A photocurable liquid phase composition for wafer thinning and a method thereof

Abstract

This invention discloses a photocurable liquid phase composition for wafer thinning and a method for using the same, belonging to the field of adhesive technology. The photocurable liquid phase composition includes: acrylic oligomer, acrylic monomer, photoinitiator, surfactant, and additives; wherein the additives include imidazole compounds containing pyridine groups. The photocurable liquid phase composition of this invention can provide a protective film with excellent substrate protection performance, good fluidity, strong adhesion, and can uniformly cover the wafer surface. Its good physicochemical properties enable it to better protect the wafer. Furthermore, it only undergoes a physical reaction, is in single-liquid and solvent-free form, is easy to use, does not volatilize at room temperature, exhibits minimal changes in physical properties, and provides good surface smoothness after film formation, making it easy to apply to substrates with complex shapes. After back grinding, the wafer warpage is minimal, and it can be peeled off with an alkaline solution of NaOH after processing, leaving no residue.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and more specifically, to a photocurable liquid phase composition for wafer thinning and a method of using the same. Background Technology

[0002] With the development of the electronics industry, semiconductor wafers and thin-film tempered glass, as substrate materials, are increasingly used in the manufacturing of key components such as semiconductors, flat panel displays, touch screens, and circuit boards. While products are becoming lighter and thinner, the linewidths of semiconductor devices are becoming increasingly smaller and their integration density is increasing, leading to higher demands for process improvements such as reducing device defect rates and enhancing reliability. Correspondingly, in the processing of semiconductor wafers or thin-film tempered glass, the use of temporary protective films on substrate surfaces is also increasing to minimize damage to the substrate and ensure more favorable process conditions.

[0003] Currently, most polishing processes used for backside thinning of wafers involve attaching an adhesive film to the wafer substrate. However, this can lead to numerous problems. For example, after the semiconductor wafer microcircuit fabrication process, in order to reduce chip weight, wafer contamination and cracks frequently occur during the backside thinning and dicing processes. This is particularly true in the DBG (Dicing Before Grinding) process, an improved wafer fabrication process where half-cut dicing is followed by polishing, which exhibits many defects such as backside chipping, cracks, and chip edge breakage.

[0004] To address the aforementioned issues, most wafer fabs use protective films, which temporarily form a protective layer and can be peeled off and removed after processing. By maintaining high adhesion, the film firmly secures the target substrate, preventing wafer damage. However, these protective films are expensive, increasing costs, and suffer from numerous problems, such as bubbles, uneven thickness, insufficient or excessive adhesion, easy residue, limited temperature resistance, difficulty in high-end packaging bonding, poor stability, and significant environmental pollution. These issues severely impact the effectiveness of the protective film and production efficiency. Furthermore, existing wafer protective films, due to uneven thickness, inability to fill microscopic irregularities on the wafer, and mismatched coefficients of thermal expansion, cause wafer warping during back-grinding, adversely affecting subsequent processes, thus limiting their use.

[0005] With the increasing sophistication of semiconductors, high-bandwidth memory (HBM) is being deployed in parallel around logic die dies (DIEs) as a new alternative for the artificial intelligence industry. This significantly increases the amount of data that can be processed, drawing considerable attention to the industry that manufactures these HBMs. The higher the number of stacked die dies (DIEs), the faster the computing power achieved. For the same chip type, thinner dies mean lower signal latency and better heat dissipation, which has profound implications for improving overall system performance and extending chip lifespan and stability. However, manufacturing thinner dies through back-side thinning has become an extremely challenging task.

[0006] Existing protective films suffer from various problems, such as uneven adhesion, frequent adhesive residue, and stress-induced wafer warping, which limit the performance of thinner DIEs. When removing the DIE, residual adhesive is easily torn off along with it, resulting in material waste. Furthermore, the adhesion between residual adhesive and the DIE is random, severely disrupting the stability and consistency of the production process. Production lines must be frequently interrupted for equipment cleaning and process adjustments, significantly reducing production efficiency, affecting back-grinding quality, limiting DIE thickness and quality, and further compromising production stability and consistency.

