Wafer glue, preparation method and application thereof

Abstract

This invention relates to the field of semiconductor packaging materials technology, specifically to a wafer adhesive, its preparation method, and its application. It comprises the following raw materials in parts by weight: 60-95 parts of matrix resin, 10-20 parts of diluent, 3-8 parts of curing agent, and 1-5 parts of additives. The matrix resin is bisphenol F type epoxy resin, naphthol type epoxy resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, and 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxymethylene)]bis(ethylene oxide), with a weight ratio of (6-9):(3-5):(2-3):(1-2). This wafer adhesive has advantages such as good storage stability, high light transmittance, low stress, and strong heat resistance, and is suitable for wafer-level packaging processes of high-performance semiconductor devices such as optical sensors and MEMS.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging materials technology, specifically to a wafer adhesive, its preparation method, and its application. Background Technology

[0002] As the semiconductor industry rapidly evolves towards high-density integration and miniaturized packaging, advanced packaging technologies such as wafer-level packaging (WLP) and 3D stacking place stringent demands on the performance of bonding materials. Wafer adhesive, as a core linking material in wafer bonding and packaging processes, not only needs excellent mechanical strength, heat resistance, and chemical stability, but also needs to meet the requirements of special scenarios such as long-cycle storage stability and high visible light transmittance.

[0003] Currently, mainstream epoxy resin-based wafer adhesives generally suffer from technical bottlenecks: First, insufficient storage stability. At room temperature, the resin and curing agent are prone to pre-curing reactions, leading to increased viscosity and decreased activity of the adhesive, making it difficult to match the material turnover cycle of 1-3 months in large-scale production. Second, low light transmittance. In traditional systems, the benzene ring structure of aromatic epoxy resins absorbs photons in the visible light band, and the average light transmittance of 400-800nm ​​is usually less than 85%, which cannot be adapted to packaging scenarios with extremely high optical performance requirements, such as optical sensors, MEMS, and other optoelectronic devices. Third, low coefficient of thermal expansion (CTE) to match silicon substrates (CTE≈2.6ppm / ℃) to avoid warping deformation caused by interfacial stress during temperature cycling. Summary of the Invention

[0004] To address the shortcomings of the existing technologies, the present invention aims to provide a wafer adhesive, its preparation method, and its applications. This invention utilizes a compound system of alicyclic epoxy resin and naphthol-type epoxy resin, combined with precise control of an encapsulating latent curing agent. While ensuring the adhesive's mechanical properties (flexural modulus 3.2-4.5 GPa) and heat resistance (5% thermal decomposition temperature > 300℃), it achieves a breakthrough with a viscosity increase rate ≤ 15% and visible light transmittance ≥ 92% after 30 days of storage at room temperature, providing a key material solution for advanced packaging processes.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A wafer adhesive is composed of the following raw materials in parts by weight: 60-95 parts of matrix resin, 10-20 parts of diluent, 3-8 parts of curing agent and 1-5 parts of additives.

[0006] The matrix resin is bisphenol F type epoxy resin, naphthol type epoxy resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate and 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxomethylene)]bis(ethylene oxide), and the weight ratio of the four is (6-9):(3-5):(2-3):(1-2).

[0007] The curing agent is a modified imidazole latent curing agent EH-3293S.

[0008] The additives are coupling agent KH-560, antioxidant 1010, and light stabilizer UV-P.

[0009] In this embodiment of the invention, the bisphenol F type epoxy resin is epoxy resin 1001, with an epoxy value of 0.51-0.55 eq / 100g, moisture content ≤0.1%, and color ≤30 APHA; the naphthol type epoxy resin is high-temperature resistant resin Ag-80, with an epoxy value of 0.80-1.00 eq / 100g and Tg ≥180℃; the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is an alicyclic epoxy resin with an epoxy value of 0.82-0.88 eq / 100g and light transmittance ≥99%; the 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxymethylene)]bis(ethylene oxide) has a moisture resistance ≥1000h@85℃ / 85%RH, a viscosity of 2500mPa·s (25℃), and a Cl content ≤50 ppm.

[0010] In this embodiment of the invention, the diluent is ethylene glycol diglycidyl ether with a viscosity ≤100 mPa·s and a refractive index of 1.53.

[0011] In this embodiment of the invention, the curing agent EH-3293S has a glass transition temperature of 150°C and a particle size of 5μm. At room temperature, the curing agent isolates the imidazole active groups from the epoxy resin through a coating layer or a passivation layer. When heated to its melting point, the coating layer softens and cracks or the passivation layer structure is destroyed, releasing the internal imidazole active groups and initiating the curing of the epoxy resin.

