The SiGe:C hetero‐structure bipolar transistor (HBT) has turned into a key technology for wireless communication. This paper describes various critical analytical techniques to bring up and maintain the SiGe:C epi‐process. Two types of analysis are critical, (1) routine monitoring SiGe base and Si cap thickness, doping dose, Ge composition profile, and their uniformity across the wafer; and (2) root‐cause analysis on problems due to non‐optimized process and variation in process conditions. A transmission electron microscopy (TEM) technique has been developed allowing a thickness measurement with a reproducibility better than 3 Å. Charge‐compensated low‐energy secondary ion mass spectrometry (SIMS) using optical conductivity enhancement (OCE) allows a Ge composition measurement to a required precision of 0.5 at. &percent;. © 2003 American Institute of Physics