Screen grid assisted pulsed ignition startup method and apparatus for microwave ion sources

Abstract

The application discloses a screen grid auxiliary pulse ignition starting method and device for a microwave ion source. The screen grid auxiliary pulse ignition starting device for the microwave ion source comprises a pulse generation module, a direct-current screen grid power supply, a switching switch and a timing and control unit, and the timing and control unit is configured to execute the screen grid auxiliary pulse ignition starting method for the microwave ion source. The application utilizes the inherent screen grid electrode of the ion source, applies a short ignition pulse on the screen grid electrode, and utilizes the pulse electric field to assist the initial ionization of the gas, so that the starting success rate is significantly improved, the starting time is shortened, and the robustness of the starting process is enhanced.

Description

Technical Field

[0001] This invention relates to a grid-assisted pulse ignition start-up method and apparatus for microwave ion sources. Background Technology

[0002] Microwave ion sources are core components of equipment such as ion implanters, neutral beam implanters, and space electric thrusters. The working principle of a microwave ion source is to inject process gases (such as argon or xenon) into an ionization chamber, and use microwave energy to excite high-density plasma under magnetic field confinement. Ions in the plasma are extracted through a multi-pole grid system such as screen grids and acceleration grids to form an ion beam.

[0003] In practical applications, cold start (i.e., starting from a completely off state) of microwave ion sources is a common technical challenge. The difficulty in starting up mainly lies in: 1. Initial ionization difficulties: In the initial stage of startup, the gas in the ionization chamber is in a neutral state and lacks initial "seed" electrons and ions. Relying solely on the microwave electric field is sometimes insufficient to effectively break down the gas and form a stable discharge channel in the first instance, resulting in the plasma failing to ignite or taking too long to ignite.

[0004] 2. Ignition instability: Even if it is occasionally ignited, the initial plasma is extremely fragile and unstable, and is prone to quenching under slight fluctuations in parameters such as microwave power and gas pressure, resulting in startup failure.

[0005] 3. Sensitive to process conditions: The success rate of startup is highly dependent on the precise matching of parameters such as gas pressure and microwave power ramp-up curve, resulting in poor fault tolerance and complex operation.

[0006] Existing technologies typically address startup problems using the following methods: Increasing the initial gas pressure: However, this may change the normal operating point and increase gas consumption.

[0007] Increasing the initial microwave power may result in excessive reflected power, damaging the microwave source or requiring more complex matching control.

[0008] Using auxiliary spark plugs or filaments: This increases the complexity of the system and the risk of contamination, and is not suitable for some high-purity applications.

[0009] Therefore, there is an urgent need for a simple, reliable auxiliary start-up method that does not affect the main structure and working purity of the ion source. Summary of the Invention

[0010] The purpose of this invention is to provide a grid-assisted pulse ignition start-up method for microwave ion sources, so as to solve the current problem of difficult cold start-up of microwave ion sources.

[0011] This invention is achieved through the following technical solution: The steps of the grid-assisted pulse ignition start-up method for microwave ion sources are as follows: S1: System Preparation S11: Introduce process gas into the ionization chamber to bring the pressure in the ionization chamber to the preset start-up pressure value; S12: Apply a confinement magnetic field to the ion source; S13: Power on the high voltage power supply for the grid, the acceleration grid power supply, and the microwave source; S2: Apply an ignition pulse to the grid electrode, and the parameters of the ignition pulse satisfy: Pulse amplitude: significantly higher than the normal voltage when the ion source is operating normally; Pulse width: a narrow pulse; Pulse polarity: Can be a positive high voltage pulse; Pulse shape: can be square wave or exponentially decaying wave; S3: During and after the application of the ignition pulse, monitor signals characterizing the plasma state, including grid current and plasma emission spectrum; S4: If the grid current is detected to be stable and exceeds the preset threshold, stop applying the ignition pulse to the grid electrode immediately or after a short delay, and switch the power supply of the grid electrode to the conventional DC high voltage power supply; if the grid current is detected to fluctuate and is less than the preset threshold, repeat steps S2 to S4.

