Relationship between Emission Spectrum and B Content in B Doped Diamond Synthesis using Mode Conversion Type Microwave Plasma CVD
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-06-26 |
| Journal | Journal of The Surface Finishing Society of Japan |
| Authors | Asuka Suzuki, Takuya Maruko, Yoshihiro Takahashi, Yukihiro Sakamoto |
| Institutions | Chiba Institute of Technology |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: Boron-Doped Diamond (BDD) Resistivity Control via OES
Section titled “Technical Analysis and Documentation: Boron-Doped Diamond (BDD) Resistivity Control via OES”Source Paper: Relationship between Emission Spectrum and B Content in B Doped Diamond Synthesis using Mode Conversion Type Microwave Plasma CVD (Vol. 71, No.7, 2020)
Executive Summary
Section titled “Executive Summary”This research successfully demonstrates a method for achieving precise, repeatable control over the electrical resistivity of Boron-Doped Diamond (BDD) films synthesized via Microwave Plasma CVD (MPCVD).
- Core Achievement: Established a strong correlation between the intensity ratio of B-containing plasma species (specifically BH/Hβ) measured by Optical Emission Spectroscopy (OES) and the resulting BDD film resistivity.
- Resistivity Range: Successfully synthesized BDD films exhibiting volume resistivity ranging from ultra-low (0.3 Ω·cm) to moderately doped (29.5 Ω·cm).
- Methodology: Utilized a Mode Conversion Type MPCVD system and a liquid boron source (B(CH₃O)₃) introduced via a bubbling method.
- Key Finding: OES monitoring provides superior control over BDD electrical properties compared to traditional methods based solely on the total B source supply (mol count), which showed high variability (Fig. 8).
- Plasma Species Identified: Critical B-containing species monitored include Atomic Boron (B, 249.7 nm), Boron Hydride (BH, 433.1 nm), and Boron Oxide (BO, 436.3 nm).
- Structural Confirmation: Raman spectroscopy confirmed the presence of high B concentration via broad peaks at 500 cm-1 (B-B bonds) and 1200 cm-1 (B-C bonds), alongside the characteristic diamond peak shift from 1333 cm-1.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the experimental conditions and results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Minimum Volume Resistivity | 0.3 | Ω·cm | Achieved under Pattern 1 conditions (highest B-containing species intensity). |
| Maximum Volume Resistivity | 29.5 | Ω·cm | Achieved under Pattern 3 conditions (lowest B-containing species intensity). |
| Target Film Thickness | 16 ± 4 | µm | Polycrystalline BDD film thickness. |
| Microwave Power | 1 | kW | Fixed parameter for Mode Conversion MPCVD. |
| Growth Pressure | 20 | kPa | Fixed parameter. |
| H₂ Flow Rate (Main) | 100 | sccm | Fixed parameter. |
| CH₄ Flow Rate | 15 | sccm | Fixed parameter (C/H ratio control). |
| Critical OES Ratio | BH/Hβ | N/A | Ratio inversely correlated with resistivity (higher ratio = lower resistivity). |
| Key OES Peak (Atomic B) | 249.7 | nm | Emission peak used for monitoring. |
| Key OES Peak (Boron Hydride) | 433.1 | nm | Emission peak used for BH/Hβ ratio calculation. |
| Substrate Material | Si (100) P-type | N/A | Used for heteroepitaxial growth. |
Key Methodologies
Section titled “Key Methodologies”The BDD films were synthesized using a Mode Conversion Type Microwave Plasma CVD system. The primary focus was on controlling the B source introduction rate and monitoring the resulting plasma chemistry via OES.
- Substrate Preparation: Si (100) P-type substrates (0.8-12 Ω·cm) were prepared using diamond powder scratching followed by ultrasonic cleaning.
- Boron Source: A liquid source, B(CH₃O)₃ (0.01 g/ml concentration), was dissolved in CH₃OH.
- Source Introduction: The liquid B source was introduced into the chamber using a bubbling method, carried by H₂ gas. The H₂ carrier flow rate was varied across three patterns (e.g., Pattern 1: 3-5 sccm; Pattern 2/3: 1-3 sccm) to control B concentration.
