PROTECTIVE SHEET FOR WORK PROCESSING AND METHOD FOR PRODUCING WORK INDUCED PRODUCT

Abstract

To provide a protection sheet for workpiece processing that can reduce the TTV of a workpiece after back grinding.SOLUTION: A protection sheet for workpiece processing includes a support material, and an adhesive layer disposed on one main surface of the support material, and the other main surface of the support material constitutes the outermost surface of the protection sheet for workpiece processing, the coefficient of dynamic friction between the outermost surface of the protection sheet for workpiece processing and the 1200-grit sandpaper is 1.40 or less, and the tensile breaking stress of the support material is 250 MPa or less.SELECTED DRAWING: Figure 1C

Description

[Technical Field]

[0001] The present invention relates to a protective sheet for workpiece processing and a method for manufacturing singulated workpieces, particularly to a protective sheet for workpiece processing that can reduce the TTV of a workpiece after backside grinding, and a method for manufacturing singulated workpieces using the protective sheet for workpiece processing. [Background technology]

[0002] Chips on which circuits such as semiconductor chips are formed are obtained as individual workpieces by dividing a workpiece such as a wafer on which multiple circuits are formed. With the rapid progress of miniaturization and multifunctionality of electronic devices incorporating such chips, there is a demand for chips to be smaller, thinner, and more dense. To reduce the size and height of chips, it is common to form circuits on the surface of the workpiece and then grind the backside of the workpiece to reduce the thickness of the chip.

[0003] When grinding the backside of a workpiece, a protective sheet called backgrind tape is attached to the surface of the workpiece to temporarily protect the circuits on the surface of the workpiece and to hold the workpiece in place.

[0004] The surface of the workpiece is formed with a protective film to protect the circuit, convex electrodes such as bump electrodes to electrically connect the chip to electrodes on the substrate, etc., and this creates differences in elevation on the surface of the workpiece.

[0005] The protective sheet attached to the surface of the workpiece follows the shape of the surface of the workpiece, so these differences in height are also reflected in the protective sheet. If the backside of the workpiece is ground when there are differences in height, the pressure applied to the workpiece during grinding will be uneven on the grinding surface, and the thickness of the workpiece will be uneven after grinding.

[0006] The difference between the maximum thickness of the workpiece after grinding and the minimum thickness of the workpiece after grinding is called TTV (Total Thickness Variation), and is used as the standard for the thickness accuracy of the workpiece after grinding. If the thickness of the workpiece after grinding is uneven, the TTV becomes larger, which can lead to problems such as the workpiece being more likely to crack or causing problems when it is separated into individual pieces.

[0007] To address this problem, Patent Documents 1 and 2 describe a method in which an adhesive sheet is attached to the surface of a semiconductor wafer, the outermost surface of the adhesive sheet is ground, and then the back surface of the semiconductor wafer is ground, thereby improving the thickness accuracy of the semiconductor wafer after grinding. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 4261260 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-175334 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Documents 1 and 2, the tensile modulus of elasticity of the outermost surface of the adhesive sheet that is ground before the backside of the semiconductor wafer is ground is set within a predetermined range.

[0010] However, the present inventors have found that the TTV of a workpiece depends not on the tensile modulus of elasticity of the outermost surface of the protective sheet attached to the workpiece, but on another parameter: the dynamic friction coefficient and tensile breaking stress of the outermost surface to be ground affect the TTV of the workpiece more than the tensile modulus of elasticity of the outermost surface of the protective sheet.

[0011] The present invention has been made in view of the above circumstances, and aims to provide a protective sheet for workpiece processing that can reduce the TTV of the workpiece after backside grinding, and a method for producing individual workpieces obtained by singulating the workpiece using the protective sheet for workpiece processing. [Means for solving the problem]

[0012] The aspects of the present invention are as follows.

[0013] [1] A protective sheet for workpiece processing having a support material and an adhesive layer disposed on one main surface of the support material, The other main surface of the support material constitutes the outermost surface of the workpiece processing protection sheet, and the dynamic friction coefficient between the outermost surface of the workpiece processing protection sheet and sandpaper having a grit size of 1200 is 1.40 or less; This is a protective sheet for workpiece processing, with the support material having a tensile breaking stress of 250 MPa or less.

[0014] [2] The protective sheet for workpiece processing according to [1], wherein the support material is composed of two or more layers.

[0015] [3] The protective sheet for workpiece processing according to [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 protective sheet for workpiece processing.

[0016] [4] A protective sheet for workpiece processing according to any one of [1] to [3], in which the adhesive layer is attached to the surface of the workpiece before the process of grinding the back surface of the workpiece having a front and back surface, and the outermost surface of the protective sheet for workpiece processing is ground before use.

[0017] [5] A protective sheet for workpiece processing described in [4], which is used in a process of dividing a workpiece into individual workpieces by grinding the back surface of the workpiece having a groove formed on the surface thereof or a modified region formed inside the workpiece.

[0018] [6] The protection sheet for workpiece processing according to any one of [1] to [5], wherein the pressure-sensitive adhesive layer is energy ray-curable.

[0019] [7] A step of attaching the adhesive layer of the protective sheet for workpiece processing according to any one of [1] to [6] to the surface of a workpiece having a front and back surface; A step of grinding the back surface of the workpiece; and a step of dividing the workpiece into individual pieces to obtain a plurality of individual workpieces.

[0020] [8] The protective sheet for workpiece processing according to [4] or [5], further comprising a step of grinding the outermost surface of the protective sheet for workpiece processing, In the method for producing individual workpieces according to [7], the step of grinding the back surface of the workpiece is carried out after the step of grinding the outermost surface of the protection sheet for workpiece processing.

[0021] [9] The method further includes a step of forming a groove on the surface of the workpiece, or a step of forming a modified region inside the workpiece from the surface or back surface of the workpiece, A method for manufacturing a workpiece singulation according to [7] or [8], wherein in the step of grinding the back surface of the workpiece, the workpiece is singulated into a plurality of workpiece singulations starting from grooves or modified regions.

[0022]

[10] A method for producing a workpiece singulated product according to any one of [7] to [9], further comprising a step of peeling off the workpiece processing protection sheet from the workpiece singulated product. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a protective sheet for workpiece processing that can reduce the TTV of the workpiece after backside grinding. Also, according to the present invention, it is possible to provide a method for producing individual workpieces obtained by singulating the workpiece using the protective sheet for workpiece processing. [Brief explanation of the drawings]

[0024] [Figure 1A]FIG. 1A is a cross-sectional view showing an example of a protection sheet for workpiece processing according to this embodiment. [Figure 1B] FIG. 1B is a cross-sectional view showing another example of the protection sheet for workpiece processing according to this embodiment. [Figure 1C] FIG. 1C is a cross-sectional view showing another example of the protection sheet for workpiece processing according to the present embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating the process of attaching the protective sheet for workpiece processing according to this embodiment to a workpiece. [Figure 3] FIG. 3 is a cross-sectional view illustrating a process of grinding the outermost surface of the protective sheet for workpiece processing according to this embodiment. [Figure 4] FIG. 4 is a cross-sectional view illustrating a process of grinding the back surface of a workpiece using the protective sheet for workpiece processing according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described in detail below based on specific embodiments with reference to the accompanying drawings. First, the main terms used in this specification will be explained.

