Heating Electrode Segmentation for Phase Change Memory Reset Current Reduction

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Solution Overview

Problem

Conventional phase change memory devices require a large reset current to change the state of the phase change material, which is limited by the contact surface between the heating electrode and the phase change material, and further size reduction is constrained by photolithography process capabilities.

Innovation Solution

The method involves forming a heating electrode with an intrinsic portion and a reduced portion within a dielectric layer, surrounded by an oxide spacer, to reduce the contact area with the phase change material layer, thereby increasing current density and reducing the reset current required for state transformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the contact surface between the heating electrode and the phase change material is reduced, then the reset current is reduced, but the photolithography process capability limits further size reduction

Engineering Contradiction:

Improvereset currentVSAvoidfeature size reduction capability

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The heating electrode is divided into two distinct portions: a first portion with a larger cross-sectional area and a second portion with a smaller cross-sectional area. This segmentation allows the electrode to provide sufficient heating area while reducing the contact area with the phase change material, thereby reducing reset current without being limited by photolithography capabilities.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The heating electrode structure transitions from a two-dimensional planar contact to a three-dimensional stacked configuration. The second portion is stacked over the first portion, creating a vertical arrangement that reduces the horizontal contact footprint while maintaining heating effectiveness through the stacked geometry.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Power

If the diameter of the heating electrode is reduced to increase current density, then the reset current is reduced, but the photolithography process limits the minimum achievable diameter

Engineering Contradiction:

Improvecurrent densityVSAvoidminimum electrode diameter

Core Design Contradiction:

PowerVSManufacturing precision

Solution Approach 1:

The heating electrode is segmented into a first portion with larger cross-sectional area and a second portion with smaller cross-sectional area. This segmentation enables the second portion to achieve high current density with reduced diameter, while the first portion provides structural support and sufficient heating area, bypassing photolithography limitations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure moves from a single-plane configuration to a stacked three-dimensional arrangement. The second portion is stacked vertically over the first portion, allowing the smaller diameter second portion to achieve high current density without being constrained by photolithography's minimum feature size in the lateral dimension.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 approach effectively decreases the reset current needed for phase change in the phase change material while allowing for smaller feature sizes beyond the limitations of conventional photolithography, enhancing the density and efficiency of phase change memory devices.

Implementation Method 1

a large current is generated by the heating electrode 16 and flows therethrough, thus heating up an interface between the phase change material layer pattern 20 and the heating electrode 16

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

an oxide spacer surrounding a sidewall of the reduced portion stacked over the intrinsic portion

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS8242034B2Phase change memory devices and methods for fabricating the same

Publication Date: 2012.08.14 POWERCHIP SEMICON MFG CORP

AI summary

Phase change memory devices and methods for manufacturing the same are provided. An exemplary embodiment of a phase change memory device includes a bottom electrode formed over a substrate. A first dielectric layer is formed over the bottom electrode. A heating electrode is formed in the first dielectric layer and partially protrudes over the first dielectric layer, wherein the heating electrode includes an intrinsic portion embedded within the first dielectric layer, a reduced portion stacked over the intrinsic portion, and an oxide spacer surrounding a sidewall of the reduced portion. A phase change material layer is formed over the first dielectric layer and covers the heating electrode, the phase change material layer contacts a top surface of the reduced portion of the heating electrode. A top electrode is formed over the phase change material layer and contacts the phase change material layer.