Droplet control apparatus and method for a fuel emitter of an extreme ultraviolet light source

Abstract

This invention discloses a droplet control device and method for a fuel emitter in an extreme ultraviolet (EUV) light source. The device includes: at least one nozzle having a fuel flow channel; a conductive body disposed on the inner wall of the nozzle and / or downstream of the nozzle outlet along the droplet flight path, comprising multiple spatially distributed conductive segments with intervals between adjacent segments; at least two wires electrically connected to the conductive body; and a magnetic field generator configured to generate a magnetic field acting on the fuel droplets. The droplet control device is configured such that the current flowing through at least one of the conductive segments is primarily determined by the electrical parameters of the circuit containing the conductive segment, rather than primarily by the number of fuel droplets simultaneously contacting the conductive segment. The fuel droplets are liquid metal droplets. This invention eliminates the randomness of current distribution caused by multiple droplets in parallel through an intermittent conductive body structure, making the current of each droplet predictable and controllable, thereby avoiding vaporization or electrical explosions caused by local overheating, necking, or excessive current density, and improving the stability of the EUV light source.

Description

Technical Field

[0001] This invention belongs to the field of extreme ultraviolet lithography technology, specifically relating to a droplet control device and method for a fuel emitter of an extreme ultraviolet light source. Background Technology

[0002] Extreme ultraviolet (EUV) lithography is currently a key technology for achieving 7nm and below process technologies. In laser-generated plasma EUV light sources, fuel droplets (usually tin droplets) need to be launched into a vacuum cavity at frequencies of tens of thousands of hertz and speeds of tens of meters per second, and then precisely bombarded by a high-power laser to generate EUV radiation. Under these extreme operating conditions of high frequency and high power, extremely high requirements are placed on the stability of the droplet launch system.

[0003] In the prior art, schemes for accelerating fuel droplets using electromagnetic force have been proposed. A common design involves placing two sets of continuously insulated axial conductors on the inner wall of the nozzle. A power supply is connected to each of the two sets of conductors (two continuous axial conductors). The conductive fuel droplet itself acts as a switch; when the droplet passes through, it simultaneously contacts both sets of conductors, forming a current loop. It is then accelerated by the Ampere force in the magnetic field (e.g., the applicant's authorized patent: ZL202310554609.2). However, the prior art fails to recognize that electromagnetic acceleration of liquid metal droplets under the high-frequency, microscale, and vacuum conditions of EUV light sources presents a series of complex problems with mutual coupling: the liquid metal droplet itself acts as a conductor carrying current, making its temperature rise difficult to predict accurately; the droplet deforms due to uneven force during acceleration (including necking and contact deformation caused by insufficient high-speed spreading), resulting in a sharp increase in local current density; and multiple droplets simultaneously contacting the continuous conductors form parallel loops, leading to random current distribution.

[0004] It is precisely the coupling problem unique to EUV operating conditions that causes electromagnetic acceleration schemes to face an extremely narrow operating current window: The lower limit of the operating current window is determined by the droplet's frictional resistance and acceleration time: if the current is reduced to avoid electro-explosion, the Ampere force is only slightly greater than the frictional force, the acceleration time is significantly prolonged, the droplet stays in the acceleration zone for too long, it is very easy to merge, and the risk of necking increases. The upper limit of the operating current window is determined by the droplet's vaporization temperature and electro-explosion threshold: increasing the current to avoid fusion will lead to excessive Joule heating and vaporization. More critically, the droplet deforms during acceleration, reducing its local cross-sectional area and causing a sharp increase in local current density.

[0005] Therefore, the existing technology has not recognized the narrowness of this operating current window, nor has it provided a structural solution to ensure that the current of each droplet falls stably into this window.

[0006] Furthermore, continuous conductors are typically metallic materials with high thermal conductivity. When a droplet comes into contact with a conductor, the Joule heat generated by the current flowing through both the droplet and the conductor is rapidly conducted along the conductor's axis, causing the overall temperature of the conductor to rise and creating a significant axial temperature gradient. Under the high-frequency, long-term continuous operation conditions required by extreme ultraviolet lithography, this Joule heat accumulation problem is significantly amplified.

[0007] This temperature gradient triggers a series of chain reactions: First, heat is easily conducted to the upstream piezoelectric drive unit, causing depolarization or performance drift of the piezoelectric material, directly affecting the stability of droplet ejection; second, heat is conducted to the nozzle and fuel channel, increasing the temperature of the molten tin and even causing local vaporization, interfering with the generation of extreme ultraviolet light; in addition, the continuous conductor will generate significant thermal stress concentration under the action of axial temperature difference, and long-term operation under high-frequency conditions will easily lead to material fatigue and aging and peeling of the surface insulation layer, seriously affecting the service life of the droplet generator.

[0008] To address the aforementioned problems, existing technologies typically rely on external cooling, reducing current, or increasing heat dissipation area. However, these measures only provide external cooling and have not yet proposed an effective solution to structurally block the conduction path of Joule heat along the conductor; local temperature gradients still need to be eliminated. Therefore, how to effectively block the conduction of Joule heat to the piezoelectric unit and nozzle flow channel from a structural perspective has become a pressing technical problem to be solved in this field.

[0009] Furthermore, as the requirements for droplet control precision in EUV light sources continue to increase, the limitations of a single axial acceleration function are gradually becoming apparent: • It is impossible to radially focus the droplets, making it difficult to correct trajectory deviations caused by emission disturbances or plasma shock waves; • It is impossible to make the droplet rotate, making it difficult to use the gyroscopic effect to stabilize the droplet attitude and improve the utilization rate of laser energy; Continuous operation in a fixed direction can easily lead to localized heat load concentration, affecting the long-term stability of the system.

[0010] Therefore, there is an urgent need in this field for a fuel launcher control system that can dynamically switch operating modes according to different operating conditions and achieve multi-objective optimized control.

[0011] In existing technologies, there are two main technical paths for the generation and acceleration of fuel droplets: piezoelectric drive and electromagnetic drive. Piezoelectric drive applies periodic pressure disturbances to the fuel within the nozzle using piezoelectric elements, forming a uniform droplet sequence based on the Rayleigh jet fracture principle, but its acceleration capability is limited. Electromagnetic drive forms a current loop between a conductor and the droplets, accelerating them under the influence of the Ampere force in a magnetic field, but droplet formation still relies on traditional pump pressure methods. Currently, there is no solution that organically combines the two and achieves closed-loop control throughout the entire process.

[0012] Furthermore, during electromagnetic acceleration, droplets undergo morphological distortion due to uneven stress, residual charge issues arise from droplet contact with conductors, and intermittent insulation gaps in conductors cause thrust interruptions ("dynamic discontinuity"), while acceleration schemes with fixed parameters struggle to guarantee consistent time intervals between droplet sequences reaching the excitation point. No effective comprehensive solution has yet been proposed in the existing technology. Summary of the Invention

[0013] This invention aims to provide a droplet control device and method for a fuel emitter of an extreme ultraviolet light source. The technical problem to be solved by this invention is "how to eliminate the randomness of current distribution caused by multiple droplets in parallel, suppress droplet deformation during acceleration, thereby stabilizing the current flowing through each droplet within an extremely narrow operating current window, and avoiding inconsistent acceleration, merging, vaporization, or electrical explosion caused by uneven current distribution." The following technical solution is provided: A droplet control device for a fuel emitter of an extreme ultraviolet light source, comprising: At least one nozzle having a fuel flow channel; A conductive element is disposed on the inner wall of the nozzle and / or on the droplet flight path downstream of the nozzle outlet, including a conductive element capable of forming at least one current loop with the fuel droplets passing through the nozzle; At least two wires are electrically connected to the conductor; A magnetic field generating device is configured to generate a magnetic field acting on the fuel droplets; The conductor and the magnetic field generating device constitute the electromagnetic acceleration unit of the droplet control device. The Ampere force generated by the interaction between the current flowing through the fuel droplet and the magnetic field has a component along the target direction, thereby accelerating, correcting the trajectory, and / or rotating the fuel droplet.

[0014] Furthermore, the conductor configuration is configured to include at least an intermittent conductor comprising a plurality of spatially distributed conductive segments with intervals between adjacent conductive segments; even further, the droplet control device is configured to ensure that the current flowing through at least one of the conductive segments is primarily determined by the electrical parameters of the circuit containing the conductive segment, rather than primarily by the number of fuel droplets simultaneously contacting the conductive segment. The fuel droplets are liquid metal droplets, and the number of fuel droplets is one or more. Furthermore, it also includes a main control unit connected to the conductor and / or the magnetic field generating device, configured to control the conductor and / or the magnetic field generating device to adjust the magnitude and / or direction of the Ampere force so that the Ampere force has a component along the target direction.

[0015] In one embodiment, the main control unit is configured to control the energizing state of the conductor according to a target operating mode and / or the state information of the fuel droplet, and cooperate with the magnetic field generating device to give the Ampere force a component along the target direction. The target operating mode includes at least one of axial acceleration mode, radial focusing mode, rotational stabilization mode, and thermal load dispersion mode. The state information is used to determine the position, motion state, deformation, and / or thermal state of the fuel droplet, including at least one of position information, arrival time, departure time, flight speed, charge quantity, morphological information, and temperature information.

[0016] In another embodiment, the main control unit is configured to perform at least one of the following operations: (1) When or after the fuel droplet is detected to be in contact with the conductor, the conductor is energized or the current flowing through the fuel droplet is increased; when or before the fuel droplet is detected to be separated from the conductor, the conductor is de-energized or the current flowing through the fuel droplet is reduced.

[0017] (2) Based on at least one of the following information, adjust the electrical signal parameters applied to the conductor and / or the magnetic field parameters of the magnetic field generating device to adjust the flight speed, flight attitude, arrival time and / or arrival position of the fuel droplet: a) Detected EUV radiation intensity; b) Position information and / or motion parameters of the fuel droplet after it leaves the nozzle, including the time and position information of the fuel droplet reaching the laser target; c) Information on the position, motion parameters, and / or flight attitude of the fuel droplets within the nozzle, including predictions of the moment of contact and / or separation between the droplets and the conductor.

[0018] (3) Make the charge polarity of adjacent fuel droplets opposite. This function is based on the principle of contact electrification. By controlling the voltage polarity of the droplet when it leaves the conductor, the droplet can be charged with a net charge of a predetermined polarity, thereby actively inhibiting droplet fusion by using the attraction between opposite charges.

[0019] (4) Independently control the energization status of each conductive segment.

[0020] (5) Controlling the energization state of the conductor, including adjusting the voltage parameters applied to the conductor and / or the resistance parameters of the circuit in which the conductor is located before the fuel droplet contacts or separates from the conductor, to ensure that when the fuel droplet contacts or separates from the conductor, the current flowing through the fuel droplet and / or the voltage between the conductors are controlled below their respective safety thresholds to avoid electric arc.

[0021] (6) Based on the thermal accumulation of fuel droplets, reduce the current flowing through at least one downstream conductor, or shorten the current flowing through that conductor, or skip that conductor, in order to avoid vaporization of the fuel droplets.

[0022] (7) Based on the initial temperature or thermal state of the fuel droplet, dynamically adjust the electrical parameters to ensure that the current flowing through the fuel droplet does not exceed the vaporization critical current value corresponding to that stage. The vaporization critical current value is determined based on the initial temperature and cumulative temperature rise of the fuel droplet in that stage, ensuring that the temperature of the fuel droplet when it leaves all acceleration stages is lower than its vaporization temperature.

[0023] (8) Based on the degree of deformation of the fuel droplet, the electrical parameters are dynamically adjusted so that the local current density at the deformation point of the fuel droplet does not exceed its electro-explosion threshold. The degree of deformation is determined by at least one of the following methods: shape detection sensor, electrical signal detection, fluid dynamics model prediction, and contact time determination.

[0024] Furthermore, the conductor configuration includes at least two sets of conductors, each set of conductors capable of forming an independent current loop with the fuel droplet; the at least two sets of conductors extend in different or the same directions, and the at least two sets of conductors include at least one of the following types: an axial conductor extending along the nozzle axis, the axial conductor being continuous or intermittent; an annular conductor extending along the nozzle circumference, the annular conductor being selected from at least one of a complete circular annulus, a segmented annulus composed of multiple mutually insulated arc-shaped conductive segments, and a gradually changing cross-section annulus with a cross-sectional area that gradually changes along the axial direction; and a non-axial conductor having the effect of simultaneously generating radial and axial components in the current flowing through the droplet, the non-axial conductor being continuous or intermittent.

[0025] Furthermore, the electrical parameters are implemented through a current setting device installed in the circuit containing the conductive segment. The current setting device is selected from at least one of the following: series current-limiting resistor, independent voltage regulating circuit, constant current source, constant voltage and constant current source, PWM control (including constant current mode and / or current regulation mode), inductor current limiting, current mirror, constant current diode, negative feedback control, feedforward control, high-speed closed-loop control based on microcontroller or FPGA, combination of Zener diode and resistor, capacitor current limiting, and RC current limiting. Those skilled in the art can select according to actual operating conditions. The current setting device is configured such that the current flowing through each fuel droplet is primarily determined by the set value of the current setting device; furthermore, the current setting device is configured to maintain a stable current flowing through the fuel droplet when the resistance of the conductive segment and / or the fuel droplet changes due to temperature changes, and / or when the resistance of the fuel droplet changes due to changes in contact position, thereby maintaining a stable magnitude of the Ampere force.

[0026] Furthermore, the spacing between adjacent conductive segments serves to achieve at least one of the following functions: (1) Enhance thermal isolation between adjacent conductive sections; (2) The fuel droplets passing through the intervals recover to a basic spherical shape due to surface tension; (3) Capture fuel vapor generated by local overheating; (4) Electrically isolate adjacent fuel droplets passing through the conductor to avoid current sharing and charge sharing between droplets, regardless of whether the fuel droplets form a complete current loop with the conductor.

[0027] Optionally, the magnetic field generating device is configured to generate a fixed magnetic field or an adjustable magnetic field, the magnetic field having at least two different geometric shapes along the flight path of the fuel droplet, the at least two different geometric shapes including at least two of the following: a straight line shape, a curved shape, a converging shape, and a diverging shape.

[0028] Furthermore, the droplet control device also includes a piezoelectric unit, which is a piezoelectric correction unit and / or a piezoelectric drive unit; (1) The piezoelectric correction unit is configured to apply vibration and / or thrust pulses to the fuel droplet after the fuel droplet forms a current loop with the conductor to control the shape of the fuel droplet, and / or to generate vibration to remove fuel droplets remaining in the nozzle; the piezoelectric correction unit is controlled by a correction control unit, which is the same control unit as the main control unit, or a separate control unit independent of the main control unit.

[0029] Furthermore, the correction control unit is also configured to, based on the state information, determine that the fuel droplet is at risk of deformation or has already deformed, and then control the piezoelectric correction unit to apply vibration and / or thrust pulses to the fuel droplet to suppress or correct the deformation of the fuel droplet; the state information is used to determine the position, motion state and / or deformation of the fuel droplet, including at least one of the following: arrival time, departure time, flight speed, charge amount, and morphological information.

[0030] (2) The piezoelectric drive unit is located upstream of the electromagnetic acceleration unit and coupled to the nozzle, and is configured to apply periodic pressure perturbation to the fuel to form a uniform droplet sequence.

[0031] Furthermore, it also includes a drive control unit, which is the same control unit as the main control unit and is connected to the piezoelectric drive unit, or the drive control unit is another control unit connected to the main control unit or the electromagnetic acceleration unit and connected to the piezoelectric drive unit, configured to control the coordinated operation of the piezoelectric drive unit and the electromagnetic acceleration unit.

[0032] Furthermore, the piezoelectric driving unit and the electromagnetic acceleration unit operate independently of each other, respectively controlling the formation and acceleration of the droplets; the driving control unit is configured to synchronize the perturbation of the piezoelectric driving unit with the timing of the applied electrical signal of the electromagnetic acceleration unit.

[0033] The piezoelectric unit can be implemented using a variety of materials with inverse piezoelectric effect, including but not limited to traditional piezoelectric ceramics, lead-free piezoelectric ceramics, high-temperature piezoelectric materials, piezoelectric single crystals, and piezoelectric composite materials. Those skilled in the art will understand that any material exhibiting inverse piezoelectric effect, capable of undergoing mechanical deformation under electrical signal excitation and applying pressure disturbance to the fuel within the nozzle, can be used to implement the piezoelectric unit of this invention.

[0034] In a preferred embodiment, the piezoelectric unit may include a piezoelectric ceramic element with a temperature resistance of ≥250°C, configured to mechanically deform in response to a voltage waveform applied by a piezoelectric control unit (correction control unit or drive control unit). The piezoelectric control unit is configured to generate a drive voltage signal having adjustable frequency, amplitude, and waveform.

[0035] In addition, the electromagnetic unit generates a large amount of Joule heat when it is working. Although most of the Joule heat is in the fuel droplets, the piezoelectric correction unit still faces the challenge of working in a high-temperature environment under high-frequency operation. When necessary, active thermal management is required, such as setting up thermal insulation materials, isolating the high-temperature area with connectors with extremely low thermal conductivity, or actively cooling down and achieving precise temperature control through real-time monitoring.

