Conductive sheets and dicing die bond films

Abstract

This electroconductive sheet comprises a binder resin and electroconductive particles, and has a 70°C viscosity of 10-10,000 kPa·s and a 70°C elongation at break of 110% or higher.

Description

Cross-reference to related applications

[0001] This application claims the priority of Japanese Patent Application No. 2021-100176, which is incorporated herein by reference.

Technical Field

[0002] The present invention relates to a conductive sheet and a dicing die bond film.

Background Art

[0003] Conventionally, as a method (die bonding method) of bonding a semiconductor element (semiconductor chip) to an adherent such as a metal lead frame in the manufacture of a semiconductor device, it is known to use a conductive sheet (for example, Patent Document 1 below).

[0004] Patent Document 1 below discloses a conductive sheet containing conductive particles and a thermosetting resin as the conductive sheet. Further, in Patent Document 1 below, after attaching a semiconductor element (semiconductor chip) to one surface of the conductive sheet and bringing the other surface of the conductive sheet into contact with an adherent such as a metal lead frame, the conductive sheet is thermally cured at a predetermined temperature (for example, 200°C) and used by adhering it to the adherent such as a metal lead frame.

[0005] By the way, in recent years, the demand for high-density integration of semiconductor devices has been increasing more and more. In order to achieve this, it is necessary to reduce the thickness of the semiconductor element (semiconductor chip). And since the semiconductor element (semiconductor chip) is obtained by dicing a semiconductor wafer by blade dicing or the like, in order to reduce the thickness of the semiconductor element (semiconductor chip), it is necessary to reduce the thickness of the semiconductor wafer. However, the thinner the thickness of the semiconductor chip, the more likely the semiconductor wafer is to warp. Thus, when a semiconductor wafer warps, it becomes difficult to perform dicing of the semiconductor wafer accurately, such as by using blade dicing.

[0006] To solve this warping problem, it is known to use semiconductor wafers (for example, TAIKO® wafers) that are manufactured by mechanically grinding the inner portion up to several tens of millimeters from the outer edge, leaving a ring shape (for example, Patent Document 2 below). Since the semiconductor wafer described above has a ring-shaped portion, even if the portion inside the ring-shaped portion is thinned, it is possible to suppress the occurrence of warping in the semiconductor wafer. Furthermore, in TAIKO® wafers, a stepped portion is formed between the ring-shaped portion and the portion inside it. The maximum height of this stepped portion is typically around 450 μm, and the thickness of the flat portion obtained by mechanical grinding is typically around 20 μm. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-21813 [Patent Document 2] Japanese Patent Application Publication No. 2013-12690 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] By the way, as mentioned above, in semiconductor wafers such as TAIKO® wafers, a stepped portion is formed between the ring-shaped portion and the portion inside it. In other words, such a semiconductor wafer is a semiconductor wafer having a stepped portion. Therefore, when attempting to attach the conductive sheet to a semiconductor wafer having the stepped portion described above when obtaining a semiconductor device (semiconductor chip), the conductive sheet may not be able to adequately follow the stepped portion. In such cases, a relatively large gap (a gap formed more than 500 μm inward from the edge of the step) may occur between the semiconductor wafer having the step and the conductive sheet, extending from the edge of the step toward the center of the semiconductor wafer having the step. Thus, when a relatively large gap is created between the semiconductor wafer having the stepped portion and the conductive sheet, the conductive sheet is more likely to peel off from the semiconductor wafer having the stepped portion during dicing or other processes, starting from that gap. Furthermore, if a gap is created between the semiconductor element (semiconductor chip) and the conductive sheet after dicing, such a semiconductor element (semiconductor chip) with a conductive sheet cannot exhibit sufficient characteristics. Therefore, if a relatively large gap occurs between the semiconductor wafer having the stepped portion and the conductive sheet, there is a problem that the proportion of semiconductor elements (semiconductor chips) with conductive sheets obtained after dicing that can be used as components for semiconductor devices decreases, in other words, the yield decreases. However, it is still difficult to say that sufficient research has been done on conductive sheets that can adequately conform to stepped areas when attached to semiconductor wafers that have stepped sections.

[0009] Therefore, the object of the present invention is to provide a conductive sheet that can sufficiently conform to stepped portions when attached to a semiconductor wafer having stepped portions, and a dicing die bond film equipped with the conductive sheet. [Means for solving the problem]

[0010] The conductive sheet according to the present invention is A conductive sheet comprising a binder resin and conductive particles, The viscosity at 70°C is between 10 kPa·s and 10,000 kPa·s. The elongation at the breaking point at 70°C is 110% or more.

[0011] In the conductive sheet, it is preferable that the content ratio of the conductive particles is 85% by mass or more and 97% by mass or less.

[0012] In the conductive sheet, it is preferable that the conductive particles contain at least one selected from the group consisting of silver particles, copper particles, silver oxide particles, and copper oxide particles.

[0013] In the conductive sheet, it is preferable that the binder resin contains a thermosetting resin.

[0014] In the conductive sheet, it is preferable to further contain a volatile component having an initial evaporation temperature of 100°C or higher.

[0015] The dicing die bond film according to the present invention includes a dicing tape having an adhesive layer laminated on a base material layer, and a conductive sheet laminated on the adhesive layer of the dicing tape. The conductive sheet is any of the above conductive sheets.

Brief Description of Drawings

[0016] [Figure 1] A cross-sectional view showing the configuration of a dicing die bond film according to an embodiment of the present invention. [Figure 2A] A schematic cross-sectional view for explaining the state of the wafer mounting process. [Figure 2B] A schematic cross-sectional view for explaining the state of the dicing die bond film placement process. [Figure 2C] A schematic cross-sectional view for explaining the state of the sealing process. [Figure 2D] A schematic cross-sectional view for explaining the state of the decompression process. [Figure 2E] A schematic cross-sectional view for explaining the state of the dicing die bond film contact process. [Figure 2F]A schematic cross-sectional diagram illustrating the dicing die bond film adhesion process. [Modes for carrying out the invention]

[0017] The following describes one embodiment of the present invention.

[0018] [Conductive sheet] The conductive sheet according to this embodiment includes a binder resin and conductive particles. In this specification, conductive particles are defined as particles with an electrical conductivity of 100 μS / cm² as measured according to JIS K 0130 (2008). That's all. It means particles.

[0019] Furthermore, the conductive sheet according to this embodiment has a viscosity of 10 kPa·s or more and 10,000 kPa·s or less at 70°C. Furthermore, the conductive sheet according to this embodiment has a breaking point elongation of 110% or more at 70°C. In the following, viscosity at 70°C may be denoted by the reference number η, and elongation at the breaking point at 70°C may be denoted by the reference number Bpe.

[0020] A viscosity of 10 kPa·s or higher at 70°C allows the conductive sheet to maintain its shape sufficiently, and a viscosity of 10,000 kPa·s or lower at 70°C allows the conductive sheet to have an appropriate hardness. Furthermore, by having a fracture elongation of 110% or more at 70°C, the conductive sheet can be made to have excellent toughness, that is, to be highly ductile and to have excellent strength. By possessing the above characteristics, the conductive sheet according to this embodiment can adequately conform to stepped portions when attached to a semiconductor wafer having stepped portions. In this specification, "being able to sufficiently follow the stepped portion" means that the void formed from the edge of the stepped portion toward the center of the semiconductor wafer having the stepped portion is 500 μm or less.

[0021] Furthermore, if the viscosity at 70°C is less than 10 kPa·s, the conductive sheet will no longer be able to maintain its sheet shape and will become a paste-like conductive composition. Because such a paste-like conductive composition is highly deformable, it can adequately conform to the stepped portion of a semiconductor wafer having a stepped portion, but it becomes difficult to apply it to the semiconductor wafer having the stepped portion with a uniform thickness. Furthermore, if the conductive sheet is a paste-like conductive composition, it becomes difficult to transfer the conductive sheet to a semiconductor wafer having stepped portions when it is in the form of a dicing die bond film. Furthermore, after the conductive sheet is attached to the semiconductor wafer having a stepped portion, it is cut inside the stepped portion to become a flat semiconductor wafer, and then the flat semiconductor wafer is diced to divide it into multiple semiconductor chips. The semiconductor chip is then attached to an substrate such as a metal lead frame and used as a component in a semiconductor device. However, as described above, if the conductive sheet is a paste-like conductive composition, it becomes impossible to perform dicing with high precision, and when it is made into a semiconductor chip and attached to a metal lead frame or the like, the paste-like conductive composition tends to creep up from the edges of the semiconductor chip. Thus, when the paste-like conductive composition creeps up, it can cause a short circuit when used as a component in a semiconductor device, which is undesirable.

