Solid-State Imaging Device Pixel Separation Trench Structure
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Solution Overview
Problem
Solid-state imaging devices face challenges in improving image quality due to light shielding and color mixing issues, particularly in rear surface illumination types, where light leakage and inclined light entry lead to shading and decreased color reproducibility, and in front surface illumination types, where thick wiring layers obstruct light and cause sensitivity issues.
Innovation Solution
A solid-state imaging device configuration with a pixel separation portion that includes a pinning layer and a light shielding layer in trenches on the incident surface side of the semiconductor substrate, where the pinning layer covers the inside surface of a wider second trench and the light shielding layer buries the inner portion of the second trench, effectively separating and shielding light between pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thick multilayer wiring layer is disposed between the microlens and the light sensing surface in front surface illumination type, then the wiring layer can provide electrical connections, but the light is shielded by the wirings and sensitivity decreases
Solution Approach 1:
The patent inverts the conventional front surface illumination structure to rear surface illumination type, where the light sensing surface is positioned on the rear surface of the semiconductor substrate opposite to the wiring layer side. This allows light to enter the photodiode directly without being shielded by the multilayer wiring layer, thereby maintaining high light sensitivity while preserving the electrical connection functionality of the wiring layer.
2Manufacturing precision
If light shielding films are provided between pixels in rear surface illumination type, then color mixing is suppressed, but device complexity increases
Solution Approach 1:
The patent introduces an isolation layer with specific optical absorption characteristics positioned between adjacent photodiodes in the rear surface illumination type. This localized structure selectively absorbs stray light and suppresses color mixing between adjacent pixels without requiring complex light shielding films over the entire device, thereby reducing device complexity while maintaining manufacturing precision.
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
This configuration enhances image quality by reducing light leakage, shading, and color mixing, while maintaining high saturation charge accumulation, thereby improving the captured image's spectral and blooming characteristics.
Implementation Method 1
a light shielding layer that buries an inner portion of the second trench
Implementation Method 2
a photoelectric conversion portion is provided on each pixel. For example, the photoelectric conversion portion is a photodiode, and 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 in a semiconductor substrate and receives incident light through a light sensing surface, and a pixel separation portion provided to electrically separate a plurality of pixels. At least a pinning layer and a light shielding layer are provided in an inner portion of a trench provided on a side portion of each of the photoelectric conversion portions in an incident surface side, the trench includes a first trench and a second trench formed to be wider than the first trench in a portion shallower than the first trench, the pinning layer is formed in an inner portion of the first trench to cover an inside surface of the second trench, and the light shielding layer is formed to bury an inner portion of the second trench at least via the pinning layer.