TWI541893B - Process apparatus and method for plasma etching process - Google Patents

Description

Processing device and method for plasma etching process

The present invention relates to the field of semiconductor technology, and more particularly to a processing apparatus and method for compensating for a plasma etching process that is asynchronous when gas delivery and bias power switching are fast, wherein the plasma etching process includes two The deposition and etching process sub-processes performed alternately with the loop.

In recent years, the requirements for microelectronics in the fields of automotive electronics, aerospace, communications, and computers have increased, requiring them to become more compact, ultra-light, ultra-thin, reliable, low-power, multi-functional, and low-cost. Therefore, the requirements for the etching process are getting higher and higher.

The etching process includes dry etching and wet etching. The dry etching is often performed by a plasma etching process. Plasma refers to a gas that is ionized, mainly composed of particles such as electrons, ions, atoms, molecules, or radicals. Plasma etching uses a high-frequency glow discharge reaction to activate a reactive gas, such as an atom or a radical, which diffuses to a permitting site where it reacts with the material being etched to form a volatile reactant. And was removed.

The plasma etching process has become an important technology in the field of semiconductor unprocessed, and as the requirements for the etching process become higher and higher, the loop etching has become a major trend, such as for the via hole etching process. The 矽-via etch process is a deep etch process using plasma dry etching, and the deep etch process is generally performed by the Bosch process. The Bosch process is an improved plasma etch process. The Bosch process is to repeatedly deposit a resist layer and a passivation sidewall on the sidewall during the reactive ion etching process to form a trench having a high aspect ratio under the condition of protecting the sidewall. During the deposition process The fluorocarbon-containing plasma gas is introduced into the reaction chamber to form a fluorinated carbon-based polymer, which is deposited on the sidewall and the bottom to function as a sidewall passivation. During the etching process, the fluorine-containing gas enters the reaction chamber to form a plasma. Due to the anisotropic etching, the protective film at the bottom is removed, and the bottom of the groove is further etched, and the polymer protective film on the sidewall disappears. A protective film is deposited before the end of the process, and the process is repeated alternately to achieve high aspect ratio etching.

Plasma Spectroscopy (OES) is the most widely used endpoint detection method. The principle is to achieve end point detection by detecting changes in the intensity of light emitted by a reactive chemical group or a volatile group in the plasma. When an atom or molecule in a plasma is excited by an electron to an excited state, it returns to another energy state, accompanied by the light emitted by the process. Light intensity changes can be observed from the observation holes on the side walls of the reaction chamber. The wavelengths of light waves excited by different atoms or molecules are different, and the change of light intensity reflects the change of atomic or molecular concentration in the plasma. A change in the emission spectrum is detected at the desired end of the etch, which is the detected etch end point. The end of the process step is monitored on the fly according to the change in the intensity of the detected light that becomes stronger or weaker.

In a conventional plasma etching process, a plasma spectrometer formed by a plasma spectroscopic detection technique is used for end point detection. A plasma spectrometer usually includes a linear array of thousands of CCD cells, and the monitored wavelength. From 200nm to 1100nm, in the plasma spectrum detector, after photoelectric conversion, A/D conversion of electrical signals and complex digital signal processing, the data is obtained, and then the data is sent to the corresponding application software for processing. Observing the plasma spectrum of the plasma change.

For example, in the Bosch process, a time control module is used to control the deposition or etching process, and a plasma spectrum detector is used to perform end point detection of the process. During the alternate process of etching or deposition, the time control module simultaneously controls the opening of the gas delivery valve and the bias power supply. However, due to the different delay times of RF power switching and gas delivery, respectively, several hundred milliseconds and 0.4- respectively. 0.8 seconds, with a large delay The difference between the RF power supply and the gas delivery creates a large phase difference. Due to the concentration of gas entering the plasma chamber, it is impossible to reach the required value at the beginning, if a bias voltage is applied at this time. The power does not form the required plasma well, resulting in a decrease in the process quality and stability of the deposition or etching process, affecting the quality and stability of the entire process, such as etching control and ER control of the pattern. It becomes difficult.

In addition, in other loop etching processes including fast switching, there is also a phenomenon in which the gas delivery and the applied bias power supply are not synchronized.

Therefore, a method is needed to compensate for the unsynchronization of gas delivery and bias power switching in the loop etching process, thereby facilitating the synchronization of gas delivery and bias power switching, further improving the stability and controllability of the entire process.

