JP3548753B2 - Control device and method for power supply for glow discharge load - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a DC power supply used in an apparatus utilizing glow discharge, such as a sputtering apparatus, in which a high impedance state until the start of a glow discharge and a smooth transition from the start of the glow discharge to a normal glow discharge are continuously and smoothly controlled. The present invention relates to a control device and a control method which can be performed at a high speed. The present invention further relates to a control device and a method for extinguishing arc discharge and returning to normal glow discharge when arc discharge occurs.
[0002]
[Prior art]
In describing the control device and method of the glow discharge load power supply of the present invention, functions required for a DC power supply used in a device using glow discharge such as a sputtering device will be described.
[0003]
FIG. 1 shows current-voltage characteristics of glow discharge. To start glow discharge, a voltage higher than the discharge start voltage must be applied. When a voltage higher than the discharge start voltage is applied, glow discharge starts, and the voltage decreases rapidly as the current density increases. Into an area called the early glow. When the current density further increases, the current enters a region called a normal glow where the voltage does not change much. When the current density further increases, the voltage enters an abnormal glow region where the voltage also increases, and finally reaches an arc discharge region.
[0004]
In the case of a sputtering apparatus, the discharge starting voltage is 1000 V to 1600 V, and the voltage of the normal glow is several hundred volts. On the other hand, at the time of arc discharge, the voltage becomes 100 V or less, and an excessive current flows. The excessive current damages a target material of the sputtering apparatus or the like, and further affects a product manufactured by the sputtering apparatus, resulting in a decrease in product quality and a decrease in yield.
[0005]
Therefore, as a function of a DC power supply used in a sputtering apparatus utilizing this glow discharge,
(1) At the start of discharge, a voltage higher than the discharge start voltage can be output, and the output impedance at that time must be large;
(2) When the glow discharge starts and the steady operation is started, the output impedance is as small as possible, and after the start of the glow discharge, the voltage is quickly reduced so as not to enter the abnormal glow region.
(3) When an arc discharge occurs, the arc discharge is quickly detected, the output voltage is set to zero V or a small reverse voltage to extinguish the arc discharge, and after a certain period of time, the arc discharge is output again to return to a normal glow discharge. Is required. The applicant has devised a DC power supply having such a function, and has already filed a patent application (Japanese Patent Application No. 2001-50315).
[0006]
FIG. 2 shows a circuit diagram of a DC power supply for a sputtering apparatus according to the above application. The DC power supply for the sputtering apparatus includes a primary rectifier 12 for converting AC to DC, an output control switching element 14 composed of, for example, a field effect transistor (FET) having a variable ON time and ON voltage, and a primary coil 16. , Primary-side capacitors 18, duty control switching elements 20 and 22, transformers 24 and 26, secondary-side rectifiers 28 and 30, secondary-side coils 32 and 34, and secondary-side capacitors 36. 38 is a sputtering device.
[0007]
The duty control switching elements 20 and 22 are operated at the maximum duty at the start of discharge, at 50% duty during normal operation, and at a phase difference of 90 degrees, and at 0% duty when output is cut off. Power is supplied to each of the rectifiers 28 and 30. The output control switching element 14 controls the power supplied to the duty control switching elements 20 and 22 by changing the ON time and the ON voltage.
[0008]
When the duty control switching elements 20 and 22 are operated by pulse width modulation (PWM) and a phase difference of 90 ° is provided between them, the current ripple is reduced only when the duty is 50%. During normal operation, this state is always maintained. The output of the DC power supply is controlled by the output control switching element 14 instead of the duty control switching elements 20 and 22.
[0009]
With the above-described control, the DC power supply can easily increase the voltage at the start of discharge and increase the output impedance, and can prevent the occurrence of overcurrent at the start of discharge. Further, at the time of steady operation, the output impedance can be reduced, and the generated undesired arc discharge can be eliminated.
[0010]
[Problems to be solved by the invention]
However, in the above-described DC power supply, at the stage of transition to the steady operation in the normal glow region after the start of discharge, the gate voltage of the output control switching element (FET) 14 is increased to reduce the impedance of the switching element, that is, the ON voltage. If the rate of reduction is too fast, the output current will increase rapidly, leading to arc discharge. Conversely, if the rate is too slow, the transition time to steady operation will take too long.
