Surface protective film

Abstract

This specification relates to a surface protection film having an intrusion depth of 3.0 μm or more, as measured by a specific method, wherein the surface protection film can minimize the undisrupted rate of the wafer.

Description

Technical Field

[0001] The present invention relates to a surface protection film, and more particularly, to a surface protection film for reducing the uncut rate in stealth dicing operations in the semiconductor field.

[0002] This application claims the benefit of the filing dates of Korean Patent Application No. 10-2023-0139225, filed with the Korean Intellectual Property Office on October 18, 2023, and Korean Patent Application No. 10-2024-0015148, filed with the Korean Intellectual Property Office on January 31, 2024, and all of its contents are incorporated herein.

Background Art

[0003] A surface protection film is a film used to protect a wafer in a semiconductor wafer processing step as a laminate having a multilayer structure including a base film, an adhesive film, and the like.

[0004] Specifically, during the processing of a semiconductor wafer, a surface protection sheet is attached to prevent damage to the circuit formation surface during the back grinding process of the back surface of the circuit formation surface.

[0005] However, before the back grinding process (back grinding process), a stealth dicing process is applied, and this stealth dicing process is an operation in which cracks (fractures) occur at the stealth dicing site and are separated into individual chips when the back grinding process is applied.

[0006] However, as the thickness of the wafer gradually decreases and the circuit surface becomes more complex, there is a problem that the uncut rate increases without being separated into individual pieces.

[0007] Therefore, research is needed to solve the above problems.

Summary of the Invention

Problems to be Solved by the Invention

[0008] To solve the aforementioned problems, the inventors discovered that by applying nanoindentation technology to the adhesive film of a surface protective film, a reduction in the unfragmentation rate can be confirmed in advance. This confirmed that the developed method can effectively reduce the unfragmentation rate when the indentation depth is 3.0 μm or more under specific conditions.

[0009] Therefore, this specification aims to provide a surface protective film to which the above-described features are applied. [Means for solving the problem]

[0010] One embodiment of this specification provides a surface protection film comprising a base film and an adhesive film on one side of the base film, wherein the adhesive film has an indentation depth of 3.0 μm or more as measured by the method 1 described below.

[0011] [Method 1] The aforementioned indentation depth refers to the depth measured when, with a glass substrate provided on the opposite side of the surface of the base film that the adhesive film is in contact with, a nanoindenter equipped with a hemispherical ball tip with a diameter of 2 mm at one end is applied to the adhesive film at an indentation speed of 0.25 mN / sec with a force of 5 mN, and the force of 5 mN is maintained for 5 seconds. [Effects of the Invention]

[0012] The surface protective film according to the embodiment of the present invention offers the advantage of significantly reducing the undisintegrated rate and minimizing defects. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of the surface protection film. [Figure 2] This is a schematic diagram of the surface protection film. [Figure 3] This is a schematic diagram illustrating the mechanism of fragmentation that occurs during grinding. [Figure 4] This is a schematic diagram illustrating the mechanism of fragmentation that occurs during grinding. [Figure 5] It is a schematic diagram of the fracture generation mechanism during grinding.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, this specification will be described in more detail.

[0015] <Definition> Before describing the present invention, first, several terms will be defined.

[0016] In this specification, when a certain part "includes" a certain component, it means that, unless otherwise specified, it does not exclude other components, but may further include other components.

[0017] In this specification, "p to q" means a range of "p or more and q or less".

[0018] In this specification, (meth)acrylate includes both acrylate and methacrylate.

[0019] In this specification, when a polymer includes a certain monomer as a monomer unit, it means that the monomer participates in a polymerization reaction and is included as a repeating unit in the polymer. In this specification, when a polymer includes a monomer, it is interpreted in the same way as when the polymer includes the monomer as a monomer unit.

[0020] In this specification, unless otherwise specified as "homopolymer", the term "polymer" is understood to be used in a broad sense including copolymers.

[0021] In this specification, the "copolymer" may be a block copolymer, an alternating copolymer, a random copolymer, or a graft copolymer, and is not particularly limited.

[0022] In this specification, the "monomer unit" means the state in which the compound polymerizes and is bonded in the polymer.

