Sheet for workpiece processing

Abstract

To provide a workpiece processing sheet which is excellent in both pick-up property and antistatic property.SOLUTION: In a workpiece processing sheet 1 including a base material 11 and an adhesive layer 12, the base material 11 includes a front surface layer 111 located to be proximal to the adhesive layer 12, a back surface layer 113 located to be distal to the adhesive layer 12, and an intermediate layer 112 located between the front surface layer 111 and the back surface layer 113. The front surface layer 111 and the back surface layer 113 contain an antistatic agent. The tensile stress at a tensile elongation of 250% is 6.5 MPa or more and 10 MPa or less when a tensile test is performed on the base material 11 under an environment of a temperature of 23°C and a relative humidity of 50%RH.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a workpiece processing sheet used for processing workpieces such as semiconductor wafers.

Background Art

[0002] Semiconductor wafers such as silicon and gallium arsenide, and various packages are manufactured in a large-diameter state, cut (diced) into chips, peeled off (picked up), and then transferred to the next step, the mounting step. At this time, a workpiece such as a semiconductor wafer is laminated on an adhesive sheet having a base material and an adhesive layer (hereinafter sometimes referred to as a "workpiece processing sheet"), and processing such as back grinding, dicing, cleaning, drying, expanding, picking up, and mounting is performed.

[0003] For example, a semiconductor wafer that has completed back grinding is attached to a sheet, and dicing is performed on the sheet. By dicing, the semiconductor wafer is separated into a plurality of semiconductor chips. Thereafter, the plurality of semiconductor chips are individually picked up from the sheet.

[0004] As another method, after the above dicing, the plurality of semiconductor chips supported on the sheet are transferred to another sheet, and the plurality of semiconductor chips are individually picked up from the other sheet.

[0005] The pickup of semiconductor chips from the sheet as described above is performed using a device such as a die ejector. This device individually pushes up the semiconductor chips from the surface opposite to the surface of the sheet to which the semiconductor chips are attached, and separates them from the other semiconductor chips. By thus pushing up one semiconductor chip, it becomes easier to perform pickup by a collet. Also, at this time, if necessary, the sheet can be expanded to create a gap between the semiconductor chips, making it easier to push up and pick up.

[0006] As a pushing-up method, there is a method using one or more pins or needles. In this method, the tip of the pin or needle touches the sheet at a point and pushes up the semiconductor chip at a point. However, in recent years, the thinning of semiconductor chips has advanced, and also, due to the progress of using harder and more brittle materials as semiconductor materials, semiconductor chips have become more brittle. When handling such semiconductor chips, if the pushing-up amount of the pin or needle is large, the semiconductor chip may be damaged.

[0007] Patent Document 1 discloses a dicing film in which a base material includes a specific random polypropylene (A) and a specific olefin-based elastomer (B) in order to obtain excellent pick-up properties together with suitable expandability, and the 100% tensile stress of the olefin-based elastomer (B) is defined.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] By the way, when the work processing sheet is peeled off from the adherend after a predetermined processing step is completed, electrostatic electricity called peeling electrification may be generated between the work processing sheet and the adherend. Such electrostatic electricity causes dust and the like to adhere to the work or the device, and also causes the destruction of the work and the like. Therefore, the work processing sheet is also required to have antistatic properties.

[0010] Also, after the step of dicing a semiconductor wafer, generally, the obtained chips may be washed. Specifically, a work processing sheet on which a plurality of chips are placed is adsorbed and fixed to a spinner table, and on the work processing sheet, the chips are washed with ultrapure water and then dried (air-dried). After these processes are completed, the work processing sheet on which the plurality of chips are placed will be separated from the spinner table, but the inventors have confirmed that peeling electrification also occurs during this separation.

[0011] However, conventional work processing sheets such as those in Patent Document 1 do not correspond to antistatic properties, and problems such as the above-mentioned peeling electrification have occurred.

[0012] The present invention has been made in view of such a situation, and an object thereof is to provide a work processing sheet excellent in both pick-up property and antistatic property.

Means for Solving the Problems

[0013] In order to achieve the above object, first, the present invention is a work processing sheet including a base material and an adhesive layer laminated on one side of the base material, wherein the base material includes a surface layer located proximal to the adhesive layer, a back surface layer located distal to the adhesive layer, and an intermediate layer located between the surface layer and the back surface layer, the surface layer and the back surface layer contain an antistatic agent, and the tensile stress at a tensile elongation of 250% when a tensile test is performed on the base material in an environment of a temperature of 23°C and a relative humidity of 50%RH is 6.5 MPa or more and 10 MPa or less. A work processing sheet is provided (Invention 1).

[0014] In the above invention (Invention 1), since the surface layer and the back surface layer contain an antistatic agent, it has excellent antistatic properties. Further, since the surface layer contains an antistatic agent and the base material has the above-mentioned tensile physical properties, it is excellent in pick-up property when picking up chips from the work processing sheet.

[0015] In the above invention (Invention 1), it is preferable that each of the surface layer, the intermediate layer, and the back surface layer contains at least one of an olefin-based thermoplastic elastomer and a polyolefin-based resin (Invention 2).

[0016] In the above inventions (Inventions 1 and 2), it is preferable that the intermediate layer contains a styrene-based thermoplastic elastomer (Invention 3).

[0017] In the above inventions (Inventions 1 to 3), it is preferable that the intermediate layer does not contain an antistatic agent, or the intermediate layer contains an antistatic agent in a content (unit: mass%) less than that of each of the surface layer and the back surface layer (Invention 4).

[0018] In the above inventions (Inventions 1 to 4), it is preferable that the antistatic agent is a polymer-type antistatic agent (Invention 5).

[0019] In the above inventions (Inventions 1 to 5), the surface resistivity of the surface on the side opposite to the base material in the adhesive layer is preferably 1.0×10 13 Ω / square or less (Invention 6).

[0020] In the above inventions (Inventions 1 to 6), it is preferably a dicing sheet (Invention 7).

Advantages of the Invention

[0021] The sheet for workpiece processing according to the present invention is excellent in both pick-up property and antistatic property.

Brief Description of the Drawings

[0022]

Figure 1

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described. FIG. 1 shows a cross-sectional view of a sheet for workpiece processing according to an embodiment of the present invention. 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 base material 11 includes a surface layer 111 located proximal to the adhesive layer 12, a back surface layer 113 located distal to the adhesive layer 12, and an intermediate layer 112 located between the surface layer 111 and the back surface layer 113.

