Method for manufacturing an adhesive sheet, method for manufacturing a semiconductor device, and adhesive sheet

Abstract

The present invention provides: an adhesive-sheet manufacturing method by which expansion of heat expandable particles during a manufacturing process is suppressed and by which it is possible to obtain an adhesive sheet that shows sufficient adhesive power when temporarily fixed and good heat peelability when thermally peeled; a method for manufacturing a semiconductor device that uses an adhesive sheet obtained by the adhesive-sheet manufacturing method; and an adhesive sheet obtained by the adhesive-sheet manufacturing method. The adhesive-sheet manufacturing method is a method for manufacturing an adhesive sheet that has: a base material (Y); and an adhesive layer (X1) that contains a polymer of energy-ray polymerizable components and heat expandable particles, the method including the following steps I and II. Step I: a step for forming, on one surface of the base material (Y), a polymerizable composition layer formed of a polymerizable composition (x-1) that contains the energy-ray polymerizable components and the heat expandable particles. Step II: a step for generating the polymer of the energy-ray polymerizable components by radiating energy rays onto the polymerizable composition layer, while cooling the polymerizable composition layer, to form the adhesive layer (X1).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an adhesive sheet, a method for manufacturing a semiconductor device, and an adhesive sheet.

Background Art

[0002] Adhesive sheets are used not only for semi-permanently fixing members, but also as temporary fixing sheets for temporarily fixing members (hereinafter also referred to as "adhered bodies") to be processed or inspected when processing or inspecting building materials, interior materials, electronic components, etc. For example, in the manufacturing process of semiconductor devices, a temporary fixing sheet is used when processing semiconductor wafers.

[0003] In the manufacturing process of semiconductor devices, semiconductor wafers are processed into semiconductor chips through a grinding process of reducing the thickness by grinding, a singulation process of cutting and separating into individual pieces, etc. At this time, the semiconductor wafer is subjected to predetermined processing in a state of being temporarily fixed to a temporary fixing sheet. The semiconductor chips obtained by performing the predetermined processing are separated from the temporary fixing sheet, and then, if necessary, an expand process of widening the interval between the semiconductor chips, a rearrangement process of arranging a plurality of semiconductor chips with widened intervals, an inversion process of inverting the front and back of the semiconductor chips, etc. are appropriately performed, and then mounted on a substrate. In each of the above processes, a temporary fixing sheet suitable for each use can be used.

[0004] Patent Document 1 discloses a heat-expandable adhesive sheet for temporary fixing during cutting of electronic components, in which a heat-expandable adhesive layer containing heat-expandable microspheres is provided on at least one side of a base material. The document describes that the heat-expandable adhesive sheet can exhibit adhesiveness capable of preventing adhesion failures such as chip jumping because it can secure a contact area of a predetermined size with respect to the adhered body during cutting of electronic components, and after use, by heating to expand the heat-expandable microspheres, the contact area with the adhered body can be reduced and it can be easily peeled off.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 3594853 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Incidentally, when mounting semiconductor chips onto a substrate, a process is employed in which the semiconductor chips are attached to the substrate via a thermosetting film-like adhesive called a die attach film (hereinafter also referred to as "DAF"). DAF is attached to one side of a semiconductor wafer or a group of individual semiconductor chips, and is divided into the same shape as the semiconductor chips either simultaneously with the individualization of the semiconductor wafer or after it has been attached to the semiconductor chips. The individualized semiconductor chips with DAF are attached to the substrate from the DAF side (die-attach), and then the semiconductor chips and substrates are fixed by heat curing the DAF. At this time, the DAF must maintain its adhesive properties through pressure or heat until it is attached to the substrate.

[0007] The heat-peelable adhesive sheet disclosed in Patent Document 1 peels off the adherend by forming irregularities on the adhesive surface through the expansion of thermally expandable microspheres. Because the formation of irregularities reduces the contact area between the adhesive layer and the semiconductor chip, this adhesive sheet has the advantage of being able to be peeled off the adherend with less force than temporary fixing sheets that harden the adhesive layer by energy ray irradiation to reduce adhesive strength. However, when a semiconductor chip with DAF is used as the substrate for a heat-peelable adhesive sheet, the heating required to expand the thermally expandable microspheres can cause the DAF to harden before die attachment, potentially reducing the adhesive strength of the DAF to the substrate. This reduction in DAF adhesive strength leads to a decrease in the reliability of the bond between the semiconductor chip and the substrate, and therefore it is desirable to suppress it. On the other hand, in order to suppress the hardening of the DAF before die attachment, if thermally expandable microspheres with a low expansion start temperature are used as the thermally expandable microspheres of the heat-peelable adhesive sheet so that it can be peeled off at low temperatures, problems may occur during the manufacturing process of the adhesive sheet, such as the thermally expandable microspheres expanding unintentionally. As a result, the performance of the sheet as a temporary fixation sheet may be impaired, such as a decrease in adhesive strength and an increased likelihood of air bubbles (air getting trapped between the adherend and the adhesive sheet) during application.

[0008] To suppress unintended expansion during the manufacturing process of adhesive sheets, it is effective to omit the heating step in the manufacturing process as much as possible. One possible method is to form a coating film using an energy-ray polymerizable component, and then irradiate it with energy rays to polymerize the energy-ray polymerizable component and form an adhesive layer. Because the energy-ray polymerizable component has a low molecular weight and its viscosity is easy to adjust, there is no need to use diluents when applying it, and the heat drying process when forming the adhesive layer can be omitted. However, even when using energy-ray polymerizable components, there were problems in the manufacturing process of adhesive sheets where thermally expandable particles expanded, resulting in insufficient adhesive strength during temporary fixing or poor heat release properties during heat peeling.

[0009] The present invention has been made in view of the above problems, and aims to provide a method for manufacturing an adhesive sheet, a method for manufacturing a semiconductor device using an adhesive sheet obtained by the method for manufacturing an adhesive sheet, and an adhesive sheet obtained by the method for manufacturing an adhesive sheet, which can be obtained by suppressing the expansion of thermally expandable particles during the manufacturing process and exhibiting sufficient adhesive strength during temporary fixing and good heat peelability during heat peeling. [Means for solving the problem]

[0010] The present inventors, after diligent research to solve the above problems, have found that the adhesive sheet can be configured to have a base material and an adhesive layer containing a polymer of an energy-ray polymerizable component and thermally expandable particles whose expansion initiation temperature is within a specific range. By irradiating a polymerizable composition layer formed on the base material using a polymerizable composition containing the energy-ray polymerizable component and the thermally expandable particles with energy rays under specific conditions to form the adhesive layer, the above problems can be solved, and the present invention has been completed. In other words, the present invention provides the following [1] to

[16] . [1] A method for producing an adhesive sheet having a base material (Y) and an adhesive layer (X1) containing a polymer of an energy ray polymerizable component and thermally expandable particles, the method comprising the following steps I and II. Step I: A step of forming a polymerizable composition layer on one side of a substrate (Y), consisting of a polymerizable composition (x-1) containing the energy ray polymerizable component and the thermally expandable particles. Step II: A step to generate a polymer of the energy-ray polymerizable component by irradiating the polymerizable composition layer with energy rays while cooling the polymerizable composition layer, thereby forming an adhesive layer (X1). [2] The method for manufacturing an adhesive sheet according to [1], wherein in step II, the polymerizable composition layer is cooled using a refrigerant while the polymerizable composition layer is irradiated with energy rays. [3] The method for manufacturing an adhesive sheet according to [2], wherein in step II, the polymerizable composition layer is cooled using a heat conductor cooled by the refrigerant while the polymerizable composition layer is irradiated with energy rays. [4] The method for manufacturing an adhesive sheet according to [3], wherein in step II, the polymerizable composition layer is cooled by bringing the heat conductor, which has been cooled by the refrigerant, into contact with the substrate (Y), while irradiating the polymerizable composition layer with energy rays. [5] A method for manufacturing an adhesive sheet according to any one of [1] to [4] above, wherein in step II, the polymerizable composition layer is cooled to a temperature lower than the expansion start temperature (t) of the thermally expandable particles while the polymerizable composition layer is irradiated with energy rays. [6] A method for manufacturing an adhesive sheet according to any one of [1] to [5] above, wherein in step II, the substrate (Y) on which the polymerizable composition layer is formed is shielded with a shielding member, and the polymerizable composition layer is irradiated with energy rays in the space shielded by the shielding member. [7] A method for manufacturing an adhesive sheet according to any one of [1] to [6] above, wherein the energy rays include ultraviolet light. [8] A method for producing an adhesive sheet according to any one of [1] to [7] above, wherein the polymerizable composition (x-1) does not contain a solvent. [9] A method for producing an adhesive sheet according to any one of [1] to [8] above, which does not include a step of heating the polymerizable composition (x-1).

[10] A method for manufacturing an adhesive sheet according to any one of [1] to [9] above, wherein in the adhesive sheet obtained in step II, the proportion of expanded particles among the thermally expandable particles present in the adhesive layer (X1) is 20% or less of the total number of thermally expandable particles.

[11] A method for manufacturing an adhesive sheet according to any one of [1] to

[10] above, further comprising the step of forming an adhesive layer (X2) on the surface of the substrate (Y) opposite to the adhesive layer (X1).

[12] The object to be processed is attached to the adhesive sheet obtained by the adhesive sheet manufacturing method described in any one of [1] to

[11] above. A method for manufacturing a semiconductor device, comprising the step of performing one or more processes selected from processing and inspection on the object to be processed, and then heating the adhesive sheet to a temperature (t) above the expansion start temperature (t) of the thermally expandable particles to expand the adhesive layer (X1).

[13] A method for manufacturing a semiconductor device, comprising the following steps 1A to 5A. Step 1A: A step of attaching the object to be processed to the adhesive layer (X2) of the adhesive sheet obtained by the adhesive sheet manufacturing method described in

[11] above, and attaching the support to the adhesive layer (X1). Step 2A: A step of applying one or more processes selected from grinding and fragmentation to the workpiece. Step 3A: A step of applying a thermosetting film to the side of the processed object opposite to the adhesive layer (X2). Step 4A: A step of heating the adhesive sheet to a temperature (t) above the expansion start temperature of the thermally expandable particles to separate the adhesive layer (X1) from the support. Step 5A: Step to separate the adhesive layer (X2) from the workpiece.

[14] The adhesive layer (X2) is an adhesive layer that hardens and loses its adhesive strength when irradiated with energy rays, The method for manufacturing a semiconductor device according to

[13] , wherein step 5A is a step of curing the adhesive layer (X2) by irradiating the adhesive layer (X2) with energy rays to separate the adhesive layer (X2) from the workpiece.

[15] An adhesive sheet comprising a base material (Y) and an adhesive layer (X1) containing a polymer of an energy ray polymerizable component and thermally expandable particles, An adhesive sheet in which, of the thermally expandable particles present in the adhesive layer (X1), the proportion of expanded particles is 20% or less of the total number of thermally expandable particles. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a method for manufacturing an adhesive sheet in which the expansion of thermally expandable particles during the manufacturing process is suppressed, and an adhesive sheet exhibiting sufficient adhesive strength during temporary fixing and good heat peelability during heat peeling is obtained, a method for manufacturing a semiconductor device using the adhesive sheet obtained by the method for manufacturing an adhesive sheet, and an adhesive sheet obtained by the method for manufacturing an adhesive sheet. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view showing an example of the structure of the adhesive sheet of the present invention. [Figure 2] This is a cross-sectional view showing an example of the structure of the adhesive sheet of the present invention. [Figure 3] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 4] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 5]This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 6] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 7] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 8] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 9] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 10] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 11] This is a cross-sectional view illustrating an example of the steps in the method for manufacturing the adhesive sheet of the present invention. [Figure 12] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Figure 13] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Figure 14] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Figure 15] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Figure 16] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Figure 17] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Figure 18] This is a cross-sectional view illustrating an example of the steps in the manufacturing method of the semiconductor device of the present invention. [Modes for carrying out the invention]

[0013] In this specification, "active ingredient" refers to the components contained in the composition in question, excluding the diluent solvent. Furthermore, in this specification, the mass-average molecular weight (Mw) is a value on a standard polystyrene basis measured by gel permeation chromatography (GPC), and specifically, it is a value measured based on the method described in the Examples.

[0014] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms. Furthermore, in this specification, the lower and upper limits described in steps for a preferred numerical range (e.g., range of content, etc.) can be combined independently. For example, from the description "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60".

[0015] In this specification, "energy beam" means an electromagnetic wave or charged particle beam that has an energy quantum, and examples include ultraviolet light, radiation, and electron beams. Ultraviolet light can be irradiated using, for example, an electrodeless lamp, high-pressure mercury lamp, metal halide lamp, or UV-LED as an ultraviolet light source. Electron beams can be irradiated using those generated by an electron beam accelerator or the like. In this specification, "energy ray polymerizability" means the property of polymerizing when irradiated with energy rays.

[0016] In this specification, whether a "layer" is a "non-thermally expandable layer" or a "thermally expandable layer" is determined as follows: If the layer being judged contains thermally expandable particles, the layer is heat-treated at the expansion start temperature (t) of the thermally expandable particles for 3 minutes. If the volume change rate calculated from the following formula is less than 5%, the layer is judged to be a "non-thermally expandable layer," and if it is 5% or more, the layer is judged to be a "thermally expandable layer." Volume change rate (%) = {(Volume of the layer after heat treatment - Volume of the layer before heat treatment) / Volume of the layer before heat treatment} × 100 Furthermore, a layer that does not contain thermally expandable particles is referred to as a "non-thermally expandable layer."

[0017] In this specification, the "front surface" of a semiconductor wafer and semiconductor chip refers to the surface on which a circuit is formed (hereinafter also referred to as the "circuit surface"), and the "back surface" of a semiconductor wafer and semiconductor chip refers to the surface on which no circuit is formed.

[0018] [Adhesive sheet] An adhesive sheet according to one aspect of the present invention is an adhesive sheet comprising a base material (Y) and an adhesive layer (X1) containing a polymer of an energy ray polymerizable component and thermally expandable particles, wherein the proportion of expanded particles among all thermally expandable particles present in the adhesive layer (X1) is 20% or less of the total number of thermally expandable particles.

[0019] An adhesive sheet according to one aspect of the present invention is peeled off from an adherend by heating the thermally expandable particles contained in the adhesive layer (X1) to a temperature above the expansion start temperature (t) to cause expansion, thereby forming irregularities on the adhesive surface of the adhesive layer (X1). In an adhesive sheet according to one aspect of the present invention, the contact area between the adhesive layer (X1) and the adherend can be reduced by the formation of the irregularities, thereby significantly reducing the adhesion between the adhesive sheet and the adherend. As a result, the adhesive sheet according to one aspect of the present invention can be peeled off from an adherend by the weight of the adhesive sheet or the weight of the adherend without applying any pulling force during heat peeling. Specifically, for example, when heat peeling an adhesive sheet according to one aspect of the present invention from an adherend, the adhesive sheet can be peeled off by orienting the adhesive sheet downwards and allowing gravity to drop the adhesive sheet from the adherend. In this specification, the state in which an adhesive sheet peels off or falls off from an adherend without the application of any force to remove it is referred to as "self-peeling." Furthermore, such a property is referred to as "self-peeling property." As described above, the adhesive sheet according to one aspect of the present invention reduces the contact area between the adhesive layer (X1) and the adherend when peeled off by heat, and therefore has superior self-peelability compared to temporary fixing sheets that harden the adhesive layer by energy ray irradiation to reduce adhesive strength.

