Non-volatile Memory Charge Accumulation Layer Using High-k Oxide

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Solution Overview

Problem

Conventional non-volatile semiconductor memories face challenges in miniaturization and low-voltage operation due to insufficient charge accumulation and threshold voltage variation in silicon nitride-based charge accumulation layers, which lead to inefficiencies in charge trapping and controllability.

Innovation Solution

A non-volatile semiconductor memory is developed using a gate multilayer material with a charge accumulation layer composed of an oxide dielectric material incorporating high-valence substances like Tc, Re, Ru, Os, Rh, Ir, Pd, Pt, Co, Ni, W, Mo, Cr, Mn, and Fe, which produces a trap level in the band gap, enabling efficient electron trapping and threshold voltage control with reduced voltage requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon nitride is used for the charge accumulation layer, then the memory structure can be formed, but the charge accumulation amount is insufficient and threshold voltage variation range cannot be assured

Engineering Contradiction:

Improvecharge accumulation amountVSAvoidthreshold voltage variation range

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent changes the material parameter of the charge accumulation layer from silicon nitride to a high-dielectric constant oxide material (such as SrTiO3, BaTiO3, PbZr1-xTixO3, or Pb1-xLaxZr1-yTiyO3) with dielectric constant k≥30. This parameter change enables sufficient charge accumulation amount and large threshold voltage variation range while maintaining the MONOS memory structure.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures including tunnel insulating films (SiO2, Si3N4, SiON), charge accumulation layers (high-k oxide materials), block insulating films (SiO2, Si3N4, SiON), and metal gate electrodes (TiN, TaN, W, Pt, Ir). This composite structure achieves both sufficient charge accumulation and reliable threshold voltage control.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If silicon nitride is used for the charge accumulation layer, then the memory can operate, but a sufficient driving voltage must be applied to the tunnel film, making it difficult to realize low-voltage operation

Engineering Contradiction:

Improvelow-voltage operation capabilityVSAvoiddriving voltage requirement

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent changes the dielectric constant parameter of the charge accumulation layer from silicon nitride (k≈7) to high-k oxide materials (k≥30). This parameter change increases the charge trapping efficiency and reduces the driving voltage requirement for tunnel film, enabling low-voltage operation.

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If TiO2 or HfO2 is damaged to produce a charge accumulation layer based on oxygen defects, then electric charges can be accumulated, but the accumulation layer behaves like an n-type semiconductor and electric charges are lost due to local defects in tunnel film

Engineering Contradiction:

Improveelectric charge accumulationVSAvoidcharge holding stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent changes the material composition parameter by selecting specific high-k oxide materials (SrTiO3, BaTiO3, PbZr1-xTixO3, Pb1-xLaxZr1-yTiyO3) with appropriate band gap characteristics, rather than relying on oxygen defects in ionic oxides. This parameter change ensures the accumulation layer does not behave like an n-type semiconductor and prevents charge loss through tunnel film defects.

Inventive Principle:

Principle #35Parameter changes

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 solution allows for high-speed memory operations at low voltages, improved charge accumulation, and increased threshold voltage shifting range, while preventing charge loss due to local defects, thus advancing miniaturization and integration in semiconductor memory technology.

Implementation Method 1

incorporating high-valence substances like Tc, Re, Ru, Os, Rh, Ir, Pd, Pt, Co, Ni, W, Mo, Cr, Mn, and Fe, which produces a trap level in the band gap, enabling efficient electron trapping

Methodology Applied

Scientific EffectBand gap trap level formation:

Implementation Method 2

A non-volatile semiconductor memory is developed using a gate multilayer material with a charge accumulation layer composed of an oxide dielectric material incorporating high-valence substances

Methodology Applied

Scientific EffectCharge accumulation:

Data Source

PatentUS8759896B2Non-volatile semiconductor memory using charge-accumulation insulating film

Publication Date: 2014.06.24 KIOXIA CORP

AI summary

There is provided a non-volatile semiconductor memory having a charge accumulation layer of a configuration where a metal oxide with a dielectric constant sufficiently higher than a silicon nitride, e.g., a Ti oxide, a Zr oxide, or a Hf oxide, is used as a base material and an appropriate amount of a high-valence substance whose valence is increased two levels or more (a VI-valence) is added to produce a trap level that enables entrance and exit of electrons with respect to the base material.