A method for preparing an extreme ultraviolet reflective film

Abstract

This invention relates to the field of extreme ultraviolet (EUV) lithography, and more particularly to a method for preparing an EUV reflective thin film. The method includes: placing a substrate in an atomic layer deposition (ALD) chamber, evacuating and stabilizing the temperature; alternately depositing Mo and Si layers using an ALD process; the Mo layer uses Mo(CO)6 as a precursor and is grown through a cycle of low-temperature adsorption, high-temperature decomposition, and purging; the Si layer uses Si3H8 and SiCl4 as precursors and is deposited in a single cycle to form 2-6 atomic layers; high-temperature annealing is performed after deposition; 30-50 pairs of Mo / Si multilayer films are formed; and finally, a surface protective layer is prepared. ALD reduces equipment and process control requirements, achieving high uniformity and consistency coating on large-size curved substrates. It offers strong precursor adaptability, low cost, and preparation efficiency comparable to magnetron sputtering but with simpler control, significantly reducing equipment requirements. The thin film exhibits excellent resistance to laser damage and is suitable for coating reflective optical components in the EUV lithography field.

Description

Technical Field

[0001] This invention relates to the field of extreme ultraviolet lithography, and more particularly to a method for preparing an extreme ultraviolet reflective thin film. Background Technology

[0002] Extreme ultraviolet (EUV) wavelengths typically refer to wavelengths of 13.5 nm and below, primarily used in EUV lithography, a core process in semiconductor manufacturing. The application scenarios of EUV reflective films heavily rely on high reflectivity and high-temperature resistance, ensuring that EUV light from the overall reflective optical system cannot penetrate any material. Imaging is achieved through an optical system composed of multiple reflective mirrors. Mo / Si multilayer films (alternating layers of Mo and Si, each layer with a thickness of ~2~7 nm) are the mainstream choice for this 13.5 nm wavelength band. A single mirror can achieve a reflectivity of over 70%, and after multiple reflections, the energy of the light source can be focused onto the silicon wafer, enabling chip manufacturing processes below 5 nm.

[0003] The core of EUV reflective films is the alternating stacking (30-50 layers) of high-refractive-index materials (Si) and low-refractive-index materials (Mo), utilizing the Bragg interference effect to achieve high reflectivity, and introducing gradient layers or interface barrier layers to prevent material interdiffusion.

[0004] The current mainstream industrial preparation method for Mo / Si extreme ultraviolet reflective thin films is magnetron sputtering. Magnetron sputtering relies on plasma bombardment of the target material, causing material atoms to be deposited on the substrate surface in gaseous form. By precisely controlling the sputtering power, gas pressure, rotation speed, and deposition time, nanometer-thick thin film stacking can be achieved. To meet the stringent requirements of EUV lithography, existing magnetron sputtering processes must simultaneously achieve several high-precision indicators: (1) High reflectivity: ensuring that the normal incident reflectivity at 13.5nm reaches more than 70%; (2) Ultra-low surface roughness: the surface roughness must be controlled below 0.1nm to avoid light scattering loss; (3) Ultra-high layer thickness precision: the single-layer thickness control precision must reach within ±0.1nm to ensure the consistency of the periodic structure of the multilayer film; (4) Large size and high uniformity of curved surfaces: it can be adapted to large-size substrates with a diameter of more than 300mm and complex curved surface mirrors such as hemispherical mirrors, and the uniformity of film thickness and optical performance must be controlled within 1%; (5) Mass production consistency: the reflectivity difference between different batches of reflective films must be less than 0.5% to meet the needs of large-scale and stable semiconductor lithography production. The above requirements place high demands on instruments and equipment, extremely strict requirements on process control, and demanding requirements on the uniformity and consistency of large curved surfaces, which are the difficulties of magnetron sputtering technology. In large-scale mass production scenarios, magnetron sputtering technology is gradually becoming unable to meet the application requirements of EUV lithography reflective thin films in terms of uniformity of complex curved surfaces, batch stability, process fault tolerance, and preparation cost. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing an extreme ultraviolet reflective thin film.