[0007] Therefore, developing a temporary protective film material that is in a balanced adhesive state, easy to peel off without residue, and can be used to obtain thinner wafers has become a key problem that urgently needs to be solved in the current semiconductor manufacturing field. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a photocurable liquid phase composition for wafer thinning that is not prone to introducing impurities, has a balanced adhesion state, is easy to peel off without residue, and has good fluidity, as well as a method of using the same. This photocurable liquid phase composition can protect the substrate during semiconductor wafer grinding and can also be used as a protective film that is easy to peel off and leaves no surface residue or contaminants after peeling.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A photocurable liquid phase composition for wafer thinning comprises the following components in parts by weight: 50-70 parts of acrylic oligomer, 20-40 parts of acrylic monomer, 2-8 parts of photoinitiator, 1-5 parts of surfactant, and 1-7 parts of additive; wherein the additive comprises an imidazole compound containing a pyridine group; the structural formula of the imidazole compound containing the pyridine group is:

[0011]

[0012] R is selected from One of them.

[0013] Optionally, the photocurable liquid phase composition comprises, by weight, the following components: 55 to 65 parts of acrylic oligomer, 25 to 35 parts of acrylic monomer, 3 to 7 parts of photoinitiator, 1 to 3 parts of surfactant, and 2 to 6 parts of additive.

[0014] Optionally, the acrylic oligomer is prepared by reacting a monomer with an anhydride functional group with a monofunctional acrylic monomer or a polyfunctional acrylic monomer.

[0015] Optionally, the acrylic monomer includes at least one of 2-hydroxyethyl acrylate, trimethylolpropane triacrylate (TMPTA), and 2-hydroxyethyl methacrylate.

[0016] Optionally, the photoinitiator includes at least one of I-184C (chemical name: 1-hydroxycyclohexylphenyl ketone) and I-907 (chemical name: 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone).

[0017] Optionally, the surfactant includes at least one of octadecylamine polyoxyethylene ether acrylate, sodium vinyl sulfonate, and reactive polyether-modified polysiloxane.

[0018] Optionally, the photocurable liquid phase composition further includes 1 to 7 parts by weight of an additive; the additive includes at least one selected from leveling agents, antistatic agents, defoamers, and dispersants.

[0019] Optionally, the leveling agent includes at least one of polyether-modified polysiloxane, fluorinated polyacrylate, and polyethylene glycol diacrylate; the antistatic agent includes at least one of phosphate acrylate and polyethylene glycol acrylate; the defoamer includes at least one of polysiloxane compound, polyethylene glycol diacrylate, and acrylic acid-functionalized polysiloxane; and the dispersant includes at least one of quaternary ammonium salt-modified acrylate and acrylic acid-styrene copolymer.

[0020] The present invention also discloses a method for forming a temporary protective film for backside thinning of a semiconductor substrate using the above-described photocurable liquid phase composition, comprising the following steps:

[0021] (1) Mix acrylic oligomer, acrylic monomer, photoinitiator, surfactant and additive to obtain a photocurable liquid phase composition;

[0022] (2) The photocurable liquid phase composition is coated on the bump surface of the wafer and attached to the upper surface of the inner perforated plate of the grinding jig, and then photocured to form a temporary protective film to obtain a photocurable wafer.

[0023] (3) The back side of the photocurable wafer is thinned using a grinding equipment and a chip bonding film (DAF film) is attached. Then, an alkaline solution is used for chemical treatment to separate the temporary protective film from the grinding fixture, thus completing the back side thinning process and obtaining the thinned wafer.

[0024] Optionally, the alkaline solution is a 20% NaOH solution at a temperature of 80℃.

[0025] Optionally, the light curing method includes ultra-high pressure mercury lamp curing or LED ultraviolet light curing.

[0026] Optionally, the photocuring time is 10s to 30s.

[0027] Optionally, the thickness deviation of the temporary protective film is less than 5 μm, which is less than the thickness of the protective film after UV exposure (100 μm). The surface smoothness of the protective film is good, which is beneficial to subsequent processing.

