Improving sidewall roughness by combined RIE-Bosch process

An approach for improving sidewall roughness of high-aspect-ratio trench is developed. This method relies on the aspect ratio dependent scalloping attenuation (ARDSA) effect in Bosch process, employs reactive ion etching (RIE) process to avoid the rippled sidewall at the top of the trench, while retains Bosch process with increasing trench depth. As both the RIE and Bosch processes are recognized production techniques, this method is easy to implement. Compared with standard Bosch process, the maximum root mean square (RMS) roughness of the sidewall is brought down from 15.1 nm to 6.89 nm.