Photoelectric Conversion Apparatus Pixel Isolation Structure
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Solution Overview
Problem
The reduction in pixel size in photoelectric conversion apparatuses leads to reduced sensitivity and performance issues due to narrowed well regions for isolation, causing variations in transistor thresholds and dynamic range narrowing.
Innovation Solution
A photoelectric conversion apparatus with a first semiconductor region of a specific conductivity type between adjacent photoelectric conversion elements and a wider second semiconductor region under the transistors to prevent performance degradation, maintaining sensitivity and reducing transistor threshold variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the pixel size is reduced to increase pixel density, then the photoelectric conversion apparatus can achieve higher resolution, but the well region width is narrowed causing reduced sensitivity and transistor performance degradation
Solution Approach 1:
The isolation structure is divided into two distinct segments: a first semiconductor region (P-type) positioned between adjacent photoelectric conversion elements for charge isolation, and a second semiconductor region (N-type) positioned beneath the transistors for electrical isolation and threshold stabilization. This segmentation allows each region to independently fulfill its specific function without interfering with the other, resolving the contradiction between compact pixel size and transistor performance.
Solution Approach 2:
Different regions of the semiconductor structure are assigned different conductivity types and dimensions tailored to their specific functions. The first semiconductor region uses P-type conductivity with dimensions optimized for charge carrier isolation between pixels, while the second semiconductor region uses N-type conductivity with dimensions optimized for transistor electrical isolation. This local differentiation of properties allows the system to maintain high pixel density while preserving transistor performance through function-specific optimization.
2Productivity
If the well region width is narrowed to accommodate smaller pixels, then pixel density increases, but transistor threshold variations increase and dynamic range narrows
Solution Approach 1:
The first semiconductor region (P-type) acts as an intermediary barrier positioned between adjacent photoelectric conversion elements. This intermediary structure prevents charge carrier leakage between pixels while the second semiconductor region (N-type) serves as an intermediary isolation layer beneath the transistors. Together, these intermediary regions provide dual isolation functionality that maintains transistor threshold consistency even as pixel density increases, resolving the contradiction between productivity and manufacturing precision.
3Area of stationary object
If the isolation region is reduced to maximize photoelectric conversion area, then pixel sensitivity improves, but charge isolation between adjacent pixels deteriorates
Solution Approach 1:
The isolation structure employs a composite semiconductor configuration combining two different conductivity types (P-type and N-type) in a layered arrangement. The first P-type semiconductor region provides charge carrier isolation between adjacent pixels, while the second N-type semiconductor region provides electrical isolation for the transistors. This composite structure achieves effective charge isolation without sacrificing photoelectric conversion area, resolving the contradiction between maximizing conversion area and preventing charge cross talk.
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 performance reduction of transistors while maintaining the sensitivity of photoelectric conversion elements by ensuring consistent charge isolation and ion implantation depth, thereby enhancing the dynamic range and image quality.
Implementation Method 1
each of pixels includes photoelectric conversion element arranged on the substrate
Data Source
AI summary
A photoelectric conversion apparatus of the present invention includes: a plurality of photoelectric conversion elements arranged on a substrate; a transistor for transferring a signal charge; and a plurality of transistors for reading out the signal charge transferred. The plurality of photoelectric conversion elements include a first photoelectric conversion element and a second photoelectric conversion element adjacent to each other. The photoelectric conversion apparatus of the present invention includes: a first semiconductor region having a first conductivity type arranged between the first photoelectric conversion element and the second photoelectric conversion element; and a second semiconductor region having the first conductivity type that is arranged on a region where the plurality of transistors are arranged and that has a width larger than that of the first semiconductor region of the first conductivity type.