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; the bonding layer is arranged on the middle supporting layer, and according to the formula 1, the change rate of the shear storage modulus of the middle supporting layer is larger than 1 and smaller than or equal to 3.

Description

Technical Field

[0001] The present invention relates to an adhesive film used to protect the surface of a wafer during the 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, that is, in the wafer back grinding process of a wafer formed with bumps, it has an excellent wafer surface protection effect (buffering effect), and at the same time, when peeling the adhesive film after back grinding, it reduces or eliminates the generation of adhesive residues, thereby showing excellent processability. 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, and the grinding process can be carried out according to the type or specifications 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 such as bumps with a large height difference can be formed. Due to this bump structure, when adhering the adhesive film for wafer back grinding, 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, resulting in cracking of the wafer or damage to the chip.

[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 the film is peeled off by irradiating energy rays. In this case, since the irradiated energy rays cannot reach the gaps formed due to the bump structure sufficiently, 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 bonding agent 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, which can prevent breakage of the wafer in the back grinding process of the wafer, especially in the back grinding process of a wafer having a bump structure, and minimize residues 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. Other objects and advantages of the present invention not mentioned can be understood from the following description and can be more clearly understood through the embodiments of the present invention. Moreover, it can be seen that the objects and advantages of the present invention can be achieved by the solutions shown in the claims of the present invention and their combinations.

[0009] Technical Solution

[0010] To solve the above problems, according to an embodiment of the present invention, the present invention includes: 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. According to the following formula 1, the shear storage modulus change rate of the intermediate support layer can be greater than 1 and less than or equal to 3.

[0011] Compared with before ultraviolet irradiation, the bonding force of the intermediate support layer to the acrylic plate is reduced after ultraviolet irradiation. At a temperature of 25 °C, the bonding force of the intermediate support layer to the acrylic plate after ultraviolet irradiation can be 200 gf / 25 mm to 1000 gf / 25 mm.

[0012] At a temperature of 25 °C, the bonding force of the intermediate support layer to the acrylic plate before ultraviolet irradiation can be 700 gf / 25 mm to 3000 gf / 25 mm.

[0013] At a temperature of 25 °C, the bonding force of the bonding layer to the wafer after ultraviolet irradiation can be 50 gf / 25 mm or less.

[0014] The adhesive force of the buffer layer after ultraviolet irradiation can be the same as that of the buffer layer before ultraviolet irradiation.

[0015] At a temperature of 25 °C, the adhesive force of the buffer layer to the acrylic plate can be from 1000 gf / 25 mm to 3000 gf / 25 mm.

[0016] The intermediate support layer may include a monomer having one unreacted vinyl group, and the monomer having one unreacted vinyl group is 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 mono vinyl ether, and combinations thereof.

[0017] The adhesive film for back grinding of a wafer is applied to the back grinding process of a wafer formed with bumps.

[0018] Effects of the Invention

[0019] The adhesive film for back grinding of a wafer according to 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. Moreover, the adhesive film for back grinding of a wafer can prevent cracking of the wafer or breakage of the chip during the back grinding of a wafer having a bump structure. Moreover, at the same time, it can also prevent the generation of residues of the adhesive layer when peeling the adhesive film for back grinding of a wafer from the wafer. Thereby, the processability of wafer processing and the quality of the manufactured semiconductor chips can be improved.

[0020] The effects of this specification are not limited to the effects mentioned above, and 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

[0021] Figure 1 A cross-sectional view of an adhesive film for back grinding of a wafer showing an example of the present invention.

[0022] Figure 2 A cross-sectional view showing the state where an adhesive film for back grinding of a wafer according to an example of the present invention is attached to a wafer formed with a bump structure.

[0023] Figure 3 An example of a cross-section showing a bump structure formed on the surface of a wafer.

[0024] Figure 4A flowchart briefly showing the process of applying the adhesive film for wafer back grinding in an example of the present invention to the wafer back grinding process and subsequent peeling is shown.

[0025] Description of reference numerals

[0026] 100: Adhesive film for wafer back grinding

[0027] 200: Wafer before back grinding process

[0028] 210: Wafer after back grinding process

[0029] 300: Bump

[0030] R: Area where residues of the adhesive remain

[0031] 10: Adhesive layer

[0032] 20: Intermediate support layer

[0033] 30: Buffer layer

[0034] 40: Substrate layer

[0035] P: Pitch between bumps. Detailed description of the preferred embodiment

[0036] The foregoing objects, features, and advantages will be described in detail with reference to the accompanying drawings, whereby those of ordinary skill in the art to which the present invention pertains can easily implement the technical idea of the present invention. In the process of describing the present invention, if it is determined that a detailed description of well-known technologies 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.

[0037] Among the contents not described in this specification, as long as they can be fully analogized technically by those of ordinary skill in the art, their description will be omitted.

[0038] In this specification, that any structure is disposed "above (or below)" a structural element or "on (or under)" a structural element not only means that the any structure is disposed in contact with the upper surface (or lower surface) of the above structural element, but also means that other structures may be interposed between the above structural element and the any structure disposed on (or under) the above structural element.

