Skip to content
6CCVD Research

Low-Temperature Deposition of Diamond Films by MPCVD with Graphite Paste Additive

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-04-16
JournalC – Journal of Carbon Research
AuthorsStephen Yang-En Guu, Fu‐Cheng Lin, Yu-Sen Chien, Alen Jhang, Yonhua Tzeng
InstitutionsNational Cheng Kung University
Citations1
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This research demonstrates a novel Microwave Plasma Chemical Vapor Deposition (MPCVD) technique for achieving high-rate, low-temperature diamond film growth, specifically targeting applications in advanced integrated circuits (ICs).

  • Low-Temperature Achievement: Diamond films were successfully deposited at a substrate temperature of 450 °C, which is compatible with back-end-of-line (BEOL) IC fabrication processes, avoiding thermal damage to existing structures.
  • Novel Growth Promoter: A graphite paste additive (containing nano-graphite, oxy-hydrocarbon binder, and solvent) was introduced to the plasma, significantly enhancing growth kinetics during the initial deposition phase.
  • High Deposition Rate: The process achieved a rapid diamond growth rate of up to 200 nm/h, allowing for the quick fabrication of films up to 200 nm thick.
  • Enhanced Film Quality: The additive promoted large lateral grain growth from 3 nm seeds, resulting in average diamond grain sizes up to 80 nm, compared to 15-25 nm without the paste.
  • High sp3 Content: Raman spectroscopy confirmed the formation of high-quality, sp3-bonded diamond (1332 cm-1 peak), crucial for maximizing thermal conductivity and dielectric performance.
  • Thermal Conductivity Improvement: The increase in grain size and high sp3/sp2 ratio minimizes phonon scattering at grain boundaries, promising high thermal conductivity necessary for advanced thermal management.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Substrate Temperature450°CMaintained for low-temperature IC compatibility.
Maximum Deposition Rate200nm/hCalculated based on 197 nm thickness achieved in 1 hour (with repetitive paste).
Final Film Thickness~200nmAchieved after three repetitive 20 min growth periods.
Average Grain Size (With Paste)Up to 80nmAchieved after three repetitive 20 min growth periods.
Average Grain Size (No Paste)15-25nmBaseline grain size without the graphite paste additive.
MPCVD Frequency2.45GHzOperating frequency of the Astex AX5010 reactor.
Microwave Power950WStandard power setting.
Gas Pressure30torrStandard operating pressure.
Total Gas Flow Rate160sccmStandard total gas flow.
Standard Paste Mass0.018gAmount of graphite paste applied per 20 min period.
Diamond Raman Peak1332cm-1Confirms sp3-bonded diamond.
Non-Diamond Carbon Peaks1350 (D Band), 1600 (G Band)cm-1Indicates presence of sp2 carbon phases.

Key Methodologies

Section titled “Key Methodologies”
  1. Substrate Seeding: P-type (001) silicon wafers were seeded using a commercial nanodiamond solution (nominal 3.7 nm particles) via an ultrasonic electrostatic seeding method for 50 minutes, followed by cleaning in methanol and DI water.
  2. Graphite Paste Application: The seeded silicon wafer was adhered to a water-cooled molybdenum plate using a graphite paste. The paste contained 10% synthetic graphite, 30% modified epoxy resin (binder), and 60% oxy-hydrocarbon solvents (methyl ethyl ketone and propylene glycol methyl ether acetate).
  3. Plasma Ignition: Pure hydrogen (H2) plasma was ignited at approximately 1 torr, then adjusted to the operating pressure of 30 torr.
  4. Gas Introduction: Methane (CH4) and Carbon Dioxide (CO2) were introduced to form the plasma gas feeds (Composition #1: 5% CH4, 1% CO2 in H2; Composition #2: 5% CH4 in H2).
  5. Initial Growth Phase (Additive Domination): During the first 10-20 minutes, the vaporized paste components (solvents, binder, and nano-graphite) dissociated in the plasma, generating a high concentration of CH and C2 radicals (confirmed by OES). This transient radical boost promoted rapid lateral growth of the diamond seeds.
  6. Repetitive Growth Strategy: To maintain the high growth rate and large grain size beyond the initial 20 minutes, the process was stopped, the substrate was removed, 0.018 g of graphite paste was reapplied, and the growth was resumed for subsequent 20-minute periods.
  7. Characterization: Film quality and morphology were assessed using Optical Emission Spectroscopy (OES) for plasma chemistry, Scanning Electron Microscopy (SEM) for grain size and thickness, and Raman spectroscopy (458 nm laser) for carbon bonding analysis (sp3/sp2 ratio).