[0006] The present invention aims to provide a method for preparing an extreme ultraviolet reflective thin film, which specifically includes the following steps: S1. Place the substrate in the atomic layer deposition chamber, evacuate the vacuum, and stabilize the substrate temperature to a first temperature; the first temperature is below 70°C; S2. Introduce Mo(CO)6 precursor into the cavity for 0.01~30s to allow Mo(CO)6 to adsorb on the substrate surface; purge with inert gas to remove unadsorbed Mo(CO)6; heat the substrate to a second temperature to thermally decompose Mo(CO)6 and form a Mo atomic layer; purge with inert gas to remove the decomposition products and lower the substrate temperature back to the first temperature; repeat several cycles to form a Mo layer of the target thickness. S3. An isolation layer is deposited on the Mo layer using atomic layer deposition (ALD) technology; S4. Heat to the third temperature, introduce Si3H8 precursor for 0.01~30s; purge with inert gas to remove unadsorbed Si3H8; heat the substrate to the fourth temperature, introduce SiCl4 precursor and react, the introduction time is 0.01~30s; purge with inert gas to remove unreacted substances; repeat several cycles to form a Si layer of the target thickness. S5. Anneal the Si layer at 400~550℃ for 1~30min; S6. An isolation layer is deposited on the Si layer using atomic layer deposition (ALD) technology; S7. Repeat steps S2 to S6 to form a multi-period Mo / Si multilayer film; S8. A surface protective layer is prepared on a multilayer film using atomic layer deposition (ALD) technology.

[0007] Preferably, the second temperature is 150℃~250℃; the third temperature is 70~300℃; and the fourth temperature is 200~400℃.

[0008] Preferably, the surface protective layer is SiC or Mo. x One of C, Ru, RuO2, RuN, Rh, AlN, SiN, ZrO2, and TiO2, with a thickness of 1~5nm.

[0009] Preferably, in step S2, 1 to 2 Mo atomic layers are deposited and grown in a single cycle.

[0010] Preferably, in step S3, 2 to 6 Si atomic layers are formed by single-cycle deposition.

[0011] Preferably, the insulating layer material includes C, Si3N4, B4C, LaN, SiC, or AlN, with a thickness of 1 to 5 atoms.

[0012] Preferably, the substrate is a planar substrate or a curved substrate.

[0013] Preferably, the inert gas is N2, and the purging time of the inert gas is 5~30s.

[0014] Compared with the prior art, the present invention can achieve the following beneficial effects: The method for preparing extreme ultraviolet reflective thin films of this invention reduces equipment and process control requirements, achieves uniformity and consistency on large curved surfaces, and significantly reduces costs. Due to atomic layer deposition, single-layer atomic deposition can be achieved on arbitrary curved surfaces, offering simple control, good uniformity, and strong repeatability. Furthermore, in the extreme ultraviolet application band, the required thickness of each layer is only a few dozen atomic layers, and the time consumed is comparable to magnetron sputtering technology, significantly reducing the requirements for equipment and processes. Attached Figure Description

