Remote plasma source pre-stage voltage reduction device and method

Abstract

The invention discloses a remote plasma source pre-stage voltage reduction device and method, and belongs to the technical field of semiconductor manufacturing. Aiming at the problems of large size, low efficiency and slow dynamic response of a traditional industrial frequency transformer, efficient voltage conversion is realized through a high-frequency direct-current converter and a zero voltage switching ZVS technology. The device comprises a rectifying and filtering module, a high-frequency inductance module, a direct-current conversion module and a control module, the six working modes are controlled in a time-sharing manner, and the zero-voltage switching-on of the MOS tubes is realized by utilizing the synergistic effect of the anti-parallel diodes and the parasitic capacitors, so that the switching loss is remarkably reduced. The device is suitable for efficient power supply of a remote plasma source in semiconductor manufacturing, and has the advantages of compactness, high reliability and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a front-stage voltage reduction device and method for a remote plasma source. Background Art

[0002] In the semiconductor manufacturing field, the input of a remote plasma source (RPS) typically requires a line voltage of 208V, while the standard line voltage of domestic three-phase power supply systems is 380V. To address this voltage mismatch, existing technologies generally use power frequency transformers to step down the voltage (e.g., from 380V AC to 208V AC). However, traditional power frequency transformers have the following significant drawbacks:

[0003] Too large volume and weight: Taking a 10kVA power frequency transformer as an example, its volume is about 0.1 to 0.2m 3 , weighing 50 to 100 kg, requires special installation space or rack, limiting the integration and miniaturization design of the equipment.

[0004] Low efficiency and severe heat loss: The iron loss (core loss) and copper loss (winding loss) of the power frequency transformer are converted into heat, causing a significant temperature rise. Heat dissipation requires heat sinks, fans, or oil cooling systems. Derating is required in high-temperature environments. Otherwise, overheating may cause insulation material aging and shorten service life.

[0005] Slow dynamic response: Traditional transformers have a delay in responding to sudden changes in input voltage or load steps, requiring additional capacitors or electronic voltage stabilization circuits to maintain output voltage stability, increasing system complexity and cost.

[0006] High material costs: Power frequency transformers rely on a large amount of copper wire and silicon steel sheets. Their costs are significantly affected by fluctuations in raw material market prices. In addition, the production process is complex and it is difficult to meet the development needs of high frequency and lightweight.

[0007] The above-mentioned defects seriously restrict the efficiency, reliability and economy of the plasma source power supply system. Therefore, a new type of step-down device is urgently needed to replace the traditional power frequency transformer and achieve efficient, compact and highly dynamic voltage conversion. Summary of the Invention

[0008] In order to solve the technical problems existing in the background technology, the present invention proposes a remote plasma source front-stage pressure reduction device and method.

[0009] The present invention provides a remote plasma source front-stage pressure reduction device, comprising:

[0010] The rectifier and filter module is used to rectify and filter the input three-phase 380V AC power and then input it into the DC conversion module for DC bus voltage conversion;

[0011] The control module is used to monitor the load demand and DC bus voltage in real time, generate a pulse width modulation drive signal, and control the DC conversion module in a time-sharing manner according to the pulse width modulation drive signal to convert the rectified DC power of 380V AC power into a 300V DC bus voltage;

[0012] The DC conversion module is used to control the on and off of four MOS tubes through pulse width modulation drive signals, cooperate with anti-parallel diodes to achieve zero voltage switching (ZVS), and complete the periodic storage and release of energy in the high-frequency inductor module through high-frequency switching, converting the rectified 380V AC power into a 300V DC bus voltage.

[0013] The high-frequency inductor module includes a high-frequency inductor L1 and a high-frequency inductor L2, which are respectively connected between the midpoints of the two bridge arms and the positive electrode of the step-down device output, and are used for periodically storing and releasing energy.

[0014] Preferably, the DC conversion module includes four MOS transistors Q1-Q4 and four parasitic capacitors C1-C4. Each MOS transistor is connected in parallel with an anti-parallel diode. MOS transistors Q1 and Q2 are connected in series between the positive and negative poles of the rectified 380V AC DC bus voltage, and are connected between MOS transistors Q1 and Q2 to a high-frequency inductor L1. MOS transistors Q3 and Q4 are connected in series between the positive and negative poles of the rectified 380V AC DC bus voltage, and are connected between MOS transistors Q3 and Q4 to a high-frequency inductor L2. A parasitic capacitor C1 is connected in parallel between the source and drain of MOS transistor Q1, a parasitic capacitor C2 is connected in parallel between the source and drain of MOS transistor Q2, a parasitic capacitor C3 is connected in parallel between the source and drain of MOS transistor Q3, and a parasitic capacitor C4 is connected in parallel between the source and drain of MOS transistor Q4.

