Ultrathin HfOxNy Gate Insulator Formation by Electron Cyclotron Resonance Ar/N2 Plasma Nitridation of HfO2 Thin Films

Abstract

HfO x N y thin films formed by the electron cyclotron resonance (ECR) Ar/N 2 plasma nitridation of HfO 2 films were investigated for high-k gate insulator applications. HfO x N y thin films formed by the ECR Ar/N 2 plasma nitridation (60s) of 1.5-nm-thick HfO 2 films, which were deposited on chemically oxidized Si(100) substrates, were found to be effective for suppressing interfacial layer growth or crystallization during postdeposition annealing (PDA) in N 2 ambient. After 900°C PDA of for 5 min in N 2 ambient, it was found that HfSiON film with a relatively high dielectric constant was formed on the HfO x N y /Si interface by Si diffusion. An equivalent oxide thickness (EOT) of 2.0 nm and a leakage current density of 1.0 x 10 -3 A/cm 2 (at V FB - 1 V) were obtained. The effective mobility of the fabricated p-channel metal-insulator-semiconductor field-effect transistor (MISFET) with the HfO x N y gate insulator was 50 cm 2 /Vs, and the gate leakage current of the MISFET with the HfO x N y gate insulator was found to be well suppressed compared with the MISFET with the HfO 2 gate insulator after 900°C PDA because of the nitridation of HfO 2 .