Somewhere around 40nm is the limit on the smallest half-pitch feature that can be formed with a single-exposure of 193-nm wavelength laser light using water immersion (193i) lithography. While multiple-patterning (MP) is needed to achieve tighter half-pitches, smaller features at the same pitch can be formed using technology extensions of 193i. “Chemistry is key player in lithography process,” is the title of a short video presentation by Dow Electronic Materials corporate fellow Peter Trefonas now hosted on the SPIE website (DOI: 10.1117/2.201608.02).
Trefonas as been working on chemistries for lithography for decades, including photoresists, antireflectant coatings, underlayers, developers, ancillary products, and environmentally safer green products. He is an inventor on 61 US patents, has over 25 additional published active U.S. patent applications, is an author of 99 journal and technical publications, and is a recipient of the 2014 ACS Heroes of Chemistry Award and the 2013 SPIE C. Grant Willson Best Paper Award in Patterning Materials and Processes. Now a Senior Member of SPIE, he earned his Ph.D. in inorganic chemistry with Prof. Robert West at the University of Wisconsin-Madison in 1985.
Trefonas explains how traditional Chemically-Amplified (CA) resists are engineered with Photo-Acid Generators (PAG) to balance the properties for advanced lithography. However, in recent years the ~40-nm half-pitch resolution limit has been extended with chemistries to shrink contact holes, smooth line-width roughness, and to do frequency-multiplication using Directed Self-Assembly (DSA). All of these resolution extension technologies rely upon chemistry to create the final desired pattern fidelity.