A method for manufacturing an extreme ultraviolet light source collection mirror and a processing apparatus

Abstract

This invention relates to a method and processing equipment for fabricating an extreme ultraviolet (EUV) light source collecting mirror. The method includes the following steps: mirror blank fabrication; preliminary processing of the substrate surface; preparation of a silicon-modified layer; polishing of the silicon-modified layer surface; testing the surface accuracy and roughness of the collecting mirror; photolithography processing of the grating structure on the collecting mirror surface; testing the processing accuracy of the grating structure; coating the grating structure surface; and testing the parameters of the collecting mirror. This invention uses silicon carbide to fabricate the collecting mirror substrate, reducing thermal deformation during operation. Silicon is used to modify the substrate surface, improving the consistency of the linear expansion coefficients between the collecting mirror substrate and the modified layer. Photolithography is used to process the grating structure on the collecting mirror surface, reducing the requirements for ultra-precision processing equipment and solving the problem of insufficient precision in processing silicon-modified collecting mirror grating structures on ultra-precision lathes. A dedicated curved surface exposure device is designed and used to solve the challenges of curved surface exposure, further improving the processing accuracy of the grating structure.

Description

Technical Field

[0001] This invention relates to the field of extreme ultraviolet lithography, and in particular to a method for preparing an extreme ultraviolet light source collecting mirror and processing equipment. Background Technology

[0002] Extreme ultraviolet (EUVL) lithography is an indispensable lithography technology for achieving large-scale mass production and industrialization of semiconductors below 7nm. EUV lithography machines are essential for the continued development of process technology. As the most crucial subsystem of an EUV lithography machine, the EUV light source system must possess high output power and conversion efficiency to provide high-purity 13.5nm extreme ultraviolet light to the exposure system. The EUV light source collector mirror is the most important optical component in the EUV light source system, playing a decisive role in the light source's collection efficiency and stability.

[0003] In EUV light source systems, the type of light-collecting mirror is determined by the method of EUV light generation. Laser plasma (LPP) and discharge plasma (DPP) light sources are the two most common types. For DPP light sources, a large amount of debris is generated along with the emitted EUV light. To prevent this debris from impacting the mirrors of the EUV lithography illumination and projection systems and causing contamination that could affect the system's lifespan, DPP light source systems use grazing-incidence collecting mirrors and are equipped with de-debris removal systems. However, this significantly limits the efficiency of EUV light collection.

[0004] Laser plasma (LPP) light source systems use high-intensity lasers to bombard liquid droplets to obtain extreme ultraviolet (EUV) light, producing relatively little debris. Furthermore, the LPP light source's collecting mirror only requires a single ellipsoidal mirror to achieve high EUV light collection efficiency, which is why this type of light source is used in mainstream EUV lithography machines abroad. However, because the EUV light is excited by an infrared-band driving light source, some infrared laser light is reflected by the collecting mirror and enters the illumination system. This infrared light can cause severe thermal damage to important optical components in the illumination and projection systems, necessitating the design of infrared light filtering elements.

[0005] Currently, the main infrared filtering methods used in extreme ultraviolet (EUV) lithography include reflective grating filtering, transmissive grating film filtering, and EUV collector mirror filtering with grating structures. Because the wavelength of EUV light at 13.5 nm is extremely short and easily absorbed by matter, the use of reflective grating filters and transmissive grating film filters results in significant loss of EUV light. In contrast, the loss of EUV light by collector mirrors with grating structures mainly comes from the microstructure on the surface of the collector mirror, resulting in relatively smaller losses. Therefore, the focus should be on developing reflective EUV light collector mirrors with grating structures that can reduce EUV light loss while filtering out infrared radiation.