[0039] In this specification, unless the context clearly indicates otherwise, singular expressions used in this specification include plural expressions. In this application, terms such as "comprising" or "including" should not be construed as necessarily including all the various structural elements described in the specification, but should be construed as possibly excluding some of the structural elements or further including additional structural elements.

[0040] In this specification, terms such as "one side", "the other side", "both sides" are used to distinguish a structural element from other structural elements, and the structural element is not limited to these terms.

[0041] In this specification, the "pitch between bumps" represents a numerical value that can be used as an index of the spacing between bumps. For example, as Figure 2 shown, it represents the distance between the highest points of the protruding shapes of adjacent bumps.

[0042] In this specification, "excellent embeddability for bump structures, bending, etc." can mean i) when the adhesive film is adhered to the semiconductor wafer, the adhesive film closely adheres to the bending well along the bending without warping or forming voids due to the bump structures, etc. formed on the semiconductor wafer, and ii) when the layers of the adhesive film of the present invention are laminated, it closely adheres to the bending existing due to the bump structures, etc.

[0043] In this specification, unless the temperature value is particularly limited, "room temperature" can be interpreted as a temperature condition of approximately 23 - 25 °C.

[0044] In this specification, "(meth)acrylate" is used as a term including acrylate and methacrylate, and the same applies to similar terms.

[0045] In the following description of the present invention, detailed descriptions of related well-known technologies that may unnecessarily confuse the gist of the present invention will be omitted.

[0046] Figure 3 is an actual magnified photograph of the bump 300 structure formed on the surface of the wafer 200. Due to the shape of the bump 300, a void is formed between the wafer 200 and the bump 300. Therefore, when the back surface of the wafer is polished, the stress applied is unevenly distributed on the wafer due to the void, resulting in the problem of wafer breakage. Also, there will be a shadow area in the gap formed by the bump structure where the irradiated energy rays cannot reach sufficiently. In such a shadow area, the curing by the energy rays is insufficient, resulting in the problem of difficulty in peeling off the adhesive film (adhesive film for back surface polishing of the wafer). In this case, as a result, it is easy to leave adhesive residues from the adhesive film on the wafer surface, thereby reducing the processability, and there is a problem of adversely affecting the quality of the manufactured semiconductor chip. Especially as Figure 3As shown, in the case of including bumps in the shape of fillers, the pitch between the bumps becomes smaller due to the dense formation of the bumps (concavities and convexities). In this case, the above problems occur more severely. This will be described in detail by referring to Figure 4 as follows.

[0047] Figure 4 The flowchart of the process of applying the adhesive film 100 for wafer back grinding according to an example of the present invention to a wafer, performing back grinding, and then peeling it off by irradiating energy rays to reduce the adhesive force is illustrated.

[0048] Specifically, Figure 4 S1 of Figure 4 is the step of preparing the wafer before the wafer back grinding process (wafer loading), showing the state where the bumps 300 are formed on the surface of the wafer 200. For simplicity of illustration, the bumps 300 are shown only as a layer structure with a surface, and actually do not have a layer structure.

[0049] Figure 4 S2 of Figure 4 is the step of attaching (adhering) the adhesive film 100 for wafer back grinding of the present invention to the surface side of the wafer, so as to protect the surface of the wafer 200 during grinding.

[0050] Figure 4 S3 of Figure 4 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 the wafer on a chuck table can be used.

[0051] Figure 4 S4 of Figure 4 briefly shows the step of irradiating energy rays (e.g., ultraviolet rays (UV)) to peel off the adhesive film 100 for wafer back grinding after the back grinding process. Compared with the wafer 200 before the back grinding process, the thickness of the wafer 210 after the back grinding process becomes thinner.

[0052] Figure 4 S5 of Figure 4 briefly shows the step of peeling off the adhesive film 100 for wafer back grinding after the back grinding process. In this case, if the adhesive film is not sufficiently cured by the energy rays, or the adhesive force is not sufficiently reduced to a level where it can be peeled off well, residues of the adhesive film 100 for wafer back grinding will be left in the peeling step. Also, in the case where the adhesive force of the adhesive layer is reduced by irradiating energy rays and the supporting force between the adhesive layer and the layer on the surface not attached to the wafer is reduced, residues of the adhesive film 100 for wafer back grinding will be left in the peeling step. In particular, when the bumps of the wafer with the adhesive film for wafer back grinding are formed densely, the smaller the pitch between the bumps, the more severe the degree of voids and bending caused by the bumps, thus causing the above problems.

[0053] Figure 4 The region R where the residue of the binder remains as described above is exemplified.

[0054] As a result of the inventors' extensive research focusing on the above problems, by including an intermediate support layer between the adhesive layer and the buffer layer, the support force of the adhesive film for wafer back grinding is improved, so that the wafer and the chip can be protected from impact and vibration during wafer grinding. Moreover, by improving the bump filling property (tight adhesion), the energy rays can reach evenly and sufficiently, thus completing the invention of the adhesive film for wafer back grinding that can prevent the residue of the adhesive layer from remaining during peeling.

