Polymer-Pen Chemical Lift-Off Lithography.

Abstract

We designed and fabricated large arrays of polymer pens having sub-20 nm tips to perform chemical lift-off lithography (CLL). As such, we developed a hybrid patterning strategy called polymer-pen chemical lift-off lithography (PPCLL). We demonstrated PPCLL patterning using pyramidal and v-shaped polymer-pen arrays. Associated simulations revealed a nanometer-scale quadratic relationship between contact line widths of the polymer pens and two other variables: polymer-pen base line widths and vertical compression distances. We devised a stamp support system consisting of interspersed arrays of flat-tipped polymer pens that are taller than all other sharp-tipped polymer pens. These supports partially or fully offset stamp weights thereby also serving as a leveling system. We investigated a series of v-shaped polymer pens with known height differences to control relative vertical positions of each polymer pen precisely at the sub-20 nm scale mimicking a high-precision scanning stage. In doing so, we obtained linear-array patterns of alkanethiols with sub-50 nm to sub-500 nm line widths and minimum sub-20 nm line width tunable increments. The CLL pattern line widths were in agreement with those predicted by simulations. Our results suggest that through informed design of a stamp support system and tuning of polymer-pen base widths, throughput can be increased by eliminating the need for a scanning stage system in PPCLL without sacrificing precision. To demonstrate functional microarrays patterned by PPCLL, we inserted probe DNA into PPCLL patterns and observed hybridization by complementary target sequences.