Abstract:
The invention broadly relates to cyclic olefin polymer bonding compositions and release compositions, to be used independently or together, that enable thin wafer handling during microelectronics manufacturing, especially during a full-wafer mechanical debonding process. The release compositions comprise compositions made from siloxane polymers and copolymers blended in a polar solvent, and that are stable at room temperature for longer than one month. The cyclic olefin polymer bonding compositions provide high thermal stability, can be bonded to fully-treated carrier wafers, can be mechanically or laser debonded after high-temperature heat treatment, and are easily removed with an industrially-acceptable solvent. Wafers bonded according to the invention demonstrate lower overall post-grind stack TTV compared to other commercial bonding materials and can survive 200° C. PECVD processing.

Description:
RELATED APPLICATION 
     This application claims the priority benefit of provisional applications entitled CYCLIC OLEFIN POLYMER COMPOSITIONS FOR USE IN TEMPORARY WAFER BONDING PROCESSES, Application No. 61/924,442, filed Jan. 7, 2014, and ULTRATHIN POLYSILOXANE COATINGS AS LOW-FORCE MECHANICAL RELEASE LAYERS FOR ADHESIVELY BONDED MICROELECTRONICS SUBSTRATES, Application No. 61/952,945, filed Mar. 14, 2014, each of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to release layers and bonding materials for temporary wafer bonding processes. 
     2. Description of the Prior Art 
     Wafer bonding materials protect device features on the front side of a device substrate, and provide adhesion to a carrier substrate and mechanical support for the thinned wafers during backside processing. 3D-IC processing, especially with through-silicon via (“TSV”) and through-glass via (“TGV”) technology, requires temporary wafer bonding materials to survive processes at high temperatures and high vacuum, such as plasma-enhanced chemical vapor deposition (“PECVD”). This technology also requires that the materials can be removed easily from the wafers after processing. Additionally, lower cost of ownership is needed for the 3D-IC to be adopted by the manufacturers. 
     Integrated circuit and semiconductor packaging manufacturers are continually looking for temporary wafer bonding technology with low cost of ownership, that uses materials capable of surviving processing at high temperatures and under high vacuum, and that can be easily cleaned after processing. So far, no single technology/material can satisfy all these requirements. Cyclic olefin copolymer (COC) bonding materials are one class of materials that are commonly used. These COCs, such as those formulated using TOPAS® and APEL® materials, are produced by chain copolymerization of cyclic monomers with ethene. These COC materials are good for some applications, but it is very difficult to obtain a clear solution in commonly-used solvents such as d-limonene and mesitylene, and it can also be difficult to clean them off the substrates after processing. 
     In some temporary bonding schemes, such as ZoneBOND® zonal bonding from Brewer Science, Inc. (described in US Patent Publication No. 2009/0218560 and application Ser. No. 12/819,680, both of which are hereby incorporated by reference), carrier wafers may require pretreatment with a coating before the wafers are bonded together. Previously, a halogenated silane in a fluorinated solvent, such as 3M FC-40 Fluorinert™ electronic liquid, was used for carrier wafer preparation. However, the silane/FC-40 solution is not a practical coating material because it is unstable, and FC-40 is restricted for use in microelectronics manufacturing because of environmental concerns. Vapor deposition of fluorinated silanes has been used previously to treat the surfaces of silicon wafers. However, vapor deposition is a process that is costly because of both the time involved and the expensive, high-quality tooling it requires. 
     There is a need for additional bonding methods and materials that overcome the shortcomings described above. 
     SUMMARY OF THE INVENTION 
     In one embodiment, a temporary bonding method is provided. The method involves providing a stack comprising:
         a first substrate having a back surface and a front surface;   a bonding layer adjacent the front surface, with the bonding layer being formed from a composition comprising a cyclic olefin polymer dissolved or dispersed in a solvent system; and   a second substrate having a first surface. The first and second substrates are separated without subjecting the stack to heat.       

     In another embodiment, the invention provides a temporary bonding method comprising providing a stack comprising:
         a first substrate having a back surface and a front surface;   a bonding layer adjacent the front surface; and   a second substrate having a first surface, with the first surface including a polysiloxane nonstick layer adjacent the bonding layer.
 
The first and second substrates are then separated.
       

