Unequal CMOS Pixel Regions for Balanced Spectral Quantum Efficiency
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Solution Overview
Problem
Modern image sensors with equal-sized pixel regions exhibit uneven quantum efficiency distribution, leading to suboptimal performance due to varying sensitivity to different light spectra, resulting in a lower signal-to-noise ratio.
Innovation Solution
The image sensor design incorporates pixel regions of different shapes and unequal sizes, where pixels sensitive to colors with higher quantum efficiency are made smaller and those sensitive to colors with lower quantum efficiency are enlarged, optimizing the total area and photon conversion efficiency across the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If equal-sized pixel regions are used in the image sensor, then manufacturing is simplified and device structure is uniform, but quantum efficiency distribution becomes uneven across different spectral regions
Solution Approach 1:
The patent applies local quality by making pixel regions of different sizes according to their specific spectral sensitivity requirements. Pixels sensitive to blue light (higher quantum efficiency) are made smaller, while pixels sensitive to red light (lower quantum efficiency) are made larger. This local differentiation optimizes quantum efficiency distribution across the image sensor while maintaining manufacturing feasibility through standardized fabrication processes.
2Area of stationary object
If pixel size is increased to improve photon capture area, then quantum efficiency for certain spectral regions improves, but overall quantum efficiency distribution becomes uneven
Solution Approach 1:
The patent applies parameter changes by varying the physical size parameter of pixel regions based on their spectral sensitivity characteristics. Specifically, pixels with higher quantum efficiency (blue-sensitive) are assigned smaller areas, while pixels with lower quantum efficiency (red-sensitive) are assigned larger areas. This parameter optimization achieves more uniform quantum efficiency distribution across all spectral regions captured by the sensor.
3Reliability
If unequal pixel sizes are used to optimize quantum efficiency distribution, then photon conversion efficiency improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the image sensor into multiple pixel regions with different sizes, each optimized for specific spectral regions. The sensor array is segmented into blue-sensitive, green-sensitive, and red-sensitive pixels with appropriately different areas. This segmentation strategy optimizes quantum efficiency for each spectral band while maintaining overall device functionality and manageable complexity through systematic layout patterns.
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 achieves a more even distribution of quantum efficiency across pixels, enhancing device performance by improving photon conversion and reducing noise, thereby improving image sensor performance.
Implementation Method 1
Each pixel region contains a photodiode configured to capture optical signals (e.g., light) and convert it to digital data
Data Source
AI summary
In some embodiments, the present disclosure relates to an image sensor, including a semiconductor substrate, a plurality of photodiodes disposed within the semiconductor substrate, and a deep trench isolation structure separating the plurality of photodiodes from one another and defining a plurality of pixel regions corresponding to the plurality of photodiodes. The plurality of pixel regions includes a first pixel region sensitive to a first region of a light spectrum, a second pixel region sensitive to a second region of the light spectrum, and a third pixel region sensitive to a third region of the light spectrum. The first pixel region is smaller than the second pixel region or the third pixel region.