JP7519917B2 - EXPANSION METHOD AND SEMICONDUCTOR DEVICE MANUFACTURING METHOD - Google Patents

Description

The present invention relates to an expansion method and a method for manufacturing a semiconductor device.

In recent years, electronic devices have become smaller, lighter, and more functional. Semiconductor devices mounted on electronic devices are also required to be smaller, thinner, and more dense. Semiconductor chips are sometimes mounted in packages close to their size. Such packages are sometimes called chip scale packages (CSPs). One type of CSP is wafer level packages (WLPs). In WLPs, external electrodes and the like are formed on a wafer before it is diced into individual pieces, and the wafer is finally diced into individual pieces. WLPs include fan-in and fan-out types. In fan-out type WLP (hereinafter sometimes abbreviated as "FO-WLP"), a semiconductor chip is covered with a sealing material so that the area is larger than the chip size to form a semiconductor chip sealing body, and redistribution layers and external electrodes are formed not only on the circuit surface of the semiconductor chip but also on the surface area of the sealing material.

For example, Patent Document 1 describes a method for manufacturing a semiconductor package in which a plurality of semiconductor chips separated from a semiconductor wafer are surrounded by a molding material to form an expanded wafer while leaving the circuit formation surface, and a rewiring pattern is extended to an area outside the semiconductor chip. In the manufacturing method described in Patent Document 1, before surrounding the plurality of separated semiconductor chips with the molding material, an expandable wafer mount tape is attached, and the wafer mount tape is expanded to increase the distance between the plurality of semiconductor chips.

Patent Document 2 also describes an adhesive sheet comprising a second base layer, a first base layer, and a first adhesive layer in this order, in which the breaking elongation of the second base layer is 400% or more. The method for manufacturing a semiconductor device described in Patent Document 2 includes a step of attaching a semiconductor wafer to the first adhesive layer of the adhesive sheet, a step of dicing the semiconductor wafer to form multiple semiconductor chips, and a step of stretching the adhesive sheet to increase the spacing between the semiconductor chips.

International Publication No. 2010/058646 JP 2017-076748 A

The tape used in the expanding process usually has an adhesive layer for fixing the semiconductor chip on the tape and a base material for supporting the adhesive layer. When the wafer mount tape for expanding is stretched as described in Patent Document 1, not only the base material of the tape but also the adhesive layer is stretched. After the expanding process, when the semiconductor chip is peeled off from the adhesive layer, a defect may occur in which the adhesive layer remains on the surface of the semiconductor chip that was in contact with the adhesive layer. In this specification, such a defect may be referred to as adhesive residue.
In addition, when the expanding step is performed using the adhesive sheet described in Patent Document 2, the adhesive layer in contact with the semiconductor chip is not stretched, so it is considered that adhesive residue is unlikely to occur. However, since the adhesive sheet described in Patent Document 2 has a tape configuration in which a second base material layer, a first base material layer, and a first adhesive layer are laminated, there is a demand for an expanding method that can prevent adhesive residue using a simpler tape configuration. In addition, in the process described in Patent Document 2, the semiconductor wafer on the adhesive sheet is diced, and the adhesive sheet is stretched as it is without transferring it to another adhesive sheet to perform the expanding step. Therefore, it is necessary to carefully control the cutting depth of the dicing blade so that the dicing blade does not reach the second base material layer during dicing, and there is also a demand for an expanding method that can prevent adhesive residue by a simpler method.
In the expanding method, the adherend supported on the pressure-sensitive adhesive sheet may be not only a semiconductor chip, but also, for example, a semiconductor device such as a wafer, a semiconductor device package, and a micro LED. As with semiconductor chips, the spacing between these semiconductor devices may be expanded.

The object of the present invention is to provide an expansion method that can simplify the tape configuration and process compared to conventional methods while suppressing glue residue, and to provide a manufacturing method for a semiconductor device that includes said expansion method.

According to one aspect of the present invention, there is provided an expanding method in which a first adhesive sheet having a first adhesive layer and a first substrate is attached to a first wafer surface of a wafer having a first wafer surface and a second wafer surface opposite the first wafer surface, a second adhesive sheet having a second adhesive layer and a second substrate is attached to the second wafer surface, the first adhesive sheet is cut by making an incision from the first adhesive sheet side, the wafer is further divided into a plurality of chips, a third adhesive sheet having a third adhesive layer and a third substrate is attached to the first substrate, the second adhesive sheet is peeled off from the second wafer surface of the wafer, and the third adhesive sheet is stretched to increase the spacing between the plurality of chips.

In the expansion method according to one aspect of the present invention, it is preferable that the incision is formed to a depth extending from the first adhesive sheet side to the second adhesive sheet.

In an expanding method according to one aspect of the present invention, it is preferable that the second wafer surface is a surface formed by back-grinding the wafer.

In an expanding method according to one aspect of the present invention, it is preferable that the first adhesive sheet is attached to the first wafer surface before the back surface of the wafer is ground.

In an expanding method according to one aspect of the present invention, it is preferable that a fourth adhesive sheet is attached to the first wafer surface before the wafer is back-ground, and that after back-grounding, the fourth adhesive sheet is peeled off from the first wafer surface and the first adhesive sheet is attached to the first wafer surface.

In an expanding method according to one embodiment of the present invention, it is preferable that the fourth adhesive sheet is a backgrind sheet, the first adhesive sheet is a surface protection sheet, and the thickness of the surface protection sheet is 5 μm or more and 500 μm or less.

In the expanding method according to one aspect of the present invention, it is preferable that the first adhesive sheet is a backgrind sheet.

In the expansion method according to one aspect of the present invention, it is preferable that the third adhesive sheet is an expandable sheet.

In the expanding method according to one aspect of the present invention, it is preferable that the wafer is a semiconductor wafer.

In an expansion method according to one aspect of the present invention, it is preferable that the first wafer surface has a circuit.

According to one aspect of the present invention, there is provided a method for manufacturing a semiconductor device, which includes an expansion method according to the above-mentioned aspect of the present invention.

According to one aspect of the present invention, it is possible to provide an expansion method that can simplify the tape configuration and process compared to conventional methods while suppressing adhesive residue. According to another aspect of the present invention, it is possible to provide a manufacturing method for a semiconductor device that includes an expansion method that can suppress adhesive residue.

1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 1A to 1C are cross-sectional views illustrating a manufacturing method according to a first embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 11A to 11C are cross-sectional views illustrating a manufacturing method according to a second embodiment. 13A to 13C are cross-sectional views illustrating a manufacturing method according to a third embodiment. 13A to 13C are cross-sectional views illustrating a manufacturing method according to a third embodiment. 13A to 13C are cross-sectional views illustrating a manufacturing method according to a third embodiment. 13A to 13C are cross-sectional views illustrating a manufacturing method according to a third embodiment. FIG. 2 is a plan view illustrating a biaxial stretching expanding device used in the examples. FIG. 1 is a schematic diagram for explaining a method for measuring chip alignment.

First Embodiment
The expanding method according to this embodiment and the manufacturing method of a semiconductor device including the expanding method will be described below.

Figures 1 (Figures 1A and 1B), 2 (Figures 2A and 2B), and 3 are cross-sectional schematic diagrams illustrating a manufacturing method for a semiconductor device including an expansion method according to this embodiment.

The expanding method according to this embodiment includes the following steps (P1) to (P5).
(P1) A step of preparing a wafer having a first wafer surface to which a first adhesive sheet is attached and a second wafer surface to which a second adhesive sheet is attached. The first adhesive sheet has a first adhesive layer and a first substrate. The second adhesive sheet has a second adhesive layer and a second substrate.
(P2) A process of cutting the first adhesive sheet by making an incision from the first adhesive sheet side, and further cutting the wafer into individual chips.
(P3) A step of attaching a third pressure-sensitive adhesive sheet to the first substrate. The third pressure-sensitive adhesive sheet has a third pressure-sensitive adhesive layer and a third substrate.
(P4) A step of peeling the second adhesive sheet from the second wafer surface of the wafer.
(P5) A process of stretching the third adhesive sheet to increase the spacing between multiple chips.

Fig. 1A is a diagram for explaining step (P1), showing a wafer W to which a first adhesive sheet 10 and a second adhesive sheet 20 are attached.
The semiconductor wafer W has a circuit surface W1 as a first wafer surface and a back surface W3 as a second wafer surface. A circuit W2 is formed on the circuit surface W1.

A first adhesive sheet 10 is attached to the circuit surface W1. A second adhesive sheet 20 is attached to the back surface W3. The first adhesive sheet 10 has a first adhesive layer 12 and a first substrate 11. The second adhesive sheet 20 has a second adhesive layer 22 and a second substrate 21. Details of the first adhesive sheet 10 and the second adhesive sheet 20 will be described later.

The semiconductor wafer W may be, for example, a silicon wafer or a compound semiconductor wafer such as a gallium arsenide wafer. Methods for forming the circuit W2 on the circuit surface W1 of the semiconductor wafer W include commonly used methods, such as an etching method and a lift-off method.

[Back grinding process]
The semiconductor wafer W prepared in the step (P1) is preferably a wafer obtained by undergoing a back-grinding step.
In the back grinding process, the surface of the semiconductor wafer W opposite to the circuit surface W1 is ground to a predetermined thickness. The back surface W3 is preferably a surface formed by back grinding the semiconductor wafer W. The surface exposed after grinding the semiconductor wafer W is referred to as the back surface W3.

The method of grinding the semiconductor wafer W is not particularly limited, and examples thereof include known methods using a grinder or the like. When grinding the semiconductor wafer W, it is preferable to attach an adhesive sheet called a backgrind sheet to the circuit surface W1 in order to protect the circuit W2. In the backgrinding of the wafer, the circuit surface W1 side of the semiconductor wafer W, i.e., the backgrind sheet side, is fixed by a chuck table or the like, and the back surface side on which the circuit is not formed is ground by a grinder. In this embodiment, it is preferable that the first adhesive sheet 10 is a backgrind sheet. When the first adhesive sheet 10 is used as the backgrind sheet, the semiconductor wafer W is attached with the circuit surface W1 facing the first adhesive layer 12 of the first adhesive sheet 10. It is preferable that the first adhesive sheet 10 as the backgrind sheet is attached to the circuit surface W1 as the first wafer surface before grinding the semiconductor wafer W on the back side. The process of attaching the first adhesive sheet 10 to the circuit surface W1 may be referred to as the attachment process of the first adhesive sheet.

The thickness of the semiconductor wafer W before grinding is not particularly limited, and is usually 500 μm or more and 1000 μm or less.
The thickness of the semiconductor wafer W after grinding is not particularly limited, but is usually 20 μm or more and 500 μm or less.

[Step of attaching second adhesive sheet]
The semiconductor wafer W prepared in the step (P1) is preferably a wafer obtained through a back grinding step and a bonding step of bonding the second adhesive sheet 20 to the back surface W3. This bonding step may be referred to as a second adhesive sheet bonding step.
As described later, in step (P2), the semiconductor wafer W is diced into a plurality of semiconductor chips CP. When dicing the semiconductor wafer W, it is preferable to attach an adhesive sheet called a dicing sheet to the back surface W3 in order to hold the semiconductor wafer W. In this embodiment, it is preferable that the second adhesive sheet 20 is the dicing sheet. When the second adhesive sheet 20 is used as the dicing sheet, the semiconductor wafer W is attached with the back surface W3 facing the second adhesive layer 22 of the second adhesive sheet 20.

[Dicing process]
1B is a diagram for explaining the step (P2). The step (P2) may be referred to as a dicing step. FIG 1B shows a plurality of semiconductor chips CP held by a second adhesive sheet 20.
The semiconductor wafer W, with the first adhesive sheet 10 attached to the circuit surface W1 and the second adhesive sheet 20 attached to the back surface W3, is diced into individual pieces to form a plurality of semiconductor chips CP. In this embodiment, an incision is made from the first adhesive sheet 10 side to cut the first adhesive sheet 10, and the semiconductor wafer W is further cut. After the dicing process, the circuit surfaces W1 of the plurality of semiconductor chips CP are each covered with the cut first adhesive sheet 10.
For the dicing, a cutting means such as a dicing saw is used.
The cutting depth during dicing is not particularly limited as long as it is a depth that can separate the first adhesive sheet 10 and the semiconductor wafer W. From the viewpoint of reliably cutting the semiconductor wafer W, the incisions in the dicing process are preferably formed to a depth that reaches the second adhesive sheet 20 from the first adhesive sheet 10 side, and more preferably to a depth that reaches the second adhesive layer 22 of the second adhesive sheet 20. The second adhesive layer 22 is also cut into the same size as the semiconductor chip CP by dicing. Furthermore, incisions may also be formed in the second base material 21 by dicing.

[Step of attaching third adhesive sheet]
Fig. 2A is a diagram for explaining the step (P3). The step (P3) may be referred to as a step of attaching a third adhesive sheet. Fig. 2A shows a state in which a third adhesive sheet 30 is attached to a plurality of semiconductor chips CP obtained by a dicing step. The third adhesive sheet 30 has a third adhesive layer 32 and a third base material 31. Details of the third adhesive sheet 30 will be described later.
In this embodiment, when the third adhesive sheet 30 is attached to the circuit surface W1 side of the multiple semiconductor chips CP, a laminated structure is obtained in which the individualized first adhesive sheet 10 is interposed between the multiple semiconductor chips CP and the third adhesive layer 32 of the third adhesive sheet 30.

[Step of Peeling Off Second Adhesive Sheet]
2B is a diagram for explaining the step (P4). The step (P4) may be referred to as a peeling step of the second adhesive sheet. FIG. 2B shows a state in which the second adhesive sheet 20 is peeled off from the rear surface W3 of the wafer W after the third adhesive sheet 30 is attached.
After the third adhesive sheet 30 is attached, the second adhesive sheet 20 is peeled off to expose the rear surfaces W3 of the multiple semiconductor chips CP.
In addition, when an energy ray-polymerizable compound is blended in the second adhesive layer 22, it is preferable to irradiate the second adhesive layer 22 with energy rays from the second substrate 21 side to harden the energy ray-polymerizable compound before peeling off the second adhesive sheet 20.

