KR102376559B1 - Adhesive sheet - Google Patents

Abstract

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet used for forming a modified portion by irradiating a plate-shaped member with a laser beam and dividing the plate-shaped member into chips, comprising: a substrate; and an adhesive layer provided on one side of the substrate; The main component is an acrylic copolymer (A) in which the base material is a copolymer of an alkyl (meth)acrylate (a) having an alkyl group having 4 to 8 carbon atoms and an alkyl (meth)acrylate (b) having an alkyl group having 1 to 3 carbon atoms. and an acrylic film containing as

Description

Adhesive sheet {ADHESIVE SHEET}

The present invention relates to a pressure-sensitive adhesive sheet used for forming a modified portion by irradiating a plate-like member with a laser beam and dividing the plate-like member into chips, and a method for manufacturing a chipped member using the adhesive sheet.

Conventionally, as one of the dicing methods, a method of performing internal processing with a laser beam and dividing a semiconductor wafer by subsequent expansion is known. can In this method, specifically, a modified portion is formed on a semiconductor wafer along a dicing line with a laser beam, and then an adhesive sheet affixed to the semiconductor wafer is expanded, whereby the semiconductor wafer is divided (diced) from the modified portion as a starting point. manufactures semiconductor chips.

In the above-described division method, since the gap, called a calf, which is generated between the divided chips is generated only by the expansion, it is necessary for the adhesive sheet to have high expandability so that the chip interval can be sufficiently expanded. Moreover, since a laser beam may be irradiated to a wafer through an adhesive sheet, a highly permeable thing is also desired for an adhesive sheet. Conventionally, a polyvinyl chloride (PVC) film is widely used as a base material of the adhesive sheet used by the said division|segmentation method at the point which can satisfy these required characteristics (for example, refer patent documents 1, 2).

Japanese Patent Laid-Open No. 2011-119548 Japanese Patent Laid-Open No. 2009-272611

However, in recent years, from the viewpoint of reducing the environmental load, development of a base material that is halogen-free and has high expandability and high permeability similar to that of PVC has been desired. In addition, in the above-described dividing method, by expanding the pressure-sensitive adhesive sheet, loosening occurs in the outer peripheral portion of the pressure-sensitive adhesive sheet. Since the relaxation becomes a factor that deteriorates transportability and the like in subsequent steps, it is preferable to shrink it by heating, and it is preferable that the shrinkage occurs uniformly.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an adhesive sheet excellent in expandability, permeability and heat shrinkability while having a low environmental load.

As a result of intensive studies, the present inventors have found that even when an acrylic film having a relatively low environmental load is used as a substrate, an alkyl (meth)acrylate having a relatively large alkyl group and an alkyl (meth)acrylate having a small alkyl group having a small carbon number are used as constituent monomers. It was discovered that the said subject could be solved by having as a main component the acrylic copolymer to do, and the following invention was completed.

(1) A pressure-sensitive adhesive sheet used for forming a modified portion by irradiating a plate-like member with laser light and dividing the plate-like member into chips, comprising: a substrate; and an adhesive layer provided on one side of the substrate; , An acrylic copolymer (A) which is a copolymer of an alkyl (meth)acrylate (a) having 4 to 8 carbon atoms in the alkyl group and an alkyl (meth)acrylate (b) having 1 to 3 carbon atoms in the alkyl group as a main component A pressure-sensitive adhesive sheet comprising an acrylic film.

(2) The acrylic copolymer (A) is described in (1) above, wherein the alkyl (meth) acrylate (a) and the alkyl (meth) acrylate (b) are copolymerized in a mass ratio of 10:90 to 40:60. adhesive sheet.

(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the acrylic copolymer (A) is a random copolymer.

(4) The above (1) to (3) wherein the acrylic copolymer (A) is a mixture of an acrylic copolymer (A1) having a weight average molecular weight of 600,000 or more and an acrylic copolymer (A2) having a weight average molecular weight of 400,000 or less ) The adhesive sheet in any one of.

(5) The adhesive sheet as described in said (4) whose mixing ratio of an acrylic copolymer (A1) and an acrylic copolymer (A2) is 5:95-35:65 by mass ratio.

(6) alkyl (meth) acrylate (a) is an alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, and alkyl (meth) acrylate (b) is an alkyl methacrylate having 1 to 3 carbon atoms in the alkyl group The pressure-sensitive adhesive sheet according to any one of (1) to (5) above.

(7) The adhesive sheet as described in said (6) whose alkyl (meth)acrylate (a) is butyl acrylate, and alkyl (meth)acrylate (b) is methyl methacrylate.

(8) The pressure-sensitive adhesive sheet according to any one of (1) to (7), wherein the Young's modulus of the substrate is 50 to 500 MPa.

(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8), wherein the centerline average roughness Ra of the surface opposite to one surface of the substrate is 0.1 µm or less.

(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9), wherein the centerline average roughness Ra of one surface of the substrate is 0.15 µm or more.

(11) The adhesive sheet in any one of said (1)-(10) whose total light transmittance is 85 % or more and HAZE is 7 % or less.

(12) The pressure-sensitive adhesive sheet according to any one of (1) to (11), wherein the pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive.

(13) a step of affixing the pressure-sensitive adhesive sheet according to any one of (1) to (12) above on one surface of the plate-like member;

forming a modified part by irradiating a laser beam to the plate-shaped member through the pressure-sensitive adhesive sheet affixed to the plate-shaped member;

A method for manufacturing a chipped member comprising the steps of dividing the plate-like member into chips by expanding the pressure-sensitive adhesive sheet to obtain a chipped member.

