Modelling electric-field-assisted post-exposure bake: role of acid dissociation and dielectrophoresis

In the past a number of studies [1]-[3] have been conducted to assess the effect of electric field on the photoacid diffusion during the post-exposure bake. Typically, it has been found that fields of order 10MV/m are sufficient to have impact on the width, depth and tapering of trench features. For DUV lithography this strategy has so far not been applied. Here we are reconsidering this strategy for EUV feature sizes and develop the theory that enables to predict how use of external electric field scales would work out for the EUV dimensions. The rationale is that stochastic variation in resist is expected to be a limiting factor further down the roadmap, and therefore any strategy improving resist performance is worth consideration. The much smaller than expected effect of E-field on trench depth as investigated in [3] can be explained by assuming incomplete ionic dissociation of photo-acids. To successfully employ E-field assisted PEB on EUV scales will be an uphill battle, although there is an opportunity to exploit dielectro-phoresis to direct the photo-acids during PEB.