JP2020145038A - Plasma processing apparatus - Google Patents

Abstract

SOLUTION: A plasma processing apparatus that includes a voltage application electrode to which an output voltage output from a power supply is applied, and that treats the object to be processed by plasma generated between the voltage application electrode and a counter electrode facing the voltage application electrode, includes: an actuator that relatively moves the voltage application electrode and the object to be processed; an insulating portion arranged between the counter electrode and the actuator; and a current detection portion that detects a current flowing through the counter electrode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a plasma processing apparatus.

Conventionally, a technique of decompressing the inside of a closed container to generate plasma and plasma-treating a work arranged in the closed container has been widely used. An example of a plasma processing apparatus that performs such plasma processing is disclosed in Patent Document 1.

The plasma processing apparatus of Patent Document 1 is an apparatus in which an object to be processed is housed in a processing chamber to perform plasma processing, and has a discharge detection sensor. The discharge detection sensor has a plate-shaped dielectric member and a probe electrode.

One surface of the dielectric member is mounted in the vacuum chamber facing the plasma generated in the processing chamber. The probe electrode is located on the other surface of the dielectric member. The probe electrode is connected to the signal recording unit via the detection lead wire.

A potential is induced in the probe electrode according to the state of plasma. The potential of the probe electrode is guided to the signal recording unit by the detection lead wire, and the signal of the potential change according to the state of plasma is recorded by the signal recording unit. As a result, when an abnormal discharge or the like occurs inside the processing chamber, the state of the plasma fluctuates, and this fluctuation is detected as a potential change of the probe electrode.

JP-A-2009-135253

However, the plasma processing apparatus is equipped with an actuator or the like that conveys an object to be processed, and the actuator may generate noise due to an electromagnetic wave received from a power source for plasma generation. The effect on the discharge detection sensor is not considered.

In particular, in recent years, a technique for stably discharging plasma under atmospheric pressure has been established, and plasma treatment in an open space has been put into practical use. In such atmospheric pressure plasma processing, since it is necessary to apply a higher voltage to the electrodes, the influence of the noise becomes larger.

In view of the above situation, it is an object of the present invention to provide a plasma processing apparatus capable of accurately detecting a plasma discharge state with a simple configuration.

The exemplary plasma processing apparatus of the present invention includes a voltage application electrode to which an output voltage output from a power supply unit is applied, and plasma generated between the voltage application electrode and the counter electrode facing the voltage application electrode. A plasma processing device that processes an object to be processed by means of an actuator that relatively moves the voltage application electrode and the object to be processed, and an insulating portion arranged between the counter electrode and the actuator. A current detection unit for detecting a current flowing through the counter electrode is provided.

According to the exemplary plasma processing apparatus of the present invention, the plasma discharge state can be detected with high accuracy by a simple configuration.

FIG. 1 is a diagram schematically showing the overall configuration of the plasma processing apparatus according to the first embodiment. FIG. 2 is a diagram showing a waveform example of an output voltage applied to a voltage application electrode in the plasma processing apparatus according to the first embodiment and a detection current signal detected by a current detection unit. FIG. 3 is a diagram showing an example of waveforms of an output voltage and a detected current signal in the plasma processing apparatus according to the comparative example. FIG. 4 is a top view showing an example of a processing process of the object to be processed. FIG. 5 is a diagram schematically showing the overall configuration of the plasma processing apparatus according to the second embodiment. FIG. 6 is a diagram schematically showing the overall configuration of the plasma processing apparatus according to the third embodiment. FIG. 7 is a diagram schematically showing the overall configuration of the plasma processing apparatus according to the fourth embodiment.

An exemplary embodiment of the present invention will be described below with reference to the drawings.

<1. First Embodiment>
FIG. 1 is a diagram schematically showing the overall configuration of the plasma processing apparatus 10 according to the first embodiment.

The plasma processing apparatus 10 shown in FIG. 1 is an apparatus that generates plasma under atmospheric pressure and performs plasma processing on a metal object 1 to be processed. The plasma processing device 10 includes a voltage application electrode 2, a dielectric unit 3, a power supply unit 4, a stage 5, an insulating unit 6, and an actuator 7.

The power supply unit 4 has a first output end 41 and a second output end 42. The power supply unit 4 applies a high-frequency, high-voltage output voltage from the first output terminal 41 to the voltage application electrode 2. The output voltage is an AC voltage. That is, the plasma processing device 10 includes a voltage application electrode 2 to which an output voltage output from the power supply unit 4 is applied. Further, the power supply unit 4 has a first output end 41 for applying an output voltage to the voltage application electrode 2, and a second output end 42 which is the other side of the first output end 41.

