Suppression of Dissolution Rate via Coordination Complex in Tungsten Chemical Mechanical Planarization

Topography of tungsten should be assured at a minimum through chemical mechanical planarization (CMP) in the metal gate structures (e.g., buried gates, replacement metal gates) and via contact in the middle of line (MOL) process for sub−7 nm semiconductor applications. However, excessive tungsten dissolution during the CMP process that results from high oxidizer concentrations and acidic atmospheres results in poor tungsten topography. In this study, we report a novel strategy to improve the tungsten topography by suppressing tungsten dissolution via coordination complex formations between picolinic acid and tungsten oxide. With 1.5 wt% picolinic acid for the inhibitor, the dissolution rate of tungsten was dramatically attenuated, and improved topography with a Ra value of 7.8 nm were demonstrated while validating CMP removal rate.