Capillary discharge three-beam plasma annulus coupling enhanced EUV light source

Abstract

The invention relates to the technical field of extreme ultraviolet (EUV) lithography, and discloses a capillary discharge three-beam plasma annulus coupling enhanced EUV light source. Through gradient configuration electrode design, diaphragm regulation and control and accurate synchronous triggering, effective coupling of three beams of discharge plasmas in a capillary under the assistance of laser plasmas is achieved, and an annular light source with the light-emitting end area remarkably increased is formed. The problem that the single light-emitting power of an existing capillary discharge EUV light source is too low is solved, so that the needed work repetition frequency can be effectively reduced, the power level of the light source is improved, discharge debris and light source impurities generated by high repetition frequency work are reduced, the thermal load of a system is reduced, and the requirements for the stability of optical elements and masks and the like are relieved; and a light source scheme with higher single light emitting power, better stability and higher industrial application potential is provided for EUV photoetching.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of extreme ultraviolet (EUV) lithography, in particular to a capillary discharge three-beam plasma ring coupling enhanced EUV light source. BACKGROUND

[0002] The manufacture of semiconductor components and very large scale integrated circuits (VLSI) is the technical cornerstone of modern industry, and its development has always followed Moore's Law, pursuing smaller feature widths. The resolution of optical lithography technology is limited by the exposure wavelength λ and the numerical aperture NA, and although ArF lithography has been pushed to 65 nm or even 45 nm nodes through immersion technology, wavefront engineering and other means, traditional optical lithography is difficult to break through the physical limit of 0.2 μm. To achieve nanoscale line width, the next generation of lithography technology, such as extreme ultraviolet lithography (EUVL), has emerged. Among them, the extreme ultraviolet (EUV) light with a wavelength of 13.5 nm has become the mainstream technology for chip manufacturing below 10 nm, because it can be efficiently matched with molybdenum-silicon multilayer mirrors and can provide sufficient focal depth.

[0003] The core difficulty of EUVL lies in the light source. An ideal EUV light source should have high power, high stability, low debris, low cost, etc. At present, the main technical routes for generating 13.5 nm EUV radiation mainly include laser plasma (LPP) light source, discharge plasma (DPP) light source and synchrotron radiation light source. Although the synchrotron radiation light source has excellent performance, its cost and operating cost are extremely high, making it difficult to apply to industrial production. The LPP light source (such as tin target laser plasma) has low energy conversion efficiency and generates a large amount of debris. The gas discharge plasma (DPP) light source, especially the capillary discharge method, has become one of the promising solutions due to its simple structure, easy operation and high energy conversion efficiency.

[0004] However, the existing capillary discharge DPP EUV light source faces a fundamental challenge: the 13.5 nm light power of a single discharge is too low. In order to reach the threshold power required by the lithography process, the discharge repetition frequency has to be increased to several kilohertz. This high repetition rate mode brings a series of problems: 1) a large amount of discharge debris and light source impurities are generated, which will absorb EUV photons and produce background "light noise", reducing the effective light power; 2) the thermal load of the electrode, discharge plasma and other components increases sharply, making it difficult to dissipate heat; 3) the stability of the support, optical system and mask of the lithography machine is extremely high, increasing the system complexity and cost. By stacking power at high repetition rate, the production efficiency and yield are essentially sacrificed, which is not a fundamental solution.

[0005] Therefore, the industry urgently needs a new light source technology capable of generating higher EUV light power in a single discharge. The key technology is how to effectively expand the light-emitting end area of the plasma without significantly increasing the system complexity and cost, thereby breaking through the bottleneck of single power. Although there is an idea of increasing the light-emitting area by coupling multiple beams of plasma, how to realize stable and controllable coupling, especially to solve the key scientific problems such as the matching of the position of the multiple beams of plasma and the laser pulse and the stress balance of the magnetic pressure-thermal pressure, a capillary discharge three-beam plasma ring belt coupling enhanced EUV light source is proposed. SUMMARY

[0006] In view of the deficiencies of the prior art, the capillary discharge three-beam plasma ring belt coupling enhanced EUV light source is provided to solve the problems in the background art.

