JP4468078B2 - Abnormal discharge suppression device for vacuum equipment - Google Patents

Description

  The present invention relates to an abnormal discharge suppressing device effective in suppressing abnormal discharge generated in a vacuum apparatus in a sputtering apparatus or etching apparatus using plasma generated in vacuum, or an electron beam evaporation apparatus.

Conventionally, a sputtering device connected to a DC power source provided with an inverter circuit, a rectifier that rectifies the output, and a filter that smoothes the output, or a vacuum such as an etching device or an electron beam evaporation device is used. In a vacuum device, the impedance of the electrode of the vacuum device may decrease, or conductive dust may short-circuit between the electrodes, and these phenomena may cause a temporary abnormal discharge of plasma, or In an electron beam evaporation apparatus, abnormal discharge may occur between a filament at a high potential and an electrode positioned around the filament.
In particular, in the sputtering apparatus, when an abnormal discharge occurs, there arises a problem that a substrate material such as a liquid crystal during sputtering is given a defect and the yield of the product is greatly reduced. In addition, the electron beam evaporation apparatus has a problem that the filament breaks due to discharge energy due to abnormal discharge.

In order to suppress these abnormal discharges, a resonance circuit consisting of a resonance inductor and a resonance capacitor is connected to the main circuit of the DC power supply, and a short-circuit semiconductor switch is connected in parallel with the vacuum device to cause abnormal discharge. By turning on the short-circuiting switch at a certain period even during steady state and resonating, the positive polarity due to resonance and reverse polarity pulse voltage are applied between the electrodes to suppress the occurrence of abnormal discharge, and abnormal discharge An abnormal discharge suppression device has already been proposed in which an abnormal discharge is extinguished by detecting this and immediately resonating the resonance circuit and applying a reverse polarity pulse voltage between the electrodes (see, for example, Patent Document 1). reference). In addition, an abnormal discharge suppression device for a vacuum apparatus that is substantially the same in principle although the circuit configuration is different has already been proposed (see, for example, Patent Document 2).
JP 08-222398 A WO99-47727

However, the abnormal discharge suppression device described in Patent Documents 1 and 2 is a method in which both ends of the load are short-circuited and at the same time a resonance voltage is applied between the electrodes of the load. Since the peak value of the pulse voltage is proportional to the charging voltage of the resonance capacitor, and the peak value of the positive pulse voltage is determined from the steady sputtering voltage, it is impossible to control only the peak value of the reverse polarity pulse voltage. is there. However, depending on the application, it may be desired to control the peak value of the reverse polarity pulse voltage to an arbitrary value, but such a conventional abnormal discharge suppression method cannot perform such control.
In addition, the pulse width of the reverse polarity pulse voltage is naturally a half period of the resonance current. In order to reliably suppress abnormal discharge, it may be desired to increase the pulse width of the reverse polarity pulse voltage. It is necessary to increase the values of the resonance inductor and the resonance capacitor constituting the circuit.

  Furthermore, after the half-cycle of the positive polarity of the resonance cycle is completed until the peak value of the reverse polarity pulse voltage is applied between the electrodes after the occurrence of the abnormal discharge, the time half of the half-cycle of the negative polarity Since the peak value is reached, of course, it may take 3/4 of the resonance period, and it is difficult to extinguish the abnormal discharge immediately. In addition, since the positive and negative resonance waveforms are almost the same, the reverse polarity pulse voltage may be too large if it is adjusted to a steady voltage value such as a desired sputtering voltage. In this case, a reverse polarity discharge occurs. There is a possibility.

The present invention relates to an abnormal discharge suppression device for a vacuum device having a function capable of applying a reverse polarity voltage to the vacuum device in order to suppress the occurrence of abnormal discharge in the vacuum device or the like, or to extinguish the generated abnormal discharge. Instead of applying a resonant voltage to the vacuum device as in the prior art, the first problem is to apply a reverse voltage of a desired value from the reverse polarity voltage circuit to the vacuum device when both ends of the load are short-circuited. A second problem is to reduce the turn-off loss of the short-circuiting semiconductor switch, which is turned on when a reverse voltage having a desired value is applied from the voltage circuit to the vacuum apparatus, by resonance.

