WO2014160067A1

WO2014160067A1 - Thermally curable silicone compositions as temporary bonding adhesives

Info

Publication number: WO2014160067A1
Application number: PCT/US2014/025751
Authority: WO
Inventors: Peng-Fei Fu; Sheng Wang
Original assignee: Dow Corning Corporation
Priority date: 2013-03-14
Filing date: 2014-03-13
Publication date: 2014-10-02
Also published as: TW201444939A

Abstract

Provided in various embodiments are silicone-based storage stable temporary bonding adhesive compositions. The storage stable TBA compositions are formed by combining (e.g., mixing or blending) an alkenyl functional siloxane polymer, an alkenyl functional filler with a particle size below one micrometer, an SiH-containing crosslinker, a hydrosilylation catalyst, and a cure inhibitor where the molar ratio of the cure inhibitor and the hydrosilylation catalyst is greater than 40/1 and less than 500/1. The resulting TBA compositions may be one-part compositions. The TBA compositions can be used in varied applications including 3D chip integration, packaging applications, semiconductor devices, radio-frequency identification tags, chip cards, high-density memory devices, and microelectronic devices.

Description

THERMALLY CURABLE SILICONE COMPOSITIONS AS TEMPORARY BONDING

ADHESIVES

BRIEF SUMMARY OF THE INVENTION

[0001] The present invention relates to novel silicone-based storage stable temporary bonding adhesives (TBA) for temporary bonding applications. The storage stable TBA compositions are formed by combining (e.g., mixing or blending) an alkenyl functional siloxane polymer, an alkenyl functional filler with a particle size below one micrometer, an SiH-containing crosslinker, a hydrosilylation catalyst, and a cure inhibitor where the molar ratio of the cure inhibitor and the hydrosilylation catalyst is greater than 40/1 and less than 500/1 . The resulting TBA compositions may be one-part compositions. The TBA compositions can be used in varied applications including 3D chip integration, packaging applications, semiconductor devices, radio-frequency identification tags, chip cards, high- density memory devices, and microelectronic devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Various advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

[0003] FIG. 1 a and 1 b are schematics of a temporary bonding adhesive (TBA) layer and additional functional layers according to embodiments of the invention.

[0004] FIG. 2 shows strain-stress curves for certain cured polydimethylsiloxane-based temporary bonding adhesives (TBAs).

[0005] FIG. 3 shows the viscosity levels for certain TBAs.

[0006] FIG. 4 shows the shelf-life of certain TBAs.

[0007] 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

[0008] According to the embodiments of the invention, silicone-based storage stable TBA compositions are formed by combining (e.g., mixing or blending) (a) an alkenyl functional siloxane polymer, (b) an alkenyl functional filler with a particle size below one micrometer (Mm), (c) an SiH-containing crosslinker, (d) a hydrosilylation catalyst, and (e) a cure inhibitor where the molar ratio of the cure inhibitor and the hydrosilylation catalyst is greater than 40/1 and less than 500/1. The resulting silicone-based storage stable TBA compositions exhibit various advantageous characteristics. The resulting storage stable TBA compositions may be one-part compositions. While the invention is susceptible to various modifications and alternative forms, specific embodiments are described by way of example herein, and the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

[0009] The silicone-based storage stable TBA compositions described herein possess good mechanical properties for post processing steps. The TBA can be coated onto a substrate to form a film. The film may be cured by heating to form a crosslinked and tacky-free film. This places the TBA composition in a more user-friendly form for its ultimate end use in applications such as, but not limited to, 3D chip integration, packaging applications, semiconductor devices, radio-frequency identification tags, chip cards, high-density memory devices, microelectronic devices.

Component (a)

[0010] The alkenyl functional siloxane polymer (component (a)) for use in the embodiments detailed herein is an alkenyl silicone organopolysiloxane fluid. In some embodiments, the alkenyl functional siloxane polymer is an alkenyl functional polysiloxane fluid having the general formula:

or

wherein R-i is an alkenyl group, including but not limited to, H₂C=CH-, H₂C=CHCH₂-,

R₂ is an alkyl or aryl group, including but not limited to, methyl, ethyl, propyl, butyl, phenyl, and naphthyl groups; x and y are the molar ratio of the two structural units, 1 > x > 0, 1 > y > 0, and x + y =1 ; 1 > o > 0, 1 > p > 0, and o + p =1 ; and m is the number of the repeating units, wherein m is an integer that is 1 or larger. Examples of such alkenyl functional polysiloxane fluids are:

CH₂=CH-SiMe₂-(OSiMe₂)m-OSiMe₂-CH=CH₂, wherein m≥ 1 , Me is a methyl group and

CH₂=CH-SiMe2-(OSiMePh)_m-OSiMe2-CH=CH₂, wherein m≥ 1 , Ph is a phenyl group. One non-limiting example of a suitable alkenyl functional siloxane polymer is a vinyl terminated polydimethylsiloxane polymer fluid where the degree of polymerization (DP) is 500.

