JP6731852B2 - Adhesive sheet and method for manufacturing processed product - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive sheet for irradiating a plate-shaped member with a laser beam to form a modified portion, and separating the plate-shaped member into individual pieces to obtain a chip-shaped processed product. The present invention also relates to a method for producing a processed product such as a chip using the above-mentioned pressure-sensitive adhesive sheet.

After a circuit is formed on the front surface of a semiconductor wafer, the back surface side of the wafer is ground to perform a back grinding step of adjusting the thickness of the wafer and a dicing step of singulating the wafer into a predetermined chip size.

Along with the recent size reduction of electronic device housings and the increasing demand for semiconductor devices using multi-layered chips, semiconductor chips, which are the constituent members, are being made thinner. For this reason, it has become necessary to reduce the thickness of a wafer, which has conventionally been about 350 μm, to 50 to 100 μm or less.

As the wafer, which is a brittle member, becomes thinner, the risk of breakage during processing and transportation increases. When such an ultra-thin wafer is cut by a dicing blade that rotates at a high speed, chipping or the like occurs particularly on the back surface side of the semiconductor wafer, and the bending strength of the chip is significantly reduced.

Therefore, a so-called stealth dicing method has been proposed in which a semiconductor wafer is cut by irradiating the inside of a semiconductor wafer with a laser beam to selectively form a modified portion while forming a dicing line and starting the modified portion. (Patent Document 1). According to the stealth dicing method, after irradiating the inside of a semiconductor wafer with a laser beam to form a modified portion, an extremely thin semiconductor wafer is attached to an adhesive sheet (dicing sheet) including a base material and an adhesive layer, By expanding the dicing sheet, the semiconductor wafer can be divided (diced) along the dicing line, and semiconductor chips can be produced with high yield. It has also been proposed to form a modified portion by irradiating laser light after attaching a semiconductor wafer to a dicing sheet. By adopting such a process, there is no step of attaching the dicing tape to the wafer that has become fragile due to the formation of the modified portion, so that the risk of damaging the fragile wafer can be reduced. In this case, since the laser is normally irradiated from the circuit non-forming surface of the wafer, it is necessary to pass the laser through the dicing sheet.

A laser may be used as a processing means in the dicing process as described above, or a laser may be used as a tool for accurately aligning a plate-shaped member such as a semiconductor wafer during the dicing process. In such a case, the pressure-sensitive adhesive sheet used in the case of using a laser beam in the dicing step (in the present specification, this pressure-sensitive adhesive sheet is also referred to as “laser dicing sheet”), the laser dicing sheet is If the laser is transparent, it must have excellent transparency to the laser light.

In order to meet such a demand, for example, in Patent Document 2, a laser dicing sheet comprising a substrate and an adhesive layer formed on one surface thereof has a total light transmittance in a wavelength range of 300 to 400 nm. Disclosed is a laser dicing sheet having a haze of 60% or more, a haze of 20% or less, and a transmission definition of 30 or more at an optical comb width of 0.25 mm.

JP, 2005-229040, A Japanese Patent No. 5124778

Patent Document 2 discloses the above laser dicing sheet, in which the center line average roughness Ra of one surface of the substrate is larger than the center line average roughness Ra of the other surface, and the surface having a large center line average roughness Ra. The pressure-sensitive adhesive layer is formed on the surface of the base material having a center line average roughness Ra of 0.3 to 0.7 μm as a pressure-sensitive adhesive layer forming surface, and the center line of the surface opposite to the surface of the base material. A laser dicing sheet having an average roughness Ra of 0.14 μm is disclosed (Patent Document 2 Example).

Since such a laser dicing sheet has a smooth surface on the side on which the laser is incident, that is, the surface on the side opposite to the pressure-sensitive adhesive layer forming surface of the base material, scattering of laser light on the base material surface is prevented. It is prevented and effective use of laser light is achieved.

By the way, a processed product such as a semiconductor chip manufactured from a plate-shaped member such as a semiconductor wafer using a laser dicing sheet tends to have a thinner thickness. Further, in recent years, the packaging density has increased, and a silicon wafer may be used as a substrate instead of which a chip may be stacked using a Si through electrode (TSV, Through-Silicon Via). When the processed product is thin or the processed product has a structure based on TSV, the adhesive layer of the laser dicing sheet is easily peeled from the processed product attached to the adhesive layer. It is preferable that it is capable (excellent in pick-up property).

On the other hand, in the laser dicing sheet described in Patent Document 2, there are cases where the pressure-sensitive adhesive layer is not properly formed on the substrate. Such a portion is observed as a defect in a plan view of the laser dicing sheet, and there is a possibility that the laser beam incident on the plate-shaped member for processing the plate-shaped member may have non-uniformity.

The present invention provides a pressure-sensitive adhesive sheet used when a laser beam is used in a dicing process, which is less likely to cause defects and has excellent pickup properties, and a plate-shaped pressure-sensitive adhesive sheet using the pressure-sensitive adhesive sheet. It is an object to provide a method for manufacturing a work piece from a member.

In order to achieve the above object, the present inventors have studied and found that the thickness of the pressure-sensitive adhesive layer is 2 μm or more and 12 μm or less, and the arithmetic average roughness Ra of both surfaces of the base material is 0.2 μm or less. The present inventors have obtained a new finding that a pressure-sensitive adhesive sheet having excellent pickup properties can be obtained while stably reducing the possibility that defects will occur.
The present invention completed based on the above findings is as follows.

