Double Cavity Bolometer Thermal Isolation
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Solution Overview
Problem
Existing infrared bolometers face challenges with high thermal loss and fragility due to the location of the bolometric element in the upper membrane, which also makes them difficult to manufacture in small dimensions and suitable for mass production.
Innovation Solution
A double cavity bolometer design is implemented, where a second membrane encloses the first membrane with a measuring element, creating two cavities that enhance thermal isolation and mechanical protection, and are manufactured using sacrificial layers and thin film deposition techniques, allowing for miniaturization and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bolometric element is located in the upper membrane, then the bolometer can be manufactured, but it suffers from high thermal loss and fragility
Solution Approach 1:
The patent implements a nested structure where the first membrane containing the bolometric element is enclosed within a second membrane, forming a double-membrane configuration. This nested arrangement provides mechanical protection to the fragile bolometric element while the enclosed volume reduces thermal coupling with the environment, thereby simultaneously improving robustness and reducing thermal loss.
Solution Approach 2:
The patent uses thin film membranes to enclose the bolometric element. The first membrane is formed by removing a first sacrificial layer, and the second membrane encloses the first membrane. These thin film structures provide mechanical protection while maintaining thermal isolation, addressing both the fragility and thermal loss issues.
2Length of moving object
If the bolometer is made in small dimensions, then miniaturization is achieved, but manufacturing difficulty increases
Solution Approach 1:
The patent employs sacrificial layers that are deposited and patterned before the final membrane structures are formed. The first sacrificial layer is removed to form the first membrane, and the second sacrificial layer is removed to form the second membrane. This preliminary action approach allows precise control of small dimensions while using standard thin film fabrication techniques, making miniaturization manufacturable.
Solution Approach 2:
The patent changes the physical and chemical parameters of the sacrificial layers to enable their selective removal. By controlling the material properties and deposition parameters of the sacrificial layers, the process achieves precise dimensional control at small scales while remaining compatible with mass manufacturing techniques.
3Reliability
If bonding is used to seal the cover to the substrate, then sealing is achieved, but the device cannot be realized in small dimensions and is expensive
Solution Approach 1:
The patent extracts the sealing function from traditional bonding methods and replaces it with a self-contained membrane structure. The second membrane encloses the first membrane to define the sensing volume, eliminating the need for separate bonding operations between cover and substrate. This approach enables miniaturization while maintaining sealing integrity through the membrane enclosure itself.
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 double cavity design significantly reduces thermal loss and increases robustness, enabling the bolometer to withstand ambient air pressure and be suitable for mass manufacturing, while maintaining sensitivity and miniaturization.
Implementation Method 1
A first cavity is formed between the substrate and the first membrane, and a second cavity is formed between the first membrane and the second membrane
Implementation Method 2
a first membrane formed by removing a first sacrificial layer on the substrate, the first membrane comprising a measuring element for measuring an amount of incident electromagnetic radiation
Data Source
AI summary
The present invention relates to a bolometer (10) comprising a substrate (12), a first membrane (16) formed by removing a first sacrificial layer (14) on the substrate (12), the first membrane (16) comprising a measuring element (18) for measuring an amount of incident electromagnetic radiation (R), a second membrane (22) formed by removing a second sacrificial layer (20) on the first membrane (16), the second membrane (22) enclosing the first membrane (16), a first cavity (24) formed between the substrate (12) and the first membrane (16), and a second cavity (26) formed between the first membrane (16) and the second membrane (22). The present invention further relates to a method of manufacturing a bolometer, as well as a thermographic image sensor and medical device.