Thermal Cycle Control for 3D Memory Tier Alignment
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Solution Overview
Problem
High temperature thermal cycles used in forming upper tier structures in three-dimensional memory devices can cause shrinkage of lower tier structures, leading to positional mismatch and damage of memory films at the joint between tiers, resulting in failure to remove memory films at the bottom of memory openings.
Innovation Solution
The method involves forming a first tier structure with a higher temperature thermal cycle than the second tier structure, using alternating stacks of insulating and conductive layers, and selectively removing sacrificial layers to align memory openings across tiers, with the second tier structure's thermal cycle maintained below 800 degrees Celsius to minimize distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high temperature thermal cycles are used in forming upper tier structures, then the upper tier structure can be formed, but the lower tier structure shrinks causing positional mismatch and damage to memory films
Solution Approach 1:
The patent forms the first tier structure and performs high temperature thermal cycles (at least 800°C) to densify the insulating layers and establish a stable reference structure before forming the second tier structure. This preliminary action ensures that the first tier structure does not shrink during subsequent processing, providing a stable foundation for precise alignment of the second tier memory openings.
Solution Approach 2:
The patent divides the thermal processing into two distinct stages: (1) high temperature thermal cycles during formation of the first tier structure to densify insulating layers, and (2) low temperature thermal cycles (below 800°C) during formation of the second tier structure to prevent shrinkage. This segmentation allows each tier to be processed under optimal temperature conditions, resolving the contradiction between forming the upper tier and maintaining alignment precision.
2Ease of manufacture
If high temperature thermal cycles are used in forming upper tier structures, then the upper tier structure can be formed, but memory films at the joint between tiers are damaged
Solution Approach 1:
The patent performs high temperature thermal cycles (at least 800°C) during the formation of the first tier structure to densify the insulating layers and establish a stable reference structure before forming the second tier structure. This preliminary action ensures that the first tier structure does not shrink during subsequent processing, providing a stable foundation for precise alignment of the second tier memory openings.
Solution Approach 2:
The patent divides the thermal processing into two distinct stages: (1) high temperature thermal cycles during formation of the first tier structure to densify insulating layers, and (2) low temperature thermal cycles (below 800°C) during formation of the second tier structure to prevent shrinkage. This segmentation allows each tier to be processed under optimal temperature conditions, resolving the contradiction between forming the upper tier and maintaining alignment precision.
3Ease of manufacture
If high temperature thermal cycles are used in forming upper tier structures, then the upper tier structure can be formed, but memory films at the bottom of memory openings cannot be removed
Solution Approach 1:
The patent performs high temperature thermal cycles (at least 800°C) during the formation of the first tier structure to densify the insulating layers and establish a stable reference structure before forming the second tier structure. This preliminary action ensures that the first tier structure does not shrink during subsequent processing, providing a stable foundation for precise alignment of the second tier memory openings.
Solution Approach 2:
The patent divides the thermal processing into two distinct stages: (1) high temperature thermal cycles during formation of the first tier structure to densify insulating layers, and (2) low temperature thermal cycles (below 800°C) during formation of the second tier structure to prevent shrinkage. This segmentation allows each tier to be processed under optimal temperature conditions, resolving the contradiction between forming the upper tier and maintaining alignment precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces positional mismatch between upper and lower memory opening portions, ensuring accurate alignment and preventing damage to memory films, thereby enhancing the reliability and integrity of the memory device.
Implementation Method 1
High temperature thermal cycles used in forming upper tier structures in three-dimensional memory devices can cause shrinkage of lower tier structures
Implementation Method 2
High temperature thermal cycles used in forming upper tier structures in three-dimensional memory devices can cause shrinkage of lower tier structures
Data Source
AI summary
A first tier structure is provided by forming first memory openings through a first alternating stack of first insulating layers and first spacer layers, and by forming sacrificial memory opening fill structures in the first memory openings. A second tier structure is formed over the first tier structure by forming a second alternating stack of second insulating layers and second spacer layers. Second memory openings are formed through the second tier structure in areas of the sacrificial memory opening fill structures. Distortion of the first tier structure and misalignment between the first and second memory openings is reduced or prevented by conducting thermal cycles at a lower temperature for the second tier structure than for the first tier structure.