Method for manufacturing adhesive sheets and semiconductor devices

Abstract

To provide an adhesive sheet that can hold a workpiece well and separate the workpiece well without requiring irradiation with active energy ray.SOLUTION: Provided is an adhesive sheet, which is an adhesive sheet for handling a workpiece that includes a substrate and an adhesive layer laminated on one side of the substrate, and in which the adhesive layer is made of a non-active energy ray-curable adhesive formed from an adhesive composition containing at least an acrylic polymer and a tackifier, and the tackifier is an alkylene glycol modified rosin ester.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive sheet for handling workpieces such as semiconductor wafers and semiconductor chips, and more particularly to an adhesive sheet that can be suitably used for sorting, inspecting, rearranging, storing, shipping, transporting, etc. of workpieces.

Background Art

[0002] Semiconductor wafers such as silicon and gallium arsenide, and semiconductor packages in which semiconductor components are encapsulated in resin are manufactured in a large-diameter state, cut (diced) into chips, peeled (picked up), and then transferred to the next step, the mounting step. At this time, workpieces such as semiconductor wafers and semiconductor packages are laminated on an adhesive sheet having a base material and an adhesive layer, and processes such as back grinding, dicing, cleaning, drying, expanding, picking up, and mounting are performed.

[0003] In the above-described adhesive sheet, as the adhesive layer, one composed of an adhesive having active energy ray curability may be used. In this case, by irradiating the adhesive layer with active energy rays, the adhesive force of the adhesive layer to the workpiece can be reduced, and thereby, separation (for example, picking up) of the workpiece from the adhesive sheet can be easily performed. Patent Documents 1 and 2 disclose examples of such adhesive sheets.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, semiconductor chips and other workpieces are sometimes temporarily attached to adhesive sheets for sorting purposes. In this case, for example, only high-quality semiconductor chips are selected from multiple chips stacked on one adhesive sheet and transferred to another adhesive sheet. This makes it possible to ship, store, etc., only high-quality semiconductor chips.

[0006] The adhesive sheets used for the above sorting purposes are required to have the ability to sufficiently hold workpieces such as semiconductor chips and the ability to easily separate the workpieces to be separated (hereinafter sometimes referred to as "easy peelability").

[0007] Here, the adhesive sheet, in which the adhesive layer is composed of an adhesive having active energy ray curability as described above, can also be used for the sorting purposes mentioned above. However, when separating workpieces from this adhesive sheet, it is necessary to irradiate the adhesive layer with active energy rays, which increases the number of steps in handling and thus increases manufacturing costs. Furthermore, it is practically difficult to irradiate the workpiece to be separated with active energy rays at a precise location, and therefore, it is not suitable for use in separating only some workpieces while leaving the rest on the adhesive sheet.

[0008] This invention has been made in view of the above circumstances, and aims to provide an adhesive sheet that can hold a workpiece well while not requiring irradiation with active energy rays and that can separate the workpiece well. [Means for solving the problem]

[0009] To achieve the above objective, firstly, the present invention provides an adhesive sheet for handling a workpiece, comprising a base material and an adhesive layer laminated on one side of the base material, wherein the adhesive layer is made of an inactive energy ray curable adhesive formed from an adhesive composition containing at least an acrylic polymer and a tackifier, and the tackifier is an alkylene glycol-modified rosin ester (Invention 1).

[0010] In the adhesive sheet according to the above invention (Invention 1), the adhesive layer consists of a non-active energy ray curable adhesive formed from the above-mentioned adhesive composition, and in particular, by using alkylene glycol-modified rosin ester as a tackifier, the workpiece can be held well, and when separating the workpiece, irradiation with active energy rays is not required, and the desired workpiece can be easily separated.

[0011] In the above invention (Invention 1), the content of the alkylene glycol-modified rosin ester as the tackifier in the adhesive composition is preferably 0.01 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the acrylic polymer (Invention 2).

[0012] In the above inventions (Inventions 1 and 2), the adhesive composition contains a crosslinking agent, and the amount of the crosslinking agent in the adhesive composition is preferably 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the acrylic polymer (Invention 3).

[0013] In the above inventions (Inventions 1 to 3), the adhesive force to the mirror surface of the silicon wafer is preferably 200 mN / 25 mm or more and 3000 mN / 25 mm or less (Invention 4).

[0014] In the above inventions (Inventions 1 to 4), when a 10 mm x 10 mm silicon chip that has been attached to the side of the adhesive layer opposite to the substrate for three months is separated from the adhesive sheet by using a 9.9 mm x 9.9 mm vacuum collet to suck the silicon chip while pushing it up from the substrate side of the adhesive sheet with a needle, it is preferable that the minimum height of the push required for separation is 750 μm or less (Invention 5).

