TW202338964A - Protective sheet for workpiece processing and method for manufacturing divided workpiece capable of reducing TTV of the workpiece after back grinding - Google Patents

Abstract

The present invention provides a protective sheet for workpiece processing capable of reducing TTV of the workpiece after back grinding. The protective sheet for workpiece processing has a support material and an adhesive layer arranged on a main surface of the support material. The other main surface of the support material forms the outermost surface of the protective sheet for workpiece processing. The dynamic friction coefficient between the outermost surface of the protective sheet for workpiece processing and 1200-grit sandpaper is 1.40 or less, and the tensile fracture stress of the supporting material is 250 MPa or less.

Description

Method for manufacturing protective sheet for workpiece processing and individualized workpieces

The present invention relates to a protective sheet for workpiece processing and a method for manufacturing individual workpiece pieces. In particular, the present invention relates to a protective sheet for workpiece processing that can reduce the TTV of a workpiece after back-grinding, and a method of manufacturing a pieced workpiece using the protective sheet for workpiece processing.

A wafer on which a circuit is formed, such as a semiconductor wafer, is obtained by dicing a workpiece such as a wafer on which a plurality of circuits are formed, and is obtained in the form of a pieced workpiece. With the rapid development of miniaturization and multi-functionality of electronic devices equipped with such chips, chips are also required to be miniaturized, low-profile, and high-density. In order to make the wafer smaller and lower in height, usually after a circuit is formed on the surface of the workpiece, the backside of the workpiece is ground to make the wafer thinner.

When back-grinding a workpiece, a protective sheet called a back-grinding tape is attached to the surface of the workpiece in order to temporarily protect the circuit on the surface of the workpiece and to hold the workpiece in place.

The surface of the workpiece is formed with a protective film for protecting the circuit, a bump electrode for electrically connecting the wafer and the electrode on the substrate, and other protruding electrodes, thereby creating a level difference on the surface of the workpiece.

Since the protective sheet attached to the surface of the workpiece follows the shape of the surface of the workpiece, the protective sheet also reflects this height difference. If the back surface of the workpiece is ground while the level difference is generated, the pressure applied to the workpiece during grinding will become uneven on the grinding surface, resulting in uneven thickness of the polished workpiece.

The difference between the maximum value of the thickness of the ground workpiece and the minimum value of the thickness of the ground workpiece is called the total thickness variation (TTV), which is regarded as a standard for the thickness accuracy of the ground workpiece. When the thickness of the polished workpiece is uneven, there are problems such as the TTV becoming larger, cracks easily occurring in the workpiece, and problems occurring when the workpiece is separated into individual pieces.

Regarding this problem, Patent Documents 1 and 2 describe that after attaching an adhesive sheet to the surface of a semiconductor wafer, polishing the outermost surface of the adhesive sheet, and then polishing the back surface of the semiconductor wafer, the polished semiconductor wafer The thickness accuracy therefore becomes good. [Prior art documents] [Patent Document]

[Patent Document 1]: Japanese Patent No. 4261260 [Patent Document 2]: Japanese Patent Application Publication No. 2014-175334

[Technical problem to be solved by this invention]

In Patent Documents 1 and 2, the tensile elastic modulus of the outermost surface of an adhesive sheet to be polished before back polishing of a semiconductor wafer is set within a predetermined range.

However, the inventor of the present application found that the TTV of a workpiece does not depend on the tensile elastic modulus of the outermost surface of the protective sheet attached to the workpiece, but depends on other parameters. That is, the inventors of the present application found that the kinetic friction coefficient and tensile fracture stress of the outermost surface to be ground affect the TTV of the workpiece more than the tensile elastic modulus of the outermost surface of the protective sheet.

The present invention was made in view of this actual situation, and an object thereof is to provide a workpiece processing protective sheet that can reduce the TTV of the workpiece after back-grinding. Furthermore, the object is to provide a method of manufacturing a workpiece into individual pieces by using the protective sheet for workpiece processing. [Technical means to solve technical problems]

The scheme of the present invention is as follows.

(1) A protective sheet for workpiece processing, which has a support material and an adhesive layer arranged on one main surface of the support material, wherein, The other main surface of the support material constitutes the outermost surface of the protective sheet for workpiece processing. The dynamic friction coefficient between the outermost surface of the protective sheet for workpiece processing and the 1200-grit sandpaper is 1.40 or less. The tensile fracture stress of the support material is below 250MPa.

(2) The protective sheet for workpiece processing according to (1), wherein the support material is composed of two or more layers.

(3) The protective sheet for workpiece processing according to (2), wherein the support material has a rigid layer and a soft layer softer than the rigid layer, and one main surface of the soft layer constitutes the outermost surface of the protective sheet for workpiece processing.

(4) The protective sheet for workpiece processing according to any one of (1) to (3), wherein the protective sheet for workpiece processing is based on the step of grinding the back surface of the workpiece having a front surface and a back surface. The surface is bonded to the adhesive layer and the outermost surface of the workpiece processing protective sheet is ground.

(5) The protective sheet for workpiece processing according to (4), which is used for a workpiece in which a groove is formed on the surface of the workpiece or a modified region is formed in the interior of the workpiece. The step of grinding the back side of the workpiece into individual workpiece pieces.

(6) The protective sheet for workpiece processing according to any one of (1) to (5), wherein the adhesive layer is energy ray curable.

(7) A method for manufacturing workpiece fragments, which has: The step of bonding the adhesive layer of the workpiece processing protective sheet described in any one of (1) to (6) to the surface of the workpiece having a front surface and a back surface; The step of grinding the back side of the workpiece; and The step of dicing a workpiece to obtain multiple pieces of the workpiece.

(8) The method for manufacturing a pieced workpiece according to (7), further comprising: polishing the outermost surface of the workpiece processing protective sheet according to (4) or (5). , The step of grinding the back surface of the workpiece is performed after the step of grinding the outermost surface of the protective sheet for workpiece processing.

(9) The method for manufacturing a pieced workpiece according to (7) or (8), which further includes the step of forming a groove on the surface of the workpiece, or forming a modification inside the workpiece from the surface or back of the workpiece. regional steps, In the step of grinding the back surface of the workpiece, the workpiece is flaked into a plurality of workpiece flakes starting from the groove or the modified area.

(10) The method for manufacturing a pieced workpiece according to any one of (7) to (9), further comprising: peeling off a protective sheet for workpiece processing from the pieced workpiece. [Effects of the invention]

According to the present invention, it is possible to provide a workpiece processing protective sheet that reduces the TTV of the workpiece after back-grinding. Furthermore, according to the present invention, it is possible to provide a method of manufacturing a workpiece into individual pieces by using the protective sheet for workpiece processing.

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

The workpiece refers to a plate-shaped body that is individually divided after the protective sheet for workpiece processing of this embodiment is attached. Examples of workpieces include circular wafers (including those with orientation planes), strips (rectangular substrates) on which rectangular panel-level packaging and molded resin sealing are implemented, and the like. Among them, the above effects are easily obtained. Starting from the perspective, the best wafer. The wafer may be, for example, a silicon wafer, a gallium arsenide wafer, a silicon carbide wafer, a gallium nitride wafer, an indium phosphide wafer and other semiconductor wafers; a glass wafer, a lithium tantalate wafer, or a lithium niobate wafer. It may be an insulator wafer such as a round, or a reconstituted wafer composed of resin and semiconductor used in the production of fan-out packages and the like. From the viewpoint of easily obtaining the above effects, the wafer is preferably a semiconductor wafer or an insulator wafer, and a semiconductor wafer is more preferred.

