3D NAND Pillar Isolation Layout Without Dummy Pillars
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Solution Overview
Problem
The challenge in microelectronic device fabrication is to increase the number of operational device features within a given footprint without negatively impacting other aspects of device design and operation, particularly in 3D NAND memory devices, where conventional designs require significant space for 'dummy' pillars that are not actively functional.
Innovation Solution
The introduction of isolation trenches that cut into active pillars, allowing them to function as select gate devices while reducing the footprint by eliminating the need for 'dummy' pillars, thereby increasing the number of active pillars or reducing the overall footprint of the pillar array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional designs use full-circle pillars with isolation structures, then device functionality is maintained, but footprint area increases due to required dummy pillars
Solution Approach 1:
The pillar structure is segmented into two distinct portions: a lower full-circle pillar portion that extends through the lower stack and provides structural support and electrical connections, and an upper partially-cut pillar portion that extends through the upper stack and functions as the active device feature. This segmentation allows the pillar to serve multiple functions while reducing the footprint area occupied by isolation structures.
Solution Approach 2:
Different portions of the pillar are given different geometries and functions: the lower pillar portion maintains a full circular cross-section for structural integrity and electrical connectivity, while the upper pillar portion is partially cut by isolation structures to reduce footprint area. This local differentiation in quality allows the device to achieve both functionality and compactness.
2Productivity
If isolation structures protrude into upper pillar portions, then footprint is reduced by eliminating dummy pillars, but manufacturing complexity increases
Solution Approach 1:
The lower pillar portion is formed first to establish the structural foundation and electrical connections. Subsequently, the upper pillar portion is formed and then selectively removed in targeted areas where isolation structures are needed. This preliminary formation followed by selective removal allows for reduced footprint without requiring complex simultaneous patterning processes.
Solution Approach 2:
The partially-cut upper pillar portions serve as intermediaries between the lower full-circle pillars and the isolation structures. They allow the isolation structures to protrude into the pillar array and reduce footprint area while maintaining the structural and electrical integrity provided by the lower pillar portions.
3Area of stationary object
If upper pillar portions are partially cut by isolation structures, then footprint area decreases, but structural integrity may be compromised
Solution Approach 1:
The pillar is divided into a lower structural portion and an upper functional portion. The lower full-circle pillar portion provides the primary structural support and electrical connectivity, while the upper partially-cut portion serves as the active device feature. This segmentation ensures that structural integrity is maintained in the lower portion while allowing footprint reduction in the upper portion.
Solution Approach 2:
The lower pillar portion maintains full circular geometry for structural integrity, while the upper pillar portion is locally modified by isolation structures to reduce footprint. This local differentiation ensures that structural strength is preserved where needed while achieving compactness where functional.
Data Source
AI summary
Microelectronic devices include a stack structure comprising a vertically alternating sequence of insulative structures and conductive structures arranged in tiers. A series of pillars extends through the stack structure. At least one isolation structure extends through an upper stack portion of the stack structure. The at least one isolation structure protrudes into pillars of neighboring columns of pillars of the series of pillars. Conductive contacts are in electrical communication with the pillars into which the at least one isolation structure protrudes. Related methods and electronic systems are also disclosed.