JP3045576B2 - Method of forming passive film on stainless steel and stainless steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a passivation film of stainless steel and a stainless steel, and more particularly to an oxidation resistant film suitable for ultra-high vacuum equipment, ultra-high cleaning equipment, ultra-pure water equipment and the like. The present invention relates to a method for forming a passive film on a passive stainless steel and a stainless steel.

[0002]

2. Description of the Related Art In recent years, a technique for realizing an ultra-high vacuum or a technique 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, but it is also very strongly desired to realize a reduced-pressure atmosphere in which contamination of impurities is reduced to the utmost.

For example, taking a semiconductor device as an example, L
With the increase in integration of SI, the size of unit elements has been decreasing year by year, from 1 μm to submicron, and further 0.5 μm.
Research and development of semiconductor devices having dimensions of less than m have been actively conducted for practical use.

In the manufacture of such a semiconductor device, a step of forming a thin film, a step of etching the formed thin film into a predetermined circuit pattern, and the like are repeatedly performed. These processes are usually performed in an ultra-high vacuum state or a reduced-pressure atmosphere into which a predetermined gas is introduced. If impurities are mixed in these steps, problems such as deterioration of the film quality of the formed thin film and inability to obtain the precision of the fine processing are caused. This is the reason why an ultra-high vacuum or an ultra-high clean reduced-pressure atmosphere is required in the semiconductor manufacturing process.

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

FIG. 9 shows the relationship between the total leak amount (the sum of the amount of gas released from the piping system and the inner surface of the reaction chamber and the external leak) of the system combining the gas piping system and the reaction chamber in the conventional apparatus and gas contamination. FIG. A plurality of lines in the figure show the relationship between the impurity concentration in the atmosphere and the total leak amount of the system when the gas flow rate is changed to various values.

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. As you can see from the figure, 10cc
In the case of using a flow rate of / min, if there is a total leakage of about 10 ⁻³ to 10 ⁻⁶ Torr · l / sec as in a device widely used at present, the impurity concentration in the gas is 10 ppm to 1 ppm. %, Which is far from a high clean process.

The inventor of the present invention invented an ultra-high-purity gas supply system, and 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. doing. However, since the gas leaks from the inside of the system, that is, the gas is released from the surface of the stainless steel, the impurity concentration in the reduced-pressure atmosphere cannot be reduced as a result.

The minimum value of the surface emission gas amount obtained by the surface treatment in the current ultra-high vacuum technology is 1 × 10 ⁻¹¹ Torr · l / sec · cm ² for stainless steel. Here, the surface area exposed inside the chamber is
For example, even if it is estimated to be as small as 1 m ² , the total leak amount is 1 × 10 ⁻⁷ Torr · l / sec, and when the gas flow rate is 10 cc / min, the impurity concentration is 1 p.
Only a gas having a purity of about pm can be obtained. If the gas flow rate is further reduced, it goes without saying that the purity is further reduced.

Therefore, the degassing component from the inner surface of the chamber is reduced to 1 × 10 ⁻¹¹ Torr, which is the same as the external leakage amount of the 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.
c · cm ² or less. Therefore, there has been a strong demand for a technology for treating the surface of stainless steel that reduces the amount of outgassing.

On the other hand, in the semiconductor manufacturing process, a wide variety of gases are used, from relatively stable general gases (O ₂ , N ₂ , Ar, H ₂ , He) to highly reactive, corrosive and toxic special gases. Is done. In particular, if there is moisture in the atmosphere, such as hydrogen chloride (HCl), chlorine (Cl ₂ ), boron trichloride (BCl ₃ ), boron trifluoride (BF ₃ ), etc. There are gases that produce hydrochloric acid and hydrofluoric acid, which are highly corrosive. Normally, stainless steel is used for piping and chamber materials that handle these gases because of its corrosion resistance, high strength, ease of secondary workability, ease of welding, and ease of polishing the inner surface. Many.

