Nanolithography in the Evanescent Field of Noble Metals

Abstract

With the rapid progress of high integrity in integrity circuit(IC) field, the finer resolution of optical lithography became more and more urgent which spurs the scientists to put a premium eye on resolution, throughput and reliability. According to Abbe’s theory, the spatial resolution can be improved by using either shorter wavelengths or higher numerical apertures. Although the semiconductor industry has made significant progress in increasing the lithography resolution in the past decades, further improvement of the resolution by accessing shorter wavelengths is facing critical challenges due to the availability of optical materials with suitable refractive index. The expansion of nanoscale science and engineering will require flexible, high spatial resolution, and low-cost nanolithographic techniques and systems other than those employed in the semiconductor industry, for reasons of both cost and limited flexibility. So far, optical projective lithography technique is of dominance in optical lithography, resolution can be extended to 32 nm or even less by using ArF light resource combined with immersion technique; however, resolution below 32 nm meets great difficulty till optical lithography being washed out. According to the International Technology Roadmap for Semiconductors(ITRS2009 Edition), next generation lithography techniques for feature size 32 nm and below are 193 nm immersion double patterning, 193 nm immersion with other fluids and lens materials, Maskless Lithography(ML2)and imprint etc., but the techniques of breaking the limitation of 32 nm resolution is far from mass production; they met the difficulties of complicated fabrication procedure, low efficiency and production. A number of near-field nanolithography techniques have been explored recently by some research groups.