Effect of extreme ultraviolet photoresist underlayer optical properties on imaging performance

Abstract

An extreme ultraviolet lithography (EUVL) suffers from the trade-off relationship among resolution, line edge roughness, and sensitivity, which is a natural limitation for chemically amplified resists. Thus, the performance of photoresist needs to be assisted by the other materials, and the resist underlayer is one of them. Using a lithography simulation tool, the authors show that the standing wave effect can also occur in the EUVL process and is dependent on the pattern pitch ratio. Although underlayers with a lower refractive index exhibit reduced in-plane line edge roughness, the difference between the refractive index of the underlayer and photoresist should be maintained below 5% in order to optimize performance.