KR20230122979A - Protective sheet for workpiece processing and manufacturing method of divided workpeice - Google Patents

Abstract

(Problem) To provide a protective sheet for workpiece processing capable of reducing the defective workpiece fragmentation material after grinding even when the workpiece is ground by LDBG to obtain a fragmented workpiece material.
(Solution Means) A protective sheet for work processing comprising a base material and an adhesive layer disposed on one main surface of the base material, wherein the pressure-sensitive adhesive layer has a shear storage modulus at 55°C of 40,000 Pa or more, and a pressure-sensitive adhesive layer at 55°C The shear stress relaxation rate after 1 second is 30% or more, and the protective sheet for workpiece processing when the tensile load reaches 30 N/15 mm after application of the tensile load to the protective sheet for workpiece processing is started at 23°C. A protective sheet for workpiece processing having an elongation of 2.5% or less.

Description

Protective sheet for work processing and method for manufacturing work pieces

The present invention relates to a protective sheet for processing a workpiece and a method for producing a pieced work product. In particular, it relates to a protective sheet for processing a workpiece, which is preferably used in a method of grinding the back side of a workpiece and splitting the workpiece into pieces by the stress or the like, and a method for producing a pieced work product using the protective sheet for processing the workpiece.

While miniaturization and multifunctionalization of various electronic devices are progressing, miniaturization and thinning of semiconductor chips mounted thereon are similarly required. In order to reduce the thickness of chips, it is common to grind the back side of a semiconductor wafer to adjust the thickness. In addition, in order to obtain a thinned chip, after forming a groove of a predetermined depth from the front side of the wafer with a dicing blade, grinding is performed from the back side of the wafer, and the wafer is separated by grinding to obtain chips. In some cases, a method called Dicing Before Grinding (DBG) is used. In DBG, since grinding of the back side of a wafer and slicing of the wafer can be performed simultaneously, thin chips can be efficiently manufactured.

Conventionally, when grinding the back side of a workpiece such as a semiconductor wafer or during the production of a divided workpiece such as a semiconductor chip by DBG, in order to protect the circuit on the surface of the workpiece and to hold the workpiece and the divided workpiece, It is common to stick an adhesive tape called a back grind sheet.

As a back grind sheet used in DBG, an adhesive tape provided with a base material and an adhesive layer formed on one surface of the base material is used. As an example of such an adhesive tape, Patent Literature 1 discloses a substrate having a high Young's modulus, an adhesive tape having an adhesive layer formed on one surface of the substrate and a buffer layer formed on the other surface.

Recently, as a modified example of the sundicing method, a method of forming a modified region inside the wafer with a laser and singling the wafer by stress or the like during grinding the backside of the wafer has been proposed. Hereinafter, this method may be described as LDBG (Laser Dicing Before Grinding). In LDBG, since the wafer is cut in the crystal direction starting from the modified region, the occurrence of chipping can be reduced compared to the pre-dicing method using a dicing blade. In addition, compared to DBG, in which a groove of a predetermined depth is formed on the wafer surface by a dicing blade, there is no area where the wafer is shaved by a dicing blade, in short, because the kerf width is extremely small, so the yield of chips is excellent do.

Japanese Unexamined Patent Publication No. 2015-183008

However, when workpieces such as wafers are separated into pieces by LDBG using the adhesive tape described in Patent Literature 1, the shear force applied to the pieces of workpieces such as chips causes the pieces of workpieces to move slightly, resulting in There was a problem that contact between reorganized cargoes occurred. As a result, cracks (unintended cracks) are generated in the shredded workpiece. The reason why cracks easily occur is also attributed to the fact that the kerf width is extremely small, as described above. In particular, when the crack generated in the divided work product is large, it is directly connected to the defective work product and has a great influence on the yield of the divided work product.

The present invention has been made in view of such a factual situation, and to provide a protective sheet for workpiece processing capable of reducing defects in a pieced work piece after grinding even when a workpiece is ground by LDBG to obtain a pieced workpiece pieced into pieces. The purpose.

The aspect of this invention is as follows.

[1] A protective sheet for work processing comprising a base material and an adhesive layer disposed on one main surface of the base material,

The shear storage modulus of the pressure-sensitive adhesive layer at 55°C is 40,000 Pa or more, and the shear stress relaxation rate after 1 second of the pressure-sensitive adhesive layer at 55°C is 30% or more,

At 23°C, after the application of the tensile load to the workpiece protective sheet is started, the elongation of the workpiece protective sheet when the tensile load reaches 30 N/15 mm is 2.5% or less.

[2] The protective sheet for work processing according to [1], wherein a buffer layer is disposed on the other main surface of the substrate.

[3] The protective sheet for work processing according to [1] or [2], wherein the tensile stress relaxation rate after 1 minute of the protective sheet for work processing at 23°C is less than 40%.

[4] The pressure-sensitive adhesive layer is composed of an energy ray-curable acrylic pressure-sensitive adhesive,

The acrylic pressure-sensitive adhesive is the protective sheet for workpiece processing described in any one of [1] to [3], comprising a polymer in which an energy ray-curable group is bonded to an acrylic polymer, and an energy ray-curable compound.

[5] The work piece according to any one of [1] to [4] used by being attached to the surface of a workpiece in the step of breaking the workpiece into pieces by grinding the back surface of the workpiece having a modified region formed therein, for processing the workpiece. It is a protective sheet.

[6] a step of attaching the protective sheet for work processing according to any one of [1] to [5] to the surface of the work;

A step of forming a modified region inside the work from the front or back side of the work;

A step of attaching a protective sheet for work processing to the front surface and grinding the work on which the modified region is formed into a plurality of pieces of work pieces starting from the modified region;

A method for producing a pieced work product comprising a step of peeling a protective sheet for work processing from a work piece that has been singulated.

ADVANTAGE OF THE INVENTION According to this invention, even when the workpiece|piece is grind|grinded by LDBG and the divided workpiece|piece material separated into pieces is obtained, the protective sheet for workpiece processing which can reduce the defect of the divided workpiece|piece material after grinding can be provided.

1A is a cross-sectional schematic diagram showing an example of a protective sheet for workpiece processing according to the present embodiment.
1B is a schematic cross-sectional view showing another example of a protective sheet for workpiece processing according to the present embodiment.
Fig. 2 is a cross-sectional schematic diagram showing how the protective sheet for processing a workpiece according to the present embodiment is adhered to the surface of a workpiece.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail using drawing based on specific embodiment. First, key terms used in this specification will be described.

A work refers to a plate-like body to which the protective sheet for work processing according to the present embodiment is attached and then separated into pieces. Examples of the work include circular wafers (including those with an orientation flat), prismatic panel-level packages, and molded resin-encapsulated strips (strip substrates). Among them, this A wafer is preferable from the viewpoint of obtaining the effect of the invention easily. The wafer may be, for example, a semiconductor wafer such as a silicon wafer, a gallium arsenic wafer, a silicon carbide wafer, a gallium nitride wafer, or an indium phosphorus wafer, or an insulator wafer such as a glass wafer, a lithium tantalate wafer, or a lithium niobate wafer, Further, it may be a reconstructed wafer made of a semiconductor and a resin used for manufacturing a fan-out package or the like. From the viewpoint of easily obtaining the effects of the present invention, the wafer is preferably a semiconductor wafer or an insulator wafer, and more preferably a semiconductor wafer.

Segmentation of work refers to obtaining a work piece by dividing the work for each circuit. For example, when the work is a wafer, the divided work product is a chip, and when the work is a panel level package or a mold resin-encapsulated strip (strip type substrate), the divided work product is a semiconductor package.

The "surface" of the work refers to the surface on which circuits, electrodes, etc. are formed, and the "rear surface" of the work refers to the surface on which circuits or the like are not formed. As the electrode, a convex electrode such as a bump may be used.

DBG refers to a method of forming a groove of a predetermined depth on the surface side of a workpiece, then grinding the workpiece from the backside side, and separating the workpiece by grinding. Grooves formed on the surface side of the work are formed by methods such as blade dicing, laser dicing, and plasma dicing.

In addition, LDBG is a modified example of DBG, in which a brittle modified region is formed inside a workpiece (e.g., a wafer) with a laser, and cracks originating from the modified region are propagated by stress during grinding of the backside of the workpiece, thereby improving the quality of the workpiece. It tells how to carry out reorganization.

The "group of divided workpieces" refers to a plurality of divided workpieces held on the protective sheet for workpiece processing according to the present invention after the workpieces have been divided into pieces. These pieces of work pieces constitute the same shape as the shape of the work as a whole. In addition, the "chip group" refers to a plurality of chips held on the protective sheet for processing a workpiece according to the present invention after the wafer as a workpiece is divided into pieces. These chips constitute the same shape as the shape of the wafer as a whole.

"(meth)acrylate" is used as a term representing both "acrylate" and "methacrylate", and the same applies to other similar terms.

"Energy rays" refer to ultraviolet rays, electron beams, and the like, and are preferably ultraviolet rays.

A "weight average molecular weight" is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method unless otherwise specified. For measurement by such a method, for example, a high-speed GPC device "HLC-8120GPC" manufactured by Tosoh Corporation, a high-speed column "TSK guard column H _XL -H", "TSK Gel GMH _XL ", "TSK Gel G2000 H" _XL ” (above, all manufactured by Tosoh Corporation) was connected in this order, and the column temperature: 40 ° C., the feed rate: 1.0 mL / min.

The peeling sheet is a sheet that supports the pressure-sensitive adhesive layer so that peeling is possible. The sheet is not limited in thickness, and is used as a concept including a film.

The mass ratio in the description of the composition, such as the composition for pressure-sensitive adhesive layer, is based on the active ingredient (solid content), and the solvent is not included unless otherwise specified.

