Dicing base film

Abstract

The present invention provides a dicing base film that exhibits excellent balance of tensile stress in the longitudinal and transverse directions, antistatic properties, and heat shrinkage, even in laminated films. [Solution] A laminated film comprising at least a surface layer, a middle layer, and a back layer, wherein the surface layer is a layer containing an ethylene copolymer resin and an antistatic agent, the back layer is a layer containing an ethylene copolymer resin and an antistatic agent, the middle layer is a layer containing an ionomer resin and an acrylic polymer, the content of the acrylic polymer is 2 to 8% by mass when the total mass of the middle layer is 100% by mass, the antistatic agent is a polyether polymer type antistatic agent, and the ratio of the thickness of the surface layer:middle layer:back layer is 1:16:1 to 1:26:1, a dicing substrate film.

Description

[Technical Field]

[0001] The present invention relates to a base film for a dicing tape used to fix a semiconductor wafer when dicing the wafer into chip units. [Background technology]

[0002] In the manufacturing process of semiconductor devices such as ICs (Integrated Circuits), it is common practice to first thin a semiconductor wafer on which a circuit pattern has been formed, and then perform a dicing process to divide the semiconductor wafer into chip units. In the dicing process, a stretchable wafer processing film (called dicing tape) is attached to the back surface of the semiconductor wafer, and then the semiconductor wafer is divided into chip units using a dicing blade or laser light. In the next expansion process, the dicing tape attached to the divided semiconductor wafer is expanded to divide it into semiconductor chips.

[0003] In the expansion process, for example, the dicing tape is expanded by pushing up an expansion table placed beneath the dicing tape. At this time, in order to divide the dicing tape into semiconductor chips, it is important that the tensile stress balance in the longitudinal (MD) and transverse (TD) directions (longitudinal-lateral balance) is excellent so that the dicing tape can be expanded uniformly across the entire surface of the expansion table. Furthermore, since the stress on the dicing tape at the periphery of the expansion table is greater than at the center of the expansion table, the dicing tape after the expansion process will sag in the part corresponding to the periphery of the expansion table. Such sagging can cause uneven spacing between the divided semiconductor chips and can even lead to product defects in subsequent processes.

[0004] As a means of eliminating sagging in dicing tape, a heat shrink process is known, in which the dicing tape is heated by blowing hot air at an actual temperature of approximately 80-100°C onto the sagging portion, causing it to shrink and return to its original state. In order to carry out this process, the dicing tape must have high heat shrinkability at a temperature of at least 80°C. The dicing tape used in these processes mainly consists of a dicing base film and an adhesive layer.

[0005] A dicing base film has been proposed for use in dicing tapes, for example, comprising a three-layer structure laminated in the order of at least layer A / layer B / layer C, wherein layer A is made of a resin composition containing an ionomer resin, layer B is made of a resin composition containing an ionomer resin and a polyolefin resin, and layer C is made of a resin composition containing an ionomer resin or a polyolefin resin (Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-191362 [Overview of the project] [Problems that the invention aims to solve]

[0007] The dicing substrate film described in Patent Document 1 was created with the aim of having good expandability, but it is a three-layer laminated film that is resistant to heat shrinkage. Also, for example, in the case of a laminated film having a surface layer, a middle layer and a back layer, when antistatic properties are required, it is common to add an antistatic agent to the surface layer and the back layer, but in that case the melting point of the layer containing the antistatic agent is higher than the melting point of the middle layer. As a result of the increased cost, there was a problem in that the material became even more difficult to shrink when heated.

[0008] The present invention aims to provide a dicing base film that exhibits excellent longitudinal and transverse balance of tensile stress, antistatic properties, and heat shrinkage even in a laminated film.