     In a final embodiment, the invention provides an article comprising a first substrate having a back surface and a front surface. There is a bonding layer adjacent the front surface. The article also comprises a second substrate having a first surface, with the first surface including a polysiloxane nonstick layer adjacent the bonding layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a schematic drawing showing a preferred embodiment of the invention; 
         FIG. 2  is a graph depicting the thermogravimetric analysis (“TGA”) data of the bonding material from Example 18; 
         FIG. 3  is a scanning acoustic microscope image of the wafer bonded in Example 19; 
         FIG. 4  is a photograph of the wafer pair of Example 20 after 300° C. heat treatment; 
         FIG. 5  is an IR image of the thinned wafer pair of Example 21 after a PECVD process; and 
         FIG. 6  is a scanning acoustic microscope image of the bonded wafer pair of Example 23 after a 260° C., 30-minute heat treatment on a hotplate. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Release Layers 
     In one embodiment, a release layer is utilized. Several types of release layers can be utilized with the present invention, as explained in more detail below, but one preferred type is a nonstick layer. Preferred compositions for use in forming a nonstick release layer according to the invention comprise siloxane polymers and copolymers (both copolymers with siloxanes as well as copolymers with non-siloxanes). Preferred siloxanes are those selected from the group consisting of epoxyl, ethoxyl, acrylic, hydroxyl, vinyl, and amine, and mixtures thereof. Especially preferred siloxanes are epoxycyclohexylethylmethylsiloxane-dimethylsiloxane copolymers (ECMS-327 from Gelest), ECMS-924 (Gelest), VDT-5035 (Gelest), EBP-234 (Gelest), AMS-2202 (Gelest), AMS-1203 (Gelest), and mixtures thereof. The composition preferably comprises from about 0.01% to about 8.0% by weight, more preferably from about 0.05% to about 5.0% by weight, and even more preferably from about 0.1% to about 0.8% by weight siloxane, based upon the total weight of the composition taken as 100% by weight. Preferably, the polymer has a weight average molecular weight of from about 200 Daltons to about 4,000,000 Daltons, more preferably from about 1,000 Daltons to about 400,000 Daltons, and even more preferably from about 2,000 Daltons to about 40,000 Daltons. 
     The nonstick compositions also preferably comprise a catalyst. Suitable catalysts include those selected from the group consisting of photoacid generators, thermal acid generators, and mixtures thereof. Especially preferred catalysts include K-PURE® TAG-2689 from King Industries or 1,1′-azobis(cyclohexanecarbonitrile). The nonstick composition preferably comprises from about 0.002% to about 0.1% by weight catalyst, more preferably from about 0.005% to about 0.1% by weight catalyst, and even more preferably from about 0.008% to about 0.1% by weight catalyst, based upon the total weight of the composition taken as 100% by weight. 
     The nonstick compositions also comprise an industry-accepted, safe solvent, which is typically a polar solvent. Suitable solvents include those selected from the group consisting of propylene glycol monomethyl ether (“PGME”), d-limonene, ethyl 3-ethoxypropionate, propoxy propanol (“PnP”), propylene glycol methyl ether acetate (“PGMEA”), ethyl lactate, and mixtures thereof. The composition preferably comprises from about 90% to about 99.99% by weight solvent, more preferably from about 92% to about 99.5% by weight solvent, and even more preferably from about 95% to about 99% by weight of this solvent, based upon the total weight of the nonstick composition taken as 100% by weight. One especially preferred solvent mixture is a mixture of PGME (from about 5% to about 40% by weight) and d-limonene (from about 60 to about 95% by weight). 
     In one embodiment, the nonstick composition is essentially free of silanes. That is, the nonstick composition comprises less than about 0.5%, preferably less than about 0.1%, and more preferably about 0% by weight silanes, based upon the total weight of the nonstick composition taken as 100% by weight. In another embodiment, the nonstick composition consists essentially of, or even consists of, a siloxane, a catalyst, and solvent (preferably a polar solvent). The nonstick composition is formed by simply mixing the above ingredients together. 
     Bonding Compositions 
     The bonding material comprises a polymer or a blend of polymers dissolved or dispersed in a solvent system. Other additives such as antioxidants, surfactants, tackifiers, and toners may be included in the bonding material, depending upon the desired coating, bonding, and debonding performance. 
     In one embodiment, the polymer or blend of polymers are selected from the group consisting of polymers and oligomers of cyclic olefins, epoxies, acrylics, styrenics, vinyl halides, vinyl esters, polyamides, polyimides, polysulfones, polyethersulfones, cyclic olefins, polyolefin rubbers, polyurethanes, ethylene-propylene rubbers, polyamide esters, polyimide esters, polyacetals, and polyvinyl buterol, with the most preferred being cyclic olefin polymers. Suitable cyclic olefin polymers include those prepared from a single monomer, such as norbornene, by metathesis polymerization techniques and then hydrogenated to produce the final product. Particularly preferred COP materials include those commercialized under the names Zeonex® 5000 and Zeonex 480R. 
     The polymer or polymer blend should be present in the bonding composition at levels of from about 1% by weight to about 60% by weight, more preferably from about 20% by weight to about 40% by weight, and even more preferably from about 25% by weight to about 35% by weight, based upon the total weight of the bonding composition taken as 100% by weight. Preferably, the polymer has a weight average molecular weight of from about 1,000 Daltons to about 200,000 Daltons, more preferably from about 5,000 Daltons to about 150,000 Daltons, and even more preferably from about 10,000 Daltons to about 100,000 Daltons. 
     Suitable solvent systems include hydrocarbon solvents such as those selected from the group consisting of d-limonene, mesitylene, cyclooctane, and bicyclohexyl. The solvent or solvents should be present in the composition at levels of from about 40% by weight to about 99% by weight, more preferably from about 60% by weight to about 80% by weight, and even more preferably from about 65% by weight to about 75% by weight, based upon the total weight of the composition taken as 100% by weight. 
     Suitable antioxidants include phenolic antioxidants such as those selected from the group consisting of 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (sold as Irganox® 1330) and benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-1,6-hexanediyl ester (Irganox® L-109). The antioxidant should be present in the composition from about 0.05% by weight to about 10% by weight, more preferably from about 1% by weight to about 5% by weight, and even more preferably from about 2% by weight to about 4% by weight, based upon the total weight of the composition taken as 100% by weight. 
     In a preferred embodiment, the bonding compositions are essentially free of cyclic olefin copolymers. That is, the bonding composition comprises less than about 0.5%, preferably less than about 0.1%, and more preferably about 0% by weight cyclic olefin copolymers, based upon the total weight of the bonding composition taken as 100% by weight. 
     In another embodiment, the bonding compositions are essentially free of pinene and poly(pinene). That is, the bonding composition comprises less than about 0.5%, preferably less than about 0.1%, and more preferably about 0% by weight pinene and poly(pinene), based upon the total weight of the bonding composition taken as 100% by weight. 
     In another embodiment, the bonding compositions are essentially free of rosin esters. That is, the bonding composition comprises less than about 0.5%, preferably less than about 0.1%, and more preferably about 0% by weight rosin esters, based upon the total weight of the bonding composition taken as 100% by weight. 
     In another embodiment, the bonding compositions are essentially free of silicones. That is, the bonding composition comprises less than about 0.5%, preferably less than about 0.1%, and more preferably about 0% by weight silicones, based upon the total weight of the bonding composition taken as 100% by weight. 
     In one embodiment, the bonding compositions consist essentially of, or even consist of, a cyclic olefin polymer, antioxidant, and solvent. In a further embodiment, the bonding compositions consist essentially of, or even consist of, a cyclic olefin polymer, antioxidant, solvent, and any surfactants, toners, and/or tackifiers. 
