WO2015113023A1 - Treatment of a surface modification layer for controlled bonding of thin sheets with carriers - Google Patents

Treatment of a surface modification layer for controlled bonding of thin sheets with carriers Download PDF

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Publication number
WO2015113023A1
WO2015113023A1 PCT/US2015/013017 US2015013017W WO2015113023A1 WO 2015113023 A1 WO2015113023 A1 WO 2015113023A1 US 2015013017 W US2015013017 W US 2015013017W WO 2015113023 A1 WO2015113023 A1 WO 2015113023A1
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WO
WIPO (PCT)
Prior art keywords
bonding
carrier
glass
gas
energy
Prior art date
Application number
PCT/US2015/013017
Other languages
French (fr)
Inventor
Robert Alan Bellman
Dana Craig Bookbinder
Theresa Chang
Shiwen Liu
Robert George MANLEY
Prantik Mazumder
Original Assignee
Corning Incorporated
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Filing date
Publication date
Priority to US201461931912P priority Critical
Priority to US61/931,912 priority
Application filed by Corning Incorporated filed Critical Corning Incorporated
Publication of WO2015113023A1 publication Critical patent/WO2015113023A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B17/00Layered products essentially comprising sheet glass, or glass, slag, or like fibres
    • B32B17/06Layered 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
    • B32B17/064Layered 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 synthetic resin
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B17/00Layered products essentially comprising sheet glass, or glass, slag, or like fibres
    • B32B17/06Layered 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B32LAYERED PRODUCTS
    • B32BLAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00Layered 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
    • B32B7/04Interconnection of layers
    • B32B7/06Interconnection of layers permitting easy separation
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL 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
    • C03C17/00Surface treatment of glass, not in the form of fibres or filaments, by coating
    • C03C17/28Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material
    • C03C17/32Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material with synthetic or natural resins
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL 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
    • C03C27/00Joining pieces of glass to pieces of other inorganic material; Joining glass to glass other than by fusing
    • C03C27/06Joining glass to glass by processes other than fusing
    • C03C27/10Joining glass to glass by processes other than fusing with the aid of adhesive specially adapted for that purpose
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIAL AS ADHESIVES
    • C09J5/00Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
    • C09J5/02Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers involving pretreatment of the surfaces to be joined
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING LIQUIDS OR OTHER FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05DPROCESSES FOR APPLYING LIQUIDS OR OTHER FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00Processes for applying liquids or other fluent materials
    • B05D1/62Plasma-deposition of organic layers
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03CCHEMICAL 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
    • C03C2218/00Methods for coating glass
    • C03C2218/30Aspects of methods for coating glass not covered above
    • C03C2218/32After-treatment
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIAL AS ADHESIVES
    • C09J2400/00Presence of inorganic and organic materials
    • C09J2400/10Presence of inorganic materials
    • C09J2400/14Glass
    • C09J2400/143Glass in the substrate
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09JADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIAL AS ADHESIVES
    • C09J2400/00Presence of inorganic and organic materials
    • C09J2400/10Presence of inorganic materials
    • C09J2400/14Glass
    • C09J2400/146Glass in the pretreated surface to be joined

Abstract

A method of controllably bonding a thin sheet to a carrier, wherein the thin sheet has a thin sheet bonding surface, and the carrier has a carrier bonding surface. Depositing a surface modification layer onto at least one of the thin sheet bonding surface and the carrier bonding surface so as to obtain a first surface energy on the one of the thin sheet bonding surface and the carrier bonding surface. Then, treating the surface modification layer so as to change the first surface energy to a second surface energy, wherein the second surface energy is greater than the first. And bonding the thin sheet bonding surface to the carrier bonding surface via the surface modification layer. Depositing the surface modification layer, and treating it, may be done by plasma polymerization processes.

Description

TREATMENT OF A SURFACE MODIFICATION LAYER FOR CONTROLLED BONDING OF THIN SHEETS WITH CARRIERS

BACKGROUND

[0001] This application claims the benefit of priority of U.S. Provisional Application Serial No. 61/931912 filed on January 27, 2014, the content of which is relied upon and

incorporated herein by reference in its entirety.