[0009] In view of the above circumstances, the present inventors conducted diligent studies and found that a dicing base film comprising at least a surface layer, a middle layer, and a back layer, wherein the surface layer and back layer are layers containing an ethylene copolymer resin and a polyether polymer-type antistatic agent, the middle layer is a layer containing an ionomer resin and an acrylic polymer in a specific content, and the ratio of the thicknesses of the surface layer, middle layer, and back layer is within a specific range, exhibits excellent longitudinal and transverse tensile stress balance, antistatic properties, and heat shrinkage properties, even as a laminated film, thus completing the present invention. [Means for solving the problem]

[0010] In other words, the present invention provides the following: [1] A laminated film comprising at least a surface layer, a middle layer, and a back layer, The aforementioned surface layer is a layer containing an ethylene copolymer resin and an antistatic agent. The aforementioned backing layer is a layer containing an ethylene copolymer resin and an antistatic agent. The aforementioned middle layer is a layer containing an ionomer resin and an acrylic polymer. When the total mass of the aforementioned middle layer is 100% by mass, the content of the acrylic polymer is 2 to 8% by mass. The aforementioned antistatic agent is a polyether-based polymer type antistatic agent. The ratio of the thickness of the surface layer, the middle layer, and the back layer is 1:16:1 to 1:26:1. Dicing base film. [2] The dicing substrate film according to [1], wherein the surface layer and / or the back layer further comprises a resin obtained by graft polymerization of maleic anhydride. [3] The ionomer resin is a resin obtained by crosslinking a binary copolymer having ethylene and (meth)acrylic acid as constituent components of the polymer or a ternary copolymer having ethylene, (meth)acrylic acid and (meth)acrylate as constituent components of the polymer with metal ions. The neutralization degree of the ionomer resin with metal ions is 50 mol% or more based on the total molar amount of acid groups in the binary copolymer or the ternary copolymer, the MFR (JIS K7210) of the ionomer resin is 3 g / 10 min or less, and the acid content of the ionomer resin is 9% by mass or more. The dicing base film according to [1] or [2].

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a dicing base film that is excellent in the balance of tensile stress in the longitudinal and transverse directions, antistatic properties, and heat shrinkage properties even in the case of a laminated film.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an embodiment of the dicing base film of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a state where a dicing tape is adhered to a semiconductor wafer. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a dicing tape and semiconductor chips after an expansion process. [Figure 4] FIG. 4 is a schematic cross-sectional view for explaining a heat shrinkage process.

Embodiments for Carrying Out the Invention

[0013] The present invention relates to a laminated film including a surface layer and a back layer containing an ethylene-based copolymer resin and an antistatic agent, and an intermediate layer containing an ionomer resin and an acrylic polymer, wherein the acrylic polymer is contained in the intermediate layer at a specific content rate. When the base film for dicing of the present invention has, for example, a three-layer structure, it includes a laminated film form including a surface layer 2, an intermediate layer 3, and a back layer 4 as shown in FIG. 1.

[0014] <Intermediate layer> The base film for dicing of the present invention (hereinafter, also simply referred to as the base film) includes an intermediate layer containing an ionomer resin and an acrylic polymer.

[0015] (Acrylic polymer) The acrylic polymer is a copolymer mainly composed of methacrylic acid alkyl units having a mass average molecular weight of 2 million to 4 million. As such a copolymer, a copolymer of methacrylic acid alkyl and acrylic acid alkyl is preferable. The content of methacrylic acid alkyl with respect to all monomers (100% by mass) forming the copolymer is preferably 50% by mass or more and less than 100% by mass, and the content of acrylic acid alkyl is preferably more than 0% by mass and 50% by mass or less. When the acrylic polymer is used as a processing aid, the molding processability of the intermediate layer is improved when the contents of methacrylic acid alkyl and acrylic acid alkyl are within the above ranges.

[0016] Examples of the methacrylic acid alkyl include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, etc. These can be used alone or in combination of two or more.

[0017] Specific examples of the acrylic acid alkyl include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, etc. Among these, n-butyl acrylate is preferable. These can be used alone or in combination of two or more.

[0018] The glass transition temperature (Tg) of the acrylic polymer is preferably 70°C or lower. When the glass transition temperature (Tg) of the acrylic polymer is 70°C or lower, the heat shrinkage property of the base film becomes better.

