JPH088983B2 - Discharge cleaning device and discharge cleaning method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a discharge cleaning apparatus suitable for removing adsorbed gas from a vacuum container or a component.

[Conventional technology]

For example, as described in Japanese Patent Publication No. 58-33009, does a conventional discharge cleaning apparatus have to be operated by a person, such as starting discharge, controlling current and voltage during discharge, and stopping discharge? Or, as described in Japanese Patent Laid-Open No. 62-160138, there is shown one in which an electric control circuit using a relay automatically controls discharge, but since there is no interlock function, it is always The workers had to monitor and prepare for any abnormalities. I have not touched on the control procedure for each power supply.

[Problems to be Solved by the Invention]

Each current and voltage value during discharge cleaning changes momentarily due to changes in the surface condition of the object to be cleaned. Until now, this has been done while making fine adjustments based on the know-how of the operator, and the control method for automation has been a problem.

Furthermore, since the interlock function is not taken into consideration and it lacks safety, it is inefficient because a supervisor is required at all times during discharge for several hours.

In addition, depending on the shape of the object to be cleaned, there is a portion where the discharge does not spread, and it is not possible to perform sufficient cleaning (removal of adsorbed gas).

An object of the present invention is to automate the electric discharge cleaning process,
An object of the present invention is to provide an electric discharge cleaning device having excellent safety.

[Means for solving the problem]

In order to achieve the above object, a cathode and an anode provided so as to cover the cathode, a vacuum container that houses the cathode and the anode, a cathode heating power source that heats the cathode, and a voltage is applied to the anode. In an electric discharge cleaning apparatus comprising an anode power source for controlling the cathode heating power source and a current voltage of the anode power source, the control device sequentially increases the voltage after energizing the cathode, and the voltage of the cathode becomes a predetermined voltage. When the cathode voltage reaches a constant value, constant voltage control is performed so that when the cathode voltage shifts to constant voltage control, there is control means for energizing the anode to keep it above a predetermined voltage. It is provided with an interlock device for substantially stopping the discharge when it occurs. Further, in order to achieve the above object, an electric discharge cleaning method of performing electric discharge cleaning of an object to be cleaned is a step of vacuuming the inside of the object to be cleaned,
When the pressure inside the article to be cleaned reaches a predetermined pressure or less, a step of energizing the cathode heating power source for heating the cathode housed inside the article to be gradually increased and a voltage of the cathode heating power source is set to a predetermined level. When the voltage reaches a predetermined value, the voltage is controlled to be constant, and when the cathode heating power source reaches a predetermined value, the anode housed in the object to be cleaned is energized to gradually increase the voltage, When the voltage reaches a predetermined value, the anode voltage is controlled to be constant.

[Action]

Since the cathode voltage is applied before the anode, discharge control is facilitated. Then, after gradually raising the cathode voltage,
Since the constant voltage control is performed with respect to the cathode voltage, it is possible to prevent an excessive rise in the temperature of the filament forming the cathode, which rises according to the applied voltage, and to suppress evaporation of the filament as much as possible. Further, since the anode voltage is set to a predetermined value or higher and the filament temperature, that is, the cathode voltage is maintained to a predetermined value, the discharge occurrence rate can be brought close to 100%.
As a result, it is possible to stably generate electric discharge and to effectively perform electric discharge cleaning. Since the discharge cleaning device is provided with a control device for controlling the above-mentioned anode voltage and cathode voltage, the most suitable control is performed by grasping the characteristics of discharge and the relationship between the discharge condition and the cleaning effect, and automatic operation is performed. As a result, the desired discharge is reliably generated, and discharge cleaning that achieves a high cleaning effect is realized.

Therefore, the worker does not need to have a high level of knowledge or experience.

Furthermore, since it has an interlock function, it is safe, and there is no need for the operator to constantly monitor it, and work can be performed efficiently.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The vacuum container 8 for electric discharge cleaning is evacuated from the exhaust port 9 by a vacuum pump, and the pressure is measured by the vacuum gauge 7. The electrode for discharging comprises a cathode 1 and an anode 2. The cathode 1 is connected to the cathode heating power source 3 and is heated thereby. Anode 2
Is connected to the anode power supply 4 through the resistor 5 and the voltage is applied thereby. The cathode heating power source 3 and the anode power source 4
Is controlled by the control device 6, and discharge cleaning is automatically performed.

