Molybdenum Deposition With Alternating Plasma for Deep Gapfill
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Solution Overview
Problem
Conventional deposition techniques face challenges in filling narrow and tall gaps between circuit elements in semiconductor devices, leading to voids and seams due to inadequate penetration of the deposition material, resulting in low throughput and poor gapfill quality.
Innovation Solution
A method involving pulsed low-power RF plasma during metal precursor exposure and high-power plasma during reducing agent exposure is used to deposit molybdenum films, with each cycle including a metal precursor and reducing agent portion, optimizing the deposition process to fill features completely without voids or seams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional plasma-enhanced deposition techniques (PECVD, PEALD) are used to deposit metal gapfills, then the deposition rate is improved, but the penetration into deep trenches deteriorates, resulting in voids and seams
Solution Approach 1:
The deposition process is segmented into multiple alternating cycles of low-power plasma exposure and high-power plasma exposure. Each cycle deposits a thin layer of metal followed by a layer with enhanced penetration capability. This segmentation allows the material to progressively fill deep trenches without forming voids or seams, while maintaining high overall deposition rates through the cumulative effect of many thin layers.
Solution Approach 2:
The invention employs periodic alternation between low-power plasma conditions (favorable for controlled deposition) and high-power plasma conditions (favorable for deep trench penetration). This periodic switching occurs within each deposition cycle, creating a rhythm that balances deposition rate with penetration quality. The periodic action ensures that material is continuously supplied to fill trenches completely without premature cutoff.
2Productivity
If the gap width shrinks making gaps taller and narrower, then the integration density is improved, but the gapfill difficulty increases due to material getting stuck and creating voids
Solution Approach 1:
Before attempting to fill the entire depth of narrow and tall gaps, the process performs preliminary deposition cycles that prepare the trench walls and surface. The alternating low-power and high-power plasma exposure creates initial nucleation sites and modifies surface properties to enhance subsequent material penetration. This preliminary action prevents material from getting stuck at intermediate depths.
Solution Approach 2:
The invention dynamically changes plasma power parameters during deposition cycles. Low-power plasma conditions (e.g., 50-200 W) are used during metal precursor exposure to ensure controlled deposition, while high-power plasma conditions (e.g., 300-1000 W) are used during reducing agent exposure to enhance penetration into narrow gaps. These parameter changes adapt the deposition process to the specific geometry of shrinking gap dimensions.
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 achieves high-quality gapfills with increased throughput by ensuring complete filling of features with molybdenum films, reducing voids and seams, and enhancing deposition kinetics.
Implementation Method 1
exposing a substrate surface having at least one feature thereon to one or more deposition cycle. Each deposition cycle includes a metal precursor exposure portion including a flow of a metal precursor and a pulsed low-power RF plasma
Implementation Method 2
a reducing agent is flowed through the processing chamber in the presence of a plasma to reduce the molybdenum film to Mo(0) at a lower temperature than would be required using thermal ALD
Data Source
AI summary
A metal deposition method including exposing a substrate surface having at least one feature thereon to one or more deposition cycle, each deposition cycle including a metal precursor exposure portion and a reducing agent exposure portion, the metal precursor exposure portion including a flow of a metal precursor and a pulsed low-power RF plasma having a pulsed RF power of 100 W or less, the reducing agent exposure portion including a flow of a reducing agent and a high-power plasma having an RF power of 300 W or higher.