Easy-to-peel and high-temperature-resistant wafer bonding adhesive as well as preparation method and application thereof

Abstract

The invention relates to an easy-to-peel and high-temperature-resistant wafer bonding adhesive as well as a preparation method and application thereof. The bonding glue is prepared from the following components in parts by weight: 10 to 40 parts of basic resin, 10 to 40 parts of bonding resin, 40 to 80 parts of high-boiling-point solvent and 0.1 to 0.8 part of wetting agent. The base resin is a modified styrene butadiene rubber-polyvinyl acetate blend. The tensile strength of the grafted styrene-butadiene rubber is increased, the grafted styrene-butadiene rubber changes the rheological property of polyvinyl acetate through blending, the rheological viscosity of the obtained blend is reduced, the softening point of the compounded bonded rubber is reduced, the bonding temperature is reduced, and the thermal stability is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor manufacturing technology, and in particular relates to an easy-to-strip, high-temperature resistant wafer bonding adhesive and a preparation method and application thereof. Background Art

[0002] Ultra-thin wafers are flexible, fragile, easy to warp and fluctuate, so the device wafer is usually first bonded to a thicker carrier with an intermediate material, and then after back thinning, TSV opening process, redistribution layer and internal interconnection production, external energy (light, electricity, heat and external force) is input to make the bonding layer ineffective, and then the device wafer is separated from the carrier. This process is the temporary bonding process of the wafer. Temporary bonding adhesives used for thin wafer processing have broad market prospects.

[0003] The performance of temporary bonding adhesive mainly depends on the properties of the polymer as the basic adhesive. At present, the mainstream temporary bonding adhesive material uses thermoplastic resin as the main raw material, and the most widely used is cycloolefin copolymer. Cyclic olefin copolymer resin has good high temperature resistance, medium resistance, high transparency and other properties, but cycloolefin copolymer resin also has the problem of greater brittleness. This also leads to stress concentration during the thinning process when it is used as a temporary bonding adhesive material, resulting in wafer breakage. In addition, since the bonding system needs to experience high temperature, oxidants, strong acids, strong alkalis and other organic solvent environments, when experiencing large temperature changes, cycloolefin copolymer resin is also prone to accumulate thermal stress, causing deformation of the device wafer.

[0004] Therefore, it is necessary to develop a temporary bonding adhesive that can be debonded at a lower temperature and has high thermal stability. Summary of the invention

[0005] The technical problem solved by the present invention is that the temporary bonding adhesive has poor thermal stability. When experiencing a large temperature change, the cycloolefin copolymer resin is prone to accumulate thermal stress, resulting in deformation of the device wafer.

[0006] In view of the technical problems existing in the prior art, the present invention designs an easy-to-peel, high-temperature resistant wafer bonding adhesive and its preparation method and application. The bonding adhesive can be debonded at a relatively low temperature, thus avoiding damage to the device wafer caused by high temperature.

[0007] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0008] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0009] An easy-to-strip, high-temperature resistant wafer bonding adhesive, characterized in that it comprises the following components, calculated by weight: 10-40 parts of a base resin, 10-40 parts of a bonding resin, 40-80 parts of a high boiling point solvent, and 0.1-0.8 parts of a wetting agent.

[0010] Furthermore, the base resin is a modified styrene-butadiene rubber-polyvinyl acetate blend (SBS / PVAc).

[0011] Furthermore, the base resin is prepared by a modification method in which a modified material is grafted onto thermoplastic styrene-butadiene rubber and then blended with polyvinyl acetate (PVAc); wherein the molar ratio of the thermoplastic styrene-butadiene rubber, the modified material and the polyvinyl acetate (PVAc) is 10:(0.5-2):10.

