Fluid sensor including an optical filter and a waveguide, and method for manufacturing the fluid sensor

Patent metadata

Field	Value
Publication number	US-11506599-B2
Application number	US-202016829364-A
Country	US
Kind code	B2
Filing date	Mar 25, 2020
Priority date	Mar 27, 2019
Publication date	Nov 22, 2022
Grant date	Nov 22, 2022

Abstract

A fluid sensor includes a substrate having a top main surface region, wherein the top main surface region of the substrate forms a common system plane of the fluid sensor, a thermal radiation emitter on the top main surface region of the substrate, an optical filter structure on the top main surface region of the substrate, a waveguide on the main top surface region of the substrate, and a thermal radiation detector on the top main surface region of the substrate, wherein the thermal radiation detector provides a detector output signal based on a radiation strength of the filtered thermal radiation received from the waveguide.

First claim

What is claimed is:

1. A fluid sensor, comprising:
a substrate having a top main surface region, wherein the top main surface region of the substrate forms a common system plane of the fluid sensor;
a thermal radiation emitter on the top main surface region of the substrate, wherein the thermal radiation emitter comprises a semiconductor strip having a main emission surface region for emitting a broadband thermal radiation in a main radiation emission direction parallel to the system plane;
an optical filter structure on the top main surface region of the substrate, wherein the optical filter structure comprises a semiconductor material and is configured to filter the broadband thermal radiation emitted by the thermal radiation emitter and to provide a filtered thermal radiation having a center wavelength λ o ;
a waveguide on the main top surface region of the substrate, wherein the waveguide comprises a semiconductor material and is configured to guide the filtered thermal radiation having the center wavelength λ o , wherein the guided thermal radiation comprises an evanescent field component for interacting with a surrounding atmosphere comprising a target fluid; and
a thermal radiation detector on the top main surface region of the substrate, wherein the thermal radiation detector is configured to provide an detector output signal based on a radiation strength of the filtered thermal radiation received from the waveguide.

2. The fluid sensor of claim 1 , further comprising:
an in-coupling structure on the top main surface region of the substrate, wherein the in-coupling structure comprises a semiconductor material and is configured to couple the filtered thermal radiation having the center wavelength λ o at least partially into the waveguide.

3. The fluid sensor of claim 2 , wherein the in-coupling structure is part of the optical filter structure or part of the waveguide.

4. The fluid sensor of claim 2 , wherein the in-coupling structure has a tapered shape between the optical filter structure and the waveguide and parallel to the system plane.

5. The fluid sensor of claim 2 , wherein the in-coupling structure is configured to couple a mode of the filtered thermal radiation that propagates in the waveguide with the center wavelengths λ o into the waveguide.

6. The fluid sensor of claim 1 , wherein the thermal radiation emitter comprises a metallic cover layer which at least partially covers the main emission surface region of the semiconductor strip.

7. The fluid sensor of claim 6 , wherein the semiconductor strip comprises a highly doped polysilicon material to form a black body radiator and is configured to have in an actuated condition an operating temperature in a range between 600 and 1000 K, and wherein the thermal radiation emitter is connected to a power source for providing electrical energy to bring the thermal radiation emitter in the actuated condition.

8. The fluid sensor of claim 1 , wherein the optical filter structure is formed as an optical resonator structure having a narrow transmission band with the center wavelength λ o , and wherein the optical filter structure comprises a photonic crystal structure or a Bragg filter structure as wavelength selective optical elements for providing the filtered thermal radiation having the center wavelength λ o .

9. The fluid sensor of claim 8 , wherein the optical filter structure comprises in a plurality of laterally spaced semiconductor strips which are arranged parallel to each other and vertical to the system plane and perpendicular to a thermal radiation propagation direction.

10. The fluid sensor of claim 1 , wherein the waveguide comprises a meander shape in the system plane.

11. The fluid sensor of claim 1 , wherein the waveguide comprises a strip waveguide, a slab waveguide, a slot waveguide or a rib waveguide.

12. The fluid sensor of claim 1 , wherein the interaction of the evanescent field component with the surrounding atmosphere results in a reduction of transmitted thermal radiation due to absorption which is a measure for target fluid concentration in the surrounding atmosphere.

13. The fluid sensor of claim 1 , wherein the thermal radiation detector comprises a pyroelectric temperature sensor, a piezoelectric temperature sensor, a pn junction temperature sensor or a resistive temperature sensor.

14. The fluid sensor of claim 1 , wherein the thermal radiation detector is configured to sense incoming thermal radiation which is a measure of a concentration of the target fluid in the surrounding atmosphere based on evanescent field absorption effected by the target fluid.

15. The fluid sensor of claim 1 , wherein the thermal radiation emitter, the optical filter structure, the waveguide, and the thermal radiation detector comprise a polysilicon material.

16. The fluid sensor of claim 1 , wherein the substrate comprises a cavity vertically below the thermal radiation emitter and/or the thermal radiation detector.

17. A method of manufacturing a fluid sensor, the method comprising:
providing a substrate having a top main surface region, wherein the top main surface region of the substrate forms a common system plane of the fluid sensor;
forming a thermal radiation emitter on the top main surface region of the substrate, wherein the thermal radiation emitter comprises a semiconductor strip having a main emission surface region for emitting a broadband thermal radiation in a main radiation emission direction parallel to the system plane;
forming an optical filter structure on the top main surface region of the substrate, wherein the optical filter structure comprises a semiconductor material and is configured to filter the broadband thermal radiation emitted by the thermal radiation emitter and to provide a filtered thermal radiation having a center wavelength λ o ;
forming a waveguide on the main top surface region of the substrate, wherein the waveguide comprises a semiconductor material and is configured to guide the filtered thermal radiation having the center wavelength λ o , wherein the guided thermal radiation comprises an evanescent field component for interacting with a surrounding atmosphere comprising a target fluid; and
forming a thermal radiation detector on the top main surface region of the substrate, wherein the thermal radiation detector is configured to provide an detector output signal based on a radiation strength of the filtered thermal radiation received from the waveguide.

18. The method of claim 17 , further comprising:
sputtering and structuring a metallic layer for at least partially covering the main emission surface region of the semiconductor strip with the metallic layer.

Assignees

• Infineon Technologies Ag

Inventors

• Grille Thomas
• Consani Cristina
• Irsigler Peter
• Jakoby Bernhard
• Ostermann Thomas Krotscheck
• Puehringer Gerald
• Ranacher Christian
• Tortschanoff Andreas

Classifications

• G01N21/3518 Primary

  Devices using gas filter correlation techniques; Devices using gas pressure modulation techniques · CPC title

• G01N2201/0833

  Fibre array at detector, resolving · CPC title

• G01N2201/0686

  Cold filter; IR filter · CPC title

• G01N21/3504 Primary

  for analysing gases, e.g. multi-gas analysis · CPC title

• G01N21/552

  Attenuated total reflection · CPC title