Droplet target generating device for EUV light source

Abstract

The invention relates to the technical field of fluid mechanics, in particular to a droplet target generating device for an EUV light source, which comprises a liquid supply assembly, a droplet spraying assembly and a piezoelectric driving assembly, positive pressure is applied to the solution in the liquid storage device through the air pressure controller, the solution is supplied to the nozzle until the jet flow is extruded, then the negative pressure is switched, the jet flow is forced to stop, and the nozzle opening is kept on an inward meniscus; then, the piezoelectric element is driven through the driving signal controller, positive and negative alternating sound pressure waves are generated in the liquid in the capillary tube through deformation of the piezoelectric element, and the sound pressure waves are transmitted to the nozzle opening so as to eject liquid drops; moreover, by setting parameters of the driving signal controller, the device can generate stable liquid drops with different frequencies, is simple to operate, accurate to control and large in adjustable range, can generate stable large-spacing monodisperse liquid drops, and is suitable for generation of liquid drop targets in an EUV light source.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid mechanics, and in particular to a droplet target generating device for an EUV light source. Background Art

[0002] The generation of droplet targets currently used in commercial EUV lithography machines is based on the Rayleigh jet breakup theory. Driven by air pressure or a pump, the liquid is ejected from a micropore or capillary to form a jet, which is then split into continuous droplets of uniform size and a certain spacing by periodic perturbations. However, it is difficult to generate stable, large-spacing monodisperse droplets using only a single long-wave perturbation, which is not conducive to target shooting. Moreover, due to the flow characteristics of the fluid itself, the jet will produce position jitter during the process of breaking and forming droplets, affecting the stability of the EUV light source. In addition, to overcome the limitations of a single perturbation frequency, a composite perturbation signal can be designed to excite high-order modal instability, merging multiple droplets to obtain a larger droplet spacing. The above modulation method increases the complexity of the device on the one hand, and inevitably increases the droplet size on the other. If droplet targets that meet the target shooting requirements can be directly generated, it will be of great significance to the development of EUV light sources.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a droplet target generating device for an EUV light source, aiming to solve the problem that the existing droplet target generating device cannot directly generate stable large-spaced monodisperse droplets.

[0005] The technical solutions of the present invention are as follows:

[0006] A droplet target generating device for an EUV light source, comprising:

[0007] a liquid supply assembly comprising an air pressure controller and a liquid reservoir connected to the air pressure controller via a pipeline;

[0008] A droplet ejection assembly comprises a capillary tube with a nozzle; a side of the capillary tube facing away from the nozzle is connected to the liquid reservoir via a pipe;

[0009] The piezoelectric driving component comprises at least one piezoelectric element sleeved on the outer wall of the capillary tube and a driving signal controller electrically connected to the piezoelectric element.

[0010] The droplet target generating device for EUV light source, wherein the liquid reservoir includes a liquid storage cavity and a top cover arranged on the top of the liquid storage cavity; the top cover is provided with an air passage, and the air passage is connected to the air pressure controller through a pipeline.

[0011] The droplet target generating device for EUV light source, wherein a filter is provided on a side of the capillary tube facing away from the nozzle, and the reservoir is connected to the capillary tube through the filter.

[0012] The droplet target generating device for EUV light source, wherein the filter is provided with a filter membrane.

[0013] The droplet target generating device for EUV light source, wherein a detachable Luer connector is used for connecting the reservoir, the filter and the capillary tube.

[0014] The droplet target generating device for EUV light source, wherein the inner diameter of the nozzle is 10μm - 50μm.

[0015] The droplet target generating device for EUV light source, wherein the control gas of the pressure controller is an inert gas; the inert gas includes nitrogen or argon.

[0016] The droplet target generating device for EUV light source, wherein the piezoelectric element is provided with a capillary fixing hole, the outer wall of the capillary tube is attached to the inner side surface of the capillary fixing hole, and an epoxy resin layer is provided on the joint surface between the capillary tube and the capillary fixing hole.

