Image Sensor Barrier Regions for Charge Isolation
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Solution Overview
Problem
Conventional image sensors face interference issues due to charge carriers generated by peripheral circuitry affecting pixel cells, particularly at the edges of the array, and blooming occurs when bright light is incident, causing image distortion and inaccurate black levels.
Innovation Solution
A barrier region with a charge accumulation region of specific conductivity type is introduced, electrically connected to a voltage source terminal, surrounding the active and black regions to prevent charge transference and isolate pixel cells from peripheral circuitry and adjacent regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If peripheral circuitry is placed adjacent to the pixel array to reduce device complexity, then device complexity is reduced, but charge carriers generated by peripheral circuitry interfere with pixel cells causing image distortion
Solution Approach 1:
An isolation region is introduced as an intermediary structure between the pixel array and peripheral circuitry. This isolation region includes a first conductivity type and is electrically connected to a voltage source, creating a potential barrier that prevents charge carriers generated by peripheral circuitry from interfering with pixel cells while allowing the peripheral circuitry to remain adjacent to the pixel array
2Device complexity
If no isolation structure is used to maintain simple device structure, then device structure remains simple, but charge transference occurs from pixel cells to adjacent regions causing blooming and inaccurate black levels
Solution Approach 1:
The isolation region acts as a mediator that blocks unwanted charge transference between adjacent pixel cells and between pixel cells and peripheral circuitry. By introducing this intermediate structure with opposite conductivity type, the patent prevents blooming effects and maintains accurate black levels while keeping the overall device structure relatively simple
3Object-affected harmful factors
If barrier regions are introduced to prevent charge interference, then charge carrier interference is reduced, but device complexity increases
Solution Approach 1:
Instead of introducing complex isolation structures throughout the entire device, the patent applies isolation regions only at specific locations where charge carrier interference occurs - namely at the boundaries between pixel array and peripheral circuitry, and between adjacent pixel cells. This localized approach reduces charge interference while minimizing the increase in device complexity
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 barrier region effectively reduces interference from peripheral circuitry and blooming, enhancing image quality by maintaining accurate black levels and minimizing distortion.
Implementation Method 1
The charge accumulation region accumulates charge and prevents charge transference from a pixel cell or peripheral circuitry on one side of the barrier region to a pixel cell on another side of the barrier region
Data Source
AI summary
Embodiments of the invention provide a barrier region for isolating devices of an image sensor. The barrier region comprises a charge accumulation region of a particular conductivity type in a substrate electrically connected to a voltage source terminal. The charge accumulation region is adjacent to at least one pixel cell of a pixel array. The charge accumulation region accumulates charge and prevents charge transference from a pixel cell or peripheral circuitry on one side of the barrier region to a pixel cell on another side of the barrier region.