Sensor for measuring a gas concentration or ion concentration

• US 20020157950A1
• Filed: 04/12/2002
• Published: 10/31/2002
• 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
• Granted Patent: US 6,929,728 B2
• Time in Patent Office: Days
• 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. Sensor for measuring a gas concentration or ion concentration which has a substrate (11) of a first charge carrier type, a drain (3) formed on the substrate of a second charge carrier type, a source (2) of the second charge carrier type 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) being provided between the gate layer and the channel area (4), characterized in that surface profiling (7, 12) is formed between guard ring (1) and channel area (4).

2. Sensor according to claim 1, characterized in that the surface profiling has elevations (7) and depressions (12).

3. Sensor according to claim 2, characterized in that elevations (7) are applied to a surface (15) between an insulating thin layer (13) in the channel area and guard ring (1) by deposition, with depressions (12) formed between them.

4. Sensor according to claim 3, characterized in that elevations (7) are applied as insulating material to one or more insulating layers, preferably thick oxide layers (14).

5. Sensor according to claim 4, characterized in that elevations (7) are formed mainly concentrically between channel area (4) and guard ring (1).

6. Sensor according to claim 5, characterized by the fact that the elevations are uniformly spaced.

7. Sensor according to claim 6, characterized in that the sensitive gate layer is a gas-sensitive gate layer (8).