Wireless self-powered plasma density testing system and testing method

Abstract

The invention discloses a wireless self-powered plasma density testing system and a testing method. The testing system comprises a wireless self-powered device, a langmuir probe and a receiving terminal, the wireless self-powered device comprises a cathode electron collection element and a circuit board. One end of the langmuir probe is mounted in the probe interface of the circuit board, and the other end of the langmuir probe extends into the plasma to be tested; a filtering voltage-stabilizing module, a voltage-reducing module, a main control chip, a voltage-boosting module, an operational amplification module and a current and voltage monitoring module which are electrically connected are sequentially arranged in the circuit board; the input end of the current and voltage monitoring module is connected with the output end of the operational amplification module, and the input end is connected with a langmuir probe through a sampling resistor and a pin header. Passive self-power supply is achieved in the magnetron sputtering cavity, the voltage does not need to be adjusted externally, meanwhile, the measured current value and the measured voltage value are transmitted to the external receiving terminal in a wireless transmission mode, wiring and vacuum cavity customization are not needed in the whole process, and cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of plasma testing, and in particular to a wireless self-powered plasma density testing system and a testing method. Background Art

[0002] Magnetron sputtering technology has been widely used in the semiconductor industry as an efficient thin film deposition method. During the magnetron sputtering process, the characteristics of the plasma have an important influence on the quality of the film and the deposition process. At present, the Langmuir probe is a commonly used plasma diagnostic tool that provides real-time plasma state information by measuring the electron temperature, ion density and potential of the plasma. The Langmuir probe can help engineers optimize sputtering parameters and ensure the stability of the plasma, thereby achieving precise control of film thickness and quality. Especially in modern semiconductor manufacturing, as the size of devices continues to shrink, the requirements for uniformity and precision of thin films become more stringent, and the real-time feedback provided by the Langmuir probe has become the key to process control.

[0003] In the existing Langmuir probe test method, the Langmuir probe is installed inside the magnetron sputtering chamber, and is connected to an external power supply through a wire passing through the magnetron sputtering chamber, and then connected to an ammeter and a voltmeter outside the magnetron sputtering chamber through another wire. In addition, the output voltage of the external power supply is adjustable. By adjusting the output voltage of the power supply, the current value and voltage value on the Langmuir probe are recorded with an ammeter and a voltmeter, and the electron density of the plasma is calculated according to the inflection point method, thereby realizing the plasma density test. When using this test method, wiring and custom vacuum chambers are required, resulting in high installation costs for the equipment. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide a wireless self-powered plasma density testing system and testing method, which realizes passive self-powering inside the magnetron sputtering chamber, and the voltage does not need to be adjusted externally. At the same time, the measured current value and voltage value are transmitted to an external receiving terminal through wireless transmission. The whole process does not require wiring and customized vacuum chamber, so as to save costs.

[0005] In a first aspect, the present invention provides a wireless self-powered plasma density testing system, comprising a wireless self-powered device disposed inside a magnetron sputtering coating chamber, a langmuir probe connected to the wireless self-powered device, and a receiving terminal disposed outside the magnetron sputtering coating chamber; The wireless self-powered device comprises a cathode electron collecting element arranged opposite to the sputtering cathode, and a circuit board installed at the bottom of the cathode electron collecting element, the circuit board is installed on a rotating grounding base, the negative pole of the circuit board is electrically connected to the cathode electron collecting element, and the positive pole of the circuit board is electrically connected to the rotating grounding base; One end of the Langmuir probe is installed in the probe interface of the circuit board, and the other end extends into the plasma to be tested; The circuit board is provided with a filtering and voltage stabilizing module, a voltage reducing module, a main control chip, a voltage boosting module, an operational amplifier module and a current and voltage monitoring module which are electrically connected in sequence; The input end of the current and voltage monitoring module is connected to the output end of the operational amplifier module, and the input end is connected to the Langmuir probe through a sampling resistor and a pin header, so as to monitor the total voltage loaded on the Langmuir probe by the operational amplifier module and the partial voltage on the sampling resistor, and calculate the voltage value and current value on the Langmuir probe, and transmit the voltage value and the current value to the receiving terminal wirelessly through the main control chip.

[0006] Preferably, the output end of the filtering and voltage stabilizing module is electrically connected to the VDD pin of the boost module, and is also electrically connected to the VIN pin of the buck module.

