Patent Application
20100178490
1. Field of the Invention
This invention relates generally to deposition of barrier layers, and, more particularly, to roll-to-roll plasma enhanced chemical vapor deposition of a barrier layer comprising silicon and carbon.
2. Description of the Related Art
Barrier layers are commonly used to provide protection from a wide variety of potentially damaging conditions in the environment. For example, hydrophobic barrier layers may be used to provide protection from water, opaque barrier layers may be used to provide protection against various types of radiation, scratch-resistant barrier layers may be used to provide protection from abrasion, and the like. Barrier layers may be used as protection against moisture and oxygen in drug and food packaging as well as in numerous flexible electronic devices, including liquid crystal and diode displays, photovoltaic and optical devices (including solar cells) and thin film batteries. Barrier layers are typically formed on a substrate, such as a flexible plastic films or a metal foil.
Films of hydrogenated silicon oxycarbide suitable for use as interlayer dielectrics or environmental barriers, and methods for producing such films are known in the art. For example, U.S. Pat. No. 6,159,871 to Loboda et al. describes a chemical vapor deposition method for producing hydrogenated silicon oxycarbide films. The CVD method described in Loboda includes introducing a reactive gas mixture comprising a methyl-containing silane and an oxygen-providing gas into a deposition chamber containing a substrate. A reaction is induced between the methyl-containing silane and oxygen-providing gas at a temperature of 25° C. to 500° C. There is a controlled amount of oxygen present during the reaction, which creates film comprising hydrogen, silicon, carbon and oxygen having a dielectric constant of 3.6 or less on the substrate.
International Application Publication No. WO 02/054484 to Loboda describes an integrated circuit including a subassembly of solid state devices formed into a substrate made of a semiconducting material. The integrated circuit also includes metal wiring connecting the solid state devices. A diffusion barrier layer is formed on at least the metal wiring and the diffusion barrier layer is an alloy film having a composition of SiwCxOyHz, where w has a value of 10 to 33, x has a value of 1 to 66, y has a value of 1 to 66, z has a value of 0.1 to 60, and w+x+y+z=100 atomic %.
U.S. Pat. No. 6,593,655 to Loboda et al. describes a semiconductor device that has a film formed thereon. The film is produced by introducing a reactive gas mixture comprising a methyl-containing silane and an oxygen providing gas into a deposition chamber containing a semiconductor device and inducing a reaction between the methyl-containing silane and oxygen-providing gas at a temperature of 25° C. to 500° C. A controlled amount of oxygen is present during the reaction, which creates a film comprising hydrogen, silicon, carbon and oxygen having a dielectric constant of 3.6 or less on the semiconductor device.
U.S. Pat. No. 6,667,553 to Cerny et al. describes a substrate, such as a liquid crystal device, a light emitting diode display device, and an organic light emitting diode display device. A film is produced on the substrate by introducing a reactive gas mixture comprising a methyl-containing silane and an oxygen-providing gas into a deposition chamber containing the substrate. A reaction is induced between the methyl-containing silane and oxygen-providing gas at a temperature of 25° C. to 500° C. A controlled amount of oxygen is present during the reaction, which creates a film comprising hydrogen, silicon, carbon and oxygen having a dielectric constant of 3.6 or less on the substrate. The film has a light transmittance of 95% or more for light with a wavelength in the range of 400 nm to 800 nm.
United States Patent 20030215652 to P. O'Connor describes a polymeric container having a plasma-polymerized surface of an organic-containing layer of the formula SiOxCyHz. The plasma-formed barrier system may be a continuous plasma-deposited coating that has a composition that varies from the formula SiOxCyHz at the interface between the plasma layer and the polymeric container's original surface to SiOx at the surface that has become the new surface of the container in the course of the deposition process. The continuum is formed by initiating plasma in the absence of an oxidizing compound, then adding an oxidizing compound to the plasma. The concentration of the oxidizing compound is increased to a concentration that is sufficient to oxidize the precursor monomer. Alternatively, a barrier system having a continuum of composition from the substrate interface may form a dense, high-barrier portion by increasing the power density and/or the plasma density without a change of oxidizing content. Further, a combination of oxygen increase and increased power density/plasma density may develop the dense portion of the gradient barrier system.
