JPH0285358A - pressure reducing device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure reducing device, and particularly to a pressure reducing device that enables ultra-high vacuum and ultra-high cleaning processes.

[Prior art and its problems] In recent years, technologies to achieve ultra-high vacuums or to create an ultra-highly clean, reduced-pressure atmosphere by flowing a small amount of a specified gas into a vacuum chamber have become extremely important. These techniques are widely used in research on material properties, formation of various thin films, and manufacturing of semiconductor devices, and as a result, increasingly high degrees of vacuum are being achieved. There is a strong desire to realize a reduced pressure atmosphere that is reduced to the utmost limit.

For example, in the case of semiconductor devices, in order to improve the degree of integration of integrated circuits, the dimensions of unit elements are becoming smaller year by year, from 1 μm to submicron to 0.5 μm.
Research and development is actively being carried out to commercialize semiconductor devices having the following dimensions.

The manufacture of such semiconductor devices involves repeated steps such as forming a thin film and etching the formed thin film into a predetermined circuit pattern. Such a process is usually carried out by placing a silicon wafer in a vacuum chamber and performing it in an ultra-high vacuum state or in a reduced pressure atmosphere with a predetermined gas introduced. If impurities are mixed into these steps, problems will occur, such as deterioration of the quality of the thin film or failure to obtain precision in microfabrication. This is the reason why ultra-high vacuum and ultra-high clean reduced pressure atmosphere are required.

One of the biggest obstacles to the realization of ultra-high vacuums and ultra-clean reduced-pressure atmospheres is the gas emitted from the surfaces of stainless steel, which is widely used in chambers and gas piping. .

In particular, the biggest source of contamination is when moisture adsorbed on the surface is desorbed in a vacuum or reduced pressure atmosphere.

Figure 8 shows the relationship between the total leakage amount (the sum of the amount of gas released from the piping system and the inner surface of the reaction chamber and the external leakage) of the system including the gas piping system and reaction chamber in a conventional device and gas contamination. This is Tagutev. A plurality of lines in the figure show results when the gas flow rate is changed to various values as a parameter.

In semiconductor processes, there is a tendency to reduce the flow rate of gas more and more in order to realize processes with higher precision.
It is common to use a flow rate of 0 cc/min or less. For example, if a flow rate of 10 cc/min is used, the flow rate will be 10-3
If there is a system total leak of ~1O-6Torr-u/sec, the gas purity will be 10ppm~1%, which is far from a highly clean process.The inventor has developed an ultra-highly clean gas supply system. He invented a system that reduces the amount of leakage from outside the system to 1×1 of the detection limit of the current detector.
0-th Torr-j! We have succeeded in keeping the speed below /sec. However, it was not possible to reduce the impurity concentration in the reduced pressure atmosphere due to leaks from inside the system, that is, gas components released from the surface of the stainless steel mentioned above. The minimum amount of surface emitted gas obtained by surface treatment in current ultra-high vacuum technology is txlO-”Torr-IL/5ec-crd for stainless steel, and the surface area exposed inside the chamber is For example, 1
Even if the smallest estimate is rrf, the total is l
The leakage amount is Xl0-'TOt"r・11/sec, and gas with a purity of about ippm can be obtained for a gas flow rate of 10 cc/min. Needless to say, if the gas flow rate is further reduced, the purity will further drop. .

The degassed components from the inner surface of the chamber were
To reduce the degassing from the stainless steel surface to the same level as ec, the degassing from the stainless steel surface should be
``There was a strong need for a stainless steel surface treatment technology that would reduce the amount of gas released.

On the other hand, in the semiconductor manufacturing process, from relatively stable general gases (O2, N2, Ar, H2, He) to reactive gases,
A wide variety of gases are used, including highly corrosive and toxic special gases. In particular, special gases include boron trichloride (BCJZ3) and boron trifluoride (BF3), which are highly corrosive and hydrolyze to produce hydrochloric acid or hydrofluoric acid when moisture is present in the atmosphere. Stainless steel is normally used for pipes and chamber materials that handle these gases due to its reactivity, corrosion resistance, high strength, ease of secondary processing, ease of welding, and ease of polishing the inner surface. Often.

