Substrate used in adhesive sheets for processing semiconductor wafers with convex portions

Abstract

The present invention provides a base material for semiconductor wafer processing, the base material being capable of enhancing adhesion to a stage in a semiconductor wafer processing step. The present invention provides a base material which is used for an adhesive sheet for processing a semiconductor wafer having a projected part, wherein the thermal shrinkages of the base material in the machine direction (MD) and in the transverse direction (TD) after heating at 130°C for 10 minutes are both 0% or more.

Description

[Technical Field]

[0001] The present invention relates to a substrate used in an adhesive sheet for semiconductor wafer processing, which is used in backgrinding and cutting of semiconductor wafers. [Background technology]

[0002] When semiconductor wafers are processed, adhesive sheets are applied to protect them from damage. For example, in the back grinding process when processing semiconductor wafers, adhesive sheets are applied to protect the patterned surface of the semiconductor wafer. The adhesive sheet is required to have adhesion to patterned surfaces with irregularities such as protruding electrodes (bumps), and to be able to follow the irregularities of the patterned surface (step-following ability) from the standpoint of reliable protection of the patterned surface.

[0003] In Patent Document 1, the base film of the adhesive tape is made to have excellent heat resistance, thereby preventing poor stage suction even when applied to a high-vacuum, high-temperature process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-155688 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have conducted extensive research into the adhesive sheet disclosed in Patent Document 1 and have found that the substrate may become loose, resulting in insufficient adhesion to the stage. Upon detailed investigation, it has become clear that conventional substrates, including the substrate film disclosed in Patent Document 1, stretch unevenly in the machine direction (MD) and / or transverse direction (TD) of the substrate when heated, causing the substrate to become loose.

[0006] The present invention has been made in view of the above circumstances, and provides a substrate for semiconductor wafer processing that can improve the adhesion of the substrate to a stage in the semiconductor wafer processing step. [Means for solving the problem]

[0007] As a result of intensive research, the inventors of the present invention found that the above-mentioned problem can be solved by setting the thermal shrinkage rate of the substrate in both the MD (Machine Direction) and TD (Transverse Direction) to 0% or more after heating at 130°C for 10 minutes, and thus completed the present invention.

[0008] According to the present invention, A substrate used in an adhesive sheet for processing semiconductor wafers having convex portions, The heat shrinkage rate of the above substrate in both the MD (Machine Direction) and TD (Transverse Direction) after heating at 130°C for 10 minutes is 0% or more. is provided.

[0009] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. Preferably, the ratio of heat shrinkage in the MD to the TD of the substrate after heating at 130° C. for 10 minutes (MD / TD) is 3.5 or less. Preferably, the substrate has a heat shrinkage rate of 1.0% or less in both MD and TD after heating at 130° C. for 10 minutes. Preferably, the substrate comprises a support layer and a cushion layer. Preferably, the cushion layer has a melting point of 70° C. or higher.

[0010] Further, according to the present invention, An adhesive sheet for processing a semiconductor wafer having a convex portion, The adhesive tape comprises the substrate and a pressure-sensitive adhesive layer provided on the substrate, an adhesive sheet configured such that the convex portions are protected by the base material when the semiconductor wafer is attached to the adhesive layer; is also provided.

[0011] Preferably, the support layer is provided on the opposite side of the cushion layer from the pressure-sensitive adhesive layer. Preferably, the protrusions are protected by being embedded in the base material. Preferably, the semiconductor wafer is attached to the pressure-sensitive adhesive layer.

[0012] Further, according to the present invention, A method for manufacturing a semiconductor element using the pressure-sensitive adhesive sheet, The method includes a frame attaching step, a wafer attaching step, a heating step, a grinding step, and a dicing step, In the frame attaching step, the adhesive sheet is attached to a ring frame, In the wafer bonding step, the pressure-sensitive adhesive sheet is bonded to the surface of the semiconductor wafer on which the convex portion is provided, In the heating step, the substrate is heated, In the grinding step, the back surface of the semiconductor wafer is ground, In the dicing step, the semiconductor wafer is divided into individual pieces. is also provided.

[0013] Preferably, the dicing step further includes a fixing step of fixing the semiconductor wafer to a table via the adhesive sheet. [Effects of the Invention]

[0014] According to the present invention, an adhesive sheet for semiconductor wafer processing can be provided which has no slack in the substrate when heated and attached to a ring frame or semiconductor wafer, and which has improved adhesion to the stage of the device on which it is set during dicing and backgrinding. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing a pressure-sensitive adhesive sheet 10 comprising a substrate 1 according to an embodiment of the present invention. [Figure 2]2A to 2D are cross-sectional views showing a method for manufacturing a semiconductor element using a pressure-sensitive adhesive sheet 10 according to an embodiment of the present invention. [Figure 3] 3A and 3B are cross-sectional views showing a method for manufacturing a semiconductor element using a pressure-sensitive adhesive sheet 10 according to an embodiment of the present invention. [Figure 4] 4A to 4E are cross-sectional views showing a method for manufacturing a semiconductor element using a pressure-sensitive adhesive sheet 10 according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0017] 1. Adhesive sheet 1 to 4E, a substrate 1 and an adhesive sheet 10 according to one embodiment of the present invention will be described. The adhesive sheet 10 of this embodiment comprises a substrate 1 and an adhesive layer 2 provided on the substrate 1. This adhesive sheet 10 is used when grinding the back surface 4b of a semiconductor wafer 4 having protrusions 5, and when dicing the semiconductor wafer 4. Each component will be described below.

