Device and method for removing gadolinium from concave mirror surface in EUV lithography light source system

Abstract

The present invention relates to the field of optical component processing technology, and in particular to a device and method for removing gadolinium from the surface of a concave mirror in an EUV lithography light source system. The device comprises: a reaction tank having a liquid injection port and a liquid discharge port provided on the sidewall and bottom, respectively; a concave vacuum carrier extending into the inner groove of the reaction tank via a carrier bracket; the concave vacuum carrier comprising a concave vacuum suction cup with air holes and a silicone composite film, the silicone composite film being attached to the bottom of the concave vacuum suction cup, and negative pressure generated by the air holes enables the silicone composite film to adsorb the concave mirror; a working electrode in an electrochemical three-electrode system is fixed to the bottom of the inner wall of the reaction tank via a working electrode clamp, and a counter electrode and a reference electrode are fixedly installed inside the reaction tank; a stirring device is fixed to the sidewall of the reaction tank; and the magnet is fixed to the bottom of the reaction tank. The advantages of the device are that surface impurities can be removed while ensuring that the surface roughness of the concave mirror is not affected and the high-reflection film layer is not damaged.

Description

Technical Field

[0001] The present invention relates to the technical field of optical component processing, and in particular to a device and method for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine. Background Art

[0002] As the level of science and technology in semiconductor chips improves, the functional diversity of a single chip is also gradually increasing. A chip that can realize complex functions needs to be obtained through design and processing steps such as integrated circuit (IC) design, IC manufacturing, and chip packaging. With the demand for complexity, diversification, and miniaturization of chip functions, more electronic components need to be built in a limited space during IC design, which adds great difficulties and challenges to the subsequent IC manufacturing process. The photolithography process is the most complex, requires the highest precision, is the longest time-consuming, and has the highest cost. The specific subdivisions include: coating, soft baking, exposure, PEB, development, measurement, and subsequent etching or ion implantation processes. Therefore, the photolithography process plays a key role in the IC manufacturing process.

[0003] As chip integration increases, building more circuits within a limited space requires lithography machines with higher resolution. Currently, my country's lithography equipment lags behind the world's top-tier machines. To achieve higher-resolution lithography equipment, it's necessary to find light sources with shorter wavelengths. Metallic gadolinium (Gd), bombarded by specialized lasers, can produce extreme ultraviolet (EUV) light close to 6.7nm, making it the best material for my country's domestic production of EUV lithography equipment. The light source system of an EUV lithography machine also includes a laser, a target system, and an EUV light collection system. Because the wavelength of EUV light is so short, it can't be focused using conventional transmission mirrors. Instead, a concave mirror coated with a tungsten / molybdenum multilayer reflective film is required. As the light collection system, the surface of this reflective mirror must be extremely smooth, free of impurities and defects, with a surface roughness below 50µm. Therefore, ensuring the smoothness of the concave mirror surface is extremely important. However, when the laser bombards the metal droplet target, a certain amount of metal ions will be generated. Although the electromagnetic field currently keeps a large number of metal ions away from the concave mirror, a small amount of metal ions will escape the control of the electromagnetic field and adhere to the surface of the concave mirror. This requires regular inspection and cleaning of surface impurities. Because the surface is very smooth and coated with a highly reflective film, it cannot be cleaned by physical methods. In this case, a specific chemical method is required to treat the surface to ensure that impurities are completely removed without damaging the surface high-reflective film.

[0004] Therefore, to achieve higher-resolution lithography machines, the first issue that needs to be addressed is the EUV light source. Because the EUV light source has a very short wavelength and is easily absorbed, transmission-based focusing is impossible. Therefore, concave mirrors are the primary tool for converging the EUV light source. Surface cleaning of concave mirrors coated with a multilayer, highly reflective silicon / molybdenum coating is also crucial. Cleaning the concave mirror without reducing the surface roughness or damaging the highly reflective coating is a significant challenge. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a device and method for removing gadolinium from the surface of a concave mirror in a light source system of an EUV lithography machine.