[0026] The workpiece refers to a plate-shaped body to which the protective sheet for workpiece processing according to this embodiment is attached and then singulated. Examples of workpieces include circular wafers (including those with orientation flats), rectangular panel-level packages, and strips (rectangular substrates) sealed with molded resin. Among these, wafers are preferred because they facilitate the above-described effects. Examples of wafers include semiconductor wafers such as silicon wafers, gallium arsenide wafers, silicon carbide wafers, gallium nitride wafers, and indium phosphide wafers, as well as insulator wafers such as glass wafers, lithium tantalate wafers, and lithium niobate wafers. They may also be reconstructed wafers made of resin and semiconductors used in the fabrication of fan-out packages, etc. Because the above-described effects are readily achieved, semiconductor wafers or insulator wafers are preferred, with semiconductor wafers being more preferred.

[0027] Singulation of a workpiece refers to dividing the workpiece into individual circuits to obtain individual workpieces. For example, if the workpiece is a wafer, the individual workpieces are chips, and if the workpiece is a panel-level package or a strip (rectangular substrate) sealed with molded resin, the individual workpieces are semiconductor packages.

[0028] The "surface" of a workpiece refers to the surface on which circuits, electrodes, etc. are formed, and the "back" of a workpiece refers to the surface on which no circuits, etc. are formed. The electrodes may be convex electrodes such as bumps.

[0029] DBG is a method in which grooves of a specified depth are formed on the surface of a workpiece, and then the workpiece is ground from the back side to separate the workpiece. The grooves formed on the surface of the workpiece are formed by methods such as blade dicing, laser dicing, and plasma dicing.

[0030] LDBG is a variation of DBG, and refers to a method in which a fragile modified area is created inside a workpiece (e.g., a wafer) using a laser, and cracks originating from the modified area are propagated by stresses, etc., generated during back grinding of the workpiece, thereby dividing the workpiece into individual pieces.

[0031] A "group of individual workpieces" refers to a plurality of individual workpieces held on the protective sheet for workpiece processing according to this embodiment after the workpiece has been singulated. These individual workpieces collectively form a shape similar to that of the workpiece. Furthermore, a "group of chips" refers to a plurality of chips held on the protective sheet for workpiece processing according to this embodiment after the wafer serving as the workpiece has been singulated. These chips collectively form a shape similar to that of the wafer.

[0032] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and similar terms.

[0033] "Energy rays" refers to ultraviolet rays, electron beams, etc., and is preferably ultraviolet rays.

[0034] Unless otherwise specified, the "weight average molecular weight" is a polystyrene equivalent value measured by gel permeation chromatography (GPC). Measurements by this method are performed, for example, using a high-speed GPC device "HLC-8120GPC" manufactured by Tosoh Corporation, with a high-speed column "TSK guard column H" XL -H", "TSK Gel GMH XL ", "TSK Gel G2000 H XL (All products of Tosoh Corporation) connected in this order are used, and the column temperature is 40°C, the liquid flow rate is 1.0 mL / min, and the detector is a differential refractometer.

[0035] The release sheet is a sheet that supports the pressure-sensitive adhesive layer in a releasable manner. The term "sheet" is not limited to a specific thickness, and is used to include films.

[0036] The mass ratios in the descriptions of compositions such as the pressure-sensitive adhesive layer composition are based on the active ingredient (solid content), and do not include the solvent unless otherwise specified.

[0037] (1. Protective sheet for workpiece processing) The protective sheet for workpiece processing is used when processing a workpiece having a circuit or the like formed on one side (front side) and no circuit or the like formed on the other side (back side). An example of processing the workpiece is backside grinding of the workpiece. Grinding the backside of the workpiece can reduce the thickness of the individual workpieces obtained by dividing the workpiece.

[0038] The workpiece processing protection sheet is applied to the surface of the workpiece before back grinding. The surface of the workpiece may be the surface on which the circuit is exposed, or the main surface of a protective layer formed on the circuit to protect the circuit. Also, convex electrodes such as bumps may be formed on the circuit. Therefore, due to elements formed on the surface of the workpiece, differences in height usually occur on the surface of the workpiece.

[0039] As a result, such height differences are also reflected in the workpiece processing protective sheet attached to the surface of the workpiece. After the workpiece is attached, the workpiece processing protective sheet is adsorbed to a grinding table such as a chuck table, and the backside of the workpiece is ground. However, if height differences occur in the workpiece processing protective sheet, gaps are formed between the workpiece processing protective sheet and the chuck table, and the force applied during backside grinding may not be transmitted evenly to the workpiece. As a result, areas on the backside of the workpiece where grinding has progressed sufficiently and areas where grinding has not progressed sufficiently occur. Such differences in the degree of grinding progress lead to uneven workpiece thickness after grinding. In other words, the presence of areas where the workpiece is thick after grinding and areas where the workpiece is thin after grinding tends to increase the TTV after grinding.

[0040] As mentioned above, if the TTV becomes large, problems such as cracks easily occurring in the workpiece and problems occurring when the workpiece is divided into individual pieces arise.

[0041] To address this problem, a known method is to improve the TTV by grinding the outermost surface of the protective sheet for workpiece processing attached to the workpiece, as described above. In this method, the tensile modulus of the outermost surface of the protective sheet for workpiece processing is set within a predetermined range.

[0042] However, the inventors have focused on the dynamic friction coefficient and tensile breaking stress of the outermost surface of the protective sheet for workpiece processing, and have discovered that optimizing these parameters has a positive effect on the back grinding of the workpiece, and can reduce the TTV of the workpiece after back grinding.

[0043] The protective sheet for workpiece processing according to this embodiment will be described in detail below.

[0044] As shown in Fig. 1A, the protective sheet for workpiece processing 1 according to this embodiment has a support material 10 and an adhesive layer 20 disposed on the support material 10. As shown in Fig. 2, the protective sheet for workpiece processing 1 is attached such that the main surface 20a of the adhesive layer 20 is attached to the surface 100a of the workpiece 100 (e.g., a wafer).

[0045] In the protective sheet for workpiece processing 1 according to this embodiment, before grinding the back surface 100b of the workpiece 100, the main surface 10b of the support material 10 of the protective sheet for workpiece processing 1, opposite to the main surface 10a on which the adhesive layer 20 is disposed, is ground. Therefore, the main surface 10b constitutes the outermost surface of the protective sheet for workpiece processing 1.

[0046] (1.1. Support material) The support material is a member that supports the adhesive layer and supports the workpiece after the workpiece processing protection sheet is attached to the workpiece. Therefore, it is preferable that the support material has rigidity. In this embodiment, the support material has the following physical properties.

[0047] (1.2. Coefficient of kinetic friction) In this embodiment, the coefficient of dynamic friction between the main surface of the support material constituting the outermost surface of the workpiece processing protective sheet and sandpaper with a grit size of 1200 is 1.40 or less. The coefficient of dynamic friction is the proportional coefficient of the dynamic friction force acting in the opposite direction to the direction of movement at the contact surface when two objects are in contact and moving relative to each other. A large coefficient of dynamic friction indicates a large force trying to stop the moving object. The sandpaper is intended as a grinding means (e.g., a grinding wheel) that grinds the main surface of the support material, and the above-mentioned coefficient of dynamic friction is an indicator of the resistance force experienced by the grinding means that grinds the main surface of the support material.

[0048] By having a dynamic friction coefficient within the above range, the outermost surface of the protective sheet for workpiece processing does not adhere to the grinding means, and the grinding of the outermost surface is properly performed, improving the smoothness of the outermost surface after grinding. If the back surface of the workpiece is ground after the outermost surface has been properly ground, the back surface of the workpiece is also properly ground, and the TTV of the workpiece after grinding can be reduced. In particular, even if the adhesive layer is relatively soft, the outermost surface is properly ground.

[0049] The dynamic friction coefficient is preferably 1.38 or less, more preferably 1.35 or less, and even more preferably 1.30 or less. From the viewpoint of enabling grinding with a grinding wheel, the dynamic friction coefficient is preferably 0.1 or more.

