JPH0747989B2 - Corrosion resistant valve for ultra high purity gas control - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrahigh-purity gas production apparatus for semiconductor manufacturing process and an ultrahigh-purity gas control corrosion resistant valve used in the semiconductor production apparatus.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a polycrystalline manufacturing process for wafers, an epitaxial process, or CVD
In the process, many chlorine-based or fluorine-based reaction gases are used. If the gas used is completely dry, the problem of corrosion does not occur, but a small amount of water may enter the pipe when opening to the atmosphere. These waters are likely to accumulate in the recesses and gaps in the apparatus and react with the above-mentioned gas to produce concentrated acid such as hydrochloric acid and hydrofluoric acid. When this generation occurs in the equipment, the corrosion progresses and becomes a corrosion product (rust), which is a particle (polluting particle) that reduces the yield of semiconductor manufacturing.
Cause the occurrence of. Therefore, the valves used here are also covered and cannot escape this problem.
The choice of this material is important because if the bellows in the valve component is apt to corrode only where the wall thickness is thinnest, it becomes a more serious problem. As a corrosion resistant valve for controlling ultra-high purity gas used in a semiconductor manufacturing process, a valve using a bellows made of a material corresponding to Ni-based corrosion resistant alloy INCONEL 625 (or 718) is known. The components of the material corresponding to Inconel 625 as a conventional product are Ni 58% or more, Cr 20.0 to 23.0%, Fe
5.0% or more, Mo 8.0-10.0%, Nb ( ⁺ Ta) 3.1
It is an alloy consisting of 5 to 4.15%, low carbon and low silicon. 4 to 7 show that one end of the bellows 9 is attached to the shaft fitting 4
Various examples in which the other end of the bellows 9 is fixed to the annular metal fitting 41 by welding are shown.
In the various examples described above, a matching clearance is generated between the bellows 9 and the shaft fitting 40 and the annular fitting 41.

[0003]

If the side where the mating clearance is generated is on the side in contact with the gas fluid, it is the worst state, and if it is on the side not in contact with the gas fluid, it gives a bad result. . In the worst case where the generation side of the mating clearance is on the contact side of the gas fluid, chlorine and hydrofluoric acid generated by the reaction gas and water are likely to accumulate in the mating clearance, so that crevice corrosion easily occurs and corrosion generation occurs. There is a problem in that particles are generated due to the object, and further, leakage is caused due to pitting corrosion using the wetted dust as a medium. On the other hand, in the process of manufacturing the bellows alone, there are many pickling and washing steps for removing stains on the outer surface, and the acid solution at this time is often used at a temperature close to the boiling point. There is a problem that the skin becomes rough and the appearance becomes bad, and the vacuum characteristics are also adversely affected due to poor degassing due to rough skin.

[0004]

In order to advantageously solve the above-mentioned problems, in the corrosion resistant valve for controlling ultra-high purity gas of the present invention, a valve housing 3 having an inflow passage 1 and an outflow passage 2 is provided. A valve chamber 5 is provided through a valve seat 4 located on the downstream side of the inflow passage 1. Inside the valve chamber 5, the valve can be opened / closed from the outside, and the valve seat 4 is provided on the base end side. A valve shaft 7 provided with a facing valve body 6 is arranged, and airtightness is maintained between a base end side of the valve shaft 7 and a bellows flange 8 which is airtightly fitted and fixed to an open side of the valve chamber 5. In a corrosion resistant valve for controlling ultra-high purity gas, which is provided with a bellows 9 for opening and closing the valve body 6 in a state, a material of the bellows 9 is N
i50% or more, Cr14.5-16.5%, Mo15.0-1
7.0%, W3.0-4.5%, Fe4.0-7.0%, low carbon,
It is composed of an alloy of low silicon. In addition, a valve chamber 5 is provided in a valve housing 3 having an inflow passage 1 and an outflow passage 2 via a valve seat 4 located on the downstream side of the inflow passage 1. A valve shaft 7 that can open and close the valve and has a valve body 6 facing the valve seat 4 is arranged on the base end side. The valve shaft 7 is provided on the base end side and the valve chamber 5 open side. In a corrosion resistant valve for controlling ultra-high purity gas, a bellows 9 for opening and closing the valve body 6 in an airtight holding state is provided between the bellows flange 8 fitted and fixed airtightly,
The material of the bellows 9 is Ni50% or more, Cr20.0
~ 22.5%, Mo12.5-14.5%, W2.5-3.5%,
The above-mentioned problems can be advantageously solved also by using an alloy composed of Fe 2.0 to 6.0%, low carbon and low silicon.

