Workpiece processing sheet

Abstract

To provide a workpiece processing sheet which suppresses change in adhesive force with time and leakage of alkali metal ions while exhibiting excellent antistatic properties.SOLUTION: There is provided a workpiece processing sheet 1 which comprises a substrate 11 and an adhesive layer 12 laminated on one surface side of the substrate 11, wherein the base material 11 comprises a surface layer 111, a rear surface layer 113 and an intermediate layer 112, each of the surface layer 111 and the rear surface layer 113 contains an antistatic agent, the antistatic agent contained in the surface layer 111 has a melt flow rate (MFR) of 15 g / 10 min or less as measured according to ASTM D1238 (190°C, 21.18 N) and the antistatic agent contained in the rear surface layer 113 has a melt flow rate (MFR) of 14 g / 10 min or more as measured according to ASTM D1238 (190°C, 21.18 N).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 large diameters, cut into chips (diced), peeled off (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 then undergo processing such as backgrinding, dicing, cleaning, drying, expanding, picking up, and mounting.

[0003] When the workpiece processing sheet is peeled off from the processed workpiece after the specified processing step is completed, static electricity called peeling electrification may occur between the workpiece processing sheet and the adherend. Such static electricity can cause dust and other particles to adhere to the workpiece or equipment, and can also cause damage to the workpiece. Therefore, workpiece processing sheets are required to have antistatic properties.

[0004] Patent Documents 1 and 2 disclose the use of a substrate containing a predetermined antistatic agent, with the aim of providing a workpiece processing sheet having antistatic properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-211314 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-244377 Summary of the Invention [Problem to be solved by the invention]

[0006] However, workpiece processing sheets having a base material containing the above-mentioned antistatic agent have the problem that their adhesive strength is easily reduced during storage. Furthermore, some antistatic agents contain alkali metal ions, and when such antistatic agents are used, the alkali metal ions can leak out of the base material and adhere to and affect the workpieces and the equipment used to handle the workpiece processing sheets.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a work processing sheet that exhibits excellent antistatic properties while suppressing changes in adhesive strength over time and the outflow of alkali metal ions. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, first, the present invention provides a workpiece processing sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, wherein the substrate comprises 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, and each of the surface layer and the back layer contains an antistatic agent, the antistatic agent contained in the surface layer having a melt flow rate (MFR) of 15 g / 10 min or less, measured in accordance with ASTM D1238 (190°C, 21.18 N), and the antistatic agent contained in the back layer having a melt flow rate (MFR) of 14 g / 10 min or more, measured in accordance with ASTM D1238 (190°C, 21.18 N) (Invention 1).

[0009] The workpiece processing sheet according to the above invention (Invention 1) has a substrate with the above three layers, of which the front and back layers contain antistatic agents, thereby exhibiting excellent antistatic properties. Meanwhile, since the melt flow rates of the antistatic agents contained in the front and back layers are within the above ranges, the change in adhesive strength over time is effectively suppressed, and the outflow of alkali metal ions into the workpiece, equipment, etc. is effectively suppressed.

[0010] In the above invention (Invention 1), it is preferable that the thickness of the surface layer is 0.5 μm or more and less than 8 μm (Invention 2).

[0011] In the above inventions (Inventions 1 and 2), the antistatic agent is preferably a polyether polyolefin block copolymer (Invention 3).

[0012] In the above inventions (inventions 1 to 3), a dicing sheet is preferred (invention 4). [Effects of the Invention]

[0013] The workpiece processing sheet according to the present invention exhibits excellent antistatic properties while suppressing the change in adhesive strength over time and the outflow of alkali metal ions. [Brief explanation of the drawings]

[0014] [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 INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described. A cross-sectional view of a workpiece processing sheet according to one embodiment is shown in Fig. 1. The workpiece processing sheet 1 shown in Fig. 1 includes a substrate 11 and an adhesive layer 12 laminated on one side of the substrate 11.

[0016] 1, the substrate 11 includes a surface layer 111 located proximal to the pressure-sensitive adhesive layer 12, a back layer 113 located distal to the pressure-sensitive adhesive layer 12, and an intermediate layer 112 located between the surface layer 111 and the back layer 113. Each of the surface layer 111 and the back layer 113 contains an antistatic agent.

[0017] As described above, the base material 11 has a layer containing an antistatic agent, so that the workpiece processing sheet 1 according to this embodiment has excellent antistatic properties. Therefore, peeling electrification can be effectively suppressed when the release sheet or workpiece is separated from the workpiece processing sheet 1.

[0018] Furthermore, in the substrate 11 of this embodiment, the melt flow rate (MFR) of the antistatic agent contained in the surface layer 111, measured in accordance with ASTM D1238 (190°C, 21.18N), is 15 g / 10 min or less, and the melt flow rate (MFR) of the antistatic agent contained in the back layer 113, measured in accordance with ASTM D1238 (190°C, 21.18N), is 14 g / 10 min or more.

[0019] The antistatic agent contained in the surface layer 111 has a relatively low MFR of 15 g / 10 min or less, which makes the viscosity of the antistatic agent itself high and makes it less likely to flow out of the surface layer 111. This prevents the antistatic agent from migrating from the surface layer 111 to the adhesive layer 12, effectively preventing the adhesive strength of the workpiece processing sheet 1 according to this embodiment from changing over time.

[0020] From this viewpoint, the MFR of the antistatic agent contained in the surface layer 111 is more preferably 13 g / 10 min or less, and particularly preferably 10 g / 10 min or less. The lower limit of the MFR is not particularly limited, and may be, for example, 1 g / 10 min or more, and particularly 2 g / 10 min or more.

