Vertical Stacked Image Sensor Resolving Pixel Density Trade-offs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state image sensors experience a reduction in light receiving area and sensitivity due to the arrangement of diffusion layers, leading to decreased electric charge generation and deteriorated image quality as the number of pixels increases.
Innovation Solution
The image sensor design includes a photoelectric conversion unit, an accumulation unit, and a transfer unit arranged along the optical axis of a microlens, with the photoelectric conversion unit on one surface and the accumulation unit on the other, and the transfer unit in between, allowing for vertical transfer of electric charge and increased light receiving area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of pixels is increased in conventional solid-state image sensors, then the pixel density is improved, but the light receiving area is reduced
Solution Approach 1:
The patent transitions from a conventional planar arrangement where photoelectric conversion units and diffusion layers are arranged side-by-side on the same surface to a vertical stacked arrangement. The photoelectric conversion unit, transfer unit, and accumulation unit are arranged along the optical axis direction, utilizing the third dimension (depth) to resolve the contradiction between increasing pixel density and maintaining light receiving area.
2Productivity
If the number of pixels is increased in conventional solid-state image sensors, then the pixel density is improved, but the sensitivity is deteriorated
Solution Approach 1:
By arranging the photoelectric conversion unit, transfer unit, and accumulation unit vertically along the optical axis, the patent maintains a large light receiving area at the photoelectric conversion unit while enabling high pixel density through vertical stacking. This preserves the amount of electric charge generated by photoelectric conversion, thereby maintaining sensitivity even as pixel density increases.
3Ease of manufacture
If diffusion layers are arranged along the surface of the semiconductor substrate, then the manufacturing process is simplified, but the light receiving area is reduced
Solution Approach 1:
The patent replaces the conventional horizontal arrangement of diffusion layers on the substrate surface with a vertical arrangement along the optical axis. The transfer unit and accumulation unit are positioned below the photoelectric conversion unit in the depth direction, allowing the photoelectric conversion unit to occupy the full pixel area on the light-receiving surface while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
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 enhances the sensitivity and signal-to-noise ratio, enabling high-quality image capture with reduced noise even at high frame rates, and allows for smaller pixel sizes without compromising image quality.
Implementation Method 1
a photoelectric conversion unit that photoelectrically converts incident light transmitted through a microlens to generate electric charge
Data Source
AI summary
An image sensor includes: a photoelectric conversion unit that photoelectrically converts incident light transmitted through a microlens to generate electric charge; an accumulation unit that accumulates the electric charge generated by the photoelectric conversion unit; and a transfer unit that transfers the electric charge generated by the photoelectric conversion unit to the accumulation unit, wherein: the photoelectric conversion unit, the transfer unit, and the accumulation unit are provided along a direction of an optical axis of the microlens.