[Expanding process]
3 is a diagram for explaining the step (P5). The step (P5) may be referred to as an expanding step. FIG. 3 shows a state in which the third adhesive sheet 30 is expanded after the second adhesive sheet 20 is peeled off, thereby expanding the intervals between the multiple semiconductor chips CP.
When expanding the intervals between the multiple semiconductor chips CP, it is preferable to expand an adhesive sheet called an expand sheet while holding the multiple semiconductor chips CP. In this embodiment, it is preferable that the third adhesive sheet 30 is an expand sheet.
The method of stretching the third adhesive sheet 30 in the expanding step is not particularly limited. Examples of the method of stretching the third adhesive sheet 30 include a method of pressing an annular or circular expander against the first adhesive sheet 10 to stretch it, and a method of gripping and stretching the outer periphery of the third adhesive sheet 30 using a gripping member or the like. In this embodiment, the interval D1 between the multiple semiconductor chips CP is not particularly limited because it depends on the size of the semiconductor chips CP. In particular, the interval D1 between adjacent semiconductor chips CP in the multiple semiconductor chips CP attached to one side of the adhesive sheet is preferably 200 μm or more. The upper limit of the interval between the semiconductor chips CP is not particularly limited. The upper limit of the interval between the semiconductor chips CP may be, for example, 6000 μm.

[First transfer step]
In this embodiment, after the expanding process, a process (hereinafter sometimes referred to as the "first transfer process") may be carried out in which the multiple semiconductor chips CP attached to the third adhesive sheet 30 are transferred to another adhesive sheet (e.g., a fifth adhesive sheet).
FIG. 4A shows a diagram illustrating the process of transferring multiple semiconductor chips CP attached to the third adhesive sheet 30 to a fifth adhesive sheet 50 (hereinafter sometimes referred to as the "transfer process").
The fifth adhesive sheet 50 is not particularly limited as long as it can hold a plurality of semiconductor chips CP. The fifth adhesive sheet 50 has a fifth base material 51 and a fifth adhesive layer 52.
When performing the transfer process in this embodiment, for example, after the expanding process, it is preferable to attach the fifth adhesive sheet 50 to the rear surfaces W3 of the multiple semiconductor chips CP, and then peel off the third adhesive sheet 30.

The fifth adhesive sheet 50 may be attached to the second ring frame together with the multiple semiconductor chips CP. In this case, the second ring frame is placed on the fifth adhesive layer 52 of the fifth adhesive sheet 50 and lightly pressed to fix it. The fifth adhesive layer 52 exposed on the inside of the ring shape of the second ring frame is then pressed against the back surface W3 of the semiconductor chip CP to fix the multiple semiconductor chips CP to the fifth adhesive sheet 50.

FIG. 4B is a diagram illustrating the step of peeling off the third adhesive sheet 30 after the attachment of the fifth adhesive sheet 50.
In this embodiment, an example will be described in which, when peeling off the third adhesive sheet 30, the singulated first adhesive sheet 10 covering the circuit surface W1 of the semiconductor chip CP is peeled off together with the third adhesive sheet 30. It is preferable that the force with which the third adhesive sheet 30 is peeled off from the first adhesive sheet 10 is greater than the force with which the first adhesive sheet 10 is peeled off from the circuit surface W1 of the semiconductor chip CP. Note that it is also possible to peel off only the third adhesive sheet 30 while leaving the singulated first adhesive sheet 10 covering the circuit surface W1 on the semiconductor chip CP.
After the fifth adhesive sheet 50 is attached, the circuit surfaces W1 of the semiconductor chips CP are exposed by peeling off the first adhesive sheet 10 and the third adhesive sheet 30. It is preferable that the distances D1 between the semiconductor chips CP expanded in the expanding step are maintained even after the first adhesive sheet 10 and the third adhesive sheet 30 are peeled off.

[Second transfer process]
Figure 5A shows a diagram illustrating the process of transferring multiple semiconductor chips CP attached to a fifth adhesive sheet 50 to a sixth adhesive sheet 60 (hereinafter sometimes referred to as the "second transfer process").
It is preferable that the plurality of semiconductor chips CP transferred from the fifth adhesive sheet 50 to the sixth adhesive sheet 60 maintain the distance D1 between the semiconductor chips CP.

There are no particular limitations on the sixth adhesive sheet 60 as long as it is able to hold a plurality of semiconductor chips CP. The sixth adhesive sheet 60 has a sixth base material 61 and a sixth adhesive layer 62.
When it is desired to seal a plurality of semiconductor chips CP on the sixth adhesive sheet 60, it is preferable to use an adhesive sheet for the sealing process, and it is more preferable to use an adhesive sheet having heat resistance, as the sixth adhesive sheet 60. Furthermore, when an adhesive sheet having heat resistance is used as the sixth adhesive sheet 60, it is preferable that the sixth base material 61 and the sixth adhesive layer 62 are each formed of a material having heat resistance capable of withstanding the temperature applied in the sealing process.

The multiple semiconductor chips CP transferred from the fifth adhesive sheet 50 to the sixth adhesive sheet 60 are attached with their circuit surfaces W1 facing the sixth adhesive layer 62.

[Sealing process]
FIG. 5B is a diagram for explaining a process of sealing a plurality of semiconductor chips CP using sealing member 300 (hereinafter, sometimes referred to as an "encapsulating process").

In this embodiment, the sealing process is performed after the multiple semiconductor chips CP are transferred to the sixth adhesive sheet 60.
In the sealing process, the sealing body 3 is formed by covering the semiconductor chips CP with the sealing member 300 while the circuit surface W1 is protected by the sixth adhesive sheet 60. The sealing member 300 is also filled between the semiconductor chips CP. Since the circuit surface W1 and the circuit W2 are covered by the sixth adhesive sheet 60, the circuit surface W1 can be prevented from being covered by the sealing member 300.

The sealing process produces a sealing body 3 in which multiple semiconductor chips CP spaced apart at a predetermined distance are embedded in the sealing member 300. In the sealing process, it is preferable that the multiple semiconductor chips CP are covered by the sealing member 300 while maintaining the spacing D1 after the expansion process is performed.

After the sealing process, the sixth adhesive sheet 60 is peeled off. When the sixth adhesive sheet 60 is peeled off, the circuit surface W1 of the semiconductor chip CP and the surface 3A of the sealing body 3 that was in contact with the sixth adhesive sheet 60 are exposed.

After the aforementioned expanding process, the transfer process and expanding process can be repeated any number of times to set the distance between the semiconductor chips CP to the desired distance and to set the orientation of the circuit surface when sealing the semiconductor chip CP to the desired orientation.

[Other steps]
After the adhesive sheet is peeled off from the sealing body 3, a rewiring layer forming process for forming a rewiring layer electrically connected to the semiconductor chip CP and a connection process for electrically connecting the rewiring layer and the external terminal electrodes are sequentially performed on the sealing body 3. The rewiring layer forming process and the connection process with the external terminal electrodes electrically connect the circuit of the semiconductor chip CP to the external terminal electrodes.
The sealing body 3 to which the external terminal electrodes are connected is diced into individual semiconductor chips CP. The method for dicing the sealing body 3 is not particularly limited. By dicing the sealing body 3, a semiconductor package is manufactured for each semiconductor chip CP. The semiconductor package to which the external electrodes fanned out to the outside of the region of the semiconductor chip CP are connected is manufactured as a fan-out type wafer level package (FO-WLP).

(First Adhesive Sheet)
The first pressure-sensitive adhesive sheet 10 has a first base material 11 and a first pressure-sensitive adhesive layer 12. The first pressure-sensitive adhesive layer 12 is laminated on the first base material 11.

First Substrate The material of the first substrate 11 according to the present embodiment is not particularly limited as long as it can function appropriately in a desired process such as a back grinding process.
The first base material 11 is preferably made of a film mainly made of a resin-based material, such as an ethylene copolymer film, a polyolefin film, a polyvinyl chloride film, a polyester film, a polyurethane film, a polyimide film, a polystyrene film, a polycarbonate film, or a fluororesin film.

Examples of ethylene-based copolymer films include ethylene-vinyl acetate copolymer films, ethylene-(meth)acrylic acid copolymer films, and ethylene-(meth)acrylic acid ester copolymer films.
In this specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid, and similar terms.

Examples of polyolefin films include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, ethylene-norbornene copolymer films, and norbornene resin films.
Examples of polyethylene films include low density polyethylene (LDPE) films, linear low density polyethylene (LLDPE) films, and high density polyethylene (HDPE) films.

Examples of polyvinyl chloride films include polyvinyl chloride films and vinyl chloride copolymer films.

Examples of polyester films include polyethylene terephthalate films and polybutylene terephthalate films.

The first substrate 11 may be a crosslinked film that is mainly made of a resin-based material. The first substrate 11 may also be a modified film such as an ionomer film.
The first substrate 11 may be a film consisting of only one type selected from the group consisting of a film mainly made of a resin-based material, a crosslinked film, and a modified film, or it may be a laminated film combining two or more types.

The first substrate 11 may contain at least one additive selected from the group consisting of, for example, pigments, flame retardants, plasticizers, antistatic agents, lubricants, and fillers in a film mainly made of the above-mentioned resin-based material.
Examples of pigments include titanium dioxide and carbon black.
Examples of the filler include organic materials such as melamine resin, inorganic materials such as fumed silica, and metal materials such as nickel particles.
The content of additives contained in the film mainly made of a resin-based material is not particularly limited, but it is preferable to keep it within a range in which the first substrate 11 exhibits the desired functions and does not lose its smoothness and flexibility.

When ultraviolet rays are used as the energy rays for curing the first pressure-sensitive adhesive layer 12, the first base material 11 preferably has transparency to ultraviolet rays.
When electron beams are used as the energy beams for curing the first pressure-sensitive adhesive layer 12, the first base material 11 preferably has transparency to the electron beams.

The first substrate 11 may be subjected to a surface treatment or primer treatment on one or both sides as desired in order to improve adhesion with the first adhesive layer 12 laminated on its surface. Examples of surface treatments include oxidation methods and roughening methods. Examples of primer treatments include a method of forming a primer layer on the substrate surface. Examples of oxidation methods include corona discharge treatment, plasma discharge treatment, chromium oxidation treatment (wet), flame treatment, hot air treatment, ozone treatment, and ultraviolet irradiation treatment. Examples of roughening methods include sandblasting and thermal spraying.

The thickness of the first substrate 11 is not limited as long as the first adhesive sheet can function appropriately in the desired process.
The thickness of the first base material 11 is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 50 μm or more.
The thickness of the first base material 11 is preferably 450 μm or less, more preferably 400 μm or less, and even more preferably 350 μm or less.

First Pressure-Sensitive Adhesive Layer There are no particular limitations on the material constituting the first pressure-sensitive adhesive layer 12, so long as it can function appropriately in the desired process, such as the back-grinding process.
In this embodiment, the first adhesive layer 12 is preferably composed of at least one adhesive selected from the group consisting of, for example, an acrylic adhesive, a urethane adhesive, a polyester adhesive, a rubber adhesive, and a silicone adhesive, and is more preferably composed of an acrylic adhesive.

It is also preferable that the first pressure-sensitive adhesive layer 12 contains an energy ray-curable pressure-sensitive adhesive. The energy ray-curable pressure-sensitive adhesive contains an energy ray-polymerizable compound.
When the first pressure-sensitive adhesive layer 12 contains an energy ray-curable pressure-sensitive adhesive, the first pressure-sensitive adhesive layer 12 is irradiated with energy rays from the first substrate 11 side to cure the energy ray-polymerizable compound. Curing the energy ray-polymerizable compound increases the cohesive force of the first pressure-sensitive adhesive layer 12, and can reduce or eliminate the adhesive force between the first pressure-sensitive adhesive layer 12 and the adherend (semiconductor wafer W or semiconductor chip CP). Examples of energy rays include ultraviolet rays (UV) and electron beams (EB), with ultraviolet rays being preferred.

Examples of energy ray curable adhesives include "X-type adhesive composition", "Y-type adhesive composition" and "XY-type adhesive composition".

An "X-type adhesive composition" is an energy ray-curable adhesive composition that contains a non-energy ray-curable adhesive resin (also referred to as "adhesive resin I") and an energy ray-curable compound other than the adhesive resin.

The "Y-type adhesive composition" is an adhesive composition that contains, as an energy ray-curable adhesive, an energy ray-curable adhesive resin (hereinafter also referred to as "adhesive resin II") in which an unsaturated group has been introduced into the side chain of a non-energy ray-curable adhesive resin as the main component, and does not contain any energy ray-curable compounds other than the adhesive resin.

An "XY-type adhesive composition" is a combination of X-type and Y-type, i.e., an energy ray-curable adhesive composition containing an energy ray-curable adhesive resin II and an energy ray-curable compound other than the adhesive resin.

Among these, it is preferable to use an XY-type adhesive composition. By using an XY-type adhesive composition, it is possible to obtain sufficient adhesive properties before curing, while at the same time sufficiently reducing the peel force against the semiconductor wafer or semiconductor chip after curing.

However, the adhesive in the first adhesive layer 12 may be formed from a non-energy ray curable adhesive composition that does not cure even when irradiated with energy rays. The non-energy ray curable adhesive composition is an adhesive composition that contains at least the non-energy ray curable adhesive resin I, but does not contain the above-mentioned energy ray curable adhesive resin II or energy ray curable compound.

In the following description, the term "adhesive resin" refers to one or both of the above-mentioned adhesive resin I and adhesive resin II. Specific examples of adhesive resins include acrylic resins, urethane resins, rubber resins, and silicone resins, with acrylic resins being preferred.

Below, we will explain in more detail about acrylic adhesives in which acrylic resin is used as the adhesive resin.

Acrylic polymer (a)
The acrylic resin used is an acrylic polymer (a). The acrylic polymer (a) is a polymer obtained by polymerizing a monomer containing at least an alkyl (meth)acrylate. The acrylic polymer (a) contains a structural unit derived from the alkyl (meth)acrylate.
The alkyl group in the alkyl (meth)acrylate preferably has 1 or more and 20 or less carbon atoms.
The alkyl group in the alkyl (meth)acrylate may be a straight chain or a branched chain.
Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate, etc. The alkyl (meth)acrylates may be used alone or in combination of two or more.

From the viewpoint of improving the adhesive strength of the pressure-sensitive adhesive layer, the acrylic polymer (a) preferably contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 4 or more carbon atoms. The number of carbon atoms in the alkyl group in the alkyl (meth)acrylate is preferably 4 or more and 12 or less, and more preferably 4 or more and 6 or less. The alkyl (meth)acrylate in which the alkyl group has 4 or more carbon atoms is preferably an alkyl acrylate.

In the acrylic polymer (a), the alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms preferably accounts for 40% by mass or more and 98% by mass or less, more preferably 45% by mass or more and 95% by mass or less, and even more preferably 50% by mass or more and 90% by mass or less, of the total amount of monomers constituting the acrylic polymer (a) (hereinafter simply referred to as "total amount of monomers").