[0017] The droplet target generating device for EUV light source, wherein the drive signal controller is used to set droplet target generation parameters and control the piezoelectric element; the droplet target generation parameters include one or more of a pulse signal, a signal amplitude, a pulse width, a frequency, a rise time and a fall time.

[0018] The droplet target generating device for EUV light source, wherein the droplet target generating device for EUV light source further includes a heat preservation layer for wrapping the reservoir and the capillary tube.

[0019] Beneficial effects: The present invention provides a droplet target generating device for an EUV light source, comprising: a liquid supply component, a droplet ejection component and a piezoelectric drive component; the liquid supply component comprises an air pressure controller, and a liquid reservoir connected to the air pressure controller through a pipeline; the droplet ejection component comprises a capillary with a nozzle; the side of the capillary facing away from the nozzle is connected to the liquid reservoir through a pipeline; the piezoelectric drive component comprises at least one piezoelectric element sleeved on the outer wall of the capillary, and a drive signal controller electrically connected to the piezoelectric element. The present invention uses an air pressure controller to apply positive pressure to the solution in the liquid reservoir, supplies droplets to the nozzle to extrude a jet, and then switches to negative pressure to force the jet to terminate. The nozzle mouth maintains an inward meniscus, and then drives the piezoelectric element through a driving signal controller. The deformation of the piezoelectric element is used to generate alternating positive and negative acoustic pressure waves in the liquid in the capillary. The acoustic pressure waves are transmitted to the nozzle mouth to eject droplets. In addition, the device can obtain the generation of stable droplets of different frequencies by setting the parameters of the driving signal controller. The device is simple to operate, precise in control, and has a large adjustable range. It can generate stable, large-spaced monodisperse droplets and is suitable for the generation of droplet targets in EUV light sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a droplet target generating device for an EUV light source according to the present invention;

[0021] Figure 2 Schematic diagram of fixing the piezoelectric element and the capillary tube by bonding the cylindrical wall;

[0022] Figure 3 Schematic diagram of fixing the piezoelectric element and the capillary tube by means of clamped bonding at both ends;

[0023] Figure 4 This is a characterization diagram of the effect of spraying deionized water droplets using a droplet target generating device in Example 1;

[0024] Explanation of the accompanying drawings: liquid supply component 10, air pressure controller 11, liquid reservoir 12, liquid storage chamber 121, top cover 122, air path 123, droplet injection component 20, nozzle 21, capillary 22, filter 23, piezoelectric drive component 30, piezoelectric element 31, drive signal controller 32, epoxy resin layer 40, gap 50. DETAILED DESCRIPTION

[0025] The present invention provides a droplet target generating device for an EUV light source. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0026] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention pertains. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with their meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as herein.

[0027] The current commercially available extreme ultraviolet (EUV) lithography machine light source is based on the physical mechanism of laser-produced plasma (LPP). Its core principle is as follows: The droplet target generator generates high-frequency and high-speed tin droplets; the pre-pulse laser precisely bombards the tin droplets in a vacuum to spread them into a disk-shaped tin film or a fine mist of tin; the main-pulse laser bombards the disk-shaped tin film or tin mist to fully ionize it and generate a dense plasma; the radiated EUV light is collected by a condenser lens and converged to a relay focus for subsequent lithography use.

[0028] The droplet target is the target form adopted by the currently only commercially available EUV lithography machine light source, and the droplet target generator is one of the core components of the EUV light source. The requirements of the LPP-EUV lithography machine light source for tin droplets are small size (diameter 10 - 50 μm), large droplet spacing (several to dozens of times the droplet diameter), and high frequency (dozens to 100 kHz) to obtain sufficient EUV light power and reduce the generation of debris during the laser bombardment process. However, the existing droplet target generating devices cannot directly generate stable large-spacing monodisperse droplets.

