JP3044361B2 - Glow discharge treatment method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glow discharge processing apparatus, and more particularly to a glow discharge processing 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 processing apparatus. In the figure, reference numeral 21 denotes a DC control unit for converting commercial power into DC using a thyristor. The extracted DC voltage is supplied to a processing apparatus main body 22. Reference numeral 23 denotes a thyristor control unit for controlling a DC output voltage by controlling a flow angle of the thyristor, and reference numeral 24 denotes a vacuum pump for maintaining the pressure in the processing apparatus main body at a pressure suitable for glow discharge and processing. Reference numeral 25 denotes a temperature detector for detecting the temperature of the processing object in the main processing chamber. The obtained temperature detection signal is supplied to the thyristor control unit 23.

In the above configuration, a DC voltage is applied between the processing object (cathode) and the main body (anode) in the main body of the processing apparatus. The processing object is wrapped in the glow discharge generated thereby, and as a result, surface treatment such as ion nitriding and magnetron sputter deposition is performed.

In order to stably perform such processing, a discharge current is detected, 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 processing object is raised and maintained by plasma generated by glow discharge. In order to maintain this temperature constant, the temperature is determined based on a temperature detection signal obtained from the temperature detector 5. The control is performed by the thyristor control unit so as to increase the DC voltage when the value is low and to decrease the DC voltage when the value is high.

The DC control section 21 and the processing apparatus main body 22
A switching means is provided between them, and a DC voltage is chopped and supplied to a 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 flow angle of the thyristor is changed to change the DC voltage. Therefore, the response of the voltage control is one cycle or half a cycle of the commercial power. A delay is inevitable.
Because of such a delay, when the discharge suddenly becomes abnormal, it is difficult to control the voltage immediately and to cope with it, and it is also difficult to maintain a stable discharge. In particular, in the case of magnetron sputter deposition, an abnormal discharge causes a reaction process to be disrupted due to, for example, an excess of reactive gas, and in the case of an optical film, the thin film characteristics are particularly greatly affected. Was a big problem.

[0008] The present invention has been made in view of the above points, and has as its object to provide a glow discharge processing method and apparatus capable of improving control responsiveness.

[0009]

To achieve this object, a first aspect of the present invention is a glow discharge processing method for processing a workpiece by supplying a DC voltage to an electrode in a processing chamber to generate a DC glow discharge. Is characterized in that the supply of the DC voltage is repeated in a predetermined cycle in a pulsed manner, and the supply power is controlled by controlling the pulse width of the supply pulse.

Furthermore, a second invention provides a glow discharge processing method for processing a workpiece by supplying a DC voltage to an electrode in a processing chamber to generate a DC glow discharge. And a control means for controlling a pulse width of a pulse generated by the pulsing means and supplied to an electrode in the processing chamber.

[0011]

According to the present invention, the supply of the DC voltage is repeated in a predetermined cycle in a pulsed manner, and the supply power is controlled by controlling the pulse width of the supply pulse. Therefore, the response of the control can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a diagram illustrating an example of a device configuration for implementing the present invention. In FIG. 2, reference numeral 1 denotes a DC control unit that converts commercial power into DC. The DC voltage taken out through the smoothing circuit 2 is sent to the inverter switching unit 3, converted into AC (rectangular wave), and supplied to the processing device main body 6 via the boosting transformer 4 and the rectifying unit 5. 7, a thyristor control unit; and 8, an inverter control unit. Reference numeral 9 denotes a current transformer provided between the step-up transformer 4 and the rectification unit 5, and 10 reads 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 denotes a temperature detector for detecting the temperature of the processing object in the main processing chamber.
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 to reduce the DC voltage Vdc obtained from the smoothing circuit 2 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 KHz.
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,
In the case of plasma CVD, magnetron sputtering, or the like, the voltage is selected to be, for example, about 800 V to 1000 V. The boosted high-frequency pulse voltage is rectified by the rectification unit 5 and supplied to the processing device main body 6 with a waveform as shown in FIG.

In the above configuration, the oscillation frequency f of the inverter is, for example, constant at 15 KHz, and Vdc is 200 V
Control by the thyristor control unit 7 is performed so as to be kept constant. During normal operation, based on the temperature detection signal obtained by detecting the temperature of the processing object in the main body processing chamber 6, the inverter control unit 8 determines the pulse width of the high frequency pulse when the processing object temperature falls below a predetermined value. , The duty is increased to increase the input power, and conversely, if the temperature of the processing object exceeds a predetermined value, the pulse width is reduced to control the duty to decrease and the input power to decrease.
For this reason, ion nitriding, plasma carburization, and plasma CVD are performed on the processing object while the temperature of the processing object is kept constant.
And the like.

