An Order-of-magnitude Calculation of Material Removal Mechanism in Chemical-mechanical Polishing at Molecular Scale

Presents a sequence of order-of-magnitude calculations based on the concepts of chemical kinetics and transport phenomena during the chemical mechanical polishing(CMP) process.The growth rate and diffusion thickness of the oxide layer were quantitatively evaluated in the magnitude analysis.The effects of the oxidizer concentration in the slurry at the wafer surface in addition to the diffusion coefficient under the defect condition were also addressed.In addition,the indentation depth of a single particle into the wafer surface was investigated using Ubi Scanning Quasistatic Nano-indentation with 70 nN force.The indentation depth was of an order of 10-11 m determined on the basis of the linear regression mechanism.The combined calculations and experimental results indicate that the CMP material was removed at the molecular scale.The results supported by published experimental data show that declining the oxide layer thickness will increase the material removal rate for advanced CMP process.This study lends further credence to the molecular-scale mechanism for the CMP material removal,as well as its underlying theoretical foundation.