Use method of target material circulating system and target material circulating system

Abstract

The invention belongs to the technical field of semiconductors, and discloses a use method of a target material circulating system and the target material circulating system. The application method of the target material circulating system comprises the following steps: S10, pre-oxidizing the target material circulating system; s20, the target material is placed in a storage assembly, and the storage assembly heats the target material to be in a liquid state; s30, the driving device drives the liquid target material to enter the liquid drop generator from the storage assembly; s40, the liquid drop generator and part of the liquid return assembly are placed in a vacuum environment, and the driving device drives the target material to drop into the liquid return assembly from the liquid drop generator; and S50, the liquid in the liquid return assembly flows back to the storage assembly. When the target material circulating system is used, the target material circulating system is firstly pre-oxidized, so that the oxygen potential in liquid metal is always kept in a specified range during the operation of a light source, and the protective layer can prevent alloy elements in steel from being dissolved by the liquid metal, so that impurities are prevented from being generated to block an outlet of a liquid drop generator; and long-time continuous circulating production is ensured.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for using a target material circulation system and a target material circulation system. Background Art

[0002] In recent years, as lithography technology has rapidly developed toward finer manufacturing, semiconductor production processes have been able to produce semiconductor devices with increasingly finer feature sizes. In the next generation of semiconductor production processes, microfabrication with a feature size of 70nm to 45nm will be required, and then microfabrication with a feature size of 32nm or less will be required. For example, in order to meet the demand for microfabrication with a feature size of 32nm or less, it is expected to develop an exposure device in which a system that generates extreme ultraviolet (EUV) light with a wavelength of about 13.5nm is combined with an optical system that reduces projection reflections.

[0003] Methods for generating EUV light include, but are not necessarily limited to, converting a material having an element (e.g., xenon, lithium, or tin) into a plasma state and emitting spectral lines in the EUV range. Laser-produced plasma ("LPP") methods are usually used to bombard tin metal (in the form of droplets, plates, strips, streams, or material clusters) with a high-energy pulsed laser to form the desired plasma that can radiate EUV. For this process, the plasma is usually generated in a sealed container (e.g., a vacuum chamber) and monitored using various types of metrology equipment.

[0004] In this process, the target material can be recycled. Since the target material is usually at a high temperature (several hundred degrees Celsius) when it is in liquid state, stainless steel alloy is usually used to transport tin liquid metal. Under the action of long-term operation, the stainless steel alloy interacts with the tin liquid metal to produce pollution sources including: i) corrosion products (mainly Fe, Ni, Cr, C, etc.) continuously generated by pipeline metal alloys under different operating temperatures, different liquid metal flow rates, etc.; ii) activation products (Po, Hg, Tl, Cs, Mn, etc.) from peeling, activation or fission of corrosion products. These impurities will clog the nozzle of the micron-sized droplet generator. At the same time, impurities will continue to accumulate with the operation of the EUV light source. The outlet diameter of the droplet generator used to drip target droplets is at the micron level, and impurities can easily clog the outlet. After clogging, the circulation has to be stopped and the outlet has to be shut down for dredging, which disrupts the production rhythm and reduces production efficiency.

[0005] Therefore, it is urgent to design a method for using a target material circulation system and a target material circulation system to solve the above problems. Summary of the invention

[0006] One object of the present invention is to provide a method for using a target material circulation system, which can reduce the generation of impurities by the reaction between the target material circulation system and the target material during use, thereby reducing the possibility of impurities clogging the outlet of the droplet generator, reducing the number of times the droplet generator is unblocked, and ensuring long-term continuous circulation production.

[0007] Another object of the present invention is to provide a target material circulation system, which reduces the possibility of impurities blocking the outlet of the droplet generator, reduces the number of times the droplet generator is unblocked, and ensures long-term continuous circulation production.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The method of using the target circulation system includes:

[0010] S10: pre-oxidizing the target material circulation system;

[0011] S20: placing the target material in a storage assembly, and the storage assembly heats the target material to a liquid state;

[0012] S30: driving the liquid target material from the storage assembly into the droplet generator by a driving device;

[0013] S40: placing the liquid droplet generator and part of the liquid return assembly in a vacuum environment, and driving the target material to drop from the liquid droplet generator into the liquid return assembly by a driving device;

[0014] S50: The liquid in the liquid return assembly flows back to the storage assembly.

