Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/06—Interconnection of layers permitting easy separation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/62—Plasma-deposition of organic layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/28—Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material
  • C03C17/32—Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material with synthetic or natural resins
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C27/00—Joining pieces of glass to pieces of other inorganic material; Joining glass to glass other than by fusing
  • C03C27/06—Joining glass to glass by processes other than fusing
  • C03C27/10—Joining glass to glass by processes other than fusing with the aid of adhesive specially adapted for that purpose
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
  • C09J5/02—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers involving pretreatment of the surfaces to be joined
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2218/00—Methods for coating glass
  • C03C2218/30—Aspects of methods for coating glass not covered above
  • C03C2218/32—After-treatment
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2400/00—Presence of inorganic and organic materials
  • C09J2400/10—Presence of inorganic materials
  • C09J2400/14—Glass
  • C09J2400/143—Glass in the substrate
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2400/00—Presence of inorganic and organic materials
  • C09J2400/10—Presence of inorganic materials
  • C09J2400/14—Glass
  • C09J2400/146—Glass in the pretreated surface to be joined

Definitions

• the present invention is directed to articles and methods for processing flexible sheets on carriers and, more particularly to articles and methods for processing flexible glass sheets on glass carriers.
• display devices can be manufactured using a glass carrier laminated to one or more thin glass substrates. It is anticipated that the low permeability and improved temperature and chemical resistance of the thin glass will enable higher performance longer lifetime flexible displays.
• FPD processes require a robust bond for thin glass bound to a carrier.
• FPD processes typically involve vacuum deposition (sputtering metals, transparent conductive oxides and oxide semiconductors, Chemical Vapor Deposition (CVD) deposition of amorphous silicon, silicon nitride, and silicon dioxide, and dry etching of metals and insulators), thermal processes (including -300 - 400°C CVD deposition, up to 600°C p-Si crystallization, 350 - 450°C oxide semiconductor annealing, up to 650°C dopant annealing, and -200 - 350°C contact annealing), acidic etching (metal etch, oxide semiconductor etch), solvent exposure (stripping photoresist, deposition of polymer encapsulation), and ultrasonic exposure (in solvent stripping of photoresist and aqueous cleaning, typically in alkaline solutions).
• vacuum deposition sputtering metals, transparent conductive oxides and oxide semiconductors, Chemical Vap
• Adhesive wafer bonding has been widely used in Micromechanical Systems (MEMS) and semiconductor processing for back end steps where processes are less harsh.
• MEMS Micromechanical Systems
• Commercial adhesives by Brewer Science and Henkel are typically thick polymer adhesive layers, 5 - 200 microns thick. The large thickness of these layers creates the potential for large amounts of volatiles, trapped solvents, and adsorbed species to contaminate FPD processes. These materials thermally decompose and outgas above ⁇ 250°C. The materials also may cause contamination in downstream steps by acting as a sink for gases, solvents and acids which can outgas in subsequent processes.
• US Provisional Application Serial No. 61/596,727 filed on February 8, 2012, entitled Processing Flexible Glass with a Carrier discloses that the concepts therein involve bonding a thin sheet, for example, a flexible glass sheet, to a carrier initially by van der Waals forces, then increasing the bond strength in certain regions while retaining the ability to remove portions of the thin sheet after processing the thin sheet/carrier to form devices (for example, electronic or display devices, components of electronic or display devices, organic light emitting device (OLED) materials, photo-voltaic (PV) structures, or thin film transistors), thereon.
• devices for example, electronic or display devices, components of electronic or display devices, organic light emitting device (OLED) materials, photo-voltaic (PV) structures, or thin film transistors
• At least a portion of the thin glass is bonded to a carrier such that there is prevented device process fluids from entering between the thin sheet and carrier, whereby there is reduced the chance of contaminating downstream processes, i.e., the bonded seal portion between the thin sheet and carrier is hermetic, and in some preferred
• this seal encompasses the outside of the article thereby preventing liquid or gas intrusion into or out of any region of the sealed article.
• US '727 goes on to disclose that in low temperature polysilicon (LTPS) (low temperature compared to solid phase crystallization processing which can be up to about 750°C) device fabrication processes, temperatures approaching 600°C or greater, vacuum, and wet etch environments may be used. These conditions limit the materials that may be used, and place high demands on the carrier/thin sheet. Accordingly, what is desired is a carrier approach that utilizes the existing capital infrastructure of the manufacturers, enables processing of thin glass, i.e., glass having a thickness ⁇ 0.3 mm thick, without contamination or loss of bond strength between the thin glass and carrier at higher processing temperatures, and wherein the thin glass de-bonds easily from the carrier at the end of the process.
• LTPS low temperature polysilicon
• the glass surfaces are cleaned to remove all metal, organic and particulate residues, and to leave a mostly silanol terminated surface.
• the glass surfaces are first brought into intimate contact where van der Waals and/or Hydrogen- bonding forces pull them together. With heat and optionally pressure, the surface silanol groups condense to form strong covalent Si-O-Si bonds across the interface, permanently fusing the glass pieces. Metal, organic and particulate residue will prevent bonding by obscuring the surface preventing the intimate contact required for bonding.
• a high silanol surface concentration is also required to form a strong bond as the number of bonds per unit area will be determined by the probability of two silanol species on opposing surfaces reacting to condense out water.
• Zhuravlel has reported the average number of hydro xyls per nm 2 for well hydrated silica as 4.6 to 4.9.
• Zhuravlel, L. T. The Surface Chemistry of Amorphous Silika, Zhuravlev Model, Colloids and Surfaces A: Physiochemical Engineering Aspects 173 (2000) 1-38.
• a non-bonding region is formed within a bonded periphery, and the primary manner described for forming such non-bonding area is increasing surface roughness.
• An average surface roughness of greater than 2 nm Ra can prevent glass to glass bonds forming during the elevated temperature of the bonding process.
• the articles and methods for processing thin sheets with carriers in US '727 and US '880 are able to withstand the harsh environments of FPD processing, undesirably for some applications, reuse of the carrier is prevented by the strong covalent bond between thin glass and glass carrier in the bonding region that is bonded by covalent, for example Si-O-Si, bonding with adhesive force -1000-2000 mJ/m 2 , on the order of the fracture strength of the glass. Prying or peeling cannot be used to separate the covalently bonded portion of the thin glass from the carrier and, thus, the entire thin sheet cannot be removed from the carrier. Instead, the non-bonded areas with the devices thereon are scribed and extracted leaving a bonded periphery of the thin glass sheet on the carrier.
• Such controlled bonding can be utilized to create an article having a re-usable carrier, or alternately an article having patterned areas of controlled bonding and covalent bonding between a carrier and a sheet.
• the present disclosure provides surface modification layers (including various materials and associated surface heat treatments), that may be provided on the thin sheet, the carrier, or both, to control both room-temperature van der Waals, and/or hydrogen, bonding and high temperature covalent bonding between the thin sheet and carrier.
• the room-temperature bonding may be controlled so as to be sufficient to hold the thin sheet and carrier together during vacuum processing, wet processing, and/or ultrasonic cleaning processing.
• the high temperature covalent bonding may be controlled so as to prevent a permanent bond between the thin sheet and carrier during high temperature processing, as well as maintain a sufficient bond to prevent delamination during high temperature processing.
• the surface modification layers may be used to create various controlled bonding areas (wherein the carrier and sheet remain sufficiently bonded through various processes, including vacuum processing, wet processing, and/or ultrasonic cleaning processing), together with covalent bonding regions to provide for further processing options, for example, maintaining hermeticity between the carrier and sheet even after dicing the article into smaller pieces for additional device processing.
• some surface modification layers provide control of the bonding between the carrier and sheet while, at the same time, reduce outgassing emissions during the harsh conditions in an FPD (for example LTPS) processing environment, including high temperature and/or vacuum processing, for example.
• FPD for example LTPS
• some surface modification layers may be used on a carrier having a glass bonding surface to controllably bond a thin sheet having a polymer bonding surface.
• the polymer bonding surface may be part of a polymer thin sheet on which electronic or other structures are formed or, alternatively, the polymer bonding surface may be part of a composite sheet comprising a glass layer on which the electronic or other structures are formed.
• FIG. 1 is a schematic side view of an article having carrier bonded to a thin sheet with a surface modification layer therebetween.
• FIG. 2 is an exploded and partially cut-away view of the article in FIG. 1.
• FIG. 3 is a graph of surface hydroxyl concentration on silica as a function of temperature.
• FIG. 4 is a graph of the surface energy of an SCI -cleaned sheet of glass as a function annealing temperature.
• FIG. 5 is a graph of the surface energy of a thin fluoropolymer film deposited on a sheet of glass as a function of the percentage of one of the constituent materials from which the film was made.
• FIG. 6 is a schematic top view of a thin sheet bonded to a carrier by bonding areas.
• FIG. 7 is a schematic side view of a stack of glass sheets
• FIG. 8 is an exploded view of one embodiment of the stack in FIG. 7.
• FIG. 9 is a schematic view of a testing setup
• FIG. 10 is a collection of graphs of surface energy (of different parts of the test setup of FIG. 9) versus time for a variety of materials under different conditions.
• FIG. 1 1 is a graph of change in % bubble area versus temperature for a variety of materials.
• FIG. 12 is another graph of change in % bubble area versus temperature for a variety of materials.
• FIG. 13 is a graph of the surface energy of a fluoropolymer film deposited on a sheet of glass as a function of the percentage of one of the gasses used during deposition.
• FIG. 13 A is a graph of the surface energy of a fluoropolymer film deposited on a sheet of glass as a function of the percentage of one of the gasses used during deposition.
• FIG. 14 is a graph of surface energy versus deposition time for a surface modification layer.
• FIG. 15 is graph of thickness versus deposition time, on a log-log scale, for a surface modification layer.
• FIG. 16 is a graph of surface energy versus treatment temperature for different surface modification layers.
• FIG. 17 is a graph of surface modification layer surface coverage.
• FIG. 18 is a summary of performance for an organic transistor fabricated on a 200 micron PEN film bonded to a glass carrier.
• Ranges can be expressed herein as from “about” one particular value, and/or to "about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
• the carrier In order to maintain advantageous surface shape characteristics, the carrier is typically a display grade glass substrate. Accordingly, in some situations, it is wasteful and expensive to merely dispose of the carrier after one use. Thus, in order to reduce costs of display manufacture, it is desirable to be able to reuse the carrier to process more than one thin sheet substrate.
• the present disclosure sets forth articles and methods for enabling a thin sheet to be processed through the harsh environment of the FPD processing lines, including high temperature processing— wherein high temperature processing is processing at a temperature > 400°C, and may vary depending upon the type of device being made, for example, temperatures up to about 450°C as in amorphous silicon or amorphous indium gallium zinc oxide (IGZO) backplane processing, up to about 500-550°C as in crystalline IGZO processing, or up to about 600-650°C as is typical in LTPS processes— and yet still allows the thin sheet to be easily removed from the carrier without damage (for example, wherein one of the carrier and the thin sheet breaks or cracks into two or more pieces) to the thin sheet or carrier, whereby the carrier may be reused.
• high temperature processing is processing at a temperature > 400°C, and may vary depending upon the type of device being made, for example, temperatures up to about 450°C as in amorphous silicon or amorphous indium gallium zinc oxide (IGZO
• an article 2 has a thickness 8, and includes a carrier 10 having a thickness 18, a thin sheet 20 (i.e., one having a thickness of ⁇ 300 microns, including but not limited to thicknesses of, for example, 10-50 microns, 50-100 microns, 100- 150 microns, 150-300 microns, 300, 250, 200 190, 180, 170, 160, 150 140, 130, 120 110 100, 90, 80, 70, 60, 50, 40 30, 20, or 10, microns) having a thickness 28, and a surface modification layer 30 having a thickness 38.
• a carrier 10 having a thickness 18, a thin sheet 20 (i.e., one having a thickness of ⁇ 300 microns, including but not limited to thicknesses of, for example, 10-50 microns, 50-100 microns, 100- 150 microns, 150-300 microns, 300, 250, 200 190, 180, 170, 160, 150 140, 130, 120 110 100, 90, 80, 70, 60, 50, 40
• the article 2 is designed to allow the processing of thin sheet 20 in equipment designed for thicker sheets (i.e., those on the order of > .4mm, e.g., .4 mm, .5 mm, .6 mm, .7 mm, .8 mm, .9 mm, or 1.0 mm) although the thin sheet 20 itself is ⁇ 300 microns. That is, the thickness 8, which is the sum of thicknesses 18, 28, and 38, is designed to be equivalent to that of the thicker sheet for which a piece of equipment— for example, equipment designed to dispose electronic device components onto substrate sheets— was designed to process.
• thickness 18 would be selected as 400 microns, assuming that thickness 38 is negligible. That is, the surface modification layer 30 is not shown to scale; instead, it is greatly exaggerated for sake of illustration only. Additionally, the surface modification layer is shown in cut-away. In actuality, the surface modification layer would be disposed uniformly over the bonding surface 14 when providing a reusable carrier.
• thickness 38 will be on the order of nanometers, for example 0.1 to 2.0, or up to 10 nm, and in some instances may be up to 100 nm. The thickness 38 may be measured by ellipsometer.
• the presence of a surface modification layer may be detected by surface chemistry analysis, for example by ToF Sims mass spectrometry. Accordingly, the contribution of thickness 38 to the article thickness 8 is negligible and may be ignored in the calculation for determining a suitable thickness 18 of carrier 10 for processing a given thin sheet 20 having a thickness 28.
• surface modification layer 30 has any significant thickness 38, such may be accounted for in determining the thickness 18 of a carrier 10 for a given thickness 28 of thin sheet 20, and a given thickness for which the processing equipment was designed.
• Carrier 10 has a first surface 12, a bonding surface 14, a perimeter 16, and thickness 18. Further, the carrier 10 may be of any suitable material including glass, for example.
• the carrier need not be glass, but instead can be ceramic, glass-ceramic, or metal (as the surface energy and/or bonding may be controlled in a manner similar to that described below in connection with a glass carrier). If made of glass, carrier 10 may be of any suitable composition including alumino-silicate, boro-silicate, alumino-boro-silicate, soda-lime- silicate, and may be either alkali containing or alkali-free depending upon its ultimate application.
• Thickness 18 may be from about 0.2 to 3 mm, or greater, for example 0.2, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7, 1.0, 2.0, or 3 mm, or greater, and will depend upon the thickness 28, and thickness 38 when such is non-negligible, as noted above.
• the carrier 10 may be made of one layer, as shown, or multiple layers (including multiple thin sheets of the same or a different material) that are bonded together. Further, the carrier may be of a Gen 1 size or larger, for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater).
• the thin sheet 20 has a first surface 22, a bonding surface 24, a perimeter 26, and thickness 28. Perimeters 16 and 26 may be of any suitable shape, may be the same as one another, or may be different from one another. Further, the thin sheet 20 may be of any suitable material including glass, ceramic, or glass-ceramic, for example. In some instances, the thin sheet 20 may be a polymer or a composite sheet having polymer and/or glass bonding surfaces. When made of glass, thin sheet 20 may be of any suitable composition, including alumino-silicate, boro-silicate, alumino-boro-silicate, soda- lime-silicate, and may be either alkali containing or alkali free depending upon its ultimate application.
• the coefficient of thermal expansion of the thin sheet could be matched relatively closely with that of the carrier to prevent warping of the article during processing at elevated temperatures.
• a polymer thin sheet can be used with a glass carrier.
• the thickness 28 of the thin sheet 20 is 300 microns or less, as noted above.
• the thin sheet may be of a Gen 1 size or larger, for example, Gen 2, Gen 3, Gen 4, Gen 5, Gen 8 or larger (e.g., sheet sizes from 100 mm x 100 mm to 3 meters x 3 meters or greater).
• flat panel display (FPD) processing may include wet ultrasonic, vacuum, and in some instances high temperature (e.g., > 400°C), processing.
• high temperature e.g., > 400°C
• the temperature may be > 500°C, or > 600°C, and up to 650°C.
• the bonding surface 14 In order to survive the harsh environment in which article 2 will be processed, as during FPD manufacture for example, the bonding surface 14 should be bonded to bonding surface 24 with sufficient strength so that the thin sheet 20 does not separate from carrier 10. And this strength should be maintained through the processing so that the thin sheet 20 does not separate from the carrier 10 during processing. Further, to allow the thin sheet 20 to be removed from carrier 10 (so that carrier 10 may be reused), the bonding surface 14 should not be bonded to bonding surface 24 too strongly either by the initially designed bonding force, and/or by a bonding force that results from a modification of the initially designed bonding force as may occur, for example, when the article undergoes processing at high temperatures, e.g., temperatures of > 400°C.
• the surface modification layer 30 may be used to control the strength of bonding between bonding surface 14 and bonding surface 24 so as to achieve both of these objectives.
• the controlled bonding force is achieved by controlling the contributions of van der Waals (and/or hydrogen bonding) and covalent attractive energies to the total adhesion energy which is controlled by modulating the polar and non-polar surface energy components of the thin sheet 20 and the carrier 10.
• This controlled bonding is strong enough to survive FPD processing (including wet, ultrasonic, vacuum, and thermal processes including temperatures > 400°C, and in some instances, processing temperatures of > 500°C, or > 600°C, and up to 650°C.) and remain de-bondable by application of sufficient separation force and yet by a force that will not cause catastrophic damage to the thin sheet 20 and/or the carrier 10.
• FPD processing including wet, ultrasonic, vacuum, and thermal processes including temperatures > 400°C, and in some instances, processing temperatures of > 500°C, or > 600°C, and up to 650°C.
• the surface modification layer 30 is shown as a solid layer between thin sheet 20 and carrier 10, such need not be the case.
• the layer 30 may be on the order of 0.1 to 2 nm thick, and may not completely cover every bit of the bonding surface 14.
• the coverage may be ⁇ 100%, from 1% to 100%, from 10% to 100%, from 20% to 90%, or from 50% to 90%.
• the layer 30 may be up to 10 nm thick, or in other embodiments even up to 100 nm thick.
• the surface modification layer 30 may be considered to be disposed between the carrier 10 and thin sheet 20 even though it may not contact one or the other of the carrier 10 and thin sheet 20.
• an important aspect of the surface modification layer 30 is that it modifies the ability of the bonding surface 14 to bond with bonding surface 24, thereby controlling the strength of the bond between the carrier 10 and the thin sheet 20.
• the material and thickness of the surface modification layer 30, as well as the treatment of the bonding surfaces 14, 24 prior to bonding, can be used to control the strength of the bond (energy of adhesion) between carrier 10 and thin sheet 20.
