As we advance into the era of nanotechnology, semiconductor devices are scaled down to their physical limits, thereby opening up venues for new transistor channel materials based on nanowires and nanotubes. Transistors based on nanowires and nanotubes inherently exhibit ambipolar behavior. While technologists aim to suppress ambipolar behavior of these transistors, new design methodologies are proposed by exploiting the phenomenon of controllable polarity. In this paper, we propose regular layout fabrics, with an emphasis on silicon nanowires (SiNWs) as the candidate technology. A double-gate ambipolar SiNW field-effect transistor operates as p-type or n-type by electrically controlling the polarity of the second gate. We propose layout techniques to address gate-level routing congestion, as every transistor has two gates to route. Novel symbolic layouts, which are technology independent, are proposed for ambipolar circuits. In the second part of this paper, we present an approach for designing an efficient regular layout called sea-of-tiles (SoTs). A logic tile is essentially an array of prefabricated transistor-pairs grouped together. We design four logic tiles, which form the basic building block of the SoT fabric. We run extensive comparisons of mapping standard benchmarks onto the SoT fabric to find the optimum tile. This paper shows that SoT with TileG2and TileG1h2, on an average, outperforms the one with TileG1by 16% and 14% in area utilization, respectively.

The quest for technologies with superior device characteristics has showcased Carbon-Nanotube Field-Effect Transistors (CNFET) into limelight. In this work we present physical design techniques to improve the yield of CNFET circuits in the presence of Carbon Nanotube (CNT) imperfections. Various layout schemes are studied for enhancing the yield of CNFET standard cell library. With the help of existing ASIC design flow, we perform system-level benchmarking of CNFET circuits and compare them to CMOS circuits at various technology nodes. With CNFET technology, we observe maximum performance gains for circuits with gate-dominated delays. Averaged across various benchmarks at 16 nm, we report 8× improvement in Energy-Delay-Product (EDP) with CNFET circuits when compared to CMOS counterpart. We also study the performance of a complete OpenRISC processor, where we see 1.5× improvement in EDP over CMOS at 16 nm technology node. Voltage scaling enabled by CNFETs can be explored in the future for further performance benefits.

In addition to scaling semiconductor devices down to their physical limit, novel devices show enhanced functionality compared to conventional CMOS. At advanced technology nodes, many devices exhibit ambipolar behavior, i.e., they show n- and p-type characteristics simultaneously. This phenomenon can be tamed using double-gate structures. In this paper, we present a complete framework relying on Double-Gate-all-around Vertically stacked NanoWire FETs (DG-NWFETs). Such device enables a compact realization of arithmetic logic functions and presents unprecedented interest for structured ASIC applications.

Vertically stacked nanowire FETs (NWFETs) with gate-all-around structure are the natural and most advanced extension of FinFETs. At advanced technology nodes, many devices exhibit ambipolar behavior, i.e., the device shows n- and p-type characteristics simultaneously. In this paper, we show that, by engineering of the contacts and by constructing independent double-gate structures, the device polarity can be electrostatically programmed to be either n- or p-type. Such a device enables a compact realization of XOR-based logic functions at the cost of a denser interconnect. To mitigate the added area/routing overhead caused by the additional gate, an approach for designing an efficient regular layout, called Sea-of-Tiles is presented. Then, specific logic synthesis techniques, supporting the higher expressive power provided by this technology, are introduced and used to showcase the performance of the controllable-polarity NWFETs circuits in comparison with traditional CMOS circuits.

Two diverse manufacturing techniques for building 3-D integrated systems are vertical integration with Through-Silicon-Vias (TSVs), also referred as 3-D TSV integration, and 3D monolithic integration. In this paper, we present a hybrid integration scheme that combines these two approaches, taking into account their existing technology limits, into a disruptive paradigm called 3.5-D integration. Our novel integration supports circuit-partitioning both at the gate and block level with unprecedented benefits in cost. To demonstrate the effectiveness of 3.5-D integration, we chose as case study a 288-core MPSoC and we made hypothesis on the manufacturing and test cost. We argue a potential 20% decrease in the manufacturing cost and 30% decrease in the test cost when compared to 3-D TSV integration. In order to study the performance improvement of the MPSoC, we benchmarked various blocks of the core and the on-chip interconnection network, connecting all the cores. Our study shows large improvement in performance of the core (average of 11.5%) and latency (average of 24%) of the Network-on-Chip (NoC) for the 3.5-D integration when compared to the corresponding 3-D TSV implementation.

3D Monolithic Integration (3DMI), also termed as sequential integration, is a potential technology for future gigascale circuits. In 3DMI technology the 3D contacts, connecting different active layers, are in the order of few 100nm. Given the advantage of such small contacts, 3DMI enables fine-grain (gate-level) partitioning of circuits. In this work we present three cell transformation techniques for standard cell-based ICs with 3DMI technology. As a major contribution of this work, we propose a design flow comprising of a cell transformation technique,cell-on-cell stacking, and a physical design technique (CELONCELPD) aimed at placing cells transformed withcell-on-cellstacking. We analyze and compare various cell transformation techniques for 3DMI technology without disrupting the regularity of the IC design flow. Our experiments demonstrate the effectiveness of CELONCEL design technique, yielding us an area reduction of 37.5%, 16.2% average reduction in wirelength, and 6.2% average improvement in overall delay, compared with a 2D case when benchmarked across various designs in 45nm technology node.