[0007] Preferably, the VCC pin of the main control chip is electrically connected to the output end of the step-down module; The output square wave pin of the main control chip is electrically connected to the SEL1 pin and the SEL2 pin of the boost module at the same time; The output PWM signal pin of the main control chip is electrically connected to the input end of the operational amplifier module.

[0008] Preferably, the positive input end of the operational amplifier module is connected in series with the tenth resistor and the ninth resistor in sequence, and then electrically connected to the output PWM signal pin of the main control chip, and is grounded through the tenth capacitor; The negative input terminal of the operational amplifier module is grounded through a twelfth resistor, and is electrically connected to the output terminal of the operational amplifier module through a third resistor; The output end of the operational amplifier module is electrically connected to the input end of the current and voltage monitoring module; The positive power supply pin of the operational amplifier module is electrically connected to the output end of the boost module; The negative power supply pin of the operational amplifier module is grounded.

[0009] Preferably, the negative input pin of the current and voltage monitoring module is electrically connected to the output end of the operational amplifier module, and is also electrically connected to the probe interface through a sampling resistor; The positive input pin of the current and voltage monitoring module is electrically connected to the probe interface; The ALERT pin of the current and voltage monitoring module is electrically connected to the VCC pin of the main control chip through a sixth resistor; The SDA pin of the current and voltage monitoring module is electrically connected to the SDA pin of the main control chip, and is electrically connected to the VS pin of the current and voltage monitoring module through a seventh resistor; The SCL pin of the current and voltage monitoring module is electrically connected to the SCL pin of the main control chip, and is also electrically connected to the VS pin of the current and voltage monitoring module through an eighth resistor.

[0010] Preferably, the Langmuir probe is made of copper wire or tungsten wire, and the outer surface is wrapped with a ceramic tube, and the tip of the Langmuir probe is exposed at the end of the ceramic tube.

[0011] Preferably, the cathode electron collecting element is made of a conductive material, and comprises a substrate, and fins or a porous foam structure arranged on the substrate.

[0012] Preferably, the surface of the circuit board is coated with a heat-resistant stable layer, and the heat-resistant stable layer is made of polytetrafluoroethylene or silicone sealant.

[0013] In a second aspect, the present invention provides a testing method for a wireless self-powered plasma density testing system, comprising the following steps: Step S11, collecting free electrons of the plasma in the cavity during the magnetron sputtering process by the cathode electron collection element to form a voltage between the cathode electron collection element and the rotating grounding base, and converting the voltage into a stable DC voltage through a filtering and voltage stabilizing module, and then stepping down the DC voltage through a step-down module to form a qualified voltage to be transmitted to the main control chip; Step S12, the pwm signal is transmitted to the operational amplifier module through the main control chip, and the high-frequency square wave is transmitted to the boost module as a control signal. After the voltage is amplified by the charge pump principle in the boost module, the amplified voltage is transmitted to the operational amplifier module; Step S13, through the in-phase amplification function in the operational amplifier module, the PWM signal is amplified to form a scanning voltage and loaded on the Langmuir probe; Step S14, monitoring the total voltage loaded on the Langmuir probe and the partial voltage on the sampling resistor through the current and voltage monitoring module, and calculating the voltage value and current value on the Langmuir probe, and transmitting the voltage value and current value to the receiving terminal through the main control chip in a wireless manner; Step S15, drawing a voltage-current curve diagram on the Langmuir probe according to the voltage value and current value received by the receiving terminal, and analyzing the voltage-current curve diagram to obtain the electron temperature and plasma density.

[0014] Preferably, in an ideal plasma environment, the voltage-current curve measured by the Langmuir probe includes an ion saturation region, a transition region, and an electron saturation region in sequence, wherein: In the ion saturation region, the ion current is: In the formula, is the ion current, is the ion density, e is the electron charge, A is the probe area, K is the Boltzmann constant, is the electron temperature, M is the ion mass; In the transition region, the electron current is: In the formula, is the electron current, is the saturation electron current, is the probe voltage, is the plasma space potential at the probe; In the electron saturation region, the saturated electron current is: In the formula, is the electron density and m is the electron mass.

