KR20040034262A - Current Limiting Circuit for Use in Plasma Processing Apparatus - Google Patents

Abstract

The present invention relates to a current limiter used in a plasma processing apparatus.

In the power supply device for generating a direct current or alternating voltage, and a current limiter used in a plasma processing device operating by receiving an input current from the power supply device, a cutoff switch for cutting off the supply of the input current is one side of the power supply device. Is connected in series, a current detector is connected in series between the cutoff switch and the plasma processing apparatus, and receives a current value detected from the current detector on one side and a reference current value on the other side. A comparator for sending a cutoff signal to turn on the cutoff switch is connected in series with the current detector and the cutoff switch, and function as a short circuit when the plasma processing apparatus is in a normal state, and when the short circuit occurs, The current limiter to suppress the sudden increase of the disconnect switch And a current limiter connected in series between the current detector and the current detector.

According to the present invention, it is possible to efficiently suppress the generation of the transient current even in a short circuit occurrence state without causing distortion of the input current waveform even in a steady state.

Description

Current Limiting Circuit for Use in Plasma Processing Units {Current Limiting Circuit for Use in Plasma Processing Apparatus}

The present invention relates to a current limiter used in a plasma processing apparatus. More particularly, the present invention relates to a current limiter used at an input terminal of a plasma processing apparatus to suppress a sudden increase in output current for a predetermined time until the power is cut off in a short circuit due to an arc generated in the plasma processing apparatus.

In general, plasma is a state in which molecules constituting a material are energized by the outside to be extremely activated to decompose some of gas molecules in a neutral state, and are composed of ions and electrons. It is a generic term for ions with and electrons with negative charge. This practical use of plasma has been steadily promoted for a long time. For example, neon lamps use glow discharge of plasma and arc welding uses arc discharge of plasma. Plasma can make new materials that were difficult to manufacture by synthesis or processing of existing materials, and can replace pollution-producing or difficult processes.

The plasma is largely divided into a high temperature plasma and a low temperature plasma. In particular, low-temperature plasma obtains a low-density plasma by applying a high voltage across two electrodes interposed between gases, and decomposes a hardly decomposable gas using high physical energy and high chemical activity of the plasma, or It is utilized for the application | cleaning of the surface of (Polymer), or coating an effective film | membrane on the surface.

However, in a plasma apparatus using low temperature plasma, a short circuit phenomenon occurs frequently due to an arc at the output terminal of the power supply due to the characteristics of high voltage electric discharge. At this time, if the excessive current supply due to the short-circuit phenomenon to the load device in which the workpiece is installed is not blocked as quickly as possible, damage to the workpiece or the load device may result in a significant deterioration in the quality of the workpiece.

In order to minimize excessive current supply due to such a short circuit, when the output current of the output stage of the plasma processing apparatus is normally detected and the output current increases by more than a predetermined value, it is determined that a short circuit phenomenon occurs due to an arc in the output stage and the power is cut off quickly. I'm using the method. However, such a method typically detects a short circuit, and a time delay of several milliseconds typically occurs to turn off the power supply for supplying power to the plasma processing apparatus. Therefore, the output current of the plasma processing apparatus increases rapidly during the time required to shut down the power source, which adversely affects the workpiece of the load apparatus.

1 is a simplified block diagram of a conventional plasma processing system for suppressing a sudden increase in output current due to a short circuit phenomenon.

Conventional plasma processing system is a power supply 110 for supplying power to the plasma processing apparatus 100 and the plasma processing apparatus 100, a cutoff switch connected in series between the plasma processing apparatus 100 and the power supply 110 ( 150, an inductor (L) 140, and a comparator 130 for comparing the output current with the current detector 120.

The current detector 120 which detects the input current I in order to determine whether a short circuit phenomenon due to an arc occurs in the plasma processing apparatus 100 in front of the input terminal of the plasma processing apparatus 100 so as to rapidly increase the value of the input current I. Is connected.

