An investigation of the spatial location of proton-induced traps in SiGe HBTs

• Published in: IEEE transactions on nuclear science Vol. 45; no. 6; pp. 2424 - 2429
• Main Authors: Roldan, J.M., Guofu Niu, Ansley, W.E., Cressler, J.D., Clark, S.D., Ahlgren, D.C.
• Format: Journal Article
• Language: English
• Published: IEEE 01.12.1998
• Subjects: Character generation; Cutoff frequency; Degradation; Electric variables; Germanium silicon alloys; Heterojunction bipolar transistors; Protons; Silicon germanium; Space charge; Vacuum technology
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/23.736481

The effects of 46 MeV proton irradiation induced trap generation and its impact on the electrical characteristics of silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) from an advanced ultrahigh vacuum/chemical vapor deposition (UHV/CVD) SiGe BiCMOS technology are examined and discussed for the first time. At proton fluences as high as 10/sup 14/ p/cm/sup 2/ the peak current gain of the devices degraded by less than 8% compared to the pre-irradiated samples. The maximum oscillation frequency and cutoff frequency of the SiGe HBTs showed only minor degradation after 10/sup 14/ p/cm/sup 2/. Calibration of 2-D device simulation (MEDICI) to measured data in both forward and inverse modes of operation was used to infer the spatial location of the proton-induced traps. Traps in the collector-base space charge region appear as generation/recombination (G/R) centers in the inverse emitter-base region and are the result of displacement damage. Traps at the emitter-base spacer oxide interface appear as G/R centers in the forward emitter-base space charge region and are the result of ionization damage. Taken together, these results suggest that UHV/CVD SiGe HBT technology is robust to proton fluences at least as high as 10/sup 13/ p/cm/sup 2/ without radiation hardening.