[0019] When the total mass of the intermediate layer is taken as 100% by mass, the content of the acrylic polymer is 2 to 8% by mass. If the content of the acrylic polymer is less than 2% by mass, there is a risk that the heat shrinkage of the base film will not be sufficiently exhibited. On the other hand, if the content of the acrylic polymer exceeds 8% by mass, there is a risk that the balance of tensile stress in the longitudinal and transverse directions will be poor.

[0020] (Ionomer resin) The ionomer resin is preferably a resin obtained by crosslinking a binary copolymer having ethylene and (meth)acrylic acid as polymer components, or a tertiary copolymer having ethylene, (meth)acrylic acid, and (meth)acrylic acid ester as polymer components, with metal ions. In this invention, (meth)acrylic acid includes both acrylic acid and methacrylic acid.

[0021] Examples of the aforementioned metal ions include potassium ions (K + ), sodium ions (Na + ), lithium ion (Li + ), magnesium ions (Mg 2+ ), zinc ions (Zn 2+ Examples include zinc ions (Zn 2+ ) is preferred. The above metal ions can be used individually or in combination of two or more.

[0022] The degree of neutralization of the ionomer resin by metal ions is preferably 50 mol% or more, and more preferably 60 mol% or more, based on the total molar amount of acid groups of the binary copolymer or the terpolymer.

[0023] The melt flow rate (MFR) of the ionomer resin is preferably 3 g / 10 min or less, and more preferably 1 g / 10 min or less. Having the MFR of the ionomer resin within this range results in a better balance of tensile stress in the longitudinal and transverse directions of the base film. In this specification, MFR values ​​are those measured under JIS K7210:1999, 190°C, and a load of 2.16 kg, unless otherwise specified.

[0024] The acid content of the ionomer resin is preferably 9% by mass or more, when the mass of the binary copolymer or terpolymer is taken as 100% by mass. Having the acid content of the ionomer resin within this range results in superior flexibility of the base film.

[0025] The melt tension of the intermediate layer-forming composition, which is obtained by melt-blending an ionomer resin and an acrylic polymer, is preferably 44 mN or higher. Furthermore, the melting point in the middle layer is preferably 100°C or lower, and more preferably 78°C to 98°C. The melting point is the value measured by DSC.

[0026] The thickness of the middle layer is preferably 5 to 465 μm, more preferably 10 to 235 μm, and even more preferably 15 to 185 μm.

[0027] <Surface and underside layers> The aforementioned surface layer and back layer are layers containing an ethylene copolymer resin and an antistatic agent.

[0028] Examples of ethylene-based copolymer resins include ethylene-vinyl acetate copolymer resin (EVA), ethylene-ethyl acrylate copolymer resin, ethylene-methyl acrylate copolymer resin, ethylene-methyl methacrylate copolymer resin (EMMA), ethylene-methacrylic acid copolymer resin (EMAA), ethylene-acrylic acid copolymer resin, ethylene-butene copolymer resin, ethylene-pentene copolymer resin, ethylene-hexene copolymer resin, and ethylene-octene copolymer resin. These resins can be used individually or in combination of multiple types.

[0029] In addition to the ethylene-based copolymer resins described above, ethylene-α-olefin copolymers can also be added, as long as they do not impair the effects of the present invention. Examples of such ethylene-α-olefin copolymers include ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), and olefin-based thermoplastic elastomers (TPO) consisting of polypropylene or a mixture of polyethylene and EPDM.

[0030] The acid content of the ethylene copolymer resin is preferably 9% by mass or more, when the mass of the ethylene copolymer resin is taken as 100% by mass. When the ratio of the acid content of the ethylene copolymer resin is within the above range, the balance of tensile stress in the longitudinal and transverse directions of the base film becomes better.

[0031] Preferably, the surface layer and / or the back layer further contain a resin obtained by graft polymerization of maleic anhydride.

