介质超构表面的CMOS兼容制备工艺的进展

Progress in CMOS-Compatible Fabrication Process of Dielectric Metasurfaces

超构表面为纳米光子器件赋予了更高的自由度与灵活度,使实用的微纳米光子器件的实现成为可能。基于高折射率半导体材料的介质超构表面制备技术可以和半导体集成电路的制作工艺结合,有希望在攻克超构表面大面积和高通量制备技术难题上发挥重要的作用,因此对其光场调控性能和制备工艺的研究是该领域近年来的重要发展方向。本文从硅、氮化硅和二氧化钛等介质超构表面出发,介绍了超构表面高通量制造技术的发展。此外,介绍了基于大面积制造技术实现实际应用的基于纳米光子器件的光学器件,如显示、成像、光调控器件。

Significance Metasurfaces are composed of sub-wavelength electromagnetic resonator arrays,and they have attracted great attention because of their flexibly controlled polarization,amplitude,and electromagnetic phase of light waves at the sub-wavelength scale.At present,metasurfaces have experienced a fast-evolving development.Compared with traditional optical components,metasurfaces have obvious advantages and may become the most critical optical components to form a new generation of micro-optical systems,so as to provide a feasible way for miniaturizing and integrating optical systems.Unlike traditional refractive and diffractive optical components,metasurfaces have only a sub-wavelength thickness,which is thinner and can meet the increasing needs of miniaturized optical systems.Although the performance of metasurfaces has been highly extended by using various advanced design and fabrication methods,the practical application of metasurfaces is still limited by challenging large-area and high-throughput fabrication of sub-wavelength structures.All-dielectric metasurfaces based on semiconductor materials with a high refractive index have attracted more and more attention since they can be fabricated by using commercial complementary metal-oxide-semiconductor(CMOS)-compatible mass manufacturing technologies.Currently,nanoimprint lithography and deep ultraviolet lithography are widely used in CMOS-compatible mass manufacturing technologies,and researchers attempt to use them to realize the patterned growth of nanomaterials.However,due to the difference between materials,researchers need to develop new processes for each material.This paper mainly introduces the fabrication process and metasurface devices of each material,so as to help researchers choose convenient methods to fabricate metasurfaces.Progress In this paper,the background of high-throughput and large-area metasurface fabrication is introduced at first.In addition,compared with metal metasurfaces,all-dielectric metasurfaces have less energy loss and can be fabricated by using commercial CMOS-compatible mass manufacturing technologies,so all-dielectric metasurfaces are regarded as an optimal choice to achieve the large-scale application of metasurfaces devices.Furthermore,the existing challenges are discussed.Second,the fabrication method of silicon-based large-scale metasurfaces is introduced,including deep ultraviolet lithography and nanoimprint lithography.Relevant cases(Fig.1 and Fig.2)are analyzed,and the reason for applying these methods is explained.Then silicon nitride and titanium dioxide metasurfaces are analyzed in the same way.In addition,functional devices based on silicon nitride and titanium dioxide metasurfaces are also presented with details.Specifically,the aspect ratio of the titanium dioxide metasurface fabricated by nanoimprint lithography is as high as 7.8(Fig.8)in the part of other materials,and methods of fabricating perovskite and graphene are introduced with the specific examples(Fig.9,Fig.10,and Fig.11).Finally,the limitations of these two methods are discussed.In addition,the femtosecond laser direct writing technology is studied,which may become a new generation of lithography.Additionally,the application and research direction of large-scale metasurfaces are predicted.Conclusions and Prospects Although nanoimprint lithography and deep ultraviolet lithography have been used for fabricating high-throughput and large-scale metasurfaces and have received positive results,they still have many limitations,including the selectivity of substrate materials and complex processes.Therefore,a new method is required to address these issues.Femtosecond laser direct writing technology has some unique advantages,including extremely small heat-affected zone and high processing compatibility with transparent substrates.Besides,the femtosecond laser-induced direct patterned growth technology does not have such a complex process compared with deep ultraviolet lithography.Furthermore,processing efficiency can also be improved by adopting parallel processing strategies.For these reasons,femtosecond laser direct writing technology may become a new generation of lithography.