[0050] The dynamic friction coefficient can be measured by a known method. For example, it is measured in accordance with JIS K 7125. That is, it is measured in the same manner 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.

[0051] (1.3. Tensile Breaking Stress) In this embodiment, the support material has a tensile breaking stress of 250 MPa or less. The tensile breaking stress is the stress at which the sample breaks when it is continuously pulled. The tensile breaking stress is an index of whether the support material is susceptible to grinding.

[0052] By having a tensile breaking stress within the above range, the outermost surface of the protective sheet for workpiece processing is easily ground, the outermost surface is properly ground, and the smoothness of the outermost surface after grinding is improved. If the backside of the workpiece is ground after the outermost surface has been properly ground, the backside of the workpiece is also properly ground, and the TTV of the workpiece after grinding can be reduced. In particular, even if the adhesive layer is relatively soft, the outermost surface is properly ground.

[0053] As will be described later, when the support material is composed of two or more layers, the above tensile breaking stress is the tensile breaking stress of the layer that constitutes the outermost surface of the protection sheet for workpiece processing.

[0054] The tensile breaking stress is preferably 240 MPa or less, more preferably 230 MPa or less, and is preferably 1 MPa or more from the viewpoint of preventing breakage during production.

[0055] The tensile breaking stress can be measured by a known method. For example, it is measured in accordance with JIS K 7161:1994 and JIS K 7127:1999. That is, it is measured in the same manner as the measurement methods specified in these standards, but the measurement conditions may be different. Specific measurement methods will be described in the examples.

[0056] (1.4. Structure of Support Material) The structure of the support material is not particularly limited as long as it has the above-mentioned physical properties. Below, we will explain the case where the support material is composed of one layer and the case where the support material is composed of two or more layers.

[0057] (1.5. When the support material consists of one layer) When the support material is composed of a single layer, it is necessary that the support material is composed of a material that can support and hold the adhesive layer and the workpiece during processing of the workpiece in addition to satisfying the above physical properties. Therefore, when the support material is composed of a single layer, it is preferable that the tensile breaking stress of the support material is within the above range and that the rigidity of the support material is relatively high.

[0058] When the support material is composed of a single layer, examples of the material for the support material include polyethylene terephthalate, polybutylene terephthalate, polyimide, polyamide, low-density polyethylene, high-density polyethylene, and biaxially oriented polypropylene. Among these, polyethylene terephthalate is preferable. On the other hand, when the support material is composed of a single layer, examples of the material for the support material that are not preferable include polyethylene naphthalate, polycarbonate, ethylene-vinyl acetate copolymer (EVA), and ethylene / methacrylic acid copolymer. Note that the above examples are general examples, and even the same material may satisfy the above physical properties of the support material depending on the manufacturing method.

[0059] (1.6. When the support material consists of two or more layers) In this embodiment, the support material preferably comprises two or more layers. When the support material comprises two or more layers, it preferably has a rigid layer and a soft layer. In this case, the main surface of the soft layer preferably constitutes the outermost surface of the protective sheet for workpiece processing 1. For example, as shown in FIG. 1B, the support material 10 comprises a rigid layer 11 and a soft layer 12, and the main surface 12b of the soft layer 12 constitutes the outermost surface of the protective sheet for workpiece processing 1. Also, as shown in FIG. 1C, the support material 10 comprises a rigid layer 11, a first soft layer 12, and a second soft layer 13, and the main surface 12b of the first soft layer 12 constitutes the outermost surface of the protective sheet for workpiece processing 1.

[0060] (1.6.1. Rigid layer) The rigid layer is a layer that provides the rigidity of the support material and is not limited as long as it is made of a material that can support the adhesive layer and the workpiece. Examples include various resin films used as the base material of backgrinding tapes. By using such a resin film, the workpiece can be held without being damaged even if the workpiece becomes thinner due to grinding. The rigid layer may be made of a single-layer film made of one resin film, or may be made of a multi-layer film made of multiple resin films stacked together.

[0061] In this embodiment, examples of the material for the rigid layer include polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, wholly aromatic polyester, polyamide, polycarbonate, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, biaxially oriented polypropylene, etc. Among these, polyester is preferred, and polyethylene terephthalate is more preferred.

[0062] The thickness of the rigid layer is not particularly limited, but may be set according to the material of the rigid layer since it affects the rigidity of the workpiece processing protection sheet. In this embodiment, the thickness of the rigid layer is preferably 10 μm or more and 200 μm or less, more preferably 15 μm or more and 150 μm or less, and even more preferably 20 μm or more and 130 μm or less.

[0063] At least one main surface of the rigid layer may be subjected to an adhesion treatment such as a corona treatment to improve adhesion with a layer formed on the main surface. Also, at least one main surface of the rigid layer may have an easy-adhesion layer formed thereon to improve adhesion with a layer (for example, a soft layer) formed on the main surface.

[0064] (1.6.2. Soft layer) The soft layer is made of a material softer than the rigid layer. In this embodiment, the soft layer is preferably the layer that forms the outermost surface of the workpiece processing protective sheet on the support material. That is, after the workpiece processing protective sheet is attached to the surface of the workpiece, the soft layer is ground before the backside of the workpiece is ground. This is because a relatively soft material is more likely to satisfy the physical properties of the support material than a relatively hard material.

[0065] (1.6.3 Soft layer material) In this embodiment, the soft layer may be made of a soft resin film, or may be formed using a soft layer composition containing an energy ray-curable compound.

[0066] Examples of soft resin films include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), biaxially oriented polypropylene, polyurethane acrylate, and the like. Among these, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyurethane acrylate, and the like are preferred. On the other hand, ethylene-vinyl acetate copolymer (EVA), ethylene-(meth)acrylic acid copolymer, vinyl chloride, and the like are not preferred as soft resin films. Note that the above examples are general examples, and the same material may satisfy the physical properties of the support material described above depending on the manufacturing method.

[0067] (1.6.4. Composition for soft layer) In this embodiment, the soft layer composition preferably contains a urethane (meth)acrylate (d1) and a polymerizable compound (d2) having an alicyclic group or heterocyclic group with 6 to 20 ring atoms and / or a polyfunctional polymerizable compound (d3). The soft layer composition may contain a polymerizable compound (d4) having a functional group in addition to the components (d1) to (d3). The soft layer composition may also contain a photopolymerization initiator in addition to the above components. Furthermore, the soft layer composition may contain other additives and resin components within a range that does not impair the above-mentioned effects.

[0068] Hereinafter, each component contained in the composition for the soft layer containing the energy ray-curable compound will be described in detail.

[0069] (1.6.4.1 Urethane (meth)acrylate (d1)) The urethane (meth)acrylate (d1) is a compound having at least a (meth)acryloyl group and a urethane bond, and has the property of being polymerized and cured by irradiation with energy rays. The urethane (meth)acrylate (d1) is an oligomer or a polymer.

[0070] The weight-average molecular weight (Mw) of component (d1) is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000. The number of (meth)acryloyl groups (hereinafter also referred to as "number of functional groups") in component (d1) may be monofunctional, bifunctional, or trifunctional or higher, but is preferably monofunctional or bifunctional.

[0071] Component (d1) can be obtained, for example, by reacting a polyol compound with a polyvalent isocyanate compound to obtain a terminal isocyanate urethane prepolymer, and then reacting the resulting prepolymer with a (meth)acrylate having a hydroxyl group. Component (d1) may be used alone or in combination of two or more.

[0072] The content of component (d1) in the soft layer composition is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and even more preferably 25 to 55 parts by mass, per 100 parts by mass of the soft layer composition.