[0025] In the workpiece processing sheet 1 according to the present embodiment, the surface layer 111 and the back surface layer 113 contain an antistatic agent. When a tensile test is performed on the base material 11 in an environment of a temperature of 23°C and a relative humidity of 50%RH, the tensile stress at a tensile elongation of 250% is 6.5 MPa or more and 10 MPa or less. Hereinafter, the physical properties related to the tensile stress may be referred to as "tensile physical properties". The specific measurement method of the tensile test in this specification is as shown in the test examples described later.

[0026] In the workpiece processing sheet 1 according to the present embodiment, since the surface layer 111 and the back surface layer 113 contain an antistatic agent, it has excellent antistatic properties. Therefore, the peeling electrification when separating the peeling sheet or the workpiece from the workpiece processing sheet 1 can be suppressed well. Furthermore, after washing and drying the workpiece on the workpiece processing sheet 1, the peeling electrification when separating the workpiece processing sheet 1 from the spinner table can also be prevented well.

[0027] In addition, in the sheet 1 for workpiece processing according to the present embodiment, since the surface layer 111 contains an antistatic agent and the base material 11 has the above-described tensile physical properties, the pick-up property when picking up a chip from the sheet 1 for workpiece processing is excellent. Specifically, the amount of pushing up of the pin or needle used to push up the chip during pick-up can be suppressed to a small value. As a result, it is possible to effectively suppress damage such as breakage of the chip due to the pushing up. The reason why excellent pick-up property is obtained by the surface layer 111 containing an antistatic agent is not necessarily clear, but it is considered to exhibit an effect as some kind of additive. Further, the reason why excellent pick-up property is obtained by the base material 11 having the above-described tensile physical properties is considered to be that the base material 11 exhibits hardness and stretchability such that the contact area between the adhesive layer 12 and the chip becomes small due to pushing up.

[0028] From the viewpoint of obtaining excellent pick-up property, in the base material 11 in the present embodiment, the tensile stress at a tensile elongation of 250% by the above-described tensile test is 6.5 MPa or more, preferably 6.6 MPa or more, particularly preferably 6.7 MPa or more, and more preferably 6.8 MPa or more. Further, from the same viewpoint of obtaining excellent pick-up property, the tensile stress at a tensile elongation of 250% is 10 MPa or less, preferably 9.8 MPa or less, particularly preferably 9.4 MPa or less, and more preferably 9.0 MPa or less.

[0029] From the viewpoint of obtaining excellent pick-up property, in the base material 11 in the present embodiment, the tensile stress at a tensile elongation of 100% by the above-described tensile test is preferably 5.0 MPa or more, particularly preferably 5.2 MPa or more, and more preferably 5.4 MPa or more. Further, from the same viewpoint of obtaining excellent pick-up property, the tensile stress at a tensile elongation of 100% is preferably 7.8 MPa or less, particularly preferably 7.4 MPa or less, and more preferably 7.0 MPa or less.

[0030] 1. Configuration of the sheet for workpiece processing 1-1. Base material As described above, the base material 11 in the present embodiment includes a surface layer 111, an intermediate layer 112, and a back surface layer 113.

[0031] (1) Surface layer In the sheet 1 for workpiece processing according to the present embodiment, the surface layer 111 contains an antistatic agent. Thereby, excellent antistatic properties can be obtained, and the pick-up property is also excellent. As will be described later, the antistatic agent causes the generation of cutting pieces during dicing. However, 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 cutting pieces can be made considerably less than when the entire base material contains the antistatic agent.

[0032] The antistatic agent in the present embodiment is not particularly limited, and known ones can be used. Examples of the antistatic agent include low molecular weight antistatic agents and high molecular weight antistatic agents. From the viewpoint of obtaining excellent pick-up properties and from the viewpoint that bleed-out hardly occurs from the formed layer, high molecular weight antistatic agents are preferred.

[0033] Examples of the high molecular weight antistatic agent include copolymers having a polyether unit such as polyether ester amide and polyether polyolefin block copolymer. These copolymers may contain metal salts such as alkali metal salts and alkaline earth metal salts, and ionic liquids.

[0034] 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 more preferably 10% by mass or more. Thereby, the antistatic property and the pick-up property become more excellent. Also, the content is preferably 40% by mass or less, particularly preferably 35% by mass or less, and more preferably 30% by mass or less. Thereby, the generation of cutting pieces can be suppressed low.

[0035] As materials other than the antistatic agent that constitutes the surface layer 111, there is no particular limitation as long as the above-described tensile physical properties are satisfied. However, in order to satisfy the above-described tensile physical properties, it is preferable to contain at least one of an olefin-based thermoplastic elastomer (hereinafter, may be referred to as an "olefin-based elastomer") and a polyolefin-based resin. In particular, it is preferable to contain at least an olefin-based elastomer and, if desired, further contain a polyolefin-based resin. According to these components, it becomes easier to satisfy the above-described tensile physical properties, and the pick-up property becomes more excellent. The "olefin-based elastomer" is a copolymer containing a structural unit derived from an olefin or its derivative (olefin-based compound), has rubber-like elasticity in a temperature range including room temperature, and has thermoplasticity.

[0036] Examples of the olefin-based elastomer include those containing at least one resin selected from the group consisting of ethylene-propylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, butene-α-olefin copolymer, ethylene-propylene-α-olefin copolymer, ethylene-butene-α-olefin copolymer, propylene-butene-α-olefin copolymer, and ethylene-propylene-butene-α-olefin copolymer. Among these, an ethylene-propylene copolymer is preferable.

[0037] The content of the olefin-based elastomer in the surface layer 111 is preferably 3% by mass or more, particularly preferably 5% by mass or more, and more preferably 7% by mass or more. Also, the content is preferably 50% by mass or less, particularly preferably 47% by mass or less, and more preferably 45% 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-described tensile physical properties, and the pick-up property becomes more excellent.

[0038] The surface layer 111 contains a polyolefin resin and is excellent in terms of film-forming properties during film formation and suppression of chipping. In this specification, the polyolefin resin refers to a homopolymer or copolymer having olefin as a monomer, or a copolymer having olefin and a molecule other than olefin as monomers, and the mass ratio of the portion based on the olefin unit in the resin after polymerization is 1.0% by mass or more.

[0039] The polyolefin resin is not particularly limited as long as it does not inhibit the above-described tensile physical properties and a desired effect can be obtained. The polymer constituting the polyolefin resin may be linear or may have side chains. It may also have an aromatic ring or an aliphatic ring.

[0040] Examples of the olefin monomer constituting the polyolefin resin 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 the olefin monomer having 2 to 8 carbon atoms include ethylene, propylene, 2-butene, and octene. Examples of the α-olefin monomer 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 the olefin monomer having a cyclic structure include norbornene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, and tetracyclododecene and derivatives thereof.

