Thermal liquid flow sensor and method of forming same

• US 20070186643A1
• Filed: 02/10/2006
• Published: 08/16/2007
• Est. Priority Date: 02/10/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bonne, Ulrich, Speldrich, Jamie, Gehman, Richard, Murray, Martin, Beck, Scott
• Granted Patent: US 7,892,488 B2
• Time in Patent Office: Days
• US Class Current: 73/204.260
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 15/006 characterised by the use of a particular material, e.g. anti-corrosive material G01F15/14 takes precedence

Abstract

A thermal liquid flow sensor and method of forming same. The sensor has a substrate and one or more sensing elements, disposed on the substrate, for sensing a property of a liquid. The liquid flow sensor, which can be for example a microsensor having a microbrick® structure, has a hydrophilic layer which is disposed on the substrate and covers the sensing element(s). The hydrophilic layer is preferably formed from a spin on glass material, such as for example a silicate or phosphosilicate. A silicon nitride layer can be disposed on the sensing element(s) and interpose the substrate and the hydrophilic layer. The silicon nitride layer can be oxidized, for example, by means of plasma oxidation or oxygen ion implantation so to form the hydrophilic layer thereon. A variety of other hydrophilic compounds can be utilized to form the hydrophilic layer such as, gold, palladium and diamond like carbon.

Claims

1. A liquid flow sensor, comprising:

a substrate;

at least one sensing element, disposed on said substrate, for sensing a property of a liquid; and

a hydrophilic layer, disposed on said substrate, covering said at least one said sensing element.

2. The sensor of claim 1, wherein said hydrophilic layer comprises a spin on glass material.

3. The sensor of claim 2, wherein said spin on glass material comprises a silicate or phosphosilicate.

4. The sensor of claim 1, further comprising a protective layer encapsulating or disposed on said at least one sensing element, said protective layer interposing said substrate and said hydrophilic layer.

5. The sensor of claim 4, wherein said protective layer comprises silicon nitride (SiNx) layer.

6. The sensor of claim 5, wherein said silicon nitride layer is oxidized so as to form said hydrophilic layer thereon.

7. The liquid flow sensor of claim 1, wherein said hydrophilic layer is formed from at least one material selected from a group comprising:

modified diamond-like carbon, zeolite, silanol group bearing silicone resin and titanium oxide, titania and a disperse phase constituted of silica or alumina, oligomer reactive with silanol, or polymer reactive with silanol, or hydrophilic metal.

8. The liquid flow sensor of claim 1, wherein said hydrophilic layer is formed from at least one material selected from a group comprising:

fluorine-containing polymer having a hydrophilic functional group, polyvinylprollidonenpolyurethane interpolymer, polyacrylic acid polymer or acrylamide-acrylic acid copolymer.

9. The liquid flow sensor of claim 8, wherein said hydrophilic functional group comprises at least one of hydroxyl, carboxyl, salt of carboxylic acid, sulfonic acid group or salt of sulfonic acid.

10. A thermal liquid flow sensor, comprising:

a microsensor die comprising;

a substrate,

a heater disposed on said substrate;

at least one pair of temperature sensing elements disposed on said substrate; and

a hydrophilic layer, disposed on a surface region of said sensor die, said hydrophilic layer covering said at least one said temperature sensing elements and/or said heater.

11. The sensor of claim 10, wherein said sensor die is fabricated in the form of a microbrick structure providing a substantially solid structure beneath said temperature and heating elements.

12. The sensor of claim 10, wherein said hydrophilic layer comprises a hydrophilic metal.

14. The sensor of claim 10, further comprising a silicon nitride (SiNx) layer encapsulating or disposed on said temperature sensing element(s), said silicon nitride layer interposing said substrate and said hydrophilic layer.

15. The sensor of claim 10, wherein said hydrophilic layer comprises a spin on glass material.

13. The sensor of claim 13, wherein said hydrophilic metal comprises gold (Au) or palladium (Pd).

16. A method of manufacturing a thermal liquid flow sensor comprising providing a substrate;

forming at least one pair of temperature sensing elements on said substrate;

forming a heating element on said substrate between said at least one pair of temperature sensing elements; and

forming a hydrophilic layer on said substrate, said hydrophilic layer covering at least said temperature sensing elements and/or said heating elements.

17. The method of claim 17, wherein forming said hydrophilic layer comprises forming a spin on glass material on said substrate by means of spin on glass deposition.

18. The method of claim 17, further comprising forming a silicon nitride layer on said substrate so as to cover said temperature sensing and heating elements, said silicon nitride layer interposing said hydrophilic layer and said substrate.

19. The method of claim 19, wherein forming said hydrophilic layer comprises oxidizing the surface of said silicon nitride layer.