Simulation of Fluid Flow in the Step and Flash Imprint Lithography Process

摘要

Step and Flash Imprint Lithography (SFIL) is a photolithography process in which the photoresist is dispensed onto thewafer in its liquid monomer form and then imprinted and cured into a desired pattern instead of using traditional opticsystems. The mask used in the SFIL process is a template of the desired features that is made using electron beamwriting. Several variable sized drops of monomer are dispensed onto the wafer for imprinting. The base layer thicknessat the end of the imprinting process is typically about 50 nm, with an approximate imprint area of one square inch. Thisdisparate length scale allows simulation of the fluid movement through the template-wafer channel by solving governingfluid equations that are simplified by lubrication theory. Capillary forces are also an important factor governing fluidmovement; a dimensionless number known as the capillary number is used to describe these forces. This paper presentsa simulation to model the flow and coalescence of the multiple fluid drops and the effect the number of drops dispensedhas on final imprint time. The imprint time is shown to decrease with the use of increasing numbers of drops or with theuse of an applied force on the template. Appropriate filling of features in the template is an important issue in SFIL, so amechanism for handling the interface movement into features using a modified boundary condition is outlined andexamples are. Fluid spreading outside of the mask edge is also an issue that is resolved by results from this study. Thesimulation is thus a useful predictive tool providing insight on the effect multiple drop configurations and applied forcehave on imprint time, as well as providing a means for predicting feature filling.