[0021] On the other hand, the MFR of the antistatic agent contained in the backing layer 113 is 14 g / 10 min or more as described above. When the MFR is relatively high, the amount of alkali metal ions contained in the antistatic agent tends to be small. By incorporating an antistatic agent exhibiting this MFR into the backing layer 113, the outflow of alkali metal ions from the workpiece processing sheet 1 according to this embodiment is effectively suppressed. In particular, when dicing is performed, alkali metal ions often leak into the cutting water or the rinse water after dicing. However, the workpiece processing sheet 1 according to this embodiment can effectively suppress this outflow into the cutting water or the rinse water. This effectively suppresses the migration of alkali metal ions to the workpiece or various devices used to handle the workpiece processing sheet 1, thereby reducing the impact of alkali metal ions.

[0022] From this viewpoint, the MFR of the antistatic agent contained in the back surface layer 113 is more preferably 14 g / 10 min or more, and particularly preferably 17 g / 10 min or more. The lower limit of the MFR is not particularly limited, and may be, for example, 30 g / 10 min or less, and particularly 25 g / 10 min or less.

[0023] Details of the method for measuring the MFR are as described in the test examples below.

[0024] 1. Composition of workpiece processing sheet (1) Base material As described above, the substrate 11 in this embodiment includes the surface layer 111, the intermediate layer 112, and the back surface layer 113. The compositions of these layers are not particularly limited as long as the surface layer 111 and the back surface layer 113 each contain an antistatic agent exhibiting the above-mentioned MFR.

[0025] Materials other than the antistatic agent in each layer constituting the substrate 11 are not particularly limited as long as they are capable of forming those layers, and it is preferable to use, for example, a resin. In particular, from the viewpoint of easily achieving the performance required of a workpiece processing sheet, such as expandability and reduction of cutting chips, it is preferable to use at least one of polyolefin resin and thermoplastic elastomer as the main material. Note that the surface layer 111 and the back layer 113 may have different compositions or may have exactly the same composition.

[0026] (1-1) Polyolefin resin Specific examples of the polyolefin resin are not particularly limited. In this specification, the polyolefin resin refers to a homopolymer or copolymer containing an olefin as a monomer, or a copolymer containing an olefin and a molecule other than an olefin as monomers, in which the mass ratio of the portion based on the olefin unit in the polymerized resin is 1.0 mass% or more.

[0027] The polymer constituting the polyolefin resin may be linear or may have a side chain, and may also have an aromatic ring or an aliphatic ring.

[0028] Examples of olefin monomers constituting polyolefin-based 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, tetracyclododecene, and derivatives thereof.

[0029] The polyolefin resins can be used singly or in combination of two or more.

[0030] 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.

[0031] As the polypropylene, for example, homopolypropylene, random polypropylene, and block polypropylene are preferably used. These may be used alone or in combination of two or more. In particular, it is preferable to use a mixture of homopolypropylene and random polypropylene.

[0032] The homopolypropylene, random polypropylene, and block polypropylene may each be a commercially available product. Examples of commercially available homopolypropylenes include those manufactured by Prime Polymer Co., Ltd. under the product names "Prime Polypro E111G," "Prime Polypro E-100GV," "Prime Polypro E-100GPL," and "Prime Polypro E-200GP." Examples of commercially available random polypropylenes include those manufactured by Prime Polymer Co., Ltd. under the product names "Prime Polypro B221WA," "Prime Polypro B241," "Prime Polypro E222," and "Prime Polypro E-333GV." Examples of commercially available block polypropylenes include those manufactured by Prime Polymer Co., Ltd. under the product names "Prime Polypro E701G," "Prime Polypro E702G," and "Prime Polypro E702MG."

[0033] The polyethylene may be any 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.

[0034] In particular, it is preferable to use low-density polyethylene as the polyethylene, and examples of commercially available products include "Novatec LL" manufactured by Mitsubishi Chemical Corporation, and the Neozex series and Ultraozex series manufactured by Prime Polymer Co., Ltd.

[0035] When any of the layers constituting the substrate 11 contains a polyolefin resin, the content of the polyolefin resin in that layer is preferably 10% by mass or more, particularly preferably 15% by mass or more, and even more preferably 20% by mass or more. Furthermore, the content is preferably 100% by mass or less, particularly preferably 95% by mass or less, and even more preferably 90% by mass or less. By ensuring that the polyolefin resin content is within the above range, the workpiece processing sheet 1 according to this embodiment is more likely to have good expandability.

[0036] (1-2) Thermoplastic elastomer The thermoplastic elastomer is not particularly limited as long as it is other than the polyolefin-based resin and can be used to form the substrate 11. Examples of the thermoplastic elastomer include olefin-based elastomers, rubber elastomers, urethane-based elastomers, styrene-based elastomers, acrylic-based elastomers, and vinyl chloride-based elastomers. These may be used alone or in combination of two or more.

[0037] Among the above-mentioned elastomers, olefin-based elastomers are preferred from the viewpoint of facilitating good expandability. In particular, it is preferred that at least one of the front surface layer 111 and the back surface layer 113 contains an olefin-based elastomer. In this specification, the term "olefin-based elastomer" refers to a copolymer containing structural units derived from olefin or its derivatives (olefin-based compounds), and is a material that has rubber-like elasticity and thermoplasticity in a temperature range including room temperature.

[0038] 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.

[0039] When any of the layers constituting the substrate 11 contains an olefin-based elastomer, the content of the olefin-based elastomer in that layer is preferably 1% by mass or more, particularly preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, the content is preferably 90% by mass or less, particularly preferably 80% by mass or less, and even more preferably 70% by mass or less. By ensuring that the olefin-based elastomer content is within the above range, the workpiece processing sheet 1 according to this embodiment is more likely to achieve good expandability.

