Patent EP0490486A2 successfully refreshed from Google Patents.
EP0490486A2
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EP
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Micromachined differential pressure transducers and method of producing the same
Assignee: Wisconsin Alumni Research Foundation
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Filing: 1991-11-11
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Granted: —
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Expires: 2011-11-11
Abstract
Abstract Microminiature pressure transducers are formed on semiconductor substrates such as silicon and include a membrane (25) which spans a cavity (35) over the substrate (21), with the membrane being mounted to and sealed to the substrate at the peripheral edges of the membrane. The bottom (36) of the cavity forms an overpressure stop to prevent over deflections of the membrane toward the substrate. An overpressure stop (27) formed as a bridge of a material such as nickel extends above the membrane and is spaced therefrom to allow the membrane to deflect freely under normal pressure situations but prevent over deflections. The thickness of the polysilicon membrane and the spacing between the membrane and the overpressure stops is preferably in the range of 10 micrometers or less, and typically in the range of one micrometer. The overpressure stop bridge is formed utilizing deep X-ray lithography to form a well-defined bridge structure. The gap between the membrane and the bottom surface (32) of the bridge is established with a sacrificial layer, such as a polyimide film, which dissolves in a solvent. The transducer is formed utilizing processing techniques which do not affect the performance of the membrane as a pressure sensor and which allow the substrate to have further micromechanical or microelectronic devices formed thereon.
Inventors
- 👤 Henry Guckel
- 👤 Todd R. Christenson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 20:16
CPC Classifications
G; G01; G01L; G01L9/00; G01L9/0041; G01L9/0042; G01L19/00; G01L19/06; G01L19/0618; G01L9/0051; G01L9/0052; G01L9/0055; G01L9/0072; G01L9/0073; H; H04; H04R; H04R19/00; H04R19/005; Y; Y10; Y10S; Y10S430/00; Y10S430/167; Y10S430/168; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49103; Y10T29/4981; Y10T29/49812
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
199 words
A micromachined differential pressure transducer comprising: (a) a substrate having top and bottom sides; (b) a deformable membrane mounted to and sealed at its peripheral edges to the top of the substrate and spaced from the substrate at its central portion to define a cavity which is sealed between the membrane and the substrate, the bottom of the cavity in the substrate being spaced from the membrane to allow normal deflections of the membrane but providing an overpressure stop for membrane deflection toward the substrate to prevent damage to the membrane; (c) at least one channel leading from a remote position in the substrate to the cavity to provide communication therefrom to the cavity; (d) an overpressure stop mounted to the top of the substrate and having a bridge portion spanning the membrane and spaced therefrom to allow normal deflections of the membrane while providing an overpressure stop to prevent displacements of the membrane away from the substrate which would damage the membrane, the spacing between the overpressure stop bridge and the membrane and between the membrane and the bottom of the cavity being less than about 10 micrometers; and (e) means for sensing the deflections of the membrane.
Claim 2
Dependent Claim
14 words
The transducer of Claim 1 wherein the substrate is formed of single crystal silicon.
Claim 3
Dependent Claim
15 words
The transducer of claim 1 or 2, wherein the membrane is formed of polycrystalline silicon.
Claim 4
Dependent Claim
22 words
The transducer of claim 1, 2 or 3, wherein the overpressure stop bridge is formed of a conductive metal, preferably electroplated nickel.
Claim 5
Dependent Claim
59 words
The transducer of claim 4, including a layer of conductive metal on the top surface of the membrane facing the overpressure stop bridge such that the layer of metal on the membrane and the bridge form two plates of a capacitor to provide the means for sensing the deflections of the membrane by changes in capacitance of such capacitor.
Claim 6
Dependent Claim
17 words
The transducer of any preceding claim, wherein the cavity is defined as an indentation in the substrate.
Claim 7
Dependent Claim
35 words
The transducer of claim 6, wherein the indentation has a deep central portion and shallow peripheral portions, and wherein the channel in the substrate is in communication with the shallower peripheral portions of the cavity.
Claim 8
Dependent Claim
28 words
The transducer of any preceding claim, wherein the channels are formed to extend from the bottom side of the substrate through the substrate to communication with the cavity.
Claim 9
Dependent Claim
66 words
The transducer of claim 1, wherein the bridge is formed of a conductive metal and further including a layer of conductive metal formed on the top surface of the membrane facing the bridge such that a capacitor is formed between the metal layer on the membrane and the bridge to provide the means for sensing deflections of the membrane by changes in capacitance of such capacitor.
Claim 10
Dependent Claim
32 words
The transducer of any preceding claim, including piezoresistive resistors formed on the polysilicon membrane to provide means for sensing the deflections in the membrane by changes in the resistance of such resistors.
