Cobalt Interconnects Protected by Metal Cap

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Solution Overview

Problem

Cobalt contacts in back-end-of-line interconnect structures are prone to etching damage during the formation of via openings and trenches, which affects the integrity and reliability of the interconnects.

Innovation Solution

A method involving the formation of cobalt contacts with a metal cap on top, where the cobalt is partially or fully reflowed and covered by a metal cap composed of copper and other elements, such as manganese or aluminum, to protect the cobalt from etching damage during the damascene process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If cobalt contacts are used in back-end-of-line interconnect structures, then electrical conductivity and low electrical resistance are achieved, but the cobalt is prone to etching damage during via opening and trench formation

Engineering Contradiction:

Improveintegrity of cobalt contactsVSAvoidetching damage to cobalt

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A metal cap layer is deposited over the cobalt contact to serve as a protective intermediary barrier. This cap layer prevents direct exposure of the cobalt to etching chemicals during via opening and trench formation processes, thereby eliminating etching damage while maintaining the electrical conductivity of the underlying cobalt contact

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The metal cap is formed on the cobalt contact before the via opening and trench etching processes occur. This preliminary protective action ensures that when etching subsequently takes place, the cobalt is already shielded and cannot be damaged by the etching chemicals

Inventive Principle:

Principle #10Preliminary action

2Reliability

If a metal cap is added to protect cobalt contacts from etching damage, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improveprotection of cobalt contactsVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The metal cap layer is designed with specific thickness parameters optimized to provide adequate protection without excessive complexity. By controlling the cap thickness to be sufficient for protection but not overly thick, the solution maintains reliability while minimizing structural complexity and fabrication complexity

Inventive Principle:

Principle #35Parameter changes

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 metal cap effectively protects the cobalt contacts from etching and cleaning processes, preserving their integrity and allowing for normal etching and cleaning procedures without damaging the cobalt, while maintaining electrical conductivity and ensuring low electrical resistance.

Implementation Method 1

the cobalt is partially or fully reflowed and covered by a metal cap

Methodology Applied

Scientific EffectReflow:

Data Source

PatentUS9799555B1Cobalt interconnects covered by a metal cap

Publication Date: 2017.10.24 GLOBALFOUNDRIES US INC

AI summary

Interconnects for a chip and methods of forming such interconnects. An opening is formed in a dielectric layer and a contact is formed in the opening. A metal cap is formed on a top surface of the contact. The contact is comprised of cobalt, and the metal cap covers the top surface of the contact.