[0012] However, stainless steel is excellent in corrosion resistance in an ultra-high purity atmosphere with a trace amount of water, 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 processing method, a passive film forming method such as Ni-WP coating (clean S coating method) for coating stainless steel with a metal having high corrosion resistance or forming a thin oxide film on the metal surface in a nitric acid solution. However, since these are wet methods, a large amount of moisture and processing solution residues are present on the film surface, in the film, and at the interface between the film and stainless steel, making them applicable to ultra-high vacuum equipment and ultra-high cleaning equipment. Has not been reached.

Therefore, stainless steel is oxidized in the gas phase,
A method for forming a passivation film has been proposed.

As a result of repeated studies on the relationship between the degassing characteristics of the oxidized passivation film and the conditions for forming the same, the moisture in the oxidizing atmosphere during the formation of the passivated film caused the surface state of the passivated film and the degassing. It was found that the characteristics were greatly affected, and the following findings were obtained for these.

An oxidation passivation film formed in a high-purity atmosphere having a water content of, for example, about 100 ppb is shown in FIG.
As shown in FIG. 1A, a passive film formed by a wet method (FIG. 1)
Although the degassing property was improved as compared with (b), it was still insufficient, and did not reach the point where it could be used as a material for an ultra-high vacuum or ultra-high clean pressure reducing device.

FIG. 10 shows a concentration profile of each component atom in the depth direction of this passivation film measured by XPS (X-ray photoelectron spectroscopy), and FIG. 11 shows a scanning electron micrograph of the film surface.
Shown in As seen in the electron micrograph of FIG. 11, a number of cracks and pinholes were observed on the surface of the passive film, and a smooth and dense film was not obtained. In addition, as shown in FIG. 10, it was found that chromium oxide having high corrosion resistance was small on the outermost surface of the passivation film, and a layer mainly composed of iron oxide was formed.

As described above, when an oxidation passivation film is formed in an oxidizing atmosphere containing moisture, even if the amount of moisture is very small, the passivation film obtained in accordance with the concentration of moisture in the atmosphere has a high smoothness. Density is affected, causing cracks and pinholes in the passive film. According to the analysis by XPS, the cracks and pinholes are present in the outermost layer containing a large amount of iron oxide, and moisture is adsorbed and occluded by the cracks and pinholes, so that the degassing property may be deteriorated. Do you get it.

On the other hand, when an oxidation passivation film is formed on the surface of stainless steel in an ultra-high purity atmosphere having a water content of 10 ppb or less, a passivation film having excellent degassing characteristics is obtained as shown in FIG. Although it can be used as a material for an ultra-high vacuum or ultra-high-purity decompression device, the passivation film has not yet reached a point where surface irregularities can be completely ignored.

That is, electrolytic polishing is performed to smooth the surface before the formation of the passivation film. The surface roughness that can be achieved by the electrolytic polishing at present is limited to Rmax 0.05 to 0.1 μm. A surface roughness of 0.5 μm is used. However, when the passivation film is formed after the electrolytic polishing, the surface roughness during the electrolytic polishing is not maintained, and the surface becomes rough. For example, if the base material (bulk part) is
When the passivation film is formed even when the surface of Rmax is finished to Rmax 0.05 to 0.1 μm, the surface roughness of the passivation film becomes Rmax
It becomes coarser than 0.1. As a result, there is no stainless steel having a passivation film and a surface roughness of less than Rmax 0.1 at present. The present inventors have clarified that the surface roughness of the passivation film greatly affects the outgassing characteristics, and that the rougher the surface roughness, the greater the amount of gas release.

The present invention has been made based on the discovery of the above-mentioned problems with respect to the oxidation passivation film.

[0022]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for forming a passivation film having excellent degassing characteristics and corrosion resistance by achieving ultra-flatness and densification of the passivation film, and a stainless steel. Aim.

[0023]

A first gist of the present invention is as follows.
Electrolytic polishing of the surface of stainless steel, oxidation in an oxidizing atmosphere gas, and then reduction of iron oxide on the surface with hydrogen gas. I do.

