ToPoliNano: Nano-magnet Logic Circuits Design and Simulation

Among the emerging technologies Field-Coupled devices like Quantum dot Cellular Automata are particularly interesting. Of all the practical implementations of this principle NanoMagnet Logic shows many important features, such as a very low power consumption and the feasibility with up-to- date technology. However, its working principle, based on the interaction among neighbor cells, is quite different with respect to CMOS devices behavior. Dedicated design and simulation tools for this technology are necessary to further study this technology, but at the moment there are no such tools available in the scientific scenario. We present here ToPoliNano, a software developed as a design and simulation tool for NanoMagnet Logic, that can be easily adapted to many others emerging technologies, particularly to any kind of Field-Coupled devices. ToPoliNano allows to design circuits following a top-down approach similar to the one used in CMOS and to simulate them using a switch model specifically targeted for high complexity circuits. This tool greatly enhances the ability to analyze, explore and improve the design of Field- Coupled circuit

ToPoliNano: Nanoarchitectures Design Made Real

Many facts about emerging nanotechnologies are yet to be assessed. There are still major concerns, for instance, about maximum achievable device density, or about which architecture is best fit for a specific application. Growing complexity requires taking into account many aspects of technology, application and architecture at the same time. Researchers face problems that are not new per se, but are now subject to very different constraints, that need to be captured by design tools. Among the emerging nanotechnologies, two-dimensional nanowire based arrays represent promising nanostructures, especially for massively parallel computing architectures. Few attempts have been done, aimed at giving the possibility to explore architectural solutions, deriving information from extensive and reliable nanoarray characterization. Moreover, in the nanotechnology arena there is still not a clear winner, so it is important to be able to target different technologies, not to miss the next big thing. We present a tool, ToPoliNano, that enables such a multi-technological characterization in terms of logic behavior, power and timing performance, area and layout constraints, on the basis of specific technological and topological descriptions. This tool can aid the design process, beside providing a comprehensive simulation framework for DC and timing simulations, and detailed power analysis. Design and simulation results will be shown for nanoarray-based circuits. ToPoliNano is the first real design tool that tackles the top down design of a circuit based on emerging technologie

ToPoliNano: Nano-magnet Logic Circuits Design and Simulation

Among the emerging technologies Field-Coupled devices like Quantum dot Cellular Automata are particularly interesting. Of all the practical implementations of this principle NanoMagnet Logic shows many important features, such as a very low power consumption and the feasibility with up-to- date technology. However, its working principle, based on the interaction among neighbor cells, is quite different with respect to CMOS devices behavior. Dedicated design and simulation tools for this technology are necessary to further study this technology, but at the moment there are no such tools available in the scientific scenario. We present here ToPoliNano, a software developed as a design and simulation tool for NanoMagnet Logic, that can be easily adapted to many others emerging technologies, particularly to any kind of Field-Coupled devices. ToPoliNano allows to design circuits following a top-down approach similar to the one used in CMOS and to simulate them using a switch model specifically targeted for high complexity circuits. This tool greatly enhances the ability to analyze, explore and improve the design of Field- Coupled circuits

Enabling Design and Simulation of Massive Parallel Nanoarchitectures

A common element in emerging nanotechnologies is the increasing complex- ity of the problems to face when attempting the design phase, because issues related to technology, specific application and architecture must be evalu- ated simultaneously. In several cases faced problems are known, but require a fresh re-think on the basis of different constraints not enforced by standard design tools. Among the emerging nanotechnologies, the two-dimensional structures based on nanowire arrays is promising in particular for massively parallel architec- tures. Several studies have been proposed on the exploration of the space of architectural solutions, but only a few derived high-level information from the results of an extended and reliable characterization of low-level structures. The tool we present is of aid in the design of circuits based on nanotech- nologies, here discussed in the specific case of nanowire arrays, as best candi- date for massively parallel architectures. It enables the designer to start from a standard High-level Description Languages (HDL), inherits constraints at physical level and applies them when organizing the physical implementation of the circuit elements and of their connections. It provides a complete simu- lation environment with two levels of refinement. One for DC analysis using a fast engine based on a simple switch level model. The other for obtaining transient performance based on automatic extraction of circuit parasitics, on detailed device (nanowire-FET) information derived by experiments or by existing accurate models, and on spice-level modeling of the nanoarray. Re- sults about the method used for the design and simulation of circuits based on nanowire-FET and nanoarray will be presente

ToPoliNano and fiction: Design Tools for Field-coupled Nanocomputing

Field-coupled Nanocomputing (FCN) is a computing concept with several promising post-CMOS candidate implementations that offer tremendously low power dissipation and highest processing performance at the same time. Two of the manifold physical implementations are Quantum-dot Cellular Automata (QCA) and Nanomagnet Logic (NML). Both inherently come with domain-specific properties and design constraints that render established conventional design algorithms inapplicable. Accordingly, dedicated design tools for those technologies are required. This paper provides an overview of two leading examples of such tools, namely fiction and ToPoliNano. Both tools provide effective methods that cover aspects such as placement, routing, clocking, design rule checking, verification, and logical as well as physical simulation. By this, both freely available tools provide platforms for future research in the FCN domain

Emerging Technologies - NanoMagnets Logic (NML)

