Shared Pixel DTI Structure for Lower Light Loss in Image Sensors
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Solution Overview
Problem
Image sensors with shared pixel structures face challenges in minimizing light loss and accurately sensing charge due to the overflow path between photodiodes, leading to reduced sensing accuracy.
Innovation Solution
The implementation of a Deep Trench Isolation (DTI) structure with an inner and outer DTI structure, including a DTI Center Cut (DCC) region, separates unit pixels in a 2*2 structure, reducing the overflow path while minimizing light loss and improving charge sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a shared pixel structure is used to increase photodiode area, then pixel size is reduced and area efficiency is improved, but light loss increases and charge sensing accuracy deteriorates due to overflow path between photodiodes
Solution Approach 1:
The shared pixel is divided into four unit pixels arranged in a 2x2 structure, with each unit pixel containing a photodiode. The DTI structure segments the pixel region to define boundaries between unit pixels while maintaining the shared pixel functionality, thereby reducing light loss and improving charge sensing accuracy.
Solution Approach 2:
A DTI (Deep Trench Isolation) structure is introduced as an intermediary element between adjacent unit pixels within the shared pixel. This DTI structure includes a pixel isolation layer and a trench structure that physically separates the unit pixels, preventing charge overflow between them while allowing the shared pixel to maintain its area efficiency.
2Area of moving object
If a shared pixel structure is used to increase photodiode area, then pixel size is reduced and area efficiency is improved, but charge sensing accuracy deteriorates due to overflow path between photodiodes
Solution Approach 1:
The shared pixel is divided into four unit pixels arranged in a 2x2 structure, with each unit pixel containing a photodiode. The DTI structure segments the pixel region to define boundaries between unit pixels while maintaining the shared pixel functionality, thereby reducing light loss and improving charge sensing accuracy.
Solution Approach 2:
A DTI (Deep Trench Isolation) structure is introduced as an intermediary element between adjacent unit pixels within the shared pixel. This DTI structure includes a pixel isolation layer and a trench structure that physically separates the unit pixels, preventing charge overflow between them while allowing the shared pixel to maintain its area efficiency.
3Measurement precision
If DTI structure is added to separate unit pixels and reduce overflow path, then charge sensing accuracy is improved, but device complexity increases
Solution Approach 1:
The pixel isolation layer and the trench structure are merged into a single DTI structure that performs both isolation functions simultaneously. This integration reduces the number of separate components and simplifies the manufacturing process while maintaining the charge sensing accuracy improvements.
Data Source
AI summary
An image sensor may include four unit pixels constituting a shared pixel in a 2*2 structure; and a Deep Trench Isolation (DTI) structure isolating the four unit pixels from each other. The DTI structure may include an inner DTI structure inside the shared pixel and an outer DTI structure surrounding the shared pixel. The inner DTI structure may include a first DTI structure passing through a center of the shared pixel and extending in a first direction or a second direction and a second DTI structure extending toward the center of the shared pixel in a direction perpendicular to a direction in which the first DTI structure extends. The shared pixel may include a DTI Center Cut (DCC) region between the first DTI structure and the second DTI structure in a direction in which the second DTI structure extends.