Reflection-transmission mixed extreme ultraviolet collimation illumination system

Abstract

The invention discloses a reflection-transmission mixed extreme ultraviolet collimation illumination system, and relates to the technical field of extreme ultraviolet optics. The system comprises a discharge plasma EUV light source, a multilayer film ellipsoid reflector and a collimating super lens. Wherein the discharge plasma EUV light source is used for generating radiation light in an extreme ultraviolet band; the multi-layer film ellipsoid reflector adopts an ellipsoid design, is plated with a high-reflectivity multi-layer film, is arranged on a transmission line of the discharge plasma EUV light source, and is used for focusing light beams of the light source; and the collimating super lens is arranged behind the focal position of the multi-layer film ellipsoid reflector and is used for collimating the focused light beams to form parallel light beams for Talbot photoetching illumination. The extreme ultraviolet illumination system is compact in structure, high in light beam energy and high in collimation, and the exposure quality in an application scene needing high-collimation extreme ultraviolet light beams is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of extreme ultraviolet optical technology, and particularly to an extreme ultraviolet collimated illumination system with a reflection-transmission hybrid structure. Background Art

[0002] Extreme ultraviolet (EUV) lithography technology is a core technology that promotes the development of semiconductor manufacturing and advanced nanolithography. Among them, Talbot lithography has broad application prospects in the research and development of EUV photoresists at the laboratory level due to its maskless, self-imaging, and high-resolution characteristics. However, Talbot lithography has extremely high requirements for the collimation, uniformity, and coherence of EUV light beams. Currently, existing EUV illumination systems still have many deficiencies in these aspects, which restrict the further development of this technology. Currently, commercial EUV lithography equipment mainly uses a laser-produced plasma (LPP) light source and conducts beam transmission and shaping through multilayer mirrors. Such systems can provide high-power EUV light, but they are large in volume and extremely costly, making it difficult to be used in a laboratory research and development environment.

[0003] In contrast, a discharge-produced plasma (DPP) light source has become an ideal light source for laboratory-level EUV lithography research due to its compact structure, low operating cost, and high EUV light conversion efficiency. However, the DPP light source has a large emission area and poor collimation, and it is difficult for existing technologies to achieve efficient beam shaping and illumination in a compact system. In the existing collimated illumination schemes for DPP light sources, an ellipsoidal mirror is usually used to collect and focus EUV light beams, and then multilayer mirrors are combined for beam shaping. However, this scheme has the following deficiencies:

[0004] First, the lithography resolution is limited: the uncollimated light beam used in Talbot lithography results in a decrease in the resolution of the exposure pattern. Second, the system volume is large: a pure reflective optical system requires multiple high-precision mirrors, increasing the complexity and size of the system, which is not conducive to the compact design of a laboratory-level EUV lithography system. Finally, the light energy utilization rate is low: multiple reflections will introduce energy losses, reducing the available EUV light flux during the lithography process. Summary of the Invention

[0005] The purpose of the present invention is to provide an extreme ultraviolet collimated illumination system with a reflection-transmission hybrid structure, which can improve the exposure quality in application scenarios that require highly collimated extreme ultraviolet light beams.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] An extreme ultraviolet collimated illumination system with a reflection-transmission hybrid structure, comprising:

[0008] A discharge plasma EUV light source for generating radiation light in the extreme ultraviolet band;

[0009] The multilayer film ellipsoidal mirror is designed with an ellipsoidal surface and coated with a multilayer film having a high reflectivity, and is disposed on the transmission path of the discharge plasma EUV light source for focusing the light beam of the light source.

[0010] The collimating superlens is disposed after the focal position of the multilayer film ellipsoidal mirror for collimating the focused light beam to form a parallel light beam for Talbot lithography illumination.

[0011] Optionally, the multilayer film ellipsoidal mirror is composed of a fused silica substrate and a Mo / Si multilayer film, and has a high reflectivity at an incident angle of 52° at a central wavelength of 13.5 nm.

[0012] Optionally, the collimating superlens is made of a metal molybdenum material and has nano-scale periodic small holes on its surface.

[0013] Optionally, a diaphragm and a filter are further disposed between the discharge plasma EUV light source and the multilayer film ellipsoidal mirror.

[0014] Optionally, the diameter of the multilayer film ellipsoidal mirror is 200 mm.

[0015] Optionally, the multilayer film ellipsoidal mirror is coated with a Mo / Si multilayer film.