(1) A pressure-sensitive adhesive sheet used for irradiating a plate-shaped member with a laser beam to form a modified portion, and dividing the plate-shaped member into chips, which comprises a base material and one of And a pressure-sensitive adhesive layer provided on a surface of the base material, and the base material is provided on both of the one surface and the surface on the opposite side of the one surface with the arithmetic prescribed in JIS B0601:2013 (ISO 4287:1997). A pressure-sensitive adhesive sheet, wherein the average roughness Ra is 0.01 μm or more and 0.2 μm or less, and the thickness of the pressure-sensitive adhesive layer is 2 μm or more and 12 μm or less.

(2) The pressure-sensitive adhesive sheet has a haze defined by JIS K7136:2000 (ISO 14782:1999) of 0.01% or more and 10% or less when the substrate side is the incident side. ) Adhesive sheet described in.

(3) The pressure-sensitive adhesive layer according to (1) or (2) above, wherein the pressure-sensitive adhesive layer contains an acrylic polymer, and the glass transition temperature Tg of the acrylic polymer is −40° C. or higher and −10° C. or lower. Sheet.

(4) The acrylic polymer contains a structural unit derived from methyl methacrylate, and the mass ratio of methyl methacrylate to the total monomers giving the acrylic polymer is 5% by mass or more and 20% by mass or less. The pressure-sensitive adhesive sheet according to (3).

(5) The pressure-sensitive adhesive sheet according to (3) or (4) above, wherein the acrylic polymer has an energy ray-polymerizable group.

(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5) above, wherein the base material contains a polyolefin material.

(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6), wherein the arithmetic average roughness Ra of the base material is set to include roll pressing of the base material.

(8) The pressure-sensitive adhesive sheet according to (7), wherein the roll used for pressing the roll is a roll having a surface made of a metal material.

(9) A surface of the pressure-sensitive adhesive sheet according to any one of (1) to (8), which is closer to the pressure-sensitive adhesive layer than the base material, is provided on one surface of an adherend including a plate-shaped member. A step of sticking to obtain a first laminate including the pressure-sensitive adhesive sheet and the plate-like member; a plate-like member on the pressure-sensitive adhesive sheet by extending the base material included in the first laminate. A dividing step for obtaining a second laminated body in which a plurality of chips each including the divided body of the plate-shaped member are arranged on the adhesive sheet; and the plurality of chips included in the second laminated body. Each of which is separated from the pressure-sensitive adhesive sheet, and comprises a pickup step of obtaining the chips as a workpiece, and by the time the division step is started, the chips are focused at a focus set inside the plate-shaped member. A method of manufacturing a processed product, comprising performing a modified portion forming step of forming a modified portion inside the plate-shaped member by irradiating a laser beam.

(10) The first laminated body provided in the dividing step includes an additional layer between the pressure-sensitive adhesive layer and the plate-shaped member, and the additional layer is also divided by the dividing step, and the pickup step. The chip separated from the adhesive sheet by means of the divided body of the plate-like member and the divided body of the additional layer formed on the surface of the divided body of the plate-like member proximal to the adhesive sheet, The method for producing a processed product according to 9).

(11) The method for manufacturing a processed product according to (10), wherein the additional layer includes a protective layer.

(12) Manufacture of the processed product according to (11) above, which includes a protective film forming step of forming the protective layer of the first laminate from a protective film forming film before the division step is started. Method.

(13) The method for manufacturing a processed product according to (10), wherein the additional layer includes a die bonding layer.

ADVANTAGE OF THE INVENTION According to this invention, the pressure-sensitive adhesive sheet which is hard to produce a defect and has the outstanding pick-up property is provided. Moreover, by using such an adhesive sheet, it becomes possible to stably manufacture a processed product from a plate-shaped member.

Hereinafter, embodiments of the present invention will be described.

1. Adhesive Sheet An adhesive sheet according to an embodiment of the present invention includes a base material and an adhesive layer.

(1) Substrate The substrate of the pressure-sensitive adhesive sheet according to the present embodiment has a surface facing the pressure-sensitive adhesive layer (also referred to as “pressure-sensitive adhesive processed surface” in the present specification) and a surface opposite to the pressure-sensitive adhesive processed surface. For both surfaces (also referred to as “laser incidence surface” in the present specification), the arithmetic mean roughness Ra (hereinafter, “arithmetic mean roughness Ra”, which is not specified, is defined in JIS B0601:2013 (ISO 4287:1997). Is used in this sense.) is 0.2 μm or less. Since the arithmetic average roughness Ra of these surfaces is 0.2 μm or less, it is difficult to observe defects in the plan view of the pressure-sensitive adhesive sheet. Therefore, the laser light incident from the base material side of the adhesive sheet easily reaches the plate-shaped member to which the adhesive sheet is attached uniformly. When such a laser beam reaches the plate-shaped member unevenly, for example, a portion in which the modified portion is not appropriately formed is formed in the plate-shaped member, and it is appropriate to separate the plate-shaped member at this portion. There is a high possibility that problems such as not being performed will occur. From the viewpoint of improving the uniformity of the incident laser light, the arithmetic mean roughness Ra is preferably 0.18 μm or less, and is 0.16 μm or less for both the pressure-sensitive adhesive processed surface and the laser incident surface. It is more preferably 0.14 μm or less, still more preferably 0.12 μm or less. From the viewpoint of obtaining a pressure-sensitive adhesive sheet that is less likely to cause defects in plan view, the lower limit of the arithmetic mean roughness Ra of the pressure-sensitive adhesive processed surface is not limited. From the viewpoint of maintaining manufacturing stability, it is preferable that the arithmetic mean roughness Ra of both the pressure-sensitive adhesive processed surface and the laser incident surface is 0.01 μm or more.

