Non-radiation hardened P-channel and N-channel MOS transistors were irradiated with Co-60 gamma rays, 0.5 to 22 MeV protons, and 1 to 7 MeV electrons to determine the correlation between the gamma rays and the charged particles. Comparison of electrons to Co-60 showed that for equal absorbed doses, the damage produced was equivalent for all bias conditions. Under zero gate bias conditions, 2 to 22 MeV protons also produced damage in the test devices that was equivalent to Co-60. However, under bias conditions for high drain-source currents, the damage for protons below 22 MeV was always less than Co-60 (the lower the proton energy, the less the damage). The 0.5 MeV proton data showed poor correlation with Co-60 results. No dose-rate dependence was observed in the data. We conclude that, for the silicon MOS devices tested, the radiation damage produced by Co-60 provided a worst case simulation of high energy electron or proton damage.

Data is presented which shows that ionizing radiation damage produced by 2 to 16 MeV protons in MOS transistors, with applied electrical fields across the gate oxides, is dependent upon the angle between the fields and the incident protons. This angular dependency can be explained by the 'columnar recombination model." For Co-60 photons and 5 to 20 MeV electrons, the data shows no angular dependency.

This paper describes the method used to calibrate a largevolume continuous-wave x-ray radiation test chamber. The xray tube has a tungsten target and emits a bremsstrahlung xray spectrum with end point energies up to 160 keV. Analytical tools and experimental dosimetry techniques were developed to map the radiation field intensity and the resulting dose-deposition profiles in a variety of materials throughout the chamber. Three detector types (x-ray vacuum diodes, silicon PIN diodes, and PMOS FETs) were used to measure spectral intensity and dose deposition in silicon devices. CEPXS and PHOTCOEF electron-photon transport codes were used to calculate the incident spectral energy distribution and the energy deposition in the detector. Calculated and experimental diode detector responses agreed to within 10 percent over the full energy range. PMOS FETs were used to demonstrate the correlation between total-dose-deposited in the x-ray chamber and in the Cobalt-60 cell. The results of this effort provide dosimetry and analysis tools needed to perform ionizing radiation testing of large area (0.5m2) electronic subsystems.

The gate induced drain leakage current (Idl) of metal oxide semiconductor (MOS) transistors changes significantly when the devices are exposed to ionizing radiation. For n-channel MOS transistors, Idl decreases, whereas for p-channel devices, it increases. The change of leakage current at higher tunneling fields is proportional to the increase of hole trap density in the gate oxide region. The leakage current measurement technique is a useful tool for characterizing radiation effects in MOS transistors because at higher bias it is dependent on increase of oxide charge while independent of interface states. The annealing of trapped charges at the tunnel junction is faster than in the channel region as determined from subthreshold characteristics. The results of the thermal annealing experiment reveal that the drain current in the control region is attributed to interface state assisted tunneling.