FIG. 2 shows the appearance of the discharge cleaning device. Control device 6
, Resistor unit 14, cathode heating power supply 3, anode power supply 4, controller 12 of vacuum gauge 7, rack 11 with caster 13
Is stored in. The control device 6 has a sequencer for controlling the output of each power supply. On the front panel,
Discharge time / anode current / cathode voltage setting device, discharge elapsed time / anode current / anode voltage / emitter current flowing between anode-cathode and cathode heating current indicator, error indicating the type of abnormality Code, buzzer for end of discharge and buzzer for error occurrence, their reset switch,
There are switches for switching between automatic operation and manual operation, a discharge start switch, a discharge stop switch, and an emergency stop switch.
The cathode heating power source 3 is a DC constant voltage power source, the anode power source 4 is a DC constant voltage constant current power source, and the resistor 14 is a variable resistor.

FIG. 3 shows a block diagram of the discharge cleaning device. AC200V of the power source of this device is received by the distribution board unit, and then, as a voltage corresponding to each device, the control device, the anode power source,
Supply to resistor unit, cathode heating power supply, vacuum gauge, and each fan. The anode power supply and the cathode heating power supply operate under the control of the control device, and apply voltage and current to the electrodes through the control device. In addition, as signals related to the interlock, pressure abnormal signal from vacuum gauge, rotation abnormal signal from fan, temperature abnormal signal from resistor unit, temperature abnormal and door abnormal signal from rack, anode power supply and cathode heating power supply. The overvoltage detection signal and the temperature abnormality signal are sent to the control device. As shown in Fig. 4, the control device turns off the power of the distribution board or sets the output of each power supply to zero, lights the error LED, and sounds the buzzer according to each abnormality (error). To take.

Next, the procedure of the electric discharge cleaning process will be described. First, as an initial operation, the output voltage value V _{F0 in} the steady state of the cathode heating power source,
The output current value I _{A0 in} the steady state of the anode power source, the discharge time t _D0 ,
Set the cathode heating time t _F0 . If the objects to be cleaned are the same, they are set first and little operation is required thereafter. After the initial operation, the actual discharge cleaning process is started. A discharge gas (here, argon gas is used) is introduced into the container to be cleaned up to about 10 ^-3 Torr. After that, when the discharge start switch in the control device 6 is turned on, discharge cleaning is automatically performed by the discharge cleaning device according to the flow shown in FIG. 5, and the operator does not need to operate until the buzzer at the end of processing sounds. . FIG. 6 shows the output status of each power supply during discharge cleaning. The operation of the apparatus will be described with reference to the flow of FIG. 5 and FIG. First, high voltage is being applied to the lamp 10
Is turned on, the voltage V _F of the cathode heating power source is increased 31 at 2 V / sec 31, and when the set cathode heating power source V _F0 is reached, constant voltage operation 32 is performed. After this, the voltage of the anode power supply V _A
Is increased to 33 at 30V / sec. Then, the discharge starts and the anode current starts flowing. The constant current operation 34 is performed when the anode current I _A reaches the set value I _A0 . In this state, the discharge cleaning process is in progress, and the walls of the vacuum container are cleaned by the ions generated by the discharge generated between the anode 2 and the vacuum container 8, and the water (H ₂ O ) Is removed. When the set cathode heating time t _D0 has elapsed, set the cathode heating power supply voltage V _f to 2
Reduce to 0V in V / sec (35). Further set discharge time t
_{When D0} has elapsed, set the anode power supply voltage V _A to 0 V (36)
The discharge is terminated, the high voltage application lamp 10 is extinguished, the buzzer for terminating the discharge cleaning process is sounded, and a series of operations is terminated. When the worker turns off the buzzer sound by resetting the buzzer and stops the introduction of the discharge gas, all the operations related to the discharge cleaning process are completed.

In the case of heating the part that does not go around the discharge, the heating is started before or at the same time as the discharge cleaning is started, and the heating is also ended at the end of the discharge cleaning.

Although the example of performing discharge cleaning with one electrode has been described above, the present invention is not limited to this. Further, when the cable between the control device and the electrode has a structure such as a socket that can be attached and detached at the electrode portion, it is possible to provide an interlock to which a voltage cannot be applied when the socket and the electrode are not connected.

