Stress-Compensating Slit Trenches for 3D Memory Warpage
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Solution Overview
Problem
Three-dimensional memory devices experience wafer warpage due to mechanical stress induced by slit trenches extending along a horizontal direction, which complicates the formation of metal interconnect structures.
Innovation Solution
Incorporation of stress-compensating slit trench structures that laterally extend perpendicular to the vertical steps of alternating insulating and sacrificial material layers, with slit trench fill structures designed to absorb mechanical stress and reduce warpage by alternating with divider trench fill structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If slit trenches are introduced to form three-dimensional memory structures, then memory device functionality is achieved, but wafer warpage occurs due to mechanical stress
Solution Approach 1:
Stress compensating trenches are formed in advance during the fabrication process to counteract the mechanical stress that will be generated by the slit trenches. These compensating trenches are strategically positioned and dimensioned to create opposing stress fields that neutralize the warpage-inducing stress from the memory structure trenches, thereby preventing wafer deformation before it occurs.
Solution Approach 2:
The depth, width, and spacing of stress compensating trenches are carefully controlled parameters that are optimized to match and counterbalance the stress profile generated by the slit trenches. By adjusting these geometric parameters, the compensating structure is tuned to achieve stress neutrality while maintaining the required memory device functionality.
2Reliability
If wafer warpage is reduced through stress compensation, then manufacturing stability is improved, but device complexity increases due to additional trench structures
Solution Approach 1:
The stress compensation mechanism is divided into discrete, localized trenches rather than requiring a continuous or global structural modification. These segmented compensating trenches are distributed only in regions where stress compensation is needed, allowing the majority of the wafer to maintain its simple, uniform structure while providing targeted stress relief where required.
Solution Approach 2:
Stress compensating trenches are selectively positioned only in specific regions of the wafer where mechanical stress concentration occurs, rather than uniformly across the entire substrate. This localized approach provides stress compensation precisely where needed while minimizing the addition of structural complexity to regions where it is not required.
Data Source
AI summary
A vertically alternating sequence of continuous insulating layers and continuous sacrificial material layers is formed over a substrate. Memory stack structures are formed through the vertically alternating sequence. Divider trenches and slit trenches are formed such that the divider trenches laterally extend along a first horizontal direction and divide the vertically alternating sequence into a plurality of alternating stacks of insulating layers and sacrificial material layers, and the slit trenches laterally extend along a second horizontal direction that is perpendicular to the first horizontal direction. The sacrificial material layers are replaced with electrically conductive layers employing the divider trenches as a conduit for an etchant and for a reactant. Each of the divider trenches and the slit trenches are filled with material portions to provide a plurality of divider trench fill structures in the divider trenches and to provide a plurality of slit trench fill structures in the slit trenches.