[0020] Furthermore, since the proportion of expanded particles among all thermally expandable particles present in the adhesive layer (X1) is 20% or less of the total number of thermally expandable particles, the adhesive sheet according to one embodiment of the present invention, while having an adhesive layer (X1) containing a polymer of an energy ray polymerizable component and thermally expandable particles, has most of the thermally expandable particles in the adhesive layer (X1) remaining unexpanded, exhibiting sufficient adhesive strength during temporary fixing and good heat release properties when heated. In this specification, the ratio of the number of expanded particles to the total number of thermally expandable particles in the adhesive layer (X1) is a value measured based on the method described in the examples. Furthermore, the adhesive layer (X1) of an adhesive sheet according to one embodiment of the present invention is a layer formed by irradiating a polymerizable composition containing an energy-ray polymerizable component and thermally expandable particles with energy rays to form a polymer of the energy-ray polymerizable component. Since the polymerizable composition is made high molecular weight by subsequent energy-ray polymerization, it may contain low molecular weight energy-ray polymerizable components when forming the layer. Therefore, the polymerizable composition can be adjusted to a viscosity suitable for application without using solvents such as diluents. As a result, when forming the adhesive layer (X1) using the polymerizable composition, heating and drying to remove solvents can be omitted, and unintended expansion of thermally expandable particles during heating and drying can be suppressed.

[0021] The adhesive sheet according to one embodiment of the present invention may have a base material (Y) and an adhesive layer (X1), but depending on the application, it may also have layers other than the base material (Y) and the adhesive layer (X1). For example, when using an adhesive sheet according to one aspect of the present invention for processing an object, it is preferable to have a configuration (i.e., a double-sided adhesive sheet configuration) that includes a base material (Y), an adhesive layer (X1) provided on one side of the base material (Y), and an adhesive layer (X2) provided on the other side of the base material (Y). This configuration allows the object to be attached to either the adhesive layer (X1) or the adhesive layer (X2), and a support to be attached to the other adhesive layer. By fixing the object to the support via the adhesive sheet, vibration, displacement, and damage to fragile workpieces can be suppressed when processing the object, thereby improving processing accuracy and processing speed. In the following explanation, unless otherwise specified, "double-sided adhesive sheet" refers to an adhesive sheet having a base material (Y), an adhesive layer (X1) provided on one side of the base material (Y), and an adhesive layer (X2) provided on the other side of the base material (Y).

[0022] An adhesive sheet according to one aspect of the present invention may have a release agent on the adhesive surface of the adhesive layer (X1). Furthermore, if the adhesive sheet according to one aspect of the present invention has a double-sided adhesive sheet configuration, a release agent may be provided on at least one of the adhesive surfaces of the adhesive layer (X1) and the adhesive layer (X2).

[0023] Next, with reference to the drawings, the configuration of an adhesive sheet according to one embodiment of the present invention will be described in more detail.

[0024] [Composition of the adhesive sheet] An example of an adhesive sheet according to one aspect of the present invention is an adhesive sheet 1a having an adhesive layer (X1) on a substrate (Y), as shown in Figure 1(a). In addition, one embodiment of the present invention may have a configuration in which a release agent 10 is further provided on the adhesive surface of the adhesive layer (X1), as shown in Figure 1(b) of the adhesive sheet 1b.

[0025] Another embodiment of the present invention is an adhesive sheet having the configuration of the double-sided adhesive sheet described above. An example of an adhesive sheet having such a configuration is a double-sided adhesive sheet 2a, as shown in Figure 2(a), in which a substrate (Y) is sandwiched between two adhesive layers (X1 and X2). Alternatively, as shown in Figure 2(b), the double-sided adhesive sheet 2b may have a release agent 10a on the adhesive surface of the adhesive layer (X1) and a release agent 10b on the adhesive surface of the adhesive layer (X2).

[0026] In the case of the double-sided adhesive sheet 2b shown in Figure 2(b), if the peeling force when peeling the release agent 10a from the adhesive layer (X1) and the peeling force when peeling the release agent 10b from the adhesive layer (X2) are approximately the same, attempting to peel both release agents by pulling them outwards may cause the adhesive layer to be separated and peeled off along with the two release agents. From the viewpoint of suppressing such a phenomenon, it is preferable to use two types of release agents 10a and 10b that are designed to have different peeling forces from the adhesive layer to which they are attached.

[0027] Other forms of adhesive sheets include the double-sided adhesive sheet 2a shown in Figure 2(a), which has a structure in which a release agent, which has been treated to release on both sides, is laminated on one of the adhesive surfaces of the adhesive layer (X1) and the adhesive layer (X2), and this is wound into a roll.

[0028] An adhesive sheet according to one aspect of the present invention may or may not have another layer between the base material (Y) and the adhesive layer (X1). Furthermore, if the adhesive sheet according to one aspect of the present invention is a double-sided adhesive sheet, in addition to the above, it may or may not have another layer between the base material (Y) and the adhesive layer (X2). However, it is preferable that a layer capable of suppressing expansion on the surface opposite to the adhesive surface of the adhesive layer (X1) is directly laminated, and it is more preferable that the substrate (Y) is directly laminated.

[0029] <Base material (Y)> Examples of materials used to form the base material (Y) include resin, metal, paper, etc., and can be appropriately selected depending on the application of the adhesive sheet according to one embodiment of the present invention.

[0030] Examples of resins include polyolefin resins such as polyethylene and polypropylene; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; urethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfone; polyetheretherketone; polyethersulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; polyamide resins; acrylic resins; and fluorine resins. Examples of metals include aluminum, tin, chromium, and titanium. Examples of paper materials include tissue paper, medium-quality paper, fine-quality paper, impregnated paper, coated paper, art paper, sulfuric acid paper, and glassine paper. Among these, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferred.

[0031] These forming materials may consist of one type, or two or more types may be used in combination. Examples of substrates (Y) using two or more forming materials in combination include paper laminated with a thermoplastic resin such as polyethylene, and resin films or sheets containing resin with a metal layer formed on the surface. Methods for forming a metal layer include, for example, depositing metal using PVD methods such as vacuum deposition, sputtering, and ion plating, and attaching metal foil using a general adhesive.

[0032] From the viewpoint of improving interlayer adhesion between the substrate (Y) and other layers to be laminated, the surface of the substrate (Y) may be subjected to surface treatments such as oxidation, embossing, easy-adhesion treatment, or primer treatment. Oxidation methods include, for example, corona discharge treatment, plasma discharge treatment, chromic acid treatment (wet method), hot air treatment, ozone irradiation treatment, and ultraviolet irradiation treatment. Furthermore, surface texture creation methods include, for example, sandblasting and solvent treatment.

[0033] The base material (Y), along with the resin mentioned above, may also contain additives for the base material, such as ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, slip agents, antiblocking agents, colorants, etc. These additives for the base material may be used individually or in combination of two or more types. When the base material (Y) contains base material additives together with the resin, the content of each base material additive is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, per 100 parts by mass of the resin.

[0034] The base material (Y) is preferably a non-thermally expandable layer. When the base material (Y) is a non-thermally expandable layer, the volume change rate (%) of the base material (Y) calculated from the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and even more preferably less than 0.01%.

[0035] The base material (Y) may contain thermally expandable particles, but it is preferable that it does not contain thermally expandable particles, as long as it does not contradict the objectives of the present invention. If the base material (Y) contains thermally expandable particles, the lower the content, the better. Preferably, the content is less than 3% by mass, more preferably less than 1% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.01% by mass, and even more preferably less than 0.001% by mass, relative to the total mass (100% by mass) of the base material (Y).

[0036] (Storage modulus E'(23) of the substrate (Y) at 23°C) The storage elastic modulus E’(23) of the base material (Y) at 23°C is preferably 5.0×10 , , 9 , 9 , 9 , 9 ,

[0038] , 6 , , , 6 , 8 , 8 , ~5.0×10 9 Pa, more preferably 5.0×10 8 ~4.5×10 9 Pa, even more preferably 1.0×10 9 ~4.0×10 9 Pa. If the storage elastic modulus E’(23) of the base material (Y) is 5.0×10 7 Pa or more, the expansion of the surface of the adhesive layer (X1) on the base material (Y) side can be effectively suppressed, and the deformation resistance of the adhesive sheet can be improved. On the other hand, if the storage elastic modulus E’(23) of the base material (Y) is 5.0×10 9 Pa or less, the handling property of the adhesive sheet can be improved. In addition, in this specification, the storage elastic modulus E’(23) of the base material (Y) means the value measured by the method described in the examples.

[0037] (Storage elastic modulus E’(t) at the expansion start temperature (t) of the base material (Y)) The storage elastic modulus E’(t) of the base material (Y) at the expansion start temperature (t) of the thermally expandable particles is preferably 5.0×10 6 ~4.0×10<00000​​​​​​​​​​​​​​​​​(Thickness of base material (Y)) The thickness of the substrate (Y) is preferably 5 to 500 μm, more preferably 15 to 300 μm, and even more preferably 20 to 200 μm. If the thickness of the substrate (Y) is 5 μm or more, the deformation resistance of the adhesive sheet can be improved. On the other hand, if the thickness of the substrate (Y) is 500 μm or less, the handling of the adhesive sheet can be improved. In this specification, the thickness of the substrate (Y) refers to the value measured by the method described in the examples.

[0039] <Adhesive layer (X1)> The adhesive layer (X1) contains a polymer of an energy ray polymerizable component and thermally expandable particles. The polymer described above is a polymer obtained by irradiating an energy ray with a polymerizable composition (hereinafter also referred to as "polymerizable composition (x-1)") which contains a monomer (a1) having an energy ray polymerizable functional group (hereinafter also referred to as "component (a1)") and a prepolymer (a2) having an energy ray polymerizable functional group (hereinafter also referred to as "component (a2)").

[0040] (Polymerizable composition (x-1)) The energy-ray polymerizable component contained in polymerizable composition (x-1) is a component that polymerizes upon irradiation with energy rays and has an energy-ray polymerizable functional group. Examples of energy-ray polymerizable functional groups include those having a carbon-carbon double bond, such as (meth)acryloyl groups, vinyl groups, and allyl groups. In this specification, functional groups that contain a vinyl group or a substituted vinyl group as part of themselves, such as (meth)acryloyl groups and allyl groups, and vinyl groups or substituted vinyl groups themselves, may be collectively referred to as "vinyl group-containing groups." The following describes each component contained in the polymerizable composition (x-1).

[0041] [Monomer having an energy-ray polymerizable functional group (a1)] The monomer (a1) having an energy-ray polymerizable functional group can be any monomer having an energy-ray polymerizable functional group, and may also have hydrocarbon groups, functional groups other than energy-ray polymerizable functional groups, etc.

[0042] (a1) Examples of hydrocarbon groups that the component may have include aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and groups that combine these. The aliphatic hydrocarbon group may be a linear or branched aliphatic hydrocarbon group, or it may be an alicyclic hydrocarbon group. Examples of linear or branched aliphatic hydrocarbon groups include aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, sec-butyl group, n-pentyl group, n-hexyl group, 2-ethylhexyl group, n-octyl group, isooctyl group, n-decyl group, n-dodecyl group, n-myristyl group, n-palmityl group, and n-stearyl group. Examples of alicyclic hydrocarbon groups include cyclopentyl groups, cyclohexyl groups, isobornyl groups, and other alicyclic hydrocarbon groups having 3 to 20 carbon atoms. Examples of aromatic hydrocarbon groups include the phenyl group. Examples of groups that combine an aliphatic hydrocarbon group and an aromatic hydrocarbon group include the phenoxyethyl group and the benzyl group. Among these, from the viewpoint of further improving the adhesive strength of the adhesive layer (X1), it is preferable that component (a1) contains monomers having an energy-ray polymerizable functional group and a linear or branched aliphatic hydrocarbon group (a1-1) (hereinafter also referred to as "component (a1-1)"), monomers having an energy-ray polymerizable functional group and an alicyclic hydrocarbon group (a1-2) (hereinafter also referred to as "component (a1-2)"), etc.

[0043] If component (a1) contains component (a1-1), its content is preferably 20 to 80% by mass, more preferably 40 to 70% by mass, and even more preferably 50 to 60% by mass, relative to the total (100% by mass) of component (a1). If component (a1) contains component (a1-2), its content is preferably 5 to 60% by mass, more preferably 10 to 40% by mass, and even more preferably 20 to 30% by mass, relative to the total (100% by mass) of component (a1).

[0044] Examples of monomers having an energy-ray polymerizable functional group and a functional group other than an energy-ray polymerizable functional group include monomers having a hydroxyl group, carboxyl group, thiol group, primary or secondary amino group, etc., as the functional group other than the energy-ray polymerizable functional group. Among these, it is preferable that component (a1) contains a monomer (a1-3) (hereinafter also referred to as "component (a1-3)") having an energy-ray polymerizable functional group and a hydroxyl group, from the viewpoint of further improving the formation of the adhesive layer (X1). If component (a1) contains components (a1-3), the amount of components (a1-3) is preferably 1 to 60% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 20% by mass, relative to the total amount (100% by mass) of components (a1).

[0045] The number of energy-ray polymerizable functional groups in component (a1) may be one or two or more. Furthermore, from the viewpoint of further improving the self-peelability of the adhesive layer (X1), it is preferable that component (a1) contains a monomer (a1-4) having three or more energy-ray polymerizable functional groups (hereinafter also referred to as "component (a1-4)"). If component (a1) contains components (a1-4), the content of these components is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass, relative to the total (100% by mass) of components (a1).

[0046] As a monomer having one energy-ray polymerizable functional group, a monomer having one vinyl group-containing group (hereinafter also referred to as "polymerizable vinyl monomer") is preferred. As monomers having two or more energy-ray polymerizable functional groups, monomers having two or more (meth)acryloyl groups (hereinafter also referred to as "polyfunctional (meth)acrylate monomers") are preferred. By having component (a1) contain the above compound, the cohesive force of the adhesive obtained by polymerizing them is improved, and an adhesive layer (X1) with less contamination of the adherend after peeling can be formed.

[0047] Polymerizable vinyl monomer The polymerizable vinyl monomer is not particularly limited as long as it has a vinyl group-containing group, and conventionally known monomers can be used as appropriate. Polymerizable vinyl monomers may be used individually or in combination of two or more types.

[0048] Examples of polymerizable vinyl monomers include compounds corresponding to component (a1-1) above, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate; compounds corresponding to component (a1-2) above, such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; and (meth)acrylates that do not have functional groups other than vinyl groups in their molecule, such as phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and polyoxyalkylene-modified (meth)acrylate. Among these, 2-ethylhexyl acrylate and isobornyl acrylate are preferred.

