TUTORIAL 02: Building in Reliability in Silicon Devices

As the device technology is progressing in the nanometer regime towards atomic scale, the famous comment “There is plenty of room at the bottom” by Richard Feynman about 60 years ago needs to be reviewed carefully and understood in detail. A recent comment “There is plenty of difficulty near the bottom” by device manufacturers depicts another face of the advancement in technology. The difficulty observed is in the path for building reliable devices. Device reliability is the resultant of various analyses of the design, process and product and understanding innumerable phenomenon to control the extension of even atomic level defects, especially when the dimensions are at nanometer level. At the early stages of technology development, the reliability estimation was through specific tests prediction to weed out defects. Many such tests are a routine and has helped to develop technology. However, at that time itself it was known that understanding device physics and solving the related problems at smaller dimensions are the key to success. As such, the device development at any technology level has been through the critical understanding of the failures through physical analysis and hence solving the issues. This procedure is the Building-in reliability in devices. It could be noted that many fundamental physics problems such as hot carriers, issues of dielectric breakdown and strength, electro migration and stress migration, electrostatic discharge issues, etc which paused the threat at different stages were solved fully or partially through physical failure analysis and understanding the related failure mechanisms. However, as the technology progressed with new materials at new dimensions, the problems also became more challenging. The tools which helped and being used for analysis itself have limitations due to the dimensional miniaturization. Moreover, the diversification in the manufacture from design to product through different vendors and stages invites a separate approach for building the product reliability. This tutorial discusses the fundamentals of reliability and failure analysis in its basic concepts and from where it can be understood using a physics based approach. The progression in devices from the conventional MOSFET and its dimensional shrinkage to nano scale MOSFET and then to new FinFET is discussed with a view to understand how the physical failure analysis can reveal the failure mechanisms to improve reliability. While evolving these processes to build reliability in nano scale devices, it is also understood that the fundamental problem remains the same as in early 1960s. That is where the “the plenty of room” is emerged as “plenty of difficulty”.