[0015] Figure 1 This is a flowchart of a method for preparing an extreme ultraviolet reflective thin film according to an embodiment of the present invention. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] See Figure 1 This invention provides a method for preparing an extreme ultraviolet reflective thin film based on atomic layer deposition (ALD) technology, specifically including the following steps: S1. Place the substrate in the atomic layer deposition chamber, evacuate the vacuum, and stabilize the substrate temperature to a first temperature; the first temperature is below 70°C; Specifically, the base is a planar base or a curved base with a diameter ≥ 300 mm; S2. A Mo layer is deposited on the substrate using atomic layer deposition (ALD) technology, including: S21. Introduce Mo(CO)6 precursor into the cavity for 0.01~30s to allow Mo(CO)6 to adsorb on the substrate surface; purge with inert gas to remove unadsorbed Mo(CO)6. S22. Heat the substrate to a second temperature to thermally decompose Mo(CO)6 and form a Mo atomic layer. The second temperature is 150℃~250℃. Inert gas is introduced to purge the decomposition products and the substrate temperature is reduced back to the first temperature. S23. Repeat steps S21~S22 for several cycles to form a Mo layer of the target thickness; Specifically, 1 to 2 Mo atomic layers are deposited and grown in each cycle; S3. An isolation layer is deposited on the Mo layer using atomic layer deposition to prevent interdiffusion between different material layers, especially between the Mo layer and the Si layer; Specifically, the insulating layer material includes C, Si3N4, B4C, LaN, SiC, or AlN, with a thickness of 1 to 5 atoms. S4. A Si layer is deposited on the Mo layer using atomic layer deposition, including: S41. Heat to the third temperature, introduce Si3H8 precursor to adsorb it, the introduction time is 0.01~30s, the third temperature is 70~300℃; introduce inert gas to purge and remove unadsorbed Si3H8. S42. Heat the substrate to the fourth temperature, introduce SiCl4 precursor and allow it to react. The introduction time is 0.01~30s, and the fourth temperature is 200~400℃. Purge with inert gas to remove unreacted precursor and byproducts. S43. Repeat steps S41~S42 for several cycles to form a Si layer of the target thickness; Specifically, a single-cycle deposition forms 2 to 6 Si atomic layers with a thickness of approximately 0.2 to 0.6 nm; S5. The Si layer is subjected to high-temperature annealing treatment at a temperature of 400~550℃ and a holding time of 1~30min, so that the internal Si-H bonds and Si-Cl bonds are fully broken, thereby improving the laser damage resistance of the film. S6. An isolation layer is deposited on the Si layer using atomic layer deposition to prevent interdiffusion between different material layers, especially between the Mo layer and the Si layer; Specifically, the insulating layer material includes C, Si3N4, B4C, LaN, SiC, or AlN, with a thickness of 1 to 5 atoms. S7. Repeat steps S2 to S6 to form a multi-period Mo / Si multilayer film; Specifically, the number of periodic pairs in Mo / Si multilayer films is 30 to 50. S8. A surface protective layer is prepared on a multilayer film using atomic layer deposition (ALD) technology; The surface protective layer is SiC and Mo. xOne of C, Ru, RuO2, RuN, Rh, AlN, SiN, ZrO2, and TiO2, with a thickness of 1~5nm; In some embodiments, the inert gas is N2, and the inert gas purging time is 5~30s; In some embodiments, step S1 evacuates the cavity to a vacuum level less than 1×10⁻⁶. -6 Torr.

[0019] Example 1 This embodiment provides a method for preparing extreme ultraviolet reflective thin films based on atomic layer deposition, including the following steps: S1. Place the substrate in the atomic layer deposition chamber, evacuate, and stabilize the substrate temperature to 60°C; S2. Deposit a Mo layer, which includes the following sub-steps: S21. Introduce Mo(CO)6 precursor into the cavity for 2s to allow it to be fully adsorbed on the substrate surface; purge with N2 for 10s to remove unadsorbed Mo(CO)6. S22. Heat to 180℃ to thermally decompose Mo(CO)6 and form a Mo atomic layer; purge with N2 for 10s to remove decomposition products, and then reduce the temperature to 60℃. S23. Repeat steps S21~S22 for a total of 8 cycles to form a Mo layer of the target thickness; After the S3.Mo layer is grown, Si3N4 or B4C with a thickness of 3 atoms is prepared by ALD as an isolation layer. S4. Deposit a Si layer, which includes the following sub-steps: S41. Heat to 150℃, introduce Si3H8 precursor for 1s; purge with N2 for 10s to remove unadsorbed Si3H8. S42. Heat to 250℃, introduce SiCl4 precursor for 1s; purge with N2 for 10s to remove unreacted precursor and byproducts. S43. Repeat steps S41~S42 for a total of 10 cycles to form a Si layer; approximately 4 Si atomic layers are grown per cycle, with a thickness of approximately 0.4 nm; S5. The Si layer is subjected to high-temperature annealing at 450℃ for 10 minutes. S6. After the Si layer is grown, use ALD to prepare a Si3N4 or B4C layer with a thickness of 3 atoms as an isolation layer; S7. Repeat steps S2 to S6 for a total of 40 cycles to form a Mo / Si multilayer film. S8. A RuO2 surface protective layer with a thickness of 3 nm was prepared on the surface of the multilayer film by atomic layer deposition.

