Auto-Focus Image Sensor Pixel Array with Deep Isolation
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Solution Overview
Problem
Conventional auto-focus image sensors require additional focus detecting devices, increasing costs and size, and existing CMOS image sensors face challenges in achieving high full well capacity (FWC) characteristics for efficient phase difference detection.
Innovation Solution
The design incorporates a pixel array with a substrate, deep device isolation region, and ground regions in an auto-focus image sensor, where first pixels detect phase differences and second pixels detect images, with the deep device isolation region and ground regions optimized to enhance FWC characteristics by reducing dark current and expanding photoelectric conversion regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional focus detecting devices are used, then phase difference detection capability is improved, but device complexity and size increase
Solution Approach 1:
The patent combines the image sensing function and phase difference detection function into a single pixel array structure. The pixel array includes both first pixels for phase difference detection and second pixels for image sensing, eliminating the need for separate focus detecting devices and reducing overall device complexity while maintaining detection precision
Solution Approach 2:
The pixel array is designed to perform multiple functions simultaneously: it can detect phase difference information for auto-focus control and capture image information. This multi-functional design allows the same hardware structure to serve both imaging and focus detection purposes
2Reliability
If photoelectric conversion region is expanded, then full well capacity is improved, but pixel size increases
Solution Approach 1:
The patent extends the photoelectric conversion region in the vertical direction (depth) rather than expanding it horizontally. By increasing the depth of the photoelectric conversion region from the first surface toward the second surface of the substrate, the full well capacity is improved without increasing the lateral pixel size
Solution Approach 2:
The patent changes the dimensional parameters of the photoelectric conversion region by controlling its depth and shape in the vertical direction. The region extends deeper into the substrate with controlled boundaries, allowing increased charge storage capacity while maintaining compact lateral dimensions
3Object-generated harmful factors
If deep device isolation region is implemented, then dark current is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent divides the substrate into isolated pixel regions using deep device isolation regions that extend from the first surface toward the second surface. These isolation regions create electrical and physical separation between adjacent pixels, preventing dark current leakage while maintaining a manufacturable structure through systematic segmentation
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 improves FWC characteristics, reduces dark current, and allows for more efficient phase difference detection, enabling smaller pixel sizes while maintaining image detection capabilities, thus enhancing the overall performance of auto-focus image sensors.
Implementation Method 1
The pixel array generates a plurality of analog pixel signals based on incident light
Data Source
AI summary
A pixel array included in an auto-focus image sensor includes a substrate, a plurality of pixels, a deep device isolation region and a plurality of first ground regions. The substrate includes a first surface on which a gate electrode is disposed and a second surface opposite to the first surface. The plurality of pixels are disposed in the substrate, and include a plurality of first pixels configured to detect a phase difference and a plurality of second pixels configured to detect an image. The deep device isolation region is disposed in the substrate, extends substantially vertically from the second surface of the substrate to isolate the plurality of pixels from each other. The plurality of first ground regions are disposed adjacent to the first surface in the substrate and adjacent to only at least some of the plurality of first pixels.