Adhesive film for back-side grinding of wafers

Abstract

This invention provides an adhesive film used in the back-side grinding (wafer back-side grinding, wafer thinning, or wafer reduction) process to protect the wafer surface. More specifically, this invention provides an adhesive film for wafer back-side grinding that exhibits uniform adhesion and excellent wafer surface protection (buffering effect) during the back-side grinding process where bumps are formed. Simultaneously, it reduces or inhibits the generation of adhesive residues when the adhesive film is removed (peeled off) after back-side grinding, and provides excellent processability.

Description

Technical Field

[0001] This invention relates to adhesive films used in the back-side grinding (wafer back grinding, wafer lapping, or wafer thinning) process to protect the surface of the wafer.

[0002] More specifically, the present invention relates to an adhesive film for back-side grinding of wafers, that is, in the back-side grinding process of wafers with bumps, it has uniform adhesion, excellent bending embedding and excellent wafer surface protection (buffering effect), and at the same time, when the adhesive film is removed (peeled) after back-side grinding, it reduces or inhibits the generation of adhesive residue and has excellent processability. Background Technology

[0003] With the advancement of technology in recent years, there is a demand for miniaturization, high density, and thinning of semiconductor chips. Consequently, wafers also require thinning. A typical method for thinning wafer chips is to reduce the thickness by grinding the back side of the wafer. The grinding process can be tailored to the type or specifications of the electronic device using the semiconductor chip, thereby achieving wafer thinning.

[0004] Since the back-side grinding of semiconductor chip wafers is a process of applying physical impact, in order to protect the wafer surface, the back-side grinding of the wafer is performed with an adhesive film for back-side grinding adhering to it.

[0005] On the circuit formation surface of a semiconductor wafer, not only circuits can be formed, but also bumps and other irregularities with significant height differences can be formed. Due to this bump structure, if a gap is formed between the back-side polishing adhesive film and the irregularities on the circuit formation surface of the semiconductor wafer when the back-side polishing adhesive film is adhered, stress distribution will occur on the surface of the semiconductor wafer when polishing the non-circuit formation surface, which may easily damage the semiconductor wafer.

[0006] Furthermore, after back-side grinding of the wafer, in order to remove the adhesive film used in the back-side grinding process from the wafer surface, energy rays are irradiated to reduce the adhesion and peel it off. In this case, since the irradiated energy rays cannot fully reach the gaps formed by the bump structure, shadowed areas may exist. In these shadowed areas, due to insufficient curing by the energy rays, the peeling force of the adhesive film is reduced, and ultimately, adhesive residue from the adhesive film is prone to remain on the wafer surface, thus hindering processability and ultimately adversely affecting the quality of the fabricated semiconductor chip. Summary of the Invention

[0007] The purpose of this invention is to provide an adhesive film for wafer back-side polishing, which can prevent wafer breakage during the wafer back-side polishing process, especially in the wafer back-side polishing process with bump structures, and minimize residue when removing the adhesive film after the wafer back-side polishing process.

[0008] The purpose of this invention is not limited to the objectives mentioned above. Other objectives and advantages of this invention not mentioned can be understood through the following description and can be more clearly understood through embodiments of this invention. Furthermore, it is understood that the objectives and advantages of this invention can be achieved through the solutions and combinations thereof shown in the claims.

[0009] From the viewpoint of solving the above problems, according to an embodiment of the present invention, an adhesive film for wafer backside polishing can be provided, comprising: a rigid substrate layer having a light scattering pattern formed thereon; a first adhesive layer disposed on the rigid substrate layer; a second adhesive layer disposed on the first adhesive layer; and a third adhesive layer disposed on the second adhesive layer, wherein the second adhesive layer is formed of a second adhesive composition comprising a second (meth)acrylate adhesive resin and an epoxy adhesive resin having a softening point of 30°C to 70°C.

[0010] Based on 100 parts by weight of the above-mentioned second adhesive composition, it may contain 5 to 45 parts by weight of the above-mentioned epoxy adhesive resin.

[0011] The total transmittance of the bonding film used for back-side grinding of the aforementioned wafer can be above 70%, and the diffuse transmittance can be above 6%.

[0012] The shear storage modulus of the second adhesive layer at a temperature of 23°C can be 0.1 MPa to 10 MPa.

[0013] The first adhesive layer may be formed from a first adhesive composition comprising a first (meth)acrylate adhesive resin, and the shear storage modulus of the first adhesive layer at a temperature of 23°C may be 0.01 MPa to 1 MPa.

[0014] The aforementioned third adhesive layer may be formed from a third adhesive composition comprising a third (meth)acrylate adhesive resin, and the shear storage modulus of the aforementioned third adhesive layer at a temperature of 23°C may be 0.01 MPa to 1 MPa.

[0015] The tensile elastic modulus of the rigid substrate layer described above can be above 1000 MPa at a temperature of 23°C.

[0016] The aforementioned rigid substrate layer may include a substrate layer made of polyethylene terephthalate (PET).

[0017] The total transmittance of the aforementioned rigid substrate layer can be above 80%, and the diffuse transmittance can be 5-20%.

[0018] The bonding film for back-side grinding of the above-mentioned wafer can satisfy the following relationship (1).

[0019] Relation (1): T (S) ×0.05≤T max(P) ≤T (S) ×0.5

[0020] In the above relation (1), T (S) T is the thickness of the aforementioned rigid substrate layer. max(P) It is the maximum height of the aforementioned light scattering pattern.