[0005]

1 to 3 show an ultrahigh-purity gas control corrosion-resistant valve according to an embodiment of the present invention, which includes a valve chamber 5 and a valve seat 4 provided at a lower central portion thereof. An inflow passage 1 of which one end communicates with the inside of the valve seat 4,
An outflow passage 2 having one end communicating with the valve chamber 5 is provided, and the inflow passage 1, the valve seat 4, the valve chamber 5, and the outflow passage 2 are communicated in this order. At the center of the valve housing 3, a valve shaft 7 having a smaller diameter from the base end side located in the valve chamber 5 toward the tip end side.
And a step portion 10 is provided between the large-diameter shaft portion and the medium-diameter shaft portion of the valve shaft 7, and a step portion 11 is provided between the medium-diameter shaft portion and the small-diameter shaft portion of the valve shaft 7. Is provided.

A recess 12 provided at the base end of the valve shaft 7.
A truncated cone valve body 6 facing the truncated cone valve seat 4
The large-diameter portion that is continuously provided with is fitted, and the tip of the recess 12 is bent by press working to form the valve body fixing claw piece 13 that engages with the peripheral edge of the large-diameter portion. As a material forming the valve body 6, a synthetic resin or synthetic rubber having acid resistance, relatively high temperature resistance, and elasticity is used.

Large-diameter step portion 1 provided on the open side of the valve chamber 5
4, a bellows flange 8 in which the valve shaft 7 is slidably fitted in a center hole is fitted and installed via a seal member 15, and a bellows 9 arranged coaxially with the valve shaft 7 and outside thereof is provided. One end is fixed in an airtight state by welding to an annular ear portion 16 provided in the small diameter portion of the bellows flange 8, and the other end portion of the bellows 9 is a large diameter portion of the base end portion of the valve shaft 7. It is fixed in an airtight state by welding to the annular ear portion 17 provided on the. With this configuration, the valve chamber 5 is completely shut off from the outside air. Further, as the material forming the sealing member 15, it is preferable to use the same material as the material of the valve body 6 or a corrosion resistant metal material.

A cylindrical bonnet metal fitting 18 is placed on the bellows flange 8 fitted to the large diameter step 14 on the open side of the valve chamber 5, and the lower portion of the bonnet metal fitting 18 has the large diameter. The female screw of the annular fastening metal fitting 20 which is fitted inside the step portion 14 and further engages with the outer flange 19 of the bonnet fitting 18 is screwed into the male screw provided on the valve housing 3 to form the annular fastening metal fitting. The bonnet fitting 18 is fastened and fixed to the bellows flange 8 and the valve housing 3 by 20.

A valve closing spring 21 made of a spiral spring is arranged in the bonnet metal fitting 18, and a washer 22 engaged with the step portion 10 of the valve shaft 7 and an inward flange of an upper end portion of the bonnet metal fitting 18 are provided. And the valve closing spring 21 is interposed in a compressed state, and the valve closing spring 21 presses the valve body 6 in the valve closing direction via the valve shaft 7 so that the valve body 6 opens. The inside of 4 is always closed. Further, the sliding portion between the upper portion of the bonnet metal fitting 18 and the valve shaft 7 is
An O-ring 23 fitted to the upper portion of the bonnet fitting 18 hermetically seals.

An actuator main body 26 having a cylinder hole 25 therein is rotatably fitted in an airtight state in a small outer diameter portion 24 on the upper side of the bonnet metal fitting 18, so that the bonnet metal fitting 18 and the actuator main body 26 are separated from each other. An O-ring 27 is interposed in the bonnet fitting 18 and a washer 28 that engages with the bottom surface of the cylinder hole 25 is fitted around the upper end of the bonnet fitting 18.
8 into the annular groove provided on the outer periphery of the upper end of the washer 2
A snap ring 29, which is a partially-notched annular metal fitting, which is engaged with the upper surface of 8, is fitted.

