JPH0261629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cryopump, and in particular provides a cryopump with significantly improved ability to adjust exhaust gas for hydrogen (ability to adjust hydrogen exhaust during exhaust of condensable gas). .

In recent years, cryopumps using small helium refrigerators with an ultimate temperature of 10 to 20 degrees have become widely used as exhaust pumps for vacuum equipment. Conventionally, this type of cryopump typically uses a small helium refrigerator with two freezing stages. Figure 1 shows a schematic diagram of the cryopump. The first freezing stage 1 of this small helium refrigerator 4 is normally 50~
The second freezing stage 2 is usually cooled to a temperature of about 10 to 20 degrees. A second condensation type cryopanel 22 for gas condensation is attached to this second cooling stage 2, and this second condensation type cryopanel 22 mainly converts gases such as Ar, N ₂ , O ₂ etc. Condensate exhaust is performed. He, Ne, _H2, etc. exhibit high saturated vapor pressures at temperatures of 10 to 20 degrees, and cannot be condensed and exhausted in this second condensing type cryopanel 22. In order to exhaust gas that cannot be condensed and exhausted by the second condensation type cryopanel 22, a third adsorption type cryopanel 3 is attached with a gas adsorbent such as activated carbon.
2 is also attached to the second freezing stage 2. (The third adsorption type cryopanel 32
It may also be attached to the second freezing stage 2 integrally with the condensing cryopanel 22. ) On the other hand, gas such as H ₂ O and CO ₂ is supplied to the first freezing stage 1 in such a way as to cover the second freezing stage 2 and the second and third cryopanels 22 and 32 attached thereto. A first condensing type cryopanel 11 for condensing is attached. The bottom portion 110 of the first condensing cryopanel 11 also serves as a radiant heat shield to prevent radiant heat from entering the second and third cryopanels 22 and 32.

The second and third cryopanels 22 and 32 both have an inverted cup-shaped structure and a cylindrical structure with a gap, with the former 22 covering the latter 32. The latter adsorption type cryopanel 32 holds an adsorbent with a significantly large surface area, such as molecular sieves or activated carbon, on its surface, and depending on the adsorption ability of the adsorbent, it can absorb gases that are difficult to condense, such as He, Ne, and _H2 . Adsorb and exhaust.

Even with conventional cryopumps having the structure described above, as long as the load is small, it is possible to pump out gas at a high velocity in almost all devices.

However, recently, the applications of cryopumps have expanded and they are now widely used in semiconductor manufacturing equipment. As this type of cryopump has come to be used in the exhaust system, the need for evacuation of a large amount of H ₂ , which has an adverse effect on the quality of the sputtering film, has increased especially when used in sputtering equipment.

It is difficult to selectively exhaust hydrogen with the conventional cryopump shown in Fig. 1, and the third adsorption type cryopump described above is particularly difficult to exhaust hydrogen in a high vacuum region or exhaust hydrogen generated during the sputtering described above. Since the incidence of _two HH molecules on adsorbents such as molecular sieves and activated carbon in panels is low, it takes a long time to exhaust hydrogen, so to shorten the time,
It was necessary to make the pump larger.

The present invention aims to solve this problem. In sputtering equipment, a large amount of H ₂ may be released from the target etc. during sputtering, and a high partial pressure of H ₂ in the sputtering chamber will seriously affect the quality of the produced film, so it is necessary to quickly exhaust H ₂ . Requires. However, in the initial evacuation before sputtering starts, the amount of H ₂ to be evacuated is extremely small. Also, even with the same sputtering,
Depending on the process, the release of H ₂ may be almost negligible.

A similar situation exists regarding the exhaust of Ar, N ₂ , and O ₂ gases, which are handled by the second condensing cryopanel 22 . In general, this method requires a large amount of N ₂ , O ₂ , etc. to be exhausted during the initial exhaust before sputtering, and the exhaust capacity is allowed to decrease considerably after sputtering starts.

By the way, as mentioned above, about 10K to 20K is attached to the second freezing stage 2 of the helium refrigerator.
The second condensing cryopanel ₂₂ , which is cooled to a temperature of
Condenses O ₂ Ar etc. at a temperature of 10〓~20〓. On the other hand, the third cryopanel 32 equipped with a gas adsorbent such as activated carbon is made by pasting a gas adsorbent such as activated carbon on a good thermal conductor such as copper, and utilizes its low temperature gas adsorption ability to He, H ₂ , which has a relatively high vapor pressure at temperatures between 〓 and 20〓 and cannot be condensed and pumped out,
Although Ne is adsorbed and exhausted, gas adsorbents generally have a limit to the amount of gas adsorbed, and when a large amount of N ₂ , ArO ₂ , etc.
Its original purpose, the ability to exhaust He, H ₂ and Ne, is significantly impaired. For this reason, the third adsorption cryopanel 32 is covered with the second condensation cryopanel 22, and most of the gas passes through the second cryopanel at least once before reaching the activated carbon surface.
Due to the structure, only He, H ₂ and Ne that cannot be condensed and exhausted by the second condensing cryopanel 22 can reach the activated carbon surface. consideration is given.

However, cryopumps with this structure have serious drawbacks as mentioned above.
In other words, a large amount of
When it becomes necessary to exhaust H ₂ , the exhaust capacity becomes insufficient.

