Analysis of mechanical properties of copper thin film in ambient, DI water and slurry environment by nanoindentation

Abstract

ABSTRACT The nanomechanical properties of chemically altered wafer surface are critical for modelling the material removal in the chemical mechanical planarization (CMP). This paper investigates the nanomechanical properties of copper thin film on the silicon wafer and the reacted passivation layer in different environmental conditions by nanoindentation. The environmental conditions are ambient air, DI water and slurry environment at 45°C temperature. Nanoindentation test is performed on Hysitron TI980 triboindenter using standard Berkovich indenter. Experimental results show that the nanohardness and Young’s modulus of the copper thin film in the ambient environment are 1.72 GPa and 118.03 GPa, respectively. The passivation in DI water results in a slight increase in nano-hardness of copper thin film, on the other hand, a significant decrease in nano-hardness is observed after passivation in the slurry environment. The reduced values of hardness and young’s modulus in the slurry environment are in line with the chemical action of slurry in CMP. The estimated nano-hardness and modulus of the wafer contact surface after the chemical action of slurry are critical process parameters for the analysis and modelling of the advanced node (CMP) process.