High reflectivity extreme ultraviolet multilayer film and method of making same

Abstract

This invention discloses a high-reflectivity extreme ultraviolet multilayer film, comprising a substrate, a periodic structure, and a protective film layer; the periodic structure, formed by repeated stacking of dual-layer units, is disposed on the substrate, and the protective film layer is disposed on the periodic structure; the dual-layer stacking units comprise Nb-Mo layers arranged sequentially. x C composite low-refractive-index layer and Si high-refractive-index layer; Nb-Mo x Within the C composite low-refractive-index layer, amorphous Mo x The C phase is uniformly dispersed within the metallic Nb phase, and the amorphous Mo... x The C phase has a volume fraction ranging from 5% to 45%, effectively suppressing diffusion mixing between film layers and the sharp reduction in interface sharpness caused by the Si reaction at the interface, ensuring a high refractive index difference between the upper and lower interfaces. Therefore, the extreme ultraviolet (EUV) multilayer film proposed in this invention possesses excellent EUV reflectivity. A method for preparing a high-reflectivity EUV multilayer film is also disclosed, which is simple, easy to control, and low in cost, suitable for large-area fabrication.

Description

Technical Field

[0001] This invention belongs to the field of extreme ultraviolet optical reflective element technology, specifically relating to a high-reflectivity extreme ultraviolet multilayer film and its preparation method. Background Technology

[0002] Extreme ultraviolet (EUV) optical reflection systems are applicable to many fields such as EUV lithography, synchrotron radiation, space astronomical observation, microscopic imaging analysis, and plasma diagnostics. In particular, as VLSI continues to develop towards miniaturization, integration, and high performance, EUV lithography technology has become an essential path for advanced node chip manufacturing. This requires that the multilayer films deposited on the surface of key components (such as EUV mirrors) in EUV light reflection systems have efficient and stable EUV light reflection characteristics.

[0003] Extreme ultraviolet (EUV) lithography, used in chip manufacturing, utilizes UV light sources with wavelengths of 10-14 nanometers. However, within this wavelength range, the real part of the refractive index of most materials is close to 1, resulting in extremely low reflectivity of their single-layer films for near-normal incident UV light. Therefore, periodic multilayer films are typically formed by alternating between relatively high and low refractive index materials to satisfy the Bragg reflection condition, thereby achieving high reflectivity for UV light. The most representative example is the Mo / Si EUV multilayer film, where the refractive index difference between Mo and Si in the EUV band is relatively large. Furthermore, the reflected light intensities at various periodic interfaces within the film can coherently superimpose, ultimately achieving high overall reflectivity of the multilayer film.

[0004] To obtain alternating multilayer films with high reflectivity to extreme ultraviolet (EUV) light, the refractive index difference between the selected film layer materials must be large, and their absorption coefficients should be as small as possible. Considering factors such as material safety and etching processability, current material combination research mainly focuses on Mo / Si, Ru / Si, and Nb / Si. Among these, multilayer films obtained by stacking Nb / Si exhibit relatively low interlayer chemical reactions and excellent resistance to EUV irradiation damage. However, during the deposition process of Nb / Si multilayer films, problems such as the sharp reduction in interface sharpness, the decrease in refractive index difference, and the reduction in interlayer roughness caused by diffusion mixing between film layers and interface Si formation reactions have not yet been resolved, hindering the improvement of the EUV reflectivity of the obtained multilayer films.