In addition to the structural units derived from alkyl (meth)acrylates having an alkyl group with 4 or more carbon atoms, the acrylic polymer (a) is preferably a copolymer containing structural units derived from alkyl (meth)acrylates having an alkyl group with 1 to 3 carbon atoms in order to adjust the elastic modulus and adhesive properties of the adhesive layer. The alkyl (meth)acrylate is preferably an alkyl (meth)acrylate having 1 or 2 carbon atoms, more preferably methyl (meth)acrylate, and most preferably methyl methacrylate. In the acrylic polymer (a), the alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 26% by mass or less, and even more preferably 6% by mass or more and 22% by mass or less, based on the total amount of monomers.

-Functional group-containing monomer The acrylic polymer (a) preferably has a structural unit derived from a functional group-containing monomer in addition to the structural unit derived from the alkyl (meth)acrylate described above. Examples of the functional group of the functional group-containing monomer include a hydroxyl group, a carboxyl group, an amino group, and an epoxy group. The functional group-containing monomer can react with a crosslinking agent described below to become a crosslinking origin, or can react with an unsaturated group-containing compound to introduce an unsaturated group into the side chain of the acrylic polymer (a).

Examples of functional group-containing monomers include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, and epoxy group-containing monomers. These functional group-containing monomers may be used alone or in combination of two or more. Among these functional group-containing monomers, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are more preferred.

Examples of hydroxyl group-containing monomers 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; unsaturated alcohols such as vinyl alcohol and allyl alcohol.

Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids and their anhydrides such as fumaric acid, itaconic acid, maleic acid and citraconic acid; 2-carboxyethyl methacrylate, etc.

The amount of the functional group-containing monomer is preferably 1% by mass or more and 35% by mass or less, more preferably 3% by mass or more and 32% by mass or less, and even more preferably 6% by mass or more and 30% by mass or less, based on the total amount of monomers constituting the acrylic polymer (a).

In addition to the above, the acrylic polymer (a) may also contain a structural unit derived from a monomer copolymerizable with the acrylic monomer. Examples of the structural unit derived from a monomer copolymerizable with the acrylic monomer include styrene, α-methylstyrene, vinyl toluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

The acrylic polymer (a) can be used as a non-energy ray curable adhesive resin I (acrylic resin). In addition, examples of energy ray curable acrylic resins include those obtained by reacting a compound having a photopolymerizable unsaturated group (also called an unsaturated group-containing compound) with the functional group of the acrylic polymer (a).

The unsaturated group-containing compound is a compound having both a substituent capable of bonding with the functional group of the acrylic polymer (a) and a photopolymerizable unsaturated group. Examples of the photopolymerizable unsaturated group include a (meth)acryloyl group, a vinyl group, an allyl group, and a vinylbenzyl group, and a (meth)acryloyl group is preferred.

In addition, examples of the substituents that can be bonded to functional groups in unsaturated group-containing compounds include isocyanate groups and glycidyl groups. Therefore, examples of unsaturated group-containing compounds include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and glycidyl (meth)acrylate.

In addition, the unsaturated group-containing compound preferably reacts with a portion of the functional groups of the acrylic polymer (a). Specifically, the unsaturated group-containing compound is preferably reacted with 50 mol % or more and 98 mol % or less of the functional groups of the acrylic polymer (a), and more preferably reacted with 55 mol % or more and 93 mol % or less of the functional groups of the acrylic polymer (a). In this way, in the energy ray-curable acrylic resin, some of the functional groups remain without reacting with the unsaturated group-containing compound, which makes it easier to crosslink with a crosslinking agent.

The weight average molecular weight (Mw) of the acrylic resin is preferably 300,000 or more and 1,600,000 or less, more preferably 400,000 or more and 1,400,000 or less, and even more preferably 500,000 or more and 1,200,000 or less. The weight average molecular weight (Mw) of the acrylic resin is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

Energy Ray-Curable Compound The energy ray-curable compound contained in the X-type or XY-type pressure-sensitive adhesive composition is preferably a monomer or oligomer that has an unsaturated group in the molecule and can be polymerized and cured by irradiation with energy rays.

Examples of such energy ray-curable compounds include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate, as well as oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate.

Among these, urethane (meth)acrylate oligomers are preferred from the viewpoint of having a relatively high molecular weight and being less likely to reduce the shear storage modulus of the adhesive layer. The molecular weight of the energy ray curable compound (weight average molecular weight in the case of an oligomer) is preferably 100 to 12,000, more preferably 200 to 10,000, even more preferably 400 to 8,000, and particularly preferably 600 to 6,000.

The content of the energy ray curable compound in the X-type adhesive composition is preferably 40 parts by mass or more and 200 parts by mass or less, more preferably 50 parts by mass or more and 150 parts by mass or less, and even more preferably 60 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the adhesive resin.

On the other hand, the content of the energy ray curable compound in the XY type adhesive composition is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 20 parts by mass or less, and even more preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the adhesive resin. In the XY type adhesive composition, since the adhesive resin is energy ray curable, even if the content of the energy ray curable compound is small, it is possible to sufficiently reduce the peel force after irradiation with energy rays.

Crosslinking Agent The adhesive composition preferably further contains a crosslinking agent. The crosslinking agent reacts with, for example, a functional group derived from a functional group monomer possessed by the adhesive resin to crosslink the adhesive resins together. Examples of the crosslinking agent include isocyanate-based crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; and chelate-based crosslinking agents such as aluminum chelate. These crosslinking agents may be used alone or in combination of two or more.

Among these, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive strength and improving adhesive strength, as well as ease of availability.

From the viewpoint of promoting the crosslinking reaction, the amount of the crosslinking agent is preferably 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.03 parts by mass or more and 7 parts by mass or less, and even more preferably 0.05 parts by mass or more and 4 parts by mass or less, per 100 parts by mass of the adhesive resin.

Photopolymerization initiator When the pressure-sensitive adhesive composition is energy ray curable, the pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator. By containing the photopolymerization initiator, the curing reaction of the pressure-sensitive adhesive composition can be sufficiently promoted even with relatively low-energy energy rays such as ultraviolet rays.

Examples of the photopolymerization initiator include a benzoin compound, an acetophenone compound, an acylphosphine oxide compound, a titanocene compound, a thioxanthone compound, and a peroxide compound. Examples of the photopolymerization initiator include a photosensitizer such as an amine or a quinone.
More specific examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyrolnitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. These photopolymerization initiators may be used alone or in combination of two or more.

The amount of photopolymerization initiator is preferably 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.03 parts by mass or more and 5 parts by mass or less, and even more preferably 0.05 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of adhesive resin.

Other Additives The adhesive composition may contain other additives within the range that does not impair the effects of the present invention. Examples of other additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, and dyes. When these additives are added, the amount of the additives is preferably 0.01 parts by mass or more and 6 parts by mass or less relative to 100 parts by mass of the adhesive resin.

In addition, from the viewpoint of improving the coatability onto the substrate, the buffer layer or the release sheet, the adhesive composition may be further diluted with an organic solvent to form a solution of the adhesive composition (sometimes referred to as a coating liquid).

Examples of organic solvents include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

In addition, these organic solvents may be the same as those used during the synthesis of the adhesive resin, or one or more organic solvents other than the organic solvent used during synthesis may be added so that the solution (coating liquid) of the adhesive composition can be applied uniformly.

The thickness of the first adhesive layer 12 is preferably less than 200 μm, more preferably 5 μm to 80 μm, and even more preferably 10 μm to 70 μm. When the thickness of the first adhesive layer 12 is in this range, the proportion of low-rigidity portions in the first adhesive sheet 10 can be reduced, making it easier to prevent chipping of the semiconductor chip during back grinding.
The above is the description of the first pressure-sensitive adhesive layer 12.

Release Sheet A release sheet may be attached to the surface of the first adhesive sheet 10. Specifically, the release sheet is attached to the surface of the first adhesive layer 12 of the first adhesive sheet 10. The release sheet protects the first adhesive layer 12 during transportation and storage by being attached to the surface of the first adhesive layer 12. The release sheet is releasably attached to the first adhesive sheet 10, and is peeled off and removed from the first adhesive sheet 10 before the first adhesive sheet 10 is used (i.e., before the wafer backside is ground).

The release sheet used is one that has at least one surface that has been subjected to a release treatment. Specifically, for example, there is a release sheet that includes a release sheet substrate and a release agent layer formed by applying a release agent to the surface of the substrate.

The release sheet substrate is preferably a resin film. Examples of the resin constituting the resin film as the release sheet substrate include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, and polyolefin resins such as polypropylene resin and polyethylene resin.
Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.

There are no particular limitations on the thickness of the release sheet, but it is preferable that it be 10 μm or more and 200 μm or less, and more preferably 20 μm or more and 150 μm or less.

Manufacturing Method of the Adhesive Sheet There are no particular limitations on the manufacturing method of the first adhesive sheet 10 and other adhesive sheets described in this specification, and they can be manufactured by known methods.

For example, an adhesive layer provided on a release sheet can be attached to one side of a substrate to produce an adhesive sheet with a release sheet attached to the surface of the adhesive layer. Alternatively, a buffer layer provided on the release sheet can be attached to the substrate and the release sheet can be removed to produce a laminate of the buffer layer and substrate. The adhesive layer provided on the release sheet can then be attached to the substrate side of the laminate to produce an adhesive sheet with a release sheet attached to the surface of the adhesive layer. When the buffer layer is provided on both sides of the substrate, the adhesive layer is formed on the buffer layer. The release sheet attached to the surface of the adhesive layer can be removed by peeling it off as appropriate before using the adhesive sheet.

A more specific example of a method for producing an adhesive sheet includes the following method. First, a coating liquid containing an adhesive composition constituting an adhesive layer and, if desired, a solvent or a dispersion medium is prepared. Next, the coating liquid is applied to one surface of a substrate by a coating means to form a coating film. Examples of the coating means include a die coater, a curtain coater, a spray coater, a slit coater, and a knife coater. Next, the coating film is dried to form an adhesive layer. The properties of the coating liquid are not particularly limited as long as it can be applied. The coating liquid may contain a component for forming the adhesive layer as a solute, or may contain a component for forming the adhesive layer as a dispersoid. Similarly, the adhesive layer may be formed by directly applying the adhesive composition to one surface of the substrate or onto the buffer layer.

Another more specific example of a method for producing a pressure-sensitive adhesive sheet is as follows. First, a coating liquid is applied onto the release surface of the release sheet to form a coating film. Next, the coating film is dried to form a laminate consisting of a pressure-sensitive adhesive layer and a release sheet. Next, a substrate may be attached to the surface of the pressure-sensitive adhesive layer of this laminate opposite to the release sheet side to obtain a laminate of the pressure-sensitive adhesive sheet and the release sheet. The release sheet in this laminate may be peeled off as a processing material, or may protect the pressure-sensitive adhesive layer until an adherend (e.g., a semiconductor chip, a semiconductor wafer, etc.) is attached to the pressure-sensitive adhesive layer.

When the coating liquid contains a crosslinking agent, the crosslinking reaction between the (meth)acrylic copolymer in the coating film and the crosslinking agent can be advanced by changing the drying conditions (e.g., temperature and time, etc.) of the coating film or by separately carrying out a heat treatment, for example, to form a crosslinked structure with a desired density in the adhesive layer. In order to advance this crosslinking reaction sufficiently, after laminating the adhesive layer on the substrate by the above-mentioned method, the obtained adhesive sheet can be cured by, for example, leaving it in an environment of 23°C and a relative humidity of 50% for several days.

The thickness of the first adhesive sheet 10 is preferably 10 μm or more, and more preferably 30 μm or more. The thickness of the first adhesive sheet 10 is preferably 500 μm or less, and more preferably 300 μm or less.

(Second Adhesive Sheet)
The second adhesive sheet 20 has a second base material 21 and a second adhesive layer 22. The second adhesive layer 22 is laminated on the second base material 21.

Second Substrate The material of the second substrate 21 according to the present embodiment is not particularly limited as long as it can function appropriately in a desired process such as a dicing process.
The second base material 21 is preferably made of a film mainly made of a resin-based material, such as an ethylene copolymer film, a polyolefin film, a polyvinyl chloride film, a polyester film, a polyurethane film, a polyimide film, a polystyrene film, a polycarbonate film, or a fluororesin film.
Specific examples of films containing a resin-based material as a main material that can be used as the second substrate 21 are similar to the films given as examples in the description of the first substrate 11 .
As the polyolefin film for the second substrate 21, in addition to the films exemplified in the description of the first substrate 11, an ethylene-propylene copolymer film can also be used.

The second substrate 21, like the first substrate 11, may be a film mainly made of the above-mentioned resin-based material, which may contain at least one additive selected from the group consisting of, for example, pigments, flame retardants, plasticizers, antistatic agents, lubricants, and fillers.

Like the first substrate 11, the second substrate 21 may, if desired, be treated on one or both sides of the second substrate 21 to improve adhesion with the second adhesive layer 22 laminated on the surface of the second substrate 21.

The thickness of the second substrate 21 is not limited as long as the second adhesive sheet 20 can function properly in the desired process. The preferred thickness range of the second substrate 21 is the same as the thickness range described for the first substrate 11. The thicknesses of the first substrate 11 and the second substrate 21 may be the same or different.

Second Pressure-Sensitive Adhesive Layer There are no particular limitations on the material constituting the second pressure-sensitive adhesive layer 22, so long as it can function appropriately in the desired process, such as a dicing process.

The second adhesive layer 22 may be composed of a non-energy ray curable adhesive or an energy ray curable adhesive.

The non-energy ray curable adhesive is preferably one having the desired adhesive strength and removability.
Examples of non-energy ray curable adhesives include acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, and polyvinyl ether adhesives. Among these non-energy ray curable adhesives, acrylic adhesives are preferred because they can effectively prevent the workpiece (semiconductor wafer W) or processed product (semiconductor chip CP) from falling off during a dicing process or the like.

On the other hand, the adhesive strength of energy ray-curable adhesives decreases when irradiated with energy rays, so when it is desired to separate the workpiece or processed object from the second adhesive sheet 20, they can be easily separated by irradiating them with energy rays.

The energy ray curable adhesive constituting the second adhesive layer 22 may be an adhesive containing an energy ray curable polymer as a main component.
In addition, the energy ray curable adhesive constituting the second adhesive layer 22 may be an adhesive containing as a main component a mixture of a polymer not having energy ray curability and at least one of an energy ray curable polyfunctional monomer and an energy ray curable polyfunctional oligomer.