[0018] <Base material 1> The substrate 1 has an oxygen permeability of 1000 ml / (m2) measured according to JIS K 7126-2 (constant pressure method) at 25°C and 0% RH. 2 The heat shrinkage of the substrate 1 after heating at 130°C for 10 minutes in both the MD (machine direction) and TD (transverse direction) of the substrate 1 may be 0% or more, and for example, it is preferable that the heat shrinkage of the substrate 1 after heating at 80-150°C for 10 minutes is 0% or more.

[0019] The heat shrinkage rate was calculated by measuring the lengths of each 100 mm substrate 1 in the MD and TD after leaving it in a 130°C oven for 10 minutes and then leaving it in a 23°C atmosphere for 2 hours, and then calculating the heat shrinkage rate using the following formula. MD heat shrinkage rate = [(100 mm - MD length after heating) / 100 mm]*100 TD heat shrinkage rate = [(100 mm - TD length after heating) / 100 mm] * 100

[0020] By using a substrate 1 having a thermal shrinkage rate of 0% or more in both MD and TD after heating at 130°C for 10 minutes, loosening of the substrate 1 can be suppressed when thermally attaching it to a ring frame and a semiconductor wafer. This improves adhesion to the stage set in the equipment for the back-grinding and dicing processes, contributing to improved yield. If the thermal shrinkage rate in MD or TD is less than 0%, loosening occurs in the substrate 1 when thermally attaching it to a ring frame and a semiconductor wafer, reducing adhesion to the stage set in the equipment for the back-grinding and dicing processes.

[0021] The ratio of heat shrinkage rates in the MD to the TD of the substrate 1 after heating at 130°C for 10 minutes (MD / TD) may be 0 to 3.5 (e.g., 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, and 0.01 or less). When the heat shrinkage rate ratio is 0 to 3.5, adhesion is improved.

[0022] The heat shrinkage rate of the substrate 1 in both the MD and TD after heating at 130°C for 10 minutes may be 1.0% or less (for example, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, 0.01). If the heat shrinkage rate in the MD or the TD is 1.0% or less, excessive shrinkage stress is not applied to the ring frame and the semiconductor wafer when the substrate is thermally attached to the ring frame and the semiconductor wafer, reducing peeling from the ring frame, cracking of the semiconductor wafer during back-grinding, and chip chipping during dicing.

[0023] 1 includes a support layer 1b and a cushion layer 1a. The support layer 1b may be attached to the cushion layer 1a via an adhesive layer (not shown).

[0024] The overall thickness of the substrate 1 is preferably 50 to 400 μm, more preferably 100 to 350 μm, and even more preferably 150 to 300 μm. Specific examples of this thickness include 50, 100, 150, 200, 250, 300, 350, and 400 μm, and may be within a range between any two of the numerical values ​​exemplified here.

[0025] The MD and TD of the substrate 1 can be adjusted by the thermal history of the substrate 1 (particularly the support layer 1b) during its production. The thermal history can be examined using a differential scanning calorimeter. The thermal history may be the strength with which the substrate 1 is stretched in the MD and TD by biaxial stretching during its production. By producing the substrate 1 so that the thermal history of the substrate 1 in the MD is the same as the thermal history of the substrate 1 in the TD, the thermal shrinkage of the substrate 1 in both the MD and TD after heating at a temperature of 130°C or less for 10 minutes can be made 0% or more. The substrate 1 has not undergone any treatment (e.g., annealing) that would change or eliminate its thermal history after its production.

[0026] <Cushion layer 1a> The cushion layer 1a has a melting point of 70°C or higher, preferably 80°C or higher, and more preferably 85°C or higher. There is no particular upper limit to the melting point of the cushion layer 1a to be laminated, but it is preferably 200°C or lower, and more preferably 150°C or lower. If the melting point is 70°C or higher, the surface opposite to the surface laminated with the base film will not have adhesiveness, and the occurrence of blocking when the base film is wound up can be reduced.

[0027] The melting point of the cushion layer 1a can be measured in accordance with JIS K7121.

[0028] The cushion layer 1a having a melting point of 70° C. or higher has an adhesive layer 2 on a part of or the entire surface opposite to where the base film is laminated. If the adhesive layer 2 is not on a part of or the entire surface, there is a possibility that the part without the adhesive layer 2 will peel off from the ring frame 3 when the cushion layer 1a is attached to the ring frame 3 by heating.