• the covalent adhesion energy is rather common, as in silicon wafer bonding where an initially hydrogen bonded pair of wafers are heated to a higher temperature to convert much or all the silanol-silanol hydrogen bonds to Si-O-Si covalent bonds. While the initial, room temperature, hydrogen bonding produces an adhesion energy of the order of ⁇ 100-200mJ/m 2 which allows separation of the bonded surfaces, a fully covalently bonded wafer pair as achieved during high temperature processing (on the order of 400 to 800 °C) has adhesion energy of - 1000- 3000 mJ/m 2 which does not allow separation of the bonded surfaces; instead, the two wafers act as a monolith.
• the adhesion energy would be that of the coating material, and would be very low leading to low or no adhesion between the bonding surfaces 14, 24, whereby the thin sheet 20 would not be able to be processed on carrier 10.
• the inventors have found various manners of providing a tunable surface modification layer 30 leading to an adhesion energy that is between these two extremes, and such that there can be produced a controlled bonding that is sufficient enough to maintain a pair of glass substrates (for example a glass carrier 10 and a thin glass sheet 20) bonded to one another through the rigors of FPD processing but also of a degree that (even after high temperature processing of, e.g. > 400°C) allows the detachment of the thin sheet 20 from the carrier 10 after processing is complete.
• the detachment of the thin sheet 20 from the carrier 10 can be performed by mechanical forces, and in such a manner that there is no catastrophic damage to at least the thin sheet 20, and preferably also so that there is no catastrophic damage to the carrier 10.
• Equation (5) describes that the adhesion energy is a function of four surface energy parameters plus the covalent and electrostatic energy, if any.
• An appropriate adhesion energy can be achieved by judicious choice of surface modifiers, i.e., of surface modification layer 30, and/or thermal treatment of the surfaces prior to bonding.
• the appropriate adhesion energy may be attained by the choice of chemical modifiers of either one or both of bonding surface 14 and bonding surface 24, which in turn control both the van der Waal (and/or hydrogen bonding, as these terms are used
• adhesion energy as well as the likely covalent bonding adhesion energy resulting from high temperature processing (e.g., on the order of > 400°C).
• high temperature processing e.g., on the order of > 400°C.
• Control of the initial van der Waals (and/or hydrogen) bonding at room temperature is performed so as to provide a bond of one surface to the other to allow vacuum and or spin-rinse-dry (SRD) type processing, and in some instances also an easily formed bond of one surface to the other— wherein the easily formed bond can be performed at room temperature without application of externally applied forces over the entire area of the thin sheet 20 as is done in pressing the thin sheet 20 to the carrier 10 with a squeegee, or with a reduced pressure environment. That is, the initial van der Waals bonding provides at least a minimum degree of bonding holding the thin sheet and carrier together so that they do not separate if one is held and the other is allowed to be subjected to the force of gravity.
• SRD spin-rinse-dry
• the initial van der Walls (and/or hydrogen) bonding will be of such an extent that the article may also go through vacuum, SRD, and ultrasonic processing without the thin sheet delaminating from the carrier.
• This precise control of both van der Waal (and/or hydrogen bonding) and covalent interactions at appropriate levels via surface modification layer 30 (including the materials from which it is made and/or the surface treatment of the surface to which it is applied), and/or by heat treatment of the bonding surfaces prior to bonding them together achieves the desired adhesion energy that allows thin sheet 20 to bond with carrier 10 throughout FPD style processing, while at the same time, allowing the thin sheet 20 to be separated (by an appropriate force avoiding damage to the thin sheet 20 and/or carrier) from the carrier 10 after FPD style processing.
• electrostatic charge could be applied to one or both glass surfaces to provide another level of control of the adhesion energy.
• FPD processing for example p-Si and oxide TFT fabrication typically involve thermal processes at temperatures above 400°C, above 500°C, and in some instances at or above 600°C, up to 650°C which would cause glass to glass bonding of a thin glass sheet 20 with a glass carrier 10 in the absence of surface modification layer 30. Therefore controlling the formation of Si-O-Si bonding leads to a reusable carrier.
• One method of controlling the formation of Si-O-Si bonding at elevated temperature is to reduce the concentration of surface hydro xyls on the surfaces to be bonded.
• FIG. 3 which is Iler's plot (R. K. Filer: The Chemistry of Silica (Wiley- Interscience, New York, 1979) of surface hydro xyl concentration on silica as a function of temperature, the number of hydro xyls (OH groups) per square nm decreases as the temperature of the surface increases.
• heating a silica surface and by analogy a glass surface, for example bonding surface 14 and/or bonding surface 24 reduces the
• a controlled bonding area that is, a bonding area that provides a sufficient room-temperature bond between the thin sheet 20 and carrier 10 to allow the article 2 to be processed in FPD type processes (including vacuum and wet processes), and yet one that controls covalent bonding between the thin sheet 20 and carrier 10 (even at elevated temperatures > 400°C) so as to allow the thin sheet 20 to be removed from the carrier 10 (without damage to at least the thin sheet, and preferably without damage to the carrier also) after the article 2 has finished high temperature processing, for example, FPD type processing or LTPS processing.
• FPD type processes including vacuum and wet processes
• covalent bonding between the thin sheet 20 and carrier 10 even at elevated temperatures > 400°C
• LTPS and Oxide TFT processes appear to be the most stringent at this time and, thus, tests representative of steps in these processes were chosen, as these are desired applications for the article 2.
• Vacuum processes, wet cleaning (including SRD and ultrasonic type processes) and wet etching are common to many FPD applications.
• Typical aSi TFT fabrication requires processing up to 320°C. Annealing at 400°C is used in oxide TFT processes, whereas crystallization and dopant activation steps over 600°C are used in LTPS processing.
• the following five tests were used to evaluate the likelihood that a particular bonding surface preparation and surface modification layer 30 would allow a thin sheet 20 to remain bonded to a carrier 10 throughout FPD processing, while allowing the thin sheet 20 to be removed from the carrier 10 (without damaging the thin sheet 20 and/or the carrier 10) after such processing (including processing at temperatures > 400°C).
• the tests were performed in order, and a sample progressed from one test to the next unless there was failure of the type that would not permit the subsequent testing.
• Vacuum testing Vacuum compatibility testing was performed in an STS Multiplex PECVD loadlock (available from SPTS, Newport, UK) -The loadlock was pumped by an Ebara A10S dry pump with a soft pump valve (available from Ebara
• Failure as indicated by a notation of "F” in the "SRD” column of the tables below, was deemed to have occurred if there was: (a) a loss of adhesion between the carrier and the thin sheet (by visual inspection with the naked eye, wherein failure was deemed to have occurred if the thin sheet had fallen off of the carrier or was partially debonded therefrom); (b) bubbling between the carrier and the thin sheet (as determined by visual inspection with the naked eye - samples were photographed before and after the processing, and then compared, failure was determined to have occurred if defects increased in size by dimensions visible to the unaided eye); or (c) movement of the thin sheet relative to the carrier (as determined by visual observation with the naked eye - samples were photographed before and after testing, wherein failure was deemed to have occurred if there was a movement of bond defects, e.g., bubbles, or if edges debonded, or if there was a movement of the thin sheet on the carrier); or (d) penetration of water under the thin sheet (as determined by visual inspection
• Failure as indicated by a notation of "F” in the "400°C” column of the tables below, was deemed to have occurred if there was: (a) a loss of adhesion between the carrier and the thin sheet (by visual inspection with the naked eye, wherein failure was deemed to have occurred if the thin sheet had fallen off of the carrier or was partially debonded therefrom); (b) bubbling between the carrier and the thin sheet (as determined by visual inspection with the naked eye - samples were photographed before and after the processing, and then compared, failure was determined to have occurred if defects increased in size by dimensions visible to the unaided eye); or (c) increased adhesion between the carrier and the thin sheet whereby such increased adhesion prevents debonding (by insertion of a razor blade between the thin sheet and carrier, and/or by sticking a piece of KaptonTM tape, 1" wide x 6" long with 2-3" attached to 100mm square thin glass ( K102 series from Saint Gobain Performance Plastic, Hoosik Y) to the thin sheet and pulling on the
• 600°C process compatibility testing was performed using an Alwin21 Accuthermo610 RTP.
• a carrier with a thin sheet was heated in a chamber cycled from room temperature to 600°C at 9.5°C/min, held at 600°C for 600seconds, and then cooled at l °C/min to 300°C. The carrier and thin sheet were then allowed to cool to room temperature.
• Failure as indicated by a notation of "F" in the "600°C” column of the tables below, was deemed to have occurred if there was: (a) a loss of adhesion between the carrier and the thin sheet (by visual inspection with the naked eye, wherein failure was deemed to have occurred if the thin sheet had fallen off of the carrier or was partially debonded therefrom); (b) bubbling between the carrier and the thin sheet (as determined by visual inspection with the naked eye - samples were photographed before and after the processing, and then compared, failure was determined to have occurred if defects increased in size by dimensions visible to the unaided eye); or (c) increased adhesion between the carrier and the thin sheet whereby such increased adhesion prevents debonding (by insertion of a razor blade between the thin sheet and carrier, and/or by sticking a piece of KaptonTM tape as described above to the thin sheet and pulling on the tape) of the thin sheet from the carrier without damaging the thin sheet or the carrier, wherein a failure was deemed to have occurred if there was damage to the
• Ultrasonic testing was performed by cleaning the article in a four tank line, wherein the article was processed in each of the tanks sequentially from tank #1 to tank #4. Tank dimensions, for each of the four tanks, were 18.4"L x 10"W x 15"D. Two cleaning tanks (#1 and #2) contained l%Semiclean KG available from
• the cleaning tank #1 was agitated with a NEY prosonik 2 104 kHz ultrasonic generator (available from Blackstone-NEY Ultrasonics, Jamestown, NY), and the cleaning tank #2 was agitated with a NEY prosonik 2 104 kHz ultrasonic generator.
• Two rinse tanks (tank #3 and tank #4) contained DI water at 50°C.
• the rinse tank #3 was agitated by NEY sweepsonik 2D 72 kHz ultrasonic generator and the rinse tank #4 was agitated by a NEY sweepsonik 2D 104 kHz ultrasonic generator.
• the bond energy is the energy it takes to separate a thin sheet from a carrier.
• the bond energy may be measured in various different manners. However, as used herein, the bond energy was measured as follows.
• Bond energy was measured using the double cantilever beam method (also known as the wedge method).
• a wedge of known thickness is placed between the bonded thin sheet and carrier glass at an edge.
• the wedge creates a characteristics delamination distance, L. This delamination distance is measured and used to calculated the bond energy, JBE in equation 6.
• Young modulus, E, for both the carrier (1) and the thin sheet (2) of EXG composition was 73.6 GPa.
• the typical thickness of the carrier, t s i, 0.7 mm and thickness of the thin sheet, t S 2, 0.13 mm. Martor 37010.20 razor blades were used for a wedge consisting of a thickness, t w , of 95 ⁇ . Samples having very high bond energy where pre-cracked with a separate wedge. This allowed easier insertion of the wedge and creation of characteristics
• delamination length For bond energy data reported, a value of 2500 indicates a test-limit condition and that the thin sheet could not be debonded from the carrier for that particular sample.
• a typical cleaning process for preparing glass for bonding is the SCI cleaning process where the glass is cleaned in a dilute hydrogen peroxide and base (commonly ammonium hydroxide, but tetramethylammonium hydroxide solutions for example JT Baker JTB-100 or JTB-1 11 may also be used). Cleaning removes particles from the bonding surfaces, and makes the surface energy known, i.e., it provides a base-line of surface energy.
• the manner of cleaning need not be SCI , other types of cleaning may be used, as the type of cleaning is likely to have only a very minor effect on the silanol groups on the surface. The results for various tests are set forth below in Table 1.
• a strong but separable initial, room temperature or van der Waal and/or Hydrogen- bond was created by simply cleaning a thin glass sheet of 100mm square x 100 micron thick, and a glass carrier 150mm diameter single mean flat (SMF) wafer 0.50 or 0.63 mm thick, each comprising Eagle XG® display glass (an alkali-free, alumino-boro-silicate glass, having an average surface roughness Ra on the order of 0.2 nm, available from Corning
• SMF single mean flat
• the above-described preparation of the bonding surfaces 14, 24 via heating alone and then bonding of the carrier 10 and the thin sheet 12, without a surface modification layer 30, is not a suitable controlled bond for FPD processes wherein the temperature will be > 400°C.
• Hydroxyl reduction as by heat treatment for example, and a surface modification layer 30 may be used together to control the interaction of bonding surfaces 14, 24.
• the bonding energy both van der Waals and/or Hydrogen-bonding at room temperature due to the polar/dispersion energy components, and covalent bonding at high temperature due to the covalent energy component
• the bonding energy of the bonding surfaces 14, 24 can be controlled so as to provide varying bond strength from that wherein room-temperature bonding is difficult, to that allowing easy room-temperature bonding and separation of the bonding surfaces after high temperature processing, to that which— after high temperature processing— prevents the surfaces from separating without damage.
• a re-usable carrier for FPD processes and the like wherein process temperatures > 500°C, or > 600°C, and up to 650°C, may be achieved
• the surface modification layer may be used to control room temperature bonding by which the thin sheet and carrier are initially put together, whereas the reduction of hydro xyl groups on the surface (as by heating the surface, or by reaction of the hydroxyl groups with the surface modification layer, for example) may be used to control the covalent bonding, particularly that at high temperatures.
• a material for the surface modification layer 30 may provide a bonding surface 14, 24 with an energy (for example, and energy ⁇ 40 mJ/m 2 , as measured for one surface, and including polar and dispersion components) whereby the surface produces only weak bonding.
• an energy for example, and energy ⁇ 40 mJ/m 2 , as measured for one surface, and including polar and dispersion components
• HMDS hexamethyldisilazane
• TMS trimethylsilyl
• HMDS as a surface modification layer may be used together with surface heating to reduce the hydroxyl concentration to control both room temperature and high temperature bonding.
• HMDS treatment of just one surface creates stronger room temperature adhesion which survives vacuum and SRD processing.
• thermal processes at 400 °C and above permanently bonded the thin glass to the carrier This is not unexpected as the maximum surface coverage of the trimethylsilyl groups on silica has been calculated by Sindorf and Maciel in J. Phys. Chem. 1982, 86, 5208-5219 to be 2.8/nm 2 and measured by Suratwala et. al. in Journal of Non-Crystalline Solids 316 (2003) 349-363 as 2.7/nm 2 , vs.
• FIG. 4 shows the surface energy of an Eagle XG® display glass carrier after annealing, and after HMDS treatment. Increased annealing temperature prior to HMDS exposure increases the total (polar and dispersion) surface energy (line 402) after HMDS exposure by increasing the polar contribution (line 404).
• the thin glass sheet was heated at a temperature of 150°C in a vacuum for one hour prior to bonding with the non-heat-treated carrier having a coating of HMDS. This heat treatment of the thin glass sheet was not sufficient to prevent permanent bonding of the thin glass sheet to the carrier at temperatures > 400°C.
• varying the annealing temperature of the glass surface prior to HMDS exposure can vary the bonding energy of the glass surface so as to control bonding between the glass carrier and the thin glass sheet.
• the carrier was annealed at a temperature of 190°C in vacuum for 1 hour, followed by HMDS exposure to provide surface modification layer 30. Additionally, the thin glass sheet was annealed at 450°C in a vacuum for 1 hour before bonding with the carrier.
• the resulting article survived the vacuum, SRD, and 400°C tests (parts a and c, but did not pass part b as there was increased bubbling), but failed the 600°C test. Accordingly, although there was increased resistance to high temperature bonding as compared with example 2b, this was not sufficient to produce an article for processing at temperatures > 600°C (for example LTPS processing) wherein the carrier is reusable.
• the carrier was annealed at a temperature of 340°C in a vacuum for 1 hour, followed by HMDS exposure to provide surface modification layer 30. Again, the thin glass sheet was annealed at 450°C for 1 hour in a vacuum before bonding with the carrier.
• the results were similar to those for example 2c, wherein the article survived the vacuum, SRD, and 400°C tests (parts a and c, but did not pass part b as there was increased bubbling), but failed the 600 °C test.
• each of the carrier and the thin sheet were Eagle XG® glass, wherein the carrier was a 150 mm diameter SMF wafer 630 microns thick and the thin sheet was 100 mm square 100 microns thick
• the HMDS was applied by pulse vapor deposition in a YES-5 HMDS oven (available from Yield Engineering Systems, San Jose CA) and was one atomic layer thick (i.e., about 0.2 to 1 nm), although the surface coverage may be less than one monolayer, i.e., some of the surface hydroxyls are not covered by the HMDS as noted by Maciel and discussed above.
• each of the carriers and thin sheets were cleaned using an SCI process prior to heat treating or any subsequent HMDS treatment.
• a comparison of example 2a with example 2b shows that the bonding energy between the thin sheet and the carrier can be controlled by varying the number of surfaces which include a surface modification layer. And controlling the bonding energy can be used to control the bonding force between two bonding surfaces. Also, a comparison of examples 2b-2e, shows that the bonding energy of a surface can be controlled by varying the parameters of a heat treatment to which the bonding surface is subjected before application of a surface modification material. Again, the heat treatment can be used to reduce the number of surface hydroxyls and, thus, control the degree of covalent bonding, especially that at high temperatures.
• a reusable carrier can also be created if one or both bonding surfaces are modified to create a moderate bonding force with a surface modification layer that either covers, or sterically hinders species for example hydroxyls to prevent the formation at elevated temperature of strong permanent covalent bonds between carrier and thin sheet.
• a surface modification layer that either covers, or sterically hinders species for example hydroxyls to prevent the formation at elevated temperature of strong permanent covalent bonds between carrier and thin sheet.
• One way to create a tunable surface energy, and cover surface hydroxyls to prevent formation of covalent bonds is deposition of plasma polymer films, for example fluoropolymer films.
• Plasma polymerization deposits a thin polymer film under atmospheric or reduced pressure and plasma excitation (DC or RF parallel plate, Inductively Coupled Plasma (ICP) Electron Cyclotron Resonance (ECR) downstream microwave or RF plasma) from source gases for example fluorocarbon sources (including CF4, CHF3, C2F6, C3F6, C2F2, CH3F, C4F8, chlorofluoro carbons, or hydrochlorofluoro carbons), hydrocarbons for example alkanes (including methane, ethane, propane, butane), alkenes (including ethylene, propylene), alkynes (including acetylene), and aromatics (including benzene, toluene), hydrogen, and other gas sources for example SF6.
