REACTIVE ION ETCHING FOR MICROELECTRICAL MECHANICAL SYSTEM FABRICATION

The suitability of reactive ion etching for the fabrication of microel ectro mechanical systems (MEMS) has been evaluated by characterizing t he change of lateral dimensions versus depth in etching deep structure s in silicon. Fluorine, chlorine, and bromine containing gases have pr ovided the basis for this investigation. A conventional planar RIE (re active ion etching) reactor has been used, in some cases with magnetic field enhancement or an inductive coupled plasma source and low subst rate temperature. For RIE based on Cl-2 or Cl-2/HBr plasma a slightly ''positive'' (top wider than bottom) slope is achieved when etching st ructures with a depth of several 10 mu m, whereas a ''negative'' slope is obtained when etching with an SF6/CCl2F2-based plasma. A pattern t ransfer with vertical walls is obtained for RIE based on SF6 (with O-2 added) when maintaining the substrate at low temperature (approximate to-70 degrees C). Further optimization of plasma chemistries and RIE procedures should result in runouts on the order of 0.1/100 mu m depth in Si as well as in organic materials. (C) 1995 American Vacuum Socie ty.