According to a second aspect of the present invention, in the first aspect, after the electrolytic polishing treatment, before forming the oxide film, 300
A method for forming a stainless steel oxidation passivation film, characterized by performing a heat treatment in an inert gas atmosphere at a temperature of up to 600 ° C. A third aspect of the present invention resides in a method for forming a passivation film of stainless steel, wherein annealing is performed in an inert gas after the hydrogen gas treatment.

The third gist of the present invention is that the surface roughness is Rmax
Present in stainless steel characterized by having a passivation film of less than 0.1 μm.

[0026]

Operation and Embodiments The operation of the present invention will be described below together with embodiments.

(Electropolishing) In the present invention, electropolishing is performed before forming a passivation film. As the electrolytic polishing method, for example, a composite electrolytic polishing method may be used. With the composite electrolytic polishing method, the polished metal to be polished is electrolytically eluted by electrolysis,
This is a method of processing a passive oxide film generated on the surface of a metal to be polished into a mirror surface by rubbing action of abrasive grains (for example,
JP-B-57-47759).

By electropolishing stainless steel,
The affected layer on the surface is removed. Further, the surface roughness is R
_max can be 1 μm or less. The surface roughness after the electropolishing is preferably as fine as possible.
It is preferable that the thickness be in the range of 0.5 to 0.1 μm.

FIG. 2 shows a change in the surface state due to electrolytic polishing. 2A shows the surface state after polishing, and FIG. 2B shows the surface state before polishing. As is clear from FIG. 2, before polishing, there are large irregularities of crystal grains, and even if an oxide passivation film is formed in this state, a continuous film cannot be obtained.
The resulting film has poor corrosion resistance. Further, since moisture and the like are absorbed and absorbed between crystal grains, a film having good degassing properties cannot be obtained. By performing the electropolishing treatment, the surface becomes uneven and the surface becomes smooth. As a result, the surface area is reduced and the amount of adsorbing and occluding water is greatly reduced.

After the electrolytic polishing, it is preferable to perform the same precision cleaning and drying as the wafer cleaning.

(High Temperature Baking Pretreatment) In the present invention, a passivation film forming treatment may be performed immediately after electrolytic polishing.
It is preferable to perform high-temperature baking before the passivation film forming process. If this high-temperature baking treatment is performed before the passivation film formation treatment, the chromium concentration on the stainless steel surface side increases, and a dense, excellent corrosion-resistant passivation film is formed.

The high-temperature baking pretreatment is performed, for example, by Ar, H
e, by introducing an inert gas such as N ₂ gas. Time is 1
-10 hours are preferred. The processing temperature is preferably from 300 to 600 ° C (Claim 2), more preferably from 400 to 520 ° C. When performed in a temperature range of 400 to 520 ° C., the surface roughness is further suppressed, and the formed oxide passivation film becomes a denser film as compared with the case performed in another temperature range, and the degassing property is further improved.

Incidentally, an oxidation passivation film is also formed in this high-temperature baking. The reason why an oxidation passivation film is formed on the surface despite baking in an inert gas atmosphere is not always clear, but oxygen (several ppm or less) contained as an impurity in the base material or inert gas It is considered that oxygen (several ppt) contained as an impurity in the gas is a source of oxygen. Further, the surface roughness of the passivation film formed by the high-temperature baking is maintained at the surface roughness after the electrolytic polishing. The thickness of the passivation film varies depending on the baking temperature and time. For example, in the case of 500 ° C. × 10 hours, the thickness becomes about 30 °, so that it can be put to practical use as it is.

(Oxidation treatment: Passive film formation treatment) After the high-temperature baking treatment, an oxidizing gas (for example, Ar / O ₂ = 4/1)
(Molar ratio) of mixed gas), for example, 350 to 45
Heat to 0 ° C. to form an oxidation passivation film on the stainless steel surface. By this oxidation treatment, a layer containing a large amount of chromium oxide is formed on the stainless steel surface, and a layer containing a large amount of iron oxide is formed thereon. The layer containing much iron oxide is a porous film having cracks and pinholes as described above. The degree of such cracks and pinholes varies depending on the amount of water in the oxidizing atmosphere, and the smaller the water content, the better.

