A method for preparing a high-reflection film layer of an extreme ultraviolet collection concave mirror

Abstract

This invention relates to the field of optical thin film fabrication technology, and particularly to a method for preparing a high-reflectivity coating for an extreme ultraviolet (EUV) collecting concave mirror. The method includes: constructing a multi-chamber magnetron sputtering apparatus containing three deposition chambers for depositing Mo, Si, and a ruthenium protective layer respectively, an annealing chamber, and a vacuum-linked transport mechanism; each chamber is sealed and interconnected; a rotating stage is provided within the deposition chamber, with sputtering units positioned directly above and to the left and right of the stage, the side units symmetrically arranged and inclined at 20°~45° to the vertical line of the concave mirror center; the concave mirror is positioned by a central protrusion and fixed to the stage by vacuum adsorption; the chamber is evacuated and pre-purified with argon gas; Mo and Si films are deposited and annealed in a cyclic manner to form a Mo / Si multilayer film; a ruthenium protective layer is deposited and annealed, and after polishing, the high-reflectivity coating for the EUV collecting concave mirror is obtained. The advantages are: it is suitable for concave mirror coating, the film has good uniformity and high density, and the process is continuous and efficient.

Description

Technical Field

[0001] This invention relates to the field of optical thin film preparation and processing technology, and in particular to a method for preparing a high-reflectivity film layer for an extreme ultraviolet collecting concave mirror. Background Technology

[0002] With the advancement of science and technology, the pace of chip product updates and iterations—characterized by high integration and diverse functions—is accelerating. While maintaining functional diversity and stable lifespan, more and more chip manufacturers are pursuing smaller chip sizes and lower power consumption. This requires building more electronic components onto a smaller area, and the key semiconductor process for achieving this goal is photolithography, which uses shorter wavelengths of light to create smaller component patterns on specific photoresist. Therefore, collecting shorter wavelengths of light to participate in the fabrication of highly integrated chips has become a crucial problem to solve.

[0003] As chip integration becomes increasingly sophisticated, the need to build more electronic components within limited space necessitates the use of higher-resolution lithography machines. During lithography, the shorter the wavelength of light hitting the photoresist, the higher the resolution of the lithography machine. Currently, foreign-made extreme ultraviolet (EUV) lithography equipment can achieve EUV output at a wavelength of 13.5nm, but the lithography machines currently used in my country lag behind in performance. In the light source system of a lithography machine, besides bombarding metal droplets to generate shorter wavelength light, the effective collection of this light is also crucial. However, during the collection process of EUV light, the short wavelength is easily absorbed, making it impossible to focus the light through transmission. Therefore, using a concave mirror with high reflectivity to collect and focus EUV light is a very effective method. The concave mirror uses SiC as the substrate, and a Mo / Si stacked film with high reflectivity is prepared on its surface using magnetron sputtering. In this structure, the thickness of a single layer must be controlled between 2.5 and 4nm. Finally, a ruthenium thin film is sputtered as a protective layer. To achieve better reflection, the film thickness deposited on the concave mirror surface needs to be kept uniform to increase its ability to focus extreme ultraviolet light sources. Therefore, magnetron sputtering is chosen as the method for preparing high-reflectivity thin films.

[0004] The use of magnetron sputtering to prepare thin films has the following advantages: (1) High uniformity and consistency: The uniformity of the prepared thin film can be controlled within ±2%, and it is suitable for large-size substrates, which can accurately meet the core requirements of uniformity of concave mirror film; (2) High density and strong adhesion: Sputtered particles can form a dense structure with low porosity during deposition, and carry a certain amount of kinetic energy, which can significantly enhance the interfacial bonding force between the thin film and the SiC substrate, effectively avoid the risk of thin film detachment, and ensure the long-term stable operation of the concave mirror; (3) High purity and low defects: The deposition process is in a high vacuum environment, which can reduce the mixing of impurities. With high-purity target materials, thin films with a purity of 99.99% can be easily prepared, ensuring that the high reflectivity of the film layer is not affected.

