JP2733454B2 - Abnormal discharge suppression device for film forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal discharge suppressing apparatus for a film forming apparatus, and more particularly to an abnormal discharge suppressing apparatus for a film forming apparatus for suppressing abnormal discharge of plasma generated by plasma DC sputtering.

[0002]

2. Description of the Related Art Factors that affect the generation of slight abnormal discharge (minority arc) generated during film formation such as plasma DC sputtering are the arrangement of a magnet portion, the state of a cathode surface, a method of manufacturing an insulating portion, and the like. There are various methods such as target quality, manufacturing method, edge shape, erosion, surface corrosion state, uniformity of surface activation, temperature control method, type of sputter gas, pressure control, and flow method.

[0003] In the abnormal discharge, first, the minority arc is generated, and then the energy is concentrated due to the temperature rise of the minority arc portion, and the state shifts to most of the abnormal discharge (majority arc).

When this majority arc occurs, the transfer of high-energy electrons, the rise in the target surface temperature, the abnormal distribution of the gas pressure, etc., cause the target material to evaporate due to the positive feedback, causing the local plasma density to rise. This triggers a large arc called a racetrack arc.

The effects of the minority arc, the majority arc, and the racetrack arc include not only physical destruction of the target, but also adverse effects such as generation of pinholes in a memory or an optical surface during film formation due to fragments. .

[0006] If there is a small oxidized portion caused by the destruction on the target, the electron density in that portion is increased, and the stored energy of the plasma itself and the absorption of the energy supplied from the DC power supply absorb the energy near the small oxidized portion. The impedance drops sharply and the absorbed energy is converted to heat. This heat evaporates the material, increasing the partial pressure and increasing the electron density.

[0007] Therefore, when a large abnormal discharge as described above occurs, it is necessary to release the heat near the target and the sample, diffuse the gas, and then turn on the power again.

FIG. 2 shows an example of a conventional film forming power supply circuit and an abnormal discharge suppressing mechanism.

First, the power supply circuit will be described. Commercial power supply 1
The AC voltage from 13 is first full-wave rectified by a rectifier circuit 114, then smoothed by a smoothing filter 115 and converted into a DC voltage with less pulsation, and then converted by an inverter circuit 11.
6. In the inverter circuit 116, the DC voltage is converted into an AC voltage at a frequency according to the output signal from the power supply drive circuit 112, and the AC voltage is
The voltage is transformed at 17 and is converted again to direct current at the rectifier circuit 118. This DC voltage is applied to a DC reactor (Ldc) 11
9. After being smoothed by the capacitor (C0) 120, it is sent to the load 126 (discharge portion for film formation).

As described above, the AC power supplied from the commercial power supply 113 is finally converted into DC power and
6 is output.

Next, the abnormal discharge suppressing mechanism will be described.
The output voltage detector 124 and the output current detector 125 are detectors for monitoring the state of the load 126. Output signals of the output voltage detector 124 and the output current detector 125 are sent to the automatic control circuit 109.

An abnormal discharge current setting device 103 is a device for setting a threshold value for abnormal discharge.
The signal of No. 5 and the signal of the abnormal discharge current setting device 103 are sent to the comparison circuit 105 for comparison. The output current detector 125 is set based on the signal level set by the abnormal discharge current setter 103.
Is normal mode when the output signal level is low, and abnormal mode when the output signal level is high. The output signal of the comparison circuit 105 is transmitted to the stop circuit 110 and the time limit circuit 111.

In the normal mode, the automatic control circuit 109 for automatically controlling the power supply output includes the stop circuit 110 and the timed circuit 1
The signal is output to the power supply drive circuit 112 without being affected by the signal from the power supply 11. As described above, the inverter circuit 1 has a frequency according to the output signal from the power supply drive circuit 112.
The AC conversion at 16 is performed, and the output is supplied to the load 126 as described above.

If an overcurrent flows through the load 126 due to abnormal discharge (minority arc or majority arc) while the automatic control circuit 109 performs constant current automatic control, the output signal of the output current detector 125 is output. The level becomes higher than the signal level of the abnormal discharge current setting device 103, and an abnormal mode is set.

In the abnormal mode, the stop circuit 110 and the time limit circuit 111 operate according to the output signal of the comparison circuit 105. Then, the stop signal from the stop circuit 110 is transmitted to the power supply drive circuit 112 via the automatic control circuit 109, and turns off the switch element of the inverter circuit 116. In this way, the load 126
The power being supplied to is cut off.