[0007] To achieve the above-mentioned purpose, the capillary discharge three-beam plasma ring belt coupling enhanced EUV light source provided by the present application comprises the following technical solutions. The first aspect of the capillary discharge three-beam plasma ring belt coupling enhanced EUV light source comprises: A capillary tube for containing a discharge plasma; Three pairs of electrodes including three high-voltage electrodes and three ground electrodes, the high-voltage electrodes and the ground electrodes are alternately and symmetrically arranged at both ends of the capillary tube, the spacing between the high-voltage electrodes is 6.8 mm, the spacing between the ground electrodes is 0.5 mm, and the discharge distance between the high-voltage electrodes and the ground electrodes is 30 mm, forming a gradient configuration of the plasma; A laser for generating a laser pulse propagating along the axis of the capillary tube to ablate part of the discharge plasma to generate a laser plasma (LPP), the LPP is used to provide thermal pressure to assist the coupling of the three beams of plasma; An aperture system comprising two apertures arranged along the optical path, the two apertures are respectively 100 mm and 1000 mm away from the laser, each aperture is divided into a light-transmitting center I region, a non-light-transmitting intermediate II region and a light-transmitting outer III region, and is used to regulate the light intensity distribution and the action area of the laser pulse; A control unit for synchronously triggering the discharge of the three pairs of electrodes and the laser pulse, so that the three beams of discharge plasma are pinched under the action of the Lorentz force and coupled under the assistance of the laser plasma to form a ring belt-shaped light source.

[0008] Preferably, the gradient configuration causes the three beams of discharge plasma to be distributed in a conical surface along the axis of the capillary tube, and the pinch radius gradually decreases from the cone mouth to the cone top, and the current density, plasma density and temperature are gradiently distributed.

[0009] Preferably, the width and radius of the II zone of the diaphragm system are designed according to the size of the discharge plasma annulus, so that the II zone projects to cover the plasma annulus, avoiding the misburning of the plasma annulus by the laser, and thus directing the laser passing through the I zone to the inside region of the plasma annulus to ablate the on-axis plasma, and directing the laser passing through the III zone to the outside region of the plasma annulus to ablate the off-axis plasma, so as to enhance the thermal pressure and expansion of the laser plasma.

[0010] Preferably, the control unit is configured to trigger the laser pulse synchronously when the three discharge plasmas are pinched to a radius of 1.2 mm-1.5 mm, so as to synchronize the expansion of the laser plasma with the pinching process of the three discharge plasmas.

[0011] Preferably, the laser pulse includes a pre-pulse and a main pulse, the pre-pulse ablates the on-axis discharge plasma through the I zone of the diaphragm to generate an initial laser plasma, and the main pulse ablates the off-axis discharge plasma through the III zone of the diaphragm to generate a laser plasma, so as to enhance the thermal pressure of the initial laser plasma.

[0012] Preferably, the emitting end area of the annular coupling light source is 3-25 times of the emitting end area of a single discharge plasma light source.

[0013] Preferably, the three discharge plasmas are similar to a hollow conical carbon target, and are used to generate a cylindrical laser plasma, so as to facilitate the shape matching with the discharge plasma cone.

[0014] In the second aspect, a coupling method for the EUV light source of the first aspect includes the following steps: Synchronously triggering the discharge of the three pairs of electrodes to form three plasmas, and mutually pinching the three plasmas to the capillary axis under the gradient configuration; When the three plasmas are pinched to a predetermined radius, triggering a laser pulse to ablate part of the discharge plasma after being regulated by the diaphragm, and generating a laser plasma; Through the shape matching, the light intensity distribution of the laser pulse is matched with the geometry of the plasma cone, and the action point of the laser pulse is located on the capillary axis; Under the action of the "outer pinching and inner expansion", the three discharge plasmas are coupled into an annular light source by the thermal pressure provided by the laser plasma and the magnetic pressure provided by the plasma current.

[0015] Preferably, the shape matching includes matching the Gaussian light intensity distribution of the laser pulse with the geometry of the plasma cone, wherein when the high-voltage electrode spacing is 6.8 mm, the plasma cone is an optimal cone shape between the wide mouth and the narrow mouth, which is matched with the wave front of the Gaussian light intensity distribution.

[0016] Preferably, the force compensation includes compensating for insufficient Lorentz force by increasing the discharge current, and / or enhancing the laser plasma thermal pressure by optimizing the laser pulse width, power and action point, and / or adopting a laser double pulse strategy, with the pre-pulse and main pulse acting on the partial discharge plasma through the aperture I region and III region, respectively.

