JPH07109560A - Discharge degassing device - Google Patents

Abstract

PURPOSE:To provide the device for desorbing a gas adsorbed in a vacuum vessel by an electric discharge only with the vacuum treating device evacuated to a high vacuum and easy to apply. CONSTITUTION:A vacuum vessel 1 is evacuated by a vacuum pump 2 to a specified pressure, and a specified amt. of a gas supplied from a plasma producing gas feed part 6. When the vessel 1 is controlled to an appropriate pressure to produce plasma, a discharge power source 4 is started to start discharge. The discharge state monitoring signals thereafter are calculated by a process controller 5 to control the discharge and to determine when finishing degassing. Consequently, the discharge state is stably maintained, the time to finish degassing is appropriately determined, and the device is conveniently applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge degassing apparatus for quickly releasing a gas adsorbed in a vacuum container or a part mounted in the container by electric discharge to bring the inside of the container into a high vacuum state in a short time. .

This apparatus is a semiconductor manufacturing facility, and the residual gas has a great influence on the characteristics after the treatment. For example, a metal sputtering apparatus used for forming a metal thin film, which is required to reduce the residual gas in the processing container. It is useful to apply.

[0003]

2. Description of the Related Art Conventionally, in the field of degassing equipment, a technique of removing gas adsorbed in a vacuum container or vacuum parts by using a discharge degassing equipment has been put into practical use (for example, Japanese Patent Laid-Open No. 62-160138). issue).

For degassing by electric discharge, an inert gas such as argon gas is introduced into the container while the vacuum container is evacuated by a vacuum pump, and the ionized gas is discharged under a pressure at which plasma discharge can be stably maintained. The adsorbed gas is knocked out from the surface by colliding with the container and parts for a preset time.

Further, in Japanese Patent Laid-Open No. 3-284345, in order to accurately grasp the optimum processing time of discharge degassing and perform efficient discharge degassing, as a detection means and method at the time of degassing completion, (i) processing A method using a discharge current detector provided separately in the container, (ii) a method of monitoring the specific gas partial pressure with a mass spectrometer, and (iii) a method of monitoring the discharge current or discharge voltage are proposed. .

Here, the vacuum processing apparatus is in a vacuum exhaust state after mounting the discharge electrode, and when a predetermined pressure is reached, the plasma generation gas is injected into the container at a predetermined flow rate through the gas supply system of the vacuum processing apparatus. Discharge is also a method of generating and maintaining a preset anode current value, filament voltage value, and stabilizing resistance value.

[0007]

In the conventional method, not only is it necessary to modify or add a gas pipe in a vacuum processing apparatus having no gas for plasma generation in its gas supply system, It is necessary to review the interlock and sequence of the vacuum processing unit when degassing.

Looking at the degassing treatment process by electric discharge, although it gradually deviates from the proper discharge condition immediately after the start due to the state change of the inner wall of the vacuum container in the process from the start of the discharge to the end of the degassing, the conventional discharge degassing The gas device only starts discharge with a preset condition value.

Further, regarding the method of determining the time point at which the discharge degassing is terminated, it is necessary to rework the vacuum container for securing the mounting position in the discharge current detection method by the detector and the gas analysis method by the mass spectrometer, and the discharge current or In the method of determining from the point where the change of the discharge voltage with time becomes almost constant, the change is gradual, and the determination time point greatly varies.

The object of the present invention is to minimize the reworking of the vacuum processing apparatus when applying discharge degassing, to maintain a stable discharge state from the start of discharge to the completion of degassing, and to detect an appropriate end point. An object of the present invention is to provide a discharge degassing device that can perform good degassing treatment.

[0011]

In the present invention, in order to achieve the above object, a discharge degassing apparatus is constituted by a plasma discharge power supply means, a plasma generation gas supply means, a discharge state monitor means and a calculation means.

The first means for solving the problems is a gas provided with a mass flowmeter for flowing a predetermined gas flow rate through a plasma generation gas intake port, a vacuum container supply port, and a gas pipe connecting these. The supply means is provided as a part of the discharge degassing device separately from the vacuum processing device.

The means for solving the second problem is to monitor the current value between the anode and the cathode of the discharge electrode during discharge, and to calculate the current value to control the heating voltage of the discharge electrode to keep the monitored current value constant. I decided to do it.

As a means for solving the third problem, the discharge impedance calculated from the monitor value at the time of discharge is obtained at predetermined intervals, and the degassing end is determined by the deviation of the value.

[0015]

The plasma generating gas supply means is one component of the degassing device, and the plasma generating gas is supplied from a system different from the system of the vacuum processing device. Therefore, the processing device is incorporated as a normal function. Only high vacuum evacuation operation is required, and discharge degassing is easily applied.

