Stepped Tier Contacts With Redundant Access in 3D NAND Stacks
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Solution Overview
Problem
Conventional microelectronic device fabrication techniques face challenges in reliably forming contact structures between conductive features in tiered stacks, leading to potential electrical communication failures and whole-stadium failures in 3D NAND memory devices.
Innovation Solution
The implementation of a multi-step-per-tier stadium structure in microelectronic devices, where each tier includes multiple steps and multiple step contacts extending to each stepped tier, providing backup electrical access to conductive structures, thereby reducing the likelihood of complete failure even if one step contact is inaccurately fabricated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single step contact is formed to each conductive structure, then the device complexity is reduced, but the reliability of electrical communication is worsened due to potential fabrication failures
Solution Approach 1:
The patent implements multiple step contacts extending to each stepped tier of the conductive structure as a backup mechanism. If one step contact fails to make proper electrical connection due to fabrication variations, the additional step contacts serve as redundant pathways to ensure electrical communication is maintained. This beforehand cushioning approach addresses the reliability concern by pre-establishing alternative connection routes before failure can occur.
Solution Approach 2:
The patent divides the contact structure into multiple discrete step contacts rather than relying on a single contact point. Each step contact is formed as a separate element that can independently establish electrical connection with the stepped tier. This segmentation allows the system to tolerate failures in individual contacts while maintaining overall electrical communication through the remaining functional contacts.
2Reliability
If multiple step contacts are formed to each stepped tier, then the reliability is improved through backup connections, but the manufacturing precision requirements are worsened due to increased fabrication complexity
Solution Approach 1:
The patent employs multiple step contacts extending to each stepped tier, forming more contacts than the minimum single connection required. This excessive action ensures that even if some contacts fail to achieve proper alignment or connection due to manufacturing tolerances, sufficient redundant contacts remain to establish reliable electrical communication. The additional contacts compensate for precision limitations in the fabrication process.
3Reliability
If multiple step contacts are implemented, then the failure rate of entire stadiums is reduced, but the device complexity increases due to additional contact structures
Solution Approach 1:
The patent establishes multiple step contacts as redundant backup connections before any failure can occur. This beforehand cushioning creates a safety margin where the system can tolerate contact failures without experiencing stadium-level failures. The additional contact structures serve as pre-positioned insurance against manufacturing defects or operational failures in individual contacts.
Data Source
AI summary
Microelectronic devices include a stack structure having a vertically alternating sequence of insulative structures and conductive structures arranged in tiers. At least one stadium, of stadiums within the stack structure, comprise staircase(s) having steps provided by a group of the conductive structures. Step contacts extend to the steps of the staircase(s) of the at least one of the stadiums. Each conductive structure of the group of conductive structures has more than one of the step contacts in contact therewith at at least one of the steps of the staircase(s). Additional microelectronic devices are also disclosed, as are methods of fabrication and electronic systems.