JPH0699003A - Cold trap - Google Patents

Abstract

PURPOSE:To automatically keep the temp. in a vacuum vessel in a specific temp. range. CONSTITUTION:A stainless steel-made metallic mesh screen 12 is laminated and housed in the heat regenerating chamber13 of a cryorefrigerator 2 attached with the end face 22 of a cylinder 11 to a cryopanel. Thus, the temp. in the vacuum vessel provided in the cryopanel is automatically kept at 70-120 K by making the specific heat content of a refrigerating material of the cryorefrigerator 2 a required specific heat content at >= 60 K and sufficiently lower specific heat content at a lower temp. than 60 K.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to improvements in cold traps.

[0002]

2. Description of the Related Art Conventionally, when selectively removing water (water vapor) in a vacuum apparatus used for manufacturing semiconductors, etc., a cold trap is installed in the vacuum apparatus through a valve so that the inside of the vacuum apparatus is about 70K. It is cooled to ~ 120K, and the moisture in the vacuum device is selectively condensed and removed from the valve.

[0003]

However, when the cold trap is used for removing water from the vacuum apparatus as described above, the refrigerating capacity of the cold trap is a refrigerating capacity corresponding to about 70K to 120K required for removing water. In case there is no problem. However, if the refrigerating capacity of the cold trap is lower than the refrigerating capacity required for removing water in the vacuum device, the water in the vacuum device cannot be selectively removed.
Further, if the refrigerating capacity required for removing water is higher than the refrigerating capacity, nitrogen gas, argon gas, etc. required for semiconductor production will also be removed.

At present, a mesh screen in which phosphor bronze wire is woven with 200 mesh is used as a regenerator material for a refrigerator used in the cold trap. However, the refrigerating capacity of a cold trap using such a cold storage material is usually too high for removing water from a vacuum device.

Therefore, conventionally, when the refrigerating capacity of the cold trap is too high, the temperature in the vacuum device is set to 70K.
A heater for adjusting the temperature must be installed in the cold trap in order to keep the temperature up to 120 K, resulting in a large energy loss and a large cost increase, and there is a problem that the reliability of the device is reduced.

Therefore, an object of the present invention is to provide a cold trap capable of automatically maintaining the temperature in a vacuum container at 70K to 120K.

[0007]

In order to achieve the above object, the invention according to claim 1 is, as illustrated in FIGS. 1 and 2, a cooling panel 5 attached to a vacuum container and a cooling panel 5. In a cold trap having a cryocooler 2 having one end attached, a cold storage material 12 having an effective cold heat exchange capacity at a temperature of 60 K or higher is provided in a cold storage chamber 13 provided in a displacer 14 of the cryocooler 2. It is characterized by being stored.

The invention according to claim 2 is the cold trap of the invention according to claim 1, wherein the cold storage material 12 is
The material is characterized by being stainless steel.

Further, the invention according to claim 3 is the cold trap of the invention according to claim 1, wherein the regenerator material 12 is
Is characterized in that it is housed so that its cold heat exchange efficiency changes in the direction of the flow of the refrigerant gas in the cold storage chamber 13.

The invention according to claim 4 is the cold trap of the invention according to claim 3, wherein the regenerator material 12 is used.
The material is characterized in that the refrigerant gas introduction side of the cold storage chamber 13 is phosphor bronze, while the cooling panel 5 side is stainless steel.

[0011]

In the invention according to claim 1, in the cold storage chamber 13 provided in the displacer 14 in the cryocooler 2 having one end attached to the cooling panel 5, the cold storage that exhibits an effective cold heat exchange capacity at a temperature of 60 K or more. The material 12 is stored. Therefore, when the cryocooler 2 operates, the temperature of the regenerator material 12 approaches 60K. As a result, the temperature inside the vacuum container attached to the cooling panel 5 is automatically maintained at 70K to 120K.

In the invention according to claim 2, the regenerator material 12 is made of stainless steel having a sufficiently small specific heat at a temperature lower than 60K. Therefore, the regenerator material 12
The temperature easily reaches 60K.

Further, in the invention according to claim 3, the regenerator material 12 is housed so that the cold heat exchange efficiency thereof changes in the direction of the flow of the refrigerant gas in the regenerator chamber 13. Therefore, on the refrigerant gas introduction side of the cold storage chamber 13, cold heat exchange with the refrigerant gas is performed with high cold heat exchange efficiency. On the other hand, on the cooling panel 5 side, it can be suppressed that the temperature of the cooling panel 5 becomes lower than 60K due to the low heat exchange efficiency.

In the invention according to claim 4, the material of the regenerator material 12 is phosphor bronze on the refrigerant gas introduction side of the regenerator 13 and stainless steel on the cooling panel 5 side. Therefore, on the refrigerant gas introduction side of the cold storage chamber 13, cold heat exchange with the refrigerant gas is efficiently performed by the cold storage material having a large specific heat. On the other hand, on the cooling panel 5 side, it is suppressed that the temperature of the cooling panel 5 becomes lower than 60K by the regenerator material exhibiting a small specific heat at a temperature lower than 60K.