The following describes the case where the energy ray-curable adhesive has as its main component a polymer having energy ray-curability.

Energy ray curable polymer (A)
The energy ray curable polymer is preferably a (meth)acrylic acid ester (co)polymer (A) having an energy ray curable functional group (energy ray curable group) introduced into a side chain (hereinafter, sometimes referred to as "energy ray curable polymer (A)"). This energy ray curable polymer (A) is preferably obtained by reacting a (meth)acrylic copolymer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a substituent bonded to the functional group.

Acrylic copolymer (a1)
The acrylic copolymer (a1) comprises a structural unit derived from a functional group-containing monomer and a structural unit derived from a (meth)acrylic acid ester monomer or a derivative thereof.

The functional group-containing monomer as a constituent unit of the acrylic copolymer (a1) is preferably a monomer having a polymerizable double bond and a functional group in the molecule. Examples of the functional group contained in the functional group-containing monomer include a hydroxy group, an amino group, a substituted amino group, and an epoxy group.

Further specific examples of the functional group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and these functional group-containing monomers may be used alone or in combination of two or more.

As the (meth)acrylic acid ester monomer constituting the acrylic copolymer (a1), an alkyl (meth)acrylate, a cycloalkyl (meth)acrylate, or a benzyl (meth)acrylate, in which the alkyl group has 1 to 20 carbon atoms, is used. Among these, an alkyl (meth)acrylate in which the alkyl group has 1 to 18 carbon atoms is preferred, and examples of the alkyl (meth)acrylate that can be used include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

The acrylic copolymer (a1) contains structural units derived from the functional group-containing monomer in a proportion of typically 3% by mass or more and 100% by mass or less, and preferably 5% by mass or more and 40% by mass or less, and contains structural units derived from a (meth)acrylic acid ester monomer or a derivative thereof in a proportion of typically 0% by mass or more and 97% by mass or less, and preferably 60% by mass or more and 95% by mass or less.

The acrylic copolymer (a1) is obtained by copolymerizing the functional group-containing monomer as described above with a (meth)acrylic acid ester monomer or a derivative thereof in a conventional manner. In addition to these monomers, the acrylic copolymer (a1) may also be copolymerized with at least one monomer selected from the group consisting of dimethylacrylamide, vinyl formate, vinyl acetate, and styrene.

The acrylic copolymer (a1) having the functional group-containing monomer unit is reacted with an unsaturated group-containing compound (a2) having a substituent bonded to the functional group to obtain an energy beam-curable polymer (A).

・Unsaturated group-containing compound (a2)
The substituent of the unsaturated group-containing compound (a2) can be appropriately selected depending on the type of functional group of the functional group-containing monomer unit of the acrylic copolymer (a1). For example, In the case of an amino group or a substituted amino group, the substituent is preferably an isocyanate group or an epoxy group, and in the case of an epoxy group, the substituent is preferably an amino group, a carboxy group or an aziridinyl group.

In addition, the unsaturated group-containing compound (a2) contains 1 or more and 5 or less, preferably 1 or more and 2 or less, energy ray-polymerizable carbon-carbon double bonds per molecule. Specific examples of such unsaturated group-containing compounds (a2) include, for example, 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

The unsaturated group-containing compound (a2) is typically used in a ratio of 10 mol% or more and 100 mol% or less, preferably 20 mol% or more and 95 mol% or less, relative to the functional group-containing monomer of the acrylic copolymer (a1).

In the reaction between the acrylic copolymer (a1) and the unsaturated group-containing compound (a2), the reaction conditions such as reaction temperature, pressure, solvent, time, the presence or absence of a catalyst, and the type of catalyst can be appropriately selected according to the combination of functional groups and substituents. By appropriately selecting such reaction conditions, the functional groups present in the acrylic copolymer (a1) react with the substituents in the unsaturated group-containing compound (a2), and the unsaturated groups are introduced into the side chains in the acrylic copolymer (a1), thereby obtaining the energy beam curable polymer (A).

The weight average molecular weight of the energy radiation curable polymer (A) thus obtained is preferably 10,000 or more, more preferably 150,000 or more and 1,500,000 or less, and even more preferably 200,000 or more and 1,000,000 or less. In this specification, the weight average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

Energy ray-curable monomer and/or oligomer (B)
Even when the energy ray-curable adhesive contains an energy ray-curable polymer as the main component, the energy ray-curable adhesive may further contain an energy ray-curable monomer and/or oligomer (B).

As the energy ray-curable monomer and/or oligomer (B), for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

Examples of energy ray-curable monomers and/or oligomers (B) include monofunctional acrylic acid esters such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, polyfunctional acrylic acid esters such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and dimethyloltricyclodecane di(meth)acrylate, polyester oligo(meth)acrylate, polyurethane oligo(meth)acrylate, etc.

When energy ray-curable monomers and/or oligomers (B) are blended, the content of the energy ray-curable monomers and/or oligomers (B) in the energy ray-curable adhesive is preferably 5% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 60% by mass or less.

Photopolymerization initiator (C)
Here, when ultraviolet rays are used as the energy rays for curing the energy ray-curable resin composition, it is preferable to add a photopolymerization initiator (C). By using this photopolymerization initiator (C), the polymerization curing time and the light irradiation dose can be reduced.

Specific examples of photopolymerization initiators (C) include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloroanthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, 2,2-dimethoxy-1,2-diphenylethan-1-one, etc. These photopolymerization initiators (C) may be used alone or in combination of two or more.

The photopolymerization initiator (C) is preferably used in an amount of 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the energy ray-curable copolymer (A) (when an energy ray-curable monomer and/or oligomer (B) is blended, the total amount of the energy ray-curable copolymer (A) and the energy ray-curable monomer and/or oligomer (B) is 100 parts by mass), and more preferably in an amount of 0.5 parts by mass or more and 6 parts by mass or less.

In addition to the above components, other components may be appropriately blended into the energy ray-curable adhesive. Examples of other components include a polymer component or oligomer component (D) that is not energy ray-curable, a crosslinking agent (E), etc.

Examples of polymer or oligomer components (D) that are not energy ray curable include polyacrylic acid esters, polyesters, polyurethanes, polycarbonates, polyolefins, etc., and polymers or oligomers having a weight average molecular weight (Mw) of 3,000 or more and 2.5 million or less are preferred.

Crosslinking agent (E)
As the crosslinking agent (E), a polyfunctional compound having reactivity with the functional group of the energy ray curable copolymer (A) etc. can be used. Examples of such polyfunctional compounds include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, aziridine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, metal alkoxide compounds, metal chelate compounds, metal salts, ammonium salts, and reactive phenolic resins.

By blending these other components (D) and (E) into the energy ray curable adhesive, it is possible to improve the adhesion and peelability before curing, the strength after curing, the adhesion to other layers, storage stability, etc. The blending amount of these other components is not particularly limited and is appropriately determined within the range of 0 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the energy ray curable copolymer (A).

Next, the case where the energy ray-curable adhesive has as its main component a mixture of a polymer component that is not energy ray-curable and an energy ray-curable polyfunctional monomer and/or oligomer will be described below.

As the polymer component that does not have energy ray curability, for example, the same component as the acrylic copolymer (a1) described above can be used. The content of the polymer component that does not have energy ray curability in the energy ray curable resin composition is preferably 20% by mass or more and 99.9% by mass or less, and more preferably 30% by mass or more and 80% by mass or less.

The energy ray curable polyfunctional monomer and/or oligomer is selected from the same components as those of component (B) described above. The blending ratio of the non-energy ray curable polymer component and the energy ray curable polyfunctional monomer and/or oligomer is preferably 10 parts by mass or more and 150 parts by mass or less, more preferably 25 parts by mass or more and 100 parts by mass or less, of the polyfunctional monomer and/or oligomer per 100 parts by mass of the polymer component.

In this case, as above, a photopolymerization initiator (C) and a crosslinking agent (E) can be appropriately blended.

The thickness of the second pressure-sensitive adhesive layer 22 is not particularly limited as long as it can function appropriately in each process in which the second pressure-sensitive adhesive sheet 20 is used. The thickness of the second pressure-sensitive adhesive layer 22 is preferably 1 μm or more and 50 μm or less, preferably 2 μm or more and 30 μm or less, and more preferably 3 μm or more and 20 μm or less.
The above is the description of the second adhesive layer 22.

Release Sheet A release sheet for protecting the second pressure-sensitive adhesive layer 22 until the second pressure-sensitive adhesive sheet 20 is used is preferably attached to the second pressure-sensitive adhesive layer 22. This release sheet may be laminated directly on the second pressure-sensitive adhesive layer 22, or another layer (such as a die-bonding film) may be laminated on the second pressure-sensitive adhesive layer 22, and the release sheet may be laminated on the other layer.

The release sheet may be of any composition, and may be, for example, a plastic film that has been treated with a release agent. Examples of plastic films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. Release agents that can be used include silicone-based, fluorine-based, and long-chain alkyl-based release agents, but among these, silicone-based release agents are preferred because they are inexpensive and provide stable performance. There are no particular limitations on the thickness of the release sheet, but it is usually about 20 μm or more and 250 μm or less.

The thickness of the second adhesive sheet 20 is preferably 10 μm or more, and more preferably 30 μm or more. The thickness of the second adhesive sheet 20 is preferably 500 μm or less, and more preferably 300 μm or less.

(Third adhesive sheet)
The third adhesive sheet 30 has a third base material 31 and a third adhesive layer 32. The third adhesive layer 32 is laminated on the third base material 31.
Third Base Material There are no particular limitations on the material constituting the third base material 31, so long as it can function appropriately in the desired process, such as the expanding process.
The third substrate 31 preferably has a first substrate surface and a second substrate surface opposite to the first substrate surface.
In the third adhesive sheet 30, it is preferable that a third adhesive layer 32 is provided on one of the first substrate surface and the second substrate surface, and it is preferable that no adhesive layer is provided on the other surface.

From the viewpoint of ease of large stretching, the material of the third substrate 31 is preferably a thermoplastic elastomer or a rubber-based material, and more preferably a thermoplastic elastomer.

In addition, from the viewpoint of ease of large stretching, it is preferable to use a resin with a relatively low glass transition temperature (Tg) as the material for the third substrate 31. The glass transition temperature (Tg) of such a resin is preferably 90°C or less, more preferably 80°C or less, and even more preferably 70°C or less.

Examples of thermoplastic elastomers include urethane-based elastomers, olefin-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, styrene-based elastomers, acrylic-based elastomers, and amide-based elastomers. The thermoplastic elastomers may be used alone or in combination of two or more. As the thermoplastic elastomer, it is preferable to use a urethane-based elastomer because it is easy to stretch the elastomer significantly.

Urethane elastomers are generally obtained by reacting a long-chain polyol, a chain extender, and a diisocyanate. Urethane elastomers consist of soft segments having structural units derived from the long-chain polyol, and hard segments having a polyurethane structure obtained by reacting a chain extender with a diisocyanate.

When urethane-based elastomers are classified according to the type of long-chain polyol, they are divided into polyester-based polyurethane elastomers, polyether-based polyurethane elastomers, polycarbonate-based polyurethane elastomers, etc. The urethane-based elastomers can be used alone or in combination of two or more types. In this embodiment, the urethane-based elastomer is preferably a polyether-based polyurethane elastomer from the viewpoint of being easily stretched to a large extent.

Examples of long-chain polyols include polyester polyols such as lactone-based polyester polyols and adipate-based polyester polyols; polyether polyols such as polypropylene (ethylene) polyols and polytetramethylene ether glycol; polycarbonate polyols, etc. In this embodiment, the long-chain polyol is preferably an adipate-based polyester polyol from the viewpoint of being easily stretched.

Examples of diisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and hexamethylene diisocyanate. In this embodiment, the diisocyanate is preferably hexamethylene diisocyanate because it is easy to stretch the diisocyanate.

Chain extenders include low molecular weight polyhydric alcohols (e.g., 1,4-butanediol, 1,6-hexanediol, etc.) and aromatic diamines. Of these, it is preferable to use 1,6-hexanediol because it is easy to extend the chain significantly.

Examples of olefin-based elastomers include elastomers containing at least one resin selected from the group consisting of ethylene-α-olefin copolymers, propylene-α-olefin copolymers, butene-α-olefin copolymers, ethylene-propylene-α-olefin copolymers, ethylene-butene-α-olefin copolymers, propylene-butene-α-olefin copolymers, ethylene-propylene-butene-α-olefin copolymers, styrene-isoprene copolymers, and styrene-ethylene-butylene copolymers. Olefin-based elastomers can be used alone or in combination of two or more.

The density of the olefin-based elastomer is not particularly limited. For example, the density of the olefin-based elastomer is preferably 0.860 g/cm ³ or more and less than 0.905 g/cm ³ , more preferably 0.862 g/cm ³ or more and less than 0.900 g/cm ³ , and particularly preferably 0.864 g/cm ³ or more and less than 0.895 g/cm ^3. When the density of the olefin-based elastomer satisfies the above range, the substrate has excellent unevenness-following properties when a semiconductor device such as a semiconductor wafer as an adherend is attached to the pressure-sensitive adhesive sheet.

It is preferable that the mass ratio of monomers consisting of olefin compounds (also referred to as "olefin content" in this specification) among all monomers used to form the olefin elastomer is 50 mass% or more and 100 mass% or less.
If the olefin content is too low, the properties of an elastomer containing structural units derived from an olefin are less likely to be exhibited, and the substrate is less likely to exhibit flexibility and rubber elasticity.
From the viewpoint of stably obtaining flexibility and rubber elasticity, the olefin content is preferably 50% by mass or more, and more preferably 60% by mass or more.

Examples of styrene-based elastomers include styrene-conjugated diene copolymers and styrene-olefin copolymers. Specific examples of styrene-conjugated diene copolymers include unhydrogenated styrene-conjugated diene copolymers such as styrene-butadiene copolymer, styrene-butadiene-styrene copolymer (SBS), styrene-butadiene-butylene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer (SIS), and styrene-ethylene-isoprene-styrene copolymer, as well as hydrogenated styrene-conjugated diene copolymers such as styrene-ethylene/propylene-styrene copolymer (SEPS, a styrene-isoprene-styrene copolymer water additive), and styrene-ethylene-butylene-styrene copolymer (SEBS, a styrene-butadiene copolymer hydrogen additive). In addition, examples of industrially usable styrene-based elastomers include trade names such as Tufprene (manufactured by Asahi Kasei Corporation), Kraton (manufactured by Kraton Polymer Japan Co., Ltd.), Sumitomo TPE-SB (manufactured by Sumitomo Chemical Co., Ltd.), Epofriend (manufactured by Daicel Corporation), Rabalon (manufactured by Mitsubishi Chemical Corporation), Septon (manufactured by Kuraray Co., Ltd.), and Tuftec (manufactured by Asahi Kasei Corporation). The styrene-based elastomer may be hydrogenated or unhydrogenated.