Component (b)

[0011] The alkenyl functional filler (component (b)) for use in the embodiments detailed herein has a particle size below one micrometer (pm). In some embodiments, the alkenyl functional filler is a vinyl functional silicone resin. In other embodiments, the alkenyl functional filler is a vinyl functional silica. In still further embodiments, the alkenyl functional filler is, for example, a vinyl functional colloidal silica, a vinyl functional nanoparticle, or a vinyl MQ resin. The acronym MQ as it relates to silicone resins is derived from the symbols M, D, T, and Q each of which represent a functionality of different types of structural units which may be present in silicone resins containing siloxane units joined by Si— O— Si bonds. Monofunctional (M) unit represents (CH₃)₃Si0_1/2. Difunctional (D) unit represents (CH₃)₂Si0_2/2- Trifunctional (T) unit represents CH₃Si0_3/2 and results in the formation of branched linear siloxanes. Tetrafunctional (Q) unit represents Si0_4/2 which results in the formation of resinous silicone compositions.

[0012] Where the alkenyl functional filler is a vinyl MQ resin, the vinyl MQ resin may have the following structural units:

(Me₃Si0_1/2)(R¹Me2Si0_1/2)(Si0_4/2),

wherein R¹ is an alkenyl group, including but not limiting to, H₂C=CH-, H₂C=CHCH₂-,

One non-limiting example of a suitable alkenyl functional filler for use in component (b) is a vinyl functional MQ resin where the vinyl content wt% is in the range of 0.5 to 5.0. Another non-limiting example of a suitable alkenyl functional filler for use in component (b) is a vinyl- functionalized oligomeric silicone resin.

Component (c)

[0013] Component (c) for use in the embodiments detailed herein is an SiH-containing crosslinker. In some embodiments, the SiH-containing crosslinker has the general formula: or

wherein R₂ is an alkyl or aryl group, including but not limiting to, methyl, ethyl, propyl, butyl, and phenyl groups; x and y are the molar ratio of the two structural units, 1≥ x≥ 0, 1≥ y≥ 0, and x + y =1 ; 1 > o > 0, 1 > p > 0, and o + p =1 ; and m is the number of the repeating units, wherein m is an integer that is 1 or larger. One non-limiting example of a suitable SiH- containing crosslinker is an SiH crosslinker with the structure MD₃D^H ₅M. Another non- limiting example of a suitable SiH-containing crosslinker for use in component (c) is an Si-H functional oligomeric silicone resin.

Component (d)

[0014] The hydrosilylation catalyst (component (d)) for use in the embodiments detailed herein is a transition metal catalyst, including, but not limited to, platinum catalysts and rhodium catalysts. One non-limiting example of a suitable platinum catalyst is a platinum- divinyl-tetramethyldisiloxane catalyst. Other suitable catalysts may also be used including, but not limited to, those disclosed in PCT Publication No. WO2012/1 18700. The catalyst may be added as a single catalyst species or as a mixture of two or more different species. Component (e)

[0015] The cure inhibitor (component (e)) for use in the embodiments detailed herein is an organic compound. The cure inhibitor is capable of interacting with the catalyst in order to delay the initiation of the catalyzed reaction. In some embodiments, the cure inhibitor is a maleate compound. The maleate compound has the general formula:

-R-OOC-CH=CH-COOR,

wherein R is an organic group. In some embodiments, the cure inhibitor is diallyl maleate. In still further embodiments, the cure inhibitor may include various hydrosilylation inhibitors such as, but not limited to, acetylenic alcohols, phosphorus-containing compounds, nitrogen- containing compounds, and sulfur-containing compounds. Further non-limiting examples of suitable cure inhibitors include ethynyl cyclohexanol, bis-2-methoxy-1 -methylethylmaleate, and Ν,Ν,Ν',Ν'-tetramethylethylenediamine. In general, the weight percent of the cure inhibitor present in the silicone-based TBA compositions is below 1 %. The weight percent of the cure inhibitor is expected to vary as each inhibitor possesses a different molecular weight.

[0016] The molar ratio of the cure inhibitor and the hydrosilylation catalyst ([cure inhibitor]/[catalyst]) is greater than 40/1 and less than 500/1. In still further embodiments, the molar ratio of the cure inhibitor and the hydrosilylation catalyst is in the range of 100/1 to 300/1 .

[0017] Where the alkenyl functional filler is a vinyl (Vi) functional silicone resin, the molar ratio of SiH/Vi ([SiH-containing crosslinker]/[alkenyl functional filler]) present in the adhesive is in the range of about 0.8 to about 3.0. In still further embodiments, the molar ratio of SiH/Vi in the adhesive is in the range of about 1.0 to about 2.0.

Optional Component(s)

[0018] One or more additional optional components can be included in the storage stable TBA compositions. These additional optional components include, but are not limited to, other fillers such as talc, silica, and calcium carbonate, stabilizers, absorbents, pigments, plasticizers, additives for improving adhesion, fluids or other materials conventionally used in gels, gelling agents, silicone fluids, silicone waxes, silicone polyethers, surfactants, and rheology modifiers such as thickening agents or thixotropic agents.

Processes

[0019] Components (a)-(e) and any optional additional components are mixed or blended by any suitable technique which results in mixing or blending of the reactants. The inventive silicone-based TBA compositions are storage stable. They may be stored for more than 2 weeks at room temperature and more than 3 months at 5°C and exhibit excellent shelf-life properties.