[0012] Furthermore, the preparation method of the base resin is specifically as follows:

[0013] S1: Using thermoplastic styrene butadiene rubber as the grafting object and ethyl benzoate as the initiator, dissolving the thermoplastic styrene butadiene rubber in a mixed solution of toluene and dioxane, then adding the modified material, and reacting at 80-100°C for 1-3h under nitrogen conditions to obtain a graft copolymer emulsion, which is purified with methanol and then dried to obtain the grafted thermoplastic styrene butadiene rubber;

[0014] S2: After drying the polyvinyl acetate (PVAc) at 100-130° C. for 10-14 hours, the polyvinyl acetate (PVAc) is blended with the grafted thermoplastic styrene-butadiene rubber in the above step S1 in a twin-screw extruder at 250-280° C. to fully disperse the grafted thermoplastic styrene-butadiene rubber in the polyvinyl acetate (PVAc) matrix;

[0015] Wherein, the amount of the initiator is 0.5-1.2% of the molar amount of the modified material;

[0016] The mass ratio of toluene to dioxane in the mixed solution of toluene and dioxane is 1:1.

[0017] The amount of the mixed solution of toluene and dioxane used is based on the amount that can completely dissolve the modified material, and is not limited in the present invention.

[0018] The modified material is one or more of dimethylaminoethyl methacrylate, glycidyl methacrylate, and Fmoc-L-aspartic acid-alpha-allyl ester.

[0019] Furthermore, the base resin is one of dimethylaminoethyl methacrylate grafted styrene butadiene rubber-polyvinyl acetate blend (SBS-g-DMAEMA / PVAc), glycidyl methacrylate grafted styrene butadiene rubber-polyvinyl acetate blend (SBS-g-GMA / PVAc), and Fmoc-L-aspartic acid-alpha-allyl ester grafted styrene butadiene rubber-polyvinyl acetate blend (SBS-g-FMAO / PVAc).

[0020] Furthermore, the high boiling point solvent is one or more of dodecane, dodecene, D-limonene, 1,8-terpene, benzyl alcohol, dibasic acid ester, ethyl benzoate, 1,1,3-trimethylcyclohexenone, N-methylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone.

[0021] Furthermore, the wetting agent is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine, and polyoxyethylene alkylamide.

[0022] Furthermore, the bonding resin is one or more of modified petroleum resin, terpene resin, terpene phenol resin and modified rosin resin.

[0023] Furthermore, the modified petroleum resin is hydrogenated petroleum resin P-125; the modified rosin resin is lime rosin HG-120.

[0024] Furthermore, the molecular weight of the bonding resin is 1000-5000.

[0025] The present invention also discloses a method for preparing the above-mentioned easy-to-peel and high-temperature resistant wafer bonding adhesive, which is characterized by comprising the following steps:

[0026] Step 1: Mix the high boiling point solvent and wetting agent evenly, and heat to 30-70°C, then add the bonding resin and base resin, mix and stir until a clear and transparent liquid is formed;

[0027] Step 2: Cool the clear and transparent liquid obtained in step 1 and filter it to obtain the easy-to-peel and high-temperature resistant wafer bonding adhesive.

[0028] Furthermore, in step 1, the stirring speed is 50-200 rpm; and the stirring time is 30-90 min.

[0029] The invention also discloses a use of the easy-to-strip and high-temperature resistant wafer bonding adhesive in thinning the back side of an ultra-thin device wafer.

[0030] In the present invention, in order to further improve the performance of the bonding adhesive, further optimization can be made for each component: 20-40 parts of base resin, 10-30 parts of adhesive resin, 50-70 parts of high boiling point solvent, and 0.1-0.5 parts of wetting agent.

[0031] In the present invention, the molar ratio of the thermoplastic styrene-butadiene rubber (SBS), the modified material and polyvinyl acetate (PVAc) is preferably 10:1:10; the molar amount of the initiator is preferably 1% of the molar amount of the modified material.

[0032] In the present invention, the base resin is more preferably a dimethylaminoethyl methacrylate grafted styrene butadiene rubber-polyvinyl acetate blend (SBS-g-DMAEMA / PVAc).

