Source/Drain Contact Stack Cleaning for Lower Contact Resistance
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Solution Overview
Problem
The increasing complexity of semiconductor devices has led to higher source/drain contact resistance, which accounts for a significant portion of the total conducting path resistance, necessitating improvements in reducing this resistance.
Innovation Solution
A plasma cleaning process using a gas mixture of N2 and H2 is applied to remove metal oxides inadvertently formed during the fabrication of silicide and conductive barrier layers, effectively reducing contact resistance by maintaining the integrity of these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometry is scaled down to increase functional density, then production efficiency improves and costs decrease, but source/drain contact resistance increases significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma cleaning process by using specific gas ratios (N2:H2 flow rate ratios between 0.03 to 0.28) and temperature parameters (300-500°C) to optimize oxide removal while preserving metal layer integrity, thereby reducing contact resistance in scaled devices
Solution Approach 2:
The patent employs an inert plasma environment created by N2 and H2 gas mixture to remove oxides from metal surfaces without introducing new contaminants or causing unwanted chemical reactions, maintaining the integrity of the conductive barrier layers while reducing contact resistance
2Reliability
If plasma cleaning process is applied to remove metal oxides, then source/drain contact resistance decreases, but process complexity and manufacturing steps increase
Solution Approach 1:
The patent performs plasma cleaning as a preliminary step before depositing the conductive barrier layer, ensuring the metal surface is free of oxides beforehand. This preliminary action prevents oxide formation from affecting the subsequent barrier layer adhesion and electrical properties
Solution Approach 2:
The patent integrates plasma cleaning into the continuous fabrication sequence between metal deposition and barrier layer formation, maintaining process continuity without requiring separate handling or interruption of the manufacturing flow
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 oxides, allowing for thinner conductive barrier layers and maintaining low sheet resistance, thereby enhancing the conductivity of semiconductor devices.
Implementation Method 1
A plasma cleaning process using a gas mixture of N2 and H2 is applied to remove metal oxides inadvertently formed during the fabrication of silicide and conductive barrier layers
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.