Effects of Amino Acids on Silicon Oxide for High Silicon Oxide Removal Rate Ceria Slurry

Abstract

Chemical mechanical polishing (CMP) is a process for flattening a wafer, and its importance is increasing as design rules are shrunk. There are Inter Level Dielectric (ILD), Shallow Trench isolation (STI), and 3D-NAND CMP processes for polishing the oxide surface in the CMP process. In the case of 3D-NAND CMP, a high removal rate (RR) slurry is required because a thick oxide film must be polished in a short time. Generally, ceria or silica slurries are used in oxide CMP. Ceria slurry shows high RR by Ce-O-Si bonding. The slurry includes additives for purpose of dispersion of abrasive, pH adjustment, change of wafer surface properties. Amino acids have various functional groups depending on the pH. Depending on the activity of the functional groups, the amino acid has various effects on the surface of the slurry or silicon oxide. Amino acids were used additive in slurry and some amino acids increased the removal rate. We investigated the effect of some amino acids on the silicon oxide wafers and ceria slurry. The effect of amino acids on the removal rate was analyzed by zeta potential, contact angle and X-ray photoelectron spectroscopy analysis. Our results indicate that some amino acid adsorb on oxide surface and increase the values of absolute zeta potential. Differences in zeta potential values between slurry and wafer surface make high removal rate. Figure 1