The current value detected by the current detector 120 is input to the comparator 130 through one terminal, and the preset reference current value Reference to determine whether a short is connected to the other terminal of the comparator 130. Is input. Accordingly, the comparator 130 determines whether a short circuit occurs in the plasma processing apparatus 100 by comparing the current value input from the current detector 120 with the reference current value. When the comparator 130 determines that a short circuit has occurred in the plasma processing apparatus 100, the comparator 130 transmits an output cutoff signal (Signal) to the cutoff switch 150 to turn off the cutoff switch 150 to the plasma processing apparatus 100. Turn off the power supply to).

However, this method has a problem in that a time delay occurs until the power supply is cut off after detecting the short circuit as described above. Therefore, a method of adding an appropriate value inductor 140 to the front end of the current detector 120 is used to suppress a situation in which the input current I increases rapidly during this time delay. As shown in FIG. 1, the addition of the inductor 140 suppresses a sudden increase in the input current I output from the power supply 110 due to the characteristic of the inductor 140 suppressing a sudden increase or decrease of the current. Can be.

However, the method described with reference to FIG. 1 has an advantage of suppressing a sudden increase in the input current I in the short circuit caused by the arc in the inductor 140, but one inductor 140 in the normal state without the arc. It functions as an unnecessary element of. In addition, since the performance of suppressing a sudden increase in the input current I in a short circuit condition is proportional to the inductance size of the inductor 140, it is common to use an inductor 140 having a large inductance. However, the use of the inductor 140 having a large inductance causes a problem of greatly distorting the waveform of the current output from the power supply 110 in the normal state. In other words, if the size of the inductance is reduced, the performance of suppressing a sudden increase in the current in a short circuit occurs is deteriorated. If the size of the inductance is increased, a problem of inducing a steady current in a steady state occurs. Further, when the waveform of the voltage output from the power supply device 110 is a pulse wave, as shown in FIG. 1, the distortion of the output waveform becomes more severe.

In order to solve the above-described problems, the present invention, the current used in the input terminal of the plasma processing apparatus to suppress the sudden increase in the output current for a predetermined time until the power is cut off in the short circuit caused by the arc generated in the plasma processing apparatus The purpose is to present a limiter.

1 is a block diagram schematically showing a conventional plasma processing system for suppressing a sudden increase in output current due to a short circuit phenomenon;

2 is a simplified block diagram of a plasma processing system according to a preferred embodiment of the present invention for suppressing a sudden increase in input current due to a short circuit phenomenon;

3 is a circuit diagram of a plasma processing system using a current limiter according to a first embodiment of the present invention;

4 is a graph showing a change in input current in a short circuit generation state according to a first embodiment of the present invention;

5 is a circuit diagram of a plasma processing system using a current limiter according to a second embodiment of the present invention;

6 is a graph showing a change in input current in a short circuit generation state according to a second embodiment of the present invention;

7 is a circuit diagram of a plasma processing system using a current limiter according to a third embodiment of the present invention;

8 is a graph showing a change in input current in a short circuit generation state according to a third embodiment of the present invention;

9 is a circuit diagram of a plasma processing system using a current limiter according to a fourth embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100, 320: plasma processing device 110: power supply device

120: current detector 130: comparator

140: inductor 150: disconnect switch

200, 310, 510, 710: current limiter 520: diode bridge

720, 930, 940: Saturated Transformer 722: Magnetization Graph

In order to solve the above problems, the present invention provides a power supply device for generating a direct current or alternating voltage, and a current limiter used for a plasma processing device operating by receiving an input current from the power supply device. A cutoff switch for cutting off the supply of the input current is connected in series to one side of the power supply device, and a current detector for detecting the input current is connected in series between the cutoff switch and the plasma processing apparatus and connected to one side. Receives a current value detected from the current detector, the other side receives a predetermined reference current value, the comparator for transmitting a cutoff signal for turning off the cutoff switch when a predetermined condition is met the current detector and the It is connected in series with the disconnect switch, the plasma processing apparatus is normal A short circuit, and a current limiter for suppressing a sudden increase in the input current for a predetermined time when the plasma processing apparatus is in a short circuit state, is connected in series between the disconnect switch and the current detector. A current limiter for use in a plasma processing apparatus is provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in using the reference numerals for the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

2 is a simplified block diagram of a plasma processing system for suppressing a sudden increase in input current due to a short circuit phenomenon according to a preferred embodiment of the present invention.

