Structure for capacitive balancing of integrated relative humidity sensor

• US 20090108852A1
• Filed: 10/26/2007
• Published: 04/30/2009
• Est. Priority Date: 10/26/2007
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Davis, Richard A., Alimi, Yousef M.
• Granted Patent: US 7,683,636 B2
• Time in Patent Office: Days
• US Class Current: 324/664
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825

Abstract

An improved relative humidity sensor apparatus that provides a more accurate measurement of humidity in the presence of water condensation. A series capacitive sensor includes a thin porous platinum top plate, a humidity sensitive polyimide dielectric, and two metal bottom plates on a semiconductor substrate. The two capacitors can be wired in series such that the metal bottom plates form independent, electrically driven connections. The thin top layer can form a top plate. Changes in humidity affect the humidity sensitive dielectric thereby causing changes in the capacitive value. A P-well layer and a P-plus layer can be added at the perimeter of the substrate to create a path for a parasitic capacitance caused by water condensation to connect to one or more connection nodes, thereby preventing erroneous measurements of humidity in the presence of water condensation.

Claims

1. An improved relative humidity sensor apparatus, comprising:

a semiconductor substrate and a first insulator layer formed on said semiconductor substrate in association with a second insulator layer formed on said first insulator layer;

a P-plus layer and a P-well layer formed on a perimeter of said semiconductor substrate wherein said P-plus layer and said P-well layer create a path for a parasitic capacitance caused by water condensation to connect to at least one node of a sensing capacitor;

a pair of contacts associated with capacitor plates formed on said first insulator layer in association with a pair of capacitor plates formed on said second insulator layer, wherein said pair of capacitor plates are isolated from one another with a space formed therein; and

a humidity sensitive dielectric layer formed on said second insulator layer and said pair of capacitor plates, wherein a relative permittivity of said humidity sensitive layer varies in accordance with a humidity such that a pair of series capacitance additionally varies in accordance with said humidity to thereby provide an increased accurate measurement of said humidity.

2. The apparatus of claim 1 further comprising a porous electrically conductive plate formed on said humidity sensitive dielectric layer, wherein said porous electrically conductive plate forms a common top plate with respect to said pair of capacitive plates.

3. The apparatus of claim 2 further comprising;

a protective layer located on said porous electrically conductive plate, wherein said protective layer protects said common top plate and said humidity sensitive layer.

4. The apparatus of claim 1 wherein said first insulator layer comprises a silicon oxide.

5. The apparatus of claim 1 wherein said second insulator layer comprises a silicon nitride.

6. The apparatus of claim 1 wherein said first insulator layer comprises a silicon oxide and said second insulator layer comprises a silicon nitride.

7. The apparatus of claim 1 further comprising:

a porous electrically conductive plate formed on said humidity sensitive dielectric layer, wherein said porous electrically conductive plate form a common top plate with respect to said pair of capacitive plates; and

a protective layer located on said porous electrically conductive plate, wherein said protective layer protects said common top plate and said humidity sensitive layer.

8. The apparatus of claim 1 further comprising

a porous electrically conductive plate formed on said humidity sensitive dielectric layer, wherein said porous electrically conductive plate form a common top plate with respect to said pair of capacitive plates;

and

a protective layer located on said porous electrically conductive plate, wherein said protective layer protects said common top plate and said humidity sensitive layer, wherein said first insulator layer comprises a silicon oxide and said second insulator layer comprises a silicon nitride.

9. The apparatus of claim 1 wherein said P-plus layer and said P-well layer are fabricated utilizing a standard silicon wafer processing technique.

10. An improved relative humidity sensor apparatus, comprising:

a semiconductor substrate and a first insulator layer formed on said semiconductor substrate in association with a second insulator layer formed on said first insulator layer;

a P-plus layer and a P-well layer formed on a perimeter of said semiconductor substrate wherein said P-plus layer and said P-well layer create a path for a parasitic capacitance caused by water condensation to connect to at least one node of a sensing capacitor;

a pair of contacts associated with capacitor plates formed on said first insulator layer in association with a pair of capacitor plates formed on said second insulator layer, wherein said pair of capacitor plates are isolated from one another with a space formed therein;

a humidity sensitive dielectric layer formed on said second insulator layer and said pair of capacitor plates;

a porous electrically conductive plate formed on said humidity sensitive dielectric layer, wherein said porous electrically conductive plate includes a common top plate with respect to said pair of capacitive plates; and

a protective layer located on said porous electrically conductive plate, wherein said protective layer protects said common top plate and said humidity sensitive layer, wherein a relative permittivity of said humidity sensitive layer varies in accordance with a humidity such that a pair of series capacitance additionally varies in accordance with said humidity to thereby provide an increased accurate measurement of said humidity.

11. The apparatus of claim 10 wherein said first insulator layer comprises a silicon oxide.

12. The apparatus of claim 10 wherein said second insulator layer comprises a silicon nitride.

13. The apparatus of claim 10 wherein said first insulator layer comprises a silicon oxide and said second insulator layer comprises a silicon nitride.

14. A method of forming an improved relative humidity sensor apparatus, comprising:

providing a semiconductor substrate and a first insulator layer formed on said semiconductor substrate in association with a second insulator layer formed on said first insulator layer;

forming a P-plus layer and a P-well formed on a perimeter of said semiconductor substrate wherein said P-plus layer and said P-well layer create a path for a parasitic capacitance caused by water condensation to connect to at least one node of a sensing capacitor;

associating a pair of contacts with capacitor plates formed on said first insulator layer in association with a pair of capacitor plates formed on said second insulator layer, wherein said pair of capacitor plates are isolated from one another with a space formed therein; and

forming a humidity sensitive dielectric layer on said second insulator layer and said pair of capacitor plates, wherein a relative permittivity of said humidity sensitive layer varies in accordance with a humidity such that a pair of series capacitance additionally varies in accordance with said humidity to thereby provide an increased accurate measurement of said humidity.

15. The method of claim 14 further comprising configuring a porous electrically conductive plate on said humidity sensitive dielectric layer, wherein said porous electrically conductive plate includes a common top plate with respect to said pair of capacitive plates.

17. The method of claim 14 wherein said first insulator layer comprises a silicon oxide.

18. The method of claim 14 wherein said second insulator layer comprises a silicon nitride.

19. The method of claim 14 wherein said first insulator layer comprises a silicon oxide and said second insulator layer comprises a silicon nitride.

20. The method of claim 14 further comprising fabricating said P-plus layer and said P-well layer utilizing a standard silicon wafer processing technique.

16. The method of claim 16 further comprising locating a protective layer on said porous electrically conductive plate, wherein said protective layer protects said common top plate and said humidity sensitive layer.