However, although stainless steel has excellent corrosion resistance in a dry gas atmosphere, it is easily corroded in a chlorine-based or fluorine-based gas atmosphere where moisture is present. Sexual treatment becomes essential. Treatment methods include N1-W-P coating (clean varnish coating method), which coats stainless steel with a highly corrosion-resistant metal, but this method not only tends to cause cracks and pinholes, but also uses wet plating. Therefore, there are problems such as the amount of moisture adsorbed on the inner surface and the amount of residual components in the solution. Another method is to make the metal surface passivated to make it anti-corrosive by creating a thin oxide film.6 Stainless steel can be passivated just by immersing it in a liquid if there is enough oxidizing agent in the liquid. , Usually, it is immersed in nitric acid solution at room temperature to perform passivation treatment.

However, since this method is also a wet method, there is a large amount of residual moisture and processing solution on the piping and the inner surface of the chamber.

In particular, moisture can cause severe damage to stainless steel if chlorine or fluorine gases are passed through it.

Therefore, it is important to construct chambers and gas supply systems using stainless steel with a passive film, which will not be damaged by corrosive gases and will not absorb or absorb moisture.Ultra-high vacuum technology and semiconductor processing However, until now, no such technology existed.

[Problem to be solved by the invention] The present invention has been made in view of the above points.

An object of the present invention is to provide an ultra-vacuum, ultra-high clean pressure reducing device that reduces impurities due to gas released from the inner surface and has excellent corrosive properties.

Furthermore, in addition to the above object, the present invention aims to provide a pressure reducing device that is capable of self-cleaning and self-maintenance.

[Means for Solving the Problems] A pressure reducing device according to the present invention is provided, firstly, in a pressure reducing device whose main portion is made of stainless steel, at least a portion of the surface of the stainless steel exposed inside the device is teeth,
There are two layers: a layer whose main component is chromium oxide formed near the interface between the stainless steel and the passive film, and a layer whose main component is iron oxide formed near the surface of the passive film. It is characterized in that it is composed of the above layers and a passive film with a thickness of 50 Å or more is formed.

The passive film is preferably a film formed by heating and oxidizing stainless steel at a temperature of 150°C or more and less than 400°C.

Second, in the pressure reducing device according to the present invention, the main portion of the pressure reducing device is made of stainless steel, and at least a portion of the surface of the stainless steel exposed inside the device has the following features:
It is characterized in that a passive film with a thickness of 50 Å or more is formed, which is composed of a layer mainly composed of a mixed oxide of chromium oxide and iron oxide.

The passive film is preferably a film with a thickness of 100 Å or more formed by heating and oxidizing stainless steel at a temperature of 400° C. or more and less than 500° C.

Thirdly, in the decompression device according to the present invention, in the decompression device whose main portion is made of stainless steel, at least a part of the surface of the stainless steel exposed inside the device includes:
50 mm thick, consisting of a layer mainly composed of chromium oxide
It is characterized by the formation of a passive film with a thickness of Å or more.

The passive film preferably has a thickness of 130 Å or more and is formed by heating and oxidizing stainless steel at a temperature of 550° C. or more for 9 hours or more.

Fourthly, in addition to the first to third features, the pressure reducing device according to the present invention has a surface of the stainless steel on which the passive film is formed, which has a convex portion and a concave portion within a circumference with a radius of 5 μm. The flatness is characterized in that the maximum value of the difference in height is 1 μm or less.

Fifthly, in addition to the first to fourth features described above, the depressurization device according to the present invention provides a gas for supplying ultra-high purity gas, the main part of which is made of stainless steel, to the decompression chamber. The present invention is characterized in that the passive film is formed on at least a portion of the surface of the stainless steel to which the gas supply device is connected and which is exposed inside the gas supply device.

Sixthly, in addition to the first to fifth features, the depressurization device according to the present invention includes a gas cylinder for supplying ultra-high purity gas, the main part of which is made of stainless steel, into the decompression chamber. The present invention is characterized in that the passive film is formed on at least a portion of the surface of the stainless steel that is connected via the gas supply device and exposed inside the gas cylinder.

Seventhly, the decompression device according to the present invention is characterized in that, in addition to the third feature, the gas supply system includes a cleaning gas supply system for etching and removing deposits attached to the wall of the insulated decompression chamber. shall be.

The cleaning gas is preferably a chlorine-based gas or a fluorine-based gas.

Eighthly, the pressure reducing device according to the present invention is characterized in that, in addition to the seventh feature, the pressure reducing chamber includes a heating device that heats the pressure reducing chamber to a temperature of about 350°C.