[0040] Furthermore, from the viewpoint of easily obtaining good expandability, it is also preferable to use a styrene-based elastomer. In particular, it is preferable that the intermediate layer 112 contains a styrene-based elastomer. In this specification, the term "styrene-based elastomer" refers to a copolymer containing structural units derived from styrene or its derivatives (styrene-based compounds), and is a material that has rubber-like elasticity and thermoplasticity in a temperature range including room temperature.

[0041] Examples of styrene-based elastomers include styrene-conjugated diene copolymers and styrene-olefin copolymers, with styrene-conjugated diene copolymers being 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 styrene-isoprene-styrene copolymer) and styrene-ethylene-butylene-styrene copolymer (SEBS: hydrogenated styrene-butadiene copolymer). The styrene-based thermoplastic elastomer may be hydrogenated or unhydrogenated, but hydrogenated products are preferred. Among the above, hydrogenated styrene-conjugated diene copolymers are preferred, and styrene-ethylene-butylene-styrene copolymers (SEBS) are particularly preferred, from the viewpoint of facilitating good expandability.

[0042] The content of structural units derived from styrene or styrene compounds in the styrene-based elastomer (styrene ratio) is preferably 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. Furthermore, from the viewpoint of easily achieving excellent film-forming properties, the content of the structural units is preferably 80% by mass or less, particularly preferably 70% by mass or less, and even more preferably 60% by mass or less. This makes it easier to achieve excellent expandability.

[0043] When any of the layers constituting the substrate 11 contains a styrene-based elastomer, the content of the styrene-based elastomer in that layer is preferably 1% by mass or more, particularly preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, the content is preferably 90% by mass or less, particularly preferably 80% by mass or less, and even more preferably 70% by mass or less. By ensuring that the content of the styrene-based elastomer is within the above range, the workpiece processing sheet 1 according to this embodiment is more likely to achieve good expandability.

[0044] (1-3) Antistatic agent 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 polymer-type antistatic agents, but polymer-type antistatic agents are preferred because they can easily suppress the generation of chips and are less likely to bleed out from the substrate 11, thereby making it easier to suppress changes in adhesive strength over time.

[0045] Examples of polymer-type antistatic agents include copolymers having polyether units, such as polyether ester amides and polyether polyolefin block copolymers, and these copolymers may contain metal salts, such as alkali metal salts and alkaline earth metal salts, or ionic liquids. Among these, polyether polyolefin block copolymers are preferred from the viewpoint of easily suppressing changes in adhesive strength over time while achieving sufficient antistatic properties.

[0046] A polyether-polyolefin block copolymer is a copolymer containing both polyether and polyolefin units. The polyether unit exhibits ionic conductivity, thereby providing antistatic properties, while the polyolefin unit provides excellent dispersibility in polyolefin resins.

[0047] Examples of commercially available polyether polyblock olefin copolymers include those manufactured by Sanyo Chemical Industries, Ltd. under the product names "Pelestat 300," "Pelestat 230," "Pelestat PVH," "Pelestat PVL," "Pelestat HS," "Pelestat 201," and "Pelestat UC," as well as those manufactured by Sanko Chemical Industries, Ltd. under the product name "Sankonol TBX-310."

[0048] Among these antistatic agents related to polyether polyolefin block copolymers, those suitable for use in the surface layer 111 (with an MFR of 15 g / 10 min or less) include those with the product name "Pelectron PVH" (MFR: 9.8 g / 10 min), those with the product name "Pelestat 230" (MFR: 9 g / 10 min), and those with the product name "Pelectron UC" (MFR: 14 g / 10 min). Those suitable for use in the back layer 113 (with an MFR of 14 g / 10 min or more) include those with the product name "Pelectron PVL" (MFR: 19 g / 10 min).

[0049] Furthermore, when 1 g of the antistatic agent is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the amount of lithium ions extracted into the pure water is preferably 50 ppm or less, more preferably 30 ppm or less, and even more preferably 10 ppm or less. Having an extractable amount of 50 ppm or less makes it easier to effectively suppress the leakage of lithium ions from the workpiece processing sheet 1 according to this embodiment. The lower limit of the extractable amount is not particularly limited and may be, for example, 0.0001 ppm or more, particularly 0.001 ppm or more. Details of the method for measuring the extractable amount are described in the test examples below.

[0050] Furthermore, when 1 g of the antistatic agent is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the amount of sodium ions extracted into the pure water is preferably 150 ppm or less, more preferably 50 ppm or less, and even more preferably 10 ppm or less. Having an extractable amount of 150 ppm or less makes it easier to effectively suppress the outflow of sodium ions from the workpiece processing sheet 1 according to this embodiment. The lower limit of the extractable amount is not particularly limited and may be, for example, 0.0001 ppm or more, particularly 0.001 ppm or more. Details of the method for measuring the extractable amount are described in the test examples below.

[0051] In the substrate 11 of this embodiment, as described above, the surface layer 111 and the back layer 113 contain an antistatic agent, but the intermediate layer 112 may also contain an antistatic agent. However, from the viewpoint of easily suppressing the generation of chips during dicing, it is preferable that the intermediate layer 112 does not contain an antistatic agent or that the intermediate layer 112 contains an antistatic agent in a content (unit: mass %) lower than that of each of the surface layer 111 and the back layer 113. In this way, by having the intermediate layer 112 containing no antistatic agent or a low content of antistatic agent between the surface layer 111 and the back layer 113, the generation of chips from the intermediate layer 112 can be effectively suppressed when a dicing blade reaches the intermediate layer 112 during dicing.

