JPH03290068A - Cryopump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a cryopump connected to a high vacuum chamber for processing semiconductor wafers, etc., productivity is improved by continuously ensuring a degree of vacuum in the chamber for a long period of time. A cryopump that connects a housing, in which at least a displacer having a plurality of parallel-arranged disk-shaped panels is disposed, to a vacuum chamber on its open side, the bulkhead having a sealed hollow part. A displacer disposed in each area inside the housing, which is divided into equal parts, is arranged in each area so that the cooling fluid can be circulated to one or all of the areas by switching the main valve. Constructed with built-in fluid pipes.

[Industrial application field]

The present invention relates to the structure of a cryopump connected to a high-vacuum chamber for processing semiconductor wafers, etc., and particularly to a cryopump that improves productivity by continuously securing a degree of vacuum within the chamber for a long period of time. .

The ion implantation process and span flange process for semiconductor wafers are performed in a high vacuum chamber, and a cryopump is often used to ensure a high degree of vacuum within the chamber.

On the other hand, cryopumps maintain a high degree of vacuum in the chamber by evacuating the chamber by adsorbing gas molecules on the surfaces of multiple cooled panels, but the amount of gas molecules adsorbed on the panel surfaces is If a certain limit is exceeded, the cooling temperature of the panel surface gradually increases, the adsorption efficiency of gas molecules decreases, and the exhaust capacity decreases, so the adsorbed gas molecules must be removed almost periodically.

On the other hand, adsorbed gas molecules can be removed by stopping the cooling of the panel surface and raising the temperature, but in order to prevent the gas molecules flying out from the panel surface from flowing back into the chamber, it is necessary to separate the gas molecules from the chamber at least during the time period required for removal. As a result, the chamber cannot be evacuated during this period, resulting in loss time for the chamber, and no improvement in productivity can be expected, and a solution to this problem is desired.

[Conventional technology]

FIG. 2 is a conceptual diagram showing an example of the configuration of the vicinity of a chamber including a conventional cryopump, and is shown cut along a plane passing approximately through the central axis.

Moreover, FIG. 3 is a diagram showing another configuration example.

In FIG. 2, a cryopump 3 is mounted at a predetermined position on the outer wall of a chamber 1 through a slit window 2 by a flange or the like that fits the chamber 1.

In particular, the cryopump 3 includes a cylindrical housing 4, a displacer 5 disposed along the central axis of the housing 4, and umbrellas attached at approximately equal intervals in parallel to a shaft 5a fixed to the distal end of the displacer 5. The displacer 5 further includes a fluid pipe 5 through which cooling fluid can circulate inside the displacer 5.
b is buried.

In this case, compressed helium gas from the compressor 7 is circulated through the fluid pipe 5b as shown by the arrow a, expanded by the displacer 5, and fixed to the shaft 5a of the placer 5 and then to the shaft 5a. When the plurality of panels 6 are cooled to about 10 Kelvin, the gas molecules scattered near the panels 6 are adsorbed and solidified on the panels 6, and the inside of the cryopump 3 is depressurized, resulting in a temperature similar to exhaust gas. exhibit a condition.

Therefore, if the inside of the chamber 1 is roughly pumped down to about 10-' Torr using a vacuum pump (not shown), and then the cryopump 3 is operated as described above, the pressure inside the cryopump 3 will be lower than that of the chamber 1. Gas molecules pl, pz+ pal... scattered in the chamber 1
・ passes through the slit window 2 as shown by the arrow and is adsorbed to the panel 6 of the cryopump 3, and as a result, the chamber 1
The pressure can be reduced to, for example, about 10-'' Torr, and the required wafer processing can be carried out.

Note that while the cryopump 3 is in operation, gas molecules scattered around it are continuously adsorbed, so that the degree of vacuum in the chamber 1 can be substantially maintained.

However, as the number of gas molecules adsorbed by the panel 6 increases, the cooling temperature of the panel 6 gradually rises and the gas molecule adsorption capacity decreases, resulting in a decrease in the displacement of the cryopump 3 and the vacuum of the chamber 1. It becomes difficult to maintain the temperature.

For example, it has been experimentally confirmed that when the temperature of the panel 6 rises to about 20 Kelvin, it becomes difficult to maintain the degree of vacuum in the chamber 1.

Therefore, based on the experimental data, at present, after using the chamber continuously for about a week, for example, work in the chamber is stopped, cooling of the cryopump 3 is stopped, and gas molecules are removed (hereinafter referred to as regeneration). I try to do this.

However, it takes about 8 hours to regenerate the cryopump 3, and during this regeneration, the chamber 1 cannot be evacuated.
There is a lot of lost time before work begins.

FIG. 3 shows a configuration for eliminating such loss time, in which the cryopump 3 described in FIG. 3 is installed in two predetermined positions in the chamber 1 in close proximity. A valve 8 is interposed between the chamber 1 and the slit window 2 described in FIG. 3, respectively.

Note that 7 is a compressor connected to each cryopump 3.

With this configuration, by alternately switching the two valves 8, it is possible to regenerate the cryopump 3 on one side while the other cryopump 3 is exhausting, resulting in the loss time explained in FIG. 3. The chamber 1 can be used continuously without any interruption.

However, in this case, a space is required to mount the two cryopumps 3, resulting in an increase in equipment size and equipment costs.

