JPH0778697A - Method and device for glow discharge processing - Google Patents

Abstract

PURPOSE:To establish a glow discharge processing method and provide an associate device with which the responsiveness in controlling can be enhanced. CONSTITUTION:A DC voltage converted from commercial AC by a DC control part 1 and taken out through a smoother circuit 2 is sent to an inverter switching part 3, converted into AC (rectangular wave), and supplied to the body 6 of a processing device concerned via a booster transformer 4 and a rectification part 5. A current sensing circuit 10 reads the current sensed by a current transformer 9 installed between the booster transformer 4 and rectification part 5 and sends accordingly a control signal to a thyristor control part 7 and inverter control part 8. The temp. sensing signal obtained by a temp. sensor 11 to sense the temp. of the object to be processed in a body processing chamber is supplied to the inverter control part 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow discharge treatment apparatus, and more particularly to a glow discharge treatment apparatus capable of controlling glow discharge at a high response speed.

[0002]

2. Description of the Related Art A glow discharge treatment apparatus for performing ion nitriding, plasma carburization, plasma CVD, magnetron sputter deposition, etc. using a DC glow discharge is widely used.

FIG. 1 shows an example of this glow discharge treatment apparatus. In the figure, reference numeral 21 denotes a DC control unit for converting commercial power to DC using a thyristor, and the DC voltage taken out is supplied to the processing apparatus main body 22. Reference numeral 23 is a thyristor control unit for controlling the DC output voltage by controlling the flow angle of the thyristor, and 24 is a vacuum pump for maintaining the pressure inside the processing apparatus main body at a pressure suitable for glow discharge and processing. Reference numeral 25 is a temperature detector for detecting the temperature of the processed material in the main body processing chamber, and the obtained temperature detection signal is supplied to the thyristor control unit 23.

In the above structure, the DC voltage is applied between the object to be treated (cathode) and the body (anode) in the processing apparatus body. Then, the object to be treated is wrapped in the glow discharge generated thereby, and as a result, a surface treatment such as ion nitriding or magnetron sputtering deposition is performed.

In order to carry out such a process stably, a discharge current is detected, this is compared with a set value, and the DC voltage supplied to the processing device is controlled based on the output of the difference. . In the case of ion nitriding, the temperature of the object to be processed is raised and maintained by the plasma generated by glow discharge, and in order to maintain this temperature constant, the temperature is detected based on the temperature detection signal obtained from the temperature detector 5. The thyristor controller controls to increase the DC voltage when it is low and decrease the DC voltage when it is high.

The DC controller 21 and the processor body 22
It is also practiced to provide a switching means between the two to chop the DC voltage and supply it to the processing device as a voltage pulse having a constant period and a constant pulse width. Also in this case, the control is performed by changing the DC voltage.

[0007]

In such a conventional device, the distribution angle of the thyristor is changed in order to change the DC voltage. Therefore, the voltage control response is one cycle or half cycle of the commercial power. There is an unavoidable delay.
Due to such a delay, when the discharge suddenly becomes abnormal, it is difficult to immediately control the voltage and cope with it, and thus it is also difficult to maintain stable discharge. In particular, in the case of magnetron sputter deposition, the reaction process is disrupted due to, for example, excess reaction gas due to abnormal discharge, and in the case of an optical film, the thin film characteristics are particularly adversely affected. Was a big problem.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a glow discharge treatment method and apparatus capable of enhancing control response.

[0009]

In order to achieve this object, a first aspect of the present invention is a glow discharge treatment method for treating an object by supplying a DC voltage to electrodes in a treatment chamber to generate a DC glow discharge. In the above, the DC voltage is repeatedly supplied in a predetermined cycle in a pulse manner, and the supply power is controlled by controlling the pulse width of the supply pulse.

Further, the second aspect of the present invention is a glow discharge treatment method for treating an object to be treated by supplying a direct current voltage to an electrode in a processing chamber to generate a direct current glow discharge, thereby supplying a direct current voltage at a predetermined cycle. And a control means for controlling the pulse width of the pulse generated by the pulsing means and supplied to the electrodes in the processing chamber.