     The compositions are formed by simply mixing the above ingredients so as to create a substantially uniform mixture of the ingredients. Preferably, any additional ingredients, such as antioxidants, are dissolved in the solvent first, and the polymer or polymers are added last. Advantageously, this results in the formation of visually clear solutions. Furthermore, wafer pairs bonded with these bonding compositions are able to survive (i.e., there are no defects in the bond line) treatment on a hot plate at about 300° C. for about 30 minutes. These bonding materials also provide excellent overall total thickness variation (“TTV,” less than about 3 μm for 50-μm bond line) and can survive a 200° C. PECVD process. 
     Inventive Method 
     Referring to  FIG. 1( a )  (not to scale), a precursor structure  10  is depicted in a schematic and cross-sectional view. Structure  10  includes a first substrate  12 . Substrate  12  has a front or device surface  14 , a back surface  16 , and an outermost edge  18 . Although substrate  12  can be of any shape, it would typically be circular in shape. Preferred first substrates  12  include device wafers such as those whose device surfaces comprise arrays of devices (not shown) selected from the group consisting of integrated circuits, MEMS, microsensors, power semiconductors, light-emitting diodes, photonic circuits, interposers, embedded passive devices, and other microdevices fabricated on or from silicon and other semiconducting materials such as silicon-germanium, gallium arsenide, gallium nitride, aluminum gallium arsenide, aluminum indium gallium phosphide, and indium gallium phosphide. The surfaces of these devices commonly comprise structures (again, not shown) formed from one or more of the following materials: silicon, polysilicon, silicon dioxide, silicon (oxy)nitride, metals (e.g., copper, aluminum, gold, tungsten, tantalum), low k dielectrics, polymer dielectrics, and various metal nitrides and silicides. The device surface  14  can also include at least one structure selected from the group consisting of: solder bumps; metal posts; metal pillars; and structures formed from a material selected from the group consisting of silicon, polysilicon, silicon dioxide, silicon (oxy)nitride, metal, low k dielectrics, polymer dielectrics, metal nitrides, and metal silicides. 
     A composition is applied to the first substrate  12  to form a bonding layer  20  on the device surface  14 , as shown in  FIG. 1( a ) . Bonding layer  20  has an upper surface  21  remote from first substrate  12 , and preferably, the bonding layer  20  is formed directly adjacent the device surface  14  (i.e., without any intermediate layers between the bonding layer  20  and substrate  12 ). Although bonding layer  20  is shown to cover the entire device surface  14  of first substrate  12 , it will be appreciated that it could be present on only portions or “zones” of device surface  14 , as shown in U.S. Patent Publication No. 2009/0218560. 
     The bonding composition can be applied by any known application method, including dip coating, roller coating, slot coating, die coating, screen printing, draw-down coating, or spray coating. Additionally, the coatings may be formed into free-standing films before application to the device substrate or carrier substrate surface. One preferred method involves spin-coating the composition at speeds of from about 200 rpm to about 3,000 rpm (preferably from about 500 rpm to about 2,000 rpm) for a time period of from about 5 seconds to about 120 seconds (preferably from about 10 seconds to about 60 seconds). After the composition is applied, it is preferably heated to a temperature of from about 40° C. to about 250° C., and more preferably from about 90° C. to about 220° C. and for time periods of from about 60 seconds to about 90 minutes (preferably from about 180 seconds to about 60 minutes). Depending upon the composition used to form the bonding layer  20 , baking can also initiate a crosslinking reaction to cure the layer  20 . In some embodiments, it is preferable to subject the layer to a multi-stage bake process, depending upon the composition utilized. Also, in some instances, the above application and bake process can be repeated on a further aliquot of the composition, so that the first bonding layer  20  is “built” on the first substrate  12  in multiple steps. The resulting layer  20  should have an average thickness (average taken over five measurements) of from about 1 μm to about 200 μm, more preferably from about 10 μm to about 150 μm, and even more preferably from about 30 μm to about 120 μm. 
     The materials from which bonding layer  20  is formed should be capable of forming a strong adhesive bond with the first and second substrates  12  and  24 , respectively. Anything with an adhesion strength of greater than about 50 psig, preferably from about 80 psig to about 250 psig, and more preferably from about 100 psig to about 150 psig, as determined by ASTM D4541/D7234, would be desirable for use as bonding layer  20 , with the exemplary compositions having been described above. 
     A second precursor structure  22  is also depicted in a schematic and cross-sectional view in  FIG. 1( a ) . Second precursor structure  22  includes a second substrate  24 . In this embodiment, second substrate  24  is a carrier wafer. That is, second substrate  24  has a front or carrier surface  26 , a back surface  28 , and an outermost edge  30 . Although second substrate  24  can be of any shape, it would typically be circular in shape and sized similarly to first substrate  12 . Preferred second substrates  24  include silicon, sapphire, quartz, metals (e.g., aluminum, copper, steel), and various glasses and ceramics. 
     A composition is applied to the second substrate  24  to form a release (preferably nonstick, in this embodiment) layer  32  on the carrier surface  26 , as shown in  FIG. 1( a ) . (Alternatively, structure  22  can be provided already formed.) Nonstick layer  32  has an upper surface  33  remote from second substrate  24 , and a lower surface  35  adjacent second substrate  24 . Preferably, the nonstick layer  32  is formed directly adjacent the carrier surface  26  (i.e., without any intermediate layers between the second bonding layer  32  and second substrate  24 ). 
     The nonstick composition can be applied by any known application method, with one preferred method being spin-coating the composition at speeds of from about 500 rpm to about 5,000 rpm (preferably from about 500 rpm to about 2,000 rpm) for a time period of from about 5 seconds to about 120 seconds (preferably from about 30 seconds to about 90 seconds). After the composition is applied, it is preferably heated to a temperature of from about 100° C. to about 300° C., and more preferably from about 150° C. to about 250° C. and for time periods of from about 30 seconds to about 5 minutes (preferably from about 90 seconds to about 3 minutes). Nonstick layer  32  preferably has an average thickness of less than about 1 μm, preferably from about 0.1 μm to about 1 μm, and more preferably from about 1 nm to about 25 nm. 
     Referring to structure  22  of  FIG. 1( a )  again, although nonstick layer  32  is shown to cover the entire surface  26  of second substrate  24 , it will be appreciated that it could be present on only portions or “zones” of carrier surface  26  similar to as was described with bonding layer  20 . Regardless, the dried/cured layer  32  will have a high contact angle with water, which effects polymer release during the debonding step (discussed below). Typical contact angles (measured as described in Example 10) will be at least about 60°, preferably from about 60° to about 120°, more preferably from about 90° to about 110°, and even more preferably from about 100° to about 110°. The nonstick layer  32  also preferably has an adhesion strength of less than about 50 psig, preferably less than about 35 psig, and more preferably from about 1 psig to about 30 psig, determined as described above. 
     Structures  10  and  22  are then pressed together in a face-to-face relationship, so that upper surface  21  of bonding layer  20  is in contact with upper surface  33  of nonstick layer  32  ( FIG. 1( b ) ). While pressing, sufficient pressure and heat are applied for a sufficient amount of time so as to effect bonding of the two structures  10  and  22  together to form bonded stack  34 . The bonding parameters will vary depending upon the composition from which bonding layer  20  is formed, but typical temperatures during this step will range from about 100° C. to about 400° C., and preferably from about 150° C. to about 250° C., with typical pressures ranging from about 100 N to about 20,000 N, and preferably from about 1,000 N to about 10,000 N, for a time period of from about 1 minute to about 20 minutes, preferably from about 2 minutes to about 10 minutes, and more preferably from about 3 minutes to about 5 minutes. 