[0023] In this specification, the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) are the molecular weights in terms of polystyrene measured by Gel Permeation Chromatography (GPC) using various monodisperse polystyrene polymers (standard samples) of different degrees of polymerization commercially available for molecular weight measurement as the standard substances. In this specification, the molecular weight means the weight-average molecular weight unless otherwise specified.

[0024] The weight-average molecular weight is one of the average molecular weights in which the molecular weight is not uniform and the molecular weight of a certain polymer substance is used as a reference, and is a value obtained by averaging the molecular weights of the component molecular species of a polymer compound having a molecular weight distribution by weight fraction.

[0025] The weight-average molecular weight can be measured by GPC (Gel Permeation Chromatography) analysis.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described here.

[0027] <Surface protection film> The surface protection film according to an embodiment of this specification is characterized in that, as described above, the indentation depth measured by the method 1 is 3.0 μm or more.

[0028] Specifically, in the method 1, with a glass substrate provided on the opposite surface of the surface of the base film to which the adhesive film is in contact, the adhesive film is targeted, and a special nanoindenter is used to measure the indentation depth at a specific indentation speed and force.

[0029] The surface film according to the above-described embodiment allows for the determination of the unfragmentation rate in advance by measuring the press-fitting depth, thereby improving the unfragmentation rate and effectively reducing the chip defect rate.

[0030] In another embodiment of the present invention, the adhesive film may be converted to an indentation depth ratio of 2% or more, 2.3% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, or 15% or more relative to the total thickness of the adhesive film when measured by Method 1.

[0031] Figures 3 to 5 illustrate the chip fragmentation mechanism. Figure 3 is a schematic diagram of stealth dicing and grinding, illustrating the process in which a surface protective film contacts one side of a wafer that has undergone stealth dicing, and grinding is performed on the back side of the contacting surface. Figure 4 illustrates the process in which compression occurs in the wafer portion where grinding is performed, and compression does not occur in the wafer portion where grinding is not performed (uncompressible region), resulting in compression deformation relative to the entire wafer and causing fragmentation. Figure 5 illustrates the fragmentation that occurs between the compressed region and the uncompressible region.

[0032] According to one embodiment of this specification, a base film and an adhesive film are included on one side of the base film, and in Figure 1, the adhesive film 1 and the base film 2 are sequentially laminated.

[0033] According to one embodiment of this specification, the adhesive film may include an adhesive composition or a cured product thereof.

[0034] In this specification, the adhesive composition may mean a homogeneous mixture containing two or more substances as a composition in its pre-curing state.

[0035] In this specification, the term "cured product" may mean a product cured by heat and / or light (UV).

[0036] In one embodiment of this specification, the adhesive composition may include a (meth)acrylate resin and a polyvalent isocyanate.

[0037] In this specification, "(meth)acrylate" is used as a general term for acrylates and methacrylates.

[0038] In one embodiment of this specification, the (meth)acrylate resin may include a copolymer of an alkyl (meth)acrylate monomer and a monofunctional or polyfunctional (meth)acrylate monomer.

[0039] In one embodiment of this specification, the monofunctional or polyfunctional (meth)acrylate monomer may include a hydroxyl group-containing (meth)acrylate monomer and may also include a polyhydric isocyanate in an amount of 60 mol% to 80 mol% relative to the total amount of the hydroxyl group-containing (meth)acrylate monomer.

[0040] In this specification, hydroxyl group-containing (meth)acrylate means a substance in which a hydroxyl group is linked to a bondable site in (meth)acrylate.

[0041] In one embodiment of this specification, the content of the hydroxyl group-containing (meth)acrylate can be adjusted as needed to the amount necessary to form (meth)acrylate units at both ends of the oligomer.

[0042] Examples of the hydroxyl group-containing (meth)acrylates used herein include, but are not limited to, 2-HEA, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0043] When the aforementioned composition and content are met, the adhesive film of the surface protection film (especially adhesive tape for semiconductor wafer processing) can achieve excellent properties such as unevenness absorption and warpage resistance, and the content-dependent melting temperature (Tm) of the polyvalent isocyanate can be controlled.

[0044] In one embodiment of this specification, the adhesive composition further comprises an additive, which may be selected from the group consisting of polymerization initiators, curing agents, and molecular weight modifiers.

[0045] In this specification, the polymerization initiator may be used in an amount of 0.01 to 2 parts by weight per 100 parts by weight of the adhesive composition, but is not particularly limited thereto.

