Preface to the First Edition

The seminal source of this book is the lack of a unified treatment of the design of three-dimensional (3-D) integrated circuits despite the significant progress that has recently been achieved in this exciting new technology. Consequently, the intention of this material is to cohesively integrate and present research milestones from different, yet interdependent, aspects of 3-D integrated circuit design. The foremost goal of the book is to propose design methodologies for 3-D circuits; methodologies that will effectively exploit the flourishing manufacturing diversity existing in 3-D integration. While the focal point is design techniques and methodologies, the material also highlights significant manufacturing strides that complete the research mosaic of 3-D integration.

3-D or vertical integration is an exciting path to boost the performance and extend the capabilities of modern integrated circuits. These capabilities are inherent to 3-D integrated circuits. The former enhancement is due to the considerably shorter interconnect length in the vertical direction and the latter is due to the ability to combine dissimilar technologies within a multiplane system. It is also worth noting that vertical integration is particularly compatible with the integrated circuit design process that has been developed over the past several decades. These distinctive characteristics make 3-D integration highly attractive as compared to other radical technological solutions that have been proposed to resolve the increasingly difficult issue of on-chip interconnect.

The opportunities offered by 3-D integration are essentially limitless. The constraints stem from the lack of design and manufacturing expertise for these circuits. The realization of these complex systems requires advanced manufacturing methods and novel design technologies across several abstraction levels. The development of these capabilities will be achieved if the physical behavior and mechanisms that govern interplane communication and manufacturing are properly understood. The focus of this book diligently serves this purpose.

This book is based upon the body of research carried out by Vasilis Pavlidis from 2002 to 2008 at the University of Rochester during his doctoral study under the supervision of Prof. Eby G. Friedman. Recognizing the importance of the vertical interconnections in 3-D circuits, these structures are central to the content of this book. Tutorial chapters are dedicated to manufacturing processes, technological challenges, and electrical models of these structures. The vertical wires are investigated not only as a communication medium but also as heat conduits within the 3-D system. From this perspective, novel and efficient algorithms are presented for improving the signal propagation delay of heterogeneous 3-D systems by analyzing the electrical behavior of the vertical interconnects. Additionally, the important role that the vertical interconnects play in global signaling and thermal amelioration is described. Measurements from a case study of a 3-D circuit increase the physical understanding and intuition of this critical interconnect structure.

The short vertical wires enable several 3-D architectures for communication centric circuits. Opportunities for improved communication bandwidth, enhanced latency, and low power in 3-D systems are investigated. Analytic models and exploratory tools for these architectures are also discussed. The intention of this part of the book is to illuminate important design issues while providing guidelines for designing these evolving 3-D architectures.

The organization of the book is based on a bottom-up approach with technology and manufacturing of 3-D systems as the starting point. The first two chapters cover the wide spectrum of available 3-D technologies and related fabrication processes. These chapters demonstrate the multitechnology palette that is available in designing a 3-D circuit. Based on these technologies and a priori interconnect models, projections of the capabilities of 3-D circuits are provided. Physical design methodologies for 3-D circuits, which are the core of this book, are considered in the next eight chapters. The added design complexity due to the multiplane nature of a 3-D system, such as placement and routing, is reviewed. Efficient approaches to manage this complexity are presented. Extensions to multiobjective methodologies are discussed with the thermal issue as a primary reference point. As the vertical interconnects can behave either obstructively or constructively within a 3-D circuit, different design methodologies to utilize these interconnects are extensively discussed. Specific emphasis is placed on the through silicon vias, the important vertical interconnection structure for 3-D circuits. Various 3-D circuit architectures, such as a processor and memory system, field programmable gate arrays (FPGAs), and on-chip networks, are discussed. Different 3-D topologies for on-chip networks and FPGAs are explored. Novel algorithms and accurate delay and power models are reviewed. The important topic of synchronization is also investigated, targeting the challenges of distributing the clock signal throughout a multiplane circuit. Experimental results from a 3-D fabricated circuit provide intuition into this global signaling issue.

3-D integration is a seminal technology that will prolong the semiconductor roadmap for several generations. The third dimension offers nonpareil opportunities for enhanced performance and functionality; vital requirements for contemporary and future integrated systems. Considerable progress in manufacturing 3-D circuits has been achieved within the last decade. 3-D circuit design methodologies, however, considerably lag these technological advancements. This book ambitiously targets to fill this gap and strengthen the design capabilities for 3-D circuits without overlooking aspects of the fabrication process of this emerging semiconductor paradigm.

2009