[0002] Field of the invention.

[0003] 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.

[0004] Technical Background.

[0005] Flexible substrates offer the promise of cheaper devices using roll-to-roll processing, and the potential to make thinner, lighter, more flexible and durable displays. However, the technology, equipment, and processes required for roll-to-roll processing of high quality displays are not yet fully developed. Since panel makers have already heavily invested in toolsets to process large sheets of glass, laminating a flexible substrate to a carrier and making display devices by a sheet-to-sheet processing offers a shorter term solution to develop the value proposition of thinner, lighter, and more flexible displays. Displays have been demonstrated on polymer sheets for example polyethylene naphthalate (PEN) where the device fabrication was sheet to sheet with the PEN laminated to a glass carrier. The upper temperature limit of the PEN limits the device quality and process that can be used. In addition, the high permeability of the polymer substrate leads to environmental degradation of OLED devices where a near hermetic package is required. Thin film encapsulation offers the promise to overcome this limitation, but it has not yet been demonstrated to offer acceptable yields at large volumes.

[0006] In a similar manner, 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.

[0007] However, the thermal, vacuum, solvent and acidic, and ultrasonic, Flat Panel Display (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).

[0008] Adhesive wafer bonding has been widely used in Micromechanical Systems (MEMS) and semiconductor processing for back end steps where processes are less harsh. 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.

[0009] US Provisional Application Serial No. 61/596,727 filed on February 8, 2012, entitled Processing Flexible Glass with a Carrier (hereinafter US '727) 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. 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

embodiments, this seal encompasses the outside of the article thereby preventing liquid or gas intrusion into or out of any region of the sealed article.

[0010] 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.

[0011] One commercial advantage to the approach disclosed in US '727 is that, as noted in US '727, manufacturers will be able to utilize their existing capital investment in processing equipment while gaining the advantages of the thin glass sheets for PV, OLED, LCDs and patterned Thin Film Transistor (TFT) electronics, for example. Additionally, that approach enables process flexibility, including: that for cleaning and surface preparation of the thin glass sheet and carrier to facilitate bonding; that for strengthening the bond between the thin sheet and carrier at the bonded area; that for maintaining releasability of the thin sheet from the carrier at the non-bonded (or reduced/low-strength bond) area; and that for cutting the thin sheets to facilitate extraction from the carrier.

[0012] In the glass-to-glass bonding process, 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 nm2 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. In US '727, 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. In US

Provisional Patent Application Serial No. 61/736,880, filed on December 13, 2012 by the same inventors and entitled Facilitated Processing for Controlling Bonding Between Sheet and Carrier (hereinafter US ' 880), a controlled bonding area is formed by controlling the van der Waals and/or hydrogen bonding between a carrier and a thin glass sheet, but a covalent bonding area is still used as well. Thus, although 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/m2, 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.

SUMMARY

[0013] In light of the above, there is a need for a thin sheet - carrier article that can withstand the rigors of the FPD processing, including high temperature processing (without outgassing that would be incompatible with the semiconductor or display making processes in which it will be used), yet allow the entire area of the thin sheet to be removed (either all at once, or in sections) from the carrier so as to allow the reuse of the carrier for processing another thin sheet. The present specification describes ways to control the adhesion between the carrier and thin sheet to create a temporary bond sufficiently strong to survive FPD processing (including LTPS processing) but weak enough to permit debonding of the sheet from the carrier, even after high-temperature processing. 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. More specifically, 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. Even more specifically, 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. And at the same time, 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. In alternative embodiments, 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. Still further, 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. Still further yet, in alternative embodiments, 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.

[0014] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the various aspects as exemplified in the written description and the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the various aspects, and are intended to provide an overview or framework to understanding the nature and character of the invention as it is claimed.

[0015] The accompanying drawings are included to provide a further understanding of principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain, by way of example, principles and operation of the invention. It is to be understood that various features disclosed in this specification and in the drawings can be used in any and all combinations. By way of non-limiting example the various features may be combined with one another as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a schematic side view of an article having carrier bonded to a thin sheet with a surface modification layer therebetween.

[0017] FIG. 2 is an exploded and partially cut-away view of the article in FIG. 1.

