Thermographic sensor with thermal transistors driven by thermo-couples

Patent metadata

Field	Value
Publication number	US-2025354870-A1
Application number	US-202519282760-A
Country	US
Kind code	A1
Filing date	Jul 28, 2025
Priority date	Nov 30, 2020
Publication date	Nov 20, 2025
Grant date	—

Abstract

A thermographic sensor is proposed. The thermographic sensor includes one or more thermo-couples, each for providing a sensing voltage depending on a difference between a temperature of a hot joint and a temperature of a cold joint of the thermo-couple; the thermographic sensor further comprises one or more sensing transistors, each driven according to the sensing voltages of one or more corresponding thermo-couples for providing a sensing electrical signal depending on its temperature and on the corresponding sensing voltages. 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

1 . A thermographic sensor, comprising:
a body including a membrane on a first surface of the body and a first cavity in the 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 second arm portion coupling the plate portion to the frame portion;
a first conductive track extending from a first joint on the frame portion to a second joint on the plate portion through the first arm portion;
a second conductive track extending from a third joint on the frame portion to the second joint on the plate portion through the second arm portion, the first conductive track and the second conductive track coupled to one another through the second joint;
a transistor on the plate portion, the transistor including a source region, a drain region and a channel region;
a third conductive track extending from a first point on the frame to the source region of the transistor through the first arm portion; and
a fourth conductive track extending from a second point on the frame to the drain region of the transistor through the second arm portion.

2 . The sensor according to claim 1 , wherein the source region, drain region and channel region of the transistor are positioned in a region of the plate portion configured to receive thermal radiation.

3 . The sensor according to claim 1 , wherein the second joint is positioned on a region of the plate portion configured to receive thermal radiation.

4 . The sensor according to claim 1 , comprising a fifth conductive track extending from a third point on the frame to the channel region of the transistor through one of the first arm portion or the second arm portion.

5 . The sensor according to claim 4 , wherein the third portion on the frame is coupled to one of the first joint or the third joint on the frame.

6 . The sensor according to claim 1 , wherein the channel region includes a cellular structure.

7 . The sensor according to claim 1 , wherein the transistor is a thermally insulated MOS transistor.

8 . A thermographic sensor, comprising:
a first body including:
a first membrane and a second membrane on a first surface of the first body, the first membrane including a first thermo-couple and a first thermally insulated MOS transistor, the second membrane including a second thermo-couple and a second thermally insulated MOS transistor; and
a first cavity and a second cavity in the first body and below the first membrane and the second membrane, respectively, the first cavity separated from the second cavity;
a second body coupled to the first body by the first surface of the first body, the second body having a third cavity facing the first membrane and a fourth cavity facing the second membrane, the third cavity separated from the fourth cavity; and a shielding layer on the second body, distal to the first body, and overlapping the fourth cavity, the shielding layer configured to prevent thermal radiation from reaching the second membrane.

9 . The sensor of claim 8 , comprising a third body coupled to the first body by a second surface of the first body, the second surface opposite to the first surface, wherein each of the first cavity and the second cavity extends into the third body.

10 . The sensor according to claim 9 , comprising a comparison circuitry configured to compare an electrical signal of the first thermally insulated MOS transistor and an electrical signal of the second thermally insulated MOS transistor.

11 . A thermographic sensor for sensing a thermal radiation, the thermographic sensor comprising:
a first body including:
a first cavity;
a second cavity;
a first membrane above the first cavity;
a second membrane above the second cavity;
a sensing circuit on the first membrane at the first cavity; and
a reference circuit on the second membrane at the second cavity.

12 . The sensor of claim 11 , comprising:
a second body on the first body, including:
a third cavity, wherein the first membrane is between the first cavity and the third cavity;
a fourth cavity, wherein the second membrane is between the second cavity and the fourth cavity.

13 . The sensor of claim 12 , wherein the second body is substantially transparent to infrared radiation.

14 . The sensor of claim 13 , comprising a shielding element on the second body above the fourth cavity and configured to shield the reference circuit from infrared radiation.

15 . The sensor of claim 14 , comprising a window in the second body separated from the third cavity and the fourth cavity.

16 . The sensor of claim 15 , comprising an I/O contact on the second body in the window.

17 . The sensor of claim 16 , comprising a comparison circuit in the first body electrically coupled to the sensing circuit, the reference circuit, and the comparison circuit.

18 . The sensor of claim 14 , comprising a third body coupled to the second body and separated from the first body by the second body.

19 . The sensor of claim 18 , comprising a first getter on the third body exposed to the first cavity.

20 . The sensor of claim 19 , comprising a second getter on the third body exposed to the second cavity.

Assignees

• St Microelectronics Srl

Inventors

• Bruno Giuseppe
• Vaiana Michele
• Castagna Maria Eloisa
• Recchia Angelo

Classifications

• H10D48/50

  Devices controlled by mechanical forces, e.g. pressure · CPC title

• G01J5/48

  Thermography; Techniques using wholly visual means · CPC title

• G01J5/14 Primary

  Electrical features thereof · CPC title

• G01J5/068

  by controlling parameters other than temperature · CPC title

• G01J5/20

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