(1. Protection sheet for workpiece processing)

As shown in FIG. 1A , the protective sheet 1 for work processing according to the present embodiment has a base material 10 and an adhesive layer 20 disposed on the base material 10 .

In this embodiment, as shown in FIG. 2 , the protective sheet 1 for workpiece processing is used by sticking the main surface 20a of the pressure-sensitive adhesive layer to the surface 100a of the workpiece 100 (eg wafer). The surface 100a of the work 100 is a surface having circuits, electrodes, and the like. The surface having the circuit may be a surface on which the circuit is exposed, or may be a main surface of a protective layer formed on the circuit to protect the circuit. Moreover, convex electrodes, such as bumps, may be formed on the circuit.

In the present embodiment, the workpiece to which the protective sheet for workpiece processing is affixed is separated into a plurality of pieces of workpieces after backside grinding. Although DBG may be employed as a method of singling a workpiece, the protective sheet 1 for workpiece processing according to the present embodiment is preferably used for singling a workpiece by LDBG.

Specifically, after the modified region is formed inside the workpiece, the workpiece 100 to which the protective sheet 1 for workpiece processing is attached to the front surface 100a has a back surface 100b, which is the main surface on the opposite side to the front surface 100a. are ground

As the grinding progresses, the workpiece becomes thinner, and at the same time, cracks are generated in the modified region due to the shear force and pressure applied to the modified region formed inside the workpiece, and propagates to both sides of the workpiece. As a result, the work is fragmented. In fragmentation by LDBG, since almost no area is cut from the workpiece, in the divided workpiece (group of divided workpieces), the interval (kerf width) between the divided workpiece and the neighboring divided workpiece is very small.

In addition, the timing at which the workpiece is singulated is not simultaneous, and grinding proceeds from when a part of the workpiece starts to be singulated until the entire workpiece is singulated. Therefore, the shearing force by the grinding wheel is continuously applied even to the pieced work piece. Since the non-smooth grinding wheel surface constantly rotates and contacts the group of divided workpieces, the same shear force is not applied to all the divided workpieces at the same time, and the shear force applied to the divided workpieces is different for each divided workpiece. Therefore, in the direction parallel to the plane of the workpiece (ie, the plane of the group of divided workpieces), the individual pieces of workpieces move independently, and the kerf width is small, so the pieces of divided workpieces may come into contact with each other. . When such a contact occurs, cracks tend to occur in the divided workpiece. Particularly, large cracks leading to defects in divided workpieces tend to occur in the divided workpieces. When such large cracks occur, a problem arises in that the yield of divided workpieces decreases. When the thickness of the workpiece and the group of separated workpieces after grinding is as thin as less than 20 µm, the divided workpiece becomes more brittle than when the thickness is 20 µm or more, so large cracks are more likely to occur.

Against such a problem, in order to suppress the movement of the divided workpieces during grinding, it is conceivable to firmly hold the divided workpieces with a hard protection sheet for workpiece processing. However, it is not possible to resist shear force or the like only by being hard, and on the contrary, shear stress resulting from the shear force or the like acts, making it easy for the divided workpieces to collide with each other, increasing cracks in the divided workpieces. Therefore, for example, shear stress is relieved by arranging a layer having high stress relaxation properties in addition to the base material and the pressure-sensitive adhesive layer. However, the problem that the elimination of the shear stress by such a layer was insufficient became present.

Regarding such a problem, the present inventor contemplated imparting stress relaxation properties to the adhesive material layer closest to the workpiece. The most important function of the adhesive layer is to bring the workpiece into close contact with the protective sheet for workpiece processing, and there has been no idea of imparting stress relaxation properties to such an adhesive layer.

The present inventors have found that generation of large cracks leading to defective pieces of workpieces can be suppressed by imparting stress relaxation properties described later to the pressure-sensitive adhesive layer while maintaining the original function of the pressure-sensitive adhesive layer.

Below, the component of the protective sheet 1 for workpiece processing shown to FIG. 1A is demonstrated in detail.

(2. Description)

The base material is a member that bears the rigidity of the protective sheet for work processing. The substrate is not limited as long as it is made of a material capable of supporting the work. For example, various resin films used as base materials for bag grind tapes are exemplified. By using such a resin film, even if the thickness of the workpiece is reduced by grinding, the workpiece can be maintained without being damaged. The substrate may be composed of a single-layer film composed of one resin film, or may be composed of a multi-layer film in which a plurality of resin films are laminated.

(2.1 Material of description)

In this embodiment, as the material of the substrate, for example, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyester such as wholly aromatic polyester, polyamide, polycarbonate, polyacetal, modified polyphenyl rene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially stretched polypropylene, and the like. Among these, polyester is preferable and polyethylene terephthalate is more preferable.

Since the thickness of the substrate affects the rigidity of the protective sheet for work processing, it may be set according to the material of the substrate. For example, the thickness of the substrate may be set such that the physical properties of the protective sheet for work processing fall within the ranges described later. In this embodiment, the thickness of the substrate is preferably 25 μm or more and 200 μm or less, more preferably 35 μm or more and 150 μm or less, and still more preferably 40 μm or more and 150 μm or less.

At least one main surface of the base material may be subjected to an adhesive treatment such as corona treatment in order to improve adhesion to a layer formed on the main surface. Moreover, in order to improve adhesiveness with the layer formed on the main surface of at least one side of a base material, an easy bonding layer may be formed.

(3. Adhesive layer)

The pressure-sensitive adhesive layer is attached to the surface of the work (that is, the surface on which circuits, electrodes, etc. are formed). The pressure-sensitive adhesive layer has a role of protecting the surface and supporting the work until it is peeled off from the surface.

The pressure-sensitive adhesive layer may be composed of one layer (single layer) or may be composed of a plurality of layers of two or more layers. When the pressure-sensitive adhesive layer has multiple layers, these multiple layers may be the same as or different from each other, and the combination of layers constituting these multiple layers is not particularly limited.

In this embodiment, the collision between the fragmented work pieces is alleviated because the pressure-sensitive adhesive layer has the following physical properties. As a result, it is possible to suppress the generation of cracks, particularly large cracks, in the divided workpieces resulting from collisions between the divided workpieces.

(3.1. Shear storage modulus of pressure-sensitive adhesive layer)

In this embodiment, the shear storage modulus (G') of the pressure-sensitive adhesive layer at 55°C is 40,000 Pa or more. When grinding the back side of a workpiece, heat is generated on the grinding surface, and the heat is also propagated to the pressure-sensitive adhesive layer. As a result, the temperature of the pressure-sensitive adhesive layer rises to about 50 to 60°C, for example. When the shear storage elastic modulus of the pressure-sensitive adhesive layer at 55°C is within the above range, the pressure-sensitive adhesive layer is kept relatively hard even during backside grinding of the workpiece. Therefore, even if the shear force or the like applied to the work during backside grinding is transmitted to the pressure-sensitive adhesive layer, deformation of the pressure-sensitive adhesive layer is suppressed. As a result, the amount of movement of the group of divided workpieces held in the pressure-sensitive adhesive layer is reduced, and collision between the divided workpieces is suppressed.

The shear storage modulus of the pressure-sensitive adhesive layer at 55°C is preferably 45,000 Pa or more, more preferably 50,000 Pa or more, and still more preferably 55,000 Pa or more.

It is preferable that the shear storage modulus of the pressure-sensitive adhesive layer at 55°C is 200,000 Pa or less, from the viewpoint that it is easy to achieve both the numerical range of the shear storage modulus of the pressure-sensitive adhesive layer and the numerical range of the shear stress relaxation rate of the pressure-sensitive adhesive layer described later. And, it is more preferably 150,000 Pa or less, and more preferably 100,000 Pa or less.

The shear storage modulus of the pressure-sensitive adhesive layer at 55°C can be measured as follows. First, the material constituting the pressure-sensitive adhesive layer is used as a sample for measurement of a predetermined size. With a dynamic viscoelasticity measuring device, within a predetermined temperature range, the sample for measurement is twisted at a predetermined frequency to impart shear strain to the sample for measurement, and the modulus of elasticity of the sample for measurement is measured. The shear storage modulus of the pressure-sensitive adhesive layer at 55°C is calculated from the measured modulus of elasticity. Details of the measurement are described in Examples.

(3.2. Shear stress relaxation rate of pressure-sensitive adhesive layer)

In this embodiment, the shear stress relaxation rate after 1 second of the adhesive layer at 55 degreeC is 30 % or more. At the timing when grinding of the work progresses and the workpiece starts to be divided into a plurality of divided workpieces, and the connected state before singling and the divided workpieces after singulation coexist, the individual workpieces are separated by the grinding wheel. In some cases, non-uniformity occurs in the shear force applied to As described above, although deformation of the pressure-sensitive adhesive layer due to shear force or the like is relatively suppressed due to the high shear storage modulus of the pressure-sensitive adhesive layer, among the pieces of workpieces in which the applied shear force is non-uniform, located in a region where the shear force is temporarily high In the pieced work product, the pressure-sensitive adhesive layer may be deformed. When the shear stress relaxation rate of the pressure-sensitive adhesive layer at 55 ° C. is not controlled within the above range, when a temporary high shear force is not applied, the time required to return to the normal state that is not deformed is short, Stronger collisions are more likely to occur between adjacent pieces of shredded workpieces. However, by controlling the shear stress relaxation rate of the pressure-sensitive adhesive layer at 55 ° C. within the above range, even when the pressure-sensitive adhesive layer is deformed by a temporary high shear force, the shear stress is relieved in a short time, and when a temporary high shear force is no longer applied , it is possible to lengthen the time required to return to a normal state that is not deformed. Accordingly, acceleration of the group of divided workpieces held in the pressure-sensitive adhesive layer is suppressed, and relatively strong collision between the divided workpieces is suppressed.

