The electron charging effects of plasma on notch profile defects

The notch occurrence factor in polysilicon etching was investigated using a newly designed test mask pattern. This pattern varied the space width, the line width of the line-and-space structure, and the pad perimeter which connected the line-and-space structure. By using this test pattern, it was found that the notch depth increases as the perimeter ratio, (i.e. the ratio of the pad perimeter to the notch line perimeter), increases. Moreover, when the perimeter ratio was very small, the notch depth was quite small. Therefore, it is considered that the notch is caused by electron supply from the periphery of the pad which collects the electrons from plasma. As a result of this electron conduction, in the case of the non-connected lines, the notch occurs only outside the line of the line-and-space structure, and in the case of the connected lines, the notch occurs at all of the connected lines. The notch depth difference between the non-connected lines and connected lines is explained by the difference in perimeter ratio.