Vertical Transistor Floating Diffusion Layer Charge Transfer
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Solution Overview
Problem
In backside illumination type solid-state image pickup devices, achieving high charge transfer efficiency from the photoelectric conversion unit to the floating diffusion layer is challenging due to potential barriers and dips along the channel rotation direction of the vertical transistor, which complicates the charge transfer process.
Innovation Solution
A solid-state image pickup device design featuring a vertical transistor with a floating diffusion layer surrounding the groove portion acting as the channel region, along with a reset transistor gate electrode positioned adjacent to the floating diffusion layer, and a uniform or gradually increasing impurity density within the floating diffusion layer to control potential distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vertical transistor is used to transfer charge from the photoelectric conversion unit to the floating diffusion layer, then charge transfer is enabled, but potential barriers and potential dips along the channel rotation direction reduce transfer efficiency
Solution Approach 1:
The patent applies local quality by forming a groove portion specifically in the channel region of the vertical transistor to locally modify the potential distribution. This groove structure creates a potential well that guides charge carriers along a smoother path, reducing potential barriers and dips only in the critical charge transfer region without affecting other parts of the device.
Solution Approach 2:
The patent introduces a spatial dimension by forming a groove portion (a three-dimensional structure) within the channel region. This groove extends in the depth direction of the substrate, adding a vertical dimension to the charge transfer path and enabling charges to navigate around potential barriers rather than moving linearly through them.
2Reliability
If the floating diffusion layer is formed to surround the groove portion, then charge transfer efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by forming the groove portion in the channel region before forming the floating diffusion layer. This sequence allows the groove structure to be established as a template, guiding the subsequent formation of the floating diffusion layer to surround it precisely, thereby reducing the actual precision requirements during the floating diffusion layer formation process.
Solution Approach 2:
The groove portion acts as an intermediary structure that mediates between the channel region and the floating diffusion layer. By surrounding the groove portion, the floating diffusion layer is automatically positioned with high precision without requiring direct complex alignment processes, as the groove serves as a physical guide and reference structure.
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 charge transfer efficiency by minimizing potential barriers and dips, allowing for effective signal charge transfer from the photoelectric conversion unit to the floating diffusion layer without the need for complex impurity forming processes or uniform gate insulating film thickness.
Implementation Method 1
a vertical transistor that performs charge transfer from a photoelectric conversion unit formed in a semiconductor substrate to a floating diffusion layer
Implementation Method 2
photoelectric conversion unit formed in a semiconductor substrate
Data Source
AI summary
The present disclosure relates to a solid-state image pickup device, a manufacturing method, and an electronic apparatus, which can obtain high charge transfer efficiency from a photoelectric conversion unit to a floating diffusion layer. The floating diffusion layer is arranged in a rectangular shape so as to surround a gate electrode of a vertical transistor whose groove portion is rectangular. A reset drain is formed so as to be adjacent to the floating diffusion layer through a reset gate. A potential of the floating diffusion layer is reset to the same potential as that of the reset drain by applying a predetermined voltage to the reset gate. It is possible to apply the present disclosure to, for example, a CMOS solid-state image pickup device used in an image pickup device such as a camera.