[0006] Currently, there are two relatively mature fabrication methods. One approach involves using an aluminum alloy substrate to fabricate a collecting mirror that removes 10.6μm infrared radiation. A nickel layer is plated onto the substrate surface and polished. Then, a grating structure is machined on the mirror surface using a diamond cutting tool on an ultra-precision lathe. Finally, a coating is applied. The collecting mirror has a diameter of 400mm, and a phase grating with a period of 1mm is fabricated on its surface. The other approach is a collecting mirror prototype designed by the German company IOF, featuring a double-layer phase grating with periods of 1mm and 100μm. The mirror substrate is made of aluminum-silicon alloy. First, the optical surface of the substrate is diamond-machined and a nickel layer is plated. Then, the nickel layer is diamond-machined to create a grating with a period of 1mm and polished. Finally, an ion beam etching process is used to directly fabricate a binary second-layer grating with a period of 100μm on the Ni layer on the AlSi substrate.

[0007] The main drawbacks of existing technologies lie in the processing technology and equipment for the collecting mirror: There are two methods for machining the grating structure on the surface of the collecting mirror using single-point diamond turning. First, the collecting mirror surface is polished before machining the grating structure. This method easily damages the original surface quality of the collecting mirror and makes it difficult to guarantee the machining accuracy of the bottom of the grating. Second, the grating structure is machined first, and then the top and bottom of the grating are polished simultaneously. This method makes it difficult to control the polishing time and guarantee the grating dimensions. In terms of equipment, existing technologies place excessively high precision requirements on the machining and polishing equipment and are difficult to process brittle and hard materials such as silicon and silicon carbide, which are more suitable for collecting mirrors. Summary of the Invention

[0008] The present invention aims to solve the technical problems in the prior art by providing a method for preparing an extreme ultraviolet light source collecting mirror and processing equipment.

[0009] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0010] A method for preparing an extreme ultraviolet light source collecting mirror includes the following steps:

[0011] Step 1: Making the mirror blank;

[0012] To create the base for the collecting mirror;

[0013] Step 2: Preliminary processing of the substrate surface;

[0014] The root mean square error of the surface profile accuracy is λ / 10.

[0015] Step 3: Prepare the silicon-modified layer;

[0016] A silicon-modified layer of a certain thickness is deposited on the surface of the silicon carbide collecting mirror substrate;

[0017] Step 4: Polishing the surface of the silicon-modified layer;

[0018] The silicon-modified layer is precision polished.

[0019] Step 5: Inspect the surface accuracy and roughness of the collecting mirror;

[0020] Step 6: Photolithography is used to fabricate the grating structure on the surface of the collecting mirror;

[0021] Step 7: Inspection of grating structure processing accuracy;

[0022] Step 8: Deposit a film on the surface of the grating structure;

[0023] Step 9: Check the parameters of the collection mirror.

[0024] In the above technical solution, step 6 specifically includes:

[0025] Step 01: Cleaning and surface pretreatment of the collection mirror coating; First, wet cleaning with deionized water is performed to remove contaminants and residual impurities adsorbed on the surface of the silicon modified layer of the collection mirror; then, an adhesion-enhancing treatment is performed to improve the adhesion between the coating and the photoresist;

[0026] Step 02: Applying and spreading the photoresist; spread the photoresist that meets the requirements evenly on the substrate to ensure that the thickness of the photoresist is uniform and stable.

[0027] Step 03: Pre-baking; This reduces the solvent content in the photoresist, making it more robust and improving the corrosion resistance of the photoresist film.

[0028] Step 04: Exposure; Expose the collecting mirror using a curved surface exposure device;

[0029] Step 05: Post-baking; The surface of the exposed collection mirror is baked to allow the photochemical reaction in the photoresist to be fully completed.

[0030] Step 06: Development and rinsing; First, wet the collecting mirror with deionized water, then spray the developing solution evenly on the photoresist surface of the collecting mirror or place the substrate in the developing solution to fully dissolve the exposed parts in the photolithography, and then rinse with deionized water.