[0029] Therefore, the present invention proposes a method of generating droplets in a drop-on-demand (DoD) manner, using an electric pulse generator to drive a piezoelectric element. The piezoelectric element is connected to a capillary tube, and the internal volume of the capillary tube is changed by changing the driving voltage, thereby extruding droplets. The size, spacing, and frequency of the droplets can be changed by adjusting the amplitude, pulse width, and frequency of the pulse signal. The DoD droplet generator can directly generate droplets with diameters and spacings that meet the requirements for target shooting, which is more convenient and stable than generating droplets by the Rayleigh jet breakup method.

[0030] Based on this, as Figure 1 shown, the present invention provides a droplet target generating device for an EUV light source, comprising:

[0031] A liquid supply assembly 10, comprising a gas pressure controller 11 and a liquid reservoir 12 connected to the gas pressure controller 11 through a pipeline;

[0032] The droplet ejection assembly 20 includes a capillary 22 with a nozzle 21; one side of the capillary 22 facing away from the nozzle 21 is connected to the liquid reservoir 12 through a pipeline;

[0033] The piezoelectric drive assembly 30 includes at least one piezoelectric element 31 sleeved on the outer wall of the capillary 22, and a drive signal controller 32 electrically connected to the piezoelectric element 31.

[0034] In this embodiment, a positive pressure is applied to the solution in the liquid reservoir 12 by using the air pressure controller 11 to supply droplets to the nozzle until a jet is ejected. Subsequently, a negative pressure is switched to force the jet to terminate, and a meniscus facing inward is maintained at the nozzle opening. Then, the piezoelectric element is driven by the drive signal controller, and positive and negative alternating acoustic pressure waves are generated in the liquid in the capillary due to the deformation of the piezoelectric element. The acoustic pressure waves are transmitted to the nozzle opening to eject droplets; moreover, by setting the parameters of the drive signal controller for this device, the generation of stable droplets with different frequencies can be obtained. It has the advantages of simple operation, precise control, and a large adjustable range, can generate stable single-dispersed droplets with a large spacing, and is suitable for the generation of droplet targets in EUV light sources.

[0035] Specifically, in the present invention, by using the method of generating acoustic pressure waves through the deformation of the piezoelectric element 31, droplets with a diameter of less than 50 μm can be directly ejected without complex signal regulation; moreover, by using parameters such as the frequency, amplitude, and pulse width of the drive signal controller 32, the generation of stable droplets with different frequencies can be obtained, which has the advantages of simple operation, precise control, and a large adjustable range, and is very suitable for the generation of droplet targets in EUV light sources; at the same time, this device has wide applicability and can realize the generation of droplets of various materials such as metal liquids and transparent liquids, so it is also applicable to applications in different fields such as additive manufacturing, micro-welding, and microcircuits.

[0036] In some embodiments, the liquid reservoir 12 includes a liquid storage chamber 121 and a top cover 122 provided at the top of the liquid storage chamber 121; the top cover 122 is provided with an air inlet 123, and the air inlet 123 is connected to the air pressure controller 11 through a pipeline. The liquid storage chamber 121 is used to provide ejection raw materials for the capillary 22. Under the action of the air pressure controller 11, when a positive pressure is provided, it can ensure that the liquid storage chamber 121 supplies liquid to the nozzle 21 and cleans the nozzle. When a negative pressure is provided, it maintains a stable meniscus at the nozzle opening to promote stable droplet ejection. Moreover, setting the top cover 122 facilitates the filling of liquid, and at the same time, the air inlet 123 can facilitate the air pressure controller 11 to provide control gas for the liquid reservoir 12.

[0037] In some embodiments, a filter 23 is provided on the side of the capillary 22 facing away from the nozzle 21, and the liquid reservoir 12 is connected to the capillary 22 through the filter 23. The filter 23 can effectively block large particle impurities and metal oxides, preventing nozzle blockage.

[0038] In some embodiments, the filter 23 is provided with a filter membrane.

[0039] Specifically, the filter 23 is made of stainless steel and used in conjunction with a nylon filter membrane. The mesh number of the filter membrane can be selected according to the liquid material and application requirements, which can effectively block large particle impurities and metal oxides and prevent nozzle blockage.

