JPH0415992Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a cryopump used to obtain high vacuum.

(Prior Art) Conventionally, as a cryopump, a cylindrical cryopanel c is provided vertically in a pump case b of a cryopump having an exhaust port a opening upward, as shown in the first diagram. These are known (Japanese Patent Publication No. 63-34316, Japanese Patent Publication No. 63-39796).

The cryopanel c is attached to the second stage head f of the refrigerator e, which extends inside a cylindrical shield d provided inside the pump case b, and the shield d is attached to the first stage head g of the refrigerator e. It will be done. Gas molecules flowing from the exhaust port a into the shield d via the buffer h are condensed on the shield d at 40 to 60K (Kelvin) and the cryopanel c below 20K and are exhausted, but the exhaust speed is It can be varied by a ring i that moves up and down between c and shield d.

(Problem to be solved by the invention) In general, when a cryopump reaches its maximum displacement with a large amount of gas molecules condensed on its cryopanel c and shield d, the condensed gas molecules are removed and the exhaust capacity is restored. Processing is performed. Determination as to whether a cryopump has reached its maximum displacement is made by measuring the partial pressure of the gas in the device pumped out by the pump, such as argon gas partial pressure, and if the partial pressure of the gas decreases. When it runs out, the pump will be regenerated.

Sputter film deposition equipment uses a large amount of argon gas, so the time to regenerate the cryopump that evacuates the equipment is determined by measuring the argon gas partial pressure. After evacuating a large amount of argon gas, but less than the maximum displacement, a phenomenon occurs in which the partial pressure of argon increases, and the measurement results indicate that it is time for pump regeneration even though the maximum displacement has not been reached. As a result, the cryopump is regenerated in a shorter period of time than necessary, resulting in a reduction in the operating rate of the device.

The reason for this phenomenon in which the partial pressure of argon gas increases is thought to be that the argon gas condensed in the buffer h, ring i, shield d, etc. connected to the first stage head g is re-released. It was proposed to raise the temperature of the first stage head g. However, the argon gas exhausted by a normal cryopump mainly condenses on the top and side surfaces of the cryopanel c below 20K, and the amount of argon solid condensed there is 1 to 2.
It is possible to pump up to a thickness of cm, and the amount sublimed from the solid argon of this cryopanel c is
It is less than 10 ^-13 Torr and is not enough to increase the pressure inside the pump, that is, the back pressure. That is, the amount condensed on the buffer h, ring i, and shield d is small. According to experiments, it was found that a large amount of solid argon condensed on the side surface of the cryopanel c fell onto the bottom surface of the shield d due to pump vibration, etc., and this was found to be the cause of the above phenomenon. To explain this further, the shield d is 40 to 60K, and the shield d
Solid argon that has fallen to the bottom of the tank will sublimate only very gradually from there, so it takes an extremely long time for even a small piece of solid argon, such as 1 mm square, to sublimate, and during that time the back pressure will exceed 10 ^-4 Torr. It was found that the cause was that the argon partial pressure was increasing. Moreover, this fall of solid argon tends to occur when the amount of condensation exceeds a certain value, and once this fall occurs, it becomes necessary to stop the cryopump, raise the temperature of each part of the pump to near room temperature, and perform a regeneration operation. During this period, the sputtering equipment is stopped and productivity decreases.

The present invention aims to prevent the phenomenon in which the gas partial pressure increases abnormally when the cryopump has not reached its maximum displacement.

(Means for Solving the Problems) In the present invention, in a cryopump in which a cryopanel is provided in a pump case of a cryopump, a cryopanel is provided below the cryopanel,
A saucer made of a thermally conductive material and having an outer diameter larger than the diameter of the cryopanel is provided to catch the condensate falling from the cryopanel, thereby achieving the above object.

(Function) When a cryopump is used to exhaust a sputtering film deposition system that uses a relatively large amount of argon gas, argon gas with a low condensation temperature flows in from the exhaust port of the pump, and solid argon is formed on the top and side surfaces of the cryopanel. It adheres as a condensate. When a cryopump is used for a long time, the solid argon condensate that has condensed on the cryopanel gradually becomes thicker, and it flakes off and falls due to vibrations of the pump. A receiver made of a thermally conductive material having a diameter larger than the diameter of the cryopanel is provided, so that the falling solid argon condensate is caught by the receiver, and the receiver has approximately the same temperature as the cryopanel. Therefore, the solid argon received will not sublimate.

Therefore, the back pressure of the cryopump does not increase before reaching the maximum displacement, and the argon gas partial pressure of the sputtering film forming apparatus does not increase, so the cryopump can be operated until the maximum displacement is reached. This improves the operating rate of the sputtering film forming equipment.

