Uniform tin droplet target generating device for inhibiting axial shaking of tin droplets

Abstract

The invention provides a uniform tin droplet target generating device for inhibiting axial shaking of tin droplets, which comprises a crucible, tin melt, a nozzle, a heating assembly and a disturbance assembly, the tin melt is located inside the crucible, and the heating assembly is located outside the crucible and is used for heating the tin melt in the crucible; the nozzle is located at the bottom of the crucible and used for spraying uniform tin liquid drops and reducing axial shaking of the tin liquid drops. The disturbance assembly comprises a signal generator, a piezoelectric transducer and a vibration transmission rod, the vibration transmission rod is located in the molten tin, the piezoelectric transducer is located above the crucible and connected with the vibration transmission rod through a connecting piece, and the signal generator is connected with the piezoelectric transducer; a sine disturbance signal generated by the signal generator is provided for the vibration transmission rod through the piezoelectric transducer, and the disturbance signal is transmitted into molten tin through the vibration transmission rod, so that the jetted tin jet flow is broken into uniform liquid drop flow; according to the device provided by the invention, the distance between the liquid drops can be regulated and controlled; the designed nozzle can reduce the axial jitter of the liquid drop flow and increase the axial stability of the liquid drop.

Description

Technical Field

[0001] The present invention relates to the technical field of tin droplet target source generation, and particularly to a uniform tin droplet target generating device for suppressing the axial jitter of tin droplets. Background Art

[0002] Laser plasma technology uses high-power lasers to continuously bombard tiny tin droplets to generate high-power extreme ultraviolet light, which is one of the core technologies of commercial extreme ultraviolet lithography machines. The tin droplets are broken and atomized under the irradiation of high-power lasers, and at the same time, plasmas are generated. The plasmas generate extreme ultraviolet light under the further action of the lasers, and the extreme ultraviolet light source for lithography is obtained after extraction and purification. In this process, the spatial position stability of the tin droplets directly affects the laser bombardment effect and the plasma generation efficiency, and thus has an important impact on the power, brightness, and stability of the generated extreme ultraviolet light. The droplet spatial stability includes droplet lateral stability and droplet axial jitter. Among them, the droplet lateral stability can be adjusted by a multi-dimensional motion platform; the axial jitter is manifested as the non-uniformity of the droplet spacing, that is, the distance fluctuation between two adjacent droplets in the droplet flight direction; it is also manifested as the time deviation required for the droplets to reach a fixed position (laser action position). The axial jitter of the droplets will affect the synchronization between the laser and the droplets, resulting in difficulty in accurately irradiating the flying tin droplets with the laser, thereby reducing the energy conversion efficiency of the extreme ultraviolet light source. Therefore, suppressing the axial jitter of tin droplets is a key to improving the power stability of the light source.

[0003] A uniform droplet flow is generated by applying a periodic external perturbation to a laminar jet, forcing the jet to become unstable and break. Theoretically, the frequency of droplet generation is the same as the perturbation frequency, and the spacing between droplets is equal to the jet velocity divided by the perturbation frequency. In the process of generating a tin droplet flow using a conventional device, the driving pressure provides the velocity to form a jet, and the sinusoidal perturbation signal causes the jet to break into a uniform tin droplet flow. The device for applying the perturbation can be a piezoelectric ceramic tube adhered to the nozzle, a vibrating rod connected to the piezoelectric ceramic, a piezoelectric film, an alternating electric field, etc. The perturbation form can be divided into axial perturbation and radial perturbation. However, due to factors such as electrical noise during the perturbation application, unnecessary clutter is generated by the vibration device. Therefore, the perturbation at the jet inlet is a sinusoidal perturbation superimposed with other perturbation clutter, and these factors will cause severe axial jitter of the droplets, resulting in the laser being unable to accurately act on the tin droplets and affecting the stability of the extreme ultraviolet light source. Summary of the Invention

[0004] In order to solve the deficiencies existing in the prior art, a uniform tin droplet target generating device for suppressing the axial jitter of tin droplets provided by the present invention is mainly used to generate uniform tin droplets with stable spatial positions. By applying a perturbation through a vibrating rod, the droplet spacing is increased; by dissipating the energy of low-frequency clutter in the cavity part of the designed nozzle, the axial jitter of the droplets is reduced.

[0005] A uniform tin droplet target generating device for suppressing the axial jitter of tin droplets provided by the present invention includes a crucible, a tin melt, a nozzle, a heating component, and a perturbation component; The tin melt is located inside the crucible, and the heating component is located outside the crucible for heating the tin melt in the crucible; The nozzle is located at the bottom of the crucible for spraying a tin jet and reducing the axial jitter of the tin jet; The perturbation component includes a signal generator, a piezoelectric transducer, and a vibration transmission rod. The vibration transmission rod is located in the tin melt, the piezoelectric transducer is located above the crucible and is connected to the vibration transmission rod through a connecting member, and the signal generator is connected to the piezoelectric transducer; the perturbation signal generated by the signal generator is provided to the vibration transmission rod through the piezoelectric transducer, and the perturbation signal is introduced into the tin melt through the vibration transmission rod to break the sprayed tin jet into a uniform droplet flow.