[0055] As an example of the present invention, as Figure 1 shown, the adhesive film 100 for wafer back grinding of the present invention includes: a substrate layer 40; a buffer layer 30 provided on the substrate layer; an intermediate support layer 20 provided on the buffer layer; and an adhesive layer 10 provided on the intermediate support layer. Herein, "provided on..." means provided on either side. Hereinafter, the adhesive film 100 for wafer back grinding and its respective structural layers will be described in detail.

[0056] Substrate layer 40

[0057] The substrate layer of the adhesive film for wafer back grinding of the present invention is formed of a material having a high tensile modulus. For example, preferably, 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 reloading of the semiconductor chip during the back grinding process, but it is not limited thereto.

[0058] 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), 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.

[0059] 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.

[0060] On the other hand, the substrate layer may also contain various additives such as a small amount of coupling agent, plasticizer, antistatic agent, antioxidant, etc. as needed.

[0061] Buffer layer 30

[0062] The buffer layer of the present invention is provided on the substrate layer, which will affect the filling property of the bumps and help absorb the vibration and impact generated during the back grinding of the wafer. Moreover, the buffer layer shows excellent adhesion to the substrate layer, so that it is possible to prevent cracks in the wafer or damage to the chip caused by the un-fixed buffer layer during wafer grinding.

[0063] Different from the adhesive layer and the intermediate support layer described later, the adhesive force of the buffer layer before ultraviolet irradiation can be the same as that after ultraviolet irradiation. At a temperature of 25 °C, the adhesive force of the buffer layer to an acrylic plate (polymethyl methacrylate, PMMA) can be 1000 gf / 25 mm to 3000 gf / 25 mm. For example, if the adhesive force of the buffer layer is less than the above range, the fluidity will increase due to the heat generated during wafer grinding, which will instead damage the wafer and / or the chip, and thus there will be a problem of residues left after removing the adhesive film. Moreover, if the adhesive force of the buffer layer is greater than the above range, the impact and vibration during wafer grinding cannot be absorbed smoothly, thus causing damage to the bumps and the wafer, but it is not limited thereto.

[0064] The buffer layer may contain a photocured product of a buffer layer forming composition. Heat is generated during the back grinding process of the wafer. If a heat-curable substance is included as the buffer layer, the fluidity will increase at high temperature, 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 with a specified thickness and the inside have no difference in curing degree, and the generation of residues and thickness deviation can be prevented by preventing the above problems.

[0065] The buffer layer can be formed by photocuring a composition containing a first (meth)acrylate-based adhesive resin within the range of showing the above-mentioned range of adhesive force.

[0066] The first (meth)acrylate-based adhesive resin can be used without limitation within the range that can achieve the object of the present invention, and components commonly used in the technical field to which the present invention belongs can be used. For example, it can be a polymer of a (meth)acrylate 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 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.

[0067] Furthermore, the composition for forming the buffer layer can also adjust the degree of crosslinking upon light irradiation by including a polyfunctional (meth)acrylic acid compound. The polyfunctional (meth)acrylic acid compound can include one or more selected from 1,6 - hexanediol diacrylate (HDDA), 1,9 - nonanediol diacrylate (NDDA), ethylene glycol diacrylate (EGDA), triethylene glycol diacrylate (TEGDA), tripropylene glycol diacrylate (TPGDA), neopentyl glycol diacrylate (NPGDA), and combinations thereof. The buffer layer can include the polyfunctional (meth)acrylic acid compound without limitation within the range of the adhesion force shown in the above range. For example, relative to 100 parts by weight of the first (meth)acrylate - based adhesive resin as the polymer of the monomer, the content of the polyfunctional (meth)acrylic acid compound can be 0.05 parts by weight to 0.3 parts by weight.

[0068] The thickness of the buffer layer is not particularly limited. For example, it can be a thickness of about 10 - 500 μm, for example, it can be about 50 - 500 μm, for example, it can be about 70 - 500 μm.

[0069] Adhesive layer 10

[0070] 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 gaps from forming between the unevenness of the adhesive film for wafer back - grinding and the circuit - forming 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 residues of the adhesive layer can be prevented from remaining when the adhesive film for wafer back - grinding is peeled off.

[0071] From such a perspective, at a temperature of 25°C, the adhesion force of the adhesive layer to the wafer before ultraviolet irradiation can be 700 - 3000 gf / 25 mm. In this way, high fillability can be exhibited to the bumps. Moreover, excellent supporting force can also be shown to the intermediate support layer. And at a temperature of 25°C, the adhesion force of the adhesive layer to the wafer after ultraviolet irradiation can be 50 gf / 25 mm or less. In this way, residues can be prevented from remaining when the adhesive film for wafer back - grinding is peeled off after wafer back - grinding.

[0072] The physical properties of the adhesive layer can be adjusted by the composition for forming the adhesive layer.

[0073] 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, and styrene-diene block copolymer adhesive compositions, which are well-known ultraviolet curable adhesive compositions, within the range of adhesive force showing the said range. Preferably, it can be formed from an acrylic adhesive composition.