Since the discharge circuit is conceptually based on the one shown in FIG. 2, the principle will be briefly described. Tungsten wire filament (cathode 3
The thermoelectrons emitted from a) are accelerated by the electric field between the thermoelectrons and the anode 3b and collide with the gas in the container to be ionized. The ionized gas molecules are then accelerated by the electric field between the anode 3b and the container 1 and collide with the inner wall of the container. At this time, the gas molecules adsorbed on the inner wall surface are knocked out and discharged by a vacuum pump.

From the above, the current ip (discharge current) between the anode 3b and the vacuum vessel 1 is related to the amount of ionized gas colliding with the inner wall, and the voltage va (discharge voltage) of the anode power source which is causing the electric field. It is understood that is a parameter related to collision energy.

The change of the discharge state and the discharge condition when the discharge degassing device is applied will be described below.

By applying discharge degassing, the adsorbed gas inside gradually decreases, and the discharge current ip
Becomes smaller. On the other hand, the discharge degassing power supply uses a constant current power supply as the anode power supply because it is necessary to supply a predetermined amount of discharge current for degassing.
The following relationship is established with a, discharge current ip, and anode / cathode current ie (emission current): ia = ip + ie (1) Here, the anode current ia is controlled to be constant, so the discharge current
The emission current ie increases as ip decreases. This is because the supply of thermoelectrons due to the progress of degassing becomes insufficient due to the change in the internal state of the vacuum container, the amount of gas ions produced decreases, and the current ie between the anode and the cathode becomes
This is the result of the relative increase in the current ip between the vacuum vessels.

That is, in order to keep the discharge current ip at a predetermined value, it is sufficient to increase the amount of thermionic supply, and keeping the discharge current ip constant is effective in shortening the degassing time. Since the current ia is constant, it is understood that it is useful to control the emission current ie, that is, the filament voltage vf.

Regarding the method for determining the end point of degassing, the discharge impedance Zp in the anode / vacuum container, which reflects the internal state of the vacuum container, is used as a monitoring parameter, and the initial state value at the start of discharge degassing and the progress of degassing are accompanied. The state values are appropriately compared, and the discharge is terminated when a difference larger than a preset value is obtained.

[0022]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a conceptual diagram of the present invention. In FIG. 1, reference numeral 1 is a vacuum container to be subject to degassing by discharge, 2 is a vacuum pump, 3 is a filament that also serves as a cathode for the discharge electrode 3a, which is connected to the vacuum container via the low potential side of the discharge power supply 4 and is grounded. . An anode 3b is connected to the high potential side of the discharge power source 4.

Reference numeral 5 denotes a process controller, which takes in a state monitor signal at the time of discharge from the discharge power source 4 and performs an arithmetic operation to control the discharge state and detect the end point.

Reference numeral 6 denotes a plasma generation gas supply unit, which is connected to a gas introduction valve 7 provided in the vacuum container 1 by a pipe and supplies a predetermined amount of gas.

Reference numeral 8 denotes a sequencer, which sends start and stop signals to the power supply 4, the process controller 5, and the gas supply unit 6.

Reference numeral 9 denotes a pressure sensor, which monitors the internal pressure of the vacuum container 1 and outputs a signal for prohibiting the activation of the power source 4 while the container is open to the atmosphere or temporarily stopping the operation when the pressure deviates from a predetermined discharge degassing execution pressure. Take advantage of.

When the vacuum vessel 1 is discharged and degassed, the vacuum vessel 1 is evacuated by the vacuum pump 2 and when the pressure sensor 9 detects a preset pressure, the sequencer 8 issues a start signal. First, the plasma generation gas is injected from the gas supply unit 6 into the vacuum container 1 through the introduction valve 7, and the discharge power supply 4 is activated when the internal pressure reaches a predetermined internal pressure (several pa), and the electrode 3
Power supply to.

After the start of discharge, a discharge control signal is issued from the sequencer 8 to the process controller 5, the discharge control and calculation for determining the end point are performed, the discharge is continued until the degassing end point condition is met, and the inner wall is ionized. Degassing proceeds by hitting the generated gas.

When the conditions for ending the degassing are met, the signal from the sequencer 8 causes the discharge power source 4 and the gas supply unit to stop operating in this order.

