Tungsten Nitride Deposition via Pulsed Nucleation
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Solution Overview
Problem
Conventional methods for depositing tungsten nitride, such as CVD, face challenges in achieving good step coverage in high aspect ratio features and adhesion to dielectric surfaces, particularly at low processing temperatures, which are essential for modern semiconductor technology.
Innovation Solution
A pulsed nucleation layer method involving a reducing agent like diborane to form a tungsten layer, followed by nitridation, which provides excellent adhesion and step coverage over high aspect ratio regions without requiring high deposition temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVD methods are used to deposit tungsten nitride, then good step coverage can be achieved, but high deposition temperatures are required which are incompatible with low-K dielectrics or nickel silicide
Solution Approach 1:
The deposition process is segmented into multiple sequential steps: forming a nucleation layer, depositing a tungsten layer, and nitriding the tungsten layer. This segmentation allows each step to be optimized independently, enabling conformal coverage at low temperatures without requiring high deposition temperatures throughout the entire process
Solution Approach 2:
A nucleation layer is formed in advance on the substrate surface before tungsten nitride deposition. This preliminary action provides suitable nucleation sites that enable subsequent low-temperature conformal deposition of tungsten nitride with excellent step coverage in high aspect ratio features
2Temperature
If conventional PVD techniques are used to deposit tungsten nitride, then low processing temperatures can be maintained, but poor step coverage is achieved in high aspect ratio trenches, vias and contacts
Solution Approach 1:
A nucleation layer acts as an intermediary between the substrate and the tungsten nitride layer. This intermediate layer provides suitable surface properties that enable subsequent conformal deposition of tungsten nitride, achieving excellent step coverage in high aspect ratio features while maintaining low processing temperatures
Solution Approach 2:
The invention changes the surface parameters of the substrate by forming a nucleation layer with specific properties (composition, roughness, surface energy) that are optimized for low-temperature tungsten nitride deposition. This parameter change enables PVD-like low temperature processing while achieving CVD-like conformal coverage
3Reliability
If tungsten nitride is deposited to provide good adhesion to dielectric films, then reliable diffusion barrier properties are achieved, but the deposition process becomes more complex
Solution Approach 1:
The nucleation layer formation and tungsten nitride deposition are merged into a single integrated process sequence within the same chamber. The nucleation layer serves dual purposes: it enables low-temperature deposition and ensures good adhesion to dielectric films, while the subsequent tungsten nitride layers provide both diffusion barrier and adhesion functions, consolidating multiple requirements into a unified process
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 method enables the deposition of tungsten nitride with improved adhesion to dielectric surfaces and conformal coverage in high aspect ratio features, suitable for advanced semiconductor applications, while maintaining low processing temperatures.
Implementation Method 1
contacting the substrate surface with a tungsten containing precursor to form a tungsten layer on the substrate
Implementation Method 2
nitriding the tungsten layer to form tungsten nitride
Implementation Method 3
The borane reducing agent may be introduced as a gas phase reactant that decomposes on the substrate surface, creating a boron containing 'sacrificial layer'
Data Source
AI summary
Methods for depositing a tungsten nitride layer are described. The methods form a tungsten nitride layer using a carefully controlled deposition technique such as pulsed nucleation layer (PNL). Initially, a tungsten layer is formed on a substrate surface. The tungsten layer is then exposed to a nitriding agent to form a tungsten nitride layer. Methods of forming relatively thick layers of involve repeated cycles of contact with reducing agent, tungsten precursor and nitriding agent. In some cases, the cycle may also include contact with a dopant precursor such as phosphine or arsine.