High Rate Chemical Mechanical Polishing of Boron-Doped Polycrystalline Silicon

Abstract

In this paper, the effect of lubrication on the polish rate and the surface quality of highly boron-doped polysilicon is presented. The mechanical effects of polishing were studied by altering the CMP process and lubrication regime. It was shown that increasing the polish velocity and slurry flow rate does not always increase the polish rate and that the lubrication behavior plays a dominant role in this process. Increasing the mechanical forces and altering the lubrication regime to boundary and dry lubrication were the key factors which resulted in a maximum polish rate. The maximum polish rate for the boron-doped polysilicon with 3.4 mΩ.cm−1 resistivity was ∼0.75μ/min and achieved in the dry lubrication regime. The coefficient of friction (COF) was also studied and agreed with the polish rate values where the dry lubrication polishing showed highest COF following the Stribeck curve. Finally the surface quality of the polished wafers were studied by AFM and it was shown that the lubrication behavior and friction force had minor effect on the surface roughness and all the wafers were perfectly smooth after polishing (Rq∼2Å).