Stepped Tier Contact Layout for Reliable 3D Memory Stack Access
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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, especially at deeper tiers, which can result in whole-stadium failures.
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 that extend 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 conventional single-step contact structures are used in tiered stacks, then device complexity is reduced, but reliability of electrical communication deteriorates due to potential fabrication failures at deeper tiers
Solution Approach 1:
The patent divides the single contact structure per tier into multiple segmented contact structures (first step contact, second step contact, etc.) extending to different steps of the same tier. This segmentation provides redundant electrical access paths, so if one contact fails due to fabrication issues, alternative contacts maintain electrical communication with the conductive structure.
Solution Approach 2:
The patent implements backup contact structures in advance before fabrication failures can occur. By providing multiple step contacts that extend to different steps of each tier, the design pre-cushions against potential fabrication defects, ensuring that electrical communication reliability is maintained even if some contacts are inaccurately formed.
2Reliability
If multiple step contacts are implemented per tier, then reliability of electrical communication improves through backup connections, but manufacturing precision requirements increase
Solution Approach 1:
By segmenting the contact access into multiple independent step contacts targeting different steps, the patent reduces the precision burden on any single contact. Each individual contact only needs to reach its specific step, not all tiers, making the manufacturing precision requirement for each contact more manageable while collectively achieving high reliability.
Solution Approach 2:
The patent applies local quality by having different step contacts extend to different steps of the same tier based on their specific fabrication characteristics. This allows optimization of each contact's formation process according to its local requirements, rather than demanding uniform high precision across all contacts to all tiers.
3Ease of operation
If contact structures extend to deeper tiers of the stack, then electrical access to all conductive structures is achieved, but difficulty of fabrication increases leading to higher failure rates
Solution Approach 1:
The patent segments the electrical access function across multiple contact structures of varying depths. Instead of requiring one contact to reach all tiers, each contact extends only to its specific target step, making fabrication easier while collectively providing complete electrical access to all conductive structures in the stack.
Solution Approach 2:
The patent introduces a dimensional variation in contact depth, where contacts extend to different vertical levels (steps) of the same tier. This dimensional differentiation allows easier fabrication of individual contacts while maintaining comprehensive electrical access through the multi-dimensional contact network.
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.