FIG. 2 shows a discharge power supply circuit.
When the filament 3a is heated by the constant voltage power supply 10, thermoelectrons fly out from the surface. The thermoelectrons are accelerated toward the anode 3b, which is kept at a high potential by the anode constant current power supply 11, and collide with a plasma-producing gas such as argon during the course to be ionized. A part of the ionized electrons contributes to the ionization of the gas again, and the other enters the anode 3b and the cathode / anode current ie (emission current)
Becomes The generated ionized gas molecules partially collide with the cathode 3a and are neutralized, and most of them collide with the vacuum container 1 and are neutralized. By this collision with the vacuum container 1, the gas adsorbed on the inner wall is knocked out and neutralized to become the current ip (discharge current) between the anode and the vacuum container.

The current ia flowing in the anode power supply 11 is the sum of the emission current ie and the discharge power supply ip, and since it is a constant current power supply, it operates so as to keep it at a constant value.

The filament voltage vf, the emission current ie, the anode current ia, and the anode voltage va can be constantly monitored.

In the present invention, in order to match the discharge current ip with the target value, the set value of the filament voltage is automatically adjusted in consideration of controlling the amount of thermionic supply.

FIG. 3 is a system block diagram of the process controller 5 for controlling discharge and determining the end point of degassing. The process controller internal values will be shown in upper case.

The emission current ie, which is the monitor value of the discharge state, is converted to a voltage level by the signal converter 12 and then set to a preset target value Ieo (that is, the discharge current ip effective for degassing).
o and the anode current set value iao are compared with the following relational expression ieo = iao-ipo obtained by the signal conversion) by the subtracter 13 to adjust the filament power supply voltage vf according to the deviation amount δ.

When the adjusting operation is not necessary, the remote / local changeover switch 15 enters the local setting mode and the filament voltage emits a signal giving a constant value vfo.

On the other hand, the discharge impedance Zp is obtained by subtracting Ie from the internal signal Ia of the anode current setting value and dividing the anode voltage Va by this. This discharge impedance Zp stores the value at that time as Zpo at a predetermined timing in the initial stage of discharge from the sequencer, and constantly compares it with the subsequent discharge impedance Zp.
The filament voltage adjustment signal is cut off when the voltage exceeds the value.

FIG. 4 is a diagram for explaining the plasma generating gas supply unit 6.

A gas supply pipe 23 is connected to a gas introduction valve 7 attached to a port flange 22 provided in the vacuum container 1 when degassing is performed.

In the case of degassing, first open the main plug 25 of the plasma generating gas cylinder 24 and confirm with the pressure gauge 26 that the internal pressure of the cylinder is at the required level.
While watching 8, the pressure adjusting valve 27 is operated to adjust to a predetermined value, and then the manual bubble 30 is opened. The above is the preparation work.

When the sequencer 7 is activated, the mass flow meter (mass flow controller) 31 is once closed before the normally closed air actuated valve 32 is operated, then the air actuated valve 32 is opened, and then the control valve of the mass flow meter 31 is opened. Gradually opens to operate so as to suppress a sudden change in the gas flow.

Here, instead of the mass flow meter, it is also possible to use a float type micro flow meter or a micro needle valve.

[0044]

As described above, according to the present invention, since the plasma generating gas can be supplied separately from the gas piping system of the vacuum processing apparatus, it suffices to perform a high vacuum exhaust state. Therefore, the discharge state is maintained at a predetermined level and the end point is automatically determined and stopped, so that efficient processing without discharge degassing time can be performed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a system configuration according to an embodiment of the present invention.

FIG. 2 is a discharge power supply circuit applied in the present invention.

FIG. 3 is a system block diagram of a process controller for discharge control and determination of a degassing end time in the present invention.

FIG. 4 is an explanatory diagram of a plasma generation gas supply unit applied in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Vacuum pump, 3 ... Discharge electrode, 4 ... Discharge power supply, 5 ... Process controller, 6 ... Plasma generation gas supply part, 7 ... Gas introduction valve, 8 ... Sequencer, 9 ... Pressure sensor.

Claims (3)

[Claims] 1. An apparatus for degassing an adsorbed gas inside a vacuum container by electric discharge, comprising a power supply means for generating and maintaining electric discharge, a tank pressure adjusting means for maintaining stable electric discharge, and discharge plasma generation. A discharge degassing device comprising a gas supply means. 2. A device for degassing an adsorbed gas inside a vacuum container by electric discharge, wherein a current value flowing between an anode and a cathode of a discharge electrode in a power supply means at the time of discharge is used as a control element, and a heating voltage of the electrode. A discharge degassing device characterized by controlling (filament voltage). 3. A device for degassing an adsorbed gas inside a vacuum container by discharging, wherein the power supply means determines the discharge degassing completion time point based on a change in impedance between the anode and the vacuum container during discharge. Discharge degasser characterized by.