TW201531168A - Impedance matching method of plasma etching system - Google Patents

Abstract

The invention relates to an impedance matching method of a plasma etching system. The impedance method comprises the steps of providing a plasma etching system, wherein the plasma etching system comprises an impedance matching device, the input end of the impedance matching device is electrically connected with a source power and a bias power supply, the output end of the impedance matching device is electrically connected with a reaction cavity, the end, connected with the source power, of the impedance matching device is electrically connected with one end of a voltage-current detector, and the other end of the voltage-current detector is connected with the source power through a frequency regulation control unit; the source power and the bias power supply simultaneously work under a continuous power mode, and a first matching frequency can be obtained by adjusting the frequency of the source power; the bias power supply is converted into a pulse power mode, and the first matching frequency serves as a benchmark frequency of the source power under a bias power supply pulse opening state, and when the bias power supply is converted to a pulse closing state from the pulse opening state, the benchmark frequency is adopted as the benchmark, so that a second matching frequency can be obtained by increasing or reducing the frequency of the source power.

Description

Impedance matching method for plasma etching system

The present invention relates to the field of semiconductor technology, and in particular, to an impedance matching method for a plasma etching system.

In semiconductor processes, plasma gas related processes are becoming more and more important in the fabrication of semiconductor devices, such as plasma etching processes, reactive ion etching processes, and the like.

The dual-frequency plasma etching system generally includes an etching chamber, a bias power source and a source power, and the source power source has a higher frequency such as 13 MHz, 27 MHz or more, and is used in the reaction chamber. The plasma is generated and maintained while controlling the density of the plasma. The frequency of the bias supply is low, typically a 2 Mhz RF power source for controlling the direction of motion of the plasma and the energy carried. The bias power source and the source power source provide RF power to the reaction chamber through an impedance matcher.

In a dual-frequency sync pulse plasma etching system, the bias supply and the source supply need to operate in pulse mode at the same time. Compared with a continuous power source, the pulse power source can reduce problems such as ultraviolet radiation, charging damage, physical sputtering, and the like which may occur during plasma generation. In the dual-frequency synchronous pulse plasma etching system, the entire system During the pulse on and pulse off, the state of the plasma in the reaction chamber changes, resulting in a mismatch between the output impedance of the source supply and the input impedance of the impedance matcher, resulting in a power supply. Power supply efficiency is reduced.

The output impedance of the source supply and the input impedance of the impedance matcher can be achieved by adjusting the frequency of the source supply or the matching capacitance within the impedance matcher. In the conventional technique, the method of adjusting the frequency of the source power source to achieve impedance matching, the frequency modulation algorithm of the source power source is inefficient, and the suitable matching frequency cannot be automatically found.

The problem solved by the present invention is to provide an impedance matching method for a plasma etching system to improve the efficiency of impedance matching.

In order to solve the above problems, the present invention provides an impedance matching method for a plasma etching system, comprising: providing a plasma etching system, the plasma etching system comprising: an impedance matching device, and an input end of the impedance matching device The source power source and the bias power source are electrically connected, the output end of the impedance matching device is electrically connected to the reaction cavity, and the connection end of the impedance matching device and the source power source is electrically connected to one end of the voltage-current detector, the voltage-current The other end of the detector is connected to the source power source through the frequency adjustment control unit; the source power source and the bias power source simultaneously operate in the continuous power mode, and the frequency of the source power source is adjusted to match the impedance of the source power source with the impedance of the input end of the matching device to obtain the first Matching frequency; converting the bias power to a pulse power mode, the pulse power mode comprising a pulse-on state and a pulse-off state, the power of the pulse-on state being the same as the power in the continuous power mode, the pulse-off state The power is less than the power of the pulse-on state, and the first matching frequency is used as a bias power pulse a reference frequency of the source power source in the on state; when the bias power source transitions from the pulse-on state to the pulse-off state, increasing or decreasing the frequency of the source power source based on the reference frequency to cause the source The source impedance is matched to the impedance of the matcher input to obtain a second matching frequency of the source supply.

