JPS6310310B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cryopump exhaust system using a helium refrigerator, and particularly to a vacuum exhaust system suitable for application to a semiconductor thin film production apparatus.

[Background of the invention]

Conventionally, the configuration and vacuum evacuation equipment of semiconductor thin film production equipment, typified by molecular beam epitaxy, are
It is generally arranged as shown in the figure.

1 is a sample exchange chamber, 2 is a vacuum valve, 3 is a high vacuum pump such as a turbo molecular pump, 4 is a leak valve, 5 is a rotary pump used for exhausting back pressure of the high vacuum pump 3, and 6 is a high vacuum The sample preparation/analysis room is a chamber; 7 is a thin film growth chamber which is also a high vacuum chamber; 8, 9, 10, and 11 are gate valves; A clean ultra-high vacuum pump with no back diffusion, 14 a sample substrate holder, 15 a manipulator for parallel translation and rotation of the sample substrate, and 16 a material supply source (for molecular beam epitaxy) that supplies a thin film material onto the sample substrate. 17 and 18 are liquid nitrogen shrouds for condensing and adsorbing gas molecules floating in the thin film growth chamber 7 and performing a vacuum evacuation action.

Next, to explain the operation of this device, the sample exchange chamber 1, sample preparation/analysis chamber 6, and thin film growth chamber 7 are all made airtight, and after the sample is put into the sample exchange chamber 1, the gate valves 9 and 11 are closed. The rotary pump 5 is driven with the gate valves 8 and 10 closed, the vacuum valve 2 opened, and the leak valve 4 closed. Then, when the vacuum evacuation space including the sample exchange chamber 1 reaches a pressure of 0.1 Torr or less, the high vacuum pump 3 is activated. When the pressure in the vacuum evacuation space has further decreased (generally
10 ^-4 Torr or less), open gate valves 9 and 11,
The gate valve 8 is closed and the clean ultra-high vacuum pumps 12 and 13 are operated.

When the pressure in the sample preparation/analysis chamber 6 and thin film growth chamber 7 is sufficiently reduced to the desired target pressure, the gate valve 10 is closed and the gate valve 8 is opened, and the sample in the sample exchange chamber 1 is transferred to the transfer device ( (not shown) into the sample preparation/analysis room 6. Next, close the gate valve 8 and open the gate valve 10,
The sample is placed in the sample substrate holder 14 in the thin film growth chamber 7.
At the same time, the gate valve 10 is closed. Meanwhile, the ultra-high vacuum pumps 12 and 13 continue to operate.

When the pressure in the thin film growth chamber 7 drops to the target value,
A semiconductor material is blown onto a sample substrate from a material supply source (molecular beam source) 16 to form a thin film.

On the other hand, non-gun materials generated during material supply in the thin film growth chamber 7 are condensed and adsorbed onto the liquid nitrogen shrouds 17 and 18, thereby preventing defects from occurring in the thin film sample. After a thin film is formed on the sample substrate in the thin film growth chamber 7, the sample is checked in the sample preparation/analysis chamber 6 to see if the desired one has been obtained, and then transported outside via the sample exchange chamber 1.

The vacuum evacuation device of such a conventional semiconductor thin film production apparatus has the following drawbacks.

That is, the liquid nitrogen that is the cooling source for the liquid nitrogen shrouds 17 and 18 has conventionally been supplied from a liquid nitrogen container installed outside, and the evaporated gas is discharged into the atmosphere, so-called disposable. Therefore,
The drawbacks were that the cost of liquid nitrogen was high and that periodic replenishment of liquid nitrogen was troublesome.

Furthermore, it is uneconomical to separately install ultra-high vacuum pumps 12 and 13 in the thin film growth chamber 7 and the sample preparation/analysis chamber 6.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the conventional vacuum evacuation apparatus for semiconductor thin film production apparatuses as described above, and to provide an economical and trouble-free evacuation apparatus.

[Summary of the invention]

A feature of the present invention is that a shroud cooled by a helium refrigerator is used instead of a liquid nitrogen shroud, and ultra-high vacuum pumps in the thin film growth chamber and sample preparation/analysis room are also cooled by the helium refrigerator. Using a cryopump, multiple helium refrigerators are connected to one helium compressor for operation.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Components that are the same as in FIG. 1 are designated by the same reference numerals. First, looking at the configuration, 21 and 22 are cryopumps to which two-stage helium refrigerators 28 and 29 are applied, and 24a and 24b are shrouds cooled by a single-stage helium refrigerator 23, respectively, which are the material supply sources. (Molecular beam source) 16 is arranged so as to surround the sample substrate holder 14. 25a, 2
5b, 25c are gas supply pipes for supplying high pressure helium gas from the helium compressor 27 to the helium refrigerators 28, 29, 23; 26a, 26b, 26;
C is a gas return pipe for circulating low-pressure helium gas from the helium refrigerators 28, 29, and 23 to the helium compressor 27.

