Local-Oxide-Thinning-Induced Deep Depletion Phenomenon in MOS Capacitors

Abstract

The influence of local oxide thinning (LOT) spots on the electrostatics of MOS capacitors was studied in this work. The capacitors are found to suffer from severe deep depletion (DD) above threshold once LOT spots that cause significant gate leakage are introduced, making them inapplicable for MOSFETs. With the help of simulation, we proposed the presence of a lateral electric field at the spot edge, which effectively drifts inversion charge toward the spot from its exterior, leading to severe depletion of inversion charge underneath the entire gate area. Capacitor size, spot size and spot thickness effects on the DD behavior were also investigated. This work demonstrates the high influence of LOT spots on device operations, as well as affirming the importance of oxide structural defect control.