CN108521707B - Two-stage regulation and control method and system for plasma density - Google Patents
Two-stage regulation and control method and system for plasma density Download PDFInfo
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- CN108521707B CN108521707B CN201810354510.7A CN201810354510A CN108521707B CN 108521707 B CN108521707 B CN 108521707B CN 201810354510 A CN201810354510 A CN 201810354510A CN 108521707 B CN108521707 B CN 108521707B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
- H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/0006—Investigating plasma, e.g. measuring the degree of ionisation or the electron temperature
- H05H1/0068—Investigating plasma, e.g. measuring the degree of ionisation or the electron temperature by thermal means
- H05H1/0075—Langmuir probes
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
- H05H1/46—Generating plasma using applied electromagnetic fields, e.g. high frequency or microwave energy
- H05H1/4645—Radiofrequency discharges
Abstract
A two-stage regulation method and a two-stage regulation system for plasma density, which belong to the field of plasma density regulationThe invention belongs to the technical field of plasma diagnosis research, and aims to solve the problems that the density of the existing gas discharge type plasma is inaccurate, unstable and untimely through a traditional single variable density control method. The method comprises the following steps: when the actual density rho and the preset density rho of the plasmaTSatisfies the condition | D ∞>60％ρTWhen in use, the plasma density is roughly adjusted by controlling the air input amount by adopting a piezoelectric crystal valve; when the actual density rho and the preset density rho of the plasmaTSatisfies the condition of 20% ρT≤|D|≤60％ρTWhen the plasma density is adjusted, the plasma density is adjusted by adjusting the power of the radio frequency power supply until the condition | D ∞ is met<ε is the allowable error.
Description
Technical Field
The invention belongs to the technical field of plasma diagnosis research, and particularly relates to a plasma density regulation and control technology.
Background
As a special electromagnetic medium, the plasma has wide application prospect in the fields of new energy, national safety, novel material preparation and treatment, life and environmental science and the like. Many plasma application techniques do not depart from the plasma generating device, i.e., the plasma source. In the laboratory, the most interesting plasma generation methods at present are gas discharge, thermal ionization, ray irradiation, photo ionization, laser radiation ionization and the like, but the most mature and dominant plasma generation methods are gas discharge methods. With the continuous development and breakthrough of plasma research and application technology in recent years, gas discharge plasma technology can be seen not only in the traditional industrial application fields (such as surface modification of materials, processing and manufacturing industries, and the like), but also in many new emerging technical fields (such as biological and environmental engineering, plasma chemical industry, aerospace science technology, and the like). The accurate measurement and control of the plasma density, which is a key parameter, are important and difficult problems affecting the application of the plasma technology. The plasma density is measured and diagnosed on line, real-time data acquisition, analysis and processing are carried out, and feedback control of the plasma density is carried out through a control algorithm, so that the problems which need to be solved by experimenters at present are solved urgently.
At present, there are two main methods for controlling plasma density: one is to adjust the gas charging valve in real time according to the change of the plasma density signal in the discharge process, and change the gas inflow, thereby achieving the effect of adjusting the plasma density. Namely, the difference between the actual plasma density and the preset density is adjusted by controlling the air inflation quantity of the piezoelectric crystal inflation valve. Controlling the plasma density in this manner is typically a programmed pulse injection method, i.e., the control of the plasma density during a discharge is achieved by presetting the gas pulse parameters according to the plasma density signal before each discharge. The method has good effect in previous experiments, but as the experiments are further advanced, the program control pulse injection method has the defects that the plasma density is difficult to effectively control due to the inherent defects, and the real-time performance is poor. Obviously, the program-controlled pulse injection method cannot adjust the air supply amount in real time according to the discharge condition, and thus cannot effectively control the density, so that the experiment cannot achieve the expected effect. Later, people improved the control method, and adopted a density feedback gas supply method, that is, adopted closed-loop control, and adjusted the gas supply amount in real time according to the change of the density signal during the discharge period, so as to achieve effective control of the plasma density. However, there is a common disadvantage between them: the control of the piezoelectric crystal charging valve to charge the vacuum chamber in the plasma source is unidirectional. From the control theory point of view, such a control system is a divergent system and is extremely unstable. When the density is lower than a preset value, controlling the pulse width to be increased and supplementing air to be increased; when the density reaches above the preset value, the actual density is larger than the preset value, and the pulse width is controlled to be reduced until the pulse width is zero. However, since the plasma density is affected by various factors, sometimes the density will not decrease quickly even if the gas supply is not performed, but the control system has no way to adjust and only waits for the density to decrease, so that the density control effect is greatly reduced, and the real-time performance is poor.