In order to solve the above-described problems, the first invention is a vacuum device, a DC power source for supplying power to the vacuum device, and a short-circuit semiconductor connected in parallel to the DC power source and the vacuum device. A switch, an anti-parallel diode connected in parallel with the short-circuiting semiconductor switch so as to have a polarity opposite to the polarity of the short-circuiting semiconductor switch, and when the abnormal discharge occurs in the vacuum device, the short-circuiting A control circuit that turns on the semiconductor switch; and a reverse polarity voltage circuit that is connected in series with the shorting semiconductor switch and applies a reverse polarity voltage to the vacuum device when the shorting semiconductor switch is turned on. In the abnormal discharge suppression device for a vacuum device, the resonance inductor and the resonance device connected in series with each other and connected in parallel with the short-circuiting semiconductor switch and the antiparallel diode Comprising a resonant circuit consisting of a capacitor, the resonant inductor and the resonant capacitor of the resonant circuit, the value is a semiconductor switch the short circuit resonance current of opposite polarity to the bypass current Ib flowing through the semiconductor switch the short wherein such period that exceeds the value of the bypass current Ib is present which flows are set each value, when the short-circuit semiconductor switch is turned on, the resonant circuit performs resonant, the short-circuit semiconductor switch is The bypass current Ib and the resonance current flow, the value of the resonance current having a polarity opposite to the polarity of the bypass current Ib is equal to the value of the bypass current Ib, and the current flowing through the short-circuit semiconductor switch is zero. with the point made to exceed the value of the bypass current Ib, the resonance current of the opposite polarity flows through the antiparallel diode The period in which the current short-circuit semiconductor switch does not flow equal between, to provide an abnormal discharge suppressing device for a vacuum device, characterized in that turning off the semiconductor switch the short.

  In the first aspect of the invention, in the first aspect of the invention, a diode that prevents the charged charge of the resonance capacitor from being discharged directly to the vacuum load through the resonance inductor is connected in series with the short-circuit semiconductor switch and Provided is an abnormal discharge suppressing device for a vacuum device, which is connected in the same direction.

According to the first aspect of the present invention, it is possible to suppress the occurrence of abnormal discharge, quickly extinguish it when abnormal discharge occurs, and reduce the turn-off loss of the short-circuiting semiconductor switch.
According to the second aspect of the invention, when an abnormal discharge occurs in the vacuum device, the charging charge of the resonance capacitor is discharged to the vacuum device during the delay of detection of the abnormal discharge or the delay of the short-circuiting semiconductor switch. Can be prevented.

[Embodiment 1]
With reference to FIG. 1, an abnormal discharge suppressing device 100 for a vacuum apparatus according to a first embodiment of the present invention will be described. In FIG. 1, a DC power source 1 composed of a DC-DC converter or the like that converts AC power from an AC power source such as a commercial power source into desired DC power, and a vacuum device 2 that is a device using a vacuum as described above. A constant current inductor 3 having a large inductance is connected between the two. One end of the vacuum device 2 and the positive terminal of the DC power source 1 are grounded. A circuit in which a short-circuiting semiconductor switch 4 such as an IGBT or a MOSFET and a reverse polarity voltage circuit 5 are connected in series is connected across the vacuum device 2. Note that the term “stretching the vacuum device 2 over the vacuum device 2” does not necessarily indicate the entire vacuum device, but means that the minimum unit is straddling the electrodes of the vacuum device 2. In response to the abnormal discharge detection signal from the abnormal discharge detection circuit 6 that detects whether or not abnormal discharge has occurred, the control circuit 7 turns on the short-circuiting semiconductor switch 4. The short-circuit semiconductor switch 4 is connected in parallel with an antiparallel diode 8 having a polarity opposite to the polarity. The antiparallel diode 8 can be replaced with an internal diode formed in the shorting semiconductor switch 4. A resonance circuit 11 including a resonance inductor 9 and a resonance capacitor 10 connected in series with each other is connected across the short-circuit semiconductor switch 4.