Claim 11
Dependent Claim
37 words
The transducer of claim 10, when appendant to claim 5, wherein the measurements of membrane displacements made by the change in capacitance and by the change in resistance of the piezoresistors can be correlated with each other.
Claim 12
Dependent Claim
20 words
The transducer of any preceding claim, wherein the membrane has a thickness in the range of 10 micrometers or less.
Claim 13
Dependent Claim
15 words
The transducer of claim 12, wherein the membrane has a thickness of approximately 1 micrometer.
Claim 14
Independent Claim
282 words
A method of making a micromachined differential pressure transducer comprising the steps of: (a) forming a deformable polysilicon membrane over a cavity between the membrane and a substrate, the membrane being sealed to the top side of the substrate at peripheral portions of the membrane to seal off the top surface of the membrane from the cavity; (b) forming at least one channel in the substrate or membrane extending from a position remote to the cavity into communication with the cavity; (c) forming a spacer release layer of hardenable material over the membrane and adjacent to the surface of the membrane which can be dissolved in a liquid which does not affect the diaphragm or the substrate; (d) applying a plating base over the spacer release layer and adjacent substrate, the plating base being formed of a metal; (e) forming a layer of casting material over the plating base to at least the desired thickness of an overpressure stop bridge which is to span over the deformable membrane, the deposited casting material being susceptible to X-rays such that the material exposed to X-rays can be dissolved in a selected solvent; (f) exposing the casting material to X-rays in a desired pattern around and including the area of the deformable membrane; (g) removing the casting material with the solvent in those areas which have been exposed to X-rays while leaving the remaining casting material to define a mold area over the diaphragm and surrounding areas; (h) depositing a solid metal into the mold area; (i) removing the remaining casting material; (j) removing the spacer release layer material to leave the deposited metal as a bridge extending across the space above the deformable membrane.
Claim 15
Dependent Claim
36 words
The method of claim 14, wherein the step of forming at least one channel is carried out by etching a channel in the substrate from the back side of the substrate into communication with the cavity.
Claim 16
Dependent Claim
23 words
The method of claim 14 or 15, wherein the step of depositing a solid material comprises electroplating a metal into the mould area.
Claim 17
Independent Claim
237 words
A method of making a micromachined structure comprising the steps of: (a) forming a sacrificial release layer of material on the surface of a substrate, the material of the sacrificial release layer being dissolvable in a liquid which does not affect the substrate; (b) applying a plating base at least over the sacrificial release layer, the plating base being formed of a metal; (c) forming a layer of casting material over the plating base to at least the desired thickness of a structure to be formed, the deposited casting material being susceptible to X-rays such that the casting material exposed to X-rays can be dissolved in a selected developer solvent; (d) exposing the casting material to X-rays in a desired pattern including at least a part of the area of the plating base; (e) removing the casting material with the developer solvent in those areas which have been exposed to X-rays while leaving the remaining casting material to define a mold area over the plating base; (f) depositing a solid metal into the mold area onto the plating base by electroplating; (g) removing the remaining casting material; (h) removing the plating base in regions where solid metal has not been deposited to allow access to the sacrificial release layer; (i) removing the sacrificial release layer material to leave the deposited metal on the plating base free of the substrate where the sacrificial release layer has been removed.
Claim 18
Dependent Claim
51 words
The method of claim 17, wherein the plating base is applied at least over a portion of the substrate as well as over the sacrificial release layer such that when the sacrificial release layer is removed, a portion of the deposited metal remains on the plating base attached to the substrate.
Claim 19
Independent Claim
19 words
The method of any one of claims 14 to 18, wherein the sacrificial release layer is formed of polyimide.
Claim 20
Independent Claim
26 words
The method of any one of claims 14 to 19, wherein the plating base includes a thin layer of titanium and a thin layer of nickel.
Claim 21
Independent Claim
21 words
The method of any one of claims 14 to 20, wherein the casting material is polymethyl methacrylate, preferably cross-linked polymethyl methacrylate.
Claim 22
Independent Claim
18 words
The method of any one of claims 14 to 21, wherein the metal which is plated is nickel.
Claim 23
Independent Claim
24 words
The method of any one of claims 14 to 22, wherein the release layer is deposited to a thickness of 10 micrometers or less.
Claim 24
Dependent Claim
18 words
The method of claim 23, wherein the release layer is deposited to a thickness of approximately 1 micrometer.
Claim 25
Independent Claim
31 words
The method of any one of claims 14 to 24, wherein the step of exposing the casting material to X-rays is carried out by exposing the casting material to synchrontron radiation.
References Cited (Backward Citations)
No citation records indexed.
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