Conventional deposition processes such as those described above use batch processing to deposit barrier layers on substrates. However, batch processing is not a continuous technique and typically requires loading the substrate into a process chamber, forming the barrier layer over the substrate, and then removing the substrate with the barrier layer formed thereon from the process chamber. Once the substrate has been removed from the process chamber, then another substrate may be placed in the process chamber so that the barrier layer may be formed on the new substrate. The time required to insert and/or remove the substrates from the chambers may increase the overall processing time required to form a barrier layer and reduce the production volume of the system.
Patent application WO 02/086185 A1 to J. Madocks relates to a Penning discharge plasma source that can be implemented in a continuous roll-to-roll method. The magnetic and electric field arrangement, similar to a Penning discharge, effectively traps the electron Hall current in a region between two surfaces. When a substrate is positioned proximate to at least one of the electrodes and is moved relative to the plasma, the substrate is plasma treated, coated or otherwise modified depending upon the process conditions.
The present invention is directed to addressing the effects of one or more of the problems set forth above.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
In one embodiment of the present invention, a method is provided for forming a barrier layer on a substrate. The method, defined as continuous roll-to-roll processing, includes providing a substrate to a processing chamber using at least one roller configured to guide the substrate through the processing chamber. The method also includes depositing a barrier layer adjacent the substrate by exposing at least one portion of the substrate that is within the processing chamber to plasma comprising a silicon-and-carbon containing precursor gas.
In another embodiment of the present invention, a barrier layer is formed on a substrate according to a process. The process includes providing the substrate to a processing chamber using at least one roller configured to guide the substrate through the processing chamber. The process, defined as Plasma Enhanced Chemical Vapor Deposition (PECVD), also includes depositing the barrier layer adjacent the substrate by exposing at least one portion of the substrate that is within the processing chamber to plasma comprising a silicon-and-carbon containing precursor gas.
In yet another embodiment of the present invention, an apparatus is provided for forming a barrier layer on a substrate. The apparatus includes a processing chamber configured to receive at least one portion of a substrate and expose said at least one portion of the substrate to plasma. The apparatus also includes at least one roller for guiding the substrate through the processing chamber so that a barrier layer is deposited adjacent the substrate by exposure to the silicon-and-carbon containing precursor gas.
In yet another embodiment of the present invention, a method is provided for forming a barrier layer on a substrate. The method includes guiding, using at least one roller, a substrate having a length, L, through a processing chamber containing plasma formed of a silicon-and-carbon containing precursor gas, with or without the addition of an inert gas and/or oxidizing reagent. The method also includes depositing a barrier layer adjacent a surface of the substrate at a selected portion of the substrate along the length, L, as the substrate is guided through the processing chamber.
The barrier layer described in the present invention has higher density and lower porosity than conventional hydrogenated silicon carbide or oxycarbide films. The barrier layer has a low water vapor transmission rate, typically in the range of 10−2-10−3 gm−2d−1.
The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
Table 1 summarizes the process parameters and properties of the barrier coatings from examples 1-4. Water permeability tests have been performed at 38° C. and 100% relative humidity (RH).