  The abnormal discharge detection circuit 6 includes a phenomenon in which the load voltage drops below a set value, a phenomenon in which the current flowing through the vacuum apparatus 2 increases to a predetermined value or more, and a load voltage drop rate (a value obtained by first-derivatizing the load voltage detection voltage). ), Load voltage decrease rate (secondary derivative of load voltage detection voltage), load current increase rate (value of load current first derivative), load current increase rate (load current secondary) Any one or a combination of phenomena in which the differentiated value) becomes equal to or greater than a set value is detected, and an abnormal discharge detection signal is output.

The control circuit 7 does not output an ON signal in a steady state where no abnormal discharge occurs, and immediately applies an ON signal to the short-circuiting semiconductor switch 4 only when receiving an abnormal discharge detection signal from the abnormal discharge detection circuit 6. It is also possible to apply a turn-on signal having a predetermined pulse width to the short-circuiting semiconductor switch 4 at a predetermined cycle in a steady state, thereby periodically turning on the short-circuiting semiconductor switch 4 and detecting abnormal discharge. When an abnormal discharge detection signal is received from the circuit 6, an on signal may be immediately applied to the shorting semiconductor switch 4.
The pulse width Ton of the ON signal given to the short-circuit semiconductor switch 4 by the control circuit 7 is approximately 50% to 100% of the series resonance period T, where T is the series resonance period of the resonance inductor 9 and the resonance capacitor 10. The time is in the range of%. Here, T = 10 μs and Ton = 7 μs. The reason for this will be described later.

  The reverse polarity voltage circuit 5 exhibits a predetermined voltage having the polarity shown in the figure suitable for extinguishing the abnormal discharge. When the short-circuit semiconductor switch 4 is turned on, the vacuum device 2 is supplied with a voltage having a polarity opposite to the normal voltage. Give. In general, since the shorting semiconductor switch 4 has a forward drop of several volts or more, even when the shorting semiconductor switch 4 is turned on, the voltage across the vacuum device 2 is applied to the forward drop of the shorting semiconductor switch 4 or the like. It does not drop below equal voltage values. Although the normal abnormal discharge disappears when the short-circuit semiconductor switch 4 is turned on, ions generated by the abnormal discharge remain immediately after that, so the load is still in a relatively low impedance state, and the low In this embodiment, the reverse polarity voltage circuit 5 quickly reverses the abnormal discharge voltage to cause abnormal discharge and further low voltage abnormal discharge. Extinguish. Therefore, it is preferable that the reverse polarity voltage circuit 5 provides a reverse polarity voltage having a width that prevents a minute current from continuing to flow.

  The constant current inductor 3 may be included in the DC power supply 1. Although not shown, when the abnormal discharge detection circuit 6 detects abnormal discharge, an abnormal discharge detection signal may be given to the DC power supply 1 to stop an inverter circuit (not shown) of the DC power supply 1. Further, a separate overcurrent detection means (not shown) may be provided in the DC power supply 1, and when an overcurrent occurs, an inverter circuit (not shown) of the DC power supply 1 may be stopped by a signal from the overcurrent detection means. In this case, since abnormal discharge can be eliminated without exchanging signals between the circuit on the short-circuiting semiconductor switch 4 side and the DC power supply 1, there is an advantage that it can be added later as an option of the DC power supply 1. In addition, there is an advantage that it can be retrofitted to the DC power source 1 as necessary in the case of a vacuum apparatus that easily causes abnormal discharge, or an application in which abnormal discharge should be avoided as much as possible, such as a sputtering apparatus for liquid crystal.

  Next, operation | movement of the abnormal discharge suppression apparatus 100 for vacuum devices of Embodiment 1 is demonstrated using FIG. 2 shows the voltage waveform and current waveform of each part, FIG. 2A shows the waveform of the reverse polarity voltage Vb applied to the vacuum device 2 from the reverse polarity voltage circuit 5, and FIG. 2C shows the bypass current Ib flowing, FIG. 2C shows the resonance current by the resonance circuit 11, and FIG. 2D shows the combined current flowing through the short-circuiting semiconductor switch 4 and the antiparallel diode 8. A negative current waveform indicated by diagonal lines is a current portion flowing through the antiparallel diode 8.

