Solid-State Image Sensor Internal Gate Layout for Higher Saturation Charge
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Solution Overview
Problem
Conventional solid-state imaging elements face challenges in achieving a higher saturation charge amount in photoelectric conversion units, particularly in global shutter type imaging elements where the photoelectric conversion and charge holding units are divided, leading to reduced dynamic range due to decreased saturation charge.
Innovation Solution
Incorporating a photoelectric conversion unit, a transfer transistor, and internal gates within the solid-state imaging element to deepen the potential of specific regions, allowing for enhanced charge transfer and accumulation, thereby improving the saturation charge amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the area of photoelectric conversion unit is increased to improve saturation charge amount, then the saturation charge amount increases, but the pixel area becomes larger which reduces the number of pixels that can be arranged
Solution Approach 1:
The patent applies local quality by creating a potential well in a specific region adjacent to the transfer transistor within the photoelectric conversion unit. This localized potential modification concentrates charge carriers in a specific area, effectively increasing the saturation charge amount without requiring an increase in the overall pixel area. The internal gate structure creates a localized potential depression that enhances charge storage capacity in a confined space.
Solution Approach 2:
The patent utilizes the depth dimension by forming a potential well that extends vertically into the semiconductor substrate. This three-dimensional potential structure allows charge carriers to be stored not only in the planar direction but also in the vertical direction, effectively increasing the saturation charge amount without increasing the surface pixel area. The potential well depth provides an additional dimension for charge storage.
2Quantity of substance
If internal gate is added to deepen potential and improve saturation charge amount, then saturation charge amount increases, but device complexity increases
Solution Approach 1:
The patent merges the internal gate structure with the transfer transistor structure, where the internal gate is formed in close proximity to the transfer transistor. This integration allows the internal gate to share fabrication processes and structural elements with the transfer transistor, reducing overall device complexity while still achieving the desired potential well formation for increased saturation charge amount.
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 solution effectively increases the saturation charge amount of the photoelectric conversion unit, enhancing the dynamic range and improving the imaging performance by ensuring all accumulated charges are transferred efficiently, even when the potential of the first region is deepened.
Implementation Method 1
a photoelectric conversion unit that photoelectrically converts incident light
Data Source
AI summary
A solid-state imaging element (1) according to the present disclosure includes a photoelectric conversion unit, a transfer transistor (TY), and an internal gate (PY). The photoelectric conversion unit photoelectrically converts incident light. The transfer transistor (TY) transfers a charge generated by the photoelectric conversion unit. The internal gate (PY) is disposed adjacent to the transfer transistor (TY) inside the photoelectric conversion unit and deepens the potential of at least a partial region in the photoelectric conversion unit.