Solid-State Imaging Element Pixel Separation for Color Mixing
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Solution Overview
Problem
Miniaturization of solid-state imaging elements that simultaneously capture visible and infrared light images is hindered by color mixing due to the leakage of infrared light into adjacent visible-light receiving pixels, especially when the pixel size is reduced below 2.2 microns.
Innovation Solution
A solid-state imaging element design that includes a semiconductor layer with shared floating diffusion regions and pixel separation regions, where the penetrating pixel separation region penetrates the semiconductor layer in the depth direction and the non-penetrating pixel separation region reaches the midway part from the light receiving surface, effectively separating visible-light and infrared-light pixels and suppressing color mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pixel size is reduced below 2.2 microns to enable miniaturization, then the device size is reduced, but color mixing occurs due to infrared light leakage into adjacent visible-light pixels
Solution Approach 1:
The pixel separation region is divided into two distinct segments: a penetrating pixel separation region that extends through the entire semiconductor layer depth, and a non-penetrating pixel separation region that extends only to a midway part. This segmentation allows each region to perform its specific function - the penetrating region blocks infrared light leakage while the non-penetrating region maintains floating diffusion sharing, thereby preventing color mixing while enabling miniaturization
Solution Approach 2:
Different regions of the pixel separation structure are given different properties: the penetrating pixel separation region has full-depth separation properties to block infrared light, while the non-penetrating pixel separation region has partial-depth properties to allow floating diffusion sharing. This local differentiation of properties enables simultaneous achievement of color mixing prevention and miniaturization
2Object-generated harmful factors
If a penetrating pixel separation region is provided to prevent infrared light leakage, then color mixing is suppressed, but the device complexity increases
Solution Approach 1:
The penetrating and non-penetrating pixel separation regions are merged into a unified pixel separation structure that performs multiple functions simultaneously. The penetrating region prevents infrared light leakage while the non-penetrating region enables floating diffusion sharing, combining both functions in one integrated structure rather than requiring separate structures, thus reducing device complexity
Solution Approach 2:
The pixel separation region is designed with multi-functionality: it simultaneously provides infrared light blocking through the penetrating region and enables floating diffusion sharing through the non-penetrating region. This multi-functional design eliminates the need for separate structures for each function, thereby reducing overall device complexity while maintaining effective infrared light leakage prevention
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
Enables miniaturization of the pixel array while maintaining image quality by reducing color mixing and improving photoelectric conversion efficiency, sensitivity, and signal-to-noise ratio even at reduced pixel sizes.
Implementation Method 1
a visible-light pixel that receives visible light and performs photoelectric conversion and an infrared-light pixel that receives infrared light and performs photoelectric conversion
Data Source
AI summary
A solid-state imaging element that includes a semiconductor layer, a floating diffusion region (FD), a penetrating pixel separation region, and a non-penetrating pixel separation region. In the semiconductor layer, a visible-light pixel (PDc) that receives visible light and an infrared-light pixel (PDw) that receives infrared light are two-dimensionally arranged. The floating diffusion region is provided in the semiconductor layer and is shared by adjacent visible-light and infrared-light pixels. The penetrating pixel separation region is provided in a region excluding a region corresponding to the floating diffusion region in an inter-pixel region of the visible-light pixel and the infrared-light pixel, and penetrates the semiconductor layer in a depth direction. The non-penetrating pixel separation region is provided in the region corresponding to the floating diffusion region in the inter-pixel region, and reaches a midway part in the depth direction from the light receiving surface of the semiconductor layer.