(14) the chip-like member is affixed to the central region of the pressure-sensitive adhesive sheet;

The method for manufacturing a chipped member according to (13), further comprising a step of heating and shrinking an outer peripheral region of the pressure-sensitive adhesive sheet, which is an outer region of the central region.

In the present invention, it is possible to provide an adhesive sheet excellent in expandability, permeability and heat shrinkability while having a low environmental load.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows the structure of the adhesive sheet of this invention.
2 is a schematic cross-sectional view showing a method for manufacturing a chip member using the pressure-sensitive adhesive sheet of the present invention, and is a view showing a step in which a modified portion is formed in a semiconductor wafer.
Fig. 3 is a schematic cross-sectional view showing a method for manufacturing a chip member using the pressure-sensitive adhesive sheet of the present invention, and is a view showing the step in which the pressure-sensitive adhesive sheet is expanded.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in more detail using embodiment. In addition, in the following description, "weight average molecular weight (Mw)" is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method, Specifically, it is a value measured based on the method described in the Example. In addition, for example, "(meth)acrylate" is used as a term showing both "acrylate" and "methacrylate", and the same applies to other similar terms.

[Adhesive sheet]

As shown in Fig. 1, the pressure-sensitive adhesive sheet 10 of the present invention includes a substrate 11 and an adhesive layer 12 provided on one side of the substrate 11, and is modified by irradiating a laser beam to the plate-shaped member. It is an adhesive sheet used by affixing to plate-shaped members, such as a semiconductor wafer, in the method of forming a part and dividing the plate-shaped member into chips. Hereinafter, the structure of each member is demonstrated in more detail.

[write]

The base material is an acrylic copolymer (A) which is a copolymer of an alkyl (meth)acrylate (a) having 4 to 8 carbon atoms in the alkyl group and an alkyl (meth)acrylate (b) having 1 to 3 carbon atoms in the alkyl group as a main component. It is an acrylic film containing.

In the present invention, the acrylic copolymer (A) contains, as constituent monomers, the component (a) having a relatively large alkyl group carbon number and (b) component having a small alkyl group carbon number, so that the substrate does not exhibit surface tackiness and has extensibility. Since this becomes favorable, it becomes what has the outstanding expandability without generating blocking. In addition, since the base material of the present invention contains an acrylic copolymer as a main component, it has excellent laser transmittance and good uniformity of shrinkage by heating, and wrinkles are less likely to occur even when shrinkage by heating as will be described later.

Since the base material does not express surface tackiness and has excellent extensibility, it is preferable that the component (a) is an alkyl acrylate, and the component (b) is preferably an alkyl methacrylate. Moreover, from a similar viewpoint, it is preferable that it is 4-6, and, as for carbon number of the alkyl group in (a) component, it is more preferable that it is 4. On the other hand, it is preferable that it is 1 or 2, and, as for carbon number of the alkyl group in (b) component, it is more preferable that it is 1.

As the component (a) usable in the present invention, specifically, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, etc. , and they may be straight-chain or branched. Moreover, in these, butyl (meth)acrylate is preferable and butyl acrylate is more preferable. (b) As a component, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and isopropyl (meth)acrylate are mentioned, Among these, methyl methacrylate, ethyl Methacrylate is preferable, and methyl methacrylate is more preferable.

It is preferable that the acrylic copolymer (A) copolymerizes (a) component and (b) component by mass ratio 10:90-40:60. By carrying out mass ratio (henceforth "mass ratio (a:b)") into the said range, it becomes easier to make extensibility into an appropriate thing, without expressing surface tackiness to a base material. From this viewpoint, the mass ratio (a:b) is more preferably 15:85 to 30:70.

Moreover, it is more preferable that the mass ratio (a:b) is 15:85 - 25:75 at the point which makes it easy to make the Young's modulus into a more suitable value.

Although the acrylic copolymer (A) can employ|adopt various structures, such as a random copolymer, a block copolymer, an alternating copolymer, it is preferable that it is a random copolymer. If the acrylic copolymer (A) is a random copolymer, process problems (for example, wrinkles are generated in the obtained film, inability to obtain a smooth film, etc.) Compared with a block copolymer, it is hard to generate|occur|produce, and film forming by melt molding, such as an extrusion method, becomes easy. In addition, if the acrylic copolymer (A) is a random copolymer, it is easier to synthesize than an alternating copolymer.

The random copolymer is not limited as long as the component (a) and the component (b) are randomly copolymerized, and for example, they are polymerized by various radical polymerization methods. As a radical polymerization method, solution polymerization, suspension polymerization, emulsion polymerization, etc. are mentioned. Moreover, as a polymerization initiator used in a radical polymer, an azo compound, a peroxide, various redox initiators, etc. are mentioned.

It is preferable that an acrylic copolymer (A) mixes the acrylic copolymer (A1) whose weight average molecular weight is 600,000 or more, and the acrylic copolymer (A2) whose weight average molecular weight is 400,000 or less. In the present invention, by mixing a copolymer having a relatively high molecular weight and a copolymer having a relatively low molecular weight in this way, the shape retaining property of the film is improved and appropriate extensibility is easily imparted to the film.