[0005] In summary, magnetron sputtering offers advantages such as enabling high-quality fabrication of high-reflectivity Mo / Si multilayer films on concave mirror surfaces, while simplifying subsequent processing and mitigating potential risks. However, current mainstream magnetron sputtering equipment is designed for planar substrates, presenting significant technical bottlenecks. It cannot adapt to the curved structure of concave mirrors, making it difficult to fabricate uniform films with performance consistent with planar substrates. Therefore, modifying and upgrading the magnetron sputtering reaction chamber to adapt it to concave mirror substrates and fabricate high-reflectivity uniform films that meet requirements without compromising the original equipment performance is crucial for achieving efficient collection and focusing of extreme ultraviolet (EUV) light, and represents a major technical challenge in this field. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for preparing a high-reflectivity film layer on an extreme ultraviolet (EUV) collecting concave mirror.

[0007] The present invention aims to provide a method for preparing a high-reflectivity film layer for an extreme ultraviolet (EUV) collecting concave mirror, which specifically includes the following steps: S1. Construct a multi-chamber magnetron sputtering apparatus, including three identical coating chambers, one annealing chamber, and a vacuum-linked conveying mechanism. The chambers are connected by a sealed vacuum channel. The three coating chambers are used to deposit Mo films, Si films, and ruthenium protective layers, respectively. A rotating stage is set at the center of the bottom of the coating chamber. A sputtering unit is set at the top, top left and top right of the rotating stage. The left sputtering unit and the right sputtering unit are symmetrically arranged on both sides of the vertical line of the stage center, and form an inclination angle of 20° to 45° with the vertical line of the concave mirror center. S2. Place the concave mirror on the rotating stage of the Mo film deposition chamber, align the central through-hole of the concave mirror with the central protrusion, and fix the concave mirror by vacuum adsorption; evacuate the chamber and pre-purge with argon gas; S3. A single-layer Mo film is deposited in the Mo film deposition chamber and transferred to the annealing chamber for annealing. After annealing, a single-layer Si film is deposited in the Si film deposition chamber and transferred to the annealing chamber for annealing. The cycle is repeated to form a Mo / Si multilayer film. S4. The concave mirror is transferred to the ruthenium film deposition chamber to deposit the ruthenium protective layer, and then transferred to the annealing chamber for annealing; S5. After removing the concave mirror, polish it to obtain the high-reflectivity coating layer of the extreme ultraviolet collecting concave mirror.

[0008] Preferably, both the left and right sputtering units include a target, an electromagnet, a target angle adjustment end, and a target distance adjustment end; The target is mounted on the target angle adjustment end, which drives the target to rotate around the horizontal axis, so that the angle between the target and the vertical line of the center of the concave mirror can be continuously adjusted within the range of 20° to 45°. The target angle adjustment end is connected to the target distance adjustment end. The target distance adjustment end drives the entire sputtering unit to translate in a direction perpendicular to the target surface, so as to achieve precise adjustment of the distance between the target and the concave mirror surface. The electromagnet has multiple independent voltage application terminals on its surface. By adjusting the magnetic field line distribution through differential voltage, the trajectory of argon ion bombardment can be changed.

[0009] Preferably, the rotating stage includes a concave mirror support stage and a stage rotating shaft. The upper surface of the concave mirror support stage is a concave support surface that matches the curvature of the concave mirror to be coated. A central protrusion is provided in the center, and the central protrusion is fitted into the central through hole of the concave mirror. A vacuum adsorption groove is opened on the surface of the concave mirror support stage, and multiple air holes are evenly distributed in the vacuum adsorption groove.

[0010] Preferably, the heating stage structure of the annealing chamber is the same as the rotating stage of the coating chamber, and the heating stage is provided with an annular heating element inside.

[0011] Preferably, the Mo film is deposited using a DC power supply, and the Si film is deposited using a radio frequency power supply. Each layer is annealed after deposition, and the cycle count is 45 to 60 times.

[0012] Preferably, the power of the DC power supply is 1200~3000W; the power of the RF power supply is 150~480W.

[0013] Preferably, the thickness of the ruthenium protective layer is 5~10nm.

[0014] Preferably, the annealing temperature is 220~500℃.