[0032] The aforementioned antistatic agent is a polyether-based polymer type antistatic agent. It also has a melting point of 130°C. The above is preferred, and more preferably 130°C to 165°C. The MFR of the antistatic agent is preferably 10 g / 10 min to 15 g / 10 min. Examples of such polyether polymer antistatic agents include polyethylene oxide, polyetheramide, polyether esteramide, polyetheramide imide, ethylene oxide-epihalohydrin copolymer, and methoxypolyethylene glycol (meth)acrylate copolymer. Examples of commercially available products that are readily available include Zeospan from Nippon Zeon Co., Ltd. and Perestat from Sanyo Chemical Industries, Ltd.

[0033] The amount of the antistatic agent is preferably 1 to 30 parts by mass, based on 100 parts by mass of the total amount of components in the surface layer forming composition or the back layer forming composition.

[0034] Examples of resins obtained by graft polymerization of maleic anhydride include polypolymers of ethylene-acrylic acid ester and / or methacrylic acid ester and carboxylic acid anhydrides having unsaturated bonds, which are adhesive resins. The melting point of the resin is preferably 100°C or higher, and more preferably 125 to 145°C. The MFR of the resin is preferably 2.7 g / 10 min to 8.7 g / 10 min. Examples of commercially available products that are readily available include the ethylene-ethyl acrylate-maleic anhydride terpolymer copolymer manufactured by Mitsubishi Chemical Corporation (product name: Modic) or the copolymer manufactured by Mitsui Chemicals Corporation (product name: Admer).

[0035] Incorporating a resin obtained by graft polymerization of maleic anhydride into the ethylene copolymer resin is preferable because the polyether polymer-type antistatic agent is uniformly dispersed in the surface layer and the back layer, exhibiting excellent electrical properties (antistatic properties).

[0036] The content of the resin obtained by graft polymerization of maleic anhydride is preferably 2 to 60 parts by mass, when the total amount of components in the surface layer-forming composition or the back layer-forming composition is 100 parts by mass.

[0037] The ratio of the layer thicknesses of the surface layer, middle layer, and back layer is preferably 1:16:1 to 1:26:1, and more preferably 1:16:1 to 1:20:1. When the layer thickness ratio is within the above range, even if the surface layer and back layer contain a polyether-based polymer type antistatic agent with a relatively high melting point, the heat shrinkage of the middle layer can follow suit, thus preventing the heat shrinkability of the middle layer from being impaired and resulting in good heat shrinkability of the base film.

[0038] It is preferable that the heat shrinkage rate of the aforementioned middle layer by heating at 135°C for 1 minute is 50% or more in the longitudinal direction (MD).

[0039] The overall thickness of the base film is preferably 10 to 500 μm, more preferably 15 to 250 μm, and even more preferably 20 to 200 μm. If the base film is too thick, the tensile stress will be high, and a large force will be required to stretch the film. If it is too thin, the tensile strength will be low, and it will be prone to tearing.

[0040] The base film is preferably subjected to electron beam irradiation. Electron beam irradiation improves the antistatic properties of the base film and suppresses the generation of fragments in the base film due to friction with the blade during dicing. For electron beam irradiation, an acceleration voltage of 150-300kV and an electron current of 450-500mA, with a cumulative irradiation dose of 50-200kGy, is preferable. If the cumulative irradiation dose is less than 50kGy, the irradiation effect will not be obtained, and if the cumulative irradiation dose exceeds 200kGy, the flexibility of the film will decrease, and there is a risk that the film itself will deteriorate, which is undesirable.

[0041] The base film may have each layer constituting the base film, provided that it does not impair the effects of the present invention. It may also contain various known additives such as fillers, colorants, antioxidants, organic lubricants, catalysts, and plasticizers.

[0042] <Method for manufacturing a substrate film for dicing> While known methods can be used to form the dicing base film of the present invention, it is preferable to use a co-extrusion method or a co-extrusion inflation method, which have a simplified manufacturing process. Furthermore, the dicing base film of the present invention can also be obtained by separately forming the surface layer, the middle layer, and the back layer by means of calendering, extrusion, inflation, etc., and then laminating them by means of heat lamination or bonding with an adhesive as appropriate.

