SiC Gate Oxide Formation at High Temperature
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Solution Overview
Problem
Silicon carbide (SiC) MOSFETs exhibit poor inversion layer mobility and high defect density at the gate oxide/SiC interface, leading to large power dissipation and efficiency loss, due to structural defects at the SiC-silicon dioxide interface.
Innovation Solution
Forming a gate oxide layer on a SiC substrate at extremely high temperatures (at least 1300°C) with low oxygen partial pressures to minimize defect generation and maximize defect annihilation, resulting in a substantially defect-free oxide layer with improved inversion layer mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional oxidation methods are used to form gate oxide on SiC substrate, then oxide layer is formed, but interface defects are generated leading to poor inversion layer mobility
Solution Approach 1:
The patent applies parameter changes by dramatically increasing the oxidation temperature to at least 1300°C and controlling oxygen partial pressure to minimize defect generation. This high-temperature parameter change transforms the oxidation process to achieve defect-free interface while maintaining oxide layer formation, directly resolving the contradiction between forming oxide and avoiding interface defects.
Solution Approach 2:
The patent employs preliminary anti-action by performing defect annihilation through high-temperature oxidation before device operation. The process proactively eliminates potential interface defects during manufacturing, preventing the harmful effects of interface traps on inversion layer mobility before they can affect device performance.
2Reliability
If oxidation is performed at high temperature to reduce defects, then interface quality improves, but process complexity and energy consumption increase
Solution Approach 1:
The patent accepts increased energy consumption as a necessary parameter change to achieve the desired interface quality. By setting oxidation temperature to at least 1300°C, the process transforms thermal energy input into defect annihilation, directly improving interface quality despite the energy cost. This parameter change is the core mechanism resolving the contradiction.
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 achieves inversion layer mobilities of at least 12 cm2/Vs and enhances long-term stability of SiC-based semiconductor devices by reducing defect density at the gate oxide/SiC interface.
Implementation Method 1
exposing the substrate to an environment comprising oxygen and at a temperature of at least about 1300° C. so that an oxide layer is formed on the substrate
Data Source
AI summary
Methods are provided for improving inversion layer mobility and providing low defect density in a semiconductor device based upon a silicon carbide (SiC) substrate. More specifically, embodiments of the present method provide for the formation of a gate oxide on a silicon carbide substrate comprising oxidizing the substrate with a gaseous mixture comprising oxygen at a temperature of at least about 1300° C. Semiconductor devices, such as MOSFETS, based upon a substrate treated according to the present method are expected to have inversion layer mobilities of at least about 12 cm2/Vs.