Stacked Photoelectric Conversion Layout With Shared Transfer Gates
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Solution Overview
Problem
The existing photoelectric conversion apparatuses, such as those disclosed in Japanese Patent Laid-Open No. 2018/113606, face limitations in the area where elements can be arranged due to the presence of through-electrodes in insulating regions, which restricts the functionality and efficiency of the semiconductor substrates.
Innovation Solution
A photoelectric conversion apparatus is designed with a stacked configuration of two substrates, where the first substrate includes photoelectric conversion circuits and transfer transistors, and the second substrate includes amplification transistors and a polysilicon gate that is electrically connected to the through-electrodes, allowing for improved signal processing and increased functionality by sharing gates and floating diffusions across multiple pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through-electrodes are provided in insulating regions to connect stacked substrates, then electrical connection between substrates is achieved, but the area available for element arrangement is reduced
Solution Approach 1:
The patent merges the gate electrodes of transfer transistors on the first substrate with the gate electrodes of amplification transistors on the second substrate by making them electrically connected through the insulating layer. This consolidation reduces the number of separate through-electrodes needed, as the shared gate structure eliminates redundant connection paths, thereby preserving more area for element arrangement while maintaining reliable electrical connection.
Solution Approach 2:
The patent implements multi-functionality by designing the gate electrode structure to serve dual purposes: it acts as the gate for transfer transistors on the first substrate and simultaneously serves as the gate for amplification transistors on the second substrate. This universal gate structure reduces the total number of through-electrodes required, increasing the effective area for arranging other circuit elements.
2Ease of operation
If multiple through-electrodes are used to connect transfer transistors and amplification transistors, then signal transfer is enabled, but device complexity increases
Solution Approach 1:
The patent combines multiple through-electrodes into a shared gate electrode structure that connects both transfer transistors and amplification transistors. By merging these connection paths, the number of individual through-electrodes is reduced, simplifying the overall device structure while maintaining effective signal transfer functionality between the stacked substrates.
3Reliability
If channel width-to-length ratio of amplification transistors is increased to improve noise performance, then noise performance improves, but device area increases
Solution Approach 1:
The patent utilizes the vertical stacking dimension to achieve improved noise performance without proportionally increasing planar area. By stacking the first substrate with photoelectric conversion circuits and the second substrate with amplification transistors in three dimensions, the design allows for optimized transistor geometries that can achieve higher channel width-to-length ratios for better noise performance while maintaining compact overall device footprint through vertical integration.
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 noise performance and reduces the number of through-electrodes, enabling more efficient signal processing and improved image quality by increasing the channel width-to-length ratio of amplification transistors and allowing for higher functionality in a compact form.
Implementation Method 1
The first photoelectric conversion circuit is configured to receive light from the second plane. The second photoelectric conversion circuit is configured to receive light from the second plane.
Implementation Method 2
The first transfer transistor is provided on a side where the first plane is provided and is configured to transfer signal charge generated in the first photoelectric conversion circuit to the floating diffusion. The second transfer transistor is provided on the side where the first plane is provided and is configured to transfer signal charge generated in the second photoelectric conversion circuit to the floating diffusion.
Implementation Method 3
The first amplification transistor is configured to receive a signal via the first transfer transistor. The second amplification transistor is configured to receive a signal via the second transfer transistor.
Data Source
AI summary
A photoelectric conversion apparatus includes first and second components. The first component includes a first semiconductor substrate (FSS), a first photoelectric conversion circuit (FPCC), a second photoelectric conversion circuit (SPCC), a floating diffusion, a first transfer transistor (FTT) that transfers signal charge generated in the FPCC to the FD, and a second transfer transistor (STT) that transfers signal charge generated in the SPCC to the floating diffusion. The second component includes a second semiconductor substrate, an insulator that penetrates through the second semiconductor substrate, a first amplification transistor that receives a signal via the FTT, and a second amplification transistor that receives a signal via the STT. The second component is stacked on the first component. A polysilicon member that is a gate of the FTT is a gate of the STT, and a through-electrode that penetrates through the insulator and the polysilicon member are electrically connected to each other.