[0016] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0017] The present invention discloses a reflective-transmissive hybrid extreme ultraviolet collimating illumination system, which includes a discharge plasma EUV light source, a multilayer film ellipsoidal mirror, and a collimating superlens; wherein, the discharge plasma EUV light source is used to generate radiation light in the extreme ultraviolet band; the multilayer film ellipsoidal mirror is designed with an ellipsoidal surface and coated with a multilayer film having a high reflectivity, and is disposed on the transmission path of the discharge plasma EUV light source for focusing the light beam of the light source; the collimating superlens is disposed after the focal position of the multilayer film ellipsoidal mirror for collimating the focused light beam to form a parallel light beam for Talbot lithography illumination. The present invention realizes an extreme ultraviolet illumination system with a compact structure, high beam energy, and high collimation, effectively improving the exposure quality in application scenarios that require high-collimation extreme ultraviolet light beams. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 is the overall optical path diagram of the lighting system in this embodiment;

[0020] Figure 2 is the schematic diagram of the ellipsoidal reflector in this embodiment;

[0021] Figure 3 is the schematic diagram of the ellipsoidal reflector in this embodiment;

[0022] Figure 4 is the schematic diagram of the reflector coating in this embodiment; among them, part (a) is the schematic diagram of the Mo / Si multilayer film structure; part (b) is the graph of reflectivity varying with wavelength and incident angle;

[0023] Figure 5 is the schematic diagram of the EUV superlens in this embodiment;

[0024] Figure 6 is the ZEMAX simulation result in this embodiment;

[0025] Figure 7 is the schematic diagram of the simulation of the optical simulation software in this embodiment; among them, part (a) is the schematic diagram of the overall optical system; part (b) is the schematic diagram of the superlens collimation.

[0026] Reference numerals: 1, discharge plasma EUV light source; 2, multilayer film ellipsoidal reflector; 3, collimating superlens; 4, aperture; 5, filter. Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] The purpose of the present invention is to provide a reflective-transmissive hybrid extreme ultraviolet collimating illumination system, which can improve the exposure quality in application scenarios that require highly collimated extreme ultraviolet beams.

[0029] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0030] As Figures 1-4As shown in the figure, the present invention provides a reflective-transmissive hybrid extreme ultraviolet collimated illumination system. By combining a DPP light source, a multilayer ellipsoidal mirror 2, and a collimating superlens 3, an extreme ultraviolet illumination system with a compact structure, high beam energy, and high collimation is realized, effectively improving the exposure quality in application scenarios that require high-collimation extreme ultraviolet beams.

[0031] The system includes a discharge plasma EUV light source 1, a multilayer ellipsoidal mirror 2, and a collimating superlens 3.

[0032] Among them, the discharge plasma EUV light source 1 is used to generate radiation light in the extreme ultraviolet band; the multilayer ellipsoidal mirror 2 is designed with an ellipsoidal surface and coated with a multilayer film with a high reflectivity, and is arranged on the transmission path of the discharge plasma EUV light source 1 for focusing the light beam of the light source; the collimating superlens 3 is arranged after the focal position of the multilayer ellipsoidal mirror 2 for collimating the focused light beam to form a parallel light beam for Talbot lithography illumination.

[0033] As a specific implementation manner, the discharge plasma (DPP) EUV light source: As the primary light source of the system, the DPP light source generates radiation light in the extreme ultraviolet band. It has a compact structure, is suitable for the laboratory environment, and helps to reduce the volume of the overall device.

[0034] As a specific implementation manner, the multilayer ellipsoidal mirror 2: Located at the output end of the light source, it is designed with an ellipsoidal surface and coated with a multilayer film with a high reflectivity. The function of this mirror is to effectively focus the divergent EUV light beam from the DPP light source, improve the light flux, and enhance the exposure energy.

[0035] As a specific implementation manner, the collimating superlens 3: It is arranged after the focal position of the multilayer ellipsoidal mirror 2 for collimating the focused EUV light beam. The collimated parallel light beam meets the requirements of Talbot lithography for the beam quality, ensuring the accuracy and consistency of the lithography process.

[0036] Based on the settings of the above components, the mutual relationship between the components is as follows: The EUV light beam emitted by the DPP light source is first focused by the multilayer ellipsoidal mirror 2, and then the focused light beam is collimated by the collimating superlens 3 to form a high-quality parallel light beam to meet the requirements of Talbot lithography.

