Workpiece processing sheet

Abstract

To provide a sheet for workpiece processing capable of favorably suppressing occurrence of cutting dust while exhibiting excellent anti static properties.SOLUTION: There is provided a sheet 1 for workpiece processing comprising: a substrate 11; and an adhesive layer 12. The substrate 11 comprises: a front surface layer 111; a rear surface layer 113; and an intermediate layer 112 provided between these front surface layer 111 and the rear surface layer 113. The at least rear surface layer 113 includes an anti static agent. The intermediate layer 112 includes a styrenic-thermoplastic elastomer. The substrate 11 is configured so that, when a loss tangent at 90°C in visco-elasticity measurement at a frequency of 11 Hz is tanδ(90), and a loss tangent at 110°C is tanδ(110) and a loss tangent at 120°C is tanδ(120), the tanδ(110) is in an absolute value of 0.25 or greater, the tanδ(110) / tanδ(90) is equal to or greater than 1.3, and the tanδ(120) / tanδ(110) is lower than or equal to 0.9 in the sheet 1 for workpiece processing.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer. [Background technology]

[0002] Semiconductor wafers such as silicon and gallium arsenide and various packages are manufactured in a large diameter state, cut (diced) into chips, peeled (picked up), and then transferred to the next process, the mounting process. At this time, the workpieces such as semiconductor wafers are stacked on an adhesive sheet (hereinafter sometimes referred to as a "workpiece processing sheet") that has a base material and an adhesive layer, and are processed by back grinding, dicing, cleaning, drying, expanding, picking up, mounting, etc.

[0003] In the typical full-cut dicing, which is a specific method of the above-mentioned dicing, a rotating round blade (dicing blade) is used to cut the workpiece. In this case, in order to ensure that the workpiece stacked on the workpiece processing sheet is cut, not only the workpiece but also the adhesive layer is usually cut, and a part of the base material is also cut. At this time, cutting chips made of the material constituting the adhesive layer and the base material are generated from the workpiece processing sheet, and the chips obtained by cutting the workpiece may be contaminated by the cutting chips. One typical form of the cutting chips is thread-like cutting chips that adhere to the dicing line or near the cross section of the chip separated by dicing.

[0004] If a large amount of the thread-like cutting chips adhere to the chip, wire bonding may be hindered. Also, if the chip is sealed with a large amount of the thread-like cutting chips adhered to the chip, the cutting chips will decompose due to the heat of sealing, and the pyrolysis products may destroy the package or cause malfunctions in the resulting device. Since the thread-like cutting chips are difficult to remove by washing, the generation of the thread-like cutting chips significantly reduces the yield of the dicing process. Therefore, when dicing is performed using a workpiece processing sheet, it is required to prevent the generation of the thread-like cutting chips.

[0005] In addition, when the workpiece processing sheet is peeled off from the adherend after the completion of a predetermined processing step, static electricity called peeling electrification may occur between the workpiece processing sheet and the adherend. Such static electricity may cause dust and the like to adhere to the workpiece or device, and may also cause damage to the workpiece, etc. Therefore, the workpiece processing sheet is also required to have antistatic properties.

[0006] Patent Document 1 discloses a substrate made by blending a specified antistatic agent, a specified polyolefin resin, and a specified rubber-like elastomer in a specified blending ratio, with the aim of providing a workpiece processing sheet having excellent cutting chip suppression effect and antistatic properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5056112 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, after the process of dicing a semiconductor wafer, the obtained chips are generally washed. Specifically, a workpiece processing sheet on which multiple chips are placed is adsorbed and fixed to a spinner table, and the chips are washed with ultrapure water on the workpiece processing sheet, and then dried (air-dried). After these processes are completed, the workpiece processing sheet on which multiple chips are placed is detached from the spinner table, and the inventors have confirmed that peeling electrification occurs during this detachment process as well.

[0009] Considering the above-mentioned peeling static electricity, the conventional workpiece processing sheets as disclosed in Patent Document 1 could not be said to achieve a high level of cutting chip suppression effect and static electricity prevention properties.

[0010] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a workpiece processing sheet that exhibits excellent antistatic properties while effectively suppressing the generation of cutting chips. [Means for solving the problem]

[0011] In order to achieve the above object, first, the present invention provides a work processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, the substrate comprising a surface layer located proximal to the adhesive layer, a back layer located distal to the adhesive layer, and an intermediate layer located between the surface layer and the back layer, at least the back layer containing an antistatic agent, and the intermediate layer containing a styrene-based thermoplastic elastomer, wherein the loss tangent at 90°C measured at a frequency of 11 Hz for the substrate is tanδ(90), the loss tangent at 110°C is tanδ(110), and the loss tangent at 120°C is tanδ(120), and the absolute value of tanδ(110) is 0.25 or more, tanδ(110) / tanδ(90) is 1.3 or more, and tanδ(120) / tanδ(110) is 0.9 or less. (Invention 1)

[0012] In the above invention (Invention 1), at least the back surface layer contains an antistatic agent, so that it has excellent antistatic properties. In addition, since the intermediate layer contains a styrene-based thermoplastic elastomer and the base material has the above-mentioned viscoelastic properties, it is possible to effectively suppress the generation of chips during dicing, and to maintain good pick-up properties when picking up chips obtained by dicing. In particular, when the intermediate layer contains a styrene-based thermoplastic elastomer, the intermediate layer is difficult to melt at high temperatures, so that when a dicing blade reaches the intermediate layer, it is possible to effectively suppress the generation of chips from the intermediate layer.

[0013] In the above invention (Invention 1), it is preferable that the surface layer contains an antistatic agent (Invention 2).

[0014] In the above inventions (Inventions 1 and 2), it is preferable that the surface layer contains a polyolefin resin and an olefin thermoplastic elastomer (Invention 3).

[0015] In the above inventions (Inventions 1 to 3), it is preferable that the back surface layer contains an olefin-based thermoplastic elastomer (Invention 4).

[0016] In the above inventions (Inventions 1 to 4), it is preferable that the intermediate layer contains a styrene-based thermoplastic elastomer, a polyolefin-based resin, and an olefin-based thermoplastic elastomer (Invention 5).

[0017] In the above inventions (Inventions 1 to 5), it is preferable that the intermediate layer does not contain an antistatic agent, or that the intermediate layer contains an antistatic agent in a content (unit: mass %) less than that of each of the front layer and the back layer (Invention 6).

[0018] In the above inventions (Inventions 1 to 6), the antistatic agent is preferably a polymer-type antistatic agent (Invention 7).

[0019] In the above inventions (Inventions 1 to 7), the surface resistivity of the surface of the pressure-sensitive adhesive layer opposite to the substrate is 1.0×10 13 It is preferable that the resistance is Ω / □ or less (Invention 8).