The frequency of the voltage applied by the power supply unit 4 is, for example, 1 kHz to 100 kHz. The waveform of the voltage applied by the power supply unit 4 is preferably a pulse waveform, but may be a sine wave, a square wave, or the like, and a known waveform used in atmospheric pressure plasma discharge may be used. The voltage applied by the power supply unit 4 is, for example, 5 kVpp to 20 kVpp, and is appropriately set by a gap between the voltage application electrode 2 and the object 1 to be processed.

The object 1 to be processed is made of metal and faces the voltage application electrode 2 in the vertical direction. The voltage application electrode 2 has an opposing electrode surface 21 as an end surface on the side facing the object 1 to be processed. The object 1 to be processed has an facing electrode surface 11 as an end face on the side facing the voltage application electrode 2.

The dielectric portion 3 is arranged on the facing electrode surface 21. As the material of the dielectric portion 3, a ceramic material such as alumina or zirconia, a free-cutting ceramic, or the like is preferably used. A gap S1 is formed between the dielectric portion 3 and the object to be processed 1. The facing electrode surface 11 as the surface to be processed of the object 1 to be processed is plasma-processed by the plasma P generated in the gap S1. The object 1 to be processed functions as a counter electrode facing the voltage application electrode 2, and the object 1 to be processed is directly processed by the plasma P generated between the dielectric portion 3 and the object 1 to be processed. That is, the plasma processing device 10 processes the object 1 to be processed by the plasma generated between the voltage application electrode 2 and the counter electrode 1 facing the voltage application electrode 2.

In the stage 5, the object to be processed 1 is placed and the object to be processed 1 is held. That is, the plasma processing apparatus 10 includes a stage 5 on which the object to be processed 1 is placed. The stage 5 is made of metal.

The insulating portion 6 is arranged between the stage 5 and the actuator 7. That is, the insulating portion 6 is arranged between the counter electrode 1 and the actuator 7. The insulating portion 6 is made of, for example, a sheet-shaped insulating material. The insulating portion 6 electrically insulates the stage 5 and the actuator 7.

The actuator 7 conveys the object 1 to be processed together with the stage 5 and the insulating portion 6 in the conveying direction. That is, the actuator 7 relatively moves the voltage application electrode 2 and the object 1 to be processed.

The stage 5 is connected to the second output end 42 via the first line L1. The signal processing box 8 houses the current detection unit 81 and the determination unit 82. The current detection unit 81 is arranged in the middle of the first line L1. That is, the current detection unit 81 is arranged on the first line L1 that conducts the counter electrode 1 and the second output end 82.

The actuator 7 is grounded by the second line L2. The first line L1 is not connected to the second line L2 that grounds the actuator 7.

The current detection unit 81 and the stage 5 are connected by a third line L3. That is, the third line L3 is a part of the first line L1.

The current detection unit 81 is composed of, for example, a resistor that converts a current into a voltage. When a discharge occurs in the gap S1, the discharge current flows through the current detection unit 81 via the object 1 to be processed and the stage 5. As a result, the current detection unit 81 detects the discharge current. That is, the current detection unit 81 detects the current flowing through the counter electrode 1.

The determination unit 82 performs the determination process based on the detection result of the current detection unit 81. A specific example of the determination by the determination unit 82 will be described later.

<2. About plasma discharge>
In the plasma processing apparatus 10 that plasma-treats the object 1 to be processed under atmospheric pressure, the dielectric portion 3 is arranged on the voltage application electrode 2, and the power supply unit 4 applies a high voltage / high frequency output voltage to the voltage application electrode 2. By applying the voltage, a dielectric barrier discharge is generated in the gap S1. The electric charge carried by the discharge current accumulates in the dielectric portion 3, so that the voltage applied to the gap S1 decreases, and the discharge is automatically stopped. As a result, the dielectric barrier discharge becomes a pulse-shaped discharge, and a stable atmospheric pressure non-thermal equilibrium plasma can be obtained.

The processing gas may be supplied to the gap S1 by the gas supply means. The treatment gas is not limited to a gas type such as nitrogen or a mixed gas of nitrogen and air.

Here, FIG. 2 is a diagram showing an example of waveforms of the output voltage V applied to the voltage application electrode 2 in the plasma processing apparatus 10 according to the present embodiment and the detection current signal I detected by the current detection unit 81. .. Note that FIG. 2 shows a case where a sinusoidal output voltage V is applied as an example.

