Location of defective cells in HBT power amplifier arrays using IR emission microscopy

Single cell electric short failure mode of HBT power amplifier is presented with a discussion of its failure signature and mechanism. HBTs with low br eakdown voltage of the base-collector junction are studied with an I-V curv e tracer. Several controlled experiments were conducted in an effort to dup licate the failure signature and identify the root cause of the short failu re. An infrared photoemission microscopy technique is demonstrated to be an efficient method to quickly locate a single weak HBT cell from the large p arallel HBT transistor cell array that comprises the power amplifier output stage. Methods to estimate and reduce the failure rate are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.