Thermopile Infrared Sensor With Elevated Radiation Collector
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Solution Overview
Problem
Existing thermopile infrared sensor arrays have a low filling factor due to a small absorber area compared to the pixel area, leading to reduced signal resolution and increased risk of incorrect measurements, especially when operated under normal or reduced pressure without high-vacuum packaging.
Innovation Solution
The design features a radiation collector construction with props and radiation collectors situated above membranes, increasing thermal resistance and mechanical stability, while maintaining a low thermal capacity and high absorption efficiency, allowing for a larger absorber area that spans the cavity in the silicon carrying body, thus enhancing the filling factor and signal sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the absorber area is reduced to a small central membrane region, then the thermal sensitivity is improved, but the filling factor and signal resolution deteriorate
Solution Approach 1:
The absorber is elevated from the planar membrane surface to a three-dimensional radiation collector structure positioned above the membrane. This vertical dimensionality change allows the absorber area to extend laterally beyond the membrane boundaries while maintaining thermal isolation through the supporting webs, thereby increasing the filling factor without compromising thermal sensitivity.
Solution Approach 2:
Thin supporting webs serve as thermal intermediaries connecting the elevated radiation collector to the membrane. These webs provide mechanical support while minimizing thermal conduction, enabling the absorber to be positioned in a location that maximizes area coverage without significantly degrading the thermal gradient necessary for sensitive detection.
2Device complexity
If the sensor operates under normal or reduced pressure, then the device complexity and manufacturing cost are reduced, but the heat conduction through residual gas reduces the temperature difference and sensitivity
Solution Approach 1:
The sensitive detection region is extracted from the gas-filled environment and positioned in the vacuum-evacuated cavity above the membrane. By separating the absorber function from the thermal conduction path through the gas, the sensor can operate effectively under normal or reduced pressure without requiring high-vacuum packaging, as the measurement occurs in the thermally isolated cavity region.
Solution Approach 2:
The device is segmented into distinct functional regions: the vacuum-evacuated cavity containing the membrane and elevated absorber for sensitive detection, and the gas-filled housing region for mechanical support and pressure equalization. This segmentation allows different pressure conditions in different regions, enabling operation without high-vacuum packaging while maintaining sensitivity.
3Area of stationary object
If the absorber area is increased to improve filling factor, then the signal resolution is improved, but the thermal capacity increases and thermal sensitivity decreases
Solution Approach 1:
The radiation collector is designed with non-uniform thickness and material properties, with thinner regions and lower thermal capacity materials positioned in areas that maximize radiation absorption while minimizing thermal mass. This local optimization allows different parts of the absorber to have different thermal characteristics, achieving high filling factor without excessive thermal capacity that would reduce temperature difference.
Solution Approach 2:
By positioning the absorber in the vertical dimension above the membrane rather than expanding it laterally on the membrane surface, the absorber area can be increased without proportionally increasing the thermal capacity. The elevated position allows the absorber to be thermally coupled to the membrane only through thin supporting webs, decoupling area expansion from thermal mass increase.
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 configuration achieves a high thermal resolution and filling factor with a small chip size, enabling cost-effective mass production without the need for complex vacuum packaging, while maintaining high sensitivity and mechanical stability.
Implementation Method 1
The absorption of infrared radiation for the most part takes place in the central region of the membrane
Implementation Method 2
absorbent central region
Implementation Method 3
thermopile infrared sensor structure... thermoelectric sensor element structures
Implementation Method 4
the heat conduction of the residual gas or of the filling gas in the sensor housing reduces the achievable temperature difference
Data Source
AI summary
Thermopile infrared sensor structure with a high filling level in a housing filled with a medium (15), consisting of a carrier substrate (11) which has electrical connections (28, 28′) to the outside and is closed with an optical assembly (13), wherein a sensor chip (14) is applied to the carrier substrate (11) in the housing, which chip has a plurality of thermoelectric sensor element structures (16), the so-called “hot contacts” (10) of which are located on individual diaphragms (3) which are stretched across a respective cavity (9) in a silicon carrying body (24) with good thermal conductivity, wherein the “cold contacts” (25) are located on or in the vicinity of the silicon carrying body (24). The problem addressed by the invention is that of specifying a thermopile infrared array sensor (sensor cell) which, with a small chip size, has a high thermal resolution and a particularly high filling level. This sensor is preferably intended to be operated in gas with a normal pressure or a reduced pressure and is intended to be able to be mass-produced in a cost-effective manner under ultra-high vacuum without complicated technologies for closing the housing. This is achieved by virtue of the fact that a radiation collector structure (17) is located above each individual diaphragm (3) of the sensor element structures (16) which spans a cavity (9).