Role of Inter-Layer Dielectric on the Electrical and Heat Dissipation Characteristics in the Heterogeneous 3D Sequential CFETs with Ge p-FETs on Si n-FETs

In this work, we first investigated the electrical and heat dissipation characteristics during the operation of top devices in a 3D sequential complementary field-effect transistors (CFETs) with Ge channel as top devices. The investigation was carried out with different inter-layer dielectric (ILD) thicknesses: 70 nm, 210 nm, and 1.4 μm. As the ILD thickness became thinner, we observed a higher body factor. This scaling of ILD thickness resulted in improved performance in the inverter gain and maximum operation frequency (f
max
) for 3D sequential CFETs. Furthermore, we studied heat dissipation properties in a 3D sequential CFET structure using thermo-reflectance microscopy (TRM), considering different ILD thicknesses. Our findings revealed a significant reduction of approximately 70 % in thermal resistance (R
th
). Additionally, the thermal time constant during the cooling phase was reduced by approximately 80 % in the CFETs with ILD thickness of 70 nm compared to the devices with ILD thickness of 1.4 μm. These results strongly indicate that ILD thickness is a crucial design parameter for determining device performance within its inherent 3D structure.