[0015] As an optional solution, in the above S10, air or oxygen is introduced into the above target material circulation system.

[0016] As an optional solution, in the above S10, the pipelines, containers and valves in the above target material circulation system are heated.

[0017] As an optional solution, the heating temperature is between 200°C and 500°C.

[0018] As an optional solution, the driving device includes a liquid inlet driving component applied to the above S30 and a liquid dripping driving component applied to the above S40, and both the liquid inlet driving component and the liquid dripping driving component use gas as a power source.

[0019] A target material circulation system, wherein the method for using the target material circulation system is applied to the target material circulation system, and the target material circulation system comprises:

[0020] The storage assembly is used to store the target material, and the storage assembly can heat the target material to a liquid state;

[0021] A liquid inlet drive assembly, comprising a first high-pressure gas cylinder and a first air inlet pipe, wherein the first high-pressure gas cylinder and the storage assembly are connected via the first air inlet pipe;

[0022] A droplet generator and a liquid inlet pipe, wherein the droplet generator is connected to the storage assembly through the liquid inlet pipe, and the height of the first gas inlet pipe in the storage assembly is higher than the height of the liquid inlet pipe in the storage assembly, so that the gas pressure of the first high-pressure gas cylinder acts on the target material and drives the liquid target material into the droplet generator;

[0023] A droplet driving assembly, comprising a second high-pressure gas cylinder and a second air inlet pipe, wherein the second high-pressure gas cylinder and the droplet generator are connected via the second air inlet pipe;

[0024] The liquid return assembly and the vacuum chamber, the liquid return assembly is used to collect the target material dripping from the droplet generator and is connected to the storage assembly, at least the liquid outlet end of the droplet generator and at least the liquid collection end of the liquid return assembly are located in the vacuum chamber;

[0025] The first air inlet pipe, the second air inlet pipe, the liquid inlet pipe and the liquid return assembly can all be opened or cut off, and the storage assembly and the droplet generator are both provided with a pressure relief valve.

[0026] As an optional solution, the storage component includes:

[0027] A storage tank for storing target materials, wherein one end of the first air inlet pipe facing away from the first high-pressure gas cylinder is inserted into the storage tank, and one end of the liquid inlet pipe facing away from the droplet generator is inserted into the storage tank;

[0028] A heating element is attached to the outside of the storage tank and is configured to heat the storage tank.

[0029] As an optional solution, the heating element is arranged around the circumference of the storage tank.

[0030] As an optional solution, a thermometer is provided in the storage tank.

[0031] As an optional solution, a pressure gauge is provided on the top of the storage tank.

[0032] The beneficial effects of the present invention are:

[0033] The present invention provides a method for using a target material circulation system. The target material circulation system is first pre-oxidized, thereby forming an oxide film on the side of parts that can react with the target material, such as pipelines, valve bodies, and containers, which are in contact with the target material. The oxide film is more difficult to react with the target material, and the target material and the inside of the parts are isolated, so that during the operation of the light source, the oxygen potential in the liquid metal is always maintained within a specified range. The protective layer can protect the alloy elements in the steel from being dissolved by the liquid metal, thereby avoiding the generation of impurities that block the outlet of the droplet generator, reducing the number of times the droplet generator is unblocked, and ensuring long-term continuous circulation production.

[0034] The present invention also provides a target material circulation system. By operating the target material circulation system using the method for using the target material circulation system, the possibility of impurities blocking the outlet of the droplet generator is reduced, the number of times the droplet generator is unblocked is reduced, and long-term continuous circulation production is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a target material circulation system provided in an embodiment of the present invention.

