Solid-State Imaging Element Stray Light Suppression
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Solution Overview
Problem
Conventional solid-state imaging elements with global shutters face insufficient light shielding, leading to stray light issues and false signal generation due to photoelectric conversion in floating diffusion (FD) units.
Innovation Solution
The implementation of a solid-state imaging element design where the FD is positioned below a cross-shaped light shielding structure, with varying lengths and thicknesses of light shielding units between pixels, and the integration of specific transistors and antireflection materials to enhance light shielding and reduce false signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the FD is disposed below a light shielding wall between pixels, then light shielding is provided, but stray light suppression is insufficient and false signals are generated
Solution Approach 1:
The light shielding structure is divided into two distinct segments: a first light shielding unit positioned between adjacent pixels and a second light shielding unit (cross portion) positioned above the charge storage unit. This segmentation allows each unit to perform specialized light shielding functions, with the first unit blocking lateral stray light and the second unit blocking vertical stray light, thereby comprehensively suppressing stray light to prevent false signals in the FD
Solution Approach 2:
The light shielding approach transitions from a single horizontal layer to a two-dimensional arrangement by adding the cross portion that extends in the thickness direction above the charge storage unit. This vertical dimension addition creates a three-dimensional light shielding network that blocks stray light from multiple directions (both lateral and vertical), significantly improving stray light suppression effectiveness compared to conventional single-layer shielding
2Object-affected harmful factors
If light shielding structures are added to suppress stray light, then false signal generation is reduced, but device complexity increases
Solution Approach 1:
The first light shielding unit and the second light shielding unit are merged into a single integrated light shielding structure formed by the same insulating film and conductive material layers. This merging allows both shielding units to be manufactured simultaneously through a unified fabrication process, reducing process complexity while maintaining the dual-unit shielding architecture. The shared structural foundation simplifies manufacturing compared to implementing two completely separate shielding structures
Solution Approach 2:
The insulating film and conductive material layers form a multi-functional structure that simultaneously serves as both the first light shielding unit and the second light shielding unit. These layers perform multiple functions: providing electrical isolation, blocking lateral stray light, and blocking vertical stray light. This multi-functionality reduces the need for additional dedicated structures, thereby controlling device complexity while achieving comprehensive stray light suppression
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 effectively suppresses stray light and reduces false signal generation, improving the accuracy of pixel signals by optimizing the placement and design of light shielding structures and transistor integration.
Implementation Method 1
a photoelectric conversion unit, and a charge storage unit that temporarily holds charge photoelectrically converted by the photoelectric conversion unit
Data Source
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AI summary
The present disclosure relates to a solid-state imaging element capable of suppressing stray light with respect to a charge storage unit such as an FD, and an electronic device. According to an aspect of the present disclosure, a solid-state imaging element constituted by many pixels includes: a photoelectric conversion unit formed for each of the pixels and configured to convert incident light into a charge; a charge storage unit configured to temporarily hold the converted charge; and a first light shielding unit formed between the pixels and having a predetermined length in a thickness direction of a substrate. The charge storage unit is formed below a cross portion where the first light shielding unit formed between pixels adjacent to each other in a longitudinal direction crosses the first light shielding unit formed between pixels adjacent to each other in a lateral direction. The present disclosure can be applied to, for example, a backside irradiation type CMOS image sensor.