Stratigraphy of a diamond epitaxial three-dimensional overgrowth using doping superlattices
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-05-02 |
| Journal | Applied Physics Letters |
| Authors | Fernando Lloret, Alexandre Fiori, D. AraĂșjo, David Eon, M.P. Villar |
| Institutions | Centre National de la Recherche Scientifique, Universidad de CĂĄdiz |
| Citations | 20 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond Epitaxial 3D Overgrowth using Doping Superlattices
Section titled âTechnical Documentation & Analysis: Diamond Epitaxial 3D Overgrowth using Doping SuperlatticesâThis document analyzes the research paper âStratigraphy of a diamond epitaxial three-dimensional overgrowth using doping superlatticesâ to provide technical specifications and align the findings with 6CCVDâs advanced MPCVD diamond capabilities, focusing on applications in power electronics and materials science research.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a novel stratigraphic approach using doping superlattices to analyze the complex 3D epitaxial overgrowth of diamond mesa structures, providing critical data for advanced power device fabrication.
- Advanced Architecture: Selective 3D overgrowth of plasma-etched cylindrical diamond mesa structures was achieved using Microwave Plasma-Assisted Chemical Vapor Deposition (MPCVD).
- Stratigraphic Markers: Thin, heavily Boron-Doped Diamond (BDD) epilayers (1020 at/cm3) were periodically embedded as time markers (superlattices) to visualize intermediate growth stages via Transmission Electron Microscopy (TEM).
- Growth Dynamics: The method allowed for the precise calculation of growth rates along various crystallographic directions, confirming the tendency toward planarization (V{100} was the slowest at 7.3 nm/min).
- Defect Analysis: TEM cross-sections revealed high densities of threading dislocations, identifying two types of Burger vectors (b112 and b011) and linking defect generation to stress accumulation at mesa corners and boron inclusion.
- Methodological Breakthrough: This technique overcomes the limitations of traditional post-growth shape analysis, enabling the study of non-faceted or planarized structures at the nanometer scale.
- Application Relevance: The controlled modulation of doping and geometry is essential for developing next-generation monolithic diamond-based power devices, such as pseudo-vertical Schottky diodes and field-effect transistors.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental methodology and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | Ib-type Single Crystal Diamond (SCD) | 3x3 mm2 | (100) orientation |
| Etched Structure Diameter | 1-50 | ”m | Cylindrical mesa patterns |
| Etch Depth | ~700 | nm | Achieved via deep reactive-ion etching |
| CVD Reactor Type | NIRIM-type | Quartz Wall | MPCVD setup |
| Microwave Power | 400 | Watt | Constant deposition parameter |
| Chamber Pressure | 33 | Torr | Constant deposition parameter |
| Boron Doping Concentration (p+) | 1020 | at/cm3 | Concentration in BDD superlattice layers |
| Diborane Ratio (B2H6/CH4) | 14000 | ppm | Used for heavily doped layers |
| Undoped Methane Ratio (CH4/H2) | 1.0 | % | Standard undoped growth recipe |
| Undoped Oxygen Ratio (O2/H2) | 0.25 | % | Oxygen additive for CVD diamond quality |
| Growth Rate V{100} | 7.3 | nm/min | Slowest growth rate, confirming planarization |
| Growth Rate V{320} | ~41 | nm/min | Fastest terminal orientation observed |
| TEM Lamella Thickness | ~80 | nm | Prepared via Focused Ion Beam (FIB) |
| Burger Vectors Identified | b112, b011 | - | Extended defects (dislocations) |
Key Methodologies
Section titled âKey MethodologiesâThe experiment relied on precise lithography, etching, and highly controlled MPCVD growth modulation:
- Masking and Patterning: Deep-UV laser lithography was used to define open disks (1-50 ”m diameter) on (100) SCD substrates, followed by electron beam evaporation of nickel to create solid masks.
- Mesa Etching: Deep Reactive-Ion Etching (DRIE) with optimized oxygen plasma was employed to etch approximately 700 nm deep cylindrical diamond structures with a high aspect ratio.