In the abnormal mode, between the time when the power is turned off and the time when the operation is restarted, the energy retained in the DC reactor (Ldc) 119 and the capacitor (C0) 120 is consumed by the load 126 and the voltage of the load 126 is reduced. It is necessary to take an interval until becomes zero. The time interval circuit 111 takes this interval, and the interval is usually set to 10 to 50 ms.

When the above-mentioned interval elapses from the occurrence of the abnormal mode, the time-limit circuit 111 outputs a time-limit end signal to the stop circuit 1.
Then, the output signal of the stop circuit 110 is changed from the stop signal to the restart signal at this time. Thus, the automatic control circuit 10
9 and the power supply drive circuit 112 are restarted, and the constant-current automatic control in the normal mode is restarted.

That is, when the abnormal discharge occurs, the conventional abnormal discharge suppressing mechanism quickly turns off the switch element of the inverter circuit 116 to cut off the power supply to the load 126, and switches the inverter circuit 116 after a predetermined interval. The element is turned on again and the load 126 is turned on.
The power supply to the power supply is restarted.

[0019]

[Problems to be Solved by the Invention] In recent years, applications such as reactive sputtering using a DC power supply have been increasing due to the progress of film forming technology, but the accuracy and quality of films required for film forming are increasingly increasing. It is becoming more advanced.

Under such circumstances, in the above-mentioned conventional abnormal plasma discharge suppression method, the time until the extinction of the abnormal arc is on the order of several tens of milliseconds. Since it grows to an arc and damages the target and the substrate, there is a problem that the growth of a high-quality film is hindered, and the accuracy, quality, yield, and the like of the film are reduced.

The present invention has been made in view of the above-mentioned problems. In an abnormal discharge state, the stored energy of the plasma itself and the energy supplied from the DC power supply are expressed in μs.
By discharging in the order of (microseconds), abnormal discharge is suppressed in the state of minority arc, and even in the normal mode of operation, repeated pulses of reverse polarity voltage are continuously generated to prevent abnormal discharge. It is an object of the present invention to provide an abnormal discharge suppressing device for a film forming apparatus that can perform the method.

[0022]

Means for Solving the Problems To solve the above problems, an abnormal discharge suppressing device for a film forming apparatus according to claim 1 (1).
Then, reactors (21, 22) and capacitors (2
0) and a high-frequency resonance circuit (40) including a switch element (23), and abnormal discharge in the load (26) based on an output value of power supplied from the high-frequency resonance circuit (40) to the load (26). An abnormal discharge detection circuit (abnormal discharge current measuring device 3, comparison circuit 5, output current detector 25) for detecting the occurrence of occurrence of a switching element, and a drive cycle of the switch element are set based on a resonance cycle of the high-frequency resonance circuit (40). Drive cycle setting circuit (frequency selector 4, oscillation circuit 6,
The pulse generation circuit 7) and the driving cycle setting circuit (4,
A drive circuit (pulse drive circuit 8) for turning on / off the switch element (23) based on a drive cycle set by (6, 7), and the abnormal discharge detection circuit (3, 5, 25). When the abnormal discharge is detected, the drive circuit (8) turns ON the switch element (23) for only one cycle based on the drive cycle set by the drive cycle setting circuit (4, 6, 7). The high frequency resonance circuit (40) performs a resonance operation of only one cycle, thereby applying a reverse polarity voltage pulse to the load (26);
The abnormal discharge is suppressed in a short period of the one cycle.

According to a second aspect of the present invention, there is provided an abnormal discharge suppressing apparatus for a film forming apparatus according to the first aspect of the present invention, wherein the current flowing through the load (26) before the occurrence of the abnormal discharge is reduced. A DC reactor (19) having a sufficiently large inductance to supply the same current again after the application of the reverse polarity voltage pulse was used.

According to a third aspect of the present invention, there is provided the abnormal discharge suppressing apparatus for a film forming apparatus according to the first or second aspect, wherein the load (26) is maintained even when the load (26) is in a normal state. 26), the application of the reverse polarity voltage pulse was repeated to suppress occurrence of abnormal discharge.

[0025]

According to the first aspect of the invention, when an abnormal discharge occurs in the load, the reverse polarity voltage can be applied to the load immediately and within a very short time of the order of microseconds. The accumulated energy of the discharged plasma itself and the energy supplied from the DC power supply
(Microseconds).
Therefore, it is possible to suppress the abnormal discharge before the minority arc generated at the beginning of the abnormal discharge grows into the majority arc,
Majority arc damages target and substrate,
The problem of hindering the growth of a high-quality film and reducing the accuracy, quality, yield, and the like of the film can be solved.

According to the second aspect of the present invention, in the abnormal discharge suppressing apparatus for a film forming apparatus according to the first aspect, a current equivalent to the current flowing to the load before the occurrence of the abnormal discharge is reduced after the abnormal discharge is suppressed. Can be supplied immediately to the load.

