Leakage current and deep levels in CoSi2 silicided junctions

In this work the leakage current of junctions with a self-aligned cobalt silicide is studied. It is shown that junctions with a self-aligned CoSi2 layer show a leakage current excess which is strongly reduced by increasing the PAI energy. This indicates that the observed leakage current excess is related to the CoSi2 formation conditions. The mechanism responsible for the leakage of CoSi2 junctions is investigated by current versus temperature measurements and by deep level transient spectroscopy. In addition, the role of the mechanical stress is investigated by comparing different isolation structures and by numerical stress calculations. It is concluded that the shallow trench isolation (STI) induced stress and the cobalt silicide formation concur to produce a junction leakage current increase by creating a deep level in silicon located close to midgap. This level can possibly identified with a level ascribed to a point defect excess.