From these viewpoints, it is more preferable that the weight average molecular weight of the acrylic copolymer (A1) is 800,000 to 1.3 million, and the weight average molecular weight of the acrylic copolymer (A2) is 10,000 to 200,000, and the acrylic copolymer (A1) While the weight average molecular weights are 900,000 to 1.1 million, it is more preferable that the weight average molecular weights of the acrylic copolymer (A2) are 30,000 to 80,000.

In addition, each of the acrylic copolymer (A1) and the acrylic copolymer (A2) may be the above-described acrylic copolymer (A), and the monomer composition constituting the acrylic copolymer (A1) (type of constituent monomers and mass ratio of each monomer) may be the same as or different from the monomer composition which comprises the acrylic copolymer (A2).

The mixing ratio (A1:A2) of the acrylic copolymer (A1) and the acrylic copolymer (A2) is preferably 5:95 to 35:65, more preferably 5:95 to 25:75 by mass. . In this invention, by setting it as such a mixing ratio, the extensibility of a base material becomes suitable while making shape retention property favorable.

The mixing ratio (A1:A2) is more preferably 8:92 to 15:85 from the viewpoint of easily setting the Young's modulus to an appropriate value, and particularly, while setting the mixing ratio (A1:A2) to 8:92 to 15:85, Most preferably, the mass ratio (a:b) is 15:85 to 25:75.

The acrylic copolymer (A) may have only the components (a) and (b) as structural units, but as long as the effects of the present invention are not impaired, the component (a), the component (b), and (a) ) and other monomers other than the component (b) may be used as a copolymer. Another monomer is 20 mass % or less in the structural monomer of an acrylic copolymer (A) normally, Preferably it is 5 mass % or less. As another monomer, carbon number of an alkyl group differs from carbon number of (a) and (b) component, for example, alkyl (meth)acrylate; (meth)acrylates having a hydroxyl group, a carboxyl group, an amino group, and the like; vinyl acetate; styrene; Acrylamide etc. are mentioned.

The substrate preferably has a Young's modulus of 50 to 500 MPa. By making the Young's modulus into this range, the mechanical strength of a base material can be improved, maintaining favorable extensibility, and process aptitude at the time of forming an adhesive layer can be made favorable. For example, when the acrylic film serving as the substrate is set in the coater, unintentional elongation of the acrylic film when tension is applied can be prevented.

The Young's modulus is more preferably 60 to 450 MPa, still more preferably 100 to 420 MPa, and more preferably 150 to 300 MPa, from the viewpoint of making it difficult to generate blocking and the like and improving the expandability while improving mechanical strength. more preferably.

As for the surface (2nd surface) opposite to the surface (1st surface) on which the adhesive layer of a base material is formed, it is preferable that center line average roughness Ra is 0.1 micrometer or less. By smoothing the surface of the base material on the side where the pressure-sensitive adhesive layer is not formed in this way, the light transmittance of the pressure-sensitive adhesive sheet is improved, and a modified portion to be described later can be formed with high accuracy by laser irradiation. In addition, although the center line average roughness Ra of a 2nd surface is not specifically limited, Usually, it is 0.02 micrometer or more, Preferably it is 0.05 micrometer or more.

Moreover, it is preferable that centerline average roughness Ra is 0.15 micrometer or more, and, as for the surface (1st surface) of the side on which the adhesive layer of a base material is formed, it is more preferable that it is 0.25 micrometer or more. Moreover, although the centerline average roughness Ra of a 1st surface is not specifically limited, Usually, it is 3.0 micrometers or less, Preferably it is 1.0 micrometer or less.

When a 1st surface has the above average roughness, even if it is a 2nd surface as a smooth surface, the blocking at the time of winding up an acrylic film can be prevented. Moreover, even if the surface on the side of the adhesive layer of a base material has rough unevenness|corrugation, since the diffusion of light in an interface is reduced by laminating|stacking an adhesive layer, the influence on the light transmittance of an adhesive sheet is small.

The thickness of the substrate is preferably in the range of 40 to 200 μm, more preferably 50 to 150 μm.

The base material further contains various additives such as lubricants, antioxidants, ultraviolet absorbers, processing aids, fillers, antistatic agents, stabilizers, antibacterial agents, flame retardants, colorants such as pigments and dyes, within the scope not impairing the object of the present invention may be Moreover, although it is preferable that the base material contains only the acrylic copolymer (A) as a resin component, it may contain resin components other than an acrylic copolymer (A) as needed. Although the acrylic polymer (A) should just be a main component for a base material, it contains 80 mass % or more of acrylic copolymer (A) normally, Preferably it is 90 mass % or more, More preferably, it contains 95 mass % or more.

Although the molding method of the base material (acrylic film) of this invention is not specifically limited, Although the inflation method, extrusion molding using a T-die etc., calender molding etc. are mentioned, Among these, extrusion molding is preferable. In addition, in order to obtain said center line average roughness Ra, the surface state of a base material can be suitably adjusted, for example by pressurizing an extruded film to an embossing roll.

[Adhesive layer]

The pressure-sensitive adhesive layer is formed of various pressure-sensitive adhesives, and the pressure-sensitive adhesive is not limited at all. For example, a rubber-based, acrylic-based, silicone-based, polyvinyl ether-based pressure-sensitive adhesive is used, and among these, an acrylic pressure-sensitive adhesive is preferred. When an acrylic adhesive is used, since an adhesive will be comprised from the polymer of the same kind as a base material, the refractive index of a base material and an adhesive layer can be approximated. Thereby, it becomes easy to prevent reflection of a laser beam at the interface of a base material and an adhesive layer.