[0021] The aforementioned light scattering pattern can be formed from a material with a pencil hardness of 2H or higher as determined by ASTM D3363.

[0022] The light scattering pattern described above can be formed by photocuring a coating composition comprising urethane (meth)acrylate oligomers, multifunctional (meth)acrylate monomers, and a photoinitiator.

[0023] The bonding film for back-side grinding of the wafer described above can satisfy equations (2) and (3).

[0024] Relation (2): T (PSA_1) ≤T (PSA_2) ≤T (PSA_1) ×10

[0025] Relation (3): T (PSA_3) ≤T (PSA_2) ≤T (PSA_3) ×10

[0026] In the above relations (2) and (3), T (PSA_1) T (PSA_2) and T (PSA_3) These represent the thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer, respectively.

[0027] The aforementioned adhesive film for wafer back-side polishing can be applied to the wafer back-side polishing process where bumps are formed.

[0028] When the bonding film for wafer back-side polishing of the present invention is applied to the wafer back-side polishing process, even if there are gaps due to the bump structure of the wafer, wafer breakage due to uneven stress distribution can be prevented. At the same time, when the bonding film is removed after the back-side polishing process, the generation of adhesive residue can be significantly reduced or suppressed, thereby improving the wafer processing processability and the quality of the prepared semiconductor chip.

[0029] The above-mentioned effects and the specific effects of the present invention will be described below while describing the specific details for carrying out the present invention. Attached Figure Description

[0030] Figure 1 A cross-sectional view of an adhesive film for wafer backside polishing according to an embodiment of the present invention is shown.

[0031] Figure 2 A perspective view of an adhesive film for back-side grinding of a wafer according to an embodiment of the present invention is shown.

[0032] Figure 3 An enlarged cross-sectional view showing a light scattering pattern formed on a rigid substrate layer of an adhesive film for back-side polishing of a wafer according to an embodiment of the present invention.

[0033] Figure 4 This is an example showing a cross-section of a bump structure formed on the surface of a wafer.

[0034] Figure 5 A flowchart briefly illustrates the application of the wafer back-side polishing adhesive film of one embodiment of the present invention to the wafer back-side polishing process and the subsequent stripping process. Detailed Implementation

[0035] The foregoing objectives, features, and advantages will be described in detail with reference to the accompanying drawings, thereby enabling those skilled in the art to readily implement the technical concept of the present invention.

[0036] In describing this invention, detailed descriptions are omitted if it is determined that a detailed description of well-known techniques related to this invention may unnecessarily obscure the spirit of the invention.

[0037] Any content not described in this specification that can be readily deduced by a person skilled in the art will be omitted from the description.

[0038] In this specification, "excellent embedding properties such as bump structure, bending, and light scattering pattern" can mean i) when the adhesive film is adhered to a semiconductor wafer, the adhesive film adheres well to the bending along the bending without lifting or forming gaps, which is present due to the bump structure or the like formed on the semiconductor wafer; ii) when each adhesive layer of the adhesive film of the present invention is adhered to the bending of the light scattering pattern formed on the rigid substrate layer.

[0039] In this specification, unless the temperature range is specifically limited, “normal temperature” can be interpreted as a temperature condition of approximately 23 to 25°C.

[0040] In this specification, "Total Transmittance (TT) (or total transmittance, total transmittance) (%)" and "Diffuse Transmittance (DT)" were measured using a turbidity measuring instrument (Nippon Denshoku, NDH5000) according to the ASTM D1003 method.

[0041] In this specification, "(meth)acrylate" may mean all acrylates and methacrylates.

[0042] In this specification, the term "any structure disposed on the upper (or lower) part" or "above (or below)" of a structural element not only means that any structure is in contact with the upper (or lower) surface of the aforementioned structural element, but also means that other structures may be located between the aforementioned structural element and any structure disposed on (or below) the aforementioned structural element.

[0043] In this specification, terms such as "one side", "the other side", and "both sides" are used to distinguish a structural element from other structural elements, but structural elements are not limited to the above terms.

[0044] In this specification, the unit "parts by weight" may mean the weight ratio between the components.

[0045] Unless otherwise expressly stated in this specification, singular expressions used herein include plural expressions. Terms such as “comprising,” “containing,” and “having” in this specification should not be construed as including all the various structural elements described herein, but rather as excluding some structural elements, or including additional structural elements.

[0046] As described above, the purpose of the wafer bonding film proposed in this invention is to improve the limitations arising in the back-side grinding process of wafers with bump structures, to have excellent bump structure embedding, to prevent wafer breakage, and to minimize or remove residue when the bonding film is removed, and this will be described in detail.

[0047] first, Figure 4 This is an actual enlarged view of the bump 300 structure formed on the surface of wafer 200. Since the bump 300 is circular, a gap is formed between wafer 200 and bump 300 (indicated by a dashed circle). Figure 4It is a bump structure, and as many bumps are formed on the wafer, the void area also increases. Therefore, due to the uneven distribution of stress applied during back-side grinding of the wafer, wafer breakage occurs. Furthermore, these voids serve as shaded areas that energy rays used to remove the bonding film for wafer processing cannot reach; this will be illustrated with a diagram of the back-side grinding process. Figure 5 Please provide a detailed explanation.

[0048] Figure 5 An exemplary flowchart illustrates the process of applying the wafer back-side polishing adhesive film 100 of an embodiment of the present invention to a wafer, and then reducing the adhesion and peeling it off by irradiating it with energy rays after back-side polishing.