[0074] The adhesive layer can be formed by thermally curing an adhesive layer-forming composition containing a second (meth)acrylate-based adhesive resin. The second (meth)acrylate-based adhesive resin can be selected without limitation within the range capable of achieving the object of the present invention. 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 2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, acrylic acid, 2-hydroxyethyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

[0075] The adhesive layer-forming composition can contain a monomer having an unreacted vinyl group. Upon ultraviolet irradiation, the unreacted vinyl groups of the monomer are bonded to each other through the initiation reaction of a photo-reactive initiator contained in the adhesive layer, thereby reducing the adhesive force of the adhesive layer. Thus, it is possible to prevent the residue of the adhesive film for wafer back grinding from remaining in the peeling step. Also, the monomer having an unreacted vinyl group can react with the monomer having an unreacted vinyl group contained in the intermediate support layer, thereby improving the support force of the adhesive film for wafer back grinding by increasing the bonding force between the adhesive layer and the intermediate support layer. As a result, it is possible to prevent the residue of the adhesive film for wafer back grinding from remaining in the peeling step.

[0076] The monomer having an unreacted vinyl group 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 mono vinyl ether, and combinations thereof. The monomer having an unreacted vinyl group can be used within the range capable of achieving the object of the present invention. For example, with respect to 100 parts by weight of the second (meth)acrylate-based adhesive resin, the content of the monomer having an unreacted vinyl group can be 3 parts by weight to 20 parts by weight. If the content of the monomer having an unreacted vinyl group is less than the said range, there will be a problem that the adhesive force is not sufficiently reduced after ultraviolet irradiation. If it is greater than the said range, the adhesive layer will crack during the peeling of the film due to over-curing, and as a result, there will be a problem of residue generation.

[0077] Moreover, the composition for forming the adhesive layer may further 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.

[0078] The photoinitiator, as a substance that initiates a 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 the like. For example, the photoinitiator 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), and 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Irgacure 1173), etc.

[0079] In addition, the composition for the adhesive layer may further contain a crosslinking agent, and its type is not particularly limited as long as it is commonly used in this technical field. For example, an isocyanate crosslinking agent can be used.

[0080] 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.

[0081] Intermediate support layer

[0082] 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 can play a role in improving the support force of the adhesive film for wafer back grinding by supporting the buffer layer and the adhesive layer. In this way, it is possible to prevent cracking of the wafer or breakage of the chip caused by the impact and vibration generated during wafer grinding. Moreover, it is possible to prevent the situation where the adhesive layer is anchored to the wafer and residues are left when peeling off the adhesive film for wafer back grinding by improving the bonding force with the adhesive layer whose bonding force decreases during UV irradiation.

[0083] Specifically, according to the following formula 1, the change rate of the shear storage modulus of the intermediate support layer can be greater than 1 and less than or equal to 3.

[0084] Formula 1

[0085] At a temperature of 25°C, the shear storage modulus of the intermediate support layer after ultraviolet irradiation / the shear storage modulus of the intermediate support layer before ultraviolet irradiation.

[0086] The change rate of the shear storage modulus before and after the ultraviolet irradiation is 1 or less. For example, when it is 1, the shear storage modulus before and after the ultraviolet irradiation does not change, and the adhesive layer with reduced adhesive force due to ultraviolet irradiation cannot be held, so residues of the adhesive layer may be left when peeling the adhesive film for wafer back grinding. In particular, with the high density of chips, bumps are formed densely, and the pitch between bumps becomes narrow, so the problem of residue may occur. Moreover, if the change rate of the shear storage modulus is greater than 3, the adhesive layer cannot be supported when peeling the adhesive film due to excessive reduction of the adhesive force and increase of the storage modulus caused by excessive hardening, so residues may be left when peeling the adhesive film for wafer back grinding.

[0087] The intermediate support layer satisfies the change rate of the shear storage modulus within the above range. At a temperature of 25°C, the shear storage modulus before the ultraviolet irradiation can be 0.03 MPa to 0.3 MPa. If the shear storage modulus of the intermediate support layer before the ultraviolet irradiation is less than the above range, heat will be generated in the wafer grinding process, and the fluidity will be too high due to the too low storage modulus at high temperature, so residues may be generated due to becoming viscous. Moreover, the wafer may be damaged because the stress that may occur in the wafer grinding process cannot be properly resolved. Moreover, if the shear storage modulus of the intermediate support layer before the ultraviolet irradiation is greater than the above range, problems such as wafer or chip breakage may occur in the grinding process due to reduced bump fillability, but it is not limited to this.

[0088] The intermediate support layer shows the shear storage modulus within the above range, further improving the bump fillability, can easily absorb the stress generated during the grinding process, and can more easily prevent the generation of residues while maintaining excellent support force.

