CN114901768A

CN114901768A - Adhesive sheet

Info

Publication number: CN114901768A
Application number: CN202180007738.9A
Authority: CN
Inventors: 佐佐木辽; 田矢直纪
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2020-03-30
Filing date: 2021-03-26
Publication date: 2022-08-12
Also published as: KR20220156515A; TW202142656A; WO2021200615A1; JPWO2021200615A1

Abstract

The present invention provides an adhesive sheet comprising a base material and an adhesive layer laminated on one surface side of the base material, wherein the base material is formed from a material containing a polyester resin having an alicyclic structure, and the heat of fusion measured by differential scanning calorimetry at a temperature rise rate of 20 ℃/min is 2J/g or more. The adhesive sheet can be produced at a reduced production cost, and the generation of cutting chips can be further reduced.

Description

Adhesive sheet

Technical Field

The present invention relates to an adhesive sheet which can be suitably used as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer.

Background

Semiconductor wafers such as silicon and gallium arsenide, and various packages (packages) are manufactured in a large-diameter state, cut (diced) into chips, and then peeled (picked up), and then transferred to a mounting (mount) step which is a next step. In this case, a work such as a semiconductor wafer is subjected to processing such as back grinding, dicing, cleaning, drying, spreading, picking up, and mounting in a state of being attached to an adhesive sheet (hereinafter, sometimes referred to as a "work processing sheet") provided with a base material and an adhesive layer.

As one of the cutting methods, there is a method of cutting a workpiece with a rotating circular blade (cutting blade). In this method, in order to ensure that the workpiece is cut, the workpiece processing sheet attached to the workpiece is also partially cut together with the workpiece.

When the workpiece-processing sheet is cut together with the workpiece in this manner, chips formed of the materials constituting the adhesive layer and the base material may be generated from the workpiece-processing sheet. In particular, such chips are often generated in the vicinity of a path (a saw lane) through which a circular blade passes in a chip or a workpiece processing sheet obtained by cutting.

If the chip is sealed in a state where a large amount of chips are attached to the chip, the chips attached to the chip are decomposed by the heat energy of the sealing, and the thermal decomposition product may damage the package or cause the operation failure of the obtained device. Since it is difficult to remove the chips by cleaning, the yield of the cutting process is significantly reduced by the generation of chips. Therefore, in the case of cutting with a rotating circular blade, it is necessary to prevent the generation of cutting chips.

In order to suppress the generation of such cutting chips, patent document 1 discloses an invention using a polyolefin film irradiated with an electron beam or Gamma ray of 1 to 80Mrad as a base film of a dicing sheet. In this invention, it is considered that the crosslinking by covalent bonds is formed in the resin constituting the base film by irradiation with electron beams or γ rays, and the generation of cutting chips is suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 5-211234

Disclosure of Invention

Technical problem to be solved by the invention

However, in the invention of patent document 1, since irradiation with radiation such as electron beams or γ rays is performed after the resin is molded into a film shape as described above, one manufacturing process is increased, and the manufacturing cost tends to be higher than that of a general base film.

The present invention has been made in view of such circumstances, and an object thereof is to provide an adhesive sheet which can be manufactured at a reduced manufacturing cost and in which the generation of cutting chips can be further reduced.

Means for solving the problems

In order to achieve the above object, the first aspect of the present invention provides an adhesive sheet comprising a base and an adhesive layer laminated on one surface side of the base, wherein the base is formed from a material containing a polyester resin having an alicyclic structure and having a heat of fusion of 2J/g or more as measured by differential scanning calorimetry at a temperature rise rate of 20 ℃/min (invention 1).

Since the base material of the adhesive sheet of the above invention (invention 1) is formed of a material containing a polyester resin having an alicyclic structure while exhibiting the above heat of fusion, the generation of cutting chips can be favorably suppressed even in the case of use for cutting with a rotating circular blade.

In the above invention (invention 1), it is preferable that the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin (invention 2).

In the above inventions (inventions 1 and 2), it is preferable that the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin (invention 3).

In the above inventions (inventions 1 to 3), the number of carbon atoms constituting a ring of the alicyclic structure is preferably 6 or more and 14 or less (invention 4).

In the above inventions (inventions 1 to 4), it is preferable that the polyester resin contains, as a monomer unit constituting the polyester resin, a dimer acid obtained by dimerizing an unsaturated fatty acid having 10 or more and 30 or less carbon atoms (invention 5).

In the above invention (invention 5), the ratio of the dimer acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less with respect to all dicarboxylic acids as a monomer unit constituting the polyester resin (invention 6).

In the above inventions (inventions 1 to 6), it is preferable that the tensile modulus of the base material at 23 ℃ is 100MPa or more and 800MPa or less (invention 7).

In the above inventions (inventions 1 to 7), the substrate preferably has an elongation at break at 23 ℃ of 200% or more and 800% or less (invention 8).

In the above inventions (inventions 1 to 8), the thickness of the base material is preferably 20 μm or more and 600 μm or less (invention 9).

In the above inventions (inventions 1 to 9), the adhesive layer is preferably made of an acrylic adhesive (invention 10).

In the above inventions (inventions 1 to 10), the pressure-sensitive adhesive sheet is preferably used as a sheet for processing a workpiece (invention 11).

In the above invention (invention 11), the work processing sheet is preferably a dicing sheet (invention 12).

