Source/Drain Contact Formation with N2/H2 Plasma Oxide Removal
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Solution Overview
Problem
The semiconductor industry faces increased source/drain contact resistance as oxygen reacts with metals to form metal oxides during the fabrication of semiconductor devices, leading to higher resistance in conducting paths, which is not effectively addressed by existing technologies.
Innovation Solution
A novel plasma cleaning process using a gas mixture of N2 and H2 is applied to remove metal oxides from the source/drain contact interface, maintaining the integrity of silicide and conductive barrier layers, thereby reducing contact resistance. The process is performed at a temperature of 300°C to 500°C with specific gas flow rate ratios to effectively remove oxides without damaging the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal layers are deposited during source/drain contact fabrication, then conductive pathways are formed, but oxygen reacts with metals to form metal oxides that increase contact resistance
Solution Approach 1:
The patent applies a plasma cleaning process before metal deposition to remove oxygen and form a reduced-oxygen environment. This preliminary action prevents oxygen from reacting with deposited metals, thereby reducing metal oxide formation and associated contact resistance
Solution Approach 2:
The patent creates an oxygen-reduced environment through plasma treatment, effectively establishing an inert-like atmosphere during metal deposition. This prevents oxidation reactions by removing oxygen from the interface between the source/drain region and metal contact
2Reliability
If plasma cleaning is applied to remove metal oxides, then contact resistance is reduced, but process temperature and gas flow rates must be precisely controlled to avoid damaging silicide and conductive barrier layers
Solution Approach 1:
The patent specifies precise parameter ranges for plasma cleaning: temperature between 300-500°C and nitrogen-to-hydrogen gas flow rate ratio between 0.03-0.28. These controlled parameter changes enable effective oxide removal while preventing damage to sensitive layers
Solution Approach 2:
The patent employs controlled plasma processing with monitored parameters to achieve the desired oxygen reduction while maintaining layer integrity. The feedback control ensures that cleaning effectiveness is achieved without exceeding damage thresholds for silicide and barrier layers
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 plasma cleaning process significantly reduces source/drain contact resistance by eliminating oxygen compounds, resulting in lower oxygen levels and improved conductivity, with the atomic ratio of oxygen to metal nitride at the interface reduced to about 1.0 or lower, enhancing the performance of semiconductor devices.
Implementation Method 1
A novel plasma cleaning process using a gas mixture of N2 and H2 is applied to remove metal oxides from the source/drain contact interface
Implementation Method 2
The plasma cleaning process uses a gas mixture including N2 gas and H2 gas to remove oxide compounds
Data Source
AI summary
A semiconductor device includes a substrate, two semiconductor fins protruding from the substrate, an epitaxial feature over the two semiconductor fins and connected to the two semiconductor fins, a silicide layer over the epitaxial feature, a barrier layer over the silicide layer, and a metal layer over the barrier layer. The barrier layer includes a metal nitride. Along a boundary between the barrier layer and the metal layer, an atomic ratio of oxygen to metal nitride is about 0.15 to about 1.0.