Moreover, energy-beam hardening type, heat foaming type, and water-swelling type adhesive can also be used for an adhesive. As an energy-beam hardening (ultraviolet-ray hardening, electron beam hardening, etc.) type adhesive, it is preferable to use especially an ultraviolet-curing type adhesive. By using an energy ray-curable pressure-sensitive adhesive, the adherend can be reliably held or protected in a state in which the pressure-sensitive adhesive sheet is affixed to an adherend such as a semiconductor wafer or a semiconductor chip. On the other hand, when the chip is peeled from the adhesive sheet by pickup or the like, the adhesive sheet can be peeled from the chip without damaging the chip and leaving the adhesive on the chip by irradiating energy rays to reduce the adhesive strength of the adhesive layer.

In addition to the adhesive component for providing adhesiveness, the adhesive composition which comprises an adhesive layer may contain other components, such as a crosslinking agent, as needed in order to improve various physical properties. Examples of the crosslinking agent include an organic polyvalent isocyanate compound, an organic polyvalent epoxy compound, and an organic polyvalent imine compound. In addition, when forming the pressure-sensitive adhesive layer with an energy ray-curable pressure-sensitive adhesive, it is preferable to form the pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition in which an energy ray-curable pressure-sensitive adhesive component and, if necessary, a photopolymerization initiator are blended.

Hereinafter, an example in which an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive will be specifically described. When an acrylic pressure-sensitive adhesive is used as the pressure-sensitive adhesive, the pressure-sensitive adhesive composition contains an acrylic polymer (X) as a pressure-sensitive adhesive component in order to impart sufficient tackiness and film formability (sheet workability). As an acrylic polymer (X), the conventionally well-known acrylic polymer used for an adhesive can be used. It is preferable that it is 10,000-2 million, and, as for the weight average molecular weight (Mw) of an acrylic polymer (X), it is more preferable that it is 100,000-1,500,000.

As a monomer which comprises the said acrylic polymer (X), a (meth)acrylic acid ester monomer or its derivative(s) is mentioned. For example, alkyl (meth) acrylates having 1 to 18 carbon atoms in the alkyl group, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth)acrylate, etc. are mentioned; (meth)acrylate having a cyclic skeleton, for example, cycloalkyl (meth)acrylate, benzyl (meth)acrylate, isobornyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclophene tenyloxyethyl acrylate and imide acrylate; 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate which have a hydroxyl group are mentioned, Acrylic acid, methacrylic acid, itaconic acid, glycidyl methacrylate, glycidyl acryl rate etc. are mentioned. Further, the acrylic polymer (X) may be an acrylic copolymer copolymerized with vinyl acetate, acrylonitrile, styrene, or the like.

In addition, when an acrylic adhesive is an energy-beam curable adhesive, an energy-beam curable adhesive component further contains an energy-beam curable compound (Y) in addition to an acrylic polymer (X). The energy-ray-curable compound (Y) contains an energy-beam polymerizable group, and when irradiated with energy rays, such as an ultraviolet-ray and an electron beam, polymerization-hardening will be carried out, and it has a function which reduces the adhesive force of an adhesive composition. In addition, as an energy ray-curable adhesive component, it combines the properties of the components (X) and (Y), and an energy ray-curable adhesive polymer in which an energy ray polymerizable group is bonded to a main chain or side chain (hereinafter referred to as (XY) component) may be used). Such an energy-ray-curable adhesive polymer (XY) has a property of having both adhesiveness and energy-beam curability.

The energy ray-curable compound (Y) is a compound that polymerizes and cures when irradiated with energy rays such as ultraviolet rays and electron beams. As an example of this energy-beam polymeric compound, the low molecular-weight compound (monofunctional and polyfunctional monomer and oligomer) which has an energy-beam polymeric group is mentioned, Specifically, trimethylol propane triacrylate, tetramethylol methane tetraacrylic rate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, etc. Cyclic aliphatic skeleton-containing acrylates such as acrylate, dicyclopentadiene dimethoxydiacrylate, and isobornyl acrylate, polyethylene glycol diacrylate, oligoester acrylate, urethane acrylate oligomer, epoxy-modified acrylate, polyether acryl An acrylate-based compound such as a lactate or itaconic acid oligomer is used. Such compounds have at least one polymerizable double bond in the molecule, and usually have a molecular weight or a weight average molecular weight (Mw) of 100 to 30000, preferably about 300 to 10000. Generally, (Y) component is 10-400 mass parts with respect to 100 mass parts of (X) component, Preferably it is used in the ratio of about 30-350 mass parts.

The energy ray-curable adhesive polymer (XY) having both the properties of the components (X) and (Y) is formed by bonding an energy ray polymerizable group to a main chain or a side chain. The main skeleton of the energy ray-curable pressure-sensitive adhesive polymer (XY) is not particularly limited, and may be the same as the above-described acrylic copolymer commonly used as an adhesive.

The energy ray polymerizable group bonded to the main chain or side chain of the energy ray-curable adhesive polymer is, for example, a group containing an energy ray polymerizable carbon-carbon double bond, and specifically, a (meth) acryloyl group may be exemplified. there is. The energy ray polymerizable group may be bonded to the energy ray curing adhesive polymer via an alkylene group, an alkyleneoxy group or a polyalkyleneoxy group.