In view of the above, it is an object of the present invention to provide an apparatus and method for compensating for gas transmission and radio frequency power that are not synchronized during fast switching in a loop plasma etching process, thereby improving stability and controllability of the entire process.

The technical means adopted by the present invention to solve the problems of the prior art provides a processing apparatus for a plasma etching process, the etching process comprising two deposition and etching process sub-processes performed alternately with each other, wherein The device comprises a plasma process chamber and a process condition auxiliary unit, and the auxiliary unit comprises a first gas delivery valve, a second gas delivery valve, a bias power source, a time control module and a detection module. a first gas delivery valve for delivering the gas in the deposition step to the plasma processing chamber; a second gas delivery valve for delivering the gas in the etching step to the plasma processing chamber; and a bias power supply for providing the deposition The bias power in the process sub-process or the bias power in the sub-process of the etching process; the time control module for controlling the time of the deposition or etching process sub-process, and the first and second inputs The opening and closing switching of the gas valve; the detecting module comprises a detecting unit and a switching unit, wherein the detecting unit is configured to detect a characteristic value formed by entering the gas concentration in the plasma processing chamber during the deposition step or the etching process; Determining, by the feature value, the deposition or etching process sub-process Entering the gas species and concentration in the plasma process chamber, and switching the bias power output to meet the bias power of the deposition or etching process sub-process according to the gas type and concentration.

Preferably, the detecting unit in the detecting module comprises a plasma spectrum detector, the plasma processing chamber has a quartz window on a sidewall thereof, and the plasma spectrum detector is detected and transported into the process chamber through the quartz window. A characteristic value of the gas, wherein the characteristic value is an intensity of a characteristic peak in a characteristic spectrum of the gas entering the process chamber.

The present invention also provides a plasma etching method for a deposition and etching process sub-process including alternating loops, the deposition and etching process sub-process specifically comprising the following steps: in the deposition process sub-process In step S11, the time control module controls to open the first gas valve to input the gas required in the deposition process, and simultaneously close the second gas delivery valve; Step S12: the detection mode The detecting unit of the group detects the characteristic value formed by the gas concentration in the plasma processing chamber; step S13: the switching unit determines, according to the characteristic value, the gas type and concentration entering the plasma processing chamber, when When the characteristic value reaches a predetermined threshold, switching the bias power supply to output the bias power of the deposition process sub-process; and in the etching process sub-process: step S21: the time control module controls to turn on the a second gas delivery valve inputs a gas required in the etching process, and simultaneously closes the first gas delivery valve; and step S22: the detection unit of the detection module detects a characteristic value formed by the gas concentration in the plasma process chamber; step S23: the switching unit determines, according to the characteristic value, a gas type and concentration entering the plasma process chamber, when the characteristic value reaches a predetermined threshold Switching the bias power supply outputs a bias power of the etching process sub-process.

Preferably, the characteristic value is the gas entering the process chamber The intensity of the characteristic peaks in the characteristic spectrum of the volume.

Preferably, the deposition process sub-process gas comprises a fluorocarbon-containing gas, and the etch process sub-process gas comprises a fluorine-containing gas.

Preferably, the fluorocarbon-containing gas is C ₄ F ₈ and the fluorine-containing gas is SF ₆ .

Preferably, the characteristic value is the intensity of a characteristic peak in a characteristic spectrum of a plasma spectrum of the input gas.

Preferably, the etching process is a germanium via etching process.

Preferably, the 矽 through hole etching process is a Bosch process.

Preferably, the bias power source is a radio frequency power source.

Preferably, the power of the RF power source of the deposition process sub-process is 0-100 W, and the RF power of the RF power supply of the etching process sub-process is 30-1500 W.

It can be seen from the above technical solution that the plasma etching processing device and the method for the gas transmission and the bias power switching are not synchronized in the compensation loop etching process provided by the present invention, and the gas delivery and the bias power switching are respectively performed by time. The control module and the detection module control, and the detection module monitors the change state of the gas flowing into the process chamber, that is, the type and concentration of the gas, so that the bias power switching time can be more accurately controlled, thereby overcoming the gas delivery and the bias voltage. The asynchronous phenomenon caused by the difference in power switching delay time improves the stability and controllability of the entire process.

The specific embodiments of the present invention will be further described by the following examples and the accompanying drawings.

