Pixel Array Layout With Trench Isolation for Low Cross-Talk Imaging
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Solution Overview
Problem
As pixel sizes in CMOS image sensors decrease, they face challenges in properly sensing incident light and experiencing noise due to interference between highly integrated elements, leading to suboptimal image quality and cross-talk between pixels.
Innovation Solution
A pixel array design featuring trench structures extending vertically through the semiconductor substrate to electrically and optically isolate photoelectric conversion elements, combined with a shared microlens and color filter configuration, which focuses incident light uniformly across the pixels and reduces cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is decreased to achieve higher resolution, then image resolution is improved, but optical sensing capability deteriorates and cross-talk between pixels increases
Solution Approach 1:
The patent divides the pixel array into multiple pixel groups, where each pixel group shares common optical components (microlens and color filter). This segmentation allows each pixel within a group to benefit from dedicated photoelectric conversion elements while sharing optical infrastructure, thereby maintaining optical sensing capability even as individual pixel sizes decrease for higher resolution.
Solution Approach 2:
The patent introduces microlenses and color filters as intermediary components positioned between the incident light and the photoelectric conversion elements. These intermediaries focus and filter light before it reaches the pixels, improving light collection efficiency and reducing cross-talk between adjacent pixels, thus maintaining optical sensing capability at smaller pixel dimensions.
2Measurement precision
If pixel size is decreased to achieve higher resolution, then image resolution is improved, but cross-talk between pixels increases
Solution Approach 1:
By organizing pixels into groups with shared optical components, the patent creates natural isolation boundaries. Each pixel group operates semi-independently, reducing optical interference and cross-talk between pixels in different groups while maintaining high resolution through increased total pixel count.
Solution Approach 2:
The microlenses act as optical intermediaries that focus light precisely onto the photoelectric conversion elements, preventing light from spilling into adjacent pixels. The color filters serve as spectral intermediaries that separate different wavelength ranges, further reducing cross-talk between pixels sensitive to different colors.
3Measurement precision
If pixel size is decreased to achieve higher resolution, then image resolution is improved, but noise increases
Solution Approach 1:
The patent merges certain optical components (microlens and color filter) at the pixel group level rather than providing dedicated instances for each pixel. This merging reduces the total number of components, minimizing sources of optical noise and interference while maintaining high resolution through increased pixel density.
Solution Approach 2:
The color filters serve as spectral intermediaries that block unwanted wavelengths from reaching the photoelectric conversion elements, reducing noise from out-of-band light. The microlenses act as spatial intermediaries that concentrate light precisely, reducing noise from scattered or stray light.
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 design enhances optical characteristics, improves image quality by reducing cross-talk, and enables auto focusing, ensuring accurate image capture and enhanced sensitivity across the sensor array.
Implementation Method 1
a microlens disposed above or below the semiconductor substrate, the microlens covering all of the photoelectric conversion elements in the plurality of unit pixels to focus an incident light to the photoelectric conversion elements
Implementation Method 2
a plurality of unit pixels respectively including photoelectric conversion elements disposed in a semiconductor substrate; The photoelectric conversion element generates an electrical signal that varies based on the quantity of incident light
Implementation Method 3
trench structures disposed in the semiconductor substrate and extending in a vertical direction from a first surface of the semiconductor substrate to a second surface of the semiconductor substrate to electrically and optically separate the photoelectric conversion elements from each other
Data Source
AI summary
A pixel array including: a plurality of pixel groups, each pixel group including: a plurality of unit pixels respectively including photoelectric conversion elements disposed in a semiconductor substrate; trench structures disposed in the semiconductor substrate and extending in a vertical direction from a first surface of the semiconductor substrate to a second surface of the semiconductor substrate to electrically and optically separate the photoelectric conversion elements from each other; and a microlens disposed above or below the semiconductor substrate, the microlens covering all of the photoelectric conversion elements in the plurality of unit pixels to focus an incident light to the photoelectric conversion elements.