[0006] The first object of the present invention is to provide a device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine, comprising: a reaction cell, a concave vacuum stage, an electrochemical three-electrode system, a stirring device, and a magnet;

[0007] The reaction tank is used to contain the reaction liquid, and a liquid injection port and a liquid discharge port are respectively provided on the side wall and the bottom of the reaction tank;

[0008] The concave vacuum stage extends into the inner groove of the reaction tank through the stage bracket; the concave vacuum stage includes a concave vacuum suction cup with air holes and a silicone composite film, the silicone composite film is attached to the bottom of the concave vacuum suction cup, and the negative pressure generated by the air holes creates a vacuum environment between the silicone composite film and the concave mirror to achieve adsorption of the concave mirror;

[0009] The electrochemical three-electrode system includes a working electrode, a counter electrode, and a reference electrode; the working electrode is fixed to the bottom of the inner wall of the reaction cell by a working electrode clamp, and the counter electrode and the reference electrode are fixed inside the reaction cell and leave a gap with the bottom of the inner wall of the reaction cell;

[0010] The stirring device is fixed to the side wall of the reaction cell; the magnet is fixed below the reaction cell to promote the attachment of gadolinium ions to the surface of the working electrode.

[0011] Preferably, the concave vacuum suction cup also includes a built-in air pressure monitor for monitoring the changes in the air pressure value inside the concave vacuum carrier in real time, and displaying the readings through an air pressure display screen arranged on the upper part of the concave vacuum suction cup; when working, the concave vacuum carrier is controlled to control the picking and placement of the concave mirror by controlling the air inlet and outlet of the exhaust port at the upper end of the concave vacuum carrier.

[0012] Preferably, the center of the concave vacuum suction cup is solid, and the surface of the concave vacuum suction cup is tightly covered by the silicone composite film; the pores are arranged in an array or divergent shape.

[0013] Preferably, two stirring devices are provided for causing the reaction liquid to rotate slowly and uniformly in the reaction tank.

[0014] Preferably, the working electrode is horizontally inserted into the working electrode clamp, and the power supply to the working electrode is completed by the power supply contact surface of the working electrode clamp contacting the conductive surface of the working electrode.

[0015] Preferably, the working electrode, the counter electrode and the reference electrode are respectively connected to corresponding power cord clamps of the electrochemical workstation via power cords.

[0016] Preferably, the reaction cell and the working electrode clamp are both made of polytetrafluoroethylene.

[0017] A second object of the present invention is to provide a method for removing gadolinium from the surface of a concave mirror in an EUV lithography light source system, wherein a device for removing gadolinium from the surface of a concave mirror in an EUV lithography light source system is used to remove gadolinium impurities, and the method specifically comprises the following steps:

[0018] S1. Place the conductive substrate on the working electrode and connect and fix it;

[0019] S2. The hydrochloric acid solution is injected into the reaction tank through the injection port and reaches a certain height;

[0020] S3. The vacuum stage adsorbs and fixes the concave mirror to be cleaned, and then moves the vacuum stage over the reaction tank and slowly descends, completely immersing the concave mirror surface in the hydrochloric acid solution;

[0021] S4. Turn on the stirring device to ensure that the hydrochloric acid solution in the reaction tank rotates slowly and evenly, so that the metallic gadolinium impurities attached to the surface of the concave mirror begin to react with the hydrochloric acid solution to form Gd 3+ And it leaves the surface of the concave mirror and mixes into the hydrochloric acid solution;

[0022] S5. Turn on the electrochemical workstation and ensure that the working electrode, counter electrode, and reference electrode are all powered normally to carry out the electrochemical reaction.

[0023] S6. The Gd ions move toward the lower magnet and undergo a redox reaction on the conductive substrate on the working electrode, forming a GdCl3 film.

[0024] S7. After the reaction is completed, slowly remove the concave mirror from the hydrochloric acid solution and place it in a container filled with high-purity water. Wash away the residual hydrochloric acid solution on the surface of the concave mirror and blow it dry to complete the removal of impurities on the surface of the concave mirror.

[0025] Preferably, the electrochemical reaction is carried out using cyclic voltammetry, chronoamperometry or chronocoulometry.

[0026] Preferably, the conductive substrate is made of ITO conductive glass or FTO conductive glass.

[0027] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0028] The device and method of the present invention solve the problem of difficulty in removing impurities from the surface of a concave mirror used to collect extreme ultraviolet light in an EUV light source system. While ensuring that the surface roughness of the concave mirror is not affected and the high-reflective film layer is not damaged, the surface impurity removal work is completed, providing a certain guarantee for the stability and accuracy of the photolithography process, and at the same time, saving the cost of replacing the concave mirror. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure is a cross-sectional schematic diagram of a device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to an embodiment of the present invention.