[0073] (1.6.4.2. Polymerizable Compound (d2) Having an Alicyclic or Heterocyclic Group with 6 to 20 Ring Atoms) Component (d2) is a polymerizable compound having an alicyclic group or heterocyclic group with 6 to 20 ring atoms, and is preferably a compound having at least one (meth)acryloyl group, more preferably a compound having one (meth)acryloyl group. Use of component (d2) can improve the film-forming properties of the resulting soft layer composition.

[0074] Although the definition of component (d2) overlaps with the definitions of components (d3) and (d4) described below, the overlapping portions are included in component (d3) or component (d4). For example, a compound having at least one (meth)acryloyl group, an alicyclic or heterocyclic group having 6 to 20 ring atoms, and a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group is included in the definitions of both component (d2) and component (d4), and in the present embodiment, such a compound is included in component (d4).

[0075] Specific examples of component (d2) include alicyclic group-containing (meth)acrylates such as isobornyl (meth)acrylate, heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, etc. Component (d2) may be used alone or in combination of two or more.

[0076] The content of component (d2) in the soft layer composition is preferably 10 to 70 parts by mass, more preferably 20 to 60 parts by mass, and even more preferably 25 to 55 parts by mass, per 100 parts by mass of the soft layer composition.

[0077] (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, such as a (meth)acryloyl group, a vinyl group, an allyl group, or a vinylbenzyl group. Two or more types of energy ray-curable groups may be used in combination. A three-dimensional network structure (crosslinked structure) is formed when the energy ray-curable group in the polyfunctional polymerizable compound reacts with the (meth)acryloyl group in component (d1) or when the energy ray-curable groups in component (d3) react with each other. When a polyfunctional polymerizable compound is used, the crosslinked structure formed by energy ray irradiation increases compared to when a compound containing only one energy ray-curable group is used. This results in a unique viscoelasticity of the soft layer, making it easier to achieve appropriate dynamic friction coefficients and tensile break stresses on the outermost surface.

[0078] Although the definition of component (d3) overlaps with the definition of component (d4) described below, the overlapping portion is included in component (d3). For example, a compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group and having two or more (meth)acryloyl groups is included in the definitions of both component (d3) and component (d4), and in this embodiment, such a compound is considered to be included in component (d3).

[0079] From the above viewpoints, 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.

[0080] The weight average molecular weight of the component (d3) is preferably 30 to 40,000, more preferably 100 to 10,000, and even more preferably 200 to 1,000.

[0081] Specific examples of component (d3) include diethylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, divinylbenzene, vinyl (meth)acrylate, divinyl adipate, and N,N'-methylenebis(meth)acrylamide. Among these, neopentyl glycol di(meth)acrylate and dipentaerythritol hexa(meth)acrylate are preferred. Component (d3) may be used alone or in combination of two or more.

[0082] The content of component (d3) in the soft layer composition is preferably 2 to 40 parts by mass, more preferably 3 to 20 parts by mass, and even more preferably 5 to 15 parts by mass, per 100 parts by mass of the soft layer composition.

[0083] (1.6.4.4 Polymerizable compound having a functional group (d4)) Component (d4) is a polymerizable compound containing a functional group such as a hydroxyl group, an epoxy group, an amide group, or an amino group, and is preferably a compound having at least one (meth)acryloyl group, more preferably a compound having one (meth)acryloyl group.

[0084] Component (d4) has good compatibility with component (d1), making it easier to adjust the viscosity of the soft layer composition within an appropriate range, and also ensuring good cushioning performance even when the soft layer is relatively thin.

[0085] Examples of component (d4) include hydroxyl group-containing (meth)acrylates, epoxy group-containing compounds, amide group-containing compounds, amino group-containing (meth)acrylates, etc. Among these, hydroxyl group-containing (meth)acrylates are preferred.

[0086] In order to improve the film-forming properties of the composition for the soft layer, the content of component (d4) in the composition for the soft layer is preferably 5 to 40 parts by mass, more preferably 7 to 35 parts by mass, and even more preferably 10 to 30 parts by mass, per 100 parts by mass of the composition for the soft layer.

[0087] (1.6.4.5 Polymerizable compound (d5) other than components (d1) to (d4)) The soft layer-forming composition may contain a polymerizable compound (d5) other than the above components (d1) to (d4) within a range that does not impair the above-mentioned effects.

[0088] Examples of the component (d5) include alkyl (meth)acrylates having an alkyl group with 1 to 20 carbon atoms; vinyl compounds, and the like.

[0089] The content of component (d5) in the soft layer composition is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and even more preferably 0 to 5 parts by mass, per 100 parts by mass of the soft layer composition.

[0090] 1.6.4.6 Photoinitiators The composition for the soft layer preferably further contains a photopolymerization initiator from the viewpoint of shortening the polymerization time by light irradiation and reducing the amount of light irradiation when forming the soft layer.

[0091] Examples of photopolymerization initiators include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specific examples include 1-hydroxycyclohexyl phenyl ketone and 2-hydroxy-2-methyl-1-phenyl-propan-1-one. These photopolymerization initiators can be used alone or in combination of two or more.

[0092] The content of the photopolymerization initiator in the composition for the soft layer is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass, relative to 100 parts by mass of the total amount of the energy ray-curable compounds.

[0093] (1.6.4.7 Other additives) The soft layer composition may contain other additives within a range that does not impair the above-mentioned effects. Examples of other additives include antistatic agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are blended, the content of each additive in the soft layer composition is preferably 0.01 to 6 parts by mass, more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the total amount of the energy ray-curable compounds.

[0094] The soft layer formed from the composition for soft layer containing the energy ray-curable compound is obtained by polymerizing and curing the composition for soft layer having the above-mentioned composition by irradiation with energy rays. In other words, the soft layer is a product obtained by curing the composition for soft layer.

[0095] The thickness of the soft material 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, and even more preferably 15 μm or more and 80 μm or less.

[0096] (2. Adhesive Layer) The adhesive layer is attached to the surface of the workpiece (i.e., the surface on which circuits, electrodes, etc. are formed) and protects the surface and supports 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 multiple layers, these multiple layers may be the same or different from each other, and the combination of layers that make up these multiple layers is not particularly limited.

[0097] In this embodiment, the pressure-sensitive adhesive layer is not particularly limited as long as it has appropriate pressure-sensitive adhesive properties at room temperature, and may be a single layer or multiple layers. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 μm or more and 200 μm or less, and more preferably 10 μm or more and 190 μm or less.

[0098] The thickness of the pressure-sensitive adhesive layer refers to the thickness of the entire pressure-sensitive adhesive layer. For example, the thickness of a pressure-sensitive adhesive layer composed of multiple layers refers to the total thickness of all layers constituting the pressure-sensitive adhesive layer.

[0099] The composition of the adhesive layer is not limited as long as it has enough adhesiveness to protect the surface of the workpiece. In this embodiment, the adhesive layer is preferably made of, for example, an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, or the like.

[0100] Furthermore, the adhesive layer is preferably formed from an energy ray-curable adhesive. By forming the adhesive layer of the workpiece processing protective sheet from an energy ray-curable adhesive, the sheet adheres to the workpiece with high adhesive strength when attached to the workpiece, and the adhesive strength can be reduced by irradiating the sheet with energy rays when peeled from the workpiece. Therefore, while adequately protecting the workpiece's circuits, etc., damage to the circuits, electrodes, etc. on the workpiece surface and adhesion of the adhesive to the workpiece are prevented when the workpiece processing protective sheet is peeled off. In other words, the energy ray-curable adhesive layer improves the peelability of the workpiece processing protective sheet.