It is preferable that it is 10,000-2 million, and, as for the weight average molecular weight (Mw) of the energy-beam-curable adhesive polymer (XY) to which the energy-beam polymeric group couple|bonded, it is more preferable that it is 100,000-1,500,000.

The energy ray-curable adhesive polymer (XY) includes, for example, an acrylic adhesive polymer containing a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, and an epoxy group, and a substituent reacting with the functional group and energy ray polymerizable carbon-carbon. It is obtained by reacting a polymerizable group-containing compound having 1 to 5 double bonds per molecule. The acrylic adhesive polymer is preferably a copolymer comprising a monomer constituting component (X) including a (meth)acrylic acid ester monomer having a functional group such as a hydroxyl group, a carboxyl group, an amino group, a substituted amino group, and an epoxy group or a derivative thereof. Examples of the polymerizable group-containing compound include (meth)acryloyloxyethyl isocyanate, meta-isopropenyl-α, α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, glycidyl (meth)acrylate; (meth)acrylic acid etc. are mentioned.

The energy-beam-curable adhesive component containing the above acrylic polymer (X) and an energy-ray-curable compound (Y), or an energy-beam-curable adhesive polymer (XY) can be hardened by energy-beam irradiation. As an energy beam, an ultraviolet-ray, an electron beam, etc. are specifically used.

As a photoinitiator, photoinitiators, such as a benzoin compound, an acetophenone compound, an acylphosphine oxide compound, a titanocene compound, a thioxanthone compound, a peroxide compound, Photosensitizers, such as an amine and a quinone, etc. are mentioned, Specifically, 1-hydroxycyclohexylphenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyro nitrile, dibenzyl, diacetyl, β-chloroanthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide and the like can be exemplified. When using an ultraviolet-ray as an energy ray, irradiation time and irradiation amount can be decreased by mix|blending a photoinitiator.

Although the thickness of an adhesive layer is not specifically limited, Preferably it is 1-20 micrometers, More preferably, it is 2-15 micrometers, More preferably, it is the range of 3-10 micrometers. When the thickness of an adhesive layer exists in the said range, a semiconductor wafer can be hold|maintained favorably, and it can prevent that a chip|tip and a ring frame fall off at the time of expansion. Moreover, when the thickness of an adhesive layer exists in the said range, the pick-up process of a semiconductor chip can be performed favorably.

It is preferable that they are 85% or more of total light transmittance and HAZE 7% or less, and, as for the adhesive sheet of this invention, it is more preferable that they are 90% or more of transmittance|permeability and 6% or less of HAZE. When the pressure-sensitive adhesive sheet has such transmittance and HAZE, even if a laser beam is irradiated to a semiconductor wafer or the like through the pressure-sensitive adhesive sheet, the workability by destroying the modified portion can be improved.

In addition, a release sheet may be laminated on the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer before use. The release sheet is not particularly limited, and for example, a film containing a resin such as polyethylene terephthalate, polypropylene, polyethylene, etc. or a foamed film thereof, or a paper such as glassine paper, coated paper, or laminated paper, silicone-based, fluorine-based, long-chain What was peeled off with release agents, such as an alkyl group containing carbamate, can be used.

In the method of forming the pressure-sensitive adhesive layer on one side of the substrate, the pressure-sensitive adhesive layer formed by coating to a predetermined film thickness on the release sheet may be transferred to the surface of the substrate, or applied directly to the surface of the substrate to form the pressure-sensitive adhesive layer. may be

[Method for manufacturing chip-like member]

Next, the method of manufacturing a chipped member using the adhesive sheet which concerns on this invention is demonstrated. The manufacturing method of the chip-like member comprises the steps of affixing the above-described pressure-sensitive adhesive sheet to one surface of the plate-like member, irradiating a laser beam to the plate-like member through the pressure-sensitive adhesive sheet affixed to the plate-like member to form a modified portion; The step of dividing the plate-like member into chips by expanding to obtain the chip-like member is provided.

Hereinafter, an example in the case of manufacturing a semiconductor chip in which a plate-shaped member is a semiconductor wafer about this manufacturing method is demonstrated in detail, referring FIG.2, FIG.3.

First, a circuit is formed on the surface of the semiconductor wafer 14 . The semiconductor wafer 14 may be a silicon wafer, or a wafer of gallium arsenide, etc. may be sufficient as it. Formation of the circuit on the wafer surface can be performed by various methods including methods commonly used conventionally, such as an etching method and a lift-off method. Although the thickness of the wafer 14 before grinding is not specifically limited, Usually, it is about 500-1000 micrometers.

Next, the back surface of the semiconductor wafer 14 is ground. In the case of back grinding, in order to protect the circuit on the surface, a surface protection sheet composed of a conventionally known adhesive tape is affixed to the circuit surface. In the back surface grinding, the circuit surface side (that is, the surface protection sheet side) of the wafer 14 is fixed by a chuck table or the like, and the back surface side on which no circuit is formed is ground with a grinder. As a result, although the thickness of the semiconductor wafer 14 after grinding is not specifically limited, Usually, it is set to about 50-200 micrometers. After the backside grinding step, a step of removing the crushed layer generated by the grinding may be performed.

Following the backside grinding step, if necessary, a processing treatment involving heat generation such as an etching treatment on the backside, or a treatment performed at a high temperature such as vapor deposition of a metal film on the backside or baking of an organic film may be performed. Moreover, when performing a process at high temperature, after peeling a surface protection sheet normally, the process with respect to the back surface is performed.

