JP3037928B2 - Stainless steel, its manufacturing method and pressure reducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stainless steel, a method for producing the same, and a pressure reducing apparatus, and more particularly to a stainless steel capable of performing an ultra-high vacuum and ultra-high cleaning process, a method for producing the same, and a pressure reducing apparatus.

[0002]

2. Description of the Related Art In recent years, a technology for realizing an ultra-high vacuum or a technology for flowing a predetermined gas into a vacuum chamber at a small flow rate to create an ultra-high-purity reduced-pressure atmosphere has become very important. These technologies are widely used for researching material properties, forming various thin films, and manufacturing semiconductor devices.As a result, higher and higher degrees of vacuum have been realized. It is very much desired to achieve a reduced pressure atmosphere that is reduced to the utmost.

For example, taking a semiconductor device as an example, in order to improve the degree of integration of an integrated circuit, the size of a unit element is decreasing year by year, and a semiconductor having a size of 1 μm to sub-micron and further, 0.5 μm or less. Research and development are being actively conducted for the practical use of devices.

[0004] The manufacture of such a semiconductor device is performed by repeating a process of forming a thin film, a process of etching the formed thin film into a predetermined circuit pattern, and the like. Such a process is usually performed in an ultra-high vacuum state or a reduced-pressure atmosphere into which a predetermined gas is introduced, usually by placing a silicon wafer in a vacuum chamber. If impurities are mixed in these steps, problems such as deterioration of the film quality of the thin film and inaccuracy of the fine processing cannot be obtained. This is the reason why an ultra-high vacuum and an ultra-high clean reduced-pressure atmosphere are required.

[0005] One of the biggest causes that has so far prevented the realization of an ultra-high vacuum or an ultra-high-purity decompressed atmosphere is gas released from the surface of stainless steel widely used in chambers and gas pipes. Is raised. In particular, the largest source of contamination is that moisture adsorbed on the surface is desorbed in a vacuum or reduced-pressure atmosphere.

FIG. 8 is a graph showing the relationship between the total leak amount (sum of the amount of gas released from the piping system and the inner surface of the reaction chamber and the external leak) and the gas contamination in the system including the gas piping system and the reaction chamber in the conventional apparatus. FIG. A plurality of lines in the figure show the results when the gas flow rate is changed to various values using the parameter as a parameter.

In a semiconductor process, a flow rate of a gas tends to be further reduced in order to realize a more accurate process. For example, a flow rate of 10 cc / min or less is generally used. Assuming that a flow rate of 10 cc / min is used, if there is a system total leak of about 10 ⁻³ to 10 ⁻⁶ Torr · l / sec as in a device widely used at present, the purity of the gas is 10 ppm to 1 ppm.
%, Which is far from a high clean process. The inventor of the present invention has invented an ultrahigh-purity gas supply system, and has succeeded in suppressing the amount of leakage from the outside of the system to 1 × 10 ⁻¹¹ Torr · l / sec or less, which is the current detection limit of the detector. . However, the impurity concentration in the reduced-pressure atmosphere could not be reduced due to the leak from the inside of the system, that is, the above-mentioned gas component released from the surface of stainless steel. The minimum value of the amount of surface emission gas obtained by surface treatment in the current ultra-high vacuum technology is 1 × 10 ⁻¹¹ Torr · l / sec · cm ^{2 in} the case of stainless steel.
Even if the surface area exposed inside the chamber is estimated to be the smallest, for example, 1 m ² , the total leak amount is 1 × 10 ⁻⁷ Torr · l / sec, which is 1 ppm for a gas flow rate of 10 cc / min. Only a gas of a degree of purity can be obtained. If the gas flow rate is further reduced, it goes without saying that the purity is further reduced.

