Nitride Sidewall Contact for Charge Diffusion in Non-Volatile Memory

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Solution Overview

Problem

Non-volatile semiconductor memories with charge trap type structures face challenges in achieving high-speed and low-voltage operation due to variations in threshold voltage caused by trapped charges, which affect data retention and endurance to repeated writing and erasing.

Innovation Solution

The introduction of a second silicon nitride film in contact with both the first silicon nitride film and the silicon substrate allows excess charges to diffuse into the substrate, reducing the influence on threshold voltage and enhancing high-speed and low-voltage memory operation by reducing the amount of charges trapped in the first silicon nitride film.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a trap layer is provided to ensure a large difference in threshold voltage, then data retention characteristics and endurance are improved, but threshold voltage varies when charges are captured in the trap layer during production process

Engineering Contradiction:

Improvedata retention characteristicsVSAvoidthreshold voltage variation

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

A nitride layer is introduced as an intermediary charge diffusion path between the trap layer and substrate. This nitride layer allows excess charges captured during production to diffuse away from the trap layer, mediating the interaction between charge storage and threshold voltage stability, thereby resolving the contradiction between improving data retention and maintaining manufacturing precision

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful effect of excess charges on threshold voltage is extracted and relocated to the nitride layer, which serves as a separate charge diffusion region. By taking out the excess charges from the trap layer through the nitride layer, the threshold voltage variation is reduced while maintaining the charge trapping capability for data retention

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If charges are captured in the trap layer during production process, then data retention is enhanced, but high-speed and low-voltage operation becomes difficult due to threshold voltage variation

Engineering Contradiction:

Improvedata retentionVSAvoidoperation speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The nitride layer acts as a mediator that separates the charge trapping function from the threshold voltage control. By providing an alternative diffusion path through the nitride layer, it enables charge capture for data retention while preventing excessive charge accumulation that would slow down operation, thus resolving the speed-reliability contradiction

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If charges are captured in the trap layer, then memory effect is strengthened, but the amount of charges trapped affects threshold voltage and reduces operation efficiency

Engineering Contradiction:

Improvememory effectVSAvoidoperation efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Excess charges that would negatively impact operation efficiency are extracted from the trap layer through the nitride layer. This selective removal of harmful charges while preserving necessary trapped charges for memory effect resolves the contradiction between strengthening memory effect and maintaining operation efficiency

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The nitride layer serves as an intermediary that regulates charge distribution between the trap layer and substrate. It allows sufficient charges to remain in the trap layer for strong memory effect while enabling excess charges to diffuse to the substrate through the nitride layer, maintaining high operation efficiency

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 configuration enables high-speed and low-voltage operation by minimizing the impact of trapped charges on threshold voltage, improving data retention and endurance, and allowing for more efficient charge diffusion through the use of a thinner third silicon oxide film or a silicide region.

Implementation Method 1

the second silicon nitride film is in contact with the first silicon nitride film and the silicon substrate, thereby allowing excess charges captured in the ONO structure in a predetermined step in production to diffuse into the silicon substrate via the second silicon nitride film in another predetermined step

Methodology Applied

Scientific EffectCharge diffusion: Diffusion

Data Source

PatentUS9461138B2Non-volatile semiconductor memory with nitride sidewall contacting nitride layer of ONO gate stack and methods for producing the same

Publication Date: 2016.10.04 SEIKO EPSON CORP

AI summary

A non-volatile semiconductor memory free from adverse effects due to process charge is provided. The non-volatile semiconductor memory includes: a silicon substrate; a first silicon oxide film; a second silicon oxide film; a first silicon nitride film; and a second silicon nitride film, wherein the first silicon oxide film is layered on the silicon substrate, the first silicon nitride film is layered on the first silicon oxide film, the second silicon oxide film is layered on the first silicon nitride film, and the second silicon nitride film is layered to have a first part that is in contact with the first silicon nitride film and a second part that is in contact with the silicon substrate.