[0028] Implementing the embodiments of the present invention will have the following beneficial effects:

[0029] This invention, through the synergistic effect of acrylic oligomers, acrylic monomers, photoinitiators, surfactants, and additives, provides a protective film with superior substrate protection performance compared to existing wafer back-grinding protective films. This liquid-phase composition exhibits good fluidity and strong adhesion, uniformly covering the wafer surface, and its excellent physicochemical properties enable better wafer protection. Furthermore, the photocurable liquid-phase composition of this invention undergoes only a physical reaction, is a single-liquid and solvent-free form, is easy to use, does not volatilize at room temperature, exhibits minimal changes in physical properties, and produces a smooth surface after film formation, making it easy to apply to substrates with complex shapes. Wafer warpage is minimal after back-grinding, and it can be peeled off with an alkaline NaOH solution after processing, leaving no residue. During use, the photocurable liquid-phase composition of this invention is coated onto the wafer, and a thin film is formed by UV irradiation, at which point the adhesion to the substrate is significantly increased. According to the 200µm peel strength test specified in JIS 2107, the peel strength of the film formed by this invention is preferably 1–2 kgf / inch, more preferably 1.5–1.8 kgf / inch. Furthermore, the thickness deviation of the protective film is less than 5 μm, and preferably less than 3 μm. Compared to a protective film thickness of 100 μm after UV exposure, a protective film within this range exhibits better surface flatness, less substrate bending deformation, and significantly improved processing performance. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method for forming a temporary protective film for backside thinning of a semiconductor substrate using a photocurable liquid phase composition according to the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0032] This invention discloses a photocurable liquid phase composition for wafer thinning, comprising the following components in parts by weight: 50 to 70 parts of acrylic oligomer, 20 to 40 parts of acrylic monomer, 2 to 8 parts of photoinitiator, 1 to 5 parts of surfactant, and 1 to 7 parts of additive.

[0033] Specifically, the photocurable liquid phase composition for wafer thinning provided by this invention can form a film layer through photocuring. It is suitable for grinding and etching semiconductor wafers, as well as acid etching, grinding, and cutting processes of objects such as tempered glass. During these processes, the composition can temporarily coat and protect the substrate surface, effectively preventing wafer warping, resulting in a thinner wafer after grinding, and exhibiting uniform and stable overall properties. The formed temporary protective film is easy to peel off, leaves no residue after peeling, and has strong filling capacity, without affecting the reduction of wafer thickness. Furthermore, the temporary protective film has good flatness, allowing it to easily flow into gaps even on complex substrates. Simultaneously, the temporary protective film has strong adhesion to the substrate, preventing foreign matter from entering between the substrate and the protective layer. It also possesses excellent physicochemical properties, ensuring that the substrate will not deform or be damaged due to uneven stress during processing, which is beneficial for further reducing the thickness of the wafer back-grinding. In addition, the protective film of this invention has the advantage of easy chemical peeling; it can be removed with an alkaline NaOH solution after processing, leaving no residue or contaminants on the surface.

[0034] Furthermore, the additives include imidazole compounds containing pyridine groups; the structural formula of the imidazole compounds containing pyridine groups is:

[0035]

[0036] R is selected from One of them.

[0037] Specifically, this invention introduces an additive containing pyridine and imidazole functional groups. Pyridine itself possesses certain semiconductor properties, thus maintaining the electrical performance of the semiconductor substrate during the thinning process. Pyridine also synergistically enhances the peelability of the protective film by interacting with imidazole in the protective film, ensuring successful peeling even under complex conditions such as high temperatures. Furthermore, imidazole exhibits thermal stability and antioxidant capacity, making it suitable not only for the high-temperature environments that may occur during semiconductor substrate thinning but also effectively inhibiting oxidation reactions, preventing the metal layer on the substrate surface from being oxidized during the thinning process, thereby maintaining the electrical performance of the substrate. Additionally, the additive contains amine groups, which have high reactivity and can chemically bond with the functional groups on the semiconductor substrate surface, thereby enhancing the adhesion between the protective film and the substrate. Simultaneously, the introduction of amine groups increases the flexibility of the temporary protective film, allowing it to better adapt to unevenness on the substrate surface and reducing damage caused by mechanical stress. The amine groups can also participate in cross-linking reactions through photocuring to form a network structure, thereby improving the thermal stability of the temporary protective film.

