SiC Growth Substrate Doping to Reduce Epitaxial Carbon Vacancies
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Solution Overview
Problem
Carbon vacancies in silicon carbide layers create electrically active levels that act as recombination centers, affecting lifetime and leakage currents in semiconductor devices.
Innovation Solution
A method for producing a growth substrate with a high concentration of a dopant, such as nitrogen, in a specific region of a silicon carbide wafer, which induces strain and forms interstitial carbon atoms, allowing direct growth of an epitaxial silicon carbide layer without a buffer layer, reducing carbon vacancies through diffusion during growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer layer is used to grow epitaxial silicon carbide layer, then the growth process is more stable, but carbon vacancies are formed which create recombination centers affecting device performance
Solution Approach 1:
The patent applies preliminary action by pre-doping the substrate with nitrogen before epitaxial growth. This preliminary doping creates a nitrogen-rich environment that prevents carbon vacancy formation during the subsequent growth process, eliminating the need for buffer layers and directly addressing the root cause of recombination center formation.
Solution Approach 2:
The patent changes the chemical composition parameter by introducing nitrogen dopant at controlled concentrations (10^18 to 10^20 atoms/cm³) in the substrate. This parameter change modifies the growth environment to suppress carbon vacancies, thereby improving device reliability without adding structural complexity.
2Reliability
If nitrogen doping concentration is increased in the substrate, then carbon vacancies are reduced, but dopant distribution control becomes more difficult
Solution Approach 1:
The patent applies local quality by creating a nitrogen-doped region specifically at the substrate surface and near-surface area, rather than uniform doping throughout the entire substrate. This localized doping approach ensures high nitrogen concentration where it is most needed (at the growth interface) while maintaining better control over overall dopant distribution and avoiding excessive diffusion into deeper regions.
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 method reduces carbon vacancies in the epitaxial silicon carbide layer, improving the electrical characteristics of semiconductor devices by decreasing on-resistance and enhancing performance.
Implementation Method 1
the element material accumulates up to the reaction depth in the top surface region
Implementation Method 2
a comparatively high concentration of the material element of the first dopant in the growth region leads to a strain in the crystal structure which, in turn, leads to the formation of interstitials, in particular interstitial carbon atoms
Implementation Method 3
a concentration of electrically active levels is advantageously reduced in such epitaxial silicon carbide layers grown on top of the growth region
Data Source
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AI summary
A method for producing a growth substrate (1) for an epitaxial silicon carbide layer (5) is specified, the method comprising: - providing an initial wafer (2), wherein the initial wafer (2) comprises silicon carbide and wherein the initial wafer (2) comprises a first dopant, and - heating the initial wafer (2) to an annealing temperature within a first gas atmosphere, wherein the first dopant and the first gas comprise the same material element, - such that a growth region (4) for the epitaxial silicon carbide layer (5) is produced, wherein a maximum concentration of the first dopant of the growth region (4) is higher than a maximum concentration of the first dopant in an initial wafer region. Furthermore, a method for producing an epitaxial silicon carbide layer (5), a growth substrate (1), an epitaxial silicon carbide layer (5), and a power semiconductor device are provided.