WO2015112330A1

WO2015112330A1 - Temporary-bonded wafer systems and methods of making the same

Info

Publication number: WO2015112330A1
Application number: PCT/US2015/010398
Authority: WO
Inventors: Herman Meynen
Original assignee: Dow Corning Corporation
Priority date: 2014-01-27
Filing date: 2015-01-07
Publication date: 2015-07-30
Also published as: TW201530610A

Abstract

Provided in various embodiments are a temporary-bonded wafer system comprising a substrate having a first surface and a second surface opposite the first surface, a release layer positioned on the first surface of the substrate, an adhesive layer positioned over the release layer, wherein outer edges of the adhesive layer contact the substrate, thereby forming an effective seal over the release layer, and a carrier wafer bonded to the adhesive layer.

Description

TEMPORARY-BONDED WAFER SYSTEMS AND METHODS OF MAKING THE SAME

[0001] This disclosure relates generally to materials and methods for the treatment of wafers used in the production of semiconductor products.

[0002] One factor for determining the success of the next level of integration of 3D IC integration using through-silicon via (TSV) is the ability to handle thin wafers through the various processing steps involved in the fabrication of TSVs. One such requirement is a temporary bonding adhesive (TBA), which may be used to form an adhesive layer (AL), that is capable of withstanding exposure to high temperatures, acids, bases, and solvents.

[0003] One road block that exists for the adoption of wafer support system technology into the high volume manufacturing semiconductor fabrication industry is the performance of the TBAs. The adhesives used for the temporary bonding of active device wafers to carrier wafers must have good thermal, chemical, and mechanical stability to withstand postprocessing steps such as those described earlier, e.g., backgrinding, lithography, metal deposition, plating, passivation, combinations thereof, and the like.

[0004] The microelectronics industry currently uses both a one-layer, a two-layer (or bi- layer), and a three-layer approach to accomplish temporary wafer bonding and de-bonding during the production of semiconductor devices. The basic requirements for temporary wafer bonding include: (i) the ability to withstand exposure to temperatures of about 260 Ό and above; (ii) the ability to survive wafer thinning processing; (iii) the ability to be easily de-bonded and cleaned; (iv) high throughput; and (v) resistance to various chemicals (solvents, acids, bases, etc.) used in the semiconductor industry. Spin coating, spray coating, or other suitable coating techniques may be used to coat the materials onto the wafers due to the thickness control, simplicity, and fast processing that can be achieved.

[0005] In a representative one-layer approach, a cross-linked oxazoline may be used to bond a patterned wafer to a support wafer. After wafer grinding and TSV processing is performed, the wafers are separated by exposing the wafers to a high temperature (about 285°C), followed by mechanically sliding the wafers apart. Since the bonding and de- bonding processes must be performed at high temperatures and harsh solvent cleaning is often required to remove any residue, this approach can lead to high cost, low yield, and/or low productivity.

[0006] The two-layer approach uses an additional layer to assist in de-bonding the support wafer from the thin patterned wafer. In a typical two-layer approach, a release layer (RL) is coated onto an active device wafer to form an RL-coated wafer. An adhesive layer followed by a carrier wafer may be bonded to the RL-coated wafer. Alternatively, an adhesive-coated carrier wafer carrier layer may be bonded onto the RL-coated wafer. The wafer may then be de-bonded using a mechanical initiation by a blade. After initiation by the blade, the bond is broken as the two substrates are pushed away from one another and room temperature de-bonding is achieved.

[0007] In existing wafer support system technologies, the RL is generally easily dissolvable by organic solvents such as propylene glycol monomethyl ether acetate (PGMEA), acetone, mesitylene, butyl acetate, methyl ethyl ketone (MEK), combinations thereof, or the like during the processing of thin wafers on a wafer or tape. Though this property is highly desirable for the easy removal of the RL after de-bonding, it is also highly undesirable because when the RL is exposed around the edges, it can cause delamination, undesired wafer de-bonding, separation of the film, and/or failure during post-bonding processes (e.g., processes occurring after the wafer system has been bonded) when exposed to chemicals in the TSV fabrication process. This generally occurs because the RL is not isolated by a chemical-resistant, solventless silicone AL. Thus, it would be desirable to engineer the wafer to prevent the exposure of the RL around the wafer edge, thereby increasing the chemical resistance of the temporary-bonded wafer pair to common solvents and/or other chemicals such as, for example, acids, bases, or combinations thereof used in the fabrication of vertical interconnects for 2.5D/3D IC integration.

BRIEF SUMMARY OF THE INVENTION

[0008] This disclosure relates generally to materials and methods for the treatment of wafers used in the production of semiconductor products. More specifically, this disclosure relates to temporary-bonded wafer systems having a release layer and a method of using the same in which the release layer is protected from dissolving in solvents during processing. The temporary-bonded wafer systems can be used in varied applications including 3D chip integration, semiconductor device packaging applications, power semiconductor devices, radio-frequency identification tags, chip cards, high-density memory devices, light emitting diodes (LED), microelectronic devices, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

[0010] FIG. 1 illustrates one example of a temporary-bonded wafer system according to prior art existing technologies.

[0011] FIGs. 2a-d illustrate a method of forming a temporary-bonded wafer system according to one embodiment of the invention.

[0012] FIGs. 3a-3e illustrate a method of forming a temporary-bonded wafer system according to another embodiment of the invention. [0013] FIGs. 4a-4d illustrate a method of forming a temporary-bonded wafer system according to yet another embodiment of the invention.

[0014] While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein, and the invention is not intended to be limited to the particular forms disclosed.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present disclosure generally provides temporary-bonded wafer systems and methods for the treatment of temporary-bonded wafer systems used in the production of semiconductor devices. More specifically, this disclosure relates to temporary-bonded wafer systems having an adhesive layer that forms an effective seal over the release layer, thereby protecting the release layer from dissolving in solvents during processing.

[0016] FIG. 1 shows a temporary-bonded wafer system 10 according to prior art existing technologies. The temporary-bonded wafer system 10 as shown in FIG. 1 comprises (1 ) an active device wafer (DW) 12, (2) a release layer (RL) 14, (3) a temporary bonding adhesive (TBA) applied over the RL 14 to form an adhesive layer (AL) 16, and (4) a top carrier wafer (CW) 18. As can be seen in FIG. 1 , the RL is exposed at the edges of the temporary- bonded wafer system 10. As such, the RL may be dissolved by solvent(s) and/or other chemicals used during post-bonding processing activities after wafer thinning. Post- bonding processing steps done after wafer thinning include one or more of backgrinding, lithography, metal deposition, plating, passivation, combinations thereof, and the like. A front edge bead removal process is generally not feasible, as the AL would likely permanently bond the DW and the CW. In fact, such existing technologies are further exposed to failure when edge-trimmed wafers are used where, after subjecting the temporary-bonded wafer system to one or more backgrinding processes, the AL and RL are even further exposed due to the device wafer becoming smaller than the carrier wafer.

