Protective sheet for workpiece processing and method for manufacturing workpiece induced product

Abstract

To provide a protective sheet for workpiece processing in which electrostatic charge generated during processing of a workpiece or a group of workpiece induced product is sufficiently suppressed, and in which adhesive residue on the workpiece, etc. is suppressed when the protective sheet for workpiece processing is peeled off from the workpiece, etc., and to provide a method for manufacturing workpiece induced product using the protective sheet for workpiece processing.SOLUTION: A protective sheet for workpiece processing includes a substrate and an adhesive layer disposed on the substrate and attached to a workpiece, the substrate includes a support material, an antistatic agent-containing soft material, and an adhesive layer that integrates the support material and the antistatic agent-containing soft material, and the protective sheet for workpiece processing is such that the antistatic agent-containing soft material and the adhesive layer are not in contact with each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a protective sheet for workpiece processing and a method for manufacturing a workpiece singulated product. In particular, the present invention relates to a protective sheet for workpiece processing suitable for use in a method for grinding the back surface of a workpiece and singulating the workpiece by the resulting stress, and a method for manufacturing a workpiece singulated product using the protective sheet for workpiece processing. [Background technology]

[0002] As various electronic devices become smaller and more multifunctional, the semiconductor chips mounted on them are also required to be smaller and thinner. In order to thin the chips, it is common to grind the backside of the semiconductor wafer to adjust the thickness. In order to obtain thin chips, a method called dicing before grinding (DBG) is sometimes used, in which grooves of a specified depth are formed on the front side of the wafer with a dicing blade, and then the wafer is ground from the backside, and the wafer is divided into individual pieces by grinding to obtain chips. With DBG, the backside grinding and wafer division can be performed simultaneously, so thin chips can be manufactured efficiently.

[0003] Conventionally, when grinding the backside of a workpiece such as a semiconductor wafer, or when manufacturing individual workpieces such as semiconductor chips by DBG, it is common to apply a backgrind tape as a protective sheet for workpiece processing, which is composed of at least a base material and an adhesive layer, to the surface of the workpiece in order to protect the circuits on the surface of the workpiece and to hold the workpiece and multiple individual workpieces (i.e., a group of individual workpieces).

[0004] As an example of a backgrind tape, Patent Documents 1 and 2 disclose an adhesive tape having a substrate with a high Young's modulus, a buffer layer on one side of the substrate, and an adhesive layer on the other side.

[0005] In recent years, a method has been proposed as a variation of the dicing-before method, in which a modified region is provided inside the wafer using a laser, and the wafer is divided into individual pieces by stress during grinding the back surface of the wafer. Hereinafter, this method may be referred to as LDBG (Laser Dicing Before Grinding). In LDBG, the wafer is cut in the crystal direction starting from the modified region, so that the occurrence of chipping can be reduced more than in the dicing-before method using a dicing blade. Also, compared to DBG, in which a groove of a predetermined depth is formed on the wafer surface by a dicing blade, there is no region where the wafer is scraped off by the dicing blade, that is, the kerf width is extremely small, so that the chip yield is excellent. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2015 / 156389 [Patent Document 2] JP 2015-183008 A Summary of the Invention [Problem to be solved by the invention]

[0007] It is known that electrostatic charging occurs during processing of a wafer, which is an example of a workpiece (for example, during dicing, back grinding, cleaning, peeling off a backgrind tape, etc.). When electrostatic charging occurs, cut dust generated when cutting the backgrind tape, minute foreign matter present in the environment, etc., tend to adhere to the wafer or a chip, which is an example of a workpiece singulated product.

[0008] For example, if cut dust or foreign matter adheres to the wafer during back grinding, the pressure during back grinding may concentrate on the foreign matter, causing damage to the wafer from the foreign matter. In particular, when performing DBG, which aims to grind the wafer thin, the wafer is likely to be damaged by even a slight concentration of pressure. In addition, for example, if the peeling charge generated when peeling the back grind tape from the wafer is excessive, it may lead to the destruction of the circuits formed on the wafer. Therefore, it is necessary to suppress the charge generated during wafer processing.

[0009] In order to suppress the static electricity generated during the processing of such wafers, an antistatic layer is provided on the backgrind tape. In this case, a process is required to form the antistatic layer, and there is a problem that the increased process reduces the production efficiency of the backgrind tape.

[0010] In addition, the adhesive layer of the backgrind tape strongly adheres to the surface of the wafer during backgrinding to adequately protect the circuits, etc. On the other hand, when the backgrind tape is peeled off from the wafer after backgrinding, it is required that the adhesive layer is peeled off without remaining on the wafer.

[0011] However, if the adhesive layer attached to the surface of the wafer does not adhere well to the other layers, the adhesive layer may not peel off from the wafer together with the substrate when the backgrind tape is peeled off, and may remain on the surface of the wafer as a residue (glue residue). If such residue is generated, an extra step such as washing the wafer is required, resulting in a problem of reduced production efficiency.

[0012] The present invention has been made in consideration of the above-described situation, and aims to provide a protective sheet for work processing in which electrostatic charge generated during processing of a workpiece, etc. (i.e., a workpiece or a group of individual workpieces) is sufficiently suppressed, and in which glue residue on the workpiece, etc. is suppressed when the protective sheet for work processing is peeled off from the workpiece, etc., and to provide a method for manufacturing individual workpieces using the protective sheet for work processing. [Means for solving the problem]

[0013] The aspects of the present invention are as follows.

[0014] [1] A protective sheet for work processing having a substrate and an adhesive layer disposed on the substrate and attached to a work, The substrate has a support material, an antistatic agent-containing soft material, and an adhesive layer that integrates the support material and the antistatic agent-containing soft material, This is a protection sheet for workpiece processing in which the antistatic agent-containing soft material and the adhesive layer are not in contact with each other.

[0015] [2] A protective sheet for workpiece processing according to [1], comprising an adhesive layer, a support material, an adhesive layer, and an antistatic agent-containing soft material laminated in this order.

[0016] [3] The protective sheet for workpiece processing according to [1] or [2], wherein the thickness of the antistatic agent-containing soft material is 20 μm or more and 70 μm or less.

[0017] [4] The surface resistivity of the adhesive layer on the surface attached to the workpiece is 1.0×10 12 The protective sheet for workpiece processing according to any one of [1] to [3], wherein the resistivity is greater than Ω / □.

[0018] [5] A protective sheet for workpiece processing according to any one of [1] to [4], which is attached to the surface of a workpiece in a process for dividing a workpiece into individual workpieces by grinding the back surface of the workpiece having a groove formed on its surface or a modified region formed inside.