Commercial Applications

Section titled “Commercial Applications”

This low-temperature, high-quality diamond deposition technology is primarily aimed at integrating diamond films into advanced semiconductor manufacturing flows.

  • High-Performance Integrated Circuits (ICs): Diamond serves as a superior dielectric material (high dielectric strength, low leakage current) for 3D nanostructures and interconnects in next-generation ICs, where conventional high-temperature CVD processes are prohibited.
  • Thermal Management in High-Power Electronics: The large-grain diamond films deposited at 450 °C are critical for fabricating high-efficiency diamond heat spreaders directly onto sensitive semiconductor materials (e.g., GaN, SiC, or Si) to manage extreme heat flux.
  • Radio Frequency (RF) and Microwave Devices: Utilizing diamond’s high thermal conductivity and low dielectric loss tangent to improve the power handling and reliability of high-frequency components.
  • Micro- and Nano-Electro-Mechanical Systems (MEMS/NEMS): Providing mechanically robust, wear-resistant, and chemically inert coatings for micro-scale moving parts and sensors.
  • Related 6ccvd.com Products:
    • Diamond-on-Silicon Wafers: Enabling the mass production of thermally enhanced silicon substrates for advanced packaging.
    • Diamond Dielectrics: Offering ultra-high quality insulating layers for advanced 3D IC architectures.
    • High-Quality Polycrystalline Diamond Films: Used in applications requiring superior thermal dissipation and mechanical hardness.
View Original Abstract

Modern integrated circuits (ICs) take advantage of three-dimensional (3D) nanostructures in devices and interconnects to achieve high-speed and ultra-low-power performance. The choice of electrical insulation materials with excellent dielectric strength, electrical resistivity, strong mechanical strength, and high thermal conductivity becomes critical. Diamond possesses these properties and is recently recognized as a promising dielectric material for the fabrication of advanced ICs, which are sensitive to detrimental high-temperature processes. Therefore, a high-rate low-temperature deposition technique for large-grain, high-quality diamond films of the thickness of a few tens to a few hundred nanometers is desirable. The diamond growth rate by microwave plasma chemical vapor deposition (MPCVD) decreases rapidly with lowering substrate temperature. In addition, the thermal conductivity of non-diamond carbon is much lower than that of diamond. Furthermore, a small-grain diamond film suffers from poor thermal conductivity due to frequent phonon scattering at grain boundaries. This paper reports a novel MPCVD process aiming at high growth rate, large grain size, and high sp3/sp2 ratio for diamond films deposited on silicon. Graphite paste containing nanoscale graphite and oxy-hydrocarbon binder and solvent vaporizes and mixes with gas feeds of hydrogen, methane, and carbon dioxide to form plasma. Rapid diamond growth of diamond seeds at 450 °C by the plasma results in large-grained diamond films on silicon at a high deposition rate of 200 nm/h.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2019 - Investigation of diamond deposition on the diamond, silicon and quartz substrates by microwave plasma chemical vapor deposition and Monte Carlo simulations [Crossref]
  2. 1991 - Towards a general concept of diamond chemical vapour deposition [Crossref]
  3. 2018 - Morphology and mechanical behavior of diamond films fabricated by IH-MPCVD [Crossref]
  4. 1992 - Unusually high thermal conductivity in diamond films [Crossref]
  5. 2006 - Thermal conduction in nanocrystal-line diamond films: Effects of the grain boundary scattering and nitrogen doping [Crossref]
  6. 2017 - Thermal conductivity of free-standing CVD diamond films by growing on both nuclear and growth sides [Crossref]
  7. 1999 - On the nature of grain boundaries in nanocrystalline diamond [Crossref]
  8. 2002 - Diamond deposition at low temperature by using CH4/H2 gas mixture [Crossref]
  9. 1996 - Low temperature limits of diamond film growth by microwave plasma-assisted CVD [Crossref]

Reads Similar to This

Heat-conducting properties of thermobarically-sintered detonation nanodiamond All‐Optical Electric Field Sensing with Nanodiamond‐Doped Polymer Thin Films Exciton dominated optical properties of atomically thin semiconductors