Revisit pattern collapse for 14nm node and beyond

In this study, we have analyzed new data sets of pattern collapse obtained from 300 mm wafers which were coated with a process-of-record (POR) EUV resist and exposed by an EUV Alpha-Demo tool (ADT) and a Vistec VB300 e-beam exposure tool. In order to minimize any processing effects on pattern collapse, the same POR EUV track process was applied to both exposures. A key metric of our analysis is the critical aspect ratio of collapse (CARC) 1 . We found that CARC of POR EUV resist decreases monotonically with spacing, in the range of ~1.8-2.2 at ~32-54 nm space (60-80 nm pitch) for EUV, and ~1.5-2.1 at ~16-50 nm space (~46-80 nm pitch) for e-beam. We also estimated an apparent Young's modulus of POR EUV resist by fitting a collapse model 2 to the CARC data. The resulting modulus ~0.30 GPa was much smaller than the modulus of typical polymer glasses (~1.0-5.0 GPa). Our findings suggest that due to a significant decrease of resist mechanical properties and a sharp increase in capillary force, it will be challenging to maintain aspect ratios above 2.0 for sub-30 nm resist spacing (sub-60 nm pitches). For patterning at these dimensions, alternate processes and materials will become increasingly necessary, e.g. surfactant-based rinse solutions 3 and other approaches.