[0006] Further, the heating component includes a heating furnace and a temperature controller. The heating furnace is located around the crucible, and the temperature controller is connected to the heating furnace for controlling the temperature of the heating furnace.

[0007] Further, the device further includes a vacuum component, which consists of a vacuum chamber and a vacuum pump. The vacuum pump is connected to the vacuum chamber for controlling the vacuum degree in the vacuum chamber; The vacuum chamber is located outside the heating component and the nozzle, and the connecting member is located above the vacuum chamber. The crucible is connected to the vacuum chamber through the connecting member.

[0008] Further, the device further includes a pressure module, which is connected to the crucible through a connecting member for controlling the working pressure of the crucible and providing the pressure for the nozzle to generate a tin jet.

[0009] Further, the nozzle is connected to the crucible through a nozzle connection assembly, and a flexible filter screen is further provided on the nozzle connection assembly. The flexible filter screen is located between the crucible and the nozzle for filtering tiny impurities in the tin melt.

[0010] Further, the nozzle is sequentially connected from bottom to top by a hollow cylindrical cavity, a cylindrical neck, and a tail hollow cylindrical cavity. The diameter of the cylindrical neck is smaller than the diameters of the hollow cylindrical cavity and the tail hollow cylindrical cavity, and the length of the cylindrical neck is greater than the length of the hollow cylindrical cavity.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: The tin droplet target generating device with a nozzle that can regulate the droplet spacing and reduce the axial jitter of droplets to achieve uniform tin droplets provided by the present invention regulates the amplitude of the working frequency by regulating the amplifier voltage, thereby regulating the droplet spacing. At the same time, the micro-vortices generated in the cavity of the designed nozzle dissipate the energy of the fluid clutter disturbance, minimizing the transmission path of the clutter to the greatest extent, playing a role in filtering (attenuating) the clutter, reducing the axial jitter of the droplet flow, and increasing the axial stability of the droplets. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below. It should be understood that the following described drawings only relate to some embodiments of the present disclosure and do not limit the present disclosure, where: Figure 1 is a schematic structural diagram of a uniform tin droplet target generating device for suppressing the axial jitter of tin droplets provided by the present invention.

[0013] Figure 2 is a schematic structural diagram of the nozzle provided by the present invention and its internal flow line diagram, where (a) is the schematic structural diagram of the nozzle, (b) is the schematic design principle diagram of the nozzle structure, and (c) is the instantaneous velocity flow line diagram of the fluid inside the nozzle.

[0014] 1 - Vacuum chamber, 2 - Vacuum pump, 3 - Temperature controller, 4 - Heating furnace, 5 - Crucible, 6 - Signal generator, 7 - Piezoelectric transducer, 8 - Vibration rod, 9 - Connector, 10 - Pressure module, 11 - Tin melt, 12 - Nozzle connection assembly, 13 - Flexible filter screen, 14 - Nozzle, 15 - Cylindrical neck, 16 - Hollow cylindrical cavity, 17 - Tail hollow cylindrical cavity. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the present invention claimed, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0017] It should be noted that like reference numerals and letters denote like items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0018] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "axis", "longitudinal", "transverse", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0019] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0020] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0021] The present invention provides a uniform tin droplet target generating device for suppressing the axial jitter of tin droplets. The device includes a crucible 5, a tin melt 11, a nozzle 14, a pressure module, a heating assembly, a perturbation assembly, and a vacuum assembly; the heating assembly includes a heating furnace 4 and a temperature controller 3, the perturbation assembly includes a signal generator 6, a piezoelectric transducer 7, and a vibration transmission rod 8; the vacuum assembly consists of a vacuum chamber 1 and a vacuum pump 2; The tin melt 11 is located inside the crucible 5, and the heating component is located outside the crucible 5 for heating the tin melt 11 in the crucible 5; the heating furnace 4 is located around the crucible 5, and the temperature controller 3 is connected to the heating furnace 4 for controlling the temperature of the heating furnace 4; the pressure module 10 is connected to the crucible 5 through the connecting member 9 for providing the pressure to generate the tin jet; the vibration transfer rod 8 is located in the tin melt 11, the piezoelectric transducer 7 is located above the crucible 5 and is connected to the vibration transfer rod 8 through the connecting member 9, and the signal generator 6 is connected to the piezoelectric transducer 7; the disturbance signal generated by the signal generator 6 is provided to the vibration transfer rod 8 through the piezoelectric transducer 7, and the disturbance signal is introduced into the tin melt 11 through the vibration transfer rod 8, so that the ejected tin jet is broken into a uniform droplet flow.

