Failure analysis of a field failure return due to VIA related process

In this paper, we reported a EVB Burn In (B/I) failed case of our ABCD part and led to the finding of VIA process fabrication issue with TiN film process marginal issue. This EVB B/I failed case was carried out by electrical failure analysis (EFA) and physical failure analysis (PFA) using FIB X-section and TEM. This paper also demonstrated different EFA technology, which included curve tracer analysis, EMMI with DUT board and nano-probing combined with layout/schematic path tracing. A detail root cause analysis and failure mechanism will also be discussed in this paper. It's a VIA process marginal issue, not enough marginality of the TiN step coverage caused underlying Ti/Al attacked by WF 6 during the via process and finally influenced VIA profile. The VIA may be high impedance after EVB burn in or extended operation.