Backside CMOS Image Sensor Pixel Isolation for Color Mixing and Dynamic Range
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Solution Overview
Problem
Existing imaging elements of the back surface irradiation type face challenges in simultaneously preventing color mixing and securing a dynamic range, as providing pixel separation sections to prevent color mixing narrows the region for photodiodes, making it difficult to maintain a sufficient electric charge accumulation.
Innovation Solution
The imaging element incorporates pixel separation sections and through electrodes formed in the inter-pixel regions, with insulating films contacting each other, and through electrodes connected to a polysilicon electrode, using impurity-doped polysilicon and high-dielectric-constant gate insulating films to ensure electrical separation and signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pixel separation section is provided between pixels to prevent color mixing, then color mixing is prevented, but the region for photodiode is narrowed and dynamic range cannot be secured
Solution Approach 1:
The pixel separation section is segmented into two functional parts: an upper pixel separation section that prevents color mixing, and a lower electron accumulation region that maintains dynamic range. This segmentation allows each part to perform its specific function without compromising the other, resolving the contradiction between color mixing prevention and charge accumulation capacity
Solution Approach 2:
The invention transitions from a two-dimensional planar separation approach to a three-dimensional vertical structure. By stacking the pixel separation section above the electron accumulation region in the vertical dimension, the patent enables both color mixing prevention and sufficient charge accumulation without the need for lateral expansion of separation structures that would reduce photodiode area
2Measurement precision
If the imaging element is made finer to improve resolution, then resolution is improved, but it becomes difficult to simultaneously prevent color mixing and secure dynamic range
Solution Approach 1:
By moving the pixel separation function to the vertical dimension through stacking, the patent enables finer lateral pixel dimensions without compromising color mixing prevention. The vertical stacking of separation sections allows reduced pixel pitch while maintaining effective separation, thus improving resolution without sacrificing reliability
Solution Approach 2:
The patent applies different structural qualities to different vertical regions: the upper region contains the pixel separation section with insulating films for color mixing prevention, while the lower region contains the electron accumulation region with doped semiconductor layers for charge storage. This local differentiation allows each region to be optimized for its specific function, enabling finer overall dimensions while maintaining both separation and accumulation capabilities
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 prevents color mixing and secures a wide dynamic range by ensuring each pixel is optically and electrically isolated, maintaining a wide electron accumulation region and preventing light or electron leakage.
Implementation Method 1
an organic photoelectric conversion film, in which color mixing can be prevented and a dynamic range can be secured
Data Source
AI summary
The present technology relates to a back surface irradiation type imaging element having an organic photoelectric conversion film capable of preventing color mixing and securing dynamic range, a method of manufacturing the same, and an electronic apparatus. An imaging element according to an aspect of the present technology includes a photoelectric conversion film provided on one side of a semiconductor substrate, a pixel separation section formed in an inter-pixel region, and a through electrode that transmits a signal, corresponding to an electric charge obtained by photoelectric conversion in the photoelectric conversion film, to a wiring layer formed on the other side of the semiconductor substrate, the through electrode being formed in the inter-pixel region. The present technology is applicable to a back surface irradiation type CMOS image sensor.