基于超材料的亚波长成像与聚焦研究
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摘要
随着信息技术的快速发展,现代高新技术都在向着更加精细的领域发展。尤其是对于高端纳米光学成像技术应用,如光学光刻、共聚焦显微技术、高密度光存储、纳米激光加工、生物显微成像以及生命科学等领域,常常需要有亚波长(纳米量级)的分辨本领。然而,由于衍射极限的存在,传统光学成像技术已经不能满足实际的要求。本文基于突破传统衍射光学极限的亚波长超分辨率成像技术-双曲透镜技术,通过将传统的提高光刻分辨率技术-相移掩膜技术(phase shift mask, PSM)与超级透镜技术相结合,提出了一种超分辨率纳米光刻成像系统。理论分析和数值仿真表明此系统能够大幅度提高现有光刻技术的分辨率。同时,基于一种具有天然材料所不具备的超常物理性质,且其特性可根据需要人为调节的超常材料,设计了一种可实现亚波长聚焦的喇叭聚光镜。这种能够工作在不同工作波长下,聚焦光斑可以达到几个纳米的超透镜将有着重要的潜在应用价值。
首先,基于对相移掩膜和双曲透镜的研究分析,提出了一种新的纳米光刻成像系统。相移掩膜不仅能够通过增加相移消除相邻刻槽间的衍射干涉,同时由于刻槽间的距离非常小,它能够在掩膜与透镜交界面激发表面等离子体波,这种沿着金属表面传输的波在各槽间又会引起干涉现象。通过调节相移器产生的相移角度,最终可以为双曲透镜成像提供更加清楚的“物”。由金属和介质弯曲层交替填充的平板透镜具有双曲色散特性,因此被称为“双曲透镜”。它不仅可以传输传输波成分,同时可以有效的传输倏失波,最终实现突破衍射极限的超分辨率成像。通过分析成像系统的成像原理和特点,并与传统模型进行对比,发现该成像系统不仅能够突破衍射极限得到更高分辨率图形,同时能够实现等比例的缩小成像。这不仅提高了纳米光刻分辨率,同时有效减小了芯片的特征尺寸,提高集成度,为微电子技术飞速发展提供了重要的理论依据,具有广泛的研究应用价值。
其次,借助超材料独特的性质以及坐标变换理论,在本文我们又自行设计了一种新型的超聚焦双曲透镜,这种透镜不仅能够通过改变填充介质的介电常数来改变其工作波长。同时,改变透镜的层数,我们可以得到不同的光斑大小和聚焦长度。这种具有高聚焦效率,聚焦光斑可以达到几个纳米高性能的超透镜,将有很大的应用空间。
综合上述结果可知,本文提出的基于相移掩膜的平板双曲透镜在纳米光刻技术中的研究及设计的新型超聚焦透镜,均能够突破衍射极限实现在亚波长的成像或聚焦。这将在纳米光学成像技术、微细加工技术及表面等离子体波导激发等领域具有重要的理论价值和应用前景。
The steadily decreasing dimensions in semiconductor devices are for filling the rapid development of the information technology, especially for the high-end nano-optical imaging technology. Subwavelength resolution is widely required in many fields, such as optical lithography, confocal microscopy, high-density optical storage, nano-laser processing, biological microscopy, life science, etc. However, traditional optical imaging techniques have been unable to meet the requirements for the diffraction limit. In this paper, based on the subwavelength super-resolution imaging technology-hyperlens, which can overcome the diffraction limit, and another resolution enhancement techniques-alternating phase shift mask (Alt-PSM), we propose a novel subdiffraction-limited photolithography design. Theoretical analysis and numerical simulation show that the combination of Alt-PSM and planar hyperlens can realize subwavelength plane-to-plane imaging beyond the diffraction limit. And in this paper, based on a new metamaterial, which is a new type of aritificial electromagnetic material or sturcture, and has electromagnetic properties that are not found in nature and can be artificially tuned at will, we also present a new structure of hyperlens called "trumpet hyperlens". It has a strong ability to focus over a broad wavelength range, and it will have important potential applications.
Firstly, based on the analysis of phase-shift mask and hyperlens, we present a novel subdiffraction-limited photolithography design. The Alt-PSM is not only acted as a distinct object with phase shifting, but also modulates the transmission by interference of diffracted evanescent waves generated by subwavelength features at the surface. The planar hyperlens, which is alternately filled thin metal and dielectric film, has the ability to convert evanescent waves from the diffraction-limited Alt-PSM immediately into propagating waves. By analyzing the imaging principles and characteristics of this imaging system, and compared it with the traditional model, we find it achieves finer resolution with a well-proportioned reduction. This not only improves the imaging resolution, but also effectively reduces the feature size of chips. This provides an important theoretical basis for the rapid development of microelectronic technology, and will have a wide range of application.
Following, with the unique characteristic of metamaterials and coordinate transformation theory, we design a novel trumpet hyperlens. By changing the permittivity of the dielectric in agreement with an effective metamaterial description, this lens is expected to focus light over a broad wavelength range. And by changing the number of layers, we can get a different spot size and focus length. This lens will have a wide range of application for it has a strong ability to focus and higher focusing efficiency.