The individualization of workpieces refers to dividing the workpieces according to circuits to obtain individual workpieces. For example, when the workpiece is a wafer, the individualized workpiece is a wafer, and when the workpiece is a strip (rectangular substrate) that has been subjected to panel level packaging or molded resin sealing, the individualized workpiece is a semiconductor package. .

The "surface" of the workpiece refers to the surface on which circuits, electrodes, etc. are formed, and the "backside" of the workpiece refers to the surface on which circuits, etc. are not formed. The electrode may be a bump-shaped electrode such as a bump.

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

In addition, LDBG is a modification of DBG, which uses laser to set up a fragile modified area inside the workpiece (such as a wafer), and cracks starting from the modified area are caused by the stress during back grinding of the workpiece. Develop a method for individualizing workpieces.

The "workpiece individualized object group" refers to a plurality of workpiece individualized objects held on the workpiece processing protective sheet of this embodiment after the workpiece is fragmented. As a whole, these workpiece fragments form the same shape as the workpiece. In addition, the "wafer set" refers to a plurality of wafers held on the workpiece processing protective sheet of this embodiment after the wafers as workpieces are separated into pieces. As a whole, these wafers form the same shape as the wafer.

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

"Energy ray" refers to ultraviolet rays, electron beams, etc., preferably ultraviolet rays.

Unless otherwise stated, "weight average molecular weight" is a polystyrene-converted value measured by gel permeation chromatography (GPC). Measurement based on this method is performed as follows: For example, a high-speed GPC device "HLC-8120GPC" manufactured by TOSOH CORPORATION is used, and high-speed chromatography columns "TSK guard column H _XL -H" and "TSK Gel GMH _XL" are connected in this order. ", "TSK Gel G2000 _H conduct.

The release sheet is a sheet that supports the adhesive layer releasably. The sheet does not define the thickness, but is used as a concept including the film.

The mass ratio in the description of compositions such as adhesive layer compositions is based on the ratio of active ingredients (solid content), and solvents are not included unless otherwise stated.

(1. Protective sheet for workpiece processing) The protective sheet for workpiece processing is used when processing a workpiece with circuits etc. formed on one side (surface) and no circuits etc. formed on the other side (back surface). As the processing of the workpiece, for example, backside grinding of the workpiece can be exemplified. By grinding the back surface of the workpiece, the individual workpieces obtained by dicing the workpiece can be made thinner.

The protective sheet for workpiece processing is attached to the surface of the workpiece before backside grinding. The surface of the workpiece may be the surface on which the circuit is exposed, or it may be the main surface of a protective layer formed on the circuit to protect the circuit. In addition, convex electrodes such as bumps can be formed on the circuit. Therefore, a level difference usually occurs on the surface of the workpiece due to elements formed on the surface of the workpiece.

As a result, this level difference is also reflected in the workpiece processing protective sheet attached to the surface of the workpiece. After being attached to the workpiece, the protective sheet for workpiece processing is adsorbed to a grinding table such as a chuck table, and the back side of the workpiece is ground. If a height difference occurs on the protective sheet for workpiece processing, the workpiece is processed. By creating a gap between the protective sheet and the chuck table, the force applied during back grinding may not be transmitted evenly to the workpiece. As a result, areas where polishing is sufficiently performed and areas where polishing is insufficient are generated on the back surface of the workpiece. This difference in the degree of grinding will lead to uneven thickness of the workpiece after grinding. That is, since there are areas where the thickness of the polished workpiece is thick and areas where the thickness of the polished workpiece is thin, there is a tendency for the TTV after polishing to become larger.

As described above, if the TTV becomes large, cracks may easily occur in the workpiece, and problems may occur when the workpiece is separated into pieces.

As described above, regarding this problem, a method of improving the TTV by polishing the outermost surface of the workpiece processing protective sheet attached to the workpiece is known. In this method, the tensile elastic modulus of the outermost surface portion of the workpiece processing protective sheet is set within a predetermined range.

However, the inventor of the present application focused on the dynamic friction coefficient and tensile fracture stress of the outermost surface of the protective sheet for workpiece processing, and found that by setting these parameters to the optimal state, it would have a good influence on the back grinding of the workpiece, thereby It can reduce the TTV of the workpiece after back grinding.

Hereinafter, the protective sheet for workpiece processing of this embodiment will be described in detail.

As shown in FIG. 1A , the protective sheet 1 for workpiece processing according to this embodiment has a support material 10 and an adhesive layer 20 arranged on the support material 10 . Furthermore, as shown in FIG. 2 , the main surface 20 a of the adhesive layer 20 of the workpiece processing protective sheet 1 is attached to the surface 100 a of the workpiece 100 (for example, a wafer).

In the workpiece processing protective sheet 1 of the present embodiment, before grinding the back surface 100 b of the workpiece 100 , the main surface of the supporting material 10 of the workpiece processing protective sheet 1 is ground opposite to the main surface 10 a on which the adhesive layer 20 is arranged. 10b. Therefore, the main surface 10b constitutes the outermost surface of the workpiece processing protective sheet 1.

(1.1. Support materials) The support material is a member that supports the adhesive layer. After the workpiece processing protective sheet is attached to the workpiece, the support material is a member that supports the workpiece. Therefore, the preferred support material is rigid. In this embodiment, the support material has the following physical properties.

(1.2. Dynamic friction coefficient) In this embodiment, the dynamic friction coefficient between the main surface of the support material constituting the outermost surface of the workpiece processing protective sheet and the 1200-grit sandpaper is 1.40 or less. The coefficient of kinetic friction is the proportional coefficient of the kinetic friction force acting on the contact surface in the opposite direction to the direction of motion when two objects move relative to each other in contact. If the coefficient of kinetic friction is large, it means that the force that stops the moving object is large. The sandpaper is assumed to be a grinding means (for example, a grinding wheel) for grinding the main surface of the supporting material, and the dynamic friction coefficient is an index of the resistance to the grinding means for grinding the main surface of the supporting material.

By setting the dynamic friction coefficient within the above range, the outermost surface of the workpiece processing protective sheet does not adhere to the polishing means, and the outermost surface can be appropriately polished, thereby improving the smoothness of the polished outermost surface. If the back surface of the workpiece is polished after appropriately performing the polishing of the outermost surface, the back surface of the workpiece can also be appropriately polished, and the TTV of the polished workpiece can be reduced. In particular, even when the adhesive layer is relatively soft, the outermost surface can be polished appropriately.

The dynamic friction coefficient is preferably 1.38 or less, more preferably 1.35 or less, further preferably 1.30 or less. In addition, from the viewpoint of enabling grinding with a grinding wheel, the dynamic friction coefficient is preferably 0.1 or more.

The above-mentioned dynamic friction coefficient can be measured by a known method. For example, measured according to JIS K 7125. That is, the measurement method is the same as the measurement method specified in JIS K 7125, but the measurement conditions may be different. Specific measurement methods will be described in the Examples.

(1.3. Tensile breaking stress) In this embodiment, the tensile fracture stress of the support material is 250 MPa or less. Tensile fracture stress is the stress when the sample is continuously stretched to cause the sample to break. Tensile breaking stress is an indicator of whether a support material is susceptible to grinding.