[0020] Example 2 This embodiment provides a method for preparing extreme ultraviolet reflective thin films based on atomic layer deposition. The difference from Embodiment 1 lies in the different process parameters and surface protective layer materials. The specific steps are as follows: S1. Place the substrate in the atomic layer deposition chamber, evacuate, and stabilize the substrate temperature to 50°C; S2. Deposited Mo layer: S21. Introduce Mo(CO)6 precursor for 1.5s; purge with N2 for 8s; S22. Heat to 200℃ for thermal decomposition; purge with N2 for 8 seconds, then cool back to 50℃; S23. Repeat steps S21-S22 for a total of 10 cycles to form the Mo layer; After the S3.Mo layer is grown, Si3N4 or B4C with a thickness of 3 atoms is prepared by ALD as an isolation layer. S4. Deposit a Si layer, which includes the following sub-steps: S41. Heat to 120℃, introduce Si3H8 precursor for 1.2s; purge with N2 for 8s; S42. Heat to 280℃, introduce SiCl4 precursor for 1.2s; purge with N2 for 8s; S43. Repeat steps S41~S42 for a total of 12 cycles to form a Si layer; approximately 4~5 Si atomic layers are grown per cycle; S5. Annealing treatment: Temperature 500℃, hold for 8 minutes; After the S6.Si layer is grown, a 3-atom-thick Si3N4 or B4C layer is prepared by ALD as an isolation layer. S7. Repeat steps S2 to S6 for a total of 45 cycles to form a Mo / Si multilayer film; S8. Finally, a Ru surface protective layer with a thickness of 1.5 nm is deposited.

[0021] Example 3 This embodiment provides a method for preparing extreme ultraviolet reflective thin films suitable for large-size, large-curvature substrates. The specific steps are as follows: S1. Place a large-sized planar or curved substrate in the atomic layer deposition chamber, evacuate the vacuum chamber, and stabilize the substrate temperature to 65°C; S2. Deposit a Mo layer, which includes the following sub-steps: S21. Introduce Mo(CO)6 precursor for 2.5s; purge with N2 for 12s; S22. Heat to 190℃ for thermal decomposition; purge with N2 for 12 seconds, then cool back to 65℃; S23. Repeat steps S21~S22 for a total of 7 cycles to form a Mo layer with a target thickness of 2.8 nm; After the S3.Mo layer is grown, a 3-atom-thick Si3N4 or B4C layer is prepared by ALD as an isolation layer with a target thickness of 1.5 nm. S4. Deposit a Si layer, which includes the following sub-steps: S41. Heat to 180℃, introduce Si3H8 precursor for 1.5s; purge with N2 for 12s; S42. Heat to 300℃, introduce SiCl4 precursor for 1.5s; purge with N2 for 12s; S43. Repeat steps S41~S42 for a total of 9 cycles to form a Si layer; approximately 3~4 Si atomic layers are grown per cycle, with a target thickness of 4.2nm; S5. Annealing treatment: Temperature 480℃, hold for 15 minutes; After the S6.Si layer is grown, a 3-atom-thick Si3N4 or B4C layer is prepared by ALD as an isolation layer. S7. Repeat steps S2 to S6 for a total of 35 cycles to form a Mo / Si multilayer film; S8. Final Mo deposition x C surface protective layer, with a thickness of 5nm.

