IEEE Photonics Society

Boston Photonics Society Chapter

Boston Chapter of the IEEE Photonics Society


April 11, 2005
6 PM

Marriott Newton Hotel

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Maskless Lithography and Imaging using Diffractive Optics

Dr. Rajesh Menon, MIT, Cambridge, MA

Co-sponsored by the New England Chapter of SPIE


Abstract:  The semiconductor industry has been driven by significant improvements in optical-lithographic capability. As feature sizes on the wafer shrink faster than the wavelength of the exposing illumination, increasingly complex and expensive steps such as immersion, resolution-enhancement techniques, phase-shift masks and optical-proximity correction are required. Traditionally, high costs in the industry have been amortized over large volumes of chips in the early years, and by progressive technological maturity in the later years. Besides the obvious economic impact, long delay times and high costs associated with developing new chips have resulted in ultra-conservative chip designs, which are often out of sync with requirements of device functionality. Optical lithography using MEMs-based spatial-light modulators provides an alternative means for patterning both wafers (for low-volume manufacturing), and masks (for chip development and mask manufacturing). Significantly lower costs-of-ownership coupled with throughputs acceptable for low-volume manufacturing are the enabling attributes of such techniques. At MIT, we have pursued a unique version of this technology, which we call Zone-Plate-Array Lithography (ZPAL).

In ZPAL, an array of high-numerical-aperture diffractive lenses (for example, zone plates) is used to create an array of tightly focused spots on the surface of a photoresist-coated substrate. Light directed to each zone plate is modulated in intensity by one pixel on an upstream spatial-light modulator. The substrate is scanned, and patterns of arbitrary geometry are written in a “dot-matrix” fashion. We have built a proof-of-concept ZPAL system, using an illumination wavelength of 400nm and a Silicon Light Machines Grating Light Valve (GLVTM) device. This system is capable of sub-200nm resolution. Field-stitching, overlay and fabrication of novel magnetic devices were experimentally demonstrated. We used gray-scale techniques to improve the pattern fidelity. The system can be easily modified to act as a parallel scanning-confocal microscope. In this presentation, we will discuss the lithographic and imaging applications of this technology.


Biography:  Rajesh Menon has been involved in the development of a novel optical-maskless-lithography system in the NanoStructures laboratory at MIT since 1998. He received his SM and PhD degrees from the Massachusetts Institute of Technology (MIT) in 2000 and 2003 respectively. He is a founding member of LumArray LLC, which is commercializing maskless lithography for research and development. Dr. Menon is responsible for over 6 patents and has published over 20 technical articles. He is currently serving as the CTO of LumArray, and also holds a post-doctoral-associate position at the NanoStructures laboratory in MIT. The focus of Dr. Menon’s research is the application of novel diffractive-optical elements for lithography, and imaging using both experiments and rigorous simulation.


Location:  Marriott Newton Hotel