[0019] [6] A process of attaching a workpiece processing protection sheet according to any one of [1] to [5] to a surface of a workpiece having a surface and a back surface opposite to the surface; A step of forming a groove on a surface of a workpiece or a step of forming a modified region inside the workpiece; A step of grinding a workpiece having a workpiece processing protection sheet attached to a surface thereof and having grooves or modified regions formed thereon from a back surface thereof to separate the workpiece into a plurality of workpiece pieces starting from the grooves or modified regions; and peeling off the workpiece processing protection sheet from the plurality of workpiece individual pieces. Effect of the Invention

[0020] According to the present invention, it is possible to provide a protective sheet for work processing in which electrostatic charge generated during processing of a workpiece, etc. (i.e., a workpiece or a group of individual workpieces) is sufficiently suppressed, and in which adhesive residue on the workpiece, etc. is suppressed when the protective sheet for work processing is peeled off from the workpiece, etc., and to provide a method for manufacturing individual workpieces using the protective sheet for work processing. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a protection sheet for workpiece processing according to this embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a state in which the protection sheet for workpiece processing according to this embodiment is attached to the surface of a wafer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings based on specific embodiments. First, the main terms used in this specification will be explained.

[0023] The work refers to a plate-like body to which a surface protection sheet is attached and then cut into individual pieces. Examples of the work include a circular wafer (including a case having an orientation flat), a rectangular panel level package, and a strip (rectangular substrate) sealed with molded resin. Among them, a wafer is preferable from the viewpoint of easily obtaining the effect of the present invention. The wafer may be, for example, a semiconductor wafer such as a silicon wafer, a gallium arsenide wafer, a silicon carbide wafer, a gallium nitride wafer, or an indium phosphide wafer, or an insulating wafer such as a glass wafer, a lithium tantalate wafer, or a lithium niobate wafer, or may be a reconstructed wafer made of a resin and a semiconductor used for producing a fan-out package or the like. From the viewpoint of easily obtaining the effect of the present invention, a semiconductor wafer or an insulating wafer is preferable, and a semiconductor wafer is more preferable.

[0024] Singulation of a work refers to dividing the work into individual circuits to obtain individual work pieces. For example, if the work is a wafer, the individual work pieces are chips, and if the work is a panel level package or a strip (rectangular substrate) sealed with molded resin, the individual work pieces are semiconductor packages.

[0025] The "front surface" of a workpiece refers to the side on which a circuit or the like is formed or on which the formation of a circuit or the like is planned, and the "back surface" of a workpiece refers to the side on which a circuit or the like is not formed or on which the formation of a circuit or the like is not planned.

[0026] DBG (Dicing Before Grinding) is a method in which grooves of a specified depth are formed on the surface of a wafer as a workpiece, and then the wafer is ground from the back side to separate the wafer by grinding. The grooves formed on the surface of the wafer are formed by methods such as blade dicing, laser dicing, and plasma dicing.

[0027] Furthermore, LDBG (Laser Dicing Before Grinding) is a modified form of DBG, in which a modified region is created inside a wafer as a workpiece using a laser, and the wafer is diced into individual pieces by using stress, etc., during grinding of the back surface of the wafer.

[0028] The term "group of individual workpieces" refers to a plurality of individual workpieces held on the surface protection sheet of the present invention after the workpiece is singulated. These individual workpieces, as a whole, form a shape similar to that of the workpiece. The term "group of chips" refers to a plurality of chips held on the surface protection sheet of the present invention after the wafer as the workpiece is singulated. These chips, as a whole, form a shape similar to that of the wafer.

[0029] "(Meth)acrylate" is used as the term to refer to both "acrylate" and "methacrylate," and similar terms.

[0030] The term "energy rays" refers to ultraviolet rays, electron beams, etc., and is preferably ultraviolet rays.

[0031] Unless otherwise specified, the "weight average molecular weight" is a polystyrene equivalent value measured by gel permeation chromatography (GPC). Measurements by such a 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 of the above are manufactured by Tosoh Corporation) connected in the above order, the column temperature was 40° C., the liquid flow rate was 1.0 mL / min, and the detector was a differential refractometer.

[0032] Mass ratios in the descriptions of compositions such as pressure sensitive adhesive compositions are based on the active ingredients (solid content), and do not include the solvent unless otherwise specified.

[0033] (1. Protective sheet for workpiece processing) The protective sheet for workpiece processing is used when processing a workpiece or the like (i.e., a workpiece or a group of individual workpieces) 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). The front side of the workpiece or the like may be the surface on which the circuit is exposed, or may be the main surface of a protective layer formed on the circuit to protect the circuit. Also, a convex electrode such as a bump may be formed on the circuit.

[0034] An example of the processing of the workpiece is back grinding of the workpiece. By grinding the back surface of the workpiece, it is possible to realize a reduction in thickness of the individual workpieces obtained by dividing the workpiece.

[0035] The protective sheet for workpiece processing is temporarily attached to the front surface of the workpiece before grinding the back surface of the workpiece to protect the front surface of the workpiece. The back surface of the workpiece is ground with the protective sheet for workpiece processing attached to the front surface of the workpiece. After grinding is completed, the protective sheet for workpiece processing is peeled off from the workpiece or the group of individual workpiece pieces.

[0036] In order to perform such a function, the protective sheet for workpiece processing usually has a base material and an adhesive layer. During back grinding of the workpiece, the base material supports the workpiece, and the adhesive layer adheres to the workpiece to fix the protective sheet for workpiece processing to the workpiece. Furthermore, in this embodiment, the base material has a support material having a rigidity sufficient to support the workpiece, and a soft material that is softer than the support material. The soft material suppresses damage and cracks of the workpiece, etc. caused by foreign matter present on the suction table to which the workpiece is fixed during back grinding.

[0037] As described above, when processing a workpiece or the like, for example, when grinding the back surface of the workpiece, charging occurs on the workpiece or a group of individual pieces of the workpiece. In addition, charging (peeling charging) also occurs, for example, when peeling off a protective sheet for workpiece processing. If such charging is not alleviated, it may lead to adhesion of foreign matter, etc. to the workpiece or the like (i.e., the workpiece or a group of individual pieces of the workpiece) due to charging, which may result in damage or cracks to the workpiece or the like. Or it may lead to destruction of the circuit formed on the workpiece or the like.

[0038] Therefore, in order to suppress such peeling static electricity, an antistatic layer is provided on the protective sheet for workpiece processing. However, when providing such an antistatic layer, a new element is added to the existing elements (for example, the above-mentioned base material and adhesive layer) in the protective sheet for workpiece processing, so an additional process is required to form the antistatic layer. In other words, there is a problem that the manufacturing lead time becomes long.

[0039] In addition, when the workpiece is ground on the back side using the workpiece processing protective sheet, the workpiece processing protective sheet is peeled off after the back side grinding. When the workpiece processing protective sheet is peeled off, it is necessary to peel off the adhesive layer of the workpiece processing protective sheet and the workpiece. Here, in the case where the adhesive layer attached to the workpiece surface and the other layers in the workpiece processing protective sheet are insufficient in adhesion, at least a part of the adhesive layer that should be peeled off from the workpiece surface when the workpiece processing protective sheet is peeled off may be peeled off from the workpiece processing protective sheet and remain as a residue (glue residue) on the surface of the workpiece or the workpiece individual pieces. When such residue occurs, there is a problem that cleaning or the like is required to remove the residue.