[0022] Examples of binder resins include thermoplastic resins and thermosetting resins. The conductive sheet according to this embodiment preferably contains a thermosetting resin. Because the conductive sheet contains a thermosetting resin, it can be heat-cured, thereby improving its adhesion to the adherend (for example, a metal lead frame). The conductive sheet according to this embodiment more preferably contains a thermoplastic resin in addition to a thermosetting resin. By including a thermoplastic resin in addition to the thermosetting resin, the conductive sheet can be made to have relatively low elasticity even after it has been heat-cured. Furthermore, because it contains a thermoplastic resin, the viscosity η of the conductive sheet at 70°C can be adjusted relatively easily to between 10 kPa·s and 10,000 kPa·s.

[0023] Examples of the thermosetting resin include epoxy resins, phenolic resins, amino resins, unsaturated polyester resins, polyurethane resins, silicone resins, and thermosetting polyimide resins. Among these, epoxy resins are preferred.

[0024] Examples of epoxy resins include bisphenol A type, bisphenol F type, bisphenol S type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol AF type, biphenyl type, naphthalene type, fluorene type, phenol novolac type, cresol novolac type, orthocresol novolac type, trishydroxyphenylmethane type, tetraphenyloleethane type, hydantoin type, trisglycidyl isocyanurate type, and glycidylamine type epoxy resins. Among these, it is preferable to use at least one of bisphenol A type epoxy resin and cresol novolac type epoxy resin, and it is more preferable to use a combination of bisphenol A type epoxy resin and cresol novolac type epoxy resin. Examples of bisphenol A type epoxy resins include aliphatic-modified bisphenol A type epoxy resins.

[0025] Examples of phenolic resins used as curing agents for epoxy resins include novolac-type phenolic resins, resol-type phenolic resins, biphenyl-type phenolic resins, and polyoxystyrenes such as polyparaoxystyrene. Among the above phenolic resins, biphenyl-type phenolic resins are preferred.

[0026] Furthermore, thermoplastic resins having thermosetting functional groups can also be used as thermosetting resins. Examples of thermoplastic resins having thermosetting functional groups include thermosetting functional group-containing acrylic resins. Examples of acrylic resins containing thermosetting functional groups include those containing monomer units derived from (meth)acrylic acid esters. In thermoplastic resins having thermosetting functional groups, the curing agent is selected according to the type of thermosetting functional group.

[0027] Examples of the thermoplastic resins include natural rubber, butyl rubber, isoprene rubber, chloroprene rubber, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, polybutadiene resin, polycarbonate resin, thermoplastic polyimide resin, polyamide resins such as polyamide 6 and polyamide 6,6, phenoxy resin, acrylic resin, saturated polyester resins such as PET and PBT, polyamide-imide resin, and fluororesin. Only one of the above thermoplastic resins may be used, or two or more may be used in combination. Among the above thermoplastic resins, acrylic resin is preferred because it has few ionic impurities and high heat resistance, making it easier to ensure connection reliability with the conductive sheet.

[0028] The above acrylic resin is preferably a polymer containing monomer units derived from (meth)acrylic acid ester as the most abundant monomer unit by mass. Examples of (meth)acrylic acid esters include alkyl (meth)acrylates, cycloalkyl (meth)acrylates, and aryl (meth)acrylates. The above acrylic resin may also contain monomer units derived from other components copolymerizable with (meth)acrylic acid esters. Examples of the above other components include carboxyl group-containing monomers, acid anhydride monomers, hydroxyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, phosphate group-containing monomers, acrylamide, acrylonitrile and other functional group-containing monomers, and various polyfunctional monomers. The above acrylic resin is preferably a carboxyl group-containing acrylic polymer.

[0029] In the conductive sheet according to this embodiment, the mass percentage of the binder resin relative to 100% by mass (parts by mass) of the conductive sheet is preferably 1.5% by mass or more and 40% by mass or less, and more preferably 4% by mass or more and 25% by mass or less. If the conductive sheet according to this embodiment contains the thermosetting resin and the thermoplastic resin as the binder resin, the mass percentage of the thermosetting resin relative to 100% by mass of the conductive sheet is preferably 1% by mass or more and 30% by mass or less, and more preferably 2% by mass or more and 18% by mass or less. Furthermore, the mass percentage of the thermoplastic resin relative to 100% by mass of the conductive sheet is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 7% by mass or less. Furthermore, when the binder resin is composed of the thermosetting resin and the thermoplastic resin, the mass ratio of the thermosetting resin to 100% by mass of the binder resin is preferably 30% by mass or more and 90% by mass or less, and more preferably 40% by mass or more and 70% by mass or less.

[0030] Examples of the conductive particles include silver particles, silver oxide particles, nickel particles, copper particles, copper oxide particles, aluminum particles, carbon black, and carbon nanotubes; particles in which the surface of a core metal particle is plated with a metal such as gold or silver (hereinafter also referred to as plated metal particles); and particles in which the surface of a core resin particle is coated with a metal (hereinafter also referred to as metal-coated resin particles). These conductive particles may be used individually or in combination of two or more types. The conductive sheet according to this embodiment preferably contains at least one type of conductive particle selected from the group consisting of silver particles, copper particles, silver oxide particles, and copper oxide particles. By including the above-described conductive particles, the conductive sheet exhibits sufficient electrical and thermal conductivity.

[0031] As for the shape of the particles, such as silver particles, silver oxide particles, nickel particles, copper particles, copper oxide particles, aluminum particles, carbon black, and carbon nanotubes, for example, flake-shaped, needle-shaped, filament-shaped, spherical, and flattened (including flaky) shapes can be used, but among these, spherical shapes are preferred. By using spherical particles, the dispersibility of these particles in the conductive sheet can be improved. Furthermore, the conductive sheet according to this embodiment is particularly preferably composed of silver particles among these particles.

[0032] The silver particles may be composed of silver element and other elements (such as metallic elements) included as unavoidable impurity elements, or they may be silver particles that have undergone surface treatment (e.g., silane coupling treatment). Examples of surface treatment agents for silver particles include fatty acid-based, amine-based, and epoxy-based coating agents. In the following text, silver particles that have been surface-treated with coating agents such as fatty acid-based, amine-based, or epoxy-based agents may be referred to as coated silver particles. In the conductive sheet according to this embodiment, it is preferable to use coated silver particles as the silver particles. By using coated silver particles as the silver particles, the affinity with the binder resin (thermosetting resin, thermoplastic resin, etc.) contained in the conductive sheet can be increased, so that the silver particles are more easily dispersed in the conductive sheet.

[0033] As plated metal particles, for example, particles can be used in which nickel particles or copper particles form a core, and the surface of the core is plated with a precious metal such as gold or silver. As metal-coated resin particles, for example, particles can be used in which a resin particle forms a core, and the surface of the core is coated with a metal such as nickel or gold. The plated metal particles and metal-coated resin particles can be in various shapes, such as flakes, needles, filaments, spheres, or flattened (including flaky) shapes, but among these, spherical particles are preferred. By using spherical plated metal particles or metal-coated resin particles, the dispersibility of these particles within the conductive sheet can be improved.

[0034] When the conductive sheet according to this embodiment contains plated metal particles, it is preferable to use particles in which copper particles form a core and the surface of the core is plated with silver (silver-coated copper particles) as the plated metal particles. Examples of silver-coated copper particles include flat copper particles coated with a 10% silver layer, and spherical copper particles coated with a 20% silver layer.

[0035] In the conductive sheet according to this embodiment, the mass percentage of the conductive particles in 100% by mass (parts by mass) of the conductive sheet (i.e., the content ratio of the conductive particles) is preferably 60% by mass or more and 98% by mass or less, more preferably 80% by mass or more and 97% by mass or less, and even more preferably 85% by mass or more and 97% by mass or less.

[0036] In this embodiment, the conductive sheet preferably contains silver particles and silver-coated copper particles as the conductive particles. In such cases, the proportion of silver particles in 100 parts by mass of conductive particles is preferably 10 parts by mass or more and 95 parts by mass or less, and more preferably 20 parts by mass or more and 90 parts by mass or less.

[0037] The viscosity η at 70°C is preferably 50 kPa·s or higher, more preferably 70 kPa·s or higher, and even more preferably 100 kPa·s or higher. Furthermore, the viscosity η at 70°C is preferably 7000 kPa·s or less, more preferably 5000 kPa·s or less, and even more preferably 3500 kPa·s or less. By having a viscosity η at 70°C within the above-mentioned numerical range, the sheet shape of the conductive sheet can be maintained more effectively, and the conductive sheet can be made to have a more appropriate hardness.