The plasma processing system of FIG. 2 is almost identical to the structure described in FIG. However, as described with reference to FIG. 1, the inductor 140 is removed and a predetermined current limiter 200 is used to remove the distortion of the input current I due to the inductor 140 in the normal state.

On the other hand, the plasma processing system using the current limiter 200 according to the preferred embodiment of the present invention does not function as an element constituting the circuit in the normal state, but functions only in a short circuit occurrence state. It functions as an element to perform. Therefore, the current limiter 200 does not cause any distortion of the input current I to the plasma processing apparatus 100 in the normal state, but suppresses a sudden increase in the input current I in the short circuit state. have. The current limiter 200 according to the preferred embodiment of the present invention will be described in more detail with reference to FIGS. 3 to 9.

3 is a circuit diagram of a plasma processing system using a current limiter 310 according to an embodiment of the present invention.

The power supply unit 300 supplies a 1000 V DC power, and the load resistance R2 of the plasma processing apparatus 320 has a value of 20 Ω. Therefore, the magnitude of the input current I1 provided from the power supply unit 300 is 50A. The current limiter 310 has a current source of 100A because the voltage V2 is 100V and the resistor R1 is 1Ω.

First, the current I1 of 50 A flows from the power supply unit 300 to the plasma processing apparatus 320 side, and the inductor L in the current limiter 310 flows to I2 of 100 A, which is the maximum allowable value of I1. Therefore, in the steady state where I1 is smaller than I2, forward current flows as much as I2-I1 = 50A in the diode D, so that node A and node B operate as if they are short-circuited, and thus the circuit element in the current limiter 310 is operated. They do not play any role in the circuit path from the power supply to the load stage.

However, when a short circuit occurs in U1 due to an arc generated in the plasma processing apparatus 320, the value of I1 flowing into the plasma processing apparatus 320 rapidly increases. Therefore, if I1 is increased to be equal to I2, no further current flows in the diode D in the forward direction, and thus the diode D is removed from the circuit, and I1 equal to I2 is equal to diode D. Instead it flows through the inductor L in the current limiter 310. That is, the inductor L does not play any role in the circuit path of the plasma processing apparatus 320 in the power supply unit 300 when I1 is smaller than I2, and is inserted in series in the path from the situation where I1 is equal to I2. Will be working.

However, in the inductor L, a current of 100 A flows in a steady state, and when the load current rapidly increases, the inductor L starts to suppress the sudden increase in current by the "Lenz's law". In other words, the inductor L of the current limiter 310 acts as a current limiting device in a short circuit occurrence state. Therefore, the I1 applied to the plasma processing apparatus 320 is suppressed by the inductor L, and the increase is gradually increased and gradually converges to the normal state 100A. At this time, the current I1 = I2 flowing in the inductor L is increased by the following equation.

(L: Inductance value, V _L is the voltage value across the inductor)

4 is a graph showing a change in input current in a short circuit generation state according to an embodiment of the present invention.

Referring to the graph of FIG. 4 with reference to FIG. 3, it can be seen that a current of 50 A is constantly input into the plasma processing apparatus 320 in the normal state. However, as shown in the graph of FIG. 4, even when a short circuit occurs in the plasma processing apparatus 320 at a time of 5 mV, it can be seen that the current value is constantly limited at about 100A. That is, it can be seen that the phenomenon in which the current can be greatly increased instantaneously by the inductor L of the current limiter 310 is suppressed. Therefore, since the current applied to the plasma processing apparatus 320 by the current limiter 310 does not increase rapidly even in a short-circuit state compared to the normal state, it is possible to protect the load device of the plasma processing apparatus 320. . Of course, such a rapid current limiting function of the current limiter 310 will be sufficient to be performed only up to the point of time when the cutoff switch 150 is operated by the comparator 130.

5 is a circuit diagram of a plasma processing system in which a current limiter 510 is used in accordance with another embodiment of the present invention.

The power supply unit 500 of FIG. 5 is an AC power supply having a frequency (FREQ) of 50 KHz, and has an RMS value of 1,000 V and a waveform characteristic of a sine wave. Of course, the inductor L, the resistors R1 and R2, the voltage V2 of the current limiter 510, the value 50A of I1 and the value 100A of I2 are the same as in FIG.

