Hinged MEMS diaphragm and method of manufacture therof

摘要

A micromechanical structure, comprising a substrate having a through hole; a residual portion of a sacrificial oxide layer peripheral to the hole; and a polysilicon layer overlying the hole, patterned to have a planar portion; a supporting portion connecting the planar portion to polysilicon on the residual portion; polysilicon stiffeners formed extending beneath the planar portion overlying the hole; and polysilicon ribs surrounding the supporting portion, attached near a periphery of the planar portion. The polysilicon ribs extend to a depth beyond the stiffeners, and extend laterally beyond an edge of the planar portion. The polysilicon ribs are released from the substrate during manufacturing after the planar region, and reduce stress on the supporting portion.

主权项

1. A method of forming a micromechanical structure, comprising:
etching at least one trench into a substrate; forming a sacrificial layer on the substrate and walls of the at least one trench; depositing a structural layer over the sacrificial layer, extending into the at least one trench; etching a peripheral boundary of a structure formed from the structural layer, wherein at least a portion of the structural layer overlying portions of the at least one trench is removed, and at least a portion of the structural layer extending into the at least one trench is preserved at the peripheral boundary, to thereby define a supporting member which extends across the peripheral boundary; etching a void through the substrate from beneath the structure in a rear etch step, the rear etch step exposing the sacrificial layer having higher residual compressive stresses than the structural layer; and removing at least a portion of the sacrificial layer, while preserving a portion of the structural layer over the removed at least a portion of the sacrificial layer, to create a fluid space separating the at least a portion of the sacrificial layer from the substrate, wherein at least a portion of the sacrificial layer formed on the walls of the at least one trench at the peripheral boundary is removed subsequent to removal of the portion of the sacrificial layer on the substrate beneath the structural layer not on the walls of the at least one trench at the peripheral boundary.