Improved Characterization of high-k Degradation with Vacuum C-AFM

Abstract

Local phenomena like trap assisted tunneling and oxide breakdown (BD) in new high-k gate oxides in advanced MOS devices hinder the acquisition of device requirements stated in the International Technology Roadmap for Semiconductors (ITRS). Conductive Atomic Force Microscopy (C-AFM) visualizes these local phenomena by measuring the local tunneling through the dielectric. In the first part of this work we show that the physical composition of surface protrusions, that are produced at sites electrically stressed with C-AFM and that distort the electrical measurements, is oxidized Si. In the second part, we illustrate that C-AFM measurements become more reliable in high vacuum (1e⁻⁵torr) as surface (oxidized Si protrusions) and tip damage is reduced. Finally, we illustrate good agreement between conventional macroscopic electrical measurements and nanometer-scale C-AFM measurements on normal and gate – removed high-k capacitors, respectively. Moreover, to illustrate the strength of the local tunneling technique, we show the possibility of locating BD spots on a high-k capacitor.