[0040] Therefore, in the workpiece processing protective sheet according to the present embodiment, an antistatic agent is contained in the soft material that is a member constituting the base material. By containing an antistatic agent during molding of the soft material, antistatic performance can be imparted to the soft material without generating an additional process. Furthermore, in the workpiece processing protective sheet, the soft material containing the antistatic agent is configured not to come into contact with the adhesive layer, so that the adhesive layer and the member of the workpiece processing protective sheet can be secured in close contact with each other. That is, the adhesive layer is prevented from peeling off from the workpiece processing protective sheet when the workpiece processing protective sheet is peeled off. Therefore, the workpiece processing protective sheet according to the present embodiment is particularly suitable as a workpiece processing protective sheet that is attached to the surface of a workpiece in a process of dividing the workpiece into individual workpieces by grinding the back surface of the workpiece having a groove formed on the surface or a modified region formed inside.

[0041] The configuration of the workpiece processing protection sheet according to this embodiment, which has such effects, will be described below.

[0042] The protective sheet for workpiece processing according to this embodiment has a substrate and an adhesive layer disposed on the substrate. The substrate also has a support material, an antistatic agent-containing soft material, and an adhesive layer that integrates the support material and the antistatic agent-containing soft material. Furthermore, the antistatic agent-containing soft material and the adhesive layer are not in contact with each other. This is because, when a composition for forming an adhesive layer is applied onto the antistatic agent-containing soft material, the antistatic agent contained in the soft material bleeds out, and the desired antistatic function cannot be achieved.

[0043] In this embodiment, as shown in FIG. 1, the protective sheet 1 for workpiece processing has a configuration in which an adhesive layer 20, a support material 12, an adhesive layer 16, and an antistatic agent-containing soft material 14 are laminated in this order.

[0044] The protective sheet for workpiece processing is not limited to the configuration shown in Fig. 1, and may have other layers as long as the effects of the present invention can be obtained. That is, as long as the substrate 10 and the adhesive layer 20 have the above-mentioned configuration, for example, an intermediate layer for mitigating the stress applied to the workpiece during back grinding may be disposed between the support material 12 and the adhesive layer 20.

[0045] In this embodiment, as shown in Fig. 2, the protective sheet for workpiece processing 1 is used by attaching the main surface 20a of the adhesive layer 20 to the surface 100a of the workpiece 100 (e.g., a wafer). The surface 100a of the workpiece 100 is a surface having circuits, electrodes, etc. The surface having the circuits may be a surface on which the circuits are exposed, or may be the main surface of a protective layer formed on the circuits to protect the circuits. Also, convex electrodes such as bumps may be formed on the circuits.

[0046] The components of the workpiece processing protection sheet will be described in detail below.

[0047] (2. Base material) The substrate is a member that provides the rigidity of the protective sheet for workpiece processing. In this embodiment, as shown in Fig. 1, the substrate 10 is a composite material having a plurality of components (support material 12, antistatic agent-containing soft material 14, adhesive layer 16). The components of the substrate, that is, the support material, antistatic agent-containing soft material, and adhesive layer, will be described below.

[0048] (2.1. Support material) The support material is a film-like member that is responsible for the rigidity of the substrate. Therefore, the support material must have a rigidity sufficient to suppress vibrations during back grinding of the workpiece and to stably support the workpiece. In this embodiment, the rigidity of the support material is evaluated by Young's modulus. Specifically, the Young's modulus of the support material at 23° C. is preferably 500 MPa or more.

[0049] By making the Young's modulus of the support material within the above range, the support and holding performance of the workpiece, etc. (i.e., the workpiece or a group of individual pieces of the workpiece) is improved, and damage and cracks of the workpiece, etc. are reduced. In addition, the workability when attaching the workpiece processing protection sheet to the workpiece is improved.

[0050] The Young's modulus of the above-mentioned support material at 23° C. is more preferably 750 MPa or more, even more preferably 1000 MPa or more, and particularly preferably 3000 MPa or more. There is no particular upper limit to the Young's modulus, but it may be 5500 MPa or less.

[0051] The Young's modulus of the support material at 23° C. is measured in accordance with JIS K 7127. That is, it is measured in the same manner as the measurement method specified in JIS K 7127, but the measurement conditions may be different. The specific measurement method will be described in the examples.

[0052] In this embodiment, the thickness of the support material is preferably 10 μm or more and 80 μm or less, more preferably 22 μm or more and 65 μm or less, and even more preferably 25 μm or more and 60 μm or less.

[0053] (2.1.1. Materials of Supports) The material of the support material may be selected according to the desired application. For example, various resin films are exemplified. The support material may be composed of a single layer film made of one resin film, or may be composed of a multi-layer film in which multiple resin films are laminated.

[0054] In this embodiment, examples of the resin film include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyesters such as fully aromatic polyesters, polyimides, polyamides, polycarbonates, polyacetals, modified polyphenylene oxides, polyphenylene sulfides, polysulfones, polyether ketones, and high-density polyethylene (HDPE, density: 942 kg / m 3The above-mentioned films and biaxially oriented polyolefin films are preferred. Among these, films of one or more types selected from polyester, polyamide, polyimide, high density polyethylene, and biaxially oriented polyolefin are preferred, polyester or high density polyethylene films are more preferred, and polyethylene terephthalate films are even more preferred.

[0055] The support material may also contain a plasticizer, a lubricant, an infrared absorbing agent, an ultraviolet absorbing agent, a filler, an antistatic agent, an antioxidant, a catalyst, etc., within the scope of not impairing the effects of the present invention. The support material may be transparent or opaque, and may contain a colorant and be colored. A colored layer may also be formed on the support material.

[0056] At least one of the main surfaces of the support material may be subjected to a surface treatment such as a corona treatment in order to improve adhesion to other layers and members.

[0057] (2.2. Soft material containing antistatic agent) The antistatic agent-containing soft material is a member that has an antistatic function and a function of mitigating the effects of stress and foreign matter on the workpiece during back grinding of the workpiece. In this embodiment, the antistatic agent-containing soft material has a configuration in which an antistatic agent is contained inside a soft material that does not have an antistatic function, and it is preferable that the antistatic component is dispersed in the soft material. Therefore, a member having a configuration in which an antistatic layer is formed on a soft material is not included in the antistatic agent-containing soft material.

