Fluorine Passivation for Ultrathin Gate Dielectrics
Solution Overview
Problem
The increasing complexity and miniaturization of semiconductor integrated circuits pose challenges in reducing interface defect density and capacitive effective thickness in current IC fabrication processes, particularly for ultrathin gate oxides, which affect carrier mobility and current leakage.
Innovation Solution
A method involving the passivation of semiconductor substrates with a mixture of hydrofluoric acid and alcohol vapors to form a fluorine-passivated surface, followed by the formation of an interfacial layer and a high-k gate dielectric layer, which reduces interface defects and current leakage without requiring high-temperature processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabrication methods are used for ultrathin gate oxides, then manufacturing process is simpler, but interface defect density is high and carrier mobility is reduced
Solution Approach 1:
The substrate surface is passivated with fluorine before gate dielectric formation, creating a pre-prepared surface that reduces interface defects. This preliminary fluorine passivation step modifies the substrate surface properties in advance, enabling subsequent formation of high-quality ultrathin gate dielectrics with lower interface defect density and improved carrier mobility.
Solution Approach 2:
The invention changes the chemical composition of the substrate surface by introducing fluorine atoms through vapor-phase hydrofluoric acid and alcohol treatment. This parameter change in surface chemistry creates a fluorine-passivated surface that reduces interface states and improves the electrical properties of the subsequent gate dielectric layer.
2Productivity
If gate dielectric thickness is reduced to increase scale, then device scaling is improved, but capacitive effective thickness control becomes more difficult
Solution Approach 1:
Fluorine passivation is performed on the substrate surface before gate dielectric deposition, preparing the surface to support formation of precisely controlled ultrathin dielectric layers. This preliminary surface treatment enables better control of capacitive effective thickness by reducing variability in interface conditions during subsequent thin film formation processes.
3Reliability
If high-temperature processing is used to reduce interface defects, then interface quality improves, but thermal budget increases and device complexity increases
Solution Approach 1:
The invention replaces thermal processing with chemical vapor-phase fluorine passivation using hydrofluoric acid and alcohol vapors. This substitution of chemical treatment for thermal treatment achieves interface defect reduction without requiring high temperatures, thereby avoiding increased thermal budget and associated device complexity.
4Ease of manufacture
If conventional surface preparation is used, then process simplicity is maintained, but current leakage increases due to higher interface defect density
Solution Approach 1:
The surface chemistry parameters are changed by introducing fluorine through vapor-phase treatment, which modifies the electrical properties of the substrate surface. This parameter change reduces interface states and minimizes current leakage while maintaining a relatively simple process flow that can be integrated into existing fabrication sequences.
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
This approach results in lower interface defect density and reduced capacitive effective thickness, enhancing carrier mobility and device reliability while maintaining the dielectric constant of gate oxide layers, thus improving the scale and reliability of IC devices.
Implementation Method 1
passivating a surface of the substrate with a mixture of hydrofluoric acid vapor and isopropyl alcohol vapor or ammonia vapor (NH3) to form a fluorine-passivated surface
Data Source
AI summary
The present disclosure provides methods and apparatus of fluorine passivation in IC device fabrication. In one embodiment, a method of fabricating a semiconductor device includes providing a substrate and passivating a surface of the substrate with a mixture of hydrofluoric acid and alcohol to form a fluorine-passivated surface. The method further includes forming a gate dielectric layer over the fluorine-passivated surface, and then forming a metal gate electrode over the gate dielectric layer. A semiconductor device fabricated by such a method is also disclosed.