An easy-to-maintain extreme ultraviolet light source droplet tin target supply device

Abstract

The present invention provides an easy-to-maintain extreme ultraviolet light source droplet tin target supply device. The present invention includes a valve body and an acoustic generation and propagation device arranged in the valve body, the two ends of the valve body are respectively provided with a first end cover plate and a second end cover plate, the output end of the acoustic generation and propagation device is connected to the target material chamber, the first end cover plate is provided with a small hole connected to the chamber, the outside of the valve body is detachably sleeved with a temperature regulating device, the second end cover plate is connected with a pressurizing pipeline that can extend into the valve body, the pressurizing pipeline is used to pressurize the target material chamber to obtain a continuous tin jet flow, the temperature regulating device is used to heat the valve body, the acoustic generation and propagation device is used to convert the continuous tin jet flow into a stable tin droplet flow, and the acoustic generation and propagation device is equipped with an active refrigeration device for cooling it. The present invention is more convenient in the later maintenance of the valve body, and can greatly shorten the maintenance time in the production process.

Description

Technical Field

[0001] The present invention relates to the field of EUV (Extreme Ultraviolet) light sources, and in particular to an easy-to-maintain EUV light source droplet tin target supply device. Background Art

[0002] The semiconductor manufacturing industry is developing rapidly, and the main lithography technology at this stage is EUVL (Extreme Ultraviolet Lithography). EUVL technology uses light with a wavelength of 13.5nm in the extreme ultraviolet band as the light source of the lithography machine to etch chips. Because the 13.5nm wavelength of light used is very short, EUVL can achieve very high chip etching accuracy. The LPP (Laser Produced Plasma) light source is currently the mainstream EUV light source in the industry. Its principle is that a high-power carbon dioxide laser is focused and interacts with the continuous tin droplets produced by a liquid tin target supply device. Under the irradiation of the laser, the tin droplets vaporize and further ionize to emit 13.5nm EUV light. The EUV light is then collected by a large-aperture mirror to obtain higher-power EUV light. The peak power at the focus of the current commercial EUV lithography light source can reach 150W or more. During chip manufacturing, the EUV light source needs to operate stably at high frequencies (on the order of kHz). In addition, the EUV light source droplet tin target supply device has a high operating temperature, and the tin is solid at room temperature, making it difficult to maintain and replace parts. This poses a great challenge to the subsequent maintenance of the EUV light source droplet tin target supply device. Summary of the Invention

[0003] In response to the current status of LPP light source research, this patent aims to provide a droplet tin target supply device that is easy to maintain for the extreme ultraviolet light source, aiming to solve the problems of difficult and long maintenance of the tin target in current research. The technical means adopted by this invention are as follows:

[0004] A device for supplying tin targets with an extreme ultraviolet light source that is easy to maintain, comprising a valve body and an acoustic generation and propagation device arranged in the valve body, wherein a first end cover plate and a second end cover plate are respectively provided at both ends of the valve body, an output end of the acoustic generation and propagation device is connected to a target material chamber, a small hole connected to the chamber is provided on the first end cover plate, a temperature regulating device is detachably sleeved on the outside of the valve body, a pressurizing pipeline that can extend into the valve body is connected to the second end cover plate, the pressurizing pipeline is used to pressurize the target material chamber to obtain a continuous tin jet stream, the temperature regulating device is used to heat the valve body, the acoustic generation and propagation device is used to convert the continuous tin jet stream into a stable tin droplet stream, and the acoustic generation and propagation device is equipped with an active refrigeration device for cooling it.

[0005] Furthermore, the temperature regulating device includes a precise heating interlayer, which is used to provide precise temperature control inside the valve body to ensure that the tin always remains in liquid form. The temperature regulating device includes an interlayer shell, a heating rod and a temperature probe. The heating rod is installed on the interlayer shell. By reading the temperature at the temperature probe, the voltage at both ends of each heating rod is feedback-regulated.

[0006] Furthermore, a plurality of valve body slots are provided on the outside of the valve body, and protrusions matching the valve body slots are provided on the inside of the interlayer shell of the precision heating interlayer.

[0007] Furthermore, the valve body and the interlayer shell are made of different materials, and when heated, the expansion rate of the precise heating interlayer is greater than the expansion rate of the valve body.

[0008] Furthermore, the temperature regulating device is externally covered with a heat-insulating shell, and the inner wall of the heat-insulating shell is coated with a coating with high infrared reflectivity.

[0009] Furthermore, the output end of the acoustic generation and propagation device is an acoustic transmission rod, which is in direct contact with the liquid target material in the target material chamber. The acoustic transmission rod includes an interlayer and a transmission rod body. The acoustic transmission rod is used to transmit the generated acoustic vibration to the target material near the small hole, thereby driving the tin droplet generating device to produce stable tin droplets.

