1 W/mm Output Power Density for H-Terminated Diamond MOSFETs With Al2O3/SiO2Bi-Layer Passivation at 2 GHz
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-12-23 |
| Journal | IEEE Journal of the Electron Devices Society |
| Authors | Xinxin Yu, Wenxiao Hu, Jianjun Zhou, Bin Liu, Tao Tao |
| Institutions | Nanjing Institute of Technology, Nanjing University |
| Citations | 19 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Power Diamond MOSFETs
Section titled “Technical Documentation & Analysis: High-Power Diamond MOSFETs”This document analyzes the research paper “1 W/mm Output Power Density for H-Terminated Diamond MOSFETs With Al₂O₃/SiO₂ Bi-Layer Passivation at 2 GHz” and outlines how 6CCVD’s advanced MPCVD diamond materials and fabrication capabilities can support and extend this high-performance semiconductor research.
Executive Summary
Section titled “Executive Summary”This study successfully demonstrates a significant breakthrough in diamond RF power electronics by achieving a record output power density using a novel bi-layer passivation scheme.
- Record Performance: Achieved a high output power density of 1.04 W/mm at 2 GHz, the highest reported value for a diamond transistor operating at this frequency.
- Novel Passivation: Utilized an ALD-Al₂O₃/PECVD-SiO₂ bi-layer dielectric structure to effectively passivate the H-terminated diamond (H-diamond) surface channel.
- Enhanced Stability: The bi-layer structure dramatically improved device stability, resulting in current saturation and stable operation over 85 days, overcoming typical instability issues in H-diamond MOSFETs.
- Low Contact Resistance: Fabrication yielded an extremely low Ohmic contact resistance of 0.87 Ω·mm, crucial for minimizing parasitic losses in high-power RF devices.
- High Frequency Metrics: The device demonstrated strong high-frequency characteristics with an extrinsic cutoff frequency (fT) of 15 GHz and a maximum oscillation frequency (fmax) of 36 GHz.
- Material Foundation: The high performance was enabled by the use of high-quality, (100)-oriented Single Crystal Diamond (SCD) substrates grown via CVD.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the device characterization results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Output Power Density (Pout) | 1.04 | W/mm | Measured at 2 GHz |
| Maximum Current Density (IDS,max) | -549 | mA/mm | Achieved after surface current saturation (Day 85) |
| Ohmic Contact Resistance (Rc) | 0.87 | Ω·mm | Lowest reported value on H-diamond |
| Sheet Resistance (Rsh) | 6.4 | kΩ/sq | 2DHG channel |
| Specific Contact Resistance (ρc) | 1.18 x 10-6 | Ω·cm2 | Calculated value |
| Extrinsic Cutoff Frequency (fT) | 15 | GHz | LG = 0.45 µm |
| Maximum Oscillation Frequency (fmax) | 36 | GHz | LG = 0.45 µm |
| Power Added Efficiency (PAE) | 13.69 | % | Measured at 2 GHz |
| Gate Dielectric Thickness (Al₂O₃) | 50 | nm | ALD layer |
| Passivation Thickness (SiO₂) | 200 | nm | PECVD layer |
| Substrate Orientation | (100) | N/A | Single Crystal Diamond (SCD) |
Key Methodologies
Section titled “Key Methodologies”The high-performance H-diamond MOSFET was fabricated using a multi-step process focused on precise surface preparation and bi-layer dielectric deposition.
- Substrate Selection: Used 5x5x0.3 mm³ (100)-oriented Single Crystal Diamond (SCD) substrates.
- Hydrogen Termination (2DHG Generation): Performed in an MPCVD system (OptoSystem ARDIS-300) at 700 °C, 2.2 kW power, for 10 minutes.
- Surface Quality Control: Post-hydrogenation surface roughness was measured to be Ra < 1.0 nm.
- Ohmic Contact Formation: 50 nm Au deposited via Electron Beam (EB) evaporation, followed by wet etching (KI solution) to define source/drain regions.
- Device Isolation: Achieved by exposing the surface to a low power oxygen plasma for 5 minutes.
- Surface Annealing: Substrate annealed in the ALD chamber at 350 °C for 10 minutes to remove adsorbates.
- First Passivation/Gate Dielectric (Al₂O₃): 50 nm Al₂O₃ deposited via Atomic Layer Deposition (ALD) at 350 °C using trimethylaluminum (TMA) and deionized water.
- Gate Metal Deposition: 20/500 nm Ti/Au stack deposited via EB evaporation.