By setting the tensile fracture stress within the above range, the outermost surface of the workpiece processing protective sheet can be easily polished, the outermost surface can be appropriately polished, and the smoothness of the polished outermost surface can be improved. If the back surface of the workpiece is polished after the uppermost surface is polished appropriately, the back surface of the workpiece can also be appropriately polished, and the TTV of the polished workpiece can be reduced. In particular, even when the adhesive layer is relatively soft, the outermost surface can be polished appropriately.

In addition, as will be described later, when the support material is composed of two or more layers, the above-mentioned tensile rupture stress is the tensile rupture stress of the outermost layer constituting the workpiece processing protective sheet.

The tensile breaking stress is preferably 240 MPa or less, more preferably 230 MPa or less. In addition, from the viewpoint of preventing breakage of the supporting material during production, the tensile breaking stress is preferably 1 MPa or more.

The above tensile breaking stress can be measured by a known method. For example, it is measured based on JIS K 7161:1994 and JIS K 7127:1999. That is, the measurement is performed in the same manner as the measurement method specified in JIS K 7161:1994 and JIS K 7127:1999, but the measurement conditions may be different. Specific measurement methods will be described in the Examples.

(1.4. Structure of supporting materials) The structure of the supporting material is not particularly limited as long as the supporting material has the above physical properties. Hereinafter, a case where the supporting material is composed of one layer and a case where the supporting material is composed of two or more layers will be described.

(1.5. When the supporting material consists of one layer) When the supporting material is composed of one layer, in addition to satisfying the above-mentioned physical properties, the supporting material needs to be composed of a material that can support and maintain the adhesive layer and the workpiece during processing of the workpiece. Therefore, when the supporting material is composed of one layer, it is preferable that the tensile fracture stress of the supporting material is within the above range and the rigidity is high.

Examples of the material of the support material when the support material is composed of one layer include polyethylene terephthalate, polybutylene terephthalate, polyimide, polyamide, low-density Polyethylene, high density polyethylene, biaxially stretched polypropylene, etc. Among them, polyethylene terephthalate is preferred. On the other hand, when the supporting material is composed of one layer, the material of the supporting material is preferably polyethylene naphthalate, polycarbonate, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl Acrylic copolymer, etc. In addition, the above-mentioned examples are general examples, and even if they are made of the same material, the physical properties of the above-mentioned supporting material can be satisfied by the manufacturing method.

(1.6. When the supporting material is composed of two layers) In this embodiment, the supporting material is preferably composed of two or more layers. When the supporting material is composed of two or more layers, it is preferable that the supporting material has a rigid layer and a soft layer. In this case, it is preferable that the main surface of the soft layer constitutes the outermost surface of the workpiece processing protective sheet 1 . For example, as shown in FIG. 1B , the support material 10 is composed of a rigid layer 11 and a soft layer 12 , and the main surface 12 b of the soft layer 12 constitutes the outermost surface of the workpiece processing protective sheet 1 . In addition, as shown in FIG. 1C , the support material 10 is composed of a rigid layer 11 , a first soft layer 12 and a second soft layer 13 . The main surface 12 b of the first soft layer 12 constitutes the outermost surface of the workpiece processing protective sheet 1 .

(1.6.1. Rigid layer) The rigid layer is a layer that bears the rigidity of the supporting material, and is not limited as long as it is made of a material that can support the adhesive layer and the workpiece. For example, various resin films used as the base material of the back-grinding tape can be exemplified. By using this resin film, even if the thickness of the workpiece becomes thin due to polishing, the workpiece can be held without damaging it. The rigid layer may be composed of a single-layer film composed of one resin film, or may be composed of a multi-layered film in which a plurality of resin films are laminated.

In this embodiment, examples of materials for the rigid layer include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and fully aromatic polyester. and other polyesters; polyamide, polycarbonate, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polypropylene, polyetherketone, biaxially stretched polypropylene, etc. Among them, polyester is preferred, and polyethylene terephthalate is more preferred.

The thickness of the rigid layer is not particularly limited, but since the thickness of the rigid layer affects the rigidity of the workpiece processing protective sheet, it may be set according to the material of the rigid layer. In this embodiment, the thickness of the rigid layer is preferably from 10 μm to 200 μm, more preferably from 15 μm to 150 μm, and even more preferably from 20 μm to 130 μm.

In order to improve the adhesion with the layer formed on the main surface, at least one main surface of the rigid layer may be subjected to an adhesion treatment such as corona treatment. In addition, in order to improve the adhesion with a layer (for example, a soft layer) formed on the main surface, an easy-adhesion layer may be formed on at least one main surface of the rigid layer.

(1.6.2. Soft layer) The soft layer is made of softer material than the rigid layer. In this embodiment, the soft layer is preferably the outermost layer of the supporting material constituting the protective sheet for workpiece processing. That is, after the protective sheet for workpiece processing is attached to the surface of the workpiece, the soft layer is polished before polishing the back surface of the workpiece. The reason for this is that a relatively soft material can more easily satisfy the physical properties of the support material than a relatively hard material.

(1.6.3 Material of soft layer) In this embodiment, the soft layer may be composed of a soft resin film, or may be formed using a soft layer composition containing an energy ray curable compound.

Examples of the soft resin film include resin films such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), biaxially stretched polypropylene, and urethane acrylate. Among them, resin films such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polyurethane acrylate are preferred. On the other hand, as the soft resin film, ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, vinyl chloride, etc. are not suitable. In addition, the above-mentioned examples are general examples, and even if they are made of the same material, the physical properties of the above-mentioned supporting material can be satisfied by the manufacturing method.

(1.6.4. Composition for soft layer) In this embodiment, a preferred soft layer composition includes: urethane (meth)acrylate (d1); a polymerizable compound having an alicyclic group or a heterocyclic group with 6 to 20 ring atoms. (d2); and/or a polyfunctional polymerizable compound (d3). In addition to the above-mentioned components (d1) to (d3), the composition for soft layer may further contain a polymerizable compound (d4) having a functional group. In addition to the above-mentioned components, the composition for soft layer may also contain a photopolymerization initiator. In addition, the composition for a soft layer may contain other additives or resin components within the range which does not impair the above-mentioned effects.

Hereinafter, each component contained in the composition for a soft layer containing an energy ray curable compound will be described in detail.

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

The weight average molecular weight (Mw) of 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 is preferably monofunctional or bifunctional. Senses.

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

In 100 parts by mass of the composition for soft layer, the content of component (d1) in the composition for soft layer 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. share.

(1.6.4.2. Polymeric compounds (d2) having an alicyclic group or heterocyclic group with 6 to 20 ring atoms) Component (d2) is a polymerizable compound having an alicyclic group or a heterocyclic group with 6 to 20 ring atoms. In addition, it is preferably a compound having at least one (meth)acrylyl group, and more preferably has one (Meth)acrylyl compound. By using component (d2), the film-forming property of the obtained composition for soft layers can be improved.

In addition, the definition of component (d2) has an overlapping portion with the definitions of components (d3) and (d4) described later, but the overlapping portion is included in component (d3) or component (d4). For example, compounds having at least one (meth)acrylyl group, an alicyclic group or a heterocyclic group with 6 to 20 ring atoms, and functional groups such as a hydroxyl group, an epoxy group, a amide group, and an amino group are included in the ingredients. in the definition of both (d2) and ingredient (d4), but in this embodiment the compound is deemed to be included in ingredient (d4).

Specific components (d2) include, for example, alicyclic group-containing (meth)acrylates such as isobornyl (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.

In 100 parts by mass of the composition for soft layer, the content of component (d2) in the composition for soft layer 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. share.

