TW202334361A - Protective sheet for workpiece processing and manufacturing method of singulated workpiece reducing defective singulated workpieces after grinding even when the singulated workpieces are obtained by grinding the workpieces using LDBG - Google Patents

Abstract

An object of the present invention is to provide a protective sheet for workpiece processing that can reduce defective singulated workpieces after grinding even when the singulated workpieces are obtained by grinding the workpieces using LDBG. A protective sheet for workpiece processing is provided with a base material and an adhesive layer disposed on one main surface of the base material, wherein the adhesive layer has a shear storage modulus of 40000 Pa or more at 55 DEG C. The shear stress relaxation rate of the adhesive layer after 1 second at 55 DEG C is 30% or more, and at 23 DEG C, after starting to apply a tensile load to the protective sheet for workpiece processing, the protective sheet for workpiece processing has an elongation of 2.5% or less when the tensile load reaches 30 N/15 mm.

Description

Protective sheet for workpiece processing and method for manufacturing workpiece individual pieces

The present invention relates to a protective sheet for workpiece processing and a method for manufacturing individual workpiece pieces. In particular, the protective sheet for workpiece processing and the method of manufacturing a pieced workpiece using the protective sheet for workpiece processing are suitable for use in a method of grinding the back side of the workpiece and dividing the workpiece into pieces based on its stress, etc.

As various electronic devices are becoming smaller and more multi-functional, the semiconductor chips mounted on these devices are also being miniaturized and thinned. In order to make the wafer thinner, the thickness is generally adjusted by grinding the back surface of the semiconductor wafer. In addition, in order to obtain a thinned wafer, a process called Dicing Before Grinding (DBG) can be used. In this method, a groove of a predetermined depth is formed from the front side of the wafer with a dicing knife, and then the groove is formed from the back side of the wafer. Grinding is performed to obtain wafers by grinding the wafers into individual wafers. In DBG, since the backside grinding of the wafer and the individualization of the wafer can be performed simultaneously, thin wafers can be manufactured efficiently.

Conventionally, when back-grinding workpieces such as semiconductor wafers or when manufacturing individual workpieces such as semiconductor wafers using DBG, scales were generally attached to the surface of the workpiece in order to protect circuits on the surface of the workpiece or to retain the workpiece and the individualized workpieces. It is an adhesive tape for back grinding sheets.

As the back polishing sheet used in DBG, an adhesive tape including a base material and an adhesive layer provided on one surface of the base material is used. As an example of such an adhesive tape, Patent Document 1 discloses an adhesive tape in which a base material with a high Young's modulus is provided with an adhesive layer on one surface of the base material and a buffer layer is further provided on the other surface.

In recent years, as a modification of the pre-dicing method, a method has been proposed in which a laser is used to set a modified area inside the wafer, and the stress during backside grinding of the wafer is used to separate the wafer into individual wafers. Hereinafter, this method may be described as LDBG (Laser Dicing Before Grinding). In LDBG, since the modified region is used as the starting point to cut the wafer along the crystallographic direction, the occurrence of chipping can be reduced compared to the pre-cutting method using a cutting knife. In addition, compared with DBG in which a groove of a predetermined depth is formed on the wafer surface by a dicing blade, since there is no area of the wafer cut by a dicing blade, that is, because the kerf width is extremely small, the yield of the wafer is excellent. . [Advanced technical documents] [Patent Document]

Patent Document 1: Japanese Patent Application Publication No. 2015-183008.

[Problem to be solved by the invention]

However, when using the adhesive tape described in Patent Document 1 to perform individualization of workpieces such as wafers by LDBG, the workpieces such as wafers may be fragmented slightly due to the cutting force applied to the individualized products of the workpieces. Problems with movement and contact between pieces of workpieces. As a result, cracks (accidental cracks) occur in the individual pieces of the workpiece. Cracks are prone to occur, as mentioned above, also due to the extremely small width of the incision. In particular, when the cracks generated in the workpiece flakes are large, it will directly lead to defective workpiece flakes and have a great impact on the productivity of the workpiece flakes.

In view of this actual situation, an object of the present invention is to provide a protective sheet for workpiece processing that can reduce the number of defective workpieces after grinding even when the workpiece is ground into pieces by LDBG. Tablets. [Means used to solve problems]

Aspects of the present invention are as follows.

[1] A protective sheet for semiconductor processing, which is a protective sheet for workpiece processing having a base material and an adhesive layer disposed on one main surface of the base material, The shear storage modulus of the adhesive layer at 55℃ is more than 40,000Pa, and the shear stress relaxation rate of the adhesive layer at 55℃ after 1 second is more than 30%. At 23°C, after the tensile load is started to be applied to the workpiece processing protective sheet, the elongation rate of the workpiece processing protective sheet when the tensile load reaches 30N/15mm is 2.5% or less.

[2] The protective sheet for workpiece processing according to [1], wherein a buffer layer is provided on the other main surface of the base material.

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

[4] The protective sheet for workpiece processing according to any one of [1] to [3], wherein the adhesive layer is composed of an energy-ray curable acrylic adhesive, and the acrylic adhesive contains bonding energy A polymer with a linear curing group to an acrylic polymer, and an energy ray curing compound.

[5] The protective sheet for workpiece processing according to any one of [1] to [4], wherein the step of grinding the back surface of the workpiece having a modified region formed therein, and dicing the workpiece into individual pieces of the workpiece , attached to the surface of the workpiece and used.

[6] A method for manufacturing workpiece fragments, which has the following steps: The step of attaching the protective sheet for workpiece processing as described in any one of [1] to [5] to the surface of the workpiece; The step of forming a modified area inside the workpiece from the surface or back of the workpiece; The step of attaching a protective sheet for workpiece processing to the surface and grinding the workpiece with a modified area from the back side, using the modified area as a starting point, and slicing it into multiple workpiece flakes; The step of peeling off the protective sheet for workpiece processing from the individualized workpiece. [Invention effect]

According to the present invention, it is possible to provide a protective sheet for workpiece processing that can reduce the number of defective workpiece pieces after grinding even when the workpiece is ground into pieces by LDBG.

[Form used to implement the invention]

Hereinafter, the present invention will be described in detail using drawings based on specific embodiments. First, the main terms used in this manual will be explained.

The workpiece refers to a plate-shaped object to which the protective sheet for workpiece processing of this embodiment is affixed and then separated into individual pieces. Examples of the workpiece include a circular (including a case with an orientation flat) wafer, a rectangular panel-level package, and a strip (short-shaped substrate) sealed with mold resin. , from the viewpoint of easily obtaining the effects of the present invention, wafers are preferred. Examples of the wafer include semiconductor wafers such as silicon wafers, gallium arsenide wafers, silicon carbide wafers, gallium nitride wafers, and indium phosphide wafers, glass wafers, lithium tantalate wafers, and niobium wafers. It may be an insulator wafer such as a lithium acid wafer, or it may be a reconstituted wafer formed of a resin and a semiconductor used for manufacturing a fan-out package or the like. From the viewpoint of easily obtaining the effects of the present invention, a semiconductor wafer or an insulator wafer is preferred as the wafer, and a semiconductor wafer is more preferred.

The individualization of workpieces means dividing the workpieces into circuit units to obtain individualized workpieces. For example, when the workpiece is a wafer, the individualized workpiece is a chip; when the workpiece is a panel-level package or a strip (short-shaped substrate) sealed with mold resin, the individualized workpiece is a semiconductor package.

The "surface" of the workpiece refers to the surface where circuits, electrodes, etc. are formed, and the "backside" of the workpiece refers to the surface where circuits, etc. are not formed. As the electrode, a convex electrode such as a bump may be used.

DBG refers to a method in which a groove of a predetermined depth is formed on the surface side of the workpiece, and then ground from the back side of the workpiece to separate the workpiece into individual pieces. The groove formed on the surface side of the workpiece can be formed by blade dicing, laser cutting, plasma cutting, etc.

In addition, LDBG is a variant of DBG. It refers to using laser to set up a fragile modified area inside the workpiece (such as a wafer). Through the stress during back grinding of the workpiece, etc., the modified area is used as the starting point to cause cracks. Progress, a method of individualizing workpieces.

The "workpiece fragmentation group" refers to a plurality of workpiece fragmentation held on the workpiece processing protective sheet of the present invention after the workpiece is fragmented. These workpiece fragments, as a whole, have the same shape as the workpiece. In addition, the "wafer group" refers to a plurality of wafers that are held on the protective sheet for workpiece processing of the present invention after being divided into wafers as workpieces. These wafers as a whole have the same shape as the wafer.

"(Meth)acrylate" is used as a term to indicate both "acrylate" and "methacrylate", and other similar terms are also the same.

"Energy rays" refer to ultraviolet rays, electron rays, etc., preferably ultraviolet rays.

