Ru-Doped NbN Barrier Layers for Low-Resistance Copper Interconnects
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Solution Overview
Problem
As microelectronic devices approach smaller feature sizes, the challenge of electromigration in copper interconnects becomes significant, and existing barrier layers, such as tantalum nitride, are not effective at nodes below 22 nm, necessitating a new method for forming reliable copper barrier layers.
Innovation Solution
A method involving the formation of ruthenium doped niobium nitride barrier layers using a combination of atomic layer deposition (ALD) and flash chemical vapor deposition processes, where a first niobium nitride barrier film is doped with ruthenium, and a second niobium nitride film is deposited on the doped layer to create a superior barrier layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If TaN barrier film thickness is increased to provide continuous coverage, then barrier reliability improves, but line resistance increases and gapfill space decreases
Solution Approach 1:
The patent changes the material composition parameter by doping TaN with Ru to create TaRuN barrier films. This compositional parameter change enables achieving continuous barrier coverage at reduced thicknesses (e.g., 40-50 Å), thereby lowering line resistance while maintaining electromigration barrier reliability through the optimized alloy composition.
Solution Approach 2:
The patent creates a composite barrier material by combining TaN with Ru dopant, forming a TaRuN composite film. This composite structure leverages the beneficial properties of both materials: TaN provides the base barrier functionality while Ru doping enhances film continuity and reduces resistivity, achieving both reliability and low resistance in a single integrated layer.
2Productivity
If barrier film thickness is reduced to provide more gapfill space, then manufacturing flexibility improves, but barrier effectiveness deteriorates
Solution Approach 1:
The patent modifies the film thickness parameter by reducing barrier film thickness from traditional values (>60 Å) to optimized thinner films (40-50 Å). This parameter change is compensated by Ru doping, which ensures that the reduced thickness films still provide effective electromigration barriers, thereby maintaining barrier effectiveness while increasing gapfill space for copper filling.
Solution Approach 2:
The patent applies local quality enhancement by introducing Ru dopant at specific concentrations within the TaN matrix. This localized compositional modification creates regions of enhanced barrier performance that compensate for the overall reduced film thickness, ensuring effective electromigration protection even in thinner films that provide more gapfill space.
3Ease of manufacture
If thermal ALD is used to deposit TaN barrier layers, then process simplicity is maintained, but barrier performance deteriorates at nodes below 22 nm
Solution Approach 1:
The patent changes the deposition parameter by introducing Ru doping during the thermal ALD process. This parameter modification transforms the simple TaN deposition into a doped TaRuN deposition, which maintains the simplicity of thermal ALD (avoiding plasma complexity) while significantly improving barrier performance at advanced nodes through compositional optimization.
Solution Approach 2:
The patent creates a composite barrier material by incorporating Ru dopant into TaN during thermal ALD deposition. This composite TaRuN film maintains the process simplicity of thermal ALD while achieving superior barrier performance at nodes below 22 nm, as the Ru doping enhances film quality and barrier effectiveness without requiring complex plasma processes.
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 niobium nitride barrier layers provide enhanced barrier properties with lower nitrogen content, better coverage, thinner layers, and reduced line resistance, effectively addressing the limitations of existing copper barrier layers at smaller node sizes.
Implementation Method 1
forming a first niobium nitride (NbN) barrier film on a substrate by a first ALD process
Implementation Method 2
doping the first barrier film with ruthenium by a flash chemical vapor deposition process
Data Source
AI summary
Described are methods for forming ruthenium doped niobium nitride barrier layers. The doped barrier layer provides improved adhesion at a thickness of less than about 15 Å. In some embodiments, the doped barrier layers disclosed herein provide improved barrier properties including a lower nitrogen content, a higher ruthenium content, better coverage, thinner layers, or lower line resistance