UC Berkeley

The problem of stochastics in photoresist patterning is gaining increased attention. Understanding this problem requires new modeling methods. Here we describe the use of the Multivariate Poisson Propagation Model (MPPM) to study the relative importance of a variety of stochastic terms in both chemically amplified and non-chemically amplified resists. The results show that for the chemically amplified case, materials stochastic effects are on par with photon stochastics effects. The model is used to study both line-width roughness (LWR) impacts as well as contact size variations (CDU). As one might expect, contact CDU follows the same trends as LWR, but places even more sever constraints on the stochastic terms when considering the same feature size. Noting the contact patterning challenge, we also describe a phase-shift mask patterning method enabling the photon effect to be greatly reduced. At equivalent CDU, we demonstrate an effective 7x reduction in required source dose when patterning 25-nm half pitch contacts.