(Hydrogen gas treatment) The oxidizing gas is exhausted, and then the hydrogen gas is introduced to reduce and remove the passivation outermost layer. By this hydrogen treatment, the outermost surface of the passivation film becomes a clean and flat surface. This is considered to be a result of a layer containing a large amount of iron oxide containing pinholes and cracks being reduced and removed by hydrogen, and a dense layer containing a large amount of chromium oxide appeared.

In general, it is said that hydrogen molecules are radicalized at a temperature of 700 ° C. or more and cause a reduction reaction.
The reason why the reduction reaction occurs at a low temperature of about ℃ has not been confirmed yet, but it is presumed that Ni contained in stainless steel works as a catalyst. The hydrogen concentration in the hydrogen treatment gas is preferably 0.1 ppm to 10% (claim 3),
0.5-100 ppm is more preferred. 0.5-100
In the ppm range, a dense passivation film having better degassing properties is formed. The temperature of the hydrogen treatment is 200 to 50.
0 ° C is preferable (claim 4), and 300 to 400 ° C is more preferable. Within this range, the hydrogen embrittlement of stainless steel is suppressed, and a passivation film containing chromium oxide as a main component and having good degassing properties can be obtained.

The surface roughness of the passivation film produced as described above is extremely smooth. For example, when the passivation film is formed by the above process after finishing to 0.05 to 0.1 μm by electrolytic polishing. , A passive film having a surface roughness of 0.01 μm or less is obtained.

(Annealing Treatment) After the hydrogen treatment, annealing is further performed in an inert gas, whereby the chromium oxide concentration on the outermost surface of the thermally oxidized passive film is further increased, and a film having more excellent corrosion resistance is obtained. 5). Annealing is 200-50
It is preferable that the annealing is performed at 0 ° C. for 1 to 10 hours (Claim 6). By performing annealing under the conditions in this range, the surface state of the thermal oxidation passivation film becomes smoother, and the chromium oxide concentration on the outermost surface is further reduced. And the corrosion resistance is further improved. In the present invention, for example, Ar, He, N ₂ or the like is used as the inert gas.

(Stainless Steel) As described in the related art section, conventionally, no stainless steel having a passivation film having a surface roughness of R _{max of} 0.1 μm or less did not exist. This is because the surface becomes rough when a passivation film is formed by the conventional technique.

However, according to the method of the present invention described above,
A stainless steel having a passive film having a surface roughness of _Rmax 0.1 μm or less (claim 8) can be easily produced. One is that the surface roughness is 0.05 by electrolytic polishing.
This is a method of performing high-temperature baking after finishing to 0.1 μm. As described above, the passivation film is formed even by the high-temperature baking, and the surface roughness during the electrolytic polishing is also maintained by the high-temperature baking as described above. Therefore, if high-temperature baking is performed after electropolishing, a passive film having a surface roughness of 0.05 to 0.1 μm can be obtained. The passivation film is extremely rich in chromium and has a Cr / Fe ratio of 1 or more.
A Cr / Fe ratio of close to 7 has been achieved (see FIG. 5), and it is a very dense passive film.

After all, this stainless steel has a surface roughness of R
_max 0.1 μm or less, and having a dense passivation film, it is extremely excellent in degassing properties.
1). Other methods of surface roughness to obtain a stainless steel having a passivation film is not more than R _max 0.1 [mu] m, the surface of the surface roughness of the base material Rmax0.05~0.1μm by electropolishing
And performing the above-described hydrogen gas treatment (high-temperature baking may be performed before the hydrogen gas treatment). According to this method, a stainless steel having a passivation film having a surface roughness of Rmax 0.01 or less can be produced.
The Cr / Fe on the passivated surface after the hydrogen gas treatment is larger than the Cr / Fe on the base material (see FIG. 7, for example, in FIG.
35) Therefore, a stainless steel excellent in degassing properties and corrosion resistance can be obtained (claim 10).

(Target Stainless Steel) The stainless steel of the present invention is, for example, Fe-Cr-based, Fe-Cr-Ni
System. In addition, ferrite,
Any of martensitic and austenitic stainless steels may be used.

