Deep Pixel Well Implant for Image Sensor Cross-talk Reduction
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Solution Overview
Problem
Image sensors suffer from cross-talk, where light and electrical signals spread between pixels, degrading spatial resolution and optical sensitivity, particularly as pixel pitch shrinks.
Innovation Solution
The method involves forming a semiconductor substrate with a P-type silicon substrate, a P-type epilayer, shallow trench isolation features, deep N-type and P-type wells, and guard-ring wells to isolate pixels and collect excess photo-electrons, reducing cross-talk without degrading device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel pitch is reduced to increase pixel density, then image sensor resolution is improved, but cross-talk between pixels increases
Solution Approach 1:
The patent introduces deep pixel wells that extend into the substrate to segment and isolate adjacent pixels vertically. These deep wells create electrical isolation regions that prevent photoelectron diffusion between neighboring pixels, thereby reducing cross-talk while maintaining high pixel density achieved through reduced pixel pitch.
Solution Approach 2:
The patent applies localized doping regions with different conductivity types (n-type and p-type) at specific depths beneath each pixel. This creates locally optimized electrical fields that confine photoelectrons to their intended pixel regions, addressing cross-talk issues without affecting the overall pixel array design and resolution.
2Object-generated harmful factors
If isolation structures are added to reduce cross-talk, then cross-talk is reduced, but device complexity increases
Solution Approach 1:
The patent combines multiple functions into the deep pixel well structure: it serves as both an isolation mechanism to prevent cross-talk and as part of the pixel's photoelectron collection structure. By integrating the isolation function into the existing pixel architecture rather than adding separate isolation layers, the patent reduces device complexity while maintaining cross-talk reduction effectiveness.
Solution Approach 2:
Instead of adding lateral isolation structures that会增加 planar complexity, the patent moves the isolation mechanism to the vertical dimension by extending pixel wells deeper into the substrate. This dimensional transition allows cross-talk reduction without increasing the lateral footprint or complicating the topological arrangement of pixels.
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 effectively reduces cross-talk and blooming by collecting excess photo-electrons in the depletion region between deep wells, maintaining operating parameters and full well capacity, thus enhancing image sensor performance even as pixel scaling continues.
Implementation Method 1
a first deep well having the first type of conductivity and substantially underlying the plurality of pixels, and a second deep well having a second type of conductivity different from the first type of conductivity and substantially underlying the first deep well
Implementation Method 2
collect photo energy to convert images into electrical signals
Data Source
AI summary
An image sensor device includes a semiconductor substrate having a first type of conductivity, a semiconductor layer having the first type of conductivity formed on the semiconductor substrate, and pixels formed in the semiconductor layer. The semiconductor layer includes a first deep well having the first type of conductivity and substantially underlying the plurality of pixels, and a second deep well having a second type of conductivity different from the first type of conductivity and substantially underlying the first deep well.