Global Shutter Pixel Shielding Layout for Light Leakage Control
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Solution Overview
Problem
In global shutter imaging elements, light leakage between band-shaped light shielding portions leads to noise in image signals due to contact between end portions of these shielding structures, compromising image quality.
Innovation Solution
The imaging element incorporates a rectangular pixel configuration with band-shaped light shielding films for both charge holding and transfer units, where the charge transfer unit light shielding film overlaps with the charge holding unit light shielding film to prevent light leakage, and these films are strategically positioned between the photoelectric conversion and charge holding units to shield incident light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If band-shaped light shielding portions are disposed alternately at different depths to shield charge holding and transfer units, then light shielding coverage is improved, but end portions contact each other causing light leakage
Solution Approach 1:
The patent transitions from a two-dimensional alternating pattern to a three-dimensional overlapping arrangement. The first light shielding portion is disposed at a first depth and the second light shielding portion is disposed at a second depth different from the first depth, with their projection areas overlapping in the thickness direction. This vertical stacking approach prevents end portion contact while maintaining comprehensive light shielding coverage.
Solution Approach 2:
The patent implements a nested structure where the second light shielding portion is positioned within the projection area of the first light shielding portion in the thickness direction. This nesting arrangement allows the lighter second shielding portion to be contained within the coverage area of the first shielding portion, creating overlapping protection without requiring the end portions to contact each other.
2Quantity of substance
If photoelectric conversion unit and charge holding unit are disposed at overlapping positions in thickness direction, then pixel density is improved, but light must be shielded from charge holding unit
Solution Approach 1:
The patent utilizes the thickness direction (vertical dimension) to resolve the spatial conflict between the photoelectric conversion unit and charge holding unit. By disposing these units at overlapping positions in the thickness direction with different depth positions, the patent achieves high pixel density while preventing light from reaching the charge holding unit through strategic light shielding.
Solution Approach 2:
The patent introduces light shielding portions as intermediary structures between the photoelectric conversion unit and the charge holding unit. These shielding portions are disposed at specific depths to block incident light from reaching the charge holding unit, while allowing the photoelectric conversion unit to receive light for charge generation.
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 significantly reduces light leakage to the charge holding unit, thereby minimizing noise in the image signal and enhancing image quality by ensuring effective light shielding.
Implementation Method 1
a photoelectric conversion unit that is disposed on a light receiving face of a semiconductor substrate and performs photoelectric conversion on incident light
Data Source
AI summary
To prevent leakage of incident light to a charge holding unit of an imaging element. The pixel includes a photoelectric conversion unit disposed on a side of the light receiving face of the semiconductor substrate, a charge holding unit disposed on a side different from the light receiving face of the semiconductor substrate, and a charge transfer unit that transfers a charge to the charge holding unit, and is configured to have a rectangular shape in a light receiving face view. The charge holding unit light shielding film is configured to have a band shape adjacent to three sides including a first side that is one of the sides of the rectangle and parallel to the first side in a light receiving face view, is adjacent to a semiconductor region including the charge transfer unit in a light receiving face view, and is disposed in the pixel between the photoelectric conversion unit and the charge holding unit to shield incident light. The charge transfer unit light shielding film is configured to have a band shape adjacent to three sides including a second side that is a side facing the first side in a light receiving face view and parallel to the second side, and is configured to be disposed in the pixel between the photoelectric conversion unit and the charge transfer unit to shield incident light and have a shape which has an end portion overlapping an end portion of the charge holding unit light shielding film in a light receiving face view.