Development of Advanced CAD Tools for the Design and Simulation of Digital Circuits Based on Emerging Nanotechnologies

Currently available electronic products and circuits are heavily based on the CMOS technology. Over the course of past decades, electronic circuit integration has become one of the determining factors in the technological advances of our time. Due to causes such as transistor scaling reaching critical limits and extremely high density of ICs, challenging today’s production processes, it is more apparent than ever that continuing to only rely on CMOS technology is leading to a slowdown in progress, and alternative solutions are being researched. These new technologies go by the name of Beyond CMOS. One of the most important is QCA (Quantum-dot Cellular Automata), capable of achieving improvements where the CMOS might be limited moving forward, such as reduced power consumption and faster signal transmission. It is based on the interaction between the electrons of bi-stable quantum cells, enabling logic operations. The most prominent implementations are Magnetic QCA (specifically iNML and pNML), in which the elementary cells are nanomagnets, and MolQCA, whose cells are made of molecules. In order to design and perform simulations of QCA circuits, new experimental software is required. The ToPoliNano framework developed at Politecnico di Torino is a set of EDA tools that allows to design QCA circuit layouts, synthesize their HDL description, simulate the circuit and visualize the results in a 3D viewer. The framework consists of three main software, namely ToPoliNano, a CAD tool able to test and simulate circuits; MagCAD, which enables custom circuit design, and FCNS Viewer, a 3D viewer that allows to view the behavior of the circuit throughout the simulation. During the course of this work, ToPoliNano and FCNS Viewer have been modified to fully support MolQCA simulations in the former, and to insert a waveform viewer in the latter. ToPoliNano has been extensively modified in order to integrate the full design flow also for Molecular QCA, whereas previously it was present only for iNML. To do this, MolQCA has been activated by importing its shared library, creating a new class of simulation settings to allow for user customization, and inserting the required parameters. The molecular clock has been changed to a four-phase clock, and the simulation controller was refactored to improve the parameter passing between classes; in addition, the simulator has been modified to support a verbose simulation, providing a more detailed representation of the system by analyzing it in smaller time steps. The result is a fully fledged molecular simulator, providing results that can be studied for MolQCA research. FCNS Viewer has been updated to provide a feature that can import the results stored in a table by the ToPoliNano simulation, containing the signal values at each time step, and translate those values in a wave chart. The new plot allows to visually analyze the behavior of each signal during the simulation, such as value and amplitude changes; it provides features such as horizontal and vertical zoom, and a line that intercepts the signals and updates the signal labels with their value at that time instant. The new implementations expand the ToPoliNano framework, moving it closer in terms of feature completeness to commercial CMOS design tools. Future developments will allow to study and research an evolution toward hybrid systems that could be capable of reaping the benefits of both CMOS and QCA. The Waveform Viewer could also be updated with increasing features, to improve its quality.