Pixel Separation Trench with Light-Absorbing Insulation for Solid-State Imaging
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Solution Overview
Problem
In solid-state imaging devices, particularly in both 'rear surface illumination' and 'front surface illumination' types, the issue of 'color mixing' occurs due to light being directed to adjacent pixels, leading to decreased image quality and difficulty in improving sensitivity and dynamic range, especially with shorter and longer wavelengths of light.
Innovation Solution
A solid-state imaging device is designed with a pixel separation portion embedded in a trench on the side of the photoelectric conversion portion, formed by an insulation material that absorbs incident light, effectively separating pixels and preventing light from entering adjacent photodiodes, thereby reducing 'color mixing' and enhancing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If light shielding films are provided between pixels to suppress color mixing, then image quality improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The pixel separation portion divides the pixel region into independent pixel units by embedding insulating materials in trenches between adjacent pixels. This segmentation prevents optical interference between pixels while maintaining a relatively simple overall structure without requiring complex light shielding films.
Solution Approach 2:
The harmful optical interference between pixels is extracted and eliminated by removing the need for complex light shielding films. Instead, the patent uses embedded insulating materials in trenches to achieve pixel separation, simplifying the device structure while maintaining image quality.
2Measurement precision
If the photoelectric conversion portion is made larger to increase saturation charge accumulation amount, then sensitivity and dynamic range improve, but the area occupied by each pixel increases
Solution Approach 1:
The patent extends the photoelectric conversion portion in the depth direction (third dimension) by forming a deep well structure. This allows the photodiode to accumulate more charge without increasing the lateral pixel area, thereby improving sensitivity and dynamic range while maintaining high pixel density.
Solution Approach 2:
The insulating material is nested within the trench structure, and the photodiode is formed within the deep well. This nested arrangement allows the photoelectric conversion portion to extend deeply into the substrate without occupying additional lateral space, enabling increased charge accumulation capacity within the same pixel footprint.
3Use of energy by moving object
If incident light enters at large angles in rear surface illumination type, then light can enter the photodiode, but color mixing occurs as light enters adjacent pixels
Solution Approach 1:
The insulating material embedded in the trench acts as an intermediary barrier between adjacent pixels. It absorbs or reflects stray light that enters at large angles, preventing this light from reaching adjacent photodiodes and causing color mixing, while still allowing intended light to reach the correct pixel.
Solution Approach 2:
The pixel separation structure provides localized optical isolation between adjacent pixels. By embedding insulating materials specifically at the boundaries between pixels, the patent creates local quality differences that prevent color mixing without affecting the overall light reception efficiency of each pixel.
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 improves image quality by preventing 'color mixing' and increasing the saturation charge accumulation amount, particularly for blue light, and enhances sensitivity by ensuring that light is directed to the intended pixel, thus improving the dynamic range and color reproducibility.
Implementation Method 1
the pixel separation portion is formed by an insulation material which absorbs the incident light entering the light sensing surface
Implementation Method 2
the photoelectric conversion portion receives incident light through the light sensing surface and generates a signal charge by performing a photoelectric conversion with respect to the received light
Data Source
AI summary
A solid-state imaging device includes a plurality of photoelectric conversion portions each provided to correspond to each of a plurality of pixels in a semiconductor substrate and receiving incident light through a light sensing surface, and a pixel separation portion that is embedded into a trench provided on a side portion of the photoelectric conversion portion and electrically separates the plurality of pixels in a side of an incident surface of the semiconductor substrate into which the incident light enters. The pixel separation portion is formed by an insulation material which absorbs the incident light entering the light sensing surface.