[0015]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a perspective view of the cold trap of this embodiment. This cold trap has a roughly wooden shape, and a cryorefrigerator 2 (indicated by diagonal lines) is mounted inside the cooling unit 1 corresponding to its handle. In addition, the flange portion 3 that hits the head has an enclosure 4 having a role of a flange to which an object to be cooled such as a vacuum device is attached,
A cryopanel 5, which is housed in the enclosure 4 and has one end of the cryocooler 2 attached to the side surface, is provided as the cooling panel.

FIG. 2 is a sectional view of the cryorefrigerator 2. The cryorefrigerator 2 will be briefly described below with reference to FIG. This cryo-refrigerator 2 has a closed cylinder 11 and a displacer 14 having a cool storage chamber 13 which is slidably fitted in the cylinder 11 and in which a metal mesh screen 12 as a cool storage material is stacked and accommodated. Is equipped with. Further, the cold storage chamber 13 of the displacer 14 is switched and communicated via a valve stem 15 and a valve 16 with a high pressure chamber 18 having an inlet 17 or a low pressure chamber 20 having an outlet 19.

Switching of the communication passage from the cold storage chamber 12 to the high pressure chamber 18 or the low pressure chamber 20 is performed by rotating the valve 16 by the valve motor 21.

In FIG. 2A, a high-pressure refrigerant gas such as helium supplied from a compressor (not shown) or the like is introduced into the inlet 1
7 is introduced into the cylinder 11 via the valve 16 and the valve stem 15. The refrigerant gas introduced into the cylinder 11 is guided into the cool storage chamber 13 of the displacer 14, and the metal mesh screen 12 in the cool storage chamber 13 is introduced.
It is cooled by exchanging cold heat with. Thus, the cold storage chamber 13 is filled with high-pressure refrigerant gas (intake process).

After that, as shown in FIG. 2 (b), the valve 16 is rotated by the valve motor 21 so that the cold storage chamber 13 is communicated with the low pressure chamber 20. Then, the high-pressure refrigerant gas introduced into the cold storage chamber 13 is expanded at a stretch and the gas temperature is lowered. Thus, the cold heat obtained by the expansion of the refrigerant gas is accumulated by the cold heat exchange with the metal mesh screen 12. In this way, the low-pressure refrigerant gas after completion of expansion and cold heat exchange is exhausted from the exhaust port 19 provided in the low-pressure chamber 20 (exhaust step).

As described above, the ultra-low temperature is obtained by repeating the introduction of the high-pressure refrigerant gas into the cold storage chamber 13 and its expansion / exhaust (that is, by repeating the refrigeration cycle consisting of the intake process and the exhaust process). Of.

As shown in FIG. 1, a cryopanel 5 is attached to the end surface 22 of the cylinder 11 of the cryocooler 2 which operates as described above, and a cooled object is placed on the cryopanel 5. Therefore, the displacer 14, the cylinder 11, and the cryopanel 5 are sequentially cooled by the cold heat accumulated in the metal mesh screen 12 as described above, and the object to be cooled is cooled.

As described above, when the cold trap is used for removing water in a vacuum device, the temperature in the vacuum device needs to be set to 70K to 120K. For that purpose, the regenerator material in the cryocooler needs to have a material having a specific heat equivalent to that of phosphor bronze at a temperature of 60 K or higher and a specific heat sufficiently lower than that of phosphor bronze at a temperature lower than 60 K.

Therefore, in the cold trap according to the present embodiment, a metal mesh screen 12 in which a stainless steel wire having a diameter of 50 μ is woven with 200 mesh is used as the metal mesh screen 12 housed in the regenerator 13 of the cryocooler 2. Of.

The above stainless steel has a specific heat equivalent to that of copper at a temperature of 60 K or higher, and a specific heat sufficiently lower than that of copper at a temperature lower than 60 K, so that the temperature of the cryopanel 5 can be easily adjusted to 70 K to 70 ° C. It can be set to 120K. Therefore, if a cold trap equipped with a cryorefrigerator having a metal mesh screen 12 made by weaving stainless steel wire with 200 mesh as a regenerator material is used, the temperature in the vacuum device is kept at 70K to 120K to selectively condense water. Can be removed. Note that FIG. 3 shows the constant pressure specific heats of copper and stainless steel.

Further, the refrigerating capacity at a temperature of 60 K or less can be lowered by reducing the surface area of the metal mesh screen in addition to changing the material of the metal mesh screen to stainless steel. That is, the mesh number of the metal mesh screen is reduced, and specifically, the mesh of the phosphor bronze wire mesh screen is set to 20.
The temperature of the cryopanel 5 can be easily set to 70K to 120K by making it coarser than 0 mesh and lowering the cold heat exchange efficiency to deteriorate the refrigerating capacity below 60K.