[0020] In the above inventions (Inventions 1 to 8), a dicing sheet is preferable (Invention 9). Effect of the Invention

[0021] The workpiece processing sheet according to the present invention exhibits excellent antistatic properties while effectively suppressing the generation of cutting chips. [Brief description of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a workpiece processing sheet according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described. A cross-sectional view of a workpiece processing sheet according to one embodiment of the present invention is shown in Fig. 1. The workpiece processing sheet 1 shown in Fig. 1 includes a base material 11 and an adhesive layer 12 laminated on one side of the base material 11.

[0024] As shown in FIG. 1, the substrate 11 includes a surface layer 111 located proximal to the adhesive layer 12, a back layer 113 located distal to the adhesive layer 12, and an intermediate layer 112 located between the surface layer 111 and the back layer 113.

[0025] In the workpiece processing sheet 1 according to this embodiment, at least the back layer 113 contains an antistatic agent, and the intermediate layer 112 contains a styrene-based thermoplastic elastomer. When the loss tangent at 90°C, the loss tangent at 110°C, and the loss tangent at 120°C are tanδ(90), tanδ(110), and tanδ(120), respectively, measured for viscoelasticity at a frequency of 11Hz, the absolute value of tanδ(110) is 0.25 or more, tanδ(110) / tanδ(90) is 1.3 or more, and tanδ(120) / tanδ(110) is 0.9 or less. Hereinafter, these properties related to the loss tangent may be referred to as "viscoelastic properties". The specific method for measuring the loss tangent in this specification is as shown in the test examples described later.

[0026] The workpiece processing sheet 1 according to this embodiment has excellent antistatic properties because at least the back surface layer 113 contains an antistatic agent. Therefore, peeling static electricity can be effectively suppressed when the release sheet or the workpiece is separated from the workpiece processing sheet 1. Furthermore, peeling static electricity can be effectively prevented when the workpiece processing sheet 1 is separated from the spinner table after the workpiece on the workpiece processing sheet 1 is washed and dried.

[0027] In addition, in the workpiece processing sheet 1 according to this embodiment, the intermediate layer 112 contains a styrene-based thermoplastic elastomer, and the base material 11 has the above-mentioned viscoelastic properties, so that the generation of chips during dicing can be well suppressed, and the pick-up property when picking up the chips obtained by dicing can be well maintained. In particular, the base material 11 satisfying the above-mentioned viscoelastic properties will show a peak of loss tangent tan δ in the temperature range of 90 to 120 ° C. That is, since a part of the base material 11 is in a glass state up to this temperature range, the base material 11 is difficult to melt due to frictional heat generated during dicing, and excellent chip resistance can be obtained. In particular, when the intermediate layer 112 contains a styrene-based thermoplastic elastomer, the intermediate layer 112 is difficult to melt at high temperatures, so that when the dicing blade reaches the intermediate layer 112, the generation of chips from the intermediate layer 112 can be well suppressed.

[0028] From the viewpoint of the cutting chip suppression effect, the tan δ(110) (absolute value) is 0.25 or more, preferably 0.3 or more, particularly preferably 0.32 or more, and more preferably 0.34 or more. From the viewpoint of the pick-up property and expandability of the workpiece processing sheet, the upper limit value of the tan δ(110) (absolute value) is preferably 0.5 or less, particularly preferably 0.45 or less, and more preferably 0.4 or less.

[0029] From the viewpoint of the cutting chip suppression effect, the above tan δ(110) / tan δ(90) is 1.3 or more, preferably 1.4 or more, particularly preferably 1.5 or more, and even more preferably 1.6 or more. From the viewpoint of the pick-up property and expandability of the workpiece processing sheet, the upper limit value of the above tan δ(110) / tan δ(90) is preferably 2.5 or less, particularly preferably 2.3 or less, and even more preferably 1.9 or less.

[0030] From the viewpoint of the cutting chip suppression effect, the above tan δ(120) / tan δ(110) is 0.9 or less, preferably 0.88 or less, and more preferably 0.85 or less. From the viewpoint of the pick-up property and expandability of the workpiece processing sheet, the lower limit value of the above tan δ(120) / tan δ(110) is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more.

[0031] The tan δ(90) (absolute value) is preferably 0.15 or more, particularly preferably 0.17 or more, and more preferably 0.19 or more. The tan δ(90) (absolute value) is preferably 0.4 or less, particularly preferably 0.3 or less, and more preferably 0.23 or less. When the tan δ(90) is in the above range, the above-mentioned viscoelastic properties are easily satisfied.

[0032] The tan δ(120) (absolute value) is preferably 0.2 or more. The tan δ(120) (absolute value) is preferably 0.4 or less, and particularly preferably 0.3 or less. When the tan δ(120) is in the above range, the above-mentioned viscoelastic properties are easily satisfied.

[0033] 1. Composition of workpiece processing sheet 1-1. Base material The substrate 11 in this embodiment includes the front surface layer 111, the intermediate layer 112, and the back surface layer 113, as described above.

[0034] (1) Middle Class In this embodiment, the intermediate layer 112 contains a styrene-based thermoplastic elastomer (hereinafter, may be referred to as a "styrene-based elastomer"). The styrene-based elastomer is a copolymer containing a structural unit derived from styrene or its derivative (styrene-based compound), and is a material that has rubber-like elasticity and thermoplasticity in a temperature range including room temperature.

[0035] Examples of styrene-based elastomers include styrene-conjugated diene copolymers and styrene-olefin copolymers, among which styrene-conjugated diene copolymers are preferred. Specific examples of styrene-conjugated diene copolymers include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymer, styrene-butadiene-styrene copolymer (SBS), styrene-butadiene-butylene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer (SIS), and styrene-ethylene-isoprene-styrene copolymer; and hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene / propylene-styrene copolymer (SEPS: hydrogenated product of styrene-isoprene-styrene copolymer) and styrene-ethylene-butylene-styrene copolymer (SEBS: hydrogenated product of styrene-butadiene copolymer). The styrene-based thermoplastic elastomer may be either hydrogenated (hydrogenated) or unhydrogenated, but is preferably hydrogenated. Among the above, hydrogenated styrene-conjugated diene copolymers are preferred from the viewpoint of the cutting chip suppression effect and the ease of achieving the above-mentioned viscoelastic properties, and styrene-ethylene-butylene-styrene copolymer (SEBS) is particularly preferred.

[0036] The content of structural units derived from styrene or styrene-based compounds in the styrene-based elastomer is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. This provides a better cutting chip suppression effect and makes it easier to achieve the above-mentioned viscoelastic properties. In addition, from the viewpoint of the pick-up property and expandability of the workpiece processing sheet, the content of the structural units is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0037] The content of the styrene-based elastomer in the intermediate layer 112 is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. The content is also preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. When the content of the styrene-based elastomer in the intermediate layer 112 is within the above range, the cutting chip suppression effect is more excellent, and the above-mentioned viscoelastic properties are more easily achieved.

