SiC MOSFET Interface Oxidation with Low-Energy Electron Pre-Treatment
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Solution Overview
Problem
The high density of interface states at the SiO2/SiC interface in silicon carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) leads to low inversion-channel mobilities and increased on-state resistance due to carbon-related defects, which existing methods like post-oxidation annealing and pre-oxidation implantation struggle to effectively address without introducing impurities or shifting the flat-band voltage.
Innovation Solution
The method employs low-energy electron irradiation to create a carbon-poor layer at the SiO2/n-type 4H-SiC interface, reducing carbon defects and improving flat band voltage by displacing carbon atoms and preventing their clustering during oxidation, thus enhancing the electronic properties of SiC MOSFETs without incorporating impurities or requiring high annealing temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If post-oxidation annealing or pre-oxidation implantation is used to reduce carbon defects at the SiO2/SiC interface, then carbon defect concentration is reduced, but impurities are introduced or flat-band voltage shifts occur
Solution Approach 1:
The patent applies preliminary low-energy electron irradiation to the SiC substrate before oxidation to create a carbon-poor layer at the interface. This pre-treatment prevents carbon clustering during the subsequent oxidation process, reducing carbon defects without introducing impurities or shifting flat-band voltage, thereby resolving the contradiction between defect reduction and harmful side effects
Solution Approach 2:
The patent changes the physical-chemical parameters of the SiC surface by applying low-energy electron irradiation (1-100 keV) to create a modified layer with reduced carbon concentration. This parameter change in carbon distribution allows the formation of a carbon-poor layer that prevents interface state formation without requiring subsequent annealing or implantation that would introduce impurities
2Manufacturing precision
If high annealing temperatures are used to reduce interface states, then carbon defects are reduced, but process complexity and energy consumption increase
Solution Approach 1:
The patent performs low-energy electron irradiation before oxidation to pre-modify the SiC surface and create a carbon-poor layer. This preliminary action eliminates the need for subsequent high-temperature annealing processes, thereby reducing interface states without increasing process complexity or energy consumption
Solution Approach 2:
The patent replaces the thermal mechanism (high-temperature annealing) with an electronic mechanism (low-energy electron irradiation). This substitution achieves carbon defect reduction and interface state elimination through electron-induced carbon displacement rather than thermal diffusion, significantly reducing energy consumption and process complexity
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 effectively reduces the concentration of carbon defects, improves on-state resistance, and maintains control over the carbon-poor layer formation, preventing normally-on conditions and allowing for reverse engineering verification, resulting in improved electronic performance of SiC MOSFETs.
Implementation Method 1
low-energy electron irradiation is used in order to improve flat band voltage, V FB , and reduce carbon, C, defects at a SiO 2 /SiC interface
Implementation Method 2
an electrical insulation layer of silicon oxide is formed on the surface
Data Source
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AI summary
In at least one embodiment, the method is for producing a power semiconductor device (1) and comprises the following steps: - providing a semiconductor body (2) based on SiC, - irradiating at least a first portion (21) of a top side (20) of the semiconductor body (2) with low-energy electron radiation (E), and - producing an electrical insulation layer (3) at least in the at least one irradiated first portion (21).