Adhesive film for wafer back surface polishing

Abstract

The present invention provides an adhesive film for wafer back surface polishing, which is characterized by comprising: a base material layer; the buffer layer is arranged on the base material layer; the middle supporting layer is arranged on the buffer layer; and an adhesive layer provided on the intermediate support layer, the thickness of the intermediate support layer being greater than 5% with respect to the total thickness of the buffer layer, the intermediate support layer, and the adhesive layer, and satisfying formula 1 and formula 2.

Description

Technical Field

[0001] The present invention relates to an adhesive film for protecting the surface of a wafer in a wafer back grinding (wafer back grinding or wafer lapping or wafer thinning) process. More specifically, the present invention relates to an adhesive film for wafer back grinding as follows: in the wafer back grinding process of a wafer formed with bumps, it maximizes the filling property for bending, has an excellent wafer surface protection effect (buffering effect), and at the same time, when peeling the adhesive film after back grinding, it shows excellent processability by reducing or eliminating the generation of residues of the binder. Background Art

[0002] With the development of technology in recent years, miniaturization, high density, and thinning of semiconductor chips are required. Therefore, wafers are also required to be thinned. A typical method for thinning wafer chips is to reduce the thickness by grinding the back surface of the wafer. The grinding process can be carried out according to the type or specification of the electronic device using the semiconductor chip, thereby realizing the thinning of the wafer.

[0003] Since the back grinding of the wafer of the semiconductor chip is a process of applying physical impact, in order to protect the surface of the wafer, the back grinding of the wafer is carried out in a state where an adhesive film for wafer back grinding is adhered.

[0004] On the circuit formation surface of the semiconductor wafer, not only circuits but also unevennesses with a large height difference such as bumps can be formed. Due to this bump structure, when an adhesive film for wafer back grinding is adhered, if a gap is formed between the unevennesses of the adhesive film for wafer back grinding and the circuit formation surface of the semiconductor wafer, when grinding the non-circuit formation surface of the semiconductor wafer, a stress distribution is generated on the semiconductor wafer surface, and there is a problem that the semiconductor wafer is easily damaged. Also, if the supporting force between the adhesive layer and the buffer layer is weak, the buffer layer is not fixed during the back grinding of the wafer, and cracks in the wafer or damage to the chip may occur.

[0005] Further, after the back grinding of the wafer, in order to remove the bonding film for the back grinding process of the wafer from the wafer surface, the bonding force is reduced and peeled off by irradiating energy rays. In this case, since the irradiated energy rays cannot sufficiently reach the gaps formed due to the bump structure, there may be shadow areas. In such shadow areas, due to insufficient curing of the energy rays, there is a problem that the bonding film is not easily peeled off. Moreover, when the supporting force between the bonding layer and the buffer layer is weak, when peeling the bonding film for back grinding of the wafer from the wafer, there is a problem that the bonding layer of the bonding film for back grinding of the wafer is not easily peeled off from the wafer. In this case, since the adhesive residue derived from the bonding film is likely to remain on the wafer surface, the processability is reduced, resulting in a problem of adversely affecting the quality of the manufactured semiconductor chip. Summary of the Invention

[0006] Technical Problem

[0007] An object of the present invention is to provide a bonding film for back grinding of a wafer as follows: maximizing the bump filling property, while improving the supporting force between the bonding layer and the buffer layer, preventing breakage of the wafer or the chip during the back grinding process of the wafer having a bump structure, and minimizing the residue during removal after the back grinding process of the wafer.

[0008] The object of the present invention is not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned can be understood through the following description and can be more clearly understood through the embodiments of the present invention. Moreover, it can be known that the objects and advantages of the present invention can be achieved by the solutions shown in the claims of the invention and their combinations.

[0009] Technical Solution

[0010] In order to solve the above technical problems, according to an embodiment of the present invention, the present invention provides a bonding film for back grinding of a wafer, including: a substrate layer; a buffer layer provided on the substrate layer; an intermediate support layer provided on the buffer layer; and a bonding layer provided on the intermediate support layer. With respect to the total thickness of the buffer layer, the intermediate support layer, and the bonding layer, the thickness of the intermediate support layer is greater than 5%, satisfying Formula 1 and Formula 2.

[0011] The intermediate support layer may be a thermoset of a composition containing a thermoplastic acrylic resin.

[0012] The storage modulus of the intermediate support layer at a temperature of 25°C may be from 0.03 MPa to 0.3 MPa.

[0013] The storage modulus of the bonding layer at a temperature of 25°C may be from 0.02 MPa to 0.2 MPa.

[0014] The storage modulus of the buffer layer at a temperature of 25 °C may be from 0.02 MPa to 0.2 MPa.

[0015] The adhesive film for back grinding of the wafer may satisfy Formula 3 and Formula 4.

[0016] The adhesive film for back grinding of the wafer may satisfy Formula 5 and Formula 6.

[0017] The total thickness of the buffer layer, the intermediate support layer, and the adhesive layer may be from 20 μm to 600 μm.

[0018] The thickness of the intermediate support layer may be from 1 μm to 40 μm.

[0019] The adhesive film for back grinding of the wafer may be applied to the back grinding process of a wafer formed with bumps.

[0020] Effects of the Invention

[0021] The adhesive film for back grinding of the wafer of the present invention can improve the supporting force between the intermediate support layer and the buffer layer and between the intermediate support layer and the adhesive layer by including the intermediate support layer. At the same time, problems such as cracking of the wafer or breakage of the chip during back grinding can be prevented by maximizing the bump filling property (embedding property). Moreover, generation of residues of the adhesive layer can be reduced or suppressed when the adhesive film for back grinding of the wafer is peeled off from the wafer. Thereby, the processability of wafer processing and the quality of the manufactured semiconductor chips can be improved.

