Workpiece processing sheet

Abstract

[Problem] To provide a workpiece processing sheet that makes it possible to suppress cracks or the like of a workpiece even when the workpiece is thinned, and to reduce the number of particles on a bonding surface of a processed workpiece, which is obtained by singulating the workpiece, when the processed workpiece is directly bonded to a wafer. [Solution] The workpiece processing sheet is used for processing a workpiece for manufacturing a processed article that is to be directly bonded, and has a configuration in which a base material and an adhesive layer are laminated. The tensile elastic modulus of the base material at 23°C is 1400 MPa or more. The surface free energy of the surface of the base material that is in contact with the adhesive layer is less than 40 mN / m.

Description

Sheet for workpiece processing

[0001] The present invention relates to a workpiece processing sheet, and more particularly to a workpiece processing sheet used when processing a workpiece for manufacturing a workpiece that will be directly joined.

[0002] A chip on which circuits such as semiconductor chips are formed is a workpiece obtained by processing (for example, back grinding, dicing) a workpiece (for example, a wafer) on which multiple circuits are formed. As a method for high-density mounting of chips, the method using chip-on-wafer (CoW) is known. In this method, multiple chips smaller in size than the wafer are placed on the circuit surface of a wafer to obtain a chip-on-wafer, and then the chip-on-wafer is diced to obtain a stacked chip.

[0003] Such chips are often placed on a wafer via a thin adhesive layer, such as a die bonding film. In recent years, a method that does not use an adhesive layer has been known: direct transfer bonding (DTB), in which the bonding surface (circuit surface) of the chip and the bonding surface (circuit surface) of the wafer are processed and then directly bonded.

[0004] Patent Document 1 discloses a method of pressing a chip having a plasma-activated surface with a chip transfer member to bring it into close contact with the plasma-activated surface of a substrate.

[0005] Patent No. 6900006

[0006] In recent years, there has been a demand for thinner chips that are directly bonded, and in order to obtain thin chips, it is necessary to thin down the wafers that are separated into individual pieces.

[0007] Wafer grinding is performed before direct bonding. In wafer grinding, for example, an adhesive sheet is attached to the surface (circuit side) of the wafer to protect it, and then the back side of the wafer is ground. At this time, if the rigidity of the adhesive sheet is low, it may not be able to adequately hold the thinned wafer, which may cause damage or cracks in the wafer.

[0008] Furthermore, for chips that are directly bonded, it is necessary to keep the bonding surface (surface) of the chip clean in order to increase the bonding strength. However, when directly bonding chips obtained by peeling off the adhesive sheet attached to the surface of a wafer and separating the wafer into individual pieces, residue (particles) originating from the adhesive sheet may be generated on the bonding surface of the chip during direct bonding. If the bonding surface of the chip and the bonding surface of the wafer are directly bonded with residue present, the bonding strength of the joint tends to decrease, and the chip may detach from the wafer.

[0009] This invention has been made in view of the above circumstances, and aims to provide a workpiece processing sheet that can suppress cracks in the workpiece even when the workpiece is thinned, and reduces the number of particles on the bonding surface of the workpiece when the workpiece processed product obtained by cutting the workpiece into individual pieces is directly bonded to a wafer.

[0010] The embodiments of the present invention are as follows.

[0011] [1] A workpiece processing sheet used for processing workpieces to manufacture workpieces to be directly joined, wherein the workpiece processing sheet has a structure in which a base material and an adhesive layer are laminated, the tensile modulus of the base material at 23°C is 1400 MPa or more, and the surface free energy of the surface of the base material in contact with the adhesive layer is less than 40 mN / m.

[0012] [2] A workpiece processing sheet as described in [1], used for grinding a workpiece.

[0013] [3] A workpiece processing sheet according to [1] or [2], wherein the base material is composed of two or more layers including a support material and a low-polarity material which has lower polarity than the support material.

[0014] [4] The workpiece processing sheet according to [3], wherein the support material is a polyethylene terephthalate film and the low-polarity material is a polyolefin film.

[0015] [5] A workpiece processing sheet according to any one of [1] to [4], wherein the following immersion test is performed on the adhesive layer, and the peak area of ​​the detected component calculated by performing the following gel permeation chromatography measurement on the toluene solvent after the immersion test is 4000 mV·s or less. (Immersion test) An adhesive layer having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C for 24 hours to obtain the toluene solvent in contact with the adhesive layer. (Gel permeation chromatography measurement) 10 μL of the obtained toluene solvent is measured by gel permeation chromatography, and the measurement result is represented as a chromatogram with the detection voltage on the vertical axis and the elution time from the introduction of the toluene solvent to elution from the column on the horizontal axis, and the peak area of ​​the detected component is calculated in the range from the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 200.

[0016] [6] A workpiece processing sheet according to any one of [1] to [5], wherein the following immersion test is performed on the workpiece processing sheet, and the peak area of ​​the detected component calculated by performing the following gel permeation chromatography measurement on the toluene solvent after the immersion test is 4000 mV·s or less. (Immersion test) A workpiece processing sheet having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C for 24 hours to obtain the toluene solvent in contact with the workpiece processing sheet. (Gel permeation chromatography measurement) 10 μL of the obtained toluene solvent is measured by gel permeation chromatography, and the measurement result is represented as a chromatogram with the detection voltage on the vertical axis and the elution time from the introduction of the toluene solvent to elution from the column on the horizontal axis, and the peak area of ​​the detected component is calculated in the range from the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 200.

[0017] According to the present invention, it is possible to provide a workpiece processing sheet that can suppress cracks in the workpiece even when the workpiece is thinned, and that reduces the number of particles on the bonding surface of the workpiece when the workpiece processed product obtained by pieceping the workpiece is directly bonded to a wafer.

[0018] Figure 1 is a schematic cross-sectional view showing an example of a workpiece processing sheet according to this embodiment. Figure 2(A) is a schematic cross-sectional view showing another example of a workpiece processing sheet according to this embodiment, and Figure 2(B) is a schematic cross-sectional view showing another example of a workpiece processing sheet according to this embodiment. Figure 3 is a diagram illustrating a method for calculating the peak area after GPC measurement of components derived from the adhesive layer. Figures 4(A) and (B) are schematic cross-sectional views illustrating the process of grinding the back surface of a wafer. Figures 5(A) and (B) are schematic cross-sectional views illustrating the process of transferring the wafer (workpiece) after back surface grinding. Figures 6(A) to (C) are schematic cross-sectional views illustrating the process of framing the wafer (workpiece) after back surface grinding. Figure 7(A) is a schematic cross-sectional diagram illustrating the process of attaching a carrier sheet to a chip (workpiece), Figure 7(B) is a schematic cross-sectional diagram illustrating the process of peeling the dicing sheet from the chip (workpiece) to which the carrier sheet has been attached, and Figure 7(C) is a schematic cross-sectional diagram illustrating the process of expanding the chip (workpiece). Figures 8(A) and (B) are schematic cross-sectional diagrams illustrating the process of directly bonding the chip (workpiece) to a wafer. Figure 9 is a schematic cross-sectional diagram of a chip-on-wafer in which the chip (workpiece) is directly bonded to the wafer.

[0019] The present invention will be described in detail below with reference to the drawings, based on specific embodiments. First, the main terms used in this specification will be explained.

[0020] A workpiece refers to a plate-like body to which a workpiece processing sheet is attached and then processed. Examples of workpieces include circular wafers (including those having an orientation flat), rectangular panel-level packages, and strips (strip-shaped substrates) with molded resin encapsulation. Among these, wafers are preferred from the viewpoint of easily obtaining the effects of the present invention. Wafers may be semiconductor wafers such as silicon wafers, gallium arsenide wafers, silicon carbide wafers, gallium nitride wafers, and indium phosphate wafers, or insulating wafers such as glass wafers, lithium tantalate wafers, and lithium niobate wafers. They may also be reconfigured wafers made of resin and semiconductors used in the manufacture of fan-out packages, etc. From the viewpoint of easily obtaining the effects of the present invention, semiconductor wafers or insulating wafers are preferred as wafers, and semiconductor wafers are more preferred.

[0021] Workpiece segmentation refers to dividing a workpiece into individual circuits to obtain processed parts. For example, if the workpiece is a wafer, the processed part is a chip; if the workpiece is a panel-level package or a strip (a strip-shaped substrate) with molded resin encapsulation, the processed part is a semiconductor package.

[0022] The "front surface" of a workpiece refers to the side on which circuits, etc., are formed or are planned to be formed, while the "back surface" of a workpiece refers to the side on which circuits, etc., are not formed or are not planned to be formed.

[0023] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

[0024] "Energy rays" refer to ultraviolet rays, electron beams, etc., and are preferably ultraviolet rays.

[0025] In descriptions of compositions such as adhesive compositions, the mass ratios are based on the active ingredient (solid content), and unless otherwise specified, the solvent is not included.

[0026] (1. Sheet for workpiece processing) The sheet for workpiece processing is a sheet used when processing a workpiece. An example of a workpiece is one on which a circuit or the like is formed on one side (front surface) and on which no circuit or the like is formed on the other side (back surface). The front surface may be the surface on which the circuit is exposed, or it may be the main surface of a protective layer formed on the circuit to protect it. Electrodes may also be formed on the circuit. The workpiece is processed to become multiple workpieces. In this embodiment, the workpiece is a workpiece for manufacturing workpieces that are directly joined together.

[0027] The workpiece processing sheet according to this embodiment is used to process workpieces for manufacturing workpieces that will be directly joined. In this embodiment, examples of workpiece processing include grinding the workpiece (e.g., back grinding of the workpiece) and dicing the workpiece.