At this time, the mesh of the metal mesh screen is not made uniform in the flow direction of the refrigerant gas, but the mesh on the valve stem 15 side in the cold storage chamber 13 is set to 200 mesh, while the end surface of the cylinder 11 is made. The mesh on the 22 side is coarser than 200. In this way, the cold heat exchange efficiency of the metal mesh screen 12 on the end surface 22 side of the cylinder 11 that contacts the cryopanel 5 is lowered, while the cold heat exchange efficiency of the metal mesh screen on the side where the refrigerant gas is introduced is increased. By this, the temperature of the cryopanel 5 is 70 K to 70 K without significantly lowering the efficiency of cold heat exchange with the refrigerant gas.
Can be kept at 120K.

Further, the change of the cold heat exchange efficiency in the direction of the flow of the refrigerant gas in the regenerator material accommodated in the regenerator 13 can be changed by the material of the metal mesh screen. That is, the phosphor stem bronze metal mesh screen is stored on the valve stem 15 side in the cold storage chamber 13, while the stainless steel metal mesh screen is stored on the end face 22 side of the cylinder 11. Thus
The end surface 2 of the cylinder 11 that contacts the cryopanel 5
By decreasing the specific heat of the metal mesh screen 12 on the second side and increasing the specific heat of the metal mesh screen on the side into which the refrigerant gas is introduced, the cryopanel 5 is not significantly reduced in efficiency of cold heat exchange with the refrigerant gas. The temperature of 70K to 120K.

The change of the cold heat exchange efficiency in the direction of the flow of the refrigerant gas in the cool storage material accommodated in the cool storage chamber 13 includes the change of the cool heat exchange area (for example, the change of the cool heat exchange area) in addition to the change of the mesh and the material. It is also possible to accommodate a metal tube on the end face 22 side of the cylinder 11 and a metal mesh screen on the valve stem 15 side).

The shape of the cold trap in the present invention is not limited to the shape shown in FIG. 1, but the mounting state of the cooling part and the flange part may be changed according to the environment around the object to be cooled. It doesn't matter.

[0030]

As is apparent from the above, the cold trap of the invention according to claim 1 exhibits an effective cold heat exchange capacity at a temperature of 60 K or more in the cold storage chamber of the cryocooler having one end attached to the cooling panel. Since the cool storage material is stored, the internal temperature of the vacuum container attached to the cooling panel can be automatically maintained at 70K to 120K, and the moisture in the vacuum container can be selectively condensed and removed. Therefore, according to the present invention, the temperature in the vacuum container is set to 70K.
It is possible to prevent energy loss and cost increase without requiring a heater to keep the temperature at 120K. In addition, the reliability of the device can be improved.

In the cold trap of the invention according to claim 2, since the material of the regenerator material is stainless steel,
The temperature in the vacuum container attached to the cooling panel can easily be 70K to 120K.

Further, in the cold trap of the invention according to claim 3, since the cold storage material is housed so that its cold heat exchange efficiency changes in the direction of the flow of the refrigerant gas in the cold storage chamber, the refrigerant in the cold storage chamber is stored. While the cold heat exchange efficiency on the gas introduction side can be increased, the cold heat exchange efficiency on the cooling panel side can be lowered. Therefore, according to the present invention, it is possible to prevent the temperature of the cooling panel from becoming lower than 60K while efficiently exchanging cold heat with the refrigerant gas.

Further, in the cold trap of the invention according to claim 4, the material of the regenerator material accommodated on the refrigerant gas introduction side in the regenerator is phosphor bronze, and the cold accumulator accommodated on the cooling panel side. Since the material of the material is stainless steel, the heat exchange with the refrigerant gas is efficiently performed on the refrigerant gas introduction side in the cold storage chamber while the temperature of the cooling panel is easily prevented from lowering below 60K on the cooling panel side. it can. That is, according to the present invention, the temperature in the vacuum container can be maintained at 70K to 120K while efficiently performing cold heat exchange with the refrigerant gas.

[Brief description of drawings]

FIG. 1 is a perspective view of a cold trap of the present invention.

FIG. 2 is a sectional view of a cryocooler used in the cold trap shown in FIG.

FIG. 3 is a diagram showing constant pressure specific heats of copper and stainless steel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cooling part, 2 ... Cryo refrigerator, 3 ... Flange part, 4 ... Enclosure, 5 ... Cryopanel, 11 ... Cylinder, 12 ... Metal mesh screen, 13 ... Regenerator, 14 ... Displacer.

Claims (4)

[Claims] 1. A cooling panel attached to a vacuum container.
In a cold trap having (5) and a cryocooler (2) having one end attached to the cooling panel (5), a cold storage chamber (13) provided in the displacer (14) of the cryocooler (2). A cold trap characterized in that a cold storage material (12) exhibiting effective cold heat exchange capacity at a temperature of 60 K or higher is housed therein. 2. The cold trap according to claim 1, wherein the material of the regenerator material (12) is stainless steel. 3. The cold trap according to claim 1, wherein the regenerator material (12) is housed in the regenerator chamber (13) such that its cold heat exchange efficiency changes in the direction of the flow of the refrigerant gas. Cold trap that is characterized by 4. The cold trap according to claim 3, wherein the material of the regenerator material (12) is phosphor bronze on the refrigerant gas introduction side of the regenerator chamber (13), and the cooling panel.
Cold trap characterized in that (5) side is stainless steel.