Light Detector Pixel Layout for Miniaturized Image Sensors
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Solution Overview
Problem
In solid-state imaging devices, the miniaturization of pixels limits the arrangement of active elements such as transfer transistors and pixel transistors within the photoelectric conversion cell, particularly in in-pixel isolation regions, reducing the degree of freedom in their placement.
Innovation Solution
The design includes a semiconductor layer with partitioned photoelectric conversion regions, isolation regions, and element formation regions, allowing for the arrangement of transfer transistors and pixel transistors across multiple photoelectric conversion regions and shared charge holding regions, increasing the degree of freedom in their placement and enabling miniaturization of pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pixels are miniaturized to increase the number of pixels for high image quality, then the number of pixels increases, but it becomes difficult to arrange active elements such as transfer transistors and pixel transistors in the photoelectric conversion cell
Solution Approach 1:
The patent extends the element formation region from a single photoelectric conversion region to multiple photoelectric conversion regions (first and second photoelectric conversion regions) in the planar direction. This spatial extension across multiple regions provides additional room for arranging active elements, thereby resolving the contradiction between pixel miniaturization and active element arrangement feasibility
2Adaptability or versatility
If the in-pixel isolation region is used for arranging active elements, then the degree of freedom in arrangement is limited, but if the element formation region is extended across multiple photoelectric conversion regions, then the degree of freedom in arrangement increases
Solution Approach 1:
The patent merges the element formation region across the first and second photoelectric conversion regions, allowing active elements to be arranged in a continuous space that spans multiple photoelectric conversion regions. This merging approach increases the degree of freedom in arrangement while the isolation regions maintain their partitioning function, thus resolving the contradiction between arrangement flexibility and isolation structure
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 enhances the degree of freedom in arranging active elements, allowing for further miniaturization of pixels while reducing noise and maintaining image quality, by utilizing shared charge holding regions and p-type contact regions between photoelectric conversion regions.
Implementation Method 1
a photoelectric conversion unit and a transfer transistor arranged in each photoelectric conversion region
Data Source
AI summary
A light detecting device includes a semiconductor layer having a first surface and a second surface located on opposite sides to each other in a thickness direction, and a photoelectric conversion cell provided in the semiconductor layer and partitioned by a first isolation region. The photoelectric conversion cell includes a first photoelectric conversion region adjacent to a second photoelectric conversion region in plan view and each having a photoelectric conversion unit and a transfer transistor, a second isolation region arranged between the first photoelectric conversion region and the second photoelectric conversion region in plan view and extending in a thickness direction of the semiconductor layer, and an element formation region partitioned on the first surface side of the semiconductor layer by a third isolation region and provided with a pixel transistor. The element formation region extends over the first and second photoelectric conversion regions in plan view.