JPS6319499A - High purity gas maintaining vessel - 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] (Industrial application field) The present invention relates to containers for maintaining high purity gases.

More specifically, we will focus on the adsorption and desorption of high-purity gases required in the semiconductor industry, especially fine particles and gases on the inner surface of containers.
This invention relates to a pressure-resistant metal container whose gas contact surface is subjected to electrolytic composite polishing in order to reduce the amount of gas.

(Conventional technology) Container cylinders (hereinafter referred to as “cylinders”) for filling compressed gas or liquefied gas
That's what it means. ) are widely used as a means of storing and transporting gas in industrial, medical, and household uses, but as the demand for gas increases, the types and number of cylinders used are changing year by year. It is on the rise.

Among these, in recent years, with the remarkable development of the semiconductor industry, large quantities of various types of high-purity gases have come to be used, and at the same time serious problems have been raised that need to be solved, such as maintaining the ultra-high purity of gases in the cellar. It became so.

Nowadays, as ultra-LSIs are manufactured with higher integration and higher performance, and the minimum processing size is on the submicron order, not only the ultra-high purity ratio of the gas itself, but also the gas supply system, such as cylinders, piping, and their components. Microscopic particles (hereinafter referred to as "li-ticles") mixed in from systems such as systems, moisture released from the inner surface, and gaseous impurities such as air components can cause crystal defects in LSIs, poor thin film quality,
This can lead to poor uniformity in film deposition process, pattern defects, etc., resulting in a decrease in product conversion rate, a decrease in film deposition speed, and affecting productivity.
As performance increases, this problem is becoming more serious.

To solve these problems, stainless steel/? High-performance materials and high-performance processes have been adopted, such as smoothing the gas-contact surfaces of piping and its components such as IZO, various valves, regulators, etc., and cleaning all the gas retention parts of the piping system from the main line. have been developed and progress is being made in the direction of solutions.

However, there is no appropriate lean technology for the cylinders in which gas remains for the longest time, where contamination is most likely to occur, and which has the greatest impact on supplying ultra-high purity gas. At present, it is used for semiconductor high-purity gases without any innovations.

The cylinder must comply with the Container Safety Regulations of the High Pressure Gas Control Law9.
Manufactured using manganese steel, stainless steel, aluminum alloy, chromium molybdenum steel, etc., using the Erhardt method or the Mannesmann method.

However, the skin roughness caused by hot processing on the bottom and head of the cylinder, scratches caused by the embossing tool during bottom molding, and the formation of a porous surface oxide film due to heat treatment, which may contain fine particles and gas components. It has a surface that is easy to absorb.

In addition, since the valve mounting screw is an internal thread type,
There are also structural problems such as metal powder getting mixed into the cylinder when the valve is installed, causing particles to be generated.

In order to solve these problems, attempts have been made to coat the inner surface of the cylinder with resins such as Teflon and vinyl chloride, but the adhesive strength between the resin and the inner wall of the cylinder is low and it may peel off during use. The technology still has many drawbacks, such as gas permeability being a problem and the plasticizer in the resin dissolving into the gas, degrading the quality of the gas, and it is difficult to say that this technology is complete. In addition, coating by dipping or spraying with phosphates such as zinc phosphate and manganese phosphate,
That is, although there is a nog-curling method, it cannot be said to be a technique that can be used for cylinders filled with ultra-high purity gas.

(Problems and Means to be Solved by the Invention) The present inventors have developed a method of mirror-finishing the inner surface using an electrolytic composite polishing method during the production process of a cylinder that generates fewer particles and has a smaller amount of gas adsorption. I realized that I could achieve my goal by doing so.

The present invention was made based on the above discovery, and by forming an extremely smooth and dense passivation film on the inner surface of the cylinder using an electrolytic composite polishing method, fine scratches are generated. To provide a cylinder that is difficult to use and has a small amount of gas adsorption.

The container referred to in the present invention is generally a pressure-resistant metal container sold under the name of cylinder. The material may be manganese steel, stainless steel, aluminum alloy, chromium molybdenum steel, etc., but is not limited to these as long as it is a metal container.

The gas filled in the container includes both compressed gas and liquefied gas, and becomes gaseous when released from the container.

According to the present invention, in order to maintain high purity gas, at least the main area of the surface in contact with the gas (inner surface) is subjected to electrolytic composite polishing, thereby making the inner surface mirror-finished, significantly reducing particles, and This makes it possible to reduce the amount of gas adsorbed and desorbed onto the inner surface and prevent contamination and corrosion caused by these gases.

Furthermore, using an external thread for the mouthpiece of the cylinder is effective in suppressing the generation of particulates.

■ As mentioned earlier, the materials used for the cylinders are those that comply with container safety regulations based on the provisions of the High Pressure Gas Control Law.

That is, heat-treated or non-heat-treated materials such as stainless steel, carbon steel, manganese steel, chromium-molybdenum steel, and aluminum alloy (having the same chemical composition as JISH4000 types 5052 and 5056) are used.