100‧‧‧plasma process chamber

101‧‧‧ Focus ring

102‧‧‧Processing chamber

103-1, 103-2‧‧‧ gas source

104‧‧‧RF power supply

105‧‧‧Vacuum pump

106‧‧‧Electrical chuck

107‧‧‧plasma confinement ring

108‧‧‧ Grounding device

109‧‧‧Upper electrode

110‧‧‧ lower electrode

111‧‧‧Base

a‧‧‧First air valve

b‧‧‧Second air valve

P‧‧‧Processing area

W‧‧‧ substrates

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of a plasma processing chamber in accordance with a preferred embodiment of the present invention, the use of which is a compensation method in accordance with a preferred embodiment of the present invention.

2 is a preferred embodiment of the auxiliary unit of the plasma etching apparatus in which the gas delivery and the bias power switching are not synchronized in the compensation loop plasma etching process of the present invention. Schematic diagram of the example.

3 is a flow chart showing a method for asynchronously switching gas delivery and bias power switching in the compensation loop plasma etching process according to the above preferred embodiment of the present invention.

Embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It is to be understood that the invention is not to be construed as being limited

Generally, the etching process includes two deposition and etching process sub-processes performed alternately with each other, and the plasma etching process of the present invention is used to compensate gas transfer and bias in the loop etching process. The problem of power switching is not synchronized, the device includes a plasma process chamber and a process condition auxiliary unit. In the present invention, the plasma process chamber can be of any kind without any limitation.

Please refer to FIG. 1. FIG. 1 is a schematic structural view of a plasma processing chamber in the embodiment. As shown, the plasma processing chamber 100 has a processing chamber 102, the processing chamber 102 is substantially cylindrical, and the sidewalls of the processing chamber 102 are substantially vertical, and the processing chamber 102 has upper electrodes disposed in parallel with each other. 109 and lower electrode 110. Typically, the area between the upper electrode 109 and the lower electrode 110 is the processing area P which will form high frequency energy to ignite and sustain the plasma. The electrostatic chuck 106 and the lower electrode 110 are disposed in the susceptor 111. A substrate W to be processed is placed over the electrostatic chuck 106, which may be a semiconductor substrate to be etched or processed or a glass plate to be processed into a flat panel display. The electrostatic chuck 106 is used to clamp the substrate W. A plasma confinement ring 107 is located on either side of the electrostatic chuck 106 for confining the plasma within the support region and grounding the plasma confinement ring through the grounding device 108.

The above-mentioned FIG. 1 is a schematic view of a plasma etching apparatus in the present embodiment, which is only for explaining the present embodiment and is not intended to limit the scope of the present invention.

The present invention will now be compensated by the specific embodiments in conjunction with Figures 2 and 3. The auxiliary unit and method of the plasma etching apparatus in which the gas delivery and the bias power switching are not synchronized in the etching process are further described in detail. It should be noted that the drawings are in a very simplified form, using a non-precise ratio, and are only used to facilitate the purpose of the embodiments of the present invention.

In the present invention, the etching process used may be, but not limited to, a germanium via etching process, and the method of etching the via holes may be, but not limited to, a Bosch process. In this embodiment, the Bosch process is used to explain the present invention in further detail, and other details are not described herein.

In the Bosch process of this embodiment, the bias power supply used is an example of a radio frequency power supply, including two process sub-processes of deposition and etching processes, but this is not intended to limit the scope of the present invention.

Please refer to FIG. 2. FIG. 2 is a block diagram of an auxiliary unit used in the above plasma etching processing apparatus. The auxiliary unit includes a first gas delivery valve, a second gas delivery valve, a bias power source, a time control module, and a detection module. In this embodiment, a is a first gas delivery valve, and b is a second gas delivery valve. The specific positions of a and b are not limited, and the detection unit of the detection module may be a plasma spectrum detector, and plasma is used in this embodiment. The body detector is explained, this is not intended to limit the scope of the invention. The reaction gas includes a gas in a deposition process and a gas in an etching process. Typically, the deposition process sub-process gas includes a fluorocarbon-containing gas, and the etch process sub-process gas includes a fluorine-containing gas. In the present embodiment, the fluorocarbon-containing gas is C4F8, and the fluorine-containing gas is SF6.

The process gases required in the deposition process and the process gases required in the etch process sub-process are input into the process chamber 102 from the gas sources 103-1 and 103-2, respectively. In the present embodiment, the first gas delivery valve a is used to transport the gas in the deposition process to the processing chamber 102; the second gas delivery valve b is used to transport the etching process to the processing cavity 102. gas.