[0028] In backside grinding of a workpiece, a workpiece processing sheet is attached to the surface of the workpiece. Then, the backside of the workpiece is ground. After grinding is complete, the workpiece processing sheet is peeled off the workpiece. By using the workpiece processing sheet, the surface of the workpiece is protected during backside grinding, and contamination of circuits, etc., by the ingress of abrasive material, cooling water, etc., into the workpiece surface, as well as damage to circuits, etc., due to the force applied during backside grinding, can be suppressed.

[0029] In the process of separating a workpiece into individual pieces, a workpiece processing sheet is attached to the front or back surface of the workpiece, and the workpiece is then fixed to a frame via the workpiece processing sheet. Subsequently, the workpiece is separated into individual pieces, and the separated pieces (workpiece processed objects) are peeled off the workpiece processing sheet. By using a workpiece processing sheet, it is possible to hold the workpiece during separation to suppress misalignment, and to suppress scattering of the workpiece processed objects after separation.

[0030] In this embodiment, the workpiece processing sheet is preferably used for grinding the workpiece, and more preferably is a back grind sheet used for grinding the back surface of the workpiece.

[0031] As mentioned above, a method using chip-on-wafer (CoW) is known as a method for densely mounting chips as workpieces. In chip-on-wafer, the circuit faces (bonding surfaces) of multiple chips are arranged on the circuit face (bonding surface) of the wafer and connected electrically and mechanically. As a method for bonding chips and wafers, a method of directly bonding chips and wafers without using a film-like adhesive (direct transfer bonding: DTB) is known.

[0032] The workpiece (chip) used in direct bonding is obtained by processing the workpiece in a pre-processing step before direct bonding. As mentioned above, during workpiece processing, a workpiece processing sheet is applied to protect the surface of the workpiece. When workpiece processing is complete, the workpiece processing sheet is peeled off from the surface of the workpiece or workpiece, but components originating from the workpiece processing sheet may remain on the surface of the workpiece or workpiece as residue (particles). Since the surface of the workpiece becomes the bonding surface in direct bonding, if particles are present on this surface, the bonding surface will be contaminated, weakening the bonding strength after direct bonding.

[0033] Furthermore, when using thin workpieces (chips) as workpieces, the back surface of the workpiece is usually ground. Since the workpiece after back surface grinding is thin and prone to damage and cracking, the workpiece processing sheet needs to have sufficient rigidity to stably hold such workpieces.

[0034] Therefore, workpiece processing sheets used to process workpieces for manufacturing directly bonded parts need to have both low contamination properties that can keep the surface of the workpiece (chip) clean, and rigidity that can hold thin workpieces.

[0035] The workpiece processing sheet according to this embodiment has the configuration and physical properties described later, so that even if the workpiece becomes thinner after processing, the workpiece processing sheet can reliably hold the workpiece, and even if the workpiece processing sheet is peeled off thereafter, it is possible to suppress the generation of residue originating from the workpiece processing sheet in the workpiece obtained by processing the workpiece.

[0036] (1.1. Structure of the workpiece processing sheet)The workpiece processing sheet according to the present embodiment has a structure in which a base material and an adhesive layer are laminated. FIG. 1 shows an example of a workpiece processing sheet 1 having a base material and an adhesive layer. In the workpiece processing sheet 1, an adhesive layer 20 is disposed on one main surface 10a of the base material 10.

[0037] The workpiece processing sheet may have other layers according to the application as long as the effects of the present invention can be obtained. For example, when the workpiece processing sheet is used for back grinding, an intermediate layer for relaxing the stress applied to the workpiece during back grinding may be disposed between the base material 10 and the adhesive layer 20, or an easy-adhesion layer for improving the adhesion between the base material and the adhesive layer may be provided. Further, a layer having a function such as an antistatic layer may be formed between the outermost layer of the base material and the adhesive layer or between other layers. Hereinafter, the components of the workpiece processing sheet will be described.

[0038] (2. Base material) The base material is a film-like member that provides the rigidity of the workpiece processing sheet. Therefore, the base material may be made of a material having such rigidity that it can stably hold the workpiece or the workpiece processed product even when the workpiece or the workpiece processed product is thinned before, during, and after the processing of the workpiece. In particular, it is preferable that the base material is made of a material having such rigidity that it can suppress the occurrence of cracks, breakage, etc. in the workpiece and the workpiece processed product even when the workpiece or the workpiece processed product is thinned during the grinding of the workpiece.

[0039] The thickness of the base material can be set according to the application of the workpiece processing sheet and the like. In the present embodiment, the thickness of the base material may be 20 μm or more, 25 μm or more, or 50 μm or more. Further, the thickness of the base material may be 450 μm or less, 400 μm or less, or 350 μm or less. [[ID=?]]

[0040] Note that the thickness of the base material means the thickness of the entire base material. For example, the thickness of a base material composed of a plurality of layers means the total thickness of all the layers constituting the base material.

[0041] (2.1. Tensile Elastic Modulus) In this embodiment, the tensile elastic modulus (Young's modulus) of the base material at 23°C is 1400 MPa or more. Thereby, even when the workpiece or the workpiece processed product is thin, the base material can sufficiently hold the workpiece or the workpiece processed product, and the occurrence of cracks, breakage, etc. can be reduced.

[0042] The tensile elastic modulus of the base material at 23°C is preferably 1500 MPa or more, more preferably 2000 MPa or more, and even more preferably 2500 MPa or more. From the viewpoint of manufacturing the base material, the upper limit of the tensile elastic modulus is 10000 MPa. The method for measuring the tensile elastic modulus of the base material at 23°C will be described in the examples.

[0043] (2.2. Surface Free Energy) In this embodiment, the surface free energy of the surface of the base material in contact with the adhesive layer is less than 40 mN / m. In the sheet for workpiece processing, usually, an adhesive layer is formed on one main surface of the base material. Therefore, in the base material, the surface in contact with the adhesive layer is the one main surface. For example, in FIG. 1, the main surface 10a of the base material 10 is the surface in contact with the adhesive layer 20.

[0044] The surface free energy corresponds to the surface tension of a solid. When the surface free energy of a solid is small, the liquid or solid in contact with that solid tends to be less wettable. Therefore, since the surface free energy of the surface in contact with the adhesive layer is within the above range, the wettability between the components constituting the base material and the components constituting the adhesive layer decreases, so that the migration of the components constituting the base material to the adhesive layer can be suppressed. That is, the contamination of the surface of the workpiece or the workpiece processed product caused by the migration of the components constituting the base material can be suppressed.

[0045] The surface free energy of the surface of the base material in contact with the adhesive layer is preferably 36 mN / m or less, more preferably 33 mN / m or less, and even more preferably 31 mN / m or less. From the viewpoint of manufacturing the base material, the lower limit of the surface free energy is 15 mN / m.

[0046] Since surface free energy cannot be measured directly, it is measured indirectly by measuring the contact angle using a liquid with a known surface tension. In this embodiment, the surface free energy is calculated using the Kitazaki-Hata formula based on the contact angles measured using water, diiodomethane, and 1-bromonaphthalene. The specific measurement method will be explained in the examples.

[0047] (2.3. Substrate composition) The substrate is not particularly limited in composition as long as it has the above physical properties. The substrate may consist of one layer (single layer) or two or more layers. In this embodiment, a resin film is an example. Therefore, the substrate may consist of a single layer film made of one resin film, or it may consist of a multi-layer film made of multiple resin films laminated together.

[0048] When the substrate consists of a single layer, the material of the substrate can be any material whose tensile modulus and surface free energy satisfy the above-mentioned ranges. Examples of such materials include polyimide (PI) films and cycloolefin polymer (COP) films. Among these, polyimide films and cycloolefin polymer films are preferred. Note that the above examples are general examples, and even with the same material, the physical properties of the material may change depending on the manufacturing method, etc.

[0049] In this embodiment, it is preferable that the base material is composed of two or more layers. When the base material is composed of two or more layers, it is preferable that the base material has a support material and a low-polarity material which has lower polarity than the support material.

[0050] (2.4. Support Material) The support material is a layer responsible for the rigidity of the base material, and should be configured such that the tensile modulus of the base material satisfies the range described above. In this embodiment, the tensile modulus of the support material at 23°C is preferably 2000 MPa or more, more preferably 2700 MPa or more, and even more preferably 3000 MPa or more. From a manufacturing standpoint, the upper limit of the tensile modulus of the support material is 10000 MPa. The tensile modulus of the support material can be measured by the same method as the tensile modulus of the base material.

[0051] Examples of support materials include various resin films used as base materials for backgrind tapes. By using such resin films, the workpiece can be held stably even if its thickness is reduced by grinding. The support material may consist of a single-layer film made of one resin film, or it may consist of a multi-layer film made by laminating multiple resin films.

[0052] In this embodiment, examples of materials for the support material include polyester films such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and fully aromatic polyesters, as well as polyimide films, polyamide films, polycarbonate films, polyacetal films, modified polyphenylene oxide films, polyphenylene sulfide films, polysulfone films, polyetherketone films, and biaxially oriented polypropylene films. Among these, polyester films are preferred, and polyethylene terephthalate films are more preferred.

[0053] The thickness of the support material can be set according to the intended use of the workpiece processing sheet. In this embodiment, the thickness of the support material may be 10 μm or more and 200 μm or less, 15 μm or more and 150 μm or less, or 20 μm or more and 130 μm or less.

[0054] At least one main surface of the support material may be subjected to an adhesive treatment such as corona treatment to improve adhesion with the layer formed on the main surface. Furthermore, at least one main surface of the support material may have an easy-adhesion layer formed on it to improve adhesion with the layer (for example, a low-polarity material) formed on that main surface.

[0055] (2.5. Low-Polarity Materials) The materials that make up the above-mentioned support materials are often highly polar or contain a large amount of impurities. Therefore, if only the above-mentioned support materials are used as the base material, components that make up the base material (components derived from the base material) tend to migrate to the adhesive layer. As a result, components derived from the base material may reach the surface of the workpiece or workpiece that is in contact with the adhesive layer, and the surface may become contaminated.

