Infrared Imaging Device Supporting Legs Thermal Insulation
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Solution Overview
Problem
Conventional non-cooling type infrared sensors face challenges in reducing the size of supporting legs while maintaining low heat conductance and mechanical strength, leading to increased costs and difficulty in producing inexpensive, high-sensitivity devices.
Innovation Solution
The use of a hollow structure between the silicon substrate and supporting legs, combined with interlayer insulating films and electric interconnects made of low heat conduction materials, allows for a reduction in the cross-sectional area of supporting legs, thereby lowering heat conductance without compromising mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the size of supporting legs is reduced to lower heat conductance, then heat insulation performance is improved, but mechanical strength deteriorates
Solution Approach 1:
The supporting leg is constructed as a composite structure with an interconnect unit made of low heat conduction material (titanium or titanium nitride) and an arching structure made of high strength material (polycrystalline silicon). This composite design allows the interconnect unit to provide thermal insulation while the arching structure provides mechanical strength, resolving the contradiction between reduced heat conductance and maintained strength.
2Loss of energy
If the size of supporting legs is reduced to improve heat insulation, then heat conductance is lowered, but manufacturing precision requirements increase
Solution Approach 1:
The supporting leg is segmented into two functional units: an interconnect unit for electrical connection and thermal insulation, and an arching structure for mechanical support. This segmentation allows each unit to be optimized independently - the interconnect unit can be made smaller with lower heat conductance without proportionally increasing precision requirements for the entire structure, as the arching structure compensates for mechanical requirements.
Solution Approach 2:
The invention changes the material parameters of the supporting leg by using low heat conduction materials (titanium, titanium nitride) for the interconnect unit while maintaining appropriate dimensions. This allows the supporting leg to achieve lower heat conductance without requiring proportional reduction in size that would demand higher mask precision.
3Strength
If the supporting leg structure is made more robust to maintain strength, then mechanical strength is improved, but heat insulation performance deteriorates
Solution Approach 1:
The supporting leg uses a composite structure where the arching structure made of polycrystalline silicon provides mechanical strength and strain relief, while the interconnect unit made of titanium or titanium nitride provides thermal insulation. This composite design resolves the contradiction by assigning different functional roles to different material components.
Solution Approach 2:
Different parts of the supporting leg have different local qualities: the arching structure is designed for mechanical strength and strain accommodation, while the interconnect unit is designed for low heat conduction. This local differentiation of properties allows the structure to simultaneously achieve both strength and heat insulation without compromise.
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 enables the production of smaller, high-sensitivity infrared imaging devices with reduced heat conductance and improved mechanical strength, while maintaining cost-effectiveness by utilizing standard CMOS process materials and techniques.
Implementation Method 1
a hollow structure between a silicon substrate and supporting legs
Implementation Method 2
interlayer insulating films and electric interconnects made of low heat conduction materials
Data Source
AI summary
Certain embodiments provide an infrared imaging device including: an SOI structure that is placed at a distance from a substrate, and includes: heat-sensitive diodes that detect infrared rays and convert the infrared rays into heat; and STI regions that separate the heat-sensitive diodes from one another; an interlayer insulating film that is stacked on the SOI structure; and supporting legs that are connected to the heat-sensitive diodes and vertical signal lines provided in outer peripheral regions of the heat-sensitive diodes. Each of the supporting legs includes: an interconnect unit that transmit signals to the vertical signal lines; and interlayer insulating layers that sandwich the interconnect unit, each bottom side of the interlayer insulating layers being located in a higher position than the SOI structure.