[0012] In this embodiment of the invention, the additives include: 0.5-2 parts of coupling agent, 0.3-1.5 parts of antioxidant and 0.2-1 parts of light stabilizer.

[0013] In this embodiment of the invention, the coupling agent is KH-560 with a purity ≥98% and hydrolyzed chlorine ≤0.1%; the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] with a melting point of 110-125℃ and ash content ≤0.1%; and the light stabilizer is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole with a transmittance ≥98%.

[0014] The method for preparing wafer adhesive according to the present invention includes the following steps: After the base resin and diluent are mixed and stirred for the first time, the additives are added and mixed and stirred for the second time. Finally, the curing agent is added and mixed and stirred for the third time to obtain the wafer adhesive.

[0015] In this embodiment of the invention, the first mixing and stirring time is 60-90 min, the stirring temperature is 50-70℃, and the stirring speed is 300-500 rpm; the second mixing and stirring is carried out under a vacuum degree ≤ -0.09 MPa for 40-80 min, the stirring temperature is 40-50℃, and the stirring speed is 600-800 rpm; the third mixing and stirring time is 20-40 min, the stirring temperature is 25-30℃, and the stirring speed is 400-600 rpm.

[0016] The post-processing of the wafer adhesive involves filtering the adhesive solution with a filtration accuracy of 0.5-2μm, followed by vacuum defoaming.

[0017] The application of the wafer adhesive described in this invention in semiconductor wafer-level packaging.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 0. This invention is composed of the following raw materials in parts by weight: 60-95 parts of matrix resin, 10-20 parts of diluent, 3-8 parts of curing agent, and 1-5 parts of additives; the matrix resin is bisphenol F type epoxy resin, naphthol type epoxy resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, and 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxomethylene)]bis(ethylene oxide), with a weight ratio of (6-9):(3-5):(2-3):(1-2). Bisphenol F type epoxy resin provides basic toughness and process adaptability, while naphthol type epoxy resin contributes a rigid structure to improve glass transition temperature and thermal stability. The combination of the two forms a soft and hard interwoven network skeleton, which imparts high strength to the material while avoiding excessive embrittlement. The alicyclic resin acts as a reactive diluent during the mixing stage, which can reduce the overall viscosity to facilitate bubble removal. The adhesive exhibits excellent thermal, optical, and mechanical properties through precise compounding. The curing agent is a modified imidazole latent curing agent, EH-3293S. The additives are coupling agent KH-560, antioxidant 1010, and light stabilizer UV-P. Using EH-3293S latent curing agent, the viscosity increase after 30 days of storage at 25℃ is ≤15% (initial viscosity 6000-8000 mPa·s), far superior to the viscosity change rate of over 30% of traditional products. In an accelerated aging test at 40℃, the storage period can still reach 15 days, meeting the requirements for long-distance transportation and production line buffering.

[0019] 2. In temperature cycling tests from -40℃ to 125℃, wafer warpage is reduced by more than 40%. Three-point bending tests show that its bending modulus is 3.2-4.5 GPa, which is 25-30% lower than similar products, effectively alleviating thermal mismatch stress.

[0020] 3. The alicyclic structure 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is introduced into the matrix resin. Combined with the refractive index matching design of the inorganic components, the cured product achieves a light transmittance of 92-95% and a haze of ≤1.5% in the visible light range of 400-800nm, meeting the stringent requirements for light transmittance in optical sensor packaging.

[0021] 4. The combination of Ag-80 and 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxomethylene)]bis(ethylene oxide) enables the product to achieve a glass transition temperature (Tg) of 150-170℃ and a thermal decomposition temperature (T5%) exceeding 380℃. After aging at 150℃ for 100 hours, the shear strength retention rate still exceeds 85% (initial strength ≥25MPa), which is significantly better than the retention rate of about 70% of existing products. Attached Figure Description

[0022] Figure 1 The viscosity change curves of Examples 1-3 and Comparative Examples 1, 4 and 5 of the present invention are shown. Detailed Implementation

[0023] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0025] Example 1: Weigh the raw materials according to the proportions in Example 1 of Table 1; add epoxy resin 1001, Ag-80, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxomethylene)]bis(ethylene oxide) and diluent to the reactor, and stir at 50°C for 90 minutes until completely mixed, with a stirring speed of 500 rpm; cool to 40°C, add KH-560, 1010 and UV-P, and stir under vacuum of -0.09 MPa for 60 minutes, with a stirring speed of 600 rpm; then cool to 25°C, add curing agent EH-3293S, continue stirring for 30 minutes, and then cool naturally to room temperature; then filter the adhesive solution with a filtration accuracy of 0.5 μm, and finally perform vacuum defoaming treatment to obtain the wafer adhesive.

