JPS63254270A - Sealing mechanism between metal and ceramics - Google Patents

Abstract

PURPOSE:To maintain perfect sealing even if the temperature change is repeated, by inserting a soft metal sealing member into between a metal member and a ceramics member and attaching a sealing assisting member for offsetting the thermal expansion of metal onto the sealing member. CONSTITUTION:A ceramics valve seat 1B is constituted by inserting a soft metal ring 6 between a gas casing 5 which contacts the valve seat 1B and a standing base and installing a cylindrical sealing assisting member 7 consisting of an invar behind the metal ring 6. When stainless steel is used for metal member, Fe-Ni alloy having a low expansion rate is suitably used for the sealing assisting member. Though thermal expansion is generated in each part, and the expanded sealing material is introduced into the expanded sealing gap, and sealing is maintained, sealing material is introduced also into the generated gap, since the thermal expansion of the assisting material 7 is small, and the swelling-out rate into the parts between the ceramics valve seat 1B, metal member 5, and a member 8 is little. Therefore, the deformation applied onto the sealing member is small, and the sealing of the ceramics valve seat can be perfectly maintained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for use under conditions involving repeated temperature changes.
Related to improvements in sealing mechanisms between metals and ceramics. The present invention has great significance especially when applied to a sealing mechanism for a gas minute flow rate regulating valve in semiconductor manufacturing equipment.

For example, recent semiconductor manufacturing equipment has been selected to operate under higher vacuum conditions, and the amount of helium, argon, oxygen, and various organometallic compound gases supplied to this equipment must be finely adjusted. It has become necessary.

When a gas with a considerable pressure is supplied from a pressure vessel such as a cylinder to semiconductor manufacturing equipment that is kept in a high vacuum, there is a large pressure difference between the secondary pressure and the secondary pressure before and after the flow rate adjustment valve. In addition to this high differential pressure, there is a large temperature change from high temperature to low temperature due to repeated shutdowns of the device. Micro flow rate adjustment valves used under such harsh conditions must not only have the ability to control minute flow rates, but also minimize the amount of leakage when closed, and must be reliable enough to maintain this for a long period of time. . Therefore, the sealing mechanism is important in minute flow rate adjustment valves.

Conventionally, rubber O-rings, adhesives, Teflon, and the like have been used as sealing materials, but drawbacks such as gas generation under high vacuum and lack of heat resistance have been pointed out.
As an alternative sealing material, an O-ring made of soft metal, such as gold or copper, is used.

However, those using a soft metal sealing material have the disadvantage that they cannot withstand repeated temperature changes and the amount of leakage gradually increases. The reason for this is that soft metals generally have a large coefficient of thermal expansion, and at high temperatures they expand and protrude into the seal gap.
This is because the deformation accumulates without being completely recovered even after cooling.

It is an object of the present invention to overcome the above-mentioned drawbacks, to absorb the deformation caused by thermal expansion and contraction cycles of soft metal sealing material, and to be able to absorb the deformation caused by the thermal expansion and contraction cycles of the soft metal sealing material, even when used under severe conditions of high differential pressure and large temperature difference. The object of the present invention is to provide a sealing mechanism between metal and ceramics that exhibits a stable sealing function.

The metal-ceramic sealing mechanism of the present invention is made by inserting a soft metal sealing material between a metal member and a ceramic member, and is used under conditions of repeated temperature changes. The present invention is characterized in that a seal auxiliary material made of a material having thermal expansion characteristics that offsets the thermal expansion of the seal material is provided in contact with the seal material.

The sealing mechanism of the present invention has leakage i 10 of the gold ring portion in thermal cycle tests 1 to 30'C←→160°C.
0-9 At cc/sec (He scum) The yield of non-defective products for the gold ring seal assembly during the manufacturing process reaches almost 100%.

One typical application example of the sealing mechanism of the present invention is minute gas flow rate adjustment for vacuum use to supply a minute amount of gas such as argon at a controlled rate into the vacuum atmosphere of the semiconductor manufacturing equipment described above. This is the seal for the valve seat.

This example will be explained below with reference to the drawings.
The figure is a longitudinal sectional view of the valve, and FIG. 2 is an enlarged view showing the sealing mechanism of the valve seat.

This valve has a structure in which a small amount of gas introduced into the gas chamber GC flows through a gap between a valve body 1A and a valve seat 1B, both of which are made of ceramics (for example, sapphire).

The gas contact casing 5 is a space partitioned by a diaphragm 9 made of metal (for example, SUS 304.316L, Monel metal, etc.) to give the valve body a degree of freedom, and gas is introduced into this space.

The standing base 8 is made of metal with good corrosion resistance (for example, SUS 3'16L), and is connected to various devices. The gas introduced into the gas chamber is
It flows through the hole in the center of the standing base.