It is preferable that it is 35 % or more, and, as for the shear stress relaxation rate of the adhesive layer in 55 degreeC, it is more preferable that it is 38 % or more.

The upper limit of the shear stress relaxation rate of the pressure-sensitive adhesive layer at 55°C is not particularly limited within the range in which the effects of the present invention can be obtained. In this embodiment, the upper limit of the shear stress relaxation rate of the pressure-sensitive adhesive layer at 55°C is preferably 65%, more preferably 60%, from the viewpoint of compatibility with other physical properties of the pressure-sensitive adhesive layer.

In this embodiment, the shear stress relaxation rate of the pressure-sensitive adhesive layer can be measured as follows. A material constituting the pressure-sensitive adhesive layer is used as a sample for measurement of a predetermined size. By means of a dynamic viscoelasticity measuring device, shear deformation is applied to the sample for measurement by twisting the sample for measurement at a temperature of 55°C. In the present embodiment, considering that the shear stress is relaxed in a short time, the shear stress relaxation rate is calculated from the shear stress immediately after strain and the shear stress 1 second after starting to strain. Details of the measurement are described in Examples.

(3. 3. Composition of the pressure-sensitive adhesive layer)

The pressure-sensitive adhesive layer is not particularly limited as long as it is composed of a pressure-sensitive adhesive that satisfies the above-mentioned physical properties. In the present embodiment, the pressure-sensitive adhesive layer is preferably formed of an energy ray-curable pressure-sensitive adhesive. Since the pressure-sensitive adhesive layer of the protective sheet for workpiece processing is formed of an energy ray-curable pressure-sensitive adhesive, the adhesive strength can be reduced by applying energy rays to the workpiece when attaching to the workpiece with high adhesive force and peeling from the workpiece. Therefore, when peeling off the protective sheet for processing a workpiece, destruction of circuitry, electrodes, etc. on the surface of the workpiece and adhesion of the adhesive onto the workpiece are prevented while appropriately protecting the circuitry and the like of the workpiece.

The composition for the pressure-sensitive adhesive layer constituting the energy ray-curable pressure-sensitive adhesive includes, for example, a non-energy ray-curable adhesive resin (also referred to as "adhesive resin I") as a main component and contains an energy ray-curable compound other than the adhesive resin. A composition for an energy ray-curable pressure-sensitive adhesive layer (hereinafter, also referred to as "composition for an X-type pressure-sensitive adhesive layer") can be used.

Further, the composition for the pressure-sensitive adhesive layer constituting the energy ray-curable pressure-sensitive adhesive contains, as a main component, an energy ray-curable pressure-sensitive adhesive resin (hereinafter also referred to as "adhesive resin II") in which an unsaturated group is introduced into the side chain of the non-energy ray-curable pressure-sensitive adhesive resin. In addition, a composition for an energy ray-curable pressure-sensitive adhesive layer (hereinafter also referred to as "a composition for a Y-type pressure-sensitive adhesive layer") that does not contain an energy ray-curable compound other than an adhesive resin may also be used.

In addition, the composition for the pressure-sensitive adhesive layer constituting the energy ray-curable pressure-sensitive adhesive is a combination of X-type and Y-type, that is, an energy ray-curable pressure-sensitive adhesive resin II containing as a main component, an energy ray-curable compound other than the pressure-sensitive adhesive resin is also included. You may use the composition for energy-beam curable adhesive layers (henceforth also called "the composition for XY-type adhesive layers").

However, the pressure-sensitive adhesive layer may be formed of a non-energy ray-curable pressure-sensitive adhesive that is not cured even when irradiated with energy rays. The composition for the pressure-sensitive adhesive layer constituting the non-energy ray-curable pressure-sensitive adhesive contains at least the non-energy ray-curable adhesive resin I, but does not contain the energy ray-curable adhesive resin II described above and the energy ray-curable compound.

In this embodiment, in order to achieve the physical properties of the pressure-sensitive adhesive layer described above, it is preferable to use an XY-type composition for pressure-sensitive adhesive layers as the energy ray-curable pressure-sensitive adhesive. By using the XY type, a fluid energy ray-curable compound is included in the polymerization structure of the adhesive resin II, and it becomes easier to control the stress relaxation property within a range that does not affect the shear storage modulus. In addition, while having sufficient adhesive properties before energy ray curing, it becomes easier to sufficiently lower the peel strength to the workpiece after energy ray curing.

In the following description, "adhesive resin" is used as a term indicating one or both of the above-described adhesive resin I and adhesive resin II. As specific adhesive resins, acrylic resins, urethane resins, rubber resins, silicone resins and the like are exemplified. In this embodiment, from the viewpoint of easy control of the shear storage modulus and shear stress relaxation rate of the pressure-sensitive adhesive layer within the above-mentioned ranges, and from the viewpoint of cost reduction, an acrylic pressure-sensitive adhesive is preferable.

Hereinafter, as the adhesive resin, an acrylic adhesive in which an acrylic resin is used will be described in more detail.

(3. 3. 1. Acrylic polymer)

An acrylic polymer is used for the acrylic resin. An acrylic polymer is obtained by polymerizing a monomer containing at least an alkyl (meth)acrylate, and contains a structural unit derived from an alkyl (meth)acrylate. Examples of the alkyl (meth)acrylate include those having 1 to 20 carbon atoms in the alkyl group, and the alkyl group may be linear or branched. As specific examples of the alkyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate rate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate , dodecyl (meth)acrylate, etc. are mentioned. You may use alkyl (meth)acrylate individually or in combination of 2 or more types.

In addition, the acrylic polymer is derived from an alkyl (meth)acrylate having 4 or more carbon atoms in the alkyl group from the viewpoint of improving the adhesive strength of the pressure-sensitive adhesive layer and the viewpoint of easily controlling the shear stress relaxation rate of the pressure-sensitive adhesive layer within the above-mentioned range. It is preferable to include a constituent unit. As carbon number of this alkyl (meth)acrylate, Preferably it is 4-12, More preferably, it is 4-6. Moreover, it is preferable that the C4 or more alkyl (meth)acrylate of an alkyl group is an alkyl acrylate. As such an alkyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, etc. are illustrated.

In the acrylic polymer, the content of the alkyl (meth)acrylate having 4 or more carbon atoms in the alkyl group, the total amount of monomers constituting the acrylic polymer (hereinafter, simply referred to as “total amount of monomers”) 100 parts by mass, is preferably 40 to 100 parts by mass. 98 parts by mass, more preferably 45 to 95 parts by mass, still more preferably 50 to 90 parts by mass.

In addition to the structural units derived from alkyl (meth)acrylates having 4 or more carbon atoms in the alkyl group, the acrylic polymer has a viewpoint of reducing glue residue in the pressure-sensitive adhesive layer, an increase in adhesive force, and a shear storage modulus and shear stress of the pressure-sensitive adhesive layer. From the standpoint of easy control of the relaxation rate within the above-mentioned range, it is preferably a copolymer containing a structural unit derived from a monomer that becomes a polymer having a relatively high glass transition temperature (Tg) when polymerized to form a homopolymer. Specifically, a monomer having a glass transition temperature of 50°C or higher when polymerized to form a homopolymer is preferable, a monomer having a glass transition temperature of 70°C or higher is more preferable, and a monomer having a glass transition temperature of 90°C or more and 150°C or less is still more preferred. desirable. As the Tg of the homopolymer, values described in the Polymer Data Handbook, the Adhesion Handbook, or the Polymer Handbook can be used.

As such a monomer, dimethyl acrylamide, methyl methacrylate, acryloyl morpholine, etc. are illustrated. Among these, dimethyl acrylamide and methyl methacrylate are preferable, and dimethyl acrylamide is more preferable.

In the acrylic polymer, the content of the monomer having a glass transition temperature of 50 ° C. or higher when the homopolymer is formed is preferably 2 to 40 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass of the total amount of monomers. , more preferably 8 to 25 parts by mass.

It is preferable that the acrylic polymer has a structural unit derived from a functional group-containing monomer in addition to the structural units described above. A hydroxyl group, a carboxy group, an amino group, an epoxy group etc. are mentioned as a functional group of a functional group containing monomer. The functional group-containing monomer can react with a crosslinking agent described later to become a crosslinking origin, or react with an unsaturated group-containing substance described later to introduce an unsaturated group into the side chain of the acrylic polymer.

As a functional group containing monomer, a hydroxyl group containing monomer, a carboxy group containing monomer, an amino group containing monomer, an epoxy group containing monomer, etc. are mentioned, These may be used individually or in combination of 2 or more types. Among these, it is preferable to use a hydroxyl group-containing monomer and a carboxy group-containing monomer, and it is more preferable to use a hydroxyl group-containing monomer.

As a hydroxyl-containing monomer, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2 - Hydroxyalkyl (meth)acrylates such as hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; Unsaturated alcohols, such as vinyl alcohol and allyl alcohol, etc. are mentioned.

Examples of the carboxy group-containing monomer 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; and 2-carboxyethyl methacrylate.

The content of the functional group-containing monomer is preferably 1 to 35 parts by mass, more preferably 3 to 32 parts by mass, still more preferably 6 to 30 parts by mass, based on 100 parts by mass of the total amount of monomers constituting the acrylic polymer. .

In addition to the above, the acrylic polymer may also contain structural units derived from monomers copolymerizable with the acrylic monomers, such as styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, and acrylonitrile.

The acrylic polymer can be used as the non-energy ray-curable adhesive resin I. Examples of the energy ray-curable adhesive resin II include those obtained by reacting and bonding a substance having an energy ray-curable group (also referred to as an unsaturated group-containing substance) to a functional group of the non-energy ray-curable acrylic polymer.