[0015] Compared with the prior art, the present invention has the following beneficial effects: First, by realizing passive self-power supply inside the magnetron sputtering chamber, no external power supply is required, the wiring is simple, and the requirements for the equipment installation environment are low; Second, the scanning voltage range is increased by the boost module, and the voltage adjustment on the Langmuir probe is realized by adjusting the resistance of the resistor in the magnetron sputtering chamber, making the adjustment more convenient; Third, multiple Langmuir probes can be installed at the same time to complete multi-point monitoring, making the test accuracy higher, and the Langmuir probe rotates with the rotating grounding base, which can realize continuous monitoring of the duration, making the test efficiency higher; Fourth, the measured current and voltage values ​​are transmitted to an external receiving terminal via wireless transmission. The entire process does not require wiring or customized vacuum chambers, thus saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the wireless self-powering device in the present invention; Figure 2 It is a circuit connection diagram of each module of the circuit board in the present invention; Figure 3 It is a schematic diagram of the process of the test system in the present invention; Figure 4 The voltage-current curve measured by the Langmuir probe in an ideal plasma environment; Figure 5 The voltage-current curve diagram on the Langmuir probe measured in the embodiment of the present invention is shown in FIG.

[0017] Description of main component symbols: 100-wireless self-powered device; 11-cathode electron collecting element; 12-circuit board; 200-Langmuir probe; 300-receiving terminal.

[0018] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0019] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0020] Before describing the technical solution provided by the embodiment of the present application, in order to facilitate the understanding of the embodiment of the present application, the present application first briefly describes the magnetron sputtering process environment: Magnetron sputtering is a physical vapor deposition technology that applies high voltage to the target under vacuum conditions to ionize the gas (usually Ar gas) into argon ions and electrons to form plasma. Under the action of the magnetic field, the electrons rotate continuously and collide with argon atoms, increasing the ionization rate of the plasma. The argon ions are positive and move toward the target under the action of the electric field. After impacting the target, the target atoms are sputtered out to form a thin film on the substrate. Magnetron sputtering has the advantages of high deposition rate, good deposition uniformity, low substrate temperature, high material utilization, wide application range and strong film adhesion.

[0021] In the magnetron sputtering process, plasma is the state of gas after ionization, and it has the ability to conduct electricity. When the wireless self-powered device is installed on a grounded base, there is a potential difference between the base and the target material. The plasma is equivalent to a conductor that connects the circuit. If the inductive electronic device can receive enough electrons to generate enough inductive power, it can drive the device to work.

[0022] See also Figures 1 to 3 In a first aspect, the present invention provides a wireless self-powered plasma density testing system, comprising a wireless self-powered device 100 disposed inside a magnetron sputtering coating chamber, a langmuir probe 200 connected to the wireless self-powered device, and a receiving terminal 300 disposed outside the magnetron sputtering coating chamber; The wireless self-powered device 100 comprises a cathode electron collecting element 11 arranged opposite to the sputtering cathode, and a circuit board 12 installed at the bottom of the cathode electron collecting element 11, the circuit board 12 is installed on a rotating grounding base, the negative electrode of the circuit board 12 is electrically connected to the cathode electron collecting element 11, and the positive electrode of the circuit board 12 is electrically connected to the rotating grounding base; One end of the Langmuir probe 200 is installed in the probe interface of the circuit board 12, and the other end extends into the plasma to be tested; The circuit board 12 is provided with a filter voltage stabilization module, a voltage reduction module, a main control chip, a voltage boost module, an operational amplifier module and a current and voltage monitoring module which are electrically connected in sequence; The input end of the current and voltage monitoring module is connected to the output end of the operational amplifier module, and the input end is connected to the Langmuir probe 200 through a sampling resistor and a pin header, so as to monitor the total voltage loaded on the Langmuir probe 200 by the operational amplifier module and the partial voltage on the sampling resistor, and calculate the voltage value and current value on the Langmuir probe 200, and transmit the voltage value and the current value to the receiving terminal 300 wirelessly through the main control chip.

[0023] It should be noted that the receiving terminal 300 is a mobile phone, a computer, a tablet or a smart TV. The wireless transmission method adopted by the present invention is low-power Bluetooth, and the microcontroller supports low-power Bluetooth, so that 2.4G Bluetooth electromagnetic waves are transmitted from the magnetron sputtering coating cavity to the receiving terminal 300 outside the cavity. It can be understood that in other embodiments, the wireless transmission method can be Wi-Fi, ZigBee, infrared or laser in addition to Bluetooth.