[0089] Moreover, when the adhesive force of the adhesive layer is reduced due to ultraviolet irradiation, the adhesive force of the intermediate support layer can also be reduced simultaneously. Specifically, the adhesive force of the intermediate support layer to the adhesive layer after ultraviolet irradiation is reduced compared to before ultraviolet irradiation. For an acrylic plate (PMMA), at a temperature of 25°C, the adhesive force of the intermediate support after ultraviolet irradiation can be from 200 gf / 25 mm to 1000 gf / 25 mm. If the adhesive force of the intermediate support layer is less than 200 gf / 25 mm, the close contact force with the buffer layer may become weak due to the reduced adhesive force when peeling the adhesive film for wafer back grinding, resulting in a problem of leaving residues. Moreover, if the adhesive force of the intermediate support layer is greater than 1000 gf / 25 mm, the adhesive force may be increased due to a decrease in the content of unreacted vinyl groups that reduce the adhesive force, resulting in insufficient chemical bonding with the adhesive layer. Even if the adhesive force is high between narrow pitches, the intermediate support layer cannot support the adhesive layer, leading to a problem of generating residues, but it is not limited thereto.

[0090] Moreover, at a temperature of 25°C, the adhesive force of the intermediate support layer to the acrylic plate before ultraviolet irradiation can be from 700 gf / 25 mm to 3000 gf / 25 m. For example, if the adhesive force of the intermediate support layer is less than 700 gf / 25 mm, problems such as peeling of the adhesive during the grinding process due to shear stress generated during the grinding process, or weakening of the filling property for bumps may occur, resulting in problems such as breakage of the wafer or chip due to the inability to absorb the impact and vibration generated during wafer grinding well. Moreover, if the adhesive force of the intermediate support layer is greater than 3000 gf / 25 mm, problems may occur during the process of attaching the adhesive film for wafer back grinding to the wafer and then cutting the edge, such as the cutting blade stopping due to the high adhesive force of the intermediate support layer.

[0091] The physical properties of the intermediate support layer can be adjusted by the composition for forming the intermediate support layer.

[0092] The intermediate support layer can be a thermoset of a composition containing a thermoplastic acrylic resin. Within the range showing the change rate of the shear storage modulus of the intermediate support layer, the thermoplastic acrylic resin can contain a third (meth)acrylate-based adhesive resin. The third (meth)acrylate-based 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 pertains.

[0093] 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 ethylhexyl (meth)acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, acrylic acid, 2-hydroxyethyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

[0094] The composition for forming the intermediate support layer may contain monomers having unreacted vinyl groups. When irradiated with ultraviolet light, the monomers having unreacted vinyl groups can also crosslink with the monomers having unreacted vinyl groups contained in the intermediate support layer, thereby improving the support force of the adhesive film for wafer back grinding by increasing the bonding strength between the adhesive layer and the intermediate support layer. As a result, residues of the adhesive film for wafer back grinding can be prevented from remaining in the peeling step.

[0095] 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 mono vinyl ether, and combinations thereof. The monomers having unreacted vinyl groups can be used within the range that can achieve the object of the present invention. For example, relative to 100 parts by weight of the third (meth)acrylate-based adhesive resin, the content of the monomers having unreacted vinyl groups can be 0.5 to 3 parts by weight. If the content of the monomers having unreacted vinyl groups is less than this range, the intermediate support layer may not be able to support the adhesive layer due to insufficient chemical bonding through the unreacted vinyl groups with the adhesive layer. If it is greater than this range, problems such as residue generation may occur due to excessive reduction in bonding strength.

[0096] Moreover, the composition for forming the adhesive layer may further contain a photoinitiator and a crosslinking agent, and there is no particular limitation as long as they are commonly used in the technical field to which the present invention pertains.

[0097] The photoinitiator, as a substance that initiates the ultraviolet curing reaction by ultraviolet irradiation, is appropriately selected in terms of its type and content considering the curing rate of the resin composition, etc. For example, the photoinitiator may include hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, α,α-methoxy-α-hydroxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, etc.

[0098] Furthermore, the composition for the adhesive layer may also contain a crosslinking agent, and there is no particular limitation on the type as long as it is commonly used in this technical field. For example, isocyanate-based crosslinking agents can be used.

[0099] The total thickness of the buffer layer, the intermediate support layer, and the adhesive layer may be from 20 μm to 600 μm. For example, it may be from 50 μm to 200 μm. Moreover, the thickness of the intermediate support layer is not particularly limited. For example, it may be from 1 μm to 40 μm.

[0100] Adhesive film 100 for back grinding of wafer

[0101] The adhesive film 100 for back grinding of a wafer according to the present invention is applied to the back grinding process of a wafer formed with bumps, and includes the intermediate support layer between the buffer layer formed on the base material layer and the adhesive layer attached to the wafer, which can improve the support force for the buffer layer and the adhesive layer.

[0102] Moreover, when applied to the back grinding process of a wafer formed with bumps, problems caused by voids and bending due to bumps and shadow areas that become problems during energy ray irradiation can be solved by maximizing bump fillability (burying property).

[0103] Moreover, after back grinding, the adhesive force of the adhesive layer can be reduced by irradiating ultraviolet rays to peel off the adhesive film for back grinding of the wafer. In this case, ultraviolet rays of 300 mJ / cm 2 to 1500 mJ / cm 2 may be irradiated, but it is not limited thereto.