[0005] To address issues such as the sharpness and roughness of interlayer interfaces in multilayer films, interface optimization engineering is typically implemented in multilayer film systems. This includes adding interfacial barrier layers to prevent interface diffusion and reflectivity reduction caused by interface roughness. However, existing sub-nanometer scale barrier layer strategies often lead to limitations in film thickness optimization and difficulty in precise fabrication. Furthermore, the refractive index difference between existing film layers (without the introduction of an interfacial barrier layer) is easily reduced, increasing process complexity (requiring the deposition of two additional barrier layers per cycle). Additionally, improving interlayer interface roughness through alloying presents challenges compared to modified pure metal layers. Precise control of the refractive index and absorption coefficient of alloy films also faces difficulties, often struggling to balance the refractive index difference between layers within the periodic structure and alloy layer absorption, resulting in a decrease in theoretical reflectivity. Moreover, introducing pure carbide absorption layers into multilayer films exacerbates issues such as film delamination or substrate deformation due to film stress. Solving these problems remains a challenge for those skilled in the art; therefore, finding high-reflectivity extreme ultraviolet (EUV) multilayer films remains crucial for the development of EUV optical reflective element technology. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a high-reflectivity extreme ultraviolet multilayer film and its preparation method. This high-reflectivity extreme ultraviolet multilayer film has a high theoretical reflectivity for extreme ultraviolet light, good interlayer interface sharpness and large refractive index difference within the multilayer film, and the film layer periodic structure design scheme is simple, which facilitates practical preparation and expanded applications.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a high-reflectivity extreme ultraviolet multilayer film, comprising a substrate, a periodic structure, and a protective film layer; the periodic structure, formed by repeated stacking of dual-layer units, is disposed on the substrate, and the protective film layer is disposed on the periodic structure; the dual-layer stacking units comprise Nb-Mo layers arranged sequentially. x C composite low-refractive-index layer and Si high-refractive-index layer;

[0009] The Nb-Mo x Within the C composite low-refractive-index layer, amorphous Mo x The C phase is uniformly dispersed within the metallic Nb phase, and the amorphous Mo... x The volume fraction of the C phase ranges from 5% to 45%, with the Nb phase serving as the functional matrix phase, and Mo... x C is used as the dopant phase for film modification. Through intermixing at different volume ratios, Nb-Mo... x The C composite low-refractive-index layer maintains a refractive index within the range of 0.932±0.15 in the extreme ultraviolet band, and the Nb-Mo... x The absorption coefficient of the C composite low-refractive-index layer is below 0.007. Nb-Mox The C composite low refractive index layer uses Nb-Mo x C composite materials, replacing traditional pure metal Nb layers, can suppress interlayer diffusion mixing and the sharp reduction in interfacial sharpness caused by interfacial Si formation reactions. Furthermore, compared to using only Nb layers, Nb-Mo... x The refractive index and absorption coefficient of the C composite low-refractive-index layer vary with Mo. x The change in C composition produces only a minor effect, which significantly mitigates the problem of decreased refractive index difference at the metal / Si interface caused by conventional metal film alloying. This is achieved using Nb-Mo. x The C composite low-refractive-index layer can maintain a stable Nb-Mo layer. x The refractive index difference between the C composite low-refractive-index layer and the Si high-refractive-index layer. More preferably, amorphous Mo... x The volume percentage of the C phase ranges from 10% to 30%.

[0010] Preferably, the Nb-Mo x Within the C composite low-refractive-index layer, amorphous Mo x The range of x in the C phase is 1-2, which is MoC or Mo2C or a mixture of both, to ensure that the optical constants of the composite film meet the requirements.

[0011] Preferably, the Nb-Mo x The thickness of the C composite low refractive index layer is 2.1-3.1 nm, and the thickness of the Si high refractive index layer is 3.8-4.8 nm, with the Si high refractive index layer serving as a spacer layer.

[0012] Preferably, the number of cycles for repeated use of the double-layer stacking unit is 30-60. The purpose of repeated use of the double-layer stacking unit is to obtain optical path accumulation that is an integer multiple of a quarter wavelength, thus satisfying the condition for constructive interference.

[0013] Preferably, the thickness of the protective film is 1-5 nm. The function of the protective film is to prevent oxidation of the uppermost high-refractive-index Si layer.

[0014] Preferably, the protective film is amorphous Mo. x C, where x ranges from 1 to 2; the protective film can also be a carbide such as B4C and SiC, or a boride such as Mo2B.

[0015] Preferably, the substrate is a single-crystal silicon wafer, quartz glass, silicon carbide, etc., and the surface roughness of the substrate is 0.1nm-0.6nm. The surface roughness of the substrate affects the roughness of the entire film layer and has a significant impact on the final reflection performance. Selecting the substrate material and controlling the surface roughness of the substrate ensures that the substrate remains flat, stable, and easy to process.

