CMOS Image Sensor Light-Shielding for Charge Holding Units
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Solution Overview
Problem
CMOS image sensors with global electronic shutters suffer from image quality deterioration due to false signals caused by light entering charge holding units, which are not adequately shielded by existing light-shielding designs.
Innovation Solution
The imaging device incorporates a light-shielding portion that extends over multiple charge holding units, aligning them in a direction orthogonal to the photoelectric conversion units, with openings only above the photoelectric conversion and readout circuit units to minimize light exposure to the charge holding units, thereby improving light-shielding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-shielding portion is provided to cover charge holding units, then light entering charge holding units is reduced, but image quality deterioration due to false signals is not sufficiently prevented
Solution Approach 1:
The light-shielding portion is extended in the row direction (second direction) to cover not only individual charge holding units but also the regions between adjacent charge holding units. This dimensional extension in the row direction effectively blocks light that would otherwise enter charge holding units through gaps between column-wise shielding structures, thereby preventing false signals and improving image quality.
2Object-generated harmful factors
If a light-shielding portion covering charge holding units is provided, then false signals are reduced, but the structural complexity of the pixel increases
Solution Approach 1:
The light-shielding portion is designed to simultaneously cover multiple charge holding units and the regions between them in a unified structure. By merging the shielding function across multiple units and directions into a single integrated light-shielding portion, the patent reduces false signals while avoiding the need for separate shielding structures for each charge holding unit, thus limiting the increase in structural complexity.
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 image quality deterioration by effectively shielding charge holding units from light, minimizing false signals and enhancing image clarity.
Implementation Method 1
a light-shielding portion arranged to cover at least the charge holding unit
Implementation Method 2
a photoelectric conversion unit configured to accumulate charges generated from an incident light
Data Source
AI summary
Provided is an imaging device including a substrate; a pixel array in which pixels are arranged in a two-dimensional manner on the substrate, each pixel including a photoelectric conversion unit that accumulates charges generated from an incident light, a charge holding unit that holds the charges transferred from the photoelectric conversion unit, and an amplification unit that receives the charges transferred from the charge holding unit; and a light-shielding portion arranged to cover at least the charge holding unit. The photoelectric conversion unit and the charge holding unit in each pixel are aligned in a first direction in a top view orthogonal to the substrate. The charge holding units of the neighboring pixels are aligned in a second direction intersecting the first direction in the top view. The light-shielding portion extends in the second direction and over the charge holding units, and covers a region between the charge holding units.