In conclusion, we have proposed the nanolithography design and the novel trumpet hyperlens in this paper. They both can break through diffraction limit, and achieve subwavelength imaging or focusing. This will have important theoretical value and application prospects in nano-optical imaging technology, microfabrication technology, surface-plasmon-polaritons waveguide excitation and so on.
首先,基于对相移掩膜和双曲透镜的研究分析,提出了一种新的纳米光刻成像系统。相移掩膜不仅能够通过增加相移消除相邻刻槽间的衍射干涉,同时由于刻槽间的距离非常小,它能够在掩膜与透镜交界面激发表面等离子体波,这种沿着金属表面传输的波在各槽间又会引起干涉现象。通过调节相移器产生的相移角度,最终可以为双曲透镜成像提供更加清楚的“物”。由金属和介质弯曲层交替填充的平板透镜具有双曲色散特性,因此被称为“双曲透镜”。它不仅可以传输传输波成分,同时可以有效的传输倏失波,最终实现突破衍射极限的超分辨率成像。通过分析成像系统的成像原理和特点,并与传统模型进行对比,发现该成像系统不仅能够突破衍射极限得到更高分辨率图形,同时能够实现等比例的缩小成像。这不仅提高了纳米光刻分辨率,同时有效减小了芯片的特征尺寸,提高集成度,为微电子技术飞速发展提供了重要的理论依据,具有广泛的研究应用价值。
其次,借助超材料独特的性质以及坐标变换理论,在本文我们又自行设计了一种新型的超聚焦双曲透镜,这种透镜不仅能够通过改变填充介质的介电常数来改变其工作波长。同时,改变透镜的层数,我们可以得到不同的光斑大小和聚焦长度。这种具有高聚焦效率,聚焦光斑可以达到几个纳米高性能的超透镜,将有很大的应用空间。
综合上述结果可知,本文提出的基于相移掩膜的平板双曲透镜在纳米光刻技术中的研究及设计的新型超聚焦透镜,均能够突破衍射极限实现在亚波长的成像或聚焦。这将在纳米光学成像技术、微细加工技术及表面等离子体波导激发等领域具有重要的理论价值和应用前景。
The steadily decreasing dimensions in semiconductor devices are for filling the rapid development of the information technology, especially for the high-end nano-optical imaging technology. Subwavelength resolution is widely required in many fields, such as optical lithography, confocal microscopy, high-density optical storage, nano-laser processing, biological microscopy, life science, etc. However, traditional optical imaging techniques have been unable to meet the requirements for the diffraction limit. In this paper, based on the subwavelength super-resolution imaging technology-hyperlens, which can overcome the diffraction limit, and another resolution enhancement techniques-alternating phase shift mask (Alt-PSM), we propose a novel subdiffraction-limited photolithography design. Theoretical analysis and numerical simulation show that the combination of Alt-PSM and planar hyperlens can realize subwavelength plane-to-plane imaging beyond the diffraction limit. And in this paper, based on a new metamaterial, which is a new type of aritificial electromagnetic material or sturcture, and has electromagnetic properties that are not found in nature and can be artificially tuned at will, we also present a new structure of hyperlens called "trumpet hyperlens". It has a strong ability to focus over a broad wavelength range, and it will have important potential applications.
Firstly, based on the analysis of phase-shift mask and hyperlens, we present a novel subdiffraction-limited photolithography design. The Alt-PSM is not only acted as a distinct object with phase shifting, but also modulates the transmission by interference of diffracted evanescent waves generated by subwavelength features at the surface. The planar hyperlens, which is alternately filled thin metal and dielectric film, has the ability to convert evanescent waves from the diffraction-limited Alt-PSM immediately into propagating waves. By analyzing the imaging principles and characteristics of this imaging system, and compared it with the traditional model, we find it achieves finer resolution with a well-proportioned reduction. This not only improves the imaging resolution, but also effectively reduces the feature size of chips. This provides an important theoretical basis for the rapid development of microelectronic technology, and will have a wide range of application.
Following, with the unique characteristic of metamaterials and coordinate transformation theory, we design a novel trumpet hyperlens. By changing the permittivity of the dielectric in agreement with an effective metamaterial description, this lens is expected to focus light over a broad wavelength range. And by changing the number of layers, we can get a different spot size and focus length. This lens will have a wide range of application for it has a strong ability to focus and higher focusing efficiency.
In conclusion, we have proposed the nanolithography design and the novel trumpet hyperlens in this paper. They both can break through diffraction limit, and achieve subwavelength imaging or focusing. This will have important theoretical value and application prospects in nano-optical imaging technology, microfabrication technology, surface-plasmon-polaritons waveguide excitation and so on.
引文
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[2]M.D. Levenson, N.S. Viswanathan, and R.A. Simpson, Improving resolution in photolithography with a phase-shifting mask, IEEE Trans. Electron. Dev.29(12),1982,1828-1836.