[0041] The polyolefin resin can be used alone or in combination of two or more.

[0042] Among the specific examples of the above-described polyolefin resin, 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.

[0043] Examples of the polypropylene generally include homopolypropylene, random polypropylene, and block polypropylene. These can be used alone or in combination of two or more. In this embodiment, from the perspective of expandability, it is preferable to use random polypropylene.

[0044] When the polyolefin resin contains polyethylene, the polyethylene may be any of high-density polyethylene, medium-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, and linear low-density polyethylene, or a mixture of two or more of these.

[0045] From the viewpoints of film-forming property and chipping suppression, the content of the polyolefin resin in the surface layer 111 is preferably 10% by mass or more, particularly preferably 13% by mass or more, and even more preferably 16% by mass or more. Also, from the viewpoint of pick-up property, the content is preferably 36% by mass or less, particularly preferably 33% by mass or less, and even more preferably 30% by mass or less.

[0046] The surface layer 111 preferably also contains a thermoplastic elastomer other than an olefin-based elastomer, particularly a styrene-based thermoplastic elastomer (hereinafter sometimes referred to as "styrene-based elastomer"). The styrene-based elastomer is a copolymer containing a structural unit derived from styrene or its derivative (styrene-based compound), and has rubber-like elasticity in a temperature range including room temperature and also has thermoplasticity. By the surface layer 111 containing the styrene-based elastomer, the generation of cutting pieces during dicing is suppressed.

[0047] Examples of styrenic 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 copolymers, styrene-butadiene-styrene copolymers (SBS), styrene-butadiene-butylene-styrene copolymers, styrene-isoprene copolymers, styrene-isoprene-styrene copolymers (SIS), and styrene-ethylene-isoprene-styrene copolymers; hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene / propylene-styrene copolymers (SEPS: hydrogenated product of styrene-isoprene-styrene copolymers) and styrene-ethylene-butylene-styrene copolymers (SEBS: hydrogenated product of styrene-butadiene copolymers). The styrenic thermoplastic elastomer may be a hydrogenated product (hydrogenated material) or an unhydrogenated material, but a hydrogenated product is preferred. Among the above, from the viewpoints of the chip suppression effect and the ease of achieving the above-described tensile physical properties, hydrogenated styrene-conjugated diene copolymers are preferred, and particularly styrene-ethylene-butylene-styrene copolymers (SEBS) are preferred.

[0048] The content of the structural unit derived from styrene or a styrenic compound in the styrenic elastomer is preferably 5% by mass or more, particularly preferably 10% by mass or more, and even more preferably 15% by mass or more. Thereby, it becomes easier to achieve the above-described tensile physical properties, and the chip suppression effect becomes more excellent. Also, the content of the above structural unit is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0049] When the surface layer 111 contains a styrene-based elastomer, the content of the styrene-based elastomer in the surface layer 111 is preferably 1% by mass or more, particularly preferably 25% by mass or more, and even more preferably 30% by mass or more. Also, the content is preferably 45% by mass or less, particularly preferably 40% by mass or less, and even more preferably 35% by mass or less. When the content of the styrene-based elastomer in the surface layer 111 is within the above range, the above-described tensile physical properties are more easily satisfied.

[0050] The surface layer 111 preferably contains an acid-modified resin as a component other than those described above. In this specification, the "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 the acid-modified resin as described above, the adhesion between the base material 11 and the adhesive layer 12 is improved, and it is possible to suppress the adhesive from remaining on the chip side during pickup.

[0051] As the main chain of the acidic resin, for example, ethylene-acrylic copolymers such as ethylene-(meth)acrylic acid copolymer and ethylene-(meth)acrylate copolymer are preferably mentioned. According to such a resin, while improving the adhesion between the surface layer 111 and the adhesive layer 12, it is easy to satisfy the above-described tensile physical properties. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms.

[0052] As the above (meth)acrylate, (meth)acrylate alkyl esters having 1 to 4 carbon atoms in the alkyl group are preferable. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, etc. are preferably mentioned. Among them, ethyl (meth)acrylate is more preferable, and particularly ethyl acrylate is preferable.

[0053] In the ethylene-(meth)acrylate copolymer, the content of the structure derived from (meth)acrylate is preferably 1% by mass or more, particularly preferably 3% by mass or more. Also, the content is preferably 30% by mass or less, particularly preferably 25% by mass or less. When the content is within the above range, it becomes easier to satisfy the above-described tensile physical properties.

[0054] To acid-modify the resin, 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, norbornenedicarboxylic anhydride, tetrahydrophthalic anhydride, and the like. These can be used alone or in combination of two or more. Among these, maleic anhydride is particularly preferable from the viewpoint of adhesion to the adhesive layer 12.

[0055] The amount of the acid component (the amount of the structure derived from the acid component) in the above acid-modified resin is preferably 1% by mass or more, particularly preferably 2% by mass or more. Also, the amount of the acid component is preferably 7% by mass or less, particularly preferably 5% by mass or less. When the amount of the acid component is within the above range, the adhesion between the surface layer 111 and the adhesive layer 12 is further improved.

[0056] 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, particularly preferably 8% by mass or more, and more preferably 10% by mass or more. Thereby, the adhesion between the surface layer 111 and the adhesive layer 12 is further improved. Also, the content is preferably 35% by mass or less, particularly preferably 30% by mass or less, and more preferably 25% by mass or less. Thereby, it becomes easier to satisfy the above-described tensile physical properties.

[0057] The surface layer 111 may contain other components in addition to the above-described components, for example, components used for the base material of a general work processing sheet. Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. Although the content of these additives is not particularly limited, it is preferably within a range in which the surface layer 111 exhibits desired functions.

[0058] (2) Intermediate layer In the present embodiment, the material constituting the intermediate layer 112 is not particularly limited as long as the above-described tensile physical properties are satisfied. However, in order to satisfy the above-described tensile physical properties, it is preferable to contain at least one of an olefin-based elastomer and a polyolefin-based resin, more preferably to contain at least an olefin-based elastomer and optionally further contain a polyolefin-based resin, and particularly preferably to contain at least an olefin-based elastomer and optionally further contain a polyolefin-based resin and a styrene-based elastomer. According to these components, it becomes easier to satisfy the above-described tensile physical properties, and the pick-up property becomes more excellent. In particular, when the intermediate layer 112 contains a styrene-based elastomer, it becomes easier to achieve the above-described tensile physical properties, and the pick-up property becomes more excellent.

[0059] Preferred olefin-based elastomers, polyolefin-based resins, and styrene-based elastomers are the same as those exemplified in the surface layer 111, respectively.