[0036] In the figure:

[0037] 10. Storage assembly; 11. Storage tank; 12. Heating element; 13. Barometer; 14. Thermometer; 15. First pressure relief valve;

[0038] 20. Liquid inlet drive assembly; 21. First high-pressure gas cylinder; 22. First air inlet pipe; 221. First valve;

[0039] 30. droplet generator; 31. second pressure relief valve; 40. liquid inlet pipe; 41. second valve;

[0040] 50. dripping driving assembly; 51. second high-pressure gas cylinder; 52. second air inlet pipe; 521. third valve;

[0041] 60. Liquid return assembly; 61. Liquid collecting part; 62. Liquid return pipe; 621. Fourth valve; 70. Vacuum chamber; 80. Heating belt. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0043] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" 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 a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0045] In the description of this embodiment, the terms "upper", "lower", "left", "right" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0046] This embodiment provides a method for using a target material circulation system, which can reduce the generation of impurities by the reaction between the target material and the target material during use, thereby reducing the possibility of impurities blocking the outlet of the droplet generator 30, reducing the number of times the droplet generator 30 is unblocked, and ensuring long-term continuous circulation production. Figure 1 As shown, the method of using the target circulation system includes:

[0047] S10: pre-oxidizing the target material circulation system;

[0048] S20: placing the target material in the storage assembly 10, and the storage assembly 10 heats the target material to a liquid state;

[0049] S30: The driving device drives the liquid target material from the storage assembly 10 into the droplet generator 30;

[0050] S40: placing the droplet generator 30 and part of the liquid return assembly 60 in a vacuum environment, and driving the target material to drop from the droplet generator 30 into the liquid return assembly 60 by a driving device;

[0051] S50 : The liquid in the liquid return assembly 60 flows back into the storage assembly 10 .

[0052] When the target material circulation system is in use, the target material circulation system is first pre-oxidized, thereby forming an oxide film on the side of the parts that can react with the target material, such as pipes, valve bodies, and containers, which are in contact with the target material. The oxide film makes it more difficult for the target material to react, and the target material and the inside of the parts are isolated, so that during the operation of the light source, the oxygen potential in the liquid metal is always maintained within the specified range. The protective layer can prevent the alloy elements in the steel from being dissolved by the liquid metal, thereby avoiding the generation of impurities that block the outlet of the droplet generator 30, reducing the number of times the droplet generator 30 is unblocked, and ensuring long-term continuous circulation production.

[0053] Alternatively, if Figure 1 As shown, the driving device includes a liquid inlet driving assembly 20 applied to S30 and a liquid drop driving assembly 50 applied to S40, and both the liquid inlet driving assembly 20 and the liquid drop driving assembly 50 are powered by gas. The above circulation system uses gas lift circulation technology to drive the liquid target material from the storage assembly 10 to the droplet generator 30 through the liquid inlet driving assembly 20, and then drips the liquid target material from the droplet generator 30 into the liquid return assembly 60 through the liquid drop driving assembly 50, avoiding the use of electromagnetic pumps and the like to drive high-temperature liquids. Gas drive has lower cost and less energy consumption. Compared with electromagnetic pumps, it will not contact with high-temperature targets, thereby not causing drive failure, and thus not causing circulation failure.

[0054] Of course, in other embodiments, the driving device may also use an electromagnetic pump or the like to drive the liquid target material to achieve the purpose of circulation, which is not limited here.

[0055] Specifically, if Figure 1As shown, the circulation system includes the above-mentioned storage component 10, the above-mentioned liquid inlet drive component 20, the above-mentioned droplet generator 30, the liquid inlet pipe 40, the above-mentioned droplet drive component 50, the above-mentioned liquid return component 60 and the vacuum chamber 70. The storage component 10 is used to store the target material. The storage component 10 can heat the target material to a liquid state. For example, the target material is metal tin. The storage component 10 heats the metal tin to 231.9°C, and the metal tin melts into a liquid state; the liquid inlet drive component 20 includes a first high-pressure gas cylinder 21 and a first air inlet pipe 22, and the first high-pressure gas cylinder 21 and the storage component 10 are connected through the first air inlet pipe 22; the droplet generator 30 is connected to the storage component 10 through the liquid inlet pipe 40, and the height of the first air inlet pipe 22 in the storage component 10 is higher than the height of the liquid inlet pipe 40 in the storage component 10 so that The gas pressure of the first high-pressure gas cylinder 21 acts on the target material to drive the liquid target material into the droplet generator 30. It can be understood that the liquid level of the liquid target material is between the first air inlet pipe 22 and the liquid inlet pipe 40. The droplet driving assembly 50 includes a second high-pressure gas cylinder 51 and a second air inlet pipe 52. The second high-pressure gas cylinder 51 and the droplet generator 30 are connected through the second air inlet pipe 52. The liquid return assembly 60 is used to collect the target material dripping from the droplet generator 30 and is connected to the storage assembly 10. At least the liquid outlet end of the droplet generator 30 and at least the liquid collecting end of the liquid return assembly 60 are located in the vacuum chamber 70. The first air inlet pipe 22, the second air inlet pipe 52, the liquid inlet pipe 40 and the liquid return assembly 60 can all be opened or cut off, and the storage assembly 10 and the droplet generator 30 are provided with pressure relief valves.

