Reduction in Interface Trap Density of Al2O3/SiGe Gate Stack by Electron Cyclotron Resonance Plasma Post-nitridation

Abstract

An electron cyclotron resonance (ECR) plasma post-nitridation method has been investigated for improving Al2O3/SiGe metal–oxide–semiconductor (MOS) interfaces. We evaluated the interface trap density (Dit) of Al/Al2O3/Si0.75Ge0.25/p-Si MOS capacitors by the conductance method, showing that Dit of the Al2O3/SiGe interfaces was reduced to 3×1011 cm-2 eV-1 at the minimum expense of equivalent oxide thickness (EOT). X-ray photoelectron spectroscopy (XPS) revealed that a SiGe–ON interfacial layer was formed between the Al2O3 and SiGe layers, which improved the interfacial properties through nitrogen passivation of SiGe interfaces. As a result, a superior Al2O3/SiGe MOS interface with a 0.2 nm EOT increase can be obtained by plasma post-nitridation.