The passivated stainless steel produced by the above-described passivation film forming method of the present invention exhibits extremely good degassing properties and corrosion resistance, and is suitable for use in ultra-vacuum devices, ultra-high clean pressure reducing devices and the like. It can be used as a constituent material.

[0044]

Embodiments of the present invention will be described below.

(Example 1) SU having a length of 2 m and a diameter of 3/8 "
S316L stainless steel tube is electropolished and the surface is radius 5μ.
maximum difference of the irregularities in the circumference of m and (R _max) 0.05μ
m mirror surface. As shown in FIG. 3, this surface state is a smooth surface where crystal grain boundaries can be seen. Next, the stainless steel tube was subjected to the same method as the wafer cleaning process, that is, ammonia peroxide (NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 4: 20,
(90 ° C.), hot water (90 ° C.), ultrapure water, and dried with isopropyl alcohol.

The stainless steel tube was set in a conventional oxidation furnace, Ar gas was flowed at a rate of 1 l / min, and after purging at room temperature for 1 hour, the temperature was raised to 450 to 550 ° C. and baked for 10 hours. FIG. 4 shows the state of the stainless steel inner surface after heat treatment at various temperatures. As is apparent from FIG. 4, the mirror surface of the stainless steel surface after electrolytic polishing was maintained even after the heat treatment at a high temperature for a long time. That is, R _max 0.
05 was maintained. FIG. 5 shows the result of XPS measurement of the inner surface of the stainless steel tube baked at 500 ° C.
Shown in By the baking treatment, chromium atoms increased on the surface side and iron atoms decreased, and the chromium / iron composition ratio was reversed from that in the bulk.

In FIG. 5, the intersection of the line of Fe and the line of O is the interface between the bulk (base material) and the passivation film. The thickness of the passivation film shown in FIG. 5 is about 30 °. In this passivation film, about 22 ° from the surface (the left end of the graph in FIG. 5)
Has more chromium oxide than iron oxide.

Subsequently, the temperature in the oxidation furnace was lowered to 400 ° C.
The r gas was replaced with a mixed gas of Ar and O ₂ containing 100 ppb of moisture (Ar / O ₂ = 4: 1), and the inner surface of the stainless steel tube was oxidized. As shown in the electron micrograph of FIG. 10, a number of cracks and pinholes were observed on the surface of the film after the oxidation.

Next, after purging the oxidizing gas with Ar gas, Ar gas containing 1 ppm of H ₂ was introduced into the stainless steel tube, and the oxide film was subjected to hydrogen reduction treatment at 400 ° C. for 10 or 30 minutes. FIG. 6 shows the surface state after the treatment, and FIG. 7 shows the concentration profile of the component elements in the oxidation passivation film. FIGS. 6, 7A and 7B show the results when the reduction processing time is 10 minutes and 30 minutes, respectively.
As shown in FIG. 6, cracks and pinholes existing after the oxidation treatment were not observed on the surface of the passivation film subjected to the hydrogen reduction treatment, and the surface became flat. On the other hand, as shown in FIG. 7, a high concentration of chromium oxide was present in the passivation film, and the chromium atomic ratio to iron was much higher than in the base material. The thickness of the passivation film shown in FIGS. 7A and 7B was about 60 °.

When the surface roughness of the passivation film was measured, it was R _max 0.01 μm.

From the above, by the hydrogen reduction treatment, the iron oxide layer having many pinholes and cracks is removed, a dense layer containing a large amount of chromium oxide appears, and the surface becomes clean and flat. It is thought that it was.

Further, it was found that the hydrogen reduction treatment time hardly affected the surface state of the passivation film and the concentration profile in the depth direction, and the reduction reaction was completed in about 10 minutes.

