furnace, and the vapor of the compound generated from this melt is transferred to WF in the CVD apparatus using a carrier gas. What is necessary is to adopt a method such as introducing it into a mixed gas.

When tungsten is vapor-deposited by the method of the present invention, the final shape and dimensions of the vapor-deposited tungsten itself can be arbitrary, but the most preferred embodiment is a pipe. According to the method of the present invention, a tungsten pipe with finer crystal grains can be easily manufactured.

FIG. 1 schematically shows an example of the arrangement of typical equipment when manufacturing tungsten pipes according to the method of the present invention. 1 is the base material pipe (
! rl vibe), and this copper pipe is heated in a heating furnace 2. Then, one end of the copper pipe 1 is connected to an exhaust pipe 4 leading to a vacuum pump 3, and the other end of the copper pipe 1 is connected to a reactant supply pipe 5. Reactant supply pipe 5 is connected to WF6 container 6 and H2 container 7 via mass flow controllers 8 and 9, respectively. The pipeline from WF and container 6 to copper vibrator 1 is heated piping (for example, piping that is externally heated to about 45°C) to prevent condensation of WF b.
The vacuum pump 3 is operated, and its displacement is adjusted to the valve 1.
Exhaust while adjusting at 0.

WF, valve 11 and H2 valve 12 so that the detected values of mass flow controllers 8 and 9 become predetermined values.
to control each supply amount to provide a predetermined amount of WF.

When W and H2 are supplied to the inside of the copper pipe 1 under heating and reduced pressure, W is precipitated inside the copper pipe 1.

At that time, the supply pipe 14 for the gas 13 of the third compound mentioned above is connected to the mixed gas pipe of WF and Ht via the valve 15, WF, and H! The third compound gas is continuously or intermittently introduced into the mixed gas in small amounts. If the third compound is a compound that is difficult to vaporize.

It is heated and melted as described above and then introduced using a carrier gas. As a result, the third compound is hydrogen-reduced or thermally decomposed, and a small amount of metal or carbon is precipitated with tungsten inside the copper pipe 1, thereby suppressing the growth of tungsten crystals into columnar shapes. When a deposited layer of a predetermined thickness is obtained, the process is terminated, and a two-layer pipe having a tungsten layer inside the copper vibe 1 is obtained. This double-layered pipe is immersed in nitric acid to dissolve and remove the copper, yielding a tungsten pipe. This tungsten pipe has fine crystal grains and has good mechanical strength, so it can be used as is for the intended purpose. It is suitable for use as parts of heaters, parts of nuclear power equipment, as well as protective tubes for thermocouples.

The above describes the case where a tungsten pipe is manufactured by dissolving and removing the base material, but the method of the present invention can also be applied to cases where the base material is used as a part element and tungsten lining is performed. The tungsten coating can be removed. Note that the method of the present invention is not limited to the thermal CVD method.

It is also applicable when performing tungsten coating by plasma CVD method. In this case, since the reaction temperature can be lowered, crystal grains can be made finer and toughness can be improved.

[Example 1] With the equipment arrangement shown in FIG. 1, tungsten was vapor-deposited inside the copper pipe 1 using benzene as the third compound. That is, the copper pipe 1 in which tungsten is deposited
was installed in the heating furnace 2, and a mixed gas of hydrogen and tungsten hexafluoride was introduced into the copper pipe while controlling the flow rate with a mass flow meter 8.9. The pressure was manually controlled to a predetermined value by adjusting the displacement of the vacuum pump 3 with the needle valve 10 while watching the vacuum gauge 16.

The piping system was maintained at 45°C with a heater to prevent condensation of the tungsten hexafluoride. Benzene was introduced into the gas mixture by adjusting valve 15. The procedure was to raise the heating furnace to a predetermined temperature while drawing a vacuum, then introduce hydrogen and tungsten hexafluoride, and at the same time, benzene was added. After a predetermined time, the supply of benzene and tungsten hexafluoride was stopped, and the pipe was cooled while flowing hydrogen. When it reached room temperature, the copper pipe was taken out, cut into a predetermined length, and the copper was melted with nitric acid to obtain a tungsten pipe. Ta.

The above experiment was carried out in 5 reaction parts at 800°C for 30 minutes per reaction time.

Vacuum level: 15 Torr, hydrogen flow: 1300cc/m1nr
The flow rate of tungsten hexafluoride was 75 cc/l1in, and the supply of benzene was 10.002 g/hr. The amount of carbon in the obtained tungsten is 0.12iit, χ
Met.

The photograph in FIG. 2 shows the cross-sectional structure (magnification: X 400) of a tungsten pipe obtained in one example.

[Comparative Example 1] A tungsten pipe was manufactured under the same conditions as in Example 1 except that benzene was not added.

The cross-sectional structure of the obtained tungsten pipe is shown in FIG.

As is clear from comparing Figures 2 and 3.

In the comparative example, tungsten grows in the form of columnar crystals, whereas in Example 1 of the method of the present invention, the growth in the form of columnar crystals is completely suppressed, and the structure has a multilayer structure.

This is considered to be because the amount of benzene supplied fluctuated because the degree of vacuum was manually set to U8. However, it can be seen that the crystal grains themselves have become significantly finer.

[Example 2] A tungsten pipe was obtained under the same conditions as in Example 1, except that titanium tetrachloride (TiCIa) was used instead of benzene. At that time, TiCln was supplied at a rate of 0.03 g/hr. T in the obtained tungsten pipe
i(7) amount is 0.06wt,! Tea Tsuta.

As a result, a fine crystal grain composite fiber similar to that of Example 1 was obtained.

[Brief explanation of the drawing]

Figure 1 is a system diagram of the equipment layout of the equipment that carried out the method of the present invention, and Figure 2 is a mirror photograph of metals showing the crystal structure of a cross section of a tungsten pipe obtained by the method of the present invention (400x magnification).
Figure 3 is a mirror photo of metals (magnification: 40
0 times). 1. Copper pipe, 2. Heating furnace, 3. Vacuum pump, 6. W F b container, 7. H2 container. 8.9 Mass flow controller, 13
... Container for third compound. Figure 1

Claims (3)

[Claims] (1) When depositing metallic tungsten on the surface of a substrate using tungsten hagelonide and hydrogen as the atmospheric gas in the CVD method, hydrocarbons,
A tungsten vapor deposition method using a CVD method, characterized in that at least one of a metal halide, a metal carbonyl compound, or an organometallic compound is entrained in a substance that is a gas at the reaction temperature. (2) The tungsten vapor deposition method according to claim 1, wherein the base material is an acid-soluble metal pipe, and tungsten is vapor-deposited on the inner surface of the pipe. (3) The tungsten vapor deposition method according to claim 2, wherein the base pipe on which tungsten is vapor-deposited is removed by dissolving it with acid.