[0049] Polymerizable vinyl monomers may further contain functional groups other than vinyl group-containing groups within the molecule. Examples of such functional groups include hydroxyl groups, carboxyl groups, thiol groups, and primary or secondary amino groups. Among these, polymerizable vinyl monomers having hydroxyl groups corresponding to the above components (a1-3) are preferred. Examples of polymerizable vinyl monomers having a hydroxyl group include hydroxyalkyl (meth)acrylates such as 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; and hydroxyl group-containing acrylamides such as N-methylolacrylamide and N-methylolmethacrylamide. Examples of polymerizable vinyl monomers having a carboxyl group include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferred.

[0050] Other polymerizable vinyl monomers include, for example, vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene monomers such as styrene and α-methylstyrene; diene monomers such as butadiene, isoprene, and chloroprene; nitrile monomers such as acrylonitrile and methacrylonitrile; amide monomers such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N-vinylpyrrolidone; and tertiary amino group-containing monomers such as N,N-diethylaminoethyl (meth)acrylate and N-(meth)acryloylmorpholine.

[0051] 《Multifunctional (meth)acrylate monomers》 The polyfunctional (meth)acrylate monomer is not particularly limited as long as it has two or more (meth)acryloyl groups in one molecule, and conventionally known monomers can be used as appropriate. The polyfunctional (meth)acrylate monomer may be used alone or in combination of two or more types.

[0052] Examples of polyfunctional (meth)acrylate monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, neopentyl glycol di(meth)acrylate hydroxypivalate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl) isocyanurate, allylated cyclohexyl di(meth)acrylate, isocyanurate ethylene oxide-modified diacrylate, and other bifunctional (meth)acrylate monomers; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate Examples of polyfunctional (meth)acrylate monomers corresponding to the above components (a1-4) include acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl) isocyanurate, bis(acryloxyethyl)hydroxyethyl isocyanurate, ethylene oxide-modified isocyanurate triacrylate, ε-caprolactone-modified tris(acryloxyethyl) isocyanurate, diglycerin tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, propionic acid-modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc.

[0053] (a1) Content of ingredient The total content of polymerizable vinyl monomers in polymerizable composition (x-1) is preferably 10 to 80% by mass, more preferably 30 to 75% by mass, and even more preferably 50 to 70% by mass, based on the total amount (100% by mass) of the active ingredients of polymerizable composition (x-1). The total content of polyfunctional (meth)acrylate monomers in polymerizable composition (x-1) is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and even more preferably 2 to 5% by mass, based on the total amount (100% by mass) of the active ingredients of polymerizable composition (x-1). The total content of component (a1) in polymerizable composition (x-1) is preferably 15 to 90% by mass, more preferably 35 to 80% by mass, and even more preferably 55 to 75% by mass, based on the total amount (100% by mass) of the active ingredients in polymerizable composition (x-1).

[0054] [Prepolymer having energy ray polymerizable functional groups (a2)] Examples of prepolymers (a2) having energy-ray polymerizable functional groups include prepolymers having one energy-ray polymerizable functional group and prepolymers having two or more energy-ray polymerizable functional groups. Among these, from the viewpoint of forming an adhesive layer that is excellent in self-peeling properties and has little contamination of the adherend after peeling, it is preferable that component (a2) contains a prepolymer having two or more energy-ray polymerizable functional groups, more preferably a prepolymer having two energy-ray polymerizable functional groups, and even more preferably a prepolymer having two energy-ray polymerizable functional groups and having the energy-ray polymerizable functional groups at both ends.

[0055] (a2) It is preferable that the component contains a prepolymer having two or more (meth)acryloyl groups as energy-ray polymerizable functional groups (hereinafter also referred to as "polyfunctional (meth)acrylate prepolymer"). By containing the above compound in component (a2), the cohesive force of the adhesive obtained by polymerizing them is improved, and an adhesive layer (X1) can be formed that has excellent self-peelability and less contamination of the adherend after peeling.

[0056] Multifunctional (meth)acrylate prepolymer The polyfunctional (meth)acrylate prepolymer is not particularly limited as long as it is a prepolymer having two or more (meth)acryloyl groups in one molecule, and conventionally known prepolymers can be used as appropriate. The polyfunctional (meth)acrylate prepolymer may be used alone or in combination of two or more types.

[0057] Examples of polyfunctional (meth)acrylate prepolymers include urethane acrylate prepolymers, polyester acrylate prepolymers, epoxy acrylate prepolymers, polyether acrylate prepolymers, polybutadiene acrylate prepolymers, silicone acrylate prepolymers, and polyacrylic acrylate prepolymers.

[0058] Urethane acrylate-based prepolymers can be obtained, for example, by reacting a compound such as a polyalkylene polyol, polyether polyol, polyester polyol, hydrogenated isoprene with a hydroxyl group terminus, or hydrogenated butadiene with a hydroxyl group terminus with a polyisocyanate, and then esterifying the resulting polyurethane prepolymer with (meth)acrylic acid or a (meth)acrylic acid derivative.

[0059] Examples of polyalkylene polyols used in the production of urethane acrylate-based prepolymers include polypropylene glycol, polyethylene glycol, polybutylene glycol, and polyhexylene glycol, with polypropylene glycol being preferred among these. If the resulting urethane acrylate-based prepolymer has three or more functional groups, appropriate combinations of glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, diethylenetriamine, sorbitol, sucrose, etc., may be used.

[0060] Examples of polyisocyanates used in the production of urethane acrylate-based prepolymers include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, and diphenyl diisocyanate; and alicyclic diisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate. Among these, aliphatic diisocyanates are preferred, and hexamethylene diisocyanate is more preferred. Polyisocyanates are not limited to bifunctional polyisocyanates; trifunctional polyisocyanates or those with three or more functions can also be used.

[0061] Examples of (meth)acrylic acid derivatives used in the production of urethane acrylate-based prepolymers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, and 1,1-bis(acryloxymethyl)ethyl isocyanate, among which 2-isocyanate ethyl acrylate is preferred.

[0062] Another method for producing urethane acrylate-based prepolymers involves reacting the hydroxyl groups of compounds such as polyalkylene polyols, polyether polyols, polyester polyols, hydrogenated isoprene with hydroxyl group termini, and hydrogenated butadiene with hydroxyl group termini with the -N=C=O moiety of isocyanate alkyl (meth)acrylate. In this case, examples of isocyanate alkyl (meth)acrylates that can be used include the above-mentioned 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, and 1,1-bis(acryloxymethyl)ethyl isocyanate.

[0063] Polyester acrylate prepolymers can be obtained, for example, by esterifying the hydroxyl groups of a polyester prepolymer having hydroxyl groups at both ends, obtained by condensation of a polycarboxylic acid and a polyhydric alcohol, with (meth)acrylic acid. Alternatively, they can be obtained by esterifying the terminal hydroxyl groups of a prepolymer obtained by adding an alkylene oxide to a polycarboxylic acid with (meth)acrylic acid.

[0064] Epoxyacrylate prepolymers can be obtained, for example, by reacting an oxirane ring of a relatively low molecular weight bisphenol-type epoxy resin or novolac-type epoxy resin with (meth)acrylic acid to esterify it. Alternatively, carboxylated epoxy acrylate prepolymers, obtained by partially modifying epoxy acrylate prepolymers with dibasic carboxylic acid anhydrides, can also be used.

[0065] Polyether acrylate prepolymers can be obtained, for example, by esterifying the hydroxyl groups of a polyether polyol with (meth)acrylic acid.

[0066] Polyacrylic acrylate prepolymers may have acryloyl groups in their side chains, or they may have acryloyl groups at both or one of their ends. Polyacrylic acrylate prepolymers having acryloyl groups in their side chains can be obtained, for example, by adding glycidyl methacrylate to the carboxyl group of polyacrylic acid. Polyacrylic acrylate prepolymers having acryloyl groups at both ends can be obtained, for example, by introducing acryloyl groups at both ends using the polymerization growth end structure of a polyacrylate prepolymer synthesized by the ATRP (Atom Transfer Radical Polymerization) method.

[0067] (a2) The mass-average molecular weight (Mw) of component is preferably 10,000 to 350,000, more preferably 15,000 to 200,000, and even more preferably 20,000 to 50,000.

[0068] (a2) Content of ingredient The total content of polyfunctional (meth)acrylate prepolymers in polymerizable composition (x-1) is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, and even more preferably 20 to 30% by mass, based on the total amount (100% by mass) of the active ingredients in polymerizable composition (x-1). The total content of component (a2) in polymerizable composition (x-1) is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, and even more preferably 20 to 30% by mass, based on the total amount (100% by mass) of the active ingredients in polymerizable composition (x-1).

[0069] The content ratio of component (a2) and component (a1) in polymerizable composition (x-1) [(a2) / (a1)] is preferably 10 / 90 to 70 / 30 by mass, more preferably 20 / 80 to 50 / 50, and even more preferably 25 / 75 to 40 / 60.

[0070] Among the energy ray polymerizable components described above, the polymerizable composition (x-1) preferably contains a polymerizable vinyl monomer, a polyfunctional (meth)acrylate monomer, and a polyfunctional (meth)acrylate prepolymer. The total content of polymerizable vinyl monomer, polyfunctional (meth)acrylate monomer, and polyfunctional (meth)acrylate prepolymer in the energy ray polymerizable component contained in polymerizable composition (x-1) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more, and may be 100% by mass, based on the total amount of energy ray polymerizable component (100% by mass).

[0071] The total content of energy ray polymerizable components in polymerizable composition (x-1) is preferably 70 to 98% by mass, more preferably 75 to 97% by mass, even more preferably 80 to 96% by mass, and even more preferably 82 to 95% by mass, based on the total amount (100% by mass) of the active ingredients in polymerizable composition (x-1).

[0072] [Thermally expanding particles] Thermally expandable particles are any particles that expand when heated. The expansion start temperature (t) of the thermally expandable particles can be appropriately adjusted within the above range depending on the application of the adhesive sheet. For example, from the viewpoint of suppressing the expansion of thermally expandable particles due to temperature rise, such as when grinding the adherend, it is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, and even more preferably 70°C or higher. From the viewpoint of suppressing the thermal change of the adherend when peeling off by heating, it is preferably 120°C or lower, more preferably 110°C or lower, even more preferably 105°C or lower, even more preferably 100°C or lower, and particularly preferably 95°C or lower. In this specification, the expansion initiation temperature (t) of thermally expandable particles refers to the value measured based on the following method. [Method for measuring the expansion onset temperature (t) of thermally expandable particles] A sample is prepared by adding 0.5 mg of the thermally expandable particles to be measured to an aluminum cup with a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm, and then placing an aluminum lid (diameter 5.6 mm, thickness 0.1 mm) on top. Using a dynamic viscoelasticity measuring device, the height of the sample is measured while a force of 0.01 N is applied to the sample from the top of the aluminum lid using a pressure bar. Then, while the force of 0.01 N is applied by the pressure bar, the sample is heated from 20°C to 300°C at a heating rate of 10°C / min, and the vertical displacement of the pressure bar is measured. The temperature at which the displacement in the positive direction begins is defined as the expansion start temperature (t).

[0073] The thermally expandable particles are preferably microencapsulated foaming agents, which consist of an outer shell made of a thermoplastic resin and an inner component enclosed within the outer shell that vaporizes when heated to a predetermined temperature. The thermoplastic resin constituting the outer shell of the microencapsulated foaming agent is not particularly limited, and any material and composition that can undergo a change of state such as melting, dissolving, or bursting at the expansion start temperature (t) of thermally expandable particles, which is 50 to 110°C, should be appropriately selected. Examples of the thermoplastic resins mentioned above include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone. These thermoplastic resins may be used individually or in combination of two or more.

[0074] The encapsulated components, which are the components contained within the outer shell of the microencapsulated foaming agent, can be any substance that expands at the expansion start temperature (t) of thermally expandable particles, which is 50 to 110°C. Examples of low-boiling point liquids include propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, n-heptane, n-octane, cyclopropane, cyclobutane, and petroleum ether. These encapsulated components may be used individually or in combination of two or more. The expansion initiation temperature (t) of thermally expandable particles can be adjusted by appropriately selecting the type of internal components.

[0075] The average particle diameter of the thermally expandable particles at 23°C before thermal expansion is preferably 1 to 30 μm, more preferably 4 to 25 μm, even more preferably 6 to 20 μm, and even more preferably 10 to 15 μm. Note that the average particle diameter (D) of thermally expandable particles 50 ) refers to the mid-volume particle size (D 50 This refers to the particle size corresponding to 50% of the cumulative volume frequency calculated from the smallest particle size in the particle distribution of thermally expandable particles before expansion, as measured using a laser diffraction particle size distribution analyzer (for example, Malvern's "Mastersizer 3000").

[0076] The 90% particle diameter (D) of thermally expandable particles at 23°C before thermal expansion. 90 The particle size is preferably 2 to 60 μm, more preferably 8 to 50 μm, even more preferably 12 to 40 μm, and even more preferably 20 to 30 μm. Note that the 90% particle diameter (D) of thermally expandable particles 90) refers to the particle size corresponding to 90% of the cumulative volume frequency calculated from the smallest particle size in the particle distribution of thermally expandable particles before expansion, as measured using the laser diffraction particle size distribution analyzer described above.

[0077] When thermally expandable particles are heated to a temperature above their expansion start temperature (t), the maximum volume expansion rate is preferably 1.5 to 200 times, more preferably 2 to 150 times, even more preferably 2.5 to 120 times, and even more preferably 3 to 100 times.

[0078] The content of thermally expandable particles is preferably 1 to 30% by mass, more preferably 2 to 25% by mass, and even more preferably 3 to 20% by mass, relative to the total amount (100% by mass) of the active ingredients of the polymerizable composition (x-1) or the total mass (100% by mass) of the adhesive layer (X1). If the content of thermally expandable particles is 1% by mass or more, it becomes easier to improve peelability when peeled off by heat. Furthermore, if the content of thermally expandable particles is 30% by mass or less, the adhesive strength of the adhesive layer (X1) is improved, and curling of the adhesive sheet when peeled off by heat is suppressed, making it easier to handle.

[0079] The proportion of expanded particles among all thermally expandable particles present in the adhesive layer (X1) can be calculated by the method described in the examples. Specifically, the surface of the adhesive layer (X1) is observed using a digital microscope (Keyence Corporation, product name "Digital Microscope VHX-5000"), and the particle diameter measured from the obtained magnified image (500 μm × 500 μm) is the 90% particle diameter (D) of the thermally expandable particles before expansion. 90 m1 is the number of thermally expandable particles below 90% of the particle size (D 90 Let m² be the number of thermally expandable particles larger than ) and count the number of each. The ratio P of the number of expanded thermal expandable particles to the total number of thermal expandable particles is calculated using the formula P = 100 × [m2 / (m1+m2)](%), where m1 and m2 are the numbers mentioned above. In the adhesive sheet according to this embodiment, this number ratio P is 20% or less, preferably less than 15%, and more preferably less than 12%. 90% particle diameter (D90 Since it is calculated based on ), theoretically, if none of the particles expand at all, P will be 10%. As the ratio P of the number of expanded particles in the adhesive layer (X1) falls within the above numerical range, the adhesive sheet exhibits sufficient adhesive strength during temporary fixing and good heat release properties during heat release. To achieve the above-mentioned ratio of expanded particles among all thermally expandable particles present in the adhesive layer (X1), this can be achieved by using a method that suppresses the expansion of thermally expandable particles during the polymerization of the energy-ray polymerizable component by cooling the polymerizable composition layer when irradiating it with energy rays to polymerize the energy-ray polymerizable component, as described later.

