Formation and Removal of Tungsten Flake and Metallic Film Defects in Tungsten Contact CMP

Abstract

Controlling defectivity levels after the CMP process is critical for yield enhancement. CMP tools are equipped with an in-situ cleaning module to remove polishing byproducts, residues, and flakes. After tungsten contact CMP, metallic flakes and films can cause leakage paths between contacts. They are detrimental to final device yield, and their impact increases as the transistor nodes shrink. This paper explores the formation mechanisms of different types of tungsten flake defects and suggests methods to eliminate them from the wafer surface. The interaction between the in-situ cleaner and wafer will be examined in order to better understand the source and formation of defects caught after CMP. Keyword: Tungsten CMP, CMP in-situ Cleaning, Dryer, Brushes, Flakes