HF contamination of 200 mm Al wafers: A parallel angle resolved XPS study

Abstract

In this work, 650 nm thick Al layers were deposited on 200 mm wafers and intentionally contaminated by exposure to controlled HF airborne concentrations in different humidity conditions. The layers were deposited with an industrial tool, in real clean room conditions. The real dose of HF contaminant was controlled on Al surfaces by LPE-IC (Liquid Phase Extraction in ultra-pure water and analysis by Ionic Chromatography). Several contaminant dose and humidity conditions were investigated and the layers were characterized over time by PAR-XPS parallel angle resolved XPS. Thanks to the full wafer loading capacity of our XPS spectrometer, the XPS measurements were synchronised very quickly after the deposition step. This allowed us to access to the first stage of the oxide/contaminated layer growth that occurs during the storage. Al–F interactions mechanisms were addressed in terms of bounding environment and oxidation/contamination competition. The parallel angle resolved capability of our spectrometer has been used to acquire a great number of angles simultaneously and then to access to accurate and significant depth resolved informations [9]. Relative depth plots profiles were then obtained from angle resolved data, giving detailed informations about the depth repartition of the chemical components, as well as their possible relative interactions. Fluorine repartition with depth has been especially studied. The aging in time of the contaminated layer has been investigated too, from the layer deposition/contamination point onto several days. Fluorine atomic percentage has been monitored at several points as well as the evolution in time of the depth profile of the fluorine components of the contaminated layer.