  If normal plasma discharge is generated in the vacuum device 2, a negative DC voltage, for example, a voltage of 600 V and a direct current Io are supplied from the DC power source 1 to the vacuum device 2 through the constant current inductor 3. At this time, the resonance capacitor 10 is charged to 600 V with the illustrated polarity. When an abnormal discharge occurs in the vacuum device 2 in this state, the abnormal discharge phenomenon is detected by the abnormal discharge detection circuit 6 and an abnormal discharge detection signal is sent to the control circuit 7. Along with this, the control circuit 7 gives an on signal to the shorting semiconductor switch 4 to turn it on. When the short-circuit semiconductor switch 4 is turned on, the direct current supplied from the direct current power source 1 to the vacuum device 2 through the constant current inductor 3 is bypassed and the vacuum device 2 is short-circuited, and at the same time from the reverse polarity voltage circuit 5 to FIG. A reverse polarity voltage Vb shown in (A) is applied to the vacuum apparatus 2. By applying the reverse polarity voltage Vb, the abnormal discharge generated in the vacuum apparatus 2 immediately disappears. The reverse polarity voltage Vb is set to an optimal value in advance, and the low voltage abnormal discharge state in which a minute current flows is also extinguished.

  On the other hand, when the shorting semiconductor switch 4 is turned on, the resonance capacitor 10 charged to the polarity shown in the figure passes through a closed circuit composed of the shorting semiconductor switch 4 and the resonance inductor 9 and has the positive polarity shown in FIG. A series resonance current Ir is passed in the direction of the arrow X. The series resonance current Ir is inverted in a half cycle, and this time, the negative series resonance current Ir is caused to flow in the arrow Y direction through a closed circuit including the antiparallel diode 8 and the resonance inductor 9. Then, the resonance capacitor 10 returns to the initial voltage of the illustrated polarity. This point will be explained in more detail. Considering that the short-circuit semiconductor switch 4 and the antiparallel diode 8 equivalently constitute a single semiconductor element, when the short-circuit semiconductor switch 4 is turned on, first, the short-circuit semiconductor switch 4 has a bypass current. A combined current is generated by adding a resonance current Ir (in the direction of the arrow X) having a positive half cycle of the resonance cycle to Ib. Next, when the resonance is reversed and becomes a negative cycle, it is considered that a current obtained by adding the positive bypass current Ib to the resonance current Ir in the negative direction (arrow Y direction) flows. When the value of the bypass current Ib becomes equal to the value of the negative half cycle resonance current Ir in the resonance cycle, the current flowing through the short-circuiting semiconductor switch 4 becomes zero, and the negative half cycle in the resonance cycle When the value of the resonance current Ir exceeds the value of the bypass current Ib, a current as shown by the oblique lines in FIG.

Therefore, the short-circuit semiconductor is controlled by the control circuit 7 during the period when the current flows through the antiparallel diode 8 from the time when the current flowing through the short-circuit semiconductor switch 4 becomes zero, that is, during the period when no current flows through the short-circuit semiconductor switch 4 If the switch 4 is turned off, the soft switching turn-off (zero current turn-off) can be performed, so that the turn-off loss can be reduced. Furthermore, as indicated by the oblique lines in FIG. 2D, the current of the antiparallel diode 8 also becomes zero according to the resonance waveform. Although the negative direction current of the resonance current Ir is slightly deformed from the resonance waveform, the short-circuiting semiconductor switch 4 does not cut off the positive-direction current shown in FIG. In order to prevent the second resonance current from flowing, it is desirable that the pulse width of the ON signal is approximately not less than half the resonance period T and not more than one period T. Assuming that the series resonance frequency of the resonance inductor 9 and the resonance capacitor 10 is 100 kHz, the resonance period T is 10 μs. Therefore, an example of the pulse width Ton of the ON signal to the shorting semiconductor switch 4 is 7 μs. It is reasonable to be. As is clear from the above, it is important to select values for the resonance inductor 9 and the resonance capacitor 10 so that there is a period in which the value of the resonance current Ir exceeds the bypass current Ib.
When the current flowing through the antiparallel diode 8 becomes zero and the antiparallel diode 8 becomes non-conductive, an overvoltage is applied to both ends of the short-circuiting semiconductor switch 4 through the reverse polarity voltage circuit 5 by the inductance action of the constant current inductor 3. This voltage is also applied to the resonance circuit 11 including the resonance inductor 9 and the resonance capacitor 10 at the same time. The resonance capacitor 10 is charged and the voltage is increased with the polarity shown in FIG. Limit the applied overvoltage. That is, at this time, the resonance capacitor 10 also functions as a snubber capacitor.