[Problem to be solved by the invention]

With conventional cryopumps, the chamber must be stopped at least during the regeneration period of the pump, so there is a problem in that loss time cannot be avoided and productivity cannot be expected to improve. If a plurality of cryopumps are installed in a chamber in order to eliminate the problem, there is a problem that the equipment becomes large, the space factor deteriorates, and the equipment cost increases.

[Means to solve the problem]

The above-mentioned problem is a cryopump in which a housing in which at least a displacer having a plurality of disk-shaped panels arranged in parallel is disposed is connected to a vacuum chamber on its open side, and a partition wall with a sealed hollow part is used. A displacer disposed in each area inside the housing, which is divided into equal parts, is arranged in each area so that the cooling fluid can be circulated to one or all of the areas by switching the main valve. The solution is a cryopump that has a built-in fluid pipe.

[Function] If a conventional cryopump is divided into two thermally and vacuum-independent regions and each region is configured as an independent cryopump, the same effect as when two cryopumps are installed can be obtained. be able to.

In the present invention, by fixing a partition wall having a hollow part in a housing having an elliptical cross section, the inside of the housing can be thermally and
It is divided into two vacuum-independent regions, and an independent cryopump is configured in each region.

Therefore, the degree of vacuum in the chamber can be continuously maintained for a long period of time without increasing the size of the equipment, and productivity can be improved.

〔Example〕

FIG. 1 is a diagram illustrating a configuration example of a cryopump according to the present invention, and (A) is a sectional view similar to FIG. 2.

(B) is a plan view of the cryopump portion taken along line bb' in (A).

In FIGS. 1(A) and 1(B), valves 12a and 12b operated by mechanical parts (not shown) are disposed at two predetermined positions adjacent to each other on the outer wall of the chamber 11. An oval flange lla is formed around the valves 12a and 12b.

The cryopump 13 is equipped with a flange 13a that is airtightly attached to the chamber 11 at the flange lla portion, and has a partition wall 14 that is elliptical in plan view and has a sealed hollow portion 14a that completely divides the interior in the short axis direction. A, 88SJ, which is partitioned by the partition wall 14.
Slit windows 16a and 16b installed in the opening of the f region, displacers 17a and 17b arranged along the central axis of each region A and B, and each displacer 17a.
, 17b, and a panel 18 consisting of an umbrella-shaped disc body similar to that shown in FIG. It passes through the bottom of the.

Note that a compressor 19 located outside the cryopump 13 is provided inside each of the displacers 17a and 17b.
A fluid pipe 20 for cooling fluid connected to the displacers 17a, 17b is buried so as to be able to circulate in order between the displacers 17a, 17b. By switching the main valve 21 disposed near the main valve 21, the circulation path of the cooling fluid can be changed, for example, by circulating the displacers 17a and 17b separately or by circulating the displacers 17a→17b continuously. It has become.

In the cryopump 13 having such a configuration, for example, the third
Similarly to the figure, with the valve 12a open and the valve 12b closed, compressed helium gas from the compressor 19 is circulated only to the displacer 17a using the main valve 21, and while the chamber 11 is being evacuated, the displacer 17t+ is regenerated. At the same time, when the displacer 17a reaches the regeneration period, the valve 12a
The chamber 11 can be continuously evacuated by switching the flow path of the fluid pipe 20 to the displacer 17b using the main valve 21 with the valve 12b closed and the valve 12b opened.

In particular, there is a sealed hollow section 14a between the region A and the region B where the displacers 17a and 17b are respectively accommodated.
Since there is a partition wall 14 therebetween, the displacers 17a and 17b are completely independent thermally and vacuum-wise.

Therefore, the loss time of the chamber 11 explained in FIG. 2 can be eliminated, and the same effect as in the case of FIG. 3 can be obtained.

Note that when the chamber 11 is opened for incidental work etc. associated with the chamber 11, the valve 12 of the cryopump 13 is opened.
By opening both a and 12b and circulating the above-mentioned cooling fluid to the displacers 17a and 17b at the same time, the chamber 11 can reach the required degree of vacuum in a short time, thereby shortening the start-up time before starting work. .

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a cryopump in which the degree of vacuum in the chamber can be continuously ensured for a long period of time, thereby improving productivity.

In the description of the present invention, the housing is divided into three equal parts, but the same effect can be obtained even if the housing is divided into three or more equal parts.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a configuration example of a cryopump according to the present invention, FIG. 2 is a conceptual diagram illustrating a configuration example near a chamber including a conventional cryopump, and FIG. 3 is a diagram illustrating another configuration example. It is. In the figure, 11 is a chamber, lla and 13a are flanges, 12a and 12b are valves, 13 is a cryopump, 14 is a partition, 14a is a sealed hollow part, 15 is a housing, 16a and 16b are slit windows, and 17a
, 17b is a displacer, 18 is a panel, 19 is a compressor, 20 is a fluid pipe, and 21 is a main valve. Structure of the cryopump according to the present invention] Figure 1

Claims (1)

[Scope of Claims] A cryopump in which a housing in which at least a displacer having a plurality of disk-shaped panels arranged in parallel is disposed is connected to a vacuum chamber at an open side thereof, the housing comprising a closed hollow part (14a). ) Displacers (17a, 17b) disposed in respective areas inside the housing (15), which are equally divided by a partition wall (14) having Alternatively, a cryopump characterized by having a built-in fluid pipe (20) arranged in each region so that cooling fluid can be circulated throughout the region.