Liner-Free Conductive Structures for Cobalt Out-Diffusion Control
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Solution Overview
Problem
Conductive structures without barrier or liner layers face challenges in preventing cobalt out-diffusion, leading to void formation and resistance degradation when integrated with ruthenium-filled structures, which complicates their integration in integrated circuits.
Innovation Solution
A cobalt layer is used as a reservoir to mitigate cobalt out-diffusion by diffusing into the ruthenium-filled conductive structures, with subsequent removal before additional wiring levels, and the ruthenium structures are recessed or partially filled to control diffusion and void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If cobalt conductive structures are integrated with ruthenium-filled structures without barrier or liner layers, then manufacturing complexity is reduced, but cobalt out-diffusion occurs leading to void formation and resistance degradation
Solution Approach 1:
A titanium nitride (TiN) liner layer is introduced as an intermediary between the cobalt conductive structure and the ruthenium-filled structure. This liner prevents direct contact between cobalt and ruthenium, thereby blocking cobalt out-diffusion into the ruthenium structure while maintaining the integration of the two materials. The liner resolves the contradiction by adding a thin protective layer that prevents reliability issues without significantly increasing manufacturing complexity.
2Reliability
If cobalt layer is used as reservoir to mitigate out-diffusion, then conductive structure reliability is improved, but additional manufacturing steps are required
Solution Approach 1:
The cobalt layer is deposited in advance as a reservoir before the ruthenium filling process. This preliminary cobalt layer serves as a diffusion barrier by providing a controlled source of cobalt that prevents out-diffusion during subsequent processing steps. The preliminary action of depositing the cobalt reservoir layer resolves the contradiction by establishing reliability protection before the potential diffusion problem occurs, while the additional manufacturing step is integrated into the existing process sequence.
3Reliability
If ruthenium structures are recessed or partially filled, then void formation is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The ruthenium filling is controlled to be partial rather than complete, creating a localized fill that stops before the top surface of the mandrel. This local quality approach ensures that ruthenium is present where needed for conductivity while preventing overfilling that would cause void formation during subsequent processing. The partial fill resolves the contradiction by optimizing the ruthenium distribution - enough to provide conductive functionality but not so much as to create voids - with the TiN liner providing additional protection.
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 reduces cobalt out-diffusion, preventing voids and resistance degradation, enhancing the integration of cobalt and ruthenium-filled conductive structures in integrated circuits.
Implementation Method 1
A cobalt layer is used as a reservoir to mitigate cobalt out-diffusion by diffusing into the ruthenium-filled conductive structures
Implementation Method 2
exposing the liner-free conductive structure to a heat treatment
Data Source
AI summary
The present disclosure describes a method for forming liner-free or barrier-free conductive structures. The method includes forming a liner-free conductive structure on a cobalt conductive structure disposed on a substrate, depositing a cobalt layer on the liner-free conductive structure and exposing the liner-free conductive structure to a heat treatment. The method further includes removing the cobalt layer from the liner-free conductive structure.