3D Numerical Simulation of a Z Gate Layout MOSFET for Radiation Tolerance

In this paper, for the first time, an n-channel metal-oxide-semiconductor field-effect transistor (NMOSFET) layout with a Z gate and an improved total ionizing dose (TID) tolerance is proposed. The novel layout can be radiation-hardened with a fixed charge density at the shallow trench isolation (STI) of 3.5 × 10¹² cm^-2. Moreover, it has the advantages of a small footprint, no limitation in W/L design, and a small gate capacitance compared with the enclosed gate layout. Beside the Z gate layout, a non-radiation-hardened single gate layout and a radiation-hardened enclosed gate layout are simulated using the Sentaurus 3D technology computer-aided design (TCAD) software. First, the transfer characteristics curves (I_d-V_g) curves of the three layouts are compared to verify the radiation tolerance characteristic of the Z gate layout; then, the threshold voltage and the leakage current of the three layouts are extracted to compare their TID responses. Lastly, the threshold voltage shift and the leakage current increment at different radiation doses for the three layouts are presented and analyzed.