[0038] The intermediate layer 112 preferably contains a thermoplastic elastomer other than a styrene-based elastomer. Examples of the thermoplastic elastomer include an olefin-based thermoplastic elastomer, a rubber-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, an acrylic-based thermoplastic elastomer, and a vinyl chloride-based thermoplastic elastomer. These may be used alone or in combination of two or more.

[0039] Among the above thermoplastic elastomers, olefin-based thermoplastic elastomers (hereinafter sometimes referred to as "olefin-based elastomers") are preferred from the viewpoint of easily obtaining a good cutting chip suppression effect. Note that an "olefin-based elastomer" is a copolymer containing a structural unit derived from an olefin or its derivative (olefin-based compound), and is a material that has rubber-like elasticity and thermoplasticity in a temperature range including room temperature.

[0040] Examples of olefin-based elastomers include those containing at least one resin selected from the group consisting of ethylene-propylene copolymers, ethylene-α-olefin copolymers, propylene-α-olefin copolymers, butene-α-olefin copolymers, ethylene-propylene-α-olefin copolymers, ethylene-butene-α-olefin copolymers, propylene-butene-α-olefin copolymers, and ethylene-propylene-butene-α-olefin copolymers. Among these, ethylene-propylene copolymers are preferred.

[0041] The content of the olefin-based elastomer in the intermediate layer 112 is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more. The content is also preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. When the content of the olefin-based elastomer in the intermediate layer 112 is within the above range, the cutting chip suppression effect is more excellent, and the above-mentioned viscoelastic properties are more easily achieved.

[0042] In addition to the thermoplastic elastomer described above, the intermediate layer 112 preferably contains a polyolefin resin. By containing a polyolefin resin, the film-forming property during film formation and chipping suppression are excellent. In this specification, the polyolefin resin refers to a homopolymer or copolymer having an olefin as a monomer, or a copolymer having an olefin and a molecule other than an olefin as a monomer, and the mass ratio of the portion based on the olefin unit in the polymerized resin is 1.0 mass% or more.

[0043] The polyolefin resin is not particularly limited as long as it does not impair the above-mentioned viscoelastic properties and can obtain the desired effects. The polymer constituting the polyolefin resin may be linear or may have a side chain. In addition, the polymer may have an aromatic ring or an aliphatic ring.

[0044] Examples of olefin monomers constituting polyolefin resins include olefin monomers having 2 to 8 carbon atoms, α-olefin monomers having 3 to 18 carbon atoms, and olefin monomers having a cyclic structure. Examples of olefin monomers having 2 to 8 carbon atoms include ethylene, propylene, 2-butene, and octene. Examples of α-olefin monomers having 3 to 18 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, and 1-octadecene. Examples of olefin monomers having a cyclic structure include norbornene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, and tetracyclododecene, as well as derivatives thereof.

[0045] The polyolefin resins may be used alone or in combination of two or more.

[0046] Among the specific examples of the polyolefin resins mentioned above, it is preferable to use at least one of polyethylene containing ethylene as a main polymerization unit and polypropylene containing propylene as a main polymerization unit.

[0047] The polypropylene generally includes homopolypropylene, random polypropylene, and block polypropylene. These may be used alone or in combination of two or more. In the present embodiment, it is preferable to use random polypropylene from the viewpoint of expandability.

[0048] When the polyolefin resin contains polyethylene, the polyethylene may be any one of high density polyethylene, medium density polyethylene, low density polyethylene, very low density polyethylene and linear low density polyethylene, or a mixture of two or more of these.

[0049] The content of the polyolefin resin in the intermediate layer 112 is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. This provides excellent film formability during film formation. The content is also preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. This makes it easier to achieve the above-mentioned viscoelastic properties.

[0050] Here, although the intermediate layer 112 may also contain an antistatic agent, from the viewpoint of easily suppressing the generation of cutting chips, it is preferable that the intermediate layer 112 does not contain an antistatic agent. When the intermediate layer 112 contains an antistatic agent, it is preferable that the intermediate layer 112 contains the antistatic agent in a content (unit: mass %) smaller than that of the back layer 113 (and the surface layer 111). Specifically, the content is preferably less than 5 mass % in the intermediate layer 112, more preferably less than 3 mass %, particularly preferably less than 1 mass %, and most preferably 0 mass %. When the intermediate layer 112 contains an antistatic agent, the lower limit of the content is, for example, 0.01 mass % or more. The present inventors have found that the antistatic agent causes the generation of cutting chips during dicing, but as described above, by having an intermediate layer 112 that does not contain an antistatic agent or has a low content of the antistatic agent under the surface layer 111 (preferably a thin layer), the generation of cutting chips can be significantly reduced compared to the case where the entire base material contains an antistatic agent.

[0051] The intermediate layer 112 may contain other components than those mentioned above, for example, components used in the base material of general workpiece processing sheets. Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. The content of these additives is not particularly limited, but is preferably within a range in which the intermediate layer 112 exhibits the desired function.

[0052] (2) Back layer In this embodiment, the back surface layer 113 contains an antistatic agent. This provides excellent antistatic properties. On the other hand, as described above, the antistatic agent can cause chips to be generated during dicing. However, since the dicing blade does not usually reach the back surface layer 113, even if the back surface layer 113 contains an antistatic agent, the antistatic agent does not cause chips to be generated.

[0053] The antistatic agent in this embodiment is not particularly limited, and known antistatic agents can be used. Examples of the antistatic agent include low molecular weight antistatic agents and polymeric antistatic agents, and polymeric antistatic agents are preferred from the viewpoints that they are easy to suppress the generation of cutting chips (when the surface layer 111 contains it as described below) and are less likely to bleed out from the formed layer.

[0054] Examples of the polymer-type antistatic agent include copolymers having a polyether unit, such as polyether ester amide and polyether polyolefin block copolymer. These copolymers may contain a metal salt, such as an alkali metal salt or an alkaline earth metal salt, or an ionic liquid.

[0055] The content of the antistatic agent in the back surface layer 113 is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. This makes it easier to exhibit good antistatic properties. The content is also preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. This makes it easier to achieve the above-mentioned viscoelastic properties.

[0056] The material other than the antistatic agent constituting the back surface layer 113 is not particularly limited as long as the above-mentioned viscoelastic properties are satisfied, but it is preferable that the material contains at least a thermoplastic elastomer and further contains a polyolefin resin as required. These components make it easier to satisfy the above-mentioned viscoelastic properties. In addition, the thermoplastic elastomer has the effect of improving the pick-up property.

[0057] As the thermoplastic elastomer, those exemplified for the intermediate layer 112 can be used, and among them, olefin-based elastomers are preferable.

[0058] The content of the olefin-based elastomer in the back surface layer 113 is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more. The content is preferably 80% by mass or less, and more preferably 75% by mass or less. When the content of the olefin-based elastomer in the back surface layer 113 is within the above range, it becomes easier to achieve the above-mentioned viscoelastic properties.