[0031] Step 07: Hard film baking; further reduce the solvent content in the photoresist to improve the etching resistance of the photoresist film;

[0032] Step 08: Etching; Dry etching is used to rapidly etch the parts of the collecting mirror surface not covered by photoresist under the ion bombardment of chemical gas;

[0033] Step 09: Resin removal and cleaning; Remove the remaining photoresist adhering to the silicon modified layer of the collecting mirror and clean the entire surface of the collecting mirror to obtain the structure of the first grating.

[0034] In the above technical solution, Step 04 specifically involves: positioning and clamping the collecting mirror onto the exposure equipment, and controlling the laser of the exposure equipment to work in conjunction with the axis of the clamping collecting mirror, so that the laser focal spot can accurately scan the photoresist surface to obtain the grating pattern required by the design.

[0035] In the above technical solution, if a binary grating structure needs to be made after Step09, the steps Step02-Step09 are repeated.

[0036] In the above technical solution, step 7 specifically includes: using a white light interferometer to detect the dimensional accuracy of the grating of the collecting mirror, and using an atomic force microscope to detect the roughness at different positions of the grating, with a roughness value of less than 0.25 nmrms.

[0037] In the above technical solution, step 8 specifically includes: depositing a Mo / Si multilayer film on the surface of the grating structure using magnetron sputtering.

[0038] In the above technical solution, step 9 specifically includes: evaluating the extreme ultraviolet collection rate and infrared radiation removal rate of the collection mirror.

[0039] A processing device for an extreme ultraviolet light source collecting mirror includes: a base disposed at the bottom, and a Z-axis and an X-axis disposed above the base; the X-axis and the Z-axis respectively perform linear reciprocating motion;

[0040] A B-axis is located above the Z-axis, and a laser mounting bracket is connected to the B-axis. The laser is connected above the laser mounting bracket. The B-axis controls the rotation of the laser around the Y-axis. By adjusting the laser mounting bracket, the center of the light emitted by the laser is ensured to be at the required height, and the laser is stably supported for operation.

[0041] The C-axis is connected above the X-axis, and the C-axis is connected to a pneumatic chuck. The collecting mirror is clamped on the pneumatic chuck; the C-axis drives the collecting mirror to rotate around the Z-axis.

[0042] The collecting mirror includes: a substrate, the surface of which is provided with a silicon-modified layer, and a light-transmitting hole in the center of the substrate; a grating structure is provided above the silicon-modified layer, and the surface of the grating structure is coated with multiple layers of film.

[0043] In the above technical solution, the material of the multilayer film is Mo / Si.

[0044] In the above technical solution, the number of cycles of the multilayer film is 42 to 48, and the thickness of a single cycle is about 6 to 7 nm.

[0045] The present invention has the following beneficial effects:

[0046] The present invention discloses a method and processing equipment for fabricating an extreme ultraviolet (EUV) light source collecting mirror. The collecting mirror substrate is made of silicon carbide, reducing thermal deformation during operation. Silicon is used to modify the substrate surface, improving the consistency of the linear expansion coefficients between the collecting mirror substrate and the modified layer. Simultaneously, photolithography is used to process the grating structure on the collecting mirror surface, reducing the requirements for ultra-precision processing equipment and solving the problem of insufficient precision in machining silicon-modified collecting mirror grating structures on ultra-precision lathes. Furthermore, a dedicated curved surface exposure device is designed to solve the challenges of curved surface exposure, further improving the processing accuracy of the grating structure. Attached Figure Description

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0048] Figure 1 A schematic diagram illustrating the steps of fabricating a light source collection mirror for an extreme ultraviolet lithography machine with a grating structure.

[0049] Figure 2 A schematic diagram illustrating the steps of fabricating and coating a grating structure on the surface of a light source collecting mirror.

[0050] Figure 3 This is a schematic diagram of the exposure equipment.

[0051] Figure 4 This is a schematic diagram of the collecting mirror.

[0052] Figure 5 This is another schematic diagram of the collecting mirror structure.

