Electromigration Lifetime Prognostic Circuit Design

With the development of microelectronic technology, the integrated circuit’s characteristic dimension decreases to less than a micrometer, even a few nanometers. In the meanwhile, the metal interconnect line endures a larger current density as a result of a smaller cross section area. According to Black’s Equation, the lifetime of a metal interconnect line declines with the rise of the current density across the line. Therefore, the electromigration of metal interconnect line has been one of the main failure mechanisms of ICs and it is necessary to predict the lifetime of the metal interconnect line precisely.Compared with traditional diagnostic technology, the prognostic and health management technology of electronics is better-recognized as a superior one since it involves in several new frontier subjects, belongs to condition-based maintenance, and has overwhelming advantages over traditional schedule maintenance and after-maintenance. At present, there are three main methods to implement this technology:"canaries" or "fuses" monitoring precursors to failure and monitoring environmental and usage loads. In this paper, we adopt the "canary" method to predict the electromigration failure of ICs. In the circuit, a canary cell is added to provide warning of failure due to special wear-out failure mechanisms in advance. We present a prognostic circuit of electromigration failure mechanism which includes a stress circuit and a measurement circuit. In a stressing cycle, a larger current is applied to the stress resistor, then electromigration accelerates and its resistance increases. However, in a measurement cycle, the value of the stress resistor will be determined, and the switch of the two cycles is controlled by a clock impulse signal. In the measurement state, when the stress resistance is less than120%, the output remains constant; Otherwise, its output turns.In this paper, a prognostic schematic diagram of electromigration lifetime is first designed based on the research and analysis of domestic and oversea literatures. Then, the implementation of circuit blocks and the whole circuit are accomplished. What is important is that we design a current source and a comparator independent of temperature and power supply. Finally, the whole circuit is simulated in different conditions and the simulation results show that this circuit functions well.