SiC Substrate Implantation for Transition Metal Gettering
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Solution Overview
Problem
Existing methods for producing SiC epilayers are hindered by the incorporation of transition metals (TMs) which form deep levels in the band gap, impairing the functionality and lifetime of high-voltage semiconductor devices.
Innovation Solution
A method involving the implantation of group Va elements into SiC substrates at specific energy and dose levels to create carbon vacancies (VCs) that form stable TM-VC complexes, trapping TMs and preventing their diffusion into the epilayer during growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transition metals are present in the crucible material during SiC bulk growth, then the SiC substrate can be produced, but transition metal impurities are incorporated into the SiC boule or substrate, forming deep levels in the band gap that harm device functionality
Solution Approach 1:
The patent applies preliminary action by implanting group Va elements (N, P, As) into the SiC substrate before epitaxial growth to pre-create carbon vacancies that will trap transition metals during subsequent processing. This advance preparation prevents TM diffusion into the epilayer without requiring post-growth corrections.
Solution Approach 2:
The patent uses group Va element-implanted carbon vacancies as an intermediary trapping mechanism. These vacancies act as mediator sites that capture transition metal impurities, preventing them from reaching the epilayer. The implanted elements serve as intermediate agents between the crucible TMs and the sensitive epilayer.
2Object-affected harmful factors
If helium implantation is used to create a gettering layer for trapping transition metals, then TM diffusion into the epilayer is reduced, but electrically active defects are created that impact leakage current, minority carrier lifetime, and on-resistance
Solution Approach 1:
The patent changes the implantation parameters by using group Va elements at specific energies (50-200 keV) and doses (10^15-10^18 ions/cm²) to create carbon vacancies without forming the electrically active defects associated with helium implantation. This parameter optimization achieves TM trapping while preserving electronic properties.
Solution Approach 2:
The patent uses low-cost group Va element ions (particularly nitrogen and phosphorus) as disposable implantation species that create effective trapping sites without the harmful side effects of helium. These elements serve as economical alternatives that achieve the same gettering function without compromising device electronics.
3Object-affected harmful factors
If the SiC substrate is irradiated with particles to modify it for trapping transition metals, then the substrate can prevent TM incorporation, but the irradiation process adds complexity to the manufacturing procedure
Solution Approach 1:
The patent merges the ion implantation step with standard semiconductor processing workflows. The group Va element implantation can be integrated into existing ion implantation equipment and process sequences, combining multiple functions (substrate modification, defect creation, and potential doping) into a single manageable step.
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 effectively reduces TM concentration in SiC epilayers, maintaining structural integrity and improving electronic properties, resulting in superior epitaxial layers with extended lifespan and unchanged electrical properties.
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
Data Source
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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; and b) 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.