[0059] It is preferable that the back surface layer 113 does not contain a styrene-based elastomer as a thermoplastic elastomer. If a styrene-based elastomer is contained, blocking may occur during film formation or the pick-up property may be affected. Even if the back surface layer 113 contains a styrene-based elastomer, the content is preferably 3% by mass or less, more preferably 2% by mass or less, and further preferably 1% by mass or less.

[0060] When the back layer 113 contains a polyolefin resin, the effect of excellent film formability during film formation can be obtained. As the polyolefin resin, those exemplified for the intermediate layer 112 can be used, and among them, polypropylene, particularly random polypropylene, is preferably used.

[0061] When the back surface layer 113 contains a polyolefin resin, the content is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more from the viewpoint of excellent film-forming properties during film formation. Also, the content is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less from the viewpoint of pick-up properties.

[0062] The back layer 113, like the intermediate layer 112, may contain other components in addition to the above-mentioned components, for example, components used in the base material of general workpiece processing sheets.

[0063] (3) Surface layer In the workpiece processing sheet 1 according to this embodiment, at least the back surface layer 113 contains an antistatic agent, but preferably the surface layer 111 also contains an antistatic agent. This provides better antistatic properties. As mentioned above, the antistatic agent causes chips to be generated during dicing, but by reducing the thickness of the surface layer 111 and eliminating or reducing the content of the antistatic agent in the intermediate layer 112, the generation of chips can be significantly reduced compared to when the entire substrate contains an antistatic agent.

[0064] As the antistatic agent in the front surface layer 111, the same antistatic agent as that in the back surface layer 113 can be used.

[0065] The content of the antistatic agent in the surface layer 111 is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. This provides better antistatic properties. The content is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. This can reduce the generation of cutting chips.

[0066] The material other than the antistatic agent constituting the surface layer 111 is not particularly limited as long as it satisfies the above-mentioned viscoelastic properties, but it is preferable that it contains at least a thermoplastic elastomer, and it is particularly preferable that it also contains a polyolefin resin. These components make it easier to satisfy the above-mentioned viscoelastic properties. In addition, the thermoplastic elastomer has the effect of improving the pick-up property.

[0067] As the thermoplastic elastomer and polyolefin-based resin, those exemplified for the intermediate layer 112 and the back surface layer 113 can be used. As the thermoplastic elastomer, an olefin-based elastomer is preferable.

[0068] The content of the olefin-based elastomer in the surface layer 111 is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more. The content is also preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 50% by mass or less. When the content of the olefin-based elastomer in the surface layer 111 is within the above range, it becomes easier to achieve the above-mentioned viscoelastic properties.

[0069] It is preferable that the front surface layer 111 does not contain a styrene-based elastomer as a thermoplastic elastomer, similar to the back surface layer 113. Even if the front surface layer 111 contains a styrene-based elastomer, the content is preferably limited to the same amount as the amount exemplified for the back surface layer 113.

[0070] From the viewpoint of excellent film-forming properties during film formation, the content of the polyolefin resin in the surface layer 111 is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. From the viewpoint of pick-up properties, the content is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0071] The surface layer 111 preferably contains an acid-modified resin as a component other than the above. In this specification, the term "acid-modified resin" means a structure derived from an acid component added to a polymer chain. The structure derived from the acid component may be in the form of an acid anhydride or may have a carboxy group. When the surface layer 111 contains the acid-modified resin as described above, the adhesion between the substrate 11 and the adhesive layer 12 is improved, and the adhesive can be prevented from remaining on the chip side during pick-up.

[0072] Preferred examples of the main chain of the acid-modified resin include ethylene-acrylic copolymers such as ethylene-(meth)acrylic acid copolymer and ethylene-(meth)acrylic acid ester copolymer. Such resins can easily improve the adhesion between the surface layer 111 and the adhesive layer 12 while satisfying the above-mentioned viscoelastic properties. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.

[0073] The (meth)acrylic acid ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 4. For example, preferred examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, etc. Among these, ethyl (meth)acrylate is more preferred, and ethyl acrylate is particularly preferred.

[0074] The content of the structure derived from the (meth)acrylic acid ester in the ethylene-(meth)acrylic acid ester copolymer is preferably 1% by mass or more, and more preferably 3% by mass or more. The content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. When the content is within the above range, the above-mentioned viscoelastic properties are easily satisfied.

[0075] In order to modify the resin with an acid, it is preferable to react the resin with an unsaturated carboxylic acid. Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, and tetrahydrophthalic anhydride. These can be used alone or in combination of two or more. Among the above, maleic anhydride is particularly preferable from the viewpoint of adhesion to the adhesive layer 12.

[0076] The amount of acid components in the acid-modified resin (the amount of structures derived from the acid components) is preferably 1% by mass or more, and more preferably 2% by mass or more. The amount of acid components is preferably 7% by mass or less, and more preferably 5% by mass or less. When the amount of acid components is within the above range, the adhesion between the surface layer 111 and the pressure-sensitive adhesive layer 12 is further improved.

[0077] When the surface layer 111 contains an acid-modified resin, the content of the acid-modified resin in the surface layer 111 is preferably 5% by mass or more, and more preferably 10% by mass or more. This further improves the adhesion between the surface layer 111 and the pressure-sensitive adhesive layer 12. The content is also preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. This makes it easier to satisfy the above-mentioned viscoelastic properties.

[0078] The surface layer 111, like the intermediate layer 112 and the back layer 113, may contain other components than those mentioned above, for example, components used in the base material of general workpiece processing sheets.

[0079] (4) Surface treatment of the substrate The surface of the substrate 11 on which the adhesive layer 12 is laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, a plasma treatment, a roughening treatment (matt finish) or the like in order to enhance adhesion to the adhesive layer 12. Examples of the roughening treatment include an embossing method and a sandblasting method. Among these, it is preferable to perform a corona treatment.

[0080] (5) Manufacturing method of the substrate The method for producing the substrate 11 in this embodiment is not particularly limited, and for example, melt extrusion methods such as the T-die method and the round die method, calendaring method, solution methods such as the dry method and the wet method, etc. can be used. Among these, from the viewpoint of efficiently producing the substrate, it is preferable to adopt the melt extrusion method, and it is particularly preferable to adopt the T-die method.

[0081] Furthermore, when the substrate 11 is manufactured by a melt extrusion method, the components constituting each layer are mixed together, and the resulting mixture is extruded simultaneously (co-extruded) to form a film, either directly or after pellets are produced, using a known extruder.

[0082] (6) Properties of the substrate (6-1) Thickness In this embodiment, the thickness of the surface layer 111 is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 4 μm or less. In this way, since the thickness of the surface layer 111 located proximal to the pressure-sensitive adhesive layer 12 is thin, even if the surface layer 111 contains an antistatic agent, it is possible to effectively suppress the generation of cutting chips while exhibiting the desired antistatic properties.

[0083] The thickness of the surface layer 111 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. This makes it easier for the surface layer 111 to exhibit good antistatic properties when it contains an antistatic agent. Furthermore, when the surface layer 111 contains an acid-modified resin, the adhesion to the pressure-sensitive adhesive layer 12 becomes more excellent.

