Atomic Oxygen Oxidation of Silicon Carbide for Low Interface State Density
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Solution Overview
Problem
The quality of oxide layers on silicon carbide (SiC) is hindered by high interface state densities and fixed oxide charges, limiting the performance of MOS devices, and existing annealing methods using nitric oxide pose health hazards and do not significantly reduce interface state density.
Innovation Solution
The method involves generating atomic oxygen using a porous sapphire wafer or ozone and using it to oxidize SiC layers at high temperatures, reducing interface state densities and improving oxide quality without introducing metallic impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal oxidation is used to form SiO2 on SiC, then oxide layer can be formed, but interface state density is high and oxide quality is poor
Solution Approach 1:
The patent changes the oxidation method from conventional thermal oxidation to atomic layer deposition (ALD) with in-situ annealing. This parameter change in the fabrication process enables precise control of oxide thickness and composition while simultaneously reducing interface state density through controlled thermal treatment, thus improving both oxide quality and interface reliability
Solution Approach 2:
The patent performs in-situ annealing immediately after oxide formation without exposing the interface to ambient conditions. This preliminary action of annealing the oxide layer while it is still in the vacuum chamber prevents interface contamination and reduces interface state density before the device is completed, thereby improving interface quality
2Reliability
If nitric oxide annealing is used to reduce interface states, then interface state density decreases, but health hazards increase and equipment safety deteriorates
Solution Approach 1:
The patent replaces the hazardous nitric oxide gas with a solid aluminum oxide source that is heated to release oxygen. This substitution eliminates the health hazards associated with nitric oxide while still achieving the desired reduction in interface state density through controlled oxygen release and in-situ annealing
Solution Approach 2:
The patent introduces aluminum oxide as an intermediary substance that mediates the annealing process. The aluminum oxide is heated to release oxygen atoms that diffuse into the oxide layer to passivate interface states, achieving the same effect as nitric oxide annealing but without the harmful health effects of handling toxic gases
3Ease of manufacture
If conventional oxidation methods are used, then oxidation process is simple, but oxidation rate is slow and productivity is low
Solution Approach 1:
The patent uses atomic oxygen from aluminum oxide decomposition as a strong oxidant in the ALD process. This provides highly reactive oxygen species that enable rapid oxide formation at lower temperatures compared to conventional thermal oxidation, thereby increasing oxidation rate and productivity while maintaining process control
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 significantly reduces interface state densities and improves the mobility of MOS devices, achieving better oxide quality and reduced on-resistance, while being safer and more efficient than conventional methods.
Implementation Method 1
oxidize SiC layers at high temperatures
Implementation Method 2
generating atomic oxygen using a porous sapphire wafer or ozone
Data Source
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AI summary
Methods of forming oxide layers on silicon carbide layers are disclosed, including placing a silicon carbide layer in a chamber such as an oxidation furnace tube that is substantially free of metallic impurities, heating an atmosphere of the chamber to a temperature of about 500°C to about 1300°C, introducing atomic oxygen in the chamber, and flowing the atomic oxygen over a surface of the silicon carbide layer to thereby form an oxide layer on the silicon carbide layer. In some embodiments, introducing atomic includes oxygen providing a source oxide in the chamber and flowing a mixture of nitrogen and oxygen gas over the source oxide. The source oxide may comprise aluminum oxide or another oxide such as manganese oxide. Some methods include forming an oxide layer on a silicon carbide layer and annealing the oxide layer in an atmosphere including atomic oxygen.