(1.6.4.3. 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 groups may be combined. It is formed by reacting the energy ray curable group in the polyfunctional polymerizable compound with the (meth)acrylyl group in the component (d1) or reacting the energy ray curable groups in the component (d3) with each other. Three-dimensional network structure (cross-linked structure). If a polyfunctional polymerizable compound is used, the cross-linked structure formed by energy ray irradiation increases compared to the case of using a compound containing only one energy ray curable group, so the soft layer exhibits special viscoelasticity, and ultimately The surface's dynamic friction coefficient and tensile fracture stress tend to be in appropriate states.

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), In this embodiment, however, the compound is considered to be included in ingredient (d3).

From the above point of view, the number of energy-ray curable groups (number of functional groups) in the multifunctional 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. Alcohol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, neopentylerythritol tri(meth)acrylate, new Pentaerythritol tetra(meth)acrylate, dineopenterythritol hexa(meth)acrylate, divinylbenzene, vinyl (meth)acrylate, divinyl adipate, N,N'-extension Methyl bis(meth)acrylamide, etc. Among them, 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.

In 100 parts by mass of the composition for a soft layer, the content of the component (d3) in the composition for a soft layer 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. share.

(1.6.4.4 Polymerizable compounds with functional groups (d4)) Component (d4) is a polymerizable compound containing functional groups such as a hydroxyl group, an epoxy group, a amide group, and an amine group. In addition, it is preferably a compound having at least one (meth)acrylyl group, and more preferably a compound having one (meth)acrylyl group. base) acrylyl compound.

The component (d4) and the component (d1) have good compatibility, and it is easy to adjust the viscosity of the composition for soft layer within an appropriate range. In addition, even if the soft layer is made relatively thin, the cushioning performance is 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 them, hydroxyl-containing (meth)acrylate is preferred.

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

(1.6.4.5 Polymerizable compounds (d5) other than ingredients (d1) ~ (d4)) The soft layer forming composition may contain other polymerizable compounds (d5) other than the above-mentioned components (d1) to (d4) within a range that does not impair the above-mentioned effects.

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

In 100 parts by mass of the composition for a soft layer, the content of the component (d5) in the composition for a soft layer 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. share.

(1.6.4.6 Photopolymerization initiator) From the viewpoint of shortening the polymerization time by light irradiation and reducing the amount of light irradiation when forming the soft layer, the composition for the soft 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 photosensitizers such as amines and quinones. More specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and the like. These photopolymerization initiators can be used alone or in combination of two or more types.

The content of the photopolymerization initiator in the composition for soft layer is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and still more preferably 0.3, based on 100 parts by mass of the total amount of energy ray curable compounds. ~5 parts by mass.

(1.6.4.7 Other additives) The composition for a soft layer may contain other additives within the range which does not impair the above-mentioned effects. 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 composition for the soft layer 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 curable compound. share.

A soft layer formed from a soft layer composition containing an energy ray curable compound is obtained by polymerizing and curing the soft layer composition having the above composition by irradiation with energy rays. That is, the soft layer is obtained by curing the composition for a soft layer.

The thickness of the soft layer is not particularly limited, but is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 90 μm or less, further preferably 15 μm or more and 80 μm or less.

(2. Adhesive layer) The adhesive layer is attached to the surface of the workpiece (that is, the surface on which circuits, electrodes, etc. are formed), 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 may be composed 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, the adhesive layer is not particularly limited as long as it has appropriate pressure-sensitive adhesiveness at normal temperature. The thickness of the adhesive layer is not particularly limited, but is preferably from 5 μm to 200 μm, more preferably from 10 μm to 190 μm.

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.

There is no limit to the composition of the adhesive layer as long as it has adhesiveness that can protect the surface of the workpiece. In this embodiment, the adhesive layer is preferably composed of, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, or the like.

In addition, the adhesive layer is preferably formed of an energy ray-curable adhesive. By forming the adhesive layer of the protective sheet for workpiece processing from an energy ray-curable adhesive, it can adhere to the workpiece with high adhesion when it is attached to the workpiece, and can be irradiated with energy rays when peeled off from the workpiece. Reduce adhesion. Therefore, the circuits of the workpiece, etc. are appropriately protected, and when the protective sheet for workpiece processing is peeled off, the circuits, electrodes, etc. on the surface of the workpiece are prevented from being damaged, and the adhesive is prevented from adhering to the workpiece. That is, since the adhesive layer is energy-ray curable, the workpiece processing protective sheet has good peelability.

In this embodiment, the energy ray-curable adhesive is preferably composed of an adhesive composition containing an acrylic adhesive. Acrylic adhesives contain acrylic polymers.

The acrylic polymer may be a known acrylic polymer, but in this embodiment, it is preferably a functional group-containing acrylic polymer. The acrylic polymer containing functional groups can be a homopolymer formed from one acrylic monomer, a copolymer formed from a variety of acrylic monomers, or a copolymer formed from one or more acrylic monomers and acrylic monomers. Copolymers formed from monomers other than monomers.

In this embodiment, the functional group-containing acrylic polymer is preferably an acrylic copolymer obtained by copolymerizing an alkyl (meth)acrylate and a functional group-containing monomer.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and (meth)acrylate. )n-butyl acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethyl (meth)acrylate Hexyl ester, isooctyl (meth)acrylate, n-octyl (meth)acrylate, etc.

Functional group-containing monomers are monomers containing reactive functional groups. The reactive functional group is a functional group capable of reacting with other compounds such as a cross-linking agent described below. Examples of the functional group in the functional group-containing monomer include a hydroxyl group, a carboxyl group, and an epoxy group, and a hydroxyl group is preferred.

Examples of the hydroxyl-containing monomer include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Ester, (meth)hydroxyalkyl acrylate such as 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; vinyl alcohol, allyl Non-(meth)acrylic unsaturated alcohols such as alcohol (unsaturated alcohols that do not have a (meth)acryl skeleton).

The acrylic polymer is more preferably one obtained by reacting (for example, an addition reaction) an energy-ray-curable substance having an energy-ray-curable group with a functional group of the acrylic polymer and having an energy-ray-curable group. Energy ray curable acrylic polymer. The energy ray curable substance having an energy ray curable group preferably has one or more compounds selected from an isocyanate group, an epoxy group, and a carboxyl group in addition to the energy ray curable group, and more preferably Preferred are compounds having an isocyanate group. The isocyanate group may undergo an addition reaction with the hydroxyl group of the functional group-containing acrylic polymer.

Examples of the compound having an isocyanate group include 2-methacryloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, methacrylyl isocyanate, and allyl isocyanate. 1,1-(bisacrylyloxymethyl)ethyl isocyanate; an acrylyl monoisocyanate compound obtained by the reaction of a diisocyanate compound or a polyisocyanate compound and hydroxyethyl (meth)acrylate; by diisocyanate Compounds or acryl monoisocyanate compounds obtained by the reaction of polyisocyanate compounds, polyol compounds and hydroxyethyl (meth)acrylate, etc.

A preferred adhesive composition contains an energy ray curable compound in addition to the acrylic polymer. As the energy ray curable compound, a monomer or oligomer which has an unsaturated group in the molecule and can be polymerized and cured by energy ray irradiation is preferred.

Examples of such energy ray curable compounds include trimethylolpropane tri(meth)acrylate, neopentylerythritol (meth)acrylate, neopentylerythritol tetra(meth)acrylate, and dimethacrylate. Neopenterythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol (meth)acrylate and other poly(meth)acrylate monomers , urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate and other oligomers.

