Image Sensor Pixel Structure With Low-Index Layer for Quantum Efficiency
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Solution Overview
Problem
The use of polycrystalline silicon electrodes in imaging devices leads to light absorption, resulting in a decrease in quantum efficiency due to the absorption of light by the electrode material.
Innovation Solution
Incorporating a light absorption inhibition section with a material of lower refractive index than the photoelectric conversion sections, such as silicon oxide or air, between the photoelectric conversion sections and the conductor, to prevent evanescent light leakage and maintain quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycrystalline silicon is used for the electrode to collect holes and prevent dark current, then reliability is improved, but light absorption occurs leading to decreased quantum efficiency
Solution Approach 1:
An intermediary layer with lower refractive index (such as silicon oxide or air) is introduced between the polycrystalline silicon electrode and the photoelectric conversion section. This intermediary prevents evanescent light generated in the photoelectric conversion section from being absorbed by the polycrystalline silicon electrode, thereby resolving the contradiction between maintaining reliability (dark current prevention) and reducing energy loss (quantum efficiency).
Solution Approach 2:
The patent converts the harmful light absorption effect of polycrystalline silicon into a beneficial configuration by strategically positioning a low refractive index material between the photoelectric conversion section and the electrode. This arrangement allows the polycrystalline silicon to maintain its electrical function while preventing its light absorption property from degrading quantum efficiency.
2Loss of energy
If a low refractive index material is introduced between the photoelectric conversion section and the electrode, then quantum efficiency is maintained, but device structure becomes more complex
Solution Approach 1:
The patent employs a thin film structure of low refractive index material (such as silicon oxide) with a thickness of 20 nm or more. This thin film approach maintains the optical benefit of preventing light absorption while minimizing the increase in device complexity and maintaining manufacturing feasibility.
Solution Approach 2:
The patent optimizes the thickness parameter of the low refractive index layer to be 20 nm or more, which is sufficient to prevent evanescent light absorption by the polycrystalline silicon electrode while keeping the overall device structure compact and manageable. This parameter optimization balances quantum efficiency improvement with device complexity control.
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 implementation of a light absorption inhibition section with a thickness of 20 nm or more and a length of 1,000 nm or more effectively prevents light absorption, thereby maintaining or improving quantum efficiency across various light wavelengths.
Implementation Method 1
the second member containing a material with a lower refractive index than that of the photoelectric conversion sections
Implementation Method 2
light absorption by the polycrystalline silicon occurs, leading to a decrease in quantum efficiency... the second member preventing evanescent light leakage
Data Source
AI summary
Provided are an imaging device capable of preventing a decrease in quantum efficiency, and an electronic apparatus using this imaging device. The imaging device of the present disclosure includes multiple photoelectric conversion sections provided for respective pixels and each having a first end portion on a light incident side and a second end portion on a side opposite to the first end portion, a first member disposed along a boundary of each of the multiple photoelectric conversion sections in a first direction that extends from the first end portion to the second end portion, and a second member provided between each of the multiple photoelectric conversion sections and the first member and at the first end portion, the second member containing a material with a lower refractive index than that of the photoelectric conversion sections.