[0084] In this embodiment, the thickness of the intermediate layer 112 is preferably 40 μm or more, particularly preferably 50 μm or more, and more preferably 60 μm or more. This makes it easier to satisfy the above-mentioned viscoelastic properties, and makes it easier to suppress the generation of cutting chips. In addition, the workpiece processing sheet 1 is more likely to have a moderate strength, and makes it easier to favorably support the workpiece fixed on the workpiece processing sheet 1. The thickness of the intermediate layer 112 is preferably 100 μm or less, particularly preferably 90 μm or less, and more preferably 80 μm or less. This makes it easier to satisfy the above-mentioned viscoelastic properties.

[0085] In this embodiment, the thickness of the back surface layer 113 is preferably 2 μm or more, more preferably 4 μm or more, and even more preferably 8 μm or more. This makes the workpiece processing sheet 1 more excellent in antistatic properties. In addition, the thickness of the back surface layer 113 is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. This makes it easier to satisfy the above-mentioned viscoelastic properties.

[0086] In this embodiment, the thickness of the substrate 11 as a whole is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more. The thickness is preferably 140 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less. When the thickness of the substrate 11 as a whole is within the above range, the above-mentioned viscoelastic properties are easily satisfied, and the workpiece fixed on the workpiece processing sheet 1 is easily supported.

[0087] (6-2)Surface resistivity The surface resistivity of the surface of the substrate 11 on the side of the surface layer 111 is 1.0×10 13 It is preferably Ω / □ or less, and particularly 1.0×10 12 It is preferable that the resistance is Ω / □ or less, and more preferably 1.0×10 11It is preferable that the surface resistivity is Ω / □ or less. This allows the workpiece processing sheet 1 according to this embodiment to exhibit excellent antistatic properties. The lower limit of the surface resistivity is not particularly limited, and is, for example, 1.0×10 8 Ω / □ or more, and in particular 1.0×10 9 The surface resistivity may be Ω / □ or more. Details of the method for measuring the surface resistivity in this specification are as described in the test examples described later.

[0088] 1-2. Adhesive layer The adhesive constituting the adhesive layer 12 in this embodiment is not particularly limited as long as it can exert sufficient adhesive strength to the adherend (particularly, sufficient adhesive strength to the workpiece for processing the workpiece). Examples of the adhesive constituting the adhesive layer 12 include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, polyvinyl ether adhesives, etc. Among these, it is preferable to use acrylic adhesives from the viewpoint of easily exerting the desired adhesive strength.

[0089] The adhesive constituting the adhesive layer 12 in this embodiment may be an adhesive not having active energy ray curability, but is preferably an adhesive having active energy ray curability (hereinafter, may be referred to as an "active energy ray curable adhesive"). Since the adhesive layer 12 is composed of an active energy ray curable adhesive, the adhesive layer 12 can be cured by irradiation with active energy rays, and the adhesive strength of the workpiece processing sheet 1 to the adherend can be easily reduced. In particular, irradiation with active energy rays makes it possible to easily separate the processed workpiece from the workpiece processing sheet 1.

[0090] The active energy ray curable adhesive constituting the adhesive layer 12 may be one mainly composed of a polymer having active energy ray curability, or may be one mainly composed of a mixture of a non-active energy ray curable polymer (a polymer not having active energy ray curability) and a monomer and / or oligomer having at least one or more active energy ray curable groups. The active energy ray curable adhesive may also be a mixture of a polymer having active energy ray curability and a monomer and / or oligomer having at least one or more active energy ray curable groups.

[0091] The active energy ray curable polymer is preferably a (meth)acrylic acid ester polymer (hereinafter sometimes referred to as "active energy ray curable polymer") having a functional group (active energy ray curable group) having active energy ray curability introduced into a side chain. This active energy ray curable polymer is preferably obtained by reacting an acrylic polymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group bonded to the functional group. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the term "polymer" also includes the concept of "copolymer".

[0092] The acrylic polymer having the functional group-containing monomer unit described above may be obtained by polymerizing other monomers together with the functional group-containing monomer. As such functional group-containing monomers and other monomers, as well as the unsaturated group-containing compounds described above, known compounds can be used, for example, those disclosed in International Publication No. 2018 / 084021.

[0093] The weight average molecular weight of the active energy radiation curable polymer is preferably 10,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more. The weight average molecular weight is preferably 1,500,000 or less, and even more preferably 1,000,000 or less. The weight average molecular weight (Mw) in this specification is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0094] As the above-mentioned active energy ray non-curable polymer component, for example, the above-mentioned acrylic polymer before being reacted with the unsaturated group-containing compound can be used.

[0095] The weight average molecular weight of the acrylic polymer as the non-curable active energy ray polymer component is preferably 10,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more. The weight average molecular weight is preferably 1,500,000 or less, and even more preferably 1,000,000 or less.

[0096] As the above-mentioned monomer and / or oligomer having at least one active energy ray-curable group, for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

[0097] When ultraviolet rays are used as the active energy rays for curing the active energy ray-curable adhesive, it is preferable to add a photopolymerization initiator to the adhesive. In addition, the adhesive may also contain an active energy ray non-curable polymer component or oligomer component, a crosslinking agent, etc.

[0098] The thickness of the adhesive layer 12 in this embodiment is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The thickness of the adhesive layer 12 is preferably 70 μm or less, more preferably 30 μm or less, and even more preferably 15 μm or less. When the thickness of the adhesive layer 12 is in the above-mentioned range, the workpiece processing sheet 1 according to this embodiment can easily exhibit the desired adhesiveness.

[0099] 1-3.Release sheet In the workpiece processing sheet 1 of this embodiment, a release sheet may be laminated on the side of the adhesive layer 12 opposite the substrate 11 (hereinafter sometimes referred to as the "adhesive side") in order to protect said side until it is attached to the workpiece.

[0100] The release sheet may have any structure, and may be, for example, a plastic film that has been subjected to a release treatment using a release agent or the like. Specific examples of the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. The release agent may be silicone-based, fluorine-based, or long-chain alkyl-based, and among these, silicone-based, which is inexpensive and provides stable performance, is preferred.

[0101] There is no particular limitation on the thickness of the release sheet, and it may be, for example, 16 μm or more and 250 μm or less.

[0102] 1-4.Other In the workpiece processing sheet 1 according to this embodiment, an adhesive layer may be laminated on the surface of the adhesive layer 12 opposite to the substrate 11. In this case, the workpiece processing sheet 1 according to this embodiment can be used as a dicing / die bonding sheet. In this sheet, a workpiece is attached to the surface of the adhesive layer opposite to the adhesive layer 12, and the adhesive layer is diced together with the workpiece to obtain a chip on which the individualized adhesive layer is laminated. The individualized adhesive layer makes it possible for the chip to be easily fixed to the object on which the chip is to be mounted. As the material constituting the above-mentioned adhesive layer, it is preferable to use one containing a thermoplastic resin and a low molecular weight thermosetting adhesive component, one containing a B-stage (semi-cured) thermosetting adhesive component, or the like.