[0024] Furthermore, in the present invention, the induced voltage is converted into a stable direct current after voltage stabilization and filtering, and then reduced to 3.3V by a step-down module, which supplies power to each module in the circuit; The main control chip outputs high-frequency square waves and pwm signals at the same time, where the high-frequency square wave is used as the switching signal of the boost module. The boost module uses the charge pump principle to change the capacitor potential to a low potential during charging, and the potential changes to a high potential during discharge to complete the boost function; the pwm signal is amplified by the operational amplifier module to form a scanning waveform loaded on the langmuir probe; The current and voltage monitoring module monitors the current and voltage on the Langmuir probe. 2 C interface is transmitted to the main control chip; The main control chip transmits the current and voltage signals to the receiving terminal wirelessly. The file received by the receiving terminal contains the current values ​​at different scanning voltages on the Langmuir probe. The horizontal axis is the probe voltage and the vertical axis is the probe current. Each point in the file is plotted on the curve to form a voltage-current curve.

[0025] See also Figure 2 and Figure 3 In a preferred embodiment of the present invention, the output end of the filtering and voltage stabilizing module is electrically connected to the VDD pin of the boost module, and is also electrically connected to the VIN pin of the buck module.

[0026] It should be noted that the buck module realizes buck conversion by high-frequency switching of high-side and low-side MOSFETs, stabilizes the output voltage by adjusting the duty cycle, and reduces the DC voltage after filtering and stabilization to the working low voltage required by each module. It should be noted that the working voltage of each module should be matched as much as possible to reduce the working mode of the buck circuit. In the present invention, the working voltage of each module is 3.3V.

[0027] See also Figure 2 and Figure 3 , in a preferred embodiment of the present invention, the VCC pin of the main control chip is electrically connected to the output end of the step-down module; The output square wave pin of the main control chip is electrically connected to the SEL1 pin and the SEL2 pin of the boost module at the same time; The output PWM signal pin of the main control chip is electrically connected to the input end of the operational amplifier module.

[0028] It should be noted that the signal transmission time of the main control chip should be slightly later than the pwm signal conversion time, and the signal should be transmitted after the current and voltage are stable. The main control chip sets the time interval of the transmission signal to match the pwm signal conversion time interval and the average number and interval time of the current and voltage monitoring module. The boost module adopts the charge pump principle, and uses the high-frequency square wave output by the main control chip as the signal source to control the on and off of the switch chip to realize the charging of the capacitor in the boost module. The capacitor is connected to the diode to ensure that the capacitor is at a high potential when discharged, thereby realizing the boost function.

[0029] See also Figure 2 and Figure 3 In a preferred embodiment of the present invention, the positive input end of the operational amplifier module is connected in series with the tenth resistor and the ninth resistor in sequence, and then electrically connected to the output pwm signal pin of the main control chip, and is grounded through the tenth capacitor; The negative input terminal of the operational amplifier module is grounded through a twelfth resistor, and is electrically connected to the output terminal of the operational amplifier module through a third resistor; The output end of the operational amplifier module is electrically connected to the input end of the current and voltage monitoring module; The positive power supply pin of the operational amplifier module is electrically connected to the output end of the boost module; The negative power supply pin of the operational amplifier module is grounded.

[0030] It should be noted that the operational amplifier module uses the PWM signal output by the main control chip as the input signal and the output end of the boost module as the positive power supply, and amplifies the PWM signal through the in-phase amplifier circuit to form a scanning voltage loaded on the Langmuir probe.

[0031] See also Figure 2 and Figure 3 , in a preferred embodiment of the present invention, the negative input pin of the current and voltage monitoring module is electrically connected to the output end of the operational amplifier module, and is also electrically connected to the probe interface through a sampling resistor; The positive input pin of the current and voltage monitoring module is electrically connected to the probe interface; The ALERT pin of the current and voltage monitoring module is electrically connected to the VCC pin of the main control chip through a sixth resistor; The SDA pin of the current and voltage monitoring module is electrically connected to the SDA pin of the main control chip, and is electrically connected to the VS pin of the current and voltage monitoring module through a seventh resistor; The SCL pin of the current and voltage monitoring module is electrically connected to the SCL pin of the main control chip, and is also electrically connected to the VS pin of the current and voltage monitoring module through an eighth resistor.