[0080] [Other ingredients] The polymerizable composition (x-1) may contain other components besides energy-ray polymerizable components and thermally expandable particles. Other components mentioned above include photopolymerization initiators, tackifiers, and general adhesive additives used in adhesives other than those listed above. Among these, it is preferable that the polymerizable composition (x-1) contains a photopolymerization initiator.

[0081] Photopolymerization initiator The polymerizable composition (x-1) contains a photopolymerization initiator, which allows the polymerization of the energy ray polymerizable component to proceed more efficiently.

[0082] Examples of photopolymerization initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, Examples include p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. The photopolymerization initiator may be used alone or in combination of two or more.

[0083] If the polymerizable composition (x-1) contains a photopolymerization initiator, its content is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, and even more preferably 0.3 to 1 part by mass, per 100 parts by mass of the energy ray polymerizable component. If the photopolymerization initiator content is 0.1 parts by mass or more, the polymerization of the energy ray polymerizable component can be carried out more efficiently. On the other hand, if the content is 10 parts by mass or less, it becomes possible to eliminate or reduce the amount of unreacted photopolymerization initiator remaining, making it easier to adjust the resulting adhesive layer (X1) to the desired physical properties.

[0084] 《Adhesion Agent》 Tackifiers are components used as needed to further improve adhesion. In this specification, "tackifier" refers to a substance with a mass-average molecular weight (Mw) of less than 10,000, and is distinct from the adhesive resin described later. The mass-average molecular weight (Mw) of the tackifier is less than 10,000, preferably 400 to 9,000, more preferably 500 to 8,000, and even more preferably 800 to 5,000.

[0085] Examples of tackifiers include rosin resins, terpene resins, styrene resins, C5 petroleum resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperine, and 1,3-pentadiene produced by the thermal decomposition of petroleum naphtha, C9 petroleum resins obtained by copolymerizing C9 fractions such as indene and vinyltoluene produced by the thermal decomposition of petroleum naphtha, and hydrogenated resins obtained by hydrogenating these.

[0086] The softening point of the tackifier is preferably 60 to 170°C, more preferably 65 to 160°C, and even more preferably 70 to 150°C. In this specification, the "softening point" of the tackifier refers to the value measured in accordance with JIS K 2531. The tackifier may be used alone, or two or more types with different softening points, structures, etc., may be used in combination. When two or more tackifiers are used, it is preferable that the weighted average of the softening points of the multiple tackifiers falls within the above range.

[0087] If the polymerizable composition (x-1) contains a tackifier, its content is preferably 0.01 to 65% by mass, more preferably 0.1 to 50% by mass, even more preferably 1 to 40% by mass, and even more preferably 2 to 30% by mass, based on the total amount (100% by mass) of the active ingredients of the polymerizable composition (x-1).

[0088] Additives for adhesives Examples of adhesive additives include silane coupling agents, antioxidants, plasticizers, rust inhibitors, pigments, dyes, retarders, reaction accelerators (catalysts), and ultraviolet absorbers. These adhesive additives may be used individually or in combination of two or more types.

[0089] If the polymerizable composition (x-1) contains adhesive additives, the content of each adhesive additive is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, per 100 parts by mass of the energy ray polymerizable component.

[0090] The polymerizable composition (x-1) may contain solvents such as diluents, as long as it does not contradict the objectives of the present invention, but it is preferable that it does not contain solvents. In other words, it is preferable that the polymerizable composition (x-1) is a solvent-free polymerizable composition. Because the polymerizable composition (x-1) is a solvent-free polymerizable composition, the heating and drying of the solvent can be omitted when forming the adhesive layer (X1), thereby suppressing the expansion of thermally expandable particles during heating and drying. Furthermore, when a solvent is used, the thermally expandable particles tend to be unevenly distributed on one side due to the volume reduction during drying, which can lead to reduced adhesion to the substrate (Y) or reduced adhesive strength of the adhesive surface. On the other hand, with a solvent-free polymerizable composition, polymerization proceeds with the thermally expandable particles remaining uniformly dispersed in the energy-ray polymerizable component, forming the adhesive layer (X1), thus making the above-mentioned problems less likely to occur. If the polymerizable composition (x-1) contains a solvent, the lower the solvent content, the better. Preferably, the solvent content is 10% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less, relative to the total amount (100% by mass) of the active ingredients of the polymerizable composition (x-1).

[0091] The polymerizable composition (x-1) can be produced by mixing an energy-ray polymerizable component, thermally expandable particles, and other components as needed. The resulting polymerizable composition (x-1) is then subjected to energy-ray polymerization to increase its molecular weight, and when forming a layer, the viscosity can be adjusted to an appropriate level using the low molecular weight energy-ray polymerizable component. Therefore, the polymerizable composition can be used directly as a coating solution to form the adhesive layer (X1) without adding any solvents such as diluents. Furthermore, the adhesive layer (X1) formed by irradiating the polymerizable composition (x-1) with energy rays contains a wide variety of polymers formed by the polymerization of energy ray polymerizable components, as well as thermally expandable particles dispersed within these polymers. However, directly identifying these polymers by their structure and physical properties is either impossible or impractical.

[0092] (Adhesion of the adhesive layer (X1) at 23°C before thermal expansion) The adhesive strength of the adhesive layer (X1) at 23°C before thermal expansion is preferably 0.1 to 12.0 N / 25 mm, more preferably 0.5 to 9.0 N / 25 mm, even more preferably 1.0 to 8.0 N / 25 mm, and even more preferably 1.2 to 7.5 N / 25 mm. If the adhesive strength of the adhesive layer (X1) at 23°C before thermal expansion is 0.1 N / 25 mm or higher, unintended peeling from the adherend and displacement of the adherend during temporary fixing can be more effectively suppressed. On the other hand, if the adhesive strength is 12.0 N / 25 mm or lower, peelability during heat peeling can be further improved. In this specification, the adhesive strength of the adhesive layer refers to the adhesive strength to the mirror surface of the silicon mirror wafer. Furthermore, in this specification, the adhesive strength of the adhesive layer (X1) at 23°C before thermal expansion specifically refers to the value measured by the method described in the examples.

[0093] (Adhesion strength of the adhesive layer (X1) at 23°C after thermal expansion) The adhesive strength of the adhesive layer (X1) at 23°C after thermal expansion is preferably 1.5 N / 25 mm or less, more preferably 0.05 N / 25 mm or less, even more preferably 0.01 N / 25 mm or less, and even more preferably 0 N / 25 mm. Note that an adhesive strength of 0 N / 25 mm means an adhesive strength below the measurement limit in the method for measuring adhesive strength at 23°C after thermal expansion, as described later, and includes cases where the adhesive sheet peels off unintentionally because the adhesive strength is too low when fixing it for measurement. In this specification, the adhesive strength of the adhesive layer (X1) at 23°C after thermal expansion specifically refers to the value measured by the method described in the examples.

[0094] (Shear storage modulus G'(23) of the adhesive layer (X1) at 23°C) The shear storage modulus G'(23) of the adhesive layer (X1) at 23°C is preferably 1.0 × 10⁻⁶. 4 ~5.0×10 7 Pa, comfortable 5.0 × 10 4 ~1.0×10 7 Pa, more preferably 1.0 × 10 5 ~5.0×10 6 It is Pa. The shear storage modulus G'(23) of the adhesive layer (X1) is 1.0 × 10⁻⁶ 4 If the shear storage modulus G'(23) is 1.0 × 10⁻⁶, it is possible to suppress displacement of the adherend during temporary fixing, excessive sinking of the adherend into the adhesive layer (X1), and to suppress curling of the peeled adhesive sheet. On the other hand, if the shear storage modulus G'(23) is 1.0 × 10⁻⁶ 7 If the Pa level is below a certain level, the expansion of thermally expandable particles makes it easier to form irregularities on the surface of the adhesive layer (X1), which improves the peelability when peeled off by heat. In this specification, the shear storage modulus G' of the adhesive layer at a predetermined temperature refers to the value measured by the method described in the examples.

[0095] The adhesive layer (X1) is a layer containing thermally expandable particles, and the shear storage modulus G' of the adhesive layer (X1) may be affected by the thermally expandable particles. From the viewpoint of measuring the shear storage modulus G' while excluding the effect of thermally expandable particles, an adhesive layer having the same configuration as the adhesive layer (X1) except that it does not contain thermally expandable particles (hereinafter also referred to as "non-expandable adhesive layer (X1')") may be prepared, and the shear storage modulus G' of the adhesive layer may be measured.

[0096] (Shear storage modulus G'(23) of the non-expanding adhesive layer (X1') at 23°C) The shear storage modulus G'(23) of the non-expandable adhesive layer (X1') at 23°C is preferably 1.0 × 10⁻⁶. 4 ~5.0×10 7 Pa, comfortable 5.0 × 10 4 ~1.0×10 7 Pa, more preferably 1.0 × 10 5 ~5.0×10 6 It is Pa. The shear storage modulus G'(23) of the non-expandable adhesive layer (X1') is 1.0 × 10⁻⁶. 4 If the shear storage modulus G'(23) is 5.0 × 10⁻¹⁰ or higher, displacement of the adherend during temporary fixing and excessive sinking of the adherend into the adhesive layer (X1) can be suppressed. 7 If the Pa level is below a certain level, the expansion of thermally expandable particles makes it easier to form irregularities on the surface of the adhesive layer (X1), which improves the peelability when peeled off by heat.

[0097] (Shear storage modulus G'(t) at the expansion initiation temperature (t) of the non-expanding adhesive layer (X1')) The shear storage modulus G'(t) of the non-expandable adhesive layer (X1') at the expansion initiation temperature (t) of the thermally expandable particles is preferably 5.0 × 10⁻⁶. 3 ~1.0×10 7 Pa, comfortable 1.0 × 10 4 ~5.0×10 6 Pa, more preferably 5.0 × 10 4 ~1.0×10 6 It is Pa. The shear storage modulus G'(t) of the non-expandable adhesive layer (X1') is 5.0 × 10 3 If the shear storage modulus G'(t) is 1.0 × 10⁻¹⁰ or higher, it can suppress displacement of the adherend during temporary fixing, excessive sinking of the adherend into the adhesive layer (X1), and also suppress curling of the adhesive sheet during heat peeling, making it easier to handle. On the other hand, if the shear storage modulus G'(t) is 1.0 × 10⁻¹⁰ 7 If the Pa level is below a certain level, the expansion of thermally expandable particles makes it easier to form irregularities on the surface of the adhesive layer (X1), which improves the peelability when peeled off by heat. In this specification, the shear storage modulus G' of the non-expandable adhesive layer (X1') at a predetermined temperature refers to the value measured by the method described in the examples.

[0098] (Thickness of the adhesive layer (X1) at 23°C) The thickness of the adhesive layer (X1) at 23°C is preferably 5 to 150 μm, more preferably 10 to 100 μm, even more preferably 20 to 70 μm, and even more preferably 30 to 50 μm. If the thickness of the adhesive layer (X1) at 23°C is 5 μm or more, sufficient adhesive strength is more easily obtained, and unintended peeling from the adherend and displacement of the adherend during temporary fixing are more easily suppressed. On the other hand, if the thickness of the adhesive layer (X1) at 23°C is 150 μm or less, peelability during heat peeling is improved, and curling of the peeled adhesive sheet is more easily suppressed. In this specification, the thickness of the adhesive layer refers to the value measured by the method described in the examples. Furthermore, the thickness of the adhesive layer (X1) is the value before the thermally expandable particles expand.

[0099] (Percentage of expanded particles in the adhesive layer (X1) after heating) When the adhesive layer (X1) is heated to a temperature above the expansion start temperature of the thermally expandable particles, it is preferable that 90% or more of the thermally expandable particles contained in the adhesive layer (X1) expand, more preferably 92% or more expand, and even more preferably 95% or more expand. The expansion of 90% or more of the thermally expandable particles creates sufficient irregularities on the surface of the adhesive layer (X1), making it easier to ensure sufficient peelability when peeled off by heat.

[0100] <Adhesive layer (X2)> The adhesive layer (X2) is a layer that is arbitrarily provided on the side of the substrate (Y) opposite to the side on which the adhesive layer (X1) is provided. The adhesive layer (X2) may be a thermally expandable layer or a non-thermally expandable layer, but it is preferable that it be a non-thermally expandable layer. By making the mechanisms for reducing the adhesive strength of the adhesive layers (X1) and (X2) different, it is possible to suppress the unintentional reduction of the adhesive strength of the other adhesive layer when performing a treatment to reduce the adhesive strength of one of the adhesive layers.

[0101] When the adhesive layer (X2) is a non-thermally expandable layer, the volume change rate (%) of the adhesive layer (X2) calculated from the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and even more preferably less than 0.01%. The adhesive layer (X2) preferably does not contain thermally expandable particles, but may contain thermally expandable particles to the extent that it does not contradict the objectives of the present invention. If the adhesive layer (X2) contains thermally expandable particles, the lower the content, the better. Preferably, the content is less than 3% by mass, more preferably less than 1% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.01% by mass, and even more preferably less than 0.001% by mass, relative to the total mass (100% by mass) of the adhesive layer (X2).

[0102] The adhesive layer (X2) is preferably formed from an adhesive composition (x-2) containing an adhesive resin. The components contained in the adhesive composition (x-2) are described below.

[0103] (Adhesive composition (x-2)) The adhesive composition (x-2) contains an adhesive resin and may optionally contain a crosslinking agent, a tackifier, a polymerizable compound, a polymerization initiator, or other general adhesive additives used in adhesives other than the above components.

[0104] [Adhesive resin] The adhesive resin can be any polymer that possesses adhesive properties on its own and has a mass-average molecular weight (Mw) of 10,000 or more. The mass-average molecular weight (Mw) of the adhesive resin is preferably 10,000 to 2,000,000, more preferably 20,000 to 1,500,000, and even more preferably 30,000 to 1,000,000, from the viewpoint of further improving the adhesive strength of the adhesive layer (X2).

[0105] Examples of adhesive resins include acrylic resins, urethane resins, rubber resins such as polyisobutylene resins, polyester resins, olefin resins, silicone resins, and polyvinyl ether resins. These adhesive resins may be used individually or in combination of two or more types. Furthermore, if these adhesive resins are copolymers having two or more constituent units, the copolymer may be in the form of a block copolymer, a random copolymer, or a graft copolymer.

[0106] The adhesive composition (x-2) containing the adhesive resin is preferably an adhesive composition that hardens upon irradiation with energy rays, from the viewpoint of differentiating the mechanism of action for the reduction of adhesive strength with the adhesive layer (X1), and the adhesive resin is more preferably a resin having energy ray polymerizable functional groups in the side chains of the above-mentioned adhesive resin. By forming the adhesive layer (X2) from this adhesive composition, the adhesive layer (X2) can be made into an adhesive layer that hardens upon irradiation with energy rays and whose adhesive strength decreases. Examples of energy-ray polymerizable functional groups include those having a carbon-carbon double bond, such as (meth)acryloyl groups, vinyl groups, and allyl groups. Among the energy rays mentioned above, ultraviolet light is preferred because it is easy to handle. Furthermore, the adhesive composition (x-2) may contain, together with, an adhesive resin having an energy-ray polymerizable functional group, or, in place of the adhesive resin having an energy-ray polymerizable functional group, a monomer or prepolymer having an energy-ray polymerizable functional group. Examples of monomers or prepolymers having energy-ray polymerizable functional groups include the same energy-ray polymerizable components contained in the polymerizable composition (x-1) described above.

