CHARACTERIZATION OF THE VERY LOW CONTACT RESISTANCE ON HEAVILY BORON DOPED (113) CVD DIAMOND
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | NANOCOM ⊠|
| Authors | J. Voves, Alexandr Laposa, Z. Ć obĂĄĆ, P. Hazdra, VojtÄch PovolnĂœ |
| Institutions | Czech Academy of Sciences, Institute of Physics, Czech Technical University in Prague |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: Ultra-Low Contact Resistance on (113) BDD Diamond
Section titled âTechnical Analysis and Documentation: Ultra-Low Contact Resistance on (113) BDD DiamondâThis documentation analyzes the research paper âCharacterization of the Very Low Contact Resistance on Heavily Boron Doped (113) CVD Diamondâ and aligns the findings with 6CCVDâs advanced MPCVD diamond manufacturing capabilities, focusing on power electronics applications.
Executive Summary
Section titled âExecutive SummaryâThis study validates the use of (113) oriented, heavily Boron-Doped Diamond (BDD) epitaxial layers combined with Ti/Au metalization to achieve ultra-low ohmic contact resistance, critical for next-generation diamond power electronic devices.
- Application Focus: Fabrication of high-voltage, fast-switching diamond power electronic devices.
- Key Achievement: Demonstrated ultra-low specific contact resistance (RCsp) of approximately 10-6 Ω·cm2, limited by the measurement resolution of the cTLM method used.
- Material Advantage: The (113) crystal orientation proved highly suitable, offering superior performance and lower contact resistance compared to traditional (100) and (111) orientations.
- Contact System: Stable ohmic contacts were achieved using a Ti (10 nm) / Au (100 nm) stack, exhibiting thermal stability up to 700 °C.
- Doping Requirement: Successful results relied on heavily doped BDD layers, with concentrations ranging from 1019 to 1021 cm-3, facilitating field-enhanced emission (tunneling).
- Methodology: Contact properties were accurately characterized using the Circular Transmission Line Model (cTLM) method, supported by TCAD simulation to correct for finite metal resistance effects.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental section and modeling results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Specific Contact Resistance (RCsp) | ~10-6 | Ω·cm2 | Lowest measured value (resolution limit) |
| Diamond Orientation | (113) | N/A | Epitaxial layer surface orientation |
| Boron Doping Concentration (Na) | 1019 to 1021 | cm-3 | Range provided in the BDD epilayer |
| Annealing Temperature | Up to 700 | °C | Post-metalization thermal stability test |
| Ti Contact Layer Thickness | 10 | nm | Ohmic contact layer |
| Au Capping Layer Thickness | 100 | nm | Thermal stability layer |
| MWPECVD Power | 700 | W | Microwave plasma power |
| Growth Pressure | 100 | mbar | Chamber pressure during growth |
| Methane Concentration (CH4) | 1 | % | Gas phase concentration |
| B/C Ratio (Gas Phase) | 100 to 2000 | ppm | Boron source concentration |
| cTLM Inner Circle Radius (L) | 75 | ”m | Measurement structure geometry |
| Diamond Relative Permittivity (Δr) | 5.5 | N/A | Used in analytical model |
Key Methodologies
Section titled âKey MethodologiesâThe experimental procedure focused on precision growth, surface treatment, and advanced characterization techniques:
- BDD Epitaxial Growth: Heavily boron-doped diamond layers were grown on (113) oriented substrates using a commercial MWPECVD reactor (AX5010). Precise control of the B/C ratio (100 to 2000 ppm) was used to achieve doping levels between 1019 and 1021 cm-3.
- Surface Preparation: The (113) diamond surface was treated with ozone prior to metal deposition to optimize the interface for ohmic contact formation.
- Metalization Stack Deposition: A bilayer metal stack consisting of 10 nm Titanium (Ti) followed by a 100 nm Gold (Au) capping layer was deposited using a PVD system (Covap) under high vacuum (< 3 x 10-7 mbar).