[0022] The effects of this specification are not limited to the effects mentioned above. Those of ordinary skill in the technical field to which the present invention pertains can clearly understand other effects not mentioned through the following descriptions. In the description of the following specific embodiments, the specific effects of the present invention will be described together with the above effects. Brief Description of the Drawings

[0023] Figure 1 A cross-sectional view of an adhesive film for back grinding of a wafer showing an example of the present invention.

[0024] Figure 2 A cross-sectional view showing a state where an adhesive film for back grinding of a wafer showing an example of the present invention is attached to a wafer formed with a bump structure.

[0025] Figure 3 An example of a cross-section of a bump structure formed on the surface of a wafer is shown.

[0026] Figure 4 A flowchart briefly showing the process of applying an adhesive film for back grinding of a wafer showing an example of the present invention to a wafer back grinding process and subsequent peeling.

[0027] Description of Reference Numerals

[0028] 100: Bonding film for wafer back grinding

[0029] 200: Wafer before back grinding process

[0030] 210: Wafer after back grinding process

[0031] 300: Bump

[0032] R: Area where residue of binder remains

[0033] 10: Bonding layer

[0034] 20: Intermediate support layer

[0035] 30: Buffer layer

[0036] 40: Substrate layer

[0037] 50: Release film. Detailed implementation manners

[0038] The foregoing objectives, features, and advantages will be described in detail with reference to the accompanying drawings. Thus, those of ordinary skill in the technical field to which the present invention pertains can easily implement the technical idea of the present invention. During the description of the present invention, if it is determined that the specific description of the well-known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or similar structural elements.

[0039] Among the contents not described in this specification, as long as they can be fully analogized technically by those of ordinary skill in the technical field, their descriptions will be omitted.

[0040] In this specification, when any structure is disposed "above (or below)" a structural element or "on (or under)" a structural element, it not only means the configuration in which any structure is in contact with the upper surface (or lower surface) of the above-mentioned structural element, but also means that other structures may be interposed between the above-mentioned structural element and any structure disposed on (or under) the above-mentioned structural element.

[0041] In this specification, unless otherwise clearly mentioned in the context, the singular expressions used in this specification include plural expressions. In this application, terms such as "composed of" or "including" should not be construed as necessarily including all the various structural elements described in the specification, but should be construed as not including some of the structural elements, or may further include additional structural elements.

[0042] 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, and the structural element is not limited to the said terms.

[0043] In this specification, "excellent embeddability for bump structures, bending, etc." may mean that i) when the adhesive film is adhered to the semiconductor wafer, the adhesive film closely adheres to the bending existing due to the bump structure or the like formed on the semiconductor wafer along the bending without warping or forming voids, and ii) when the layers of the adhesive film of the present invention are laminated, they closely adhere to the bending existing due to the bump structure or the like.

[0044] In this specification, unless the temperature value is particularly limited, "room temperature" can be interpreted as a temperature condition of approximately 23 to 25 °C.

[0045] In this specification, "(meth)acrylate" is used as a term including acrylate and methacrylate, and the same applies to similar terms.

[0046] In the following description of the present invention, detailed descriptions of related known technologies that may unnecessarily confuse the gist of the present invention will be omitted.

[0047] Figure 3 is an actual magnified photograph of the bump 300 structure formed on the surface of the wafer 200. Due to the circular shape of the bump 300, voids are formed between the wafer 200 and the bump 300 (illustrated by a dotted circle). Figure 3 Shows the structure of one bump. As many bumps are formed on the wafer, the area of the voids also increases. Therefore, the stress applied during back grinding of the wafer is unevenly distributed on the wafer due to the voids, resulting in a problem of wafer breakage. In addition, the voids also act as shadow areas where the energy rays irradiated to remove the adhesive film for wafer processing cannot reach. Therefore, an adhesive film for back grinding of a wafer that can maximize bump filling is required.

[0048] Figure 4 Illustrates a flowchart of a process of applying the adhesive film 100 for back grinding of a wafer according to an example of the present invention to a wafer, and reducing the adhesive force by irradiating energy rays to peel it off after back grinding.

[0049] Specifically, Figure 4 S1 is a step of preparing the wafer before the back grinding process of the wafer (loading the wafer), showing that the surface of the wafer 200 is formed with bumps 300. For simplicity of illustration, the bumps 300 are shown only as a layer structure having a surface and do not actually have a layer structure.

[0050] Figure 4 S2 is a step of attaching (or adding) the adhesive film 100 for back grinding of a wafer of the present invention to the surface side of the wafer, thereby protecting the surface of the wafer 200 during back grinding.

[0051] Figure 4S3 briefly shows the situation of performing the back grinding process. The back grinding process can use various back grinding devices in the technical field to which the present invention belongs without limitation. For example, a device that can rotate a grinding wheel after loading a wafer on a chuck table can be used.

[0052] Figure 4 S4 is a step of irradiating energy rays (e.g., ultraviolet rays (UV)) to peel the adhesive film 100 for back grinding of the wafer after the back grinding process. Briefly, it shows that the thickness of the wafer 210 after the back grinding process becomes thinner compared to the wafer 200 before the back grinding process.

[0053] Figure 4 S5 briefly shows the step of peeling the adhesive film 100 for back grinding of the wafer after the back grinding process. In this case, if the energy rays reaching the adhesive film 100 for back grinding of the wafer are insufficient, the adhesive force cannot be sufficiently reduced to a level sufficient for good peeling. Moreover, if the supporting force between the adhesive layer and the layer thereon is reduced, residues of the adhesive film 100 for back grinding of the wafer will be left in the peeling step. Figure 4 The area R where residues of the binder are left as described above is illustrated.

