Pressure-sensitive adhesive tape for dicing

Abstract

Provided is a pressure-sensitive adhesive tape for dicing which comprises a substrate film and a pressure-sensitive adhesive layer formed thereon, wherein the substrate film has a melting point of 150°C or lower, the surface A of the substrate film on the reverse side from the pressure-sensitive adhesive layer has a surface roughness Ra of 0.10 μm or less, and the surface A has a needle penetration temperature of 80°C or higher.

Description

Dicing adhesive tape

[0001] The present invention relates to an adhesive tape for dicing.

[0002] The process of processing a semiconductor wafer or the like into semiconductor chips and mounting them on semiconductor devices such as integrated circuits (ICs) includes, for example, a process of attaching a semiconductor wafer surface protection tape or a back-grinding substrate to the patterned surface of the semiconductor wafer, a process of grinding the back surface of the semiconductor wafer to reduce its thickness, a process of mounting the thinned semiconductor wafer on a dicing adhesive tape, a process of peeling the semiconductor wafer surface protection tape or the back-grinding substrate from the semiconductor wafer, a process of dividing the semiconductor wafer by dicing, a pick-up process of picking up the divided semiconductor chips, a die-bonding process of bonding the picked-up semiconductor chips to a lead frame, and a molding process of sealing the semiconductor chips with resin after the die-bonding process. The dicing adhesive tape functions as a support for the semiconductor chips not only in the dicing process but also in the pick-up process. A method of performing the dicing process using laser irradiation is known. Specifically, a method is known in which a laser is irradiated from the adhesive dicing tape side to form a modified region inside the semiconductor wafer, which serves as the starting point for division, and then the adhesive dicing tape is expanded to separate the modified region into individual semiconductor chips. This dicing method is known as stealth dicing. In stealth dicing, high transparency has become a requirement for dicing adhesive tapes in order to irradiate the wafer with a laser with high precision and to enable visual inspection, etc.

[0003] Patent Document 1 describes a stealth dicing adhesive sheet comprising a substrate and an adhesive layer laminated on one side of the substrate, and a thermomechanical analyzer is used to measure the change in the substrate, obtained by subtracting the initial length of the substrate from the length of the substrate at 60°C, when the substrate is pulled with a load of 0.2 g while being heated from 25°C to 120°C at a temperature increase rate of 20°C / min, as ΔL ６０℃The change in the substrate obtained by subtracting the initial length of the substrate from the length of the substrate at 90° C. is ΔL ９０℃ When this is the case, the formula (1): ΔL ９０℃ -ΔL ６０℃ A stealth dicing adhesive sheet has been proposed that satisfies the relationship of <0 μm. According to Patent Document 1, this stealth dicing adhesive sheet is said to have excellent heat shrinkability. Patent Document 2 proposes a dicing sheet comprising a substrate and an adhesive layer laminated on the first surface side of the substrate, in which the arithmetic mean roughness (Ra) of the second surface of the substrate is 0.01 μm or more and 0.5 μm or less, and the maximum height roughness (Rz) of the second surface of the substrate is 3 μm or less. This dicing sheet is said to have light transmittance suitable for high-magnification imaging of a workpiece.

[0004] International Publication No. 2018 / 083986 International Publication No. 2018 / 084021

[0005] Flip-chip bonding is a well-known method for mounting semiconductor chips to wiring substrates. In this method, a resin is filled between the semiconductor chip and the wiring substrate. To improve work efficiency, the resin is typically an adhesive film, such as a non-conductive film (NCF), which is then attached to the wafer before dicing and singulated simultaneously with the wafer. In this method using an adhesive film, a dicing tape is attached to the wafer, and then another adhesive film is attached to the side of the wafer that is not attached to the dicing tape. This attachment is more specifically performed as follows: The laminate of the dicing tape and the wafer is placed on a chuck table (CT) heated to approximately 80°C, with the dicing tape side in contact with the chuck table, and then fixed by vacuum suction. In this fixed state, an adhesive film is attached to the side of the wafer opposite the dicing tape side. The inventors have found that the transmittance of the dicing adhesive tape is likely to decrease after the above-described fixation, and that using a dicing adhesive tape with reduced transmittance can easily cause meandering of the modified region during the subsequent stealth dicing process, resulting in poor processing accuracy. The decrease in transmittance is thought to be due to the fact that the unevenness of the chuck table surface is transferred to the dicing adhesive tape by vacuum suction at high temperatures, resulting in a rough back surface of the dicing adhesive tape. This problem can be improved by increasing the heat resistance (e.g., melting point) of the substrate film constituting the dicing adhesive tape. However, highly heat-resistant materials generally have high rigidity, and dicing adhesive tapes made from such materials suffer from the problem of reduced expandability (elongation) of the dicing adhesive tape during expansion and separation.

