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Vitex Systems has developed a patented system, Barix™, which uses thin
polymer layers that are deposited alternatively with thin barrier layers.
This multilayer organic/inorganic structure has several unique features
that enable superior barrier performance.
polymer layers that are deposited alternatively with thin barrier layers.
This multilayer organic/inorganic structure has several unique features
that enable superior barrier performance.
Planarization and coverage of particles
The polymer layer is created by depositing a liquid precursor onto the surface. This
material, the Barix™ Resin System, is a low viscosity liquid that wets the surface
resulting in a coating that levels particles, surface roughness and device
topography. The liquid film is typically between 0.25 and 1.0 microns thick.
Objects and topography of several microns or more height can be planarized by the
thin liquid layer because of excellent wetting and surface tension. See the image on
the "What is Barix™?" page.
Immediately after the liquid film is formed on the surface, the liquid is converted
through the process of polymerization to a solid by exposure to ultraviolet light.
The overall process leads to the next key feature.
Clean, smooth and uniform surface
The polymer layer is formed just prior to the deposition of the barrier layer, which
completes one dyad (dyad: a barrier layer on a polymer layer). The barrier layer is
deposited by a physical vapor deposition process. This process creates a thin film
by depositing atomic and/or molecular species onto a surface. As more is
deposited, small clusters (nuclei) of material are formed. Eventually, these nuclei
combine together to form a continuous thin film.
The thickness at which the nuclei form a continuous film depends on many factors.
However, having a very clean, smooth and uniform surface, as provided by the
polymer layer, promotes consistent nucleation and the formation of a dense barrier
layer with ultra-low defect density. Vitex has shown that films as thin as 20 nm can
provide excellent barrier performance when used as part of the Barix™ structure.
Without the polymer layer, the barrier layer will exhibit non-uniform nucleation that
will lead to defects formed at the intersection of different nucleation regions. These
are often referred to as intrinsic defects, as they are created during the formation
of the film itself. In addition, the physical vapor deposition process may not be able
to cover with a continuous film the various structures and irregular particles on a
surface that has not been coated with the polymer.
Decoupling of defects
Defects that form during the growth of the thin barrier layer tend to propagate
through the thickness of the growing film. The result is that barrier performance
cannot be indefinitely improved simply by increasing the thickness of the deposited
film. Barrier layers are typically brittle materials, so thick coatings are subject to
cracking and detrimental to flexibility.
The polymer separates the barrier layers from one another and prevents the few
remaining intrinsic defects in the bottom oxide layer from propagating to the top
oxide layer. This decoupling of defects avoids the short-circuiting through the
barrier layers by forcing the water vapor to diffuse throughout the polymer layer to
reach another defect before it can penetrate the next barrier layer. The net effect
is to create a very long lag time, required for the life of the device, for the water
vapor to reach the device. This lag-time mechanism of the multilayer Barix™
structure contrasts to the more commonly measured steady-state water vapor
transmission rate (WVTR) measured by commercial instruments, such as the
MOCON Permatran™ and Aquatran™.
Click this link to see how Barix™ protects individual devices on one substrate.
The polymer layer is created by depositing a liquid precursor onto the surface. This
material, the Barix™ Resin System, is a low viscosity liquid that wets the surface
resulting in a coating that levels particles, surface roughness and device
topography. The liquid film is typically between 0.25 and 1.0 microns thick.
Objects and topography of several microns or more height can be planarized by the
thin liquid layer because of excellent wetting and surface tension. See the image on
the "What is Barix™?" page.
Immediately after the liquid film is formed on the surface, the liquid is converted
through the process of polymerization to a solid by exposure to ultraviolet light.
The overall process leads to the next key feature.
Clean, smooth and uniform surface
The polymer layer is formed just prior to the deposition of the barrier layer, which
completes one dyad (dyad: a barrier layer on a polymer layer). The barrier layer is
deposited by a physical vapor deposition process. This process creates a thin film
by depositing atomic and/or molecular species onto a surface. As more is
deposited, small clusters (nuclei) of material are formed. Eventually, these nuclei
combine together to form a continuous thin film.
The thickness at which the nuclei form a continuous film depends on many factors.
However, having a very clean, smooth and uniform surface, as provided by the
polymer layer, promotes consistent nucleation and the formation of a dense barrier
layer with ultra-low defect density. Vitex has shown that films as thin as 20 nm can
provide excellent barrier performance when used as part of the Barix™ structure.
Without the polymer layer, the barrier layer will exhibit non-uniform nucleation that
will lead to defects formed at the intersection of different nucleation regions. These
are often referred to as intrinsic defects, as they are created during the formation
of the film itself. In addition, the physical vapor deposition process may not be able
to cover with a continuous film the various structures and irregular particles on a
surface that has not been coated with the polymer.
Decoupling of defects
Defects that form during the growth of the thin barrier layer tend to propagate
through the thickness of the growing film. The result is that barrier performance
cannot be indefinitely improved simply by increasing the thickness of the deposited
film. Barrier layers are typically brittle materials, so thick coatings are subject to
cracking and detrimental to flexibility.
The polymer separates the barrier layers from one another and prevents the few
remaining intrinsic defects in the bottom oxide layer from propagating to the top
oxide layer. This decoupling of defects avoids the short-circuiting through the
barrier layers by forcing the water vapor to diffuse throughout the polymer layer to
reach another defect before it can penetrate the next barrier layer. The net effect
is to create a very long lag time, required for the life of the device, for the water
vapor to reach the device. This lag-time mechanism of the multilayer Barix™
structure contrasts to the more commonly measured steady-state water vapor
transmission rate (WVTR) measured by commercial instruments, such as the
MOCON Permatran™ and Aquatran™.
Click this link to see how Barix™ protects individual devices on one substrate.
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| How does Barix™ work? |
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| Scanning probe microscope (SPM) images of uncoated PET and after Barix coating. Surface features have been planarized. |