[0107] When the adhesive composition (x-2) is an adhesive composition that hardens by irradiation with energy rays, it is preferable that the adhesive composition further contains a photopolymerization initiator. By including a photopolymerization initiator, the polymerization of energy ray polymerizable components can be carried out more efficiently. Examples of photopolymerization initiators include those that may be contained in polymerizable composition (x-1). The content of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.05 to 2 parts by mass, based on 100 parts by mass of the total amount of the adhesive resin, monomer, and prepolymer having energy-ray polymerizable functional groups.

[0108] From the viewpoint of exhibiting excellent adhesive strength, the adhesive resin preferably contains an acrylic resin. The content of acrylic resin in the adhesive composition (x-2) is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, even more preferably 70 to 100% by mass, and even more preferably 85 to 100% by mass, based on the total amount (100% by mass) of adhesive resin contained in the adhesive composition (x-2).

[0109] The content of the adhesive resin in the adhesive composition (x-2) is preferably 35 to 100% by mass, more preferably 50 to 100% by mass, even more preferably 60 to 98% by mass, and even more preferably 70 to 95% by mass, based on the total amount (100% by mass) of the active ingredients of the adhesive composition (x-2).

[0110] [Crosslinking agent] In one embodiment of the present invention, if the adhesive composition (x-2) contains an adhesive resin having a functional group, it is preferable that the adhesive composition (x-2) further contains a crosslinking agent. The crosslinking agent reacts with adhesive resins having functional groups, and crosslinks the adhesive resins with each other, using the functional groups as the starting point for crosslinking.

[0111] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents. The crosslinking agent may be used alone or in combination of two or more types. Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoint of increasing cohesive force and improving adhesiveness, as well as from the viewpoint of availability.

[0112] The amount of crosslinking agent is adjusted as appropriate depending on the number of functional groups in the adhesive resin, but is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass per 100 parts by mass of the adhesive resin having functional groups.

[0113] [Tackifier] In one embodiment of the present invention, the adhesive composition (x-2) may further contain a tackifier from the viewpoint of further improving the adhesive strength. As the tackifier that may be contained in the adhesive composition (x-2), one equivalent to the tackifier that may be contained in the polymerizable composition (x-1) can be used.

[0114] [Additives for adhesives] Examples of adhesive additives include those that may be contained in polymerizable composition (x-1) and are the same as other adhesive additives. Furthermore, if the adhesive composition (x-2) does not contain thermally expandable particles, there is no need to avoid heating and drying to a temperature (t) above the expansion start temperature of the thermally expandable particles; therefore, the adhesive composition (x-2) may contain a solvent as needed.

[0115] The adhesive composition (x-2) can be manufactured by mixing an adhesive resin, a crosslinking agent, a tackifier, an adhesive additive, etc., as needed.

[0116] [Adhesive strength of the adhesive layer (X2)] The adhesive strength on the adhesive surface of the adhesive layer (X2) is preferably 0.1 to 10.0 N / 25 mm, more preferably 0.2 to 8.0 N / 25 mm, even more preferably 0.4 to 6.0 N / 25 mm, and even more preferably 0.5 to 4.0 N / 25 mm. If the adhesive strength on the adhesive surface of the adhesive layer (X2) is 0.1 N / 25 mm or higher, unintended peeling from the adherend and displacement of the adherend during temporary fixing can be more effectively suppressed. On the other hand, if the adhesive strength is 10.0 N / 25 mm or lower, it becomes easier to peel off without damaging the adherend.

[0117] [Shear storage modulus G'(23) of the adhesive layer (X2) at 23°C] The shear storage modulus G'(23) of the adhesive layer (X2) at 23°C is preferably 5.0 × 10⁻⁶. 3 ~1.0×10 7 Pa, comfortable 1.0 × 10 4 ~5.0×10 6 Pa, more preferably 5.0 × 10 4 ~1.0×10 6 It is Pa. The shear storage modulus G'(23) of the adhesive layer (X2) is 5.0 × 10 3 If the shear storage modulus G'(23) is 1.0 × 10⁻⁶, it becomes easier to suppress displacement of the adherend during temporary fixing and excessive sinking of the adherend into the adhesive layer (X2).7 If the pressure is below Pa, it becomes easier to improve adhesion to the substrate. In this specification, the shear storage modulus G'(23) of the adhesive layer (X2) at 23°C can be measured by the same method as the shear storage modulus G' of the adhesive layer (X1) at 23°C.

[0118] [Thickness of the adhesive layer (X2) at 23°C] The thickness of the adhesive layer (X2) at 23°C is preferably 5 to 150 μm, more preferably 8 to 100 μm, even more preferably 12 to 70 μm, and even more preferably 15 to 50 μm. If the thickness of the adhesive layer (X2) at 23°C is 5 μm or more, sufficient adhesive strength is more easily obtained, making it easier to suppress unintended peeling from the adherend and displacement of the adherend during temporary fixing. On the other hand, if the thickness of the adhesive layer (X2) at 23°C is 150 μm or less, the handling of the adhesive sheet becomes easier.

[0119] <Release agent> Examples of release agents include release sheets that have been treated on both sides, release sheets that have been treated on one side, and release agents applied to a base material for release agents. Examples of substrates for release agents include paper and plastic films. Examples of paper include fine paper, glassine paper, and kraft paper, and examples of plastic films include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; and olefin resin films such as polypropylene resin and polyethylene resin.

[0120] Examples of release agents include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; long-chain alkyl resins, alkyd resins, and fluororesins. A single release agent may be used, or two or more may be used in combination.

[0121] The thickness of the release agent is preferably 10 to 200 μm, more preferably 25 to 170 μm, and even more preferably 35 to 80 μm.

[0122] [Method for manufacturing adhesive sheets] A method for manufacturing an adhesive sheet according to one aspect of the present invention is a method for manufacturing an adhesive sheet having a base material (Y) and an adhesive layer (X1) containing a polymer of an energy ray polymerizable component and thermally expandable particles, the method comprising the following steps I and II. Step I: A step of forming a polymerizable composition layer consisting of polymerizable composition (x-1) on one side of the substrate (Y). Step II: A step of irradiating the polymerizable composition layer with energy rays to form a polymer of the energy ray polymerizable component, thereby forming an adhesive layer (X1) containing the polymer and the thermally expandable particles.

[0123] <Process I> Step I is not particularly limited as long as it is a step of forming a polymerizable composition layer on one side of the substrate (Y), but it is preferable to include the following steps I-1 to I-3. Step I-1: Step of applying a polymerizable composition (x-1) onto the release treatment surface of the release agent to form a polymerizable composition layer. Step I-2: A step in which the polymerizable composition layer is subjected to first energy ray irradiation to prepolymerize the energy ray polymerizable components in the polymerizable composition layer. Step I-3: Step of attaching the substrate (Y) to the polymerizable composition layer after irradiation with the first energy ray.

[0124] (Process I-1) Step I-1 is a step in which a polymerizable composition (x-1) is applied to the peeling surface of the release agent to form a polymerizable composition layer. Figure 3 shows a cross-sectional view illustrating a process in which a release agent 10 is placed on a cooling jig 31 having multiple tubular through-holes 31a through which a refrigerant circulates, and a polymerizable composition (x1) is applied to the release treatment surface of the release agent 10. In step I-1, examples of methods for applying the polymerizable composition (x-1) to the release agent include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0125] As described above, the polymerizable composition (x-1) is preferably a solvent-free polymerizable composition. If the polymerizable composition (x-1) is a solvent-free polymerizable composition, the solvent heating and drying step in this process does not need to be performed. On the other hand, if the polymerizable composition (x-1) contains a solvent to the extent that it does not contradict the purpose of the present invention, heating and drying may be performed after coating the polymerizable composition (x-1), but in that case the heating temperature should be less than the expansion start temperature (t) of the thermally expandable particles.

[0126] (Process I-2) Step I-2 is a step in which the polymerizable composition layer formed in Step I-1 is subjected to a first energy ray irradiation to prepolymerize the energy ray polymerizable components in the polymerizable composition layer. Figure 4 shows a cross-sectional view illustrating the process of irradiating a layer of polymerizable composition (x-1) applied to the release agent 10 on the cooling jig 31 with a first energy ray indicated by the symbol PR. Figure 5 also shows a cross-sectional view illustrating the formation of a prepolymerized layer (x-11) of the polymerizable composition (x-1). The first energy ray irradiation is performed with the aim of increasing the viscosity of the polymerizable composition by prepolymerizing the energy ray polymerizable component, thereby improving the shape retention of the polymerizable composition layer. In the first energy ray irradiation, the energy ray polymerizable component is not completely polymerized, but only pre-polymerized. This improves the adhesion between the polymerizable composition layer and the substrate (Y) in step I-3.

[0127] Among the above, ultraviolet light is preferred as the energy ray used for the first energy ray irradiation in step I-2 because it is easy to handle. The irradiance of ultraviolet light in the first energy ray irradiation is preferably 70 to 250 mW / cm².2 More preferably 100-200 mW / cm² 2 More preferably 130-170 mW / cm² 2 Furthermore, the amount of ultraviolet light in the first energy ray irradiation is preferably 40 to 200 mJ / cm². 2 , more preferably 60-150 mJ / cm² 2 More preferably 80-120 mJ / cm² 2 That is the case. The first energy ray irradiation may be performed in a single step or in multiple steps. Furthermore, to suppress the temperature rise of the polymerizable composition layer due to polymerization heat, etc., the irradiation may be performed while cooling the polymerizable composition layer. The energy ray irradiation in step I-2 may be performed in a space shielded by the shielding member 32, as shown in Figure 4. The polymerizable composition layer can be cooled, for example, using a cooling jig 31 which is a heat conductor having through-holes 31a, as shown in Figure 4. In this case, the polymerizable composition layer can be cooled by placing the cooling jig 31, which has been cooled by filling or circulating a coolant inside the through-holes 31a, adjacent to the polymerizable composition layer via a release agent 10, or by bringing it into direct contact with the polymerizable composition.

[0128] (Process I-3) Step I-3 is a step of attaching the substrate (Y) to the polymerizable composition layer after the first energy ray irradiation. The method for attaching the substrate (Y) to the polymerizable composition layer is not particularly limited, and one example is to laminate the substrate (Y) to the exposed surface of the polymerizable composition layer. Figure 6 shows a cross-sectional view illustrating how a layer (x-11) of polymerizable composition (x-1) is formed on the release agent 10 on the cooling jig 31, and how the substrate (Y) is further laminated on top of the prepolymerized layer (x-11). Lamination may be performed with or without heating, but it is preferable to perform it without heating from the viewpoint of suppressing the expansion of thermally expandable particles. In this case, the polymerizable composition layer prepolymerized by the first energy ray irradiation has good adhesion to the substrate (Y) even without heating.

[0129] <Process II> Step II is a step in which an energy ray polymerizable polymer is formed by irradiating the polymerizable composition layer formed in Step I with energy rays, thereby forming an adhesive layer (X1) containing the polymer and thermally expandable particles. Figure 7 shows a cross-sectional view illustrating the process of irradiating a layer (x-11) of a polymerizable composition (x-1), on which a substrate (Y) is laminated, with a second energy ray indicated by the symbol TR. Figure 8 shows a cross-sectional view illustrating the formation of an adhesive layer (X1) containing polymers and thermally expandable particles. In the example shown in Figure 8, adhesive sheet 1a is formed by the adhesive layer (X1) and the substrate (Y), and adhesive sheet 1b is formed by the adhesive layer (X1), the substrate (Y), and the release agent 10. As will be described later, adhesive sheet 2a is formed by providing an adhesive layer (X2) on adhesive sheet 1a.

[0130] In this case, if the first energy beam irradiation is performed in step I, the energy beam irradiation in step II is the second energy beam irradiation performed on the polymerizable composition layer after prepolymerization. Unlike the first energy ray irradiation, the energy ray irradiation in step II is preferably performed to the extent that further irradiation with energy rays does not substantially advance the polymerization of the energy ray polymerizable component. The energy ray irradiation in step II promotes the polymerization of the energy ray polymerizable component, forming a polymer of the energy ray polymerizable component that constitutes the adhesive layer (X1).

[0131] When a polymerizable composition layer is irradiated with energy rays, the thermally expandable particles contained in the polymerizable composition layer may unintentionally expand due to heat radiated from the energy ray irradiation source and heat generated by the polymerization reaction of the energy ray polymerizable components. For this reason, in the method for manufacturing an adhesive sheet according to one embodiment of the present invention, the polymerizable composition layer is irradiated with energy rays while being cooled. As a method for cooling the polymerizable composition layer, for example, as shown in Figure 7, a cooling jig 31 having through-holes 31a can be used, by filling or circulating a refrigerant through the through-holes 31a, and then bringing the cooling jig 31 into contact with the polymerizable composition layer or placing it adjacent to it via a release sheet 10 or the like. With this method, the cooling effect is high because the refrigerant constantly removes heat, and the expansion of thermally expandable particles is easily suppressed. In addition to this, cooling methods such as air cooling or contact with a metal roller with high thermal conductivity can also be used.

[0132] As a refrigerant used to cool the polymerizable composition layer, it is preferable to use a refrigerant such as water or an organic solvent that is kept at a temperature lower than the expansion start temperature (t), more preferably at or below the expansion start temperature (t) - 5°C, even more preferably at or below the expansion start temperature (t) - 10°C, and even more preferably at or below the expansion start temperature (t) - 15°C. Furthermore, the same method as described above can be used when cooling the polymerizable composition layer in the prepolymerization described above.

[0133] In step II, as shown in Figure 7, the polymerizable composition layer may be shielded by the shielding member 32, and the polymerizable composition layer may be irradiated with energy rays within the space shielded by the shielding member 32. By using the shielding member 32, harmful ultraviolet rays and the like can be blocked. On the other hand, heat radiated from the energy source tends to accumulate in the shielded space, creating an environment where thermally expandable particles tend to expand during energy ray irradiation. However, as described above, cooling can suppress the expansion of thermally expandable particles.

[0134] Among the above, ultraviolet light is preferred as the energy ray used for energy ray irradiation in step II because it is easy to handle. The irradiance of ultraviolet light in the energy ray irradiation of step II is preferably 100 to 350 mW / cm². 2 More preferably 150-300 mW / cm² 2 More preferably 180-250 mW / cm² 2 That is the case. The amount of ultraviolet light in the energy ray irradiation in step II is preferably 500 to 4,000 mJ / cm². 2 More preferably 1,000 to 3,000 mJ / cm² 2 More preferably 1,500 to 2,500 mJ / cm² 2 That is the case. The energy beam irradiation in step II may be performed in a single step or in multiple steps. Furthermore, to suppress the temperature rise of the polymerizable composition layer due to polymerization heat, etc., the process may be carried out while cooling the polymerizable composition layer.

