Monolithic 3D Integrated Circuits

3D IC´s promise to solve the 2D communication bottleneck, and enable the integration of heterogeneous materials, devices and systems. There are at least three approaches to realize 3D IC´s : chip stacking, wafer stacking and full monolithic integration. Each approach is at a different level of maturity and offers various degree of improvement. This paper will focus on the monolithic 3D approach, which offers a high density of device-dimension vertical interconnects and thereby facilitates the optimal assembly of transistors and interconnects in a 3D volume. The performance advantages of such a technology are demonstrated with a 3D-FPGA. Technology challenges of monolithic approach are discussed.