Performance of deep-submicrometer very large scale integrated (VLSI) circuits is being increasingly dominated by the interconnects due to decreasing wire pitch and increasing die size. Additionally, heterogeneous integration of different technologies in one single chip is becoming increasingly desirable, for which planar (two-dimensional) ICs may not be suitable. This paper analyzes the limitations of the existing interconnect technologies and design methodologies and presents a novel three-dimensional (3-D) chip design strategy that exploits the vertical dimension to alleviate the interconnect related problems and to facilitate heterogeneous integration of technologies to realize a system-on-a-chip (SoC) design. A comprehensive analytical treatment of these 3-D ICs has been presented and it has been shown that by simply dividing a planar chip into separate blocks, each occurring a separate physical level interconnected by short and vertical interlayer interconnects (VILICs), significant improvement in performance and reduction in wire-limited chip area can be achieved, without the aid of any other circuit or design innovations. A scheme to optimize the interconnect distribution among different interconnect tiers is presented and the effect of transferring the repeaters to upper Si layers has been quantified in this analysis for a two-layer 3-D chip. Furthermore, one of the major concerns in 3-D ICs arising due to power dissipation problems has been analyzed and an analytical model has been presented to estimate the temperatures of the different active layers. It is demonstrated that advancement in heat sinking technology will be necessary in order to extract maximum performance from these chips. Implications of 3-D device architecture on several design issues have also been discussed with special attention to SoC design strategies. Finally some of the promising technologies for manufacturing 3-D ICs have been outlined.

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3-D ICs: a novel chip design for improving deep-submicrometer interconnect performance and systems-on-chip integration

With vastly increased complexity and functionality in the "nanometer era" (i.e. hundreds of millions of transistors on one chip), increasing the performance of integrated circuits has become a challenging task. This is due primarily to the inevitable increase in the distance among circuit elements and interconnect design solutions have become the greatest determining factor in overall performance. 

Three-dimensional (3D) integrated circuits (ICs), which contain multiple layers of active devices, have the potential to enhance dramatically chip performance and functionality, while reducing the distance among devices on a chip. They promise solutions to the current "interconnect bottleneck" challenges faced by IC designers. They also may facilitate the integration of heterogeneous materials, devices, and signals. However, before these advantages can be realized, key technology challenges of 3D ICs must be addressed. 

This is the first book on 3-D integrated circuit design, covering all of the technological and design aspects of this emerging design paradigm, while proposing effective solutions to specific challenging problems concerning the design of three-dimensional integrated circuits. A handy, comprehensive reference or a practical design guide, this book provides a sound foundation for the design of three-dimensional integrated circuits.




* Demonstrates how to overcome "Interconnect Bottleneck" with 3D Integrated Circuit Design...leading edge design techniques offer solutions to problems (performance/power consumption/price) faced by all circuit designers.
* The FIRST book on 3D Integrated Circuit Design...provides up-to-date information that is otherwise difficult to find;
* Focuses on design issues key to the product development cyle...good design plays a major role in exploiting the implementation flexibilities offered in the third dimension;
* Provides broad coverage of 3D IC Design, including Interconnect Prediction Models, Thermal Management Techniques, and Timing Optimization...offers practical view of designing 3D circuits.

Three-Dimensional Integrated Circuit Design

Continuous scaling of VLSI circuits is reducing gate delays but rapidly increasing interconnect delays. Semiconductor Industry Association (SIA) roadmap predicts that, beyond the 130 nm technology node, performance improvement of advanced VLSI is likely to begin to saturate unless a paradigm shift from present IC architecture is introduced. This paper presents a comprehensive analytical treatment of ICs with multiple Si layers (3-D ICs). It is shown that significant improvement in performance (more than 145%) and reduction in wire-limited chip area can be achieved with 3-D ICs with vertical inter-layer interconnects (VILICs). This analysis is based on dividing a chip into separate blocks, each occupying a separate physical level. A scheme to optimize interconnect distribution among different interconnect tiers is presented and the effect of transferring the repeaters to upper Si layers has been quantified in this analysis. Furthermore, thermal analysis of ICs with two Si layers is presented. It is demonstrated that using a thermally responsible design and/or a high-performance heat sinking technology, die temperatures for ICs with two Si layers can be reduced well below present die temperatures. Finally, implications of 3-D architecture on several circuit designs are also discussed.