First, the current I1 having a peak value of 50 A flows from the power supply unit 500 to the plasma processing apparatus 320 side, and the inductor L in the current limiter 510 is set such that 100 A of allowable maximum I1 flows. In a steady state where the absolute value of I1 is smaller than I2, voltages are applied to the diodes D1, D2, D3, and D4 in the diode bridge 520 in the forward direction, so that node A and node B are short-circuited. The circuit elements in the current limiter 510 do not play any role in the circuit path from the power supply 500 to the load terminal.

However, in the short circuit generation state, as in the case of FIG. 3, since the resistance of the plasma processing apparatus 320 becomes almost zero, the current I1 applied from the power supply unit 500 increases rapidly. Therefore, if I1 is increased to be equal to I2, the voltage is not applied to the diode bridge 520 in the forward direction anymore, so the diode bridge 520 is removed from the circuit, and I1 equal to I2 is equal to the diode D. Instead it flows through the inductor L in the current limiter 510. That is, the inductor L does not play any role in the circuit path of the plasma processing apparatus 320 in the power supply unit 500 when I1 is smaller than I2, and is inserted in series in the path from the situation where I1 is equal to I2. Will be working. At this time, the inductor L serves as an element for suppressing a sudden increase in current as described with reference to FIG. 3 to protect the load device of the plasma processing apparatus 320.

6 is a graph illustrating a change in input current in a short circuit generation state according to another exemplary embodiment of the present invention.

Referring to the graph of FIG. 6 with reference to FIG. 5, in a steady state, a constant sine wave (I = −sin 2 π ft = −sin (2π × 5 × 10 ⁴ t)) is within the range of ± 50 A by the plasma processing apparatus 320. It can be seen that it is flowing. However, as shown in the graph of FIG. 4, even if a short circuit occurs in the plasma processing apparatus 320 at a time of 100 μs, the current value is constantly limited by the current limiter 510 within a range of about ± 100 A. It can be seen.

7 is a circuit diagram of a plasma processing system using a current limiter 710 according to another embodiment of the present invention.

Referring to FIG. 7, it can be seen that a saturable cored transformer 720 is used as the current limiter 710. Here, a saturable transformer is a kind of transformer that can saturate a core by flowing a DC current over a winding of one side of the transformer, and when saturated, the core exhibits an air core characteristic and has a very low magnetization inductance. When not in use, the transformer has a very large magnetizing inductance and operates like a normal transformer. Saturable transformer 720 according to an embodiment of the present invention is installed in a saturated state in the opposite direction of the normal load current. That is, the saturable transformer 720 of FIG. 7 operates in an inverse saturation state (S1) in the normal section of the hysteresis curve 722. Here, it is assumed that the magnetization inductance when the saturable transformer 722 is not saturated is sufficiently large compared to the value of L1.

First, since the saturable transformer 720 is in a saturation state and has a very low magnetization inductance, the saturable transformer 720 operates as a short circuit in a circuit path formed by the power supply unit 700 and the plasma processing apparatus 320. Therefore, the current I1 applied from the power supply unit 700 passes through the left winding of the saturable transformer 720 in a state such as a short circuit and flows to the plasma processing apparatus 320.

However, when a short circuit occurs in U2 of the plasma processing apparatus 320, the I1 applied from the power supply unit 700 rapidly increases. Therefore, since a large amount of current suddenly flows into the left winding (control winding) of the saturable transformer 720, the saturable transformer 720 breaks the saturation state of the magnetization graph 722 and removes the curve ① of the short circuit generation period. As a result, it begins to operate as a general transformer 720 with increased magnetization. That is, since the magnetization inductance of the saturable transformer 720 increases, I1 tries to flow through L1.

On the other hand, when the saturable transformer 720 reaches the positive saturation state S2 along the magnetization degree graph 722, on the contrary, it attempts to progress to the inverse saturation state S1 along the curve ②. Therefore, the current detector 120 and the comparator 130 described in FIG. 2 should be designed to cut off the power by operating the cutoff switch 150 before the saturable transformer 720 reaches the positive saturation state S2. will be.