[0032] It should be noted that the current and voltage monitoring module is connected in series with the Langmuir probe through a sampling resistor, monitors the total voltage on the Langmuir probe and the partial voltage on the sampling resistor, and calculates the current and voltage on the probe. At the same time, the monitoring results are obtained by I 2 The result is transmitted to the main control chip through the C interface, and the main control chip transmits the result to the receiving terminal in a wireless manner.

[0033] In a preferred embodiment of the present application, the Langmuir probe is made of copper wire or tungsten wire, and a ceramic tube is wrapped on the outer surface, and the tip of the Langmuir probe is exposed at the end of the ceramic tube.

[0034] In a preferred embodiment of the present application, the cathode electron collecting element is made of a conductive material, including a substrate, and fins or a porous foam structure (such as foam metal) disposed on the substrate. The fins or the porous foam structure allow the cathode electron collecting element to have a larger surface area, thereby enhancing its attraction to free electrons in the plasma.

[0035] In a preferred embodiment of the present application, the surface of the circuit board is coated with a heat-resistant stable layer, and the heat-resistant stable layer is made of polytetrafluoroethylene or silicone sealant to prevent particles from being directly deposited on the circuit board and causing device failure.

[0036] In a preferred embodiment of the present application, the sputtering power supply adopts DC, pulsed DC or medium frequency power supply with a power of 20-200W, wherein the pulsed DC discharge frequency ranges from 20 to 40 kHz, and the flow rate of the inert gas is 20 to 100 sccm.

[0037] In a second aspect, the present invention provides a testing method for a wireless self-powered plasma density testing system, comprising the following steps: Step S11, collecting free electrons of the plasma in the cavity during the magnetron sputtering process by the cathode electron collection element to form a voltage between the cathode electron collection element and the rotating grounding base, and converting the voltage into a stable DC voltage through a filtering and voltage stabilizing module, and then stepping down the DC voltage through a step-down module to form a qualified voltage to be transmitted to the main control chip; Step S12, the pwm signal is transmitted to the operational amplifier module through the main control chip, and the high-frequency square wave is transmitted to the boost module as a control signal. After the voltage is amplified by the charge pump principle in the boost module, the amplified voltage is transmitted to the operational amplifier module; Step S13, through the in-phase amplification function in the operational amplifier module, the PWM signal is amplified to form a scanning voltage and loaded on the Langmuir probe; Step S14, monitoring the total voltage loaded on the Langmuir probe and the partial voltage on the sampling resistor through the current and voltage monitoring module, and calculating the voltage value and current value on the Langmuir probe, and transmitting the voltage value and current value to the receiving terminal through the main control chip in a wireless manner; Step S15, drawing a voltage-current curve diagram on the Langmuir probe according to the voltage value and current value received by the receiving terminal, and analyzing the voltage-current curve diagram to obtain the electron temperature and plasma density.

[0038] See also Figure 4 In an ideal plasma environment, the voltage-current curve measured by the Langmuir probe includes the ion saturation region, transition region and electron saturation region in sequence, among which, In the ion saturation region, the ion current is: In the formula, is the ion current, is the ion density, e is the electron charge, A is the probe area, K is the Boltzmann constant, is the electron temperature, M is the ion mass; In the transition region, the electron current is: In the formula, is the electron current, is the saturation electron current, is the probe voltage, is the plasma space potential at the probe; In the electron saturation region, the saturated electron current is: In the formula, is the electron density and m is the electron mass.

[0039] The present application is described in detail below with specific implementation methods: This embodiment uses the wireless self-powered device of the present invention to monitor the electron temperature and plasma density of the magnetron sputtering process in real time, including the following steps: Step 1: Reference Figures 1 to 3 , write a program to the main control chip to implement the following functions: output high-frequency square wave and PWM signal, monitor the current and voltage values ​​of the Langmuir probe, and set the transmission interval to transmit the current and voltage values.

[0040] Step 2: Reference Figure 1 ,Install the test system in the magnetron sputtering coating chamber; Step 3: Close the chamber door and evacuate to 5×10 -3 Pa, rotate the base so that the device faces the target, introduce 30sccm argon gas, and the process vacuum is 0.18 Pa. Start the power supply and set the power supply power to 200W.

