Growth and surface structrue of hydrogen terminal diamond thin films
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Meng-Yu Ma, Cui Yu, Ze-Zhao He, Jian-Chao Guo, Qingbin Liu |
| Institutions | Hebei Semiconductor Research Institute, China Electronics Technology Group Corporation |
| Citations | 1 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Performance H-Terminated SCD
Section titled âTechnical Documentation & Analysis: High-Performance H-Terminated SCDâExecutive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the MPCVD homoepitaxial growth of ultra-high-purity, hydrogen-terminated Single Crystal Diamond (SCD) thin films, achieving electrical properties critical for high-power device applications.
- High Purity Achieved: Epitaxial layer nitrogen concentration was confirmed to be extremely low (< 1x1016 atom/cm3), minimizing defect scattering and enhancing performance.
- Surface Morphology Control: Optimized $\text{CH}_4$ concentration (4%) enabled two-dimensional planar growth, resulting in an atomically flat surface with a record-low RMS roughness of 0.225 nm (for a 10 ”m x 10 ”m scan).
- Structural Confirmation: LEED and XPS confirmed a successful transition from O-terminated to the desired P-type, H-terminated (2x1: H) surface reconstruction.
- Superior Electrical Performance: The optimized film exhibited a high hole mobility ($\mu_h$) of 207 $\text{cm}^2/(\text{V}\cdot\text{s})$ and a low sheet resistance ($R_s$) of 4981 $\Omega$/square.
- Application Focus: These results provide essential material foundation for the development and commercialization of high-frequency, high-power diamond field-effect transistors (FETs).
- 6CCVD Value: 6CCVD specializes in supplying the high-purity SCD substrates and custom epitaxial layers required to replicate and scale this advanced research.
Technical Specifications
Section titled âTechnical SpecificationsâThe following data points were extracted from the analysis of the optimal sample (4% $\text{CH}_4$ concentration, Sample 2).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | N-doped CVD SCD | - | (001) orientation, $\theta_{off} \approx 1.5^\circ$ |
| Substrate Dimensions | 10 x 10 x 0.5 | mm | Standard size used in experiment |
| Epitaxial Layer Thickness | 590 | nm | Sample 2 (4% $\text{CH}_4$) |
| Epitaxial N Concentration | $\le 1 \times 10^{16}$ | atom/cm3 | SIMS detection limit |
| Growth Rate (4% $\text{CH}_4$) | 59 | nm/min | Calculated over 10 min growth |
| Surface Roughness (RMS) | 0.225 | nm | 10 ”m x 10 ”m AFM scan |
| Hole Mobility ($\mu_h$) | 207 | $\text{cm}^2/(\text{V}\cdot\text{s})$ | Hall test result (P-type conductivity) |
| Sheet Resistance ($R_s$) | 4981 | $\Omega$/square | Hall test result |
| Growth Temperature | 860 | °C | Constant for all samples |
| Microwave Power | 3500 | W | Constant for all samples (2.45 GHz) |
| H2 Flow Rate | 192 | sccm | Sample 2 (4% $\text{CH}_4$) |
| $\text{CH}_4$ Concentration | 4 | % | Optimal concentration for planar growth |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized Microwave Plasma Chemical Vapor Deposition (MPCVD) to achieve high-purity homoepitaxy.
- Substrate Selection: Nitrogen-doped CVD SCD substrates (10 mm x 10 mm x 0.5 mm) with (001) orientation and a slight off-cut angle ($\theta_{off} \approx 1.5^\circ$) were used.
- Cleaning Protocol: Substrates underwent high-temperature cleaning using a mixed acid solution ($\text{H}_2\text{SO}_4:\text{HNO}_3 = 3:1$) for 20 min, followed by rinsing in organic solvents and deionized water.
- Chamber Environment: The MPCVD chamber was evacuated to $5.0 \times 10^{-6}$ mbar prior to gas introduction.
- Plasma Generation and Heating: High-purity $\text{H}_2$ gas (200 sccm) was introduced and excited by 3500 W microwave power (2.45 GHz) to heat the substrate to 860 °C.
- Pre-Etching: A pre-etching step using $\text{H}_2$ or $\text{H}_2/\text{O}_2$ plasma was performed to remove surface contaminants and relieve polishing-induced stress, enhancing epitaxial quality.
- Epitaxial Growth: $\text{CH}_4$ gas was introduced at varying concentrations (3%, 4%, 5%) for a short growth time (10 min) at 860 °C.