[0040] In some embodiments, a detachable Luer connector is used to connect the liquid reservoir 12, the filter 23 and the capillary 22. This facilitates the subsequent disassembly of the device and the maintenance of components, reducing the maintenance cost of the device.

[0041] In some embodiments, the inner diameter of the nozzle is 10μm - 50μm. By controlling the inner diameter of the nozzle within this range and combining with the deformation of the piezoelectric element to generate positive and negative alternating acoustic pressure waves in the liquid in the capillary, droplets with a diameter of less than 50μm can be directly ejected from the nozzle.

[0042] In some embodiments, the nozzle and the capillary adopt an integrated structure, which has a simple structure and avoids the risk of liquid leakage.

[0043] In some embodiments, the integrated capillary and nozzle can be formed by forging a glass tube needle or prepared from materials such as stainless steel and ceramics.

[0044] In some embodiments, the control gas of the pneumatic controller is an inert gas; the inert gas includes but is not limited to nitrogen or argon. When using the pneumatic controller 11 to provide positive pressure to the liquid reservoir 12, it can ensure the supply of liquid to the nozzle and clean the nozzle; when providing negative pressure, it can maintain a stable and inward meniscus at the nozzle opening, promoting stable droplet ejection.

[0045] In some embodiments, as Figure 2 shown, the piezoelectric element is fixed to the capillary by means of cylindrical wall surface bonding; the piezoelectric element 31 is provided with a capillary fixing hole; the outer wall of the capillary 22 is fitted with the inner side surface of the capillary fixing hole, and an epoxy resin layer 40 is provided on the fitting surface of the capillary 22 and the capillary fixing hole.

[0046] In some embodiments, as Figure 3As shown, the piezoelectric element is fixed to the capillary by a method of fixing both ends by bonding; the piezoelectric element 31 annularly surrounds the capillary 22, and a suspended design is adopted between the piezoelectric element and the capillary, and the two end faces of the piezoelectric element are adhesively fixed to the outer wall of the capillary. That is, a gap 50 is left between the inner side of the capillary fixing hole and the outer wall of the capillary, and the two end faces of the piezoelectric element 31 in the length direction of the capillary 22 are adhesively fixed to the outer wall of the capillary 22 through an epoxy resin layer 40.

[0047] In some embodiments, there are two or more piezoelectric elements, and the two or more piezoelectric elements can sense each other and suppress the generation of satellite droplets.

[0048] In some embodiments, the drive signal controller is used to set droplet target generation parameters and control the piezoelectric element; the droplet target generation parameters include one or more of a pulse signal, a signal amplitude, a pulse width, a frequency, a rise time, and a fall time. By setting the droplet target generation parameters, the generation of stable droplets with different frequencies can be obtained, and stable large-spacing monodisperse droplets can be generated.

[0049] In some embodiments, the length of the capillary with a nozzle is 20 mm - 50 mm, which has a small size, forms a split design with the liquid reservoir, and is convenient for placing the capillary with a nozzle in a vacuum chamber to generate droplets.

[0050] In some embodiments, the thickness of the piezoelectric element is much smaller than the length of the capillary with a nozzle, ranging from 1 / 5 to 1 / 25 of the capillary length; by setting the position of the piezoelectric element on the capillary and cooperating with the drive signal, the driving force of the piezoelectric element can be effectively improved.

[0051] In some embodiments, the droplet target generation device for an EUV light source further includes a heating and heat preservation layer that wraps the liquid reservoir and the capillary. With the setting of the heating and heat preservation layer, the device can be suitable for the generation of metal droplets with different melting points.

[0052] The following further gives embodiments to illustrate the present invention in detail. It should also be understood that the following embodiments are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention.

[0053] Embodiment 1

[0054] A droplet target generator is assembled by a capillary tube with a length of 50 mm and a piezoelectric element with a thickness of 2 mm. The two ends are fixed and bonded, and the inner diameter of its nozzle is 30 μm. Under the parameter conditions of a pulse signal amplitude of 90 V, a pulse width of 75 μs, and a frequency of 10 Hz, deionized water droplets with a diameter of 35 μm can be stably ejected, as Figure 4 shown. Under the parameter conditions of a pulse signal amplitude of 125 V, a pulse width of 65 μs, and a frequency of 100 Hz, gallium-indium-tin alloy droplets with a diameter of 50 μm can be stably ejected.