  When an IGBT is selected as the short-circuiting semiconductor switch 4, turn-on can be speeded up by devising a drive circuit such as overdrive, but the turn-off characteristic depends greatly on the characteristics of the semiconductor element used, and it is difficult to speed up by the drive circuit. It is. According to the first embodiment, it is possible to achieve a reduction in loss at turn-off, which is not good for semiconductor elements such as IGBTs, so that the repetition frequency can be set to several tens of kHz.

  Next, a modified example of the first embodiment will be described. Although the circuit configuration is as shown in FIG. 1, the control circuit 7 has a function of generating an ON signal having a predetermined cycle and a predetermined ON pulse width, and the ON signal and the abnormal discharge detection circuit described above. 6 has a function of ORing the abnormal discharge detection signal from 6 separately. Therefore, in a state where no abnormal discharge has occurred, the control circuit 7 periodically turns on the ON signal by adding it to the shorting semiconductor switch 4 and periodically applies the reverse polarity voltage from the reverse polarity voltage circuit 5 to the vacuum device 2. The occurrence of abnormal discharge is suppressed by applying the voltage to. In this case, the vacuum device 2 periodically applies the reverse polarity voltage from the reverse polarity voltage circuit 5 at an arbitrary frequency lower than the series resonance frequency (100 kHz) of the resonance inductor 9 and the resonance capacitor 10, for example, at a repetition frequency of 20 kHz. You may apply to.

  If an abnormal discharge occurs on the way, the short-circuit semiconductor switch 4 is immediately turned on when the occurrence of the abnormal discharge is detected without waiting for the application of the next periodic reverse polarity voltage as described above. Turn on and apply reverse polarity voltage to the vacuum device 2 to quickly extinguish the abnormal discharge. If the repetition frequency at which the reverse polarity voltage is periodically applied to the vacuum apparatus 2 is high to some extent (for example, 20 kHz or more), even if abnormal discharge occurs in the middle, if the time of 50 μsec or less passes, The periodic reverse polarity voltage is applied to the vacuum device 2, and the abnormal discharge can be extinguished by the reverse polarity voltage.

  Although not shown in FIG. 1, the operation at the time of abnormal discharge can be improved by connecting a diode (not shown) in series and in the same direction with the shorting semiconductor switch 4 to the conductor L. In the diode, when an abnormal discharge occurs in the vacuum device 2, the charging charge of the resonance capacitor 10 passes through the resonance inductor 9 during the delay time of the abnormal discharge detection circuit 6 and the delay time of the short-circuit semiconductor switch 4. It serves to prevent direct discharge to the vacuum device 2, but is not necessarily a necessary diode. In this case, it operates in an open loop that does not detect the current flowing through the vacuum device 2, and the control circuit 7 turns on and off the shorting switch 4 at a predetermined frequency, and applies a reverse polarity voltage to the vacuum device 2 each time. The resonance circuit 11 resonates at a resonance frequency higher than the predetermined frequency to turn off the short-circuiting semiconductor switch 4 in a soft switching manner.

[Embodiment 2]
With reference to FIG. 3, a second abnormal discharge suppressing device 200 for vacuum apparatus according to another embodiment 2 of the present invention will be described. 3, the same symbols as those used in FIG. 1 indicate members having the same names. In the second embodiment, the reverse polarity voltage circuit 5 is directed in the same direction as the conduction direction of the reverse voltage capacitor 5 </ b> A connected in series to the anode side of the short circuit semiconductor switch 4 and the short circuit semiconductor switch 4. It consists of a diode 5B connected in parallel to the voltage capacitor 5A and a charger 5C that charges the reverse voltage capacitor 5A. The charger 5C charges the reverse voltage capacitor 5A to a predetermined voltage in the illustrated polarity, and the diode 5B functions to prevent reverse charging of the reverse voltage capacitor 5A. The predetermined voltage is not limited to this, but is, for example, 20% or less of the steady discharge voltage of the vacuum apparatus 2. Usually, in the vacuum device, the plasma discharge voltage of the vacuum device 2 is 200 to 800V, so the output voltage of the charger 5C is set to 40 to 160V according to the plasma discharge voltage, and the short-circuit semiconductor switch 4 It is charged to 40 to 160 V with a cycle shorter than the switching cycle. The output voltage of the charger 5C may be a fixed value or may be a voltage that is automatically changed according to the plasma discharge voltage of the vacuum device 2.

