Plasma Enhanced Atomic Layer Deposition of ZrO₂ Gate Dielectric

Abstract

Zirconium oxide (ZrO₂) films were investigated as a potential replacement for silicon dioxide gate dielectric. ZrO₂ films were deposited by both atomic layer deposition (ALD) and plasma enhanced ALD (PEALD) techniques using Zr t-butoxide and Zr(NEt₂)₄ as Zr precursors and oxygen as reactant gas. The XTEM images showed a randomly oriented polycrystalline structure of ZrO₂ and amorphous characteristics of the interfacial layer. The calculated dielectric constant value of the ZrO₂ films are about 10∼18 and these low values are believed due to the low dielectric constant interface layer. ZrO₂ films deposited with oxygen plasma using Zr(NEt₂)₄ showed the leakage current of 3.12X10^-9 A/cm² at the gate bias voltage of -1.0 Volt with the equivalent oxide thickness value of 1.39 nm. ZrO₂ films deposited with the oxygen plasma showed generally improved film quality with relatively low leakage current, small hysteresis and low carbon incorporation as well as the higher growth rate compared to the films deposited with the oxygen gas. Also, ZrO₂ films deposited using Zr(NEt₂)₄ showed relatively improved film properties compared to the films deposited using Zr t-butoxide. This study demonstrated the possible application of PEALD technique for the high quality ZrO₂ gate dielectric film deposition.