As shown in FIG. 2, a pulsed discharge current is generated near the timing at which the polarity of the output voltage V is switched. For example, in the region A of FIG. 2, a discharge current is generated. In FIG. 2, the influence of noise on the detected current signal I is small, and the peak to peak value of the discharge current is large and clear. It is considered that this is because the inflow of noise from the actuator 7 into the current detection unit 81 can be suppressed by the insulating unit 6, and the outflow of the discharge current flowing through the object 1 to the actuator 7 to the actuator 7 can be suppressed by the insulating unit 6. As a result, the S / N ratio of the discharge current detected by the current detection unit 81 can be improved. Therefore, the plasma discharge state can be detected accurately with a simple configuration.

For reference, FIG. 3 is a diagram showing an example of waveforms of an output voltage and a detected current signal when the actuator 7 and the stage 5 are not insulated. In this case, the influence of noise on the detection current signal I becomes large, and the discharge current is unclear because the peak to peak value becomes small as shown in the B region, for example. As a result, the S / N ratio of the discharge current is deteriorated.

The noise from the actuator 7 includes not only the noise generated when the actuator 7 is driven, but also the noise based on the electromagnetic wave received by the actuator 7 from the power supply unit 4. The plasma processing apparatus 10 of the present embodiment processes the object 1 to be processed by plasma discharge at atmospheric pressure. In plasma discharge at atmospheric pressure, a high voltage / high frequency output voltage is applied to the voltage application electrode 2 by the power supply unit 4, so noise is likely to be generated by the electromagnetic waves received by the actuator 7 from the power supply unit 4, but the insulation unit 6 Therefore, the inflow of noise into the current detection unit 81 can be suppressed.

Further, in the present embodiment, the counter electrode is the object 1 to be processed. As a result, in the plasma processing apparatus 10 that performs plasma processing by the direct method, the plasma discharge state can be detected with high accuracy by a simple configuration.

Further, since the actuator 7 is grounded by the second line L2, the noise generated by the actuator 7 is absorbed by the grounding, and the inflow of the noise into the current detection unit 81 can be further suppressed.

Further, since the first line L1 is not connected to the second line L2 that grounds the actuator 7, noise from the ground can be suppressed from flowing into the current detection unit 81.

Further, since the current detection unit 81 and the stage 5 are connected by the third line L3, it is not necessary to connect the current detection unit 81 to the object 1 to be processed by the line, and the processing process can be simplified.

<3. Processing process of the object to be processed>
Next, an example of the processing process of the object 1 to be processed will be described. FIG. 4 is a top view showing an example of the processing process of the object 1 to be processed. In FIG. 4, the Y-axis direction indicates the direction in which the object 1 to be processed is conveyed by the actuator 7, the Z-axis direction indicates the vertical direction, and the X-axis direction is a direction orthogonal to the Y-axis direction and the Z-axis direction.

First, in step ST1, the object to be processed 1 is set in the stage 5. Here, the object to be processed 1 is, for example, a member having a cylindrical shape, and has an annular surface as an upper surface to be processed. That is, the torus surface is the facing electrode surface 11.

The object 1 to be processed placed on the stage 5 is conveyed to one side in the Y-axis direction by the actuator 7. Then, in step ST2, the height of the surface to be processed of the object to be processed 1 is measured by the displacement meter 15. At this time, the object 1 to be processed is controlled to move in the Y-axis direction by the actuator 7, and the displacement meter 15 is controlled to move in the X-axis direction. As a result, the height of the torus surface, which is the surface to be processed, can be measured.

Next, the object 1 to be processed is conveyed to one side in the Y-axis direction by the actuator 7. Then, in step ST3, the surface to be processed of the object to be processed 1 is plasma-treated by the plasma generated by the voltage application electrode 2 to which the voltage is applied. Specifically, the object 1 to be processed is controlled to move in the Y-axis direction by the actuator 7, and the voltage application electrode 2 is controlled to move in the X-axis direction. At this time, since the voltage application electrode 2 is controlled to move in the Z-axis direction based on the measurement result in the step ST2, the gap between the voltage application electrode 2 and the surface to be processed is in the circumferential direction of the torus. It is controlled constantly.

Then, the object to be processed 1 is conveyed to one side in the Y-axis direction by the actuator 7, and the object to be processed 1 is removed from the stage 5 and carried out in the step ST4.