[0046] In this specification, the polymerization initiator may be a thermal polymerization initiator, a photopolymerization initiator, or a combination thereof.

[0047] The thermal polymerization initiator is not particularly limited as long as it is known in the industry, but may be selected from peroxide-based initiators, azo-based initiators, etc., and may be azobisisobutyronitrile (AIBN), for example.

[0048] The aforementioned photopolymerization initiator is not particularly limited as long as it is known in the industry.

[0049] In this specification, molecular weight modifiers may be referred to as polymerization inhibitors, and are substances that can be used as chain transfer agents during radical polymerization of polymers, and can adjust molecular weight, particle size, etc., depending on the concentration. Examples of molecular weight modifiers include, but are not limited to, n-DDM (N-Dodecyl mercaptan) and S,S-dibenzyl trithiocarbonate.

[0050] In one embodiment of this specification, the weight-average molecular weight (MW) of the (meth)acrylate resin may be 500,000 g / mol or more and 5,000,000 g / mol or less.

[0051] In one embodiment of this specification, the thickness of the adhesive film may be 10 μm or more and 40 μm or less.

[0052] In other embodiments of this specification, the thickness of the adhesive film may be 15 μm or more, or 20 μm or more, and 35 μm or less, or 30 μm or less.

[0053] When the thickness of the adhesive film falls within the aforementioned range, the rate of air bubble generation within the adhesive film can be reduced, resulting in excellent adhesive strength when adhering to the substrate, no lifting phenomenon, and no dents.

[0054] According to one embodiment of the present invention, the glass transition temperature (Tg) of the (meth)acrylate resin may be -80°C or higher and -30°C or lower.

[0055] Specifically, the glass transition temperature of the (meth)acrylate resin may be -80°C or higher and -30°C or lower, and more specifically, -75°C or higher and -40°C or lower.

[0056] Surface protection films using (meth)acrylate resins having the aforementioned glass transition temperature range can exhibit excellent chip-breaking effects and can achieve suitable physical properties for use as adhesive films for semiconductor surface protection in the future.

[0057] The content of the curing agent is 0.1 parts by weight or more and 1.5 parts by weight or less per 100 parts by weight of (meth)acrylate resin.

[0058] Specifically, the content of the curing agent may be 0.1 parts by weight or more and 1.5 parts by weight or less, 0.2 parts by weight or more and 1.2 parts by weight or less, or 0.3 parts by weight or more and 1.0 part by weight or less per 100 parts by weight of (meth)acrylate resin.

[0059] By having the aforementioned range, the surface protection film can achieve high peeling strength of the adhesive film before light irradiation, thereby fully exhibiting its semiconductor surface protection function during grinding and providing excellent chip breakage performance during the grinding process.

[0060] According to one embodiment of the present invention, the (meth)acrylate resin contained in the adhesive film-forming composition (adhesive composition) may be a reaction product of a (meth)acrylate copolymer and an isocyanate group-containing (meth)acrylate. The adhesive composition may further contain a polymerization initiator and a curing agent as additives.

[0061] According to one embodiment of the present invention, the weight-average molecular weight of the (meth)acrylate resin may be about 300,000 g / mol to about 1,500,000 g / mol.

[0062] Having a weight-average molecular weight within the aforementioned range ensures that the adhesive composition has a suitable viscosity and that uniform coating properties can be ensured during the formation of the adhesive film in the manufacturing process of the surface protective film.

[0063] According to one embodiment of the present invention, the (meth)acrylate copolymer may be copolymerized from a mixture of (meth)acrylate monomers containing an alkyl group (meth)acrylate monomer and a hydroxyl group (meth)acrylate monomer.

[0064] According to one embodiment of the present invention, the (meth)acrylate copolymer may be copolymerized from a mixture of (meth)acrylate monomers comprising a C5-C10 alkyl group-containing first (meth)acrylate monomer; a C1-C4 alkyl group-containing second (meth)acrylate monomer; and a hydroxyl group-containing third (meth)acrylate monomer.

[0065] Specifically, the C5-C10 alkyl-containing first (meth)acrylate monomer may contain at least one of the following: n-pentyl(meth)acrylate, isopentyl(meth)acrylate, n-hexyl(meth)acrylate, isohexyl(meth)acrylate, n-heptyl(meth)acrylate, isoheptyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, ethylhexyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, and isodecyl(meth)acrylate.