[0015] Secondly, the present invention provides a method for manufacturing a semiconductor device, comprising the steps of: attaching one or more workpieces to the adhesive layer side of the adhesive sheet (Inventions 1 to 5); and separating at least one of the workpieces from the adhesive sheet and placing it on a predetermined object (Invention 6). [Effects of the Invention]

[0016] The adhesive sheet according to the present invention can hold a workpiece well while separating it effectively without requiring irradiation with active energy rays. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below. The adhesive sheet according to this embodiment comprises a base material and an adhesive layer laminated on one side of the base material. In the adhesive sheet according to this embodiment, the adhesive layer is made of an inactive energy ray curable adhesive formed from an adhesive composition containing at least an acrylic polymer and a tackifier. Furthermore, the tackifier is an alkylene glycol-modified rosin ester.

[0018] As described above, the adhesive sheet according to this embodiment can exhibit sufficient adhesive force to the workpiece because the adhesive layer is made of an adhesive composition containing at least an acrylic polymer and a tackifier. Therefore, even when multiple workpieces such as semiconductor chips are laminated on the side of the adhesive layer opposite to the substrate (hereinafter sometimes referred to as the "adhesive surface"), it is possible to prevent detachment and displacement and to sufficiently hold each individual workpiece.

[0019] On the other hand, the adhesive sheet according to this embodiment allows for easy separation of the workpiece from the adhesive sheet by using alkylene glycol-modified rosin ester as the tackifier. Furthermore, this easy separation can be achieved without irradiation with active energy rays. Therefore, the adhesive sheet according to this embodiment allows for easy separation of the intended workpiece without increasing the equipment or processes required for active energy ray irradiation.

[0020] As described above, the adhesive sheet can achieve both excellent adhesive strength and easy peelability. For example, when multiple semiconductor chips are attached to the adhesive sheet, it is possible to reliably separate only the desired chip without causing adjacent chips to detach or shift. Therefore, according to the adhesive sheet of this embodiment, it is possible to selectively pick up a desired chip from among multiple semiconductor chips.

[0021] Furthermore, the adhesive sheet according to this embodiment can maintain the above-mentioned easy peelability even after a long period of time has elapsed since a workpiece was attached. In particular, the adhesive sheet according to this embodiment can achieve excellent easy peelability without irradiation with active energy rays, even after a long period of time has elapsed since a workpiece was attached. Therefore, the adhesive sheet according to this embodiment is suitable for applications such as storing multiple semiconductor chips attached to it.

[0022] 1. Base material The base material in this embodiment is not particularly limited as long as it exhibits desired functions when the adhesive sheet is used. In particular, the base material is preferably a resin film mainly made of a resin-based material. Specific examples thereof include polyolefin-based films such as polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, and norbornene resin film; polyester-based films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate; ethylene-vinyl acetate copolymer film; ethylene-based copolymer films such as ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)acrylic acid methyl copolymer film, and other ethylene-(meth)acrylic acid ester copolymer films; polyvinyl chloride-based films such as polyvinyl chloride film and vinyl chloride copolymer film; (meth)acrylic acid ester copolymer film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; fluororesin film, and the like. Also, modified films such as crosslinked films and ionomer films of these are also used. Further, the base material may be a laminated film formed by laminating a plurality of the above-described films. In this laminated film, the materials constituting each layer may be the same or different. In the present specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. The same applies to other similar terms. Also, the "polymer" in the present specification shall include the concept of "copolymer".

[0023] The base material may contain various additives such as flame retardants, plasticizers, lubricants, antioxidants, colorants, infrared absorbers, ultraviolet absorbers, and ion scavengers. Although the content of these additives is not particularly limited, it is preferably within a range in which the base material exhibits desired functions. Although the base material in this embodiment may contain an antistatic agent, it is also preferable that it does not contain an antistatic agent.

[0024] On the surface of the base material to which the adhesive layer is laminated, surface treatments such as primer treatment, corona treatment, plasma treatment, etc. may be performed in order to enhance the adhesion to the adhesive layer.

[0025] Although the thickness of the base material can be appropriately set according to the method of using the adhesive sheet, for example, it is preferably 200 μm or less, particularly preferably 150 μm or less. Also, the thickness of the base material is preferably 10 μm or more, particularly preferably 25 μm or more.

[0026] 2. Adhesive layer As described above, the adhesive layer in the present embodiment is composed of an adhesive formed from an adhesive composition containing at least an acrylic polymer and an adhesion promoter. It is also preferable that the adhesive composition further contains a crosslinking agent.

[0027] (1) Acrylic polymer As the above acrylic polymer, conventionally known acrylic polymers can be used. The acrylic polymer may be a homopolymer formed from one type of acrylic monomer, a copolymer formed from a plurality of types of acrylic monomers, or a copolymer formed from one type or a plurality of types of acrylic monomers and monomers other than acrylic monomers.