[0011]

In the present invention, the DC voltage is repeatedly supplied in a predetermined cycle in a pulsed manner, and the pulse width of the supply pulse is controlled to control the supply power, so that the control response can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a diagram showing an example of a device configuration for carrying out the present invention. In FIG. 2, reference numeral 1 is a DC controller that converts commercial power to DC. The DC voltage extracted through the smoothing circuit 2 is sent to the inverter switching unit 3, converted into an AC (rectangular wave), and supplied to the processing device body 6 via the step-up transformer 4 and the rectifying unit 5. Reference numeral 7 is a thyristor controller, and 8 is an inverter controller. Reference numeral 9 is a current transformer provided between the step-up transformer 4 and the rectification unit 5, 10 is a current detected by the current transformer, and sends a control signal to the thyristor control unit 7 and the inverter control unit 8 according to the value. It is a current detection circuit. 1
Reference numeral 1 is a temperature detector for detecting the temperature of the processing object in the main body processing chamber, and the obtained temperature detection signal is used for the inverter control unit 8
Is supplied to.

The DC control unit 1 is composed of a thyristor and a diode, and controls the conduction timing of the thyristor based on a control signal from the thyristor control unit 7 so that the DC voltage Vdc obtained from the smoothing circuit 2 is changed from 0V. It can be arbitrarily set up to about 300V.

The inverter switching unit 3 employs a full-bridge inverter system using four high-speed switching elements (IGBT: insulated gate bipolar transistor, MOSFET, SIT, etc.) or four sets in parallel. Due to the inverter composed of the inverter switching unit 3 and the inverter control unit 8, the DC output voltage from the smoothing unit 2 has a repetition frequency f of several KHz to several.
It is converted into a high-frequency pulse waveform of 100 KHz as shown in FIG. At this time, the inverter controller 8 controls the temperature detector 1
Based on the temperature detection signal from 1 or the control signal from the current detection circuit, the duty of the high frequency pulse is controlled (for example, in the range of 0% to 80%) as shown by the broken line in FIG.

The step-up transformer 4 steps up the high frequency pulse voltage to a predetermined amplitude. Ion nitriding, plasma carburization,
For plasma CVD, magnetron sputtering, etc., for example, about 800V to 1000V is selected. The boosted high frequency pulse voltage is rectified by the rectification unit 5 and supplied to the processing apparatus main body 6 in a waveform as shown in FIG.

In the above structure, the oscillation frequency f of the inverter is fixed at, for example, 15 kHz, and Vdc is 200 V.
The control of the thyristor control unit 7 is performed so that the thyristor control unit 7 maintains the constant value. Then, during normal operation, based on the temperature detection signal obtained by detecting the temperature of the object to be processed in the main body processing chamber 6, the inverter control unit 8 causes the pulse width of the high frequency pulse when the object temperature falls below a predetermined value. Is increased to increase the input power, and conversely, when the temperature of the object to be processed exceeds a predetermined value, the pulse width is narrowed to decrease the duty and reduce the input power.
For this reason, ion nitriding, plasma carburization, plasma CVD are performed on the processed product while the processed product temperature is kept constant.
Can be processed.

Since such duty control does not depend on the cycle of the commercial power source as in the case of changing the DC voltage, it can be performed at an extremely high speed.

In the case of reactive magnetron sputtering vapor deposition, an appropriate reaction gas is supplied to the inside of the processing apparatus main body 6 at an appropriate pressure, and based on a control signal corresponding to the supply current obtained from the current detection circuit 10, Similarly, duty control of the high frequency pulse is performed. As a result, the duty is quickly controlled so as to cancel the slight fluctuation of the discharge, and the reaction process is stably maintained under a constant reaction gas pressure.

At the time of starting the discharge, the thyristor control unit 7 first sets Vdc to a voltage sufficiently higher than 200 V, and exceeds the discharge start voltage (higher than the voltage during normal operation) in the processing apparatus main body. The voltage is supplied and Vdc is returned to 200V when the discharge starts.

Next, the case where arc discharge occurs will be described. FIG. 5A shows the current detection output of the current transformer, which represents the change in the discharge current before and after the arc discharge occurs. The discharge current in the period A shows a regular pulse current waveform, and the discharge is controlled by adjusting the duty as described above. V shown in FIG.
dc is also kept constant at 200V.