[0135] Furthermore, if step I includes steps I-1 to I-3 described above, the polymerizable composition layer is obtained as an intermediate layer of a laminate in which the release agent, polymerizable composition layer, and substrate (Y) are laminated in this order. In this case, the second energy ray irradiation may be performed on the laminate having this configuration. In this case, from the viewpoint of enabling sufficient energy ray irradiation to be applied to the polymerizable composition layer present as an intermediate layer of the laminate, it is preferable that at least one of the release agent and substrate (Y) is energy ray permeable.

[0136] In either of the steps included in steps I and II described above, it is preferable that the step of heating the polymerizable composition is not included, from the viewpoint of suppressing the expansion of thermally expandable particles. In this context, "heating" refers to intentional heating, such as during drying or lamination, and does not include temperature increases due to heat imparted to the polymerizable composition by energy ray irradiation or polymerization heat generated by the polymerization of the energy ray polymerizable composition. If the process includes a step of heating the polymerizable composition as needed, the heating temperature is preferably "lower than the expansion initiation temperature (t)", more preferably "5°C or less below the expansion initiation temperature (t)", even more preferably "10°C or less below the expansion initiation temperature (t)", and even more preferably "15°C or less below the expansion initiation temperature (t)". ​​Furthermore, if the temperature of the polymerizable composition rises unintentionally, it is preferable to cool the polymerizable composition so that its temperature falls within the above temperature range.

[0137] If the adhesive sheet according to one embodiment of the present invention has the configuration of the double-sided adhesive sheet described above, the method for manufacturing the adhesive sheet according to one embodiment of the present invention preferably further includes the following step III.

[0138] <Process III> Step III: Step of forming an adhesive layer (X2) on the other side of the substrate (Y).

[0139] The method for forming the adhesive layer (X2) can be appropriately determined depending on the type of composition constituting the adhesive layer (X2). For example, when forming the adhesive layer (X2) using an adhesive composition (x-2), step III preferably includes the following steps III-1 and III-2. Step III-1: Step of applying the adhesive composition (x-2) to one side of the release agent to form an adhesive layer (X2). Step III-2: A step in which the adhesive layer (X2) formed in Step III-1 is attached to the side of the substrate (Y) opposite to the adhesive layer (X1).

[0140] Figure 9 shows a cross-sectional view illustrating how an adhesive layer (X1) and a base material (Y) are laminated on a release agent 10 on a cooling jig 31, and how another adhesive layer (X2) is laminated on top of them. In the example shown in Figure 9, the adhesive sheet 2a is composed of the adhesive layer (X1), the base material (Y), and the adhesive layer (X2). In step III-1, the method for applying the adhesive composition (x-2) is the same as the method for applying the polymerizable composition (x-1) in step I-1. Furthermore, if the adhesive layer (X2) contains a solvent, the process may include a step of drying the coating after applying the adhesive composition (x-2). Furthermore, as described above, it is preferable that the release agent used in step III-1 and the release agent used in step I-1 be designed to have different release forces, in order to suppress the phenomenon in which the adhesive layer is separated and peeled off by the two release agents.

[0141] In step III-2, the method for attaching the adhesive composition layer to the substrate (Y) is the same as the method for attaching the substrate (Y) to the polymerizable composition layer in step I-3, and the preferred embodiment is also the same.

[0142] Subsequently, in order to use the adhesive sheet in the manner described later, for example, as shown in Figure 10, the release agent 10 is separated at an appropriate timing to expose one side of the adhesive layer (X1), and the adhesive layer (X1) of the adhesive sheet 2a is attached to a suitable support 3 as shown in Figure 11.

[0143] [Uses and methods of using adhesive sheets] An adhesive sheet according to one aspect of the present invention can be applied to a variety of uses because it has sufficient adhesive strength when temporarily fixed, yet can be peeled off by heating at low temperatures. Specifically, it is suitable for applications such as a dicing sheet used when dicing a substrate such as a semiconductor wafer, a backgrinding sheet used in the process of grinding a substrate, an expandable tape used to increase the distance between substrates such as semiconductor chips that have been separated by dicing, a transfer tape used to reverse the front and back sides of a substrate such as a semiconductor chip, and a temporary fixing sheet used to temporarily fix an object to be inspected.

[0144] The adherend of the adhesive sheet according to one embodiment of the present invention is not particularly limited, but examples include semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, sapphire substrates, displays, panel substrates, etc. Since the adhesive sheet according to one embodiment of the present invention can be peeled off by heating at low temperatures, it is suitable for temporarily fixing adherends that are susceptible to thermal changes, such as semiconductor chips with DAF.

[0145] When peeling off an adhesive sheet according to one embodiment of the present invention from an adherend by heating, the heating temperature is equal to or greater than the expansion start temperature (t) of the thermally expandable particles, preferably "expansion start temperature (t) + 2°C" or higher, more preferably "expansion start temperature (t) + 4°C" or higher, and even more preferably "expansion start temperature (t) + 5°C" or higher. Furthermore, from the viewpoint of energy saving and suppressing thermal changes of the adherend during heat peeling, it is preferably "expansion start temperature (t) + 50°C" or lower, more preferably "expansion start temperature (t) + 40°C" or lower, and even more preferably "expansion start temperature (t) + 20°C" or lower. Furthermore, the heating temperature during heat peeling is preferably 120°C or lower, more preferably 115°C or lower, even more preferably 110°C or lower, and even more preferably 105°C or lower, within the range of the expansion start temperature (t), from the viewpoint of suppressing thermal changes of the adherend.

[0146] The heating method is not particularly limited as long as it can heat the material to a temperature above the expansion temperature of the thermally expandable particles. For example, electric heaters, dielectric heating, magnetic heating, and heating using electromagnetic waves such as near-infrared, mid-infrared, and far-infrared rays can be used as appropriate. The heating method may be either direct heating or indirect heating.

[0147] [Manufacturing method for semiconductor devices] The present invention also provides a method for manufacturing a semiconductor device using an adhesive sheet according to one aspect of the present invention. One embodiment of the semiconductor device manufacturing method of the present invention is an embodiment in which the adhesive sheet according to one embodiment of the present invention is used as a temporary fixing sheet for processing an object to be adhered to (hereinafter also referred to as "the first embodiment of the semiconductor device manufacturing method").

[0148] <Method for manufacturing a semiconductor device according to the first embodiment> A more specific embodiment of the first embodiment of the method for manufacturing a semiconductor device is a method for manufacturing a semiconductor device which includes the steps of: attaching a workpiece to an adhesive sheet according to one embodiment of the present invention; performing one or more processes selected from grinding and fragmentation (hereinafter also referred to as "processing processes") on the workpiece; and after performing the processes, heating the adhesive sheet to a temperature above the expansion start temperature (t) to expand the adhesive layer (X1). In this specification, "semiconductor device" refers to any device that can function by utilizing semiconductor properties. Examples include wafers equipped with integrated circuits, thinned wafers equipped with integrated circuits, chips equipped with integrated circuits, thinned chips equipped with integrated circuits, electronic components including these chips, and electronic devices equipped with such electronic components.

[0149] In the first embodiment of the method for manufacturing a semiconductor device, the adhesive layer of the adhesive sheet to which the workpiece is attached may be an adhesive layer (X1), or if the adhesive sheet is a double-sided adhesive sheet, it may be an adhesive layer (X2). When the adhesive sheet is a double-sided adhesive sheet, it is preferable to attach the workpiece to one adhesive layer and the support to the other adhesive layer. By fixing the workpiece to the support via the adhesive sheet, vibration, displacement, and damage to fragile workpieces can be suppressed during processing, thereby improving processing accuracy and processing speed. In this case, the support may be attached to the adhesive layer (X1) and the workpiece to the adhesive layer (X2), or the workpiece may be attached to the adhesive layer (X1) and the support may be attached to the adhesive layer (X2). In a configuration where a support is attached to an adhesive layer (X1) and a workpiece is attached to an adhesive layer (X2), the support is attached to an adhesive layer (X1) that has excellent peelability after heat treatment, so even if the support is made of a hard material, it can be peeled off by heat without bending the adhesive sheet and the support. Furthermore, the composition of the adhesive layer (X2) can be appropriately selected according to the type of workpiece, etc. For example, if the adhesive layer (X2) is an adhesive layer whose adhesive strength decreases by energy ray irradiation, the workpiece can be peeled off without contaminating it with residues derived from thermally expandable particles, etc. On the other hand, in a configuration where the workpiece is attached to an adhesive layer (X1) and the support is attached to an adhesive layer (X2), the workpiece is attached to an adhesive layer (X1) that has excellent peelability after heat treatment. Therefore, when the workpiece is peeled off by heat after processing, it can be peeled off from the adhesive sheet by self-peeling, thereby reducing damage to the workpiece.

[0150] When a double-sided adhesive sheet is used as the adhesive sheet in one embodiment of the present invention, the method for manufacturing a semiconductor device in the first embodiment is preferably a manufacturing method that includes the following steps 1A to 5A (hereinafter also referred to as "manufacturing method A"). Step 1A: A step in which the workpiece is attached to the adhesive layer (X2) of the adhesive sheet, and the support is attached to the adhesive layer (X1). Step 2A: A step of applying one or more processes selected from grinding and fragmentation to the workpiece. Step 3A: A step of applying a thermosetting film to the side of the processed object opposite to the adhesive layer (X2). Step 4A: A step of heating the adhesive sheet to a temperature above the expansion start temperature (t) to separate the adhesive layer (X1) from the support. Step 5A: Step to separate the adhesive layer (X2) from the workpiece.

[0151] The following describes the manufacturing method of a semiconductor device, including steps 1A to 5A, with reference to the drawings. While the following explanation primarily focuses on the case where a semiconductor wafer is used as the workpiece, the process is similar for other workpieces.

[0152] (Process 1A) Step 1A is a step in which the workpiece is attached to the adhesive layer (X2) of the adhesive sheet and the support is attached to the adhesive layer (X1). Figure 12 shows a cross-sectional view illustrating the process of attaching a semiconductor wafer W to the adhesive layer (X2) of the adhesive sheet 2a and attaching a support 3 to the adhesive layer (X1). The semiconductor wafer W is attached so that the surface W1, which is the circuit side, faces the adhesive layer (X2). There are no particular restrictions on the order in which the semiconductor wafer W is attached to the adhesive layer (X2) and the support 3 is attached to the adhesive layer (X1); the former can come first, the latter first, or both can be done simultaneously. In the example shown in Figure 12, as explained in Figure 11, the semiconductor wafer W is attached to the adhesive layer (X2) of the adhesive sheet 2a provided on the support 3. The semiconductor wafer W may be a silicon wafer, or it may be a wafer made of gallium arsenide, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, or a glass wafer. The thickness of a semiconductor wafer W before grinding is typically 500 to 1000 μm. Circuits on the surface W1 of a semiconductor wafer W can be formed by conventionally used methods such as etching and lift-off methods.

[0153] The material of the support 3 should be appropriately selected, taking into consideration the required properties such as mechanical strength and heat resistance, depending on the type of workpiece and the processing content. Examples of materials for the support 3 include metal materials such as SUS; non-metallic inorganic materials such as glass and silicon wafers; resin materials such as epoxy resin, ABS resin, acrylic resin, engineering plastics, super engineering plastics, polyimide resin, and polyamide-imide resin; and composite materials such as glass epoxy resin. Among these, SUS, glass, and silicon wafers are preferred. Examples of the engineering plastics mentioned above include nylon, polycarbonate (PC), and polyethylene terephthalate (PET). Examples of the above-mentioned super engineering plastics include polyphenylene sulfide (PPS), polyethersulfone (PES), and polyetheretherketone (PEEK).

[0154] It is preferable that the support 3 is attached to the entire adhesive surface of the adhesive layer (X1). Therefore, it is preferable that the surface area of ​​the support 3 on the side that is attached to the adhesive surface of the adhesive layer (X1) is greater than or equal to the surface area of ​​the adhesive surface of the adhesive layer (X1). Furthermore, it is preferable that the surface of the support 3 on the side that is attached to the adhesive surface of the adhesive layer (X1) is flat. The shape of the support 3 is not particularly limited, but it is preferably plate-shaped. The thickness of the support 3 can be appropriately selected considering the required characteristics, but is preferably 20 μm or more and 50 mm or less, and more preferably 60 μm or more and 20 mm or less.

[0155] (Process 2A) Step 2A is a step of applying one or more processes to the workpiece, selected from grinding and fragmentation. One or more processes selected from grinding and dicing include, for example, grinding using a grinder, etc., and dicing by blade dicing, laser dicing, stealth dicing (registered trademark) method, blade tip dicing method, stealth tip dicing method, etc. Among these, the stealth dicing method for fragmentation, the blade tip dicing method for grinding and fragmentation, and the stealth tip dicing method for grinding and fragmentation are preferred, with the blade tip dicing method for grinding and fragmentation and the stealth tip dicing method for grinding and fragmentation being more preferred.

[0156] Stealth dicing is a method of forming a modified region inside a semiconductor wafer by irradiating it with laser light, and then separating the semiconductor wafer into individual chips using this modified region as the dividing point. The modified region formed on the semiconductor wafer is a part that has been brittleened by multiphoton absorption. When the semiconductor wafer is expanded, stress is applied parallel to the wafer surface and in the direction in which the wafer expands, causing cracks to extend from the modified region toward the front and back surfaces of the semiconductor wafer, thereby separating it into semiconductor chips. In other words, the modified region is formed along the dividing line during the dicing process. The modified region is formed inside the semiconductor wafer by irradiating it with laser light focused on the interior of the semiconductor wafer. The laser light incident surface may be either the front or back surface of the semiconductor wafer. Furthermore, the laser light incident surface may be the surface to which an adhesive sheet is attached; in this case, the laser light is irradiated onto the semiconductor wafer through the adhesive sheet.

[0157] The blade-tip dicing method is also known as the DBG method (Dicing Before Grinding). In the blade-tip dicing method, grooves are formed in advance on a semiconductor wafer along the lines to be divided, to a depth shallower than the wafer's thickness. Then, the semiconductor wafer is thinned and divided into individual pieces by back-grinding until the grinding surface reaches at least the grooves. The grooves reached by the grinding surface become cuts that penetrate the semiconductor wafer, and the semiconductor wafer is divided into individual semiconductor chips by these cuts. The grooves formed in advance are usually provided on the surface (circuit side) of the semiconductor wafer and can be formed, for example, by dicing using a conventionally known wafer dicing apparatus.

[0158] Stealth Dicing Before Grinding (SDBG) is a method of separating semiconductor wafers into individual chips by forming a modified region inside the semiconductor wafer using laser irradiation, similar to stealth dicing. However, it differs from stealth dicing in that it thins the semiconductor wafer through grinding while separating it into semiconductor chips. Specifically, the semiconductor wafer with the modified region is thinned by grinding the back surface, and the pressure applied to the semiconductor wafer during this process causes cracks to extend from the modified region toward the adhesive layer of the semiconductor wafer, thereby separating the semiconductor wafer into semiconductor chips. Furthermore, the grinding thickness after forming the modified region may be the thickness that reaches the modified region, but it is also acceptable to grind to a position close to the modified region and then fracture it using the processing pressure of a grinding wheel or the like, even if it does not strictly reach the modified region.