[0020] The inventive silicone-based TBA compositions may be stored as one-part compositions. Thus, they can be taken directly from the shelf by an end user and used without the need for mixing and/or de-airing. The inventive silicone-based TBA compositions have pre-gel times greater than 1 min at a temperature below 100°C. Pre-gel time is a time, starting from t=0 to the time after the TBA is baked at a specific temperature, when the surface of the TBA is still tacky and not flowable when tilted, but flowable under slight pressure. Having a TBA formulation with a long pre-gel time is desirable for successful temporary bonding in a temporary bonding chamber.

[0021] The inventive silicone-based TBA compositions are advantageous as they are solventless. In other words, by "solventless", the inventive silicone-based TBA compositions require no solvent in order for the various components (the (a) alkenyl functional siloxane polymer, (b) alkenyl functional filler, (c) SiH-containing crosslinker, (d) hydrosilylation catalyst, and (e) cure inhibitor) to be combined to form the silicone-based TBA compositions. This saves on, for example, materials, process steps, and facilities for handling solvents as well as makes the inventive silicone-based TBA compositions environmentally-friendly as they can be formed using fewer chemicals and fewer processing steps.

[0022] Optionally, once the inventive silicone-based TBA compositions are formulated (that is, by combining components (a)-(e) without solvent to form the silicone-based TBAs), they can be diluted with an organic solvent or a mixture of organic solvents to form solvent based TBAs. In this scenario, the silicone-based TBA composition is a solvent based composition further comprising an organic solvent or a mixture of organic solvents to form the solvent based composition. This may be desirable in situations, for example, where a thinner adhesive film is desired or required for post-processing steps or desired end uses of the silicone-based TBA compositions. Non-limiting examples of suitable organic solvents include butyl acetate, propylene glycol methyl ether acetate (PGMEA), methyl isobutyl ketone (MIBK), xylene, mesitylene, cyclohexanone, and 2-heptanone.

[0023] Once the components are combined to form the silicone TBA compositions, processes may be employed to process the TBA composition into a form more desired for the end user. The storage stable TBA compositions described herein possess good mechanical properties for post processing steps.

[0024] The temporary bonding composition can be coated onto a substrate (including, but not limited to, silicon, glass, SiC, metal wafers or panels, etc.) to form a film on the substrate. The coating may be applied by spin coating, spray coating, flow coating, or other suitable coating methods. Spin coating provides thickness control, simplicity and fast processing. When spin coating is used, the temporary bonding compositions are coatable to a film thickness from about 1 micrometer (μηη) to about 500 μηη. In alternative embodiments, the film thickness resulting from the spin coating may be from about 10 μηη to about 200 μηη or from about 20 μηη to about 100 μηη.

[0025] A thermal process may be employed to cure the film and form a tacky free and crosslinked film. The silicone TBA compositions described herein can be cured quickly at a temperature above 80°C to form a crosslinked film. In alternative embodiments, the temperature is above 100°C. At these temperatures, the silicone TBA compositions described herein can be cured within a few minutes (generally within 5 minutes). The fast curing property places the silicone TBA composition in a more user-friendly form for its ultimate end uses as discussed below.

[0026] A schematic of a temporary bonding structure is shown in Fig. 1 a. A substrate or device wafer 104 (described below) is coated with a release layer 103 to form a release layer coated substrate (or release layer coated device wafer). A carrier wafer 101 is coated with an inventive TBA composition (as described herein) in the form of a TBA film 102 to form a carrier wafer coated substrate (also referred to as an adhesive coated carrier wafer). Subsequently, the release layer coated substrate (substrate 104 coated with release layer 103) is bonded with the carrier wafer coated substrate (carrier wafer 101 coated with the inventive TBA composition 102) to form a bonded wafer pair (also referred to as a bonded wafer system).

[0027] A schematic of an alternative temporary bonding structure formed by an alternative processing technique is shown in Fig. 1 b. Alternatively, a substrate or device wafer 104' is first coated with a release layer 103'. An inventive TBA composition (as described herein) in the form of a TBA film 102' is then coated onto the release layer 103' to form a TBA layered structure (also referred to as an adhesive/release coated device wafer). A carrier wafer 101 ' is then placed on the formed TBA layered structure to form a bonded wafer pair (also referred to as a bonded wafer system). The wafer pair is bonded by thermally curing the TBA layer 102' to form a bonded wafer pair shown as Fig. 1 b. The bonded wafer pair is then subject to wafer thinning and other fabrication processes detailed below.

[0028] According to another aspect of the present disclosure, a release layer is provided as part of the bonding system in which the release layer is formed from a material selected from a silsesquioxane-based resin and a thermoplastic material such as a thermoplastic resin. Suitable thermoplastic materials include, but are not limited to, polysulfones, polyimides, and polyetherketones, among others, that can be dissolved in various solvents, such as, but not limited to, N-methylpyrrolidinone and Ν,Ν-dimethylacetamide. One non-limiting example of a suitable release layer material is described in PCT Publication No. WO2012/1 18700. It is contemplated that the release layer is capable of withstanding exposure up to about 180°C without the occurrence of substantial cross-linking.