[0049] Specifically, Figure 5 S1 is the wafer preparation step (wafer loading) before the wafer back-side grinding process. It shows that bump 300 is formed on the surface of wafer 200. The bump 300 is shown as a layer structure with a surface for the sake of simplicity and does not actually have a layer structure.

[0050] Figure 5 S2 is the step of adhering (or attaching) the wafer back-side polishing adhesive film 100 of the present invention to the surface side of the wafer, thereby protecting the surface of the wafer 200 during back-side polishing.

[0051] Figure 5 S3 briefly illustrates the steps of performing a back-side grinding process, in which various back-side grinding equipment used in this art can be used without limitation, such as equipment that can rotate a grinding wheel after loading a wafer on a chuck table.

[0052] Figure 5 S4 briefly illustrates the step of irradiating the wafer back-grinding adhesive film 100 with energy rays (typically ultraviolet (UV)) after the back-grinding process to peel it off. The thickness of the wafer 210 after the back-grinding process is reduced compared to the wafer 200 before the back-grinding process. Thus, the adhesive layer of the wafer back-grinding adhesive film 100 is typically formed by an energy-ray cured adhesive composition.

[0053] Figure 5 S5 briefly illustrates the step of peeling off the wafer back-side polishing adhesive film 100 after the back-side polishing process. In this case, if the exposure of the energy rays reaching the wafer back-side polishing adhesive film 100 is insufficient, the adhesion cannot be sufficiently reduced to a level that allows for good peeling. Therefore, residue of the wafer back-side polishing adhesive film 100 may remain in the peeling step. As described above, in Figure 5The image illustrates the adhesive residue area R.

[0054] If residues of the back-side polishing adhesive film 100 remain on the wafer, it can adversely affect the processability and the quality of the fabricated semiconductor chip. Furthermore, as the gaps and curvature of the bumps formed on the wafer 200 increase, the shadowed areas that energy rays cannot reach also increase, thus exacerbating the aforementioned problems.

[0055] Based on the results of the inventors’ dedicated research into the problems described above, the following inventions have been made regarding adhesive films for back-side grinding of wafers: in order to distribute stress evenly during back-side grinding of wafers and to give them excellent bump structure embedding properties, the energy rays irradiated during the preparation of the adhesive film can reach the wafers evenly and fully.

[0056] As a preferred embodiment of the present invention, such as Figure 1 and Figure 2 As shown, the wafer back-side polishing adhesive film 100 of the present invention may have the following structure, including: a rigid substrate layer S on which a light scattering pattern P is formed; a first adhesive layer 10 disposed on the rigid substrate layer S; a second adhesive layer 20 disposed on the first adhesive layer 10; and a third adhesive layer 30 disposed on the second adhesive layer 20. The wafer back-side polishing adhesive film 100 and its structural layers will be described in detail.

[0057] A rigid substrate layer S with a light scattering pattern P is formed.

[0058] The substrate layer of the adhesive film for wafer back-side polishing of the present invention can be a rigid substrate layer S formed of a rigid material with a high tensile modulus of elasticity. Preferably, it can have a tensile modulus of elasticity of 1000 MPa or more, for example, 1200 MPa or more, 1500 MPa or more, 2000 MPa or more, or 3000 MPa or more. There is no particular limitation on the upper limit of the tensile modulus of elasticity; for example, it can be 5000 MPa or less. Furthermore, the tensile modulus of elasticity in this case is based on a value measured at a temperature of 23°C. When the tensile modulus of elasticity is relatively low, less than 1000 MPa, the support force on the wafer or semiconductor chip is low, which may lead to collisions with the semiconductor chip during the back-side polishing process (back grinding process).

[0059] For example, the aforementioned rigid substrate layer S may include a substrate layer made of a material selected from the group consisting of polyester, polyimide (PI), polyamide (PA), polycarbonate (PC), polyacetal, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyetherketone, and oriented polypropylene, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and fully aromatic polyesters. Preferably, it may include a substrate layer made of polyethylene terephthalate (PET).

[0060] The rigid substrate layer S of the present invention is characterized by having a light scattering pattern P formed thereon, and the light scattering pattern P is capable of scattering light even in shadow areas formed due to the bump structure, so that energy rays can reach uniformly. From the viewpoint of withstanding the stress of the wafer backside grinding process, the light scattering pattern P can be formed of a material with a pencil hardness of 2H or higher as determined according to ASTM D3363, preferably a material of 3H or higher, more preferably a material of 4H or higher, and most preferably a material of 5H or higher. There is no particular limitation on the type of material, as long as it achieves the purpose of the present invention.

[0061] For example, the light scattering pattern described above can be formed by photocuring a coating composition comprising urethane (meth)acrylate oligomers, multifunctional (meth)acrylate monomers, and a photoinitiator. Preferably, the multifunctional (meth)acrylate monomers may include 4-6 functional (meth)acrylate monomers containing (bis)pentaerythritol. Conventional photoinitiators used in this art can be used as the photoinitiator, for example, acetophenone-based photoinitiators.

[0062] And, as Figure 3 As exemplarily shown, the geometry of the light scattering pattern P can be applied without particular restrictions; for example, the shape of the pattern can be a rectangle, square, triangle, trapezoid, hemisphere, etc. Figure 3 The solid arrows represent energy rays irradiated along the S direction of the rigid substrate layer, while the dashed arrows represent energy rays scattered by the light scattering pattern P.

