Cryo-electron tomography reconstructs polymer in liquid film for fab-compatible lithography.

Abstract

Liquid film is ubiquitous in nature and serves as the critical medium for the dissolution of photoresist to create nanoscale circuit patterns in lithography, which is a core task since the birth of semiconductor industry. However, despite decades of research, the microscopic behaviors of photoresist in liquid film and at interfaces remain elusive, leading to industrial effort for pattern defect control largely a trial-and-error process. Here, we unravel the nanostructures and dynamics of photoresist polymers in liquid film and at gas-liquid interface using a cryo-electron tomography (cryo-ET) methodology. The native-state three-dimensional structures of photoresist polymers are reconstructed by cryo-ET at significantly improved resolution compared to conventional methods. Cryo-ET reconstructions resolve the spatial distributions of photoresist polymers across gas-liquid interface into bulk solution, revealing the cohesional entanglements between polymer chains. By inhibiting the polymer entanglements and leveraging photoresist's adsorption at gas-liquid interface, the contaminations across 12 inch wafers have been eliminated under industrial conditions, yielding a > 99% improvement in minimizing the pattern defects for fab-compatible lithography.