"Weight average molecular weight", unless otherwise specified, is a polystyrene-converted value measured by gel permeation chromatography (GPC). For measurement by such a method, for example, the high-speed GPC device "HLC-8120GPC" manufactured by Tosoh Corporation is connected in sequence to the high-speed columns "TSK guard column H _XL -H", "TSK Gel GMH _XL ", and "TSK Gel G2000 H _XL" ” (the above are all manufactured by Tosoh Co., Ltd.), column temperature: 40°C, liquid delivery rate: 1.0 mL/min, and the detector is used as a differential refractive index detector (differential refractive index detector).

The release sheet is a sheet that supports the adhesive layer releasably. Sheet refers to the concept of film without limiting the thickness.

The mass ratio in the description of compositions such as the adhesive layer composition is based on the active ingredient (solid content) and does not include the solvent unless otherwise specified.

(1.Protective sheet for workpiece processing) The protective sheet 1 for workpiece processing of this embodiment has a base material 10 and an adhesive layer 20 arranged on the base material 10 as shown in FIG. 1A .

In this embodiment, as shown in FIG. 2 , the workpiece processing protective sheet 1 is used to attach the main surface 20a of the adhesive layer to the surface 100a of the workpiece 100 (for example, a wafer). The surface 100a of the workpiece 100 is a surface having circuits, electrodes, and the like. The surface with the circuit may be the surface on which the circuit is exposed, or may be the main surface of a protective layer formed on the circuit for protecting the circuit. In addition, convex electrodes such as bumps may be formed on the circuit.

In this embodiment, the workpiece to which the protective sheet for workpiece processing is affixed is sliced into a plurality of workpiece pieces after back-grinding. As a method of singulating workpieces, DBG can be used, but the workpiece processing protective sheet 1 of this embodiment is suitable for singulating workpieces using LDBG.

Specifically, after the modified region is formed inside the workpiece, the workpiece processing protective sheet 1 is attached to the surface 100a of the workpiece 100, and the back surface 100b of the main surface opposite to the surface 100a is polished.

As grinding proceeds, the workpiece becomes thinner, and at the same time, due to the shear force and pressure exerted by the modified area formed inside the workpiece, cracks occur in the modified area and progress to both sides of the workpiece. As a result, the workpiece is fragmented. In singulation using LDBG, since there is almost no area to be cut out from the workpiece, the distance (kerf width) between the workpiece singulated product (workpiece singulated product group) and the adjacent workpiece singulated product is very small. .

In addition, the timing of individualizing the workpiece may be different. After part of the workpiece begins to be individualized, grinding is performed until the entire workpiece is individualized. Therefore, a grinding wheel can also be used to continuously apply shearing force to the workpiece fragments. Since the uneven grinding wheel surface is constantly rotating while contacting the workpiece fragments, the same shear force is not applied to all the workpiece fragments at the same time, but different shear force is applied to each workpiece fragment. Cutting force. Therefore, in a direction parallel to the workpiece plane (that is, the plane of the workpiece individualized object group), since the movement of each workpiece individualized object occurs separately and the kerf width is small, the workpiece individualized objects may come into contact with each other. If such contact occurs, cracks may easily occur in the individual pieces of the workpiece. In particular, large cracks associated with defective workpiece flakes are likely to occur in the workpiece flakes. If such large cracks occur, the yield of individual pieces of workpieces will decrease. When the thickness of the workpiece and the workpiece fragments after grinding is less than 20 μm, the workpiece fragments are more fragile and large cracks are more likely to occur than when the thickness is more than 20 μm.

To solve such a problem, in order to suppress the movement of the workpiece pieces during polishing, it is considered that the workpiece pieces can be firmly held by a hard workpiece processing protective sheet. However, hard work alone cannot resist shearing force, etc. On the contrary, shearing stress due to shearing force, etc. causes the workpiece fragments to easily collide with each other, thereby increasing the number of cracks in the workpiece fragments. Therefore, for example, in addition to the base material and the adhesive layer, a layer with high stress relaxation properties can be provided to eliminate shear stress. However, a problem arises that shear stress cannot be sufficiently relieved with such a layer.

In response to such a problem, the inventor of the present invention thought of imparting stress relaxation properties to the adhesive material layer closest to the workpiece and in contact with it. The adhesive layer has the most important function of making the workpiece and the protective sheet for workpiece processing closely adhere to each other. There is no idea of imparting stress relaxation properties to such an adhesive layer.

The inventor of the present invention discovered that by maintaining the original function of the adhesive layer and at the same time providing the adhesive layer with stress relaxation properties described below, the occurrence of large cracks associated with defective workpiece fragmentation can be suppressed.

Hereinafter, the components of the workpiece processing protective sheet 1 shown in FIG. 1A will be described in detail.

(2.Substrate) The base material is the component responsible for the rigidity of the protective sheet used for workpiece processing. The base material is not particularly limited as long as it is made of a material that can support the workpiece. For example, various resin films used as the base material of the back polishing tape can be exemplified. By using such a resin film, even if the thickness of the workpiece becomes thin due to polishing, the workpiece can be retained without being damaged. The base material may be composed of a single-layer film composed of one resin film, or may be composed of a plurality of layers of films in which a plurality of resin films are laminated.

(2.1 Material of base material) In this embodiment, examples of the material of the base material include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and fully aromatic polyester. Polyester, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfide, polyetherketone, biaxially stretched polypropylene, etc. Among these, polyester is preferred, and polyethylene terephthalate is more preferred.

Since the thickness of the base material affects the rigidity of the protective sheet for workpiece processing, it can be set according to the material of the base material. For example, the thickness of the base material can be set so that the physical properties of the workpiece processing protective sheet fall within the range described below. In this embodiment, the thickness of the base material 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.

In order to improve the adhesion with the layer formed on the main surface, at least one main surface of the base material may be subjected to an adhesion treatment such as corona treatment. In addition, in order to improve the adhesion with the layer formed on the main surface, an easy-adhesion layer may be formed on at least one main surface of the base material.

(3. Adhesive layer) The adhesive layer is attached to the surface of the workpiece (ie, the surface where circuits, electrodes, etc. are formed). The adhesive layer has the function of protecting the surface and supporting the workpiece until it is peeled off from the surface.

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

In this embodiment, since the adhesive layer has the following physical properties, the collision between the individual pieces of the workpiece can be alleviated. As a result, the occurrence of cracks, particularly large cracks, in the workpiece fragments caused by collisions between the workpiece fragments can be suppressed.

(3.1. Shear storage modulus of adhesive layer) In this embodiment, the shear storage modulus (G') of the adhesive layer at 55°C is 40,000 Pa or more. When the back side of the workpiece is ground, heat is generated on the grinding surface, and this heat is also conducted to the adhesive layer. As a result, the temperature of the adhesive layer rises from about 50°C to about 60°C, for example. Because the shear storage modulus of the adhesive layer at 55°C is within the above range, a relatively hard adhesive layer can still be maintained when back grinding the workpiece. Therefore, even the shear force exerted on the workpiece during back grinding is transmitted to the adhesive layer, suppressing deformation of the adhesive layer. As a result, the amount of movement of the group of workpiece fragments held by the adhesive layer is reduced, and collisions between the workpiece fragments can be suppressed.

The shear storage modulus of the 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.

From the viewpoint that it is easy to achieve a numerical range that has both the shear storage modulus of the adhesive layer and the numerical range of the shear stress relaxation rate of the adhesive layer described later, the shear storage modulus of the adhesive layer at 55°C, It is preferably 200,000 Pa or less, more preferably 150,000 Pa or less, and still more preferably 100,000 Pa or less.

The shear storage modulus of the adhesive layer at 55°C can be measured in the following manner. First, the material constituting the adhesive layer is used as a measurement sample of a predetermined size. The dynamic viscoelasticity measuring device twists the measurement sample at a predetermined frequency within a predetermined temperature range, applies shear strain to the measurement sample, and measures the modulus of the measurement sample. The shear storage modulus of the adhesive layer at 55° C. was calculated from the measured modulus. Details of the measurement are described in the Examples.

