SiC MOSFET Gate Interface Treatment for Higher Carrier Mobility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in manufacturing silicon carbide (SiC) semiconductor devices, such as MOSFETs, is the decrease in carrier mobility due to carbon vacancies and interface states between the SiC layer and the gate insulating layer, which affects the performance of the devices.
Innovation Solution
A semiconductor device manufacturing method that involves ion implanting aluminum and carbon into the SiC layer, followed by a heat treatment and etching processes using plasma and hydrogen, to reduce carbon vacancy density and form a silicon oxide film, thereby improving the interface termination and mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional manufacturing methods are used for SiC MOSFETs, then the device structure can be formed, but carrier mobility decreases due to carbon vacancies and interface states
Solution Approach 1:
The patent performs preliminary actions by conducting multiple etching processes (CF4 plasma etching, HF solution etching, and O2 plasma etching) and heat treatments before forming the gate insulating layer. These preliminary steps remove carbon vacancies and interface states from the SiC substrate surface, creating a clean interface that prevents subsequent degradation of carrier mobility. The preliminary cleaning actions ensure that when the gate insulating layer is formed, there are minimal defects to cause interface trapping states.
Solution Approach 2:
The patent changes physical and chemical parameters through controlled etching processes and heat treatments. Specifically, it uses CF4 plasma to etch carbon-containing contaminants, followed by HF solution to remove oxide layers, and O2 plasma to further clean the surface. The heat treatment at 400-600°C modifies the surface chemistry and removes residual contaminants. These parameter changes transform the SiC surface from a defect-rich state to a clean state, eliminating carbon vacancies and interface states that would otherwise reduce carrier mobility.
2Manufacturing precision
If the SiC layer interface is not properly treated, then the manufacturing process is simple, but the Hall mobility of electrons remains low
Solution Approach 1:
The patent segments the interface treatment process into three distinct etching steps followed by heat treatment: (1) CF4 plasma etching to remove carbon contaminants, (2) HF solution etching to remove oxide layers, and (3) O2 plasma etching to further clean the surface. Each step targets specific types of contaminants or defects. This segmentation allows systematic removal of different harmful factors that would otherwise be difficult to eliminate with a single process, thereby achieving high interface termination quality.
Solution Approach 2:
The patent uses intermediary substances and processes to achieve interface termination. HF solution acts as an intermediary chemical agent that selectively removes oxide layers without damaging the SiC substrate. Heat treatment at 400-600°C serves as an intermediary thermal process that modifies surface chemistry and removes residual contaminants. These intermediary steps facilitate the transition from a contaminated surface to a clean interface, enabling high-quality gate insulating layer formation without requiring direct contact between the insulating layer material and defective surface.
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 method effectively reduces carbon vacancy density, enhancing the Hall mobility of electrons in the channel region to above 200 cm2/V·s, thereby improving the field effect mobility and suppressing the decrease in carrier mobility.
Implementation Method 1
performing a first ion implantation implanting aluminum into a silicon carbide layer
Implementation Method 2
performing a first heat treatment at a temperature equal to or more than 1600° C.
Implementation Method 3
performing a first etching process etching a surface of the silicon carbide layer in an atmosphere containing plasma generated from a gas containing halogen and oxygen
Implementation Method 4
performing a second etching process etching the surface in an atmosphere containing hydrogen plasma or atomic hydrogen
Implementation Method 5
forming a silicon oxide film on the surface
Data Source
AI summary
A semiconductor device manufacturing method of embodiments includes: performing first ion implantation for implanting aluminum into a silicon carbide layer with a first dose amount; performing first heat treatment at a temperature equal to or more than 1600° C.; performing first etching process for etching a surface of the silicon carbide layer in an atmosphere containing plasma generated from a gas containing halogen and oxygen; performing second etching process for etching the surface in an atmosphere containing hydrogen plasma or atomic hydrogen; forming a silicon oxide film on the surface; and forming a gate electrode on the silicon oxide film.