[0043] <Dicing Tape> A dicing tape (dicing film) can be obtained by providing an adhesive layer on the surface layer of the dicing base film of the present invention. The dicing tape can be attached to a semiconductor wafer via this adhesive layer, and the semiconductor wafer can be diced. Furthermore, if the surface layer contains a resin obtained by graft polymerization of maleic anhydride, the resin obtained by graft polymerization of maleic anhydride is adhesive, so there is no need to apply an adhesive layer after the base film is formed, which is particularly advantageous.

[0044] Dicing tapes are required to have excellent balance of tensile stress in both the longitudinal and lateral directions. In other words, if a dicing tape has excellent balance of tensile stress in both directions, it is possible to form uniform gaps between each semiconductor chip when the dicing tape is expanded, and therefore the workability of picking up the semiconductor chips becomes extremely good.

[0045] (Adhesive layer) Conventional known adhesives can be used as the adhesive constituting the adhesive layer. Examples of adhesives include rubber-based, acrylic-based, silicone-based, and polyvinyl ether-based adhesives; radiation-curing adhesives; and heat-foaming adhesives. In particular, considering the peelability of the dicing tape from the semiconductor wafer, it is preferable that the adhesive layer contains an ultraviolet-curing adhesive. The thickness of the adhesive layer depends on the type of adhesive, but is preferably 3 to 100 μm, and more preferably 3 to 50 μm.

[0046] It is preferable to attach a separator to the surface of the adhesive layer of the dicing tape of the present invention. By attaching a separator, the surface of the adhesive layer can be kept smooth. In addition, the handling and transportation of the dicing tape becomes easier, and it also becomes possible to apply a label to the separator.

[0047] The separator may be paper, or a synthetic resin film such as polyethylene, polypropylene, or polyethylene terephthalate. Furthermore, the surface of the separator that comes into contact with the adhesive layer may be treated with a release agent such as silicone or fluorine to improve its release properties from the adhesive layer. The thickness of the separator is typically 10 to 200 μm, preferably about 25 to 100 μm.

[0048] <Method for manufacturing dicing tape> When manufacturing the dicing tape of the present invention, the adhesive can be applied directly to the dicing base film using known methods, such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater, or the adhesive can be applied to a release sheet using the above known methods to create an adhesive layer, which can then be attached to the surface of the dicing base film to transfer the adhesive layer. These can be used.

[0049] Furthermore, a dicing tape, which is a laminate of the dicing base film and adhesive layer of the present invention, can be obtained by co-extruding the surface layer, back layer, and middle layer forming composition of the present invention with the material constituting the adhesive layer (co-extrusion molding method).

[0050] Furthermore, the adhesive composition constituting the adhesive layer may be subjected to heat crosslinking as needed to form the adhesive layer. In addition, a separator may be attached to the surface of the adhesive layer.

[0051] <How to use dicing tape> The dicing tape of the present invention is used in the semiconductor chip manufacturing process for dicing semiconductor wafers, which are the basis for semiconductor chips. The method of using the dicing tape will be explained with reference to Figures 2 to 4.

[0052] As shown in Figure 2, the dicing tape 5 of the present invention is used by being attached to a semiconductor wafer W (attachment process). The ends of the dicing tape 5 are fixed by a ring frame 10 and a fixing member 12. Next, a dicing process is performed to divide the semiconductor wafer W into chip units. Here, for example, if the stealth dicing (registered trademark) method is used as the dicing method, a laser beam is used to form cracks inside the semiconductor wafer, rather than on the surface.

