Transfer Gate Trench Layout for Flexible Image Sensor Active Areas
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Solution Overview
Problem
Existing image sensor designs face limitations in design freedom due to the conventional method of forming trenches only in active areas, which restricts the shape and size of the active area, affecting the overall performance and flexibility of the image sensor.
Innovation Solution
The proposed solution involves forming trenches through element isolation patterns, allowing the electrode to extend through the bottom surface of the element isolation pattern and adjacent to its sidewall, thereby providing more design flexibility for the active area and improving the image sensor's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If trenches are formed only through active areas, then manufacturing process is simple, but design freedom of active area is limited
Solution Approach 1:
The trench formation process is segmented into two distinct stages: first forming trenches through the active area, then forming additional trenches through the element isolation pattern. This segmentation allows each stage to serve a specific purpose - the first stage ensures proper electrode positioning in the active area, while the second stage enables design flexibility by allowing electrodes to extend into the element isolation region, thereby resolving the contradiction between manufacturing simplicity and design freedom.
Solution Approach 2:
The element isolation pattern is formed preliminarily before the second trench formation step, establishing a defined boundary structure that guides subsequent electrode extension. This preliminary action creates a controlled environment where electrodes can extend into the element isolation region without compromising the integrity of the active area, thus enabling design freedom while maintaining manufacturing control.
2Adaptability or versatility
If electrode extends through element isolation pattern, then design freedom is improved, but manufacturing complexity increases
Solution Approach 1:
The element isolation pattern serves multiple functions: it provides electrical isolation between adjacent pixels, defines the boundary of the active area, and acts as a guide structure for electrode extension. By making the element isolation pattern multi-functional, the patent enables electrode extension into this region without requiring additional specialized structures, thus improving design freedom while limiting the increase in manufacturing complexity to a single additional etching step.
3Adaptability or versatility
If electrode bottom surface is below element isolation pattern bottom surface, then layout flexibility is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The element isolation pattern acts as an intermediary structure that mediates between the active area and the underlying substrate. By forming trenches through this intermediary pattern, the patent creates a controlled pathway for electrode extension that naturally guides the electrode bottom surface below the element isolation pattern bottom surface. This intermediary structure provides physical references for alignment, thereby enabling layout flexibility while managing manufacturing precision requirements through the use of existing structural features.
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 enhances the design freedom of the active area, leading to improved image sensor performance by allowing for more flexible and efficient layout configurations, which can enhance light reception and image processing capabilities.
Implementation Method 1
Image sensors include semiconductor devices that convert optical information into electrical signals
Data Source
AI summary
An image sensor includes a substrate including a first face and a second face, the second face being opposite the first face in a first direction; a photoelectric conversion area disposed in the substrate; an active area disposed in the substrate and on the photoelectric conversion area; an element isolation pattern extending from the first face of the substrate into the substrate and defining the active area; and a transfer gate electrode including: a first portion extending from the first face of the substrate and extending through the element isolation pattern; and a second portion disposed on the active area, wherein the first portion extends through a bottom face of the element isolation pattern, wherein a vertical level of a bottom face of the first portion is lower than a vertical level of the bottom face of the element isolation pattern.