[0036] Optionally, the droplet control device further includes a charge management unit disposed downstream of the conductor and configured to manage the residual charge of the fuel droplet. The charge management unit includes at least one of the following: an electron emission source configured to emit electrons into the fuel droplet; an ion source configured to emit ions with the opposite polarity to the residual charge into the fuel droplet; and a grounded conductor configured to eliminate the residual charge of the fuel droplet through physical contact or electric field induction.

[0037] Furthermore, it also includes multi-stage electromagnetic acceleration units arranged sequentially along the droplet's flight direction. Each stage includes at least one pair of conductors, and each stage's conductors have independent current regulation units. The main control unit is configured to independently adjust the current regulation units of each stage based on the droplet arrival signal and control the energizing state of each stage, such that in each stage's conductors, at most one fuel droplet forms a current loop with the conductor at any given time. The current regulation unit includes at least one of the following: an adjustable resistor, a digital potentiometer, a constant current source, a constant voltage and constant current source, a PWM current regulation circuit, a constant current diode, a current mirror, an independent power supply for each stage, an independent switch for each stage, and other circuits or components known in the art capable of independently regulating the current of that stage.

[0038] The present invention also provides a method for accelerating droplets in a fuel emitter for an extreme ultraviolet light source, comprising the following steps: A nozzle is provided, and a conductive configuration is provided on the inner wall of the nozzle and / or on the droplet flight path downstream of the nozzle outlet. This configuration includes a conductor capable of forming at least one current loop with a fuel droplet passing through the nozzle. The conductor is configured to include at least an intermittent conductor comprising a plurality of spatially distributed conductive segments spaced apart from adjacent segments, such that the current flowing through at least one of the conductive segments is primarily determined by the electrical parameters of the loop containing that segment, rather than primarily by the number of fuel droplets simultaneously contacting that segment. The fuel droplets are liquid metal droplets, and the number of fuel droplets is one or more. A magnetic field is generated outside the nozzle; The fuel droplet passing through the nozzle forms a current loop with the conductor, and the Ampere force generated by the interaction of the current flowing through the fuel droplet and the magnetic field has a component along the target direction, thereby accelerating, correcting the trajectory, and / or rotating the fuel droplet.

[0039] Furthermore, it also includes a main control unit, which selectively activates one or more groups of conductors according to a target operating mode and / or according to an electrical signal that forms a current loop between the fuel droplets and the conductors, so that the Ampere force has a component along the target direction. The target operating mode includes at least one of an axial acceleration mode, a radial focusing mode, a rotational stabilization mode, and a heat load dispersion mode.

[0040] Furthermore, it also includes a multi-stage acceleration unit, each stage of which is equipped with a conductor and a current adjustment unit. The method further includes: accelerating the droplet through the multi-stage electromagnetic acceleration unit; the main control unit independently adjusts the current magnitude of each stage of the current adjustment unit according to the droplet arrival information, and controls the energizing state of each stage, so that in each stage of the conductor, at most only one droplet forms a current loop with the conductor at any given time.

[0041] Furthermore, the method also includes a piezoelectric drive unit and a drive control unit, and further includes: applying periodic pressure perturbation to the fuel in the nozzle through the piezoelectric drive unit, so that the fuel forms a uniform droplet sequence at the nozzle outlet; and synchronizing the perturbation frequency of the piezoelectric drive unit with the timing of the electrical signal applied to the conductor through the drive control unit.

[0042] The present invention also provides an extreme ultraviolet light source device, including the droplet control device described in any of the preceding claims.

[0043] Compared with the prior art, the present invention has the following beneficial effects: 1. Functional decoupling and separate optimization: piezoelectric drive is responsible for droplet formation, while electromagnetic drive is responsible for acceleration. Parameters can be optimized independently, avoiding performance trade-offs.

[0044] 2. Multi-mode control: By selectively activating different conductor groups, multiple functions such as axial acceleration, radial focusing, rotational stabilization, and heat load dispersion can be achieved.

[0045] 3. Intelligent closed-loop control: The state of the droplet is evaluated by the electrical signal generated by the contact between the droplet and the conductor, eliminating the need for a complex external detection system and achieving precise droplet-by-drop control.

[0046] 4. Shape correction, charge management and thrust compensation: The piezoelectric correction unit and charge management unit solve the problems of shape distortion and trajectory deviation caused by uneven force and contact electrification; at the same time, the piezoelectric correction unit provides microsecond-level positive thrust pulses at the insulation interval to eliminate the "dynamic discontinuity" phenomenon and maintain the continuous force on the droplet.

[0047] 5. Suppressing deformation oscillations and stabilizing flight trajectory: By applying vibration or thrust pulses to the droplets through the piezoelectric correction unit, not only is the droplet shape corrected, but also the oscillations caused by the droplets' deformation recovery are suppressed, preventing the droplets from shifting laterally during high-speed flight and ensuring that the flight trajectories of the droplet sequence are consistent.

[0048] 6. Active heat load management: Intermittent conductors reduce Joule heating at the source through low duty cycle control and multi-mode switching.

[0049] 7. Simplified system control: Multi-stage acceleration combination can ensure a unique current path and stable current output, enabling droplets to obtain a consistent acceleration force and simplifying the reliance on real-time monitoring and feedback adjustment.

[0050] 8. End-of-pipe fine adjustment: The last one or two fine adjustment units ensure that the droplets leave the nozzle at a consistent speed and time interval, improving the laser synchronization accuracy.

[0051] 9. Avoid electric arc and extend lifespan: The control unit adjusts the voltage or resistance parameters before the droplet contacts and / or separates, so that the current flowing through the droplet and / or the voltage between the conductors are reduced to below their respective safety thresholds, thus avoiding electric arc and reducing electrode erosion and debris contamination.

[0052] 10. Multi-source closed-loop intelligent control: By adjusting electromagnetic acceleration parameters based on multi-source information feedback such as EUV intensity and / or fuel droplet position, the timing of laser impact is automatically optimized, further improving the stability of the light source and energy utilization.

[0053] 11. Electrical insulation and thermal isolation: The gap between adjacent conductive sections serves both electrical insulation and thermal isolation, suppressing Joule heat conduction along the conductor axis, reducing temperature gradient, and minimizing thermal stress and material aging; the gap can also serve as the location for external cooling or active control.

[0054] 12. Preventing vaporization and electrical explosion, and suppressing deformation (including necking and insufficient spreading): By ensuring that the current flowing through each conductive segment is primarily determined independently by the circuit's electrical parameters, the randomness of parallel current distribution is eliminated. This makes the current received by each droplet predictable and controllable, stabilizing the current of each droplet within an extremely narrow operating current window. This effectively prevents localized vaporization or electrical explosions caused by individual droplets receiving excessive current. Simultaneously, the microsecond-level short contact prevents droplets from undergoing severe deformation before separation, avoiding a dynamic decrease in the electrical explosion threshold caused by a surge in local current density. During the free-flight phase between stages, the droplets recover from surface tension to a near-spherical shape, ensuring acceleration stability. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the system structure of Embodiment 1 of the present invention (taking a continuous conductor as an example); Figure 2 This is a schematic diagram of the axial conductor structure of the present invention; Figure 3 is a schematic diagram of the ring conductor structure of the present invention, wherein: Figure 3(a) shows a complete circular ring. Figure 3(b) shows a segmented ring. Figure 3(c) shows a ring with a gradually changing cross section; Figure 4 This is a schematic diagram of the spiral conductor structure of the present invention; Figure 5 This is a schematic diagram of the intermittent conductor structure of the present invention, taking an axially intermittent conductor as an example; Figure 6 This is a schematic diagram of the system structure of Embodiment 3 of the present invention; Figure 7a This is a schematic diagram of the system structure of Embodiment 5 of the present invention; Figure 7bThis is a longitudinal cross-sectional view of the piezoelectric drive unit in Embodiment 5 of the present invention; Figure 8 This is a schematic diagram of the system structure of Embodiment 7 of the present invention; Figure 9 This is a schematic diagram of the system structure of Embodiment 10 of the present invention; Figure 10 The diagram shows the equivalent circuit model of multiple droplets connected in parallel. Attached Figure

[0056] 100. Nozzle; 111. Axial conductor; 112. Ring conductor; 112a. Segmented ring conductor; 112a1. Arc-shaped conductive segment; 112a2. Insulating layer; 113. Helical conductor; 114. Intermittent conductor; 114a. Spacing; 115. Wire; 120. Magnetic field generating device; 130. Main control unit; 131. Correction control unit; 132. Drive control unit; 140. Piezoelectric correction unit; 150. Piezoelectric drive unit; 160. Charge management unit; 170. Shape detection sensor; 180. Electromagnetic acceleration unit; 200. Fuel droplet; 210. Fuel; 300. Multi-stage electromagnetic acceleration unit; 301. Interstage vacuum gap; 400. Fuel vapor collection structure; Rs. Current limiting resistor.

[0057] It should be noted that, to more clearly illustrate the layout of the conductors, an appendix is ​​attached. Figure 1 The shape of the conductor is simplified in the diagram. In the actual structure, the conductor is disposed on the inner wall of the nozzle 100, and its surface is flush with the inner wall substrate of the nozzle 100, or an insulating layer is provided to keep the inner wall of the flow channel smooth, so as to avoid deformation or disturbance of the fuel droplets 200 due to uneven surface. Those skilled in the art will understand that this can be achieved through conventional micro-nano fabrication processes (such as deposition, etching, planarization, etc.). Detailed Implementation

[0058] The core of this invention lies in: through the configuration of the conductive structure, the current flowing through each conductive segment is independently determined by the electrical parameters of the circuit to which that segment belongs, thereby eliminating the randomness of current distribution when multiple droplets are connected in parallel; simultaneously, microsecond-level short contact is used to suppress droplet deformation, avoiding a sharp increase in local current density. Thus, the current flowing through each fuel droplet stably falls within an extremely narrow operating current window between the lower limit determined by friction and acceleration time and the upper limit determined by vaporization / electro-explosion, fundamentally preventing local overheating, vaporization, or electro-explosion caused by random parallel connection or deformation, ensuring long-term stable operation of the system. Based on this, this invention can also be combined with control units, piezoelectric units, charge management units, multi-stage electromagnetic acceleration units, etc., to achieve precise control of droplet morphology, charge, and velocity, meeting the complex requirements of high-end EUV light sources.

[0059] like Figures 1-10 As shown, a droplet control device for a fuel emitter of an extreme ultraviolet light source includes: At least one nozzle 100 has a fuel flow channel, typically a cylindrical insulator (such as boron nitride), with an inner diameter adapted to the size of the fuel droplet 200 (typically 20-30 μm). A conductive configuration, disposed on the inner wall of the nozzle 100 and / or on the droplet flight path downstream of the nozzle 100 outlet, includes a conductor capable of forming at least one current loop with the fuel droplet 200 passing through the nozzle 100. This conductive configuration may consist of one or more sets of conductors, and its specific forms vary, as detailed below.

[0060] At least two wires 115 are electrically connected to the conductor and configured to apply an electrical signal to the conductor; The magnetic field generating device 120 is configured to generate a magnetic field acting on the fuel droplet 200; the device may be multiple independently controlled electromagnet units, a specially designed permanent magnet array, or a hybrid configuration of electromagnets and permanent magnets. Furthermore, the conductor configuration is configured to include at least an intermittent conductor comprising multiple spatially distributed conductive segments with intervals between adjacent conductive segments; even further, the droplet control device is configured to ensure that the current flowing through at least one of the conductive segments is primarily determined by the electrical parameters of the circuit containing the conductive segment, rather than primarily determined by the number of fuel droplets simultaneously contacting the conductive segment. The fuel droplets 200 are liquid metal droplets, and the number of fuel droplets 200 is one or more. In this document, "the current is primarily determined by electrical parameters" means that, under conditions where the number of fuel droplets simultaneously contacting the conductive segment increases from 1 to 3, the rate of change of the current flowing through the conductive segment is less than 10%, and the rate of change of the current is defined as (I3-I1) / I1, where I1 is the current when one droplet is in contact, and I3 is the current when three droplets are in contact simultaneously. Those skilled in the art can measure the rate of change of the circuit current by applying a simulated equivalent load of droplets (using equivalent resistance and capacitance to simulate the parallel state of 1 to 3 droplets). This measurement method is a conventional experimental technique. In a preferred embodiment, the electrical parameters can also be set or adjusted according to the target acceleration requirements or the thermal state of the fuel droplets to output the required current. Those skilled in the art will understand that the "setting or adjustment" includes both factory-selected fixed parameters and dynamically adjusted parameters during use, both of which fall within the scope of this invention.

[0061] Furthermore, it also includes a main control unit 130, connected to the conductor and / or the magnetic field generating device 120, configured to control the conductor and / or the magnetic field generating device 120 to adjust the magnitude and / or direction of the Ampere force so that the Ampere force has a component along the target direction.

[0062] In one embodiment, the main control unit 130 is configured to: control the energization state of the conductor according to a target operating mode and / or the state information of the fuel droplet 200, and cooperate with the magnetic field generating device 120 to give the Ampere force a component along the target direction. The target operating mode includes at least one of axial acceleration mode, radial focusing mode, rotational stabilization mode, and heat load dispersion mode. The state information is used to determine the position, motion state, deformation, and / or thermal state of the fuel droplet, including at least one of position information, arrival time, departure time, flight speed, charge quantity, morphological information, and temperature information.

[0063] The connection between the main control unit 130 and the magnetic field generator 120 includes both wired and wireless connections. The "cooperation" includes both direct and indirect control: direct control refers to the main control unit 130 sending real-time adjustment signals to the magnetic field generator 120 via wired or wireless means to change the strength, direction, or distribution of the magnetic field; indirect control refers to the main control unit 130 selecting a fixed magnetic field configuration generated by the magnetic field generator 120 that matches a preset operating mode, without sending real-time adjustment signals to the magnetic field generator 120. Regardless of the method used, as long as the conductor group selected by the main control unit 130 and the magnetic field generated by the magnetic field generator 120 work together to produce an Ampere force with a target directional component, it falls within the scope of the "cooperation" described in this invention.

[0064] In another embodiment, the main control unit 130 is configured to perform at least one of the following operations: (1) When the fuel droplet 200 is detected to be in contact with the conductor or after contact, the conductor is controlled to be energized or the current flowing through the fuel droplet 200 is increased; when the fuel droplet 200 is detected to be separated from the conductor or before separation, the conductor is controlled to be de-energized or the current flowing through the fuel droplet 200 is reduced. (2) Based on at least one of the following information, adjust the electrical signal parameters applied to the conductor and / or the magnetic field parameters of the magnetic field generating device 120 to adjust the flight speed, flight attitude, arrival time and / or arrival position of the fuel droplet 200: a) Detected EUV radiation intensity b) Position information and / or motion parameters of the fuel droplet 200 after it leaves the nozzle 100, including the time and position information of the fuel droplet reaching the laser target; c) Position information, motion parameters and / or flight attitude of fuel droplet 200 within nozzle 100, including prediction of the moment of contact and / or separation of droplet with conductor.

[0065] (3) Make the charge polarities of adjacent fuel droplets 200 opposite. This function is based on the principle of contact electrification. By controlling the voltage polarity of the droplet when it leaves the conductor, the droplet can be charged with a net charge of a predetermined polarity, thereby actively inhibiting droplet fusion by using the attraction between opposite charges.

[0066] (4) Independently control the energization status of each conductive segment.

[0067] (5) Controlling the energization state of the conductor, including adjusting the voltage parameters applied to the conductor and / or the resistance parameters of the circuit in which the conductor is located before the fuel droplet 200 contacts or separates from the conductor, to ensure that when the fuel droplet 200 contacts or separates from the conductor, the current flowing through the fuel droplet 200 and / or the voltage between the conductors are controlled below their respective safety thresholds to avoid electric arc.

[0068] (6) Based on the thermal accumulation of fuel droplets 200, reduce the current of at least one downstream conductor, or shorten the current of that conductor, or skip that conductor, in order to avoid vaporization of fuel droplets 200.

[0069] (7) Based on the initial temperature or thermal state of the fuel droplet 200, the electrical parameters are dynamically adjusted so that the current flowing through the fuel droplet 200 does not exceed the vaporization critical current value corresponding to that stage. The vaporization critical current value is determined based on the initial temperature and cumulative temperature rise of the fuel droplet 200 in that stage, ensuring that the temperature of the fuel droplet 200 when it leaves all acceleration stages is lower than its vaporization temperature.

[0070] Definition and determination method of "critical vaporization current value" The vaporization critical current value refers to the upper limit of the current at which the fuel droplet 200 will not vaporize after leaving all acceleration stages. The threshold values ​​for each stage can be different, determined based on the droplet's entry temperature into that stage, the expected temperature rise in subsequent stages, and the allowable final temperature, ensuring that the droplet's temperature is below the vaporization temperature when it leaves all acceleration stages. In this invention, the vaporization critical current value and energizing time for each stage are determined as follows: Step 1: Set the initial droplet velocity v1 and initial temperature T1 (which can be determined by preset values, heating power models, or non-contact methods such as infrared thermometry).

[0071] Step 2: For stage i, determine the exit target velocity v of that stage based on the target velocity curve. （i+1） Calculate the required acceleration a i = [v （i+1） 2 - v i 2 ] / (2L i ), where the inlet velocity of the i-th stage is v. iIt is determined based on the exit velocity of the previous stage and the velocity variation of the droplets within the interval.