The degassing component from the chamber inner surface is reduced to 1 × 10 ^-11 Torr, which is the same as the external leak amount of the total system.
To reduce the pressure to about the same level as r · l / sec, degassing from the surface of stainless steel is performed at 1 × 10 ⁻¹⁵ Torr · l / sec.
There needs to be c · cm ² or less, therefore, the processing techniques of the surface of stainless steel to reduce the outgassing amount is strongly demanded.

On the other hand, in the semiconductor manufacturing process, a wide variety of gases from relatively stable general gases (O ₂ , N ₂ , Ar, H ₂ , He) to highly reactive, corrosive and toxic special gases are used. Is done. Particularly, among special gases, there are boron trichloride (BCl ₃ ) and boron trifluoride (BF ₃ ) which are hydrolyzed when moisture is present in the atmosphere to generate hydrochloric acid or hydrofluoric acid and exhibit strong corrosiveness. . Normally, stainless steel is used for piping and chamber materials handling these gases because of its reactivity, corrosion resistance, high strength, ease of secondary workability, ease of welding, and ease of polishing the inner surface. Often.

[0010] However, stainless steel is excellent in corrosion resistance in a dry gas atmosphere, but is easily corroded in a chlorine-based or fluorine-based gas atmosphere where water is present. For this reason, a corrosion resistance treatment is indispensable after polishing the surface of stainless steel. As a treatment method, there is Ni-WP coating (clean S coating method) for coating stainless steel with a metal having high corrosion resistance, and this method not only tends to cause cracks and pinholes, but also
Since the method uses wet plating, there are problems such as a large amount of adsorbed water on the inner surface and a large amount of residual components in the solution. Another method is a corrosion resistance treatment by a passivation treatment for forming a thin oxide film on the metal surface. Since stainless steel is passivated only by immersion if there is a sufficient oxidizing agent in the liquid, passivation treatment is usually performed by immersion in a nitric acid solution at room temperature.

However, since this method is also a wet method,
A large amount of residual moisture and processing solution is present on the piping and the inner surface of the chamber. In particular, when chlorine-based or fluorine-based gas is flowed, the stainless steel will be severely damaged.

Therefore, it is possible to form a chamber and a gas supply system with stainless steel on which a passive film is formed without being damaged by corrosive gas and having little occlusion and adsorption of moisture. Although it is very important for semiconductor processes, there has been no such technology.

[0013]

The present invention has been made in view of the above points.

It is an object of the present invention to provide an ultra-vacuum and ultra-high-purity decompression device that reduces impurities due to gas released from the inner surface and has excellent corrosion resistance.

A further object of the present invention is to provide a decompression device capable of performing self-cleaning and self-maintenance in addition to the above objects.

[0016]

The stainless steel according to the present invention is characterized in that a passivation film having a layer containing more chromium oxide than iron oxide on the outer surface is formed on the electropolished surface. .

Here, the outermost surface preferably contains no chromium oxide and does not contain iron oxide.

Preferably, the thickness of the passivation film is 5 nm or more.

The passivation film is preferably a film having a thickness of 13 nm or more formed by heating and oxidizing stainless steel at a temperature of 550 ° C. or more for 9 hours or more.

In particular, the surface of the stainless steel on which the passivation film is formed has a flatness in which the maximum value of the height difference between the convex portion and the concave portion in the circumference having a radius of 5 μm is 1 μm or less. Is preferred.

The method for producing stainless steel according to the present invention comprises:
After the electropolishing, moisture is removed from the surface of the base material by performing baking, and then the surface of the base material is heated by heating at a temperature of 550 ° C. or more in an oxidizing gas atmosphere having an impurity content of 1 ppb or less. It is characterized by forming a dynamic film.

[0022] The baking temperature is preferably 150 to 400 ° C.

In the pressure reducing device according to the present invention, in a pressure reducing device whose main part is made of stainless steel, at least a part of the electropolished surface of the stainless steel exposed inside the device is made of chromium rather than iron oxide. A passivation film having a layer containing a large amount of oxide on the outer surface is formed.