     In an alternative embodiment, it will be appreciated that bonding layer  20  could be applied to upper surface  33  of nonstick layer  32 , using the application process described previously, rather than being applied to surface  14  of first substrate  12 . In this instance, the first substrate  12  would then be subjected to the above bonding process so as to bond surface  14  of first substrate  12  to bonding layer  20 , which was previously formed on upper surface  33  of nonstick layer  32 . 
     Regardless of which embodiment was used to form the bonded stack  34 , the first substrate  12  can now be safely handled and subjected to further processing that might otherwise have damaged first substrate  12  without being bonded to second substrate  24 . Thus, the structure can safely be subjected to backside processing such as back-grinding, chemical-mechanical polishing (“CMP”), etching, metallizing, dielectric deposition, patterning (e.g., photolithography, via etching), passivation, annealing, and combinations thereof, without separation of substrates  12  and  24  occurring, and without infiltration of any chemistries encountered during these subsequent processing steps. Not only can bonding layer  20  survive these processes, it can also survive processing temperatures up to about 450° C., preferably from about 200° C. to about 400° C., and more preferably from about 200° C. to about 350° C. 
     Once processing is complete, the substrates  12  and  24  can be separated by any number of separation methods (not shown). One method involves dissolving the bonding layer  20  in a solvent (e.g., limonene, dodecene, PGME). Alternatively, substrates  12  and  24  can also be separated by first mechanically disrupting or destroying bonding layer  20  using laser ablation, plasma etching, water jetting, or other high energy techniques that effectively etch or decompose bonding layer  20 . It is also suitable to first saw or cut through the bonding layer  20  or cleave the layer  20  by some equivalent means. Furthermore, it will be appreciated that other layers (not shown) might be included in the stack, and debonding could take place at that other layer instead of at bonding layer  20 . For example, a cleaning layer might be included, and debonding could be carried out by dissolving that cleaning layer. As another example, a laser release layer could be included, and debonding could be effected by laser ablation across that laser release layer. 
     In situations where a bonding composition other than a cyclic olefin polymer-containing composition is utilized, a suitable separation method involves heating the bonded stack  34  to temperatures of at least about 100° C., preferably from about 150° C. to about 220° C., and more preferably from about 180° C. to about 200° C. It will be appreciated that at these temperatures, the bonding layer  20  will soften, allowing the substrates  12  and  24  to be separated (e.g., by a slide debonding method, such as that described in U.S. Patent Publication No. 2008/0200011, incorporated by reference herein). 
     It will be appreciated that embodiments using the inventive cyclic olefin polymer-containing compositions avoids the need to heat the bonding layer  20  prior to separation. That is, after processing has been completed, the stack  34  can be separated without any heat exposure, using a low-force mechanical debonding method. In this instance, the stack  34  is exposed to temperatures of less than about 100° C., preferably less than about 75° C., more preferably less than about 50° C., even more preferably less than about 30° C., and most preferably about ambient temperatures (and certainly no lower than ambient temperatures), prior to and during the separating. It will be understood that a lack of heat exposure during separation does not exclude heat exposure that occurs during the stack processing, prior to separation, but simply that heat exposure stops after processing is complete. So, for example, the heat exposure that might have occurred during stack processing will have ended at least about 60 seconds, and more preferably at least about 300 seconds prior to stack separation. 
     Regardless of which of the above means is utilized, a low mechanical force (e.g., finger pressure, gentle wedging) can then be applied to completely separate the substrates  12  and  24 . After separation, any remaining bonding layer  20  can be removed with a solvent capable of dissolving the particular layer  20 . In fact, the inventive bonding layer  20  is highly removable by conventionally-used solvents. That is, the bonding layer  20  can be at least about 95% removed, preferably at least about 98% removed, and more preferably about 100% removed, upon being in contact with a typical cleaning solvent (e.g., d-limonene) at ambient temperatures for a time period of from about 1 minute to about 10 minutes, and preferably from about 3 minutes to about 5 minutes. 
     In the above embodiments, the nonstick layer  32  is shown on a second substrate  24  that is a carrier wafer, while bonding layer  20  is shown on a first substrate  12  that is a device wafer. It will be appreciated that this substrate/layer scheme could be reversed. That is, the nonstick layer  32  could be formed on first substrate  12  (the device wafer) while bonding layer  20  is formed on second substrate  24  (the carrier wafer). The same compositions and processing conditions would apply to this embodiment as those described above. Additionally, the use of the nonstick layer  32  is optional. Bonding layer  20  could be used alone, without the presence of nonstick layer  32 . Bonding layer  20  could also be used with additional bonding materials, structural support layers, other types of release layers (as noted previously, including, but not limited to, mechanical debonding, laser debonding, and thermal or chemical debonding), lamination aid layers, tie layers (for adhesion to initial substrate), contamination control layers, and cleaning layers. Preferred structures and application techniques will be dictated by application and process flow. 
     Polymeric structural support layers that can be used in combination with the COP bonding materials can comprise monomers, oligomers, polymers, suspended particles, and/or combinations thereof. Examples of suitable monomers, oligomers, and polymers include those selected from the group consisting of cyclic olefin polymers and copolymers, polyimides, polyisobutylenes, hydrocarbon resins, epoxy resins, fluoropolymers, polysulfones, polyethersulfones, polyether ether ketones, polyhydroxyethers, and polyvinylbutyrals. Suitable suspended particles include those selected from the group consisting of alumina, ceria, titania, silica, zirconia, graphite, and nanoparticles, sol-gel particles, and mixtures thereof. Preferred compositions will be structurally rigid at the temperature of use as indicated by glass transition temperature, coefficient of thermal expansion, and modulus. 
     Mechanical carrier release layers (in addition to, or in lieu of, the polysiloxane layers discussed above) used in conjunction with the COP bonding materials can be composed of monomers, oligomers, and/or polymers. Examples of suitable monomers, oligomers, and polymers include cyclic olefin polymers and copolymers, polyisobutylenes, hydrocarbon resins, epoxy resins, fluoropolymers, polyimides, polysulfones, polyhydroxyethers, polyvinylbutyrals, amorphous fluoropolymers with high atomic fluorine content such as fluorinated siloxane polymers, fluorinated ethylene-propylene copolymers, tetrafluoroethylene hexafluoropropylene, vinylidene fluoride terpolymer, hexafluoropropylene, vinyldene fluoride copolymer, vinylidene fluoride polymer, and polymers with pendant perfluoroalkoxy groups. 
     Laser carrier release layers used in conjunction with the COP bonding materials can be composed of monomers, oligomers, and/or polymers. One example of a suitable laser release layer is polyimides. 
     EXAMPLES 
     The following examples set forth preferred methods in accordance with the invention. It is to be understood, however, that these examples are provided by way of illustration and nothing therein should be taken as a limitation upon the overall scope of the invention. 
     Example 1 
     Formulation of a 0.5% ECMS-327 Siloxane Solution 
     To a 250 ml glass bottle, 0.02 gram of K-PURE® TAG-2689 (King Industries Inc. Norwalk, Conn.) and 19.9 grams of propylene glycol monomethyl ether (“PGME,” Ultra Pure, Inc., Castroville, Calif.) were added. The solution was mixed for 5-10 minutes until all of K-PURE® TAG-2689 dissolved. Next, 79.58 grams of d-limonene (Florida Chemical Co. Winter Haven, Fla.) and 0.5 gram of ECMS-327 (polysiloxane, structure shown below; Gelest, Morrisville, Pa.) were then added to the solution. The final solution was mixed for 30-60 minutes until all of polysiloxane was dissolved, after which the solution was filtered once through 0.1-μm disk filter (Whatman Inc., Florham Park N.J.). The total concentration of polysiloxane in this solution was 0.5% by weight. 
     
