Unusual room-temperature intermixing and oxidation in copper deposited on a fluorinated amorphous silicon system

The room-temperature behavior of Cu thin films on crystalline and amorphous silicon (c-Si and a-Si) substrates was studied by Auger electron spectroscopy. All samples, except Cu/ a-Si:F, behaved as usual metal on silicon systems. It was found that F greatly enhances Cu-Si intermixing which proceeds up to the sample surface. After prolonged room-temperature exposure to air, this system settles into the unusual configuration: Cu/SiO2/a-Si:F. The effect is explained in terms of the permeability of Cu3Si to oxygen and the low solubility of Cu in SiO2.