Dual-Layer FIR Sensor Structure for Broader IR Absorption

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Solution Overview

Problem

Conventional FIR sensors face challenges in accurately controlling and calibrating the thickness of the dielectric layer, affecting sensing efficiency and frame rate due to limitations in the CMOS manufacturing process.

Innovation Solution

The FIR sensor is redesigned with a thinner heat absorption layer and multiple layers, incorporating a silicon nitride layer to enhance absorption efficiency, and a manufacturing method involving etching processes to form a hollow space and connect heat absorption layers with a smaller cross-section connection layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the dielectric layer thickness is increased to improve heat absorption, then the heat absorption efficiency is improved, but the frame rate decreases and the sensing efficiency cannot be accurately controlled

Engineering Contradiction:

Improveheat absorption efficiencyVSAvoidframe rate

Core Design Contradiction:

Loss of energyVSProductivity

Solution Approach 1:

The heat absorption layer is divided into multiple discrete layers (first heat absorption layer, second heat absorption layer, third heat absorption layer) with different thicknesses and materials. This segmentation allows independent optimization of each layer's thickness to balance heat absorption efficiency and thermal response time, resolving the contradiction between improved heat absorption and maintained frame rate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the heat absorption structure are assigned different local properties: the first heat absorption layer has a specific thickness optimized for certain wavelengths, the second layer has different thickness for complementary wavelengths, and the third layer provides additional absorption. This local quality variation enables simultaneous optimization of heat absorption across different spectral regions while controlling overall thermal mass for acceptable frame rates.

Inventive Principle:

Principle #3Local quality

2Productivity

If the dielectric layer thickness is decreased to improve frame rate, then the frame rate is improved, but the heat absorption efficiency decreases

Engineering Contradiction:

Improveframe rateVSAvoidheat absorption efficiency

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The heat absorption function is segmented across multiple layers with varying thicknesses. Thinner layers respond faster to thermal changes, while thicker layers provide greater absorption capacity. The combination maintains overall heat absorption efficiency while the thinner portions improve the frame rate response.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structure with different heat absorption layers made of varying materials and thicknesses. This composite approach allows the system to achieve both high heat absorption efficiency (through optimized material composition and total thickness) and improved frame rate (through thinner individual layers and strategic material selection with different thermal properties).

Inventive Principle:

Principle #40Composite materials

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 range is limited

Engineering Contradiction:

Improvestructure complexityVSAvoidabsorbable FIR spectrum range

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The single heat absorption layer is segmented into multiple layers (first, second, and third heat absorption layers) with different thicknesses and material compositions. Each layer is optimized to absorb specific wavelength ranges within the FIR spectrum, collectively expanding the overall absorbable spectrum while maintaining a relatively simple stacked structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses composite material layers with different optical and thermal properties. The first heat absorption layer, second heat absorption layer, and third heat absorption layer are composed of different materials and thicknesses, creating a composite structure that expands the absorbable FIR spectrum range while keeping the overall device complexity manageable through systematic material selection and layer arrangement.

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, enhancing the sensor's heat collection capabilities.

Implementation Method 1

The first heat absorption layer and the second heat absorption layer are connected by a connection layer... improves heat absorption efficiency and expands the absorbable FIR spectrum

Methodology Applied

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

Data Source

PatentUS12484446B2FIR infrared (FIR) sensor with two absorption layers

Publication Date: 2025.11.25 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.