Three-dimensional integration (3DI) of semiconductor circuit layers: New devices and fabrication process

The device density of Integrated Circuits (ICs) manufactured by current VLSI technology is reaching its theoretical limit. Nevertheless, the demand for integration of more devices per chip is growing. To accommodate this need three main possibilities can be explored: Wafer Scale Integration (WSI), Ultra Large Scale Integration (ULSI), and Three Dimensional Integration (3DI). A brief review of these techniques along with their comparative advantages and disadvantages is presented. It has been concluded that 3DI technology is superior to others. Therefore, an attempt is made to develop a viable fabrication process for this technology. This is done by first reviewing the current technologies that are utilized for fabrication of Integrated Circuits (ICs) and their compatibility with 3DI stringent requirements. Based on this review, a set of fabrication procedure for realization of 3DI technology, are presented in chapter 3.;In Chapter 1 the compatibility of the currently used devices, such as BJTs and FETs, with 3DI technology is examined. Moreover, a new active device is developed for 3DI technology to replace BJTs and FETs in circuits. This new device is more compatible to the constrains of 3DI technology.;Chapter 2 is devoted to solving the overall problems of 3DI circuits. The problem of heat and power dispassion and signal coupling (Cross-Talk) between the layers are reviewed, and an inter-layer shield is proposed to overcome these problems. The effectiveness of such a thin shield is considered theoretically.;In Chapter 3 a fabrication process for 3DI technology is proposed. This is done after a short analysis of previous attempts in developing 3DI technologies.;Chapter 4 focuses on analog extension of 3DI technology. Moreover, in this chapter microwave 3DI circuits or 3DI MMIC is investigated.;Practical considerations in choice of material for the proposed device is the subject of study in Chapter 5. Low temperature ohmic contact and utilization of metal-silicides for the proposed device are considered in this chapter.;Finally in Chapter 6 various computer verifications for this work is presented, and in Chapter 7 experimental results to support this work is included.