Comparison of resist collapse properties for deep ultraviolet and 193 nm resist platforms

Abstract

A comparison of collapse behavior was made for photoresist features with linewidths from 80 to 200 nm, spacing from 100 to 350 nm, and aspect ratios from 2 to 6 for four different resist platforms: acrylic based resists, acrylic resists based upon the Fujitsu platform, cyclo-olefin–maleic anhydride based resists, and Apex E, a poly(hydroxystyrene) based resist. The percentage of collapse for different gratings was determined using top-down scanning electron microscope images. A methodology was introduced to compare collapse properties between platforms by determining the critical aspect ratio of collapse (CARC) as a function of spacing between resist structures. We demonstrated the validity of this approach using an extensive set of statistically significant data for Apex E, and we determined that the CARC decreased linearly as the spacing between lines of resist decreased. The physical origin of the approach was discussed in terms of the mechanics of beam bending and the thermodynamics of surface tension. The methodology was applied to limited data sets for other resist platforms. The four resist platforms exhibited different values of CARC at constant spacing and a different dependence of CARC as a function of spacing. Resist performance in terms of collapse properties was ranked in the following order: cyclo-olefin–maleic anhydride resists > poly(hydroxystyrene) resist and acrylic resists based on the Fujitsu platform > acrylic resists.