Molecular transfer lithography for pseudomaskless, high-throughput, aligned nanolithography

Abstract

A class of high-resolution printing methods, collectively called molecular transfer lithography (MxL), involves the replication of surface patterns as water-soluble templates. The templates are manufactured by spin-casting a polyvinyl alcohol (PVA) film-forming solution on a master pattern. The resultant water-soluble templates are then bonded to the substrate using an intervening adhesive layer that solidifies through photocuring, thermal, or two-part reactive schemes. The templates are chemically removed by dissolution with water yielding a formed pattern in the adhesion layer. Other variations of MxL include the transfer of materials to the substrate such as metals deposited on the template surface. For higher quality prints and overlay, contact alignment tools for MxL are needed. This article describes the implementation of MxL transfer schemes by adaptation of standard contact aligners normally used for photolithography. The primary modification required for integration is the replacement of the quartz photomask with the conformable water-soluble template. Results are presented to demonstrate the replication capability of MxL to sub-100 nm and the use of contact aligners to achieve deep submicron feature sizes and to enable three-dimensional printing while providing an intermediate level of overlay accuracy.