[0066] Specifically, the C1-C4 alkyl-containing secondary (meth)acrylate monomer may contain at least one of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and t-butyl (meth)acrylate.

[0067] Specifically, the hydroxyl group-containing third (meth)acrylate monomer may contain at least one of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, and 2-hydroxypropylene glycol (meth)acrylate.

[0068] According to one embodiment of the present invention, the (meth)acrylate monomer mixture may contain the first (meth)acrylate monomer in an amount of 50 to 75 parts by weight, the second (meth)acrylate monomer in an amount of 0 to 15 parts by weight, and the third (meth)acrylate monomer in an amount of 25 to 45 parts by weight.

[0069] According to one embodiment of the present invention, the isocyanate group-containing (meth)acrylate may contain at least one of 2-methacryloyloxyethyl isocyanate (MOI) and 2-acryloyloxyethyl isocyanate (AOI).

[0070] According to one embodiment of the present invention, the content of the isocyanate group-containing (meth)acrylate may be 30 mol% to 70 mol% or 35 mol% to 65 mol% based on 100 mol% of the hydroxyl group-containing third (meth)acrylate monomer. When the content is within the above range, the surface protective film can undergo a sufficient crosslinking reaction upon light irradiation, thereby reducing its peeling strength.

[0071] According to one embodiment of the present invention, the adhesive film has a thickness of 10 μm or more and 30 μm or less. Specifically, the adhesive film may have a thickness of 15 μm or more and 35 μm or less, or 20 μm or more and 30 μm or less. Having a thickness within the above range allows the semiconductor surface protection tape to maintain adhesive strength with the adherend.

[0072] According to one embodiment of the present invention, the adhesive film may have a peel force of 1000 gf / inch or more on the wafer surface at 25°C, or a peel force of 30 gf / inch or less on the wafer surface at 25°C after irradiation with light of 0.5 J energy. Having a peel force on the wafer surface within the range described above, the surface protection film adheres well to the semiconductor surface during grinding, effectively preventing damage and deformation of semiconductor circuits, etc. After grinding, when peeling off the surface protection film, the peel force is reduced by light irradiation, allowing it to be easily peeled off from the semiconductor surface.

[0073] According to one embodiment of the present invention, the adhesive film may have a peeling force of 1000 gf / inch or more on the wafer surface. Alternatively, the peeling force on the wafer surface after light irradiation may be 30 gf / inch or less. Having a peeling force within the above range allows the adhesive film to fully perform its function of protecting the semiconductor surface during grinding, and after grinding, the peeling force decreases due to light irradiation, allowing it to be easily peeled off without damaging the semiconductor surface.

[0074] In one embodiment of this specification, the base film may be selected from the group consisting of polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyolefin film, polyvinyl chloride film, polyurethane film, ethylene-vinyl acetate copolymer film, ethylene-alkyl acrylate copolymer film, and combinations thereof, but is not particularly limited as long as it corresponds to a rigid base material, and further examples include polyester such as fully aromatic polyester, polyamide, polyimide polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially oriented polypropylene, and the like.

[0075] In one embodiment of this specification, a hard coating layer may be further included on the surface of the base film opposite to the surface in contact with the adhesive film. Referring to Figure 2, the adhesive film 1, the base film 2, and the hard coating layer 3 are sequentially laminated.

[0076] A surface protection film according to one embodiment of the present invention, further provided with a hard coating layer, can prevent the substrate film from being contaminated and / or damaged by external factors, and can be attached to the surface of a wafer to protect the surface of the substrate film until use.

[0077] In one embodiment of this specification, a release film may be further included on the side of the adhesive film opposite to the side in contact with the base film. Referring to Figure 2, a release film 4 is laminated on the side of the adhesive film 1 opposite to the side in contact with the base film 2.

[0078] A surface protection film according to one embodiment of the present invention, further provided with a release film, can prevent the adhesive film from being contaminated and / or damaged by external factors, and can be attached to the surface of a wafer and protect the surface of the adhesive film until use.

[0079] In one embodiment of the present invention, the release film may be a polyethylene terephthalate film, a polyolefin film, an ethylene vinyl acetate film, a polybutylene terephthalate film, a polypropylene film, or a polyethylene film, but the type of release film is not limited.