Effects of the invention

The adhesive sheet of the present invention can be produced at a reduced production cost, and the generation of cutting chips can be further reduced.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

The adhesive sheet of the present embodiment includes a substrate and an adhesive layer laminated on one surface of the substrate. The adhesive sheet can be used for various purposes as in a general adhesive sheet, but is particularly suitable as a sheet for processing a workpiece such as a semiconductor wafer, and is particularly suitable as a dicing sheet for dicing the workpiece.

1. Structure of adhesive sheet

(1) Base material

The base material of the present embodiment is formed of a material containing a polyester resin. The polyester resin has an alicyclic structure and has a heat of fusion of 2J/g or more as measured by differential scanning calorimetry at a temperature rise rate of 20 ℃/min. Since the base material is formed of a material containing a polyester resin having an alicyclic structure and exhibiting the above-described heat of fusion, the adhesive sheet of the present embodiment can favorably suppress the generation of cutting chips when used for cutting a workpiece using a rotating circular blade.

The reason why such a chip-suppressing effect can be obtained is presumed as follows. However, the following reasons are not excluded from the possibility of obtaining the above-described effects in cooperation with other reasons, and the possibility of obtaining the above-described effects for reasons other than the following reasons is also excluded.

First, it is presumed that when a cutting force is applied to a substrate made of the polyester resin, the polyester resin is easily cut at the position of an ester bond. Further, as described above, since the polyester resin of the present embodiment has an alicyclic structure and exhibits the above-described heat of fusion, a part of the polymer chain thereof has a properly regular folded structure (lamellar structure). Therefore, it is presumed that the polyester resin is easily cut at the position of the laminated structure even when a cutting force is applied. Thus, the polyester resin of the present embodiment is more likely to be cut at a specific position when a cutting force is applied thereto, as compared with a resin used for a conventional base material.

Here, as a mechanism of generating chips from a base material of a general dicing blade, it is presumed that the base material is softened by frictional heat generated at the time of dicing, and then, a force of stretching a cut portion of the base material is applied by contacting a rotating circular blade, and the cut portion of the base material is shaved while being elongated. In particular, most of the thus produced chipbreakers have a filiform morphology.

On the other hand, it is considered that the substrate of the present embodiment is effectively cut in the ester bond and the vicinity of the layered structure before being elongated as described above, and as a result, the generation of cutting chips is suppressed.

This chipping suppressing effect can be exhibited even without irradiating the substrate of the present embodiment with radiation such as electron beams or γ rays. Therefore, the adhesive sheet having the substrate can be manufactured at a lower cost than a conventional dicing sheet manufactured by a method including a radiation irradiation step.

In addition, the polyester resin as a material of the substrate can easily exhibit good flexibility. Therefore, the adhesive sheet of the present embodiment can also obtain the following effects: an effect (spreadability) that the adhesive sheet is easily spread well in the spreading step; in the pickup step, the chip is easily lifted from the back surface, and thus the effect (pickup property) of picking up the chip is easily achieved. Further, since the base material made of the polyester resin has good transparency, it is easy to visually check or inspect a workpiece through the adhesive sheet.

Further, the heat of fusion of the polyester resin measured by differential scanning calorimetry at a temperature rise rate of 20 ℃/min is preferably 5J/g or more, particularly preferably 10J/g or more, and more preferably 15J/g or more, from the viewpoint of more easily achieving the effect of suppressing chips. On the other hand, the upper limit of the heat of fusion is not particularly limited, and may be, for example, 150J/g or less, or may be 100J/g or less, or may be, in particular, 70J/g or less, or may be, further, 50J/g or less, or may be, in particular, 30J/g or less. The details of the method for measuring the heat of fusion are described in the section of examples below.

(1-1) polyester resin

The specific composition of the polyester resin is not particularly limited as long as the polyester resin has an alicyclic structure and exhibits the above-described heat of fusion or the like.

The number of carbon atoms constituting the alicyclic structure of the polyester resin is preferably 6 or more, from the viewpoint of more satisfactory effect of suppressing chips. The number of carbon atoms is preferably 14 or less, and particularly preferably 10 or less. The number of carbon atoms is particularly preferably 6. The alicyclic structure may be a monocyclic structure composed of one ring, a bicyclic structure composed of two rings, or an alicyclic structure composed of three or more rings.

In addition, from the viewpoint of easily satisfying the above two conditions, the polyester resin preferably contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin. From the same viewpoint, the polyester resin preferably contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin. The polyester resin may contain only any one of such dicarboxylic acid and diol, but from the viewpoint of more easily satisfying the above-described conditions, it is preferable that the polyester resin contains both such dicarboxylic acid and diol.

The structure of the dicarboxylic acid is not particularly limited as long as it has two carboxyl groups in addition to the alicyclic structure. For example, the dicarboxylic acid may have a structure in which two carboxyl groups are bonded to an alicyclic structure, or may have a structure in which an alkyl group or the like is further inserted between such an alicyclic structure and a carboxyl group. Preferred examples of such dicarboxylic acids include 1, 2-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, decahydronaphthalene-1, 4-dicarboxylic acid, decahydronaphthalene-1, 5-dicarboxylic acid, decahydronaphthalene-2, 6-dicarboxylic acid, decahydronaphthalene-2, 7-dicarboxylic acid, and the like, and among these, 1, 4-cyclohexanedicarboxylic acid is preferably used. These dicarboxylic acids may be derivatives of alkyl esters and the like. Such an alkyl ester derivative may be, for example, an alkyl ester having 1 to 10 carbon atoms. More specific examples thereof include dimethyl ester and diethyl ester, and dimethyl ester is particularly preferable.