Optionally, the method for adjusting the frequency of the source power source comprises: the voltage-current detector obtaining a short input current and a voltage connected to the source power source and the impedance matching device, and obtaining the impedance of the impedance matching device input through the current and voltage data. a power reflection coefficient, wherein the power reflection coefficient is a ratio of the reflected power to the source power output power; the input impedance and the power reflection coefficient of the impedance matcher are fed back to the frequency adjustment controller; and the frequency adjustment controller is obtained according to the The input impedance value and the power reflection coefficient adjust the frequency of the source power supply.

Optionally, the frequency adjustment control unit controls the direction of the source power frequency adjustment by a sine value of the phase angle of the impedance of the input end of the impedance matching device: if the sine value of the phase angle is greater than 0, the frequency of the source power source is decreased; If the sine value of the phase angle is less than 0, the frequency of the source power source is increased. When the sine value of the phase angle is 0, the frequency modulation is stopped, and the frequency of the source power source is second matched to the frequency.

Optionally, in the process of adjusting the source power frequency, the value of the frequency of the source power supply that is once reduced or increased is a frequency step, and the value of the frequency step is adjusted according to the magnitude of the power reflection coefficient.

Optionally, the larger the power reflection coefficient is, the larger the value of the frequency step is.

Optionally, the power reflection coefficient is greater than 0.25, and the value of the frequency step is 100 KHz.

Optionally, the value of the frequency step decreases as the power reflection coefficient decreases.

Optionally, the value of the frequency step is proportionally reduced as the power reflection coefficient decreases.

Optionally, after the bias power is converted to the pulse power mode, the power reflection coefficient obtained by the voltage-current detector changes to trigger the frequency adjustment of the frequency adjustment control unit to the source power.

Optionally, the power reflection coefficient that triggers the frequency adjustment of the source power source ranges from 0.1 to 0.9.

Optionally, when the source source impedance matches the impedance of the matcher input, the power reflectance of the impedance matcher input is zero.

Optionally, the source power source and the bias power source work together in a pulse power mode.

Optionally, the output power of the source power source in the pulse power mode ranges from 200W to 1000W.

Optionally, the frequency of the bias power source is automatically set by a bias power source.

Optionally, an impedance matching capacitor is disposed in the impedance matching device, and the impedance matching capacitor does not change according to a preset value.

Compared with the prior art, the technical solution of the present invention has the following advantages:

In summary, in the embodiment of the present invention, when the bias power is changed from the pulse-on state to the pulse-off state, causing the impedance of the plasma etching system to change, the frequency of the source power source is adjusted. Find the matching frequency in the pulse off mode. Adjusting the frequency of the source power source as the reference frequency in the continuous power operation mode, and determining the direction of the frequency adjustment according to the positive and negative values of the sine value of the phase angle of the impedance of the impedance matching regulator input, if the phase angle is The sine value is positive to reduce the frequency of the source power source, and if the sine value of the phase angle is negative, the frequency of the source power source is increased. By determining the direction of the frequency adjustment by the positive and negative phases of the impedance phase angle, the frequency sweep range of the source power frequency adjustment can be reduced, and the efficiency of frequency adjustment can be improved.

Moreover, the frequency adjustment of the source power source is a frequency step, and the magnitude of the frequency step may be determined according to a power reflection coefficient of the impedance matching device input end, and the frequency step may be according to the power. The reduction of the reflection coefficient is gradually reduced, so that the sine value of the phase angle of the impedance gradually becomes 0, and the reflection coefficient can be gradually approached to 0, thereby avoiding the accuracy of the frequency sweep due to excessive frequency change. Lower, while missing the second matching frequency, further improving the efficiency of impedance matching of the plasma etching system, the plasma etching can be quickly realized when the bias power source is switched in the pulse-on and pulse-off modes The impedance matching of the system improves the efficiency of the power supply palace.

According to the prior art, the prior art is less efficient in impedance matching of a plasma etching system.