[0010] Furthermore, the acoustic generation and propagation device includes a piezoelectric ceramic and an acoustic transmission rod. The output end of the piezoelectric ceramic is connected to the acoustic transmission rod. A flexible gasket is placed between the piezoelectric ceramic cover and the tail of the acoustic transmission rod. The second end cover presses the piezoelectric ceramic, and a buffer is added between them to isolate the sound. The size, spacing, and frequency of the formed tin droplet target are adjusted based on the excitation signal of the piezoelectric ceramic.

[0011] Furthermore, the refrigeration module includes refrigeration fins and / or liquid cooling pipelines, and the active refrigeration module is located outside the valve body.

[0012] The present invention has the following advantages:

[0013] Compared to previous tin droplet target material supply devices, this device produces tin droplets that are more convenient for valve body replacement while ensuring high stability and high efficiency. After the tin target material in the valve body is sprayed, the valve body and the precision heating interlayer can be easily separated by cooling. The special design makes the valve body heating more efficient and the heating element easier to replace. Utilizing this invention, extremely high spatial stability and excellent high-frequency repeatability of the tin droplets can be achieved, thus providing an excellent tin droplet beam source for the LPP light source. It also makes subsequent maintenance of the valve body more convenient, significantly reducing maintenance time during the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0015] Figure 1 A schematic structural diagram of an easy-to-maintain extreme ultraviolet light source droplet tin target supply device provided by an embodiment of the present invention;

[0016] Figure 2 (a) Yes Figure 1 A cross-sectional diagram of Figure 2 (b) Yes Figure 1 Right view of .

[0017] Figure 3 Schematic diagram of the structure of the valve body in an embodiment of the present invention.

[0018] Figure 4 Schematic diagram of the structure of the precise heating interlayer in an embodiment of the present invention.

[0019] Figure 5 Schematic diagram of the position of the small holes of the present invention, (a), (b), and (c) are three different designs.

[0020] Figure 6 The diagram is a schematic diagram of a supply tank of a liquid droplet tin target supply device for an extreme ultraviolet light source.

[0021] In the figure: 1. First end cover plate; 2. Second end cover plate; 3. Valve body; 4. Precision heating interlayer; 5. Insulation shell; 6. Active cooling module; 7. Piezoelectric ceramics; 8. Acoustic transmission rod tail pressure plate; 9. Piezoelectric ceramic cover plate; 10. Acoustic transmission rod; 11. Acoustic transmission rod head pressure plate; 12. Filter; 13. Sealer; 14. Small hole; 15. Heating rod; 16. Pressurized pipeline; 17. Valve body slot; 18. Bump; 19. Heating rod slot; 20. Precision heating interlayer fixing pressure foot. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0023] An embodiment of the present invention provides a droplet tin target supply device for an extreme ultraviolet light source. When the device is operating, vibration excitation is generated by an acoustic generating device, and is transmitted to the tin droplet vibration chamber through an acoustic propagation device, causing the tin jet to produce Rayleigh rupture, thereby obtaining a tin droplet target with extremely high spatial stability and good high-frequency repeatability. Moreover, by changing the excitation waveform of the acoustic generating device, the generated tin droplet target can be frequency modulated. In addition, changing the pressure difference on both sides of the orifice can also adjust the size of the tin droplets and the spacing between the tin droplets. This can save time when replacing the valve body of the droplet tin target supply device and repairing the heating structure in the later stage.

[0024] like Figure 1 、 Figure 2 As shown, the embodiment of the present invention discloses an easy-to-maintain extreme ultraviolet light source droplet tin target supply device, including Figure 3 The valve body 3 shown and the acoustic generation and propagation device disposed therein are provided with a first end cover plate 1 and a second end cover plate 2 at each end of the valve body. The output end of the acoustic generation and propagation device is connected to the target chamber, and the acoustic generation and propagation device are mounted on the second end cover plate. The first end cover plate is provided with a small hole connected to the chamber. A temperature adjustment device is detachably mounted on the exterior of the valve body, and a pressurizing line that can extend into the valve body is connected to the second end cover plate. The pressurizing line is used to pressurize the target chamber to produce a continuous tin jet stream. The temperature adjustment device is used to heat the valve body, and the acoustic generation and propagation device is used to convert the continuous tin jet stream into a stable stream of tin droplets. The acoustic generation and propagation device is equipped with an active cooling device 6 for cooling it. In some embodiments, the assembly between the above components is independent installation. In some embodiments, the components are not independently installed.