- Thermal Processing: The Ti/Au contacts were subjected to annealing at temperatures up to 700 °C to ensure stable, low-resistance ohmic behavior and good thermal stability.
- Patterning: Circular Transmission Line Model (cTLM) patterns were defined using laser lithography (Microwriter ML) and wet chemical etching, featuring an inner circle radius (L) of 75 ”m and electrode gap spacing (d) from 10 to 75 ”m.
- Electrical Characterization: Current-voltage (I-V) characteristics were measured using the Kelvin method and a semiconductor parameter analyzer to extract sheet resistance (Rsh) and specific contact resistance (RCsp).
- Simulation and Correction: Analytical models (Thermionic Field Emission and Field Emission) and Silvaco TCAD 2D simulations were employed to correct experimental data for measurement errors associated with the finite resistivity of the metal layer and the low diamond/metal sheet resistance ratio.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical role of highly controlled material propertiesâspecifically crystal orientation, heavy doping, and precise metalizationâin achieving high-performance diamond power devices. 6CCVD is uniquely positioned to supply the necessary materials and processing services to replicate and advance this work.
| Research Requirement | 6CCVD Solution & Value Proposition |
|---|---|
| Heavily Boron-Doped Diamond (BDD) | High-Purity BDD Materials: 6CCVD specializes in MPCVD growth of BDD layers. We guarantee precise, heavy doping control (up to 1021 cm-3) necessary to facilitate the tunneling mechanism required for ultra-low RCsp. |
| (113) Oriented Substrates | Custom Crystal Orientation: While (100) is common, 6CCVD offers custom Single Crystal Diamond (SCD) substrates and epitaxial growth on specific orientations, including (113), which this study confirms provides superior surface morphology and lower contact resistance for power applications. |
| Ti/Au Metalization Stack | Internal Metalization Capability: We offer in-house deposition of the exact metal stack used (Ti, Au) and other critical materials (Pt, Pd, W, Cu). We ensure precise thickness control (e.g., 10 nm Ti / 100 nm Au) and high uniformity across large wafers. |
| High-Volume/Large Area Devices | Scalable Wafers: 6CCVD supplies both SCD and Polycrystalline Diamond (PCD) plates/wafers up to 125mm in diameter, enabling the scaling of these low-resistance contact designs for commercial high-voltage power modules. |
| Surface Quality & Polishing | Ultra-Low Roughness: To ensure optimal interface quality for epitaxial growth and metal adhesion, 6CCVD provides SCD polishing down to Ra < 1nm and inch-size PCD polishing down to Ra < 5nm. |
| Complex Patterning (cTLM) | Custom Laser Cutting & Etching: We provide precision laser cutting and etching services to define complex geometries, such as the cTLM structures (L=75 ”m, d=10 to 75 ”m), ensuring accurate device fabrication and characterization. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team provides expert consultation on material selection, doping profiles, and surface preparation techniques required for high-performance diamond power devices. We can assist researchers and engineers in optimizing BDD growth recipes to achieve the specific carrier concentrations (1019 to 1021 cm-3) and low RCsp demonstrated in this study.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The low resistance of ohmic contacts on diamond layers is important for the fabrication of diamond power electronic devices with fast switching capabilities for future high voltage applications.The low barrier height between the metal and diamond, high level of boron doping and annealing at elevated temperatures are the most critical parameters to reach the lowest contact resistivity.In this work, we report on titanium/gold ohmic contacts prepared on the heavily boron-doped (113) epitaxial diamond layers.The contact resistance has been characterized by the Circular Transmission Line Model (cTLM) structures.We used the analytical model of field enhanced emission, tunneling and the image force influence including Fermi level position dependence on the boron concentration for theoretical Ti/Au contact analysis and the Silvaco TCAD 2D simulation to estimate the measurement error associated with the nonzero metal resistance.We show that the resulting simulation values are consistent with the experimental results.