SiC Layer Carbon Vacancy Reduction via Thermal Annealing
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face issues with shortened minority carrier lifetime and decreased channel mobility due to carbon vacancies and defects caused by ion implantation, leading to high on-voltage and on-resistance in devices like PIN diodes and MOSFETs.
Innovation Solution
A manufacturing method involving a first heat treatment to anneal or oxidize the SiC layer in an atmosphere with carbon gas, reducing carbon vacancies and defects, thereby forming a low level density region with reduced carbon vacancy concentration, which improves device performance by introducing carbon from the gas phase rather than ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation method is used to introduce carbon into SiC, then carbon vacancies are reduced, but on-voltage and on-resistance increase
Solution Approach 1:
The patent replaces the mechanical ion implantation process with a chemical vapor phase process. Instead of physically bombarding the SiC surface with carbon ions, the invention uses carbon-containing gas (such as methane or carbon monoxide) that reacts with the SiC surface at elevated temperatures to deposit carbon atoms, thereby reducing carbon vacancies without the damaging effects of ion implantation
Solution Approach 2:
The patent changes the fundamental parameters of the carbon introduction process: instead of using high-energy ion bombardment, it employs thermal energy (heating to 1000-1500°C) combined with chemical reactions in a carbon-containing atmosphere. This parameter change allows carbon to be introduced in a gentler, non-damaging manner that preserves minority carrier lifetime while still reducing carbon vacancies
2Ease of manufacture
If traditional manufacturing method is used, then device structure is formed, but defects are generated and device performance is degraded
Solution Approach 1:
The patent applies carbon-containing gas treatment to the SiC layer before completing the device fabrication process. This preliminary action reduces carbon vacancies and prevents defect formation in advance, ensuring that subsequent processing steps occur on a defect-free substrate, thereby improving overall device reliability without complicating the manufacturing process
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 concentrations, resulting in lower on-voltage and on-resistance in SiC semiconductor devices, enhancing their operational efficiency and reducing the risk of defect generation compared to traditional ion implantation methods.
Implementation Method 1
a first heat treatment to anneal or oxidize an SiC layer in an atmosphere where a gas including carbon (C) exists is performed
Implementation Method 2
a first heat treatment to anneal or oxidize an SiC layer in an atmosphere where a gas including carbon (C) exists is performed
Implementation Method 3
introducing carbon (C) into the SiC layer by a heat treatment
Data Source
AI summary
A semiconductor device includes: an SiC substrate having a first surface and a second surface; a first conductivity type SiC layer disposed on the first surface side of the SiC substrate, and including a low level density region having Z1/2 level density of 1×1011 cm−3 or less measured by deep level transient spectroscopy (DLTS); a second conductivity type SiC region disposed on a surface of the SiC layer; a first electrode disposed on the SiC region; and a second electrode disposed on the second surface side of the SiC substrate.