[0006] The present invention has been made in consideration of the problems associated with the above-mentioned conventional technology, and has as its object to provide an adhesive tape for dicing that exhibits sufficiently high transmittance to laser light even after being vacuum-adsorbed to a chuck table under heating, and that also has excellent expandability when expanded and cut.

[0007] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that, even when a resin with a low melting point is used for the base film of a dicing pressure-sensitive adhesive tape, the above-mentioned problems can be solved by setting the penetration temperature to a specific temperature or higher and controlling the surface roughness to a specific value or lower.

[0008] [1] A dicing pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on a base film, wherein the melting point of the base film is 150°C or lower, the surface roughness Ra of a surface A of the base film opposite the pressure-sensitive adhesive layer is 0.10 μm or lower, and the penetration temperature of this surface A is 80°C or higher. [2] The dicing pressure-sensitive adhesive tape according to [1], wherein the base film does not have a yield point up to an elongation of 50% in a stress-elongation curve at -15°C. [3] The dicing pressure-sensitive adhesive tape according to [1] or [2], wherein, in a tensile test at -15°C, the absolute value of the difference between the stress (MD stress, S1) (MPa) at an elongation of 30% when stretched in the MD direction and the stress (TD stress, S2) at an elongation of 30% when stretched in the TD direction is 4 MPa or lower. [4] The pressure-sensitive adhesive tape for dicing according to any one of [1] to [3], wherein the base film consists of at least two layers, and the relationship between the penetration temperature (T1) of the surface on which the pressure-sensitive adhesive layer is formed and the penetration temperature (T2) of the surface on which the pressure-sensitive adhesive layer is not formed satisfies [(T2) - (T1)] > 0°C. [5] The pressure-sensitive adhesive tape for dicing according to any one of [1] to [4], wherein the base film contains at least one of an ethylene-(meth)acrylic acid alkyl ester copolymer resin and an ionomer resin. [6] The pressure-sensitive adhesive tape for dicing according to any one of [1] to [5], wherein the pressure-sensitive adhesive tape is a pressure-sensitive adhesive tape for use in stealth dicing.

[0009] In the present invention, a numerical range expressed using "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits. In the present invention, (meth)acrylic means one or both of acrylic and methacrylic. The same applies to (meth)acrylate. In the present invention, the MD direction is the flow direction during film formation, and the TD direction is the direction perpendicular to the MD direction.

[0010] The pressure-sensitive adhesive tape for dicing of the present invention exhibits sufficiently high transmittance to laser light even after being vacuum-adsorbed to a chuck table under heating, and also has excellent expandability when expanded and cut.

[0011] Fig. 1 is a cross-sectional view showing one embodiment of the dicing pressure-sensitive adhesive tape of the present invention. Fig. 2 is a schematic vertical cross-sectional view showing an adhesive film laminating step in a preferred embodiment of the method for manufacturing a semiconductor device using the dicing pressure-sensitive adhesive tape of the present invention. Fig. 3 is a schematic vertical cross-sectional view showing a state after release film peeling in a preferred embodiment of the method for manufacturing a semiconductor device using the dicing pressure-sensitive adhesive tape of the present invention. Fig. 4 is a schematic vertical cross-sectional view showing a state after removal from a chuck table in a preferred embodiment of the method for manufacturing a semiconductor device using the dicing pressure-sensitive adhesive tape of the present invention. Fig. 5 is a schematic vertical cross-sectional view showing a modified region forming step in a preferred embodiment of the method for manufacturing a semiconductor device using the dicing pressure-sensitive adhesive tape of the present invention. Fig. 6 is a schematic vertical cross-sectional view showing a state after heat shrinking in a preferred embodiment of the method for manufacturing a semiconductor device using the dicing pressure-sensitive adhesive tape of the present invention. An explanatory diagram showing the measurement points of the kerf width in the evaluation of Examples and Comparative Examples.

[0012] The adhesive tape for dicing of the present invention (hereinafter also referred to as "adhesive tape of the present invention") has a base film and an adhesive layer. The adhesive tape of the present invention is used as a so-called dicing film. The adhesive tape of the present invention is suitable as an adhesive tape for stealth dicing that has expandability and heat shrinkability. In the adhesive tape of the present invention, the base film has a melting point of 150°C or lower as measured by differential scanning calorimetry (DSC). Furthermore, the surface of the base film opposite the adhesive layer has a surface roughness Ra of 0.10 μm or lower. Furthermore, the penetration temperature of the opposite surface is 80°C or higher. Before dicing, the adhesive tape of the present invention is resistant to transfer of irregularities on the surface of a chuck table even when heated (e.g., heated at a temperature of 80°C or higher for several minutes) when adhering the adhesive film to a semiconductor wafer (hereinafter also simply referred to as "wafer"), and therefore can sufficiently maintain laser light transmittance even after being vacuum-adsorbed to the chuck table under heating. As a result, modified regions can be formed with high precision by laser irradiation from the adhesive tape side. Furthermore, the expandability in the expanding step after dicing is excellent, and the efficiency of dividing the wafer into wafer chips (semiconductor chips) can be further improved. Furthermore, according to a preferred embodiment of the present invention, more uniform heat shrinkage is possible during heat shrinking, and it becomes easier to set the kerf width within an appropriate range in the MD and TD directions.

