Recessed Via Metallization for BEOL Electromigration Resistance
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Solution Overview
Problem
Conventional BEOL metallization processes face issues with void formation during the deposition of materials like tantalum nitride or titanium nitride, which are used to fill via openings, and copper is prone to electromigration, affecting the reliability of interconnect structures, especially as devices scale to smaller dimensions.
Innovation Solution
A recessed via structure is created using copper for the initial metal fill, followed by a second metal layer with barrier properties, such as tantalum, tungsten, or ruthenium, to prevent electromigration and ensure reliable conductive pathways between interconnect structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tantalum nitride or titanium nitride is deposited to fill via openings for barrier properties, then electromigration resistance is improved, but voids form during deposition
Solution Approach 1:
The via fill process is segmented into two separate steps: first depositing the barrier metal layer to provide electromigration resistance, then filling the remaining space with copper. This segmentation allows each material to be deposited under optimal conditions, preventing void formation while maintaining barrier properties.
Solution Approach 2:
The barrier metal layer is deposited to partially fill the via opening, providing sufficient electromigration protection without completely filling the via. This partial action approach allows the subsequent copper fill to complete the via without encountering deposition issues that would cause voids, while still achieving the required barrier function.
2Productivity
If devices are scaled to smaller dimensions to increase integration density, then productivity is improved, but void formation and electromigration become more pronounced
Solution Approach 1:
The composite via structure with copper fill and barrier metal layer becomes increasingly important as devices scale down. The barrier metal layer provides robust electromigration protection that is critical at smaller dimensions where current density increases, while the copper maintains conductivity despite the reduced via size, enabling continued scaling without reliability degradation.
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 recessed via structure provides a robust and reliable conductive connection with a planar surface, enhancing the reliability of BEOL metallization by minimizing voids and electromigration concerns, suitable for applications like MRAM devices.
Implementation Method 1
A first metal layer is deposited onto the liner layer so as to fill the via opening
Implementation Method 2
copper is prone to electromigration
Implementation Method 3
An overburden of the first metal layer is removed from the liner layer on the second interlayer dielectric by a first planarizing process
Implementation Method 4
A second metal layer different from the first metal layer is deposited so as to fill the recess with the second metal, wherein the second metal layer includes tantalum, titanium, tungsten, cobalt, ruthenium, iridium, rhodium, nitrides thereof, alloys thereof, or mixtures thereof
Data Source
AI summary
Back end of line (BEOL) metallization structures and methods according to aspects of the invention generally include forming an interconnect structure including a recessed via structure in an interlayer dielectric. The recessed via structure is lined with a liner layer and filled with a first metal such as copper, tungsten, aluminum, alloys thereof or mixtures thereof. The recessed portion is filled with a second metal such as tantalum, titanium, tungsten, cobalt, ruthenium, iridium, platinum, nitrides thereof, or mixtures thereof, which in combination with the liner layer provides effective barrier properties for the bulk first metal.