Synchrotron Bragg diffraction imaging characterization of synthetic diamond crystals for optical and electronic power device applications
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-03-29 |
| Journal | Journal of Applied Crystallography |
| Authors | Thu Nhi Tran Thi, J. Morse, Damien Caliste, Bruno Fernandez, David Eon |
| Institutions | CEA Grenoble, Centre National de la Recherche Scientifique |
| Citations | 49 |
| Analysis | Full AI Review Included |
Technical Analysis and Material Solutions from 6CCVD
Section titled âTechnical Analysis and Material Solutions from 6CCVDâSynchrotron Characterization of Synthetic Diamond for Optical and Power Electronics
Section titled âSynchrotron Characterization of Synthetic Diamond for Optical and Power ElectronicsâThis documentation analyzes the key findings of the research paper âSynchrotron Bragg diffraction imaging characterization of synthetic diamond crystals for optical and electronic power device applications,â focusing on the material requirements, performance limiting factors, and how 6CCVDâs advanced MPCVD diamond products meet the demanding specifications of this field.
Executive Summary
Section titled âExecutive SummaryâThe paper successfully demonstrates the critical importance of high-resolution X-ray diffraction imaging (RCI) for validating the quality of synthetic diamond necessary for X-ray optics (monochromators, phase plates) and high-power electronics.
- Quantitative Defect Mapping: Synchrotron-based RCI provides quantitative, microradian-precision maps of local lattice distortion (FWHM, PPOS) essential for qualifying single-crystal diamond (SCD) substrates and overgrown layers.
- Material Quality Variation: Characterization of commercial HPHT and CVD diamond plates revealed vast sample-to-sample quality variations, underscoring the necessity of strict quality control for demanding applications.
- Polishing Damage Mitigation: RCI identified that conventional abrasive polishing methods (resin wheel) can introduce deep crack damage (>250 ”m deep), severely compromising the bulk quality required for devices.
- Boron Doping Stress Management: The technique successfully measured lattice parameter variations (âd/d ~ 3 x 10-5) induced by highly concentrated Boron-Doping (BDD) and variations in impurity concentration (Nitrogen) between the HPHT substrate and the CVD overlayer.
- Critical Applications: The research supports the fabrication of advanced devices, including high-voltage diodes and structural diamond superlattices (undulators), where defect propagation must be precisely controlled.
- 6CCVD Relevance: Replication and extension of this research require highly controlled MPCVD Single-Crystal Diamond (SCD) and Boron-Doped Diamond (BDD) with ultra-low surface roughness (Ra < 1 nm) and exceptional crystal homogeneity, all available through 6CCVDâs custom capabilities.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table extracts key performance parameters and material specifications from the characterized diamond samples and the RCI experimental setup.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Orientation | (100) or (111) | N/A | Required for X-ray optics and electronics. |
| Substrate Thickness | ~500 | ”m | Typical starting plate size. |
| CVD Overlayer Thickness | 0.7 - 25 | ”m | Tested layer thickness range. |
| Boron Doping Concentration (High) | ~1021 | atom cm-3 | Used for high-voltage diode fabrication (BDD). |
| Boron Doping Concentration (Graded) | 2 x 1020 to 8 x 1020 | atom cm-3 | Used for diamond undulator superlattice. |
| Lattice Parameter Variation (Measured âd/d) | ~3 x 10-5 | N/A | Mismatch stress due to substrate Nitrogen content. |
| Estimated Dislocation Density (Low-Grade) | 103 - 104 | cm-2 | Estimated from White-Beam Topography. |
| Effective Pixel Resolution (RCI) | 0.7 | ”m | Spatial resolution for defect mapping. |
| Angular Step (RCI) | ~10-4 | ° | Precision of rocking curve rotation step. |
| Bulk FWHM (High Quality HPHT IIa) | ~3 x 10-3 | ° | Target crystallinity quality (Section RCI). |
| Surface Damage Depth | >250 | ”m | Observed depth of crack propagation from polishing. |
| RCI X-ray Energy | 20 | keV | Used with Si(111) monochromator. |
Key Methodologies
Section titled âKey MethodologiesâThe study relied on a combination of synthesis and advanced synchrotron characterization techniques. 6CCVD specializes in replicating the material synthesis aspect of this work (MPCVD).
A. Material Synthesis and Processing
Section titled âA. Material Synthesis and Processingâ- Substrate Preparation: Use of high-quality (100) and (111) oriented diamond substrates, primarily HPHT Type Ib (nitrogen-containing) and HPHT Type IIa (high-purity).
- Overlayer Growth: Boron-doped (BDD) diamond layers were deposited via Microwave-Assisted Plasma Chemical Vapour Deposition (MWCVD), allowing for precise control of doping profiles (e.g., graded concentration for undulators).
- Surface Processing: Samples were either provided âas-grownâ or underwent standard post-growth processing, including hot acid cleaning and mechanical polishing (using resin wheels).
