Characterization of channel strain evolution upon the silicidation of recessed source/drain Si1-xGex structures

This letter reports on Ni germanosilicide formation on recessed Si0.82Ge0.18 source/drain structures and its effects on channel strain. A combination of transmission electron microscopy techniques, including nanobeam diffraction, shed some light on a previously unrecognized factor in the channel strain evolution during silicidation: a Ge accumulation layer produced at the bottom of the germanosilicide layer. The formation of such a Ge rich layer added an additional compressive strain to the channel strain upon moderate silicidation, while the contribution of thermal strain arising from the cooling cycle became dominant in an excessively silicided sample, which turned the channel strain into a tensile value. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3633346]