Effect of ionic strength on amorphous carbon during chemical mechanical planarization

Abstract

A hard mask is an essential to prevent pattern collapse resulting from leaning, wiggling, or other defects. It is critical to achieve high removal rates of hard masks. The process of amorphous carbon chemical mechanical planarization (CMP) forms OH radicals on the surface by an oxidation and breaks bonds in the weakest area. Electrolytes with different ionic strengths were added, to facilitate the formation of OH radicals. When electrolytes were added, the removal rates increased by approximately 2.3 times over those without any additives. The increase in surface roughness is another significant factor. The roughness increased in all cases. In particular, a mixed slurry achieved the best results, with a mean surface roughness value of 0.147 nm for a scanning area of 5 × 5 μm2. Thus, the ionic strength of the electrolyte is critical in the CMP of amorphous carbon.