[0054] If residues of the adhesive film 100 for back grinding of the wafer are left on the wafer, problems will occur that have an adverse impact on the processability and the quality of the manufactured semiconductor chips.

[0055] If the degree of voids and bending caused by the bumps formed on the wafer 200 is severe and the fillability is insufficient, further increasing the shadow area where the energy rays cannot reach, the above problems are likely to occur. Moreover, if the adhesive layer is not supported by the layer thereon, the problem is more serious.

[0056] As a result of extensive research by the present inventors focusing on the above problems, a target adhesive film for back grinding of a wafer has been found, which sequentially includes a base layer, a buffer layer, an intermediate support layer, and an adhesive layer, and the relationship between the thickness and storage modulus of the intermediate support layer in relation to other layers. That is, the invention regarding the adhesive film for back grinding of a wafer is completed: sequentially including a base layer, a buffer layer, an intermediate support layer, and an adhesive layer, adjusting the thickness of the intermediate support layer and adjusting the storage modulus in relation to other layers, can prevent the formation of voids by maximizing the bump fillability (embedding property) and make the irradiated energy rays reach uniformly and sufficiently when removing the adhesive film, and improve the supporting force between the buffer layer, the intermediate support layer, and the adhesive layer by including the intermediate support layer, thereby preventing residues of the adhesive layer from being left during peeling.

[0057] In an example of the present invention, asFigure 1 As shown, the adhesive film 100 for wafer back grinding of the present invention may have the following structure: a substrate layer; a buffer layer provided on the substrate layer; an intermediate support layer provided on the buffer layer; and an adhesive layer provided on the intermediate support layer. The adhesive film 100 for wafer back grinding and its respective structural layers will be described in detail below.

[0058] Base material layer

[0059] The substrate layer of the adhesive film for wafer back grinding of the present invention may be formed of a material having a high tensile modulus. For example, the substrate layer may have a tensile modulus of 1000 MPa or more, 1200 MPa or more, 1500 MPa or more, 2000 MPa or more, or 3000 MPa or more. In this case, the tensile modulus is based on the measured value at 23°C. If the tensile modulus of the substrate layer is relatively low, less than 1000 MPa, the support force for the wafer or semiconductor chip is low, and there is a possibility of collision of the semiconductor chip occurring during the back grinding process.

[0060] The substrate layer may contain one or more materials selected from the group consisting of polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and wholly aromatic polyesters, polyimide (PI), polyamide (PA), polycarbonate (PC), polyacetal, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyether ketone, and oriented polypropylene. Preferably, the substrate layer may include a polyethylene terephthalate material.

[0061] The thickness of the substrate layer is not particularly limited. For example, the substrate layer may have a thickness of about 10 μm to 150 μm, respectively.

[0062] On the other hand, the substrate layer may also contain a small amount of various additives such as coupling agents, plasticizers, antistatic agents, and antioxidants as needed.

[0063] Buffer layer

[0064] The buffer layer of the present invention is provided on the substrate layer, which will affect the bump filling property and can play a role in absorbing the vibration and impact generated during wafer back grinding. Moreover, the buffer layer shows excellent support force with the intermediate support layer, thereby preventing cracking of the wafer or breakage of the chip caused by the un-fixed buffer layer during grinding.

[0065] From this perspective, the storage modulus of the buffer layer at a temperature of 25°C can be from 0.02 MPa to 0.2 MPa. Moreover, the storage modulus of the buffer layer at a temperature of 60°C can be from 0.01 MPa to 0.1 MPa. Thereby, the bump fillability can be improved, the impact and vibration during grinding can be fully absorbed, and at the same time, the adhesion to the intermediate support layer can be maintained to prevent the remaining residues. For example, if the storage modulus of the buffer layer is less than the above range at each temperature, there will be a problem that the binder sticks to the blade during cutting after attaching the tape to the wafer, the fluidity will increase due to the heat generated during grinding, and instead, the wafer and / or chip will be damaged, thus having a problem of remaining residues after removing the tape. Moreover, if the storage modulus at each temperature is greater than the above range, the voids will increase due to the decrease in bump fillability, and the impact and vibration during grinding cannot be smoothly absorbed, thereby causing damage to the bumps and the wafer. For example, the storage modulus of the buffer layer at a temperature of 25°C can be 0.02 MPa or more, 0.05 MPa or more, and can be 0.2 MPa or less or 0.1 MPa or less. Moreover, the storage modulus of the buffer layer at a temperature of 60°C can be 0.01 MPa or more or 0.05 MPa or more, and can be 0.1 MPa or less or 0.07 MPa or less. The buffer layer is not particularly limited as long as it can exhibit the above characteristics. For example, the above characteristics of the buffer layer can be adjusted by the buffer layer-forming composition or the preparation method, etc.

[0066] The buffer layer may contain a photocured product of a buffer layer-forming composition. Heat is generated during the back grinding process. If a heat-curable substance is included as the buffer layer, the fluidity will increase at high temperatures, resulting in viscosity and leaving residues or the thickness of the film changing, and ultimately, the thickness of the chip will deviate. On the contrary, the buffer layer may contain a photocured product to be cured in such a way that the surface and the inside with a specified thickness have no difference in curing degree, and the generation of residues and the thickness deviation can be prevented by preventing the above problems.

[0067] The buffer layer can be formed by photocuring a composition containing a first (meth)acrylate-based binder resin within the range of the storage modulus shown in the above range.

[0068] The first (meth)acrylate-based adhesive resin can use the components commonly used in the technical field to which the present invention pertains without limitation within the scope that can achieve the object of the present invention. For example, it can be a polymer of (meth)acrylate monomers having an alkyl group with 1 to 14 carbon atoms. Specifically, it can be a polymer of one or more selected from the group consisting of 2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, acrylic acid, 2-hydroxyethyl (meth)acrylate, isobornyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. Preferably, it can be a polymer obtained by polymerizing monomers containing 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, and methyl (meth)acrylate.