[0028] From the viewpoint of easily exhibiting a desired adhesive force in the adhesive sheet according to the present embodiment, the acrylic polymer preferably contains, as monomer units constituting the polymer, an alkyl (meth)acrylate, a monomer having a polar group (polar group-containing monomer), and a monomer having a functional group (functional group-containing monomer).

[0029] Acrylic polymers can easily achieve the desired adhesive strength by containing the above-mentioned alkyl (meth)acrylate as monomer units constituting the polymer. Preferably, the alkyl (meth)acrylate has 1 to 18 carbon atoms in the alkyl group, and particularly preferably 1 to 8 carbon atoms. Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. These may be used individually or in combination of two or more.

[0030] The acrylic polymer preferably contains 70% by mass or more of alkyl (meth)acrylate as a monomer unit constituting the polymer, more preferably 75% by mass or more, and even more preferably 80% by mass or more. Furthermore, the acrylic polymer preferably contains 97% by mass or less of alkyl (meth)acrylate as a monomer unit constituting the polymer, more preferably 95% by mass or less, and even more preferably 92% by mass or less. The above range for alkyl (meth)acrylate content makes it easier to achieve the desired adhesive strength.

[0031] By including the above-mentioned polar group-containing monomers as monomer units constituting the polymer, the polarity of the resulting adhesive is improved, making it easier to achieve sufficient adhesion when using silicon wafers as the workpiece. Examples of polar group-containing monomers include methyl methacrylate, acryloyl morpholine, isobornyl acrylate, vinyl acetate, benzyl acrylate, and glycidyl methacrylate, among which methyl methacrylate is particularly preferred.

[0032] When an acrylic polymer contains polar group-containing monomers as monomer units constituting the polymer, it is preferable that the acrylic polymer contains 1% by mass or more of polar group-containing monomers, particularly 3% by mass or more, and even more preferably 5% by mass or more. Furthermore, it is preferable that the acrylic polymer contains 30% by mass or less of polar group-containing monomers as monomer units constituting the polymer, particularly 20% by mass or less, and even more preferably 15% by mass or less. By having a polar group-containing monomer content within the above range, the adhesive layer is more likely to exhibit the desired polarity.

[0033] Acrylic polymers, by containing the above-mentioned functional group-containing monomers as monomer units constituting the polymer, can react with the crosslinking agent described later via the functional groups derived from the functional group-containing monomers to form a crosslinked structure (three-dimensional network structure). This yields an adhesive with the desired cohesive force.

[0034] The above-mentioned functional group-containing monomers are preferably monomers that have a polymerizable double bond and a functional group such as a hydroxyl group, carboxyl group, amino group, substituted amino group, or epoxy group within their molecule. Among these, from the viewpoint of excellent reactivity with crosslinking agents, monomers having a hydroxyl group within their molecule (hydroxyl group-containing monomers), monomers having a carboxyl group within their molecule (carboxyl group-containing monomers), monomers having an amino group within their molecule (amino group-containing monomers), etc., are preferred.

[0035] Examples of the above-mentioned hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, which can be used individually or in combination of two or more.

[0036] Examples of the above-mentioned carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually or in combination of two or more.

[0037] The acrylic polymer preferably contains 3% by mass or more of functional group-containing monomers as monomer units constituting the polymer, more preferably 4% by mass or more, and even more preferably 5% by mass or more. Furthermore, the acrylic polymer preferably contains 30% by mass or less of functional group-containing monomers as monomer units constituting the polymer, more preferably 25% by mass or less, and even more preferably 20% by mass or less. By having the functional group-containing monomer content within the above range, the resulting adhesive is more likely to have the desired cohesive force.

[0038] Acrylic polymers may contain other monomers as monomer units in addition to the (meth)acrylate alkyl esters, polar group-containing monomers, and functional group-containing monomers mentioned above.

[0039] Other monomers mentioned above include, for example, alkoxyalkyl group-containing (meth)acrylic acid esters such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate; aliphatic ring-containing (meth)acrylic acid esters such as cyclohexyl (meth)acrylate; aromatic ring-containing (meth)acrylic acid esters such as phenyl (meth)acrylate; nitrogen-containing heterocyclic monomers such as N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, and N-(meth)acryloylpyrrolidone; non-crosslinked acrylamides such as (meth)acrylamide and N,N-dimethyl(meth)acrylamide; non-crosslinked tertiary amino group-containing (meth)acrylic acid esters such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; and styrene.

[0040] The polymerization mode of the acrylic polymer may be random copolymer or block copolymer. Furthermore, the polymerization method is not particularly limited and can be carried out by general polymerization methods, such as solution polymerization.

