Uncooled Infrared Image Sensor Pixel Segmentation for Mechanical Strength
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Solution Overview
Problem
Uncooled infrared image sensors face mechanical strength issues due to cavity formation below pixels during manufacturing, which affects reliability, especially in sensors with many pixels like QVGA, and existing fine etching techniques like DTI process are challenging to perform.
Innovation Solution
The design includes first pixels above cavities on a semiconductor substrate with supporting parts and second pixels fixed directly on the substrate, using isotropic etching to form cavities below the first pixels while keeping the second pixels on the substrate, improving mechanical strength and sensitivity by varying the etching hole intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If anisotropic etching is used to form cavities below pixels, then thermal insulation of pixels is improved, but mechanical strength of the pixel region deteriorates
Solution Approach 1:
The pixel array is segmented into two types: first pixels with cavities for thermal insulation and second pixels without cavities for mechanical support. This segmentation allows simultaneous achievement of thermal isolation and structural strength by distributing different functional pixels across the array.
Solution Approach 2:
Different regions of the pixel array are assigned different structures: regions with first pixels have cavities for thermal insulation, while regions with second pixels have solid substrate for mechanical strength. This local differentiation optimizes both thermal and mechanical properties in their respective zones.
2Strength
If DTI process is used to form etching stopper film between adjacent pixels, then cavity formation below entire pixel region is prevented, but manufacturing complexity increases
Solution Approach 1:
Instead of adding a stopper film to prevent cavity formation (conventional approach), the invention inverts the approach by selectively forming cavities in first pixels while intentionally leaving second pixels without cavities, achieving the same mechanical support effect through structural design rather than process complexity.
Solution Approach 2:
The complex DTI process step is extracted and replaced by a simpler pixel configuration approach. The manufacturing process is simplified by removing the need for fine etching techniques and stopper film formation, while maintaining the mechanical strength benefit through the second pixel design.
3Temperature
If cavities are formed below the entire pixel region, then thermal insulation of all pixels is improved, but reliability of the sensor deteriorates
Solution Approach 1:
The pixel array is segmented into first pixels with cavities for thermal insulation and second pixels without cavities for structural reliability. This segmentation ensures that not the entire pixel region has cavities, maintaining overall sensor reliability while improving thermal insulation where needed.
Solution Approach 2:
Thermal insulation is applied locally to first pixels through cavity formation, while second pixels maintain solid substrate contact for reliability. This local quality differentiation ensures thermal insulation is provided where required without compromising overall sensor reliability.
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 configuration enhances the mechanical strength of the pixel region and improves sensitivity by maintaining thermal insulation while simplifying the manufacturing process and reducing the complexity of fine etching techniques.
Implementation Method 1
Each infrared absorbing layer converts an infrared ray into heat
Implementation Method 2
each thermal conversion element converts this heat into an electric signal
Implementation Method 3
a cavity is provided between a semiconductor substrate and pixels, thereby supporting the pixels above each cavity. With this arrangement, the pixels are thermally isolated from other pixels and the semiconductor substrate
Implementation Method 4
forming the cavities below the first pixels while keeping the second pixels set on semiconductor substrate, by using isotropically etching the semiconductor substrate via the first and second etching holes
Data Source
AI summary
An image sensor includes a semiconductor substrate; first pixels laid out above cavities provided within the semiconductor substrate, the first pixels converting thermal energy generated by incident light into an electric signal; supporting parts connected between the first pixels and the semiconductor substrate, the supporting parts supporting the first pixels above the cavities; and second pixels fixedly provided on the semiconductor substrate without via the cavities, wherein a plurality of the first pixels and a plurality of the second pixels are laid out two-dimensionally to form a pixel region, and each of the second pixels is adjacent to the first pixels.