[0011]
In addition, if the duty of the duty control switching element is changed from the maximum duty to the 50% duty too quickly at the stage of transition to the steady operation in the normal glow region after the start of the discharge, the output voltage becomes too low and the glow discharge occurs. Is stopped.
[0012]
Therefore, an object of the present invention is to provide a control device and a method for such a DC power supply for a glow discharge load that, after the start of a glow discharge, transition to a steady operation continuously, promptly, and without generating an overcurrent. It is in.
[0013]
It is still another object of the present invention to provide a control device and a control method for extinguishing arc discharge and returning to normal glow discharge when arc discharge occurs.
[0014]
[Means for Solving the Problems]
In the present invention, an amplification circuit that sets a maximum current value determined from the rating of the load device as a set value, amplifies the difference only when the detected value exceeds the set value as compared with the detected value of the output current of the DC power supply, and outputs the amplified difference. The output current of the amplifying circuit is subtracted from the output of the constant current regulator for controlling the ON time of the output control switching element, so that the output current is controlled so as not to be an overcurrent. The glow discharge start is detected on condition that the glow discharge start current exceeds several tens mA to several hundred mA and the output voltage drops to the initial glow voltage or the normal glow voltage of several hundred V, and output control is performed based on the detection signal. The on-state voltage of the switching element for switching at a proper speed to make a transition to the steady operation state, and then the duty control switch By shifting the duty of the glow element from the maximum duty to the 50% duty by a ramp function, it is possible to shift to the steady operation continuously, promptly and without generating an overcurrent after the start of the glow discharge of the glow discharge load. .
[0015]
Also, if the output voltage is abnormally low compared to the rated voltage (about 10% of the rated voltage), or if the output current is abnormally large (120 to 150% of the rated current) compared to the rated current, arc discharge occurs. Is determined to have occurred, the output voltage is set to zero volts by turning off the duty control switching element to extinguish the arc discharge, and the glow discharge is returned to normal glow discharge by turning it on again after a certain time.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
3 and 4 show circuit examples of the control device according to the present invention. 3 shows the main circuit section 10 including a DC power supply, and FIG. 4 shows the control circuit section 50.
[0017]
The configuration of the DC power supply of the main circuit unit 10 in FIG. 3 is the same as that shown in FIG. 2, and the same elements are denoted by the same reference numerals. The main circuit section 10 includes a gate driver (GD) 40 for driving the output control switching element 14, a gate driver (GD) 42 for driving the duty control switching elements 20 and 22, and a shunt resistor for detecting the output current of the DC power supply. 44, voltage dividing resistors 46 and 48 for detecting the output voltage of the DC power supply.
[0018]
In FIG. 3, the symbols A, B, C, D, E, and F are given for easy understanding of the connection relation with the circuit of FIG.
[0019]
4 includes a pulse width modulation (PWM) control circuit 52 for controlling the gate driver 40, a duty control circuit 54 for controlling the gate driver 42 , a constant power regulator (AWR) 56, and a constant current regulator ( An ACR 58, a current limiter proportional amplifier 60, an on-voltage control circuit 62, a timer 64, and a detector 66 are mainly provided.
[0020]
The duty control circuit 54 includes a maximum duty setting switch 80, a 50% duty setting switch 82, a voltage generation circuit 84 having a ramp function, and a PWM control circuit 86.
[0021]
The on-voltage control circuit 62 includes a high-impedance setting switch 76, a high-impedance release switch 78, and a voltage generation circuit 74 having a ramp function.
[0022]
The detector 66 is a circuit for taking in an output current and an output voltage from a DC power supply and performing output voltage detection, output current detection, glow discharge start detection, and arc discharge detection. FIG. 5 shows details of the detector 66. The output current from the shunt resistor 44 is detected by the current detection circuit 100, and the output voltage from the voltage dividing resistor 46 is detected by the voltage detection circuit 102. The glow discharge start detection is performed under the condition that the output current exceeds the glow discharge start current of several tens mA to several hundred mA, and that the output voltage drops to the initial glow voltage of several hundred V or the normal glow voltage. It is configured. Further, in arc discharge, the output voltage is abnormally low compared to the rated voltage (about 10% of the rated voltage), or the output current is abnormally large compared to the rated current (120 to 150% of the rated current). In such a case, it is determined that an arc discharge has occurred. The glow discharge start detection flip-flop 104 and the arc discharge detection flip-flop 106 are configured to be reset by a start signal.