[0041] The weight-average molecular weight (Mw) of the acrylic polymer is preferably 300,000 or more, particularly preferably 400,000 or more, and even more preferably 500,000 or more. Furthermore, the weight-average molecular weight (Mw) is preferably 1,500,000 or less, particularly preferably 1,200,000 or less, and even more preferably 1,000,000 or less. When the weight-average molecular weight (Mw) of the acrylic polymer is within the above range, it is easier to obtain an adhesive that has an excellent balance between tackiness and peelability. In this specification, the weight-average molecular weight (Mw) is a value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0042] (2) Tackifier As mentioned above, the tackifier in this embodiment is an alkylene glycol-modified rosin ester. There are no particular limitations on the alkylene glycol-modified rosin ester, but for example, rosins, polyaldehydes, etc. Sharpness It is preferable that the product is obtained by esterifying an glycol monoalkyl ether, a polyhydric alcohol, and an α,β-unsaturated carboxylic acid.

[0043] Furthermore, it is preferable to use an alkylene glycol-modified rosin ester with a softening point of 50°C or lower, particularly preferably 20°C or lower, and even more preferably 0°C or lower. A softening point of 50°C or lower results in higher fluidity of the alkylene glycol-modified rosin ester, making it easier to achieve the desired adhesive strength. The lower limit of the softening point is not particularly limited, but it is preferably -100°C or higher, particularly preferably -70°C or higher, and even more preferably -40°C or higher.

[0044] Furthermore, it is preferable to use an alkylene glycol-modified rosin ester having a weight-average molecular weight of 1000 or more, particularly preferably 2000 or more, and even more preferably 3000 or more. A weight-average molecular weight of 1000 or more makes it easier for the alkylene glycol-modified rosin ester to moderately decrease in compatibility with other components in the adhesive composition, thereby making it easier to achieve the desired adhesive strength. The upper limit of the weight-average molecular weight is preferably 1,000,000 or less, more preferably 100,000 or less, particularly preferably 50,000 or less, and even more preferably 8,000 or less, from the viewpoint of compatibility with the adhesive composition.

[0045] The content of alkylene glycol-modified rosin ester as a tackifier in the adhesive composition is preferably 0.01 parts by mass or more, particularly preferably 0.1 parts by mass or more, and more preferably 0.2 parts by mass or more, per 100 parts by mass of the acrylic polymer. A content of 0.01 parts by mass or more makes it easier to achieve better peelability. Furthermore, the content is preferably 5.0 parts by mass or less, particularly preferably 4.0 parts by mass or less, and more preferably 3.0 parts by mass or less, per 100 parts by mass of the acrylic polymer. A content of 5.0 parts by mass or less makes it easier to achieve excellent adhesive strength.

[0046] (3) Crosslinking agent Any crosslinking agent that reacts with the functional groups of the acrylic copolymer is acceptable, and examples include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. The crosslinking agent can be used individually or in combination of two or more.

[0047] In this case, if the acrylic copolymer contains a hydroxyl group-containing monomer as a constituent monomer unit, it is preferable to use an isocyanate-based crosslinking agent that has excellent reactivity with hydroxyl groups as the crosslinking agent.

[0048] The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and their biuret and isocyanurate forms, as well as adducts which are reaction products with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferred from the viewpoint of reactivity with hydroxyl groups.

[0049] The amount of crosslinking agent is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and more preferably 3 parts by mass or more, per 100 parts by mass of the acrylic copolymer. Furthermore, the amount of crosslinking agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the acrylic copolymer. By having the amount of crosslinking agent within the above range, an adhesive is obtained that has a predetermined adhesive strength and a crosslink density suitable for pick-up properties.

[0050] (4) Others The adhesive composition in this embodiment may contain desired additives, such as silane coupling agents, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, and refractive index modifiers, as long as they do not impair the effects of the adhesive sheet according to this embodiment. Note that polymerization solvents and diluent solvents described later are not included in the additives that constitute the adhesive composition.

[0051] (5) Method for preparing an adhesive composition The adhesive composition in this embodiment can be produced by manufacturing an acrylic copolymer and mixing the obtained acrylic copolymer with a tackifier, optionally a crosslinking agent, and other components.

[0052] Acrylic copolymers can be produced by polymerizing a mixture of monomers constituting the polymer using a conventional radical polymerization method. Preferably, this polymerization is carried out by solution polymerization, with the optional use of a polymerization initiator. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more solvents may be used in combination.

[0053] Examples of polymerization initiators include azo compounds and organic peroxides, and two or more may be used in combination. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane1-carbonitride), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0054] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, and diacetyl peroxide.

[0055] Furthermore, in the polymerization process described above, the weight-average molecular weight of the resulting polymer can be adjusted by incorporating a chain transfer agent such as 2-mercaptoethanol.

[0056] Once an acrylic copolymer is obtained, an adhesive coating solution can be obtained by adding an active energy ray curable component, a tackifier, and optionally a crosslinking agent, other components, and a diluent solvent to the acrylic copolymer solution and mixing thoroughly. If any of the above components are used in solid form, or if precipitation occurs when mixed with other components in an undiluted state, that component may be dissolved or diluted in a diluent solvent beforehand before mixing with the other components.

