X-ray damage in low temperature ultrathin silicon dioxide

The electrical characteristics of ultrathin oxides used in an x-ray lithography n-channel metal-oxide-silicon process grown at 700 and 950°C were studied. The breakdown field exceeded 15 MV/cm for both low and high temperature oxides and the interface trap density of the fresh oxide was of order of 10¹⁰ cm^-2 eV^-1. Oxides grown at 950°C had a lower interface trap density than 700°C oxides, but 950°C oxides are more sensitive to x-ray radiation damage. After 350°C hydrogen annealing about 80% of the radiation damage in the form of interface traps was recovered.