[0060] The content of the olefin-based elastomer in the intermediate layer 112 is preferably 30% by mass or more, particularly preferably 35% by mass or more, and even more preferably 40% by mass or more. Also, the content is preferably 60% by mass or less, particularly 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, it becomes easier to achieve the above-described tensile physical properties, and the pick-up property becomes more excellent.

[0061] The content of the polyolefin resin in the intermediate layer 112 is preferably 15% by mass or more, particularly preferably 20% by mass or more, and even more preferably 25% by mass or more. Also, the content is preferably 45% by mass or less, particularly preferably 40% by mass or less, and even more preferably 35% by mass or less. When the content of the polyolefin resin in the intermediate layer 112 is within the above range, it becomes easier to achieve the above-described tensile physical properties, and the pick-up property becomes more excellent.

[0062] The content of the styrene-based elastomer in the intermediate layer 112 is preferably 10% by mass or more, particularly preferably 15% by mass or more, and even more preferably 20% by mass or more. Also, the content 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 styrene-based elastomer in the intermediate layer 112 is within the above range, it becomes easier to achieve the above-described tensile physical properties, and the pick-up property becomes more excellent.

[0063] Here, although the intermediate layer 112 may also contain an antistatic agent, from the viewpoint of being likely to suppress the generation of cutting pieces, 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%) less than that of the surface layer 111 and the back surface layer 113. Specifically, the content is preferably less than 5% by mass, more preferably less than 3% by mass, particularly preferably less than 1% by mass, and most preferably 0% by mass in the intermediate layer 112. When the intermediate layer 112 contains an antistatic agent, the lower limit value of the content is, for example, 0.01% by mass or more. The inventors have found that the antistatic agent causes the generation of cutting pieces during dicing. However, as described above, when the intermediate layer 112 that does not contain an antistatic agent or has a small content thereof exists under the surface layer 111 (preferably a thin layer), the generation of cutting pieces can be made considerably less than when the entire substrate contains an antistatic agent.

[0064] Similar to the surface layer 111, the intermediate layer 112 may contain other components other than the components described above, for example, components used for the base material of a general work processing sheet.

[0065] (3) Back surface layer In the present embodiment, the back surface layer 113 contains an antistatic agent. Thereby, excellent antistatic properties can be obtained. On the other hand, as described above, the antistatic agent causes the generation of cutting pieces during dicing. However, usually, the dicing blade does not reach the back surface layer 113. Therefore, even if the back surface layer 113 contains an antistatic agent, it does not cause the generation of cutting pieces.

[0066] As the antistatic agent in the back surface layer 113, the same one as the antistatic agent in the surface layer 111 can be used.

[0067] The content of the antistatic agent in the inner 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. Thereby, it becomes easy to exhibit good antistatic properties. Also, the content is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less. Thereby, it becomes easier to achieve the above-described tensile physical properties.

[0068] The material other than the antistatic agent constituting the inner layer 113 is not particularly limited as long as the above-described tensile physical properties are satisfied. However, in order to satisfy the above-described tensile physical properties, it is preferable to contain at least one of an olefin-based elastomer and a polyolefin-based resin. In particular, it is preferable to contain at least an olefin-based elastomer and, if desired, further contain a polyolefin-based resin. According to these components, it becomes easy to satisfy the above-described tensile physical properties, and the pick-up property becomes more excellent.

[0069] The preferable olefin-based elastomer and polyolefin-based resin are the same as those exemplified in the surface layer 111, respectively.

[0070] The content of the olefin-based elastomer in the inner layer 113 is preferably 30% by mass or more, particularly preferably 35% by mass or more, and even more preferably 40% by mass or more. Also, the content is preferably 85% by mass or less, particularly preferably 80% by mass or less, and even more preferably 75% by mass or less. When the content of the olefin-based elastomer in the inner layer 113 is within the above range, it becomes easier to achieve the above-described tensile physical properties.

[0071] When the back surface layer 113 contains a polyolefin resin, its content is preferably 10% by mass or more, particularly preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoints of film formability and chipping suppression. Also, from the viewpoint of pick-up property, the content is preferably 50% by mass or less, particularly preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0072] In addition, the back surface layer 113 preferably does not contain a styrene-based elastomer as a thermoplastic elastomer. If it contains a styrene-based elastomer, there is a possibility of causing blocking during film formation or affecting the pick-up property. Even if the back surface layer 113 contains a styrene-based elastomer, its content is preferably 2% by mass or less, particularly preferably 1% by mass or less.

[0073] The back surface layer 113 may contain other components other than the above-described components, for example, components used for the base material of a general work processing sheet, in the same manner as the surface layer 111 and the intermediate layer 112.

[0074] (4) Surface treatment of the base material On the surface of the base material 11 where the adhesive layer 12 is laminated, surface treatments such as primer treatment, corona treatment, plasma treatment, roughening treatment (mat processing), etc. may be performed in order to enhance the 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.

[0075] (5) Manufacturing method of the base material The manufacturing method of the base material 11 in the present embodiment is not particularly limited, and for example, melt extrusion methods such as a T-die method and a round die method; a calendar method; solution methods such as a dry method and a wet method can be used. Among these, from the viewpoint of efficiently manufacturing the base material, it is preferable to adopt a melt extrusion method, and particularly preferable to adopt a T-die method.

[0076] When the base material 11 is produced by the melt extrusion method, the components constituting each layer are kneaded respectively, and then, from the obtained kneaded product, directly or after once producing pellets, a plurality of layers may be simultaneously extruded (co-extruded) using a known extruder to form a film.

[0077] (6) Physical properties of the base material, etc. (6-1) Thickness In the present embodiment, the thickness of the surface layer 111 is preferably 10 μm or less, particularly preferably 8 μm or less, and even more preferably 4 μm or less. Thus, since the thickness of the surface layer 111 located proximal to the adhesive layer 12 is thin, generation of cutting pieces can be favorably suppressed while exhibiting desired antistatic properties.

[0078] Also, the thickness of the surface layer 111 is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 3 μm or more. Thereby, it becomes easier to favorably exhibit antistatic properties, and the pick-up property becomes more excellent. Further, when the surface layer 111 contains an acid-modified resin, the adhesion to the adhesive layer 12 becomes more excellent.

[0079] In the present 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. Thereby, it becomes easier to satisfy the above-described tensile physical properties, and the pick-up property becomes more excellent. Also, the work processing sheet 1 is likely to have appropriate strength, and it becomes easier to favorably support the work fixed on the work processing sheet 1. 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. Thereby, it becomes easier to satisfy the above-described tensile physical properties.