[0069] Moreover, the composition for the buffer layer may further contain a photoinitiator and a curing agent. The photoinitiator and the photocuring agent can be used without limitation those commonly used in the technical field to which the present invention pertains. For example, as a photopolymerization initiator, the photoinitiator can be hydroxycyclohexyl phenyl ketone (Irgacure 184), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Irgacure 907), α,α-methoxy-α-hydroxyacetophenone (Irgacure 651), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Irgacure 1173), etc. Furthermore, 1,6-hexanediol diacrylate (HDDA) can be included as a curing agent. Moreover, the composition for the buffer layer may further contain a crosslinking agent. As long as it is commonly used in this technical field, the type is not particularly limited. For example, an isocyanate-based crosslinking agent can be used.

[0070] The thickness of the buffer layer is not particularly limited. For example, it can be a thickness of about 10 to 500 μm. For example, it can be about 50 to 500 μm. For example, it can be about 70 to 500 μm.

[0071] Adhesive layer

[0072] The adhesive layer of the present invention is the part that bonds (or adheres) to the wafer, shows high fillability to the bumps, and prevents the formation of gaps between the unevenness of the bonding film for wafer back grinding and the circuit formation surface of the semiconductor wafer. Therefore, it is required to prevent the situation where the energy rays do not reach sufficiently and there are shadow areas. Moreover, the adhesive layer and the intermediate support layer show excellent supporting force, so that the residue of the adhesive layer can be prevented from remaining when the bonding film for wafer back grinding is peeled off.

[0073] From such a viewpoint, the storage modulus of the adhesive layer at a temperature of 25°C may be from 0.02 MPa to 0.2 MPa. Moreover, the storage modulus of the adhesive layer at a temperature of 60°C may be from 0.01 MPa to 0.1 MPa. If the storage modulus of the adhesive layer at each temperature is less than the above range, there will be a problem that residues of the adhesive layer are left during peeling due to too low degree of aggregation, there will be a problem that the adhesive sticks to the blade during cutting after the tape is attached to the wafer, and the fluidity will increase due to the heat generated during grinding, and instead, there will be problems of damaging the wafer and / or the chip. Moreover, if the storage modulus of the adhesive layer at each temperature is greater than the above range, there will be a problem with the close contact force when bonding to the wafer. Moreover, due to the reduction of the bump filling property, a gap is formed between the concave portion of the circuit formation surface of the semiconductor wafer and the adhesive film for back grinding of the wafer, and the stress distribution is uneven during grinding, so there will be a problem that the wafer is easily broken. Moreover, since the energy rays cannot reach sufficiently, it is difficult to peel the adhesive film for back grinding of the wafer, and thus there will be a problem of leaving residues of the adhesive layer. For example, the storage modulus of the adhesive layer at a temperature of 25°C may be 0.02 MPa or more or 0.05 MPa or more, and may be 0.2 MPa or less or 0.15 MPa or less. Moreover, the storage modulus of the adhesive layer at a temperature of 60°C may be 0.01 MPa or more or 0.05 MPa or more, and may be 0.1 MPa or less or 0.09 MPa or less.

[0074] The storage modulus of the adhesive layer can be adjusted by the composition for forming the adhesive layer.

[0075] The adhesive layer can be formed from various adhesive compositions such as acrylic adhesive compositions, silicone-based adhesive compositions, polyester-based adhesive compositions, polyamide-based adhesive compositions, urethane-based adhesive compositions, styrene-diene block copolymer adhesive compositions, etc., which are well-known ultraviolet curable adhesive compositions, within the range of the storage modulus showing the above range. Preferably, it can be formed from an acrylic adhesive composition.

[0076] The adhesive layer can be formed by thermally curing the composition for the adhesive layer containing a second (meth)acrylate adhesive resin. The adhesive layer can undergo an additional polymerization reaction when irradiated with ultraviolet rays before peeling the film after grinding.

[0077] For example, the second (meth)acrylate bonding resin can be selected without limitation from those commonly used in the technical field to which the present invention pertains within the scope that can achieve the object of the present invention. For example, it can be a polymer of (meth)acrylic monomers having an alkyl group with 1 to 14 carbon atoms. Specifically, it can be one or more polymers selected from the group consisting of 2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, acrylic acid, 2-hydroxyethyl (meth)acrylate, isobornyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. For example, it can be a polymer obtained by polymerizing monomers including 2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, methyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate, but is not limited thereto.

[0078] The composition for forming the bonding layer may contain monomers having unreacted vinyl groups. Upon ultraviolet irradiation, the unreacted vinyl groups of the monomers react with each other through the initiation reaction of the photoinitiator contained in the bonding layer to reduce the bonding force of the bonding layer, thereby preventing the residue of the bonding film for back grinding of the wafer from remaining in the peeling step. Moreover, the monomers having unreacted vinyl groups can also react with the monomers having unreacted vinyl groups contained in the intermediate support layer, thereby further improving the supporting force of the bonding film for back grinding of the wafer by increasing the bonding force between the bonding layer and the intermediate support layer. Thus, it is easier to prevent the residue of the bonding film for back grinding of the wafer from remaining in the peeling step.