[0029] The resin of the cushion layer 1a may contain additives as required. The cushion layer 1a may be made of one type of resin alone or two or more types of resins in combination.

[0030] The resin for the cushion layer 1a having a melting point of 70°C or higher is not particularly limited, but examples thereof include ionomer resin, ethylene-vinyl acetate copolymer, soft polypropylene resin, ethylene-(meth)acrylic acid copolymer resin, styrene-butadiene copolymer resin, hydrogenated styrene-butadiene copolymer resin, ethylene-1-butene copolymer resin, soft acrylic resin, etc. The resins may be used alone or in combination of two or more.

[0031] The ionomer resin is not particularly limited as long as it is a resin in which a predetermined polymer is intermolecularly bonded by a metal ion, and examples thereof include polyolefin-based ionomers, acrylic-based ionomers, polystyrene-based ionomers, and polyester-based ionomers. These ionomer resins may be used alone or in combination of two or more. Among these, polyolefin-based ionomers and acrylic-based ionomers are preferred, and polyolefin-based ionomers are more preferred. Use of such resins tends to further improve tracking and releasability.

[0032] The polyolefin ionomer is not particularly limited, but examples thereof include ethylene-methacrylate copolymer, ethylene-acrylate copolymer, ethylene-methacrylate-acrylate copolymer, and the like.

[0033] The acrylic ionomer is not particularly limited, but examples thereof include an acrylic acid ester-acrylate copolymer, an acrylic acid ester-methacrylate copolymer, a methacrylic acid ester-acrylate copolymer, and a methacrylic acid ester-methacrylate copolymer.

[0034] The polystyrene ionomer is not particularly limited, but examples thereof include a styrene-styrene sulfonate copolymer, a styrene-acrylate copolymer, a styrene-methacrylate copolymer, a styrene-styrene carboxylate copolymer, and a styrene-N-methyl 4-vinylpyridinium salt copolymer.

[0035] The polyester ionomer is not particularly limited, but examples thereof include sulfoterephthalic acid salt copolymerized polyethylene terephthalate, sulfoisophthalic acid salt copolymerized polyethylene terephthalate, sulfoterephthalic acid copolymerized polybutylene terephthalate, and sulfoisophthalic acid copolymerized polybutylene terephthalate.

[0036] The metal ions constituting the salt of the ionomer resin are not particularly limited, and examples thereof include monovalent metal ions such as sodium ions and lithium ions; divalent metal ions such as zinc ions, calcium ions and magnesium ions; and trivalent metal ions such as aluminum ions. The polymer and metal ions in the ionomer resin can be used in any combination based on the ionic functional group in the polymer and the valence of the metal ion.

[0037] The ethylene-vinyl acetate copolymer is not particularly limited as long as it is a copolymer of ethylene and vinyl acetate. The vinyl acetate content in the ethylene-vinyl acetate copolymer is preferably 1 to 35 mol%, more preferably 3 to 25 mol%, and even more preferably 3 to 15 mol%, based on the total number of moles of structural units derived from ethylene and vinyl acetate. When the vinyl acetate content is within the above range, followability and peelability tend to be further improved.

[0038] The flexible polypropylene resin is not particularly limited, but examples thereof include a blend of a rubber component or a polyolefin resin with a polypropylene resin, and a propylene-α-olefin random copolymer. The rubber component used here is not particularly limited, but examples thereof include styrene-butadiene copolymer rubber, hydrogenated styrene-butadiene copolymer rubber, styrene-butadiene-styrene block copolymer rubber, hydrogenated styrene-butadiene-styrene block copolymer rubber, styrene-isoprene-styrene block copolymer rubber, and ethylene-propylene copolymer rubber. Examples of the polyolefin resin used here include polyethylene resin, polypropylene resin, and cycloolefin polymer resin. Polyethylene resin is preferred. Examples of the α-olefin copolymer component used here include ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene. Specific examples of the propylene-α-olefin random copolymer include a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, a propylene-1-hexene random copolymer, a propylene-ethylene-1-butene copolymer, etc. Preferably, a propylene-ethylene random copolymer is used.

[0039] The weight average molecular weight (Mw) of the resin of the cushion layer 1a having a melting point of 70° C. or higher is preferably 10,000 to 1,000,000, and more preferably 50,000 to 500,000.

[0040] The weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of polystyrene under the measurement conditions described below. Device name: SYSTEM-21 Shodex (Showa Denko Co., Ltd.) Column: Three PL gel MIXED-B columns in series Temperature: 40℃ Detection: Differential refractive index Solvent: tetrahydrofuran Concentration: 2% by mass Calibration curve: Prepared using standard polystyrene (PS) (manufactured by PL).

[0041] The thickness of the cushion layer 1a having a melting point of 70° C. or higher is preferably 50 to 500 μm, more preferably 70 to 400 μm, and even more preferably 100 to 300 μm. When the thickness of the cushion layer 1a having a melting point of 70° C. or higher is within the above range, sufficient conformability and adhesiveness to irregularities caused by scratches on the surface of the ring frame and irregularities on the surface of the semiconductor wafer are exhibited.