[0038] The viscosity η at 70°C can be evaluated using a rheometer (Thermo Fisher Scientific, rotary rheometer HAAKE MARS). Specifically, by using a gap value of 250 μm, a frequency of 1 Hz, and a strain of 0.1%, and then heating the temperature from 30°C to 180°C at a heating rate of 10°C / min, the reading of 70°C can be obtained.

[0039] The elongation at break Bpe at 70°C is preferably 112% or more, more preferably 113% or more, and even more preferably 114% or more. By having the elongation at the breaking point Bpe at 70°C within the above-mentioned numerical range, the conductive sheet can be made even more tough. In other words, the conductive sheet can be made even more ductile and even stronger. The upper limit of the elongation at break (Bpe) at 70°C is typically 200%.

[0040] The elongation at the breaking point (Bpe) at 70°C can be evaluated using a tensile testing machine (for example, the "AGS-X" model manufactured by Shimadzu Corporation). Specifically, it can be evaluated as follows: (1) Prepare a conductive sheet with a width of 10 mm, a length of 30 mm, and a thickness of 200 μm. (2) A test specimen is obtained by attaching polyimide tape to both ends of the conductive sheet in the longitudinal direction. Specifically, a test specimen is obtained by attaching polyimide tape to the conductive sheet in the longitudinal direction from the upper edge to 10 mm along the length, and also by attaching polyimide tape to the longitudinal direction from the lower edge to 10 mm along the length. (3) The upper end of the specimen in the longitudinal direction is attached to one chuck of the tensile testing machine, and the lower end of the specimen in the longitudinal direction is attached to the other chuck of the tensile testing machine. (4) After placing the tensile testing machine with the test specimen attached inside the constant temperature bath, the temperature inside the constant temperature bath is raised to 70°C. (5) After 3 minutes have elapsed since the temperature in the constant temperature bath reached 70°C, the test specimen is pulled in the length direction under the conditions of a chuck distance of 10 mm and a tensile speed of 50 mm / min, and the data obtained during the tensile test is plotted on a graph with stroke (in mm) on the horizontal axis and test force (tensile strength, in N) on the vertical axis. (6) In the graph, the point at which the test force is maximum is considered to be the point at which the conductive sheet breaks, and the stroke value at which the test force is maximum is read. The stroke value is then divided by the effective length of the conductive sheet (10 mm, the length of the part to which the polyimide tape is not attached), and the result is multiplied by 100 to calculate the elongation at the breaking point at 70°C.

[0041] The conductive sheet according to this embodiment can be obtained by appropriately adjusting the viscosity η at 70°C and the elongation at the breaking point Bpe at 70°C by appropriately adjusting the content ratio of the binder resin and the content ratio of the conductive particles in the conductive sheet. For example, the viscosity η at 70°C can be adjusted to a higher value by increasing the content ratio of the conductive particles in the conductive sheet, or to a lower value by decreasing the content ratio of the conductive particles. Furthermore, the elongation at the breaking point at 70°C can be adjusted to a higher value by lowering the content ratio of conductive particles in the conductive sheet, or to a lower value by increasing the content ratio of conductive particles. Furthermore, if the conductive sheet according to this embodiment contains a thermosetting resin and a thermoplastic resin as the matrix resin, the viscosity η at 70°C and the elongation at the break point Bpe at 70°C can be appropriately adjusted by appropriately adjusting the content ratio of the thermosetting resin and the content ratio of the thermoplastic resin.

[0042] The conductive sheet according to this embodiment preferably further contains a volatile component whose volatilization initiation temperature is 100°C or higher. The volatile component is more preferably a component that volatilizes at 200°C or higher, and more preferably a component that volatilizes at 250°C or higher. Examples of such volatile components include organic compounds that contain one or more hydroxyl groups and have a volatilization onset temperature of 100°C or higher. The boiling point of the organic compound is preferably 200°C or higher, and more preferably 250°C or higher. Furthermore, the boiling point of the organic compound is preferably 350°C or lower. Examples of such organic compounds include terpene compounds. Among terpene compounds, isobornylcyclohexanol, represented by the following formula (1), is preferred as a volatile component. Isobornylcyclohexanol is an organic compound with a boiling point of 308-318°C. When heated from room temperature (23±2°C) to 600°C under a nitrogen gas flow of 200 mL / min and a heating rate of 10°C / min, it exhibits a significant mass decrease (volatilization begins) above 100°C, with volatilization completed at 245°C (no further mass decrease is observed). It also exhibits an extremely high viscosity of 1,000,000 mPa·s at 25°C, but a relatively low viscosity of less than 1,000 mPa·s at 60°C. The mass decrease is calculated with the mass decrease rate at the measurement start temperature (room temperature) set to 0%. Thus, isobornylcyclohexanol exhibits extremely high viscosity at 25°C, as described above, allowing it to maintain its sheet shape at room temperature. However, at 60°C, as described above, it exhibits relatively low viscosity, resulting in tackiness. In other words, a conductive sheet containing isobornylcyclohexanol maintains its sheet shape well at room temperature and exhibits tackiness at temperatures above 60°C. Therefore, when mounting a semiconductor element attached to one side of a conductive sheet onto a metal lead frame or the like, the semiconductor element is usually temporarily attached (temporarily fixed) to the adherend such as a metal lead frame via the conductive sheet at a temperature of 60 to 80°C. However, as described above, isobornylcyclohexanol becomes tacky at temperatures above 60°C. Therefore, when the conductive sheet according to this embodiment contains isobornylcyclohexanol as a volatile component, the temporary adhesion of the conductive sheet to the adherend such as a metal lead frame is further improved. In other words, when temporarily attached, the mounting position of the semiconductor element is less likely to shift, and the lifting of the conductive sheet from the adherend is suppressed. Furthermore, if the conductive sheet contains a thermosetting resin and the conductive sheet is heat-cured to bond the semiconductor element to the substrate, reliable bonding can be achieved.

[0043] [ka]

[0044] In this embodiment, the conductive sheet preferably contains 10 parts by mass or more of the volatile component with respect to 100 parts by mass of the binder resin. Furthermore, the conductive sheet according to this embodiment preferably contains 200 parts by mass or less of the volatile component per 100 parts by mass of the binder resin, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less.

[0045] Furthermore, if the conductive sheet contains volatile components that volatilize at temperatures above 200°C, the volume of the conductive sheet can be reduced by heating the conductive sheet to temperatures above 200°C to volatilize the volatile components. Thus, when the volume of the conductive sheet is reduced, the conductive particles become closer to each other within the conductive sheet due to the reduction in volume, making it easier for the conductive particles to form heat conduction paths. This makes it possible to achieve a relatively high thermal conductivity for the conductive sheet.

[0046] Furthermore, if the conductive sheet according to this embodiment contains silver particles and silver-coated copper particles as described above, using spherical particles as the silver-coated copper particles may result in a smaller contact area between the silver-coated copper particles and the silver particles compared to using spherical particles as the silver particles and flat particles as the silver-coated copper particles, which may be disadvantageous from the viewpoint of electrical conductivity and thermal conductivity. However, if the conductive sheet according to this embodiment contains volatile components whose volatilization start temperature is 100°C or higher, as described above, the volatile components can be relatively sufficiently volatilized when the conductive sheet is heated to a temperature of 150 to 200°C for thermal curing or the like. This allows the volume of the conductive sheet to be reduced relatively sufficiently, or in other words, the volume of the conductive sheet to be reduced relatively sufficiently, so that the silver-coated copper particles and silver particles can be placed in a close positional relationship. Therefore, even when spherical particles are used as silver-coated copper particles, a sufficient contact area between the silver-coated copper particles and silver particles can be ensured, thereby ensuring sufficient electrical and thermal conductivity.

[0047] If the conductive sheet according to this embodiment contains a thermosetting resin, a thermosetting catalyst may be included to ensure sufficient curing of the thermosetting resin or to increase the curing reaction rate. Examples of thermosetting catalysts include imidazole compounds, triphenylphosphine compounds, amine compounds, and trihalogen borane compounds.

[0048] The thickness of the conductive sheet according to this embodiment is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, the thickness of the conductive sheet is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less. By reducing the thickness of the conductive sheet to 150 μm or less, thermal conductivity can be further improved. The thickness of a conductive sheet can be determined, for example, by measuring the thickness of five randomly selected points using a dial gauge (PEACOCK, model R-205) and then taking the arithmetic mean of these thicknesses.

