Protocol optimisation for work-function measurements of metal gates using Kelvin force microscopy

Currently, the work-functions of metal gates are determined using capacitance-versus-gate-voltage measurements of a dedicated MOS capacitor structure. Alternatively, Kelvin Force Microscopy (KFM) is a promising technique which allows the work-function to be measured with high spatial resolution (< 100 nm) coupled with a high sensitivity (10 meV). Nevertheless, before becoming a standard technique, there are still challenges facing a reliable operating protocol such as careful specimen preparation and environmental control to avoid surface artifacts. In the paper we show that the presence of an oxide, confirmed by Auger Electron Spectroscopy (AES), on a WSix metallic layer surface have a detrimental effect on the work-function measurement using KFM.