[0053] Next, an expansion process is performed to expand the dicing tape 5 and widen the gaps between the divided semiconductor wafer W to divide it into semiconductor chips 20. As shown in Figure 3, with the ring frame 10 fixed, the expansion stage 11 is raised and the dicing tape 5 is expanded. When using the Stealth Dicing (registered trademark) method, the dicing tape 5 is stretched radially across the semiconductor wafer W, causing the semiconductor wafer W to be divided into semiconductor chips 20 starting from the cracks. Then, the expand stage 11 is returned to its original position, and a heat shrink process is performed to heat and shrink the slack in the dicing tape 5 that occurred in the previous expand process, restoring it to its original state. This process ensures that the spacing between the semiconductor chips 20 is stably maintained. As shown in Figure 4, in this process, for example, hot air is applied using a hot air nozzle 15 to heat the dicing tape 5 to shrink the slack (represented by a dashed line) in the region between the area of ​​the dicing tape 5 where the semiconductor chips 20 are located and the ring frame 10 (heat shrink region 13), thereby restoring it to its original state.

[0054] <Method of manufacturing semiconductor chips> After going through each step described in the above <Method of using dicing tape>, the semiconductor chip 20 is obtained by performing a step of picking up the semiconductor chip 20 (pickup step). In other words, the method for manufacturing a semiconductor chip of the present invention is as follows. The present invention includes a bonding step for bonding a dicing tape to a semiconductor wafer, A dicing process in which the semiconductor wafer is diced and divided into chip units, The dicing tape is expanded, and the spaces between the divided semiconductor wafers are expanded to divide them into semiconductor chips. A heat shrinking step is performed to restore the slack in the dicing tape that occurred in the expansion step to its original state by heating and shrinking it. A pickup step for picking up the aforementioned semiconductor chip, A method for manufacturing semiconductor chips, including [Examples]

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples, the abbreviations have the following meanings. (Surface and underside layers) ECo1: Ethylene copolymer resin (Acid content: 9% by mass, MFR: 9g / 10 min, Ethylene-methacrylic acid copolymer resin) AG1: Polyether-based polymer antistatic agent [manufactured by Sanyo Chemical Industries, Ltd., Perestat® 230, melting point 160℃] MGR1: A resin obtained by graft polymerization of maleic anhydride (ethylene-ethyl acrylate-maleic anhydride terpolymer) [Manufactured by Mitsubishi Chemical Corporation, Modic® PLA] (middle layer) IoR1: Ionomer resin (degree of neutralization: 23 mol%, MFR: 5 g / 10 min, ethylene-methacrylic acid copolymer resin, Zn type) IoR2: Ionomer resin (degree of neutralization: 60 mol%, MFR: 1 g / 10 min, ethylene-methacrylic acid copolymer resin, Zn type) PA: Acrylic polymer (Mass-average molecular weight: 3 million, Tg: 70℃)

[0056] (Example 1) ECo1, AG1, and MGR1 were dry-blended in the proportions shown in Table 1 (the numbers in Table 1 represent mass %). Next, the dry-blended mixture was put into the resin inlet of a single-screw extruder and melt-kneaded to obtain a surface layer-forming composition and a back layer-forming composition.

[0057] IoR2 and PA were dry-blended in the proportions shown in Table 1. Next, the dry-blended mixture was put into the resin inlet of a single-screw extruder and melt-kneaded to obtain the middle layer forming composition.

[0058] The obtained surface layer forming composition, back layer forming composition, and middle layer forming composition were fed into a two-type, three-layer T-die film extruder [Plateau Co., Ltd.], cooled between a cooling roll and a touch roll, and a base film of Example 1 was produced, which was a laminated film of two types and three layers with a width of 100 cm and a thickness of 90 μm. In the base film of Example 1, the ratio of the layer thicknesses of the surface layer:middle layer:back layer was 1:20:1.

[0059] (Examples 2, 3, 4, and 9) Examples 2, 3, 4, and 9, each consisting of two types of three layers with a thickness of 90 μm, were obtained in the same manner as in Example 1, except that the composition of the intermediate layer forming composition was changed as shown in Table 1 below.