[0056] Therefore, when the substrate is composed of two or more layers, in order to suppress the migration of such components, it is preferable to place a low-polarity material 12 between the adhesive layer 20 and the support material 11 in the workpiece processing sheet 1, as shown in Figure 2(A), which has lower polarity than the support material. Low-polarity materials tend to have low surface free energy. In this embodiment, it is preferable that the surface free energy of the low-polarity material is less than 40 mN / m. As a result, the adhesive layer 20 is in contact with the low-polarity material 12, so even if the support material contains components that are easily migrated to the adhesive layer, the low-polarity material acts as a barrier, and the migration of components originating from the substrate to the adhesive layer can be suppressed.

[0057] The surface free energy of the low-polarity material is preferably 35 mN / m or less, more preferably 33 mN / m or less, and even more preferably 30 mN / m or less. From the viewpoint of manufacturing the low-polarity material, the lower limit of the surface free energy is 15 mN / m. The surface free energy of the low-polarity material can be measured by the same method as the surface free energy of the substrate.

[0058] The low-polarity material only needs to be composed of a material whose surface free energy satisfies the above-mentioned range. This makes it possible to suppress the migration of components derived from the support material to the adhesive layer. The low-polarity material may be composed of a single-layer film made of one resin film, or it may be composed of a multi-layer film made by laminating multiple resin films.

[0059] In this embodiment, examples of low-polarity materials include resin films such as low-density polyethylene (LDPE) films, high-density polyethylene (HDPE) films, linear low-density polyethylene (LLDPE) films, polyethylene (PE) films, biaxially oriented polypropylene films, and polyurethane acrylate films. Among these, low-density polyethylene (LDPE) films are preferred. Note that the above examples are general examples, and even with the same material, the physical properties of the material may change depending on the manufacturing method, etc.

[0060] The thickness of the low-polarity material can be set according to the application of the workpiece processing sheet. In this embodiment, the thickness of the low-polarity material may be 10 μm or more and 200 μm or less, 15 μm or more and 150 μm or less, or 20 μm or more and 130 μm or less.

[0061] (2.6. Soft Material) In this embodiment, if the base material is composed of two or more layers, the base material may have a support material and a soft material that is softer than the support material, or it may have a support material, a low-polarity material and a soft material. "Softer than the support material" means that the tensile modulus of the soft material at 23°C is lower than the tensile modulus of the support material at 23°C.

[0062] In the support material, the soft material is preferably placed on the main surface opposite to the main surface on which the adhesive layer is located, and more preferably, as shown in Figure 2(B), in the workpiece processing sheet 1, the soft material 13 is placed on the main surface 11b of the support material 11. By placing the soft material on the side of the support material that is not in contact with the adhesive layer, the soft material comes into contact with the suction table when fixing a workpiece to which the workpiece processing sheet has been attached for grinding (for example, back grinding) to the suction table. Therefore, even if foreign matter is attached to the suction table, the soft material can embed the foreign matter, and damage or cracking of the workpiece caused by foreign matter can be suppressed during grinding.

[0063] The tensile modulus of the soft material at 23°C may be between 100 MPa and 1000 MPa, or between 100 MPa and 500 MPa. The tensile modulus of the soft material can be measured by the same method as the tensile modulus of the base material.

[0064] The thickness of the soft material can be set according to the intended use of the workpiece processing sheet. In this embodiment, the thickness of the soft material may be 10 μm or more and 100 μm or less, or 20 μm or more and 50 μm or less. When the thickness of the soft material is within the above range, sufficient adhesion between the support material and the soft material tends to be ensured.

[0065] In this embodiment, the flexible material is preferably made of a resin film. The flexible material may be made of a single-layer film consisting of one resin film, or it may be made of a multi-layer film in which multiple resin films are laminated together.

[0066] The resin film is preferably a polyolefin resin film. Examples of polyolefin resins include polyethylene resins such as very low-density polyethylene (VLDPE), low-density polyethylene (LDPE), and high-density polyethylene (HDPE), polypropylene resins, polyethylene-polypropylene copolymers, olefin elastomers (TPO), cycloolefin polymers (COP), polyvinyl chloride (PVC), ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl acetate-maleic anhydride copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, ethylene-(meth)acrylic acid ester-maleic anhydride copolymer, and ionomer resins. These polyolefin resins can be used individually or in combination of two or more.

[0067] The base material, support material, low-polarity material, and soft material may contain lubricants, infrared absorbers, ultraviolet absorbers, fillers, colorants, antistatic agents, antioxidants, catalysts, etc., to the extent that they do not impair the effects of the present invention. Furthermore, the base material, support material, low-polarity material, and soft material may be transparent or opaque, but they are preferably transparent.

[0068] (3. Adhesive Layer) The adhesive layer is attached to the surface of the workpiece (i.e., the surface on which circuits, etc., are formed: the circuit surface), protecting the surface and holding the workpiece or workpiece processed object. Furthermore, when the adhesive layer of the workpiece processing sheet according to this embodiment is peeled off from the surface, it suppresses the generation of residue (particles) originating from the adhesive layer on the surface of the workpiece processed object. In addition, as described above, since the migration of components derived from the substrate to the adhesive layer is suppressed, surface contamination of workpiece processed objects used for direct bonding can be reduced.

[0069] The adhesive layer may consist of one layer (single layer) or of two or more layers. If the adhesive layer has multiple layers, these layers may be identical or different from each other, and there are no particular restrictions on the combination of layers that make up these multiple layers.

[0070] The thickness of the adhesive layer can be set according to the intended use of the workpiece processing sheet. In this embodiment, the thickness of the adhesive layer may be 3 μm or more and 30 μm or less, 5 μm or more and 20 μm or less, or 7 μm or more and 15 μm or less.

[0071] Note that the thickness of the adhesive layer refers to the total thickness of the adhesive layer. For example, the thickness of an adhesive layer composed of multiple layers refers to the sum of the thicknesses of all the layers that make up the adhesive layer.

[0072] (3.1. Composition of the adhesive layer) The composition of the adhesive layer should be determined so as to exhibit sufficient tackiness and re-peelability to protect or hold the surface of the workpiece or workpiece and then peel off. In this embodiment, the adhesive layer is preferably composed of an adhesive formed using an adhesive composition. Examples of adhesives include acrylic adhesives, urethane adhesives, rubber adhesives, silicone adhesives, polyester adhesives, and polyvinyl ether adhesives. In this embodiment, the adhesive is preferably an acrylic adhesive.

[0073] The adhesive may be energy-ray curable, energy-ray non-curable, energy-ray foamable, or heat-foamable. In this embodiment, the adhesive is preferably energy-ray curable. Since the adhesive strength of an energy-ray curable adhesive decreases upon energy-ray irradiation, when peeling the workpiece processing sheet from the workpiece or workpiece, irradiating the adhesive layer with energy rays makes it easier to peel off the workpiece processing sheet.

[0074] In this embodiment, the energy-ray curable adhesive may be mainly composed of an energy-ray curable polymer, or it may be mainly composed of a mixture of an energy-ray curable polymer and an energy-ray curable polyfunctional monomer and / or oligomer. Furthermore, it may be mainly composed of a mixture of an energy-ray curable polymer and an energy-ray curable polyfunctional monomer and / or oligomer.

[0075] In this embodiment, the energy-ray curable adhesive is preferably an acrylic adhesive formed using an acrylic adhesive composition. The acrylic adhesive composition contains an acrylic polymer.

[0076] The 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 more types of acrylic monomers and monomers other than acrylic monomers.

[0077] First, we will explain the case where the energy-ray curable adhesive is mainly composed of an acrylic polymer that has energy-ray curability.

[0078] The energy-ray curable acrylic polymer is preferably a (meth)acrylic acid ester (co)polymer (A) (hereinafter sometimes referred to as "energy-ray curable polymer (A)") in which an energy-ray curable functional group (energy-ray curable group) is introduced into the side chain. This energy-ray curable polymer (A) is preferably obtained by reacting an acrylic copolymer (a1) having a functional group-containing monomer unit with an unsaturated group-containing compound (a2) having a substituent bonded to the functional group.

[0079] The acrylic copolymer (a1) consists of structural units derived from functional group-containing monomers and structural units derived from (meth)acrylic acid ester monomers or their derivatives.

[0080] The functional group-containing monomer as a constituent unit of the acrylic copolymer (a1) is preferably a monomer having a polymerizable double bond and a functional group such as a hydroxyl group, amino group, substituted amino group, or epoxy group within its molecule.

[0081] More specific examples of the above-mentioned functional group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc., which can be used individually or in combination of two or more.

[0082] As the (meth)acrylic acid ester monomer constituting the acrylic copolymer (a1), alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and benzyl (meth)acrylates with an alkyl group having 1 to 20 carbon atoms are used. Among these, alkyl (meth)acrylates with an alkyl group having 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are particularly preferred.

[0083] The acrylic copolymer (a1) typically contains 3 to 100% by mass, preferably 5 to 40% by mass, of structural units derived from the functional group-containing monomer, and typically contains 0 to 97% by mass, preferably 60 to 95% by mass, of structural units derived from (meth)acrylic acid ester monomer or its derivative.

[0084] The acrylic copolymer (a1) can be obtained by copolymerizing a functional group-containing monomer as described above with a (meth)acrylic acid ester monomer or its derivative by a conventional method. In addition to these monomers, dimethylacrylamide, vinyl formate, vinyl acetate, styrene, etc., may also be copolymerized.

[0085] An energy-ray curable polymer (A) is obtained by reacting an acrylic copolymer (a1) having the above-mentioned functional group-containing monomer units with an unsaturated group-containing compound (a2) having substituents bonded to the functional group.

