Emitter base junction ESD reliability of an epitaxial base silicon germanium heterojunction bipolar transistor

摘要

These results show the ESD reliability for emitter base junction for two different types of SiGe HBT devices. In the first, the design represents a "self-aligned" transistor where the extrinsic base is self-aligned to the emitter. In this design, the forward-bias characteristic improves with salicide blocking. In the reverse characteristic, no ESD variation has been observed since the extrinsic-base implant position does not vary relative to the emitter. In the second type of SiGe HBT design, the extrinsic-base implant can be varied relative to the emitter junction. In the "non-self aligned" device, the ESD robustness is variable in both the positive and negative ESD stress. As the base link resistance is decreased, the forward-bias ESD result improves with the better f{sub}(MAX) but the reverse-bias ESD results degrades. This has been experimentally verified with TLP measurements that the reverse failure is associated with the peak breakdown voltage followed by a rapid increase in leakage. TLP measurements also demonstrated a low level leakage increase tracking with the I-V current of the emitter-base junction prior to the failure mechanism rapid current increase.