The bias supply is used to provide bias power during the deposition process or to provide bias power during the etch process. In the embodiment of the invention, the bias power supply It can be an RF power supply. In this embodiment, the RF power supply is taken as an example for explanation, but this is not intended to limit the scope of the present invention.

As shown in FIG. 1, a radio frequency power source 104 can be applied to the upper electrode 109 and the lower electrode 110 for generating a radio frequency power source to generate a large electric field inside the processing chamber 102. It is known that most of the electric field lines are contained in the processing region P between the upper electrode 109 and the lower electrode 110, and this electric field accelerates a small amount of electrons existing inside the processing chamber 102 to the gas molecules of the input reaction gas. collision. These collisions result in ionization of the reactive gas and excitation of the plasma, thereby generating a plasma within the processing chamber 102. The neutral gas molecules of the reactive gas lose electrons when subjected to these strong electric fields, leaving positively charged ions. The positively charged ions accelerate toward the lower electrode and combine with the neutral species in the substrate being processed to excite the substrate processing, that is, the etching, deposition process, and the like.

An exhaust region is provided at a suitable location of the plasma processing chamber 100, the exhaust region being coupled to an external exhaust device (eg, vacuum pump 105) for use in the process during processing The gas and byproduct gases are withdrawn from the process chamber 100. The focus ring 101 is located on the electrostatic chuck 106 to surround the substrate W. The focus ring 101 serves to provide a relatively closed environment around the substrate W, improving the uniformity of the plasma on the W side of the substrate. At the same time, it is also possible to avoid that the back side of the edge of the substrate W is affected by the processing.

We know that the deposition or etching process sub-process time is different, and the gas input during the deposition or etching process is different. The time control module is used to control the time switching of the deposition or etching process. And, at the same time as the time switching, the opening and closing switching of the first gas delivery valve a and the second gas delivery valve b is performed. That is to say, when the time control module controls the conversion from the deposition process sub-process to the etching process sub-process, the first gas delivery valve a is closed, the gas input in the sub-process of the deposition process is stopped, and the first The second gas delivery valve b inputs the gas input during the etching process to the inside of the processing chamber 102.

Under normal circumstances, due to the bias power during the deposition process Or providing the bias power in the etching process is different. In this embodiment, the power of the RF power source of the deposition process may be 0-100 W, and the RF power of the RF power source of the etching process sub-process Can be 30-1500W.

The time control module also controls the bias power in the deposition process sub-process or provides switching of the bias power during the etch process sub-process. As described in the background art, the time control module is controlled by the end point detecting means. Since the gas input has a delay, and the delay time of the radio frequency power is less than the delay time of the gas input, the concentration of the gas entering the plasma chamber cannot be started. To achieve the desired value, if a bias power that satisfies the requirements is applied at this time, the desired plasma is not formed well, resulting in a decrease in the process quality and stability of the deposition or etching process.

In order to solve the above problem well, in the embodiment of the present invention, a detection module is added, the module includes a detecting unit and a switching unit, and the detecting unit is configured to detect entering the depositing step or the etching process sub-process The characteristic value of the plasma spectrum formed by the gas inside the processing chamber 102; the switching unit determines the gas type and concentration entering the processing chamber 102 during the deposition or etching process by the characteristic value, and according to the gas type and concentration, Switching the bias power supply output meets the bias power of the deposition or etching process sub-process. In the present invention, any type of detecting device capable of detecting the type and concentration of gas inside the processing chamber 102 can be applied to the present invention. In the present embodiment, a plasma spectrum detecting technique is employed.

The principle of plasma spectroscopic detection technology is to detect the gas performance by detecting the change of the light intensity of a certain reactive chemical group or a volatile group in the plasma, for example, the type and concentration of the gas. When atoms or molecules in the plasma are excited by electrons to an excited state, the wavelengths of light waves excited by different atoms or molecules are different when returning to another energy state.

The plasma spectrum detector usually includes a linear array of thousands of CCD units. In the plasma spectrum detector, data is obtained after photoelectric conversion, A/D conversion of electrical signals, and complex digital signal processing, and then the data is sent. To corresponding After the application software is processed, the plasma spectrum of the plasma change can be observed immediately, and the change of the characteristic value such as the light intensity in the plasma spectrum can reflect the change of the atomic or molecular concentration in the plasma.