In automating discharge cleaning, it is necessary to understand discharge parameters that are effective for cleaning, and to know discharge procedures and discharge conditions for reliably generating and maintaining stable discharge.

First, let us look at the discharge procedure. When the anode voltage is increased without heating the hot cathode, as shown in Fig. 7 F ₀ , the discharge current suddenly increases when the voltage reaches a certain voltage V _B (discharge start voltage).
I _B begins to flow. Once the discharge occurs, it is maintained at a current lower than I _B even at a voltage lower than V _B. Therefore, the discharge current I ₀ required for discharge cleaning is the discharge start current I _B
If smaller, it requires a power supply capable of outputting a high voltage only to generate a discharge. On the contrary, when the hot cathode is first heated and then the anode voltage is increased,
As shown in FIG. F _W , it was found that the discharge current gradually flows as the anode voltage rises. Therefore, in the present invention, after the latter hot cathode is heated, the anode voltage is raised to gradually raise the anode voltage so that the necessary discharge current I ₀ flows. This makes it easy to control, and the output voltage of the anode power supply may be a voltage required to maintain the discharge, and the power supply capacity is free from waste.

Next, FIG. 8 shows the relationship between the amount of electrons emitted from the hot cathode and the discharge occurrence rate obtained by the experiments of the present inventors. Here, the discharge occurrence rate means the probability of occurrence of discharge current, which is represented by F _W in FIG. 7 and increases as the anode voltage increases.
If the amount of electrons is small, as in the case of not heating the hot cathode as in Fig. 7 F ₀ , the discharge type will start to flow suddenly when the voltage is raised to a high voltage. Discharge between the anode and the cleaning container, and no discharge occurs between the anode and the cleaning container. From this, it can be seen that there is an appropriate electron amount range. Here, as shown in FIG. 9, in the region B where the anode voltage is high, the amount of emitted electrons is equal to the temperatures T ₁ , T ₂ , T ₃ (T ₁ <T ₂ <T ₃ ) of the hot cathode. Depends on
It does not depend on the anode voltage. The temperature of the hot cathode depends on the heating voltage or the heating current when the shapes of the hot cathode are the same. Therefore, in this embodiment, the hot cathode heating voltage or hot cathode heating current was set to 10% when the discharge occurrence rate shown in FIG.
Set the condition to be 0%.

The hot cathode material itself may come out in a vacuum atmosphere due to evaporation or sputtering, but if you want to reduce this as much as possible, heat the hot cathode only at the start of discharge to supply thermionic electrons, and after the discharge has occurred. Sets the operating time of the cathode heating power supply and the operating time of the anode power supply separately so that the heating can be stopped.

During discharge, the shape of the hot cathode, for example, a wire-shaped hot cathode may change due to evaporation or sputtering by ions. Fig. 11 shows changes in the amount of electrons when the cathode heating power source was controlled by using a wire-shaped hot cathode and only considering the thinning of the wire due to evaporation of the hot cathode. C _I is
This is a change in the amount of emitted electrons when the hot cathode is heated at a constant current. Since the current is constant, the temperature of the hot cathode rises as the diameter becomes smaller, and the evaporation amount of the hot cathode gradually increases, causing a sharp increase in the electron amount. On the other hand, the case of heating by applying a constant voltage is C _V in FIG. When the voltage is constant, the temperature decreases as the diameter decreases, and the evaporation amount of the wire decreases and the electron amount decreases. Then, although a large decrease in the amount of electrons occurs at first, the amount of decrease decreases with time. Therefore, in this embodiment, the hot cathode is heated by constant voltage control. This makes it possible to extend the life of the filament formed in a wire shape and reduce the change in the amount of emitted electrons.

By the way, it was found that the effect of discharge cleaning depends more on the discharge current than the discharge voltage. FIG. 10 shows the relationship between the discharge current and the amount of degassing (corresponding to the cleaning effect) when discharge cleaning is performed for a certain period of time. The amount of gas removed increases as the current value increases. Therefore, in this embodiment, control is performed to keep the discharge current constant. This ensures that the expected cleaning effect can be obtained.