[0030] Figure 2 1 is an overall schematic diagram of a device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to an embodiment of the present invention.

[0031] Figure 3 Schematic diagram of a concave vacuum stage adsorbing a concave mirror according to an embodiment of the present invention.

[0032] Figure 4 4 is a cross-sectional schematic diagram of a concave vacuum stage provided according to an embodiment of the present invention.

[0033] Figure 5 1 is a schematic diagram of the operation of a gadolinium removal device on a concave mirror surface in an EUV lithography light source system according to an embodiment of the present invention when removing impurities from the surface of a reflective mirror.

[0034] Reference numerals:

[0035] 1. Reaction pool;

[0036] 101. Liquid injection port; 102. Liquid discharge port; 103. Hydrochloric acid solution; 104. Gd2O3 impurity;

[0037] 2. Concave vacuum stage;

[0038] 201. Concave vacuum suction cup; 202. Air hole; 203. Silicone composite membrane; 204. Exhaust port; 205. Air pressure monitor; 206. Air pressure display;

[0039] 3. Working electrode;

[0040] 301. Working electrode clamp;

[0041] 4. Counter electrode;

[0042] 5. Reference electrode;

[0043] 6. Stirring device;

[0044] 7. Magnet;

[0045] 8. Reflector. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0048] Example 1

[0049] Figure 1-Figure 5 The present invention shows a device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine, comprising: a reaction cell 1, a concave vacuum stage 2, an electrochemical three-electrode system, a stirring device 6, and a magnet 7;

[0050] The reaction tank 1 is used to hold the reaction liquid, and a liquid injection port 101 and a liquid discharge port 102 are respectively provided on the side wall and bottom of the reaction tank 1; the reaction tank 1 is made of polytetrafluoroethylene to ensure that it will not produce pollutants to damage the surface of the concave mirror 8 and will not react with the reaction liquid.

[0051] The concave vacuum carrier 2 extends into the inner groove of the reaction tank 1 through the carrier bracket. The carrier bracket is adjustable in three directions and is used to adjust the position of the concave vacuum carrier 2 so that the adsorbed concave mirror 8 is immersed in the reaction liquid; the concave vacuum carrier 2 includes a concave vacuum suction cup 201 with an air hole 202 and a silicone composite film 203. The silicone composite film 203 is attached to the bottom of the concave vacuum suction cup 201. The negative pressure generated at the position of the air hole 202 creates a vacuum environment between the silicone composite film 203 and the concave mirror 8 to achieve adsorption of the concave mirror 8; in addition, the concave vacuum suction cup 201 also includes a built-in air pressure monitor 205 for real-time monitoring of the air pressure value changes inside the concave vacuum carrier 2 and displaying the readings through the air pressure value display screen 206 arranged on the upper part of the concave vacuum suction cup 201; during operation, according to the size and weight of the concave mirror 8, the concave vacuum carrier 2 is controlled by controlling the air inlet and outlet of the exhaust port 204 at the upper end of the concave vacuum carrier 2 to control the picking and placement of the concave mirror 8;

[0052] Since the concave mirror 8 is hollow in the middle, the center of the concave vacuum suction cup 201 is solid, the air holes 202 are arranged in an array or divergent shape, and the surface of the concave vacuum suction cup 201 is tightly covered by the silicone composite film 203.

[0053] The electrochemical three-electrode system includes a working electrode 3, a counter electrode 4, and a reference electrode 5; the working electrode 3 is fixed to the bottom of the inner wall of the reaction cell 1 by a working electrode clamp 301, and the counter electrode 4 and the reference electrode 5 are fixed inside the reaction cell 1 and leave a gap with the bottom of the inner wall of the reaction cell 1; the working electrode 3, the counter electrode 4, and the reference electrode 5 are respectively connected to the corresponding power cord clamps of the electrochemical workstation via power cords;

[0054] The working electrode 3 is horizontally inserted into the working electrode holder 301, and the power supply contact surface of the working electrode holder 301 contacts the conductive surface of the working electrode 3 to complete the power supply to the working electrode 3;

[0055] The material of the working electrode holder 301 is polytetrafluoroethylene.