In the above, the pressure reduction device includes, for example, one or a combination of one or more of semiconductor manufacturing equipment, gas cylinders, gas pulp, and vibrators.

[Function] According to the present invention, by providing an oxide film without pinholes etc. on the inner surface of the pressure reducing device made of stainless steel,
It is possible to reduce impurities due to gas released from the inner surface, and to obtain an ultra-vacuum and ultra-highly clean pressure reducing device with excellent corrosive properties.

(Margin below) [Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a pressure reducing device showing an embodiment of the present invention. In FIG. 1, 201 is a vacuum evacuation device, for example, a turbo molecular pump with a displacement of 20,001/min. 202 is a decompression chamber, made of stainless steel m5Us316L
The inner wall of the chamber has a passive film 20.
3 is formed. Furthermore, 204 is a gas supply system, which supplies gas at a small flow rate to the decompression chamber 202, for example, 0.01 to 10
By supplying about 0 cc/min, the decompression chamber is filled with a predetermined gas, e.g.
It is possible to create a reduced pressure state of about r. Therefore, the gas supply system 204 is composed of stainless steel pipes, joints, valves, muff throw controllers, pressure reducing valves, ceramic filters, etc., and detailed explanation thereof will be omitted here.

A gas cylinder 205 supplies a predetermined gas to the gas supply device, and may be Ar or Ha depending on the purpose.

In addition to general gases such as H,, O, etc., H(1!, CJ2□.

Corrosive gases such as BCfi3 and BF3 are often used.Only one cylinder is shown in the N1 diagram for convenience.
Connect multiple cylinders if necessary.

In addition, although only the passive film 203 on the inner surface of the decompression chamber 202 is shown in FIG. 1, the main parts of the gas supply system, gas cylinder, etc. are made of stainless steel 114 (
(SUS316L, 5US304L, etc.), and the passive film of the present invention is formed on all inner surfaces in contact with gas.

To form a passive film, first, the surface of stainless steel is mirror-polished, for example, electrolytically polished, and the flatness is set to 0.1 to 1.0 μm with the maximum difference in unevenness R□8, and then the surface is placed in a pure oxygen atmosphere. The oxidation was carried out by heating stainless steel to 400° C. and oxidizing it for about 1 hour. As a result, approximately 110 oxide films 203 were formed.

The main component of the oxide differs depending on the position, and the main component is an iron oxide film on the surface, and the main component is a Cr oxide near the interface with stainless steel #202. Note that detailed analysis results of the oxide film will be explained in detail later using Table 2, Table 3, and FIG. 6.

Mirror polishing of the stainless steel surface was performed using, for example, electric field polishing for the inner surface of the vibrator, and using techniques such as electrolytic composite polishing for the inner surfaces of the chamber and cylinder. The oxidation method is, for example, ultra-high purity Ar or H in the case of a vibrator.
After purging the inner surface of the vibrator and thoroughly removing moisture using water (moisture content of IPPb or less),
After raising the temperature to about 0℃ and purging to almost completely remove the H20 molecules adsorbed on the inner surface, pure oxygen with a moisture content of about 1 ppb or less is passed through the vibrator, and a current is applied directly to the vibrator. The inner surface was oxidized by raising the temperature to 400° C. using an electrical heating method in which water was applied.

Among such pressure reducing devices, the formation of a passive film is most important in gas cylinders. Since cylinders are containers that store reactive gases for long periods of time, in order to maintain the purity of the gas, it is essential to form a passive film that has excellent corrosion resistance and hardly absorbs or absorbs impurity gases. I was able to make it happen. FIG. 2 shows an example of a method for oxidizing this cylinder.

For example, when oxidizing the inner surface of the gas cylinder 301, ultra-high purity Ar or He is supplied from the gas introduction line 302 at a rate of, for example, 101 min. Remove moisture by introducing the liquid into a cylinder and thoroughly purging at room temperature. Whether water removal is sufficient can be determined by, for example, monitoring the dew point of the purge gas with a dew point meter 305 provided in the purge line 304. After that, the cylinder 3 is further heated by the electric furnace 303.
The whole of 01 is heated to about 150 to 400°C to almost completely remove the H20 molecules adsorbed on the inner surface. Next, ultra-high purity 02 is introduced into the cylinder, and the temperature of the entire cylinder is raised to a predetermined temperature (for example, 400 to 600°C) using an electric furnace to oxidize the inner surface. The passive films thus formed were HCfL, CIL2, BCl2. It is extremely stable against corrosive gases such as BF3, and it has been experimentally confirmed that gas cylinders with this passive film will not be damaged at all even if they are filled with corrosive gases and stored for long periods of time. .

