3D Stacked Imaging Device Transistor Threshold Voltage Stabilization
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Solution Overview
Problem
Imaging devices with a three-dimensional structure face challenges in achieving high image quality due to the influence of electric fields from through wiring lines on transistors, leading to variations in transistor characteristics and potential current leakage.
Innovation Solution
Incorporating adjusters on the side surfaces and back surfaces of the semiconductor substrate to adjust the threshold voltage of transistors, and positioning through wiring lines in a way that minimizes their electric field influence, such as embedding the end of the gate of the transistor adjacent to the through wiring line in an insulating film or shifting the through wiring line's position relative to the transistor's gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through wiring lines are provided to electrically couple stacked substrates, then substrate electrical coupling is achieved, but electric field influence on transistors causes threshold voltage variations and current leakage
Solution Approach 1:
An adjuster is introduced as an intermediary element between the through wiring line and the transistor. The adjuster compensates for the electric field influence by providing counteracting charges, thereby stabilizing the transistor threshold voltage despite the presence of the through wiring line.
Solution Approach 2:
The threshold voltage of the transistor is adjusted by modifying the electrical parameters of the adjuster element. By changing the charge state or electrical properties of the adjuster, the threshold voltage can be compensated for variations caused by the through wiring line's electric field.
2Productivity
If transistor density is increased in three-dimensional stacked structure, then pixel density and imaging device compactness are improved, but electric field interference from through wiring lines increases
Solution Approach 1:
The compensation mechanism is applied selectively to specific transistors that are most affected by the through wiring lines. Rather than compensating for all transistors uniformly, the adjusters are strategically placed or activated only where needed, allowing high transistor density while providing targeted interference compensation.
3Reliability
If adjusters are provided on side surfaces and back surfaces of semiconductor substrate, then transistor threshold voltage is stabilized, but device structure and manufacturing complexity increase
Solution Approach 1:
The adjuster structure is merged with existing device components where possible. The adjuster is integrated into the transistor structure or substrate architecture, combining multiple functions into unified structures to reduce overall device complexity while maintaining threshold voltage stabilization capability.
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 reduces the impact of electric fields on transistors, stabilizes transistor characteristics, and prevents current leakage, thereby enhancing image quality and reducing noise in imaging devices.
Implementation Method 1
The adjuster adjusts a threshold voltage of the second transistor... reduces the impact of electric fields on transistors
Implementation Method 2
The through wiring line electrically couples the first substrate and the second substrate
Implementation Method 3
embedding the end of the gate of the transistor adjacent to the through wiring line in an insulating film
Data Source
AI summary
An imaging device according to an embodiment of the present disclosure includes: a first substrate; a second substrate; and a through wiring line. The first substrate includes a photoelectric conversion section and a first transistor in a first semiconductor substrate. The photoelectric conversion section and the first transistor are included in a sensor pixel. The second substrate is stacked on the first substrate and includes a second transistor and an opening that extends through a second semiconductor substrate. The second substrate has an adjuster on at least one of a side surface of the opening near a gate of the second transistor or a region of a surface opposed to the first transistor. The second transistor is included in the sensor pixel. The adjuster adjusts a threshold voltage of the second transistor. The through wiring line is in the opening and electrically couples the first substrate and the second substrate.