[0072] Step 3: Calculate the required current I based on the acceleration. i = m(a i + a f ) / (B·L path ·sinθ), where θ is the angle between the direction of the current and the direction of the magnetic field; a f For frictional deceleration, the a f It can be determined through routine experimental measurements, with typical values ​​around 10. 4 ~10 6 m / s 2 Within the order of magnitude, L path The path length of the current flowing through the droplet depends on the arrangement of the conductive segments, which can be determined by those skilled in the art based on actual operating conditions. In preliminary design calculations, friction can be temporarily ignored, and only the upper limit of the current can be calculated based on electromagnetic force, which can then be corrected through experiments.

[0073] Step 4: Calculate the energizing time t of this stage. i = [v (i+1) - v i ] / a i And the Joule heat Q of this level i = I i 2 Rt i Here, the resistance R is a variable that dynamically changes due to random temperature, deformation, and contact degree. To retain a safety margin, this step takes the equivalent resistance R under the worst-case operating condition. max calculate.

[0074] Fifth step, according to the temperature rise formula ΔT = Q / (mc p Calculate the temperature rise of this stage to obtain the stage outlet temperature T. （i+1) Check T （i+1) Does it exceed the preset upper limit of the outlet temperature for this stage? If it does not exceed the limit, the outlet velocity and temperature of this stage are used as the inlet parameters for the next stage, and the calculation continues for the next stage; if it exceeds the limit, the target outlet velocity or current of this stage is reduced, and the calculation is repeated until the limit is met.

[0075] Repeat the above process until the last stage. The upper limit of the exit temperature of each stage is lower than the boiling point of tin, and a temperature rise margin is reserved for subsequent stages to ensure that the temperature of the droplets is below the vaporization critical temperature when they leave all acceleration stages.

[0076] It should be noted that the above calculations regarding acceleration, current, and temperature rise are conservative estimates based on an idealized model. In actual operating conditions, the initial current of the droplet upon entering the conductor is zero or below the safety threshold, and the current drops to zero or below the safety threshold before leaving the conductor. Within these two dead zones, the droplet is only decelerated by friction. Due to the existence of these dead zones, the actual effective acceleration distance is less than the physical length of the conductive segment. The target acceleration a... i Compensation is needed for the velocity loss caused by the dead zone deceleration; furthermore, the droplet undergoes deformation and internal viscous dissipation within the conductor. These factors will cause the actual required accelerating current to be slightly higher than the calculated value. Those skilled in the art can modify the above model through conventional experiments or numerical simulations to obtain more accurate current parameters. This invention is not limited to the specific values ​​conservatively estimated above.

[0077] (8) Based on the degree of deformation of the fuel droplet 200, the electrical parameters are dynamically adjusted so that the local current density at the deformation point of the fuel droplet 200 does not exceed its electro-explosion threshold. The degree of deformation can be determined by at least one of the following methods: a) The aspect ratio of the droplet is directly measured by a shape detection sensor 170 located downstream of the conductive section; b) By detecting the electrical signal flowing through the conductive section, the change in the equivalent resistance of the droplet can be indirectly estimated based on the change in the electrical signal flowing through the conductive section, and thus the degree of deformation can be estimated. c) Based on the length of the conductive segment, the droplet velocity, the magnitude of the Ampere force, and the droplet's physical properties, the degree of deformation is predicted using a fluid dynamics model; d) Determine the degree of deformation based on the ratio of the contact time of the droplet through the conductive section to the capillary recovery time.

[0078] The above methods can be used individually or in combination.

[0079] Detailed description of conductor configuration To fully protect the concept of this invention and prevent competitors from circumventing it through simple variations, the conductor of this invention can have a variety of specific implementations.

[0080] In a preferred embodiment, the conductor configuration includes at least two sets of conductors, each set of conductors being able to form an independent current loop with the fuel droplet 200; the main control unit 130 is configured to selectively activate one or more of the at least two sets of conductors to change the direction of the current flowing through the droplet.

[0081] • The at least two sets of conductors can extend in different directions, so that the different activated sets of conductors generate currents in different directions in the droplet, thereby realizing different functional modes.

[0082] • The at least two sets of conductors may also extend in the same direction (e.g., two sets of parallel axial conductors 111), and the heat load distribution can be adjusted (to avoid overheating of a single conductor) or redundant control can be achieved by switching to activate different sets of conductors (to activate a backup set when one set fails).

[0083] It should be noted that the "conductor disposed on the inner wall of the nozzle 100" mentioned in this invention refers to the conductive portion exposed on the inner wall of the nozzle 100 that can form electrical contact with the fuel droplets 200 passing through the nozzle 100. The specific routing method (e.g., radial routing, curved routing, etc.) and connection method (e.g., the location of the connection point with the wire) of the conductor within the nozzle 100 wall can be arbitrarily set according to actual needs, as long as its exposed portion can achieve the function of this invention. Those skilled in the art will understand that the overall geometry of the conductor is determined by its exposed portion and is not affected by the routing within the wall.

[0084] Specifically, the conductor configuration includes at least one of the following types: 1. Axial conductor 111: Extends along the axis of nozzle 100. When activated, the current flowing through the droplet has a predominantly radial component.

[0085] 2. Ring conductor 112: Extends circumferentially. When activated, the current flowing through the droplet has primarily an axial component.

[0086] As shown in Figure 3, the ring conductor 112 type can also have further variant forms: • Complete circular ring: continuously surrounds the inner wall of the nozzle 100 once.

[0087] • Segmented ring conductor 112a: Composed of multiple mutually insulated arc-shaped conductive segments 112a1 spliced ​​together. This design allows for more flexible current path selection, for example, only some arc segments can be activated to produce an asymmetrical current distribution.

[0088] • Gradual cross-section ring: The cross-sectional area of ​​the conductor gradually changes (increases or decreases) along the axial direction, thereby adjusting the current density distribution and optimizing the location of Joule heating and the distribution characteristics of electromagnetic force.

[0089] 3. Non-axial conductor: Any conductor that can cause the current flowing through the droplet to generate both radial and axial components, regardless of its specific geometric shape (whether it is helical, inclined straight, zigzag, or other non-axial extension forms), is considered a non-axial conductor according to the present invention.

[0090] According to their structure, the conductor configuration can be further divided into continuous conductors and discontinuous conductors. 1. Continuous conductor: a single continuous line, wherein the continuous conductor comprises a conductive material; 2. Intermittent Conductor 114: Composed of multiple conductive segments with gaps between adjacent segments. The conductive segments include conductive material, and the gaps are selected from at least one of vacuum gaps, insulating material filling, or an insulating coating on the surface of a conductive substrate. Each conductive segment can be any shape, such as a ring conductor 112 and variations thereof, stripes, dots, inclined shapes, zigzag shapes, wavy shapes, etc. The overall arrangement direction of the multiple conductive segments is axial, circumferential, non-axial, or irregularly distributed. In a preferred embodiment, each conductive segment is connected to the main control unit 130 for independent control; in another preferred embodiment, the gaps are configured to provide free-flight sections, allowing the fuel droplets 200 to recover to a basic spherical shape from surface tension when passing through the gaps. Specifically, the gaps are vacuum gaps or have through channels, allowing the fuel droplets 200 passing through the gaps to be unconstrained by the walls, and the length of the gaps is configured such that the flight time of the fuel droplets 200 when passing through the gaps is not less than the capillary recovery time of the fuel droplets 200.

[0091] Explanation of the principle of electrical isolation The "electrical isolation" described in this invention refers to making the current loops formed by adjacent fuel droplets 200 and the conductor relatively independent, avoiding current and charge sharing between droplets, regardless of whether the fuel droplets 200 form a complete current loop with the conductor. The physical principle is that when multiple droplets are in the same parallel circuit, they share the same potential, leading to charge sharing and current competition between them. Charge sharing causes adjacent droplets to acquire the same charge, generating repulsive forces that disturb their trajectories; current competition results in uneven force on the droplets, causing velocity fluctuations that lead to merging and chasing.

[0092] Specifically: (1) The droplet and the conductor form an independent current loop; (2) The droplet does not form a current loop with the conductor, for example: the droplet is in the gap, or the droplet is in contact with the conductor but does not form an effective current loop (e.g., it is disconnected by the control unit). (3) The droplet is crossing the gap between adjacent conductive segments. The aforementioned electrical coupling can be fundamentally severed by ensuring that each droplet has an independent current loop or does not form a current loop. Specific implementation methods include: 1. Spatial isolation: The discontinuous conductor 114 structure (such as being composed of multiple short conductive segments arranged along the axial direction) makes each segment independent through intervals, and each droplet has an independent circuit when passing through different time periods; 2. Time isolation: Power is supplied by the main control unit in 130-minute intervals, so that at most one fuel droplet 200 can form a current loop with the same conductor (or the same group of conductors) at the same time; 3. Circuit isolation: Provides independent current paths for different droplets, making the current loops between droplets independent of each other in the circuit.

[0093] Those skilled in the art will understand that, regardless of the method used, as long as the independence of the current loop between droplets is achieved, electrical coupling can be reduced, thereby suppressing fusion.

[0094] Detailed explanation of the target working mode The main control unit 130 is configured to adjust the conductor configuration and the magnetic field generating device 120 according to a target operating mode, the target operating mode including at least one of the following: 1. Axial acceleration mode: • Objective: To enable the droplet to achieve a velocity increment along the axis of nozzle 100.

[0095] • Typical configuration: Activate the axial conductor 111 (current is mainly radial) and coordinate to give the magnetic field direction a tangential component (e.g., the magnetic field direction is perpendicular to the axis), thereby generating an axial Ampere force.

[0096] • Technical effect: Achieve basic acceleration of droplets.

[0097] 2. Radial Focusing Mode: • Objective: To pull droplets that have deviated from the axis back to the center, or to suppress radial drift of droplets.

[0098] • Typical configuration: Multiple annular conductors 112 are arranged along the axial direction of nozzle 100, with insulation between adjacent ones. The droplet simultaneously contacts two annular conductors 112 (current axis) and works together to give the magnetic field direction a tangential component, thereby generating a radial Ampere force pointing towards or away from the axis (depending on the specific configuration of the current and magnetic field directions, centripetal or centrifugal force can be selected, usually centripetal force to achieve focusing).

[0099] • Technical effect: Corrects trajectory deviation and improves droplet hit accuracy.

[0100] 3. Rotationally Stabilized Mode: • Objective: To make the droplet rotate around its own axis and stabilize its attitude using the gyroscopic effect.

[0101] • Typical configuration: Activate the axial conductor 111 (current radial) and coordinate to give the magnetic field direction an axial component, thereby generating an Ampere force in the tangential direction, forming a force couple to drive the droplet rotation; or activate the annular conductor 112 (current mainly axial) and coordinate to give the magnetic field direction a radial component (such as perpendicular to the axis of nozzle 100), thereby generating an Ampere force in the tangential direction to achieve a rotationally stable mode.

[0102] • Technical benefits: Improves droplet sphericity, reduces oscillation, and enhances EUV output stability.

[0103] 4. Distributed heat load mode: • Objective: To avoid localized overheating caused by continuous operation of a single conductor group or in a single direction.

[0104] • Implementation method: Periodically switch the activation of different conductor groups at different time periods or for different droplets (e.g., alternately use two sets of axial conductors 111), or cycle between different working modes (e.g., acceleration, focusing, rotation) to disperse Joule heat to different conductor groups and different regions.

[0105] • Technical benefits: Reduces peak temperature and extends system lifespan.

[0106] 5. Polarity Control Mode The main control unit 130 of the present invention can also be configured to make the charge polarities of adjacent fuel droplets 200 opposite. This function aims to actively suppress the tendency of droplets to merge under high-frequency operating conditions. Its physical principle is based on contact electrification: when a droplet comes into contact with a conductor, charge transfer occurs due to the difference in work functions between the two. By controlling the voltage polarity of the conductor at the moment the droplet leaves, the droplet can be made to carry a net charge of a predetermined polarity.

[0107] The specific mechanism for achieving opposite polarities is as follows: • When a droplet comes into contact with a positively charged conductor, electrons in the droplet are attracted to one side of the conductor. When the droplet leaves, it becomes positively charged because it has lost electrons. • When a droplet comes into contact with a negatively charged conductor, the droplet gains extra electrons and becomes negatively charged.

[0108] By applying voltages of opposite polarities to the conductors in contact with different droplets, adjacent droplets can acquire opposite charges. The Coulomb attraction between these opposite charges actively counteracts the tendency for them to merge due to velocity differences, thereby improving the stability of the droplet sequence. The voltage polarity, application timing, and other parameters required to achieve this function can be determined by those skilled in the art through routine experiments.

[0109] 6. Feedback Control Mode As an extended embodiment of the present invention, the main control unit 130 may also be configured to adjust the electromagnetic acceleration parameters based on feedback signals from the laser-droplet interaction and / or droplet state information. The feedback signals include, but are not limited to: (1) EUV radiation intensity: At least one EUV sensor can be set to detect the EUV radiation intensity generated by the laser bombarding the droplet. When the detected EUV intensity is lower than a preset threshold, it indicates that the synchronization accuracy between the laser and the droplet has decreased. The main control unit 130 adjusts the electrical signal parameters and / or magnetic field parameters applied to the conductor accordingly, so that subsequent droplets arrive at the excitation point at the correct time / position, and the EUV intensity is restored.

[0110] (2) Position information and motion parameters of the droplet after leaving the nozzle 100: At least one optical sensor (such as a photoelectric sensor) can be set to detect the flight trajectory of the droplet, the time and / or position information of the arrival point of the laser target. When the droplet is detected to deviate from the predetermined trajectory or the arrival time is deviated, the main control unit 130 adjusts the electromagnetic acceleration parameters to correct the droplet in real time to ensure accurate laser strike.

[0111] (3) Position and motion parameters of the droplet within the nozzle 100: At least one capacitive or photoelectric sensor can be installed to detect and predict the position, flight speed, and / or contact / separation time of the droplet with the conductor within the nozzle 100. Based on the above information, the main control unit 130 adjusts the electromagnetic parameters in real time to adjust the flight speed of the droplet and / or activate different conductor groups, applying Ampere forces in the corresponding directions to adjust the flight attitude, thereby achieving active control of the droplet's flight speed and / or flight attitude.

[0112] (4) Contact / separation time and prediction between droplet and conductor: A capacitive sensor can be installed on the inner wall of nozzle 100, or the contact and separation time between droplet and conductor can be determined by detecting the electrical signal of the conductor circuit. The main control unit 130 controls the on / off state or adjusts the electrical parameters in advance to avoid arcing during contact and separation.

[0113] (5) Flight attitude: Multiple sensors (such as a capacitive sensor array or photoelectric sensor) can be installed in the nozzle 100 to detect the shape, tilt direction and eccentricity of the droplet. The main control unit 130 selectively activates different conductive groups (such as axial group, annular group or spiral group) according to the flight attitude, and applies Ampere force in the corresponding direction to correct the droplet attitude, correct the trajectory or stabilize its rotation.

[0114] 7. Degradation Protection Mode As another extended embodiment of the present invention, the main control unit 130 is further configured to enter a degradation protection mode when the heat accumulation or temperature of the fuel droplet 200 exceeds a preset threshold. In the degradation protection mode, the main control unit 130 reduces the current flowing through at least one downstream conductor, or shortens the energizing time of that stage, or skips that stage conductor, in order to reduce subsequent heat input, thereby preventing the fuel droplet 200 from vaporizing due to continued heating at the expense of the droplet's acceleration.

[0115] Because the intermittent conductor 114 geometrically confines the Joule heating generation location within the contact segment, the main control unit 130 can accurately estimate the heat accumulation of each droplet. This allows the degradation protection mode to precisely apply to the droplet requiring protection without affecting other normal droplets or only affecting a few droplets in contact with the droplet requiring protection at the same conductor level. In the continuous conductor scheme, because the temperature gradient of the fuel droplet 200 along the axial direction is unpredictable, it is impossible to determine which current level should be reduced, making the degradation protection mode difficult to implement effectively.

[0116] 8. Security-based rate limiting mode Objective: To prevent droplets from overheating and vaporizing, and to prevent them from exploding due to deformation causing local current density to exceed the electrical explosion threshold.

[0117] Implementation method: The main control unit 130 dynamically adjusts electrical parameters based on the initial temperature and / or cumulative temperature rise of the fuel droplets and the degree of droplet deformation, limiting the current flowing through the droplets to below the vaporization critical current value, and ensuring that the local current density at the point of droplet deformation does not exceed its electro-explosion threshold.

[0118] Technical effect: Ensures that the temperature rise of droplets is below the vaporization temperature when they leave the entire acceleration stage, and that the local current density is always below the electro-explosion threshold, thus avoiding vaporization or electro-explosion caused by overheating of individual droplets.

[0119] For the specific methods for determining the vaporization critical current value and the method for determining the degree of deformation, please refer to the detailed description in the operation (7) and (8) of the main control unit 130 above.

[0120] Regarding the diversity of magnetic field forms To further enhance control capabilities, the magnetic field generating device 120 can be configured to generate a spatially non-uniformly distributed magnetic field, for example: • Linear magnetic field: The magnetic field lines are basically parallel.