[0013] FIG. 1 is a cross-sectional view showing an embodiment of a pressure-sensitive adhesive tape 10 according to an embodiment of the present invention. The pressure-sensitive adhesive tape 10 of the present invention has a substrate film 11 and a pressure-sensitive adhesive layer 12. When using the pressure-sensitive adhesive tape 10 of the present invention, the back surface of a wafer is laminated onto the pressure-sensitive adhesive layer 12. The pressure-sensitive adhesive layer 12 may be pre-cut into a predetermined shape in accordance with the process and equipment used. The pressure-sensitive adhesive tape 10 of the present invention may be cut into pieces corresponding to individual wafers, or may be in the form of a long sheet formed by cutting a plurality of pieces corresponding to individual wafers and then wound into a roll. In the present invention, the pressure-sensitive adhesive layer refers to a coating layer of a pressure-sensitive adhesive composition, in which the polymer contained in the pressure-sensitive adhesive exerts adhesive or cohesive force. Furthermore, if the pressure-sensitive adhesive layer is energy ray-curable, the pressure-sensitive adhesive layer is in a state prior to being cured by energy ray irradiation. The structure of each layer will be described below.

[0014] <Base Film> The base film 11 may be a single layer or a laminate of multiple layers. In the case of a laminate, it is preferable that the layers are made of different materials.

[0015] The base film 11 has a melting point of 150°C or lower. The melting point is preferably 140°C or lower, more preferably 130°C or lower, more preferably 120°C or lower, more preferably 110°C or lower, even more preferably 100°C or lower, and particularly preferably 90°C or lower. There is no particular lower limit, but a practical range is 50°C or higher, preferably 60°C or higher, and even more preferably 70°C or higher. Therefore, the preferred range for the melting point of the base film 11 is preferably 50 to 150°C, more preferably 50 to 140°C, even more preferably 50 to 130°C, even more preferably 60 to 120°C, even more preferably 60 to 110°C, even more preferably 70 to 100°C, and even more preferably 70 to 90°C. The melting point of the base film 11 can be measured by differential scanning calorimetry (DSC) using the method described in the Examples. The melting point of the base film 11 can be set within the above range by controlling the material, layer structure, and blending with other materials of the base film 11 .

[0016] The surface roughness (arithmetic mean roughness) Ra of the surface of the base film 11 opposite to the surface on which the pressure-sensitive adhesive layer 12 is formed (hereinafter sometimes referred to as the "back surface") is 0.10 μm or less, preferably 0.08 μm or less, more preferably 0.06 μm or less, and even more preferably 0.04 μm or less. There is no particular lower limit for the surface roughness Ra of the back surface, but a practical range is 0.01 μm or more. Therefore, the preferred range for the Ra of the back surface of the base film 11 is preferably 0.01 to 0.10 μm, more preferably 0.01 to 0.08 μm, even more preferably 0.01 to 0.06 μm, and even more preferably 0.01 to 0.04 μm. When the base film 11 is composed of multiple layers, it is sufficient that the surface roughness Ra of the outermost layer on the back surface of the base film 11 is within the above range. The surface roughness Ra of the back surface of the base film 11 can be controlled by the method for preparing the base film 11. For example, in the case of the T-die method and the calendar method, it can be controlled by adjusting the surface roughness of the cooling roll during film extrusion, and in the case of the solution casting method, it can be controlled by adjusting the surface roughness of the drum or belt. The surface roughness Ra of the surface of the base film 11 on which the pressure-sensitive adhesive layer 12 is formed is not particularly limited. The surface roughness Ra of the base film 11 can be measured in accordance with JIS B0601:2001 by the method described in the Examples.