[0101] In this embodiment, the energy ray-curable adhesive is preferably composed of an adhesive composition containing an acrylic adhesive, which contains an acrylic polymer.

[0102] The acrylic polymer may be any known acrylic polymer, but in this embodiment, a functional group-containing acrylic polymer is preferred. The functional group-containing acrylic polymer may be a homopolymer formed from one type of acrylic monomer, a copolymer formed from multiple types of acrylic monomers, or a copolymer formed from one or multiple types of acrylic monomers and a monomer other than the acrylic monomer.

[0103] In this embodiment, the functional group-containing acrylic polymer is preferably an acrylic copolymer obtained by copolymerizing alkyl (meth)acrylate and a functional group-containing monomer.

[0104] Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and n-octyl (meth)acrylate.

[0105] The functional group-containing monomer is a monomer containing a reactive functional group. The reactive functional group is a functional group capable of reacting with other compounds such as a crosslinking agent, which will be described later. Examples of the functional group in the functional group-containing monomer include a hydroxyl group, a carboxyl group, and an epoxy group, with a hydroxyl group being preferred.

[0106] Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and non-(meth)acrylic unsaturated alcohols (unsaturated alcohols not having a (meth)acryloyl skeleton) such as vinyl alcohol and allyl alcohol.

[0107] The acrylic polymer is preferably an energy ray-curable acrylic polymer having an energy ray-curable group, obtained by reacting (e.g., adding) an energy ray-curable substance having an energy ray-curable group with a functional group of the acrylic polymer. The energy ray-curable substance having an energy ray-curable group is preferably a compound having, in addition to the energy ray-curable group, one or more groups selected from an isocyanate group, an epoxy group, and a carboxy group, and more preferably a compound having an isocyanate group. The isocyanate group can be added to a hydroxyl group of the functional group-containing acrylic polymer.

[0108] Examples of compounds having an isocyanate group include 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with hydroxyethyl (meth)acrylate; and acryloyl monoisocyanate compounds obtained by reacting a diisocyanate compound or a polyisocyanate compound with a polyol compound and hydroxyethyl (meth)acrylate.

[0109] The pressure-sensitive adhesive composition preferably contains, in addition to the acrylic polymer, an energy ray-curable compound. The energy ray-curable compound is preferably a monomer or oligomer having an unsaturated group in the molecule and capable of being polymerized and cured by energy ray irradiation.

[0110] Examples of such energy ray-curable compounds include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate, and oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate.

[0111] Among these, urethane (meth)acrylate oligomers are preferred.

[0112] The molecular weight of the energy ray-curable compound (weight average molecular weight in the case of an oligomer) is preferably 100 to 12,000, more preferably 200 to 10,000, still more preferably 400 to 8,000, and particularly preferably 600 to 6,000.

[0113] The content of the energy ray-curable compound in the pressure-sensitive adhesive composition is preferably 5 to 100 parts by mass, more preferably 10 to 70 parts by mass, and even more preferably 15 to 40 parts by mass, relative to 100 parts by mass of the acrylic polymer.

[0114] The pressure-sensitive adhesive composition preferably further contains a crosslinking agent, which reacts with functional groups to crosslink resins contained in the functional group-containing acrylic polymer, for example.

[0115] Examples of crosslinking agents include isocyanate-based crosslinking agents (crosslinking agents having an isocyanate group) such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and adducts of these diisocyanates; epoxy-based crosslinking agents (crosslinking agents having a glycidyl group) such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents (crosslinking agents having an aziridinyl group) such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; metal chelate-based crosslinking agents (crosslinking agents having a metal chelate structure) such as aluminum chelate; and isocyanurate-based crosslinking agents (crosslinking agents having an isocyanuric acid skeleton).

[0116] From the viewpoint of improving the cohesive strength of the pressure-sensitive adhesive and thereby improving the adhesive strength of the pressure-sensitive adhesive layer, and from the viewpoint of ease of availability, the crosslinking agent is preferably an isocyanate-based crosslinking agent.

[0117] The pressure-sensitive adhesive composition may further contain a photopolymerization initiator. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the curing reaction proceeds sufficiently even when irradiated with relatively low-energy energy rays such as ultraviolet rays.

[0118] Examples of the photopolymerization initiator include the photopolymerization initiators explained in the soft layer composition.

[0119] (3. Manufacturing method of protective sheet for workpiece processing) The method for producing the protection sheet for workpiece processing according to this embodiment may be any known method.

[0120] First, a support material is prepared. When the support material is composed of one layer, a resin film or the like that constitutes the support material may be prepared. When the support material is composed of two or more layers, for example, a resin film that constitutes a rigid layer and a resin film that constitutes a soft layer are laminated to manufacture the support material.

[0121] An example of a method for laminating resin films is the dry lamination method, in which one resin film (e.g., a resin film constituting a rigid layer) is laminated with another resin film (e.g., a resin film constituting a soft layer) via an easy-adhesion layer formed on one main surface of the other resin film.

[0122] In the dry lamination method, a resin film having an easy-adhesion layer may be used, or a resin film having an easy-adhesion layer formed by applying a composition for forming an easy-adhesion layer onto a surface that has been subjected to an adhesion treatment such as corona treatment may be used.

[0123] Another example is a method in which the resin that constitutes the soft material is melted and kneaded using a T-die film-forming machine or the like, and the molten resin is extruded onto one side of the support material while moving the support material at a constant speed to laminate it. Another example is a method in which the soft material is directly laminated onto the support material by heat sealing or the like.

[0124] Furthermore, when a soft layer is formed on one main surface of the rigid layer using a soft layer composition, the soft layer composition or a composition obtained by diluting the soft layer composition with a solvent (these two compositions are referred to as "soft layer coating agent"). The prepared soft layer coating agent is applied to the release surface of a release film, and if necessary, dried to form a coating film on the release film. The coating film is then cured (for example, by irradiation with energy rays) to form a soft layer. Thereafter, one main surface of the rigid layer and the soft layer are bonded together. If this soft layer still has energy ray curability, it may be further cured (for example, by irradiation with energy rays) if necessary.

[0125] After producing the support material, a composition for forming the adhesive layer is prepared, for example, a composition for the adhesive layer that constitutes the adhesive layer, or a composition obtained by diluting the composition for the adhesive layer with a solvent (these two compositions are referred to as "adhesive layer coating agent"). The prepared adhesive layer coating agent is applied to the release surface of a release film and, if necessary, dried to form an adhesive layer on the release film. The adhesive layer is then bonded to the main surface of the support material opposite to the main surface whose dynamic friction coefficient with sandpaper is controlled within the above range, thereby obtaining a protective sheet for workpiece processing in which an adhesive layer is formed on one main surface of the support material. Alternatively, the prepared adhesive layer coating agent may be directly applied to the main surface of the support material opposite to the main surface whose dynamic friction coefficient with sandpaper is controlled within the above range to form an adhesive layer.

[0126] (4. Method for manufacturing individual workpieces) As described above, the protective sheet for workpiece processing according to this embodiment is suitable for use in back grinding of a workpiece having circuits etc. formed on one side (front surface) and no circuits etc. formed on the other side (back surface), and during or after back surface grinding, the workpiece is diced into individual pieces, and multiple individual workpieces (group of individual workpieces) are obtained.

[0127] As a non-limiting example of the use of the protection sheet for workpiece processing, a method for producing individual workpieces (for example, chips) will be specifically described below.

[0128] Specifically, the method for producing the workpiece singulation preferably includes at least the following steps 1 to 4. Step 1: A process of attaching the above-mentioned workpiece processing protection sheet to the surface of the workpiece. Step 2: A step of grinding the main surface of the support material that constitutes the outermost surface of the workpiece processing protection sheet Process 3: Grinding the back surface of the workpiece Step 4: A step of dividing the work into individual pieces to obtain a plurality of individual work pieces.