Also in this decompression device, it is preferable that the outermost surface does not contain iron oxide and is made of chromium oxide.

The thickness of the passivation film is preferably 5 nm or more.

Further, it is preferable that the passivation film is a film having a thickness of 13 nm or more formed by heating and oxidizing stainless steel at a temperature of 550 ° C. or more for 9 hours or more.

Also, the surface of the stainless steel on which the passivation film is formed has a flatness in which the maximum value of the height difference between the convex portion and the concave portion in the circumference of a radius of 5 μm is 1 μm or less. Is preferred.

A gas supply device for supplying an ultra-high purity gas whose main part is made of stainless steel is connected to the decompression device, and a stainless steel material exposed inside the gas supply device is connected to the gas supply device. It is preferable that the passivation film is formed on at least a part of the surface.

A gas cylinder for supplying an ultra-high purity gas whose main part is made of stainless steel is connected to the decompression device via the gas supply device, and is exposed inside the gas cylinder. It is preferable that the passivation film is formed on at least a part of the surface of the stainless steel.

Further, it is preferable that the gas supply device includes a cleaning gas supply system for etching and removing deposits adhering to the inner wall of the insulated depressurized chamber, thereby enabling self-cleaning. Decompressible device.

Preferably, the cleaning gas is a chlorine-based gas or a fluorine-based gas.

Further, it is preferable that the decompression device is provided with a heating device for heating to a temperature of about 350 ° C.

Here, the pressure reducing device is, for example, one or a combination of two or more selected from a semiconductor manufacturing device, a gas cylinder, a gas valve and a pipe.

The semiconductor device is, for example, a film forming apparatus using plasma.

[0035]

According to the present invention, by providing an oxide film having no pinholes or the like on the inner surface of a pressure reducing device made of stainless steel, impurities due to gas released from the inner surface are reduced,
Further, it is possible to obtain a stainless steel or an ultra-vacuum, ultra-high clean pressure reducing device having excellent corrosiveness.

[0036]

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 one embodiment of the present invention. In FIG. 1, reference numeral 201 denotes a vacuum exhaust device, which is, for example, a turbo molecular pump with an exhaust volume of 2000 L / min. Reference numeral 202 denotes a decompression chamber, which is made of stainless steel SUS.
316L, and a passivation film 203 is formed on the inner wall of the chamber. Reference numeral 204 denotes a gas supply system, and a small flow rate gas, for example, 0.0
By supplying about 1 to 100 cc / min, the decompression chamber is filled with a predetermined gas, for example, 1 × 10 ^-4 to 1 × 10 ^-1 T.
The pressure can be reduced to about orr. Therefore, the gas supply system 204 is made of stainless steel piping,
It is composed of a second step, a valve, a mass flow controller, a pressure reducing valve, a ceramic filter and the like, and a detailed description thereof will be omitted here.

Reference numeral 205 denotes a gas cylinder for supplying a predetermined gas to a gas supply device, and Ar, He, and
H _2, other HCl common gas such as O _2, Cl _2, BCl _3, B
It is often used corrosive gases F ₃ and the like. In FIG. 1, only one cylinder is drawn for convenience, but a plurality of cylinders are connected as needed.

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, the gas cylinder and the like are made of stainless steel (SUS316L, SUS304L etc.) due to the flow of corrosive gas. ), And the passivation film of the present invention is formed on all inner surfaces in contact with the gas.

The formation of the passivation film, the surface of the stainless steel finish mirror polishing First, for example, electrolytic polishing, after the 0.1~1.0μm a maximum value R _max of the difference between irregularities the flatness, pure This was performed by heating the stainless steel to 400 ° C. in an oxygen atmosphere and performing oxidation for about 1 hour. As a result, the oxide film 20 having a thickness of about 11 nm (110 Å) is formed.
3 was formed.