[0086] The substituents of the unsaturated group-containing compound (a2) can be appropriately selected depending on the type of functional group of the functional group-containing monomer unit of the acrylic copolymer (a1). For example, when the functional group is a hydroxyl group, an amino group, or a substituted amino group, an isocyanate group or an epoxy group is preferred as the substituent, and when the functional group is an epoxy group, an amino group, a carboxyl group, or an aziridinyl group is preferred as the substituent.

[0087] Furthermore, the unsaturated group-containing compound (a2) contains 1 to 5, preferably 1 to 2, energy-ray polymerizable carbon-carbon double bonds per molecule. Specific examples of such unsaturated group-containing compounds (a2) include, for example, 2-methacryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, methacryloyl isocyanate, allyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate; acryloyl monoisocyanate compounds obtained by the reaction of a diisocyanate compound or polyisocyanate compound with hydroxyethyl (meth)acrylate; acryloyl monoisocyanate compounds obtained by the reaction of a diisocyanate compound or polyisocyanate compound with a polyol compound with hydroxyethyl (meth)acrylate; glycidyl (meth)acrylate; (meth)acrylic acid, 2-(1-aziridinyl)ethyl (meth)acrylate, 2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and the like.

[0088] The unsaturated group-containing compound (a2) is usually used in a ratio of 10 to 100 mol%, preferably 20 to 95 mol%, relative to the functional group-containing monomer of the acrylic copolymer (a1).

[0089] In the reaction between the acrylic copolymer (a1) and the unsaturated group-containing compound (a2), the reaction temperature, pressure, solvent, time, presence or absence of a catalyst, and type of catalyst can be appropriately selected depending on the combination of functional groups and substituents. As a result, the functional groups present in the acrylic copolymer (a1) react with the substituents in the unsaturated group-containing compound (a2), introducing unsaturated groups into the side chains of the acrylic copolymer (a1), and yielding an energy-ray curable polymer (A).

[0090] The weight-average molecular weight of the energy-ray curable polymer (A) obtained in this manner is preferably 10,000 or more, particularly preferably 150,000 to 1,500,000, and even more preferably 200,000 to 1,000,000. The above weight-average molecular weight (Mw) is a standard polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0091] Even if the energy-ray curable adhesive mainly consists of an energy-ray curable polymer (A), the energy-ray curable adhesive may further contain an energy-ray curable monomer and / or oligomer (B).

[0092] As the energy-ray curable monomer and / or oligomer (B), for example, an ester of a polyhydric alcohol and (meth)acrylic acid can be used.

[0093] Examples of such energy-ray curable monomers and / or oligomers (B) include monofunctional acrylic acid esters such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate, polyfunctional acrylic acid esters such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and dimethylol tricyclodecane di(meth)acrylate, as well as polyester oligo(meth)acrylate and polyurethane oligo(meth)acrylate.

[0094] When an energy-ray-curable monomer and / or oligomer (B) is incorporated, the content of the energy-ray-curable monomer and / or oligomer (B) in the energy-ray-curable adhesive is preferably 5 to 80% by mass, and particularly preferably 20 to 60% by mass.

[0095] In this case, when ultraviolet light is used as the energy ray for curing the energy ray-curable adhesive, it is preferable to add a photopolymerization initiator (C). This reduces the polymerization curing time and the amount of light irradiation.

[0096] Examples of photopolymerization initiators (C) include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexylphenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloranthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, 2-benzothiazole-N,N-diethyldithiocarbamate, oligo{2-hydroxy-2-methyl-1-[4-(1-propenyl)phenyl]propanone}, and 2,2-dimethoxy-1,2-diphenylethane-1-one. These may be used individually or in combination of two or more.

[0097] The photopolymerization initiator (C) is preferably used in an amount of 0.1 to 10 parts by mass, particularly 0.5 to 6 parts by mass, per 100 parts by mass of the energy-ray curable polymer (A) (or, if an energy-ray curable monomer and / or oligomer (B) is included, per 100 parts by mass of the total amount of the energy-ray curable polymer (A) and the energy-ray curable monomer and / or oligomer (B)).

[0098] In energy-ray curable adhesives, other components may be added as appropriate, in addition to the components mentioned above. Examples of other components include polymer components or oligomer components (D) that do not possess energy-ray curability, crosslinking agents (E), and the like.

[0099] Examples of polymer components or oligomer components (D) that do not possess energy ray curability include polyacrylic acid esters, polyesters, polyurethanes, polycarbonates, and polyolefins, with a preferred polymer or oligomer having a weight-average molecular weight (Mw) of 3,000 to 2,500,000.

[0100] As the crosslinking agent (E), a polyfunctional compound that has reactivity with the functional groups of the energy ray curable polymer (A) can be used. Examples of such polyfunctional compounds include isocyanate compounds, epoxy compounds, amine compounds, melamine compounds, aziridine compounds, hydrazine compounds, aldehyde compounds, oxazoline compounds, metal alkoxide compounds, metal chelate compounds, metal salts, ammonium salts, and reactive phenolic resins.

[0101] By incorporating a polymer component or oligomer component (D) that does not possess energy ray curability and a crosslinking agent (E) into an energy ray curable adhesive, the tackiness and peelability before curing, strength after curing, adhesion to other layers, and storage stability can be improved. The amounts of components (D) and (E) are not particularly limited and are appropriately determined in the range of 0 to 40 parts by mass per 100 parts by mass of the energy ray curable polymer (A).

[0102] Next, we will describe a case in which the energy-ray curable adhesive mainly consists of a mixture of a polymer component that does not possess energy-ray curability and an energy-ray curable polyfunctional monomer and / or oligomer.

[0103] As a polymer component that does not possess energy-ray curability, for example, a component similar to the acrylic copolymer (a1) described above can be used. The content of the polymer component that does not possess energy-ray curability in the energy-ray curable adhesive is preferably 20 to 99.9% by mass, and particularly preferably 30 to 80% by mass.

[0104] As the energy-ray curable polyfunctional monomer and / or oligomer, the same as component (B) described above is selected. The blending ratio of the non-energy-ray curable polymer component to the energy-ray curable polyfunctional monomer and / or oligomer is preferably 10 to 150 parts by mass of the polyfunctional monomer and / or oligomer per 100 parts by mass of the polymer component, and particularly preferably 25 to 100 parts by mass of the polyfunctional monomer and / or oligomer.

[0105] In this case as well, a photopolymerization initiator (C) and a crosslinking agent (E) can be appropriately added, similar to the above.

[0106] (3.2. Peak area of ​​components derived from the adhesive layer after GPC measurement) As described above, since the adhesive layer is in contact with the surface of the workpiece or workpiece, it is thought that migration from the adhesive layer occurs over time when various processing is performed after the adhesive layer is attached to the workpiece, resulting in residue on the surface. The inventors hypothesized that such residue consists of components of the adhesive layer that readily migrate to the substance in contact with it and exist independently (freely) from the adhesive layer.

[0107] In this embodiment, it is preferable to employ a method for evaluating easily transferable components by immersing the adhesive layer in a solvent and evaluating the solvent after immersion using gel permeation chromatography (GPC). This allows for the extraction and analysis of components that are presumed to directly affect the feasibility of bonding. In other words, components that readily dissolve in the solvent upon immersion are considered to be easily transferable components.

[0108] In this embodiment, first, the following immersion test is performed. An adhesive layer having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C as a solvent for 24 hours. The adhesive layer to be used for the immersion test may be an adhesive layer having the above size, or an adhesive layer may be processed from a predetermined adhesive layer to a size of 80 mm × 100 mm. If the adhesive layer is energy ray curable, the adhesive layer after energy ray irradiation is used. The adhesive layer having a size of 80 mm × 100 mm is immersed so that its entire surface is in contact with the toluene. The thickness of the adhesive layer is arbitrary as long as it is thick enough to allow the entire surface to be in contact with the toluene. In this embodiment, considering handling and other factors, it is preferable to wrap the adhesive layer in a mesh sheet or the like made of a material insoluble in toluene before immersion. After the immersion is complete, the adhesive layer and, if necessary, the mesh sheet or the like are removed from the toluene to obtain the toluene solvent in which the adhesive layer was in contact. If components leach out from the adhesive layer upon immersion, the resulting toluene solvent will contain those components.

[0109] Next, the obtained toluene solvent is analyzed by gel permeation chromatography (GPC). In this embodiment, the easily transferable components are evaluated using the following GPC measurement principle.

[0110] When a sample solution containing the target molecule is introduced into a column packed with porous granular packing material, the distance the molecules travel through the column differs depending on their size. Therefore, the time it takes for molecules to reach the column outlet after being introduced (elution time) differs depending on their molecular size. For example, larger molecules have difficulty entering the pores of the packing material and are discharged from the column without reaching the deepest part of the column (without penetration). As a result, the elution time is short. On the other hand, smaller molecules can easily enter the pores of the packing material and are discharged from the column after reaching the deepest part of the column (after penetration). As a result, the elution time is long. Therefore, the molecular size can be measured by the difference in elution time from the column.

[0111] Molecules eluted from the column are detected by a detector. An example of a detector is an RI detector. When many molecules of the same size are detected, the detection intensity increases. Therefore, by plotting the elution time from the column against the detection intensity, a distribution of molecules by size (chromatogram) can be obtained. Figure 3 shows an example of a chromatogram. In Figure 3, the detection voltage is shown on the vertical axis as the detection intensity.

[0112] Furthermore, a calibration curve showing the relationship between elution time and molecular weight is created using standard samples with known molecular weights. From the created calibration curve, the relationship between elution time and the molecular weight of the standard sample is calculated. In this embodiment, polystyrene is used as the standard sample, and the elution time is correlated with the number-average molecular weight (Mn) of standard polystyrene. By using the number-average molecular weight of the molecule to be detected, evaluation can be performed with high sensitivity.