[0056] The pressure relief valve on the storage component 10 is defined as the first pressure relief valve 15, and the pressure relief valve on the droplet generator 30 is defined as the second pressure relief valve 31. After the pre-oxidation of the circulation system is completed, the storage component 10 is first heated to heat the target material to complete melting; the first high-pressure gas cylinder 21 is opened, the first air inlet pipe 22 is opened, the first pressure relief valve 15 is closed, the liquid inlet pipe 40 is opened, and the second pressure relief valve 31 is opened. The vacuum chamber 70 is connected to the atmosphere, and the target material moves along the liquid inlet pipe 40 under the action of the air pressure. Enter the droplet generator 30 until the droplet generator 30 is filled with the target material, cut off the first air inlet pipe 22, and cut off the liquid inlet pipe 40; then, close the second pressure relief valve 31, evacuate the vacuum chamber 70, open the second high-pressure gas cylinder 51, open the second air inlet pipe 52, and the target material drips from the droplet generator 30 into the liquid return assembly 60 under its own weight; open the liquid return assembly 60, open the first pressure relief valve 15, and the target material in the liquid return assembly 60 flows back to the storage assembly 10.

[0057] The target material circulation system provided in this embodiment reduces the possibility of impurities blocking the outlet of the droplet generator, reduces the number of times the droplet generator is unblocked, and ensures long-term continuous circulation production.

[0058] Alternatively, if Figure 1As shown, the storage assembly 10 includes a storage tank 11 and a heating element 12. The storage tank 11 is used to store target materials. The end of the first air inlet pipe 22 away from the first high-pressure gas cylinder 21 is inserted into the storage tank 11, and the end of the liquid inlet pipe 40 away from the droplet generator 30 is inserted into the storage tank 11. The heating element 12 is attached to the outside of the storage tank 11, and the heating element 12 is configured to heat the storage tank 11. Through the above configuration, the storage tank 11 is heated by the heating element 12, thereby achieving the temperature increase of the target material in the storage tank 11.

[0059] Optionally, the heating element 12 is disposed around the storage tank 11. This can improve the heating efficiency and uniformity of the storage tank 11 by the heating element 12, and ensure that the target material is heated evenly.

[0060] Optionally, a thermometer 14 is provided in the storage tank 11. Through the above arrangement, the temperature of the target material can be reasonably controlled. Further, the thermometer 14 is connected to the heating element 12 in communication. When the temperature reaches the melting point of the target material, the heating element 12 stops heating.

[0061] Optionally, a pressure gauge 13 is provided on the top of the storage tank 11 to detect the air pressure in the storage tank 11 and thereby control the speed at which the target material enters the droplet generator 30 from the liquid inlet pipe 40 .

[0062] Optionally, the first high-pressure gas cylinder 21 and the second high-pressure gas cylinder 51 are filled with inert gas to prevent the gas from reacting with the target material to produce impurities, etc. Specifically, the inert gas includes argon, helium, neon, nitrogen, hydrogen and the like, and the gas in the first high-pressure gas cylinder 21 and the second high-pressure gas cylinder 51 can be a single gas or a mixed gas, which is not limited here.

[0063] At the same time, the use of inert gas avoids contact between the target and the air, and the droplets flow in a completely sealed structure, reducing the rate at which the target is oxidized. It is understandable that the use of pumps for driving will inevitably cause agitation of the liquid target and contact with the air. This method increases the contact area between the target and the air, which can easily cause oxidation of the target to form impurities and block the droplet generator 30.