Since the source power source is used to generate the plasma in the reaction chamber, the frequency of the source power source has a large influence on the impedance of the plasma, and the frequency variation of the bias power source has little influence on the impedance of the plasma, so it can be adjusted. The frequency of the source supply finds the appropriate matching frequency to achieve impedance matching.

Since the bias supply is in the pulse on and pulse off states, the impedance of the system is quite different. At the moment when the bias power is switched from the pulse-on state to the pulse-off state, the impedance of the output of the impedance matcher changes, which causes the reflection coefficient of the power supply to rise, triggering the coarse adjustment of the source power frequency, thereby causing the whole The plasma state is unstable. Since the switching rate of the pulse-off state of the pulse-on state is faster, the current source power frequency adjustment rate cannot keep up with the rate of the pulse change, so that the matching frequency in the pulse-on and pulse-off states cannot be quickly found.

In the technical solution of the present invention, the direction of the source power frequency adjustment is determined by the impedance phase of the impedance matching device input end, the frequency sweep range of the source power source can be reduced, and the frequency adjustment rate can be increased, thereby obtaining a suitable matching frequency faster.

The above described objects, features, and advantages of the present invention will be more apparent from the aspects of the invention.

Referring to FIG. 1, a plasma impedance matching system is provided. The plasma impedance matching system includes an impedance matching unit 30, and an input end of the impedance matching unit 30 is electrically connected to a source power source 10 and a bias power source 20, the impedance. The output end of the matcher 30 is electrically connected to the reaction chamber 40, and the connection end of the impedance matching unit 30 and the source power source 10 is electrically connected to one end of the voltage-current detector 50, and the other end of the voltage-current detector 50 passes the frequency. The adjustment control unit 60 is connected to the source power source 10.

The source power source 10 is configured to supply a high frequency power source to the reaction chamber for generating a plasma in the reaction chamber 40, the source power source 10 controlling the density of the generated plasma; and the bias power source 20 for reacting The cavity 40 provides a low frequency power supply that controls the direction of the plasma within the reaction chamber 40 and the energy carried by the plasma.

The input end of the impedance matcher 30 is connected to the source power source 10 and the bias power source 20, and the output end is connected to the reaction chamber 40. The impedance matcher 30 can generate the power source generated by the source power source 10 and the bias power source 20. Transmission to the reaction chamber reduces power loss of the source power supply 10 and the bias power supply 20 output.

The impedance matching device 30 includes a matching capacitor. In the prior art, impedance matching of the plasma etching system can be achieved by adjusting the matching capacitor. In the embodiment of the present invention, the capacitance in the impedance matcher 30 adopts a preset capacitance value, and in the subsequent process, the capacitance value of the matching capacitor in the impedance matcher 30 is not changed, but is adjusted. The frequency of the source power source 10 achieves impedance matching of the system.

The reaction chamber 40 serves as an etching chamber for performing plasma etching. The reaction chamber has two upper and lower plates, and the substrate to be etched is located on the lower plate. The impedance matcher 30 can simultaneously apply the voltages of the source power source 10 and the bias power source 20 to the upper and lower plates, respectively, or to the same plate.

The voltage-current detector 50 is coupled to an input of the impedance matcher 30 for detecting voltage and current signals on a transmission line to which the input of the impedance matcher 30 is connected to the source power source 10, through the voltage and current Signal, the power PI input from the source power source 10 at the input of the impedance matcher 30 can be obtained, and the voltage-current detector 50 compares the input power PI with the output power Po of the source power source 10 through its built-in computing unit. Obtaining a reflected power Pf, Pf=Po-PI of the input end of the impedance matching device 30, thereby obtaining a power reflection coefficient R=Pf/Po=(Po-PI)/Po at the input end of the impedance matching device; The current detector 50, through its built-in computing unit, acquires the impedance Z, Z=voltage/current of the input of the impedance matcher through the voltage and current signals.