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions should be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present invention will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present invention with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present invention. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
Two rollers 120(1-2) may be used to provide portions of a flexible substrate 125 to the process chamber. The flexible substrate 125 may be a plastic substrate or a metal foil. In alternative embodiments, the plastic film substrate 125 may be formed of a polyethylene naphthalate (PEN), a polyethylene terephthalate (PET), polyester, polyethersulfone, polycarbonate, polyimide, polyfluorocarbon, and the like. The rollers 120 are also coupled to a voltage source (not shown) that may be used to establish a voltage difference between the rollers 120 and chamber walls. For example, the rollers 120 may act as a cathode or as an anode so that an electric field is formed in the process chamber. In the preferred embodiment, additional rollers may also be provided to guide the substrate 125 and/or to adjust or maintain the tension in the substrate 125. However, persons of ordinary skill in the art having benefit of the present disclosure should appreciate that the present invention is not limited to the particular number and/or configuration of rollers 120 shown in
A gas source 130 is used to provide one or more gases to the process chamber. Although a single gas source 130 is depicted in
In operation, the substrate 125 passes over the roller 120(2) into the process chamber, exposing one side of the substrate 125 to the plasma in the process chamber. A barrier layer may then be deposited on the substrate 125 while it is exposed to the plasma. For example, a barrier layer may be deposited on the portion of the substrate 125 that it is exposed to the plasma as the substrate 125 is guided through the process chamber by the rollers 120. For example, if the plasma is formed from a gas including silicon, carbon, and hydrogen, a non-gradient barrier layer may be formed of hydrogenated silicon carbide based on the structural unit SiC:H. For another example, if the plasma is formed from a gas including silicon, carbon, hydrogen, and oxygen, a barrier layer may be formed of hydrogenated silicon oxycarbide based on the structural unit SiOC:H. The substrate 125 may then pass out of the process zone 150, over the additional rollers, and be guided back into the process zone by another roller 120(2), where it is again exposed to the plasma in the process chamber so that additional portions of the barrier layer may be formed. In this way a continuous barrier coated plastic film can be manufactured.
Referring back to
The properties of barrier layers formed using the techniques described herein may be determined applying various types of metrology. Exemplary metrology techniques include determining the thickness and thickness uniformity of the barrier layer using a Tristan spectrometer; analyzing barrier layer performance using a MOCON Permatran-W permeation test system and/or the conventional Ca test, determining optical properties of the barrier layer via UV-VIS spectrometry performed with a Shimadzu UV 2401 PC spectrometer, determining the composition of the barrier layer using energy dispersion analysis of X-rays (EDAX), Rutherford backscattering spectroscopy (RBS) and Fourier transformed InfraRed (FTIR) spectroscopy, determining the surface wetability by optical measurement of the water contact angle of the barrier layer, determining the adhesion properties of the barrier layer by the standard tape test, determining the scratch resistance of the barrier layer by applying the Steelwool test, determining the film surface roughness of the barrier layer using atomic force microscopy (AFM) in tapping mode with Veeco's Dimension 5000 AFM, determining thermal stability using the conventional boiling water test, as well as using a scanning electron microscope (SEM) and/or optical microscope examinations.
Barrier coatings formed on flexible plastic substrates in this manner have low water vapor transmission rates (WVTR) that are in the range of 10−2-10−3 g.m−2d−1, as it has been determined by the Permatran-W permeability tester from Mocon Inc., and by the calcium (Ca) degradation test performed in Dow Corning Co. The barrier layers are also highly hydrophobic, e.g. the water contact angle of the barrier layers may be above 85°. The thickness of the deposited barrier layers may also depend on the web speed and the speed is typically adjusted so that the barrier layer thickness is between 0.5 and 2.0 μm. Further, the silicon carbide barrier layers are smooth. Depending on the thickness of the barrier layer, root mean square roughness (rms) is in the limits of 2-6 nm, as has been determined by atomic force microscopy (AFM). The barrier layers are transparent, typically at least 55% for light in the visible region of the electromagnetic spectrum as indicated from the ultraviolet-visual spectra of blank substrates and substrates coated with a barrier layer depicted in
The barrier layers formed using the techniques described herein can be used as protection against moisture and oxygen in food, beverage and drug packaging as well as in numerous flexible electronic devices including liquid crystal and diode displays, photovoltaic and optical devices (including solar cells) and thin film batteries.