[0038] In one specific embodiment, the photocurable liquid phase composition comprises, by weight parts: 55 to 65 parts of acrylic oligomer, 25 to 35 parts of acrylic monomer, 3 to 7 parts of photoinitiator, 1 to 3 parts of surfactant, and 2 to 6 parts of additive.

[0039] In one specific embodiment, the acrylic oligomer is prepared by reacting a monomer with an anhydride functional group with a monofunctional acrylic monomer or a polyfunctional acrylic monomer.

[0040] In one specific embodiment, the monomer with the anhydride functional group includes phthalic anhydride or tetrahydrophthalic anhydride.

[0041] In one specific embodiment, the monofunctional acrylic monomer includes at least one of 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.

[0042] In one specific embodiment, the multifunctional acrylic monomer includes at least one of trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA).

[0043] In one specific embodiment, the acrylic monomer includes at least one of 2-hydroxyethyl acrylate, TMPTA, and 2-hydroxyethyl methacrylate.

[0044] In one specific embodiment, the photoinitiator includes at least one of I-184C (chemical name 1-hydroxycyclohexylphenyl ketone) and I-907 (chemical name 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone).

[0045] In one specific embodiment, the surfactant includes at least one of octadecylamine polyoxyethylene ether acrylate, sodium vinyl sulfonate, and reactive polyether-modified polysiloxane.

[0046] In one specific embodiment, the photocurable liquid phase composition further includes 1 to 7 parts by weight of an additive; the additive includes at least one selected from leveling agents, antistatic agents, defoamers, and dispersants.

[0047] In one specific embodiment, the leveling agent includes at least one of polyether-modified polysiloxane, fluorinated polyacrylate, and polyethylene glycol diacrylate; the antistatic agent includes at least one of phosphate acrylate and polyethylene glycol acrylate; the defoamer includes at least one of polysiloxane compound, polyethylene glycol diacrylate, and acrylic acid-functionalized polysiloxane; and the dispersant includes at least one of quaternary ammonium salt-modified acrylate and acrylic acid-styrene copolymer.

[0048] The present invention also discloses a method for forming a temporary protective film for backside thinning of a semiconductor substrate using the above-described photocurable liquid phase composition, such as... Figure 1 As shown, it includes the following steps:

[0049] (1) Mix acrylic oligomer, acrylic monomer, photoinitiator, surfactant and additive to obtain a photocurable liquid phase composition;

[0050] (2) The photocurable liquid phase composition is coated on the bump surface of the wafer and attached to the upper surface of the inner perforated plate of the grinding jig, and then photocured to form a temporary protective film to obtain a photocurable wafer.

[0051] (3) The back side of the photocurable wafer is thinned using a grinding equipment and a DAF film is attached. Then, an alkaline solution is used for chemical treatment to separate the temporary protective film from the grinding fixture, thus completing the back side thinning process and obtaining the thinned wafer.

[0052] In one specific embodiment, the alkaline solution is a NaOH solution with a temperature of 80°C and a concentration of 20%.

[0053] In one specific embodiment, the photocuring method includes ultra-high pressure mercury lamp curing or LED ultraviolet light curing.

[0054] In one specific embodiment, the photocuring time is 10s to 30s.

[0055] In one specific embodiment, the thickness deviation of the temporary protective film is less than 5 μm, which is less than the thickness of the protective film after UV exposure, which is 100 μm. The surface smoothness of the protective film is good, which is beneficial to subsequent processing.

[0056] Specifically, this invention proposes a novel semiconductor bump wafer backside thinning process. This process uses photopolymerization to cure the wafer protective liquid phase composition, resulting in good adhesion to the wafer surface after curing and effective protection of the wafer. After grinding, a thinner DIE can be obtained. Furthermore, this process uses an inorganic alkaline solution as the stripping liquid. Before stripping, the wafer is chemically treated with NaOH solution, simplifying the subsequent stripping process and eliminating stripping residue.

[0057] The following are specific embodiments.