[0049] If the conductive sheet according to this embodiment contains a thermosetting resin, the thermal conductivity after heat curing is preferably 1 W / m·K or higher, more preferably 3 W / m·K or higher, and even more preferably 10 W / m·K or higher. By ensuring that the thermal conductivity after heat curing meets the above numerical range, the conductivity of the conductive sheet can be further increased. In this embodiment, the upper limit of the thermal conductivity after heat curing of the conductive sheet is a maximum of 420 W / m·K. In the conductive sheet according to this embodiment, the upper limit of the thermal conductivity after heat curing may be 200 W / m·K. The thermal conductivity after heat curing can be calculated using the following formula for a conductive sheet that has been heat-cured by treating it at 200°C for 1 hour under a pressure of 0.5 MPa in a pressure cooker device.

[0050]

number

[0051] In the above formula, the thermal diffusivity (m 2 The temperature ( / s) can be measured using the TWA method (thermal wave thermal analysis, measuring device: iPhase Mobile, manufactured by iPhase Corporation). Furthermore, the specific heat (J / g·℃) in the above formula can be measured by the DSC method. Specific heat measurement is performed using a DSC6220 manufactured by SII Nanotechnology Co., Ltd., under conditions of a heating rate of 10℃ / min and a temperature range of 20~300℃. Based on the obtained data, the specific heat can be calculated using the method described in the JIS Handbook (Specific Heat Capacity Measurement Method K-7123). Furthermore, the specific gravity in the above formula can be measured by the Archimedes method.

[0052] The conductive sheet according to this embodiment may contain one or more other components as needed. Examples of other components include filler dispersants, flame retardants, silane coupling agents, and ion trapping agents.

[0053] In this embodiment, the conductive sheet has at least one side that is an adhesive surface that is bonded to the adherend. In other words, the conductive sheet according to this embodiment can be used to adhere to an object whose surface, at least a portion of which is an adhesive area to which the conductive sheet is adhered. The conductive sheet according to this embodiment exhibits good conformability to uneven surfaces, even when such uneven surfaces are formed in the adhesive region. The conductive sheet according to this embodiment has an adhesive surface that adheres to both the circular recess and the annular protrusion of a semiconductor wafer, which has a circular recess on one side and an annular protrusion surrounding the circular recess, thereby significantly demonstrating its effectiveness. Since the annular protrusions on the semiconductor wafer are formed in a state that protrudes from the surface of the circular recesses, a step is formed at the boundary between the two. However, the conductive sheet according to this embodiment exhibits good conformability even at locations where such step is formed.

[0054] The conductive sheet according to this embodiment may have an adhesive surface large enough to cover the entire circular recess, or it may have an adhesive surface that covers the entire circular recess and further covers part or all of the annular protrusion.

[0055] The height of the stepped portion may be 50 μm or more and 500 μm or less.

[0056] [Dicing die bond film] Next, the dicing die bond film 20 will be described with reference to Figure 1. Note that in the following explanation, parts that overlap with the description of the conductive sheet will not be repeated.

[0057] As shown in Figure 1, the dicing die bond film 20 according to this embodiment comprises a dicing tape 10 in which an adhesive layer 2 is laminated on a base layer 1, and a conductive sheet 3 laminated on the adhesive layer 2 of the dicing tape 10. In the dicing die bond film 20, a semiconductor element is attached to the conductive sheet 3. The semiconductor element may be a bare wafer. The bare wafer attached to the dicing die bond film 20 according to this embodiment is diced into multiple bare chips by blade dicing, DBG (Dicing Before Grinding), or SDBG (Stealth Dicing Before Grinding), etc. During the dicing process as described above, the conductive sheet 3 is also diced along with the bare wafer. The conductive sheet 3 is diced into pieces corresponding to the size of the multiple individual bare chips. This makes it possible to obtain multiple bare chips with conductive sheets 3 attached.

[0058] The conductive sheet 3 of the dicing die bond film 20 contains a binder resin and conductive particles, as described above. Furthermore, as described above, the conductive sheet 3 of the dicing die bond film 20 has a viscosity of 10 kPa·s or more and 10,000 kPa·s or less at 70°C. Furthermore, as described above, the conductive sheet 3 of the dicing die bond film 20 has a break point elongation of 110% or more at 70°C.

[0059] The base layer 1 supports the adhesive layer 2 and the conductive sheet 3 laminated on the adhesive layer 2. The base layer 1 contains a resin. Examples of resins include olefin resins such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; copolymers with ethylene as a monomer component such as ethylene-vinyl acetate copolymer (EVA), ionomer resin, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester (random, alternating) copolymer; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); acrylic resins; polyvinyl chloride (PVC); polyurethane; polycarbonate; polyphenylene sulfide (PPS); amide resins such as polyamide and fully aromatic polyamide (aramid); polyether ether ketone (PEEK); polyimide; polyetherimide; polyvinylidene chloride; ABS (acrylonitrile-butadiene-styrene copolymer); cellulose resins; silicone resins; and fluororesins. From the viewpoint of improving elasticity, it is preferable that the base layer 1 contains at least one resin selected from the group consisting of polypropylene (PP), polyvinyl chloride (PVC), and ethylene-vinyl acetate copolymer (EVA). Furthermore, the base layer 1 may be a laminate in which a first resin layer containing ethylene-vinyl acetate copolymer (EVA) is used as the central layer, and a second resin layer containing polypropylene (PP) and a third resin layer containing polyvinyl chloride (PVC) are laminated on both surfaces of the first resin layer, respectively.

[0060] The base layer 1 may contain one of the aforementioned resins, or it may contain two or more of the aforementioned resins.

[0061] Examples of materials for the base layer 1 include polymers such as crosslinked resins (for example, plastic films). The plastic film may be used in an unstretched state, or it may be used after being subjected to uniaxial or biaxial stretching as needed. By using a resin sheet that has been given heat-shrinkability through stretching or the like, the adhesive area between the adhesive layer 2 and the conductive sheet 3 can be reduced by heat-shrinking the base layer 1 after dicing, thereby facilitating the recovery of the semiconductor chip (semiconductor device).

[0062] The surface of the substrate layer 1 may be subjected to general surface treatments to improve adhesion and retention with adjacent layers. Examples of such surface treatments include chemical or physical treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, and ionizing radiation treatment, as well as coating treatments with primers.

[0063] The thickness of the substrate layer 1 is preferably 1 μm or more and 1000 μm or less, more preferably 10 μm or more and 500 μm or less, even more preferably 20 μm or more and 300 μm or less, and particularly preferably 30 μm or more and 200 μm or less. The thickness of the base layer 1 can be determined using a dial gauge (PEACOCK, model R-205) in the same way as the thickness of the conductive sheet 3 described above.

[0064] The base layer 1 may contain various additives. Examples of such additives include colorants, fillers, plasticizers, antioxidants, surfactants, and flame retardants.

[0065] The adhesive used to form the adhesive layer 2 is not particularly limited, and general pressure-sensitive adhesives such as acrylic adhesives and rubber adhesives can be used. As the pressure-sensitive adhesive, an acrylic adhesive with an acrylic polymer as the base polymer is preferred from the viewpoint of cleaning properties with ultrapure water or organic solvents such as alcohol for electronic components that are undesirable to be contaminated, such as semiconductor wafers and glass.

[0066] Examples of the acrylic polymer include acrylic polymers using one or more alkyl (meth)acrylates and cycloalkyl (meth)acrylates as monomer components. Examples of alkyl (meth)acrylates include methyl esters, ethyl esters, propyl esters, isopropyl esters, butyl esters, isobutyl esters, s-butyl esters, t-butyl esters, pentyl esters, isopentyl esters, hexyl esters, heptyl esters, octyl esters, 2-ethylhexyl esters, isooctyl esters, nonyl esters, decyl esters, isodecyl esters, undecyl esters, dodecyl esters, tridecyl esters, tetradecyl esters, hexadecyl esters, octadecyl esters, eicosyl esters, etc., with alkyl groups having 1 to 30 carbon atoms, particularly linear or branched alkyl esters having 4 to 18 carbon atoms. Examples of cycloalkyl (meth)acrylates include cyclopentyl esters and cyclohexyl esters. Furthermore, (meth)acrylic acid ester means at least one of acrylic acid ester and methacrylic acid ester, and all instances of (meth) in this invention have the same meaning as described above.

