Etching Bottom Punch-Through Openings in Multi-Tier 3D Memory Films
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Solution Overview
Problem
Current methods for forming three-dimensional memory devices face challenges in efficiently creating bottom punch-through openings in memory films, particularly in multi-tier structures, which affects the integrity and performance of the memory device.
Innovation Solution
A method involving the formation of alternating stacks of insulating and spacer material layers, followed by selective etching and filling with memory films and sacrificial liners, allows for the creation of vertical semiconductor channels through the memory openings, enabling the formation of a monolithic three-dimensional NAND string memory device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching methods are used to form bottom punch-through openings in multi-tier memory films, then the manufacturing process is simpler, but the structural integrity and performance of the memory device deteriorates
Solution Approach 1:
The patent applies preliminary action by forming sacrificial liner layers and opening fill material portions before the final etching process. These preliminary structures serve as etch stops and guides during the formation of bottom punch-through openings, ensuring precise control over the etching depth and preventing damage to underlying layers. The sacrificial liners are strategically placed to protect critical structures while enabling the etching process to proceed safely.
Solution Approach 2:
The patent uses sacrificial liner layers as intermediary elements that facilitate the etching process. These liners act as temporary mediators between the etching tool and the underlying memory film structures. The liners are removed after serving their protective function, leaving clean, precisely-formed openings without damaging the surrounding structures.
2Manufacturing precision
If selective etching is performed to remove opening fill material portions, then the bottom punch-through openings are precisely formed, but the manufacturing time increases
Solution Approach 1:
The patent applies parameter changes by selecting materials with distinct etch selectivity parameters. The opening fill material portions are made of materials that have significantly different etch rates compared to the memory film materials, allowing for highly selective removal. This enables precise formation of bottom punch-through openings through a single targeted etching step rather than multiple sequential steps, reducing overall manufacturing time while maintaining high precision.
Solution Approach 2:
The patent implements local quality by applying different material properties to different regions of the structure. The opening fill material portions have locally optimized properties (etch selectivity) that differ from the surrounding memory film materials. This allows the etching process to selectively remove only the opening fill material in specific locations without affecting adjacent structures, achieving precise local modification efficiently.
Data Source
AI summary
First memory openings are formed through a first alternating stack of first insulating layers and first spacer material layers. Each first memory opening is filled with a first memory film, a sacrificial dielectric liner, and a first-tier opening fill material portion. Second memory openings are formed through a second alternating stack of second insulating layers and second spacer material layers. A second memory film is formed in each second memory opening. The first-tier opening fill material portions are removed selective to the sacrificial dielectric liners. The sacrificial dielectric liners are removed selective to the second memory films and the first memory films. A vertical semiconductor channel can be formed on each vertical stack of a first memory film and a second memory film.