[0058] Example 1

[0059] 1. Take 1 mol of phthalic anhydride and 0.5 mol of 2-hydroxyethyl acrylate and add them to a 500 ml inclined four-necked round bottom flask. Set the heating mantle temperature to 90 °C, install a stirrer, and stir to dissolve under nitrogen purging. After dissolution, keep at 90 °C for 10 min, add 5 ml of triethylamine as a catalyst, and stir for 3 h to synthesize acrylic acid oligomers.

[0060] 2. Take 60 parts of acrylic oligomer, 20 parts of 2-hydroxyethyl acrylate, 10 parts of TMPTA, 1 part of surfactant octadecylamine polyoxyethylene ether acrylate, 5 parts of photoinitiator I-184C, and 4 parts of additives, add them to a 500ml glass beaker and mix and stir to prepare a photocurable liquid phase composition; wherein, the structural formula of the additive is (CAS No.: 39588-26-6):

[0061]

[0062] 3. After coating the prepared photocurable liquid phase composition onto the bumping wafer, the wafer is placed on a grinding fixture and photocured by UV irradiation. The back side of the wafer is thinned using a grinding device, and then a DAF film is attached.

[0063] 4. Heat a 20% NaOH solution to 80°C and use chemical treatment to separate the UV-cured film from the grinding fixture to complete the back-side thinning process.

[0064] Example 2

[0065] 1. Take 1 mol of tetrahydrophthalic anhydride and 0.5 mol of 2-hydroxyethyl acrylate and add them to a 500 ml inclined four-necked round bottom flask. Set the heating mantle temperature to 90 °C, install a stirrer and stir to dissolve. After dissolution, keep the temperature at 90 °C for 10 min, add 5 ml of triethylamine as a catalyst, stir for 3 h, and synthesize acrylic acid oligomers.

[0066] 2. Take 60 parts of acrylic oligomer, 20 parts of 2-hydroxyethyl acrylate, 10 parts of TMPTA, 1 part of surfactant octadecylamine polyoxyethylene ether acrylate, 5 parts of photoinitiator I-184C, and 4 parts of additives, add them to a 500ml glass beaker and mix and stir to prepare a photocurable liquid phase composition; wherein, the structural formula of the additive is (CAS No.: 43170-96-3):

[0067]

[0068] 3. After coating the prepared photocurable liquid phase composition onto the bumping wafer, the wafer is placed on a grinding fixture and photocured by UV irradiation. The back side of the wafer is thinned using a grinding device, and then a DAF film is attached.

[0069] 4. Heat a 20% NaOH solution to 80°C and use chemical treatment to separate the UV-cured film from the grinding fixture to complete the back-side thinning process.

[0070] Example 3

[0071] 1. Add 1 mol of phthalic anhydride and 0.5 mol of 2-hydroxyethyl methacrylate to a 500 ml inclined four-necked round-bottom flask. Set the heating mantle temperature to 90 °C, install a stirrer and stir. After dissolution, keep the temperature at 90 °C for 10 min, add 5 ml of triethylamine as a catalyst, and stir for 3 h to synthesize acrylic acid oligomers.

[0072] 2. Take 60 parts of acrylic oligomer, 20 parts of 2-hydroxyethyl acrylate, 10 parts of TMPTA, 1 part of surfactant octadecylamine polyoxyethylene ether acrylate, 5 parts of photoinitiator I-184C, and 4 parts of additives, add them to a 500ml glass beaker and mix and stir to prepare a photocurable liquid phase composition; wherein, the structural formula of the additive is (CAS No.: 39588-26-6):

[0073]

[0074] 3. After coating the prepared photocurable liquid phase composition onto the bumping wafer, the wafer is placed on a grinding fixture and photocured by UV irradiation. The back side of the wafer is thinned using a grinding device, and then a DAF film is attached.

[0075] 4. Heat a 20% NaOH solution to 80°C and use chemical treatment to separate the UV-cured film from the grinding fixture to complete the back-side thinning process.

[0076] Example 4

[0077] 1. Add 1 mol of phthalic anhydride and 0.5 mol of 2-hydroxyethyl acrylate to a 500 ml inclined four-necked round-bottom flask. Set the heating mantle temperature to 90 °C, install a stirrer and stir. After dissolution, keep the temperature at 90 °C for 10 min, add 5 ml of triethylamine as a catalyst, and stir for 3 h to synthesize acrylic acid oligomers.

