A new simulation model of coupled electro-thermal performance for MOSFET devices

Electronic devices are getting smaller, faster, more efficient, and more reliable. However, reliability assessment remains paramount to predict average lifetime of a device typically made up of many integrated circuits. The assessment is usually accomplished by monitoring the performance of a device under working conditions for long periods of time, which can be costly and time consuming. Therefore, it is desirable to minimize testing duration. To that end, a reliable prediction tool capable of simulating the device life-performance relationship is essential. The majority of the work that has been done in this area has been focused on determining the effects of degradation by the use of electrical simulation and modeling. Since temperature usually is taken to play a small part in these models, the effects of temperature levels (and variations) on device functionality are not captured. But in order to better understand the effects of degradation, the thermal effects must be fully coupled with the electrical effects within a comprehensive electro-thermal simulation method, particularly since elevated temperatures contribute to the contamination of the silicon oxide barrier layer, a phenomenon known as hot carrier injection. The local temperature also plays a big role in a second, yet more important degradation effect called charge trapping.; This work introduces a new electro-thermal degradation simulation method and suggests its use in determining the approximate lifetime of an active MOSFET subjected to hot carrier injection stress and charge trapping. Hot carrier injection is used to an advantage in EPROM applications, but in other MOSFET applications it is the main reason for device failure. Carriers, which gather enough energy from higher temperatures to jump the silicon dioxide barrier can get trapped inside the oxide layer, deteriorating the electrical properties of the latter, and thereby shifting device properties and causing performance degradation.; Charge trapping, although important for photorefractive effect, is generally an undesired phenomenon occurring in MOSFET devices. The most common form is the creation of interface traps that lead to high recombination rates along the gate and drop the general performance of the gate.; In extreme cases, these processes may lead eventually to the breakdown of the silicon dioxide layer. It is necessary to accurately predict the change in local parameters as a result of the elevated temperature field and translate that information into a performance drop function, which leads to an approximation of useful life span of a MOSFET.