Specific site device failure analysis: A case history

Abstract

Failure analysis application of analytical TEM analysis was handicapped in the past by the difficulty associated with specimen preparation of specific devices in complicated integrated circuit arrays. We have published several papers detailing methods for preparing TEM specimens with high specimen preparation spatial resolution in periods of about two to four hours. This paper offers a case history of a TEM failure analysis that combines high spatial resolution specimen preparation and the utilization of chemical junction delineation techniques.The device failure came to light in a chip tester prior to shipment. Tester electrical diagnostics identified a particular cell within a large array as defective. The fail's electrical signature further narrowed-down the potential candidates to a small number of devices within the cell. The chip was examined in transmission in an IR microscope. Anomalous IR contrast was observed in the emitter of one bipolar device in the suspect region (Fig. 1). A series of conventional light-optical photographs, with increasing magnification, were taken to define the failure location. Using the light-optical photos as a guide, the failed emitter was bracketed with laser craters. The specimen preparation polishing operation used the laser craters to achieve a plane-of-polish through the suspect emitter.

Analytical Microscopy in the Real Semiconductor Processing World

“…State-of-the-art specimen preparation apparati include: (1) advanced mechanical polishing tool sets designed to thin the specimen so that ion milling is eliminated or reduced to minutes (Anderson and Benedict, 1992;Anderson et al, 1995;Anderson and Klepeis, 1997;Benedict et al, 1992Benedict et al, , 1997Humiston, 1997); (2) a new class of ion-milling machines that can mill at very low angles as suggested by Barna (1992); and (3) a focused ion beam (FIB) machine for preparing specimens (Kirk et al, 1989). Low-angle ion milling polishes specimens and is not as sensitive to the dissimilar materials making up a semiconductor stack as conventional ion milling.…”