Wafer polishing tape

Abstract

This invention proposes a wafer polishing tape, which sequentially includes a substrate layer, a pressure-sensitive adhesive layer 1, and a pressure-sensitive adhesive layer 2. The pressure-sensitive adhesive layer 1 has appropriate thickness and adhesion, enabling it to bond the substrate layer and the pressure-sensitive adhesive layer 2, while providing appropriate flexibility. Therefore, the wafer polishing tape of this invention is less likely to cause surface damage, water seepage, or excessive flatness and damage to the polished wafer during application, polishing, and removal.

Description

Technical Field

[0001] This invention relates to a wafer polishing tape, particularly a tape used in wafer backside polishing processes. Background Technology

[0002] In semiconductor wafer fabrication, wafers must be thinned before packaging or dicing, which involves a back-side polishing process. Before polishing, a protective film is applied to the wafer surface to prevent damage to bumps or circuits; this film is then removed after polishing.

[0003] Currently, the most commonly used wafer polishing tape is the UV-resistant tape. After polishing, UV light can be used to reduce or even remove its tackiness, allowing the tape to be removed from the wafer surface. UV-resistant tape mainly consists of a substrate layer and an adhesive layer. The substrate layer is typically made of polyolefin (PO) or polyethylene terephthalate (PET). The adhesive layer is usually made of polyacrylates, such as poly(methylmethacrylate) (PMMA), and may contain hardeners, UV light initiators, inhibitors, crosslinking agents, etc., as needed. During the tape application and wafer polishing processes, the elasticity and stress can lead to breakage, water seepage, or excessive flatness or sagging of the polished wafer. Removing the tape after polishing also frequently damages semiconductor components.

[0004] Known solutions primarily involve increasing the rigidity of the substrate layer to reduce wafer curvature and suppress issues such as wafer breakage, water seepage, or excessive wafer flatness after grinding. However, this solution still carries practical risks; increasing the thickness of the substrate makes it difficult for adhesive tape to adhere properly and remove from the delicate wafer surface.

[0005] To address this problem, this invention develops a novel wafer polishing tape with a dual pressure-sensitive adhesive layer design. In this configuration, pressure-sensitive adhesive layer 1 is disposed on the substrate layer, while pressure-sensitive adhesive layer 2 is disposed on adhesive layer 1, thereby providing appropriate adhesion and flexibility. This structure effectively reduces wafer breakage without increasing the thickness of any substrate layer. The dual pressure-sensitive adhesive layer design not only effectively covers solder balls, copper pillars, and other related components, preventing wafer breakage, water seepage, or excessive wafer flatness after polishing, but also facilitates easier adhesion and removal without compromising adhesive effectiveness. Summary of the Invention

[0006] The purpose of this invention is to provide a wafer polishing tape that can effectively cover solder balls, copper pillars and other related designs during the back-side polishing process of the wafer, avoiding wafer damage, water seepage or excessive flatness of the polished wafer, while being easy to adhere and remove.

[0007] To achieve the above objectives, the present invention provides a wafer grinding tape, wherein a substrate layer, a pressure-sensitive adhesive layer 1 and a pressure-sensitive adhesive layer 2 are sequentially laminated.

[0008] The thickness of the substrate layer is 30–100 μm, and the material can be polyolefin (PO), polyethylene terephthalate (PET), or other suitable materials.

[0009] The thickness of the pressure-sensitive adhesive layer 1 is 50–200 μm, preferably 100–170 μm; it mainly includes polyurethane acrylate oligomer and hydroxyl-containing monomer.

[0010] The polyurethane acrylate oligomer is preferably aliphatic urethanediacrylate; accounting for 45-90% by weight of the pressure-sensitive adhesive layer 1, more preferably 55-80% by weight, and even more preferably 60-75% by weight.

[0011] The hydroxyl-containing monomer is preferably hydroxyethyl acrylate (HEA) and accounts for 5 to 40% by weight of the pressure-sensitive adhesive layer 1, more preferably 10 to 30% by weight, and even more preferably 10 to 20% by weight.

[0012] The adhesion of pressure-sensitive adhesive layer 1 is 400-2000 gf / 25 mm (180°, tensile speed 300 mm / min, stainless steel surface), preferably 600-1000 gf / 25 mm.

[0013] The pressure-sensitive adhesive layer 1 may further include 2-ethyl hexyl acrylate (EHA), cyclic trimethylolpropane formal acrylate (CTFA), and ethyl(2,4,6-trimethylbenzoyl)phenylphosphonate.