[0029] According to another aspect of the present disclosure, a method of using the TBA and the release layer for providing a temporary bond between a device wafer or substrate and a carrier wafer in order to perform at least one wafer processing operation to form a processed wafer or processed wafer system, debonding the wafers, and subsequently cleaning the processed device wafer. This method generally comprises providing a device wafer and a carrier wafer for subsequent coating. The release layer is coated onto the surface of the device wafer to form a release layer coated device wafer. The release layer may be coated using conventional techniques known to one skilled in the art, including but not limited to, spin coating, spray coating, flow coating, and the like. Similarly, the TBA is coated onto the surface of the carrier wafer using conventional techniques to form an adhesive coated wafer with a film thickness from about 1 micrometer to about 500 micrometer. The adhesive coated wafer may be prebaked at a temperature in the range of about 40 to about 80°C in order to thermoset the adhesive. Alternatively, a temperature range of about 90 to about 1 10°C may be used when desirable. The release layer coated device wafer may be prebaked at a temperature in the range of about 80 to about 180°C.

[0030] The adhesive coated carrier wafer and the release layer coated device wafer are then bonded together by placing the TBA in contact with the release layer to form a bonded wafer system. The coated wafers are bonded by curing in a vacuum oven at a predetermined reduced pressure and temperature level or in a conventional oven at a higher temperature.

[0031] In the bonded wafer system, the carrier wafer provides the necessary support to the device wafer in order for subsequent operations or processes, such as wafer grinding, among others to be performed. Still referring to Fig. 1 a and 1 b, wafer processing is performed on the device wafer. Once the device wafer is processed into a very thin wafer, additional processes, such as through-silicon vias (TSV), may be optionally performed on the processed wafer system when desired.

[0032] The processed wafer system can be mechanically debonded by initiating an indentation with a sharp knife, such as a razor blade, at the edge of the interface between the release layer and the adhesive. The separation of the release layer from the TBA leads to the formation of a thin processed wafer. In the bonded wafer system, the adhesive layer is used to support the device wafer. The release layer is used to promote debonding in the processed wafer system when the grinding and any subsequent processing is completed.

[0033] Optionally, in order to handle and use the thin processed device wafer after being debonded and cleaned, the back-side surface of the processed device wafer may be laminated or permanently bonded to dicing tape. The back-side surface of the processed device wafer is defined as the side of the wafer that is not in contact with either the release layer or the adhesive. The lamination or bonding to the dicing tape may be performed prior to exposing the process wafer system to the debonding and cleaning steps.

[0034] The processed device wafer may then be exposed to an organic solvent that will act as a surface cleaning agent. The release layer or any residue thereof can be removed from the processed device wafer by spraying a solvent onto the processed device wafer or by soaking the processed device wafer in an organic solvent in which the release layer is soluble. The organic solvent also cleans the surface of the wafer upon which the release layer was coated. Any organic solvent can be used to clean the processed device wafer provided that the solvent is capable of dissolving the release layer and can meet any necessary regulatory requirements. Several examples of an organic solvent include but are not limited to, toluene, xylene, mesitylene, propylene glycol methyl ether acetate (PGMEA), and butyl acetate.

[0035] One skilled in the art will understand that the method may be modified to allow the adhesive to be applied to the release layer coated device wafer prior to bonding to a uncoated carrier wafer or another release layer coated carrier wafer. The subsequent bonding process and other processes should be similar.

[0036] The inventive silicone TBA compositions can be used in varied applications including, but not limited to, 3D chip integration, packaging applications, light emitting diodes (LEDs), nanoimprint lithography (NIL), micropatterning and nanopatterning to form patterned free-standing films, etc. The inventive TBAs are also useful in semiconductor devices where manufacturers desire to limit the thickness of devices and wafers as the inventive adhesives meet the manufacturing challenges associated with such semiconductor products and processes. More specifically, the inventive TBAs may also be used in varied products requiring increasingly thinner substrates such as, but not limited to, radio-frequency identification (RFID) tags, sophisticated chip cards, high-density memory devices, microelectronic devices, temporary wafer bonding applications, and advanced packaging technologies for a variety of products ranging from logic to memory to image sensors.

[0037] While ultrathin silicon wafers, such as those in the thickness range of 20 μηη to 100 μηη, exhibit increased flexibility, such wafers also exhibit increased instability and fragility. The lack of mechanical integrity and the increased fragility can present a challenge to maintaining high yield production in volume manufacturing environments and given the high level of data processing speed required of the wafers. Thus, the handling of these wafers during the production of semiconductor and other devices requires processes and materials that are specifically designed to keep the wafer from being damaged.

[0038] A reliable thin wafer support and handling solution is needed to overcome the aforementioned challenges, which must enable safe, reliable handling of the substrates through back-thinning and backside processing while being compatible with existing equipment lines and manufacturing processes. The use of temporary bonding and debonding techniques utilizing a carrier wafer to provide mechanical support provides one handling solution for ultrathin wafers. The debonding may include mechanical debonding techniques such as indentation with a sharp knife, such as a razor blade or a debonding initiator, at the edge of the interface between the adhesive and a release layer. Once a device wafer is temporarily bonded to a carrier wafer, it is ready for backside processing including back-thinning, through-silicon via formation, etc. The backside surface of a processed wafer is the side of the wafer that is not in contact with either the adhesive or a release layer. After completion of the backside processing steps on the backside surface, the device wafer can be debonded or released from the carrier wafer and proceed to final packaging processes. The inventive TBAs are particularly useful in ultrathin silicon wafer applications as the inventive TBAs provide mechanical support to the ultrathin silicon wafer. EXAMPLES

[0039] 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. All parts and percentages in the examples are on a weight basis and all measurements were indicated at about 23°C, unless indicated to the contrary.