  In the abnormal discharge suppressing device 200 for vacuum device, the charging power for the reverse voltage capacitor 5 </ b> A is also supplied from the surge voltage absorption circuit 12. The surge voltage absorption circuit 12 absorbs and limits the surge voltage due to the wiring inductance between the short-circuiting semiconductor switch 4 and the vacuum device 2, and further supplements the charging voltage of the reverse voltage capacitor 5A of the reverse polarity voltage circuit 5. It is. The surge voltage absorption circuit 12 is connected in parallel with the vacuum device 2 and is composed of a backflow prevention diode 12A, a surge absorption capacitor 12B, and a power supply voltage holding capacitor 12C connected in series with each other. A DC input terminal of the inverter circuit 13 is connected to both ends of the surge absorbing capacitor 12B. The AC output terminal of the inverter circuit 13 is connected to both ends of the reverse voltage capacitor 5 </ b> A through the insulating transformer 14 and the rectifier 15. The surge absorbing capacitor 12A absorbs an overvoltage surge that occurs when the antiparallel diode 8 is turned off. Normally, a resistor (not shown) is connected in parallel to the surge absorbing capacitor 12A to consume the surge voltage rise. In the second embodiment, power corresponding to the surge voltage rise is supplied to the inverter circuit 13. Is converted into high frequency power by the rectifier 14 and further converted into direct current by the rectifier 14 and supplied to the reverse voltage capacitor 5A as charging power. Both ends of the power supply voltage holding capacitor 12C are directly connected to the output terminal of the DC power supply 1, and are charged to the power supply voltage. The surge absorbing capacitor 12B is charged by a surge voltage higher than the power supply voltage. The surge voltage absorbing circuit 12 not only performs a surge absorbing function, but also constitutes an auxiliary charging circuit that performs auxiliary charging of the reverse voltage capacitor 5A together with the inverter circuit 13, the insulating transformer 14, and the rectifier 15.

Since the main operation of the abnormal discharge suppression device for vacuum device 200 according to the second embodiment is substantially the same as the operation of the abnormal discharge suppression device for vacuum device 100, a description thereof will be omitted, but a periodic on signal from the control circuit 7 or When the short circuit semiconductor switch 4 is turned on in response to the ON signal due to the occurrence of abnormal discharge, the charging voltage of the reverse voltage capacitor 5A of the reverse polarity voltage circuit 5 is discharged to the vacuum device 2 through the short circuit semiconductor switch 4, The abnormal discharge is instantaneously extinguished by reverse-biasing the electrodes (not shown) of the vacuum apparatus 2.
As described above, when the current flowing through the anti-parallel diode 8 becomes zero and the anti-parallel diode 8 becomes non-conductive, an overvoltage is generated by the inductance action of the constant current inductor 3, and this voltage is the resonance of the resonance circuit 11. The capacitor 10 for charging is charged, and the capacitor 12A for absorbing surge is charged by a surge voltage higher than the output voltage of the DC power supply 1. Therefore, the voltage applied to both ends of the shorting semiconductor switch 4 is limited.

[Embodiment 3]
With reference to FIG. 4, an abnormal discharge suppression device 300 for a vacuum apparatus according to Embodiment 3 of the present invention will be described. In FIG. 4, the same symbols as those used in FIG. 3 indicate members having the same names. The vacuum device abnormal discharge suppression device 300 is different from the vacuum device abnormal discharge suppression device 200 in that the vacuum device abnormal discharge suppression device 200 includes the surge voltage absorption circuit 12, the inverter circuit 13, the insulation transformer 14, and the rectifier 15. The charging circuit is removed and a diode circuit composed of two diodes 16 and 17 is connected instead. Unlike the vacuum device abnormal discharge suppressing device 200, the diodes 16 and 17 are used to charge the reverse voltage capacitor 5A of the reverse polarity voltage circuit 5 with a half wave of the resonance current. The diode 16 is connected between the connection point between the short-circuit semiconductor switch 4 and the reverse voltage capacitor 5A and one end of the resonance circuit 11 with the cathode side facing the short-circuit semiconductor switch 4. Between the connection point of the resonant circuit 11 and the diode 16 and the positive electrode of the DC power source 1, the anode side is connected to the positive electrode of the DC power source 1. In this embodiment, a diode circuit composed of the diodes 16 and 17 cooperates with the antiparallel diode 8 and the resonance circuit 11 to constitute an auxiliary charging circuit.

