SiC Substrate Implantation to Trap Transition Metals Before Epitaxy
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Solution Overview
Problem
Existing methods for manufacturing SiC epilayers suffer from the incorporation of transition metal impurities, which degrade the electronic properties and functionality of high-voltage semiconductor devices, particularly due to the formation of deep levels in the band gap and diffusion during homoepitaxy.
Innovation Solution
A method involving the implantation of group Va elements, such as nitrogen or phosphorus ions, into SiC substrates at specific energy and dose levels to create carbon vacancies that form stable transition metal-carbon vacancy complexes, effectively trapping transition metals before epilayer growth, thereby reducing their diffusion and maintaining the substrate's electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transition metals are present in the crucible material during SiC boule growth, then the SiC substrate can be manufactured, but transition metal impurities are incorporated into the SiC substrate and epilayer, degrading device performance
Solution Approach 1:
The patent applies preliminary action by pre-modifying the SiC substrate through group Va element implantation before epitaxial growth. This creates carbon vacancies and trapping sites in advance, which then capture transition metals during subsequent processing, preventing their incorporation into the epilayer and thus resolving the contradiction between ease of manufacture and device reliability
Solution Approach 2:
The patent introduces group Va elements (nitrogen, phosphorus) as intermediary substances that mediate between the transition metal impurities and the SiC substrate. These elements create carbon vacancies that act as trapping sites, effectively intercepting transition metals and preventing them from reaching the epilayer, thus protecting device functionality while maintaining manufacturing feasibility
2Reliability
If ion implantation is performed in the epilayer to create a gettering layer, then transition metals can be trapped, but electrically active defects are created, impacting leakage current and on-resistance
Solution Approach 1:
The patent performs the ion implantation modification on the substrate before epitaxial growth rather than in the finished epilayer. This preliminary timing allows transition metals to be trapped during growth without creating harmful electrically active defects in the final device structure, thus resolving the contradiction between effective metal trapping and maintaining electrical properties
Solution Approach 2:
The patent inverts the conventional approach by modifying the substrate instead of the epilayer. Instead of implanting ions into the finished epilayer to create gettering layers, the method implants group Va elements into the substrate to create carbon vacancies that trap transition metals during growth, thereby avoiding the creation of harmful electrically active defects while achieving effective trapping
3Reliability
If transition metal concentration in the epilayer is reduced, then device performance improves, but requiring additional processing steps increases manufacturing complexity
Solution Approach 1:
The patent merges the substrate modification and transition metal trapping functions into a single integrated process. By implanting group Va elements into the substrate to create carbon vacancies that inherently trap transition metals during epitaxial growth, the method combines multiple functions (substrate preparation, impurity trapping, and quality enhancement) into one unified approach, thus improving epilayer quality without significantly increasing processing complexity
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 approach results in SiC epilayers with improved structural and electrical properties, reducing TM contamination and enhancing the lifespan and performance of high-voltage semiconductor devices by preventing TM diffusion during epitaxial growth.
Implementation Method 1
implanting group Va elements in the SiC-substrate by irradiating at least a part of the SiC-substrate with group Va ions
Implementation Method 2
irradiation is performed at an energy of greater than or equal to 100 keV and less than or equal to 200 keV
Implementation Method 3
the SiC-substrate is modified to trap Transition Metals (TM)
Data Source
AI summary
The invention relates to a method for manufacturing a Silicon Carbide (SiC) substrate, at least comprising the steps of:a) providing the SiC-substrate, wherein the SiC-substrate is suitable for growing a SiC-epilayer thereon; andb) implanting group Va elements in the SiC-substrate by irradiating at least a part of the SiC-substrate with group Va ions, wherein the irradiation is performed at an energy of greater than or equal to 100 keV and less than or equal to 200 keV and an irradiation dose of greater than or equal to 105 cm−2 and less than or equal to 1010 cm−2. Furthermore, the invention relates to a method for manufacturing a Silicon Carbide epilayer, a SiC substrate and a semiconductor device.