[0052] The content of the antistatic agent in the surface layer 111 is preferably 3% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. When the content of the antistatic agent is 3% by mass or more, good antistatic properties are easily exhibited. Furthermore, the content of the antistatic agent in the surface layer 111 is preferably 40% by mass or less, particularly preferably 35% by mass or less, and even more preferably 30% by mass or less. When the content of the antistatic agent is 40% by mass or less, changes over time of the pressure-sensitive adhesive layer 12 are easily suppressed.

[0053] The content of the antistatic agent in the back surface layer 113 is preferably 10% by mass or more, particularly preferably 20% by mass or more, and even more preferably 30% by mass or more. When the content of the antistatic agent is 10% by mass or more, good antistatic properties are easily exhibited. Furthermore, the content of the antistatic agent in the back surface layer 113 is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less. When the content of the antistatic agent is 50% by mass or less, the outflow of alkali metal ions is easily suppressed.

[0054] As described above, it is preferable that intermediate layer 112 does not contain an antistatic agent, or that intermediate layer 112 contains an antistatic agent in a content (unit: mass %) lower than that of each of front surface layer 111 and back surface layer 113. If intermediate layer 112 contains an antistatic agent, the content thereof in intermediate layer 112 is preferably 10 mass % or less, particularly preferably 5 mass % or less, and further preferably 3 mass % or less. By ensuring that the content of antistatic agent in intermediate layer 112 is 10 mass % or less, it becomes easier to suppress the generation of cuttings. It is also preferable that the lower limit of the content be, for example, 0.01 mass % or more.

[0055] (1-4) Acid-modified resin Each layer constituting the substrate 11 preferably contains an acid-modified resin. In particular, the surface layer 111 preferably contains an acid-modified resin. In this specification, "acid-modified resin" means a resin in which a structure derived from an acid component is 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 an acid-modified resin as described above, the adhesion between the substrate 11 and the adhesive layer 12 is further improved, and the adhesive can be further prevented from remaining on the chip side during pick-up.

[0056] Preferred examples of the main chain of the acid-modified resin include ethylene-acrylic copolymers such as ethylene-(meth)acrylic acid copolymers and ethylene-(meth)acrylic acid ester copolymers. Such resins can easily improve the adhesion between the surface layer 111 and the pressure-sensitive adhesive layer 12. In this specification, (meth)acrylic acid refers to both acrylic acid and methacrylic acid. The same applies to other similar terms.

[0057] The (meth)acrylic acid ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 4 carbon atoms. Preferred examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and n-butyl (meth)acrylate. Of these, ethyl (meth)acrylate is more preferred, and ethyl acrylate is particularly preferred.

[0058] 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, particularly preferably 3% by mass or more, and is preferably 20% by mass or less, particularly preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0059] To acid-modify the resin, it is preferable to react the resin with an unsaturated carboxylic acid. Examples of unsaturated carboxylic acids 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 these, maleic anhydride is particularly preferred from the viewpoint of adhesion to the pressure-sensitive adhesive layer 12.

[0060] The amount of acid component (amount of structure derived from acid component) in the acid-modified resin is preferably 1% by mass or more, particularly preferably 2% by mass or more. Furthermore, the amount of acid component is preferably 7% by mass or less, particularly preferably 5% by mass or less. By having the amount of acid component in the above range, the adhesion between the surface layer 111 and the pressure-sensitive adhesive layer 12 is further improved.

[0061] 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 particularly 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, particularly preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0062] (1-5) Other ingredients The layers constituting the substrate 11 may contain components other than those described above. In particular, the resin composition may contain components used in the substrate of a general workpiece processing sheet.

[0063] Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, ion scavengers, etc. The content of these additives is not particularly limited, but is preferably set within a range in which the substrate exhibits the desired functions.

[0064] (1-6) Surface treatment of substrate The surface of the substrate 11 on which the pressure-sensitive adhesive layer 12 is laminated may be subjected to a surface treatment such as a primer treatment, a corona treatment, a plasma treatment, or a roughening treatment (matt finish) in order to improve adhesion to the pressure-sensitive adhesive layer 12. Examples of roughening treatments include embossing and sandblasting. Of these, corona treatment is preferred.

[0065] (1-7) Manufacturing method of substrate The method for producing the substrate 11 in this embodiment is not particularly limited, and for example, melt extrusion methods such as a T-die method or a round die method, a calendar method, a solution method such as a dry method or a wet method, etc. 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.

[0066] Furthermore, when the substrate 11 is manufactured by a melt extrusion method, the components constituting each layer are kneaded together, and then the resulting kneaded mixture is extruded directly or after pellets are first produced, using a known extruder to simultaneously extrude multiple layers to form a film.

[0067] (1-8) Physical properties of the substrate In this embodiment, when 1 g of the substrate 11 is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the amount of lithium ions extracted into the pure water is preferably 1 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.3 ppm or less. Having an extractable amount of 1 ppm or less makes it easier to effectively suppress the leakage of lithium ions from the workpiece processing sheet 1 according to this embodiment. The lower limit of the extractable amount is not particularly limited and may be, for example, 0.001 ppm or more, particularly 0.01 ppm or more. Details of the method for measuring the extractable amount are as described in the test examples below.

[0068] Furthermore, when 1 g of the substrate 11 in this embodiment is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the amount of sodium ions extracted into the pure water is preferably 1 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.3 ppm or less. Having this amount of extraction of 1 ppm or less makes it easier to effectively suppress the outflow of sodium ions from the workpiece processing sheet 1 according to this embodiment. The lower limit of this amount of extraction is not particularly limited and may be, for example, 0.001 ppm or more, particularly 0.01 ppm or more. Details of the method for measuring the amount of extraction are as described in the test examples below.

