On the reliability and failure analysis of Very large Scale Integrated Circuits (VLSI Chips)

摘要

Elevated temperature has been considered as a dominant factor of stress which lowers the reliability and life expectancy of the microelectronics devices. Arrhenius model is commonly used for predicting the reliability and failure rate of the microelectronics devices as a function of ambient temperature. Arrhenuis model extrapolates life data, obtained from units tested at constant elevated temperatures, to the working temperatures. Generally, the temperatures of microelectronics devices are lowered using an appropriate cooling method to achieve a desired reliability and life expectancy. However, during the cooling process the chips are subjected to transient temperature change that enhances the chance of fracture and eventually failure of chips. Cyclic thermal stresses are the common cause of the fracture of mechanical structures. Accordingly, when cooling microelectronics devices, the following questions are raised; 1. Considering the possibility of the fracture of microelectronics devices when subjected to cyclic thermal loading, how does this effect in life expectancy and reliability of chips (by lowering the temperature) as predicted by Arrhenius model. 2. Considering the cost of lowering the temperature of these devices, could there be an optimal temperature yielding an acceptable reliability and life expectancy with lower cooling cost? This problem in particular becomes more critical in case of VLSI chips, where highly dense circuits occupy almost all area of the die. Hence the probability of failure due to fracture in VLSI chips is highly expected. For this case a different model than Arhenuis model is needed to correctly predict the reliability and life expectancy of VLSI chips when subjected to thermal cycling. This paper presents a methodology for developing such a model that includes the possibility of the fracture of VLSI chips subjected to cyclic thermal loading.