• Plasma polymerization creates a layer of highly cross-linked material. Control of reaction conditions and source gases can be used to control the film thickness, density, and chemistry to tailor the functional groups to the desired application.
• FIG. 5 shows the total (line 502) surface energy (including polar (line 504) and dispersion (line 506) components) of plasma polymerized fluoropolymer (PPFP) films deposited from CF4-C4F8 mixtures with an Oxford ICP380 etch tool (available from Oxford Instruments, Oxfordshire UK). The films were deposited onto a sheet of Eagle XG ® glass, and spectroscopic ellipsometry showed the films to be 1 -10 nm thick. As seen from FIG. 5, glass carriers treated with plasma polymerized fluoropolymer films containing less than 40% C4F8 exhibit a surface energy >40 mJ/m 2 and produce controlled bonding between the thin glass and carrier at room temperature by van der Waal or hydrogen bonding.
• PPFP plasma polymerized fluoropolymer
• the surface modification layer of PPFP2 may be useful for some applications, as where ultrasonic processing is not necessary.
• each of the carrier and the thin sheet were Eagle XG® glass, wherein the carrier was a 150 mm diameter SMF wafer 630 microns thick and the thin sheet was 100 mm square 100 microns thick. Because of the small thickness in the surface modification layer, there is little risk of outgassing which can cause contamination in the device fabrication. Further, because the surface modification layer did not appear to degrade, again, there is even less risk of outgassing. Also, as indicated in Table 3, each of the thin sheets was cleaned using an SCI process prior to heat treating at 150°C for one hour in a vacuum.
• Still other materials may be used as the surface modification layer to control the room temperature and high temperature bonding forces between the thin sheet and the carrier.
• a bonding surface that can produce controlled bonding can be created by silane treating a glass carrier and/or glass thin sheet.
• Silanes are chosen so as to produce a suitable surface energy, and so as to have sufficient thermal stability for the application.
• the carrier or thin glass to be treated may be cleaned by a process for example 02 plasma or UV-ozone, and SCI or standard clean two (SC2, as is known in the art) cleaning to remove organics and other impurities (metals, for example) that would interfere with the silane reacting with the surface silanol groups.
• Washes based on other chemistries may also be used, for example, HF, or H2S04 wash chemistries.
• the carrier or thin glass may be heated to control the surface hydroxyl concentration prior to silane application (as discussed above in connection with the surface modification layer of HMDS), and/or may be heated after silane application to complete silane condensation with the surface hydroxyls.
• concentration of unreacted hydroxyl groups after silanization may be made low enough prior to bonding as to prevent permanent bonding between the thin glass and carrier at temperatures > 400°C, that is, to form a controlled bond. This approach is described below.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% dodecyltriethoxysilane (DDTS) in toluene, and annealed at 150°C in vacuum for 1 hr. to complete condensation.
• DDTS treated surfaces exhibit a surface energy of 45 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the DDTS surface modification layer thereon. This article survived wet and vacuum process tests but did not survive thermal processes over 400 °C without bubbles forming under the carrier due to thermal decomposition of the silane.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% 3,3,3, trifluoropropyltritheoxysilane (TFTS) in toluene, and annealed at 150°C in vacuum for 1 hr. to complete condensation.
• TFTS treated surfaces exhibit a surface energy of 47 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the TFTS surface modification layer thereon. This article survived the vacuum, SRD, and 400°C process tests without permanent bonding of the glass thin sheet to the glass carrier.
• the 600°C test produced bubbles forming under the carrier due to thermal decomposition of the silane. This was not unexpected because of the limited thermal stability of the propyl group. Although this sample failed the 600°C test due to the bubbling, the material and heat treatment of this example may be used for some applications wherein bubbles and the adverse effects thereof, for example reduction in surface flatness, or increased waviness, can be tolerated.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% phenyltriethoxysilane (PTS) in toluene, and annealed at 200°C in vacuum for 1 hr. to complete condensation.
• PTS treated surfaces exhibit a surface energy of 54 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the PTS surface modification layer. This article survived the vacuum, SRD, and thermal processes up to 600°C without permanent bonding of the glass thin sheet with the glass carrier.
• a glass carrier with its bonding surface 02 plasma and SCI treated was then treated with 1% diphenyldiethoxysilane (DPDS) in toluene, and annealed at 200°C in vacuum for 1 hr. to complete condensation.
• DPDS treated surfaces exhibit a surface energy of 47 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400°C in a vacuum for one hour) was bonded to the carrier bonding surface having the DPDS surface modification layer. This article survived the vacuum and SRD tests, as well as thermal processes up to 600°C without permanent bonding of the glass thin sheet with the glass carrier
• a glass carrier having its bonding surface 02 plasma and SCI treated was then treated with 1% 4-pentafluorophenyltriethoxysilane (PFPTS) in toluene, and annealed at 200°C in vacuum for 1 hr. to complete condensation.
• PFPTS treated surfaces exhibit a surface energy of 57 mJ/m 2 .
• Table 4 a glass thin sheet (having been SCI cleaned and then heated at 400 °C in a vacuum for one hour) was bonded to the carrier bonding surface having the PFPTS surface modification layer. This article survived the vacuum and SRD tests, as well as thermal processes up to 600°C without permanent bonding of the glass thin sheet with the glass carrier.
• each of the carrier and the thin sheet were Eagle XG® glass, wherein the carrier was a 150 mm diameter SMF wafer 630 microns thick and the thin sheet was 100 mm square 100 microns thick.
• the silane layers were self-assembled monolayers (SAM), and thus were on the order of less than about 2 nm thick.
• SAM was created using an organosilane with an aryl or alkyl non-polar tail and a mono, di, or tri-alkoxide head group. These react with the silanol surface on the glass to directly attach the organic functionality. Weaker interactions between the non-polar head groups organize the organic layer.
• each of the glass thin sheets was cleaned using an SCI process prior to heat treating at 400 °C for one hour in a vacuum.
• each carrier had a surface energy above 40 mJ/m 2 , which facilitated initial room temperature bonding so that the article survived vacuum and SRD processing.
• examples 4a and 4b did not pass 600°C processing test.
• Another example of using plasma polymerized films to tune the surface energy of, and create alternative polar bonding sites on, a bonding surface is deposition of a surface modification layer thin film from a mixture of fluorocarbon gas sources, and then forming nitrogen based polar groups on the surface modification layer by using various methods.
• the surface modification layer may be formed by plasma polymerization of various mixtures of fluorocarbon gas sources so as to provide a variety of surface energies, including a surface energy of greater than about 50 mJ/m 2 as calculated by fitting a theoretical model developed by S. Wu (1971) to the contact angles (CA) of three different test liquids (in this case, de-ionized water (Water), hexadecane (HD), and di-iodomethane (DIM). (Reference: S. Wu, J. Polym. Sci. C, 34, 19, 1971, hereinafter the "Wu model").
• a surface energy of greater than about 50 mJ/m2 on a carrier bonding surface is beneficial for bonding the carrier to a thin glass sheet, as it facilitates initial room-temperature bonding of the carrier to the thin glass sheet, and enables FPD processing of the carrier/thin glass sheet without them debonding in process.
• a surface modification layer having this surface energy is capable of allowing debonding by peeling, even after processing the carrier and thin glass sheet at temperatures up to about 600°C, and in some cases even higher.
• the source gasses include a mixture of an etching gas and a polymer forming gas. As discussed above in connection with FIG.
• the etching gas may be CF4, whereas the polymer forming gas may be C4F8.
• the etching gas may be CF4, whereas the polymer forming gas may be CHF3.
• the lower the percentage of polymer forming gas the higher the total surface energy 502, 1312 of the resulting bonding surface, wherein the total surface energy is a combination of polar 504, 1314 (triangle data points) and dispersion 506, 1316 (square data points) components.
• the percentage of polymer forming gas (for example CHF3) during the plasma polymerization may be controlled in a similar manner, to control the resultant surface energy, by using an inert gas (for example Ar), as shown in FIG. 13 A which shows total surface energy in mJ/m2.
• an inert gas for example Ar
• the inert gas may act as an etchant, a diluent, or both.
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure, and is performed with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material. Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application. And by controlling the film properties, the surface energy of a carrier bonding surface can be tuned. However, surface energy is just one consideration in controlling the degree of bonding.
• the degree of controlled bonding, or moderate bonding can be further tuned by controlling the polar bond used to achieve the desired surface energy.
• One manner of controlling the polar bond is to expose the surface modification layer (as formed above) to a further treatment to incorporate polar groups, for example treatment by a nitrogen containing plasma. This treatment increases the adhesion force through the formation of nitrogen-based polar functional groups on the thin surface modification layer.
• the nitrogen based polar groups, formed during the subsequent treatment do not condense with silanol groups to cause permanent covalent bonding and, thus, are able to control the degree of bonding between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• the methods of forming nitrogen based polar groups include, for example, nitrogen plasma treatment (examples 5b-d, k, 1), ammonia plasma treatment (examples 5e, f, h-j), and nitrogen/hydrogen plasma treatment (example 5m).
• Thin glass sheets and glass carriers bonded with a surface modification layer that was treated with nitrogen-containing plasma are observed not to permanently adhere after annealing at 600°C, i.e., they pass part (c) of the 600°C temperature testing. Also, this moderate bonding is strong enough to survive FPD processing (including the above-described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remain de- bondable by application of sufficient peeling force. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• the nitrogen plasma treatment of the surface modification layer may obtain one or more of the following advantages: high surface energy and low water contact angle, leading to strong adherence between the thin sheet and carrier with minimal bubble defects after initial bonding (see examples 5b-f, and i-1);
• the base material of and deposition process for the surface modification layer itself may be formulated so as to optimize interaction between the surface modification layer and the carrier bonding surface. Then, separately, after deposition of the surface modification layer on the carrier, the properties of the surface modification layer may be modified by treatment to optimize interaction of the surface modification layer with the thin sheet to be disposed thereon.
• the glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (available from Corning
• the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• the films were deposited in an Oxford Plasmalab 380 Inductively Coupled Plasma (ICP) system with 13.56 MHz RF sources on both the coil and platen, and the platen temperature was fixed at 30C.
• ICP Inductively Coupled Plasma
• Nitrogen and ammonia plasma treatments of the surface modification layer for samples 5a-5j were performed in an STS Multiplex PECVD apparatus (available from SPTS, Newport, UK) with triode electrode configuration mode wherein the carrier sat on a platen heated to 200C to which a specified number of Watts of 380 kHz RF energy was applied, above the platen there was disposed a shower head to which a specified number of Watts of 13.5 MHz RF energy was applied.
• STS Multiplex PECVD apparatus available from SPTS, Newport, UK
• the numbers are shown as a #/#W, wherein the number before the slash is the Wattage applied to the top electrode( coil on ICP or shower head on PECVD), and the number after the slash is the Wattage applied to the platen. Where there is only one number shown, this is for the top electrode.
• the flow-rates of the gasses into the chamber were as shown in Table 5 (flowrates being in standard cubic centimeters per minute— seem).
• the notation in the "Surface Treatment" column of Table 5 for example5g is read as follows: in an Oxford ICP apparatus, 30 seem of CF4, 10 seem of C4F8, and 20 seem of H2, were flowed together into a chamber having a pressure of 5 mTorr; 1000 W of 13.5 MHz RF energy was applied to the coil 50 W of 13.56 MHz RF energy was applied to the 30C platen on which the carrier sat; and the deposition time was 60 seconds.
• the notation in the Surface Treatment column for the remaining examples can be read in a similar manner.
• the notation for the treatment in example 5h is read as follows: after the surface modification layer is formed as per the parameters in the Surface Treatment column of example 5h, then 100 seem of NH3 is supplied to the STS PECVD chamber having a pressure of 1 Torr, and a temperature of 200°C; 100 W of 13.56 MHz is applied to the showerhead; and the treatment is carried out for 30 seconds.
• the notation in the "Plasma Treatment” column for the remaining examples is read in a similar manner.
• nitrogen based polar groups are formed on the surface modification layer, wherein these polar groups create moderate adhesion between a carrier and thin sheet (for example a glass carrier and a glass thin sheet) to create a temporary bond sufficiently strong to survive FPD processing but weak enough to permit debonding.
• the polar group concentration on the surface of the surface modification layer is greater than that in the bulk of the surface modification layer.
• a moderate surface energy SML was deposited in an ICP plasma system from 30 seem CF4 10 seem C4F8 20 seem H2 at 5mT with 1500W coil and 50W platen RF power (control example 5a), and another from 30 seem CF4 10 seem C4F8 20 seem H2 at 5mT with 1000W coil and 50W platen RF power (control example 5g).
• Surface energy of the untreated fluoropolymer films are shown in the Table 5. Samples were transferred to an STS PECVD system and exposed to an ammonia plasma with the conditions listed in Table 5 (examples 5e, 5f, 5h-j).
• a moderate surface energy SML was deposited in an ICP plasma system from 30 seem CF4 10 seem C4F8 20 seem H2 at 5mT with 1500W coil and 50W platen RF power (control example 5a), and another from 30 seem CF4 10 seem C4F8 20 seem H2 at 5mT with 1000W coil and 50W platen RF power (control example 5g).
• Surface energy of the untreated fluoropolymer films is shown in Table 5.
• Samples 5c, d, k, 1, were N2 plasma treated in-situ in the ICP system with the conditions listed in Table 5. Surface energy increased from about 40 to over 70 mJ/m2 depending on plasma conditions.
• a thin glass sheet was bonded to each of these samples. The thin glass sheet of all the samples were easily de-bonded by hand after 600°C temperature testing.
• a moderate surface energy SML was deposited in an ICP plasma system from 30 seem CF4 10 seem C4F8 20 seem H2 at 5mT with 1000W coil and 50W platen RF power (control example 5g).
• Surface tension of the untreated fluoropolymer is shown in Table 5.
• Sample 5m was subjected to simultaneous N2+H2 plasma treatment in-situ in the ICP system with the conditions listed in Table 5. Surface energy was not shown to differ from the untreated fluoropolymer film.
• a moderate surface energy SML was deposited in an ICP plasma system from 30 seem CF4 10 seem C4F8 20 seem H2 at 5mT with 1500W coil and 50W platen RF power (control example 5a). Surface energy of the untreated fluoropolymer is shown in Table 5. This sample was then subjected to sequential N2 and H2 plasma treated in-situ in the ICP system with the conditions listed in Table 5. Surface energy rose to over 70 mJ/m2. This value is similar to values obtained with ammonia or nitrogen plasma. A thin glass sheet was bonded to this sample, and underwent 600°C temperature testing, after which the thin glass sheet could be de-bonded from the carrier, i.e., this sample passed part (c) of the 600°C processing test.
• XPS data revealed that the impact of ammonia and nitrogen plasma treatments on the surface modification layer.
• ammonia plasma treatment roughly halves the carbon content of the surface modification and diminishes the fluorine concentration by about a quarter and adds about 0.4 at% nitrogen.
• Silicon, oxygen, and other glass constituents are seen to increase as well, consistent with the ammonia plasma removing the fluoropolymer while adding a small amount of nitrogen species to the surface.
• Nitrogen plasma treatment increases nitrogen content to 2 at%, but also decreases carbon and fluorine content similar to ammonia. Silicon, oxygen and other glass constituents also increase consistent with a decrease in film thickness.
• the ammonia and nitrogen plasma treatments are shown to add polar groups to the surface modification layer, but also decrease the surface layer thickness. The resulting thickness of the surface modification layer was generally less than 20 nm.
• an effective surface modification layer will generally balance surface modification layer thickness with subsequent surface treatment time to achieve controlled bonding.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• the fluoropolymer surface modification treatment prevents permanent bonding of the thin sheet to the carrier at temperature up to 600°C relevant for device fabrication.
• the carrier needs to be re-usable. This is a concern when using a fluorinated surface modification layer, as the fluoropolymer deposition process etches the carrier surface. While re-use of carriers has been demonstrated with those surface modification layers, the surface roughness increases from 0.3 nm to about 1.2 nm Ra. This increase in roughness can impact carrier reusability by reducing the bond energy (on carriers that have been re-used after deposition, removal, and re-deposition of the surface
• the surface roughness increase can limit the carrier reuse in other applications, such as using the carrier itself as a display substrate, by not meeting specifications for roughness of incoming glass. It has also been observed that after annealing a bonded pair of thin glass sheet and carrier at temperature >300°C, a roughness has been induced on the bonding surface side of the thin glass sheet. The increased roughness on the thin sheet bonding surface is likely due to etching of the thin glass bonding surface by desorbed fluorine containing gases from the surface-modification- layer treated carrier bonding surface. In some cases, this increase in roughness of the bonding surface is not consequential.
• the roughness increase is small, this increase may not be acceptable, as it may limit re-use of a carrier, for example. Additionally, there may be reasons, for example health and safety, for not wanting to use fluorinated gasses in certain manufacturing operations.
• the carbonaceous layer surface energy should be greater than about 50 mJ/m 2 for the carbonaceous layer to bond with glass.
• the carbonaceous surface modification layer should have a surface energy of 65 mJ/m2 or higher. At 65 mJ/m2, the surface energy of the carrier (for bonding to a thin glass sheet) is sufficient for preventing liquid (for example water) infiltration between the carrier and thin sheet during subsequent processing.
• the bond to a thin glass sheet may be sufficient for most FPD processing, but may need heat treatment to prevent liquid infiltration.
• the polar component of the hydrocarbon layer needs to be increased in-order to achieve strong dipole-dipole bonds directly with the silanol groups of the thin glass sheet or mediated by hydrogen-bonded molecular water.
• the carbonaceous layer should also exhibit thermal, chemical, and vacuum compatibility so that it will be useful for a carrier-thin-sheet article that will undergo at least amorphous silicon (aSi) TFT, color filter (CF), or capacitive touch device making processes. This appeared possible as aliphatic hydrocarbons like polyethylene exhibit great thermal stability in an inert atmosphere.
• HDPE simply chars. Even though the HDPE may char, if the thickness of polymer is low enough, one can still see through it.
• a final concern was that mechanical stability and wet process compatibility appeared to require a higher adhesion than can be achieved with Van der Waals forces alone. It was seen that about 250 to about 275 mJ/m2 bond energy was beneficial for surviving wet ultrasonic processing with the glass thin sheets used. This large bond energy may be due to particles and edge defects rather than fundamental requirements of the bonding processes. At best bonding two clean glass surfaces can produce a bond energy of about 150 mJ/m2. Some covalent bonding is required to achieve the 250-275 mJ/m2 bond strength.