[0033] The advantages and mechanisms of the base resin prepared by the present invention are:

[0034] Thermoplastic styrene butadiene rubber has good wear resistance, heat resistance and aging resistance, but its adhesive strength is low and its bonding performance is poor.

[0035] The invention adopts modified materials to graft thermoplastic styrene butadiene rubber. Since the molecular weight and molecular structure of the copolymer are changed after grafting, the modified thermoplastic styrene butadiene rubber has better solubility, increased tensile strength, increased bonding force and better processing performance.

[0036] The modified thermoplastic styrene butadiene rubber is blended with PVAc. Due to the interaction between the modified styrene butadiene rubber and PVAc, a more uniform mixture is formed. In the blending system, the presence of SBS can limit the movement of PVAc chain segments, making PVAc easier to crystallize at a smaller scale. The flexible chain segments of SBS can act as nucleating agents, which reduces the crystal size of the blended resin and enhances the mechanical properties. The crystal size of the modified styrene butadiene rubber-polyvinyl acetate blend is reduced, the toughness is increased, the rheological properties of the blended resin are changed, and the rheological viscosity is reduced.

[0037] The advantages of the bonding resin in the present invention are:

[0038] The adhesive resin used in the present invention has the advantages of good wettability, low brittleness, and not easy to oxidize. The low molecular weight adhesive resin has similar polarity to the base resin, so that the compatibility between the resins is good, the solid content of the system is increased, and the thickness of the adhesive layer is increased. The adhesive resin with a low softening point is selected to reduce the softening point of the system, so that the bonding process is easier to carry out at a lower temperature, reducing the thermal damage to the wafer.

[0039] The advantages of the high boiling point solvent in the present invention are:

[0040] The high boiling point solvent has better solubility in resin, which enhances the fluidity of bonding adhesive during processing, reduces the phenomenon of polymerizing in grooves, and makes it easy to clean. In addition, the high boiling point solvent can infiltrate the polymer, enter the gap between the polymer, reduce the interaction force between polymer chain segments, alleviate the cracking of resin, and has a certain plasticizing effect.

[0041] The present invention provides an easy-to-peel, high-temperature resistant wafer bonding adhesive and a preparation method and application thereof, which have the following beneficial effects:

[0042] 1. The tensile strength of the thermoplastic styrene-butadiene rubber after grafting the modified material of the present invention is increased, and the blending makes the grafted thermoplastic styrene-butadiene rubber (SBS-g-DMAEMA) change the rheological properties of polyvinyl acetate (PVAc), thereby ensuring that the rheological viscosity of the modified styrene-butadiene rubber-polyvinyl acetate blend is reduced. Especially when DMAEMA is selected as the modified material, the obtained SBS-g-DMAEMA / PVAc bonding glue has a softening point of 110° C., a bonding temperature as low as 140° C., and a thermal stability of 300° C.

[0043] 2. The wetting agent and high boiling point solvent used in the present invention have a synergistic effect. The addition of the high boiling point solvent delays the curing rate of the bonding adhesive, so that the wetting agent has time to play a role in the entire curing process, thereby ensuring the uniformity and strength of the contact between the bonding adhesive and the material surface, and achieving a stronger bonding effect and better processing characteristics of the bonding adhesive.

[0044] 3. The bonding adhesive of the present invention can be completely peeled off by soaking in an ethanol solution or an N-methylpyrrolidone (NMP) solution at room temperature for 10 minutes, and is easy to clean without any residue. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 : A diagram showing the bonding adhesive in Example 1 of the present invention being peeled off from a 6-inch sapphire after being immersed in an ethanol solution for 10 minutes;

[0046] Figure 2 : is a state diagram of the bonding adhesive in Example 1 of the present invention after bonding on a 6-inch single crystal silicon;

[0047] Figure 3 : A photo of the thickness difference of the bonding glue in Example 1 of the present invention after spin coating and drying of the 6-inch single crystal silicon bonding glue;