[0041] Step 4: Use the receiving terminal to receive Bluetooth data (as shown in Table 1) and draw a curve to process the data.

[0042] Table 1 Bluetooth data received by the receiving terminal See also Figure 4 and Figure 5 The file transmitted to the receiving terminal by Bluetooth contains the current value of the probe at different scanning voltages. Based on this, the probe voltage-current curve is drawn, with the horizontal axis as the probe voltage and the vertical axis as the probe current, and each point in the file is plotted on the curve. It can be seen from the figure that when the voltage is low, the current value generated is small, around -9uA. As the voltage increases, the current basically does not change. This is because the curve is in the ion saturation section in this area, and the current generated is limited by the area of ​​the Langmuir probe. When the voltage continues to increase, the current continues to increase, but the increase is slowing down, which is in the transition section.

[0043] See also Figure 5 , due to the ion current For electron current There is an effect, so the ion current in the current I is eliminated Partially obtained electron current , draw UI, U- , U-ln|I| and U-ln| |The curve diagram shows that in the curve U-ln| |There is a linear region in the middle section. The linear fitting of this region shows that the slope of the curve is 0.28, R 2 is 0.9995, and the electron temperature of this section can be obtained .

[0044] Use in ion saturation zone , the density of the plasma can be calculated, where K is the Boltzmann constant, K=1.380649 × 10 -23 J / K, M is the mass of argon ions, which is 6.6335×10 -26 kg, e is the charge of the electron, which is 1.602×10 −19 C, A is the probe exposure area, which is 5×10 -6 m 2 , calculate the plasma density 6.38×1015 m -3 , the plasma is neutral, the electron density is equal to the ion density and also equal to the plasma density.

[0045] In summary, the present invention has the following advantages: First, the wireless self-powered device collects electrons inside the coating chamber to form a self-powered power supply, without the need for battery power or external power supply, thus avoiding the risk of using lithium batteries in a vacuum plasma environment; Second, the scanning voltage range is increased by the boost module, and the voltage adjustment on the Langmuir probe is realized by adjusting the resistance of the resistor in the magnetron sputtering chamber, making the adjustment more convenient; Third, multiple Langmuir probes can be installed at the same time to complete multi-point monitoring, making the test accuracy higher, and the Langmuir probe rotates with the rotating grounding base, which can realize continuous monitoring of the duration, making the test efficiency higher; Fourth, the measured current and voltage values ​​are transmitted to an external receiving terminal via wireless transmission. The entire process does not require wiring or customized vacuum chambers, thus saving costs.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A wireless self-powered plasma density testing system, characterized in that: It includes a wireless self-powering device arranged inside a magnetron sputtering coating chamber, a Langmuir probe connected to the wireless self-powering device, and a receiving terminal arranged outside the magnetron sputtering coating chamber; The wireless self-powered device comprises a cathode electron collecting element arranged opposite to the sputtering cathode, and a circuit board installed at the bottom of the cathode electron collecting element, the circuit board is installed on a rotating grounding base, the negative pole of the circuit board is electrically connected to the cathode electron collecting element, and the positive pole of the circuit board is electrically connected to the rotating grounding base; One end of the Langmuir probe is installed in the probe interface of the circuit board, and the other end extends into the plasma to be tested; The circuit board is provided with a filtering and voltage stabilizing module, a voltage reducing module, a main control chip, a voltage boosting module, an operational amplifier module and a current and voltage monitoring module which are electrically connected in sequence; The input end of the current and voltage monitoring module is connected to the output end of the operational amplifier module, and the input end is connected to the Langmuir probe through a sampling resistor and a pin header, so as to monitor the total voltage loaded on the Langmuir probe by the operational amplifier module and the partial voltage on the sampling resistor, and calculate the voltage value and current value on the Langmuir probe, and transmit the voltage value and the current value to the receiving terminal wirelessly through the main control chip.

2. The wireless self-powered plasma density testing system according to claim 1, characterized in that: The output end of the filtering and voltage stabilizing module is electrically connected to the VDD pin of the boost module, and is also electrically connected to the VIN pin of the buck module.