■ The manufacturing method for high-pressure gas cylinders and liquefied gas cylinders involves the following steps when heat-treated materials are used.

A, Seamless steel pipe → Mouth, Cutting to length → No., Bottom hot processing → Two, Bottom embossing → E Head hot processing → To, Heat treatment → G, Neck link sugar → H, Thread part cutting → S , Internal cleaning → Nu, Pressure test Note that heat treatment is not required when non-heat treated materials are used. In addition, when producing a cylinder from a billet, the above steps are performed after drilling, heat stretching, and hot working of the head.

However, the cylinders manufactured using this method have an extremely scratched and uneven inner surface with many folds, contain a seal, and absorb a huge amount of gas, which can cause a decline in the quality of the high-purity gas filled. Become.

Therefore, in order to improve these defects, an electrolytic composite polishing process was added between the bottom embossing, the head hot processing (head processing in the case of non-heat-treated materials), and the inner surface was perfected. We have developed a method for manufacturing cylinders with smooth surfaces.

■ The electrolytic composite polishing method applied in the present invention is to electrolytically elute the anodic metal to be polished, and at the same time remove the passivation oxide film generated on the surface of the metal to be polished by the abrasive action of abrasive grains. This is a method of polishing the surface to a mirror finish, giving the abrasive grains a speed above a certain level to abrade the polished surface, and at the same time,
This method is characterized by generating an anodic reaction of elution and oxidation on the polishing surface at an electrolytic current rate of several A/crrL2 or less through an electrolytic solution. (Tokuko Sho 57-477
59. 58-19409).

This will be explained in more detail with reference to FIG. Figure 1 shows −'A of the tool used in the mirror finishing method of the present invention, 1 is a tool connected to a drive shaft and rotated by a drive device, and 2 is a tool formed at the bottom of tool 1. A disk-shaped cathode made of plate A; 3 is an exposed surface formed in a cross shape on the lower surface of the cathode 2; 4 is an outlet for the electrolytic solution 5 provided through the center of the cathode 2; 6 is the lower surface of the cathode 2 The abrasive grains 7 are pasted on the entire surface except for the exposed surface 3 and the outlet 4, and 7 is a thin film of electrically insulating paint, which removes useless waste from the circumferential surface of the cathode 2 and the circumferential surface of the tool 1. To prevent leakage current from flowing out, the electrolytic solution 5
The electrolyte is fed under pressure from the electrolyte supply device through the drive shaft of the tool 1, supplied from the outlet 4 to the gap between the exposed surface 3 and the metal to be polished (not shown), and discharged out of the tool. The cathode 2 of the tool 1 and the metal to be polished are connected to the cathode and anode sides of a direct current or Noculus voltage, respectively.

During the polishing process, the full voltage is applied as described above between the cathode 2 of the tool 1 and the metal to be polished, and the electrolytic solution 5 is supplied in between, and the cathode 2 is rotated while being pressed against the metal to be polished. The metal to be polished is anodic-dissolved by the action, and the convex parts of the passivated oxide film generated on the uneven parts of the surface of the metal to be polished are removed by abrasion by the abrasive grains 6, and the convex parts of the metal to be polished are removed. The parts are preferentially electrolytically eluted and finished to a mirror surface.

To give an example of polishing, +120-$1500 S
When abrading the inner surface of a SU8.316 cylinder with an initial surface roughness of 5 to 1 μmRmax using iC-based abrasive grains, use a 20% NaNOs aqueous solution as the passivation type electrolyte and adjust the electrolytic current density to 0 to 6 A/CrIL2. As a result of polishing within a range, an inner surface with a roughness of 0.1 μmRmax was obtained.

Furthermore, manganese steel, aluminum alloy, etc. can also be polished using the same method.

■ Conventionally, by cutting a tapered female thread in the valve mounting hole of the valve, cutting a tapered male thread in the leg of the valve, and fitting the leg of the pulp into the valve mounting hole of the valve. The common method is to ensure airtightness under high pressure, but the mating surfaces of screws rub against each other under extremely high surface pressure, generating metal abrasion fine powder, which is a contributing factor to the deterioration of the quality of high-purity gas. It becomes.

Therefore? For complete electrolytic composite polishing of the inner surface of the cylinder: At the same time, by mirror-finishing the cylinder mouthpiece and using the valve shown in Utility Model Application No. 61-67875, for example, a synergistic effect can be obtained and the generation of particles can be suppressed. You can.

(Example) Examples and comparative examples are shown below to specifically explain the present invention.

Example 1 Using the apparatus shown in Fig. 2, a clean cylinder whose inner surface was polished to a mirror finish by electrolytic polishing (hereinafter referred to as "clean cylinder"), an ordinary SUS cylinder (comparative example 1), and ordinary manganese were transferred. The base tickle generated from the steel cylinder (Comparative Example 2) was measured.

The measurement method will be explained with reference to FIG.

