Deposited Gate Dielectric Stack for SiC MOSFET Interface Traps
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Solution Overview
Problem
Metal-oxide-semiconductor field-effect transistors using silicon carbide substrates face degradation in electrical properties due to interface traps formed during thermal oxidation, which lowers carrier mobility in the inversion layer.
Innovation Solution
A structure for a field-effect transistor is formed with a semiconductor substrate of wide bandgap material, featuring a first gate dielectric layer and a second gate dielectric layer disposed between the first layer and the gate electrode, deposited using atomic layer deposition and chemical vapor deposition techniques to minimize carbon incorporation and reduce interface traps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal oxidation process is used to form gate dielectric layer on silicon carbide substrate, then silicon dioxide layer is formed, but carbon is incorporated from substrate into the oxide layer resulting in interface traps and degradation of electrical properties
Solution Approach 1:
The patent extracts and removes the problematic thermal oxidation process that causes carbon incorporation. Instead of using thermal oxidation to form the gate dielectric layer, the invention deposits silicon dioxide or other dielectric materials using alternative methods such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), thereby eliminating the source of interface traps while maintaining the necessary insulating function of the gate dielectric layer
Solution Approach 2:
The patent changes the fundamental parameters of the gate dielectric formation process. Rather than using thermal oxidation at high temperatures that cause carbon diffusion into the oxide, the invention employs deposition processes with controlled temperature and chemistry parameters that prevent carbon incorporation, thus forming a clean interface between the gate dielectric and silicon carbide substrate
2Reliability
If thermal oxidation is used to form gate dielectric, then silicon dioxide layer is created, but carrier mobility in inversion layer is lowered due to interface traps
Solution Approach 1:
The invention removes the thermal oxidation step that generates interface traps, thereby eliminating the harmful factor that degrades carrier mobility in the inversion layer. The alternative deposition methods create a cleaner interface that does not introduce the same level of interface states
Solution Approach 2:
The patent employs composite gate dielectric structures, such as combining silicon nitride and silicon oxide layers, or using silicon dioxide deposited by CVD/ALD methods. These composite or alternatively-deposited structures provide both the necessary electrical insulation and a clean interface that preserves high carrier mobility in the inversion layer
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 multiple gate dielectric layers reduce interface trap density, enhancing carrier mobility and maintaining high electrical properties by limiting carbon incorporation and optimizing substrate temperatures for deposition.
Implementation Method 1
deposited using atomic layer deposition and chemical vapor deposition techniques
Implementation Method 2
deposited using atomic layer deposition and chemical vapor deposition techniques
Implementation Method 3
a gate dielectric layer that contains silicon dioxide formed by thermal oxidation process of the silicon carbide substrate
Data Source
AI summary
Structures for a field-effect transistor and methods of forming a structure for a field-effect transistor. The structure comprises a semiconductor substrate comprising a wide bandgap semiconductor material, a gate electrode, a first gate dielectric layer disposed on the semiconductor substrate, and a second gate dielectric layer disposed between the first gate dielectric layer and the gate electrode.