Examples of rubber-based materials include natural rubber, synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber, acrylic rubber, urethane rubber, and polysulfide rubber. These rubber-based materials can be used alone or in combination of two or more.

It is preferable that the third substrate 31 is a single layer film, not a laminate film in which multiple films made of the above-mentioned materials (e.g., thermoplastic elastomer or rubber-based material) are laminated. It is also preferable that the third substrate 31 is a single layer film, not a laminate film in which a film made of the above-mentioned materials (e.g., thermoplastic elastomer or rubber-based material) is laminated with another film.

The third substrate 31 may contain additives in a film mainly made of the above-mentioned resin-based material. Specific examples of additives are the same as those listed in the description of the first substrate 11 and the second substrate 21. The content of the additive that may be contained in the film is not particularly limited, but it is preferable to keep it within a range in which the third substrate 31 can exert the desired function.

Similar to the first substrate 11 and the second substrate 21, the third substrate 31 may be treated on one or both sides thereof to improve adhesion with the third adhesive layer 32 laminated on the surface of the third substrate 31.

When the third adhesive layer 32 contains an energy ray-curable adhesive, it is preferable that the third substrate 31 has transparency to energy rays. When ultraviolet rays are used as the energy rays, it is preferable that the third substrate 31 has transparency to ultraviolet rays. When electron beams are used as the energy rays, it is preferable that the third substrate 31 has transparency to electron beams.

The thickness of the third substrate 31 is not limited as long as the third adhesive sheet 30 can function properly in the desired process. The thickness of the third substrate 31 is preferably 20 μm or more, and more preferably 40 μm or more. The thickness of the third substrate 31 is preferably 250 μm or less, and more preferably 200 μm or less.

In addition, when the thickness of the third substrate 31 is measured at multiple locations at 2 cm intervals in the in-plane direction of the first substrate surface or the second substrate surface of the third substrate 31, the standard deviation of the thickness of the third substrate 31 is preferably 2 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less. With the standard deviation being 2 μm or less, the third adhesive sheet 30 has a highly accurate thickness, and it becomes possible to stretch the third adhesive sheet 30 uniformly.

It is preferable that the tensile modulus of elasticity in the MD and CD directions of the third substrate 31 at 23°C is 10 MPa or more and 350 MPa or less, respectively, and that the 100% stress in the MD and CD directions of the third substrate 31 at 23°C is 3 MPa or more and 20 MPa or less, respectively.
When the tensile modulus and 100% stress are within the above ranges, the third adhesive sheet 30 can be stretched significantly.
The 100% stress of the third substrate 31 is a value obtained as follows. A test piece having a size of 150 mm (length direction) x 15 mm (width direction) is cut out from the third substrate 31. Both ends of the cut out test piece in the length direction are gripped by grippers so that the length between the grippers is 100 mm. After gripping the test piece with the grippers, it is pulled in the length direction at a speed of 200 mm/min, and the measured value of the tensile force when the length between the grippers becomes 200 mm is read. The 100% stress of the third substrate 31 is a value obtained by dividing the measured value of the tensile force read by the cross-sectional area of the substrate. The cross-sectional area of the third substrate 31 is calculated by the width direction length of 15 mm x the thickness of the third substrate 31 (test piece). The cutting is performed so that the machine direction (MD direction) or the direction perpendicular to the MD direction (CD direction) during the manufacture of the substrate coincides with the length direction of the test piece. In this tensile test, the thickness of the test piece is not particularly limited, and may be the same as the thickness of the substrate to be tested.

At 23° C., it is preferable that the breaking elongation of the third base material 31 in both the MD direction and the CD direction is 100% or more.
When the breaking elongation of the third base material 31 in both the MD direction and the CD direction is 100% or more, the third adhesive sheet 30 can be largely stretched without breaking.

The tensile modulus (MPa) and breaking elongation (%) of the substrate can be measured as follows. The substrate is cut into 15 mm x 140 mm to obtain a test piece. The breaking elongation and tensile modulus of the test piece are measured at 23°C in accordance with JIS K7161:2014 and JIS K7127:1999. Specifically, the test piece is subjected to a tensile test at a speed of 200 mm/min using a tensile tester (Shimadzu Corporation, product name "Autograph AG-IS 500N") with the chuck distance set to 100 mm, and the breaking elongation (%) and tensile modulus (MPa) are measured. The measurements are performed in both the machine direction (MD) during the manufacture of the substrate and the direction perpendicular to the machine direction (CD).

Third Adhesive Layer The constituent material of the third adhesive layer 32 is not particularly limited as long as it can function appropriately in a desired process such as an expanding process. Examples of adhesives contained in the third adhesive layer 32 include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, polyester-based adhesives, and urethane-based adhesives.

Energy ray curable resin (ax1)
The third pressure-sensitive adhesive layer 32 preferably contains an energy ray curable resin (ax1). The energy ray curable resin (ax1) has an energy ray curable double bond in the molecule.
The pressure-sensitive adhesive layer containing the energy ray-curable resin is cured by irradiation with energy rays, and the adhesive strength is reduced. When it is desired to separate the adhesive sheet from the adherend, separation can be easily achieved by irradiating the pressure-sensitive adhesive layer with energy rays.

The energy ray curable resin (ax1) is preferably a (meth)acrylic resin.

The energy ray curable resin (ax1) is preferably an ultraviolet ray curable resin, and more preferably an ultraviolet ray curable (meth)acrylic resin.

The energy ray curable resin (ax1) is a resin that is polymerized and cured when irradiated with energy rays. Examples of the energy rays include ultraviolet rays and electron beams.
Examples of the energy ray curable resin (ax1) include low molecular weight compounds having an energy ray polymerizable group (monofunctional monomers, polyfunctional monomers, monofunctional oligomers, and polyfunctional oligomers). Specific examples of the energy ray curable resin (ax1) include acrylates such as trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, dipentaerythritol monohydroxypentaacrylate, dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, and 1,6-hexanediol diacrylate, cyclic aliphatic skeleton-containing acrylates such as dicyclopentadiene dimethoxy diacrylate and isobornyl acrylate, and acrylate compounds such as polyethylene glycol diacrylate, oligoester acrylate, urethane acrylate oligomer, epoxy modified acrylate, polyether acrylate, and itaconic acid oligomer. The energy ray-curable resin (a1) may be used alone or in combination of two or more.

The molecular weight of the energy ray curable resin (ax1) is typically 100 or more and 30,000 or less, and preferably 300 or more and 10,000 or less.

(Meth)acrylic copolymer (b1)
The pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32) according to this embodiment preferably further contains a (meth)acrylic copolymer (b1). The (meth)acrylic copolymer is different from the energy ray curable resin (ax1) described above.

The (meth)acrylic copolymer (b1) preferably has an energy ray-curable carbon-carbon double bond. That is, in this embodiment, the adhesive layer (third adhesive layer 32) preferably contains an energy ray-curable resin (ax1) and an energy ray-curable (meth)acrylic copolymer (b1).

The pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32) in this embodiment preferably contains 10 parts by mass or more of the energy ray curable resin (ax1) relative to 100 parts by mass of the (meth)acrylic copolymer (b1), more preferably contains 20 parts by mass or more, and even more preferably contains 25 parts by mass or more.
The pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32) in this embodiment preferably contains 80 parts by mass or less of the energy ray curable resin (ax1) relative to 100 parts by mass of the (meth)acrylic copolymer (b1), more preferably contains 70 parts by mass or less, and even more preferably contains 60 parts by mass or less.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer (b1) is preferably 10,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more.
The weight average molecular weight (Mw) of the (meth)acrylic copolymer (b1) is preferably 1.5 million or less, and more preferably 1 million or less.
In this specification, the weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

It is preferable that the (meth)acrylic copolymer (b1) is a (meth)acrylic acid ester polymer (b2) (hereinafter sometimes referred to as "energy ray-curable polymer (b2)") having a functional group having energy ray curability (energy ray-curable group) introduced into the side chain.

Energy radiation curable polymer (b2)
The energy ray curable polymer (b2) is preferably a copolymer obtained by reacting an acrylic copolymer (b21) having a functional group-containing monomer unit with an unsaturated group-containing compound (b22) having a functional group bonded to the functional group.

In this specification, (meth)acrylic acid ester means both acrylic acid ester and methacrylic acid ester, as well as other similar terms.

It is preferable that the acrylic copolymer (b21) contains a structural unit derived from a functional group-containing monomer and a structural unit derived from a (meth)acrylic acid ester monomer or a derivative of a (meth)acrylic acid ester monomer.

The functional group-containing monomer as a constituent unit of the acrylic copolymer (b21) is preferably a monomer having a polymerizable double bond and a functional group in the molecule. The functional group is preferably at least one functional group selected from the group consisting of a hydroxy group, a carboxy group, an amino group, a substituted amino group, an epoxy group, and the like.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. The hydroxyl group-containing monomers may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. The carboxyl group-containing monomer may be used alone or in combination of two or more.

Examples of amino group-containing monomers or substituted amino group-containing monomers include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. The amino group-containing monomers or substituted amino group-containing monomers may be used alone or in combination of two or more.

As the (meth)acrylic acid ester monomer constituting the acrylic copolymer (b21), in addition to alkyl (meth)acrylates in which the alkyl group has 1 to 20 carbon atoms, for example, monomers having an alicyclic structure in the molecule (alicyclic structure-containing monomers) are preferably used.

As the alkyl (meth)acrylate, an alkyl (meth)acrylate in which the number of carbon atoms in the alkyl group is 1 or more and 18 or less is preferred. Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. The alkyl (meth)acrylate may be used alone or in combination of two or more.

Preferred examples of alicyclic structure-containing monomers include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. The alicyclic structure-containing monomers may be used alone or in combination of two or more.

The acrylic copolymer (b21) preferably contains the structural unit derived from the functional group-containing monomer in a proportion of 1 mass % or more, more preferably 5 mass % or more, and even more preferably 10 mass % or more.
In addition, the acrylic copolymer (b21) preferably contains the structural units derived from the functional group-containing monomer in a proportion of 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

Furthermore, the acrylic copolymer (b21) preferably contains a structural unit derived from a (meth)acrylic acid ester monomer or a derivative thereof in a proportion of 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.
In addition, the acrylic copolymer (b21) preferably contains a structural unit derived from a (meth)acrylic acid ester monomer or a derivative thereof in a proportion of 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

The acrylic copolymer (b21) can be obtained by copolymerizing the above-mentioned functional group-containing monomer with a (meth)acrylic acid ester monomer or a derivative thereof in a conventional manner.
The acrylic copolymer (b21) may contain, in addition to the above-mentioned monomers, at least one structural unit selected from the group consisting of dimethylacrylamide, vinyl formate, vinyl acetate, styrene, and the like.

The energy ray curable polymer (b2) is obtained by reacting the acrylic copolymer (b21) having the above-mentioned functional group-containing monomer unit with an unsaturated group-containing compound (b22) having a functional group bonded to the functional group.

The functional group of the unsaturated group-containing compound (b22) can be appropriately selected depending on the type of functional group of the functional group-containing monomer unit of the acrylic copolymer (b21). For example, when the functional group of the acrylic copolymer (b21) is a hydroxy group, an amino group, or a substituted amino group, the functional group of the unsaturated group-containing compound (b22) is preferably an isocyanate group or an epoxy group, and when the functional group of the acrylic copolymer (b21) is an epoxy group, the functional group of the unsaturated group-containing compound (b22) is preferably an amino group, a carboxy group, or an aziridinyl group.

The unsaturated group-containing compound (b22) contains at least one energy ray-polymerizable carbon-carbon double bond in one molecule, preferably 1 to 6, and more preferably 1 to 4.

Examples of unsaturated group-containing compounds (b22) include 2-methacryloyloxyethyl isocyanate (2-isocyanatoethyl methacrylate), meth-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

The unsaturated group-containing compound (b22) is preferably used in a proportion (addition rate) of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more, based on the number of moles of the functional group-containing monomer in the acrylic copolymer (b21).
In addition, the unsaturated group-containing compound (b22) is preferably used in a proportion of 95 mol % or less, more preferably 93 mol % or less, and even more preferably 90 mol % or less, based on the number of moles of the functional group-containing monomer in the acrylic copolymer (b21).

In the reaction between the acrylic copolymer (b21) and the unsaturated group-containing compound (b22), the reaction temperature, pressure, solvent, time, presence or absence of a catalyst, and type of catalyst can be appropriately selected according to the combination of the functional group of the acrylic copolymer (b21) and the functional group of the unsaturated group-containing compound (b22). As a result, the functional group of the acrylic copolymer (b21) reacts with the functional group of the unsaturated group-containing compound (b22), and the unsaturated group is introduced into the side chain of the acrylic copolymer (b21), thereby obtaining an energy radiation curable polymer (b2).

The weight average molecular weight (Mw) of the energy ray curable polymer (b2) is preferably 10,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more.
The weight average molecular weight (Mw) of the energy ray curable polymer (b2) is preferably 1.5 million or less, and more preferably 1 million or less.

Photopolymerization initiator (CX)
When the adhesive layer (third adhesive layer 32) contains an ultraviolet-curable compound (e.g., an ultraviolet-curable resin), it is preferable that the adhesive layer (third adhesive layer 32) contains a photopolymerization initiator (CX).
By including a photopolymerization initiator (CX) in the pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32), the polymerization curing time and the amount of light irradiation can be reduced.

Specific examples of the photopolymerization initiator (CX) are the same as the specific examples of the photopolymerization initiator (C) in the description of the second adhesive sheet 20. In the third adhesive sheet 30, the photopolymerization initiator (CX) may be used alone or in combination of two or more types.

When the energy ray curable resin (ax1) and the (meth)acrylic copolymer (b1) are blended in the pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32), the photopolymerization initiator (CX) is preferably used in an amount of 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the total amount of the energy ray curable resin (ax1) and the (meth)acrylic copolymer (b1).
In addition, when the energy ray curable resin (ax1) and the (meth)acrylic copolymer (b1) are blended in the pressure-sensitive adhesive layer (third pressure-sensitive adhesive layer 32), the photopolymerization initiator (CX) is preferably used in an amount of 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the total amount of the energy ray curable resin (ax1) and the (meth)acrylic copolymer (b1).

