Ruthenium and Cobalt Capping Layers for Interconnect Reliability
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Solution Overview
Problem
As semiconductor device nodes shrink, challenges such as degrading electromigration lifetimes and reduced device reliability arise due to copper diffusion and poor adhesion between capping layers in metal interconnect structures, particularly with cobalt and ruthenium liners, which are not adequately contained or adhered.
Innovation Solution
The method involves selectively depositing two capping layers atop a substrate, with a first layer of ruthenium and a second layer of cobalt, or their combinations, to improve adhesion and reliability in copper interconnect structures, particularly for device nodes of 25 nm or less, using techniques like chemical vapor deposition, physical vapor deposition, or atomic layer deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper is used in metal filled vias to achieve excellent conductivity at smaller sizes, then electrical functionality is improved, but copper diffusion throughout surroundings or along weak interfaces occurs, degrading reliability
Solution Approach 1:
A ruthenium liner layer is introduced as an intermediary between the copper fill and the surrounding dielectric material. This ruthenium layer acts as a diffusion barrier that prevents copper atoms from migrating into the low-k dielectric, thereby eliminating the harmful copper diffusion effect while maintaining the excellent electrical conductivity of the copper interconnect
Solution Approach 2:
The interconnect structure employs a composite material system consisting of multiple layers: copper fill material for conductivity, ruthenium liner for diffusion barrier properties, and potentially cobalt capping layers. This composite structure combines materials with complementary properties to simultaneously achieve electrical functionality and prevent copper diffusion
2Quantity of substance
If device nodes are reduced to 22 nm or less to increase density, then circuit element density is improved, but electromigration lifetimes degrade and device reliability reduces
Solution Approach 1:
The ruthenium liner serves as a protective intermediary layer that enhances electromigration resistance. By preventing copper diffusion and maintaining sharp material interfaces, the ruthenium layer reduces scattering sites and interface defects that would otherwise accelerate electromigration failures at scaled dimensions
Solution Approach 2:
The invention changes the material composition parameter of the liner from conventional materials to ruthenium, which has superior electromigration barrier properties. This material parameter change fundamentally improves the electromigration lifetime of the interconnect structure at scaled device nodes
3Object-generated harmful factors
If cobalt and ruthenium liners are used to contain copper, then copper diffusion is reduced, but the liners become mobile in current and adhesion between capping layers deteriorates
Solution Approach 1:
The invention uses a composite liner structure with ruthenium as the primary diffusion barrier material. Ruthenium forms a stable, adherent interface with both copper and low-k dielectric materials, preventing the mobility issues observed with cobalt-based liners while maintaining effective copper containment
Solution Approach 2:
The material selection changes from cobalt-based liners to ruthenium-based liners, fundamentally altering the chemical and physical properties of the liner layer. Ruthenium exhibits superior thermal stability, lower current-induced mobility, and better adhesion characteristics compared to cobalt, thereby resolving the adhesion and mobility problems
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 copper interconnect interface adhesion and improves device properties like electron migration and time-dependent dielectric breakdown, thereby increasing the reliability of semiconductor devices.
Implementation Method 1
using techniques like chemical vapor deposition, physical vapor deposition, or atomic layer deposition
Implementation Method 2
using techniques like chemical vapor deposition, physical vapor deposition, or atomic layer deposition
Implementation Method 3
copper problematically diffuses throughout its surroundings or along a weak interface, unless contained, for example in a liner and/or by a capping layer
Data Source
AI summary
Methods and apparatus for forming an interconnect structure, the method including selectively depositing two or more capping layers atop a top surface of a via within a low-k dielectric layer, wherein the two or more capping layers include a first layer of ruthenium and a second layer of cobalt.