[0080] In this embodiment, the thickness of the back surface layer 113 is preferably 2 μm or more, particularly preferably 4 μm or more, and even more preferably 8 μm or more. Thereby, the antistatic property of the work processing sheet 1 becomes more excellent. Further, the thickness of the back surface layer 113 is preferably 40 μm or less, particularly preferably 30 μm or less, and even more preferably 25 μm or less. Thereby, it becomes easier to satisfy the above-described tensile physical properties.

[0081] In this embodiment, the thickness of the entire base material 11 is preferably 50 μm or more, particularly preferably 60 μm or more, and even more preferably 70 μm or more. Further, the thickness is preferably 140 μm or less, particularly preferably 120 μm or less, and even more preferably 100 μm or less. When the thickness of the entire base material 11 is within the above range, it becomes easier to satisfy the above-described tensile physical properties, and it also becomes easier to satisfactorily support the work fixed on the work processing sheet 1.

[0082] (6-2) Surface resistivity The surface resistivity of the surface on the surface layer 111 side of the base material 11 is preferably 1.0×10 13 Ω / square or less, particularly preferably 1.0×10 12 Ω / square or less, and even more preferably 1.0×10 11 Ω / square or less. Thereby, the work processing sheet 1 according to this embodiment can exhibit excellent antistatic property. Note that the lower limit value of the above surface resistivity is not particularly limited, and for example, it may be 1.0×10 8 Ω / square or more, particularly preferably 1.0×10 9 Ω / square or more. Details of the method for measuring the surface resistivity in this specification are as described in the test examples described later.

[0083] 1-2. Adhesive layer The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 12 in the present embodiment is not particularly limited as long as it can exhibit sufficient adhesive force to the adherend (particularly, the adhesive force to the work sufficient for processing the work). Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 12 include acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, polyvinyl ether-based pressure-sensitive adhesives, and the like. Among these, from the viewpoint of easily exhibiting a desired adhesive force, it is preferable to use an acrylic pressure-sensitive adhesive.

[0084] The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 12 in the present embodiment may be a pressure-sensitive adhesive having no active energy ray curability, but is preferably a pressure-sensitive adhesive having active energy ray curability (hereinafter sometimes referred to as "active energy ray curable pressure-sensitive adhesive"). Since the pressure-sensitive adhesive layer 12 is composed of an active energy ray curable pressure-sensitive adhesive, the pressure-sensitive adhesive layer 12 can be cured by irradiation with active energy rays, and the adhesive force of the work processing sheet 1 to the adherend can be easily reduced. In particular, by irradiation with active energy rays, the processed work can be easily separated from the work processing sheet 1.

[0085] The active energy ray curable pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 12 may be mainly composed of a polymer having active energy ray curability, or may be mainly composed of a mixture of an active energy ray non-curable polymer (a polymer having no active energy ray curability) and at least one monomer and / or oligomer having an active energy ray curable group. Further, the active energy ray curable pressure-sensitive adhesive may be a mixture of a polymer having active energy ray curability and at least one monomer and / or oligomer having an active energy ray curable group.

[0086] The polymer having the above-described active energy ray curability is preferably a (meth)acrylic acid ester polymer (hereinafter sometimes referred to as "active energy ray curable polymer") in which a functional group having active energy ray curability (active energy ray curable group) is introduced into the 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 that binds to the functional group. In the present specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Further, the concept of "copolymer" is also included in "polymer".

[0087] The above-described acrylic polymer having a functional group-containing monomer unit may be obtained by polymerizing other monomers together with the functional group-containing monomer. As such a functional group-containing monomer and other monomers, as well as the above-described unsaturated group-containing compound, known ones can be used, for example, those disclosed in International Publication No. 2018 / 084021 can be used.

[0088] The weight average molecular weight of the above-described active energy ray curable polymer is preferably 10,000 or more, particularly preferably 150,000 or more, and more preferably 200,000 or more. Further, 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 the present specification is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC method).

[0089] As the above-described active energy ray non-curable polymer component, for example, the above-described acrylic polymer before reacting with the unsaturated group-containing compound can be used.

[0090] The weight average molecular weight of the acrylic polymer as the active energy ray non-curable polymer component is preferably 10,000 or more, particularly preferably 150,000 or more, and even more preferably 200,000 or more. Also, the weight average molecular weight is preferably 1,500,000 or less, particularly preferably 1,000,000 or less.

[0091] In addition, as the monomer and / or oligomer having at least one or more active energy ray curable groups described above, for example, esters of polyhydric alcohols and (meth)acrylic acid can be used.

[0092] When ultraviolet rays are used as the active energy rays for curing the active energy ray curable pressure-sensitive adhesive, it is preferable to add a photopolymerization initiator to the pressure-sensitive adhesive. Further, an active energy ray non-curable polymer component or oligomer component, a crosslinking agent, etc. may be added to the pressure-sensitive adhesive.

[0093] The thickness of the pressure-sensitive adhesive layer 12 in the present embodiment is preferably 1 μm or more, particularly preferably 3 μm or more, and even more preferably 5 μm or more. Also, the thickness of the pressure-sensitive adhesive layer 12 is preferably 70 μm or less, particularly preferably 30 μm or less, and even more preferably 15 μm or less. When the thickness of the pressure-sensitive adhesive layer 12 is within the above-described range, the work processing sheet 1 according to the present embodiment is likely to exhibit a desired adhesiveness.

[0094] 1-3. Release Sheet In the work processing sheet 1 according to the present embodiment, a release sheet may be laminated on the surface of the pressure-sensitive adhesive layer 12 on the side opposite to the base material 11 (hereinafter sometimes referred to as the "adhesive surface") for the purpose of protecting the surface until it is attached to the work.

[0095] The configuration of the release sheet is arbitrary, and examples thereof include a plastic film subjected to a release treatment with 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. As the release agent, silicone-based, fluorine-based, long-chain alkyl-based, etc. can be used, and among these, silicone-based which can obtain inexpensive and stable performance is preferable.

[0096] There is no particular limitation on the thickness of the release sheet, and for example, it may be 16 μm or more and 250 μm or less.

[0097] 1-4. Others 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 base material 11. In this case, the workpiece processing sheet 1 according to this embodiment can be used as a dicing / die bonding sheet. In the 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, whereby chips with the fragmented adhesive layers laminated thereon can be obtained. The chips can be easily fixed to the object on which the chips are mounted by the fragmented adhesive layers. As the material constituting the above-described adhesive layer, it is preferable to use those containing a thermoplastic resin and a low molecular weight thermosetting adhesive component, those containing a B-stage (semi-cured state) thermosetting adhesive component, and the like.

