SiC MOSFET Interface Stabilization via Nitrogen-CO2 Heat Treatment
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Solution Overview
Problem
The mobility of carriers in silicon carbide-based MOSFETs is lowered due to interface states between the silicon carbide layer and the gate insulating layer, primarily caused by dangling bonds at the surface.
Innovation Solution
A method involving the formation of an interface termination region with a specific nitrogen-based bond structure, achieved through a heat treatment process in an atmosphere containing nitrogen and carbon dioxide gas, which reduces dangling bonds and enhances the stability of the interface, thereby improving carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate insulating layer is formed on a silicon carbide layer to create a MOSFET, then the device structure is completed and can function, but interface states caused by dangling bonds reduce carrier mobility
Solution Approach 1:
The patent applies preliminary action by performing heat treatment in a nitrogen and carbon dioxide atmosphere before forming the gate insulating layer. This pre-treatment modifies the silicon carbide surface to reduce dangling bonds and improve the interface quality, thereby preventing the formation of harmful interface states that would otherwise reduce carrier mobility.
Solution Approach 2:
The patent utilizes parameter changes by controlling the heat treatment conditions, specifically maintaining a temperature of 1200°C or higher in a nitrogen and carbon dioxide atmosphere. This temperature and atmospheric composition change the surface properties of the silicon carbide layer, reducing interface states and improving the interface between the silicon carbide and gate insulating layer.
2Manufacturing precision
If heat treatment is performed at high temperature to reduce interface states, then carrier mobility improves, but carbon defects may form in the gate insulating layer
Solution Approach 1:
The patent applies composite materials by using a combination of nitrogen and carbon dioxide gases during heat treatment. This gas mixture creates a controlled atmosphere that prevents carbon defects in the gate insulating layer while still allowing the heat treatment to reduce interface states and improve carrier mobility.
Solution Approach 2:
The patent utilizes parameter changes by precisely controlling the heat treatment temperature to be 1200°C or higher and maintaining specific atmospheric composition (nitrogen and carbon dioxide). These parameter changes enable the reduction of interface states without causing carbon defects in the gate insulating layer.
3Manufacturing precision
If the interface between silicon carbide and gate insulating layer is stabilized, then carrier mobility is maintained, but additional process steps are required
Solution Approach 1:
The patent applies merging by combining the heat treatment step with the preparation process before gate insulating layer formation. This integrated approach achieves interface state reduction and stability improvement in a single process step, avoiding the need for additional separate treatment steps.
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 effectively suppresses the reduction in carrier mobility and enhances the reliability of the MOSFET by stabilizing the interface and preventing carbon defects in the gate insulating layer, leading to improved device performance and reduced leakage current.
Implementation Method 1
performing first heat treatment at 1200° C. or more in an atmosphere including nitrogen gas and carbon dioxide gas
Implementation Method 2
performing first heat treatment at 1200° C. or more in an atmosphere including nitrogen gas and carbon dioxide gas
Implementation Method 3
performing first heat treatment at 1200° C. or more in an atmosphere including nitrogen gas and carbon dioxide gas
Data Source
AI summary
A method for manufacturing a semiconductor device according to an embodiment includes: forming a first silicon oxide film on a surface of a silicon carbide layer; and performing first heat treatment at 1200° C. or more in an atmosphere including nitrogen gas and carbon dioxide gas.