Rapid thermal chemical vapor deposition of zirconium oxide for metal-oxide-semiconductor field effect transistor application

Abstract

ZrO 2 is investigated in this work to replace SiO2 as the gate dielectric material in metal-oxide-semiconductor devices for its high dielectric constant, good thermal stability on silicon, and large band gap. ZrO2 films were deposited on p-Si(100) wafers by a rapid thermal chemical vapor deposition process using a zirconium (IV) t-butoxide Zr(OC4H9)4 precursor and oxygen. At temperatures between 300 and 400 °C, the reaction was thermally activated with an activation energy of 29 kcal/mol, consistent with a β-hydride elimination mechanism leading to ZrO2 deposition. In this regime at substrate temperatures below 350 °C, one atomic layer of ZrO2 can be deposited after each alternating exposure to the precursor and oxygen, ideal for achieving conformal coverage of ZrO2 over high aspect ratio features. Stoichiometric, uniform, and amorphous ZrO2 was obtained, and highly conformal step coverage of the deposited ZrO2 was observed on 300 nm features with an aspect ratio of 4. The dielectric constant of ZrO2 achieved in this work ranged from 15 to 18 depending upon process conditions and small C–V hysteresis and low interfacial state density were observed, ideal for metal-oxide-semiconductor field effect transistor application.