Image Sensor Pillar with Concave-Convex Sidewall
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to develop an image sensor with improved performance that can integrate a high number of unit pixels within a limited area without deteriorating their characteristics, particularly addressing the short channel effect and varying channel lengths for different transistors, while maintaining high-pixel image quality.
Innovation Solution
The image sensor incorporates a substrate with a photoelectric conversion element, pillars with a concave-convex sidewall structure, and channel films made of polysilicon, where the pillars are formed using a stack structure of insulating layers with different etch selectivity, and transfer gates are designed to optimize channel length and prevent dark current generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of unit pixels is increased within a limited area, then integration density is improved, but pixel characteristics deteriorate due to short channel effect
Solution Approach 1:
The patent introduces a vertical pillar structure with concave-convex sidewalls, transitioning from a planar transistor layout to a three-dimensional architecture. This vertical dimension allows the channel length to be extended along the sidewall surface, effectively increasing the channel length without occupying additional horizontal area, thus maintaining pixel characteristics while achieving high integration density
Solution Approach 2:
The pillar sidewalls are designed with concave-convex curved profiles instead of straight vertical lines. This curvature increases the surface area of the pillar sidewall, thereby extending the channel length along the curved surface. The curved geometry allows for longer channel paths within the same footprint, mitigating the short channel effect while maintaining compact pixel structures
2Reliability
If different channel lengths are required for different transistors, then transistor performance is optimized, but device complexity increases
Solution Approach 1:
The patent applies different local geometries to different pillars: some pillars have concave-convex sidewalls for longer channel lengths, while others have vertical sidewalls for shorter channel lengths. This local differentiation allows each transistor to have its channel length optimized according to its specific performance requirements, while the overall fabrication process remains relatively simple through selective application of the concave-convex structure
Data Source
AI summary
This technology relates to an image sensor. The image sensor may include a substrate including a photoelectric conversion element; a pillar formed over the photoelectric conversion element and having a concave-convex sidewall; a channel film formed along a surface of the pillar and for having at least one end coupled to the photoelectric conversion element; and a transfer gate formed over the channel film.