Precursor ion damage and angular dependence of single event gate rupture in thin oxides

No correlation was observed between single-event gate rupture (SEGR) and pr ecursor damage by heavy-ion irradiation for 7-nm thermal and nitrided oxide s. Precursor ion damage at biases below SEGR threshold for fluence variatio ns over three orders of magnitude had no significant effect on SEGR thresho lds. These data support a true single ion model for SEGR. A physical model based on the concept of a conducting pipe is developed that explains the em pirical equation for the linear dependence of inverse critical field to rup ture with LET. This model also explains the dependence of critical voltage on angle of incidence. As the oxide thickness approaches the diameter of th e conducting pipe, the angular dependence of the critical voltage disappear s. A model fit to the data suggests a central core diameter of 6 and 8 nm f or conducting pipes induced in MOS oxides by Br and Au ions, respectively. The buildup of precursor ion damage in the oxides depends on ion species an d bias during irradiation, but is not consistent with the accumulation of t otal ionizing dose damage. Some 5-nm oxides exhibited the characteristic hi gh leakage current of SEGR; however, most 5-nm devices showed only soft bre akdown during heavy ion exposure with electric fields up to 12 MV/cm.