[0015] Preferably, the output end of the control module is respectively connected to the gate of the MOS transistors Q1-Q4, and the state switching of the MOS transistors is driven by the pulse width modulation drive signal; the control module receives the current changes of the high-frequency inductors L1 and L2 in real time, and dynamically adjusts the duty cycle of the pulse width modulation drive signal according to the current changes.

[0016] Preferably, it further comprises: an output filtering module, comprising an electrolytic capacitor C7 and a capacitor C8, which are connected in parallel with the output end of the DC conversion module to perform filtering operations on the converted 300V DC bus voltage.

[0017] Preferably, in the DC conversion module, the driving signals of the MOS transistors Q1 and Q4, and the driving signals of the MOS transistors Q2 and Q3 are complementary, and the conduction intervals of adjacent MOS transistors include a dead time to avoid shoot-through current.

[0018] Preferably, the rectifier and filter module specifically includes a rectifier bridge D1, an electrolytic capacitor C5 and a capacitor C6. The rectifier bridge D1, the electrolytic capacitor C5 and the capacitor C6 are connected in parallel, wherein the positive electrode of the electrolytic capacitor C5 is electrically connected to the output positive end of the rectifier bridge D1, and the negative electrode of the electrolytic capacitor C5 is electrically connected to the output negative end of the rectifier bridge D1.

[0019] The present invention proposes a method for reducing pressure in the front stage of a remote plasma source, which is applied to the remote plasma source front stage reducing pressure device as described in any one of the above items, and the method comprises:

[0020] Real-time acquisition of three-phase AC input voltage signal and load current signal;

[0021] Convert the three-phase AC input voltage into a DC bus voltage through a DC conversion module;

[0022] Calculate the target duty cycle according to the output voltage signal and generate the corresponding pulse width modulation drive signal;

[0023] According to the pulse width modulation drive signal, the mode switching of the four MOS tubes in the DC conversion module is controlled to achieve zero voltage switching (ZVS).

[0024] Through the alternating energy storage and release of the high-frequency inductor module, a stable DC bus voltage is output.

[0025] Preferably, the modes of the four-way MOS tubes specifically include:

[0026] Mode 1: In the initial stage, the control module sends a pulse width modulation drive signal to drive MOS transistors Q1 and Q4 to turn on, causing inductor L1 to store energy and inductor L2 to release energy in a freewheeling manner.

[0027] Mode 2: The control module sends a pulse width modulation drive signal to turn off all MOS tubes. The current of inductor L1 discharges the parasitic capacitance C2 of MOS tube Q2 to a voltage of 0.01, and the current of inductor L2 charges the parasitic capacitance C3 of MOS tube Q3 to a voltage equal to the DC bus voltage.

[0028] Mode 3: After the parasitic capacitance is charged and discharged, the dead time begins. During the dead time, the current in inductor L1 continues to flow through the anti-parallel diode of MOS tube Q2, and the current in inductor L2 continues to flow through the anti-parallel diode of MOS tube Q3 until the current change rate approaches zero.

[0029] Mode 4: The control module sends a pulse width modulation drive signal to drive MOS transistors Q2 and Q3 to zero voltage switching (ZVS), switching the direction of inductive energy transfer.

[0030] Mode 5: The control module sends a pulse width modulation drive signal to turn off all MOS tubes and complete the charging and discharging of parasitic capacitors C1-C4;

[0031] Mode 6: After the parasitic capacitance is charged and discharged, the current in the inductor L1 continues to flow through the anti-parallel diode of Q1, and the current in the inductor L2 continues to flow through the anti-parallel diode of Q4, presetting the voltage condition for the next cycle of ZVS operation.

[0032] Preferably, in mode 2 and mode 5, the drain-source voltage V ds , when V ds When ≤1V, the ZVS condition is determined to be met, triggering the switching action of the next mode;

[0033] In Mode 3 and Mode 6, by monitoring the inductor current change rate di / dt, when When the dead time ends, enter the next mode, where V dc is the DC bus voltage; L is the inductance of inductor L1 or inductor L2.

