Solid-State Image Sensor Minority Carrier Barrier
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Solution Overview
Problem
In solid-state image capturing apparatuses, minority carriers flowing through contact plugs can reach photoelectric conversion portions, degrading image quality due to potential barriers that are not always effective in preventing such carriers.
Innovation Solution
A semiconductor structure is implemented where a second semiconductor region of a different conductivity type is positioned between photoelectric conversion portions to act as a potential barrier, guiding minority carriers away from the conversion regions and maintaining a higher potential to suppress dark current components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a region with higher impurity concentration is formed between the photoelectric conversion portion and the contact plug to create a potential barrier, then minority carrier flow is partially blocked, but minority carriers with sufficient energy can still overcome the barrier and reach the photoelectric conversion portion
Solution Approach 1:
A second semiconductor region of opposite conductivity type is introduced as an intermediary between the first semiconductor region (containing photoelectric conversion portions) and the contact plug. This intermediate region creates a dual pn junction structure that forms two potential barriers, effectively blocking minority carriers from reaching the photoelectric conversion portions while maintaining electrical connection through the contact plug.
Solution Approach 2:
The conductivity type parameter is changed in the second semiconductor region compared to the first semiconductor region. By forming a region with opposite conductivity type, the patent creates pn junctions that generate potential barriers to block minority carrier flow, thereby changing the electrical parameter profile to solve the carrier leakage problem.
2Object-affected harmful factors
If a single potential barrier region is formed to block minority carriers, then some protection is provided, but carriers with energy exceeding the barrier potential can still reach the photoelectric conversion portion
Solution Approach 1:
The single potential barrier is segmented into two separate potential barriers by introducing the second semiconductor region of opposite conductivity type. This segmentation creates a dual-barrier structure where minority carriers must overcome two potential barriers instead of one, significantly reducing the probability that any single carrier can penetrate through both barriers to reach the photoelectric conversion portions.
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 structure effectively prevents minority carriers from reaching photoelectric conversion portions, enhancing image quality by reducing dark current and maintaining consistent potential across the semiconductor regions.
Implementation Method 1
a region having an impurity concentration higher than that of the well is formed between the photoelectric conversion portion and a connecting portion of the well to the contact plug. According to this structure, the region functions as a potential barrier against the above-described minority carrier.
Data Source
AI summary
A solid-state image capturing apparatus, comprising a plurality of photoelectric conversion portions disposed in a first semiconductor region of a first conductivity type, a first portion of the first conductivity type disposed in the first semiconductor region and configured to supply a first potential to the first semiconductor region, and a second semiconductor region of a second conductivity type configured to receive a second potential, wherein the first portion is disposed between first and second photoelectric conversion portions neighboring each other, and the second semiconductor region is disposed between the first portion and each of the first and second photoelectric conversion portions.