[0079] The monomers having unreacted vinyl groups can be one selected from the group consisting of 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, glycidyl methacrylate, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and their combinations. The monomers having unreacted vinyl groups can be used within the scope that can achieve the object of the present invention. For example, relative to 100 parts by weight of the second (meth)acrylate-based bonding resin, the content of the monomers having unreacted vinyl groups can be 3 parts by weight to 20 parts by weight. If the content of the monomers having unreacted vinyl groups is less than this range, there will be a problem that the bonding force is not sufficiently reduced after ultraviolet irradiation. If it is greater than this range, the bonding layer will crack during the peeling of the film due to over-curing, and thus there will be a problem of residue generation.

[0080] Furthermore, the composition for forming the bonding layer may also contain a photoinitiator and a crosslinking agent, which are not particularly limited as long as they are commonly used in the technical field to which the present invention pertains.

[0081] The photoinitiator, as a substance that initiates the UV curing reaction by UV irradiation, is appropriately selected in terms of its type and content considering the curing rate of the resin composition and used. For example, as the photoinitiator, it may include hydroxycyclohexyl phenyl ketone (Irgacure 184), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one (Irgacure 907), α,α-methoxy-α-hydroxyacetophenone (Irgacure 651), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Irgacure 1173), etc.

[0082] Moreover, the composition for the adhesive layer may further contain a crosslinking agent. As long as it is commonly used in the technical field, the type is not particularly limited. For example, isocyanate crosslinking agents can be used.

[0083] On the other hand, the thickness of the adhesive layer 30 is not particularly limited. For example, it can be a thickness of about 5 - 30 μm or 10 - 30 μm.

[0084] Intermediate support layer

[0085] The intermediate support layer of the present invention is located between the buffer layer formed on the substrate layer and the adhesive layer attached to the wafer, and functions to support the buffer layer and the adhesive layer. Moreover, it can well fix the buffer layer during grinding to prevent the wafer from cracking or the chip from being damaged due to the impact or vibration during grinding. Moreover, it can also prevent the situation where the adhesive layer is anchored to the wafer and residues are left during peeling due to the excellent supporting force between the adhesive layer.

[0086] From such a perspective, the storage modulus of the intermediate support layer at a temperature of 25°C can be from 0.03 MPa to 0.3 MPa. Moreover, the storage modulus of the intermediate support layer at a temperature of 60°C can be from 0.02 MPa to 0.2 MPa. For example, if the storage modulus of the intermediate support layer at each temperature is less than the above range, due to insufficient support force for the buffer layer and the adhesive layer, the buffer layer cannot be well fixed during grinding, and the wafer may crack or the chip may be damaged due to the impact and vibration during the grinding process, resulting in the problem of leaving residues of the adhesive layer during peeling. Moreover, if the storage modulus of the intermediate support layer at each temperature is greater than the above range, although the support force for the buffer layer and the adhesive layer can be increased, the semiconductor chip will collide during the back grinding process, resulting in a decrease in the filling property of the bumps. Moreover, the bumps and the wafer will be damaged because the impact and vibration during grinding cannot be smoothly absorbed. For example, the storage modulus of the intermediate support layer at a temperature of 25°C can be 0.03 MPa or more or 0.05 MPa or more or 0.1 MPa or more, and can be 0.3 MPa or less or 0.2 MPa or less. Moreover, the storage modulus of the intermediate support layer at a temperature of 60°C can be 0.02 MPa or more or 0.1 MPa or more, and can be 0.2 MPa or less or 0.15 MPa or less. The intermediate support layer is not particularly limited as long as it can exhibit the above characteristics. For example, the above characteristics of the intermediate support layer can be adjusted by the composition for forming the intermediate support layer or the preparation method, etc.

[0087] The intermediate support layer can be a thermoset of a composition containing a thermoplastic acrylic resin. The intermediate support layer can make the thermoplastic acrylic resin contain a third (meth)acrylate adhesive resin within the range of showing the above-mentioned storage modulus. The third (meth)acrylate adhesive resin can be selected without limitation within the range that can achieve the object of the present invention from the resins commonly used in the technical field to which the present invention belongs. For example, it can be a polymer of a (meth)acrylic monomer having an alkyl group with 1 to 14 carbon atoms. Specifically, it can be one or more polymers selected from the group consisting of ethylhexyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, acrylic acid, 2-hydroxyethyl (meth)acrylate, isobornyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. For example, it can be a polymer obtained by polymerizing monomers containing n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and acrylic acid, but is not limited thereto.

[0088] Moreover, the composition for forming the intermediate support layer may further contain a crosslinking agent, which is not particularly limited as long as it is commonly used in the technical field. For example, isocyanate crosslinking agents can be used. With respect to the total thickness of the buffer layer, the intermediate support layer, and the adhesive layer, the thickness of the intermediate support layer is greater than 5%. For example, it can be greater than 5% and 30% or less. Thereby, when peeling the adhesive film for wafer back grinding from the wafer, the adhesive residue originating from the adhesive film for wafer back grinding can be prevented from being left without reducing the filling property of the bumps. For example, with respect to the total thickness of the buffer layer, the intermediate support layer, and the adhesive layer, the thickness of the intermediate support layer can be greater than 5% or 7% or more, and can be 30% or less, 25% or less, or 20% or less.

[0089] The total thickness of the buffer layer, the intermediate support layer, and the adhesive layer can be 20 μm to 600 μm. For example, it can be 50 μm to 200 μm. Moreover, the thickness of the intermediate support layer is not particularly limited. For example, it can be 1 μm to 40 μm.

[0090] Adhesive film 100 for back grinding of wafer

[0091] The adhesive film 100 for wafer back grinding of the present invention includes the intermediate support layer between the buffer layer formed on the substrate layer and the adhesive layer attached to the wafer, thereby improving the support force for the buffer layer and the adhesive layer. At the same time, when the adhesive film for wafer back grinding is applied to the back grinding process of the wafer formed with bumps, the problems caused by the voids and bending caused by the bumps and the shadow area that becomes a problem during energy ray irradiation can be solved by maximizing the bump filling property (embedding property).