The main component of the oxide differs depending on the position. The surface is mainly composed of an oxide film of iron, and the portion near the interface with the stainless steel 202 is mainly composed of the oxide of Cr. The detailed analysis result of the oxide film will be described later in detail with reference to Tables 2 and 3 and FIG.

The mirror polishing of the stainless steel surface was performed by using, for example, electrolytic polishing on the inner surface of the pipe, and using electrolytic combined polishing on the inner surface of the chamber or cylinder. The oxidation method is, for example, in the case of pipes,
After purging the inner surface of the pipe with r or He (water content of about 1 ppb or less) to sufficiently remove water, the temperature is further increased to about 150 to 200 ° C. to perform purging, and H adsorbed on the inner surface is removed. After almost completely desorbing ₂ O molecules,
Also, pure oxygen having a water content of about 1 ppb or less is passed, and current is directly supplied to the pipe.
The temperature was raised to ° C. to oxidize the inner surface.

The most important thing for forming a passive film in such a pressure reducing device is a gas cylinder. Since a cylinder is a container for storing a reactive gas for a long time, it is indispensable to form a passive film having excellent corrosion resistance and almost no adsorption and occlusion of impurity gas in order to maintain the purity of the gas. I realized it. FIG. 2 shows an example of a method for oxidizing the cylinder.

For example, when oxidizing the inner surface of the gas cylinder 301, ultrapure Ar or He is introduced into the cylinder at a rate of, for example, about 10 liters per minute from the gas introduction line 302 and sufficiently purged at room temperature to remove moisture. . Whether the moisture removal is sufficient may be determined by monitoring the dew point of the purge gas with a dew point meter 305 provided in the purge line 304, for example. Thereafter, the entire cylinder 301 is further heated to about 150 to 400 ° C. by the electric furnace 303,
H ₂ O molecules adsorbed almost completely on the inner surface are desorbed. Next, ultra-high purity O ₂ is introduced into the cylinder, and the temperature of the entire cylinder is adjusted to a predetermined temperature (for example, 400 to 60) by an electric furnace.
(0 ° C.) to oxidize the inner surface. The passivation film thus formed is extremely stable against corrosive gases such as HCl, Cl ₂ , BCl ₃ and BF ₃ , and the gas cylinder formed with this passivation film is filled with a corrosive gas for a long time. It was experimentally confirmed that no damage was caused when stored.

Next, the results of experiments on the degassing characteristics of the passivation film will be described. The experiment was performed on a 3/8 inch diameter pipe having a total length of 2 m. FIG. 3 shows the configuration of the experimental apparatus. That is, the Ar gas passed through the gas purifier 401
The amount of water contained in the gas was measured by an APIMS (atmospheric pressure ionization mass analyzer) 403 at a flow rate of L / min through a SUS pipe 402 of the sample.

The result of purging at room temperature is shown in the graph of FIG. The types of pipes tested were those in which the inner surface of the pipe was electropolished (A), those in which passivation treatment with nitric acid was performed after electropolishing (B), and those in which the passivation film of the present invention was formed (C). There are three types. In FIG.
This is indicated by the line C. Each pipe was left in a clean room at a relative humidity of 50% and a temperature of 20 ° C. for about one week, and then this experiment was performed.

As is clear from FIGS. 4A and 4B, it can be seen that a large amount of water is detected in both the electropolishing tube (A) and the electropolishing tube (B) that has been passivated with nitric acid. You. Even after passing the gas for about 1 hour, as much as 68 ppb of water was detected in A and as much as 36 ppb of water in B. It can be seen that the amount of water does not readily decrease at 41 ppb and 27 ppb respectively after 2 hours. On the other hand, in the case of C using the passivation film of the present invention, the level dropped to 7 ppb 5 minutes after gas passage, and fell to 3 ppb or less in the background after 15 minutes. As described above, C was found to have extremely excellent adsorption gas desorption characteristics.

