Image Sensor Pixel Isolation Trenches Reduce Cross Talk
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Solution Overview
Problem
As semiconductor devices become more highly integrated, image sensors experience increased cross talk and noise due to scaled-down pixels, which reduces light receiving capability and sensitivity.
Innovation Solution
The implementation of a method for fabricating image sensors that includes forming a trench between pixel regions, filling it with a buried insulating layer, and creating potential barrier regions using ion implantation to minimize cross talk, along with forming device isolation layers and wells to enhance pixel separation and light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixels are scaled down to achieve high integration, then device integration is improved, but cross talk between pixels increases and noise is generated
Solution Approach 1:
The patent divides the semiconductor substrate into multiple pixel regions separated by device isolation regions. Each pixel region is independently isolated using trenches filled with insulating material, preventing electrical interaction between adjacent pixels while maintaining high integration density.
Solution Approach 2:
The patent applies different doping types and concentrations in specific regions: first type potential barrier regions are formed at the bottom of trenches, second type potential barrier regions on sidewalls, and third type potential barrier regions in pixel regions. This localized doping strategy creates electric fields that selectively block carrier diffusion at pixel boundaries while preserving photoelectric conversion efficiency in active regions.
2Object-affected harmful factors
If device isolation regions are formed to prevent cross talk, then cross talk is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent forms potential barrier regions during the device isolation fabrication process itself, before final pixel region processing. By implanting dopants into the trench bottom and sidewalls during the isolation structure formation, the patent eliminates the need for separate potential barrier formation steps, reducing overall manufacturing complexity.
Solution Approach 2:
The patent combines multiple functions into the device isolation structure: the trench provides physical separation, the insulating fill provides electrical isolation, and the doped potential barrier regions provide carrier blocking. This multi-functional integration achieves cross talk prevention without requiring additional separate structures or processes.
3Object-affected harmful factors
If potential barrier regions are formed using ion implantation, then cross talk is prevented, but device complexity increases
Solution Approach 1:
The patent creates potential barrier regions with specific doping types and concentrations at precise locations: first type at trench bottom, second type on sidewalls, and third type in pixel regions. This localized doping approach prevents cross talk through electric field barriers without requiring complex three-dimensional structures or additional material layers.
Solution Approach 2:
The patent forms potential barrier regions during the device isolation fabrication sequence, utilizing the trench structure and insulating layers already in place. By implanting dopants into these pre-formed structures, the patent integrates potential barrier formation into the isolation process, avoiding additional fabrication steps and reducing overall device structural 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
This approach reduces or prevents cross talk between pixels, improves light receiving capability, and enhances photo sensitivity by creating effective potential barriers and device isolation regions.
Implementation Method 1
performing an ion implantation process using the first mask pattern as an ion implantation mask to form a first type potential barrier region in a bottom of the trench
Data Source
AI summary
An image sensor and a method for fabricating the image sensor are provided. The method for fabricating the image sensor includes forming a first insulating layer on a semiconductor epitaxial layer having multiple pixel regions; patterning a portion of the semiconductor epitaxial layer and the first insulating layer in a boundary region between the pixel regions to form a trench; forming a buried insulating layer on the first insulating layer, filling the trench, the buried insulating layer having a planar top surface; forming a second insulating layer on the buried insulating layer; forming a first mask pattern on the second insulating layer, the first mask pattern defining an opening overlapping the trench; and performing an ion implantation process using the first mask pattern as an ion implantation mask to form a first type potential barrier region in a bottom of the trench.