Memory Cell Active Fragment Layout for Tight-Pitch Isolation
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Solution Overview
Problem
The miniaturization of semiconductor devices poses challenges in maintaining performance due to the shrinking size and complexity of integrated circuits, particularly in the fabrication of active areas and the reduced pitch between them, which limits the practicality of semiconductor memory devices.
Innovation Solution
The semiconductor memory device employs a substrate with an active structure comprising first and second active fragments, surrounded by shallow trench isolation, where the second active fragments with varying lengths act as a protective periphery for the first active fragments, and dummy word lines are used to prevent direct connection with bit lines, ensuring better device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pitch between active areas is reduced to achieve miniaturization, then the device size is reduced, but the manufacturing precision and reliability deteriorate
Solution Approach 1:
The active area is divided into multiple fragments (first active fragments and second active fragments) arranged in a specific pattern. This segmentation allows the photolithography and etching processes to define each fragment independently, improving manufacturing precision while maintaining reduced pitch between active areas.
Solution Approach 2:
Shallow trench isolations are introduced as intermediary structures between the active fragments. These isolations act as protective barriers that prevent direct connection between adjacent active areas, thereby improving reliability and preventing short circuits in miniaturized devices.
2Volume of moving object
If the width of active areas is reduced to achieve miniaturization, then the device size is reduced, but the reliability deteriorates due to direct connection risks
Solution Approach 1:
Shallow trench isolations serve as intermediary protective structures positioned between active fragments and around periphery active fragments. These isolations prevent direct electrical connection between adjacent active areas, thereby maintaining reliability even as active area width is reduced for miniaturization.
Solution Approach 2:
The active area is segmented into inner first active fragments and outer second active fragments. This segmentation creates distinct functional zones where the outer fragments act as protective elements, preventing direct connection issues that would compromise reliability in smaller devices.
3Reliability
If dummy word lines are added to protect inner word lines, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The outer second active fragments serve multiple functions: they act as dummy structures to protect inner active fragments from direct connection, while also serving as functional active areas themselves. This multi-functionality improves reliability without proportionally increasing device complexity.
Solution Approach 2:
The protective dummy word lines are merged with the active area structure itself. The outer second active fragments are both protective elements and functional elements, combining the protection function with the active area function to minimize additional complexity.
Data Source
AI summary
A semiconductor memory device includes a substrate, an active structure, a shallow trench isolation and a plurality of word lines. The active structure is disposed in the substrate, and includes a plurality of first active fragments and a plurality of second active fragments extended parallel to each other along a first direction and the second active fragments are disposed outside a periphery of all of the first active fragments. The shallow trench isolation is disposed in the substrate to surround the active structure, and which includes a plurality of first portions and a plurality of second portions. The word lines are disposed in the substrate, parallel with each other to extend along a second direction, wherein at least one of the word lines are only intersected with the second active fragments, or at least one of the word lines does not pass through any one of the second portions.