(3.2. Shear stress relaxation rate of adhesive layer) In this embodiment, the shear stress relaxation rate of the adhesive layer at 55°C after 1 second is 30% or more. Grinding the workpiece starts from the time when the workpiece is flaked into multiple workpiece flakes. In the state of connection before flakes and at the time when the workpiece flakes are mixed after flakes, the grinding wheel is used to grind each workpiece individually. The shear force exerted by the flakes may be non-uniform. As mentioned above, due to the high shear storage modulus of the adhesive layer, although the deformation of the adhesive layer due to shear force, etc. can be relatively suppressed, the applied shear force is uneven among the workpiece pieces. , workpiece fragments located in areas where shear forces are temporarily high may deform the adhesive layer. When the shear stress relaxation rate of the adhesive layer at 55°C is not suppressed within the above range, when a temporarily high shear force is no longer applied, the time required to return to the normal state without deformation is short, and the individual adjacent workpieces The flakes tend to collide more strongly with each other. However, by suppressing the shear stress relaxation rate of the adhesive layer at 55°C within the above range, even if the adhesive layer is deformed due to temporarily high shear force, the shear stress can be relaxed in a short time. , when the temporarily high shear force is no longer applied, the time required to return to the normal state without deformation becomes longer. Therefore, it is possible to suppress the acceleration of the group of workpiece fragments held by the adhesive layer and to suppress strong collisions between the workpiece fragments.

The shear stress relaxation rate of the adhesive layer at 55°C is preferably 35% or more, and more preferably 38% or more.

The upper limit of the shear stress relaxation rate of the adhesive layer at 55° C. is not particularly limited as long as it is within a 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 adhesive layer at 55°C is preferably 65%, and more preferably 60%, from the viewpoint of taking into account other physical properties of the adhesive layer.

In this embodiment, the shear stress relaxation rate of the adhesive layer can be measured in the following manner. The material constituting the adhesive layer is used as a measurement sample of a predetermined size. The dynamic viscoelasticity measuring device twists the measurement sample with a temperature of 55°C and applies shear strain to the measurement sample. In this embodiment, the shear stress relaxation rate is calculated from the shear stress after the strain is applied and the shear stress one second after the strain is started to be applied in consideration of the short-time relaxation of the shear stress. Details of the measurement are described in the Examples.

(3.3. Composition of adhesive layer) The adhesive layer is not particularly limited as long as it is composed of an adhesive that satisfies the above physical properties. In this embodiment, the adhesive layer is preferably formed of an energy ray curable adhesive. The adhesive layer of the protective sheet for workpiece processing is formed by energy ray curable adhesive. When it is attached to the workpiece, it adheres to the workpiece with high adhesion. When it is peeled off from the workpiece, it can be peeled off by irradiation. Energy lines reduce adhesion. Therefore, it is possible to appropriately protect the circuits of the workpiece, etc., and at the same time, when peeling off the protective sheet for workpiece processing, it is possible to prevent damage to the circuits, electrodes, etc. on the surface of the workpiece and the adhesion of the adhesive to the workpiece.

As a composition for an adhesive layer constituting an energy ray curable adhesive, for example, a composition containing a non-energy ray curable adhesive resin (also referred to as "adhesive resin I") as a main component and an adhesive resin containing A composition for an energy ray curable adhesive layer that is an energy ray curable compound other than a resin (hereinafter, sometimes referred to as an "X-type adhesive layer composition").

In addition, as the composition for the adhesive layer constituting the energy ray curable adhesive, it is also possible to use an energy ray curable adhesive resin containing an unsaturated group introduced into the side chain of a non-energy ray curable adhesive resin (hereinafter , sometimes called "adhesive resin II"), an energy ray curable adhesive layer composition that does not contain an energy ray curable compound other than the adhesive resin as a main component (hereinafter, sometimes called "Y-type "Composition for adhesive layer").

Furthermore, as the composition for the adhesive layer constituting the energy ray curable adhesive, it is also possible to use a combination of X type and Y type, that is, it contains energy ray curable adhesive resin II as a main component, and also contains adhesive resin II. A composition for an energy ray curable adhesive layer that is an energy ray curable compound other than a flexible resin (hereinafter, sometimes referred to as an "XY type adhesive layer composition").

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

In this embodiment, in order to achieve the physical properties of the adhesive layer described above, it is preferable to use an XY-type adhesive layer composition as the energy ray curable adhesive. By using the XY type, the polymer structure of the adhesive resin II contains a fluid energy-beam curable compound, making it easier to control stress relaxation without affecting the range of the shear storage modulus. Furthermore, it can become easier to achieve: before energy ray hardening, it has sufficient adhesive properties, and after energy ray hardening, the peel strength to the workpiece is fully reduced.

In addition, in the following description, "adhesive resin" is a term used to refer to one or both of the above-mentioned adhesive resin I and adhesive resin II. Specific examples of the adhesive resin include acrylic resin, urethane resin, rubber resin, silicone resin, and the like. In this embodiment, an acrylic adhesive is preferable from the viewpoint of easily controlling the shear storage modulus and the shear stress relaxation rate of the adhesive layer within the above ranges and from the viewpoint of cost reduction.

Hereinafter, an acrylic adhesive using an acrylic resin as the adhesive resin will be described in more detail.

(3.3.1. Acrylic polymer) As the acrylic resin, an acrylic polymer is used. The acrylic polymer is obtained by polymerizing a monomer containing at least (meth)acrylic acid alkyl ester, and contains a structural unit derived from (meth)acrylic acid alkyl ester. As the alkyl (meth)acrylate, the alkyl group may have 1 to 20 carbon atoms, and the alkyl group may be linear or branched. Specific examples of alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-Butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, (meth)acrylate ) Decyl acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, etc. Alkyl (meth)acrylate can be used alone or in combination of two or more types.

In addition, from the viewpoint of improving the adhesive force of the adhesive layer and easily controlling the shear stress relaxation rate of the adhesive layer to the above range, the acrylic polymer is derived from ( The structural unit of alkyl methacrylate is preferred. The carbon number of the (meth)acrylic acid alkyl ester is preferably 4 to 12, and more preferably 4 to 6. In addition, the (meth)acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms is preferably an acrylic acid alkyl ester. Examples of such alkyl acrylate include n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl acrylate.

In an acrylic polymer, the content of alkyl (meth)acrylate with an alkyl group having 4 or more carbon atoms, relative to the total amount of monomers constituting the acrylic polymer (hereinafter sometimes referred to as "the total amount of monomers") )100 parts by mass, preferably 40 to 98 parts by mass, more preferably 45 to 95 parts by mass, further preferably 50 to 90 parts by mass.

Acrylic polymers, in addition to structural units derived from alkyl (meth)acrylate with an alkyl group having 4 or more carbon atoms, can reduce paste residues in the adhesive layer, increase adhesion, and are easy to control. From the viewpoint that the shear storage modulus and shear stress relaxation rate of the adhesive layer are within the above range, it is preferable to use a copolymer containing a structural unit derived from a monomer. When this monomer is polymerized to form a homopolymer, it becomes Polymers with higher glass transition temperatures (Tg). Specifically, when polymerizing to form a homopolymer, monomers with a glass transition temperature of 50°C or above are preferred, monomers with a glass transition temperature of 70°C or above are more preferred, and monomers with a glass transition temperature of 90°C or above, 150°C are preferred. The following monomers are further preferred. Polymer data can be used for the Tg of the homopolymer. The value recorded in the manual (polymer data handbook), adhesive handbook (adhesive handbook), or Polymer Handbook, etc.

Examples of such monomers include dimethacrylamide, methyl methacrylate, acrylomorpholine, and the like. Among these, dimethacrylamide and methyl methacrylate are preferred, and dimethylacrylamide is more preferred.

When the acrylic polymer forms a homopolymer, the content of monomers with a glass transition temperature of 50°C or above is preferably 2 to 40 parts by mass, more preferably 5 to 30 parts by mass relative to 100 parts by mass of the total monomers. parts, preferably 8 to 25 parts by mass.

The acrylic polymer preferably has a structural unit derived from a functional group-containing monomer in addition to the above-mentioned structural units. Examples of the functional group of the functional group-containing monomer include a hydroxyl group, a carboxyl group, an amino group, an epoxy group, and the like. The functional group-containing monomer can react with the cross-linking agent described below to become a cross-linking starting point; it can react with the unsaturated group-containing substance described below to introduce the unsaturated group into the side chain of the acrylic polymer.

Examples of the functional group-containing monomer include hydroxyl group-containing monomers, carboxyl group-containing monomers, amine group-containing monomers, epoxy group-containing monomers, and the like, and these may be used alone or in combination of two or more types. Among these, it is preferable to use a hydroxyl group-containing monomer and a carboxyl group-containing monomer, and it is more preferable to use a hydroxyl group-containing monomer.

Examples of the hydroxyl-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, ( Hydroxyalkyl (meth)acrylate, such as 2-hydroxybutyl methacrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.; vinyl alcohol, allyl alcohol, etc. of unsaturated alcohols, etc.

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

The content of the functional group-containing monomer is preferably 1 to 35 parts by mass, more preferably 3 to 32 parts by mass, and further preferably 6 to 30 parts by mass relative to 100 parts by mass of the total monomers constituting the acrylic polymer. share.

In addition to the above, the acrylic polymer may also contain the above-mentioned acrylic monomers copolymerizable with styrene, α-methylstyrene, vinyl toluene, vinyl formate, vinyl acetate, acrylonitrile, etc. The constituent unit of the monomer.