[0067] The acrylic polymer may, if necessary, contain units corresponding to other monomer components copolymerizable with the alkyl (meth)acrylate or cycloalkyl (meth)acrylate, for the purpose of modifying properties such as cohesiveness and heat resistance. Examples of such monomer components include carboxyl-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 10-hydroxydecyl (meth)acrylate. Examples include hydroxyl group-containing monomers such as 12-hydroxylauryl (meth)acrylate and (4-hydroxymethylcyclohexyl)methyl(meth)acrylate; sulfonic acid-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acryloyloxynaphthalenesulfonic acid, sulfopropyl(meth)acrylate and (meth)acryloyloxynaphthalenesulfonic acid; phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate; acrylamide, acrylonitrile, etc. One or more of these copolymerizable monomer components can be used. The amount of these copolymerizable monomers used is preferably 40% by mass or less of the total monomer components.

[0068] Furthermore, in order to crosslink the acrylic polymer, polyfunctional monomers may be included as copolymerization monomer components as needed. Examples of such polyfunctional monomers include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy(meth)acrylate, polyester(meth)acrylate, and urethane(meth)acrylate. One or more of these polyfunctional monomers can be used. From the viewpoint of adhesive properties, the amount of polyfunctional monomer used is preferably 30% by mass or less of the total monomer components.

[0069] The acrylic polymer can be obtained by polymerizing a single monomer or a mixture of two or more monomers. Polymerization may be carried out by any method, such as solution polymerization, emulsion polymerization, bulk polymerization, or suspension polymerization. From the viewpoint of preventing contamination of a clean substrate, it is preferable to have a low content of low molecular weight substances. From this viewpoint, the number average molecular weight of the acrylic polymer is preferably 300,000 or more, and more preferably around 400,000 to 3,000,000.

[0070] Furthermore, external crosslinking agents may be added to the adhesive as appropriate to increase the number-average molecular weight of the base polymer, such as an acrylic polymer. Specific methods for external crosslinking include adding and reacting crosslinking agents such as polyisocyanate compounds, epoxy compounds, aziridine compounds, and melamine-based crosslinking agents. When using an external crosslinking agent, the amount used is determined appropriately, taking into account the balance with the base polymer to be crosslinked and the intended use as an adhesive. Generally, it is preferable to blend the external crosslinking agent in amounts of about 5 parts by mass or less, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the base polymer.

[0071] In addition to the above-mentioned components, the adhesive may optionally contain various known additives such as tackifiers and anti-aging agents.

[0072] The adhesive layer 2 can be formed using a radiation-curable adhesive. Radiation-curable adhesives can be easily de-crosslinked and their adhesive strength reduced by irradiation with radiation such as ultraviolet light. In other words, by forming the adhesive layer 2 with a radiation-curable adhesive, the conductive sheet 3 can be sufficiently adhered to the adhesive layer 2 before dicing without irradiating the adhesive layer 2 with radiation, and after dicing, the adhesive layer 2 can be irradiated with radiation to reduce its adhesive strength, thereby making it easy to pick up (recover) the semiconductor chip (semiconductor device).

[0073] Radiation-curable adhesives can be used without particular limitations, as long as they have radiation-curable functional groups such as carbon-carbon double bonds and exhibit adhesive properties. Examples of radiation-curable adhesives include additive-type radiation-curable adhesives that combine radiation-curable monomer components or oligomer components with general pressure-sensitive adhesives such as acrylic adhesives and rubber adhesives.

[0074] Examples of the radiation-curable monomer component include urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Examples of the radiation-curable oligomer component include various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers, with a molecular weight in the range of approximately 100 to 30,000 being preferred. The amount of the radiation-curable monomer component and the radiation-curable oligomer component blended is preferably such that the adhesive strength of the adhesive layer 2 is suitably reduced after radiation irradiation. Generally, the amount of the radiation-curable monomer component and the radiation-curable oligomer component is preferably, for example, 5 to 500 parts by mass, and more preferably 40 to 150 parts by mass, per 100 parts by mass of the base polymer such as the acrylic polymer that constitutes the adhesive.

[0075] In addition to the additive-type radiation-curing adhesives described above, other radiation-curing adhesives include intrinsic radiation-curing adhesives that use a base polymer having carbon-carbon double bonds in the polymer side chains, main chain, or main chain ends. These intrinsic radiation-curing adhesives do not need to contain low-molecular-weight components such as oligomer components, or contain relatively small amounts of such components. Therefore, when these intrinsic radiation-curing adhesives are used, the movement of the oligomer components in the adhesive layer 2 over time is suppressed. As a result, the adhesive layer 2 can have a relatively stable layer structure.

[0076] The base polymer having a carbon-carbon double bond can be used without particular limitations, as long as it has a carbon-carbon double bond and is adhesive. A preferred base polymer is one that uses an acrylic polymer as its basic structure. Examples of acrylic polymers with a basic structure include the acrylic polymers described above.

[0077] The method for introducing carbon-carbon double bonds into the acrylic polymer is not particularly limited, and various methods can be employed. However, adopting a method of introducing carbon-carbon double bonds into the polymer side chains facilitates molecular design. For example, one method involves copolymerizing an acrylic polymer with a monomer having a functional group, and then carrying out a condensation or addition reaction with a compound having a functional group that can react with this functional group and a carbon-carbon double bond, while maintaining the radiation-curable nature of the carbon-carbon double bond.

[0078] Examples of these functional group combinations include carboxylate and epoxy groups, carboxylate and aziridyl groups, and hydroxyl and isocyanate groups. Among these functional group combinations, the combination of a hydroxyl group and an isocyanate group is preferred in terms of ease of reaction tracking. Furthermore, any combination of these functional groups may be on the acrylic polymer side or the compound side having the carbon-carbon double bond, as long as it produces an acrylic polymer having the carbon-carbon double bond. However, in the case of the above preferred combination, it is preferable that the acrylic polymer has a hydroxyl group and the compound having the carbon-carbon double bond has an isocyanate group. In this case, examples of isocyanate compounds having a carbon-carbon bond include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. Furthermore, as acrylic polymers, copolymers of the above-mentioned hydroxyl group-containing monomers, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and other ether compounds can be used.

[0079] The aforementioned intrinsically charged radiation-curable adhesive can use the base polymer having the carbon-carbon double bond (particularly an acrylic polymer) alone, but it can also be blended with the radiation-curable monomer component or the radiation-curable oligomer component to an extent that does not degrade its properties. The radiation-curable oligomer component, etc., is usually included in an amount of 30 parts by mass or less per 100 parts by mass of the base polymer, and is preferably included in an amount of 1 to 10 parts by mass.

[0080] The aforementioned radiation-curable adhesive contains a photopolymerization initiator when cured by ultraviolet light or the like. Examples of photopolymerization initiators include α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; and ketal compounds such as benzyldimethyl ketal. Examples include aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphinoxides; and acylphosphonates. The amount of photopolymerization initiator added is, for example, 0.05 to 20 parts by mass per 100 parts by mass of the base polymer, such as an acrylic polymer, that constitutes the adhesive.

[0081] Furthermore, examples of radiation-curable adhesives include rubber-based adhesives and acrylic-based adhesives containing a photopolymerizable compound such as an addition polymerizable compound having two or more unsaturated bonds, or an alkoxysilane having an epoxy group, as disclosed in Japanese Patent Publication No. 60-196956, and a photopolymerization initiator such as a carbonyl compound, an organosulfur compound, a peroxide, an amine, or an onium salt compound.

[0082] If oxygen inhibits curing during radiation irradiation, it is desirable to block oxygen (air) from the surface of the radiation-curable adhesive layer 2 by some means. Examples include covering the surface of the adhesive layer 2 with a separator, or irradiating it with ultraviolet light or other radiation in a nitrogen gas atmosphere.

[0083] The thickness of the adhesive layer 2 is not particularly limited, but it is preferably 1 to 50 μm, and more preferably 2 to 30 μm, in order to achieve both prevention of chipping of the chip cut surface and secure retention of the conductive sheet 3.

[0084] The dicing die bond film 20 according to this embodiment is attached to a semiconductor wafer having stepped portions, such as a TAIKO® wafer, using, for example, a film attachment device. The following describes an example of attaching the dicing die bond film 20 according to this embodiment to a semiconductor wafer having a stepped portion using a film attachment apparatus, with reference to Figures 2A to 2F.

[0085] As shown in Figures 2A to 2E, the film mounting device 100 has a storage space S formed by a storage chamber bottom wall portion 101a and a storage chamber side wall portion 101b extending vertically upward from the edge of the storage chamber bottom wall portion 101a, and a storage chamber 101 which is open on the top side, and a stage 102 which is disposed within the storage space S of the storage chamber 101, is formed in a circular shape when viewed from above, and is configured so that the object to be attached to the film can be placed on its upper side, and the storage chamber bottom of the storage chamber 101 The structure includes a lifting device 103 that is mounted on the lower side of the stage 102 so as to be able to move up and down, with a portion of the wall portion 101a penetrating it, and a lid 104 that is positioned above the storage chamber 101, is formed in a circular shape when viewed from above, and has a lid bottom wall portion 104a and a lid side wall portion 104b that extends vertically downward from the edge of the lid bottom wall portion 104a, and is configured to close the storage chamber 101 by bringing the lower side of the lid side wall portion 104b into contact with the upper side of the storage chamber side wall portion 101b.