[0014] phenylphosphinate, TPO-L), etc.

[0015] The pressure-sensitive adhesive layer 1 is preferably a radiation-cured pressure-sensitive adhesive.

[0016] The thickness of the pressure-sensitive adhesive layer 2 is 1–50 μm, preferably 15–50 μm, and mainly includes acrylate polymer and isocyanide crosslinker.

[0017] The adhesion of the pressure-sensitive adhesive layer 2 is 300-1500 gf / 25 mm (180°, tensile speed 300 mm / min, stainless steel surface), preferably 400-1000 gf / 25 mm.

[0018] The pressure-sensitive adhesive layer 2 is preferably a radiation-induced tack-reducing pressure-sensitive adhesive.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention provides a wafer polishing tape whose double-layer structure not only provides superior flexibility and coverage but also suitable adhesion. It offers better protection for dense, spherical wafer patterns during the back-side polishing process. Detailed Implementation

[0021] The following examples are only for illustrating the wafer grinding tape of the present invention, but should not be construed as limiting.

[0022] The wafer grinding tape of the present invention having a dual-layer adhesive structure includes, in sequence, a substrate layer, a pressure-sensitive adhesive layer 1, and a pressure-sensitive adhesive layer 2.

[0023] The substrate layer is 50μm thick and made of polyethylene terephthalate (PET), which can provide appropriate support for the wafer grinding tape.

[0024] The thickness of the pressure-sensitive adhesive layer 1 is typically between 50 and 200 μm, preferably between 100 and 170 μm. A thickness less than 50 μm may cause accidental breakage of the fragile adhesive after grinding. In this embodiment, the thickness of the pressure-sensitive adhesive layer 1 is 100 μm.

[0025] The pressure-sensitive adhesive layer 1 is formed from a variety of monomers, functional groups, and additives to achieve optimal performance for semiconductor applications. These components enhance the mechanical strength and thermal stability of the adhesive, which is crucial for high-precision applications such as wafer fabrication. The main components are urethane acrylate oligomers and hydroxy-containing monomers.

[0026] Polyurethane acrylate oligomers can be combined with UV-curable oligomers to enhance the mechanical integrity and shape stability of adhesive layers due to their low viscosity and excellent crosslinking properties. The UV-curable oligomers can be cyclic trimethylolpropane formal acrylate (CTFA) or polyester acrylates. The examples use aliphatic polyurethane diacrylate from Double Bond Chemicals. 5500 or DM5500).

[0027] Hydroxyl-containing monomers help improve heat resistance and cohesive strength, ensuring the adhesive layer functions effectively under challenging processing conditions. The combination of hydroxyl-containing monomers, such as hydroxyethyl acrylate (HEA), with 2-ethylhexyl acrylate (EHA) can effectively improve crosslinking efficiency and flexibility.

[0028] Multifunctional monomers HEA and EHA are combined with oligomers CTFA and aliphatic polyurethane diacrylate.

[0029] A mixture of (DM5500) and UV-initiated polymerization and curing with the photoinitiator ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L) forms a dense cross-linked network, resulting in an adhesive layer with excellent elasticity, adhesion, and environmental resilience. UV curing offers several advantages, including faster polymerization rates, lower energy consumption, and the ability to obtain high molecular weight polymers with minimal thermal impact. By optimizing UV irradiation parameters and TPO-L concentration, a uniform cross-linked polymer network can be achieved to meet the specific application requirements of pressure-sensitive adhesive layer 1. This method ensures enhanced adhesion, thermal stability, and cohesive strength, making it suitable for high-precision semiconductor applications.

[0030] Tables 1 and 2 show the adhesion of the laminated pressure-sensitive adhesive layer 1 on the substrate layer with different formulations (100% solid content). The UV irradiation dose was 1100 MJ / cm². 2 The adhesion test was conducted on a stainless steel surface at a 180° angle and a tensile speed of 300 mm / min.

[0031] Table 1

[0032]

[0033] Table 2

[0034]

[0035] In Table 1, when the HEA content of formulation A is close to 100 wt%, the adhesion is only 141 gf / 25 mm. The HEA content of formulations B to H is reduced from 60 wt% and 40 wt% to 20 wt%, respectively, while DM5500, CTFA, and / or EHA are added. The results show that when the HEA content is 20 wt% and the DM5500 content is 80 wt%, the adhesion can be increased to 474 gf / 25 mm.