[0057] Examples of the diluent solvents used include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

[0058] The concentration and viscosity of the coating solution prepared in this manner are not particularly limited, as long as they are within the range of coating, and can be appropriately selected depending on the situation. For example, the adhesive composition is diluted to a concentration of 10% by mass or more and 60% by mass or less. Note that the addition of a diluent is not a necessary condition when obtaining the coating solution; if the adhesive composition has a viscosity suitable for coating, a diluent may not be added. In this case, the adhesive composition becomes a coating solution where the polymerization solvent of the acrylic copolymer is used directly as the diluent.

[0059] (6) Thickness of the adhesive layer In this embodiment, the thickness of the adhesive layer is preferably 1 μm or more, particularly preferably 2 μm or more, and even more preferably 3 μm or more. A thickness of 1 μm or more in the adhesive layer makes it easier for the adhesive sheet to achieve good adhesive strength. Furthermore, the thickness is preferably 50 μm or less, particularly preferably 30 μm or less, and even more preferably 20 μm or less. A thickness of 20 μm or less in the adhesive layer makes it easier for the adhesive sheet to achieve good peelability.

[0060] 3. Other components (1) Release sheet In the adhesive sheet according to this embodiment, a release sheet may be laminated on the adhesive surface of the adhesive layer to protect the adhesive surface until it is attached to the workpiece. The structure of the release sheet is arbitrary, and examples include a plastic film that has been treated with a release agent. Specific examples of plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. As the release agent, silicone-based, fluorine-based, and long-chain alkyl-based release agents can be used, and among these, silicone-based release agents are preferred because they are inexpensive and provide stable performance. There are no particular restrictions on the thickness of the release sheet, but it is usually 20 μm or more and 250 μm or less.

[0061] (2) Adhesive layer In the adhesive sheet according to this embodiment, an adhesive layer may be laminated on the side of the adhesive layer opposite to the substrate. In this case, the adhesive sheet according to this embodiment can be used as a dicing / die bonding sheet. With this sheet, a workpiece can be attached to the side of the adhesive layer opposite to the adhesive layer, and by dicing the adhesive layer together with the workpiece, a chip can be obtained in which individual pieces of the adhesive layer are laminated. The chip can be easily fixed to the object on which it is mounted by these individual pieces of adhesive layer. As the material constituting the adhesive layer described above, it is preferable to use one that contains a thermoplastic resin and a low molecular weight thermosetting adhesive component, or one that contains a B-stage (semi-cured) thermosetting adhesive component.

[0062] (3) Protective film forming layer Furthermore, in the adhesive sheet according to this embodiment, a protective film forming layer may be laminated on the adhesive surface of the adhesive layer. In this case, the adhesive sheet according to this embodiment can be used as a protective film forming and dicing sheet. With such a sheet, a workpiece is attached to the side of the protective film forming layer opposite to the adhesive layer, and the protective film forming layer is diced together with the workpiece to obtain a chip with individual pieces of the protective film forming layer laminated on it. Preferably, a workpiece with a circuit formed on one side is used, and in this case, the protective film forming layer is usually laminated on the side opposite to the side with the circuit formed. By curing the individual pieces of the protective film forming layer at a predetermined timing, a protective film with sufficient durability can be formed on the chip. Preferably, the protective film forming layer is made of an uncured curable adhesive.

[0063] 4. Physical properties (1) Minimum thrust height In the adhesive sheet according to this embodiment, when a 10 mm x 10 mm silicon chip that has been attached to the side of the adhesive layer opposite to the substrate for 24 hours is separated from the adhesive sheet by pushing up the silicon chip with a needle from the substrate side of the adhesive sheet and sucking the silicon chip with a vacuum collet of size 9.9 mm x 9.9 mm, the minimum height of the push-up required for separation (minimum push-up height) is preferably 750 μm or less, particularly preferably 550 μm or less, and even more preferably 500 μm or less. In the adhesive sheet according to this embodiment, the above-mentioned minimum push-up height can be achieved by using alkylene glycol-modified rosin ester as the tackifier. Furthermore, having the minimum push-up height within the above range makes it easier to separate the workpiece. Note that the lower limit of the above-mentioned minimum push-up height is not particularly limited and may be, for example, 50 μm or more.