[0026] Example 2: Weigh the raw materials according to the proportions of each raw material in Example 2 in Table 1; the remaining steps are the same as in Example 1.

[0027] Example 3: Weigh the raw materials according to the proportions of each raw material in Example 3 in Table 1; the remaining steps are the same as in Example 1.

[0028] Comparative Example 1: Weigh the raw materials according to the proportions of each raw material in Comparative Example 1 in Table 1; the remaining steps are the same as in Example 1.

[0029] Comparative Example 2: Weigh the raw materials according to the proportions of each raw material in Comparative Example 2 in Table 1; the remaining steps are the same as in Example 1.

[0030] Comparative Example 3 Weigh the raw materials according to the proportions of each raw material in Comparative Example 3 in Table 1; the remaining steps are the same as in Example 1.

[0031] Comparative Example 4: Weigh the raw materials according to the proportions of each raw material in Comparative Example 4 in Table 1; the remaining steps are the same as in Example 1.

[0032] Comparative Example 5: Commercially available bisphenol A epoxy adhesive is used, with E-51 epoxy resin as the base resin and methyl hexahydrophthalic anhydride as the curing agent. No nano-SiO2 is added.

[0033] Table 1 shows the proportions of raw materials in Examples 1-3 and Comparative Examples 1-4. Results Analysis Viscosity test: Viscosity was tested using a Brookfield DV2T rotational viscometer under the following conditions: 25°C and 10 rpm.

[0034] Storage stability test: Store in a sealed container at 25°C, and measure viscosity changes every 10 days.

[0035] Transmittance test: Tested using a UV-3600 UV-Vis spectrophotometer, wavelength range: 400-800 nm.

[0036] Thermal performance testing: The adhesive was applied to the smooth surface of copper foil and cured in a 165℃ oven for 30 minutes; the Tg was determined using a TAQ2000 DSC. A 5mg sample was weighed, and the test method involved heating from room temperature to 300℃ at a rate of 20℃ / min, then rapidly cooling to room temperature, and then heating back to 300℃ at a rate of 20℃ / min; the 5% thermal decomposition temperature (Tg) was determined using a TGA Q500. d,5% The test gas was N2 atmosphere, the temperature was room temperature to 700℃, the temperature was increased at 20℃ / min, and the sample weight was 5 to 8 mg.

[0037] Mechanical property testing: Aluminum plates were used as test substrates for simulated performance testing. Wafer adhesive was uniformly coated onto an aluminum plate, with the adhesive layer thickness controlled at 0.1-0.2 mm and the bonding area at (12.50±0.25) mm × 25.00 mm. Another aluminum plate was placed over it and cured in a 165℃ oven for 30 min. Shear strength (GB / T 7124-2008) was tested using an Instron 5967 universal testing machine at a tensile speed of 1 mm / min. Three samples were tested per group, and the average value was taken. The adhesive was then injected into a mold and cured in a 165℃ oven for 30 min. After cooling, samples of 80 mm × 10 mm × 4 mm were prepared. Flexural modulus (GB / T 9341-2008) was tested using an Instron 5967 universal testing machine at a speed of 1 mm / min. Three samples were tested per group, and the average value was taken.

[0038] Temperature cycling test: Place the sample in a high and low temperature cycling chamber. Temperature setting: -40℃~125℃, temperature increase of 10℃ / min, holding time of 30min, and measure the shear strength retention rate after 1000 cycles. Shear strength retention rate = (shear strength after cycling / initial shear strength) × 100%. Measure 3 samples in each group and take the average value.

[0039] As shown in Table 2, the products prepared in Examples 1, 2, and 3 all exhibit excellent overall performance. Comparative Examples 1, 2, 3, and 4 show outstanding performance in individual performance indicators, but their overall performance is inferior to that of the Examples. Furthermore, when the initial viscosity of the adhesive is low, it is prone to flow and overflow during application, which can contaminate wafer devices or cause misalignment during bonding. Conversely, when the viscosity is too high, stringing is likely to occur, which is detrimental to operation. The viscosity growth rates of Examples 1, 2, and 3 within 30 days were 12.3%, respectively. The increases of 14.5% and 14.7% were significantly lower than those of Comparative Examples 2 (79.41%), 3 (75.0%), 4 (46.3%), and 5 (53.3%). Meanwhile, the room temperature storage time of Examples 1, 2, and 3 was ≥60 days, which was significantly better than the 10-28 days of Comparative Examples 1-5. Furthermore, while the light transmittance of the product of this invention increased by 14.6%, the flexural modulus decreased by 32.1%, which significantly improved the stress buffering capacity. At the same time, the thermal decomposition temperature increased by more than 10%, which fully verified the advanced nature of the formulation design.