[0025] In some embodiments, since tin can react with oxygen in the air when molten, the tiny particles of tin oxide formed by the reaction will be distributed near the small hole 14, interfering with the formation of a stable tin droplet target. Therefore, the main body of the device is in a vacuum environment during operation.

[0026] As an optional embodiment, the first end cover plate and the valve body and the second end cover plate and the valve body are pressed tightly to squeeze the gaskets between the surfaces to achieve a seal. As another optional embodiment, the first end cover plate and the valve body and the second end cover plate and the valve body are sealed by bonding or welding.

[0027] The temperature regulating device includes Figure 4The precision heating interlayer 4 shown is used to provide precise temperature control within the valve body, ensuring that the tin remains in a liquid state. In this embodiment, the precision heating interlayer integrates a feedback heating system. The temperature control device includes an interlayer housing, heating rods, and temperature probes. The heating rods are mounted on the interlayer housing via heating plate slots 19. Specifically, the heating rod slots 19 are located outside the precision heating interlayer 4, facilitating the replacement of damaged heating rods. By reading the temperature at the temperature probes, the voltage across each heating rod is feedback-adjusted, forming a closed-loop control. This ensures that the temperature of the tin-containing area in the valve body reaches or exceeds the melting point of the tin through feedback control. In this embodiment, two or more heating rods are inserted into different perforations of the precision heating interlayer. When the liquid tin target supply device is in operation, the number of heating rods can be adjusted based on the required heating power. The temperature probes can be placed in the tin inside the valve body. The temperature probes can be thermistors or thermocouples. Thermally conductive silicone grease can also be applied between the heating rods and the heating rod slots 19 to achieve better heating results.

[0028] As another optional embodiment, the precise heating interlayer 4 can be heated by wrapping a surrounding heating belt. The heating belt and the temperature value returned by the temperature sensor immersed in the tin liquid inside the valve body 3 are adjusted to form a closed loop control.

[0029] To increase the thermal conductivity between the valve body and the precision heating interlayer, a preferred embodiment features a sliding slot in the valve body sidewall that mates with the precision heating interlayer, increasing the contact area between the valve body 3 and the precision heating interlayer 4. The interlayer shell of the precision heating interlayer is equipped with a bump 18 that mates with the valve body slot 17. This effectively increases the contact area during heating. Furthermore, this slide-like design ensures a more precise concentric fit between the valve body 3 and the precision heating interlayer 4, facilitating installation.

[0030] As a preferred embodiment, the valve body and interlayer shell are made of different materials. During heating, the expansion rate of the precision heating interlayer is greater than that of the valve body. The valve body is made of stainless steel, while the precision heating interlayer is made of oxygen-free copper or aircraft aluminum. This allows for tight contact between the valve body 3 and the precision heating interlayer 4. These design considerations significantly improve the heating efficiency of the precision heating interlayer.

[0031] The heat of the precise heating interlayer 4 is effectively transmitted to the valve body 3 as much as possible. In order to minimize the external transmission as much as possible, it is necessary to assemble a heat-insulating shell 5 on the outside of the precise heating interlayer 4. Therefore, as an optional embodiment, the outer sleeve of the temperature regulating device is provided with a heat-insulating shell 5, and the inner wall of the heat-insulating shell is coated with an infrared light high reflectivity coating, the purpose of which is to reduce the heat diffusion of the precise heating interlayer used to heat the outside of the valve body, and reflect the external heat radiation of the precise heating interlayer 4 back to the inside of the heat-insulating shell 5 to reduce heat loss. The heat-insulating shell can prevent the heat loss caused by the heat radiation on the surface of the precise heating interlayer, and also facilitate the assembly of the tin target supply device body and external components. The precise heating interlayer 4 is matched with the heat-insulating shell 5 through several precise heating interlayer fixed pressure feet 20, the purpose of which is to reduce the contact area between the two and reduce the heat conduction from the precise heating interlayer 4 to the outside.

[0032] Specifically, the small holes on the first end cover plate are secured by a specially designed small hole cover plate, which is then pressed together and sealed by squeezing a small hole cover plate gasket between the first end cover plate and the small hole cover plate. The small holes can be made of ceramic, diamond, stainless steel, chromium-nickel alloy, or other alloys. The small hole cover plate gasket can be made of a soft metal or alloy such as oxygen-free copper or silver.

[0033] In this embodiment, the number of the pressurized pipelines may be one or more, and the pressurized pipeline and the second end cover plate are sealed and connected by bonding or welding.