Next, we will show experimental results regarding the degassing properties of this passive film. The experiment was conducted using a 3/8 inch diameter vibrator with a total length of 2 m. The configuration of the experimental apparatus is shown in Figure 3. That is, the Ar gas that has passed through the gas purifier 401 is passed through the SUS vibe 402 of the sample at a flow rate of 1.2 JZ/min, and the amount of water contained in the gas is measured using an APIMS (Atmospheric Pressure Ionization Mass Spectrometer).
403.

The results of purging at room temperature are shown in the graph of FIG. The type of vibrator tested was one whose inner surface was electropolished (
A), one that was subjected to passivation treatment with nitric acid after electropolishing (B), and one that was formed with the passive film of the present invention (C)
3fi class, and are shown by lines A, B, and C in FIG. 4, respectively. Each vibrator has a relative humidity of 50% and a temperature of 20%
After leaving it in a clean room at ℃ for about one week, this experiment was carried out.

As is clear from A and B in Figure 4, the electropolishing tube (A)
It can be seen that a large amount of water was detected in both of the electropolishing tubes (B) which were subjected to passivation treatment with nitric acid. Even after passing gas for about 1 hour, 68 PPb of moisture was detected in A and 36 ppb in B. Even after 2 hours, the moisture content was 41 ppb and 27 ppb, respectively, indicating that the moisture content did not decrease easily. On the other hand, in C using the passive film of the present invention, the concentration dropped to 7 ppb 5 minutes after passing the gas, and after 15 minutes, the background level dropped to 3 ppb or less. Thus, it was found that C has extremely excellent adsorbed gas desorption properties.

Next, the test vibrator 402 was energized and heated by the power source 404, and the temperature of the vibrator was changed according to the temperature increase time chart shown in FIG. Temperature from room temperature to 120℃, 1・20℃
Table 1 summarizes the average values of the amount of water that comes out when changing the temperature from 200°C to 200°C to 300°C. As is clear from this result, the stainless steel piping according to the present invention releases moisture by an order of magnitude less than other pipes. This means that the amount of adsorption is small and that it can be easily desorbed, making it ideal for supplying ultra-high purity gas. In addition, after baking the vacuum chamber 202 (Fig. 1) of the present invention
It has been found that a degree of vacuum of 0-12 Torr has been achieved and it has very excellent characteristics as an ultra-high vacuum device.Next, the oxide film obtained by oxidizing the stainless steel surface will be explained. Table 2 shows 5US316L, 5US304
When L is oxidized with ultra-high purity oxygen, the thickness and refractive index of the oxide film formed on the surface are shown as a relationship between oxidation temperature and time. Table 3 shows 5US316L, 400
It shows the oxide film thickness and refractive index when oxidized for 1 to 9 hours at a temperature of .degree. C. to 600.degree. What should be noted is the temperature of 400
In oxidation at ~500°C, the oxide film thickness does not depend on time but is determined only by temperature. This is because the oxidation of SUS is C.
This suggests that the process is explained by the model of Abrera and Mott. That is, if the temperature is controlled and kept constant, the oxide film will grow to a predetermined thickness, so a dense oxide film with a uniform thickness and no pinholes can be formed.

On the other hand, when the temperature rises to 550.degree. C. or 600.degree. C., the process of supplying oxygen through diffusion into the oxide film also overlaps, so as the oxidation time increases, the oxide film thickness gradually increases.

Figure 6 shows the results of ESCA analysis of the elemental distribution on the surface after oxidizing Sυ5316L at 500°C for about 1 hour.9
It can be seen that the concentration of Fe is high near the surface, and the concentration of Cr is high in deep parts.

This means that near the surface, the Fe oxide is separated from the oxide film by the SU
It is shown that near the interface with the S substrate, there is a two-layer structure consisting of Cr oxides. This means that as a result of the energy analysis of the ESCA spectrum, a chemical shift due to oxide formation is observed in Fe near the surface, but not in the deep part, and a chemical shift due to oxide formation is observed only in the deep part of Cr. It has also been confirmed. Until now, there has been no report on the formation of such a two-layer film by oxidation of SUS, and the mechanism by which the pressure reducing device of the present invention exhibits excellent corrosion resistance and adsorbed gas desorption properties is not yet clear. Na2
This is thought to be due to the formation of a layered film.