When the polyester resin of the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin, the ratio of the dicarboxylic acid monomer to all monomer units constituting the polyester resin is preferably 20 mol% or more, more preferably 25 mol% or more, particularly preferably 30 mol% or more, and further preferably 35 mol% or more. The ratio is preferably 60 mol% or less, more preferably 55 mol% or less, particularly preferably 50 mol% or less, and further preferably 45 mol% or less. By setting the range above, the polyester resin tends to exhibit the above heat of fusion, and as a result, the adhesive sheet of the present embodiment tends to achieve a more excellent chip-suppressing effect.

When the polyester resin of the present embodiment contains a dicarboxylic acid having an alicyclic structure as a monomer unit constituting the polyester resin, the proportion of the dicarboxylic acid having an alicyclic structure to the whole dicarboxylic acid having a ring structure constituting the polyester resin is preferably 60% or more, more preferably 70% or more, particularly preferably 80% or more, and further preferably 90% or more. By setting the above ratio to 60% or more, the adhesive sheet of the present embodiment is likely to achieve a more excellent chip-inhibiting effect. The upper limit of the ratio is not particularly limited, and may be, for example, 100% or less. The dicarboxylic acid having a ring structure includes dicarboxylic acids having an alicyclic structure, and dicarboxylic acids having an aromatic ring structure.

The structure of the diol is not particularly limited as long as it has two hydroxyl groups in addition to the alicyclic structure. For example, the diol may have a structure in which two hydroxyl groups are bonded to an alicyclic structure, or may have a structure in which an alkyl group is further inserted between such an alicyclic structure and a hydroxyl group. Preferred examples of such diols include 1, 2-cyclohexanediol (particularly 1, 2-cyclohexanedimethanol), 1, 3-cyclohexanediol (particularly 1, 3-cyclohexanedimethanol), 1, 4-cyclohexanediol (particularly 1, 4-cyclohexanedimethanol), and 2, 2-bis- (4-hydroxycyclohexyl) -propane, and among these, 1, 4-cyclohexanedimethanol is preferably used.

When the polyester resin of the present embodiment contains a diol having an alicyclic structure as a monomer unit constituting the polyester resin, the proportion of the diol monomer with respect to all monomer units constituting the polyester resin is preferably 35 mol% or more, particularly preferably 40 mol% or more, and further preferably 45 mol% or more. The ratio is preferably 65 mol% or less, particularly preferably 60 mol% or less, and further preferably 55 mol% or less. By setting the range above, the polyester resin tends to exhibit the above heat of fusion, and as a result, the adhesive sheet of the present embodiment tends to achieve a more excellent chip-suppressing effect.

The polyester resin of the present embodiment preferably further contains a dimer acid obtained by dimerizing an unsaturated fatty acid as a monomer unit constituting the polyester resin, from the viewpoint that the base material is likely to have desired flexibility. Here, the number of carbon atoms of the unsaturated fatty acid is preferably 10 or more, and particularly preferably 15 or more. The number of carbon atoms is preferably 30 or less, and particularly preferably 25 or less. Examples of such a dimer acid include a dicarboxylic acid having 36 carbon atoms obtained by dimerizing an unsaturated fatty acid having 18 carbon atoms such as oleic acid or linoleic acid, and a dicarboxylic acid having 44 carbon atoms obtained by dimerizing an unsaturated fatty acid having 22 carbon atoms such as erucic acid. In addition, when the dimer acid is obtained, a small amount of trimer acid formed by trimerization of the unsaturated fatty acid may be generated. The polyester resin of the present embodiment may contain the above-described dimer acid as well as such trimer acid.

When the polyester resin of the present embodiment contains the dimer acid as a monomer unit constituting the polyester resin, the ratio of the dimer acid to all dicarboxylic acid units constituting the polyester resin is preferably 2 mol% or more, particularly preferably 5 mol% or more, and more preferably 10 mol% or more. The ratio is preferably 25 mol% or less, particularly preferably 23 mol% or less, and further preferably 20 mol% or less. By setting the range above, the polyester resin tends to have desired flexibility, and as a result, the adhesive sheet of the present embodiment can also realize excellent spreadability and pickup properties.

The polyester resin of the present embodiment may contain monomers other than the above-mentioned dicarboxylic acid, diol and dimer acid as monomer units constituting the polyester resin. Examples of such monomers include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, and 4, 4' -biphenyldicarboxylic acid. Further, a diol component other than the diol having an alicyclic structure may be contained. For example, ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, octylene glycol, and decylene glycol; ethylene oxide adducts of bisphenol a, bisphenol S and the like; trimethylolpropane, and the like.