Mechanical Properties Test

[0040] A cured blanket film with a thickness of approximately 20 mil (0.508 μηη) was cut into three dog-bone specimens with a metal cutter. The dimension of the dog-bone was 62 mm (length) x 15 mm (wide end width) x 4 mm (middle width). The dog-bone was then placed on a MTS machine where a stress-strain curve was obtained. The final data is an average of three measurements.

Examples 1-4: Preparation of TBA Layer Materials

[0041] Four formulations containing different amounts of a vinyl functional MQ resin were prepared as listed in Table A. Each sample in Examples 1 -4 contained (a) a vinyl terminated polydimethylsiloxane polymer fluid (DP=500) (alkenyl functional siloxane polymer); (b) a vinyl functional MQ resin (Vi% wt. approximately 3.0%) (alkenyl functional filler); (c) a SiH crosslinker fluid with a structure of MD₃D^H ₅M (SiH-containing crosslinker); (d) a platinum- divinyl-tetramethyldisiloxane catalyst (CAS# 68478-92-2) (hydrosilylation catalyst); and (e) diallyl maleate (cure inhibitor). The molar ratio of SiH/Vi for each of Examples 1 -4 was approximately 2.0. The molar ratio of diallyl maleate to platinum for each of Examples 1-4 was 80.

Table A

[0042] Upon blending, each of the four samples (Examples 1-4) was cured in a mold sandwiched between two stainless steel plates at 150°C for 5 min. The hardness and mechanical properties of the adhesive upon cure were tested. The results for each of the

1 U four samples are shown in Table B. The prepared formulations offered a very good working time and controllable cure rate at high temperature.

Table B

[0043] The higher the filler loading in the particular formulation, the higher the hardness and modulus of the resulting materials. On the other hand, the elongation dropped with the increase of filler as shown in Fig. 2. The strain-stress curves of the cured polydimethylsiloxane-based TBAs with different amount of filler loadings of Examples 1-4 are shown in Fig. 2.

Examples 5-12: Shelf-Life and Pre-Gel Time Results

[0044] Four one-part TBA formulations containing different molar ratios of cure inhibitor to platinum catalyst were prepared. Each sample in Examples 5-8 contained (a) a vinyl terminated polydimethylsiloxane polymer fluid (DP=500) (alkenyl functional siloxane polymer); (b) a vinyl functional MQ resin (Vi% wt. approximately 3.0%) (alkenyl functional filler); (c) an SiH crosslinker fluid with a structure of MD₃D^H ₅M) (SiH-containing crosslinker); (d) platinum-divinyl-tetramethyldisiloxane catalyst (CAS# 68478-92-2) (hydrosilylation catalyst); and (e) diallyl maleate (cure inhibitor). The amount of the MQ resin in each of Examples 5-8 was 30.0 wt.%. The molar ratio of SiH/Vi for each of Examples 5-8 was approximately 2.0. The amount of platinum in each of Examples 5-8 was 40 ppm. The viscosity change of each of the formulations was monitored using a viscometer at both room temperature (23°C) and refrigerator temperature (3-5°C). The molar ratio of diallyl maleate to platinum and the viscosity data for each of the four samples in Examples 5-8 is shown in Table C.

Table C

7 80/1 Gelled within 6 day Gelled within 9 days

5303 cP (30 days) 4365 cP (30 days)

8 120/1

[0045] The viscosity results at room temperature (23°C) are graphically illustrated in Fig. 3. More specifically, Fig. 3 illustrates the viscosity change with time at 23°C with the variation of the molar ratio of diallyl maleate to platinum ([DAM]/[Pt] molar ratio) for each of the four samples in Examples 5-8.

[0046] It was found that increasing the molar ratio of diallyl maleate to platinum slowed down the viscosity increase of the corresponding formulation. This is illustrated in Fig. 3. However, the improvement was not linear; for example, the storage stability improved at 23°C from about 6 hrs to 2 days to 6 days when the [DAM]/[Pt] molar ratio was set at 40/1 , 60/1 and 80/1 , respectively. However, when the [DAM]/[Pt] molar ratio was adjusted to 120/1 , significant improvement of the formulation's shelf-life was observed. This is illustrated in Figs. 3 and 4. More specifically, Fig. 4 illustrates the dependence of the formulation's shelf-life on the [DAM]/[Pt] molar ratio at a platinum catalyst level of 40 ppm.

[0047] The improvement of the TBA's shelf-life by increasing the [DAM]/[Pt] molar ratio led to the exploration of the platinum concentration. As shown in Table D, the platinum catalyst concentration was reduced from 40 ppm to 20 ppm, 10 ppm, and 5 ppm at a constant [DAM]/[Pt] molar ratio of 120/1 in Examples 9-12, respectively, under otherwise identical formulation conditions (30% of the vinyl functional MQ resin and molar ratio of SiH/Vi of approximately 2.0) and compared to the sample of Example 3. As also shown in Table D, the corresponding cure inhibitor (diallyl maleate) concentration in the various formulations was also decreased.

Table D

¹ wt.% in the formulation [0048] The cure properties of the formulations were investigated. A thin-film layer (approximately 100 m) was cast onto a 4" (100 mm) silicon wafer. The wafer was then placed in a pre-heated oven or a hot plate, and the cure status was charged based on the tackiness of the liquid adhesive layer surface using a Q-tip. A pre-gel time was recorded from t=0 to the time when the adhesive layer surface was still tacky and not flowable when tilted, but flowable under slight pressure. The gel time is the point where the adhesive layer completely lost its flowability and became non-tacky.