[0080] In this specification, the base film 2 may be treated with an antistatic agent.

[0081] In this specification, the thickness of the base film 2 is 25 μm or more, or 50 μm or more, and may be 150 μm or less, or 125 μm or less.

[0082] When the thickness of the base film 2 falls within the aforementioned range, the laminated surface protection film 100 has the characteristic of being able to be made into a thin film, and has the characteristic of being able to sufficiently protect the adherend from external impact when applied to subsequent processes.

[0083] Referring to Figure 2, the surface protective film 100 is laminated in the order of the adhesive film 1 and the base film 2, and the release film 4 is laminated on the side of the adhesive film 1 opposite to the base film 2.

[0084] In this specification, the release film may be a hydrophobic film, and it refers to a transparent layer that is attached to one side of the adhesive film and is a layer for protecting a very thin adhesive sheet. A film with excellent mechanical strength, thermal stability, moisture shielding properties, isotropy, etc. may be used. For example, acetate-based films such as triacetylcellulose (TAC), polyester-based films, polyethersulfone-based films, polycarbonate-based films, polyamide-based films, polyimide-based films, polyolefin-based films, cycloolefin-based films, polyurethane-based films, and acrylic resin films may be used, but are not limited to these as long as they are commercially available silicone-treated release sheets. The release film can be completely removed when applied to process surface protection applications.

[0085] In this specification, the thickness of the release film is 10 μm or more, 12 μm or more, or 15 μm or more, and may be 100 μm or less, 75 μm or less, or 50 μm or less.

[0086] Referring to Figures 1 and 2, the surface of the base film 2 that comes into contact with the adhesive film 1 may further include an antistatic layer.

[0087] In this specification, the term "antistatic layer" means a layer intended to suppress the generation of static electricity.

[0088] By providing the adhesive film 1 on one side of the antistatic layer, the cumulative amount of static electricity can be reduced. Furthermore, because the surface resistance of the adhesive film 1 is reduced, the generation of static electricity on the surface of the adhesive film can be further reduced when peeling the protective layer from the surface protective film 100.

[0089] Therefore, when removing the protective layer from the surface protective film or peeling the surface protective film from the surface of the adherend in order to attach the adhesive film 1 to the surface of the adherend, it is possible to prevent foreign matter from being attached to the adhesive film or adherend by static electricity. Furthermore, contamination of the adherend surface during the process can be prevented, and the deterioration of the adherend surface properties can be further prevented.

[0090] The antistatic layer may be formed by known methods to achieve the desired effect. For example, the antistatic layer may be formed on one or both sides of the base film by an in-line coating method.

[0091] In the present invention, the antistatic layer may be formed from a suitable antistatic composition, taking into consideration the purpose of this application. For example, the antistatic layer may include, but is not limited to, one selected from the group consisting of acrylic resins, urethane resins, urethane-acrylic copolymers, ester resins, ether resins, amide resins, epoxy resins, and melamine resins, or a mixture thereof.

[0092] As an example, the antistatic layer may contain a conductive material. The conductive material may contain, but is not limited to, a conductive polymer or carbon nanotubes.

[0093] The conductive polymer may, but is not limited to, polyaniline, polypyrrole, polythiophene, derivatives or copolymers thereof.

[0094] The carbon nanotube may have a tubular shape formed by winding a graphite plate-like structure in which hexagonal rings made of six carbon atoms are interconnected. The carbon nanotube has excellent rigidity and electrical conductivity, and when used as an antistatic layer for a surface protective film, it can increase the hardness of the antistatic layer and improve its antistatic function.

[0095] The thickness of the antistatic layer can be appropriately selected as needed, and the thickness of the antistatic layer may be 10 nm or more; or 20 nm or more. In one embodiment, the thickness of the antistatic layer may be 400 nm or less, 300 nm or less, or 100 nm or less. By satisfying the condition that the thickness of the antistatic layer is between 10 nm and 400 nm, excellent coating properties can be obtained for the substrate film.

[0096] <Evaluation Method for Adhesive Films> A method for evaluating an adhesive film according to one embodiment of this specification includes the step of measuring the intrusion depth by the following method 1.