[0012] Furthermore, in step S2, the pulse amplitude is 2-2.5 times that of the conventional voltage.

[0013] Furthermore, the standard voltage is 300-500V, and the pulse amplitude is 800-1200V.

[0014] Furthermore, in step S2, the pulse width ranges from 10ms to 500ms.

[0015] Furthermore, in step S2, when the microwave power is turned on, an ignition pulse is applied to the grid electrode for the first time immediately or after a settable time.

[0016] Furthermore, the preset threshold value range is 1-5I.

[0017] To address the current problem of difficult cold start-up of microwave ion sources, this invention provides a grid-assisted pulse ignition start-up method for microwave ion sources. Correspondingly, a grid-assisted pulse ignition device for implementing the above method is provided, comprising: Pulse generation module: Its high-voltage output terminal is connected to the grid electrode via a switching switch to generate ignition pulses with adjustable parameters; DC grid power supply: used to provide the grid voltage during steady-state operation of the ion source; Switch: Used to connect the grid electrodes to the DC grid power supply or pulse generation module; Timing and control unit: It is linked with the microwave source controller, gas flow controller, pulse generation module, DC grid power supply and switching switch, and is configured to execute the above-mentioned grid-assisted pulse ignition start method for microwave ion source.

[0018] Furthermore, when the microwave power is turned on, the timing and control unit triggers the pulse generation module immediately or after a settable time delay, and controls the switching switch to connect the grid electrode to the pulse generation module. When the grid current is stable and exceeds a preset threshold, the timing and control unit controls the switching switch to switch the grid electrode to the DC grid power supply and turns off the pulse generation module.

[0019] The advantages of this technical solution are: 1. High start-up success rate: The ignition pulse generates an extremely strong instantaneous electric field near the grid, which can effectively accelerate a small number of initial electrons, enabling them to obtain enough energy to ionize neutral gas molecules, thereby reliably generating "seed" plasma and solving the problem of the "first ignition" in cold start.

[0020] 2. Fast start-up speed: The pulse ignition process is usually completed within milliseconds to seconds, which greatly shortens the start-up time compared to repeatedly trying microwave matching or adjusting the air pressure.

[0021] 3. Strong robustness: This method reduces the stringent requirements on the absolute values ​​of gas pressure and microwave power during startup, and improves the system's adaptability to startup under different operating conditions.

[0022] 4. No pollution is introduced: By using the existing grid electrode as the "ignition electrode", there is no need to add any additional components such as filaments or spark plugs that may cause pollution in the ionization chamber, thus maintaining the purity of the ion source.

[0023] 5. High system integration and low cost: The device is mainly composed of an external pulse power supply and switching circuit, which can be easily integrated into the existing ion source power supply and control system, resulting in low modification cost and high reliability.

[0024] 6. Intelligent: It can be integrated with plasma detection signals to achieve automatic judgment of successful ignition and switching, without the need for manual intervention throughout the process. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0027] Figure 1 This is a flowchart of the screen-assisted pulse ignition start-up method for a microwave ion source according to Embodiment 1 of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: As Figure 1 As shown, the screen-assisted pulse ignition start-up method for a microwave ion source comprises the following steps: S1: System Preparation S11: Introduce process gas into the ionization chamber to bring the pressure in the ionization chamber to the preset start-up pressure value; S12: Apply a confinement magnetic field to the ion source; S13: Power on the high voltage power supply for the grid, the acceleration grid power supply, and the microwave source; S2: Apply an ignition pulse to the grid electrode, and the parameters of the ignition pulse satisfy: Pulse amplitude: significantly higher than the normal voltage when the ion source is operating normally; Pulse width: a narrow pulse; Pulse polarity: If positive ions are extracted, the pulse polarity is a positive high voltage pulse; Pulse shape: can be a square wave, an exponentially decaying wave, or a specific waveform; S3: During and after the application of the ignition pulse, monitor signals characterizing the plasma state, including grid current and plasma emission spectrum; S4: If the grid current is detected to be stable and exceeds the preset threshold, stop applying the ignition pulse to the grid electrode immediately or after a short delay, and switch the power supply of the grid electrode to the conventional DC high voltage power supply so that it outputs the set normal operating grid voltage; if the grid current is detected to fluctuate and is less than the preset threshold, repeat steps S2 to S4.

