Electrical breakdown of amorphous hydrogenated silicon rich silicon nitride thin film diodes

Electrical breakdown, both intrinsic and extrinsic, of thin film diodes used as switches in active matrix addressed liquid crystal displays has been studied using electrical measurements, thermal measurements, thermal 3D simulations, electrical simulations and post breakdown observations. The diodes used in this study consist of a layer of 30 nm amorphous hydrogenated silicon rich silicon nitride, sandwiched between metal electrodes. It will be shown that breakdown under dc bias is a thermal process. Thermal breakdown is shown to occur above a temperature level of 234°C and is triggered by the onset of hydrogen effusion. Under certain conditions, low ohmic links are formed as a result of breakdown. Breakdown due to very short pulses (50-500 ns) shows a remarkable asymmetry in breakdown current between polarities. A hypothesis on this asymmetry is presented. Measurements suggest that a relation exists between current flow induced state creation in the nitride and breakdown phenomena. Furthermore, a statistical measurement technique is presented that uses breakdown to monitor the switch reliability in active matrix LCD production