(Embodiment) An embodiment of the present invention will be explained based on Fig. 2 of the drawing. An exhaust pipe, 2, a pump case of a cryopump having an upwardly opening exhaust port 3 connected to the exhaust pipe 1; 4, a pump case 4 provided in the pump case 2 so as to open toward the exhaust port 3; A cylindrical shield 5 indicates a cylindrical cryopanel installed vertically within the shield 4 with an interval 6 therebetween, and the shield 4 is connected to the first stage head of the refrigerator 7 in the case 2. 8, and the cryopanel 5 was attached to the second stage head 9 of the refrigerator 7 extending inside the shield 4. Reference numeral 10 denotes a circular flat buffle having approximately the same diameter as the cylinder diameter of the cryopanel 5 provided in the opening 4a of the shield 4, and 11 the distance 6 between the deep part of the shield 4 and the opening 4a using a rod 13. The shielding plate 11 is an annular shielding plate that is reciprocated up and down between the shielding plates 11 and 11. The shielding plate 11 is formed with an extension portion 11a extending along the inner wall of the shield 4.

The configuration described above is not particularly different from the configuration of a conventional cryopump for sputtering film formation. When the refrigerator 7 is operated, the shield 4 is heated to a temperature of 40 to 60K, the cryopanel 5 is heated to a low temperature of 20K or less, and the exhaust pipe 1 Among the gas molecules flowing in through the exhaust port 3, gas molecules such as moisture that condense at a relatively high temperature condense on the shield 4, and argon gas molecules and the like that condense at a relatively low temperature condense on the cryopanel 5. and shielding plate 11
By moving the exhaust port 3 to an appropriate position,
The exposed area of the cryopanel 5 changes, and the effect of varying the pumping speed remains the same as in the conventional case.

In the above configuration, when a large amount of argon gas is pumped out, condensate such as solid argon that has condensed on the cryopanel 5 falls to the bottom of the shield 4 and sublimates, increasing the back pressure of the cryopump and exhausting the gas. This causes a phenomenon in which the partial pressure of gas such as argon in the sputter film forming apparatus connected to the tube 1 increases, but in the present invention, a structure made of a thermally conductive material such as aluminum is installed below the cryopanel 5. A receiving tray 12 whose outer diameter is larger than the outer diameter of the cryopanel 5 is provided to catch the condensate falling from the cryopanel 5, thereby preventing the occurrence of this phenomenon.

In the case shown in the second figure, the saucer 12 is formed by extending a cylindrical connecting portion 12a made of a thermally conductive material that enters the cylindrical inside of the cryopanel 5.
Although the cryopanel 5 is integrally connected to the cryopanel 5, the lower part of the cryopanel 5 may be bent outward into a dish shape to form a saucer 12 as shown in the third figure.

The saucer 12 is made of a thermally conductive material and is attached integrally with the cryopanel 5, so the temperature is approximately the same as that of the cryopanel 5, 20K or less, and the saucer 1
The condensate such as solid argon that has fallen onto 2 does not sublimate, and the occurrence of the above phenomenon is prevented.

In addition, in the case of FIGS. 2 and 3, the saucer 1
2 is always shielded from the pump inlet 3 by the ring 11, so that a large amount of argon will not condense, and solid argon will not fall from there to the bottom of the shield 4.

In addition to the examples shown in Figures 2 and 3, even when the cryopump is used horizontally, a ring with a structure that shields the cryopanel and the saucer from the inlet and a ring underneath the cryopanel are integrated with the cryopanel. The same effect can be obtained by using a structure that includes a saucer made of a material with good thermal conductivity.

(Effects of the invention) As described above, in the present invention, a receiving tray made of a thermally conductive material and having an outer diameter larger than the diameter of the cryopanel is provided below the cryopanel of the cryopump. Since the condensate falling from the cryopanel is caught in a low-temperature saucer, the gas partial pressure in the sputtering film deposition equipment connected to the cryopump increases before the cryopump reaches its maximum displacement. Without a doubt,
This eliminates unnecessary regeneration of the cryopump until the maximum displacement is exhausted, and has the effect of increasing the operating rate of a device that is evacuated by the cryopump.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view of a conventional example, FIG. 2 is a cross-sectional side view of an embodiment of the present invention, and FIG. 3 is a cross-sectional side view of main parts of another embodiment of the present invention. 2...Pump case, 3...Exhaust port, 5...Cryopanel, 12...Saucer.

Claims (1)

[Scope of utility model registration request] In a cryopump in which a cryopanel is provided inside the pump case, an outer diameter that receives condensate falling from the cryopanel is set below the cryopanel and integrally with the cryopanel. A cryopump characterized by having a saucer made of a thermally conductive material that is larger than that of the cryopump.