JPH0466120A - Venting method for vacuum vessel - Google Patents

Abstract

PURPOSE:To make a treatment cycle shorter and improve productivity by adjusting the pressure of gas to a pressure lower than specific pressure when the pressure in a vacuum vessel is low and the flow of gas from a vent pipe into the vessel is non-viscous at the initial stage, and on the other hand adjusting said pressure to a pressure higher than the specific pressure at the latter stage. CONSTITUTION:When gas is introduced via a vent pipe 4 and a vent valve 5 into a vacuum vessel 1 and when the pressure in the vessel 1 is low and the flow of the gas into the vessel is non-viscous, that is, at the initial stage of venting, the pressure of gas on the side of a gas source for the valve 5 is adjusted to a pressure lower than 760Torr, whereas, at the latter stage, that is, when the flow of gas becomes viscous, said pressure is adjusted to a pressure higher than 760Torr. In this manner, degradation of surface quality of articles to be treated due to attachment of dusts can be avoided and cycle of vacuum treatment is made shorter, resulting in improved productivity.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for venting a vacuum container, and more particularly, to a method for venting a vacuum container, and more specifically, for a method for venting a vacuum container. After loading the object to be processed into a vacuum container, evacuating the inside of the vacuum container, and processing the object, before unloading the object, gas is introduced into the vacuum container to increase the pressure inside the vacuum container. This invention relates to a method for venting a vacuum container to restore atmospheric pressure.

(Prior art) When performing vacuum processing using a batch-type vacuum processing apparatus, as shown in the vacuum processing cycle in Figure 2, the object to be processed is charged (
Loading), evacuate the vacuum container and perform vacuum processing such as vacuum evaporation, and then take out the processed object (unloading). Before unloading, gas is introduced into the vacuum container. It is necessary to vent the vacuum container to restore the pressure to atmospheric pressure.

Conventionally, venting of the vacuum container is performed by opening a vent valve connected to the vacuum container and introducing atmospheric air or dry N2 (nitrogen) gas at a constant pressure into the vacuum container.

For example, as shown in the vacuum processing apparatus in Figure 3, a vacuum container (
1) by a vent pipe (4) at one end and a vent valve (5) connected at the other end to a pipe that is open to the atmosphere, by opening the vent valve (5) and introducing the atmosphere into the vacuum container (1). , the vacuum container is vented. In addition, in Figure 3,
(2) shows an exhaust port valve, and (3) shows a vacuum exhaust system.

That is, the object to be treated is loaded into the container (1) through the opening (not shown) of the vacuum container (1), the vent valve (5) is closed, the exhaust port valve (2) is opened, and the vacuum exhaust system ( 3), and perform the operation of vacuum evacuation → vacuum treatment. When the process is completed, the exhaust port valve (2) is closed and the vent valve (5) is opened to introduce atmospheric air and perform venting. After venting, the object to be processed is asyloded to complete the vacuum processing cycle.

The pressure inside the container (1) during the above treatment is usually 10-'
~1O-7 Torr, and the pressure difference at the initial stage of venting when atmospheric air is introduced is about 760 Torr. The inner diameter of the vent pipe (4) is generally about φ5 to φ10 mm.

(Invention or Problem to be Solved) When gas is ejected through a conduit into a space whose pressure is lower than that of the gas, if the pressure of the space is high, the flow within the conduit is a Poisieux flow, and the gas molecules are heated. In addition to exercise, we also perform collective movements as a whole, creating a flow. The flow either continues as it is after being released into a space wider than the outlet of the conduit, or it gradually attenuates due to the viscous force acting between it and the surrounding stationary gas, and the directional distribution of gas molecules changes in front. The flow spreads laterally (viscous flow), so the flow does not reach far.

On the other hand, when gas is ejected through a conduit into a space where the pressure is extremely low, as in the initial stage of venting when gas is introduced into a vacuum, the molecular conditions for the gas within the conduit are established, and the gas molecules Each becomes a free molecule, and the attenuation after being ejected into space is small, so compared to the viscous flow mentioned above, the directional distribution of gas molecules becomes a flow that is sharply constricted forward (inviscid flow), and therefore the flow extends over a long distance. reach. This distance increases as the difference between the pressure of the gas and the pressure of the space increases. Note that the gas flow state is divided into three types: viscous flow, intermediate region flow, and single molecule flow. The inviscid flow refers to an intermediate region flow and/or a molecular flow among the above three types, that is, a flow other than a viscous flow (hereinafter referred to as an inviscid flow).

