Plasma Enhanced Chemical Vapor Deposition of Organic Polymers

At a Glance

Metadata	Details
Publication Date	2021-06-01
Journal	Processes
Authors	Gerhard Franz
Institutions	Munich University of Applied Sciences
Citations	25
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for Advanced PECVD Applications

This document analyzes the research paper “Plasma Enhanced Chemical Vapor Deposition of Organic Polymers” (Franz, 2021) to highlight the critical role of high-purity MPCVD diamond in advanced material synthesis and to position 6CCVD as the premier supplier for researchers and engineers working in this domain.

Executive Summary

The reviewed paper validates Plasma Enhanced Chemical Vapor Deposition (PECVD) as the definitive method for synthesizing high-purity, high-performance materials, including diamond, Carbon Nanotubes (CNTs), and specialized polymers (Parylene).

PECVD Validation: Plasma activation is confirmed to be essential for breaking strong chemical bonds (e.g., CH₄) at significantly lower temperatures (e.g., SiO₂ at 300 °C) than conventional thermal CVD.
Diamond Purity Standard: The paper emphasizes that spectroscopic purity in diamond is confirmed solely by Raman spectroscopy, specifically the symmetric valence vibration peak at 1332 cm^-1, validating the quality of MPCVD-grown Single Crystal Diamond (SCD).
Conformal Coating Superiority: PECVD offers superior conformal coating capabilities compared to Physical Vapor Deposition (PVD) techniques, crucial for complex microstructures and device integration.
Process Control Requirement: Achieving high-quality films (low porosity, smooth surface, controlled crystallinity) requires precise control over plasma parameters, including RF power (e.g., 1200 W for ICP diamond) and gas flow ratios (e.g., Ar:H₂:CH₄).
Surface Functionalization: PECVD allows for precise surface functionalization, demonstrated by switching Parylene surfaces from hydrophobic to hydrophilic character in just 15 seconds using mild oxygen plasma.
6CCVD Positioning: 6CCVD specializes in supplying the ultra-high purity, highly characterized SCD and PCD materials necessary to serve as substrates or active components in the advanced PECVD systems described.

Technical Specifications

The following hard data points were extracted from the analysis of PECVD and CVD processes described in the review:

Parameter	Value	Unit	Context
SCD Purity Confirmation Peak	1332	cm^-1	Raman spectroscopy signature for sp³ hybridized diamond
CNT Purity Confirmation Peak (G Band)	1575	cm^-1	Raman signature for sp² hybridized graphene C atoms
ICP Diamond Deposition Pressure	3	Torr	Typical operating pressure in Inductively Coupled Plasma
ICP Diamond Deposition RF Power	1200	W	Power input for polycrystalline diamond growth
PECVD SiO₂ Deposition Temperature	300	°C	Achieved using plasma enhancement (vs. 500-600 °C thermal CVD)
LPCVD Polysilicon Temperature	600-650	°C	Required for SiH₄ decomposition
Parylene Precursor Sublimation Temp	120-150	°C	Conversion of di-parylene N (DPX) solid to gas
Parylene Cracking/Pyrolysis Temp	Typically 700	°C	Thermal cleavage of DPX to monomer (MPX)
Parylene N Density	1.1	g/cm³	Density used for calculating layer growth rate
Standard RF Excitation Frequencies	13.56 / 27.12	MHz	Capacitively-Coupled Plasmas (CCPs)

Key Methodologies

The research highlights several critical deposition and characterization methodologies relevant to advanced material science:

Plasma Enhanced Chemical Vapor Deposition (PECVD): Utilizes low-pressure athermic plasma to supply the energy required for breaking chemical bonds, enabling deposition at significantly lower substrate temperatures than conventional CVD.
High-Density Plasma Sources: The use of Inductively-Coupled Plasmas (ICPs) and Microwave-Driven (MW) plasmas is preferred for high-rate, high-purity synthesis (like diamond and CNTs) due to their high plasma density (up to 10¹¹ cm^-3).
Thermal CVD (Gorham Method): Employed for Parylene deposition, relying on a two-step thermal process: sublimation of the dimeric precursor (DPX) at 120-150 °C, followed by high-temperature pyrolysis (700 °C) to generate the reactive monomer (MPX).
Inert Gas Dilution: Diluting the reactive vapor with inert gases (e.g., Argon) is a key strategy to suppress volume polymerization (“snow formation”) and force the reaction toward surface polymerization, resulting in higher quality, less porous films.
Spectroscopic Characterization:
- Raman Spectroscopy: Confirmed as the definitive method for assessing the purity and sp³ hybridization of diamond (1332 cm^-1 peak) and characterizing the sp² structure of CNTs.
- FTIR Spectroscopy: Used to identify functional groups and confirm the survival of the aromatic ring structure in plasma-polymerized organic films.
Surface Analysis: Atomic Force Microscopy (AFM) and contact angle measurements are used to correlate plasma parameters (power, pressure) with surface morphology (roughness) and functional properties (hydrophobicity/hydrophilicity).

6CCVD Solutions & Capabilities

The research paper underscores the need for ultra-high purity, precisely characterized, and customizable materials—particularly diamond—to serve as substrates or active layers in advanced PECVD systems. 6CCVD’s expertise in MPCVD diamond directly addresses these requirements, offering materials that meet or exceed the purity standards discussed.