[0015] Preferably, in step S2, the vacuum level after evacuation of the chamber is ≤1×10⁻⁶. -4 Pa, the argon gas pre-purge time is 6~10 seconds, and the argon gas flow rate is 40~80 sccm.

[0016] Preferably, in step S5, the polishing process uses laser-assisted chemical mechanical polishing to polish the film surface.

[0017] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention, by modifying the structure of a magnetron sputtering (PVD) chamber, precisely prepares a high-reflectivity film on the surface of an extreme ultraviolet (EUV) collecting concave mirror. This effectively solves the technical challenge in existing EUV light source systems where the extremely short wavelength of EUV light is easily absorbed by the medium, making it difficult to efficiently collect and focus it. The high-reflectivity film prepared by this invention significantly improves the reflection efficiency of EUV light, ensuring efficient collection and focusing of specific wavelengths of EUV light, meeting the usage requirements of EUV light source systems. Simultaneously, the film effectively protects the concave mirror body, significantly extending its service life, reducing the frequency of mirror replacement, thereby lowering equipment maintenance costs and improving the operational stability and economy of the entire EUV light source system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the internal structure of the coating chamber of a multi-chamber magnetron sputtering apparatus provided according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a sputtering unit structure provided according to an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of a rotating platform structure provided according to an embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the surface structure of the rotating stage according to an embodiment of the present invention.

[0022] Figure 5 The results are SEM test results of Mo thin films sputtered by concave mirrors according to embodiments of the present invention.

[0023] Figure label: 1. Top sputtering unit; 2. Left sputtering unit; 3. Right-side sputtering unit; 31. Target material; 32. Voltage application terminal; 33. Electromagnet; 34. Target angle adjustment terminal; 35. Target distance adjustment terminal; 4. Concave mirror; 5. Rotating stage; 51. Concave mirror support stage; 52. Stage rotation shaft; 53. Central protrusion; 54. Air hole; 55. Vacuum adsorption tank. Detailed Implementation

[0024] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0026] This invention provides a method for preparing a high-reflectivity film on an extreme ultraviolet (EUV) concave mirror. By improving existing multi-target magnetron sputtering equipment, it overcomes the limitation of current mainstream magnetron sputtering equipment, which can only prepare thin films on planar substrates. Without reducing equipment performance, it enables the preparation of thin films with the same excellent performance as planar substrates on concave mirror substrates, thus achieving the preparation of a high-reflectivity film on an EUV concave mirror. The specific steps include: S1. Equipment Modification and Parameter Preset: S11. Equipment Modification: Design a multi-chamber magnetron sputtering system, including three identical deposition chambers, an annealing chamber, and a vacuum-linked transport mechanism. Each chamber is connected via a sealed vacuum channel, enabling automated processing with no atmospheric exposure to the substrate throughout the entire process. The three deposition chambers are used to deposit different film layers respectively. The transport chamber is located in the center, with the three deposition chambers and the annealing chamber arranged around it. This arrangement reduces the transport time of the concave mirror during film preparation and annealing, thereby improving overall efficiency. Adjacent chambers are spaced apart (e.g., 50 cm), and each chamber is equipped with an independent vacuum pumping system and gas supply system, allowing for the independent deposition of Mo, Si, and ruthenium protective layers, avoiding cross-contamination during different film layer preparations. The annealing chamber is connected to the deposition chambers via a vacuum transport channel for post-deposition crystallization treatment, improving film density and interfacial adhesion.