[0016] In summary, the embodiments of the present invention provide a high-reflectivity extreme ultraviolet multilayer film, wherein the Nb-Mo film is used. x The C composite low refractive index layer will incorporate amorphous Mo x The introduction of the C phase into the metallic Nb phase regulates the nucleation and growth behavior of Nb, thereby densifying the entire Nb-Mo phase. x C composite low refractive index layer and smooth its upper and lower interfaces, while utilizing Mo x The segregation effect of C at the grain boundaries and surface of the Nb layer pins the Nb nanostructure, inhibits its outward diffusion, and blocks the diffusion of foreign Si into the Nb layer at the interface. More importantly, Nb-Mo x Within the C composite low-refractive-index layer, the entire Nb-Mo layer is affected by the nanoscale non-dissolution intermixing between the two phases. x C composite low-refractive-index layers can serve as equivalent dielectric layers. Based on this, Nb and Mo... x The Nb-Mo alloy exhibits a very close extreme ultraviolet refractive index and absorption coefficient between carbon atoms, resulting in... x The equivalent refractive index and absorption coefficient of the C composite low-refractive-index layer will be very close to those of pure Nb, meaning that the introduction of the heterophase will not damage the relatively low refractive index and low absorption characteristics of the Nb film. On the contrary, by modifying the Nb-Mo composite layer... x Optimization of the surface morphology and roughness control of the C composite low-refractive-index layer improves the sharpness of the interface between the stacked units of the double-layer structure throughout the periodic structure and ensures a sufficiently large refractive index difference between the layers, thereby pursuing higher extreme ultraviolet reflectivity. Simultaneously, by utilizing Nb-Mo... x The differences in physical properties and microstructure between the two phases within the C composite low-refractive-index layer can also provide freedom for the control of stress in the entire film.

[0017] To achieve the above-mentioned objective, this invention also provides a method for preparing a high-reflectivity extreme ultraviolet multilayer film, comprising the following steps:

[0018] (1) Pretreatment of the substrate;

[0019] (2) Select Nb, Si and Mo x C is used as a target to control Nb and Mo. x Simultaneously, the C target operates, and magnetron co-sputtering deposition is performed on the substrate surface pretreated in step (1) to obtain Nb-Mo. x A C composite low-refractive-index layer was then created; subsequently, the Si target was controlled to operate within the Nb-Mo composite layer. x A high-refractive-index Si layer was deposited by magnetron sputtering on a C composite low-refractive-index layer to obtain Nb-Mo. x C / Si dual-layer stacked unit; subsequently, the aforementioned process is repeated to deposit 30-60 Nb-Mo layers according to the number of cycles. x C / Si dual-layer stacked unit, and finally sputter a layer of Mo. xC protective film layer, to complete the preparation of high reflectivity extreme ultraviolet multilayer film.

[0020] Preferably, the pretreatment of the substrate includes ultrasonic cleaning with acetone, isopropanol and deionized water or immersion in a piranha solution, followed by heating desorption and plasma etching cleaning to optimize the cleanliness of the substrate surface. After the above pretreatment, the substrate surface is more conducive to the growth of smooth multilayer films.

[0021] Preferably, the Nb target, Si target, and Mo target are used. x The C target is driven by a DC, DC pulse, or RF power supply. More preferably, the magnetron sputtering of the Nb and Si targets is DC magnetron sputtering. x For C-target magnetron sputtering, DC pulse or RF magnetron sputtering is preferred, as it facilitates control of the properties of each film layer. The sputtering working gas is high-purity argon. The sputtering pressure range is 0.1-0.2 Pa, more preferably 0.12-0.15 Pa, ensuring appropriate energy for the deposited particles and better stability of the sputtering process. The background vacuum is 1.0 × 10⁻⁶. -4 Pa or less, more preferably 5×10 Pa -5 Below Pa, it is beneficial to control the oxygen content in the film layer, ensuring the excellent optical performance of each film layer.