- CVD Parameters: Fixed parameters included 1 kW microwave power, 20 kPa pressure, 100 sccm H₂, and 15 sccm CH₄.
- In-Situ Monitoring (OES): Optical Emission Spectroscopy (200-800 nm) was used to measure the intensity of plasma species (B, BH, BO, Hα, Hβ, CH, C₂).
- Characterization: Films were analyzed using Scanning Electron Microscopy (SEM) for morphology, Raman Spectroscopy (532 nm Ar laser) for structural quality and B incorporation, and the four-point probe method (JIS K 7194) for electrical resistivity.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research highlights the critical need for precise, repeatable control over boron incorporation to achieve targeted electrical properties in BDD films. 6CCVD is uniquely positioned to supply the high-quality, customized BDD materials required to replicate and advance this work, eliminating the variability inherent in traditional B source methods.
Applicable Materials
Section titled “Applicable Materials”To replicate the low-resistivity films (0.3 Ω·cm) achieved in this study, researchers require highly uniform, heavily doped polycrystalline diamond.
| Material Requirement | 6CCVD Material Solution | Key Specifications |
|---|---|---|
| Heavily Doped Diamond | Heavy Boron-Doped PCD Wafers | Tailored resistivity from 0.001 Ω·cm (metallic) up to 100 Ω·cm. |
| Electrochemical/Sensor Applications | Boron-Doped Diamond (BDD) Electrodes | Excellent chemical stability, wide potential window, and high conductivity for electrochemical sensing and water treatment. |
| High Purity Substrates | Optical Grade SCD (Undoped) | Available for subsequent epitaxial growth or use as high-power optical windows. |
Customization Potential
Section titled “Customization Potential”The paper demonstrated the synthesis of films with a specific thickness (16 ± 4 µm) on Si substrates. 6CCVD offers comprehensive customization capabilities essential for scaling this research into practical devices.
| Research Need | 6CCVD Customization Service | Technical Capability |
|---|---|---|
| Custom Dimensions | Large Area PCD Wafers | Plates/wafers available up to 125 mm diameter. |
| Precision Thickness | SCD/PCD Thickness Control | SCD and PCD films available from 0.1 µm up to 500 µm. |
| Surface Finish | Advanced Polishing | Polishing available to achieve Ra < 5 nm for inch-size PCD, crucial for uniform electrode performance. |
| Device Integration | Custom Metalization | In-house deposition of standard contacts and electrodes (Au, Pt, Pd, Ti, W, Cu) for immediate device integration. |
| Substrate Flexibility | Custom Substrates | Ability to grow BDD films on various substrates (Si, Mo, W, or free-standing). |
Engineering Support
Section titled “Engineering Support”The correlation between plasma chemistry (BH/Hβ ratio) and resistivity is a sophisticated control mechanism. 6CCVD’s in-house PhD team specializes in optimizing CVD recipes to deliver materials with guaranteed electrical specifications.
- Material Selection: Our experts can assist researchers in selecting the optimal BDD grade (PCD or SCD) and doping level required for specific electrochemical, electronic, or sensor applications.
- Recipe Translation: We translate complex laboratory recipes, such as those involving OES monitoring for resistivity control, into scalable, high-yield manufacturing processes, ensuring batch-to-batch consistency that surpasses the variability noted in the paper’s mol count method.
- Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure your custom materials arrive safely and promptly, regardless of location.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
As described herein, we investigate the effects of the plasma state on boron（B）-doped diamond（BDD）resistivity. Preparing BDD of various volume resistivities is difficult. Various studies have examined control of the BDD resistance value, necessitating systematic investigations of the relation between resistivity and B contents in plasma. Therefore, plasma during growth was measured using optical emission spectroscopy （OES）to clarify the relation between emission species and resistance values. For each condition, OES revealed peaks of B（249.7 nm）, BH （433.1 nm）, BO（436.3 nm）, Hα, Hβ, CH, and C2. Electrical resistivity measurements obtained using the four-point probe method with mini mum volume resistivity of 0.3 Ω·cm were obtained. With increasing B-containing emission species such as B, BH, and BO intensity in OES spectra, resistivity was decreased. Results suggest that B-containing emission species in OES spectra influence the resistivity of BDD.