[0064] Furthermore, in the adhesive sheet according to this embodiment, when a 10 mm x 10 mm silicon chip that has been attached to the side of the adhesive layer opposite to the substrate for 3 months is separated from the adhesive sheet by pushing up the silicon chip with a needle from the substrate side of the adhesive sheet and sucking the silicon chip with a vacuum collet of size 9.9 mm x 9.9 mm, the minimum height of the push-up required to separate the chip (minimum push-up height) is preferably 750 μm or less, particularly preferably 550 μm or less, and even more preferably 500 μm or less. According to the adhesive sheet according to this embodiment, by using alkylene glycol-modified rosin ester as the tackifier, the above-mentioned minimum push-up height can be achieved even after a long period of time, such as 3 months, has elapsed since attachment. And, because the minimum push-up height is within the above range, the workpiece is easier to separate. Note that the lower limit of the above-mentioned minimum push-up height is not particularly limited and may be, for example, 50 μm or more.

[0065] Further details regarding the measurement method for the minimum thrust height are described in the test examples below.

[0066] (2) Adhesive strength In the adhesive sheet according to this embodiment, the adhesive force to the mirror surface of the silicon wafer is preferably 200 mN / 25 mm or more, particularly preferably 300 mN / 25 mm or more, and even more preferably 400 mN / 25 mm or more. An adhesive force of 200 mN / 25 mm or more makes it easier to hold the workpiece well on the adhesive sheet. Furthermore, the adhesive force is preferably 3000 mN / 25 mm or less, particularly preferably 2000 mN / 25 mm or less, and even more preferably 1500 mN / 25 mm or less. An adhesive force of 3000 mN / 25 mm or less makes it easier to achieve the minimum push-up height mentioned above. Details of the method for measuring the adhesive force are described in the test examples below.

[0067] 5. Method for manufacturing adhesive sheets The method for manufacturing the adhesive sheet according to this embodiment is not particularly limited, and is preferably manufactured by laminating an adhesive layer on one side of a substrate.

[0068] Lamination of an adhesive layer onto one side of a substrate can be carried out by known methods. For example, it is preferable to transfer an adhesive layer formed on a release sheet to one side of the substrate. In this case, a coating liquid containing an adhesive composition constituting the adhesive layer, and optionally a solvent or dispersion medium, is prepared, and the coating liquid is applied to the peeled surface of the release sheet (hereinafter sometimes referred to as the "release surface") using a die coater, curtain coater, spray coater, slit coater, knife coater, applicator, etc. to form a coating film, and the adhesive layer can be formed by drying the coating film. The properties of the coating liquid are not particularly limited as long as it can be applied, and it may contain components for forming the adhesive layer as a solute or as a dispersed phase. The release sheet in this laminate may be peeled off as a process material, or it may be used to protect the adhesive surface of the adhesive layer until the adhesive sheet is attached to the adherend.

[0069] If the coating liquid used to form the adhesive layer contains a crosslinking agent, the crosslinking reaction between the acrylic copolymer and the crosslinking agent in the coating film can be promoted by changing the drying conditions (temperature, time, etc.) or by providing a separate heat treatment, thereby forming a crosslinked structure with a desired density in the adhesive layer. To ensure that this crosslinking reaction proceeds sufficiently, after laminating the adhesive layer onto the substrate by the method described above, the resulting adhesive sheet may be cured by, for example, leaving it undisturbed for several days in an environment of 23°C and 50% relative humidity.

[0070] Instead of transferring the adhesive layer formed on the release sheet to one side of the substrate as described above, the adhesive layer may be formed directly on the substrate. In this case, the coating liquid for forming the adhesive layer is applied to one side of the substrate to form a coating film, and the adhesive layer is formed by drying the coating film.

[0071] 6. How to use the adhesive sheet The adhesive sheet according to this embodiment can be used for handling workpieces such as semiconductor chips. Specifically, it can be used for sorting, rearranging, inspecting, storing, shipping, and transporting workpieces such as semiconductor chips.

[0072] For example, when sorting workpieces, generally only workpieces that meet a predetermined standard are transferred from one adhesive sheet to another. However, the adhesive sheet according to this embodiment can be used on either the first adhesive sheet or the other adhesive sheet. Furthermore, workpieces can be rearranged by stacking workpieces already laminated on adhesive sheets, etc., on the adhesive sheet according to this embodiment in a predetermined arrangement. In addition, workpieces can be inspected, stored, shipped, transported, etc., while they are stacked on the adhesive sheet according to this embodiment.

[0073] Furthermore, the adhesive sheet according to this embodiment can also be used for processing workpieces such as semiconductor wafers. That is, after attaching the adhesive surface of the adhesive sheet according to this embodiment to a workpiece, processing of the workpiece can be performed on the adhesive sheet. Depending on the processing, the adhesive sheet according to this embodiment can be used as a backgrind sheet, dicing sheet, expand sheet, pickup sheet, etc.

[0074] Furthermore, if the adhesive sheet according to this embodiment includes the aforementioned adhesive layer, the adhesive sheet can be used as a dicing and die bonding sheet. In addition, if the adhesive sheet according to this embodiment includes the aforementioned protective film forming layer, the adhesive sheet can be used as a protective film forming and dicing sheet.