[0017] According to one embodiment of the present invention, a temporary-bonded wafer system includes (a) a release layer (RL) positioned on a first surface (i.e., the frontside, relative to the system in use) of a first substrate or semiconductor wafer (e.g., a device wafer (DW)); (b) a temporary bonding adhesive (TBA) positioned over the RL to form an adhesive layer (AL) such that outer edges of the AL contact the first semiconductor wafer, thereby forming an effective seal over the RL; and (c) a second semiconductor wafer (e.g., a carrier wafer (CW)) bonded (e.g., in vacuum) to the AL. The wafer system may be baked/cured inside or outside of a bond chamber such that it is possible to later de-bond the wafer system. If the bake is conducted outside of the bond chamber, a hotplate or a furnace may be used. It may be desirable that the system is kept in a horizontal position during the baking process. Such structures are illustrated in, e.g., FIGs. 2d, 3e, and 4d. The AL may include a solventless silicone, solventless polyimides silicones, and/or other solventless coatings that provide a desirable chemical resistance. The word "solvent" as used in the term "solventless" refers to an organic solvent or mixture of two or more organic solvents. Such "solventless" (e.g., solvent free) ALs, solventless silicone, solventless polyimides silicones, and other solventless coatings independently lack organic solvent (i.e., are free of organic solvent) or include, at most, a solvent concentration level that is low enough such that there is no intermixing with and/or dissolving of the RL. In some embodiments, the solventless ALs, solventless silicone, solventless polyimides silicones, and the other solventless coatings lack, i.e., are free of, organic solvent. The organic solvent that is lacking or at most is at a low enough concentration level, may be one or more organic solvents that are used in post-processing steps. For example, the organic solvent may be a glycol monoether monoester derivative thereof; an alcohol; a tetraalkylammonium hydroxide; a ketone; an aromatic hydrocarbon; a carboxylic acid ester; a carboxylic amide; a lactam; or a combination of any two or more thereof. The glycol monoether monoester may be ethylene glycol monomethyl propionate, propylene glycol monomethyl ether acetate (PGMEA; CH₃OCH₂CH(CH3)OC(0)CH3), or the like. The alcohol may be ethanol, 2-propanol (IPA), butanol, or the like. The tetraalkylammonium hydroxide may be tetramethylammonium hydroxide (TMAH). The ketone may be acetone, methyl ethyl ketone (MEK), or the like. The aromatic hydrocarbon may be toluene, a xylene, mesitylene, or the like. The carboxylic acid ester may be ethyl propionate, butyl acetate, or the like. The carboxylic amide may be Ν,Ν-dimethylacetamide. The lactam may be N- methyl-2-pyrrolidone (NMP). The combination of two or more organic solvents may be PGMEA and MEK, PGMEA and butyl acetate, IPA and acetone, xylenes, mesitylene and butyl acetate, and the like. The organic solvent may, alternatively may not also contain water. E.g., organic solvents that contain water may be IPA/water and TMAH/water. It is contemplated that silicone fluids such as PDMS fluid, hexamethyldisiloxane, and/or octamethyltetrasiloxane; alternatively hexamethyldisiloxane and octamethyltetrasiloxane, which do not dissolve the RL, may be added to the AL, and the resulting AL containing same may still be "solventless" because it lacks, or at most contains the low enough solvent concentration level of, the organic solvent(s). As used herein, the term "organic solvent" means a liquid consisting of carbon atoms and at least one or more atoms selected from the group consisting of hydrogen, oxygen, halogen, nitrogen, and sulfur; alternatively hydrogen, oxygen, halogen, and nitrogen; alternatively hydrogen, oxygen, and halogen; alternatively hydrogen, nitrogen, and oxygen; alternatively hydrogen and nitrogen; alternatively hydrogen and oxygen. The organic solvent may consist of any one of the foregoing embodiments of atoms and have a molecular weight of from 40 to 500 grams per mole (g/mol), alternatively from 50 to 400 g/mol. The effective seal may be generally chemical-resistant, e.g., such that the structure survives a solvent bath of about 30 minutes without producing evidence of delamination. Delamination may be detected using the naked eye (before or after wafer debonding) or using metrology tools such as C-Mode Sound Acoustic Microscopy or Interferometry. When in other aspects the adhesive layer includes a solvent-containing silicone, the method further comprises soft baking the adhesive layer-coated second substrate to remove solvent from the adhesive layer prior to contacting the adhesive layer to the release layer and the one or more sides of the first substrate. As used herein, "soft baking" means gently heating to volatilize solvent. When an adhesive material containing solvent is soft baked, it may also become slightly cured so as to slightly increase viscosity of the material without causing the material to cure to such an extent that diminishes its adhesive functionality. Slightly increasing viscosity of the adhesive material may be desired when the adhesive material is too runny for use in a subsequent step of the method. For analogous reasons, a release layer material that may contain solvent may be soft baked to remove the solvent therefrom before contacting the release layer with the adhesive layer. A "hard baking" refers to curing the adhesive layer.

[0018] The temporary-bonded wafer systems and the components thereof described herein may have any suitable dimensions. In one non-limiting example, the DW and the CW may each have a thickness of about 750 μηι, the RL may have a thickness of about 0.2 μηι, and the AL may have a thickness of about 20-150 μηι.

[0019] The AL protects the RL from post-processing solvents that would otherwise dissolve the RL, e.g., the AL protects the RL from organic solvents and other chemicals like acids and bases used in post-bonding processing steps ("post-processing solvents"), especially those organic solvents that would otherwise dissolve the RL. Examples of such acids are HF/HN03 and examples of such bases are potassium hydroxide and tetramethylammonium hydroxide, which acids and bases may be used as silicon etchants in post-bonding processing steps. The TBA of the AL provides a temporary bond between the RL-coated DW and the CW to form the temporary-bonded wafer system. A temporary bond is one in which the material does not remain on the final device, and, thus, bonding is only temporary. Temporary bonding may assist with executing post-bonding steps to create a thin substrate and add functionality (e.g., passivation, redistribution, etc.). If not removed during the de-bonding steps, the temporary bond materials may be chemically removed. For example, the RL remaining on the DW may be dissolved with a solvent, e.g., an organic solvent used as a cleaning solvent in post-debonding processing step, while the AL may be chemically removed from the CW in a batch process (e.g., wet bench).

[0020] In another embodiment of the present disclosure, a temporary-bonded wafer system may include two (or more) RLs. As shown in FIG. 3e, a temporary-bonded wafer system 210 comprises (a) a device wafer (DW) 201 , (b) a first release layer (RL1 ) 202 applied over the DW 201 , (c) a carrier wafer (CW) 206, (d) a second release layer (RL2) 208 applied over the CW 206, and (e) a temporary bonding adhesive (TBA) forming an adhesive layer (AL) 204 positioned between the RL1 202 and the RL2 208. In the embodiment of FIG. 3e, the outer edges of the AL 204 contact a frontside 212 of the DW

201 and a frontside 214 of the CW 206, thereby forming an effective seal over the RL1 202 and a second effective seal over the RL2 208. As such, the RL1 202 and the RL2 208 are generally protected from post-processing solvents that would otherwise dissolve the RL1

202 and the RL2 208, e.g., the RL1 202 and the RL2 208 are generally protected from post-processing organic solvents, especially those organic solvents that would otherwise dissolve the RL1 202 and/or the RL2 208. After the bonding step, the wafer system may be baked/cured.

[0021] In the embodiments described herein, the AL is in a generally wet state. As such, the AL may shift, e.g., due to the weight of the wafer when the CW and DW are stacked.

[0022] The coating of the RL onto the DW and/or the CW in the embodiments described herein may be accomplished using any suitable techniques including conventional techniques such as spin coating, spray coating, other suitable coating techniques, and combinations thereof. Similarly, the AL may be applied using any suitable techniques, including conventional techniques such as spin coating, spray coating, other suitable coating techniques, and combinations thereof.

