Feasibility Study for Usage of Diluted Fluorine for Chamber Clean Etch Applications as an Environmental Friendly Replacement of NF₃

Abstract

Deposition steps in CVD and ALD applications usually not only cover the surface of the substrate surface but also the walls of the chamber inside. Regular removal of those residuals has to be done to obtain stable and repeatable deposition results with uniform surfaces at acceptable particle levels. The high requirements to sustain stable processes has lead to more frequent chamber cleans. NF₃ has emerged as the main clean gas for remote clean applications. While it meets the above mentioned requirements and is considered to fit easily into the fab gas supply it is relatively expensive. The work presented here investigates argon/nitrogen diluted fluorine (F₂) as an alternative clean gas with a significantly reduced environmentally destructive global warming emission (GWP). The cleaning behaviour with respect to different materials (SiON, TaN, TiN, W, SiO₂) was studied. It is found that in general argon/nitrogen diluted fluorine achieves etch rates comparable to those obtained by NF₃ when the comparison is based on the amount of fluorine transported into the reactor.