[0036] In Table 2, the HEA content of formulations I through O was maintained at 20 wt%, and the DM5500 content was 70 wt% and 65 wt%, respectively. With the appropriate addition of CTFA and / or EHA, the adhesion was significantly improved.

[0037] 525gf / 25mm~798gf / 25mm.

[0038] The composition and formulation in Table 2 not only provide the required adhesion and flexibility between the substrate layer and the pressure-sensitive adhesive layer 2, but also avoid excessive flow characteristics or tackiness. The HEA introduces hydroxyl groups that enhance hydrogen bonding, generating stronger adhesion between the substrate layer and the pressure-sensitive adhesive layer 2. In addition to balancing properties, the HEA increases flexibility, further improving compatibility and adhesion performance. The polyurethane functional groups of the DM5500 oligomer can perform crosslinking, thereby forming a highly durable and environmentally resistant intermediate layer. Furthermore, the formulation of this invention avoids monomer migration, ensuring a clean and stable adhesive interface, which is particularly useful in processes where contamination is unacceptable.

[0039] The shear modulus (25°C) of pressure-sensitive adhesive layer 1 is 0.0001 MPa lower than the instrument's detection limit, indicating that it has appropriate flexibility and is suitable for being sandwiched between the substrate layer and pressure-sensitive adhesive layer 2 without causing deformation of the wafer during processing or grinding.

[0040] The thickness of the pressure-sensitive adhesive layer 2 can be 1–50 μm, preferably 5–30 μm. A thickness less than 1 μm may result in insufficient adhesion, leading to brittleness after grinding. A thickness greater than 50 μm may result in excessive stiffness, which is economically disadvantageous for material use; it may also inhibit wafer grinding tape deformation, making it difficult to form a peeling start point. In this embodiment of the invention, the thickness is 20 μm.

[0041] Pressure-sensitive adhesive layer 2 is an active energy radiation-cured adhesive, comprising a base polymer (such as acrylic pressure-sensitive adhesive) and an active energy radiation-cured compound. Pressure-sensitive adhesive layer 2 exhibits high adhesion at room temperature, allowing for wafer grinding and polishing. When exposed to UV radiation, the photoinitiator in pressure-sensitive adhesive layer 2 initiates a cross-linking mechanism, reducing adhesion.

[0042] In this embodiment, the components used in the pressure-sensitive adhesive layer 2 include: adhesives from Nanpao Resin Chemical. (A mixture of ethyl acetate and acrylate polymer), a curing agent from Nanpo Resin Chemicals. (A mixture of modified polyisocyanate, N-butylacetate, and xylene), photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), additive 2,4-pentanedione, and solvent methyl ethyl ketone.

[0043] If the formula uses adhesive For 100 parts by weight, the hardener The product contains 0.5 parts by weight of TPO (photoinitiator), 2 parts by weight of 2,4-pentanedione (additive), and 5 parts by weight of butanone (solvent), with a solid content of 44.0%. (Curing agent) The modified polyisocyanate in this material exhibits excellent adhesion and flexibility to the wafer surface. Under ultraviolet light irradiation, it undergoes a cross-linking reaction to form a robust three-dimensional network structure, reducing its adhesion and allowing the adhesive to be effectively separated.

[0044] Pressure-sensitive adhesive layer 2 was deposited on the substrate layer, and its adhesion was tested. The test conditions were 180°, tensile speed 300 mm / min, and performed on a stainless steel surface. The adhesion was found to be 469 gf / 25 mm, indicating good adhesion and ensuring effective wafer protection during polishing. After UV irradiation, the adhesion of pressure-sensitive adhesive layer 2 decreased to 20 gf / 25 mm, allowing it to be easily peeled off without damaging the fragile wafer.

[0045] The pressure-sensitive adhesive layer 2 has a shear modulus of less than 0.2 MPa at 80°C, making it suitable for temporary bonding with the wafer. For compact wafer ball patterns, the flexibility of the pressure-sensitive adhesive layer 2 ensures that the adhesive can conformally cover every corner of the sphere without damaging the wafer.

[0046] To obtain a wafer grinding tape with a double-layer adhesive structure, pressure-sensitive adhesive layer 1 and pressure-sensitive adhesive layer 2 of formulations 1-1 to 1-0 were sequentially laminated onto a substrate layer. Table 3 shows the results of the adhesion test; the test conditions were 180°, tensile speed 300 mm / min, and the test was conducted on a stainless steel surface.