However, in the polyester resin of the present embodiment, it is preferable to contain a larger amount of the monomer having an alicyclic structure (the dicarboxylic acid having an alicyclic structure, or the diol having an aliphatic structure) than the monomer having an aromatic ring structure, from the viewpoint of easily achieving an excellent chip-suppressing effect. In particular, in the monomer units constituting the polyester resin of the present embodiment, the molar ratio of the monomer unit having an aromatic ring structure to the monomer unit having an alicyclic ring structure is preferably less than 1, more preferably 0.5 or less, more preferably 0.2 or less, more preferably 0.1 or less, more preferably 0.05 or less, more preferably 0.03 or less, more preferably 0.01 or less, particularly preferably 0.005 or less, further preferably 0.001 or less, and most preferably 0.

The method for producing the polyester resin of the present embodiment is not particularly limited, and the polyester resin can be obtained by polymerizing the monomer components using a known catalyst.

The proportion of the polyester resin to all the components constituting the base material of the present embodiment is preferably 50% or more, particularly preferably 60% or more, and more preferably 70% or more. By setting the above ratio to 50% or more, the adhesive sheet of the present embodiment is likely to achieve a more excellent chip-inhibiting effect. The upper limit of the above ratio is not particularly limited, and may be, for example, 100% or less.

(1-2) other Components

The material used for the base material of the present embodiment may contain other components than the above polyester resin. In particular, the material may contain a component used for a base material of a general pressure-sensitive adhesive sheet (in particular, a base material of a general sheet for processing a work).

Examples of such components include various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. The content of these additives is not particularly limited, but is preferably set within a range in which the base material exerts a desired function.

(1-3) Structure of substrate

The layer structure of the substrate of the present embodiment may be a single layer or a plurality of layers as long as it includes a layer formed of a material containing the polyester resin (hereinafter, may be referred to as a "polyester resin layer"). The substrate of the present embodiment is preferably a single layer (only a polyester resin layer) from the viewpoint of being able to reduce the production cost.

On the other hand, when the multilayer structure is used, a plurality of polyester resin layers may be laminated, or a polyester resin layer and a layer other than the polyester resin layer may be laminated. In the latter case, the polyester resin layer is preferably a layer in which an adhesive layer is laminated in the layer structure of the base material. In this case, the chip-suppressing effect of the polyester resin layer and the desired effect of the other layer can be achieved at the same time.

In addition, in order to improve adhesion to the adhesive agent layer, the surface of the substrate on which the adhesive agent layer is laminated may be subjected to surface treatment such as primer treatment, corona treatment, plasma treatment, or the like.

(1-4) method for producing substrate

The method for producing the base material of the present embodiment is not particularly limited as long as the material containing the polyester resin is used, and for example, a melt extrusion method such as a T-die method or a circular die method; a rolling method; solution methods such as dry method and wet method. Among them, from the viewpoint of efficiently producing the base material, it is preferable to use a melt extrusion method or a rolling method.

When the substrate composed of a single layer is produced by a melt extrusion method, the material of the substrate (the material containing the polyester resin) may be kneaded and film-formed directly from the obtained kneaded mass using a known extruder, or the material of the substrate (the material containing the polyester resin) may be kneaded and film-formed first into pellets (pellets) and then using a known extruder.

In the case of producing a substrate composed of a plurality of layers by the melt extrusion method, it is sufficient to knead the components constituting each layer separately and extrude a plurality of layers simultaneously from the obtained kneaded mass directly using a known extruder to form a film, or to knead the components constituting each layer separately and produce the obtained kneaded mass into pellets first and then extrude a plurality of layers simultaneously using a known extruder to form a film.

(1-5) physical Properties of base Material, etc

The tensile modulus of the substrate of the present embodiment at 23 ℃ is preferably 800MPa or less, particularly preferably 600MPa or less, and more preferably 500MPa or less. The tensile modulus is preferably 100MPa or more, particularly preferably 200MPa or more, and more preferably 300MPa or more. When the tensile modulus is 800MPa or less, the substrate of the present embodiment tends to have desired flexibility, and the adhesive sheet of the present embodiment tends to realize excellent extensibility and pickup properties. Further, by setting the tensile modulus to 100MPa or more, the substrate of the present embodiment is likely to have appropriate strength, and the adhesive sheet has good workability and is likely to perform desired work processing well. The details of the method for measuring the tensile modulus are described in the test examples described later.

The breaking point stress of the substrate of the present embodiment at 23 ℃ is preferably 60MPa or less, particularly preferably 50MPa or less, and more preferably 40MPa or less. The breaking point stress is preferably 15MPa or more, particularly preferably 20MPa or more, and more preferably 25MPa or more. By setting the breaking point stress to 60MPa or less, the substrate film of the present embodiment has better workability. Further, by setting the above breaking point stress to 15MPa or more, the base material of the present embodiment is likely to have appropriate strength, and the adhesive sheet has good workability and is likely to perform desired work processing well. Further, the base material film of the present embodiment has good extensibility by setting the breaking point stress to 15MPa or more. The details of the method for measuring the breaking point stress are described in the test examples described later.

The elongation at break of the substrate in the present embodiment at 23 ℃ is preferably 200% or more, more preferably 250% or more, particularly preferably 300% or more, and further preferably 350% or more. By setting the elongation at break to 200% or more, the substrate of the present embodiment is likely to have desired extensibility, and the adhesive sheet of the present embodiment is likely to realize excellent extensibility and pickup properties. The elongation at break is preferably 800% or less, more preferably 700% or less, particularly preferably 600% or less, and further preferably 500% or less. By setting the elongation at break to 800% or less, the workability of the base material is further improved, and the desired sheet for workpiece processing can be easily produced. The details of the method for measuring the elongation at break are described in the test examples described later.

