JPH07167391A - High purity gas filling container and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the generation of particles and the discharge of adsorbed water content by smoothing the inner surface of the head part, subjected to contraction of opening, of a high purity gas filling container made of nonmagnetic material, by magnetic polishing so that the surface roughness becomes the specific value or less. CONSTITUTION:A container formed by applying opening contraction work to the head part 10 of a seamless steel pipe made of nonmagnetic material such as austenite stainless steel is installed with the head part 10 facing downward. Magnetic poles 3 are installed obliquely downward. Magnetic abrasive material is charged in the container and attracted to the magnetic poles 3 so as to be in contact with the inner surface of the opening-contracted part. In this state, the container is rotated to smooth the inner surface of the opening- contracted part by magnetic polishing. The surface roughness of the smoothed part is to be 10mum or less at Rmax, thus obtaining a high purity gas filling container having a small quantity of water content and reduced in the discharge of particles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container for filling a high-purity gas used in a semiconductor manufacturing process or the like, the inner surface of which is smooth so that the filled high-purity gas is not contaminated. And a method for manufacturing the same.

[0002]

2. Description of the Related Art In the field of semiconductor manufacturing, progress in high integration has been remarkable in recent years, and devices called VLSIs are required to process fine patterns of 1 μm or less. In such a VLSI manufacturing process, a minute amount of dust or a trace amount of impurity gas may be attached to and adsorbed on the wiring pattern to cause a circuit failure. Therefore, both the reaction gas and the carrier gas to be used must have high purity. That is, it is necessary that the amount of fine particles (particles) and the impurity gas in the gas be small. Therefore, high purity gas pipes and filling containers used in semiconductor manufacturing processes, etc.
It is required that particles as contaminants released from the inner surface and adsorbed moisture as impurity gas be as small as possible.

As a measure for preventing the generation of particles and the adsorption of water on the inner surface as described above, it is important to smooth the inner surfaces of pipes and containers. In the case of a pipe material for piping or a container having a large opening on one side, smoothing of the inner surface can be relatively easily performed by mechanical polishing, electrolytic polishing, or the like. However, with a container having a closed bottom and a narrowed mouth, that is, a gas filling container (cylinder), it is difficult to make the entire inner surface of the container smooth.

FIG. 3 is a diagram showing an outline of a normal manufacturing process of a gas filling container. As shown in the drawing, first, the raw pipe (seamless steel pipe) 31 is cut into a predetermined length (step of). Next, one end thereof is hot drawn and closed to form a bottom portion (step of,). The bottomed tube made in this way is 32. The open end of this raw pipe is hot drawn to form the head (step of). After that, necessary heat treatment () and head screw processing () are applied, and the product undergoes inspection () and painting () steps.

The above-mentioned inner surface smoothing can be carried out by mechanical polishing or electrolytic polishing in the state of the shell 32 shown in FIG. However, if hot drawing is performed in the subsequent process, the inner surface of the head becomes rough again and becomes rough. Moreover, since the opening of the head is reduced by the mouth stop and the container is in a substantially sealed state, it is extremely difficult to polish the roughened portion again. Therefore, conventionally, the inner surface of the head has not been sufficiently re-polished, and the head has been used.

When the container manufactured as described above is used as a high-purity gas filling container, there is a problem that generation of particles and release of adsorbed moisture cannot be sufficiently prevented.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the conventional gas filling container, the present invention sufficiently smooths the entire inner surface including the inner surface of the head to prevent generation of particles and adsorption moisture. It is an object of the present invention to provide a high purity gas filling container that emits extremely little and a method for producing the same.

[0008]

The gist of the present invention is the following (1) high-purity gas filling container and (2) a method for producing the same.

(1) A high-purity gas characterized in that the inner surface of the head subjected to the mouth-drawing processing is smoothed by magnetic polishing, and the surface roughness of the smoothed portion is Rmax of 10 μm or less. Filling container.

(2) The head of which the mouth is processed is placed with the head facing downward, and the magnetic poles are placed diagonally below the head,
For high-purity gas filling, characterized in that the magnetic polishing material charged in the container is attracted by the magnetic poles and is brought into contact with the inner surface of the orifice portion to rotate the container around its central axis for magnetic polishing. Method for polishing inner surface of container.