[0053] The reference numerals in the figure are:

[0054] 1-Base; 2-Z-axis; 3-B-axis; 4-Laser mounting bracket; 5-Laser; 6-Collecting mirror; 7-Pneumatic chuck; 8-C-axis; 9-X-axis;

[0055] 10-Substrate; 11-Silicon modified layer; 12-Light-transmitting hole; 13-Multilayer film; 14-Grate structure. Detailed Implementation

[0056] The inventive concept of this invention is as follows:

[0057] This invention proposes a method for fabricating an extreme ultraviolet (EUV) light source collecting mirror and develops an exposure device for curved surface lithography. The laser-plasma light source collecting mirror with microstructures on its surface can efficiently collect EUV light while effectively removing infrared radiation, and reflects some of the infrared radiation back onto the molten tin droplet to excite EUV light, thus improving energy utilization. The phase grating structure fabricated on the surface primarily serves to remove infrared radiation. When a Fresnel zone plate pattern is fabricated on the surface, the IR light can be effectively refocused onto the molten tin droplet (recovery rate 37%, up to 90%).

[0058] Regarding the choice of substrate material, for collecting mirrors with the same structure, those using silicon-aluminum alloy as the substrate exhibit greater thermal deformation than those using SiC substrates under the same operating conditions, thus affecting the focusing performance of the collecting mirror. As for the choice of surface modification materials, the difference between the linear expansion coefficients of AlSi alloy and the modified materials Ni or NiP is significant. In contrast, the linear expansion coefficients of SiC and Si are closer. Furthermore, mirrors with a silicon layer deposited on a silicon carbide substrate are more favorable for depositing Mo / Si multilayer films than mirrors with a nickel layer on the surface.

[0059] This invention uses silicon carbide to fabricate the collecting mirror substrate, reducing thermal deformation. Silicon is used to modify the surface of the collecting mirror on the silicon carbide substrate, reducing the difference in the coefficient of linear expansion between the substrate material and the surface coating material. High surface quality is then achieved by polishing the silicon layer on the collecting mirror surface. To fabricate a grating structure on the collecting mirror surface that meets usage requirements, this invention uses photolithography. First, photoresist is uniformly coated onto the polished collecting mirror surface. After drying, it is exposed on an exposure device designed in this invention. The exposed collecting mirror surface is then developed and rinsed, followed by etching on an etching device. Finally, photoresist removal and cleaning are performed to complete the fabrication of one layer of the grating structure on the collecting mirror. If a binary grating structure needs to be fabricated, the above processing steps are repeated. Using curved surface photolithography to fabricate the grating structure on the collecting mirror surface solves the problem of insufficient precision in fabricating grating structures on silicon-modified collecting mirror surfaces using ultra-precision lathes. It also avoids damaging the surface quality of the already polished collecting mirror and can produce high-precision grating dimensions. Meanwhile, in order to solve the exposure problem after photolithography processing of microstructures on the surface of curved mirrors, an exposure device for photolithography processing of microstructures on the surface of curved mirrors was developed.

[0060] This invention uses silicon carbide (SiC) as the reflector substrate, solving the problem of large thermal deformation of AlSi substrates. Silicon is used to modify the surface of the collecting mirror on the SiC substrate, avoiding the significant difference in linear expansion coefficients between the silicon-aluminum alloy substrate and the nickel layer material, thus improving the surface stability and focusing performance of the collecting mirror. To reduce the processing difficulty of the grating structure on the collecting mirror surface, curved surface photolithography is used to process the grating structure, solving the problem of insufficient precision in machining the silicon-modified collecting mirror surface grating structure on ultra-precision lathes, while avoiding damage to the already polished collecting mirror surface quality. Furthermore, an exposure device for photolithographic processing of microstructures on curved reflector surfaces was developed, solving the exposure problem after photolithographic processing and resist coating of microstructures on curved reflector surfaces.