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 a substance having an energy ray curable group (also referred to as an unsaturated group-containing substance) and a functional group of the above-mentioned non-energy ray curable acrylic polymer. Reaction and bonding.

The unsaturated group-containing substance is a substance that has both a substituent that can be bonded to the functional group of the acrylic polymer and an energy ray curable group. Examples of the energy ray curable group include (meth)acrylyl group, vinyl group, allyl group, vinylbenzyl group, etc., but the (meth)acrylyl group is preferred. In addition, examples of substituents that have an unsaturated group-containing substance and can be bonded to the functional group of the acrylic polymer include an isocyanate group, a glycidyl group, and the like. Therefore, examples of the unsaturated group-containing substance include (meth)acryloxyethyl isocyanate, (meth)acrylyl isocyanate, glycidyl (meth)acrylate, and the like.

In addition, it is preferable that the unsaturated group-containing substance reacts with a part of the functional groups of the acrylic polymer. Specifically, 50 to 98 mol% of the functional groups of the acrylic polymer react with the unsaturated group-containing substance. It is better to react with substances, and it is more preferable that 55 to 93 mol% of the functional groups of the acrylic polymer react with substances containing unsaturated groups. In this way, the energy ray curable acrylic resin becomes easily cross-linked by the cross-linking agent because part of the functional groups remains without reacting with the unsaturated group-containing substance. In addition, the weight average molecular weight (Mw) of the acrylic resin is preferably 300,000 to 1.6 million, more preferably 400,000 to 1.4 million, and further preferably 500,000 to 1.2 million.

(3.3.2. Energy ray hardening compounds) The energy ray curable compound contained in the X-type or XY-type adhesive layer composition is preferably a monomer or oligomer that has an unsaturated group in the molecule and can be polymerized and cured by energy ray irradiation. Examples of such energy ray-curable compounds include trimethylolpropane tri(meth)acrylate, neopentylerythritol (meth)acrylate, neopentylerythritol tetra(meth)acrylate, Polyvalent (methyl) monomers such as dipenterythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate monomers ) Acrylate monomer; oligomers of urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate, etc.

Among these, urethane (meth)acrylate oligomer is preferable from the viewpoint that the molecular weight is relatively high and it is difficult to reduce the shear storage modulus of the adhesive layer. The molecular weight of the energy ray curable compound (in the case of an oligomer, the weight average molecular weight) is preferably 100 to 12,000, more preferably 200 to 10,000, further preferably 400 to 8,000, and particularly preferably 600 to 6,000.

The content of the energy ray curable compound in the X-type adhesive layer composition is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass, and further preferably 60 to 100 parts by mass relative to 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 adhesive layer composition is preferably 4 to 90 parts by mass, more preferably 7 to 50 parts by mass based on 100 parts by mass of the adhesive resin. The optimal amount is 9 to 25 parts by mass. By setting the content of the energy ray curable compound within the above range, it is easier to control the shear stress relaxation rate of the adhesive layer. In addition, in the XY-type adhesive layer composition, since the adhesive resin is energy ray curable, even if the content of the energy ray curable compound is small, the peel strength can be sufficiently reduced after energy ray irradiation.

(3.3.3. Cross-linking agent) From the viewpoint of making it easier to increase the shear storage modulus of the adhesive layer, the composition for the adhesive layer preferably further contains a cross-linking agent. The cross-linking agent, for example, reacts with the functional group of the adhesive resin to cross-link the resins with each other.

Examples of the cross-linking agent include isocyanate-based cross-linking agents (cross-linking agents having an isocyanate group) such as toluene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, and adducts of these diisocyanates; Epoxy cross-linking agents (cross-linking agents with glycidyl groups) such as ethylene glycol glycidyl ether; aziridines such as hexa[1-(2-methyl)-aziridinyl]triazine triphosphate Cross-linking agents (cross-linking agents having an aziridine group); metal chelate-based cross-linking agents (cross-linking agents having a metal chelate structure) such as aluminum chelates (cross-linking agents); urate Cross-linking agents (cross-linking agents with isocyanurate skeleton), etc. These cross-linking agents can be used alone or in combination of two or more types.

From the viewpoint of improving the cohesiveness of the adhesive and reducing the paste residue when peeling off the adhesive layer from individual pieces of the workpiece, from the viewpoint of easily controlling the shear storage modulus of the adhesive layer to rise to the above range, and from the viewpoint of ease of acquisition. It seems that the best cross-linking agent is isocyanate cross-linking agent.

From the viewpoint of promoting the cross-linking reaction, the amount of the cross-linking agent is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and further preferably 0.05 to 4 parts by mass relative to 100 parts by mass of the adhesive resin. parts by mass.

(3.3.4. Photopolymerization initiator) When the composition for an adhesive layer is energy-ray curable, it is preferable that the composition for an adhesive layer further contains a photopolymerization initiator. Since the composition for an adhesive layer contains a photopolymerization initiator, even if it is irradiated with relatively low-energy energy rays such as ultraviolet rays, the curing reaction will fully proceed.

Examples of photopolymerization initiators include photoinitiators such as benzoin compounds, acetophenone compounds, phosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxides; photosensitizers such as amines and quinones; Agents, etc. Specific examples include α-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, benzyl dimethyl ketal, and tetramethylthiuram. Ammonosulfide, azobisisobutyronitrile, dibenzyl, diethyl, β-chloroanthraquinone, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, 2,4, 6-Trimethylbenzoyldiphenylphosphine oxide, etc. These photopolymerization initiators can be used individually or in combination of 2 or more types.

The compounding amount of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and further preferably 0.05 to 5 parts by mass relative to 100 parts by mass of the adhesive resin.

(3.3.5. Other additives) The composition for an adhesive layer may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and the like. When these additives are blended, the blending amount of the additive is preferably 0.01 to 6 parts by mass relative to 100 parts by mass of the adhesive resin.

(3.4. Glass transition temperature of adhesive layer) In this embodiment, the glass transition temperature (Tg) of the adhesive layer is preferably -50°C or more and 30°C or less. As mentioned above, during backside grinding, the workpiece (including a group of workpiece pieces that have been pieced into pieces) is heated to about 50 to 60°C by the grinding heat. Heating is not performed at the same heating rate on the entire surface of the workpiece, but depending on the progress of grinding, uneven temperatures may occur within the grinding surface of the workpiece. Along with this heating, the adhesive layer directly in contact with the workpiece is also heated to the same temperature. On the other hand, when the adhesive layer is composed of an adhesive resin, the physical properties of the adhesive resin tend to change significantly near the glass transition temperature of the adhesive resin.

For example, if the glass transition temperature of the adhesive layer is larger than the above range, the physical properties of the adhesive layer will easily change depending on the progress of back grinding. In particular, if the temperature of the workpiece becomes uneven within the surface as mentioned above, the adhesive layer will The physical properties of the layer also tend to become uneven within the plane. Accompanying this phenomenon, cracks in the workpiece fragments tend to occur more easily. Therefore, in order to prevent the physical properties of the adhesive layer from changing significantly during back grinding, it is best to keep the glass transition temperature of the adhesive layer away from the temperature at which the adhesive layer is heated (50~60°C) during back grinding.

Incidentally, as mentioned above, in this embodiment, for the purpose of reducing the paste residue in the adhesive layer and increasing the adhesive force, the composition for the adhesive layer contains a monomer with a high glass transition temperature that is a homopolymer. good. Therefore, even when the composition for an adhesive layer contains a monomer with a high glass transition temperature as a homopolymer, the glass transition temperature of the adhesive layer is preferably controlled within the above range.

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

The glass transition temperature of the adhesive layer can be measured in the following manner. First, the material constituting the adhesive layer is used as a measurement sample of a predetermined size. The dynamic viscoelasticity measuring device twists the measurement sample at a predetermined frequency within a predetermined temperature range, applies shear strain to the measurement sample, measures the storage modulus and loss modulus of the measurement sample, and calculates the Loss tangent (tanδ). The peak temperature of the measured loss tangent was set as the glass transition temperature (Tg) of the adhesive layer. Details of the measurement are described in the Examples.

In this embodiment, the thickness of the 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 adhesive layer is within the above range, minute movement of the workpiece fragments due to the pressure applied to the workpiece or the workpiece fragments group during polishing can be suppressed. As a result, the probability that individual pieces of the workpiece come into contact with each other is reduced, and the occurrence rate of cracks can be further suppressed.

On the other hand, from the viewpoint that circuits, electrodes, etc. formed on the workpiece are embedded in the adhesive layer, the thickness of the adhesive layer is preferably 10 μm or more.

