Unitary Support for Cylindrical Structures in DRAM
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Solution Overview
Problem
Semiconductor memory devices with high aspect ratio cylindrical structures are prone to tilting or breaking during manufacturing due to lack of effective support, leading to reduced capacitance and reliability, particularly in DRAM devices where smaller capacitance increases soft error rates.
Innovation Solution
A semiconductor device design featuring a two-dimensional array of cylindrical structures supported by a contiguous structure with vertically extending openings, exposing parts of the cylindrical structures to facilitate uniform dielectric layer deposition and prevent tilting, with an open ratio of 65% or higher to ensure stable and conformal layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cylindrical lower electrodes with high aspect ratio are formed to maximize cell capacitance, then capacitance is improved, but the cylindrical structures are likely to tilt or tip over during manufacturing
Solution Approach 1:
The support structure is segmented into multiple discrete support regions positioned at specific locations around the cylindrical lower electrodes. Each support region provides localized stabilization, allowing the cylindrical structures to maintain high aspect ratio for maximum capacitance while preventing tilting through distributed support points rather than a continuous rigid support.
Solution Approach 2:
A dielectric layer is introduced as an intermediary between the cylindrical lower electrodes and the upper electrode. This dielectric layer consolidates the lower electrodes and provides a stabilizing medium that prevents tilting while allowing the cylindrical structures to maintain their high aspect ratio configuration for maximum capacitance.
2Reliability
If a contiguous support structure is added to prevent tilting, then structural stability is improved, but the complexity of the device increases
Solution Approach 1:
Rather than implementing a single complex continuous support structure, the solution segments the support function into multiple simple discrete support regions. Each support region is positioned at optimized locations to provide stabilization with minimal material and structural complexity, reducing fabrication difficulty while maintaining reliability.
Solution Approach 2:
The support structure is designed with local quality by providing support only at specific critical locations around the cylindrical lower electrodes rather than uniform continuous support. This localized approach reduces overall device complexity and material usage while maintaining structural stability where it is most needed.
3Manufacturing precision
If the open ratio of the support is increased to improve step coverage, then dielectric layer deposition quality is improved, but the support may become less effective at preventing tilting
Solution Approach 1:
The open ratio of the support structure is optimized as a critical parameter, balancing the need for sufficient dielectric layer deposition access (requiring higher open ratio for better step coverage) with the need for adequate tilt prevention (requiring sufficient support material). The specific open ratio value is tuned to achieve both objectives simultaneously.
Solution Approach 2:
The support structure exhibits local quality variations where regions providing tilt prevention have higher material density, while regions allowing dielectric deposition have higher openness. This spatial variation in local quality enables simultaneous optimization of both tilt prevention and step coverage without compromise.
Data Source
AI summary
A semiconductor device includes a plurality of cylindrical structures located at vertices and central points of a plurality of hexagons in a honeycomb pattern, and a unitary support having a plurality of openings. Each of the openings exposes a part each of four of the cylindrical structures. Each of the openings has the shape of a parallelogram or an oval substantially. A first distance between opposite cylindrical structures of a first pair of the four cylindrical structures exposed by each opening is shorter than a second distance between opposite cylindrical structures of a second pair of the four cylindrical structures exposed by the opening. The first distance is equal to a distance between the central point and each of the vertices of the hexagon.