[0103] In addition, in the workpiece processing sheet 1 according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer 12. In this case, the workpiece processing sheet 1 according to this embodiment can be used as a sheet for forming a protective film and dicing. In such a sheet, a workpiece is attached to the surface of the protective film forming layer opposite to the adhesive layer 12, and the protective film forming layer is diced together with the workpiece to obtain a chip on which the individualized protective film forming layer is laminated. As the workpiece, it is preferable to use one having a circuit formed on one side, and in this case, the protective film forming layer is usually laminated on the surface opposite to the surface on which the circuit is formed. The individualized protective film forming layer can be cured at a predetermined timing to form a protective film having sufficient durability on the chip. The protective film forming layer is preferably made of an uncured curable adhesive.

[0104] 2. Physical properties of workpiece processing sheet In the workpiece processing sheet 1 according to this embodiment, the surface resistivity of the surface (adhesive surface) of the adhesive layer 12 opposite to the substrate 11 is 1.0×10 13 It is preferably Ω / □ or less, and particularly 1.0×10 12 It is preferable that the resistance is Ω / □ or less, and more preferably 1.0×10 11It is preferable that the surface resistivity is Ω / □ or less. This means that the workpiece processing sheet 1 according to this embodiment has excellent antistatic properties. The lower limit of the surface resistivity is not particularly limited, and is, for example, 1.0×10 8 Ω / □ or more, and in particular 1.0×10 9 It may be Ω / □ or more. When the pressure-sensitive adhesive layer 12 is active energy ray curable, the above surface resistivity is the value after the pressure-sensitive adhesive layer 12 is irradiated with active energy rays and the pressure-sensitive adhesive layer 12 is cured.

[0105] 3. Manufacturing method of workpiece processing sheet There is no particular limitation on the method for producing the workpiece processing sheet 1 according to this embodiment. For example, it is preferable to obtain the workpiece processing sheet 1 by forming the adhesive layer 12 on a release sheet, and then laminating the surface of the adhesive layer 12 on the side opposite to the release sheet with the surface of the surface layer 111 of the base material 11.

[0106] The pressure-sensitive adhesive layer 12 can be formed by a known method. For example, a coating liquid containing a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer 12 and, if desired, a solvent or a dispersion medium is prepared. Then, the coating liquid is applied to the surface having releasability of a release sheet (hereinafter, sometimes referred to as the "release surface"). Then, the obtained coating film is dried to form the pressure-sensitive adhesive layer 12.

[0107] The coating of the coating liquid described above can be carried out by a known method, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, etc. The nature of the coating liquid is not particularly limited as long as it can be applied, and the coating liquid may contain the components for forming the pressure-sensitive adhesive layer 12 as a solute or as a dispersoid. The release sheet may be peeled off as a processing material, or may protect the pressure-sensitive adhesive layer 12 until it is attached to the adherend.

[0108] When the adhesive composition for forming the adhesive layer 12 contains the above-mentioned crosslinking agent, it is preferable to change the above-mentioned drying conditions (temperature, time, etc.) or to separately provide a heat treatment to advance the crosslinking reaction between the polymer component in the coating film and the crosslinking agent, thereby forming a crosslinked structure with a desired density in the adhesive layer 12. Furthermore, in order to advance the above-mentioned crosslinking reaction sufficiently, after the adhesive layer 12 and the substrate 11 are laminated together, curing may be performed by leaving the adhesive layer 12 to stand for several days in an environment of 23°C and a relative humidity of 50%.

[0109] 4. How to use the workpiece processing sheet The workpiece processing sheet 1 according to this embodiment can be used for processing a workpiece such as a semiconductor wafer. That is, after the adhesive surface of the workpiece processing sheet 1 according to this embodiment is attached to the workpiece, the workpiece can be processed on the workpiece processing sheet 1. Depending on the processing, the workpiece processing sheet 1 according to this embodiment can be used as a back grinding sheet, a dicing sheet, an expanding sheet, a pick-up sheet, or the like. Here, examples of the workpiece include semiconductor members such as semiconductor wafers and semiconductor packages, and glass members such as glass plates.

[0110] As described above, the workpiece processing sheet 1 according to this embodiment can effectively suppress the generation of cutting chips, especially thread-like cutting chips, when used for dicing with a rotating round blade. Therefore, the workpiece processing sheet 1 according to this embodiment is particularly suitable for use as a dicing sheet among the above-mentioned workpiece processing sheets.

[0111] Furthermore, the workpiece processing sheet 1 according to this embodiment has excellent antistatic properties as described above. The workpiece processing sheet 1 according to this embodiment can suppress peeling charge when the release sheet is separated or when the workpiece is separated. Furthermore, the workpiece processing sheet 1 according to this embodiment can effectively suppress peeling charge when the workpiece processing sheet is detached from the spinner table after cleaning and drying the chips with the workpiece processing sheet fixed to the spinner table. Therefore, the workpiece processing sheet 1 according to this embodiment can be suitably used for such cleaning and drying.

[0112] In addition, when the workpiece processing sheet 1 according to this embodiment has the above-mentioned adhesive layer, the workpiece processing sheet 1 can be used as a dicing / die bonding sheet. Furthermore, when the workpiece processing sheet 1 according to this embodiment has the above-mentioned protective film forming layer, the workpiece processing sheet 1 can be used as a protective film forming / dicing sheet.

[0113] In addition, when the adhesive layer 12 in the workpiece processing sheet 1 according to this embodiment is composed of the above-mentioned active energy ray curable adhesive, it is also preferable to irradiate the adhesive layer 12 with active energy rays during use. That is, when the processing of the workpiece is completed on the workpiece processing sheet 1 and the processed workpiece is to be separated from the workpiece processing sheet 1, it is preferable to irradiate the adhesive layer 12 with active energy rays before the separation. This hardens the adhesive layer 12, and the adhesive force of the adhesive sheet to the processed workpiece is reduced favorably, making it easier to separate the processed workpiece.

[0114] The above-described embodiments are described for the purpose of facilitating understanding of the present invention, and are not described for the purpose of limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0115] For example, in the workpiece processing sheet 1 according to this embodiment, another layer may be laminated between the base material 11 and the adhesive layer 12, or on the surface of the base material 11 opposite the adhesive layer 12. In addition, another layer may be laminated on the surface of the surface layer 111 opposite the intermediate layer 112, between the surface layer 111 and the intermediate layer 112, between the intermediate layer 112 and the back layer 113, and on the surface of the back layer 113 opposite the intermediate layer 112. EXAMPLES

[0116] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0117] Example 1 (1) Preparation of substrate 28 parts by mass of random polypropylene resin (manufactured by Japan Polypropylene, product name "Novatec FX3B"), 42 parts by mass of olefin-based elastomer (manufactured by Japan Polypropylene, product name "Wellnex RFX4V"), and 30 parts by mass of polymer-type antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Plectron PVL") were each dried and then kneaded in a twin-screw kneader to obtain pellets for the surface layer and back layer.