[0061] The present invention will now be described in detail with reference to the accompanying drawings.

[0062] The extreme ultraviolet light source collecting mirror with a grating structure of the present invention uses silicon carbide material to fabricate a collecting mirror substrate with an ellipsoidal structure. First, the surface of the silicon carbide substrate is processed to improve the surface accuracy. A silicon-modified layer is prepared on the surface of the collecting mirror substrate using physical vapor deposition. The silicon-modified layer is then precision polished according to relevant processing parameters. The grating structure on the surface of the collecting mirror is fabricated through steps such as photoresist coating, exposure, development, and etching. The grating structure is shown in the attached figure. Figure 4 and 5 As shown, after the fabrication quality of the grating structure was inspected, a multilayer Mo / Si film was deposited. Finally, the focusing performance and infrared filtering performance of the mirror were tested. The fabrication process flow chart is attached. Figure 1 During the fabrication process, high-precision exposure of the coated collecting mirror is required. This is a crucial step in determining the processing accuracy of the grating structure on the collecting mirror surface. This invention utilizes a dedicated exposure device. Figure 3 This is a schematic diagram of the equipment structure.

[0063] The technical solution of this invention, concerning the fabrication of an extreme ultraviolet light source collecting mirror with a grating structure, is divided into the following three parts:

[0064] Part 1: Substrate preparation, surface modification, and polishing of the laser plasma source collection mirror.

[0065] like Figure 1 As shown, after obtaining the design parameters of the collecting mirror, the first step is to complete the fabrication of the mirror blank of the laser plasma source collecting mirror of the corresponding size, and to select silicon carbide (SiC) material with excellent physical, thermal and mechanical properties to make the collecting mirror substrate.

[0066] After the substrate preparation is completed, the second step is to perform preliminary processing on the surface of the silicon carbide substrate until the root mean square (RMS) value of the surface accuracy error is about λ / 10 (λ=632.8nm).

[0067] After completing the initial processing error detection of the substrate, the third step is to prepare a silicon modified layer using physical vapor deposition. A silicon modified layer of a certain thickness is deposited on the surface of the silicon carbide collecting mirror. The specific thickness is determined by the design parameters, generally around 10 μm.

[0068] The fourth step is to perform precision polishing on the silicon-modified layer from the third step. The polishing method used here can be small grinding head polishing, ion beam polishing, or magnetorheological polishing.

[0069] After polishing, the surface shape error and surface roughness of the collecting mirror are inspected using at least two inspection methods. Once the design requirements are met, the second part of the processing steps can begin.

[0070] Part Two: Fabrication and Coating of the Grating Structure on the Surface of the Laser Plasma (LPP) Source Collector Mirror. The fabrication flowchart is shown below. Figure 2 As shown, the specific process is as follows:

[0071] Step 01: Cleaning and surface pretreatment of the collection mirror coating. First, wet cleaning with deionized water is performed to remove contaminants and residues from the previous process adsorbed on the surface of the polished silicon modified layer of the collection mirror; then, an adhesion-enhancing treatment is performed to improve the adhesion between the coating and the photoresist.

[0072] Step 02: Apply and spread the photoresist evenly on the substrate after completing the previous step. Ensure that the photoresist thickness is uniform and stable.

[0073] Step 03: Pre-baking. This reduces the solvent content in the photoresist, making it more robust and improving the corrosion resistance of the photoresist film.

[0074] Step 04: Exposure. The collected mirror from the previous step is exposed using the developed curved surface exposure equipment. Specifically, the collected mirror from the previous step is first positioned and clamped onto the exposure equipment. By controlling the laser of the exposure equipment to be linked with the axis of the clamped collected mirror, the laser spot is precisely scanned on the photoresist surface to obtain the grating pattern required by the design.

[0075] Step 05: Post-baking. To compensate for insufficient exposure intensity, the surface of the collection mirror is baked after exposure to allow the photochemical reaction in the photoresist to be fully completed.