[0048] Figure 4 : This is a thermogravimetric test result diagram of the SBS-g-DMAEMA / PVAc-1 resin in Example 1 of the present invention. DETAILED DESCRIPTION

[0049] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

[0050] Table 1 Base resin preparation

[0051]

[0052] Table 2 Temporary bonding adhesive Example 1-Example 5

[0053]

[0054]

[0055] Table 3 Temporary bonding adhesive Comparative Example 1-Comparative Example 3

[0056]

[0057] Table 4 Temporary bonding adhesive performance test data

[0058] Softening point / ℃ Debonding rate μm / s Thermal stability℃ Example 1 110 1250 300 Example 2 120 1200 280 Example 3 121 1205 270 Example 4 124 1101 230 Example 5 127 1012 280 Comparative Example 1 140 503 250 Comparative Example 2 163 500 260 Comparative Example 3 182 407 300

[0059] About the preparation method of the base resin of the present invention:

[0060] The preparation methods of the multiple groups of base resins involved in Table 1 of the present invention are all prepared according to the following method:

[0061] S1: Using thermoplastic styrene butadiene rubber as the grafting object and ethyl benzoate as the initiator, the thermoplastic styrene butadiene rubber is dissolved in a mixed solution of toluene and dioxane, and then the modified material is added and reacted at 90°C for 2h under nitrogen to obtain a graft copolymer emulsion, which is purified with methanol and then dried to obtain the grafted thermoplastic styrene butadiene rubber;

[0062] S2: After drying the polyvinyl acetate (PVAc) at 120°C for 13 hours, the polyvinyl acetate (PVAc) is blended with the thermoplastic styrene-butadiene rubber grafted in the above step S1 in a twin-screw extruder at 260°C to fully disperse the grafted thermoplastic styrene-butadiene rubber in the polyvinyl acetate (PVAc) matrix;

[0063] Wherein, the amount of the initiator is 0.5-1.2% of the molar amount of the modified material;

[0064] The mass ratio of toluene to dioxane in the mixed solution of toluene and dioxane is 1:1.

[0065] The amount of the mixed solution of toluene and dioxane used is based on the amount that can completely dissolve the modified material, and is not limited in the present invention.

[0066] About the preparation method of the bonding adhesive of the present invention:

[0067] The preparation methods of the bonding adhesives in the multiple groups of embodiments and comparative examples in Table 2 and Table 3 of the present invention are all prepared according to the following method:

[0068] Step 1: Add a high boiling point solvent and a wetting agent to a kettle according to the ratio, and stir and mix them evenly at 200 rpm; then heat the obtained solution to 60°C, add a binder resin and a base resin under continuous stirring, and stir for 60 minutes until a clear and transparent liquid is formed;

[0069] Step 2: Cool the clear and transparent liquid obtained in step 1 and filter it to obtain the easy-to-peel and high-temperature resistant wafer bonding adhesive.

[0070] About performance testing and description:

[0071] Performance 1 Softening point test method is:

[0072] The present invention uses the ring and ball method to test the softening point of the bonding adhesive. The specific method is:

[0073] Take a bonding glue as thick as a one-yuan coin and place it on a 140℃ hot plate to melt it. Transfer the bonding glue to a sample ring at the same temperature. After cooling to room temperature, place it in a softening point tester. Set the preheating temperature to 50℃, the preheating heating rate to 10℃ / min, the final heating temperature to 120℃, and the final heating rate to 1℃ / min.

[0074] Start the test and record the temperature of the steel ball when it falls. The test results are shown in Table 4.

[0075] Performance 2 The test method for the bond debonding rate after glue coating is:

[0076] Taking a 6-inch silicon wafer as an example, the temporary bonding adhesive of the present invention was used for verification. A silicon wafer-carrier bonding pair with no bonding defects was placed on a debonding machine, and the temperature was raised to 140° C. to start the separation of the silicon wafer and the carrier, and the debonding rate was recorded. The test results are shown in Table 4.