[0023] The temporary-bonded wafer systems described herein possess improved properties for post-processing steps. This makes the inventive temporary-bonded wafer systems desirable for their ultimate end uses in applications such as, but not limited to, 2.5D and 3D chip integration, semiconductor device packaging applications, power semiconductor devices, radio-frequency identification tags, chip cards, high-density memory devices, LEDs, microelectronic devices.

[0024] Device Wafer

[0025] DWs may include various kinds of devices such as microprocessors, memories, power, and the like that are not yet diced and packaged in, e.g., a plastic package such as an epoxy molding compound. An interposer may be used to bridge two different devices, e.g., a PCB and a die having dimensions that do not otherwise match. The active device wafers of the embodiments described herein may include silicon, glass, sapphire, SiC, metal wafers or panels, GaN or Si, GaAs, any lll-V-containing wafers, or any other type of active wafer.

[0026] Carrier Wafer

[0027] A CW is a supporting structure for assisting with handling a thin substrate that is temporary bonded on the CW. Such thin substrates cannot otherwise be handled, e.g., by automated equipment. CWs generally do not include any devices and differ from interposers in that they do not include any supporting structures. The carrier wafers of the embodiments described herein may include silicon, glass, sapphire, SiC, metal wafers or panels, GaN or Si, GaAs, any lll-V-containing wafers, or any other type of carrier wafer. The length and width of the CW are typically the same as or substantially the same as the length and width of the DW.

[0028] Release Layers

[0029] The RL of the embodiments described herein may be selected from, e.g., a silicone resin or an organic polymer-based resin, wherein the RL is capable of withstanding exposure of about 280^ and above. The RL may include pure resin, solvent, and, optionally, additives for, e.g., reducing the surface tension or promoting adhesion. The RL is generally removable or dissolvable using suitable removal or dissolving techniques including, but not limited to, using one or more solvents (a cleaning solvent), using plasma etch processes that are well known in the art, and the like. The solvents used may be one or more of the organic solvents described earlier and may include, for example, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), butyl acetate, toluene, xylene, mesitylene, or the like. The RL may be completely dissolvable or a combination of cleaning steps may be applied to remove the RL from the DW. The silicone resin and/or organic polymer-based resin may be solventless. Where a silicone resin is used in either the first RL or the second RL, the silicone resin is an SiO-containing polymer with a silanol (SiOH%) content ranging from greater than 0 up to about 30%, wherein the silicone resin contains structural units selected from:

-(R₁ R2R₃Si0₁/2)-(M)_>

-(R₄R₅Si02/2)-(D),

-(R₆Si0₃/₂)-(T), or

-(Si0₂)-(Q).

[0030] Temporary Bonding Adhesive Layer [0031] The temporary bonding adhesive (TBA) compositions in the temporary-bonded wafer systems described herein may be silicone-based thermosetting materials. Specifically, where the TBA is applied directly onto the RL, the TBA compositions described herein are generally solventless (e.g., solventless silicones) as described earlier. More specifically, the TBA compositions may be or may comprise, for example, a vinyl- functionalized oligomeric resin, a Si-H functional oligomeric resin, an alkenyl functional filler, and/or a metal catalyst. In one embodiment, the TBA includes vinyl PDMS fluids, vinyl MQ resins, and SiH X-linker. Where the TBA is applied to the CW, the TBA may initially include solvent and may be baked to substantially remove the solvent therefrom to give a solventless TBA prior to bonding with the RL on the DW. The TBA typically has a very good storage shelf life (e.g., it may be stored in a refrigerator or freezer for about four months or more) and cures rapidly (e.g., in about 2 to about 5 minutes) upon heating at elevated temperatures (e.g., at about 150°C) to form a cross-linked network. The cured thermoset coating is generally no longer soluble in organic solvents (organic solvent resistance) and/or other chemicals and mixtures. In addition, the cured coating includes a hydrophobic surface due to the surface segregation of the low surface energy dimethylsilyl (-SiMe2) group, which provides a barrier layer from various aqueous acid or base attacks.

[0032] Wafer Processing Operations

[0033] At least one wafer processing operation (e.g., wafer thinning, wet Si etching, dry Si- etching, etc.) may be performed on the bonded DW and CW to form a processed wafer system. For example, the DW may be thinned down to a desired thickness for a particular end use.

[0034] De-bonding Processes

[0035] Once the DW is processed into a very thin wafer (e.g., about 10 μηι to 150 μηι, or about 50 μηι), additional processes (e.g., TSV reveal) may be performed on the processed wafer system. To accomplish a 3D TSV temporary bonding process, the TBA should be mechanically room temperature (RT) de-bondable and should not require any additional treatment (such as laser or UV treatment), which may reduce the throughput of the process. The systems and methods described herein are advantageous as they facilitate 3D TSV temporary bonding applications at room temperature without special treatments. Other suitable de-bonding techniques may also be used. The wafer pair may then be laminated on film/tape on a frame so that the thinned DW may further be handled after de- bonding.

[0036] The film-laminated wafer pair may also be de-bonded using a mechanical initiation by a blade or by other mechanical means (e.g., gripping and pulling the CW off of the DW). In some embodiments, mechanical RT de-bonding may be used. In embodiments including a bi-layer system, the RL may remain on the DW after de-bonding on the tape, which is generally cleaning solvent compatible, and may be later removed by one or more solvents or potential plasma, depending on the application. The AL (e.g., silicone layer) typically remains on the CW after separation and may require chemical treatment to remove.

[0037] In some embodiments including a tri-layer system, after mechanical RT de-bonding, solvent or tape may be used to peel the AL off from the DW or CW. Proper removal of the RL by solvent or plasma or any other chemical treatment that is compatible with the materials present on the DW may follow.

[0038] Removal/Cleaning Processes

[0039] The RL coated on the DW and/or the CW may be removed or dissolved with one or more solvent(s). The solvent(s) may be any solvent that is capable of dissolving the RL(s) or any residue thereof and is generally incapable of dissolving the AL. Suitable representative solvents include, but are not limited to, organic solvents as described earlier, such as MEK, PGMEA, butyl acetate, toluene, xylene, mesitylene, any combination thereof, or the like. In one example, the RL may be removed by using a spray bottle to manually push out the solvent when placing the DW on a spin coater chuck. Dedicated tools may also be used where, as in a fully-automated mode, the solvent is dispensed onto the wafer. This process may be repeated one or more times to obtain optimum cleaning performance, depending on the device design. In some embodiments, the solvent(s) is sprayed onto the processed wafer, or the processed wafer is soaked in the organic solvent(s). Any solvent or combination thereof may be used to clean the processed wafer provided that the solvent(s) is capable of dissolving the respective RL or any residue thereof. The solvent(s) may be selected based on the RL material. In a tri-layer system, this may eliminate the need for a silicone remover, which is generally made from harsh chemicals such as mixtures including H2SO4 or an etchant based on tetramethylammonium hydroxide (TMAH).

[0040] Further Processing

[0041] To handle and use the processed wafer prior to being de-bonded and cleaned, the backside surface of the processed DW may be laminated or temporary-bonded to a dicing tape. The backside surface of the processed wafer is defined as the side of the wafer that is not in contact with either the RL or the TBA/AL. The lamination or bonding to the dicing tape may be performed prior to exposing the processed wafer system to the de-bonding and cleaning steps.