[0129] Each step of the method for manufacturing the above-mentioned workpiece singulation will be described in detail below, using a wafer as a specific example of the workpiece and a chip as a specific example of the workpiece singulation.

[0130] (4.1.Process 1) In step 1, the adhesive layer of the protective sheet for workpiece processing according to this embodiment is attached to the surface of a wafer, as shown in Fig. 2. By attaching the protective sheet for workpiece processing to the surface of the wafer, the surface of the wafer is sufficiently protected.

[0131] The thickness of the wafer used in this manufacturing method before grinding is not particularly limited, but is usually about 500 to 1000 μm. In addition, a circuit is formed on the surface of the wafer. Formation of the circuit on the wafer surface can be performed by various methods, including conventionally widely used methods such as etching and lift-off.

[0132] The formed circuit may be exposed, or a circuit protection layer may be formed to protect the circuit. The circuit protection layer is usually formed by applying a composition constituting the circuit protection layer and thermally curing it. Furthermore, convex electrodes such as bumps and pillars may be formed on the circuit.

[0133] (4.2.Process 2) Step 2 is performed after step 1. In step 2, as shown in Fig. 3, the main surface 10b (12b) constituting the outermost surface of the protective sheet for workpiece processing 1 is ground on the support material. The main surface constituting the outermost surface of the protective sheet for workpiece processing is the main surface 10b in the protective sheet for workpiece processing shown in Fig. 1A, and is the main surface 12b in the protective sheets for workpiece processing shown in Figs. 1B and 1C.

[0134] From the viewpoint of improving the efficiency and simplifying step 2, the device used for grinding is preferably a grinding device that grinds the back surface of a wafer. In such a grinding device, as shown in Fig. 3, the back surface 100b of the wafer 100 is held on a chuck table 60 so that the grinding wheel 50 and the main surface 10b (12b) that constitutes the outermost surface of the protective sheet for workpiece processing face each other. Next, the grinding wheel 50, the wafer 100, and the protective sheet for workpiece processing 1 come into contact with each other while rotating relative to each other, and the main surface 10b (12b) is ground by the abrasive grains of the grinding wheel 50.

[0135] The main surface of the support material that constitutes the outermost surface of the protection sheet for workpiece processing has the above-mentioned physical properties, so that the main surface is easily ground during grinding and is less likely to adhere to the grinding wheel, resulting in an appropriate grinding of the main surface and a surface with minimal irregularities.

[0136] (4.3.Process 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 a chuck table 60, and then the back surface 100b of the wafer 100 is ground using a grinding wheel 50. Because the main surface 10b (12b) of the support material ground in step 2 has minimal irregularities, almost no gap is formed between the support material of the workpiece processing protection sheet 1 and the chuck table 60. Therefore, the force applied during back surface grinding is evenly transmitted to the back surface 100b of the wafer 100, and the back surface 100b of the wafer 100 is ground uniformly. As a result, the wafer thickness after grinding is less uneven, and the TTV of the wafer after grinding can be reduced.

[0137] (4.4.Step 4) In step 4, the wafer is divided into individual chips (chip groups). The wafer may be divided into individual chips after step 3 or during step 3.

[0138] When the wafer is singulated after step 3, for example, the suction between the support material and the chuck table is released, and the wafer is transported to the dicing step with the workpiece processing protection sheet and the wafer attached. In the dicing step, the wafer is singulated into a plurality of chips. As a singulation method, a known method can be adopted. For example, a method is exemplified in which a rotary blade such as a dicer is used to form grooves penetrating the front and back surfaces of the wafer, thereby cutting the wafer to obtain a plurality of singulated chips.

[0139] In this embodiment, step 4 is preferably a step of singulating by DBG or LDBG. In this case, step 4 is performed in step 3.

[0140] When singulating by DBG or LDBG, in addition to the above steps 1 to 4, there is a step of forming a groove from the front surface side of the workpiece (step 5a), or a step of forming a modified region inside the workpiece from the front or back surface of the workpiece (step 5b).

[0141] (4.5.Step 5a) Step 5a is performed before steps 1 to 3. The grooves formed in step 5a are shallower than the thickness of the wafer. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like. These grooves serve as starting points for dividing the wafer. In other words, the grooves are formed so as to follow the dividing lines that will be used when the wafer is divided into individual chips in step 3.

[0142] (4.6.Step 5b) Step 5b is performed before step 3. Step 5b may be performed before steps 1 and 2, or after step 1 and before step 2, or after steps 1 and 2. In this embodiment, step 5b is preferably performed after steps 1 and 2.

[0143] The modified region formed in step 5b is an embrittled portion of the wafer. The modified region is prone to cracking due to the shear force and pressure applied to the wafer during backside grinding. Such cracks become the starting point for wafer division. In other words, the modified region is formed along the division line when the wafer is divided into individual chips in step 3.

[0144] The modified region is formed by irradiating a laser focused on the inside of the wafer. Therefore, the modified region is formed inside the wafer. The laser irradiation may be performed from the front side or the back side of the wafer. Note that when step 5b is performed after step 1 and the laser is irradiated from the front side of the wafer, the laser is irradiated onto the wafer through a workpiece processing protective sheet.

[0145] Step 3 is performed after step 5a or step 5b. That is, after the grooves or modified regions are formed on the wafer, the back surface of the wafer is ground to separate the wafer into multiple chips. In other words, step 4 is performed in step 3.

[0146] In step 3 after step 5a, back grinding is performed to thin the wafer at least to the bottom of the grooves. This back grinding turns the grooves into notches that penetrate the wafer, and the wafer is divided by the notches into individual chips.

[0147] In step 3 after step 5b, back grinding may be performed until the ground surface (wafer back surface) reaches the modified region, but the ground surface does not have to reach the modified region exactly. That is, grinding may be performed to a position close to the modified region so that the wafer is divided starting from the modified region and individual chips are obtained. For example, grinding may be performed to a position close to the modified region, and the wafer may be completely singulated by cracks that occur in the modified region. Alternatively, the wafer may be partially singulated by cracks that occur in the modified region, and then the wafer may be completely singulated by applying a pickup tape (described later) and stretching the pickup tape. Alternatively, the wafer may be completely singulated by stretching the pickup tape.

[0148] After the backside grinding using the grinding wheel is completed, stress relief such as dry polishing may be carried out.

[0149] The shape of the chips separated through step 4 may be square or may be elongated, such as rectangular. The thickness of the separated chips is not particularly limited, but is preferably about 5 to 100 μm, more preferably 10 to 45 μm. LDBG makes it easy to make the thickness of the separated chips 50 μm or less, more preferably 10 to 45 μm. The size of the separated chips is not particularly limited. For example, the chip area is preferably 600 mm 2 Less than 400mm, preferably 2 Less than 120mm, more preferably 2 is less than.

[0150] (4.7.Step 6) In this embodiment, the method for producing the workpiece singulation preferably includes a step (step 6) of peeling off the workpiece processing protection sheet from the singulated workpiece (i.e., a plurality of workpiece singulations). Step 6 is performed after step 4. Step 6 is performed, for example, by the following method.

[0151] First, when the adhesive layer of the protective sheet for workpiece processing is formed from an energy ray-curable adhesive, a step (step 6a) of curing the adhesive layer by irradiating with energy rays is performed. As described above, step 6a is a step of reducing the adhesive strength of the adhesive layer by irradiating with 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 sufficiently protected by the adhesive strength of the adhesive layer in steps 1 to 5, while suppressing damage to circuits, electrodes, etc. on the workpiece surface and adhesion of the adhesive to the workpiece.

