METHOD FOR MANUFACTURING A SENSOR DEVICE OF A GASEOUS SUBSTANCE OF INTEREST

• US 20120096928A1
• Filed: 10/21/2011
• Published: 04/26/2012
• Est. Priority Date: 10/22/2010
• Status: Active Grant

• Current Assignee: Ea3tech LLC
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Occhipinti, Luigi Giuseppe
• Granted Patent: US 9,006,796 B2
• Time in Patent Office: Days
• US Class Current: 73/31.06
• CPC Class Codes: G01N 27/4141 specially adapted for gases

Abstract

A method manufactures a sensor device for sensing a gaseous substance and includes a thin film transistor, which includes a source electrode, a drain electrode and a gate electrode; and an element sensitive to the gaseous substance. In particular, the method includes: forming a first metallic layer on a substrate; defining and patterning the first metallic layer for realizing the gate electrode; depositing a dielectric layer above the gate electrode; depositing a second metallic layer above the layer of dielectric material, defining and patterning the second metallic layer for realizing the source electrode and the drain electrode, and forming the sensitive element by filling a channel region of the thin film transistor with an active layer sensitive to the gaseous substance.

Claims

1. A method, comprising:

manufacturing a sensor device configured to sense a gaseous substance and including a thin film transistor, which includes a source electrode, a drain electrode;

a gate electrode; and

a sensitive element sensitive to said gaseous substance, said manufacturing including;

forming a first metallic layer on a substrate;

forming said gate electrode by defining and patterning said first metallic layer;

depositing a first dielectric layer above said gate electrode;

depositing a second metallic layer above said first dielectric layer,

forming the source and drain electrodes by defining and patterning said second metallic layer; and

forming said sensitive element by filling a channel region of said thin film transistor with an active layer sensitive to said gaseous substance.

2. A method according to claim 1, wherein said filling step of said channel region realizes as active layer a thin layer of zinc oxide or of a derivative thereof

3. A method according to claim 1, wherein said filling includes forming the active layer of at least one among zinc oxide, ternary derivatives of zinc oxide, and quaternary derivatives of zinc oxide.

4. A method according to claim 1, wherein said filling is performed after defining said source electrode and said drain electrode.

5. A method according to claim 1, wherein depositing the first dielectric layer includes depositing a layer of an organic substance or of a metallic-organic compound.

6. A method according to claim 1, wherein said substrate is silicon covered by a layer that includes at least one of:

silicon oxide;

glass; and

quartz.

7. A method according to claim 1, comprising forming said substrate by depositing a film of naphthalate polyester on a rigid support using a thermal release adhesive paste.

8. A method according to claim 7, comprising, after forming the sensor device, delaminating said film of naphthalate polyester from said rigid support.

9. A method according to claim 1, comprising treating said substrate with oxygen plasma prior to depositing the first metallic layer.

10. A method according to claim 1, comprising treating a surface of said first dielectric layer with oxygen plasma.

11. A method according to claim 1, wherein defining and patterning said first metallic layer also forms a first plurality of circuit interconnections and defining and patterning said second metallic layer also forms a second plurality of circuit interconnections, the method comprising forming holes through said first dielectric layer and forming conductive paths between said first plurality of circuit interconnections and said second plurality of circuit interconnections.

12. A method according to claim 1, wherein forming the sensitive element comprises one of the following:

depositing a thin layer of zinc oxide or of a derivative thereof with low temperature, via sputtering;

depositing a thin layer of zinc oxide or of a derivative thereof with low temperature, via RF magnetron sputtering;

forming thin layer of zinc oxide or of a derivative thereof by depositing a solution of a precursor of zinc oxide or of a derivative thereof and thermally activating the solution; and

forming a thin layer of zinc oxide or of a derivative thereof by depositing solution containing a precursor of zinc oxide or of a derivative thereof suitably dispersed in a polymeric matrix, and thermally activating the solution.

13. A method according to claim 1, comprising encapsulating said sensor device by depositing a second dielectric layer above said thin film transistor.

14. A method according to claim 13, comprising forming an opening through said second dielectric layer in correspondence with said sensitive element of said thin film transistor so as to directly expose said sensitive element to said gaseous substance.

15. A method according to claim 13, wherein said second dielectric layer is of material permeable by said gaseous substance, so as to allow the transport of said gaseous substance to said sensitive element through said second dielectric layer.

16. A sensor device for sensing a gaseous substance, the sensor device comprising:

a thin film transistor integrated on a substrate and including a source electrode, a drain electrode a gate electrode, a first dielectric layer, and a channel region that included a sensitive element, the sensitive element including an active layer sensitive to said gaseous substance.

17. A sensor device according to claim 16, wherein said active layer comprises a thin layer of zinc oxide or of a derivative thereof

18. A sensor device according to claim 16, wherein said active layer comprises zinc oxide nanoparticles and polyaniline nanofibers.

19. A sensor device according to claim 16, wherein said dielectric layer is a layer of an organic substance or of a metallic-organic compound.

20. A sensor device according to claim 16, comprising:

an encapsulating layer encapsulating said thin film transistor and including a second dielectric layer above said thin film transistor.

21. A sensor device according to claim 19, wherein the encapsulating layer includes an opening through said second dielectric layer in correspondence with said sensitive element of said thin film transistor and configured to directly expose said sensitive element to said gaseous substance.

22. A sensor device according to claim 19, wherein said second dielectric layer is of material permeable by said gaseous substance and is configured to allow said gaseous substance to transport to said sensitive element through said second dielectric layer.

23. A sensing system for sensing a gaseous substance, the sensing system comprising:

first and a second voltage reference terminals;

a voltage generator configured to generate an input voltage;

an output terminal suitable for supplying an output signal that is varied depending on whether the gaseous substance is detected;

a sensing transistor and a load transistor coupled to each other between said first and second voltage reference terminal and interconnected in correspondence with said output terminal, said sensing transistor being a thin film transistor that includes a semiconductor channel having an active layer sensitive to said gaseous substance and configured to vary a threshold voltage of said sensing transistor according to an amount of charge entrapped in the active layer as a result of exposure to said gaseous substance.

24. A sensing system according to claim 23, wherein said sensing transistor and said load comprise a CMOS inverter and have respective control terminals coupled to each other and to said voltage generator.

25. A sensing system according to claim 23, wherein said load transistor is a p-type transistor configured to serve as active load.

26. A sensing system according to claim 23, wherein said sensing transistor has a control terminal coupled to said voltage generator and said second load transistor is diode-configured and has a control terminal coupled to said output terminal.

27. A sensing system according to claim 23, wherein said active layer of said sensing transistor comprises a thin layer of zinc oxide or of a derivative thereof.

28. A sensing system according to claim 23, comprising:

an encapsulating layer encapsulating said thin film transistor and including a dielectric layer above said thin film transistor.

29. A sensing system according to claim 28, wherein the encapsulating layer includes an opening through said dielectric layer in correspondence with said active layer of said thin film transistor and configured to directly expose said active layer to said gaseous substance.

30. A sensing system according to claim 28, wherein said dielectric layer is of material permeable to said gaseous substance and is configured to allow said gaseous substance to transport to said active layer through said dielectric layer.