3D Memory Trench Formation Using Merged Cavities and Buried Etch Stops
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Solution Overview
Problem
In three-dimensional memory arrays, the formation of trenches with a greater degree of taper leads to misalignment, structural defects, and increased process costs due to large aspect ratios, affecting memory die layout and manufacturing efficiency.
Innovation Solution
The technique involves merging patterns of cavities to form trenches, reducing the degree of taper and improving process margins by forming etch stopping material portions before the cavity etching process, which enhances the accuracy and reduces misalignments and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If trenches are formed with large aspect ratios by direct material removal, then the desired trench depth and width are achieved, but excessive tapering occurs leading to misalignment and structural defects
Solution Approach 1:
The trench formation process is segmented into multiple stages: first forming cavities with controlled dimensions, then merging adjacent cavities to form trenches. This segmentation allows precise control over trench geometry without the excessive tapering that occurs in single-step direct removal, thereby improving alignment precision while managing process complexity through systematic division of operations.
Solution Approach 2:
Cavities are formed as preliminary structures before merging them into trenches. By pre-forming cavities with controlled aspect ratios and dimensions, the process establishes a foundation that reduces subsequent tapering issues. This preliminary action enables better control over the final trench geometry and minimizes misalignment defects.
2Reliability
If direct material removal is used to form trenches, then the process is simpler, but misalignment and structural defects increase
Solution Approach 1:
By segmenting the trench formation into cavity formation followed by cavity merging, the process achieves higher reliability with fewer structural defects. The segmented approach allows controlled material removal in stages, preventing the excessive tapering and misalignment that occur in direct single-step removal, while the merging step consolidates the cavity structures into the desired trench configuration.
Solution Approach 2:
Adjacent cavities are merged to form trenches, combining multiple controlled cavity structures into the final trench geometry. This merging process eliminates the harmful effects of direct material removal (excessive tapering, misalignment) while maintaining ease of manufacture through a systematic two-step approach that leverages existing cavity structures.
3Manufacturing precision
If cavities are merged to form trenches, then tapering is reduced and alignment improves, but the manufacturing process becomes more complex
Solution Approach 1:
The process is segmented into cavity formation and cavity merging steps. This segmentation enables precise control over trench geometry by first establishing cavities with controlled dimensions and aspect ratios, then merging them to form the final trench structure. The segmentation manages complexity through systematic division of operations, each with well-defined parameters and objectives.
Solution Approach 2:
Cavities are formed as preliminary structures with controlled geometry before merging. This preliminary action establishes the geometric foundation that determines final trench precision. By pre-forming cavities with controlled aspect ratios and dimensions, the process reduces subsequent tapering issues and achieves better overall geometry precision while managing complexity through preparatory structuring.
Data Source
AI summary
Methods, systems, and devices for merged cavities and buried etch stops for three-dimensional memory arrays are described. For example, a row of cavities may be formed using a cavity etching process and material separating cavities of the row may be removed to merge the row of cavities to form a trench. In some cases, a trench may be formed from multiple rows of cavities. Additionally, or alternatively, a trench may be formed from a pattern of cavities that includes different quantities of rows at different locations along the trench. In some examples, etch stopping material portions (e.g., etch stops) may be formed at locations corresponding to cavities prior to the cavity etching process. For example, exposed material surfaces at locations corresponding to cavities or trenches may be oxidized to form etch stops.