The container (1) is made of a non-magnetic material capable of magnetic polishing, for example, an austenitic stainless steel such as JIS SUS 316L.

The magnetic polishing in the method (2) is a polishing method in which a magnetic material and a magnetic polishing material are used to relatively move the material to be polished and the magnetic polishing material in contact with each other. Further, in this polishing method, it is desirable to perform wet magnetic polishing using a magnetic abrasive composed of magnetic abrasive grains, ferromagnetic grains and a wetting agent. Further, this polishing is performed in steps of rough polishing and finish polishing. It is preferable to carry out separately.

[0013]

FIG. 4 is a view for explaining the principle of magnetic polishing, taking the inner surface of a circular tube as an example. As shown, a magnetic pole 3 is provided in the vicinity of the outside of the rotating non-magnetic circular tube 1, and an exciting coil 4 is provided.
Magnetic flux is generated by the magnetic pole 3 when electricity is applied to the non-magnetic circular tube 1
The magnetic flux passes through the inner surface of the tube without being affected by Therefore, the magnetic abrasive 2 loaded in the non-magnetic circular tube 1 is attracted to the N-S magnetic pole 3 by the magnetic force,
It is pressed against the inner surface of the non-magnetic circular tube 1. Therefore, when the non-magnetic circular tube 1 is rotated, the inner surface of the tube and the magnetic polishing material 2 cause relative movement, and the inner surface of the non-magnetic circular tube 1 is polished.

The force acting on the magnetic polishing, that is, the magnetic force (ΔF _x and ΔF _y ) for pressing the magnetic polishing material 2 against the inner surface of the tube, which is the processing region, can be expressed as follows.

[0015] _{ΔF x = V 0 χΔK x =} πD 3/6 · χH (αH / αx) ··· (1) ΔF y = V 0 χΔK y = πD 3/6 · χH (αH / αy) ··· (2) Here, V ₀ : volume of particles, χ: magnetic susceptibility of particles, D: particle size when the particles are assumed to be spheres, Δ
K: product of magnetic field strength and change rate of magnetic field, H: magnetic field strength However, subscripts x and y indicate x: direction of magnetic force line, y: direction perpendicular to magnetic force line.

In magnetic polishing accompanied by rotation of a workpiece, if the so-called "rotation" of the abrasive, which is caused by rotation of the abrasive with the processed portion, occurs, polishing cannot be performed. Therefore, the "rotation" of the abrasive must be avoided. I won't. In general, FIG.
In the magnetic pole arrangement as shown in, by increasing ΔF _x and ΔF _y represented by the above equations (1) and (2),
Since the magnetic polishing material 2 is strongly bound to the processing area, the "blur" of the polishing material is less likely to occur.

It is a feature of the method of the present invention that magnetic polishing based on the above principle is applied as a method for smoothing the inner surface of the head of a gas filling container that is in a substantially sealed state. That is,
Even in the case of a container after head molding, if some opening can be secured in a part of the container, for example, the head of the container for charging and discharging the abrasive for the inner surface polishing, the inner surface can be polished by the magnetic polishing. It will be possible. Further, as a high-purity gas filling container, austenitic steel, typically SUS 316L steel can prevent generation of particles and adsorption of water on the inner surface,
Commonly used. Therefore, it is also non-magnetic as a steel grade and does not hinder the application of magnetic polishing. However, in order to properly perform the inner surface polishing for filling the high-purity gas, it is necessary to consider the selection of the polishing material and the processing conditions as described below.

A. Abrasive In the magnetic polishing of the present invention, magnetic abrasive grains as an abrasive,
Wet magnetic polishing is preferably performed using ferromagnetic particles and a wetting agent.

The magnetic abrasive grains are composed of iron powder sensitive to magnetism and aluminum oxide type abrasive grains (Al ₂ O ₃ , hereinafter referred to as WA abrasive grains) for polishing the processed portion. As an example of a specific method for producing magnetic abrasive grains, iron powder and WA abrasive grains are mixed at a weight ratio of iron: WA abrasive grains = 4: 1 to obtain high temperature (1300 ° C) and high pressure. There is a method of sintering under vacuum (about 5 MPa) or in an inert gas atmosphere, and then pulverizing and sizing. Table 1 summarizes the types of magnetic abrasive grains thus produced (magnetic abrasive grains No. 1 to No. 3), the grain size and the grain size of the WA abrasive grains used therein.

