JP2021157916A - Method of detecting state of plasma source and plasma source - Google Patents

Abstract

To provide a method capable of more accurately detecting the change of plasma from CCP to ICP, and a plasma source.SOLUTION: In a method of detecting the state of an inductively coupled plasma source, the plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit. The method includes: a step of generating a capacitively coupled plasma in the discharge portion; a step of acquiring a voltage and a current at an output end of the DC power supply circuit after the capacitively coupled plasma is generated; a step of acquiring a current increase rate representing the ratio of the increase of the current to the increase of the voltage; and a step of outputting a first signal according to the change of the current increase rate.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for detecting the state of a plasma source and a plasma source.

Inductively coupled plasma (hereinafter referred to as "ICP") is used for various purposes including the manufacture of semiconductor devices. For example, in the manufacture of semiconductor devices, it is used for etching processes on silicon wafers, film formation by the CVD method, and the like. Used. Patent Documents 1 and 2 disclose a technique for manufacturing a semiconductor device using ICP.

In the plasma source that generates ICP (inductively coupled plasma source), in order to generate ICP, it is known that capacitively coupled plasma (hereinafter referred to as "CCP") is first generated and then converted into ICP. Has been done. In this case, it is important to detect that the plasma has changed from CCP to ICP.

In the prior art, when detecting a change from CCP to ICP, the light emission from the plasma was measured and confirmed based on the light emission intensity. Patent Documents 1 and 2 also make a determination based on the emission intensity.

JP-A-2002-343600 Japanese Unexamined Patent Publication No. 2008-198695

However, in the conventional technique, there is a problem that it is difficult to accurately detect that the plasma has changed from CCP to ICP.

For example, in the case of determination based on the emission intensity as in Patent Documents 1 and 2, since plasma emits light when ignited as CCP in the first place, the occurrence of CCP and the change from CCP to ICP are distinguished and determined. Difficult to do. It is generally known that ICP is brighter and has a higher emission intensity, but it is difficult to set a threshold value that can be accurately determined.

Further, since the emission intensity of CCP and ICP changes depending on the type of gas constituting the plasma, it is difficult to set a threshold value that can be commonly used for various gases, and a single threshold value functions effectively. The conditions are limited.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a method and a plasma source capable of more accurately detecting the change of plasma from CCP to ICP.

An example of the method according to the present invention is
A method of detecting the state of an inductively coupled plasma source.
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The method is
The step of generating capacitively coupled plasma in the discharge section,
After the capacitively coupled plasma is generated, the step of acquiring the voltage and current at the output end of the DC power supply circuit, and
The step of acquiring the current increase rate representing the ratio of the current increase to the voltage increase, and
The step of outputting the first signal according to the change of the current increase rate, and
To be equipped.

In one example, in the step of acquiring the current increase rate,
The first current increase rate, which is the current increase rate in the state where the capacitively coupled plasma is generated, and
The second current increase rate, which is the current increase rate acquired after the first current increase rate, and
Is obtained,
The first signal is output when the ratio of the second current increase rate to the first current increase rate exceeds a predetermined threshold value.

An example of the method according to the present invention is
A method of detecting the state of an inductively coupled plasma source.
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The method is
The step of generating capacitively coupled plasma in the discharge section,
After the capacitively coupled plasma is generated, the step of acquiring the power and current at the output end of the DC power supply circuit or the power and voltage at the output end of the DC power supply circuit, and
A step of outputting a first signal when the value obtained by differentiating the current with the electric power changes from an increase to a decrease, or when the value obtained by differentiating the voltage with the electric power changes from a decrease to an increase.
To be equipped.

In one example, the first signal is a signal indicating that the plasma has changed from the capacitively coupled plasma to an inductively coupled plasma.

An example of a plasma source according to the present invention is
An inductively coupled plasma source
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The plasma source is
Capacitively coupled plasma is generated in the discharge section to generate
After the capacitively coupled plasma is generated, the voltage and current at the output end of the DC power supply circuit are acquired.
Obtain the current increase rate representing the ratio of the increase in the current to the increase in the voltage.
The first signal is output according to the change in the current increase rate.

An example of a plasma source according to the present invention is
An inductively coupled plasma source
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The plasma source is
Capacitively coupled plasma is generated in the discharge section to generate
After the capacitively coupled plasma is generated, the power and current at the output end of the DC power supply circuit or the power and voltage at the output end of the DC power supply circuit are acquired.
The first signal is output when the value obtained by differentiating the current with the electric power changes from increasing to decreasing, or when the value obtained by differentiating the voltage with the electric power changes from decreasing to increasing.

