JP3989083B2 - Vacuum vessel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum vessel made of a metal material or the like and capable of being evacuated, and more particularly to a vacuum vessel capable of reducing the time required for evacuation.
[0002]
[Prior art]
In FIG. 3A, reference numeral 100 denotes a conventional vacuum vessel. The vacuum vessel 100 is used in a vacuum processing apparatus such as a semiconductor device manufacturing apparatus, and is made of a material that hardly corrodes, such as stainless steel.
[0003]
When vacuum processing such as sputtering or etching is performed using the vacuum vessel 100 in a vacuum processing apparatus, the inside of the vacuum vessel 100 is first evacuated by an exhaust system (not shown), and the inside reaches a desired vacuum state. After that, a semiconductor substrate or the like to be processed is carried into the vacuum vessel 100 while maintaining a vacuum state, and a film forming process or an etching process is started. Therefore, the exhaust time until reaching the vacuum state and the exhaust time for recovering to the vacuum state after the introduction of the process gas have a great influence on the processing capacity, and therefore there is a demand for reducing the exhaust time as much as possible.
[0004]
Generally, since the surface of the inner wall of the vacuum vessel 100 has irregularities 102 as shown in FIG. 3B, the surface area of the inner wall is large and a large amount of gas molecules are adsorbed on the surface. In addition, the adsorbed gas molecules that have entered the recesses of the projections and depressions 102 are difficult to be exhausted during the vacuum exhaust, and there is a problem that the exhaust time until reaching a predetermined vacuum state becomes long.
[0005]
Therefore, as shown in FIG. 3C, a countermeasure is taken in which the surface of the inner wall is subjected to a polishing process such as electrolytic polishing or buffing to be flattened. According to this countermeasure, the recesses on the surface of the inner wall are reduced and gas is easily discharged, and the surface area is reduced, so the amount of gas adsorbed on the inner wall surface is reduced, so the exhaust time to the target pressure is shortened. can do.
[0006]
However, even with such a polishing process, there is a problem that the exhaust time until the vacuum state is reached cannot be sufficiently shortened.
[0007]
[Problems to be solved by the invention]
The present invention was created to solve the problems of the conventional technology, and its purpose is to provide a technology capable of shortening the time required for evacuation as compared with a conventional vacuum vessel. There is to do.
[0008]
[Means for Solving the Problems]
The inventors of the present invention have come up with the presence of moisture when considering the reason why the evacuation time until reaching a predetermined vacuum state cannot be sufficiently shortened even if the vacuum vessel is polished.
[0009]
The release rate of the moisture once adsorbed on the inner wall surface of the container is larger due to the surface material than the surface shape such as irregularities, and the surface of a substance that easily adsorbs moisture such as stainless steel If moisture is adsorbed on the surface, the exhaust time cannot be shortened sufficiently because the surface is flattened by polishing and is difficult to be exhausted during vacuum exhaust.
[0010]
The present invention made on the basis of such knowledge is a vacuum container which can be evacuated as described in claim 1, and has a container body and a coating film made of silicon , and the coating film includes the container body. The vacuum vessel is arranged on the entire surface in contact with the internal vacuum atmosphere.
A second aspect of the present invention is the vacuum container according to the first aspect, wherein the coating has a thickness of 5 μm or less.
[0011]
Semiconductor materials such as silicon and germanium have a low initial deposition probability of water, and these semiconductor materials are naturally oxidized by water and oxygen in the atmosphere to become oxides or hydroxides having a stable surface. The oxides and hydroxides thus formed are inactive and have the property that water is less likely to adsorb than stainless steel, aluminum alloys and the like that are usually used as materials for vacuum vessels.
[0012]
Even when silicon or germanium is used as the coating, they are naturally oxidized to become oxides of silicon or germanium, so that a coating made of these oxides is formed. Since it is difficult for water to be adsorbed on the inner wall of the container covered with the oxide film, the water in the container is likely to be discharged during evacuation, and the evacuation time until the target vacuum state is reached. Can be shortened.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments for quantitatively verifying the effects of the present invention will be described with reference to the drawings.
