Porous low-k material etch for 32 nm and beyond

Abstract

The challenges facing back-end-of-line (BEOL) etch as technology nodes progress are becoming increasingly difficult as the challenges due to shrinking dimensions are compounded by the challenges from new materials integration. Considering a via-first-trench-last (VFTL) patterning scheme, as critical dimensions decrease, key dimension-related etch challenges include CD control, aspect ratio of trench litho film stacks, RIE lag, and LER. The inclusion of low k dielectrics, including porous materials (k ≤ 2.4), requires the etch to consider the sensitivity of the films to compositional modification (i.e., dielectric damage), polymer interactions with the pores (i.e., rough etch front), and consideration of diffusion effects possible with porous materials. These materials issues have driven the bulk of the novel etch development in recent years. However, as the minimum pitch approaches sub-100nm, new interactions of the materials with this critical dimension need to be considered. The ability of low k materials to be patterned at the aspect ratios required without losing structural integrity will be the key challenge for future technologies' success. This paper will review the key etch challenges as a function of dimensions vs. materials and highlight where their interactions which will drive future work. © 2009 Materials Research Society.