[0060] (Examples 5 to 7) Examples 5 to 7 were obtained in the same manner as in Example 1, with two types and three layers, each having a thickness of 90 μm, except that the composition of the intermediate layer-forming composition and the ratio of the layer thicknesses of the surface layer, intermediate layer, and back layer were changed as shown in Table 1 below.

[0061] (Example 8) Except for replacing the composition of the intermediate layer-forming composition as shown in Table 1 below and performing electron beam irradiation treatment on the film (acceleration voltage 200kV, electron current 470mA, integrated irradiation dose 100kGy), a substrate film of Example 8 with a thickness of 90μm and consisting of two types and three layers was obtained in the same manner as in Example 1.

[0062] (Comparative Examples 1 to 3) Comparative Examples 1 to 3, each having a thickness of 90 μm and consisting of two types and three layers, were obtained in the same manner as in Example 1, except that the composition of the intermediate layer forming composition was changed as shown in Table 1 below.

[0063] (Comparative Example 4) A 90 μm thick substrate film of Comparative Example 4 was obtained in the same manner as in Example 1, with two types and three layers, except that the composition of the intermediate layer forming composition and the ratio of the layer thicknesses of the surface layer, intermediate layer, and back layer were changed as shown in Table 1 below.

[0064] [Table 1]

[0065] <Vertical and Horizontal Balance Evaluation> Based on JIS K 6732, test specimens for evaluating the longitudinal and transverse balance were taken from the base films (thickness 90 μm) of Examples 1 to 9 and Comparative Examples 1 to 4. Then, the modulus (tensile stress) in the longitudinal (MD) and transverse (TD) directions was measured when a 5% elongation was applied to the test specimens using a Tensilon universal material tester (RTF-1310, Orientec Co., Ltd.). The ratio of the modulus of MD to the modulus of TD (MD / TD) (hereinafter also referred to as the modulus ratio (MD / TD)) was calculated. This was evaluated as the longitudinal and transverse balance according to the following criteria: ○, △, and ×. The results are shown in Table 2. ○: The modulus ratio (MD / TD) is 1.2 or less. △: The modulus ratio (MD / TD) is greater than 1.2 and less than or equal to 1.5. ×: The modulus ratio (MD / TD) exceeds 1.5.

[0066] <Evaluation of heat shrinkage> The base films (thickness: 90 μm) of Examples 1 to 9 and Comparative Examples 1 to 4 were each cut into a size of 25 mm in the width direction × 150 mm in the length direction to obtain test pieces, and the length of 150 mm in the longitudinal direction (MD) was taken as the (initial value). On the other hand, after preheating an oven to 140°C in advance, the oven was set to 135°C, and then the test pieces were placed in the oven and heated at 135°C for 1 minute. The length of the MD of the test piece after heating was measured, and this length was taken as the (length after heat shrinkage), and the change rate (%) was calculated from the following formula. Change rate (%) = ((initial value - length after heat shrinkage) / initial value) × 100 This was evaluated as the heat shrinkage property according to the following criteria ○, Δ, and ×. The results are shown in Table 2. ○: The change rate is 50% or more. Δ: The change rate is 45% or more and less than 50%. ×: The change rate is less than 45%.

[0067] <Electrical Property Evaluation> Based on JIS K 6911, test pieces for electrical property evaluation were taken from the base films (thickness: 90 μm) of Examples 1 to 9 and Comparative Examples 1 to 4. A voltage of 500 V was applied using a resistivity meter ("Hi Rester" manufactured by Nitto Seiko Analytic Co., Ltd.), and the surface resistance value under the conditions of 20 ± 2°C and 65 ± 5 RH% was measured by contacting the probe of the resistivity meter with each surface of the test piece. This was expressed as the electrical property and evaluated according to the following criteria ○, Δ, and ×. The results are shown in Table 2. ○: The surface resistance value is less than 1.0×10 10 Ω. Δ: The surface resistance value is 10 10 or more and less than 10 12 Ω. ×: The surface resistance value is 10 12 Ω or more.

