Study of the effect of gamma radiation on MOSFET for space applications

Metal Oxide Field Effect Transistor (MOSFET) is a basic component of VLSI and ULSI circuits and finds applications in many electronic systems used in satellite design. These devices are susceptible to degradation due to radiation in outer space. Conventional MOSFET can survive 3-10 krad (Si) of total dose without much parametric degradation. However, ionising radiation dose in excess of 35 krad (Si) may turn out to be detrimental to the functioning of the device. The space environment is hostile to the most integrated components such as those for navigation, communication, data processing function in satellites and various space missions. The radiation generally encountered in space includes α, β, γ, X-ray, energetic electrons, protons, neutrons and ions of various kinds. Gamma ray photons deposit energy in the components mainly by ionisation. In this paper, we report the gamma ray induced changes in the electrical characteristics of MOSFET 2N6796 (JANTXV) used in satellites. Pre-irradiation measurements of electrical parameters have been made using TESEC measurement system. Selected devices have been exposed to different gamma dose using a Board of Radiation and Isotope Technology (BRIT) gamma irradiator. Post-irradiation measurements of electrical characteristics display significant degradation in threshold voltages and the leakage current increases as the gamma dose increases. (author)