[0017] In comparison with the prior art, the present application has the following beneficial effects: The present application realizes effective coupling of three discharge plasmas under the assistance of laser plasma by discharge plasma gradient configuration electrode design, aperture regulation and precise synchronous triggering, forms a ring belt-shaped coupling light source with significantly increased light-emitting end area. The problem of low single light-emitting power of the existing capillary discharge EUV light source is solved, thereby effectively reducing the required working repetition frequency, improving the power level of the light source, reducing the discharge debris and light source impurities generated due to high repetition frequency work, reducing the system thermal load, alleviating the stability requirements of optical elements and masks, and providing a light source scheme with higher single power, better stability and more industrial application potential for EUV lithography.

[0018] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a schematic diagram of the light source device of the present application; Figure 2 It is a coupling process diagram of the capillary discharge three-beam plasma of the present application; Figure 3 It is a curve diagram of the pinch radius and Lorentz force of the three-beam discharge plasma of the present application; Figure 4 It is a gradient configuration diagram of the three-beam discharge plasma of the present application; Figure 5 It is a plasma image of the laser pulse acting on a planar carbon target and a hollow conical carbon target of the present application; Figure 6 It is a laser pulse light intensity distribution and various plasma conical surface schematic diagram of the present application; Figure 7 It is a plasma conical surface current schematic diagram of the present application; Figure 8 It is a schematic diagram of the laser pulse passing through the aperture of the present application; Figure 9 It is a diagram of the capillary discharge multi-beam plasma and laser pulse of the present application; Figure 10Figure of the variation of the pinch radius and the expansion factor of the plasma annulus of the application with the discharge current; Figure 11 Evolution image of the three-beam discharge plasma of the application; Figure 12 Trigger data diagram of the synchronization of the discharge and the laser of the application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the application will be apparently and completely described below with the accompanying drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by the ordinary skilled in the art without any creative work belong to the protection scope of the application.

[0021] Please refer to Figures 1-12 , the capillary discharge three-beam plasma annulus coupling enhanced EUV light source in the application. The embodiment elaborates the specific implementation scheme of the light source of the application, and the core is that through the "outer hoop and inner bulge" mechanism, the three-beam discharge plasma is coupled to form an annular light source with the assistance of the laser plasma (LPP), so as to improve the light-emitting end area and the EUV light power.

[0022] Embodiment one: light source device The capillary discharge three-beam plasma annulus coupling enhanced EUV light source device of the embodiment has a test schematic diagram as shown in Figure 1 , mainly including a discharge chamber, a capillary tube, an electrode system, a laser, an aperture system and a control unit, specifically: Discharge chamber: providing a vacuum environment for the internal components.

[0023] Capillary tube: installed in the discharge chamber, used for accommodating the plasma generated by discharge.

[0024] Electrode system: referring to Figure 4 , three high-voltage electrodes (1, 3, 5) and three grounded electrodes (2, 4, 6) are alternately and symmetrically arranged at both ends of the capillary tube. The preferred parameters are: the distance between the high-voltage electrodes is 6.8 mm, the distance between the grounded electrodes is 0.5 mm, and the discharge distance between the high-voltage electrodes and the grounded electrodes is 30 mm. The gradient configuration makes the three-beam plasma generated by discharge distributed in a conical surface along the capillary tube axis, from the conical opening ( Figure 4 a cross section) to the conical top ( Figure 4 c cross section), the pinch radius of the plasma gradually decreases, and the current density, the plasma density and the temperature show a clear gradient distribution, which is the basis for realizing the subsequent selective coupling.

[0025] Laser: Preferably a Nd:YAG laser (wavelength λ = 1.06 μm) is used to generate laser pulses propagating along the capillary axis to ablate part of the discharge plasma to create a laser plasma (LPP). The discharge plasma is similar to a hollow cone carbon target. As shown in Figure 5 Figure 1, compared to the irregularly shaped plasma created by laser acting on a planar carbon target (a), the hollow cone carbon target can create a cylindrical laser plasma (b) with its head and root connected as one without a waist, which is more beneficial for the coupling of three discharge plasmas. Figure 5 Figure 5 b), this shape is more beneficial for the coupling of three discharge plasmas.

