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Home > Nanotechnology Columns > HZO > Rethink Thin: Plasma-Enhanced Chemical Vapor Deposition for Nanocoating Protection

Benjamin Lawrence
Engineering Consultant
HZO

Abstract:
While several methodologies exist to apply nanocoatings to substrates, plasma-enhanced chemical vapor deposition (PECVD) draws attention due to appealing physical film properties and enhanced process control. This article offers a high-level look at the deposition methodology.

March 19th, 2021

Rethink Thin: Plasma-Enhanced Chemical Vapor Deposition for Nanocoating Protection

Among the numerous purposes that nanocoatings serve, protecting electronic components from harmful elements - such as contaminants or corrosion - is top of the list for many engineers. At exceptional thinness, protective nanocoatings provide OEMs and product design teams with the capacity to drive down costs associated with warranty claims and repairs, mitigate risk, such as downtime, and cultivate brand loyalty and market confidence with impressively reliable products.

While several methodologies exist to apply nanocoatings to substrates, plasma-enhanced chemical vapor deposition (PECVD) draws attention due to appealing physical film properties and enhanced process control. This article offers a high-level look at the deposition methodology.

PECVD harnesses plasma energy created by direct current, microwave discharge, or radiofrequency, among others, to deposit nanocoatings. Regardless of the power source, PECVD equipment energizes gases to form a plasma and a mixture of radicals, ions, free electrons, molecules, and excited atoms to deposit nanocoatings to substrates. It is possible to draw upon a wide range of materials to form thin-film protection, including oxides, metals, nitrides, and polymers (fluorocarbons, silicones, hydrocarbons).

These protective films are uniform, generally resistant to thermal and chemical changes, and highly cross-linked, all attributes that lend to excellent physical properties. Furthermore, it is easy to control these film properties for varying thermal, chemical, electrical, mechanical, and optical benefits.

PECVD Applications

Plasma polymers are used in applications that require lower cost and high efficiency, including optical coatings, corrosion resistance, and dielectric films. For example, the semiconductor industry utilizes nanocoatings for device encapsulation, isolation of conductive layers, and surface passivation. Plasma-polymerized nanocoatings are also a popular means of avoiding corrosion for dielectric and optical requirements.

Other applications include:

Solar cells, semiconductor devices, and optically active device applications due to optical, mechanical, and electrical properties

Processing of printable electronic devices due to high process efficiency, large-scale patternability, lower cost, and environmentally-friendly nature

SiC (silicon carbide) PECVD films have demonstrated promise in the development of high temperature withstanding MEMs devices

SiN (silicon nitride) PECVD films are used for semiconductor applications due to higher capacitance density, breakdown voltage, and particle performance

PECVD Parameters to Consider for Optimal Performance

Internal plasma parameters, including homogeneity of discharge, the precursors used, the distribution of various species in the plasma, and the species' energy may be modified to affect the polymerized film. It is necessary to consider external plasma parameters for optimal film performance as well, including temperature, total pressure, applied voltage, flow rate, and reactor geometry.

PECVD Benefits and Drawbacks

Because it utilizes plasma energy, as opposed to just heat, PECVD allows for a wide range of precursor (material) usage, including unconventional precursors that can be used for deposition on surfaces with complex geometries, typically with lower temperature processes. These precursors can be tightly and efficiently controlled while generating few by-products. Additionally, tight control of film uniformity and composition is possible. The resulting chemistry of PECVD nanocoatings is unique and cannot be obtained by standard liquid coating deposition methods.

However, the PECVD process does have some drawbacks. For instance, ion bombardment during the process could damage some sensitive substrates. And without proper process optimization, residual and undesirable compressive stresses can occur in the deposited coating, leading to cracking.

That said, PECVD opens the door to a wide range of protection capabilities unique to the process. It is low cost and efficient and therefore proves to be a compelling candidate for the deposition of protective nanocoatings.

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