[0042] The cushion layer 1a having a melting point of 70°C or higher can be produced according to well-known techniques. The molding method is not particularly limited, but may involve mixing the various materials described above using a conventional melt kneader or various mixing devices (single-screw or twin-screw extruder, roll, Banbury mixer, various kneaders, etc.) so that the components are uniformly dispersed, molding the mixture into a film using a T-die method, calendar method, or inflation method, and laminating it with the support layer 1b via an adhesive.

[0043] The resin of the cushion layer 1a having a melting point of 70°C or higher may contain other additives such as known plasticizers, heat stabilizers, colorants, organic lubricants, inorganic lubricants, surfactants, processing aids, etc., as necessary.

[0044] <Support layer 1b> The support layer 1b is a layer for maintaining the flatness of the wafer after grinding. Without the support layer, unevenness would occur on the back surface of the base material due to the protrusions 5 of the wafer, which would result in poor back surface grindability.

[0045] As will be described later, the adhesive sheet 10 can be attached to the semiconductor wafer 4 under normal pressure or reduced pressure. When the adhesive sheet 10 is attached to the semiconductor wafer 4 under reduced pressure, the support layer 1b preferably has gas barrier properties.

[0046] When the support layer 1b has low oxygen permeability, it usually also has low air permeability, so providing the support layer 1b prevents outside air from entering the sealed space 2b through the base material 1, thereby making it easier for the base material 1 to conform to the convex portion 5.

[0047] The support layer 1b has an oxygen permeability of 1000 ml / (m2) measured based on JIS K 7126-2 (constant pressure method) at 25°C and 0% RH. 2 In order to set the oxygen permeability of the substrate 1 in this range, it is preferable that the oxygen permeability of the support layer 1b alone under the same conditions is 1000 ml / (m2·24h·atm) or less. In this case, the above-mentioned effect is easily exhibited. The oxygen permeability of the substrate 1 or the support layer 1b is, for example, 0 to 1000 ml / (m 2 ·24h·atm) and 0~500ml / (m 2 24h atm), and specifically, for example, 0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 ml / (m 2 ·24h·atm) and may be within a range between any two of the values ​​given here as examples.

[0048] Under the above conditions, the oxygen permeability of the support layer 1b is preferably lower than that of the cushion layer 1a. The value of (oxygen permeability of the cushion layer 1a - oxygen permeability of the support layer 1b) is 100 ml / (m 2 This value is preferably 100 to 3000 ml / (m 2 ·24h·atm), and specifically, for example, 100, 500, 1000, 1500, 2000, 2500, 3000 ml / (m 2 ·24h·atm) and may be within a range between any two of the values ​​given here as examples.

[0049] The support layer 1b is preferably made of polyester (for example, polyethylene terephthalate (PET)), polyimide, or polyamide (for example, nylon) from the viewpoint of being hard and resistant to deformation.

[0050] The thickness of the support layer 1b is, for example, 5 to 50 μm, and preferably 10 to 30 μm. If the support layer 1b is too thin, the flatness of the wafer after grinding will be reduced. If the support layer 1b is too thick, the ability to conform to the protrusions 5 of the substrate 1 may be poor. Specific examples of this thickness are 5, 10, 11, 12, 13, 14, 15, 20, 21, 23, 24, 25, 30, 35, 40, 45, and 50 μm, and may be within a range between any two of the numerical values ​​exemplified here.

[0051] To maintain the flatness of the wafer after grinding, the Young's modulus of the support layer 1b is 500 MPa to 5000 MPa, preferably 1000 MPa to 4500 MPa. In this embodiment, the Young's modulus can be measured at a temperature of 23±2°C, a humidity of 50±5%, and a tension speed of 300 mm / min.

[0052] <Adhesive layer 2> The adhesive layer 2 is a layer for adhering the adhesive sheet 10 to the semiconductor wafer 4, and is formed from an adhesive. The shape of the adhesive layer 2 is not particularly limited as long as it is a shape that allows the adhesive sheet 10 to be adhered to the semiconductor wafer 4. The adhesive layer 2 may be configured to have an opening with a diameter smaller than the diameter of the semiconductor wafer 4. The opening is a portion where no adhesive is provided, and has a diameter smaller than the diameter of the semiconductor wafer 4. The ratio of the diameter of the opening to the diameter of the semiconductor wafer 4 is preferably 0.950 to 0.995, and more preferably 0.960 to 0.990.

[0053] When an opening is provided, the outer peripheral portion 4a of the semiconductor wafer 4 is attached to the adhesive layer 2 so that the protrusions 5 of the semiconductor wafer 4 are positioned within the opening. Therefore, the protrusions 5 do not come into contact with the adhesive, and adhesive residue on the protrusions 5 is prevented.