Such duty control does not depend on the cycle of the commercial power supply as in the case of changing the DC voltage, and can be performed at a very high speed.

In the case of reactive magnetron sputtering deposition, an appropriate reactive 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 a supply current obtained from the current detection circuit 10, Similarly, the duty control of the high frequency pulse is performed. As a result, the duty is quickly controlled so as to cancel subtle fluctuations in the discharge, and the reaction process is stably maintained under a constant reaction gas pressure.

When the discharge is started, the thyristor control unit 7 sets Vdc to a voltage sufficiently higher than 200 V at first, and exceeds the discharge start voltage (higher than the voltage during normal operation) in the main processing unit. A voltage is supplied, and Vdc is returned to 200 V when the discharge starts.

Next, a case where an arc discharge occurs will be described. FIG. 5A shows a current detection output of the current transformer which indicates a change in discharge current before and after the occurrence of arc discharge. 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 the period B, the transition from the glow discharge to the arc discharge has occurred, and the current has increased sharply. The current detection circuit 10 generates an arc detection signal p shown in FIG. 5C based on a comparison with an appropriate threshold level L, and outputs the arc detection signal p 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,
(For example, several tens μsec to 100 μsec). When an 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 after the DC output Vdc of the smoothing circuit 2 once decreases as shown in FIG. Try to rise.

The inverter control section 8 restarts the oscillation of the inverter at the same frequency f in the return period D after the end of the cutoff period C. At this time, the duty of the high frequency pulse is changed as shown in FIG. The duty is gradually increased from zero to the duty before the arc is detected. The discharge current value also gradually increases in the same manner as the duty in accordance with the change in Vdc in FIG. 4B, and returns to the state before arc detection at the end of the return period D.

Conventionally, the duty of the high-frequency pulse is always constant, and during the return period D, the high-frequency pulse is supplied to the processing apparatus main body at the same time as the start of the oscillation of the inverter and at the same time as the duty before the arc detection. It is highly possible that the cutoff period C
Must be set as long as about 1 mSec to 5 mSec.

In this regard, if the duty of the high-frequency pulse is gradually increased from zero during the return period D, in other words, if the pulse width is gradually increased, the transition to the arc is prevented by the first narrow pulse. Since the discharge is gradually started while the discharge is being started, the transition to the arc discharge is suppressed very effectively. Therefore, the cut-off period C is set to, for example, several tens μsec to 1
Even if the time is set to be as short as 00 μSec, it is possible to return without shifting to the arc. Also, the return period D can be shortened at the same time.
It was confirmed that the transition to the arc could be avoided even if the setting was as short as about 600 μSec.

The gist of the present invention is that the discharge process is controlled by adjusting the duty (adjusting the pulse width at a constant frequency). It is not always essential to gradually increase the duty from zero. For the return period only, for example, a soft start by adjusting only the DC voltage or current with a constant duty as in the related art may be employed. However, it goes without saying that it is actually preferable to use the duty adjustment function also in the return period to shorten the cutoff period.

[0026]

As described above in detail, in the present invention, since the control of the discharge process is performed by adjusting the duty (adjusting the pulse width at a constant frequency), the responsiveness of the control is improved and the control is more stable than in the prior art. It is possible to maintain the discharged discharge. In particular, in the case of reactive magnetron sputter deposition, it is possible to prevent the reaction process from being disrupted by a quick response to abnormal discharge, and to prevent a bad influence on thin film characteristics.

[Brief description of the drawings]

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

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC control part 2 Smoothing circuit 3 Inverter switching part 4 Step-up transformer 5 Rectifier part 6 Processing device main body 7 Thyristor control part 8 Inverter control part 9 Current transformer 10 Current detection circuit 11 Temperature detector

Claims (2)

(57) [Claims] In a glow discharge processing method for processing a workpiece by supplying a DC voltage to an electrode in a processing chamber to generate a DC glow discharge, the DC voltage is repeatedly supplied at a predetermined cycle in a pulsed manner. Controlling the supply power by controlling the pulse width of the supply pulse. 2. A glow discharge processing method for processing a workpiece by supplying a DC voltage to an electrode in a processing chamber to generate a DC glow discharge, wherein the DC voltage is supplied in a predetermined cycle in a pulsed manner. A glow discharge processing apparatus comprising: a pulsing unit; and a control unit that controls a pulse width of a pulse generated by the pulsing unit and supplied to an electrode in a processing chamber.