[0022] Preferably, sputtering deposition of Nb-Mo x When using a C composite low-refractive-index layer, the power density range for the Nb target is 4-11 W / cm². 2 More preferably 6-9 W / cm 2 Mo x The power density range used for the C target is 2-7 W / cm². 2 More preferably 2.5-5 W / cm 2 Through sputtering processes, Nb target and Mo x By controlling the C target power density and combining it with matching sputtering pressure, Nb-Mo can be easily controlled. x Amorphous Mo in C composite low refractive index layer x The proportion and arrangement of the C phase were adjusted extensively, and Nb-Mo were also affected. x The microstructure of the C composite low-refractive-index layer was controlled to densify the entire Nb-Mo composite. x C composite low refractive index layer and its surface are smoothed, while Nb-Mo is suppressed. x Nb-Mo in C composite low refractive index layer x Intermixing of C material with Si material in a high-refractive-index Si layer. Nb-Mo with different microstructural characteristics. x By matching C composite low-refractive-index layers with Si high-refractive-index layers of varying thicknesses, extreme ultraviolet (EUV) reflection can be controlled to meet the desired parameters, thereby obtaining high-reflectivity EUV multilayer films.

[0023] Preferably, when sputtering to deposit a high-refractive-index Si layer, the power density used on the Si target is in the range of 5-13 W / cm². 2 The optimal value is 9-11 W / cm². 2 This allows the obtained high-refractive-index Si layer to have a roughness and corresponding optical constants that are conducive to obtaining higher extreme ultraviolet reflectivity in multilayer films.

[0024] Preferably, during sputtering deposition of the protective film, Mo x The power density range used for the C-target is 5-10 W / cm². 2 The optimal value is 6-8 W / cm². 2 The ability to obtain Mo x The C protective film layer has a better stoichiometry and ideal microstructure and optical constant control.

[0025] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0026] (1) In this invention, metallic Nb is directly reacted with refractory carbide Mo. x C composite method to obtain dense Nb-Mo with smooth surface and interface x By starting with a C composite low-refractive-index layer, the interface sharpness between the C and Si high-refractive-index layers is improved, thereby ensuring a large interface refractive index difference within the double-layer stacked unit in the periodic structure and effectively suppressing interlayer diffusion mixing and interface Si formation reaction.

[0027] (2) For Nb-Mo x The C-composite low-refractive-index layer uses Nb and Mo x The C material exhibits very similar refractive index and absorption coefficient in the extreme ultraviolet (EUV) band. Through mixing with different volume ratios, the refractive index in the EUV band remains within the range of 0.932 ± 0.15, and the Nb-Mo... x The absorption coefficient of the C composite low-refractive-index layer is below 0.007; Nb and Mo x As a composite low-refractive-index layer material, C can effectively meet the requirements of large refractive index difference and low extinction coefficient. It has a significant effect on improving reflectivity in the application of extreme ultraviolet multilayer films, providing material support for the construction of new extreme ultraviolet multilayer films.

[0028] (3) Selection of protective film and Nb-Mo x The C-composite low-refractive-index layer is doped with the same material, Mo. x C, thus simplifying the preparation process, and at the same time making it easy to control the refractive index matching and extreme ultraviolet reflection characteristics of the entire multilayer film.

[0029] (4) This invention employs magnetron co-sputtering to directly deposit Nb-Mo. xC composite low refractive index layers not only have simple structure and preparation process and low cost, but more importantly, even if the deposition parameters fluctuate within a certain range, the optical constant of the composite layer can remain stable. As a result, it is easier to ensure the consistency of extreme ultraviolet high reflectivity of multilayer films, making them suitable for large-area preparation. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of the high-reflectivity extreme ultraviolet multilayer film provided in the embodiment of the present invention;

[0032] Figure 2 This is a flowchart of the preparation method of a high-reflectivity extreme ultraviolet multilayer film provided in the embodiments of the present invention;

[0033] Figure 3 This is a schematic diagram of the theoretical reflectance curves of the extreme ultraviolet multilayer films prepared in Examples 1 and 2, and Comparative Examples 1 and 2 of the present invention.

[0034] The specific symbols in the attached diagram are as follows:

[0035] 100. Substrate; 101. Periodic structure; 102. Protective film layer; 103. Double-layer stacked unit; 104. Nb-Mo x C composite low refractive index layer; 105, Si high refractive index layer. Detailed Implementation