In addition, the thickness of the adhesive layer refers to the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer composed of a plurality of layers refers to the total thickness of all the layers constituting the adhesive layer.

(4. Physical properties of protective sheets for workpiece processing) In this embodiment, in addition to the physical properties of the adhesive layer described above, the physical properties of the 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 rate is the elongation rate when the tensile load first reaches 30N/15mm after stretching from both ends of the workpiece processing protective sheet.

This parameter assumes that the protective sheet for workpiece processing is attached to the workpiece while applying tension. The environment in which the protective sheet for workpiece processing is attached to the workpiece is usually room temperature, so the elongation rate of the protective sheet for workpiece processing at 23°C is defined as a parameter.

By having the elongation rate of the workpiece processing protective sheet within the above range at 23°C, the tensile stress caused by the tension applied when the workpiece processing protective sheet is attached can suppress the workpiece generated during back grinding. Deformation of protective sheet for processing. As a result, it is possible to suppress the shift of the workpiece pieces due to deformation of the workpiece processing protective sheet.

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

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

(4.2. Tensile stress relaxation rate of protective sheet for workpiece processing) In this embodiment, the tensile stress relaxation rate of the protective sheet for workpiece processing at 23°C is preferably less than 40%. This tensile stress relaxation rate is the stress when the two ends of the protective sheet for workpiece processing are stretched by 10% from the length before stretching, and the stress 1 minute after the stretching is stopped when the stretching is 10%. And the calculated mitigation rate.

When the tensile stress relaxation rate is within the above range, the entire workpiece processing protective sheet is supported and fixed to the adsorption table without deformation during back grinding. As a result, the amount of movement of the workpieces (group of individual workpieces) held by the workpiece processing protective sheet can be suppressed, and cracks caused by collision of the individual workpieces with each other can be suppressed.

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

In addition, the lower limit value of the tensile stress relaxation rate of the workpiece processing protective sheet at 23°C is not particularly limited, but from the viewpoint of the workability and cost of attaching the workpiece processing protective sheet, 5% or more is considered to be Good, more than 10% is better.

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

(5. Buffer layer) In this embodiment, the workpiece processing protective sheet is not limited to the structure shown in FIG. 1A , and may have other layers as long as the effects of the present invention can be obtained. That is, as long as the adhesive layer 20 is arranged on the base material 10, for example, another layer may be formed between the base material 10 and the adhesive layer 20, or in order to protect the adhesive layer 20 until the adhesive layer 20 is attached, On the adherend, a release sheet is arranged on the main surface 20a of the adhesive layer 20.

In particular, in this embodiment, as shown in FIG. 1B , the protective sheet 1 for workpiece processing preferably has a buffer layer 30 in addition to the base material 10 and the adhesive layer 20 . The buffer layer 30 is formed on the main surface 10b opposite to the main surface 10a of the base material on which the adhesive layer 20 is formed.

In addition, the outermost surface of the workpiece processing protective sheet shown in FIGS. 1A and 1B may be formed with a layer that exerts a desired function if necessary.

Compared with the base material, the buffer layer 30 is a soft layer, which can further alleviate the stress generated during back grinding of the workpiece and further prevent cracks from occurring in the workpiece. In addition, when the workpiece with the workpiece processing protective sheet attached is placed on the suction table via the workpiece processing protective sheet during back grinding, it becomes easier by having a buffer layer as a constituent layer of the workpiece processing protective sheet. Keep properly on the adsorption table.

On the other hand, from the viewpoint of reducing the cost of raw materials and reducing the risk of thickness changes caused by increasing the thickness of the constituent layers during the production of the protective sheet for workpiece processing, it is preferable to substantially not have the buffer layer 30 . Substantially absent means that the buffer layer does not exist at all or the thickness is less than 1 μm.

The thickness of the buffer layer is preferably 1 to 100 μm, more preferably 5 to 80 μm, and further 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 back grinding.

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

In addition, the base material having a buffer layer can be obtained by laminating a buffer layer on the base material.

(5.1 Composition for buffer layer) The buffer layer composition containing an energy ray polymerizable compound can be hardened by irradiation with energy rays.

Furthermore, the composition for a buffer layer containing an energy ray polymerizable compound, more specifically, contains urethane (meth)acrylate (d1) and an alicyclic group having 6 to 20 ring atoms or The heterocyclic polymerizable compound (d2) and/or the polyfunctional polymerizable compound (d3) are preferred. In addition, the buffer layer composition may contain, in addition to the above-mentioned components (d1) to (d3), a polymerizable compound (d4) having a functional group. In addition, the composition for a buffer layer may contain a photopolymerization initiator in addition to the above-mentioned components. Furthermore, the composition for a buffer layer may contain other additives, resin components, etc. within the range which does not impair the effect of the present invention.

Each component contained in the composition for a buffer layer containing an energy ray polymerizable compound will be described in detail below.

(5.1.1 Urethane (meth)acrylate (d1)) Urethane (meth)acrylate (d1) refers to a compound having at least a (meth)acryl group and a urethane bond, and has a property of polymerization and hardening 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, further preferably 3,000 to 20,000. In addition, the number of (meth)acrylyl groups (hereinafter also referred to as "the number of functional groups") in component (d1) may be monofunctional, bifunctional, or trifunctional or higher, but monofunctional or bifunctional is preferred. .

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

The content of component (d1) in the buffer layer composition is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and further preferably 25 to 55 parts by mass based on 100 parts by mass of the composition for buffer layer. share.

(5.1.2. Polymeric compounds (d2) having an alicyclic group or heterocyclic group forming a ring number of 6 to 20) Component (b2) is a polymerizable compound having an alicyclic group or a heterocyclic group with 6 to 20 ring atoms, preferably a compound having at least 1 (meth)acrylyl group, more preferably a compound having 1 (meth)acrylyl compound. By using component (d2), the film-forming property of the obtained buffer layer composition can be improved.

In addition, the definition of component (d2) has overlapping parts with the definitions of component (d3) and component (d4) described later, but the overlapping parts are also included in component (d3) or component (d4). For example, compounds having at least one (meth)acrylyl group, a functional group forming an alicyclic group or a heterocyclic group with 6 to 20 ring atoms, a hydroxyl group, an epoxy group, a amide group, an amino group, etc. include In the definitions of both component (d2) and component (d4), in the present invention, this compound is included in component (d4).

Specific components (d2) include, for example, alicyclic group-containing (meth)acrylates such as isocamphenyl (meth)acrylate; heterocyclic group-containing esters such as tetrahydrofurfuryl (meth)acrylate; (meth)acrylate; etc. In addition, component (d2) can be used 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, and further preferably 25 to 55 parts by mass based on 100 parts by mass of the composition for buffer layer. share.

(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 (meth)acrylyl, vinyl, allyl, vinylbenzyl, and the like. Two or more types of energy ray curable bases may be combined. The energy ray curable group in the multifunctional polymerizable compound reacts with the (meth)acrylyl group in the component (d1), and the energy ray curable groups in the component (d3) react with each other to form a three-dimensional network structure (intersection). connection structure). When a multifunctional polymerizable compound is used, compared to a compound containing only one energy ray curable group, the cross-linked structure formed by energy ray irradiation is increased, thereby exhibiting the unique viscoelasticity of the buffer layer. Easier to relieve stress during back grinding.

In addition, the definition of component (d3) has an overlapping part with the definition of component (d4) described later, but the overlapping part is included in component (d3). For example, compounds containing functional groups such as hydroxyl groups, epoxy groups, amide groups, and amine groups, and having two or more (meth)acrylyl groups are included in the definitions of both component (d3) and component (d4). , however, in the present invention, this compound is included in 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.

In addition, the weight average molecular weight of component (d3) is preferably 30 to 40,000, more preferably 100 to 10,000, and further preferably 200 to 1,000.

Specific components (d3) include, for example, diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and neopentyl glycol. Glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, neopentylerythritol tri(meth)acrylate, Neopenterythritol tetra(meth)acrylate, dineopenterythritol hexa(meth)acrylate, divinylbenzene, vinyl (meth)acrylate, divinyl adipate, N,N'- Methylene bis(meth)acrylamide, etc. Among these, neopentyl glycol di(meth)acrylate and dineopenterythritol hexa(meth)acrylate are preferred. In addition, component (d3) can be used individually or in combination of 2 or more types.

The content of the component (d3) in the buffer layer composition is preferably 2 to 40 parts by mass, more preferably 3 to 20 parts by mass, and further preferably 5 to 15 parts by mass based on 100 parts by mass of the composition for buffer layer. share.

(5.1.4 Polymeric compounds with functional groups (d4)) Component (d4) is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, a amide group, an amine group, etc., and further preferably a compound having at least one (meth)acrylyl group, more preferably A compound with one (meth)acrylyl group.

