The effects of adding H2 or CBrF3 to Cl2 plasma to control the pattern profile in polysilicon etching are studied using a magnetron reactive ion etching system. It is found that the sidewalls of patterns etched with pure Cl2 plasma at the pressure of 12 Pa are vertical or sloped depending on whether a radio frequency (rf) power of 600 W (0.77 W/cm2) or 700 W (0.9 W/cm2) is applied. By increasing the content of H2, the angle of the sidewall taper of the pattern etched at 600 W rf power reaches 70°. Adding CBrF3 makes it possible to adjust the slope of the sidewall over a range from 77° to 65° at a rf power of 700 W. These observed results are attributed to plasma polymerization.

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