[0063] The total transmittance of the rigid substrate layer S can be above 80%, and the diffuse transmittance can be above 5% to 20%. If the total transmittance of the rigid substrate layer is less than 80%, during ultraviolet (UV) exposure, the curing degree of the wafer adhesive will decrease, making it difficult to ensure sufficiently low adhesion. Therefore, when removing the tape, there may be damage problems such as wafer chip breakage. If the diffuse transmittance is less than 5%, there may be problems with residual adhesive in the shadow areas formed by bumps. If the diffuse transmittance is greater than 20%, there may be problems with increased turbidity, making pattern visibility difficult.

[0064] Furthermore, the thickness relationship between the rigid substrate layer S and the light scattering pattern P can satisfy the following relationship (1).

[0065] Relation (1): T (S) ×0.05≤ Tmax(P) ≤T (S) ×0.5

[0066] In the above relation (1), T (S) T is the thickness of the aforementioned rigid substrate layer. max(P) It is the maximum height of the aforementioned light scattering pattern.

[0067] First adhesive layer 10

[0068] The first adhesive layer 10 of the present invention is disposed on the rigid substrate layer. Since it is located between the second adhesive layer 20 and the rigid substrate layer S and acts as an interlayer adhesive layer, the required physical properties of the first adhesive layer 10 are related to the properties of the second adhesive layer 20 and the rigid substrate layer S.

[0069] Specifically, as described later, since the second adhesive layer 20 has a high shear storage modulus value, the adhesion between the second adhesive layer 20 and the rigid substrate layer S should be ensured. Furthermore, the rigid substrate layer S has uneven thickness due to the light scattering pattern P formed thereon, so it needs to be supplemented, and the embedding of voids formed due to bumps on the wafer should also be considered.

[0070] From this perspective, preferably, the shear storage modulus of the first adhesive layer 10 at a temperature of 23°C is 0.01 MPa to 1 MPa, more preferably, 0.05 MPa to 1 MPa, and most preferably, 0.05 MPa to 0.5 MPa. If the shear storage modulus of the first adhesive layer 10 is less than 0.01 MPa, there may be a problem of adhesive sticking to the cutting edge when cutting after the tape is adhered to the wafer. If it is greater than 1 MPa, bubbles may be generated due to insufficient embedding of the light scattering pattern when bonding with the rigid substrate layer, thus there may be a problem of poor adhesion between the interface of the rigid substrate layer and the first adhesive layer.

[0071] The first adhesive layer 10 of the present invention can be formed by thermosetting a first adhesive composition comprising a first (meth)acrylate adhesive resin.

[0072] The aforementioned first (meth)acrylate adhesive resin is commonly used in this art and can be selected without limitation within the scope of achieving the objectives of this invention. For example, it can be a polymer of (meth)acrylate monomers having alkyl groups having 1 to 14 carbon atoms. Specifically, it can be a polymer selected from one or more polymers of the group consisting of ethylhexyl acrylate, butyl acrylate, ethyl acrylate, methyl acrylate, acrylic acid, hydroxyethyl acrylate, and hydroxybutyl acrylate. Preferably, it can be a polymer comprising monomer polymerization, wherein the monomers include monomers bonded to carboxyl or hydroxyl groups.

[0073] Furthermore, the first adhesive composition may also contain a crosslinking agent, which is not particularly limited in type as long as it is commonly used in this art. For example, isocyanate crosslinking agents may be used.

[0074] On the other hand, there is no particular limitation on the thickness of the first adhesive layer 10. For example, the thickness can be about 10 μm to 100 μm, or about 10 μm to 70 μm, or about 10 μm to 50 μm.

[0075] Second adhesive layer 20

[0076] The second adhesive layer 20 of the present invention can withstand the stress during wafer back-side grinding and also achieve excellent embedding properties for bends (concave and convex) and voids formed due to the bump structure, thus functioning as a concave and convex absorption layer.

[0077] Preferably, the shear storage modulus of the second adhesive layer 20 of the present invention at a temperature of 23°C is 0.1 MPa to 10 MPa, more preferably 0.1 MPa to 5 MPa. If the shear storage modulus of the second adhesive layer 20 is less than 0.1 MPa, there may be problems in fixing and supporting the wafer chip during back-side grinding; if it exceeds 10 MPa, there may be problems in reducing the embedding of bumps.

[0078] On the other hand, the adhesive layer that typically includes the bonding film for grinding the back side of the wafer may contain acrylic adhesive resin, but it is difficult to ensure excellent adhesion (filling) of the wafer with gaps formed due to bumps with such existing adhesive layers.

[0079] Based on this perspective, the inventors conducted intensive research and found that when an additive with a softening point of 30°C to 70°C is added to the composition used to prepare the adhesive layer in a (meth)acrylate adhesive resin, the adhesion (filling) of voids formed by bumps is significantly improved within the temperature range of room temperature to 70°C, which is the general bonding process temperature range. Thus, experiments have confirmed that this method can solve the problem of warping or voids between the adhesive film used for wafer back-side grinding.

[0080] More specifically, for the wafer back-side polishing process, when the wafer back-side polishing adhesive film is bonded to the wafer, since lamination is performed at a temperature of about room temperature to 70°C, the softening point of the adhesive resin used as an additive is preferably 30°C to 70°C, more preferably 30°C to 60°C, and the adhesive resin having the above softening point is preferably an epoxy adhesive resin.

[0081] Therefore, the second adhesive layer can be formed from a second adhesive composition comprising a second (meth)acrylate adhesive resin and an epoxy adhesive resin with a softening point of 30°C to 70°C.