[0069] In this embodiment, the surface resistivity of the surface of the substrate 11 on the surface layer 111 side 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 11 It is preferable that the surface resistivity is 1.0×10 Ω / □ or less. 13 When the surface resistivity is Ω / □ or less, the workpiece processing sheet 1 according to this embodiment is likely to have good antistatic properties. The lower limit of the surface resistivity is not particularly limited, and is, for example, 1.0 × 10 8 It may be 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 are as described in the test examples below.

[0070] In this embodiment, the thickness of the surface layer 111 is preferably 0.5 μm or more, more preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 4 μm or more. Furthermore, the thickness of the surface layer 111 is preferably less than 8 μm, particularly preferably 4 μm or less. Having the thickness of the surface layer 111 within the above range makes it easier for the workpiece processing sheet 1 to have excellent antistatic properties. Furthermore, having the thickness of the surface layer 111 less than 8 μm makes it easier to suppress changes in the adhesive strength of the workpiece processing sheet 1 over time.

[0071] In this embodiment, the thickness of the intermediate layer 112 is preferably 40 μm or more, particularly preferably 50 μm or more, and even more preferably 60 μm or more. The thickness of the intermediate layer 112 is preferably 100 μm or less, particularly preferably 90 μm or less, and even more preferably 80 μm or less. Having the thickness of the intermediate layer 112 within the above range makes it easier for the workpiece processing sheet 1 to achieve excellent expandability and to impart the desired performance to the workpiece processing sheet 1.

[0072] In this embodiment, the thickness of the back layer 113 is preferably 2 μm or more, particularly preferably 4 μm or more, and even more preferably 8 μm or more. Having a thickness of 2 μm or more for the back layer 113 makes it easier for the workpiece processing sheet 1 to have excellent antistatic properties. Furthermore, the thickness of the back layer 113 is preferably 40 μm or less, particularly preferably 30 μm or less, and even more preferably 25 μm or less. Having a thickness of 40 μm or less for the back layer 112 makes it easier to suppress the outflow of alkali metal ions from the workpiece processing sheet 1.

[0073] (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, adhesive strength to the workpiece sufficient for processing the workpiece). Examples of adhesives 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 because they can easily exert the desired adhesive strength.

[0074] The adhesive constituting the adhesive layer 12 in this embodiment may be an adhesive that is not active energy ray curable, but is preferably an adhesive that is active energy ray curable (hereinafter, may be referred to as an "active energy ray curable adhesive"). When 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.

[0075] The active energy ray-curable adhesive constituting the adhesive layer 12 may be one whose main component is a polymer having active energy ray curability, or one whose main component is 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 active energy ray-curable group. 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 active energy ray-curable group.

[0076] 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 an active energy ray-curable functional group (active energy ray-curable group) introduced into its side chain. This active energy ray-curable polymer is preferably one 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."

[0077] The acrylic polymer having the functional group-containing monomer unit may be obtained by polymerizing other monomers together with the functional group-containing monomer. As such functional group-containing monomers and other monomers, and the unsaturated group-containing compounds, known compounds can be used, for example, those disclosed in WO 2018 / 084021.

[0078] The weight-average molecular weight of the active energy radiation-curable polymer is preferably 10,000 or more, particularly 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, particularly 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.

[0079] 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.

[0080] The weight-average molecular weight of the acrylic polymer as the non-active energy ray-curable polymer component is preferably 10,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 1,500,000 or less, and even more preferably 1,000,000 or less.

[0081] Furthermore, 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.

[0082] 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.

[0083] In this embodiment, the thickness of the adhesive layer 12 is preferably 1 μm or more, particularly preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, the thickness of the adhesive layer 12 is preferably 70 μm or less, particularly preferably 30 μm or less, and even more preferably 15 μm or less. By keeping the thickness of the adhesive layer 12 within the above-mentioned range, the workpiece processing sheet 1 according to this embodiment can easily exhibit the desired adhesiveness.

[0084] (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 that side until it is attached to the workpiece.

[0085] The release sheet may have any configuration, 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 such plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. Silicone-based, fluorine-based, and long-chain alkyl-based release agents can be used, and among these, silicone-based ones are preferred because they are inexpensive and provide stable performance.

[0086] There are no particular limitations on the thickness of the release sheet, and it may be, for example, 16 μm or more and 250 μm or less.

[0087] (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 the substrate 11. In this case, the workpiece processing sheet 1 according to this embodiment can be used as a dicing / die bonding sheet. A workpiece is attached to the surface of the adhesive layer opposite the adhesive layer 12, and the adhesive layer is diced together with the workpiece to obtain a chip on which the individual adhesive layers are laminated. The individual adhesive layers allow the chip to be easily fixed to the object on which it is to be mounted. The material constituting the adhesive layer described above is preferably a material containing a thermoplastic resin and a low-molecular-weight thermosetting adhesive component, or a material containing a B-stage (semi-cured) thermosetting adhesive component.

[0088] Furthermore, 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 both protective film formation and dicing. With such a sheet, a workpiece is attached to the surface of the protective film forming layer opposite the adhesive layer 12, and the protective film forming layer is diced together with the workpiece to obtain a chip on which a singulated protective film forming layer is laminated. The workpiece preferably has a circuit formed on one side. In this case, the protective film forming layer is typically laminated on the side opposite the side on which the circuit is formed. The singulated protective film forming layer can be cured at a predetermined time to form a protective film with sufficient durability on the chip. The protective film forming layer is preferably made of an uncured curable adhesive.