According to the third aspect of the present invention, in the abnormal discharge suppressing apparatus for a film forming apparatus according to the first or second aspect, the application of the reverse polarity voltage pulse to the load is performed even when the load is normal. Since the repetition is performed, occurrence of abnormal discharge can be prevented.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an electric circuit in which an embodiment of the abnormal discharge suppressing apparatus for a film forming apparatus according to the present invention is applied to a film forming apparatus.

The DC power supply 30 is the same as the DC power supply 30 described in the prior art.
The load 26 is a DC power supply corresponding to 13 to 118 or a general DC power supply, and the load 26 is a part where DC discharge for film formation is performed.

An abnormal discharge suppressing device 1 for a film forming apparatus according to the present embodiment.
Are the switching element drive unit 2, the high-frequency resonance circuit 40,
It comprises a DC reactor (Ldc) 19 for smoothing and an output current detector 25.

The high-frequency resonance circuit 40 for applying a reverse polarity voltage pulse to the load 26 includes a capacitor (C) 20, a reactor (L1) 21, a reactor (L2) 22, and a switching element 23. The switching element driving unit 2 that outputs a signal for turning ON / OFF the switching element 23 inside includes an abnormal discharge current setting unit 3, a comparison circuit 5, a frequency selector 4, an oscillation circuit 6, a pulse generation circuit 7, and a pulse drive. It consists of a circuit 8.

The DC current supplied from the DC power supply 30 is
DC reactor (L
dc) 19, the current of the load 26 is detected by the output current detector 25.

As in the conventional example, the output current detector 25
And the signal from the abnormal discharge current setting device 3 are sent to the comparison circuit 5 for comparison. When the output signal level of the output current detector 25 is lower than the signal level of the abnormal discharge current setting device 3, the normal mode is set. If it is high, the mode is abnormal.

In this embodiment, in both the normal mode and the abnormal mode, a reverse polarity voltage is applied to the load 26 by turning on / off the switching element 23.

Hereinafter, ON / OFF of the switching element 23 will be described.
The application of the reverse polarity voltage pulse to the load 26 due to the OFF state will be described.

When the switching element 23 is turned on, free oscillation of the resonance frequency represented by F in the equation (1) occurs due to the capacitor (C) 20, the reactor (L1) 21 and the reactor (L2) 22.

[0038]

(Equation 1)

After the switching element 23 is turned on, the high-frequency resonance circuit 40 performs a resonance operation of only one cycle of the resonance frequency F. Immediately thereafter, the switching element 23 is turned off.

As a result, a capacitor (C) 20 is connected to the load 26 as shown in FIG.
The voltage of the opposite polarity proportional to the voltage Vc held just before the ON of No. 3 is applied.

The peak value of the voltage of the opposite polarity applied to the load 26 is Vr in the equation (2).

[0042]

(Equation 2)

The approximate time Tr during which a voltage of opposite polarity is applied to the load 26 when the switching element 23 is turned on is expressed by the following equation (3).

[0044]

(Equation 3)

At the end of the resonance operation of only one cycle (when the switching element 23 is OFF), the capacitor (C) 20
Returns to the voltage before the switching element 23 was turned on.

The capacitor (C) in the high-frequency resonance circuit 40
20, reactor (L1) 21, reactor (L2) 2
2, the values of C, L1, and L2 are such that the value of Tr is 5 to 10 μm.
It is selected to be on the order of s microseconds.

Hereinafter, a description will be given of how the opposite polarity voltage pulse is repeatedly generated in the normal mode according to the present embodiment.

The oscillation circuit 6 oscillates the original oscillation at the frequency set by the frequency selector 4, and the pulse generation circuit 7 generates a pulse signal according to the original oscillation (at intervals of an integral multiple of the period of the original oscillation). Then, the pulse signal is sent to the switching element 23 by the pulse drive circuit 8. Switching element 23
Is turned on by the input of the pulse signal, and turned off after twice the time of the Tr (after the period of the free vibration). The pulse length (pulse duration) generated by the pulse generation circuit 7 is the switching element 23 for the above time interval (Tr × 2).
Is set to be ON.

In the normal mode, the pulse generation circuit 7
Repeats the above-described pulse generating operation for driving the switching element without being affected by the signal from the comparison circuit 5. Therefore, in the normal mode, the pulse generation operation is performed every integer multiple of the frequency set in the frequency selector 4. , The reverse polarity voltage pulse of magnitude Vr is repeatedly applied to the load 26.

The manner of application of a reverse polarity voltage pulse to the load 26 when an abnormal mode occurs in this embodiment will be described below.

