Influence of encapsulation films on the properties of Si/SiO2interface of MOS-structures when exposed to radiation

We have observed that some of the radiation induced Qflike positive charges at the Si/SiO2interface get converted into fast interface states, and that the rate of conversion is a function of the ambient temperature and the encapsulation material (caps). Detailed experimental characterization unambiguously and consistently shows that in the presence of plasma deposited silicon nitride encapsulation (SiN caps) the rate of conversion is significantly faster even at room temperature than that in presence of other caps (e.g. SiO2). Furthermore, when other caps are used the rate of conversion is extremely slow even at 300°C temperature. The hold-time degradation of DRAMs due to radiation was studied with respect to encapsulation materials, and we observed that the memories with SiN caps degrade much more rapidly than those with other caps.