[0121] • Curved magnetic field: The magnetic field lines are curved.

[0122] • Converging magnetic field: Magnetic field lines converge toward the axis.

[0123] • Divergent magnetic field: Magnetic field lines diverge away from the axis.

[0124] By selecting different magnetic field patterns under different operating modes, more precise control of droplets can be achieved.

[0125] Various implementation methods for heat load distribution mode The heat load dispersion mode described in this invention aims to avoid localized overheating caused by continuous operation of a single conductor group or a single working mode, and can be achieved in a variety of ways.

[0126] 1. Dynamic switching based on temperature sensor feedback: As a preferred implementation, at least one temperature sensor (e.g., thermocouple, thermistor, infrared sensor, etc.) can be placed near the nozzle 100. The main control unit 130 adjusts the selected operating mode or switching frequency in real time based on the detection signal from the temperature sensor. For example, when the temperature of a certain group of conductors is detected to exceed a preset threshold, the main control unit 130 can temporarily switch to the operating mode of using other groups of conductors to allow the overheated area to rest and cool down; once the temperature returns to normal, it will return to the original mode.

[0127] 2. Periodic switching based on preset timing: As another implementation method, heat load distribution can be achieved using a preset timing sequence, eliminating the need for temperature sensor feedback. The main control unit 130 has a fixed preset timing cycle. Within each cycle, different conductor groups are activated sequentially (e.g., axial conductor 111, annular conductor 112, and spiral conductor 113 are activated sequentially) or different operating modes are switched sequentially (e.g., axial acceleration mode, radial focusing mode, and rotational stabilization mode are switched sequentially). Through this periodic switching, Joule heat is distributed to different conductor groups and different operating areas.

[0128] 3. Manual switching based on human intervention: As another implementation method, operators can manually switch to different conductor groups or working modes by means of manual operation (such as DIP switches, knobs, multiplex switches, etc.) based on the observed temperature distribution or system operating status, so as to realize the dynamic distribution of heat load.

[0129] 4. External command-triggered switching: As another implementation method, the main control unit 130 can receive commands from a host computer or other external systems and switch to a specified conductor group or operating mode according to the command requirements. This method is suitable for scenarios that require collaboration with external systems.

[0130] 5. Indirect feedback based on other sensors: As another implementation method, the heat load distribution can be indirectly determined by detecting other temperature-related physical quantities (such as current, voltage, flow rate, etc.), and switching control can be performed accordingly. For example, when an abnormal increase in the resistance of a group of conductors is detected (such as a decrease in current in constant voltage mode or an increase in voltage in constant current mode), it can be inferred that its temperature may be rising, thereby triggering switching.

[0131] 6. Low Duty Cycle Control Based on Intermittent Conductors: When using an intermittent conductor structure, the main control unit 130 can be configured to be energized only for a brief period of time as the fuel droplets 200 pass through each conductive segment, and de-energized immediately after the droplets leave. Because the time a single droplet spends passing through a conductive segment is extremely short (e.g., 0.6 μs), while the droplet intervals are relatively long (e.g., 20 μs), the actual duty cycle of the conductor can be as low as below 3%. This "on-demand energization" control method fundamentally reduces the total amount of Joule heat generated and is an effective supplement to other heat dissipation methods.

[0132] Those skilled in the art will understand that all the above-described implementations utilize the core concept of this invention—dispersing heat load by dynamically adjusting the current path distribution. Regardless of the specific means employed, as long as it involves switching conductor groups or operating modes to avoid localized overheating, it falls within the scope of the heat load dispersion mode described in this invention.

[0133] In a preferred embodiment of the present invention, a piezoelectric correction unit 140 is further included, configured to apply vibration and / or thrust pulses to the fuel droplet 200 after the fuel droplet 200 forms a current loop with the conductor, in order to control the shape of the fuel droplet 200, and / or configured to generate vibration to remove residual droplets. Optionally, the device further includes a charge management unit 160, located downstream of the conductor, configured to manage residual charge on the fuel droplets 200. The charge management unit 160 is connected to the main control unit 130 and / or the correction control unit 131, and is further configured to control the operation of the charge management unit 160 based on status information.

[0134] Optionally, the device further includes a shape detection sensor 170, disposed downstream of the conductor, configured to detect shape parameters of the fuel droplet 200 (such as sphericity, aspect ratio, etc.) and feed the detection results back to the main control unit 130 and / or the correction control unit 131. The correction control unit 131 is the same control unit as the main control unit 130, or a separate control unit independent of the main control unit 130.

[0135] The piezoelectric correction unit 140 can be a piezoelectric ceramic tube, a piezoelectric sheet, or a piezoelectric stack structure. Its driving frequency is matched with the passing frequency of the fuel droplet 200, typically 20-100 kHz. The structure of the piezoelectric correction unit 140 is not limited to the above example. Any piezoelectric structure capable of generating high-frequency vibrations and / or thrust pulses and acting on the droplet can be used in this invention.

[0136] As a preferred embodiment of the present invention, the timing control logic of the correction control unit 131 is as follows: When the droplet reaches the conductive area, it forms an electrical contact with the conductor. The correction control unit 131 determines the initial arrival time t0 of the droplet by acquiring the droplet's state information (in this embodiment, detecting the current signal flowing through the conductor). The correction control unit 131 calculates the delay time ΔT based on the droplet's real-time velocity or calibrated velocity (in this embodiment, the velocity is calculated based on the time interval of the current signal or determined through pre-calibration) and the distance of the droplet from the conductor to the working area of ​​the piezoelectric correction unit 140. At time t1 (=t0+ΔT), the correction control unit 131 sends a trigger signal to the piezoelectric correction unit 140, which then starts vibrating to apply high-frequency micro-vibration to the droplet that has reached its working area, correcting the droplet's shape.

[0137] When the droplet leaves the conductive area, the correction control unit 131 determines the end time t2 of the droplet's departure (in this embodiment, the falling edge of the detected current signal), and calculates the delay time of the stop signal based on t2 and the distance of the droplet from the conductor to the working area of ​​the piezoelectric correction unit 140. After the piezoelectric correction unit 140 completes the correction of the droplet, it sends a stop signal to it, and the piezoelectric correction unit 140 stops vibrating and waits for the arrival of the next droplet.

[0138] The amplitude I of the current signal is positively correlated with the charge Q of the droplet. When the droplet carries a large charge, the contact electrification effect is stronger, and the current amplitude is higher. The main control unit 130 and / or the correction control unit 131 can detect the current amplitude to assess the charge state of the droplet in real time, and adjust the operating parameters of the charge management unit 160 (such as neutralization current intensity, electron emission power, etc.) accordingly to control the residual charge of the droplet within an acceptable range or below a threshold.

[0139] In another preferred embodiment of the invention, a piezoelectric drive unit 150 is further included, coupled to the nozzle 100, and configured to apply periodic pressure disturbances to the fuel 210. Typical implementations include a piezoelectric ceramic tube surrounding the nozzle, a piezoelectric sheet, etc.

[0140] It also includes a drive control unit 132, which is the same control unit as the main control unit 130 and is connected to the piezoelectric drive unit 150, or the drive control unit 132 is another control unit, connected to the main control unit 130 or the electromagnetic acceleration unit 180, and connected to the piezoelectric drive unit 150, configured to control the cooperative operation of the piezoelectric drive unit 150 and the electromagnetic acceleration unit 180.

[0141] Those skilled in the art will understand that the "connection" includes, but is not limited to, direct electrical connection, indirect electrical connection, and wireless communication connection. The drive control unit 132 sends control signals to the piezoelectric drive unit 150 and the electromagnetic acceleration unit 180 through the connection, achieving timing synchronization and functional coordination between the two. In some embodiments, the drive control unit 132 can also automatically operate each unit according to a predetermined program through a preset operating mode; as long as the coordinated operation of piezoelectric drive and electromagnetic acceleration can be achieved, it falls within the scope of this invention.

[0142] The piezoelectric drive unit 150 can be implemented using a variety of materials with inverse piezoelectric effect, including but not limited to: Traditional piezoelectric ceramics, such as lead zirconate titanate (PZT) ceramics, have a high piezoelectric coefficient. • Lead-free piezoelectric ceramics: such as barium titanate (BT) based, sodium bismuth titanate (BNT) based, and potassium sodium niobate (KNN) based ceramics; • High-temperature piezoelectric materials: such as half-Heusler compounds TiNiSn, ZrNiSn, TiCoSb, etc.; • Piezoelectric single crystals: such as quartz; • Piezoelectric composite materials.

[0143] Those skilled in the art will understand that as long as a material has the inverse piezoelectric effect and can generate mechanical deformation under electrical signal excitation and apply pressure disturbance to the fuel 210 in the nozzle 100, it can be used to realize the piezoelectric drive unit 150 of the present invention.

[0144] Typical parameters include: • Drive frequency: 20-100kHz (adjustable) • Droplet diameter: 20-100μm (controlled by nozzle orifice diameter and drive parameters) • Temperature resistance requirement: ≥250℃ (suitable for the operating temperature of tin fuel) The above parameters are conventional ranges in the field, and those skilled in the art can adjust them as needed. The scope of protection of this invention is not limited thereto.

[0145] There can be one or more piezoelectric drive units 150, configured according to actual needs.

[0146] In the basic configuration, a piezoelectric drive unit 150 is used to achieve periodic pressure perturbation of fuel 210 to form a droplet sequence.

[0147] To further improve control accuracy, a dual piezoelectric drive unit configuration can be adopted, including a first piezoelectric drive unit and a second piezoelectric drive unit: • First piezoelectric drive unit: coupled to nozzle 100, configured to apply periodic pressure perturbation to fuel 210 to form a uniform droplet sequence.

[0148] • Second piezoelectric driving unit: Located downstream of the first piezoelectric driving unit and upstream of the electromagnetic acceleration unit 180, it is configured to regulate the passing droplet. The regulation includes at least one of the following: size adjustment, attitude adjustment, and trajectory fine-tuning. The second piezoelectric driving unit may employ a piezoelectric ceramic tube, piezoelectric sheet, or piezoelectric stack, etc., and achieves secondary shaping or attitude correction of the droplet through high-frequency micro-vibration.

[0149] Dual piezoelectric co-control enables more precise droplet size control, attitude correction, and trajectory optimization, thereby improving droplet quality and meeting the stringent requirements of high-frequency EUV light sources.

[0150] Those skilled in the art will understand that the number and specific functions of the piezoelectric drive units can be adjusted according to actual needs, and are not limited to the examples above.

[0151] The drive control unit 132 is the core of this invention for achieving piezoelectric-electromagnetic coordinated operation. Its main functions include: Timing synchronization: To ensure precise matching between the droplet formation timing of the piezoelectric drive unit 150 and the applied electrical signal timing of the electromagnetic acceleration unit 180, each droplet is accelerated promptly upon arrival at the electromagnetic acceleration unit 180. Let the piezoelectric drive period be T, the initial droplet velocity be v, and the distance between the outlet of the piezoelectric drive unit 150 and the inlet of the electromagnetic acceleration unit 180 be L, then the droplet flight time t... flight = L / v.

[0152] Depending on the structure of the conductor, the drive control unit 132 can adopt corresponding control strategies: (A) When using intermittent short conductors (each segment length less than the droplet spacing), the droplets pass through each segment sequentially, and the drive control unit 132 can delay by t after the piezoelectric drive signal is issued. flight The system sends a trigger signal to the first conductor, and then the main control unit 130 triggers the subsequent segments accordingly, thus achieving precise segment-by-segment control.

[0153] (B) When a continuous long conductor (length greater than the droplet spacing) is used, multiple droplets are always present in the conductor, forming a continuous path. However, to avoid arcing, each droplet still needs to be triggered individually. The drive control unit 132 continuously adjusts electrical parameters (such as amplitude, direction, and waveform) according to the target working mode or droplet position information. It cuts off power or controls the current intensity and voltage to below their respective safety thresholds before the droplet arrives, and then turns on power or increases the current intensity after the droplet arrives, thereby avoiding arcing. Alternatively, it can switch between multiple sets of conductors to control the type of conductor that forms a current loop with the droplet, especially the type of the first conductor, so that each droplet is subjected to a continuous but variable Ampere force during its passage through the conductor.

[0154] Those skilled in the art will understand that both of the above control methods fall within the scope of this invention, and the specific choice depends on the geometry of the conductor and the system design objectives.

[0155] Independent adjustment: The piezoelectric drive parameters (frequency, amplitude, waveform) and electromagnetic acceleration parameters (current intensity, magnetic field direction) can be adjusted separately without affecting each other.

[0156] Dual piezoelectric synergy: When a dual piezoelectric configuration is used, the drive control unit 132 also needs to synchronize the timing of the first piezoelectric unit, the second piezoelectric unit, and the electromagnetic unit.

[0157] During flight, droplets may be affected by factors such as friction, droplet size fluctuations, and launch velocity fluctuations, resulting in slight deviations between the actual arrival time and the theoretical calculation value. Those skilled in the art can ensure synchronization accuracy through pre-calibration (calibrating the delay parameter by actually measuring the droplet arrival time) or real-time feedback adjustment (such as detecting the droplet position with a sensor and dynamically adjusting the trigger signal).

[0158] Technical Problem Analysis: Circuit models where multiple droplets in parallel cause unpredictable current EUV fuel droplets 200 are continuously emitted at a frequency of 50 kHz. In a continuous conductor, multiple droplets simultaneously contact the same conductor, forming a parallel current loop. For example... Figure 10 As shown, three droplets simultaneously contact two conductive segments, forming a parallel circuit. The contact positions, contact areas, and temperatures of the droplets fluctuate randomly, causing the droplet resistances R1, R2, and R3 to change randomly on the microsecond level. The currents I1, I2, and I3 flowing through each droplet are determined by the parallel current splitting, making them unpredictable, and the Joule heating is uncontrollable.

[0159] This invention achieves predictable current control through two synergistic mechanisms: The total current can be forced to stabilize by setting electrical parameters (such as making the current-limiting resistor Rs much larger than the droplet resistance); Under the premise of stable total current, the number of parallel droplets is physically limited by the intermittent conductor structure.

[0160] Let R be the equivalent resistance of the parallel connection formed by other droplets. other Then 1 / R other =1 / R² + 1 / R³ + ... + 1 / R n The current I1 of droplet 1 is I total ×R other / (R1+R other )=I total / (1+R1 / R other ) When there is only one droplet 1 in the circuit, I1 = I total ; When other droplets are connected in parallel in the circuit, the fewer the number of droplets connected in parallel, the lower the R value. other The larger the value, the greater the impact of the random distribution of the parallel circuit on droplet 1. According to the above formula, the impact of the resistance fluctuation of droplet 1 itself, as well as the resistance fluctuation of other droplets, on the current flowing through droplet 1 decreases accordingly. That is, the degree of influence of the random distribution of the parallel circuit on droplet 1 decreases significantly as the number of parallel droplets decreases.

[0161] Calculation of droplet electro-explosion threshold and temperature rise estimation using a square flow channel model; 1. Droplet mass and geometric parameters The droplet is spherical before entering the nozzle. Assuming the droplet diameter d = 30 μm, then the radius r = 15 μm. The density of liquid tin ρ = 7000 kg / m³. 3 Droplet mass: m = ρ·4 / 3πr 3 ≈9.9×10 -11 kg; For ease of estimation, the following explanation uses a square flow channel as an example. The shape of the droplet in the flow channel is estimated according to the equivalent curved surface model (the two ends of the droplet are hemispheres and the middle is a square column). For other shapes of flow channels (such as circles, ellipses, etc.), the cross-sectional shape of the droplet is consistent with that of the flow channel. Those skilled in the art can perform equivalent calculations based on the same principle. This invention is not limited to square flow channels.

[0162] Assume the side length of the square flow channel is a = 20 μm, and the volume at both ends of the droplet is 2 × 2 / 3π(a / 2). 3 ≈4.19×10 3 μm 3 The volume of the central square prism = 4 / 3πr 3 -2×2 / 3π(a / 2) 3 ≈9.95×10 3 μm 3 Column segment length L cyl =9.95×10 3 / a 2 ≈24.9μm 2. Analysis of Droplet Morphology Changes 2.1 Force Analysis at Various Locations During electromagnetic acceleration, the Ampere force acts only on the region through which the current flows (the middle column), while the resistance is distributed along the front and rear contact lines and the middle contact layer. The points of application of the force and the points of application of the resistance do not coincide, resulting in a velocity gradient inside the droplet.

[0163] Location Ampere wall friction motion state Front surface none None (does not contact the wall surface) Pushed along by the middle section Intermediate column section (contact layer) have have Deceleration due to friction Intermediate column segment (core layer) have none Accelerated by Ampere force Back end surface none None (does not contact the wall surface) Being pulled along by the middle section The intermediate column is divided into two parts: a contact layer (e.g., 1 μm thick) that contacts the nozzle wall and is subject to wall friction; and a core layer (e.g., 18 μm thick) that does not contact the wall and is not subject to wall friction. The core layer has a high velocity, while the contact layer has a low velocity, resulting in viscous shearing within the core.