[0030] When the screen grid current is detected to be stable and exceeds the preset threshold, it indicates that the plasma has been successfully established and has begun to stably extract ions.

[0031] Among them, the grid voltage supplied by the DC grid power supply for the steady-state operation of the ion source is defined as the conventional voltage.

[0032] This embodiment provides a grid-assisted pulse ignition start-up method for microwave ion sources to solve the current problem of difficult cold start-up of microwave ion sources. This method utilizes the inherent grid electrodes of the ion source, applying a brief ignition pulse to them. The pulsed electric field assists in the initial ionization of the gas, thereby significantly improving the start-up success rate, shortening the start-up time, and enhancing the robustness of the start-up process. The advantages are as follows: 1. High start-up success rate: The ignition pulse generates an extremely strong instantaneous electric field near the grid, which can effectively accelerate a small number of initial electrons, enabling them to obtain enough energy to ionize neutral gas molecules, thereby reliably generating "seed" plasma and solving the problem of the "first ignition" in cold start.

[0033] 2. Fast start-up speed: The pulse ignition process is usually completed within milliseconds to seconds, which greatly shortens the start-up time compared to repeatedly trying microwave matching or adjusting the air pressure.

[0034] 3. Strong robustness: This method reduces the stringent requirements on the absolute values ​​of gas pressure and microwave power during startup, and improves the system's adaptability to startup under different operating conditions.

[0035] 4. No pollution is introduced: By using the existing grid electrode as the "ignition electrode", there is no need to add any additional components such as filaments or spark plugs that may cause pollution in the ionization chamber, thus maintaining the purity of the ion source.

[0036] 5. High system integration and low cost: The device is mainly composed of an external pulse power supply and switching circuit, which can be easily integrated into the existing ion source power supply and control system, resulting in low modification cost and high reliability.

[0037] 6. Intelligent: It can be integrated with plasma detection signals to achieve automatic judgment of successful ignition and switching, without the need for manual intervention throughout the process.

[0038] In Embodiment 1 of the present invention, in step S2, the pulse amplitude is 2-2.5 times that of the conventional voltage. Specifically, the conventional voltage is 300-500V, and the pulse amplitude is 800-1200V.

[0039] In Embodiment 1 of the present invention, in step S2, the pulse width ranges from 10ms to 500ms. This setting avoids overloading the grid and power supply system.

[0040] In Embodiment 1 of the present invention, in step S2, when the microwave power is turned on, an ignition pulse is applied to the grid electrode immediately or after a settable time. This settable time can be set as needed, and may be, but is not limited to, 200-500 ms.

[0041] In Embodiment 1 of the present invention, the range of the preset threshold value is 1-5I.

[0042] Example 2: The screen-assisted pulse ignition device for implementing the above method includes: Pulse generation module: Its high-voltage output terminal is connected to the grid electrode via a switching switch to generate ignition pulses with adjustable parameters; DC grid power supply: used to provide the grid voltage during steady-state operation of the ion source; Switch: Used to connect the grid electrodes to the DC grid power supply or pulse generation module; Timing and control unit: It is linked with the microwave source controller, gas flow controller, pulse generation module, DC grid power supply and switching switch, and is configured to execute the above-mentioned grid-assisted pulse ignition start method for microwave ion source.

[0043] The switching device ensures that there is no electric arc or voltage change during the switching process.

[0044] Among them, the grid voltage supplied by the DC grid power supply for the steady-state operation of the ion source is defined as the conventional voltage.