The constituent material of the base material according to the embodiment of the present invention can satisfy the above conditions regarding the arithmetic mean roughness Ra and can be used as a base material of a laser dicing sheet, that is, a laser beam having a desired wavelength can be used. It is possible to transmit with a transmittance within a practical range, as long as it satisfies the request that it is difficult to break even if it is stretched in the in-plane direction or locally projected in the thickness direction. There is no limitation. The base material according to the embodiment of the present invention is usually composed of a film containing a resin material as a main material. This film may be a single layer or a laminate.

Specific examples of the resin material contained in the film include polypropylene such as random copolymer polypropylene and block copolymer polypropylene, polyethylene such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). Ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, ethylene-norbornene copolymer and other ethylene-based copolymers, norbornene resin, etc. Cycloolefin polymer (COP) Polyolefin materials such as polybutene, polybutadiene and polymethylpentene; Polyvinyl chloride materials such as polyvinyl chloride and vinyl chloride copolymer; Polyester materials such as polyethylene terephthalate and polybutylene terephthalate; Polyurethane materials Materials; Polyimide materials; Ionomer resin materials; Polyacrylic materials such as alkyl (meth)acrylate homopolymers and alkyl (meth)acrylate copolymers; Polystyrene materials; Polycarbonate materials; Fluororesin materials; In addition, resin-based materials whose main materials are water additives and modified products of these resin-based materials, and the like. The resin material may be a cross-linked product of the above material and a cross-linking agent. In addition, in this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. The resin-based material that provides the above-mentioned substrate may be a single type or a mixture of two or more types. The substrate according to one embodiment of the present invention contains a polyolefin-based material from the viewpoint of high laser transparency, easy in-plane extension and local deformation in the thickness direction, and low environmental load. Among the polyolefin-based materials, it is more preferable to contain polypropylene such as random copolymer polypropylene.

When the resin-based material contained in the base material is a polyolefin-based material, generally, the arithmetic surface roughness Ra of both surfaces of the base material is controlled by two rolls sandwiching the base material. It is performed by pressurization. The arithmetic surface roughness Ra of both surfaces of the base material is set by adjusting the material constituting the surface of these rolls and the roughness of the surface. In the past, the surface of these rolls was generally made of one metal and the other elastic material such as rubber. For this reason, although the arithmetic surface roughness Ra of the surface of the base material in contact with the roll made of a metal surface could be made to be a relatively low value relatively easily, the arithmetic surface roughness Ra of the base material in contact with the roll made of an elastic material was It was difficult to reduce the arithmetic surface roughness Ra of the surface to a low value. Therefore, when it is desired to reduce the arithmetic surface roughness Ra of both surfaces of the base material like the base material according to the present embodiment, both of the rolls required for roll pressurization are surfaces made of metal. It is preferable. However, in this case, it is necessary to more strictly control the relative arrangement of both rolls and the base material as compared with the case where the surface of one roll is made of an elastic material. When the resin-based material contained in the base material is a polyvinyl chloride-based material, the base material can be manufactured by inflation molding, and therefore the arithmetic surface roughness Ra of both surfaces of the base material is low. It is easy to set the value. However, since the polyvinyl chloride-based material contains a halogen element, it is preferable not to use it as the material of the base material when it is required to reduce the environmental load.

The base material may contain various additives such as a colorant, a flame retardant, a plasticizer, an antistatic agent, a lubricant, and a filler in the film containing the resin material as a main material. Examples of the colorant include pigments such as titanium dioxide and carbon black, and various dyes. Examples of the filler include organic materials such as melamine resin, inorganic materials such as fumed silica, and metal materials such as nickel particles. The content of such an additive is not particularly limited, but it should be kept within a range in which the substrate exhibits a desired function, particularly a laser transmitting function, and does not lose desired smoothness and flexibility.

When ultraviolet rays are used as the energy rays for irradiating to cure the pressure-sensitive adhesive layer, it is preferable that the substrate has transparency to ultraviolet rays. When an electron beam is used as the energy beam, the base material preferably has electron beam permeability.

The thickness of the substrate is not limited as long as the pressure-sensitive adhesive sheet can properly function in each of the above steps. It is preferably in the range of 20 to 450 μm, more preferably 25 to 200 μm, and particularly preferably 50 to 150 μm.

The base material preferably has a Young's modulus of 50 to 500 MPa. By setting the Young's modulus within this range, it is possible to improve the mechanical strength of the base material while maintaining good extensibility and to improve the process suitability when forming the pressure-sensitive adhesive layer. For example, it is possible to prevent unintended elongation of the base material when tension is applied when setting a film containing the base material polyolefin-based resin in a coater.
The Young's modulus is more preferably 60 to 450 MPa, further preferably 100 to 420 MPa, from the viewpoint of making blocking less likely to occur and improving the expandability while improving the mechanical strength. , 150 to 300 MPa is even more preferable.

(2) Pressure-sensitive adhesive layer The pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet according to the present embodiment has a thickness of 2 μm or more and 12 μm or less. When the thickness of the pressure-sensitive adhesive layer is within the above range and the arithmetic average roughness Ra of both surfaces of the base material is within the above range, defects are less likely to occur in plan view and excellent pick-up properties are provided. An adhesive sheet can be obtained. From the viewpoint of more stably reducing the possibility of the above defects, the thickness of the pressure-sensitive adhesive layer is preferably 3 μm or more, more preferably 4 μm or more. The thickness of the pressure-sensitive adhesive layer is preferably 10 μm or less, more preferably 8 μm or less, and more preferably 6 μm or less, from the viewpoint of more stably realizing the pressure-sensitive adhesive sheet having excellent pickup properties. Is particularly preferable.

The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet according to the present embodiment is not limited. Examples of the pressure-sensitive adhesive contained in the pressure-sensitive adhesive composition include rubber-based, acrylic-based, silicone-based, polyvinyl ether, and other pressure-sensitive adhesives. Hereinafter, the case where the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an acrylic pressure-sensitive adhesive will be described as an example. Since the acrylic adhesive has excellent transparency, it easily transmits a laser beam.