[0036] 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 embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0037] The inventive concept of this invention is as follows: Addressing the problems of precise fabrication and complex processes in existing technologies for preparing high-reflectivity extreme ultraviolet (EUV) multilayer films, which involve adding interfacial barrier layers or metal / alloy layers to solve issues related to the sharpness and roughness of the interfaces within the multilayer films, this invention provides a high-reflectivity EUV multilayer film and its preparation method, using Nb-Mo... xThe C composite low-refractive-index layer and the Si high-refractive-index layer form a double-layer stacked unit and repeatedly form a periodic structure, effectively suppressing interlayer diffusion mixing and interfacial Si formation reactions, improving interfacial sharpness, and ensuring a high refractive index difference and low absorption coefficient at the interface within the double-layer stacked unit of the periodic structure. This makes it easier to control during precise fabrication. The selection of the protective film is similar to that of Nb-Mo. x The C-composite low-refractive-index layer is doped with the same material, Mo. x This simplifies the preparation process, ultimately yielding a high-reflectivity extreme ultraviolet multilayer film. The preparation process is simple and low-cost, making it suitable for large-area preparation in practical applications.

[0038] Figure 1 This is a schematic diagram of the structure of the high-reflectivity extreme ultraviolet multilayer film provided in an embodiment of the present invention. Figure 1 As shown, the embodiment provides a high-reflectivity extreme ultraviolet multilayer film, including a smooth substrate 100, a periodic structure 101 formed by repeated double-layer stacking units 103, and a protective film layer 102 disposed on the periodic structure 101; the double-layer stacking units 103 include Nb-Mo layers arranged sequentially. x C composite low-refractive-index layer 104 and Si high-refractive-index layer 105. Among them, Nb-Mo x The C-composite low-refractive-index layer 104 uses a Nb target and Mo. x The Si high-refractive-index layer 105 was prepared by C-target magnetron co-sputtering deposition, and the protective film 102 was prepared by Si-target direct magnetron sputtering deposition. x Preparation by direct magnetron sputtering deposition on a C-target.

[0039] Based on the same inventive concept, the embodiments also provide a method for preparing a high-reflectivity extreme ultraviolet multilayer film, such as... Figure 2 As shown, it includes the following steps:

[0040] S1, Pre-process the substrate 100.

[0041] In this embodiment, the substrate 100 was ultrasonically cleaned (or immersed in a piranha solution) sequentially with acetone, isopropanol, and deionized water, followed by heating desorption and plasma etching to optimize the surface cleanliness of the substrate 100. After the above pretreatment, the surface of the substrate 100 is more conducive to the growth of smooth multilayer films.

[0042] S2, Nb-Mo deposition by magnetron co-sputtering x C composite low refractive index layer 104.

[0043] Select Nb and Mo x C is used as a target to control Nb and Mo. xSimultaneously, the C target operates, and magnetron co-sputtering deposition is performed on the substrate 100 surface pretreated in step S1. The power density used for the Nb target ranges from 4 to 11 W / cm². 2 The optimal value is 6-9 W / cm². 2 Mo x The power density range used for the C target is 2-7 W / cm². 2 The optimal value is 2.5-5 W / cm². 2 Obtain Nb-Mo x C composite low refractive index layer 104.

[0044] S3, a high-refractive-index Si layer 105 was deposited by magnetron sputtering.

[0045] Si was selected as the target material, and the operation of the Si target was controlled in Nb-Mo x A high-refractive-index Si layer 105 is deposited by magnetron sputtering on a C composite low-refractive-index layer 104, with the power density of the Si target ranging from 5 to 13 W / cm². 2 The optimal value is 9-11 W / cm². 2 Obtain Nb-Mo x C / Si double-layer stacked unit 103.

[0046] S4, repeated Nb-Mo deposition x A periodic structure 101 is obtained by combining a C composite low-refractive-index layer 104 and a Si high-refractive-index layer 105.

[0047] Repeat the aforementioned process steps S2-S3 to deposit 30-60 layers of Nb-Mo according to the number of cycles. x The C / Si double-film stacked unit 103 yields a periodic structure 101.

[0048] S5, protective film layer 102 deposited by magnetron sputtering.

[0049] Select Mo x Using C as the target material, a layer of Mo is sputtered onto the top layer of the periodic structure 101. x C protective film layer 102, Mo x The power density range used for the C-target is 5-10 W / cm². 2 The optimal value is 6-8 W / cm². 2 Finally, the preparation of a high-reflectivity extreme ultraviolet multilayer film was completed.

