Radiation-enhanced short channel effects due to multi-dimensional influence from charge at trench isolation oxides

Radiation enhanced drain induced barrier lowering (DIBL) was experimentally observed and verified by 3-D simulations for submicron devices with trench isolation oxides. Submicron MOSFETs with shallow trench isolation were exp osed to total-ionizing-dose radiation. Prior to irradiation, the devices ex hibited near-ideal current-voltage characteristics, with no significant sho rt-channel effects for as-drawn gate lengths of 0.4 mu m. Following irradia tion, the off-state leakage current increased significantly for total doses above about 650 krad(SiO2). In addition, the irradiated devices exhibited DIBL that increased the drain current by 5-10x for a gate length of 0.4 mu m (the nominal minimum gate length for this process) and much more for slig htly shorter devices (0.35 mu m). The increase in the off-stale leakage cur rent and the accompanying DIBL are shown to be associated with a parasitic field-effect transistor that: is present at the edge of the shallow trench. Three-dimensional simulations are used to illustrate the effect. Simulatio ns show that trapped charge at the trench sidewalls enhance the DIBL by dep leting the edges of the channel. Radiation-induced charge may decrease the effectiveness of short-channel engineering.