Tapered Pillar Structures for Memory Alignment and Contact Resistance
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Solution Overview
Problem
The challenge in semiconductor device fabrication is the increasing difficulty in aligning contacts between closely spaced conductive lines, leading to misalignment and elevated contact resistance, which decreases the drive current and performance of memory devices due to shrinking design rules and feature sizes.
Innovation Solution
The method involves forming pillar structures with upper portions wider than lower portions, allowing for increased alignment margin and reduced contact resistance by creating a larger cross-sectional area at the upper portions and a smaller critical dimension at the lower portions, facilitating enhanced isolation and improved contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If design rules are reduced to increase integration density, then feature size and spacing are reduced, but alignment precision deteriorates leading to misalignment between contacts and conductive lines
Solution Approach 1:
The pillar structure implements local quality by having different cross-sectional dimensions at different heights. The upper portion has a larger cross-sectional area than the lower portion, creating a tapered geometry that provides a larger alignment margin at the contact region while maintaining small overall dimensions for high density integration.
Solution Approach 2:
The invention transitions from a two-dimensional planar contact structure to a three-dimensional tapered pillar structure. By utilizing the vertical dimension with different cross-sectional areas at different heights, the structure provides additional alignment tolerance without increasing the lateral footprint, thus maintaining high integration density.
2Quantity of substance
If contact dimensions are reduced to increase integration, then contact area is reduced, but contact resistance increases dramatically
Solution Approach 1:
The pillar structure provides local quality enhancement at the contact region by having a larger cross-sectional area at the upper portion where the contact is formed. This localized enlargement reduces contact resistance at the critical contact interface while keeping the lower portion dimensions small to maintain high integration density.
3Quantity of substance
If separation distance between neighboring features is reduced to increase density, then alignment margin is reduced, but misalignment occurs leading to performance degradation
Solution Approach 1:
By utilizing the vertical dimension with a tapered geometry, the invention provides additional alignment tolerance in the lateral direction. The larger upper cross-sectional area creates a bigger target for alignment, effectively increasing the alignment margin even when lateral spacing between features is reduced for high density integration.
Data Source
AI summary
A method of forming an apparatus comprises forming pillar structures extending from a base material. Upper portions of the pillar structures may exhibit a lateral width that is relatively greater than a lateral width of lower portions of the pillar structures. The method also comprises forming access lines laterally adjacent to the lower portions of the pillar structures and forming digit lines above upper surfaces of the pillar structures. Memory devices and electronic systems are also described.