Spherical microgrid.

摘要

Spherically convex microgrids may be prepared from a flat microgrid structure by using a process depending on the differential thermal expansion between the material of the flat structure and a layer of other material applied thereto. A flat process blank 2 is etched with grid apertures in a microgrid area to which a curvature is to be added during fabrication. The blank is then subject to the deposition of a thin layer 4 of aluminium nitride (or other differential thermal expansion material having a positive thermal expansion mismatch with the material of the microgrid substrate) over at least the microgrid area (Step A). The differential thermal expansion layer is coextensively with the grid area, so as to confine the warping substantially to the grid area where curvature is desired. Curvature (Step B) is accomplished by a controlled heat warping step in an inert atmosphere (for a silicon microgrid structure of 250 micrometers thickness, heating at 1200C to soften the silicon). Permanent deformation, occuring as a result of the differential thermal expansion, is controlled by selection of temperature and time of heat treatment to achieve the desired curvature. The aluminium nitride layer (Step C) is removed prior to cooling.