The adhesive layer (third adhesive layer 32) may contain other components in addition to the above components. Examples of other components include a crosslinking agent (EX).

Crosslinking agent (EX)
As the crosslinking agent (EX), a polyfunctional compound having reactivity with the functional group of the (meth)acrylic copolymer (b1) etc. can be used. Examples of the polyfunctional compound in the third adhesive sheet 30 are the same as the specific examples of the polyfunctional compound as the crosslinking agent (E) in the description of the second adhesive sheet 20.

The amount of the crosslinking agent (EX) is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, and even more preferably 0.04 parts by mass or more, based on 100 parts by mass of the (meth)acrylic copolymer (b1).
The amount of the crosslinking agent (EX) is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3.5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic copolymer (b1).

The thickness of the adhesive layer (third adhesive layer 32) is not particularly limited. The thickness of the adhesive layer (third adhesive layer 32) is, for example, preferably 10 μm or more, and more preferably 20 μm or more. The thickness of the adhesive layer (third adhesive layer 32) is preferably 150 μm or less, and more preferably 100 μm or less.

The recovery rate of the third adhesive sheet 30 is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. The recovery rate of the third adhesive sheet 30 is preferably 100% or less. When the recovery rate is in the above range, the adhesive sheet can be greatly stretched.
The recovery rate was measured by cutting a test piece of 150 mm (length direction) x 15 mm (width direction) from a pressure-sensitive adhesive sheet, gripping both ends in the length direction with grippers so that the length between the grippers was 100 mm, pulling the test piece at a speed of 200 mm/min until the length between the grippers was 200 mm, holding the test piece in this expanded state of 200 mm for 1 minute, and then returning the test piece in the length direction at a speed of 200 mm/min until the length between the grippers was 100 mm. The length between the grippers is returned to 100 mm and held in that state for 1 minute, and then pulled in the longitudinal direction at a speed of 60 mm/min. The length between the grippers is measured when the measured tensile force is 0.1 N/15 mm. L2 (mm) is the length obtained by subtracting the initial length between the grippers of 100 mm from the measured length, and L1 (mm) is the length between the grippers in the expanded state of 200 mm minus the initial length between the grippers of 100 mm. L2 can be calculated using the following formula (Equation 2).
Restoration rate (%) = {1 - (L2 ÷ L1)} × 100 (Equation 2)

When the recovery rate is within the above range, it means that the adhesive sheet is easy to restore even after being greatly stretched. In general, when a sheet having a yield point is stretched beyond the yield point, the sheet undergoes plastic deformation, and the plastically deformed portion, i.e., the extremely stretched portion, becomes unevenly distributed. When a sheet in such a state is further stretched, the extremely stretched portion breaks, or even if no break occurs, the expansion becomes uneven. In addition, even if a sheet does not have a clear yield point and does not take a stress value where the slope dx/dy changes from a positive value to a 0 or negative value in a stress-strain diagram in which the strain is plotted on the x-axis and the elongation is plotted on the y-axis, as the amount of tension increases, the sheet undergoes plastic deformation, and similarly breaks or becomes unevenly expanded. On the other hand, when elastic deformation occurs instead of plastic deformation, the sheet is easy to restore to its original shape by removing the stress. Therefore, by having the recovery rate, which is an index showing the degree of recovery after 100% elongation, which is a sufficiently large tensile amount, within the above range, plastic deformation of the film is minimized when the adhesive sheet is significantly stretched, making it less likely to break and enabling uniform expansion.

Release sheet The third adhesive sheet 30 may have a release sheet laminated on its adhesive surface for the purpose of protecting the adhesive surface until the adhesive surface is attached to an adherend (e.g., a semiconductor chip, etc.). The configuration of the release sheet is arbitrary, and an example is a plastic film that has been subjected to a release treatment with a release agent, etc. The release sheet may be a release sheet that can be used for the first adhesive sheet 10 and the second adhesive sheet 20.

The thickness of the third adhesive sheet 30 is preferably 30 μm or more, and more preferably 50 μm or more. The thickness of the third adhesive sheet 30 is preferably 400 μm or less, and more preferably 300 μm or less.

[Effects of this embodiment]
According to the expanding method of this embodiment, when the third adhesive sheet 30 is expanded, the circuit surface W1 of the semiconductor chip CP is not in contact with the third adhesive layer 32 of the third adhesive sheet 30. Since the first adhesive sheet 10, which has been singulated in the dicing process, is interposed between the circuit surface W1 and the third adhesive layer 32 in each semiconductor chip CP, the first adhesive layer 12 of the first adhesive sheet 10, which is in contact with the circuit surface W1, is not stretched even when the third adhesive sheet 30 is expanded. As a result, according to the expanding method of this embodiment, it is possible to suppress adhesive residue.
In addition, the adhesive sheets used in the expanding method according to the present embodiment are all simply configured to be composed of a substrate and an adhesive layer. In addition, since the adhesive sheet used in the dicing step is replaced with an adhesive sheet for the expanding step before the expanding step, there is no need to carefully control the cutting depth so that the dicing blade does not reach the substrate of the dicing sheet in the dicing step.
Therefore, according to the expanding method of this embodiment, the pressure-sensitive adhesive sheet configuration and process can be simplified compared to conventional methods, and adhesive residue can be suppressed.
Furthermore, it is possible to provide a method for manufacturing a semiconductor device including the expanding method according to this embodiment.

Second Embodiment
Next, a second embodiment of the present invention will be described.
The first embodiment and the second embodiment differ mainly in the following respects: In the first embodiment, the adhesive sheet attached to the circuit surface of the semiconductor wafer in the back-grinding process and the dicing process is the same adhesive sheet, whereas in the second embodiment, the adhesive sheet attached to the semiconductor wafer in the back-grinding process is different from the adhesive sheet attached to the circuit surface of the semiconductor wafer in the dicing process.
In the following description, differences from the first embodiment will be mainly described, and overlapping descriptions will be omitted or simplified. The same components as those in the first embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted or simplified.

The expanding method according to this embodiment further includes steps (PX1), (PX2) and (PX3) in addition to steps (P1) to (P5) described in the first embodiment. Steps (PX1), (PX2) and (PX3) are performed before step (P1).

(PX1) A process of adhering a fourth adhesive sheet to the first wafer surface before backgrinding the semiconductor wafer.
(PX2) A process of grinding the backside of the semiconductor wafer to which the fourth adhesive sheet is attached.
(PX3) A process of peeling the fourth adhesive sheet from the first wafer surface after grinding the backside of the semiconductor wafer, and attaching the first adhesive sheet to the first wafer surface.

[Back grinding process]
FIG. 6A is a diagram for explaining the step (PX1) and the step (PX2).
In the back grinding process of this embodiment, the back surface W6 opposite to the circuit surface W1 is ground by the grinder 500 to a predetermined thickness of the semiconductor wafer W. The back surface W6 of the semiconductor wafer W is ground to form the back surface W3.

In the backgrinding step of this embodiment, a fourth adhesive sheet 40 is attached to the circuit surface W1 of the semiconductor wafer W. The fourth adhesive sheet 40 has a fourth adhesive layer 42 and a fourth base material 41. In this embodiment, it is preferable that the fourth adhesive sheet 40 is a backgrind sheet. When the fourth adhesive sheet 40 is used as the backgrind sheet, the semiconductor wafer W is attached with the circuit surface W1 facing the fourth adhesive layer 42 of the fourth adhesive sheet 40. It is preferable that the fourth adhesive sheet 40 as the backgrind sheet is attached to the circuit surface W1 as the first wafer surface before the semiconductor wafer W is backgrinded.
The fourth adhesive sheet 40 is preferably an adhesive sheet similar to the first adhesive sheet 10 in the first embodiment.

[Step of Peeling Off Fourth Pressure-Sensitive Adhesive Sheet and Step of Sticking First Pressure-Sensitive Adhesive Sheet]
Fig. 6B is a diagram for explaining the step (PX3). Fig. 6B shows a state in which the semiconductor wafer W is back-ground, the fourth adhesive sheet 40 is peeled off from the circuit surface W1, and then the first adhesive sheet 70 is attached to the circuit surface W1.
In this embodiment, as described above, after the backgrinding step, instead of proceeding to the next step with the backgrind sheet (fourth adhesive sheet 40) attached to the circuit surface W1, another adhesive sheet (first adhesive sheet 70) is attached to the circuit surface W1. The first adhesive sheet 70 as this other adhesive sheet is preferably a surface protection sheet for protecting the circuit surface W1. Note that while the first adhesive sheet is used as a backgrind sheet in the first embodiment, the first adhesive sheet is used as a surface protection sheet in the present embodiment, and thus the positioning of the first adhesive sheet is different. Therefore, the first adhesive sheet is designated by the reference number 10 in the first embodiment, and the first adhesive sheet is designated by the reference number 70 in the present embodiment, to distinguish between them.
The thickness of the first adhesive sheet 70 as a surface protection sheet is preferably thinner than the thickness of the fourth adhesive sheet 40 as a backgrind sheet. By making the thickness of the first adhesive sheet 70 thinner than the thickness of the fourth adhesive sheet 40, it becomes easier to dicing the first adhesive sheet 70 and the semiconductor wafer W in the dicing step.
The thickness of the first adhesive sheet 70 serving as a surface protection sheet is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 30 μm or more.
The thickness of the first adhesive sheet 70 serving as a surface protection sheet is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 100 μm or less.

[Step of attaching second adhesive sheet]
In this embodiment, as in the first embodiment, it is preferable that the semiconductor wafer W prepared in step (P1) is a wafer obtained through a back grinding step and then a bonding step of bonding a second adhesive sheet 20 to the back surface W3.
7A is a diagram illustrating a bonding step of bonding the second adhesive sheet 20 to the back surface W3. In this embodiment, similar to the first embodiment, the second adhesive sheet 20 is preferably a dicing sheet. When the second adhesive sheet 20 is used as a dicing sheet, the semiconductor wafer W is bonded with the back surface W3 facing the second adhesive layer 22 of the second adhesive sheet 20.

[Dicing process]
7B is a diagram for explaining step (P2) in this embodiment. Step (P2) may be referred to as a dicing step. FIG. 7B shows a plurality of semiconductor chips CP obtained by dicing the semiconductor wafer W.
The step (P2) in this embodiment differs from the first embodiment in that the first adhesive sheet 70 is attached to the circuit surface W1, and other points can be performed in the same manner as in the first embodiment. In this embodiment as well, an incision is made from the first adhesive sheet 70 side to cut the first adhesive sheet 70, and the semiconductor wafer W is further cut.

[Step of attaching third adhesive sheet]
Fig. 8A is a diagram for explaining the step (P3). The step (P3) may be referred to as a step of attaching a third adhesive sheet. Fig. 8A shows a state in which the third adhesive sheet 30 is attached to a plurality of semiconductor chips CP obtained by the dicing step. The third adhesive sheet 30 is the same as that in the first embodiment.
The step (P3) in this embodiment differs from the first embodiment in that a third adhesive sheet 30 is attached to a first adhesive sheet 70 serving as a surface protection sheet, but the other steps can be performed in the same manner as in the first embodiment.

[Step of Peeling Off Second Adhesive Sheet]
Fig. 8B is a diagram for explaining step (P4) in this embodiment. Step (P4) may be referred to as a second adhesive sheet peeling step. Fig. 8B shows a state in which the second adhesive sheet 20 is peeled off from the rear surface W3 of the wafer W after the third adhesive sheet 30 is attached. Step (P4) in this embodiment can be performed in the same manner as in the first embodiment.

[Expanding process]
9 is a diagram for explaining step (P5) in this embodiment. Step (P5) may be referred to as an expanding step. FIG. 9 shows a state in which the third adhesive sheet 30 is expanded after the second adhesive sheet 20 is peeled off to expand the intervals between the multiple semiconductor chips CP. In this embodiment, it is preferable that the third adhesive sheet 30 is an expanding sheet. Step (P5) in this embodiment can be performed in the same manner as in the first embodiment. In this embodiment, it is preferable that the intervals D1 between the multiple semiconductor chips CP are the same as in the first embodiment.

[Sealing process and other processes]
In this embodiment, similarly to the first embodiment, a sealing step and other steps (a rewiring layer forming step and a connection step with external terminal electrodes) may be performed.

(Fourth adhesive sheet)
The fourth adhesive sheet 40 is preferably an adhesive sheet similar to the first adhesive sheet 10 described in the first embodiment.

(First Adhesive Sheet)
The first adhesive sheet 70 in this embodiment has a seventh base material 71 and a seventh adhesive layer 72. The seventh adhesive layer 72 is laminated on the seventh base material 71.

Seventh Substrate The seventh substrate 71 is a member that supports the seventh pressure-sensitive adhesive layer 72. The material constituting the seventh substrate 71 is not particularly limited as long as it can function appropriately in a desired process such as a dicing process.

The thickness of the seventh base material 71 is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more.
The thickness of the seventh base material 71 is preferably 100 μm or less, more preferably 75 μm or less, and even more preferably 50 μm or less.

As the seventh substrate 71, for example, a sheet material such as a synthetic resin film can be used. Examples of synthetic resin films include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene vinyl acetate copolymer films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, and polyimide films. Other examples of the seventh substrate 71 include crosslinked films and laminated films of these.

The seventh base material 71 preferably contains a polyester-based resin, and more preferably is made of a material mainly composed of a polyester-based resin. In this specification, a material mainly composed of a polyester-based resin means that the mass ratio of the polyester-based resin to the mass of the entire material constituting the base material is 50 mass% or more.
The polyester-based resin is preferably any resin selected from the group consisting of, for example, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, and copolymer resins of these resins, and more preferably polyethylene terephthalate resin.
A polyethylene terephthalate film and a polyethylene naphthalate film are preferable, and a polyethylene terephthalate film is more preferable, as the seventh base material 71. The oligomer contained in the polyester film is derived from a polyester-forming monomer, a dimer, a trimer, or the like.

Seventh Adhesive Layer There are no particular limitations on the material constituting the seventh adhesive layer 72, so long as it can function appropriately in the desired process, such as a dicing process.
In this embodiment, the seventh adhesive layer 72 is preferably composed of at least one adhesive selected from the group consisting of, for example, an acrylic adhesive, a urethane adhesive, a polyester adhesive, a rubber adhesive, and a silicone adhesive, and is more preferably composed of an acrylic adhesive.