[0037] This system uses a DPP-EUV light source to emit broadband light in the EUV band. The divergent EUV light beam is first captured and focused by the multilayer ellipsoidal mirror 2, which consists of a fused silica substrate and a molybdenum / silicon (Mo / Si) multilayer film, and has a high reflectivity at a 52° incidence at a central wavelength of 13.5 nm, such as Figure 4As shown, the average reflectivity at an incident angle of 52° is 53.5%, the average reflectivity at a central wavelength of 13.5 nm is greater than 50%, and the filtering performance is 6% full width at half maximum. The focused beam is collimated by the collimating superlens 3, which is made of molybdenum (Mo) material and has nanoscale periodic holes on its surface. The collimated parallel beam is used to illuminate the mask or grating in the Talbot lithography system to generate the required interference pattern and achieve high-resolution lithography processing. Through this design, the present invention realizes the miniaturization and high performance of the device. Among them, in this embodiment, the diameter of the multilayer ellipsoidal mirror 2 is 200 mm.

[0038] As a specific embodiment, the experimental results as shown in Figures 5-7 are provided.

[0039] This solution uses the EUV superlens as shown in Figure 5 The core of which is to use nanostructures to regulate the phase of EUV light to achieve functions similar to traditional lenses, but without relying on optical refraction or reflection, but based on the diffraction effect of nanostructures. The superlens is small and thin and can be used in a compact optical system. Similar to a focusing lens, after the divergent beam passes through, it is collimated into a parallel beam.

[0040] Through ZEMAX simulation, the results as shown in Figure 6 can be obtained, and through simulation and simulation with optical simulation software, after focusing by the ellipsoidal mirror, the energy of the beam is increased by more than 40,000 times compared to before focusing, and the superlens collimates the beam to below °. As shown in Figure 7 it is possible to adjust the size and focal length of the corresponding superlens according to actual needs to obtain different exposure areas.

[0041] In addition, for the multilayer ellipsoidal mirror 2, different coatings can be selected according to different incident angles. The reflectivity and incident angle are affected by the multilayer film structure parameters (thickness and number of layers). Different incident angles and materials require different design parameters to ensure high reflectivity. When the incident angle is about 50°, the MO / SI film is selected, and when the grazing incidence (about 85°) is used, the Ru / Si film, B4C / Si film or B4C / Si film is selected.

[0042] This application has the following beneficial effects:

[0043] The reflection-transmission hybrid extreme ultraviolet illumination system in this solution uses the form of DPP light source + ellipsoidal mirror + collimating superlens 3. On the premise of ensuring the compactness of the optical system, an EUV beam with high luminous flux and high collimation is obtained. The introduction of the superlens avoids the high alignment difficulty of traditional parabolic collimation, and at the same time, the small and thin characteristics of the superlens further streamline the volume of the system.

[0044] In this specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0045] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A reflection-transmission hybrid extreme ultraviolet collimated illumination system, characterized in that: include: Discharge plasma EUV light source, used to generate radiation light in the extreme ultraviolet band; A multi-layer film ellipsoidal reflector, which adopts an ellipsoidal design and is coated with a multi-layer film with high reflectivity, and is arranged on the transmission path of the discharge plasma EUV light source to focus the light beam of the light source; The collimating superlens is arranged behind the focal position of the multilayer film ellipsoidal reflector and is used to collimate the focused light beam to form a parallel light beam for Talbot lithography illumination.

2. The reflection-transmission hybrid extreme ultraviolet collimated illumination system according to claim 1, characterized in that: The multilayer film ellipsoidal reflector is composed of a fused quartz substrate and a molybdenum / silicon multilayer film, and has high reflectivity at an incident angle of 52° at a central wavelength of 13.5 nm.

3. The reflection-transmission hybrid extreme ultraviolet collimated illumination system according to claim 1, characterized in that: The collimating superlens is made of metal molybdenum material, and has nanometer-scale periodic small holes on its surface.

4. The reflection-transmission hybrid extreme ultraviolet collimated illumination system according to claim 1, characterized in that: An aperture and a filter are also arranged between the discharge plasma EUV light source and the multi-layer film ellipsoidal reflector.

5. The reflection-transmission hybrid extreme ultraviolet collimated illumination system according to claim 1, characterized in that: The diameter of the multi-layer film ellipsoidal reflector is 200 mm.

6. The reflection-transmission hybrid extreme ultraviolet collimated illumination system according to claim 1, characterized in that: The multi-layer film ellipsoidal reflector is plated with a Mo / Si multi-layer film.

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