3D Memory Staircase Support Structure for Stress and Crack Control
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Solution Overview
Problem
Existing 3D NAND memory devices face challenges in supporting conductive layers due to mechanical stress, leading to bending and potential short circuits, as the density of support structures is limited by the space occupied by gate lines and contact plugs, causing deviations and etching issues.
Innovation Solution
Incorporating bead-embedded strip shape support structures in the staircase region, which break elongated seams into shorter pieces, reducing stress concentration and crack formation risk through stress redistribution, and providing enhanced mechanical support to conductive layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If support structures are added to support conductive layers, then mechanical strength is improved, but device complexity increases due to space constraints from gate lines and contact plugs
Solution Approach 1:
The support structure is segmented into multiple discrete support structures distributed across the staircase region, rather than a single continuous structure. This segmentation allows the support function to be distributed while maintaining space efficiency around gate lines and contact plugs, reducing overall device complexity while providing adequate mechanical support.
Solution Approach 2:
Support structures are strategically positioned in specific locations within the staircase region where mechanical support is most needed, rather than uniformly distributing them throughout. This local quality approach provides targeted support to conductive layers at critical stress points while minimizing interference with gate lines and contact plugs, thus improving strength without proportionally increasing device complexity.
2Reliability
If support structures are placed densely to provide adequate support, then reliability is improved, but manufacturing precision becomes more difficult due to space constraints
Solution Approach 1:
The support structure is divided into multiple smaller, discrete support structures that can be manufactured with standard precision tolerances. This segmentation avoids the need for a single large continuous structure that would require extremely high manufacturing precision to form accurately in the constrained staircase region.
Solution Approach 2:
The support structures are formed as part of the staircase region fabrication process itself, rather than as a separate subsequent step. This preliminary action integrates the support structure formation with the existing manufacturing flow, reducing the need for additional high-precision alignment steps and making the overall process more manufacturable.
3Ease of manufacture
If elongated seams are formed in support structures, then ease of manufacture is improved, but stress concentration increases leading to crack formation
Solution Approach 1:
The support structure is segmented into multiple discrete elements rather than a single elongated continuous structure. This segmentation breaks up potential elongated seams that would concentrate stress, while each individual segment can still be manufactured using standard processes. The multiple segments work together to provide distributed support without the stress concentration problems of elongated seams.
Solution Approach 2:
The potential harm of seams in support structures is converted into a benefit by using multiple small segments rather than one large structure. The seams between segments are shorter and fewer in number, and the segmented architecture actually improves reliability by preventing stress concentration that would occur in elongated continuous structures. The manufacturing simplicity of forming segments is retained while the reliability harm is eliminated.
Data Source
AI summary
Three-dimensional (3D) memory devices and methods for forming the same are disclosed. In certain aspects, a 3D memory device includes a stack structure containing a core region and a staircase region, a channel structure extending through the stack structure in the core region, and a first support structure extending through the stack structure in the staircase region. The first support structure includes a first portion extending along a first direction and a second portion protruding from the first portion along a second direction perpendicular to the first direction.