[0049] The cure profile of the one-part TBA materials and the pre-gel and gel time values are shown in Table E.

Table E

² Based on viscosity change (<20%) at room temperature (23°C) storage

³ Surface tackiness tested by Q-tip on a bare-Si wafer

As shown in Table E, the pre-gel time increased with the decrease of the corresponding platinum catalyst concentration. Surprisingly, these formulations were able to be fully cured as a thin film when heated at 150°C for 2 min, regardless of their long pre-gel times. Examples 13-16: Bonding and Debonding Examples with 4" Silicon Bare Wafers

[0050] Sixteen 4" (100 mm) silicon wafers were prepared for bonding and debonding testing. The first eight wafers were coated with one of the release materials as noted below. The remaining eight wafers were coated with one of the adhesive materials as noted below. The coating materials and cure conditions are summarized below:

• Release Material (8 wafers prepared)

- A SSQ resin solution

- Spin-coating rate: 2,000 rpm

- Prebake at 130°C for 1 min

- Coating thickness: 150-200 nm

Adhesive Material (8 wafers prepared)

- Each adhesive material (from Examples 1-4) was coated on two 4" wafers (2x4) in each of Samples 13-16

- Coating thickness: approximately 65 pm

[0051] A bonding procedure was performed under vacuum. A wafer coated with a release material was placed on the top of an adhesive layer coated wafer in a vacuum chamber. Each pair of wafers was bonded at 96KPa (0.95 atm) under vacuum for 2 min. Then, the pair of wafers were released from the chamber. For the 180°C cure, the pair of wafers were heated on a hotplate at 180°C for 2 min (2x4 pair wafers). For the 250°C cure, four pairs of the above wafers were heated at 250°C for 1 hr (4 wafers).

[0052] Debonding was performed and rated. A razor blade was used as a debonding initiator to separate the two wafers from each other manually. The easiness of debonding was rated with a scale of 1-5:

1 - Very easy to separate (may not have adequate adhesion)

• 2 - Easy to separate

3 - Just acceptable to separate

• 4 - Hard to separate

5 - Very hard to separate

The debonding evaluation results (the debonding rating of TBAs after cure at 180°C and 250°C) are listed in Table F. Table F

[0053] It was observed that the coating was very smooth (good total thickness variation (TTV): approximately 3-4 μπι). Before debonding, the bonding wafer pair held very tightly and there was no slippage or movement observed when strong shear force was applied. All four formulations of Examples 13-16 were debonded easily (rating 2-3). The debonding worked well at both 180°C and 250°C with no significant difference observed between the two temperatures. The debonding was very clean for each formulation of Examples 13-16 and no residue was transferred to the release layer and vice versa. After debonding, the two wafers were able to be re-bonded together. The re-bonding wafers also showed no slippage or movement when shear force was applied. Furthermore, the wafers were able to be debonded again easily. The adhesive coating thickness remained the same (approximately 65 μηι) after bonding/debonding.

Example 17: Bonding and Debonding Examples with 12" (300 mm) Silicon Bare Wafers

[0054] A 12" (300 mm) bare wafer was spin-coated with a SSQ solution in butyl acetate at 2000 rpm/20 sec. The bare wafer was baked at 150°C for 1 min. The adhesive material from Example 3 (viscosity: 4850 cp; 1000 rpm/30 sec) was spin-coated onto a 12" silicon carrier wafer to form a 90 μιτι thick adhesive layer coating. The adhesive layer-coated wafer was then pre-cured at 80°C for 90 sec, followed by dropping the release layer-coated bare wafer on the top of the adhesive-coated carrier wafer in a commercial bonding chamber. The bonded pair was cured at 150°C for 3 min. After the bonding wafer pair went through back grinding whereby the bare wafer was thinned to about 100 μηι, the thinned wafer pair was mechanically de-bonded at room temperature with a commercial de-bonder. The de-bonding was easy and clean and there was no adhesive layer residue transferred to the release layer on the bare wafer. The release layer on the bare wafer was then removed by butyl acetate.

Example 18: Bonding and Debonding Examples with 12" (300 mm) Silicon Device Wafers

[0055] A 12" (300 mm) device wafer with 65 μηη bump height was spin-coated with a SSQ solution in butyl acetate at 2000 rpm/20 sec. The device wafer was baked at 150°C for 1 min. The adhesive material from Example 3 (viscosity: 4850 cp; 1000 rpm/30 sec) was spin-coated onto a 12" silicon carrier wafer to form a 92 μπι thick adhesive layer coating. The adhesive layer-coated carrier wafer was then pre-cured at 80°C for 90 sec, followed by dropping the release layer-coated device wafer on the top of the adhesive-coated carrier wafer in a commercial bonding chamber. The bonded pair was cured at 150°C for 3 min. After the bonding wafer went through back grinding whereby the device wafer was thinned to about 100 μηι, the thinned wafer pair was mechanically de-bonded at room temperature with a commercial de-bonder. The de-bonding was easy and clean and there was no adhesive layer residue transferred to the release layer on the device wafer. The release layer on the device wafer was then removed by butyl acetate.