[0075] The adhesive sheet according to this embodiment is not limited in that it can be used as a workpiece. Examples include semiconductor wafers, semiconductor packages and other semiconductor components, and glass plates and other glass components.

[0076] When the semiconductor material described above is used as the workpiece, the adhesive sheet according to this embodiment is also preferably used in a method for manufacturing a semiconductor device. This manufacturing method includes, for example, the steps of attaching one or more workpieces to the adhesive layer side of the adhesive sheet according to this embodiment, and separating at least one of the workpieces from the adhesive sheet and placing it on a predetermined object. The attachment and separation described above can be carried out using known methods.

[0077] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0078] For example, other layers may be provided between the substrate and the adhesive layer, or on the surface of the substrate opposite to the adhesive layer. [Examples]

[0079] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0080] [Example 1] (1) Preparation of acrylic polymers An acrylic polymer was obtained by polymerizing 78 parts by mass of 2-ethylhexyl acrylate, 12 parts by mass of methyl acrylate, and 10 parts by mass of 2-hydroxyethyl acrylate using a solution polymerization method. The weight-average molecular weight (Mw) of this acrylic polymer was 800,000.

[0081] (2) Preparation of tackifier 711 g of gum rosin, 107 g of glycerin, 189 g of fumaric acid, 2100 g of polypropylene glycol with a weight-average molecular weight of 1000, and 150 g of xylene were placed in a flask, and after purging with nitrogen, the mixture was heated at 280°C for 13 hours while stirring. Then, the xylene was removed under reduced pressure at 200°C for 20 minutes. Subsequently, the contents were removed from the flask and cooled to room temperature to solidify, thereby obtaining alkylene glycol-modified rosin ester as a tackifier.

[0082] (3) Preparation of adhesive composition 100 parts by mass (solid content equivalent; the same applies hereinafter) of the acrylic polymer obtained in (1) above, 0.075 parts by mass of the alkylene glycol-modified rosin ester obtained in (2) above as a tackifier, and 4.69 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate L") as a crosslinking agent were mixed in a solvent to obtain a coating solution of an adhesive composition with a solid content concentration of 30% by mass.

[0083] (4) Formation of the adhesive layer A release sheet (Lintec Corporation, product name "SP-PET381031"), which has a silicone-based release agent layer formed on one side of a 38 μm thick polyethylene terephthalate film, was coated with the adhesive composition solution prepared in (3) above using a comma coater, and then heated at 100°C for 1 minute to dry, thereby forming a 5 μm thick adhesive layer on the release sheet.

[0084] (5) Preparation of adhesive sheets After bonding the exposed surface of the adhesive layer formed in (4) above to one side of an ethylene-methacrylic acid copolymer film with a thickness of 80 μm as the base material, an adhesive sheet was obtained by leaving it undisturbed for one week in an environment of 23°C and 50% relative humidity.

[0085] Here, the weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight on a standard polystyrene basis, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> • GPC measuring device: Tosoh Corporation, HLC-8320 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Gel Super H-H TSK gel superHM-H TSK Gel Super H2000 • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0086] [Examples 2-10 and Comparative Examples 1-7] An adhesive sheet was obtained in the same manner as in Example 1, except that the composition of the adhesive composition was changed as shown in Tables 1 and 2.

[0087] Further details regarding the abbreviations and other terms listed in Tables 1 and 2 are as follows: 2EHA: 2-ethylhexyl acrylate MMA: Methyl methacrylate HEA: 2-hydroxyethyl acrylate BA: Butyl acrylate Alcon M-90: Hydrogenated petroleum resin (manufactured by Arakawa Chemical Industries, Ltd., product name "Alcon M-90") YS Polystar K125: Terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., product name "YS Polystar K125") YS Polystar U115: Terpene phenol resin (manufactured by Yasuhara Chemical, product name "YS Polystar U115") Ester Gum AA-G: Rosin ester (manufactured by Arakawa Chemical Industries, Ltd., product name "Ester Gum AA-G") Pine Crystal KE-100: Ultra-pale rosin ester (manufactured by Arakawa Chemical Industries, Ltd., product name "Pine Crystal KE-100")

[0088] [Test Example 1] (Evaluation of ease of peeling) The release liner was peeled off the adhesive sheets manufactured in the examples and comparative examples to expose the adhesive layer. Then, the exposed surface of the adhesive layer, as described above, was attached to the polished surface of a #2000 polished silicon wafer using a tape mounter (Lintec Corporation, "Adwill RAD2510F / 12"). Subsequently, a dicing ring frame was attached to the peripheral edge of the exposed surface of the adhesive sheet (a position that does not overlap with the silicon wafer). Furthermore, the adhesive sheet was cut to match the outer diameter of the ring frame.

[0089] Subsequently, using a dicing device (DISCO Corporation, product name "DFD6362"), the silicon wafer was diced on an adhesive sheet under the following conditions, resulting in individual silicon chips measuring 10mm x 10mm each.