The unsaturated group-containing substance is a substance having both a substituent bondable to a functional group of an acrylic polymer and an energy ray curable group. Examples of the energy ray-curable group include a (meth)acryloyl group, a vinyl group, an allyl group, and a vinylbenzyl group, and a (meth)acryloyl group is preferable. Moreover, as a substituent which can bind|bond with the functional group of an acrylic polymer which an unsaturated group-containing substance has, an isocyanate group, a glycidyl group, etc. are mentioned. Therefore, as a substance containing an unsaturated group, (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, glycidyl (meth)acrylate, etc. are mentioned, for example.

In addition, it is preferable that the unsaturated group-containing substance reacts with a part of the functional groups of the acrylic polymer, and specifically, it is preferable to react the unsaturated group-containing substance with 50 to 98 mol% of the functional groups of the acrylic polymer. It is more preferable to make it react with -93 mol%. In this way, in the energy ray-curable acrylic resin, when a part of the functional group remains without reacting with the unsaturated group-containing substance, it becomes easy to crosslink with the crosslinking agent. In addition, the weight average molecular weight (Mw) of acrylic resin is preferably 300,000 to 1.6 million, more preferably 400,000 to 1,400,000, still more preferably 500,000 to 1,200,000.

(3. 3. 2. Energy ray curable compound)

As the energy ray-curable compound contained in the X-type or XY-type pressure-sensitive adhesive layer composition, a monomer or oligomer that has an unsaturated group in the molecule and can be polymerized and cured by energy ray irradiation is preferable. Examples of such an energy ray-curable compound include trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Polyvalent (meth)acrylate monomers such as acrylate, 1,4-butylene glycol di(meth)acrylate, 1,6-hexanediol (meth)acrylate, urethane (meth)acrylate, polyester (meth) Oligomers, such as an acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate, are mentioned.

Among these, a urethane (meth)acrylate oligomer is preferable from the viewpoint of having a relatively high molecular weight and making it difficult to reduce the shear storage modulus of the pressure-sensitive adhesive layer. The molecular weight (weight average molecular weight in the case of an oligomer) of the energy ray-curable compound is preferably 100 to 12000, more preferably 200 to 10000, still more preferably 400 to 8000, and particularly preferably 600 to 6000.

The content of the energy ray-curable compound in the X-type PSA layer composition is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass, still more preferably 60 to 100 parts by mass, based on 100 parts by mass of the adhesive resin. 90 parts by mass.

On the other hand, the content of the energy ray-curable compound in the XY-type pressure-sensitive adhesive layer composition is preferably 4 to 90 parts by mass, more preferably 7 to 50 parts by mass, still more preferably based on 100 parts by mass of the adhesive resin. It is 9-25 mass parts. By setting the content of the energy ray-curable compound within the above range, it becomes easier to control the shear stress relaxation rate of the pressure-sensitive adhesive layer. In addition, in the composition for an XY-type pressure-sensitive adhesive layer, 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 strength after energy ray irradiation.

(3. 3. 3. Crosslinking agent)

It is preferable that the composition for pressure-sensitive adhesive layers further contains a crosslinking agent from the viewpoint of being more likely to increase the shear storage modulus of the pressure-sensitive adhesive layer. A crosslinking agent reacts with the functional group which adhesive resin has, and bridge|crosslinks resin.

Examples of the crosslinking agent include isocyanate-based crosslinking agents (crosslinking agents having an isocyanate group) such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and adducts of these diisocyanates; Epoxy type crosslinking agents (crosslinking agent having a glycidyl group) such as ethylene glycol glycidyl ether; aziridine crosslinking agents (crosslinking agents having aziridinyl groups) such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; metal chelate-based crosslinking agents such as aluminum chelate (crosslinking agent having a metal chelate structure); An isocyanurate-type crosslinking agent (a crosslinking agent having an isocyanuric acid skeleton); and the like. You may use these crosslinking agents individually or in combination of 2 or more types.

From the viewpoint of improving the cohesive force of the pressure-sensitive adhesive to reduce glue residue when the pressure-sensitive adhesive layer is peeled from the work pieces, from the viewpoint of increasing the shear storage modulus of the pressure-sensitive adhesive layer to easily control it within the above-mentioned range, and from the viewpoint of availability, The crosslinking agent is preferably an isocyanate type crosslinking agent.

The blending amount of the crosslinking agent is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, still more preferably 0.05 to 4 parts by mass with respect to 100 parts by mass of the adhesive resin, from the viewpoint of accelerating the crosslinking reaction. .

(3. 3. 4. Photopolymerization initiator)

When the composition for pressure-sensitive adhesive layers is energy ray-curable, it is preferable that the composition for pressure-sensitive adhesive layers further contains a photopolymerization initiator. Even if it irradiates comparatively low-energy energy rays, such as an ultraviolet-ray, a hardening reaction fully advances because the composition for adhesive layers contains a photoinitiator.

Examples of the photopolymerization initiator include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds and peroxide compounds, and photosensitizers such as amines and quinones. Specifically, α-hydroxycyclohexylphenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide, benzyldimethylketal, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. is exemplified You may use these photoinitiators individually or in combination of 2 or more types.

The blending amount of the photopolymerization initiator is preferably from 0.01 to 10 parts by mass, more preferably from 0.03 to 5 parts by mass, still more preferably from 0.05 to 5 parts by mass, based on 100 parts by mass of the adhesive resin.

(3. 3. 5. Other additives)

The composition for pressure-sensitive adhesive layers may contain other additives within a 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 blending these additives, the compounding amount of the additive is preferably 0.01 to 6 parts by mass with respect to 100 parts by mass of the adhesive resin.

(3. 4. Glass transition temperature of the pressure-sensitive adhesive layer)

In this embodiment, it is preferable that the glass transition temperature (Tg) of an adhesive layer is -50 degreeC or more and 30 degrees C or less. As described above, at the time of grinding the back side, the workpiece (including the case of a group of pieces of work pieces that have been piecewise divided) is heated to about 50 to 60°C by grinding heat. Heating is not performed at the same heating rate over the entire surface of the workpiece, and temperature unevenness may occur within the grinding surface of the workpiece as the grinding progresses. Accompanying this heating, the pressure-sensitive adhesive layer directly in contact with the workpiece is also heated to the same degree of temperature. On the other hand, when the pressure-sensitive adhesive layer is composed of an adhesive resin, the physical properties of the adhesive resin tend to change greatly in the vicinity of the glass transition temperature of the adhesive resin.

For example, when the glass transition temperature of the pressure-sensitive adhesive layer is greater than the above range, the physical properties of the pressure-sensitive adhesive layer tend to change with the progress of backside grinding, and in particular, as described above, when the temperature of the workpiece is non-uniform within the surface, The physical properties of the pressure-sensitive adhesive layer also tend to be non-uniform within the plane. Accordingly, there is a tendency that cracks in the divided work product are more likely to occur. Therefore, the glass transition temperature of the pressure-sensitive adhesive layer is preferably away from the temperature at which the pressure-sensitive adhesive layer is heated during backside grinding (50 to 60°C) so that the physical properties of the pressure-sensitive adhesive layer do not change significantly during backside grinding.

By the way, as described above, in the present embodiment, for the purpose of reducing the residual paste of the pressure-sensitive adhesive layer and increasing the adhesive strength, the composition for the pressure-sensitive adhesive layer preferably contains a monomer having a high glass transition temperature of the homopolymer. . Therefore, even when the composition for the pressure-sensitive adhesive layer contains a monomer having a high homopolymer glass transition temperature, it is preferable to control the glass transition temperature of the pressure-sensitive adhesive layer within the above range.

The glass transition temperature of the pressure-sensitive adhesive layer is more preferably -40°C or higher, further preferably -30°C or higher, still more preferably -20°C or higher, and particularly preferably -10°C or higher. On the other hand, the glass transition temperature of the pressure-sensitive adhesive layer is more preferably 20°C or less, further preferably 10°C or less, and particularly preferably less than 0°C.

The glass transition temperature of the pressure-sensitive adhesive layer can be measured as follows. First, the material constituting the pressure-sensitive adhesive layer is used as a sample for measurement of a predetermined size. The dynamic viscoelasticity measuring device twists the measurement sample at a predetermined frequency within a predetermined temperature range to impart shear strain to the measurement sample, measures the storage modulus and loss modulus of the measurement sample, and at each temperature Calculate the loss tangent (tanδ) of Let the peak temperature of the measured loss tangent be the glass transition temperature (Tg) of an adhesive layer. Details of the measurement are described in Examples.

In this embodiment, the thickness of the pressure-sensitive adhesive layer is preferably less than 50 μm, more preferably 45 μm or less, and still more preferably 40 μm or less. When the thickness of the pressure-sensitive adhesive layer is within the above range, it is possible to suppress minute movement of the divided workpieces due to the pressure applied to the workpieces or the group of separated workpieces during grinding. As a result, the probability of contact between the pieces of workpieces is lowered, and the crack generation rate can be further suppressed.

On the other hand, from the viewpoint of embedding circuits, electrodes, etc. formed on the workpiece in the pressure-sensitive adhesive layer, the thickness of the pressure-sensitive adhesive layer is preferably 10 μm or more.

In addition, the thickness of an adhesive layer means the thickness of the whole adhesive layer. For example, the thickness of the pressure-sensitive adhesive layer composed of a plurality of layers means the total thickness of all layers constituting the pressure-sensitive adhesive layer.

(4. Physical properties of protective sheet for work processing)

In this embodiment, in addition to the physical properties of the pressure-sensitive adhesive layer, the physical properties as a protective sheet for workpiece processing are controlled as follows.