[0034] In the present invention, the proposed remote plasma source pre-stage voltage reduction device and method adopts a high-frequency inductor design, reducing the volume to 1 / 10 of a traditional transformer, thereby realizing miniaturization of the device; the ZVS technology is used to control the conduction and shutdown of the MOS tube, thereby reducing switching losses; combined with a high-frequency control loop, it can quickly respond to sudden load changes; at the same time, the use of silicon steel sheets and copper wires is reduced, thereby lowering material costs; in addition, the coordinated design of the dead time and the anti-parallel diode effectively avoids the risk of shoot-through current, suppresses voltage spikes, and significantly improves system stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the circuit architecture of a front-stage voltage reduction device for a remote plasma source proposed by the present invention;

[0036] Figure 2 This is a schematic diagram of the driving waveform structure of MOS tubes Q1-Q4 of a DC conversion module of a remote plasma source front-stage step-down device proposed by the present invention. DETAILED DESCRIPTION

[0037] Reference Figure 1 and Figure 2 The present invention proposes a remote plasma source front-stage pressure reduction device, comprising:

[0038] The rectifier and filter module is used to rectify and filter the input three-phase 380V AC power and then input it into the DC conversion module for DC bus voltage conversion.

[0039] In this embodiment, the rectifier and filter module specifically includes a diode D1, an electrolytic capacitor C5, and a capacitor C6. The diode D1, the electrolytic capacitor C5, and the capacitor C6 are connected in parallel, wherein the positive electrode of the electrolytic capacitor C5 is electrically connected to the negative electrode of the diode D1, and the negative electrode of the electrolytic capacitor C5 is electrically connected to the positive electrode of the diode D1.

[0040] The control module is used to monitor the load demand and DC bus voltage in real time, generate a pulse width modulation drive signal, and control the DC conversion module to convert the rectified DC power of 380V AC into a 300V DC bus voltage according to the pulse width modulation drive signal.

[0041] In this embodiment, the output end of the control module is connected to the gates of the MOS transistors Q1-Q4 respectively, and the state switching of the MOS transistors is driven by the pulse width modulation drive signal; the control module receives the current changes of the high-frequency inductors L1 and L2 in real time, and dynamically adjusts the duty cycle of the pulse width modulation drive signal according to the current changes.

[0042] The DC conversion module is used to control the on and off of the four MOS tubes through pulse width modulation drive signals, cooperate with anti-parallel diodes to achieve zero voltage switching (ZVS), and complete the periodic storage and release of energy in the high-frequency inductor module through high-frequency switching, converting the DC power after rectification of 380V AC power into a 300V DC bus voltage.

[0043] In this embodiment, in the DC conversion module, the driving signals of the MOS transistors Q1 and Q4, and the driving signals of the MOS transistors Q2 and Q3 are complementary, and the conduction intervals of adjacent MOS transistors include a dead time to avoid shoot-through current.

[0044] The high-frequency inductor module includes a high-frequency inductor L1 and a high-frequency inductor L2, which are respectively connected between the midpoints of the two bridge arms and the positive electrode of the step-down device output, and are used for periodically storing and releasing energy.

[0045] In this embodiment, the DC conversion module includes four MOS transistors Q1-Q4 and four parasitic capacitors C1-C4. Each MOS transistor is connected in parallel with an anti-parallel diode. MOS transistors Q1 and Q2 are connected in series between the positive and negative electrodes of a rectified 380 V AC DC bus voltage, and a high-frequency inductor L1 is connected between MOS transistors Q1 and Q2. MOS transistors Q3 and Q4 are connected in series between the positive and negative electrodes of the rectified 380 V AC DC bus voltage, and a high-frequency inductor L2 is connected between MOS transistors Q3 and Q4. A parasitic capacitor C1 is connected in parallel between the source and drain of MOS transistor Q1, a parasitic capacitor C2 is connected in parallel between the source and drain of MOS transistor Q2, a parasitic capacitor C3 is connected in parallel between the source and drain of MOS transistor Q3, and a parasitic capacitor C4 is connected in parallel between the source and drain of MOS transistor Q4.

[0046] In this embodiment, it also includes: an output filtering module, including an electrolytic capacitor C7 and a capacitor C8, which are connected in parallel with the output end of the DC conversion module to perform a filtering operation on the converted 300V DC bus voltage.