The thickness of the substrate in the present embodiment is preferably 20 μm or more, particularly preferably 40 μm or more, and further preferably 60 μm or more. The thickness of the base material is preferably 600 μm or less, particularly preferably 300 μm or less, and more preferably 200 μm or less. By setting the thickness of the base material to 20 μm or more, the adhesive sheet can easily have appropriate strength, and the work fixed to the adhesive sheet can be easily supported satisfactorily. As a result, chipping (chipping) and the like can be effectively suppressed during dicing. Further, the above elongation at break can be easily achieved by setting the thickness of the base material to 600 μm or less. Further, by setting the thickness of the base film to 600 μm or less, the base film has more excellent processability.

(2) Adhesive layer

The adhesive constituting the adhesive layer of the present embodiment is not particularly limited as long as it can exhibit sufficient adhesive force to an adherend (in particular, sufficient adhesive force to a work for working a work). Examples of the adhesive constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, and polyvinyl ether adhesives. Among them, acrylic adhesives are preferably used from the viewpoint of easily exhibiting a desired adhesive force.

The adhesive constituting the adhesive layer of the present embodiment may be an adhesive having no active energy ray-curing property, but is preferably an adhesive having an active energy ray-curing property (hereinafter, may be referred to as "active energy ray-curing adhesive"). When the adhesive layer is made of an active energy ray-curable adhesive, the adhesive layer can be cured by irradiation with an active energy ray, and the adhesive force of the adhesive sheet to an adherend can be easily reduced. In particular, when the adhesive sheet of the present embodiment is used as a sheet for processing a workpiece, the processed workpiece can be easily separated from the adhesive sheet by irradiation with an active energy ray.

The active energy ray-curable adhesive constituting the adhesive layer may contain, as a main component, a polymer having active energy ray-curability, or may contain, as a main component, a mixture of a non-active energy ray-curable polymer (a polymer having no active energy ray-curability) and a monomer and/or oligomer having at least one or more active energy ray-curable groups.

The active energy ray-curable polymer is preferably a (meth) acrylate polymer having a functional group curable with an active energy ray (active energy ray-curable group) introduced into a side chain thereof (hereinafter, may be referred to as "active energy ray-curable polymer"). Preferably, the active energy ray-curable polymer is obtained by reacting an acrylic copolymer having a functional group-containing monomer unit with an unsaturated group-containing compound having a functional group bonded to the functional group. In the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. The same is true for other similar terms. Further, "polymer" also includes the concept of "copolymer".

The weight average molecular weight of the active energy ray-curable polymer is preferably 1 ten thousand or more, particularly preferably 15 ten thousand or more, and more preferably 20 ten thousand or more. The weight average molecular weight is preferably 250 ten thousand or less, particularly preferably 200 ten thousand or less, and more preferably 150 ten thousand 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).

On the other hand, when the active energy ray-curable adhesive contains, as a main component, a mixture of an inactive energy ray-curable polymer component and a monomer and/or oligomer having at least one or more active energy ray-curable groups, the above-mentioned acrylic copolymer before the reaction with the unsaturated group-containing compound can be used as the inactive energy ray-curable polymer component. As the active energy ray-curable monomer and/or oligomer, for example, an ester of a polyol and (meth) acrylic acid, or the like can be used.

The weight average molecular weight of the acrylic polymer as the non-active energy ray-curable polymer component is preferably 1 ten thousand or more, particularly preferably 15 ten thousand or more, and more preferably 20 ten thousand or more. The weight average molecular weight is preferably 250 ten thousand or less, particularly preferably 200 ten thousand or less, and more preferably 150 ten thousand or less.

When ultraviolet rays are used as active energy rays for curing the active energy ray-curable adhesive, a photopolymerization initiator is preferably added to the adhesive. In addition, an inactive energy ray-curable polymer component, an oligomer component, a crosslinking agent, or the like may be added to the adhesive.

The thickness of the adhesive agent layer of the present embodiment is preferably 1 μm or more, particularly preferably 2 μm or more, and more preferably 3 μm or more. The thickness of the adhesive layer is preferably 50 μm or less, particularly preferably 40 μm or less, and more preferably 30 μm or less. The adhesive sheet of the present embodiment can easily exhibit desired adhesiveness by setting the thickness of the adhesive layer to 1 μm or more. Further, when the thickness of the adhesive agent layer is 50 μm or less, separation of the adherend from the cured adhesive agent layer is facilitated.

(3) Release sheet

In the pressure-sensitive adhesive sheet of the present embodiment, before a surface of the pressure-sensitive adhesive layer on the opposite side to the substrate (hereinafter, sometimes referred to as "pressure-sensitive adhesive surface") is attached to an adherend, a release sheet may be laminated on the surface for the purpose of protecting the surface.

The release sheet is optionally configured, and for example, a release sheet obtained by peeling a plastic film with a release agent or the like is exemplified. 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, silicones, fluorines, long-chain alkyl groups, and the like can be used, and among them, silicones which are inexpensive and can provide stable performance are preferable.

The thickness of the release sheet is not particularly limited, and may be, for example, 20 μm or more and 250 μm or less.