Next, the test pipe 402 is connected to the power supply 404.
, And the temperature of the pipe was changed according to the heating time chart of FIG. Temperature from room temperature to 120 ° C,
Table 1 summarizes the average values of the amounts of water that appear when the temperature is changed from 120 ° C to 200 ° C and from 200 ° C to 300 ° C. As is apparent from these results, the stainless steel pipe according to the present invention emits less than one digit of water as compared with the others. This means that the amount of adsorption is small and that it can be easily desorbed, indicating that it is optimal for supplying ultra-high purity gas. Further, after baking of the decompression chamber (vacuum chamber) 202 (FIG. 1) of the present invention, 10 ^-11.
It has been found that a degree of vacuum of 10 to 10 ^-12 Torr has been realized, and that the device has very excellent characteristics even as an ultrahigh vacuum device.

Next, an oxide film obtained by oxidizing the stainless steel surface will be described. Table 2 shows SUS316L, S
In the case where US304L is oxidized with ultra-high purity oxygen, the thickness and refractive index of an oxide film formed on the surface are shown as a relationship between the oxidation temperature and time. Table 3 is SUS316L
Shows the oxide film thickness and the refractive index when oxidized at a temperature of 400 ° C. to 600 ° C. for 1 to 9 hours. It should be noted that in the oxidation at a temperature of 400 to 500 ° C., the oxide film thickness is determined only by the temperature without depending on the time. This is SUS
Suggests that the oxidation of is progressing through a process described by the Cabrera and Mott model. That is, if the temperature is controlled and kept constant, the oxide film grows to a predetermined thickness, so that a dense oxide film having a uniform thickness and no pinholes can be formed.

On the other hand, when the temperature rises to 550 ° C. or 600 ° C., a process in which oxygen is supplied by diffusion in the oxide film is also overlapped. Therefore, as the oxidation time becomes longer, the oxide film thickness gradually increases.

FIG. 6 shows the results obtained by oxidizing SUS316L at 500 ° C. for about 1 hour and then examining the element distribution on the surface by ESCA. The concentration of Fe is high near the surface, and C
It can be seen that the concentration of r is high. This indicates that the oxide has a two-layer structure in which the oxide of Fe is formed near the surface and the oxide of Cr is formed near the interface between the oxide film and the SUS substrate. 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, which is no longer at a deep portion, and a chemical shift due to oxide formation is observed only at deep portions of Cr. Has been confirmed from. To date, there has been no report that such a two-layer film was formed by SUS oxidation, and the mechanism by which the decompression device according to the present invention exhibits excellent corrosion resistance and desorption characteristics of adsorbed gas is not yet clear. It is considered that this is due to the formation of a suitable two-layer film.

Further, in order to form a dense oxide film, it is important to remove the degenerated layer during the processing of the stainless steel surface and to flatten the surface. Although R _max as the surface roughness in the present embodiment is used as a 0.1 to 1.0 [mu] m,
As a result of experiments, it has been found that a sufficiently good passivation film can be formed up to a maximum value of the difference between the heights of the projections and the recesses of about 1 μm in a circumference having a radius of 5 μm.

FIG. 7 shows the element distribution from the surface of the passivation film when the oxidation conditions are changed, corresponding to FIG.

The oxidation conditions in FIGS. 7A, 7B, 7C, and 7D are as follows: (a) 400 ° C., 4 hours, (b)
500 ° C, 4 hours, (c) 550 ° C, 4 hours (d) 55
0 ° C., 9 hours.

In FIG. 7C, the outermost surface has no iron oxide but only chromium oxide (claim 2).

In FIG. 7D, chromium oxide is larger than iron oxide on the surface side.

