Research status of metal/diamond interface
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2018-01-01 |
| Journal | Proceedings of the 2018 3rd International Conference on Advances in Materials, Mechatronics and Civil Engineering (ICAMMCE 2018) |
| Authors | Chang Zhang, Fengbin Liu |
| Institutions | North China University of Technology |
| Analysis | Full AI Review Included |
Metal-Diamond Interface Research: Technical & Commercial Analysis
Section titled âMetal-Diamond Interface Research: Technical & Commercial AnalysisâDocumentation Prepared for 6CCVD Technical Sales & Engineering
Executive Summary
Section titled âExecutive SummaryâThis research review emphasizes the critical challenge of forming stable, high-performance metal/diamond interfaces, essential for leveraging diamondâs exceptional properties (especially high thermal conductivity) in advanced semiconductor and electronic devices.
- Core Challenge: Establishing stable, low-resistance Ohmic contacts remains difficult due to diamondâs chemical inertness and high Schottky barriers at the interface.
- Adhesion Strategy: Carbide-forming metals (e.g., Titanium, Chromium) are identified as key materials, providing superior mechanical adhesion to diamond surfaces, especially when coupled with post-deposition annealing (e.g., 600 °C) to facilitate carbide layer formation (TiC).
- Electrical Strategy: Inert noble metals (e.g., Gold, Platinum) are necessary as capping layers to prevent oxidation of the carbide-forming adhesion layers, ensuring stable electrical performance and high conductivity.
- Optimal Structure: The prevailing solution involves complex multi-layer metal stacks (e.g., Ti/Cr/Au or Au/Pt/Ti) designed to balance strong mechanical bond strength with stable electrical conductivity and diffusion resistance.
- Surface Termination Impact: Interface performance is highly dependent on the diamond surface termination (Hydrogen- or Oxygen-terminated), which directly affects the Schottky barrier height and overall contact quality.
- Application Relevance: The findings are crucial for developing high-performance diamond field effect transistors (FETs), diodes, and electrochemical sensors based on Boron-Doped Diamond (BDD).
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points and material characteristics were extracted from the analysis of high-performance metal/diamond interfaces.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Required Annealing Temperature | 600 | °C | Minimum temperature for optimal TiC formation and interfacial adhesion (Ref [9]). |
| Standard Ti Adhesion Layer Thickness | 0.03 | ”m | Thickness for the adhesion layer in Ti/Cr/Au stacks (Ref [15]). |
| Standard Cr Barrier Layer Thickness | 0.03 | ”m | Thickness for the diffusion barrier layer in Ti/Cr/Au stacks (Ref [15]). |
| Standard Au Contact Layer Thickness | 0.5 | ”m | Thickness for the top, low-resistance contact layer (Ref [15]). |
| Strongest Calculated Adhesion Energy | 4.08 | J/m2 | Theoretical adhesion strength for Al on C(111)-(1x1) surface (Ref [23]). |
| H-Termination Weakened Adhesion Energy | 0.02 | J/m2 | Theoretical adhesion strength for Al on C(111)-1x1:H surface (Ref [23]), indicating H-termination severely weakens Al bond. |
| Optimized Metal Stack Example 1 | Ti/Cr/Au | N/A | Balanced stack for strong adhesion (Ti/Cr) and low resistance/stability (Au). |
| Optimized Metal Stack Example 2 | Au/Pt/Ti | N/A | Stack verified for high thermal stability by restricting Ti diffusion (Ref [18]). |
| Measured Surface Roughness (SCD) | Ra < 1 | nm | 6CCVD capability, critical for reproducible interface formation. |
Key Methodologies
Section titled âKey MethodologiesâResearch into metal/diamond interfaces relies on precise fabrication techniques and detailed characterization methods to optimize adhesion, conductivity, and stability.
- Chemical Vapor Deposition (CVD): Growth of high-quality Single Crystal Diamond (SCD) or Polycrystalline Diamond (PCD) thin films, often followed by specific surface termination procedures (e.g., Hydrogen or Oxygen termination).
- Metal Deposition Techniques:
- Physical Vapor Deposition (PVD): Including Vacuum Thermal Evaporation and Sputtering (RF Magnetron Sputtering), commonly used to deposit Ti, Cr, Au, and Pt layers.
- Electrodeposition/Chemical Plating: Used for synthesizing metal nanoparticle arrays (Au, Ag, Cu) on BDD surfaces for sensor applications.
- Post-Deposition Thermal Annealing: High-temperature treatment (up to 600 °C or higher) in vacuum or inert atmosphere to promote the solid-state reaction and formation of stable metal carbide layers (e.g., TiC) at the interface, improving adhesion and reducing the Schottky barrier.
