SiC-SiO2 Interface Structure With Carbon Gradient for Low Defects
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Solution Overview
Problem
The existing methods for forming a SiO2 layer on a SiC semiconductor layer face challenges in reducing interfacial defects, with methods either leaving carbon atoms in the SiO2 layer, affecting insulating properties, or introducing phosphorus which can lead to charge trapping and time-dependent deterioration.
Innovation Solution
A semiconductor device with a SiC semiconductor layer and a SiO2 layer that includes a carbon-density-decreasing region and a low carbon density region, formed by introducing oxygen atoms into the SiO2 layer during annealing in a low-oxygen partial pressure atmosphere, reducing interfacial defects and preventing phosphorus from acting as a charge trap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is applied in inert gas atmosphere to detach carbon atoms from interfacial region, then interfacial defects are reduced, but carbon atoms remain in SiO2 layer causing poor insulating properties
Solution Approach 1:
The patent changes the atmospheric parameters from inert gas to low-oxygen partial pressure atmosphere during annealing treatment. This parameter change enables oxygen to react with and remove carbon atoms from the SiO2 layer while maintaining low interface state density, thus improving insulating properties without compromising interface quality.
2Reliability
If phosphorus is added to SiO2 layer to remove carbon atoms, then interfacial defects are reduced, but phosphorus acts as charge trap causing time-dependent deterioration
Solution Approach 1:
The patent extracts the harmful carbon atoms from the SiO2 layer through chemical reaction with oxygen in a low-oxygen partial pressure atmosphere, eliminating the need to introduce phosphorus. This extraction approach removes carbon atoms without introducing charge traps, thereby preventing time-dependent deterioration while maintaining low interface state density.
3Reliability
If interface state density is reduced to improve channel mobility, then carrier mobility increases, but existing methods cannot simultaneously ensure good insulating properties
Solution Approach 1:
The patent changes the annealing atmosphere parameter to low-oxygen partial pressure, which enables simultaneous achievement of low interface state density (improving channel mobility) and low carbon density in SiO2 layer (maintaining insulating properties). This parameter change resolves the contradiction between mobility improvement and insulation quality.
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 interfacial defects and maintains good-quality SiO2 layer properties, enhancing channel mobility and preventing time-dependent deterioration.
Implementation Method 1
allow the carbon atoms in the SiO2 layer and the oxygen atoms in the atmosphere to react together. This makes it possible to remove the carbon atoms in the SiO2 layer
Implementation Method 2
applying annealing treatment in a low-oxygen partial pressure atmosphere
Data Source
AI summary
A semiconductor device includes a SiC semiconductor layer that has a carbon density of 1.0×1022 cm−3 or more, a SiO2 layer that is formed on the SiC semiconductor layer and that has a connection surface contiguous to the SiC semiconductor layer and a non-connection surface positioned on a side opposite to the connection surface, a carbon-density-decreasing region that is formed at a surface layer portion of the connection surface of the SiO2 layer and in which a carbon density gradually decreases toward the non-connection surface of the SiO2 layer, and a low carbon density region that is formed at a surface layer portion of the non-connection surface of the SiO2 layer and that has a carbon density of 1.0×1019 cm−3 or less.