Analysis of Self-Heating Effects in Multi-Nanosheet FET Considering Bottom Isolation and Package Options

Abstract

Self-heating effects (SHEs) of multi-nanosheet FET (mNS-FET) at the 3-nm technology node were analyzed at the device and circuit level considering the introduction of punchthrough-stopper (PTS) doping and bottom oxide (BO), which are substrate processes to reduce leakage current. Changes in the heat path according to the back-end-of-line (BEOL) configuration and package type were also considered. After optimizing the PTS doping and BO process through six case analyses using three-dimensional (3-D) TCAD simulations, SHE characteristics were investigated. As a result, the channel temperature risen due to SHE was larger when BO was applied than when BO was not applied, and that the face-down package was more effective in heat dissipation than the face-up package. Next, the SHE behavior during dynamic operation of logic and analog circuits was analyzed through SPICE modeling, and the effect of this on circuit performance and reliability was analyzed. As a result, in the logic ring oscillator circuit, the SHE shows a slight AC performance degradation of ~1.3%, but in terms of reliability, it causes a decrease in the lifetime of 15.1%–22.1%. In the two types of analog circuits, the possibility of circuit malfunction can be confirmed by SHE, and in terms of reliability, it causes a reduction in lifetime of 53.5%–89.9%. Therefore, it is expected that device and circuit design that can reduce SHE are required in consideration of the various processes analyzed in this work.