Selective Tungsten Gap Fill on PVD W Liner Without Pinch-Off
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Solution Overview
Problem
Conventional tungsten metal gap fill processes are prone to voids during gap fill due to early pinch-off at overhangs, particularly in features with high aspect ratios, which affects the integrity and conductivity of integrated circuits.
Innovation Solution
A method involving a physical vapor deposition (PVD) of a tungsten seed layer followed by a chemical vapor deposition (CVD) of a bulk layer, utilizing specific gas flow rates and pressures to achieve selective deposition within features, thereby avoiding voids and ensuring complete fill without pinch-off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional tungsten metal gap fill processes are used, then deposition can be performed, but voids form during gap fill due to early pinch-off at overhangs
Solution Approach 1:
The patent changes the deposition parameters by using a CVD process with specific gas flow rates (H2 at 10-500 sccm, W precursor at 100-1000 sccm) and pressure conditions to achieve selective deposition. This parameter optimization allows the deposition to continue uniformly without early pinch-off, eliminating voids while maintaining complete gap fill.
Solution Approach 2:
The patent applies a PVD tungsten seed layer (liner) before the CVD bulk deposition. This preliminary action creates a foundation that enables subsequent selective CVD deposition to proceed uniformly, preventing void formation by ensuring proper nucleation and growth conditions from the start.
2Manufacturing precision
If selective deposition is achieved within features, then void-free fill is obtained, but deposition in field region and overhangs must be prevented
Solution Approach 1:
The patent achieves local quality by making the deposition process selective to feature interiors. The CVD process parameters are optimized so that deposition occurs preferentially within the features (where the seed layer provides nucleation sites) while suppressing deposition in field regions and on overhangs, creating spatially differentiated deposition quality.
Solution Approach 2:
The patent uses excessive H2 flow rate relative to the W precursor flow rate (first flow rate less than second flow rate) to create a hydrogen-rich environment that suppresses deposition in field regions. This partial action approach allows selective fill within features while preventing unwanted deposition elsewhere through controlled chemical environment.
3Volume of moving object
If features with high aspect ratios are filled, then complete gap fill is achieved, but pinch-off at overhangs occurs earlier
Solution Approach 1:
The patent employs a periodic or controlled deposition process where H2 and W precursor gases are introduced in specific sequences and at controlled rates. This periodic action allows uniform deposition progression through high aspect ratio features without premature pinch-off, maintaining precision even as fill volume increases.
Solution Approach 2:
The patent uses dynamic control of gas flow rates during deposition, with H2 flowing at 10-500 sccm and W precursor at 100-1000 sccm. This dynamic parameter adjustment allows the deposition process to adapt to the evolving feature geometry, preventing pinch-off by maintaining optimal deposition conditions throughout the fill 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
The method ensures void-free or substantially void-free tungsten gap fill in features with aspect ratios up to 80:1, maintaining the integrity and conductivity of the circuit by preventing deposition in the field region and overhangs.
Implementation Method 1
depositing a seed layer consisting essentially of tungsten in the features via a physical vapor deposition (PVD) process
Implementation Method 2
depositing a bulk layer consisting essentially of tungsten in the features via a chemical vapor deposition (CVD) process
Data Source
AI summary
Embodiments of methods and associated apparatus for filling a feature in a substrate are provided herein. In some embodiments, a method of depositing tungsten in features of a substrate includes: depositing a seed layer consisting essentially of tungsten in the features via a physical vapor deposition (PVD) process; and depositing a bulk layer consisting essentially of tungsten in the features via a chemical vapor deposition (CVD) process to fill the features such that the deposition of the bulk layer is selective to within the features as compared to a field region of the substrate, wherein the CVD process is performed by flowing hydrogen gas (H2) at a first flow rate and a tungsten precursor at a second flow rate, and wherein the first flow rate is less than the second flow rate.