The following examples are presented to better illustrate the coated substrates and methods of the present invention. However, these examples are intended to be illustrative and not to limit the present invention. In the examples, barrier coating deposition has been performed utilizing a single- and/or dual-asymmetric Penning discharge plasma source that operates in the medium frequency range. The temperature of the rollers in the deposition chamber has been maintained at 18-25° C. Tables 1 and 2 present some of the physical properties of the barrier layers formed according to the present examples and
Barrier coating deposition has been performed at a plasma power range of 300-500 W (Table 1). The deposition process has been conducted introducing a silicon-carbon containing precursor, namely trimethylsilane ((CH3)3SiH), in the deposition chamber or a reactive gas mixture comprising trimethylsilane ((CH3)3SiH), and argon (Ar) with gas flow rate ratios of Ar/((CH3)3SiH) up to 2.5 at a pressure range of 20-30 mTorr (Table 1). Barrier coatings have been deposited on polyethylenterephtalate (PET) film material. The thickness of the deposited barrier layers is typically around 0.75 μm. Barrier coatings contain silicon (Si), carbon (C), oxygen (O) as contaminant and hydrogen (H) in compositional ratios of Si/C=0.60-0.65 and O/Si=0.075-0.10, i.e. the material can be classified as hydrogenated silicon carbide based on the structural unit SiC:H (Table 1, FIG. 3—solid line). Barrier layer has a low water vapor transmission rate (WVTR), in the range of 10−3-10−2 g.m−2d−1, as it has been determined by the Permatran-W permeability tester from Mocon Inc. Barrier layers are smooth and well-adhered. The barrier layers could be highly absorbent in the 400 nm range of the visible light spectrum and the coated plastic substrates possess transparency, typically more than 50% for the visible light at a wavelength of 600 nm and above (
Barrier coating deposition has been performed at the power range of 250-300 W (Table 1). The deposition process has been conducted introducing a reactive gas mixture in the deposition system comprising silicon-carbon containing precursor, namely trimethylsilane ((CH3)3SiH), argon (Ar) and oxygen (O2) with gas flow ratios of Ar/((CH3)3SiH)=1.0-1.5 and O2/((CH3)3SiH)=0.5-1.25 at a pressure range of 30-50 mTorr (Table 1). In this example, the barrier layer has been deposited on both PET and PEN flexible substrates. The thickness of the deposited barrier is typically in the range of 1.5-2.0 μm. Barrier coating contains silicon (Si), carbon (C), oxygen (O) and hydrogen (H) in compositional ratios of Si/C=0.95-1.10 and O/Si=0.35-1.0, i.e. the material can be classified as hydrogenated silicon oxycarbide based on the structural unit SiOC:H (Table 1, FIG. 3—dash and dotted lines). Barrier layers have low water vapor transmission rate (WVTR), in the range of 10−3 g.m−2d−1, as it has been determined by the Permatran-W permeability tester from Mocon Inc. Barrier coatings are smooth—the root mean square roughness (rms) is in the limits of 4-6 nm. The coated plastic substrates possess transparency, typically more than 75% for the visible light at a wavelength of 500 nm and above (
Roll-to-roll deposition of barrier layers comprising silicon, carbon, hydrogen, and/or oxygen may be a very effective technique for forming barrier coated films, such as barrier plastics that may be utilized in flexible electronic devices. For example, embodiments of the trimethylsilane PECVD barrier technology described herein have been tested and successfully adapted using roll-to-roll coating system. The barrier layer deposition techniques described herein exhibit a wide range of tunability with respect to process operating conditions and barrier properties and a dynamic deposition rate up to 150 nm.m/min has been realized. Due to the energy input provided by the Penning Discharge Plasma Source, “soft” process conditions (plasma power between 200 and 300 W) may be established. Soft process conditions may be particularly appropriate for deposition of stress-reduced, crack-resistant and transparent coatings with a high level of barrier protection, namely WVTR<10−3 g.m−2d−1 and barrier improvement factor BIF>1000.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design of the equipment, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2008/055436 | 2/29/2008 | WO | 00 | 3/8/2010 |
| Number | Date | Country | |
|---|---|---|---|
| 60908498 | Mar 2007 | US |