[0022] The key technical points and advantages of this invention are as follows: In existing technologies, the deposition of Mo layers often uses precursors such as MoCl5 and MoF6, while the deposition of Si layers commonly uses gaseous Si2H6. These methods suffer from drawbacks such as strong precursor corrosivity, high cost, and complex storage and gas supply systems. In this invention, the Mo layer uses Mo(CO)6 as a precursor, achieving atomic layer deposition through low-temperature adsorption and high-temperature thermal decomposition. This process is mild, non-corrosive, and friendly to equipment and substrates, while offering higher precision in layer thickness control. The Si layer uses Si3H8 and SiCl4 as precursors, with Si3H8 being a room-temperature liquid source. Compared to the commonly used gaseous Si2H6, this method offers lower raw material costs, simpler storage and transportation, and is more suitable for large-scale production, while also enabling stable and controllable growth of 2-6 Si atomic layers.

[0023] Compared to existing magnetron sputtering technology, this invention utilizes the self-limiting growth characteristics of atomic layer deposition to achieve high-precision deposition of single-atom-layer or few-atom-layer films on arbitrary curved substrates. The resulting films exhibit excellent uniformity and high repeatability, eliminating the need for high-precision motion control and online thickness compensation systems, significantly reducing equipment requirements and process control complexity. Furthermore, the required film thickness for the extreme ultraviolet (EUV) band is only a few dozen atomic layers. While the preparation time using this method is comparable to magnetron sputtering, it offers a wider process window, higher batch consistency, and significantly reduced preparation costs. This meets the demands for high-quality, low-cost, and large-scale fabrication of large-size, complex curved EUV reflective films.

[0024] 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.

[0025] 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 an extreme ultraviolet reflective thin film, characterized in that: Specifically, the following steps are included: S1. Place the substrate in the atomic layer deposition chamber, evacuate the vacuum, and stabilize the substrate temperature to a first temperature; the first temperature is below 70°C; S2. Introduce Mo(CO)6 precursor into the cavity for 0.01~30s to allow Mo(CO)6 to adsorb on the substrate surface; Inert gas is introduced to purge and remove unadsorbed Mo(CO)6; the substrate is heated to a second temperature to thermally decompose Mo(CO)6 and form a Mo atomic layer. Inert gas is introduced to purge the decomposition products and the substrate temperature is brought back to the first temperature; this process is repeated several times to form a Mo layer of the target thickness. S3. An isolation layer is deposited on the Mo layer using atomic layer deposition (ALD) technology; S4. Heat to the third temperature, introduce Si3H8 precursor for 0.01~30s; purge with inert gas to remove unadsorbed Si3H8; heat the substrate to the fourth temperature, introduce SiCl4 precursor and react, the introduction time is 0.01~30s; purge with inert gas to remove unreacted substances; repeat several cycles to form a Si layer of the target thickness. S5. Anneal the Si layer at 400~550℃ for 1~30min; S6. An isolation layer is deposited on the Si layer using atomic layer deposition (ALD) technology; S7. Repeat steps S2 to S6 to form a multi-period Mo / Si multilayer film; S8. A surface protective layer is prepared on a multilayer film using atomic layer deposition (ALD) technology.

2. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: The second temperature is 150℃~250℃; the third temperature is 70~300℃; and the fourth temperature is 200~400℃.

3. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: The surface protective layer is SiC or Mo. x One of C, Ru, RuO2, RuN, Rh, AlN, SiN, ZrO2, and TiO2, with a thickness of 1~5nm.

4. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: In step S2, 1 to 2 Mo atomic layers are deposited and grown in a single cycle.

5. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: In step S3, 2 to 6 Si atomic layers are formed by single-cycle deposition.

6. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: The isolation layer material includes C, Si3N4, B4C, LaN, SiC, or AlN, with a thickness of 1 to 5 atoms.

7. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: The substrate can be a planar substrate or a curved substrate.

8. The method for preparing an extreme ultraviolet reflective thin film according to claim 1, characterized in that: The inert gas is N2, and the purging time of the inert gas is 5~30s.

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