[0077] Performance 3 thermal stability test method is:

[0078] Place the flawless bond pair in an oven, preheat to 100°C, and heat at a rate of 10°C / h until snowflake-like bubbles appear on the surface of the bond pair. Stop heating and record the temperature. For test results, see Figure 2 and Table 4.

[0079] Performance 4 Thermogravimetric test method is:

[0080] 10 mg of the dried bonding glue sample was placed in the TG instrument. Under the condition of nitrogen flow rate of 20 mL / min, the temperature was increased at a rate of 20 °C / min to obtain the thermal decomposition curve. The test results are shown in Figure 4 .

[0081] Performance 5 adhesive layer peeling test method is:

[0082] Taking a 6-inch sapphire sheet as an example, the temporary bonding adhesive of the present invention was used for verification. The spin-coated sapphire sheet was placed on a hot plate at 160°C and baked for 2 minutes to evaporate the solvent. The dried sapphire sheet was taken out and placed in an anhydrous ethanol solution at room temperature to observe the peeling phenomenon. The test results are shown in Figure 1 .

[0083] Performance 6 The test method for the difference in adhesive layer thickness is:

[0084] Taking a 6-inch silicon wafer as an example, the temporary bonding adhesive of the present invention is used for verification. The spin-coated silicon wafer is placed on a hot plate at 160°C and baked for 2 minutes to evaporate the solvent. The dried silicon wafer is taken out and placed in a thickness tester to measure the thickness of the adhesive layer. The thickness difference TTV is calculated as TTV = maximum test thickness - minimum test thickness. The test results are shown in Figure 3 .

[0085] Analysis of the test results:

[0086] Based on the data in Table 4, it can be seen that the bonding adhesive provided by the embodiment of the present invention has a low softening point, a fast bond debonding rate, and good thermal stability.

[0087] Compared with the examples, the comparative example 1 uses unmodified SBS / PVAc as the base resin, resulting in a decrease in the solid content of the solvent-dissolved base resin and a significantly higher softening point than the modified resin.

[0088] Comparative Example 2 uses SBS-g-DMAEMA as the base resin, and the high softening point modified SBS is compounded with petroleum resin, resulting in an increase in the softening point and an increase in thermal stability.

[0089] In Comparative Example 3, no binding resin was added, the solid content was reduced, the softening point was higher, and the debonding rate was slow.

[0090] Further comparison is made through the attached drawings in the specification:

[0091] Figure 1 The bonding glue in Example 1 of the present invention is peeled off from a 6-inch sapphire after being soaked in an ethanol solution for 10 minutes. Figure 1 It can be seen that the whole piece is peeled off after being immersed in the ethanol solution for 10 minutes, which shows that the bonding adhesive of the present invention is easy to peel off.

[0092] Figure 2 The state diagram of the bonding adhesive in Example 1 of the present invention after bonding on a 6-inch single crystal silicon. Figure 2 It can be seen that the surface of the 6-inch single crystal silicon is smooth after bonding, and there are no obvious voids and snowflake-shaped bubbles at 300℃ for 1h.

[0093] Figure 3This is a photo of the thickness difference of the bonding glue in Example 1 of the present invention after spin coating and drying of the 6-inch single crystal silicon bonding glue. Figure 3 It can be seen that the bonding glue prepared in Example 1 of the present invention is spin-coated evenly, with a uniformity of 0.007, a small difference in the thickness of the glue layer, and a smooth coating.

[0094] Figure 4 The thermogravimetric test result of SBS-g-DMAEMA / PVAc-1 resin in Example 1 of the present invention is shown in FIG. Figure 4 It can be seen that the initial decomposition temperature of SBS-g-DMAEMA / PVAc-1 is about 300°C, and the complete decomposition temperature is about 480°C. It loses 0.5% of its weight at 312°C and 5% of its weight at 390°C, and has high thermal stability.

