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.

Interconnect-Based Design Methodologies for Three-Dimensional Integrated Circuits : Vertical integration is a novel communications paradigm where interconnect design is a primary focus

Block copolymer thin films

Dynamic thermal gradient-based processes for directed self-assembly of block copolymer (BCP) thin films such as cold zone annealing (CZA) have demonstrated much potential for rapidly fabricating highly ordered patterns of BCP domains with facile orientation control As a demonstration, hexagonally packed predominantly vertical cylindrical morphology, technologically relevant for applications such as membranes and lithography, was achieved in 1 μm thick cylinder-forming PS-b-PMMA (cBCP) films by applying sharp thermal gradients (CZA-Sharp) at optimum sample sweep rates A thorough understanding of the molecular level mechanisms and pathways of the BCP ordering that occur during this CZA-S process is presented, useful to fully exploit the potential of CZA-S for large-scale BCP-based device fabrication To that end, we developed a customized CZA-S assembly to probe the dynamic structure evolution and ordering of the PS-b-PMMA cBCP film in situ as it undergoes the CZA-S process using the grazing incidence sma

Ordering Pathway of Block Copolymers under Dynamic Thermal Gradients Studied by in Situ GISAXS

Self-consistent field theory with a dynamic extension is exploited to investigate the kinetics of the lamellar formation of symmetric block copolymers under the direction of external fields. In particular, three types of directed self-assembly methods - a permanent field for chemo-epitaxy, a dynamic field for zone annealing and an integrated permanent/dynamic field - are examined. For the chemo-epitaxy involving sparsely prepatterned substrates or zone annealing, the block copolymers generally develop into polycrystalline nanostructures with multiple orientations due to the lack of strong driving forces for eliminating the long-lived imperfections in a limited time. As the integrated chemo-epitaxy and zone annealing method is applied to the block copolymer systems, single-crystalline nanostructures with precisely registered orientations are achieved in a short annealing time owing to the mutual acceleration of defect annihilations, which cannot be produced by the conventional techniques alone. Furthermore, the integrated method allows the rapid fabrication of well-ordered nanostructures on the extremely sparse prepatterned substrates. Our theoretical work may serve to rationalize the faster modern nanolithographic fabrication of smaller microelectronic components using lower-spatial-frequency templates.

Ordering kinetics of lamella-forming block copolymers under the guidance of various external fields studied by dynamic self-consistent field theory

Designing High χ Copolymer Materials for Nanotechnology Applications: A Systematic Bulk vs. Thin Films Approach

A theoretical method based on dynamic version of self-consistent field theory is extended to investigate directed self-assembly behaviors of block copolymers subjected to zone annealing. The ordering mechanisms and orientation modulation of microphase-separated nanostructures of block copolymers are discussed in terms of sweep velocity, wall preference, and Flory-Huggins interaction parameter. The simulated results demonstrate that the long-range ordered nanopatterns are achieved by lowering the sweep velocity of zone annealing due to the incorporation of templated ordering of block copolymers. The surface enrichment by one of the two polymer species induces the orientation modulation of defect-free nanostructures through finely tuning the composition of block copolymers and the preference of walls. Additionally, the Flory-Huggins interaction parameters of block copolymers in the distinct regions are main factors to design the zone annealing process for creating the highly ordered nanostructures with single orientation.

Understanding the ordering mechanisms of self-assembled nanostructures of block copolymers during zone annealing

It is an extremely challenging task to construct three-dimensional (3D) well-ordered superstructures with controllable morphologies and predictable internal components. Using computational modeling, we conceive and demonstrate a novel class of templates with topographically and chemically patterned surfaces for directing the self-assembly of symmetric block copolymers. Large-cell simulations of self-consistent field theory corroborate that 3D sophisticated structures of vertical lamellae with different in-plane orientations are achieved and the placements of grain interfaces are regulated by post height and commensurability conditions. Notably, non-orthogonally crossed structures are created by simply modulating the periodicities of post arrays. This work may provide a novel route for experimentalists to fabricate 3D long-range ordered structures with tunable local characteristics.

Robust control over morphologies and grain interfaces of three-dimensional well-ordered superstructures programmed by hybrid topographical-chemical templates

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Understanding the ordering mechanisms of self-assembled nanostructures of block copolymers during zone annealing

Robust control over morphologies and grain interfaces of three-dimensional well-ordered superstructures programmed by hybrid topographical-chemical templates