In addition, in order to form a dense oxide film, it is important to remove the altered layer during processing of the stainless steel surface and to make the surface flat. In this example, the surface roughness is R, □
Although a film with a diameter of 0.1 to 1.0 μm was used, experimental results show that a sufficiently good passive film is obtained when the maximum height difference between convex and concave portions within a circumference with a radius of 5 μm is about 1 μm. known to be formed.

FIG. 7 shows, corresponding to FIG. 6, the element distribution from the surface of the passive film under different oxidation conditions.

The oxidation conditions in Figure 7 (a), (b), (c), and (d) are (a) 400°C for 4 hours, (b) 500°C,
(c) 550°C for 4 hours; (d) 550°C for 9 hours. As the oxidation temperature increases and the oxidation time increases, the ratio of the chromium oxide film near the surface increases, and 5
In oxidation at 50° C. for 9 hours, the chromium oxide film is more abundant near the surface than the iron oxide film.As the chromium oxide film increases near the surface, it becomes chemically stronger. For example, C12 and HCJl, which are chlorine-based gases, no longer corrode at all. In semiconductor manufacturing equipment, St single crystal, SiO□, St, N4. AJ! Insulators such as N, AJ2. AIL-Si, AJ2-Cu-S
L, W.

Multilayer thin films of metals such as Mo, Ta, Ti, TiN, and Cu are often deposited. Typically, these thin films are
CV D (Che+++1cal Vapor De
The film is formed by posi-tron) or sputtering.

At this time, in the conventional apparatus, a thin film is not only deposited on the semiconductor wafer, but also a large amount of deposits is deposited on the inner wall of the reaction chamber. These deposits cause dust,
To prevent pattern defects, for example, in a CVD apparatus, the chamber is opened almost every day to remove deposits adhering to the inner walls of the chamber, and the operating rate of the apparatus is extremely low. However, in the case of a reaction chamber provided with the passive film of the present invention on its surface, the temperature of the reaction chamber is periodically raised to 200 to 350°C at predetermined time intervals, and, for example, cu
2. Chlorine gas such as HCJZ. Alternatively, deposits adhering to the inner walls of the reaction chamber can be removed by etching by flowing a cleaning gas such as a fluorine-based gas. Because the inner surface of the reaction chamber is extremely flat and has a passive film with excellent chemical and mechanical strength, the adhesion of deposits to the inner walls of the reaction chamber is extremely weak. Removal is extremely effective. In other words, the present invention has made it possible for the first time to provide a semiconductor manufacturing apparatus with self-cleaning and self-maintenant functions.

The development of semiconductor manufacturing equipment with self-cleaning and self-maintenance functions made it possible for the first time to completely automate semiconductor manufacturing lines.

As shown in Tables 2 and 3, after finishing the stainless steel surface to a mirror-like surface with no damaged layer, it is thoroughly washed and dried, and then oxidized in high-purity oxygen to form a passive film. If the oxidation temperature is 400° C. or higher, the thickness of the passive film is always 100 Å or higher.

The apparatus shown in FIG. 1 has been described above as an embodiment of the invention, but this may be an ultra-high vacuum experimental apparatus, or a semiconductor manufacturing apparatus such as an RIE apparatus, a sputtering apparatus, or a CVD apparatus. I don't mind. As shown in Figure 1, everything including the gas supply system and cylinder constitutes one pressure reducing device, and the passive film of the present invention is formed on the inner surface of the cylinder, gas pulp, and pipe. It goes without saying that all of these are included in the pressure reducing device of the present invention.

The same applies to the inner surface of the vacuum pump. Furthermore, it is clear that mechanical parts installed in the decompression chamber 202, for example, for transporting wafers, are also included in the depressurization apparatus of the present invention even when the passive film of the present invention is formed thereon.

In this example, an oxide film is provided on almost the entire surface exposed inside the device, but it is applied only to areas where the internal surface area is large and the effect of forming an oxide film is high, such as in a decompression chamber. An oxide film may be formed.

Furthermore, in the above embodiment, 5 is used as the stainless steel.
Although we took US304L and 5US316L as examples, stainless steels include Fe-Cr series, Fe-Cr-
It may be Ni-based. In addition, as for the structure, ferrite type,
Either martensitic or austenitic stainless steel may be used.

