Four-band extreme ultraviolet multilayer film mirror

Abstract

The application belongs to the technical field of optical film, and particularly relates to a four-waveband extreme ultraviolet multilayer film mirror. The four-waveband extreme ultraviolet multilayer film mirror comprises a substrate and 17.1 nm Al / Zr period multilayer film, 19.3 nm Al / Zr period multilayer film, 30.4 nm Al / Zr period multilayer film and 46.5 nm cap layer deposited on the surface of the substrate from bottom to top. The application adopts two kinds of material pairs of Al / Zr and Si / Ir, and realizes the four wavebands of 17.1 nm, 19.3 nm, 30.4 nm and 46.5 nm through film system optimization design, and all have reflectivity better than 10%.

Description

Technical Field

[0001] This invention belongs to the field of optical thin film technology, and particularly relates to a four-band extreme ultraviolet multilayer film reflector. Background Technology

[0002] Extreme ultraviolet (EUV) multilayer mirrors are core optical components for space exploration in the EUV band. They enhance the reflectivity of light in this band and filter out light from other bands. In the EUV band, material absorption is significant, while the reflectivity is only 10. -4 To improve the reflectivity of optical lenses in the extreme ultraviolet (EUV) band, thin film materials with high and low atomic numbers are typically deposited alternately on the lens. High atomic number films usually have higher refractive indices and absorption, and are called absorption layers; low atomic number films usually have lower refractive indices and absorption, and are called spacer layers. The two materials are in a fixed ratio to form a periodic multilayer film, creating an artificial crystal structure. When the periodic thickness satisfies the Bragg diffraction condition, interference enhancement occurs in a specific EUV band; while in other bands, the Bragg diffraction condition is not met, resulting in lower reflectivity; thus achieving the goal of improving reflectivity in a specific band.

[0003] With the development of extreme ultraviolet (EUV) space exploration, the cost of control payloads has become a major concern. Multi-band detection has become mainstream, such as GOES-R's six-band (9.4nm, 13.1nm, 17.1nm, 19.5nm, 28.4nm, 30.4nm) EUV detection, SDO's seven-band (9.4nm, 13.1nm, 17.1nm, 19.3nm, 21.1nm, 30.4nm, 33.5nm) EUV detection, and SolarOrbiter's dual-band (17.1nm and 30.4nm) EUV detection. Ground-based calibration equipment also requires collimators capable of detecting multiple bands simultaneously, thus avoiding the need for mirrors coated with different bands, further saving costs and improving detection efficiency.

[0004] The mainstream mature solution for extreme ultraviolet (EUV) multi-band reflectors is the zoned coating technology. This technology divides a single reflector into several regions, and deposits multilayer films adapted to different operating wavelengths in different regions. Both the GOES-R and SDO satellites use this method. This technology has the advantage of excellent reflectivity in a single band, but it has significant drawbacks such as small light-gathering area, high assembly difficulty, and complex coating processes. Precise shielding techniques are required during the coating process to avoid spectral crosstalk caused by the cross-stacking of different film systems. The shadowing effect produced by the tooling shielding further reduces the effective light-gathering area of ​​the reflector. Another technical solution does not require regional division of the optical substrate. By selecting multiple thin film materials and optimizing the film system structure design, multi-band high reflectivity can be achieved. The Solar Orbiter satellite uses this solution. Its research team used an Al / Mo / SiC thin film system and, through film system optimization design, stacked multilayer films adapted to two operating wavelengths, 17.1 nm and 30.4 nm, successfully achieving dual-band high reflectivity imaging. The core advantage of this scheme is its large effective light-gathering area. However, due to the strong absorption characteristics of the material in the extreme ultraviolet band, the number of bands in which this technology can achieve high reflectivity is usually no more than two. Summary of the Invention

[0005] In view of this, the present invention aims to provide a four-band extreme ultraviolet multilayer film reflector to solve the problems of small light-gathering area and few effective bands in existing multi-band reflectors. The present invention uses two material pairs, Al / Zr and Si / Ir, and through film system optimization design, achieves reflectivity better than 10% in four bands: 17.1nm, 19.3nm, 30.4nm, and 46.5nm.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A four-band extreme ultraviolet multilayer mirror includes a substrate and, from bottom to top, a 17.1 nm Al / Zr periodic multilayer film, a 19.3 nm Al / Zr periodic multilayer film, a 30.4 nm Al / Zr periodic multilayer film, and a 46.5 nm cap layer deposited on the substrate surface.

[0007] Furthermore, the 46.5nm cap layer is a Si / Ir periodic multilayer film. The Si / Ir periodic multilayer film has 1 period, and the thickness of a single period is 14.0nm-17.0nm. The proportion of Ir in the thickness of a single period is 20%-50%.