According to the method for detecting the state of the plasma source and the plasma source according to the present invention, it is possible to more accurately detect that the plasma has changed from CCP to ICP.

The figure which shows the example of the structure of the plasma source which concerns on Embodiment 1 of this invention. The graph which shows the relationship between the voltage and the current measured in Embodiment 1. The flowchart of the method of detecting the state of the plasma source which concerns on Embodiment 1. The graph which shows the relationship between the electric power measured in Embodiment 2 and a current and a voltage. The graph which showed the result of FIG. 4 by differentiation. The flowchart of the method of detecting the state of the plasma source which concerns on Embodiment 2.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1.
FIG. 1 shows an example of the configuration of the plasma source 10 according to the first embodiment. The plasma source 10 is an inductively coupled plasma source. In the first embodiment, the detection is performed according to the behavior of the current with respect to the increase in the voltage in the plasma source 10.

The plasma source 10 includes a DC power supply circuit 20, an inverter circuit 30, a resonance circuit 40, a discharge unit 50, and a control means 60.

The DC power supply circuit 20, the inverter circuit 30, the resonance circuit 40, and the discharge unit 50 are connected in this order. That is, the output end of the DC power supply circuit 20 and the input end of the inverter circuit 30 are connected, the output end of the inverter circuit 30 and the input end of the resonance circuit 40 are connected, and the output end of the resonance circuit 40 and the discharge unit 50 are connected. The input end is connected.

The DC power supply circuit 20 supplies a DC voltage. The inverter circuit 30 converts a DC voltage into an AC voltage. The frequency of the AC voltage is, for example, the RF frequency, more specifically 2 MHz or about 2 MHz.

The resonance circuit 40 uses an AC voltage to cause a resonance phenomenon, and supplies the resonated voltage to the discharge unit 50. In the present embodiment, the resonance circuit 40 includes an LC circuit section 41 and a capacitor 42, and the capacitor 42 is connected to the LC circuit section 41 in parallel with the discharge section 50. The configuration of the resonance circuit 40 is not limited to the one shown in the figure.

The discharge unit 50 includes a discharge tube (not particularly shown) and an antenna 51.
The discharge tube is, for example, a cylindrical discharge container made of a dielectric (insulator), and plasma is generated inside the discharge tube. The antenna 51 is a conductor formed in a coil shape so as to surround the discharge tube, and is connected to the resonance circuit 40. FIG. 1 shows a resistor 52 connected in series to the antenna 51 in the discharge section 50, and this resistor 52 is a resistance value of the coil when no load is applied.

The shape of the antenna 51 is not limited to the coil shape. Further, the antenna 51 may have a pipe shape in which a refrigerant such as water may flow inside in order to cool the discharge pipe. Further, the antenna 51 does not necessarily have to be formed so as to surround the discharge tube, and may be formed inside the dielectric (insulator) forming the discharge tube.

The discharge unit 50 uses the supplied voltage to generate plasma. For example, when an AC voltage is applied to the antenna 51 while the gas is flowing in the discharge container, the gas is ionized by the voltage between the terminals of the coil of the antenna 51 to generate plasma. This is a plasma coupled by an electric field between the terminals of the coil, i.e. CCP.

When the voltage applied to the antenna 51 is further increased while CCP is being generated, a magnetic field is formed around the coil to generate an induced electric field, which causes ICP. ICP is a plasma used in the manufacture of semiconductor devices and the like, and is maintained and managed according to the application.

The control means 60 controls the operation of the plasma source 10. For example, the control means 60 is connected to the DC power supply circuit 20 via the driver amplifier 70, and is connected to the inverter circuit 30 via the driver amplifier 80.

The control means 60 acquires measurement signals (for example, voltage signal C1 and current signal C2) representing the state of the DC power supply circuit 20, and controls the plasma source 10 accordingly. The control of the plasma source 10 is performed, for example, by transmitting the control signal C3 to the DC power supply circuit 20 and transmitting the control signal C4 to the inverter circuit 30.

Further, the control means 60 can acquire the voltage and the current in the circuit of the plasma source 10. For this purpose, the plasma source 10 is provided with measuring means. In the first embodiment, the measuring means is a VI sensor 90, which is arranged between the inverter circuit 30 and the resonance circuit 40. The control means 60 acquires the voltage and current by receiving the measurement signal C5 from the VI sensor 90. The position of the VI sensor 90 in FIG. 1 is an example, and the voltage and current can be changed to an appropriate position according to the circuit portion to be measured.

