3D IC is approaching the centre of activity in the semiconductor business with many justified theoretical reasons and convincing technical results. The unprecedented growth of the computer and the Information technology industry is demanding Very Large Scale Integrated (VLSI) circuits with increasing functionality and performance at minimum cost and power dissipation. VLSI circuits are being aggressively scaled to meet this Demand, which in turn has some serious problems for the semiconductor industry.

With skyrocketing cost for lithography and IC fabrication 3D IC seems clearly a way to go. The question is when, and in what applications first. Despite many papers on the processing and assembly technology and design methodology for 3D IC, there are, however, a horde of problems yet to be solved. Roughly these issues are classified into process technology, manufacturing, thermal-related, applications-related, or design.

For each of these problems there will be either some solutions or detours; technology and manufacturing issues will be solved, thermal physics have to be obeyed and some good guidelines and design methods will be developed in time. Eventually commercial 3D IC will make its debut first in application areas where cost issue prefers 3D IC to 2D implementation or SiP.

Mobile, ubiquitous, and medical applications will be serious markets for 3D IC, because of the clear and urgent need for low energy consumption, functional integration, reliability, and low/medium cost in those applications. These application calls for independent or autonomous devices in that they not only perform a spectra of functions from sensing, conversion, storage, processing, and external wireless interaction but also monitoring and managing the energy resource according to the dynamic workload estimation. Deploying independent/autonomous systems on 3D IC to these market is expected be quite relevant in a near future due to the technology readiness, cost affordability, and rising applications demand. Additionally heterogeneous integration of different technologies in one single chip (SoC) is becoming increasingly desirable, for which planar (2-D) ICs may not be suitable. 3-D ICs are an attractive chip architecture that can alleviate interconnects related problems such as delay and power dissipation and can also facilitate integration of heterogeneous technologies in one chip (SoC). The multi-layer chip industry opens up a whole new world of design. With the Introduction of 3-D ICs, the world of chips may never look the same again.