Reference numeral 10 in FIG. 1 denotes a vacuum container according to an embodiment of the present invention. The vacuum vessel 10 is configured by coating the inner wall of a vessel body 11 made of stainless steel with a coating 12 made of silicon and having a thickness of 0.4 μm. The volume of the vacuum vessel 10 is 2 × 10 ⁻² m ³ and the inner surface area is 0.4 m ² .
[0014]
The coating film 12 of this example was formed on the entire inner wall of the container body 11 by RF magnetron sputtering under the conditions of argon pressure 0.6 Pa, RF power 800 W, and film formation rate 15 nm / min.
[0015]
The inventors of the present invention measured the pressure inside the vacuum vessel 10 while evacuating the vacuum vessel 10. In FIG. 1, reference numeral 30 denotes a measuring apparatus used in this measurement.
The measuring device 30 includes an exhaust system 20, a B-A vacuum gauge 1 and a Pirani vacuum gauge 2. The exhaust system 20 includes an orifice 3, a turbo molecular pump 4, and an oil rotary pump 5 connected in series, and is configured so that vacuum exhaust can be performed while adjusting the exhaust speed with the orifice 3. Here, the orifice 3 having an exhaust conductance of 6 × 10 ⁻² m ³ / sec was used. The exhaust speeds of the turbo molecular pump 4 and the oil rotary pump 5 are 0.3 respectively. m ³ / sec, 0.3 m ³ / min.
[0016]
The B-A vacuum gauge 1 is a kind of ionization vacuum gauge, and measures the pressure in a high to ultrahigh vacuum state. The Pirani gauge 2 measures a relatively high pressure such as near atmospheric pressure.
[0017]
In this embodiment, after the exhaust system 20, the B-A vacuum gauge 1 and the Pirani vacuum gauge 2 are attached to the vacuum container 10, the oil rotary pump 5 is activated to evacuate the vacuum container 10, and the Pirani vacuum gauge 2 The measurement of the internal pressure of the vacuum vessel 10 was started.
[0018]
And after the internal pressure of the vacuum vessel 10 fell and the measured value of the Pirani vacuum gauge 2 reached 10 Pa, the turbo molecular pump 4 was started. After the turbo molecular pump 4 was in a steady operation, the BA vacuum gauge 1 was turned on and the pressure in the vacuum vessel 10 was measured.
[0019]
The measurement result thus made is shown in the curve (A) of FIG. FIG. 3 is a graph showing the change over time of the measured value of the B-A vacuum gauge 1. The horizontal axis indicates the exhaust time, the vertical axis indicates the internal pressure, and the time when the oil rotary pump 5 starts exhausting is 0. It's time.
[0020]
This curve (A) shows that when the exhaust time is 10 hours, the internal pressure has already decreased to 10 ⁻⁷ Pa or less and has reached an ultra-high vacuum state of nearly 10 ⁻⁸ Pa. It is shown.
[0021]
When the measurement of the vacuum container 10 of the present example was completed, it was removed, and the same measurement was performed on a vacuum container that had been subjected to conventional electrolytic polishing for comparison purposes. Here, a vacuum vessel made of stainless steel and having the same volume and inner surface area as the vacuum vessel 10 was used. The measurement result of such a conventional vacuum vessel is shown in the curve (B) of FIG.
[0022]
This curve (B) shows that the internal pressure has not yet decreased below 10 ⁻⁷ Pa when the exhaust time is 10 hours. At this point, the internal pressure has already reached nearly 10 ⁻⁸ Pa in the curve (A), and it can be seen that the pressure drop rate of the container is larger in the vacuum container of this embodiment shown in the curve (A).
[0023]
Further, it can be seen from FIG. 3 that the curve (A) requires about 2 hours until the internal pressure reaches 10 ⁻⁷ Pa, whereas the curve (B) requires 20 hours or more. . Therefore, in the vacuum container 10 of the present Example, it turned out that the time until it reaches the same pressure is shortened to about 1/10 of the conventional vacuum container.