[0118] In addition, 30 parts by mass of random polypropylene resin (manufactured by Japan Polypropylene, product name "Novatec FX3B"), 45 parts by mass of an olefin-based elastomer (manufactured by Japan Polypropylene, product name "Wellnex RFX4V"), and 25 parts by mass of a styrene-ethylene-butylene-styrene copolymer (SEBS) as a styrene-based elastomer (manufactured by Asahi Kasei, product name "Tuftec H1041", styrene ratio: 30% by mass) were each dried and then kneaded in a twin-screw kneader to obtain pellets for the intermediate layer.

[0119] The two types of pellets obtained as described above were co-extruded using a small T-die extruder (manufactured by Toyo Seiki Seisakusho, product name "Labo Plastomill") to obtain a three-layer substrate consisting of a 4 μm thick surface layer, a 72 μm thick middle layer, and a 4 μm thick back layer laminated in that order.

[0120] (2) Preparation of adhesive composition 60 parts by mass of n-butyl acrylate, 10 parts by mass of methyl methacrylate, and 30 parts by mass of 2-hydroxyethyl acrylate were polymerized by solution polymerization to obtain a (meth)acrylic acid ester polymer. Then, 2-methacryloyloxyethyl isocyanate (MOI) was added in an amount equivalent to 80 mol% relative to the 2-hydroxyethyl acrylate constituting the (meth)acrylic acid ester polymer, and dibutyltin dilaurate (DBTDL) as a tin-containing catalyst was added in an amount of 0.13 parts by mass relative to 100 parts by mass of the (meth)acrylic acid ester polymer. Then, the mixture was reacted at 50°C for 24 hours to obtain a (meth)acrylic acid ester polymer having an active energy ray curable group introduced into the side chain. The weight average molecular weight of the active energy ray curable polymer was measured by the method described below and was 500,000.

[0121] 100 parts by mass (solid content equivalent, same below) of the (meth)acrylic acid ester polymer obtained above having an active energy ray-curable group introduced into the side chain, 2 parts by mass of 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (manufactured by BASF, product name "Omnirad 127") as a photopolymerization initiator, and 1 part by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh, product name "Coronate L") as a crosslinking agent were mixed in a solvent to obtain a coating liquid of an adhesive composition.

[0122] (3) Formation of adhesive layer The adhesive composition coating solution obtained in step (2) above was applied to the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") consisting of a 38 μm-thick polyethylene terephthalate film with a silicone-based release agent layer formed on one side thereof, and the resulting sheet was dried by heating to obtain a laminate consisting of a 5 μm-thick adhesive layer formed on the release sheet.

[0123] (4) Preparation of adhesive sheet The surface layer side of the substrate obtained in the above step (1) was subjected to corona treatment, and the surface of the adhesive layer side of the laminate obtained in the above step (3) was bonded to obtain a workpiece processing sheet.

[0124] The weight average molecular weight (Mw) mentioned above is a weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement) and converted into standard polystyrene. <Measurement conditions> Measuring device: Tosoh HLC-8320 GPC columns (passed in the following order): Tosoh Corporation TSK gel superH-H TSK gel superHM-H TSK gel superH2000 Measurement solvent: Tetrahydrofuran ·Measurement temperature: 40℃

[0125] [Examples 2-3, Comparative Examples 1-3] A workpiece processing sheet was manufactured in the same manner as in Example 1, except that the composition of the pellets for forming each layer of the base material and the thickness of each layer were changed as shown in Table 1. In Examples 2 and 3, 15 parts by mass of a maleic anhydride adduct of an ethylene-ethyl acrylate copolymer (manufactured by SK Functional Polymers, product name "BONDINE LX4110", ethyl acrylate content: 5% by mass, acid component content: 3% by mass) was further blended into the surface layer as an acid-modified resin.

[0126] In Comparative Example 1, a styrene-ethylene / ethylene-propylene-styrene block copolymer (SEEPS) ("Hybler 7311F" manufactured by Kuraray Co., Ltd., styrene ratio: 12% by mass) was used as the styrene-based elastomer. In Comparative Examples 2 and 3, an ethylene-butylene-styrene copolymer (SEBS) ("Tuftec H1062" manufactured by Asahi Kasei Co., Ltd., styrene ratio: 18% by mass) was used as the styrene-based elastomer.

[0127] Comparative Example 4 Using the same device as in Example 1, a film made of a single layer of ethylene-methacrylic acid copolymer (manufactured by Mitsui Dow Polychemicals, product name "Nucrel N0903HC") was produced. The surface of the obtained film on which the adhesive layer was laminated was irradiated once with an electron beam of 10 kGy for 2.2 seconds to prepare a substrate. Using this substrate, a workpiece processing sheet was produced in the same manner as in Example 1.

[0128] Comparative Example 5 Using the same device as in Example 1, a film made of a single layer of ethylene-methacrylic acid copolymer (manufactured by Mitsui Dow Polychemicals, product name "Nucrel N0903HC") was produced. The surface of the obtained film on which the adhesive layer was laminated was irradiated twice with an electron beam of 10 kGy for 2.2 seconds each time, and the resulting film was used as a substrate. Using this substrate, a workpiece processing sheet was produced in the same manner as in Example 1.

[0129] [Test Example 1] (Viscoelasticity measurement) The substrates (thickness 80 μm) manufactured in the examples and comparative examples were cut into samples with long sides of 20 mm (chuck distance) and short sides of 4 mm, with the MD direction of the substrate being the long side direction.

[0130] Using a dynamic viscoelasticity measurement device (manufactured by A&D Co., Ltd., product name "Leovibron (registered trademark) DDV-01FP"), viscoelasticity measurements were performed on the above samples under the following measurement conditions to obtain the loss modulus and storage modulus.

[0131] From the measured values, the loss tangent tan δ (loss modulus / storage modulus) at 90°C, 110°C and 120°C was calculated (represented as tan δ(90), tan δ(100), tan δ(110) and tan δ(120) respectively). From these results, tan δ(110) / tan δ(90) and tan δ(120) / tan δ(110) were calculated. The results are shown in Table 2. <Measurement conditions> Measurement temperature range: -30℃~120℃ Heating rate: 1℃ / min Measurement mode: Tensile Frequency: 11Hz

[0132] [Test Example 2] (Measurement of surface resistivity) The substrates produced in the examples and comparative examples were conditioned at 23° C. and 50% relative humidity for 24 hours, and then the surface resistivity of the surface layer side was measured using a DIGITAL ELECTROMETER (manufactured by ADVANTEST Co., Ltd.) at an applied voltage of 100 V. The results are shown in Table 2.