[0050] The preparation method and characteristics of the high-reflectivity extreme ultraviolet multilayer film prepared according to the present invention will be described below with reference to Examples 1 and 2, as well as Comparative Examples 1 and 2. In the following examples, a silicon wafer or quartz wafer is used as the substrate 100, and the low refractive index layer material in the multilayer film is selected as Nb-Mo. xC composite material (where x ranges from 1 to 2), Si is chosen as the high refractive index layer medium material, and Mo is chosen as the material for the surface protective film layer 102. x C (where x ranges from 1 to 2). By adjusting the relevant sputtering parameters, the Nb-Mo... x C composite low refractive index layer 104 inner amorphous Mo x The size and distribution of the C-phase microstructure, combined with Mo x By adjusting the volume percentage of the C phase, extreme ultraviolet (EUV) multilayer films were prepared. Based on the transfer matrix method, MATLAB software was used to perform theoretical calculations on the theoretical reflectance spectra of the multilayer films involved in the examples and comparative examples, and to analyze their reflectance characteristics to EUV light.

[0051] Example 1

[0052] In this embodiment, an ultra-smooth single-crystal silicon wafer with a surface roughness of 0.32 nm was selected as the substrate. The silicon wafer was sequentially immersed in acetone, isopropanol, and deionized water, ultrasonically cleaned, and dried with nitrogen gas. The silicon wafer was then fixed on a tray. The tray was placed in the deposition chamber of the magnetron sputtering equipment, and a pre-vacuum of 5 × 10⁻⁶ was applied. -5 Below Pa, argon gas is introduced, and Nb and Si targets are cleaned by DC sputtering, while Mo is cleaned by DC pulse sputtering. x The silicon wafer is subjected to plasma bombardment and cleaning with a C target. After etching and cleaning, the argon gas flow is adjusted to reduce the pressure in the deposition chamber to 0.16 Pa.

[0053] Turn off the power supply to the Si target, and then connect the Nb target and Mo target. x The sputtering power density of the C target was adjusted to 9 W / cm². 2 and 4W / cm 2 Among them, Nb target and Mo x The C targets are inclined towards each other at a certain angle to complete the Nb-Mo... x Magnetron co-sputtering deposition of a C-composite low-refractive-index layer 104. Nb target and Mo were switched off. x The C target driving power supply is activated simultaneously, and the Si target driving power supply is set to a power density of 10 W / cm². 2 In the newly deposited Nb-Mo x A Si high-refractive-index layer 105 is deposited on the C composite low-refractive-index layer 104 to form Nb-Mo. x C / Si double-layer stacked unit 103. Then the above Nb-Mo process is repeated. x The C / Si dual-layer stacked unit 103 was deposited 57 times to complete the deposition of the entire periodic structure 101 (a total of 58 Nb-Mo layers). x C / Si double-layer stacked unit 103), then Mo is restarted. x C-target drive power supply, power density set to 7W / cm² 2Mo deposition x C protective film layer 102, finally obtaining an extreme ultraviolet multilayer film with high reflectivity.

[0054] Through corresponding component and microstructure characterization analysis, the Nb-Mo content in the above-mentioned extreme ultraviolet multilayer film was determined. x The C composite low-refractive-index layer 104 has a thickness of 2.74 nm and x = 1.9 ± 0.05, while the Si high-refractive-index layer 105 has a thickness of 4.18 nm, i.e., Nb-Mo x The C / Si double-layer stacked unit 103 has a thickness of 6.92 nm, and Mo... x The C protective film layer 102 has a thickness of 2.0 nm. Nb-Mo x C composite low refractive index layer 104 inner Mo x The C phase volume percentage was 23.6%, of which nano-Mo... x The C-phase structure is dispersed within the metallic Nb matrix. Simultaneously, based on the effective medium theory, Nb-Mo... x The C-composite low-refractive-index layer 104 has an equivalent refractive index of 0.932 in the extreme ultraviolet (EUV) band and an absorption coefficient on the order of 0.0056. Its theoretical reflectivity for 13.5 nm EUV light can reach over 74.5%. Figure 3 As shown.

