3D Memory Bit Line Rounding for Electric Field Uniformity
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Solution Overview
Problem
In three-dimensional memory devices with a gate-all-around structure, the high local electric field at the corners of bit lines affects local charge storage uniformity, necessitating an improved bit line shape to enhance electric field uniformity.
Innovation Solution
The memory device features bit lines with alternating wide and narrow parts, where the narrow parts have an ellipse-like shape with a rounding ratio greater than 30%, and supporting structures between the wide parts, along with a charge storage layer and conductive layers that cover the bit lines and supporting structures, formed through a process involving etching and rounding processes to improve bit line curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional planar or vertical gate structure is used, then the manufacturing process is simpler, but the local electric field uniformity at bit line corners deteriorates
Solution Approach 1:
The bit line cross-section is designed with a rounded corner configuration instead of sharp corners, creating a more uniform curvature distribution. This spherical/curved geometry reduces electric field concentration at corners, achieving more uniform electric field distribution and improved charge storage uniformity while maintaining the three-dimensional gate-all-around structure
Solution Approach 2:
The bit line structure implements different cross-sectional shapes at different locations: rounded corners at bit line ends versus straight sections in the middle. This local differentiation optimizes electric field uniformity where needed (at corners) while maintaining structural integrity and charge storage capacity in other regions
2Quantity of substance
If the bit line size is decreased to increase storage density, then the storage capacity increases, but the structural stability deteriorates
Solution Approach 1:
The rounded corner configuration reduces stress concentration at bit line ends by eliminating sharp corners that would act as stress initiation points. The smooth curved transitions distribute mechanical stresses more uniformly, enhancing structural stability and reliability of the scaled-down three-dimensional memory device
Data Source
AI summary
Provided is a memory device including a plurality of bit line layers and a plurality of supporting structures. Each bit line layer extends in a plane defined by a first direction and a second direction and has a plurality of bit lines extending along the first direction. Each bit line has a plurality of wide parts and a plurality of narrow parts arranged alternately. The supporting structures are disposed between the wide parts of the corresponding bit lines of adjacent bit line layers. Besides, each narrow part of each bit line substantially has an ellipse-like shape in cross section, and each narrow part has a rounding ratio (RR) of greater than about 30%.