The frequency adjustment controller 60 is connected to the source power source 10 for adjusting the frequency of the source power source 10 according to the frequency reflection coefficient R and the impedance Z fed back by the voltage-current detector.

First, the source power source 10 and the bias power source 20 are operated in a continuous power mode, and in the case where a matching capacitor is preset in the impedance matcher 30, the frequency of the source power source is adjusted to match the impedance of the source power source with the impedance. The impedance of the input of the device is matched to obtain the first matching frequency f0. The frequency of the bias power source 20 is automatically set by the bias power source 20. In the continuous power mode, the output power of the source power source 10 and the bias power source 20 are both 1000W.

Since the source power source 10 determines the plasma density in the reaction chamber 40, the impedance of the reaction chamber 40 is very sensitive to the frequency change of the source power source 10, and the frequency of the source power source 10 can be adjusted relatively quickly. The plasma etching system achieves impedance matching; and the bias power source 20 affects the energy and direction of the plasma, and the frequency of the parametric power source 20 can make the plasma etching system in a large range. The impedance remains matched. Therefore, in the embodiment, a frequency is automatically set by the bias power supply 20, and then the impedance of the entire plasma etching system is matched by adjusting the frequency of the source power source 10 to obtain a first match. Frequency f0. Moreover, after the bias power supply 20 is switched to the pulse mode, resulting in a change in the impedance of the system, the impedance is matched by the frequency adjustment of the source power source 10.

Then, the operating mode of the bias power supply 20 is converted into a pulse power mode, and one cycle of the pulse power mode includes a pulse-on state and a pulse-off state, and the power of the pulse-on state is the same as the power in the continuous power mode. The power of the pulse off state is less than the power of the pulse on state.

In this embodiment, the source power source 10 still operates in the continuous power mode, and the output power of the source power source 10 is still 1000 W; the output power of the bias power source 20 in the pulse-on state and the continuous power mode The output power is the same, and is still 1000W. Therefore, when the bias power supply 20 transitions to the pulse-on state, the impedance of the system does not change. The source power source 10 is at the first matching frequency f0. The impedance of the plasma system still matches.

However, when the bias power supply 20 transitions from the pulse-on state to the pulse-off state, the state of the plasma changes due to the change in the output power of the bias power source 20, thereby causing the impedance of the reaction chamber 40 to occur. The changes are such that the impedance of the entire plasma etch system no longer matches. The impedance mismatch causes the power reflection coefficient of the input of the impedance matcher 30 to increase, so that the power received at the input of the impedance matcher 30 is partially reflected back, resulting in a decrease in the power supply efficiency of the power supply.

Please refer to Figure 2 for the location of the system impedance matching point on the Smith chart.

When the bias power supply 20 is in the pulse-on state, the impedance matching point of the system is at point A, which is located at the center A of the Smith chart. At this time, the power reflection coefficient of the input end of the impedance matcher 30 is 0; The bias power supply 20 transitions from a pulse-on state to a pulse-off state, causing a change in impedance such that the matching point deviates from the center A point and changes to point B or point C. It is necessary to adjust the frequency of the source power source 10 so that the matching point returns to the center point A in the state where the pulse is off, so that the power reflection coefficient of the input end of the impedance matching unit 30 is 0, and the plasma etching is improved. The system's power supply efficiency.

Since the power variation of the bias power source 20 does not affect the density of the plasma in the reaction chamber, it affects the thickness of the sheath generated by the plasma in the reaction chamber 40, and the sheath of the plasma is caused. The thickness changes to cause a change in capacitance between the two plates within the reaction chamber, and the change in capacitance affects the imaginary part of the impedance of the reaction chamber, and has substantially no effect on the real part of the impedance, The impedance includes the real part and the imaginary part, specifically, the impedance Z = Re (Z) + jIm (Z).

The angle between the AB line or the AC line and the real axis of the level at point A is the phase angle of the impedance.

