Atomic layer deposition of Al2O3 process emissions

Abstract

The ALD process emissions and the associated chemical reaction mechanism in the ALD of the Al₂O₃ system are studied and reported. In gaseous emissions, 3.22 vol% of CH₄ and 6.01 × 10⁻² vol% of C₂H₆ are found. Net peak emissions of aerosols are found between 1 × 10³ and 1 × 10⁴ # cm⁻³ and net total emissions of 25 cycles are in the range of 6.0 × 10⁵ and 2.5 × 10⁶ particles. Most aerosols are determined as ultrafine particles with diameter smaller than 100 nm. Purging time has significant impacts on emission concentrations but no effect on size distribution. Both main and side chemical reactions are observed in the ALD system. X-ray photoelectron spectroscopy (XPS) shows that besides O–Al which represents the existence of Al₂O₃, a significant amount of C-containing by-products are also generated. Chemical bonds observed in C-containing products are C–H, C–O and CO. The main reactions can be considered stable to a certain extent, while side reactions accelerate along internal tubes and finally exceed the speed of the main reactions near the outlet of the ALD system. These results could help us to understand the potential environmental impacts of ALD nanotechnology and guide the technology's sustainable scale-up in the future.