Stacked Pixel Charge Storage Layout for Higher Saturation Charge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Imaging devices face challenges in achieving larger saturation charge and improved sensitivity.
Innovation Solution
An imaging device with a first semiconductor substrate having a photoelectric conversion unit on one surface and two charge storage units on the opposite surface, connected by charge transfer units, allowing for expanded area and improved layout efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If two charge storage units are provided with respect to a single photoelectric conversion unit on the same surface, then the saturation charge is increased, but the area occupied in the sensor pixel increases
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional stacked arrangement by placing the photoelectric conversion unit on the first surface and the two charge storage units on the second surface of the semiconductor substrate. This vertical stacking in the third dimension allows multiple functional units to coexist without increasing the lateral area occupied in each sensor pixel, thereby resolving the contradiction between increasing saturation charge and maintaining compact pixel area.
2Measurement precision
If multiple charge storage units are added to increase saturation charge, then the sensitivity is improved, but the device complexity increases
Solution Approach 1:
By stacking charge storage units vertically on the opposite surface of the semiconductor substrate, the patent achieves higher sensitivity through increased charge storage capacity without significantly increasing lateral device complexity. The vertical arrangement allows for more efficient use of space and simpler routing of charge transfer paths compared to adding multiple units horizontally.
Solution Approach 2:
The patent divides the charge storage function into two separate units (first charge storage unit and second charge storage unit) that are stacked vertically. This segmentation allows each unit to be optimized independently while working together to achieve higher overall saturation charge and sensitivity, managing complexity through functional division.
3Adaptability or versatility
If charge storage units are stacked on the opposite surface, then layout freedom is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The vertical stacking approach provides greater layout freedom by decoupling the spatial arrangement of functional units from the two-dimensional plane. This allows for more flexible positioning and routing in the lateral dimensions while the vertical connections are established through standardized through-substrate paths, managing the trade-off between layout flexibility and manufacturing precision.
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
Enhances saturation charge and sensitivity while reducing false signals by stacking charge storage units and using light-shielding isolations, thereby improving layout freedom.
Implementation Method 1
a photoelectric conversion unit of a second conductivity type, embedded into the first surface of the first semiconductor substrate, that generates a charge corresponding to an amount of received light by photoelectric conversion
Data Source
AI summary
There is provided an imaging device including a first semiconductor substrate of a first conductivity type that includes a first surface and a second surface on an opposite side from the first surface, a photoelectric conversion unit of a second conductivity type, embedded into the first surface of the first semiconductor substrate, that generates a charge corresponding to an amount of received light by photoelectric conversion, a first charge storage unit and a second charge storage unit of the second conductivity type, embedded in parallel into the second surface of the first semiconductor substrate, that store the charge generated in the photoelectric conversion unit, a first charge transfer unit that transfers the charge from the photoelectric conversion unit to the first charge storage unit, and a second charge transfer unit that transfers the charge from the photoelectric conversion unit to the second charge storage unit.