Evaluation of Si etching yields by Cl+ Br+ and HBr+ ion irradiation

Cl2 and HBr plasmas are widely used for poly-Si gate electrode etching processes in the semiconductor industry. In this study, sputtering yields of poly Si by Br+ and HBr+ion injections, simultaneous injections of thermal H atoms and energetic Br+ ions, and successive injections of an energetic H+ and Br+ ion beams, have been evaluated with the use of a multi-beam system equipped with a mass-selected ion beam injector and a H radical source. It has been shown that there is little difference in sputtering yields among all these processes, which indicates that such hydrogen has little effect on the Si sputtering yield by Br+ ion injections. The result contrasts with an earlier speculation that hydrogen in HBr plasmas significantly enhances the Si sputtering yield by Br+ ion injections. In addition sputtering yields of poly Si by Cl+ ion bombardment obtained from similar beam experiments have been presented for comparison.