Characteristics of Al2O3 Films Deposited by Plasma-Assisted Atomic Layer Deposition with Varying RF Powers

Abstract

Hydrogenated aluminium oxide (Al2O3) was investigated as a passivation layer for p-type silicon. Al2O3 thin films with a thickness of 10 nm were deposited by plasma-assisted atomic layer deposition (PAALD). Trimethylaluminium and oxygen gas were the precursors for the PAALD process. A correlation of the hydrogen content, fixed charge density, interface trap density (D-it) and lifetime was presented. The interface and passivation properties of the Al2O3 thin films were investigated by capacitance-voltage (C-V) measurements, conductance-voltage (G-V) measurements and quasi-steady-state photoconductance (QSSPC). The hydrogen contents in the Al(2)O(3 )thin films were characterized by X-ray photoelectron spectroscopy (XPS). As the RF power increased, the number of hydroxyl groups in the Al2O3 thin films increased. The minority carrier lifetime results were correlated with the hydrogen contents and D-it values. As the RF power increased, the lifetime increased. Dissociated hydroxyl groups generated hydrogen gas, which both passivated the surface and resulted in blistering. The minority carrier lifetime of the film deposited at a RF power of 800 W decreased due to high D-it and blistering. The highest passivation effect was achieved at a RF power of 700 W.