After the back surface grinding, the adhesive sheet 10 according to the present invention is attached to the back surface of the wafer 14 through the adhesive layer 12 . In addition, when the surface protection sheet is affixed on the wafer surface, the surface protection sheet is peeled before or after pasting of the adhesive sheet 10. Although sticking of the adhesive sheet 10 to the back surface of a wafer is generally performed by the apparatus called a mounter, there is no restriction|limiting in particular. Normally, the semiconductor wafer 14 is affixed to the central region 10A of the pressure-sensitive adhesive sheet 10 as shown in Fig. 2, and to the periphery 10B of the outer peripheral region 10C outside the central region 10A A ring frame 13 is affixed. A ring frame supports an adhesive sheet in each process mentioned later.

Then, as shown in FIG. 2 , a laser beam is irradiated to the wafer 14 through the adhesive sheet 10 from the base 11 side of the adhesive sheet 10 . The laser light source 15 for irradiating laser light is a device that generates light with even wavelength and phase, and the types of laser light include Nd-YAG laser, Nd-YVO laser, Nd-YLF laser, and titanium that generate pulsed laser light. What causes multiphoton absorption, such as a sapphire laser, is mentioned. 800-1100 nm is preferable and, as for the wavelength of a laser beam, 1064 nm is more preferable.

The laser beam is irradiated into the wafer to form the modified portion 16 in the wafer along the line to be cut. The number of times the laser beam scans one line to be cut may be one or a plurality of times. Preferably, the laser beam is irradiated while the position of the laser beam is irradiated and the position of the line to be cut between circuits is monitored, and the laser beam is aligned.

After the reforming portion 16 is formed inside the wafer by laser light irradiation, expansion is performed. Although the expand is not specifically limited, Usually, it is performed by providing the tension|tensile_strength from the center of the adhesive sheet 10 toward the surface direction outer side. More specifically, as shown in FIG. 3 , an outer peripheral region that is a region between the central region 10A of the pressure-sensitive adhesive sheet 10 provided with a plurality of semiconductor chips and the peripheral portion 10B supported by the ring frame 13 . A method in which, for example, a tubular jig 20 is applied to a part of (10C), the peripheral portion 10B is pulled toward the direction of gravity, and descended is exemplified.

By the expansion of this adhesive sheet 10, the semiconductor wafer 11 is cut and separated into individual chips 18 with the reforming part 16 inside the wafer as a starting point. In addition, the wafer 10 may be cut and separated into chips 18 by vigorously scraping the adhesive sheet 10 from the base 11 side using a jig or the like simultaneously with the expansion. The expand is preferably performed at a speed of 5 to 600 mm/min.

Thereafter, the periphery 10B lowered in the gravitational direction is raised and returned to its original position, and the outer periphery region 10C (more specifically, the region between the periphery 10B and the central region 10A) is removed. By heating by a heating means (not shown), the pressure-sensitive adhesive sheet at a portion corresponding to the heated region is heat-shrinked. Relaxation of the outer peripheral region 10C is prevented by this step, and the transportability of the pressure-sensitive adhesive sheet 10 to which the semiconductor chip 18 is affixed is not lowered when being transported to a pickup device or the like.

Thereafter, each chip 18 is picked up by a pickup device, and a semiconductor device is manufactured through a bonding process. In addition, when the pressure-sensitive adhesive layer 12 is formed of an energy-beam curable pressure-sensitive adhesive, it is preferable to irradiate the energy-beam before the pick-up process to reduce the adhesive force of the pressure-sensitive adhesive to facilitate peeling of the chip 18 .

As mentioned above, although the use example of the adhesive sheet of this invention was demonstrated, the adhesive sheet of this invention is various plate-shaped members, such as a metal material, such as organic material substrates, such as a glass substrate, a ceramic substrate, FPC, or precision components, in addition to a semiconductor wafer. It can be used in a method of obtaining various chip-like members by dicing.

<Example>

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these examples.

The measuring method and evaluation method in this invention are as follows.

[Weight Average Molecular Weight (Mw)]

About the acrylic copolymer used for the base material, it measured on the following conditions.

Device: Painter HLC-8121GPC/HT

Column: Shodex GPC HT-806M×2

Oven temperature: 135℃

Eluent: dichlorobenzene

In addition, about the acrylic polymer used for the adhesive composition, it measured on the following conditions.

It measured under the following conditions using the gel permeation chromatography apparatus (The Tosoh Corporation make, product name "HLC-8020"), and the value measured by standard polystyrene conversion was used.

(Measuring conditions)

Column: "TSK guard column HXL-H" "TSK gel GMHXL (x2)" "TSK gel G2000HXL" (all manufactured by Tosoh Corporation)

·Column temperature: 40℃

·Developing solvent: tetrahydrofuran

·Flow rate: 1.0mL/min

[Young's modulus evaluation]

Using a universal tensile testing machine (Tensilon RTA-T-2M manufactured by Orientec Co., Ltd.), the tensile strength and elongation of the substrate were measured at 23° C. 50 RH% environment, with a width of 15 mm and a length between chucks of 100 mm and a tensile rate of 200 mm/min. It measured and obtained the Young's modulus from these.