[0020]

[Table 1]

In addition to the magnetic abrasive grains, it is preferable to mix electrolytic iron powder and shot grains as ferromagnetic grains. The reason why the ferromagnetic particles are mixed is that the magnetic field force is small and the predetermined polishing force may not be ensured by polishing only the magnetic abrasive grains, and the use of the ferromagnetic grains as the core of the abrasive is effective. Here, the electrolytic iron powder can be used for rough polishing because it is a relatively irregular type and has a large particle size, and can be used for finish polishing because the shot particles have a spherical shape and a small particle size. In the examination of the polishing step described later, two types of electrolytic iron powders having different particle sizes (electrolytic iron powders No1 and No2) were used, and the particle size of the ferromagnetic particles is as shown in Table 2.

[0022]

[Table 2]

The wet magnetic polishing method is preferably used for the inner surface polishing in order to improve the surface roughness after polishing. As a wetting agent, it is preferable to use a machine oil or a polishing compound that has a grinding action and exerts an excellent effect on rust prevention and gloss finish after polishing. In particular, the polishing compound is suitable for improving the polishing gloss after polishing.

In order to improve the surface roughness of the material to be polished, it is necessary to set the mixing ratio of the magnetic abrasive grains in the polishing material in the range of 25 to 75% by weight. When the mixing ratio of the magnetic abrasive grains is less than 25% by weight, there are many ferromagnetic grains, so the relative permeability of the abrasive increases and polishing force is generated, but since there are few magnetic abrasive grains involved in polishing, the inner surface roughness is It doesn't get better. On the other hand, when the mixing ratio of the magnetic abrasive grains exceeds 75% by weight, the magnetic abrasive grains are abundant, but the polishing force becomes small, and the inner surface roughness is not improved. Particularly, when the mixing ratio of the magnetic abrasive grains is 60% by weight, the polishing efficiency is the best.

B. Polishing speed Normally, assuming a small-diameter high-purity gas filling container (outer diameter 90 mm or less), the number of rotations of the material to be polished is 500 to 90.
The range of 0 rpm is desirable as a condition for ensuring a constant surface roughness.

FIG. 5 is a diagram showing the relationship between the number of revolutions of the material to be polished (stainless steel pipe) and the inner surface roughness after polishing. In the figure, a stainless steel pipe (SUS 316L, outer diameter 50.8 mm × wall thickness 4.0 mm × length 300 mm, inner surface roughness Rmax of about 12 μm as cold drawn) was used as the test material and electrolytic iron powder was used as the polishing material.
No1 + magnetic abrasive grain No1 + machine oil and electrolytic iron powder No2 +
Using two types of magnetic abrasive grains No. 1 + machine oil, the inner surface roughness after polishing (polishing time: 10 minutes) was measured.

From the figure, no matter which abrasive material is used, the inner surface roughness tends to improve as the number of revolutions of the material to be polished increases, but the inner surface roughness is in the range of 500 to 900 rpm. It will be constant. When the rotation speed was less than 500 rpm, the polishing time was insufficient and the polishing time was 10 minutes. On the other hand, the rotation speed is 1100 rpm
Then, the polishing material does not rotate together with the material to be polished, but it slightly flows in the rotating direction, and the polishing force decreases. However, the rotation speed of the material to be polished compensates for this, and the inner surface roughness is improved due to the shallow polishing of the WA abrasive grains and the high polishing amount due to the high rotation.

C. Polishing process Generally, in high-purity gas piping and members, as a measure to prevent the generation of particles and the adsorption of moisture on the inner surface, the contact area between the surface of these members and gas or pure water should be as small as possible. As a standard, the inner surface roughness (Rmax) is 1 to 2 μm or less. In order to make the surface of the material to be polished have such an inner surface roughness, it is preferable to divide the inner surface polishing of the present invention into a rough polishing step and a finish polishing step.