In period B, the glow discharge is transitioning to arc discharge, and the current is rapidly increasing. The current detection circuit 10 generates an arc detection signal p shown in FIG. 5C based on comparison with an appropriate threshold level L, and the inverter control unit 8 and the thyristor control unit 7
Send to. The inverter control unit 8 immediately stops the oscillation of the inverter based on the arc detection signal p and cuts off the interruption period C.
It is stopped for (for example, several tens of μsec to 100 μsec). When the IGBT element is used, it can be stopped in 2 to 5 μSec. At the same time, the thyristor control unit 7 controls the thyristor of the DC control unit 1 based on the arc detection signal p, and the DC output Vdc of the smoothing circuit 2 once decreases as shown in FIG. Try to rise.

The inverter control unit 8 restarts the oscillation of the inverter at the same frequency f in the recovery period D after the end of the cutoff period C. At this time, the duty of the high frequency pulse is set as shown in FIG. 5 (a). Gradually increase from zero to the duty before arc detection. The discharge current value also gradually rises in accordance with the change in Vdc in FIG. 4B like the duty, and returns to the state before arc detection at the end of the recovery period D.

Conventionally, the duty of the high frequency pulse is always constant, and the high frequency pulse is supplied to the main body of the processing apparatus at the duty before arc detection at the same time as the start of the oscillation of the inverter in the recovery period D. There is a high possibility that it will occur, and in order to avoid it, the cutoff period C
Had to be set as long as about 1 mSec to 5 mSec.

In that respect, when the duty of the high frequency pulse is gradually increased from zero in the recovery period D, in other words, when the pulse width is gradually widened, the transition to the arc is avoided by the first narrow pulse. However, since the discharge is gradually started, the transition to the arc discharge is extremely effectively suppressed. Therefore, the cutoff period C is, for example, several tens of μsec −1.
Even if it is set to 00 μSec, which is much shorter than in the past, it is possible to recover without arc transition. Also, the return period D can be shortened together, for example, 150 μSec.
It was confirmed that the transition to the arc can be avoided even if it is set to about 600 μSec.

Note that the gist of the present invention is to control the discharge process by adjusting the duty (adjusting the pulse width at a constant frequency). Therefore, as in the above embodiment, the high frequency pulse of the high frequency pulse is returned. It is not always essential to gradually increase the duty from zero, and for the recovery period only, for example, soft start by adjusting only the DC voltage or current with a constant duty may be adopted as in the conventional case. However, it goes without saying that it is actually preferable to utilize the duty adjusting function also in the return period to shorten the cutoff period.

[0026]

As described above in detail, in the present invention, the discharge process is controlled by adjusting the duty (adjusting the pulse width at a constant frequency), so that the control response is improved and stable. It has become possible to maintain the generated discharge. In particular, in the case of reactive magnetron sputter deposition, it is possible to prevent the reaction process from being disrupted due to a quick response to abnormal discharge, and prevent adverse effects on thin film characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional example of a glow discharge treatment apparatus.

FIG. 2 is a diagram showing an example of a device configuration for carrying out the present invention.

FIG. 3 is a diagram showing a high frequency pulse waveform.

FIG. 4 is a diagram showing a high-frequency pulse waveform supplied to the processing apparatus main body.

FIG. 5 is a diagram showing signal waveforms of various parts of the device before and after arc discharge occurs.

[Explanation of symbols]

 1 DC control unit 2 Smoothing circuit 3 Inverter switching unit 4 Step-up transformer 5 Rectification unit 6 Processing device body 7 Thyristor control unit 8 Inverter control unit 9 Current transformer 10 Current detection circuit 11 Temperature detector

Claims (2)

[Claims] 1. A glow discharge treatment method for treating an object to be treated by supplying a direct current voltage to electrodes in a processing chamber to generate a direct current glow discharge, wherein the direct current voltage is repeatedly supplied in a predetermined cycle in a pulsed manner. A glow discharge processing method, characterized in that the supply power is controlled by controlling the pulse width of the supply pulse. 2. A glow discharge treatment method for treating an object to be treated by supplying a direct current voltage to an electrode in a processing chamber to generate a direct current glow discharge, wherein the direct current voltage is supplied in a pulsed manner at a predetermined cycle. A glow discharge treatment apparatus comprising: a pulsing means and a control means for controlling a pulse width of a pulse generated by the pulsing means and supplied to an electrode in a processing chamber.