[Transmittance evaluation]

According to JIS 7361-1:1997, the total light transmittance of the adhesive sheet was measured using a haze meter (NDH-5000 manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[HAZE evaluation]

Based on JIS 7136:2000, the HAZE of the adhesive sheet was measured using the haze meter (NDH-5000 manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[Centerline Average Roughness Ra]

The center line average roughness Ra was measured according to JIS B-6001 using SV-3000S4 manufactured by Mitsutoyo Corporation.

[Division aptitude evaluation]

A silicon wafer and a ring frame were attached to the pressure-sensitive adhesive sheet, and a laser was irradiated through the pressure-sensitive adhesive sheet under the following division conditions to form a modified portion inside the wafer.

(division condition)

Laser: Nd-YAG

Wavelength: 1064nm

Repetition Frequency: 100kHz

Pulse width: 30nm

Machining speed: 100mm/min

Silicon wafer: diameter 200 mmφ, thickness 10 μm

Chip size: 5mm×5mm

Then, using the expand apparatus (ME-300B made from JCM), the periphery of the adhesive sheet was sagged by 25 mm of sag, and it expanded, and the silicon wafer was divided into pieces.

(Processability evaluation)

The cross section of the fragmented chip was observed with a digital microscope (VHX-1000 manufactured by KEYENCE), and "A", in the case where the reformed parts by the laser were formed in a straight line at regular intervals, the spacing of the reformed parts was non-uniform. Otherwise, the case where the line connecting the modified portion did not become a straight line was evaluated as “E”.

(Expandability evaluation)

Moreover, the chip|tip divided into pieces as mentioned above was transcribe|transferred to the transfer sheet, and the chip|tip space|interval was measured with the digital microscope (VHX-1000 manufactured by Keyens Corporation). For the chip spacing, an average value was calculated by measuring 9 arbitrary points.

(Evaluation of heat shrinkability (HS))

After transferring the chip, the workpiece (i.e., the adhesive sheet attached to the ring frame) is placed on a hot plate (made of heated surface iron) heated to 50°C for 30 seconds, and the loosening of the adhesive sheet is completely eliminated. ", the case where relaxation was not resolved or wrinkles occurred was designated as "E".

[Example 1]

(Preparation of adhesive composition)

34 parts by mass of an acrylic polymer (constituting monomer ratio: butyl acrylate/acrylic acid = 90/10 (mass ratio), weight average molecular weight: 600,000, a diluted solution having a concentration of 34% by mass diluted with a solvent), an energy-beam polymerizable compound (hexafunctionality) 30 parts by mass of an acrylate oligomer, Mw=2000, a diluent having a concentration of 90% by mass diluted with a solvent), 0.1 parts by mass of a photopolymerization initiator ("Irgacure 184" manufactured by BASF), an epoxy-based crosslinking agent (tetrad ( TETRAD)-C Mitsubishi Gas Chemical Co., Ltd.) 0.04 mass parts (all are parts in conversion of solid content) were mix|blended, and the adhesive composition diluted with the solvent was obtained.

(production of equipment)

By random copolymerizing butyl acrylate (BA) and methyl methacrylate (MAA) in a mass ratio of 30:70, an acrylic copolymer (A1) having a weight average molecular weight of 1 million and an acrylic polymer (A2) having a weight average molecular weight of 50,000 were obtained, respectively. was produced, and a mixture of these at a mixing ratio of 10:90 was extruded and pressed to an embossing roll while forming a film to obtain an acrylic film having a thickness of 80 µm. The acrylic film had a centerline average roughness Ra of 0.281 µm on one surface (first surface), and a centerline average roughness Ra of 0.084 µm on the other surface (second surface).

(Production of adhesive sheet)

The pressure-sensitive adhesive composition prepared above is applied on a release film (SP-PET381031, manufactured by Lintec Co., Ltd.) so that the thickness after drying becomes 5 μm, and dried at 80° C. for 1 minute. The formed pressure-sensitive adhesive layer is applied to an acrylic film as a substrate It bonded and obtained the adhesive sheet provided with the peeling sheet. In addition, bonding of the adhesive layer was performed with respect to the 1st surface.

[Example 2]

An acrylic copolymer (A1) having a weight average molecular weight of 1,000,000 obtained by random copolymerizing butyl acrylate and methyl methacrylate in a mass ratio of 30:70 to an acrylic copolymer (A2) having a weight average molecular weight of 50,000 (A2) in a mass ratio of 20 : It carried out similarly to Example 1 except having changed into the 80-micrometer-thick acrylic film obtained by mixing in the ratio of :80 and forming the mixture into a film by extrusion molding.

[Example 3]

An acrylic copolymer (A1) having a weight average molecular weight of 1 million, obtained by random copolymerizing butyl acrylate and methyl methacrylate in a mass ratio of 20:80, and an acrylic copolymer (A2) having a weight average molecular weight of 50,000, as the substrate, in a mass ratio of 10 : It carried out similarly to Example 1 except having changed into the 80-micrometer-thick acrylic film obtained by mixing in the ratio of:90 and forming the mixture into a film by extrusion molding.

[Example 4]

An acrylic copolymer (A1) having a weight average molecular weight of 1,000,000 obtained by random copolymerization of butyl acrylate and methyl methacrylate in a mass ratio of 20:80 to an acrylic copolymer (A2) having a weight average molecular weight of 50,000 as the base material in a mass ratio of 20 : It carried out similarly to Example 1 except having changed into the 80-micrometer-thick acrylic film obtained by mixing in the ratio of :80 and forming the mixture into a film by extrusion molding.