[0164] 2.2 Deformation and Necking • Front end: Compressed by the middle section, it gradually approaches a plane from a hemisphere; • Rear end: Pulled by the middle section, it gradually elongates from the hemisphere, even forming a slender tail; • Middle section: The core layer moves quickly, while the contact layer moves slowly, resulting in necking—the cross-sectional area decreases at the narrowest point in the middle.

[0165] Surface tension always attempts to reduce the contact area and restore the droplet to its spherical shape. However, in a continuous conductor, the droplet remains in contact with the conductor, and the wall adhesion and viscous drag forces hinder restoration, causing deformation to accumulate continuously.

[0166] 2.3 Virtual connection The cross-sectional area at the necking point decreases sharply; simultaneously, due to the extremely high droplet velocity, the dynamic spreading time of the droplet leading edge on the conductive segment surface is insufficient, resulting in a contact area smaller than the theoretical value. Under the combined effect of these two factors, a highly unstable virtual connection state is easily formed: according to R = ρL / A, the local resistance increases sharply, the current density is locally amplified, and an electrical explosion is highly likely. When multiple droplets are connected in parallel, the necking and contact states of each droplet are different, the contact resistance fluctuates randomly, and the current distribution is unpredictable.

[0167] 3. Dynamic changes in the electrical explosion threshold The electrical explosion threshold current density of tin is approximately: J c ≈ 10 6 A / cm 2 Static droplet: Conductive cross-sectional area: A0 = L cyl × a=498μm 2 Threshold current: I max = J c × A0 ≈ 5A; After accelerated stretching: the conduction cross-sectional area A1 increases to approximately 602 μm. 2 Threshold current: I max = J c × A1 ≈ 6A; Under necking conditions: if the conduction cross-sectional area is reduced to 50% of its original value, the threshold current drops to approximately 3A; if reduced to 25%, the threshold current drops to approximately 1.5A. Conclusion: The electro-explosion threshold of droplets during acceleration dynamically varies between 3 and 6 Å, with a lower threshold indicating more severe necking.

[0168] 4. Estimation of total friction and temperature rise As the droplet moves within the flow channel, the main resistance comes from the capillary resistance at the contact lines at the front and rear ends. F cap =γ· P · (cosθ R - cosθ A ) Where γ is the surface tension of liquid tin (typical value: 0.544 N / m), P is the contact line perimeter (4a = 80 μm), and θ R and θ A Let these be the retreating contact angle and the advancing contact angle (the typical value of the contact angle hysteresis term Δcosθ is 0.35), then... Capillary resistance F cap =0.544×80×10 -6 ×0.35≈1.5 × 10 -5 N.

[0169] The intermediate contact layer is extremely thin (submicron to micron scale). The core layer drags the contact layer through viscous forces, with part of the contact layer being carried into the droplet to participate in circulation, while the liquid at the front end is pushed against the wall to replenish the contact layer. Because the contact layer is extremely thin and in dynamic circulation, the force it consumes is relatively small and can be ignored. Total frictional force f≈F cap =1.5 × 10 -5 N, frictional deceleration: a f =f / m ≈1.51×10 5 m / s 2 .

[0170] In the square model, the current path length L = a = 20 μm, let v1 be the target velocity, v0 be the initial velocity, and the acceleration time be: t=m(v1-v0) / (B·I·L-f), Joule fever: Q=I 2 R t=I 2 R·m·(v1-v0) / (B·I·L - f) Taking the derivative of I and setting it to zero, we obtain the optimal current that minimizes Joule heating: I opt =2f / (B·L) At this point, the Ampere force F = B·L·I opt =2f, t=m(v1-v0) / f; Minimum temperature rise: ΔT = Q min / (m ×c p ) = 4f·R(v1-v0) / (B 2 ·L 2 ·c p ) The resistivity of liquid tin is ρ≈4.8×10⁻⁶. -7 Under the fully contact model, the droplet resistance R = ρ·a / A0 ≈ 0.019Ω. Considering temperature rise and deformation, the reasonable fluctuation range of the total resistance is 0.02Ω~0.1Ω, with a typical value of 0.02Ω~0.05Ω. Taking R = 0.03Ω, v1 = 80m / s, v0 = 10m / s, and specific heat capacity c... p =240J (kg·K), after substituting the parameters, the minimum temperature rise is: ΔT≈ 1312 / B 2 Acceleration time t≈462μs, assuming the initial temperature of the tin droplet is 250℃, the parameters corresponding to different B values ​​are shown in the table below. Magnetic field B(T) <![CDATA[Optimal current I opt (A)]]> Temperature rise ΔT (K) Final temperature (°C) 1.0 1.5 1312 1562 1.5 1.0 583 833 2.0 0.75 328 578 2.5 0.6 210 460 3.0 0.5 146 396 5. The fatal contradiction of continuous conductors Contradiction 1: Low current prevents explosion, but leads to fusion. When the optimal current is taken (B=3T, 0.5A), the temperature rise is only 146K, which is safe; however, the acceleration time is as long as 462μs, which is much longer than the droplet interval of 20μs. In a continuous conductor, multiple droplets will inevitably accelerate at the same time, resulting in fusion, and there is also a risk of necking.

[0171] Contradiction 2: High current prevents fusion, but triggers dynamic electrical explosion and vaporization. To avoid fusion, the current needs to be increased. The net acceleration is taken as 5A. f ~10a f At B=3T, the current is 1.5~2.75A and the temperature rise is 263~441K, which seems safe; however, after the droplet necks, the dynamic threshold drops to 3A or even 1.5A, and 2.75A is close to or exceeds the threshold. Moreover, the parallel distribution is random, and individual droplets may receive excess current, resulting in direct electrical explosion. At B=1T, the current is 4.5~8.25A and the temperature rise is 2362~3970K, far exceeding the boiling point, posing an extremely high risk of vaporization and electrical explosion.

[0172] Although the data is derived solely from calculations and may deviate from reality, the above calculations physically demonstrate the existence of risk. The operating current has a lower limit determined by friction and acceleration time, and an upper limit determined by vaporization and electrical explosion, limiting the range of choices. The fundamental problem with continuous conductors is that the window is already narrow; the random distribution of parallel current causes individual droplets to receive excessive or insufficient current, directly exceeding the window; simultaneously, droplet necking reduces the dynamic threshold from approximately 5A to 3A or even 1.5A, further narrowing the window and making the system unable to operate stably.

[0173] 6. The function of intermittent conductors This invention provides a structural solution to three fatal problems of continuous conductors (random distribution of parallel current, risk of local overheating and vaporization, droplet deformation (insufficient necking and spreading) and electrical explosion) through intermittent conductors, thereby controlling the current flowing through each droplet within an extremely narrow operating current window.

[0174] First, it eliminates random current distribution in parallel circuits, ensuring consistent acceleration. The current in each conductive stage is independently determined by the circuit's electrical parameters, unaffected by the number of droplets simultaneously contacting it. This significantly reduces inconsistencies in acceleration, arrival time deviations, and droplet merging issues caused by random current shunting.

[0175] Second, Joule heating is controlled to prevent vaporization. Because the current is predictable and controllable, the current flowing through each droplet is stabilized within a safe range, preventing individual droplets from experiencing localized overheating and vaporization due to receiving excessive current.

[0176] Third, by shortening the contact time, necking is suppressed, thus avoiding electrical explosion. The contact time between the droplet and each conductive segment is configured to be insufficient to cause severe necking before separation, thereby cutting off the cumulative process of deformation (necking and insufficient spreading), avoiding a sharp increase in current density caused by a reduction in local cross-sectional area, and avoiding the risk of electrical explosion under optimal operating conditions.

[0177] It is important to emphasize that the aforementioned problems do not exist in isolation. The parallel connection of multiple droplets leads to random current distribution, which in turn causes localized deformation and a surge in current density, increasing the risk of electrical explosion. Simultaneously, reducing the current to avoid electrical explosion lengthens the acceleration time, potentially causing droplet fusion, and the increased acceleration time also increases the risk of necking. This coupled effect of multiple problems—random parallel connection, deformation, heat accumulation, and electrical explosion—is dramatically amplified under the high-frequency, microscale, and vacuum conditions of EUV, resulting in an extremely narrow operating current window. Existing technologies have never recognized this coupling effect, nor have they proposed a solution.

[0178] The electrical parameters can be implemented in at least one of the following ways: series current-limiting resistor, independent voltage regulating circuit, constant current source, constant voltage and constant current source, PWM control (including constant current mode and / or current regulation mode), inductor current limiting, current mirror, constant current diode, negative feedback control, feedforward control, high-speed closed-loop control based on microcontroller or FPGA, combination of Zener diode and resistor, capacitor current limiting, RC current limiting, etc. The electrical parameters can also be implemented in other ways known in the art, as long as the current flowing through the conductive section meets the following criterion (i.e., when the number of fuel droplets simultaneously contacting the conductive section increases from 1 to 3, the rate of change of current is less than 10%), all of which fall within the protection scope of this invention. Those skilled in the art can choose a suitable implementation method according to actual working conditions. When the conductor configuration of the present invention includes multiple conductive segments, the electrical parameters of each conductive segment can be set independently to adapt to the differences in the working conditions of different conductive segments. The present invention controls the current of at least one conductive segment through electrical parameters (e.g., accelerating the segment with the highest temperature of the last stage droplet or the segment with a low electro-explosion threshold), so that the current flowing through each conductive segment can fall within the safety window of its corresponding working condition.

[0179] Additionally, the metallic conductor has a positive temperature coefficient of resistance, and its resistivity increases with increasing temperature. The electrical parameters can also keep the current flowing through the conductive section and / or fuel droplet 200 stable when the resistance changes due to temperature changes in the conductor and / or fuel droplet 200, thereby maintaining the stability of the Ampere force.

[0180] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0181] Example 1: Multi-mode control system System components: • Nozzle 100: made of boron nitride, with an inner diameter of 30μm and a length of 5mm; • Conductors: Multiple sets of conductors, including axial conductor 111 (two conductors insulated from each other), annular conductor 112, and spiral conductor 113; • Magnetic field generating device 120: Three independently controlled electromagnet units are arranged along the axial direction of nozzle 100; • Main control unit 130: FPGA-based, sampling rate 100kHz.

[0182] Conductor configuration: The conductor configuration includes at least one of the following types: 1. Axial conductor 111: Extends along the axial direction of nozzle 100. Optionally, it consists of two conductors that are insulated from each other, symmetrically arranged on both sides of the inner wall of nozzle 100.

[0183] 2. Ring conductor 112: Extends circumferentially. Optionally, it is selected from at least one of the following: a complete circular ring, a segmented ring composed of multiple mutually insulated arc-shaped conductive segments 112a1, and a ring with a gradually changing cross-section whose cross-sectional area gradually changes along the axial direction. In the segmented ring, an insulating layer 112a2 (such as silicon dioxide or silicon nitride) is provided between each arc segment, and each arc segment is connected to the main control unit 130 through an independent wire 115; in the gradually changing cross-section ring, the resistance is high and Joule heat is high where the cross-sectional area is small, and the resistance is low and Joule heat is low where the cross-sectional area is large, thereby optimizing the heat distribution.

[0184] 3. Spiral conductor 113: Encircles the inner wall of nozzle 100 along the spiral direction. Optionally, it can be replaced with a non-axial conductor such as an inclined straight line, a broken line, a wave, a sawtooth, or an arc, as long as it can make the current flowing through the droplet have both radial and axial components.

[0185] Based on their structure, the aforementioned conductors can be further divided into continuous conductors and discontinuous conductors.114 A continuous conductor is a single, continuous line. Intermittent conductor 114: Composed of multiple conductive segments, with gaps between adjacent segments, isolated from each other by an insulating layer or gap. Each conductive segment can be any shape (such as strip, dot, inclined, zigzag, wavy, etc.), and the overall arrangement direction can be axial, circumferential, non-axial, or irregularly distributed. Preferably, each conductive segment is connected to the main control unit 130 to achieve independent control.

[0186] Work process: 1. Start-up phase: The main control unit 130 selects the axial acceleration mode, activates the axial conductor 111, and adjusts the electromagnet to generate a tangential magnetic field, thus accelerating the droplet; 2. During flight: Radial deviation is detected, switch to radial focusing mode, activate the ring conductor 112, and the droplet is pulled back to the center; 3. Before excitation: Rotational stabilization mode, activate the helical conductor 113 or the axial conductor 111 in conjunction with the axial magnetic field to make the droplet rotate; 4. After prolonged operation: Activate the heat load dispersion mode, periodically switch between different conductor groups or different operating modes to disperse Joule heat.

[0187] 5. Degradation Protection Mode: When the conductor configuration includes, for example... Figure 5When the intermittent conductor 114 is shown, since each conductive segment can be controlled independently, the main control unit 130 can actively select which conductive segments are energized, thereby controlling which droplets simultaneously form a circuit. When the heat accumulation of a droplet exceeds a preset threshold, the main control unit 130 enters a degradation protection mode: reducing the current flowing through at least one stage of the downstream conductor of the droplet, or shortening the energizing time of that stage, or skipping that stage of the conductor. The final velocity of the droplet may be lower than the target value, but vaporization due to continued heating is avoided, and it does not affect other normal droplets, or only affects a few droplets that are in contact with the same stage of the conductor as the droplet that needs protection.

[0188] 6. End fine adjustment: The intermittent conductor 114 is configured in the last two stages of conductors. The first stage performs the main acceleration, and the second stage serves as a fine adjustment unit. Based on the droplet velocity detected by the previous stage, its energizing time is adjusted to ensure that the exit velocity is consistent.

[0189] Control method (optionally at least one of the following): • Timer switching: The hardware switching circuit consists of relays and timers, with an adjustable timing period, which sequentially activates different groups of conductors; • Droplet triggering: Miniature sensors (capacitive, photoelectric, etc.) are installed at the inlet of each conductive section. When a droplet arrives, it triggers the power supply and de-energizes it when the droplet leaves. Furthermore, detection devices are installed at the inlet and outlet respectively to form a control strategy that combines feedforward prediction and feedback correction. • Temperature feedback: Thermocouples are placed near each group of conductors. When the temperature of a group exceeds the threshold, the system switches to other groups. • Preset timing: The main control unit 130 presets a fixed timing cycle to switch different conductor groups or working modes in sequence; • Manual intervention: Switch manually via DIP switches, knobs, etc.; • External commands: Receive commands from the host computer to switch.

[0190] It should be noted that the appendix Figure 1 In this design, two axial conductors 111, one helical conductor 113, and three annular conductors 112 are provided. This is merely an exemplary configuration of the present invention. In actual operation, the conductors described above can all adopt an intermittent structure, i.e., composed of multiple conductive segments with intervals between adjacent segments. The specific number, placement, arrangement, extension direction, and continuous or intermittent form of the conductors are not fixed and can be adapted by those skilled in the art according to actual needs, all of which fall within the scope of protection of the present invention.

[0191] Example 2: Diversification of magnetic field patterns: System components: • Five independent magnetic field generating units are set along the axial direction of the nozzle 100, at positions of 1mm, 2mm, 3mm, 4mm and 5mm respectively.

[0192] Each unit can independently generate magnetic fields of different shapes.

[0193] Magnetic field configuration • 1mm, 2mm: linear shape, tangential direction → axial acceleration.

[0194] • 3mm, 4mm: Curved shape, bending towards the axis → radial focus.

[0195] • 5mm: Converging morphology → Droplet compression.

[0196] Working process: The droplets pass through each unit in sequence, where they are accelerated, focused, and compressed in turn, achieving optimization throughout the process.

[0197] A straight magnetic field can be generated by a uniform coil, while a curved magnetic field can be achieved by adjusting the shape of the magnetic poles.

[0198] Example 3: Integrated System of Electromagnetic Acceleration and Piezoelectric Correction System components: • Nozzle 100: Boron nitride, inner diameter 30μm; • Two sets of intermittent conductors 114 extending axially are insulated from each other; • Correction control unit 131: Based on FPGA, with built-in current detection circuit; • Piezoelectric correction unit 140: a piezoelectric ceramic sheet disposed downstream of the conductor; • Charge management unit 160: an electron emission source and ion source, located downstream of each stage of conductors or the last stage of conductors and before the laser target; • Shape detection sensor 170: located downstream of the conductive area.

[0199] Work process: 1. Fuel droplets 200 pass through nozzle 100 at a speed of approximately 50 m / s, simultaneously contacting the two poles of the conductor to form a current loop; 2. The control unit 131 detects the current signal flowing through the conductor, determines the arrival time t0 based on the rising edge, determines the departure time t2 based on the falling edge, evaluates the charge amount based on the amplitude, and calculates the speed based on the time interval; 3. The correction control unit 131 calculates the time t1 when the fuel droplet 200 arrives at the piezoelectric correction unit 140 from the conductor based on the motion parameters of the fuel droplet 200 and the known distance. At time t1, the correction control unit 131 sends a trigger signal to the piezoelectric correction unit 140 to generate high-frequency micro-vibration (50kHz, 50V) to correct the droplet shape. 4. The amount of droplet charge is assessed based on the current amplitude. When the charge exceeds the threshold, the charge management unit 160 is controlled to emit electrons or ions to neutralize the residual charge. The charge of the neutralized droplet is lower than the threshold, and it enters the subsequent area in a state of electrical neutrality or residual charge lower than the preset threshold, thus avoiding the influence of residual charge on the flight trajectory. 5. After issuing a trigger signal, the correction control unit 131 sends a stop signal to the piezoelectric correction unit after a predetermined period of time (the time is determined based on the time required for the piezoelectric correction unit 140 to complete vibration correction). The corrected fuel droplets 200 then enter the subsequent laser bombardment area.

