Double-Layer FIR Sensor Absorber for Spectrum and Sensitivity Control

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Solution Overview

Problem

Conventional FIR sensors face challenges in accurately controlling and calibrating the sensing efficiency and frame rate due to the inability to adjust the thickness of the dielectric layer effectively during the CMOS manufacturing process.

Innovation Solution

The FIR sensor is designed with a thinner heat absorption layer and multiple absorption layers, incorporating a silicon nitride layer to enhance absorption efficiency, and a manufacturing method that involves etching sacrificial metal layers to form a double-layer heat absorption structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the dielectric layer thickness is increased to improve heat absorption, then the heat absorption efficiency is improved, but the sensing efficiency and frame rate control become inaccurate

Engineering Contradiction:

Improveheat absorption efficiencyVSAvoidsensing efficiency control

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The heat absorption layer is segmented into multiple layers with different materials (silicon nitride layer and silicon oxide layer) rather than using a single thick dielectric layer. This segmentation allows independent optimization of each layer's thickness and material properties to achieve both high heat absorption efficiency and precise sensing performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite materials by combining silicon nitride and silicon oxide in a multi-layer structure. Each material contributes different thermal and optical properties, enabling the system to achieve superior heat absorption while maintaining controllable sensing characteristics that cannot be achieved with a single material

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If the dielectric layer thickness is decreased to improve sensing efficiency control, then the sensing efficiency and frame rate control are improved, but the heat absorption efficiency deteriorates

Engineering Contradiction:

Improvesensing efficiency controlVSAvoidheat absorption efficiency

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

Instead of using a single thin dielectric layer, the heat absorption function is segmented across multiple layers with different materials. The silicon nitride layer provides high heat absorption efficiency while the silicon oxide layer allows for precise thickness control to maintain sensing performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the material parameters by selecting specific materials (silicon nitride with high heat absorption coefficient) and optimizing their thickness parameters. This allows achieving high heat absorption efficiency without requiring excessive thickness that would compromise sensing control

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single heat absorption layer is used to simplify the structure, then the device complexity is reduced, but the absorbable FIR spectrum is limited

Engineering Contradiction:

Improvestructure simplicityVSAvoidabsorbable FIR spectrum

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The heat absorption function is segmented into multiple layers with different materials (silicon nitride layer and silicon oxide layer), where each layer absorbs different portions of the FIR spectrum. This segmentation expands the overall absorbable spectrum while maintaining a relatively simple layered structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

By using composite materials with different optical and thermal properties, the multi-layer structure achieves broader FIR spectrum absorption. The silicon nitride layer absorbs certain wavelength ranges while the silicon oxide layer absorbs complementary ranges, creating a versatile spectral response

Inventive Principle:

Principle #40Composite materials

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

This design improves heat absorption efficiency and expands the absorbable FIR spectrum, resulting in enhanced heat collection capabilities.

Implementation Method 1

forming a thermopile structure on a substrate

Methodology Applied

Scientific EffectThermopile: Thermopile

Implementation Method 2

forming a double-layer heat absorption layer... expands the absorbable FIR spectrum

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS20260040824A1Manufacturing method of fir sensor with two absorption layers

Publication Date: 2026.02.05 PIXART IMAGING INC

AI summary

There is provided a far infrared (FIR) sensor device including a substrate, a thermopile structure and a heat absorption layer. The thermopile structure is arranged on the substrate. The heat absorption layer covers upon the thermopile structure, wherein the heat absorption layer has a hollow space which is formed by etching a metal layer in the heat absorption layer.