The relative movement of the actuator 7 and the object 1 to be processed by the mechanism for moving the displacement meter 15 and the voltage application electrode 2 and the displacement meter 15 and the voltage application electrode 2 may be arbitrarily shared in the three axial directions. For example, the displacement meter 15 and the voltage application electrode 2 may be fixed, and the actuator 7 may move the object 1 to be processed in the three axial directions. Alternatively, the object 1 to be processed may be fixed, the displacement meter 15 may be moved in the biaxial direction, and the voltage application electrode 2 may be moved in the triaxial direction. In this case, the actuator moves the voltage application electrode 2. That is, the actuator 7 relatively moves the voltage application electrode 2 and the object 1 to be processed.

<4. Judgment processing by the judgment unit>
The determination unit 82 can perform various determination processes based on the detection result by the current detection unit 81. An example of the determination process will be described below.

For example, the determination unit 82 may compare the detected current value detected by the current detection unit 81 with the first threshold value and the second threshold value higher than the first threshold value. In this case, if the detected current value is equal to or higher than the first threshold value and equal to or lower than the second threshold value, it is determined to be in the normal discharge state, and if the detected current value is lower than the first threshold value, it is determined to be in the non-discharged state. If the current value is higher than the second threshold value, it is determined that the state is abnormally discharged. As the detected current value, for example, the peak to peak value of the detected current signal is used.

The abnormal discharge state is a state in which an arc discharge occurs due to dielectric breakdown of the dielectric portion 3 or mixing of foreign matter into the gap S1.

Further, the determination unit 82 may determine whether the level of the detected current value has decreased with time. In this case, the determination unit 82 can also use, for example, a display unit (not shown) to give a warning to urge the replacement of the voltage application electrode 2.

Further, the determination unit 82 may determine whether the number of times the detected current value exceeds a predetermined threshold value increases with time.

That is, the plasma processing device 10 includes a determination unit 82 that determines whether the plasma discharge is in a normal state based on the detection result of the current detection unit 81. As a result, it is possible to accurately determine whether the plasma discharge is in a normal state.

Further, the determination unit 82 detects a change with time with respect to the current value detected by the current detection unit 81. As a result, various warnings can be issued.

<5. Second Embodiment>
FIG. 5 is a diagram schematically showing the overall configuration of the plasma processing apparatus 101 according to the second embodiment.

The difference between the plasma processing device 101 and the plasma processing device 10 according to the first embodiment is that the fourth line L4 is connected to the stage 5 and the current detection unit 81 is arranged in the middle, and the fourth line L4 is connected to the actuator 7. The 5th line L5 and the 6th line L6 connected to the 2nd output terminal 42 are both grounded.

<6. Third Embodiment>
FIG. 6 is a diagram schematically showing the overall configuration of the plasma processing apparatus 102 according to the third embodiment.

The difference between the plasma processing device 102 and the plasma processing device 10 according to the first embodiment is that the actuator 7 is not grounded and is in a floating state. When the noise generated from the actuator 7 is small, the noise flowing into the current detection unit 81 can be sufficiently suppressed by the insulating unit 6 even in the configuration of the plasma processing device 102.

<7. Fourth Embodiment>
FIG. 7 is a diagram schematically showing the overall configuration of the plasma processing apparatus 103 according to the fourth embodiment.

The plasma processing device 103 includes a voltage application electrode 20, a dielectric unit 30, a power supply unit 40, a counter electrode 50, an insulating unit 60, an actuator 70, and a signal processing box 80.

The voltage application electrode 20 is an electrode to which an output voltage output from the first output end 401 of the power supply unit 40 is applied, and is configured in, for example, a columnar shape extending in the vertical direction. The counter electrode 50 is an electrode that faces the voltage application electrode 20 in the radial direction with respect to the axial direction, and is formed, for example, in a tubular body that surrounds the radial outside of the voltage application electrode 20.

The dielectric portion 30 is arranged on the facing electrode surface 201, which is the outer peripheral surface of the voltage applying electrode 20, and has a cylindrical shape, and is arranged between the facing electrode 50 and the voltage applying electrode 20. As a result, a cylindrical gap S2 is formed between the dielectric portion 30 and the counter electrode 50.

The counter electrode 50 is connected to the second output end 402 of the power supply unit 40 by the seventh line L7. The signal processing box 80 houses the current detection unit 801 and the determination unit 802. The current detection unit 801 is arranged in the middle of the seventh line L7.

The object 90 to be processed is arranged below the voltage application electrode 20. By guiding the processing gas to the gap S2 from above and applying a high voltage / high frequency output voltage to the voltage application electrode 20 by the power supply unit 40, a dielectric barrier discharge is generated in the gap S2 under atmospheric pressure, and the dielectric barrier discharge is generated in the gap S2. Plasma is generated. The generated plasma is guided to the surface to be processed of the object to be processed 90, and the surface to be processed is plasma-treated. That is, the plasma processing apparatus 103 according to the present embodiment performs plasma processing by a remote method.