(4.1. Elongation of protective sheet for workpiece processing)

In this embodiment, the elongation of the protective sheet for workpiece processing at 23°C is 2.5% or less. This elongation is the elongation when the tensile load first reaches 30 N/15 mm after the both ends of the protective sheet for workpiece processing are started to be pulled.

This parameter assumes a situation in which the protective sheet for workpiece processing is adhered to the workpiece while applying tension. Since the atmosphere in which the protective sheet for workpiece processing is affixed to the workpiece is usually room temperature, the elongation of the protective sheet for workpiece processing at 23°C is specified as a parameter.

When the elongation of the protective sheet for processing a workpiece at 23°C is within the above range, deformation of the protective sheet for processing a workpiece during grinding of the back side caused by tensile stress caused by the tension applied at the time of attaching the protective sheet for processing a workpiece can be suppressed. can As a result, it is possible to suppress the shift of the fragmented work product resulting from the deformation of the protective sheet for work processing.

The elongation of the protective sheet for workpiece processing at 23°C is preferably 2.1% or less, more preferably 1.8% or less, still more preferably 1.5% or less.

The elongation of the protective sheet for workpiece processing at 23°C can be measured using a tensile tester. Details of the measurement are described in Examples.

(4.2. Tensile stress relaxation rate of protection sheet for workpiece processing)

In the present embodiment, it is preferable that the tensile stress relaxation rate of the protective sheet for workpiece processing at 23°C is less than 40%. This tensile stress relaxation rate is calculated from the stress at the time when both ends of the protective sheet for workpiece processing are stretched and elongated by 10% from the length before stretching, and the stress at which the tension is stopped at the time of stretching by 10% and the stress 1 minute after the stop. is the relaxation rate.

When the tensile stress relaxation rate is within the above range, the protective sheet for workpiece processing as a whole is supported without deformation and fixed to the suction table during backside grinding. As a result, since the amount of movement of the workpieces (group of divided workpieces) held by the protection sheet for workpiece processing is also suppressed, cracks resulting from collision between the divided workpieces can be further suppressed.

The tensile stress relaxation rate of the protective sheet for workpiece processing at 23°C is more preferably 38% or less, further preferably 36% or less, and particularly preferably 34% or less.

In addition, the lower limit of the tensile stress relaxation rate of the protective sheet for workpiece processing at 23°C is not particularly limited, but is preferably 5% or more, and is preferably 10% or more from the viewpoints of affixing workability and cost of the protective sheet for workpiece processing. more preferable

The tensile stress relaxation rate of the protective sheet for workpiece processing at 23°C can be measured using a tensile tester. Details of the measurement are described in Examples.

(5. Buffer layer)

In this embodiment, the protective sheet for workpiece processing is not limited to the configuration described in Fig. 1A, and may have other layers as long as the effect of the present invention is obtained. That is, as long as it has a configuration in which the pressure-sensitive adhesive layer 20 is disposed on the base material 10, another layer may be formed between the base material 10 and the pressure-sensitive adhesive layer 20, for example, and the pressure-sensitive adhesive layer 20 ) to the adherend, in order to protect the pressure-sensitive adhesive layer 20, a release sheet may be disposed on the main surface 20a of the pressure-sensitive adhesive layer 20.

In particular, in this embodiment, as shown in Fig. 1B, the protective sheet 1 for work processing preferably has a buffer layer 30 in addition to the substrate 10 and the pressure-sensitive adhesive layer 20. The buffer layer 30 is formed on the main surface 10b on the opposite side to the main surface 10a of the substrate on which the pressure-sensitive adhesive layer 20 is formed.

In addition, a layer exhibiting a desired function may be formed on the outermost surface of the protective sheet for workpiece processing shown in FIGS. 1A and 1B as necessary.

The buffer layer 30 is a layer that is softer than the base material, and can further relieve stress generated during backside grinding of the workpiece, thereby further preventing cracks from occurring in the workpiece in some cases. In addition, the workpiece to which the protective sheet for workpiece processing is attached is disposed on the suction table via the protective sheet for workpiece processing during backside grinding, but is appropriately held on the suction table by having a buffer layer as a constituent layer of the protective sheet for workpiece processing It gets easier.

On the other hand, from the viewpoint of reducing the cost of raw materials and reducing the risk of thickness variations occurring during the production of the protective sheet for work processing due to the increase in the number of constituting thick layers, it is preferable to substantially not have the buffer layer 30. do. Substantially not having means that the buffer layer does not exist at all or has a thickness of less than 1 μm.

The thickness of the buffer layer is preferably 1 to 100 μm, more preferably 5 to 80 μm, and still more preferably 10 to 60 μm. By setting the thickness of the buffer layer within the above range, the buffer layer can appropriately relax the stress during backside grinding.

The buffer layer may be a layer formed of a composition for a buffer layer containing an energy ray polymerizable compound, and may be a polypropylene film, an ethylene-vinyl acetate copolymer film, an ionomer resin film, an ethylene/(meth)acrylic acid copolymer film, or an ethylene/vinyl acetate copolymer film. Films, such as a (meth)acrylic acid ester copolymer film, an LDPE film, and a LLDPE film, may be sufficient.

In addition, a substrate having a buffer layer is obtained by laminating a buffer layer on a substrate.

(5.1 Composition for Buffer Layer)

The composition for a buffer layer containing an energy ray polymerizable compound can be cured by being irradiated with an energy ray.

Further, the composition for a buffer layer containing an energy ray polymerizable compound is, more specifically, a polymerizable compound having a urethane (meth)acrylate (d1) and an alicyclic or heterocyclic group having 6 to 20 ring atoms ( d2) and/or a polyfunctional polymerizable compound (d3) is preferably included. Moreover, the composition for a buffer layer may contain the polymeric compound (d4) which has a functional group in addition to the said component (d1) to (d3). Moreover, the composition for buffer layers may contain a photoinitiator in addition to the said component. Further, the composition for a buffer layer may contain other additives and resin components within a range that does not impair the effects of the present invention.

Hereinafter, each component included in the composition for a buffer layer containing an energy ray polymerizable compound will be described in detail.

(5.1.1 urethane (meth)acrylate (d1))

Urethane (meth)acrylate (d1) is a compound having at least a (meth)acryloyl group and a urethane bond, and has a property to be polymerized and cured by energy ray irradiation. Urethane (meth)acrylate (d1) is an oligomer or polymer.

The weight average molecular weight (Mw) of the component (d1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, still more preferably 3,000 to 20,000. In addition, the number of (meth)acryloyl groups (hereinafter also referred to as “functional group number”) in the component (d1) may be monofunctional, bifunctional or trifunctional or higher, but is preferably monofunctional or bifunctional.

Component (d1) can be obtained, for example, by reacting (meth)acrylate having a hydroxyl group with a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound and a polyhydric isocyanate compound. In addition, you may use a component (d1) individually or in combination of 2 or more types.

The content of the component (d1) in the composition for buffer layer is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, still more preferably 25 to 55 parts by mass with respect to 100 parts by mass of the composition for buffer layer. .

(5.1.2. Polymerizable compound (d2) having an alicyclic or heterocyclic group having 6 to 20 ring atoms)

Component (d2) is preferably a polymerizable compound having an alicyclic group or heterocyclic group having 6 to 20 ring atoms, and further preferably a compound having at least one (meth)acryloyl group, more preferably It is a compound having one (meth)acryloyl group. By using the component (d2), the film formability of the composition for buffer layers obtained can be improved.

In addition, there is an overlap between the definition of component (d2) and the definition of component (d3) or component (d4) described later, but the overlapping portion is included in component (d3) or component (d4). For example, a compound having at least one (meth)acryloyl group, an alicyclic or heterocyclic group having 6 to 20 ring atoms, and a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group is a component (d2) and component (d4) are included in both definitions, but in the present invention, the compound is included in component (d4).

Examples of the specific component (d2) include alicyclic group-containing (meth)acrylates such as isobornyl (meth)acrylate; heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate; etc. can be mentioned. In addition, you may use a component (d2) individually or in combination of 2 or more types.

The content of the component (d2) in the buffer layer composition is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, still more preferably 25 to 55 parts by mass, based on 100 parts by mass of the composition for buffer layer. .

(5.1.3. Polyfunctional polymerizable compound (d3))

A polyfunctional polymerizable compound refers to a compound having two or more energy ray-curable groups. The energy ray-curable group is a functional group containing a carbon-carbon double bond, and examples thereof include a (meth)acryloyl group, a vinyl group, an allyl group, and a vinylbenzyl group. An energy ray-curable group may combine 2 or more types. A three-dimensional network structure (crosslinked structure) is formed when the energy ray-curable group in the polyfunctional polymerizable compound reacts with the (meth)acryloyl group in the component (d1) or when the energy ray-curable groups in the component (d3) react with each other. When a polyfunctional polymerizable compound is used, compared to the case where a compound containing only one energy ray curable group is used, the crosslinked structure formed by energy ray irradiation increases, so that the buffer layer exhibits unique viscoelasticity, It becomes easier to relax the stress at the time of grinding.

In addition, there is an overlap between the definition of component (d3) and the definition of component (d4) described later, and the overlapping portion is included in component (d3). For example, a compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group and having two or more (meth)acryloyl groups is included in the definition of both the component (d3) and the component (d4), In the present invention, the compound is included in the component (d3).

From the above viewpoint, the number of energy ray-curable groups (number of functional groups) in the polyfunctional polymerizable compound is preferably 2 to 10, and more preferably 3 to 6.

Moreover, the weight average molecular weight of component (d3) is preferably 30 to 40000, more preferably 100 to 10000, still more preferably 200 to 1000.