[0152] On the other hand, since the energy ray-curable adhesive layer is cured by irradiation with energy rays, it is preferable that the adhesive layer is hard when grinding the back surface of the wafer, from the viewpoint of stably grinding the back surface of the wafer and improving the thickness accuracy of the wafer after grinding.

[0153] That is, there is a trade-off between the precision of the wafer thickness after grinding and the removability of the workpiece processing protection sheet when it is peeled off.

[0154] In this embodiment, even if the curable adhesive layer is uncured or the non-curable adhesive layer is relatively soft, the main surface of the support material that constitutes the outermost surface of the workpiece processing protective sheet has the above-mentioned physical properties, so that the main surface can be properly ground to obtain a surface with little unevenness. As a result, even if the adhesive layer is relatively soft, the TTV of the wafer after grinding can be reduced. In other words, it is possible to achieve both the thickness accuracy of the wafer after grinding and the releasability of the workpiece processing protective sheet when peeling it off.

[0155] Therefore, step 6a may be performed after step 1, step 2, or step 5b, but is preferably performed after step 3.

[0156] The conditions for energy ray irradiation are, for example, the irradiance of the energy ray is 120 to 280 mW / cm 2 The energy ray dose is 100-1000mJ / cm 2 The energy ray is preferably ultraviolet light.

[0157] After the adhesive layer has hardened, a pickup tape is attached to the backside of the multiple workpieces, and the positions and orientations are adjusted to allow pickup. At this time, a ring frame located on the outer periphery of the wafer is also attached to the pickup tape, and the outer edge of the pickup tape is fixed to the ring frame. The wafer and ring frame may be attached to the pickup tape simultaneously or at different times. Next, the workpiece processing protective sheet is peeled off from the multiple chips held on the pickup tape.

[0158] The pickup tape is not particularly limited, but may be, for example, an adhesive sheet including a substrate and an adhesive layer provided on one surface of the substrate.

[0159] Although the present embodiment has been described above, the present invention is not limited to the above embodiment and may be modified in various ways within the scope of the present invention. [Example]

[0160] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0161] The measurement and evaluation methods in the present examples are as follows.

[0162] (Coefficient of dynamic friction between support and sandpaper) The support materials prepared in the Examples and Comparative Examples were cut to a length of 200 mm and a width of 80 mm to obtain test samples for measuring the coefficient of kinetic friction. The test sample was placed on 1200-grit sandpaper. A 63-mm-long sliding strip with a felt surface in contact with the test sample was placed on the test sample. A weight was then placed on the sliding strip so that the total mass of the sliding strip and the weight was 1000 g. The test sample was pulled in the longitudinal direction at a rate of 100 mm / min. The average load measured from the start of relative shear movement between the contact surfaces of the test sample and the sandpaper until the sample had moved 60 mm was used as the kinetic friction force, ignoring the load at the time the test sample began to move. The coefficient of kinetic friction was calculated by dividing the obtained kinetic friction force by the normal force generated by the combined mass of the sliding strip and the weight. The results are shown in Table 1.

[0163] (Tensile breaking stress of support material) The support materials prepared in the Examples and Comparative Examples were cut to a length of 140 mm and a width of 15 mm to obtain measurement samples for measuring tensile stress at break. Film tension labels were attached to 20 mm sections on both ends of the obtained measurement samples to prepare samples measuring 15 mm x 100 mm. The tensile stress at break of the samples was measured using a tensile tester (Shimadzu Corporation, product name "Autograph AG-IS 1kN") under conditions of a chuck distance of 100 mm and a tensile speed of 200 mm / min. The results are shown in Table 1. In Examples 1 to 3 and 5 and Comparative Examples 1, 3, and 4, where the support materials were composed of two or more layers, the tensile stress at break of the layer constituting the outermost surface of the protective sheet for workpiece processing, i.e., the soft layer, was measured as the tensile stress at break.

[0164] (TTV evaluation of wafer after grinding) In Examples 1 to 4 and Comparative Examples 1 to 4, the protective sheets for workpiece processing prepared in the Examples and Comparative Examples were attached to a silicon wafer having a diameter of 12 inches and a thickness of 775 μm using a back-grinding tape laminator (manufactured by Lintec Corporation, device name "RAD-3510F / 12"). Next, the outermost surface of the protective sheet for workpiece processing was ground by 12 μm using a grinder (manufactured by Disco Corporation, device name "DGP8760").

[0165] Next, using a back grinding device (manufactured by Disco Corporation, device name "DGP8761"), grinding (including dry polishing) was carried out until the thickness reached 30 μm.

[0166] In Example 5, as described above, a workpiece processing protection sheet was attached to a silicon wafer, and the top surface of the workpiece processing protection sheet was ground by 12 μm. Then, a laser saw (manufactured by Disco Corporation, device name "DFL7361") was used to form a modified region on the wafer so that the grid size was 10 mm × 10 mm. Next, as described above, the back surface of the wafer was ground to a thickness of 30 μm, and the wafer was divided into multiple chips.

[0167] The thickness of the ground wafer or the entire surface of each of the individual chips was measured at a measurement pitch of 10 mm using a wafer thickness mapping system (manufactured by Hamamatsu Photonics K.K., device name "C8870-02"), and the TTV of the ground wafer was calculated from the maximum and minimum thickness values ​​and evaluated according to the following criteria. The results are shown in Table 1. ◎: The outermost surface of the protection sheet for workpiece processing can be ground, and the TTV is less than 5 μm ○: The outermost surface of the protection sheet for workpiece processing can be ground, and the TTV is 5 μm or more and less than 10 μm ×: The outermost surface of the protection sheet for workpiece processing can be ground, and the TTV is 10 μm or more ××: The outermost surface of the protection sheet for workpiece processing cannot be ground.

[0168] Example 1 (1) Support material First, a polyethylene terephthalate (PET) film (thickness: 50 μm) was prepared as a rigid layer.

[0169] Next, low-density polyethylene was melted and extruded using a T-die method. The extrudate was biaxially stretched using a cooling roll to obtain a 25 μm-thick LDPE film (tensile modulus: 420 MPa). A 2.5 μm-thick easy-adhesion layer was provided on one side of the prepared PET film, and the resulting LDPE film was bonded to the soft layer by dry lamination. Next, a 2.5 μm-thick easy-adhesion layer was provided on the other side of the PET film, and the resulting LDPE film was bonded to the soft layer by dry lamination to obtain a support material consisting of a three-layer structure: soft layer / rigid layer / soft layer, with a rigid layer and a soft layer laminated together. The support material had a thickness of 105 μm.

[0170] (2) Adhesive layer (Preparation of Composition for Pressure-Sensitive Adhesive Layer) An energy beam-curable acrylic copolymer (Mw: 500,000) was obtained by reacting 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) with 2-methacryloyloxyethyl isocyanate (MOI) so that MOI was added to 80 equivalents of the total hydroxyl groups (100 equivalents) of the acrylic polymer.

[0171] 100 parts by mass of this energy ray-curable acrylic copolymer was mixed with 10 parts by mass of a multifunctional urethane acrylate ultraviolet-curable compound (manufactured by Mitsubishi Chemical Corporation, product name "UT-4332"), 0.38 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator, and the mixture was diluted with methyl ethyl ketone to prepare a coating agent for a pressure-sensitive adhesive layer composition with a solids concentration of 34% by mass.

[0172] (Production of protective sheets for workpiece processing) The adhesive layer composition obtained above was applied to the silicone release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") and dried by heating to form an adhesive layer 20 μm thick on the release sheet.

