Copper Metallization Capping Layer Thermal-Chemical Pretreatment

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Solution Overview

Problem

Conventional techniques for forming copper-based metallization layers in integrated circuits face challenges with copper diffusion and electromigration, particularly at high current densities, where the interface between copper and capping layers affects adhesion and conductivity, leading to signal propagation delays and reliability issues.

Innovation Solution

A thermal-chemical pretreatment is used instead of plasma treatment to clean the exposed copper surface, followed by in situ deposition of a capping layer, enhancing the interface quality and reducing process time, thereby improving electromigration resistance and adhesion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If plasma treatment is used to clean the copper surface before capping layer deposition, then adhesion is improved, but process time is increased and electromigration resistance is insufficient

Engineering Contradiction:

Improveelectromigration resistanceVSAvoidprocess time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The invention changes the chemical composition parameters of the capping layer by incorporating nitrogen-rich materials (such as silicon nitride, silicon carbide nitride, or nitrogen-enriched low-k dielectric materials) to enhance electromigration resistance. This compositional parameter change allows the capping layer to provide both adhesion and electromigration protection without requiring additional plasma treatment steps, thereby reducing process time while improving reliability.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional dielectric materials (silicon dioxide, silicon nitride) are used as capping layers, then copper diffusion barrier is provided, but interface adhesion and electromigration resistance are insufficient

Engineering Contradiction:

ImproveadhesionVSAvoidcopper diffusion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention employs composite capping layer structures that combine multiple materials with complementary properties. For example, a stack comprising silicon nitride, silicon carbide nitride, and nitrogen-enriched low-k dielectric materials creates a composite structure that simultaneously provides copper diffusion barrier, adhesion enhancement, and electromigration resistance. The synergistic combination of these materials resolves the contradiction between diffusion protection and interface quality.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention applies different material compositions at different locations within the capping layer structure. The layer adjacent to the copper surface is specifically engineered with nitrogen-rich materials to maximize adhesion and electromigration resistance at the critical interface, while upper layers provide overall diffusion protection and mechanical support. This local optimization of material quality addresses the adhesion-electromigration contradiction effectively.

Inventive Principle:

Principle #3Local quality

3Reliability

If copper-based metallization is used to reduce electrical resistance, then conductivity is improved, but copper diffusion and electromigration become significant problems

Engineering Contradiction:

Improveelectrical conductivityVSAvoidcopper diffusion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention introduces a specially designed capping layer as an intermediary between the copper metallization and the surrounding dielectric environment. This intermediate layer acts as a protective mediator that prevents copper diffusion into the dielectric while also providing adhesion and electromigration resistance. The intermediary layer thus enables the use of copper for its superior conductivity without suffering from its inherent diffusion and electromigration problems.

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

This approach results in significantly improved electromigration performance, with enhanced resistance and adhesion characteristics, reducing process time and production costs, and achieving up to 3-5 times better performance compared to conventional methods.

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 capping layer is deposited on the exposed surface within the specified environment

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS7491638B2Method of forming an insulating capping layer for a copper metallization layer

Publication Date: 2009.02.17 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 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.