Characteristics of Al2O3 thin films deposited using dimethylaluminum isopropoxide and trimethylaluminum precursors by the plasma-enhanced atomic-layer deposition method

Abstract

Al2O3 thin films were deposited by using the plasma-enhanced atomic-layer deposition (PEALD) method and then investigated as a, replacement for SiO2 gate dielectric films. Two different precursors, dimethylaluminum isopropoxide [DMAI, (CH3)(2)AlOCH(CH3)(2)] and trimethylaluminum [TMA, Al(CH3)(3)], were used to deposit the Al2O3. An oxygen plasma was used as the reactant gas. The process window of the Al2O3 films deposited using the DMAI precursor was wider than that of the Al2O3 films deposited using the TMA precursor. A linear relationship between film thickness and the number of process cycles was observed after the initial 50 cycles of Al2O3 deposition. The linear film growth rates were 0.14 nm/cycle and 0.12 nm/cycle using TMA and DMAI, respectively. Both Al2O3 films showed an amorphous structure with an Al silicate phase. The leakage currents of as-deposited Al2O3 with TMA and DMAI were approximately 7.9 x 10(-9) and 3.3 x 10(-9) A/cm(2) with calculated EOT values of approximately 3.2 and 3.3 nm, respectively. In particular, the Al2O3 films deposited using the newly synthesized DMAI precursor, which is non-pyrophoric and safe, had comparable electrical properties to those of the Al2O3 films deposited using the TMA precursor.