In order to solve this problem, the present invention provides a structure in which an opening is provided in the second condensing cryopanel 22, and the opening ratio is made variable so that the conductance can be adjusted from outside the vacuum.

Hereinafter, the present invention will be explained in detail by way of examples and with reference to the drawings. FIGS. 2 and 3 show a cryopump according to an embodiment of the present invention, which is used in the main exhaust system of a sputtering device. The same members as in FIG. 1 are given the same reference numerals. In this embodiment, the second condensing cryopanel 22 in FIG. 1 is composed of a fixed panel 221 and a movable panel 222, both of which have an inverted top shape and are made of oxygen-free copper and overlap coaxially. . Both panels have some radial gap 220. Fixed panel 22
1 is fixed to the second freezing stage 2, and a shaft 24 is projected upward at the shaft center 20, and this projection shaft 2
4 is loosely inserted into the hole 26 of the movable panel 222, and the movable panel 222 is rotatably movable around the shaft 24.

A padding 25 is placed in the upper axial sliding gap between the fixed panel 221 and the movable panel 222 to ensure sufficient heat transfer between them.
For example, a wide-area, thin oxygen-free copper mesh is used.

A large number of openings 21 and 23 are provided in the skirt portions of both panels 221 and 222 at mutually overlapping positions. In order to ensure uniformity of temperature distribution in the panel, the shape of the opening holes is oval.
Moreover, the arrangement of the opening holes is also symmetrical with respect to the rotation axis.

The arm 27 that rotates the movable panel 222 is
A pivot shaft 2 made of a thermally poor conductor material, whose tip part is loosely inserted into the protruding shaft 28 at the upper edge of the movable panel 222, and whose base part is fixed to the play plate 31 of the bellows 30.
9 is loosely inserted. Play plate 31 of this bellows 30
The pump can be moved forward and backward by turning a screw 32' screwed into a frame 81 fixed to the pump container 8 using a handle 33 outside the vacuum.
Therefore, the movable panel 222 can be rotated around the axis 20 by operating the handle 33 and the axis 20, and in this case, the opening holes 21 and 23 are deviated from overlapping, and the third suction type cryopanel is moved. When viewed from outside, the opening area shrinks and the gas conductance decreases.

The cryopump of the present invention configured as described above operates as follows. That is, in the initial exhaust process of the sputtering device, the overlap between the openings 21 and 23 is made zero, and therefore the opening area is eliminated,
N ₂ , O _{2 ,} etc. are sufficiently condensed on the panels 221 and 222, and are prevented from reaching the adsorption cryopanel as much as possible, thereby preventing a decrease in the adsorption capacity of the adsorbent. In the sputtering process after N ₂ O ₂ etc. have been sufficiently exhausted, the movable panel 222 is rotated by operating the handle 33 in order to exhaust a large amount of H ₂ etc. generated from the target etc. The conductance is increased so that H ₂ molecules collide with the third adsorption cryopanel more frequently. Adjustment of conductance during the sputtering process is performed according to changes in the composition of Ar gas and H ₂ gas. This operation of changing the conductance of the gas is used in processes other than those described above that utilize vacuum equipment, and is highly effective.

In the above-mentioned embodiment, the second condensation cryopanel is constructed by a combination of two panels that overlap each other and are movable relative to each other, and each of the two panels has an opening hole at the overlapping position. Although the structure of the opening and the method of changing the opening area of the present invention are not limited to this, the opening area is changed by the relative movement. There are various shapes and configurations of condensing cryopanels, and the present invention has embodiments suitable for each of them.

The cryopump of the present invention is as described above, and is a cryopump equipped with a condensing type cryopanel and an adsorption type cryopanel covered with the condensing type cryopanel, both of which are operated at 20ⓓ or less. By making it possible to change the opening area, the H ₂ exhaust capacity can be adjusted significantly. According to the apparatus of the present invention, a small-capacity cryopump can sufficiently cope with large-scale sputtering equipment that generates a large amount of _H2 , and can perform high-quality processing.
This produces great economic efficiency. The contribution of the cryopump of the present invention to the manufacture of semiconductor devices is enormous. This can be said to be an industrially useful invention.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional cryopump. Second
The figure is a sectional view of a cryopanel according to an embodiment of the present invention.
FIG. 3 is an enlarged exploded view of the second condensing cryopanel. 1: 1st freezing stage, 2: 2nd freezing stage, 11: 1st condensing cryopanel, 2
2,221+222: second condensation cryopanel, 32: absorption cryopanel, 21,23:
Opening hole, 24: Projection shaft, 26: Hole, 27: Arm, 221: Fixed panel, 222: Movable panel,
30: bellows, 33: handle.

Claims (1)

[Claims] 1. A condensation type cryopanel for condensing gas that is cooled to a temperature of approximately 20㎓ or less, and an adsorption type cryopanel that is covered with the panel and equipped with a gas adsorbent that is cooled to a temperature of approximately 20ん or less. In the cryopump, the condensing cryopanel is configured by a combination of two panels that overlap each other and are movable relative to each other, and each of the two panels is provided with an opening at the overlapping position, A cryopump characterized in that the overlapping of the apertures is shifted by the relative movement, thereby changing the opening area of the aperture.