Among them, urethane (meth)acrylate oligomer is preferred.

The molecular weight (weight average molecular weight in the case of an oligomer) of the energy ray curable compound 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 adhesive composition is preferably 5 to 100 parts by mass, more preferably 10 to 70 parts by mass, and further preferably 15 to 40 parts by mass relative to 100 parts by mass of the acrylic polymer. .

The adhesive composition preferably further contains a cross-linking agent. The crosslinking agent reacts with a functional group, for example, to crosslink resins contained in the functional group-containing acrylic polymer.

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, xylylene diisocyanate, and adducts of these diisocyanates; B Epoxy cross-linking agents such as glycol glycidyl ether (cross-linking agents with glycidyl groups); aziridine cross-linking agents such as hexa[1-(2-methyl)-aziridinyl] triphosphate triphosphate agent (cross-linking agent with aziridine group); metal chelate cross-linking agent such as aluminum chelate (cross-linking agent with metal chelate structure); isocyanurate cross-linking agent (with Cross-linking agent with isocyanuric acid skeleton), etc.

From the perspective of improving the cohesion of the adhesive and thereby improving the adhesion of the adhesive layer and being easily available, the cross-linking agent is preferably an isocyanate cross-linking agent.

The adhesive composition may further contain a photopolymerization initiator. By including a photopolymerization initiator in the adhesive composition, the curing reaction can fully proceed even if low-energy energy rays such as ultraviolet rays are irradiated.

Examples of the photopolymerization initiator include the photopolymerization initiators described in the composition for soft layers.

(3. Method of manufacturing protective sheet for workpiece processing) The method of manufacturing the workpiece processing protective sheet of this embodiment may be a known method.

First, prepare the support material. When the supporting material is composed of one layer, a resin film or the like constituting the supporting material may be prepared. When the support material is composed of two or more layers, for example, a resin film constituting the rigid layer and a resin film constituting the soft layer are laminated to produce the support material.

An example of a method of laminating a resin film is to laminate another resin film (for example, a resin film constituting a soft layer) via an easy-adhesion layer formed on one main surface of the resin film (for example, a resin film constituting a rigid layer). The dry lamination method of laminating resin film).

In the dry lamination method, a resin film having an easy-adhesion layer can be used, or a resin film in which an easy-adhesion layer-forming composition is applied to a surface that has been subjected to an adhesion treatment such as corona treatment to form an easy-adhesion layer can be used. .

In addition, for example, the resin constituting the soft layer is melted and kneaded using a T-molding film molding machine, the resin film constituting the rigid layer is moved at a constant speed, and the molten resin is extruded from one side of the resin film. And the method of lamination. In addition, a method of directly laminating the resin film constituting the soft layer on the resin film constituting the rigid layer by heat sealing or the like can be exemplified.

In addition, when a soft layer is formed on one main surface of the rigid layer using a composition for a soft layer, a composition for a soft layer or a composition in which the composition for a soft layer is diluted with a solvent is prepared (this is The two compositions are called "coating agents for soft layers"). The prepared coating agent for the soft layer is coated on the peeling surface of the release film, dried as necessary to form a coating film on the release film, and the coating film is cured (for example, irradiated with energy rays). This enables the formation of a soft layer. Then, attach one main surface of the rigid layer to the soft layer. If the soft layer still has energy ray curability, it may be further cured (for example, irradiated with energy rays) if necessary.

After the support material is produced, as the composition for forming the adhesive layer, for example, a composition for an adhesive layer constituting the adhesive layer is prepared, or a composition in which the composition for an adhesive layer is diluted with a solvent (the composition for the adhesive layer is diluted with a solvent). These two compositions are called "coating agents for adhesive layers"). The prepared adhesive layer coating agent is applied to the release surface of the release film, and dried as necessary to form an adhesive layer on the release film. Then, the main surface on the opposite side of the main surface of the support material and the adhesive layer are bonded so that the dynamic friction coefficient with the sandpaper is controlled within the above range, thereby obtaining a workpiece processing device with an adhesive layer formed on one main surface of the support material. Protective sheet. Alternatively, the prepared coating agent for the adhesive layer may be directly coated on the main surface of the supporting material on the opposite side to the main surface whose dynamic friction coefficient with the sandpaper is controlled within the above range to form an adhesive layer.

(4. Method for manufacturing workpiece fragments) As described above, the protective sheet for workpiece processing of this embodiment is suitable for back grinding of a workpiece in which a circuit or the like is formed on one surface (front surface) and no circuit or the like is formed on the other surface (back surface). When performing back grinding or After back-grinding, the workpiece is flaked to obtain a plurality of flaked workpieces (group of flaked workpieces).

As a non-limiting use example of a protective sheet for workpiece processing, a method for manufacturing a workpiece piece (for example, a wafer) will be specifically described below.

Specifically, the manufacturing method of the workpiece fragments preferably has at least the following steps 1 to 4: Step 1: The step of attaching the above-mentioned protective sheet for workpiece processing to the surface of the workpiece having a front surface and a back surface; Step 2: The step of grinding the main surface of the support material that constitutes the outermost surface of the protective sheet for workpiece processing; Step 3: The step of grinding the back side of the workpiece; Step 4: The step of dicing the workpiece into pieces to obtain multiple pieces of the workpiece.

Hereinafter, each step of the manufacturing method of the above-mentioned workpiece flakes will be described in detail. In the description, a wafer is used as a specific example of the workpiece, and a wafer is used as a specific example of the workpiece piece.

(4.1. Step 1) In step 1, as shown in FIG. 2, the main surface 20a of the adhesive layer of the workpiece processing protective sheet 1 of this embodiment is attached to the wafer surface 100a. By attaching the protective sheet for workpiece processing to the surface of the wafer, the surface of the wafer is fully protected.

The thickness of the wafer used in this manufacturing method before polishing is not particularly limited, but is usually about 500 to 1000 μm. In addition, circuits are formed on the surface of the wafer. Circuits can be formed on the wafer surface by various methods including etching, lift-off and other conventional methods.

The formed circuit may be exposed, or a circuit protection layer may be formed to protect the circuit. The circuit protective layer is usually formed by applying a composition constituting the circuit protective layer and thermally curing the composition. In addition, convex electrodes such as bumps and pillars may also be formed in the circuit.

(4.2. Step 2) Step 2 follows step 1. In step 2, as shown in FIG. 3, the main surface 10b (12b) constituting the outermost surface of the workpiece processing protective sheet 1 among the support materials is polished. The main surface constituting the outermost surface of the workpiece processing protective sheet is the main surface 10b in the workpiece processing protective sheet shown in FIG. 1A, and the main surface 12b in the workpiece processing protective sheet shown in FIGS. 1B and 1C.

From the perspective of efficiency and simplification of step 2, the device used for polishing is preferably a polishing device that performs backside polishing of the wafer. In such a polishing device, as shown in FIG. 3 , the back surface 100 b side of the wafer 100 is held on the card in such a manner that the grinding wheel 50 faces the main surface 10 b ( 12 b ) constituting the outermost surface of the workpiece processing protective sheet 1 . on the disk workbench 60. Next, the grinding wheel 50 is brought into contact with the wafer 100 and the workpiece processing protective sheet 1 while relatively rotating, and the main surface 10 b ( 12 b ) is ground using the abrasive grains of the grinding wheel 50 .

