This paper discusses the physics, definitions, and nanoprobing flow of a flash bit memory. In addition, a case study showing the effectiveness of nanoprobing in detecting the Single Bit Fail Data Gain and Data Loss in Flash Memory is also discussed. The paper also includes cases where no passive voltage contrast was observed at the SEM and no leakage was observed at AFM, yet the units failing SBF DG, SBF DL and depletion, were detected by nanoprobing of the single bit. The major finding of this paper is a way to resolve data gain, data loss, and depletion failures of flash memory by nanoprobing procedure, despite no PVC seen at the SEM and no leakage seen at the AFM.

Production yield verification for a complex device, such as the flash memory, is a problem of primary importance due to high design density and current testing capabilities of such design. In this paper, the flow byte issue in the one time programmable block is investigated through physical failure analysis (PFA). The customer reported fail for this unit was flow byte error with flipped data loss in one of the bit. Various experiments were done on numerous units to identify the yield related issue and prevent shipment of such units to customers. The case study from this paper is beneficial to the FA community by showing the exact methodology in identifying the problem, its containment, and implementation of corrective actions on the ATE to prevent shipment of low yield units to customer. The yield was enhanced by implementing the containment and corrective actions on the ATE.

Flash memory is one of the most mysterious and difficult structures in the semiconductor industry. Excessive data gain and data loss may cause errors in reading the flash memory. This paper discusses the data gain mechanism and the various failure mechanisms (i.e., CoSi at Mux, CoSi at bit, particle at Mux, resistive contact, erasing defect at failing bit, programming fail at bit, misaligned contact, passive voltage contrast (PVC) at multiple gates in Mux region, particle and missing via, poly residue defect etc.) causing single bit flash data gain. Presented in the paper are the definitions involved, Flash cell theory and physics involved, and the theory explaining why leakage in the 8:1 mux causes the single bit flash data gain. This is followed by a case study involving various failure mechanisms and a final conclusion. Knowing the fail mechanisms and correcting them promptly enhances the yield.