7A and FIG. 7B, FIG.
7 (c) and FIG. 7 (d), as the oxidation temperature increases, the ratio of the chromium oxide film near the surface increases,
In the oxidation at 550 ° C. for 9 hours, the chromium oxide film is larger than the iron oxide film even near the surface. As the chromium oxide film increases near the surface, it becomes chemically stronger.
For example, even chlorine gas such as Cl ₂ or HCl is not corroded at all. In a semiconductor manufacturing apparatus, insulators such as Si single crystal, SiO ₂ , Si ₃ N ₄ , and AlN, Al, Al—Si, Al—Cu—Si, W,
Thin films of metals such as Mo, Ta, Ti, TiN, and Cu are often deposited in multiple layers. Usually these films are
The film is formed by CVD (Chemical Vapor Deposition) or sputtering. At that time, in the conventional apparatus, not only a thin film is deposited on a semiconductor wafer but also a large amount of deposit adheres to the inner wall of the reaction chamber. Since such deposits cause dust and cause pattern defects, for example, in a CVD apparatus, the chamber is opened almost every day to remove deposits adhering to the inner wall of the chamber, and the operation rate of the apparatus is extremely low. there were. However, in the case of a reaction chamber provided with the passivation film of the present invention on the surface, the temperature of the reaction chamber is periodically raised to 200 to 350 ° C. at predetermined time intervals, and for example, a chlorine-based gas such as Cl ₂ or HCl is used. Alternatively, a deposit attached to the inner wall of the reaction chamber can be removed by etching by flowing a cleaning gas such as a fluorine-based gas. Since the inner surface of the reaction chamber is extremely flat and a passivation film with excellent chemical and mechanical strength is provided, the adhesion strength of deposits to the inner wall of the reaction chamber is extremely low. Removal works very effectively. In other words, a semiconductor manufacturing apparatus having self-cleaning and self-maintenance functions has been made possible for the first time by the present invention.

The development of a semiconductor manufacturing apparatus having self-cleaning and self-maintenance functions makes it possible for the first time to completely automate a semiconductor manufacturing line.

As shown in Tables 2 and 3, after the stainless steel surface was finished to a mirror surface without a work-affected layer, it was sufficiently washed and dried, and oxidized in high-purity oxygen to form a passivation film. Then, if the oxidation temperature is 400 ° C. or higher, the thickness of the passivation film is always 10 nm or higher.

The apparatus shown in FIG. 1 has been described as an embodiment of the present invention. This apparatus 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. It doesn't matter. As shown in FIG. 1, all of the components including the gas supply system and the cylinder constitute a single decompression device, and those in which the passivation film of the present invention is formed on the inner surface of the cylinder or the inner surface of the gas valve or pipe are: It goes without saying that all of them are included in the decompression device of the present invention. The same applies to the inner surface of the vacuum pump. Further, it is clear that, for example, a mechanical component for transferring a wafer, which is installed in the decompression chamber 202, is also included in the decompression device of the present invention even when the passivation film of the present invention is formed.

In this embodiment, an oxide film is provided on almost the entire surface exposed to the inside of the apparatus. However, for example, the internal surface area is large as in a decompression chamber, and the effect of forming the oxide film is high. An oxide film may be formed only on a part.

Further, in the above embodiment, SUS304L and SUS316L are taken as examples of stainless steel.
Fe-Cr-Ni may be used. Further, the structure may be any of ferritic, martensitic, and austenitic stainless steels.

[0063]

According to the present invention, it is possible to realize a decompression device having a passivation film having excellent corrosion resistance and extremely low outgassing on its inner surface, thereby enabling an ultra-high vacuum, an ultra-high clean pressure reduction process and the like. became.

Further, in addition to the above effects, self-cleaning and self-maintenance can be performed.

[0065]

[Table 1]

[0066]

[Table 2]

[0067]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a schematic view of a pressure reducing device showing one embodiment of the present invention.

FIG. 2 is a schematic view showing an example of a method for oxidizing a cylinder.

FIG. 3 is a configuration diagram of an experimental device for examining degassing characteristics.

FIG. 4 is a graph showing experimental results.

FIG. 5 is a heating time chart in an experiment.

FIG. 6 is a graph showing element distribution on a surface after oxidation.