[0092] From such a viewpoint, the adhesive film for wafer back grinding can satisfy the following Formula 1 and Formula 2.

[0093] Formula 1: At a temperature of 25 °C, the storage modulus of the adhesive layer < the storage modulus of the intermediate support layer

[0094] Formula 2: At a temperature of 25 °C, the storage modulus of the buffer layer < the storage modulus of the intermediate support layer

[0095] Among them, the storage modulus in Formula 1 and 2 represents the storage modulus when the adhesive film for wafer back grinding is attached to the wafer.

[0096] The intermediate support layer can show the targeted support force by having a higher storage modulus in the relationship between the buffer layer and the adhesive layer. Moreover, the buffer layer located on the substrate layer and the adhesive layer attached to the wafer show a lower storage modulus, thereby maximizing the filling property of the bumps.

[0097] Specifically, the adhesive film for wafer back grinding can satisfy the following Formula 3 and Formula 4.

[0098] Formula 3: At a temperature of 25°C, the storage modulus of the adhesive layer: the storage modulus of the intermediate support layer = 1:1.1 to 1:4

[0099] Formula 4: At a temperature of 25°C, the storage modulus of the buffer layer: the storage modulus of the intermediate support layer = 1:1.1 to 1:4

[0100] In relation to the adhesive layer and the buffer layer, if the storage modulus of the intermediate support layer is less than each of the above ranges, residues of the adhesive layer will be generated when the adhesive film for wafer back grinding is peeled off from the wafer, and thus the bumps and the wafer will be damaged because the impact and vibration during grinding cannot be smoothly absorbed. Moreover, if the storage modulus of the intermediate support layer is greater than each of the above ranges, a gap will be formed between the adhesive film for wafer back grinding and the depression on the circuit formation surface of the semiconductor wafer due to the reduced bump filling property, and the stress distribution will be uneven during grinding, thus having the problem of wafer breakage.

[0101] Furthermore, the adhesive film for wafer back grinding can satisfy the following Formula 5 and Formula 6.

[0102] Formula 5: At a temperature of 60°C, the storage modulus of the adhesive layer: the storage modulus of the intermediate support layer = 1:1.1 to 1:3

[0103] Formula 6: At a temperature of 60°C, the storage modulus of the buffer layer: the storage modulus of the intermediate support layer = 1:1.1 to 1:3

[0104] Heat is generated during the back grinding process of the wafer. If the storage modulus at high temperature is too low, the fluidity of each layer will increase at high temperature, resulting in viscosity and leaving residues or a change in the thickness of the film, and ultimately causing a deviation in the thickness of the chip.

[0105] The adhesive film for wafer back grinding shows the storage modulus within the above range at a temperature of 60°C, so that the desired effect can also be achieved during the back grinding process of the wafer.

[0106] The adhesive film for wafer back grinding includes the buffer layer, the intermediate support layer, and the adhesive layer. The total storage modulus of the buffer layer, the intermediate support layer, and the adhesive layer can be 0.01 MPa to 0.3 MPa at a temperature of 25°C, and can be 0.01 MPa to 0.1 MPa at a temperature of 60°C.

[0107] Hereinafter, the structure and function of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and should not be construed as limiting the present invention in any sense.

[0108] Example

[0109] Preparation Example 1 (C1): Preparation of a composition for forming a buffer layer

[0110] In a reactor with nitrogen reflux and a cooling device that is easy to adjust the temperature, a mixture of monomers is placed, which is a mixture of 63 parts by weight of 2-ethylhexyl acrylate (2-EHA), 30 parts by weight of isobornyl acrylate (IBOA), and 7 parts by weight of methyl acrylate (MA). Then, after adding 0.4 parts by weight of azobisisobutyronitrile (AIBN) as a reaction initiator, polymerization is carried out at a temperature of 60 °C for 6 hours in a nitrogen atmosphere to obtain an acrylic photocurable polymer with a weight-average molecular weight of 700,000 g / mol.

[0111] To the acrylic photocurable polymer, 0.7 parts by weight of Irgacure 651 as a photoinitiator and 0.2 parts by weight of 1,6-hexanediol diacrylate (HDDA) as a curing agent are added to prepare a buffer layer composition having a storage modulus shown in Table 2.

[0112] Preparation Example 2-1 (B1): Preparation of a composition for forming an intermediate support layer

[0113] In a reactor with nitrogen reflux and a cooling device that is easy to adjust the temperature, a mixture of monomers is placed, which is a mixture of 60 parts by weight of n-butyl acrylate (BA), 10 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of methyl acrylate (MA), 10 parts by weight of 2-hydroxyethyl acrylate (2-HEA), and 5 parts by weight of acrylic acid (AA). Then, 100 parts by weight of ethyl acetate (EAc) is placed as a solvent relative to 100 parts by weight of the monomer mixture. Then, azobisisobutyronitrile is placed as a reaction initiator at a concentration of 0.1 parts by weight, and polymerization is carried out at a temperature of 60 °C for 6 hours to obtain an acrylic adhesive resin with a weight-average molecular weight of 800,000 g / mol.

[0114] After adding 1 part by weight of an isocyanate crosslinking agent (Nippon Polyurethane Kogyo Co., Ltd., trade name “Coronate C”) to the acrylic adhesive resin and thoroughly mixing, a middle support layer composition for forming a middle support layer having a storage modulus shown in Table 2 is prepared.

