Thermographic sensor with thermo-couples on a suspended grid and processing circuits in frames thereof

Patent metadata

Field	Value
Publication number	US-11725990-B2
Application number	US-202117537086-A
Country	US
Kind code	B2
Filing date	Nov 29, 2021
Priority date	Nov 30, 2020
Publication date	Aug 15, 2023
Grant date	Aug 15, 2023

Abstract

A thermographic sensor is proposed. The thermographic sensor includes a plurality of sensing elements each comprising at least one thermo-couple. The thermographic sensor is integrated on a semiconductor on insulator body that is patterned to define a grid suspended from a substrate; for each sensing element, the grid has a frame with the cold joint of the thermo-couple, a plate with the hot joint of the thermo-couple and one or more arms sustaining the plate from the frame. The frames include one or more conductive layers of thermally conductive material for thermally equalizing the cold joints with the substrate. Moreover, each sensing element may also include a processing circuit for the thermo-couple that is integrated on the corresponding frame. A thermographic device including the thermographic sensor and a corresponding signal processing circuit, and a system including one or more thermographic devices are also proposed.

First claim

The invention claimed is:

1. A thermographic sensor for sensing a thermal radiation, the thermographic sensor including a plurality of sensing elements each comprising:
a semiconductor on insulator body including a substrate;
a functional layer and an insulating layer interposed between the substrate and the functional layer, the functional layer and the insulating layer including one or more grids, a grid of the functional layer and the insulating layer suspended from the substrate, the grid including:
a frame, a plate and one or more arms sustaining the plate from the frame, the frame including one or more conductive layers of a thermally conductive material; and

a thermo-couple having a hot joint and a cold joint in the grid, the thermo-couple configured to provide a sensing voltage based on a difference between a temperature of the hot joint and a temperature of the cold joint, the cold joint including a first sensing terminal and a second sensing terminal, the thermo-couple having a first conductor of a first electrically conductive material extending from the first sensing terminal of the cold joint in the frame to the plate through one of the arms and a second conductor of a second electrically conductive material, different from the first electrically conductive material, extending from the second sensing terminal of the cold joint in the frame to the plate through one of the arms, the first conductor and the second conductor being short-circuited at the plate into the hot joint.

2. The thermographic sensor according to claim 1 , wherein each of the sensing elements comprises a processing circuit for the thermo-couple, the processing circuit being integrated on a corresponding frame.

3. The thermographic sensor according to claim 2 , wherein the processing circuit comprises a pre-amplification circuit for pre-amplifying the sensing voltage provided by the thermo-couple.

4. The thermographic sensor according to claim 2 , wherein the processing circuit comprises a selection circuit for selecting the sensing element.

5. The thermographic sensor according to claim 4 , wherein for each sensing element the pre-amplification circuit comprises a pre-amplification transistor having a control terminal, a first conduction terminal and a second conduction terminal, the control terminal of the pre-amplification transistor being coupled with the first sensing terminal of the thermo-couple, and wherein the selection circuit comprises a selection transistor having a control terminal, a first conduction terminal and second conduction terminal, the first conduction terminal of the selection transistor being coupled with the second conduction terminal of the pre-amplification transistor.

6. The thermographic sensor according to claim 5 , wherein the sensing elements are arranged in an array with a plurality of rows and a plurality of columns, the thermographic sensor comprising corresponding column selection lines coupled with the control terminals of the selection transistors of the columns, corresponding row selection lines coupled with the first conduction terminals of the pre-amplification transistors of the rows, and corresponding sensing lines coupled with the second conduction terminals of the selection transistors of the columns.

7. The thermographic sensor according to claim 1 , wherein the thermographic sensor comprises a first semiconductor body and a second semiconductor body, the first semiconductor body includes a first cavity, the semiconductor on insulator body at the grid includes a second cavity, the first cavity corresponding to the second cavity, the first semiconductor body and the second semiconductor body being bonded to the semiconductor on insulator body to form a vacuum-sealed structure containing the plurality of sensing elements.

8. The thermographic sensor according to claim 7 , wherein the semiconductor on insulator body comprises an absorption layer for absorbing infrared radiations.

9. The thermographic sensor according to claim 7 , wherein the second semiconductor body comprises a vacuum getter for improving a vacuum of the vacuum-sealed structure.

10. The thermographic sensor according to claim 1 , wherein the one or more conductive layers of the frames thermally equalize the cold joint with the substrate.

11. A sensor, comprising:
a first body including a membrane on a first surface of the first body and a first cavity in the first body and below the membrane, the membrane including a frame portion, a plate portion, a first arm portion coupling the plate portion to the frame portion, and a first conductive track extending from a first point on the frame portion to a second point on the plate portion through the first arm portion;
a second body coupled to the first body by the first surface of the first body, the second body having a second cavity facing the membrane; and
a third body coupled to the first body by a second surface of the first body, the second surface opposite to the first surface.

12. The sensor according to claim 11 , wherein the first cavity extends into the third body.

13. The sensor according to claim 11 , comprising a getter film on the first cavity.

14. The sensor according to claim 11 , comprising an absorption layer on the membrane.

15. The sensor according to claim 11 , wherein the first body includes a second arm portion coupling the plate portion to the frame portion and a second conductive track extending from a third point on the frame portion to the second point on the plate portion through the second arm portion.

16. The sensor according to claim 15 , wherein the first conductive track and the second conductive track form a P-N junction.

17. The sensor according to claim 16 , wherein the first conductive track includes P+ polysilicon and the second conductive track includes N+ polysilicon.

18. A thermographic device comprising:
a thermographic sensor configured to provide an electrical signal indicative of thermal radiation; and
a signal processing circuit being coupled with the thermographic sensor configured to process the electrical signal,
wherein the thermographic sensor includes:
a first body including a membrane on a first surface of the first body and a first cavity in the first body and below the membrane, the membrane including a frame portion, a plate portion, a first arm portion coupling the plate portion to the frame portion, and a first conductive track extending from a first point on the frame portion to a second point on the plate portion through the first arm portion; and
a second body coupled to the first body by the first surface of the first body, the second body having a second cavity facing the membrane.

19. The device according to claim 18 , wherein the first body includes a second arm portion coupling the plate portion to the frame portion and a second conductive track extending from a third point on the frame portion to the second point on the plate portion through the second arm portion.

20. The device according to claim 19 , wherein the first conductive track and the second conductive track form a P-N junction.

Assignees

• St Microelectronics Srl

Inventors

• Castagna Maria Eloisa
• Bruno Giuseppe

Classifications

• H04N23/23

  from thermal infrared radiation · CPC title

• H10F39/193

  Infrared image sensors · CPC title

• G01J5/16 Primary

  Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables · CPC title

• G01J5/20

  using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices · CPC title

• H01L27/14669

  Electricity · mapped topic