- MPCVD Overgrowth: Growth was conducted in a NIRIM-type quartz wall reactor, maintaining constant conditions (400 Watt, 33 Torr).
- Doping Superlattice Growth: A periodic flow sequence automatically switched the gas composition to alternate between:
- Undoped Layers: CH4/H2 = 1% and O2/H2 = 0.25%.
- Heavily Boron-Doped Layers: CH4/H2 = 0.5% and B2H6/CH4 = 14000 ppm (resulting in 1020 at/cm3 concentration).
- Cross-Sectional Preparation: Focused Ion Beam (FIB) was used to prepare ultra-thin lamellas (approx. 80 nm) along specific crystallographic directions ([010] and [011]) for internal structure analysis.
- Stratigraphic Analysis: Transmission Electron Microscopy (TEM) in bright field (BF) and dark field (DF) modes utilized the contrast from the boron-doped layers to map the evolution of the growth front and track dislocation propagation.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and extension of this advanced 3D epitaxial growth research requires materials and fabrication control that aligns perfectly with 6CCVDâs core expertise in MPCVD diamond. We provide the necessary high-quality substrates, precise doping control, and custom fabrication services to support next-generation power electronics development.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High-Purity Substrates | Optical Grade SCD (100) | Provides the ultra-low defect density starting material required to minimize initial defect generation and ensure high-quality epitaxial overgrowth, crucial for high-voltage power devices. |
| Precise Doping Control | Heavy Boron-Doped Diamond (BDD) | We specialize in highly controlled BDD layers, enabling the exact doping concentration (e.g., 1020 at/cm3) and thickness modulation necessary for creating high-contrast superlattices and functional p-type layers. |
| Scaling & Dimensions | Custom SCD/PCD Plates up to 125mm | While the study used small 3x3 mm2 samples, 6CCVD offers the capability to scale this research to production-relevant sizes, providing SCD and PCD wafers up to 125mm in diameter. |
| Epitaxial Thickness Control | SCD Thickness from 0.1”m to 500”m | Our MPCVD expertise ensures precise control over the thickness of both undoped and doped epilayers, critical for managing strain, achieving planarization, and optimizing device performance. |
| Advanced Fabrication Support | Custom Metalization & Polishing | We offer in-house metalization (Au, Pt, Ti, W, Cu) for masking or contact formation, and ultra-smooth polishing (Ra < 1nm for SCD) to reduce the microscopic roughness that generates strain at etched edges. |
| Defect Management | Engineering Consultation | 6CCVDâs in-house PhD team provides expert assistance in optimizing growth recipes (e.g., CH4/H2 and O2/H2 ratios) to manage growth anisotropy, minimize threading dislocation propagation, and control strain in complex 3D overgrowth projects. |
For custom specifications or material consultation regarding 3D epitaxial growth, BDD superlattices, or advanced power device architectures, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The selective doped overgrowth of 3D mesa patterns and trenches has become an essential fabrication step of advanced monolithic diamond-based power devices. The methodology here proposed combines the overgrowth of plasma-etched cylindrical mesa structures with the sequential growth of doping superlattices. The latter involve thin heavily boron doped epilayers separating thicker undoped epilayers in a periodic fashion. Besides the classical shape analysis under the scanning electron microscope relying on the appearance of facets corresponding to the main crystallographic directions and their evolution toward slow growing facets, the doping superlattices were used as markers in oriented cross-sectional lamellas prepared by focused ion beam and observed by transmission electron microscopy. This stratigraphic approach is shown here to be applicable to overgrown structures where faceting was not detectable. Intermediate growth directions were detected at different times of the growth process and the periodicity of the superlattice allowed to calculate the growth rates and parameters, providing an original insight into the planarization mechanism. Different configurations of the growth front were obtained for different sample orientations, illustrating the anisotropy of the 3D growth. Dislocations were also observed along the lateral growth fronts with two types of Burger vector: b011ÂŻ=12[011ÂŻ] and b112=16[112]. Moreover, the clustering of these extended defects in specific regions of the overgrowth prompted a proposal of two different dislocation generation mechanisms.