[0054] The thickness of the adhesive layer 2 is usually 1 to 200 μm, preferably 2 to 170 μm, and more preferably 5 to 150 μm. If the thickness of the adhesive layer 2 is less than 1 μm, it will not be possible to ensure sufficient adhesive strength to the surface of the ring frame 3 or the surface of the semiconductor wafer 4. On the other hand, if the thickness of the adhesive layer 2 is greater than 200 μm, adhesive residue may be left when the adhesive layer is peeled off from the surface of the ring frame 3 or the surface of the semiconductor wafer 4, and economic efficiency will be reduced.

[0055] The adhesive of the adhesive layer 2 is not particularly limited, and may contain, for example, a polymer and a curing agent, and may contain other components as necessary. The polymer contained in the adhesive layer 2 is not particularly limited, and examples thereof include (meth)acrylic acid ester copolymers having a linear, branched, or crosslinked structure. Here, the branches possessed by branched polymers are classified into two types: short-chain branches, which are branches with a length of up to several carbon atoms, and long-chain branches, which are branches with a length comparable to that of the main chain. Furthermore, the crosslinked polymer may have a three-dimensional network structure. Note that crosslinked polymers also include those formed by the reaction of a polymer with a curing agent, which will be described later.

[0056] Examples of structural units constituting a (meth)acrylic acid ester copolymer include structural units having an alkyl group, structural units having a hydroxyl group, structural units having a carboxyl group, and other structural units. These structural units are mainly derived from (meth)acrylic acid monomers or (meth)acrylic acid ester monomers, but the (meth)acrylic acid ester copolymer is not limited to polymers composed only of (meth)acrylic acid or its esters, and may also contain structural units derived from monomers having polymerizable double bonds other than (meth)acrylic acid, etc.

[0057] The (meth)acrylic acid ester copolymer can undergo a crosslinking reaction with a curing agent (described later) due to the structural units having a hydroxyl group or a carboxyl group. This crosslinked structure can improve the cohesive strength of the adhesive after application. Furthermore, by adjusting the degree of crosslinking, it is possible to adjust the storage modulus, loss modulus, 180°C peel strength against a ring frame or semiconductor wafer, and tackiness.

[0058] Examples of structural units having an alkyl group include monomers that do not have a functional group that undergoes a crosslinking reaction with the curing agent described below. Monomers that constitute such structural units having a hydrocarbon group are not particularly limited, but include, for example, alkyl (meth)acrylates having a linear, branched, or branched alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, cyclohexyl, 2-ethylhexyl, octyl, isooctyl, nonyl, isononyl, decyl, isodecyl, undecyl, lauryl, tridecyl, tetradecyl, stearyl, octadecyl, and dodecyl. These may be used alone or in combination of two or more.

[0059] The monomer constituting the structural unit having a hydroxyl group is not particularly limited, and examples thereof include hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 1-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. These may be used alone or in combination of two or more.

[0060] The monomer constituting the structural unit having a carboxyl group is not particularly limited, but examples thereof include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. These may be used alone or in combination of two or more.

[0061] Monomers constituting other structural units other than those described above are not particularly limited, and examples thereof include acid anhydride monomers such as maleic anhydride and itaconic anhydride; sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloylphosphate.

[0062] The curing agent constituting the pressure-sensitive adhesive layer 2 is not particularly limited, but examples thereof include isocyanate-based curing agents, epoxy-based curing agents, and amine-based curing agents, which may be used alone or in combination. Among these, isocyanate compounds are preferred.

[0063] Such isocyanate compounds are not particularly limited, and examples thereof include aromatic diisocyanates such as tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate and methylenebis(4-cyclohexylisocyanate); and aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate. These may be used alone or in combination of two or more.

[0064] If necessary, a chemical or physical surface treatment may be performed to improve the adhesion between the cushion layer 1a having a melting point of 70°C or higher and the pressure-sensitive adhesive layer 2. Examples of the surface treatment include corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage shock exposure, and ionizing radiation treatment.

[0065] The pressure-sensitive adhesive layer 4 can be produced according to well-known techniques. The molding method is not particularly limited, but may be such that the various materials are dissolved in a solvent such as an organic solvent to form a varnish, which is then coated on the protective film by knife coating, roll coating, spray coating, gravure coating, bar coating, curtain coating, screen printing, or the like, and the solvent is removed to form the pressure-sensitive adhesive layer 2.

[0066] <Semiconductor wafer 4> The semiconductor wafer 4 has a protrusion 5. The protrusion 5 is any structure that protrudes out of the plane of the semiconductor wafer 4. Examples of the protrusion 5 include a protruding electrode and a protrusion of a circuit having irregularities.

[0067] Examples of the semiconductor wafer 4 include not only silicon wafers but also germanium wafers, gallium arsenide wafers, gallium phosphide wafers, gallium arsenide aluminum wafers, sapphire wafers, glass wafers, and silicon carbide wafers. The diameter of the semiconductor wafer 4 is preferably 1 to 16 inches, and more preferably 4 to 12 inches. The thickness of the semiconductor wafer 4 is not particularly limited, but is preferably 500 to 800 μm, and more preferably 520 to 775 μm.