[0104] The adhesive film for back grinding of the wafer includes an intermediate support layer having a shear storage modulus change rate within a specific range of the foregoing formula (1), which can prevent problems such as cracking of the wafer or breakage of the chip caused by impact and vibration generated during wafer grinding. Moreover, by improving the bonding force with the adhesive layer that decreases in adhesive force during ultraviolet ray irradiation, it is possible to prevent the situation where the adhesive layer is fixed to the wafer and residues are left when peeling off the adhesive film for back grinding of the wafer. In particular, in the case where bumps are densely formed and the pitch between bumps becomes narrow, excellent effects can also be shown in preventing the generation of residues. The adhesive film for back grinding of the wafer can prevent the generation of residues due to excellent peeling effects even for wafers with a pitch between bumps of 40 μm or more. The upper limit of the pitch between bumps is not particularly limited and may be 500 μm or less.

[0105] Hereinafter, the structure and operation 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. Contents not described herein can be fully analogized technically by those of ordinary skill in the art, and thus their descriptions are omitted.

[0106] Examples

[0107] Preparation example 1 (C1): Preparation of composition C1 for forming buffer layer

[0108] In a reactor with nitrogen reflux and a cooling device that is easy to adjust the temperature, a mixture of monomers consisting of 50 g of 2-ethylhexyl acrylate (2-EHA) monomer, 35 g of isobornyl acrylate (IBOA), 10 g of 2-hydroxyethyl acrylate (2-HEA), and 5 g of 2-ethylhexyl methacrylate (2-EHMA) is placed. To remove oxygen in the reactor, nitrogen is injected therein and thoroughly mixed at room temperature for 30 minutes. Then, 0.5 part by weight of azobisisobutyronitrile (AIBN) as a reaction initiator is added, and the temperature of the reactor is raised to 60 °C and maintained for 6 hours to perform polymerization, thereby preparing a primary reactant, which is an acrylic photocurable polymer with a weight average molecular weight of 700,000 g / mol.

[0109] 0.2 part by weight of 1,6-hexanediol diacrylate (HDDA) as a polyfunctional (meth)acrylate compound and 0.5 part by weight of Irgacure 651 as a photoinitiator are mixed in 100 parts by weight of the primary reactant to prepare Composition C1 for forming a buffer layer, which is a photocurable adhesive composition.

[0110] Preparation example 2 (A1): Preparation of composition A1 for forming adhesive layer

[0111] In a reactor with nitrogen reflux and a cooling device that is easy to adjust the temperature, a mixture of monomers consisting of 42 g of 2-ethylhexyl acrylate, 27 g of n-butyl acrylate (BA), 25 g of 2-hydroxyethyl acrylate (HEA), and 6 g of methyl acrylate (MA) is placed. Then, 100 parts by weight of ethyl acetate (EAc) as a solvent is added to 100 parts by weight of the monomer mixture. To remove oxygen in the reactor, nitrogen is injected therein and thoroughly mixed at room temperature for 30 minutes or more. Then, 0.1 part by weight of azobisisobutyronitrile as a reaction initiator is added, and the temperature of the reactor is raised to 60 °C and maintained for 24 hours to perform polymerization, thereby preparing a primary reactant.

[0112] 15 parts by weight of 2-methacryloyloxyethyl isocyanate (MOI) and 1 part by weight of a catalyst (dibutyl tin dilaurate (DBTDL)) relative to MOI are added to the primary reactant, and the reaction is carried out at a temperature of 40 °C for 24 hours to obtain an acrylic resin with a weight average molecular weight of 600,000.

[0113] In the polymerization liquid (acrylic polymer, content: 100 parts by weight) obtained through the said operation, 0.3 part by weight of Irgacure 184 (manufactured by BASF Corporation, trade name), which is a photopolymerization initiator, is blended, and 2 parts by weight of an isocyanate crosslinking agent (Nippon Polyurethane Kogyo Co., Ltd., trade name "Coronate C") is added to prepare Composition A1 for forming a bonding layer.

[0114] Preparation example 3 (A2): Preparation of composition A2 for forming adhesive layer

[0115] In Preparation Example 2, except that 2-ethylhexyl acrylate is changed to 21 g, n-butyl acrylate is changed to 23 g, 2-hydroxyethyl acrylate is changed to 19 g, 2-ethylhexyl methacrylate is changed to 20 g, methyl acrylate is changed to 17 g, and the isocyanate crosslinking agent is changed to 3 parts by weight, Composition A2 for forming a bonding layer is prepared in the same manner as in Preparation Example 2.

[0116] Preparation example 4 (B1): Preparation of composition B1 for forming intermediate support layer

[0117] In a reactor with nitrogen reflux and a cooling device that is easy to adjust the temperature, a mixture of monomers composed of 35 g of 2-ethylhexyl acrylate, 30 g of n-butyl acrylate, 30 g of 2-hydroxyethyl acrylate, and 5 g of methyl acrylate is placed. Next, 100 parts by weight of ethyl acetate as a solvent is added to 100 parts by weight of the said monomer mixture. In order to remove the oxygen in the reactor, nitrogen is injected therein and thoroughly mixed at room temperature for 30 minutes or more. Then, the temperature of the reactor is raised to 60 °C and maintained, and 0.07 part by weight of azobisisobutyronitrile as a reaction initiator is added to initiate the reaction and then polymerized for 24 hours to prepare a primary reaction product.