[0024]
By the way, for the purpose of increasing the pressure drop speed of the container, there is a vacuum container in which a TiN film is formed on the inner wall of the container, but the inventors of the present invention measure the same pressure drop speed for such a container. went.
[0025]
Here, the same stainless steel as the vacuum container 10 of the present embodiment was used as the material of the vacuum container, and both the volume and the inner surface area were the same as those of the vacuum container 10. On the inner wall of such a vacuum container, a film thickness of 0.1 Pa under the conditions of an argon pressure of 0.1 Pa, a nitrogen pressure of 0.1 Pa, a bias voltage of −100 V, and a film formation rate of 80 nm / min is applied by a reactive vapor deposition method using a holocathode discharge. A 5 μm TiN film was formed.
[0026]
The measurement result of the pressure drop rate of the vacuum vessel whose inner wall is covered with the TiN film is shown in the curve (C) of FIG. Looking at this curve (C), it can be seen that the exhaust time is slightly shortened compared to the curve (B) which is the measurement result of the conventional container. The fact that the pressure has not yet dropped below 10 ⁻⁷ Pa is the same as curve (B), and does not reach the pressure drop rate of the container of curve (A).
Moreover, it takes about 20 hours for the internal pressure to reach 10 ⁻⁷ Pa, which is considerably different from the 2 hours of curve (A).
[0027]
Thus, it can be seen that the pressure drop rate of the vacuum vessel 10 of the present embodiment is large even when compared with the vacuum vessel having the TiN film formed therein, and the effect of the present invention that the pressure drop rate of the vessel is increased. Proven.
[0028]
In the present embodiment, silicon is used as the material of the coating 12, but the material is not limited to this, and any film of silicon oxide, germanium, or germanium oxide that hardly adsorbs water may be used.
[0029]
Further, although the sputtering method is used to form the film 12, a vacuum vapor deposition method, a chemical vapor deposition method, or the like may be used, for example. Further, although stainless steel is used as the material of the container body 11, a metal material that is not easily corroded, such as an aluminum alloy or a titanium alloy, may be used.
[0030]
Furthermore, although the thickness of the coating 12 is 0.4 μm, it may be 0.005 μm or more as long as the surface can be completely covered. Further, in order to prevent the coating film 12 from being peeled off by stress, it may be 5 μm or less.
[0031]
Further, when a component is provided in the container, a film may be formed on the surface of the component. In this case, for example, a silicon oxide film may be formed on the inner wall of the container main body 11 and a germanium oxide film may be formed on the component.
[0032]
Furthermore, in the present embodiment, the coating 12 covers the entire inner wall of the container body 11, but it does not necessarily have to cover the entire surface, and the coating 12 covers most of the inner wall of the container body 11. For example, the pressure drop rate of the container can be increased as compared with the conventional case.
[0033]
【The invention's effect】
The exhaust time can be shortened as compared with a conventional vacuum vessel.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the configuration of a measuring apparatus for measuring the time required for evacuation of a vacuum container according to an embodiment of the present invention. FIG. 2 shows the evacuation time and the interior of the vacuum container according to the present embodiment and a conventional vacuum container. Graph showing the relationship with pressure [Fig. 3] (a): Cross-sectional view showing the structure of a conventional vacuum vessel
(b): The figure explaining the surface state of the inner wall of the conventional vacuum vessel
(c): Diagram explaining the surface condition of the vacuum vessel with the inner wall being electropolished [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... BA vacuum gauge 2 ... Pirani vacuum gauge 3 ... Orifice 4 ... Turbo molecular pump 5 ... Oil rotary pump 10 ... Vacuum container 11 ... Vessel main body 12 ... Coating 20 ... Exhaust system 30 ... Measurement apparatus

Claims (2)

A vacuum vessel that can be evacuated,
Having a container body and a coating made of silicon ;
The vacuum container, wherein the coating is disposed on the entire surface in contact with the vacuum atmosphere inside the container body. The vacuum container according to claim 1, wherein the coating has a thickness of 5 μm or less.

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