The acrylic pressure-sensitive adhesive contains an acrylic polymer. The acrylic polymer is a polymer containing a structural unit based on an acrylic compound as a unit constituting its skeleton. The acrylic polymer may be a homopolymer formed by polymerizing one kind of monomer or a copolymer formed by polymerizing a plurality of kinds of monomers. From the viewpoint of easily controlling the physical properties and chemical properties of the polymer, the acrylic polymer is preferably a copolymer.

The glass transition temperature Tg of the acrylic polymer is preferably -40°C or higher and -10°C or lower. When the pressure-sensitive adhesive composition contains an acrylic polymer having a glass transition temperature Tg of −40° C. or higher, the pressure-sensitive adhesive layer has reduced adhesiveness, and the pickup property can be further improved. From the viewpoint of more stably obtaining the effect of improving the pickup property, the glass transition temperature Tg of the acrylic polymer is more preferably −35° C. or higher. The glass transition temperature Tg of the acrylic polymer is preferably −20° C. or lower from the viewpoint of easily maintaining the performance of holding the chip after dividing the wafer into chips.

The weight average molecular weight (Mw) of the acrylic polymer is not limited. Usually, it is preferably 100,000 to 2,000,000, and more preferably 300,000 to 1,500,000. Further, the molecular weight distribution (Mw/Mn, Mn is a number average molecular weight) is not limited. Generally, it is preferably 1.0 to 10 and more preferably 1.0 to 3.0.

The specific type of the monomer that gives the acrylic polymer is not limited. Examples of such a monomer include (meth)acrylic acid, (meth)acrylic acid ester, and acrylonitrile. Specific examples of the (meth)acrylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, dodecyl. (Meth)acrylate, pentadecyl (meth)acrylate, octadecyl (meth)acrylate, etc., alkyl (meth)acrylate having an alkyl group having 1 to 18 carbon atoms; cycloalkyl (meth)acrylate, benzyl (meth)acrylate, iso (Meth)acrylate having a cyclic skeleton such as bornyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclopentenyl oxyethyl acrylate, and imide acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth ) A (meth)acrylate having a hydroxyl group such as acrylate; and a (meth)acrylate having an epoxy group such as glycidyl methacrylate and glycidyl acrylate.

The acrylic polymer preferably contains methyl methacrylate from the viewpoint of increasing its glass transition temperature Tg. From the viewpoint of more stably enjoying the effect brought by the acrylic polymer containing methyl methacrylate, the mass ratio of methyl methacrylate to the total amount of monomers giving the acrylic polymer is from 5% by mass to 20% by mass. It is preferably at most 7% by mass and more preferably at most 15% by mass.

The acrylic polymer may be a copolymer containing vinyl acetate, styrene, vinyl acetate or the like as a monomer.

The acrylic polymer may have at least one of an energy ray-polymerizable group and a reactive functional group capable of reacting with a crosslinking agent (hereinafter abbreviated as “reactive functional group”).

When the acrylic polymer contains an energy ray-polymerizable group, by irradiating the adhesive layer with energy rays, the adhesiveness to an adherend can be reduced, and the adhesive sheet has excellent pickup properties. Will be easier to obtain. Examples of the energy ray-polymerizable group include groups containing a polymerizable double bond. The method for preparing the acrylic polymer having an energy ray-polymerizable group is not limited. As an example of such a preparation method, for an acrylic polymer having a functional group having active hydrogen such as a hydroxyl group, a carboxylic acid group, an amino group, a functional group capable of reacting with the above functional group such as an isocyanate group and energy ray polymerization It is possible to react a substance having a functional group (a specific example thereof is (meth)acryloyloxyethyl isocyanate). In addition, when the acrylic pressure-sensitive adhesive contains an acrylic polymer containing an energy ray-polymerizable group by such an adjusting method, the glass transition temperature Tg of the above-mentioned acrylic polymer is Indicates Tg before reacting a substance having a functional group capable of reacting with a group and an energy ray-polymerizable group.

When the acrylic polymer has a reactive functional group, the cohesiveness of the pressure-sensitive adhesive layer is adjusted by reacting this reactive functional group with a cross-linking agent, and the adhesive sheet is adhered to the adherend after peeling. It becomes easy to suppress the generation of a residue and to lower the adhesiveness of the adhesive layer to further improve the pickup property. The combination of the reactive functional group and the crosslinking agent is not limited. Examples of the reactive functional group include a group having active hydrogen such as a hydroxyl group, a carboxylic acid group and an amino group. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, and metal chelate crosslinking agents.
The isocyanate crosslinking agent contains at least a polyisocyanate compound having a plurality of isocyanate groups. Specific examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; dicyclohexylmethane-4,4'-diisocyanate, bicycloheptane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methyl. Alicyclic isocyanate compounds such as cyclohexylene diisocyanate and hydrogenated xylylene diisocyanate; acyclic aliphatic isocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate, and their biuret and isocyanurate bodies, and compounds having isocyanate groups And a modified product such as an adduct which is a reaction product of a non-aromatic low-molecular-weight active hydrogen-containing compound such as ethylene glycol, trimethylolpropane, or castor oil.

Examples of the epoxy cross-linking agent include 1,3-bis(N,N′-diglycidylaminomethyl)cyclohexane, N,N,N′,N′-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl. Examples thereof include ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidyl amine.

Examples of the aziridine-based cross-linking agent include diphenylmethane-4,4′-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinyl propionate, and tetramethylolmethane tri-β-aziridinyl. Propionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, Trimethylolpropane tri-β-(2-methylaziridine)propionate and the like can be mentioned.