The step portion 11 of the valve shaft 7 is arranged in the cylinder hole 25, and the piston 31 fitted with the O-ring 30 on the outer periphery is slidably fitted in the cylinder hole 25, and the step portion An O-ring 33 is interposed between a receiving washer 32 engaged with 11 and an annular recess at the center of the piston 31, and a piston fixing snap is provided in an annular groove provided at the upper end of the valve shaft 7. The ring 34 is fitted.

An airtight chamber 35 is provided between the piston 31 and the bottom side of the cylinder hole 25, and the control fluid introduction hole 36 and the airtight chamber 35 provided in the actuator body 26 are connected via a communication hole 37. Is connected and a little hydraulic oil is applied to the inside of the cylinder hole 25, but the actuator body 26, the bonnet metal fitting 18, and the valve shaft 7 are connected.
The space between the piston 31 and the piston 31 is sealed as described above.
Since the space between the cylinder hole 25 and the cylinder hole 25 is also sealed as described above, the hydraulic oil does not leak to the outside. A lid 39 having a ventilation hole 38 is screwed onto the opening side of the actuator body 26.

When the control fluid is introduced into the airtight chamber 35 and the fluid pressure causes the piston 31 to move against the pressure of the valve closing spring 21, the outer surface of the snap ring 34 of the piston 31 is removed. The movement of the piston 31 is restricted by hitting the inner surface of the lid body 39. When the piston 31 moves, the lid 3 of the piston 31
Since air enters and leaves the 9 side through the ventilation hole 38, the piston 31 moves according to the control fluid pressure without receiving back pressure.

When the piston 31 moves, the valve body 6 moves via the valve shaft 7 to open or close the valve.

As a material for forming the bellows 9,
Ni50% or more, Cr14.5-16.5%, Mo15.0-
17.0%, W3.0-4.5%, Fe4.0-7.0%, low carbon, low silicon alloy or Ni50% or more, C
r20.0 to 22.5%, Mo12.5 to 14.5%, W2.5 to
An alloy composed of 3.5%, Fe 2.0 to 6.0%, low carbon and low silicon is used.

Table 1 compares the alloy components of the conventional bellows and the bellows of the present invention.

[Table 1]

In Table 1, each bellows is N
It contains i, Cr, Fe and Mo. However, the bellows of the present invention contains 3.0 to 4.5% or 2.5 to 3.5% of W, whereas the conventional bellows does not contain W but contains Nb and Ta. There is.

Nb and Ta used in conventional bellows are effective for improving the strength of the material, but are not effective for improving the corrosion resistance of the material. Mo is particularly effective in improving the corrosion resistance and pitting corrosion resistance in a reducing environment, and as shown in Table 1, in the bellows of the present invention, Mo is 4.5 times higher than that of the conventional bellows.
By adding as much as ~ 7.0%, corrosion resistance performance such as pitting corrosion and crevice corrosion is greatly improved.

Similar to Mo, W is effective in improving corrosion resistance and pitting corrosion resistance in a reducing environment, and when an appropriate amount of W is added, corrosion resistance such as pitting corrosion and crevice corrosion can be significantly improved. Can be improved. W is also effective in improving the strength at high temperatures. However, if the amount of W added is too large, the material forming the bellows becomes brittle, so it must be determined in balance with other components.

Ni is important as a constituent element of the alloy,
In the present invention, 50% or more is added. Also Cr
Is important as a constituent element of the alloy and serves to impart oxidation resistance due to a stable oxide film.

Next, the performance comparison test results of the bellows of the present invention and the conventional bellows will be described. (1) Pitting corrosion resistance Aqueous solution (4% NaCl + 0.1% Fe ₂ (SO ₄ ) ₃ + 0.1%
The lowest temperature at which pitting corrosion occurred was determined by immersing each test piece in 01 M HCl 24,300 ppm Cl ⁻ , pH 2). In addition, the temperature of the aqueous solution is increased by 5 ° C., and the presence or absence of pitting corrosion at each temperature is checked with a microscope. If pitting corrosion does not occur, proceed to the next temperature, and check one after another. It was The immersion time at each temperature is 24 hours
s. The results of the pitting corrosion resistance test are shown in Table 2.