Since the main surface of the support material constituting the outermost surface of the workpiece processing protective sheet has the above-mentioned physical properties, the main surface is easily polished during grinding and is less likely to adhere to the grinding wheel. As a result, the main surface can be appropriately polished to obtain a surface with few irregularities.

(4.3. Step 3) In step 3, as shown in FIG. 4, the main surface 10b (12b) of the support material ground in step 2 is held on the chuck table 60, and then the backside 100b of the wafer 100 is ground using the grinding wheel 50. The main surface 10b (12b) of the support material ground in step 2 has few irregularities, so there is almost no gap formed between the support material of the workpiece processing protective sheet 1 and the chuck table 60. Therefore, the force applied during backside grinding is evenly transmitted to the backside 100b of the wafer 100, and the backside 100b of the wafer 100 is polished uniformly. As a result, the thickness variation of the polished wafer is small, and the TTV of the polished wafer can be reduced.

(4.4. Step 4) In step 4, the wafer is divided into individual wafers to obtain a plurality of wafers (wafer groups). The individualization of the wafer can be performed after step 3 or during step 3.

When wafers are to be separated into individual wafers after step 3, for example, the adsorption between the support material and the chuck table is released, and the wafer is transported to the dicing step in a state where the workpiece processing protective sheet and the wafer are bonded. In the dicing step, the wafer is sliced into multiple wafers. As a method of individualizing, a known method can be used. For example, there can be exemplified a method of forming a groove penetrating the front and back surfaces of the wafer using a rotary blade such as a dicing machine, thereby cutting the wafer to obtain a plurality of individual wafers.

In this embodiment, step 4 is preferably a step of individualizing by DBG or LDBG. In this case, step 4 is performed in step 3.

When singulating by DBG or LDBG, in addition to the above-mentioned steps 1 to 4, there is also a step of forming a groove from the surface side of the workpiece (step 5a), or forming a groove from the surface or back side of the workpiece. The step of forming a modified area inside the workpiece (step 5b).

(4.5. Step 5a) Step 5a is performed before steps 1 to 3. The trench formed in step 5a is a trench with a depth shallower than the thickness of the wafer. The trenches can be formed by dicing using a conventionally known wafer dicing device or the like. This trench becomes the starting point for wafer segmentation. That is, trenches are formed along the dividing lines when the wafer is divided into individual wafers in step 3.

(4.6. Step 5b) Step 5b occurs before step 3. In addition, step 5b may be performed before step 1 and step 2, may be performed after step 1 and before step 2, or may be performed after step 1 and step 2. In this embodiment, step 5b is preferably performed after step 1 and step 2.

The modified area formed in step 5b is the embrittled portion of the wafer. In the modified area, cracks are likely to occur due to the shear force and pressure exerted on the wafer during back grinding. Such cracks become the starting point for wafer segmentation. That is, the modified region is formed along the dividing lines when the wafer is divided into wafers in step 3.

The modified area is formed by irradiating a 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 performing step 5b after step 1 and irradiating the laser from the surface of the wafer, the laser is irradiated to the wafer through the protective sheet for workpiece processing.

After step 5a or step 5b, proceed to step 3. That is, after trenches or modified areas are formed in the wafer, the back surface of the wafer is polished to separate the wafer into multiple wafers. In other words, proceed to step 4 in step 3.

In step 3 after step 5a, back grinding is performed in such a manner that the wafer is thinned to at least the bottom of the trench. By this back grinding, the trenches become incisions penetrating the wafer, and the wafer is divided by the incisions and separated into individual wafers.

In step 3 after step 5b, 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, it is sufficient to grind the wafer to a position close to the modified region so that the wafer is divided using the modified region as a starting point to obtain individualized wafers. For example, the wafer can be polished to a position close to the modified region, and the wafer can be completely singulated by cracks generated in the modified region. Alternatively, a part of the wafer may be singulated by using cracks generated in the modified region, and then a pick-up tape described below may be attached and then the pick-up tape may be stretched, thereby completely singulating the wafer. In addition, the wafer can be completely singulated by stretching the pickup tape.

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

The shape of the wafer that has been sliced through the four steps can be square, or it can be 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, it is easy to set the thickness of individual wafers to 50 μm or less, and it is more preferable to set it to 10 to 45 μm. In addition, the size of individualized wafers is not particularly limited. For example, the chip area is preferably less than 600mm ² , more preferably less than 400mm ² , and further preferably less than 120mm ² .

(4.7. Step 6) In this embodiment, the method for manufacturing a pieced workpiece preferably includes the step of peeling off a protective sheet for workpiece processing from the pieced workpiece (that is, a plurality of pieced workpieces) (step 6). Step 6 follows step 4. Step 6 is performed, for example, by the following method.

First, when the adhesive layer of the workpiece processing protective sheet is formed of an energy ray-curable adhesive, a step of irradiating energy rays to solidify the adhesive layer is performed (step 6a). As described above, step 6a is a step of reducing the adhesive force of the adhesive layer by irradiating energy rays. By performing step 6a, the protective sheet for workpiece processing can be peeled off from the surface of the wafer that has been fully protected by the adhesive force of the adhesive layer in steps 1 to 5, and at the same time, the damage to the circuits, electrodes, etc. on the surface of the workpiece can be suppressed, and the adhesive can be suppressed. Attached to the work piece.

On the other hand, since the energy ray-curable adhesive layer is cured by irradiation with energy rays, it is preferable to polish the back surface of the wafer and improve the thickness accuracy of the polished wafer. The adhesive layer is harder when grinding the back.

That is, there is a trade-off relationship between the thickness accuracy of the polished wafer and the peelability when peeling off the protective sheet for workpiece processing.

In this embodiment, even if the curable adhesive layer is not cured or the non-curable adhesive layer is relatively soft, since the main surface of the support material constituting the outermost surface of the workpiece processing protective sheet has the above physical properties, the main surface is The surface will be properly ground to obtain a surface with less unevenness. As a result, even if the adhesive layer is relatively soft, the TTV of the polished wafer can be reduced. That is, it is possible to achieve both thickness accuracy of the polished wafer and peelability when peeling off the protective sheet for workpiece processing.

Therefore, step 6a can be performed after step 1, step 2, or step 5b, but is preferably performed after step 3.

Regarding the conditions when irradiating energy rays, for example, the preferred illumination intensity of energy rays is 120~280mW/cm ² and the light amount of energy rays is 100~1000mJ/cm ² . As the energy ray, ultraviolet rays are preferred.

After the adhesive layer is cured, pick-up tape is attached to the back side of the multiple workpiece pieces to align the position and direction so that they can be picked up. At this time, the annular frame located on the outer peripheral side of the wafer is also bonded to the pickup tape, and the outer peripheral edge of the pickup tape is fixed to the annular frame. The wafer and ring frame can be bonded to the pick-up tape at the same time or at different points in time. Next, the workpiece processing protective sheet is peeled off from the plurality of wafers held on the pickup tape.

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

The present embodiment has been described above. However, the present invention is not limited to the above-described embodiment and may be modified in various ways 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 in this example are as follows.

