Refractive Index Variation Layer for Light Detection
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Solution Overview
Problem
Existing light detection devices face challenges in reducing reflection of incident light, which varies with the image height position due to differing incident angles, leading to issues like decreased quantum efficiency and flaring.
Innovation Solution
A light detection device with a pixel array unit where each pixel includes a refractive index variation layer with at least two regions, a first region containing a first matter and a second region containing a second matter, and a photoelectric conversion unit. The effective refractive index of the refractive index variation layer is configured to differ depending on the image height position of the pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform anti-reflection structure is used across all pixels, then manufacturing is simplified, but reflection cannot be reduced effectively at different image height positions due to varying incident angles
Solution Approach 1:
The patent applies local quality by configuring different effective refractive indices in the refractive index variation layer according to the image height position. Pixels at different vertical positions have different incident angles, so the refractive index is optimized locally for each region to maximize light transmission at that specific angle, thereby resolving the contradiction between manufacturing simplicity and reflection reduction effectiveness.
2Reliability
If the refractive index variation layer has complex regional configurations optimized for each image height position, then reflection is reduced effectively, but device structure becomes more complex
Solution Approach 1:
The patent segments the refractive index variation layer into multiple regions with different effective refractive indices, corresponding to different image height positions. Each region is optimized for its specific incident angle characteristics. This segmentation allows effective reflection reduction across the entire pixel array while maintaining a systematic and manageable structure that can be manufactured using standard semiconductor processing techniques.
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 reduces reflection of incident light across different image height positions, enhancing quantum efficiency and minimizing flaring issues.
Implementation Method 1
The refractive index of a silicon substrate used as a semiconductor substrate in a CMOS image sensor is high, and the difference from the refractive index of a color filter layer formed on an incident surface side of the silicon substrate is large. As such, when the color filter layer is formed directly on the silicon substrate, the difference in the refractive indices results in a large amount of the incident light being reflected.
Implementation Method 2
PTL 1 discloses a technique for reducing the reflection of incident light by forming a moth-eye structure as an anti-reflection structure between the color filter layer and the silicon substrate.
Implementation Method 3
a photoelectric conversion unit that photoelectrically converts light incident through the refractive index variation layer
Data Source
AI summary
The present disclosure relates to a light detection device and an electronic device capable of reducing reflection of incident light depending on an image height position. The light detection device includes a pixel array unit in which a plurality of pixels is arranged in a two-dimensional array. Each pixel includes: a refractive index variation layer having at least two regions in the same layer, the two regions being a first region containing a first matter and a second region containing a second matter; and a photoelectric conversion unit that photoelectrically converts light incident through the refractive index variation layer. An effective refractive index of the refractive index variation layer is configured to differ depending on an image height position of the pixel. The present disclosure can be applied in, for example, a solid-state image capturing device, a light-receiving device of a rangefinding system, or the like.