Three-dimensional numerical investigations of air bubble defects during antireflective pattern fabrication via ultraviolet nanoimprint lithography

This study uses three-dimensional computational fluid dynamics analysis to investigate air bubble formation during the cavity-filling process of ultraviolet nanoimprint lithography. The three distinct antireflective patterns of pyramid-, cone-, and modified cone-shaped patterns are considered, and a parametric study is performed to analyze the effects upon air bubble formation that come by varying the pattern period (p), height (hp), and the resist thickness (ThR). Based on the simulation results, matching equations in terms of hp/ThR versus ThR/p are obtained by curve fitting for the air bubble formation. The obtained equations themselves can be very useful to avoid air bubble defects, especially when the pattern geometries are fixed, because the resist thickness can be controlled. Using the obtained equations, changes in the values of p and hp are investigated with regard to their effects upon the conditions for maximum antireflectivity and for reliability of being free from air bubble defects. It is found that small p and large hp values make it increasingly difficult to choose appropriate values of p, hp, and ThR, wherein both of the antireflectivity and air bubble-free conditions are met. The cone pattern is found to be the least suitable, whereas the most suitable pattern satisfying both conditions is the pyramid pattern.