- Second Passivation Layer (SiO₂): 200 nm SiO₂ deposited via Plasma Enhanced Chemical Vapor Deposition (PECVD) at 280 °C.
- Test Pad Metalization: Final 20/500 nm Ti/Au stack deposited.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The successful replication and scaling of this high-power diamond MOSFET technology require ultra-high purity, precisely engineered diamond substrates and advanced metalization capabilities—all core competencies of 6CCVD.
Applicable Materials
Section titled “Applicable Materials”To achieve the high mobility and breakdown characteristics necessary for 1 W/mm performance, the following 6CCVD material is required:
- Optical Grade Single Crystal Diamond (SCD): High-purity, low-defect, (100)-oriented SCD is essential for maximizing the concentration and stability of the Two-Dimensional Hole Gas (2DHG) channel. 6CCVD provides SCD optimized for electronic applications.
Customization Potential
Section titled “Customization Potential”6CCVD’s in-house manufacturing capabilities directly address the critical material and dimensional requirements of this research:
| Research Requirement | 6CCVD Capability & Solution | Value Proposition |
|---|---|---|
| Substrate Dimensions | Custom plates/wafers up to 125 mm (PCD) and large-area SCD. | We can supply the 5x5 mm² SCD wafers used, or scale up to larger formats for high-volume device runs. |
| Substrate Thickness | SCD thickness range: 0.1 µm to 500 µm. Substrates up to 10 mm. | We match the 0.3 mm thickness used and offer precise thickness control for thermal management optimization. |
| Surface Quality (H-Termination) | Guaranteed SCD polishing to Ra < 1 nm. | Ensures the ultra-smooth surface required for stable 2DHG formation and effective, low-damage ALD/PECVD dielectric deposition. |
| Custom Metal Stacks | In-house deposition of Ti, Au, Pt, Pd, W, and Cu. | We can pre-deposit the required Ti/Au gate and test pad stacks, or the Au ohmic contacts, ensuring high adhesion and minimizing customer fabrication steps. |
| Patterning & Shaping | High-precision laser cutting and shaping services. | Allows for rapid prototyping of custom device geometries and precise definition of the 5x5 mm² chips from larger wafers. |
Engineering Support
Section titled “Engineering Support”The success of this MOSFET relies heavily on the interface quality between the H-diamond and the Al₂O₃/SiO₂ bi-layer.
- Interface Optimization: 6CCVD’s in-house PhD team specializes in MPCVD growth and surface preparation techniques. We offer consultation to optimize the hydrogenation recipe (700 °C, 2.2 kW) and subsequent surface cleaning protocols to ensure maximum C-H bond integrity before ALD deposition.
- Material Selection for High-Power RF: Our experts can assist researchers in selecting the optimal diamond grade (SCD vs. PCD) and orientation for scaling similar High-Power Diamond MOSFET projects, balancing cost, size, and performance requirements.
- Boron Doping (BDD): For applications requiring stable, integrated resistors or alternative contact schemes, 6CCVD offers custom Boron-Doped Diamond (BDD) materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We have demonstrated a novel method of depositing ALD-Al<sub>2</sub>O<sub>3</sub>/PECVD-SiO<sub>2</sub> bi-layer dielectric to passive the surface channels of the hydrogen-terminated diamond (H-diamond). After Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> passivation, the surface current increased with time and then tended to be saturated. Afterwards, it became much more stable and showed a larger current than an unpassivated counterpart. The H-diamond MOSFETs were fabricated by using this bi-layer passivation structure and an extremely low Ohmic contact resistance of <inline-formula> <tex-math notation=“LaTeX”>$0.87~\Omega \cdot $ </tex-math></inline-formula>mm was obtained. The H-diamond RF MOSFET with gate length of <inline-formula> <tex-math notation=“LaTeX”>$0.45~{\mu }\text{m}$ </tex-math></inline-formula> achieved a high current density of −549 mA/mm and an extrinsic <inline-formula> <tex-math notation=“LaTeX”>${f} {\mathrm{ T}}/{f}{\max }$ </tex-math></inline-formula> of 15/36 GHz. By load-pull measurement, a high output power density of 1.04 W/mm was obtained at frequency of 2 GHz. The results reveal that it is a promising solution for high-stable and high-power diamond transistors by using the Al<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> bi-layer passivation.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2014 - High-reliability passivation of hydrogen-terminated diamond surface by atomic layer deposition of Al2O3 [Crossref]
- 2015 - Isotope analysis of diamond-surface passivation effect of high-temperature H2O-grown atomic layer deposition-Al2O3 films [Crossref]