Ion-Implanted Bridge Material for Memory Block Stability
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Solution Overview
Problem
The technical challenge lies in preventing 'block-bending' during the fabrication of memory arrays, where vertically-stacked memory cells can tilt or bend sideways, leading to structural instability and potential defects in the memory array formation.
Innovation Solution
The method involves forming a memory array with vertically-alternating insulative and conductive tiers, where horizontally-elongated trenches are created to define laterally-spaced memory-block regions, and bridge material is deposited across these trenches to stabilize the structure. The bridge material, comprising alternating regions, is ion implanted differently to control the etch rate, allowing for selective etching to form insulating bridges that extend between memory-block regions, thereby maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If vertically-stacked memory cells are formed without additional support structures, then device complexity is reduced, but structural stability deteriorates causing block-bending
Solution Approach 1:
The patent introduces intermediate support structures (sacrificial bridges and replacement gates) between the vertically-stacked memory cells and the substrate. These intermediary elements provide mechanical support during fabrication to prevent block-bending, while being designed to be removed or replaced later in the process to achieve the final simplified structure.
Solution Approach 2:
The patent applies preliminary actions by forming sacrificial bridge structures and replacement gates before completing the vertical stack formation. These preliminary support structures are created to prevent block-bending during subsequent fabrication steps, and are later removed or replaced to achieve the final device structure.
2Stability of the object's composition
If sacrificial bridges are used to prevent block-bending, then structural stability is improved, but manufacturing complexity increases due to additional etching steps
Solution Approach 1:
The patent changes material parameters by using sacrificial bridge material with distinct etch selectivity compared to surrounding structures. This parameter change enables selective removal of sacrificial bridges through targeted etching processes, managing the added manufacturing complexity through material property differentiation.
Solution Approach 2:
The patent employs sacrificial bridges that are intentionally created and then discarded through selective etching. These temporary structures serve their support function during fabrication and are subsequently removed, with their material and function recovered or replaced by the final replacement gate structures.
3Reliability
If replacement gates are formed after sacrificial bridge removal, then electrical functionality is improved, but process time increases
Solution Approach 1:
The patent performs preliminary actions by preparing replacement gate structures in advance and positioning them before sacrificial bridge removal. This preliminary preparation allows for more efficient subsequent steps where the replacement gates are finalized after bridge removal, reducing overall process time while maintaining electrical functionality.
Solution Approach 2:
The patent merges multiple process steps by combining the replacement gate formation with the sacrificial bridge removal process. The replacement gates are formed in the same etching chambers and using similar process conditions as the bridge removal, consolidating operations that could otherwise be separate sequential steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents block-bending by creating stable, insulating bridges across trenches, ensuring the memory array's structural integrity and enabling precise electrical isolation between memory blocks, thus enhancing the reliability of the memory array formation process.
Implementation Method 1
The bridge material comprises longitudinally-alternating first and second regions. The first regions of the bridge material are ion implanted differently than the second regions of the bridge material to change relative etch rate of one of the first or second regions relative to the other in an etching process.
Data Source
AI summary
A method used in forming a memory array comprising strings of memory cells comprises forming a stack comprising vertically-alternating first tiers and second tiers. Horizontally-elongated trenches are formed into the stack to form laterally-spaced memory-block regions. Bridge material is formed across the trenches laterally-between and longitudinally-along immediately-laterally-adjacent of the memory-block regions. The bridge material comprises longitudinally-alternating first and second regions. The first regions of the bridge material are ion implanted differently than the second regions of the bridge material to change relative etch rate of one of the first or second regions relative to the other in an etching process. The first and second regions are subjected to the etching process to selectively etch away one of the first and second regions relative to the other to form bridges that extend across the trenches laterally-between and longitudinally-spaced-along the immediately-laterally-adjacent memory-block regions. Other embodiments and structure independent of method are disclosed.