Examples of the metal chelate-based cross-linking agent include chelate compounds having metal atoms such as aluminum, zirconium, titanium, zinc, iron and tin. Among these, aluminum chelate compounds are preferable because of their excellent performance. Examples of the aluminum chelate compound include diisopropoxy aluminum monooleyl acetoacetate, monoisopropoxy aluminum bisoleyl acetoacetate, monoisopropoxy aluminum monooleate monoethyl acetoacetate, diisopropoxy aluminum monolauryl acetoacetate, diisopropoxy. Examples thereof include aluminum monostearyl acetoacetate and diisopropoxy aluminum monoisostearyl acetoacetate.

When the pressure-sensitive adhesive composition contains an acrylic polymer, the pressure-sensitive adhesive composition may contain components other than the acrylic polymer. Examples of such materials include energy ray-polymerizable compounds. The energy ray-polymerizable compound is a compound that polymerizes when irradiated with energy rays such as ultraviolet rays and electron rays. Examples of the energy ray-polymerizable compound include low molecular weight compounds having an energy ray-polymerizable group (monofunctional and polyfunctional monomers and oligomers), and specific examples include trimethylolpropane triacrylate and tetramethylolmethane. Tetraacrylate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate or 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, dicyclopentadiene dimethoxydiacrylate, isobornyl Acrylate compounds such as acrylate-containing cycloaliphatic skeleton-containing acrylate, polyethylene glycol diacrylate, oligoester acrylate, urethane acrylate oligomer, epoxy-modified acrylate, and polyether acrylate are used. Such a compound has at least one polymerizable double bond in the molecule, and usually has a molecular weight of 100 to 30,000, preferably about 300 to 10,000. When the pressure-sensitive adhesive composition is an acrylic pressure-sensitive adhesive and contains an acrylic polymer having an energy ray-polymerizable group, the pressure-sensitive adhesive composition contains a low molecular weight compound having an energy ray-polymerizable group. Even if it does not contain it or contains only a small amount, the adhesiveness to the adherend can be lowered by irradiating the adhesive layer with energy rays. When the content of the low molecular weight compound having an energy ray-polymerizable group in the pressure-sensitive adhesive composition is large, the pick-up property tends to be deteriorated. Therefore, the pressure-sensitive adhesive composition is an acrylic pressure-sensitive adhesive, and by containing an acrylic polymer having an energy ray-polymerizable group, the amount of the low molecular weight compound having an energy ray-polymerizable group is reduced, The pickup property can be further improved. When the pressure-sensitive adhesive composition is an acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive composition preferably contains 0 to 30 parts by mass of the energy ray-polymerizable compound with respect to 100 parts by mass of the acrylic polymer, The content is more preferably 0 to 15 parts by mass, further preferably 0 to 10 parts by mass.

When the pressure-sensitive adhesive composition contains an acrylic polymer having an energy ray-polymerizable group or contains an energy ray-polymerizable compound, it is preferable to also contain a photopolymerization initiator. Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, photoinitiators such as peroxide compounds, and photosensitizers such as amines and quinones. Examples include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, tetramethyl thiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloranthraquinone. 2,4,6-trimethylbenzoyldiphenylphosphine oxide and the like can be exemplified. By including a photopolymerization initiator, when ultraviolet rays are used as energy rays, the irradiation time and irradiation amount can be reduced.

Examples of the energy ray for reacting the energy ray-polymerizable group or the energy ray-polymerizable compound include ionizing radiation, that is, X-rays, ultraviolet rays, electron rays and the like. Among these, ultraviolet rays, which are relatively easy to introduce irradiation equipment, are preferable.

When ultraviolet rays are used as the ionizing radiation, near ultraviolet rays including ultraviolet rays having a wavelength of about 200 to 380 nm may be used for easy handling. The amount of ultraviolet light may be appropriately selected according to the type of energy ray-polymerizable group or energy ray-polymerizable compound contained in the pressure-sensitive adhesive layer and the thickness of the pressure-sensitive adhesive layer, and is usually about 50 to 500 mJ/cm ^2. And 100 to 450 mJ/cm ² is preferable, and 150 to 400 mJ/cm ² is more preferable. The ultraviolet illumination is usually 50 to 500 mW / cm ² or so, preferably from ^{100~450mW / cm 2, 150~400mW / cm} 2 is more preferable. The ultraviolet ray source is not particularly limited, and for example, a high pressure mercury lamp, a metal halide lamp or the like is used.

When an electron beam is used as the ionizing radiation, its accelerating voltage may be appropriately selected according to the type of energy ray-polymerizable group or energy ray-polymerizable compound contained in the pressure-sensitive adhesive layer and the thickness of the pressure-sensitive adhesive layer. It is sufficient that the acceleration voltage is usually about 10 to 1000 kV. Further, the irradiation dose may be set in a range in which the reaction of the energy ray-polymerizable group or the energy ray-polymerizable compound contained in the pressure-sensitive adhesive layer appropriately proceeds, and is usually selected in the range of 10 to 1000 krad. The electron beam source is not particularly limited, and for example, various electron beam accelerators such as Cockloft-Walton type, Van de Graft type, resonance transformer type, insulating core transformer type, or linear type, dynamitron type, high frequency type, etc. are used. be able to.

(3) Optical Properties In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the haze defined in JIS K7136:2000 (ISO 14782:1999) is such that the surface closer to the base material than the pressure-sensitive adhesive layer is the incident surface. When it does, it is preferable that it is 0.01% or more and 10% or less. When the haze is 10% or less, the laser light incident on the adhesive sheet can be effectively used. The haze is preferably 5% or less, more preferably 2.5% or less, from the viewpoint of enabling more stable and effective utilization of the laser light incident on the adhesive sheet. .. From the viewpoint of effectively utilizing the laser light incident on the adhesive sheet, the above-mentioned lower limit of haze is not set. From the viewpoint of enhancing manufacturing stability, the haze is preferably set to about 0.01% or more.

