Fundamentals and applications of the hydrogen/deuterium isotope effect in improved hot-carrier reliability of MOS devices

The reliability due to hot-carrier effects poses increasing constraints on the downscaling of CMOS transistors. This thesis attempts to provide a thorough study on both fundamentals and applications of enhancing CMOS reliability by incorporation of deuterium at the oxide/silicon interface. The impacts of the high pressure deuterium process on device characteristics and reliability are first investigated. The effectiveness of the use of deuterium to improve reliability of fully processed 0.18μm silicon-on-insulator (SOI) devices is then demonstrated. A practical issue for deuterium annealing process is the ubiquitous presence of hydrogen during device fabrication. The replacement of the pre-existing hydrogen by deuterium is found to be the rate-limiting step for deuterium incorporation. A new technique that is solely based on electrical testing is then developed to quantify deuterium passivation fraction at the interface. The deuterium fraction in deep submicron devices can be directly measured by this technique. An analytical model to predict the improvement of device lifetime by deuterium is also proposed.; The hydrogen/deuterium isotope effect is also being used in this thesis as an important scientific tool to probe the fundamental mechanisms for device degradation. Based on the isotope effect, a new method is developed to separate and quantify the effects of interface trap creation and oxide charge trapping on the device degradation. Furthermore, it is shown that interface trap generation under both uniform stress and non-uniform stress essentially follows the same mechanism, which is related to the breaking of Si-H(D) bonds and the release of hydrogen/deuterium at the oxide/silicon interface. Interface degradation cannot be simply scaled away by lowering the operation voltages. This is due to the fact that Si-H(D) bonds can still be broken by low-energy electrons through the multiple vibrational heating mechanism. Unlike the uniform energy distribution of Si-H(D) on silicon surfaces, experimental results show that the disordered interface environment introduces a variation of Si-H(D) bond strength at oxide/silicon interfaces.*; *Originally published in DAI Vol. 62, No. 6. Reprinted here with corrected author name.