Tungsten Liner Passivation for Seamless Feature Fill
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Solution Overview
Problem
As critical dimensions in semiconductor devices shrink, existing methods for forming tungsten features face challenges such as void formation and seam creation due to uneven deposition and the presence of tungsten oxides, which increase resistivity and lead to defects during CMP polishing.
Innovation Solution
A method involving physical vapor deposition (PVD) of a tungsten liner layer followed by exposure to nitrogen-containing radicals and tungsten-containing precursor gases in a single processing chamber without vacuum breaks, allowing for seamless tungsten fill layer formation with reduced resistivity and minimized defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tungsten fill layer is deposited using conventional CVD process, then feature filling is achieved, but voids and seams form due to uneven deposition
Solution Approach 1:
A PVD tungsten liner layer is deposited beforehand on the feature walls and bottom surface before the CVD tungsten fill layer is formed. This preliminary liner layer provides a uniform nucleation base that enables more uniform subsequent CVD deposition, preventing void and seam formation in the final fill layer.
Solution Approach 2:
The patent employs a two-stage deposition process with different parameters: PVD process for the liner layer followed by CVD process for the fill layer. The PVD process parameters (physical vapor deposition) differ from CVD parameters (chemical vapor deposition), allowing optimization of each stage for its specific purpose - liner formation versus bulk filling.
2Adaptability or versatility
If vacuum break occurs between PVD and CVD processes, then process flexibility is maintained, but tungsten oxides form increasing resistivity
Solution Approach 1:
The PVD and CVD processes are performed in sequence without breaking the vacuum, maintaining continuous protective atmosphere. This prevents exposure of the deposited tungsten liner layer to oxygen, avoiding oxide formation that would increase resistivity and cause CMP defects.
Solution Approach 2:
The vacuum environment serves as an inert atmosphere that protects the tungsten liner layer from oxidation during the transfer and processing steps between PVD and CVD deposition, maintaining low resistivity of the tungsten material.
3Reliability
If tungsten liner layer is fully passivated, then oxidation is prevented, but nucleation of CVD tungsten is inhibited
Solution Approach 1:
The nitrogen-containing radical exposure selectively passivates only the upper portions of the tungsten liner layer that are exposed to oxygen, while leaving the bottom surface near the feature base unpassivated. This creates a gradient of passivation that protects against oxidation where needed while maintaining nucleation capability where required.
Solution Approach 2:
Nitrogen-containing radicals are introduced to preemptively passivate the tungsten liner layer surface, creating a protective nitrogen layer that prevents subsequent oxidation. This preliminary protective action is applied selectively to balance oxidation prevention with nucleation promotion.
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 eliminates voids and seams, reduces resistivity, and decreases CMP defects by preventing tungsten oxide formation, resulting in improved tungsten gap-fill performance and device reliability.
Implementation Method 1
exposing at least one feature formed in a substrate to a physical vapor deposition (PVD) process to deposit a tungsten liner layer over the at least one feature
Implementation Method 2
exposing the tungsten liner layer to nitrogen-containing radicals in the second processing region to passivate exposed portions of the tungsten liner layer
Implementation Method 3
exposing the feature to a tungsten-containing precursor gas to form a tungsten fill layer over the tungsten liner layer within the at least one feature
Data Source
AI summary
A method and apparatus for forming tungsten features in semiconductor devices is provided. The method includes exposing a top opening of a feature formed in a substrate to a physical vapor deposition (PVD) process to deposit a tungsten liner layer within the feature. The PVD process is performed in a first processing region of a first processing chamber and the tungsten liner layer forms an overhang portion, which partially obstructs the top opening of the feature. The substrate is transferred from the first processing region of the first processing chamber to a second processing region of a second processing chamber without breaking vacuum. The overhang portion is exposed to nitrogen-containing radicals in the second processing region to inhibit subsequent growth of tungsten along the overhang portion. The feature is exposed to a tungsten-containing precursor gas to form a tungsten fill layer over the tungsten liner layer within the feature.