[0082] The epoxy adhesive resins mentioned above are not particularly limited as long as their softening point is between 30°C and 70°C. However, for example, they can be bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novolac type epoxy resin, ortho-cresol novolac type epoxy resin, xylok type epoxy resin, etc. Preferably, it can be ortho-cresol type YDCN-500-1P (Kookdo Chemical, South Korea).

[0083] Furthermore, the second adhesive composition may also contain a crosslinking agent, which is not particularly limited in type as long as it is commonly used in this art. For example, isocyanate crosslinking agents may be used.

[0084] The aforementioned second (meth)acrylate adhesive resin is commonly used in this technical field and can be selected without limitation within the scope of achieving the objectives of this invention, and the specific types are the same as those described above regarding the "first (meth)acrylate adhesive resin".

[0085] Based on 100 parts by weight of the aforementioned second adhesive composition, it may contain 5 to 45 parts by weight of the aforementioned epoxy adhesive resin, for example, 5 to 40 parts by weight, 5 to 30 parts by weight, 5 to 20 parts by weight, or 10 to 20 parts by weight. If the content of the aforementioned epoxy adhesive resin is less than 5 parts by weight, the modulus may decrease at room temperature, and the reduced support function for the wafer chip during polishing may become a problem. If it exceeds 45 parts by weight, the embedding of bumps may become a problem when bonding to the wafer.

[0086] On the other hand, the thickness of the second adhesive layer 20 is not particularly limited. For example, the thickness can be about 10 μm to 200 μm, about 20 μm to 150 μm, or about 30 μm to 100 μm.

[0087] Third adhesive layer 30

[0088] The third adhesive layer 30 of the present invention is an adhesive (or adherent) portion that adheres to the wafer. The third adhesive layer 30 is not particularly limited as long as it has suitable adhesion under room temperature conditions, and can be formed from various adhesive compositions that are known ultraviolet (UV) curable adhesive compositions, such as acrylic adhesive compositions, silicone adhesive compositions, polyester adhesive compositions, polyamide adhesive compositions, urethane adhesive compositions, and styrene-diene block copolymer adhesive compositions. Preferably, it can be formed from an acrylic adhesive composition.

[0089] The third adhesive layer 30 of the present invention can be formed by photocuring a third adhesive composition comprising a third (meth)acrylate adhesive resin, and the shear storage modulus at a temperature of 23°C is preferably 0.01 MPa to 1 MPa. If the shear storage modulus at a temperature of 23°C is less than 0.01 MPa, the agglomeration becomes too low, and there may be a problem of transfer when removing the tape; if it exceeds 1 MPa, there may be a problem of adhesion when bonding to the wafer.

[0090] The third adhesive composition described above may also contain a photopolymerization initiator and a crosslinking agent, whichever is commonly used in this art and is not particularly limited thereto.

[0091] The aforementioned photopolymerization initiators, as substances that initiate ultraviolet curing reactions through ultraviolet irradiation, are appropriately selected and used considering factors such as the curing speed of the resin composition. For example, photopolymerization initiators may include hydroxycyclohexylphenylketone (Irgacure 184), 2-methyl-1-[4-(methythio)phenyl]-2-morpholino-propan-1-one (Irgacure 907), α,α-methoxy-α-hydroxyacetophenone (Irgacure 651), and 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Irgacure 1173), etc.

[0092] Furthermore, the aforementioned third adhesive composition may also contain a crosslinking agent, which is not particularly limited in type as long as it is commonly used in this art; for example, isocyanate crosslinking agents may be used.

[0093] The aforementioned third (meth)acrylate adhesive resin is commonly used in this technical field and can be selected without limitation within the scope of achieving the objectives of this invention, and the specific types are the same as those described above regarding the "first (meth)acrylate adhesive resin".

[0094] On the other hand, there is no particular limitation on the thickness of the third adhesive layer 30. For example, the thickness can be about 10 μm to 100 μm, the thickness can be 10 μm to 70 μm, or the thickness can be 10 μm to 50 μm.

[0095] 100 Adhesive film for back-side grinding of wafers

[0096] When applied to a wafer back-side polishing process with bumps, the wafer back-side polishing adhesive film 100 of the present invention is highly effective in solving problems of voids and bends caused by bumps and shadow areas that become problematic when irradiated with energy rays.

[0097] Preferably, the total transmittance of the wafer backside polishing adhesive film 100 of the present invention is 70% or more, and the diffuse transmittance is 6% or more.

[0098] Specifically, in order to peel off the wafer backing polishing adhesive film 100 from the wafer, and to reduce the adhesion, a curing reaction is carried out by irradiating with energy rays (typically ultraviolet light). In this case, in order to ensure that the energy ray-based curing reaction can proceed sufficiently, the total transmittance is preferably 70% or more.

[0099] On the other hand, since the rigid substrate layer S of the present invention contains a light scattering pattern P, the light scattering or light diffusion effect is manifested in the overall structure of the adhesive film 100 for wafer backside polishing. In order to fully display the light scattering or light diffusion effect, it is preferable that the diffuse transmittance of the overall structure of the adhesive film 100 for wafer backside polishing is 6% or more. The aforementioned diffuse transmittance can be 35% or less, but is not limited to this.