[0056] The stirring device 6 is fixed to the side wall of the reaction tank 1; two stirring devices 6 are provided; when working, the stirring device 6 causes the reaction liquid to rotate slowly and uniformly in the reaction tank 1, on the one hand, it can ensure that the gadolinium (Gd) impurities on the surface of the concave mirror 8 can fully react with the reaction liquid, and on the other hand, it can also keep the temperature of the reaction liquid in the reaction tank 1 stable.

[0057] The magnet 7 is fixed below the reaction cell 1 and is used to promote the attachment of gadolinium (Gd) ions to the surface of the working electrode 3 and improve the cleaning efficiency of impurities on the surface of the concave mirror 8.

[0058] Example 2

[0059] This embodiment provides a method for removing gadolinium from the surface of a concave mirror in an EUV lithography light source system (eg Figure 5 As shown in FIG, a gadolinium removal device on the concave mirror surface in the EUV lithography light source system is used for removal, specifically comprising the following steps:

[0060] S1. Place a conductive substrate on the working electrode 3 and connect and fix it; the conductive substrate is made of ITO or FTO conductive glass (or, in other words, any material that ensures surface conductivity and does not react with the solution can be used, not limited to the materials provided in the embodiment);

[0061] S2. A hydrochloric acid solution of a specific concentration 103 is injected into the reaction tank 1 through the injection port 101 and reaches a certain height; in this embodiment, the concentration of the hydrochloric acid solution is 9.85 to 12.39 mol / L;

[0062] S3. The vacuum stage 2 adsorbs and secures the concave mirror 8 to be cleaned. The vacuum stage 2 is then moved above the reaction tank 1 and slowly lowered, completely immersing the surface of the concave mirror 8 in the hydrochloric acid solution 103. This process must be performed slowly to prevent the surface film of the concave mirror 8 from being damaged by the tension of the solution when it comes into contact with the hydrochloric acid solution 103. This also causes the metallic Gd impurities to come into contact with air during this process, forming Gd2O3 impurities 104.

[0063] S4. Turn on the stirring device 6 to ensure that the hydrochloric acid solution 103 in the reaction tank 1 rotates slowly and uniformly; at this time, the metal Gd impurities attached to the surface of the concave mirror 8 begin to react with the hydrochloric acid solution 103 to form Gd 3+ and detach from its surface and mix into the hydrochloric acid solution 103;

[0064] S5. Turn on the electrochemical workstation and ensure that the working electrode 3, the counter electrode 4, and the reference electrode 5 are all energized. Cyclic voltammetry (CV) is used to perform an electrochemical reaction to make the electrons in the hydrochloric acid solution 103 more active, thereby promoting the reaction between the metal impurity Gd and the hydrochloric acid solution 103.

[0065] S6. Because Gd ions have a certain degree of ferromagnetism at room temperature, they will move toward the position of the magnet below. At the same time, a redox reaction will occur on the conductive substrate on the working electrode, forming a GdCl3 film.

[0066] S7. Slowly remove the concave mirror 8 from the hydrochloric acid solution 103 and place it in a container filled with high-purity water to wash away the hydrochloric acid solution remaining on the surface of the concave mirror 8. Finally, slowly blow dry the surface water with a rare gas to complete the removal of impurities on the surface of the concave mirror 8.

[0067] In the present invention, electrochemical reactions can also be measured using methods such as chronoamperomet (CA) and chronocoulometry (CC).

[0068] The present invention designs a device and method for removing metallic Gd impurities from the surface of a concave mirror in an EUV light source system. This device ensures that the treated concave mirror surface remains smooth and undamaged, and does not damage the reflective film layer on the mirror surface, allowing it to retain excellent reflective capabilities. Specifically, when cleaning the concave mirror surface, the mirror is placed in a reaction tank filled with hydrochloric acid at a specific concentration. A three-electrode electrochemical system, utilizing its high redox properties, chemically decomposes the metallic impurities adhering to the concave mirror surface in the hydrochloric acid solution and adheres to the substrate of the working electrode, thereby achieving concave mirror surface cleaning. The specific chemical reaction is:

[0069] Gd2O3+6HCl→2GdCl3+3H2O;

[0070] The hydrochloric acid solution itself does not react with the silicon / molybdenum film, so it will not damage the highly reflective film on the concave mirror surface, nor will it affect the roughness. Gd ions have a certain degree of ferromagnetism at room temperature, so placing a magnet below the reaction cell will also promote the adhesion of Gd ions to the working electrode surface, improving the efficiency of cleaning impurities on the concave mirror surface.

