Self-Heating and Corner Rounding Effects on Time Dependent Dielectric Breakdown of Stacked Multi-Nanosheet FETs

In this work, by employing the developed kinetic Monte Carlo (kMC)-based time-dependent dielectric breakdown (TDDB) analysis simulator, the lifetime characteristics change by TDDB in the stacked multi-nanosheet field-effect transistor (mNS-FET) of the 3-nm technology node was investigated. The influence of the self-heating (SH) and electric field crowding effects due to channel corner rounding observed in the channel region of the mNS-FET on TDDB was verified by linking the commercial technology computer-aided design (TCAD) simulator with the developed TDDB simulator. Analysis with a well-calibrated simulator shows that the static SH effect by DC voltage in single-unit operation can significantly reduce TDDB lifetime by more than 90%, but the dynamic SH effect during actual logic circuit operation is attenuated, resulting in a decrease in TDDB lifetime of 42.7%-51.4%, which depends on the circuit behaviors. In addition, it was verified that electric field crowding effect and effective width variation, according to the degree of corner rounding of the gate-all-around channel, influence TDDB lifetime characteristics. The effect of the corner rounding effect on the TDDB lifetime characteristics is explained by an effective width variations and the electrical field enhancement of the corner edge area due to electrical field crowding. Through these analysis results, it is confirmed that the SH effect should be considered when analyzing the TDDB lifetime characteristics for robust circuit design, and the TDDB characteristics can also be improved by optimizing the channel shape.