Bolometric Membrane Shell Core Architecture Noise Reduction
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Solution Overview
Problem
Micro bolometer detectors face limitations in achieving high absorption efficiency and signal-to-noise ratio (SNR) due to the sharing of space between metallized zones for radiation absorption and transducer material, leading to increased low-frequency noise and reduced performance, especially in small pixel sizes.
Innovation Solution
A bolometric detection device with a membrane architecture featuring a shell and core structure, where the core has a lower resistivity than the shell, allowing for reduced low-frequency noise and compatibility with aggressive sacrificial layer release chemistry, and the shell is made inert to chemical attacks, enabling high-performance manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the membrane uses a single transducer material layer, then the manufacturing process is simple, but the signal-to-noise ratio is reduced due to increased low-frequency noise
Solution Approach 1:
The transducer material is segmented into multiple layers with different resistivities. The first layer has higher resistivity and the second layer has lower resistivity, allowing each layer to contribute differently to noise reduction while maintaining manufacturability through sequential deposition processes
Solution Approach 2:
The membrane uses a composite structure combining two different transducer materials with distinct electrical resistivities. This composite approach enables optimization of both noise performance and manufacturing compatibility, as each material can be selected for specific properties
2Reliability
If the membrane uses material with low resistivity to reduce noise, then the signal-to-noise ratio improves, but the compatibility with aggressive sacrificial layer release chemistry is lost
Solution Approach 1:
The transducer structure is divided into two functional segments: an outer layer made of chemically inert material for manufacturing compatibility, and an inner layer made of low-resistivity material for noise reduction. This segmentation allows each layer to fulfill its specific function without compromise
Solution Approach 2:
Different regions of the transducer have different material properties optimized for their specific functions. The outer surface facing the sacrificial layer release process uses inert material, while the interior region contributes to noise reduction through low resistivity material
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 significantly enhances the SNR and absorption efficiency by reducing low-frequency noise and maintaining manufacturing compatibility with aggressive chemical processes, particularly beneficial for small pixel sizes.
Implementation Method 1
Each membrane heats up by absorbing the incident radiation coming from the observed thermal scene
Implementation Method 2
notably comprises a layer of a 'transducer' material whose electrical property, the resistivity in the case of micro bolometers, changes significantly when the temperature changes, generating for example a variation in current under constant voltage polarization
Data Source
Figure 1~3
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Figure 7~8
AI summary
A bolometric sensing device comprises: - a substrate (14) including a readout circuit; - an array of elementary detectors each comprising a membrane (12) suspended above the substrate (14) and connected to the readout circuit by at least two electrical conductors (16, 18), said membrane comprising two electrically conductive electrodes (20, 22) respectively connected to the two electrical conductors, and a volume of transducer material (24) electrically connecting the two electrodes, in which the readout circuit is configured to apply an electrical stimulus between the two electrodes (20, 22) of the membrane (12) and to form an electrical signal in response to said application.Said volume comprises: - a volume (34, 38, 40) of a first transducer material electrically connecting the two electrodes (20, 22) of the membrane (12) and forming walls of a closed enclosure (42) in which each of the electrodes (20, 22) is housed at least partially; and - a volume (44) of a second transducer material electrically connecting the two electrodes (20, 22) and housed in the enclosure (42), the electrical resistivity of the second material being lower than the electrical resistivity of the first material; and the two transducer materials having a negative thermal resistivity coefficient TCR.