Study on self-ceasing met etching technology for mesa SiGe HBT

Emitter mesa formation is most crucial in SiGe HBT fabrication. Because its base is so thin and etching velocity is so difficult to control that it is easy to damage external base surface for dry etching technology, self-ceasing wet etching is popular in fabricating emitter mesa SiGe HBT. This paper explores self-ceasing etching technology issues in fabricating SiGe HBT, including the select of etching solution and masking layers, the effects of temperature and ultrasonic power on etching velocity and uniformity, the optimum conditions are obtained. Finally, The SiGe HBT of current gainβ>;70 has been developed through using this technology.