Gradient Metal Nitride Liner for Low-Resistance Metal Fill
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Solution Overview
Problem
As semiconductor devices scale down to the 10 nm node and lower, line and via contact resistance in metal interconnects increase due to reduced current-carrying cross-section and electron scattering, along with challenges in filling narrow features with conductive materials like tungsten.
Innovation Solution
A gradient metal nitride layer is deposited in features, decreasing in thickness and/or nitrogen concentration with depth, serving as an adhesion layer and occupying less volume in the mid-section and bottom section to improve resistivity, and allowing bulk metal deposition without an intervening nucleation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a uniform thickness metal nitride layer is deposited in the feature, then adhesion is improved, but resistivity increases due to excessive volume occupation
Solution Approach 1:
The patent applies local quality by creating a gradient metal nitride layer where the thickness and nitrogen concentration vary spatially within the feature. The layer is thickest and most nitrogen-rich at the top (providing strong adhesion) and becomes progressively thinner and metal-rich toward the bottom (minimizing resistivity). This non-uniform structure optimizes both adhesion and electrical properties in different regions of the same feature.
Solution Approach 2:
The patent employs parameter changes by systematically varying the thickness and nitrogen concentration of the metal nitride layer as a function of depth within the feature. The gradient profile transitions from high nitrogen content at the top to low nitrogen content at the bottom, creating a continuous parameter change that balances adhesion requirements at the interface with electrical conductivity requirements in the bulk.
2Ease of manufacture
If a metal nitride layer is deposited to improve adhesion, then filling challenges are addressed, but an additional nucleation layer deposition step is required
Solution Approach 1:
The gradient metal nitride layer serves multiple functions simultaneously: it provides adhesion at the top interface, acts as a nucleation layer for bulk metal deposition in the mid-section, and minimizes resistivity at the bottom. This multi-functionality eliminates the need for separate adhesion and nucleation layer deposition steps, simplifying the manufacturing process while maintaining all necessary functions.
Solution Approach 2:
The patent merges the adhesion layer and nucleation layer functions into a single gradient metal nitride layer structure. By combining these two previously separate functional layers into one continuously varying structure, the process complexity is reduced while achieving both adhesion and nucleation purposes in a single deposition sequence.
3Area of moving object
If feature size is reduced to scale down devices, then device density increases, but contact resistance increases rapidly
Solution Approach 1:
The gradient structure applies local quality by optimizing the metal nitride layer composition and thickness at different positions within the narrow feature. The metal-rich bottom region minimizes electron scattering and contact resistance in the critical current-carrying path, while the nitrogen-rich top region ensures adequate adhesion, thereby maintaining low contact resistance even in scaled-down features.
Solution Approach 2:
The gradient metal nitride layer effectively creates a composite structure with varying composition from nitrogen-rich at the top to metal-rich at the bottom. This composite approach combines the adhesive benefits of metal nitride with the low-resistivity benefits of pure metal, achieving both strong bonding and low contact resistance in sub-10 nm features.
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 gradient metal nitride layer enhances resistivity and facilitates efficient bulk metal deposition within narrow features, reducing contact resistance and improving fill performance in sub-10 nm node interconnects.
Implementation Method 1
non-conformally depositing a metal nitride layer in the feature such that the metal nitride layer lines at least part of the feature sidewalls
Implementation Method 2
delivering pulses of ammonia (NH3) and a metal-containing precursor to a chamber housing the substrate
Implementation Method 3
At the top of the feature, the gradient metal nitride layer can serve as an adhesion layer during a subsequent planarization
Implementation Method 4
The metal-rich portions of the gradient metal nitride layer serve as a nucleation layer for subsequent bulk metal deposition
Data Source
AI summary
Methods of filling a features of partially fabricated semiconductor substrates with metal include depositing a gradient metal nitride layer in the feature. The gradient metal nitride layer decreases in thickness and/or nitrogen concentration with feature depth. At the top of the feature, the gradient metal nitride layer can serve as an adhesion layer during a subsequent planarization. Because the gradient metal nitride layer deceases in thickness and/or nitrogen concentration further into the feature, it occupies less volume in the mid-section and bottom section of the feature. This improves resistivity in the feature. The feature is filled with metal.