(dynamic friction coefficient between support material and sandpaper) The support materials produced in Examples and Comparative Examples were cut into sizes of 200 mm in length and 80 mm in width to obtain measurement samples for measuring the dynamic friction coefficient. The measurement sample is placed on 1200-grit sandpaper, and a sliding piece with a side length of 63 mm and a felt contact surface with the measuring sample is placed on the measurement sample. Further, the total mass of the measuring sample and the sliding piece is Place a weight on the slide for 1000g. Pull the measurement sample along the length direction of the measurement sample at a speed of 100 mm/min. Regardless of the load when the measurement sample starts to move, the relative offset movement between the contact surface of the measurement sample and the sandpaper will The average value of the load from the beginning to the time of movement of 60 mm is used as the dynamic friction force. The kinetic friction coefficient is calculated by dividing the resulting kinetic friction force by the normal force due to the combined mass of the sliding plate and weight. The results are shown in Table 1.

(tensile fracture stress of support material) The support materials prepared in Examples and Comparative Examples were cut into a size of 140 mm in length and 15 mm in width to obtain a measurement sample for measuring tensile fracture stress. Labels for film stretching were attached to the 20 mm portions of both ends of the obtained measurement sample to prepare a sample with a measurement object portion of 15 mm × 100 mm. For this sample, a tensile testing machine (manufactured by Shimadzu Corporation, device name "Autograph AG-IS 1kN") was used to measure the tensile breaking stress under the conditions of a clamp distance of 100 mm and a tensile speed of 200 mm/min. The results are shown in Table 1. In addition, in Examples 1 to 3 and 5 and Comparative Examples 1, 3 and 4 in which the support material is composed of two or more layers, the soft layer, which is the outermost layer constituting the workpiece processing protective sheet, was measured as the tensile fracture stress. tensile breaking stress.

(TTV evaluation of polished wafers) In Examples 1 to 4 and Comparative Examples 1 to 4, a tape laminator for back grinding (manufactured by LINTEC Corporation, device name "RAD-3510F/12") was used to process the workpieces produced in the Examples and Comparative Examples. The protective sheet is attached to a silicon wafer with a diameter of 12 inches and a thickness of 775 μm. Next, a grinder (manufactured by DISCO Corporation, device name "DGP8760") was used to grind the outermost surface of the workpiece processing protective sheet to 12 μm.

Next, a back polishing device (manufactured by DISCO Corporation, device name "DGP8761") was used to perform polishing (including dry polishing) until the thickness became 30 μm.

In Example 5, as described above, a protective sheet for workpiece processing was attached to the silicon wafer, and after grinding the outermost surface of the protective sheet for workpiece processing to 12 μm, a laser cutting machine (manufactured by DISCO Corporation, device name "DFL7361" "), a modified area is formed on the wafer with a grid size of 10mm × 10mm. Next, as described above, the wafer is back-polished until the thickness becomes 30 μm, and the wafer is divided into multiple wafers.

A wafer thickness mapping system (manufactured by Hamamatsu Photonics K.K., device name "C8870-02") is used to measure the thickness of the wafer at a measurement pitch of 10 mm over the entire surface of the polished wafer or multiple individual wafers. The TTV of the polished wafer is calculated based on the maximum thickness and the minimum thickness, and evaluated based on the following criteria. The results are shown in Table 1. ◎: The outermost surface of the protective sheet for workpiece processing can be ground, and the TTV is less than 5 μm. ○: The outermost surface of the protective sheet for workpiece processing can be polished, and the TTV is 5 μm or more and less than 10 μm. ×: The outermost surface of the protective sheet for workpiece processing can be polished, and the TTV is 10 μm or more ××: The outermost surface of the protective sheet for workpiece processing cannot be ground.

(Example 1) (1)Supporting material First, as a rigid layer, a polyethylene terephthalate (PET) film (thickness: 50 μm) is prepared.

Next, low-density polyethylene is melted, the melt is extruded by the T-die method, and the extrudate is biaxially stretched using a cooling roll to obtain an LDPE film with a thickness of 25 μm (tensile elastic modulus: 420 MPa). . On one side of the prepared PET film, an easy-adhesion layer with a thickness of 2.5 μm was provided, and the obtained LDPE film was laminated as a soft layer by a dry lamination method. Next, an easy-adhesion layer with a thickness of 2.5 μm was formed on the other side of the PET film, and the obtained LDPE film as a soft layer was laminated by a dry lamination method to obtain a laminated rigid layer and a soft layer. The support material consists of three layers: soft layer/rigid layer/soft layer. The thickness of the support material is 105 μm.

(2)Adhesive layer (Preparation of composition for adhesive layer) An acrylic polymer obtained by copolymerizing 65 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA) and 15 parts by mass of 2-hydroxyethyl acrylate (2HEA) and 2- Methacryloyloxyethyl isocyanate (MOI) reacts to add 80 equivalents of hydroxyl groups out of the total hydroxyl groups (100 equivalents) of the acrylic polymer, thereby obtaining an energy-ray curable acrylic copolymer (Mw : 500,000).

To 100 parts by mass of this energy ray-curable acrylic copolymer, 10 parts by mass of a polyfunctional urethane acrylate ultraviolet curable compound (manufactured by Mitsubishi Chemical Corporation, product name "UT-4332") was blended. , 0.38 parts by mass of an isocyanate cross-linking agent (manufactured by TOSOH CORPORATION, product name "Coronate L"), 1 part by mass of phenylbis(2,4,6-trimethylbenzoyl) as a photopolymerization initiator ) phosphine oxide was diluted with methyl ethyl ketone to prepare a coating agent of a composition for an adhesive layer having a solid content concentration of 34% by mass.

(Production of protective sheets for workpiece processing) The coating agent of the adhesive layer composition obtained above was applied to the silicone release-treated surface of a release sheet (manufactured by LINTEC Corporation, trade name "SP-PET381031"), and heated and dried to form a 20 μm-thick layer on the release sheet. adhesive layer.

Then, a soft layer of the support material and an adhesive layer are bonded together to create a protective sheet for workpiece processing. That is, the workpiece processing protective sheet shown in FIG. 1C is manufactured.

(Example 2) The workpiece processing protective sheet shown in FIG. 1B was produced in the same manner as in Example 1, except that a support material composed of two layers of soft layer/rigid layer was produced in the following manner.

As a rigid layer, a PET film (thickness: 50 μm) was prepared. Next, a soft layer composition for forming a soft layer is prepared in the following manner.

First, the terminal isocyanate urethane prepolymer obtained by reacting polyester diol and isophorone diisocyanate is reacted with 2-hydroxyethyl acrylate to obtain a bifunctional amine with a weight average molecular weight (Mw) of 5000 Ethyl formate acrylate oligomer (UA-1).

As the energy ray curable compound, 50 parts by mass of the above-synthesized urethane acrylate oligomer (UA-1), 45 parts by mass of isobornyl acrylate (IBXA), and 5 parts by mass of poly Ethylene glycol 600 diacrylate was further blended with 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins, product name "OMNIRAD 1173") as a photopolymerization initiator to prepare a composition for a soft layer.

The above-described composition for soft layer was applied to the silicone release-treated surface of a release sheet (manufactured by LINTEC Corporation, 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 soft layer having a thickness of 55 μm.

In addition, a conveyor-type ultraviolet irradiation device (manufactured by EYE GRAPHICS Co., Ltd., ECS-401GX) and a high-pressure mercury lamp (manufactured by EYE GRAPHICS Co., Ltd., H04-L41) were used, with a lamp height of 260mm and an output of 80W/ cm, the illumination intensity is 70 mW/cm ² , and the irradiation dose is 30 mW/cm ² , the above-mentioned ultraviolet irradiation is performed. Then, the surface of the formed semi-cured film was bonded to one main surface of the PET film as a rigid layer, and ultraviolet rays were irradiated again from the release sheet side of the semi-cured film to completely cure the semi-cured film, forming a soft 55 μm thick film. layer.