Applicable Materials

Research Application / Material Need	6CCVD Material Recommendation	Key Specification Match
High-Purity Diamond (Spectroscopic Purity 1332 cm^-1)	Optical Grade Single Crystal Diamond (SCD)	Ultra-low defect density, superior sp³ purity, and high thermal conductivity.
Conductive Diamond Electrodes (e.g., for electrochemical sensors)	Boron-Doped Diamond (BDD) (SCD or PCD)	Tailored conductivity for high-power electronics and electrochemistry.
Large-Area Hard Coatings / Substrates (DLC replacement)	Polycrystalline Diamond (PCD) Wafers	Available up to 125mm diameter, ideal for scaling industrial PECVD processes.
High-Quality Thin Films (Gate Dielectrics, Optical Windows)	Thin Film SCD (0.1µm to 500µm thickness)	Precision thickness control and exceptional surface finish (Ra < 1nm).

Customization Potential

The paper highlights the importance of substrate quality, dimensions, and surface integration for successful thin-film deposition and functionalization (e.g., for medical implants or semiconductor devices). 6CCVD offers comprehensive customization services:

Custom Dimensions and Thickness: 6CCVD provides plates and wafers up to 125mm in diameter (PCD) and offers precise thickness control for SCD and PCD films ranging from 0.1µm to 500µm. Substrates up to 10mm thick are available.
Precision Polishing: To ensure optimal interface quality for subsequent PECVD layers (like the Parylene films discussed), 6CCVD guarantees ultra-smooth surfaces: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD.
Integrated Metalization: The integration of thin films into devices often requires robust electrical contacts. 6CCVD offers in-house metalization services, including the deposition of Au, Pt, Pd, Ti, W, and Cu layers, allowing researchers to bypass external fabrication steps.
Complex Geometries: For specialized PECVD reactors or micro-device integration, 6CCVD provides custom laser cutting and shaping services.

Engineering Support

The mechanistic complexity of PECVD, particularly the trade-off between dissociation, polymerization, and surface functionalization, requires deep material expertise. 6CCVD’s in-house PhD team specializes in MPCVD growth parameters and material characterization (including Raman analysis, as emphasized in the paper). We offer consultation to assist engineers and scientists with:

Material selection for high-performance applications (e.g., selecting the appropriate BDD doping level for electrochemical projects).
Optimizing substrate preparation and surface finish to enhance adhesion and quality of subsequent PECVD coatings (like the Parylene or DLC films discussed).
Characterization services to verify the purity and crystalline quality of diamond materials used in similar PECVD synthesis and thin-film deposition projects.

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

View Original Abstract

Chemical Vapor Deposition (CVD) with its plasma-enhanced variation (PECVD) is a mighty instrument in the toolbox of surface refinement to cover it with a layer with very even thickness. Remarkable the lateral and vertical conformity which is second to none. Originating from the evaporation of elements, this was soon applied to deposit compound layers by simultaneous evaporation of two or three elemental sources and today, CVD is rather applied for vaporous reactants, whereas the evaporation of solid sources has almost completely shifted to epitaxial processes with even lower deposition rates but growth which is adapted to the crystalline substrate. CVD means first breaking of chemical bonds which is followed by an atomic reorientation. As result, a new compound has been generated. Breaking of bonds requires energy, i.e., heat. Therefore, it was a giant step forward to use plasmas for this rate-limiting step. In most cases, the maximum temperature could be significantly reduced, and eventually, also organic compounds moved into the preparative focus. Even molecules with saturated bonds (CH4) were subjected to plasmas—and the result was diamond! In this article, some of these strategies are portrayed. One issue is the variety of reaction paths which can happen in a low-pressure plasma. It can act as a source for deposition and etching which turn out to be two sides of the same medal. Therefore, the view is directed to the reasons for this behavior. The advantages and disadvantages of three of the widest-spread types, namely microwave-driven plasmas and the two types of radio frequency-driven plasmas denoted Capacitively-Coupled Plasmas (CCPs) and Inductively-Coupled Plasmas (ICPs) are described. The view is also directed towards the surface analytics of the deposited layers—a very delicate issue because carbon is the most prominent atom to form multiple bonds and branched polymers which causes multifold reaction paths in almost all cases. Purification of a mixture of volatile compounds is not at all an easy task, but it is impossible for solids. Therefore, the characterization of the film properties is often more orientated towards typical surface properties, e.g., hydrophobicity, or dielectric strength instead of chemical parameters, e.g., certain spectra which characterize the purity (infrared or Raman). Besides diamond and Carbon Nano Tubes, CNTs, one of the polymers which exhibit an almost threadlike character is poly-pxylylene, commercially denoted parylene, which has turned out a film with outstanding properties when compared to other synthetics. Therefore, CVD deposition of parylene is making inroads in several technical fields. Even applications demanding tight requirements on coating quality, like gate dielectrics for semiconductor industry and semi-permeable layers for drug eluting implants in medical science, are coming within its purview. Plasma-enhancement of chemical vapor deposition has opened the window for coatings with remarkable surface qualities. In the case of diamond and CNTs, their purity can be proven by spectroscopic methods. In all the other cases, quantitative measurements of other parameters of bulk or surface parameters, resp., are more appropriate to describe and to evaluate the quality of the coatings.

Tech Support

Original Source

DOI: https://doi.org/10.3390/pr9060980

References

1968 - Epitaxial GaAs Films Deposited by Vacuum Evaporation [Crossref]
1975 - Molecular Beam Epitaxy [Crossref]
2009 - Characterization of microwave plasmas for deposition of polyparylene [Crossref]
1997 - Improved growth and thermal stability of parylene films [Crossref]
1960 - The Chemistry of Xylylenes. III. Some Reactions of p-Xylylene that Occur by Free Radical Intermediates [Crossref]
1960 - The Chemistry of Xylylenes. VI. The Polymerization of p-Xylylene [Crossref]
1984 - Polymerization of Para-Xylylene Derivatives Parylene Polymerization. I. Deposition Kinetics for Parylene N and Parylene C
1990 - A growth mechanism for the vacuum deposition of polymeric materials [Crossref]