(4) Others

In the adhesive sheet of the present embodiment, a pressure-sensitive adhesive layer may be laminated on the surface of the pressure-sensitive adhesive layer opposite to the substrate. In this case, the adhesive sheet of the present embodiment can be used as a dicing die. A work is attached to the surface of the adhesive layer of the sheet opposite to the adhesive layer, and the adhesive layer is cut together with the work, whereby a chip having a singulated adhesive layer laminated thereon can be obtained. The chip can be easily fixed to an object to which the chip is to be mounted by the singulated adhesive layer. As a material constituting the pressure-sensitive adhesive layer, a material containing a thermoplastic resin and a low-molecular-weight thermosetting pressure-sensitive adhesive component, a material containing a B-stage (semi-cured) thermosetting pressure-sensitive adhesive component, or the like is preferably used.

In the adhesive sheet of the present embodiment, a protective film-forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the adhesive sheet of the present embodiment can be used as a protective film forming and cutting sheet. A work is attached to the surface of the protective film forming layer of the sheet opposite to the adhesive layer, and the protective film forming layer is cut together with the work, whereby a chip in which the singulated protective film forming layers are stacked can be obtained. In this case, a protective film forming layer is generally laminated on the surface opposite to the surface on which the circuit is formed. By curing the singulated protective film forming layer at a predetermined timing, a protective film having sufficient durability can be formed on the chip. The protective film-forming layer is preferably composed of an uncured curable adhesive.

2. Method for producing adhesive sheet

The method for producing the adhesive sheet of the present embodiment is not particularly limited. For example, after the adhesive layer is formed on the release sheet, one surface of the substrate is preferably laminated on the surface of the adhesive layer opposite to the release sheet, thereby obtaining an adhesive sheet.

The adhesive layer can be formed by a known method. For example, a coating liquid is prepared which contains an adhesive composition for forming an adhesive layer, and further contains a solvent or a dispersion medium as necessary. Then, the coating liquid is applied to a releasable surface (hereinafter, sometimes referred to as a "releasable surface") of a release sheet. Then, the obtained coating film is dried, whereby an adhesive layer can be formed.

The coating liquid can be applied by a known method, for example, by a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like. The coating liquid is not particularly limited in its properties as long as it can be applied, and may contain a component for forming the adhesive layer as a solute or a component for forming the adhesive layer as a dispersion medium. The release sheet may be released as a process material, or may protect the adhesive layer until the adhesive layer is attached to an adherend.

When the adhesive composition for forming the adhesive layer contains the above-mentioned crosslinking agent, it is preferable to form a crosslinked structure in the adhesive layer at a desired existing density by causing a crosslinking reaction between the polymer component in the coating film and the crosslinking agent by changing the above-mentioned drying conditions (temperature, time, etc.) or by additionally providing a heating treatment. Further, in order to sufficiently progress the crosslinking reaction, aging may be performed by leaving the adhesive layer and the substrate to stand for several days at 23 ℃ under an environment with a relative humidity of 50%, for example, after the adhesive layer and the substrate are bonded.

3. Method for using adhesive sheet

The adhesive sheet of the present embodiment can be used for various purposes as in a general adhesive sheet, but is particularly suitable for use as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer. In this case, the work may be processed on the adhesive sheet after the adhesive surface of the adhesive sheet of the present embodiment is attached to the work. The pressure-sensitive adhesive sheet of the present embodiment can be used as a sheet for processing a workpiece such as a back-grinding sheet, a dicing sheet, an expanding sheet, or a picking-up sheet. Examples of the work include semiconductor wafers, semiconductor members such as semiconductor packages, and glass members such as glass plates.

As described above, when the adhesive sheet of the present embodiment is used for cutting with a rotating circular blade, the generation of chips can be favorably suppressed. Therefore, the adhesive sheet of the present embodiment is particularly suitable for use as a dicing sheet in the above-described sheet for processing a workpiece.

In addition, when the adhesive sheet of the present embodiment includes the adhesive layer, the adhesive sheet can be used as a dicing die. Further, when the adhesive sheet of the present embodiment includes the protective film forming layer, the adhesive sheet can be used as a protective film forming and dicing sheet.

In addition, when the adhesive layer in the adhesive sheet of 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 at the time of use. That is, when the work is processed on the adhesive sheet and the processed work is separated from the adhesive sheet, it is preferable to irradiate the adhesive layer with an active energy ray before the separation. This cures the adhesive layer, thereby reducing the adhesive force of the adhesive sheet to the processed work satisfactorily, and facilitating the separation of the processed work.

The embodiments described above are described for easy understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiments also includes all design changes and equivalents within the technical scope of the present invention.

Examples

The present invention will be described in more detail with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.