[0018] FIG. 3 is a graph of surface hydroxyl concentration on silica as a function of temperature.

[0019] FIG. 4 is a graph of the surface energy of an SCI -cleaned sheet of glass as a function annealing temperature.

[0020] 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.

[0021] FIG. 6 is a schematic top view of a thin sheet bonded to a carrier by bonding areas.

[0022] FIG. 7 is a schematic side view of a stack of glass sheets

[0023] FIG. 8 is an exploded view of one embodiment of the stack in FIG. 7. [0024] FIG. 9 is a schematic view of a testing setup

[0025] 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.

[0026] FIG. 1 1 is a graph of change in % bubble area versus temperature for a variety of materials.

[0027] FIG. 12 is another graph of change in % bubble area versus temperature for a variety of materials.

[0028] 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.

[0029] 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.

[0030] FIG. 14 is a graph of surface energy versus deposition time for a surface modification layer.

[0031] FIG. 15 is graph of thickness versus deposition time, on a log-log scale, for a surface modification layer.

[0032] FIG. 16 is a graph of surface energy versus treatment temperature for different surface modification layers.

[0033] FIG. 17 is a graph of surface modification layer surface coverage.

[0034] FIG. 18 is a summary of performance for an organic transistor fabricated on a 200 micron PEN film bonded to a glass carrier.

DETAILED DESCRIPTION

[0035] In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of various principles of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

[0036] 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.

[0037] Directional terms as used herein— for example up, down, right, left, front, back, top, bottom— are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0038] As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a "component" includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0039] In both US '727, and US '880, there are provided solutions for allowing the processing of a thin glass sheet on a carrier, whereby at least portions of the thin glass sheet remain "non-bonded" so that devices processed on the thin glass sheet may be removed from the carrier. However, the periphery of the thin glass is permanently (or covalently, or hermetically) bonded to the carrier glass through the formation of covalent Si-O-Si bonds. This covalently bonded perimeter prevents reuse of the carrier, as the thin glass cannot be removed in this permanently bonded zone without damaging the thin glass and carrier.

[0040] 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.

[0041] As shown in FIGS. 1 and 2, 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. 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. For example, if the processing equipment was designed for a 700 micron sheet, and the thin sheet had a thickness 28 of 300 microns, then 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. Typically, 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. Additionally, 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.

However, to the extent that 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.

[0042] 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. Additionally, 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).

[0043] 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. When the article 2 is processed at lower temperatures, where CTE matching is not such a concern, then a polymer thin sheet can be used with a glass carrier. Of course, there may be other instances where a polymer sheet may be used with a glass carrier. The thickness 28 of the thin sheet 20 is 300 microns or less, as noted above. Further, 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).

[0044] Not only does the article 2 need to have the correct thickness to be processed in the existing equipment, sometimes it will also need to be able to survive the harsh environment in which the processing takes place. For example, flat panel display (FPD) processing may include wet ultrasonic, vacuum, and in some instances high temperature (e.g., > 400°C), processing. For some processes, as noted above, the temperature may be > 500°C, or > 600°C, and up to 650°C.

[0045] 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. Such de-bonding permits removal of thin sheet 20 and the devices fabricated thereon, and also allows for re-use of the carrier 10.

[0046] Although the surface modification layer 30 is shown as a solid layer between thin sheet 20 and carrier 10, such need not be the case. For example, 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. For example, the coverage may be < 100%, from 1% to 100%, from 10% to 100%, from 20% to 90%, or from 50% to 90%. In other embodiments, 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. In any event, 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.

[0047] In general, the energy of adhesion between two surfaces is given by ("A theory for the estimation of surface and interfacial energies. I. derivation and application to interfacial tension", L. A. Girifalco and R. J. Good, J. Phys. Chem., V 61, p904):

W= Y1 + Y2 - Y 12 (1) where, Yir Y2 and Yl2 are the surface energies of surface 1, surface 2 and the interfacial energy of surface 1 and 2 respectively. The individual surface energies are usually a combination of two terms; a dispersion component yd, and a polar component γρ y= yd + yv (2) [0048] When the adhesion is mostly due to Lond