Trench etching using a CBrF3 plasma and its study by optical emission spectroscopy

Silicon trenches are used for modern device isolation or three-dimensional capacitors in dynamic memories. For etching of such deep trenches in silicon a process using a gas mixture of CBrF3 and O2 has been investigated. In our experiments, a triode etcher was used to control the plasma density and ion energy independently. In this paper, the dependence of the silicon etch rate, the selectivity to the oxide mask, the trench profile and the formation of a side-wall protection film on the etching parameters is described. Further, an analysis of the CBrF3/O2 plasma by optical emission spectroscopy is given. Finally, using these results in connection with dc bias voltage measurements some aspects of the etching mechanism are discussed.