[0017] The penetration temperature of the back surface of the substrate film 11 is 80°C or higher, preferably 83°C or higher, more preferably 85°C or higher, more preferably 88°C or higher, even more preferably 90°C or higher, and particularly preferably 92°C or higher. The upper limit of the penetration temperature of the back surface of the substrate film 11 is preferably 100°C or lower, more preferably 98°C or lower, and even more preferably 95°C or lower. Therefore, the preferred range for the penetration temperature of the back surface of the substrate film 11 is preferably 80 to 100°C, more preferably 83 to 98°C, even more preferably 85 to 98°C, even more preferably 88 to 98°C, even more preferably 90 to 95°C, and particularly preferably 92 to 95°C. The penetration temperature can be measured in accordance with JIS K7196:2012 by thermomechanical analysis (TMA) using the method described in the examples. The penetration temperature can be controlled by selecting the material constituting the substrate film, using a substrate film composed of multiple layers of different materials, or controlling the thickness of the resin layers constituting the laminate. For example, the penetration temperature tends to be higher when a material with a high softening onset temperature is used as the material constituting the substrate film. Furthermore, the penetration temperature tends to be higher when a material with a high softening onset temperature is laminated on the back side of the substrate film and the thickness is increased. Even when a material with a high softening onset temperature is laminated on the back side of the substrate film, the penetration temperature tends to be lower when the thickness of the layer is thin or when the softening onset temperature of the resin in the other layer is low. When the penetration temperature of the back side of the substrate film 11 is 80°C or higher, even when a material with a relatively low melting point and not very high rigidity is used as the material constituting the substrate film, the unevenness of the chuck table surface can be effectively prevented from being transferred to the substrate film by vacuum suction at high temperatures.

[0018] When the base film 11 is a laminate consisting of at least two layers, the relationship between the penetration temperature (T1) of the surface on which the pressure-sensitive adhesive layer 12 is formed and the penetration temperature (T2) of the surface on which the pressure-sensitive adhesive layer 12 is not formed (the back surface) is preferably [(T2) - (T1)] > 0°C (i.e., T2 > T1). Such a base film has excellent heat shrinkability during heat shrinking. The relationship between T1 and T2 is more preferably [(T2) - (T1)] > 20°C, even more preferably [(T2) - (T1)] > 30°C, even more preferably [(T2) - (T1)] > 40°C, and particularly preferably [(T2) - (T1)] > 50°C. The relationship between T1 and T2 can also be [(T2) - (T1)] > 80°C. There is no particular upper limit to [(T2) - (T1)], but 100°C is practical. Therefore, the relationship between T1 and T2 is preferably 100°C > [(T2) - (T1)] > 0°C, more preferably 100°C > [(T2) - (T1)] > 20°C, even more preferably 100°C > [(T2) - (T1)] > 30°C, even more preferably 100°C > [(T2) - (T1)] > 40°C, and even more preferably 100°C > [(T2) - (T1)] > 50°C.

[0019] It is preferable that the base film 11 has no yield point between 0% and 50% elongation in its stress-strain curve at -15°C. Such a base film allows for more uniform expansion (especially cool expansion), makes the adhesive tape less likely to break, and maintains a sufficient kerf width after heat shrinking. The yield point can be determined by the method described in the Examples. In the present invention, the above stress-strain curve is a curve obtained by elongation in the TD direction.

[0020] In a tensile test at -15°C, the substrate film 11 preferably has an absolute value of 4 MPa or less between the stress (MD stress, S1) (MPa) at an elongation of 30% when stretched in the MD direction and the stress (TD stress, S2) (MPa) at an elongation of 30% when stretched in the TD direction (satisfies 4 MPa ≥ |(S1) - (S2)|). If S1 and S2 satisfy the above relationship, this is preferable because it allows the difference in kerf width between the MD and TD directions after heat shrinking to be further reduced. It is more preferable that the absolute value of the difference between S1 and S2 is 3 MPa or less.

[0021] The material of the base film 11 is not particularly limited as long as it can achieve the above melting point, surface roughness Ra, and penetration temperature. It is preferable that the base film 11 has uniform and isotropic expandability, since this allows the wafer to be cut evenly in all directions during the expanding process. From these viewpoints, the material of the base film 11 is preferably selected from polyolefin resins and polyvinyl chloride resins.

[0022] Examples of the polyolefin resin include α-olefin homopolymer or copolymer resins such as polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid alkyl ester copolymer (ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, etc.), ethylene-acrylic acid copolymer, and ionomer, as well as mixtures thereof.

[0023] In particular, ionomer resins, which are synthetic resins that utilize the cohesive force of metal ions to form polymer aggregates, are preferred. Examples include ionomer resins obtained by crosslinking ethylene-(meth)acrylic acid binary copolymers or ethylene-(meth)acrylic acid-(meth)acrylic acid alkyl ester terpolymers with metal ions. These resins are suitable for the expanding process in terms of uniform expandability. The metal ions contained in the ionomer resins are not particularly limited, but examples include zinc ions and sodium ions. Zinc ions are preferred due to their low elution and low contamination. Generally, ionomer resins have a greater restoring force against tension than resins without metal ions, and experience greater shrinkage stress when heat is applied to the expanded state after the expanding process. Therefore, ionomer resins are preferred in that they allow for a heat shrink process in which slack generated in the tape after the expanding process is removed by thermal shrinkage, and the tape is tensioned to stably maintain the spacing between individual wafer chips.

