JP2011222292A - Apparatus and method for power supply for plasma discharge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply for plasma discharge that can, even if there occurs an arc discharge, recover to stable glow-discharging.SOLUTION: The voltage is turned to a pulse voltage by a first switching element before power is supplied to the body of a plasma discharge device from a DC power supply via an inductor. A potential holding circuit in which a resistor, a capacitor and a second switching element are serially connected is operated while the first switching element is OFF, to thereby restrict arc discharge current at arc discharging.

Description

  The present invention relates to a plasma discharge power supply device using a direct current glow discharge for pulse-modulating direct current power.

  Conventionally, glow discharge treatment apparatuses that perform ion nitriding, plasma carburization, plasma CVD, plasma sputter deposition, magnetron sputter deposition, etc. using direct current glow discharge have been widely used. When arc discharge occurs in the glow discharge treatment apparatus, the object to be treated is damaged, or a stable reaction process cannot be maintained due to fluctuations in the glow discharge treatment time. In particular, in the case of an optical film used for a lens or the like, a required accuracy is high and a problem has become apparent.

  Japanese Patent Application Laid-Open No. 7-62521 (Patent Document 1) describes a treatment method for arc discharge by a glow discharge treatment apparatus. FIG. 5 is a circuit diagram showing an electrical configuration of the glow discharge treatment apparatus in Patent Document 1, and FIG. 6 is a graph showing signal waveforms of respective parts before and after arc discharge.

  In FIG. 5, 1 is a DC power source, 8 is a plasma discharge processing apparatus main body (chamber), 9 is an anode, 10 is a cathode, 16 is a switching element, 17 is an arc current detection circuit, and 18 is a control unit. In FIG. 6, the vertical axis represents voltage and the horizontal axis represents time. FIG. 6A shows the waveform of the discharge current of the cathode 10. FIG. 6B shows a voltage waveform of the DC power source 1, and FIG. 6C shows an arc current detection signal by the cake current detection circuit 17. FIG. 6D is a waveform showing the timing of the ON / OFF operation of the switching element 16.

  5 and 6, during glow discharge, the switching element 16 connected in series with the DC power source 1 is switched as shown in FIG. 6D, so that the pulse voltage is supplied from the DC power source 1 to the anode. Is done. (Equivalent to the first three pulses in FIG. 6A) Next, when arc discharge occurs, the discharge current rapidly rises as shown in the fourth pulse in FIG. Over. When the arc determination level L is exceeded, the arc current detection circuit 17 detects the arc detection signal P. Based on the detection signal P, the control unit 18 turns off the switching element 16 and cuts off the power supply to the anode 9. As a result, the voltage of the DC power supply 1 is reduced at once. Thereafter, after a predetermined shut-off period has elapsed, the voltage of the DC power supply 1 is restored and the pulse of the switching element 17 is controlled to gradually start glow discharge while gradually increasing the pulse duty value of the discharge current, The normal glow discharge state is restored.

JP-A-7-62521

  As described above, Japanese Patent Application Laid-Open No. 7-62521 employs a method in which a discharge current value is compared with an arc determination level and power feeding is interrupted. However, in the case of Japanese Patent Laid-Open No. 7-62521, a large arc current flows through the circuit after the arc determination level L is detected after the occurrence of arc discharge until the power supply to the discharge device is stopped. Therefore, it is necessary to take a long interruption period for recovery to glow discharge. In order to recover to a stable glow discharge after the discharge is stopped, it is necessary to have a soft start function for gradually increasing the pulse duty value of the discharge current, and a recovery period is always required. If the recovery period is insufficient, film formation with the required accuracy cannot be realized, and if the recovery period is sufficient, the processing time becomes long and the cost of the product increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma discharge power supply apparatus that can significantly suppress and suppress adverse effects on an glow discharge treatment object due to arc discharge in a short time.

  In order to achieve this object, in the present invention, a plasma discharge processing apparatus main body is connected to a DC power supply, and a first switching element and a first resistor are provided between the DC power supply and the plasma discharge processing apparatus main body. And a potential holding circuit in which a first capacitor and a second switching element are connected in series, and an inductor is connected to the DC power supply side from the first switching element and the potential holding circuit. Proposed is a plasma discharge processing apparatus that is connected in series and that continuously performs plasma discharge processing by alternately turning on and off the first and second switching elements.