[0045] In Embodiment 2 of the present invention, the timing and control unit triggers the pulse generation module immediately or after a settable time delay when the microwave power is turned on, and controls the switching switch to connect the grid electrode to the pulse generation module. When the grid current is stable and exceeds a preset threshold, the timing and control unit controls the switching switch to switch the grid electrode to the DC grid power supply and turns off the pulse generation module.

[0046] It should be understood that the terms "first," "second," etc., are used in this invention to describe various information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this invention, "first" information can also be referred to as "second" information, and similarly, "second" information can also be referred to as "first" information. In addition, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0047] The above description provides one or more embodiments in conjunction with specific content, and does not imply that the specific implementation of the present invention is limited to these descriptions. Any methods or structures that are similar to or identical to those of the present invention, or any technical deductions or substitutions made based on the concept of the present invention, should be considered as protected by the present invention.

Claims

1. A grid-assisted pulse ignition start-up method for a microwave ion source, characterized in that, The steps are as follows: S1: System Preparation S11: Introduce process gas into the ionization chamber to bring the pressure in the ionization chamber to the preset start-up pressure value; S12: Apply a confinement magnetic field to the ion source; S13: Power on the high voltage power supply for the grid, the acceleration grid power supply, and the microwave source; S2: Apply an ignition pulse to the grid electrode, and the parameters of the ignition pulse satisfy: Pulse amplitude: significantly higher than the normal voltage when the ion source is operating normally; Pulse width: a narrow pulse; Pulse polarity: Can be a positive high voltage pulse; Pulse shape: can be square wave or exponentially decaying wave; S3: During and after the application of the ignition pulse, monitor signals characterizing the plasma state, including grid current and plasma emission spectrum; S4: If the grid current is detected to be stable and exceeds the preset threshold, stop applying the ignition pulse to the grid electrode immediately or after a short delay, and switch the power supply of the grid electrode to the conventional DC high voltage power supply; if the grid current is detected to fluctuate and is less than the preset threshold, repeat steps S2 to S4.

2. The screen-assisted pulse ignition start-up method for a microwave ion source according to claim 1, characterized in that, In step S2, the pulse amplitude is 2-2.5 times that of the normal voltage.

3. The grid-assisted pulse ignition start-up method for a microwave ion source according to claim 1, characterized in that, The standard voltage is 300-500V, and the pulse amplitude is 800-1200V.

4. The grating-assisted pulse ignition start-up method for a microwave ion source according to claim 1, characterized in that, In step S2, the pulse width ranges from 10ms to 500ms.

5. The screen-assisted pulse ignition start-up method for a microwave ion source according to claim 1, characterized in that, In step S2, when the microwave power is turned on, an ignition pulse is applied to the grid electrode for the first time immediately or after a settable time.

6. The screen-assisted pulse ignition start-up method for a microwave ion source according to claim 1, characterized in that, The preset threshold value range is 1-5I.

7. A grid-assisted pulse ignition device for implementing the above method, characterized in that, include: Pulse generation module: Its high-voltage output terminal is connected to the grid electrode via a switching switch to generate ignition pulses with adjustable parameters; DC grid power supply: used to provide the grid voltage during steady-state operation of the ion source; Switch: Used to connect the grid electrodes to the DC grid power supply or pulse generation module; Timing and control unit: linked with microwave source controller, gas flow controller, pulse generation module, DC grid power supply and switching switch, configured to execute the grid-assisted pulse ignition start method for microwave ion source as described in any one of claims 1 to 6.

8. The grid-assisted pulse ignition device for implementing the above method according to claim 7, characterized in that, The timing and control unit triggers the pulse generation module immediately or after a settable time delay when the microwave power is turned on, and controls the switching switch to connect the screen electrode to the pulse generation module. When the grid current stabilizes and exceeds a preset threshold, the timing and control unit controls the switching switch to connect the grid electrodes to the DC grid power supply and shuts down the pulse generation module.

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