[0113] In this embodiment, 10 μL is taken from the toluene solvent after the immersion test, and the 10 μL of toluene solvent is measured by gel permeation chromatography. From the measurement results, a chromatogram is obtained with the detection voltage on the vertical axis and the elution time on the horizontal axis. If the toluene solvent after the immersion test does not contain components derived from the adhesive layer, the detection voltage will be constant regardless of the elution time (baseline B in Figure 3).

[0114] On the other hand, if the toluene solvent after the immersion test contains components derived from the adhesive layer (detectable components), the detection voltage changes relative to the baseline and forms a peak P, as shown in Figure 3, depending on the number-average molecular weight (elution time) and amount of the component in terms of standard polystyrene. Multiple peaks may be present. The amount of the detected component can be calculated as the peak area from the chromatogram shown in Figure 3. Specifically, the peak area is calculated as the area enclosed by the baseline and the line indicating the change in detection voltage in the chromatogram.

[0115] In this embodiment, the peak area of ​​the detected component (hatched area PA in Figure 3) is calculated in the obtained chromatogram within the range from the elution time corresponding to a standard polystyrene-equivalent number-average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene-equivalent number-average molecular weight of 200. The peak area is preferably 4000 mV·s or less.

[0116] The peak area reflects the amount of the detected component whose number-average molecular weight is in the range of 2 to 2.5 million. Furthermore, by limiting the range of the number-average molecular weight, the molecular weight of the detected component reflected in the peak area is limited to a predetermined range, thus eliminating the influence of toluene, etc., used in the immersion test on the peak area. Therefore, a peak area of ​​4000 mV·s or less indicates that the amount of the component with a number-average molecular weight in the range of 2 to 2.5 million is below a predetermined amount. By having a low amount of such components, residue originating from the adhesive layer can be suppressed. In the examples described later, the corresponding elution time when the number-average molecular weight in standard polystyrene equivalent is 200 is 960 seconds (16 minutes), and the corresponding elution time when the number-average molecular weight in standard polystyrene equivalent is 2.5 million is 522 seconds (8.7 minutes).

[0117] The peak area is preferably small, and may be 3000 mV·s or less, 2000 mV·s or less, 1000 mV·s or less, or 300 mV·s or less. The lower limit of the peak area is 0 mV·s. The peak area can be calculated, for example, using analysis software attached to the GPC measurement device. If the adhesive layer is energy ray curable, the peak area is the peak area of ​​the adhesive layer after energy ray irradiation.

[0118] Furthermore, in the chromatogram, it is preferable that the peak area of ​​the detected component in a range narrower than the above range for the number-average molecular weight equivalent to standard polystyrene is within a predetermined range. Specifically, it is preferable that the peak area of ​​the detected component in the range from the elution time corresponding to a number-average molecular weight equivalent to 10,000 to the elution time corresponding to a number-average molecular weight equivalent to 200 is 4,000 mV·s or less. By keeping the amount of components with a number-average molecular weight in the range of 200 to 10,000 below a predetermined amount, residue originating from the adhesive layer can be suppressed. The elution time corresponding to a number-average molecular weight equivalent to 10,000 is 750 seconds (12.5 minutes).

[0119] The peak area is preferably small, and may be 3000 mV·s or less, 2000 mV·s or less, 1000 mV·s or less, or 300 mV·s or less. The lower limit of the peak area is 0 mV·s.

[0120] (3.3. Gel fraction of the adhesive layer) In this embodiment, the gel fraction of the adhesive layer is preferably 90% or more. This strengthens the solid properties of the crosslinked structure in the adhesive layer and suppresses the amount of easily migrated components. As a result, it becomes easier to set the peak area of ​​the components derived from the adhesive layer after GPC measurement within the range described above. The gel fraction may be 93% or more, 95% or more, or 97% or more. Note that if the adhesive layer is energy ray curable, the gel fraction is the gel fraction of the adhesive layer after energy ray irradiation.

[0121] In this embodiment, the method for measuring the gel fraction of the adhesive layer can utilize the immersion test described above, similar to the method for measuring the gel fraction of the adhesive layer. Specifically, an adhesive layer having a size of 80 mm x 100 mm is immersed in 15 g of toluene at 25°C for 24 hours. At this time, it is preferable to wrap the adhesive layer with the mesh sheet or the like described above. After the immersion is complete, the adhesive layer and, if necessary, the mesh sheet or the like are recovered from the toluene, and the gel fraction can be calculated from the mass of the adhesive layer before and after immersion, and, if necessary, the mass of the mesh sheet or the like. A specific method for measuring the gel fraction will be described in the examples below.

[0122] (4. Peak area of ​​components derived from workpiece processing sheet after GPC measurement) In this embodiment, instead of the adhesive layer, it is preferable that the peak area obtained by performing the immersion test and GPC measurement described in (3.2) on the workpiece processing sheet is 3000 mV·s or less. By keeping the peak area of ​​components derived from the workpiece processing sheet after GPC measurement within the above range, the surface of the workpiece or workpiece can be kept clean. The peak area of ​​components derived from the workpiece processing sheet after GPC measurement may be 1000 mV·s or less, 500 mV·s or less, or 200 mV·s or less. The lower limit of the peak area is 0 mV·s.

[0123] (5. Method for manufacturing workpiece processing sheets) The method for manufacturing workpiece processing sheets according to this embodiment can employ known methods.

[0124] First, the base material is prepared. If the base material consists of one layer, the resin film or other material that makes up the base material should be prepared. If the base material consists of two or more layers, for example, the base material is manufactured by laminating a resin film that makes up the support material and a resin film that makes up the low-polarity material.

[0125] One example of a method for laminating resin films is the dry lamination method, in which one resin film (for example, a resin film constituting a low-polarity material) is bonded to another resin film (for example, a resin film constituting a support material) via an easily adhesive layer formed on one main surface of the first resin film.

[0126] 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 coating a composition for forming an easy-adhesion layer onto a surface that has undergone an adhesive treatment such as corona treatment may be used.

[0127] Furthermore, an example is a method in which the resin constituting the low-polarity material is melted and kneaded using a T-die film-forming machine, and the molten resin is extruded and laminated onto one side of the support material while the support material is moved at a constant speed. In addition, an example is a method in which the low-polarity material is directly laminated onto the support material by heat sealing or the like.

[0128] As an adhesive composition for forming an adhesive layer, for example, an adhesive composition containing the above-mentioned components, or a composition obtained by diluting the adhesive composition with a solvent or the like (hereinafter sometimes referred to as an adhesive coating agent) is prepared.

[0129] Examples of solvents include organic solvents such as methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol.

[0130] Next, an adhesive composition or a coating agent of the adhesive composition is applied to the release 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 substrate are bonded together to obtain a workpiece processing sheet in which the adhesive layer and the substrate are laminated. At this time, the surface of the substrate in which the surface free energy is within the above range is bonded to the adhesive layer. The release sheet may be removed as necessary when using the workpiece processing sheet.

[0131] (6. Method for processing workpieces and method for manufacturing workpieces) The workpiece processing sheet according to this embodiment is used for processing workpieces. In this embodiment, as a non-limiting example of the use of the workpiece processing sheet, a method of using the workpiece processing sheet as a back grind sheet when grinding the back surface of a workpiece as part of the processing of a workpiece will be described in more detail below.

[0132] The workpiece processing method according to this embodiment specifically comprises at least the following steps 1 to 3. The workpiece is a workpiece for manufacturing a workpiece that will be directly joined. Step 1: A step of attaching the workpiece processing sheet to the surface of a workpiece having a surface and a back surface facing the surface. Step 2: A step of grinding the back surface of the workpiece to which the workpiece processing sheet has been attached. Step 3: A step of peeling the workpiece processing sheet off the processed workpiece.

[0133] The following describes in detail each step of the processing method for the above-mentioned workpiece. In the following explanation, a wafer will be used as a specific example of the workpiece.

[0134] (Step 1) In Step 1, as shown in Figure 4(A), the surface 50a of the wafer 50 is attached to the main surface 20a of the adhesive layer 20 of the workpiece processing sheet 1 according to this embodiment. By attaching the workpiece processing sheet to the surface of the wafer, the migration of components derived from the substrate to the adhesive layer is suppressed, and the surface of the wafer is kept clean. 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 280 to 780 μm.

[0135] Circuits are formed on the surface of the wafer. The formed circuits may be exposed, or a circuit protection layer may be formed to protect the circuits.

[0136] (Step 2) In Step 2, the wafer 50 fixed to the workpiece processing sheet 1 is placed on the chuck table with its front side facing up and held by the chuck table. That is, the workpiece processing sheet is held by the chuck table. After that, the back surface of the wafer is ground using, for example, a grinding wheel or the like provided by a grinding device (not shown). That is, in Step 2, the workpiece processing sheet functions as a back-grinding sheet. The thickness of the wafer after back-grinding is, for example, about 5 μm to 300 μm. Even if the wafer is thin after back-grinding, the rigidity of the base material of the workpiece processing sheet is sufficient, so the occurrence of damage and cracks is suppressed.

[0137] (Step 3) Next, the workpiece processing sheet is peeled off the processed wafer. In this embodiment, the workpiece processing sheet 1 is peeled off from the surface 50a of the wafer 50 after back grinding as shown in Figure 4(B). If the adhesive layer of the workpiece processing sheet is energy ray curable, the adhesive layer is hardened and shrunk by irradiating it with energy rays to reduce its adhesive strength to the adherend (wafer after back grinding) before peeling it off.

[0138] In this embodiment, the workpiece processing method preferably includes a step (step 4) of dividing the workpiece into individual pieces to obtain multiple workpieces. The workpiece processing method including steps 1 to 4 is a method for manufacturing workpieces.