[0115] Preparation Example 2-2 (B2): Preparation of a composition for forming an intermediate support layer

[0116] In Preparation Example 2-1 (B1), the amounts were changed to 55 parts by weight of n-butyl acrylate, 25 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of methyl acrylate, 10 parts by weight of 2-hydroxyethyl acrylate, 5 parts by weight of acrylic acid, 0.2 parts by weight of azobisisobutyronitrile, and 100 parts by weight of ethyl acetate, and then they were mixed. Then, in a nitrogen atmosphere, the mixture thus obtained was polymerized at a temperature of 60°C for 6 hours to obtain an acrylic adhesive resin having a weight average molecular weight of 500,000 g / mol. In addition, an intermediate support layer composition for forming an intermediate support layer having a storage modulus shown in Table 2 was prepared in the same manner as Preparation Example 2-1 (B1).

[0117] Preparation Example 3-1 (A1): Preparation of a composition for forming an adhesive layer

[0118] In a reactor with nitrogen reflux and a cooling device that is easy to adjust the temperature, a mixture of monomers obtained by mixing 60 parts by weight of 2-ethylhexyl acrylate, 30 parts by weight of 2-ethylhexyl methacrylate (2-EHMA), and 10 parts by weight of 2-hydroxyethyl acrylate was placed.

[0119] Next, with respect to 100 parts by weight of the monomer mixture, 100 parts by weight of ethyl acetate as a solvent was added. In order to remove oxygen in the reactor, nitrogen was injected therein and thoroughly mixed at a temperature of 30°C for 30 minutes or more. Then, the temperature was raised and maintained at 50°C, and 0.6 parts by weight of azobisisobutyronitrile as a reaction initiator was added to start the reaction, and then polymerization was carried out for 24 hours to prepare a primary reaction product.

[0120] 1 part by weight of 2-methacryloyloxyethyl isocyanate (MOI) and 0.2 parts by weight of a catalyst (dibutyltin dilaurate (DBTDL)) relative to the MOI were added to the primary reaction product, and the reaction was carried out at a temperature of 40°C for 24 hours to obtain an acrylic adhesive resin having a weight average molecular weight of 500,000 g / mol.

[0121] With respect to 100 parts by weight of the acrylic adhesive resin, 0.5 parts by weight of Irgacure 184 (manufactured by BASF) as a photoinitiator and 1 part by weight of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name “Coronate C”) as a crosslinking agent were added and thoroughly mixed to prepare an adhesive layer composition for forming an adhesive layer having a storage modulus shown in Table 2.

[0122] Preparation Example 3-2 (A2): Preparation of a composition for forming an adhesive layer

[0123] In Preparation Example 3-1(A1), a mixture of monomers consisting of 71 parts by weight of n-butyl acrylate, 19 parts by weight of methyl acrylate (MA), and 10 parts by weight of 2-hydroxyethyl acrylate (HEA) was used in place of the monomer mixture in Preparation Example 3-1(A1) to obtain an acrylic adhesive resin having a weight average molecular weight of 500,000 g / mol. In addition, a composition for forming an adhesive layer having a storage modulus shown in Table 2 was prepared in the same manner as in Preparation Example 3-1(A1).

[0124] Example 1

[0125] The composition for the buffer layer of Preparation Example 1(C1) was coated on a PET (polyethylene terephthalate film, thickness 50 μm) so that the thickness of the buffer layer was 70 μm. Then, ultraviolet rays of 1 J / cm 2 were irradiated (ultraviolet irradiation equipment: UV Scan Conveyor; LKUV system company) to form a cured buffer layer.

[0126] The composition for the intermediate support layer of Preparation Example 2-1(B1) was coated on the release-treated PET (thickness 50 μm) to a thickness of 20 μm. After coating, it was dried at a temperature of 100 °C for 3 minutes. Then, the buffer layer and the intermediate support layer were bonded to prepare a first composite film having a buffer layer and an intermediate support layer.

[0127] Next, the composition for the adhesive layer of Preparation Example 3-2(A2) was coated on a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 25 μm to a thickness of 10 μm, and then dried at a temperature of 100 °C for 3 minutes. Thus, a second composite film having an adhesive layer was prepared.

[0128] After removing the release-treated PET of the first composite film, it was laminated with the second composite film to prepare an adhesive film for wafer back grinding having a total thickness of 100 μm (in the total thickness, the thicknesses of the substrate layer and the release layer were removed) (buffer layer 70 μm + intermediate support layer 20 μm + adhesive layer 10 μm).

[0129] Examples 2 to 3 and Comparative Examples 1 to 5

[0130] In the adhesive film for wafer back grinding of Example 1, the types and thicknesses of the respective layers constituting the adhesive film for wafer back grinding were changed as shown in Table 1 to prepare each adhesive film for wafer back grinding.

[0131] Table 1

[0132]

[0133] - Evaluation

[0134] Experimental Example 1: Storage modulus (MPa)

[0135] The shear storage modulus was measured for each using a rheometer (TA instruments; ARES-G2) as a shear storage modulus measuring device. Specifically, samples having a size of 8 mm in diameter × 1 mm in thickness were prepared from each single layer formed of the compositions of the respective layers of the wafer back grinding adhesive films constituting Examples 1 to 3 and Comparative Examples 1 to 5. Then, for each sample, the shear storage modulus was measured in an environment from -20°C to 120°C under the condition of 1 Hz, and the shear storage moduli at the temperatures of 25°C and 60°C were recorded. The results are shown in Table 2 below.

[0136] Then, the ratio of the storage modulus of the adhesive layer: the storage modulus of the intermediate support layer (Equations 3 and 5) and the ratio of the storage modulus of the buffer layer: the storage modulus of the intermediate support layer (Equations 4 and 6) was calculated and recorded in Table 2.

