Wing-Type Wordline Projections for Flash Memory Isolation
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Solution Overview
Problem
Previous flash memory layouts are prone to inadvertent shorts between neighboring memory cells due to the formation of continuous voids between wordlines during manufacturing, leading to failure of memory cells.
Innovation Solution
Incorporating lateral 'wings' on the edges of wordlines that extend outward from one wordline towards another, preventing the formation of continuous voids and ensuring proper isolation between adjacent contacts, thus preventing metal piping and enhancing memory cell yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flash memory layout is used, then manufacturing process is simple, but continuous voids form between wordlines causing inadvertent shorts between neighboring memory cells
Solution Approach 1:
The wordline structure is segmented by adding lateral wings that extend from the main wordline body towards adjacent wordlines. These wings divide the continuous void space into separate regions, preventing the formation of continuous conductive paths between neighboring memory cells. The segmentation occurs in the planar view where wings from opposite sides meet or overlap, effectively breaking up the void continuity without requiring complex 3D structures.
Solution Approach 2:
The lateral wings act as intermediary structures between adjacent wordlines. By extending laterally towards neighboring wordlines, the wings create an intermediate barrier that prevents direct contact or continuous void formation between adjacent memory cell regions. This intermediary structure eliminates the need for more complex isolation mechanisms while maintaining reliable cell separation.
2Reliability
If wordline wings are added to prevent continuous voids, then memory cell isolation improves, but manufacturing precision requirements increase
Solution Approach 1:
The lateral wings are formed as part of the wordline structure during the standard manufacturing process, before the metal deposition and patterning steps that create the bitlines and contacts. By pre-forming the wings with the wordlines, the isolation structure is already in place to guide subsequent manufacturing steps, ensuring that contacts are properly positioned and isolated without requiring additional precision-critical alignment steps.
Solution Approach 2:
The lateral wings modify the geometric parameters of the wordline structure by extending laterally in the planar view. This parameter change affects the void space configuration, transforming it from continuous to segmented. The wings can be designed with specific dimensions and orientations that optimize isolation while accommodating standard manufacturing tolerances, reducing the precision requirements compared to alternative isolation structures.
Data Source
AI summary
A flash memory device is disposed on a semiconductor substrate. The flash memory device includes flash memory cells arranged in rows and columns. Respective flash memory cells include respective access transistors and respective floating gate transistors. The respective access transistors have respective access gates, and the respective floating gate transistors have respective control gates arranged over respective floating gates. First and second wordlines extend substantially in parallel with one another and correspond to first and second rows which neighbor one another. The first wordline is coupled to access gates of access transistors along the first row. The second wordline is coupled to access gates of access transistors along the second row. Nearest edges of the first and second wordlines include at least one wing which extends laterally outward from a sidewall of one of the first and second wordlines towards a sidewall the other of the first and second wordlines.