Selective and non-selective growth of self-aligned SiGeHBT structures by LPCVD epitaxy

Silicon-germanium (SiGe) heterojunction bipolar transistors (HBT) have beco me increasingly important for high speed applications. Novel device structu res are often required to fully exploit the advantages from incorporation o f a heterojunction. In this work, a growth technique is described which use s both selective and non-selective growth of Si and SiGe to produce an adva nced SiGe HBT structure. The surface morphology of the material grown is ex amined using Nomarski contrast optical microscopy and scanning electron mic roscopy (SEM), and the surface of the epitaxial areas appears smooth with a low defect density. The growth surface is reasonably planar, as needed for further device processing, which suggests the required thicknesses of both selective and non-selective epitaxy were achieved. The Ge and B profiles o f the material are measured using secondary ion mass spectroscopy (SIMS), a nd the layer thicknesses are found to meet the device specification. The cr ystallinity and defects in the material are examined by transmission electr on microscopy (TEM). The material produced is shown to be suitable for fabr ication into the proposed device.