[0026] Diaphragm system: used to precisely regulate the laser pulse. The arrangement is shown in Figure 8 Figure 2. The system includes two diaphragms: the first diaphragm is 100 mm away from the laser, and the second diaphragm is 1000 mm away from the laser. Each diaphragm is divided into three zones from inside to outside: a light-transmitting center I zone, a non-light-transmitting middle II zone, and a light-transmitting outer III zone. The width and radius of the II zone are designed to continuously cover and protect the final plasma annulus. This diaphragm system specifically realizes four functions: The laser pulse passing through the I zone ablates the discharge plasma in the inner region of the annulus to form a cylindrical LPP; The II zone avoids the laser from ablating the discharge plasma in the annulus itself; The laser pulse passing through the III zone ablates the discharge plasma in the outer region of the annulus, and the ablation products help to convert the axial ejection of the LPP into lateral expansion; The laser pulse is collimated to reduce the drift of the action point.

[0027] Control unit: used to realize the precise synchronization triggering of discharge and laser. The unit is configured to trigger the laser pulse when the three plasma pinches reach a certain radius range (1.2 mm-1.5 mm, see Figure 3 for the relationship between the pinch radius and time). Figure 12 The signal timing of (a) laser lagging discharge, (b) synchronization, and (c) laser leading discharge is shown, with blue representing the laser signal and yellow representing the discharge signal, where Figure 12 b is the ideal synchronization state.

[0028] Example Two: Coupling method This example describes in detail the method of coupling three plasma annuli using the above device.

[0029] S1: Synchronous discharge forms three plasmas.

[0030] The control unit synchronously triggers the discharge of the three pairs of electrodes to form three discharge plasmas in the capillary that are axisymmetric about the axis. Gradient configuration electrodes (​Figure 4 After discharging, the formation and evolution of the three plasmas can be observed, as shown in Figure 11 Fig. 2, Figure 11 (a) and Figure 11 (b) respectively, which are the evolution images of the three plasmas taken by a color digital camera and a CCD camera respectively. The three plasmas start to pinch each other under the magnetic field generated by the self-current and move towards the capillary axis.

[0031] S2: Laser synchronization triggering and LPP injection.

[0032] The control unit monitors the pinching process in real time, and when the three plasmas are pinched to a predetermined radius (about 1.2-1.5 mm), the laser pulse is triggered accurately (synchronization timing see Figure 12 b). After being shaped by the diaphragm system Figure 8 , the light intensity distribution of the laser pulse is precisely controlled, and the action point is limited, and then a cylindrical LPP is generated by ablating part of the discharge plasma.

[0033] S3: Coupling under the matching of the shape and the balance of the force.

[0034] This step is the core of realizing coupling: 1. Shape matching: In order to ensure the effective action of the laser pulse and the plasma cone surface, the present application realizes the matching of their geometric shapes by controlling the electrode spacing. As shown in Figure 6 , when the high-voltage electrode spacing is 6.8 mm, the plasma cone surface (purple dotted line) formed can basically match the wave front of the Gaussian light intensity distribution of the laser pulse (red solid line). The diaphragm system further ensures the accuracy of the matching.

[0035] 2. Force compensation and balance: Coupling requires the balance of magnetic pressure (provided by Lorentz force) and thermal pressure (provided by LPP).

[0036] Magnetic pressure compensation: In the gradient configuration, the vertical component of the plasma current will weaken the parallel component used for mutual pinching. As shown in Figure 7 , by increasing the total discharge current, the deficiency of the parallel component can be compensated to ensure sufficient magnetic pressure.

[0037] Thermal pressure provision: By optimizing the laser parameters (such as using a double-pulse strategy of generating LPP by pre-pulse through region I and enhancing LPP by main pulse through region III), it is ensured that LPP can provide sufficient and stable thermal pressure to resist the magnetic pressure.

[0038] Under the above conditions, the three plasmas undergo a dynamic coupling process, as shown in Figure 2 : Initial stage Figure 2 (a): The three plasmas self-pinch and start to move towards the capillary axis.

[0039] Deformation stage ( Figure 2 b): Current density rearrangement, external constriction and strengthening, plasma shape change.

[0040] Integration phase ( Figure 2 c): The outer edges of the three plasma beams contact and begin to merge.

[0041] LPP plastic surgery stage ( Figure 2 d): The LPP expands laterally, compressing the plasma to make its inner envelope surface smooth.

[0042] Coupling complete ( Figure 2 e): Under the action of "outer hoop and inner expansion", a high-temperature and high-density annular coupled light source is eventually formed.

[0043] This coupling process mainly occurs near a specific cross section in the gradient configuration where the Lorentz force reaches approximately 230 N (e.g., ...). Figure 4 (As shown in c). This force value is based on the conditions required for plasma to radiate 13.5 nm EUV light (electron temperature 20~50 eV, density >10^18 / cm). 3 The lower limit value is calculated after performing a stress analysis.