[0100] Furthermore, from the viewpoint of ensuring sufficient embedding of the thicknesses of the first adhesive layer 10, the second adhesive layer 20, and the third adhesive layer 30 of the wafer backside polishing adhesive film 100 for various bump heights, the following relationships (2) and (3) can be satisfied. The following relationships (2) and (3) limit the thickness of the second adhesive layer 20 to be within the range of 1 to 10 times the respective thicknesses of the first adhesive layer 10 and the third adhesive layer 30.

[0101] Relation (2): T (PSA_1) ≤T (PSA_2) ≤T (PSA_1) ×10

[0102] Relation (3): T (PSA_3) ≤T (PSA_2) ≤T (PSA_3) ×10

[0103] In the above relations (2) and (3), T (PSA_1) T (PSA_2) and T (PS A_3) These represent the thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer, respectively.

[0104] The structure and function of the present invention will be described in more detail below through preferred embodiments. However, this is presented as a preferred example of the present invention and should not be construed as limiting the present invention in any way. Content not described herein is omitted as it can be readily deduced by those skilled in the art.

[0105] Preparation Example 1: Preparation of a first adhesive composition for forming a first adhesive layer

[0106] An acrylic adhesive resin with a weight average molecular weight of 600,000 was obtained by mixing 42 parts by weight of n-butyl acrylate, 10 parts by weight of ethylhexyl acrylate, 30 parts by weight of methyl acrylate, 5 parts by weight of 2-hydroxyethyl acrylate, 13 parts by weight of acrylic acid, 0.05 parts by weight of azobisisobutyronitrile and 100 parts by weight of ethyl acetate.

[0107] Based on 100 parts by weight of the above-mentioned acrylic adhesive resin, 3 parts by weight of an isocyanate crosslinking agent (Nippon Polyurethane Kogyo Co., Ltd., trade name "CoronateC") was added and thoroughly mixed to prepare a first adhesive composition for forming a first adhesive layer.

[0108] Preparation Example 2: Preparation of a second adhesive composition for forming a second adhesive layer

[0109] An acrylic adhesive resin with a weight average molecular weight of 500,000 was obtained by mixing 20 parts by weight of n-butyl acrylate, 10 parts by weight of ethylhexyl acrylate, 55 parts by weight of methyl acrylate, 7 parts by weight of 2-hydroxyethyl acrylate, 8 parts by weight of acrylic acid, 0.1 parts by weight of azobisisobutyronitrile and 100 parts by weight of ethyl acetate.

[0110] Based on 100 parts by weight of the above-mentioned acrylic adhesive resin, 3 parts by weight of an isocyanate crosslinking agent (Nippon Polyurethane Kogyo Co., Ltd., trade name "CoronateC") was added and thoroughly mixed to prepare a second adhesive composition for forming a second adhesive layer.

[0111] Preparation Example 3: Preparation of a third adhesive composition for forming a third adhesive layer

[0112] A monomer mixture consisting of 50 grams of n-butyl acrylate (BA), 40 grams of methyl acrylate (MA), and 4 grams of hydroxyethyl acrylate (HEA) is placed in a reactor. A cooling device is installed in the reactor to allow nitrogen to reflux and the temperature to be easily adjusted.

[0113] Next, 100 parts by weight of ethyl acetate (EAc) as a solvent were added relative to 100 parts by weight of the above monomer mixture. To remove oxygen from the reactor, nitrogen gas was injected and the mixture was thoroughly mixed at 30°C for at least 30 minutes. Afterward, the temperature was raised to 50°C and maintained. 0.1 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and the reaction was initiated. The first reactant was prepared by polymerization over 24 hours.

[0114] Four parts by weight of 2-methacryloyloxyethyl isocyanate (MOI) and one part by weight of catalyst (dibutyltin dilaurate (DBTDL)) relative to MOI were combined with the above first reactant and reacted at 40°C for 24 hours to obtain an acrylic adhesive resin with a weight average molecular weight of 500,000.

[0115] Based on 100 parts by weight of the above-mentioned acrylic adhesive resin, 0.1 parts by weight of Irgacure 184 (BASF) as a photopolymerization initiator and 2 parts by weight of an isocyanate crosslinking agent (Nippon Polyurethane Kogyo Co., Ltd., trade name "Coronate C") as a crosslinking agent were added and thoroughly mixed to prepare a third adhesive composition for forming a third adhesive layer.

[0116] Preparation Example 4: Preparation of a rigid substrate layer with a light scattering pattern

[0117] After adding 1030g of a mixture of pentaerythritol diacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate in a weight ratio of 3% by weight, the mixture was heated to 70°C and 2 equivalents of isophorone diisocyanate were added dropwise for 1 hour, and the reaction was maintained for 6 hours.

[0118] After confirming the absence of NCO peaks using infrared spectrophotometry (IR), the mixture was cooled to 60°C and diluted with 537.3 g of 2-hydroxyethyl methacrylate to prepare urethane acrylate oligomers.

[0119] A UV-curable coating composition is prepared by uniformly mixing 50% by weight of the above-prepared urethane acrylate oligomer, 31% by weight of pentaerythritol triacrylate, 10% by weight of dipentaerythritol hexaacrylate, 8% by weight of 1-hydroxydimethylphenyl ketone as an acetophenone photoinitiator, and 1% by weight of additives.

[0120] After diluting the above-mentioned UV-curable coating composition to 50% by weight using a mixed solvent of ethyl acetate / butyl acetate in a 1:1 ratio, the coating composition was applied to a polyethylene terephthalate (PET) film (50 μm thick, tensile modulus of elasticity 2400 MPa) serving as a rigid substrate layer, with a thickness of 5 μm. Then, after passing it through a pattern-forming roller with a specific shape, it was cured using a UV curing machine (800–800 °C). 2 The light scattering pattern is formed by complete UV curing.