[0042] Multi-layered combinations other than the temporary-bonded wafer systems specifically described herein may also be used with the embodiments of the present invention. For example, certain wafers in the stack may be coated with underfill or other non-conductive film(s) to create a permanent bond, whereas other wafers in the same stack may be coated with one or more TBAs.

[0043] Methods

[0044] According to one method of the present disclosure, a method of forming a structure including a semiconductor wafer includes (a) coating an RL onto a first surface (i.e., a frontside) of the semiconductor wafer (e.g., a device wafer); (b) removing a portion of the RL from the backside and/or from the side (e.g., the bevel) of the DW of the semiconductor wafer; (c) applying an AL over the RL such that the RL is coated therewith, and the AL contacts one or more sides of the semiconductor wafer; and (d) contacting a first surface of a carrier wafer to the AL to form the structure. After the bonding step, the wafer system may be baked/cured.

[0045] As shown in FIG. 2a, an RL 102 may be coated onto the DW 101 using, for example, conventional techniques including, but not limited to, spin coating, spray coating, another suitable coating technique, combinations thereof, or the like. For example, the RL 102 may be spin coated using an open cup to obtain a good quality thin film so turbulence can occur at the wafer edge in the spin cup, leading to material deposition on the backside and/or the side(s) that bridge the backside and the frontside of the DW 101 . The RL-coated DW 101 may be prebaked at a temperature lower than about 285 'Ό to ensure that solvent is removed prior to applying the AL. The bake temperature is typically based on the boiling point of the solvent. For example, the bake temperature may be about δ'Ό higher than the boiling point of the solvent used. In one embodiment, the temperature is in the range of about 70 °C to about 180°C. Alternatively, a temperature range of about 80 'Ό to about 150°C may be used. Alternatively, a temperature range of about 130°C to about Ι δΟ'Ό may be applied for about 1 minute on a hotplate. Any suitable temperature/time may be used such that all or substantially all of the solvent in the RL is removed.

[0046] A backside edge bead removal (BEBR) process (also called a backside rinse (BSR)) may be performed after coating the RL 102 onto the DW 101 to remove a desired portion of the RL 102, the result of which, according to one example, is shown in FIG. 2b. Solvents such as organic solvents described earlier, including, but not limited to, toluene, xylene, mesitylene, PGMEA, butyl acetate, methyl ethyl ketone (MEK), combinations thereof, or the like may be used. BEBR typically includes dispensing of solvent on the edge of the backside of the wafer while rotating the wafer to clean the backside. In some embodiments, the wafer is placed on a chuck that has a diameter that is substantially smaller than the diameter of the wafer. By controlling the spin speed, time, and/or other variables during the BEBR process, solvent may attempt to creep onto the frontside of the wafer and dissolve a minimal amount of RL around the edges. The centrifugal force pushes the solvent to the wafer edge at the backside. By controlling the spin speed, the strength of the centrifugal force impacting fluidic dynamics is also controlled, and solvent may be allowed to creep along the wafer edge toward the frontside. The solvent generally does not dissolve RL on the frontside of the DW, since removing too much of the RL on the DW may result in glue residues when the DW is not edge-trimmed. If the DW is edge-trimmed, the RL may be removed from the edge-trimmed area of the frontside of the DW. The resulting RL 102 is shown in FIG. 2b- 2d. By virtue of the BEBR process, the portions of the RL located on the backside and the side(s) of the DW 101 are removed as part of the coating process step.

[0047] In one embodiment, a BEBR process is used, which may include spinning a solvent on a second surface opposite the first surface (i.e., the backside) of the DW. Non-limiting examples of solvents that may be used include organic solvents as described earlier, such as butyl acetate, PGMEA, combinations thereof, and the like. The speed and duration of the spinning of the BEBR depends, at least in part, on the equipment (e.g., the type of spin coater) and wafer size being used in such equipment. In some embodiments, the spin speed should be below the nominal spin speed to fix the thickness of the coating. The spinning of the BEBR may, for example, be performed at a spin speed of about 800 rpm to about 2500 rpm for about 3 seconds to about 60 seconds. In one example using a Suss Microtec (Suss Microtec, AG, Germany) spin coater, a spin speed of about 800 rpm for about 9 seconds achieved a good BEBR, while a spin speed of about 400 rpm failed for a wafer having a size of about 300mm. In another example using an EVG spin coater (Suss Microtec), a spin speed of about 2500 rpm for about 3 seconds achieved a good BEBR on a 100 mm wafer that had a major and a minor flat. The BEBR step was followed by a drying step using substantially the same speed and duration.

[0048] The location of and/or the shape of the spin coater's BEBR needle/dispenser may also play a role in the BEBR process. For example, when a 200 mm coater was used for

100 mm wafers, there was generally found to be a substantial amount of free area between the edge of the spin cup and the wafer edge, which created more turbulence. To reduce the turbulence, the needle dispenser of the coater was placed closer to the wafer edge.

[0049] The removed portion of the RL material may be from one or more sides of the DW

101 such that the side of the edge-trimmed DW 101 is exposed. An AL 104, which is applied over the RL 102 on the first surface (i.e., the frontside) of the edge-trimmed DW 101 , may contact the exposed side(s) of the DW 101 to form the effective seal over the RL

102, as shown in FIG. 2c.

[0050] The development of backside EBR processes includes three major functions. First, in embodiments where the RL is spin coated using an open cup method, the RL wraps around the backside of the wafer, thereby contaminating the backside of the wafer. Thus, the backside of the wafer is cleaned to avoid contamination of the bond chamber and hot plates during bake processes, bond processes, and post-bonding processes. Second, the RL is cleaned from the side(s) of the wafer to create a region free of RL. The cleaning of the bevel(s)/side(s) of the wafer may be performed during the same process as the cleaning of the backside. Third, the wafer backside needs to be dry before the wafer is moved to the hot plate for the RL bake process.

[0051] A TBA is applied on top of one of the RL-coated, edge-trimmed DW 101 to form an AL 104. To prevent or substantially reduce intermixing of the RL 102 with the AL 104, the AL 104 is generally solventless when applied directly over the RL 102. For example, the AL 104 may include a solventless silicone. The AL 104 may be coated (by spin coating, spray coating, using another suitable coating technique, combinations thereof, or the like). In one embodiment, the TBA of the AL 104 is spin coated over the RL 102 with, e.g., a closed cup, providing no or substantially no deposition of the AL material on the backside of the device wafer 101 .

[0052] An open cup may also be used to apply the AL. Use of an open cup may require BEBR of the AL so that the AL is not deposited on the side(s) and/or on the backside of the wafer. In embodiments where the AL is solventless (e.g., applied over the RL), the main difference between using BEBR for the RL versus the AL is that the solvent in the RL gradually evaporates during the spin coating, thereby setting the RL. The solventless AL, on the other hand, typically continues to run and will further reduce because the thickness is not set, which allows the AL to properly coat the RL. The AL will also be pushed back by the BEBR so that no (or substantially no) AL enters the backside of the wafer.

[0053] The layers are then temporary bonded together in vacuum to form a temporary bonded wafer system. The temporary-bonded wafer system is then cured. The curing can be by any suitable technique for solidifying the TBA including, but not limited to, thermal (heat) curing such as by using a vacuum oven at a predetermined reduced pressure and temperature level, a conventional oven or a hot plate at a certain temperature. As such, an effective seal is formed over the RL 103.