[0055] Example 2

[0056] In this embodiment, a polished quartz sheet with a surface roughness of 0.5 nm was selected as the substrate 100. The quartz sheet was ultrasonically cleaned in acetone and isopropanol sequentially, then immersed in a piranha solution, and finally dried with nitrogen gas. The quartz sheet was then fixed on a tray. The tray was loaded into the deposition chamber of the magnetron sputtering equipment, and a pre-vacuum of 5 × 10⁻⁶ was applied. -5 Below Pa, argon gas is introduced, and Nb and Si targets are cleaned by DC sputtering, while Mo is cleaned by DC pulse sputtering. x C target material, and apply plasma bombardment to clean the quartz wafer; after etching and cleaning, adjust the argon gas flow to make the deposition chamber pressure 0.14 Pa.

[0057] Turn off the Si target power supply and adjust the sputtering power density of the niobium and molybdenum carbide targets to 7.5 W / cm². 2 and 3.5W / cm 2 Among them, Nb target and Mo x The C targets are inclined towards each other at a certain angle to complete the Nb-Mo... x Magnetron co-sputtering deposition of a C-composite low-refractive-index layer 104. Nb target and Mo were switched off. x The C target driving power supply is activated simultaneously, and the Si target driving power supply is set to a power density of 10.5 W / cm². 2 In the newly deposited Nb-Mox A Si high-refractive-index layer 105 is deposited on the C composite low-refractive-index layer 104 to form Nb-Mo. x C / Si double-layer stacked unit 103. Then the above Nb-Mo process is repeated. x The C / Si dual-layer stacked unit 103 was deposited 59 times to complete the deposition of the entire periodic structure 101 (a total of 60 Nb-Mo layers). x C / Si double-layer stacked unit 103), then Mo is restarted. x C-target drive power supply, power density set to 7W / cm² 2 Mo deposition x C protective film layer 102, finally obtaining an extreme ultraviolet multilayer film with high reflectivity.

[0058] Through corresponding component and microstructure characterization analysis, the Nb-Mo content in the above-mentioned extreme ultraviolet multilayer film was determined. x The C composite low-refractive-index layer 104 has a thickness of 2.48 nm and x is 1.1 ± 0.05, while the Si high-refractive-index layer 105 has a thickness of 4.39 nm, i.e., Nb-Mo x The C / Si double-layer stacked unit 103 has a thickness of 6.87 nm, and the Mo... x The C protective film layer 102 has a thickness of 2.0 nm. Nb-Mo x C composite low refractive index layer 104 inner Mo x The C phase volume percentage is 15.6%, of which nano-Mo x The C-phase structure is dispersed within the metallic Nb matrix. Simultaneously, based on the effective medium theory, Nb-Mo... x The C-composite low-refractive-index layer 104 has an equivalent refractive index of 0.933 in the extreme ultraviolet (EUV) band and an absorption coefficient on the order of 0.0055. Its theoretical reflectivity at 13.5 nm EUV can reach over 74%. Figure 3 As shown.

[0059] Comparative Example 1

[0060] Extreme ultraviolet (EUV) multilayer films were deposited according to the preparation process and film structure of Example 1, except that the double-layer stacking unit 103 used an Nb / Si layer instead of the Nb-Mo layer in Example 1. x The C / Si layer is provided, and the surface protective film layer 102 is set as an Nb layer.

[0061] Comparative Example 2

[0062] Extreme ultraviolet (EUV) multilayer films were deposited according to the preparation process and film structure of Example 2, except that the dual-layer stacking unit 103 used an Nb / Si layer instead of the Nb-Mo layer in Example 2. xThe C / Si layer is provided, and the surface protective film layer 102 is set as an Nb layer.

[0063] Based on a comprehensive analysis of the above embodiments and comparative examples, Figure 3 The theoretical reflectance curves of the extreme ultraviolet multilayer films prepared in Examples 1, 2, 1, and 2 are also provided. The theoretical reflectance of the extreme ultraviolet multilayer films prepared in Examples 1, 2, 1, and 2 for 13.5 nm extreme ultraviolet light is extracted based on the theoretical reflectance curves, and the corresponding values ​​are listed in Table 1 for comparison.