[0023]
The glow discharge start detection signal output from the detector 66 is input to the ON voltage control circuit 62 and the timer 64, while the arc discharge detection signal output from the detector 66 is output to the gate driver 42 for the duty control switching element. Is output.
[0024]
The output current value and the output voltage value detected by the current detector 100 and the voltage detector 102 in the detector 66 are input to the multiplier 68, the output power is calculated by the multiplier 68, and the constant power controller 56 Is the detection signal. The constant power adjuster 56 outputs an output signal so that the difference between the detection signal and the power set value becomes zero, and the signal becomes the set value of the constant current adjuster 58. The constant current controller 58 outputs a constant current control signal such that the set value and the output current detection value I _det from the current detection circuit 100 of the detector 66 become equal.
[0025]
On the other hand, the subtractor 59 in the input side of the proportional amplifier 60 includes a current limiter setting I _max is the maximum current value determined from the rating of the load device, and the detected output current detection value I _det by the detector 66 Input, I _max is subtracted from I _det , and input to proportional amplifier 60. In the proportional amplifier, the input value is multiplied by the gain and output. On the output side of the proportional amplifier 60, a clamp circuit 70 for clamping a negative output to zero is provided. In the present invention, the subtractor 59, the proportional amplifier 60, and the clamp circuit 70 are referred to as an amplifier circuit. In this amplifier circuit, when the detected value I _det exceeds the set value I _max , a value obtained by multiplying the difference by a gain is input to the subtractor 72, and the detected value I _det does not exceed the set value I _max. Is input to the subtractor 72 on the output side of the constant current regulator 58.
[0026]
The subtractor 72 subtracts the output signal of the amplifier circuit from the constant current control signal of the constant current regulator 58, and the subtracted signal is input to the PWM control unit 52. The PWM control unit 52 determines the ON time of the output control switching element 14 by comparing this signal with, for example, a triangular wave. Accordingly, the voltage on the input side of the duty control switching elements 20 and 22 is controlled, and the output voltage of the DC power supply is controlled, so that the current is controlled and the power is also controlled.
[0027]
As described above, the detector 66 is a circuit for taking in the output current and the output voltage and detecting the output voltage, the output current, the glow discharge start, and the arc discharge. Here, when the start of glow discharge is detected, a signal from the flip-flop 104 is input to the on-voltage control circuit 62. The on-voltage control circuit 62 switches from the high impedance mode to the high impedance release mode, and the gate voltage generation circuit 74 raises the generated gate voltage by the ramp function during the time T1. As a result, the gate voltage of the output control switching element 14 is controlled to increase during the time T1, and to be turned on in the saturation region. As a result, the impedance of the switching element for output control, that is, the ON voltage, decreases with a ramp function.
[0028]
Also, after a time T1 measured by the timer 64 from the start of glow discharge detection by the detector 66, the duty control circuit 62 changes the duty of the duty control switching elements 20, 22 from the maximum duty to the 50% duty by a ramp function. Works.
[0029]
FIG. 6 shows changes in the output voltage and output current of the DC power supply from the start of glow discharge to the transition to steady operation in the control method according to the present invention in relation to load characteristics. Hereinafter, the operation will be described with reference to FIGS.
[0030]
At the start of discharging, the high-impedance switch 76 of the on-voltage control circuit 62 is turned on to increase the output impedance, and the gate voltage of the output control switching element 14 is reduced to increase the impedance, that is, the on-voltage. In order to make the output voltage higher than in the normal operation, the maximum duty switch 80 of the duty control circuit 54 is turned on, and the duty of the duty control switching elements 20 and 22 is operated at the maximum duty. The straight line 1 in FIG. 6 shows the relationship between the output current and the output voltage of the DC power supply when the output voltage is 1600 V and the output impedance is 20 kΩ, for example. The intersection A between the straight line and the load characteristic is the operating point immediately after the start of the glow discharge. If the discharge voltage is 300 V, the output current is 65 mA.
[0031]
Next, the detector 66 detects that the output current is equal to or higher than the set value (50 mA in FIG. 6) and the output voltage is equal to or lower than the set value (500 V in FIG. 6), and the glow discharge is started. When this is detected, the on-voltage control circuit 62 switches the mode so as to release the high impedance state of the switching element 14, and increases the gate voltage by the ramp function at the time T1. Impedance or ON voltage of the switching element 14 decreases when the gate voltage increases, the output current increases, eventually reaches the current limiter setting I _max. The straight line 2 in FIG. 6 shows the relationship between the output current and the output voltage of the DC power supply at this time. The intersection B between the straight line and the load characteristic corresponds to the current limiter set value.
