Design of Holographic Condenser Lens for Visible Light Lithography

Abstract

Photolithography with visible light at λ = 405 nm utilizing the concept of nonlinear saturable absorption effect where the size of the spot is diminished to the nanometer scale as proposed by several researchers is an alluring proposition for cost-effective projection lithography. Costly conventional condenser lenses can be replaced by monochromatic aberration-free and cost-effective volume phase holographic lenses for visible light photolithography with enhanced resolution utilizing the concept of off-axis illumination. However, the diffraction efficiency of holographic lenses depends on the wavelength of illuminating light and the angle of illumination. Angular and spectral characteristics of volume phase holograms can be controlled by optimizing processing parameters. The results on the theoretical optimization of three important processing parameters, namely fringe spacing ($\wedge$), thickness of the film ($d$), and refractive index modulation ($\mathrm{\Delta }n$) in the light of coupled wave theory for recording holographic lenses of high diffraction efficiency at $\lambda =405\text{nm}$ are presented. It is pointed out that a properly designed single holographic lens can be used for off-axis illumination of a photomask with a parallel beam of light, whereas a system of two identical holographic lenses cemented together has to be used to realize a condenser lens similar to a converging lens.

KEYWORDS:

• Diffraction efficiency
• Holographic lens;  Holographic optical element
• Off-axis illumination
• Optical lithography
• Resolution enhancement

ACKNOWLEDGEMENTS

The authors are thankful to Prof. H.L. Yadav, head of the department of physics, the National Institute of Technology Jamshedpur for his valuable suggestions throughout the work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Shweta Yadav

Shweta Yadav received a Btech in electronics and communication engineering and an Mtech degree in communication systems from the affiliated College of Biju Patnaik University, Odisha, India, in 2016 and 2020, respectively. She is pursuing a Phd in the National Institute of Technology Jamshedpur, Jamshedpur, Jharkhand.Corresponding author. Email: [email protected]

Rashmi Sinha

Rashmi Sinha received a BSc (engineering) degree in electrical engineering and an MSc (engineering) in power electronics in 1995 and 2003, respectively, from the National Institute of Technology, Jamshedpur, India. She joined the National Institute of Technology, Jamshedpur, as a lecturer in 1997. She received her PhD from the National Institute of Technology, Jamshedpur. Presently, she is an associate professor in the same organization. Her area of interest includes antenna design, array synthesis, microwave, metamaterial, and soft computing. Sinha has published two books, 14 book chapters, nine papers in international conferences, and 40 research articles in the Journal of repute. She has more than 25 years of teaching experience. Email: [email protected]

Nirmalendu Deo

Nirmalendu Deo received a PhD in micro-electronics engineering from Queen’s University of Belfast, UK in 2004. He received his master of science in physics from the National Institute of Technology, Jamshedpur and his master of technology degree from the Indian Institute of Technology-Kharagpur. His areas of research are semiconductor process engineering, which includes semiconductor device fabrication and process control, thin films CVD/PVD, dry etching processes, and photolithography. He has over 30 publications in thin films and dry etching processes, photolithography, and holography. Presently, he is working as a director, semiconductor division at Next Generation Technology Inc, Illinois, USA. Email: [email protected]

Vijay Nath

Vijay Nath received his BSc degree in physics from DDU University Gorakhpur, India in 1998 and his PG diploma in computer networking from MMM University of Technology Gorakhpur, India in 1999 and an MSc degree in electronics from DDU University Gorakhpur, India in 2001 and a PhD degree in electronics from Dr. Ram Manohar Lohiya Avadh University Ayodhya (UP) and in association with CEERI Pilani (Raj), India in 2008. His areas of interest are low-power very large-scale integration design, ultra-low power temperature sensors for missile applications, micro-electronics engineering, mixed-signal design, application-specific integrated circuit design, embedded system design, cardiac pacemaker, internet of things, artificial intelligence & machine learning, and computational intelligence. Email: [email protected]