[0121] Example 1

[0122] By applying the first adhesive composition of Preparation Example 1 onto the PET (polyethylene terephthalate film, thickness 50 μm) in Preparation Example 4, which has a light diffusion pattern (maximum height: 5 μm) formed on a curved surface (semi-circular shape), the thickness of the first adhesive layer reaches 20 μm. On the PET (polyethylene terephthalate film, thickness 50 μm) after release treatment, 10 parts by weight of YDC N-500-1P (softening point 50℃~54℃) as an epoxy adhesive resin is added to the second adhesive composition of Preparation Example 2 and applied to a thickness of 100 μm. Then, a first composite film having a first adhesive layer and a second adhesive layer with a thickness of 225 μm is prepared by bonding.

[0123] Next, based on 100 parts by weight of the third adhesive composition of Preparation Example 3, it was coated onto a biaxially oriented polyethylene terephthalate (PET) film with a thickness of 25 μm to achieve a thickness of 25 μm, thereby preparing a second composite film having a third adhesive layer with a thickness of 50 μm.

[0124] The PET with the release treatment of the first composite film removed is used to prepare a wafer back-side polishing adhesive film with an overall thickness of 200 μm (the overall thickness does not include the thickness of the release PET) by bonding a second composite film.

[0125] Example 2

[0126] In preparing the second adhesive composition, the adhesive film was prepared in the same manner as in Example 1 above, except that it contained 20 parts by weight of YDCN-500-1P as an epoxy adhesive resin instead of 10 parts by weight, and a light scattering pattern was formed by using a trapezoidal pattern (maximum height: 5 μm) forming roller instead of a curved pattern forming roller.

[0127] Example 3

[0128] In preparing the second adhesive composition, the adhesive film was prepared in the same manner as in Example 1 above, except that it contained 40 parts by weight of YDCN-500-1P as an epoxy adhesive resin instead of 10 parts by weight, and the light scattering pattern was formed by using a triangular pattern (maximum height: 5 μm) forming roller instead of a curved pattern forming roller.

[0129] Comparative Example 1

[0130] In preparing the second adhesive composition, the adhesive film was prepared in the same manner as in Example 1 above, except that it contained 50 parts by weight instead of 10 parts by weight of YDCN-500-1P as an epoxy adhesive resin.

[0131] Comparative Example 2

[0132] Except that there is no first adhesive layer and the second adhesive layer is directly bonded to the rigid substrate layer, the adhesive film is prepared in the same manner as in Example 1 above.

[0133] Comparative Example 3

[0134] In preparing the second adhesive composition, the adhesive film was prepared in the same manner as in Example 1 above, except that YDCN-500-1P was used as the epoxy adhesive resin.

[0135] Comparative Example 4

[0136] Except that only a PET film (50 μm thick, 2400 MPa tensile modulus) was used as the rigid substrate layer and no light scattering pattern was formed, the adhesive film was prepared in the same manner as in Example 1 above.

[0137] Comparative Example 5

[0138] In preparing the second adhesive composition, the adhesive film was prepared in the same manner as in Example 1 above, except that 30 parts by weight of YDCN-90P (softening point of 90°C) was used instead of YDCN-500-1P as the epoxy adhesive resin.

[0139] The results of measurements and evaluations based on Experimental Examples 1 to 4, as described above, are shown in Tables 1 to 3 below, relative to the objects prepared in the preparation examples, embodiments, and comparative examples.

[0140] Experimental Example 1: Evaluation of Optical Properties

[0141] Compared to the rigid substrate layer prepared in Preparation Example 4 and the wafer back-side polishing adhesive film prepared in the Examples and Comparative Examples, the total transmittance (TT, %) and diffuse transmittance (DT, %) were measured using a hazemeter (Nippon Denshoku, NDH5000).

[0142] Experimental Example 2: Determination of Shear Storage Modulus

[0143] Using a rheometer (TA Instruments, ARES-G2) as the shear storage modulus measuring device, a sample with a diameter of 8 mm and a thickness of 1 mm was obtained by stacking a monolayer adhesive layer formed by the first adhesive composition, the second adhesive composition and the third adhesive composition solution prepared in Preparation Examples 1 to 3, respectively. The shear storage modulus was measured at a temperature range of -20°C to 120°C at 1 Hz, and the shear storage modulus was recorded at a temperature of 23°C.

[0144] Experiment Example 3: Measuring a dimple

[0145] After the adhesive film for wafer back-side polishing is adhered to the semiconductor circuit surface (= wafer surface) where bumps are formed, the wafer with a thickness of 725μm is back-polished to a thickness of 80μm using a back-side polishing machine (DISCO; DGP8760).

[0146] After the back-side grinding process is completed, the thickness height difference of the ground surface of the wafer is confirmed by reflected light. After placing the ground surface upward on the stage of a three-dimensional optical profilometer (Profilm3D, FILME TRICS (USA)), the thickness height difference is measured. When the depth difference is greater than ±1μm compared with the normally ground surface, it is evaluated as "poor (×)" and when the difference is less than ±1μm, it is evaluated as "good (○)".

[0147] Experimental Example 4: Evaluation of Crack Initiation in Wafers

[0148] After the adhesive film for wafer back-side polishing is adhered to the semiconductor circuit surface (= wafer surface), the wafer with a thickness of 725μm is back-polished to a thickness of 100μm using a back-side polishing machine (DISCO; DGP8760).