[0047] Table 3

[0048]

[0049] The results show that the dual-layer adhesive structure of the present invention not only provides superior flexibility and coverage but also possesses suitable adhesion. It offers better protection for dense wafer spherical patterns during the wafer back-side polishing process.

[0050] Many factors influence the effectiveness of wafer polishing and protection, such as the source and composition of raw materials, the thickness and hardness of each layer, wafer surface conditions, and bonding temperature, which will not be discussed in detail here. The above embodiments are only used to demonstrate that the structure and composition of the present invention are indeed feasible as a wafer polishing tape and have industrial applicability.

Claims

1. A wafer grinding tape, characterized in that, A pressure-sensitive adhesive layer 1 and a pressure-sensitive adhesive layer 2 are sequentially laminated on a substrate layer, wherein, The substrate layer has a thickness of 30–100 μm and is made of polyolefin or polyethylene terephthalate. The pressure-sensitive adhesive layer 1 has a thickness of 50-200 μm and includes polyurethane acrylate oligomer and hydroxyl-containing monomers, with an adhesion of 400-2000 gf / 25 mm. The pressure-sensitive adhesive layer 2 has a thickness of 1 to 50 μm and includes an acrylate polymer and an isocyanate crosslinking agent, with an adhesion of 300 to 1500 gf / 25 mm.

2. The wafer grinding tape as described in claim 1, characterized in that, The thickness of the pressure-sensitive adhesive layer 1 is 100–170 μm.

3. The wafer grinding tape as described in claim 1, characterized in that, The polyurethane acrylate oligomer of the pressure-sensitive adhesive layer 1 is an aliphatic polyurethane diacrylate.

4. The wafer grinding tape as described in claim 1, characterized in that, The polyurethane acrylate oligomer accounts for 45-90% by weight of the pressure-sensitive adhesive layer 1.

5. The wafer grinding tape as described in claim 1, characterized in that, The polyurethane acrylate oligomer accounts for 55-80% by weight of the pressure-sensitive adhesive layer 1.

6. The wafer grinding tape as described in claim 1, characterized in that, The polyurethane acrylate oligomer accounts for 60-75% by weight of the pressure-sensitive adhesive layer 1.

7. The wafer grinding tape as described in claim 1, characterized in that, The hydroxyl-containing monomer of the pressure-sensitive adhesive layer 1 is hydroxyethyl acrylate.

8. The wafer grinding tape as described in claim 1, characterized in that, The hydroxyl-containing monomer accounts for 5 to 40% by weight of the pressure-sensitive adhesive layer 1.

9. The wafer grinding tape as described in claim 1, characterized in that, The hydroxyl-containing monomer accounts for 10-30% by weight of the pressure-sensitive adhesive layer 1.

10. The wafer grinding tape as described in claim 1, characterized in that, The hydroxyl-containing monomer accounts for 10-20% by weight of the pressure-sensitive adhesive layer 1.

11. The wafer grinding tape as described in claim 1, characterized in that, The pressure-sensitive adhesive layer 1 also includes isooctyl acrylate.

12. The wafer grinding tape as described in claim 1, characterized in that, The pressure-sensitive adhesive layer 1 also includes cyclotrimethylolpropane methyl acetal acrylate.

13. The wafer grinding tape as described in claim 1, characterized in that, The pressure-sensitive adhesive layer 1 also includes ethyl 2,4,6-trimethylbenzoylphenylphosphonate.

14. The wafer grinding tape as described in claim 1, characterized in that, The adhesion of the pressure-sensitive adhesive layer 1 is 600-1000 gf / 25 mm.

15. The wafer grinding tape as described in claim 1, characterized in that, The pressure-sensitive adhesive layer 1 is a radiation-cured pressure-sensitive adhesive.

16. The wafer grinding tape as described in claim 1, characterized in that, The thickness of the pressure-sensitive adhesive layer 2 is 15–50 μm.

17. The wafer grinding tape as described in claim 1, characterized in that, The pressure-sensitive adhesive layer 2 is a radiation-induced tack-reducing pressure-sensitive adhesive.

18. The wafer grinding tape as described in claim 1, characterized in that, The adhesion of the pressure-sensitive adhesive layer 2 is 400-1000 gf / 25 mm.

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