       
                 
         
             
             
         
      
     
     Example 2 
     Formulation of a 0.5% ECMS-924 Siloxane Solution 
     To a 250 ml glass bottle, 0.02 gram of K-PURE® TAG-2689 (King Industries Inc. Norwalk, Conn.) and 19.9 grams of PGME (Ultra Pure, Inc., Castroville, Calif.) were added. The solution was mixed for 5-10 minutes until all of K-PURE® TAG-2689 dissolved. 79.58 grams of d-limonene (Florida Chemical Co. Winter Haven, Fla.) and 0.5 gram of ECMS-924 (polysiloxane, Gelest, Morrisville, Pa.) were then added to the solution. (The structure of this polymer is similar to that shown for Example 1, with the difference in numbers denoting a difference in molecular weights.) The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved and then was filtered once through 0.1-μm disk filter (Whatman Inc., Florham Park N.J.). The total concentration of polysiloxane in this solution was 0.5% by weight. 
     Example 3 
     Formulation of a 0.5% VDT-5035 Siloxane Solution 
     To a 250 ml glass bottle, 100 grams of PGME (Ultra Pure, Inc., Castroville, Calif.), 0.5 gram of VDT-5035 (Gelest, structure shown below; Morrisville, Pa.), and 0.025 gram of 1,1′-azobis(cyclohexanecarbonitrile) (Sigma-Aldrich, St Louis, Mo.) were added. The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved. The total concentration of polysiloxane in this solution was about 0.5% by weight. 
     
       
                 
         
             
             
         
      
     
     Example 4 
     Formulation of a 0.5% EBP-234 Siloxane Solution 
     To a 250 ml glass bottle, 100 grams of PGME (Ultra Pure, Inc., Castroville, Calif.), 0.5 gram of EBP-234 (Gelest, structure shown below; Morrisville, Pa.), and 0.027 gram of K-PURE® TAG-2689 were added. The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved. The total concentration of polysiloxane in this solution was about 0.5% by weight. 
     