[0064] Table 1. Theoretical reflectance of extreme ultraviolet multilayer films prepared in Examples 1 and 2 and Comparative Examples 1 and 2 for 13.5 nm extreme ultraviolet light:

[0065] project Example 1 Comparative Example 1 Example 2 Comparative Example 2 Theoretical reflectivity 74.68％ 71.69％ 74.03％ 71.66％

[0066] In summary Figure 3 The comparison between the theoretical reflectance curve and Table 1 shows that the extreme ultraviolet (EUV) multilayer film prepared in this embodiment of the invention has a higher theoretical reflectance than existing EUV multilayer films. Specifically, the comparison between Example 1 and Comparative Example 1, and between Example 2 and Comparative Example 2, shows that the composite low refractive index layer uses Nb-Mo... x The C composite layer, replacing the traditional pure metal Nb layer, can suppress interlayer diffusion mixing and the sharp reduction in interface sharpness caused by the Si reaction at the interface. Furthermore, compared to the Nb layer, the refractive index and absorption coefficient of the composite low-refractive-index layer increase with increasing Mo content. x The change in C composition produces only a minor alteration, effectively mitigating the decrease in refractive index difference at the metal / Si interface caused by conventional metal film alloying. The combined effect of these factors ultimately enhances the reflectivity of the high-reflectivity extreme ultraviolet (EUV) multilayer film proposed in this invention. The preparation method provided in this invention is simple, low-cost, and can maintain a stable refractive index difference and absorption coefficient even with minor changes in process conditions, thus preserving the high reflectivity of the EUV multilayer film. This method is suitable for large-area fabrication in practical applications.

[0067] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-reflectivity extreme ultraviolet multilayer film, characterized in that, It includes a substrate, a periodic structure, and a protective film layer; the periodic structure, formed by repeated stacking of dual-layer units, is disposed on the substrate, and the protective film layer is disposed on the periodic structure; the dual-layer stacking units include Nb-Mo layers arranged sequentially. x C composite low refractive index layer and Si high refractive index layer, of which Nb-Mo x The thickness of the C composite low refractive index layer is 2.1-3.1 nm, the thickness of the Si high refractive index layer is 3.8-4.8 nm, and the number of cycles set for the repeated stacking of the double film layer unit is 30-60. The Nb-Mo x Within the C composite low-refractive-index layer, amorphous Mo x The C phase is uniformly dispersed within the metallic Nb phase, and the amorphous Mo... x The volume fraction of the C phase ranges from 5% to 45%, and amorphous Mo... x The range of x in phase C is 1-2.

2. The high-reflectivity extreme ultraviolet multilayer film according to claim 1, characterized in that, The thickness of the protective film is 1-5 nm.

3. The high-reflectivity extreme ultraviolet multilayer film according to claim 1, characterized in that, The protective film is amorphous Mo. x C, where x ranges from 1 to 2.

4. The high-reflectivity extreme ultraviolet multilayer film according to claim 1, characterized in that, The surface roughness of the substrate is 0.1 nm to 0.6 nm.

5. A method for preparing a high-reflectivity extreme ultraviolet multilayer film according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Pretreatment of the substrate; (2) Select Nb, Si and Mo x C is used as a target to control Nb and Mo. x Simultaneously, the C target operates, and magnetron co-sputtering deposition is performed on the substrate surface pretreated in step (1) to obtain Nb-Mo. x A C composite low-refractive-index layer was then created; subsequently, the Si target was controlled to operate within the Nb-Mo composite layer. x A high-refractive-index Si layer was deposited by magnetron sputtering on a C composite low-refractive-index layer to obtain Nb-Mo. x C / Si double-layer stacked unit; Subsequently, the aforementioned process was repeated multiple times to deposit Nb-Mo. x C / Si dual-layer stacked unit, and finally sputter a layer of Mo. x C protective film layer, to complete the preparation of high reflectivity extreme ultraviolet multilayer film.

6. The method for preparing a high-reflectivity extreme ultraviolet multilayer film according to claim 5, characterized in that, Nb target, Si target and Mo x The C target is driven by DC, DC pulse, or RF power supply. The sputtering working gas is high-purity argon, with a sputtering pressure range of 0.1-0.2 Pa and a background vacuum of 1.0 × 10⁻⁶ Pa. -4 Below Pa.

7. The method for preparing a high-reflectivity extreme ultraviolet multilayer film according to claim 5, characterized in that, Sputter deposition of Nb-Mo x When using a C composite low-refractive-index layer, the power density range for the Nb target is 4-11 W / cm². 2 Mo x The power density range used for the C target is 2-7 W / cm². 2 .

Images