[0024] In addition to the above-mentioned ionomer resins, thermoplastic crosslinked resins obtained by crosslinking a resin selected from low-density polyethylene with a specific gravity of 0.910 or more but less than 0.930, ultra-low-density polyethylene with a specific gravity of less than 0.910, and ethylene-vinyl acetate copolymer are also suitable. Examples of crosslinking methods include irradiating the above-mentioned resins with energy beams such as electron beams. Such thermoplastic crosslinked resins have a certain degree of uniform extensibility because crosslinked and non-crosslinked regions coexist within the resin. Furthermore, since such thermoplastic crosslinked resins contain almost no chlorine atoms in the molecular chain structure, incineration of used tapes does not generate chlorinated aromatic hydrocarbons such as dioxins and their analogs, thereby minimizing the environmental impact. By appropriately adjusting the amount of energy beams irradiated onto the above-mentioned polyethylene or ethylene-vinyl acetate copolymer, resins with sufficient uniform extensibility can be obtained.

[0025] In the example shown in FIG. 1 , the substrate film 11 is a single layer, but is not limited thereto and may be a multilayer. The multilayer may be a multilayer formed by laminating two or more layers made of different resins, or a multilayer formed by laminating layers made of a single resin. If the two or more resins are crosslinked resins or non-crosslinked resins, it is preferable from the viewpoint of enhancing the properties of each resin. Laminating a combination of crosslinked and non-crosslinked resins is preferable from the viewpoint of compensating for the drawbacks of each resin. Conventional extrusion methods, lamination methods, etc. can be used to manufacture the multilayer substrate film 11. When using the lamination method, an adhesive may be interposed between the layers. Conventional adhesives can be used as the adhesive.

[0026] The base film 11 preferably contains at least one of an ethylene-(meth)acrylic acid alkyl ester copolymer resin and an ionomer resin. It is also preferable that the base film 11 is a laminate in which a layer containing an ethylene-(meth)acrylic acid alkyl ester copolymer resin and a layer containing an ionomer resin are laminated.

[0027] The thickness of the base film 11 is not particularly limited, but is preferably 50 to 200 μm, more preferably 70 to 160 μm, even more preferably 100 to 150 μm, still more preferably 100 to 140 μm, and even more preferably 100 to 120 μm.

[0028] <Adhesive Layer> The adhesive layer 12 constituting the adhesive tape 10 of the present invention is not particularly limited as long as it has sufficient retention to prevent peeling from the wafer during the dicing process, the ability to transmit stress due to expansion to the modified region of the wafer, and the ability to peel from the wafer chip during pickup. The adhesive constituting the adhesive layer 12 is not particularly limited as long as it exhibits the above properties, and an energy ray-curable adhesive is preferred. If the energy ray-curable adhesive is cured before the pickup process, pickup becomes easier. Here, energy rays refer to light rays such as ultraviolet rays or ionizing radiation such as electron beams. The adhesive constituting the adhesive layer 12 can be any adhesive commonly used as an adhesive for dicing adhesive tapes, without any particular restrictions. For the components, properties, and manufacturing method of the pressure-sensitive adhesive, see, for example, Japanese Patent No. 6928852, paragraphs

[0039] to

[0076] , Japanese Patent No. 6989561, paragraphs

[0033] to

[0052] , and Japanese Patent Laid-Open No. 2023-13022, paragraphs

[0031] to

[0057] .

[0029] The adhesive constituting the adhesive layer 12 is preferably an acrylic adhesive containing a (meth)acrylic resin as a base polymer, and more preferably an acrylic adhesive containing a (meth)acrylic acid alkyl ester as a constituent. The (meth)acrylic acid alkyl ester preferably further has a radiation-curable group introduced into the side chain, and more preferably has a (meth)acrylic acid ester having an isocyanate group added thereto. The adhesive may further contain a radiation-curable oligomer, such as a urethane (meth)acrylate oligomer.

[0030] The thickness of the pressure-sensitive adhesive layer 12 is not particularly limited, but a thickness of 2 μm or more provides excellent tackiness, with a thickness of 5 μm or more being more preferable, and 10 μm or more being even more preferable. A thickness of 35 μm or less provides excellent pickup, with a thickness of 30 μm or less being even more preferable. Therefore, the thickness of the pressure-sensitive adhesive layer 12 is preferably 2 to 35 μm, more preferably 5 to 35 μm, even more preferably 5 to 30 μm, and even more preferably 10 to 30 μm.