(Example 3) In the support material composed of three layers: soft layer/rigid layer/soft layer, linear low density polyethylene (LLDPE) was formed into a soft layer with a thickness of 25 μm. The same method as in Example 1 was used. , manufacturing the protective sheet for workpiece processing shown in Figure 1C. LLDPE is obtained by melting linear low-density polyethylene, extruding the melt using the T-die method, and biaxially stretching the extrudate using a cooling roll. The tensile elastic modulus of LLDPE is 90MPa.

(Example 4) A protective sheet for workpiece processing was manufactured in the same manner as in Example 1, except that a support material composed of a layer of PET film (manufactured by Toray Advanced Materials Co., Ltd., product name "XG7PH8", thickness: 50 μm) was used. That is, the protective sheet for workpiece processing shown in FIG. 1A is manufactured.

(Example 5) A protective sheet for workpiece processing was produced in the same manner as in Example 2.

(Comparative example 1) In the supporting material composed of two layers of soft layer/rigid layer, except that the soft layer composition shown below was used to form the soft layer, the same method as in Example 2 was used to produce the support material shown in FIG. 1B Protective sheet for workpiece processing.

The terminal isocyanate urethane prepolymer obtained by reacting polycarbonate diol and isophorone diisocyanate is reacted with 2-hydroxyethyl acrylate to obtain urethane with a weight average molecular weight (Mw) of about 25,000 Acrylate oligomer (UA-2).

As the energy ray curable compound, 25 parts by mass of the above-synthesized urethane acrylate oligomer (UA-2), 65 parts by mass of isobornyl acrylate (IBXA), and 10 parts by mass of acrylic acid were blended. Phenyl hydroxypropyl ester (HPPA) was further blended with 2.0 parts by mass of 2-hydroxy-2-methyl-1-phenyl-propan-1-one as a photopolymerization initiator (manufactured by IGM Resins, product name " Omnirad 1173"), a composition for preparing a soft layer.

(Comparative example 2) A protective sheet for workpiece processing was manufactured in the same manner as in Example 4, except that a support material composed of a layer of polyethylene naphthalate (PEN) film (thickness: 50 μm) was used.

(Comparative example 3) In the support material composed of three layers: soft layer/rigid layer/soft layer, the colorless and transparent ethylene-methacrylic acid copolymer was formed into a soft layer with a thickness of 25 μm. The same method as in Example 1 was used. The method shown in Figure 1C is used to manufacture the protective sheet for workpiece processing.

(Comparative example 4) In the support material composed of three layers: soft layer/rigid layer/soft layer, the same process as in Example 1 was performed except that a colorless and transparent ethylene-vinyl acetate copolymer was formed into a soft layer with a thickness of 25 μm. The method shown in Figure 1C is used to manufacture the protective sheet for workpiece processing.

The above-described measurement and evaluation were performed on the obtained samples (Examples 1 to 5 and Comparative Examples 1 to 4). The results are shown in Table 1.

[Table 1] support material Evaluation constitute dynamic friction coefficient Tensile fracture stress of the outermost layer (MPa) TTV of polished wafer Example 1 Soft layer/rigid layer/soft layer 1.09 11 ◎ Example 2 Soft layer/rigid layer 1.27 twenty four ◎ Example 3 Soft layer/rigid layer/soft layer 1.11 17 ◎ Example 4 first floor 0.69 220 ○ Example 5 Soft layer/rigid layer 1.27 twenty four ◎ Comparative example 1 Soft layer/rigid layer 1.44 61 ×× Comparative example 2 first floor 0.68 270 ×× Comparative example 3 Soft layer/rigid layer/soft layer 1.46 28 ×× Comparative example 4 Soft layer/rigid layer/soft layer 1.56 16 ××

It was confirmed from Table 1 that when the dynamic friction coefficient between the support material and the sandpaper and the tensile fracture stress of the support material are within the above ranges, by polishing the main surface of the outermost surface of the workpiece processing protective sheet in the support material , perform back-grinding on the wafer, and the TTV of the wafer after back-grinding is small.

1: Protective sheet for workpiece processing 10: Support material 11: Rigid layer 12:Soft layer 20: Adhesive layer

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. 1C is a schematic cross-sectional view showing another example of the protective sheet for workpiece processing according to this embodiment. 2 is a schematic cross-sectional view for explaining the step of bonding the workpiece processing protective sheet and the workpiece according to this embodiment. 3 is a schematic cross-sectional view for explaining the step of grinding the outermost surface of the protective sheet for workpiece processing of the protective sheet for workpiece processing according to this embodiment. 4 is a schematic cross-sectional view for explaining the step of grinding the back surface of the workpiece according to the protective sheet for workpiece processing according to this embodiment.

1: Protective sheet for workpiece processing

10: Support material

11: Rigid layer

12:Soft layer

12b: Main side

13:Soft layer

20: Adhesive layer

20a: Main side

Claims (10)

A protective sheet for workpiece processing, which has a support material and an adhesive layer arranged on one main surface of the support material, wherein: The other main surface of the support material constitutes the outermost surface of the protective sheet for workpiece processing, and the dynamic friction coefficient between the outermost surface of the protective sheet for workpiece processing and the 1200-mesh sandpaper is 1.40 or less, The tensile fracture stress of the support material is below 250 MPa. The protective sheet for workpiece processing according to claim 1, wherein, The support material is composed of two or more layers. The protective sheet for workpiece processing as described in claim 2, wherein, The support material has a rigid layer and a soft layer that is softer than the rigid layer, and one main surface of the soft layer constitutes the outermost surface of the workpiece processing protective sheet. The protective sheet for workpiece processing according to any one of claims 1 to 3, wherein, The protective sheet for workpiece processing is such that before the step of grinding the back surface of the workpiece having a front surface and a back surface, the surface of the workpiece is bonded to the adhesive layer, and the outermost surface of the protective sheet for workpiece processing is ground. method to use. The protective sheet for workpiece processing as described in claim 4, wherein, The protective sheet for workpiece processing is used to grind the back surface of a workpiece having grooves formed on the surface of the workpiece or a modified region formed inside the workpiece, thereby dividing the workpiece into individual pieces. The step of individualizing the workpiece. The protective sheet for workpiece processing according to any one of claims 1 to 5, wherein, The adhesive layer is energy ray curable. A method for manufacturing workpiece fragments, which has: The step of bonding the adhesive layer of the workpiece processing protective sheet as described in any one of claims 1 to 6 to the surface of the workpiece having a front surface and a back surface; the step of grinding the back side of said workpiece; and The step of dicing the workpiece into pieces to obtain a plurality of diced workpieces. The method for manufacturing a pieced workpiece according to claim 7, further comprising the step of grinding the outermost surface of the protective sheet for workpiece processing according to claim 4 or 5, The step of grinding the back surface of the workpiece is performed after the step of grinding the outermost surface of the workpiece processing protective sheet. The method for manufacturing a pieced workpiece according to claim 7 or 8, which further includes the step of forming a groove on the surface of the workpiece, or forming a groove inside the workpiece from the surface or back of the workpiece. Steps in the qualitative area, In the step of grinding the back surface of the workpiece, the groove or the modified region is used as a starting point to slice the workpiece into a plurality of workpiece slices. The method for manufacturing a pieced workpiece according to any one of claims 7 to 9, further comprising: peeling off the protective sheet for workpiece processing from the pieced workpiece.

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