       
                 
         
             
             
         
      
     
     Example 5 
     Formulation of a 0.6% ECMS-327 Siloxane Solution 
     To a 250 ml plastic bottle, 0.02 gram of K-PURE® TAG-2689 (King Industries Inc. Norwalk, Conn.) and 4.969 grams of PGME (Ultra Pure, Inc., Castroville, Calif.) were added. The solution was mixed for 5-10 minutes until all of K-PURE® TAG-2689 dissolved. 94.411 grams of 3-ethoxypropionate (EEP, Sigma-Aldrich Inc., St. Louis, Mo.) and 0.6 gram of ECMS-327 (polysiloxane, Gelest, Morrisville, Pa.) were then added to the solution. The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved and then was filtered once through a 0.1-μm disk filter (Whatman Inc., Florham Park N.J.). The total concentration of polysiloxane in this solution was 0.6% by weight. 
     Example 6 
     Formulation of a 0.1% ECMS-327 Siloxane Solution 
     To a 250 ml plastic bottle, 0.004 gram of K-PURE® TAG-2689 (King Industries Inc. Norwalk, Conn.) and 4.9948 grams of PGME (Ultra Pure, Inc., Castroville, Calif.) were added. The solution was mixed for 5-10 minutes until all of K-PURE® TAG-2689 dissolved. Next, 94.9012 grams of 3-ethoxypropionate (EEP, Sigma-Aldrich Inc., St. Louis, Mo.) and 0.1 gram of ECMS-327 (polysiloxane, Gelest, Morrisville, Pa.) were then added to the solution. The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved and then was filtered once through 0.1-μm disk filter (Whatman Inc., Florham Park N.J.). The total concentration of polysiloxane in this solution was 0.1% by weight. 
     Example 7 
     Formulation of a 0.2% ECMS-327 Siloxane Solution 
     To a 250 ml plastic bottle, 0.008 gram of K-PURE® TAG-2689 (King Industries Inc. Norwalk, Conn.) and 4.9896 grams of PGME (Ultra Pure, Inc., Castroville, Calif.) were added. The solution was mixed for 5-10 minutes until all of K-PURE® TAG-2689 dissolved. Next, 94.8024 grams of 3-ethoxypropionate (EEP, Sigma-Aldrich Inc., St. Louis, Mo.) and 0.2 gram of ECMS-327 (polysiloxane, Gelest, Morrisville, Pa.) were added to the solution. The final solution was mixed for 30-60 minutes until all of the polysiloxane had dissolved, followed by filtering once through 0.1-μm disk filter (Whatman Inc., Florham Park N.J.). The total concentration of polysiloxane in this solution was 0.2% by weight. 
     Example 8 
     Formulation of a 0.6% AMS-2202 Siloxane Solution 
     To a 250 ml plastic bottle, 49.7 grams of PGME (Ultra Pure, Inc., Castroville, Calif.) and 0.3 gram of AMS-2202 (Gelest, structure shown below; Morrisville, Pa.) were added. The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved. The total concentration of polysiloxane in this solution was about 0.6% by weight. 
     
       
                 
         
             
             
         
      
     
     Example 9 
     Formulation of a 0.6% AMS-1203 Siloxane Solution 
     To a 250 ml plastic bottle, 49.7 grams of PGME (Ultra Pure, Inc., Castroville, Calif.) and 0.3 gram of AMS-1203 (Gelest, Morrisville, Pa.) were added. The final solution was mixed for 30-60 minutes until all of polysiloxane dissolved. The total concentration of polysiloxane in this solution was about 0.6% by weight. 
     Example 10 
     Testing of Siloxane Solutions 
     The solutions formulated in Examples 1 to 9 were spin-coated onto 100-mm silicon wafers by spinning at 1,500 rpm with 10,000 rpm/s ramp for 30 seconds, and then baked at 205° C. for 60 seconds. All wafers had good coat quality via visual observation. The thickness was measured with ellipsometer. The contact angle with water was measured using VCA Optima Tool from AST Products, Inc. Billerica, Mass. The results are listed in the Table 1. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Solution appearance, thickness, and contact angle of siloxane solutions. 
               
             
          
           
               
                 Sample 
                 Solution appearance 
                 Thickness, Å 
                 Contact angle 
               
               
                   
               
             
          
           
               
                 Example 1 
                 Clear 
                 123 
                 105° 
               
               
                 Example 2 
                 Clear 
                 105 
                 101° 
               
               
                 Example 3 
                 Clear 
                 108 
                 106° 
               
               
                 Example 4 
                 Clear 
                 104 
                  96° 
               
               
                 Example 5 
                 Clear 
                 120 
                 104° 
               
               
                 Example 6 
                 Clear 
                 16 
                  96° 
               
               
                 Example 7 
                 Clear 
                 32 
                 106° 
               
               
                 Example 8 
                 Clear 
                 287 
                 103° 
               
               
                 Example 9 
                 Clear 
                 305 
                 103° 
               
               
                   
               
             
          
         
       
     
