A silicon trench 2um deep was etched in a PlasmaTherm 2406 RIE tool using an SF6/C02 chemistry with an oxide mask. The single crystal silicon etch rate was 1100A/min, with a high selectivity to oxide. A trench slope approximately 50 degrees was obtained, with no undercut of the oxide mask.
Wiseman, Joseph W.
"Development of a Deep Trench RIE Etch for Capacitor and Isolation Technologies,"
Journal of the Microelectronic Engineering Conference: Vol. 5
, Article 29.
Available at: https://scholarworks.rit.edu/ritamec/vol5/iss1/29