• the surface modification layers explored in the examples of Tables 6-12 are organic ones based on source materials that did not contain fluorine. As will be described in more detail below, an amorphous hydrocarbon layer (or simply a carbonaceous layer) could be produced on the glass carrier (Table 6), but the surface energy did not produce sufficient adhesion to a clean glass surface to survive FPD processing. This was not surprising, because the organic surface modification layer based on methane and hydrogen contained no strongly polar groups. In order to increase the polar groups available for bonding to the thin glass sheet, additional gasses were added during the plasma polymerization, and could achieve sufficient surface energy (Table 7).
• this one-step process involves a certain amount of complexity in obtaining an appropriate mix of source materials. Therefore, a two-step process was developed, where: in the first step, a surface modification layer was formed (for example, from two gasses similar to the manner in which this was done in the examples of Table 6); then, in the second step, the surface modification layer was treated in various manners to increase the surface energy and polar groups available for bonding to the thin glass sheet. Although more steps, this process was less complex to manage to obtain desirable results. The treatments increase the polar groups at the surface of the surface modification layer that will be bonded to the thin sheet.
• polar groups are available for bonding the carbonaceous layer to the thin sheet, even though the bulk of the surface modification layer may not, in some instances, contain polar groups.
• the various manners of treating the initial surface modification layer are explored in the examples of Tables 8-12, wherein: in the examples of Table 8, the surface modification layer is treated with H3; in the examples of Table 9, the surface modification layer is treated with 2; in the examples of Table 10, the surface modification layer is treated sequentially with N2 then H2; the examples of Table 1 1, the surface modification layer is treated sequentially with N2-02 and then with N2; in the examples of Table 12, the surface modification layer is treated with N2- 02; and in the alternative examples following Table 12, the surface modification layer is treated with 02 alone.
• These example show the use of nitrogen and oxygen polar groups, but other polar groups may be possible.
• a surface modification layer thin film from a carbon-containing gas, for example, a hydrocarbon gas, for example methane, optionally together with another gas (for example, hydrogen H2) during plasma polymerization.
• a carbon-containing gas for example, a hydrocarbon gas, for example methane
• another gas for example, hydrogen H2
• hydrogen flow is preferred because otherwise the deposited material tends to be graphitic, dark and has a low band gap. This is the same throughout the carbonaceous surface modification layer examples of Tables 6-12 and 16.
• the surface modification layer may be formed in atmospheric or reduced pressure, and is performed with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the surface energy can be tuned so as to control the degree of bonding, i.e., so as to prevent permanent covalent bonding, between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• the films were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) Inductively Coupled Plasma (ICP) tool wherein the carrier sat on a platen to which a specified number of Watts (noted in the "RF Bias” column) of 13.56 MHz RF energy was applied, above the platen there was disposed a coil to which a specified number of Watts (noted in the "Coil” column) of 13.5 MHz RF energy was applied.
• the flow-rates of the methane (CH4) and hydrogen (H2) source into the chamber were as shown in the CH4 and H2 columns respectively (flowrates being in standard cubic centimeters per minute— seem).
• the CH4 and H2 gasses were flowed together.
• the ratio of H2:CH4 source gasses in the "H2/CH4" column, and the pressure of the chamber (in mTorr) in the "Pressure” column is also shown.
• Table 6 for example6a is read as follows: in an Oxford ICP apparatus, 6.7 seem of CH4 and 33.3 seem of H2 were flowed together into a chamber having a pressure of 20 mTorr; 1500 W of 13.5 MHz RF energy was applied to the coil and 300 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat. Platen temperature was 30C for all depositions.
• the notation for the remaining examples can be read in a similar manner.
• the surface energies for examples 6a-6j varied from about 40 to about 50 mJ/m 2 . However, by and large, the surface energies for these examples were less than about 50 mJ/m 2 (considered appropriate for controllably bonding a glass carrier to a glass thin sheet). The thickness of the surface modification layer was about 6 nm. These examples did not produce sufficient adhesion between the carrier and a thin glass sheet to survive FPD processing, i.e., they were observed to bubble during vacuum testing, and were observed to have hot water infiltration during the wet process testing.
• these surface modification layers themselves were not suitable for bonding to a thin glass sheet, they may be used in other applications, for example, applying a polymer thin sheet to a glass carrier for processing electronic or other structures onto the thin polymer sheet, as discussed below.
• the thin sheet may be a composite sheet having a polymer surface that may be bonded to the glass carrier.
• the composite sheet may include a glass layer on which electronic or other structures may be disposed, whereas the polymer portion forms the bonding surface for controlled bonding with a glass carrier.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• FIG. 1 Another example of using plasma polymerized films to tune the surface energy of, and cover surface hydroxyls on, a bonding surface is deposition of a surface modification layer thin film from a mixture of non-fluorinated gas sources, including a carbon-containing gas, for example, a hydrocarbon.
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure, and is performed with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both. As noted above in connection with the examples of Table 3, plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application, and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the surface energy can be tuned so as to control the degree of bonding, i.e., so as to prevent permanent covalent bonding, between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• the glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (Available from Corning
• the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• the films were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) in
• ICP Inductively Coupled Plasma
• the ratio of N2:CH4 source gasses in the "N2/CH4" column, and the pressure of the chamber (in mTorr) in the "Pressure” column is also shown.
• Table 7 for example7g is read as follows: in an Oxford 380 ICP apparatus, 15.4 seem of CH4, 3.8 seem of N2, and 30.8 seem of H2 were flowed together into the chamber having a pressure of 5 mTorr; 1500 W of 13.5 MHz RF energy was applied to the shower head; and 50 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat. Platen temperature was 30C for all samples in Table 7.
• the notation for the remaining examples can be read in a similar manner.
• Example 7a shows a surface modification layer made from methane alone. Under these deposition conditions, the methane-formed surface modification layer achieved on the carrier a surface energy of only about 44 mJ/m 2 . Although this is not at the desired level for glass to glass controlled bonding, it may be useful for bonding a polymer bonding surface to a glass carrier.
• Examples 7b to 7e show a surface modification layer made from plasma polymerization of methane and nitrogen at various ratios of N2:CH4. Under these deposition conditions, the methane-nitrogen formed surface modification layer achieved on the carrier a surface energy of from about 61 mJ/m 2 (example 7e) to about 64 mJ/m 2 (example 7d). These surface energies are sufficient for controllably bonding a thin glass sheet to a glass carrier.
• Example 7f shows a surface modification layer made from plasma polymerization of methane and hydrogen (H2). Under these deposition conditions, the methane-hydrogen formed surface modification layer achieved on the carrier a surface energy of about 60 mJ/m 2 , which is sufficient for controllably bonding a thin glass sheet to a glass carrier.
• Examples 7g to 7j show a surface modification layer made from plasma polymerization of methane, nitrogen, and hydrogen. Under these deposition conditions, the methane-nitrogen-hydrogen formed surface modification layer achieved on the carrier a surface energy of from about 58 mJ/m 2 (example 7g) to about 67 mJ/m 2 (example 7j), which are sufficient for controllably bonding a thin glass sheet to a glass carrier.
• Thin glass and carriers bonded with a surface modification layer formed as per examples7b to 7j were observed not to permanently adhere after annealing at 450°C, i.e., they pass part (c) of the 400°C temperature testing. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• the thin glass sheet bonded to each of the carriers as per the examples (7b to 7j) of Table 7 was a substrate made from Corning ® Willow® Glass, an alumino boro silicate alkali-free glass (Available from Corning Incorporated, Corning NY), and having a thickness of 100, 130, and 150, microns. Before bonding, the Willow® Glass was cleaned using an oxygen plasma followed by SCI and/or SC2 chemistry and standard cleaning techniques.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• the surface modification layers of the examples of Table 7 are formed in a one-step process. That is, appropriate surface energy and polar group inclusion are achieved by depositing the surface modification layer from a select mixture of gasses under appropriate conditions. Although the appropriate gasses and conditions were achieved, the process involves a certain amount of complexity to carry out the appropriate gas mixture. Thus, a simpler process was sought. It was postulated that an appropriate surface energy and appropriate polar groups could be achieved from a two-step process, wherein each step would be simple and stable.
• Another example of using plasma polymerized films to tune the surface energy of, and create alternative polar bonding sites on, a bonding surface is deposition of a thin surface modification layer film from a carbon source, for example, methane (a carbon-containing gas source), and from hydrogen H2, followed by nitrogen treatment of the just-formed surface modification layer.
• the nitrogen treatment may be performed with an ammonia plasma treatment, for example.
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure, and with plasma excitation for example DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the film thickness, density, and chemistry to tailor the functional groups to the desired application and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the nitrogen based polar groups, formed during the subsequent ammonia plasma treatment do not condense with silanol groups to cause permanent covalent bonding and, thus, are able to control the degree of bonding between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• various conditions were used to deposit a plasma polymerized surface modification layer film onto a glass carrier.
• the glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (Available from Corning Incorporated, Corning NY). Before film deposition, the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques. The surface treatments were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) in Inductively Coupled Plasma (ICP) configuration mode wherein the carrier sat on a platen to which a specified number of Watts of 13.56 MHz RF energy was applied, above the platen there was disposed a coil to which a specified number of Watts of 13.5 MHz RF energy was applied.
• ICP Inductively Coupled Plasma
• the numbers are shown as a #/#W, wherein the number before the slash is the Wattage applied to the coil (shower head), and the number after the slash is the Wattage applied to the platen. Where there is only one number shown, this is for the coil.
• the flow-rates of the gasses into the chamber were as shown in Table 8 (flowrates being in standard cubic centimeters per minute— seem).
• the temperature of the chamber was 30°C.
• the notation in the "Surface Treatment" column of Table 8 for example8a is read as follows: in an Oxford ICP apparatus, 40 seem of CH4, was flowed into a chamber having a pressure of 5 mTorr; 1500 W of 13.5 MHz RF energy was applied to the shower head; 50 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat; the chamber was at a temperature of 30°C; and the deposition time was 60 seconds.
• the notation in the Surface Treatment column for the remaining examples can be read in a similar manner except that surface treatments were performed in an STS Multiplex PECVD (available from SPTS, Newport, UK).
• the notation for the treatment in example 8a is read as follows: after the surface modification layer is formed as per the parameters in the Surface Treatment column of example 8a, then 100 seem of NH3 is supplied to the chamber having a pressure of 1 Torr, and a temperature of 200°C; 300 W of 13.56 MHz RF is applied to the showerhead and the treatment is carried out for 60 seconds.
• the notation in the "Plasma Treatment” column for the remaining examples is read in a similar manner.
• Examples 8a and 8b show a plasma polymerized hydrocarbon surface modification layer that was subsequently treated with a nitrogen-containing gas (ammonia).
• a nitrogen-containing gas ammonia
• the ammonia was used by itself with 300 W of power
• the ammonia was diluted with helium and the polymerization carried out at a lower power of 50W.
• a sufficient surface energy was attained on the carrier bonding surface to allow it to be controllably bonded to a thin glass sheet.
• Examples 8c and 8d show a plasma polymerized hydrocarbon surface modification layer that was formed by hydrocarbon-containing (methane) and hydrogen-containing (H2) gasses and then subsequently treated with a nitrogen-containing gas (ammonia).
• example 8c the ammonia was used by itself with 300 W of power
• example 8d the ammonia was diluted with helium and the polymerization carried out at a lower power of 50W.
• Thin glass and carriers bonded with a surface modification layer formed as per examples 8a-8d were observed not to permanently adhere after annealing at 450°C, i.e., they were able to survive part (c) of the 400°C temperature testing. Outgassing tests were not performed on these samples. Also, these examples were strong enough to survive FPD processing (including the above-described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remained de-bondable by application of sufficient peeling force. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• the thin glass sheet bonded to each of the carriers as per the examples of Table 8 was a substrate made from Corning ® Willow® Glass, an alumino boro silicate alkali- free glass (Available from Corning Incorporated, Corning NY), and having a thickness of 100, 130, and 150, microns. Before bonding, the Willow® Glass was cleaned using an oxygen plasma followed by SCI and/or SC2 chemistry and standard cleaning techniques.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• a surface modification layer thin film from a carbon source (for example a carbon-containing gas, for example, methane), and from hydrogen H2, followed by nitrogen treatment of the just- formed surface modification layer.
• the nitrogen treatment to form nitrogen based polar groups on the surface modification layer, may be performed by plasma treatment with N2 gas.
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure, and with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• ICP Inductively Coupled Plasma
• ECR Electron Cyclotron Resonance
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the nitrogen based polar groups, formed during the subsequent plasma treatment do not condense with silanol groups to cause permanent covalent bonding and, thus, are able to control the degree of bonding between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• the glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (Available from Corning Incorporated, Corning NY). Before surface modification layer deposition, the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• the surface modification layers were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) in Inductively Coupled Plasma (ICP) configuration mode wherein the carrier sat on a platen to which 50W of 13.56 MHz energy was applied, above the platen there was disposed a coil to which 1500 W of 13.5 MHz RF energy was applied.
• 20 seem of methane (CH4) and 40 seem of hydrogen (H2) were flowed into a chamber at a pressure of 5 mTorr.
• Surface treatment times were 60sec, and platen temperature was 30C for all samples listed in Table 9. After the foregoing deposition, the surface modification layer was treated with nitrogen.
• the notation for nitrogen treatment in Table 9 for example9a is read as follows: in an Oxford ICP apparatus, 40 seem of N2 was flowed into a chamber having a pressure of 5 mTorr; 1500 W of 13.5 MHz RF energy was applied to the shower head; and 300 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat which was temperature controlled to 30C, and the treatment was carried out for 10 seconds.
• the notation for the remaining examples can be read in a similar manner.
• Examples 9a-9j show that various conditions may be used for the nitrogen treatment of a methane/hydrogen formed surface modification layer, whereby a variety of surface energies may be obtained, i.e., from about 53 mJ/m 2 (example 9i) to about 63 mJ/m 2 (example 9b), which are suitable for bonding to a thin glass sheet. These surface energies, obtained after nitrogen treatment, were increased from about 42 mJ/m 2 (obtained from the base layer formed from methane-hydrogen plasma polymerization).
• Thin glass and carriers bonded with a surface modification layer formed as per examples 9a-9j were observed not to permanently adhere after annealing at 450°C, i.e., they pass part (c) of the 400°C temperature testing. Outgassing tests were not performed on these samples. Also, these examples were strong enough to survive FPD processing (including the above-described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remained de-bondable by application of sufficient peeling force. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• the thin glass sheet bonded to each of the carriers as per the examples of Table 9 was a substrate made from Corning ® Willow® Glass, an alumino boro silicate alkali- free glass (Available from Corning Incorporated, Corning NY), and having a thickness of 100, 130, and 150, microns. Before bonding, the Willow® Glass was cleaned using an oxygen plasma followed by SCI and/or SC2 chemistry and standard cleaning techniques.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• a surface modification layer thin film from a carbon source, for example methane (a carbon-containing gas), and from hydrogen H2, followed by sequential nitrogen then hydrogen treatment of the just- formed surface modification layer.
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure, and is performed with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application, and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the nitrogen based polar groups, formed during the subsequent plasma treatment do not condense with silanol groups to cause permanent covalent bonding and, thus, are able to control the degree of bonding between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• a plasma polymerized film deposited onto a glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali- free display glass (Available from Corning Incorporated, Corning NY). Before film deposition, the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• the films were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) in Inductively Coupled Plasma (ICP) configuration mode wherein the carrier sat on a platen to which 50W of 13.56 MHz energy was applied, above the platen there was disposed a coil to which 1500 W of 13.5 MHz RF energy was applied.
• 20 seem of methane (CH4) and 40 seem of hydrogen (H2) were flowed into a chamber at a pressure of 5 mTorr.
• Surface treatment times were 60sec, and platen temperature was 30C for all samples listed in Table 9. After the foregoing deposition, the surface modification layer was treated sequentially with nitrogen and then with hydrogen.
• H2 was flowed into the chamber at a rate of 40 seem for the time (in seconds - s) listed in the table.
• the notation for hydrogen treatment (carried out after the thin film deposition, and the N2 treating thereof as described above) in Table 10 for examplelOa is read as follows: in an Oxford ICP apparatus, 40 seem of H2 was flowed into a chamber having a pressure of 20 mTorr; 750 W of 13.5 MHz RF energy was applied to the shower head; and 50 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat, and the treating was carried out for 15 seconds.
• the notation for the remaining examples can be read in a similar manner.
• Sequential N2 and then H2 plasma treatment, of a methane-hydrogen formed plasma polymerized surface modification layer can be carried out under various conditions to achieve a variety of surface energies.
• the surface energies varied from about 60 mJ/m 2 (example lOd) to about 64 mJ/m 2 (examples 10a, 10 ⁇ , 10 ⁇ , and lOp), which are suitable for bonding to a thin glass sheet.
• Thin glass and carriers bonded with a surface modification layer formed as per examples lOa- ⁇ were observed not to permanently adhere after annealing at 450°C, i.e., they were able to pass part (c) of the 400°C processing test.
• the thin glass sheet bonded to each of the carriers as per the examples of Table 10 was a substrate made from Corning ® Willow® Glass, an alumino boro silicate alkali- free glass (Available from Corning Incorporated, Corning NY), and having a thickness of 100, 130, and 150, microns. Before bonding, the Willow® Glass was cleaned using an oxygen plasma followed by SCI and/or SC2 chemistry and standard cleaning techniques.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• Sequential N2 and H2 treatment of the carbonaceous surface modification layer achieves a surface energy of about 64 mJ/m2 and forms an initial room- temperature bond to the thin glass sheet with a bond front speed slightly less than typical with the fluorinated surface modification layers.
• these samples were observed not to permanently adhere after annealing at 450°C, i.e., they were able to pass part (c) of the 400°C processing test.
• these examples were strong enough to survive FPD processing (including the above-described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remained de-bondable by application of sufficient peeling force. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• carbonaceous surface modification layer thin film from a carbon source, for example a carbon-containing gas, (for example methane), and from hydrogen H2, followed by sequential N2-02 and then N2 treatment of the just-formed surface modification layer.
