A Radiation Hardened Field Oxide

This paper describes the results of a radiation-tolerant field oxide development compatible with both MOS and bipolar technologies. Data is presented which illustrates that nonguardbanded devices utilizing conventional field oxide structures cannot be expected to survive an ionizing radiation dose above approximately 5 × 104 rads (Si) due to inversion of p-type silicon surfaces under metallized areas. The radiation hardened oxide was evaluated with both aluminum and polycrystalline silicon gate MOS structures which conclusively demonstrates that this oxide eliminates the field inversion problem for radiation levels in excess of 106 rads (Si).