Mechanisms for Substrate-Enhanced Growth during the Early Stages of Atomic Layer Deposition of Alumina onto Silicon Nitride Surfaces

Abstract

The atomic layer deposition (ALD) of aluminum oxide (Al 2 O 3 ) from trimethylaluminium and water on silicon nitride was studied on as-received and HF-cleaned Si 3 N 4 surfaces. In situ spectroscopic ellipsometry during ALD, X-ray photoelectron spectroscopy, X-ray reflectivity, and time-of-flight secondary ion mass spectrometry were used to elucidate the growth rate, the chemical composition, and the density of Al 2 O 3 . The effect of the substrate cleaning and of the growth temperature -varied in the 150–300 °C range- were analyzed by considering first-principles calculations of the early stages of the growth on both Si 3 N 4 and SiO 2 surfaces. Our work evidenced how not only complete ALD cycles but also complementary non-ALD reactions can account for the observed peculiarities related to the enhanced or inhibited growth rates on the Si 3 N 4 surfaces as a function of temperature.