A power supply (not shown) is connected to the DC power supply circuit 20, the control means 60, the driver amplifier 70, and the driver amplifier 80 to supply electric power to them.

FIG. 2 is a graph showing the relationship between measured voltage and current when ICP is generated using the plasma source 10. The horizontal axis is the voltage [V] at the output end of the DC power supply circuit 20 measured by the voltage measuring means (not shown). The vertical axis represents the current [A] at the output end of the DC power supply circuit 20 measured by the voltage measuring means (not shown).

In the first embodiment, a mixture of oxygen and nitrogen was supplied as the gas in the discharge container. The total pressure of the gas was 100 Pa, and the measurement was performed a plurality of times with different gas flow rates.

In FIG. 2, the ● symbol indicates a graph when the oxygen flow rate is 1000 sccm (Standard Cubic Centimeter per Minute) and the nitrogen flow rate is 100 sccm. The ▲ symbol shows a graph when the flow rate of oxygen is 1500 sccm and the flow rate of nitrogen is 100 sccm.

The low voltage range (roughly about 35V or less) corresponds to the no-load state in which plasma is not generated, and the current increases at a substantially constant rate of increase with respect to the increase in voltage. When the voltage increases and roughly exceeds about 35 V, CCP is generated, but even after that, the current increases at a substantially constant rate of increase with respect to the increase in voltage.

As the voltage increases further, the plasma changes from CCP to ICP. This voltage is about 120 V (indicated by the broken line) in the case of oxygen 1000 sccm and nitrogen 100 sccm (corresponding to the graph), and in the case of oxygen 1500 sccm and nitrogen 100 sccm (corresponding to the graph). It was about 130 V (indicated by the alternate long and short dash line).

In the example of the graph (oxygen 1000 sccm, nitrogen 100 sccm) of FIG. 2, when the voltage exceeds about 120 V (broken line), the rate of increase of the current changes to a larger value. Further, in the example of the graph (oxygen 1500 sccm, nitrogen 100 sccm) of FIG. 2, when the voltage exceeds about 130 V (dotted chain line), the rate of increase of the current changes to a larger value. In this way, the voltage at the point where the plasma changes from CCP to ICP and the voltage at the point where the rate of increase in current changes are in good agreement.

Although not shown in FIG. 2, when the voltage is further increased thereafter, the rate of increase of the current returns to a low value.

FIG. 3 is a flowchart of a method for detecting the state of the plasma source according to the first embodiment. The plasma source 10 detects the state of the plasma source 10 by executing this method. The state of the plasma source 10 includes, for example, the state of the plasma generated by the plasma source 10. The state of the plasma represents, for example, whether the plasma is CCP or ICP. The method of FIG. 3 is started with the gas flowing through the discharge container of the plasma source 10.

First, a voltage is applied to the discharge unit 50 of the plasma source 10, thereby generating a CCP in the discharge unit 50 (step S1). After the CCP is generated, the control means 60 measures and acquires the voltage and current related to the plasma source 10 (step S2).

In the example of FIG. 1, this measurement is made via the VI sensor 90. That is, the control means 60 includes the voltage at the connection point of the inverter circuit 30 and the resonance circuit 40 (for example, the voltage between the connection point and the ground) and the current flowing through the connection point. To measure.

Here, since the output voltage of the DC power supply circuit 20 can be calculated based on the voltage measured by the VI sensor 90, the voltage measured by the VI sensor 90 is said to be equivalent to the voltage at the output end of the DC power supply circuit 20. be able to. Similarly, since the output current of the DC power supply circuit 20 can be calculated based on the current measured by the VI sensor 90, the current measured by the VI sensor 90 is equivalent to the current at the output end of the DC power supply circuit 20. be able to.

In this embodiment, the voltage and current are assumed to have positive values. Further, in the case of alternating current, it may be an effective value, a maximum value, an average value, or another appropriately calculated value.

The method of measuring the voltage and current acquired in step S2 is not limited to the method using the VI sensor 90 shown in FIG. For example, the voltage is equivalent as long as it can be converted into the voltage at the output end of the DC power supply circuit 20, and may be, for example, a value obtained by directly measuring the voltage itself at the output end of the DC power supply circuit 20 or an inverter. It may be a measured value of the voltage at the input end of the circuit 30, a measured value of the voltage at the output end of the inverter circuit 30, or a measured value of the voltage at the input end of the resonance circuit 40. It may be a value obtained by measuring the voltage at the output end of the resonance circuit 40, or it may be a value obtained by measuring the voltage at the input end of the discharge unit 50.