[0054] By selectively removing a portion(s) of the RL 102 from the side(s) of the DW 101 using a BEBR process, the AL 104 is able to contact the DW 101 . As such, the AL 104 seals the RL 102 and acts as a barrier for the RL 102, shielding it from chemicals (e.g., process chemicals and cleaning chemicals) used during post-bonding processes of thin wafers to achieve, for example, a photoresist, thereby assisting in preventing delamination. The BEBR process is typically robust enough such that no or substantially no residue remains. The effective seal formed by the AL 104 is generally chemical-resistant during post-bonding processes.

[0055] A first surface (i.e., frontside) of a CW 106 may then be bonded to the AL 104. The CW 106 and the AL 104 may be bonded in vacuum at about room temperature or above, followed by curing (e.g., in a vacuum) on a hotplate at a predetermined reduced pressure underneath the wafer pair.

[0056] In another embodiment illustrated in FIGs. 4a-4d, a method of forming a structure including a semiconductor includes (a) coating an RL 276 onto a first surface (i.e., frontside) of a first semiconductor wafer 274 (see FIG. 4a); (b) selectively removing a portion of the RL 276 from the first semiconductor wafer 274 such that the backside RL contamination and bevel RL coating is removed and the first semiconductor wafer 274 has only has RL on the frontside (see FIG. 4b); (c) coating an AL 270 (which underwent a BSR or used a closed cup to achieve its shape) onto a first surface of a second semiconductor wafer 272 (see FIG. 4c); and (d) contacting the AL 270 to the RL 276 of the first semiconductor wafer 274 such that the outer edges of the AL 270 contact the first semiconductor wafer 274 and a bond is formed (see FIG. 4d), thereby forming the structure. After the bonding step, the structure may be baked/cured. The first wafer 274 may be a DW, and the second wafer 272 may be a CW. The act of removing the RL 276 from the one or more sides 275 may include a BEBR process, which may include dispensing and spinning a solvent on the backside of the first semiconductor wafer 274. The act of contacting the AL 270 to the RL 276 may be conducted in a bond chamber. The act of contacting the AL 270 to the RL 276 and the one or more sides 275 of the first semiconductor wafer 274 forms an effective seal over the RL 276. The process is typically robust.

[0057] It is contemplated that a frontside edge bead removal (FEBR) and BSR may be applied to the AL 270 of the embodiment of FIGs. 4a-4d to assist in preventing the AL from "squeezing out" and contaminating the backside of the wafer when the AL-coated CW is bonded to the RL-coated DW. "Squeeze out" is generally not desirable, as it can generate particles that may contaminate equipment during further processing. Because there is no RL present on the CW, there is no need to select a solvent that is specific to the RL material when applying the FEBR and BSR of the AL. As such, there are more potential solvents that can be used. During the FEBR and BSR of the AL, some AL is removed not only from the backside of the CW but also from the edge of the frontside of the CW. The amount of AL removed from the frontside of the CW may range, e.g., from about 0.1 mm to about 2 mm and depends on various factors such as the AL thickness, the topography on the CW and/or the DW, and the edge trim dimensions. Some pressure may be used during the bonding process (after proper degassing but prior to bonding) to ensure that the AL properly contacts the RL. By doing this, the RL is protected by the AL as the AL is flowing and pushed over the RL.

[0058] The AL 270 may include a solventless silicone or solventless polyimide silicones. Because the AL 270 is not applied to the RL, however, the AL 270 of the embodiment of FIGs. 4a-4d may also include a solvent. In such embodiments, the AL-coated CW 272 is baked (e.g., on a hot plate or oven) at a temperature and duration sufficient to eliminate or substantially eliminate the solvent from the AL 270 prior to contacting the AL 270 to the RL 276 and DW 274. The baking may be performed inside a vacuum bond chamber prior to effective bonding.

[0059] An effective seal as used herein is achieved when there is essentially no delamination of the CW from the DW. Another way to determine whether an effective seal has been formed is to de-bond the wafers to check the thickness of the RL and/or whether there has been any degradation of the RL. A temporary-bonded wafer pair must survive a solvent bath of about 30 minutes to about 60 minutes without producing evidence of delamination to qualify as a good BEBR process that forms an effective seal. To determine if a BEBR process is effective such that an effective seal has been formed, the wafer pair may be de-bonded to determine whether the RL has been dissolved or etched away, e.g., at the outer about 1 cm of the front edge of the wafer. Robust processes forming effective seals typically lead to little to no degradation of the RL.

[0060] Referring back to FIGs. 3a-3e, a second release layer (RL2) 208 may be coated on the first surface (i.e., frontside) of the CW 206 prior to bonding the first surface of the CW 206 to the AL 204. The AL 204 is coated on the frontside of the RL2-coated CW 206 using, e.g., a closed cup or an open cup (see FIG. 3a). A BEBR process, similar to that described above with respect to the DW, may also be performed on the RL2-coated CW 206 (see FIG. 3b). In such embodiments, the frontsides of the DW 201 and the CW 206 are brought together in a bond chamber (e.g., in vacuum) to assure that an effective seal/barrier protection over the RL 202 and RL2 208 results (see FIG. 3e), followed by a post-bonding cure in or outside the bond chamber. It may be desirable for the post-bonding cure to be carried out outside the bond chamber so as to not limit the throughput of the bond chamber. In another embodiment, the material is first de-gased in vacuum, and the bonding is carried out at or about atmospheric pressure. As shown in FIGs. 3c-3d, in some embodiments in which the AL is applied to the CW, the AL-coated CW 206 may need to be flipped prior to contacting the DW 201 so that the frontside of the AL-coated CW 206 may be bonded to the frontside of the DW 201 .

[0061] Subsequent operations or processes such as, e.g., wafer grinding, may be performed on any of the wafer systems described herein. For example, the wafer processing may include grinding of the DW to form a processed wafer system. Once the temporary-bonded wafer system is processed into a very thin wafer, additional processes such as, but not limited to, through-silicon via (TSV) reveal may be optionally performed on the processed wafer system.

[0062] After de-bonding, the film-laminated processed wafer when thinned may be exposed to an organic solvent, wherein the organic solvent is as described earlier (e.g., PGMEA, butyl acetate, MEK) that will act as a surface cleaning agent or as a solvent to assist in removing the RL. The organic solvent generally cleans the surface of the device wafer and/or the carrier wafer upon which the respective RL was coated. Any organic solvent can be used to clean the processed wafer provided that the solvent is capable of dissolving the RL. Depending on the type of surface, the RL may or may not be completely dissolved. For example, if the surface is, e.g., silicon, then a monolayer may remain, but if the surface is, e.g., CVD nitride, all of the RL may be dissolved. Several examples of organic solvents that may be used include, but are not limited to, toluene, xylene, mesitylene, PGMEA, butyl acetate, combinations thereof, or the like.

[0063] In some, but not all, embodiments the invention comprises any one of the following numbered aspects:

[0064] Aspect 1 . A temporary-bonded wafer system comprising: a substrate having a first surface and a second surface opposite the first surface; a release layer positioned on the first surface of the substrate; an adhesive layer positioned over the release layer, wherein outer edges of the adhesive layer contact the substrate, thereby forming an effective seal over the release layer; and a carrier wafer bonded to the adhesive layer.

[0065] Aspect 2. The system of aspect 1 , wherein the adhesive layer includes a solventless silicone.

[0066] Aspect 3. The system of any one of aspects 1 and 2, wherein the effective seal is generally chemical-resistant.