  In addition, a plasma discharge processing apparatus main body is connected to the DC power supply. Between the DC power supply and the plasma discharge processing apparatus main body, a first switching element, a first resistor, a first capacitor, A potential holding circuit in which two switching elements are connected in series is connected in parallel, and an inductor is connected in series on the DC power supply side with respect to the first switching element and the potential holding circuit. When the discharge occurs, the first switching element is turned off and the first switching element is turned on. When the plasma discharge is stopped, the first switching element is turned on and the first switching element is turned off. And a plasma discharge processing method for continuously performing plasma discharge processing by alternately turning on and off the first and second switching elements. To have.

  As described above, according to the plasma discharge power supply device of the invention of the present application, when arc discharge occurs, the arc current is limited to a small value, and after the arc discharge in one section, a stable glow is generated in the next section. It can be recovered to discharge. That is, the arc discharge current is small, the arc treatment period is short, and the adverse effect of the arc on the processed material, particularly in the case of the optical film, can be greatly suppressed.

Circuit diagram of power supply device for plasma discharge according to first embodiment The graph for operation | movement description which concerns on 1st Embodiment Operation flow diagram according to the first embodiment Circuit diagram of power supply device for plasma discharge according to second embodiment Circuit diagram of power supply device for plasma discharge according to conventional example Graph for explaining operation according to conventional example

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an electrical configuration of the plasma discharge power supply device according to the first embodiment, and FIG. 2 is a graph showing signal waveforms of respective parts before and after arc discharge.

  In FIG. 1, 1 is a DC power source, 2 is an inductor, 3 is a first switching element, 4 is a potential holding circuit, 5 is a second switching element, 6 is a first capacitor, 7 is a first resistor, 8 Is a plasma discharge treatment device main body, 9 is an anode, and 10 is a cathode.

  2A shows the waveform of the discharge voltage of the cathode 10, and FIG. 2B shows the waveform of the discharge current of the cathode 10. FIG. 2C shows the waveform of the voltage of the capacitor 6, and FIG. 2D is a waveform showing the timing of the ON / OFF operation of the first switching element 3. FIG. 2E is a waveform showing the timing of the ON / OFF operation of the second switching element 5, and FIG. 2F shows the discharge state in the plasma discharge processing apparatus main body 8.

  Next, the recovery operation when arc discharge occurs in the plasma discharge power supply device according to the first embodiment will be described. FIG. 3 is an operation flow of the plasma discharge power supply device.

  First, the discharge stop state which is “state S1” in FIG. 3 will be described. In the discharge stop state (state S1) (corresponding to before the first pulse application in FIG. 2A), the first switching element 3 (Q1) is turned on and the second switching element 5 (Q2) is turned off. As a result, the voltage between the anode 9 and the cathode 10 of the plasma discharge treatment apparatus main body 8 becomes 0 V, the power supply to the plasma discharge treatment apparatus main body 8 is stopped, and the discharge stop period is entered. Therefore, the discharge current in the plasma discharge treatment apparatus main body 8 becomes zero, and the discharge voltage becomes zero. Further, since the second switching element 5 is in the OFF state, the operation of the potential holding circuit 4 is in a stopped state, and the capacitor 6 is maintained in a state charged in advance to the glow discharge voltage Vgrow necessary for discharging.

  Next, the glow discharge state which is “state S2” in FIG. 3 will be described. In the glow discharge state (state S2) (corresponding to the first pulse in FIG. 2A), the first switching element 3 (Q1) is turned off and the second switching element 5 (Q2) is turned on. As a result, a potential necessary for discharge is applied in advance between the anode 9 and the cathode 10 of the plasma discharge processing apparatus body 8 from the first capacitor 6 via the first resistor 7. The discharge is started between. When the discharge is started, power is supplied from the DC power source 1 to the plasma discharge processing apparatus main body 8 via the inductor 2. A glow discharge state is formed near the cathode between the anode 9 and the cathode 10.

