Solid-State Image Sensor Protrusions Trenches Reduce IR Leakage
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Solution Overview
Problem
Conventional solid-state image pickup elements face issues with light leakage between infrared (IR) and visible-light pixels, leading to color mixture and insufficient sensitivity, particularly under low illumination conditions.
Innovation Solution
A solid-state image pickup element with protrusions on the light-receiving surface, surrounded by a trench and a buried member, is designed to reduce reflectance and prevent light leakage. The protrusions have an interval of 250 nanometers or more, and the trench is at least 2 micrometers deep, with the buried member having a lower refractive index than the pixel, often made of metal. This configuration is applied to both IR and visible-light pixels, and an IR interrupting filter is used between the pixels and the image pickup lens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fine asperities are provided on the light-receiving surface of an IR pixel to improve sensitivity, then the transmittance increases and sensitivity improves, but light may leak into adjacent visible-light pixels causing color mixture
Solution Approach 1:
The invention divides the light-receiving surface into distinct regions by forming trenches around each pixel. These trenches physically segment the optical paths of adjacent pixels, preventing light from one pixel from leaking into neighboring pixels. This segmentation resolves the contradiction by maintaining the fine asperities for high transmittance while adding spatial separation to prevent color mixture.
Solution Approach 2:
The invention introduces an intermediary structure (trench with reflective coating) between adjacent pixels. This intermediary element acts as a barrier that reflects stray light back to its origin pixel while allowing the fine asperities to maintain high light transmission. The trench serves as a mediating structure that prevents direct optical coupling between pixels, thereby preventing color mixture while preserving sensitivity.
2Measurement precision
If the amount of infrared light is less than visible light under low illumination, then the sensitivity of IR pixel must be improved preferentially, but improving sensitivity may cause light to leak into visible-light pixels
Solution Approach 1:
The trench structure segments the optical paths of IR and visible-light pixels, allowing the IR pixel to have enhanced sensitivity through fine asperities without compromising overall image quality. The segmentation ensures that even with high sensitivity, light from the IR pixel cannot leak into visible-light pixels, maintaining reliable color accuracy.
Solution Approach 2:
The invention applies different surface structures to different pixel types: fine asperities are provided on IR pixels to maximize their sensitivity under low illumination, while visible-light pixels maintain their original structure. The trenches are selectively positioned around IR pixels to prevent light leakage. This local differentiation allows preferential sensitivity improvement for IR pixels without degrading overall image quality.
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 inhibits color mixture and enhances the sensitivity of both IR and visible-light pixels, improving image quality by reducing light reflection and absorption, thereby addressing the limitations of existing technologies.
Implementation Method 1
The plurality of protrusions allows the reflectance on the light-receiving surface to fall and the transmittance to rise relatively
Implementation Method 2
a pixel having a plurality of protrusions formed on a light-receiving surface
Implementation Method 3
a light-receiving-surface-sided member buried in the light-receiving-surface-sided trench
Implementation Method 4
the light-receiving-surface-sided member may include metal
Data Source
AI summary
Provided is a solid-state image pickup element that includes a pixel, a light-receiving-surface-sided trench, and a light-receiving-surface-sided shielding member. A plurality of protrusions is formed on the light-receiving surface of the pixel in the solid-state image pickup element. In addition, the light-receiving-surface-sided trench is formed around the pixel having the plurality of protrusions formed, at the light-receiving surface in the solid-state image pickup element. In addition, the light-receiving-surface-sided member is buried in the light-receiving-surface-sided trench formed around the pixel having the plurality of protrusions formed on the light-receiving surface in the solid-state image pickup element. In addition, the photoelectric conversion region of a near-infrared-light pixel expands to the surface side opposed to the light-receiving surface of the photoelectric conversion region of a visible-light pixel. In addition, a trench is further formed inside the pixel at a surface opposed to the light-receiving surface.