[0098] In addition, in the work processing sheet 1 according to the present embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer 12. In this case, the work processing sheet 1 according to the present embodiment can be used as a sheet for forming a protective film and dicing. In such a sheet, a work 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 work, whereby chips with the fragmented protective film forming layers laminated thereon can be obtained. As the work, it is preferable to use one having a circuit formed on one side. In this case, usually, the protective film forming layer is laminated on the surface opposite to the surface on which the circuit is formed. The fragmented 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.

[0099] 2. Physical properties of the work processing sheet In the work processing sheet 1 according to the present embodiment, the surface resistivity of the surface (adhesive surface) on the side opposite to the base material 11 in the adhesive layer 12 is 1.0×10 13 Ω / square or less, preferably 1.0×10 12 Ω / square or less, more preferably 1.0×10 11 Ω / square or less. Thereby, it can be said that the work processing sheet 1 according to the present embodiment has excellent antistatic properties. Note that the lower limit value of the surface resistivity is not particularly limited. For example, it may be 1.0×10 8 Ω / square or more, particularly 1.0×10 9 Ω / square or more. When the adhesive layer 12 is curable by active energy rays, the surface resistivity is the value after irradiating the adhesive layer 12 with active energy rays to cure the adhesive layer 12.

[0100] 3. Manufacturing method of the work processing sheet The manufacturing method of the sheet 1 for workpiece processing according to this embodiment is not particularly limited. For example, after forming the adhesive layer 12 on the release sheet, it is preferable to obtain the sheet 1 for workpiece processing by laminating the surface of the base material 11 on the surface layer 111 side on the surface of the adhesive layer 12 opposite to the release sheet.

[0101] The formation of the above-described adhesive layer 12 can be performed by a known method. For example, an adhesive composition for forming the adhesive layer 12 and, if desired, a coating solution further containing a solvent or a dispersion medium are prepared. Then, the above coating solution is applied to the surface of the release sheet having releasability (hereinafter sometimes referred to as the "release surface"). Subsequently, the obtained coating film can be dried to form the adhesive layer 12.

[0102] The application of the above-described coating solution can be performed by a known method, for example, by a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like. Note that the properties of the coating solution are not particularly limited as long as it can be applied, and it may contain the components for forming the adhesive layer 12 as a solute or as a dispersed substance. Further, the release sheet may be peeled off as a process material, or may protect the adhesive layer 12 until it is attached to the adherend.

[0103] When the adhesive composition for forming the adhesive layer 12 contains the above-described crosslinking agent, by changing the above drying conditions (temperature, time, etc.) or by providing a separate heat treatment, the crosslinking reaction between the polymer component in the coating film and the crosslinking agent is advanced, and it is preferable to form a crosslinked structure at a desired density of existence in the adhesive layer 12. Further, in order to sufficiently advance the above-described crosslinking reaction, after laminating the adhesive layer 12 and the base material 11, curing may be performed, for example, by leaving it standing in an environment of 23°C and a relative humidity of 50% for several days.

[0104] 4. Method of using the sheet for workpiece processing The work processing sheet 1 according to this embodiment can be used for processing works such as semiconductor wafers. That is, after attaching the adhesive surface of the work processing sheet 1 according to this embodiment to the work, the work can be processed on the work processing sheet 1. Depending on the processing, the work processing sheet 1 according to this embodiment will be used as a back grind sheet, a dicing sheet, an expand sheet, a pickup sheet, or the like. Here, examples of the work include semiconductor members such as semiconductor wafers and semiconductor packages, and glass members such as glass plates.

[0105] As described above, since the work processing sheet 1 according to this embodiment is excellent in pick-up property, it is preferably a sheet used in a process including at least a pick-up process. For example, it may be a dicing sheet used from dicing to pick-up, or a transfer sheet to which chips obtained by dicing are transferred and used for pick-up.

[0106] Also, as described above, the work processing sheet 1 according to this embodiment can preferably suppress the generation of cutting pieces during dicing by appropriately selecting the materials and thicknesses of the surface layer 111 and the intermediate layer 112. In this case, the work processing sheet 1 according to this embodiment is particularly suitable for use as a dicing sheet among the above-described work processing sheets.

[0107] Furthermore, as described above, the work processing sheet 1 according to this embodiment has excellent antistatic properties. The work processing sheet 1 according to this embodiment can suppress peeling charge when separating the release sheet or separating the work. Furthermore, the work processing sheet 1 according to this embodiment can also effectively suppress peeling charge when pulling the work processing sheet from the spinner table after cleaning and drying the chips while the work processing sheet is fixed to the spinner table. Therefore, the work processing sheet 1 according to this embodiment can also be suitably used for such cleaning and drying.

[0108] In addition, when the workpiece processing sheet 1 according to the present embodiment includes the adhesive layer described above, the workpiece processing sheet 1 can be used as a dicing and die bonding sheet. Further, when the workpiece processing sheet 1 according to the present embodiment includes the protective film forming layer described above, the workpiece processing sheet 1 can be used as a sheet for forming a protective film and dicing.

[0109] Also, when the adhesive layer 12 in the workpiece processing sheet 1 according to the present embodiment is composed of the above-described active energy ray curable adhesive, it is also preferable to irradiate the following 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 (chip) is separated (picked up) from the workpiece processing sheet 1, it is preferable to irradiate the adhesive layer 12 with active energy rays before the separation. Thereby, the adhesive layer 12 is cured, the adhesive force of the adhesive sheet to the processed workpiece is favorably reduced, and the separation of the processed workpiece becomes easy.

[0110] The embodiments described above are described to facilitate the understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0111] For example, another layer may be laminated between the base material 11 and the adhesive layer 12 in the workpiece processing sheet 1 according to the present embodiment, or on the surface of the base material 11 on the side opposite to the adhesive layer 12. Further, other layers may be laminated on the surface of the surface layer 111 opposite to the intermediate layer 112, between the surface layer 111 and the intermediate layer 112, between the intermediate layer 112 and the back surface layer 113, and on the surface of the back surface layer 113 opposite to the intermediate layer 112, respectively.

Example

[0112] Hereinafter, the present invention will be described more specifically by way of examples and the like, but the scope of the present invention is not limited to these examples and the like.

[0113] 〔Example 1〕 (1) Preparation of base material 28 parts by mass of random polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec FX3B"), 42 parts by mass of olefin-based elastomer (manufactured by Nippon Polypropylene Co., Ltd., product name "Wellnex RFX4V"), and 30 parts by mass of polymer-type antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Perektron PVL") were each dried and then kneaded in a twin-screw kneader to obtain pellets for the surface layer and the back layer.