[0067] Aspect 4. The system of any one of aspects 1 to 3, wherein the substrate is a semiconductor device wafer. [0068] Aspect 5. The system of aspect 4, further comprising a second release layer positioned between the carrier wafer and the adhesive layer, the adhesive layer forming a second effective seal over the second release layer.

[0069] Aspect 6. A method of forming a temporary-bonded wafer system including a substrate, the substrate including a first surface, a second surface, and one or more sides, the method comprising: coating a release layer material onto the first surface of the substrate; removing a portion of the release layer material from the one or more sides of the substrate; applying an adhesive layer over the release layer such that the release layer is coated with the adhesive layer and edges of the adhesive layer contact the one or more sides of the substrate, thereby forming a generally chemical-resistant seal over the release layer material; contacting a first surface of a carrier wafer to the adhesive layer to form the system; and curing the system.

[0070] Aspect 7. The method of aspect 6, wherein the adhesive layer includes a solventless silicone.

[0071] Aspect 8. The method of any one of aspects 6 and 7, wherein the applying the release layer material includes spin coating or spray coating.

[0072] Aspect 9. The method of any one of aspects 6 to 8, further comprising applying a second release layer on the first surface of the carrier wafer prior to contacting the first surface of the carrier wafer to the adhesive layer, the adhesive layer forming a second effective seal over the second release layer.

[0073] Aspect 10. The method of any one of aspects 6 to 9, wherein the removing a portion of the release layer material includes a backside edge bead removal process.

[0074] Aspect 1 1 . The method of aspect 10, wherein the backside edge bead removal process includes spinning and dispensing a solvent on the second surface of the substrate.

[0075] Aspect 12. The method of aspect 1 1 , wherein the solvent includes methyl ethyl ketone, propylene glycol monomethyl ether acetate, butyl acetate, toluene, xylene, mesitylene, or any combination thereof.

[0076] Aspect 13. The method of aspect 1 1 , wherein the spinning is performed at a speed of about 100 rpm to about 2500 rpm for about 5 seconds to about 60 seconds.

[0077] Aspect 14. The method of any one of aspects 6 to 13, wherein the substrate is a device wafer.

[0078] Aspect 15. A method of forming a temporary-bonded wafer system including a first substrate and a second substrate, each of the first and second substrate including a first surface, a second surface, and one or more sides, the method comprising: coating a release layer material onto the first surface of the first substrate; selectively removing the release layer material from the one or more sides of the first surface of the first substrate such that the one or more sides of the first substrate are exposed; coating an adhesive layer onto the first surface of the second substrate; contacting the adhesive layer to the release layer material and the one or more sides of the first substrate such that a bond is formed, thereby forming the system; and curing the system.

[0079] Aspect 16. The method of aspect 15, wherein the first substrate is a device wafer and the second substrate is a carrier wafer.

[0080] Aspect 17. The method of any one of aspects 15 and 16, wherein the contacting the adhesive layer to the release layer material is conducted in a bond chamber.

[0081] Aspect 18. The method of any one of aspects 15 to 17, wherein the adhesive layer includes silicone.

[0082] Aspect 19. The method of any one of aspects 15 to 18, further comprising baking the adhesive layer-coated second substrate to remove solvent from the adhesive layer prior to contacting the adhesive layer to the release layer material and the one or more sides of the first substrate.

[0083] Aspect 20. The method of any one of aspects 15 to 19, wherein the contacting the adhesive layer to the release layer material and the one or more sides of the first surface of the first substrate forms a generally chemical-resistant seal over the release layer material.

[0084] Aspect 21 . The method of any one of aspects 15 to 20, wherein the removing the release layer material includes a backside edge bead removal process.

[0085] Aspect 22. The method of aspect 21 , wherein the backside edge bead removal process includes dispensing and spinning a solvent on an outer edge of the second surface of the first substrate.

[0086] Aspect 23. The method of any one of aspects 15 to 22, further comprising, prior to contacting the adhesive layer onto the first surface of the second substrate, coating a second release layer material onto the first surface of the second substrate and selectively removing the second release layer material from the one or more sides of the first surface of the second substrate such that the one or more sides of the second substrate are exposed.

[0087] Aspect 24. The method of aspect one of aspects 15 to 22, wherein the act of selectively removing the release layer material includes dissolving a portion of the release layer material in one or more solvents, the one or more solvents being generally incapable of dissolving the adhesive layer. [0088] Aspect 25. The method of aspect 24, wherein the one or more solvents include methyl ethyl ketone, propylene glycol monomethyl ether acetate, butyl acetate, toluene, xylene, mesitylene, or any combination thereof.

[0089] In other, but not all, embodiments the invention includes any one of the following numbered embodiments.

[0090] Embodiment 1 . A temporary-bonded wafer system comprising: a substrate having a first surface and a second surface opposite the first surface; a release layer positioned on the first surface of the substrate; an adhesive layer positioned over the release layer, wherein outer edges of the adhesive layer contact the substrate, thereby forming an effective seal over the release layer; and a carrier wafer bonded to the adhesive layer.

[0091] Embodiment 2. The system of embodiment 1 , wherein the adhesive layer includes a solventless silicone.

[0092] Embodiment 3. The system of embodiment 1 or 2, wherein the effective seal is generally chemical-resistant.

[0093] Embodiment 4. The system of any one of embodiments 1 to 3, wherein the substrate is a semiconductor device wafer.

[0094] Embodiment 5. The system of embodiment 4, further comprising a second release layer positioned between the carrier wafer and the adhesive layer, the adhesive layer forming a second effective seal over the second release layer.

[0095] Embodiment 6. A method of forming a temporary-bonded wafer system including a first substrate, release layer, adhesive layer, and second substrate, the first and second substrates each independently including a first surface, a second surface, and one or more sides, the method comprising: coating a release layer material onto the first surface of the first substrate and onto the one or more sides so as to cover the first surface and at least partially cover the one or more sides of the first substrate with the release layer material; removing a portion of the release layer material from the one or more sides of the first substrate without removing the portion of the release layer material that covers the first surface of the first substrate so as to expose (i.e., uncover) the one or more sides and give a release layer positioned on the first surface of the first substrate but not positioned on the one or more sides of the first substrate, and, when the release layer material contains solvent, removing solvent from the release layer; applying an adhesive layer over the release layer and over the exposed one or more sides of the first substrate such that the release layer is coated with the adhesive layer and edges of the adhesive layer contact the one or more sides of the first substrate, thereby forming a generally chemical-resistant seal over the release layer; contacting the first surface of the second substrate to the adhesive layer under vacuum to form an uncured system; and curing the uncured system to give the temporary-bonded wafer system of any one of embodiments 1 to 4; wherein the contacting step is performed after the applying step.

[0096] Embodiment 7. The method of embodiment 6, wherein the adhesive layer includes a solventless silicone.

[0097] Embodiment 8. The method of embodiment 6 or 7, wherein the second substrate is a carrier wafer, and the method further comprising applying a second release layer on the first surface of the carrier wafer, removing solvent, if any, from the adhesive layer, and then contacting the second release layer to the adhesive layer, the adhesive layer forming a second effective seal over the second release layer.

[0098] Embodiment 9. The method of any one of embodiments 6 to 8, wherein the removing a portion of the release layer material includes a backside edge bead removal process.

[0099] Embodiment 10. The method of embodiment 9, wherein the backside edge bead removal process includes spinning and dispensing a solvent on the second surface of the substrate.