[0173] Thereafter, one soft layer of the support material was attached to the adhesive layer to prepare a protection sheet for workpiece processing, i.e., the protection sheet for workpiece processing shown in Fig. 1C was produced.

[0174] Example 2 The protection sheet for workpiece processing shown in FIG. 1B was produced in the same manner as in Example 1, except that a support material composed of two layers, a soft layer / a rigid layer, was produced as follows.

[0175] A PET film (thickness: 50 μm) was prepared as a rigid layer. Next, a composition for forming a soft layer was prepared as follows.

[0176] First, a terminal isocyanate urethane prepolymer obtained by reacting polyester diol with isophorone diisocyanate was reacted with 2-hydroxyethyl acrylate to obtain a bifunctional urethane acrylate oligomer (UA-1) with a weight average molecular weight (Mw) of 5,000.

[0177] A composition for the soft layer was prepared by blending 50 parts by mass of the urethane acrylate oligomer (UA-1) synthesized above, 45 parts by mass of isobornyl acrylate (IBXA), and 5 parts by mass of polyethylene glycol 600 diacrylate as energy ray-curable compounds, and further blending 2 parts by mass of 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins, product name "OMNIRAD1173") as a photopolymerization initiator.

[0178] The soft layer composition was applied to the silicone release-treated surface of a release sheet (SP-PET381031, manufactured by Lintec Corporation, thickness: 38 μm) to form a coating film, which was then semi-cured by irradiating the coating film with ultraviolet light to form a semi-cured soft layer film with a thickness of 55 μm.

[0179] The ultraviolet irradiation was performed using a belt conveyor type ultraviolet irradiation device (Eye Graphics, ECS-401GX) and a high-pressure mercury lamp (Eye Graphics, H04-L41), with a lamp height of 260 mm, output of 80 W / cm, and illuminance of 70 mW / cm. 2 , irradiation amount 30mW / cm 2 The surface of the semi-cured film thus formed was then bonded to one main surface of a PET film serving as a rigid layer, and ultraviolet light was again irradiated from the release sheet side of the semi-cured film to completely cure the semi-cured film and form a soft layer having a thickness of 55 μm.

[0180] Example 3 The protective sheet for workpiece processing shown in Figure 1C was produced in the same manner as in Example 1, except that a 25 μm-thick linear low-density polyethylene (LLDPE) was formed as the soft layer in a support material composed of three layers: soft layer / rigid layer / soft layer. The LLDPE was obtained by melting the linear low-density polyethylene, extruding the melt using a T-die method, and biaxially stretching the extrudate using a cooling roll. The tensile modulus of the LLDPE was 90 MPa.

[0181] Example 4 A protection sheet for workpiece processing was produced in the same manner as in Example 1, except that a support material consisting of one layer of PET film (manufactured by Toray Advanced Materials Co., Ltd., product name "XG7PH8", thickness: 50 μm) was used. That is, a protection sheet for workpiece processing shown in FIG. 1A was produced.

[0182] Example 5 A protection sheet for workpiece processing was produced in the same manner as in Example 2.

[0183] (Comparative Example 1) A protective sheet for workpiece processing shown in Figure 1B was produced in the same manner as in Example 2, except that the soft layer was formed using the soft layer composition shown below in a support material composed of two layers: a soft layer / a rigid layer.

[0184] A urethane acrylate oligomer (UA-2) with a weight average molecular weight (Mw) of approximately 25,000 was obtained by reacting 2-hydroxyethyl acrylate with a terminal isocyanate urethane prepolymer obtained by reacting polycarbonate diol with isophorone diisocyanate.

[0185] A composition for the soft layer was prepared by blending 25 parts by mass of the urethane acrylate oligomer (UA-2) synthesized above, 65 parts by mass of isobornyl acrylate (IBXA), and 10 parts by mass of phenylhydroxypropyl acrylate (HPPA) as energy ray-curable compounds, and further blending 2.0 parts by mass of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by IGM Resins, product name "Omnirad 1173") as a photopolymerization initiator.

[0186] (Comparative Example 2) A protection sheet for workpiece processing was produced in the same manner as in Example 4, except that a support material consisting of one layer of polyethylene naphthalate (PEN) film (thickness: 50 μm) was used.

[0187] (Comparative Example 3) The protective sheet for workpiece processing shown in FIG. 1C was produced in the same manner as in Example 1, except that a colorless and transparent ethylene-methacrylic acid copolymer having a thickness of 25 μm was formed as the soft layer in a support material composed of three layers: soft layer / rigid layer / soft layer.

[0188] Comparative Example 4 The protective sheet for workpiece processing shown in Figure 1C was produced in the same manner as in Example 1, except that a colorless and transparent ethylene-vinyl acetate copolymer with a thickness of 25 μm was formed as the soft layer in a support material composed of three layers: soft layer / rigid layer / soft layer.

[0189] The above measurements and evaluations were carried out on the obtained samples (Examples 1 to 5 and Comparative Examples 1 to 4). The results are shown in Table 1.

[0190] [Table 1]

[0191] From Table 1, it was confirmed that when the coefficient of dynamic friction between the support material and sandpaper and the tensile breaking stress of the support material are within the above-mentioned ranges, the main surface that forms the outermost surface of the workpiece processing protection sheet is ground on the support material, and then the wafer is ground on the back side, and the TTV of the wafer after back side grinding is small. [Explanation of symbols]

[0192] 1...Protection sheet for workpiece processing 10...Support material 11...Rigid layer 12…Soft layer 20...Adhesive layer

Claims

1. A protective sheet for workpiece processing having a support material and an adhesive layer disposed on one main surface of the support material, The other main surface of the support material constitutes the outermost surface of the workpiece processing protection sheet, and the dynamic friction coefficient between the outermost surface of the workpiece processing protection sheet and sandpaper having a grit size of 1200 is 1.40 or less; A protective sheet for workpiece processing, wherein the support material has a tensile breaking stress of 250 MPa or less.

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

3. The workpiece processing protective sheet according to 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.

4. A workpiece processing protective sheet according to any one of claims 1 to 3, wherein the surface of the workpiece and the adhesive layer are attached before the process of grinding the back surface of the workpiece having a front and back surface, and the outermost surface of the workpiece processing protective sheet is ground before use.

5. A protective sheet for workpiece processing as described in claim 4, which is used in a process of dividing a workpiece into individual workpieces by grinding the back surface of the workpiece having a groove formed on the surface thereof or a modified region formed inside the workpiece.

6. The protection sheet for workpiece processing according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer is energy ray-curable.

7. A step of attaching the adhesive layer of the protective sheet for workpiece processing according to any one of claims 1 to 6 to the surface of a workpiece having a front and back surfaces; grinding the back surface of the workpiece; and a step of dividing the work into individual pieces to obtain a plurality of individual work pieces.

8. The workpiece processing protective sheet according to claim 4 or 5, further comprising a step of grinding the outermost surface of the workpiece processing protective sheet, The method for producing individual workpieces according to claim 7, wherein the step of grinding the back surface of the workpiece is carried out after the step of grinding the outermost surface of the protection sheet for workpiece processing.

9. The method further includes a step of forming a groove on the surface of the workpiece, or a step of forming a modified region inside the workpiece from the surface or back surface of the workpiece, The method for manufacturing a workpiece singulation product according to claim 7 or 8, wherein in the step of grinding the back surface of the workpiece, the workpiece is singulated into a plurality of workpiece singulation products starting from the groove or the modified region.

10. 10. The method for manufacturing a workpiece singulated product according to claim 7, further comprising a step of peeling off the workpiece processing protection sheet from the workpiece singulated product.

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