3. The wireless self-powered plasma density testing system according to claim 2, characterized in that: The VCC pin of the main control chip is electrically connected to the output end of the step-down module; The output square wave pin of the main control chip is electrically connected to the SEL1 pin and the SEL2 pin of the boost module at the same time; The output PWM signal pin of the main control chip is electrically connected to the input end of the operational amplifier module.

4. The wireless self-powered plasma density testing system according to claim 3, characterized in that: The positive input end of the operational amplifier module is connected in series with the tenth resistor and the ninth resistor in sequence, and then electrically connected to the output PWM signal pin of the main control chip, and is grounded through the tenth capacitor; The negative input terminal of the operational amplifier module is grounded through a twelfth resistor, and is electrically connected to the output terminal of the operational amplifier module through a third resistor; The output end of the operational amplifier module is electrically connected to the input end of the current and voltage monitoring module; The positive power supply pin of the operational amplifier module is electrically connected to the output end of the boost module; The negative power supply pin of the operational amplifier module is grounded.

5. The wireless self-powered plasma density testing system according to claim 4, characterized in that: The negative input pin of the current and voltage monitoring module is electrically connected to the output end of the operational amplifier module, and is also electrically connected to the probe interface through a sampling resistor; The positive input pin of the current and voltage monitoring module is electrically connected to the probe interface; The ALERT pin of the current and voltage monitoring module is electrically connected to the VCC pin of the main control chip through a sixth resistor; The SDA pin of the current and voltage monitoring module is electrically connected to the SDA pin of the main control chip, and is electrically connected to the VS pin of the current and voltage monitoring module through a seventh resistor; The SCL pin of the current and voltage monitoring module is electrically connected to the SCL pin of the main control chip, and is also electrically connected to the VS pin of the current and voltage monitoring module through an eighth resistor.

6. The wireless self-powered plasma density testing system according to claim 1, characterized in that: The Langmuir probe is made of copper wire or tungsten wire, and a ceramic tube is wrapped on the outer surface. The tip of the Langmuir probe is exposed from the end of the ceramic tube.

7. The wireless self-powered plasma density testing system according to claim 1, characterized in that: The cathode electron collecting element is made of conductive material and comprises a substrate and a fin or a porous foam structure arranged on the substrate.

8. The wireless self-powered plasma density testing system according to claim 1, characterized in that: The surface of the circuit board is coated with a heat-resistant stable layer, and the heat-resistant stable layer is made of polytetrafluoroethylene or silicone sealant.

9. The testing method of the wireless self-powered plasma density testing system according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step S11, collecting free electrons of the plasma in the cavity during the magnetron sputtering process by the cathode electron collection element to form a voltage between the cathode electron collection element and the rotating grounding base, and converting the voltage into a stable DC voltage through a filtering and voltage stabilizing module, and then stepping down the DC voltage through a step-down module to form a qualified voltage to be transmitted to the main control chip; Step S12, the pwm signal is transmitted to the operational amplifier module through the main control chip, and the high-frequency square wave is transmitted to the boost module as a control signal. After the voltage is amplified by the charge pump principle in the boost module, the amplified voltage is transmitted to the operational amplifier module; Step S13, through the in-phase amplification function in the operational amplifier module, the PWM signal is amplified to form a scanning voltage and loaded on the Langmuir probe; Step S14, monitoring the total voltage loaded on the Langmuir probe and the partial voltage on the sampling resistor through the current and voltage monitoring module, and calculating the voltage value and current value on the Langmuir probe, and transmitting the voltage value and current value to the receiving terminal through the main control chip in a wireless manner; Step S15, drawing a voltage-current curve diagram on the Langmuir probe according to the voltage value and current value received by the receiving terminal, and analyzing the voltage-current curve diagram to obtain the electron temperature and plasma density.

10. The testing method of the wireless self-powered plasma density testing system according to claim 9, characterized in that: In an ideal plasma environment, it includes the ion saturation region, transition region and electron saturation region in sequence, among which: In the ion saturation region, the ion current is: In the formula, is the ion current, is the ion density, e is the electron charge, A is the probe area, K is the Boltzmann constant, is the electron temperature, M is the ion mass; In the transition region, the electron current is: In the formula, is the electron current, is the saturation electron current, is the probe voltage, is the plasma space potential at the probe; In the electron saturation region, the saturated electron current is: In the formula, is the electron density and m is the electron mass.

Images