In actual use, the sidewall of the plasma processing chamber 100 may have a quartz window, and the plasma spectrum detector may include a plasma spectrometer placed outside the plasma processing chamber 100, and the processing is detected through the quartz window. The characteristic value of the gas inside the cavity 102, wherein the characteristic value is the intensity of the characteristic peak in the characteristic spectrum. It should be noted that, if the end point detecting means adopts the plasma spectrum detecting technology in this embodiment, the detecting unit in the detecting module in the embodiment can be combined with the plasma spectrum emitting apparatus in the end point detecting means. The difference is that the data in the subsequent processing of the plasma spectrum is different, and the trigger signals and methods are different.

The compensation method for the gas transmission and the bias power switching unsynchronized in the compensation loop etching process of the present embodiment of the present invention will be described in detail below with reference to FIG.

First, at the beginning of the Bosch process, the deposition process sub-process can be performed, but not limited to. During the deposition process, the time control module controls the delivery of gas, and the detection module controls the RF power of the deposition process. The gas at this time may be, but is not limited to, C ₄ F ₈ .

Step S11: The time control module sends a signal, the first gas delivery valve a is opened, and the second gas delivery valve b is closed, and the C ₄ F ₈ gas enters the processing chamber 102.

Step S12: the detecting unit of the detecting module detects the characteristic value formed by the gas concentration inside the processing chamber 102. The characteristic value in the present invention can input the intensity of the characteristic peak of the gas, etc., and the input can be determined according to the peak intensity of the characteristic value. The type and concentration of the gas. In the present embodiment, the characteristic value is the intensity of the characteristic peak of the plasma spectrum of the input gas.

Step S13: When it is determined that the characteristic value in the characteristic spectrum of the gas reaches a predetermined threshold value, for example, the concentration of C ₄ F ₈ in the processing chamber 102 reaches 80%, the switching unit controls the RF power source, and changes the RF power to the deposition process. The RF power of the process. In this embodiment, when the switching unit determines that the characteristic peak intensity displayed in the characteristic spectrum of the plasma spectrum reaches a predetermined threshold, the RF power is changed by controlling the RF power source to be the RF power of the deposition process; it should be noted that the reservation here is The threshold value is based on the intensity of the characteristic line of the plasma spectrum when the gas reaches the process chamber in the actual process (ie, the gas concentration reaches a predetermined threshold). In the deposition process of the embodiment, the characteristic line of 703 nm of F is selected.

In this embodiment, the RF power of the deposition process may be, but is not limited to, 0-100 W. After the RF power is changed to the RF power of the deposition process, the plasma stabilization time in the gas may be, but is not limited to, 0.2-0.4. Second, this is not intended to limit the scope of the invention.

Then, the etching process sub-process can be performed, but not limited to. During the etching process, the time control module controls the gas delivery, and the detection module controls the RF power switching of the etching process sub-process. The gas at this time may be, but not limited to, SF ₆ .

Step S21: The time control module respectively sends signals to the first gas delivery valve a and the second gas delivery valve b of the deposition process sub-process and the etching process sub-process, and then the first gas delivery valve a of the deposition process is closed, and engraved The second gas delivery valve b of the etching process is opened, at which time the SF ₆ gas enters the interior of the processing chamber 102.

Step S22: The plasma spectrum detector of the detection module monitors the characteristic value formed by the gas concentration in the process chamber, and the characteristic value in the present invention may be the intensity of the characteristic peak of the input gas or the like. In the present embodiment, the characteristic value is the intensity of the characteristic peak of the plasma spectrum of the input gas, so that the type and concentration of the gas inside the processing chamber 102 can be judged by detecting the characteristic value of the gas.

Step S23: When it is determined that the characteristic value in the characteristic spectrum of the gas reaches a predetermined threshold, for example, the concentration of the SF ₆ in the processing chamber 102 reaches 80%, the switching unit controls the RF power source, and the RF power is changed into an etching process sub-process. RF power.

In the present embodiment, when the switching unit determines the characteristics of the plasma spectrum When the characteristic peak intensity displayed in the spectrum reaches a predetermined threshold, the RF power is changed to control the RF power of the etching process. It should be noted that the predetermined threshold value is based on the intensity of the characteristic line of the plasma spectrum when the gas reaches the process chamber in the actual process (ie, the gas concentration reaches a predetermined threshold), and is selected in the deposition process sub-process of the embodiment. The characteristic line of 703 nm of F.

In this embodiment, the RF power of the etching process may be, but is not limited to, 30-1500 W. After the RF power is changed to the RF power of the etching process, the plasma stabilization time in the gas may be, but is not limited to, 0.2. - 0.4 seconds, this is not intended to limit the scope of the invention.

