Two-dimensional simulation of total dose effects on NMOSFET with lateral parasitic transistor

The trapped charge density in the LOCOS bird's beak resulting from irradiating a conventional NMOSFET has been analysed using a 2D finite element simulation. This paper shows a maximum of trapped charge density in the bird's beak region. The resulting voltage shift of the lateral parasitic transistor in the bird's beak region induces a high leakage current, and prevents any normal circuit operation. The silicon doping level, the supply voltage and the bird's beak shape are key parameters for device hardening of rad-tolerant technologies.