Photoelectric Conversion Apparatus Gate Electrode Charge Transfer
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Solution Overview
Problem
Conventional photoelectric conversion apparatuses face challenges in controlling the electrical connection between the photoelectric conversion element and the drain region, leading to potential punch-through and reduced transfer efficiency of signal charges, especially as pixel size decreases.
Innovation Solution
A photoelectric conversion apparatus is designed with a semiconductor substrate having specific conductivity type regions and gate electrodes, where a fourth semiconductor region with higher impurity concentration is positioned closer to the surface, facilitating controlled electrical connection and improved signal charge transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the photodiode is formed deeply under the first gate electrode and the pixel size is reduced, then the integration density is improved, but punch-through occurs in the bulk resulting in electrical conduction between the photoelectric conversion element and drain region
Solution Approach 1:
The invention introduces a fourth semiconductor region with higher impurity concentration positioned between the first semiconductor region (photoelectric conversion element) and the third semiconductor region (drain region). This segmentation creates an intermediate zone that controls electrical connection, preventing direct contact and punch-through effects while allowing controlled charge transfer when needed.
Solution Approach 2:
The fourth semiconductor region acts as an intermediary structure between the photoelectric conversion element and the drain region. By positioning this high impurity concentration region closer to the surface, it serves as a mediator that prevents direct electrical conduction (punch-through) while still enabling controlled charge transfer through the second gate electrode, thus resolving the contradiction between integration density and electrical connection control.
2Productivity
If the photodiode is formed deeply under the first gate electrode, then the signal charge transfer efficiency is improved, but the electrical connection control between photoelectric conversion element and drain region becomes difficult
Solution Approach 1:
The fourth semiconductor region segments the electrical path between the photoelectric conversion element and drain region, creating a controlled interface that maintains high transfer efficiency while enabling precise electrical connection control through gate voltage manipulation.
Solution Approach 2:
The invention employs dynamic control of the second gate electrode to regulate electrical connection between the photoelectric conversion element and drain region. By adjusting gate voltages, the system can dynamically switch between connected and disconnected states, maintaining high transfer efficiency when needed while preventing unwanted conduction at other times.
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 transfer efficiency of signal charges while reducing dark current and allowing for operation at lower voltages, effectively addressing the challenges of punch-through and electrical connection control.
Implementation Method 1
a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type stacked on the first semiconductor region, and forming a part of a photoelectric conversion element
Implementation Method 2
a first gate electrode arranged over the fourth semiconductor region... and a second gate electrode arranged between the third and fourth semiconductor regions
Data Source
AI summary
A photoelectric conversion apparatus includes: a first semiconductor region forming a part of a photoelectric conversion element; a second semiconductor region stacked on the first semiconductor region, and forming a part of the photoelectric conversion element; a third semiconductor region to which a signal charge transferred from the photoelectric conversion element; a fourth semiconductor region of the first conductivity type having an higher impurity concentration, between the first and third semiconductor region and between the second and third semiconductor regions, closer to a main surface than the first semiconductor region, and connected to the first semiconductor region; a first gate electrode over the fourth semiconductor region, an insulating film on the main surface and between the first gate electrode and the fourth semiconductor region; and a second gate electrode between the third and fourth semiconductor regions, and over the insulating film.