SiC MOS Interface State Reduction via Plasma Nitride Annealing
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Solution Overview
Problem
Existing methods for forming silicon oxide films on silicon carbide substrates fail to achieve optimal interface properties, leading to high interface state densities and threshold voltages, which hinder the practical application of voltage-driven-type devices with a MOS structure.
Innovation Solution
A method involving plasma irradiation to grow a silicon nitride film on a silicon carbide substrate, followed by depositing a silicon oxide film using plasma chemical vapor deposition, and subsequent annealing in a nitrogen atmosphere to reduce interface state density and achieve a flat band voltage close to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon oxide film is formed on a silicon carbide substrate by conventional methods (dry oxidation, CVD with preliminary NH3 treatment, or CVD with Si3N4 layer), then a gate insulator film can be obtained, but the interface state density remains high and interface properties are insufficient for practical MOS device application
Solution Approach 1:
The patent applies preliminary action by performing plasma treatment on the silicon carbide substrate surface before forming the silicon oxide film. This preliminary plasma treatment modifies the substrate surface to reduce interface state density, which is then maintained through the subsequent oxidation process. The plasma treatment prepares the surface in advance to achieve better interface properties without requiring additional post-processing steps.
Solution Approach 2:
The patent employs parameter changes by controlling the plasma treatment conditions (power, gas flow rate, treatment time) and oxidation conditions (temperature, oxygen flow rate, atmosphere composition) to optimize the interface properties. By adjusting these parameters, the interface state density is reduced to acceptable levels while maintaining the gate insulator film quality.
2Adaptability or versatility
If the interface state density is reduced to achieve better interface properties, then voltage-driven-type devices with MOS structure can be practically applied, but this requires sophisticated plasma treatment and controlled oxidation processes
Solution Approach 1:
The patent merges the plasma treatment step with the oxidation process by performing both operations in the same reaction chamber without breaking vacuum. This combination eliminates the need for separate treatment chambers and reduces the overall process complexity while achieving the required interface properties for practical MOS device application.
Solution Approach 2:
The oxidation chamber is designed to perform multiple functions: it can conduct both the plasma treatment and the subsequent oxidation process. This multi-functionality reduces the need for additional specialized equipment and simplifies the overall manufacturing process while achieving the desired interface 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 significantly reduces interface state density to the order of 1×10^11 cm^-2·eV^-1 and brings the flat band voltage close to zero, enhancing the interface properties necessary for practical use of voltage-driven-type devices with a MOS structure.
Implementation Method 1
irradiating a plasma for growing a silicon nitride film on a silicon carbide substrate
Implementation Method 2
depositing a silicon oxide film using plasma chemical vapor deposition
Implementation Method 3
subsequent annealing in a nitrogen atmosphere to reduce interface state density
Data Source
AI summary
A method of manufacturing a semiconductor device according to the invention includes the step S1 of cleaning the silicon carbide substrate 1 surface, the step S2 of bringing a material gas into a plasma and irradiating the atoms contained in the material gas to silicon carbide substrate 1 for growing silicon nitride film 2 on silicon carbide substrate 1, the step S3 of depositing silicon oxide film 3 on silicon nitride film 2 by the ECR plasma CVD method, and the step S4 of annealing silicon carbide substrate 1 including silicon nitride film 2 and silicon oxide film 3 formed thereon in a nitrogen atmosphere. By the method of manufacturing a semiconductor device according to the invention, a semiconductor device that exhibits excellent interface properties including an interface state density and a flat band voltage is obtained.