The following tests were conducted in selecting the polishing process. Using the same stainless steel tube as above (however, the inner surface roughness is Rmax about 60 μm) as the test material, the stainless steel tube was polished at a rotation speed of 850 rpm, and the relationship between the polishing time and the inner surface roughness after polishing was investigated. did. The abrasive used at this time was electrolytic iron powder assuming that it would be used for rough polishing as No. 1 abrasive.
Electrolytic iron powder with No1 (particle size 1700 μm) + magnetic abrasive No1 + machine oil mixed, assuming No.2 abrasive for finish polishing
No2 (particle size 300 μm) + magnetic abrasive grain No1 + machine oil was mixed. The mixing ratio of magnetic abrasive grains in the abrasive is
It was set to 50% by weight.

FIG. 6 is a diagram showing the relationship between the polishing time and the inner surface roughness. The polishing time with the No. 1 polishing material was set to 10 to 80 minutes, but when the polishing time exceeds 50 minutes, the inner surface roughness becomes 7 μm or less. On the other hand, polishing with No. 2 abrasive is
It is assumed that after polishing for 40 minutes, further polishing for 10 to 30 minutes is performed to finish polishing after rough polishing. From the figure, while the polishing time with No.1 abrasive is 70 minutes and the inner surface roughness is 3.4 μm, which is the best, when switching to No.2 abrasive, the inner surface roughness is 1.8 ~ 1.4
μm, which is a significant improvement. From this, it is understood that in the magnetic polishing, it is preferable to carry out finish polishing by changing the polishing material after rough polishing.

[0031]

EXAMPLES A method for polishing an inner surface of a gas filling container according to the present invention is described below.
Description will be made based on specific (Example 1) and (Example 2).

Example 1 As a test material, a head 10 of a gas filling container having a vertical cross-sectional shape shown in FIG. 2 was prepared and magnetically polished under the following conditions. 1A and 1B are views showing the arrangement of the magnetic poles 3 with respect to the head 10 of the container, where FIG. 1A is a front view and FIG. 1B is a bottom view taken along the line AA. N-S
The magnetic pole 3 was manufactured on the premise of the shape of the container head 10, and the magnetic poles were arranged as shown in FIG. In this case, the smaller the distance between the container and the magnetic pole, the greater the magnetic field strength and the polishing power can be increased. Therefore, the distance between the container and the magnetic pole should be as small as possible so that the gap between the container and the magnetic pole is 1 mm or less. I arranged the magnetic poles.

1. Specimen material: SUS 316L, dimensions: as shown in Fig. 2 Inner surface roughness before polishing: Rmax 23μm 2. Abrasives Two types of abrasives were prepared for rough polishing and three types for finish polishing. Table 3 shows the mixing conditions of the abrasives.

[0034]

[Table 3]

3. Polishing Conditions Table 4 shows the conditions for polishing the head of the gas filling container. Here, sample materials No. 1 to No. 5 were magnetically polished as examples of the present invention based on the conditions specified by the present invention or the conditions that are preferable. After polishing, the inner surface roughness was measured, and the surface gloss, the image quality (the sharpness of the screen projected on the surface, see Table 5 for details) and the polishing residue were evaluated as ◯: good, ×: poor. . The results are summarized in Table 5.

[0036]

[Table 4]

[0037]

[Table 5]

As is clear from Table 5, in any of the examples of the present invention, the inner surface roughness was Rmax of 1 to 2 μm or less, smoothing was achieved, and the surface gloss, image quality and polishing residue were all good results. Therefore, it can be seen that the inner surface polishing method of the present invention is most suitable as a smoothing method for a high-purity gas filling container.

As shown in Table 4, in the final polishing, the exciting current of the magnetic pole was changed to 0.7A and 1.0A. As for the relationship between the exciting current and the magnetic field force, the magnetic field force increases as the exciting current increases if magnetic saturation is not achieved, but the inner surface roughness is greatly affected by other factors, and the exciting current is It's just a small factor.

(Example 2) The main body was polished by a normal mechanical polishing method, and the head was polished by the inner surface polishing method of the present invention to produce a gas filling container having an internal volume of 330 cc, which was tested. As a container, water content measurement and particle measurement were performed to evaluate the characteristics as a high purity gas filling container.