[0076] Step 06: Development and Rinsing. First, wet the collecting mirror obtained in the previous step with deionized water. Then, evenly spray the developer onto the photoresist surface of the collecting mirror or place the substrate in the developer to fully dissolve the exposed parts during photolithography. Finally, rinse with deionized water. This step preserves the unexposed parts, creating the designed grating pattern on the surface of the collecting mirror.

[0077] Step 07: Hardening and Baking. This further reduces the solvent content in the photoresist to improve the photoresist film's resistance to etching, preventing it from affecting subsequent etching steps and improving etching precision.

[0078] Step 08: Etching. Dry etching is used to rapidly corrode the areas of the collecting mirror surface not covered by photoresist under ion bombardment with chemical gases. Etching methods can include plasma etching, ion beam etching, and reactive ion etching. Wet etching can also be used, where the collecting mirror treated in the previous step is quantitatively etched using an etchant.

[0079] Step 09: Photoresist Removal and Cleaning. Remove any remaining photoresist adhering to the modified layer of the collecting mirror and clean the entire surface of the collecting mirror to obtain the structure of the first grating layer. Repeat the above steps if a binary grating structure is required.

[0080] Step 10: Inspection and Coating. Use a white light interferometer to inspect the dimensional accuracy of the grating of the collecting mirror completed in the previous step, and use an atomic force microscope to inspect the roughness at different locations of the grating. The roughness value must be less than 0.25 nm rms.

[0081] After inspection, a Mo / Si multilayer film was deposited on the grating surface using magnetron sputtering. The Mo / Si periodic multilayer film had 42–48 periods, with a single period thickness of approximately 6–7 nm, of which the Mo layer accounted for approximately 43%.

[0082] Finally, by evaluating the extreme ultraviolet collection rate and infrared radiation removal rate of the collection mirror after completing the above steps, the collection mirror can be used in the extreme ultraviolet lithography machine light source system after meeting the design requirements.

[0083] Steps 01-09 in the above steps correspond to the attached... Figure 2 S01-S09 in the middle.

[0084] Part Three: The structure and working principle of the curved surface lithography exposure system.

[0085] As attached Figure 3 The diagram shows the structure of the exposure system, the processing equipment designed in this invention. The bottom is the base 1 of the exposure equipment, with Z-axis 2 and X-axis 9 above it. X-axis 9 and Z-axis 2 perform linear reciprocating motion. Above Z-axis 2 is B-axis 3, connected to a laser mounting bracket 4. A laser 5 is connected above the laser mounting bracket 4. B-axis 3 controls the rotation of laser 5 around the Y-axis. Adjusting the laser mounting bracket 4 ensures the center of the light emitted by laser 5 is at the required height and provides stable support for the laser 5 used for exposure. Above X-axis 9 is C-axis 8, connected to a pneumatic chuck 7. A collecting mirror 6 is clamped in the pneumatic chuck 7. C-axis 8 drives the collecting mirror 6 to rotate around Z-axis 2.

[0086] The structure of collecting mirror 6 is as follows Figure 4 and 5 As shown, a silicon-modified layer 11 is provided on the surface of the substrate 10, and a light-transmitting hole 12 is provided at the center of the substrate 10; a grating structure 14 is provided above the silicon-modified layer 11, and a multilayer film 13 of Mo / Si material is deposited on the surface of the grating structure 14. The multilayer film 13 has 42 to 48 periods, and the thickness of a single period is about 6 to 7 nm, of which the Mo layer accounts for about 43%.

[0087] In the exposure process of the collecting mirror, firstly, the collecting mirror 6, which has already been coated with adhesive, is clamped onto the pneumatic chuck 7. The rotation center line of the laser 5 around the B-axis 3 is adjusted to the required position, the specific position of which is determined by the design parameters of the collecting mirror 6. The four-axis linkage of the exposure system is controlled to complete the exposure. Through the joint control of the C-axis 8 and the laser 5, after completing one circle of circular grating exposure, the B-axis 3 rotates by a certain angle, while the Z-axis 2 is adjusted to perform the next circle of grating structure exposure. The above is a direct-write exposure without a mask. The laser 5 can be replaced and a mask can be made for masked exposure.