[0068] The height of the protrusions 5 is preferably 10 to 500 μm, and more preferably 100 to 300 μm. Specific examples of the height include 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 μm, and may be within a range between any two of the values ​​exemplified here.

[0069] The semiconductor wafer 4 may have an outer periphery 4a that is not provided with the protrusions 5. The width of the outer periphery 4a is preferably 1.0 to 3.0 mm, more preferably 1.5 to 2.5 mm.

[0070] Final products using the semiconductor wafer 4 having the protrusions 5 include electronic components for logic, memory, sensors, power supplies, and the like.

[0071] 2. Manufacturing method of semiconductor element A method for manufacturing a semiconductor element using adhesive sheet 10 will be described using Figures 1 to 4E. This manufacturing method comprises a frame attaching step, a heating step, a grinding step, and a dicing step. The order in which these steps are performed is not limited to this order, and the order can be changed as appropriate. Each step will be described below.

[0072] <Frame attachment process> As shown in Figures 2A and 2B, in the frame attachment step, the adhesive sheet 10 is attached to the ring frame 3. The ring frame 3 has an opening 3a with a smaller diameter than the adhesive layer 2, and the ring frame 3 can be attached to the adhesive layer 2. This allows the adhesive sheet 10 to be stably held by the ring frame 3, making the adhesive sheet 10 easy to handle.

[0073] <Wafer bonding process / heating process> As shown in FIGS. 2B and 2C, in the wafer bonding step, adhesive sheet 10 is bonded to the surface of semiconductor wafer 4 on which convex portions 5 are provided, under normal pressure or reduced pressure.

[0074] This step can be performed by attaching the semiconductor wafer 4 to the adhesive sheet 10 in a decompression chamber 16. The pressure in the decompression chamber 16 should be lower than atmospheric pressure, and is preferably 1000 Pa or less, more preferably 500 Pa or less, and even more preferably 100 Pa or less. The lower limit of the pressure in the decompression chamber 16 is not particularly specified, but is, for example, 10 Pa.

[0075] By attaching the semiconductor wafer 4 to the adhesive sheet 10 under reduced pressure in this manner, the inside of the sealed space 2b surrounded by the semiconductor wafer 4 and the adhesive sheet 10 becomes a reduced pressure state.

[0076] When the adhesive sheet 10 with the semiconductor wafer 4 attached thereto is removed from the decompression chamber 16 and exposed to atmospheric pressure, the substrate 1 is pushed by the atmospheric pressure and attempts to enter the sealed space 2b. The substrate 1 has high rigidity when not heated, and therefore does not enter the sealed space 2b at all. On the other hand, when the substrate 1 is heated to 60 to 150°C in the heating step, the substrate 1 is softened, and the sealed space 2b disappears or almost disappears, as shown in FIG. 2D. Therefore, the protrusions 5 are embedded in the substrate 1, and the protrusions 5 are protected by the substrate 1. The ratio of the height of the embedded portion of the protrusions 5 to the total height of the protrusions 5 is preferably 0.9 to 1, more preferably 0.95 to 1, and even more preferably 0.99 to 1. The heating temperature of the substrate 1 is preferably 80 to 120°C. The heating time of the substrate 1 is preferably 3 to 120 seconds, more preferably 5 to 60 seconds.

[0077] The substrate 1 may be heated before or after the semiconductor wafer 4 is attached to the adhesive sheet 10. Furthermore, this heating may be performed inside or outside the reduced pressure chamber 16.

[0078] <Grinding process> 3A and 3B, the grinding step grinds the back surface 4b of the semiconductor wafer 4. The semiconductor wafer 4 is fixed to the suction table 6 via an adhesive sheet .

[0079] The back surface 4b of the semiconductor wafer 4 is the surface opposite to the surface on which the protrusions 5 are provided. There are no particular limitations on the method for grinding the back surface of the wafer, and any known grinding method can be used. Grinding is preferably performed while cooling the wafer and grinding stone (diamond, etc.) by spraying water on them. The thickness of the thinned wafer is preferably 300 μm or less, and more preferably 150 μm or less.

[0080] During back grinding, a load is applied to the protrusions 5 in the in-plane direction of the semiconductor wafer 4, which makes the protrusions 5 prone to breakage. However, in this embodiment, at least a portion of the protrusions 5 is embedded in the base material 1, and the protrusions 5 are stably supported by the base material 1, making the protrusions 5 less likely to break. Note that if the support of the protrusions 5 by the base material 1 is unstable, grinding performance may decrease.

[0081] A curable resin may be used to prevent damage to the protrusions 5. The curable resin is a resin that hardens when stimulated by energy rays (e.g., ultraviolet rays) or heat. The curable resin is preferably supported on a support film and disposed between the support layer 1b of the pressure-sensitive adhesive sheet 10 and the support film.

