Scanning Deposition Method for Large-Area Diamond Film Synthesis Using Multiple Microwave Plasma Sources

At a Glance

Metadata	Details
Publication Date	2022-06-08
Journal	Nanomaterials
Authors	Seung Pyo Hong, Kang-Il Lee, Hyun Jong You, Soo Ouk Jang, Young Sup Choi
Institutions	Korea Institute of Fusion Energy
Citations	8
Analysis	Full AI Review Included

Technical Documentation & Analysis: Large-Area Diamond Film Synthesis via Scanning MPCVD

Executive Summary

This research successfully demonstrates a novel scanning deposition method utilizing multiple surface-wave microwave plasma sources to achieve large-area diamond film uniformity, addressing a critical bottleneck in traditional resonant cavity MPCVD.

Core Achievement: Synthesis of microcrystalline diamond (MCD) films with a thickness uniformity of ±6.25% across a 70 mm wafer width.
Methodology: A unit array of three 700 W surface-wave plasma sources was combined with a reciprocating substrate motion (scanning deposition) to overcome plasma non-uniformity inherent in large-area CVD.
Material Quality: High-purity diamond was confirmed via UV-Raman spectroscopy, achieving an I_Dia/I_G ratio up to 2.75, indicating a high sp³/sp² carbon ratio.
Target Application: The resulting large-area films are critical for next-generation semiconductor devices, high-performance power electronics (heat dissipation), and quantum computing applications.
6CCVD Value Proposition: While the scanning method achieves uniformity, the paper notes limitations in deposition rate and crystallinity. 6CCVD specializes in high-quality, high-rate MPCVD (SCD/PCD) that can meet or exceed the required material purity and thermal properties for these demanding applications.

Technical Specifications

The following hard data points were extracted from the process optimization and large-area synthesis results:

Parameter	Value	Unit	Context
Target Wafer Size (Demonstrated)	70	mm	Width achieved using triple-source scanning array
Target Wafer Size (Maximum Capacity)	150	mm	Maximum substrate size placed on SiC heater
Film Thickness Uniformity	±6.25	%	Measured over the 70 mm deposition width
Optimized Substrate Temperature	950	°C	For high-purity microcrystalline diamond (MCD)
Optimized Operating Pressure	600	mTorr	Used for multi-source scanning deposition
Optimized Gas Ratio (CH₄/H₂)	0.50	%	Yielded clear diamond peaks (0.40% also successful)
Microwave Power (Per Source)	700	W	Used for the triple-source scanning array
Diamond Purity Ratio (I_Dia/I_G)	Up to 2.75	N/A	Measured via UV-Raman spectroscopy
Deposited Grain Size	0.1-1	µm	Verified using FE-SEM (Microcrystalline Diamond)
Average Crystallite Size	14.9	nm	Calculated from XRD FWHM of the (111) peak

Key Methodologies

The large-area diamond synthesis was achieved through the following sequential steps, focusing on optimizing the surface-wave plasma source and implementing the scanning technique:

Source Improvement: The single surface-wave plasma generator was modified, replacing the rectangular waveguide with a coaxial cable and shortening the source region to extract a stable, ball-shaped plasma.
Process Optimization (Single Source): Initial experiments optimized parameters (Temperature: 950 °C, Pressure: 600 mTorr, CH₄/H₂ Ratio: 0.50%) to maximize diamond crystallinity (I_Dia/I_G up to 2.75) and achieve MCD grain sizes up to 1 µm.
Substrate Seeding: Ultrasonic seeding using a 5% nanodiamond solution (3-10 nm core particle size) in ethanol was employed, resulting in a film density approximately 2.5 times higher than mechanical scratching.
Array Configuration: A minimum unit array of three single surface-wave plasma sources (700 W each) was arranged linearly in a two-row, zigzag pattern to minimize the space between sources.
Scanning Deposition: A 4-inch Si wafer was reciprocally moved perpendicular to the source arrangement direction for a distance of 50 mm at a speed of 0.2 mm/s over a 12-hour period.
Characterization: Film thickness uniformity, surface morphology (FE-SEM), crystallinity (XRD), and purity (UV-Raman) were measured across the 70 mm deposition width.