[0086] As described above, since the containment chamber 101 and the lid 104 are formed in a circular shape when viewed from above, in the example shown in Figures 2A to 2E, the containment chamber side wall portion 101b extends vertically upward so as to encircle the edge of the containment chamber bottom wall portion 101a, and the lid side wall portion 104b extends vertically downward so as to encircle the edge of the lid bottom wall portion 104a. Furthermore, the storage chamber 101 is equipped with a storage chamber packing P1 that is provided on the storage chamber side wall portion 101b so as to encircle the storage chamber side wall portion 101b, and the lid 104 is equipped with a lid packing P2 that is provided on the lid side wall portion 104b so as to encircle the lid side wall portion 104b. It is preferable to use rubber gaskets for the storage chamber gasket P1 and the lid gasket P2. Furthermore, the film mounting device 100 does not necessarily need to be equipped with both the storage chamber packing P1 and the lid packing P2; it is sufficient to have at least one of them. Furthermore, in the examples shown in Figures 2A to 2E, the stage 102 comprises a stage bottom wall portion 102a and a stage side wall portion 102b that is provided to protrude vertically upward from the edge of the stage bottom wall portion 102a. As described above, since the stage 102 is formed in a circular shape when viewed from above, in the example shown in Figures 2A to 2E, the stage side wall portion 102b is provided to protrude vertically upward so as to encircle the edge of the stage bottom wall portion 102a.

[0087] The film mounting device 100 is equipped with a depressurizing pump (not shown) for reducing the pressure in the storage space S when the storage chamber 101 is closed with the lid 104. The film mounting device 100 is equipped with a release valve (not shown) for releasing the reduced pressure state of the containment space S.

[0088] A method for attaching a dicing die bond film to a semiconductor wafer having a stepped portion includes: a wafer placement step of placing the semiconductor wafer SW having the stepped portion on the upper surface of a stage 102; a dicing die bond film placement step of arranging the dicing die bond film 20 on the upper edge of the side wall portion 101b of the housing chamber 101 so as to cover a part of the upper opening; a sealing step of closing the housing chamber 101 with a lid 104 from above the dicing die bond film 20; a depressurization step of depressurizing the housing space S of the housing chamber 101 in order to bend a part of the dicing die bond film 20 downward; a dicing die bond film contact step of raising the stage 102 to bring the semiconductor wafer SW having the stepped portion into contact with the bent dicing die bond film 20; and a dicing die bond film contact step of releasing the depressurized state of the housing space S of the housing chamber 101 to bring the semiconductor wafer SW having the stepped portion into close contact with the bent dicing die bond film 20.

[0089] In the wafer placement process, as shown in Figure 2A, the semiconductor wafer SW having the stepped portion SW1 is placed on the upper surface of the stage 102 such that the side having the stepped portion SW1 is facing upwards. In more detail, during the wafer placement process, the stepped portion SW1 is placed on the stage side wall portion 102b, thereby placing the semiconductor wafer SW having the stepped portion on the upper surface of the stage 102. Here, the side without the stepped portion SW1 becomes the surface on which the circuit is formed (i.e., the circuit-forming surface). However, as described above, by placing the stepped portion SW1 on the stage side wall portion 102b, it is possible to prevent the circuit-forming surface from coming into direct contact with the stage bottom wall portion 102a of the stage 102, thereby suppressing damage to the circuit-forming surface.

[0090] In the dicing die bond film placement process, as shown in Figure 2B, the dicing die bond film 20 is placed on the storage chamber packing P1 located on the storage chamber side wall 101b in the storage chamber 101, such that the conductive sheet 3 side faces the semiconductor wafer SW which has a stepped portion. Furthermore, in the dicing die bond film placement process, the dicing die bond film 20 is placed on the storage chamber packing P1 located on the storage chamber side wall 101b in the storage chamber 101 so that the dicing die bond film 20 covers the semiconductor wafer SW having a stepped portion (so that the dicing die bond film 20 and the semiconductor wafer SW having a stepped portion overlap). Since the dicing die bond film 20 is usually stored in a rolled state, the film unwound from the roll is placed on the storage chamber packing P1. However, in Figure 2B and other figures, the process of unwounding the dicing die bond film 20 from the rolled state is omitted from the illustration.

[0091] In the sealing process, as shown in Figure 2C, the lid 104 is brought into contact with the base material layer 1 of the dicing die bond film 20 from above, thereby closing and sealing the containment chamber 101. In more detail, during the sealing process, as shown in Figure 2C, the lid packing P2, which is positioned on the lid side wall portion 104b of the lid 104, is brought into contact with the base material layer 1 side of the dicing die bond film 20, thereby closing and sealing the containment chamber 101.

[0092] In the depressurization process, as shown in Figure 2D, the depressurization pump (not shown) is used to reduce the pressure in the containment space S of the containment chamber 101, causing a portion of the dicing die bond film 20 to bend downwards. More specifically, by using the depressurizing pump to reduce the pressure in the containment space S to a level lower than the space S' formed between the dicing die bond film 20 and the lid 104, a differential pressure is created between space S' and the containment space S, and this differential pressure causes the dicing die bond film 20 to bend downwards, pulling it into the containment space S. In the depressurization process, it is preferable to reduce the pressure of the containment space S in the containment chamber 101 to 100 Pa or less.

[0093] In the dicing die bond film contact process, as shown in Figure 2E, the stage 102 is raised by the lifting device 103 to bring the semiconductor wafer SW having a stepped portion into contact with the dicing die bond film 20 in a bent state. In the dicing die bond film contact process, it is preferable to raise the stage 102 at a speed of 0.1 cm / min to 10 cm / min. Here, as shown in Figure 2E, the dicing die bond film 20 is partially bent. Therefore, although the dicing die bond film 20 is in contact with the stepped portion SW1 of the semiconductor wafer SW having a stepped portion, it is not following the stepped portion SW1 sufficiently, and a relatively large gap (a gap formed more than 500 μm inward from the edge of the stepped portion SW1) is created from the edge of the stepped portion SW1 toward the center of the semiconductor wafer SW having the stepped portion.

[0094] In the dicing die bond film adhesion process, as shown in Figure 2F, the release valve (not shown) is opened to release the reduced pressure in the containment space S of the containment chamber 101, thereby further deforming the dicing die bond film 20 that is in contact with the stepped portion SW1 of the semiconductor wafer SW having a stepped portion, and causing the dicing die bond film 20 to follow the stepped portion SW1. As described above, in the dicing die bond film 20 according to this embodiment, the conductive sheet 3 has a viscosity of 10 kPa·s or more and 10,000 kPa·s or less at 70°C, and an elongation at the breaking point of 110% or more at 70°C, so it can sufficiently follow the stepped portion SW1. The dicing die bond film adhesion process may be carried out at atmospheric pressure after releasing the reduced pressure, or it may be carried out under pressurized conditions. When the dicing die bond film adhesion process is carried out under pressurized conditions, the film mounting device 100 may be equipped with a pressurizing mechanism, and the dicing die bond film adhesion process may be carried out by applying pressure with the pressurizing mechanism. Alternatively, the semiconductor wafer SW having a stepped portion and the dicing die bond film 20 in contact with the stepped portion SW1 may be removed from the film mounting device 100, placed in a pressurizing device separate from the film mounting device 100, and then pressurized within the pressurizing device to perform the dicing die bond film adhesion process. When the dicing die bond film adhesion process is carried out under pressurized conditions, the pressurized conditions include applying pressure at a pressure of 0.2 MPa to 0.7 MPa for 10 seconds to 3 minutes. Furthermore, when the dicing die bond film adhesion process is carried out under pressurized conditions, the pressurization may be carried out under heated conditions. Examples of heated conditions include heating at a temperature of 40°C to 90°C.

[0095] Furthermore, after the dicing die bond film adhesion process, the semiconductor wafer SW having a stepped portion is cut at the position inside the stepped portion SW1, and the dicing die bond film 20 is attached to it, resulting in a flat semiconductor wafer (hereinafter referred to as a flat semiconductor wafer with a dicing die bond film). Then, the flat semiconductor wafer with the dicing die bond film attached is diced into multiple semiconductor chips (hereinafter referred to as semiconductor chips with dicing die bond film) to which the dicing die bond film 20 is attached, by a blade dicing or the like. Subsequently, in the semiconductor chip with the dicing die bond film, the conductive sheet 3 is separated from the adhesive layer 2 to obtain a semiconductor chip with the conductive sheet 3 attached (hereinafter referred to as a semiconductor chip with a conductive sheet). The conductive sheet-attached semiconductor chip obtained in this way is attached to a substrate such as a metal lead frame and used as a component in a semiconductor device.