[00100] Embodiment 1 1 . The method of embodiment 10, wherein the solvent includes a glycol monoether monoester derivative thereof; an alcohol;; a ketone; an aromatic hydrocarbon; a carboxylic acid ester; a carboxylic amide; a lactam; or a combination of any two or more thereof.

[00101] Embodiment 12. The method of embodiment 1 1 , wherein the solvent includes methyl ethyl ketone, propylene glycol monomethyl ether acetate, butyl acetate, toluene, xylene, mesitylene, or any combination thereof.

[00102] Embodiment 13. The method of any one of embodiments 6 to 12, wherein the first substrate is a device wafer.

[00103] Embodiment 14. The method of any one of embodiments 6 to 13, wherein the contacting the adhesive layer to the release layer is conducted in a bond chamber under vacuum.

[00104] Embodiment 15. The method of any one of embodiments 6 to 14, further comprising, prior to contacting the adhesive layer onto the first surface of the second substrate, coating a second release layer material onto the first surface of the second substrate so as to cover the first surface and at least partially cover the one or more sides of the second substrate with the second release layer material, and selectively removing the second release layer material from the one or more sides of the first surface of the second substrate without removing the portion of the second release layer material that covers the first surface of the second substrate such that the one or more sides of the second substrate are exposed (i.e., uncovered) and a second release layer is positioned on the first surface of the second substrate but is not positioned on the one or more sides of the second substrate.

[00105] Embodiment 16. The method of embodiment any one of embodiments 6 to 15, wherein the step of selectively removing the release layer material includes dissolving a portion of the release layer material in one or more solvents, the one or more solvents being generally incapable of dissolving the adhesive layer.

[00106] Embodiment 17. The method of embodiment 16, wherein the one or more solvents include methyl ethyl ketone, propylene glycol monomethyl ether acetate, butyl acetate, toluene, xylene, mesitylene, or any combination thereof.

EXAMPLES

[00107] These examples are intended to illustrate the invention to one of ordinary skill in the art and should not be interpreted as limiting the scope of the invention set forth in the claims.

Example 1 - Blanket Wafer Tests

[00108] Chemical Resistance of the AL

[00109] The chemical resistance of the AL described herein was tested by using a spin coater to coat two different solventless ALs including a polydimethylsiloxane material with a viscosity of about 5,000 cP onto blanket silicon wafers and curing them at a temperature of about 150°C for about 2 minutes on a hotplate. Wafer weight measurements were made prior to coating, after coating, and after exposure to the chemicals such as solvents (e.g., organic solvents), acids, or bases as described earlier. The AL provides chemical resistance to solvents, acids and bases used in post-bond processes. Measuring the weight change due to exposure to typical chemicals used in the post-processing steps after wafer thinning provided an indication of which chemicals are the harshest for the solventless silicone adhesive and which acted as effective chemical seals for the temporary-bonded wafer pair. Tables 1 a and 1 b show the experimental data regarding the chemical resistance of the ALs.

Table 1 a - Chemical Resistance of the AL

Table 1 b - Chemical Resistance of the AL

Impact Weight

thickness change

85% Acetone + 15% IPA 25 ^<C 20 min -0.52% 0.05%

PGMEA 25°C 10 min -2.30% 0.05%

IPA 25°C 20 min -1 .34% 0.05%

TMAH 25 ^<C 10 min -0.49% 0.00%

NMP 25 ^<C 10 min -0.64% 0.00%

1 .5%H₃P0₄ + 0.4%H₂O₂ 30 ^<C 2 min -0.44% 0.00%

0.05% NH4OH + 0.1 %H₂O₂ 30^<C 10

min 0.13% 0.00%

0.2 HF + 0.3 HNO3 + 7% HAc 35 ^<C 1

min -0.39% 0.00%

0.5%HF +9% HNO3 40 ^<C 2 min 0.10% 0.00%

8%H₃P0₄ 45 ^<C 8 min -0.08% 0.00%

IPA Vapor 80°C 20 min -0.15% 0.00%

NO Exposure Reference Wafer with

coating. 0.18% 0.00%

HAc is acetic acid.

[00110] Chemical Resistance of the RL

[00111] The chemical resistance of the RL described herein was tested by coating blanket wafers with an RL at the nominal spin conditions. Low spin speeds typically resulted in thicker layers, while high spin speeds typically resulted in thinner layers. The thickness of the layers also depended on the solid content of the RL formulation.

[00112] The coated wafer was then cured at about 150°C for about 1 minute to drive all the residual solvent from the thin film coating. The wafer was then exposed to several chemicals and the evidence of failure or pass of the solvent/chemical resistant test was noted based upon the discoloration or removal of the RL on the surface of the wafer. Table

2 shows the solvent list and the resistance of the RL to each solvent. Table 2: Resistance of RL to chemicals

[00113] During the next step of the evaluation, the AL was coated over the RL- coated wafer to demonstrate failure of existing bi-layer wafer bonding approaches (not utilizing BEBR processes). The AL was cured at about 150°C for about 3 minutes to ensure that the cure was complete. PGMEA was then sprayed onto the wafer, and the wafer was observed for any RL discoloration. It was clear that a temporary-bonded wafer according to existing technologies can be susceptible to failure due to wrinkling of the AL and/or dissolving of the RL. As such, it would be desirable to protect the RL, as a pure AL may resist the chemicals.

Example 2 - Backside EBR Process Development

[00114] The process was developed on a DNS spin coater (Dainippon Screen Manufacturing Co., Japan) by running a design of experiment (DOE) (see Table 4) to examine the most appropriate spin speeds for the BEBR process using BA as the backside rinse solvent. The RL material was a silicone resin that was an SiO-containing polymer with a silanol (SiOH%) content ranging from greater than 0 up to about 30%, wherein the silicone resin contained structural units selected from, -(R-| R2R3SiO-|/2)-(M), -

(R4R5SiC>2/2)-(D), -(ReSi03/2)-(T), or -(SiC>2)-(Q). Table 3 shows the range of spin speeds for each step in the backside EBR process.

Table 3: Backside EBR Process Flow

[00115] As shown in Table 4, the higher the BEBR spin speed for the particular configuration used, the less effective the BEBR process was due to a minimal amount of material being removed. As discussed above, however, the results depend, at least in part, on the type of spin coater used. Thus, according to one embodiment in which a point dispense is applied for backside EBR, a spin speed of between about 150 to about 300 rpm for a minimum of about 20 seconds may be used. In another embodiment in which a multiple point dispense spin cup (e.g., Suss MicroTec) is used, slightly higher spin speeds may be used, such as about 400 rpm to about 1000 rpm for about 8 seconds to about 20 seconds, or the spin speeds may be about 150 rpm to about 300 rpm for shorter amounts of time. 300 mm wafers were coated using a Suss MicroTec hardware configuration at a spin speed of about 800 rpm for about 9 seconds. EVG spin coaters were used at spin speeds of up to about 2500 rpm for about 3 seconds for 100 mm wafers with a major and a minor flat.

[00116] The location of the BEBR is a factor in determining spin speed and durations, since some spin coaters are designed to be used for several wafer sizes. This results in the BEBR taking place at varying distances from the wafer edge depending on the size of the wafer used. Adjustments may be made to the spin speed and duration to account for this varying distance.