At the instant when the bias power supply 20 transitions from the pulse-on mode to the pulse-off mode, the impedance changes, causing the impedance of the plasma etch system to no longer match, and the input power of the input section of the impedance matcher 30 is reflected. . The voltage-current detector 50 detects voltage and current signals on the transmission line of the source power source 10 and the input of the impedance matcher 30, and thereby can obtain the power reflection coefficient R of the input of the impedance matcher 30, and The input impedance Z of the impedance matcher; the voltage-current detector feeds the power reflection coefficient R and the impedance value Z to the frequency adjustment controller 60, and triggers when the power reflection coefficient R reaches the system-set coarse adjustment coefficient The frequency adjustment controller 60 adjusts the frequency of the source power source 10, and the coarse adjustment coefficient may be set according to the requirements of the product, and the coarse adjustment coefficient may be 0.1 to 0.9, and the coarse adjustment coefficient in the implementation force is 0.25, that is, when the power reflection coefficient is greater than 0.25, the frequency adjustment controller 60 is triggered to adjust the frequency of the source power source 10.

The frequency adjustment controller 60 adjusts the frequency of the source power source 10 with the reflection coefficient and the impedance value fed back by the voltage-current detector 50, and uses the first matching frequency f0 as a reference frequency to find the bias power source 20 in the pulse. The second matching frequency in the off state.

As can be seen from the original Smith chart, the impedance has a phase angle greater than zero in the event that the impedance of the plasma etch system does not match. When the sine value of the phase angle is greater than 0, the matching point is above the real axis; when the sine value of the phase angle is less than 0, the matching point is below the real axis. The phase angle of the impedance is θ, and the sine value of the phase angle Sin(θ)= Im(Z)/[Im(Z)2+Re(Z)2]1/2, so the voltage-current The detector 50 can obtain the positive and negative sinusoidal values of the phase angle of the impedance by detecting the obtained impedance value. The sine value of the impedance phase angle is positive, that is, the imaginary part of the impedance is positive; the sine value of the phase angle of the impedance is negative, that is, the imaginary part of the impedance is negative.

When the sine value of the phase angle of the impedance is a positive number (the imaginary part of the impedance is positive), the frequency adjustment control unit 60 gradually decreases the frequency of the source power source 10 on the basis of the first matching frequency f0; When the sine value of the phase angle of the impedance is a negative number (the imaginary part of the impedance is negative), the frequency adjustment control unit 60 gradually increases the frequency of the source power source 10 based on the first matching frequency f0.

And, in the process of adjusting the frequency of the source power source 10, the frequency of the frequency at which the source power source is increased or decreased a single time is a frequency step, and the magnitude of the frequency step is determined according to The size of the power reflection coefficient is adjusted.

Specifically, in a case where the power reflection coefficient is large, a larger frequency step may be selected. For example, in a case where the power reflection coefficient is greater than 0.25, the value of the frequency step may be 100 KHz; With the frequency adjustment of the source power source 10, the power reflection coefficient is gradually reduced, and the value of the frequency step can also be reduced as the power reflection coefficient is decreased. In one embodiment, the value of the frequency step is proportionally reduced as the power reflection coefficient decreases, for example, the power transmission coefficient is reduced by 1/2, and the frequency step is also reduced accordingly. /2.

After the frequency adjustment control unit adjusts the frequency of the source power source 10 once, the voltage-current detector 50 synchronizes the detection of the power reflection coefficient R and the input impedance Z of the impedance-matcher input of the frequency-adjusted source power supply 10 And promptly feeding back to the frequency adjustment controller, the frequency adjustment controller instantly adjusts the value of the frequency step of the frequency change of the source power source 10 according to the obtained power reflection coefficient and the sine value of the phase angle of the impedance, The power reflection coefficient is getting smaller and smaller, and the frequency of the source power source 10 is also closer to the second matching frequency of the bias power source 20 in the pulse off mode. Finally, when the sine value of the phase angle of the impedance is 0, the frequency adjustment of the source power source 10 is stopped. At this time, the power reflection coefficient of the input end of the impedance matching unit 30 is equal to 0, and the plasma is engraved. Impedance matching of the etch system.

