3D Memory Block Isolation With Backside Trenches and Contact Vias
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in achieving effective lateral isolation and stairless layer contact via structures, which are crucial for efficient memory array formation and inter-block word line isolation.
Innovation Solution
The solution involves forming a three-dimensional memory device with alternating stacks of insulating and sacrificial material layers, where backside trenches and dielectric etch stop structures are created to laterally isolate electrically conductive strips, and sacrificial material layers are replaced with conductive strips to form composite layers with dielectric connection plates, enabling efficient lateral isolation and contact via structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backside trenches are formed to laterally isolate electrically conductive strips, then lateral isolation between memory blocks is improved, but device complexity increases due to additional trench formation and fill structures
Solution Approach 1:
The device is divided into separate memory blocks by backside trenches that extend through the substrate, physically segmenting the device into isolated regions. Each memory block contains its own electrically conductive strips confined within trench boundaries, preventing electrical interference between blocks while maintaining clear structural organization.
Solution Approach 2:
Dielectric etch stop structures are introduced as intermediary elements within the backside trenches, positioned between the substrate and the electrically conductive strips. These etch stop structures serve as mediators that provide both mechanical support and electrical isolation, enabling the trenches to effectively separate memory blocks without requiring the entire trench depth to be filled with insulating material.
2Reliability
If dielectric etch stop structures are formed within backside trenches, then electrical isolation and structural support are improved, but manufacturing complexity increases due to additional formation steps
Solution Approach 1:
Dielectric etch stop structures are formed in advance within the backside trenches before the electrically conductive strips are deposited. This preliminary action ensures that the isolation and support structures are already in place to guide subsequent processing steps, preventing defects and ensuring proper alignment of the conductive strips within the trench regions.
Solution Approach 2:
The dielectric etch stop structures change the physical and electrical parameters within the backside trenches, providing regions of different dielectric constant and electrical conductivity. This parameter variation enables selective etching and deposition processes, allowing the conductive strips to be formed with precise control over their position and electrical characteristics within the isolated trench regions.
3Reliability
If sacrificial material layers are replaced with electrically conductive strips to form composite layers, then functional performance is improved, but manufacturing precision requirements increase
Solution Approach 1:
Dielectric etch stop structures serve as intermediary reference structures that define the precise locations where sacrificial material should be replaced with conductive strips. These etch stop structures act as physical guides and alignment markers during the replacement process, ensuring that conductive strips are formed with high precision at the correct positions within the alternating stack architecture.
Solution Approach 2:
The replacement of sacrificial material with electrically conductive strips is performed selectively at specific locations defined by the dielectric etch stop structures. This local quality approach ensures that conductive properties are introduced only where needed, maintaining high manufacturing precision by confining the complex replacement process to localized regions rather than requiring uniform precision across the entire device.
Data Source
AI summary
A three-dimensional memory device includes alternating stacks of insulating strips and electrically conductive strips, backside trenches located between neighboring pairs of alternating stacks, memory openings vertically extending through the alternating stacks, and memory opening fill structures located within the memory openings. In some embodiments, dielectric etch stop structures may be located within or outside the backside trenches such that each of the dielectric etch stop structures includes a respective pair of dielectric sidewalls that are located within a pair of lengthwise sidewalls of the respective one of the backside trenches. In some other embodiments, a dielectric isolation structure can laterally contact each of the insulating strips within the alternating stacks. Laterally insulated contact via structures can be provided to provide electrical contact to a respective one of the electrically conductive strips.