Failure in CMOS circuits induced by hot carriers in multi-gate transistors

The problem of vertical isolation in circuits fabricated using shallow n-well epitaxial CMOS technology is analyzed. Unexpectedly high substrate current resulting in circuit failure has been observed during accelerated reliability tests. The substrate current is a result of enhanced hole injection from multi-gate p-channel transistors with interdigitated source and drain. The electron current generated from impact ionization near the drain forward biases the source junctions, causing hole injection to the substrate. The current is sensitive to the supply voltage and temperature. Consequently, unanticipated failures may occur at the high voltages and temperatures encountered during burn-in. Design and process solutions are discussed.<>