[0027] See Figures 1-4 A rotating stage 5 is set at the center of the bottom of the coating chamber. A sputtering unit is set at the top, top left and top right of the rotating stage 5. The left sputtering unit 2 and the right sputtering unit 3 have the same structure. The rotating stage 5 includes a concave mirror support stage 51 and a carrier shaft 52 for supporting the concave mirror support stage. The concave mirror support stage 51 has a circular structure, and its upper surface is machined into a concave support surface that perfectly matches the curvature of the EUV collecting concave mirror to be coated. A central protrusion 53 is set in the center (the diameter is tolerance-matched with the central through hole of the concave mirror 4, with a tolerance range of ±0.02mm, and the height is consistent with the thickness of the central through hole of the concave mirror 4) to ensure that the geometric center of the concave mirror 4 coincides with the rotation center of the stage after placement. A vacuum adsorption groove 55 is opened on the surface of the concave mirror support stage 51. Eight air holes 54 (1mm in diameter) for vacuum adsorption are evenly distributed in the vacuum adsorption groove 55. The air holes 54 are connected to the vacuum pump group outside the chamber through the internal air channel of the stage. When opened, it can form a vacuum pump group of ≤5×10⁻⁶ mm. -3 The negative pressure of Pa firmly adsorbs and fixes the concave mirror, preventing displacement or shifting during the coating process. The bottom of the concave mirror support stage 51 is rigidly connected to the stage rotating shaft 52, which extends downward to the outside of the chamber and is coaxially connected to the output end of the variable frequency motor. This allows for stepless speed regulation of 5~30r / min with a rotation accuracy of ±0.1r / min. Combined with the three-target layout, this further improves the uniformity of the film layer. The concave mirror support stage 51 can rotate clockwise or counterclockwise, and the rotation speed is controllable. In some embodiments, the vacuum adsorption tank is an annular tank, arranged in concentric circles with the central protrusion as the center, with a tank width of 2~3mm and a depth of 1~2mm.

[0028] A set of sputtering units is set directly above, to the upper left and to the upper right of the rotating stage 5. The three sets of units are triangularly symmetrically distributed and are at a certain horizontal distance (e.g., 100~150mm) from the rotation center of the stage. The left sputtering unit 2 and the right sputtering unit 3 are symmetrically arranged on both sides of the vertical line of the stage center, forming a certain horizontal angle (e.g., 60°) with the sputtering unit directly above, ensuring that the sputtering range of the three sets of sputtering units completely covers the entire curved surface area of ​​the concave mirror 4. The left sputtering unit 2 and the right sputtering unit 3 each include a target, an electromagnet, a target angle adjustment end (servo mechanism) and a target distance adjustment end (screw assembly). Taking the right-side sputtering unit 3 as an example, the right-side sputtering unit 3 includes a target 31, an electromagnet 33, a target angle adjustment end 34, and a target distance adjustment end 35; The target 31 is a circular high-purity target (Mo / Si / ruthenium, purity ≥99.99%), and the back of the target 31 is kept horizontal with the electromagnet 33. In specific embodiments, the target 31 adopts a circular structure (diameter 200~400mm, thickness 4~8mm), and the materials are high-purity Mo target (purity ≥99.99%), high-purity Si target (purity ≥99.999%), and high-purity ruthenium target (purity ≥99.99%), respectively. In some embodiments, the target size can be determined according to the size of the concave mirror, and the target diameter can also be greater than 400mm. Several independent voltage application terminals 32 are evenly arranged on the surface of the electromagnet 33. Differential voltage signals are output through the overall control system to regulate the distribution of magnetic field lines and change the trajectory of argon ions bombarding the target material 31, so that sputtered particles are deposited on the surface of the concave mirror 4 along a preset path, thus solving the problem of uneven deposition thickness on curved surfaces. The target angle adjustment end 34 can be fixed by either the top flange of the chamber or the side wall bracket. The output shaft is rigidly connected to the connecting shafts at both ends of the electromagnet 33, which can drive the target 31 to rotate around the horizontal axis, so that the angle between the target 31 and the center vertical line of the rotating stage 5 can be continuously adjusted from 20° to 45° with an adjustment accuracy of ±0.5°, which can adapt to the coating requirements of concave mirrors with different curvatures. The target distance adjustment end 35 and the target angle adjustment end 34 are fixed and driven by a stepper motor. The stepper motor can drive the entire sputtering unit to translate along a direction perpendicular to the surface of the target 31, so as to achieve precise adjustment of the distance between the target 31 and the surface of the concave mirror 4 with an adjustment accuracy of ±0.1mm. The sputtering distance can be flexibly adjusted according to the size, curvature and film deposition requirements of the concave mirror 4 to ensure the uniformity of sputtered particle deposition.

