Non-volatile Memory Select Gate Disturb Countermeasure

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Solution Overview

Problem

Program disturb in memory systems leads to unintended programming of memory locations during the programming process, causing errors in data storage due to electrons being accelerated from one side of a dummy word line to another and redirected into a select gate, resulting in inaccurate data retrieval.

Innovation Solution

A countermeasure is proposed where the channel is opened from one side of the dummy word line to the other side prior to applying subsequent programming signals, by applying a voltage to the dummy word line before pre-charging, to prevent electrons from being trapped and causing program disturb. This involves a control circuit that pre-charges the channel and turns on the dummy memory cell before applying selection voltages to the select gate, ensuring electrons can escape and reducing the risk of hot electron injection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If boosting signals are applied to unselected word lines to inhibit programming, then programming accuracy is improved, but electrons may be trapped in the channel and redirected into the select gate causing program disturb

Engineering Contradiction:

Improveprogramming accuracyVSAvoidprogram disturb

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The dummy memory cell is activated before the boosting phase to create a safe escape path for electrons. By turning on the dummy memory cell in advance, the channel is opened from one side of the dummy word line to the other, allowing electrons to be drained before they can be trapped and redirected into the select gate during subsequent programming operations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dummy memory cell acts as an intermediary component between the channel and the select gate. It provides a controlled path for electron flow, serving as a mediator that prevents electrons from directly entering the select gate while still allowing the boosting mechanism to function for programming inhibition.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the programming process is performed without opening the channel, then the programming speed is maintained, but electrons are trapped and cause unintended programming

Engineering Contradiction:

Improveprogramming speedVSAvoiddata accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

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

This approach effectively reduces the risk of errors in programming, reading, and erasing by preventing unintended programming, thereby enhancing the reliability and accuracy of data storage operations in memory systems.

Implementation Method 1

electrons being accelerated from one side of a dummy word line to another and redirected into a select gate

Methodology Applied

Scientific EffectElectron movement: Electron Beam

Implementation Method 2

applying boosting signals to unselected word lines to boost a channel for the second set of memory cells

Methodology Applied

Scientific EffectChannel boosting: Electric Field

Data Source

PatentUS10553298B1Non-volatile memory with countermeasure for select gate disturb

Publication Date: 2020.02.04 SANDISK TECHNOLOGIES LLC

AI summary

Program disturb is a condition that includes the unintended programming while performing a programming process for other memory cells. Such unintended programming can cause an error in the data being stored. In some cases, program disturb can result from electrons trapped in the channel being accelerated from one side of a dummy word line to another side of the dummy word line and redirected into a select gate. To prevent such program disturb, it is proposed to open the channel from one side of the dummy word line to the other side of the dummy word line after a sensing operation for program verify and prior to a subsequent programming voltage being applied. For example, the channel can be opened up by applying a voltage to the dummy word line prior to pre-charging unselected memory cells.