[0118] In the said primary reaction product, 1 part by weight of 2-methacryloyloxyethyl isocyanate (MOI) and 0.2 part by weight of a catalyst (dibutyltin dilaurate) relative to MOI are blended, and the reaction is carried out at a temperature of 40 °C for 24 hours to obtain an acrylic resin with a weight average molecular weight of 850,000.

[0119] In the polymerization liquid (acrylic polymer, content: 100 parts by weight) obtained through the said operation, 0.3 part by weight of Irgacure 184 (manufactured by BASF Corporation, trade name), which is a photopolymerization initiator, is blended, and 2 parts by weight of an isocyanate crosslinking agent (Nippon Polyurethane Kogyo Co., Ltd., trade name "Coronate C") is added to prepare Composition B1 for forming an intermediate support layer.

[0120] Preparation example 5 (B2): Preparation of composition B2 for forming intermediate support layer

[0121] In Preparation Example 4, except that 2-ethylhexyl acrylate was changed to 23 g, n-butyl acrylate was changed to 47 g, 2-hydroxyethyl acrylate was changed to 16 g, 2-ethylhexyl methacrylate was changed to 5 g, methyl acrylate was changed to 9 g, and the isocyanate crosslinking agent was changed to 2.5 parts by weight, Composition B2 for forming an intermediate support layer was prepared in the same manner as in Preparation Example 4.

[0122] Preparation example 6 (B3): Preparation of composition B3 for forming intermediate support layer

[0123] Composition B3 for forming an intermediate support layer was prepared in the same manner as in Preparation Example 4, except that the contents of 2-methacryloyloxyethyl isocyanate and the catalyst (DBTDL) were changed to 0 parts by weight.

[0124] Preparation example 7 (B4): Preparation of composition B4 for forming intermediate support layer

[0125] Composition B4 for forming an intermediate support layer was prepared in the same manner as in Preparation Example 5, except that the content of 2-methacryloyloxyethyl isocyanate was changed to 4 parts by weight.

[0126] Example 1

[0127] The buffer layer-forming composition C1 of Preparation Example 1 was coated on a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 100 μm to a thickness of 100 μm. Then, a PET subjected to a release treatment having a thickness of 38 μm was disposed on the coating with the release surface facing the coating of C1 to form a first composite film (X).

[0128] The first composite film (X) was irradiated with ultraviolet rays of 1 J / cm 2 (ultraviolet irradiation equipment: ultraviolet scan conveyor (UV Scan Conveyor); manufactured by LKUV system Co., Ltd.) to prepare a cured first composite film (X).

[0129] The intermediate support layer-forming composition B1 of Preparation Example 4 was coated on a PET film subjected to a release treatment having a thickness of 38 μm to form a coating having a thickness of 10 μm, and then dried at a temperature of 100 °C for 3 minutes. Then, the release film (release-treated PET) of the cured first composite film (X) was removed, and the coating of B1 was laminated thereto to prepare a second composite film (Y).

[0130] Next, the composition A1 for forming the adhesive layer of Preparation Example 2 was applied onto a release film with a thickness of 38 μm to a thickness of 10 μm, and then dried at a temperature of 100 °C for 3 minutes. Then, after removing the release film (release-treated PET) of the second composite film (Y), the coating of A1 was laminated to prepare an adhesive film for wafer back grinding with a total thickness of 258 μm (biaxially stretched polyethylene terephthalate film (thickness 100 μm) / buffer layer C1 (thickness 100 μm) / intermediate support layer B1 (thickness 10 μm) / adhesive layer A1 (thickness 10 μm) / release film (thickness 38 μm)).

[0131] Example 2 and Comparative examples 1 - 2

[0132] In Example 1, adhesive films for wafer back grinding of Example 2 and Comparative Examples 1 to 2 were prepared by changing the buffer layer, intermediate support layer, and composition for forming the adhesive layer as shown in Table 1 below.

[0133] Table 1

[0134] Classification (thickness) Example 1 Example 2 Comparative example 1 Comparative example 2 Adhesive layer (A) A1 A2 A1 A2 Intermediate support layer (B) B1 B2 B3 B4 Buffer layer (C) C1 C1 C1 C1

[0135] - Evaluation

[0136] Experimental example 1: Adhesive force (gf / 25mm)

[0137] The composite films (X) and (Y) and the adhesive film for wafer back grinding of the examples and comparative examples were cut into a size of 25 mm × 100 mm. Then, after removing the release film, the exposed surfaces of the composite films (X) and (Y) were attached to an acrylic plate (polymethyl methacrylate) using a 2 kg roller, and the exposed surface of the adhesive film for wafer back grinding was attached to a silicon mirror wafer, and then left at room temperature (25 ± 1 °C) for 30 minutes to prepare adhesion measurement samples.