[0029] The core component of the annealing chamber is the heating stage, whose basic structure is consistent with the rotating stage 5 of the coating chamber, ensuring that the positioning reference of the concave mirror during the annealing process remains consistent with that during the coating stage. The heating stage is internally fitted with embedded annular heating elements (made of high-purity nickel-chromium alloy), evenly distributed concentrically around the central protrusion 53. The spacing between adjacent heating elements is 15~25mm, and the total heating power ranges from 0~3000W, enabling precise temperature control from 220℃ to 500℃ with a control accuracy of ±5℃. In some embodiments, a platinum resistance temperature probe is configured inside the annealing chamber to provide real-time temperature data feedback to the central control system, forming a closed-loop regulation.

[0030] The vacuum linkage conveying mechanism uses a vacuum robotic arm as its core conveying component. The robotic arm is positioned within a sealed channel between the chambers, with a repeatability of ±0.1mm and a maximum load of 5kg. The vacuum robotic arm can accurately identify the position of the concave mirror 4 on the rotating stage 5, ensuring collision-free and displacement-free handling during the loading and unloading process. An independent vacuum maintenance system is configured within the conveying channel to ensure a vacuum level ≤1×10⁻⁶ within the channel during conveying. -4 Pa, to prevent the concave mirror surface film from being exposed to the atmosphere and oxidizing.

[0031] The multi-chamber magnetron sputtering equipment of the present invention can be equipped with an existing industrial PLC or industrial computer as a central control unit for preset process parameters, monitoring chamber status and controlling the linkage of each unit. Its control logic and hardware selection are implemented using mature industrial control solutions in the existing technology.

[0032] S12. Parameter Preset: The high-reflectivity membrane layer is optimized using TFC membrane system design software to determine the core process parameters, which are then input into the central control system. The system automatically distributes these parameters to each chamber for execution. Film system parameters: The total number of Mo / Si stack layers is 45~60, with the thickness of a single Mo layer being 1.5~4.5nm, the thickness of a single Si layer being 1.5~4.5nm, and the thickness of the ruthenium protective layer being 5~10nm; Coating chamber parameters: Argon flow rate 40~80 sccm (preferably 60 sccm), chamber vacuum degree ≤1×10 -4 Pa, argon gas pre-purging time 6~10 seconds; Mo film deposition chamber DC power 1200~3000W (preferably 2000W), Si film deposition chamber RF power 150~480W (preferably 300W), ruthenium film deposition chamber DC power 3000~7200W (preferably 5000W); stage rotation speed 5~20r / min (preferably 5r / min); the two sputtering units on both sides maintain an inclination angle of 20°-45° with the center vertical line of the concave mirror 4; Annealing chamber parameters: annealing temperature 220~500℃ (preferably 350℃), holding time 8~15min (preferably 10min), heating rate 5℃ / min, cooling rate 3℃ / min; stage rotation speed 8~15r / min to ensure uniform heating of the film layer.

[0033] S2. Concave Mirror Loading and Chamber Pretreatment: Place the concave mirror 4 on the rotating stage 5 of the Mo film deposition chamber, ensuring precise engagement between the central through-hole of the concave mirror 4 and the central protrusion 53 on the concave mirror stage 51. Activate the vacuum adsorption system, forming a ≤5×10⁻⁵ m² / m² structure through the pores 54. -3 A negative pressure of Pa securely adheres the concave mirror 4 to the concave mirror support stage 51; the chamber door is closed, and the vacuum system is activated to evacuate the chamber to a vacuum level ≤1×10⁻⁶. -4 Pa, then argon gas is pre-purged into the chamber to purify the chamber environment and ensure the stability of the sputtering process.

[0034] In some embodiments, the concave mirror 4 is made of SiC; the pre-purging time of argon gas is 8 seconds.

