RADIATION-INDUCED CHARGE IN SIMOX BURIED OXIDES - LACK OF THICKNESS DEPENDENCE AT LOW APPLIED FIELDS

Commercially prepared Separation-by-IMplantation-of-OXygen (SIMOX) waf ers having buried-oxide (BOX) thicknesses ranging from 80 to 400 nm, a nd thermal oxides of similar thicknesses, were exposed to various dose s of 10 keV x-rays. The net positive charge trapped in the buried-oxid es during the radiation was determined by dual capacitance-voltage (C- V) and point-contact current voltage (I-V) measurements. For the therm al oxides, using metal-oxide-semiconductor (MOS) CV techniques, the am ount of trapped charge was found to have the expected linear dependenc e on oxide thickness. For the SIMOX buried oxides, however, the amount of net trapped charge was found to be independent of BOX thickness wh en the oxides were biased at 0.05 MV/cm (a typical operating field). T he SIMOX results are explained in terms of bulk-oxide hole and electro n trapping.