3D NAND Tiered Stack Isolation Trenches Against Slit Deformation
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Solution Overview
Problem
The challenge in forming 3D NAND memory devices lies in retaining the structural integrity of insulating materials during the removal of sacrificial materials and replacement with conductive materials, as conventional methods struggle with material expansion and bending issues during the slit formation process.
Innovation Solution
The approach involves forming conductive structures for select gate drains before creating openings in the access line stack, ensuring that any material expansion or bending does not impact the design, and using pre-formed conductive structures in the select gate drains to provide additional structural integrity during slit formation, thereby preventing material expansion or bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sacrificial materials are removed and replaced with conductive materials in conventional methods, then the conductive structures are formed, but material expansion and bending occur during the process
Solution Approach 1:
The patent applies preliminary action by forming the conductive structures for select gate drains before creating openings in the access line stack. This sequence ensures that material expansion or bending during subsequent processing does not impact the already-formed conductive structures, thereby maintaining patterning accuracy and structural integrity
Solution Approach 2:
The patent segments the fabrication process into distinct sequential steps: first forming conductive structures in select gate drains, then creating openings in access line stacks, and finally forming slits. This segmentation allows each step to be optimized independently and prevents cumulative deformation effects
2Ease of manufacture
If openings and slits are formed in the stack structure, then access lines are created, but material expansion and bending occur affecting the structural integrity
Solution Approach 1:
The patent performs preliminary formation of conductive structures before creating openings and slits. This preliminary action provides structural support that prevents material expansion and bending during the opening and slit formation processes, ensuring both ease of manufacture and structural integrity
Solution Approach 2:
The pre-formed conductive structures act as a cushioning support before openings and slits are formed. This beforehand cushioning prevents the insulating materials from expanding or bending during the subsequent material removal and deposition processes
Data Source
AI summary
Methods for forming microelectronic devices include forming lower and upper stack structures, each comprising vertically alternating sequences of insulative and other structures arranged in tiers. Lower and upper pillar structures are formed to extend through the lower and upper stack structures, respectively. An opening is formed through the upper stack structure, and at least a portion of the other structures of the upper stack are replaced by (e.g., chemically converted into) conductive structures, which may be configured as select gate structures. Subsequently, a slit is formed, extending through both the upper and lower stack structures, and at least a portion of the other structures of the lower stack structure are replaced by a conductive material within a liner to form additional conductive structures, which may be configured as access lines (e.g., word lines). Microelectronic devices and structures and related electronic systems are also disclosed.