SiC MOSFET Gate Interface Nitrogen Termination for Threshold Stability
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face issues with decreased carrier mobility and threshold voltage changes due to carbon defects in the gate insulating layer, which affect the reliability and performance of MOSFETs.
Innovation Solution
Incorporating a nitrogen-rich interface termination region between the silicon carbide layer and the silicon oxide gate insulating layer, with a specific nitrogen concentration distribution to reduce dangling bonds and carbon defects, thereby improving the interface quality and carrier mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal oxide semiconductor field effect transistor is formed using silicon carbide, then low loss and high-temperature operation can be implemented, but carrier mobility decreases or threshold voltage changes due to carbon defects in the gate insulating layer
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment in a nitrogen-containing atmosphere before forming the gate insulating layer. This pre-treatment introduces nitrogen into the silicon carbide layer in advance, creating a nitrogen-rich region that will later suppress carbon defect formation when the gate insulating layer is formed, thereby improving interface quality and device performance stability
Solution Approach 2:
The patent uses nitrogen as an intermediary element. The nitrogen-rich region formed in the silicon carbide layer acts as a mediator that suppresses the formation of carbon defects at the interface with the gate insulating layer. The nitrogen atoms fill vacancies and reduce dangling bonds, thereby improving the interface quality and preventing threshold voltage shifts and carrier mobility degradation
2Ease of manufacture
If a gate insulating layer is formed on silicon carbide, then device operation is enabled, but carbon defects form in the gate insulating layer causing threshold voltage changes
Solution Approach 1:
The patent performs preliminary nitrogen-containing heat treatment before gate insulating layer formation. This pre-treatment creates a nitrogen-rich region in the silicon carbide layer that will suppress carbon defect formation during subsequent gate insulating layer formation processes, ensuring threshold voltage stability while maintaining ease of manufacture
Solution Approach 2:
The patent changes the chemical composition parameter of the silicon carbide layer by introducing nitrogen through heat treatment. This parameter change creates a nitrogen-rich region that fundamentally alters the interface chemistry, suppressing carbon defect formation and threshold voltage shifts during gate insulating layer formation
3Device complexity
If standard heat treatment is performed to form the gate insulating layer, then the manufacturing process is simplified, but carbon defects increase due to carbon atom diffusion into the gate insulating layer
Solution Approach 1:
The patent performs preliminary nitrogen-containing heat treatment before gate insulating layer formation. This pre-treatment creates a nitrogen-rich region that suppresses carbon defect formation, allowing standard heat treatment processes to be used without increasing carbon defects, thereby maintaining both process simplicity and interface quality
Solution Approach 2:
Nitrogen acts as an intermediary that suppresses carbon diffusion into the gate insulating layer. The nitrogen-rich region created by preliminary heat treatment serves as a barrier that prevents carbon atoms from diffusing into the gate insulating layer during standard manufacturing processes, maintaining interface quality without increasing 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
The approach effectively suppresses the decrease in carrier mobility and threshold voltage changes, enhancing the reliability and performance of SiC MOSFETs by reducing carbon defects and trap levels in the gate insulating layer.
Implementation Method 1
Incorporating a nitrogen-rich interface termination region between the silicon carbide layer and the silicon oxide gate insulating layer, with a specific nitrogen concentration distribution to reduce dangling bonds and carbon defects
Data Source
AI summary
A semiconductor device according to an embodiment includes: a silicon carbide layer; a silicon oxide layer; and a region disposed between the silicon carbide layer and the silicon oxide layer and having a nitrogen concentration equal to or more than 1×1021 cm−3. Nitrogen concentration distribution in the silicon carbide layer, the silicon oxide layer, and the region have a peak in the region, a nitrogen concentration at a position 1 nm away from the peak to the side of the silicon oxide layer is equal to or less than 1×1018 cm−3, and a carbon concentration at the position is equal to or less than 1×1018 cm−3.