• a carbon source for example a carbon-containing gas, (for example methane)
• hydrogen H2 for example hydrogen
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure, and with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material. Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the nitrogen based polar groups, formed during the subsequent plasma treatment, do not condense with silanol groups to cause permanent covalent bonding and, thus, are able to control the degree of bonding between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• the glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali- free display glass (Available from Corning Incorporated, Corning NY). Before surface modification layer deposition, the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• step 1 the surface modification layers were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) in Inductively Coupled Plasma (ICP) configuration mode wherein the carrier sat on a platen to which 50W of 13.56 MHz energy was applied, above the platen there was disposed a coil to which 1500 W of 13.5 MHz RF energy was applied. 20 seem of methane (CH4) and 40 seem of hydrogen (H2) were flowed into a chamber at a pressure of 5 mTorr. Surface treatment times were 60sec, and platen temperature was 30C for all samples listed in Table 1 1. [00170] After the foregoing deposition of step 1 , in step 2 the surface modification layer was treated with nitrogen and oxygen.
• ICP Inductively Coupled Plasma
• step 2 treatment 50W of 13.56 MHz RF energy was applied to the platen, above the platen there was disposed a coil to which 800W of 13.5 MHz RF energy was applied. N2 and 02 were flowed into the chamber at the specified rate (in seem) for the time (in seconds - s) listed in the table.
• the notation for Step 2 in Table 11 for example 1 la is read as follows: after the surface modification layer deposition in step 1, in an Oxford ICP apparatus, 35 seem of N2 was flowed together with 5 seem 02 into a chamber having a pressure of 15 mTorr; 800 W of 13.5 MHz RF energy was applied to the shower head; and 50 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat which was temperature controlled to 30°C, and the treatment was carried out for 5 seconds.
• the notation for the remaining examples can be read in a similar manner.
• step 3 the surface modification layer was treated with nitrogen. Specifically, during the step 3 treatment, 50W of 13.56 MHz RF energy was applied to the platen, above the platen there was disposed a coil to which 1500W of 13.5 MHz RF energy was applied. N2 was flowed into the chamber at the specified rate (in seem) for the time (in seconds - s) listed in the table.
• the notation for Step 3 in Table 1 1 for example 1 la is read as follows: after the surface modification layer deposition in step 1 , and after the nitrogen-oxygen treatment in step 2, in an Oxford ICP apparatus, 40 seem of N2 was flowed into a chamber having a pressure of 5 mTorr; 1500 W of 13.5 MHz RF energy was applied to the shower head; and 50 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat which was temperature controlled to 30°C, and the treatment was carried out for 15 seconds.
• the notation for the remaining examples can be read in a similar manner.
• Examples 1 1 a- 1 1 e show that various conditions may be used for the sequential nitrogen-oxygen and then nitrogen treatment of a methane/hydrogen formed surface modification layer, whereby a variety of surface energies may be obtained, i.e., from about 65 mJ/m 2 (examples 11a and 1 le) to about 70 mJ/m 2 (examples 1 lb and 1 Id), which are suitable for bonding to a thin glass sheet.
• These surface energies, obtained after sequential nitrogen- oxygen and then nitrogen treatments, were increased from about 40-50 mJ/m 2 (obtained from the base layer formed from methane-hydrogen plasma polymerization).
• step 3 may not be necessary to obtain similar no outgassing results as obtained with step 3 for examples l l a-e. Also, these examples were strong enough to survive FPD processing (including the above- described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remained de-bondable by application of sufficient peeling force after 400°C temperature testing. De- bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• the thin glass sheet bonded to each of the carriers as per the examples of Table 11 was a substrate made from Corning ® Willow® Glass, an alumino boro silicate alkali- free glass (Available from Corning Incorporated, Corning NY), and having a thickness of 100, 130, and 150, microns. Before bonding, the Willow® Glass was cleaned using an oxygen plasma followed by SCI and/or SC2 chemistry and standard cleaning techniques.
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• ICP inductively coupled plasma
• a thin organic surface modification layer suitable for controllably bonding a thin glass sheet to a glass carrier for device processing.
• ICP tools utilize a planar, cylindrical, or hemispherical coil to inductively couple electrical current to create time varying magnetic fields which cause ions to circulate.
• a second RF source is connected to the platen upon which the substrate sits.
• RIE reactive ion etch
• H2/CH4 and C2H6/CH4 ratios could be matched at 40: 1 H2/CH4, 25 mTorr 275 W RF.
• a carbonaceous RIE mode surface modification layer deposited with this condition matched the about 6 nm thickness and 1.6 eV optical band gap of ICP mode carbonaceous surface modification layer.
• Initial experiments with nitrogen plasma treatment of the carbonaceous RIE surface modification layers also showed low bubbling.
• FIGS. 14 and 15 The kinetics of RIE mode carbonaceous surface modification layer deposition using the process identified by the RGA experiment is shown in FIGS. 14 and 15.
• T total
• P polar
• D dispersion
• FIG. 14 surface energy is relatively unchanged, with a slight peak at 60 sec deposition time, whereas in FIG. 15 it can be seen that film thickness increases nearly linearly on a log-log scale. This is not a self-limited process as the etch-back from hydrogen cannot keep up with the polymer deposition.
• a surface energy of > about 50 or > 65 mJ/m2 is beneficial in minimizing bubble area both at initial room-temperature bonding, as well as during thermal cycling. From FIG. 14, it can be seen that the surface energy is right on the borderline. In some instances, this may be suitable for bonding a thin sheet to a carrier, depending upon the time-temperature cycle through which it will undergo, as well as depending upon the other FPD processes which it must endure. On the other hand, though, it would be beneficial to raise the surface energy of this surface modification layer. Any of the above-described subsequent treatments could be used, for example, ammonia treatment, nitrogen treatment, sequential nitrogen then hydrogen treatment, nitrogen-oxygen treatment, sequential nitrogen-oxygen then nitrogen treatment. As an example, a nitrogen- oxygen treatment will be described in connection with Table 12.
• Another example of using plasma polymerized films to tune the surface energy of, and create alternative polar bonding sites on, a bonding surface is deposition of a thin surface modification layer film in RIE mode from a carbon source (for example, methane, a carbon- containing gas), and from hydrogen (H2), followed by nitrogen-oxygen treatment of the just- formed surface modification layer.
• the nitrogen-oxygen treatment may be performed with a nitrogen-oxygen plasma treatment, for example.
• Deposition of the surface modification layer may take place in atmospheric or reduced pressure.
• the plasma polymerized surface modification layer may be disposed on a carrier, a thin sheet, or both. As noted above in connection with the examples of Table 3, plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the film thickness, density, and chemistry to tailor the functional groups to the desired application and by controlling the film properties, the surface energy of a bonding surface can be tuned.
• the nitrogen based polar groups, formed during the subsequent nitrogen-oxygen treatment do not condense with silanol groups to cause permanent covalent bonding and, thus, are able to control the degree of bonding between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• a plasma polymerized surface modification layer film onto a glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (Available from Corning Incorporated, Corning NY).
• the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• the surface modification layers were deposited in an Oxford Plasmalab 380 ICP (available from Oxford Instruments, Oxfordshire UK) in RIE configuration mode wherein the carrier sat on a platen to which 275 W of RF energy was applied, above the platen there was disposed a coil to which no energy was applied.
• step 1 2 seem of methane (CH4) and 38 seem of hydrogen (H2) were flowed into a chamber at a pressure of 25 mTorr. Surface treatment times were 60sec, and platen temperature was 30C, for all samples listed in Table 12. After the foregoing deposition, the surface modification layer was treated in Step 2 with nitrogen and oxygen. Specifically, during the Step 2 treatment a specified number of Watts (noted in the "RF" column) of 13.56 MHz RF energy was applied to the platen, above the platen there was disposed a coil to which no energy was applied.
• RF power
• N2 was flowed into the chamber at a rate of seem listed in the "N2" column, and 02 was flowed into the chamber at a rate of seem listed in the "02" column, for the time (in seconds - s) listed in the 'Time (s)" column of the table.
• the chamber was at a pressure, in mTorr, as listed in the "Pr" column.
• the notation for the Step 2 nitrogen and oxygen treatment in Table 12 for example 12b is read as follows: in an Oxford ICP apparatus, 25 seem of N2 was flowed together with 25 seem of 02 into a chamber having a pressure of 10 mTorr; 300 W of 13.56 MHz RF energy was applied to the platen on which the carrier sat which was temperature controlled to 30C, and the treatment was carried out for 10 seconds.
• the notation for the remaining examples can be read in a similar manner.
• th in Angstroms
• Ra the average surface roughness of the carrier after the deposition of the surface modification layer and the N2-02 treatment thereof
• BE bond energy
• % Bubble area ⁇ Bubble Area
• the thin glass sheet bonded to each of the carriers as per the examples of Table 12 was a substrate made from Corning ® Willow® Glass, an alumino boro silicate alkali- free glass (Available from Corning Incorporated, Corning NY), and having a thickness of 100, 130, and 150, microns. Before bonding, the Willow® Glass was cleaned using an oxygen plasma followed by SCI and/or SC2 chemistry and standard cleaning techniques. [00188] In the examples of Table 12, although the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• examples 12a to 12j all had a change in percent bubble area of less than 2, which is consistent with no outgassing at this temperature, see Bubble% column in Table 12; and also that samples 12a, 12b, 12c, 12g, and 12j, each had a bond energy that allowed debonding of the thin sheet from the carrier after this temperature test, see the BE column in Table 12; but examples 12d, 12e, 12f, 12h, and 12i, were not able to be debonded after 400°C process testing, as indicated by the value of 2500 in the BE column of Table 12.
• example 12d treated at a pressure of 40 mTorr, having a Bond Energy of 2500
• example 12e having a pressure of 70 mTorr and a Bond Energy of 2500
• a bond energy in the "BE" column of 2500 indicates that the thin glass sheet could not be debonded from the carrier.
• the surface energy of all the treated films was 65-72 mJ/m2 independent of thickness. See examples 12a to 12i, and 12k.
• Bubble area does increase with increasing surface modification layer deposition time, so simply increasing the thickness of the surface modification layer to avoid too much ablation during subsequent N2-02 surface treatment is not beneficial. Accordingly, a good compromise between bonding and bubble area is a balance of surface modification layer deposition time and N2-02 treatment time. Based on balancing surface modification layer deposition time (not too long, as such would lead to greater thickness that results in increased outgassing) with N2-02 treatment time— one not too long so as to ablate or remove the surface modification layer (which leads to permanent bonding of the carrier to the thin sheet) but long enough to incorporate polar groups with the surface modification layer. A good compromise is 60 seconds RIE deposition of the carbonaceous layer followed by a short N2-02 treatment time of 5-10 seconds. Examples 12a, 12b, 12c,12g, and 12k, work well for RIE mode.
• XPS Nls speciation was used to study the mechanism N2-02 plasma treatments create a highly polar surface.
• N2-02 plasma treatments create a highly polar surface.
• the advantage of the thick hydrocarbon film is that allows us to distinguish those nitrogen species that occur only hydrocarbon film and separate these from those occurring on the exposed glass.
• NH3+ species are detected only when substantial amounts of the carbonaceous film has been etched away. This very strongly suggests that the NH3+ species are likely present only on the glass and the other species involve primarily reaction between nitrogen and the carbonaceous layer.
• the speciation of nitrogen species as a percentage of all atoms on the surface i.e. fraction of species x fraction of nitrogen detected is presented in Table 13, below.
• N2-02 treatment the primary effect of this N2-02 treatment is the etching of the carbonaceous surface modification layer. In fact very little carbonaceous material is present on the surface for the 60 and 600 second treatments. The other observation is that nitrogen species are present on the surface modification layer even after very short N2-02 treatment times, e.g., 5 and 15 seconds. Thereafter, the nitrogen species rapidly decrease, whereas the ammonia species (indicating presence of the underlying glass surface) rapidly increases.
• An XPS evaluation of the carbon speciation for the 5 second N2-02 plasma treatment of the carbonaceous surface modification layer also reveals that several different species containing oxygen and nitrogen are present on the surface modification layer. That oxygen-containing species were present lead to the thought that 02 plasma alone may be sufficient to impart polar groups to the surface modification layer. Indeed, this was found to be the case, and is discussed below.
• a model of the N2-02 plasma treatment of the carbonaceous surface modification layer is as follows.
• the CH4-H2 deposition produces a continuous hydrocarbon layer.
• polar -NH2 groups are formed on the polymer surface as the hydrocarbon layer is oxidized and ablated. Imide or amide groups may also be formed in this time but the XPS is inconclusive.
• polymer removal reaches the glass surface where polar -NH3+ groups are formed from interaction of the N2-02 plasma and the glass surface.
• N2-02 treatment of the carbonaceous layer there was also explored the use of 02 alone to increase surface energy and create polar groups on the carbonaceous layer.
• an XPS carbon speciation of the 5 second N2-02 plasma treatment of the carbonaceous layer showed that oxygen-containing species were, indeed, present on the surface modification layer.
• an 02 treatment of the carbonaceous layer was tried. The 02 treatment was performed in both ICP mode, and in RJE mode.
• a base carbonaceous layer was formed as per step 1 in Table 11 above.
• a step 2 surface treatment was then performed by flowing 40 seem 02, 0 seem N2, with 800/50W power under 15 mTorr pressure, which produced the desired increase in surface energy and the desired polar groups on the surface of the carbonaceous layer.
• the thin glass sheet easily bonded to the surface modification layer at room temperature. Also, this sample was observed not to permanently adhere after annealing at 450°C, i.e., it was able to pass part (c) of the 400°C processing test.
• this sample was strong enough to survive FPD processing (including the above-described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remained de-bondable by application of sufficient peeling force. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• RIE mode a base carbonaceous layer was formed as per Step 1 in Table 12.
• a step 2 surface treatment was then performed by flowing 50 seem 02, 0 seem N2, with 200 W power under 50 mTorr pressure.
• these conditions also produced the desired increase in surface energy and the desired polar groups on the surface of the carbonaceous layer.
• the thin glass sheet easily bonded to the surface modification layer at room temperature. Also, this sample was observed not to permanently adhere after annealing at 450°C, i.e., it was able to pass part (c) of the 400°C processing test.
• this sample was strong enough to survive FPD processing (including the above-described vacuum testing (1), wet process testing (2), and ultrasonic testing (5)) and remained de-bondable by application of sufficient peeling force. De-bonding permits removal of devices fabricated on thin glass, and re-use of the carrier.
• Figure 16 shows the impact of skipping the H2 plasma step with a hydrocarbon surface modification layer. Bond energy is lowered, displacing permanent bonding until 600 °C with no large increase in bubbling. Thus, a small amount of fluorine, i.e., at least up to about 3%, in the hydrocarbon surface modification layer is beneficial.
• a third carrier (example 14c) was used as a reference and had no surface modification layer applied thereto.
• AFM was used to evaluate the surface roughness of the surface-modification-layer applied and then stripped carrier (example 14a), the carrier still having a surface modification layer thereon (example 14b), and the reference carrier (example 14c).
• the Rq, Ra, and Rz, ranges from the AFM measurements are shown in the unit of nm (nanometers) in Table 14.
• the roughness of examples 14a and 14b, are indistinguishable from that of example 14c. It should be noted that for example 14c, the excessive z-range in the 5x5 micron scan was due to a particle in the scanned area.
• the hydrocarbon-formed surface modification layers of the present disclosure do not change the surface roughness of the glass bonding surface.
• the unchanged surface roughness of the bonding surface may be advantageous, for example, for re-use of the carrier.
• the glass carriers in these examples were substrates made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (Available from Corning Incorporated, Corning NY).
• the surface modification layers of examples 3 and 5-12 are thin organic layers, they are sensitive to oxygen in thermal and plasma processing. Accordingly, these surface modification layers should be protected during device fabrication.
• the surface modification layers may be protected by the use of a non-oxygen containing environment (for example a N2 environment) during thermal processing.
• a protective coating for example a thin metal layer, over the edge of the interface between the bonded thin glass sheet and carrier is sufficient to protect the surface modification layer against the effects of an oxygen environment at elevated temperature.
• the surface modification materials described above in examples 3 through 12 can be applied to the carrier, to the thin sheet, or to both the carrier and thin sheet surfaces that will be bonded together.
• one bonding surface is a polymer bonding surface and the other bonding surface is a glass bonding surface (as further described below)
• appropriate surface modification materials based on surface energy of the polymer bonding surface described above in examples 3 through 12 will be applied to the glass bonding surface.
• the entire carrier or thin sheet need not be made of the same material, but may include different layers and/or materials therein, as long as the bonding surface thereof is suited to receiving the surface modification layer of interest.
• the bonding surface may be glass, glass-ceramic, ceramic, silicon, or metal, wherein the remainder of the carrier and/or thin sheet may be of a different material.
• the thin sheet 20 bonding surface may be of any suitable material including silicon, polysilicon, single crystal silicon, sapphire, quartz, glass, ceramic, or glass-ceramic, for example.
• the carrier 10 bonding surface may be a glass substrate, or another suitable material having a similar surface energy as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• the surface modification layers together with the subsequent treatments thereof, provide a manner of widely varying the surface energy on a glass bonding surface.
• the surface energy of a glass bonding surface may be varied from about 36 mJ/m2 (as in example 5g) to about 80 mJ/m2 (example 5f).
• the surface energy of a glass bonding surface may be varied from about 37 mJ/m2 (example 16b) to about 67 mJ/m2 (examples 7h and 7j).
• the surface energy of a glass bonding surface may be varied from about 52 mJ/m2 (example 12j) to about 74 mJ/m2 (example 8a).
• the surface energy of a glass bonding surface may be varied from about 37 mJ/m2 (example 16b) to about 74 mJ/m2 (example 8a).
• the surface energy of a glass bonding surface may be varied from about 41 mJ/m2 (example 5m) to about 80 mJ/m2 (example 5f).
• the thickness of the surface modification layer can be varied greatly. Desirable results were attained with a surface modification layer thickness in the range of from about 2 nm (as in example 3) to about 8.8 nm (as in example 12c).
• One use of controlled bonding via surface modification layers is to provide reuse of the carrier in an article undergoing processes requiring a temperature > 600°C, as in LTPS processing, for example.
• Surface modification layers including the materials and bonding surface heat treatments
• these surface modification layers may be used to provide reuse of the carrier under such temperature conditions.
• these surface modification layers may be used to modify the surface energy of the area of overlap between the bonding areas of the thin sheet (having a glass bonding surface) and carrier (having a glass bonding surface), whereby the entire thin sheet may be separated from the carrier after processing.
• the thin sheet maybe separated all at once, or may be separated in sections as, for example, when first removing devices produced on portions of the thin sheet and thereafter removing the remaining portions to clean the carrier for reuse.