In the last decades CMOS technology has ruled the electronic scenario thanks to the constant scaling of transistor sizes. With the reduction of transistor sizes circuit area decreases, clock frequency increases and power consumption decreases accordingly. However CMOS scaling is now approaching its physical limits and many believe that CMOS technology will not be able to reach the end of the Roadmap. This is mainly due to increasing difficulties in the fabrication process, that is becoming very expensive, and to the unavoidable impact of leakage losses, particularly thanks to gate tunnel current. In this scenario many alternative technologies are studied to overcome the limitations of CMOS transistors. Among these possibilities, magnetic based technologies, like NanoMagnet Logic (NML) are among the most interesting. The reason of this interest lies in their magnetic nature, that opens up entire new possibilities in the design of logic circuits, like the possibility to mix logic and memory in the same device. Moreover they have no standby power consumption and potentially a much lower power consumption of CMOS transistors. In literature NML logic is well studied and theoretical and experimental proofs of concept were already found. However two important points are not enough considered in the analysis approach followed by most of the work in literature. First of all, no complex circuits are analyzed. NML logic is very different from CMOS technologies, so to completely understand the potential of this technology it is mandatory to investigate complex architectures. Secondly, most of the solutions proposed do not take into account the constraints derived from fabrication process, making them unrealistic and difficult to be fabricated experimentally. This thesis focuses therefore on NML logic keeping into account these two important limitations in the research approach followed in literature. The aim is to obtain a complete and accurate overview of NML logic, finding realistic circuital solutions and trying to improve at the same time their performance. After a brief and complete introduction (Chapter 1), the thesis is divided in two parts, which cover the two fundamental points followed in this three years of research: A circuits architecture analysis and a technological analysis. In the architecture analysis first an innovative VHDL model is described in Chapter 2. This model is extensively used in the analysis because it allows fast simulation of complex circuits, with, at the same time, the possibility to estimate circuit per- formance, like area and power consumption. In Chapter 3 the problem of signals synchronization in complex NML circuits is analyzed and solved, using as benchmark a simple but complete NML microprocessor. Different solutions based on asynchronous logic are studied and a new asynchronous solution, specifically designed to exploit the potential of NML logic, is developed. In Chapter 4 the layout of NML circuits is studied on a more physical level, considering the limitations of fabrication processes. The layout of NML circuits is therefore changed accordingly to these constraints. Secondly CMOS circuits architectures are compared to more simple architectures, evaluating therefore which one is more suited for NML logic. Finally the problem of interconnections in NML technology is analyzed and solutions to improve it are found. In Chapter 5 the problem of feedback signals in heavy pipelined technologies, like NML, is studied. Solutions to improve performances and synchronize signals are developed. Systolic arrays are then analyzed as possible candidate to exploit NML potential. Finally in Chapter 6 ToPoliNano, a simulator dedicated to NML and other emerging technologies, that we are developing, is described. This simulator allows to follow the same top-down approach followed for CMOS technology. The layout generator and the simulation engine are detailed described. In the first chapter of the technological analysis (Chapter 7), the performance of NML logic is explored throughout low level simulations. The aim is to understand if these circuits can be fabricated with optical lithography, allowing therefore the commercial development of NML logic. Basic logic gates and the clock system are there analyzed from a low level perspective. In Chapter 8 an innovative electric clock system for NML technology is shown and the first experimental results are reported. This clock system allows to achieve true low power for NML technology, obtaining a reduction of power consumption of 20 times considering the best CMOS transistors available. This power consumption takes into account all the losses, also the clock system losses. Moreover the solution presented can be fabricated with current technological processes. The research work behind this thesis represents an important breakthrough in NML logic. The solutions here presented allow the design and fabrication of complex NML circuits, considering the particular characteristics of this technology and considerably improving the performance. Moreover the technological solutions here presented allow the design and fabrication of circuits with available fabrication process with a considerable advantage over CMOS in terms of power consumption. This thesis represents therefore a considerable step froward in the study and development of NML technolog

Asynchronous Solutions for Nano-Magnetic Logic Circuits

In the years to come new solutions will be required to overcome the limitations of scaled CMOS technology. One approach is to adopt Nano-Magnetic Logic Circuits, highly appealing for their extremely reduced power consumption. Despite the interesting nature of this approach, many problems arise when this technology is considered for real designs. The wire is the most critical of these problems from the circuit implementation point of view. It works as a pipelined interconnection, and its delay in terms of clock cycles depends on its length. Serious complications arise at the design phase, both in terms of synthesis and of physical design. One possible solution is the use of a delay insensitive asynchronous logic, Null Convention Logic (NCL TM ). Nevertheless its use has many negative consequences in terms of area occupation and speed loss with respect to a Boolean version. In this article we analyze and compare different solutions: nanomagnetic circuits based on full NCL, mixed Boolean-NCL, and fully Boolean logic. We discuss the advantages of these logics, but also the issues they raise. In particular we analyze feedback signals, which, due to their intrinsic pipelined nature, cause errors that still have not found a solution in the literature. The innovative arrangement we propose solves most of the problems and thus soundly increases the knowledge of this technology. The analysis is performed using a VHDL behavioral model we developed and a microprocessor we designed based on this model, as a sound and realistic test bench. </jats:p

Silicon Atomic Quantum Dots Enable Beyond-CMOS Electronics

We review our recent efforts in building atom-scale quantum-dot cellular automata circuits on a silicon surface. Our building block consists of silicon dangling bond on a H-Si(001) surface, which has been shown to act as a quantum dot. First the fabrication, experimental imaging, and charging character of the dangling bond are discussed. We then show how precise assemblies of such dots can be created to form artificial molecules. Such complex structures can be used as systems with custom optical properties, circuit elements for quantum-dot cellular automata, and quantum computing. Considerations on macro-to-atom connections are discussed.Comment: 28 pages, 19 figure