SiGe heteroepitaxy for high frequency circuits

We have determined the process capability of Low Pressure (Rapid Thermal) Chemical Vapor Deposition (LP(RT)CVD) of epitaxial Si/SiGe/Si stacks for heterojunction bipolar transistors (HBTs). The transistor parameters primarily influenced by the epitaxial characteristics were measured for 600 identically processed 4 " wafers. The results demonstrate that it is possible to control accurately the epitaxial process for a 25 nm thick graded SiGe base profile with 20 % Ge and very narrow B doping (5 nm). The pipe limited device yield of about 90 % for an emitter area of 10(4) mu m(2) indicates a very low defect density in the epitaxial layer stack, The process capability indices determined from about 40,000 data points demonstrate the stability and capability of the LP(RT)CVD epitaxy with regard to manufacturing requirements.