End-Point Detection of Ta/TaN Chemical Mechanical Planarization via Forces Analysis

Abstract

This study explores the transition of shear force spectral fingerprints during tantalum (Ta) and/or tantalum nitride (TaN) chemical mechanical planarization on patterned wafers using a polisher and tribometer that has the unique ability to measure shear force and down force in real-time. Fast Fourier Transformation is performed to convert the raw force data from time domain to frequency domain and to illustrate the amplitude distribution of shear force and down force. Results show that coefficient of friction, variance of shear force and variance of down force increase during polishing when the Ta/TaN layer is removed thus exposing the inter-layer dielectric layer. Unique and consistent spectral fingerprints are generated from shear force data showing significant changes in several fundamental peaks before, during and after Ta/TaN clearing. Results show that a combination of unique spectral fingerprinting, coefficient of friction and analysis of force variance can be used to monitor in real-time the polishing progress during Ta/TaN chemical mechanical planarization for optimal polishing time.