[0139] (Step 4) In Step 4, before peeling off the workpiece processing sheet from the wafer after processing in Step 3, a transfer sheet is attached to the side of the wafer that does not have the workpiece processing sheet attached. In this embodiment, as shown in Figure 5(A), the adhesive layer 82 of a transfer sheet 80, which comprises a base material 81 and an adhesive layer 82, is attached to the back surface 50b of the wafer 50 after back surface grinding. Then, as shown in Figure 5(B), the workpiece processing sheet 1 is peeled off from the front surface 50a of the wafer 50 after back surface grinding, and the wafer 50 after back surface grinding is transferred from the workpiece processing sheet 1 to the transfer sheet 80.

[0140] Next, a dicing sheet is attached to the surface of the wafer after back-grinding, which is attached to the transfer sheet. The dicing sheet is a laminate of an adhesive layer and a substrate. In this embodiment, it is preferable that the adhesive layer is formed from the adhesive composition described above, and it is more preferable that the substrate is made of the low-polarity material described above. As shown in Figure 6(A), the surface 50a of the wafer 50 after back-grinding and the ring frame 100 are attached to the main surface 92a of the adhesive layer 92 of the dicing sheet 90 to fix the wafer 50 and the ring frame 100. This makes it possible to suppress contamination of the wafer surface following the workpiece processing sheet. Subsequently, after attaching the dicing sheet to the surface of the wafer, the transfer sheet 80 is peeled off from the back surface 50b of the wafer 50, as shown in Figure 6(B). If the adhesive layer of the transfer sheet is energy-ray curable, the adhesive layer is cured and shrunk by irradiating it with energy rays to reduce the adhesive force to the adherend (wafer after back-grinding) before peeling it off.

[0141] Next, the wafer with the dicing sheet attached is divided into individual pieces. As shown in Figure 6(C), the wafer 50 fixed to the dicing sheet 90 and the ring frame 100 are set in a dicing apparatus (not shown), and the wafer 50 is divided into individual pieces (diced) to obtain a plurality of chips 51. Examples of known dicing methods for dividing a wafer into individual pieces include blade dicing, stealth dicing (registered trademark), plasma dicing, laser dicing, and water dicing.

[0142] By performing steps 1 to 4, the back surface of the workpiece (wafer) is ground, and the workpiece after back surface grinding is broken down into individual pieces, resulting in multiple workpiece chips. In other words, it is possible to manufacture workpieces with a clean surface that are suitable for direct bonding.

[0143] Alternatively, step 4 may be performed without removing the workpiece processing sheet from the wafer after backside grinding. In other words, the workpiece processing sheet may be used as a dicing sheet. Even in this case, contamination of the wafer surface can be suppressed.

[0144] Alternatively, steps 2 and 4 may be performed integrally. In this case, methods such as DBG (Dicing Before Grinding) or pre-grinding stealth dicing (registered trademark) can be employed. That is, by forming grooves or modified layer regions on the wafer and then performing backside grinding, the wafer can be separated into individual pieces.

[0145] (7. Method for joining workpieces) The resulting workpieces are suitable for direct joining. The method for directly joining workpieces (DTB) will be described in detail below.

[0146] The method for joining workpieces preferably comprises the following steps 5 and 6: Step 5: A step of transferring the obtained workpieces to a carrier sheet. Step 6: A step of directly joining the workpieces to a wafer.

[0147] The following describes each step of the joining method for workpieces. A wafer will be used as a specific example of the workpiece, and a chip will be used as a specific example of the workpiece.

[0148] (Step 5) In Step 5, a plurality of chips held on the dicing sheet or workpiece processing sheet are transferred onto a carrier sheet. The carrier sheet is preferably adhesive in order to hold the chips. In this embodiment, the carrier sheet is preferably made of a base material and an adhesive layer formed on one of the main surfaces of the base material. Furthermore, the adhesive layer of the carrier sheet is preferably energy ray curable.

[0149] If the adhesive layer of the dicing sheet or workpiece processing sheet is energy ray curable, the adhesive layer is cured by irradiating it with energy rays before transfer to reduce its adhesive strength. First, as shown in Figure 7(A), the adhesive layer 87 of a carrier sheet 85, which comprises a base material 86 and an adhesive layer 87, is attached to the back surface 51b of the obtained chips 51. Next, as shown in Figure 7(B), the dicing sheet 90 (or workpiece processing sheet) is peeled off from the surface 51a of the chips 51 held on the carrier sheet 85. As a result, the chips are transferred from the dicing sheet or workpiece processing sheet to the carrier sheet.

[0150] Furthermore, in step 5, as shown in Figure 7(C), the carrier sheet 85 may be stretched to widen the spacing between the chips 51 to facilitate direct bonding of the chips, or to completely divide the wafer. If the adhesive layer of the carrier sheet is energy ray curable, it is preferable to irradiate the adhesive layer with energy rays before expanding to cure it and reduce its adhesive strength.

[0151] (Step 6) In Step 6, the chip is directly bonded to the wafer. Before direct bonding, it is preferable that the bonding surface (surface) of the chip and the bonding surface (circuit surface) of the wafer are treated to improve bonding properties. Such treatment may be a physical treatment or a chemical treatment. Specifically, plasma treatment to activate the bonding surface is an example.

[0152] As shown in Figure 8(A), the chip 51 held on the carrier sheet 85 is transported so that the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 face each other, and is aligned to the planned bonding position by an alignment mechanism (not shown). Next, as shown in Figure 8(B), the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 are brought into contact and fixed to the planned bonding position for bonding. An example of a method for bringing the bonding surface 51a of the chip 51 and the bonding surface 60a of the wafer 60 into contact is to use a pressing mechanism 110 to press from the back surface 51b side (carrier sheet 85 side) of the chip 51 to bring it into contact with the wafer 60.

[0153] Subsequently, if the adhesive layer of the carrier sheet is energy-ray curable, the adhesive layer is irradiated with energy rays to harden it, reducing its adhesive strength and allowing the carrier sheet to be peeled off the chip. By repeating this process, a chip-on-wafer 70 is obtained in which multiple chips 51 are directly bonded to a wafer 60, as shown in Figure 8. Since the generation of particles at the bonding surface of the wafer or chip is suppressed, the bonding state after direct bonding is good.

[0154] In step 6, it is preferable to further anneal the wafer on which the multiple chips are fixed in order to improve the bonding between the chips and the wafer. An example of an annealing process is a process in which the chips and wafer are heated while being pressed together.

[0155] By performing steps 5 and 6, the workpiece (wafer) is fragmented, and the resulting workpiece (chip) is directly bonded to the wafer. In other words, the workpiece (chip) can be directly bonded while maintaining a clean surface.

[0156] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and may be modified in various ways within the scope of the present invention.

[0157] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0158] (Example 1) (1) Base material A support material and a low-polarity material constituting the base material were prepared. A polyethylene terephthalate (PET) film (thickness: 50 μm, tensile modulus at 23°C: 4500 MPa) was prepared as the support material. A low-polarity polyethylene (LDPE) film (thickness: 25 μm, tensile modulus at 23°C: 200 MPa) was prepared as the low-polarity material.

[0159] A 2.5 μm thick easy-adhesion layer was provided on one main surface of the prepared PET film, and the prepared LDPE film was laminated onto it by dry lamination to create a substrate A having the structure of "LDPE (25 μm) / easy-adhesion layer (2.5 μm) / PET (50 μm)".

[0160] (2) Adhesive layer (Preparation of adhesive composition) An acrylic polymer was obtained by copolymerizing 80 parts by mass of 2-ethylhexyl acrylate (2EHA) and 20 parts by mass of 2-hydroxyethyl acrylate (2HEA). This polymer was then reacted with 2-methacryloyloxyethyl isocyanate (MOI) to add to 80 mol% of the total hydroxyl groups of the acrylic polymer, thereby obtaining an energy-ray curable acrylic polymer. The molecular weight of the obtained acrylic polymer was measured by the method shown below, and the weight-average molecular weight (Mw) was 500,000.

[0161] The weight-average molecular weight (Mw) is the weight-average molecular weight on a standard polystyrene basis, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). (Measurement conditions) ・GPC analyzer: HLC-8020, manufactured by Tosoh Corporation ・GPC column (passed in the following order): TSK guard column HXL-H, TSK gel GMHXL (x2), TSK gel G2000HXL, manufactured by Tosoh Corporation ・Measurement solvent: Tetrahydrofuran ・Measurement temperature: 40°C

[0162] To 100 parts by mass of this energy-ray curable acrylic polymer, 1 part by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L") and 3 parts by mass of a photopolymerization initiator (manufactured by IGM Resins, product name "Omnirad 184") were added, and the mixture was diluted with methyl ethyl ketone to prepare a coating agent for an adhesive composition.

[0163] (Formation of adhesive layer) The adhesive composition described above was applied to the release-treated surface of a release sheet (Lintec Corporation, product name "SP-PET381031", polyethylene terephthalate (PET) film with silicone release treatment, thickness: 38 μm), and dried to form an energy-ray curable adhesive layer with a thickness of 20 μm on the release sheet.

[0164] (3) Preparation of workpiece processing sheet Using the base material A prepared in (1), the main surface of the adhesive layer of the release sheet was bonded to the main surface of the exposed LDPE film to prepare a workpiece processing sheet having the configuration of "base material A / adhesive layer / release sheet".

[0165] (Example 2) Substrate B was prepared in place of substrate A as follows. As a flexible material, a low-density polyethylene (LDPE) film (thickness: 25 μm, tensile modulus at 23°C: 200 MPa), the same as that used for the low-polarity material, was prepared. An easy-adhesion layer with a thickness of 2.5 μm was provided on both main surfaces of the PET film, and the prepared LDPE film was laminated onto each easy-adhesion layer by dry lamination to produce substrate B having the configuration of "LDPE (25 μm) / easy-adhesion layer (2.5 μm) / PET (50 μm) / easy-adhesion layer (2.5 μm) / LDPE (25 μm)".

