Curing defects in plasma-enhanced atomic layer deposition of Al2O3 by six methods

Abstract

In this paper, the Al2O3 film was fabricated by plasma-enhanced ALD (PEALD) using trimethylaluminium (TMA, Al(CH3)3) precursor. For curing defects such as hydroxyl (OH), Hydrogen, and Carbon inside Al2O3, six types of treatments combining rapid thermal annealing (RTA) or H2 plasma were applied. The comprehensive electrical characteristics such as C-VG, flat-band voltage (Vfb) were quantitatively analyzed by comparing interface trap density (Dit), oxide trapped charge density (Not), permittivity, and breakdown field. RTA is crucial to reduce Dit, Not by ∼78.2% and ∼86.7%, respectively, and enhance the breakdown field from 9 MV/cm to 14 MV/cm or higher by forming the interfacial layer. However, it was not adequate to prevent the severe Vfb shift and decrease of permittivity. H2 plasma pre-treatment could be a solution for these problems as well as slightly improve the breakdown property. But the widening of Vfb variation was still concerned because the amount of carbon reduced by H2 plasma treatment is not consistent. Thus, a more precise H2 plasma treatment is necessary for reliable threshold voltage distribution.