[0032]
When the output current exceeds the current limiter setting I _max, which the difference between the current limiter setting I _max and the current detection value I _det by the operation of the proportional amplifier 60 and gain-multiplied is, subtractor 72 in the constant current regulator 58 , And the value is input to the PWM control device 52. The PWM control device reduces the output voltage by reducing the on-time of the switching element 14. As a result, the relationship between the output current and the output voltage of the DC power supply moves in the direction of the straight line 3 in FIG. 6, and the current decreases. On the other hand, since the on-voltage control circuit 62 keeps reducing the on-voltage of the switching element 14, the relationship between the output current and the output voltage of the DC power supply further moves in the direction of the straight line 4 in FIG. Here, the output voltage decreases again by the operation of the proportional amplifier 60, and moves in the direction of the straight line 5 in FIG. After all, this operation is performed continuously, and as a result, it moves from the straight line 2 to the straight line 6 with the point B as a base point. By the above operation, after the start of the glow discharge, the operation is shifted to the steady operation state continuously and quickly without overcurrent.
[0033]
Next, when a time T1 elapses after the start of glow discharge detection, the output of the duty control circuit 54 switches from the maximum duty to the 50% duty by the ramp function of the time T2. At this time, since the steady operation has already been started, the output is kept constant by the operation of the constant power regulator 56 and the constant current regulator 58 even if the output voltage is going to decrease by this switching.
[0034]
As described above, it is possible to shift to the steady operation continuously and promptly after the start of the glow discharge and without generating an overcurrent.
[0035]
When the glow discharge load shifts to the arc discharge during the steady operation, the detector 66 determines whether the output voltage of the DC power supply is abnormally low (about 10% of the rated voltage) as compared with the rated voltage, or the output current. Is abnormally large (120 to 150% of the rated current) compared to the rated current, an arc discharge detection signal is input to the gate driver 42, and the output is obtained by turning off the duty control switching elements 20 and 22. The arc discharge is extinguished by setting the voltage to zero V, and the glow discharge is returned to a normal glow discharge by turning on again after a predetermined time.
[0036]
In the above embodiments, the case where the output control switching element is an FET has been described. However, instead of the FET, an insulated gate bipolar transistor in which a MOSFET and a bipolar transistor are combined into one chip may be used.
[0037]
Although two duty control switching elements are used, three or more switching elements can be used.
[0038]
【The invention's effect】
As described above, according to the control device and the method of the present invention, in the DC power supply for a glow discharge load, it is possible to shift to the steady operation continuously, promptly, and without generating an overcurrent after the start of the glow discharge. it can. Further, when an arc discharge is generated, it is possible to detect the arc discharge and promptly shift to the glow discharge.
[Brief description of the drawings]
FIG. 1 is a diagram showing current-voltage characteristics of glow discharge.
FIG. 2 is a circuit diagram of a DC power supply for a sputtering apparatus.
FIG. 3 is a circuit diagram of a circuit unit including a DC power supply.
FIG. 4 is a circuit diagram of a control circuit unit.
FIG. 5 is a detailed diagram of a detection unit.
FIG. 6 is a diagram showing changes in the output voltage and output current of the DC power supply from the start of glow discharge to the transition to steady operation in the control method according to the present invention in relation to load characteristics.
[Explanation of symbols]
Reference Signs List 10 Main circuit section 12 Primary side rectifier 14 Output control switching element 16 Primary side coil 18 Primary side capacitor 20, 22 Duty control switching element 24, 26 Transformer 28, 30 Secondary side rectifier 32, 34 Secondary side Coil 36 Secondary capacitors 40, 42 Gate driver 44 Shunt resistor 46, 48 Voltage dividing resistor 50 Control circuit unit 52 PWM control circuit 54 Duty control circuit 56 Constant power regulator 58 Constant current regulator 60 Proportional amplifier 62 On-voltage control circuit 64 Timer 66 Detector

Claims (11)

A DC power supply for supplying main power to the glow discharge load device, a plurality of secondary rectifiers for supplying DC, a maximum duty at the start of discharge of the glow discharge load device, and 50% during normal operation. A plurality of duty control switching elements for supplying power to each of the secondary rectifiers, which are operated at a duty and a phase difference of 90 degrees, and power supplied to the duty control switching elements. For controlling the output of the DC power supply by controlling, in a DC power supply control device comprising an ON-time and ON-voltage variable output control switching element,
A constant current regulator that outputs a constant current control signal for controlling the on time of the output control switching element,
The maximum current value determined from the rating of the load device as a current limiter set value, compared with the detected value of the output current of the DC power supply, amplifying the difference only when the detected value exceeds the current limiter set value An output amplifier circuit,
A subtraction circuit that subtracts the output of the amplifying circuit from the output of the constant current regulator so that the output current of the DC power supply does not become an overcurrent .