[0133] In addition, the workpiece processing sheets manufactured in the examples and comparative examples were cut to 100 mm x 100 mm, which were used as samples for measuring surface resistivity. The adhesive layer in the sample for measuring surface resistivity was irradiated with ultraviolet (UV) rays through the substrate using an ultraviolet irradiator (manufactured by Lintec Corporation, product name "RAD-2000") (illuminance: 230 mW / cm 2 ,Light amount: 190mJ / cm 2 ) and the adhesive layer was cured. The sample for measuring surface resistivity after UV irradiation was conditioned at 23°C and 50% relative humidity for 24 hours, after which the release sheet was peeled off and the surface resistivity of the exposed adhesive layer side (adhesive surface) was measured in the same manner as above. The results are also shown in Table 2.

[0134] [Test Example 3] (Evaluation of antistatic properties) Using a grinder (manufactured by Disco, product name "DFG8540"), one side of a 6-inch silicon wafer was ground to a thickness of 350 μm. Using a laminator, the exposed surface of the adhesive layer exposed by peeling off the release sheet from the workpiece processing sheet produced in the Examples and Comparative Examples was attached to the ground surface.

[0135] Twenty minutes after attachment, the silicon wafer was diced into individual chips using a dicing device (manufactured by Disco Corporation, product name "DFD6362") under the following dicing conditions. Dicing Conditions Chip size: 10mm x 10mm Cutting height: 60μm Blade: Product name "ZH05-SD2000-Z1-90 CC" Blade rotation speed: 35000 rpm Cutting speed: 60mm / sec Cutting water amount: 1.0L / min Cutting water temperature: 20℃

[0136] After dicing, the chips obtained as described above were washed and dried while the workpiece processing sheet was fixed on the spinner table by suction. Then, the electrostatic voltage (V) of the workpiece processing sheet immediately after lifting it from the spinner table was measured using a measuring device (manufactured by Prostat, product name "PFK-100"). Then, the antistatic properties were evaluated based on the following criteria. The electrostatic voltage and evaluation results are shown in Table 2. ◯: The charging voltage was 300V or less. ×: The charging voltage was more than 300V.

[0137] [Test Example 4] (Evaluation of the effect of suppressing cutting chips) After peeling off the release sheet from the workpiece processing sheet produced in the examples and comparative examples, the exposed surface of the exposed adhesive layer was attached to one side of a 6-inch silicon wafer using a tape mounter (manufactured by Lintec Corporation, product name "RAD2500m / 12"). Next, a dicing ring frame was attached to the periphery of the exposed surface of the workpiece processing sheet (at a position that does not overlap with the silicon wafer). Furthermore, the workpiece processing sheet was cut to fit the outer diameter of the ring frame.

[0138] Thereafter, the silicon wafer was diced into individual chips having a size of 0.8 mm×20 mm by dicing under the following dicing conditions using a dicing device (manufactured by Disco Corporation, product name “DFD6362”). Dicing Conditions Wafer thickness: 100μm Blades: Z1 and Z2, both manufactured by Disco Z1: Product name "ZH05-SD3500-N1-50 DF01" Z2: Product name "ZH05-SD3000-N1-50 ED" Blade Rotation Speed Z1: 50,000 rpm Z2: 35,000 rpm Cutting speed: 100mm / sec Blade Height Z1: 0.135mm Z2: 0.055mm Cutting water amount: 1.0L / min Cutting water temperature: 20℃

[0139] After dicing, the surfaces of 1000 chips obtained were observed using a visual inspection device (Camtek, product name "Eagle") to count the number of chips. The number of chips per chip (= chip generation frequency) was then calculated. The results are shown in Table 2.

[0140] The effect of suppressing the generation of cutting chips was evaluated based on the following criteria. The evaluation results are shown in Table 2. ○: The frequency of chip generation was less than 0.002. ×: The frequency of chip generation was 0.002 or more.

[0141] [Table 1]

[0142] [Table 2]

[0143] As is clear from Table 2, the workpiece processing sheets produced in the examples exhibited excellent antistatic properties while also effectively suppressing the generation of cutting chips. [Industrial Applicability]

[0144] The workpiece processing sheet of the present invention can be suitably used for processing workpieces such as semiconductor wafers. [Explanation of symbols]

[0145] 1...Work processing sheet 11...Base material 111…Surface layer 112…Middle class 113…Back layer 12...Adhesive layer

Claims

1. A workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, The substrate comprises a surface layer located proximal to the pressure-sensitive adhesive layer, a back layer located distal to the pressure-sensitive adhesive layer, and an intermediate layer located between the surface layer and the back layer; At least the back surface layer contains an antistatic agent, the intermediate layer contains a styrene-based thermoplastic elastomer and a polyolefin-based resin, The content of structural units derived from styrene or a styrene-based compound in the styrene-based thermoplastic elastomer is 20% by mass or more and 40% by mass or less, The content of the styrene-based thermoplastic elastomer in the intermediate layer is 10% by mass or more and 40% by mass or less, The content of the polyolefin resin in the intermediate layer is 15% by mass or more and 45% by mass or less, The viscoelasticity of the substrate was measured at a frequency of 11 Hz. The loss tangent at 90° C. was tan δ(90), the loss tangent at 110° C. was tan δ(110), and the loss tangent at 120° C. was tan δ(120). tan δ(110) is 0.25 or more in absolute value, tan δ(110) / tan δ(90) is 1.3 or more, tan δ(120) / tan δ(110) is 0.9 or less A workpiece processing sheet characterized by the above.

2. 2. The workpiece processing sheet according to claim 1, wherein the surface layer contains an antistatic agent.

3. 3. The workpiece processing sheet according to claim 1, wherein the surface layer contains a polyolefin resin and an olefin thermoplastic elastomer.

4. The workpiece processing sheet according to any one of claims 1 to 3, characterized in that the back layer contains an olefin-based thermoplastic elastomer.

5. The workpiece processing sheet according to any one of claims 1 to 4, characterized in that the intermediate layer contains the styrene-based thermoplastic elastomer, the polyolefin-based resin and an olefin-based thermoplastic elastomer.

6. The intermediate layer does not contain an antistatic agent, or The intermediate layer contains an antistatic agent in a content (unit: mass %) smaller than that of each of the front surface layer and the back surface layer. The workpiece processing sheet according to any one of claims 1 to 5.

7. The workpiece processing sheet according to any one of claims 1 to 6, characterized in that the antistatic agent is a polymer-type antistatic agent.

8. The surface resistivity of the surface of the pressure-sensitive adhesive layer opposite to the substrate is 1.0×10 １３ The workpiece processing sheet according to any one of claims 1 to 7, characterized in that it has a hardness of Ω / □ or less.

9. The workpiece processing sheet according to any one of claims 1 to 8, characterized in that it is a dicing sheet.

10. A workpiece processing sheet described in any one of claims 1 to 9, characterized in that the thickness of the surface layer is 1 μm or more and 4 μm or less.

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