3D Memory Contact Vias in Undulating Trenches
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming through-memory-level contact via structures in laterally-undulating trenches, which affects the performance and density of memory arrays.
Innovation Solution
The formation of three-dimensional memory devices involves alternating stacks of insulating and conductive layers over a semiconductor material, with laterally-undulating backside trenches and cavity-containing dielectric fill structures that include vertically-extending cavities for contact via structures, allowing for efficient electrical connections through the semiconductor material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact via formation methods are used in laterally-undulating trenches, then manufacturing process is simpler, but electrical connectivity and memory performance deteriorate
Solution Approach 1:
The laterally-undulating trench is segmented into alternating straight segments and bulging segments. The straight segments provide structural stability and alignment references, while the bulging segments create lateral spacing that improves electrical isolation and contact via formation. This segmentation resolves the contradiction by making the complex trench structure manufacturable through standardized processing steps.
Solution Approach 2:
The trench structure transitions from a two-dimensional planar trench to a three-dimensional laterally-undulating trench with varying width along its length. This dimensional change creates additional spatial relationships that improve electrical connectivity by enabling better contact via positioning and enhanced isolation between adjacent structures.
2Productivity
If laterally-undulating trenches with bulging segments are formed, then electrical connectivity and memory density improve, but manufacturing precision requirements increase
Solution Approach 1:
Different segments of the trench have different local qualities: straight segments have uniform width for precise alignment and structural support, while bulging segments have variable width for improved electrical isolation and contact formation. This local differentiation allows each segment to be optimized for its specific function, improving overall memory density without requiring ultra-precise control across the entire trench.
Solution Approach 2:
The laterally-undulating trench structure is formed preliminarily before contact via formation. This preliminary structuring creates predetermined spaces and alignment references that guide subsequent contact via fabrication, reducing the precision requirements for later steps while achieving high memory density.
3Ease of manufacture
If straight trench segments with uniform width are used, then manufacturing is easier, but electrical isolation and contact via performance worsen
Solution Approach 1:
The trench is divided into straight segments and bulging segments that alternate along its length. The straight segments are easier to manufacture with uniform width control, while the bulging segments provide the lateral spacing needed for electrical isolation. This segmentation allows the structure to achieve both ease of manufacture and electrical isolation performance.
Data Source
AI summary
A three-dimensional memory device includes alternating stacks of insulating layers and electrically conductive layers located over a semiconductor material layer, and memory stack structures extending through one of the alternating stacks. Laterally-undulating backside trenches are present between alternating stacks, and include a laterally alternating sequence of straight trench segments and bulging trench segments. Cavity-containing dielectric fill structures and contact via structures are present in the laterally-undulating backside trenches. The contact via structures are located within the bulging trench segments. The contact via structures are self-aligned to sidewalls of the alternating stacks. Additional contact via structures may vertically extend through a dielectric alternating stack of a subset of the insulating layers and dielectric spacer layers laterally adjoining one of the alternating stacks.