• the carrier can be reused as is by simply by placing another thin sheet thereon.
• the carrier may be cleaned and once again prepared to carry a thin sheet by forming a surface modification layer anew. Because the surface modification layers prevent permanent bonding of the thin sheet with the carrier, they may be used for processes wherein temperatures are > 600°C.
• these surface modification layers may control bonding surface energy during processing at temperatures > 600°C, they may also be used to produce a thin sheet and carrier combination that will withstand processing at lower temperatures, and may be used in such lower temperature applications to control bonding.
• surface modification layers as exemplified by the examples 2c, 2d, 4b, the examples of tables 7-11 (including the examples discussed as alternatives of the examples of table 10), examples 12a, 12b, 12c, 12g, 12g, and the examples of a surface treatment with 02 alone, may also be used in this same manner.
• One advantage to using the surface modification layers described herein, for example those including the examples of table 3, examples 4b, 4c, 4d, 4e, the examples of tables 5 and 7-1 1, examples 12a, 12b, 12c, 12g, 12j, and the examples of a surface treatment with 02 alone, is that the carrier can be re-used at the same size. That is, the thin sheet may be removed from the carrier, the surface modification layer removed from the carrier by a non-destructive manner (for example 02 or other plasma cleaning), and re-used without having to cut the carrier in any manner (for example, at its edges).
• a second use of controlled bonding via surface modification layers is to provide a controlled bonding area, between a glass carrier and a glass thin sheet. More specifically, with the use of the surface modification layers an area of controlled bonding can be formed wherein a sufficient separation force can separate the thin sheet portion from the carrier without damage to either the thin sheet or the carrier caused by the bond, yet there is maintained throughout processing a sufficient bonding force to hold the thin sheet relative to the carrier.
• a glass thin sheet 20 may be bonded to a glass carrier 10 by a bonded area 40. In the bonded area 40, the carrier 10 and thin sheet 20 are covalently bonded to one another so that they act as a monolith.
• controlled bonding areas 50 having perimeters 52, wherein the carrier 10 and thin sheet 20 are connected, but may be separated from one another, even after high temperature processing, e.g. processing at temperatures > 600°C. Although ten controlled bonding areas 50 are shown in FIG. 6, any suitable number, including one, may be provided.
• the surface modification layers 30, including the materials and bonding surface heat treatments, as exemplified by the examples 2a, 2e, 3 a, 3b, 4c, 4d, and 4e, the examples of table 5, above, may be used to provide the controlled bonding areas 50 between the carrier 10 having a glass bonding surface and the thin sheet 20 having a glass bonding surface.
• these surface modification layers may be formed within the perimeters 52 of controlled bonding areas 50 either on the carrier 10 or on the thin sheet 20. Accordingly, when the article 2 is processed at high temperature, either to form covalent bonding in the bonding area 40 or during device processing, there can be provided a controlled bond between the carrier 10 and the thin sheet 20 within the areas bounded by perimeters 52 whereby a separation force may separate (without catastrophic damage to the thin sheet or carrier) the thin sheet and carrier in this region, yet the thin sheet and carrier will not delaminate during processing, including ultrasonic processing.
• the controlled bonding of the present application as provided by the surface modification layers and any associated heat treatments, is thus able to improve upon the carrier concept in US '727.
• This problem can be eliminated by minimizing the gap between the thin glass and the carrier and by providing sufficient adhesion, or controlled bonding between the carrier 20 and thin glass 10 in these areas 50.
• Surface modification layers including materials and any associated heat treatments as exemplified by examples 2a, 2e, 3a, 3b, 4c, 4d, 4e, and the examples of Table 5, of the bonding surfaces control the bonding energy so as to provide a sufficient bond between a glass bonding surface on the thin sheet 20 and a glass surface on the carrier 10 to avoid these unwanted vibrations in the controlled bonding region.
• the portions of thin sheet 20 within the perimeters 52 may simply be separated from the carrier 10 after processing and after separation of the thin sheet along perimeters 57.
• the surface modification layers control bonding energy to prevent permanent bonding of the thin sheet with the carrier, they may be used for processes wherein temperatures are > 600°C.
• these surface modification layers may control bonding surface energy during processing at temperatures > 600°C, they may also be used to produce a thin sheet and carrier combination that will withstand processing at lower temperatures, and may be used in such lower temperature applications.
• a third use of controlled bonding via surface modification layers is to provide a bonding area between a glass carrier and a glass thin sheet.
• a glass thin sheet 20 may be bonded to a glass carrier 10 by a bonded area 40.
• the bonded area 40, the carrier 10 and thin sheet 20 may be covalently bonded to one another so that they act as a monolith.
• controlled bonding areas 50 having perimeters 52, wherein the carrier 10 and thin sheet 20 are bonded to one another sufficient to withstand processing, and still allow separation of the thin sheet from the carrier even after high temperature processing, e.g. processing at temperatures > 600°C.
• surface modification layers 30 including materials and bonding surface heat treatments as exemplified by the examples la, lb, lc, 2b, 2c, 2d, 4a, 4b, 12d, 12e, 12f, 12h, and 12i, above, may be used to provide the bonding areas 40 between the carrier 10 and the thin sheet 20.
• these surface modification layers and heat treatments may be formed outside of the perimeters 52 of controlled bonding areas 50 either on the carrier 10 or on the thin sheet 20.
• the carrier and the thin sheet 20 will bond to one another within the bonding area 40 outside of the areas bounded by perimeters 52. Then, during extraction of the desired parts 56 having perimeters 57, when it is desired to dice the thin sheet 20 and carrier 10, the article may be separated along lines 5 because these surface modification layers and heat treatments covalently bond the thin sheet 20 with the carrier 10 so they act as a monolith in this area. Because the surface modification layers provide permanent covalent bonding of the thin sheet with the carrier, they may be used for processes wherein temperatures are > 600°C.
• thermal processing of the article, or of the initial formation of the bonding area 40 will be > 400°C but less than 600°C
• surface modification layers as exemplified by the materials and heat treatments in example 4a may also be used in this same manner.
• the carrier 10 and thin sheet 20 may be bonded to one another by controlled bonding via various surface modification layers described above. Additionally, there are controlled bonding areas 50, having perimeters 52, wherein the carrier 10 and thin sheet 20 are bonded to one another sufficient to withstand processing, and still allow separation of the thin sheet from the carrier even after high temperature processing, e.g. processing at temperatures > 600°C.
• these surface modification layers and heat treatments may be formed outside of the perimeters 52 of controlled bonding areas 50, and may be formed either on the carrier 10 or on the thin sheet 20.
• the controlled bonding areas 50 may be formed with the same, or with a different, surface modification layer as was formed in the bonding area 40.
• surface modification layers 30 including materials and bonding surface heat treatments as exemplified by the examples 2c, 2d, 2e, 3a, 3b, 4b, 4c, 4d, 4e, the examples of table 5, the examples of tables 7-11 (including the examples discussed as alternatives of the examples of table 10), examples 12a, 12b, 12c, 12g, 12g, and the examples of a surface treatment with 02 alone, above, may be used to provide the bonding areas 40 between the a glass bonding surface of carrier 10 and a glass bonding surface of the thin sheet 20.
• non-bonding regions in areas 50, wherein the non-bonding regions may be areas of increased surface roughness as described in US '727, or may be provided by surface modification layers as exemplified by example 2 a.
• a fourth use of the above-described manners of controlling bonding is for bulk annealing of a stack of glass sheets.
• Annealing is a thermal process for achieving compaction of the glass. Compaction involves reheating a glass body to a temperature below the glass softening point, but above the maximum temperature reached in a subsequent processing step. This achieves structural rearrangement and dimensional relaxation in the glass prior to, rather than during, the subsequent processing.
• Annealing prior to subsequent processing is beneficial to maintain precise alignment and/or flatness in a glass body during the subsequent processing, as in the manufacture of flat panel display devices, wherein structures made of many layers need to be aligned with a very tight tolerance, even after being subject to high temperature environments. If the glass compacts in one high temperature process, the layers of the structures deposited onto the glass prior to the high temperature process may not align correctly with the layers of the structures deposited after the high temperature process.
• anneal a stack of glass sheets wherein selected ones of the glass sheets are prevented from permanently bonding with one another, while at the same time, allowing other ones of the glass sheets, or portions of those other glass sheets, e.g., their perimeters, to permanently bond with each other.
• the above-described manners of controlling bonding between glass sheets may be used to achieve the foregoing bulk annealing and/or selective bonding.
• a surface modification layer on at least one of the major surfaces facing that interface.
• FIG. 7 is a schematic side view of a stack 760 of glass sheets 770-772
• FIG. 8 is an exploded view thereof for purposes of further explanation.
• a stack 760 of glass sheets may include glass sheets 770-772, and surface modification layers 790 to control the bonding between the glass sheets 770-772.
• the stack 760 may include cover sheets 780, 781 disposed on the top and bottom of the stack, and may include surface modification layers 790 between the covers and the adjacent glass sheets.
• each of the glass sheets 770-772 includes a first major surface 776 and a second major surface 778.
• the glass sheets may be made of any suitable glass material, for example, an alumino-silicate glass, a boro-silicate glass, or an alumino-boro- silicate glass. Additionally, the glass may be alkali containing, or may be alkali- free.
• Each of the glass sheets 770-772 may be of the same composition, or the sheets may be of different compositions. Further, the glass sheets may be of any suitable type. That is, for example, the glass sheets 770-772 may be all carriers as described above, may be all thin sheets as described above, or may alternately be carriers and thin sheets.
• any one glass sheet may include no surface modification layers, one surface modification layer, or two surface modification layers.
• sheet 770 includes no surface modification layers
• sheet 771 includes one surface modification layer 790 on its second major surface 778
• sheet 772 includes two surface modification layers 790 wherein one such surface modification layer is on each of its major surfaces 776, 778.
• the cover sheets 780, 781 may be any material that will suitably withstand (not only in terms of time and temperature, but also with respect to other pertinent considerations like outgassing, for example) the time-temperature cycle for a given process.
• the cover sheets may be made of the same material as the glass sheets being processed.
• a surface modification layer 790 may be included between the glass sheet 771 and the cover sheet 781 and/or between the glass sheet 772 and the cover sheet 780, as appropriate.
• the surface modification layer may be on the cover (as shown with cover 781 and adjacent sheet 771), may be on the glass sheet (as shown with cover 780 and sheet 772), or may be on both the cover and the adjacent sheet (not shown).
• cover sheets 780, 781 are present, but are of a material that will not bond with the adjacent sheets 772, 772, then surface modification layers 790 need not be present therebetween.
• an interface Between adjacent sheets in the stack, there is an interface. For example, between adjacent ones of the glass sheets 770-772, there is defined an interface, i.e., there is an interface 791 between sheet 770 and sheet 771, and interface 792 between sheet 770 and sheet 772. Additionally, when the cover sheets 780, 781 are present, there is an interface 793 between cover 781 and sheet 771, as well as an interface 794 between sheet 772 and cover 780.
• a surface modification layer 790 In order to control bonding at a given interface 791, 792 between adjacent glass sheets, or at a given interface 793, 794 between a glass sheet and a cover sheet, there may be used a surface modification layer 790.
• a surface modification layer 790 there is present at each interface 791, 792, a surface modification layer 790 on at least one of the major surfaces facing that interface.
• the second major surface 778 of glass sheet 771 includes a surface modification layer 790 to control the bonding between sheet 771 and adjacent sheet 770.
• the first major surface 776 of sheet 770 could also include a surface modification layer790 thereon to control bonding with sheet 771, i.e., there may be a surface modification layer on each of the major surfaces facing any particular interface.
• the particular surface modification layer 790 (and any associated surface modification treatment - for example a heat treatment on a particular surface prior to application of a particular surface modification layer to that surface, or a surface heat treatment of a surface with which a surface modification layer may contact) at any given interface 791-794, may be selected for the major surfaces 776, 778 facing that particular interface 791-794 to control bonding between adjacent sheets and, thereby, achieve a desired outcome for a given time-temperature cycle to which the stack 760 is subjected.
• any particular interface for example interface 791
• bonding at any particular interface could be controlled using a material according to any one of the examples 2a, 2c, 2d, 2e, 3a, 3b, 4b-4e, the examples of table 5, the examples of tables 7-11 (including the examples discussed as alternatives of the examples of table 10), examples 12a, 12b, 12c, 12g, 12g, or the examples of a surface treatment with 02 alone, together with any associated surface preparation.
• first surface 776 of sheet 770 would be treated as the "Thin Glass” in Tables 2-4, whereas the second surface 778 of sheet 771, would treated as the "Carrier” in Tables 2- 4, or vice versa.
• a suitable time-temperature cycle having a temperature up to 400°C, could then be chosen based on the desired degree of compaction, number of sheets in the stack, as well as size and thickness of the sheets, so as to achieve the requisite time-temperature throughout the stack.
• any particular interface for example interface 791
• bonding at any particular interface could be controlled using a material according to any one of the examples 2a, 2e, 3 a, 3b, 4c, 4d, 4e, or the examples of table 5, together with any associated surface preparation. More specifically, the first surface 776 of sheet 770 would be treated as the "Thin Glass” in Tables 2-4, whereas the second surface 778 of sheet 771, would treated as the "Carrier” in Tables 2- 4, or vice versa.
• a suitable time-temperature cycle having a temperature up to 600°C, could then be chosen based on the desired degree of compaction, number of sheets in the stack, as well as size and thickness of the sheets, so as to achieve the requisite time-temperature throughout the stack.
• the bonding at the interface between pairs of glass sheets to be formed into an article 2 could be controlled using: (i) a material according to any one of the examples 2c, 2d, 4b, the examples of tables 7-1 1 (including the examples discussed as alternatives of the examples of table 10), examples 12a, 12b, 12c, 12g, 12g, or the examples of a surface treatment with 02 alone, together with any associated surface preparation, around the perimeter (or other desired bonding area 40) of the sheets 770, 771 ; and (ii) a material according to any one of the examples 2a, 2e, 3a, 3b, 4c, 4d, 4e, or the examples of table 5, together with any associated surface preparation, on an interior area (i.e., an area interior of the perimeter as treated in (i), or in desired controlled bonding areas 50 where separation of one sheet from the other is desired) of the sheets 770, 771.
• device i.e., an area interior of the perimeter as treated in (i), or in desired controlled bonding areas 50 where separation of
• Materials and heat treatments could be appropriately selected for compatibility with one another.
• any of the materials 2c, 2d, or 4b could be used for the bonding areas 40 with a material according to example 2a for the controlled bonding areas.
• the heat treatment for the bonding areas and controlled bonding areas could be appropriately controlled to minimize the effect of heat treatment in one area adversely affecting the desired degree of bonding in an adjacent area.
• the bonding at the interface between one pair of sheets that are to be covalently bonded by bonding areas 40 to form an article 2, and another pair of such sheets forming a separate but adjacent article 2, could be controlled with the materials and associated heat treatments of examples 2a, 2e, 3a, 3b, 4c, 4d, 4e, the examples of table 5, so that adjacent articles 2 would not be covalently bonded to one another.
• the heating above about 400°C should be performed in an oxygen-free atmosphere when it is desired to prevent covalent bonding in the area of the HMDS. That is, if the HMDS is exposed to an amount of oxygen in the atmosphere (at a temperature above about 400°C) sufficient to oxidize the HMDS, the bonding in any such area where the HMDS has been oxidized will become covalent bonding between adjacent glass sheets.
• alkyl hydrocarbon silanes similarly can be affected by exposure to oxygen at higher temperatures, e.g., above about 400°C, e.g., ethyl, propyl, butyl, or steryl, silanes.
• oxygen free may mean an oxygen concentration of less than 1000 ppm by volume, more preferred less than 100 ppm by volume.
• individual sheets may be separated from the stack.
• the individual sheets can be treated (for example, by oxygen plasma, heating in an oxygen environment at a temperature > 400°C, or by chemical oxidation, SCI, or SC2) to remove the surface modification layer 790.
• the individual sheets can be used as desired, for example, as electronic device substrates, for example OLED, FPD, or PV devices).
• the above-described methods of bulk annealing, or bulk processing have the advantage of maintaining clean sheet surfaces in an economical manner. More specifically, the sheets do not need to be kept in a clean environment from start to finish, as in a clean- room annealing lehr. Instead, the stack can be formed in a clean environment, and then processed in a standard annealing lehr (i.e., one in which cleanliness is not controlled) without the sheet surfaces getting dirty with particles because there is no fluid flow between the sheets. Accordingly, the sheet surfaces are protected from the environment in which the stack of sheets is annealed.
• the stack of sheets can be easily transported to a further processing area (either in the same or a different facility) because the sheets maintain some degree of adhesion, yet remain separable from one another upon sufficient force without damaging the sheets. That is, a glass manufacturer (for example) can assemble and anneal a stack of glass sheets, and then ship the sheets as a stack wherein they remain together during shipping (without fear of them separating in transit), whereupon arriving at their destination the sheets may be separated from the stack by a customer who may use the sheets individually or in smaller groups. Once separation is desired, the stack of sheets can again be processed in a clean environment (after washing the stack as necessary).
• fusion drawn glass composition was (in mole %): Si02 (67.7), A1203 (11.0), B203 (9.8), CaO (8.7), MgO (2.3), SrO (0.5). Seven (7), 0.7 mm thick by 150 mm diameter, fusion drawn glass substrates were patterned by lithographic methods with 200 nm deep fiducials/verniers using HF.
• the 7 coated individual glass substrates were placed together to form a single, thick substrate (referred to as the "glass stack").
• the glass stack was annealed in a nitrogen purged tube furnace ramping from 30°C to 590°C over a 15 minute period, holding 30 minutes at 590°C, then ramping down to about 230°C over a 50 minute period, then removing the glass stack from the furnace and cooling to room temperature of about 30°C in about 10 minutes.
• the substrates were removed from the furnace and easily separated into individual sheets (i.e., the samples did not permanently bond, globally or locally) using a razor wedge.
• Compaction was measured on each individual substrate by comparing the glass fiducials to a non-annealed quartz reference. The individual substrates were found to compact about 185 ppm. Two of the substrates as individual samples (not stacked together) went through a second anneal cycle as described above (590°C/30 minute hold). Compaction was measured again and the substrates were found to further compact less than 10 ppm (actually 0 to 2.5 ppm) due to the second heat treatment (change in glass dimensions— as compared with original glass dimension— after the second heat treatment minus the change in glass dimensions after the first heat treatment).
