Doped Pixel Isolation Pillars for High-Aspect-Ratio Image Sensors
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Solution Overview
Problem
High aspect ratios of sensing areas in image sensors lead to process failures such as undesired leaning and collapse of patterns during manufacturing, which affects the sensitivity and resolution of the image sensors.
Innovation Solution
The image sensor design includes a pixel isolation structure with an outer isolation film, inner isolation films, a doped isolation liner, and doped isolation pillars to define the size of sub-pixels, preventing process failures by supporting the sensing areas during manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the widths of sensing areas are reduced and heights are increased to increase integration density, then the integration density increases, but process failures such as pattern leaning and collapse occur
Solution Approach 1:
The pixel isolation structure is divided into multiple components: outer isolation film, inner isolation films, doped isolation liner, and doped isolation pillars. This segmentation allows each component to perform specific functions in supporting the high aspect ratio sensing areas, preventing pattern collapse while maintaining integration density.
Solution Approach 2:
The pixel isolation structure extends in multiple dimensions with outer isolation films providing lateral support and inner isolation films providing vertical support. This multi-dimensional approach stabilizes the high aspect ratio sensing areas by distributing mechanical stress across different spatial dimensions, preventing pattern leaning and collapse.
2Quantity of substance
If the aspect ratios of sensing areas are increased to improve integration density, then the integration density improves, but pattern leaning and collapse occur during manufacturing
Solution Approach 1:
The pixel isolation structure is formed before the sensing area patterns are created. The outer isolation films and inner isolation films are deposited and patterned in advance to provide a pre-formed support framework. This preliminary action ensures that when high aspect ratio sensing areas are subsequently formed, they have immediate structural support to prevent leaning and collapse during manufacturing processes.
Solution Approach 2:
The doped isolation liner acts as an intermediary layer between the inner isolation films and the sensing areas. This intermediate structure provides additional mechanical support and adhesion, mediating the stress distribution to prevent pattern formation failures in high aspect ratio sensing areas.
3Reliability
If the pixel isolation structure is enhanced to prevent pattern failures, then the manufacturing reliability improves, but the device complexity increases
Solution Approach 1:
The pixel isolation structure components serve multiple functions: outer isolation films provide lateral isolation and structural support, inner isolation films provide vertical support and isolation, doped isolation liners provide adhesion and stress relief, and doped isolation pillars provide additional mechanical support. This multi-functionality allows a single integrated structure to achieve manufacturing reliability without requiring separate complex systems for each function.
Solution Approach 2:
The pixel isolation structure utilizes controlled variations in material properties and geometric parameters. By adjusting the thickness, doping concentration, and dimensional ratios of different isolation components, the structure achieves optimal mechanical support for high aspect ratio sensing areas. These parameter optimizations enable manufacturing reliability while keeping the overall structure manageable and manufacturable.
Data Source
AI summary
An image sensor includes a color unit pixel comprising sub-pixels arranged in an m×n matrix on a substrate, and a pixel isolation structure isolating the sub-pixels from each other in the color unit pixel. The pixel isolation structure includes an outer isolation film surrounding the color unit pixel, at least one inner isolation film including a portion between two sub-pixels, which are adjacent to each other, among the sub-pixels, a doped isolation liner covering opposite sidewalls of the at least one inner isolation film, and at least one doped isolation pillar contacting at least two sub-pixels selected from the sub-pixels. The at least one doped isolation pillar and the at least one inner isolation film are arranged to define a size of a partial region of each of the sub-pixels.