Radiation Detector Spacer Design for Thermal Isolation
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Solution Overview
Problem
Conventional microbolometers face challenges in achieving good thermal insulation and maintaining high performance due to limitations in scaling down pixel size, leading to reduced absorber area and increased thermal conductance, which affects noise equivalent temperature difference (NETD) and overall detector performance.
Innovation Solution
The use of a thin, uniform conductive spacer for thermal insulation, produced via Atomic Layer Deposition, which also functions as an electrical contact, allows for reduced membrane area losses and improved thermal isolation, enabling a longer spacer length while maintaining the resonator condition, and optionally incorporating a web for further insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is scaled down to increase resolution, then the number of pixels per area increases, but the absorber area is reduced and thermal conductance increases
Solution Approach 1:
The patent transitions from planar (2D) web structures to three-dimensional (3D) spacer structures that extend vertically from the substrate to support the membrane. This dimensional change allows thermal insulation to occur through the thickness dimension rather than relying solely on lateral web structures, enabling better thermal isolation even as pixel dimensions are reduced in the planar direction.
Solution Approach 2:
The patent employs thin-film spacer structures (typically 1-10 micrometers thick) that provide effective thermal insulation through their reduced thickness and low thermal conductivity materials. These thin-film spacers maintain mechanical support while minimizing thermal conductance, allowing the membrane to be thermally isolated from the substrate even in scaled-down pixel configurations.
2Productivity
If pixel size is scaled down, then resolution increases, but the membrane area yield is reduced due to proportionally larger web area
Solution Approach 1:
By moving thermal support structures into the third dimension (vertical spacers), the patent reduces the lateral footprint required for thermal management. This allows the membrane to extend over a larger area within the pixel boundary without being constrained by lateral web structures, thereby improving membrane area yield while maintaining high resolution through small pixel pitch.
Solution Approach 2:
The patent segments the thermal support function from the lateral membrane plane by implementing vertical spacer structures. This segmentation allows the membrane area to be maximized in the lateral direction while thermal support is provided through the vertical dimension, resolving the conflict between high resolution (small pixels) and adequate membrane area.
3Stability of the object's composition
If conventional thick metal contacts are used for stability, then mechanical stability is maintained, but thermal insulation is compromised
Solution Approach 1:
The patent replaces thick metal contacts with thin-film spacer structures that are sufficiently thin to provide thermal insulation while maintaining mechanical stability through careful material selection and structural design. The thin-film nature (1-10 micrometers) ensures low thermal conductance while the vertical configuration and material properties maintain adequate mechanical support for the membrane.
Solution Approach 2:
The patent employs composite spacer structures that may combine multiple materials with complementary properties - such as low thermal conductivity materials combined with mechanically robust materials - to achieve both thermal insulation and mechanical stability simultaneously, overcoming the limitation of conventional single-material thick metal contacts.
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, increases the effective absorber area, and enhances detector performance by minimizing the area consumed by webs, thereby improving the noise equivalent temperature difference (NETD) and overall sensitivity.
Implementation Method 1
the spacer 45 thermally isolating a radiation sensor formed in the membrane 10 from the substrate 20
Implementation Method 2
produced via Atomic Layer Deposition
Implementation Method 3
Due to the absorption of the incident infrared radiation, the thermally insulated membrane 10 can heat up
Implementation Method 4
The cavity 40 between the absorber layer 25 and the lower reflector forms an optical resonator
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
A radiation detector is described comprising a substrate and a membrane suspended above the substrate by a spacer, wherein the spacer thermally isolates a radiation sensor formed in the membrane from the substrate. Furthermore, the spacer comprises a first electrically conductive layer that contacts a first pole of the radiation sensor and the substrate, and a second electrically conductive layer that is electrically insulated from the first electrically conductive layer and contacts a second pole of the radiation sensor and the substrate, the second pole being of a different polarity than the first pole.