[ example 1]

(1) Production of the substrate

12.90kg of dimethyl 1, 4-cyclohexanedicarboxylate (the proportion of the trans isomer is 98%), 11.47kg of 1, 4-cyclohexanedimethanol, 0.3kg of ethylene glycol and 0.11kg of an ethylene glycol solution containing 10% manganese acetate tetrahydrate were charged into a reactor equipped with a stirrer, a distillation tube and a pressure reducing device, heated to 200 ℃ under a nitrogen stream, and then heated to 230 ℃ over 1 hour. After the transesterification was carried out while maintaining this state for 2 hours, 10.30kg of dimer acid derived from erucic acid (having 44 carbon atoms, manufactured by Croda International Plc, under the product name "PRIPOL 1004") and 0.11kg of an ethylene glycol solution containing 10% trimethyl phosphate were added to the reaction system, followed by esterification at 230 ℃ for 1 hour. Then, 300ppm germanium dioxide as a polycondensation catalyst was added and stirred, and after that, the pressure was reduced to 133Pa or less over 1 hour, while the internal temperature was raised from 230 ℃ to 270 ℃, and the mixture was stirred until the mixture became a predetermined viscosity under a high vacuum of 133Pa or less to perform a polycondensation reaction. The resulting polymer was extruded in water into strands (strand) and cut into pellets.

The pellets of the polyester resin obtained in the above manner were dried at 85 ℃ for 4 hours or more, and then placed in a hopper of a single-screw extruder equipped with a T-die. Then, the resin was extruded from the T die in a melt-kneaded state under conditions of a cylinder temperature of 220 ℃ and a die temperature of 220 ℃ and cooled by a cooling roll, thereby obtaining a sheet-like substrate having a thickness of 80 μm.

In addition, the polyester resin contains about 50 mol% of 1, 4-cyclohexanedimethanol, about 40.5 mol% of dimethyl 1, 4-cyclohexanedicarboxylate, and 9.5 mol% of dimer acid derived from erucic acid as monomers constituting the resin. Further, the proportion of the dimer acid to all the dicarboxylic acid units constituting the polyester resin was 19.1 mol%. Further, the heat of fusion of the polyester resin was measured by the method described later, and the result was 20J/g.

(2) Preparation of adhesive composition

A (meth) acrylate polymer was obtained by polymerizing 95 parts by mass of n-butyl acrylate and 5 parts by mass of acrylic acid by a solution polymerization method. The weight average molecular weight (Mw) of the acrylic polymer was measured by the method described below, and found to be 50 ten thousand.

An energy ray-curable adhesive composition was obtained by mixing 100 parts by mass (in terms of solid content, the same applies hereinafter) of the (meth) acrylate polymer obtained in the above-described manner, 120 parts by mass of a urethane acrylate oligomer (Mw: 8,000), 5 parts by mass of an isocyanate-based crosslinking agent (manufactured by TOSOH CORPORATION, product name "CORONATE L"), and 4 parts by mass of a photopolymerization initiator (manufactured by IGM Resins b.v., company, product name "Omnirad 184").

(3) Formation of adhesive layer

The adhesive composition obtained in the step (2) was applied to a release-treated surface of a release sheet (product name "SP-PET 381031" manufactured by LINTEC Corporation) having a thickness of 38 μm and obtained by releasing one surface of a polyethylene terephthalate film with a silicone-based release agent, and the obtained coating film was dried at 100 ℃ for 1 minute. Thus, a laminate in which an adhesive layer having a thickness of 10 μm was formed on the release surface of the release sheet was obtained.

(4) Production of adhesive sheet

The adhesive sheet is obtained by bonding one surface of the substrate obtained in the step (1) to the surface of the adhesive layer side of the laminate obtained in the step (3).

Here, the heat of fusion of the polyester resin was measured using a differential scanning calorimeter (DSC, product name "DSC Q2000" manufactured by TA instruments) based on JIS K7121: 2012.

Specifically, first, the steel sheet is heated from room temperature to 250 ℃ at a temperature rising rate of 20 ℃/min and maintained at 250 ℃ for 10 minutes, and is reduced to-60 ℃ at a temperature lowering rate of 20 ℃/min and maintained at-60 ℃ for 10 minutes. Then, the mixture was heated to 250 ℃ again at a temperature rise rate of 20 ℃ per minute to obtain a DSC curve, and the melting point was measured.

The weight average molecular weight (Mw) is a weight average molecular weight in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< measurement Condition >

The measurement device: HLC-8320, manufactured by TOSOH CORPORATION

GPC column (run through in the following order): TOSOH CORPORATION, Inc

TSK gel superH-H

TSK gel superHM-H

TSK gel superH2000

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

Comparative example 1

An adhesive sheet was obtained in the same manner as in example 1, except that a polyvinyl chloride resin sheet having a thickness of 80 μm was used as the base material. The heat of fusion of the polyvinyl chloride resin was measured by the above-mentioned method, and the result was 0J/g.

Comparative example 2

An adhesive sheet was obtained in the same manner as in example 1, except that a substrate (thickness 80 μm) composed of an ethylene-methacrylic acid copolymer (EMAA) and having one surface subjected to electron beam irradiation treatment was used as the substrate, and an adhesive layer was laminated on the surface of the substrate subjected to electron beam irradiation. The heat of fusion of the ethylene-methacrylic acid copolymer was measured by the above-mentioned method, and the result was 81J/g.

Comparative example 3

An adhesive sheet was obtained in the same manner as in example 1, except that a substrate (thickness 80 μm) composed of EMAA and having one surface subjected to electron beam irradiation treatment was used as the substrate, and an adhesive layer was laminated on the surface of the substrate subjected to electron beam irradiation. The irradiation amount of the electron beam with respect to the base material used in comparative example 3 was 2 times as large as the irradiation amount of the electron beam with respect to the base material used in comparative example 2. Further, the heat of fusion of the above ethylene-methacrylic acid copolymer was measured by the above method, and as a result, it was 79J/g.