The drive system uses a pneumatic type in the illustrated example, but other types (electromagnetic type or electrostrictive type) may be used. The driving force is transferred to the valve body IA
Stem 2 is used to convey this information. A pressing force is applied to the valve body 1A by a spring 4, and in order to adjust this pressing force, air pressure is applied to a rubber diaphragm 3 to generate a force in the opposite direction to the pressing force of the spring.

By using this drive system, when air pressure is not applied, the valve body 1A is pushed against the valve seat 1B, and gas does not flow. When air pressure is applied and the pressing force of the spring decreases, the gas is distributed.

FIG. 2 shows an example of a sealing mechanism. In this sealing mechanism, a ring 6 of soft metal such as gold is inserted between a ceramic valve seat 1B, a gas-contact casing 5 and a standing base 8, and a ring 6 of soft metal such as gold is inserted behind this ring. ) is provided with a cylindrical seal auxiliary material 7 made of.

A typical soft metal used as a sealant is gold. Indium, copper, silver, aluminum, etc. can also be used.

When stainless steel is used as the metal member, a low expansion Fe--Ni alloy is suitable as the sealing aid.
Some low expansion alloys have various coefficients of thermal expansion depending on the alloy composition, so it is best to select an appropriate one depending on the usage situation.

In the sealing mechanism according to the present invention, sealing is performed as shown in FIG. 3 at normal temperature, and as shown in FIG. 4 when the temperature rises. Thermal expansion of each part occurs here,
The expanded seal material comes out into the expanded seal gap and maintains the seal, but the thermal expansion of the seal auxiliary material 7 is small, and the seal material also comes out into the gap created by this, so the ceramic valve seat 1B and the metal The degree of protrusion between the members 5 and 8 is small. Therefore, the degree of deformation that the sealing material undergoes is relaxed compared to the case of FIG. 6, and the amount of deformation that accumulates due to repeated temperature changes is much smaller.

In this way, the seal of the ceramic valve seat remains intact over a long period of time.

When only the gold ring is used without using the sealing aid used in the present invention, sealing is performed as shown in FIG. 5 at room temperature, but changes as shown in FIG. 6 as the temperature rises.

In other words, all the constituent parts of the seal mechanism undergo thermal expansion, but if the coefficient of linear expansion is α for the metal member, α2 for the seal member, and α3 for the ceramic, the relationship is α2>α1>α3, so the ceramic valve seat 1B and the member The seal gap between 5 and 8 expands as the temperature rises, and the sealing material that expands the most protrudes into it.
Seal is maintained. However, in the conventional structure, the sealing material regains almost its original shape as the temperature decreases;
Since it is soft and easily deformed, deformation accumulates little by little as temperature changes, and the integrity of the seal is eventually compromised.

The above drawbacks have been overcome by the present invention. That is, the sealing mechanism of the present invention maintains the integrity of the seal well even with repeated temperature changes in conventional metal-to-ceramic seals.

Therefore, this sealing mechanism is particularly useful when used for sealing a valve that adjusts the minute flow rate of atmospheric gas supplied to a semiconductor manufacturing apparatus operated in a vacuum, as described by way of example. It will be easily understood that the present invention can also be applied to other devices under similar conditions.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the structure of a minute gas flow rate adjustment valve to which the sealing mechanism of the present invention is applied. FIG. 2 is an enlarged view showing the main parts of FIG. 1. 3 to 6 are schematic cross-sectional views corresponding to FIG. 2 for explaining the operation of the sealing mechanism of the present invention, and FIG. 3 is a schematic cross-sectional view corresponding to FIG. FIG. 4 shows the normal temperature state, and FIG. 4 shows the high temperature state. FIG. 5 shows the normal temperature state when a soft metal ring is simply used, and FIG. 6 shows the high temperature state. 1A... Valve body 1B... Valve seat 5... Gas contact casing 6... Seal material (soft metal ring) 7... Seal auxiliary material (low expansion alloy cylinder) 8... Standing Base Patent Applicant JGC Corporation Representative Patent Attorney Souo Suga Figure 1 Figure 2 14 Opening UG3-25427 (1 (4) Figure 3
Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) A soft metal sealing material is inserted between a metal member and a ceramic member, and has thermal expansion characteristics that offset the thermal expansion of the soft metal in a sealing mechanism used under conditions of repeated temperature changes. A sealing mechanism between metal and ceramics characterized by a sealing auxiliary material made of a material provided in contact with the sealing material. (2) The sealing mechanism according to claim 1, wherein the sealing auxiliary material is provided behind the sealing material with respect to the sealing gap. (3) The sealing mechanism according to claim 1, wherein the metal member is stainless steel, gold is used as the sealing material, and Fe-Ni low expansion alloy is used as the sealing auxiliary material.