Gas sensors with contact pads

• US 9,970,914 B1
• Filed: 04/06/2015
• Issued: 05/15/2018
• Est. Priority Date: 04/04/2014
• Status: Active Grant

• Current Assignee: United States of America as represented by the Administrator of NASA
• Original Assignee: United States Administrator of National Aeronautics and Space Administration
• Inventors: Xu, Jennifer, Hunter, Gary W.
• Primary Examiner(s): Tankersley, Blake A
• Application Number:
  US14/679,278
• Time in Patent Office: 1,135 Days
• CPC Class Codes: G01N 27/02 by investigating impedance
• CPC Class Codes: G01N 27/129 Diode type sensors, e.g. gas sensitive Schottky diodes capacitor type sensors G01N27/227; field-effect transistor type sensors G01N27/414
• CPC Class Codes: G01N 33/0036 Specially adapted to detect a particular component all the other sub-groups of G01N33/0004 take precedence
• CPC Class Codes: G01N 33/0047 for organic compounds
• CPC Class Codes: G01N 33/225 Gaseous fuels, e.g. natural gas
• CPC Class Codes: H01L 21/0495 Schottky electrodes
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/47 Schottky barrier electrodes H01L29/435 takes precedence
• CPC Class Codes: H01L 29/6606 the devices being controllable only by variation of the electric current supplied or the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched, e.g. two-terminal devices
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

Systems, methods, and other embodiments associated with gas detecting sensors. According to one embodiment, a gas sensor includes a metal layer, a barrier interlayer, a substrate layer, a first insulating layer, a conduction path, a contact pad, and a second insulating layer. The conduction path connects the metal layer to the contact pad. The second insulating layer prevents diffusion through the contact pad, the conduction path, or the metal layer. The sensor includes a wire bonded electrical connection to the contact pad such that voltage can be determined and/or applied.

Claims

1. A sensor having a plurality of layers, the layers comprising:

a substrate;

a metal layer having a sensing area for detecting atmospheric conditions and a contact area for conveying an electrical readout;

a contact pad for conducting electrical readouts;

a first insulating layer to shield at least a portion of the contact area from atmospheric conditions;

a conduction path disposed through the first insulating layer to connect the contact area of the metal layer to the contact pad; and

a second insulating layer covering a portion of the contact pad where the contact pad meets the conduction path, the covered portion forming an insulated area of the contact pad, and wherein the insulated area prevents direct diffusion through the insulated area to the contact pad, the conduction path, the metal layer, and an exposed area of the contact pad.

2. The sensor of claim 1, wherein:

the first insulating layer is deposited between the metal layer and the contact pad, wherein the contact pad overlaps the contact area of the metal layer and does not overlap the sensing area of the metal layer.

3. The sensor of claim 2, wherein the conduction path has less area than the first insulating layer.

4. The sensor of claim 3, wherein the conduction path is made of a noble metal.

5. The sensor of claim 3, wherein the insulated area is beneath the second insulating layer and prevents diffusion through the contact pad and the conduction path, into the metal layer.

6. The sensor of claim 5, wherein the exposed area of the contact pad is not covered by the second insulating layer and is electrically connected to a wire from which an electrical signal can be determined or applied.

7. The sensor of claim 1, further comprising:

a metal oxide layer to inhibit chemical reactions between the substrate and the metal layer.

8. The sensor of claim 1, wherein the sensor is a Schottky diode, capacitor, or transistor.

9. The sensor of claim 1, wherein the metal layer, having been selected from the group consisting of Pt, Pd, Au, Ir, Ag, Ru, Rh, In, Os, Cr, and Ti or alloy of any two or more of the group, and the substrate, having been made of Silicon Carbide (Sic), forms a diode;

and a PdO_x barrier interlayer is provided between the metal layer and substrate, wherein said PdO_x barrier interlayer is approximately 50 to 200 Angstroms thick.