[0166] A workpiece processing sheet having the configuration of "substrate B / adhesive layer / release sheet" was prepared using the same method as in Example 1, except that the prepared substrate B was used.

[0167] (Example 3) Substrate C was prepared in place of substrate A as follows. Except for using a polyimide (PI) film (thickness: 50 μm, tensile modulus at 23°C: 4000 MPa) instead of a PET film as a support material, substrate C having the configuration of "LDPE (25 μm) / easy-adhesion layer (2.5 μm) / PI (50 μm)" was prepared in the same manner as in Example 1.

[0168] A workpiece processing sheet having the configuration of "substrate C / adhesive layer / release sheet" was prepared using the same method as in Example 1, except that the prepared substrate C was used.

[0169] (Example 4) Substrate D was prepared in place of substrate B as follows. Except for using a polyimide (PI) film (thickness: 50 μm, tensile modulus at 23°C: 4000 MPa) instead of a PET film as a support material, substrate D having the configuration of "LDPE (25 μm) / easy-adhesion layer (2.5 μm) / PI (50 μm) / easy-adhesion layer (2.5 μm) / LDPE (25 μm)" was prepared in the same manner as in Example 1.

[0170] A workpiece processing sheet having the configuration of "substrate D / adhesive layer / release sheet" was prepared using the same method as in Example 1, except that the prepared substrate D was used.

[0171] (Example 5) Substrate E was prepared in place of substrate A as follows. Except for using a cycloolefin polymer (COP) film (thickness: 50 μm, tensile modulus at 23°C: 2700 MPa) instead of a PET film as a support material, substrate E having the configuration of "LDPE (25 μm) / easy-adhesion layer (2.5 μm) / COP (50 μm)" was prepared in the same manner as in Example 1.

[0172] A workpiece processing sheet having the configuration of "substrate E / adhesive layer / release sheet" was prepared using the same method as in Example 1, except that the prepared substrate E was used.

[0173] (Example 6) Substrate F was prepared in place of substrate B as follows. Except for using a cycloolefin polymer (COP) film (thickness: 50 μm, tensile modulus at 23°C: 2700 MPa) instead of a PET film as a support material, substrate F having the configuration of "LDPE (25 μm) / easy-adhesion layer (2.5 μm) / COP (50 μm) / easy-adhesion layer (2.5 μm) / LDPE (25 μm)" was prepared in the same manner as in Example 1.

[0174] A workpiece processing sheet having the configuration of "base material F / adhesive layer / release sheet" was prepared using the same method as in Example 1, except that the prepared base material F was used.

[0175] (Example 7) A single layer of polyimide (PI) film (thickness: 50 μm, tensile modulus at 23°C: 4000 MPa) was used as the base material G. A workpiece processing sheet having the configuration of "base material G / adhesive layer / release sheet" was prepared by the same method as in Example 1, except that the main surface of the adhesive layer of the release sheet was bonded to the main surface of the base material G (PI film).

[0176] (Example 8) A single layer of cycloolefin polymer (COP) film (thickness: 50 μm, tensile modulus of elasticity at 23°C: 2700 MPa) was used as the base material H. A workpiece processing sheet having the configuration of "base material H / adhesive layer / release sheet" was prepared in the same manner as in Example 1, except that the main surface of the adhesive layer of the release sheet was bonded to the main surface of the base material H (COP film).

[0177] (Comparative Example 1) A single layer of polyethylene terephthalate (PET) film (thickness: 50 μm, tensile modulus of elasticity at 23°C: 4500 MPa) was used as the base material I. A workpiece processing sheet having the configuration of "base material I / adhesive layer / release sheet" was prepared by the same method as in Example 1, except that the main surface of the adhesive layer of the release sheet was bonded to the main surface of the base material I (PET film).

[0178] (Comparative Example 2) A single layer of low-density polyethylene (LDPE) film (thickness: 110 μm, tensile modulus of elasticity at 23°C: 200 MPa) was used as the base material J. A workpiece processing sheet having the configuration of "base material J / adhesive layer / release sheet" was prepared by the same method as in Example 1, except that the main surface of the adhesive layer of the release sheet was bonded to the main surface of the base material J (LDPE film).

[0179] (Comparative Example 3) A single layer of polyethylene (PE) film (thickness: 70 μm, tensile modulus of elasticity at 23°C: 180 MPa) was used as the base material K. A workpiece processing sheet having the configuration of "base material K / adhesive layer / release sheet" was prepared by the same method as in Example 1, except that the main surface of the adhesive layer of the release sheet was bonded to the main surface of the base material K (PE film).

[0180] (Comparative Example 4) A single layer of polyvinyl chloride (PVC) film (thickness: 80 μm, tensile modulus of elasticity at 23°C: 200 MPa) was used as the base material L. A workpiece processing sheet having the configuration of "base material L / adhesive layer / release sheet" was prepared by the same method as in Example 1, except that the main surface of the adhesive layer of the release sheet was bonded to the main surface of the base material L (PVC film).

[0181] The obtained samples (Examples 1 to 8 and Comparative Examples 1 to 4) were evaluated as follows. The results are shown in Table 1.

[0182] (Tensile modulus of the base material) Base materials A to L prepared in the examples and comparative examples were cut to a size of 130 mm in length and 15 mm in width to obtain measurement samples for measuring the tensile modulus. The obtained measurement samples were placed in a precision universal testing machine (manufactured by Shimadzu Corporation, product name "Shimadzu Triple Tensile Testing Machine") with a chuck distance of 100 mm. Under conditions of 23°C and 50% relative humidity, the measurement samples obtained were pulled in the longitudinal direction of the measurement samples using the precision universal testing machine at a test speed of 200 mm / min, and the value of the tensile modulus at 23°C was calculated from the measurement results. This value was taken as the tensile modulus of the base material at 23°C (unit: MPa). In this example, it is preferable that the tensile modulus of the base material be 1400 MPa or higher. The results are shown in Table 1.

[0183] (Surface free energy of the surface in contact with the adhesive layer on the substrate) For substrates A to L prepared in the examples and comparative examples, the contact angles of various droplets with respect to the surface in contact with the adhesive layer were measured, and the surface free energy (mN / m) was determined from these values ​​using the Kitazaki-Hata formula. The contact angles were measured using a contact angle meter (Kyowa Interface Science Co., Ltd., product name "DM-701") by the static droplet method in accordance with JIS R3257. For the droplets, diiodomethane was used as the "dispersion component", 1-bromonaphthalene as the "dipole component", and distilled water as the "hydrogen bonding component". In this example, it is preferable that the surface free energy of the surface in contact with the adhesive layer on the substrate is less than 40 mN / m. The results are shown in Table 1.

[0184] (Peak area after GPC measurement of components derived from the adhesive layer) For the adhesive layer prepared above, at an illuminance of 230 mW / cm² 2 Total light intensity 190 mJ / cm 2 After irradiation with energy rays under the specified irradiation conditions, the adhesive layer was cut into 80 mm x 100 mm sections. These sections were wrapped in a nylon mesh sheet measuring 100 mm x 150 mm with a mesh size of 200, and secured with staples or other fasteners to form the sample for measurement. This sample was then subjected to an immersion test by soaking it in 15 g of toluene at 25°C for 24 hours. After the test, all remaining sections, nylon mesh sheets, and fasteners were removed from the toluene, and the toluene solvent was recovered.

[0185] The recovered toluene solvent was measured by gel permeation chromatography (GPC) under the following conditions. From the measurement results, the peak area was calculated from the elution time from 8.7 minutes (corresponding to a standard polystyrene number-average molecular weight of 2.5 million) to 16 minutes (corresponding to a standard polystyrene number-average molecular weight of 200) using the software attached to the GPC analyzer (EcoSEC Data Analysis Version 1.16). In this example, a peak area of ​​4000 mV·s or less is preferable. The results are shown in Table 1. <Measurement Conditions> ・GPC measuring device: Tosoh Corporation, HLC-8320 ・GPC column (passed in the following order): Tosoh Corporation TSK gel superHZ1000 (1 column), TSK gel superHZ2000 (2 columns), TSK gel superHZ2500 (1 column), TSK gel superHZM-M (2 columns) ・Measurement solvent: Tetrahydrofuran ・Measurement temperature: 40℃ ・Sample input volume: 10 μL ・Detector: RI detector

[0186] (Gel fraction of the adhesive layer) After the immersion test described above, the section, nylon mesh sheet, and fasteners were all removed from toluene and dried at 90°C for 3 hours. They were then allowed to stand for 1 hour at 23°C and 50% relative humidity to adjust the humidity. The total mass of the section, nylon mesh sheet, and fasteners after humidity adjustment (M51) was measured. Using this M51, along with the mass of the section before the immersion test (M11), the mass of the nylon mesh sheet (M2), and the mass of the fasteners (M3), the gel fraction of the adhesive layer was calculated using the following formula (1). In this example, a gel fraction of 90% or more is preferable. The results are shown in Table 1. Gel fraction of the adhesive layer = 100 × (M51 - M2 - M3) / (M11 - M2 - M3) (1)

[0187] (Peak area after GPC measurement of components derived from workpiece processing sheets) Instead of an adhesive layer, the workpiece processing sheets of Examples 1 to 8 and Comparative Examples 1 to 4 were subjected to an illuminance of 230 mW / cm². 2 Total light intensity 190 mJ / cm 2After irradiating the workpiece sheet with energy rays under the specified irradiation conditions, the immersion test described above was performed on the workpiece sheet. GPC measurements were then performed on the recovered toluene solvent under the specified measurement conditions, and the peak area of ​​the workpiece sheet after GPC measurement was calculated. In this example, a peak area of ​​4000 mV·s or less is preferable. The results are shown in Table 1.

