Degradation induced by X-ray Irradiation and Channel Hot Carrier Stresses in 130-nm NMOSFETs With Enclosed Layout

We present new experimental results about channel hot carrier degradation of enclosed layout transistors as a function of previous accumulated total ionizing dose, stress temperature, and transistor geometry. We show that the parametric degradation follows a power law, whose exponent is higher than in conventional open layout transistors, possibly due to a different diffusion geometry of hydrogen. Through physical simulation we attribute this effect to the electric field at the device corners, which leads to a non-uniform impact ionization. Previous irradiation reduces the channel hot carrier degradation in MOSFETs with 5.2-nm gate oxide, while having a minor influence with 2.2-nm gate dielectric.