Molybdenum Conductive Lines in Vertical Memory Arrays for Tier Isolation
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Solution Overview
Problem
Existing memory arrays face challenges in efficiently forming vertical stacks of memory cells with stable and reliable connections between conductive tiers, leading to potential short circuits and limited voltage range.
Innovation Solution
The formation of memory arrays involves creating a vertical stack with alternating insulative and conductive tiers, where channel-material strings extend through these tiers, and a conductive molybdenum-containing metal material is used with a different composition conductive or semiconductive material to enhance electrical isolation and increase the voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive materials are used in vertical stacks of memory cells, then the manufacturing process is simpler, but the connections become unstable and short circuits occur
Solution Approach 1:
The patent uses a composite material structure consisting of a first conductive material (e.g., tungsten) and a second conductive material (e.g., cobalt or cobalt alloy) in different tiers of the vertical stack. This composite approach provides stable connections between memory cells while preventing short circuits, resolving the reliability issue without requiring overly complex manufacturing processes.
Solution Approach 2:
Different conductive materials are assigned to different tiers (levels) of the vertical stack based on their specific electrical properties. The first conductive material is used in lower tiers while the second conductive material is used in upper tiers, optimizing connection stability at each level and preventing short circuits where they are most likely to occur.
2Adaptability or versatility
If conventional conductive materials are used in memory arrays, then the device structure is simpler, but the voltage range is limited
Solution Approach 1:
The patent changes the electrical parameters of the conductive tiers by using different materials with distinct properties. The first conductive material and second conductive material have different electrical characteristics that enable the memory array to operate across a broader voltage range, enhancing adaptability while managing structural complexity through systematic material assignment.
3Reliability
If uniform conductive material is used throughout the vertical stack, then the manufacturing process is easier, but electrical isolation between tiers is insufficient
Solution Approach 1:
The patent employs composite conductive materials with different compositions in alternating tiers, where the first conductive material and second conductive material provide complementary electrical isolation properties. This composite structure achieves superior electrical isolation between tiers while maintaining a manufacturable process through sequential deposition of the different materials.
Data Source
AI summary
A method used in forming a memory array comprising strings of memory cells comprises forming memory block regions individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers. Channel-material strings extend through the insulative tiers and the conductive tiers. The conductive tiers individually comprise a void-space extending laterally-across individual of the memory-block regions. At least one of conductive or semiconductive material is formed in the void-space laterally-outward of individual of the channel-material strings. Conductive molybdenum-containing metal material is formed in the void-space directly against the at least one of the conductive or the semiconductive material and a conductive line comprising the conductive molybdenum-containing metal material is formed therefrom. The at least one of the conductive or the semiconductive material is of different composition from that of the conductive molybdenum-containing metal material. Other embodiments, including structure independent of method, are disclosed.