Drain junction leakage current in SIMOX/MOSFETs

Abstract

Summary form only given. The drain junction leakage current, which is representative of the silicon film quality, can be separated from the subthreshold leakage by applying proper biases to the front and back gates. Preliminary results indicate that the junction leakage increases superlinearly with the drain voltage and cannot be explained by S-R-H generation. In addition, the leakage current shows two distinctive regions in the drain voltage. In the low voltage region, below 5 V, its voltage dependence is relatively weak. In the higher voltage region (but below the avalanche breakdown) the leakage depends much more strongly on the drain voltage. The junction leakage in the lower drain voltage region is also found to be very sensitive to temperature. Measurements of leakage as a function of temperature show that the activation energy slightly decreases with increasing voltage, indicating the lowering of an emission barrier by increasing electric field. This leakage current can be well explained by the Poole Frenkel emission model. More rigorous analyses indicate that the leakage mechanism is a mixture of field-enhanced thermal emission and thermally assisted field emission. Drain junction leakage in the higher voltage region shows a good fit to the Fowler-Nordheim field-emission model. Soft breakdown in p/n junction diodes containing metallic impurities has been ascribed to Fowler-Nordheim field emission due to localized high electric fields near metallic precipitates. This argument may be applicable to SIMOX/MOSFETs.<>