Read Threshold Calibration for Non-Volatile Memory
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Solution Overview
Problem
In non-volatile memory systems, maintaining process uniformity across diverse conditions such as endurance, retention, temperature, and disturbance is challenging due to variability among memory dies, blocks, and pages, which affects read throughput and Quality of Service (QoS).
Innovation Solution
A method for read threshold management that determines compound read parameters by averaging optimal parameters from selected physical dies and applies them to the group, identifying outlier dies through bit error rate (BER) estimation and performing parallel read threshold calibration across multiple dies to reduce calibration overhead and improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If read threshold calibration is performed sequentially on each physical die individually, then measurement precision is improved, but productivity deteriorates due to the large number of calibration operations required
Solution Approach 1:
The patent combines calibration operations across multiple physical dies by identifying compound read parameters that are common to groups of dies. Instead of calibrating each die separately, the system merges calibration efforts by determining compound parameters once and applying them to multiple dies, significantly reducing the total number of calibration operations while maintaining accuracy through outlier detection mechanisms.
Solution Approach 2:
The patent creates universal compound read parameters that can be applied across multiple physical dies simultaneously. These compound parameters serve a universal function for groups of dies that exhibit similar characteristics, allowing a single calibration result to benefit multiple dies rather than requiring individual calibration for each die.
2Reliability
If read threshold calibration is performed frequently to maintain process uniformity, then reliability is improved, but loss of time increases due to calibration overhead
Solution Approach 1:
The patent reduces calibration overhead by merging calibration operations across multiple dies. By determining compound read parameters that apply to groups of dies simultaneously, the system performs fewer calibration operations overall, reducing the time lost to calibration while maintaining process uniformity through the compound parameter approach.
Solution Approach 2:
The patent uses compound read parameters as templates that can be copied and applied to multiple physical dies. Once a compound parameter is determined through calibration, it serves as a reusable template for groups of dies with similar characteristics, eliminating the need to repeat full calibration procedures and reducing time overhead.
3Adaptability or versatility
If individual read parameters are maintained for each physical die to account for variability, then adaptability is improved, but device complexity increases due to managing multiple parameters
Solution Approach 1:
The patent merges individual die parameters into compound read parameters that represent groups of dies. Instead of managing separate parameters for each die, the system combines them into compound parameters that capture the essential characteristics of die groups, significantly reducing parameter management complexity while maintaining adaptability through outlier detection.
Solution Approach 2:
The patent creates universal compound parameters that serve multiple dies simultaneously. These compound parameters provide a simplified interface for handling die variability, allowing the system to adapt to individual die characteristics through outlier detection while maintaining manageable complexity through universal parameter application.
4Productivity
If compound read parameters are applied to all physical dies to reduce calibration operations, then productivity is improved, but measurement precision deteriorates due to outlier dies
Solution Approach 1:
The patent extracts and identifies outlier dies from groups that would otherwise share compound read parameters. By detecting dies that do not conform to the compound parameter characteristics, the system separates these outliers from the main group, ensuring they receive appropriate individual calibration while the majority benefits from efficient compound parameter application.
Solution Approach 2:
The patent applies local quality by treating outlier dies differently from the main group. While compound parameters are applied universally to most dies for efficiency, outlier dies receive localized individual attention through separate calibration procedures, ensuring measurement precision is maintained for all dies regardless of their characteristics.
Data Source
AI summary
A system and method for read threshold calibration in a non-volatile memory are provided. Physical dies in the memory are divided into groups based on device-level parameters such as time and temperature parameters. An outlier die may be identified outside of the plurality of groups based on a comparison of a bit error rate (BER) indicator for each die to a threshold. For each group of dies, a read parameter is determined for at least one die, and applied to each of the plurality of dies of the group. The read parameter may be determined based on a threshold measurement of a representative one or more word lines.