Chemical Vapor Jet Deposition of Parylene Polymer Films in Air

Abstract

Parylene films are commonly used as transparent, flexible coatings in electronic devices and biomedical applications, exhibiting barrier properties against corrosion, low dielectric constant, and moisture resistance. Reactive vapor deposition of parylene results in conformal coverage of features at room temperature, which is advantageous for passivating, for example, organic optoelectronic devices. Conventional parylene deposition methods, however, coat surfaces virtually indiscriminately and utilize separate chambers for vaporization, pyrolysis, and polymerization, resulting in a large footprint and limited processing integration ability, especially at a laboratory scale. Here, we demonstrate the vaporization and pyrolysis of the di-p-xylylene (parylene dimer) in a single compact nozzle, producing a jet of monomer that polymerizes into a film upon contact with the substrate at room temperature. A guard flow jet is employed to shield the reactive monomer molecules en route to the substrate, thereby enabling polymer deposition and patterning in ambient atmosphere. We present an analytical model predicting film growth rate as a function of process parameters (e.g., gas flow rate and source, pyrolysis & substrate temperatures). The effect of jet flow dynamics on film morphology is also discussed. A 100% increase in the lifetime of air-sensitive OLEDs is demonstrated upon encapsulation of the devices with parylene-N film deposited by this technique. Potential advantages of this approach include increased material utilization efficiency, localized conformal coating capabilities, and an apparatus that is compact, inexpensive, and does not require vacuum.

Micro- and nano-surface structures based on vapor-deposited polymers

“…A more general problem of the vapor deposition process us that the process mostly requires vacuum conditions to protect the reactive vapor species (monomers) from side reactions, which hampers the application as a continuous mass production process. A vacuum-free method [ 44 ] may solve the problem, but several engineering works and system parameters for other vapor deposition systems must be optimized. Nevertheless, vapor-deposited polymers offer unrivaled coating fidelity and precise control over the surface chemistry.…”

“…An effective maskless approach using directed UV light, for which the light passes through a previously patterned microscopic lens or is projected through a digital micromirror device, was performed to create defined patterns on vapor-deposited poly( p -xylylene) surfaces of curved microcolloids [ 38 ], microfluidic channels [ 39 ], complex stent devices [ 40 – 42 ], and intraocular lens (IOL) devices [ 43 ]. Jet deposition was used to prepare a poly( p -xylylene) coating under atmospheric conditions and enabled the possibility of direct patterning/writing during the vapor deposition process [ 44 ]. A patterning mask made of colloidal crystals has also been demonstrated for the vapor deposition of polymers without requiring photolithographic processes or a stamp [ 45 ].…”

Polymer-Based Gate Dielectrics for Organic Field-Effect Transistors

“…The most widely studied class of CVDcoated polymers is parylene and its derivatives. Shtein et al 92 reported the chemical vapor jet deposition of parylene polymers, which resulted in conformal coverage of features at room temperature and under air condition. This process included the vaporization and pyrolysis of the di-p-xylylene (parylene dimer) in a single compact nozzle, producing a jet of monomer that polymerized into a film toward the substrate in contact.…”

Physical Supercritical Fluid Deposition: Patterning Solution Processable Materials on Curved and Flexible Surfaces

“…Most commercial technologies using organic semiconductors employ physical vapor deposition to create thin films. The technique is robust and scalable, and fine shadow masks can be used for micrometer-scale resolution. − However, the technique requires that the molecules of interest sublime at a temperature lower than their decomposition temperature, limiting the molecular weight of the materials that can be deposited.…”