     Example 11 
     Bonding Testing of Siloxane Solution from Example 1 with Cyclic Olefin Polymer 
     The solution formulated in Example 1 was spin-coated onto 200-mm silicon wafers by spinning at 1,500 rpm with 10,000 rpm/s ramp for 30 seconds, and then baked at 205° C. for 60 seconds. The contact angle of the fully-coated wafer was determined to be 105. A 50-μm film of the cyclic olefin polymer bonding material from Example 16 was coated onto another 200-mm silicon wafer by spin-coating at 1,000 rpm with a 3,000 rpm/s ramp for 30 seconds, and then baking at 60° C. for 3 minutes, 160° C. for 2 minutes, and 205° C. for 2 minutes. 
     The two wafers were bonded in a face-to-face relationship at 200° C. for 3 minutes in a heated vacuum and under pressure chamber with 1,800 N of bonding pressure on an EVG510 bonder. After cooling to room temperature, the bonded wafers were separated easily by a peeling process using a ZoneBOND® separation tool. 
     Example 12 
     Bonding Testing of Siloxane Solution from Example 5 with Cyclic Olefin Polymer 
     The solution formulated in Example 5 was spin-coated onto 200-mm silicon wafers by spinning at 1,500 rpm with 10,000 rpm/s ramp for 30 seconds, and then baked at 205° C. for 60 seconds. The contact angle of the fully-coated wafer was measured to be 105. A 50-μm film of the cyclic olefin polymer bonding material from Example 16 was coated onto another 200-mm silicon wafer by spin-coating at 1,000 rpm with a 3,000 rpm/s ramp for 30 seconds, and then baking at 60° C. for 3 minutes, 160° C. for 2 minutes, and 205° C. for 2 minutes. 
     The two wafers were bonded in a face-to-face relationship at 200° C. for 3 minutes in a heated vacuum and under pressure chamber with 1,800 N of bonding pressure on an EVG510 bonder. After cooling to room temperature, the bonded wafers were separated easily by a peeling process using a ZoneBOND® separation tool. 
     Example 13 
     Bonding and Backside Processing Testing of Siloxane Solution from Example 5 with Cyclic Olefin Polymer 
     The solution formulated in Example 5 was spin-coated onto 200-mm silicon wafers by spinning at 1,500 rpm with 10,000 rpm/s ramp for 30 seconds, and then baked at 205° C. for 60 seconds. The contact angle of the fully-coated wafer was measured to be 105. A 50-μm film of the cyclic olefin polymer bonding material from Example 16 was coated onto another 200-mm silicon wafer by spin-coating at 1,000 rpm with a 3,000 rpm/s ramp for 30 seconds, and then baking at 60° C. for 3 minutes, 160° C. for 2 minutes, and 205° C. for 2 minutes. 
     The two wafers were bonded in a face-to-face relationship at 200° C. for 3 minutes in a heated vacuum and under pressure chamber with 1,800 N of bonding pressure on an EVG510 bonder. The wafer pair was then cooled down to room temperature. The wafer pair was subjected to a backgrinding process, which thinned the device wafer to 50 μm in thickness. The wafer pair was then heat-treated for 30 minutes at 260° C. and cooled again to room temperature. 
     The bonded wafers were separated easily by a peeling process using a ZoneBOND® separation tool. 
     Example 14 
     Bonding Testing of Siloxane Solution from Example 5 with WaferBOND® HT-10.10 Material 
     The solution formulated in Example 5 was spin-coated onto 200-mm silicon wafers by spinning at 1,500 rpm with a 10,000 rpm/s ramp for 30 seconds, and then baked at 205° C. for 60 seconds. The contact angle of the fully-coated wafer was measured to be 105. A 50-μm film of WaferBOND® HT-10.10 material (Brewer Science, Inc.) was coated onto another 200-mm silicon wafer by spin-coating at 400 rpm with a 500 rpm/s ramp for 35 seconds, and then baking at 120° C. for 3 minutes and 180° C. for 4 minutes. 
     The two wafers were bonded in a face-to-face relationship at 180° C. for 3 minutes in a heated vacuum and under pressure chamber with 1,800 N of bonding pressure on an EVG510 bonder. After cooling down to room temperature, the bonded wafers were separated easily by a peeling process using a ZoneBOND® separation tool. 
     Example 15 
     Bonding and Backside Processing Testing of Siloxane Solution from Example 5 with WaferBOND® HT-10.10 Material 
     The solution formulated in Example 5 was spin-coated onto 200-mm silicon wafers by spinning at 1,500 rpm with 10,000 rpm/s ramp for 30 seconds, and then baked at 205° C. for 60 seconds. The contact angle of the fully-coated wafer was measured to be 105. A 50-μm film of WaferBOND® HT-10.10 material (Brewer Science, Inc.) was coated onto another 200-mm silicon wafer by spin-coating at 400 rpm with a 500 rpm/s ramp for 35 seconds, and then baking at 120° C. for 3 minutes and 180° C. for 4 minutes. 
     The two wafers were bonded in a face-to-face relationship at 180° C. for 3 minutes in a heated vacuum and under pressure chamber with 1,800 N of bonding pressure on an EVG510 bonder. The wafer pair was then cooled down to room temperature. The wafer pair was subjected to a backgrinding process, which thinned the device wafer to 50 μm thickness. The wafer pair was then heat treated for 30 minutes at 260° C. and cooled again to room temperature. The bonded wafers were then separated easily by a peeling process using a ZoneBOND® separation tool. 
     Example 16 
     Formulation of Bonding Material 1 
     First, 1.8 grams of Irganox® 1330 antioxidant (Sigma-Aldrich, Mo.) was dissolved in 138.2 grams of d-limonene (Florida Chemical Company, Fla.). Then, 60 grams of ZEONEX® 5000 cyclic olefin polymer (Zeon Corporation, Japan) was added to the solution, and the solution was rotated on a rotating wheel until the polymer was fully dissolved. The solution was then filtered with a 0.2-μm Meissner Vangard filter. 
     Example 17 
     Formulation of Bonding Material 2 
     First, 1.8 grams of Irganox® 1330 antioxidant was dissolved in 140 grams of d-limonene. Then, 54 grams of ZEONEX® 5000 and 6 grams of ZEONEX® 480R cyclic olefin polymers (Zeon Corporation, Japan) were added to the solution, and the solution was rotated on a rotating wheel until the polymer was fully dissolved. The solution was then filtered with a 0.2-μm Meissner Vangard filter. 
     Example 18 
     Thermal Stability Testing of Bonding Material 
     The bonding material from Example 16 was spin coated onto an eight-inch wafer at 750 rpm, with 3,000 rpm/s acceleration for 30 seconds. The wafer was then baked at 60° C. for 2 minutes, 160° C. for 2 minutes, and 200° C. for 13 minutes. The film was scratched off of the wafer for TGA. TGA was performed using a 10° C./min ramp in air. The result is in  FIG. 2 . The decomposition temperature was 436° C., and the 2% weight loss point was at 363° C. 
     Example 19 
     Bonding of Substrates Using Bonding Material 
     In this Example, a 50-μm coat of the bonding material from Example 16 was coated on an eight-inch Si wafer by spin coating the material at 1,000 rpm, with 3,000 rpm/s acceleration for 30 seconds. The wafer was then baked at 60° C. for 3 minutes, 160° C. for 2 minutes, and 200° C. for 2 minutes. A carrier Si wafer was coated with Brewer Science® ZoneBOND® 3500-02 anti-stiction material by spin coating at 1,250 rpm, with 250 rpm/s acceleration for 30 seconds. The carrier wafer was then baked at 160° C. for 3 minutes. The wafer pair was then bonded at 200° C., 1,800 N for 3 minutes under vacuum (&lt;5 mbar) using an EVG Model 510 bonder. The bonded pair was examined with a scanning acoustic microscope from Sonoscan. The images showed that the wafer pair was bonded well, and there were no voids detected ( FIG. 3 ). 
     Example 20 
     Heat Treatment of Wafer Pair Bonded with Bonding Material from Example 16 
     In this Example, a 50-μm coating of the bonding material from Example 16 was coated on an eight-inch silicon wafer by spin coating the material at 1,000 rpm, with 3,000 rpm/s acceleration for 30 seconds. The wafer was then baked at 60° C. for 3 minutes, 160° C. for 2 minutes, and 205° C. for 2 minutes. A glass carrier wafer was coated with Brewer Science® ZoneBOND® 3500-02 anti-stiction material by spin coating at 1,250 rpm, with 250 rpm/s acceleration for 30 seconds. The carrier wafer was then baked at 160° C. for 3 minutes. The wafer pair was then bonded at 200° C., 1,800 N for 3 minutes under vacuum (&lt;5 mbar) in an EVG510 bonder. The bonded pair was then placed on a hot plate at 300° C. for 30 minutes. There were no voids or defects observed after the heat treatment, as can be seen in  FIG. 4 . After heat treatment, the wafers were separated with a Brewer Science® peel debonder without edge soaking or cleaning. 
     Example 21 
     PECVD of Bonded, Thinned Wafer Pair 
     In this Example, a 50-μm coat of the bonding material from Example 16 was coated on an eight-inch Si wafer by spin coating the material at 1,000 rpm, with 3,000 rpm/s acceleration for 30 seconds. The wafer was then baked at 60° C. for 3 minutes, 160° C. for 2 minutes, and 200° C. for 2 minutes. A glass carrier was coated with Brewer Science® ZoneBOND® 3500-02 anti-stiction material by spin coating at 1,250 rpm, with 250 rpm/s acceleration for 30 seconds. The carrier wafer was then baked at 160° C. for 3 minutes. The wafer pair was then bonded at 200° C., 1,800 N for 3 minutes under vacuum (&lt;5 mbar) in EVG510 bonder. The device wafer was thinned to 50-μm thickness using a commercial DISCO® brand wafer grinding tool. A SiOx layer was deposited on the thinned wafer in a PECVD chamber at 200° C. for 2 minutes. The wafer pair was bonded very well, and there were no voids detected by IR observation ( FIG. 5 ). 
     Example 22 
     Cleaning of Bonding Material After Debonding 
     In this Example, a 50-μm film of the material from Example 16 was coated on an eight-inch blank silicon wafer. The silicon carrier wafer was coated with Brewer Science® ZoneBOND® 3500-02 anti-stiction material. The wafer pair was then bonded at 210° C., 1,800 N for 3 min under vacuum (&lt;5 mbar) using an EVG Model 510 bonder. The wafer pair was then debonded on Brewer Science peel debonder at room temperature. The device wafer was then cleaned on a Brewer Science® Cee® 200FX spin coater with 400 ml of d-limonene using a central dispense process with the conditions listed in Table 2. After cleaning, the wafer was visually clean under green light with no residue. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Cleaning process to remove 50-μm layer of bonding 
               