[0090] <Dicing conditions> Wafer thickness: 150 μm Blade: ZH05-SD2000-N1-90 CC Blade rotation speed: 35,000 rpm Feed rate: 50 mm / min Blade height: 0.06mm Cutting water amount: 1.0L / min Cutting water temperature: 20℃

[0091] After 24 hours had elapsed since attaching a silicon wafer to an adhesive sheet, a single chip located near the center of the adhesive sheet when viewed from above was picked up using a pickup device (Canon Machinery Co., Ltd., product name "BESTEM D-510") at room temperature. The pickup speed was set to 20 mm / sec, the holding time to 0.1 msec, and the pickup amount was varied from 300 to 1000 μm. Simultaneously with this pickup, an attempt was made to separate the chip from the adhesive sheet using a 9.9 mm × 9.9 mm vacuum collet. These chip pickup and collet separation processes were repeated, with the pickup amount gradually changing. The minimum pickup height (μm) was determined when the chip could be picked up three times consecutively without any abnormalities. This minimum value is shown in Tables 1 and 2 as the minimum pickup height (μm) 24 hours after attachment.

[0092] Furthermore, the minimum push-up height (μm) was measured three months after the silicon wafer was attached to the adhesive sheet, in the same manner as described above. This is shown in Tables 1 and 2 as the minimum push-up height (μm) three months after attachment.

[0093] Furthermore, in both cases—24 hours after application and 3 months after application—if the minimum upward thrust height is 650 μm or less, it can be easily picked up, indicating excellent ease of removal.

[0094] [Test Example 2] (Measurement of Adhesion) The adhesive sheets produced in the examples and comparative examples were cut into strips 25 mm wide. The release sheet was peeled off from the resulting strip-shaped adhesive sheets, and the adhesive surface of the exposed adhesive layer was attached to the mirror-finished surface of a silicon wafer using a 2 kg rubber roller at a temperature of 23°C and a relative humidity of 50%, and left to stand for 20 minutes to be used as a sample for measurement.

[0095] For the obtained measurement samples, an adhesive sheet was peeled from the silicon wafer using a universal tensile testing machine (Orientec Co., Ltd., product name "Tensilon UTM-4-100") at a peeling speed of 300 mm / min and a peeling angle of 180°. The adhesive force (mN / 25mm) to the silicon wafer was measured using the 180° peeling method in accordance with JIS Z0237:2009. The results are shown in Tables 1 and 2.

[0096] [Table 1]

[0097] [Table 2]

[0098] As can be seen from Tables 1 and 2, the adhesive sheets obtained in the examples exhibited sufficient adhesive strength to silicon wafers and also showed excellent peelability. In particular, it was found that the adhesive sheets obtained in the examples could be easily peeled off the workpiece even after 3 months had elapsed since application. [Industrial applicability]

[0099] The adhesive sheet of the present invention can be suitably used for sorting, inspecting, rearranging, storing, shipping, and transporting workpieces.

Claims

1. An adhesive sheet for handling a workpiece, comprising a base material and an adhesive layer laminated on one side of the base material, The adhesive layer is made of an inactive energy ray curable adhesive formed from an adhesive composition containing at least an acrylic polymer and a tackifier. The tackifier is an alkylene glycol-modified rosin ester obtained by esterifying rosins, polyalkylene glycol monoalkyl ethers, polyhydric alcohols, and α,β-unsaturated carboxylic acids. An adhesive sheet characterized by the following features.

2. The adhesive sheet according to claim 1, characterized in that the content of the alkylene glycol-modified rosin ester as the tackifier in the adhesive composition is 0.01 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the acrylic polymer.

3. The aforementioned adhesive composition contains a crosslinking agent, The amount of the crosslinking agent in the adhesive composition is 0.1 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the acrylic polymer. The adhesive sheet according to feature 1 or 2.

4. The adhesive sheet according to any one of claims 1 to 3, characterized in that the adhesive force to the mirror surface of a silicon wafer is 200 mN / 25 mm or more and 3000 mN / 25 mm or less.

5. The adhesive sheet according to any one of claims 1 to 4, characterized in that, when a 10 mm x 10 mm silicon chip that has been attached to the side of the adhesive layer opposite to the substrate for three months is separated from the adhesive sheet by using a needle to push up the silicon chip from the substrate side of the adhesive sheet and sucking up the silicon chip with a vacuum collet of size 9.9 mm x 9.9 mm, the minimum height of the push-up required for separation is 750 μm or less.

6. A step of attaching one or more workpieces to the adhesive layer side of the adhesive sheet according to any one of claims 1 to 5, A step of separating at least one of the workpieces from the adhesive sheet and placing it on a predetermined object. A method for manufacturing a semiconductor device, characterized by comprising the above.

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