The pressure-sensitive adhesive sheet according to one embodiment of the present invention has a total light transmittance of 85% or more when the surface closer to the base material than the pressure-sensitive adhesive layer is the incident surface, as defined by JIS K7375:2000. It is preferable to have. When the total light transmittance is 85% or more, the laser light incident on the adhesive sheet can be effectively used. From the viewpoint of enabling more stable and effective utilization of the laser light incident on the adhesive sheet, the total light transmittance is preferably 90% or more. From the viewpoint of effectively utilizing the laser light incident on the adhesive sheet, the upper limit of the total light transmittance is not set. From the viewpoint of improving the manufacturing stability, the total light transmittance is preferably about 99.99% or less.

(4) Additional layer The pressure-sensitive adhesive sheet according to one embodiment of the present invention is provided with an additional layer on the surface of the pressure-sensitive adhesive layer and is an adherend of the pressure-sensitive adhesive sheet when the pressure-sensitive adhesive sheet is used. The above additional layer may be attached to the plate member. The structure of the additional layer is not limited. Specific examples of the additional layer include a case where the additional layer includes a protective film forming film and a case where the additional layer includes a die bonding layer.

The protective film forming film is made of a material capable of forming a protective film by being cured by external energy such as heat. The protective film forming film or the protective film is separated from the pressure-sensitive adhesive layer in a state where the divided body is attached to the chip-shaped member formed by dividing the plate-shaped member into individual pieces. Therefore, when the additional layer is a protective film forming film, it is possible to obtain a processed product in which the protective film forming film or a divided body of the protective film is laminated on one surface of the chip-shaped member.

Even when the additional layer is a die bonding layer, it is separated from the pressure-sensitive adhesive layer in a state in which the divided pieces of the die bonding layer are attached to the chip-shaped member obtained by dividing the plate-shaped member into individual pieces. Therefore, when the additional layer is the die bonding layer, it is possible to obtain a processed product in which the divided pieces of the die bonding layer are laminated on one surface of the chip-shaped member.

(5) Release Sheet The pressure-sensitive adhesive sheet according to one embodiment of the present invention is for the purpose of protecting the pressure-sensitive adhesive layer or the additional layer until the pressure-sensitive adhesive layer or the additional layer is attached to the plate-shaped member that is the adherend. The release surface of the release sheet may be attached to the surface of the pressure-sensitive adhesive sheet which is closer to the pressure-sensitive adhesive layer than the base material, specifically, the surface of the pressure-sensitive adhesive layer or the surface of the additional layer. The constitution of the release sheet is arbitrary, and a plastic film coated with a release agent 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, a silicone-based agent, a fluorine-based agent, a long-chain alkyl-based agent, or the like can be used, and among these, a silicone-based agent that is inexpensive and can obtain stable performance is preferable. Instead of the plastic film of the release sheet, a paper base material such as glassine paper, coated paper, high-quality paper or a laminated paper obtained by laminating a thermoplastic resin such as polyethylene on a paper base material may be used. The thickness of the release sheet is not particularly limited, but is usually about 20 μm or more and 250 μm or less.

2. Method for Manufacturing Workpiece By using the pressure-sensitive adhesive sheet according to one embodiment of the present invention, it is possible to manufacture a workpiece from a plate-shaped member as described below.

(1) Pasting Step First, in the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the surface closer to the pressure-sensitive adhesive layer than the base material, specifically, the surface of the pressure-sensitive adhesive layer or the surface of the additional layer, It is attached to one surface of an adherend including a plate member to obtain a first laminated body including an adhesive sheet and a plate member. The plate member is not limited. Examples thereof include semiconductor wafers such as silicon wafers and laminated bodies having a structure based on TSV. The thickness of the plate member is also not limited. The range of several tens μm to several hundreds μm is exemplified.

The first laminated body may include an additional layer. Examples of the additional layer include a protective film forming film, a protective film formed from the protective film forming film, and a die bonding layer. The additional layer may be attached to the plate-shaped member as a part of the pressure-sensitive adhesive sheet, or the additional layer may be previously laminated on one surface of the plate-shaped member. In the latter case, the surface of the additional layer opposite to the surface facing the plate-shaped member is the surface to which the adhesive sheet is attached as one surface of the adherend including the plate-shaped member.

(2) Dividing Step The plate-shaped member on the pressure-sensitive adhesive sheet is divided by extending the base material included in the first laminated body, and a plurality of chips having the divided body of the plate-shaped member are arranged on the pressure-sensitive adhesive sheet. To obtain a second laminated body. If the first laminate comprises additional layers, the additional layers are also split by stretching the substrate. After the dividing step is performed, a portion of the base material having a large degree of extension may be shrunk by means such as heating to eliminate excessive slack in the pressure-sensitive adhesive sheet.

(3) Step of forming modified portion By the start of the above dividing step, laser light is irradiated so as to be focused on a focal point set inside the plate-shaped member to reform the inside of the plate-shaped member. To form a part. The wavelength of the laser light and the irradiation method are appropriately set according to the composition such as the composition and thickness of the plate-shaped member. When the modified portion forming step is performed after the attaching step is performed, the plate-shaped member may be irradiated with laser light via the adhesive sheet. Even in such a case, since the pressure-sensitive adhesive sheet according to an embodiment of the present invention is less likely to cause a defect in a plan view, the degree of irradiation of laser light varies in the defect and the vicinity thereof, resulting in a plate. It is unlikely that the generation of the modified portion in the cylindrical member becomes locally inappropriate. As described above, if the reformed material is locally formed inadequately in the plate-shaped member, the plate-shaped member may not be properly divided in the above dividing step. Improper division of the plate-shaped member increases the possibility that the quality of the workpiece will deteriorate.

