Memory Die Grouping to Mitigate Read-Disturb Voltage Downshift
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Solution Overview
Problem
Memory dies with semi-circular shaped memory holes experience significant voltage downshifts due to read disturb events, leading to increased noisy bits and fail bit counts during erase program cycles.
Innovation Solution
Organize memory dies into groups based on their biasing voltage values, assigning those with higher bias voltage to less read-intensive applications and those with lower bias voltage to more read-intensive applications, and relocate data within these groups based on read frequency to maintain storage efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory dies with semi-circular shaped memory holes are used, then manufacturing efficiency is improved, but voltage stability deteriorates due to significant voltage downshifts during read disturb events
Solution Approach 1:
The patent applies parameter changes by measuring and comparing the bias voltage value of each memory die against a threshold, then assigning dies to different groups based on their voltage characteristics. This parameter-based classification allows the system to account for voltage downshift variations in semi-circular memory holes without changing the manufacturing process itself.
Solution Approach 2:
The patent segments memory dies into distinct groups (first group and second group) based on their bias voltage values relative to a threshold. This segmentation enables differential handling of dies with different voltage stability characteristics, allowing the system to manage voltage downshift effects by organizing dies into volatility-based groups.
2Reliability
If memory dies are organized by bias voltage value, then voltage downshift impact is reduced, but device complexity increases due to additional sorting and grouping operations
Solution Approach 1:
The patent performs preliminary action by measuring and comparing bias voltage values during an initial sorting phase, assigning memory dies to appropriate groups before actual data storage operations begin. This advance organization based on voltage characteristics reduces the impact of voltage downshifts on future read operations without adding complexity to the core storage functions.
Solution Approach 2:
The patent uses parameter changes by establishing a voltage threshold and comparing each die's bias voltage against it, creating a simple binary classification system that divides dies into two groups. This parameter-based approach provides a straightforward method for organizing dies by voltage stability without requiring complex multi-dimensional sorting criteria.
3Reliability
If memory dies with higher bias voltage are assigned to less read-intensive applications, then voltage stability is improved, but adaptability decreases due to fixed assignment rules
Solution Approach 1:
The patent applies dynamics by enabling the system to adaptively assign data to memory dies based on read intensity requirements and measured voltage characteristics. The controller can dynamically determine which group to use for specific data based on the application's read patterns, allowing flexible allocation that matches die properties with workload requirements rather than using fixed assignments.
Solution Approach 2:
The patent implements local quality by matching specific data placement decisions to the local characteristics of individual memory die groups. High-read-intensity data is placed in the second group (lower bias voltage, more stable), while low-read-intensity data can use the first group (higher bias voltage), creating a localized optimization where each data placement decision considers the specific properties of the target memory die group.
Data Source
AI summary
Memory die management based on biasing voltages. Some memory dies are formed of memory holes having a semi-circular shape. This semi-circular shape results in a decrease in biasing voltage compared to memory holes having a circular shape. Systems and methods described herein organize memory dies into memory die groups according to their biasing voltages. During operation, data is relocated between the memory die groups based on how often the data is read. Data may be scrambled within their respective memory die groups to maintain appropriate storage space.