Interconnect Metal Capping for Low-Resistance Via Openings
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Solution Overview
Problem
The exposure of copper during the formation of via openings in interconnect structures leads to issues such as electro migration and difficulty in forming a conductive barrier, resulting in increased resistance and potential voids due to the removal or thinning of the metal cap during the damascene process.
Innovation Solution
A method involving the selective re-deposition of a metal cap and the formation of an inhibitor film followed by a conductive barrier to prevent the conductive barrier from forming at the bottom of the via opening, thereby maintaining the integrity of the metal cap and reducing electro migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the metal cap is removed or thinned during the damascene process to form via openings, then the via opening can be formed, but electro migration occurs and the conductive barrier formation becomes difficult
Solution Approach 1:
A new metal cap layer is deposited over the conductive feature before the via opening formation process. This preliminary action ensures that the metal cap is present and protective during subsequent processing steps, preventing electro migration and facilitating proper conductive barrier formation while still allowing via openings to be created through the dielectric layers.
2Ease of manufacture
If the metal cap is removed or thinned during the damascene process, then via openings can be formed, but resistance increases and voids form
Solution Approach 1:
The metal cap layer is deposited in advance over the conductive feature before via opening formation. This preliminary protective layer prevents damage, resistance increase, and void formation during the via opening process, while still allowing the via openings to be successfully formed through the dielectric layers.
3Reliability
If the conductive barrier is formed at the bottom of the via opening, then barrier coverage is achieved, but resistance increases
Solution Approach 1:
The inhibitor film is selectively deposited only at the bottom of the via opening, creating a local quality difference. This allows the conductive barrier to be formed on the sidewalls and top surfaces with proper coverage, while the bottom surface remains free of barrier material, thus maintaining low resistance at the critical interface with the conductive feature.
4Manufacturing precision
If the inhibitor film is formed uniformly, then selectivity in conductive barrier deposition is improved, but the process complexity increases
Solution Approach 1:
An inhibitor film is introduced as an intermediary layer between the metal cap and the conductive barrier deposition process. This intermediary film provides the necessary selectivity for conductive barrier formation by preventing barrier deposition at the bottom of the via opening while allowing it on the sidewalls and top surfaces, achieving precise control without excessive process complexity.
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 ensures a uniform inhibitor film formation, improves selectivity in conductive barrier deposition, and reduces resistance and electro migration issues, enhancing the reliability of the interconnect structure.
Implementation Method 1
selectively re-deposition of a metal cap
Implementation Method 2
selectively re-deposition of a metal cap
Implementation Method 3
formation of an inhibitor film followed by a conductive barrier
Implementation Method 4
formation of an inhibitor film followed by a conductive barrier
Data Source
AI summary
A method includes forming a first conductive feature in a first dielectric layer, forming a first metal cap over and contacting the first conductive feature, forming an etch stop layer over the first dielectric layer and the first metal cap, forming a second dielectric layer over the etch stop layer; and etching the second dielectric layer and the etch stop layer to form an opening. The first conductive feature is exposed to the opening. The method further includes selectively depositing a second metal cap at a bottom of the opening, forming an inhibitor film at the bottom of the opening and on the second metal cap, selectively depositing a conductive barrier in the opening, removing the inhibitor film, and filling remaining portions of the opening with a conductive material to form a second conductive feature.