Next, to explain the operation of this device, until the high vacuum pump 3 is activated and the vacuum evacuation spaces such as the sample exchange chamber 1, sample preparation/analysis chamber 6, and thin film growth chamber 7 are brought to about 10 ^-4 Torr, Follow the same procedure as before. After that, the gate valve 8 is closed, the gate valves 9 and 11 are opened, and the helium compressor 2
7. Start operating the helium refrigerators 23, 28, and 29.

As the temperature of the helium refrigerators 23, 28, 29 decreases, the cryopumps 21, 22 begin to function as ultra-high vacuum pumps. Furthermore, the shrouds 24a and 24b are also cooled and begin to function as a vacuum pump.

Meanwhile, the high vacuum pump 3 is kept operating during this time, and when the pressure in the sample exchange chamber 1 becomes low enough (for example, down to about 10 ^-8 Torr), the gate valves 8 and 10 are opened and the sample is removed. The sample is transferred from the sample exchange chamber 1 to the sample substrate holder 14 in the thin film growth chamber 7 via the sample preparation/analysis chamber 6 by a transport device (not shown).

Next, the gate valves 8 and 10 are closed, and when the pressure in the thin film growth chamber 7 has decreased to the initial target, the semiconductor material is blown onto the sample substrate from the material supply source (molecular beam source) 16 to form a thin film. and,
Floating substances such as impurities generated when the material is blown away in the thin film growth chamber 7 are condensed and adsorbed on the shrouds 24a and 24b cooled by the helium refrigerator 23, and these floating impurities mix into the thin film sample and cause defects. It acts to prevent this from happening.

Among the helium refrigerators used in this embodiment, the helium refrigerators 28 and 29 used in the cryopumps 21 and 22 are of a two-stage type because they obtain a low temperature sufficient to function as an ultra-high vacuum pump. This is because it is necessary, and the low temperature end of the second stage in the current product is around 15K.

Here, an overview of the current Kryon pump will be explained with reference to Fig. 3.The first stage panel 34 attached to the low temperature end of the first stage cylinder 31 has a temperature of about 50 to 70K, and is mainly used for moisture and carbon dioxide gas in the air. The second stage panel 36 attached to the low temperature end of the second stage cylinder 32 condenses and adsorbs gases with a high boiling point, and the temperature reaches approximately 15K, and condenses and adsorbs low boiling point gases such as oxygen, nitrogen, and argon. Further, hydrogen, helium gas, etc. having a low boiling point are adsorbed by an adsorbent 37 (for example, activated carbon, molecular sieve, etc.) attached to the inner surface of the second stage panel 36.

In particular, since the performance of the ultra-high vacuum pump is determined by how low the temperature of the second stage panel 36 can be made, at least a two-stage helium refrigerator is required.

The Chevron 35 has a function of preventing the low boiling point gas adsorption ability of the second stage panel 36 from being reduced due to direct condensation and adsorption of a high boiling point gas on the low temperature second stage panel 36.

On the other hand, the helium refrigerator 23 used for cooling the shrouds 24a and 24b is of a single-stage type because its main role in the shrouds 24a and 24b is to condense and adsorb the gas of the semiconductor material, which has a relatively high boiling point. Therefore, there is no need to make the temperature very low, and therefore a one-stage type is sufficient.

According to this embodiment, the shrouds 24a, 24b
can be cooled by the single-stage helium refrigerator 23, so there is no need for liquid nitrogen, which has the effect of reducing running costs and eliminating the hassle of replenishing liquid nitrogen.

Furthermore, cryopumps 28 and 29 are used as ultra-high vacuum pumps for the thin film growth chamber 7 and the sample preparation/analysis chamber 6.
By using a single helium compressor 27, helium gas can be supplied to the two-stage helium refrigerators 21 and 22 of the cryopump and the single-stage helium refrigerator 23 for the shroud, so it can be used as a vacuum evacuation device. Another advantage is that the configuration is simple and economical.

FIG. 4 is a diagram showing another embodiment of the present invention,
The amount of gas helium supplied to a plurality of helium refrigerators connected to the helium compressor 27 can be controlled according to the requirements of each helium refrigerator.