[0040] Table 2 Performance Test Data Figure 1The viscosity change curves of Examples 1-3 and Comparative Examples 1, 4, and 5 of the present invention are shown. It can be seen that the 30-day viscosity growth rates of Examples 1, 2, and 3 of the present invention are 12.3%, 14.5%, and 14.7%, respectively, which are significantly lower than the growth rates of Comparative Example 4 (46.3%) and Comparative Example 5 (53.3%). Furthermore, Examples 1, 2, and 3 of the present invention still have good fluidity after being stored at room temperature for 60 days, while Comparative Example 1 solidifies between 10 and 20 days. Comparative Example 4 shows a slow viscosity increase during the storage period at room temperature, but the viscosity increases significantly after the storage period at room temperature. Comparative Example 5 solidifies between 35 and 40 days. Therefore, it is shown that the products of the present invention have better storage stability.

[0041] This invention utilizes EH-3293S latent curing agent, resulting in a viscosity increase of ≤15% (initial viscosity 6000-8000 mPa·s) after 30 days of storage at 25°C, far superior to the viscosity change rate of over 30% of traditional products. In accelerated aging tests at 40°C, the storage period still reaches 15 days, meeting the requirements for long-distance transportation and production line buffering.

[0042] In temperature cycling tests ranging from -40℃ to 125℃, wafer warpage was reduced by more than 40%. Three-point bending tests showed that its bending modulus was 3.2-4.5 GPa, which is 25-30% lower than similar products, effectively alleviating thermal mismatch stress.

[0043] The alicyclic structure 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is introduced into the matrix resin, and the refractive index matching design of the inorganic components enables the cured product to achieve a light transmittance of 92-95% in the visible light range of 400-800nm ​​and a haze of ≤1.5%, which meets the stringent requirements of optical sensor packaging for light transmittance.

[0044] The combination of Ag-80 and 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxomethylene)]bis(ethylene oxide) enables the product to achieve a glass transition temperature (Tg) of 150-170℃ and a thermal decomposition temperature (T5%) exceeding 380℃. After aging at 150℃ for 100 hours, the shear strength retention rate still exceeds 85% (initial strength ≥25MPa), which is significantly better than the retention rate of about 70% of existing products.

[0045] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0046] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A wafer adhesive, characterized in that, It is composed of the following raw materials in parts by weight: 60-95 parts of matrix resin, 10-20 parts of diluent, 3-8 parts of curing agent and 1-5 parts of additives; The matrix resin is bisphenol F type epoxy resin, naphthol type epoxy resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate and 2,2'-[(3,3',5,5'-tetramethylbiphenyl-4,4'-diyl)bis(oxomethylene)]bis(ethylene oxide), and the weight ratio of the four is (6-9):(3-5):(2-3):(1-2).

2. The wafer adhesive according to claim 1, characterized in that, Bisphenol F type epoxy resin is epoxy resin 1001 with an epoxy value of 0.51-0.55 eq / 100g; naphthol type epoxy resin is high temperature resistant resin Ag-80 with an epoxy value of 0.80-1.00 eq / 100g; 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate is an alicyclic epoxy resin with an epoxy value of 0.82-0.88 eq / 100g.

3. The wafer adhesive according to claim 1, characterized in that, The diluent is ethylene glycol diglycidyl ether with a viscosity ≤100 mPa·s.

4. The wafer adhesive according to claim 1, characterized in that, The curing agent is a modified imidazole latent curing agent EH-3293S; the additives are coupling agent KH-560, antioxidant 1010 and light stabilizer UV-P.

5. The wafer adhesive according to claim 4, characterized in that, The coupling agent is KH-560; the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and the light stabilizer is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole.

6. The method for preparing wafer adhesive according to claim 1, characterized in that, Includes the following steps: After the base resin and diluent are mixed and stirred for the first time, the additives are added and mixed and stirred for the second time. Finally, the curing agent is added and mixed and stirred for the third time to obtain the wafer adhesive.

7. The method for preparing wafer adhesive according to claim 6, characterized in that, The first mixing time is 60-90 minutes, the mixing temperature is 50-70℃, and the mixing speed is 300-500 rpm; the second mixing time is 40-80 minutes, the mixing temperature is 40-50℃, and the mixing speed is 600-800 rpm; the third mixing time is 20-40 minutes, the mixing temperature is 25-30℃, and the mixing speed is 400-600 rpm.

8. The application of the wafer adhesive according to claim 7 in semiconductor wafer-level packaging.

Images