CMOS Image Sensor Pixel Isolation for Higher Signal Charge
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Solution Overview
Problem
Conventional solid-state imaging elements can suppress color mixture and increase light receiving sensitivity, but they fail to easily enhance the signal charge amount that each pixel can accumulate.
Innovation Solution
A solid-state imaging element with a photoelectric conversion section and an inter-pixel separation section that includes a protruding section, where the inter-pixel separation section is formed in a grid pattern and can vary in shape, material, and conductivity type, and includes a Deep Trench Isolation (DTI) structure to increase the surface area of PN joint portions and optical path length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an insulative and/or reflective wall is formed between pixels to suppress color mixture, then color mixture is suppressed, but the signal charge amount that each pixel can accumulate cannot be easily increased
Solution Approach 1:
The patent introduces a protruding section that extends in the depth direction (third dimension) from the inter-pixel separation section toward the photoelectric conversion section. This dimensional extension increases the surface area of the PN joint portion without increasing the lateral footprint, thereby increasing signal charge accumulation capacity while maintaining effective pixel separation for suppressing color mixture.
Solution Approach 2:
The protruding section is nested within the depth direction of the pixel structure, extending from the inter-pixel separation section into the photoelectric conversion section's depth. This nesting approach allows the separation structure to occupy vertical space rather than lateral space, increasing functional area without expanding the pixel's horizontal dimensions.
2Use of energy by moving object
If an anti-reflection film with moth-eye structure is formed to confine incident light and increase optical path length, then light receiving sensitivity is increased, but the signal charge amount that each pixel can accumulate cannot be easily increased
Solution Approach 1:
The patent combines the light confinement function (achieved through the moth-eye structure on the Si interface) with the signal charge accumulation function (achieved through the protruding section increasing PN joint surface area) into a single integrated structure. This merging allows both light receiving sensitivity and signal charge amount to be increased simultaneously without requiring separate structural modifications.
3Quantity of substance
If the inter-pixel separation section is formed with a protruding section toward the photoelectric conversion section, then the surface area of PN joint portion is increased and signal charge amount is increased, but device complexity increases
Solution Approach 1:
The inter-pixel separation section is segmented into a base portion and a protruding section, where the protruding section is formed only in specific regions where increased signal charge accumulation is needed. This segmentation allows the structure to be simplified in areas where it is not needed, reducing overall device complexity while maintaining the benefits of increased PN joint surface area in critical regions.
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 allows for an increase in the signal charge amount and light receiving sensitivity of each pixel while suppressing color mixture and improving light confinement within pixels.
Implementation Method 1
another method proposed forms an anti-reflection film with a moth-eye structure on an Si interface on a light incident side of each pixel of a solid-state imaging element to confine incident light within the pixels and increase the optical path length
Implementation Method 2
a photoelectric conversion section formed in each pixel
Data Source
AI summary
The present technology relates to a solid-state imaging element and electronic equipment that allow an increase in the signal charge amount Qs that each pixel can accumulate. A solid-state imaging element according to the first aspect of the present technology includes: a photoelectric conversion section formed in each pixel; and an inter-pixel separation section separating the photoelectric conversion section of each pixel, in which the inter-pixel separation section includes a protruding section having a shape protruding toward the photoelectric conversion section. The present technology can be applied to a back-illuminated CMOS image sensor, for example.