FET based humidity sensor with barrier layer protecting gate dielectric

• US 10,585,058 B2
• Filed: 05/12/2017
• Issued: 03/10/2020
• Est. Priority Date: 05/13/2016
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cobianu, Cornel, Stratulat, Alisa, Serban, Bogdan, Buiu, Octavian, Bostan, Cazimir Gabriel, Brezeanu, Mihai, Costea, Stefan Dan, Davis, Richard
• Primary Examiner(s): Fitzgerald, John
• Assistant Examiner(s): Frank, Rodney T
• Application Number:
  US15/594,184
• Publication Number:
  US 20170328855A1
• Time in Patent Office: 1,033 Days
• Field of Search: 7333504
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: G01N 27/4141 specially adapted for gases
• CPC Class Codes: H01L 29/4966 the conductor material next to the insulator being a composite material, e.g. organic material, TiN, MoSi2 H01L29/4908, H01L29/4983 take precedence
• CPC Class Codes: H01L 29/51 Insulating materials associated therewith for MIS structures on thin film semiconductor H01L29/4908

Abstract

An illustrative humidity sensor may include a substrate having a source and a drain, wherein the drain is laterally spaced from the source. A gate stack is provided in the space between the source and the drain to form a transistor. The gate stack may include a gate insulator situated on the substrate to form a gate insulator/substrate interface. The gate stack may further include a barrier layer above the gate insulator. The barrier layer may be configured to act as a barrier to mobile charge, humidity and/or other contaminates, and may help prevent such contaminates from reaching the gate insulator/substrate interface. The gate stack may further include a humidity sensing layer above the barrier layer. The humidity sensing layer, when exposed to humidity, may modulate the conduction channel in the substrate under the gate insulator and between the source and the drain. In some cases, the humidity level may be determined by monitoring the current flowing between the source and drain.

Claims

1. A humidity sensor comprising:

a substrate having a source and a drain, wherein the drain is laterally spaced from the source;

a gate stack comprising;

a gate insulator situated in the space between the source and the drain;

a barrier positioned over the gate insulator;

a sensing polymer positioned over the barrier;

a source electrode electrically coupled to the source;

a drain electrode electrically coupled to the drain;

a porous gate electrode positioned over the sensing polymer; and

a protective porous polymer layer that extends over the porous gate electrode.

2. The humidity sensor of claim 1, wherein:

the substrate comprises silicon;

the gate insulator comprises SiO₂.

3. The humidity sensor of claim 2, wherein the barrier comprises one or more of Ta₂O₅, Al₂O₃, HfO₂ and silicon nitride (Si₃N₄).

4. The humidity sensor of claim 1, wherein the sensing polymer comprises a polyimide.

5. The humidity sensor of claim 1, wherein the sensing polymer comprises a polysulfone.

6. The humidity sensor of claim 1, wherein the sensing polymer comprises at least one of a polyimide and a polysulfone which has been cross-linked using one member of:

2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol;

1,5-pentanediol;

1,10-decanediol; and

1,4-benzenedimethanol.

7. The humidity sensor of claim 1, wherein the sensing polymer comprises a reaction product of a polysulfone with bis(pinacolato)diboron and diterbutylbipyridine in a presence of an iridium catalyst followed by reaction with 4-formyl-4′

-bromo diphenyl in a presence of a palladium catalyst followed by mild oxidation and crosslinking with octofluorohexanediol.

8. The humidity sensor of claim 1, wherein the barrier comprises a metal oxide.

9. The humidity sensor of claim 8, wherein the metal oxide comprises Ta₂O₅, Al₂O₃, or HfO₂.

10. The humidity sensor of claim 1, wherein the barrier comprises silicon nitride (Si₃N₄).

11. The humidity sensor of claim 1, further comprising a passivation layer over a portion of the protective porous polymer layer.

12. The humidity sensor of claim 11, wherein the passivation layer does not extend over at least part of the protective porous polymer layer that is over the porous gate electrode.

13. The humidity sensor of claim 11, wherein the passivation layer comprises SiO₂, Ta₂O₅, Al₂O₃, HfO₂, or silicon nitride (Si₃N₄).

14. A humidity sensor comprising:

a silicon substrate having a source and a drain, wherein the drain is laterally spaced from the source;

a gate stack comprising;

an SiO₂ gate insulator situated in the space between the source and the drain;

a barrier positioned over the SiO₂ gate insulator, the barrier comprising one or more of Ta₂O₅, Al₂O₃, HfO₂ and silicon nitride (Si₃N₄);

a sensing polymer positioned over the barrier, the sensing polymer comprising at least one of a polyimide and a polysulfone which has been cross-linked using one member of;

2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol;

1,5-pentanediol;

1,10-decanediol;

1,4-benzenedimethanol;

a source electrode electrically coupled to the source;

a drain electrode electrically coupled to the drain;

a porous gate electrode positioned over the sensing polymer; and

a protective porous polymer layer that extends over the porous gate electrode.

15. The humidity sensor of claim 14, further comprising a passivation layer over a portion of the protective porous polymer layer.

16. The humidity sensor of claim 15, wherein the passivation layer does not extend over at least part of the protective porous polymer layer that is over the porous gate electrode.

17. The humidity sensor of claim 15, wherein the passivation layer comprises SiO₂, Ta₂O₅, Al₂O₃, HfO₂, or silicon nitride (Si₃N₄).

18. The humidity sensor of claim 14, further comprising:

a reference field effect transistor formed on the substrate.

19. The humidity sensor of claim 18, wherein the reference field effect transistor comprises:

a second source and a second drain formed on the substrate, wherein the second drain is laterally spaced from the second source;

a second gate stack comprising;

a second gate insulator situated in the space between the second source and the second drain;

a second barrier positioned over the second gate insulator;

a second sensing polymer positioned over the second barrier;

a second source electrode electrically coupled to the second source;

a second drain electrode electrically coupled to the second drain; and

a metal layer positioned over the second sensing polymer.

20. The humidity sensor of claim 14, wherein the metal layer is configured to prevent the second sensing polymer from being exposed to the environment.