6CCVD Solutions & Capabilities

The research highlights the growing demand for large-area, high-quality diamond films for advanced thermal management and semiconductor applications. 6CCVD’s specialized MPCVD capabilities directly address the material requirements and noted limitations of the scanning surface-wave plasma method.

Applicable Materials

The paper focuses on synthesizing Microcrystalline Diamond (MCD) and Nanocrystalline Diamond (NCD) films on Si wafers for thermal and electronic applications. 6CCVD offers superior, scalable alternatives:

Research Requirement	6CCVD Material Solution	Key Benefit
Large-Area MCD/NCD for Heat Sinks	Polycrystalline Diamond (PCD)	Available in plates/wafers up to 125 mm in diameter, meeting the large-area goal with superior thermal conductivity (up to 2000 W/mK).
High-Purity Diamond for Electronics	Optical Grade Single Crystal Diamond (SCD)	SCD offers the highest purity and electron/hole mobility, ideal for quantum sensors or high-power RF devices where the low crystallinity noted in the paper’s method is unacceptable.
Doping for Active Devices	Boron-Doped Diamond (BDD)	Available in both SCD and PCD formats, BDD provides p-type semiconducting properties necessary for fabricating active power devices (e.g., Schottky diodes, FETs).

Customization Potential

The scanning method utilized a 4-inch (approx. 100 mm) Si wafer and required precise control over substrate heating and plasma interaction. 6CCVD provides comprehensive customization services to replicate and extend this research:

Large-Area Substrates: We provide PCD wafers up to 125 mm, exceeding the 70 mm uniform area demonstrated in the paper.
Custom Thickness: We offer precise thickness control for both SCD and PCD films, ranging from 0.1 µm (for thin-film integration) up to 500 µm (for robust heat spreaders).
Advanced Metalization: The integration of diamond films into semiconductor stacks often requires specific contact layers. 6CCVD offers in-house deposition of standard metal stacks (e.g., Ti/Pt/Au, W, Cu) tailored to specific device architectures.
Ultra-Low Roughness: For high-quality interfaces required in semiconductor integration, 6CCVD guarantees polishing to achieve surface roughness (Ra) of < 1 nm for SCD and < 5 nm for inch-size PCD.

Engineering Support

The authors noted limitations in their scanning method, including decreased deposition rate and reduced crystallinity compared to established MPCVD techniques. 6CCVD’s in-house PhD team specializes in optimizing high-pressure, high-quality resonant cavity MPCVD, offering solutions that overcome these challenges:

Crystallinity Improvement: We assist researchers in selecting the optimal diamond material (SCD or high-quality PCD) to ensure the highest sp³ purity and thermal performance, crucial for high-performance power semiconductor devices.
Process Scaling: Our experts provide consultation on scaling diamond deposition processes from R&D to production, ensuring material specifications meet the stringent requirements of next-generation electronics.
Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) for time-sensitive research and development projects worldwide.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

The demand for synthetic diamonds and research on their use in next-generation semiconductor devices have recently increased. Microwave plasma chemical vapor deposition (MPCVD) is considered one of the most promising techniques for the mass production of large-sized and high-quality single-, micro- and nanocrystalline diamond films. Although the low-pressure resonant cavity MPCVD method can synthesize high-quality diamonds, improvements are needed in terms of the resulting area. In this study, a large-area diamond synthesis method was developed by arranging several point plasma sources capable of processing a small area and scanning a wafer. A unit combination of three plasma sources afforded a diamond film thickness uniformity of ±6.25% at a wafer width of 70 mm with a power of 700 W for each plasma source. Even distribution of the diamond grains in a size range of 0.1-1 μm on the thin-film surface was verified using field-emission scanning electron microscopy. Therefore, the proposed novel diamond synthesis method can be theoretically expanded to achieve large-area films.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano12121959

References

2002 - Diamond tool performance in machining metal-matrix composites [Crossref]
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2014 - Diamond electron emission [Crossref]
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2021 - Diamond quantum sensors: From physics to applications on condensed matter research [Crossref]
2014 - Single crystal diamond for infrared sensing applications [Crossref]
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1955 - Man-made diamonds [Crossref]