Copper Seed Layer Oxide Treatment for Void-Free Gap Fill

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Solution Overview

Problem

Current semiconductor device manufacturing faces challenges in achieving improved gap fill characteristics in copper interconnects, leading to voids and other undesirable structures due to poor interaction between metal and dielectric layers, especially as device sizes shrink and circuit density increases.

Innovation Solution

A method involving the formation of an oxide layer on a copper seed layer using an oxygen-bearing species to protect it from contamination, followed by dissolving the oxide layer to facilitate copper plating, ensuring a void-free and contaminant-free copper fill in the interconnect structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If copper interconnects are used to improve conductivity and signal propagation, then electrical performance is improved, but gap fill characteristics deteriorate leading to voids and defective structures

Engineering Contradiction:

Improveelectrical conductivityVSAvoidgap fill characteristics

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies a preliminary oxygen plasma treatment to the copper seed layer before the copper fill plating process. This preliminary action modifies the surface properties of the seed layer by forming a controlled oxide layer, which then serves as a better interface for copper deposition. The oxygen plasma exposure creates surface sites that promote uniform copper nucleation and growth, preventing the void formation that plagues conventional direct plating approaches.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If device geometry is reduced to increase circuit density, then productivity and cost-effectiveness are improved, but manufacturing precision deteriorates due to process limits at smaller feature sizes

Engineering Contradiction:

Improvecircuit densityVSAvoidprocess capability at small geometry

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the chemical and physical parameters of the seed layer surface through oxygen plasma treatment. By controlling the oxygen exposure time, power, and pressure, the surface oxide thickness and composition are precisely controlled to optimize copper deposition. This parameter control enables reliable copper gap fill in sub-0.25 micron geometries where conventional processes fail, allowing continued scaling to increase circuit density.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional copper plating is used without oxide layer treatment, then process simplicity is maintained, but manufacturing precision deteriorates due to poor copper-seed layer interaction

Engineering Contradiction:

Improveprocess simplicityVSAvoidcopper film quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent introduces an oxygen plasma treatment step that acts as an intermediary between the copper seed layer deposition and the copper fill plating. This intermediary treatment modifies the seed layer surface to create optimal conditions for copper deposition. The oxygen plasma creates a controlled oxide interface that promotes uniform copper growth, serving as a chemical mediator that improves the interaction between the seed layer and incoming copper atoms during plating.

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 enhances device yields by improving gap fill characteristics, reducing voids and wettability issues, and is compatible with conventional processes without requiring substantial equipment or technology modifications, resulting in higher quality interconnect structures.

Implementation Method 1

applying an oxygen bearing species to treat the seed layer to cause an oxide layer of predetermined thickness to form on the seed layer

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 2

contacting a copper bearing material overlying the oxide layer to dissolve the oxide layer while forming a thickness of copper bearing material to fill the contact structure

Methodology Applied

Scientific EffectChemical reduction: Reduction

Implementation Method 3

using a copper plating bath to dissolve the oxide layer and expose the clean seed surface for copper plating

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentUS8242017B2Method and structure for copper gap fill plating of interconnect structures for semiconductor integrated circuits

Publication Date: 2012.08.14 SEMICON MFG INT (SHANGHAI) CORP

AI summary

A method for forming an integrated circuit device including an interconnect structure, e.g., copper dual damascene. The method includes providing a substrate and forming an interlayer dielectric layer overlying the substrate. The method also includes patterning the interlayer dielectric layer to form a contact structure and forming a barrier metal layer overlying the contact structure. The method includes forming a seed layer comprising copper bearing species overlying the barrier metal layer and applying an oxygen bearing species to treat the seed layer to cause an oxide layer of predetermined thickness to form on the seed layer. The method protects the seed layer from contamination using the oxide layer while the substrate is transferred from the step of applying the seed layer and contacts a copper bearing material in liquid form overlying the oxide layer to dissolve the oxide layer while forming a thickness of copper bearing material using a plating process to begin filling the contact structure.