Selective Molybdenum Silicide Deposition for Low-Resistance Contacts
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Solution Overview
Problem
Existing plasma enhanced processes for forming metal silicide layers in semiconductor devices result in non-selective deposition on sidewalls and field regions, leading to poor contact resistance and reduced device performance.
Innovation Solution
A method involving a controlled plasma process with specific gas delivery phases, including pretreatment, deposition, and post-treatment stages, to selectively deposit a molybdenum silicide layer on exposed substrate surfaces within features like cavities or trenches, using gases such as hydrogen and molybdenum-containing precursors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a plasma enhanced process is used to form a metal silicide layer on an exposed portion of a substrate, then the metal silicide layer can be formed, but the metal silicide layer is also deposited on the sidewalls and field region, resulting in poor selectivity
Solution Approach 1:
The patent applies preliminary action by performing a pretreatment plasma process before the main deposition process. The pretreatment process modifies the surface properties of the substrate, creating a condition that enables selective deposition only on the exposed portion. This preliminary surface modification is crucial for achieving the desired selectivity in the subsequent deposition step.
Solution Approach 2:
The patent employs periodic action by using a pulsed gas delivery system with distinct time periods. The process alternates between delivering processing gas, delivering reactive gas to form pretreatment gas, delivering deposition gas with precursor, and delivering post-treatment gas. This periodic gas delivery creates controlled plasma conditions that enable selective deposition while preventing deposition on sidewalls and field regions.
2Manufacturing precision
If a traditional plasma enhanced process is used, then metal silicide layer formation is achieved, but the density, homogeneity, and thickness uniformity are poor
Solution Approach 1:
The patent uses periodic action with precisely controlled time periods for gas delivery. Each gas (processing gas, reactive gas, deposition gas, post-treatment gas) is delivered during specific time periods, creating a rhythmic process that ensures uniform deposition. This periodic control allows for consistent density, homogeneity, and thickness across the exposed substrate portion.
Solution Approach 2:
The patent applies parameter changes by systematically varying multiple process parameters including gas flow rates, RF power levels, pressure, and temperature throughout the different time periods. These parameter changes are coordinated to optimize the deposition process, achieving poor parameters in traditional processes such as improved density, homogeneity, and thickness uniformity.
3Manufacturing precision
If plasma enhanced deposition is used, then metal silicide layer is formed, but impurity levels are high
Solution Approach 1:
The patent applies preliminary action by implementing a pretreatment plasma process that cleans and prepares the substrate surface before deposition. This pretreatment removes contaminants and activates the surface, creating optimal conditions for pure film formation. The preliminary action ensures that deposition occurs on a clean surface, reducing impurity incorporation.
Solution Approach 2:
The patent uses an intermediary approach by introducing a post-treatment gas phase after the precursor gas is halted. This post-treatment phase acts as a mediator to complete the deposition process and remove any residual impurities or unstable species. The intermediary post-treatment step ensures high purity of the final metal silicide layer.
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
Achieves selective deposition of a metal silicide layer on exposed substrate surfaces, improving contact resistance and overall device performance by ensuring uniformity and purity of the metal silicide layer.
Implementation Method 1
delivering an RF power to the processing chamber to generate a plasma over the substrate
Implementation Method 2
delivering a deposition gas during a third time period, the deposition gas comprising a precursor gas and the pretreatment gas
Data Source
AI summary
A method includes positioning a substrate within a processing chamber that comprises a feature formed within a dielectric layer formed over an underlayer, delivering an RF power to the processing chamber to generate a plasma over the substrate including: delivering a processing gas during a first time period, delivering a reactive gas into a flow of the processing gas during a second time period to form a pretreatment gas, delivering a deposition gas during a third time period, the deposition gas comprising a precursor gas and the pretreatment gas; and delivering a post-treatment gas during a fourth time period comprising halting the delivering of the precursor gas during the fourth time period, halting the delivering of the RF power and delivering the precursor gas into a flow of the post-treatment gas during a fifth time period, and purging the processing chamber during a sixth time period.