From the output current and output voltage of the DC power supply, a detection circuit that detects at least the start of glow discharge,
An on-voltage control circuit that controls the on-voltage of the output control switching element to decrease at a predetermined speed with a detection signal indicating the detection of the start of glow discharge,
When the ON voltage of the output control switching element decreases, the impedance of the output control switching element decreases, and the output current of the DC power supply increases, so that the glow discharge load device is continuously, promptly, and A DC current control device for shifting from a glow discharge start state to a steady operation state without generating an overcurrent. The output control switching element is a field-effect transistor or an insulated gate bipolar transistor , and the reduction of the on-voltage is performed by the on-voltage control circuit by increasing the gate voltage of the transistor by a ramp function. The control device for a DC power supply according to claim 1 , wherein: The detection circuit for detecting the start of glow discharge, wherein the output current exceeds the glow discharge start current, and detects the start of glow discharge on the condition that the output voltage has decreased to the previous glow voltage or the normal glow voltage. The DC current control device according to claim 1 or 2 , wherein Claims the glow discharge load device, after the transition to the steady operation state, the duty of the plurality of duty control switching element, characterized in that it comprises a duty control circuit for shifting a ramp function to a 50% duty from the maximum duty Item 4. The control device for a DC power supply according to item 1, 2, or 3 . The detection circuit further detects the occurrence of arc discharge from the output current and output voltage of the DC power supply, and, when the occurrence of arc discharge is detected, turns off the duty control switching element to output the output voltage of the DC power supply. The DC power supply according to any one of claims 1 to 4, wherein the arc discharge is extinguished by setting the voltage to zero V, and after a predetermined time, the duty control switching element is turned on again to return to a steady operation state. Control device. The control device for a DC power supply according to any one of claims 1 to 5, wherein the glow discharge load device is a sputtering device. A DC power supply for supplying main power to the glow discharge load device, a plurality of secondary rectifiers for supplying DC, a maximum duty at the start of discharge of the glow discharge load device, and 50% during normal operation. A plurality of duty control switching elements for supplying power to each of the secondary rectifiers, which are operated at a duty and a phase difference of 90 degrees, and power supplied to the duty control switching elements. By controlling, a control method of a DC power supply including an on-time and an on-voltage for controlling an output of the DC power supply, and a variable output control switching element.
The maximum current value determined from the rating of the load device as a current limiter set value, compared with the detected value of the output current of the DC power supply, and only when the detected value exceeds the set value, amplifies the difference and outputs the amplified value. By subtracting the amplified output from the constant current control signal for controlling the ON time of the control switching element, the output current is controlled so as not to be an overcurrent, and at the same time, the glow discharge is started from the output current and the output voltage. And the detection signal reduces the on-voltage of the output control switching element at a predetermined speed, thereby lowering the impedance of the output control switching element and increasing the output current of the DC power supply. A method for controlling a DC power supply, wherein the method is shifted to an operation state. The output control switching element is a field-effect transistor or an insulated gate bipolar transistor , and the reduction of the ON voltage is performed by the ON voltage control device by increasing the gate voltage of the transistor by a ramp function. The method of controlling a DC power supply according to claim 7, wherein 9. The method of controlling a DC power supply according to claim 7 , wherein the duty of the plurality of duty control switching elements is shifted from a maximum duty to a 50% duty by a ramp function after shifting to a steady operation state. By judging that arc discharge has occurred when the output voltage is abnormally low compared to the rated voltage or when the output current is abnormally large compared to the rated current, the duty control switching element is turned off. 10. The method of controlling a DC power supply according to claim 7, wherein the output voltage is set to zero V, the arc discharge is extinguished, and the glow discharge is returned to a normal glow discharge by turning on again after a predetermined time. The method according to any one of claims 7 to 10, wherein the glow discharge load device is a sputtering device.

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