[0064] Alternatively, if Figure 1 As shown, the liquid return assembly 60 includes a liquid collection member 61 and a liquid return pipe 62. The liquid collection member 61 is disposed below the droplet generator 30 and at least a portion of the liquid collection member 61 is located in the vacuum chamber 70. The liquid collection member 61 is connected to the storage assembly 10 through the liquid return pipe 62, and the liquid return pipe 62 can be opened or cut off. The liquid collection member 61 has a certain volume, and can collect liquid for a certain period of time and then open the liquid return pipe 62 for circulation.

[0065] Optionally, the liquid collecting member 61 can heat the target material to prevent the liquid target material from solidifying during the circulation process, thereby ensuring the fluidity of the liquid and further ensuring the smoothness of the circulation.

[0066] Optionally, heating belts 80 are provided in the liquid inlet pipe 40 and the liquid return pipe 62. The heating belts 80 can heat the pipelines in which they are located, that is, the pipelines through which the liquid target material passes have a heat preservation or heating effect, ensuring that the liquid will not solidify in the pipelines and ensuring that the liquid flows smoothly in the pipelines.

[0067] Optionally, the first air inlet pipe 22 , the second air inlet pipe 52 , the liquid inlet pipe 40 and the liquid return pipe 62 are all made of stainless steel, which has relatively stable performance and is not easy to react with the target material.

[0068] Optionally, an oxide film is formed on the inner side of the liquid inlet pipe 40 and the liquid return pipe 62 , and the oxide film acts as a sealing layer on the surface of the pipe to further prevent the target material from reacting with carbon or other elements in the liquid inlet pipe 40 or the liquid return pipe 62 to generate impurities.

[0069] Alternatively, if Figure 1 As shown, a first valve 221 is provided on the first air inlet pipe 22, and the first air inlet pipe 22 is opened and closed by switching the first valve 221. Preferably, the first valve 221 is a solenoid valve, which can be switched intelligently. In other embodiments, the first valve 221 can also be a manual valve, which is not limited here.

[0070] Optionally, a second valve 41 is provided on the liquid inlet pipe 40, and the liquid inlet pipe 40 is opened and closed by switching the second valve 41. Preferably, the second valve 41 is a solenoid valve, which can be switched intelligently. In other embodiments, the second valve 41 can also be a manual valve, which is not limited here.

[0071] Optionally, a third valve 521 is provided on the second air inlet pipe 52, and the second air inlet pipe 52 is opened and closed by switching the third valve 521. Preferably, the third valve 521 is a solenoid valve, which can be switched intelligently. In other embodiments, the third valve 521 can also be a manual valve, which is not limited here.

[0072] Optionally, a fourth valve 621 is provided on the liquid return pipe 62, and the opening and closing of the liquid return pipe 62 are realized by switching the fourth valve 621. Preferably, the fourth valve 621 is a solenoid valve, which can realize intelligent switching. In other embodiments, the fourth valve 621 can also be a manual valve, which is not limited here.

[0073] It should be noted that the generation of extreme ultraviolet light requires the use of lasers, which is not shown in the attached drawings. This structure is a prior art and will not be described in detail here.

[0074] Optionally, in S10, air or oxygen is introduced into the target material circulation system to increase the oxidation rate of the target material circulation system.

[0075] Furthermore, the target material circulation system is oxidized, and the oxidation of the pipes (liquid inlet pipe 40 and liquid return pipe 62), containers (storage tank 11, droplet generator 30 and liquid collecting part 61) and valves (second valve 41 and fourth valve 621) in contact with the target material in the oxidized parts plays a role in avoiding the generation of impurities.

[0076] In order to improve the oxidation effect, in S10, the pipes, containers and valves in the target material circulation system are heated. Heating can increase the degree of oxidation of each part, make the oxide film thicker, and improve the isolation effect of the oxide film on the target material.

[0077] Among them, the liquid inlet pipe 40 and the liquid return pipe 62 are heated by the heating belt 80, the storage tank 11 is heated by the heating element 12, and the surfaces of the droplet generator 30, the liquid collecting element 61, the second valve 41 and the fourth valve 621 can be heated by PCT, which is not limited here.