[0047] In this embodiment, first, the internal DC conversion of the step-down device uses high-frequency inductance to transfer energy. According to the inductance energy formula At high frequencies, miniaturization can be achieved by reducing the number of turns (N) and the core cross-sectional area (Ae). For example: a power frequency transformer (50Hz, 100W): weighs about 1-2kg and has a volume of 500cm 3 High-frequency inductor (100kHz, 100W): weight 50-100g, volume 20-50cm 3 , which can reduce the size of the step-down device by nearly 10 times. Secondly, the DC converter MOS tube inside the device operates in the zero voltage switching (ZVS) state, which can reduce losses during the switching process and thus improve overall efficiency.

[0048] In addition, the high-frequency inductance of the DC converter inside this device quickly completes energy storage and release during the switching cycle. The inductor current slope di / dt in the circuit is U / L. At high frequencies, L is small and the current changes quickly. The control loop bandwidth is high, and the feedback loop response frequency of the power supply can reach tens of kHz. It can quickly adjust the duty cycle to cope with load changes, thereby achieving a very fast dynamic response.

[0049] Reference Figure 1 and Figure 2 The present invention proposes a method for reducing pressure in the front stage of a remote plasma source, which is applied to any of the above-mentioned devices for reducing pressure in the front stage of a remote plasma source, and the method comprises:

[0050] Real-time acquisition of three-phase AC input voltage signal and load current signal;

[0051] Convert the three-phase AC input voltage into a DC bus voltage through a DC conversion module;

[0052] Calculate the target duty cycle based on the output voltage and generate the corresponding pulse width modulation drive signal;

[0053] According to the pulse width modulation drive signal, the mode switching of the four MOS tubes in the DC conversion module is controlled to achieve zero voltage switching (ZVS).

[0054] Through the alternating energy storage and release of the high-frequency inductor module, a stable DC bus voltage is output.

[0055] In this embodiment, the modes of the four MOS transistors specifically include:

[0056] Mode 1: In the initial stage, the control module issues a pulse-width modulated drive signal, turning on MOSFETs Q1 and Q4, allowing inductor L1 to store energy and inductor L2 to freewheel and release it. Mode 2: The control module issues a pulse-width modulated drive signal, turning off all MOSFETs. The current in inductor L1 discharges the parasitic capacitance C2 of MOSFET Q2 to a voltage of 0.001, while the current in inductor L2 charges the parasitic capacitance C3 of MOSFET Q3 to a voltage equal to the DC bus voltage. Mode 3: After the parasitic capacitance charging and discharging are complete, the dead time begins. During this dead time, the current in inductor L1 freewheels through the antiparallel diode of MOSFET Q2, and the current in inductor L2 freewheels through the antiparallel diode of MOSFET Q3, until the rate of change of current approaches zero. Mode 4: The control module issues a pulse-width modulated drive signal, driving MOSFETs Q2 and Q3 to a zero-voltage switching (ZVS) state, switching the direction of energy transfer in the inductors. Mode 5: The control module issues a pulse-width modulated drive signal, turning off all MOSFETs and completing the charging and discharging of parasitic capacitors C1-C4. Mode 6: After the parasitic capacitors are charged and discharged, the current in inductor L1 continues to flow through the anti-parallel diode of Q1, and the current in inductor L2 continues to flow through the anti-parallel diode of Q4, setting the voltage conditions for the next cycle of ZVS operation.

