Configurable NAND Parameters for 3D Memory Array Optimization
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Solution Overview
Problem
In three-dimensional NAND memory arrays, variations in memory cell dimensions, such as memory hole diameter, lead to inconsistent programming and read performance due to differences in device characteristics across the array, resulting in issues like overprogramming and reduced array usability.
Innovation Solution
Configurable parameters are determined based on the predicted variation in memory cell dimensions within the array, allowing for distinct sets of parameters to be used for different regions, such as adjusting programming voltage, number of pulses, read voltage, and erase voltage to compensate for geometric variations, and updating these parameters according to write-erase cycle counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uniform programming parameters are used across the entire memory array, then device complexity is reduced, but manufacturing precision deteriorates due to geometry variations causing overprogramming and reliability issues
Solution Approach 1:
The patent divides the memory array into multiple zones based on memory cell geometry characteristics. Each zone is assigned specific programming parameters (pulse numbers, voltage levels, pulse widths) tailored to its local geometry features. This localized parameter optimization ensures accurate programming for each zone while compensating for geometry variations, thereby resolving the contradiction between device complexity and manufacturing precision.
2Manufacturing precision
If location-specific programming parameters are implemented, then manufacturing precision is improved, but device complexity increases due to multiple parameter sets
Solution Approach 1:
The memory array is segmented into multiple zones based on geometry characteristics. Each zone has its own optimized parameter set, but the segmentation is systematic and hierarchical. The controller manages these parameter sets through a structured approach, reducing the operational complexity despite having multiple parameter configurations. This segmentation allows precise control for each zone while maintaining manageable system complexity.
Solution Approach 2:
Programming parameters for each zone are predetermined and stored in lookup tables or configuration memory based on pre-characterized geometry data. When a programming operation is initiated, the appropriate parameter set is automatically selected based on the target zone, eliminating the need for real-time parameter calculation and reducing operational complexity during actual programming.
3Manufacturing precision
If higher programming voltages are applied to compensate for geometry variations, then manufacturing precision is improved, but use of energy increases
Solution Approach 1:
Instead of uniformly increasing programming voltage across all zones, the patent optimizes multiple parameters including pulse numbers, voltage levels, and pulse widths specific to each zone's geometry. This multi-parameter optimization achieves precise threshold voltage control for each zone while minimizing energy consumption by applying only the necessary programming strength required for each specific geometry configuration.
Data Source
AI summary
Configurable parameters may be used to access NAND flash memory according to schemes that optimize such parameters according to predicted characteristics of memory cells, for example, as a function of certain memory cell device geometry, which may be predicted based on the location of a particular device within a memory array.