[Table 2]

(2) Crevice corrosion resistance Aqueous solution (4% NaCl + 0.1% Fe ₂ (SO ₄ ) ₃ + 0.1%
Each test piece was immersed in 01M HCl 24,300 ppm Cl ⁻ , pH 2) to determine the lowest temperature at which crevice corrosion occurs. In addition, increase the temperature of the aqueous solution by 5 ° C and check for crevice corrosion at each temperature with a microscope. If crevice corrosion does not occur, proceed to the next temperature and check one after another. It was The immersion time at each temperature is 100 hrs. Table 3 shows the results of the crevice corrosion resistance test.

[Table 3]

(3) Stress Corrosion Cracking Resistance It was immersed in a boiling aqueous solution (42% MgCl ₂ ) and the cracking time was observed. As a result, no cracking occurred even after 1000 hrs, and no significant difference was observed between the alloys.

(4) Acid resistance The test pieces were immersed in an aqueous solution under the conditions shown in Table 4 and the corrosion rate (mm / Yr) was observed.

[Table 4]

As is clear from the above comparison, the bellows of the present invention show a significant improvement of 160% or more in pitting corrosion resistance and crevice corrosion resistance as compared with the conventional bellows. In addition, the acid resistance in the boiling liquid was significantly improved by 200% or more.

Regarding the pitting corrosion resistance and the crevice corrosion resistance, the alloy 2 of the present invention is further superior to the alloy 1 of the present invention. Regarding the acid resistance, although it depends on the acid concentration, there is no difference between the alloy 1 and the alloy 2 of the present invention, and almost the same effect can be obtained.

Further, in the vacuum circuit breaker, the improvement of the corrosion resistance performance of 160% or more improves the overall performance of the power transmission system device by 16%.
It will be improved by 0% or more. Furthermore, 200%
The above-mentioned improvement in acid resistance means that the roughness of the outer surface of the bellows is prevented by 200% or more in the process of manufacturing the bellows alone, which improves the appearance of the bellows and improves the degassing property. The high vacuum characteristic is improved, and therefore the reliability of the vacuum circuit breaker can be further enhanced.

As the ultrahigh-purity gas manufacturing apparatus for semiconductor manufacturing process and the gas control corrosion resistant valve used in the semiconductor manufacturing apparatus, there are one that automatically controls the opening / closing operation of the valve element from a distance and one that is manually operated. is there. Although the valves shown in FIGS. 1 to 3 are automatic control valves, the present invention can also be implemented in the latter manually operated valves.

In the case of the embodiment of the present invention, the occurrence side of the fitting gap between the bellows 9 and the metal fitting such as the bellows flange 8 for fixing the bellows may be the contact side with the gas fluid by design. Even at this time, the pitting corrosion resistance and the crevice corrosion resistance are improved by 160% or more, and therefore the generation of particles due to corrosion products is prevented by 160% or more, so that the reliability of the valve is further improved. In addition, as shown in the embodiments of the present invention, when the clearance generation side is on the non-contact side, the reliability of the valve can be further improved. In addition, the bellows 9 in the example of the present invention has an acid resistance improved by 200% or more.
% Or more, the surface roughness of the outer surface of the bellows is prevented by 200% or more in the manufacturing process of the bellows alone, thereby improving the outer surface of the bellows 9 and degassing property. Is improved, the vacuum characteristics are improved, and therefore the reliability of the valve for a semiconductor manufacturing process can be further enhanced.

