Influence of sheet resistance on N2O-grown polyoxide

Abstract

The influence of sheet resistance on polyoxide was explored in this paper. Polyoxides were grown on polysilicon with different sheet resistances (30-150 Omega/cm(2)). It was found that as the sheet resistance increased from 30 Omega/cm(2) to 50 Omega/cm(2) the characteristics of polyoxide was improved with higher breakdown electric field and higher charge-to-breakdown. However, as the sheet resistance continued to increase (> 110 Omega/cm(2)), the characteristics of polyoxide became worse again. This phenomenon is explained by phosphorus concentration incorporated into polyoxide. Phosphorus concentration helps to form a smoother polyoxide/polysilicon interface. Thus, the characteristics of polyoxide with high sheet resistance (>110 Omega/cm(2)) was worse than that of polyoxide with low sheet resistance due to a rough polyoxide interface. However, too much. phosphorus incorporated into polyoxide degrades the quality of polyoxide. So the characteristics of polyoxide with low sheet resistance (<50 Omega/cm(2)) became worse again. Consequently, high quality of polyoxide should he grown on the polysilicon with middle sheet resistance (50-110 Omega/cm(2)).