Gate Insulation Annealing for Stable SiC MOSFET Threshold Voltage
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Solution Overview
Problem
Wide band gap semiconductor devices, such as SiC MOSFETs, face challenges with low inversion channel mobility and high threshold voltage instability, leading to higher on-resistance and lower reliability compared to silicon MOSFETs.
Innovation Solution
A method for forming a wide band gap semiconductor device involves forming a gate insulation layer on a semiconductor substrate and annealing it using a combination of at least two different reactive gas species, followed by an annealing process in an inert gas atmosphere. This approach reduces point defects at the interface, enhancing inversion channel mobility and reducing threshold voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate insulation layer is formed on a wide band gap semiconductor substrate using conventional annealing methods, then the device can be manufactured, but the inversion channel mobility remains low and threshold voltage instability is high
Solution Approach 1:
The patent applies parameter changes by using multiple reactive gas species (oxygen, nitrogen, hydrogen) during annealing at elevated temperatures (900-1200°C). This changes the chemical and physical parameters of the gate insulation layer and substrate interface, reducing point defects and improving both inversion channel mobility and threshold voltage stability simultaneously
Solution Approach 2:
The patent creates a composite treatment approach by combining multiple gas species annealing processes. The interaction of oxygen, nitrogen, and hydrogen at the interface creates a composite effect that reduces point defects more effectively than single-gas annealing, improving device performance
2Manufacturing precision
If conventional annealing is used on the gate insulation layer, then the manufacturing process is simple, but the on-resistance is high due to low inversion channel mobility
Solution Approach 1:
The patent merges multiple annealing steps with different gas species into a coordinated process sequence. By combining oxygen annealing (for oxidation), nitrogen annealing (for nitridation), and hydrogen annealing (for reduction and passivation), the process achieves superior interface quality while managing complexity through systematic integration
3Manufacturing precision
If the gate insulation layer is annealed to improve interface quality, then inversion channel mobility increases, but threshold voltage drift may occur without proper gas atmosphere control
Solution Approach 1:
The patent employs periodic action through sequential annealing steps with different gas atmospheres. Each gas species is applied in a specific sequence (oxygen, then nitrogen, then hydrogen), creating periodic chemical treatments that progressively improve the interface while maintaining threshold voltage stability through controlled oxidation, nitridation, and reduction phases
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 proposed method significantly increases the inversion channel mobility and reduces the on-resistance of wide band gap semiconductor devices, while also improving reliability by limiting threshold voltage instability and bias temperature instability.
Implementation Method 1
annealing the gate insulation layer using at least a first reactive gas species and at least a second reactive gas species
Implementation Method 2
annealing the gate insulation layer in a reactive gas atmosphere comprising at least a reactive gas species
Implementation Method 3
annealing the gate insulation layer in an inert gas atmosphere after annealing the gate insulation layer in the reactive gas atmosphere
Data Source
AI summary
A method for forming a wide band gap semiconductor device is provided. The method includes forming a gate insulation layer on a wide band gap semiconductor substrate and annealing the gate insulation layer using at least a first reactive gas species and a second reactive gas species, wherein the first reactive gas species differs from the second reactive gas species. The method can include forming a gate electrode on the gate insulation layer after annealing the gate insulation layer.