Optimization of performance and self-heating effects through selective nanosheet thickness modulation in 4-stack nanosheet FETs

This study investigates the impact of nanosheet thickness on performance and self-heating effects (SHEs) in 4-stack nanosheet FETs for sub-2 nm logic technology using TCAD simulations. Unlike previous approaches that used a uniform nanosheet thickness, we selectively adjusted the thickness based on stacking levels. Configurations with one or two selectively thickened nanosheets showed a 2.3% increase in on-current (I_on) and a 1.0% improvement in frequency at V_dd = 0.7 V, while maintaining good short-channel characteristics. These improvements were primarily due to a reduction in channel resistance (R_ch), leading to further gains in I_on (+4.3%) and frequency (+2.1%) at high V_dd (=1.1 V), where gate overdrive voltage more effectively reduces R_ch. The optimized configuration also demonstrated enhanced thermal characteristics, including a 2.2% reduction in maximum temperature increase (ΔT_max), a 4.6% decrease in thermal resistance (R_th), and a 10.8% improvement in bias temperature instability lifetime. These thermal benefits arise from the increased thermal conductivity of thickened nanosheets. Overall, our findings suggest that selectively modulating nanosheet thickness is a promising strategy to enhance both performance and thermal stability without increasing process costs or yield risks, particularly for high-performance computing applications.