In other embodiments of the present invention, the source power source 10 can also operate in the pulse power mode together with the bias power source 20, and the output power of the source power source 10 ranges from 200 W to 1000 W. Source source 10 may or may not be synchronized with the pulse of bias supply 20. Since the frequency change of the source power source 10 changes the density of the plasma within the reaction chamber 40, it also affects the real part of the impedance of the reaction chamber 40. Subsequently, the frequency of the source power source 10 is adjusted by using the method in this embodiment, and a suitable frequency can also be found to make the sine value of the phase angle of the impedance equal to 0, but the real part of the impedance also changes. The power reflection coefficient at the input of impedance matcher 30 will still be greater than zero. In the case where the pulse-on state of the source power source 10 is not much different from the output power of the pulse-off state, the reflection coefficient may be smaller than the case where the sine value of the phase angle of the impedance is equal to 0 after the frequency adjustment. The coarse adjustment coefficient set by the system can still meet the actual production requirement; and if the difference between the output power of the source power source in the pulse-on state and the input power in the pulse-off state is large, the source power source 10 is passed. The frequency adjustment also fails to make the power reflection coefficient at the input of the impedance matcher 30 less than the system-set coarse adjustment coefficient. In one embodiment, the output power of the pulsed-on state of the source power source 10 is 1000 W, and the output power of the pulse-off state of the source power source 10 is greater than 200 W.

In summary, in the embodiment of the present invention, when the bias power supply 20 is changed from the pulse-on state to the pulse-off state, causing the impedance of the plasma etching system to change, the frequency of the source power source 10 is passed. An adjustment is made to find the matching frequency of the bias supply 20 in the pulse off mode. The frequency adjustment controller 60 uses the first matching frequency of the source power source 10 in the continuous power operation mode as the reference frequency, and determines the direction of the frequency adjustment according to the positive and negative values of the sine value of the phase angle of the impedance of the input end of the impedance matching adjuster 30. When the sine value of the phase angle is positive, the frequency of the source power source 10 is lowered, and if the sine value of the phase angle is negative, the frequency of the source power source 10 is increased. By determining the direction of the frequency adjustment by the positive and negative phases of the impedance phase angle, the frequency sweep range of the source power supply 10 can be reduced, and the efficiency of the frequency adjustment can be improved.

Moreover, the frequency of the source power supply 10 is adjusted by a single frequency step, and the magnitude of the frequency step can be determined according to the power reflection coefficient of the input end of the impedance matching unit 30, and the frequency step can be determined according to the The reduction of the power reflection coefficient is gradually reduced, so that the sine value of the phase angle of the impedance gradually becomes 0, and the reflection coefficient can be gradually approached to 0 to avoid sweeping due to excessive frequency change. The accuracy is low, and the second matching frequency is missed, further improving the efficiency of the impedance matching of the plasma etching system, and the plasma can be quickly realized when the bias power source 20 is switched in the pulse-on and pulse-off modes. The impedance matching of the body etching system improves the power supply efficiency of the power supply.

Although the present invention has been disclosed above, the present invention is not limited thereto. Any changes and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be determined by the scope of the claims.

10‧‧‧Power supply
20‧‧‧Paranoid power supply
30‧‧‧impedance matcher
40‧‧‧Mirror cavity
50‧‧‧Voltage-current detector
60‧‧‧frequency adjustment controller

1 is a schematic view of a plasma etching system of an embodiment of the present invention; and FIG. 2 is a schematic view of an impedance matching point of a plasma etching system according to an embodiment of the present invention on a Smith chart.