[0057] Specifically, if Figure 2As shown, in mode 1: at time t0, Q1 and Q4 are turned on, inductor L1 stores energy, and the inductor current rises linearly to its maximum value; inductor L2 releases energy through the freewheeling circuit of Q4, and the inductor current decreases linearly to reach its minimum and negative value at time t1. Mode 2: from t1 to t2, Q1, Q2, Q3, and Q4 are all turned off. The forward current in inductor L1 discharges the parasitic capacitance of Q2 through the freewheeling circuit, while charging the parasitic capacitance of the upper tube. Inductor L1 is subjected to reverse voltage, and the current decreases linearly; inductor L2 now has a reverse current, which charges the parasitic capacitance of Q4 and discharges the parasitic capacitance of Q3. The reverse current of L2 decreases linearly, and the charging and discharging of the parasitic capacitances of Q1, Q2, Q3, and Q4 are completed at time t2. Mode 3: t2-t3, during the dead time after charge and discharge, all MOSFETs are non-conductive. The forward current of inductor L1 flows through the parallel diode of Q2, forming a freewheeling path, and the current continues to decrease. The reverse current of L2 flows through the parallel diode of Q3, and the reverse current continues to decrease. Mode 4: t3-t4, at time t3, Q2 and Q3 are turned on. At this moment, the voltage across the D and S terminals of Q2 and Q3 are clamped to a diode voltage drop (close to 0V) by the anti-parallel diodes, achieving zero-voltage turn-on of Q2 and Q3. Simultaneously, the current in inductor L1 decreases linearly, reaching its minimum value at time t4, and becomes a reverse current. Inductor L2 is subjected to positive voltage, and after the negative current decreases to zero, the forward current increases linearly to its maximum value. Mode 5: From t4 to t5, Q1, Q2, Q3, and Q4 are all off. At this point, the current in inductor L1 is negative, while the current in inductor L2 is positive. The negative current in inductor L1 discharges Q1's parasitic capacitance and charges Q2's parasitic capacitance, causing the current to decrease in the reverse direction due to the input power supply. The positive current in inductor L2 discharges Q4's parasitic capacitance and charges Q3's parasitic capacitance. As a result, inductor L2 experiences reverse voltage and the current begins to decrease. By t5, both capacitor charging and discharging are complete. Mode 6: From t5 to t6, after the parasitic capacitance charging and discharging are complete, the negative current in inductor L1 completes the circuit through Q1's antiparallel diode, causing the current to decrease in the reverse direction. The positive current in inductor L2 continues through Q4's antiparallel diode, releasing energy and causing the current to decrease linearly. The voltages across Q1 and Q4 are clamped by the antiparallel diodes to a single diode drop (nearly 0V), preparing for the next stage of ZVS operation for both transistors. After these mode transitions, the DC converter finally enters stable operation.

[0058] In this embodiment, in mode 2 and mode 5, the drain-source voltage V ds , when V ds When ≤1V, the ZVS condition is determined to be met, triggering the switching action of the next mode;

[0059] In Mode 3 and Mode 6, by monitoring the inductor current change rate di / dt, when When the dead time ends, enter the next mode, where V dcis the DC bus voltage; L is the inductance of inductor L1 or inductor L2.

[0060] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A remote plasma source front-stage pressure reduction device, characterized in that: include: The rectifier and filter module is used to rectify and filter the input three-phase 380V AC power and then input it into the DC conversion module for DC bus voltage conversion; The control module is used to monitor the load demand and DC bus voltage in real time, generate a pulse width modulation drive signal, and control the DC conversion module in a time-sharing manner according to the pulse width modulation drive signal to convert the rectified DC power of 380V AC power into a 300V DC bus voltage; The DC conversion module is used to control the on and off of four MOS tubes through pulse width modulation drive signals, cooperate with anti-parallel diodes to achieve zero voltage switching (ZVS), and complete the periodic storage and release of energy in the high-frequency inductor module through high-frequency switching, converting the rectified 380V AC power into a 300V DC bus voltage. The high-frequency inductor module includes a high-frequency inductor L1 and a high-frequency inductor L2, which are respectively connected between the midpoints of the two bridge arms and the positive electrode of the step-down device output, and are used for periodically storing and releasing energy.

2. The remote plasma source front-stage pressure reduction device according to claim 1, characterized in that: The DC conversion module includes four MOS transistors Q1-Q4 and four parasitic capacitors C1-C4. Each MOS transistor is connected in parallel with an anti-parallel diode. MOS transistors Q1 and Q2 are connected in series between the positive and negative poles of a rectified 380V AC DC bus voltage, and a high-frequency inductor L1 is connected between MOS transistors Q1 and Q2. MOS transistors Q3 and Q4 are connected in series between the positive and negative poles of a rectified 380V AC DC bus voltage, and a high-frequency inductor L2 is connected between MOS transistors Q3 and Q4. A parasitic capacitor C1 is connected in parallel between the source and drain of MOS transistor Q1, a parasitic capacitor C2 is connected in parallel between the source and drain of MOS transistor Q2, a parasitic capacitor C3 is connected in parallel between the source and drain of MOS transistor Q3, and a parasitic capacitor C4 is connected in parallel between the source and drain of MOS transistor Q4.