- Doping Measurement: Secondary Ion Mass Spectrometry (SIMS) was used to verify Boron doping concentration profiles in the CVD overlayers.
B. Synchrotron Characterization Techniques
Section titled âB. Synchrotron Characterization Techniquesâ- White-Beam X-ray Topography (Laue Mode): Used for fast, qualitative, non-destructive identification of extended defects (dislocations, stacking faults, overall curvature) across large areas (>100 mm2).
- Monochromatic Rocking Curve Imaging (RCI): A quantitative technique using a monochromatic beam (20 keV) to generate series of diffraction images by rotating the sample through the Bragg peak.
- RCI Analysis (RCIA Software): Calculation of 2D maps of Integrated Intensity (INT), Full Width at Half Maximum (FWHM), and Peak Position (PPOS) on a pixel-by-pixel basis to quantify local lattice distortions (tilt and lattice parameter variation).
- Section Topography (RCI): Use of a narrow, 10 ”m wide strip beam (often multi-strip) to investigate a virtual cross-section of the diamond, enabling the distinction and quantification of defects in the bulk versus the surface (depth-resolved analysis).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights two critical challenges: the need for perfectly tailored SCD/PCD materials and the absolute necessity of damage-free processing. 6CCVD is uniquely positioned as an expert MPCVD supplier to address these requirements for next-generation power electronics and X-ray optics.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend the advanced device fabrication described in this paper, researchers require materials that eliminate the bulk and surface defects shown to compromise performance.
| Paper Requirement | 6CCVD Solution | Technical Advantage |
|---|---|---|
| High-Purity Substrates (HPHT IIa equivalent) | Optical Grade Single-Crystal Diamond (SCD) | Low-defect material suitable for X-ray optics (Shvydâko requirements) and high-power switches. Plate sizes up to 125mm. |
| Boron-Doped Layers (for Diodes/Undulators) | Custom Boron-Doped Diamond (BDD) | Precise control over B-doping concentration (e.g., 1020 to 1021 atom cm-3) and thickness profiles (graded layers) necessary for engineered lattice strain and high conductivity. |
| Thick Layers (for high power/bulk) | SCD/PCD up to 500 ”m | 6CCVD offers extensive thickness control across both SCD and PCD for bulk material applications and device design flexibility. |
Customization Potential
Section titled âCustomization PotentialâThe quantitative analysis of lattice strain (âd/d) and defect density mandates extremely tight specifications for layer structure and processing. 6CCVDâs capabilities ensure these parameters are met.
- Precision Polishing & Surface Quality: The paper illustrates deep sub-surface damage (>250 ”m) caused by poor commercial polishing. 6CCVD guarantees ultra-low roughness polishing: Ra < 1 nm for SCD and Ra < 5 nm for Inch-size PCD. This eliminates polishing-induced bulk damage, maximizing the functional thickness of the device layer.
- Custom Dimensions: While the samples tested were small (3x3 mm), 6CCVD provides custom diamond wafers (PCD up to 125 mm) and plates in a range of thicknesses (0.1 ”m to 500 ”m), enabling scaling of device prototypes.
- Integrated Metallization: For the high-power MOS transistors and diodes mentioned in the paper, reliable ohmic and Schottky contacts are essential. 6CCVD offers in-house custom metalization stacks, including Au, Pt, Pd, Ti, W, and Cu, crucial for robust electrical and thermal performance.
- Tailored Geometries: Custom laser cutting and shaping services ensure precise geometric conformity for complex device architectures, such as micro-scale X-ray optics structures.
Engineering Support
Section titled âEngineering SupportâThe technical complexity involved in managing lattice mismatch due to intentional doping (B) or unintentional impurities (N, H) requires expert input during the material selection phase.
- Lattice Matching Consultation: 6CCVDâs in-house PhD engineering team possesses deep expertise in MPCVD growth dynamics and can assist researchers in selecting the optimal substrate/overlayer combination to minimize intrinsic lattice parameter variations and maximize crystal quality (as measured by FWHM).
- Application-Specific Material Selection: We provide dedicated support for complex X-ray optics projects (requiring near-perfect SCD with FWHM comparable to 10-3 °) and power electronics projects (requiring robust BDD layers with controlled doping profiles).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc. ) within the crystal. This allows easy and quick comparison of the crystal quality of diamond plates available from various commercial suppliers. When needed, rocking curve imaging (RCI) is also employed, which is the quantitative counterpart of monochromatic Bragg diffraction imaging. RCI enables the local determination of both the effective misorientation, which results from lattice parameter variation and the local lattice tilt, and the local Bragg position. Maps derived from these parameters are used to measure the magnitude of the distortions associated with polishing damage and the depth of this damage within the volume of the crystal. For overgrown layers, these maps also reveal the distortion induced by the incorporation of impurities such as boron, or the lattice parameter variations associated with the presence of growth-incorporated nitrogen. These techniques are described, and their capabilities for studying the quality of diamond substrates and overgrown layers, and the surface damage caused by mechanical polishing, are illustrated by examples.