Flash Memory Programming Method Reducing Insulating Layer Electric Field

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Solution Overview

Problem

Conventional programming methods for NAND-type flash memory devices apply high electric fields to the insulating layer, leading to reliability issues and limited data rewriting times due to electron capture and storage, which can result in data loss over time.

Innovation Solution

A programming method that electrically isolates cell units with programming units from bit lines, applies a programming voltage to selected word lines, and generates hot carriers in the semiconductor region to inject them into the programming unit, reducing the electric field on the insulating layer and improving its reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high electric field is applied to the insulating layer for programming, then electron injection into floating gate is achieved, but reliability of the insulating layer deteriorates

Engineering Contradiction:

Improvereliability of insulating layerVSAvoidelectron capture and storage in oxide layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a depletion region as an intermediary structure between the source/drain and the floating gate. This depletion region acts as a mediator that enables hot carrier injection without requiring extremely high electric fields across the entire insulating layer, thus reducing direct harmful effects on the oxide layer while still achieving effective electron injection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical parameters by creating a depletion region with specific voltage characteristics. By controlling the voltage across the depletion region, the system achieves hot carrier generation at lower overall electric fields, transforming the programming mechanism to reduce stress on the insulating layer while maintaining functionality.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of moving object

If high voltage is applied to programming units, then data rewriting capability is enabled, but insulating layer deteriorates over time

Engineering Contradiction:

Improvedata rewriting timesVSAvoidinsulating layer characteristic

Core Design Contradiction:

Duration of action of moving objectVSReliability

Solution Approach 1:

The patent segments the cell unit into programming units and non-programming units, creating distinct functional zones. This segmentation allows the depletion region to be formed only where needed, enabling localized hot carrier injection that reduces overall voltage stress on the insulating layer while maintaining data rewriting capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The depletion region serves as an intermediary structure that mediates between the applied voltage and the floating gate. It provides a controlled path for hot carrier injection that reduces direct voltage stress on the insulating layer, thereby extending data rewriting times without compromising reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If conventional programming method is used, then programming operation is simple, but data loss occurs over time due to charge release

Engineering Contradiction:

Improveprogramming operation simplicityVSAvoidstored data loss

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The depletion region acts as an intermediary that improves charge retention in the floating gate. By controlling the hot carrier injection process through this intermediate structure, the system reduces charge leakage and data loss over time while maintaining programming operation simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 method enhances the reliability of the insulating layer by reducing the electric field applied to it, thereby suppressing deterioration and extending data rewriting capabilities.

Implementation Method 1

generating carriers in the first semiconductor region during a period of applying the programming voltage; and injecting hot carriers into the programming unit

Methodology Applied

Scientific EffectHot carrier injection:

Implementation Method 2

When FN (Fowler-Nordheim) tunneling current flows through the gate oxide layer, if a portion of the electrons are captured by the oxide layer and stored in the oxide layer

Methodology Applied

Scientific EffectFowler-Nordheim tunneling:

Data Source

PatentUS9136004B2Semiconductor memory device and programming method for flash memory for improving reliabilty of insulating layer of memory cell

Publication Date: 2015.09.15 WINBOND ELECTRONICS CORP

AI summary

A programming method for suppressing deterioration of an insulating layer in a memory cell is provided. In the programming method for a flash memory of the invention, a cell unit including programming units that have been programmed is electrically isolated from a bit line; a cell unit not including programming units is electrically coupled with the bit line; a programming voltage is applied to selected word lines; and a pass voltage is applied to non-selected word lines. Moreover, during a period of applying the programming voltage, carriers are generated in a P-well, and hot carriers passing through a depletion region and accelerated by an electric field are injected into the memory cell.