TID Response of IBM Gate-All-Around Stacked Nanosheet Transistors

The total ionizing dose (TID) response of International Business Machines (IBM) gate-all-around (GAA) stacked nanosheet transistors was investigated. Both bulk and substrate-isolated nFET and pFET GAA nanosheet transistors, along with ring oscillators (ROs), were tested with 10-keV X-rays. Key parameters such as off-state leakage current, drive current, threshold voltage, and maximum transconductance were analyzed before and after radiation exposure. Only small shifts were observed up to the maximum doses delivered: 10 Mrad(SiO2). Substrate-isolated devices showed even less degradation than bulk devices, highlighting the effectiveness of substrate isolation (SI). ROs also showed minor frequency degradation up to 10 Mrad(SiO2). Finite-element simulations demonstrate that even if significant charge trapping occurs in dielectrics, the metal wrapped around the nanosheet channels prevents the electric fields from penetrating the channels, which likely caused the observed TID hardness. These results demonstrate the TID tolerance of GAA field-effect transistors (FETs), making them suitable for high-dose environments.