Impact of metals on silicon devices and circuits

Abstract

This Chapter overviews the possible impact of metal impurities on the operation, reliability and yield of devices and circuits. In a first part, the presence of metal centers in a MOS capacitor will be described. Both dissolved atoms and precipitates can cause deleterious effects on the MOS characteristics, giving rise to excess gate leakage, hysteresis and instability and in the worst case, early breakdown (failure). A second part will have a look on p-n junctions and Schottky barriers. Again, excess leakage current can be generated in reverse operation and soft breakdown characteristics may be obtained. In forward operation, excess recombination mediated by metal-related deep levels gives rise to an ideality factor between 1 and 2. A third part considers the impact on transistors and circuits, including CCDs and CMOS Imager Sensors (CIS).