The component (d4) and the component (d1) have good compatibility, and it is easy to adjust the viscosity of the buffer layer composition to an appropriate range. In addition, even if the buffer layer is made thin, the buffering performance is still good.

Examples of the component (d4) include hydroxyl group-containing (meth)acrylate, epoxy group-containing compound, amide group-containing compound, amine group-containing (meth)acrylate, and the like. Among these, hydroxyl-containing (meth)acrylate is preferred.

In order to improve the film-forming property of the buffer layer composition, the content of component (d4) in the buffer layer composition is preferably 5 to 40 parts by mass, and more preferably 7 parts per 100 parts by mass of the buffer layer composition. ~35 parts by mass, preferably 10~30 parts by mass.

(5.1.5 Polymerizable compounds (d5) other than components (d1) ~ (d4)) The composition for forming a buffer layer may contain other polymerizable compounds (d5) other than the above-mentioned components (d1) to (d4) within a range that does not impair the effects of the present invention.

Examples of the component (d5) include alkyl (meth)acrylate having an alkyl group having 1 to 20 carbon atoms; vinyl compounds and the like.

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, and further preferably 0 to 5 parts by mass based on 100 parts by mass of the composition for buffer layer. share.

(5.1.6 Photopolymerization initiator) From the viewpoint of shortening the polymerization time by light irradiation or reducing the amount of light irradiation when forming the buffer layer, the composition for the buffer layer preferably further contains a photopolymerization initiator.

Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, phosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and further, amines, quinones, and the like. More specific examples of photosensitizers include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and the like. These photopolymerization initiators 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, and further preferably 100 parts by mass of the total amount of energy ray polymerizable compounds. 0.3~5 parts by mass.

(5.1.7 Other additives) The buffer layer composition 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, dyes, and the like. When these additives are blended, 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 relative to 100 parts by mass of the total amount of the energy ray polymerizable compound. share.

A buffer layer formed from a buffer layer composition containing an energy ray polymerizable compound can be obtained by polymerizing and curing the buffer layer composition having the above composition by irradiation with energy rays. That is, this buffer layer is made of a hardened composition for the buffer layer.

(6. Manufacturing method of protective sheet for workpiece processing) The method of manufacturing the workpiece processing protective sheet of this embodiment can be a well-known method. For example, a workpiece processing protective sheet having a base material and an adhesive layer formed on one main surface of the base material can be produced in the following manner.

First, as a composition for forming an adhesive layer, for example, a composition for an adhesive layer constituting an adhesive layer is prepared, or a composition in which a composition for an adhesive layer is diluted with a solvent (these two compositions are called "Coating agent for adhesive layer"). The prepared adhesive layer coating agent can be applied to the release surface of the release film and dried as necessary to form an adhesive layer on the release film. Thereafter, one main surface of the base material can be bonded to the adhesive layer to obtain a workpiece processing protective sheet with an adhesive layer formed on one main surface of the base material. Alternatively, the prepared adhesive layer coating agent may be directly applied to one main surface of the base material to form an adhesive layer.

In addition, a workpiece processing protective sheet having a base material, an adhesive layer formed on one main surface of the base material, and a buffer layer formed on the other main surface of the base material can be produced in the following manner.

In the same manner as described above, an adhesive layer coating agent for forming an adhesive layer is prepared. Next, as a composition for forming the buffer layer, for example, a buffer layer composition constituting the buffer layer is prepared, or a composition in which the buffer layer composition is diluted with a solvent (these two compositions are called "buffer layer Use coating agent"). The prepared coating agent for the buffer layer can be applied to the release surface of the release film and dried as necessary to form a coating film on the release film. By curing the coating film (for example, irradiation with energy rays), Form a buffer layer. Thereafter, one main surface of the base material and the buffer layer may be bonded together. If the buffer layer still has energy ray hardening properties, it can be further hardened (for example, by irradiation with energy rays) if necessary.

In addition, the prepared coating agent for the adhesive layer is applied to the release surface of the release film and dried as necessary to form an adhesive layer on the release film. Thereafter, the main surface of the base material on which the buffer layer is not formed is bonded to the adhesive layer, so that an adhesive layer is formed on one main surface of the base material and an adhesive layer is formed on the other main surface of the base material. Buffer layer protective sheet for workpiece processing. Similar to the case of forming the adhesive layer, the buffer layer coating agent may be directly applied to one main surface of the base material to form the buffer layer.

(7. Method for manufacturing workpiece fragments) The protective sheet for workpiece processing of the present invention, as described above, is suitable for the method of singulating workpieces using LDBG.

As a non-limiting use example of the protective sheet for workpiece processing, a method for manufacturing a workpiece into individual pieces (for example, a wafer) using LDBG will be specifically described below.

Specifically, the manufacturing method of individualized workpieces includes at least the following steps 1 to 4. Step 1: Attach the above protective sheet for workpiece processing to the surface of the workpiece; Step 2: The step of forming a modified area inside the workpiece from the surface or back of the workpiece; Step 3: The protective sheet for workpiece processing is attached to the surface, and the workpiece with the modified area is ground from the back side, and the modified area is used as the starting point to separate into multiple workpiece pieces; Step 4: The step of peeling off the protective sheet for workpiece processing from the workpiece that has been individually divided into pieces (that is, a plurality of workpiece pieces). Hereinafter, each step of the manufacturing method of the above-mentioned workpiece into pieces will be described in detail. In the description, a wafer is used as a specific example of a workpiece, and a wafer is used as a specific example of a pieced workpiece.

(step 1) In step 1, the adhesive layer of the workpiece processing protective sheet of this embodiment is attached to the wafer surface. At this time, tension is applied to the workpiece processing protective sheet. However, since the tensile stress relaxation rate of the workpiece processing protective sheet is within the above range, the workpiece processing protective sheet is not deformed during back grinding and is sufficiently fixed to the adsorption table. As a result, movement of the wafer during back grinding can be suppressed, and the occurrence of cracks can be suppressed. This step may be performed after step 2 described below, but from the viewpoint of reducing the risk of unintended wafer singulation when attaching a protective sheet for workpiece processing, it is preferably performed before step 2.

In addition, circuits are formed on the surface of the wafer. The circuits on the wafer surface can be formed by various methods including conventionally widely used methods such as etching and lift-off methods.

The formed circuit may be exposed, or a circuit protection layer may be formed to protect the circuit. In addition, convex electrodes such as bumps and pillars may be formed on the circuit.

(step 2) In step 2, a modified area is formed inside the wafer from the surface or back of the wafer.

The modified area formed in this step is the embrittled portion of the wafer. In the modified area, cracks are easily generated due to the shear force and pressure exerted on the wafer. Such cracks become the starting point for wafer segmentation. That is, the modified region in step 2 is formed along the dividing line when the wafer is divided into individual wafers in step 3 described below.

The modified region is formed by irradiation of laser focused on the inside of the wafer. Therefore, the modified region is formed inside the wafer. Laser irradiation can be performed from the front side or the back side of the wafer. In addition, when step 2 is performed after step 1 and laser irradiation is performed from the surface of the wafer, the wafer is irradiated with laser through a protective sheet for workpiece processing.

The wafer with the protective sheet for workpiece processing attached and the modified area formed thereon is placed on the suction table and held by the suction table. At this time, the surface side of the wafer is arranged on the suction table side via the workpiece processing protective sheet and is suctioned.

(step 3) After steps 1 and 2, grind the backside of the wafer on the adsorption table to separate the wafers into multiple wafers.

Here, backside polishing may be performed until the polishing surface (wafer backside) reaches the modified region, but the polished surface may not strictly reach the modified region. That is, using the modified region as a starting point, in order to obtain individual wafers divided into wafers, the wafer can be polished to a position close to the modified region.

In addition, after back grinding using a grinding wheel, stress relief such as dry polishing can also be performed.

The shape of the individualized wafer may be a square shape or an elongated shape such as a rectangle. In addition, the thickness of the individualized wafers is not particularly limited, but is preferably about 5 to 100 μm, and more preferably 10 to 45 μm. According to LDBG, the thickness of individualized wafers can be easily set to 50 μm or less, and more preferably 10 to 45 μm. In addition, the size of individualized wafers is not particularly limited. For example, the wafer area is preferably less than 600mm ² , more preferably less than 400mm ² , and further preferably less than 120mm ² .

By using the workpiece processing protective sheet of this embodiment, large cracks related to wafer defects can be reduced in the wafer after back grinding (step 3).

(Step 4) Next, the workpiece processing protective sheet is peeled off from the individualized wafers (that is, the wafer group). This step is performed, for example, by the following method.

