Interfacial reaction between chemically vapor-deposited HfO2 thin films and a HF-cleaned Si substrate during film growth and postannealing

Abstract
Interfacial reactions between HfO 2 thin films and a Si substrate during thin-filmgrowth and postannealing under a N 2 atmosphere were investigated by high-resolution transmission electron microscopy,Auger electron spectroscopy, and electrical measurements of metal–insulator–semiconductor capacitors. HfO 2 thin films were deposited on HF-cleaned Si wafers by a chemical-vapor-deposition technique at a wafer temperature of 200 °C using a carbon-free precursor [ Hf ( NO 3 ) 4 ]. The film thicknesses ranged from 1.5 to 5.6 nm. During the initial stage of film growth, the Si surface oxidized to form a Si-rich hafnium silicate film. With increasing deposition time, Hf-rich hafnium silicate films grew. Postannealing resulted in a double-layered filmstructure with upper and interfacial layers having dielectric constants of approximately 9.3 and 5.6, respectively. The results were compared with the results from HfO 2 filmsgrown on SiO 2 -passivated Si wafers.