[0056] Alternative Aspects

[0057] (1 ) A silicone-based storage stable temporary bonding adhesive composition comprising at least: (a) an alkenyl functional siloxane polymer; (b) an alkenyl functional filler with a particle size below one micrometer; (c) an SiH-containing crosslinker; (d) a hydrosilylation catalyst; and (e) a cure inhibitor, wherein the molar ratio of the cure inhibitor and the hydrosilylation catalyst is greater than 40/1 and less than 500/1.

[0058] (2) The adhesive composition of aspect 1 , wherein the alkenyl functional siloxane polymer has a general formula:

or

wherein R-i is an alkenyl group; R₂ is an alkyl or aryl group; 1 > x≥ 0, 1 > y > 0, and x + y =1 ; 1 > o > 0, 1 > p > 0, and o + p =1 ; and m is an integer that is 1 or larger.

[0059] (3) The adhesive composition of aspect 1 or aspect 2, wherein the alkenyl functional siloxane polymer is a vinyl terminated polydimethylsiloxane fluid having the general formula:

CH2=CH-SiMe2-(OSiMe₂)m-OSiMe2-CH=CH2, wherein m is an integer .; 1. [0060] (4) The adhesive composition of any one of aspects 1 -3, wherein the alkenyl functional filler is a vinyl functional silicone resin or a vinyl functional silica.

[0061] (5) The adhesive composition of any one of aspects 1 -4, wherein the hydrosilylation catalyst is a platinum catalyst or a rhodium catalyst.

[0062] (6) The adhesive composition of any one of aspects 1 -5, wherein the cure inhibitor is a maleate compound, wherein the maleate compound has the general formula:

-R-OOC-CH=CH-COOR,

wherein R is an organic group.

[0063] (7) The adhesive composition of any one of aspects 1-6, wherein the SiH- containing crosslinker has a general formula:

or

wherein R₂ is an alkyl or aryl group; 1≥ x≥ 0, 1≥ y≥ 0, and x + y =1 ; 1 > o > 0, 1 > p > 0, and o + p =1 , and m is an integer that is 1 or larger.

[0064] (8) The adhesive composition of any one of aspects 1-7, wherein the adhesive composition is coated on a substrate to form a film with a thickness from about 1 micrometer to about 500 micrometers and can be cured within 5 minutes at a temperature above 80°C to form a crosslinked film.

[0065] (9) A silicone-based storage stable temporary bonding adhesive composition comprising: (a) a vinyl polydimethylsiloxane fluid; (b) a vinyl MQ resin; (c) an SiH crosslinker; (d) a platinum catalyst; and (e) a maleate compound cure inhibitor, wherein the molar ratio of the maleate compound cure inhibitor and the platinum catalyst is greater than 40/1 and less than 500/1.

[0066] (10) The adhesive composition of any one of the preceding aspects, wherein the adhesive composition is a one-part type composition. [0067] (1 1 ) The adhesive composition of any one of the preceding aspects, wherein the adhesive composition is a solvent based composition further comprising an organic solvent or a mixture of organic solvents to form the solvent based composition.

[0068] (12) A curable composition comprising the adhesive composition of any one of the preceding aspects.

[0069] (13) A semiconductor coated with the adhesive composition of any one of aspects 1 to 1 1 .

[0070] (14) A method of making an article of manufacture, wherein the method comprises: (1 ) blending (a) an alkenyl functional siloxane polymer; (b) an alkenyl functional filler with a particle size below one micrometer; (c) an SiH-containing crosslinker; (d) a hydrosilylation catalyst; and (e) a cure inhibitor to produce a temporary bonding adhesive formulation, wherein the molar ratio of the cure inhibitor and the hydrosilyation catalyst is greater than 40/1 and less than 500/1 ; (2) providing a device wafer and a carrier wafer; (3) applying a release layer to a surface of a device wafer to form a release layer coated device wafer; (4) applying the temporary bonding adhesive onto the release layer of the release layer coated device wafer to form an adhesive coated device wafer with a film thickness of from about 1 micrometer to about 500 micrometer; (5) applying the carrier wafer onto the temporary bonding adhesive and then curing the temporary bonding adhesive at an elevated temperature to form a bonded wafer system; (6) performing at least one wafer processing operation on the device wafer to form a processed wafer system; (7) debonding the processed wafer system by initiating separation between the release layer and the temporary bonding adhesive to obtain a thin processed device wafer; and (8) cleaning a surface of the processed device wafer with an organic solvent, wherein the organic solvent is capable of dissolving the release layer.

[0071] (15) A method of making an article of manufacture, wherein the method comprises: (1 ) blending (a) an alkenyl functional siloxane polymer; (b) an alkenyl functional filler with a particle size below one micrometer; (c) an SiH-containing crosslinker; (d) a hydrosilylation catalyst; and (e) a cure inhibitor to produce a temporary bonding adhesive formulation, wherein the molar ratio of the cure inhibitor and the hydrosilyation catalyst is greater than 40/1 and less than 500/1 ; (2) providing a device wafer and a carrier wafer; (3) applying a release layer to a surface of a device wafer to form a release layer coated device wafer; (4) applying the temporary bonding adhesive to a surface of the carrier wafer to form an adhesive coated carrier wafer with a film thickness from about 1 micrometer to about 500 micrometer; (5) bonding the release layer coated device wafer and the adhesive coated carrier wafer together by curing the temporary bonding adhesive at an elevated temperature to form a bonded wafer system where the temporary bonding adhesive is placed in contact with the release layer; (6) performing at least one wafer processing operation on the device wafer to form a processed wafer system; (7) debonding the processed wafer system by initiating separation between the release layer and the temporary bonding adhesive to obtain a thin processed device wafer; and (8) cleaning the surface of the processed device wafer with an organic solvent, wherein the organic solvent is capable of dissolving the release layer.

