Ultimate Monolithic-3D Integration With 2D Materials: Rationale, Prospects, and Challenges

As a possible pathway to continue Moore's law indefinitely into the future as well as unprecedented beyond-Moore heterogeneous integration, we examine the prospects of building monolithic 3D integrated circuits (M3D-IC) with atomically-thin or 2D van der Waals materials in terms of overcoming the major drawbacks of current 3D-ICs, including low process thermal budget, inter-tier signal delay, chip-overheating, and inter-tier electrical interference problems. Our holistic evaluation includes consideration of the electrical performance, thermal issues, and electromagnetic interference as well as attention to the synthesis methods necessary for low-temperature transfer-free 2D materials growth in M3D fabrication. Both in-plane and out-of-plane heat-dissipation in 3D-ICs made with 2D materials are evaluated and compared with those of bulk materials. Electrostatic and high-frequency electric-field simulations are conducted to assess the screening effect by graphene and effect of scaling down the inter-layer dielectric (ILD) thickness. Our analysis reveals for the first time that the 2D-based M3D integration can offer >ten-folds higher integration density compared with through-silicon-via (TSV)-based 3D integration, and >150% integration density improvement with respect to conventional M3D integration. Therefore, 2D materials provide a significantly better platform, with respect to bulk materials (such as Si, Ge, GaN), for realizing ultra-high-density M3D-ICs of ultimate thinness for next-generation electronics.