First, when the adhesive layer of the workpiece processing protective sheet is formed from an energy ray-curable adhesive, energy rays are irradiated to harden the adhesive layer. For example, the illumination intensity of the energy ray is preferably 120~280mW/cm ² and the light intensity of the energy ray is 100~1000mJ/cm ² . As energy rays, ultraviolet rays are preferred. Next, a pick-up tape is attached to the back side of the wafer group, and the position and direction are adjusted in a pick-up manner. At this time, the ring frame located on the outer peripheral side of the wafer is also attached to the pickup tape, and the outer peripheral edge of the pickup tape is fixed to the ring frame. The pick-up tape can attach the wafer to the ring frame at the same time or at different timing points. Next, the workpiece processing protective sheet is peeled off from the plurality of wafers held on the pickup tape.

Thereafter, a plurality of wafers on the pickup tape are picked up. Next, the wafer is fixed on a device substrate or the like to manufacture a device. For example, when the wafer is a semiconductor, the wafer is fixed on a substrate for a semiconductor device or the like to manufacture the semiconductor device.

In addition, the pick-up tape is not particularly limited, but may be, for example, an adhesive sheet including a base material and an adhesive layer provided on one side of the base material.

The embodiments of the present invention have been described above. However, the present invention is not limited to any of the above-described embodiments, and can be modified in various aspects within the scope of the present invention. [Example]

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

The measurement method and evaluation method of this example are as follows.

(shear storage modulus of adhesive layer) In Examples and Comparative Examples described below, the composition for an adhesive layer is used to form an adhesive layer on a release film. By preparing a plurality of adhesive layers formed in this way, peeling off the release films, and combining the peeling surfaces together and laminating them, a laminate of adhesive layers having a thickness of 1 mm was produced.

The obtained laminate of the adhesive layer was punched into a cylindrical shape with a diameter of 8 mm and used as a sample for measuring the shear storage modulus.

The shear storage modulus (G') of the adhesive layer was measured using a rheometer (Rheometer) MCR302 manufactured by Anton Paar. The two ends of the sample in the thickness direction are sandwiched between parallel plates. Under the conditions of measuring temperature -40~100℃, heating rate 3℃/min, gap 1mm, strain 0.05~0.5%, and angular frequency 1Hz, the thickness of the sample is The direction is used as the axis of rotation, the sample is twisted and shear force is applied to the sample, and the shear storage modulus is determined. The shear storage modulus (G') at 55°C was calculated from the obtained measured values. .

(Shear Stress Relaxation Rate of Adhesive Layer) A sample for measuring the shear stress relaxation rate was prepared in the same manner as the sample for measuring the shear storage modulus. The shear stress relaxation rate of the adhesive layer was measured using a rheometer MCR302 manufactured by Anton Paar. Heating the sample, while maintaining 55°C, under the conditions of a gap of 1 mm and an angular frequency of 1 Hz, use the thickness direction of the sample as the axis of rotation, twist the sample, and apply shear stress to the sample until the strain of the sample reaches 5% (angle 18° ) is A ₀ , and while maintaining a strain of 5%, the stress generated after 1 second is A ₁ , and the shear stress relaxation rate is calculated from the following equation. Shear stress relaxation rate={(A ₀ -A ₁ )/A ₀ }×100(%).

(Glass transition temperature (Tg) of adhesive layer) A sample for measuring the glass transition temperature (Tg) was prepared in the same manner as the sample for measuring the shear storage modulus. The glass transition temperature of the adhesive layer was measured using a rheometer MCR302 manufactured by Anton Paar. The two ends of the sample in the thickness direction are sandwiched between parallel plates. Under the conditions of measuring temperature -40~100℃, heating rate 3℃/min, gap 1mm, strain 0.05~0.5%, and angular frequency 1Hz, the sample is Using the thickness direction as the rotation axis, twist the sample and apply shear force to the sample, measure the loss modulus, and calculate the loss tangent tan δ at each temperature using the loss modulus and the above-mentioned shear storage modulus. The peak temperature was confirmed from the obtained table of tan δ at each temperature, and this was set as the glass transition temperature (Tg) of the adhesive layer.

(Elongation rate and tensile stress relaxation rate of protective sheets for workpiece processing) The protective sheets for workpiece processing produced in Examples and Comparative Examples were cut into sizes of 140 mm in length and 15 mm in width to obtain samples for measuring elongation and tensile stress relaxation rates. Using a universal tensile testing device (Autograph (registered trademark) AG-10kNIS manufactured by SHIMADZU Co., Ltd.), clamp both ends of the sample 20 mm in the length direction with clamps (i.e., the initial distance between the clamps is 100 mm), and record the tensile load while , while stretching the sample in the length direction of the sample at a speed of 200mm/min in an environment of 23°C. The elongation of the sample is measured at the time when the tensile load first reaches 30N/15mm.

In addition, the sample is stretched in the length direction of the sample under the above conditions, and the stretching is stopped at the time point when the sample is stretched by 10% (that is, the distance between the clamps is 110 mm). Let the maximum stress be A (N/m ² ) among the stresses from stretching to stopping, and measure the stress B (N/m ² ) after stopping stretching the sample for 1 minute. From the measured values of stresses A and B, the tensile stress relaxation rate is calculated by the following equation. Tensile stress relaxation rate={(AB)/A}×100(%)

(crack occurrence rate) Using a tape laminator for back grinding (RAD-3510F/12 manufactured by Lintec Corporation), a silicon mirror wafer with a diameter of 300 mm and a thickness of 780 μm was used as a workpiece, and the workpiece processing protective sheet produced in the Example and Comparative Example was attached. The attaching temperature is 50℃. Next, a stealth dicing device (manufactured by Disco, DFL7361) is used to perform stealth dicing processing on the wafer to form a grid-shaped modified area. The grid size is 10mm×10mm.

Next, using a back polishing device (DGP8761 manufactured by Disco Corporation), polishing (including dry polishing) was performed until the surface of the wafer in which the modified region was formed, opposite to the surface on which the workpiece processing protective sheet was attached, became 18 μm thick. The wafer is divided into a plurality of wafers to form a wafer group. After the polishing step, in order to easily observe the cracks generated in the wafer, the surface of the wafer group with the workpiece processing protective sheet (that is, the surface to be polished) and the 12-inch ring frame are used. A wafer mounter (RAD-2510F/12, manufactured by Lintec) is attached with a dicing tape (D-175D, manufactured by Lintec).

Next, the protective sheet for workpiece processing is irradiated with energy rays (ultraviolet), and the protective sheet for workpiece processing is peeled off to expose the surface of the wafer (wafer group). Using an infrared camera embedded in a stealth dicing device (DFL7361 manufactured by Disco Corporation), cracks on the wafer from the wafer surface side were observed and counted. The observation range was set to a radius of 145 mm from the center of the wafer (diameter: 290 mm). Using the length of the observed crack as a basis, the classification is as follows. ． A crack with the longest length less than 10 μm is defined as a small crack. ． The longest length of a crack is 10 μm or more and less than 20 μm, which is defined as a medium crack. ． Among the cracks, the longest length is more than 20 μm, which is defined as a large crack.

Using the classified crack types, the crack score is calculated from the following equation. Crack score = 0 × number of small cracks + 1 × number of medium cracks + 10 × number of large cracks. In this example, the case where the crack score is 0 or more and 20 or less is judged as A, the case where the crack score is 21 or more and 40 or less is judged as B, the case where the crack score is 41 or more and 55 or less is judged as C, and the crack score is The situation above 56 is judged as D. Samples A and B are judged to be qualified.

(Example 1) (1)Substrate First, as a base material, a PET film (thickness: 50 μm, Young's modulus at 23° C.: 4000 MPa) with easily adhesive coating layers on both sides was prepared.

(2)Adhesive layer 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) was added 90 equivalents of hydroxyl groups out of the total hydroxyl groups (100 equivalents) of the acrylic polymer are reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy ray curable acrylic copolymer (Mw : About 750,000) (BA/DMAA/HEA(MOI)=52/20/28(90mol%)(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, SHIKOH UT-4332), an energy ray-curable resin, and an isocyanate cross-linked resin were prepared. 1.07 parts by mass of agent (CORONATE L manufactured by TOSOH Co., Ltd.) and 1.4 parts by mass of bis(2,4,6-trimethylbenzyl)phenylphosphine oxide as a photopolymerization initiator were diluted with methyl ethyl ketone to prepare a solid content Coating agent of a composition for an adhesive layer with a concentration of 34% by mass.

(3)Buffer layer (Combined modulation for buffer layer formation) As the energy ray polymerizable compound, 50 parts by mass of urethane acrylate oligomer (CN8888 manufactured by Sartomer Co., Ltd.) (component d1), 40 parts by mass of isocamphenyl acrylate (IBXA) (component d2), and neopentanol were prepared. 10 parts by mass of glycol diacrylate (component d3), and further blended with 2.0 2-hydroxy-2-methyl-1-phenyl-propan-1-one (BASF, Omnirad 1173) as a photopolymerization initiator parts by mass to prepare a buffer layer forming composition.

