Trends and Future Directions in Nano Structure Based Computing and Fabrication

As silicon CMOS devices are scaled down into the nanoscale regime, new challenges at both the device and system level are arising. While some of these challenges will be overcome in the near future, nanoscale devices will have high manufacturing defect rates and will operate at reduced noise margins, exposing computation to higher soft error rates. Thus, a key challenge for the future will be building fault and defect-tolerant computing systems. Researchers are looking to develop hybrid systems that combine on the same chip CMOS-based circuitry with any number of alternatives, including circuits composed of nanowire or carbon nanotube devices. The big advantage of including these new devices on the same chip is the increased device densities, and potential drop in fabrication costs. On the other hand, integrating very large numbers of devices on a single chip leads to questions of how to manage so many devices with tight constraints on cost, performance, power, and reliability, without having it become a design complexity nightmare. In this paper, we review some key issues and trends arising from nanostructure based computing and fabrication, while providing a few examples of defect-tolerant circuits and architectures currently being proposed as alternatives to "traditional" computing based exclusively on CMOS technology. These include hybrid nanowire/CMOS designs, reconfigurable or redundant architectures, and designs based on probabilistic computing. We end with a discussion on future challenges and direction in nanoscale computing.