[0034] When the droplet tin target supply device is operating, the tin liquid chamber within valve body 3 is filled with tin liquid and is under positive pressure, maintained by pressurized pipe 16. Heating rods 15 are either fully or partially open to provide heating. Temperature feedback collected by temperature sensors distributed within valve body 3 allows for accurate evaluation of the heating profile. The heating principle ensures that the tin liquid within the tin liquid chamber of valve body 3 remains molten. At this point, the tin liquid is ejected from orifice 14 into the working environment.

[0035] In particular, in order to reduce the possibility of debris blocking the small hole 14, a filter 12 is added before the small hole 14 to filter the debris.

[0036] The second end cover plate integrates a piezoelectric ceramic driven acoustic generating unit, which is responsible for providing acoustic vibration. The acoustic generating and propagating device specifically includes piezoelectric ceramics and acoustic transmission rods. The output end of the piezoelectric ceramic 7 is connected to the acoustic transmission rod. In this embodiment, the piezoelectric ceramics are bonded to the acoustic transmission rod. The piezoelectric ceramics 7 are installed on the second end cover plate 2 through the piezoelectric ceramic cover plate 9. A flexible gasket is placed between the piezoelectric ceramic cover plate and the tail of the acoustic transmission rod. The second end cover plate presses the piezoelectric ceramics, which can ensure that the acoustic signal generated by the piezoelectric ceramics is more effectively transmitted to the other end of the acoustic transmission rod. A buffer is added between them to isolate the sound. The size, spacing, and frequency of the tin droplet target formed are adjusted based on the excitation signal of the piezoelectric ceramic. It should be noted that the tin liquid level in the tin liquid chamber inside the valve body 3 cannot contact the piezoelectric ceramic pressure plate to avoid damage to the piezoelectric ceramic due to excessive working temperature of the piezoelectric ceramic.

[0037] The output end of the acoustic generation and propagation device is an acoustic transmission rod 10, and the head and tail ends of the acoustic transmission rod are respectively installed on the tin liquid chamber and the piezoelectric ceramic through the acoustic transmission rod head pressure plate 11 and the acoustic transmission rod tail pressure plate 8. The acoustic transmission rod is in direct contact with the liquid target material in the target material chamber. Since the temperature of the liquid target material is above the melting temperature of the target material, it has exceeded the normal operating temperature of the piezoelectric ceramic. In order to reduce the heat conducted to the piezoelectric ceramic, the acoustic transmission rod adopts a sandwich design. Specifically, the acoustic transmission rod includes an interlayer and a transmission rod body, and the interlayer and the transmission rod body are connected by laser welding. The end of the acoustic transmission rod close to the small hole is also connected to the transmission rod body by laser welding, and the acoustic vibration generated by the piezoelectric ceramic is transmitted to the target material near the small hole, thereby driving the tin droplet generating device to produce stable tin droplets.

[0038] In particular, in order to enhance the acoustic vibration and make it propagate more effectively to the small hole 14 , a collector 13 is added before the small hole 14 to further collect the acoustic signal to the small hole 14 .

[0039] When in working state, the valve body 3 is in a high temperature state. In order to avoid the local temperature of the acoustic generating device 7 being too high, it is necessary to adopt active cooling. The active cooling module includes a cooling plate and / or a liquid cooling pipeline. The active cooling module is located outside the valve body, as close as possible to the fixed position of the piezoelectric ceramic to ensure that the acoustic generating device is not affected by high temperature. The liquid used for liquid cooling can be water, alcohol or oil, etc. Specifically, in some embodiments, the active cooling module 6 is a flat cooling plate. During assembly, it can be fixed to the second end cover plate 2 by bonding or welding. The active cooling module 6 is located outside the valve body 3 to facilitate the addition of external accessories such as liquid cooling. In some embodiments, the active cooling module 6 is a liquid nitrogen circulation pipeline. During assembly, it can be fixed to the second end cover plate 2 by bonding or welding. The active cooling module 6 is located outside the valve body 3 to facilitate the connection of an external liquid nitrogen supply device.

[0040] As a specific implementation, one or more conductive terminals are integrated on the second end cover plate for connecting the internal temperature probe of the tin target generating device and the acoustic generating device. The sealing can be achieved by bonding or welding.

[0041] refer to Figure 5 In Figures (a) to (c), the tin liquid chamber within valve body 3, near aperture 14, features a tapered design, which allows for better coupling of the acoustic vibration excitation signal to aperture 14. The operating pressure applied by pressurized line 16 primarily drops at aperture 14, so first end cover 1 is designed to gradually open away from aperture 14. This facilitates pressure bearing and prevents deformation of aperture 14 caused by excessive operating pressure.

