RuO2 Oxidation Barrier for MIM Capacitor Leakage Current

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Solution Overview

Problem

Current oxidation barriers, such as TiN, are insufficient to prevent oxidation of underlying metals during the formation of Ru or RuO2 electrodes in MIM capacitor devices, leading to increased leakage current and contact resistance.

Innovation Solution

A method involving the conformal deposition and oxidation of Ru-based materials below 500°C to form a strong oxidation barrier, which prevents oxidation of underlying layers and reduces contact resistance by using RuO2 as a diffusion barrier, allowing for the formation of MIM capacitors with reduced EOT and leakage current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If TiN is used as oxidation barrier, then manufacturing simplicity is maintained, but oxidation protection of underlying metals is insufficient leading to increased leakage current and contact resistance

Engineering Contradiction:

Improveoxidation protectionVSAvoidbarrier strength requirement

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses a composite barrier structure consisting of TiN layer combined with Ru/RuO2 layers. The TiN provides initial oxidation protection while the Ru/RuO2 layers form a stronger secondary barrier that prevents oxygen diffusion to the underlying metals. This composite approach achieves superior oxidation protection compared to TiN alone while maintaining process compatibility.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The TiN layer is deposited first as a preliminary oxidation barrier before Ru or RuO2 electrode formation. This preliminary barrier prevents initial oxidation of underlying metals during subsequent processing steps, creating a protected interface for the stronger Ru/RuO2 barrier to form upon.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If RuO2 is formed by oxidation of Ru, then conductive electrode is created, but surface roughness increases degrading leakage current

Engineering Contradiction:

Improveelectrode conductivityVSAvoidsurface morphology

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies different quality requirements to different regions: the Ru/RuO2 barrier layer provides strong oxidation protection at the interface with underlying metals, while the top electrode surface is kept smooth for low leakage current. The oxidation is controlled to form RuO2 primarily at the barrier interface rather than uniformly throughout the layer.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The oxidation process parameters are carefully controlled (temperature, oxygen partial pressure, duration) to achieve partial oxidation that forms sufficient RuO2 for barrier function while limiting surface roughness. By adjusting oxidation conditions, the patent balances conductivity enhancement against surface morphology degradation.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If CVD Ru or as-deposited RuO2 process is used, then electrode formation is achieved, but substrate oxidation occurs increasing contact resistance

Engineering Contradiction:

Improveelectrode formation efficiencyVSAvoidsubstrate oxidation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The TiN layer is deposited beforehand as a protective counter-action against oxidation during Ru/CVD processes. This preliminary barrier prevents oxygen from reaching and oxidizing the substrate and underlying metals during the electrode formation process, eliminating the need for subsequent oxidation reversal steps.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The TiN layer acts as an intermediary barrier between the oxidizing CVD Ru/RuO2 process and the substrate. It absorbs or blocks oxygen during deposition, protecting the underlying conductive plug and substrate from oxidation while allowing the Ru electrode to form above it.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 method effectively reduces leakage current and contact resistance between the storage node and electrical contact plug, providing a stronger oxidation barrier than traditional TiN, thus enhancing the performance of MIM capacitor structures.

Implementation Method 1

oxidation of Ru-comprising material below 500°C to form RuO2

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

RuO2 as an oxygen diffusion barrier

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 3

conformal deposition of a Ru-comprising material layer in the recess

Methodology Applied

Scientific EffectConformal deposition: Deposition (physical)

Data Source

PatentEP2584588B1Method of forming MIM capacitor with Ru-comprising oxygen diffusion barrier

Publication Date: 2017.10.04 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

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AI summary

A method for forming a MIM capacitor structure comprises the steps of: - obtaining a base structure provided with a recess, the recess exposing a conductive bottom electrode plug (33), - selectively growing Ru (40) on the bottom electrode plug, based on a difference in incubation time of Ru growth on the bottom electrode plug compared to the base structure material, - oxidizing the selectively grown Ru, - depositing a Ru-comprising bottom electrode (60) over the oxidized Ru (50), - forming a dielectric layer (70) on the Ru-comprising bottom electrode, and - forming a conductive top electrode (71) over the dielectric layer.