[0089] 2. Physical properties of workpiece processing sheets When 1 g of the workpiece processing sheet 1 according to this embodiment is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the amount of lithium ions extracted into the pure water is preferably 1 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.3 ppm or less. Having an extractable amount of 1 ppm or less effectively prevents lithium ions from leaking from the workpiece processing sheet 1 according to this embodiment. The lower limit of the extractable amount is not particularly limited and may be, for example, 0.001 ppm or more, particularly 0.01 ppm or more. Details of the method for measuring the extractable amount are described in the test examples below.

[0090] Furthermore, when 1 g of the workpiece processing sheet 1 according to this embodiment is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the amount of sodium ions extracted into the pure water is preferably 1 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.3 ppm or less. Having an extractable amount of 1 ppm or less makes it easier to effectively suppress the outflow of sodium ions from the workpiece processing sheet 1 according to this embodiment. The lower limit of the extractable amount is not particularly limited and may be, for example, 0.001 ppm or more, particularly 0.01 ppm or more. Details of the method for measuring the extractable amount are described in the test examples below.

[0091] Furthermore, when 1 g of the workpiece processing sheet 1 according to this embodiment is mixed with 20 ml of pure water and the resulting sample solution is heated at 121°C for 24 hours, the total amount of lithium ions and sodium ions extracted into the pure water is preferably 2 ppm or less, more preferably 1.5 ppm or less, and even more preferably 1 ppm or less. Having an extractable amount of 2 ppm or less effectively prevents the outflow of lithium ions and sodium ions from the workpiece processing sheet 1 according to this embodiment. The lower limit of the extractable amount is not particularly limited and may be, for example, 0.001 ppm or more, particularly 0.02 ppm or more. Details of the method for measuring the extractable amount are described in the test examples below.

[0092] In the workpiece processing sheet 1 according to this embodiment, the adhesive strength of the workpiece processing sheet to the mirror surface of a silicon wafer (adhesive strength before irradiation with active energy rays and before storage, as described below) (hereinafter sometimes referred to as "adhesive strength before storage") is preferably 3000 mN / 25 mm or more, more preferably 4000 mN / 25 mm or more, and even more preferably 5000 mN / 25 mm or more. Having an adhesive strength before storage of 3000 mN / 25 mm or more facilitates favorable fixation of the workpiece on the workpiece processing sheet 1. The upper limit of the adhesive strength before storage is not particularly limited, and may be 20,000 mN / 25 mm or less, particularly 10,000 mN / 25 mm or less, or even 8,000 mN / 25 mm or less. Details of the method for measuring the adhesive strength before storage are as described in the test examples below.

[0093] Furthermore, in the workpiece processing sheet 1 according to this embodiment, the adhesive strength of the workpiece processing sheet to the mirror surface of a silicon wafer (adhesive strength before irradiation with active energy rays) (hereinafter sometimes referred to as "adhesive strength after storage") after storage for two days in an environment of 60°C is preferably 3000 mN / 25 mm or more, particularly 4000 mN / 25 mm or more, and even more preferably 5000 mN / 25 mm or more. Having an adhesive strength of 3000 mN / 25 mm or more after storage facilitates favorable fixation of the workpiece on the workpiece processing sheet 1. The upper limit of the adhesive strength after storage is not particularly limited, and may be 20,000 mN / 25 mm or less, particularly 10,000 mN / 25 mm or less, or even 8,000 mN / 25 mm or less. Details of the method for measuring the adhesive strength after storage are as described in the test examples below.

[0094] Furthermore, in the workpiece processing sheet 1 according to this embodiment, the ratio of the adhesive strength after storage to the adhesive strength before storage (hereinafter sometimes referred to as the "adhesive strength retention rate") is preferably 70 or more, particularly preferably 80 or more, and even more preferably 90 or more. As described above, the workpiece processing sheet 1 according to this embodiment has an antistatic agent in the surface layer 111 having the above-mentioned MFR, so that it exhibits good antistatic properties while achieving a high adhesive strength retention rate as described above. The upper limit of the adhesive strength retention rate is not particularly limited and may be, for example, 100 or less, particularly 95 or less.

[0095] 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 an adhesive layer 12 on a release sheet, and then laminating one side of the substrate 11 on the surface of the adhesive layer 12 opposite to the release sheet.

[0096] 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 dispersion medium is prepared. The coating liquid is then applied to the releasable surface of a release sheet (hereinafter sometimes referred to as the "release surface"). The resulting coating film is then dried to form the pressure-sensitive adhesive layer 12.

[0097] The coating liquid can be applied by a known method, such as bar coating, knife coating, roll coating, blade coating, die coating, or gravure coating. The properties of the coating liquid are not particularly limited as long as it allows application, and the liquid may contain 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.

[0098] 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 perform a heat treatment to promote 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 promote the above-mentioned crosslinking reaction sufficiently, after the adhesive layer 12 and the substrate 11 are bonded together, curing may be performed, for example, by leaving the adhesive layer 12 to stand in an environment of 23°C and a relative humidity of 50% for several days.

[0099] 4. How to use the workpiece processing sheet The workpiece processing sheet 1 according to this embodiment can be used for processing workpieces such as semiconductor wafers. 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, dicing sheet, expanding sheet, pickup sheet, etc. Examples of workpieces include semiconductor components such as semiconductor wafers and semiconductor packages, and glass components such as glass plates.

[0100] As described above, the workpiece processing sheet 1 according to this embodiment has excellent antistatic properties while suppressing changes in adhesive strength over time and the outflow of alkali metal ions. In particular, the workpiece processing sheet 1 according to this embodiment can effectively suppress the outflow of alkali metal ions into the cutting water used during dicing and the washing water after dicing. 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.

