Solid-State Imaging Pixel Active Region Width Optimization
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Solution Overview
Problem
The existing solid-state imaging apparatus configurations, such as those described in Japanese Patent Laid-Open No. 2008-103647, face inefficiencies in electric carrier transfer from the photoelectric conversion portion to the electric-carrier accumulation portion due to small potential differences, leading to partial electrons returning to the photoelectric conversion portion instead of being transferred.
Innovation Solution
A solid-state imaging apparatus with a matrix of pixels, each comprising a photoelectric conversion portion, first and second transfer transistors, and a floating diffusion, where the active region under the gate of the first transfer transistor has a wider width in the electric-carrier accumulation portion than in the photoelectric conversion portion, enhancing the efficiency of electric carrier transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a small potential difference is maintained between the photoelectric conversion portion and the electric-carrier accumulation portion, then energy consumption is reduced, but electric carrier transfer efficiency deteriorates
Solution Approach 1:
The patent applies local quality by creating a potential gradient specifically in the region under the transfer transistor gate. The impurity concentration is increased locally in this region to form a potential slope that guides carriers from the photoelectric conversion portion to the accumulation portion, while maintaining small potential differences in other regions to reduce overall energy consumption.
Solution Approach 2:
The patent changes the impurity concentration parameter locally under the transfer transistor gate to create the desired potential distribution. By increasing impurity concentration in this specific region, a potential slope is formed that enhances carrier transfer efficiency without requiring a large overall potential difference between the photoelectric conversion portion and accumulation portion.
2Productivity
If the active region width is increased under the transfer transistor gate, then electric carrier transfer efficiency is improved, but device area increases
Solution Approach 1:
The patent applies local quality by increasing the active region width specifically under the transfer transistor gate where it is most needed for carrier transfer, while keeping the active region width compact in other areas such as the photoelectric conversion portion and accumulation portion. This localized expansion minimizes the overall device area increase while achieving the transfer efficiency improvement.
3Productivity
If impurity concentration is increased under the transfer transistor gate, then potential gradient is improved for better carrier transfer, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by concentrating the impurity concentration modification specifically in the region under the transfer transistor gate. This localized doping approach is more manufacturable than global impurity concentration changes, as it can be achieved through targeted ion implantation or diffusion processes in the specific region of interest.
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 improves the efficiency of electric carrier transfer from the photoelectric conversion portion to the electric-carrier accumulation portion by maintaining a lower potential in the photoelectric conversion portion relative to the electric-carrier accumulation portion, reducing carrier loss and enhancing overall transfer efficiency.
Implementation Method 1
a photoelectric conversion portion
Data Source
AI summary
An inventive solid-state imaging apparatus is provided which can improve the efficiency of the electric carrier transfer from a photoelectric conversion portion to an electric-carrier accumulation portion. The solid-state imaging apparatus includes an active region having the photoelectric conversion portion, the electric-carrier accumulation portion, and a floating diffusion, and an element isolation region having an insulator defining the active region. In planer view, the width of the active region in the electric-carrier accumulation portion under a gate of the first transfer transistor is larger than the width of the active region in the photoelectric conversion portion under the gate of the first transfer transistor.