Non-volatile Memory With Non-uniform Tunnel Barrier

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Solution Overview

Problem

The physical size of phase change cells in non-volatile memories is limited by the resistive heater, and existing methods to reduce cell size, such as current constriction, face challenges in reliability and manufacturability, hindering the adoption of phase change memories in high-density applications.

Innovation Solution

A non-volatile memory structure incorporating a non-uniform tunnel barrier adjacent to the phase change material to constrict current flow, allowing for localized heating and reduced cell size, which is manufacturable with current integrated circuit equipment, enabling higher density memory devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a narrow resistive heater is used to constrict current flow, then localized heating is improved, but reliability and manufacturability deteriorate

Engineering Contradiction:

Improvelocalized heatingVSAvoiddevice reliability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent introduces a non-uniform tunnel barrier as an intermediary element between the electrodes and phase change material. This tunnel barrier with varying thickness creates natural current constriction through its non-uniform resistance profile, eliminating the need for narrow resistive heaters while achieving localized heating. The tunnel barrier mediates the current flow to concentrate it in specific regions without requiring physically constricted heater structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the parameter of tunnel barrier thickness from uniform to non-uniform. By varying the thickness of the tunnel barrier across different regions, the current density is naturally modulated - thinner regions conduct more current while thicker regions conduct less. This parameter change enables current constriction and localized heating without the reliability issues of narrow resistive heaters.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If a narrow resistive heater is used to constrict current flow, then localized heating is improved, but ease of manufacture deteriorates

Engineering Contradiction:

Improvelocalized heatingVSAvoidmanufacturability

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The non-uniform tunnel barrier serves as an intermediary that enables current constriction through its inherent electrical properties rather than through physical geometric constraints. This approach is easier to manufacture because it relies on depositing layers with controlled thickness variations using standard semiconductor fabrication techniques, rather than requiring precise patterning of narrow heater structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical/geometric approach of narrow resistive heaters with an electrical field-based approach using non-uniform tunnel barriers. Instead of constraining current through physical geometry, the current flow is controlled through electrical resistance variations in the tunnel barrier, which can be more easily manufactured using conventional semiconductor processes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Quantity of substance

If phase change cell size is reduced, then memory density is improved, but manufacturing precision requirements worsen

Engineering Contradiction:

Improvememory densityVSAvoidcell fabrication precision

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent changes the tunnel barrier thickness parameter to create non-uniform regions within the phase change cell. This allows current constriction and localized heating to be achieved through electrical parameter variation rather than through reducing the overall cell dimensions. Consequently, memory density can be increased without proportionally increasing manufacturing precision requirements.

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

The non-uniform tunnel barrier achieves localized heating, enabling smaller phase change cells and faster data storage with improved reliability and manufacturability, supporting higher densities for integrated phase change memory devices.

Implementation Method 1

a non-uniform tunnel barrier adjacent the recording layer... for electrically communicating with the second electrode via the tunnel barrier

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

recording layer comprising a plurality of phase change cells variable in resistance

Methodology Applied

Scientific EffectElectrical resistance: Electrical Resistance

Implementation Method 3

phase change cells variable in resistance... phase change material

Methodology Applied

Scientific EffectPhase change: Phase Change

Data Source

PatentUS9496490B2Non-volatile memory

Publication Date: 2016.11.15 NXP BV

AI summary

A non-volatile memory (50) is disclosed. A second electrode (56) is provided. A first electrode (51) is also provided. A recording layer having a plurality of phase change cells (54) variable in resistance is provided between the first electrode (51) and the second electrode (56). A non-uniform tunnel barrier (540) is provided adjacent each of the recording layer and the first electrode. In use, the first electrode is in electrical communication with the non-uniform tunnel barrier, the first electrode for electrically communicating with the second electrode via the non-uniform tunnel barrier.