[0097] [Method 1] The aforementioned indentation depth refers to the depth measured when, with a glass substrate provided on the opposite side of the surface of the base film that the adhesive film is in contact with, a nanoindenter equipped with a hemispherical ball tip with a diameter of 2 mm at one end is applied to the adhesive film at an indentation speed of 0.25 mN / sec with a force of 5 mN, and the force of 5 mN is maintained for 5 seconds.

[0098] The measurement method described in Method 1 above can provide the effect of reducing the undivided rate when the indentation depth is 3.0 μm or more, or when the value is converted to an indentation depth ratio of 2% or more, 2.3% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, or 15% or more relative to the total thickness of the adhesive film.

[0099] Furthermore, the matters described above regarding the surface protective film are applicable to this embodiment. [Examples]

[0100] The following examples will be given in detail to illustrate this specification. However, the examples provided herein can be modified in various other forms, and the scope of this specification should not be construed as being limited to the examples described below. The examples provided herein are provided to give a more complete explanation of this specification to a person of average knowledge in the industry.

[0101] <Manufacturing Example> Manufacturing of an adhesive composition containing (meth)acrylate resin Ethylhexyl acrylate (EHA), methyl acrylate (MA), and hydroxyethyl acrylate (HEA) were added to ethyl acetate (EA) in a weight ratio of 65:0:35 (molecular weight 1 million g / mol, MOI modification 50%). Then, azobisisobutyronitrile (AIBN) was added as a thermal polymerization initiator to produce the (meth)acrylate resin of Production Example 1 with a weight-average molecular weight of 1,000,000 g / mol. Its glass transition temperature is shown in Table 1 below.

[0102] In addition, manufacturing examples 2 and 3 were produced according to the composition and content (based on weight ratio) listed in Table 1 below.

[0103] [Table 1]

[0104] Next, 70 mol% MOI (2-methacryloyloxyethyl isocyanate) was added to the HEA, and the mixture was stirred for 24 hours or more to produce an adhesive composition.

[0105] <Examples 1-3, Comparative Examples 1 and 2> Manufacturing of surface protective films To 100 parts by weight of the (meth)acrylate resin solids produced in the above production examples 1 to 3, 0.4 parts by weight of an isocyanate-based curing agent (MHG-80B, Asahi KASEI Co., Ltd.) and 3 parts by weight of a photoinitiator (Irgacure 184) were added as curing agents. Then, methyl ethyl ketone (MEK) solvent was added to bring the solids content to 30%, thereby producing adhesive compositions (compositions for forming adhesive films) in each case.

[0106] Subsequently, the adhesive composition was applied to one side of a base film (PET film) having a thickness of 100 μm, and then dried in an oven at 120°C for 2 minutes to form an adhesive film with a thickness of 25 μm. Next, a release film was laminated to the other side of the adhesive film to produce the surface protection films of Examples 1 to 3 and Comparative Examples 1 and 2 shown in Table 2 below.

[0107] Each of the aforementioned surface protective films was aged in an oven at a temperature of 50°C for at least two days.

[0108] <Example of experiment> 1. Manufacturing of test specimens After cutting the surface protective films of Examples 1-3 and Comparative Examples 1 and 2 into 10cm x 10cm pieces, the release film was removed, and the pieces were fixed onto a glass plate with the exposed adhesive film facing upwards to prepare the test specimens.

[0109] 2. Experimental Example 1: Measurement of Press-In Depth The indentation depth of a test specimen of the surface protective film, fixed onto a glass plate, was measured using a nanoindenter (Helmut Fischer MH-2000).

[0110] The aforementioned press-fitting depth is determined by the following method 1.

[0111] [Method 1] The aforementioned indentation depth refers to the depth measured when, with a glass substrate provided on the opposite side of the surface of the base film that the adhesive film is in contact with, a nanoindenter equipped with a hemispherical ball tip with a diameter of 2 mm at one end is applied to the adhesive film at an indentation speed of 0.25 mN / sec with a force of 5 mN, and the force of 5 mN is maintained for 5 seconds.

[0112] 3. Experimental Example 2: Measurement of Unfraction Rate The surface protective film was attached to the circuit surface of a 12-inch wafer with a thickness of 750 μm on which the circuit was formed.

[0113] After stealth dicing, the wafer was ground until its final thickness was 50 μm, and then the undivided rate was calculated.

