Tapered Light Pipe with Reflective Lining for Imaging Array
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Solution Overview
Problem
Existing imaging array technologies face challenges in efficiently capturing light at larger angles without compromising pixel resolution, as current solutions like increasing pixel size or using light pipes with high-index polymers lead to decreased resolution or undesirable crosstalk.
Innovation Solution
A pixel sensor array design featuring tapered light pipes lined with a fully reflective Al-Cu metal layer, filled with a transparent filler material, and strategically positioned metal interconnects to block flare light, allowing for improved light capture at increased angles while maintaining resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pixel sensors are increased in size to capture light at larger angles, then light capture capability is improved, but resolution decreases
Solution Approach 1:
The patent segments the light capture function by introducing separate light pipe structures for each pixel sensor. These light pipes guide light at various angles to the photodiode without requiring larger pixel areas, thus maintaining resolution while improving light capture capability.
Solution Approach 2:
The patent introduces light pipes as intermediary structures between the lens and photodiode. These light pipes mediate the light transmission process, allowing light at larger angles to be effectively directed to the photodiode surface without increasing pixel size.
2Illumination intensity
If high-index polymer light pipes are used to capture light at larger angles, then light capture capability is improved, but crosstalk between adjacent pixels increases
Solution Approach 1:
The patent applies different material properties to different regions: the light pipe core uses high-index polymer for light guidance, while the interface region between adjacent light pipes uses low-index dielectric material to prevent crosstalk. This local differentiation allows simultaneous achievement of light capture and crosstalk reduction.
Solution Approach 2:
The patent converts the potentially harmful effect of light leakage at polymer-dielectric interfaces into a beneficial crosstalk reduction mechanism by strategically positioning low-index dielectric regions to reflect stray light back into the light pipe rather than allowing it to enter adjacent pixels.
3Illumination intensity
If light pipe structures are added to improve light capture, then device complexity increases
Solution Approach 1:
The patent merges the light pipe structure with the existing pixel sensor architecture by forming light pipes within the interlayer dielectric regions that already exist in CMOS imaging arrays. This integration approach minimizes additional complexity while achieving improved light capture.
Solution Approach 2:
The patent makes the interlayer dielectric material serve multiple functions: it provides electrical insulation for CMOS circuits and simultaneously acts as the light pipe structure for optical guidance. This multi-functionality reduces the need for separate components and simplifies the overall device structure.
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 solution effectively captures light at larger angles without crosstalk, maintaining high resolution and reducing flare light effects, thereby enhancing the performance of imaging arrays.
Implementation Method 1
A lining layer is formed on the inner side wall of each aperture and is substantially fully reflective to visible light
Implementation Method 2
A filler material substantially transparent to visible light is disposed inside of the reflective lining layer
Implementation Method 3
A microlens is disposed over the top surface of each aperture
Implementation Method 4
the plurality of first and second metal interconnect vias laterally positioned with respect to one another to block flare light from passing through any of the vertical structures
Data Source
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AI summary
A pixel sensor array includes a plurality of surface pixel sensors disposed in a substrate, a layer of dielectric material formed over the surface of the pixel sensors, a plurality of apertures formed in the dielectric layer each aligned with one of the surface pixel sensors and having an inner side wall. A lining layer is formed on the inner side wall of each aperture and is substantially fully reflective to visible light. The lining layer is spaced apart from the surface of the substrate and has a smaller cross-sectional area than a cross-sectional area of each surface pixel sensor. A filler material substantially transparent to visible light is disposed inside of the reflective lining layer and has a top surface lying in the plane with the top surface of the layer of dielectric material. A microlens is disposed over the top surface of each aperture.