[0159] When a semiconductor wafer W is divided into individual pieces by a blade-tip dicing method, it is preferable to pre-form grooves on the surface W1 of the semiconductor wafer W that will be attached to the adhesive layer (X2) in step 1A. On the other hand, when the semiconductor wafer W is diced into individual pieces by the stealth pre-dicing method, the semiconductor wafer W to be attached to the adhesive layer (X2) in step 1A may be irradiated with laser light to form a modified region in advance, or the semiconductor wafer W attached to the adhesive layer (X2) may be irradiated with laser light to form a modified region.

[0160] Figure 13 shows a cross-sectional view illustrating the process of forming multiple modified regions 5 on a semiconductor wafer W attached to an adhesive layer (X2) using a laser light irradiation device 4. The laser light is irradiated from the back side W2 of the semiconductor wafer W, and multiple modified regions 5 are formed at approximately equal intervals inside the semiconductor wafer W.

[0161] Figure 14 shows a cross-sectional view illustrating the process of thinning the semiconductor wafer W and separating it into multiple semiconductor chips CP by grinding the back surface W2 of the semiconductor wafer W on which the modified region 5 has been formed with a grinder 6, and cutting the wafer starting from the modified region 5. The semiconductor wafer W on which the modified region 5 has been formed is ground on its back surface W2, for example, while the support 3 supporting the semiconductor wafer W is fixed on a fixed table such as a chuck table.

[0162] The thickness of the semiconductor chip CP after grinding is preferably 5 to 100 μm, more preferably 10 to 45 μm. Furthermore, when grinding and dicing are performed by the stealth dicing method, it becomes easy to make the thickness of the ground semiconductor chip CP 50 μm or less, more preferably 10 to 45 μm. The size of the semiconductor chip CP after grinding, in a plan view, is preferably 600 mm. 2 Less than, more preferably 400 mm 2 Less than, more preferably 300 mm 2 It is less than [value]. Note that "planar view" refers to viewing in the thickness direction. The shape of the semiconductor chip CP after individualization, when viewed from a planar perspective, may be rectangular or elongated, such as a rectangle.

[0163] (Process 3A) Step 3A is a step of attaching a thermosetting film to the side of the processed object that has undergone the above treatment, on the side opposite to the adhesive layer (X2). Figure 15 shows a cross-sectional view illustrating the process of attaching a thermosetting film 7, which includes a support sheet 8, to the side of a plurality of semiconductor chips CP obtained by the above process that is opposite to the adhesive layer (X2).

[0164] The thermosetting film 7 is a thermosetting film obtained by forming a film of a resin composition containing at least a thermosetting resin, and is used as an adhesive when mounting a semiconductor chip CP onto a substrate. The thermosetting film 7 may optionally contain a curing agent for the thermosetting resin, a thermoplastic resin, an inorganic filler, a curing accelerator, etc. As the thermosetting film 7, for example, a thermosetting film generally used as a die bonding film, a die attach film, etc. can be used. The thickness of the thermosetting film 7 is not particularly limited, but is usually 1 to 200 μm, preferably 3 to 100 μm, more preferably 5 to 50 μm. The support sheet 8 only needs to be able to support the thermosetting film 7, and examples thereof include paper materials, resins, metals, etc. listed as the base material (Y) of the adhesive sheet of one aspect of the present invention.

[0165] As a method of attaching the thermosetting film 7 to a plurality of semiconductor chips CP, for example, a method by lamination can be mentioned. The lamination may be performed while heating or without heating. When performing the lamination while heating, the heating temperature is preferably "a temperature lower than the expansion start temperature (t)", more preferably "expansion start temperature (t) - 5°C" or lower, still more preferably "expansion start temperature (t) - 10°C" or lower, and even more preferably "expansion start temperature (t) - 15°C" or lower, from the viewpoints of suppressing the expansion of the thermally expandable particles and suppressing the thermal change of the adherend.

[0166] (Step 4A) Step 4A is a step of heating the adhesive sheet to a temperature equal to or higher than the expansion start temperature (t) to separate the adhesive layer (X1) and the support 3. FIG. 16 shows a cross-sectional view for explaining the step of heating the adhesive sheet 2a to separate the adhesive layer (X1) and the support 3.

[0167] The heating temperature in Step 4A is equal to or higher than the expansion start temperature (t) of the thermally expandable particles, preferably "a temperature higher than the expansion start temperature (t)", more preferably "equal to or higher than the expansion start temperature (t) + 2°C", still more preferably "equal to or higher than the expansion start temperature (t) + 4°C", and even more preferably "equal to or higher than the expansion start temperature (t) + 5°C". Also, from the viewpoints of energy conservation and suppressing the thermal change of the adherent during heat peeling, the heating temperature in Step 4A is preferably in the range of 120°C or lower, more preferably "equal to or lower than the expansion start temperature (t) + 50°C", still more preferably "equal to or lower than the expansion start temperature (t) + 40°C", and particularly preferably "equal to or lower than the expansion start temperature (t) + 20°C". From the viewpoint of suppressing the thermal change of the adherent, the heating temperature in Step 4A is preferably 115°C or lower, more preferably 110°C or lower, and still more preferably 105°C or lower within the range equal to or higher than the expansion start temperature (t).

[0168] (Step 5A) Step 5A is a step of separating the adhesive layer (X2) and the object to be processed. FIG. 17 shows a cross-sectional view illustrating the step of separating the adhesive layer (X2) and a plurality of semiconductor chips CP. The method of separating the adhesive layer (X2) and a plurality of semiconductor chips CP may be appropriately selected according to the type of the adhesive layer (X2). For example, when the adhesive layer (X2) is an adhesive layer whose adhesive force decreases by energy ray irradiation, energy ray irradiation may be performed on the adhesive layer (X2) to decrease the adhesive force and then separation may be performed.

[0169] Through the above Steps 1A to 5A, a plurality of semiconductor chips CP attached on the thermosetting film 7 are obtained. Next, it is preferable to divide the thermosetting film 7 to which a plurality of semiconductor chips CP are attached into the same shape as the semiconductor chips CP to obtain semiconductor chips CP with the thermosetting film 7. As the method of dividing the thermosetting film 7, for example, methods such as laser dicing, expand, and fusing by laser light can be applied. Figure 18 shows a semiconductor chip CP with a thermosetting film 7 that has been divided into the same shape as the semiconductor chip CP.

[0170] The semiconductor chip CP with the thermosetting film 7 is further subjected to processes such as an expansion process to widen the spacing between multiple semiconductor chips CP, a rearrangement process to arrange the widened semiconductor chips CP, and an inversion process to reverse the front and back sides of the semiconductor chips CP, as needed, before being attached (die-attached) to the substrate from the thermosetting film 7 side. Subsequently, the semiconductor chip and the substrate can be fixed by thermal curing the thermosetting film 7.

[0171] In one embodiment of the present invention, the manufacturing method A may omit step 3A. If step 3A is omitted, step 4A may be replaced with the following step 4A'. Step 4A': A step of heating the adhesive sheet to a temperature above the expansion start temperature (t) to separate the adhesive layer (X1) from the support.

[0172] When a double-sided adhesive sheet is used as the adhesive sheet in one embodiment of the present invention, the method for manufacturing a semiconductor device in the first embodiment may be a manufacturing method including the following steps 1B to 4B (hereinafter also referred to as "manufacturing method B"). Step 1B: A step of attaching the workpiece to the adhesive layer (X1) of the adhesive sheet, and attaching the support to the adhesive layer (X2) of the adhesive sheet. Step 2B: A step of applying one or more processes selected from grinding and fragmentation to the workpiece. Step 3B: A step of applying a thermosetting film having thermosetting properties to the side of the processed object opposite to the adhesive layer (X1) that has undergone the above treatment. Step 4B: A step of heating the adhesive sheet to a temperature above the expansion start temperature (t) to separate the adhesive layer (X1) from the workpiece.

[0173] Steps 1B to 3B are explained by replacing the adhesive layer (X1) with adhesive layer (X2) and the adhesive layer (X2) with adhesive layer (X1) as in the explanation of steps 1A to 3A.

[0174] Step 4B is a step in which the adhesive sheet is heated to a temperature above the expansion start temperature (t) to separate the adhesive layer (X1) from the workpiece. The heating conditions, such as the heating temperature of the adhesive sheet in step 4B, are the same as those described in step 4A. Step 4B yields multiple semiconductor chips attached to a thermosetting film. Subsequently, in the same manner as in manufacturing method A described above, the thermosetting film is divided to obtain semiconductor chips with thermosetting films.

[0175] Manufacturing method B may include a step 5B after step 4B in which the adhesive layer (X2) and the support are separated. The method for separating the adhesive layer (X2) from the support can be appropriately selected depending on the type of adhesive layer (X2). For example, if the adhesive layer (X2) is one in which the adhesive strength decreases due to energy ray irradiation, the adhesive layer (X2) can be irradiated with energy rays to reduce its adhesive strength before separation.

[0176] In one embodiment of the present invention, the manufacturing method B may omit step 3B. If step 3B is omitted, step 4B may be replaced with the following step 4B'. Step 4B': A step of heating the adhesive sheet to a temperature above the expansion start temperature (t) to separate the adhesive layer (X1) from the workpiece.

[0177] <Another embodiment of a method for manufacturing a semiconductor device> The semiconductor device manufacturing method of the present invention is not limited to the semiconductor device manufacturing method of the first embodiment described above, and may also be a semiconductor device manufacturing method of a different embodiment from the first embodiment. Another example of a method for manufacturing a semiconductor device is to use an adhesive sheet according to one aspect of the present invention as a temporary fixing sheet for inspecting an object to be inspected as part of the manufacturing process. Examples of inspections performed on the object to be inspected include defect inspection using an optical microscope or laser (e.g., dust inspection, surface scratch inspection, wiring pattern inspection, etc.) and visual surface inspection. Examples of items to be inspected include semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, LED elements, sapphire substrates, displays, and panel substrates. When an adhesive sheet according to one aspect of the present invention is used as a temporary fixing sheet for inspecting an object to be inspected, the inspection can be performed with multiple objects to be inspected attached to the adhesive layer (X1) of the adhesive sheet. After the inspection, for example, a portion of the adhesive layer (X1) to which the multiple objects to be inspected are attached can be locally heated to selectively heat-peel off specific objects attached to that portion. In this case, since the adhesive sheet according to one aspect of the present invention can be heat-peeled at low temperatures, it offers excellent workability and energy saving in the heat-peeling operation, and can also suppress thermal changes caused by heating during heat-peeling, even if the object to be inspected is susceptible to thermal changes.

[0178] Another example of a method for manufacturing a semiconductor device in a different embodiment is a method of separating an object to be processed, which is attached to another sheet, from the other sheet using an adhesive sheet according to an embodiment of the present invention. For example, multiple semiconductor chips spaced apart on an expandable tape are attached to the adhesive surface of the expandable tape, but picking up these chips one by one is a cumbersome process. According to a semiconductor device manufacturing method in one aspect of the present invention, an adhesive layer (X1) of an adhesive sheet in one aspect of the present invention is attached to the exposed surface of multiple semiconductor chips attached to the expandable tape, and then the expandable tape is peeled off from the multiple semiconductor chips, thereby separating the multiple semiconductor chips from the expandable tape all at once. Through the above steps, a plurality of semiconductor chips attached to an adhesive sheet according to one embodiment of the present invention are obtained. The plurality of semiconductor chips can then be easily separated by heating the adhesive layer (X1) to a temperature equal to or higher than the expansion start temperature (t) of the thermally expandable particles. At this time, since the adhesive sheet according to one embodiment of the present invention can be peeled off by heating at a low temperature, it is excellent in workability and energy saving of the heating peeling operation, and even when the adherend is likely to undergo thermal changes, it is possible to suppress thermal changes due to heating during heating peeling. The plurality of separated semiconductor chips may be transferred to another adhesive sheet, or after being separated once, they may be subjected to a rearrangement process of aligning the plurality of semiconductor chips.

Examples

[0179] The present invention will be specifically described by the following examples, but the present invention is not limited to the following examples. In the following description, the "non-expandable adhesive layer (X1')" means an adhesive layer that does not contain thermally expandable particles, and the adhesive layer that does not contain thermally expandable particles prepared for measuring the shear storage modulus G' corresponds to the non-expandable adhesive layer (X1'). The physical property values in the following synthesis examples, production examples and examples are the values measured by the following methods.

[0180] [Mass average molecular weight (Mw)] Using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020"), measurement was carried out under the following conditions, and the value measured in terms of standard polystyrene was used. (Measurement conditions) · Column: A series of "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", "TSK gel G1000HXL" (all manufactured by Tosoh Corporation) connected in sequence · Column temperature: 40 °C · Developing solvent: Tetrahydrofuran · Flow rate: 1.0 mL / min

[0181] [Thickness of each layer] The measurement was performed using a constant-pressure thickness gauge manufactured by Teclock Co., Ltd. (model number: "PG-02J", compliant with standards: JIS K6783, Z1702, Z1709).

[0182] [Average particle size of thermally expandable particles (D 50 ), 90% particle size (D 90 )] The particle distribution of thermally expandable particles before expansion at 23°C was measured using a laser diffraction particle size distribution analyzer (for example, Malvern's "Mastersizer 3000"). Then, the particle sizes corresponding to the cumulative volume frequencies of 50% and 90% calculated from the smallest particle size in the particle distribution are defined as the "average particle size of thermally expandable particles (D)". 50 ) and "90% particle diameter of thermally expandable particles (D 90 )”

[0183] [Storage modulus E' of the base material (Y)] Using a substrate (Y) cut to 5 mm x 30 mm as a test sample, the storage modulus E' at a specified temperature was measured using a dynamic viscoelasticity analyzer (TA Instruments, product name "DMAQ800") under the following conditions: test start temperature 0°C, test end temperature 300°C, heating rate 3°C / min, vibration frequency 1 Hz, and amplitude 20 μm.

[0184] [Shear storage modulus G'(23) of the adhesive layer (X1) at 23°C] A test sample was prepared with an adhesive layer (X1) measuring 8 mm in diameter and 3 mm in thickness. Using a viscoelasticity measuring device (Anton Paar, device name "MCR300"), the shear storage modulus G'(23) at 23°C was measured by the torsional shear method under the following conditions: test start temperature 0°C, test end temperature 300°C, heating rate 3°C / min, and vibration frequency 1 Hz.

[0185] [Shear storage modulus G' of the non-expanding adhesive layer (X1')] To measure the shear storage modulus G' while excluding the influence of thermally expandable particles, in each example, a non-expandable adhesive layer (X1') having the same configuration as the adhesive layer (X1), except that it does not contain thermally expandable particles, was prepared as a shear storage modulus measurement sample corresponding to the adhesive layer (X1) in each example, and its shear storage modulus G' was measured. A non-expandable adhesive layer (X1') with a diameter of 8 mm and a thickness of 3 mm was used as a test sample, and using a viscoelasticity measuring device (Anton Paar, device name "MCR300"), the shear storage modulus G'(23) at 23°C and the shear storage modulus G'(t) at the expansion start temperature (t) of the thermally expandable particles were measured by the torsional shear method under the conditions of a test start temperature of 0°C, a test end temperature of 300°C, a heating rate of 3°C / min, and a vibration frequency of 1 Hz. Furthermore, the expansion onset temperature (t) of the thermally expandable particles in the non-expandable adhesive layer (X1'), which is the sample for measuring the shear storage modulus, refers to the expansion onset temperature (t) of the thermally expandable particles contained in the adhesive layer (X1) of the example corresponding to the sample for measuring the shear storage modulus, and in this example, it refers to 88°C, as will be described later.