[0044] Example 3: Effect Verification and Data Analysis To verify the beneficial effects of the present invention, thorough experimental testing and theoretical analysis were conducted.

[0045] Analysis of theoretical advantages: refer to Figure 1 Traditional capillary discharge single-beam plasma has a pinch diameter of approximately 250 μm and a luminous end area of ​​approximately 0.049 mm². 2 . Figure 1 This is the capillary discharge three-beam plasma structure of the present invention. Figure 9 The diagrams show the luminescent end areas of (a) single-beam, (b) three-beam, and (c) eight-beam plasmas under LPP irradiation. Theoretical analysis indicates that increasing the number of beams may actually decrease the amplification factor (approximately 15 for eight beams), and also increases the difficulty of synchronous discharge and the stringency of coupling conditions. Three-beam plasma achieves the optimal balance between amplification factor and engineering feasibility, as theoretically calculated ( Figure 10 This indicates that the annular light source formed by the coupling of three plasma beams (the annular radius is approximately 3 mm, and the width is approximately 40 μm, as shown in the image) is a ring-shaped light source. Figure 9 The area of ​​the light-emitting end (as shown in b) can reach approximately 1.1304 mm². 2 It is a single-beam light source ( Figure 9 a) is approximately 23 times that of a), approaching the theoretical maximum amplification factor of 25. And eight beams of plasma ( Figure 9c) Although it can form a larger radius annulus, its maximum theoretical magnification factor is reduced to about 15, and the difficulty of simultaneous discharge and coupling is sharply increased. Therefore, the three-beam configuration achieves the best balance between magnification factor and engineering feasibility.

[0046] 2. Experimental data and results: Experiments were conducted on the device as shown in Figure 1 at two N2 pressures, 30 Pa and 90 Pa. The key measurement results are summarized in Table 1.

[0047] Table 1. Coupling effect measurement results 3. Coupling effect verification: The formula for calculating the energy coupling efficiency is: Taking 90 Pa pressure as an example, the average optical power increases from 55.59 pA to 78.05 pA after coupling, and the average energy coupling efficiency is about 28%.

[0048] The magnification factor of the coupled light source is relative to the single-beam plasma light source. First, divide the total light power of the three-beam plasma in the uncoupled (only discharge) state by 3 to get the equivalent single-beam light power, and then compare it with the light power in the coupled state. The results are the same as directly multiplying the light power increase factor of the coupled state relative to the only discharge by 3.

[0049] Results verification: The following shows that the increase in optical power is due to the coupling of the three-beam plasma, rather than other factors: Light power source analysis: The light detector has no response to 1.06 μm laser pulses itself. LPP is generated inside the plasma cone near the cone top, and its light emission mainly faces the cone direction. The cone top area forms a shield, making it difficult for the light detector to directly receive the light emission of LPP. Therefore, the doubling of light power is mainly due to the expansion of the light emission area of the coupled plasma annulus.

[0050] Direct evidence of laser participation in coupling: Use infrared photosensitive film for imaging experiments. When the laser is triggered alone, a laser spot can be observed on the film; when the laser and discharge are triggered at the same time, the central part of the laser spot on the film is missing, leaving only irregular edge parts, and the laser energy meter still has a reading at this time. This indicates that the central part of the laser pulse energy has been consumed by the coupling process.

[0051] Parameter correlation evidence: under different gas pressures (30 Pa and 90 Pa), the parameters such as the laser energy involved in coupling, energy coupling efficiency, amplification factor, etc. all changed significantly. This fact indirectly proves that the three plasmas are coupled, because if they are not coupled, the degree of influence of the laser pulse on the three plasmas should be basically the same, and there should be no regular changes in the above parameters.