[0114] The undissociation rate is measured for each type of film, with the undissociation rate of four wafers measured separately and the average value being used. An average undissociation rate of 0.1% or higher is considered NG, and an average undissociation rate of less than 0.1% is considered OK.

[0115] 4. Experimental Example 3: Measurement of Peeling Force The adhesive film of the aforementioned surface protection film was attached to a stainless steel substrate by moving a 2kg rubber roller back and forth once, and then left at 23°C for 30 minutes or more.

[0116] Next, using a texture analyzer (Stable Micro Systems), the initial peel force (before UV exposure) of the adhesive film of the surface protection film was measured at a peel angle of 180° and a peel speed of 1800 mm / min.

[0117] Next, the adhesive film of the surface protective film was further photocured by irradiating it with light of 0.5 J energy, and the post-UV peel strength was measured.

[0118] The results of Experimental Examples 1-3 are shown in Table 2 below.

[0119] [Table 2]

[0120] According to Table 2, while the surface protection films of Comparative Examples 1 and 2 with an indentation depth of less than 3.0 μm had an unfragmentation rate exceeding 0.15% even at a level of excellent peel strength, the surface protection films of Examples 1 to 3 with an indentation depth of 3.0 μm or more showed an improvement in the unfragmentation rate to less than 0.1%, and were confirmed to have a level of excellent peel strength. This allowed us to confirm the relationship between the indentation depth and the unfragmentation rate measured by the method applying the nanoindentation technique described herein to the adhesive film of the surface protection film (i.e., Method 1), and to confirm that it is useful in improving the unfragmentation rate. [Explanation of symbols]

[0121] 1. Adhesive film 2 ···Base film 3. Hard coating layer 4 ···Release film 100 ···Surface protective film

Claims

1. A base film; and an adhesive film included on one side of the base film, The aforementioned adhesive film is a surface protective film having an indentation depth of 3.0 μm or more, as measured by the following method 1: [Method 1] The aforementioned indentation depth refers to the depth measured when, with a glass substrate provided on the opposite side of the surface of the base film that the adhesive film is in contact with, a nanoindenter equipped with a hemispherical ball tip with a diameter of 2 mm at one end is applied to the adhesive film at an indentation speed of 0.25 mN / sec, and the force of 5 mN is maintained for 5 seconds.

2. The surface protective film according to claim 1, wherein the adhesive film comprises an adhesive composition or a cured product thereof.

3. The surface protective film according to claim 2, wherein the adhesive composition comprises a (meth)acrylate resin and a polyvalent isocyanate.

4. The surface protective film according to claim 3, wherein the glass transition temperature (Tg) of the (meth)acrylate resin is -80°C or higher and -30°C or lower.

5. The surface protective film according to claim 3, wherein the (meth)acrylate resin comprises a copolymer of an alkyl (meth)acrylate monomer and a monofunctional or polyfunctional (meth)acrylate monomer.

6. The monofunctional or polyfunctional (meth)acrylate monomer includes a hydroxyl group-containing (meth)acrylate monomer. The surface protective film according to claim 5, comprising 60 mol% to 80 mol% of a polyhydric isocyanate based on the total amount of the hydroxyl group-containing (meth)acrylate monomer.

7. The adhesive composition further comprises an additive, The surface protective film according to claim 2, wherein the additive is selected from the group consisting of polymerization initiators, curing agents, and molecular weight modifiers.

8. The surface protective film according to claim 3, wherein the weight-average molecular weight (MW) of the (meth)acrylate resin is 500,000 g / mol or more and 5,000,000 g / mol or less.

9. The surface protective film according to claim 1, wherein the thickness of the adhesive film is 10 μm or more and 40 μm or less.

10. The surface protective film according to claim 1, wherein the base film is selected from the group consisting of polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyolefin film, polyvinyl chloride film, polyurethane film, ethylene-vinyl acetate copolymer film, ethylene-alkyl acrylate copolymer film, and combinations thereof.

11. The surface protection film according to claim 1, further comprising a hard coating layer on the surface of the base film opposite to the surface in contact with the adhesive film.

12. The surface protection film according to claim 1, further comprising a release film on the side of the adhesive film opposite to the side of the adhesive film that is in contact with the base film.

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