Influence of poly-si potential on profile distortion caused by charge accumulation

The appearance of local side etch in polysilicon etching was investigated using a pattern of lines and spaces (L&S) with spaces of various widths. The local side etch is found to appear at lines connected to the silicon substrate even when there is no exposed area of the silicon substrate. It is also found that the degree of local side etch decreases as the area of exposed silicon substrate increases. From these results, it is considered that the cause of the local side etch is the electron supplied from the silicon substrate to polysilicon through the connection, where the source of electrons is, electron irradiation at the sidewall of the lines which have connection and are facing to the wide spaces. The results also show that the electric potential of the silicon substrate in the case when there is no exposed area is lower than the potential of the exposed area of the silicon substrate.