The ability of chemically amplified resists to transfer an aerial image at increasingly smaller dimensions is critical to EUV lithography success at increasingly smaller process nodes. Stochastic inhomogeneities in resist exposure and patterning have been studied, which include photon shot noise and resist chemical segregation. Previous work has indicated that inhomogeneities are present in multicomponent resists beyond those predicted by random statistics. This is thought to be due to self-segregation of components in the multi-component chemically amplified resist (CAR).
We will show that the most critical part of the resist chemical segregation occurs during the spin coating process after a significant amount of the solvent has evaporated, but while there is still enough solvent to enable molecular mobility within the resist. These non-random molecular distributions within chemically amplified EUV photoresists can be caused by a combination of thermodynamics and kinetics.
The opportunity to control the amount of resist segregation and reduce the chemical segregation and defectivity is therefore primarily during the spin coating process. We will show results of varying the composition and spin coating parameters and how that affects the resist segregation. This includes spin coating at sub-atmospheric pressure, elevated temperatures, and with varying spin speeds to increase the rate of evaporation and decrease the time available for the resist segregation during the drying phase of the spin coating process.
We will also discuss directions for future non-chemically amplified resists that still require significant research but may lead toward better performing materials for EUV lithography, especially for the high numerical aperture EUV tools that are starting to ship from ASML.
Bio: Greg Denbeaux received his B.A. degree in physics from Wesleyan University in 1993. He studied free electron lasers and x-ray microscopy for his Ph.D. from Duke University in 1999. He was a staff scientist at Lawrence Berkeley National Laboratory until becoming faculty at the College of Nanoscale Science and Engineering, Albany, New York. Currently, he is an associate professor at University at Albany and studies fundamentals of photoresists including stochastic effects, outgassing, and secondary electron interactions. He also has a research program in nanoparticle detection, quantification, identification and transport, all aimed at defectivity reduction in semiconductor manufacturing. He has published over 200 papers on this research which have been cited over 2,500 times. He has organized the IEUVI Resist Technical Working Group for the last few years.