[0114] Also, 30 parts by mass of random polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., product name "Novatec FX3B"), 45 parts by mass of olefin-based elastomer (manufactured by Nippon Polypropylene Co., Ltd., product name "Wellnex RFX4V"), and 25 parts by mass of styrene-ethylene / ethylene·propylene-styrene block copolymer (SEEPS) as a styrene-based elastomer (manufactured by Kuraray Co., Ltd., "Hybrar 7311F", styrene ratio: 12% by mass) were each dried and then kneaded in a twin-screw kneader to obtain pellets for the intermediate layer.

[0115] Using the two types of pellets obtained as described above, coextrusion molding was performed with a small T-die extruder (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "Laboplastmill") to obtain a base material having a three-layer structure in which a surface layer with a thickness of 4 μm, an intermediate layer with a thickness of 72 μm, and a back layer with a thickness of 4 μm were laminated in that order.

[0116] (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)acrylate polymer. Subsequently, 2-methacryloyloxyethyl isocyanate (MOI) in an amount corresponding to 80 mol% with respect to 2-hydroxyethyl acrylate constituting the (meth)acrylate polymer was added, and dibutyltin dilaurate (DBTDL) as a tin-containing catalyst was added in an amount of 0.13 parts by mass with respect to 100 parts by mass of the (meth)acrylate polymer. Thereafter, by reacting at 50 °C for 24 hours, a (meth)acrylate polymer having an active energy ray curable group introduced into the side chain was obtained. When the weight average molecular weight of the active energy ray curable polymer was measured by the method described later, it was 500,000.

[0117] 100 parts by mass (in terms of solid content, the same hereinafter) of the (meth)acrylate polymer having an active energy ray curable group introduced into the side chain obtained above, 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 "Irgacure 127") as a photoinitiator, and 1 part by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate L") as a crosslinking agent were mixed in a solvent to obtain a coating solution of the pressure-sensitive adhesive composition.

[0118] (3) Formation of the pressure-sensitive adhesive layer The coating solution of the pressure-sensitive adhesive composition obtained in the above step (2) was applied to the release surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") having a silicone-based release agent layer formed on one side of a polyethylene terephthalate film with a thickness of 38 μm, and dried by heating to obtain a laminate having a pressure-sensitive adhesive layer with a thickness of 5 μm formed on the release sheet.

[0119] (4) Production of the pressure-sensitive adhesive sheet The surface layer side of the substrate obtained in the above step (1) was subjected to corona treatment and bonded to the adhesive layer side of the laminate obtained in the above step (3) to obtain a sheet for workpiece processing.

[0120] Here, the weight average molecular weight (Mw) described above is the weight average molecular weight in terms of standard polystyrene measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC). <Measurement conditions> · Measuring device: HLC-8320 manufactured by Tosoh Corporation · GPC column (passing in the following order): manufactured by Tosoh Corporation TSK gel superH-H TSK gel superHM-H TSK gel superH2000 · Measuring solvent: Tetrahydrofuran · Measuring temperature: 40 °C

[0121] 〔Examples 2 to 5, Comparative Example 1〕 A sheet for workpiece processing was produced in the same manner as in Example 1, except that the composition of the pellets for forming each layer of the substrate and the thickness of each layer were changed as shown in Table 1.

[0122] In Examples 2 to 5, an adduct of maleic anhydride of ethylene-ethyl acrylate copolymer (manufactured by SK Functional polymer, product name "BONDINE LX4110", ethyl acrylate content: 5% by mass, acid component amount: 3% by mass) as an acid-modified resin was further blended in the surface layer.

[0123] In addition, in Example 3, 32 parts by mass of a styrene-ethylene-butylene-styrene copolymer (SEBS) (manufactured by Asahi Kasei Corporation, product name "Tuftec H1062", styrene ratio: 18% by mass) as a styrene-based elastomer was further blended in the surface layer.

[0124] Furthermore, in Examples 2 and 3, as the styrenic elastomer of the intermediate layer, a styrene-ethylene-butylene-styrene copolymer (SEBS) (manufactured by Asahi Kasei Corporation, product name "Tuftec H1062", styrene ratio: 18% by mass) was used. In Example 4, as the styrenic elastomer of the intermediate layer, a styrene-ethylene-butylene-styrene copolymer (SEBS) (manufactured by Asahi Kasei Corporation, product name "Tuftec H1041", styrene ratio: 30% by mass) was used. In Example 5, as the styrenic elastomer of the intermediate layer, a styrene-ethylene-butylene-styrene copolymer (SEBS) (manufactured by Asahi Kasei Corporation, product name "Tuftec H1517", styrene ratio: 43% by mass) was used.

[0125] 〔Comparative Example 2〕 Using the same apparatus as in Example 1, a film (thickness: 80 μm) made of a single-layer ethylene-methacrylic acid copolymer (manufactured by Mitsui Dow Chemical Co., Ltd., product name "Nuclel N0903HC") was produced. The film obtained was used as a base material after irradiating the surface on the adhesive layer lamination side with an electron beam of 10 kGy for 2.2 seconds once. Using this base material, a work processing sheet was manufactured in the same manner as in Example 1.

[0126] 〔Comparative Example 3〕 Using the same apparatus as in Example 1, a film (thickness: 80 μm) made of a single-layer ethylene-methacrylic acid copolymer (manufactured by Mitsui Dow Chemical Co., Ltd., product name "Nuclel N0903HC") was produced. The film obtained was used as a base material after irradiating the surface on the adhesive layer lamination side with an electron beam of 10 kGy for 2.2 seconds twice. Using this base material, a work processing sheet was manufactured in the same manner as in Example 1.

[0127] 〔Test Example 1〕(Tensile Test) The base materials produced in the examples and comparative examples were cut into test pieces measuring 10 mm × 140 mm, and the tensile elastic modulus at a temperature of 23°C and a relative humidity of 50% RH was measured in accordance with JIS K7161:2014. Specifically, the above test pieces were set at a chuck distance of 100 mm using a tensile testing machine (manufactured by Orientec, product name "Tensilon RTA-T-2M"), and then a tensile test was performed at a speed of 200 mm / min, and the tensile stress (MPa) at a tensile elongation of 100% and 250% was measured. The measurement was carried out in the extrusion direction (MD direction) during the molding of the base material. The results are shown in Table 2.

[0128] 〔Test Example 2〕(Evaluation of Pick-up Property) A silicon wafer (inline) immediately after grinding to 150 μm with #2000 using a grinder (manufactured by DISCO, product name "DFG8540"), and a silicon wafer 7 days after grinding (7 days later) were prepared.