Austenitic stainless steel (SUS316L) was used as the material of the sample container, and the sample No. 1 abrasive material (Tables 3 and 4) and polishing conditions (Table 4) of Example 1 were used. )
After polishing, the finished inner surface roughness of the test container is Rmax
It was set to 1 μm or less.

FIG. 7 is a view for explaining the outline of the test apparatus for measuring the water content. After assembling the test apparatus, the inside of the system was purged with high-purity gas to confirm that the water content was stable. The sample gas was supplied and the water content was measured by APIMS 12.

FIG. 8 is a diagram showing the measurement results of the water content. Immediately after opening the valve, the container under test (gas filling pressure 150
(When Kgf / cm ² ), the amount of water released is stable and shows 1 ppb or less, and the background value of high-purity gas is 0.73 pp
Considering that it is b, it is clear that the water content is extremely small and there is no problem for semiconductor manufacturing.

FIG. 9 is a diagram for explaining the outline of the particle measuring device. As in the case of measuring the water content, the test apparatus was purged with a high-purity gas to stabilize the system, and then the sample gas was supplied, and the total number was measured by the particle counter 16.

FIG. 10 is a diagram showing the results of particle measurement of the test container. The results shown in the figure show that the total number of particles (size ≧ 0.1 μm) is 9 and that there is no problem as a high-purity gas filling container.

[0046]

According to the manufacturing method of the present invention, the entire inner surface including the inner surface of the head is sufficiently smoothed. The container of the present invention manufactured by this method is an excellent container for high-purity gas filling, which has a small amount of water content and has a reduced amount of emitted particles for semiconductor manufacturing.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of magnetic poles with respect to a head of a gas filling container which is a material to be polished.

FIG. 2 is a diagram showing an example of the shape and dimensions of the head of a gas filling container that is a material to be polished.

FIG. 3 is a diagram showing an outline of a manufacturing process of a gas filling container.

FIG. 4 is a view for explaining the principle of magnetic polishing, taking the inner surface of a circular tube as an example.

FIG. 5 is a diagram showing the relationship between the rotation speed of a stainless steel pipe and the inner surface roughness after polishing.

FIG. 6 is a diagram showing the relationship between the polishing time and the inner surface roughness in rough polishing and finish polishing.

FIG. 7 is a diagram illustrating an outline of a test apparatus for measuring water content.

FIG. 8 is a diagram showing a measurement result of water content in a test container.

FIG. 9 is a diagram illustrating an outline of a particle measuring device.

FIG. 10 is a diagram showing a particle measurement result of a test container.

[Explanation of symbols]

1 ... Non-magnetic circular tube, 2 ... Magnetic abrasive material, 3 ... Magnetic pole, 4 ... Excitation coil 10 ... Container head, 11 ... Test container, 12 ... APIMS, 13 ... Getter, 14 ... Pressure reducing valve 15 ... Flowmeter, 16 ... Particle counter, 17 ... Pressure regulator, 18 ... Filter 31 ... Original tube, 32 ... Element tube

Claims (4)

[Claims] 1. A high-purity gas filling characterized in that the inner surface of the head subjected to the mouth-drawing process is smoothed by magnetic polishing, and the surface roughness of the smoothed part is Rmax of 10 μm or less. Container. 2. A container having a head with a mouth-drawing process is installed with the head facing downward, a magnetic pole is installed obliquely below the container, and the magnetic abrasive material charged inside the container is attracted by the magnetic pole to draw the mouth. A method for polishing an inner surface of a high-purity gas-filled container, which comprises magnetically polishing the container by rotating the container around its central axis while being in contact with the inner surface of the narrowed portion. 3. The high purity gas filling container according to claim 2, wherein wet magnetic polishing is performed by using an abrasive composed of magnetic abrasive grains, ferromagnetic grains and a wetting agent as the magnetic abrasive. Internal polishing method. 4. The method for polishing the inner surface of a high-purity gas filling container according to claim 2 or 3, wherein the magnetic polishing is performed in steps of rough polishing and finish polishing.