■ Line filter that can retain particles larger than 0.01 μm 12.14. Valve 13+15+17.1
8. In the line connecting the dust meter 19 and the mother gas filled in the cylinder 11, high-purity nitrogen gas or Freon 1
4 was washed with a dust meter until zeticles were no longer counted.

(2) Next, valve 17 was closed and valves 20 and 21° were opened to thoroughly clean the test cylinder line.

■ Continue with valves 17, 21. Close test cylinder 2
2. Open the main valve and insert the pressure gauge 1 into the test cylinder 22.
While looking at 6, change the mother gas to 30 to 9/crn2. It was filled until a pressure of G was reached.

In addition, before the measurement, please add 30 to 22 in the cylinder! 9/cr
rL2. The opening degree of the needle valve 13 was adjusted in advance so that the time required to fill up to G was 20 minutes.

■ Next, close the valve 15, open the valve 17,
Particles in the gas were measured for a total of 10 minutes using a dust meter. In addition, the valve 18 is a needle valve, and when the pressure of the test cylinder 22 is 30k19/(-:, G, IQL
The flow rate was adjusted in advance to be 1/min. Further, the amount of gas that passes through the dust meter 19 and is released from the line 24 is constant at 300 mL/min, and the remaining gas is blown through the air pass line 23.

■ Filling pressure of test cylinder 22, 9/c at 30'!
rL2. After measuring the particle with G as the starting point,
Subsequently, the nozzle takele was measured at a pressure of 10 kg/ctrt'' with G as the starting point.

As shown in Table 1, the measurement results showed a significant cleaning effect (reduction in the number of particles).

Comparative Example 1 A normal SUS, t'' frame was selected as a T&S frame, and the generated particles were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 An ordinary manganese steel cylinder was selected as a test cylinder and the generated tsukuticle was measured in the same manner as in Example 2, and the results are shown in Table 1.

Example 2 The partial pressure of each gas released from the inner surface of a clean cylinder in a vacuum system was measured. The measurement method will be explained with reference to FIG. The measurement cylinder 31 is pumped at a pumping speed of 300 as a vacuum pumping system.
1/see turbo molecular pump 34 and pumping speed 2307
Directly connect the diffusion 2-in f35 with /sec, and further 90
The apparatus was constructed using a 1/min oil rotary pump 36. The degree of vacuum was measured with a nude ion gauge 33, and the partial pressure was measured with a mass spectrometer 32. The temperature at the time of measurement was 1 at 20'C.
It was evacuated for ~2 hours, then heated to 160-180°C, baked for 60 hours, and cooled to room temperature. The measurement results are shown in Figures 4 and 5. In Figure 4, the vertical axis shows the 820 partial pressure in the released gas, and the horizontal axis shows time and 9.8
It shows the change in pressure over time for 20 minutes, and the smaller the amount of released gas, the higher the degree of vacuum. FIG. 5 shows the temporal change in partial pressure (of CO and N2). The 820 partial pressure after baking and cooling to room temperature was 7.9XIQ-12Torr.

The partial pressure of (Co + N2) is 1. OX 10-1'T
The orrO high vacuum degree was reached, indicating that the amount of gas degassed from the inner surface of the cylinder was extremely small.

Comparative Example 3 The partial pressure of gas released from the inner surface of an ordinary SUS 304 cylinder in a vacuum system was measured under the same conditions as in Example 2.

820 partial pressure after cooling to room temperature is 1.3X10-10Torr
, the partial pressure of (C0+N2) is 1.9 x 10-10To
It only reached rr.

Figure 4 shows the measurement time and N20 partial pressure change, and the measurement time and (
Figure 5 shows the change in partial pressure of CO and N2.

(Effects of the present invention) By using the container of the present invention, the amount of particles generated is extremely small, and the amount of gas released from the inner surface can also be significantly reduced, maintaining high purity gas. It is.

[Brief explanation of drawings]

Fig. 1(a) is a bottom view of an example of a tool used in the present invention, Fig. 1(15) is a s-s' sectional view of Fig. a1, Fig. 2 is a particle measuring device, Fig. 3 is a gas partial pressure measuring device, Figure 4 is a diagram of changes in 820 partial pressure due to baking, and Figure 5 is a diagram of changes in CO+N2 partial pressure due to baking. 1...Tool, 2...Cathode, 3...・Exposed surface, 4...
・Outlet, 5... Electrolyte, 6... Polishing abrasive grain, 11.
...Mother gas, 19...Dust meter, 22...Tess) & 31...Measurement cylinder, 32...Mass spectrometer, 34...Turbo molecular pump. 1 leg passing 1 @ 1〆, shouting Yazu 3s dedication Mr.゛145, h
(236.n Figure 1 Figure 2 Figure 3 Figure 4 TIME (hr) 1 Clean'') Cylinder 2: 5UIS 304
Boshibe Figure 5 TIME (Haru)

Claims (1)

[Claims] A high-purity gas maintenance container characterized by having the gas contacting surface of the pressure-resistant metal container subjected to electrolytic composite polishing.