Silicon Carbide Epitaxy on Silicon With Defect Leakage Suppression
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Solution Overview
Problem
The primary inadequacy of 3c SiC epitaxial layers produced on silicon is the presence of significant extended planar defects such as stacking faults and microtwins, which are electrically active and contribute to unacceptable leakage currents in devices.
Innovation Solution
Reducing or preventing the oxidation of silicon during the growth of the silicon carbide epitaxial layer to block the preferential uptake of nitrogen at defects, thereby reducing their electrical activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 3c SiC epitaxial layers are grown on silicon substrates to reduce cost, then manufacturing cost is reduced, but electrical leakage increases due to electrically active defects
Solution Approach 1:
The patent changes the chemical environment parameters during epitaxial growth by introducing oxygen and controlling temperature to induce silicon oxidation at defects. This parameter change transforms the electrical properties of defects, converting them from electrically active to electrically inactive, thereby reducing leakage current while maintaining cost-effective silicon substrate usage
Solution Approach 2:
The patent introduces oxygen as an intermediary substance during the growth process. This oxygen acts as a mediator that reacts with silicon at the defect sites to form silicon oxide, which passivates the defects and eliminates their electrical activity, thus resolving the contradiction between cost and reliability
2Reliability
If extended planar defects are eliminated to reduce electrical activity, then electrical leakage is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the harmful electrical activity from defects without removing the defects themselves. By selectively oxidizing silicon at defect sites through controlled oxygen introduction, the method separates the physical presence of defects from their harmful electrical function, eliminating leakage without requiring complex defect elimination processes
Solution Approach 2:
The patent converts the harmful effect of defects (electrical activity causing leakage) into a beneficial state by using the same defect sites as reaction locations for silicon oxidation. The defects become the precise locations where passivation occurs, transforming from sources of leakage to sites of controlled chemical modification that eliminate the leakage problem
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 effectively reduces the electrical activity of defects in silicon carbide epitaxial layers grown on silicon, enabling the use of these layers in devices without the need to eliminate defects, thus simplifying and cost-reducing the manufacturing process.
Implementation Method 1
the incorporation of nitrogen at the defects is not a direct process, but rather takes place via a reaction between silicon and oxygen to form an intermediate species (i.e. silicon dioxide)
Implementation Method 2
which subsequently undergoes carbothermal reduction by nitrogen during epitaxial growth
Data Source
AI summary
A method is provided for reducing the electrical activity of defects in a silicon carbide epitaxial layer grown on a silicon wafer, the method comprising reducing oxidation of silicon during growth of the silicon carbide epitaxial layer. We also describe a semiconductor structure comprising: a silicon wafer; and a silicon carbide epitaxial layer grown on the silicon wafer; wherein the silicon carbide epitaxial layer is doped with a precursor, the precursor being configured to reduce oxidation of silicon during growth of the silicon carbide epitaxial layer. Reducing the oxidation of silicon may advantageously reduce or prevent the preferential uptake of nitrogen at defects by reducing the formation of the intermediate species (i.e. silicon dioxide) in the reaction.