[0008] Furthermore, the 17.1nm Al / Zr periodic multilayer film has 20-40 periods, a single period thickness of 8.0nm-8.5nm, and Zr accounts for 20%-40% of the single period thickness.

[0009] Furthermore, the 19.3nm Al / Zr periodic multilayer film has 5-10 periods, a single period thickness of 9.9nm-10.1nm, and Zr accounts for 20%-40% of the single period thickness.

[0010] Furthermore, the 30.4nm Al / Zr periodic multilayer film has 2 periods, a single period thickness of 16.0nm-16.8nm, and Zr accounts for 20%-40% of the single period thickness.

[0011] Furthermore, the substrate is ultra-smooth fused silica with a surface roughness of less than 0.3 nm.

[0012] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention creates a four-band extreme ultraviolet (EUV) multilayer mirror, aiming to solve the technical problem of limited effective reflection wavelengths in traditional multilayer mirrors without sacrificing the light-gathering area. This invention uses Al / Zr materials with high reflectivity in the 17.1nm, 19.3nm, and 30.4nm bands as the main multilayer structure, and adds a Si / Ir cap layer to effectively improve the reflectivity in the 46.5nm band. This invention employs a multilayer composite structure combining 17.1nm Al / Zr, 19.3nm Al / Zr, and 30.4nm Al / Zr films with a 46.5nm Si / Ir film. It eliminates the need for traditional partitioned coating technology, achieving reflectivity better than 10% in all four EUV bands (17.1nm, 19.3nm, 30.4nm, and 46.5nm) on a single optical substrate without sacrificing the light-gathering area. Traditional technologies require a four-band zoned coating scheme that compromises the light-gathering area, or the use of four independent reflectors. This invention, however, requires only a single reflector to achieve efficient reflection across four extreme ultraviolet bands without sacrificing the light-gathering area. Applying this multi-layered reflector can effectively reduce the research and development and usage costs of space exploration payloads and ground-based detection, significantly improving the efficiency of both. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 A schematic diagram of the structure of the four-band extreme ultraviolet multilayer reflector described in the embodiment of the present invention; Figure 2 The theoretical reflectivity curve of the four-band extreme ultraviolet multilayer film mirror described in the embodiment of the present invention; Figure 3The measured reflectivity curve of the four-band extreme ultraviolet multilayer mirror described in the embodiment of the present invention.

[0014] Explanation of reference numerals in the attached figures: 1. Substrate; 2. 17.1nm Al / Zr periodic multilayer film; 3. 19.3nm Al / Zr periodic multilayer film; 4. 30.4nm Al / Zr periodic multilayer film; 5. 46.5nm cap layer. Detailed Implementation

[0015] 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.

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0017] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0018] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] like Figure 1As shown, the present invention provides a four-band extreme ultraviolet multilayer mirror, comprising a substrate 1 and, from bottom to top, a 17.1nm Al / Zr periodic multilayer film 2, a 19.3nm Al / Zr periodic multilayer film 3, a 30.4nm Al / Zr periodic multilayer film 4, and a 46.5nm cap layer 5 deposited on the surface of the substrate 1.

[0021] It should be noted that Al and Zr have good refractive index contrast and low absorption in the 17.1, 19.5, and 30.4 nm bands, resulting in high reflectivity in all three bands. More importantly, the 30.4 nm band has a wide bandwidth. Therefore, this invention comprehensively employs four types of periodic multilayer film stacking, capping technology, and Al / Zr and Si / Ir material pairs to solve the problems of small light-gathering area and limited effective bands in multi-band reflectors. Without sacrificing the light-gathering area, reflectivity of 12.9%, 12.5%, 10.4%, and 18.4% is achieved in four bands: 17.1 nm, 19.3 nm, 30.4 nm, and 46.5 nm, respectively. This improves the efficiency of space detection and ground detection while reducing costs.

[0022] like Figure 1 As shown, the main film structure of this invention is as follows: Periodic multilayer films with center wavelengths of 17.1 nm, 19.3 nm, 30.4 nm, and a cap layer with a center wavelength of 46.5 nm are sequentially deposited on substrate 1. To avoid loss of reflectivity at 30.4 nm, the cap layer with a center wavelength of 46.5 nm is selected with a periodic structure corresponding to the high reflectivity at 30.4 nm. The high reflectivity at 46.5 nm is actually achieved by an Ir thin film. Substrate 1 is ultra-smooth fused silica with a surface roughness better than 0.3 nm and an incident angle of 6°.

[0023] In some embodiments, the 46.5nm cap layer 5 is a Si / Ir periodic multilayer film, the Si / Ir periodic multilayer film has 1 period, the thickness of a single period is 14.0nm-17.0nm, and the proportion of Ir in the thickness of a single period is 20%-50%.

[0024] In some embodiments, the number of cycles of the 17.1nm Al / Zr periodic multilayer film 2 is 20-40, the thickness of a single cycle is 8.0nm-8.5nm, and the proportion of Zr in the thickness of a single cycle is 20%-40%.

