Vertical Image Sensor Transistor With Charge Transfer Layer
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Solution Overview
Problem
The vertical transistor in solid-state image pickup devices experiences defects in signal electric charge transfer due to variations in the position of the gate electrode's bottom face, leading to yield reduction.
Innovation Solution
Incorporating an electric charge transfer layer between the gate electrode and the photodiode in the semiconductor substrate, which helps to suppress defects in signal electric charge transfer by providing a consistent transfer path regardless of the gate electrode's position variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a vertical transistor is used to read signal electric charge from the photodiode, then the device integration and miniaturization are improved, but defects in charge transfer occur due to variations in gate electrode position
Solution Approach 1:
An electric charge transfer layer is introduced as an intermediary component between the gate electrode and the photodiode. This transfer layer ensures reliable charge transfer even when the gate electrode position varies, by providing a dedicated path for charge carriers that is less sensitive to positional misalignment.
Solution Approach 2:
The invention addresses the positional variation problem (a positional tolerance issue in three dimensions) by introducing a fourth dimension - a temporal or sequential layer in the device structure. The charge transfer layer is positioned to accommodate variations in the vertical position of the gate electrode bottom face, effectively adding a degree of freedom to handle positional uncertainty.
2Device complexity
If the gate electrode is embedded in the semiconductor substrate, then the device complexity is reduced, but manufacturing precision requirements increase due to position variations
Solution Approach 1:
The electric charge transfer layer acts as a cushioning element that compensates for manufacturing variations in gate electrode position. By providing an intermediate charge transfer path, it cushions against the effects of positional deviations, reducing the stringency of manufacturing precision requirements.
3Adaptability or versatility
If multiple photodiodes are laminated in one pixel, then the spectroscopic characteristics are enhanced, but the charge transfer path becomes more complex
Solution Approach 1:
The electric charge transfer layer serves multiple functions: it facilitates charge transfer from multiple laminated photodiodes, accommodates positional variations of gate electrodes, and maintains reliable charge collection. This universal component simplifies the overall charge transfer path complexity by providing a common interface for multiple photodiodes.
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
The electric charge transfer layer effectively reduces defects in signal electric charge transfer, improving the yield and spectroscopic characteristics of the photodiodes by ensuring reliable charge transfer across varying gate electrode positions.
Implementation Method 1
a photodiode formed in the semiconductor substrate... the transistor being configured to read a signal electric charge from the photodiode via the gate electrode
Data Source
AI summary
There is provided a solid-state image pickup device including: a semiconductor substrate; a photodiode formed in the semiconductor substrate; a transistor having a gate electrode part or all of which is embedded in the semiconductor substrate, the transistor being configured to read a signal electric charge from the photodiode via the gate electrode; and an electric charge transfer layer provided between the gate electrode and the photodiode.