  When the shorting semiconductor switch 4 is turned on by an ON signal from the control circuit 7, the resonance capacitor 10 of the resonance circuit 11 discharges electric charge in the direction of the arrow X through the added diode 16 and causes the resonance current Ir to flow. Then, when the voltage of the resonance capacitor 10 is inverted and the resonance current Ir flows in the direction of the arrow Y, the half-wave current of the resonance current Ir flowing through the antiparallel diode 8 is blocked by the diode 16, and the reverse voltage capacitor 5A. And flows through the diode 17 to charge the reverse voltage capacitor 5A to the polarity shown. In the experiment, this circuit can reduce the required power of the charger 5C by 70% or more, which is very effective. On the other hand, when the shorting semiconductor switch 4 is turned on, the charging voltage of the reverse voltage capacitor 5A is discharged through the shorting semiconductor switch 4 and the vacuum device 2 to reverse bias the vacuum device 2 as in the above embodiment. To eliminate the abnormal discharge promptly. In the reverse polarity voltage circuit 5, the current flowing through the vacuum device 2 once becomes zero, and when the ions generated by the abnormal discharge disappear, the impedance of the vacuum device 2 increases, until a minute current does not flow again. It is preferable to apply a reverse polarity voltage to the vacuum device 2.

  Also in the third embodiment, the direction of the bypass current Ib flowing through the wiring L and the resonance current Ir having the negative half cycle of the resonance cycle (in the arrow Y direction) is opposite to each other, as in the case of the abnormal discharge suppressing device 100 for vacuum device. Therefore, actually, a current obtained by subtracting the resonance current Ir having a negative half cycle of the resonance period from the bypass current Ib flows through the short-circuit semiconductor switch 4. Therefore, when the value of the bypass current Ib becomes equal to the value of the resonance current Ir in the negative half cycle of the resonance cycle, the current flowing through the short-circuiting semiconductor switch 4 becomes zero, and the negative half cycle of the resonance cycle. When the value of the resonance current Ir exceeds the value of the bypass current Ib, the current indicated by the diagonal lines in FIG. Therefore, the short-circuiting semiconductor switch 4 becomes a soft switching turn-off in which the current naturally becomes zero, and the turn-off negative loss is minimized. Therefore, the short-circuiting semiconductor switch 4 can be turned on / off at a high frequency of several tens of kHz.

As described above, the short-circuit semiconductor switch 4 has been described as a single semiconductor switch in the present invention. However, since the sputtering apparatus is several hundred volts, when an IGBT, a MOSFET, or the like is used as the short-circuit semiconductor switch 4, it is about 1200V. This can be realized by using one withstand voltage. However, in the case of an electron beam apparatus, since it is about 10 kV, it can be realized by connecting a plurality of IGBTs and MOSFETs having a withstand voltage of about 1200 V in series. In this case, the forward drop of the short-circuiting semiconductor switch 4 becomes large, so that the function of the reverse polarity voltage circuit 5 becomes more effective.
Further, when the internal diode of the IGBT or MOSFET to be used is used as the anti-parallel diode 8, if the reverse recovery characteristic of the internal diode is bad, so-called recovery time is long, a surge voltage is generated when the internal diode is turned off. In this case, a reverse current prevention diode (not shown) is connected in the same direction in series with the short-circuiting semiconductor switch 4 so that the internal diode does not work effectively, and the external switch having an excellent reverse recovery characteristic is connected across the series circuit. It is desirable to connect a diode and use it as the antiparallel diode 8.