http://eda.ee.ucla.edu/EE201A-04Spring/3D-overview.pdf

Multiple Si layer ICs: motivation, performance analysis, and design implications

In an effort to increase processor speeds, 3D IC architecture is being aggressively pursued by researchers and chip manufacturers. This architecture allows extremely high level of integration with enhanced electrical performance and expanded functionality, and facilitates realization of VLSI and ULSI technologies. However, utilizing the third dimension to provide additional device layers poses thermal challenges due to the increased heat dissipation and complex electrical interconnects among different layers. The conflicting needs of the cooling system requiring larger flow passage dimensions to limit the pressure drop, and the IC architecture necessitating short interconnect distances to reduce signal latency warrant paradigm shifts in both of their design approach. Additional considerations include the effects due to temperature nonuniformity, localized hot spots, complex fluidic connections, and mechanical design. This paper reviews the advances in 3D IC cooling in the last decade and provides a vision for codesigning 3D IC architecture and integrated cooling systems. For heat fluxes of 50‐100W/cm 2 on each side of a chip in a 3D IC package, the current single-phase cooling technology is projected to provide adequate cooling, albeit with high pressure drops. For future applications with coolant surface heat fluxes from 100 to 500W/cm 2 , significant changes need to be made in both electrical and cooling technologies through a new level of codesign. Effectively mitigating the high temperatures surrounding local hot spots remains a challenging issue. The codesign approach with circuit, software and thermal designers working together is seen as essential. The through silicon vias (TSVs) in the current designs place a stringent limit on the channel height in the cooling layer. It is projected that integration of wireless network on chip architecture could alleviate these height restrictions since the data bandwidth is independent of the communication lengths. Microchannels that are 200lm or larger in depth are expected to allow dissipation of large heat fluxes with significantly lower pressure drops. [DOI: 10.1115/1.4027175]

Review and Projections of Integrated Cooling Systems for Three-Dimensional Integrated Circuits

Design techniques for three-dimensional (3-D) ICs considerably lag the significant strides achieved in 3-D manufacturing technologies. Advanced design methodologies for two-dimensional circuits are not sufficient to manage the added complexity caused by the third dimension. Consequently, design methodologies that efficiently handle the added complexity and inherent heterogeneity of 3-D circuits are necessary. These 3-D design methodologies should support robust and reliable 3-D circuits while considering different forms of vertical integration, such as system-in-package and 3-D ICs with fine grain vertical interconnections. Global signaling issues, such as clock and power distribution networks, are further exacerbated in vertical integration due to the limited number of package pins, the distance of these pins from other planes within the 3-D system, and the impedance characteristics of the through silicon vias (TSVs). In addition to these dedicated networks, global signaling techniques that incorporate the diverse traits of complex 3-D systems are required. One possible approach, potentially significantly reducing the complexity of interconnect issues in 3-D circuits, is 3-D networks-on-chip (NoC). Design methodologies that exploit the diversity of 3-D structures to further enhance the performance of multiplane integrated systems are necessary. The longest interconnects within a 3-D circuit are those interconnects comprising several TSVs and traversing multiple physical planes. Consequently, minimizing the delay of the interplane nets is of great importance. By considering the nonuniform impedance characteristics of the interplane interconnects while placing the TSVs, the delay of these nets is decreased. In addition, the difference in electrical behavior between the horizontal and vertical interconnects suggests that asymmetric structures can be useful candidates for distributing the clock signal within a 3-D circuit. A 3-D test circuit fabricated with a 180 nm silicon-on-insulator (SOI) technology, manufactured by MIT Lincoln Laboratories, exploring several clock distribution topologies is described. Correct operation at 1 GHz has been demonstrated. Several 3-D NoC topologies incorporating dissimilar 3-D interconnect structures are reviewed as a promising solution for communication limited systems-on-chip (SoC). Appropriate performance models are described to evaluate these topologies. Several forms of vertical integration, such as system-in-package and different candidate technologies for 3-D circuits, such as SOI, are considered. The techniques described in this paper address fundamental interconnect structures in the 3-D design process. Several interesting research problems in the design of 3-D circuits are also discussed.

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Interconnect-Based Design Methodologies for Three-Dimensional Integrated Circuits

Multilayer CMOS devices were fabricated by a laser recrystallization technology. The single crystalline silicon islands embedded in an insulator on the top of MOS IC were studied. To minimize the thermal influence on a lower IC during the fabrication process, a CVD-SiO 2 was used as a retaining wall of silicon islands instead of a LOCOS. In addition, a planarized heat sink (PHS) polysilicon layer was employed to eliminate the impediment to a grain growth at the steps due to a lower IC. The single crystalline silicon islands were successfully obtained. The field effect mobility of NMOS transistors fabricated on single-crystallied silicon islands was calculated as about 400 cm2/V.sec, 490cm2/V.sec. The 10 bit CMOS shift register fabricated just on a lower IC was successfully operated at V DD =6.5 V, f CLK = 1 MHz. The 4 bit CMOS shift register, stacking PMOS on NMOS was also successfully operated.

Multilayer CMOS device fabricated on laser recrystallized silicon islands

Characteristics of micro-groove zone-melting recrystallised Si islands

http://link.springer.com/content/pdf/10.1007/978-94-009-5311-6_5.pdf

N. Yoshii

Papers

Multilayer CMOS device fabricated on laser recrystallized silicon islands

Characteristics of micro-groove zone-melting recrystallised Si islands

Nucleation and Crystal Growth Characteristics in Energy Beam Crystallization of Silicon Islands