FIG. 7 is a graph showing element distribution on a surface after oxidation.

FIG. 8 is a graph showing the relationship between the total leak amount and the impurity concentration of the conventional device.

[Explanation of symbols]

 201 exhaust device, 202 decompression chamber, 203 passivation membrane, 204 gas supply system, 205,301 gas cylinder, 302 gas introduction line, 303 electric furnace, 304 purge line, 305 dew point meter, 401 gas purification device, 402 SUS pipe, 403 APIMS, 404 power supply.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ identification code FI H01L 21/3065 H01L 21/302 B (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 8/10-8 / 18

Claims (20)

(57) [Claims] 1. A passivation film having a layer containing more chromium oxide than iron oxide on an outer surface is formed on an electropolished surface, and a surface of the stainless steel on which the passivation film is formed has a radius of 5 μm. Characterized in that the maximum value of the difference in height between the convex portion and the concave portion in the circumference of the above has a flatness of 1 μm or less. 2. The stainless steel according to claim 1, wherein the outermost surface does not contain iron oxide and is made of chromium oxide. 3. The stainless steel according to claim 1, wherein the thickness of the passivation film is 5 nm or more. 4. The stainless steel according to claim 3, wherein the passivation film is a film having a thickness of 13 nm or more formed by heating and oxidizing stainless steel at a temperature of 550 ° C. or more for 9 hours or more. 5. After electrolytic polishing, to remove water from the surface of the base material by performing baking, then the content of impurities in the following oxidizing gas atmosphere 1 ppb, 550
A method for producing stainless steel, comprising forming a passivation film on the surface of a base material by heating at a temperature of not less than ° C. 6. The baking temperature is 150 to 400 ° C.
The method for producing stainless steel according to claim 5, wherein: 7. A decompression device characterized in that a main part is made of the stainless steel according to any one of claims 1 to 4. 8. A gas supply device for supplying an ultra-high-purity gas whose main part is made of stainless steel is connected to the decompression device, and a stainless steel material exposed inside the gas supply device is provided. The pressure reducing device according to claim 7, wherein the passivation film is formed on at least a part of a surface. 9. A gas cylinder for supplying an ultra-high purity gas whose main part is made of stainless steel is connected to the decompression device via the gas supply device, and is exposed inside the gas cylinder. 9. The pressure reducing device according to claim 7, wherein the passivation film is formed on at least a part of a surface of the stainless steel. 10. The self-cleaning decompression according to claim 8, wherein the gas supply device includes a cleaning gas supply system for etching and removing deposits attached to the inner wall of the insulating decompression chamber. apparatus. 11. The self-cleaning pressure reducing device according to claim 10, wherein the cleaning gas is a chlorine-based gas or a fluorine-based gas. 12. The self-cleaning-capable pressure reducing device according to claim 10, wherein the pressure reducing device includes a heating device that is heated to a temperature of about 350 ° C. 13. The pressure reducing device is selected from a semiconductor manufacturing device, a gas cylinder, a gas valve and a pipe.
13. A combination of one or two or more.
The pressure reducing device according to any one of the above. 14. The pressure reducing device according to claim 13, wherein the semiconductor device is a film forming device using plasma. 15. The stainless steel according to claim 1, wherein the stainless steel is an austenitic stainless steel. 16. The stainless steel according to claim 1, wherein the stainless steel is a ferritic stainless steel.
The stainless steel according to any one of the above. 17. The method according to claim 5, wherein the stainless steel is an austenitic stainless steel. 18. The stainless steel according to claim 5, wherein the stainless steel is a ferritic stainless steel.
3. The method for producing stainless steel according to item 1. 19. The pressure reducing device according to claim 7, wherein the stainless steel is an austenitic stainless steel. 20. The stainless steel according to claim 7, wherein the stainless steel is a ferritic stainless steel.
5. The pressure reducing device according to any one of items 4 to 5.