Table 4: Backside EBR DOE for RL Spin Coat

Thus, depending on the spin coater used and the BEBR capability of the spin coater, an optimal process may be achieved such that the RL is removed on the backside of the wafer and the outer wafer edge (e.g., the sidewall).

Example 3 - Thick Non-Edge Trimmed Temporary-Bonded Wafers

[00117] The next phase was to implement the process and create temporary- bonded wafer pairs that were tested by soaking the temporary-bonded wafer pair in different solvents that readily dissolved the RL. The soaked wafer was dried using a N₂ gun and de-bonded, and the thicknesses of the RL and AL were measured using a Filmetrics optical thickness tool (Filmetrics, San Diego, California) to monitor the thickness of the RL.

[00118] Bonding experiments were completed by creating temporary-bonded pairs using the BEBR process flow for RL coating and a "drop bond" process developed for room temperature bonding. The drop bond approach drops the top wafer over the other wafer, thereby utilizing the weight of the top wafer to exert a force on the AL-coated on the other wafer in a vacuum environment (about 3 mbar to about 5 mbar) after degassing without applying any external force to create void free, no "squeeze out" temporary- bonded wafer pairs. Twenty temporary-bonded wafer pairs were generated using the BEBR process and were tested as described above. Upon inspecting the de-bonded wafer, which was de-bonded manually with a razor blade inserted between the wafer pair and pushed up and down to create a vertical force, the RL was intact on the wafer, evidencing the feasibility of protecting the temporary-bonded wafer pair from failure caused by dissolving the RL. Table 5 shows the solvents, conditions, and results of the tests.

Table 5: Resistance of RL to Solvents of Temporary-Bonded Wafer Pairs Processed by the

BEBR Process

The thickness measurements completed on the RL and AL of the de-bonded wafer also demonstrated that the RL was generally not attacked by the exposure to the solvents. Example 4 - Thick Edge-Trimmed Temporary-Bonded Wafers

[00119] Temporary-bonded wafer pairs were then created in which the wafer with the RL coating was an edge-trimmed wafer. By virtue of the edge trimming, the silicon was removed from the side(s) of the wafer to overcome potential edge chipping and/or other problems with the wafer. The edge-trimmed wafer had a sharper edge compared to the non-edge trimmed wafer. Edge-trimmed wafers were coated with RL using the backside EBR process and then bonded to an AL-coated carrier wafer using the "drop bond" approach described above. The wafer stack was then cured, and the temporary-bonded wafer pairs were again tested by soaking the wafer pairs in different solvents, as shown in Table 6 below. No failures were detected for the typical exposure times, but the RL was dissolved when a temporary-bonded wafer pair was allowed to soak in the BA solution for about 6 hours, which indicates that the protection seal produced by the AL is not completely impenetrable but could withstand typical process steps involving typical chemicals used in the device manufacturing process. Table 6 shows the results of the chemical resistance testing completed on edge-trimmed temporary-bonded wafer pairs. Table 6: Resistance of RL to Solvents of Edge-Trimmed Temporary-Bonded Pairs

Processed by BEBR Process

[00120] Thus, because the effective chemical seal blocked or delayed the penetration of the solvent to the RL, the temporary-bonded wafer pairs did not show degradation or delamination. This was confirmed by de-bonding the wafer pair, as no degradation was observed for the wafer with the RL.

[00121] While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and described in detail herein. The invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

Claims:

1 . A temporary-bonded wafer system comprising:

a substrate having a first surface and a second surface opposite the first surface; a release layer positioned on the first surface of the substrate;

an adhesive layer positioned over the release layer, wherein outer edges of the adhesive layer contact the substrate, thereby forming an effective seal over the release layer; and

a carrier wafer bonded to the adhesive layer.

2. The system of claim 1 , wherein the adhesive layer includes a solventless silicone.

3. The system of claim 1 or 2, wherein the effective seal is generally chemical- resistant.

4. The system of any one of claims 1 to 3, wherein the substrate is a semiconductor device wafer.

5. The system of claim 4, further comprising a second release layer positioned between the carrier wafer and the adhesive layer, the adhesive layer forming a second effective seal over the second release layer.

6. A method of forming a temporary-bonded wafer system including a first substrate, release layer, adhesive layer, and second substrate, the first and second substrates each independently including a first surface, a second surface, and one or more sides, the method comprising:

coating a release layer material onto the first surface of the first substrate and onto the one or more sides so as to cover the first surface and at least partially cover the one or more sides of the first substrate with the release layer material;

removing a portion of the release layer material from the one or more sides of the first substrate without removing the portion of the release layer material that covers the first surface of the first substrate so as to expose (i.e., uncover) the one or more sides and give a release layer positioned on the first surface of the first substrate but not positioned on the one or more sides of the first substrate, and, when the release layer material contains solvent, removing solvent from the release layer;

applying an adhesive layer over the release layer and over the exposed one or more sides of the first substrate such that the release layer is coated with the adhesive layer and edges of the adhesive layer contact the one or more sides of the first substrate, thereby forming a generally chemical-resistant seal over the release layer;

contacting the first surface of the second substrate to the adhesive layer under vacuum to form an uncured system; and curing the uncured system to give the temporary-bonded wafer system of any one of claims 1 to 4;

wherein the contacting step is performed after the applying step.

7. The method of claim 6, wherein the adhesive layer includes a solventless silicone.

8. The method of claim 6 or 7, wherein the second substrate is a carrier wafer, and the method further comprising applying a second release layer on the first surface of the carrier wafer, removing solvent, if any, from the adhesive layer, and then contacting the second release layer to the adhesive layer, the adhesive layer forming a second effective seal over the second release layer.

9. The method of any one of claims 6 to 8, wherein the removing a portion of the release layer material includes a backside edge bead removal process.

10. The method of claim 9, wherein the backside edge bead removal process includes spinning and dispensing a solvent on the second surface of the substrate.

1 1 . The method of claim 10, wherein the solvent includes a glycol monoether monoester derivative thereof; an alcohol;; a ketone; an aromatic hydrocarbon; a carboxylic acid ester; a carboxylic amide; a lactam; or a combination of any two or more thereof.

12. The method of claim 1 1 , wherein the solvent includes methyl ethyl ketone, propylene glycol monomethyl ether acetate, butyl acetate, toluene, xylene, mesitylene, or any combination thereof.

13. The method of any one of claims 6 to 12, wherein the first substrate is a device wafer.

14. The method of any one of claims 6 to 13, wherein the contacting the adhesive layer to the release layer is conducted in a bond chamber under vacuum.

15. The method of any one of claims 6 to 14, further comprising, prior to contacting the adhesive layer onto the first surface of the second substrate, coating a second release layer material onto the first surface of the second substrate so as to cover the first surface and at least partially cover the one or more sides of the second substrate with the second release layer material, and selectively removing the second release layer material from the one or more sides of the first surface of the second substrate without removing the portion of the second release layer material that covers the first surface of the second substrate such that the one or more sides of the second substrate are exposed (i.e., uncovered) and a second release layer is positioned on the first surface of the second substrate but is not positioned on the one or more sides of the second substrate.

16. The method of claim any one of claims 6 to 15, wherein the step of selectively removing the release layer material includes dissolving a portion of the release layer material in one or more solvents, the one or more solvents being generally incapable of dissolving the adhesive layer.

17. The method of claim 16, wherein the one or more solvents include methyl ethyl ketone, propylene glycol monomethyl ether acetate, butyl acetate, toluene, xylene, mesitylene, or any combination thereof.