Radiation effects on fluorinated field oxides and associated devices

Fluorine has been introduced into the LOCOS field oxide by high-energy (2-MeV) F implantation and subsequent annealing at 950°C for 60 min. Improved radiation hardness of the field oxide and its associated device parameters was observed. N-channel MOSFETs isolated by the fluorinated oxide exhibit a lower radiation-induced source-drain leakage current. This is attributed to the smaller density of radiation-induced positive oxide charge in the fluorinated field oxide compared to its control. This is consistent with experimental results showing that threshold voltage shifts of the field-oxide FETs are smaller than their control. In addition, the radiation-induced leakage currents of reverse biased n⁺p-junction diodes fabricated with the F implantation process are suppressed, suggesting that the generation of interface traps at the gate SiO₂-Si and the field SiO₂-Si interfaces is also reduced in the fluorinated devices