[0200] 6. Perform cleaning mode: During the time interval between adjacent droplets or during maintenance shutdown, apply a cleaning drive signal (pulse train or sweep frequency signal, frequency 20-200kHz) to the piezoelectric correction unit 140 to generate mechanical vibration and remove fuel droplets 200 remaining on the inner wall of the nozzle 100 and / or the surface of the conductor.

[0201] The control method of the modified control unit 131 (optionally, at least one of the following) is adopted: 1. Timing controller + waveform generator: The timing controller is electrically connected to the sensor assembly or conductor to receive droplet state information and calculate the trigger time point; the waveform generator is connected to the timing controller and the piezoelectric correction unit 140 to generate square waves, sine waves, trapezoidal waves or custom waveforms under the trigger command of the timing controller to drive the piezoelectric correction unit 140. 2. PID closed-loop control: The comparator is electrically connected to the sensor assembly or conductor to acquire the real-time state information of the droplet and compare the real-time state of the droplet with the target value to generate a deviation signal; the PID controller is connected to the comparator and the piezoelectric correction unit 140 to generate a control signal based on the deviation signal and adjust the driving parameters of the piezoelectric correction unit 140 in real time. 3. Dual trigger signal control: The correction control unit 131 generates a start signal based on the rising edge of the current signal and a stop signal based on the falling edge, precisely controlling the working window of the piezoelectric correction unit 140; 4. Open-loop feedforward control: The correction control unit 131 pre-calculates the arrival time based on the predetermined droplet velocity and sends a trigger signal with a fixed time delay; 5. Open-loop + long-cycle closed-loop calibration: Based on the open-loop, the correction control unit 131 adjusts the reference parameters when the long-term average effect detected by the shape detection sensor 170 (such as the average droplet sphericity over the past 1 second or 1 minute) is detected to show a slow drift in the long-term average effect. The calibration cycle is much longer than the droplet passage cycle, so it will not interfere with the consistency of each droplet processing. 6. Closed-loop feedback control: A shape detection sensor 170 is set downstream of the piezoelectric correction unit 140 to detect the droplet shape parameters in real time and provide feedback. The correction control unit 131 adjusts the drive parameters accordingly.

[0202] Example 4 (Cooperative Compensation Control Based on Electrical Signals and Morphological Detection) The system composition is the same as in Example 3. The correction control unit 131 is configured to control the piezoelectric correction unit 140 to apply vibration and / or thrust pulses to the fuel droplet 200 when it is determined that the fuel droplet 200 is at risk of deformation or has already deformed based on the detection result of the shape detection sensor 170 and / or the electrical signal flowing through the conductor, so as to suppress or correct the deformation and restore the droplet to the target shape.

[0203] The deformation risks include: stretching caused by the velocity difference between the front and rear ends when entering the section (the droplet tip is in contact with the conductive section and has Ampere force, while the rear end is not in contact with the conductive section and has no Ampere force); deformation caused by uneven force when passing through the conductive section; and stretching caused by interruption of thrust or wall constraint when passing through the insulating gap. Specifically, a shape detection sensor 170 can be set downstream of the conductor. The shape detection sensor 170 can detect whether the length-to-diameter ratio of the droplet exceeds a preset threshold (e.g., 1.5) or whether the sphericity is lower than a preset threshold to determine whether there is a deformation risk or whether deformation has occurred. Alternatively, the correction control unit 131 can detect whether the change in the electrical signal flowing through the conductor exceeds a preset threshold (to exclude normal fluctuations caused by factors such as temperature and droplet quantity) to determine whether the equivalent resistance of the droplet has increased, and thereby determine whether there is a deformation risk or whether deformation has occurred. When it is determined that the droplet is at risk of deformation or has already deformed, the correction control unit 131 calculates the delay time based on the real-time velocity of the fuel droplet 200, and controls the piezoelectric control unit 140 to apply high-frequency micro-vibration and / or positive thrust pulses to restore the droplet to the target shape. The position and number of the piezoelectric correction units 140 can be set according to the actual working conditions, and the present invention is not limited thereto.

[0204] Those skilled in the art will understand that electrical signals can be affected by various factors under operating conditions such as changes in the number of droplets and temperature fluctuations. Therefore, in a preferred embodiment, a shape detection sensor 170 is used for direct determination; the correction control unit 131 can also determine the deformation risk or deformation by detecting changes in the electrical signal between two conductive segments. For example, in constant current control mode, when a droplet deforms (e.g., necking), its equivalent resistance increases, leading to an increase in voltage between the two conductive segments; in constant voltage control mode, an increase in equivalent resistance leads to a decrease in current. To eliminate normal fluctuations caused by factors such as temperature fluctuations and changes in the number of droplets, the correction control unit 131 compares the detected change in electrical signal with a preset threshold. Only when the change exceeds the preset threshold is it determined that there is a deformation risk or deformation has occurred. The preset threshold can be determined through experimental calibration according to different operating conditions (e.g., temperature range, droplet number range), for example, by measuring the natural fluctuation range of the electrical signal under standard operating conditions without deformation and taking its upper limit as the threshold. The correction control unit 131 can further combine droplet quantity information or temperature information to correct the change in electrical signal, so as to extract the resistance change component caused by deformation more accurately.

[0205] Example 5: Piezoelectric-electromagnetic hybrid drive system System components: • Nozzle 100: made of boron nitride, with an inner diameter of 20μm; • Piezoelectric drive unit 150: A piezoelectric ceramic tube surrounds the nozzle 100, with a temperature resistance of 300℃ and an adjustable drive frequency; • Electromagnetic acceleration unit 180: disposed downstream of nozzle 100, including a conductor configuration and a magnetic field generating device 120; • Drive control unit 132: Based on FPGA, it is the same control unit as the main control unit 130, synchronizes the piezoelectric drive signal and the electromagnetic acceleration signal, and selects the corresponding control mode according to the structure of the conductor; In this embodiment, the piezoelectric drive unit 150 and the electromagnetic acceleration unit 180 are coupled to the same nozzle 100. The Joule heat generated by the electromagnetic acceleration unit 180 may be conducted along the nozzle 100 to the upstream piezoelectric drive unit 150, thus requiring thermal management. Since the piezoelectric drive unit 150 and the electromagnetic acceleration unit 180 are located in different regions, they can be thermally managed separately. In one embodiment, the piezoelectric drive unit 150 uses a high-temperature piezoelectric material with a temperature resistance ≥500℃, such as Half-Heusler compounds or piezoelectric single crystals. In another embodiment, a heat-insulating material or a low-thermal-conductivity connector is provided between the piezoelectric drive unit 150 and the electromagnetic acceleration unit 180, and / or an active cooling channel is provided, allowing independent temperature control for the two regions. In yet another embodiment, a temperature sensor is placed near the piezoelectric drive unit 150, and the cooling or heating power is adjusted according to the detected temperature to ensure the piezoelectric drive unit operates within a safe temperature range. Those skilled in the art can select an appropriate temperature control method based on actual operating conditions.

[0206] Piezoelectric drive unit 150: The piezoelectric drive unit 150 can be made of traditional piezoelectric ceramics (PZT), lead-free piezoelectric ceramics (BT-based, BNT-based, KNN-based), high-temperature piezoelectric materials (Half-Heusler compounds TiNiSn, ZrNiSn, TiCoSb, etc.), piezoelectric single crystals (quartz), piezoelectric composite materials, etc. Typical parameters: drive frequency 20-100kHz, droplet diameter 20-100μm, temperature resistance ≥250℃.

[0207] Electromagnetic Acceleration Unit 180: Conductors can take one of the following structures: • Continuous long conductors: Two conductors extending axially, each 5 mm in length, insulated from each other, are disposed on the downstream section of the inner wall of the nozzle 100. • Intermittent short conductor: It consists of multiple short conductive segments arranged along the axial direction, each segment is 30μm long, with a 20μm gap between adjacent segments, and a total coverage length of 5mm.

[0208] Work process: 1. Droplet formation: After fuel 210 passes through the piezoelectric drive unit 150 at the fuel inlet, the drive control unit 132 applies a 20kHz periodic voltage to the piezoelectric ceramic tube. The piezoelectric tube expands / contracts radially, applying pressure disturbance to the molten tin, forming a uniform droplet sequence with a diameter of about 30μm at the nozzle 100 outlet. The initial velocity can be adjusted by the drive voltage amplitude and the reservoir pressure. 2. Electromagnetic acceleration: • Continuous long conductor: Multiple fuel droplets 200 are always present in the conductor, forming a continuous path. However, to avoid arcing, they still need to be triggered one by one. The drive control unit 132 continuously adjusts the electrical parameters (amplitude, direction, waveform) according to the target working mode or droplet position information. Before the fuel droplet 200 arrives, the power is cut off or the voltage parameters applied to the conductor or the resistance parameters of the circuit in which the conductor is located are adjusted to ensure that when the fuel droplet 200 comes into contact with the conductor, the current flowing through the fuel droplet 200 and the voltage between the conductor droplets ...

[0209] • Intermittent short conductor: Each segment is 30μm long. The fuel droplet 200 passes through each segment in a very short time (e.g., about 0.6μs). The drive control unit 132 independently triggers power to each segment according to the real-time position of the droplet. Power is applied or the current value is increased after the droplet arrives, and power is cut off or the current and voltage values ​​are controlled below their respective safety thresholds before the droplet leaves, so as to achieve precise control drop by drop and segment by segment. 3. Acceleration effect: When the droplet leaves the electromagnetic acceleration unit by 180 degrees, it is accelerated to the target speed (e.g., 50 m / s) and can achieve multiple functions.

[0210] Timing matching strategy: • Intermittent short conductor (segment-by-segment triggering): Method 1 (pre-calibration) – During the system debugging phase, the actual time it takes for the droplet to reach the first segment is measured to obtain the precise value t1. cal And store, with a delay of t1 during actual runtime. cal Time applies an electrical signal to the first segment; Method 2 (real-time feedback) – a sensor is set at the entrance for precise triggering, and a sensor is set at the exit to detect the departure time and estimate the instantaneous speed, predicting the arrival time of the next segment, forming “feedforward prediction + real-time correction”; • Continuous long conductor (continuous modulation): Multiple droplets are always present in the conductor. The drive control unit 132 continuously adjusts the electrical parameters according to the target working mode, or switches between multiple sets of conductors. The time window is determined by pre-calibration or real-time feedback, and segmented modulation (such as initial acceleration, middle focusing, and subsequent continued acceleration) is implemented within the window. • Hybrid configuration: Using multiple long conductors, the drive control unit 132 combines the above two strategies to continuously modulate each segment while switching between segments.

[0211] Simplified variant: A fixed delay circuit can be used to replace the intelligent controller. Only the main controller triggers the first conductor, and subsequent conductors are triggered sequentially through a preset delay chain.

[0212] In one embodiment, the piezoelectric-electromagnetic hybrid drive system further includes a shape detection sensor 170, disposed downstream of the electromagnetic acceleration unit 180. The shape detection sensor 170 detects the droplet's morphological parameters (such as sphericity and aspect ratio) and feeds the detection results back to the drive control unit 132. When the droplet shape deviates from the target value, the drive control unit 132 selectively activates different conductor groups according to the direction and degree of the shape deviation, applying Ampere forces in the corresponding directions to correct the droplet shape. For example, when the droplet is elongated, the annular conductor 112 is activated to generate radial compressive force; when the droplet is tilted, the non-axial conductor is activated to generate tangential force to rotate and reset it.

[0213] Example 6: Dual Piezoelectric Cooperative Control System System components: • Nozzle 100: Same as in Example 5; • First piezoelectric drive unit: piezoelectric ceramic tube, coupled to nozzle 100, responsible for droplet formation; • Second piezoelectric drive unit: Located downstream of the first piezoelectric unit and upstream of the electromagnetic acceleration unit 180, it is a piezoelectric ceramic tube or piezoelectric sheet, configured to apply high-frequency micro-vibration to the passing droplet; • Electromagnetic acceleration unit 180: Same as in embodiment 5; • Drive control unit 132: Connected to the first and second piezoelectric units and the main control unit 130 or the electromagnetic acceleration unit 180, and synchronizes the working timing of the three.

[0214] Work process: 1. Droplet formation: The first piezoelectric unit forms an initial droplet at the nozzle 100 outlet. The initial droplet may have an irregular shape (such as an elongated cylindrical shape). 2. Droplet shaping: The initial droplet enters the working region of the second piezoelectric unit. The drive control unit 132 applies a driving voltage of a specific frequency and amplitude to the second piezoelectric unit according to a preset target, generating high-frequency micro-vibrations to reshape the droplet. • Size adjustment: Allows droplets to contract or stretch, achieving continuous size adjustment within the range of 20-100μm; • Attitude adjustment: Corrects droplet eccentricity or tilt to ensure it enters the subsequent acceleration zone in the optimal attitude; • Track fine-tuning: The flight trajectory is slightly corrected by asymmetric vibration or by cooperating with a weak electric field; 3. Acceleration phase: The adjusted droplet enters the electromagnetic acceleration unit 180 and is accelerated to the target speed.

[0215] Charged droplet generation (optional): The second piezoelectric driving unit is configured to charge the droplet. When the droplet passes through the second piezoelectric unit, the drive control unit 132 applies a voltage pulse of preset polarity to the second piezoelectric unit. Contact electrification occurs instantaneously when the droplet contacts the piezoelectric material. Due to the different voltage polarities, the droplet acquires a net positive or negative charge. The amount of charge can be controlled by adjusting the voltage pulse amplitude, and the charge polarity can be controlled by changing the voltage polarity. The charged droplet can be used for subsequent electrostatic acceleration or deflection control.

[0216] Technical effects: It breaks through the limitation of a single piezoelectric unit in controlling droplet morphology, and realizes multi-parameter collaborative optimization of size, attitude and trajectory; it reduces the dependence on the driving accuracy of the first piezoelectric unit and improves the robustness of the system.

[0217] Example 7: Short Conductor Scheme System components: • Nozzle 100: Boron nitride, inner diameter 10μm; • Conductors: Two mutually insulated axial conductors 111 are positioned downstream of the nozzle 100 outlet along the droplet's flight path, with a length L = 150 μm along the droplet's flight direction and a spacing d = 200 μm between adjacent droplets. <d; • Piezoelectric drive unit 150: A piezoelectric ceramic tube surrounds the nozzle 100, with a temperature resistance of 300℃ and an adjustable drive frequency; • Magnetic field generator 120: generates a uniform magnetic field perpendicular to the axis; Working process: After fuel 210 enters the piezoelectric drive unit 150 through the fuel inlet, the piezoelectric drive unit 150 applies pressure disturbance to the molten tin, forming a uniform droplet sequence with a diameter of about 30μm at the outlet of nozzle 100. When the droplets pass through two conductors, at most one droplet can contact both conductors at the same time, forming a unique current loop.

[0218] Technical effects: • It avoids the competition for current in parallel among multiple droplets, making the heat distribution predictable; • The two conductors are short in length, resulting in a small temperature difference along the conductors, which reduces the risk of thermal stress concentration and material fatigue; A low-current, low-voltage scheme can be adopted, ensuring that the current intensity flowing into the droplet is below the current safety threshold and the power supply voltage is below the voltage safety threshold. This achieves the simplest configuration, eliminating the need for complex timing coordination of control units, while still achieving droplet-by-drop acceleration and avoiding arcing. The magnetic field can be a pulsed magnetic field (limited by droplet instability and heating), allowing the droplet to accelerate before significant magnetostriction occurs; or a piezoelectric correction unit can be used to correct magnetostriction.

[0219] It can be combined with various conductor groups, such as multiple short conductors arranged axially to form an intermittent conductor configuration to achieve step-by-step acceleration, or add a ring conductor configuration to add rotation function.

[0220] Example 8: Current control and safety threshold based on contact / separation prediction System components: • Conductors: Two axially insulated conductors 111; • Sensor: A capacitive or photoelectric sensor is installed inside the nozzle 100 to detect the position and velocity of the droplet; • Current control circuit: an adjustable resistor (digital potentiometer, 1Ω-100Ω) or an adjustable voltage source (0-5V) connected in series with a conductor. • Main control unit 130: Based on FPGA, including a current and voltage detection unit configured to detect the current flowing through a conductor and the voltage between the conductors.

[0221] Safety threshold confirmation: • Current safety threshold: The maximum current value that prevents an electric arc from occurring between the droplet and the conductor. When the droplet and the conductor are in full contact, the contact area is large, and the current that can be withstood is large; when the droplet and the conductor are about to separate or the contact is insufficient (virtual connection), the contact area is small, and even a small total current may cause an electric arc. Those skilled in the art can determine this threshold by: in a vacuum environment simulating actual working conditions, forming a circuit between the droplet and the conductor, gradually increasing the current, and recording the current value at which a detectable arc first appears (e.g., determined by an optical sensor or voltage waveform distortion); this value is the safety threshold. Before the droplet contacts and separates, the main control unit 130 adjusts the voltage parameters applied to the conductor or the resistance parameters of the circuit containing the conductor to ensure that when the fuel droplet contacts or separates from the conductor, the current flowing through the fuel droplet drops below the safety threshold, thus avoiding an electric arc.