[0031] <Uses> The pressure-sensitive adhesive tape 10 of the present invention is suitable for use in a semiconductor device manufacturing method that includes at least an adhesive film bonding step, which includes fixing the pressure-sensitive adhesive tape 10 onto a heated chuck table by vacuum suction, a modified region forming step, which forms a modified region in a wafer by irradiating laser light from the pressure-sensitive adhesive tape side, and an expanding step, which divides the wafer by expanding. Therefore, the other steps and the order of the steps are not particularly limited. For example, the pressure-sensitive adhesive tape 10 can be suitable for use in the following semiconductor device manufacturing method (A).

[0032] (A) Manufacturing Method of Semiconductor Device (a) A step of laminating a back-grinding substrate to the surface of a wafer having a circuit pattern formed thereon; (b) A back-grinding step of grinding the back surface of the wafer; (c) A step of laminating an adhesive tape of the present invention to the back surface of the wafer and fixing it to a ring frame; (d) A step of peeling off the back-grinding substrate from the wafer; (e) An adhesive film laminating step of fixing the adhesive tape of the present invention, to which the wafer has been laminated, on a heated chuck table by vacuum suction from the base film side of the adhesive tape, and laminating an adhesive film to the surface of the wafer opposite to the adhesive tape; (f) A modified region forming step of irradiating a laser beam from the adhesive tape side to a portion of the wafer to be divided, thereby forming a modified region inside the wafer by multiphoton absorption; (g) An expanding step of expanding the adhesive tape to divide the wafer and adhesive film along a division line, thereby obtaining a plurality of wafer chips with an adhesive layer; (h) a heat shrinking step of heating and shrinking the outer periphery of the adhesive tape where the wafer chips are arranged to remove the slack generated in the expanding step and maintain the spacing between the chips, and (i) a pick-up step of picking up the wafer chips with adhesive layers from the adhesive layer of the adhesive tape. This semiconductor device manufacturing method uses stealth dicing.

[0033] <Method of Use> A method of using the adhesive tape 10 of the present invention when it is applied to the above-described method (A) for manufacturing a semiconductor device will be described with reference to FIGS. 2 to 5. FIG.

[0034] First, a back-grinding substrate is bonded to the front surface of the wafer 30 on which the circuit pattern 31 is formed (step (a)), and then a back-grinding step (step (b)) (not shown) is carried out to grind the back surface of the wafer 30. A normal back-grinding substrate, such as a glass substrate, can be used as the back-grinding substrate.

[0035] After the back-grinding step, the pressure-sensitive adhesive tape 10 of the present invention is laminated to the back surface of the wafer 30 and further bonded and fixed to a ring frame 20 (step (c)). At this time, the pressure-sensitive adhesive layer 12 of the pressure-sensitive adhesive tape 10 of the present invention is arranged so as to contact the back surface of the wafer 30, and the ring frame 20 is arranged around the wafer 30 in the area where the pressure-sensitive adhesive layer 12 is exposed. The back-grinding substrate (not shown) is peeled off from the wafer 30 (step (d)). As shown in FIG. 2, the pressure-sensitive adhesive tape 10 of the present invention, to which the wafer 30 has been laminated, is fixed on a heated chuck table 70 by vacuum suction from the base film 11 side, while an adhesive film 40 with a release film, consisting of an adhesive film 41 and a release film 42, is laminated to the surface of the wafer 30 (step (e)). The heating temperature of the chuck table 70 at this time can be 80° C. or higher, taking into account the lamination of an adhesive film such as NCF.

[0036] The release film 42 is peeled off from the adhesive film 41. The state after the release film 42 has been peeled off is shown in FIG.

[0037] 4, the wafer 30 to which the adhesive tape 10 has been attached is carried out from the chuck table 70. If an adhesive tape other than the adhesive tape of the present invention is used at this time, the unevenness of the surface of the chuck table will be transferred to the back surface of the base film 11, resulting in a reduced transmittance of the laser light. However, if the adhesive tape 10 of the present invention is used, this transfer can be effectively suppressed, and the transmittance of the laser light can be sufficiently maintained.

[0038] Next, as shown in Fig. 5, a laser beam 60 is irradiated onto the portion of the wafer 30 to be divided from the adhesive tape 10 side to form modified regions 32 by multiphoton absorption inside the wafer 30 (step (f)). In Fig. 5, the modified regions 32 are formed at four intermittent locations.

