Ion beam modification of residual stress gradients in thin film polycrystalline silicon membranes
AssigneeTrustees of Boston University
InventorThomas G. Bifano
Life of this patent
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Abstract
Method and apparatus for reducing the curvature of a micromachined structure having lamella (12). Surface treatment by an ion beam (30) of the lamella (12) such as by sputtering removes regions of stress allowing the lamella (12) to return to a planar condition. The resulting outer surface is made suitable for use as a reflector and other purposes needing a substantially planar surface.
Claims28
A process for reducing curvature in isolated micromachined elements comprising the steps of:
- providing a micromachined structure having an upper surface and a substantially matching lower surface with said upper surface having a curvature positioning it out of plane and created by processing stresses distributed non uniformly throughout a depth of said structure;
- applying surface modifying energy to said structure to remove an entire surface layer from said structure to alter the distribution of the stresses throughout said structure to reduce the out of plane curvature.
Apparatus for reducing curvature in isolated micromachined elements comprising:
- a housing for a micromachined structure having an upper surface and a substantially matching lower surface with said upper surface having a curvature positioning it out of plane and created by processing stresses distributed non uniformly throughout a depth of said structure;
- a source of a surface modifying energy for application to said structure to remove an entire surface layer from said structure to alter the distribution of the stresses throughout said structure to reduce the out of plane curvature.
The apparatus 19 wherein said surface modifying energy is an ion beam.
The apparatus 15 wherein said surface modifying energy is an ion beam.
Dependencies are inferred from the claim text.