Abstract
This paper presents a powerful modeling approach to the X-ray exposure operating space of a silicon nitride clear phase-shifter mask to produce sub-50 nm features. By first developing a central composite experimental design, we then used a wavefront modeling toolset to calculate intensity and linewidth responses for each of the response surface cells. Excellent second-order models were fit to the data for each of the responses. Analysis of the response surface data revealed curvature of the response surface for linewidth at the 70% maximum intensity threshold as a function of the absorber wall slope. The effect of the other three factors was more linear, and it was found that: 1) for every 100 nm increase in absorber thickness, the linewidth decreased 1.0 nm 2) for every 1.0 µm increase in gap, the linewidth increased 0.8 nm and 3) for every 1.0 nm increase in critical dimension (CD), the linewidth increased 0.1 nm.