Next, an evaluation test of the degassing characteristics was performed on the stainless steel tube subjected to the above passivation treatment. After leaving the stainless steel tube in a clean room at a relative humidity of 50% and a temperature of 20 ° C. for one week, Ar gas was flowed at a flow rate of 1.2 l / min, and the amount of water contained in the Ar gas was measured at the outlet of the tube by AP.
It was measured by IMS (atmospheric pressure ionization mass spectrometer). The results are shown in FIG. 20 minutes after passing the gas, the water content in the Ar gas was reduced to 10 ppb, and after 30 minutes, it became 3 ppb or less of the background level.

As compared with the oxidation passivation film produced by the conventional method shown in FIG. 1 (a), the degassing characteristics are greatly improved. It is shown that it can be applied to ultra-high clean pressure reduction equipment.

(Example 2) An oxidation passivated stainless steel tube was prepared in the same manner as in Example 1 except that the baking treatment in an Ar atmosphere was omitted, and the degassing characteristics were evaluated. The results are shown in FIG.

As is apparent from FIG.
After 3 minutes, the water content becomes 3 ppb, and the degassing property is
Although it is inferior to the oxidation passivation film of No. 1, it is greatly improved over the conventional oxidation passivation film.

Example 3 The temperature of the hydrogen reduction treatment was set to 600
° C, and the other treatment conditions were the same as in Example 1, an oxidation passivation film was formed on the inner surface of the stainless steel tube, and the same evaluation was performed.

The results are shown in FIG. The surface of the passivation film produced here is slightly rough and the degassing properties are inferior to those of Examples 1 and 2, but the water content is about 70% after passing the gas.
Min to 3 ppb and clearly improved compared to the conventional example.

(Example 4) An oxidation passivation film was formed on the inner surface of a stainless steel tube under the same conditions as in Example 1 except that the hydrogen reduction treatment gas was Ar gas containing 20% hydrogen, and the same evaluation was performed. Was.

The results are shown in FIG. Although the surface of the passivation film is slightly rough and the degassing properties are inferior to those of Examples 1 and 2, the water content is reduced to 3 ppb in about 70 minutes after passing the gas, which is clearly improved as compared with the conventional example. Was done.

(Example 5) The oxidizing atmosphere was changed to a water concentration of 5 p.
An oxidation-passive stainless steel tube was prepared in the same manner as in Example 1 except that the atmosphere was set to an ultrapure atmosphere of pb, and the degassing characteristics were evaluated. The result is as shown in FIG. Ten minutes after passing the gas, the water content in the Ar gas became 3 ppb or less of the background level, and it was found that the degassing characteristics were improved by the treatment of this embodiment even with the current highest level film. .

(Example 6) After hydrogen reduction treatment in the same manner as in Example 1, annealing treatment was further performed at various temperatures for 10 hours in Ar gas. XPS on thermal oxidation passivation film surface
FIG. 8 shows the concentration profile in the depth direction according to.

As is apparent from FIG. 8, the concentration of chromium having high corrosion resistance in the outermost surface layer was increased by Ar annealing. In addition, it was found that the chromium concentration further increased with an increase in the treatment temperature, and that the concentration of chromium and iron was reversed above 475 ° C. The thickness of the passivation film shown in FIGS. 8A to 8F was about 70A.

Further, the oxidation passivation film of this embodiment has improved corrosion resistance due to an increase in the chromium concentration on the outermost surface, and has a 36% HC content.
It showed very good corrosion resistance even to 1 strongly corrosive solution.

[0065]

According to the present invention, it is possible to form a passivation film having extremely excellent degassing characteristics and corrosion resistance.
It is possible to supply an oxidized passivated stainless steel applicable to an ultra-high vacuum, ultra-high clean pressure reducing device, and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing the degassing characteristics of an oxidized passive stainless tube manufactured by various methods. (A) A thermally oxidized passivation film produced by a conventional method. (B) An oxidation passivation film produced by a wet method. (C) A thermally oxidized passive film formed in an ultra-high purity oxidizing atmosphere having a water content of 10 ppb or less. (D) The thermal oxidation passivation film of Example 1. (E) The thermal oxidation passivation film of Example 2. (F) The thermal oxidation passivation film of Example 3. (G) The thermal oxidation passivation film of Example 4. (H) The thermal oxidation passivation film of Example 5.