[0058] (2.2.1. Soft materials) The soft material is a member that is softer than the support material. Specifically, the Young's modulus of the soft material at 23°C is lower than the Young's modulus of the support material at 23°C. Since the protective sheet for workpiece processing contains a soft material, the stress applied to the workpiece or the like (i.e., the workpiece or a group of individual pieces of the workpiece) during back grinding can be alleviated, and damage to the workpiece or the like and the occurrence of cracks can be suppressed. Furthermore, before back grinding of the workpiece, the workpiece to which the protective sheet for workpiece processing is attached is fixed to the suction table. At this time, even if foreign matter or the like is attached to the suction table, the soft material can embed the foreign matter or the like, and damage to the workpiece or the like and the occurrence of cracks caused by the foreign matter or the like can be suppressed during back grinding.

[0059] The Young's modulus of the soft material at 23° C. is preferably 50 MPa or more and 1000 MPa or less, more preferably 100 MPa or more and 750 MPa or less, and even more preferably 120 MPa or more and 450 MPa or less.

[0060] The Young's modulus of the soft material at 23°C can be measured in the same manner as for the Young's modulus of the support material at 23°C.

[0061] The thickness of the soft material is preferably 20 μm to 70 μm, more preferably 25 μm to 60 μm, and even more preferably 30 μm to 55 μm. By making the thickness of the soft material within the above range, as described above, it becomes easier to suppress damage and cracks of the workpiece caused by foreign matter during back grinding.

[0062] In this embodiment, the soft material is preferably made of a resin film. The soft material may be made of a single-layer film made of one resin film, or may be made of a multi-layer film in which multiple resin films are laminated.

[0063] The resin film is preferably a polyolefin resin film. Examples of polyolefin resin include very low density polyethylene (VLDPE, density: 880 kg / m3 More than 910kg / m 3 less than 910kg / m), low density polyethylene (LDPE, density: 910kg / m 3 Above, 942kg / m 3 less than 942 kg / m 3 Examples of the polyolefin resin include polyethylene resins such as those mentioned above, polypropylene resins, polyethylene-polypropylene copolymers, olefin-based elastomers (TPO), cycloolefin resins, polyvinyl chloride (PVC), ethylene-vinyl acetate copolymers (EVA), ethylene-vinyl acetate-maleic anhydride copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, ethylene-(meth)acrylic acid ester-maleic anhydride copolymers, and ionomer resins. These polyolefin resins can be used alone or in combination of two or more.

[0064] In this embodiment, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, very low density polyethylene (VLDPE, density: 880 kg / m 3 More than 910kg / m 3 less than 910kg / m), low density polyethylene (LDPE, density: 910kg / m 3 Above, 942kg / m 3 It is preferable that the polyethylene be a low density polyethylene or the like, and it is more preferable that the polyethylene be a low density polyethylene.

[0065] The soft material may contain a plasticizer, a lubricant, an infrared absorbing agent, an ultraviolet absorbing agent, a filler, an antistatic agent, an antioxidant, a catalyst, etc., within a range that does not impair the effects of the present invention. The soft material may be transparent or opaque, and may contain a colorant and be colored. Also, a colored layer may be formed on the soft material.

[0066] At least one of the main surfaces of the soft material may be subjected to a surface treatment such as a corona treatment in order to improve adhesion to other layers and members.

[0067] (2.2.2. Antistatic Agents) In this embodiment, the antistatic agent is present in the soft material. As the antistatic agent, an antistatic agent that is solid at room temperature is preferable from the viewpoints of kneadability in extrusion by the T-die method and the fact that bleeding out from the soft material is unlikely to occur.

[0068] In addition, the type of the antistatic agent may be a low molecular weight antistatic agent, a polymeric antistatic agent, etc. In this embodiment, a polymeric antistatic agent is preferred from the viewpoints of kneadability in extrusion by the T-die method, and the fact that bleeding out from the soft material is unlikely to occur, thereby making it easy to suppress changes in adhesion to the substrate over time.

[0069] Examples of polymer-type antistatic agents include copolymers having polyether units, such as polyether ester amides and polyether polyolefin block copolymers, and these copolymers may contain metal salts, such as alkali metal salts and alkaline earth metal salts, and ionic liquids. Among these, polyether polyolefin block copolymers are preferred from the viewpoint of easily suppressing changes in adhesive strength over time while achieving sufficient antistatic properties.

[0070] A polyether polyolefin block copolymer is a copolymer that has both polyether and polyolefin units. The polyether unit exhibits ion conductivity, thereby exerting antistatic properties, and the polyolefin unit provides excellent dispersibility in polyolefin resins.

[0071] Examples of commercially available polyether polyblock olefin copolymers include those manufactured by Sanyo Chemical Industries Co., Ltd. under the product names "Pellestat 300," "Pellestat 230," "Pelletron PVH," "Pelletron PVL," "Pellestat HS," "Pellestat 201," and "Pelletron UC," as well as those manufactured by Sanko Chemical Industries Co., Ltd. under the product name "Sankonol TBX-310."

[0072] (2.2.3. Adhesive layer) The adhesive layer is a layer for adhering the support material and the soft material and improving the adhesion between the support material and the soft material. The adhesive layer may be formed in consideration of the material and surface condition of the support material and the soft material. For example, the adhesive layer may be formed by disposing an adhesive film between the support material and the soft material, or the adhesive layer may be formed by applying the adhesive layer forming composition onto the support material and / or the soft material. The adhesive layer forming composition is not particularly limited, but examples thereof include compositions containing polyester resins, urethane resins, polyester urethane resins, acrylic resins, etc. The adhesive layer forming composition may contain a crosslinking agent, a photopolymerization initiator, an antioxidant, a softener (plasticizer), a filler, an anti-rust agent, a colorant, etc., as necessary.

[0073] The adhesive layer may be a single layer or may be composed of multiple layers. When composed of multiple layers, the adhesive layer may include a layer that does not have adhesiveness as long as the adhesive layer as a whole has adhesiveness.

[0074] The adhesive layer may have any thickness that ensures adhesion between the support material and the soft material. In this embodiment, the adhesive layer has a thickness of preferably 0.01 to 10 μm, and more preferably 0.03 to 5 μm.

[0075] (3. Adhesive Layer) The adhesive layer is attached to the surface of a workpiece having a front and back surface (i.e., the surface on which circuits, electrodes, etc. are formed), and protects the surface and supports the workpiece or a group of individual workpieces until it is peeled off from the surface. In this embodiment, the adhesive layer is preferably composed of one layer (single layer). This is because if the adhesive layer has multiple layers, when the protective sheet for workpiece processing is peeled off, the adhesive layers may peel off from each other, with one adhesive layer remaining on the protective sheet for workpiece processing and the other adhesive layer remaining on the workpiece, resulting in residue on the workpiece.

[0076] 1, the distance D between the surface 20a of the adhesive layer 20 that is attached to the workpiece and the surface 14a of the antistatic agent-containing soft material 14 that is located on the support material 12 side is preferably 300 μm or less. In the protective sheet for workpiece processing 1 shown in FIG. 1, this distance D corresponds to the sum of the thickness of the adhesive layer 20, the thickness of the support material 12, and the thickness of the adhesive layer 16.