(4) Pickup Step By separating each of the plurality of chips included in the second laminate from the adhesive sheet, the chips can be obtained as a processed product. The separation method is not limited. Usually, the adhesiveness of the adhesive layer to the chip to be separated is reduced by pushing up a pin or the like from the surface of the adhesive sheet opposite to the chip to locally deform the adhesive sheet. Next, the chip to be separated is separated from the adhesive sheet by peeling off the chip to be separated from the adhesive sheet using a vacuum collet or the like. In this case, when the pin is pushed up or the chip is pulled up by the vacuum collet, a force for peeling off the adhesive layer from the chip is applied. If the chip is thin or has a structure based on TSV, the chip may be cracked during this peeling. However, in the pressure-sensitive adhesive sheet according to one embodiment of the present invention, since the thickness of the pressure-sensitive adhesive layer is appropriately controlled, the possibility that the chip will break during this peeling is appropriately reduced. That is, the pressure-sensitive adhesive sheet according to one embodiment of the present invention has excellent pick-up properties.

When the first laminated body includes an additional layer, the chip separated from the adhesive sheet by the pickup step is provided on the divided body of the plate-shaped member and on the surface of the divided body of the plate-shaped member proximal to the adhesive sheet. The divided body of the formed additional layer is provided. That is, in the pickup step, peeling occurs between the pressure-sensitive adhesive layer and the divided body of the additional layer, and the processed product is separated from the pressure-sensitive adhesive sheet.

When the additional layer that provides the divided body of the additional layer is the protective film, the time when the protective film is formed from the protective film-forming film is not limited. The additional layer included in the first laminate is a protective film forming film, and the work of forming the protective film from the protective film forming film may be performed before the start of the separation step. The additional layer that provides the divided body of the additional layer is a protective film-forming film, and the protective film may be formed from the divided body of the protective film-forming film included in the workpiece.

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

Hereinafter, the present invention will be described more specifically 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) Fabrication of base material A small T-die extruder (“Laboplast Mill” manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used to perform extrusion molding using a resin composition composed of a random copolymer polypropylene resin, and one side (adhesive processing Surface) Ra having an arithmetic surface roughness Ra of 0.03 μm and the other surface (corresponding to a laser incident surface) having an arithmetic surface roughness Ra of 0.03 μm. did. The surface roughness of the base material was measured using a surface roughness measuring device (“SV-3000” manufactured by Mitutoyo Corporation).

(2) Preparation of adhesive composition Copolymer obtained by copolymerizing 62 parts by mass of butyl acrylate, 10 parts by mass of methyl methacrylate and 28 parts by mass of 2-hydroxyethyl acrylate (HEA) (glass transition temperature Tg-34° C.) and 80 mol% of methacryloyloxyethyl isocyanate (MOI) are reacted with HEA of the copolymer to obtain an acrylic polymer (weight average molecular weight 500,000) having an energy ray-polymerizable group. It was
With respect to 100 parts by mass of the acrylic polymer, 3.0 parts by mass of a photopolymerization initiator (“IRGACURE 184” manufactured by BASF, concentration: 100%), an isocyanate compound (“BHS-8515” manufactured by Toyo Ink Co., Ltd.) 1.0 part by mass was blended to obtain a pressure-sensitive adhesive composition diluted with a solvent.

(3) Preparation of pressure-sensitive adhesive sheet The above-mentioned pressure-sensitive adhesive composition was applied onto the release surface of the release sheet. The obtained coating film was allowed to stand together with the release sheet in an environment of 80° C. for 1 minute to obtain a laminate including the release sheet and the pressure-sensitive adhesive layer (the measured thickness was 10 μm).
On the pressure-sensitive adhesive processed surface of the above-mentioned base material, the pressure-sensitive adhesive layer side surface of the above-mentioned laminate is stuck, and a pressure-sensitive adhesive sheet comprising the base material and the pressure-sensitive adhesive layer is formed on the pressure-sensitive adhesive layer side surface. It was obtained in a further laminated state.

[Example 2]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer was 5 μm, with the release sheet laminated on the surface on the pressure-sensitive adhesive layer side.

[Example 3]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except for the following changes, with a release sheet laminated on the pressure-sensitive adhesive layer side surface.
(Changes) By changing the molding conditions of the base material, the arithmetic surface roughness Ra of the pressure-sensitive adhesive processed surface of the base material was 0.16 μm, and the arithmetic surface roughness Ra of the laser incident surface was 0.03 μm.

[Comparative Example 1]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 3 except that the thickness of the pressure-sensitive adhesive layer was 15 μm, with the release sheet laminated on the surface on the pressure-sensitive adhesive layer side.

[Comparative Example 2]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except for the following changes 1 and 2, with the release sheet laminated on the pressure-sensitive adhesive layer side surface.
(Change point 1) By changing the molding conditions of the base material, the arithmetic surface roughness Ra of the pressure-sensitive adhesive processed surface of the base material was 1.3 μm and the arithmetic surface roughness Ra of the laser incident surface was 0.04 μm.
(Change point 2) The thickness of the pressure-sensitive adhesive layer was set to 15 μm.

[Comparative Example 3]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Comparative Example 2 except that the thickness of the pressure-sensitive adhesive layer was 10 μm, with the release sheet laminated on the surface on the pressure-sensitive adhesive layer side.

[Comparative Example 4]
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except for the following changes, with a release sheet laminated on the pressure-sensitive adhesive layer side surface.
(Changes) By changing the molding conditions of the base material, the arithmetic surface roughness Ra of the adhesive processed surface of the base material was 0.04 μm, and the arithmetic surface roughness Ra of the laser incident surface was 1.3 μm.