Specific examples of the component (d3) include diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and neopentyl glycol di(meth)acrylate. , 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa( meth)acrylate, divinylbenzene, vinyl (meth)acrylate, divinyl adipate, N,N'-methylenebis(meth)acrylamide, and the like. Among these, neopentyl glycol di(meth)acrylate and dipentaerythritol hexa(meth)acrylate are preferable. In addition, you may use component (d3) individually or in combination of 2 or more types.

The content of the component (d3) in the composition for buffer layer is preferably 2 to 40 parts by mass, more preferably 3 to 20 parts by mass, still more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the composition for buffer layer. .

(5.1.Polymerizable compound having 4 functional groups (d4))

Component (d4) is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, an amino group, and the like, and is preferably a compound having at least one (meth)acryloyl group, more preferably 1 It is a compound having two (meth)acryloyl groups.

Component (d4) has good compatibility with component (d1), and it becomes easy to adjust the viscosity of the composition for a buffer layer to an appropriate range. Further, even when the buffer layer is made relatively thin, the buffer performance is improved.

Examples of the component (d4) include hydroxyl group-containing (meth)acrylates, epoxy group-containing compounds, amide group-containing compounds, and amino group-containing (meth)acrylates. Among these, hydroxyl group-containing (meth)acrylate is preferable.

The content of the component (d4) in the buffer layer composition is preferably 5 to 40 parts by mass, more preferably 7 to 35 parts by mass with respect to 100 parts by mass of the composition for buffer layer in order to improve the film formability of the composition for buffer layer. , more preferably 10 to 30 parts by mass.

(5.1.5 component (d1) to polymeric compound (d5) other than (d4))

The composition for forming a buffer layer may contain other polymerizable compounds (d5) other than the above components (d1) to (d4) within a range not impairing the effect of the present invention.

Examples of the component (d5) include alkyl (meth)acrylates having an alkyl group of 1 to 20 carbon atoms; A vinyl compound etc. are mentioned.

The content of the component (d5) in the buffer layer composition is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, still more preferably 0 to 5 parts by mass, based on 100 parts by mass of the composition for buffer layer. .

(5. 1. 6 photopolymerization initiator)

The composition for a buffer layer preferably further contains a photopolymerization initiator from the viewpoint of shortening the polymerization time by light irradiation and reducing the amount of light irradiation when forming the buffer layer.

Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, examples thereof include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and the like. These photoinitiators can be used individually or in combination of 2 or more types.

The content of the photopolymerization initiator in the buffer layer composition is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, still more preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the total amount of the energy ray polymerizable compound. It is wealth.

(5.1.7 Other additives)

The composition for a buffer layer may contain other additives within a range not impairing the effect of the present invention. Examples of other additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, and dyes. When blending these additives, the content of each additive in the buffer layer composition is preferably 0.01 to 6 parts by mass, more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the total amount of the energy ray polymerizable compound.

A buffer layer formed from a composition for a buffer layer containing an energy ray polymerizable compound is obtained by polymerizing and curing the composition for a buffer layer having the above composition by irradiation with an energy ray. In short, the said buffer layer is what hardened the composition for buffer layers.

(6. Manufacturing method of protective sheet for workpiece processing)

A method for manufacturing the protective sheet for workpiece processing according to the present embodiment may be a known method. For example, a protective sheet for work processing having a base material and an adhesive layer formed on one main surface of the base material may be manufactured as follows.

First, as a composition for forming the pressure-sensitive adhesive layer, for example, a composition for the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive layer, or a composition obtained by diluting the composition for the pressure-sensitive adhesive layer with a solvent (these two compositions are referred to as "coating agents for pressure-sensitive adhesive layers". ) is prepared. The prepared coating agent for the pressure-sensitive adhesive layer is applied to the release surface of the release film and, if necessary, dried to form an adhesive layer on the release film. Thereafter, one main surface of the base material and the pressure-sensitive adhesive layer are bonded together to obtain a protective sheet for work processing in which the pressure-sensitive adhesive layer is formed on one main surface of the base material. Alternatively, the prepared coating agent for the pressure-sensitive adhesive layer may be directly applied to one main surface of the substrate to form the pressure-sensitive adhesive layer.

Moreover, what is necessary is just to manufacture the protective sheet for work processing which has a base material, the adhesive layer formed on one main surface of a base material, and the buffer layer formed on the other main surface of a base material as follows.

Similarly to the above, the coating agent for the pressure-sensitive adhesive layer for forming the pressure-sensitive adhesive layer is prepared. Subsequently, as a composition for forming a buffer layer, for example, a composition for a buffer layer constituting a buffer layer, or a composition obtained by diluting the composition for a buffer layer with a solvent (these two compositions are referred to as "coating agent for a buffer layer"). prepare The buffer layer can be formed by applying the prepared coating agent for the buffer layer to the release surface of the release film, drying it as necessary to form a coating film on the release film, and curing the coating film (for example, irradiation with energy rays). . After that, one main surface of the base material and the buffer layer are bonded together. In the case where this buffer layer still has energy ray curability, it may be further cured (eg, energy ray irradiation) as needed.

Moreover, the prepared coating agent for adhesive layers is apply|coated to the peeling surface of a peeling film, and it is made to dry as needed, and an adhesive layer is formed on the peeling film. After that, in the base material, the main surface of the side on which the buffer layer is not formed and the pressure-sensitive adhesive layer are bonded, the pressure-sensitive adhesive layer is formed on one main surface of the base material, and the buffer layer is formed on the other main surface of the base material. A sheet is obtained. As in the case of forming the pressure-sensitive adhesive layer, the coating agent for the buffer layer may be directly applied to one main surface of the substrate to form the buffer layer.

(7. Manufacturing method of shredded work cargo)

As described above, the protective sheet for processing a workpiece according to the present invention is suitably used for a method of separating a workpiece into pieces using LDBG.

As a non-limiting use example of the protective sheet for workpiece processing, a method for producing a pieced work piece (eg chip) using LDBG will be specifically described below.

The manufacturing method of a pieced workpiece material is specifically, equipped with at least the following process 1 - process 4.

Step 1: Step of attaching the protective sheet for processing the work to the surface of the work

Step 2: Step of forming a modified region inside the workpiece from the front or backside of the workpiece

Step 3: A step in which a protective sheet for work processing is applied to the front surface and the workpiece on which the modified region is formed is ground from the back side to separate the workpiece into a plurality of fragmented products using the modified region as the starting point

Step 4: A step of peeling the protective sheet for workpiece processing from the work pieces that have been singulated (ie, a plurality of pieces of work pieces)

Hereinafter, each process of the manufacturing method of the above-mentioned work piece product is explained in detail. In the description, a wafer is used as a specific example of a work, and a chip is used as a specific example of a pieced work product.

(Process 1)

In Step 1, the pressure-sensitive adhesive layer of the protective sheet for workpiece processing according to the present embodiment is applied to the surface of the wafer. At this time, tension is applied to the protective sheet for processing the workpiece, but since the tensile stress relaxation rate of the protective sheet for processing the workpiece is within the above range, the protective sheet for processing the workpiece is not deformed during back grinding and is sufficiently fixed to the suction table. As a result, chip movement is suppressed during backside grinding, and cracking is suppressed. Although this step may be performed after step 2 described later, it is preferable to perform before step 2 from the viewpoint of reducing the risk of unintentional splitting of the wafer when attaching the protective sheet for workpiece processing.

Further, a circuit is formed on the surface of the wafer. Circuit formation on the wafer surface can be performed by various methods including conventionally general methods such as an etching method and a lift-off method.

The formed circuit may be exposed, or a circuit protective layer may be formed to protect the circuit. Moreover, convex electrodes, such as a bump and a filler, may be formed in the circuit.

(Process 2)

In Step 2, a modified region is formed inside the wafer from the front or rear surface of the wafer.

The modified region formed in this step is a brittle portion of the wafer. In the modified region, cracks are likely to occur due to shear force and pressure applied to the wafer. Such a crack becomes the starting point of division of the wafer. That is, the modified region in Step 2 is formed along the dividing line when the wafer is divided into chips in Step 3 described later.

Formation of the modified region is performed by laser irradiation focused on the inside of the wafer. Therefore, the modified region is formed inside the wafer. Laser irradiation may be performed from the front side of the wafer or from the back side. In addition, when process 2 is performed after process 1 and laser irradiation is performed from the surface of a wafer, a laser is irradiated to a wafer through the protective sheet for work processing.

The wafer to which the protective sheet for work processing is affixed and the modified region is formed is placed on the suction table and held by the suction table. At this time, the surface side of the wafer is placed on the side of the suction table with the protective sheet for workpiece processing interposed therebetween, and is attracted.

(Process 3)

After steps 1 and 2, the back side of the wafer on the suction table is ground to separate the wafer into a plurality of chips.

Here, the back surface grinding may be performed until the grinding surface (wafer back surface) reaches the modified region, but the grinding surface does not have to strictly reach the modified region. That is, it is only necessary to grind to a position close to the modified region so that the wafer is divided from the modified region as a starting point to obtain chipped chips.

Moreover, you may perform stress relief, such as dry polish, after completion|finish of back surface grinding using a grinding wheel.

The shape of the individualized chip may be a square or an elongated shape such as a rectangle. Further, the thickness of the individual chips is not particularly limited, but is preferably about 5 to 100 μm, more preferably 10 to 45 μm. According to LDBG, it becomes easy to make the thickness of the chip|divided chip 50 micrometers or less, More preferably, 10-45 micrometers. In addition, the size of the individualized chip is not particularly limited. For example, the chip area is preferably less than 600 mm 2 , more preferably less than 400 mm 2 , still more preferably less than 120 mm 2 .