The switching element 23 is turned on in the normal mode.
If an abnormal discharge occurs during the OFF period and an overcurrent flows through the load 26, the output signal level of the output current detector 25 becomes an abnormal mode higher than the signal level of the abnormal discharge current setting unit 3, and the comparison circuit 5 Outputs an abnormal mode signal to the pulse generation circuit 7.

Upon receiving the abnormal mode signal, the pulse generation circuit 7 immediately generates a pulse and sets the switching element 23 to O
N, and the same time interval (T
r × 2) Turn off after the lapse of time.

Thus, when an overcurrent flows due to the occurrence of abnormal discharge or the like, immediately and for a very short time (T
A reverse polarity voltage of the magnitude of Vr can be applied to the load 26 during the order of microseconds (r order), and the energy stored in the plasma itself and the energy supplied from the DC power supply can be released.

After the application of the reverse voltage Vr, the load 2
6 begins to apply DC power to the DC reactor (Ldc) 19 at this time in order to supply again the same current as that flowing to the load 26 in the normal mode.
Uses a DC reactor having a sufficiently large inductance.

According to the method of the above embodiment, when an abnormal discharge occurs, a reverse polarity voltage can be applied to the load 26 for a very short time (on the order of microseconds of the above Tr). A minority arc can be prevented from growing into a majority arc. In addition, even in the normal mode of operation, the reverse polarity pulse voltage is repeatedly applied to the load 26, so that abnormal discharge can be prevented.

[0056]

According to the first aspect of the present invention, when an abnormal discharge occurs in a load, a reverse polarity voltage can be applied to the load immediately and within a very short time on the order of microseconds. In addition, the stored energy of the plasma itself in the abnormal discharge state and the energy supplied from the DC power supply can be released in the order of μs (microsecond). Therefore, the abnormal discharge can be suppressed before the minority arc generated at the beginning of the abnormal discharge grows into the majority arc. The problem that the majority arc damages the target and the substrate, hinders the growth of a high-quality film, and reduces the accuracy, quality, yield, and the like of the film can be solved.

Since the resonance circuit is used in the present invention, there is almost no switching loss of the switching element, and the switching frequency can be set high.

According to the second aspect of the present invention, in the abnormal discharge suppressing apparatus for a film forming apparatus according to the first aspect, a current equivalent to the current flowing to the load before the occurrence of the abnormal discharge is reduced after the abnormal discharge is suppressed. Can be supplied immediately to the load.

According to the third aspect of the present invention, in the abnormal discharge suppressing apparatus for a film forming apparatus according to the first or second aspect, the reverse polarity voltage pulse is applied to the load even when the load is normal. Since the repetition is performed, occurrence of abnormal discharge can be prevented.

As described above, since it is possible to generate a good reverse polarity voltage pulse on the order of microseconds, it is used for an optical film, an abrasion resistant film, a transparent conductive film, etc., for which a high-speed arc cutoff function is indispensable. It can be widely applied to the plasma DC sputtering process and the like to be performed.

[Brief description of the drawings]

FIG. 1 is an electric circuit in which an embodiment of an abnormal discharge suppressing apparatus for a film forming apparatus according to the present invention is applied to a film forming apparatus.

FIG. 2 is a circuit diagram of a conventional power supply circuit for film formation and an abnormal discharge suppressing mechanism.

FIG. 3 is a schematic time chart of voltage changes of a capacitor (C) 20 and a load 26 after occurrence of an abnormal mode in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Abnormal discharge suppression apparatus for film forming apparatus 19 DC reactor (Ldc) 20 Capacitor (C) 21 Reactor (L1) 22 Reactor (L2) 23 Switching element 26 Load 40 High frequency resonance circuit

Claims (1)

(57) [Claims] A high-frequency resonance circuit including a reactor, a capacitor, and a switch element, and an abnormal discharge detection circuit that detects occurrence of abnormal discharge in the load based on an output value of power supplied from the high-frequency resonance circuit to the load. A drive cycle setting circuit for setting a drive cycle of the switch element based on a resonance cycle in the high frequency resonance circuit; and driving the switch element on / off based on a drive cycle set by the drive cycle setting circuit. A drive circuit that performs ON operation of the switch element by the drive circuit for one cycle based on a drive cycle set by the drive cycle setting circuit when an abnormal discharge is detected by the abnormal discharge detection circuit. The high frequency resonance circuit performs a resonance operation of only one cycle, thereby impressing a reverse polarity voltage pulse on the load. To, the abnormal discharge anomaly film forming apparatus which comprises suppressing a short time of the one cycle discharge suppression device.