FIG. 2 is a scanning electron micrograph showing the inner surface state of a stainless steel tube before and after electrolytic polishing.

FIG. 3 is a scanning electron micrograph showing the inner surface state of a stainless steel tube after electrolytic polishing.

FIG. 4 is a scanning electron micrograph showing the inner surface state of a stainless steel tube after baking in an Ar gas atmosphere.

FIG. 5 is a graph showing a concentration profile in a depth direction by XPS of an electropolished surface after baking in an Ar gas atmosphere.

FIG. 6a is a scanning electron micrograph showing the surface state of a thermal oxidation passivation film after hydrogen reduction treatment for 10 minutes.

FIG. 6B is a scanning electron micrograph showing the surface state of the thermal oxidation passivation film after the hydrogen reduction treatment for 30 minutes.

FIG. 7 is a graph showing a concentration profile in the depth direction by XPS of the surface of a thermally oxidized passivation film after a hydrogen reduction treatment. (A) Processing time 10 minutes (b) Processing time 30 minutes

FIG. 8 shows X on the surface of a thermally oxidized passivation film after Ar annealing.
7 is a graph showing a depth concentration profile by PS. (A) Annealing temperature 375 ° C (b) Annealing temperature 400 ° C (c) Annealing temperature 425 ° C (d) Annealing temperature 450 ° C (e) Annealing temperature 475 ° C (f) Annealing temperature 500 ° C

FIG. 9 is a graph showing a relationship between an impurity concentration in an atmospheric gas and a system leak amount at various gas flow rates.

FIG. 10 is a graph showing a concentration profile in the depth direction by XPS of the surface of a thermally oxidized passivation film manufactured by a conventional method.

FIG. 11 is a scanning electron micrograph showing the surface state of a thermally oxidized passivation film manufactured by a conventional method.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C23C 22/00 C23C 22/00 C25F 3/06 C25F 3/06 (56) References JP-A-57-149473 (JP, A) JP-A-63-278760 (JP, A) JP-A-63-169391 (JP, A) JP-A-64-31956 (JP, A) JP-A-3-285049 (JP, A) JP-A-5-33156 (JP, A) JP-A-5-125518 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D 1/76 C23C 8/02 C23C 8/14 C23C 8/80 C23C 22 / 00 C25F 3/06

Claims (11)

(57) [Claims] 1. A stainless steel passivation film characterized in that after a surface of stainless steel is electropolished, an oxidation treatment is carried out in an oxidizing atmosphere gas, and subsequently, iron oxide on the surface is reduced and removed by hydrogen gas. Forming method. 2. The method according to claim 1, wherein the heat treatment is performed in an inert gas atmosphere at 300 to 600 ° C. after the electrolytic polishing and before the oxide film is formed. . 3. The method for forming a stainless steel oxide passivation film according to claim 1, wherein in the hydrogen gas treatment, a hydrogen concentration in a gas atmosphere is 0.1 ppm to 10%. 4. The method for forming an oxide passivation film on stainless steel according to claim 1, wherein the processing temperature in the hydrogen gas processing is 200 to 500 ° C. 5. The method for forming an oxidized passivation film of stainless steel according to claim 1, wherein annealing is performed in an inert gas after the hydrogen gas treatment. 6. The condition of the inert gas annealing treatment is 2
The method for forming an oxide passivation film on stainless steel according to claim 5, wherein the temperature is from 00 to 500C for 1 to 10 hours. 7. The condition of the inert gas annealing treatment is 4
The method according to claim 6, wherein the temperature is 75 ° C or higher. 8. A stainless steel having a passivation film having a surface roughness of Rmax 0.1 μm or less. 9. The stainless steel according to claim 8, having a passivation film having a surface roughness of Rmax 0.01 μm or less. 10. Cr / Fe on the surface of a passivation film
10. The atomic ratio (hereinafter, the same) is larger than Cr / Fe in the base material portion.
Stainless steel as described. 11. The stainless steel according to claim 8, wherein Cr / Fe on the surface of the passivation film is 1 or more.