[0137] Experimental Example 2: Degree of landfill

[0138] The wafer back grinding adhesive films of the examples and comparative examples were bonded to the semiconductor circuit surface (= wafer surface) formed with bumps (diameter 65 μm, height 70 μm) using a bonding device (CUON Solution; CUWLS-12) under the conditions of an applied pressure of 500 KPa, a roll temperature of 50°C, and a speed of 5 mm / s.

[0139] Then, the diameter (Df) of the wafer back grinding adhesive film wrapping the bumps was measured at a magnification of 20 using an optical microscope (Nikon; MM-40). As shown in Equation 7, the filling degree was calculated by dividing it by the diameter of the bumps (Di, 65 μm). The closer the filling degree is to 1, the higher the filling property for the bumps.

[0140] Equation 7: Filling degree = Df / Di

[0141] Experimental Example 3: Presence or absence of residues

[0142] After attaching the wafer back grinding adhesive films of the examples and comparative examples to the semiconductor circuit surface (= wafer surface), a wafer having a thickness of 725 μm was back ground to a thickness of 170 μm using a back grinding device (DISCO; DGP8760).

[0143] After the back grinding process was completed, 300 mJ / cm was irradiated using an exposure device (Seimei VACTRON; TRSJ-3000) 2Ultraviolet A. Then, a heat-sealing tape (Heat Sealing tape; MBS-100R) was thermocompression bonded to the outer periphery of one side of the adhesive film for wafer back grinding at a temperature of 230 °C, and then the adhesive film for wafer back grinding was removed.

[0144] After the back grinding process, 20 points on the surface of the wafer from which the adhesive film was removed were observed through a microscope to confirm whether adhesive residues were generated. The specific method is as follows.

[0145] The size of the residues at 20 points within the wafer after back grinding was measured. When there were no residues, it was evaluated as "good (none)". When residues with a size of 10 μm or more were generated, it was evaluated as "bad (yes)".

[0146] Table 2

[0147]

[0148] As shown in Table 1 above, the thickness ratio of the intermediate support layer of the adhesive film for wafer back grinding in the examples to the total thickness of the buffer layer, intermediate support layer, and adhesive layer is greater than 5%. As shown in Table 2, the adhesive layer, intermediate support layer, and buffer layer satisfy Formula 1 and Formula 2, and it was confirmed that the filling degree of the bumps was excellent and no residues were generated after the process.

[0149] On the contrary, it can be confirmed that Comparative Example 1 without an intermediate support layer, Comparative Example 2 and Comparative Example 3 that do not satisfy Formula 1 and Formula 2, and Comparative Example 4 and Comparative Example 5 in which the thickness ratio of the intermediate support layer deviated from the scope of the present invention had insufficient filling degree, or the supporting force between the adhesive layer and the buffer layer was weak, resulting in the generation of residues.

[0150] The present invention has been described above, but the present invention is not limited to the embodiments disclosed in this specification. Obviously, those of ordinary skill in the art can achieve various modifications within the scope of the technical idea of the present invention. Moreover, even if the effects of the structure of the present invention were not clearly described when the embodiments of the present invention were described above, the effects that can be predicted by the corresponding structure should also be recognized.

Claims

1. An adhesive film for wafer backside grinding, characterized in that: include: substrate layer; A buffer layer, disposed on the substrate layer; an intermediate support layer, disposed on the buffer layer; and A bonding layer is provided on the intermediate supporting layer, The thickness of the intermediate support layer is greater than 5% relative to the total thickness of the buffer layer, the intermediate support layer and the bonding layer. Satisfying the following equations 1 and 2, Formula 1: At a temperature of 25°C, the storage modulus of the bonding layer is less than the storage modulus of the intermediate support layer, Formula 2: At a temperature of 25° C., the storage modulus of the buffer layer is less than the storage modulus of the intermediate support layer.

2. The adhesive film for wafer backside grinding according to claim 1, characterized in that: The intermediate support layer is a heat-cured product of a composition comprising a thermoplastic acrylic resin.

3. The adhesive film for wafer backside grinding according to claim 1, characterized in that: The storage modulus of the intermediate support layer at a temperature of 25° C. is 0.03 MPa to 0.3 MPa.

4. The adhesive film for wafer backside grinding according to claim 1, characterized in that: The storage modulus of the bonding layer at a temperature of 25° C. is 0.02 MPa to 0.2 MPa.

5. The adhesive film for wafer backside grinding according to claim 1, wherein: The buffer layer has a storage modulus of 0.02 MPa to 0.2 MPa at a temperature of 25°C.

6. The adhesive film for wafer backside grinding according to claim 1, wherein: Satisfying the following equations 3 and 4, Formula 3: At a temperature of 25° C., the storage modulus of the bonding layer: the storage modulus of the intermediate support layer = 1:1.1 to 1:4, Formula 4: At a temperature of 25° C., the storage modulus of the buffer layer: the storage modulus of the intermediate support layer=1:1.1 to 1:

4.

7. The adhesive film for wafer backside grinding according to claim 1, characterized in that: Satisfying the following equations 5 and 6, Formula 5: At a temperature of 60° C., the storage modulus of the bonding layer: the storage modulus of the intermediate support layer = 1:1.1 to 1:3, Formula 6: At a temperature of 60° C., the storage modulus of the buffer layer: the storage modulus of the intermediate support layer=1:1.1 to 1:

3.

8. The adhesive film for wafer backside grinding according to claim 1, wherein: The total thickness of the buffer layer, the intermediate support layer and the bonding layer is 20 μm to 600 μm.

9. The adhesive film for wafer backside grinding according to claim 1, wherein: The thickness of the intermediate support layer is 1 μm to 40 μm.

10. The adhesive film for wafer backside grinding according to any one of claims 1 to 9, characterized in that: The adhesive film for wafer backside grinding is applied to a backside grinding process of a wafer on which bumps are formed.

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