Similarly, the current is equivalent as long as it can be converted into a current at the output end of the DC power supply circuit 20, and may be, for example, a value obtained by directly measuring the current itself at the output end of the DC power supply circuit 20. , The value may be the measured value of the current at the input end of the inverter circuit 30, the value may be the measured value of the current at the output end of the inverter circuit 30, or between the input end and the output end of the resonance circuit 40. It may be a value obtained by measuring the current in the capacitor 42, a value obtained by measuring the current in the capacitor 42, or a value obtained by measuring the current in the discharge unit 50.

After step S2, the control means 60 acquires the ratio of the increase in the current acquired in step S2 (current increase rate) to the increase in voltage acquired in step S2 (step S3). The current increase rate corresponds to the slope in the graph of FIG.

Next, the control means 60 determines whether or not the current increase rate has changed (step S4). Here, the control means 60 may monitor the behavior of the current and the current increase rate while controlling the DC power supply circuit 20 so that the voltage increases. In the first embodiment, it is determined whether or not the current increase rate is larger. The specific determination method in step S4 can be arbitrarily designed, but an example will be described below.

Prior to the determination in step S4, the control means 60 acquires the current increase rate (first current increase rate) in the state where the CCP is generated. The method for acquiring the first current increase rate can be arbitrarily designed, but for example, the voltage can be calculated as the current increase rate in a predetermined CCP voltage range (for example, 20V to 100V, but not limited to this). .. The CCP voltage range is a voltage range in which CCP can be reliably generated and maintained under the operating conditions of the plasma source 10, and can be appropriately designed by those skilled in the art.

After acquiring the first current increase rate, the control means 60 obtains the current increase rate based on the newly measured voltage and current and the voltage and current measured immediately before each time steps S2 and S3 are executed. (Second current increase rate) is calculated. Then, it is determined whether or not the ratio of the second current increase rate to the first current increase rate exceeds a predetermined threshold value (for example, 1.1, but not limited to this). If this ratio exceeds the threshold value, it is determined that the current increase rate has changed, and if not, it is determined that the current increase rate has not changed.

If the current increase rate has not changed, steps S2 to S4 are repeated. Here, for example, the control means 60 increases the voltage each time steps S2 to S4 are executed.

On the other hand, when the current increase rate changes, the control means 60 outputs a signal (first signal) indicating that the current increase rate has changed (step S5). This corresponds to determining that the plasma has changed from CCP to ICP. That is, it can be said that the first signal is a signal indicating that the plasma has changed from CCP to ICP.

In the first embodiment, since the emission intensity is not used for this determination, the determination can be performed more accurately than in the prior art. In particular, since this method does not depend on the emission intensity, it can be applied to various types of gases having different emission intensities, and can also be applied to different gas pressures. As a modification, it is also possible to use the emission intensity together with the determination.

Those skilled in the art can appropriately design the content, format, output mode, and usage of the first signal. For example, a display device may be connected to the control means 60, and information indicating that the first signal has been output may be displayed on the display device. A specific example of the information can be a message or image indicating that the plasma state has changed from CCP to ICP.

Further, for example, the control means 60 may start executing a specific process according to the output of the first signal. As a more specific example, a timer may be activated. The value of this timer can be used as a value indicating the elapsed time since the ICP was generated.

As described above, according to the plasma source 10 and the method shown in FIG. 3 according to the first embodiment, it is possible to more accurately detect that the plasma has changed from CCP to ICP.

Embodiment 2.
In the second embodiment, the detection is performed according to the behavior of the voltage or current with respect to the increase in electric power in the plasma source 10. Hereinafter, the difference from the first embodiment will be described.

FIG. 4 is a graph showing the relationship between the power at the output terminal of the DC power supply circuit 20 and the current and voltage measured by using the VI sensor 90 or the like under conditions different from those of the first embodiment. In the second embodiment, a mixture of hydrogen and nitrogen was supplied as the gas in the discharge container. The flow rates of hydrogen and nitrogen were both 1000 sccm, and the total gas pressure was 87 Pa.