[0025] In some embodiments, the 19.3nm Al / Zr periodic multilayer film 3 has 5-10 periods, a single period thickness of 9.9nm-10.1nm, and Zr accounts for 20%-40% of the single period thickness.

[0026] In some embodiments, the 30.4nm Al / Zr periodic multilayer film 4 has 2 periods, a single period thickness of 16.0nm-16.8nm, and Zr accounts for 20%-40% of the single period thickness.

[0027] In some embodiments, the substrate 1 is an ultra-smooth fused silica with a surface roughness of less than 0.3 nm.

[0028] It should be noted that the periodic multilayer film composed of Al / Zr material pairs exhibits high reflectivity at 17.1 nm, 19.3 nm, and 30.4 nm. Based on this material foundation, this invention uses Al / Zr and Si / Ir material pairs, employing methods such as... Figure 1 Four periodic multilayer film structures were shown, and four-band extreme ultraviolet (EUV) multilayer films with wavelengths of 17.1 nm, 19.3 nm, 30.4 nm, and 46.5 nm were designed and fabricated. It involved sequentially depositing periodic multilayer films of 17.1 nm, 19.3 nm, and 30.4 nm, and a 46.5 nm cap layer 5 on substrate 1. The periodic multilayer films with center wavelengths of 17.1 nm, 19.3 nm, and 30.4 nm employed an Al / Zr material pair. A periodic multilayer film with a center wavelength of 17.1 nm, 40 periods, and a period thickness of 8.5 nm, with Zr accounting for 0.4% of the period thickness; a periodic multilayer film with a center wavelength of 19.3 nm, 10 periods, and a period thickness of 10.1 nm, with Zr accounting for 0.4% of the period thickness; a periodic multilayer film with a center wavelength of 30.4 nm, 2 periods, and a period thickness of 16.4 nm, with Zr accounting for 0.28% of the period thickness; among the three Al / Zr periodic multilayer films, the Al layer is the bottom layer, close to substrate 1, and the Zr layer is the top layer, far from substrate 1. The cap layer with a target wavelength of 46.5 nm adopts a Si / Ir periodic multilayer film structure, with 1 period, a period thickness of 17.0 nm, and Ir accounting for 0.35% of the period thickness. It should be noted that in the cap structure with a target wavelength of 46.5nm, the Ir film plays a role in the reflection of 46.5nm, while the role of Si is to form a periodic multilayer film with Ir. Si is in the bottom layer, close to the substrate 1, and Ir is in the top layer, far from the substrate 1, which has a certain reflectivity for 30.4nm. This can avoid the suppression of 30.4nm reflection by the 46.5nm cap layer 5.

[0029] like Figure 2 As shown, the corresponding theoretical reflectance curves are given, with reflectances of 14.1%, 19.8%, 17.9%, and 13.8% at 17.1 nm, 19.3 nm, 30.4 nm, and 46.5 nm, respectively. Figure 3As shown, the corresponding measured reflectance curves are given. Its reflectances at 17.1 nm, 19.3 nm, 30.4 nm and 46.5 nm are 12.9%, 12.5%, 10.4% and 18.4%, respectively.

[0030] 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.

[0031] 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 four-band extreme ultraviolet multilayer reflector, characterized in that: It includes a substrate and, from bottom to top, a 17.1 nm Al / Zr periodic multilayer film, a 19.3 nm Al / Zr periodic multilayer film, a 30.4 nm Al / Zr periodic multilayer film, and a 46.5 nm cap layer deposited on the substrate surface.

2. The four-band extreme ultraviolet multilayer reflector according to claim 1, characterized in that: The 46.5nm cap layer is a Si / Ir periodic multilayer film with one period, a single period thickness of 14.0nm-17.0nm, and Ir accounting for 20%-50% of the single period thickness.

3. The four-band extreme ultraviolet multilayer reflector according to claim 1, characterized in that: The 17.1nm Al / Zr periodic multilayer film has 20-40 periods, a single period thickness of 8.0nm-8.5nm, and Zr accounts for 20%-40% of the single period thickness.

4. The four-band extreme ultraviolet multilayer reflector according to claim 1, characterized in that: The 19.3nm Al / Zr periodic multilayer film has 5-10 periods, a single period thickness of 9.9nm-10.1nm, and Zr accounts for 20%-40% of the single period thickness.

5. The four-band extreme ultraviolet multilayer reflector according to claim 1, characterized in that: The 30.4nm Al / Zr periodic multilayer film has 2 periods, a single period thickness of 16.0nm-16.8nm, and Zr accounts for 20%-40% of the single period thickness.

6. The four-band extreme ultraviolet multilayer reflector according to claim 1, characterized in that: The substrate is ultra-smooth fused silica with a surface roughness of less than 0.3 nm.

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