28nm-pitch Ru interconnects patterned with 0.33NA-EUV single exposure

Abstract

In this work we studied the impact of stochastic resist defects on electrical measurements of BEOL structures, and seek to demonstrate that large electrical test structures, built with a relatively simple patterning flow, can be used in the early stages of resist, and patterning development, as the electrical failures are almost exclusively caused by resist defects. To that end, single-layer electrically testable metal patterns at minimum metal pitch of 28nm were created using a single 0.33NA-EUV exposure and a metal damascene process flow. A bright field mask was exposed with a metal-organic, negative-tone-development resist process to create trench structures that are transferred into an oxide dielectric layer. Following this, the trenches were filled with ruthenium (Ru) for electrical testing of meander resistor and fork-fork structures.