[0088] The present invention discloses a method and processing equipment for fabricating an extreme ultraviolet (EUV) light source collecting mirror. By using silicon carbide as the collecting mirror substrate, thermal deformation during operation is reduced. Furthermore, silicon is used to modify the substrate surface, improving the consistency of the linear expansion coefficients between the collecting mirror substrate and the modified layer. Simultaneously, photolithography is employed to process the grating structure on the collecting mirror surface, reducing the requirements for ultra-precision processing equipment and solving the problem of insufficient precision in machining silicon-modified collecting mirror grating structures on ultra-precision lathes. Moreover, a dedicated curved surface exposure device is designed to solve the challenges of curved surface exposure, further improving the processing accuracy of the grating structure.

[0089] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing an extreme ultraviolet light source collecting mirror, characterized in that, Includes the following steps: The processing equipment applicable to the preparation method includes: a base (1) set at the bottom, and a Z-axis (2) and an X-axis (9) provided above the base (1); the X-axis (9) and the Z-axis (2) respectively perform linear reciprocating motion; A B-axis (3) is located above the Z-axis (2), and a laser mounting bracket (4) is connected to the B-axis (3). A laser (5) is connected above the laser mounting bracket (4). The B-axis (3) controls the laser (5) to rotate around the Y-axis. By adjusting the laser mounting bracket (4), the center of the light emitted by the laser (5) is ensured to be at the required height, and the laser (5) is stably supported to operate. The C-axis (8) is connected above the X-axis (9). The C-axis (8) is connected to the pneumatic chuck (7). The collecting mirror (6) is clamped on the pneumatic chuck (7). The C-axis (8) drives the collecting mirror (6) to rotate around the Z-axis (2). The collecting mirror (6) includes: a substrate (10), the surface of which is provided with a silicon modified layer (11), and a light-transmitting hole (12) is provided at the center of the substrate (10); a grating structure (14) is provided above the silicon modified layer (11), and a multilayer film (13) is deposited on the surface of the grating structure (14). The preparation method includes the following steps: Step 1: Mirror blank preparation; Make the base (10) for the collecting mirror (6); Step 2: Preliminary surface processing of the substrate (10); The root mean square error of the surface profile accuracy is λ / 10. Step 3: Prepare silicon-modified layer (11); A silicon-modified layer (11) of a certain thickness is deposited on the substrate (10) surface of the silicon carbide collecting mirror (6). Step 4: Polishing the surface of the silicon-modified layer (11); The silicon-modified layer (11) is precision polished; Step 5: Inspect the surface accuracy and roughness of the collecting mirror (6); Step 6: Photolithography is used to process the grating structure (14) on the surface of the collecting mirror (6); Step 7: Inspection of the processing accuracy of the grating structure (14); Step 8: Deposit a film on the surface of the grating structure (14); Step 9: Detect the parameters of the collection mirror (6).