[0035] S3.Mo / Si film cyclic deposition and annealing; specifically including: S31. Mo Film Deposition and Annealing: Start the DC power supply and electromagnet of the Mo film deposition chamber. The DC power supply power is in the range of 1200~3000W. Argon ions bombard the Mo target under the control of magnetic field lines. The rotating stage 5 continues to rotate to make the sputtered particles uniformly deposited on the surface of the concave mirror 4. After the preset deposition time is reached, the power supply is turned off to complete the preparation of one layer of Mo film. Transfer the concave mirror 4 from the Mo film deposition chamber to the annealing chamber. Start the heating element to 220~500℃. Anneal at this temperature for 5~15min to allow the Mo film to fully crystallize and improve the film density and stability. S32. Si film deposition and annealing: The concave mirror 4 is transferred to the Si film deposition chamber, and the radio frequency (RF) power supply and electromagnet of the Mo film deposition chamber are turned on. The RF power supply power is in the range of 150~480W. Argon ions bombard the Si target material under the control of magnetic field lines. The rotating stage 5 continues to rotate so that the sputtered particles are uniformly deposited on the surface of the concave mirror 4. After the preset deposition time is reached, the power supply is turned off to complete the preparation of one layer of Si film. The concave mirror 4 is transferred from the Si film deposition chamber to the annealing chamber and annealed at 220~500℃ for 5~15min. S33. Repeat steps S31 to S32 to complete the cyclic deposition and annealing of 45 to 60 layers of Mo / Si film. The deposition time for each layer is automatically and precisely controlled by the system according to the film thickness.

[0036] S4. Ruthenium protective layer preparation and annealing: The concave mirror 4 is transferred to the ruthenium film deposition chamber to deposit a ruthenium thin film protective layer of 5~10 nm. The DC power supply is in the range of 3000~7200W. The concave mirror 4 is transferred to the annealing chamber and annealed at 220~500℃ for 5~15 min.

[0037] In some embodiments, the total number of Mo / Si film layers is 50, the thickness of a single Mo film layer is 2.5 nm, the thickness of a single Si film layer is 3 nm, and the thickness of the ruthenium protective layer is 8 nm.

[0038] S5. Unloading and post-processing: After annealing, the concave mirror 4 is transferred to the unloading position and the vacuum adsorption system is turned off; the concave mirror 4 is taken out and the surface of the film is polished by laser-assisted chemical mechanical polishing technology to remove surface defects, and finally a high-reflectivity film layer of extreme ultraviolet collecting concave mirror with a reflectivity of ≥70% at 13.5nm is obtained.

[0039] In some embodiments, the polishing pressure is 0.08 MPa and the polishing time is 15 min.

[0040] Figure 5 The SEM test results of the Mo film sputtered by the concave mirror using the chamber modified by the present invention are shown. Figure 5Figures (a), (b), and (c) show the actual thickness results at three locations from the center to the edge of the concave mirror, respectively. As can be seen from the figures, the film thickness remains around 200 Å at each location, indicating uniform thickness.

[0041] The key technical points and advantages of this invention are as follows: Three sputtering units are arranged symmetrically in a triangular pattern at the top and left / right sides of the coating chamber. Combined with a dual-dimensional adjustment mechanism for the target angle (adjustable from 20° to 45°) and distance, this overcomes the limitation of traditional single / dual-target equipment being unable to adapt to concave substrates, achieving uniform sputtering across the entire curved surface. Multiple independent voltage application terminals are set on the electromagnet surface. Differential voltage outputs precisely control the distribution of magnetic field lines, altering the trajectory of argon ions bombarding the target, causing sputtered particles to deposit along a preset path, effectively solving the technical bottleneck of uneven film thickness between the center and edges of concave mirrors. A cyclic process of Mo film deposition, annealing, Si film deposition, and annealing is employed, combined with full-process vacuum transport, avoiding film oxidation and contamination, improving film density and interfacial adhesion, ultimately achieving the preparation of a high-reflectivity film with a reflectivity ≥70% at 13.5nm. The entire process is automated, reducing manual intervention and improving production efficiency and product consistency. Based on the modification of existing magnetron sputtering equipment, no major hardware replacement is required, reducing equipment upgrade costs.

