Stacked Photodiode Signal Charge Transfer Path
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Solution Overview
Problem
In solid-state imaging devices, stacking multiple photodiodes increases space requirements and design complexity due to the need for an equal number of vertical transistors, making it difficult to form transistors that extend from the circuit surface to deep photodiodes, especially when three or more photodiodes are stacked.
Innovation Solution
The solution involves stacking photodiodes in a semiconductor layer where one or more photodiodes act as a signal charge transfer path for others, eliminating the need for transistors to extend to the surface and reducing the transfer distance, thus saving space and simplifying the design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple photodiodes are stacked in a semiconductor substrate, then saturation capacity of pixels is increased, but space for disposition of vertical transistors is increased and design complexity increases
Solution Approach 1:
The patent applies multi-functionality by enabling intermediate photodiodes to serve dual purposes: they function as signal charge accumulation regions for specific wavelengths while simultaneously acting as transfer paths for signal charges from other photodiodes. This eliminates the need for separate vertical transistors for each photodiode, reducing the area required for transistor disposition while maintaining the stacked configuration's saturation capacity.
Solution Approach 2:
The patent merges the transfer path function with the photodiode structure itself. Instead of having separate vertical transistors extending from each photodiode to the surface, the signal charge transfer is achieved through the semiconductor layer and intermediate photodiodes, combining multiple functions into a unified structure that reduces overall space requirements.
2Ease of operation
If vertical transistors extend from circuit surface to deep photodiodes, then signal charge reading is enabled, but manufacturing difficulty increases and design complexity increases
Solution Approach 1:
The patent inverts the conventional approach by having signal charges move upward through intermediate photodiodes to reach the surface, rather than requiring transistors to extend downward from the surface to deep photodiodes. This reversal of the charge transfer direction eliminates the need for deep transistor formation, significantly reducing manufacturing difficulty while maintaining effective signal charge reading.
Solution Approach 2:
The patent introduces intermediate photodiodes as mediators in the signal charge transfer process. These intermediate structures facilitate charge transfer between deep photodiodes and the surface without requiring direct vertical transistor connections, thereby simplifying the manufacturing process while enabling effective signal charge reading.
3Quantity of substance
If three or more photodiodes are stacked, then saturation capacity is further increased, but space requirements and design complexity become prohibitive
Solution Approach 1:
The patent applies multi-functionality to enable intermediate photodiodes in a three-or-more stacked configuration to serve dual purposes: accumulating signal charges for specific wavelengths and simultaneously acting as transfer paths for charges from other photodiodes. This eliminates the need for separate vertical transistors for each photodiode, reducing design complexity while maintaining high saturation capacity.
Solution Approach 2:
The patent merges multiple functions into a unified stacked photodiode structure where intermediate layers perform both signal accumulation and charge transfer. This consolidation reduces the number of separate components and simplifies the overall design, making three-or-more photodiode stacking feasible without prohibitive complexity.
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 approach allows for a compact, efficient stacked configuration of photodiodes, reducing space requirements and design complexity while maintaining effective signal charge transfer, enabling space-saving and easier manufacturing.
Implementation Method 1
a plurality of photodiodes stacked in the semiconductor layer, wherein one or more photodiodes of the plurality of photodiodes also serve as a transfer path of a signal charge accumulated in other photodiodes
Data Source
AI summary
A solid-state imaging device includes: a semiconductor layer having a first surface and a second surface that oppose each other; and a plurality of photodiodes stacked in the semiconductor layer. One or more photodiodes of the plurality of photodiodes also serve as a transfer path of a signal charge accumulated in other photodiodes.