[3]J. Bokor, A. R. Neureuther, and W. G. Oldham, Advanced lithography for ULSI, IEEE Circuits Devices Mag.12,1996,11-15.
[4]A. Jeanmaire, P. Rochat, Rubidium atomic clock for Galileo[C]. The 31th TTI meeting,1999:627.
[5]黄国胜,李艳秋,张飞,离轴照明对ArF浸没式光刻的影响.微细加工技术,2005,1：43-47.
[6]冯伯儒,张锦,侯德胜等,相移掩模和光学邻近效应校正光刻技术[J].光电工程,2001,28(1)：1-5.
[7]Y. Aksenov, P. Zandbergen, and M. Yoshizawa, Compensation of high-NA mask topography effects by using object modified Kirchhoff model for 65 and 45nm nodes [C], Proc. of SPIE,2006, Vol.6154.
[8]J. Tominaga, T. Nakano, and N. Atoda, "An approach for recording and readout beyond the diffraction limit with an Sb thin film," Appl. Phys. Lett.73(15),1998,2078-2080.
[9]J.B. Pendry, Negative Refraction Makes a Perfect Lens [J], Phys. Rev. Lett.85,2000,3966.
[10]B.D. Terris, H.J. Mamin, and D. Rugar, Near-field optical data storage, Appl. Phys. Lett.68,1996, 141-143.
[11]K. Lindfors, T. Kalkbrenner, P. Stoller, and V. Sandoghdar, Detection and spectroscopy of gold nanoparticles using super continuum white light confocal microscopy, Phys. Rev. Lett.93,2004, 037401.
[12]Y.X. Mao, S.D. Chang, S. Sherie, and C. Flueraru, Graded-index fiber lens proposed for ultra small probes used in biomedical imaging, Appl. Opt.46,2007,5887-5894.
[13]R. A. Shelby, D. R. Smith, and S. Schultz, Experimental verification of a negative index of refraction, Science,292,2001,77-79.
[14]D.R. Smith, D. Schurig, M. Rosenbluth, S. Schultz, S. A. Ramakrishna and J. B. Pendry, Limitmions on subdiffraction imaging with a negative refractive index slab, Appl. Phys. Lett.82,2003, 1506-1508.
[15]T. Xu, C. Du, C.Wang, and X. Luo, Sub-wavelength imaging by metallic slab lens with nanoslits, Appl. Phys. Lett.91,2007,201501.
[16]S. Kim, Y. Lim, H. Kim, J. Park, and B. Lee, Optical beam focusing by a single subwavelength metal slit surrounded by chirped dielectric surface gratings, Appl. Phys. Lett.92,2008,013103.
[17]P. Wei, W. Chang, K. Lee, and E. Lin, Focusing subwavelength light by using nanoholes in a transparent thin film, Opt. Lett.34,2009,1867-1869.
[18]V. G. Veselago, The electrodynamics of substances with simultaneously negative values of permittivity and permeability [J], Sov. Phys. Usp.10(4),1968,509-514.
[19]V. M. Shalaev, Optical negative-index metamaterials, Nat. Photonics,2007,1:41-48.
[20]D. R. Smith and N. Kroll, Negative refractive index in left-handed materials, Phys. Rev. Lett.85,2000, 4184-4187.
[21]J.B. Pendry, A.J. Holden, W.J. Stewart, and I. Youngs, Extremely Low Frequency Plasmons in Metallic Mesostructures[J].Phys. Rev. Lett.76,1996,4773-4776.
[22]N. Seddon, and T. Bearpark, Observation of the Inverse Doppler Effect, Science 302,2003,1537.
[23]J. Lu, T. M. Grzegorczyk, Y. Zhang, J. Pacheco, B.-I. Wu, and J. A. Kong, Cerenkov radiation in materials with negative permittivity and permeability, Express 11,2003,723-734.
[24]L.V. Shadrivov, A.A. Zharov, and Y.S. Kivshar, Goos-Hanchen effect at the reflection from left-handed metamaterials, Appl. Phys. Lett.83,2003,2713-2715.
[25]X.L. Hu, Y.D. Huang, W. Zhang, Opposite Goos-Hanchen shifts for transverse-electirc and transverse-magnetic beams at the interface associated with single-negative materials, Opt. Left.30, 2005,899-901.
[26]Y. Tamayama, T. Nakanishi, K. Sugiyama, and M. Kitano, Observation of Brewster's effect for transverse-electric electromagnetic waves in metamaterials:Experiment and theory, Phys. Rev. B.73, 2006,193104.
[27]刘建海,陈开盛,曹庄琪.光刻技术在微细加工中的应用[J].半导体技术,26(8),2001,37-39.
[28]冯伯儒,光刻技术及其极限和发展前景[J].光电工程,21,1994,57-64.
[29]苏平,冯伯儒,张锦,提高光刻图形质量的双曝光技术[J].微细加工技术,(2),2001,20-23.
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