10‧‧‧ source power

20‧‧‧Paranoid power supply

30‧‧‧impedance matcher

40‧‧‧Mirror cavity

50‧‧‧Voltage-current detector

60‧‧‧frequency adjustment controller

Claims (15)

An impedance matching method for a plasma etching system, comprising: providing a plasma etching system, the plasma etching system comprising: an impedance matching device, wherein an input end of the impedance matching device is electrically connected to a source power source and a bias power source The output end of the impedance matching device is electrically connected to the reaction cavity, the connection end of the impedance matching device and the source power source is electrically connected to one end of the voltage-current detector, and the other end of the voltage-current detector is controlled by frequency adjustment The unit is connected to the source power source; the source power source and the bias power source are simultaneously operated in the continuous power mode, and the frequency of the source power source is adjusted to match the source power source impedance with the impedance of the matcher input terminal to obtain a first matching frequency; The power source is converted into a pulse power mode, the pulse power mode including a pulse on state and a pulse off state, the power of the pulse on state being the same as the power in the continuous power mode, and the power of the pulse off state is less than the pulse on state Power, the first matching frequency is used as a reference for the source power source in the biased power pulse on state Rate; when the bias power is changed from a pulse-on state to a pulse-off state, increasing or decreasing the frequency of the source power source based on the reference frequency to make the source power source impedance and the impedance of the input end of the matcher Match to obtain the second matching frequency of the source power. The impedance matching method of the plasma etching system of claim 1, wherein the method of adjusting a frequency of the source power source comprises: the voltage-current detector obtaining a short input current and voltage connected to the source power source and the impedance matching device, The current and voltage data are obtained as impedance and power reflection coefficients at an input of the impedance matching device, and the power reflection coefficient is a ratio of the reflected power to the output power of the source power source; and the impedance and power reflection coefficient of the impedance matching device are fed back to a frequency adjustment controller; the frequency adjustment controller adjusts a frequency of the source power source according to the obtained input impedance value and the power reflection coefficient. The impedance matching method of a plasma etching system according to claim 2, wherein the frequency adjustment control unit controls a direction of source power frequency adjustment by a sine value of a phase angle of an impedance of an input end of the impedance matching device: if the phase If the sine value of the angle is greater than 0, the frequency of the source power source is lowered; if the sine value of the phase angle is less than 0, the frequency of the source power source is increased, and when the sine value of the phase angle is 0, the frequency modulation is stopped. The frequency of the source power supply is the second matching frequency. The impedance matching method of the plasma etching system according to claim 3, wherein in the process of adjusting the source power frequency, the value of the frequency of the source power supply that is reduced or increased a single time is a frequency step, according to the power reflection coefficient The size of the frequency is adjusted by the stepping value. The impedance matching method of the plasma etching system of claim 4, wherein the larger the power reflection coefficient, the larger the value of the frequency step. The impedance matching method of the plasma etching system of claim 5, wherein the power reflection coefficient is greater than 0.25, and the value of the frequency step is 100 kHz. The bulk impedance matching method of the plasma etching system of claim 4, wherein the value of the frequency step decreases as the power reflection coefficient decreases. The impedance matching method of the plasma etching system of claim 7, wherein the value of the frequency step is proportionally reduced as the power reflection coefficient decreases. The impedance matching method of the plasma etching system of claim 1, wherein after the bias power source is converted into a pulse power mode, a power reflection coefficient obtained by the voltage-current detector changes to trigger the frequency adjustment control unit Frequency adjustment of the source power supply. The impedance matching method of the plasma etching system of claim 9, wherein the power reflection coefficient for triggering the frequency adjustment of the source power source ranges from 0.1 to 0.9. The impedance matching method of the plasma etching system according to claim 1, wherein a power reflection coefficient of the impedance matching device input terminal is 0 when the source power source impedance is matched with the impedance of the matcher input terminal. The impedance matching method of the plasma etching system of claim 1, wherein the source power source and the bias power source work together in a pulse power mode. The impedance matching method of the plasma etching system of claim 1, wherein the output power of the source power source in the pulse power mode ranges from 200 W to 1000 W. The impedance matching method of the plasma etching system of claim 1, wherein the frequency of the bias power source is automatically set by a bias power source. The impedance matching method of the plasma etching system of claim 1, wherein the impedance matching device is provided with an impedance matching capacitor, and the impedance matching capacitor does not change according to a preset value.