[0022] In some embodiments of the present invention, the temperature controller 3 controls the heating furnace 4 to heat the tin material in the crucible 5 into the molten tin melt 11 and keep the tin melt 11 at a constant temperature; the pressure module 10 is connected to the crucible 5 through the connecting member 9, and applies pressure to make the tin melt 11 eject from the nozzle 14 to form a tin jet; the signal generator 6 outputs a driving signal to control the piezoelectric transducer 7, and the vibration rod 8 is connected below the piezoelectric transducer 7 to introduce the output excitation disturbance into the molten tin melt 11, so that the tin jet is broken into a uniform tin droplet flow.

[0023] The nozzle 14 is located at the bottom of the crucible 5 for ejecting the tin jet and reducing the axial jitter of the tin jet; the nozzle 14 is connected to the crucible 5 through the nozzle connection assembly 12. Among them, a flexible filter screen 13 is further provided on the nozzle connection assembly 12. The flexible filter screen 13 is located between the crucible 5 and the nozzle 14 for filtering out the tiny impurities in the tin melt 11.

[0024] In some embodiments of the present invention, the nozzle connection assembly 12 connects the nozzle 14 below the crucible 5, and the flexible filter screen 13 filters out the tiny impurities in the tin melt 11 to obtain a clean tin melt. Among them, the aperture size of the nozzle 14 can control the size of the tin jet.

[0025] The nozzle 14 is successively composed of a hollow cylindrical cavity 16, a cylindrical neck 15 and a tail hollow cylindrical cavity 17 from bottom to top. The diameter of the cylindrical neck 15 is smaller than the diameters of the hollow cylindrical cavity 16 and the tail hollow cylindrical cavity 17, and the length of the cylindrical neck 15 is greater than the length of the hollow cylindrical cavity 16.

[0026] In some embodiments of the present invention, as Figure 2 shown, the resonance frequency of the nozzle 14 is , where f H is the resonance frequency, C0 is the adiabatic sound speed. A is the cross-sectional area of the neck, V is the volume of the cavity, d1, L1 and d2, L2 are the diameters and actual lengths of the cylindrical neck 15 and the hollow cylindrical cavity 16 respectively; L cis the effective length of the neck with an end correction coefficient, and the end correction coefficient is an important parameter for obtaining an accurate resonance frequency value. The effective length is L c = L + 0.85d1; During the process that the tin melt 11 forms a tin jet through the nozzle 14, the tin melt 11 successively passes through the tail hollow cylindrical cavity 17, the cylindrical neck 15, and the hollow cylindrical cavity 16. When the tin melt 11 passes through the cylindrical neck 15, the energy of the fluid clutter disturbance is dissipated through the micro-vortex flow generated in the cavity, thereby reducing the transmission path of the clutter and playing a role in filtering or attenuating the clutter.

[0027] The vacuum pump 2 is connected to the vacuum chamber 1 and is used to control the vacuum degree in the vacuum chamber 1; the vacuum chamber 1 is located outside the heating assembly and the nozzle 14, and the connecting member 9 is located above the vacuum chamber 1. The crucible 5 is connected to the vacuum chamber 1 through the connecting member 9.

[0028] In some embodiments of the present invention, the vacuum pump 2 and the vacuum chamber 1 provide a vacuum environment inside the crucible 5 to prevent the tin liquid from being oxidized. The injection body is in the vacuum chamber 1, and the vacuum environment is achieved by pumping vacuum through the vacuum pump 2; the upper end of the crucible 5 is connected to the upper end of the vacuum chamber 1; the pressure module 10 enters the crucible 5 through the connecting member 9 above the vacuum chamber 1 to control the working pressure inside the crucible 5.

[0029] In some embodiments of the present invention, the crucible 5 is processed from stainless steel, forms a tin melt injection channel with the flexible filter screen 13 and the nozzle 14, and the whole device is evacuated to below 10 Pa before heating and then filled with an inert protective gas to prevent the tin melt 11 from being oxidized.

