Methodology for manufacturing hinged diaphragms for semiconductor sensors

Abstract

Manufacturing hinged diaphragms for semiconductor sensors (e.g., accelerometers, pressure transducers, etc.), from a SIMOX wafer (W, FIG. 3 A), in which the internal, insulating, silicon dioxide (SiO.sub.2) layer (3) is used as an etch stop in removing silicon from the underside of the wafer by etching with an appropriately selective etch, producing the reduced thickness, peripheral 'hinge' areas (9; FIG. 3 A to FIG. 3 B), with the exposed part of the silicon dioxide layer being removed in a subsequent etching step (FIG. 3 B to FIG. 3C) using a different, selective etch. This produces a single layer, single-crystal, silicon 'hinge' (9'; FIG. 3C) of uniform, continuous material, enhancing the linearity of diaphragm movement during use and the sensor's sensitivity and accuracy. (See FIG. 4 for methodological steps.) If the top, silicon region of the SIMOX wafer is insufficiently thick for the desired diaphragm thickness, additional layer(s) of epitaxial silicon are grown on the upper side of the silicon crystal until the desired thickness is reached; the same being true for increasing the thickness of the silicon substrate. If having reduced thickness areas for the 'hinge' on both sides of the diaphragm are desired, a SIMOX wafer having an intermediate, silicon dioxide layer on both the 'bottom' and the 'top' of the wafer is used, with each layer serving as an etch stop on its respective side, with the then exposed portions of the silicon dioxide layers thereafter being removed, leaving flanking, alternating, silicon 'hinge' bridges (90a/90b; FIG. 5A-C).