[0082] The viscosity of the curable resin before curing is preferably 100 to 3000 mPa·s, and more preferably 200 to 1000 mPa·s. When the viscosity is 100 mPa·s or higher, the curable resin forms point contact rather than surface contact, resulting in excellent grindability. When the viscosity is 3000 mPa·s or lower, the curable resin is less likely to entrap air bubbles when flowing between adjacent protrusions 5, resulting in excellent grindability. Viscosity is measured using an E-type viscometer at 23°C and 50 rpm.

[0083] The curable resin preferably has a Shore D hardness after curing of 5 to 70, more preferably 10 to 60. When the Shore D hardness is 5 or more, the retention of the convex portions 5 is high, resulting in excellent grinding properties. When the Shore D hardness is 70 or less, the adhesive sheet 10 is easily curved when peeled off from the semiconductor wafer 4. The Shore D hardness is measured under conditions in accordance with JIS K 6253.

[0084] The curable resin is preferably a photocurable resin, more preferably an ultraviolet curable resin.

[0085] The curable resin is preferably based on an acrylic resin, and although its composition is not particularly limited, a curable resin containing 1,2-hydrogenated polybutadiene terminated urethane (meth)acrylate, isobornyl acrylate, or diethylacrylamide is preferred because it can improve the adhesion between the substrate 1 and the support film 7.

[0086] The cure shrinkage rate of the curable resin is preferably 7% or less.

[0087] When the height of the protrusions 5 is Td (μm), the thickness of the curable resin is preferably (Td+20) to (Td+200) μm, and more preferably (Td+50) to (Td+150) μm.

[0088] The support film is any film capable of supporting a curable resin, and can be formed from polyolefins such as ethylene vinyl acetate, polyethylene, polypropylene, polybutene, and polybutadiene, as well as polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyimide, and the like.

[0089] The thickness of the support film is preferably 10 to 300 μm, more preferably 30 to 250 μm.

[0090] <Dicing process> As shown in Figures 4A to 4E, in the dicing step, the semiconductor wafer is divided into individual pieces. In the dicing step, the ground semiconductor wafer 4 is diced to divide the semiconductor wafer 4 into a plurality of semiconductor chips. The dicing method is not particularly limited, and may be any method such as blade dicing, laser dicing, stealth dicing, or plasma dicing.

[0091] The dicing step may include a coating step of coating the ground back surface 4b with a mask 8 that can form a dicing pattern (groove) using a patterning means (e.g., a laser) (FIG. 4A). The dicing pattern indicates the position where dicing will be performed. The mask 8 may be, for example, a (meth)acrylic copolymer. In the coating step, the ground semiconductor wafer 4 is fixed to a suction table 6' via an adhesive sheet 10.

[0092] The dicing step may also include a pattern formation step in which, after the coating step, a dicing pattern 8a is formed on a mask 8 by a pattern formation means (FIG. 4B). By dicing along this pattern 8a, the semiconductor wafer 4 can be easily divided into semiconductor chips of a desired size. In the pattern formation step, the ground semiconductor wafer 4 is fixed to a suction table 6'' via an adhesive sheet 10.

[0093] 4C shows a dicing step in which dicing is performed along the pattern 8a. The dicing step may further include a fixing step of fixing the semiconductor wafer 4 to a fixing table 7 (e.g., an electrostatic table or an adsorption table) via an adhesive sheet 10 before dicing.

[0094] After the dicing step, multiple semiconductor chips are attached to the adhesive sheet 10. For this reason, the dicing step may include a dicing tape application step of applying a dicing tape 9 to the back surface 4b of the diced semiconductor wafer 4 (FIG. 4D). The dicing tape 9 may be applied to the back surface 4b of the semiconductor wafer 4, or to the back surface 4b of the semiconductor wafer 4 and the ring frame 3. This prevents one or more semiconductor chips from remaining attached to the adhesive sheet 10 during the peeling step (FIG. 4E) of peeling the adhesive sheet 10 from the semiconductor wafer 4. The dicing tape 9 may be, for example, an ultraviolet-curing dicing tape or a general pressure-sensitive dicing tape with low adhesive strength, and the base material of the dicing tape may be a polyolefin-based material such as polyvinyl chloride, polyethylene, or polypropylene. In the dicing tape application step, the semiconductor wafer 4 is fixed to a fixing table 6''' (e.g., an electrostatic table or a suction table) via the adhesive sheet 10. [Example]

[0095] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0096] Example 1 A 25 μm thick polyethylene terephthalate film (manufactured by Toray, product number: Lumirror S10) and an ionomer film (melting point 82°C) formed to a thickness of 150 μm using the T-die method were dry-laminated to form a substrate film.

[0097] Example 2 The same procedure as in Example 1 was carried out except that the polyethylene terephthalate film was changed to a nylon film having a thickness of 15 μm (manufactured by Toyobo Co., Ltd., product number: N1202).

[0098] Example 3 The same procedure as in Example 1 was repeated except that the polyethylene terephthalate film was replaced with a 12 μm thick polyimide film (manufactured by SKC KOLON PI, product number: GF050).

