A new deep reactive ion etching process by dual sidewall protection layer

This paper describes a new deep reactive ion etching (D-RIE) process which drastically improves the aspect ratio of the etched trench. The conventional D-RIE process obtains the high aspect ratio trench etching with the protection layer, such as a polymeric layer. The etching anisotropy is limited in this process because this protection layer prevents not only lateral etching, but also vertical etching. In contrast, the new process we developed intensively prevents lateral etching with a dual protection layer consists of a polymeric layer and a SiO₂ layer on the trench sidewall. Therefore the etching anisotropy and the aspect ratio can be improved. Furthermore, this process can only be performed by switching the introducing gas into the etching chamber