Self-Aligned Contact Structures for Dense Vertical Memory Arrays
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Solution Overview
Problem
Conventional vertical memory arrays face challenges in forming aligned contacts to conductive structures due to increased complexity and reduced spacing between memory strings, leading to difficulties in electrical connection formation without shorting.
Innovation Solution
The formation of self-aligned contact structures with an enlarged area by creating pillars with a larger lateral dimension, allowing for improved alignment and electrical connections before replacing insulative structures with conductive materials, thereby reducing block bending and facilitating precise contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of tiers of conductive structures is increased to provide additional memory density, then memory density is improved, but the difficulty of forming aligned contacts to various components increases
Solution Approach 1:
The patent applies preliminary action by forming contact structures to the pillars before replacing the insulative structures with conductive structures. This sequence ensures that contact alignment is established when the pillar positions are most stable and accessible, before subsequent processing steps could complicate alignment. The contact structures are formed with enlarged cross-sectional areas at this preliminary stage, facilitating precise alignment and formation.
2Quantity of substance
If the spacing between adjacent vertical memory strings is reduced to increase memory density, then memory density is improved, but the difficulty of forming individual electrical connections without shorting increases
Solution Approach 1:
The patent applies local quality by creating contact structures with enlarged cross-sectional areas at specific locations where electrical connections are needed. These enlarged contact structures provide sufficient separation and control in high-density regions, ensuring reliable individual electrical connections without shorting between adjacent memory strings. The local enlargement of contact area provides the necessary electrical isolation while maintaining the overall high density architecture.
3Ease of operation
If conventional staircase structures are used to provide contact regions, then electrical access is achieved, but alignment precision and structural integrity deteriorate with increased tiers
Solution Approach 1:
The patent applies dimensionality change by transitioning from conventional two-dimensional staircase structures to three-dimensional pillar-based contact structures with enlarged cross-sectional areas. These vertical pillars extend through multiple tiers and provide contact regions that are accessible from the top surface, eliminating the need for complex lateral staircase formations. This dimensional transformation simplifies the alignment process and maintains structural integrity regardless of the number of tiers.
Data Source
AI summary
A microelectronic device comprises a stack structure comprising alternating conductive structures and insulative structures arranged in tiers, each of the tiers individually comprising a conductive structure and an insulative structure, strings of memory cells vertically extending through the stack structure, the strings of memory cells comprising a channel material vertically extending through the stack structure, another stack structure vertically overlying the stack structure and comprising alternating levels of other conductive structures and other insulative structures, the other stack structure comprising pillars vertically overlying the strings of memory cells, each pillar comprising an other channel material in electrical communication with the channel material of the strings of memory cells, and conductive contact structures vertically overlying the other stack structure, each conductive contact structure comprising an electrically conductive contact at least partially extending into the pillars and a portion extending outside of the pillars having a larger cross-sectional area than the pillars. Related microelectronic devices including self-aligned conductive contact structures, and related electronic systems and methods are also described.