• individual glass sheets can be coated, stacked, heat treated at a high temperature to achieve compaction, cooled, separated into individual sheets and have ⁇ 10 ppm, and even ⁇ 5 ppm in dimension change (as compared to their size after the first heat treatment) after a second heat treatment.
• annealing furnaces may also be purged with other gasses including, air, argon, oxygen, C02, or combinations thereof, depending upon the annealing temperature, and the stability of the surface modification layer material at those temperatures in a particular environment.
• the furnace in the above-described annealing could be a vacuum environment.
• the glass may be annealed in a spool, instead of sheet, form. That is, a suitable surface modification layer may be formed on one or both sides of a glass ribbon, and the ribbon then rolled. The entire roll could be subject to the same treatment as noted above for sheets, whereupon the glass of the entire spool would be annealed without sticking one wrap of the glass to an adjacent one. Upon un-rolling, the surface modification layer may be removed by any suitable process.
• Polymer adhesives used in typical wafer bonding applications are generally 10-100 microns thick and lose about 5% of their mass at or near their temperature limit.
• mass-spectrometry For such materials, evolved from thick polymer films, it is easy to quantify the amount of mass loss, or outgassing, by mass-spectrometry.
• mass-spectrometry On the other hand, it is more challenging to measure the outgassing from thin surface treatments that are on the order of 10 nm thick or less, for example the plasma polymer or self-assembled monolayer surface modification layers described above, as well as for a thin layer of pyrolyzed silicone oil.
• mass-spectrometry is not sensitive enough. There are a number of other ways to measure outgassing, however.
• a first manner of measuring small amounts of outgassing is based on surface energy measurements, and will be described with reference to FIG. 9.
• a setup as shown in FIG. 9 may be used.
• a first substrate, or carrier, 900 having the to-be- tested surface modification layer thereon presents a surface 902, i.e., a surface modification layer corresponding in composition and thickness to the surface modification layer 30 to be tested.
• a second substrate, or cover, 910 is placed so that its surface 912 is in close proximity to the surface 902 of the carrier 900, but not in contact therewith.
• the surface 912 is an uncoated surface, i.e., a surface of bare material from which the cover is made.
• Spacers 920 are placed at various points between the carrier 900 and cover 910 to hold them in spaced relation from one another.
• the spacers 920 should be thick enough to separate the cover 910 from the carrier 900 to allow a movement of material from one to the other, but thin enough so that during testing the amount of contamination from the chamber atmosphere on the surfaces 902 and 912 is minimized.
• the surface energy of bare surface 912 is measured, as is the surface energy of the surface 902, i.e., the surface of carrier 900 having the surface modification layer provided thereon.
• test article 901 is placed into a heating chamber 930, and is heated through a time-temperature cycle.
• the heating is performed at atmospheric pressure and under flowing N2 gas, i.e., flowing in the direction of arrows 940 at a rate of 2 standard liters per minute.
• changes in the surface 902 are evidenced by a change in the surface energy of surface 902.
• a change in the surface energy of surface 902 by itself does not necessarily mean that the surface modification layer has outgassed, but does indicate a general instability of the material at that temperature as its character is changing due to the mechanisms noted above, for example.
• the less the change in surface energy of surface 902 the more stable the surface modification layer.
• any material outgassed from surface 902 will be collected on surface 912 and will change the surface energy of surface 912. Accordingly, the change in surface energy of surface 912 is a proxy for outgassing of the surface modification layer present on surface 902.
• one test for outgassing uses the change in surface energy of the cover surface 912. Specifically, if there is a change in surface energy— of surface 912— of > 10 mJ/m2, then there is outgassing. Changes in surface energy of this magnitude are consistent with contamination which can lead to loss of film adhesion or degradation in material properties and device performance. A change in surface energy of ⁇ 5 mJ/m2 is close to the repeatability of surface energy measurements and inhomogeneity of the surface energy. This small change is consistent with minimal outgassing.
• the carrier 900, the cover 910, and the spacers 920 were made of Eagle XG glass, an alkali-free alumino-boro-silicate display-grade glass available from Corning Incorporated, Corning, NY, although such need not be the case.
• the carrier 900 and cover 910 were 150mm diameter 0.63mm thick.
• the carrier 910 and cover 920 will be made of the same material as carrier 10 and thin sheet 20, respectively, for which an outgassing test is desired.
• silicon spacers 0.63 mm thick, 2mm wide, and 8cm long, thereby forming a gap of 0.63 mm between surfaces 902 and 912.
• the chamber 930 was incorporated in MPT- RTP600s rapid thermal processing equipment that was cycled from room temperature to the test limit temperature at a rate of 9.2°C per minute, held at the test limit temperature for varying times as shown in the graphs as "Anneal Time", and then cooled at furnace rate to 200°C.
• the test article was removed, and after the test article had cooled to room temperature, the surface energies of each surface 902 and 912 were again measured.
• the data was collected as follows. The data point at 0 minutes shows a surface energy of 75 mJ/m2 (milli- Joules per square meter), and is the surface energy of the bare glass, i.e., there has been no time-temperature cycle yet run.
• the data point at one minute indicates the surface energy as measured after a time-temperature cycle performed as follows: the article 901 (having Material #1 used as a surface modification layer on the carrier 900 to present surface 902) was placed in a heating chamber 930 at room temperature, and atmospheric pressure; the chamber was heated to the test-limit temperature of 450°C at a rate of 9.2°C per minute, with a N2 gas flow at two standard liters per minute, and held at the test-limit temperature of 450°C for 1 minute; the chamber was then allowed to cool to 300°C at a rate of 1 °C per minute, and the article 901 was then removed from the chamber 930; the article was then allowed to cool to room temperature (without N2 flowing atmosphere); the surface energy of surface 912 was then measured and plotted as the point for 1 minute on line 1003.
• Material #1 is a CHF3 -CF4 plasma polymerized fluoropolymer. This material is consistent with the surface modification layer in example 3b, above. As shown in FIG. 10, lines 1001 and 1002 show that the surface energy of the carrier did not significantly change. Thus, this material is very stable at temperatures from 450°C to 600°C. Additionally, as shown by the lines 1003 and 1004, the surface energy of the cover did not significantly change either, i.e., the change is ⁇ 5mJ/m2. Accordingly, there was no outgassing associated with this material from 450°C to 600°C.
• Material #2 is a phenylsilane, a self-assembled monolayer (SAM) deposited form 1% toluene solution of phenyltriethoxysilane and cured in vacuum oven 30 minutes at 190°C.
• SAM self-assembled monolayer
• Material #3 is a pentafluorophenylsilane, a SAM deposited from 1% toluene solution of pentafluorophenyltriethoxysilane and cured in vacuum oven 30 minutes at 190°C. This material is consistent with the surface modification layer in example 4e, above. As shown in FIG. 10, lines 1301 and 1302 indicate some change in surface energy on the carrier. As noted above, this indicates some change in the surface modification layer, and
• Material #4 is hexamethyldisilazane (HMDS) deposited from vapor in a YES HMDS oven at 140°C. This material is consistent with the surface modification layer in Example 2b, of Table 2, above. As shown in FIG. 10, lines 1401 and 1402 indicate some change in surface energy on the carrier. As noted above, this indicates some change in the surface modification layer, and comparatively, Material #4 is somewhat less stable than Material #1. Additionally, the change in surface energy of the carrier for Material #4 is greater than that for any of Materials #2 and #3 indicating, comparatively, that Material #4 is somewhat less stable than Materials #2 and #3.
• HMDS hexamethyldisilazane
• Material #5 is Glycidoxypropylsilane, a SAM deposited from 1% toluene solution of glycidoxypropyltriethoxysilane and cured in vacuum oven 30 minutes at 190°C. This is a comparative example material. Although there is relatively little change in the surface energy of the carrier, as shown by lines 1501 and 1502, there is significant change in surface energy of the cover as shown by lines 1503 and 1504. That is, although Material #5 was relatively stable on the carrier surface, it did, indeed outgas a significant amount of material onto the cover surface whereby the cover surface energy changed by > 10mJ/m2.
• Material #6 is DC704 a silicone coating prepared by dispensing 5 ml Dow Corning 704 diffusion pump oil tetramethyltetraphenyl trisiloxane (available from Dow Corning) onto the carrier, placing it on a 500°C hot plate in air for 8 minutes. Completion of sample preparation is noted by the end of visible smoking. After preparing the sample in the above manner, the outgassing testing described above was carried out. This is a comparative example material. As shown in FIG. 10, lines 1601 and 1602 indicate some change in surface energy on the carrier. As noted above, this indicates some change in the surface modification layer, and comparatively, Material #6 is less stable than Material #1.
• the change in surface energy of the carrier is > 10mJ/m2, showing significant outgassing. More particularly, at the test-limit temperature of 450°C, the data point for 10 minutes shows a decrease in surface energy of about 15 mJ/m2, and even greater decrease in surface energy for the points at 1 and 5 minutes. Similarly, the change in surface energy of the cover during cycling at the 600°C test-limit temperature, the decrease in surface energy of the cover was about 25 mJ/m2 at the 10 minute data point, somewhat more at 5 minutes, and somewhat less at 1 minute. Altogether, though, a significant amount of outgassing was shown for this material over the entire range of testing.
• Material #7 is a is CH4-H2 plasma deposited polymer sequentially treated with brief N2-02 and N2 plasmas. This material is similar to the surface modification layer in the examples of Table 1 1, above. As shown in FIG. 10, lines 7001 and 7002 show that the surface energy of the carrier did not significantly change. Thus, this material is very stable at temperatures from 450°C to 600°C. Additionally, as shown by the lines 7003 and 7004, the surface energy of the cover did not significantly change either, i.e., the change is ⁇ 5mJ/m2. Accordingly, there was no outgassing associated with this material from 450°C to 600°C.
• a second manner of measuring small amounts of outgassing is based on an assembled article, i.e., one in which a thin sheet is bonded to a carrier via a surface modification layer, and uses a change in percent bubble area to determine outgassing. That is, during heating of the article, bubbles formed between the carrier and the thin sheet indicate outgassing of the surface modification layer. As noted above in connection with the first outgassing test, it is difficult to measure outgassing of very thin surface modification layers. In this second test, the outgassing under the thin sheet may be limited by strong adhesion between the thin sheet and carrier.
• layers ⁇ 10 nm thick may still create bubbles during thermal treatment, despite their smaller absolute mass loss.
• the creation of bubbles between the thin sheet and carrier may cause problems with pattern generation, photolithography processing, and/or alignment during device processing onto the thin sheet.
• bubbling at the boundary of the bonded area between the thin sheet and the carrier may cause problems with process fluids from one process contaminating a downstream process.
• a change in % bubble area of > 5 is significant, indicative of outgassing, and is not desirable.
• a change in % bubble area of ⁇ 1 is insignificant and an indication that there has been no outgassing.
• the average bubble area of bonded thin glass in a class 1000 clean room with manual bonding is 1%.
• the %bubbles in bonded carriers is a function of cleanliness of the carrier, thin glass sheet, and surface preparation. Because these initial defects act as nucleation sites for bubble growth after heat treatment, any change in bubble area upon heat treatment less than 1% is within the variability of sample preparation.
• a commercially available desktop scanner with transparency unit (Epson Expression l OOOOXL Photo) was used to make a first scan image of the area bonding the thin sheet and carrier immediately after bonding. The parts were scanned using the standard Epson software using 508 dpi (50 micron/pixel) and 24 bit RGB.
• the image processing software first prepares an image by stitching, as necessary, images of different sections of a sample into a single image and removing scanner artifacts (by using a calibration reference scan performed without a sample in the scanner).
• the bonded area is then analyzed using standard image processing techniques such as thresholding, hole filling, erosion/dilation, and blob analysis.
• the newer Epson Expression 11000XL Photo may also be used in a similar manner. In transmission mode, bubbles in the bonding area are visible in the scanned image and a value for bubble area can be determined.
• the bubble area is compared to the total bonding area (i.e., the total overlap area between the thin sheet and the carrier) to calculate a % area of the bubbles in the bonding area relative to the total bonding area.
• the samples are then heat treated in a MPT-RTP600s Rapid Thermal Processing system under N2 atmosphere at test-limit temperatures of 300°C, 450°C, and 600°C, for up to 10 minutes.
• the time- temperature cycle carried out included: inserting the article into the heating chamber at room temperature and atmospheric pressure; the chamber was then heated to the test-limit temperature at a rate of 9°C per minute; the chamber was held at the test- limit temperature for
• % bubble area from the second scan was then calculated as above and compared with the % bubble area from the first scan to determine a change in % bubble area ( ⁇ % bubble area).
• a change in bubble area of > 5% is significant and an indication of outgassing.
• a change in % bubble area was selected as the measurement criterion because of the variability in original % bubble area. That is, most surface modification layers have a bubble area of about 2% in the first scan due to handling and cleanliness after the thin sheet and carrier have been prepared and before they are bonded. However, variations may occur between materials.
• PEN polyethylene naphthalate
• PET polyethylene terephthalate
• PI polyimide
• the present application describes use of thin surface modification layers to form moderate adhesion between a glass carrier and a polymer sheet to create a controlled temporary bond sufficiently strong to survive TFT processing but weak enough to permit debonding.
• thermal, vacuum, solvent and acidic, and ultrasonic Flat Panel Display (FPD) processes require a robust bond for thin polymer sheet bound to carrier
• various ones of the present surface modification layers discussed herein were able to achieve such a controlled bonding for processing a polymer thin sheet on a glass carrier.
• the controlled bonding was able to allow the polymer thin sheet to be removed from the carrier, without catastrophic damage to either the polymer thin sheet or the glass carrier and, thereby, provide a re-usable glass carrier.
• amorphous silicon (aSi) bottom gate TFT amorphous silicon (aSi) bottom gate TFT
• polycrystalline silicon (pSi) top gate TFT amorphous oxide (IGZO) bottom gate TFT.
• IGZO amorphous oxide
• Metal, dielectric, and semiconductor materials are deposited by vacuum processes, for example, sputtering metals, transparent conductive oxides and oxide semiconductors, Chemical Vapor Deposition (CVD) deposition of amorphous silicon, silicon nitride, and silicon dioxide at elevated temperature.
• CVD Chemical Vapor Deposition
• Laser and flash lamp annealing permit p-Si crystallization without excessive substrate heating, but uniformity is challenging and performance poor compared to glass substrates.
• Layers are patterned by a photolithographic patterning of polymer resist, and etching, followed by resist strip. Both vacuum plasma (dry) etch and acidic wet etch processes are used. In FPD processing, photoresist is typically stripped by a hot solvent, typically with ultrasonic or megasonic agitation.
• the present application describes a method for controlled temporary bonding of polymer sheets to glass carriers for FPD processes and describes a reusable glass carrier for sheet to sheet processing of thin polymer substrates.
• the formation of a surface modification layer on the glass carrier creates temporary bonding with moderate adhesion between the thin polymer sheet and carrier.
• the moderate adhesion is achieved by optimizing the contributions of van der Waals and covalent attractive energies to the total adhesion energy which is controlled by modulating the polar and non-polar surface energy components of the thin sheet and the carrier.
• This moderate bonding is strong enough to survive FPD processing (including wet ultrasonic, vacuum, and thermal processes) and yet allow the polymer sheet to remain de- bondable from the carrier by application of sufficient peeling force. De-bonding permits removal of devices fabricated on the thin polymer sheet, and re-use of the carrier since the surface modification layer is ⁇ 1 micron thick and readily removed in oxygen plasma.
• PEN and PET are the among the typically-chosen polymer substrates available in roll form for electronic fabrication. Compared to most polymers they are relatively chemically inert, have low water absorption, low expansion, and are temperature resistant. However these properties are inferior to those of glass. For example, the maximum temperature for non-heat stabilized PEN is 155°C, whereas that for PET is only 120°C. These temperatures are low compared to the >600°C use temperatures of display glass suitable for pSi processing. Thermal expansion is about 20 ppm for PEN as opposed to 3.5ppm for display glass. And shrinkage at temperature is about 0.1% after 30 min at 150°C, which is far in excess of relaxation and compaction in glass at considerably higher temperature. These inferior physical properties of the polymer substrate require process adaptations to deposit high quality devices at high yields. For example, silicon dioxide, silicon nitride and amorphous silicon deposition temperatures must be lowered to stay within the limits for the polymer substrate.
• thermal expansion of the polymer sheets is typically more than 6x that of display glass.
• thermal stress is large enough to create warp and bow, and cause delamination when using conventional bonding techniques.
• high expansion glass such as soda lime or higher expansion metal carriers helps manage the warp challenge, but these carriers typically have challenges with respect to contamination, compatibility or roughness (thermal transfer).
• PEN and PET are also considerably lower than that of glass.
• Corning® Eagle XG® glass exhibits a surface energy of about 77 mJ/m2 after cleaning with SCI chemistry and standard cleaning techniques. See example 16e.
• PEN and PET are non-polar with a surface energy of 43-45 mJ/m2 ( 43-45 dyn/cm).
• Plasma cleaning treatment greatly increases the surface energy to 55-65 mJ/m2 (55-65 dyn/cm, "plasma") by increasing the polar component.
• UV ozone treatment, or corona discharge may be used to clean the polymer and briefly raise its surface energy. However, over time the surface
• an appropriate surface modification layer to adjust the surface energy of the glass carrier appropriately, adequate wetting and adhesion strength can be achieved to controllably bond a polymer, for example, PEN or PET, to a glass carrier in a manner suitable for organic-TFT processing (including a one hour 120°C vacuum anneal and a one minute 150°C post bake step) while allowing removability of the polymer from the carrier after processing.
• the polymer sheet can be successfully removed from the carrier, i.e., the polymer sheet is controllably bonded to the carrier, if even after the above processing there is seen no noticeable difference in transistor geometry between the OTFT on the polymer sheet and that on the mask used to produce it.
• the surface modification layer may be chosen from among the various materials and treatments exemplified throughout the specification.
• the polymer material advantageously maybe plasma cleaned prior to bonding (to increase the polar component of its surface energy so as to facilitate initial bonding), but need not be, as the surface energies of the glass carrier can be varied greatly so as to achieve a suitable level for controlled bonding with the polymer in its current state (i.e., either as received, as cleaned, or as aged).
• a range of surface energies from about 36 mJ/m2 (example 5g) to about 80 mJ/m2 (example 5f) can be attained on a glass carrier bonding surface.
• Several of the above-described methods of surface modification are suitable for adhesive bonding of polymer sheets to a glass carrier, including those formed from carbon sources, for example from plasma polymerization of hydrocarbon gasses.