Further, in this embodiment, the computer or the sequencer is made to remember a possible abnormal state, and when the abnormality occurs, the discharge is stopped or interlocked so that the discharge cannot be performed. The type is displayed and a warning is given. Further, as a monitor, it has a function of displaying a hot cathode heating voltage and current, an anode voltage and current, a hot cathode-anode current, or outputting to a recorder or the like. As a result, it is possible to check the discharge state and grasp the situation when an abnormality occurs.

Depending on the shape of the container to be cleaned, there may be a part where the discharge does not go around. Such parts are not cleaned,
The adsorbed gas remains, and even if evacuation is continued, that part becomes a net and the pressure is less likely to drop. In view of this, in this embodiment, a heater is provided in a portion that does not go around the discharge so that this portion can be heated simultaneously with the discharge cleaning. By partially using heating in this way, the conventional exhaust curve E shown in FIG. 12 can be exhausted in a short time like F.

[Effects of the Invention] By using the discharge cleaning apparatus having the sequencer or the computer according to the present invention, it is possible to surely generate a desired discharge and obtain a higher cleaning effect by the automatic operation, and safely. There is an effect that discharge can be performed. As described above, since the electric discharge cleaning process can be easily performed, no experience or skill is required for the operation. In addition, it has an interlock function for possible abnormalities,
It is designed to prevent harm to humans, and it also has a buzzer function to notify of abnormalities.
The need for constant monitoring is eliminated, discharge cleaning can be performed easily, and work efficiency is improved.

Further, since the discharge is generated at a low voltage, the capacity of the anode power source can be reduced, which has the effect of contributing to the downsizing of the device. Furthermore, since the life of the hot cathode is extended, maintenance can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an external view of the discharge cleaning device excluding the electrode part of FIG. 1, FIG. 3 is a block diagram in the discharge cleaning device, and FIG. Interlock function diagram, Fig. 5 is a flow diagram of automatic operation of the electric discharge cleaning device, Fig. 6
FIG. 7 is an output state diagram of each power source of the discharge cleaning apparatus, FIG. 7 is a diagram showing current-voltage characteristics at the start of discharge according to the discharge procedure, and FIG.
The figure shows the relationship between the amount of emitted electrons and the discharge occurrence rate. Figure 9 shows the relationship between the amount of emitted electrons and the anode voltage when the hot cathode temperature is changed.
Figure 10 shows the relationship between the discharge current and the amount of degassing, Figure 11 shows the change in the amount of emitted electrons when the hot cathode is heated at a constant voltage and when it is heated at a constant current, and Figure 12 is the discharge. FIG. 9 is an exhaust characteristic diagram when heating is partially performed with cleaning and when heating is not performed. 1 ... Cathode, 2 ... Anode, 3 ... Cathode heating power source, 4 ...
Anode power supply, 5 ... Resistor, 6 ... Control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Kambara 502 Jinritsucho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hiritsu Seisakusho Co., Ltd. (56) Reference JP-A-62-160138 (JP, A)

Claims (2)

[Claims] 1. A cathode, an anode provided so as to cover the cathode, a vacuum container accommodating the cathode and the anode, a cathode heating power source for heating the cathode, and an anode power source for applying a voltage to the anode. In the discharge cleaning apparatus including the cathode heating power supply and the control device for controlling the current voltage of the anode power supply, the control device sequentially boosts the current after energizing the cathode, and when the voltage of the cathode reaches a predetermined voltage, the cathode Constant voltage control so that the voltage of the constant voltage becomes a constant value, and when the cathode voltage shifts to the constant voltage control, it has a control means for energizing the anode to make it a predetermined voltage or more, and when an abnormality occurs in this discharge device An electric discharge cleaning device comprising an interlock device for substantially stopping the electric discharge. 2. A discharge cleaning method for discharging an object to be cleaned in a vacuum by discharging the interior of the object to be vacuumed, and when the pressure inside the object reaches a predetermined pressure or less,
A step of energizing a cathode heating power source for heating the cathode housed inside the object to be cleaned and gradually increasing its voltage; and a step of controlling the voltage of the cathode heating power source to be constant when the voltage of the cathode heating power source reaches a predetermined value, When the cathode heating power source reaches a predetermined value, the step of energizing the anode housed in the object to be cleaned to gradually increase its voltage; and the step of controlling the anode voltage to a constant value when the anode voltage reaches a predetermined value And a discharge cleaning method.