On the other hand, the current limiter 710 described in FIG. 7 and the unipolar power supply unit 300, 700 for supplying the power for the plasma processing of (+) or (-) together with the current limiter 310 described in FIG. Used together.

8 is a graph showing a change in input current in a short circuit generation state according to another embodiment of the present invention.

Referring to the graph of FIG. 8 with reference to FIG. 7, graph ① shows an input current input to the plasma processing apparatus 320, and graph ② shows a magnetization of the saturable transformer 720.

First, since the saturable transformer 720 appears to be shorted in the normal state, the current I1 has a constant value. However, when a short circuit occurs in U2 at the point of 5 의 of FIG. 8, since flux increases as shown in the graph ②, the saturation state of the saturable transformer 720 is released to act as a general transformer to act as a current transformer 710. A sudden increase in the input current is suppressed within the limit set at 100A. That is, when the saturable transformer 720 is switched to a general transformer, the magnetization inductance is increased, so that the input current flows through the secondary winding of the transformer, so that a sudden increase in the input current is suppressed by the inductor L.

However, as shown in FIG. 8, when the saturable transformer 720 reaches the positive saturation state S2 at a point of about 7 μs, the saturable transformer 720 is shown in FIG. 7. As shown in graph 722, the degree of magnetization begins to decrease along the curve ②. Therefore, since the input current starts to increase again in the opposite direction as in the case of reverse saturation (S1), as shown in the graph ① of FIG. 8, the input current increases rapidly again at the point of 7 ㎲. Therefore, as described above, the saturable transformer 720 will have to be turned off before reaching the positive saturation state (S2).

9 is a circuit diagram of a plasma processing system in which current limiters 910 and 920 are used in accordance with another embodiment of the present invention.

The circuit diagram of FIG. 9 is similar to that of FIG. 7, except that an AC power source (VMAG = 1000V, FREQ = 1KHz) is applied from the power supply unit 900 and that two current limiters are connected in series. That is, if FIG. 7 is a unidirectional current limiter for a DC power supply, FIG. 9 shows a bidirectional current limiter for an AC power supply.

First, in the normal state, since the saturable transformer A 930 and the saturable transformer B 940 set to the reverse saturation state S1 as shown in FIG. 7 appear to be short-circuited, the input current I1 is the plasma processing apparatus 320. ) Just flows into. However, if a short circuit occurs in U3, the magnetization inductance of saturable transformer A 930 or saturable transformer B 940 increases, and the secondary winding and inductor of saturable transformer A 930 and saturable transformer B 940 are increased. Since the input current flows through (L), a sudden increase in the input current is suppressed by the inductor (L).

On the other hand, the current limiter 910 and 920 described in FIG. 9 is a bipolar power supply unit for supplying the power for plasma processing in which (+) and (-) are alternately applied together with the current limiter 510 described in FIG. 500, 900).

On the other hand, in the case of the bidirectional current limiter as shown in FIG. 9, it will be appreciated that the changing state of the input current waveform in the short circuit occurrence state is the same as that described with reference to FIG. 8.

The above description is merely illustrative of the present invention, and those skilled in the art to which the present invention pertains may various modifications without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed herein are not intended to limit the present invention but to describe the present invention, and the spirit and scope of the present invention are not limited by these embodiments. It is intended that the scope of the invention be interpreted by the following claims, and that all descriptions within the scope equivalent thereto shall be construed as being included in the scope of the present invention.

As described above, the inductor used in the conventional current limiting circuit operates in the normal state, causing a problem of distorting the waveform of the input current. However, the current limiting circuit according to the present invention operates as if it is shorted in the normal state. This has the advantage of not damaging the waveform at all.

In addition, by implementing a variety of current limiting circuits for each type of power applied from the power supply unit (AC and DC), it is possible to use both AC and DC power in the plasma processing apparatus, and load devices by efficiently suppressing the generation of transient current. There is an effect that can improve the quality of the product generated from.