[0072] 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. It should be understood, however, that 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 silicone-based storage stable temporary bonding adhesive composition comprising at least:

a. an alkenyl functional siloxane polymer;

b. an alkenyl functional filler with a particle size below one micrometer; c. an SiH-containing crosslinker;

d. a hydrosilylation catalyst; and

e. a cure inhibitor,

wherein the molar ratio of the cure inhibitor and the hydrosilylation catalyst is greater than 40/1 and less than 500/1.

2. The adhesive composition of claim 1 , wherein the alkenyl functional siloxane polymer has a general formula:

or

3. The adhesive composition of claim 1 or claim 2, wherein the alkenyl functional siloxane polymer is a vinyl terminated polydimethylsiloxane fluid having the general formula:

CH₂=CH-SiMe₂-(OSiMe₂)m-OSiMe₂-CH=CH₂, wherein m is an integer > 1.

4. The adhesive composition of any one of claims 1-3, wherein the alkenyl functional filler is a vinyl functional silicone resin or a vinyl functional silica.

5. The adhesive composition of any one of claims 1 -4, wherein the hydrosilylation catalyst is a platinum catalyst or a rhodium catalyst.

6. The adhesive composition of any one of claims 1-5, wherein the cure inhibitor is a maleate compound, wherein the maleate compound has the general formula:

cis-R-OOC-CH=CH-COOR,

wherein R is an organic group.

7. The adhesive composition of any one of claims 1-6, wherein the SiH-containing crosslinker has a general formula:

or

8. The adhesive composition of any one of claims 1 -7, wherein the adhesive composition is coated on a substrate to form a film with a thickness from about 1 micrometer to about 500 micrometers and can be cured within 5 minutes at a temperature above 80°C to form a crosslinked film.

9. A silicone-based storage stable temporary bonding adhesive composition comprising:

a. a vinyl polydimethylsiloxane fluid;

b. a vinyl MQ resin;

c. an SiH crosslinker;

d. a platinum catalyst; and e. a maleate compound cure inhibitor,

wherein the molar ratio of the maleate compound cure inhibitor and the platinum catalyst is greater than 40/1 and less than 500/1 .

10. The adhesive composition of any one of the preceding claims, wherein the adhesive composition is a one-part type composition.

1 1 . The adhesive composition of any one of the preceding claims, wherein the adhesive composition is a solvent based composition further comprising an organic solvent or a mixture of organic solvents to form the solvent based composition.

12. A curable composition comprising the adhesive composition of any one of the preceding claims.

13. A semiconductor coated with the adhesive composition of any one of claims 1 to

1 1 .

14. A method of making an article of manufacture, wherein the method comprises:

(1 ) blending

a. an alkenyl functional siloxane polymer;

b. an alkenyl functional filler with a particle size below one micrometer;

c. an SiH-containing crosslinker;

d. a hydrosilylation catalyst; and

e. a cure inhibitor,

to produce a temporary bonding adhesive formulation, wherein the molar ratio of the cure inhibitor and the hydrosilyation catalyst is greater than 40/1 and less than 500/1 ;

(2) providing a device wafer and a carrier wafer;

(3) applying a release layer to a surface of a device wafer to form a release layer coated device wafer;

(4) applying the temporary bonding adhesive onto the release layer of the release layer coated device wafer to form an adhesive coated device wafer with a film thickness of from about 1 micrometer to about 500 micrometer;

(5) applying the carrier wafer onto the temporary bonding adhesive and then curing the temporary bonding adhesive at an elevated temperature to form a bonded wafer system; (6) performing at least one wafer processing operation on the device wafer to form a processed wafer system;

(7) debonding the processed wafer system by initiating separation between the release layer and the temporary bonding adhesive to obtain a thin processed device wafer; and

(8) cleaning a surface of the processed device wafer with an organic solvent, wherein the organic solvent is capable of dissolving the release layer.

15. A method of making an article of manufacture, wherein the method comprises:

(1 ) blending

a. an alkenyl functional siloxane polymer;

b. an alkenyl functional filler with a particle size below one micrometer;

c. an SiH-containing crosslinker;

d. a hydrosilylation catalyst; and

e. a cure inhibitor,

(2) providing a device wafer and a carrier wafer;

(4) applying the temporary bonding adhesive to a surface of the carrier wafer to form an adhesive coated carrier wafer with a film thickness from about 1 micrometer to about 500 micrometer;

(5) bonding the release layer coated device wafer and the adhesive coated carrier wafer together by curing the temporary bonding adhesive at an elevated temperature to form a bonded wafer system where the temporary bonding adhesive is placed in contact with the release layer;

(6) performing at least one wafer processing operation on the device wafer to form a processed wafer system;

(8) cleaning the surface of the processed device wafer with an organic solvent, wherein the organic solvent is capable of dissolving the release layer.