[0077] By setting the distance D within the above range, the antistatic performance of the antistatic agent-containing soft material is easily exhibited, and as a result, excessive charging (particularly peeling charging) can be sufficiently suppressed.

[0078] The distance D is more preferably 250 μm or less, even more preferably 200 μm or less, and particularly preferably 150 μm or less. The lower limit of the distance is not limited as long as the above-mentioned configuration is satisfied, but from the viewpoint of easily obtaining a workpiece processing protection sheet with more stable performance, it may be, for example, 20 μm or more, or 35 μm or more.

[0079] The thickness of the adhesive layer is preferably 20 μm or more and 210 μm or less, more preferably 25 μm or more and 60 μm or less. By having the thickness of the adhesive layer within the above range, the adhesive layer can fully exhibit its adhesive properties, and can also fully conform to irregularities (electrodes, grooves, etc.) present on the surface of the workpiece to easily fill the irregularities, and can also facilitate subsequent peeling from the workpiece, etc.

[0080] The thickness of the adhesive layer means the thickness of the entire adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers means the total thickness of all layers constituting the adhesive layer.

[0081] In this embodiment, the pressure-sensitive adhesive layer preferably has the following physical properties.

[0082] (3.1 Surface resistivity) In this embodiment, the surface resistivity of the pressure-sensitive adhesive layer is 1.0×10 12It is preferable that the surface resistivity is larger than Ω / □. Note that this surface resistivity is the surface resistivity of the surface of the adhesive layer that is attached to the workpiece as the adherend (surface 20a of the adhesive layer in FIG. 1). In addition, when the adhesive layer is energy ray curable, this surface resistivity is the surface resistivity after energy ray curing.

[0083] When the surface resistivity is lower than the above range, for example, when a protective sheet for workpiece processing is used in the DBG process, after the workpiece is singulated, grinding water from the grinder may penetrate between the workpiece singulated pieces (kerf portion) and the grinding water may come into contact with the adhesive surface. The contact with the grinding water may cause the surface resistivity of the adhesive layer to fluctuate, particularly the surface resistivity to decrease. On the other hand, the grinding water does not come into contact with the adhesive layer in contact with the workpiece singulated piece. Therefore, the surface resistivity of the adhesive layer surface, which was adjusted uniformly before grinding in the area corresponding to the kerf portion and the area corresponding to the workpiece singulated piece, may be unintentionally lost and become non-uniform after grinding. Furthermore, if an antistatic component is added to the adhesive to reduce the surface resistivity of the adhesive surface, when the adhesive layer is peeled off from the workpiece or the group of individual workpieces, the adhesive layer may peel off and become a residue on the workpiece or the group of individual workpieces, which may have an adverse effect on the workpiece or the group of individual workpieces.

[0084] Surface resistivity is 5.0 x 10 12 Ω / □ or more is preferable, and 8.0×10 12 It is more preferable that the surface resistivity is 9.9×10 13 It is preferable that the resistance is Ω / □ or less, and 6.0×10 13 It is more preferable that the resistance is Ω / □ or less.

[0085] In this embodiment, the surface resistivity is measured in accordance with JIS K 7194. That is, the surface resistivity is measured in the same manner as the measurement method specified in JIS K 7194, but the measurement conditions may be different. Specific measurement conditions will be described later in the examples.

[0086] (3.2 Composition of Adhesive Layer) The composition of the adhesive layer is not limited as long as it has enough adhesiveness to protect the surface of the workpiece or the group of individual pieces of the workpiece. In this embodiment, the adhesive layer is composed of an adhesive composition, and is preferably composed of, for example, an acrylic adhesive composition, a urethane adhesive composition, a rubber adhesive composition, a silicone adhesive composition, or the like.

[0087] In addition, the adhesive layer is preferably an energy ray curable adhesive layer composed of an energy ray curable adhesive composition. Since the adhesive layer of the protective sheet for workpiece processing is an energy ray curable adhesive layer, when it is attached to the workpiece, it is attached to the workpiece with high adhesive strength, and when it is peeled off from the workpiece or the group of workpiece pieces, the adhesive strength can be reduced by irradiating with energy rays. Therefore, when the protective sheet for workpiece processing is peeled off, while appropriately protecting the circuits of the workpiece or the group of workpiece pieces, damage to the circuits, electrodes, etc. on the surface of the workpiece or the group of workpiece pieces is prevented.

[0088] In this embodiment, the energy ray curable pressure-sensitive adhesive composition is preferably composed of an acrylic pressure-sensitive adhesive composition. The acrylic pressure-sensitive adhesive composition contains an acrylic polymer.

[0089] 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.

[0090] In this embodiment, the functional group-containing acrylic polymer is preferably an acrylic copolymer obtained by copolymerizing an alkyl (meth)acrylate with a functional group-containing monomer.

[0091] Examples of the alkyl (meth)acrylate 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.

[0092] 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 described later. 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.

[0093] 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.

[0094] The acrylic polymer is preferably an energy ray curable acrylic polymer having an energy ray curable group, obtained by reacting (for example, by addition reaction) 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 one or more groups selected from an isocyanate group, an epoxy group, and a carboxy group in addition to the energy ray curable 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.

[0095] 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.

[0096] The pressure-sensitive adhesive composition preferably contains an energy ray-curable compound in addition to the acrylic polymer. 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 irradiation with energy rays.

[0097] 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.

[0098] Among these, urethane (meth)acrylate oligomers having a relatively high molecular weight are preferred.

[0099] 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, further preferably 400 to 8,000, and particularly preferably 600 to 6,000.

[0100] The content of the energy ray-curable compound in the pressure-sensitive adhesive composition is preferably 3 to 100 parts by mass, more preferably 5 to 70 parts by mass, and further preferably 7 to 40 parts by mass, based on 100 parts by mass of the acrylic polymer.

[0101] The pressure-sensitive adhesive composition preferably further contains a crosslinking agent, which reacts with functional groups, for example, to crosslink molecules contained in the functional-group-containing acrylic polymer.

[0102] Examples of the crosslinking agent include isocyanate-based crosslinking agents (crosslinking agents having an isocyanate group) such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and adducts of these diisocyanates; epoxy-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).

[0103] 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.

[0104] 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.

[0105] Examples of the photopolymerization initiator include photoinitiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and peroxide compounds, and photosensitizers such as amines and quinones.Specific examples include α-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl diphenyl sulfide, benzyl dimethyl ketal, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0106] The pressure-sensitive adhesive composition may contain other additives within the range that does not impair the effects of the present invention. Examples of other additives include tackifiers, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, etc. When these additives are contained, the content of each additive is preferably 0.01 to 6 parts by mass, more preferably 0.02 to 2 parts by mass, based on 100 parts by mass of the acrylic polymer.