[0030]

According to the present invention, the valve chamber 5 is provided in the valve housing 3 having the inflow passage 1 and the outflow passage 2 via the valve seat 4 located on the downstream side of the inflow passage 1. , This valve chamber 5
A valve shaft 7 having a valve body 6 that can be opened and closed from the outside and provided with a valve body 6 facing the valve seat 4 on the base end side is disposed inside, and the base end side of the valve shaft 7 and the valve chamber In a corrosion-resistant valve for controlling ultra-high purity gas, a bellows 9 for opening and closing the valve body 6 in an airtight holding state is provided between the bellows flange 8 which is airtightly fitted and fixed to the open side of , The material of the bellows 9 is Ni 50% or more, Cr 14.5 to 16.5
%, Mo 15.0 to 17.0%, W 3.0 to 4.5%, Fe 4.0
〜7.0%, low carbon, low silicon alloy or Ni50% or more, Cr20.0-22.5%, Mo
12.5 ~ 14.5%, W2.5 ~ 3.5%, Fe2.0 ~ 6.0
%, Low carbon, low silicon because it is composed of an alloy,
Among the corrosion resistance performances of the bellows 9 in the corrosion resistant valve for ultra-high purity gas control, particularly pitting corrosion resistance and crevice corrosion resistance can be remarkably improved, and acid resistance in a boiling liquid state can be remarkably improved. A highly reliable corrosion resistant valve can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical side view showing a corrosion resistant valve for controlling ultra-high purity gas according to an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional side view showing a lower portion of FIG. 1 in an enlarged manner.

FIG. 3 is a vertical sectional side view showing an upper portion of FIG. 1 in an enlarged manner.

FIG. 4 is a vertical cross-sectional side view showing an example in which a bellows is fixed to a metal object by welding.

FIG. 5 is a vertical cross-sectional side view showing another example of fixing the bellows to the metal object by welding.

FIG. 6 is a vertical sectional side view showing another example in which a bellows is fixed to a metal object by welding.

FIG. 7 is a vertical sectional side view showing another example in which a bellows is fixed to a metal object by welding.

[Explanation of symbols] 1 inflow passage 2 outflow passage 3 valve housing 4 valve seat 5 valve chamber 6 valve body 7 valve shaft 8 bellows flange 9 bellows 10 step 11 step 12 recess 13 claw piece 14 for fixing valve body 14 large diameter Step portion 15 Sealing member 16 Annular ear portion 17 Annular ear portion 18 Bonnet fitting 19 External flange 20 Annular tightening fitting 21 Valve closing spring 22 Washer 23 O-ring 24 Small outer diameter portion 25 Cylinder hole 26 Actuator body 27 O-ring 28 Washer 29 snap ring 30 O ring 31 piston 32 washer 33 O ring 34 snap ring 35 airtight chamber 36 control fluid introduction hole 37 communication hole 38 vent hole 39 lid 40 shaft metal fitting 41 annular metal fitting

Claims (2)

[Claims] 1. A valve chamber (5) is provided in a valve housing (3) having an inflow passage (1) and an outflow passage (2) via a valve seat (4) located on the downstream side of the inflow passage (1). Is provided with a valve shaft 7 that can be opened and closed from the outside and provided with a valve body 6 facing the valve seat 4 on the base end side, and the base end side of the valve shaft 7 and the valve chamber 5 In the corrosion resistant valve for controlling ultra-high purity gas, a bellows 9 for opening and closing the valve body 6 in an airtight state is provided between the bellows flange 8 which is airtightly fitted and fixed to the open side of The material of the bellows 9 is
Ni50% or more, Cr14.5-16.5%, Mo15.0-
A corrosion resistant valve for controlling ultra-high purity gas, characterized by being composed of an alloy of 17.0%, W3.0-4.5%, Fe4.0-7.0%, low carbon and low silicon. 2. A valve chamber (5) is provided in a valve casing (3) having an inflow passage (1) and an outflow passage (2) via a valve seat (4) located on the downstream side of the inflow passage (1). Is provided with a valve shaft 7 that can be opened and closed from the outside and provided with a valve body 6 facing the valve seat 4 on the base end side, and the base end side of the valve shaft 7 and the valve chamber 5 In the corrosion resistant valve for controlling ultra-high purity gas, a bellows 9 for opening and closing the valve body 6 in an airtight state is provided between the bellows flange 8 which is airtightly fitted and fixed to the open side of The material of the bellows 9 is
Ni50% or more, Cr20.0-22.5%, Mo12.5-
A corrosion resistant valve for controlling ultra-high purity gas, characterized by being composed of an alloy of 14.5%, W2.5 to 3.5%, Fe2.0 to 6.0%, low carbon and low silicon.