SiC MOS Gate Oxide Interface Passivation for Threshold Stability
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Solution Overview
Problem
The use of silicon carbide in semiconductor devices, such as MOSFETs, results in decreased carrier mobility and fluctuating threshold voltages due to harmful defects and interface states in the gate insulating layer, particularly caused by oxygen vacancies and defects in the silicon oxide layer.
Innovation Solution
A semiconductor device with a silicon carbide layer and a gate insulating layer containing nitrogen, carbon, and hydrogen, featuring an interface termination region with a high nitrogen concentration to terminate dangling bonds and reduce harmful defects, is manufactured through a series of heat treatments in specific gas atmospheres to form CONH compounds, thereby stabilizing the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a silicon carbide layer is used to form a MOSFET, then high temperature operation capability is improved, but carrier mobility decreases and threshold voltage fluctuates due to harmful defects in the gate insulating layer
Solution Approach 1:
The patent applies parameter changes by performing multiple heat treatments at different temperatures in different gas atmospheres. Specifically, a first heat treatment is performed at 1100-1300°C in a nitrogen oxide atmosphere to form an interface termination region with high nitrogen concentration, followed by a second heat treatment at 100-600°C in an oxygen atmosphere to reduce oxygen vacancies. These controlled parameter changes transform the gate insulating layer's composition and structure to eliminate harmful defects while maintaining high temperature operation capability.
Solution Approach 2:
The patent implements local quality by creating an interface termination region with distinct local properties at the interface between the silicon carbide layer and gate insulating layer. This region has a nitrogen concentration of 1×10^21 cm^-3 or more, which is significantly higher than in other regions. The localized high nitrogen concentration terminates dangling bonds specifically at the interface, reducing interface states without affecting the bulk properties of the gate insulating layer, thus improving carrier mobility and threshold voltage stability.
2Ease of manufacture
If a conventional gate insulating layer is formed on silicon carbide, then device fabrication is simplified, but harmful defects such as oxygen vacancies and interface states increase
Solution Approach 1:
The patent applies preliminary action by performing a first heat treatment in a nitrogen oxide atmosphere before final device completion. This preliminary treatment introduces nitrogen into the gate insulating layer to form an interface termination region that terminates dangling bonds and reduces interface states. Subsequently, a second heat treatment in an oxygen atmosphere is performed to fill oxygen vacancies. These preliminary actions prepare the gate insulating layer in advance to prevent harmful defects from forming during subsequent processing and device operation.
Solution Approach 2:
The patent converts harmful factors into beneficial effects by transforming oxygen vacancies (harmful) into oxygen-filled sites (beneficial) through the second heat treatment in oxygen atmosphere. Additionally, the nitrogen oxide atmosphere during the first heat treatment converts nitrogen oxide into nitrogen that terminates dangling bonds, transforming a potential contaminant into a beneficial interface termination agent. This approach turns what would normally be harmful defects into mechanisms that improve device performance.
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 solution effectively suppresses the decrease in carrier mobility, fluctuation in threshold voltage, and reduces leakage current while enhancing the reliability of the gate insulating layer by minimizing interface states and defects.
Implementation Method 1
a region provided between the silicon carbide layer and the silicon oxide layer and having a nitrogen concentration equal to or more than 1×10^21 cm^−3, in which a nitrogen concentration distribution
Implementation Method 2
performing a first heat treatment in an atmosphere containing nitrogen oxide gas
Implementation Method 3
performing a second heat treatment in an atmosphere containing oxygen gas
Implementation Method 4
performing a third heat treatment in an atmosphere containing hydrogen gas
Data Source
AI summary
A semiconductor device of an embodiment includes a silicon carbide layer, a gate electrode, a silicon oxide layer between the silicon carbide layer and the gate electrode, and containing carbon (C), nitrogen (N), and hydrogen (H), and a region between the silicon carbide layer and the silicon oxide layer and having a nitrogen concentration equal to or more than 1×1021 cm−3, in which a nitrogen concentration distribution has a peak in the region, a first concentration of nitrogen, a second concentration of carbon, and a third concentration of hydrogen at a first position 10 nm away from the peak toward the silicon oxide layer are equal to or more than 1×1018 cm−3, the second concentration is 80% or more and 120% or less of the first concentration, and the third concentration is 80% or more and 120% or less of the first concentration.