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

Abstract

Radiation enhanced drain induced barrier lowering (DIBL) was experimentally observed and verified by 3D simulations for submicron devices with trench isolation oxides. Submicron MOSFETs with shallow trench isolation were exposed to total-ionizing-dose radiation. Prior to irradiation, the devices exhibited near-ideal current-voltage characteristics, with no significant short-channel effects for as-drawn gate lengths of 0.4 /spl mu/m. Following irradiation, the off-state leakage current increased significantly for total doses above about 650 krad(SiO/sub 2/). In addition, the irradiated devices exhibited DIBL that increased the drain current by 5-10/spl times/ for a gate length of 0.4 /spl mu/m (the nominal minimum gate length for this process) and much more for slightly shorter devices (0.35 /spl mu/m). The increase in the off-state leakage current 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. Simulations show that trapped charge at the trench sidewalls enhances the DIBL by depleting the edges of the channel. Radiation-induced charge may decrease the effectiveness of short-channel engineering.