[0186] Synthesis Example 1 (Synthesis of urethane acrylate-based prepolymers) 100 parts by mass (based on solid content; the same applies hereafter) of polypropylene glycol with a mass-average molecular weight (Mw) of 3,000, 4 parts by mass of hexamethylene diisocyanate, and 0.02 parts by mass of dioctyl tin dilaurate were mixed and stirred at 80°C for 6 hours to obtain a reaction product. When the IR spectrum of the obtained reaction product was measured by infrared spectroscopy, it was confirmed that the isocyanate groups had almost completely disappeared. Subsequently, 1 part by mass of 2-isocyanate ethyl acrylate was mixed with the total amount of the obtained reactants and stirred at 80°C for 3 hours to obtain a urethane acrylate-based prepolymer. The IR spectrum of the obtained urethane acrylate-based prepolymer was measured by infrared spectroscopy, confirming that the isocyanate groups had almost completely disappeared. The mass-average molecular weight (Mw) of the obtained urethane acrylate-based prepolymer was 25,000.

[0187] Manufacturing Examples 1-3 (Manufacturing of polymerizable compositions) A solvent-free polymerizable composition was obtained by mixing each component listed in Table 1 in the formulations listed in Table 1. Details of each component listed in Table 1 are as follows. [Polymerizable vinyl monomer] 2EHA: 2-Ethylhexyl acrylate ((a1-1) component) IBXA: Isobornyl acrylate (components (a1-2)) HEA: 2-Hydroxyethyl acrylate ((a1-3) components) 4HBA: 4-Hydroxybutyl acrylate ((a1-3) components) [Polyfunctional (meth)acrylate monomers] Trifunctional monomer: Ethylene oxide-modified isocyanurate triacrylate (components (a1-4)) [Multifunctional (meth)acrylate prepolymer] Urethane acrylate prepolymer: Prepared in Synthesis Example 1 (component (a2)) Polyacrylic acrylate prepolymer: "KANEKA XMAP(registered trademark) RC100C" (manufactured by Kaneka Corporation, a polyacrylic prepolymer having acryloyl groups at both ends, mass-average molecular weight (Mw): 21,500) (component (a2)) [Photopolymerization initiator] 1-Hydroxycyclohexylphenyl ketone [Thermally expanding particles] AkzoNobel Co., Ltd., product name "Expancel(registered trademark) 031-40" (DU type), expansion start temperature (t) = 88°C, average particle size (D 50 )=12.6μm, 90% particle diameter (D 90 ) = 26.2 μm In addition, in the "Composition of the adhesive layer (X1) or non-expanding adhesive layer (X1')" in Table 1, "-" means that the component in question was not included.

[0188] (Manufacturing of adhesive sheets) Using the solvent-free polymerizable composition prepared as described above, an adhesive sheet was manufactured according to the following procedure. The solvent-free polymerizable composition was applied onto the release-treated surface of a polyethylene terephthalate (PET) release film (manufactured by Lintec Corporation, product name "SP-PET381031", thickness: 38 μm) to form a polymerizable composition layer. With respect to the polymerizable composition layer, ultraviolet rays were irradiated under the conditions of an illuminance of 150 mW / cm 2 and a light quantity of 100 mJ / cm 2 to conduct preliminary polymerization. At this time, in the examples, the release film and the polymerizable composition layer were placed on a stainless steel cooling jig incorporating refrigerant circulation piping having the same configuration as shown in FIG. 4, and a refrigerant at 20°C was circulated through the piping to cool the polymerizable composition layer through the release film. The thickness of the polymerizable composition layer was adjusted so that the thickness of the resulting adhesive layer (X1) would be the thickness described in Table 1. Next, a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., Cosmo Shine (registered trademark), product number "PET50A4300", thickness: 50 μm) as the base material (Y) was pasted onto the exposed surface of the polymerizable composition layer to obtain a laminate in which the release film, the polymerizable composition layer, and the base material (Y) were laminated in this order. The storage elastic modulus E'(23) of the base material (Y) at 23°C was 3.0×10 9 Pa, and the storage elastic modulus E'(t) of the base material (Y) at the expansion start temperature (t) of the thermally expandable particles was 2.4×10 9 Pa. With respect to the laminate obtained above, ultraviolet rays were irradiated from the release film side under the conditions of an illuminance of 200 mW / cm 2 and a light quantity of 2,000 mJ / cm 2 (irradiated 4 times with 500 mJ / cm 2 ) to form an adhesive layer (X1), and an adhesive sheet in which the release film, the adhesive layer (X1), and the base material (Y) were laminated in this order was obtained. The illuminance and light quantity during ultraviolet irradiation are values measured using an illuminance·light quantity meter (manufactured by EIT, product name "UV Power Puck II").

[0189] Next, the following evaluations were performed on the adhesive sheets produced in each example. The evaluation results are shown in Table 2.

[0190] [Measurement of adhesive strength of the adhesive layer (X1) at 23°C before thermal expansion] The release film was removed from the adhesive layer (X1) of an adhesive sheet cut to 25 mm x 250 mm, and the surface of the exposed adhesive layer (X1) was bonded to the mirror surface of a silicon mirror wafer using a 2 kg rubber roller in accordance with JIS Z0237:2000. Immediately afterward, it was left to stand for 20 minutes in an environment of 23°C and 50% RH (relative humidity). After standing under the above conditions, the adhesive strength of the adhesive layer (X1) was measured at a tensile testing machine (manufactured by A&D Co., Ltd., product name "Tensilon®") at a tensile speed of 300 mm / min using the 180° peel method in accordance with JIS Z0237:2000, under conditions of 23°C and 50% RH (relative humidity).

[0191] [Measurement of adhesive strength at 23°C after thermal expansion of the adhesive layer (X1)] Furthermore, the above test sample was placed on a hot plate with the silicon mirror wafer facing the hot plate and the adhesive sheet facing the hot plate. It was heated at 100°C for 1 minute, which is above the expansion initiation temperature of thermally expandable particles, and then left to stand for 60 minutes in a standard environment (23°C, 50% RH (relative humidity)). The adhesive strength of the adhesive layer (X1) was then measured at a pulling speed of 300 mm / min using the 180° peel method based on JIS Z0237:2000. Furthermore, if the adhesive strength of the adhesive sheet was too weak to be fixed for measurement, causing it to peel off unintentionally and making measurement of the adhesive strength difficult, the adhesive strength was considered to be 0 N / 25 mm.

[0192] [Evaluation of self-detachability] The release film was removed from the adhesive layer (X1) of an adhesive sheet cut to 50 mm x 50 mm, and the surface of the exposed adhesive layer (X1) was bonded to the mirror surface of a silicon mirror wafer using a 2 kg rubber roller in accordance with JIS Z0237:2000. Immediately afterward, the sample was left to stand for 20 minutes in an environment of 23°C and 50% RH (relative humidity) to serve as the test sample. Next, the test sample was placed on a hot plate with the silicon mirror wafer side in contact with the hot plate and the adhesive sheet side not in contact with the hot plate, and heated at 100°C, which is above the expansion start temperature of thermally expandable particles, for a maximum of 60 seconds. The percentage of the peeled area of ​​the adhesive sheet at the point of 60 seconds of heating (%) (peeled area × 100 / total area of ​​the adhesive sheet) was calculated and evaluated based on the following criteria. A: The adhesive sheet will completely peel off within 60 seconds. B: After heating for 60 seconds, the peeled area is 30% or more but less than 100%. C: After heating for 60 seconds, the peeled area is less than 30%. For items rated "A," the time (in seconds) required for complete removal was also measured.

[0193] [Percentage of expanded thermally expandable particles in the adhesive layer (X1)] The adhesive sheet obtained in the example was cut to a size of 5 mm x 5 mm, the release film was removed from the adhesive layer (X1), and the surface of the exposed adhesive layer (X1) was observed using a digital microscope (Keyence Corporation, product name "Digital Microscope VHX-5000"), and the particle size measured from the obtained magnified image (500 μm x 500 μm) was the 90% particle size (D) of the thermally expandable particles before expansion. 90 m1 is the number of thermally expandable particles below 90% of the particle size (D 90 The number of thermally expandable particles larger than ) was defined as m2, and the number of each was counted. The ratio of the number of expanded thermally expandable particles to the total number of thermally expandable particles was calculated as P = 100 × [m² / (m1 + m²)] (%), and evaluated based on the following criteria. A:P is 12% or less. The B:P ratio is between 12% and 15%. The cost-to-price ratio (C:P) is between 15% and 20%. The F:P ratio is over 20%.

[0194] [Table 1]

[0195] [Table 2]

[0196] Table 2 shows that, before heating and peeling, all of the adhesive sheets in the examples contained a sufficient amount of unexpanded, heat-expandable particles in the adhesive layer (X1), and while possessing sufficient adhesive strength, they could be heated and peeled at a low temperature (100°C). Furthermore, it can be seen that by adjusting the composition of the polymerizable composition and the thickness of the adhesive layer (X1), the adhesive strength, self-peelability, and shear storage modulus of these adhesive sheets can be adjusted to an appropriate range, and consequently, the degree of curl can also be appropriately adjusted. [Explanation of Symbols]

[0197] 1a, 1b, 2a, 2b Adhesive sheets 10, 10a, 10b release agent 3 Support 4. Laser light irradiation device 5. Modification Area 6 Grinder 7 Thermosetting film 8. Support Sheet 31 Cooling fixture 31a Through hole 32 Shielding member W Semiconductor wafer W1 Circuit surface of semiconductor wafer and semiconductor chip W2 Back surface of semiconductor wafer and semiconductor chip CP semiconductor chip

Claims

1. A method for producing an adhesive sheet comprising a base material (Y) and an adhesive layer (X1) containing a polymer of an energy-ray polymerizable component and thermally expandable particles, comprising the following steps I and II, wherein the polymer of the energy-ray polymerizable component is a polymerizable vinyl monomer having one vinyl group-containing group, and comprising a monomer containing an energy-ray polymerizable functional group and an alicyclic hydrocarbon group, and a polymerizable composition comprising a polyfunctional (meth)acrylate prepolymer having two or more (meth)acryloyl groups, wherein the polymerizable composition contains 10 to 60% by mass of the prepolymer having two or more (meth)acryloyl groups, the polymerizable composition being a polymer of the polymerizable composition. Step I: A step of forming a polymerizable composition layer on one side of the substrate (Y), consisting of a polymerizable composition (x-1) containing the energy ray polymerizable component and the thermally expandable particles. Step II: A step to generate a polymer of the energy-ray polymerizable component by irradiating the polymerizable composition layer with energy rays while cooling the polymerizable composition layer, thereby forming an adhesive layer (X1).

2. The method for manufacturing an adhesive sheet according to claim 1, wherein in step II, the polymerizable composition layer is cooled using a refrigerant while the polymerizable composition layer is irradiated with energy rays.

3. The method for manufacturing an adhesive sheet according to claim 2, wherein in step II, the polymerizable composition layer is cooled using a heat conductor cooled by the refrigerant while the polymerizable composition layer is irradiated with energy rays.

4. The method for manufacturing an adhesive sheet according to claim 3, wherein in step II, the polymerizable composition layer is cooled by bringing the heat conductor, which has been cooled by the refrigerant, into contact with the substrate (Y), while irradiating the polymerizable composition layer with energy rays.

5. A method for manufacturing an adhesive sheet according to any one of claims 1 to 4, wherein in step II, the polymerizable composition layer is cooled to a temperature lower than the expansion start temperature (t) of the thermally expandable particles while the polymerizable composition layer is irradiated with energy rays.

6. A method for manufacturing an adhesive sheet according to any one of claims 1 to 5, wherein in step II, the substrate (Y) on which the polymerizable composition layer is formed is shielded with a shielding member, and the polymerizable composition layer is irradiated with energy rays in the space shielded by the shielding member.

7. The method for manufacturing an adhesive sheet according to any one of claims 1 to 6, wherein the energy rays include ultraviolet light.

8. A method for producing an adhesive sheet according to any one of claims 1 to 7, wherein the polymerizable composition (x-1) does not contain a solvent.

9. A method for producing an adhesive sheet according to any one of claims 1 to 8, which does not include the step of heating the polymerizable composition (x-1).

10. A method for manufacturing an adhesive sheet according to any one of claims 1 to 9, wherein in the adhesive sheet obtained in step II, the proportion of expanded particles among the thermally expandable particles present in the adhesive layer (X1) is 20% or less of the total number of thermally expandable particles.

11. A method for manufacturing an adhesive sheet according to any one of claims 1 to 10, further comprising the step of forming an adhesive layer (X2) on the surface of the substrate (Y) opposite to the adhesive layer (X1).

12. The object to be processed is attached to the adhesive sheet obtained by the adhesive sheet manufacturing method described in any one of claims 1 to 11. A method for manufacturing a semiconductor device, comprising the step of performing one or more processes selected from processing and inspection on the object to be processed, and then heating the adhesive sheet to a temperature (t) above the expansion start temperature (t) of the thermally expandable particles to expand the adhesive layer (X1).

13. A method for manufacturing a semiconductor device, comprising the following steps 1A to 5A. Step 1A: A step of attaching an object to be processed to the adhesive layer (X2) of an adhesive sheet obtained by the method for manufacturing an adhesive sheet according to claim 11, and attaching a support to the adhesive layer (X1). Step 2A: A step of applying one or more processes selected from grinding and fragmentation to the workpiece. Step 3A: A step of applying a thermosetting film to the side of the processed object opposite to the adhesive layer (X2). Step 4A: A step of heating the adhesive sheet to a temperature (t) above the expansion start temperature of the thermally expandable particles to separate the adhesive layer (X1) from the support. Step 5A: Step to separate the adhesive layer (X2) from the workpiece.

14. The adhesive layer (X2) is an adhesive layer that hardens and loses its adhesive strength when irradiated with energy rays. The method for manufacturing a semiconductor device according to claim 13, wherein step 5A is a step of curing the adhesive layer (X2) by irradiating the adhesive layer (X2) with energy rays to separate the adhesive layer (X2) from the workpiece.

15. An adhesive sheet comprising a base material (Y) and an adhesive layer (X1) containing a polymer of an energy ray polymerizable component and thermally expandable particles, The polymer of the energy ray polymerizable component is a polymerizable vinyl monomer having one vinyl group-containing group, comprising a monomer containing an energy ray polymerizable functional group and an alicyclic hydrocarbon group, and a polyfunctional (meth)acrylate prepolymer having two or more (meth)acryloyl groups, wherein the polymer of the polymerizable composition contains 10 to 60% by mass of the prepolymer having two or more (meth)acryloyl groups. An adhesive sheet in which, of the thermally expandable particles present in the adhesive layer (X1), the proportion of expanded particles is 20% or less of the total number of thermally expandable particles.

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