[0096] As described above, the conductive sheet according to this embodiment is suitable for use by attaching it to the side of a semiconductor wafer having stepped portions, such as a TAIKO® wafer, where the stepped portions are formed, and is particularly suitable for use by attaching it to the side of a semiconductor wafer having multiple stepped portions where the stepped portions are formed. Furthermore, the conductive sheet according to this embodiment is suitable for use in power semiconductor devices for mounting power semiconductor chips onto a substrate.

[0097] The conductive sheet and dicing die bond film according to this embodiment are configured as described above and have the following advantages.

[0098] (1) A conductive sheet comprising a binder resin and conductive particles, The viscosity at 70°C is between 10 kPa·s and 10,000 kPa·s. The elongation at the breaking point at 70°C is 110% or more. Conductive sheet.

[0099] With this configuration, the conductive sheet can be made to conform sufficiently to the stepped portion when attached to a semiconductor wafer having a stepped portion.

[0100] (2) The content ratio of the conductive particles is 85% by mass or more and 97% by mass or less. The conductive sheet described in (1) above.

[0101] With this configuration, the conductive sheet can be sufficiently conformed to the stepped portion when attached to a semiconductor wafer having a stepped portion, and also exhibits sufficient conductivity.

[0102] (3) The conductive particles include at least one selected from the group consisting of silver particles, copper particles, silver oxide particles, and copper oxide particles. The conductive sheet described in (1) or (2) above.

[0103] With this configuration, the conductive sheet can be sufficiently conformed to the stepped portion when attached to a semiconductor wafer having a stepped portion, and in addition, it exhibits sufficient electrical and thermal conductivity.

[0104] (4) The binder resin includes a thermosetting resin. A conductive sheet as described in any of (1) to (3) above.

[0105] With this configuration, the conductive sheet can be heat-cured, thereby improving adhesion to the adherend (for example, a metal lead frame).

[0106] (5) It further contains volatile components whose volatilization initiation temperature is 100°C or higher. A conductive sheet as described in any of (1) to (4) above.

[0107] With this configuration, since it further contains volatile components whose volatilization start temperature is 100°C or higher, when the conductive sheet is heated to a temperature of 150-200°C for thermal curing or the like, the volatile components can be volatilized relatively sufficiently. This allows for a relatively sufficient reduction in the volume of the conductive sheet. Furthermore, because the volume of the conductive sheet is reduced, the conductive particles are in closer proximity to each other within the conductive sheet, making it easier for the conductive particles to form heat conduction paths within the conductive sheet. This makes it possible to achieve a relatively high thermal conductivity for the conductive sheet.

[0108] (6) A dicing tape having an adhesive layer laminated on a base layer, The dicing tape comprises a conductive sheet laminated on the adhesive layer of the dicing tape, The conductive sheet is the conductive sheet described in any of (1) to (5) above. Dicing die bond film.

[0109] With this configuration, the dicing die bond film can be made to conform sufficiently to the stepped portion when attached to a semiconductor wafer having a stepped portion via the conductive sheet.

[0110] Furthermore, the conductive sheet and dicing die bond film according to the present invention are not limited to the embodiments described above. Also, the conductive sheet and dicing die bond film according to the present invention are not limited by the effects described above. The conductive sheet and dicing die bond film according to the present invention can be modified in various ways without departing from the spirit of the present invention. [Examples]

[0111] Next, the present invention will be described in more detail with reference to examples. The following examples are provided to further illustrate the present invention and do not limit its scope.

[0112] [Example 1] (Reference example 1) Using a hybrid mixer (manufactured by Keyence Corporation, product name: HM-500), a mixture containing each material in the mass ratio shown in Example 1 of Table 1 below was stirred and mixed for 3 minutes to prepare the varnish. This varnish was applied to one side of a release treatment film (manufactured by Mitsubishi Chemical Corporation, product name: MRA38, thickness 38 μm), and then dried at 100°C for 2 minutes to obtain a conductive sheet with a thickness of 30 μm. The materials used were as follows, as shown in Table 1 below. • Phenolic resin MEHC-7851S (biphenyl-type phenolic resin, phenol equivalent 209 g / eq) manufactured by Meiwa Kasei Co., Ltd. • Solid epoxy resin KI-3000-4 (cresol novolac type polyfunctional epoxy resin, epoxy equivalent 200g / eq) manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd. • Liquid epoxy resin EXA-4816 (aliphatic-modified bisphenol A type epoxy resin (bifunctional), epoxy equivalent 403 g / eq) manufactured by DIC Corporation. ·Silver (Ag) coated copper (Cu) particles Flattened copper particles coated with a 10% by mass silver layer (average particle size 3.5 μm, irregular shape; hereinafter referred to as 10% coated silver-coated copper particles). ·Silver (Ag) particles Aggregated nanoparticles (amorphous, average particle size of aggregates 1.8 μm; hereinafter referred to as aggregated silver particles) • Volatile agent (isobornylcyclohexanol (MTPH)) MTPH manufactured by Nippon Terpene Chemical Co., Ltd. • Acrylic resin solution Teisan Resin SG-70L manufactured by Nagase Chemitech Co., Ltd. (contains MEK and toluene as solvents, solids content 12.5%, glass transition temperature -13℃, mass-average molecular weight 900,000, acid value 5 mg / KOH, carboxyl group-containing acrylic copolymer) • Coupling agent KBE-846 (bis(triethoxysilylpropyl)tetrasulfide) manufactured by Shin-Etsu Chemical Co., Ltd. ·catalyst TPP-MK (tetraphenylphosphonium tetra-p-tolylborate) manufactured by Hokko Chemical Industry Co., Ltd. ·solvent Methyl ethyl ketone (MEK) Furthermore, the mass ratio (parts by mass) of thermoplastic resin (acrylic resin) per 100 parts by mass of thermosetting resin (epoxy resin (solid and liquid) and phenolic resin), the mass ratio (parts by mass) of volatile material (isobornylcyclohexanol (MTPH)) per 100 parts by mass of thermosetting resin, and the mass ratio (parts by mass) of conductive particles per 100 parts by mass of thermosetting resin are shown in Table 2 below. Furthermore, the mass ratios of silver-coated copper particles and silver particles in 100 parts by mass of conductive particles (silver-coated copper particles and silver particles) are shown in Table 3 below.

[0113] [Example 2] A conductive sheet according to Example 2 was obtained in the same manner as in Example 1, except that the liquid epoxy resin was YL980 manufactured by Mitsubishi Chemical Corporation, the silver particles were silver particles surface-treated with a fatty acid-based coating agent (fatty acid-treated silver particles; particle shape is spherical; hereinafter referred to as fatty acid-treated silver particles), and the silver-coated copper particles were spherical copper particles coated with a 20% by mass silver layer (particle shape is spherical; hereinafter referred to as 20% coated silver-coated copper particles), and a mixture containing each material was obtained in the mass ratio shown in the section for Example 2 in Table 1 below.

[0114] [Example 3] A conductive sheet according to Example 3 was obtained in the same manner as in Example 1, except that the liquid epoxy resin was YL980 manufactured by Mitsubishi Chemical Corporation, the silver particles were fatty acid treated silver particles, and the silver-coated copper particles were 20% coated silver-coated copper particles, and a mixture containing each material was obtained in the mass ratio shown in the section for Example 3 in Table 1 below.

[0115] [Example 4] A conductive sheet according to Example 4 was obtained in the same manner as in Example 1, except that the liquid epoxy resin was YL980 manufactured by Mitsubishi Chemical Corporation, and the silver particles were silver particles surface-treated with an epoxy coating agent (epoxy-treated silver particles; particle shape is spherical; hereinafter referred to as epoxy-treated silver particles), and a mixture containing each material was obtained in the mass ratio shown in the section for Example 4 in Table 1 below.

[0116] [Comparative Example 1] A conductive sheet according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the liquid epoxy resin was YL980 manufactured by Mitsubishi Chemical Corporation, the silver particles were fatty acid treated silver particles, and the silver-coated copper particles were 20% coated silver-coated copper particles, and a mixture containing each material was obtained in the mass ratio shown in the Comparative Example 1 section of Table 1 below.