[Test Example 1] <Measurement of haze>
The haze of the test piece obtained by peeling off the release sheet from the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples and cutting into an appropriate size was measured according to JIS K7136:2000, and HAZE METER (Nippon Denshoku Industries Co., Ltd.) was used. Manufactured by "NDH-5000"). The measurement light was incident from the surface of the adhesive sheet on the base material side. The results are shown in Table 1.

[Test Example 2] <Observation of defects>
The release sheet was peeled off from the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, and an arbitrary range of 100 mm×100 mm on the pressure-sensitive adhesive layer side surface of each pressure-sensitive adhesive sheet was set as an observation range. Each of these observation ranges was observed using an optical microscope, and based on the degree of existence of defects, the following criteria were used for evaluation. The results are shown in Table 1.
A: No defect was observed in the observation range.
B: Five or less defects were observed within the observation range.
C: Six or less defects were observed within the observation range.

[Test Example 3] <Evaluation of pickup property>
The pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were cut into a circle in a plan view, the release sheet was peeled off, and the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was attached to a silicon wafer (thickness: 100 μm) and a ring frame.

A laser irradiation device is used to cut a laser focused on the inside of the wafer from the side facing the adhesive layer of the silicon wafer through the adhesive sheet so that a chip of 8 mm x 8 mm is formed. Irradiation was performed while scanning along the planned line. After irradiating all the planned cutting lines with a laser, the expander is used to pull down the 10 mm pressure sensitive adhesive sheet at a speed of 10 mm/sec, and the area where the silicon wafer is bonded on the surface of the pressure sensitive adhesive layer side of the pressure sensitive adhesive sheet is inside or outside the main surface. Stretched in the direction of orientation.

In this state, the pressure-sensitive adhesive sheet was irradiated with ultraviolet rays under the following irradiation conditions.
Illuminance: 220 mW/cm ²
Light intensity: 190mJ/cm ²

Then, the load at the time of pickup was measured with a push-pull gauge (push-up jig: 1 pin) manufactured by Aiko Engineering. The load required for pushing up was measured, and the pickup property was evaluated according to the following criteria based on the measured value. The results are shown in Table 1.
A: 1.7N or less B: 1.7N or more

As can be seen from Table 1, the pressure-sensitive adhesive sheets of Examples satisfying the conditions of the present invention had low haze, were less likely to cause defects, and were excellent in pick-up properties, and were suitable as laser dicing sheets.

The pressure-sensitive adhesive sheet according to the present invention is preferably used as a laser dicing sheet.

Claims (11)

A pressure-sensitive adhesive sheet used for irradiating a plate member with a laser beam to form a modified portion, and dividing the plate member into chips.
A base material and an adhesive layer provided on one surface of the base material,
The base material has an arithmetic average roughness Ra of 0.01 μm or more and 0.2 μm or less defined by JIS B0601:2013 (ISO 4287:1997) on both the one surface and the surface opposite to the one surface. Is less than
The base material is made of a polyolefin material,
The pressure-sensitive adhesive layer contains an acrylic polymer, and the acrylic polymer has a glass transition temperature Tg of −40° C. or higher and −10° C. or lower,
The acrylic polymer has an energy ray-polymerizable group,
A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a thickness of 2 μm or more and 12 μm or less. The pressure-sensitive adhesive sheet according to claim 1, wherein the haze defined by JIS K7136:2000 (ISO 14782:1999) is 0.01% or more and 10% or less when the substrate side is the incident side. Adhesive sheet. 2. The acrylic polymer contains a constituent unit derived from methyl methacrylate, and the mass ratio of methyl methacrylate to all the monomers giving the acrylic polymer is 5% by mass or more and 20% by mass or less. The pressure-sensitive adhesive sheet according to item 2. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the acrylic polymer does not contain a low molecular weight compound having an energy ray-polymerizable group. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4 , wherein the arithmetic average roughness Ra of the base material is set to include rolling the base material. The pressure-sensitive adhesive sheet according to claim 5 , wherein the roll used for pressing the roll is a roll having a surface made of a metal material. The surface of the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 that is closer to the pressure-sensitive adhesive layer than the base material is affixed to one surface of an adherend including a plate-shaped member to form the pressure-sensitive adhesive sheet. A sticking step of obtaining a first laminated body including a sheet and the plate-shaped member;
By extending the base material included in the first stacked body, the plate-shaped member on the pressure-sensitive adhesive sheet is divided, and a plurality of chips each including the divided body of the plate-shaped member are arranged on the pressure-sensitive adhesive sheet. And a pickup step of separating each of the plurality of chips included in the second laminated body from the adhesive sheet to obtain the chips as a processed product,
A reforming unit that irradiates a laser beam so as to be focused at a focus set inside the plate-shaped member and forms a reforming unit inside the plate-shaped member by the time the dividing step is started. A method of manufacturing a processed product, which comprises performing a forming step. The first laminate provided in the dividing step includes an additional layer between the pressure-sensitive adhesive layer and the plate-shaped member, the additional layer is also divided by the dividing step, and the adhesive layer is obtained by the picking-up step. chip separating from the sheet comprises a split body of said plate-like member divided body and the plate-like member the additional layer in the adhesive sheet of the divided bodies are formed on the proximal surface of the, according to claim 7 Of manufacturing processed products of. 9. The method of manufacturing a work piece according to claim 8 , wherein the additional layer comprises a protective layer. The method for manufacturing a workpiece according to claim 9 , further comprising: a protective film forming step of forming the protective layer of the first laminated body from a protective film forming film before the dividing step is started. The method of manufacturing a work piece according to claim 8 , wherein the additional layer comprises a die bonding layer.