[0068]

Table 2

[0069] As shown in Table 2, the electrical properties were good for both the dicing substrate films of the present invention (Examples 1 to 9) and Comparative Examples 1 to 4.

[0070] The dicing base film of Example 1 of the present invention, even when a layer containing an antistatic agent is laminated, showed uniform expansion in the MD and TD directions and excellent longitudinal and transverse balance. Furthermore, it showed a large rate of change in the base film upon heating and excellent heat shrinkage properties. Similarly, the dicing base films of Examples 2 to 9 of the present invention showed excellent longitudinal and transverse balance as well as excellent heat shrinkage properties. In contrast, the dicing substrate film of Comparative Example 3, which did not contain an acrylic polymer in the middle layer, had excellent balance between the longitudinal and transverse directions, but exhibited poor heat shrinkage. Furthermore, while Comparative Example 2, a dicing substrate film containing an acrylic polymer in the middle layer, had excellent heat shrinkage properties, but its balance between longitudinal and transverse properties was poor, as the acrylic polymer content exceeded 8% by mass when the total mass of the middle layer was taken as 100% by mass. Furthermore, although the middle layer contains an acrylic polymer, the acrylic polymer content is in the middle layer Comparative Example 1, a dicing base film with a total mass of less than 2% by mass (when the total mass is set to 100% by mass), had excellent longitudinal and transverse balance, but exhibited poor heat shrinkage. Furthermore, in Comparative Example 4, the dicing substrate film in which the ratio of the middle layer thickness to the surface and back layers thickness was smaller than the specific ratio mentioned above, i.e., the thickness of the surface and back layers was increased, tended to have poor longitudinal-to-horizontal balance and reduced heat shrinkage. Therefore, the advantages of the present invention, which exhibits excellent balance between vertical and horizontal dimensions as well as superior heat shrinkage properties, have been demonstrated. [Industrial applicability]

[0071] The dicing substrate film of the present invention, even as a laminated film, exhibits excellent balance of tensile stress in the longitudinal and transverse directions, antistatic properties, and heat shrinkage properties. Therefore, in the heat shrinking process, it can eliminate sagging of the dicing tape after expansion and restore it to its original state, making it suitable for use in the manufacture of semiconductor chips.

[0072] 1. Dicing base film 2 Surface layer 3 Middle layer 4. Underlayer 5 Dicing Tape 10 Ring Frames 11 Expand Stage 12 Fixing member 13 Heat shrinkage area 15 Hot air nozzle 20 semiconductor chips W Semiconductor wafer

Claims

1. A laminated film comprising at least a surface layer, a middle layer, and a back layer, The aforementioned surface layer is a layer containing an ethylene copolymer resin and an antistatic agent. The aforementioned backing layer is a layer containing an ethylene copolymer resin and an antistatic agent. The aforementioned middle layer is a layer containing an ionomer resin and an acrylic polymer. When the total mass of the aforementioned middle layer is 100% by mass, the content of the acrylic polymer is 2 to 8% by mass. The aforementioned antistatic agent is a polyether-based polymer type antistatic agent. The ratio of the thickness of the surface layer, the middle layer, and the back layer is 1:16:1 to 1:26:

1. Dicing base film.

2. The dicing substrate film according to claim 1, wherein the surface layer and / or the back layer further comprises a resin obtained by graft polymerization of maleic anhydride.

3. The ionomer resin is a resin obtained by crosslinking a binary copolymer having ethylene and (meth)acrylic acid as polymer components, or a tertiary copolymer having ethylene, (meth)acrylic acid, and (meth)acrylic acid ester as polymer components, with metal ions. The dicing substrate film according to claim 1 or 2, wherein the degree of neutralization of the ionomer resin by metal ions is 50 mol% or more based on the total molar amount of acid groups of the binary copolymer or the tertiary copolymer, the MFR (JIS K7210) of the ionomer resin is 3 g / 10 min or less, and the acid content of the ionomer resin is 9% by mass or more.

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