Effect of different total ionizing dose sources on charge loss from programmed floating gate cells

We irradiated programmed Floating Gate (FG) memory arrays with different radiation sources, including 10 keV X-rays, /sup 60/Co /spl gamma/-rays, and 27 MeV protons. After irradiation, FGs experience a net charge loss which can degrade the stored information in terms of MOSFET threshold voltage. The charge loss is the result of two different phenomena: charge generation/recombination in the oxides and photoemission from the FG. The threshold voltage shift in irradiated devices depends on the radiation source: strong dose enhancement phenomena were found after X-ray irradiation, whereas proton results closely follow /spl gamma/-ray results.