2. The method for preparing the extreme ultraviolet light source collecting mirror according to claim 1, characterized in that, Step 6 specifically includes: Step 01: Cleaning and surface pretreatment of the coating of the collecting mirror (6); first, wet cleaning with deionized water to remove contaminants and residual impurities adsorbed on the surface of the silicon modified layer (11) of the collecting mirror (6); then, the adhesion between the coating and the photoresist is improved through adhesion enhancement treatment. Step 02: Applying and spreading the photoresist; spread the photoresist that meets the requirements evenly on the substrate to ensure that the thickness of the photoresist is uniform and stable. Step 03: Pre-baking; This reduces the solvent content in the photoresist, making it more robust and improving the corrosion resistance of the photoresist film. Step 04: Exposure; Expose the collecting mirror (6) using a curved surface exposure device; Step 05: Post-baking; The surface of the exposed collection mirror (6) is baked to allow the photochemical reaction in the photoresist to be fully completed. Step 06: Development and rinsing; First, wet the collecting mirror (6) with deionized water, then spray the developing solution evenly on the photoresist surface of the collecting mirror (6) or place the substrate in the developing solution to fully dissolve the exposed part in the photolithography, and then rinse with deionized water. Step 07: Hard film baking; further reduce the solvent content in the photoresist to improve the etching resistance of the photoresist film; Step 08: Etching; Use dry etching to allow the part of the surface of the collecting mirror (6) not covered by photoresist to be rapidly etched under the ion bombardment of chemical gas; Step 09: Removal and cleaning; Remove the remaining photoresist adhering to the silicon modified layer (11) on the collecting mirror (6) and clean the entire surface of the collecting mirror (6) to obtain the structure of the first grating.

3. The method for preparing the extreme ultraviolet light source collecting mirror according to claim 2, characterized in that, Step 04 specifically involves positioning and clamping the collecting mirror (6) onto the exposure equipment, and controlling the laser of the exposure equipment to link with the axis of the collecting mirror (6) so that the laser spot can accurately scan the photoresist surface to obtain the grating pattern required by the design.

4. The method for preparing the extreme ultraviolet light source collecting mirror according to claim 2, characterized in that, After Step09, a binary grating structure (14) needs to be made, so repeat the steps: Step02-Step09.

5. The method for preparing the extreme ultraviolet light source collecting mirror according to claim 1, characterized in that, Step 7 specifically includes: using a white light interferometer to detect the dimensional accuracy of the grating of the collecting mirror (6), and using an atomic force microscope to detect the roughness at different positions of the grating, with a roughness value of less than 0.25 nm rms.

6. The method for preparing the extreme ultraviolet light source collecting mirror according to claim 1, characterized in that, Step 8 specifically includes: depositing a Mo / Si multilayer film (13) on the surface of the grating structure (14) using magnetron sputtering.

7. The method for preparing the extreme ultraviolet light source collecting mirror according to claim 1, characterized in that, Step 9 specifically includes: evaluating the extreme ultraviolet collection rate and infrared radiation removal rate of the collection mirror (6).

8. A processing device for an extreme ultraviolet light source collecting mirror, characterized in that, include: A base (1) is set at the bottom, and a Z-axis (2) and an X-axis (9) are provided above the base (1); the X-axis (9) and the Z-axis (2) respectively perform linear reciprocating motion; A B-axis (3) is located above the Z-axis (2), and a laser mounting bracket (4) is connected to the B-axis (3). A laser (5) is connected above the laser mounting bracket (4). The B-axis (3) controls the laser (5) to rotate around the Y-axis. By adjusting the laser mounting bracket (4), the center of the light emitted by the laser (5) is ensured to be at the required height, and the laser (5) is stably supported to operate. The C-axis (8) is connected above the X-axis (9). The C-axis (8) is connected to the pneumatic chuck (7). The collecting mirror (6) is clamped on the pneumatic chuck (7). The C-axis (8) drives the collecting mirror (6) to rotate around the Z-axis (2). The collecting mirror (6) includes: a substrate (10), the surface of which is provided with a silicon modified layer (11), and a light-transmitting hole (12) is provided at the center of the substrate (10); a grating structure (14) is provided above the silicon modified layer (11), and the surface of the grating structure (14) is coated with a multilayer film (13).

9. The processing equipment for the extreme ultraviolet light source collecting mirror according to claim 8, characterized in that, The material of the multilayer film (13) is Mo / Si.

10. The processing equipment for the extreme ultraviolet light source collecting mirror according to claim 9, characterized in that, The number of cycles of the multilayer film (13) is 42 to 48, and the thickness of a single cycle is 6 to 7 nm.

Images