In the conventional method for venting a vacuum container, the vent valve is opened to directly introduce atmospheric air or nitrogen gas at a constant pressure, so that the gas introduced into the vacuum container ( The difference ΔP between the pressure P (atmospheric pressure, nitrogen gas, etc.) (atmospheric pressure, nitrogen gas pressure, etc.) and the pressure P2 inside the vacuum container is as large as 760 Toor or more. Therefore, the gas flow from the vent pipe into the vacuum container reaches a long distance, and this reaching distance becomes large. Therefore, the flow of gas blows up dust and foreign matter that is generated during the processing process and accumulates on the bottom and walls of the container, and these adhere to the surface of the object to be processed and have a negative impact on the processing surface. There is a problem.

In the late stage of venting, when air or nitrogen gas is introduced into the vacuum vessel, the pressure inside the vacuum vessel rises, and the gas flow from the vent pipe into the vacuum vessel becomes a viscous flow. Soaring will no longer occur. However, as the pressure P inside the vacuum container approaches atmospheric pressure, the pressure difference ΔP
becomes small and the amount of gas flowing in gradually decreases, which poses a problem in that it takes a long time to restore the pressure P2 inside the container to atmospheric pressure. This leads to the problem that the processing cycle takes a long time and productivity decreases.

The present invention has been made in view of these circumstances, and its purpose is to solve the above-mentioned problems of the conventional ones, and to eliminate dust and foreign matter on the bottom and walls of the vacuum vessel during the initial stage of venting. It is an object of the present invention to provide a method for venting a vacuum container, which can reduce the degree of soaring and shorten the time required for the inside of the vacuum container to return to atmospheric pressure in the latter stage of venting.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for venting a vacuum container having the following configuration.

That is, the method for venting a vacuum container according to the present invention involves loading a processing object into a vacuum container, evacuating the inside of the vacuum container, processing the processing object, and then venting the vacuum container before unloading the processing object. In a method for venting a vacuum container, in which the pressure in the vacuum container is restored to atmospheric pressure by introducing gas into the vacuum container from a gas supply source connected via a pipe and a vent valve, the gas supply source side of the vent valve is The gas pressure is adjusted to be lower than 760 Torr at the beginning of venting, when the pressure inside the vacuum vessel is small and the gas flows from the vent pipe into the vacuum vessel or becomes an inviscid flow. This venting method for a vacuum container is characterized in that in the latter stage of venting when the flow becomes a viscous flow, gas is introduced into the vacuum container by adjusting the pressure to 760 Torr or higher.

(Function) As explained above, the method for venting a vacuum container according to the present invention is to At the beginning of venting, when the pressure inside the container is low and the gas flows from the vent pipe into the vacuum container or becomes an inviscid flow, the gas pressure on the gas supply source side of the vent valve is set to 760°C.
Since it is adjusted to be lower than Torr, the pressure P1 of the gas introduced into the vacuum container and the pressure P inside the vacuum container are
The difference ΔP from 2 is lower than 760Toor. Therefore, the distance that gas flows from the vent pipe into the vacuum container can be reduced. In other words, even if gas flows into a wide vacuum vessel through a small pipe diameter of a vent valve, the state will be similar to that of normal viscous flow, and the directional distribution of gas molecules will be close to circular, causing the gas flow to The pressure P2 inside the vacuum container can be increased without strongly blowing to the bottom of the vacuum container. Therefore, it is possible to reduce the extent to which dust, foreign matter, etc., fly up from the bottom or wall of the vacuum container at the initial stage of venting. Note that the degree of this decrease becomes smaller as the pressure difference ΔP is made smaller (
It is possible.

When the pressure inside the vacuum container rises a little, for example to about 1 Torr, the gas flow from the vent pipe into the vacuum container becomes a viscous flow, so dust and foreign matter at the bottom of the vacuum container no longer fly up. . In the latter stage of venting, when such a viscous flow occurs, the gas pressure on the gas supply source side of the vent valve is adjusted to 760 TOrr or more to introduce gas into the vacuum container, so that in the case of the conventional method described above, Compared to this, the difference ΔP between the pressure PI of the gas introduced into the vacuum container and the pressure P inside the vacuum container can be increased, and therefore the amount of gas flowing in can be significantly increased. Therefore, the time required for the inside of the vacuum container to return to atmospheric pressure in the latter stage of venting can be shortened without causing dust or foreign matter on the bottom or wall of the vacuum container to fly up. As a result, the time required for the processing cycle can be shortened and productivity can be improved.