[0030] Working principle: First, clean the nozzle 14. Since the diameter of the nozzle 14 of the device of the present invention is small, the nozzle 14 may be blocked by dust in the air before starting work. To ensure that the nozzle 14 is not blocked, the cleaning and loading processes should be carried out in a clean room. Parts such as the nozzle 14, the flexible filter screen 13, and the nozzle connection assembly 12 are ultrasonically cleaned for 15 - 20 minutes respectively to remove the dust on the surface. Conduct a dredging inspection on the nozzle 14 to ensure that the nozzle 14 is unblocked, unbroken, and has a good jet condition. After cleaning, connect the nozzle 14 to the crucible 5 through the nozzle connection assembly 12 and add solder. The heating furnace 4 is installed outside the crucible 5 and is connected to the vacuum chamber 1 through the connecting piece 9. After installation, it is moved into the vacuum chamber 1. The heating component of the crucible 5 is connected to the temperature controller 3. Open the valve connecting the vacuum pump 2 to the crucible 5 and the vacuum chamber 1. At this time, the pressure module 10 is closed, and the inside of the crucible 5 and the vacuum chamber 1 are evacuated to a pressure below 10 Pa. Adjust the heating parameters to make the set temperature value of the temperature controller 3 slightly higher than the melting point of the solid metal, and heat the solder to melt it into a tin melt 11. The upper part of the crucible 5 is connected to the air pressure, and the tin melt 11 flows to the flexible filter screen 13 and then into the nozzle 14. The pressure module 10 adjusts the back pressure in the crucible 5 to obtain a tin jet ejected from the nozzle 14. The signal generator 6 generates a sinusoidal disturbance signal and applies it to the piezoelectric transducer 7, which is transmitted into the tin melt 11 by the vibration transmission rod 8, and the tin jet breaks into a uniform droplet flow. By regulating the voltage of the signal generator 6, the disturbance amplitude of the vibration transmission rod 7 is further regulated, so as to regulate the droplet spacing and make the ejected tin droplets uniform and controllable.

[0031] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A uniform tin droplet target generating device for suppressing axial vibration of tin droplets, characterized in that: The device comprises a crucible (5), molten tin (11), a nozzle (14), a heating component and a disturbance component; The tin melt (11) is located inside the crucible (5), and the heating component is located outside the crucible (5) and is used to heat the tin melt (11) in the crucible (5); The nozzle (14) is located at the bottom of the crucible and is used to spray the tin jet and reduce the axial vibration of the tin jet; The disturbance component comprises a signal generator (6), a piezoelectric transducer (7) and a vibration transmission rod (8); the vibration transmission rod (8) is located in the tin melt (11); the piezoelectric transducer (7) is located above the crucible (5) and is connected to the vibration transmission rod (8) via a connecting piece (9); the signal generator (6) is connected to the piezoelectric transducer (7); a disturbance signal generated by the signal generator (6) is provided to the vibration transmission rod (8) via the piezoelectric transducer (7); the disturbance signal is transmitted to the tin melt (11) via the vibration transmission rod (8), so that the ejected tin jet is broken into a uniform droplet flow.

2. The uniform tin droplet target generating device for suppressing axial vibration of tin droplets according to claim 1, characterized in that: The heating assembly comprises a heating furnace (4) and a temperature controller (3); the heating furnace (4) is located around the crucible (5); and the temperature controller (3) is connected to the heating furnace (4) and is used to control the temperature of the heating furnace (4).

3. The uniform tin droplet target generating device for suppressing axial vibration of tin droplets according to claim 1, characterized in that: The device further comprises a vacuum component, the vacuum component comprising a vacuum chamber (1) and a vacuum pump (2), the vacuum pump (2) being connected to the vacuum chamber (1) and being used to control the vacuum degree in the vacuum chamber (1); The vacuum chamber (1) is located outside the heating component and the nozzle (14), and the connecting piece (9) is located above the vacuum chamber (1), and the crucible (5) is connected to the vacuum chamber (1) via the connecting piece (9).

4. The uniform tin droplet target generating device for suppressing axial vibration of tin droplets according to claim 3, characterized in that: The device further comprises a pressure module (10), wherein the pressure module (10) is connected to the crucible (5) via the connecting piece (9) and is used to control the working pressure of the crucible (5) and provide the nozzle (14) with pressure for generating a tin jet.

5. The uniform tin droplet target generating device for suppressing axial vibration of tin droplets according to claim 1, characterized in that: The nozzle (14) is connected to the crucible (5) via a nozzle connection assembly (12). A flexible filter screen (13) is also provided on the nozzle connection assembly (12). The flexible filter screen (13) is located between the crucible (5) and the nozzle (14) and is used to filter tiny impurities in the molten tin (11).

6. The uniform tin droplet target generating device for suppressing axial vibration of tin droplets according to claim 1, characterized in that: The nozzle (14) is composed of a hollow cylindrical cavity (16), a cylindrical neck (15) and a tail hollow cylindrical cavity (17) connected in sequence from bottom to top, the diameter of the cylindrical neck (15) is smaller than the diameters of the hollow cylindrical cavity (16) and the tail hollow cylindrical cavity (17), and the length of the cylindrical neck (15) is greater than the length of the hollow cylindrical cavity (16).

Images