[0101] When the workpiece processing sheet 1 according to this embodiment has the adhesive layer described above, 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 protective film forming layer described above, the workpiece processing sheet 1 can be used as a protective film forming / dicing sheet.

[0102] Furthermore, when the adhesive layer 12 in the workpiece processing sheet 1 according to this embodiment is composed of the aforementioned active energy ray-curable adhesive, it is also preferable to irradiate the adhesive layer 12 with active energy rays during use. That is, when processing of a workpiece on the workpiece processing sheet 1 is completed 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, effectively reducing the adhesive strength of the adhesive sheet to the processed workpiece, and facilitating separation of the processed workpiece.

[0103] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0104] 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. [Example]

[0105] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0106] Example 1 (1) Preparation of the substrate 28 parts by mass of random polypropylene resin (manufactured by Japan Polypropylene Corporation, product name "Novatec FX3B"), 47 parts by mass of olefin-based thermoplastic elastomer (manufactured by Japan Polypropylene Corporation, product name "Wellnex RFX4V"), and 25 parts by mass of antistatic agent (manufactured by Sanyo Chemical Industry Co., Ltd., product name "Pelectron PVH", melt flow rate: 9.8 g / 10 min) were dried and then kneaded in a twin-screw kneader to obtain pellets for the surface layer.

[0107] In addition, 80 parts by mass of random polypropylene resin (manufactured by Japan Polypropylene Corporation, product name "Novatec FX3B") and 20 parts by mass of olefin-based thermoplastic elastomer (manufactured by Japan Polypropylene Corporation, product name "Wellnex RFX4V") were each dried and then kneaded in a twin-screw kneader to obtain pellets for the intermediate layer.

[0108] Furthermore, 70 parts by mass of an olefin-based thermoplastic elastomer (manufactured by Japan Polypropylene Corporation, product name "Wellnex RFX4V") and 30 parts by mass of an antistatic agent (manufactured by Sanyo Chemical Industry Co., Ltd., product name "Pelectron UC", melt flow rate: 14 g / 10 min) were each dried and then kneaded in a twin-screw kneader to obtain pellets for the back layer.

[0109] The three 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 2 μm thick surface layer, a 70 μm thick middle layer, and an 8 μm thick back layer laminated in that order.

[0110] The melt flow rate values of the antistatic agents described above were measured as described in Test Example 1 below.

[0111] (2) Preparation of adhesive composition A (meth)acrylic acid ester polymer was obtained by polymerizing 62 parts by weight of n-butyl acrylate, 10 parts by weight of methyl methacrylate, and 28 parts by weight of 2-hydroxyethyl acrylate by solution polymerization. Subsequently, 2-methacryloyloxyethyl isocyanate (MOI) was added in an amount equivalent to 80 mol% of the 2-hydroxyethyl acrylate constituting the (meth)acrylic acid ester polymer, and dibutyltin dilaurate (DBTDL) was added as a tin-containing catalyst in an amount of 0.025 parts by weight per 100 parts by weight of the (meth)acrylic acid ester polymer. The mixture was then allowed to react at 50°C for 24 hours to obtain a (meth)acrylic acid ester polymer with active energy ray-curable groups introduced into its side chains. The weight-average molecular weight of the active energy ray-curable polymer was measured using the method described below and found to be 500,000.

[0112] 100 parts by mass (solid content equivalent, same below) of the (meth)acrylic acid ester polymer obtained above, having active energy ray-curable groups introduced into the side chains, 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 5.71 parts 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.

[0113] (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"), which was made of a 38 μm thick polyethylene terephthalate film with a silicone-based release agent layer formed on one side, and dried at 90°C for 1 minute, using a comma coater to obtain a laminate in which a 5 μm thick adhesive layer was formed on the release sheet.

[0114] (4) Preparation of workpiece processing sheet After corona treatment was applied to the surface layer side of the substrate obtained in the above step (1), the corona treated surface was bonded to the adhesive layer side of the laminate obtained in the above step (3) to obtain a work processing sheet.

[0115] Here, the weight average molecular weight (Mw) is a weight average molecular weight measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement) and converted into standard polystyrene. <Measurement conditions> Measurement equipment: Tosoh HLC-8320 GPC columns (passed in the following order): Tosoh Corporation TSK gel superH-H TSK gel super HM-H TSK gel superH2000 Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0116] [Examples 2 to 6, Comparative Examples 1 to 3] A workpiece processing sheet was obtained 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.

[0117] Comparative Example 4 Ethylene-methacrylic acid copolymer (EMAA) (manufactured by DuPont-Mitsui Polychemicals, product name "Nucrel N0903HC") was extruded using a small T-die extruder (manufactured by Toyo Seiki Seisakusho, product name "Labo Plastomill") to obtain an 80 μm-thick EMAA film. A workpiece processing sheet was obtained in the same manner as in Example 1, except that the EMAA film was used as the substrate.

[0118] [Test Example 1] (Measurement of MFR of antistatic agent) The melt flow rate (MFR) (g / 10 min) of the antistatic agents used in the examples and comparative examples was measured according to ASTM D1238 (190°C, 21.18 N) using a flow tester (Shimadzu Corporation, product name "CFT-100D"). The results are shown in Table 2.

[0119] [Test Example 2] (Measurement of the amount of extracted ions from antistatic agents) A sample solution was prepared by mixing 1 g of the antistatic agent used in the Examples and Comparative Examples with 20 ml of pure water. The sample solution was placed in a Teflon (registered trademark) container for ion concentration measurement, sealed, and heated at 121°C for 24 hours to extract alkali metal ions. The concentrations (ppm) of lithium ions and sodium ions in the resulting extract were measured using an ion chromatograph (Thermo Fisher Scientific, product name "DIONEX ICS-2100"). The results are shown in Table 2.

