Non-Volatile Memory Charge Storage Region Design

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Solution Overview

Problem

Current non-volatile memory cells face challenges in programming speed and data retention due to the distribution of charge storage in charge storage regions, which affects the threshold voltage and electron migration.

Innovation Solution

The non-volatile memory cell design incorporates a charge storage region with a middle charge storage material having a higher density of charges than outer materials, separated by thin oxide regions, allowing for efficient electron capture and retention, thereby enhancing programming speed and data retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If charge storage is distributed uniformly in the charge storage region, then the structure is simple, but programming speed is slow and data retention is poor

Engineering Contradiction:

Improveprogramming speedVSAvoidcharge storage region structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The charge storage region is segmented into multiple distinct layers: a first charge storage layer, a second charge storage layer, and an intermediate charge storage layer positioned between them. This segmentation allows each layer to serve specific functions - the intermediate layer with higher trap density captures electrons rapidly during programming, while the outer layers provide stable charge retention, thereby resolving the contradiction between programming speed and structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the charge storage structure are assigned different properties - the intermediate charge storage layer has a higher density of trap states compared to the first and second charge storage layers. This local quality differentiation enables the intermediate layer to excel at rapid electron capture (improving programming speed) while the overall multi-layer structure maintains data retention, thus resolving the technical contradiction.

Inventive Principle:

Principle #3Local quality

2Speed

If charge storage region has high electron capture rate, then programming speed improves, but electron loss increases reducing data retention

Engineering Contradiction:

Improveprogramming speedVSAvoiddata retention

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The charge storage region is divided into functionally distinct layers: the intermediate charge storage layer with higher trap density serves as the primary electron capture zone during programming (high speed), while the first and second charge storage layers act as retention zones with lower trap densities that minimize electron loss (high reliability). This segmentation resolves the contradiction between fast programming and data retention.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The intermediate charge storage layer acts as an intermediary structure between the tunnel dielectric and the control gate dielectric. It mediates the electron storage function by providing high trap density for rapid capture during programming while the surrounding first and second charge storage layers with lower trap densities reduce electron loss, thus balancing programming speed and data retention.

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 design enables faster programming and improved data retention by concentrating charge storage in the middle layer, reducing built-in electric fields at the edges and minimizing electron loss, thus maintaining the threshold voltage and data integrity.

Implementation Method 1

The charge storage region has a middle charge storage material that stores a higher density of charges than two outer charge storage materials

Methodology Applied

Scientific EffectElectron trapping: Absorption (physical)

Implementation Method 2

The oxide regions of one embodiment are thin (e.g., less than one nanometer) such that during operation charges may easily pass through the oxide regions

Methodology Applied

Scientific EffectQuantum tunneling:

Implementation Method 3

the threshold voltage of the transistor controlled by the amount of charge that is retained in the charge storage region

Methodology Applied

Scientific EffectElectrostatic field effect: Electric Field

Data Source

PatentUS10115737B2Charge storage region in non-volatile memory

Publication Date: 2018.10.30 SANDISK TECHNOLOGIES LLC

AI summary

Disclosed herein is a non-volatile storage system with memory cells having a charge storage region that may be configured to store a higher density of charges (e.g., electrons) in the middle than nearer to the control gate or channel. The charge storage region has a middle charge storage material that stores a higher density of charges than two outer charge storage materials that are nearer to the control gate or channel, in one aspect. The charge storage region of one aspect has oxide regions between the middle charge storage material and the two outer charge storage materials. The oxide regions of one embodiment are thin (e.g., less than one nanometer) such that during operation charges may easily pass through the oxide regions. The non-volatile memory cell programs quickly and has high data retention.