[0055] In summary, a droplet target generating device for an EUV light source provided by the present invention includes: a liquid supply assembly, a droplet ejection assembly, and a piezoelectric drive assembly; the liquid supply assembly includes a pressure controller and a liquid reservoir connected to the pressure controller through a pipeline; the droplet ejection assembly includes a capillary tube with a nozzle; the side of the capillary tube facing away from the nozzle is connected to the liquid reservoir through a pipeline; the piezoelectric drive assembly includes at least one piezoelectric element sleeved on the outer wall of the capillary tube and a drive signal controller electrically connected to the piezoelectric element. The present invention applies a positive pressure to the solution in the liquid reservoir by the pressure controller to supply the liquid droplets to the nozzle until the jet is extruded, and then switches to a negative pressure to force the termination of the jet. The nozzle mouth maintains a meniscus facing inward. Then, the piezoelectric element is driven by the drive signal controller, and positive and negative alternating acoustic pressure waves are generated in the liquid in the capillary tube by the deformation of the piezoelectric element. The acoustic pressure waves are transmitted to the nozzle mouth to eject the liquid droplets; moreover, by setting the parameters of the drive signal controller, the device can obtain the generation of stable liquid droplets with different frequencies, has simple operation, precise control, a large adjustable range, can generate stable large-spacing monodisperse liquid droplets, and is suitable for the generation of droplet targets in EUV light sources.

[0056] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A droplet target generating device for an EUV light source, characterized in that, include: a liquid supply assembly comprising an air pressure controller and a liquid reservoir connected to the air pressure controller via a pipeline; a droplet ejection assembly including a capillary tube with a nozzle; The side of the capillary tube facing away from the nozzle is connected to the liquid reservoir through a pipeline; The piezoelectric driving component comprises at least one piezoelectric element sleeved on the outer wall of the capillary tube and a driving signal controller electrically connected to the piezoelectric element.

2. The droplet target generating device for an EUV light source according to claim 1, wherein, The liquid reservoir includes a liquid storage cavity and a top cover arranged on the top of the liquid storage cavity; the top cover is provided with an air passage, and the air passage is connected to the air pressure controller through a pipeline.

3. The droplet target generating device for an EUV light source according to claim 1, wherein A filter is provided on the side of the capillary tube facing away from the nozzle, and the liquid reservoir is connected to the capillary tube through the filter.

4. The droplet target generating device for an EUV light source according to claim 3, characterized in that, The filter is provided with a filter membrane.

5. The droplet target generating device for an EUV light source according to claim 3, characterized in that, The liquid reservoir, the filter and the capillary tube are connected by a detachable Luer connector.

6. The droplet target generating device for EUV light source according to claim 1, characterized in that, The inner diameter of the nozzle is 10 μm-50 μm.

7. The droplet target generating device for an EUV light source according to claim 1, characterized in that, The control gas of the air pressure controller is an inert gas; the inert gas includes nitrogen or argon.

8. The droplet target generating device for EUV light source according to claim 1, characterized in that, The piezoelectric element is provided with a capillary fixing hole, the outer wall of the capillary is fitted with the inner side of the capillary fixing hole, and an epoxy resin layer is provided on the fitting surface of the capillary and the capillary fixing hole.

9. The droplet target generating device for an EUV light source according to claim 1, characterized in that, The driving signal controller is used to set the droplet target generation parameters and control the piezoelectric element; the droplet target generation parameters include one or more of pulse signal, signal amplitude, pulse width, frequency, rising edge time and falling edge time.

10. The droplet target generating device for an EUV light source according to claim 1, characterized in that, The droplet target generating device for an EUV light source further includes a heating and heat-insulating layer that wraps the liquid reservoir and the capillary.

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