Effect of non-spherical colloidal silica particles on removal rate in oxide CMP

Abstract

Oxide CMP generally has used colloidal silica slurry and fumed silica slurry. To compensate the lower removal rate (RR) of colloidal silica slurry compared to the one of fumed silica slurry, the multi-step feeding method was used to produce a non-spherical silica particle, for which the existing spherical colloidal silica particle was combined with two to three particles. To improve the performances, the prepared non-spherical colloidal silica particles were assessed by both single and mixed abrasive slurry. The slurry has two different sizes, 30 nm and 70 nm, of spherical colloidal silica particles and 70nm of non-spherical colloidal silica particles. Through the experiments, it was found out that non-spherical colloidal silica slurry had the higher RR than spherical colloidal silica slurry, and its RR was similar to the one of fumed silica slurry. For mixed abrasive slurry, the combinations of spherical and spherical or spherical and non-spherical showed higher RR, which were 152.8% higher than single abrasive slurry and 19.3% higher than fumed silica slurry, and better surface roughness than the fumed silica slurry. Therefore, non-spherical colloidal silica particles are found to be efficient to gain a higher RR and a better surface roughness than the ones of fumed silica particles.