Continuous and cyclic deep reactive ion etching of borosilicate glass by using SF ₆ and SF ₆/Ar inductively coupled plasmas

In this study, deep reactive ion etching (DRIE) of borosilicate glass with a Ni hard mask was carried out in SF ₆ and SF ₆/Ar inductively coupled plasmas under continuous and cyclic etching modes. Continuous etching in SF ₆ plasma resulted in glass channel profiles with an under-cut below the Ni hard mask and micro-trenching at the bottom of the etched channel. Continuous etching in SF ₆/Ar plasma, on the other hand, removed the under-cut and micro-trenching but reduced the etch rate significantly. In order to enhance the glass etch rate in SF ₆ plasma as well as to solve the problems such as under-cut and micro-trenching in SF ₆ plasma, a cyclic etching process using SF ₆/Ar (A-step) and SF ₆ (B-step) plasmas was investigated by varying the period time and duty ratio. As a result, it was observed that the average etch rate during the cyclic etching process was slightly increased compared to that of the continuous SF ₆ plasma etching and the profile angle was improved to >89° without under-cut and micro-trenching.