- Electrical Characterization: Temperature-dependent current-voltage (I-V) measurements to assess Schottky barrier height and determine if the contact exhibits Ohmic or Schottky behavior.
- Mechanical Testing:
- Nano-Indentation and Nano-Scratching: Utilizing instruments to measure the mechanical properties of the deposited metal layer and the adhesion strength (critical load for peeling/delamination) between the metal and the diamond substrate.
- Theoretical Modeling: Use of Density Functional Theory (DFT) (e.g., VASP, Quantum-ESPRESSO) to analyze equilibrium geometric structures, adsorption energy, and electronic properties of different metal atoms (Ti, Al, Cu, Mo, Pd) on various diamond terminations.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to support and advance research and development in metal/diamond interfaces due to our advanced MPCVD growth capabilities and comprehensive in-house fabrication services, which directly address the preparation complexities highlighted in this paper.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend the research into stable metal/diamond contacts for electronic and electrochemical devices, 6CCVD recommends the following materials:
| Material Grade | Description & Application | 6CCVD Specifications |
|---|---|---|
| Electronic Grade SCD | Required for fundamental studies of interface physics and high-power discrete devices (FETs, Diodes). Highly controlled crystal orientation (e.g., (111) or (100)). | Thickness: 0.1 ”m - 500 ”m. Max Wafer Size: 10mm. Polishing: Ra < 1 nm. |
| Heavy Boron-Doped PCD (BDD) | Essential for Ohmic contact formation and electrochemical applications (sensors, electrodes). Dopant concentration can be tailored to minimize contact resistance. | Thickness: 0.1 ”m - 500 ”m. Max Wafer Size: 125mm. |
| Large Format PCD | Ideal for scaling up sensor arrays, heat spreaders, and polycrystalline transistor matrices requiring uniform coating over wide areas. | Max Wafer Size: Up to 125mm (Inch-size). Polishing: Ra < 5 nm. |
Customization Potential: Advanced Metalization Stacks
Section titled âCustomization Potential: Advanced Metalization StacksâThe paper demonstrates that reliable metal/diamond interfaces necessitate custom, multi-layer metal stacks (e.g., Ti/Cr/Au). 6CCVD offers internal, expert PVD metalization services that meet these exact requirements, ensuring material compatibility and precise layer control (critical given the 30 nm scale layers mentioned).
| Research Requirement | 6CCVD Solution | Technical Advantage |
|---|---|---|
| Need for carbide-forming adhesion layers (Ti, Cr, W). | Full Internal Capability: We deposit Ti and W adhesion layers using high-purity sources. | Guarantees superior bond strength post-annealing, forming the necessary carbide interlayer. |
| Need for stable, low-resistance noble metal layers (Au, Pt, Pd). | Contact & Diffusion Barrier Deposition: We provide high-fidelity layers of Au, Pt, and Pd for diffusion barriers and inert top contacts. | Ensures long-term stability and prevents oxidation or interdiffusion at operating temperatures (e.g., Au capping layer stability). |
| Need for precise layer thickness control (e.g., 30 nm layers). | Micro-Precision Deposition: Layer thicknesses controlled from 10 nm to several microns, supporting complex stacks like Ti/W/Au or Au/Pt/Ti. | Eliminates process variations associated with external metallization providers, crucial for reproducible device fabrication. |
| Need for specific geometry definition (e.g., contacts on FETs). | Precision Laser Cutting and Patterning: In addition to metal deposition, we offer custom laser machining services to define electrode geometries, pads, and microstructures. | Facilitates direct integration of R&D concepts into fabricated device layouts. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and technical engineers specializes in MPCVD diamond growth, surface termination, and metallization physics. We are prepared to assist clients in optimizing material selection and processing parameters for complex metal/diamond contact projects.
We provide consultation on:
- Selecting the appropriate diamond crystal orientation (100 vs. 111) for specific electronic or mechanical requirements.
- Controlling surface termination (Hydrogen or Oxygen) to fine-tune the Schottky barrier height, critical for achieving true Ohmic contact.
- Designing robust multi-layer metal stacks (e.g., selecting the appropriate barrier metal, such as W or Pt, against Ti diffusion).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship high-performance CVD diamond globally (DDU default, DDP available).
View Original Abstract
The high thermal conductivity of diamond makes it very promising in the field of semiconductor devices, and the application of diamond film in electronic devices will inevitably involve the problem of contact with metal.What kind of metal/diamond interface that has good electrical and mechanical properties.Which method can obtain a more stable interface between the metal/diamond.Scientists have done a lot of research in these aspects, but there is no definite conclusion at present.This paper focuses on the preparation methods of metal/diamond interfaces, and the electrical and mechanical properties of the interfaces.