Selective epitaxial growth of SiGe:C for high speed HBTs

The technique of selective epitaxial growth (SEG) of Si, SiGe, and SiGe:C is described in general and with respect to the application in hetero bipolar transistors (HBTs). Advantages like easy fabrication of self-aligned transistor structures are accompanied by a more complicated dependence of layer properties on process conditions in comparison to non-selective growth. Nevertheless, after careful analysis SEG related difficulties have been solved and selectively grown SiGe:C layers are successfully used in high speed HBTs. Good manufacturability and performance of these devices are demonstrated by a high yield and a ring oscillator gate delay as low as 4.7ps.