3D Memory Array Channel Coupling With Conductive Mass Contacts
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Solution Overview
Problem
Existing memory array fabrication methods often result in electrically-resistant contact interfaces between upper and lower channel-material strings, which can hinder efficient electrical coupling and performance.
Innovation Solution
The method involves forming conductive masses atop and directly electrically coupling them to lower channel-material strings, with upper channel-material strings of select-gate transistors formed above, allowing for improved electrical connection and reducing resistance at these interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication methods are used to form memory arrays, then manufacturing process is simpler, but electrical coupling between upper and lower channel-material strings has high resistance
Solution Approach 1:
The method forms a conductive layer between upper and lower channel-material strings before completing the memory array fabrication. This preliminary action ensures that the conductive coupling is established early, preventing resistance issues that would be difficult to correct later in the manufacturing process.
Solution Approach 2:
A conductive layer is introduced as an intermediary element between the upper and lower channel-material strings. This intermediate conductive structure facilitates electrical coupling that would otherwise be resistive or non-existent in conventional direct-contact configurations.
2Reliability
If direct contact between channel-material strings is formed, then manufacturing is easier, but electrical resistance at the contact interface is high
Solution Approach 1:
A conductive layer serves as an intermediary between the channel-material strings, replacing direct contact with an engineered conductive interface. This intermediary structure reduces contact resistance while adding controlled complexity to the contact formation process.
Solution Approach 2:
The electrical parameters at the contact interface are improved by introducing a conductive layer with optimized conductivity properties. This changes the electrical characteristics of the contact from high-resistance direct contact to low-resistance mediated contact.
Data Source
AI summary
A method used in forming a memory array comprising strings of memory cells comprises forming a stack comprising vertically-alternating different-composition first tiers and second tiers. The stack comprises lower channel-material strings extending through the first tiers and the second tiers. Conductive masses are formed that comprise at least one of conductively-doped semiconductive material or conductive metal material. Individual of the conductive masses are atop and directly electrically coupled to individual of the lower channel-material strings. Upper channel-material strings of select-gate transistors are formed directly above the stack. Individual of the upper channel-material strings are directly above and directly electrically coupled to individual of the conductive masses. Other embodiments, including structure, are disclosed.