Furthermore, if necessary, a IGBT or MOSFET connected in parallel with a snubber circuit made up of a resistor, a capacitor or the like may be used as a short-circuiting semiconductor switch.
Further, although the constant current inductor 3 is described as being connected to the output terminal of the DC power supply 1, it may be a filter inductor of the DC power supply 2. Although not shown, a secondary winding is provided in the constant current inductor 3, the AC power of the secondary winding is rectified by a rectifier circuit and converted to DC power, and the DC power is converted to a reverse voltage of the reverse polarity voltage circuit 5. It may be supplied as a part of the charging power of the capacitor 5A. In this case, the constant current inductor 3 having a secondary winding (not shown) constitutes an auxiliary charging circuit together with the rectifier circuit and the resistor.
When the DC power supply 1 is equipped with a transformer, the charger 5C is provided with an additional winding in the transformer (not shown), and a rectifier is connected to the additional winding to obtain the necessary DC power. A simple configuration may be used.
When the voltage of the vacuum device 2 exceeds a predetermined set voltage, power loss at the time of turn-on of the short-circuiting semiconductor switch becomes large. Therefore, if necessary, a voltage interlock circuit that does not turn on the short-circuiting semiconductor switch is provided. You may have.

It is a figure which shows the abnormal discharge suppression apparatus 100 for vacuum devices which is 1st Embodiment which concerns on this invention. It is a wave form diagram for explaining abnormal discharge suppression device 100 for vacuum devices which is a 1st embodiment concerning the present invention. It is a figure which shows the abnormal discharge suppression apparatus 200 for vacuum devices which is the 2nd Embodiment which concerns on this invention. It is a figure which shows the abnormal discharge suppression apparatus 300 for vacuum devices which is the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... Vacuum apparatus 3 ... Inductor for constant current 4 ... Semiconductor switch for short circuit 5 ... Reverse polarity voltage circuit 5A ... Reverse voltage capacitor 5B ... Diode 5C ... Charger 6 ... Abnormal discharge detection circuit 7 ... Control circuit 8 ... Antiparallel diode 9 ... Resonant inductor 10 ... Resonant capacitor 11 ... Resonant circuit 12 ... Surge voltage absorption circuit 13 ... Inverter circuit

Claims (2)

A vacuum device;
A DC power source for supplying power to the vacuum device;
A short-circuiting semiconductor switch connected in parallel to the DC power source and the vacuum device;
An anti-parallel diode connected in parallel with the short-circuiting semiconductor switch so as to have a polarity opposite to the polarity of the short-circuiting semiconductor switch;
A control circuit for turning on the short-circuiting semiconductor switch when an abnormal discharge occurs in the vacuum device;
A reverse polarity voltage circuit connected in series with the shorting semiconductor switch and applying a reverse polarity voltage to the vacuum device when the shorting semiconductor switch is turned on;
In the abnormal discharge suppression device for a vacuum device comprising:
A resonance circuit comprising a resonance inductor and a resonance capacitor connected in series with each other and connected in parallel with the short-circuiting semiconductor switch and the antiparallel diode;
The resonant inductor and the resonant capacitor of the resonant circuit, exceeds the value of the bypass current Ib the value of the opposite polarity of the resonant current flows through the semiconductor switch the short and bypass current Ib flowing through the semiconductor switch the short Each value is set so that a period exists,
When the shorting semiconductor switch is turned on, the resonance circuit resonates, the bypass current Ib and the resonance current flow through the shorting semiconductor switch, and the resonance having a polarity opposite to the polarity of the bypass current Ib. As the value of the current becomes equal to the value of the bypass current Ib and the value of the current flowing through the shorting semiconductor switch becomes zero, the value of the bypass current Ib exceeds the value of the bypass current Ib. An abnormal discharge suppressing device for a vacuum apparatus, wherein the short-circuiting semiconductor switch is turned off during a period in which no current flows through the short-circuiting semiconductor switch, which is equal to a period in which the diode flows. In claim 1,
For a vacuum device, characterized in that a diode for preventing the charging charge of the resonance capacitor from being directly discharged to the vacuum load through the resonance inductor is connected in series and in the same direction as the short-circuit semiconductor switch . Abnormal discharge suppression device.

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