In the present embodiment, the deposition and etching process sub-processes are repeated until the through holes are formed. However, this is not intended to limit the scope of the invention.

In summary, the present invention provides a processing device and an etching method for a plasma etching process that compensates for gas delivery and bias power in an etch process, and uses a detection module to control a change in bias power, a time control mode. The group controls the delivery of gas, thereby facilitating the synchronization of gas delivery and bias power switching, improving the stability and controllability of the entire process.

The above description is only for the preferred embodiment of the present invention, and those skilled in the art can make other improvements according to the above description, but these changes still belong to the inventive spirit of the present invention and the patents defined below. In the scope.

Claims (9)

A processing apparatus for a plasma etching process, the etching process comprising two deposition and etching process sub-processes performed alternately with a loop, the device comprising a plasma process chamber and a process condition auxiliary unit, characterized in that The auxiliary unit includes: a first gas delivery valve for conveying the gas in the deposition step to the plasma processing chamber; and a second gas delivery valve for conveying the gas in the etching step to the plasma processing chamber; a power source for providing bias power in the deposition process sub-process or providing bias power in the etching process sub-process; a time control module for controlling the time of the deposition or etching process sub-process And the opening and closing switching of the first and second gas delivery valves; the detecting module comprises: a detecting unit, configured to detect a gas concentration entering the plasma processing chamber during the deposition step or the etching process sub-process a characteristic value; a switching unit that determines, by the feature value, a gas species and a concentration entering the plasma process chamber during the deposition or etching process, and according to the gas species And a concentration, switching the bias power supply output to meet a bias power of the deposition or etching process sub-process, wherein the first gas delivery valve to the plasma processing chamber is connected to the second gas delivery valve The gas pipeline to the plasma processing chamber is a different gas pipeline, and the gas delivered from the first gas delivery valve to the gas pipeline of the plasma processing chamber is different from the second gas delivery valve to the plasma processing chamber The gas conveyed by the gas pipeline, wherein the detecting unit in the detecting module comprises a plasma spectrum detector for maintaining the type and concentration of gas entering the plasma processing chamber, and the detecting system is located at the a quartz window on a sidewall of the plasma processing chamber for detecting a characteristic value of gas transported into the process chamber, the characteristic value being entered The intensity of the characteristic peak in the characteristic spectrum of the gas in the process chamber, the bias power of the deposition process sub-process is 0-100 W, and the bias power of the etching process sub-process is 30-1500 W. The apparatus of claim 1 comprising a deposition and etching process sub-process performed alternately with a loop, wherein the deposition and etching process sub-process comprises the step of: in the deposition process sub-process Step S11: The time control module controls to open the first gas valve to input the gas required in the deposition process, and simultaneously close the second gas delivery valve; Step S12: the detection module The detecting unit detects a characteristic value formed by the concentration of the gas in the plasma processing chamber; step S13: the switching unit determines, according to the characteristic value, the gas type and concentration entering the plasma processing chamber, when When the characteristic value reaches a predetermined threshold, the bias power supply is switched to output a bias power of the deposition process sub-process, the bias power of the deposition process sub-process is 0-100 W; and in the etching process sub-process In step S21, the time control module controls to open the second gas delivery valve to input the gas required in the etching process, and simultaneously close the first gas delivery valve; step S22 The detecting unit of the detecting module detects a characteristic value formed by the gas concentration in the plasma processing chamber; and step S23: the switching unit determines, according to the characteristic value, the gas type and concentration entering the plasma processing chamber When the characteristic value reaches a predetermined threshold, the bias power supply is switched to output a bias power of the etching process sub-process, and the bias power of the etching process sub-process is 30-1500W. The method of plasma etching according to claim 2, wherein the characteristic value is an intensity of a characteristic peak entering a characteristic spectrum of the gas in the process chamber. The method of plasma etching according to claim 2, wherein the deposition process sub-process gas comprises a fluorocarbon-containing gas, and the etch process sub-process gas comprises a fluorine-containing gas. The method of plasma etching according to claim 4, wherein the fluorocarbon-containing gas is C ₄ F ₈ and the fluorine-containing gas is SF ₆ . The method of plasma etching according to claim 2, wherein the characteristic value is an intensity of a characteristic peak in a characteristic spectrum of a plasma spectrum of the input gas. The method of plasma etching according to claim 2, wherein the etching process is a germanium via etching process. The method of plasma etching according to claim 7, wherein the meandering via process is a Bosch process. The method of plasma etching according to claim 2, wherein the bias power source is a radio frequency power source.