1/f noise in poly-Si MOSFET and strong correlation with oxide traps and grain boundaries

The poly-Si MOSFET has become a key device for mega-bit SRAMs. Performance and stability are, however, still insufficient owing to the poor quality of active poly-Si films, gate oxides and their interfaces. We have studied 1/f noise in poly-Si MOSFETs, since this noise measurement is an effective approach to characterizing the MOS interface and gate oxides. We found the noise very strong compared with that in single crystalline-Si (bulk-Si) MOSFETs. It is important to clarify the generation mechanism of such large noise, in order to realize high-performance, high-stability, low-noise devices. In this paper, we introduce a noise-generation mechanism that is characteristic of poly-Si MOSFETs. It is related to the quality of gate oxides and poly-Si films, that is, the oxide trap and grain boundary properties. Also we explain a method for reducing the noise. Furthermore, we demonstrate that the 1/f noise measurement is very useful for process monitoring. >