[0120] [Test Example 3] (Measurement of extracted ions from the substrate alone and the sheet) A 1-gram sample was cut from each of the substrates prepared in the Examples and Comparative Examples and mixed with 20 ml of pure water to prepare a sample solution. The sample solution was placed in a Teflon (registered trademark) container for ion concentration measurement, sealed, and heated at 121°C for 24 hours to extract alkali metal ions. The concentrations (ppm) of lithium ions and sodium ions in the resulting extract were measured using an ion chromatograph (Thermo Fisher Scientific, product name "DIONEX ICS-2100"). The results are shown in Table 3. Table 3 also shows the total amount of these ions.

[0121] Furthermore, for the workpiece processing sheets produced in the examples and comparative examples, sample solutions were prepared in the same manner as above, and the concentrations (ppm) of lithium ions and sodium ions in the extracts were measured. The results are shown in Table 3. The total amount of these ions is also shown in Table 3. Note that the notation "ND" in the table means that the sodium ion concentration was less than 0.002 ppm and the lithium ion concentration was less than 0.0005 ppm.

[0122] [Test Example 4] (Measurement of adhesive strength) The workpiece processing sheets produced in the Examples and Comparative Examples were cut into 25 mm wide strips. The release sheet was peeled off from the resulting strips, and the exposed adhesive surface of the pressure-sensitive adhesive layer was attached to the mirror-finished surface of a silicon wafer using a 2 kg rubber roller at a temperature of 23°C and a relative humidity of 50%, and then left to stand for 20 minutes to prepare measurement samples.

[0123] Using a universal tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon UTM-4-100"), the workpiece processing sheet was peeled from the silicon wafer at a peeling speed of 300 mm / min and a peeling angle of 180°, and the adhesive strength (mN / 25 mm) to the silicon wafer was measured using the 180° peeling method in accordance with JIS Z0237: 2009. The adhesive strength obtained in this way is shown in Table 3 as the adhesive strength before storage.

[0124] Furthermore, measurement samples prepared in the same manner as above were stored in an environment at 60°C for 2 days. After this storage, the adhesive strength (mN / 25 mm) of the measurement samples was also measured in the same manner as above. The adhesive strength thus obtained is shown in Table 3 as the adhesive strength after storage at 60°C for 2 days.

[0125] Furthermore, the ratio of the adhesive strength after the storage to the adhesive strength before the storage was calculated, and this value is shown in Table 3 as the adhesive strength maintenance rate.

[0126] [Test Example 5] (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) at an applied voltage of 100 V. The results are shown in Table 3.

[0127] Test Example 6 (Evaluation of Antistatic Properties) Using a grinder (manufactured by Disco Corporation, product name "DFG8540"), one side of a 6-inch silicon wafer was ground to a thickness of 350 μm. Using a laminator, the release sheet was peeled off from the workpiece processing sheet produced in the Examples and Comparative Examples, and the exposed surface of the adhesive layer exposed was attached to the ground surface.

[0128] 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: 60 μm Blade: Product name "ZH05-SD2000-Z1-90 CC" Blade rotation speed: 35,000 rpm Cutting speed: 60mm / sec Cutting water amount: 1.0L / min Cutting water temperature: 20℃

[0129] After dicing, the workpiece processing sheet was fixed to the spinner table by suction, and the resulting chips were washed and dried as described above. The electrostatic charge (V) of the workpiece processing sheet immediately after lifting it from the spinner table was measured using a measuring device (Prostat, product name "PFK-100"). The antistatic properties were evaluated based on the following criteria. The electrostatic charge and evaluation results are shown in Table 3. ⊚: The charging voltage was 100V or less. ○: The charging voltage was more than 100V and 500V or less. ×: The charging voltage was more than 500V.

[0130] [Table 1]

[0131] [Table 2]

[0132] [Table 3]

[0133] As is clear from Table 3, the workpiece processing sheets produced in the examples have good antistatic properties, while also exhibiting a high adhesive strength retention rate and being able to keep the amount of alkali metal ion leakage low. [Industrial Applicability]

[0134] The workpiece processing sheet of the present invention can be suitably used for processing workpieces such as semiconductor wafers. [Explanation of symbols]

[0135] 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; each of the front surface layer and the back surface layer contains an antistatic agent; the antistatic agent is a polyether polyolefin block copolymer, the antistatic agent has an extractable amount of lithium ions in pure water of 0.0001 ppm or more and 50 ppm or less when a sample liquid obtained by mixing 1 g of the antistatic agent with 20 ml of pure water is heated at 121°C for 24 hours; the antistatic agent has an extractable amount of sodium ions in pure water of 0.0001 ppm or more and 150 ppm or less when a sample liquid obtained by mixing 1 g of the antistatic agent with 20 ml of pure water is heated at 121°C for 24 hours; all of the antistatic agents contained in the surface layer have a melt flow rate (MFR) of 13 g / 10 min or less, as measured in accordance with ASTM D1238 (190°C, 21.18 N); All of the antistatic agents contained in the backing layer have a melt flow rate (MFR) of 14 g / 10 min or more as measured in accordance with ASTM D1238 (190°C, 21.18 N). A workpiece processing sheet characterized by:

2. 2. The workpiece processing sheet according to claim 1, wherein the thickness of the surface layer is 0.5 μm or more and less than 8 μm.

3. 3. The workpiece processing sheet according to claim 1, which is a dicing sheet.

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