Thermopile Sensor Absorption Stack for Infrared Detection
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Solution Overview
Problem
Thermopile sensors require enhanced sensitivity for infrared radiation in the 8-14 micrometer wavelength range to effectively measure body temperature and other thermal applications, but existing designs struggle with efficient absorption and conversion of this radiation into electrical energy.
Innovation Solution
A CMOS semiconductor process is used to form an absorption stack proximate to a thermopile sensor, comprising layers with absorption and reflective characteristics to improve the sensor's ability to absorb and convert long wavelength infrared radiation, including a first layer with reflective properties, a second layer with wave phase shift characteristics, and a third layer with absorption and reflective properties, optimized for the 8-14 micrometer wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a simple single-layer absorption structure is used, then the device complexity is low, but the infrared radiation absorption efficiency is insufficient
Solution Approach 1:
The patent employs a multi-layer composite absorption stack structure consisting of alternating layers of materials with different optical properties (e.g., high-refractive-index materials like silicon and low-refractive-index materials like silicon dioxide). This composite structure creates constructive and destructive interference patterns that enhance infrared radiation absorption in the 8-14 micrometer wavelength range, directly resolving the contradiction between absorption efficiency and structural simplicity.
Solution Approach 2:
The invention transitions from a single-layer planar absorption structure to a multi-layer stacked configuration, adding the dimension of layering. Each layer is designed with specific thicknesses (typically quarter-wavelength thicknesses) to create optical interference effects that maximize absorption. This dimensional change from one layer to multiple layers enables superior infrared absorption while maintaining a relatively compact and manufacturable structure.
2Measurement precision
If conventional absorption structures are used, then the manufacturing process is simple, but the sensitivity for 8-14 micrometer infrared radiation is insufficient
Solution Approach 1:
The patent optimizes specific parameters of the absorption stack, including layer thicknesses (typically designed as quarter-wavelength thicknesses of approximately 7-10 micrometers for the 8-14 micrometer infrared range), material refractive indices, and layer sequences. These parameter changes are tailored to maximize absorption of long-wavelength infrared radiation corresponding to body temperature measurements, thereby enhancing measurement sensitivity while remaining compatible with standard semiconductor manufacturing processes.
Solution Approach 2:
The absorption stack is segmented into multiple discrete layers, each with specific functions. Some layers are designed for maximum absorption, others for reflection, and others for thermal isolation. This segmentation allows each layer to be independently optimized for its specific function while being fabricated using standard CMOS processes, thus achieving high sensitivity without excessive manufacturing complexity.
3Power
If a multi-layer absorption stack is formed, then the infrared radiation conversion efficiency is enhanced, but the manufacturing process complexity increases
Solution Approach 1:
The absorption stack is designed to perform multiple functions simultaneously: maximizing infrared radiation absorption, providing thermal isolation between the thermopile junctions and the substrate, and maintaining mechanical stability. By integrating these multiple functions into a single multi-layer structure that can be fabricated using standard CMOS processes, the patent achieves enhanced conversion efficiency without proportionally increasing manufacturing process complexity.
Solution Approach 2:
The multi-layer absorption stack acts as an intermediary structure between the incident infrared radiation and the thermopile sensor. It is designed to maximize the coupling of infrared energy to the thermopile while minimizing heat loss to the substrate. The alternating high and low refractive index layers create optical interference patterns that enhance absorption, and the structure serves as a thermal barrier, thereby improving overall conversion efficiency through this intermediary function.
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 solution enhances the thermopile sensor's sensitivity and efficiency in converting infrared radiation into electrical energy, improving its performance in medical and other thermal measurement applications by effectively absorbing and converting long wavelength infrared radiation.
Implementation Method 1
The first layer may be a material having absorption and/or reflective characteristics
Implementation Method 2
These sensors may utilize several thermocouples to generate an output voltage proportional to a local temperature difference
Implementation Method 3
The third layer may be a material having a reflective characteristic
Data Source
AI summary
Techniques are described to form an absorption stack proximate to a thermopile sensor. In one or more implementations, a thermopile sensor is formed proximate to a semiconductor wafer. An absorption stack is formed proximate to the semiconductor wafer and includes a first layer, a second layer, and a third layer. The first layer may be a material having absorption and/or reflective characteristics. The second layer may be a material having wave phase shift characteristic characteristics. The third layer may be a material having a reflective characteristic.