Image Sensor Symmetrical Transistors Integration Density
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 image quality, as reducing pixel size leads to reduced photon reception and increased noise due to differences in the forms and sizes of transfer and reset transistors.
Innovation Solution
The image sensor incorporates symmetrical transfer and reset transistors with vertically overlapping photoelectric conversion elements, maximizing fill factor and integration density, and using undoped or P-type polysilicon channel layers to maintain image quality by ensuring consistent charge transfer and reset operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pixel size is reduced to increase integration density, then the number of unit pixels per area increases, but the photon reception area decreases and noise increases
Solution Approach 1:
The patent applies asymmetry by configuring the transfer transistor and reset transistor with different structures (different channel layer types or doping configurations) to optimize their respective functions. The transfer transistor uses a channel layer configuration optimized for charge transfer, while the reset transistor uses a configuration optimized for reset operations, thereby maintaining low noise and high performance even in reduced pixel sizes
Solution Approach 2:
The patent utilizes vertical stacking of transistors and photoelectric conversion elements to transition from a planar layout to a three-dimensional structure. This allows multiple functional elements to be integrated within a smaller footprint area, increasing integration density without proportionally reducing the photoelectric conversion area, thereby maintaining photon reception capability while reducing pixel size
2Productivity
If the pixel size is reduced to increase integration density, then the number of unit pixels per area increases, but image quality deteriorates
Solution Approach 1:
The patent employs asymmetric design where the transfer transistor and reset transistor have different structural configurations optimized for their specific functions. This allows each transistor to perform its operation more efficiently, maintaining high image quality through precise charge transfer and reset operations even when pixel dimensions are reduced for higher integration density
Solution Approach 2:
The patent changes material parameters by using different polysilicon channel layer types (undoped vs. doped) for the transfer and reset transistors. This parameter variation optimizes the electrical characteristics of each transistor, ensuring high-performance charge transfer and reset operations that maintain image quality in high-density pixel arrays
3Adaptability or versatility
If different forms and sizes of transfer and reset transistors are used, then functional optimization is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the transistor design into distinct functional units with different channel layer configurations. By dividing the transistor structure into separable components (gate, channel layer, source/drain regions) with specific optimizations for transfer or reset functions, the design achieves functional optimization while maintaining manufacturing feasibility through modular 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 design enhances image quality by maintaining consistent charge transfer and reset operations, reducing noise, and allowing for higher integration density without deteriorating pixel characteristics, thus providing high-quality images.
Implementation Method 1
An image sensor converts an optical image into an electrical signal
Data Source
AI summary
An image sensor, comprising: a photoelectric conversion element; a transfer transistor formed over the photoelectric conversion element; and a reset transistor formed over the photoelectric conversion element, formed substantially at the same level as the transfer transistor, and spaced apart from the transfer transistor by a gap, wherein the transfer transistor and the reset transistor are trench-type transistors and are symmetrical structure to each other with respect to the gap, wherein the photoelectric conversion element is a continuous layer under both the transfer transistor and the reset transistor, and is completely below the transfer transistor and the reset transistor.