[0149] After the back-side grinding process is completed, three chips are sampled from the top, bottom, left, right, and center positions of the wafer and observed under a microscope to determine the number of cracks. When the number of cracks is less than three, it is rated as "Good (○)"; when there are more than three, it is rated as "Poor (×)".

[0150] Experimental Example 5: Residue Test After Wafer Backside Grinding

[0151] After the adhesive film for wafer back-side polishing is adhered to the semiconductor circuit surface (= wafer surface), the wafer with a thickness of 725μm is back-polished to a thickness of 80μm using a back-side polishing machine (DISCO; DGP8760).

[0152] After the back-side grinding process, the sample is irradiated with 300 mJ / cm using an exposure device (VACTRON; TRSJ-3000). 2 Ultraviolet A. Then, heat-sealing tape (MBS-100R) is heat-pressed onto one outer periphery of the wafer back-side polishing adhesive film at a temperature of 230°C, and then the wafer back-side polishing adhesive film is removed.

[0153] After the back-side grinding process, 20 points on the wafer surface after the adhesive film has been removed are observed under a microscope to confirm whether adhesive residue has been generated. The specific method is as follows.

[0154] The size of the residue at 20 points within the back-grinding wafer is measured. When there is no residue, it is rated as "Good (○)"; when residue larger than 10 μm is produced, it is rated as "Poor (×)".

[0155] Table 1

[0156]

[0157] Table 2

[0158]

[0159] Table 3

[0160] Determining the pit Crack generation evaluation Residual without testing Example 1 ○ ○ ○ Example 2 ○ ○ ○ Example 3 ○ ○ ○ Comparative Example 1 ○ × ○ Comparative Example 2 × × ○ Comparative Example 3 ○ × ○ Comparative Example 4 ○ ○ × Comparative Example 5 × × ×

[0161] As described above, although the present invention has been described with reference to exemplary embodiments, the present invention is not limited to the embodiments disclosed in this specification. It is evident that those skilled in the art can implement various modifications within the scope of the technical concept of the present invention. Furthermore, even if the effects of the structure of the present invention are not explicitly described in the initial description of the embodiments, the effects that can be predicted through the corresponding structure should be acknowledged.

Claims

1. An adhesive film for back-side grinding of a wafer, characterized in that, include: A rigid substrate layer is formed with a light scattering pattern; A first adhesive layer is disposed on the aforementioned rigid substrate layer; A second adhesive layer is disposed on the first adhesive layer; and A third adhesive layer is disposed on the second adhesive layer. The second adhesive layer is formed from a second adhesive composition comprising a second (meth)acrylate adhesive resin and an epoxy adhesive resin having a softening point of 30°C to 70°C. Based on 100 parts by weight of the above-mentioned second adhesive composition, it comprises 5 to 45 parts by weight of the above-mentioned epoxy adhesive resin. The total transmittance of the aforementioned rigid substrate layer is over 80%, and the diffuse transmittance is 5% to 20%.

2. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The total transmittance of the bonding film used for back-side grinding of the aforementioned wafer is above 70%, and the diffuse transmittance is above 6%.

3. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The shear storage modulus of the second adhesive layer at a temperature of 23°C is 0.1 MPa to 10 MPa.

4. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The first adhesive layer is formed from a first adhesive composition comprising a first (meth)acrylate adhesive resin. The shear storage modulus of the first adhesive layer at a temperature of 23°C is 0.01 MPa to 1 MPa.

5. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The aforementioned third adhesive layer is formed from a third adhesive composition comprising a third (meth)acrylate adhesive resin. The shear storage modulus of the third adhesive layer at a temperature of 23°C is 0.01 MPa to 1 MPa.

6. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The tensile elastic modulus of the rigid substrate layer described above is 1000 MPa or more at a temperature of 23°C.

7. The adhesive film for wafer backside grinding according to claim 6, characterized in that, The aforementioned rigid substrate layer includes a substrate layer made of polyethylene terephthalate.

8. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The following relation (1) must be satisfied: Relation (1): T (S) ×0.05≤T max(P) ≤T (S) ×0.5 In the above relation (1), T (S) T is the thickness of the aforementioned rigid substrate layer. max(P) It is the maximum height of the aforementioned light scattering pattern.

9. The adhesive film for wafer backside grinding according to claim 1, characterized in that, The light scattering pattern described above is formed from a material with a pencil hardness of 2H or higher as determined by ASTM D3363.

10. The adhesive film for wafer backside polishing according to claim 1, characterized in that, The light scattering pattern is formed by photocuring a coating composition, which includes urethane (meth)acrylate oligomers, multifunctional (meth)acrylate monomers, and a photoinitiator.

11. The adhesive film for wafer backside polishing according to claim 1, characterized in that, Satisfy the following relations (2) and (3): Relation (2): T (PSA_1) ≤T (PSA_2) ≤T (PSA_1) ×10 Relation (3): T (PSA_3) ≤T (PSA_2) ≤T (PSA_3) ×10 In the above relations (2) and (3), T (PSA_1) T (PSA_2) and T (PSA_3) These represent the thicknesses of the first adhesive layer, the second adhesive layer, and the third adhesive layer, respectively.

12. The adhesive film for wafer backside polishing according to any one of claims 1 to 11, characterized in that, It is suitable for the back-side grinding process of wafers with bumps.

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