Claims (11)

In the power supply device for generating a direct current or alternating voltage, and the current limiter used in the plasma processing device that operates by receiving an input current from the power supply device, A cutoff switch for cutting off the supply of the input current to the plasma processing apparatus is connected in series to one side of the power supply apparatus, A current detector for detecting the input current is connected in series between the cutoff switch and the plasma processing apparatus; A comparator for receiving a current value detected from the current detector on one side and a preset reference current value (Reference) on the other side, and transmitting a cutoff signal for turning off the cutoff switch when a predetermined condition is met. Connected in series with the current detector and the disconnect switch, The plasma processing apparatus functions as a short circuit when the plasma processing apparatus is in a normal state, and a current limiter for suppressing a sudden increase in the input current for a predetermined time when the plasma processing apparatus is in a short circuit generating state is provided with the cutoff switch and the current detector. A current limiter for use in a plasma processing apparatus, characterized in that connected in series between. The method of claim 1, The current limiter may include a series of inductors, resistors, and power supplies, in which a diode is connected in series with the power supply and the plasma processing device, and in series with a cathode side of the diode when the power supply generates a DC voltage. The diode is connected in series with both ends of the diode, and in the normal state, the diode functions as a short, and in the short-circuit state, the inductor operates as a device for limiting a sudden increase in the input current. Current limiters used in plasma processing apparatus. The method of claim 2, And the diode is connected in a direction opposite to the flow of the input current in the steady state and the short circuit occurrence state. The method of claim 1, In the current limiter, when the power supply generates an alternating voltage, the power supply is connected in series between two diodes D1 and D2 of a diode bridge, and the plasma processing device is connected between two diodes D3 and D4. Is connected in series, and an inductor, a resistor, and a power supply are connected in series between two diode bridges D2 and D4. In the normal state, the AC voltage is forwarded to all diodes D1 to D4 of the diode bridge. And the diode bridge functions as a short, and in the short circuit occurrence state, the AC voltage is not applied to the diode bridge in a forward direction, so that the inductor operates as an element for limiting a sudden increase in the input current. Current limiters used in plasma processing equipment. The method of claim 1, And the predetermined condition is a state in which the detected current value starts to exceed the reference current value. The method of claim 1, The predetermined time period is a current limiter used in the plasma processing apparatus, characterized in that it takes a period from the time of detecting the occurrence of a short circuit to the transition of the cutoff switch to the off state. The method of claim 1, In the current limiter, when the power supply generates a DC voltage, one winding of the saturable transformer set to the reverse saturation state S1 is connected in series with the power supply and the plasma processing apparatus, and The other winding is connected in series with an inductor, a resistor and a power supply in series. In the normal state, the saturable transformer and the inductor function as a short, and in the short circuit state, the saturable transformer and the inductor are connected to each other. A current limiter for use in a plasma processing apparatus, characterized in that it acts as an element to limit the rapid increase. The method according to claim 1 or 7, The current detector and the comparator have a function of turning off the cutoff switch before the saturable transformer escapes the inverse saturation state S1 and reaches a positive saturation state S2 along the magnetization curve ①. A current limiter for use in a plasma processing apparatus. The method of claim 1, In the current limiter, when the power supply generates an alternating voltage, windings of one side of the saturable transformer A and the saturable transformer B set to reverse saturation state S1 are connected in series with the power supply device and the plasma processing device. The other winding of the saturable transformer A is connected in series with a series of inductors, resistors, and power supplies, and is connected in series with the other winding of the saturable transformer B, and in the normal state, the saturable transformer A, the inductor And the saturable transformer B functions as a short, and the saturable transformer A, the inductor, and the saturable transformer B operate as elements that limit a sudden increase in the input current in the short circuit occurrence state. Current limiters used in processing units. The method of claim 9, In the short circuit generating state, the saturable transformer A operates when a positive alternating voltage is generated in the power supply device, and the saturable transformer B operates when a negative alternating voltage is generated in the power supply device. A current limiter used in a plasma processing apparatus, characterized in that. The method according to claim 1 or 9, The current detector and the comparator turn off the disconnect switch before the saturable transformer A or the saturable transformer B escapes the inverse saturation state S1 and reaches a positive saturation state S2 along the magnetization curve ①. A current limiter for use in a plasma processing apparatus, characterized in that it has a function to make it possible.