SiC Epitaxial Buffer Layer for BPD Reduction
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Solution Overview
Problem
The commercialization of silicon carbide power electronics is limited by structural defects in the silicon carbide epitaxial layer, particularly basal plane dislocation density, which degrades device performance and increases conduction voltage drop and on-state energy loss.
Innovation Solution
A method involving the growth of a silicon carbide epitaxial layer with a composite buffer layer structure, where each buffer layer undergoes interfacial high-temperature hydrogen etching and doping, promoting the conversion of basal plane dislocations to threading edge dislocations, reducing defect density and simplifying the process while minimizing substrate damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If KOH or KOH-NaOH-MgO co-molten etching is used to reduce BPD defects in the epitaxial layer, then BPD defect density is reduced, but the substrate surface is severely damaged and the process becomes cumbersome
Solution Approach 1:
The patent changes the etching parameters by using in-situ HCl/H2 etching instead of KOH molten etching, performing the etching at high temperature (1550-1700°C) in a controlled atmosphere within the epitaxial reactor. This parameter change achieves BPD defect reduction without the severe surface damage caused by chemical etchants.
Solution Approach 2:
The patent introduces a buffer layer as an intermediary between the substrate and the active device region. This buffer layer serves as a sacrificial layer that absorbs and converts BPD defects into TED defects through lateral epitaxial growth, protecting the active region from BPD defects while avoiding direct chemical etching of the substrate surface.
2Manufacturing precision
If KOH molten etching or KOH-NaOH-MgO co-molten etching is used to convert BPD defects to TED defects, then defect conversion is achieved, but the process is not suitable for epitaxial process integration
Solution Approach 1:
The patent merges the defect conversion process with the epitaxial growth process by performing in-situ HCl/H2 etching and buffer layer growth in the same epitaxial reactor without removing the substrate. This consolidation eliminates the need for separate chemical etching and cleaning steps, making the process suitable for epitaxial process integration.
Solution Approach 2:
The patent performs preliminary in-situ HCl/H2 etching of the substrate surface before epitaxial buffer layer growth to remove surface contaminants and prepare the substrate. This preliminary action ensures optimal buffer layer formation and defect conversion while maintaining process integration.
3Manufacturing precision
If multiple buffer layers with doping are grown to reduce BPD defects, then BPD defect density is greatly reduced, but the epitaxial process complexity increases
Solution Approach 1:
The patent uses parameter changes in doping concentration and layer thickness to optimize defect conversion. By controlling doping levels (2 to 5E18 cm-3) and layer thickness (0.2 to 0.5 μm), the process achieves effective BPD reduction while maintaining manageable process complexity through precise parameter control rather than excessive process steps.
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 significantly reduces basal plane dislocation density in the epitaxial layer, improving device performance by converting defects and simplifying the epitaxial process integration, with a defect reduction rate up to 99.95% and reduced substrate surface damage.
Implementation Method 1
introducing hydrogen into the reaction chamber, gradually increasing the flow rate of the hydrogen to 60 to 120 L/min, setting a pressure in the reaction chamber to be 80 to 200 mbar, gradually heating the reaction chamber to 1,550 to 1,700°C, maintaining all parameters constant after the temperature reaches a set temperature, and performing in-situ hydrogen etching treatment on the silicon carbide substrate for 5 to 15 min
Implementation Method 2
introducing a silicon source and a carbon source into the reaction chamber such that the flow rate ratio of the silicon source to the hydrogen is smaller than 0,03%, the C/Si ratio at the gas inlet end is controlled to be 0.9, and introducing a doping source to grow a buffer layer
Data Source
Figure 1~2
Figure 3
AI summary
The present invention discloses a method for reducing a silicon carbide epitaxial basal plane dislocation density, which mainly comprises the steps of epitaxially growing a high-low doping concentration composite buffer layer having a plurality of cycles on an SiC substrate, performing interfacial high-temperature hydrogen etching treatment on each single layer of buffer layer, introducing a plurality of interfaces using the interfacial high-temperature treatment and doping induction, and promoting conversion of BPD (Basal plane dislocation) defects to TED (Threading Edge Dislocation) defects using an interfacial image force. The method greatly reduces the BPD defects in an epitaxial layer, and may effectively reduce the BPD defect density in the epitaxial layer. The method is simple and favorable for epitaxial process integration. Meanwhile, complicated pretreatment of the SiC substrate is avoided, and damage to the surface of the substrate is reduced.