Vertical Image Sensor Photoelectric Conversion Crosstalk Reduction
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Solution Overview
Problem
As CMOS image sensors are miniaturized to increase pixel density, crosstalk occurs due to reduced spacing between wiring layers, leading to decreased light sensitivity and color intensity characteristics.
Innovation Solution
The image sensor design incorporates a first and second photoelectric conversion portion spaced apart vertically, with a color filter and organic light receiving portion to absorb different wavelengths of light, allowing for increased pixel density without crosstalk by maintaining adequate spacing between wiring layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pixel size is reduced to increase pixel density, then the number of pixels per area is increased, but crosstalk occurs due to reduced spacing between wiring layers leading to decreased light sensitivity and color intensity
Solution Approach 1:
The patent introduces a dual-layer photoelectric conversion structure where first and second photoelectric conversion portions are arranged at different vertical levels. This three-dimensional arrangement allows light to be converted to electrical signals at multiple depths, effectively utilizing the vertical dimension to increase pixel density without compromising horizontal spacing between wiring layers, thus preventing crosstalk while maintaining light sensitivity.
Solution Approach 2:
The photoelectric conversion function is segmented into multiple portions (first and second photoelectric conversion portions) with different spectral responses. This segmentation allows each portion to specialize in detecting specific wavelength ranges, improving overall color accuracy and sensitivity while enabling closer wiring layer spacing through the vertical distribution of functional elements.
2Quantity of substance
If pixel size is reduced to increase pixel density, then the number of pixels per area is increased, but color intensity characteristic is deteriorated
Solution Approach 1:
By arranging photoelectric conversion portions at different vertical levels and equipping each with color filters for different wavelength ranges, the patent captures light intensity information across multiple dimensions. This multi-level structure increases the effective light collection area without increasing the planar pixel footprint, thereby maintaining color intensity characteristics while achieving higher pixel density.
Solution Approach 2:
The patent employs a composite structure combining multiple photoelectric conversion portions with different spectral characteristics, color filters, and microlenses. This composite approach enables each pixel to simultaneously capture multiple wavelength ranges with high efficiency, maintaining superior color intensity and accuracy while reducing overall pixel size through vertical integration.
3Quantity of substance
If wiring layer spacing is reduced to accommodate smaller pixels, then pixel density is increased, but crosstalk phenomenon occurs where light collides against wiring layers and is scattered
Solution Approach 1:
The patent relocates photoelectric conversion functions to multiple vertical levels, effectively moving sensitive elements away from the plane where crosstalk occurs between wiring layers. This vertical displacement reduces the impact of light scattering from wiring layers on photoelectric conversion, allowing tighter wiring spacing without compromising signal quality.
Solution Approach 2:
The patent introduces charge storage nodes and transfer transistors as intermediary elements between the color filters/microlenses and the final readout circuitry. These intermediaries are positioned at optimized vertical levels to collect and transfer photogenerated charges while minimizing interference from wiring layer crosstalk, thereby protecting signal integrity even with reduced wiring spacing.
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 design enables a 100% increase in pixel area margin, preventing crosstalk and enhancing light sensitivity and color clarity, while maintaining the reduced pixel size.
Implementation Method 1
a first photoelectric conversion portion configured to receive plural lights, except for a light of first wavelength, to generate an electric charge
Implementation Method 2
a second photoelectric conversion portion configured to receive the light of the first wavelength to generate an electric charge
Implementation Method 3
an organic light receiving portion formed on the substrate to be spaced apart from the charge storing portion in the vertical direction
Data Source
AI summary
An image sensor and an operating method thereof are disclosed. The image sensor includes a first photoelectric conversion portion configured to receive plural lights, except for a light of first wavelength, to generate an electric charge; and a second photoelectric conversion portion configured to receive the light of the first wavelength to generate an electric charge, wherein at least a portion of the first photoelectric conversion portion and the second photoelectric conversion portion is spaced apart from each other in a vertical direction.