[0188] (Evaluation of low contamination) The release sheets were peeled off the workpiece processing sheets of Examples 1 to 8 and Comparative Examples 1 to 4, and attached to a particle-controlled wafer in an environment of 23°C and 50% relative humidity. After 1 hour, the wafers were irradiated with ultraviolet (UV) light using an ultraviolet irradiation device (Lintec Corporation, product name "RAD-2000m / 12") in an environment of 23°C and 50% relative humidity (illuminance: 230 mW / cm²). 2 , Light amount: 190mJ / cm 2 After the workpiece processing sheet was removed from the wafer, the number of particles (size: 0.27 μm or larger) remaining on the wafer was measured using a wafer inspection machine (manufactured by Takano Corporation, product name "WM-7SR"). The measurement results were evaluated according to the following criteria. In this example, "A" or "B" is preferred. The results are shown in Table 1. A: Number of particles is 100 or less B: Number of particles is 101 to 1000 F: Number of particles is 1001 to 10000

[0189] (Grinding Performance Evaluation) The release sheets were peeled off the workpiece processing sheets of Examples 1 to 8 and Comparative Examples 1 to 4, and attached to an 8-inch diameter, 725 μm thick silicon wafer using a backgrinding tape laminator (Lintec Corporation, device name "RAD-3510F / 12"). Then, back grinding was performed using a back grinding device (Disco Corporation, device name "DGP8760") until the silicon wafer was 30 μm thick. The silicon wafer after back grinding was visually inspected for the presence or absence of cracks. The observation results were evaluated according to the following criteria. In this example, "A" is preferred. The results are shown in Table 1. A: No cracks F: Cracks present

[0190] (Direct Bonding Evaluation) The release sheets of the workpiece processing sheets of Examples 1 to 8 and Comparative Example 1 produced were peeled off, and the surface on which the thermal oxide film of the silicon wafer with a thermal oxide film having a diameter of 8 inches and a thickness of 725 μm was formed (referred to as the front surface in this example) was pasted using a back grinding tape laminator (manufactured by Lintec Corporation, device name "RAD-3510F / 12"). Then, using a back grinding device (manufactured by DISCO Corporation, device name "DGP8760"), the surface on which the thermal oxide film was not formed (referred to as the back surface in this example) of the silicon wafer with a thermal oxide film was ground until the thickness of the silicon wafer with a thermal oxide film reached 150 μm.

[0191] After grinding, an adhesive layer formed from the composition for an adhesive prepared in the above example and a base material composed of a polyethylene (PE) film (thickness: 70 μm) were pasted on the grinding surface (back surface). After pasting, ultraviolet (UV) irradiation (irradiance: 230 mW / cm 2 , light quantity: 190 mJ / cm 2 ) was performed on the adhesive layer of the workpiece processing sheet using an ultraviolet irradiation device (manufactured by Lintec Corporation, product name "RAD-2000m / 12"), and then the workpiece processing sheet was peeled off from the surface (front surface) on which the thermal oxide film of the silicon wafer with a thermal oxide film was formed.

[0192] Subsequently, ultraviolet (UV) irradiation (irradiance: 230 mW / cm 2 , light quantity: 190 mJ / cm 2Subsequently, the adhesive layer of a dicing sheet, which comprises an adhesive layer formed from the adhesive composition prepared in the above example and a substrate made of ethylene-methacrylic acid copolymer (EMAA) (Mitsui DuPont Polychemicals, product name "Nucrel 80", thickness: 80 μm, surface free energy: 30 mN / m), was attached to the non-ground surface (front surface) of the silicon wafer with a thermal oxide film using a tape mounter device (Lintec Corporation, product name "RAD-2700F / 12"), and the adhesive layer was also attached to the ring frame. After that, the transfer sheet was peeled off from the ground surface (back surface) of the silicon wafer with a thermal oxide film.

[0193] Next, the silicon wafer was placed together with a ring frame in a dicing apparatus (DISCO Corporation, product name "DFD6362") and blade dicing was performed to obtain silicon chips from the silicon wafer. The dicing size was 8 mm x 8 mm. An ultraviolet irradiation device (Lintec Corporation, RAD-2000m / 12) was used to irradiate the substrate at an illuminance of 230 mW / cm². 2 Total light intensity 190 mJ / cm 2 The adhesive layer of the dicing sheet was cured by irradiating it with ultraviolet light under the specified irradiation conditions.

[0194] Next, using a tape mounter device (Lintec Corporation, product name "RAD-2700F / 12"), the adhesive layer of a carrier sheet, which comprises an adhesive layer formed from the adhesive composition prepared in the above example and a base material made of polyethylene (PE) film (thickness 70 μm), was attached to the side of the silicon chip where the dicing sheet was not attached (the grinding surface (back surface)). After attaching the carrier sheet, the dicing sheet was peeled off from the side of the silicon chip opposite the polished surface (the non-grinding surface (front surface)) using a tape peeling device, and the silicon chip was transferred from the dicing sheet to the carrier sheet. Subsequently, the carrier sheet was stretched using an expander device, and the spacing between the silicon chips was widened to 0.03 mm.

[0195] Next, the exposed surface (non-grinding surface (front surface)) of the silicon chip held on the carrier sheet was subjected to plasma irradiation using the plasma cleaner PDC210. ​​Similarly, the thermal oxide film formation surface of the thermal oxide film-coated silicon wafer (diameter: 8 inches, thickness: 750 μm) to which the silicon chip would be bonded was also subjected to plasma irradiation using the plasma cleaner PDC210.

[0196] Direct bonding (DTB) was performed by pressing the bonding surface (front surface) of a silicon chip against the bonding surface (thermal oxide film formation surface) of a silicon wafer after plasma irradiation using a pressing tool at 5N for 1 second. In each example and comparative example, the above direct bonding was performed on 30 silicon chips, and the bonding state was evaluated according to the following criteria. The results are shown in Table 1. Note that for Comparative Examples 2 to 4, direct bonding was not evaluated because cracks etc. occurred in the wafer after grinding. A: The number of silicon chips that maintained a bonded state for 1 minute or more after inverting the silicon wafer immediately after direct bonding was 20 or more. B: The number of silicon chips that maintained a bonded state for 1 minute or more after inverting the silicon wafer immediately after direct bonding was 10 to 19. F: The number of silicon chips that maintained a bonded state for 1 minute or more after inverting the silicon wafer immediately after direct bonding was 9 or less.

[0197]

[0198] As shown in Table 1, in Examples 1 to 8, where the workpiece processing sheet has the above-described physical properties, no cracks or other defects occurred in the wafer when the wafer was ground using the workpiece processing sheet, and the wafer surface (front surface) remained clean. Therefore, it was confirmed that even when the chip was directly bonded to the wafer, the bonding state of the bonded portion was good.

[0199] On the other hand, in Comparative Example 1, although no cracks or other defects occurred in the wafer after grinding, it was confirmed that the number of particles present in the wafer increased, indicating poor bonding conditions.

[0200] 1...Workpiece processing sheet 10...Base material 11...Support material 12...Low polarity material 13...Soft material 20...Adhesive layer 50...Workpiece (wafer) 51...Workpiece processed product (chip) 60...Wafer 70...Chip-on-wafer 85...Carrier sheet 90...Dicing sheet

Claims

1. A workpiece processing sheet used for processing workpieces to manufacture workpieces to be directly joined, wherein the workpiece processing sheet has a structure in which a base material and an adhesive layer are laminated, the tensile modulus of the base material at 23°C is 1400 MPa or more, and the surface free energy of the surface of the base material in contact with the adhesive layer is less than 40 mN / m.

2. The workpiece processing sheet according to claim 1, used for grinding the workpiece.

3. The workpiece processing sheet according to claim 1 or 2, wherein the base material is composed of two or more layers including a support material and a low-polarity material which has lower polarity than the support material.

4. The workpiece processing sheet according to claim 3, wherein the support material is a polyethylene terephthalate film and the low-polarity material is a polyolefin film.

5. A workpiece processing sheet according to claim 1 or 2, wherein the following immersion test is performed on the adhesive layer, and the peak area of ​​the detected component calculated by performing the following gel permeation chromatography measurement on the toluene solvent after the immersion test is 4000 mV·s or less. (Immersion test) An adhesive layer having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C for 24 hours to obtain the toluene solvent in contact with the adhesive layer. (Gel permeation chromatography measurement) 10 μL of the obtained toluene solvent is measured by gel permeation chromatography, and the measurement result is represented as a chromatogram with the detection voltage on the vertical axis and the elution time from the introduction of the toluene solvent to elution from the column on the horizontal axis, and the peak area of ​​the detected component is calculated in the range from the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 200.

6. The workpiece processing sheet according to claim 1 or 2, wherein the following immersion test is performed on the workpiece processing sheet, and the peak area of ​​the detected component calculated by performing the following gel permeation chromatography measurement on the toluene solvent after the immersion test is 4000 mV·s or less. (Immersion test) A workpiece processing sheet having a size of 80 mm × 100 mm is immersed in 15 g of toluene at 25°C for 24 hours to obtain the toluene solvent in contact with the workpiece processing sheet. (Gel permeation chromatography measurement) 10 μL of the obtained toluene solvent is measured by gel permeation chromatography, and the measurement result is represented as a chromatogram with the detection voltage on the vertical axis and the elution time from the introduction of toluene solvent to elution from the column on the horizontal axis, and the peak area of ​​the detected component is calculated in the range from the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 2.5 million to the elution time corresponding to a standard polystyrene equivalent number average molecular weight of 200.

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