(Example) An example of the present invention will be described below based on the vacuum processing apparatus shown in FIG.

A vacuum exhaust system (3) is attached to the vacuum container (1) via an exhaust valve (2), and a vent valve (5) is attached to the wall of the vacuum container (1) via a vent pipe (4). . Two vacuum valves (6) and (9) are connected to the next side of the vent valve (5) via a T-joint, and the next side of the vacuum valve (6) is connected via a pressure control valve (7). Gas supply source (8) such as compressed air or nitrogen gas (pressure crab 4 to 6 k
gf/an 2G) is connected, and a vacuum exhaust system α0) is connected to the negative side of the vacuum valve (9).

As a pressure measurement gauge, the vacuum container Tl) has a pressure measuring gauge of 760~1.
A high pressure measurement gauge αD such as a hot wire vacuum gauge that measures pressure at 0-'Torr, and a pressure at or below 10-'Torr (
Low pressure measurement gauge α such as an ionization vacuum gauge that measures the degree of vacuum)
2, and a high pressure measuring gauge α3 such as a Bourdon tube that measures pressures of 760 Torr or more and a hot wire vacuum that measures pressures of 760-10” Torr are connected to the T-joint on the downstream side of the vent valve (5). The four pressure measuring gauges are each converted to an electrical output signal, and the signals are combined two by two and added to the three subtractors α5αθα, and the outputs are sent to the three comparators. 08
Q9) In addition to ■, compare with each set value, and apply the output to the controller (22) via the switch (21), and use the output to adjust the spring pressure of the pressure regulating valve (7).

The operation of the above-mentioned components will be described with reference to the evacuation→processing→venting process shown in FIG. In the evacuation process, the vent valve (5) is closed, the exhaust port valve (2) is opened, the evacuation system (3) is activated, and the vacuum container (1) is activated.
1 is evacuated to a high vacuum (e.g., below 10-' to 10-'' Torr). At the same time, the vacuum valve (6)
Close the vacuum valve (9) and open the vent valve (5).
The T-joint on the next side is evacuated to a low vacuum (for example, I Torr) using a vacuum evacuation system α0). When the inside of the vacuum container (1) reaches a predetermined vacuum, a process such as vapor deposition is performed on the surface of the processing object loaded in advance into the vacuum container (1). When the process is completed, the process moves to the step of venting the inside of the vacuum container (1) to atmospheric pressure.

In the venting process, first, the exhaust port valve (2) and the vacuum valve (9) are closed, the vent valve (5) and the vacuum valve (6) are opened, and the pressure control valve (7) is used to close the vent valve (5). With the next side pressure PI adjusted to about 100 Torr, gas from the gas supply source (8) is introduced into the vacuum container (1). As mentioned above, since the T-joint on the next side of the vent valve (5) is evacuated to a low vacuum using the vacuum exhaust system α0), there will be a transient period until the pressure l1m valve (7) operates normally. It is possible to reliably prevent high-pressure gas from flowing into the vacuum container full.

Due to the introduction of the gas, the pressure P2 inside the vacuum container (1) increases. During the initial stage of venting when the gas flow from the vent pipe into the vacuum container is an inviscid flow, that is, until the pressure inside the vacuum container (11 reaches the pressure pt), the pressure P
The gas is continued to be introduced with the pressure adjusted to about 100 Torr. Further, in the above-mentioned pressure adjustment state, the introduction of gas is continued until the pressure inside the vacuum container (1) reaches a pressure Pv slightly higher than Pt. Note that between the pressures Pt and Pv, the gas flows from the vent pipe into the vacuum container, or is a viscous flow.

Here, a viscous flow occurs when the ratio of the mean free path l of the gas in the pipe to the diameter d of the pipe is less than a certain value. When this ratio is above a certain value, the flow is not attenuated by viscous force and becomes a free molecular flow (inviscid flow). In the device of the example, the diameter d of the pipe (4) of the vent valve (5) is 5 to 1 OI.
lun and the differential pressure ΔP is about 100 Torr, so the pressure pt at which the inviscid flow changes from viscous flow is 0. I To
It will be about rr. Therefore, the pressure P: 10
Adjusting to 0 Torr is equivalent to controlling the differential pressure ΔP to about 100 Torr.