[0042] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0043] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a high-reflectivity film layer for an extreme ultraviolet (EUV) collecting concave mirror, characterized in that: Specifically, the steps include the following: S1. Construct a multi-chamber magnetron sputtering apparatus, including three identical coating chambers, one annealing chamber, and a vacuum-linked conveying mechanism. The chambers are connected by a sealed vacuum channel. The three coating chambers are used to deposit Mo films, Si films, and ruthenium protective layers, respectively. A rotating stage is set at the center of the bottom of the coating chamber. A sputtering unit is set at the top, top left and top right of the rotating stage. The left sputtering unit and the right sputtering unit are symmetrically arranged on both sides of the vertical line of the stage center, and form an inclination angle of 20° to 45° with the vertical line of the concave mirror center. S2. Place the concave mirror on the rotating stage of the Mo film deposition chamber, align the central through-hole of the concave mirror with the central protrusion, and fix the concave mirror by vacuum adsorption; evacuate the chamber and pre-purge with argon gas; S3. A single-layer Mo film is deposited in the Mo film deposition chamber and transferred to the annealing chamber for annealing. After annealing, a single-layer Si film is deposited in the Si film deposition chamber and transferred to the annealing chamber for annealing. The cycle is repeated to form a Mo / Si multilayer film. S4. The concave mirror is transferred to the ruthenium film deposition chamber to deposit the ruthenium protective layer, and then transferred to the annealing chamber for annealing; S5. After removing the concave mirror, polish it to obtain the high-reflectivity coating layer of the extreme ultraviolet collecting concave mirror.

2. The method for preparing a high-reflectivity film layer for an extreme ultraviolet (EUV) collecting concave mirror according to claim 1, characterized in that: Both the left and right sputtering units include a target, an electromagnet, a target angle adjustment end, and a target distance adjustment end; The target is mounted on the target angle adjustment end, which drives the target to rotate around the horizontal axis, so that the angle between the target and the vertical line of the center of the concave mirror can be continuously adjusted within the range of 20° to 45°. The target angle adjustment end is connected to the target distance adjustment end. The target distance adjustment end drives the entire sputtering unit to translate in a direction perpendicular to the target surface, so as to achieve precise adjustment of the distance between the target and the concave mirror surface. The electromagnet has multiple independent voltage application terminals on its surface. By adjusting the magnetic field line distribution through differential voltage, the trajectory of argon ion bombardment can be changed.

3. The method for preparing a high-reflectivity film for an extreme ultraviolet (EUV) collecting concave mirror according to claim 1, characterized in that: The rotating stage includes a concave mirror support stage and a stage shaft. The upper surface of the concave mirror support stage is a concave support surface that matches the curvature of the concave mirror to be coated. A central protrusion is provided in the center, and the central protrusion is fitted into the central through hole of the concave mirror. A vacuum adsorption groove is opened on the surface of the concave mirror support stage, and multiple air holes are evenly distributed in the vacuum adsorption groove.

4. The method for preparing a high-reflectivity film layer for an extreme ultraviolet collecting concave mirror according to claim 1, characterized in that: The heating stage structure of the annealing chamber is the same as that of the rotating stage of the coating chamber, and the heating stage is provided with an annular heating element inside.

5. The method for preparing a high-reflectivity film layer for an extreme ultraviolet collecting concave mirror according to claim 1, characterized in that: The Mo film is deposited using a DC power supply, and the Si film is deposited using a radio frequency power supply. Each layer is annealed after deposition, and the cycle count is 45 to 60 times.

6. The method for preparing a high-reflectivity film layer for an extreme ultraviolet (EUV) collecting concave mirror according to claim 5, characterized in that: The power of the DC power supply is 1200~3000W; the power of the RF power supply is 150~480W.

7. The method for preparing a high-reflectivity film for an extreme ultraviolet (EUV) collecting concave mirror according to claim 1, characterized in that: The thickness of the ruthenium protective layer is 5~10 nm.

8. The method for preparing a high-reflectivity film layer for an extreme ultraviolet collecting concave mirror according to claim 1, characterized in that: The annealing temperature is 220~500℃.

9. The method for preparing a high-reflectivity film layer for an extreme ultraviolet collecting concave mirror according to claim 1, characterized in that: In step S2, the vacuum level after evacuation of the chamber is ≤1×10⁻⁶. -4 Pa, the argon gas pre-purge time is 6~10 seconds, and the argon gas flow rate is 40~80 sccm.

10. The method for preparing a high-reflectivity film layer for an extreme ultraviolet collecting concave mirror according to claim 1, characterized in that: In step S5, the polishing process uses laser-assisted chemical mechanical polishing to polish the surface of the film layer.

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