Dual Vertical Gate Image Sensor for Fine-Pixel Noise Control
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Solution Overview
Problem
Current image sensors face challenges in maintaining interfacial and noise characteristics, particularly in fine pixel areas, and are prone to misalignment issues as pixel sizes decrease.
Innovation Solution
The development of an image sensor with a dual vertical gate structure, featuring two vertically extending portions with different inclination angles and a connection portion, which improves interface characteristics and noise performance by minimizing substrate etching and allowing for precise formation in smaller pixel areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the integration density of image sensors is increased to improve productivity, then the output per unit area is improved, but the pixel size and component sizes decrease leading to degraded manufacturing precision and alignment issues
Solution Approach 1:
The gate electrode is divided into two separate vertical gates (first vertical gate and second vertical gate) positioned at different locations. This segmentation allows each gate to be independently formed and aligned, reducing the cumulative alignment errors that would occur with a single complex gate structure, thereby maintaining manufacturing precision while enabling higher integration density
Solution Approach 2:
The patent transitions from a conventional planar gate structure to a three-dimensional vertical gate structure that extends in the depth direction (second direction) perpendicular to the substrate surface. This dimensional change allows the gate to occupy vertical space rather than only horizontal space, enabling higher integration density without compromising the horizontal pixel dimensions and maintaining alignment precision
2Area of stationary object
If the pixel size is decreased to improve integration density, then the area per pixel is reduced, but the interfacial characteristics and noise characteristics are degraded
Solution Approach 1:
The vertical gates extend in the depth direction (second direction) perpendicular to the substrate, utilizing the third dimension to provide sufficient gate length and control without reducing the horizontal pixel area. This allows small pixel areas while maintaining adequate gate dimensions for good interfacial characteristics and noise performance
Solution Approach 2:
The patent employs a composite structure with device isolation layers (first and second device isolation layers) positioned at different depths, combined with the vertical gate structure. This composite arrangement provides electrical isolation and noise reduction while maintaining compact pixel dimensions, thereby preserving reliability despite reduced pixel area
Data Source
AI summary
An image sensor includes a dual vertical gate including two vertical portions apart from each other by an isolation area in a first direction and vertically extending into a substrate, a connection portion configured to connect the two vertical portions to each other on the two vertical portions, and a device isolation layer on side surfaces of the vertical portions in the first direction, wherein each of the two vertical portions includes an upper vertical portion and a lower vertical portion, a sidewall of the upper vertical portion forms a first inclination angle with a line extending in the first direction, a sidewall of the lower vertical portion forms a second inclination angle with the line extending in the first direction, and the first inclination angle is different from the second inclination angle.