In this embodiment, the seventh adhesive layer 72 preferably contains an adhesive composition. This adhesive composition preferably contains an acrylic copolymer having 2-ethylhexyl acrylate as the main monomer. In this specification, having 2-ethylhexyl acrylate as the main monomer means that the mass ratio of the copolymer component derived from 2-ethylhexyl acrylate to the mass of the entire acrylic copolymer is 50 mass% or more. In this embodiment, the proportion of the copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is preferably 50 mass% or more and 95 mass% or less, more preferably 60 mass% or more and 95 mass% or less, even more preferably 80 mass% or more and 95 mass% or less, and even more preferably 85 mass% or more and 93 mass% or less.

The type and number of copolymer components other than 2-ethylhexyl acrylate in the acrylic copolymer are not particularly limited. For example, as the second copolymer component, a functional group-containing monomer having a reactive functional group is preferable. When a crosslinking agent described later is used, the reactive functional group of the second copolymer component is preferably a functional group that can react with the crosslinking agent. This reactive functional group is preferably at least one of the substituents selected from the group consisting of, for example, a carboxy group, a hydroxyl group, an amino group, a substituted amino group, and an epoxy group, more preferably at least one of the substituents of a carboxy group and a hydroxyl group, and even more preferably a carboxy group.

Examples of monomers having a carboxy group (carboxy group-containing monomers) include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among the carboxy group-containing monomers, acrylic acid is preferred in terms of reactivity and copolymerizability. The carboxy group-containing monomers may be used alone or in combination of two or more.

Examples of monomers having a hydroxyl group (hydroxyl group-containing monomers) include (meth)acrylic acid hydroxyalkyl esters 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. Among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth)acrylate is preferred in terms of the reactivity and copolymerizability of the hydroxyl group. One type of hydroxyl group-containing monomer may be used alone, or two or more types may be used in combination.

Examples of acrylic esters having epoxy groups include glycidyl acrylate and glycidyl methacrylate.

Other copolymer components in the acrylic copolymer include (meth)acrylic acid alkyl esters having an alkyl group with 2 to 20 carbon atoms. Examples of (meth)acrylic acid alkyl esters include ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl methacrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. Among these (meth)acrylic acid alkyl esters, from the viewpoint of further improving adhesion, (meth)acrylic acid esters having an alkyl group with 2 to 4 carbon atoms are preferred, and n-butyl (meth)acrylate is more preferred. The (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

Examples of other copolymer components in the acrylic copolymer include copolymer components derived from at least any one monomer selected from the group consisting of alkoxyalkyl group-containing (meth)acrylic acid esters, (meth)acrylic acid esters having an aliphatic ring, (meth)acrylic acid esters having an aromatic ring, non-crosslinkable acrylamide, (meth)acrylic acid esters having a non-crosslinkable tertiary amino group, vinyl acetate, and styrene.
Examples of alkoxyalkyl group-containing (meth)acrylic acid esters include methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate.
An example of the (meth)acrylic acid ester having an aliphatic ring is cyclohexyl (meth)acrylate.
An example of the (meth)acrylic acid ester having an aromatic ring is phenyl (meth)acrylate.
Non-crosslinkable acrylamides include, for example, acrylamide and methacrylamide.
Examples of (meth)acrylic acid esters having a non-crosslinkable tertiary amino group include (N,N-dimethylamino)ethyl (meth)acrylate and (N,N-dimethylamino)propyl (meth)acrylate.
These monomers may be used alone or in combination of two or more.

In this embodiment, the second copolymer component is preferably a carboxyl group-containing monomer or a hydroxyl group-containing monomer, and more preferably acrylic acid. When the acrylic copolymer contains a copolymer component derived from 2-ethylhexyl acrylate and a copolymer component derived from acrylic acid, the mass ratio of the copolymer component derived from acrylic acid to the mass of the entire acrylic copolymer is preferably 1% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less. If the proportion of acrylic acid is 1% by mass or less, crosslinking of the acrylic copolymer can be prevented from proceeding too quickly when a crosslinking agent is contained in the pressure-sensitive adhesive composition.

The acrylic copolymer may contain copolymer components derived from two or more types of functional group-containing monomers. For example, the acrylic copolymer may be a ternary copolymer, and is preferably an acrylic copolymer obtained by copolymerizing 2-ethylhexyl acrylate, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer, and the carboxyl group-containing monomer is preferably acrylic acid, and the hydroxyl group-containing monomer is preferably 2-hydroxyethyl acrylate. It is preferable that the proportion of the copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is 80% by mass or more and 95% by mass or less, the proportion of the mass of the copolymer component derived from acrylic acid is 1% by mass or less, and the remainder is a copolymer component derived from 2-hydroxyethyl acrylate.

The weight average molecular weight (Mw) of the acrylic copolymer is preferably 300,000 or more and 2,000,000 or less, more preferably 600,000 or more and 1,500,000 or less, and even more preferably 800,000 or more and 1,200,000 or less. If the weight average molecular weight Mw of the acrylic copolymer is 300,000 or more, it can be peeled off without leaving any adhesive residue on the adherend. If the weight average molecular weight Mw of the acrylic copolymer is 2,000,000 or less, it can be reliably attached to the adherend.
The weight average molecular weight Mw of the acrylic copolymer is a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC).

Acrylic copolymers can be produced using the various raw material monomers mentioned above according to conventional methods.

The copolymerization form of the acrylic copolymer is not particularly limited, and may be any of a block copolymer, a random copolymer, and a graft copolymer.
In this embodiment, the content of the acrylic copolymer in the pressure-sensitive adhesive composition is preferably 40% by mass or more and 90% by mass or less, and more preferably 50% by mass or more and 90% by mass or less.

The adhesive composition constituting the seventh adhesive layer 72 preferably contains at least an adhesive obtained by crosslinking a composition containing the above-mentioned acrylic copolymer and a crosslinking agent. It is also preferable that the adhesive composition essentially consists of an adhesive obtained by crosslinking the above-mentioned acrylic copolymer and a crosslinking agent as described above. Here, "substantially" means that the adhesive composition consists only of the adhesive, excluding trace amounts of impurities that are inevitably mixed into the adhesive.

Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a metal chelate-based crosslinking agent, an amine-based crosslinking agent, and an amino resin-based crosslinking agent. These crosslinking agents may be used alone or in combination of two or more.
Among these crosslinking agents, a crosslinking agent containing a compound having an isocyanate group as a main component (isocyanate-based crosslinking agent) is preferable from the viewpoint of improving the heat resistance and adhesive strength of the seventh adhesive layer 72. Examples of the isocyanate-based crosslinking agent include polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate.
The polyisocyanate compound may be a trimethylolpropane adduct type modified product of the above compound, a biuret type modified product obtained by reacting with water, or an isocyanurate type modified product having an isocyanurate ring.
In this specification, a crosslinking agent containing a compound having an isocyanate group as a main component means that the proportion of the mass of the compound having an isocyanate group in the mass of all the components constituting the crosslinking agent is 50 mass% or more.

In this embodiment, the content of the crosslinking agent in the adhesive composition is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, and even more preferably 5 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the acrylic copolymer. If the content of the crosslinking agent in the adhesive composition is within such a range, the adhesion between the seventh adhesive layer 72 and the seventh substrate 71 can be improved, and the curing period for stabilizing the adhesive properties after production of the adhesive sheet can be shortened.

In the present embodiment, when the adhesive composition constituting the seventh adhesive layer 72 contains a crosslinking agent, it is preferable that the adhesive composition further contains a crosslinking accelerator. It is preferable to select and use an appropriate crosslinking accelerator depending on the type of crosslinking agent, etc. For example, when the adhesive composition contains a polyisocyanate compound as a crosslinking agent, it is preferable that the adhesive composition further contains an organometallic compound-based crosslinking accelerator such as an organotin compound.

In addition, it is also preferable that the adhesive composition constituting the seventh adhesive layer 72 contains a reactive adhesive aid. Examples of reactive adhesive aids include polybutadiene resins having reactive functional groups, and hydrogenated polybutadiene resins having reactive functional groups. The reactive functional groups possessed by the reactive adhesive aid are preferably one or more functional groups selected from the group consisting of hydroxyl groups, isocyanate groups, amino groups, oxirane groups, acid anhydride groups, alkoxy groups, acryloyl groups, and methacryloyl groups. When the adhesive composition contains a reactive adhesive aid, it is possible to reduce adhesive residue when the first adhesive sheet 70 is peeled off from the adherend.

In this embodiment, the adhesive composition constituting the seventh adhesive layer 72 may contain other components to the extent that the effects of the present invention are not impaired. Examples of other components that may be contained in the adhesive composition include organic solvents, flame retardants, tackifiers, UV absorbers, antioxidants, preservatives, antifungal agents, plasticizers, defoamers, and wettability adjusters.

The thickness of the seventh pressure-sensitive adhesive layer 72 is appropriately determined depending on the application of the first pressure-sensitive adhesive sheet 70. In the present embodiment, the thickness of the seventh pressure-sensitive adhesive layer 72 is preferably 5 μm or more. The thickness of the seventh pressure-sensitive adhesive layer 72 is preferably 60 μm or less, and more preferably 50 μm or less.
The above is the description of the seventh adhesive layer 72.

Release sheet A release sheet may be laminated on the adhesive surface of the first adhesive sheet 70 in order to protect the adhesive surface until the adhesive surface is attached to an adherend (e.g., a semiconductor wafer W or a semiconductor chip CP). The configuration of the release sheet is arbitrary, and an example of the release sheet is a plastic film that has been subjected to a release treatment using a release agent or the like. The release sheet may be a release sheet that can be used for the first adhesive sheet 10 and the second adhesive sheet 20.

[Effects of this embodiment]
The expanding method according to the present embodiment can simplify the adhesive sheet configuration and process compared to the conventional method, and can suppress adhesive residue, as in the first embodiment. Furthermore, a manufacturing method for a semiconductor device including the expanding method according to the present embodiment can be provided.

In addition, in the expanding method according to this embodiment, after the backgrinding process and before the dicing process, the fourth adhesive sheet 40 used in the backgrinding process is replaced with a first adhesive sheet 70 that is thinner than the fourth adhesive sheet 40 used in the backgrinding process. This makes it possible to reduce the thickness of the adhesive sheet to be cut in the dicing process, thereby reducing the load on the dicing blade.

Third Embodiment
Next, a third embodiment of the present invention will be described.
The first and third embodiments differ mainly in the following respects. In the first embodiment, a dicing process is performed after a back grinding process, whereas in the third embodiment, a process called a first dicing method is performed. The first dicing method is a process in which grooves of a predetermined depth are formed on the front side of a semiconductor wafer, and then grinding is performed on the back side of the wafer, the bottoms of the grooves are removed by grinding, and the wafer is divided into individual chips.
In the following description, differences from the first embodiment will be mainly described, and overlapping descriptions will be omitted or simplified. The same components as those in the first embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted or simplified.

The expanding method according to this embodiment includes the following steps (PY1) to (PY4) and a step (P5) similar to that of the first embodiment.
(PY1) A process of adhering an eighth adhesive sheet to the first wafer surface of the wafer before backgrinding.
(PY2) A process of forming a groove of a predetermined depth from the first wafer surface side of the wafer.
(PY3) A process of grinding the back surface of the second wafer surface of the wafer having the grooves formed therein to remove the bottoms of the grooves and obtain chips.
(PY4) A process of attaching the third adhesive sheet to the eighth adhesive sheet after backgrinding the wafer.
(P5) A process of stretching the third adhesive sheet to increase the spacing between multiple chips.

[Step of attaching eighth adhesive sheet]
FIG. 10A is a diagram for explaining the step (PY1). FIG. 10A shows a state in which the eighth adhesive sheet 80 is attached to the circuit surface W1 as the first wafer surface of the semiconductor wafer W before the back grinding. The eighth adhesive sheet 80 has an eighth adhesive layer 82 and an eighth base material 81. In this embodiment, it is preferable that the eighth adhesive sheet 80 is a backgrind sheet. It is preferable to use an adhesive sheet similar to the first adhesive sheet 10 in the first embodiment or the fourth adhesive sheet 40 in the second embodiment as the backgrind sheet for the eighth adhesive sheet 80. When the eighth adhesive sheet 80 is used as the backgrind sheet, the semiconductor wafer W is attached with the circuit surface W1 facing the eighth adhesive layer 82 of the eighth adhesive sheet 80. It is preferable that the eighth adhesive sheet 80 as the backgrind sheet is attached to the circuit surface W1 as the first wafer surface before the step of forming a groove of a predetermined depth in the semiconductor wafer W.

[Groove forming process]
Fig. 10B is a diagram for explaining the step (PY2). Fig. 10B shows a diagram for explaining the step of forming a groove of a predetermined depth from the circuit surface W1 side of the semiconductor wafer W (sometimes referred to as a groove forming step).
In the groove forming process, a cut is made in the semiconductor wafer from the eighth adhesive sheet 80 side using a dicing blade of a dicing device or the like. At that time, the eighth adhesive sheet 80 is completely cut, and a cut is made from the circuit surface W1 of the semiconductor wafer W to a depth shallower than the thickness of the semiconductor wafer W to form the groove W5. The groove W5 is formed so as to partition the multiple circuits W2 formed on the circuit surface W1 of the semiconductor wafer W. The depth of the groove W5 is not particularly limited as long as it is slightly deeper than the thickness of the target semiconductor chip. When the groove W5 is formed, cutting chips are generated from the semiconductor wafer W. In this embodiment, the groove W5 is formed in a state where the circuit surface W1 is protected by the eighth adhesive sheet 80, so that contamination and damage of the circuit surface W1 and the circuit W2 due to cutting chips can be prevented.

[Grinding process]
Fig. 10C is a diagram for explaining the step (PY3). Fig. 10C shows a diagram for explaining a step of adhering the third adhesive sheet 30 to the individualized eighth adhesive sheet 80 after forming the grooves W5 (a third adhesive sheet adhering step), and a step of grinding the back surface W6 as the second surface of the semiconductor wafer W (sometimes referred to as a grinding step).
In this embodiment, the semiconductor wafer W is ground from the back surface W6 side using a grinder 500. Grinding reduces the thickness of the semiconductor wafer W, and the semiconductor wafer W is finally divided into a plurality of semiconductor chips CP. Grinding is performed from the back surface W6 side until the bottom of the groove W5 is removed, and the semiconductor wafer W is divided into individual circuits W2. Thereafter, as necessary, further back surface grinding is performed to obtain semiconductor chips CP of a predetermined thickness. In this embodiment, grinding is performed until the back surface W3 as the second wafer surface is obtained. The method including the groove forming step and the grinding step of this embodiment corresponds to the first dicing method. In the grinding step of this embodiment, it is preferable to grind the back surface W6 while supporting the eighth base material 81 side of the eighth adhesive sheet 80 by a method of fixing it with a transfer tape or fixing it to a vacuum suction cup.