[0039] Next, the adhesive tape 10 of the present invention, in which the wafer 30 and the ring frame 20 are bonded together, is placed with the substrate film 11 side facing down on the stage of an expanding device. Next, with the ring frame 20 fixed, the hollow cylindrical push-up member of the expanding device is raised to expand (expand) the adhesive tape 10 (step (g)). The expansion conditions include an expansion speed of, for example, 5 to 500 mm / sec and an expansion amount (push-up amount) of, for example, 5 to 25 mm. By stretching the adhesive tape 10 in the radial direction of the wafer 30 in this manner, the wafer 30 is divided into chips 33 starting from the modified regions 32. At this time, the adhesive film 41 is not broken at the portions bonded to the wafer 30 because stretching (deformation) due to expansion is suppressed, but breaks do not occur at positions between the chips 33 due to the concentrated tension caused by the film expansion. Therefore, the adhesive film 41 is divided along with the wafer 30. As a result, a plurality of chips 33 with adhesive film pieces 43 attached can be obtained as shown in FIG.

[0040] Next, the push-up member is returned to its original position, and the slack in the adhesive tape 10 that occurred in the previous expanding step is removed, thereby carrying out a step of stably maintaining the spacing between the chips 33. In this step, for example, a hot air nozzle is used to blow hot air at 40 to 120°C onto the annular heat-shrinkable region between the region of the adhesive tape 10 where the chips 33 are present and the ring frame 20, thereby causing the base film 11 to heat-shrink and restore the adhesive tape 10 to its taut state (step (h)). Thereafter, the adhesive layer 12 is subjected to an energy ray curing treatment, a heat curing treatment, or the like to weaken the adhesive force of the adhesive layer 12 to the chips 33, and then the chips 33 are picked up (step (i)).

[0041] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0042] The following components were used. (Adhesive) Base resin A: To an acrylic copolymer (glass transition temperature: -65°C) whose constituent units were 70% by mass of 2-ethylhexyl acrylate, 29% by mass of 2-hydroxyethyl acrylate, and 1% by mass of methacrylic acid, 2-methacryloyloxyethyl isocyanate was added so that the double bond content was 0.9 (meq / g). 0.3 parts by mass of a urethane acrylate oligomer having a weight average molecular weight of 850 was added to 100 parts by mass of this acrylic copolymer to form base resin A. Photopolymerization initiator: Irgacure 184 (trade name, manufactured by Nippon Ciba-Geigy Ltd.) Curing agent: Coronate L (isocyanate-based curing agent, trade name, manufactured by Tosoh Corporation) Surface modifier: TEGORad 2200N (trade name, manufactured by Tego Chemie Co., Ltd.)

[0043] (Base film) EMMA: ethylene-methyl methacrylate copolymer (AN4214C (trade name), manufactured by Mitsui-Dow Polychemicals) ION (1): ionomer (Himilan 1855 (trade name), manufactured by Mitsui-Dow Polychemicals) ION (2): ionomer (Himilan 1652 (trade name), manufactured by Mitsui-Dow Polychemicals) ION (3): ionomer (Himilan AM7326 (trade name), manufactured by Mitsui-Dow Polychemicals) PP: polypropylene (F724P (trade name), manufactured by Prime Polymer)

[0044] <Examples> 1) Preparation of substrate film (Substrate film 1) EMMA was melt-kneaded at 220°C using a multi-layer T-die extruder, and extruded onto a metal roll (hereinafter also referred to as "mirror roll (1)") with one side mirror-finished. In this way, a substrate film 1 with a thickness of 100 μm was formed on the mirror roll (1). The surface shape of the metal roll was transferred to the surface of this substrate film 1 facing the mirror roll (1). The surface roughness Ra of the surface of the obtained substrate film 1 facing the mirror roll (1) was 0.03 μm.

[0045] (Substrate Film 2) Substrate film 2 was prepared in the same manner as in the preparation of substrate film 1, except that mirror-finished roll (2) was used instead of mirror-finished roll (1).

[0046] (Substrate Film 3) Substrate film 3 was prepared in the same manner as in the preparation of substrate film 1, except that ION (3) was used instead of EMMA.

[0047] (Substrate film 4) Substrate film 4 having an ION (1) layer and an EMMA layer and a total thickness of 100 μm was prepared in the same manner as substrate film 1, except that in preparation of substrate film 1, ION (1) and EMMA were co-extruded in a multilayer T-die extruder instead of EMMA, with EMMA facing the mirror-finish roll (1). Of the total amount of resin components in substrate film 4, ION (1) accounted for 50 mass% and EMMA for 50 mass%. The ION (1) layer had a thickness of 50 μm, and the EMMA layer had a thickness of 50 μm.

[0048] (Substrate film 5) Substrate film 5 was prepared in the same manner as substrate film 4, except that the amounts of ION (1) and EMMA in the preparation of substrate film 4 were 20 mass% and 80 mass% of the EMMA layer, based on the total amount of resin components of the substrate film. The ION (1) layer had a thickness of 20 μm, and the EMMA layer had a thickness of 80 μm.

