Characteristics of Hf-silicate Interfacial Layers Formed by Wet Etching

Interfacial layers of Hf-silicate films grown on Si substrates by using atomic layer deposition and wet etched with buered hydrogen fluoride were investigated. After etching the Hf-silicate film, the remaining gate dielectric is an interfacial layer, composed mainly of SiO2. By etching, the thickness of the Hf-silicate films was reduced and the C-V curves exhibited an increasing hysteresis window, as compared to as-deposited samples, due to charges trapped at the interface and to etching impurities. Also, we found that an increase in the capacitance was obtained after etching. The dielectric constant after an etching time of 20 seconds was lower than that of the unetched sample and this value was calculated as 7.97. However, a large leakage current density was the result of direct tunneling in the thinned films.