  As shown in FIG. 2C, the voltage of the capacitor 6 is charged with a glow discharge voltage (Vgrow), the current from the potential holding circuit 4 does not flow, and the current flowing through the cathode 10 is the current IL flowing through the inductor 2. It is. The rate of change of the current IL flowing through the inductor 2 depends on the voltage difference between the voltage value (Vdc) of the DC power supply 1 and the glow discharge voltage (Vgrow), and changes according to (Vdc−Vgrow) ÷ (inductance value of the inductor 2). To do. By making the inductance value of the inductor 2 sufficiently large, for example, 10 mH, the current IL flowing through the inductor 2 becomes a substantially constant glow discharge current (Igrow). In the glow discharge state, the power supply voltage of the DC voltage 1 is controlled so that the discharge voltage between the anode 9 and the cathode 10 is maintained at Vgrow and the discharge current is maintained at Igrow.

  Next, when the arc discharge does not occur in the glow discharge state and the discharge does not stop, as shown in FIG. 3, the discharge stop state “state S1” (between the second pulse of the first pulse in FIG. 2A) (Equivalent between the second pulse and the third pulse) and the glow discharge state “state S2” (corresponding to the second and third pulses in FIG. 2A) are repeated. . Thereby, the extinction and generation of the plasma state are repeated. When arc discharge occurs in the glow discharge state, an arc discharge state “state S3” is obtained (corresponding to the fourth pulse in FIG. 2A).

  Next, a state where arc discharge has occurred in the glow discharge state which is “state S3” in FIG. 3 will be described. (Corresponding to the fourth pulse in FIG. 2A) In the arc discharge state (state S3), the first switching element 3 is OFF, the second switching element 5 is ON, and the state has changed from “state S2”. Absent.

  In the arc discharge state, the discharge voltage between the anode 9 and the cathode 10 drops from the voltage Vgrow at the time of glow discharge and becomes the voltage Varc at the time of arc discharge. Accordingly, the current (Iarc) flowing through the cathode 10 tends to increase rapidly, and the voltage of the capacitor 6 is discharged through the resistor 7. However, since the current Iarc is the sum of the current IL flowing through the inductor 2 and the current Ir flowing through the resistor 7, an increase in the current Iarc can be reduced by suppressing the current IL and the current Ir.

  The current IL flowing through the inductor 2 depends on the voltage difference between the voltage value (Vdc) of the DC power supply 1 and the discharge voltage (Varc) between the anode 9 and the cathode 10, and (Vdc−Varc) ÷ (inductance of the inductor 2). Value). By making the value of the inductor 2 sufficiently large, for example, 10 mH, the current IL flowing through the inductor 2 is set to a substantially constant glow discharge current Igrow. The current Ir flowing through the first resistor 7 depends on the voltage difference between the glow discharge voltage (Vgrow) and the discharge voltage (Varc) between the anode 9 and the cathode 10, and (Vgrow−Varc) ÷ (resistance 7 Resistance value) and a constant value Iarcr. Therefore, the current (Iarc) flowing through the cathode 10 during arc discharge is Igrow + Iarcr. That is, for example, by determining the resistance value of the resistor 7 so that Iarcr is about one fifth of Igrow, the arc current can be kept low even during arc discharge.

  Next, when the first switching element 3 (Q1) is turned on and the second switching element 5 (Q2) is turned off, the discharge is stopped (state S1) (the fourth pulse in FIG. 2A). And equivalent to the fifth pulse).

  Next, the first switching element 3 (Q1) is turned OFF and the second switching element 5 (Q2) is turned ON, so that a glow discharge state (state S2) is obtained (the fifth pulse in FIG. 2A). Equivalent).

  In this way, in the arc discharge state (state S3), the discharge current is limited by the potential holding circuit 4 so that the arc current is kept low. Therefore, the switching timing to the glow discharge state of the fifth pulse can be continued without being changed. That is, in the present embodiment, by providing the potential holding circuit 4 shown in FIG. 1, even if the normal glow discharge state ON / OFF switching is continued as it is, pulses other than the pulse in which arc discharge has occurred are included. Without any influence, it is possible to prevent an increase in arc discharge current and to recover to glow discharge immediately after a single discharge stop period. Also, no means for detecting the rapidly rising arc current and controlling the discharge is required.

  The discharge voltage of the voltage of the first capacitor 6 depends on the capacitor and resistance time constant and the arc discharge time. The voltage drop of the capacitor 6 can be suppressed by increasing the time constant of the capacitor and the resistor than the period in which the first and second switching elements 3 and 5 are alternately turned on and off. By reducing the voltage drop of the first capacitor 6, it is possible to recover a more stable glow discharge at the start of the next discharge.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4A is a circuit diagram showing an electrical configuration of the plasma discharge power supply device. In addition, the same code | symbol is attached | subjected to the same member as 1st Embodiment shown in FIG. 1, and the description is abbreviate | omitted.