[0099] (Comparative Example 1) The same procedure as in Example 1 was repeated except that the polyethylene terephthalate film was changed to a polyethylene terephthalate film having a thickness of 12 μm (manufactured by SHINKONG MATERIALS TECHNOLOGY, product number: P121).

[0100] (Comparative Example 2) The same process as in Comparative Example 1 was carried out except that the polyethylene terephthalate film of Comparative Example 1 was annealed (at 200° C. for 5 minutes).

[0101] (Comparative Example 3) The same process as in Example 1 was carried out except that the polyethylene terephthalate film of Example 1 was annealed (at 200° C. for 5 minutes).

[0102] The details of the evaluation method are as follows: The evaluation results are shown in Table 1. <Loosening of the base layer> The silicon wafer is placed on a stage with the same diameter as the silicon wafer, and the base layer bonded to the ring frame is pressed against the silicon wafer from above. The wafer is then heated at 130°C for 10 minutes, and the silicon wafer is then removed from the stage. After leaving the wafer to stand for 30 minutes in an atmosphere at 23°C, the presence or absence of slack in the base layer between the inner edge of the ring frame and the edge of the silicon wafer is confirmed. A (Excellent): No slack B (unacceptable): loose

[0103] <Wrinkles in the base layer on the silicon wafer surface> The silicon wafer is placed on a stage with the same diameter as the silicon wafer, and the base layer bonded to the ring frame is pressed against the silicon wafer from above. After heating at 130°C for 10 minutes, the silicon wafer is removed from the stage. After leaving it to stand for 30 minutes in an atmosphere of 23°C, the surface of the silicon wafer where the base layer is bonded is checked for wrinkles. A (Excellent): No wrinkles B (unacceptable): wrinkled

[0104] [Table 1]

[0105] <Consideration> All of the Examples achieved excellent results in all evaluation items, while all of the Comparative Examples achieved unsatisfactory results in at least one evaluation item. [Explanation of symbols]

[0106] 1: substrate, 1a: cushion layer, 1b: support layer, 2: adhesive layer, 2b: sealed space, 3: ring frame, 3a: opening, 4: semiconductor wafer, 4a: outer periphery, 4b: back surface, 5: convex portion, 6, 6', 6'', 6': suction table, 7: dicing table, 8: mask, 9: dicing tape, 10: adhesive sheet, 16: decompression chamber

Claims

1. A substrate used in an adhesive sheet for processing semiconductor wafers having convex portions, The heat shrinkage rate of the substrate after heating at 130°C for 10 minutes in both MD (Machine Direction) and TD (Transverse Direction) is 0% or more, The substrate includes a support layer and a cushion layer, The cushion layer has a melting point of 70°C or higher, the support layer is made of polyimide, polyamide, or polyethylene terephthalate (PET); When the support layer is made of polyimide, the ratio of heat shrinkage rates in the MD and TD of the base material after heating at 130°C for 10 minutes (MD / TD) is 0.9 or less; A substrate, wherein when the support layer is made of polyamide or PET, the ratio of heat shrinkage rates in MD and TD of the substrate after heating at 130°C for 10 minutes (MD / TD) is 3.5 or less.

2. 2. The substrate according to claim 1, wherein the heat shrinkage of the substrate in both MD and TD after heating at 130°C for 10 minutes is 1.0% or less.

3. The substrate described in claim 1, wherein when the support layer is made of PET, the thickness of the support layer is 5 to 50 μm.

4. The substrate described in claim 1, wherein the cushion layer is laminated to the support layer by dry lamination.

5. The substrate described in claim 1, wherein the support layer is made of polyimide or polyamide.

6. An adhesive sheet for processing a semiconductor wafer having a convex portion, A film comprising the substrate according to claim 1 and a pressure-sensitive adhesive layer provided on the substrate, The adhesive sheet is configured so that the convex portions are protected by the base material when the semiconductor wafer is attached to the adhesive layer.

7. The pressure-sensitive adhesive sheet according to claim 6, The support layer is provided on the opposite side of the cushion layer from the pressure-sensitive adhesive layer.

8. The pressure-sensitive adhesive sheet according to claim 6, The pressure-sensitive adhesive sheet, wherein the convex portions are protected by being embedded in the base material.

9. The pressure-sensitive adhesive sheet according to claim 6, The semiconductor wafer is attached to the adhesive layer.

10. A method for manufacturing a semiconductor element using the pressure-sensitive adhesive sheet according to any one of claims 6 to 9, The method includes a frame attaching step, a wafer attaching step, a heating step, a grinding step, and a dicing step, In the frame attaching step, the adhesive sheet is attached to a ring frame, In the wafer attaching step, the adhesive sheet is attached to the surface of the semiconductor wafer on which the convex portion is provided, In the heating step, the substrate is heated, In the grinding step, the back surface of the semiconductor wafer is ground, In the dicing step, the semiconductor wafer is divided into individual pieces.

11. The method for manufacturing a semiconductor device according to claim 10 , wherein the dicing step further comprises a fixing step of fixing the semiconductor wafer to a table via the adhesive sheet.

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