Nonvolatile Memory Read Method Managing Channel Charge Imbalance

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Solution Overview

Problem

Nonvolatile memory devices experience read disturbances due to channel charge imbalances during sensing operations, leading to data integrity issues and reduced performance, especially in high-program/erase cycle conditions.

Innovation Solution

The method involves applying a read pass voltage to unselected wordlines and a turn-on voltage to the selected wordline, followed by sequential discharge of voltages across zones, to share and manage channel charges before and after sensing, thereby reducing read disturbances and improving data reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a read voltage is applied to a selected wordline during sensing operation, then data can be read from memory cells, but channel charge imbalances occur causing read disturbances

Engineering Contradiction:

Improvedata reading accuracyVSAvoiddata integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies a read pass voltage to unselected wordlines before the sensing operation to prevent channel charge buildup that would cause read disturbances. This preliminary action counteracts the potential harmful effect of charge imbalance before it occurs during the read operation, thereby maintaining both reading accuracy and data integrity.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The read pass voltage is applied to unselected wordlines in advance of the sensing operation to prepare the memory device for accurate reading. This preliminary voltage application ensures that channel charges are properly managed before the actual data read occurs, preventing read disturbances and ensuring reliable operation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If read pass voltage is applied to unselected wordlines, then read disturbances are reduced, but device complexity increases due to additional voltage control

Engineering Contradiction:

Improvedata integrityVSAvoidvoltage control circuitry

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The read pass voltage applied to unselected wordlines serves multiple functions: it prevents read disturbances by managing channel charges, and it prepares the memory device for subsequent operations. This multi-functionality reduces the need for separate dedicated circuits, thereby limiting the increase in device complexity while maintaining data integrity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If sequential discharge of voltages is applied across zones, then channel charge sharing is improved, but operation time increases

Engineering Contradiction:

Improvechannel charge balanceVSAvoidread operation duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent divides the wordlines into different zones and applies discharge voltages sequentially to each zone rather than simultaneously to all wordlines. This segmentation allows for controlled charge sharing while managing the time required for the operation, balancing reliability improvement with acceptable operation duration.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9183939B2Nonvolatile memory device, a memory system having the same, and a read method thereof, the read method applying a read pass voltage to a selected wordline after a sensing

Publication Date: 2015.11.10 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of reading a nonvolatile memory device including: applying a read voltage to a selected wordline of the nonvolatile memory device; applying a read pass voltage to unselected wordlines of the nonvolatile memory device; sensing a state of a memory cell connected to the selected wordline; and applying the read pass voltage to the selected wordline after the sensing.