A high speed bipolar transistor using 2-step epitaxial base technology

The 2-step selective epitaxial growth technology has been extended to the base formation of the transistor for the purpose of improving the cut-off frequency (fT), the base-collector junction capacitance (Cjc) and the base resistance (Rb) which are very influential parameters for the high speed performance of bipolar LSI. By utilizing the 2-step base epitaxy, the actual base width reduction that improves the base transit time of the electrons has been able to be realized, although the total base epitaxial thickness that affects Cjc has not been changed. As a result, the maximum cut-off frequency (fTmax) has been improved to 40 GHz in the case that the doping layer thickness has been reduced to 30 nm by 2-step base epitaxy, though fTmax remains 14 GHz in the case that the 150 nm single epitaxial layer has been deposited.