[0078] 2. Take 60 parts of acrylic oligomer, 20 parts of 2-hydroxyethyl methacrylate, 10 parts of TMPTA, 1 part of surfactant octadecylamine polyoxyethylene ether acrylate, 5 parts of photoinitiator I-907, and 4 parts of additives, add them to a 500ml glass beaker and mix and stir to prepare a photocurable liquid phase composition; wherein, the structural formula of the additive is (CAS No.: 39588-26-6):

[0079]

[0080] 3. After coating the prepared photocurable liquid phase composition onto the bumping wafer, the wafer is placed on a grinding fixture and photocured by UV irradiation. The back side of the wafer is thinned using a grinding device, and then a DAF film is attached.

[0081] 4. Heat a 20% NaOH solution to 80°C and use chemical treatment to separate the UV-cured film from the grinding fixture to complete the back-side thinning process.

[0082] Example 5

[0083] The only difference between Example 5 and Example 1 is that the photocurable liquid phase composition includes the following components in parts by weight: 70 parts of acrylic oligomer, 25 parts of 2-hydroxyethyl methacrylate, 15 parts of TMPTA, 5 parts of surfactant octadecylamine polyoxyethylene ether acrylate, 8 parts of photoinitiator I-907, and 7 parts of additives.

[0084] Example 6

[0085] The only difference between Example 6 and Example 1 is that the photocurable liquid phase composition includes the following components in parts by weight: 50 parts of acrylic oligomer, 15 parts of 2-hydroxyethyl methacrylate, 5 parts of TMPTA, 1 part of surfactant octadecylamine polyoxyethylene ether acrylate, 2 parts of photoinitiator I-907, and 1 part of additive.

[0086] Example 7

[0087] The only difference between Example 7 and Example 1 is that the photocurable liquid phase composition further includes 1 part of leveling agent polyether modified polysiloxane, 1 part of antistatic agent polyethylene glycol acrylate, 1 part of defoamer polyethylene glycol diacrylate and 1 part of dispersant quaternary ammonium salt modified acrylate.

[0088] Example 8

[0089] The only difference between Example 8 and Example 1 is that the light curing method is ultra-high pressure mercury lamp curing.

[0090] Comparative Example 1

[0091] 1. Take 1 mol of maleic anhydride and 0.5 mol of 2-hydroxyethyl acrylate and add them to a 500 ml inclined four-necked round bottom flask. Set the heating mantle temperature to 90 °C, install a stirrer and stir. After dissolution, keep it at 90 °C for 10 min, add 5 ml of triethylamine (TEA) as a catalyst, stir for 3 h, and synthesize acrylic acid oligomers.

[0092] 3. Take 40 parts of the polymerized acrylic oligomer, 40 parts of 2-hydroxyethyl acrylate, 15 parts of TMPTA, 6 parts of the surfactant sodium vinyl sulfonate, 1 part of the photoinitiator I-184C, and 8 parts of the additive, add them to a 500ml glass beaker and mix and stir to prepare a photocurable liquid phase composition; wherein, the structural formula of the additive is (CAS No.: 39588-26-6):

[0093]

[0094] 4. After coating the prepared photocurable liquid phase composition onto the Bumping wafer, the wafer is placed on a grinding fixture and photocured by UV irradiation. The back side of the wafer is thinned using a grinding device, and then a DAF film is attached.

[0095] 5. Heat a 20% NaOH solution to 80°C and use chemical treatment to separate the UV-cured film from the grinding fixture to complete the back-side thinning process.

[0096] Comparative Example 2

[0097] 1. Take 1 mol of maleic anhydride and 0.5 mol of 2-hydroxyethyl methacrylate and add them to a 500 ml inclined four-necked round bottom flask. Set the heating mantle temperature to 90 °C, install a stirrer and stir. After dissolution, keep the temperature at 90 °C for 10 min, add 5 ml of TEA as a catalyst, and stir for 3 h to synthesize acrylic acid oligomers.

