Superblock Temperature-Aware Reference Voltage Adjustment
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Solution Overview
Problem
The cross-temperature effect in NAND memory cells causes high Fail Bits Count (FBC) during read operations due to shifts in threshold voltage distributions and reference voltages resulting from temperature changes.
Innovation Solution
A controller and method that incorporate superblock-based programming temperature awareness, using a look-up table to adjust reference voltages based on the programming temperature of superblocks, which are groups of blocks across multiple dies, to mitigate the cross-temperature effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reference voltages are adjusted to compensate for temperature changes, then read reliability is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary characterization of NAND memory cells at multiple temperatures and stores the resulting reference voltage values in a lookup table. This preliminary action allows the system to quickly retrieve appropriate reference voltages during actual read operations without complex real-time calculations, thereby improving read reliability while limiting the increase in device complexity to mainly storage space.
Solution Approach 2:
The system changes the reference voltage parameter based on the programming temperature of the superblock. By storing reference voltage values corresponding to different programming temperatures in a lookup table, the system adjusts the reference voltage parameter to match the actual temperature conditions, thereby improving read reliability across varying temperature ranges.
2Adaptability or versatility
If superblock-based temperature tracking is implemented, then temperature awareness is improved, but storage space consumption increases
Solution Approach 1:
The system segments the storage device into superblocks that group blocks from multiple dies together. By organizing temperature tracking at the superblock level rather than at the individual block or die level, the system reduces the granularity of temperature tracking while maintaining sufficient temperature awareness. This segmentation approach decreases the total storage space required for temperature records while preserving adaptability to temperature variations.
Solution Approach 2:
The superblock structure serves multiple functions: it groups blocks from multiple dies for unified management, provides a common temperature tracking mechanism for all blocks in the superblock, and enables efficient read operations across distributed blocks. This multi-functionality reduces the need for separate temperature tracking mechanisms for each block, thereby reducing overall storage space consumption while maintaining temperature awareness.
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
Reduces the Fail Bits Count (FBC) by accurately adjusting reference voltages according to temperature variations, enhancing data read reliability in non-volatile storage systems.
Implementation Method 1
It is known that cell conductance, sensing trip level, and the reference voltages used for verifying the programmed data and during read operations are influenced by temperature. This phenomenon is commonly known as the cross-temperature effect.
Data Source
AI summary
A controller, a method, a system, and a non-transitory machine-readable medium are provided for reducing Fail Bits Count (FBC) caused by the cross-temperature effect. In one embodiment, a controller may comprise a processor configured to obtain a record from a storage. The record comprises a representation of a programing temperature of a superblock of non-volatile memories. The non-volatile memories are on a plurality of dies. The superblock comprises blocks of the non-volatile memories and the blocks are not on the same die. The processor is further configured to determine a reference voltage based on the representation of the programing temperature and to read a page of the superblock using the reference voltage.