Another method is to adjust the power by controlling the power of the rf power source. And a matching network is arranged between the radio frequency power supply and the plasma source, so that the relation between the internal resistance of the power supply and the impedance of the plasma is well matched, the power of the power supply is completely coupled to the plasma, and no energy loss exists. If the plasma density is changed in a large range, the power is adjusted greatly, so that the adjustment period is long and the impedance matching relationship is poor, a part of energy is reflected back to the power supply, the energy reaching the inside of the plasma is not the result which is wanted, and the stability of the system cannot be maintained.
Disclosure of Invention
The invention provides a two-stage regulation and control method and a two-stage regulation and control system for plasma density, aiming at solving the problems of inaccuracy, instability and untimely time of the density of the existing gas discharge type plasma through a traditional single variable density control method.
The invention relates to a two-stage regulation and control method of plasma density, which comprises the following steps:
when the actual density rho and the preset density rho of the plasmaTSatisfies the condition | D ∞>60％ρTWhen in use, the plasma density is roughly adjusted by controlling the air input amount by adopting a piezoelectric crystal valve; when the actual density rho and the preset density rho of the plasmaTSatisfies the condition of 20% ρT≤|D|≤60％ρTWhen the plasma density is adjusted, the plasma density is adjusted by adjusting the power of the radio frequency power supply until the condition | D ∞ is met<ε is the allowable error.
Preferably, the allowable error ∈ is 10% ρT～20％ρT。
A system for implementing a two-stage regulation method of the plasma density comprises a density acquisition unit, a density comparison unit and a controller;
the density acquisition unit is used for acquiring the actual density of the plasma in the plasma vacuum chamber and sending the actual density of the plasma to the density comparison unit;
the density comparison unit is used for comparing the actual density of the plasma with the preset plasma density and sending the deviation value of the actual density of the plasma and the preset plasma density to the controller;
the controller is used for sending a control signal to the radio frequency power supply or the power amplifier according to the deviation value, and controlling the air input of the piezoelectric crystal valve by adjusting the power of the power amplifier so as to roughly adjust the plasma density; or to fine tune the plasma density by adjusting the power of the rf power supply.
Preferably, the density acquisition unit comprises a langmuir probe, a data processing circuit and a data acquisition card, wherein the front end of the langmuir probe extends into the plasma vacuum chamber, and a signal of the langmuir probe is transmitted to the data acquisition card through the data processing circuit.
The invention has the beneficial effects that:
(1) under the condition of ensuring the stability of the system, the deviation between the actual density value and the given density value is smaller, and the accuracy is improved.
(2) When the given plasma density value is greatly different from the actual plasma density value, the density control method of inflating the plasma source by controlling the piezoelectric crystal inflation valve is adopted for rough adjustment, and then the mode of adjusting the radio frequency power is adopted for fine adjustment, so that the stability of the system is improved.
(3) When the actual density reaches above the preset value, the density is reduced to a proper value by adopting a mode of adjusting the discharge power without waiting for the density to be reduced, and the response time of the system is reduced.
(4) The invention can quickly reach the preset value of the density, reduces the gas consumption, has simple device, strong operability and reduced cost, and is suitable for the requirements of engineering application.
Drawings
FIG. 1 is a schematic diagram of a two-stage regulation system for plasma density according to the present invention;
FIG. 2 is a schematic diagram of a two-stage method of regulating plasma density according to the present invention;
FIG. 3 is a block diagram of density regulation closed loop control.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
Example (b): the gas in the gas source is input into a piezoelectric crystal valve through a pressure reducing valve, and the piezoelectric crystal valve is connected with a vacuum chamber gas inlet of the plasma source. The computer outputs control signal, which is sent to the piezoelectric crystal valve through the power amplifier to control its opening and supply gas to the inside of the plasma source.
The rf power supply couples all of the power supply power to the plasma source through a matching network, the rf power supply connecting the electrodes of the vacuum chamber of the plasma source through the matching network.
The mechanical pump set and the molecular pump set are both connected with the vacuum chamber, the mechanical pump set is used as a first-stage vacuumizing unit and can reduce the air pressure in the vacuum chamber to 1Pa, and the molecular pump set is used as a second-stage vacuumizing unit and can reduce the air pressure to 1.0 multiplied by 10 < -4 > Pa. The vacuum chamber body is fixed inside the radio frequency shielding box.
The two-stage regulation and control method is completed by a computer, a data acquisition card is arranged in the computer, the front end of the Langmuir probe is inserted into a plasma vacuum chamber, the signal of the Langmuir probe is sent to the data acquisition card through a data processing circuit, and the electrical signal acquired by the Langmuir probe is an analog signal and is converted into a digital signal through the data acquisition card, and the digital signal is input into the computer. The computer outputs digital signals, and the digital signals are converted by a data acquisition card to generate analog signals to act on a radio frequency power supply and a piezoelectric crystal valve. The signal applied to the piezoelectric crystal valve is processed by a power amplifier.