• plasma polymer films deposited from fluorocarbon gasses (examples 5a and 5g); plasma polymer films deposited from fluorocarbon gasses and subsequently treated simultaneously with nitrogen and hydrogen (example 5m); plasma polymer films deposited from various non-fluorine-containing gasses (examples 6a-6j); plasma polymer films deposited from various mixtures of hydrocarbon, optionally nitrogen, and hydrogen, gasses (examples 7a-g, 12j); plasma polymer films deposited from various non-fluorine-containing gasses and subsequently treated with nitrogen (examples 9a-9j), wherein these surface energies may be useful with polymers in various states of cleanliness and/or aging; and plasma polymer films deposited from various non-fluorine-containing gasses and subsequently treated sequentially with nitrogen then
• One example of using plasma polymerized films to tune the surface energy of, and cover surface hydroxyls on and/or control the type of polar bond on, a bonding surface is deposition of a surface modification layer thin film from a mixture of source gasses, including a hydrocarbon (for example, methane).
• Deposition of the surface modification layer may take place in atmospheric or in reduced pressure, and is performed with plasma excitation for example, DC or RF parallel plate, Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance (ECR), downstream microwave or RF plasma.
• the plasma polymerized surface modification layer may be disposed on the bonding surface of a carrier, a thin sheet, or both.
• plasma polymerization creates a layer of highly cross-linked material.
• Control of reaction conditions and source gases can be used to control the surface modification layer film thickness, density, and chemistry to tailor the functional groups to the desired application.
• the surface energy of a carrier bonding surface can be tuned. The surface energy can be tuned so as to control the degree of bonding, i.e., so as to prevent permanent covalent bonding, between the thin sheet and the carrier during subsequent treatments performed to dispose films or structures on the thin sheet.
• the glass carrier was a substrate made from Corning ® Eagle XG®, alumino boro silicate alkali-free display glass (available from Corning Incorporated, Corning NY). Before film deposition, the carriers were cleaned using an SCI and/or an SC2 chemistry and standard cleaning techniques.
• the films were deposited in an STS Multiplex PECVD apparatus (available from SPTS, Newport, UK) in triode electrode configuration mode wherein the carrier sat on a platen to which 50Watts of 380 kHz RF energy was applied, above the platen there was disposed a coil (shower head) to which 300 Watts of 13.5 MHz RF energy was applied, the temperature of the platen was 200°C, and the flow-rates of the gasses through the shower head were as shown in Table 16 (flowrates being in standard cubic centimeters per minute— seem).
• the notation in the "Surface Modification Layer Deposition Process" column of Table 16 for example 16b is read as follows: in the STS Multiplex PECVD apparatus, at a platen temperature of 200°C, 200 seem of H2, 50 seem of CH4, and 50 seem of C2F6, were flowed together through the shower head, into a chamber having a pressure of 300 mTorr; 300 W of 13.5 MHz RF energy was applied to the shower head; 50 W of 380 kHz RF energy was applied to the platen on which the carrier sat; and the deposition time was 120 seconds.
• the notation in the surface treatment column for the remaining examples can be read in a similar manner.
• Example 16e is a bare piece of Eagle XG® glass after having been cleaned with SCI chemistry and standard cleaning techniques.
• Example 16e shows that after cleaning, the surface energy of the glass was about 77 mJ/m 2 .
• Examples 16a to 16d show that surface modification layers may be deposited onto the glass surface to modify the surface energy thereof, so that the surface of the glass may be tailored to a particular bonding application.
• the examples of table 16 are examples of a one step process, as were the examples of tables 6 and 7, for deposition of a surface modification layer having desired surface energy and polar groups.
• Example 16a shows that the surface modification layer may be a plasma polymerized film deposited from a mixture of hydrogen and methane (hydrocarbon) gasses.
• the surface modification layer was deposited onto a cleaned glass carrier. Accordingly, the deposition of the surface modification layer is shown to reduce the surface energy from about 77 to about 49 mJ/m 2 , which is in the range of that on typical polymer bonding surfaces.
• Example 16b shows that the surface modification layer may be a plasma polymerized film deposited form a mixture of hydrogen, methane (hydrocarbon), and a fluorine-containing gas (for example, C2F6, a fluorocarbon).
• the surface modification layer was deposited onto a cleaned glass substrate. Accordingly, the deposition of the surface modification layer is shown to reduce the surface energy from about 77 to about 37 mJ/m 2 , about in the range of that on typical polymer bonding surfaces.
• the surface energy achieved in example 16b is lower than that achieved in example 16a, showing that an addition of fluorine to the deposition gasses can lower the surface energy achieved by otherwise similar surface modification layer deposition conditions.
• Example 16c shows that the surface modification layer may be a plasma polymerized film deposited from a mixture of hydrogen, methane (hydrocarbon), and a nitrogen-containing gas (for example, N2).
• the surface modification layer was deposited onto a cleaned glass carrier. Accordingly, the deposition of the surface modification layer is shown to reduce the surface energy from about 77 to about 61 mJ/m 2 , which is in the range of that on a typical polymer bonding surface that has been 02 plasma treated, as during cleaning of the polymer sheet. This surface energy is also in the range for suitability of bonding a thin glass sheet to the carrier.
• Example 16d shows that the surface modification layer may be a plasma polymerized film deposited form a mixture of methane (hydrocarbon), and a nitrogen- containing gas (for example, NH3).
• the surface modification layer was deposited onto a cleaned glass substrate. Accordingly, the deposition of the surface modification layer is shown to reduce the surface energy from about 77 to about 57 mJ/m 2 , again, in the range of that on typical polymer bonding surfaces. Also, for some applications, this may be suitable for bonding the carrier to a thin glass sheet.
• the surface energy obtained by the surface modification layer of example 16b was below 50 mJ/m 2 (considered as being suitable for controlled bonding of a glass thin sheet to a glass carrier), however this surface modification layers is suitable for bonding of a polymer bonding surface to a glass bonding surface. Additionally, it should be noted that the surface energy produced by the surface modification layers of examples 16c and 16d, (formed from plasma polymerization of hydrocarbon (methane), optionally hydrogen-containing (H2), and nitrogen-containing (N2 or ammonia) gasses) are greater than about 50 mJ/m 2 and, thus, in some instances may be suitable for bonding a thin glass sheet to a glass carrier.
• the thin sheet bonded to the carriers having surface modification layers disposed thereon as per the examples 16a to 16d of Table 16 was a substrate made from TEONEX® Q65 PEN (available from DuPont) and having a thickness of 200 microns .
• the bonding surface on which the surface modification layers were disposed was glass, such need not be the case. Instead, the bonding surface may be another suitable material having a similar surface energy and properties as glass, for example, silicon, polysilicon, single crystal silicon, ceramic, glass-ceramic, sapphire, or quartz.
• Plasma polymerized hydrocarbon polymer films may be deposited from methane and hydrogen (example 16a), with optional fluorocarbon (example 16b), optional nitrogen (example 16c), or optional ammonia (example 16d) additions in an STS Multiplex CVD in triode mode.
• Surface energy as low as 37mJ/m2 (example 16b) and higher surface energy (about 61 mJ./m2, example 16c) can be achieved with fluorocarbon, or nitrogen additions.
• Surface energies between the levels of examples 16b and 16c i.e., about 49 mJ/m2 as in example 16a, and about 57 mJ/m2 as in example 16d) can also be achieved, thus
• a polymer film was disposed onto a bare glass carrier as SCI cleaned (example 16e).
• the polymer sheet did not stick well enough to the carrier to allow processing of structures onto the polymer sheet.
• PEN TEONEX® Q65 200 micron thick sheet from DuPont
• Corning® Eagle XG® glass carrier Very good bonding performance was found with an amorphous carbon layer deposited with the following conditions: 50CH4 200H2 300W 13.56 MHz RF to showerhead, 50W 380 kHz RF to 200 °C platen and 2 minute deposition time.
• PEN was exposed to UV-Ozone cleaner for 5 minutes prior to bonding as this was found to improve adhesion.
• a Teflon squeegee was used to apply the PEN.
• An about 150nm thick cycloaliphatic epoxy layer was spun and cured on the PEN to smooth out the surface defects.
• the organic gate insulator (OGI) was a photopatternaable cycloaliphatic epoxy.
• An array of bottom gate bottom contact organic thin film transistors was formed by the following process.
• a lOOnm Al gate metal was deposited by sputtering in AJA, and lithographically pattern with Fuji 6512 resist, and the gate patterned by wet etch in Type A Al etchant.
• Photoresist was removed by 3min in a room temperature PGMEA bath, followed by IPA/DI rinse (NMP based stripers were incompatible with the epoxy layer).
• a second epoxy gate insulator layer was spun over the patterned gate and cured.
• a 1 OOnm thick Ag S/D metal was sputtered and lithographically patterned with Fuji 6512 and etched with a 1 : 1 mix of Transene TFS: pH 10 buffer.
• Etching was challenging because the Ag etch rate was fast, but dissolution of the etch products was slow. Very good results were obtained by etching 5s, removing etch products with spraying DI water, and repeating four to five times.
• OSC organic semiconductor
• OSC adhesion was promoted by HMDS treatment in a YES oven at 120°C.
• OSC polymer was dissolved in 6 parts decalin : 4 parts toluene at 5mg/mL concentration. The OSC was applied by spinning in the Laurel spinner with manual dispense, 20 second rest 500 rpm 30 second 1000 rpm 60 second.
• the OSC film was soft baked 90°C 2min on a hot plate, and vacuum annealed at 120°C for lhr in the Salvis oven under rough vacuum to remove residual decalin.
• a third OGI layer was spun over the OSC and directly photo patterned with a 2.5 second exposure, 1 min rest, and l min 150°C post bake.
• the active pattern was tray developed in PGMEA for lmin followed by IPA and DI rinse. Dry etching in the Unaxis 790 RTE using 30 seem 02 10 seem Ar 20 seem CHF3 50mT 200W 15s was used to pattern the active and expose the gate metal.
• Performance of the 75/75 um TFT's is summarized in the table shown in Figure 18, which shows drain current versus gate voltage and performance for a typical transistor with 75 micron channel width and 75 micron channel length, bottom gate bottom contact organic thin film transistors fabricated on PEN controllably bonded to a glass carrier as described above.
• the PEN was easily debonded by using a razor blade to initiate a crack and then peeling off.
• the polymer sheet was successfully removed from the carrier, even after the above processing, as there was seen no noticeable difference in transistor geometry between the OTFT on the polymer sheet and that on the mask used to produce it.
• the polymer may itself be the substrate on which other devices are fabricated.
• the polymer may be a polymer surface on a composite material substrate, for example, a glass/polymer composite.
• the polymer surface of the glass/polymer composite would face the carrier and would be bonded thereto as described above, whereas the glass surface of the glass/polymer composite would be exposed as a surface on which electronic or other structures may be fabricated.
• the polymer surface of the composite may be peeled from the surface modification layer on the carrier.
• This embodiment may be advantageous as the glass layer in the glass/polymer composite becomes particularly thin, for example, having a thickness of ⁇ 50 microns, ⁇ 40 microns, ⁇ 30 microns, ⁇ 20 microns, ⁇ 10 microns, or ⁇ 5 microns.
• the polymer portion of the glass/polymer composite would not only act as a bonding surface to attach the composite to a carrier, it may also lend some handling advantages to the composite when the composite is not on the carrier.
• the surface modification layer 30 of many embodiments is shown and discussed as being formed on the carrier 10, it may instead, or in addition, be formed on the thin sheet 20. That is, as appropriate, the materials as set forth in the examples of tables 3-12 and 16 may be applied to the carrier 10, to the thin sheet 20, or to both the carrier 10 and thin sheet 20 on faces that will be bonded together.
• controlled bonding concepts have been described herein as being used with a carrier and a thin sheet, in certain circumstances they are applicable to controlling bonding between thicker sheets of glass, ceramic, or glass ceramic, wherein it may be desired to detach the sheets (or portions of them) from each other.
• the carrier may be made of other materials, for example, ceramic, glass ceramic, or metal.
• the sheet controllably bonded to the carrier may be made of other materials, for example, ceramic or glass ceramic.
• the carbonaceous surface modification layer formed by plasma polymerization of examples 6-12 were formed using methane as a polymer forming gas
• the carbon- containing source could include at least one of: 1) a hydrocarbon (alkane, alkene, alkyne or aromatic.
• Alkanes include but are not limited to: methane, ethane, propane and butane; alkenes include but are not limited to: ethylene, propylene and butylene; alkynes include but are not limited to: acetylene, methylacetylene, ethylacetylene and dimethylacetylene;
• aromatics include but are not limited to: benzene, toluene, xylene, ethylbenzene); 2) an alcohol (including: methanol, ethanol, propanol); 3) an aldehyde or ketone (including:
• the carbon- containing source could include one or more of the following: 1) a saturated or unsaturated hydrocarbon, or 2) a nitrogen-containing or 3) oxygen-containing saturated or unsaturated hydrocarbon, or 4) CO or C02.
• Some generally typical carbon-containing source materials include carbon-containing gasses, for example methane, ethane, propane, butane, ethylene, propylene, propyne, acetylene, MAPP, CO, and C02.
• polar groups used to treat the surface modification layer, and thereby increase its surface energy as in examples 5 and 8-12, or used in the formation of the surface modification layer itself as in examples 7, 16c, 16d, were nitrogen and oxygen, other polar groups may be possible, for example, sulfur and/or phosphorous.
• N2 and NH3 were used as nitrogen-containing gasses, other nitrogen-containing materials may possibly be used, for example, hydrazine, N20, NO, N204, methylamine, dimethylamine, trimethylamine and ethylamine, acetonitrile.
• oxygen-containing gasses used were N2-02 and 02, it may be possible to use other oxygen-containing gasses, for example, 03, H20, methanol, ethanol, propanol,N20, NO, and N204.
• the surface modification layers can achieve a thickness from about 1 nm (example 16b) or 2 nm (examples 3, 4) to about 10 nm (example 12c, 8.8 nm).
• thicker surface modification layers are also possible, as explained with respect to FIG. 15.
• thickness becomes greater than about 70 nm the surface modification layer starts to become translucent, which may be undesirable for applications that benefit from optical clarity.
• a method of controllably bonding a thin sheet to a carrier comprising:
• first gas is one of a nitrogen-containing gas and a hydrogen-containing gas
• second gas is the other one of the nitrogen-containing gas and the hydrogen-containing gas
• the carbon-containing gas comprises at least one of a hydrocarbon, an alkane, an alkene, an alkyne, or aromatic.
• the method of aspect 3 wherein the carbon-containing gas comprises at least one of methane, ethane, propane, butane, ethylene, propylene, propyne, acetylene, CO, and C02.
• the hydrogen-containing gas comprises H2
• the nitrogen-containing gas comprises at least one of ammonia, N2, hydrazine, N20, NO, N204, methylamine, dimethylamine, trimethylamine, ethylamine, and acetonitrile.
• the hydrogen-containing gas comprises H2
• the oxygen-containing gas comprises at least one of 02, 03, H20, methanol, ethanol, propanol, N20, NO, and N204.
• the method of any one of aspects 2-8 wherein the surface modification layer is deposited from a mixture of a polymer- forming gas and a second gas, wherein the second gas is > 30% of the total mixture.
• the method of aspect 13 wherein the at least one of the thin sheet bonding surface and the carrier bonding surface comprises an average surface roughness Ra ⁇ 1 nm prior to deposition of the surface modification layer.
• the method of aspect 13 or aspect 14 wherein the at least one of the thin sheet bonding surface and the carrier bonding surface comprises an average surface roughness Ra ⁇ 1 nm after deposition, and subsequent removal by 02 plasma, of the surface modification layer.
• the carrier bonding surface has a first average surface roughness Ral prior to deposition of the surface modification layer, wherein the carrier has a second surface roughness Ra2 after the surface modification layer has been disposed thereon and subsequently removed by 02 plasma cleaning, and the difference between Ral and Ra2 is ⁇ lnm, when average surface roughness measurement is taken over a 5x5 micron area.
• the method of any one of aspects 1-16 wherein the thin sheet has a thickness ⁇ 300 microns.
• the method of any one of aspects 1-19 wherein the at least one of the thin sheet bonding surface and the carrier bonding surface comprises glass, and further wherein the surface modification layer and treatment thereof achieve on the bonding surface a second surface energy of 41 to 80 mJ/m 2 .
• a glass article comprising:
• a surface modification layer disposed on the carrier bonding surface, wherein the surface modification layer is configured so that when the carrier bonding surface is bonded with a glass sheet bonding surface with the surface modification layer therebetween, after subjecting the article to a temperature cycle by heating in an chamber cycled from room temperature to 600°C at a rate of 9.2 °C per minute, held at a temperature of 600°C for 10 minutes, and then cooled at 1 °C per minute to 300 °C, and then removing the article from the chamber and allowing the article to cool to room temperature, the carrier and sheet do not separate from one another if one is held and the other subjected to the force of gravity, there is no outgassing from the surface modification layer during the temperature cycle, and the sheet may be separated from the carrier without breaking the thinner one of the carrier and the sheet into two or more pieces.
• a glass article comprising:
• the carrier bonding surface being bonded with the sheet bonding surface with the surface modification layer therebetween, wherein the surface energy bonding the sheet to the carrier is of such a character that after subjecting the article to a temperature cycle by heating in an chamber cycled from room temperature to 600°C at a rate of 9.2 °C per minute, held at a temperature of 600°C for 10 minutes, and then cooled at 1 °C per minute to 300 °C, and then removing the article from the chamber and allowing the article to cool to room temperature, the carrier and sheet do not separate from one another if one is held and the other subjected to the force of gravity, there is no outgassing from the surface modification layer during the temperature cycle, and the sheet may be separated from the carrier without breaking the thinner one of the carrier and the sheet into two or more pieces.
• any one of aspects F there is provided the glass article of any one of aspects A to E or 1-20, wherein the carrier is a glass comprising an alkali- free, alumino- silicate or boro-silicate or alumino-boro-silicate, glass having arsenic and antimony each at a level ⁇ 0.05 wt.%.
• the carrier is a glass comprising an alkali- free, alumino- silicate or boro-silicate or alumino-boro-silicate, glass having arsenic and antimony each at a level ⁇ 0.05 wt.%.
• any one of aspects G there is provided the glass article of any one of aspects A to F or 1-20, wherein each of the carrier and the sheet is of a size 100 mm x 100 mm or larger.

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• 2015
  • 2015-01-27 EP EP15703682.3A patent/EP3099484A1/de not_active Withdrawn
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