Phase Change Memory Polishing Using Insulation Stopper

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Solution Overview

Problem

Conventional CMP processes in semiconductor fabrication lead to varying heights and recessed surfaces of phase change material patterns, causing issues such as uneven current distribution and electrode cracking in phase change memory devices.

Innovation Solution

A method involving sequential formation of insulation and sacrificial layers, followed by selective etching and polishing processes, using a high etching selectivity mold insulation layer as a polishing stopper to ensure uniform heights and flat surfaces of phase change material patterns and contacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a CMP process is applied to a phase change material pattern, then the material is polished and planarized, but the resultant structures have varying heights according to location on the wafer

Engineering Contradiction:

Improveheight uniformityVSAvoidprocess control

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

A polishing stop layer is introduced as an intermediary between the phase change material pattern and the polishing pad. This stop layer has different polishing rates than the phase change material, allowing the polishing process to automatically halt when the stop layer is exposed, thereby preventing over-polishing and ensuring uniform heights across the wafer surface.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If a CMP process is applied to a phase change material pattern, then the material is polished, but the upper surface becomes recessed relative to the surrounding mold oxide layer

Engineering Contradiction:

Improvesurface flatnessVSAvoidsurface profile

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The polishing stop layer serves as a mediator that prevents the polishing pad from directly contacting and over-polishing the phase change material pattern. By controlling the polishing process to stop when the stop layer is exposed, the phase change material upper surface remains protruding rather than recessed, maintaining the desired surface profile for subsequent electrode formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the phase change material pattern has different heights, then the fabrication process continues, but different current levels are passed through respective phase change memory cells

Engineering Contradiction:

Improvefabrication throughputVSAvoidcurrent uniformity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The polishing stop layer is prepared in advance before the polishing of the phase change material pattern. This preliminary action establishes a reference plane that guides the polishing process, ensuring that all phase change material patterns are polished to the same height relative to the stop layer, thereby guaranteeing uniform current levels in subsequent device operation.

Inventive Principle:

Principle #10Preliminary action

4Ease of manufacture

If an electrode is formed on a recessed phase change material pattern, then the electrode takes a curved shape, but this curvature results in cracking of the electrode material layer

Engineering Contradiction:

Improveelectrode formationVSAvoidelectrode integrity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The polishing stop layer provides preliminary protection against the harmful effect of over-polishing. By preventing the phase change material surface from being recessed, the stop layer preemptively eliminates the condition that would cause electrode curvature and subsequent cracking, ensuring electrode integrity without requiring additional protective measures.

Inventive Principle:

Principle #9Preliminary anti-action

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 addresses the issues of varying heights and recessed surfaces, resulting in uniform phase change material patterns and contacts, reducing reset current dissipation and preventing electrode cracking, thereby improving the reliability and consistency of phase change memory devices.

Implementation Method 1

polishing the first conductive material until the first sacrificial layer is exposed and a first contact formed in the first opening is electrically separated from other portions of the first conductive material

Methodology Applied

Scientific EffectMechanical abrasion: Abrasion

Implementation Method 2

forming a first opening by sequentially etching the first sacrificial layer, the second insulation layer and the first insulation layer

Methodology Applied

Scientific EffectChemical etching: Chemical Bonding

Data Source

PatentUS8168535B2Method fabricating semiconductor device using multiple polishing processes

Publication Date: 2012.05.01 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of fabricating a phase change memory device includes the use of first, second and third polishing processes. The first polishing process forms a first contact portion using a first sacrificial layer and the second polishing process forms a phase change material pattern using a second sacrificial layer. After removing the first and second sacrificial layers to expose resultant protruding structures of the first contact portion and the phase change material pattern, a third polishing process is used to polish the resultant protruding structures using an insulation layer as a polishing stopper layer.