We have designed and fabricated double-gate ambipolar field-effect transistors, which exhibit p-type and n-type characteristics by controlling the polarity of the second gate. In this work, we present an approach for designing an efficient regular layout, called Sea-of-Tiles (SoTs). First, we address gate-level routing congestion by proposing compact layout techniques and novel symbolic-layout styles. Second, we design four logic tiles, which form the basic building block of the SoT fabric. We run extensive comparisons of mapping standard benchmarks on the SoT. Our study shows that SoT with TileG2 and TileG1h2, on an average, outperforms the one with TileG1 and TileG3 by 16% and 10% in area utilization, respectively.

The invention of the memristor enables new possibilities for computation and non-volatile memory storage. In this paper we propose a Generic Memristive Structure (GMS) for 3-D FPGA applications. The GMS cell is demonstrated to be utilized for steering logic useful for multiplexing signals, thus replacing the traditional pass-gates in FPGAs. Moreover, the same GMS cell can be utilized for programmable memories as a replacement for the SRAMs employed in the look-up tables of FPGAs. A fabricated GMS cell is presented and its use in FPGA architecture is demonstrated by the area and delay improvement for several architectural benchmarks.

3-D monolithic integration (3DMI), also termed as sequential integration, is a potential technology for future gigascale circuits. Since the device layers are processed in sequential order, the size of the vertical contacts is similar to traditional contacts unlike in the case of parallel 3-D integration with through silicon vias (TSVs). Given the advantage of such small contacts, 3DMI enables manufacturing multiple active layers very close to each other. In this work we propose two different strategies of stacking standard cells in 3-D without breaking the regularity of the conventional design flow: a) Vertical stacking of diffusion areas (Intra-Cell stacking) that supports complete reuse of 2-D physical design tools and b) vertical stacking of cells over others (Cell-on-Cell stacking). A placement tool (CELONCEL-placer) targeting the Cell-on-Cell placement problem is proposed to allow high quality 3-D layout generation. Our experiments demonstrate the effectiveness of CELONCEL technique, fetching us an area gain of 37.5%, 15.51% reduction in wirelength, and 13.49% improvement in overall delay, compared with a 2-D case when benchmarked across an interconnect dominated low-density-parity-check (LDPC) decoder at 45nm technology node.

Carbon Nanotubes (CNTs) are grown using chemical synthesis, and the exact positioning and chirality of CNTs are very difficult to control. As a result, "small-width" Carbon Nanotube Field-Effect Transistors (CNFETs) can have a high probability of containing no semiconducting CNTs, resulting in CNFET failures. Upsizing these vulnerable small-width CNFETs is an expensive design choice since it can result in substantial area/power penalties. This paper introduces a processing/design co-optimization approach to reduce probability of CNFET failures at the chip-level. Large degree of spatial correlation observed in directional CNT growth presents a unique opportunity for such optimization. Maximum benefits from such correlation can be realized by enforcing the active regions of CNFETs to be aligned with each other. This approach relaxes the device-level failure probability requirement by 350X at the 45nm technology node, leading to significantly reduced costs associated with upsizing the small-width CNFETs.

Bio-detection specially dedicated to distributed diagnostics is emerging as a quite important application for Nano-bioelectronics. Bio-detection is required to be highly sensitive in order to succeed in sensing small amount of bio-markers in patient's blood sample. Carbon Nanotubes (CNTs) provides devices in the scale of the target molecules, thereby opening up possibilities to sense few bio-markers. Moreover, bio-detection is also required to be highly specific in order to succeed in disease discrimination. FET technology provides control in multi-panel biochip to enhance specificity. The aim of the present paper is to design an array of Carbon Nanotube Field Effect Transistors (CNFETs) to provide nano-biosensing based on cytochromes P450. In particular, a novel CNFET biosensor array design is proposed which is robust to the imperfections in the CNTs thereby achieving high level of sensitivity. The proposed CNFET based design assures the improved specificity by means of a multi-gate controller at the nano-scale. The proposed application in distributed diagnostics is on detection of drugs in multi-components samples by multiplexing different P450 probes.

The quest for technologies with superior device characteristics has showcased Carbon Nanotube Field Effect Transistors (CNFETs) into limelight. Among the several design aspects necessary for today's grail in CNFET technology, achieving functional immunity to Carbon Nanotube (CNT) manufacturing issues (such as mispositioned CNTs and metallic CNTs) is of paramount importance. In this work we present a new design technique to build compact layouts while ensuring 100% functional immunity to mispositioned CNTs. Then, as second contribution of this work, we have developed a CNFET Design Kit (DK) to realize a complete design flow from logic-to-GDSII traversing the conventional CMOS design flow. This flow enables a framework that allows accurate comparison between CMOS and CNFET-based circuits. This paper also presents simulation results to illustrate such analysis, namely, a CNFET-based inverter can achieve gains, with respect to the Energy-Delay Product (EDP) metric, of more than 4× in delay, 2× in energy/cycle and significant area savings (more than 30%) when compared to a corresponding CMOS inverter benchmarked with an industrial 65nm technology.