[0042] In particular, since the first end cover plate 1 is at high temperature during operation, the assembly error caused by the thermal expansion and contraction of its assembled parts needs to be considered. Therefore, an interference fit is selected for the gasket at the small hole 14, and a material with a greater expansion rate than stainless steel is selected, such as silver.

[0043] The gasket mentioned in this embodiment can be made of metal, perfluororubber, polyimide, etc.

[0044] In some embodiments, the material of the small hole 14 can be ceramic, diamond, stainless steel, chrome-nickel alloy or other alloys. It is generally processed by ultrafast laser drilling or plasma drilling technology. The small hole can be a straight hole or a tapered hole.

[0045] In some embodiments, the pressure applied to the pressurized pipe 16 is 80 psi, a 100 KHz sinusoidal signal is applied to the piezoelectric ceramic, the aperture 14 is 25 μm, the outlet is 30 mm away, the tin droplet size is about 30 microns, the spacing is about 100 μm, and the frequency is 100 KHz.

[0046] This embodiment is achieved by Figure 6 The tin material supply tank is used to feed the device. It should be noted that the working environment temperature of the tank should be above the melting point of tin, and there are pressurizing end and discharging end.

[0047] The present invention provides a liquid tin target supply device with an easy-to-maintain extreme ultraviolet light source, providing a tin liquid target with extremely high spatial stability and good high-frequency repeatability. The device is simple to operate and reliable. Its detachable design facilitates replacement of the valve body (3) and some accessories.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An easy-to-maintain extreme ultraviolet light source droplet tin target supply device, characterized in that: It comprises a valve body and an acoustic generation and propagation device arranged in the valve body, wherein the two ends of the valve body are respectively provided with a first end cover plate and a second end cover plate, the output end of the acoustic generation and propagation device is connected to a target material chamber, the first end cover plate is provided with a small hole connected to the chamber, the outside of the valve body is detachably sleeved with a temperature regulating device, the second end cover plate is connected with a pressurizing pipeline that can extend into the valve body, the pressurizing pipeline is used to pressurize the target material chamber to obtain a continuous tin jet flow, the temperature regulating device is used to heat the valve body, the acoustic generation and propagation device is used to convert the continuous tin jet flow into a stable tin droplet flow, and the acoustic generation and propagation device is equipped with an active cooling device for cooling the temperature thereof; The output end of the acoustic generation and propagation device is an acoustic transmission rod, which is in direct contact with the liquid target material in the target material chamber. The acoustic transmission rod includes an interlayer and a transmission rod body. The acoustic transmission rod is used to transmit the generated acoustic vibration to the target material near the small hole, thereby driving the tin droplet generation device to generate stable tin droplets. The acoustic generation and propagation device includes piezoelectric ceramics and an acoustic transmission rod. The output end of the piezoelectric ceramics is connected to the acoustic transmission rod. A flexible gasket is placed between the piezoelectric ceramic cover plate and the tail of the acoustic transmission rod. The second end cover plate presses the piezoelectric ceramics, and a buffer is added between them to isolate the sound. The size, spacing and frequency of the formed tin droplet target are adjusted based on the excitation signal of the piezoelectric ceramics.

2. The easy-to-maintain extreme ultraviolet light source droplet tin target supply device according to claim 1, characterized in that: The temperature regulating device includes a precise heating interlayer, which is used to provide precise temperature control inside the valve body to ensure that the tin always remains in liquid form. The temperature regulating device includes an interlayer shell, a heating rod and a temperature probe. The heating rod is installed on the interlayer shell. By reading the temperature at the temperature probe, the voltage at both ends of each heating rod is feedback-regulated.

3. The easy-to-maintain extreme ultraviolet light source droplet tin target supply device according to claim 2, characterized in that: The exterior of the valve body is provided with a plurality of valve body slots, and the interior of the sandwich shell of the precision heating sandwich is provided with protrusions matching the valve body slots.

4. The easy-to-maintain extreme ultraviolet light source droplet tin target supply device according to claim 2 or 3, characterized in that: The valve body and the sandwich shell are made of different materials. When heated, the expansion rate of the precise heating sandwich is greater than the expansion rate of the valve body.

5. The easy-to-maintain extreme ultraviolet light source droplet tin target supply device according to any one of claims 1 to 3, characterized in that: The temperature regulating device is externally covered with a heat-insulating shell, and the inner wall of the heat-insulating shell is coated with an infrared light high-reflectivity coating.

6. The easy-to-maintain extreme ultraviolet light source droplet tin target supply device according to claim 1, characterized in that: The refrigeration module includes refrigeration fins and / or liquid cooling pipelines, and the active refrigeration module is located outside the valve body.

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