[0117] [Table 1]

[0118] [Table 2]

[0119] <Thermal conductivity of conductive sheets> The conductive sheets for each example were heat-cured in a pressure cooker at 200°C for 1 hour under a pressure of 0.5 MPa. The thermal conductivity of the heat-cured conductive sheets for each example was calculated using the following formula.

[0120]

number

[0121] Thermal diffusivity α(m 2 The value ( / s) was measured using the TWA method (Thermal Wave Analysis, measuring device: iPhase Mobile, manufactured by iPhase Corporation). Specific heat C p The specific heat (J / g·℃) was measured by the DSC method. Specific heat was measured using a DSC6220 manufactured by SII Nanotechnology, under conditions of a heating rate of 10℃ / min and a temperature range of 20~300℃. Based on the obtained data, the specific heat was calculated using the method described in the JIS Handbook (Specific Heat Capacity Measurement Method K-7123). The specific gravity was measured using the Archimedes method. The results of calculating the thermal conductivity of the heat-cured conductive sheets for each example are shown in Table 3 below.

[0122] <Viscosity η at 70°C> For each example of conductive sheet, the viscosity η at 70°C was measured using a rheometer (Thermo Fisher Scientific, rotary rheometer HAAKE MARS). Specifically, a gap value of 250 μm, a frequency of 1 Hz, and a strain of 0.1% were used, and the temperature was increased from 30°C to 180°C at a heating rate of 10°C / min. The measurement was taken by reading the reading at 70°C. The results are shown in Table 3 below.

[0123] <Elongation at break (Bpe) at 70°C> For each example of conductive sheet, the elongation at the breaking point Bpe at 70°C was measured using a tensile testing machine (model "AGS-X" manufactured by Shimadzu Corporation). Specifically, the measurements were taken as follows: (1) Prepare a conductive sheet with a width of 10 mm, a length of 30 mm, and a thickness of 200 μm. (2) A test specimen is obtained by attaching polyimide tape to both ends of the conductive sheet in the longitudinal direction. Specifically, a test specimen is obtained by attaching polyimide tape to the conductive sheet in the longitudinal direction from the upper edge to 10 mm along the length, and also by attaching polyimide tape to the longitudinal direction from the lower edge to 10 mm along the length. (3) The upper end of the specimen in the longitudinal direction is attached to one chuck of the tensile testing machine, and the lower end of the specimen in the longitudinal direction is attached to the other chuck of the tensile testing machine. (4) After placing the tensile testing machine with the test specimen attached inside the constant temperature bath, the temperature inside the constant temperature bath is raised to 70°C. (5) After 3 minutes have elapsed since the temperature in the constant temperature bath reached 70°C, the test specimen is pulled in the length direction under the conditions of a chuck distance of 10 mm and a tensile speed of 50 mm / min, and the data obtained during the tensile test is plotted on a graph with stroke (in mm) on the horizontal axis and test force (tensile strength, in N) on the vertical axis. (6) In the graph, the point at which the test force is maximum is considered to be the point at which the conductive sheet breaks, and the stroke value at which the test force is maximum is read. The stroke value is then divided by the effective length of the conductive sheet (10 mm, the length of the part to which the polyimide tape is not attached), and the result is multiplied by 100 to calculate the elongation at the breaking point at 70°C. The results are shown in Table 3 below.

[0124] <Followability to uneven surfaces> For each example, the conformability of the conductive sheet to stepped areas was evaluated using a vacuum wafer mounter (Nitto Seiki Co., Ltd., Vacuum Mounter MSA840VIII). Specifically, the evaluation was conducted as follows: (1) Using a first die bond film (manufactured by Nitto Denko Corporation, product name "EM-310V", thickness 7 μm), a first bare chip with planar dimensions of 10 mm × 10 mm and a thickness of 100 μm is fixed to one side of a microscope slide. Then, using a second die bond film (manufactured by Nitto Denko Corporation, product name "EM-310V", thickness 7 μm), a second bare chip with planar dimensions of 9 mm × 9 mm and a thickness of 300 μm is fixed to the exposed surface of the first bare chip to obtain a bare chip laminate. The second bare tip is fixed to the exposed surface of the first bare tip such that the center of the second bare tip coincides with the center of the first bare tip. Furthermore, one set of bare chip laminates is formed on a glass slide. (2) The bare chip laminate is fixed together with the wafer ring onto the adhesive layer of the dicing tape (manufactured by Nitto Denko Corporation, product name "ELP V-12SR") to obtain a test specimen. The bare chip laminate is fixed to the adhesive layer of the dicing tape on the slide glass side. (3) Place the specimen on a stage located inside the storage chamber of the vacuum wafer mounter, with the dicing tape side facing downwards. The stage is preheated to 70°C. (4) A dicing die bond film is placed on the upper edge of the side wall of the housing chamber so as to cover the bare chip laminate in the test specimen and so as to face the conductive sheet side toward the bare chip laminate. The dicing die bond film is obtained by laminating the conductive sheet according to each example onto the adhesive layer of a dicing tape (manufactured by Nitto Denko Corporation, product name "ELP V-12SR") as a die bond film. (5) After closing the lid of the vacuum wafer mounter, the storage space in the storage chamber is depressurized to 0 MPa. (6) After releasing the reduced pressure in the containment space of the containment chamber and placing the vacuum wafer mounter into the autoclave, the vacuum wafer mounter is pressurized at 0.5 MPa at a temperature of 70°C for 1 minute inside the autoclave. (7) Remove the bare chip stack from the vacuum wafer mounter and observe the bare chip stack with a microscope from the slide glass side to confirm how far the gap extends from the edge of the first bare chip. The ability to follow uneven surfaces was judged according to the following criteria. Excellent: The void is formed at a distance of 500 μm or less from the edge of the first bare tip. Unacceptable: A void is formed extending more than 500 μm from the edge of the first bare tip. The results of the evaluation of the ability to follow uneven surfaces are shown in Table 3 below.

[0125] [Table 3]

[0126] Table 3 shows that for each example of the conductive sheet, the viscosity η at 70°C falls within the range of 10 kPa·s to 10,000 kPa·s, and the elongation at the breaking point Bpe at 70°C is 110% or more. In all cases, the evaluation of conformability to stepped areas is excellent, indicating that it conforms sufficiently. In contrast, the conductive sheet according to Comparative Example 1 has a viscosity η value at 70°C that exceeds 10,000 kPa·s, and a fracture elongation Bpe value at 70°C that is less than 110%, making it impossible to evaluate its ability to conform to stepped sections, indicating that it does not conform sufficiently. From these results, it is understood that by making the conductive sheet contain a binder resin and conductive particles, and further setting the viscosity η at 70°C to be between 10 kPa·s and 10,000 kPa·s, and the elongation at the breaking point at 70°C to be 110% or more, the conductive sheet can adequately follow the stepped portion of a semiconductor wafer.

[0127] Furthermore, Table 3 shows that the conductive sheets in each example exhibit a thermal conductivity of 1 W / m·K or higher after heat curing, which is a sufficient value. The conductive sheets in Examples 2-5 exhibit a thermal conductivity of 5 W / m·K or higher after heat curing, which is a more sufficient value. In particular, the conductive sheets in Examples 3-5 exhibit a thermal conductivity of 20 W / m·K or higher after heat curing, which is an even more sufficient value. [Explanation of Symbols]

[0128] 1 base layer, 2 adhesive layer, 3 conductive sheet, 10 dicing tape, 20 dicing die bond film, 100 film mounting device, 101 storage chamber, 102 stage, 103 lifting device, 104 lid, 101a bottom wall of storage chamber, 101b side wall of storage chamber, 104a bottom wall of lid, 104b side wall of lid, P1 storage chamber packing, P2 lid packing, S storage space, S' space, SW semiconductor wafer with step, SW1 step portion.

Claims

1. A conductive sheet comprising a binder resin and conductive particles, The conductive particles are contained in an amount of 85% by mass or more and 98% by mass or less. The binder resin comprises a thermoplastic resin and a thermosetting resin. The viscosity at 70°C is between 10 kPa·s and 10,000 kPa·s. The elongation at the breaking point at 70°C is 110% or more. Conductive sheet.

2. The content ratio of the conductive particles is 85% by mass or more and 97% by mass or less. The conductive sheet according to claim 1.

3. It further contains volatile components whose volatilization initiation temperature is 100°C or higher. The conductive sheet according to claim 1 or 2.

4. A dicing tape having an adhesive layer laminated on a base layer, The dicing tape comprises a conductive sheet laminated on the adhesive layer of the dicing tape, The conductive sheet is the conductive sheet described in any one of claims 1 to 3. Dicing die bond film.

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