[0107] From the viewpoint of preventing contamination of the workpiece, it is preferable that the pressure-sensitive adhesive composition does not contain an antistatic agent.

[0108] (4. Protection for workpiece processing) As a method for producing the protective sheet for workpiece processing according to this embodiment, a known method such as the one shown below can be adopted.

[0109] First, the support material and the antistatic agent-containing soft material constituting the substrate are prepared. For example, the resin film constituting the support material and the resin film constituting the antistatic agent-containing soft material may be used, or the raw material compositions of the support material and the antistatic agent-containing soft material may be melt-kneaded and extruded into a sheet shape by an extruder. In this embodiment, the raw material composition of the antistatic agent-containing soft material is preferably obtained as pellets by kneading the above-mentioned antistatic agent and the components constituting the soft material with a known kneader. By preparing such pellets, it is possible to easily obtain an antistatic agent-containing soft material in which the antistatic agent is sufficiently dispersed in the soft material. In addition, the T-die method is preferable as the extrusion molding.

[0110] Next, the obtained support material and the antistatic agent-containing soft material are laminated via an adhesive layer to prepare a substrate. The lamination method is, for example, a dry lamination method.

[0111] In the dry lamination method, a support material and an antistatic agent-containing soft material may be bonded together using a resin film having an adhesive layer, or an adhesive layer may be formed on one member by applying an adhesive layer-forming composition, and then the other member may be bonded together. The adhesive layer may be composed of multiple layers as described above. In this case, the adhesive layer may include a coloring layer to enhance the identification of the workpiece processing protection sheet.

[0112] Next, the adhesive composition or the adhesive composition coating agent is applied to the release treatment surface of the release sheet by a known method, and if necessary, heated and dried to form an adhesive layer on the release sheet.Then, the adhesive layer on the release sheet and the support material of the base material are laminated together to obtain a workpiece processing protection sheet in which the adhesive layer, the support material, the adhesive layer, and the antistatic agent-containing soft material are laminated in this order.That is, the workpiece processing protection sheet shown in FIG. 1 is obtained.The release sheet may be removed as necessary.

[0113] (5. Method for manufacturing workpieces) The protective sheet for workpiece processing according to the present invention is preferably used in a processing method (DBG, LDBG, etc.) for dividing a workpiece when grinding the back surface of the workpiece. As a non-limiting example of the use of the protective sheet for workpiece processing, a method for manufacturing a divided workpiece will be described in more detail below.

[0114] Specifically, the method for producing the workpiece individual pieces includes at least the following steps 1 to 4. Step 1: A step of attaching the above-mentioned workpiece processing protection sheet to the surface of a workpiece having a surface and a back surface opposite to the surface. Step 2: A step of forming a groove on the surface of the workpiece, or a step of forming a modified region inside the workpiece Step 3: A step of grinding the workpiece having a protective sheet for workpiece processing attached to its surface and having grooves or modified regions formed thereon from its back surface to separate the workpiece into a plurality of workpiece pieces starting from the grooves or modified regions. Step 4: A step of peeling off the workpiece processing protective sheet from a plurality of workpiece individual pieces (i.e., a group of workpiece individual pieces).

[0115] Each step of the manufacturing method for the above-mentioned workpiece singulation will be described in detail below. In the description, a wafer is used as a specific example of the workpiece, and a chip is used as a specific example of the workpiece singulation.

[0116] (Process 1) In step 1, as shown in FIG. 2, the main surface 20a of the adhesive layer 20 of the protective sheet for workpiece processing 1 according to this embodiment is attached to the surface 100a of the wafer 100. The wafer may be a silicon wafer, or may be a wafer of gallium arsenide, silicon carbide, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, or the like, a glass wafer, or a reconstructed wafer. In this embodiment, the wafer is preferably a silicon wafer. The thickness of the wafer before grinding is not particularly limited, but is usually about 500 to 1000 μm.

[0117] A circuit is formed on the surface of the wafer. 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.

[0118] The surface of the wafer is sufficiently protected by attaching the protective sheet for workpiece processing to the surface 100a of the wafer. The excess protective sheet for workpiece processing remaining on the outer periphery of the wafer can be cut to fit the wafer shape and removed as necessary.

[0119] This step 1 may be performed before or after step 2, which will be described later. For example, when forming a modified region on a wafer, it is preferable to perform step 1 before step 2 from the viewpoint of reducing the risk of the wafer being unintentionally divided when the protective sheet for workpiece processing is attached. On the other hand, when grooves are formed on the wafer surface 100a by dicing or the like, step 1 is performed after step 2. That is, the protective sheet for workpiece processing is attached to the surface of the wafer on which grooves have been formed in step 2, which will be described later.

[0120] (Process 2) In step 2, grooves are formed on the surface of the wafer. Alternatively, modified regions are formed inside the wafer. In step 2, the grooves and modified regions are formed so as to follow the dividing lines that will be formed when the wafer is divided into individual chips in step 3, which will be described later.

[0121] The grooves formed in step 2 have a depth shallower than the thickness of the wafer. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

[0122] In addition, the modified region is a brittle portion of the wafer, and is the starting point for the wafer to be destroyed and diced into chips due to the grinding process, either by thinning the wafer or by the application of grinding force.

[0123] The modified region is formed by irradiating a laser focused on the inside of the wafer, and the modified region is formed inside the wafer. The laser may be irradiated from the front surface 100a side of the wafer or from the back surface 100b side. In the embodiment in which the modified region is formed, when step 2 is performed after step 1 and the laser is irradiated from the wafer front surface 100a, the laser is irradiated to the wafer through a protective sheet for workpiece processing.

[0124] The wafer with the workpiece processing protection sheet attached and the grooves or modified regions formed thereon is placed on the chuck table and adsorbed to the chuck table. At this time, the wafer is adsorbed with its front side placed on the table side. At this time, the workpiece processing protection sheet contains a soft material containing an antistatic agent, so that the influence of foreign matter, etc. can be suppressed.

[0125] (Step 3) After steps 1 and 2, the back surface 100b of the wafer on the chuck table is ground to separate the wafer into a plurality of chips, thereby obtaining a group of chips.

[0126] When grooves are formed in the wafer, the back grinding is performed to thin the wafer at least to the bottom of the groove, so that the grooves become cuts that penetrate the wafer and the wafer is divided by the cuts into individual chips.

[0127] On the other hand, when a modified region is formed, the grinding surface (wafer back surface) may reach the modified region by grinding, but it does not have to reach the modified region strictly. That is, it is sufficient to grind to a position close to the modified region so that the wafer is broken and divided into chips starting from the modified region. In addition, the actual division into chips may be performed by attaching a pick-up tape described later and then stretching the pick-up tape.

[0128] After the back surface has been ground with the grinding wheel, dry polishing may be performed prior to picking up the chip.

