Silane Pretreated Copper Metallization Capping Layer

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Solution Overview

Problem

In modern integrated circuits, the increased circuit density and high current densities lead to signal propagation delays and electromigration issues in copper-based metallization layers, where conventional capping layers fail to provide adequate resistance against electromigration, especially at the interface between copper and the capping layer.

Innovation Solution

A thermal-chemical pretreatment of the copper surface using silicon-containing precursors like silane, followed by in situ deposition of the capping layer in the absence of a plasma ambient, enhances the interface and reduces surface irregularities, thereby improving adhesion and electromigration resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional plasma-based cleaning steps are used before capping layer deposition, then copper surface cleanliness is improved, but process time is increased and interface quality is insufficient for high current density applications

Engineering Contradiction:

Improveelectromigration resistanceVSAvoidprocess time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent replaces the conventional plasma-based cleaning method (physical/chemical process) with a thermal-chemical treatment method using silane vapor. This substitution achieves equivalent or superior surface preparation while significantly reducing process time and improving interface quality for electromigration resistance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental parameters of the surface treatment process by using thermal-chemical reactions at controlled temperatures (e.g., 400-600°C) with silane-containing precursors, rather than relying on plasma physics. This parameter change enables faster processing and better interface characteristics.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If copper-based metallization layers are used to reduce electrical resistance, then conductivity is improved, but electromigration resistance deteriorates at high current densities

Engineering Contradiction:

Improveelectromigration resistanceVSAvoidelectromigration at interface

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a modified copper surface layer formed by thermal-chemical treatment with silane as an intermediary between the copper metal and the capping layer. This intermediate layer acts as a buffer that prevents direct harmful interactions at the interface, reducing electromigration while maintaining the low resistivity benefits of copper.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite interface structure consisting of copper metal combined with a thermally-treated silane-modified surface layer. This composite structure combines the electrical conductivity of copper with the protective properties of the modified surface, achieving both low resistance and high electromigration resistance.

Inventive Principle:

Principle #40Composite materials

3Speed

If circuit density is increased to improve performance, then speed and power consumption are improved, but parasitic capacitance increases causing signal propagation delay

Engineering Contradiction:

Improveswitching speedVSAvoidsignal propagation delay

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent employs an ultra-thin capping layer (50-200 nm) that provides effective diffusion barrier and protective functions without adding significant thickness to the overall structure. This thin film approach minimizes parasitic capacitance while maintaining the benefits of high circuit density.

Inventive Principle:

Principle #30Flexible shells and thin films

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 results in a significantly improved interface between copper and the capping layer, enhancing electromigration resistance by 3-5 times compared to conventional nitrogen-enriched silicon carbide capping layers and reducing process time, while maintaining high adhesion and mechanical stability.

Implementation Method 1

the exposed surface is pretreated by means of a thermal-chemical reaction

Methodology Applied

Scientific EffectThermal-chemical reaction:

Implementation Method 2

a surface modification of the chemically cleaned copper surface can be generated on the basis of a silicon-containing precursor

Methodology Applied

Scientific EffectSurface modification:

Implementation Method 3

the capping layer is deposited on the exposed surface in an in situ process

Methodology Applied

Scientific EffectIn situ deposition:

Data Source

PatentUS7678699B2Method of forming an insulating capping layer for a copper metallization layer by using a silane reaction

Publication Date: 2010.03.16 ADVANCED MICRO DEVICES INC

AI summary

A new technique is disclosed in which a barrier/capping layer for a copper-based metal line is formed by using a thermal-chemical treatment with a surface modification on the basis of a silicon-containing precursor followed by an in situ plasma-based deposition of silicon nitride and/or silicon carbon nitride. The thermal-chemical treatment is performed on the basis of an ammonium/nitrogen mixture in the absence of any plasma ambient.