  In FIG. 4A, the difference from FIG. 1 of the first embodiment is that a second resistor 12 and a first diode 13 connected in series are provided in parallel with the first resistor 7. This is the point.

  Similar to the first embodiment, the capacitor 6 is charged with a voltage of Vgrow in the glow discharge state (state S2) of FIG. When arc discharge occurs and the arc discharge state (state S3) is entered, the discharge voltage between the anode 9 and the cathode 10 changes from the voltage Vgrow during glow discharge to the voltage Varc during arc discharge. The voltage of the first capacitor 6 is discharged through the first resistor 7.

  When the arc discharge state (state S3) is changed to the glow discharge state via the discharge stop state (state S1), the first switching element 3 is turned off. At this time, in order to make the current flowing through the inductor 2 easy to flow, the output voltage rises to the discharge start voltage. Discharge starts and glow discharge begins. The difference between the potential of the glow discharge and the capacitor 6 causes not only the resistor 7 but also the first diode 13 to conduct, current flows through the second resistor 12, the first capacitor 6 is quickly charged, and the voltage of the capacitor is reduced. It recovers quickly and can recover to a more stable glow discharge.

  In addition, the surge voltage from the inductor 2 is also absorbed by the capacitor 6, the diode 13, and the resistor 12 at the start of normal discharge from the state S1 to the state S2. As another embodiment of the resistor circuit, as shown in FIG. 4B, a third resistor 15 and a second diode connected in parallel with each other in series with the first resistor 7 are provided. 14 is connected. In the arc discharge, the current flows through the first resistor 7 in FIG. 4A, whereas in FIG. 4B, the current flows through the first resistor 7 and the third resistor 15, and the same effect is obtained. When the discharge stop state (state S1) is changed to the state S2, current flows through the first resistor 7, the first diode 13, and the second resistor 12, while the second diode 14 and the third diode are mainly used. A current flows through the resistor 15 and the same effect is obtained. That is, after the arc discharge, during the next discharge, the surge voltage due to the inductor is suppressed by the resistor circuit, and the voltage of the capacitor is recovered quickly, so that a more stable glow discharge can be recovered.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inductor 3, 5, 16 Switching element 4 Potential holding circuit 6 Capacitor 7, 12, 15 Resistance 8 Plasma discharge processing apparatus main body 9 Anode 10 Cathode 11 Resistance circuit 13, 14 Diode 17 Arc current detection circuit 18 Control part

Claims (5)

  A plasma discharge processing apparatus main body is connected to the DC power supply, and a first switching element, a first resistor, a first capacitor, a second capacitor are connected between the DC power supply and the plasma discharge processing apparatus main body. A potential holding circuit in which switching elements are connected in series is connected in parallel, and an inductor is connected in series on the DC power supply side with respect to the first switching element and the potential holding circuit, and the first A plasma discharge treatment apparatus that performs plasma discharge treatment continuously by alternately turning on and off the second switching element.   2. The plasma discharge power supply device according to claim 1, wherein a time constant between a resistor and a capacitor of the potential holding circuit is equal to or longer than a period in which the first and second switching elements are alternately turned on and off. .   2. The plasma discharge according to claim 1, wherein a first diode and a second resistor connected in series are further connected to the potential holding circuit in parallel with the first resistor. Power supply.   2. The potential holding circuit further comprises a third resistor and a second diode connected in parallel with each other in series with the first resistor. The power supply device for plasma discharge as described.   A plasma discharge processing apparatus main body is connected to the DC power supply, and a first switching element, a first resistor, a first capacitor, a second capacitor are connected between the DC power supply and the plasma discharge processing apparatus main body. A potential holding circuit in which switching elements are connected in series is connected in parallel, and an inductor is connected in series to the DC power supply side from the first switching element and the potential holding circuit, and plasma discharge is performed. When waking up, the first switching element is turned off, the first switching element is turned on, and when the plasma discharge is stopped, the first switching element is turned on, and the first switching element is turned off, The plasma discharge process is performed continuously by alternately turning on and off the first and second switching elements. Law.

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