Hi Li, I have tried to use DRIE to etch silicon probe tips with metal mask and experienced from loading effect to grass effect. Basically, you need a good balance between the SF6 and C4F8 flows. Please check one of my publication for more details: Fei Wang, Xinxin Li, Nanxiang Guo, Yuelin Wang, and Songlin Feng, “A silicon cantilever probe card with tip-to-pad electric feed-through and automatic isolation of the metal coating,” Journal of Micromechanics and Microengineering, Volume 16, Issue 7, pp. 1215-1220, 2006. Hope it helps, good luck! Fei 2010/2/20, Li. Zhang: > Hey Renil, > > The hard mask is sputtered Al with thickness of 1500A and the the depth > etched down to silicon is about 10um. > > I applied an etching cycle of 3s and a passivation cycle of 1s. The flow > rate of SF6 = 200sccm and C4F8 = 100sccm. > > I've heard lowing the passivation flow rate might help with grass problem, > but not quite sure. > > My Best, > > Li. Zhang -- Best regards, Yours sincerely Fei Wang ______________ Postdoctoral researcher, Dr MIC - Department of Micro and Nanotechnology Technical University of Denmark (DTU) Building 344, 1st floor, Room no. 130 DK-2800, Kgs. Lyngby Denmark Tel: +45 4525 6311 Fax: +45 4588 7762 Email: fei.wang@nanotech.dtu.dk http://www.nanotech.dtu.dk