3D Memory Array Etch-Stop Plugs for Critical-Dimension Uniformity
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Solution Overview
Problem
Current memory array fabrication methods face challenges in achieving uniform critical-dimension uniformity and risk of over-etching when forming memory cells, particularly in the formation of plugs and rails, which affect the electrical integrity and reliability of the memory cells.
Innovation Solution
The use of combination metal oxide/metal material etch-stop plugs and rails, which are formed with sacrificial materials and processed through specific etching steps to create channel-material strings that extend through insulative and conductive tiers, ensuring precise etching and reducing the risk of over-etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form plugs and rails, then fabrication process is simpler, but critical-dimension uniformity deteriorates and over-etching risk increases
Solution Approach 1:
The patent introduces an intermediary etch-stop layer comprising metal oxide material between the sacrificial plug/rail material and the underlying substrate. This etch-stop layer acts as a mediator that provides a distinct etching endpoint, allowing precise control of etching depth and preventing over-etching while maintaining critical-dimension uniformity. The etch-stop layer is selectively etched to reveal the sacrificial material at a controlled depth, enabling accurate formation of plugs and rails without compromising fabrication simplicity.
2Measurement precision
If etch-stop function is enhanced with metal oxide/metal material combination, then etching precision improves, but process steps increase
Solution Approach 1:
The patent merges the etch-stop function with the existing sacrificial plug/rail formation process by using metal oxide materials that can serve dual purposes: as part of the sacrificial structure and as an etch-stop layer. The metal oxide/metal material combination is deposited as an integrated structure where the metal oxide portion provides etch-stop functionality while the metal portion becomes part of the final plug or rail structure. This merging eliminates separate etch-stop deposition steps, maintaining fabrication throughput while achieving precise etching depth control.
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 improves critical-dimension uniformity and enhances the etch-stop function, leading to more reliable and consistent memory cell formation, thereby improving the overall performance and reliability of the memory array.
Implementation Method 1
The plugs comprise sacrificial material that comprises metal oxide directly above metal material. The metal oxide and the metal material comprise different compositions relative one another.
Data Source
AI summary
A memory array comprising strings of memory cells comprises laterally-spaced memory blocks individually comprising a first vertical stack comprising vertically-alternating insulative tiers and conductive tiers. Strings of memory cells comprise channel-material strings that extend through the insulative tiers and the conductive tiers. A second vertical stack is aside the first vertical stack. The second vertical stack comprises an upper portion directly above a lower portion. The upper portion comprises vertically-alternating tiers that are of different composition relative one another. The lower portion comprises dummy plugs that comprise metal oxide directly above metal material. The metal oxide and the metal material comprise different compositions relative one another. Other embodiments, including method, are disclosed.