Digitline Formation Using Composite Metal Nitride and Conductive Layers
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Solution Overview
Problem
Current memory array fabrication methods face challenges in efficiently forming digitlines that are uniform and have controlled critical dimensions, particularly when using carbon-containing walls, which can lead to increased resistance and complexity in forming airgaps and digitline formation.
Innovation Solution
The method involves forming a stack with vertically-alternating insulative and conductive tiers, using carbon-containing sacrificial walls to create void spaces for digitlines, where a conductive metal nitride is selectively deposited to form a lower portion of the digitlines, and a higher conductivity material is used to form an upper portion, allowing for better control over digitline uniformity and height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If carbon-containing walls are used to form airgaps and digitlines, then airgap formation is simplified, but digitline resistance increases and manufacturing complexity increases
Solution Approach 1:
The digitline formation process is segmented into multiple deposition steps: first depositing conductive metal nitride in spaced openings and atop insulating material, then forming a separate upper conductive portion. This segmentation allows different materials and deposition conditions to be optimized independently, reducing overall resistance while maintaining the simplified airgap formation benefits of carbon-containing walls.
Solution Approach 2:
The digitline structure uses composite materials consisting of conductive metal nitride combined with additional conductive material deposited in subsequent steps. This composite approach leverages the low-resistance properties of the metal nitride while adding supplementary conductive layers to further reduce resistance, resolving the contradiction between ease of manufacture and electrical performance.
2Manufacturing precision
If uniform digitline critical dimensions are required, then manufacturing precision improves, but process complexity and difficulty increase
Solution Approach 1:
Carbon-containing sacrificial walls are formed in advance to define the precise geometry and critical dimensions of the future digitlines. These pre-formed walls serve as templates that guide subsequent material deposition, ensuring uniform digitline dimensions are achieved before the actual conductive materials are deposited, thereby simplifying the overall process while maintaining high precision.
Solution Approach 2:
The carbon-containing sacrificial walls act as an intermediary structure that temporarily holds the geometric information needed for uniform digitline formation. These walls mediate between the deposition process and the final digitline structure, allowing precise critical dimensions to be transferred without requiring complex real-time control during material deposition.
3Reliability
If more conductive metal nitride material is used to reduce resistance, then digitline conductivity improves, but material quantity and cost increase
Solution Approach 1:
Instead of using large quantities of conductive metal nitride alone, the invention employs composite digitline structures where conductive metal nitride is combined with additional conductive materials deposited in subsequent processing steps. This composite approach achieves superior overall conductivity while using less conductive metal nitride material, as the additional conductive layers contribute to the total conductive cross-section.
Solution Approach 2:
The solution adds a vertical dimension to the digitline structure by forming multi-layered conductive stacks rather than relying solely on increasing the lateral dimensions or thickness of a single conductive metal nitride layer. This dimensional transition allows conductivity to be enhanced through the accumulation of multiple thin conductive layers, reducing the total material quantity needed while maintaining or improving overall conductivity.
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 the quantity of less-conductive conductive metal nitride material needed, improves digitline uniformity, and simplifies the formation of airgaps, leading to more efficient and reliable memory array construction.
Implementation Method 1
a conductive metal nitride is selectively deposited in the void space, in the spaced openings
Data Source
AI summary
A method used in forming a memory array comprising strings of memory cells comprises forming a stack comprising vertically-alternating insulative tiers and conductive tiers having channel-material strings therein. Walls are formed above insulating material that is directly above the channel-material strings. Void space is laterally-between immediately-adjacent of the walls and that comprises a longitudinal outline of individual digitlines to be formed. Spaced openings are in the insulating material directly below the void space. Relative to the walls, a conductive metal nitride is selectively deposited in the void space, in the spaced openings, and atop the insulating material laterally-between the walls and the spaced openings to form a lower portion of the individual digitlines laterally-between the immediately-adjacent walls. The conductive metal nitride that is in individual of the spaced openings is directly electrically coupled to individual of the channel-material strings. A conductive material is formed in the void space directly above and directly electrically coupled to the lower portion of the individual digitlines to form an upper portion thereof. Other embodiments, including structure independent of method, are disclosed.