Observation of dopant-mediated intermixing at Ge/Si interface

Rapid intermixing of Ge deposited onto a Si substrate during 900 degreesC rapid thermal annealing was analyzed using secondary ion mass spectroscopy. In undoped Ge samples, a 50 nm thick graded Si1-xGex layer was formed in 1 min, consuming 30 nm Ge and 20 nm Si. Negligible profile change was seen after an additional 1 min anneal. With dopants inside the deposited Ge layer, the extent of the intermixing is increased: For B doping, 30 nm Ge and 30 nm Si are consumed; for As doping, 5 nm Ge and 100 nm Si are consumed. In the case of B, Ge-B codiffusion from the Si1-xGex/Si heterojunction edge was also observed. The p-n junction depth difference between the two dopants can be explained by the difference in their solubilities, while the Ge-B codiffusion is attributed to excess vacancies generated during the initial intermixing. (C) 2002 American Institute of Physics.