[0098] 3. Take 40 parts of the polymerized acrylic oligomer, 40 parts of 2-hydroxyethyl acrylate, 15 parts of TMPTA, 6 parts of the surfactant sodium vinyl sulfonate, 1 part of the photoinitiator I-184C, and 8 parts of the additive, add them to a 500ml glass beaker and mix and stir to prepare a photocurable liquid phase composition; wherein, the structural formula of the additive is (CAS No.: 39588-26-6):

[0099]

[0100] 4. After coating the prepared photocurable liquid phase composition onto the Bumping wafer, the wafer is placed on a grinding fixture and photocured by UV irradiation. The back side of the wafer is thinned using a grinding device, and then a DAF film is attached.

[0101] 5. Heat a 20% NaOH solution to 80°C and use chemical treatment to separate the UV-cured film from the grinding fixture to complete the back-side thinning process.

[0102] Comparative Example 3

[0103] The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not contain any additives.

[0104] Comparative Example 4

[0105] The only difference between Comparative Example 4 and Example 2 is that Comparative Example 4 does not contain any additives.

[0106] Comparative Example 5

[0107] The only difference between Comparative Example 5 and Example 1 is that the additive in Comparative Example 5 is 0.5 parts by mass in the composition.

[0108] Comparative Example 6

[0109] The only difference between Comparative Example 6 and Example 1 is that the additive in Comparative Example 6 is 9 parts by mass in the composition.

[0110] Comparative Example 7

[0111] The only difference between Comparative Example 7 and Example 2 is that the additive in Comparative Example 7 is 0.5 parts by mass in the composition.

[0112] Comparative Example 8

[0113] The only difference between Comparative Example 8 and Example 2 is that the additive in Comparative Example 8 is 9 parts by mass in the composition.

[0114] Comparative Example 9

[0115] This comparative example uses existing conventional PET wafer back-grinding protective tape.

[0116] Test case

[0117] The wafers obtained in Examples 1-8 and Comparative Examples 1-9 were subjected to performance testing. The specific testing methods or standards are as follows:

[0118] (1) Analysis of residue after stripping: Test method: Chemically treat the wafer and protective film with 80℃, 20% NaOH solution and strip the protective film. Place the wafer with the protective film stripped on the table and observe with the naked eye whether there are any visible white / transparent spots, flocculent matter or film residue on the surface. Test standard: ≤2 particles per square centimeter is considered as no residue.

[0119] (2) Detection of bubble formation. Test method: Inspect the center and edges of the protective film using a microscope. Test standard: The number of bubbles per wafer ≤ 5, and the maximum diameter < 50 μm. Bubbles are not allowed in the active area (central region) of the chip.

[0120] (3) Test the peel strength (kgf / 25mm) before immersion in NaOH solution. Test method: Peel the back-grinding protective film directly from the wafer and cut it into samples 25mm wide and 300mm long. Use a 2kg pressure roller to attach the sample to the test plate to obtain a sample for testing the peel strength before immersion in NaOH solution. The protective film is peeled from the wafer surface at a 180° angle. Refer to the test standard: JIS2107 standard.

[0121] (4) Detect warpage deviation (wafer warpage degree) (um). Test method: chemically treat the wafer and protective film with 80℃, 20% NaOH solution. Place the wafer with the protective film removed on the table and measure the wafer thickness after removing the back-grinding protective film with a thickness gauge. The maximum value of the thickness minus the minimum value of the thickness is the warpage deviation.

[0122] (5) Test the maximum operating temperature (°C). Test method: Cut the wafer back-grinding protective film directly peeled off into small pieces of 5cm×5cm. Set up several control groups, with three pieces in each group. Start testing from 80°C, increasing the temperature by 1°C each time. After the oven temperature stabilizes, place one group of samples in the oven and keep them warm for 30 minutes. Check the condition of the protective film. Test standard: If there is no color change, no bubbles, no curling, no melting, etc., continue to increase the temperature for testing until color change, bubbles, curling, melting, etc. appear.

[0123] (6) Test the UV curing time (seconds). Test method: Record the time required for Examples 1-8 and Comparative Examples 1-9 to be completely cured by UV irradiation, which is the UV curing time.