[0129] After peeling off the release sheet from the work processing sheets produced in the examples and comparative examples, the exposed surface of the exposed adhesive layer was attached to the ground surface of the above silicon wafer using a tape mounter (manufactured by Lintec, product name "Adwill RAD2500m / 12"). Subsequently, a dicing ring frame was attached to the peripheral edge of the exposed surface in the work processing sheet (a position that does not overlap with the silicon wafer). Further, the work processing sheet was cut according to the outer diameter of the ring frame.

[0130] Next, using a dicing device (manufactured by DISCO, product name "DFD6362"), dicing was performed under the following dicing conditions to individualize the silicon wafer into chips with a size of 10 mm × 10 mm. <Dicing Conditions> Wafer thickness: 150 μm Blade: Manufactured by DISCO, product name "ZH05-SD2000-N1-50CC" Blade rotation speed: 30000 rpm Cutting speed: 60 mm / sec Blade height: 0.060 mm Cutting water volume: 1.0 L / min Cutting water temperature: 20°C

[0131] After dicing, in a nitrogen atmosphere, ultraviolet rays (UV) were irradiated onto the adhesive layer of the workpiece processing sheet through the substrate using an ultraviolet irradiation device (manufactured by Rintec Co., Ltd., product name "RAD-2000m / 12") (illuminance: 230 mW / cm 2 , light quantity: 190 mJ / cm 2 ), and the adhesive layer was cured.

[0132] Next, a chip was picked up from the workpiece processing sheet using a pickup device (manufactured by Canon Machinery Co., Ltd., product name "BESTEM D02") under the following pickup conditions. <Pickup conditions> · Pickup method: 4 pins · Pickup speed: 20 mm / s · Pin pushing-up amount: 150 - 450 μm

[0133] The results of the pin pushing-up amounts required for chip pickup are shown in Table 2 for the cases of in-line silicon wafers and silicon wafers 7 days after grinding, respectively. Then, the larger value of the pushing-up amount between the in-line result and the 7-day result was adopted, and the pickup property was evaluated based on the following criteria. The evaluation results are shown in Table 2. ◎: Pushing-up amount less than 200 μm 〇: Pushing-up amount of 200 μm or more and less than 250 μm ×: Pushing-up amount of 250 μm or more

[0134] 〔Test Example 3〕(Measurement of surface resistivity) After conditioning the substrates manufactured in the examples and comparative examples at 23°C and 50% relative humidity for 24 hours, the surface resistivity of the surface layer side was measured at an applied voltage of 100 V using a DIGITAL ELECTROMETER (manufactured by Advantest Corporation). The results are shown in Table 2.

[0135] Also, the work processing sheets manufactured in the examples and comparative examples were cut into 100 mm × 100 mm, and these were used as samples for measuring the surface resistivity. With respect to the adhesive layer in the sample for measuring the surface resistivity, ultraviolet rays (UV) were irradiated through the substrate using an ultraviolet irradiation device (manufactured by Rintec Co., Ltd., product name "RAD-2000") (illuminance: 230 mW / cm 2 , light quantity: 190 mJ / cm 2 ) to cure the adhesive layer. After conditioning the sample for measuring the surface resistivity after the UV irradiation at 23°C and 50% relative humidity for 24 hours, the release sheet was peeled off, and the surface resistivity of the surface (adhesive surface) on the exposed adhesive layer side was measured in the same manner as above. These results are also shown in Table 2.

[0136] 〔Test Example 4〕(Evaluation of Antistatic Property) Using a grinder (manufactured by DISCO Corporation, product name "DFG8540"), one side of a 6-inch silicon wafer was ground until it reached a thickness of 350 μm. With respect to the ground surface, using a laminator, the exposed surface of the adhesive layer exposed by peeling off the release sheet from the work processing sheets manufactured in the examples and comparative examples was pasted.

[0137] Twenty minutes after pasting, dicing was performed in the same manner as in Test Example 2 to individualize the silicon wafer into chips. After dicing, with the work processing sheet fixed by adsorption on a spinner table, the chips obtained as described above were washed and dried. Then, immediately after lifting the work processing sheet from the spinner table, the charging voltage (V) of the work processing sheet was measured using a measuring instrument (manufactured by Prostat Co., Ltd., product name "PFK-100"). And based on the following criteria, the antistatic property was evaluated. The charging voltage and the evaluation results are shown in Table 2. ○: Charging voltage is 300 V or less ×: Charging voltage exceeds 300 V

[0138]

Table 1

[0139]

Table 2

[0140] As is clear from Table 2, the sheet for workpiece processing produced in the examples was excellent in both pick-up property and antistatic property.

Industrial Applicability

[0141] The sheet for workpiece processing of the present invention can be suitably used for processing workpieces such as semiconductor wafers.

Explanation of Signs

[0142] 1... Sheet for workpiece processing 11... Base material 111... Surface layer 112... Intermediate layer 113... Back layer 12... Adhesive layer

Claims

1. A sheet for workpiece processing, comprising a base material and an adhesive layer laminated on one side of the base material, wherein the base material includes a surface layer positioned proximal to the adhesive layer, a back surface layer positioned distal to the adhesive layer, and an intermediate layer positioned between the surface layer and the back surface layer, the surface layer and the back surface layer contain an antistatic agent, and the tensile stress at a tensile elongation of 250% when a tensile test is performed on the base material in an environment of a temperature of 23°C and a relative humidity of 50% RH is 6.5 MPa or more and 10 MPa or less. A sheet for workpiece processing, characterized by the above.

2. The sheet for workpiece processing according to claim 1, characterized in that each of the surface layer, the intermediate layer, and the back surface layer contains at least one of an olefin-based thermoplastic elastomer and a polyolefin-based resin.

3. The sheet for workpiece processing according to claim 1 or 2, characterized in that the intermediate layer contains a styrene-based thermoplastic elastomer.

4. The intermediate layer either does not contain an antistatic agent, or the intermediate layer contains an antistatic agent in a content (unit: mass%) less than that of each of the surface layer and the back surface layer. The sheet for workpiece processing according to any one of claims 1 to 3, characterized by the above.

5. The sheet for workpiece processing according to any one of claims 1 to 4, characterized in that the antistatic agent is a polymer-type antistatic agent.

6. The surface resistivity of the surface on the side opposite to the base material in the adhesive layer is 1.0×10 １３ Ω / square or less, and the sheet for work processing according to any one of claims 1 to 5, characterized in that.

7. The sheet for workpiece processing according to any one of claims 1 to 6, characterized in that it is a dicing sheet.

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