Solid-State Imaging Dark Current Suppression via Diffusion Prevention
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Solution Overview
Problem
Existing solid-state imaging apparatuses face challenges in suppressing dark current components generated on the interfacial surface of element isolation units, which affect image quality due to the diffusion of electrons into photoelectric conversion units.
Innovation Solution
Incorporating a diffusion prevention unit that prevents the diffusion of dark current components generated on the interfacial surface of the element isolation unit, by forming a conductive type region with higher impurity concentration along the bottom surface and side walls of the element isolation unit, and using a fixed potential to attract and direct the dark current into an element region opposite to the photoelectric conversion unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a concentrated P-type region is formed to suppress dark current generation on the interfacial surface, then the generation amount of dark current is reduced, but the dark current component still diffuses to surrounding regions and flows into the photoelectric conversion unit
Solution Approach 1:
The patent applies local quality by forming a P-type region with locally higher impurity concentration specifically at the interfacial surface of the element isolation unit, while maintaining different impurity concentrations in surrounding regions. This localized impurity concentration gradient creates an electric field that confines dark current electrons to the generation region, preventing their diffusion into the photoelectric conversion unit while preserving the beneficial suppression effect at the interface.
Solution Approach 2:
The patent utilizes parameter changes by varying the impurity concentration of the P-type region in a gradient manner, with higher concentration at the interfacial surface and lower concentration in surrounding areas. This parameter gradient creates an internal electric field that directs electron movement, effectively containing dark current within the isolation region while allowing the high-concentration region to maintain its dark current suppression capability.
2Object-generated harmful factors
If the concentration of the P-type region is increased to suppress dark current generation, then the generation amount is reduced, but electrons still diffuse toward regions with lower or equal concentration
Solution Approach 1:
The patent implements local quality by creating a non-uniform impurity concentration distribution within the P-type region, with the highest concentration localized at the interfacial surface where dark current generation occurs. This localized high-concentration zone acts as an electron trap and creates an electric field boundary that prevents electron diffusion to surrounding lower-concentration regions, while still maintaining overall suppression of dark current generation.
Solution Approach 2:
The patent applies equipotentiality principles by creating an impurity concentration gradient that establishes an internal electric field, effectively creating potential barriers that confine electrons. The gradient from high to low concentration establishes equipotential surfaces that guide electron movement, preventing diffusion toward regions with lower impurity concentration while maintaining the suppression effect at the high-concentration interface.
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 approach effectively reduces the negative impact of dark current components on the photoelectric conversion units, improving image quality by preventing their diffusion into surrounding regions.
Implementation Method 1
a diffusion prevention unit that prevents diffusion of a dark current component generated on an interfacial surface of the element isolation unit to a region surrounding the dark current component generation region
Implementation Method 2
using a fixed potential to attract and direct the dark current into an element region opposite to the photoelectric conversion unit
Data Source
AI summary
Provided is a solid-state imaging apparatus including: a plurality of photoelectric conversion units; an element isolation unit that performs element isolation between the plurality of photoelectric conversion units; and a diffusion prevention unit that prevents diffusion of a dark current component generated on an interfacial surface of the element isolation unit to a region surrounding the dark current component generation region.