RF functional-based complete FA flow

Abstract

In this paper, we present a case study on Radio Frequency device, where a complete failure analysis flow has been applied, built through integration of transversal competences from design, testing, and application teams.Key point is using functional failure as electrical fault activation. Indeed this approach allows enlarging the coverage of Failure Analysis to many functional failures reproducible through application board.The device under analysis is a frequency synthesizer, operating in the range of 2GHz to 4GHz, built in BiCMOS technology, failing on application at low temperature (−36°C). Fault Isolation step is based on the replication of functional failure mode, through application board as electrical stimulus to activate the fault. Moreover, since failure is depending on temperature and voltage conditions, a Dynamic analysis through Laser Stimulus has been implemented (DLS) with a RTVM-like approach. This setup required specific adaption of application board in order to cope with mechanical and electrical constraints of DLS while reproducing failure mode in the GHz range. The amplitude variation of failing RF output signal was monitored by an additional circuitry that converted information of loss of signal in a suitable logic signal for DLS analysis. Fault Isolation pointed out to specific high frequency bipolar transistors on a divider block. Physical Analysis addressed to these components, which are key for this kind of products, put in evidence dislocations inside Si–Ge layer.