Effects of cavity shapes and rounded corners of mold on polymer filling process in nanoimprint lithography

Abstract

The effects of cavity shapes and rounded corners on polymer filling and mold stress distributions of nanoimprint lithography are investigated using a numerical simulation approach. Three types of mold cavities including a rectangular cavity with vertical sidewalls, a trapezoidal cavity with inclined sidewalls, and a semicircular cavity with curved sidewalls are used to study the polymer flow and the filling situation in the embossing stage. Stress distributions of three types of molds are compared to evaluate the mold durability under different imprint pressures. To further optimize filling ratios and the stress concentration, three molds with round corners are proposed. Simulation results show that the mold with a semicircular cavity can achieve complete filling under the lowest pressure, but the maximum von Mises stress is greater than that of others. The filling ratio of the trapezoidal cavity is better than that of the rectangular cavity, and the maximum von Mises stress is the smallest among three types of molds. With the increase in the radius of round corners for three molds, filling ratios are improved and the maximum stresses decrease apparently, which not only improve the pattern transferring fidelity but also prolong the service life of the mold effectively.