3. The remote plasma source front-stage pressure reduction device according to claim 2, characterized in that: The output end of the control module is respectively connected to the gate of the MOS transistors Q1-Q4, and the state switching of the MOS transistors is driven by the pulse width modulation drive signal; the control module receives the current changes of the high-frequency inductors L1 and L2 in real time, and dynamically adjusts the duty cycle of the pulse width modulation drive signal according to the current changes.

4. The remote plasma source front-stage pressure reduction device according to claim 1, characterized in that: Also includes: The output filter module includes an electrolytic capacitor C7 and a capacitor C8. The electrolytic capacitor C7 and the capacitor C8 are connected in parallel with the output end of the DC conversion module to perform a filtering operation on the converted 300V DC bus voltage.

5. The remote plasma source front-stage pressure reduction device according to claim 2, characterized in that: In the DC conversion module, the driving signals of the MOS transistors Q1 and Q4, and the driving signals of the MOS transistors Q2 and Q3 are complementary, and the conduction intervals of adjacent MOS transistors include a dead time to avoid shoot-through current.

6. The remote plasma source front-stage pressure reduction device according to claim 1, characterized in that: The rectifier and filter module specifically includes a rectifier bridge D1, an electrolytic capacitor C5 and a capacitor C6. The rectifier bridge D1, the electrolytic capacitor C5 and the capacitor C6 are connected in parallel. The positive electrode of the electrolytic capacitor C5 is electrically connected to the positive output terminal of the rectifier bridge D1, and the negative electrode of the electrolytic capacitor C5 is electrically connected to the negative output terminal of the rectifier bridge D1.

7. A method for reducing pressure in the front stage of a remote plasma source, characterized in that: Applied to the remote plasma source front-stage pressure reduction device according to any one of claims 1 to 6, the method comprises: Real-time acquisition of three-phase AC input voltage signal and load current signal; Convert the three-phase AC input voltage into a DC bus voltage through a DC conversion module; Calculating a target duty cycle based on the output voltage of the step-down device and generating a corresponding pulse width modulation drive signal; According to the pulse width modulation drive signal, the mode switching of the four MOS tubes in the DC conversion module is controlled to achieve zero voltage switching (ZVS). Through the alternating energy storage and release of the high-frequency inductor module, a stable DC bus voltage is output.

8. The method for reducing pressure at the front stage of a remote plasma source according to claim 7, wherein: The modes of the four-way MOS tube specifically include: Mode 1: In the initial stage, the control module sends a pulse width modulation drive signal to drive MOS transistors Q1 and Q4 to turn on, causing inductor L1 to store energy and inductor L2 to release energy in a freewheeling manner. Mode 2: The control module sends a pulse width modulation drive signal to turn off all MOS tubes. The current of inductor L1 discharges the parasitic capacitance C2 of MOS tube Q2 to a voltage close to 0V. The current of inductor L2 charges the parasitic capacitance C3 of MOS tube Q3 to a voltage equal to the DC bus voltage. Mode 3: After the parasitic capacitance is charged and discharged, the dead time begins. During the dead time, the current in inductor L1 continues to flow through the anti-parallel diode of MOS tube Q2, and the current in inductor L2 continues to flow through the anti-parallel diode of MOS tube Q3 until the current change rate approaches zero. Mode 4: The control module sends a pulse width modulation drive signal to drive MOS transistors Q2 and Q3 to zero voltage switching (ZVS), switching the direction of inductive energy transfer. Mode 5: The control module sends a pulse width modulation drive signal to turn off all MOS tubes and complete the charging and discharging of parasitic capacitors C1-C4; Mode 6: After the parasitic capacitance is charged and discharged, the current in the inductor L1 continues to flow through the anti-parallel diode of Q1, and the current in the inductor L2 continues to flow through the anti-parallel diode of Q4, presetting the voltage condition for the next cycle of ZVS operation.

9. The method for reducing pressure at the front stage of a remote plasma source according to claim 8, wherein: In mode 2 and mode 5, the drain-source voltage V ds , when V ds When ≤1V, the ZVS condition is determined to be met, triggering the switching action of the next mode; In Mode 3 and Mode 6, by monitoring the inductor current change rate di / dt, when When the dead time ends, enter the next mode, where V dc is the DC bus voltage; L is the inductance of inductor L1 or inductor L2.

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