By using the protective sheet for work processing according to the present embodiment, large cracks leading to chip defects are reduced in the chips after the backside grinding (Step 3) is completed.

(Process 4)

Next, the protective sheet for workpiece processing is peeled off from the individualized wafers (namely, chip groups). This process is implemented by the following method, for example.

First, when the pressure-sensitive adhesive layer of the protective sheet for work processing is formed of an energy ray-curable pressure-sensitive adhesive, energy rays are irradiated to cure the pressure-sensitive adhesive layer. For example, the illuminance of the energy ray is preferably 120 to 280 mW/cm 2 , and the light quantity of the energy ray is preferably 100 to 1000 mJ/cm 2 . As an energy ray, an ultraviolet-ray is preferable. Next, a pick-up tape is attached to the back side of the chip group, and positioning and orientation are performed so that pick-up is possible. At this time, the ring frame located on the outer periphery side of the wafer is also bonded to the pick-up tape, and the outer periphery of the pick-up tape is fixed to the ring frame. The wafer and the ring frame may be bonded simultaneously to the pick-up tape, or may be bonded at separate timings. Next, the protective sheet for work processing is peeled from the plurality of chips held on the pick-up tape.

After that, a plurality of chips on the pick-up tape are picked up. Next, the chip is fixed on a substrate for the device or the like to manufacture the device. For example, when a chip is a semiconductor, a semiconductor device is manufactured by fixing the chip on a substrate or the like for a semiconductor device.

In addition, although a pick-up tape is not specifically limited, For example, it is an adhesive sheet provided with the base material and the adhesive layer formed on one surface of the base material.

As mentioned above, although embodiment of this invention has been described, this invention is not limited at all to the said embodiment, You may modify in various aspects within the scope of this invention.

Example

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

The measurement method and evaluation method in this Example are as follows.

(Shear storage modulus of pressure-sensitive adhesive layer)

In Examples and Comparative Examples to be described later, a pressure-sensitive adhesive layer was formed on a release film using a composition for a pressure-sensitive adhesive layer. A plurality of pressure-sensitive adhesive layers formed in this way were prepared, and a laminate of pressure-sensitive adhesive layers having a thickness of 1 mm was produced by peeling the release film and laminating the release surfaces together.

The laminated body of the obtained pressure-sensitive adhesive layer was punched out in a cylindrical shape with a diameter of 8 mm, and it was set as a sample for measuring the shear storage modulus.

The shear storage modulus (G') of the pressure-sensitive adhesive layer was measured using a rheometer MCR302 manufactured by Anton Paar. Both ends in the thickness direction of the sample were clamped with parallel plates, and the sample was measured under the conditions of -40 to 100 ° C., temperature increase rate of 3 ° C./min, gap of 1 mm, strain of 0.05 to 0.5%, and angular frequency of 1 Hz. Using the thickness direction as the axis of rotation, the sample was twisted and a shear force was applied to the sample, and the shear storage modulus was measured. The shear storage modulus (G') at 55°C was calculated from the obtained measured values.

(Shear stress relaxation rate of pressure-sensitive adhesive layer)

In the same way as the sample for measuring the shear storage modulus, a sample for measuring the shear stress relaxation rate was prepared. The measurement of the shear stress relaxation rate of the pressure-sensitive adhesive layer was performed using a rheometer MCR302 manufactured by Anton Paar. While heating the sample and maintaining the temperature at 55°C, a shear force is applied to the sample by twisting the sample with the thickness direction of the sample as the axis of rotation under the conditions of a gap of 1 mm and an angular frequency of 1 Hz, and the sample is deformed by 5% (angle of 18 °). The shear stress relaxation rate was calculated from the following formula when the stress at the moment (0 second) reached A ₀ and the stress occurring 1 second later was A ₁ while maintaining a strain of 5%.

Shear stress relaxation rate = {(A ₀ -A ₁ )/A ₀ }×100 (%)

(Glass transition temperature (Tg) of the pressure-sensitive adhesive layer)

A sample for measuring the glass transition temperature (Tg) was produced in the same manner as the sample for measuring the shear storage modulus. The glass transition temperature of the pressure-sensitive adhesive layer was measured using a rheometer MCR302 manufactured by Anton Paar. Both ends in the thickness direction of the sample were clamped with parallel plates, and the sample was measured under the conditions of -40 to 100 ° C., temperature increase rate of 3 ° C./min, gap of 1 mm, strain of 0.05 to 0.5%, and angular frequency of 1 Hz. Shearing force was applied to the sample by twisting the sample with the thickness direction as the axis of rotation, the loss elastic modulus was measured, and the loss tangent tanδ at each temperature was calculated using the loss elastic modulus and the shear storage modulus. The peak temperature was confirmed from the chart of tan δ at each obtained temperature, and this was made the glass transition temperature (Tg) of the pressure-sensitive adhesive layer.

(Elongation and tensile stress relaxation rate of protective sheet for workpiece processing)

The protective sheets for workpiece processing produced in Examples and Comparative Examples were cut to a size of 140 mm in length and 15 mm in width, and samples for measuring elongation and tensile stress relaxation were obtained. Using a universal tensile tester (manufactured by SHIMADZU, Autograph (registered trademark) AG-10kNIS), both ends in the longitudinal direction of the sample were gripped by 20 mm with grippers (ie, the initial gripping distance was 100 mm), and the tensile load was measured. While recording, the sample was stretched in the longitudinal direction of the sample at a rate of 200 mm/min in an environment of 23°C. The elongation of the sample was measured when the tensile load first reached 30 N/15 mm.

Further, the sample was stretched in the longitudinal direction of the sample under the above conditions, and the tension was stopped at the time point when the sample was stretched by 10% (that is, the gripping distance was 110 mm). Among the stresses from the start of tension to the end, the maximum stress was denoted as A (N/m 2 ), and the stress B (N/m 2 ) 1 minute after the end of elongation of the sample was measured. From the values of the measured stresses A and B, the tensile stress relaxation rate was calculated by the following formula.

Tensile stress relaxation rate = {(A-B)/A} × 100 (%)

(crack occurrence rate)

Using a tape laminator for back grinding (RAD-3510 F/12 manufactured by Lintec Co., Ltd.), the protective sheet for workpiece processing produced in Examples and Comparative Examples was affixed to a silicon mirror wafer as a workpiece having a diameter of 300 mm and a thickness of 780 μm. did The sticking temperature was 50 degreeC. Subsequently, a stealth dicing process was applied to the wafer using a stealth dicing device (DFL7361 manufactured by Disco Co., Ltd.) to form a lattice-like modified region. In addition, the lattice size was 10 mm x 10 mm.

Next, using a backside grinding machine (DGP8761 manufactured by Disco Co., Ltd.), the surface on the opposite side of the surface to which the protective sheet for work processing of the wafer on which the modified region was formed was adhered was ground until the thickness was 18 μm (including dry polish ) was performed, and the wafer was divided into a plurality of chips to form a group of chips. After the grinding step, in order to easily observe cracks generated in the chips, a wafer mounter is applied to the surface of the chip group (ie, the ground surface) of the chip group to which the protective sheet for work processing is attached, and to the 12-inch ring frame. (RAD-2510F/12, manufactured by Lintec) was used to affix a dicing tape (D-175D, manufactured by Lintec).

Next, the protective sheet for work processing was irradiated with energy rays (ultraviolet rays), and the protective sheet for work processing was peeled off to expose the surface of the wafer (chip group). Using an infrared camera incorporated in a stealth dicing device (DFL7361 manufactured by Disco Corporation), chip cracks were observed and counted from the wafer surface side. The observation range was a range of 145 mm in radius from the center of the wafer (290 mm in diameter). The observed cracks were classified as shown below on the basis of length.

· One crack WHEREIN: A thing with the longest length less than 10 micrometers was defined as a small crack.

· One crack WHEREIN: A thing with the longest length of 10 micrometers or more and less than 20 micrometers was defined as a medium crack.

· One crack WHEREIN: A thing with the longest length of 20 micrometers or more was defined as a large crack.

The crack score was calculated from the following formula using the classified crack species.

Crack score = 0 × number of small cracks + 1 × number of medium cracks + 10 × number of large cracks

In this embodiment, the case where the crack score is 0 or more and 20 or less is judged A, the case where the crack score is 21 or more and 40 or less is judged B, the case where the crack score is 41 or more and 55 or less is judged C, and the crack score is A case of 56 or more was determined as D. Samples of A and B judgments were judged to be acceptable.

(Example 1)

(1) description

First, as a base material, a PET film (thickness: 50 µm, Young's modulus at 23°C: 4000 MPa) with a coating layer for easy adhesion on both sides was prepared.

(2) adhesive layer

(Preparation of composition for pressure-sensitive adhesive layer)

To an acrylic polymer obtained by copolymerizing 52 parts by mass of n-butyl acrylate (BA), 20 parts by mass of dimethylacrylamide (DMAA), and 28 parts by mass of 2-hydroxyethyl acrylate (HEA), all hydroxyl groups (100 2-methacryloyloxyethyl isocyanate (MOI) was reacted so as to add 90 equivalents of hydroxyl groups in the equivalent) to obtain an energy ray-curable acrylic copolymer (Mw: about 750,000) (BA/DMAA/HEA (BA/DMAA/HEA (BA/DMAA/HEA)) MOI) = 52/20/28 (90 mol %) (A-1).

To 100 parts by mass of this energy ray-curable acrylic copolymer, 12 parts by mass of polyfunctional urethane acrylate (manufactured by Mitsubishi Chemical Corporation, Shikou UT-4332) as an energy ray-curable resin, an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, Colonate L) was mixed with 1.07 parts by mass and 1.4 parts by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator, diluted with methyl ethyl ketone, and a coating agent for a composition for an adhesive layer having a solid content concentration of 34% by mass. was prepared.

