Suspended Membrane Radiation Detector with ALD Spacers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional microbolometers face challenges in achieving good thermal insulation and maintaining a large absorber area due to the limitations of pixel pitch scaling, leading to reduced performance and increased thermal conductance, especially as pixel sizes decrease.
Innovation Solution
The use of thin, long spacers made from low thermal conductivity materials, produced using Atomic Layer Deposition (ALD), which act as both thermal insulation and electrical contacts, allowing for independent adjustment of the membrane-reflector distance to maintain optimal absorption while reducing the need for lateral webs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel pitch is reduced to increase resolution, then measurement precision is improved, but thermal insulation deteriorates due to reduced absorber area
Solution Approach 1:
The patent transitions from planar (2D) absorber design to three-dimensional (3D) cavity structure. The membrane is suspended at a height above the substrate, creating a vertical cavity space. This dimensional change allows the absorber area to extend vertically rather than being constrained to the horizontal plane, effectively increasing the absorber area within a smaller pixel pitch footprint while maintaining thermal insulation through the suspended membrane structure.
Solution Approach 2:
The patent implements a nested structure where the membrane with absorber layer is suspended within the pixel area above the substrate. The cavity formed between the membrane and substrate contains the optical resonator, creating a nested arrangement where the functional absorber volume is embedded within the pixel structure. This allows maximum utilization of the pixel volume for absorption while minimizing the footprint.
2Measurement precision
If pixel pitch is reduced to increase resolution, then measurement precision is improved, but absorber area decreases
Solution Approach 1:
The patent transitions from planar (2D) absorber design to three-dimensional (3D) cavity structure. The membrane is suspended at a height above the substrate, creating a vertical cavity space. This dimensional change allows the absorber area to extend vertically rather than being constrained to the horizontal plane, effectively increasing the absorber area within a smaller pixel pitch footprint.
Solution Approach 2:
The patent changes the geometric parameters of the absorber structure by introducing vertical height (z-dimension) as a key parameter. The membrane suspension height, cavity depth, and layer thicknesses are optimized to maximize the effective absorber volume. This parameter transformation from 2D area to 3D volume enables maintaining or increasing absorber area despite reduced pixel pitch.
3Temperature
If thermal conductivity is reduced to improve thermal insulation, then temperature stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the thermal conduction path by removing direct contact between the membrane and substrate. The membrane is suspended by thin struts that minimize thermal conduction, effectively taking out the dominant heat transfer pathway. This extraction approach achieves excellent thermal insulation without requiring complex multi-layer insulation structures, as the simple suspended geometry inherently provides thermal isolation.
Solution Approach 2:
The patent introduces thin struts as intermediary elements between the membrane and substrate. These struts serve as minimal thermal conduction pathways while providing necessary mechanical support and electrical connection. The struts act as intermediaries that decouple the membrane thermally from the substrate while maintaining structural integrity, achieving thermal insulation through a simple intermediary structure rather than complex insulation layers.
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 approach significantly reduces thermal conductance and maximizes the absorber area, enhancing the performance of radiation detectors by allowing for flexible scaling of pixel pitch without compromising thermal insulation or absorption efficiency.
Implementation Method 1
The spacers 45...provide thermal insulation of the membrane 10 from the substrate 20
Implementation Method 2
The spacers 45...electrically contacting the electromagnetic radiation detectors
Implementation Method 3
Due to the absorption of the incident infrared radiation, the thermally insulated membrane 10 can heat up
Implementation Method 4
a metal layer (reflector) 35 can be located on the substrate 20 below the membrane, reflecting back some of the transmitted radiation
Implementation Method 5
The cavity 40 between the absorber layer 25 and the lower reflector forms an optical resonator
Implementation Method 6
produced using Atomic Layer Deposition (ALD)
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Described is a radiation detector comprising a substrate and a membrane that is suspended above the substrate by means of spacers; the spacers electrically contact a radiation sensor in the membrane and thermally insulate the membrane from the substrate.