Global Shutter Light-Blocking Layout for Stable Dark Characteristics
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Solution Overview
Problem
Conventional CMOS image sensors with global shutter functions face limitations in improving image quality due to distortions caused by stress differences in the light blocking unit and the semiconductor substrate, leading to degradation of dark characteristics.
Innovation Solution
A solid-state imaging device with a light blocking unit featuring a lid portion and embedded portions on a semiconductor substrate, where the light blocking unit includes recessed structures to alleviate planar continuous stress and maintain electrical stability, preventing distortions and improving dark characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light blocking unit is formed as a continuous planar structure on the back surface side of the semiconductor substrate, then light blocking effectiveness is improved, but stress differences cause distortions and degradation of dark characteristics
Solution Approach 1:
The continuous planar light blocking unit is divided into multiple separate light blocking units arranged in an alternating pattern. This segmentation reduces the cumulative stress difference between the light blocking unit and the semiconductor substrate, preventing image plane distortion while maintaining effective light blocking through the alternating configuration that ensures complete light coverage.
Solution Approach 2:
The patent employs an alternating arrangement of light blocking units and non-light blocking units, creating an asymmetric pattern that breaks the continuous planar structure. This asymmetric segmentation allows stress to be distributed more evenly across the substrate, reducing distortions while the alternating pattern ensures that light paths are still effectively blocked where needed.
2Stability of the object's composition
If a global shutter method is adopted with a charge retention unit, then simultaneous exposure timing for all pixels is achieved, but image quality improvement is limited due to stress-induced distortions
Solution Approach 1:
By segmenting the light blocking structure into multiple discrete units arranged alternately, the patent reduces stress-induced distortions that would otherwise degrade image quality. This segmented approach maintains the global shutter's simultaneous exposure capability while eliminating the distortion problem that limited image quality improvement.
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 enhances image quality by reducing distortions and maintaining consistent dark characteristics, thereby improving the overall performance of the solid-state imaging device.
Implementation Method 1
Light that has entered a CMOS image sensor is photoelectrically converted by the photodiodes (PDs) included in the pixels
Data Source
AI summary
Provided is a solid-state imaging device including: a photoelectric conversion unit that converts received light into an electric charge; a memory unit that holds the electric charge; and a light blocking unit that blocks light. The photoelectric conversion unit and the memory unit are formed in a semiconductor substrate. The light blocking unit is formed as a lid portion on the back surface side of the semiconductor substrate, which is the side at which light to the memory unit enters, and is also continuously formed including a first embedded portion and a second embedded portion that are embedded between the photoelectric conversion unit and the memory unit so as to extend in the semiconductor substrate. The first embedded portion is in a transfer region for transferring the electric charge, and the second embedded portion is outside the transfer region. The lid portion includes at least one recessed structure.