It is proven that introduction of graphene into typical heterostructures can effectively reduce the high interfacial thermal resistance in semiconductor chips. The crystallinity of graphene varies greatly; thus, we have investigated the effects of single-crystal and polycrystalline graphene on the thermal transport of AlN/graphene/3C-SiC heterostructures by molecular dynamics. The results show that polycrystalline graphene contributes more to the interfacial thermal conductance (ITC) inside the chip with a maximum increase of 75.09%, which is further confirmed by the energy transport and thermal relaxation time. Multiple analyses indicate that grain boundaries lead to the increase in C-Si covalent bonds, and thus, strong interactions improve the ITC. However, covalent bonding further causes local tensile strain and wrinkles in graphene. The former decreases the ITC, and the latter leads to the fluctuation of the van der Waals interaction at the interface. The combined effect of various influential factors results in the increase in the ITC, which are confirmed by phonon transmission with 0-18 THz. In addition, wrinkles and covalent bonding lead to increased stress concentration in polycrystalline graphene. This leads to a maximum reduction of 19.23% in the in-plane thermal conductivity, which is not conducive to the lateral diffusion of hot spots within the chip. The research results would provide important guidance in designing for high thermal transport performance high-power chips.
Keywords: AlN/graphene/3C-SiC; interfacial thermal conductance; molecular dynamics; polycrystalline graphene; thermal conductivity.