Sensor arrangement

• US 5,685,969 A
• Filed: 09/28/1994
• Issued: 11/11/1997
• Est. Priority Date: 09/28/1993
• Status: Expired due to Fees

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Hoenig, Eckhardt, Buerker, Ulf, Lehmann, Volker
• Primary Examiner(s): Warden, Robert J.
• Assistant Examiner(s): CARRILLO, BIBI SHARIDAN
• Application Number:
  US08/313,884
• Time in Patent Office: 1,140 Days
• Field of Search: 205/674, 205/665, 205/667, 205/666, 205/640, 205/210, 205/157, 205/123, 205/333, 205/229, 422/82.01
• US Class Current: 205/123
• CPC Class Codes: G01N 27/16 caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
• CPC Class Codes: G01N 27/221 by investigating the dielectric properties using microwaves G01N22/00; measuring loss factors or dielectric constants per se G01R27/26

Abstract

A sensor arrangement having a substrate of doped silicon with channels in a principal face, a selective means for detecting a material, the selective means covering the principal face without filling the channels, and a measuring instrument for registering a physical quantity dependent on the influence of a material is provided. A catalytic layer is particularly used as selective means and a temperature sensor is particularly used as measuring instrument. Alternatively, the sensor arrangement is fashioned as a capacitor having a porous cooperating electrode. The channels are preferably produced by electrochemical etching.

Claims

1. A method for manufacturing a sensor arrangement for sensing a material, comprising the steps of:

providing a substrate of n-doped silicon having a principal face;

forming channels in said principal face by electrochemically etching said principal face in a fluoride-containing, acidic electrolyte in contact with said principal face while applying a voltage between said electrolyte and said substrate with said substrate connected as an anode, to set a current density influencing erosion of said principal face by said etching, said channels respectively having channel surfaces;

depositing a catalytic layer on said channel surfaces, without filling said channels, which reacts exothermally with the material to be sensed; and

providing a temperature sensor in temperature-sensing relationship to said catalytic layer to sense a temperature produced by the exothermal reaction of said catalytic layer and said material.

2. Method according to claim 1, wherein said step of providing a substrate of n-doped silicon is further defined by providing a <

100>

wafer.

3. Method according to claim 1, wherein said step of forming channels in said principal face includes illuminating a second principal face of said substrate lying opposite said principal face.

4. Method according to claim 1, wherein said step of forming channels in said principal face includes providing an electrolyte containing 1-50% by weight hydrofluoric acid as said fluoride-containing, acidic electrolyte.

5. Method according to claim 4, wherein said step of forming channels in said principal face includes providing an electrolyte additionally containing an oxidation agent as said fluoride-containing, acidic electrolyte.

6. Method according to claim 1, further comprising the step of:

providing said principal face of said substrate with a surface topology before forming said channels, said surface topology defining an arrangement of said channels.

7. Method according to claim 1, wherein the step of depositing said catalytic layer comprises forming a dielectric layer on said channel surfaces by a process selected from a group consisting of:

thermal oxidation of TiO₂, anodic oxidation of TiO₂, vapor phase deposition of TiO₂, and combined deposition of a sequence of respective layer of SiO₂ and Si₃ N₄ and SiO₂ ; and

forming of a conductive layer on said dielectric layer by vapor phase deposition.

8. A method for manufacturing a sensor arrangement for sensing a material, comprising the steps of:

providing a substrate of n-doped silicon having a principal face;

forming channels in said principal face by electrochemically etching said principal face in a fluoride-containing, acidic electrolyte in contact with said principal face while applying a voltage between said electrolyte and said substrate with said substrate connected as an anode, to set a current density influencing erosion of said principal face by said etching, said channels respectively having channel surfaces;

depositing a dielectric layer on said channel surfaces by a process selected from a group consisting of thermal oxidation of TiS₂, anodic oxidation of TiO₂, vapor phase deposition of TiO₂, and combined deposition of a sequence of respective layers of SiO₂ and Si₃ N₄ and SiO₂, and forming a conductive layer on said dielectric layer by vapor phase deposition, without filling said channels, said conductive layer, said dielectric layer and said substrate forming a capacitor having a capacitance which changes dependent on the material to be sensed; and

providing a thin film coil on said substrate in series with said capacitor to form a resonant circuit having a resonant frequency which changes dependent on said changes in capacitance.

9. Method according to claim 8, wherein said step of providing a substrate of n-doped silicon is further defined by providing a <

100>

wafer.

10. Method according to claim 8, wherein said step of forming channels in said principal face includes illuminating a further principal face of said substrate lying opposite said principal face.

11. Method according to claim 8, wherein said step of forming channels in said principal face includes providing an electrolyte containing 1-50% by weight hydrofluoric acid as said fluoride-containing, acidic electrolyte.

12. Method according to claim 11, wherein said step of forming channels in said principal face includes providing an electrolyte additionally containing an oxidation agent as said fluoride-containing, acidic electrolyte.

13. Method according to claim 8, further comprising the step of:

providing said principal face of said substrate with a surface topology before forming said channels, said surface topology defining an arrangement of said channels.