Polysilicon Fluid Sensor with Evanescent Field Waveguide
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Solution Overview
Problem
There is a need for gas sensors that can be produced cost-effectively while maintaining or improving reliability and sensitivity, particularly for monitoring air quality and gas composition, as existing optical gas sensors are often bulky and require extensive fabrication processes.
Innovation Solution
A fluid sensor design featuring a substrate with a thermal radiation emitter, optical filter structure, waveguide, and thermal radiation detector, utilizing semiconductor materials and CMOS processes to emit and guide broadband thermal radiation with an evanescent field component for interaction with target fluids, allowing for sensitive detection with reduced fabrication requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical gas sensors are used, then detection sensitivity is achieved, but device size becomes bulky and fabrication complexity increases
Solution Approach 1:
The patent merges the light source, optical filter, waveguide, and detector into a single integrated sensor device. The thermal radiation emitter is formed on the same substrate as the detector, with the optical filter and waveguide structures connecting them in a compact arrangement, eliminating the need for separate components and reducing overall device volume while maintaining detection sensitivity.
Solution Approach 2:
The patent transitions from a three-dimensional bulk optical path to a two-dimensional planar waveguide structure. The evanescent field extends perpendicular to the waveguide plane, enabling interaction with gases in the third dimension while keeping the device footprint small in the plane, thus reducing device size without compromising detection capability.
2Measurement precision
If traditional optical gas sensors are used, then detection sensitivity is achieved, but fabrication requirements become extensive and costly
Solution Approach 1:
The patent employs polysilicon material that serves multiple functions: as the thermal radiation emitter, as the optical filter structure, as the waveguide material, and as the detector material. This multi-functionality reduces the number of different materials and fabrication processes required, simplifying manufacturing while maintaining detection sensitivity through the material's inherent optical and thermal properties.
Solution Approach 2:
The patent utilizes the temperature-dependent optical properties of polysilicon to achieve wavelength-selective filtering and radiation emission. By controlling the doping concentration and thermal characteristics of the polysilicon, the device achieves sensitive gas detection without requiring complex additional filtering or modulation components, thereby reducing fabrication complexity.
3Volume of moving object
If compact sensor design is implemented, then device size is reduced, but maintaining sensitivity and reliability becomes challenging
Solution Approach 1:
By integrating all functional components on a single substrate, the patent eliminates interfaces and connections between separate components that could introduce failure points. The merged design reduces the number of assembly steps and potential misalignments, thereby enhancing reliability while achieving compact dimensions.
Solution Approach 2:
The patent uses polysilicon as a composite material system that combines thermal emission, optical filtering, waveguiding, and detection functions. This composite approach ensures consistent performance across all functions using a single material platform, reducing variability and improving manufacturing yield and device reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor achieves efficient detection of target gases or liquids with a compact footprint, maintaining sensitivity and reliability through the use of a CMOS-based, polysilicon material construction and evanescent field interaction, enabling cost-effective production and small size.
Implementation Method 1
a thermal radiation emitter (120) on the first main surface region (110-A) of the substrate, wherein the thermal radiation emitter comprises a semiconductor strip (122) having a main emission surface region (122-C) for emitting a broadband thermal radiation (R) in a main radiation emission direction (x)
Implementation Method 2
an optical filter structure (130) on the first main surface region (110-A) of the substrate, wherein the optical filter structure comprises a semiconductor material and is configured to filter the broadband thermal radiation (R) emitted by the thermal radiation emitter (120) and to provide a filtered thermal radiation (Ro) having a center wavelength λo
Implementation Method 3
a waveguide (140) on the first main surface region (110-A) of the substrate, wherein the waveguide comprises a semiconductor material and is configured to guide the filtered thermal radiation (Ro) having the center wavelength λo
Implementation Method 4
wherein the guided thermal radiation comprises an evanescent field component for interacting with the surrounding atmosphere (10) comprising a target fluid
Implementation Method 5
a thermal radiation detector (150) on the first main surface region (110-A) of the substrate, wherein the thermal radiation detector is configured to provide an detector output signal (SOUT) based on a radiation strength of the filtered thermal radiation (Ro) received from the waveguide (140)
Data Source
AI summary
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.