[0095] The tensile strength of the grafted styrene butadiene rubber of the present invention is increased, and the grafted styrene butadiene rubber changes the rheological properties of polyvinyl acetate through blending, and the rheological viscosity of the obtained modified styrene butadiene rubber-polyvinyl acetate blend is reduced, the softening point of the compounded bonding glue is reduced, the bonding temperature is reduced, and the thermal stability is greatly improved.

[0096] The present invention is described exemplarily above in conjunction with the embodiments and drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned methods. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. An easy-to-peel, high-temperature resistant wafer bonding adhesive, characterized in that: Calculated by weight, the composition includes: 10-40 parts of base resin, 10-40 parts of bonding resin, 40-80 parts of high boiling point solvent and 0.1-0.8 parts of wetting agent.

2. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 1, characterized in that: The base resin is a modified styrene-butadiene rubber-polyvinyl acetate blend.

3. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 2, characterized in that: The base resin is prepared by a modification method in which a modified material is grafted onto thermoplastic styrene-butadiene rubber and then blended with polyvinyl acetate; wherein the molar ratio of the thermoplastic styrene-butadiene rubber, the modified material and the polyvinyl acetate is 10:(0.5-2):

10.

4. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 3, characterized in that: The preparation method of the base resin is specifically as follows: S1: Using thermoplastic styrene butadiene rubber as the grafting object and ethyl benzoate as the initiator, dissolving the thermoplastic styrene butadiene rubber in a mixed solution of toluene and dioxane, then adding the modified material, and reacting at 80-100°C for 1-3h under nitrogen conditions to obtain a graft copolymer emulsion, which is purified with methanol and then dried to obtain the grafted thermoplastic styrene butadiene rubber; S2: After drying the polyvinyl acetate at 100-130° C. for 10-14 hours, the polyvinyl acetate is blended with the thermoplastic styrene-butadiene rubber grafted in step S1 in a twin-screw extruder at 250-280° C. to fully disperse the grafted thermoplastic styrene-butadiene rubber in the polyvinyl acetate; The modified material is one or more of dimethylaminoethyl methacrylate, glycidyl methacrylate, and Fmoc-L-aspartic acid-alpha-allyl ester.

5. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 4, characterized in that: The base resin is one of dimethylaminoethyl methacrylate grafted styrene butadiene rubber-polyvinyl acetate blend, glycidyl methacrylate grafted styrene butadiene rubber-polyvinyl acetate blend, and Fmoc-L-aspartic acid-alpha-allyl ester grafted styrene butadiene rubber-polyvinyl acetate blend.

6. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 1, characterized in that: The high boiling point solvent is one or more of dodecane, dodecene, D-limonene, 1,8-terpene, benzyl alcohol, dibasic acid ester, ethyl benzoate, 1,1,3-trimethylcyclohexenone, N-methylpyrrolidone and 1,3-dimethyl-2-imidazolidinone.

7. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 1, characterized in that: The wetting agent is one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine and polyoxyethylene alkylamide.

8. The easy-to-peel, high-temperature resistant wafer bonding adhesive according to claim 1, characterized in that: The bonding resin is one or more of modified petroleum resin, terpene resin, terpene phenol resin and modified rosin resin.

9. A method for preparing the easy-to-peel, high-temperature resistant wafer bonding adhesive according to any one of claims 1 to 8, characterized in that The following steps are involved: Step 1: Mix the high boiling point solvent and wetting agent evenly, and heat to 30-70°C, then add the bonding resin and base resin, mix and stir until a clear and transparent liquid is formed; Step 2: Cool the clear and transparent liquid obtained in step 1 and filter it to obtain the easy-to-peel and high-temperature resistant wafer bonding adhesive.

10. Use of the easy-to-peel, high-temperature resistant wafer bonding adhesive according to any one of claims 1 to 8 in thinning the back side of an ultra-thin device wafer.

Images