(3) buffer layer

(Preparation of composition for forming buffer layer)

As an energy ray polymerizable compound, 50 parts by mass of urethane acrylate oligomer (manufactured by Sartomer, CN8888) (component d1), 40 parts by mass of isobornyl acrylate (IBXA) (component d2), neopentyl glycol diacrylate 10 2.0 parts by mass of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by BASF, Omnirad 1173) was blended as a photopolymerization initiator (component d3), and for buffer layer formation. A composition was prepared.

The silicone release-treated surface of a release sheet (SP-PET381031 manufactured by Lintec Co., Ltd., thickness: 38 μm) was coated with the composition for forming a buffer layer to form a coating film. And the said coating film was irradiated with ultraviolet rays, the said coating film was semi-hardened, and the semi-cured film of a buffer layer of 30 micrometers in thickness was formed.

In addition, the ultraviolet irradiation was carried out using a belt conveyor type ultraviolet irradiation device (ECS-401GX, manufactured by Eye Graphics) and a high-pressure mercury lamp (H04-L41, manufactured by Eye Graphics, Inc.) with a lamp height of 260 mm and an output of 80 W/ cm, illumination intensity of 70 mW/cm 2 , and irradiation amount of 30 mW/cm 2 . Then, the surface of the formed semi-cured film was bonded to the first coating layer of the base material, and ultraviolet rays were again irradiated from the release sheet side on the semi-cured film to completely cure the semi-cured film to form a buffer layer having a thickness of 30 μm. .

(Manufacture of protective sheet for work processing)

On the release sheet (SP-PET381031 manufactured by Lintec Co., Ltd., thickness: 38 μm) treated with silicone release, a coating agent of the composition for the pressure-sensitive adhesive layer was applied and dried by heating to form a pressure-sensitive adhesive layer having a thickness of 20 μm on the release sheet did The glass transition temperature (Tg) of the pressure-sensitive adhesive layer was 7.4°C.

Next, the adhesive layer of the release sheet with an adhesive layer was bonded onto the second coating layer of the PET film with a double-sided coating layer to prepare a protective sheet for work processing. That is, the protective sheet for work processing shown in FIG. 1B was manufactured.

(Example 2)

A protective sheet for workpiece processing was obtained in the same manner as in Example 1 except that the addition amount of the isocyanate-based crosslinking agent (Colonate L, manufactured by Tosoh Corporation) was changed to 0.27 parts by mass using the acrylic copolymer obtained below as the acrylic copolymer. got Table 1 shows the glass transition temperature of the pressure-sensitive adhesive layer.

To an acrylic polymer obtained by copolymerizing 70 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 10 parts by mass of 2-hydroxyethyl acrylate (HEA), all hydroxyl groups of the acrylic polymer ( 100 equivalents) was reacted with 2-methacryloyloxyethyl isocyanate (MOI) to add 70 equivalents of hydroxyl groups to obtain an energy ray-curable acrylic copolymer (Mw: about 750,000) (BA/MMA/HEA (MOI) = 70/20/10 (70 mol%) (A-4).

(Example 3)

A protective sheet for workpiece processing was obtained in the same manner as in Example 2 except that the addition amount of the isocyanate-based crosslinking agent (Colonate L, manufactured by Tosoh Corporation) was changed to 0.54 parts by mass. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive layer.

(Example 4)

A protective sheet for workpiece processing was obtained in the same manner as in Example 2 except that the addition amount of the isocyanate-based crosslinking agent (Colonate L, manufactured by Tosoh Corporation) was changed to 1.07 parts by mass. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive layer.

(Example 5)

A protective sheet for workpiece processing was prepared in the same manner as in Example 1 except that the addition amount of the isocyanate-based crosslinking agent (Colonate L, manufactured by Tosoh Corporation) was changed to 0.27 parts by mass using the acrylic copolymer obtained below as the acrylic copolymer. got it Table 1 shows the glass transition temperature of the pressure-sensitive adhesive layer.

To an acrylic polymer obtained by copolymerizing 80 parts by mass of n-butyl acrylate (BA), 10 parts by mass of methyl methacrylate (MMA), and 10 parts by mass of 2-hydroxyethyl acrylate (HEA), all hydroxyl groups of the acrylic polymer ( 100 equivalents) was reacted with 2-methacryloyloxyethyl isocyanate (MOI) to add 70 equivalents of hydroxyl groups to obtain an energy ray-curable acrylic copolymer (Mw: about 750,000) (BA/MMA/HEA (MOI) = 80/10/10 (70 mol %) (A-3).

(Example 6)

A protective sheet for workpiece processing was manufactured in the same manner as in Example 1 except that the buffer layer was not formed. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

(Example 7)

A protective sheet for workpiece processing was manufactured in the same manner as in Example 2 except that the buffer layer was not formed. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

(Example 8)

A protective sheet for workpiece processing was manufactured in the same manner as in Example 3 except that the buffer layer was not formed. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

(Example 9)

A protective sheet for workpiece processing was manufactured in the same manner as in Example 4 except that the buffer layer was not formed. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

(Example 10)

A protective sheet for workpiece processing was manufactured in the same manner as in Example 5 except that the buffer layer was not formed. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

(Comparative Example 1)

A protective sheet for workpiece processing was obtained in the same manner as in Example 1 except that the addition amount of the isocyanate-based crosslinking agent (Colonate L, manufactured by Tosoh Corporation) was changed to 0.27 parts by mass using the acrylic copolymer obtained below as the acrylic copolymer. got Table 1 shows the glass transition temperature of the pressure-sensitive adhesive layer.

To the acrylic polymer obtained by copolymerizing 90 parts by mass of n-butyl acrylate (BA) and 10 parts by mass of 2-hydroxyethyl acrylate (HEA), 70 equivalents of hydroxyl groups among all hydroxyl groups (100 equivalents) of the acrylic polymer are added, 2-methacryloyloxyethyl isocyanate (MOI) was reacted to obtain an energy ray-curable acrylic copolymer (Mw: about 750,000) (BA/HEA (MOI) = 90/10 (70 mol%) (A -2).

(Comparative Example 2)

A protective sheet for workpiece processing was obtained in the same manner as in Example 1 except for using the acrylic copolymer obtained below as the acrylic copolymer. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive layer.

To an acrylic polymer obtained by copolymerizing 85 parts by mass of n-butyl acrylate (BA), 5 parts by mass of methyl methacrylate (MMA), and 10 parts by mass of 2-hydroxyethyl acrylate (HEA), all hydroxyl groups of the acrylic polymer ( 100 equivalents) was reacted with 2-methacryloyloxyethyl isocyanate (MOI) to add 70 equivalents of hydroxyl groups to obtain an energy ray-curable acrylic copolymer (Mw: about 750,000) (BA/MMA/HEA (MOI) = 85/5/10 (70 mol%) (A-5).

(Comparative Example 3)

A protective sheet for workpiece processing was obtained in the same manner as in Comparative Example 1 except that the addition amount of the isocyanate-based crosslinking agent (Colonate L, manufactured by Tosoh Corporation) was changed to 4 parts by mass. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

(Comparative Example 4)

A protective sheet for workpiece processing was obtained in the same manner as in Example 2 except that the thickness of the substrate was changed to 20 μm. Table 1 shows the glass transition temperature of the pressure-sensitive adhesive.

The above measurement and evaluation were performed on the obtained samples (Examples 1 to 10 and Comparative Examples 1 to 4). A result is shown in Table 1.

From Table 1, when the shear storage modulus and shear stress relaxation rate of the pressure-sensitive adhesive and the elongation of the protective sheet for work processing are within the ranges described above, even if the wafer is separated by LDBG, chip defects (i.e., defective pieces of work pieces) It was confirmed that it was difficult for large cracks to occur.

1: Protection sheet for work processing
10: materials
20: adhesive layer
30: buffer layer

Claims (6)

A protective sheet for work processing comprising a base material and an adhesive layer disposed on one main surface of the base material,
The shear storage modulus of the pressure-sensitive adhesive layer at 55°C is 40,000 Pa or more, and the shear stress relaxation rate after 1 second of the pressure-sensitive adhesive layer at 55°C is 30% or more,
At 23°C, after application of a tensile load to the workpiece protection sheet is started, the elongation of the workpiece protection sheet when the tensile load reaches 30 N/15 mm is 2.5% or less. According to claim 1,
A protective sheet for work processing in which a buffer layer is disposed on the other main surface of the base material. According to claim 1 or 2,
A protective sheet for workpiece processing in which the tensile stress relaxation rate of the protective sheet for workpiece processing at 23°C after 1 minute is less than 40%. According to any one of claims 1 to 3,
The pressure-sensitive adhesive layer is composed of an energy ray-curable acrylic pressure-sensitive adhesive,
The acrylic pressure-sensitive adhesive comprises a polymer in which an energy ray curable group is bonded to an acrylic polymer, and an energy ray curable compound. According to any one of claims 1 to 4,
A protective sheet for workpiece processing used by being attached to a surface of a workpiece in a step of separating a workpiece into a pieced workpiece by grinding the back surface of the workpiece having a modified region formed therein. A step of attaching the protective sheet for workpiece processing according to any one of claims 1 to 5 to the surface of the workpiece;
Forming a modified region inside the workpiece from the front or backside of the workpiece;
a step in which the protective sheet for processing the workpiece is adhered to the front surface and the workpiece on which the modified region is formed is ground from the rear side to separate the work into a plurality of pieces of workpieces starting from the modified region;
A method for producing a pieced work product comprising a step of peeling the protective sheet for processing the work from the work pieced into pieces.