[0129] The shape of the individual chips may be square or elongated, such as rectangular. The thickness of the individual chips is not particularly limited, but is preferably about 5 to 100 μm, and more preferably 10 to 45 μm. LDBG makes it easy to make the thickness of the individual chips 50 μm or less, and more preferably 10 to 45 μm. The size of the individual chips is not particularly limited, but the chip size is preferably 600 mm or less. 2 Less than 400mm, more preferably 2 Less than 120mm, more preferably 2 is less than.

[0130] In the protective sheet for workpiece processing according to this embodiment, the soft material containing an antistatic agent has antistatic properties, so that even in the case of thin and / or small chips, static electricity is suppressed during wafer processing, and adhesion of cut dust and foreign matter is reduced, thereby suppressing the occurrence of cracks in the chips.

[0131] (Step 4) Next, the protective sheet for workpiece processing is peeled off from the individual wafers (i.e., a plurality of chips). This step is carried out, for example, by the following method.

[0132] When the adhesive layer of the protective sheet for workpiece processing is an energy ray curable adhesive layer, the adhesive layer is cured and shrunk by irradiating it with energy rays, thereby reducing the adhesive strength to the adherend (diced wafer). For example, the illuminance of the energy rays is 120 to 280 mW / cm 2 The amount of energy is 100-1000mJ / cm 2It is preferable that the energy beam is ultraviolet light. Next, a pick-up tape is attached to the back side of the individualized wafer, and the position and direction are adjusted so that the wafer can be picked up. At this time, a ring frame arranged on the outer periphery of the wafer is also attached to the pick-up tape, and the outer periphery of the pick-up tape is fixed to the ring frame. The wafer and the ring frame may be attached to the pick-up tape at the same time, or may be attached at different times. Next, the protective sheet for workpiece processing is peeled off from the multiple chips (i.e., chip group) held on the pick-up tape by a tape peeling mechanism provided in a specified device.

[0133] Since the workpiece processing protective sheet of this embodiment has the above-described configuration, even when the workpiece processing protective sheet is peeled off from the wafer, excessive peeling static electricity is suppressed, and the adhesive layer is prevented from peeling off from the workpiece processing protective sheet and remaining on the wafer (glue residue).

[0134] Then, the multiple chips on the pickup tape are picked up and fixed onto a substrate or the like, and the chips are mounted.

[0135] The pickup tape is not particularly limited, but may be composed of, for example, a substrate and an adhesive sheet having an adhesive layer provided on one surface of the substrate.

[0136] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and may be modified in various aspects within the scope of the present invention. EXAMPLES

[0137] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0138] Example 1 (1) Adhesive layer (Preparation of Pressure-Sensitive Adhesive Composition) An energy ray-curable acrylic polymer (Mw: 500,000) was obtained by reacting an acrylic polymer obtained by copolymerizing 50 parts by mass of n-butyl acrylate (BA), 20 parts by mass of methyl methacrylate (MMA), and 30 parts by mass of 2-hydroxyethyl acrylate (2HEA) with 2-methacryloyloxyethyl isocyanate (MOI) so as to add to 80 mol % of the total hydroxyl groups of the acrylic polymer.

[0139] To 100 parts by mass of this energy ray-curable acrylic polymer, 10 parts by mass of a multifunctional urethane acrylate ultraviolet-curable compound (manufactured by Mitsubishi Chemical Corporation, product name "Shikoh UT-4332") as an energy ray-curable compound, 0.38 parts by mass (solids basis) of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating agent for a pressure-sensitive adhesive composition with a solids concentration of 34% by mass.

[0140] (Formation of adhesive layer) The above adhesive composition coating agent was applied onto the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031", a polyethylene terephthalate (PET) film with a silicone release treatment, thickness: 38 μm) and dried to produce a release sheet with an adhesive layer having a thickness of 40 μm.

[0141] (2) Base material (Preparation of soft material containing antistatic agent) The antistatic agent-containing soft material was produced as follows. 100 parts by mass of low-density polyethylene (manufactured by Sumitomo Chemical Co., Ltd., product name "Sumikasen F238-1") as a soft material and 20 parts by mass of an antistatic agent (manufactured by Sanyo Kasei Co., Ltd., product name "Pelestat 230") were dried, then fed into a twin-screw kneader and kneaded to obtain pellets. These pellets were extrusion molded using a small T-die extruder (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name "Labo Plastomill") to produce an antistatic agent-containing soft material with a thickness of 32 μm.

[0142] (Preparation of substrate) Next, a 1 μm-thick blue colored layer was formed on one side of a PET film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine 4300", thickness 50 μm) as a support material, and a 2 μm-thick adhesive layer was further provided on the surface of the blue colored layer. The adhesive layer of the PET film and the above-mentioned antistatic agent-containing soft material were bonded together by dry lamination to produce a laminate (substrate) of antistatic agent-containing soft material / adhesive layer / colored layer / PET film.

[0143] (3) Preparation of protective sheet for workpiece processing The obtained PET film of the substrate and the adhesive layer of the release sheet with the adhesive layer were laminated together to produce a protective sheet for work processing with a release sheet, in which the adhesive layer, PET film, blue colored layer, adhesive layer, and antistatic agent-containing soft material were formed in this order. The layer structure of the protective sheet for work processing is shown in Table 1.

[0144] Example 2 A protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1, except that the blending amount of the antistatic agent was set to the amount shown in Table 1. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0145] Example 3 A protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1, except that an antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pellestat 300") was used instead of an antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pellestat 230"). The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0146] Example 4 A protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1, except that an antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pelestat 230") was used instead of an antistatic agent (manufactured by Sanyo Chemical Industries, Ltd., product name "Pelectron PVL"). The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0147] Example 5 A protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1, except that the adhesive layer was formed using the following adhesive composition. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0148] (Preparation of Pressure-Sensitive Adhesive Composition) An energy beam-curable acrylic polymer (Mw: 500,000) was obtained by reacting 2-methacryloyloxyethyl isocyanate (MOI) with an acrylic polymer obtained by copolymerizing 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA) so that MOI was added to 80 mol % of the total hydroxyl groups of the acrylic polymer.

[0149] To 100 parts by mass of this energy ray-curable acrylic polymer, 0.38 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-101E") based on solid content and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating agent for a pressure-sensitive adhesive composition with a solid content concentration of 30% by mass.

[0150] Example 6 Except for changing the thickness of the adhesive layer to 80 μm, a protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0151] Example 7 Except for preparing an antistatic agent-containing soft material having a thickness of 52 μm, a protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0152] Example 8 Except for not forming the blue colored layer, a protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0153] Example 9 Except for not forming the blue colored layer, a protective sheet for work processing with a release sheet was obtained in the same manner as in Example 4. The layer structure of the protective sheet for work processing is shown in Table 1.

