Dual Phase Change Material Layer for Void-Free Gap Fill

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Solution Overview

Problem

Phase change memory devices face challenges in completely filling high aspect ratio structures without generating voids, seams, or overhangs in the phase change material layer, especially as design rules become more stringent and integration increases.

Innovation Solution

A phase change structure comprising a first phase change material layer that partially fills a high aspect ratio structure and a second phase change material layer that completely fills it, using an in-situ reflow mechanism to achieve desired step coverage and gap fill characteristics, with the second layer having a composition different from the first, formed through a physical vapor deposition process at elevated temperatures to reduce surface energy and enhance diffusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a single phase change material layer is formed to fill a high aspect ratio structure, then the structure should be completely filled, but voids, seams, or overhangs are generated in the phase change material layer

Engineering Contradiction:

Improvefilling completenessVSAvoiddefect generation

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The phase change material layer is divided into multiple sub-layers (first phase change material layer and second phase change material layer) with different compositions. The first layer partially fills the high aspect ratio structure, and the second layer completely fills it, eliminating voids and seams while maintaining compositional differences for reliable phase transitions.

Inventive Principle:

Principle #1Segmentation

2Productivity

If design rules are reduced for higher integration, then device density increases, but the phase change material layer cannot completely fill minute structures without defects

Engineering Contradiction:

Improveintegration densityVSAvoidfilling completeness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Different regions of the phase change material layer are assigned different compositions: the first layer has a composition optimized for partial filling, while the second layer has a different composition optimized for complete filling of minute structures. This local compositional variation enables defect-free filling in highly integrated devices.

Inventive Principle:

Principle #3Local quality

3Reliability

If a phase change material layer is formed to ensure apparent phase transition, then reliability improves, but the layer may not fully fill minute three dimensional structures without defects

Engineering Contradiction:

Improvephase transition reliabilityVSAvoidstructural completeness

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The phase change memory device uses a composite structure with two different phase change materials (Ge-Sb-Te alloy and Sb-Te alloy) in distinct layers. This composite approach ensures both complete structural filling of minute three dimensional structures and reliable phase transitions for data storage.

Inventive Principle:

Principle #40Composite materials

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 solution ensures complete filling of minute structures like contact holes and trenches without defects, improving the reliability and data retention of phase change memory devices by maintaining phase transitions and increasing the resistance margin between set and reset states.

Implementation Method 1

formed through a physical vapor deposition process at elevated temperatures to reduce surface energy and enhance diffusion

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 2

elevated temperatures to reduce surface energy and enhance diffusion

Methodology Applied

Scientific EffectSurface energy reduction: Surface Tension

Implementation Method 3

elevated temperatures to reduce surface energy and enhance diffusion

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 4

data may be recorded into the phase change memory or the data may be read from the phase change memory device using phase transition of a chalcogenide compound in a phase change material layer

Methodology Applied

Scientific EffectPhase transition: Phase Change

Implementation Method 5

data may be recorded or read using resistance difference between amorphous state and crystalline state of the chalcogenide compound

Methodology Applied

Scientific EffectResistivity change: Electrical Resistance

Data Source

PatentUS8557627B2Methods of forming a phase change layer and methods of fabricating a phase change memory device including the same

Publication Date: 2013.10.15 SAMSUNG ELECTRONICS CO LTD

AI summary

A phase change structure includes a first phase change material layer pattern and a second phase change material layer pattern. The first phase change material layer pattern may partially fill a minute structure, and the second phase change material layer pattern may fully fill the minute structure. The first phase change material layer pattern may include a first phase change material, and the second phase change material layer pattern may include a second phase change material having a composition substantially different from a composition of the first phase change material.