Challenge of Boron-Doped Silicon Hard Mask Removal

In this paper, we studied the etching of boron-doped silicon using etching gases such as Cl2/HBr, and finally stopped it on the SiN film layer (SiN loss<10nm), focusing on solving the problems of polymer on the SiB surface and SiN sidewall during the etching process, as well as insufficient SiB/SiN selection ratio. During the process, we found that adding an appropriate amount of O2 to Cl2 and HBr can improve the selectivity of SiB to SiN. In addition, using pulse mode etching or reducing pressure within an appropriate range, increasing bass power, and adjusting O2 content can effectively remove the presence of polymers on the SiB surface and SiN sidewalls. This can be applied to other boron doped silicon etching processes that require high selectivity.