[Comparative Example 1]

It implemented similarly to Example 1 except the point which changed the acrylic film into the 80-micrometer-thick EMAA (ethylene methacrylic acid copolymer resin) film whose constituent monomer ratio is ethylene/methacrylic acid =91/9 (mass ratio).

[Comparative Example 2]

It implemented similarly to Example 1 except having changed the acrylic film into EVA (ethylene vinyl acetate copolymer resin) film ("Funcle LEB" manufactured by Gunze Corporation, thickness 120 micrometers).

[Comparative Example 3]

It implemented similarly to Example 1 except having changed the acrylic film of Example 1 into the PVC film (25 mass % of diethylhexyl phthalate addition amount, 80 micrometers in thickness).

[Comparative Example 4]

It implemented similarly to Example 1 except the point which changed the acrylic film of Example 1 into the PP (polypropylene) film of thickness 80 micrometers.

Table 1 shows the measurement results and evaluation results for the substrates and pressure-sensitive adhesive sheets of the above Examples and Comparative Examples.

As is clear from Examples 1 to 4 above, the base material is an alkyl (meth)acrylate (a) having 4 to 8 carbon atoms in the alkyl group, and an alkyl (meth)acrylate (b) having 1 to 3 carbon atoms in the alkyl group. By comprising the acrylic copolymer (A), which is a copolymer of Therefore, the chip gap was sufficiently widened by the expansion, and the relaxation caused by the expansion due to the thermal shrinkage could be appropriately eliminated. Moreover, since the transmittance|permeability and HAZE became favorable values by the base material being comprised with the acrylic copolymer (A), a modified part was able to be formed with high precision by laser processing. Further, the substrate had an appropriate Young's modulus, and had excellent mechanical strength and blocking resistance.

On the other hand, in Comparative Examples 1 to 4 in which the base material other than the acrylic copolymer (A) was used, any one of the expandability, heat shrinkability, and laser transmittance of the base material did not become satisfactory, and the plate-like member was irradiated with laser light to form a modified portion It did not exhibit the outstanding performance as an adhesive sheet used for forming and dividing a plate-shaped member into chips.

10 adhesive sheet
10A central area
10B starring
10C Outer area
11 description
12 Adhesive layer
13 ring frame
14 Semiconductor wafer (plate-shaped member)
15 laser light source
16 reformers
18 semiconductor chip
20 jig

Claims (15)

A pressure-sensitive adhesive sheet used for forming a modified portion by irradiating a plate-shaped member with a laser beam, and dividing the plate-shaped member into chips, comprising:
A substrate and an adhesive layer provided on one side of the substrate,
The base material is an acrylic copolymer (A) which is a copolymer of an alkyl (meth)acrylate (a) having 4 to 8 carbon atoms in the alkyl group and an alkyl (meth)acrylate (b) having 1 to 3 carbon atoms in the alkyl group The adhesive sheet containing the acrylic film containing. The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic copolymer (A) is a copolymer of an alkyl (meth) acrylate (a) and an alkyl (meth) acrylate (b) in a mass ratio of 10:90 to 40:60. . The adhesive sheet according to claim 1 or 2, wherein the acrylic copolymer (A) is a random copolymer. The acrylic copolymer (A) according to claim 1 or 2, wherein the acrylic copolymer (A) has an acrylic copolymer (A1) having a weight average molecular weight of 600,000 or more and 1.3 million or less, and an acrylic copolymer (A1) having a weight average molecular weight of 10,000 or more and 400,000 or less ( A2) is mixed, the adhesive sheet. The pressure-sensitive adhesive sheet according to claim 4, wherein the mixing ratio of the acrylic copolymer (A1) and the acrylic copolymer (A2) is 5:95 to 35:65 by mass. The alkyl (meth)acrylate (a) is an alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, and the alkyl (meth)acrylate (b) has 1 carbon atom in the alkyl group. to 3 alkyl methacrylate, the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet according to claim 6, wherein the alkyl (meth)acrylate (a) is butyl acrylate, and the alkyl (meth)acrylate (b) is methyl methacrylate. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the substrate has a Young's modulus of 50 to 500 MPa. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the centerline average roughness Ra of the surface opposite to one surface of the substrate is 0.02 µm or more and 0.1 µm or less. The adhesive sheet of Claim 1 or 2 whose centerline average roughness Ra of one side of the said base material is 0.15 micrometer or more and 3.0 micrometers or less. The adhesive sheet according to claim 1 or 2, wherein the total light transmittance is 85% or more and the HAZE is 7% or less. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is formed from an acrylic pressure-sensitive adhesive. A step of affixing the pressure-sensitive adhesive sheet according to claim 1 or 2 on one surface of the plate-like member;
forming a modified part by irradiating a laser beam to the plate-shaped member through the pressure-sensitive adhesive sheet affixed to the plate-shaped member;
The method for manufacturing a chipped member comprising the steps of dividing the plate-like member into chips by expanding the pressure-sensitive adhesive sheet to obtain a chipped member. 14. The method according to claim 13, wherein the chip-like member is affixed to the central region of the pressure-sensitive adhesive sheet,
The manufacturing method of the chip|tip member further comprising the process of heating and shrinking|contracting the outer peripheral area|region of the adhesive sheet which is an outer area|region of the said center area|region. 3. The method of claim 1 or 2,
The said base material is an adhesive sheet in which the said acrylic copolymer (A) contains the acrylic film containing 80 mass % or more.

Images