[Effects of the Invention] The present invention has realized a pressure reducing device that has a passive film on its inner surface that is excellent in corrosion resistance and has extremely low gas release, thereby enabling ultra-high vacuum, ultra-high cleanliness, and other depressurizing processes. became.

In addition to the above effects, self-cleaning and self-maintenance are now possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an intraocular pressure device showing an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a method of oxidizing a cylinder. Figure 3 is a configuration diagram of the experimental equipment for investigating degassing characteristics, Figure 4 is a graph showing the experimental results, and Figure 5 is a graph showing the experimental results.
The figure is a temperature rise time chart in the experiment. FIGS. 6 and 7 are graphs showing the element distribution on the surface after oxidation. FIG. 8 is a graph showing the relationship between total leakage amount and impurity concentration in a conventional device. 201... Exhaust device, 202... Decompression chamber, 203...
... Passive film, 204 ... Gas supply system, 205
゜301...-Gas cylinder, 302... Gas introduction line, 303... Electric furnace, 304... Purge line,
305... Dew point meter, 401-... Gas purifier, 40
2...SUS vibe, ・403...-APIMS, 4
04...Power supply. Attachment 1 Attachment 2 Table 1 Amount of water desorbed from sample piping (temperature dependence) Table 2 Passive film thickness unit (ppb) Paper 31 Figure Figure Figure Figure Time (Hr,) Figure Procedural amendment September 7, 1986

Claims (13)

[Claims] (1) In a pressure reducing device whose main part is made of stainless steel, at least a portion of the surface of the stainless steel exposed inside the device is covered with chromium formed near the interface between the stainless steel and the passive film. It is composed of two or more layers: a layer mainly composed of oxide and a layer mainly composed of iron oxide formed near the surface of the passive film, and has a thickness of 50 mm.
A decompression device characterized in that a passive film is formed on the substrate. (2) The pressure reducing device according to claim 1, wherein the passive film is a film formed by heating and oxidizing stainless steel at a temperature of 150° C. or more and less than 400° C. (3) In a pressure reducing device whose main part is made of stainless steel, at least a portion of the surface of the stainless steel exposed inside the device mainly contains a mixed oxide of chromium oxide and iron oxide. consisting of layers with a thickness of 50
A decompression device characterized by forming a passive film with a thickness of Å or more. (4) The pressure reducing device according to claim 3, wherein the passive film is a film with a thickness of 100 Å or more formed by heating and oxidizing stainless steel at a temperature of 400° C. or more and less than 500° C. (5) In a pressure reducing device whose main part is made of stainless steel, at least a portion of the surface of the stainless steel exposed inside the device has a thickness of a layer mainly composed of chromium oxide. A decompression device characterized in that a passive film with a thickness of 50 Å is formed. (6) The passive film has a temperature of 9
The pressure reducing device according to claim S, wherein the film is formed by heating and oxidizing stainless steel for more than 1 hour and has a thickness of 130 Å or more. (7) The surface of the stainless steel on which the passive film is formed has a flatness in which the maximum difference in height between the convex portion and the concave portion within a circumference with a radius of 5 μm is 1 μm or less. A pressure reducing device according to any one of claims 1 to 6. (8) A gas supply device for supplying ultra-high purity gas, the main part of which is made of stainless steel, is connected to the decompression chamber, and the surface of the stainless steel exposed inside the gas supply device is 8. The pressure reducing device according to claim 1, wherein the passive film is formed on at least a portion of the pressure reducing device. (9) A gas cylinder for supplying ultra-high purity gas, the main part of which is made of stainless steel, is connected to the decompression chamber via the gas supply device, and stainless steel is exposed inside the gas cylinder. 9. The pressure reducing device according to claim 1, wherein the passive film is formed on at least a part of the surface of the pressure reducing device. (10) According to either claim 5 or 6, the gas supply system includes a cleaning gas supply system for etching away deposits attached to the wall of the insulating vacuum chamber. Self-cleaning pressure reducing device as described. (11) The pressure reducing device capable of self-cleaning according to claim 10, wherein the cleaning gas is a chlorine-based gas or a fluorine-based gas. (12) A self-cleaning vacuum according to claim 11 or 12, wherein the vacuum chamber is equipped with a heating device that heats the vacuum chamber to a temperature of about 350°C. Device. (13) The pressure reducing device is one or more selected from semiconductor manufacturing equipment, gas cylinders, gas pulp, and pipes.
Claims 1 to 12 which are a combination of two or more
The pressure reducing device according to any of paragraphs.