The pressure measurement at the initial stage of venting is P 2 <10-'T
When orr, use pressure measuring gauge αz (14, PV
>P2 When >1O-3Torr, pressure measuring gauge αD
α4 is used.

When P, <1o-2 Torr, the differential pressure ΔPL is obtained by using the subtractor αη from the output signals P Ll and PLII of the pressure measuring gauge αZ (14), and the target 100 of the differential pressure ΔP is calculated.
The command value ΔPLC corresponding to Torr is compared with the comparator (A), and the deviation eL is sent to the controller (2I) via the switch (2I).
22) as an input signal to set the differential pressure ΔP to the target 10
The opening degree of the pressure regulator (7) is controlled to control the pressure to 0 Torr.

Even when Pv > P2 >10-'Torr, the differential pressure ΔPIl is obtained by using the subtractor αe from the output signal P Ll of the pressure measuring gauge aυα4 and the output of P□2, and the differential pressure ΔP is set to the target 1.
The opening degree of the pressure regulator (7) is controlled to 00 Torr.

(Introduction of gas until CP' becomes Pv)
The latter stage corresponds to the latter stage of venting, and since both the vacuum container (1) and the vent pipe (4) are in a gas flow or sufficiently viscous flow state, until the pressure P in the vacuum container (11) reaches atmospheric pressure. Even if the differential pressure ΔP is increased and the gas introduction speed is increased, the directional distribution of gas molecules is not as sharp as the state of molecular flow, and the vacuum vessel (
11 There is no dust from the bottom or walls coming from above.

Therefore, the pressure P1 on the negative side of the vent valve (5) was set to 760
The gas from the gas supply source (8) is introduced into the vacuum container (1) in a state where it is adjusted to be at or above TOrr. At this time, the output signal of the pressure measuring gauge αυα3 is P M! And the differential pressure ΔP is obtained by subtractor α9 from the output of P□2.

was determined, and the opening degree of the pressure regulator (7) was controlled to control the differential pressure ΔP to 500 Torr.

As a result, it was possible to vent the vacuum container without causing dust or foreign matter to clump up on the bottom or wall of the vacuum container, and the venting time could be significantly shortened compared to the conventional method.

(Effects of the Invention) According to the method for venting a vacuum vessel according to the present invention, it is possible to reduce the degree of clumping of dust, foreign matter, etc. on the bottom and wall of the vacuum vessel in the early stage of venting, and to reduce the amount of dust and foreign matter in the vacuum vessel in the late stage of venting. This makes it possible to shorten the time required to restore atmospheric pressure. Therefore, it is possible to prevent deterioration of the surface quality of the object to be processed due to the adhesion of the dust, etc., and it is also possible to shorten the vacuum processing cycle time and improve productivity.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of a vacuum processing apparatus according to an embodiment;
FIG. 2 is a diagram showing a flow of a vacuum processing cycle, and FIG. 3 is a diagram showing an outline of a conventional vacuum processing apparatus. m-1 vacuum container (21- vacuum exhaust port valve (
3) αα - Vacuum exhaust system (4) - Vent pipe (51
--Bent pulp (6) (91-Vacuum valve (
7) - Pressure regulator +81 - Vent gas source αD ~ α4 - Pressure measurement gauge αS ~ αη - Subtractor αε ~ ■ - Comparator (21) - Switcher (22
) - - Controller patent applicant Kobe Steel, Ltd. Agent Akira Kanemaru Patent attorney Fig. 1

Claims (1)

[Claims] (1) After loading the object to be processed into the vacuum container, evacuating the inside of the vacuum container, and processing the object, before unloading the object, connect the pipe to the vacuum container via a vent pipe and a vent valve. In a method for venting a vacuum container in which the pressure inside the vacuum container is restored to atmospheric pressure by introducing gas into the vacuum container from a gas supply source, the gas pressure on the gas supply source side of the vent valve is set to the pressure inside the vacuum container. In the early stages of venting, when the pressure is small and the gas flow from the vent pipe into the vacuum container becomes an inviscid flow, adjust it to a value lower than 760 Torr.
A method for venting a vacuum container, characterized in that the gas is introduced into the vacuum container by adjusting the pressure to 760 Torr or higher in the latter stage of venting, when the flow of gas from the vent pipe into the vacuum container becomes a viscous flow.