Hinged MEMS diaphragm and method of manufacture therof
First Claim
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.
2 Assignments
0 Petitions
Accused Products
Abstract
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.
286 Citations
24 Claims
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1. A method of forming a micromechanical structure, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of forming a micromechanical structure, comprising:
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forming at least one trench having walls in a surface of a substrate during a first etch; forming a sacrificial oxide layer on the surface of the substrate and the walls of the at least one trench; depositing a polysilicon layer over the sacrificial oxide layer, extending onto the walls of the at least one trench; defining at least one supporting portion from the polysilicon layer in a second etch, by removing at least a portion of the polysilicon layer overlying portions of the at least one trench, while preserving the polysilicon layer on the walls of the at least one trench; backside etching the substrate to form a through hole to the sacrificial oxide layer beneath the at least one supporting portion; and removing at least a portion of the sacrificial oxide layer, while preserving a portion of the polysilicon layer spaced from the surface of the substrate by a fluid space formed where the sacrificial oxide layer is removed, wherein at least a portion of the sacrificial layer on the walls of the at least one trench is removed subsequent to removal of a portion of the sacrificial layer on the surface of the substrate, the formed micromechanical structure comprising; the substrate having a through hole; a residual portion of the sacrificial oxide layer peripheral to the through hole formed on the substrate; and the polysilicon layer overlying the through hole, patterned to have; a planar portion; the at least one supporting portion corresponding to the at least one trench, connecting the planar portion to a portion of the polysilicon layer on the residual portion of the sacrificial oxide layer peripheral to the through hole, the at least one supporting portion having a depth greater than a depth of the planar portion. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A micromechanical structure, comprising a substrate having a through hole;
- a residual portion of a sacrificial oxide layer peripheral to the through hole formed on the substrate; and
a polysilicon layer overlying the through hole, patterned to have;
(a) a planar portion;
(b) at least one supporting portion connecting the planar portion to a portion of the polysilicon layer on the residual portion of the sacrificial oxide layer peripheral to the through hole;
(c) a first pattern of polysilicon stiffeners formed extending beneath the planar portion overlying the through hole, configured to stiffen the planar portion; and
(d) a second pattern of polysilicon ribs selectively disposed surrounding the at least one supporting portion, attached near a periphery of the planar portion, wherein the polysilicon ribs extend from the planar portion to a depth beyond a depth of the polysilicon stiffeners, and extend laterally beyond an edge of the planar portion, formed by a method comprising;forming at least one trench having walls in a surface of the substrate during a first etch; forming the sacrificial oxide layer on the surface of the substrate and the walls of the at least one trench; depositing the polysilicon layer over the sacrificial oxide layer, extending onto the walls of the at least one trench; defining the at least one supporting portion from the polysilicon layer in a second etch, by removing at least a portion of the polysilicon layer overlying portions of the at least one trench, while preserving the polysilicon layer on the walls of the at least one trench; forming a through hole beneath the at least one supporting portion; and removing at least a portion of the sacrificial oxide layer, while preserving a portion of the polysilicon layer spaced from the surface of the substrate by a fluid space formed where the sacrificial oxide layer is removed, wherein at least a portion of the sacrificial layer on the walls of the at least one trench is removed subsequent to removal of a portion of the sacrificial layer on the surface of the substrate.
- a residual portion of a sacrificial oxide layer peripheral to the through hole formed on the substrate; and
Specification