Effect of the substrate crystalline orientation on the surface morphology and boron incorporation into epitaxial diamond layers
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | NANOCOM ⊠|
| Authors | J. Voves, Alexandr PoĆĄta, Marina Davydova, Alexandr Laposa, VojtÄch PovolnĂœ |
| Institutions | Czech Academy of Sciences, Institute of Physics, Czech Technical University in Prague |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study compares the homo-epitaxial growth of heavily boron-doped diamond on conventional (100), (111), and emerging (113) oriented substrates using Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD).
- Core Achievement: Epitaxial growth on (113) vicinal surfaces demonstrated superior material quality, achieving a smooth surface morphology and highly homogeneous boron incorporation.
- Surface Quality: The (113) layer exhibited a very smooth surface with a Root-Mean-Squared (RMS) roughness of approximately 1 nm, contrasting sharply with the rough (111) layer (RMS 50 nm) and the hillock-covered (100) layer.
- Growth Rate: The (113) orientation yielded the highest deposition rate (3-5 ”m/h), enabling the rapid fabrication of thick, highly doped templates required for vertical devices.
- Doping Efficiency: The Boron Incorporation Efficiency (BIE) on the (113) surface reached approximately 2%, substantially higher than the BIE achieved on (100) (0.14% < BIE < 1%) and (111) (BIE = 0.28%) surfaces.
- Doping Homogeneity: Raman mapping confirmed excellent spatial homogeneity of the boron concentration (7.2 x 1020 cm-3) across the (113) layer, minimizing variations associated with defects.
- Conclusion: The results confirm that (113) oriented substrates are the most promising solution for developing high-quality, thick, heavily boron-doped diamond templates necessary for advanced power electronic devices.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Growth System | AX5010 | N/A | Resonance cavity MWPECVD (Seki Diamond Systems) |
| Laser Wavelength | 532 | nm | Raman Spectroscopy Mapping |
| (113) Layer Specifications | |||
| Microwave Power | 700 | W | Used for (100) and (113) growth |
| Deposition Pressure | 100 | mbar | Used for (100) and (113) growth |
| Methane Concentration | 1 | % | Used for (100) and (113) growth |
| B/C Ratio | 2,000 | ppm | Boron precursor concentration |
| Boron Concentration | 7.2 x 1020 | cm-3 | Determined via ZCP peak analysis |
| Deposition Rate | 3 - 5 | ”m/h | Highest rate achieved |
| RMS Roughness | ~1 | nm | Measured via AFM (very smooth surface) |
| Boron Incorporation Efficiency (BIE) | ~2 | % | Highest efficiency observed |
| (100) Layer Specifications | |||
| B/C Ratio | 4,000 | ppm | Boron precursor concentration |
| Boron Concentration Range | 1.3 x 1020 to 1021 | cm-3 | Highly inhomogeneous incorporation |
| Deposition Rate | 1.8 - 2 | ”m/h | Intermediate rate |
| Defect Morphology | Pyramidal hillocks | N/A | Approx. 100x100 ”m base, 100 nm height |
| (111) Layer Specifications | |||
| B/C Ratio | 10,000 | ppm | Boron precursor concentration |
| Boron Concentration | 5.3 x 1020 | cm-3 | Determined via ZCP peak analysis |
| Deposition Rate | 0.9 - 1 | ”m/h | Lowest rate observed |
| RMS Roughness | 50 | nm | Inhomogeneous surface with trenches |
| Reference ZCP Peak | 1332 | cm-1 | Undoped diamond zone-center phonon peak |
Key Methodologies
Section titled âKey MethodologiesâThe heavily boron-doped homo-epitaxial diamond layers were grown using a resonance cavity MWPECVD system (AX5010).
-
Substrate Cleaning Procedure (Multi-Step):
- Chemical Etching: Cleaning in hot H2SO4 + KNO3 for 10 min.
- Rinsing: Two cycles of rinsing in deionized water using an ultrasound bath (10 min each).
- Organic Removal: Cleaning in acetone with ultrasound (10 min), followed by cleaning in isopropyl alcohol with ultrasound (10 min).
- In-Situ Plasma Etching: Exposure of the substrate to pure hydrogen microwave plasma at high temperature for 10 min immediately prior to growth initiation.
-
Epitaxial Growth:
- Layers were grown on polished diamond substrates with (111), (100), and (113) orientations.
- Precursor gases included Methane (CH4) and a boron precursor, with B/C ratios ranging from 2,000 ppm ((113) layer) to 10,000 ppm ((111) layer).
-
Surface Characterization:
- Macroscopic Morphology: Observed using Olympus BX60 optical microscopy.
- Microscopic Morphology: Studied using Atomic Force Microscopy (AFM) to determine RMS roughness and defect structure.
-
Boron Incorporation Analysis (Raman Spectroscopy):
- Mapping: Raman surface mapping (532 nm laser) was used to study the spatial homogeneity of boron incorporation, utilizing the shift of the wide Raman band centered around 500 cm-1.
- Quantification: Exact boron concentration was determined from the width of the diamondâs zone-center phonon (ZCP) peak (1332 cm-1).
Commercial Applications
Section titled âCommercial ApplicationsâThe successful growth of highly homogeneous, heavily boron-doped diamond layers on (113) substrates is crucial for next-generation wide-bandgap semiconductor technology.
- Vertical Power Devices: The primary application is the development of vertical diamond power devices, which require thick, highly conductive (metallic) boron-doped templates (p-type layers) to serve as substrates or contact layers.
- High Power Electronics (HPE): Utilizing diamondâs superior physical properties (high breakdown voltage, high thermal conductivity, wide bandgap) to create high-efficiency, high-frequency, and high-temperature switching devices.
- High-Voltage Diodes and Transistors: Fabrication of p-n junctions and Schottky barrier diodes (SBDs) where the quality and homogeneity of the doped layer directly impact device performance and reliability.
- Thermal Management: Integration into devices requiring exceptional heat dissipation due to diamondâs unmatched thermal conductivity, especially critical in high-power modules.
- Advanced Semiconductor Templates: Providing high-quality, low-defect templates for subsequent epitaxial growth of complex diamond device structures.
View Original Abstract
Epitaxial growth of diamond is critically important for the fabrication of diamond-based electronic devices.The emerging study of the epitaxial diamond growth on the (113) vicinal surfaces evidences highly needed high growth rates and low structural defects concentrations with both p-and n-type doping.In this work, we compare the morphology and dopant concentration incorporation of heavily boron-doped (113) epitaxial diamond layers with conventionally studied (100) and ( 111) epitaxial layers.Epitaxial layers were grown using resonance cavity Microwave Plasma Enhanced Chemical Vapor Deposition (MWPECVD) system.The surface morphology of epitaxial layers was studied by optical microscopy and atomic force microscopy, whereas the boron incorporation homogeneity was determined by Raman spectroscopy mapping.Heavily boron-doped (113) epitaxial diamond layers can be grown at a high growth rate with a smooth surface, without pyramidal hillocks or non-epitaxial crystallite defects, and with homogeneous boron concentration.These results confirm that epitaxial diamond growth on (113) vicinal surfaces is a promising solution for the development and fabrication of diamond-based electronic devices.