Study of interfacial reaction and its impact on electric properties of Hf-Al-O high-k gate dielectric thin films grown on Si

Abstract

Amorphous thin films of Hf-Al-O (with atomic ratio of Al/Hf of about 1.4) were deposited on (100) p-Si substrates by pulsed-laser deposition using a HfO₂ and Al₂O₃ composite target. Transmission electron microscopy was employed for a detailed study of the interfacial reaction between the Hf-Al-O films and the Si substrates. Islands of Hf silicide formed from interfacial reaction were observed on the surface of the Si substrate. The formation of Hf silicide is attributed to the presence of Al oxide in the films that triggers the reaction between Hf atoms in the amorphous Hf-Al-O films and Si under an oxygen deficient condition. The impact of silicide formation on the electrical properties was revealed by high-frequency capacitance-voltage (C-V) measurements on metal-oxide-semiconductor capacitors. The observed abnormal C-V curve due to interfacial reaction was discussed.