An Aluminum Gate Chemical Mechanical Planarization Model for HKMG Process Incorporating Chemical and Mechanical Effects

Abstract

In this work, a new aluminum gate chemical mechanical planarization (CMP) model is proposed in high-k metal gate (HKMG) process for controlling and simulating the metal gate height variation. It systematically captures the effects of mechanical abrasion and concentrations of different types of chemical reagents on material removal rate and surface height evolution. Based on the fundamentals of steady-state oxidation reaction and etched removal in addition to mechanical abrasion, the combinational synergistic interaction is described by separate kinetic parameters such as process parameters, pad properties and slurry chemistry. It can be seen that the removal rate and the coupled effects of the chemical additives are determined from a closed-form equation, making use of the concepts of chemical mechanical equilibrium, chemical kinetics and contact mechanics. The model prediction results show good agreement with the collected experimental data. The metal gate dishing post-Al-CMP is found to increase with increasing the pattern density when the line space is fixed. The dishing value increases with increasing the pattern density up to a certain maximum and then it decreases for a fixed pitch. The present model can be adopted to analyze the influence of the design pattern structures, slurry properties, pad characteristics and polishing conditions on removal rate and wafer surface evolution. The governing equation of aluminum removal and dishing effect reveal some insights into the polishing process and can be used for assisting in HKMG test pattern design and performing the sensitivity analyzes of operating parameters on surface topography during Al-CMP.