               
                 material after debonding. 
               
             
          
           
               
                   
                   
                 Spin speed 
                 Acceleration 
                 Time 
                   
               
               
                   
                 Step 
                 rpm 
                 rpm/sec 
                 second 
                 Dispense 
               
               
                   
                   
               
             
          
           
               
                   
                 1 
                 500 
                 250 
                 10 
                 d-limonene 
               
               
                   
                 2 
                 20 
                 300 
                 20 
                 d-limonene 
               
               
                   
                 3 
                 0 
                 20 
                 60 
               
               
                   
                 4 
                 1000 
                 750 
                 240 
                 d-limonene 
               
               
                   
                 5 
                 1200 
                 500 
                 35 
               
               
                   
                   
               
             
          
         
       
     
     Example 23 
     Heat Treatment of Wafer Pair Bonded with Material from Example 17 
     In this Example, a 44-μm coating of the bonding material from Example 17 was coated on an eight-inch silicon wafer by spin coating the material at 1,000 rpm, with 3,000 rpm/s acceleration for 30 seconds. The wafer was then baked at 60° C. for 3 minutes, 160° C. for 2 minutes, and 200° C. for 2 minutes. A carrier Si wafer was coated with the release material of Example 7 by spin coating at 1,500 rpm, with 10,000 rpm/s acceleration for 30 seconds. The carrier wafer was then baked at 205° C. for 1 minutes. The wafer pair was then bonded at 200° C., 1,800 N for 3 minutes under vacuum (&lt;5 mbar) using an EVG510 bonder. The bonded pair was then placed on a hot plate at 260° C. for 30 minutes. There were no voids or defects observed after the heat treatment as can be seen in  FIG. 6 . After heat treatment, the wafers were separated with a Brewer Science® peel debonder without edge soaking or cleaning. 
     Example 24 
     Laser Debonding of Wafer Pair Bonded with Material from Example 16 After Heat Treatment 
     In this example, a 50-μm coating of the bonding material from Example 16 was coated on an eight-inch silicon wafer by spin coating the material at 1,000 rpm, with 3,000 rpm/s acceleration for 30 seconds. The wafer was then baked at 60° C. for 3 minutes, 160° C. for 2 minutes, and 200° C. for 2 minutes. A carrier glass wafer was coated with an experimental polyimide laser release material (Brewer Science, Inc.) by spin coating at 2,500 rpm with 5,000 rpm/s acceleration for 60 seconds. The carrier wafer was baked at 300° C. for 5 minutes, and the wafer pair was then bonded at 200° C. and 1,800 N for 3 minutes under vacuum (&lt;5 mbar) using an EVG510 bonder. There were no voids or defects observed by visual inspection after bonding. The wafer pair was then laser debonded at a wavelength of 308 nm and a fluence of 175 mJ/cm 2  on a SUSS laser debonding tool. A second wafer pair, coated and bonded at the same conditions as above, was also successfully laser debonded on a Kingyoup laser debonding tool at 3.2 W. The wavelength of the Kingyoup tool was 355 nm.