[0124] (7) Wafer thickness after grinding (µm), test method: measured by a thickness gauge and averaged.

[0125] (8) Total thickness variation (TTV, μm), test method: the maximum value of the wafer thickness after grinding is obtained by subtracting the minimum value.

[0126] The results are shown in Table 1.

[0127] Table 1 Comparison of the effects of Examples 1-8 and Comparative Examples 1-7

[0128]

[0129]

[0130] As shown in Table 1, the peel strength data before immersion demonstrates that the photocurable liquid phase composition of this invention can perfectly flow into the wafer surface, and no bubbles are generated after photocuring, effectively covering the wafer. Chemical treatment of the wafer with NaOH solution simplifies the subsequent peeling process and eliminates peeling residue. Furthermore, the curing time of this invention is significantly shorter than that of the comparative example, effectively improving production efficiency. Most importantly, the wafer thickness after grinding is significantly reduced compared to the comparative example, and the wafer warpage is also significantly better, ensuring wafer quality and allowing for the fabrication of thinner DIEs. Therefore, compared to existing wafer protection liquid phase compositions, this invention provides better wafer protection, not only eliminating peeling residue but also enabling the manufacture of thinner DIEs, thus possessing broader application prospects.

[0131] In summary, the wafer protection liquid phase composition and semiconductor bump wafer backside thinning process of the present invention are cheaper, easier to operate, provide better wafer protection, are easy to peel off and leave no residue after peeling, and can promote the widespread use of thinner DIEs.

[0132] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A photocurable liquid phase composition for wafer thinning, characterized in that, The components include the following parts by mass: 50 to 70 parts of acrylic oligomer, 20 to 40 parts of acrylic monomer, 2 to 8 parts of photoinitiator, 1 to 5 parts of surfactant and 1 to 7 parts of additive; The additives include imidazole compounds containing pyridine groups; The structural formula of the imidazole compound containing the pyridine group is: ； R is selected from either -NH2 or -CH2-CH2-NH2; The acrylic oligomers were obtained by reacting an anhydride-functionalized monomer with a monofunctional acrylic monomer. The monomers of the anhydride functional group are selected from phthalic anhydride or tetrahydrophthalic anhydride. The monofunctional acrylic monomer is selected from 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

2. The photocurable liquid phase composition for wafer thinning according to claim 1, characterized in that, The photocurable liquid phase composition comprises, by mass parts: 55 to 65 parts of acrylic oligomer, 25 to 35 parts of acrylic monomer, 3 to 7 parts of photoinitiator, 1 to 3 parts of surfactant, and 2 to 6 parts of additive.

3. The photocurable liquid phase composition for wafer thinning according to claim 1, characterized in that, The photoinitiator includes at least one of I-184C and I-907.

4. The photocurable liquid phase composition for wafer thinning according to claim 1, characterized in that, The photocurable liquid phase composition further includes 1 to 7 parts by weight of additives; The additives include at least one of leveling agents, antistatic agents, defoamers, and dispersants.

5. A method for forming a temporary protective film for backside thinning of a semiconductor substrate using a photocurable liquid phase composition as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) The acrylic oligomer, acrylic monomer, photoinitiator, surfactant and additives are mixed to obtain a photocurable liquid phase composition; (2) The photocurable liquid phase composition is coated on the bump surface of the wafer and attached to the upper surface of the inner perforated plate of the grinding jig, and photocured to form a temporary protective film to obtain a photocurable wafer; (3) The back side of the photocurable wafer is thinned using a grinding equipment and a DAF film is attached. Then, an alkaline solution is used for chemical treatment to separate the temporary protective film from the grinding fixture, thus completing the back side thinning process and obtaining the thinned wafer.

6. The method for forming a temporary protective film for backside thinning of a semiconductor substrate using a photocurable liquid phase composition according to claim 5, characterized in that, The light curing methods include ultra-high pressure mercury lamp curing or LED ultraviolet light curing.

7. The method for forming a temporary protective film for backside thinning of a semiconductor substrate using a photocurable liquid phase composition according to claim 5, characterized in that, The photocuring time is 10s~30s.

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