Ultrathin zirconium oxide films as alternative gate dielectrics

Abstract

ZrO 2 films were deposited on Si(100) wafers by the rapid thermal chemical vapor deposition process using a zirconium (IV) t-butoxide Zr(OC4H9)4 precursor and oxygen. Interfacial zirconium silicate formation was observed by high resolution transmission electron microscopy and medium energy ion scattering. The intermixing of the interface can be suppressed by forming a thin silicon nitride layer on the silicon substrate prior to ZrO2 deposition. The dielectric constant of ZrO2 achieved in this work is 15–18 with very small capacitance–voltage hysteresis, ideal for metal–oxide–semiconductor field effect transistor (MOSFET) application. The NMOSFET device has good turn-on characteristics, however, the transconductance is lower than expected due to the incomplete removal of zirconium silicate at the source and drain contacts and poses integration challenges to use ZrO2 as the gate dielectric material.