[0071] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0072] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A device for removing gadolinium from a concave mirror in an EUV lithography light source system, characterized in that: include: Reaction cell, concave vacuum stage, electrochemical three-electrode system, stirring device and magnet; The reaction tank is used to contain the reaction liquid, and a liquid injection port and a liquid discharge port are respectively provided on the side wall and the bottom of the reaction tank; The concave vacuum stage extends into the inner groove of the reaction tank through the stage bracket; the concave vacuum stage includes a concave vacuum suction cup with air holes and a silicone composite film, the silicone composite film is attached to the bottom of the concave vacuum suction cup, and the negative pressure generated by the air holes creates a vacuum environment between the silicone composite film and the concave mirror to achieve adsorption of the concave mirror; The electrochemical three-electrode system includes a working electrode, a counter electrode, and a reference electrode; the working electrode is fixed to the bottom of the inner wall of the reaction cell by a working electrode clamp, and the counter electrode and the reference electrode are fixed inside the reaction cell and leave a gap with the bottom of the inner wall of the reaction cell; The stirring device is fixed to the side wall of the reaction cell; the magnet is fixed below the reaction cell to promote the attachment of gadolinium ions to the surface of the working electrode.

2. The device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 1, characterized in that: The concave vacuum suction cup also includes a built-in air pressure monitor for real-time monitoring of the air pressure changes inside the concave vacuum carrier, and displays the readings on an air pressure display screen arranged on the upper part of the concave vacuum suction cup; when working, the concave vacuum carrier is controlled to pick up and place the concave mirror by controlling the air inlet and outlet of the exhaust port at the upper end of the concave vacuum carrier.

3. The device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 2, characterized in that: The center of the concave vacuum suction cup is in a solid state, and the surface of the concave vacuum suction cup is tightly covered by the silica gel composite film; the pores are arranged in an array or divergent shape.

4. The device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 3, characterized in that: The stirring devices are provided with two for causing the reaction liquid to rotate slowly and uniformly in the reaction tank.

5. The device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 4, characterized in that: The working electrode is horizontally inserted into the working electrode clamp, and the power supply contact surface of the working electrode clamp contacts the conductive surface of the working electrode to complete power supply to the working electrode.

6. The device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 5, characterized in that: The working electrode, the counter electrode and the reference electrode are respectively connected to the corresponding power line clamps of the electrochemical workstation via power lines.

7. The device for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 6, characterized in that: The reaction cell and the working electrode holder are both made of polytetrafluoroethylene.

8. A method for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine, comprising removing gadolinium impurities from a concave mirror in a light source system of an EUV lithography machine using a gadolinium removal device according to any one of claims 1 to 7, wherein: The specific steps include: S1. Place the conductive substrate on the working electrode and connect and fix it; S2. The hydrochloric acid solution is injected into the reaction tank through the injection port and reaches a certain height; S3. The vacuum stage adsorbs and fixes the concave mirror to be cleaned, and then moves the vacuum stage over the reaction tank and slowly descends, completely immersing the concave mirror surface in the hydrochloric acid solution; S4. Turn on the stirring device to ensure that the hydrochloric acid solution in the reaction tank rotates slowly and evenly, so that the metallic gadolinium impurities attached to the surface of the concave mirror begin to react with the hydrochloric acid solution to form Gd 3+ And it leaves the surface of the concave mirror and mixes into the hydrochloric acid solution; S5. Turn on the electrochemical workstation and ensure that the working electrode, counter electrode, and reference electrode are all powered normally to carry out the electrochemical reaction. S6. The Gd ions move toward the lower magnet and undergo a redox reaction on the conductive substrate on the working electrode, forming a GdCl3 film. S7. After the reaction is completed, slowly remove the concave mirror from the hydrochloric acid solution and place it in a container filled with high-purity water. Wash away the residual hydrochloric acid solution on the surface of the concave mirror and blow it dry to complete the removal of impurities on the surface of the concave mirror.

9. The method for removing gadolinium from a concave mirror in a light source system of an EUV lithography machine according to claim 8, wherein: The electrochemical reaction adopts cyclic voltammetry, chronoamperometry or chronocoulometry.

10. The method for removing gadolinium from the surface of a concave mirror in a light source system of an EUV lithography machine according to claim 9, characterized in that: The conductive substrate is made of ITO conductive glass or FTO conductive glass.

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