[0154] Comparative Example 1 Except for preparing the soft material without containing an antistatic agent, a protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0155] Comparative Example 2 A protective sheet for workpiece processing with a release sheet was obtained in the same manner as in Example 1, except that the antistatic agent-containing soft material of the substrate and the adhesive layer of the release sheet with an adhesive layer were bonded together. The layer structure of the protective sheet for workpiece processing is shown in Table 1.

[0156] [Table 1]

[0157] The measurement and evaluation methods in the present examples are as follows.

[0158] (Surface resistivity of adhesive layer after energy ray curing) The protective sheets for workpiece processing prepared in the examples and comparative examples were cut to a size of 10 cm x 10 cm, and were irradiated with ultraviolet light of sufficient intensity and quantity to cure the adhesive layer from the soft material side of the protective sheets for workpiece processing with a release sheet. Specifically, an ultraviolet irradiation device (manufactured by Lintec Corporation, product name "RAD-2000") was used to irradiate the adhesive layer with an illuminance of 230 mW / cm. 2 , light intensity 500mJ / cm 2 The release sheet was peeled off, and the surface resistivity of the cured adhesive layer was measured using a surface resistivity meter (Advantest, product name "R8252") in accordance with JIS K 7194 under conditions of 23°C, relative humidity of 50%, and applied voltage of 100V. The same measurement was performed twice for each protective sheet for workpiece processing, and the average was taken as the surface resistivity of the adhesive layer.

[0159] (Peeling charge voltage of protective sheet for workpiece processing) In an environment of 23°C and 50% relative humidity, the release sheet of the workpiece processing protective sheet with release sheet prepared in the examples and comparative examples was peeled off, and the workpiece processing protective sheet was attached to the surface of a silicon wafer (mirror surface, 8 inches) using a backgrind tape laminator (manufactured by Lintec, product name "RAD-3510", table temperature: 23°C), and left to stand for 30 minutes in the same environment. In the same environment, the workpiece processing protective sheet was peeled off from the silicon wafer at a peeling speed of 600 mm / min and a table temperature of 40°C using a tape peeling mechanism of a wafer mounter (manufactured by Lintec, product name "RAD-2700F / 12"), and the voltage (maximum voltage during peeling) was measured at a location 10 mm away vertically from the wafer surface from the peeled location of the adhesive layer on the wafer surface, and the voltage on the wafer side was taken as the measured value. The same measurement was performed for each of the workpiece processing protection sheets for five wafers, and the average of the five measured values ​​was taken as the peeling electrification voltage value. In this example, samples with a peeling electrification voltage of 500 V or less were judged to be good.

[0160] (Adhesion evaluation) The protective sheets for workpiece processing with release sheets prepared in the examples and comparative examples were irradiated with ultraviolet light from the soft material side using an ultraviolet irradiator (manufactured by Lintec Corporation, product name "RAD-2000") with an illuminance of 230 mW / cm. 2 , light intensity 500mJ / cm 2 The adhesive layer was cured by irradiating it with ultraviolet light of 1000 nm.

[0161] Next, the release sheet of the protective sheet for workpiece processing with release sheet was removed, and 11 vertical and 11 horizontal lines were cut at 5 mm intervals into the cured adhesive layer to form a grid pattern (number of squares: 100). The depth of the cuts was greater than or equal to the thickness of the adhesive layer.

[0162] Then, a cellophane adhesive tape (manufactured by Nichiban Co., Ltd., product name "Cellotape (registered trademark)") was applied to the surface of the adhesive layer, and after leaving it to stand for 20 minutes at 23°C and a relative humidity of 50%, while holding the workpiece processing protective sheet with one hand, the end of the cellophane adhesive tape was held with the other hand and the cellophane adhesive tape was pulled in a direction perpendicular to the workpiece processing protective sheet, and instantly peeled off from the surface of the adhesive layer.

[0163] After peeling off the cellophane adhesive tape, the grid cuts on the adhesive layer of the protective sheet for workpiece processing were visually confirmed, and the number of squares in which peeling between the adhesive layer and the surface where the adhesive layer was in contact was counted, and the adhesion between the adhesive layer and the surface where the adhesive layer was in contact of the protective sheet for workpiece processing after ultraviolet irradiation was evaluated. Table 2 shows the number of squares (OK number) in which peeling between the adhesive layer and the surface where the adhesive layer was in contact was not observed out of 100 squares. The greater the number of squares listed in Table 2, the better the adhesion between the adhesive layer and the surface where the adhesive layer was in contact in the protective sheet for workpiece processing after ultraviolet irradiation. In other words, when the protective sheet for workpiece processing attached to the workpiece is peeled off from the workpiece, the risk of glue remaining on the workpiece is reduced.

[0164] The above measurements and evaluations were carried out on the obtained samples (Examples 1 to 9 and Comparative Examples 1 and 2). The results are shown in Table 2.

[0165] [Table 2]

[0166] From Table 2, it was confirmed that when the protection sheet for workpiece processing has the above-mentioned configuration, peeling static electricity is suppressed and adhesive residue of the adhesive layer can be suppressed. [Explanation of symbols]

[0167] 1…Protection sheet for workpiece processing 10...Base material 12...Support material 14...Soft material containing antistatic agent 16...adhesive layer 20...Adhesive layer

Claims

1. A protective sheet for work processing having a substrate and an adhesive layer disposed on the substrate and attached to a work, The substrate has a support material, an antistatic agent-containing soft material, and an adhesive layer that integrates the support material and the antistatic agent-containing soft material, A protection sheet for workpiece processing, in which the antistatic agent-containing soft material and the adhesive layer are not in contact with each other.

2. 2. The protective sheet for workpiece processing according to claim 1, wherein the pressure-sensitive adhesive layer, the support material, the adhesive layer, and the soft material containing an antistatic agent are laminated in this order.

3. 3. The protection sheet for workpiece processing according to claim 1, wherein the antistatic agent-containing soft material has a thickness of 20 μm or more and 70 μm or less.

4. The surface resistivity of the surface of the adhesive layer that is attached to the workpiece is 1.0×10 12 The protective sheet for workpiece processing according to claim 1 or 2, wherein the resistance of the protective sheet is greater than Ω / □.

5. A protective sheet for workpiece processing as described in claim 1 or 2, which is attached to the surface of a workpiece 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 or a modified region formed inside.

6. A step of attaching the protective sheet for workpiece processing according to claim 1 or 2 to a surface of a workpiece having a surface and a back surface opposite to the surface; A step of forming a groove on a surface of the workpiece or a step of forming a modified region inside the workpiece; A step of grinding a workpiece having a surface on which the workpiece processing protective sheet is attached and on which the groove or the modified region is formed from a back side to separate the workpiece into a plurality of workpiece pieces starting from the groove or the modified region; A method for manufacturing a workpiece singulated product, comprising a step of peeling off the workpiece processing protection sheet from the plurality of workpiece singulated products.

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