[0138] Then, the samples were peeled at a speed of 300 mm / min and at 180° using a UTM device (QC-506M1F, COMETECH). In this way, the adhesion of the adhesive layer, intermediate support layer, and buffer layer to the adherend before ultraviolet irradiation was measured respectively. Then, after irradiating ultraviolet light with 80 mW / cm 2 (luminance) and 1000 mJ / cm 2 (light quantity), the adhesion of each layer after ultraviolet irradiation was measured according to the above method.

[0139] Experimental example 2: Shear storage modulus of intermediate support layer

[0140] Regarding the shear storage modulus, circular specimens 4 to 7 with a diameter of 8 mm and a thickness of 500 μm were respectively prepared by laminating intermediate support layers formed from the composition for forming intermediate support layers of Preparation Examples 4 to 7. Then, using a rheometer (ARES G2, TA Instruments) for measuring the shear storage modulus with the measurement temperature set at 25°C and the measurement frequency set at 0.796 Hz, the shear storage modulus of Specimens 4 to 7 before and after ultraviolet irradiation was measured for 10 minutes respectively.

[0141] Then, the rate of change of the storage modulus was measured according to the following Equation 1, and the results are shown in Table 2 below.

[0142] Equation 1

[0143]

[0144] Experimental example 3: Evaluation of residue

[0145] A silicon wafer with a thickness of 725 μm was prepared, on which bumps (Ea) with a height of 70 μm, a diameter of 50 μm, and a pitch between bumps of 200 μm, or bumps (Eb) with a height of 70 μm, a diameter of 50 μm, and a pitch between bumps of 50 μm were formed. Then, after attaching the backside grinding adhesive film for wafers of the examples and comparative examples to the wafer under the conditions of 50°C and 0.5 MPa, the wafer was ground to a thickness of 150 μm using a wafer grinding device (DGF - 8560). After the grinding process was completed, ultraviolet rays were irradiated onto the surface of the backside grinding adhesive film for wafers of the examples and comparative examples under the condition of 1000 mJ / cm 2 , and then the backside grinding adhesive film for wafers was peeled off. In this case, the presence or absence of residues (scum) peeled off from the backside grinding adhesive film for wafers on the wafer was checked. The presence of residues was evaluated as scum generation (F), and the absence of residues was evaluated as no scum generation (P), and the results are shown in Table 2 below.

[0146] Table 2

[0147]

[0148] As shown in Table 1 above, it was confirmed that the backside grinding adhesive film for wafers of the examples satisfied Equation 1 and no residues (scum) were generated. In particular, it was confirmed that no residues (scum) were generated even when the pitch between bumps was narrow.

[0149] In contrast, the shear storage modulus before and after ultraviolet irradiation in Comparative Example 1 did not change. Although this is not a problem in the case of a wide pitch between bumps, in the case of narrow and dense bumps, residues are generated, and thus it is confirmed that the target effect cannot be achieved. Moreover, the change rate of the storage modulus after ultraviolet irradiation in Comparative Example 2 is greater than 3, and it is confirmed that residues are generated.

[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 implement 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 are not explicitly described when the embodiments of the present invention are 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, According to the following formula 1, the shear storage modulus change rate of the intermediate support layer is greater than 1 and less than or equal to 3, Formula 1: At a temperature of 25°C, the shear storage modulus of the intermediate support layer after ultraviolet irradiation / the shear storage modulus of the intermediate support layer before ultraviolet irradiation.

2. The adhesive film for wafer backside grinding according to claim 1, characterized in that: Compared with before ultraviolet irradiation, the bonding force of the intermediate support layer to the acrylic plate is reduced after ultraviolet irradiation. At a temperature of 25° C., after ultraviolet irradiation, the bonding force of the intermediate support layer to the acrylic plate is 200 gf / 25 mm to 1000 gf / 25 mm.

3. The adhesive film for wafer backside grinding according to claim 1, characterized in that: At a temperature of 25° C., before ultraviolet irradiation, the bonding force of the intermediate support layer to the acrylic plate is 700 gf / 25 mm to 3000 gf / 25 mm.

4. The adhesive film for wafer backside grinding according to claim 1, characterized in that: At a temperature of 25° C., after ultraviolet irradiation, the adhesive force of the adhesive layer to the wafer is less than 50 gf / 25 mm.

5. The adhesive film for wafer backside grinding according to claim 1, wherein: The adhesive force of the buffer layer after ultraviolet irradiation is the same as the adhesive force of the buffer layer before ultraviolet irradiation.

6. The adhesive film for wafer backside grinding according to claim 1, wherein: At a temperature of 25° C., the buffer layer has an adhesive force on the acrylic plate of 1000 gf / 25 mm to 3000 gf / 25 mm.

7. The adhesive film for wafer backside grinding according to claim 1, characterized in that: The intermediate support layer contains a monomer having an unreacted vinyl group, and the monomer having an unreacted vinyl group is one selected from the group consisting of 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, m-isopropenyl-a,a-dimethylbenzyl isocyanate, glycidyl methacrylate, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and combinations thereof.

8. The adhesive film for wafer backside grinding according to claim 1, wherein: 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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