Claims

1. A capillary discharge three-beam plasma annular coupling enhanced EUV light source, characterized in that, include: Capillary tubes are used to contain discharge plasma; Three pairs of electrodes, including three high-voltage electrodes and three ground electrodes, are alternately and symmetrically arranged at both ends of the capillary. The spacing between the high-voltage electrodes is 6.8 mm, the spacing between the ground electrodes is 0.5 mm, and the discharge distance between the high-voltage electrodes and the ground electrodes is 30 mm, forming a gradient configuration of plasma. A laser is used to generate laser pulses propagating along the capillary axis to ablate a portion of the discharge plasma to generate laser plasma (LPP), the LPP being used to provide thermal pressure to assist in the coupling of three plasma beams. The aperture system includes two apertures set along the optical path, which are 100 mm and 1000 mm away from the laser, respectively. Each aperture is divided into a light-transmitting central region I, an opaque middle region II, and a light-transmitting outer region III, which are used to control the light intensity distribution and the area of ​​action of the laser pulse. The control unit is used to synchronously trigger the discharge of three pairs of electrodes and the laser pulse, so that the three discharge plasmas are mutually clamped under the action of Lorentz force and coupled with the assistance of laser plasma to form a ring-shaped light source.

2. The capillary discharge three-beam plasma annular coupling enhanced EUV light source according to claim 1, characterized in that, The gradient configuration causes the three discharge plasma beams to be distributed in a conical shape along the capillary axis. From the cone opening to the cone apex, the constriction radius gradually decreases, and the current density, plasma density, and temperature are all distributed in a gradient.

3. The capillary discharge three-beam plasma annular coupling enhanced EUV light source according to claim 1, characterized in that, The width and radius of region II of the aperture system are designed according to the size of the plasma ring, so that the projection of region II covers the plasma ring, avoiding accidental burning of the plasma ring by the laser. This guides the laser pulse that passes through region I to the inner region of the plasma ring, ablating the discharge plasma in that region, and guides the laser pulse that passes through region III to the outer region of the plasma ring, ablating the discharge plasma in that region, thereby enhancing the thermal pressure and expansion effect of the laser plasma.

4. The capillary discharge three-beam plasma annular coupling enhanced EUV light source according to claim 1, characterized in that, The control unit is configured to synchronously trigger a laser pulse when the three discharge plasma beams are constricted to a radius of 1.2 mm-1.5 mm, thereby synchronizing the expansion of the laser plasma with the constriction process of the three discharge plasma beams.

5. The capillary discharge three-beam plasma annular coupling enhanced EUV light source according to claim 1, characterized in that, The laser pulse includes a pre-pulse and a main pulse. The pre-pulse ablates the paraxial discharge plasma in region I of the aperture to generate the initial laser plasma, and the main pulse ablates the off-axis discharge plasma in region III of the aperture to generate the laser plasma, thereby enhancing the thermal pressure of the initial laser plasma.

6. The capillary discharge three-beam plasma annular coupling enhanced EUV light source according to claim 1, characterized in that, The area of ​​the light-emitting end of the ring-shaped coupled light source is 3 to 25 times that of the light-emitting end of the single-beam discharge plasma light source.

7. The capillary discharge three-beam plasma annular coupling enhanced EUV light source according to claim 1, characterized in that, The three discharge plasma beams are similar to hollow conical carbon targets, used to generate cylindrical laser plasma to facilitate configuration matching with the discharge plasma cone surface.

8. A coupling method for the EUV light source according to any one of claims 1-7, characterized in that, Includes the following steps: Simultaneous triggering of discharge from three pairs of electrodes generates three beams of plasma, which mutually constrict towards the capillary axis under the gradient configuration. When the three plasma beams are constricted to a predetermined radius, a laser pulse is triggered. After being controlled by an aperture, a portion of the discharge plasma is ablated to generate laser plasma. By using configuration matching, the intensity distribution of the laser pulse is geometrically matched with the plasma cone surface, and the point of action of the laser pulse is located on the capillary axis. By utilizing the thermal pressure provided by laser plasma and the magnetic pressure provided by plasma current, three beams of discharge plasma are coupled into a ring-shaped light source under the action of "outer hoop and inner expansion".

9. The coupling method of the EUV light source according to claim 8, characterized in that, The configuration matching includes making the Gaussian intensity distribution of the laser pulse geometrically match the plasma cone surface, wherein when the high-voltage electrode spacing is 6.8 mm, the plasma cone surface is an optimal cone shape between a wide and narrow aperture that matches the wavefront of the Gaussian intensity distribution.

10. The coupling method of the EUV light source according to claim 8, characterized in that, The force compensation includes increasing the discharge current to compensate for insufficient Lorentz force, and / or optimizing the laser pulse width, power and application point to enhance laser plasma thermo-pressure, and / or employing a laser dual-pulse strategy to apply the pre-pulse and main pulse to a portion of the discharge plasma via aperture I and aperture III, respectively.

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