Comparative example 4

An adhesive sheet was obtained in the same manner as in example 1, except that a resin sheet having a thickness of 80 μm was produced using a diol-modified polyester resin having a structure represented by the following general formula (1) and used as a substrate. The heat of fusion of the above-mentioned glycol-modified polyester resin was measured by the above-mentioned method, and the result was 0J/g.

[ chemical formula 1]

Comparative example 5

An adhesive sheet was obtained in the same manner as in example 1, except that a resin sheet having a thickness of 80 μm was produced using an amorphous polyester resin having a structure represented by the following general formula (2) and used as a base material. The heat of fusion of the amorphous polyester resin was measured by the above method, and the result was 0J/g.

[ chemical formula 2]

[ test example 1] (measurement of tensile Properties of base Material)

The substrates prepared in examples and comparative examples were cut into test pieces of 15mm × 150 mm. At this time, the cutting was performed such that the 150mm side was parallel to the MD direction of the base material (the flow direction when the base material was manufactured) and the 15mm side was parallel to the TD direction of the base material film (the direction perpendicular to the MD direction). Then, the tensile modulus, elongation at break and stress at break of the test piece were measured in accordance with JIS K7127: 1999.

Specifically, the tensile modulus (MPa), the elongation at break (%), and the stress at break (MPa) of the test piece were measured by performing a tensile test of the test piece in the MD direction of the base film at a speed of 200 mm/min under an environment of 23 ℃ with a collet pitch of 100mm using a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph AG-Xplus 100N"). The results are shown in Table 1.

[ test example 2] (measurement of the amount of chips)

The release sheet was peeled from the adhesive sheet produced in examples and comparative examples, the exposed surface of the exposed adhesive layer was attached to one surface of a silicon wafer having a thickness of 40 μm, and then a dicing ring frame was attached to the peripheral portion (a position not overlapping with the silicon wafer) of the exposed surface of the adhesive sheet. Next, the silicon wafer was cut using a dicing saw (manufactured by DISCO Corporation, product name "DFD 6362") under the following conditions.

Workpiece (adherend): silicon wafer

Workpiece size: 6 inches in diameter and 40 μm thick

Cutting blade: manufactured by DISCO Corporation, product name "27 HECC", Diamond blade

Blade rotation speed: 50,000rpm

Cutting speed: 100 mm/sec

Cutting depth: cutting to a depth of 20 μm from the surface of the substrate

Cut size: 8mm

After dicing, an electron microscope (product name, manufactured by KEYENCE CORPORATION) was used with the chip formed by singulating the silicon wafer being attached to the adhesive sheet

"VHX-5000", magnification: 500 times) the number of chips generated on the saw lane (the cutting blade passes through the generated cutting path). At this time, the number of chips on the 3 paths existing near the center in the longitudinal direction and the 3 paths existing near the center in the lateral direction among the plurality of saw lanes existing in the longitudinal direction and the lateral direction, respectively, is counted. The counting results are shown in table 1.

[ Table 1]

As can be seen from table 1, the adhesive sheet produced in the examples effectively suppressed the generation of cutting chips at the time of cutting.

Industrial applicability

The adhesive sheet of the present invention can be suitably used as a workpiece processing sheet used for processing a workpiece such as a semiconductor wafer.

Claims

1. An adhesive sheet comprising a base and an adhesive layer laminated on one surface of the base,

the base material is formed of a material containing a polyester resin,

the polyester resin has an alicyclic structure, and has a heat of fusion of 2J/g or more as measured by differential scanning calorimetry at a temperature rise rate of 20 ℃/min.

2. The adhesive sheet according to claim 1, wherein the polyester resin contains a dicarboxylic acid having the alicyclic structure as a monomer unit constituting the polyester resin.

3. The adhesive sheet according to claim 1 or 2, wherein the polyester resin contains a diol having the alicyclic structure as a monomer unit constituting the polyester resin.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the number of carbon atoms constituting a ring of the alicyclic structure is 6 or more and 14 or less.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the polyester resin contains, as a monomer unit constituting the polyester resin, a dimer acid obtained by dimerizing an unsaturated fatty acid,

the unsaturated fatty acid has 10 to 30 carbon atoms.

6. The pressure-sensitive adhesive sheet according to claim 5, wherein the proportion of the dimer acid as a monomer unit constituting the polyester resin is 2 mol% or more and 25 mol% or less with respect to all dicarboxylic acids as a monomer unit constituting the polyester resin.

7. The adhesive sheet according to any one of claims 1 to 6, wherein the tensile modulus of the base material at 23 ℃ is 100MPa or more and 800MPa or less.

8. The adhesive sheet according to any one of claims 1 to 7, wherein the substrate has an elongation at break at 23 ℃ of 200% or more and 800% or less.

9. The adhesive sheet according to any one of claims 1 to 8, wherein the thickness of the substrate is 20 μm or more and 600 μm or less.

10. The adhesive sheet according to any one of claims 1 to 9, wherein the adhesive layer is composed of an acrylic adhesive.

11. The adhesive sheet according to any one of claims 1 to 10, which is used as a sheet for processing a workpiece.

12. The adhesive sheet according to claim 11, wherein the workpiece processing sheet is a dicing sheet.