Suraj K. Patil

Alternative materials for high numerical aperture extreme ultraviolet lithography mask stacks

In this paper we compare the imaging performance of several options currently under consideration for use in 0.33 and higher numerical aperture (NA) extreme ultraviolet (EUV) mask stacks, Mo/Si ML reflective coatings with 40 bilayers, Ru/Si multilayer (ML) reflective coatings with 20 bilayers, and a new thinner Ni-based absorber layer on each of these mask stacks. The use of a Ru/Si ML coating with its shallower effective reflectance plane and a 2x thinner Ni-based absorber is expected to significantly reduce both shadow bias requirements and mask telecentricity errors. The conclusions of the paper are supported with the results of both experimental measurements and rigorous simulations.

Elimination of Tungsten-voids in middle-of-line contacts for advanced planar CMOS AND FinFET technology

As dimension of middle-of-line contacts scale down, the Tungsten (W) gap-fill capability is critical, and we started to see function failure in SRAM and logic circuit caused by W-voids. We had observed that formation of W-voids is related to the contact profile, nucleation/barrier on sidewall, and deposition methods. Furthermore, even those initially “good” W-plugs are formed, the subsequent process steps may damage the W-plug and cause voids. These W voids lead to high resistance and failures in logic and SRAM circuit (see Fig.1). We analyzed mechanisms and illustrated solutions systematically with in-line detection method. We also discussed these solutions for technology development as well as manufacturing in this paper.