The above-mentioned composition for forming a buffer layer was applied to the silicone release-treated surface of a release sheet (manufactured by Lintec, SP-PET381031, thickness: 38 μm) to form a coating film. Then, the coating film was irradiated with ultraviolet rays to semi-cure the coating film, thereby forming a semi-cured film of a buffer layer with a thickness of 30 μm.

In addition, the above-mentioned ultraviolet irradiation uses a belt conveyor type ultraviolet irradiation device (manufactured by EYE GRAPHICS, ECS-401GX) and a high-pressure mercury lamp (manufactured by EYE GRAPHICS, H04-L41), with a lamp height of 260mm, an output of 80W/cm, and an illumination of 70mW. /cm ² and the irradiation dose is 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 irradiated from the release sheet side of the semi-cured film again to completely cure the semi-cured film to form a buffer layer with a thickness of 30 μm.

(Production of protective sheets for workpiece processing) The coating agent of the above adhesive layer composition is applied to the silicone release-treated surface of a release sheet (Lintec, SP-PET381031, thickness: 38 μm), and is heated and dried to form an adhesive layer with a thickness of 20 μm on the release sheet. agent layer. The glass transition temperature (Tg) of the adhesive layer is 7.4°C.

Next, a protective sheet for workpiece processing is produced by bonding the adhesive layer of the release sheet with the adhesive layer to the second coating layer of the PET film with the double-sided coating layer. That is, the protective sheet for workpiece processing shown in FIG. 1B is manufactured.

(Example 2) As the acrylic copolymer, the acrylic copolymer obtained below was used, and the addition amount of the isocyanate cross-linking agent (CORONATE L manufactured by TOSOH Co., Ltd.) was changed to 0.27 parts by mass. The method was the same as in Example 1. , to obtain a protective sheet for workpiece processing. The glass transition temperature of the adhesive layer is shown in Table 1.

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) was added to the acrylic acid 70 equivalents of hydroxyl groups out of the total hydroxyl groups (100 equivalents) of the polymer are reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy ray curable acrylic copolymer (Mw: approx. 750,000) (BA/MMA/HEA(MOI)=70/20/10(70mol%)(A-4).

(Example 3) A protective sheet for workpiece processing was obtained in the same manner as in Example 2, except that the added amount of the isocyanate cross-linking agent (CORONATE L manufactured by TOSOH Co., Ltd.) was changed to 0.54 parts by mass. The glass transition temperature of the adhesive layer is shown in Table 1.

(Example 4) A protective sheet for workpiece processing was obtained in the same manner as in Example 2, except that the added amount of the isocyanate cross-linking agent (CORONATE L manufactured by TOSOH Co., Ltd.) was changed to 1.07 parts by mass. The glass transition temperature of the adhesive layer is shown in Table 1.

(Example 5) As the acrylic copolymer, the acrylic copolymer obtained below was used, except that the addition amount of the isocyanate cross-linking agent (CORONATE L manufactured by TOSOH Co., Ltd.) was changed to 0.27 parts by mass, and the same method as in Example 1 was used. Obtain a protective sheet for workpiece processing. The glass transition temperature of the adhesive layer is shown in Table 1.

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) was added to the acrylic acid 70 equivalents of hydroxyl groups out of the total hydroxyl groups (100 equivalents) of the polymer are reacted with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy ray curable acrylic copolymer (Mw: approx. 750,000) (BA/MMA/HEA(MOI)=80/10/10(70mol%)(A-3).

(Example 6) A protective sheet for workpiece processing was produced in the same manner as in Example 1 except that the buffer layer was not formed. The glass transition temperature of the adhesive is shown in Table 1.

(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. The glass transition temperature of the adhesive is shown in Table 1.

(Example 8) A protective sheet for workpiece processing was produced in the same manner as in Example 3 except that the buffer layer was not formed. The glass transition temperature of the adhesive is shown in Table 1.

(Example 9) A protective sheet for workpiece processing was produced in the same manner as in Example 4 except that the buffer layer was not formed. The glass transition temperature of the adhesive is shown in Table 1.

(Example 10) A protective sheet for workpiece processing was produced in the same manner as in Example 5 except that the buffer layer was not formed. The glass transition temperature of the adhesive is shown in Table 1.

(Comparative example 1) As the acrylic copolymer, the acrylic copolymer obtained below was used, and the method was the same as in Example 1 except that the addition amount of the isocyanate cross-linking agent (CORONATE L manufactured by TOSOH Co., Ltd.) was changed to 0.27 parts by mass. , to obtain a protective sheet for workpiece processing. The glass transition temperature of the adhesive layer is shown in Table 1.

An acrylic polymer obtained by copolymerizing 90 parts by mass of n-butyl acrylate (BA) and 10 parts by mass of 2-hydroxyethyl acrylate (HEA) was added to the total hydroxyl groups (100 equivalents) of the acrylic polymer. In the form of 70 equivalents of hydroxyl groups, it reacts with 2-methacryloyloxyethyl isocyanate (MOI) to obtain an energy-beam curable acrylic copolymer (Mw: about 750,000) (BA/HEA(MOI)=90 /10(70mol%)(A-2).

(Comparative example 2) A protective sheet for workpiece processing was obtained in the same manner as in Example 1, except that the acrylic copolymer obtained below was used as the acrylic copolymer. The glass transition temperature of the adhesive layer is shown in Table 1.

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) was added to The energy ray curable acrylic copolymer (Mw: About 750,000) (BA/MMA/HEA(MOI)=85/5/10(70mol%)(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 added amount of the isocyanate cross-linking agent (CORONATE L manufactured by TOSOH Co., Ltd.) was changed to 4 parts by mass. The glass transition temperature of the adhesive is shown in Table 1.

(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 base material was changed to 20 μm. The glass transition temperature of the adhesive is shown in Table 1.

The above-described measurement and evaluation were performed on the obtained samples (Examples 1 to 10 and Comparative Examples 1 to 4). The results are shown in Table 1.

[Table 1]

From Table 1, it can be confirmed that when the shear storage modulus and shear stress relaxation rate of the adhesive and the elongation of the protective sheet for workpiece processing are within the above ranges, even if the wafer is singulated by LDBG , it is difficult to generate large cracks related to wafer defects (ie, defective workpiece individualization).

1: Protective sheet for workpiece processing 10:Substrate 10a: Main side 10b: Main side 20: Adhesive layer 20a: Main side 30: Buffer layer 100:Artifact 100a: Surface 100b: back

FIG. 1A is a schematic cross-sectional view showing an example of the protective sheet for workpiece processing according to this embodiment. 1B is a schematic cross-sectional view showing another example of the protective sheet for workpiece processing according to this embodiment. FIG. 2 is a schematic cross-sectional view showing how the protective sheet for workpiece processing according to this embodiment is attached to the workpiece.

1: Protective sheet for workpiece processing

10:Substrate

20: Adhesive layer

20a: Main side

Claims (6)

A protective sheet for workpiece processing, which is a protective sheet for workpiece processing having a base material and an adhesive layer arranged on one main surface of the base material, The shear storage modulus of the adhesive layer at 55°C is more than 40,000 Pa, and the shear stress relaxation rate of the adhesive layer after 1 second at 55°C is more than 30%. After the tensile load is started to be applied to the workpiece processing protective sheet at 23° C., the elongation rate of the workpiece processing protective sheet when the tensile load reaches 30 N/15 mm is 2.5% or less. The protective sheet for workpiece processing according to claim 1, wherein a buffer layer is provided on the other main surface of the base material. The protective sheet for workpiece processing according to claim 1 or 2, wherein the tensile stress relaxation rate of the protective sheet for workpiece processing after 1 minute at 23°C is less than 40%. The protective sheet for workpiece processing according to any one of claims 1 to 3, wherein the adhesive layer is composed of an energy ray curable acrylic adhesive, The aforesaid acrylic adhesive includes a polymer bonded with an energy ray curable group to an acrylic polymer, and an energy ray curable compound. The protective sheet for workpiece processing according to any one of claims 1 to 4, wherein in the step of grinding the back surface of the workpiece with a modified area formed therein, the workpiece is divided into individual workpiece pieces, and affixed Used on the surface of the workpiece. A method for manufacturing workpiece fragments, which has the following steps: The step of attaching the protective sheet for workpiece processing as described in any one of claims 1 to 5 to the surface of the workpiece; The step of forming a modified area inside the workpiece from the surface or back of the workpiece; The step of attaching the protective sheet for workpiece processing to the surface and grinding the workpiece on which the modified area is formed from the back side, and using the modified area as a starting point to separate into multiple workpiece pieces; The step of peeling off the protective sheet for workpiece processing from the pieced workpiece.