[Step of attaching third adhesive sheet]
Fig. 10D is a diagram for explaining the step (PY4). Fig. 10D shows a diagram for explaining the step of adhering the third adhesive sheet 30 to the eighth adhesive sheet 80 side of the semiconductor wafer W after the backside grinding after the grinding step (sometimes referred to as a third adhesive sheet adhering step).
As shown in FIG. 10D, a state in which a plurality of separated semiconductor chips CP are held by an eighth adhesive sheet 80 and a third adhesive sheet 30 is shown.

[Expanding process]
In this embodiment, after the step of attaching the third adhesive sheet in step (PY4), a step (expanding step: step (P5)) of expanding the third adhesive sheet 30 to expand the spacing between the multiple semiconductor chips CP is carried out in the same manner as in the first embodiment. In this embodiment as well, it is preferable that the third adhesive sheet 30 is an expanding sheet. Step (P5) in this embodiment can be carried out in the same manner as in the first embodiment. In this embodiment as well, it is preferable that the spacing D1 between the multiple semiconductor chips CP is the same as in the first embodiment.

[Sealing process and other processes]
In this embodiment, similarly to the first embodiment, a sealing step and other steps (a rewiring layer forming step and a connection step with external terminal electrodes) may be performed.

[Effects of this embodiment]
The expanding method according to the present embodiment, which employs the pre-dicing method, can simplify the adhesive sheet configuration and process compared to the conventional method, while suppressing adhesive residue, as in the first embodiment. Furthermore, a manufacturing method for a semiconductor device including the expanding method according to the present embodiment can be provided.

In addition, by using an expandable sheet as the third adhesive sheet 30 used in the grinding process in this embodiment, the expandable process can be carried out directly after the grinding process, further simplifying the process.

[Modifications of the embodiment]
The present invention is not limited to the above-described embodiment, and includes modifications of the above-described embodiment within the scope of the invention.

For example, circuits in a semiconductor wafer or semiconductor chip are not limited to the arrangement or shape shown in the figure. The connection structure with external terminal electrodes in a semiconductor package is also not limited to the aspects described in the above-mentioned embodiment. In the above-mentioned embodiment, an aspect of manufacturing a FO-WLP type semiconductor package was described as an example, but the present invention can also be applied to aspects of manufacturing other semiconductor packages, such as a fan-in type WLP.

In the above-mentioned manufacturing method for FO-WLP, some steps may be modified or some steps may be omitted.

Dicing in the dicing process may be performed by irradiating a laser beam onto the semiconductor wafer instead of using the above-mentioned cutting means. For example, the semiconductor wafer may be completely divided by irradiation with a laser beam and divided into a plurality of semiconductor chips. Alternatively, after forming a modified layer inside the semiconductor wafer by irradiation with a laser beam, the semiconductor wafer may be broken at the position of the modified layer by stretching the adhesive sheet in the expanding process described later, and divided into semiconductor chips CP (stealth dicing. Stealth dicing is a registered trademark). When a process for forming a modified layer on the semiconductor wafer W is adopted, in one aspect, the backgrind sheet (e.g., the first adhesive sheet 10) or the surface protection sheet during dicing (e.g., the first adhesive sheet 70 of the second embodiment) is divided into individual pieces together with the formation of the modified layer by the laser beam for forming the modified layer. In addition, when a process for forming a modified layer on the semiconductor wafer W is adopted, in another aspect, the backgrind sheet or the surface protection sheet during dicing is divided into individual pieces by separately irradiating the laser beam for dividing the backgrind sheet or the surface protection sheet during dicing. In the case of stealth dicing, the laser light is irradiated so as to be focused on a focal point set inside the semiconductor wafer, for example, in the infrared region. In these methods, the laser light may be irradiated from either side of the semiconductor wafer.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples.

(Preparation of adhesive sheet)
[Example 1]
An acrylic copolymer was obtained by copolymerizing 62 parts by mass of butyl acrylate (BA), 10 parts by mass of methyl methacrylate (MMA), and 28 parts by mass of 2-hydroxyethyl acrylate (2HEA). A solution of a resin (acrylic A) (adhesive base, solid content 35.0% by mass) was prepared by adding 2-isocyanatoethyl methacrylate (manufactured by Showa Denko K.K., product name "Karens MOI" (registered trademark)) to this acrylic copolymer. The addition ratio was 90 mol % of 2-isocyanatoethyl methacrylate to 100 mol % of 2HEA in the acrylic copolymer.
The weight average molecular weight (Mw) of the obtained resin (acrylic A) was 600,000, and Mw/Mn was 4.5. The weight average molecular weight Mw and number average molecular weight Mn in terms of standard polystyrene were measured by gel permeation chromatography (GPC), and the molecular weight distribution (Mw/Mn) was calculated from the respective measured values.
To this adhesive base, UV resin A (10-functional urethane acrylate, manufactured by Mitsubishi Chemical Corporation, product name "UV-5806", Mw = 1740, containing a photopolymerization initiator) and a tolylene diisocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., product name "Coronate L") were added as a crosslinking agent. 50 parts by mass of UV resin A and 0.2 parts by mass of the crosslinking agent were added relative to 100 parts by mass of the solid content in the adhesive base. After the addition, the mixture was stirred for 30 minutes to prepare adhesive composition A1.
Next, the prepared solution of pressure-sensitive adhesive composition A1 was applied to a polyethylene terephthalate (PET)-based release film (manufactured by Lintec Corporation, product name "SP-PET381031", thickness 38 μm) and dried to form a pressure-sensitive adhesive layer with a thickness of 40 μm on the release film.
A polyester-based polyurethane elastomer sheet (manufactured by Seedam Co., Ltd., product name "Higress DUS202", thickness 100 μm) was bonded to the adhesive layer as a substrate, and unnecessary portions of the ends in the width direction were cut and removed to produce adhesive sheet SA1.

(Method of measuring tip spacing)
The pressure-sensitive adhesive sheet obtained in Example 1 was cut to a size of 210 mm x 210 mm to obtain a test sheet. At this time, the cut sheet was cut so that each side of the cut sheet was parallel or perpendicular to the MD direction of the substrate in the pressure-sensitive adhesive sheet.
The semiconductor chips to be attached to the adhesive sheet were prepared by the following procedure. A backgrind sheet (manufactured by Lintec Corporation, product name "E-3125KL") was attached to a 6-inch silicon wafer. Next, the 6-inch silicon wafer was diced from the backgrind sheet side to cut out a total of 25 chips, each 3 mm x 3 mm in size, in five rows in the X-axis direction and five rows in the Y-axis direction. A diced backgrind sheet was attached to each of the chips.
The release film of the test sheet was peeled off, and the back-grind sheet side of the 25 chips cut out as described above was attached to the center of the exposed adhesive layer. At this time, the chips were arranged in 5 rows in the X-axis direction and 5 rows in the Y-axis direction.

Next, the test sheet with the chips attached was placed in a biaxially stretchable expanding device (spacing device). FIG. 11 shows a plan view of the expanding device 100. In FIG. 11, the X-axis and the Y-axis are perpendicular to each other, with the positive direction of the X-axis being the +X-axis direction, the negative direction of the X-axis being the -X-axis direction, the positive direction of the Y-axis being the +Y-axis direction, and the negative direction of the Y-axis being the -Y-axis direction. The test sheet 200 was placed in the expanding device 100 so that each side was parallel to the X-axis or Y-axis. As a result, the MD direction of the substrate in the test sheet 200 was parallel to the X-axis or Y-axis. Note that the chips are omitted in FIG. 11.

As shown in Figure 11, the expanding device 100 has five holding means 101 in each of the +X-axis direction, -X-axis direction, +Y-axis direction and -Y-axis direction (a total of 20 holding means 101). Of the five holding means 101 in each direction, holding means 101A are located at both ends, holding means 101C is located in the center, and holding means 101B is located between holding means 101A and holding means 101C. Each side of the test sheet 200 was gripped by these holding means 101.

As shown in Fig. 11, one side of the test sheet 200 is 210 mm. The distance between the holding means 101 on each side is 40 mm. The distance between the end of one side of the test sheet 200 (the apex of the sheet) and the holding means 101A on that side that is closest to that end is 25 mm.

Next, a plurality of tension applying means (not shown) corresponding to each of the holding means 101 were driven to move each of the holding means 101 independently. The four sides of the test sheet were fixed with a gripping jig, and the test sheet was expanded by an expansion amount of 200 mm at a speed of 5 mm/s in each of the X-axis direction and the Y-axis direction. Thereafter, the expanded state of the test sheet 200 was maintained by a ring frame.
While the expanded state was maintained, the distance between each tip was measured using a digital microscope, and the average value of the distance between each tip was taken as the tip interval.
If the chip spacing was 1800 μm or more, it was judged as pass "A", and if the chip spacing was less than 1800 μm, it was judged as fail "B".

(Method of measuring chip alignment)
The deviation rates from the center lines of adjacent tips in the X-axis and Y-axis directions of the workpiece for which the tip intervals were measured were then measured.
FIG. 12 shows a schematic diagram of a specific measurement method.
A row of five chips arranged in the X-axis direction was selected, and the distance Dy between the top end of the chip and the bottom end of the chip in the row was measured using a digital microscope. The deviation rate in the Y-axis direction was calculated based on the following formula (Equation 3). Sy is the chip size in the Y-axis direction, which was set to 3 mm in this embodiment.
Deviation rate in the Y-axis direction [%] = [(Dy - Sy) / 2] / Sy x 100 ... (Equation 3)
The deviation rates in the Y-axis direction were calculated in the same manner for the other four rows in which five chips were arranged in the X-axis direction.
A row of five chips arranged in the Y-axis direction was selected, and the distance Dx between the leftmost end of the chip and the rightmost end of the chip in the row was measured using a digital microscope. The deviation rate in the X-axis direction was calculated based on the following formula (Math. 4). Sx is the chip size in the X-axis direction, which was set to 3 mm in this embodiment.
Deviation rate in the X-axis direction [%] = [(Dx - Sx) / 2] / Sx x 100 ... (Equation 4)
The deviation rates in the X-axis direction were calculated in the same manner for the other four rows in which five chips were arranged in the Y-axis direction.
In the formulas (3) and (4), the reason for dividing by 2 is to express the maximum distance that the chip deviates from the predetermined position after expansion in an absolute value.
In all columns in the X-axis and Y-axis directions (10 columns in total), if the deviation rate was less than ±10%, it was judged as pass "A", and if it was ±10% or more in one or more columns, it was judged as fail "B".

(Method for evaluating adhesive residue)
After expanding under the conditions described in the above-mentioned chip spacing measurement method, the adhesive sheet of Example 1 was irradiated with ultraviolet light from the side opposite to the side on which the chips were mounted, using an ultraviolet light irradiation device ("RAD-2000 m/12" manufactured by Lintec Corporation) under conditions of an illuminance of 220 mW/ ^cm2 and a light quantity of 460 mJ/ ^cm2 . After ultraviolet light irradiation, the chip was held on a suction table and the adhesive sheet was peeled off. After the adhesive sheet was peeled off, the chip surface to which the adhesive sheet had been attached was observed with an optical microscope. The case where no adhesive residue was observed on the chip surface was judged as pass "A", and the case where adhesive residue was observed was judged as fail "B".

When the adhesive sheet according to Example 1 was used for expansion, the evaluation result for the chip spacing was rated as pass "A", and the evaluation result for the chip alignment was rated as pass "A".
When a backgrind sheet was interposed between the chip and the adhesive sheet of the example and the adhesive sheet was expanded, the adhesive residue evaluation result on the chip surface was rated as "A", which is acceptable.

10...first adhesive sheet, 11...first substrate, 12...first adhesive layer, 20...second adhesive sheet, 21...second substrate, 22...second adhesive layer, 30...third adhesive sheet, 31...third substrate, 32...third adhesive layer, 40...fourth adhesive sheet, 41...fourth substrate, 42...fourth adhesive layer, 70...first adhesive sheet, 71...seventh substrate, 72...seventh adhesive layer, CP...semiconductor chip, W...semiconductor wafer (wafer), W1...circuit surface (first wafer surface), W2...circuit, W3...rear surface (second wafer surface).

Claims (11)

a wafer having a first wafer surface and a second wafer surface opposite to the first wafer surface, a first adhesive sheet having a first adhesive layer and a first base material is attached to the first wafer surface, and a second adhesive sheet having a second adhesive layer and a second base material is attached to the second wafer surface;
making an incision from the first adhesive sheet side to cut the first adhesive sheet, and further dividing the wafer into a plurality of chips;
attaching a third pressure-sensitive adhesive sheet having a third pressure-sensitive adhesive layer and a third substrate to the first substrate;
peeling the second adhesive sheet from the second wafer surface of the wafer;
Stretching the third adhesive sheet to increase the spacing between the chips;
When the third adhesive sheet is stretched, the first wafer surface is not in contact with the third adhesive layer of the third adhesive sheet.
Expand method. In the expanding method according to claim 1,
The incision is formed to a depth extending from the first adhesive sheet side to the second adhesive sheet.
Expand method. In the expanding method according to claim 1 or 2,
The second wafer surface is a surface formed by back-grinding the wafer.
Expand method. In the expanding method according to claim 3,
The first adhesive sheet is attached to the first wafer surface before the back surface of the wafer is ground.
Expand method. In the expanding method according to claim 3,
a fourth adhesive sheet is attached to the first wafer surface before the backside of the wafer is ground;
peeling the fourth adhesive sheet from the first wafer surface after the back surface grinding;
The first adhesive sheet is attached to the first wafer surface.
Expand method. In the expanding method according to claim 5,
the fourth adhesive sheet is a backgrind sheet,
the first adhesive sheet is a surface protection sheet,
The thickness of the surface protective sheet is 5 μm or more and 500 μm or less.
Expand method. In the expanding method according to any one of claims 1 to 6,
The first adhesive sheet is a backgrind sheet.
Expand method. In the expanding method according to any one of claims 1 to 7,
The third adhesive sheet is an expandable sheet.
Expand method. In the expanding method according to any one of claims 1 to 8,
The wafer is a semiconductor wafer.
Expand method. In the expanding method according to any one of claims 1 to 9,
the first wafer surface having circuitry;
Expand method. A method for manufacturing a semiconductor device comprising the expansion method according to any one of claims 1 to 10.

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