Highly Selective Polishing Rate Between a Tungsten Film and a Silicon-Dioxide Film by Using a Malic-Acid Selectivity Agent in Tungsten-Film Chemical-Mechanical Planarization

Abstract

For achieving a highly selective polishing rate between a tungsten (W) film and a silicon-dioxide (SiO2) film in W chemical-mechanical planarization (CMP), we designed W-film CMP slurry by mixing a small-molecule having two carboxylic functional groups (i.e., malic acid) as a selectivity agent. The selectivity was principally controlled by the malic acid concentration: it rapidly increased with increasing malic acid concentration in the W-film CMP slurry, and a W-film polishing rate:SiO2-film polishing rate of >100:1 was achieved. We found that the selectivity was mainly determined by the chemical properties, such as the corrosion and the chemical reaction between the films and malic acid rather than by the mechanical property, i.e., the electrostatic force between the ZrO2 abrasive and the films.