Sensor for measuring a gas concentration or ion concentration

• US 6,929,728 B2
• Filed: 04/12/2002
• Issued: 08/16/2005
• Est. Priority Date: 04/12/2001
• Status: Active Grant

• Current Assignee: Tdk-Micronas Gmbh (TDK Corporation)
• Original Assignee: Micronas Gmbh (TDK Corporation)
• Inventors: Frerichs, Heinz-Peter
• Primary Examiner(s): Olsen, Kaj K.
• Application Number:
  US10/121,935
• Publication Number:
  US 20020157950A1
• Time in Patent Office: 1,222 Days
• Field of Search: 204/416, 204/431, 422/82.03, 257/253
• US Class Current: 204/416
• CPC Class Codes: G01N 27/4143 Air gap between gate and channel, i.e. suspended gate [SG] FETs work function measurement per se G01N27/002

Abstract

The invention relates to a sensor for measuring a gas concentration or ion concentration which has a substrate (11), a drain (3) formed on the substrate, a source (2) formed on the substrate, a channel area (4) of the substrate located between drain (3) and source (2), a conductive guard ring (1) located outside the channel area, and a sensitive gate layer (8) whose potential depends on the surrounding gas or ion concentration, with an air gap (10) provided between the gate layer and channel area (4). In order to create a sensor that can be made economically and compactly which nevertheless ensures exact measurement of a change in concentration with time, it is provided that surface profiling (7 and 12) be formed between guard ring (1) and channel area (4).

Claims

1. A sensor for measuring a gas concentration or ion concentration, said sensor comprising:

a substrate of a first charge carrier type, a drain of a second charge carrier type formed on the substrate, a source of the second charge carrier type formed on the substrate, a channel area of the substrate located between the drain and the source, a conductive guard ring located outside the channel area, and a sensitive gate layer whose potential depends on the surrounding gas or ion concentration, with an air gap being provided between the gate layer and the channel area, wherein surface profiling is formed between the guard ring and the channel area, the surface profiling having elevations and depressions, the elevations being applied to a surface between an insulating thin layer in the channel area and the guard ring by deposition with the depressions formed between the elevations, the elevations being applied as insulating material to one or more insulating layers, and wherein the elevations are formed substantially concentrically with respect to the channel area.

2. The sensor as claimed in claim 1, wherein the elevations are uniformly spaced.

3. The sensor as claimed in claim 1, wherein the sensitive gate layer is a gas-sensitive gate layer.

4. The sensor as claimed in claim 1, wherein the one or more insulating layers include at least one thick oxide layer.

5. A sensor for measuring a gas concentration or ion concentration, said sensor comprising:

a substrate of a first charge carrier type;

a drain of a second charge carrier type formed on the substrate;

a source of the second charge carrier type formed on the substrate;

a channel area of the substrate located between the drain and the source;

a conductive guard ring located outside the channel area;

a sensitive gate layer whose potential depends on the surrounding gas or ion concentration;

an air gap provided between the gate layer and the channel area; and

a contoured surface including at least one elevation and at least one depression, the contoured surface being formed between the guard ring and the channel area, wherein the at least one elevation is formed substantially concentrically with respect to the channel area.

6. The sensor as claimed in claim 5, wherein the contoured surface includes a plurality of alternating elevations and depressions.

7. The sensor as claimed in claim 5, wherein the at least one elevation is applied to a surface between an insulating thin layer in the channel area and the guard ring by deposition with the depressions being formed there between.

8. The sensor as claimed in claim 5, wherein the at least one elevation is applied as insulating material to one or more insulating layers.

9. The sensor as claimed in claim 5, wherein the sensor includes a plurality of elevations that are uniformly spaced.

10. A sensor for measuring a gas concentration or ion concentration, said sensor comprising:

a substrate of a first charge carrier type;

a drain of a second charge carrier type formed on the substrate;

a source of the second charge carrier type formed on the substrate;

a channel area of the substrate located between the drain and the source;

a conductive guard ring located outside the channel area;

a sensitive gate layer whose potential depends on the surrounding gas or ion concentration;

an air gap provided between the gate layer and the channel area; and

a contoured surface including a plurality of elevations and a plurality of depressions that are formed between the guard ring and the channel area, wherein the plurality of elevations are substantially concentric with respect to the channel area.