Memory Subsystem Charge Loss State Detection

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Solution Overview

Problem

Existing memory sub-systems face challenges in accurately determining the charge loss state of blocks, particularly in mixed SCL blocks, which can lead to reduced performance and reliability due to variations in charge loss rates among memory cells.

Innovation Solution

The proposed solution involves using a temperature-compensated time estimate and measuring representative charge losses to determine if a block has reached a uniform charge loss state. This allows the memory sub-system controller to apply appropriate compensation techniques during read operations, improving accuracy and reducing errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If representative charge losses are measured to determine uniform charge loss state, then measurement precision is improved, but device complexity increases

Engineering Contradiction:

Improvecharge loss state determination accuracyVSAvoidmeasurement and control system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The memory cells themselves are used to provide the measurement data by performing read operations that reveal their charge loss states. The system leverages the inherent electrical characteristics of the memory cells during normal read operations to determine charge loss, rather than requiring separate dedicated measurement circuits or external testing equipment.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The block is divided into multiple wordlines, and charge loss measurements are performed on representative wordlines rather than all wordlines. This segmentation allows the system to infer the charge loss state of the entire block by sampling specific representative wordlines, reducing measurement complexity while maintaining accuracy.

Inventive Principle:

Principle #1Segmentation

2Reliability

If temperature compensation is applied to predict uniform charge loss state, then reliability is improved, but computational requirements increase

Engineering Contradiction:

Improvecharge loss state prediction accuracyVSAvoidcomputational power consumption

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The system changes the temperature parameter by actively controlling and varying the temperature of the memory device during operations. By measuring charge loss at different temperatures and using these measurements to predict the uniform charge loss state, the system improves reliability while the temperature control process itself manages the computational burden through physical rather than purely computational means.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250147683A1Measurement of representative charge loss in a block to determine charge loss state

Publication Date: 2025.05.08 MICRON TECHNOLOGY INC

AI summary

A processing device in a memory sub-system detects an occurrence of a triggering event, determines respective levels of charge loss associated with a first representative wordline of a block of a memory device and with a second representative wordline of the block of the memory device, and determines whether a difference between the respective levels of charge loss satisfies a threshold criterion. Responsive to determining that the difference between the respective levels of charge loss satisfies the threshold criterion, the processing device further determines that the block is in a uniform charge loss state.