- Characterization: The resulting films were analyzed using SIMS (purity), AFM (roughness/morphology), LEED (surface structure), XPS (chemical termination), and Hall testing (electrical properties).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the critical need for ultra-high-purity, precisely controlled SCD material for advanced high-power electronics. 6CCVD is uniquely positioned to supply the necessary substrates and custom epitaxial layers to replicate and scale this technology.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the high-performance results of this study, researchers require substrates that minimize defect introduction and maximize surface quality.
- Electronic Grade Single Crystal Diamond (SCD): 6CCVD supplies SCD substrates with guaranteed ultra-low impurity levels (Nitrogen typically < 1 ppb), essential for achieving the epitaxial purity ($\le 1 \times 10^{16} \text{ atom/cm}^3$) demonstrated in the paper.
- Custom SCD Homoepitaxy: We offer custom MPCVD growth services to deposit the required sub-micron SCD thin films (0.1 ”m to 500 ”m) with controlled H-termination, ensuring P-type conductivity and high mobility.
Customization Potential
Section titled âCustomization PotentialâThe success of this research hinges on precise control over substrate orientation, surface preparation, and subsequent device metalization.
| Requirement from Paper | 6CCVD Capability | Technical Advantage |
|---|---|---|
| Substrate Dimensions | Custom plates/wafers up to 125 mm (PCD) or large SCD plates (up to 15 mm). | Enables scaling from R&D (10x10 mm) to commercial production. |
| Surface Flatness | SCD polishing to $\text{Ra} < 1 \text{ nm}$. | Guarantees an ideal starting surface, critical for achieving the 0.225 nm RMS roughness required for 2D planar growth. |
| Orientation Control | Precise (001) orientation with guaranteed off-cut angles ($\theta_{off}$). | Essential for controlling the step-flow growth mode and achieving uniform, defect-free epitaxy. |
| Metalization for Devices | In-house custom metalization (Au, Pt, Pd, Ti, W, Cu). | Necessary for subsequent fabrication of high-power FETs, providing reliable ohmic contacts to the H-terminated P-type layer. |
| Epitaxial Thickness | SCD thickness control from 0.1 ”m to 500 ”m. | Allows precise replication of the 590 nm active layer thickness or optimization for specific device designs. |
Engineering Support
Section titled âEngineering Supportâ6CCVD understands that achieving high-performance H-terminated diamond requires expertise beyond simple material supply.
- Application Expertise: Our in-house PhD team specializes in diamond surface physics and MPCVD growth optimization. We can assist clients with material selection, surface preparation protocols (e.g., acid cleaning and pre-etching recipes), and growth parameter tuning to maximize hole mobility for similar H-terminated diamond FET projects.
- Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure sensitive, high-value diamond materials reach your lab safely and efficiently.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The conductivity of hydrogen-terminated diamond is a limiting factor in its application in field-effect transistor devices. The traditional preparation process hinders the improvement of the electrical properties of hydrogen-terminated diamond due to impurity elements in the diamond bulk and surface damage caused by processing near the diamond surface. To overcome this, researchers have explored the epitaxial growth of a high-purity and flat-surfaced diamond thin film on a diamond substrate. However, this approach still faces challenges in film characterization and achieving high surface smoothness. In this study, microwave plasma chemical vapor deposition technology is used to epitaxially grow a sub-micron thick diamond film on a nitrogen-doping chemical vapor deposition diamond substrate of 10 mm Ă 10 mm Ă 0.5 mm in size. The influence of methane concentration on the growth and conductivity of diamond film is investigated. The test results reveal that the growth thickness of the diamond film ranges from 230 to 810 nm, and the nitrogen concentration in the epitaxial layer is lower than 1Ă10<sup>16</sup> atom/cm<sup>3</sup>. Three growth modes are observed for the homoepitaxial growth of the diamond thin film under different methane concentrations. A methane concentration of 4% enables two-dimensional planar growth of diamond, resulting in a smooth and flat surface with a roughness of 0.225 nm (10 ÎŒmĂ10 ÎŒm). The formation of different surface morphologies is attributed to the growing process and etching process of diamond. Surface low-energy electron diffraction testing indicates that the surface of the diamond film undergoes a structural transition from oxygen terminal (1Ă1: O) to hydrogen terminal (2Ă1: H) when grown for a short period of time. X-ray photoelectron spectroscopy analysis reveals an extremely low ratio of oxygen element to nitrogen element, giving the grown diamond film P-type conductivity characteristics. The Hall test results demonstrate that the hydrogen-terminated diamond film grown with a methane concentration of 4% exhibits the highest conductivity, with a square resistance of 4981 Ω/square and a hole mobility of 207 cm<sup>2</sup>/(V·s). This enhanced conductivity can be attributed to the lower defect density observed under these specific conditions. The findings of this study effectively improve the electrical properties of hydrogen-terminated diamond, and contribute to the development and practical application of high-power diamond devices.