The horizontal axis represents the power [W] at the output end of the DC power supply circuit 20 measured by the power measuring means (not shown). The vertical axis on the left side represents the voltage [V] at the output end of the DC power supply circuit 20 measured by the voltage measuring means (not shown). The vertical axis on the right side represents the current [A] at the output end of the DC power supply circuit 20 measured by the current measuring means (not shown). In FIG. 4, the x symbol indicates the current and the ▲ symbol indicates the voltage.

FIG. 5 is a graph showing the results of FIG. 4 differentiated. The horizontal axis is the same as in FIG. The vertical axis represents the value obtained by differentiating the current [A] with electric power and the value obtained by differentiating the voltage [V] with electric power. These values may be referred to simply as "differential values" below. Also called derivative or derivative. For convenience of illustration, the change in current is shown as a 10-fold value.

A specific method for obtaining the differential value can be appropriately designed by those skilled in the art based on known techniques. For example, when the power increases from a certain value P to another value P + ΔP, the current is different from the certain value C. When the value changes to C + ΔC, ΔC / ΔP can be calculated as a derivative value of the current. The same applies to the voltage. As another example, a known differentiator or differentiating circuit may be used.

The x symbol in FIG. 5 indicates the differential value of the current, and the ▲ symbol indicates the differential value of the voltage. When the derivative value of the current is positive, it indicates that the current increases with increasing power, and when the derivative value of current is negative, it indicates that the current decreases with increasing power. The same applies to the differential value of voltage.

The range where the electric power is low (roughly about 1800 W or less) corresponds to the state of no load in which plasma is not generated and the state in which CCP is generated. In this range, the current increases monotonically and the voltage decreases monotonically with increasing power.

When the power reaches about 1800 W (shown by the dashed line), the plasma changes from CCP to ICP. In the graph of FIG. 5, when the electric power exceeds about 1800 W (broken line), the differential value of the current changes from an increase to a decrease (inflection point of the current), and the differential value of the voltage changes from a decrease to an increase. (Voltage inflection point). In this way, the power at the point where the plasma changes from CCP to ICP and the power at the point where the increase / decrease in the differential values of the current and voltage are reversed are in good agreement.

FIG. 6 is a flowchart of a method for detecting the state of the plasma source according to the second embodiment. The plasma source 10 detects the state of the plasma source by executing this method. The method of FIG. 6 is started with the gas flowing through the discharge container of the plasma source 10.

First, a voltage is applied to the discharge unit 50 of the plasma source 10, thereby generating a CCP in the discharge unit 50 (step S11). After the CCP is generated, the control means 60 measures and acquires the electric power and the voltage or current related to the plasma source 10 (step S12). This measurement is made, for example, via the VI sensor 90.

Since the power acquired here can be converted into the output power of the DC power supply circuit 20, it can be said that it is equivalent to the power at the output end of the DC power supply circuit 20. Further, since the current and voltage measured by the VI sensor 90 can be converted into the current and voltage at the output end of the DC power supply circuit 20, it can be said that they are equivalent to the current and voltage at the output end of the DC power supply circuit 20. can.

In this embodiment, the power, voltage and current are assumed to have positive values. Further, in the case of alternating current, it may be an effective value, a maximum value, an average value, or another appropriately calculated value.

The method for measuring the power, voltage, and current acquired in step S12 is not limited to the method using the VI sensor 90 shown in FIG. For example, the electric power may be any part of electric power as long as it can be converted into electric power at the output end of the DC power supply circuit 20, and is, for example, a value obtained by directly measuring the electric power itself at the output end of the DC power supply circuit 20. It may be a value obtained by measuring the electric power at the input end of the inverter circuit 30, a value obtained by measuring the electric power at the output end of the inverter circuit 30, or a value measured at the input end of the resonance circuit 40. It may be a value obtained by measuring the electric power, a value obtained by measuring the electric power at the output end of the resonance circuit 40, or a value obtained by measuring the electric power at the input end of the discharge unit 50.

Similarly, the current and voltage are equivalent as long as they can be converted into the current at the output end of the DC power supply circuit 20.

After step S12, the control means 60 determines whether or not the differential value of the voltage acquired in step S12 has changed from decreasing to increasing (step S13). Alternatively, the control means 60 determines in step S13 whether or not the differential value of the current acquired in step S12 has changed from an increase to a decrease. For example, the control means 60 may monitor the behavior of the current or voltage while controlling the DC power supply circuit 20 so that the power increases.