[0222] • Voltage safety threshold: The maximum voltage value that prevents breakdown (arc) between the droplet and the conductor. This threshold is related to factors such as gap distance, vacuum level, and electrode surface condition. In multi-droplet parallel mode, the equivalent resistance of the loop is extremely small, and the voltage is usually low; however, at the moment of contact or separation of a single droplet, the contact resistance increases sharply, and the voltage must be controlled to not exceed the voltage safety threshold. Those skilled in the art can determine this by applying a gradually increasing voltage between the droplet and the conductor under the actual gap conditions of the nozzle 100, and recording the voltage value at the first occurrence of a sudden increase in current or voltage waveform distortion (i.e., breakdown). This value is the breakdown threshold. The main control unit 130 sets the operating voltage to a safety margin below this breakdown threshold, for example, below 50% of the breakdown threshold.

[0223] Work process: 1. The main control unit 130 predicts the contact time of the droplet reaching the conductor and the separation time from the conductor based on the droplet position and velocity detected by the sensor; 2. Before the contact moment, increase the resistance or decrease the voltage so that when the droplet contacts the conductor, the current intensity and the electric field intensity between the conductors are below the safety threshold. 3. After the droplets have made complete contact, lower the resistance or increase the voltage to bring the current to the operating value and generate an Ampere force; 4. Before the separation time, increase the resistance or decrease the voltage again to reduce the current intensity and electric field intensity below the safe threshold. 5. After the droplet leaves, the conductor is de-energized or kept below a safe threshold, waiting for the next droplet.

[0224] Optional Implementation Method 1: Soft switching based on current signal and preset time (1) When the main control unit 130 does not detect an electrical signal, it adjusts the voltage parameter applied to the conductor or the resistance parameter of the circuit in which the conductor is located to ensure that when the droplet comes into contact with the conductor, the current flowing through the droplet and the voltage between the conductor are controlled below a safe threshold. (2) When the rising edge of the current signal is detected, the main control unit 130, after a short delay, confirms that the contact is stable and then increases the current to the working current, so that the droplet is accelerated by the Ampere force in the magnetic field. (3) The main control unit 130 calculates the expected time when the droplet leaves the current conductive segment based on the preset flight time of the droplet and the measured arrival and departure times of the previous few drops, and controls the current and voltage below their respective safety thresholds by adjusting the voltage or resistance before the expected time.

[0225] The preset time can be calculated based on the calibrated speed or corrected based on the measured speed from the previous stage of detection. This method requires no external sensors and achieves arc-proof soft switching solely through electrical signals and timing control.

[0226] Optional Implementation Method Two: Series Large Resistor Constant Current Control A large resistor is connected in series in the circuit containing the conductor. The resistance of this large resistor is much larger than the resistance of the droplet, so that the circuit current is mainly determined by the large resistor and is not affected by fluctuations in the droplet contact resistance. The main control unit 130 controls the current to the desired value by adjusting the voltage applied to the conductor or adjusting the resistance of the large resistor. Before the droplet contacts and separates, the main control unit 130 reduces the voltage or increases the resistance to keep the current and voltage below their respective safety thresholds. This method results in a simple circuit, stable current, and is suitable for operating conditions where high current consistency is required.

[0227] Optional Implementation Method 3: Control Based on Forward Feedback Prediction and Feedback Correction The main control unit 130 estimates the arrival time of the droplet at the next stage based on the actual arrival time or velocity of the droplet detected in the previous stage, and adjusts the power supply state of the next stage accordingly. Simultaneously, a sensor is installed at the inlet of the next stage to detect the actual arrival time of the droplet and compare it with the estimated value, correcting the triggering time of subsequent stages. This method forms a "feedforward estimation + feedback correction" control strategy, which can compensate for droplet velocity fluctuations and improve the synchronization accuracy of multi-stage acceleration.

[0228] In addition, acoustic detection, thermal detection, magnetic field change detection, and other current regulation methods or voltage spike suppression methods known in the art (e.g., through pulse modulation, freewheeling, absorption circuits) can also be used to achieve this. Those skilled in the art can choose according to the actual operating conditions. The above methods can be used individually or in combination. Those skilled in the art can choose the appropriate method according to the operating conditions. Regardless of the method used, as long as the energizing state of the conductor is controlled to avoid electric arcing, it falls within the protection scope of this invention.

[0229] Example 9: Thermal Insulation Structure The spacing between adjacent conductive segments can be enhanced in terms of thermal isolation by at least one of the following methods: Method 1 (Low thermal conductivity gap): The gap is made of zirconia ceramic with a thermal conductivity of about 2 W / (m·K), which is much lower than the 170 W / (m·K) of the tungsten conductive section, thus forming a high thermal resistance between adjacent conductive sections.

[0230] Method 2 (Aerogel filling): The spacer is filled with aerogel, which uses its porous structure to block the solid heat conduction path, thereby inhibiting heat conduction along the axis.

[0231] Method 3 (Radiation Shielding): An infrared reflective film (such as a gold film) is placed in the gap to reflect the heat radiated from the adjacent conductive section and suppress radiative heat transfer.

[0232] Method 4 (Active Cooling Channel): Miniature cooling channels are set in the interval, and cooling medium is introduced to remove heat, further enhancing the thermal isolation effect.

[0233] Method 5 (Thermal Break Structure): A thermal break structure is provided within the interval between adjacent conductive segments, including a support member connecting the adjacent conductive segments. The support member employs at least one of the following: a tortuous path, a necked structure, a small contact area, or a porous structure, to extend the heat conduction path or increase contact thermal resistance. The support member is made of a low thermal conductivity material, such as zirconia ceramic, alumina ceramic, or aerogel. During operation, heat must pass through the thermal break structure when conducted along the axial direction of the conductor. Its thermal resistance is significantly greater than the axial thermal resistance of the continuous conductor, thereby inhibiting heat conduction to adjacent conductive segments and upstream, reducing temperature gradient and thermal stress.

[0234] Method 6 (Vacuum Gap): The gap is a vacuum gap, whose thermal conductivity is lower than that of the conductor, thereby suppressing heat conduction along the axial direction of the conductor.

[0235] Method 7 (Phase Change Material Filling): The interval is filled with phase change material. The phase change temperature of the phase change material is lower than the operating temperature of the conductive section but higher than the normal operating ambient temperature of the EUV light source. When the temperature of the conductive section rises, the phase change material undergoes a phase change (such as melting, evaporation, or crystal transformation), absorbing heat and thus delaying the temperature rise of adjacent conductive sections and upstream components. In multi-stage electromagnetic acceleration mode, phase change materials with different phase change temperatures can be placed in the intervals of different stages. Along the droplet flight direction, the phase change temperature of the phase change material at each stage increases progressively, matching the operating temperature of each stage. For example, the upstream stage uses a material with a lower phase change temperature, and the downstream stage uses a material with a higher phase change temperature, so that the phase change material of each stage absorbs heat when it reaches its phase change temperature, thus progressively delaying the temperature rise.

[0236] Method 8 (Low Emissivity Coating): A low emissivity coating is provided on the surface of the conductive segment. The emissivity of the low emissivity coating is lower than that of the substrate material of the conductive segment, thereby reducing radiative heat transfer. The low emissivity coating can be made of a material with matching temperature resistance according to the operating temperature, such as high-temperature resistant metals like tungsten, molybdenum, and platinum, and is applied to the surface of the conductive segment.

[0237] The above methods can be used individually or in combination. Those skilled in the art can choose according to the actual working conditions.

[0238] Example 10: Multi-stage Acceleration Droplet Control Device This embodiment provides a droplet control device for a fuel emitter of an extreme ultraviolet light source, comprising: • Multiple nozzles 100, each with a fuel flow path.

[0239] • The piezoelectric drive unit 150, coupled to the nozzle 100, is configured to apply periodic pressure perturbation to the fuel 210, so that the fuel 210 forms a uniform droplet sequence at the outlet of the nozzle 100.

[0240] • A multi-stage electromagnetic acceleration unit 300, arranged sequentially along the droplet's flight direction, includes: • Intermittent Conductor Configuration: Multiple nozzles 100 are arranged axially, and a section of conductor is provided on the inner wall of each nozzle 100. A vacuum gap is provided between adjacent nozzles 100. The conductors within the multiple nozzles 100 constitute an intermittent conductor configuration. Each stage of the conductor is connected to an independent current regulating unit, which is configured to regulate the current flowing through that stage of the conductor. The current regulating unit can be a series current-limiting resistor, a constant current source, an independent voltage regulating circuit, etc. • At least one magnetic field generating device 120 is configured to generate a magnetic field acting on the droplet; • The main control unit 130 is connected to each stage of conductors via independent wires 115, with attached Figure 9 In the diagram, only the connections at levels 1 and 5 are shown schematically; the remaining levels are connected in the same way and configured as follows: • Detect the electrical signals of each conductor, independently adjust the current regulation unit at each stage, and control the energizing state of each stage; • Determine the arrival and departure times of the droplet based on the rising and falling edges of the current signal, and calculate the actual velocity of the droplet; • Power is applied only when a droplet passes through the conductive section, and power is immediately cut off after the droplet leaves, so that the duty cycle is less than 5%; • Based on the droplet velocity detected in the previous stage, the trigger time of the next stage is adjusted by feedforward to ensure that the droplet is energized when it is in full contact; • Before the droplet comes into contact with and separates from the conductor, adjust the voltage parameters applied to the conductor or the resistance parameters of the circuit in which the conductor is located to ensure that when the droplet comes into contact with or separates from the conductor, the current flowing through the droplet and the voltage between the conductor are controlled below a safe threshold to avoid electric arc; • Fine-tune the last one or two stages by independently adjusting the energizing time, voltage, or series resistance based on the actual droplet velocity detected by the previous stage, to ensure that the droplets leave the nozzle at the target velocity and time interval.

[0241] Thermal management and degradation protection: • Because each stage uses intermittent conductors, adjacent conductive segments are insulated from each other, and only the conductive segment in contact with the droplet carries the current, the location of Joule heating is limited by the geometry to the contact segment.

[0242] • The main control unit 130 estimates the Joule heat accumulation of each droplet as it passes through each stage based on the energizing current, energizing time, and droplet resistance of each stage.

[0243] • When the accumulated heat of a droplet exceeds a preset threshold (which is below the boiling point of tin, with a safety margin of not less than 200°C), the main control unit 130 enters a degradation protection mode: reducing the current flowing through at least one downstream conductor of the droplet, shortening the energizing time, or skipping that stage. The final velocity of the droplet may be lower than the target value, but vaporization due to continued heating is avoided.

[0244] • The main control unit 130 calculates the vaporization critical current value of the stage based on the droplet temperature, and controls the current regulation unit to ensure that the current flowing through the stage does not exceed the critical value.

[0245] Working process: The droplet passes through each acceleration unit in sequence. At each stage, the main control unit 130 energizes or increases the current to ensure full contact between the droplet and the target, causing the droplet to accelerate under the Ampere force in the magnetic field. Before the droplet leaves the target stage, the power is cut off or the current and voltage are reduced to below their respective safety thresholds. Vacuum gaps are provided between each stage to achieve electrical and thermal isolation. After multiple stages of acceleration, the droplet reaches the target velocity.

[0246] In a preferred embodiment, the length of the conductive segment is configured such that the maximum length of the droplet stretched during its passage through the conductive segment does not exceed a preset multiple (e.g., 2 to 3 times) of its initial diameter, preferably not exceeding the cross-sectional perimeter of the nozzle channel, thereby ensuring that the droplet can recover to a substantially spherical shape from surface tension before entering the next stage; the length of the interval and the velocity of the droplet are configured such that the flight time of the droplet within the interval is not less than the capillary recovery time τ of the droplet. c ≈√(ρa 3 / γ) (typical value is on the order of 10 microseconds).

[0247] Optional variants • An active cooling channel or a radiation shielding layer can be installed in the interstage vacuum gap 301 to enhance the thermal isolation effect.

[0248] • The main control unit 130 can automatically optimize the timing of laser strikes by adjusting the acceleration parameters at each stage in a closed loop based on EUV radiation intensity or droplet position information.

[0249] • A fuel vapor collection structure 400 is provided in the vacuum gap of the multi-stage electromagnetic acceleration unit 300. The fuel vapor collection structure 400 is positioned off the droplet flight path and is selected from at least one of a cold trap, adsorbent, metal mesh, and porous ceramic. It is configured to capture tin vapor or splashing droplets vaporized due to localized overheating. Because the multi-nozzle 100 structure provides physical spacing between adjacent conductive sections, this collection structure can be integrated at this location without affecting the electrical and thermal functions of the conductor.

[0250] Example 11: Current Stabilization Control Based on Current-Limiting Resistor System components: • Conductive section 114 is disposed on the inner wall of the nozzle; • A current-limiting resistor Rs is connected in series in the circuit containing the conductive segment 114; • Power supply, which supplies power to the conductive section 114 through the current-limiting resistor Rs; • Magnetic field generator 120 generates a magnetic field that acts on the droplet.

[0251] Work process: When a fuel droplet comes into contact with conductive section 114, the circuit is completed. Since the resistance of the current-limiting resistor Rs is much greater than the droplet resistance (e.g., Rs ≥ 0.5Ω, droplet resistance approximately 0.02Ω), the current flowing through conductive section 114 is mainly determined by the current-limiting resistor Rs and the power supply voltage, and is minimally affected by the number of droplets simultaneously contacting the conductive section. Even if the number of droplets or their own resistance fluctuates, the total current remains essentially stable. Therefore, the current allocated to each droplet is mainly determined by this stable total current and the number of droplets simultaneously contacting the conductive section, rather than by the random resistance fluctuations of other droplets. This makes Joule heating predictable and controllable, and ensures that the local current density at the point of droplet deformation is below its electrical explosion threshold, preventing vaporization and electrical explosion. When the droplet temperature or contact position changes, causing a change in resistance, the current remains stable because the current-limiting resistor is much greater than the droplet resistance, and the current is still mainly determined by the current-limiting resistor.

[0252] As a variation of this embodiment, the current-limiting resistor may not be a separate discrete component, but may be implemented by the conductive segment itself. In another preferred embodiment, the current-limiting resistor Rs may be an adjustable resistor, used to dynamically adjust the upper limit of the current according to the initial temperature or thermal state of the droplet, ensuring that the droplet does not vaporize and that the local current density at the point of droplet deformation does not exceed its electro-explosion threshold.

[0253] Other electrical parameter implementation methods In addition to the aforementioned series current-limiting resistor, the electrical parameters can also be achieved in at least one of the following ways. All of the following methods are connected in series in the circuit containing the conductive segment: (1) Constant current source: A negative feedback constant current circuit composed of an operational amplifier and a power transistor can be used, or an integrated constant current source chip can be used. The output current is determined by the set value.

[0254] (2) Constant voltage and constant current source: configured to work in constant current mode, with constant output current and voltage automatically adjusted according to load.

[0255] (3) PWM constant current control: The duty cycle of the switching transistor is adjusted by current sampling feedback to keep the average current constant.

[0256] (4) PWM current regulation control: The average current can be adjusted by changing the PWM duty cycle setting value, and can be controlled in open loop or closed loop.

[0257] (5) Independent voltage regulation circuit: An adjustable voltage regulator or PWM voltage regulation circuit can be used to independently adjust the voltage applied to the circuit so that the current remains stable.

[0258] (6) Current mirror: Using a matched pair of transistors, the reference current is copied to the conductive segment loop.

[0259] (7) Constant current diode: Its current is limited to near the rated value and is not affected by voltage fluctuations.

[0260] (8) Negative feedback / feedforward control circuit: an operational amplifier, comparator or microcontroller is used to adjust the equivalent resistance or voltage of the series adjustment element according to the current sampling value or droplet state information.

[0261] (9) Inductance, capacitance, and RC current limiting: utilize their impedance characteristics to suppress current fluctuations.

[0262] (10) Zener diode and resistor combination: The voltage is clamped by the Zener diode and the current is limited by the resistor.

[0263] (11) High-speed closed-loop control based on microcontroller or FPGA: The series adjustment element is adjusted in real time through high-speed sampling and digital algorithm, and the response time is preferably less than the time it takes for the droplet to pass through a single-stage conductive segment.

[0264] The methods described above are all conventional circuits in the art and can be used individually or in combination. Other conventional circuits not listed that can make the current less affected by the number of droplets than by electrical parameters are also within the scope of protection of this invention.

[0265] Implementation method of the control unit In this invention, the main control unit, drive control unit, and correction control unit can be implemented using intelligent controllers (such as microcontrollers or FPGAs), hardware circuits (such as relays or timers), or manual operating devices. They can be the same control unit or independent control units; those skilled in the art can choose according to actual needs.

[0266] The functions of the control unit include, but are not limited to: controlling the energization state of the conductor; adjusting the electrical signal parameters applied to the conductor; adjusting the magnetic field parameters of the magnetic field generator; selectively activating one or more groups of conductors; synchronizing the timing of the piezoelectric drive unit and the electromagnetic acceleration unit; controlling the piezoelectric correction unit to apply vibration and / or thrust pulses to the droplet; controlling the charge management unit to manage the residual charge of the droplet; dynamically adjusting the electrical parameters according to the initial temperature or thermal state of the fuel droplet to ensure that the current does not exceed the vaporization critical current value; and ensuring that the local current density flowing through the deformation section of the fuel droplet is lower than its electro-explosion threshold.