The computer is also used for realizing the input of the preset value of the plasma density and the calculation of the plasma density.
The two-stage regulation and control method comprises the following steps: and a radio frequency power supply is adopted for discharging, a Langmuir probe is arranged on the outer wall of the vacuum chamber to collect electric signals inside the plasma, then the electric signals are transmitted to a computer for density calculation, the density calculation result is compared with a preset density value, the deviation D between the actual density and the preset value is calculated, and a control signal is output according to the size of the deviation D.
If the deviation D is small (20%. rho.)T≤|D|≤60％ρT) When in use, the density is adjusted by directly adopting a mode of adjusting the radio frequency power, the precision is high, and the method comprises two conditions: actual density ρ>Preset density ρTTrue density ρ<Preset density ρTCan be fine-tuned to a predetermined density.
If the deviation D is larger (| D +)>60％ρT) In the first step, the plasma density is roughly adjusted by controlling the air inflow by adopting a piezoelectric crystal valve; after coarse adjustment, the actual density value is close to the preset density, and if the measured plasma actual density rho is close to the preset density rhoTSatisfies the condition of 20% ρT≤|D|≤60％ρTThen, the plasma density is finely adjusted by adjusting the power of the radio frequency power supply until the actual density rho and the preset density rho are achievedTThe deviation D of the two satisfies the condition | D +<Until epsilon, the allowable error epsilon is set to 20% rhoT. And if the requirement of the preset density is not met, repeatedly executing the operation.
Based on the above analysis, it can be seen that the present embodiment can bring the following beneficial effects: the system does not depend on manual frequent operation in the whole control process, is realized through a hardware automatic control function, and carries out two-stage control by adjusting the piezoelectric crystal valve and the radio frequency power, thereby greatly improving the problem of inaccurate regulation and control of the plasma density and improving the efficiency and the performance of the whole application system.
Although the embodiments of the present invention have been described above, the above descriptions are only for the convenience of understanding the present invention, and are not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (3)
1. The two-stage regulation and control method of the plasma density is characterized by comprising the following steps:
when the actual density rho and the preset density rho of the plasmaTSatisfies the condition | D ∞>60％ρTWhen in use, the plasma density is roughly adjusted by controlling the air input amount by adopting a piezoelectric crystal valve; when the actual density rho and the preset density rho of the plasmaTSatisfies the condition of 20% ρT≤|D|≤60％ρTWhen the plasma density is adjusted, the plasma density is adjusted by adjusting the power of the radio frequency power supply until the condition | D ∞ is met<Until epsilon, epsilon is allowable error, epsilon is 20% rhoT。
2. A system for implementing the two-stage regulation method of plasma density of claim 1, wherein the system comprises a density acquisition unit, a density comparison unit and a controller;
the density acquisition unit is used for acquiring the actual density of the plasma in the plasma vacuum chamber and sending the actual density of the plasma to the density comparison unit;
the density comparison unit is used for comparing the actual density of the plasma with the preset plasma density and sending the deviation value of the actual density of the plasma and the preset plasma density to the controller;
the controller is used for sending a control signal to the radio frequency power supply or the power amplifier according to the deviation value, and controlling the air input of the piezoelectric crystal valve by adjusting the power of the power amplifier so as to roughly adjust the plasma density; or to fine tune the plasma density by adjusting the power of the rf power supply.
3. The system of claim 2, wherein the density acquisition unit comprises a Langmuir probe, a data processing circuit, and a data acquisition card, wherein a front end of the Langmuir probe extends into the plasma vacuum chamber, and wherein a signal from the Langmuir probe is transmitted to the data acquisition card through the data processing circuit.
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| CN110949015B (en) * | 2018-09-26 | 2021-12-14 | 海德堡印刷机械股份公司 | Two-stage density compensation method |
| CN109600900A (en) * | 2019-01-23 | 2019-04-09 | 电子科技大学 | A kind of plasma jet array inhomogeneous plasma generation device |
| CN110418489B (en) * | 2019-07-17 | 2021-11-23 | 中国科学院近代物理研究所 | Ion source beam stability control system and method |
| CN111988901B (en) * | 2020-08-12 | 2023-01-13 | 河北大学 | Device and method for generating plasma photonic crystal with adjustable electron density |
| CN113113283A (en) * | 2021-04-08 | 2021-07-13 | 中国科学院光电技术研究所 | Plasma density distribution regulation and control method based on air inlet distribution control |
| CN114501764B (en) * | 2022-01-26 | 2024-02-09 | 江苏神州半导体科技有限公司 | Gas dissociation circuit control device and system based on multi-coil coupling |
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