Dummy Pillars in 3D NAND Transition Areas

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Solution Overview

Problem

Conventional microelectronic device fabrication techniques face challenges in forming reliable features due to uneven material stresses and strains, leading to structural deformations, misalignments, electrical shorting, and defects in 3D NAND memory devices.

Innovation Solution

Incorporating dummy pillars in the upper deck of a tiered stack structure, horizontally interposed between live pillars and source/drain contacts, to inhibit block bending and facilitate reliable fabrication by balancing material stresses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional fabrication techniques are used without dummy pillars, then the device structure is simpler and fabrication is easier, but material stresses and strains become uneven causing structural deformations and misalignments

Engineering Contradiction:

Improvefeature alignment precisionVSAvoidstack structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Dummy pillars are introduced as intermediary structures between source/drain contacts and live pillars. These dummy pillars act as stress mediators that absorb and distribute material stresses uniformly, preventing direct stress transmission to live pillars and thereby maintaining feature alignment precision without requiring complex fabrication processes

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The dummy pillars are selectively placed only in transition areas where stress concentration occurs, rather than uniformly throughout the entire device. This localized approach provides stress relief precisely where needed while minimizing additional device complexity and maintaining fabrication simplicity in other regions

Inventive Principle:

Principle #3Local quality

2Reliability

If dummy pillars are added to balance material stresses, then structural integrity and feature alignment improve, but device complexity and fabrication difficulty increase

Engineering Contradiction:

Improvefeature formation reliabilityVSAvoidfabrication ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Dummy pillars are formed using the same fabrication processes and materials as live pillars, essentially creating identical structures that are subsequently removed or left as sacrificial elements. This copying approach allows the use of existing, well-established fabrication processes without requiring new manufacturing techniques, thereby maintaining fabrication ease while improving reliability

Inventive Principle:

Principle #26Copying

Solution Approach 2:

Dummy pillars are formed in advance during the stack structure fabrication process, before final feature formation occurs. This preliminary placement of stress-balancing structures prevents stress-induced deformations during subsequent fabrication steps, ensuring feature formation reliability without requiring additional complex processes

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If dummy pillars are placed adjacent to source/drain contacts, then block bending is inhibited and structural deformation is reduced, but the risk of electrical shorting increases

Engineering Contradiction:

Improveblock structural stabilityVSAvoidelectrical shorting risk

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The dummy pillars are strategically positioned in transition areas and selectively removed or isolated from direct electrical contact with source/drain contacts. This extraction of potentially harmful electrical interaction while maintaining the mechanical stress-balancing function reduces block bending and prevents electrical shorting simultaneously

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Dummy pillars serve as electrical intermediaries that are spaced from source/drain contacts by controlled dielectric layers. This intermediary positioning allows the dummy pillars to perform their mechanical stress-balancing function while the dielectric spacing prevents direct electrical contact, thereby eliminating shorting risk while maintaining structural stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20230069399A1Microelectronic devices having transition areas including upper dummy pillars spaced from source/drain contacts, and related methods and systems

Publication Date: 2023.03.02 MICRON TECHNOLOGY INC

AI summary

A microelectronic device includes a stack structure comprising a vertically alternating sequence of insulative structures and conductive structures arranged in tiers and the tiers arranged in decks. At least one live pillar, comprising a channel material, extends through the decks to a source/drain region. At least one source/drain contact also extends through the decks. In a transition area horizontally between the live pillar(s) and the source/drain contact(s), at least one dummy pillar extends through at least one of the decks. The dummy pillar(s) are separated from the source/drain region by at least one of the tiers of a lower of the decks. The dummy pillar(s) are also spaced from the source/drain contact(s). Additional microelectronic devices are also disclosed, as are related methods and electronic systems.