[0267] Any device or method capable of achieving at least one of the above-mentioned control functions falls within the scope of the control unit of this invention.

[0268] Regarding the connection method between the wire and the conductor assembly.

[0269] The connection between the wire and the conductor assembly can be a direct electrical connection, whereby the power supply continuously supplies power to the conductor, and a circuit is formed by the droplet contacting the conductive segment; alternatively, an electrical connection can be achieved through a selective connection device, such as a relay, a DIP switch, or any other device or method capable of selectively introducing an external power supply signal into the activated conductor assembly. This invention is not limited to the above connection methods; any connection method that enables the conductive segment and the droplet to form a current loop falls within the scope of protection of this invention.

[0270] Explanation of the implementation of conductors The conductors of this invention can all be fabricated using conventional micro / nano fabrication processes, for example: The gradient cross-section annular conductor can be achieved by tilt deposition, grayscale lithography, electrochemical direct-write deposition, etc.

[0271] The intermittent conductor can be achieved using photolithography, electrochemical deposition, laser micromachining, etc. The gap between adjacent conductive segments can be formed by etching away part of the conductive material or depositing insulating material (such as silicon dioxide, silicon nitride, etc.); the gap can also be a vacuum gap, that is, no material is filled between adjacent conductive segments.

[0272] The spiral conductor can be achieved using electrochemical direct-write deposition, laser etching, or other methods. Typical parameters of the spiral conductor can be optimized based on the target droplet size and the required current component ratio; for example, the pitch can be on the order of hundreds of micrometers, and the linewidth and thickness can be on the order of micrometers.

[0273] The specific method can be selected by those skilled in the art based on actual conditions. The scope of protection of this invention is not limited to the specific preparation method; any process capable of forming the corresponding conductor is considered an equivalent embodiment of this invention.

[0274] Explanation of piezoelectric ceramic elements The piezoelectric drive unit of the present invention can be prepared using piezoelectric ceramic materials known in the art. Taking the commonly used lead zirconate titanate (PZT) piezoelectric ceramic as an example, its preparation process is familiar to those skilled in the art, and mainly includes steps such as raw material mixing, pre-firing synthesis, molding, sintering, electrode application, and polarization.

[0275] Based on common knowledge in the field of piezoelectric ceramics, the typical parameter range for the above process is as follows: Preheating temperature: 850-950℃ • Sintering temperature: 1200-1300℃ • Polarization electric field: 2-4kV / mm Those skilled in the art can determine the optimal process parameters through a limited number of conventional experiments based on the actual material system and performance requirements. The scope of protection of this invention is not limited to specific preparation methods; any process capable of obtaining piezoelectric ceramic elements exhibiting the inverse piezoelectric effect can be used to implement this invention.

[0276] Explanation of the time window "after the formation of the current loop" It should be noted that, in this invention, "after the formation of a current loop" refers to any point in time after the droplet makes electrical contact with the conductor and generates a current signal, including the stage when the droplet is still within the conductor's region, is passing through the conductor, and has left the conductor. This point in time is triggered by the formation of a current loop between the droplet and the conductor, and is not limited by whether the droplet has left the conductor.

[0277] Feasibility explanation regarding thrust pulse compensation: The thrust pulse is used to achieve thrust compensation. Piezoelectric elements deform or vibrate when energized, which is a fundamental characteristic of piezoelectric materials. This solution utilizes this characteristic by energizing the piezoelectric correction unit when the droplet is about to cross or is crossing an insulating gap, causing it to generate a mechanical action. This action acts on the droplet, thus providing it with thrust. The specific voltage and pulse width can be determined during debugging based on the actual droplet velocity. Using multiple piezoelectric elements in combination or adding transmission components to increase thrust is also a conventional practice; those skilled in the art can choose according to actual needs.

[0278] Location description of the charge management unit and shape detection sensor It should be noted that in this invention, the charge management unit and shape detection sensor are located downstream of the conductor. However, "downstream" refers to any position along the droplet's flight direction after the droplet forms a current loop with any conductor. That is, whether the sensor is located downstream of the conductor or inside the conductor near the outlet (such as the gap between adjacent conductive segments), it falls within the scope of "downstream" as described in this invention. In some embodiments, the shape detection sensor may also be partially or entirely located within the area where the conductor is located. Those skilled in the art will understand that the specific relative positions of the charge management unit and shape detection sensor to the conductor can be adjusted according to actual needs, and all such adjustments fall within the scope of protection of this invention.

[0279] Industrial applicability The droplet control device and method provided by this invention can be widely applied in fields such as extreme ultraviolet lithography light sources, free-electron lasers, and laser plasma light sources. This invention fully utilizes the advantages of piezoelectric and electromagnetic actuation to achieve optimized separation of droplet formation and acceleration. Through intelligent correction, charge management, thrust pulse compensation, and end-effector fine-tuning, it significantly improves the droplet's morphological accuracy, trajectory stability, and velocity consistency, demonstrating good industrial applicability and promising prospects for industrialization.

[0280] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A droplet control device for a fuel emitter of an extreme ultraviolet light source, characterized in that, include: At least one nozzle having a fuel flow channel; A conductive configuration is disposed on the inner wall of the nozzle and / or on the droplet flight path downstream of the nozzle outlet, including a conductive body capable of forming at least one current loop with the fuel droplets passing through the nozzle, the conductive configuration being configured to include at least an intermittent conductive body comprising a plurality of spatially distributed conductive segments with intervals between adjacent conductive segments; At least two wires are electrically connected to the conductor; A magnetic field generating device is configured to generate a magnetic field acting on the fuel droplets; The conductor and the magnetic field generating device constitute the electromagnetic acceleration unit of the droplet control device. The Ampere force generated by the interaction between the current flowing through the fuel droplet and the magnetic field has a component along the target direction, thereby accelerating, correcting the trajectory, and / or rotating the fuel droplet. The droplet control device is further configured such that the current flowing through at least one of the conductive segments is determined primarily by the electrical parameters of the circuit containing the conductive segment, rather than primarily by the number of fuel droplets simultaneously contacting the conductive segment. The fuel droplets are liquid metal droplets, and the number of fuel droplets is one or more.

2. The droplet control device according to claim 1, characterized in that, It also includes a main control unit connected to the conductor and / or the magnetic field generating device, configured to control the conductor and / or the magnetic field generating device to adjust the magnitude and / or direction of the Ampere force so that the Ampere force has a component along the target direction.

3. The droplet control device according to claim 2, characterized in that, The main control unit is configured to: control the energization state of the conductor according to the target operating mode and / or the state information of the fuel droplet, and cooperate with the magnetic field generating device to make the Ampere force have a component along the target direction. The target operating mode includes at least one of axial acceleration mode, radial focusing mode, rotational stabilization mode, and thermal load dispersion mode. The state information is used to determine the position, motion state, deformation, and / or thermal state of the fuel droplet, including at least one of position information, arrival time, departure time, flight speed, charge quantity, morphological information, and temperature information.

4. The droplet control device according to claim 2, characterized in that, The main control unit is configured to perform at least one of the following operations: (1) When the fuel droplet is detected to be in contact with the conductor or after contact is detected, the conductor is controlled to be energized or the current flowing through the fuel droplet is increased; when the fuel droplet is detected to be separated from the conductor or before separation is detected, the conductor is controlled to be de-energized or the current flowing through the fuel droplet is reduced. (2) Based on at least one of the following information, adjust the electrical signal parameters applied to the conductor and / or the magnetic field parameters of the magnetic field generating device to adjust the flight speed, flight attitude, arrival time and / or arrival position of the fuel droplet: a) Detected EUV radiation intensity; b) Position information and / or motion parameters of the fuel droplet after it leaves the nozzle, including the time and position information of the fuel droplet reaching the laser target; c) Information on the position, motion parameters and / or flight attitude of the fuel droplets within the nozzle, including predictions of the moment of contact and / or separation between the droplets and the conductor; (3) Make the charge polarities of adjacent fuel droplets opposite; (4) Independently control the energizing state of each conductive segment; (5) Controlling the energization state of the conductor, including adjusting the voltage parameters applied to the conductor and / or the resistance parameters of the circuit in which the conductor is located before the fuel droplet contacts or separates from the conductor, to ensure that when the fuel droplet contacts or separates from the conductor, the current flowing through the fuel droplet and / or the voltage between the conductors are controlled below their respective safety thresholds to avoid electric arc; (6) Based on the thermal accumulation of fuel droplets, reduce the current flowing through at least one downstream conductor, or shorten the current flowing through that conductor, or skip that conductor, in order to avoid vaporization of fuel droplets; (7) Based on the initial temperature or thermal state of the fuel droplet, dynamically adjust the electrical parameters so that the current flowing through the fuel droplet does not exceed the vaporization critical current value corresponding to that stage. The vaporization critical current value is determined based on the initial temperature and cumulative temperature rise of the fuel droplet in that stage, ensuring that the temperature of the fuel droplet when it leaves all acceleration stages is lower than its vaporization temperature; (8) Based on the degree of deformation of the fuel droplet, the electrical parameters are dynamically adjusted so that the local current density at the deformation point of the fuel droplet does not exceed its electro-explosion threshold. The degree of deformation is determined by at least one of the following methods: shape detection sensor, electrical signal detection, fluid dynamics model prediction, and contact time determination.

5. The droplet control device according to claim 1, characterized in that, The conductor configuration includes at least two sets of conductors, each set of conductors capable of forming an independent current loop with the fuel droplet; the at least two sets of conductors extend in different or the same directions, and the at least two sets of conductors include at least one of the following types: an axial conductor extending along the nozzle axis, the axial conductor being continuous or intermittent; an annular conductor extending circumferentially along the nozzle, the annular conductor being selected from at least one of a complete circular annulus, a segmented annulus composed of multiple mutually insulated arc-shaped conductive segments, and a gradually changing cross-section annulus with a cross-sectional area that gradually changes along the axial direction; and a non-axial conductor having the effect of simultaneously generating radial and axial components in the current flowing through the droplet, the non-axial conductor being continuous or intermittent.

6. The droplet control device according to claim 1, characterized in that, The electrical parameters are implemented by a current setting device installed in the circuit containing the conductive segment. The current setting device is selected from at least one of the following methods: series current-limiting resistor, independent voltage regulating circuit, constant current source, constant voltage and constant current source, PWM control (including constant current mode and / or current regulation mode), inductor current limiting, current mirror, constant current diode, negative feedback control, feedforward control, high-speed closed-loop control based on microcontroller or FPGA, combination of Zener diode and resistor, capacitor current limiting, and RC current limiting. The current setting device is configured such that the current flowing through each fuel droplet is primarily determined by the set value of the current setting device; and is configured to maintain a stable current flowing through the fuel droplet when the resistance of the conductive segment and / or the fuel droplet changes due to temperature changes, and / or when the resistance of the fuel droplet changes due to changes in contact position, thereby maintaining a stable magnitude of the Ampere force.

7. The droplet control device according to claim 1, characterized in that, The spacing between adjacent conductive segments is used to achieve at least one of the following functions: (1) Enhance thermal isolation between adjacent conductive sections; (2) The fuel droplets passing through the intervals recover to a basic spherical shape due to surface tension; (3) Capture fuel vapor generated by local overheating; (4) Electrically isolate adjacent fuel droplets passing through the conductor to avoid current sharing and charge sharing between droplets, regardless of whether the fuel droplets form a complete current loop with the conductor.

8. The droplet control device according to claim 1, characterized in that, The magnetic field generating device is configured to generate a fixed magnetic field or an adjustable magnetic field, and the magnetic field has at least two different geometric shapes on the flight path of the fuel droplet, including at least two of the following: a straight line shape, a curved shape, a converging shape, and a diverging shape.

9. The droplet control device according to claim 1 or 2, characterized in that, It also includes a piezoelectric unit, which is a piezoelectric correction unit and / or a piezoelectric drive unit; The piezoelectric correction unit is configured to apply vibration and / or thrust pulses to the fuel droplet after the fuel droplet forms a current loop with the conductor to control the shape of the fuel droplet, and / or to generate vibration to remove fuel droplets remaining in the nozzle; the piezoelectric correction unit is controlled by a correction control unit, which is the same control unit as the main control unit, or a separate control unit independent of the main control unit; The piezoelectric drive unit is located upstream of the electromagnetic acceleration unit and coupled to the nozzle, configured to apply periodic pressure perturbations to the fuel to form a uniform droplet sequence.

10. The droplet control device according to claim 9, characterized in that, The correction control unit is further configured to, based on state information, determine if the fuel droplet is at risk of deformation or has already deformed, and then control the piezoelectric correction unit to apply vibration and / or thrust pulses to the fuel droplet to suppress or correct the deformation of the fuel droplet. The state information is used to determine the position, motion state, and / or deformation of the fuel droplet, and includes at least one of the following: arrival time, departure time, flight speed, charge quantity, and morphological information.

11. The droplet control device according to claim 9, characterized in that, It also includes a drive control unit, which is the same control unit as the main control unit and is connected to the piezoelectric drive unit, or the drive control unit is another control unit connected to the main control unit or the electromagnetic acceleration unit and connected to the piezoelectric drive unit, configured to control the coordinated operation of the piezoelectric drive unit and the electromagnetic acceleration unit.

12. The droplet control device according to claim 11, characterized in that, The piezoelectric drive unit and the electromagnetic acceleration unit operate independently of each other, respectively controlling the formation and acceleration of droplets; the drive control unit is configured to synchronize the perturbation of the piezoelectric drive unit with the timing of the applied electrical signal of the electromagnetic acceleration unit.

13. The droplet control device according to claim 1 or 2, characterized in that, It also includes a charge management unit disposed downstream of the conductor and configured to manage the residual charge of the fuel droplet. The charge management unit includes at least one of the following: an electron emission source configured to emit electrons to the fuel droplet; an ion source configured to emit ions with the opposite polarity to the residual charge to the fuel droplet; and a grounded conductor configured to eliminate the residual charge of the fuel droplet through physical contact or electric field induction.

14. The droplet control device according to claim 2, characterized in that, It also includes a multi-stage electromagnetic acceleration unit, which is arranged sequentially along the droplet flight direction. Each stage includes at least one pair of conductors. Each stage of conductor has an independent current regulation unit. The main control unit is configured to independently adjust the current regulation unit of each stage according to the droplet arrival signal and control the power supply state of each stage, so that in each stage of conductor, at most one fuel droplet forms a current loop with the conductor at the same time.

15. A method for accelerating droplets in a fuel emitter for an extreme ultraviolet light source, characterized in that, Includes the following steps: A nozzle is provided, and a conductive configuration is provided on the inner wall of the nozzle and / or on the droplet flight path downstream of the nozzle outlet. This configuration includes a conductor capable of forming at least one current loop with a fuel droplet passing through the nozzle. The conductor is configured to include at least an intermittent conductor comprising a plurality of spatially distributed conductive segments spaced apart from adjacent segments, such that the current flowing through at least one of the conductive segments is primarily determined by the electrical parameters of the loop containing that segment, rather than primarily by the number of fuel droplets simultaneously contacting that segment. The fuel droplets are liquid metal droplets, and the number of fuel droplets is one or more. A magnetic field is generated outside the nozzle; The fuel droplet passing through the nozzle forms a current loop with the conductor, and the Ampere force generated by the interaction of the current flowing through the fuel droplet and the magnetic field has a component along the target direction, thereby accelerating, correcting the trajectory, and / or rotating the fuel droplet.

16. A method for accelerating droplets in a fuel emitter for an extreme ultraviolet light source according to claim 15, characterized in that, It also includes a main control unit, which selectively activates one or more groups of conductors according to a target operating mode and / or according to an electrical signal that forms a current loop between the fuel droplets and the conductors, so that the Ampere force has a component along the target direction. The target operating mode includes at least one of an axial acceleration mode, a radial focusing mode, a rotational stabilization mode, and a heat load dispersion mode.

17. A method for accelerating droplets in a fuel emitter for an extreme ultraviolet light source according to claim 15, characterized in that, It also includes a multi-stage acceleration unit, each stage of which is equipped with a conductor and a current regulation unit. The method further includes: accelerating the droplet through the multi-stage electromagnetic acceleration unit; the main control unit independently adjusts the current magnitude of each stage of the current regulation unit according to the droplet arrival information, and controls the energizing sequence of each stage, so that in each stage of the conductor, at most only one droplet forms a current loop with the conductor at any given time.

18. The droplet acceleration method for a fuel emitter of an extreme ultraviolet light source according to claim 15, further comprising a piezoelectric drive unit and a drive control unit, characterized in that, Also includes: The piezoelectric drive unit applies periodic pressure disturbances to the fuel inside the nozzle, causing the fuel to form a uniform droplet sequence at the nozzle outlet. The drive control unit synchronizes the perturbation frequency of the piezoelectric drive unit with the timing of the electrical signal applied to the conductor.

19. An extreme ultraviolet light source device, characterized in that, Includes the droplet control device as described in any one of claims 1 to 14.

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