[0078] Optionally, the heating temperature is between 200°C and 500°C, and the preheating temperature does not exceed the maximum operating temperature of the equipment and instruments installed in the facility, ensuring the normal use of subsequent parts.

[0079] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for using a target material circulation system, characterized in that: include: S10: pre-oxidizing the target material circulation system; S20: placing the target material in a storage assembly (10), wherein the storage assembly (10) heats the target material to a liquid state; S30: driving the target material in liquid state from the storage assembly (10) into the droplet generator (30) by a driving device; S40: placing the liquid droplet generator (30) and part of the liquid return component (60) in a vacuum environment, and driving the target material to drop from the liquid droplet generator (30) into the liquid return component (60) by a driving device; S50: The liquid in the liquid return assembly (60) flows back into the storage assembly (10).

2. The method for using the target material circulation system according to claim 1, characterized in that: In S10, air or oxygen is introduced into the target material circulation system.

3. The method for using the target material circulation system according to claim 1, characterized in that: In S10, the pipelines, containers and valves in the target material circulation system are heated.

4. The method for using the target material circulation system according to claim 3, characterized in that: The heating temperature is between 200°C and 500°C.

5. The method for using the target material circulation system according to any one of claims 1 to 4, characterized in that: The driving device comprises a liquid inlet driving component (20) applied to the S30 and a liquid drop driving component (50) applied to the S40, and both the liquid inlet driving component (20) and the liquid drop driving component (50) use gas as a power source.

6. Target material circulation system, characterized in that: The method for using the target material circulation system according to any one of claims 1 to 5 is applied to the target material circulation system, and the target material circulation system comprises: The storage component (10) is used to store the target material, and the storage component (10) can heat the target material to a liquid state; A liquid inlet drive assembly (20), comprising a first high-pressure gas cylinder (21) and a first air inlet pipe (22), wherein the first high-pressure gas cylinder (21) and the storage assembly (10) are connected via the first air inlet pipe (22); a droplet generator (30) and a liquid inlet pipe (40), wherein the droplet generator (30) is connected to the storage assembly (10) through the liquid inlet pipe (40), and the height of the first gas inlet pipe (22) in the storage assembly (10) is higher than the height of the liquid inlet pipe (40) in the storage assembly (10), so that the gas pressure of the first high-pressure gas cylinder (21) acts on the target material and drives the liquid target material to enter the droplet generator (30); A liquid drop drive assembly (50), comprising a second high-pressure gas cylinder (51) and a second air inlet pipe (52), wherein the second high-pressure gas cylinder (51) and the liquid drop generator (30) are connected via the second air inlet pipe (52); The liquid return component (60) and the vacuum chamber (70), wherein the liquid return component (60) is used to collect the target material dripping from the liquid droplet generator (30) and is connected to the storage component (10), and at least the liquid outlet end of the liquid droplet generator (30) and at least the liquid collection end of the liquid return component (60) are located in the vacuum chamber (70); The first air inlet pipe (22), the second air inlet pipe (52), the liquid inlet pipe (40) and the liquid return assembly (60) can all be opened or cut off, and the storage assembly (10) and the liquid droplet generator (30) are both provided with a pressure relief valve.

7. The target material circulation system according to claim 6, characterized in that: The storage assembly (10) comprises: A storage tank (11) for storing target materials, wherein one end of the first gas inlet pipe (22) facing away from the first high-pressure gas cylinder (21) is inserted into the storage tank (11), and one end of the liquid inlet pipe (40) facing away from the droplet generator (30) is inserted into the storage tank (11); A heating element (12) is attached to the outside of the storage tank (11), and the heating element (12) is configured to heat the storage tank (11).

8. The target material circulation system according to claim 7, characterized in that: The heating element (12) is arranged around the circumference of the storage tank (11).

9. The target material circulation system according to claim 7, characterized in that: A thermometer (14) is arranged in the storage tank (11).

10. The target material circulation system according to claim 7, characterized in that: A pressure gauge (13) is provided on the top of the storage tank (11).

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