That is, the gas supply pipes 25a, 25b, 25c to the helium refrigerators 28, 29, 23 are equipped with gas flow rate adjustment valves 41a, 41b, 41c, and when it is desired to lower the pressure in the sample preparation/analysis chamber 6, the adjustment valve 4 is provided.
Open 1a, adjust 41b and 41c,
Further, when it is desired to lower the pressure in the thin film growth chamber 7, the regulating valve 41b is opened and the valves 41a and 41c are slightly throttled. Further, when it is desired to improve the functions of the shrouds 24a and 24b, the regulating valve 41c is opened to slightly throttle the shrouds 41a and 41b.

According to this embodiment, when supplying gas to multiple helium refrigerators, the amount of gas supplied to each helium refrigerator can be adjusted as necessary, so the helium compressor has a relatively small capacity. This has the effect of making it more economical.

As a modification of this embodiment, supply pipes 25a, 25
Gas return pipe 2 instead of providing adjustment valves in b and 25c
A similar effect can be obtained by providing regulating valves 6a, 26b, and 26c. In addition, helium refrigerator 28,2
The rotational speed of a motor (not shown) controlling the reciprocating frequencies of 9 and 23 may be controlled.

FIG. 5 shows still another embodiment of the present invention, in which instead of cooling the shrouds 24a, 24b and the helium refrigerator 23 by directly thermally connecting them, the shrouds 24a, 24b are cooled with liquid nitrogen, and the evaporated nitrogen gas is cooled. is reliquefied using a helium refrigerator 23.

In this case, the evaporated nitrogen gas is guided into the upper gas storage chamber 42 and cooled by bringing the low temperature end of the helium refrigerator 23 into thermal contact with the storage chamber 42, where it is liquefied and the shroud 24a, 24b
Since the shroud is circulated, the temperature of the shroud can be maintained almost uniformly even if the shroud becomes large, and there is no need to be restricted by the position relative to the helium refrigerator 23. Of course, in this case, the nitrogen gas for shroud cooling is reliquefied in the helium refrigerator, so running costs do not increase.

〔Effect of the invention〕

According to the present invention, since the shroud can be cooled by a helium refrigerator, running costs can be reduced and work is simplified, and multiple helium refrigerators for cooling the cryopump and shroud can be combined into one. Since it can be operated in conjunction with a single helium compressor, it has the effect of being economical.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing the configuration of a conventional semiconductor thin film production device, Fig. 2 is a system diagram of a semiconductor thin film production device having a vacuum evacuation device of the present invention, and Fig. 3 shows the general structure of a cryopump. 4 is a system diagram of a semiconductor thin film production apparatus according to another embodiment of the present invention, and FIG. 5 is a system diagram of a semiconductor thin film production apparatus according to still another embodiment of the present invention. 1...Sample exchange room, 2...Vacuum valve, 3...
High vacuum pump, 4...Leak valve, 5...Rotary pump, 6...Sample preparation/analysis room, 7...
Thin film growth chamber, 8, 9, 10, 11... gate valve, 14... sample substrate holder, 15... manipulator, 16... material supply source, 21, 22...
Cryopump, 23... Single-stage helium refrigerator, 24a, 24b... Shroud, 27... Helium compressor, 28, 29... Helium refrigerator.

Claims (1)

[Claims] 1. Consisting of a plurality of vacuum chambers and a gate valve connecting them, at least one of the vacuum chambers has a material supply source for producing a semiconductor thin film on a substrate, and a source for holding and moving a sample substrate. In a semiconductor thin film production apparatus that is equipped with a manipulator for performing the process and a shroud for condensing and adsorbing the floating gas of the semiconductor material, a cryopump with a helium refrigerator is provided for evacuating at least one vacuum chamber, and a cryopump with a helium refrigerator is provided for cooling the shroud. A vacuum evacuation device characterized in that a helium refrigerator is provided as a helium refrigerator, and the helium refrigerator for cryopump and the helium refrigerator for shroud cooling are connected to one helium compressor. 2. The vacuum evacuation device according to claim 1, characterized in that a pipe connecting the helium compressor and the helium refrigerator is provided with a helium gas flow rate adjusting means. 3. The vacuum evacuation device according to claim 1, wherein each helium refrigerator is provided with reciprocating frequency control means. 4. The vacuum evacuation device according to claim 1, characterized in that an evaporated nitrogen gas storage chamber is provided in a part of the shroud, and a low temperature end of a helium refrigerator is brought into thermal contact with the nitrogen gas storage chamber. . 5. The evacuation device according to claim 1, wherein the cryopump is equipped with a two-stage helium refrigerator, and the shroud is equipped with a single-stage helium refrigerator.