If the derivative of the voltage does not change from decreasing to increasing (for example, if the derivative is increasing without decreasing, if the derivative continues to decrease, etc.), or if the derivative of the current is , Steps S12 and S13 are repeated when the increase has not changed to decrease (for example, when the differential value decreases without increasing, when the differential value continues to increase, etc.). For example, the control means 60 increases the power each time steps S12 and S13 are executed.

On the other hand, when the differential value of the voltage changes from decrease to increase, or when the differential value of current changes from increase to decrease, the control means 60 outputs a signal (first signal) representing this (step). S14). This corresponds to determining that the plasma has changed from CCP to ICP. That is, it can be said that the first signal is a signal indicating that the plasma has changed from CCP to ICP.

Although FIG. 5 shows the differential values of both the current and the voltage, as is clear from the above, the method according to the second embodiment can be used even if only one of these differential values is used. It can also be carried out using. For example, the power and current may be measured in step S12 and determined using the differential value of the current in step S14, or the power and voltage may be measured in step S12 and determined using the differential value of the voltage in step S14. You may. When both current and voltage are used, the first signal is output only when the differential value of the current changes from an increase to a decrease and the differential value of the voltage changes from a decrease to an increase (AND condition) in step S14. Alternatively, in step S14, the first signal may be output when the differential value of the current changes from an increase to a decrease or the differential value of the voltage changes from a decrease to an increase (OR condition).

Even in the second embodiment, since the emission intensity is not used for the determination, the determination can be performed more accurately than in the prior art. In particular, since this method does not depend on the emission intensity, it can be applied to various types of gases having different emission intensities, and can also be applied to different gas pressures. As a modification, it is also possible to use the emission intensity together with the determination.

As described above, according to the plasma source 10 and the method shown in FIG. 6 according to the second embodiment, it is possible to more accurately detect that the plasma has changed from CCP to ICP.

10 ... Plasma source 20 ... DC power supply circuit 30 ... Inverter circuit 40 ... Resonance circuit 41 ... LC circuit section 42 ... Capacitor 50 ... Discharge section 51 ... Antenna 52 ... Resistance 60 ... Control means 70, 80 ... Driver amplifier 90 ... VI sensor

Claims (6)

A method of detecting the state of an inductively coupled plasma source.
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The method is
The step of generating capacitively coupled plasma in the discharge section,
After the capacitively coupled plasma is generated, the step of acquiring the voltage and current at the output end of the DC power supply circuit, and
The step of acquiring the current increase rate representing the ratio of the current increase to the voltage increase, and
The step of outputting the first signal according to the change of the current increase rate, and
A method. In the step of acquiring the current increase rate,
The first current increase rate, which is the current increase rate in the state where the capacitively coupled plasma is generated, and
The second current increase rate, which is the current increase rate acquired after the first current increase rate, and
Is obtained,
The first signal is output when the ratio of the second current increase rate to the first current increase rate exceeds a predetermined threshold value.
The method according to claim 1. A method of detecting the state of an inductively coupled plasma source.
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The method is
The step of generating capacitively coupled plasma in the discharge section,
After the capacitively coupled plasma is generated, the step of acquiring the power and current at the output end of the DC power supply circuit or the power and voltage at the output end of the DC power supply circuit, and
A step of outputting a first signal when the value obtained by differentiating the current with the electric power changes from an increase to a decrease, or when the value obtained by differentiating the voltage with the electric power changes from a decrease to an increase.
A method. The method according to any one of claims 1 to 3, wherein the first signal is a signal indicating that the plasma has changed from the capacitively coupled plasma to an inductively coupled plasma. An inductively coupled plasma source
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The plasma source is
Capacitively coupled plasma is generated in the discharge section to generate
After the capacitively coupled plasma is generated, the voltage and current at the output end of the DC power supply circuit are acquired.
Obtain the current increase rate representing the ratio of the increase in the current to the increase in the voltage.
The first signal is output according to the change in the current increase rate.
Plasma source. An inductively coupled plasma source
The plasma source includes a DC power supply circuit, an inverter circuit, a resonance circuit, and a discharge unit.
The plasma source is
Capacitively coupled plasma is generated in the discharge section to generate
After the capacitively coupled plasma is generated, the power and current at the output end of the DC power supply circuit or the power and voltage at the output end of the DC power supply circuit are acquired.
The first signal is output when the value obtained by differentiating the current with the electric power changes from increasing to decreasing, or when the value obtained by differentiating the voltage with the electric power changes from decreasing to increasing.
Plasma source.

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