Tungsten Nucleation Deposition for High Step Coverage
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Solution Overview
Problem
The challenge in semiconductor fabrication is achieving good step coverage and conformality of tungsten films in features with narrow openings and high aspect ratios, as conventional deposition techniques often result in voids and reduced step coverage due to parasitic chemical vapor deposition reactions.
Innovation Solution
A method involving multiple cycles of pulsing a boron-containing reducing agent and a tungsten-containing precursor in a chemical vapor deposition process, with hydrogen flow only during the reducing agent pulse to suppress thermal decomposition and enhance chemisorption, achieving a tungsten nucleation layer with high step coverage and conformality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CVD techniques are used for tungsten film deposition, then deposition speed is maintained, but step coverage deteriorates and voids form in high aspect ratio features
Solution Approach 1:
The patent employs periodic pulsed delivery of tungsten precursor and reducing agent gases, with each pulse lasting a controlled duration followed by a purge phase. This periodic action allows sequential surface reactions to complete before the next pulse, ensuring uniform nucleation layer deposition with step coverage ≥90% while maintaining viable deposition rates for high aspect ratio features
Solution Approach 2:
The deposition process is segmented into distinct cycles: precursor pulse, purge, reducing agent pulse, and purge. Each cycle deposits a controlled amount of tungsten nucleation layer, building up the film uniformly across the substrate surface and within feature openings, achieving both high step coverage and acceptable productivity
2Productivity
If hydrogen is flowed during tungsten precursor pulse, then deposition rate increases, but thermal decomposition of reducing agent occurs reducing conformality
Solution Approach 1:
Hydrogen is introduced in periodic pulses that are temporally separated from the tungsten precursor pulses. During the reducing agent pulse phase, hydrogen is supplied to prevent reducing agent decomposition and maintain conformal deposition. During the precursor pulse phase, hydrogen is excluded to avoid thermal decomposition, thus achieving both high deposition rate and excellent conformality
Solution Approach 2:
Hydrogen is supplied in advance during the reducing agent pulse before the precursor arrives, preparing the surface and preventing reducing agent decomposition. This preliminary action ensures that when the precursor is introduced, the reducing agent is already in the correct state for reaction, preventing decomposition and maintaining conformality while enabling high deposition rates
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 approach ensures a tungsten nucleation layer with step coverage of at least 90% and conformality, preventing voids and improving the fill quality of features with complex geometries, such as vertical vias and 3D memory structures.
Implementation Method 1
hydrogen (H2) is flowed during the boron-containing reducing agent pulse and no H2 is flowed during the tungsten-containing precursor pulse and wherein H2 suppresses thermal decomposition of the boron-containing reducing agent
Implementation Method 2
the boron-containing reducing agent is adsorbed to the feature sidewall and feature bottom
Implementation Method 3
flowing a tungsten-containing precursor pulse in the chamber to react with the adsorbed boron-containing reducing agent
Data Source
AI summary
Methods of depositing a tungsten nucleation layers that achieve very good step coverage are provided. The methods involve a sequence of alternating pulses of a tungsten-containing precursor and a boron-containing reducing agent, while co-flowing hydrogen (H2) with the boron-containing reducing agent. The H2 flow is stopped prior to the tungsten-containing precursor flow. By co-flowing H2 with the boron-containing reducing agent but not with the tungsten-containing precursor flow, a parasitic CVD component is reduced, resulting in a more self-limiting process. This in turn improves step coverage and conformality of the nucleation layer. Related apparatuses are also provided.