Multi-Metal Interconnect Liner for Higher Copper Gapfill
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Solution Overview
Problem
As critical dimensions in semiconductor interconnects decrease, the resistivity of interconnects increases due to reduced copper gapfill volume, primarily because the liner layer thickness cannot be reduced without affecting its performance, leading to defects and voids in smaller vias.
Innovation Solution
A method for forming a metal liner layer using a ruthenium-doped cobalt combination with reduced thickness, deposited via chemical vapor deposition, which enhances copper gapfill volume and reduces interconnect resistivity by preventing underlayer copper voiding and maintaining copper reflow properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the liner layer thickness is reduced to increase copper gapfill volume, then the interconnect resistivity improves, but the liner performance is affected and defects/voids occur
Solution Approach 1:
The liner layer is segmented into multiple thin sub-layers (e.g., ruthenium layer, cobalt layer, and additional ruthenium layer) instead of using a single thick layer. This segmentation allows the total liner thickness to be reduced while maintaining protective function, thereby increasing copper gapfill volume and reducing interconnect resistivity without compromising liner performance
Solution Approach 2:
The invention uses composite material structure combining different metals (ruthenium and cobalt) with complementary properties. Ruthenium provides diffusion barrier and adhesion properties, while cobalt provides structural stability. This composite approach enables thinner total thickness while maintaining or improving liner performance compared to single-material liners
2Productivity
If the critical dimensions are scaled down to increase component density, then the interconnect density improves, but the interconnect resistivity increases
Solution Approach 1:
The invention changes the physical parameters of the liner layer, specifically reducing the thickness parameter while changing the material composition parameters. This allows the liner to be thin enough to permit adequate copper gapfill in scaled-down interconnects, thereby maintaining low resistivity even as critical dimensions decrease and interconnect density increases
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 ruthenium-doped cobalt metal liner achieves improved thermal stability and increased copper gapfill volume, reducing interconnect resistivity and enabling more dense interconnects while maintaining performance at smaller dimensions.
Implementation Method 1
depositing the metal liner layer including depositing a first ruthenium layer with a first thickness of approximately 5 angstroms or less and depositing a first cobalt layer with a second thickness of approximately 20 angstroms or less
Implementation Method 2
depositing copper gapfill material in an opening in which the metal liner layer has been deposited and annealing the copper gapfill material to reflow the copper gapfill material into the opening
Data Source
AI summary
A method for forming a metal liner layer for an interconnect uses a multi-metal deposition process to produce a reduced thickness liner. The back-end-of-the-line packaging process may include forming a metal liner layer by depositing a ruthenium layer with a first thickness of approximately 5 angstroms or less and depositing a first cobalt layer with a second thickness of approximately 20 angstroms or less. In some embodiments, the ruthenium layer may be deposited on a previously formed barrier layer and then undergoes a treatment process before depositing the first cobalt layer. In some embodiments, the first cobalt layer may be deposited on the ruthenium layer or the ruthenium layer maybe deposited on the first cobalt layer. In some embodiments, the ruthenium layer is deposited on the first cobalt layer and a second cobalt layer is deposited on the ruthenium layer.