The insulating portion 60 electrically insulates the counter electrode 50 and the actuator 70. The actuator 70 moves the voltage application electrode 20, the dielectric portion 30, and the counter electrode 50 with respect to the object to be processed 90. The actuator 70 may move the object to be processed 90. That is, the actuator 70 relatively moves the voltage application electrode and the object to be processed. The actuator 70 is grounded.

When a discharge occurs in the gap S2, the discharge current flowing through the counter electrode 50 is detected by the current detection unit 801. At this time, the discharge current is suppressed from flowing out to the actuator 70 by the insulating portion 60. Further, the inflow of noise from the actuator into the current detection unit 801 can be suppressed by the insulating unit 60. As a result, the S / N ratio of the discharge current detected by the current detection unit 801 can be improved.

The dielectric portion 30 may be provided on the facing electrode surface 501 of the facing electrode 50 instead of the facing electrode surface 201 of the voltage application electrode 20, or both the facing electrode surface 201 and the facing electrode surface 501. It may be provided in. That is, the dielectric portion 30 is arranged on at least one opposite electrode surface of the voltage application electrode 20 and the counter electrode 50. As a result, in the dielectric barrier discharge method, even when an arc discharge occurs due to dielectric breakdown of the dielectric portion 30 or foreign matter mixed in the discharge space, abnormal discharge can be detected with high accuracy.

<8. Others>
Although the embodiments of the present invention have been described above, the embodiments can be variously modified within the scope of the gist of the present invention.

The present invention can be used for various plasma treatments on an object to be treated.

1 ... Object to be processed, 11 ... Opposite side electrode surface, 2 ... Voltage application electrode, 21 ... Opposite side electrode surface, 3 ... Dielectric part, 4 ... Power supply part, 41 ... 1st output end, 42 ... 2nd output end, 5 ... Stage, 6 ... Insulation part, 7 ... Actuator, 8 ... Signal processing box, 81 ... Current detection Unit, 82 ... Judgment unit, 10 ... Plasma processing device, 15 ... Displacement meter, 101-103 ... Plasma processing device, 20 ... Voltage application electrode, 201 ... Opposing electrode surface , 30 ... dielectric part, 40 ... power supply part, 401 ... first output end, 402 ... second output end, 50 ... counter electrode, 501 ... opposite electrode surface, 60 ... Insulation unit, 70 ... Actuator, 80 ... Signal processing box, 801 ... Current detection unit, 802 ... Judgment unit, 90 ... Object to be processed, L1 ... First Line, L2 ... 2nd line, L3 ... 3rd line, L4 ... 4th line, L5 ... 5th line, L6 ... 6th line, L7 ... 7th line

Claims (9)

A plasma processing apparatus having a voltage application electrode to which an output voltage output from a power supply unit is applied, and processing an object to be processed by plasma generated between the voltage application electrode and the counter electrode facing the voltage application electrode. There,
An actuator that relatively moves the voltage application electrode and the object to be processed,
An insulating portion arranged between the counter electrode and the actuator,
A current detection unit that detects the current flowing through the counter electrode and
A plasma processing device. The plasma processing apparatus according to claim 1, wherein the counter electrode is the object to be processed. The plasma processing apparatus according to claim 1 or 2, wherein the actuator is grounded. The power supply unit has a first output end for applying the output voltage to the voltage application electrode, and a second output end opposite to the first output end.
The current detection unit is arranged in a first line that conducts the counter electrode and the second output end.
The plasma processing apparatus according to claim 3, wherein the first line is not connected to the second line that grounds the actuator. Further provided with a stage on which the object to be processed is placed,
The insulating portion is arranged between the stage and the actuator.
The plasma processing apparatus according to claim 2, wherein the current detection unit and the stage are connected by a third line. The plasma processing apparatus according to any one of claims 1 to 5, wherein the object to be processed is processed by plasma discharge at atmospheric pressure. The plasma processing apparatus according to claim 6, wherein a dielectric portion is arranged on at least one opposite electrode surface of the voltage application electrode and the counter electrode. The plasma processing apparatus according to any one of claims 1 to 7, further comprising a determination unit for determining whether or not plasma discharge is in a normal state based on the detection result of the current detection unit. The plasma processing apparatus according to claim 8, wherein the determination unit detects a change with time with respect to a current value detected by the current detection unit.

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