Demonstration of a Nanosheet FET With High Thermal Conductivity Material as Buried Oxide: Mitigation of Self-Heating Effect

Self-heating-induced thermal degradation is a severe issue in nonplanar MOS architectures. Especially in stacked gate-all-around (GAA) nanosheet FET (NSFET), the self-heating effect (SHE) is a prime concern as the channels are surrounded by low-thermal conductivity material (i.e., a stack of SiO2 and HfO2 layers). In this article, through well-calibrated TCAD models, we propose a buried oxide (BOX) engineered NSFET structure, which provides an appropriate heat flow path and mitigates the SHE-induced degradation. Unlike the conventional NSFET, where SiO2 is kept as a BOX layer, in the proposed NSFET, a crystalline-diamond-like carbon (DLC) is placed ubiquitously beneath the lower sheet, resulting in a reduction in the lattice temperature from the device active region (channel/sheet) toward the DLC substrate. Furthermore, the impact of device geometry, such as channel length (
${L}_{g}$
), channel width (
${T}_{w}$
), BOX thickness (
${T}_{{\text {BOX}}}$
), and the number of vertically stacked sheets (
${N}_{S}$
), on the thermal and electrical reliability of the proposed device has been investigated.