Anomalous behavior of semi-insulating silicon rich amorphous silicon nitride

Silicon rich PECVD amorphous silicon nitride has been used as an inter-level metal dielectric for making laser programmable connections on restructurable VLSI. There is an apparent Schottky barrier characteristic that has a 0.11 eV lower barrier for Ti than for Al. The stoichiometry was analyzed using RBS and HFS, and found to contain approximately 55% Si, 25% N, and 20% H by atomic percentages. The optical bandgap is 2.01 eV as found by the Tauc method. The insulating behavior depends on time in an anomalous manner at applied fields greater than about 0.2 MV/cm, whereby the current increases with time for several seconds until it reaches an equilibrium value. The current decays in a normal charging manner at lower fields and in samples with insulating sub-layers between the electrodes and the nitride. When used as a gate dielectric, there is a long-time charging behavior that shifts the flat band voltage in the opposite direction of the applied stress. This shift is indicative of polarization, within the dielectric. This behavior is similar to that of a reverse biased a-Si:H p-i-n diode.