[0049] (Substrate film 6) Substrate film 6 was prepared in the same manner as substrate film 5, except that the total thickness was 150 μm. The ION (1) layer had a thickness of 30 μm, and the EMMA layer had a thickness of 120 μm.

[0050] (Substrate Film 7) Substrate film 7 was prepared in the same manner as in the preparation of substrate film 1, except that PP was used instead of EMMA.

[0051] (Substrate Film 8) Substrate film 8 was prepared in the same manner as in the preparation of substrate film 1, except that ION(1) was used instead of EMMA.

[0052] (Substrate Film 9) Substrate film 9 was prepared in the same manner as in the preparation of substrate film 1, except that ION(2) was used instead of EMMA.

[0053] (Substrate film 10) A substrate film 10 having an EMMA layer and an ION (1) layer and a total thickness of 100 μm was prepared in the same manner as for the substrate film 1, except that in the preparation of the substrate film 1, EMMA and ION (1) were co-extruded instead of EMMA, with ION (1) facing the mirror-finished roll (1). Of the total amount of resin components in the substrate film 10, EMMA accounted for 50 mass% and ION (1) for 50 mass%. The EMMA layer had a thickness of 50 μm, and the ION (1) layer had a thickness of 50 μm.

[0054] (Substrate Film 11) Substrate film 11 was prepared in the same manner as in the preparation of substrate film 1, except that the textured roll (1) was used instead of the mirrored roll (1).

[0055] (Substrate Film 12) Substrate film 12 was prepared in the same manner as in the preparation of substrate film 1, except that the textured roll (2) was used instead of the mirrored roll (1).

[0056] 2) Preparation of Pressure-Sensitive Adhesive Composition 100 parts by mass of base resin A were mixed with 3 parts by mass of a photopolymerization initiator, 1 part by mass of a curing agent, and 0.6 parts by mass of a surface modifier to obtain a pressure-sensitive adhesive composition having an acrylic resin as a base polymer.

[0057] 3) Preparation of Pressure-Sensitive Adhesive Tapes The pressure-sensitive adhesive composition obtained above was applied to a release liner made of a release-treated polyethylene terephthalate film so that the thickness after drying would be 20 μm, and the applied coating was dried at 110° C. for 3 minutes to obtain a pressure-sensitive adhesive film with a release liner. Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film with a release liner was bonded to the side of each of the above-mentioned base films 1 to 12 that was not in contact with the roll, and the release liner was peeled off to obtain the pressure-sensitive adhesive tapes of Examples 1 to 6 and Comparative Examples 1 to 6 in which a pressure-sensitive adhesive layer was formed on the base films 1 to 12. In this case, the two-layer structure base films 4 to 6 and 10 had the arrangement of each layer constituting the base film as shown in Table 1.

[0058] The melting point, surface roughness Ra, and penetration temperature of each substrate film used in each pressure-sensitive adhesive tape of the Examples and Comparative Examples were measured as follows.

[0059] (Melting Point of Base Film) The melting point of the base film was determined by measuring the melting peak temperature according to DSC (JIS K 7121:2001). The base films 1 to 12 obtained above were used as samples. When multiple melting peaks were observed, the temperature of the lowest melting peak was determined as the melting point.

[0060] (Penetration Temperature of Back Surface of Substrate Film) The pressure-sensitive adhesive layer of each pressure-sensitive adhesive tape obtained above was attached to a quartz base, and the back surface of the substrate film was measured. The measurement was performed in accordance with JIS K7196:2012, applying a load of 500 mN to the tip of a 1 mm diameter indenter at a temperature rise rate of 5°C / min. A TMA curve (horizontal axis: temperature, vertical axis: deformation amount) was obtained, and the penetration temperature was determined. The measurement was performed in penetration mode using a TMA8311 (trade name, manufactured by Rigaku Corporation) as the measuring device. Note that for substrate films 4 to 6 and 10 consisting of multiple layers, the penetration temperature was also measured on the surface (front surface) of the substrate film on which the pressure-sensitive adhesive layer was formed. In this case, pressure-sensitive adhesive tapes were formed and measured in the same manner as in 3) Preparation of Pressure-sensitive Adhesive Tapes above, except that a pressure-sensitive adhesive layer was formed on the back surface of the substrate film. The penetration temperature (T2) of the back surface of the base film is shown in the "Penetration temperature of base film" column of Table 1, and the difference ((T2) - (T1)) between the penetration temperature (T2) of the back surface of the base film and the penetration temperature (T1) of the surface of the base film is shown in the "Penetration temperature difference (T2) - (T1) (°C)" column of Table 1. "-" indicates that no measurement was performed.

[0061] (Surface roughness Ra of rear surface of substrate film) The surface roughness Ra of the rear surface of the substrate film was measured by adhering and fixing the adhesive layer of each adhesive tape obtained above to a smooth silicon mirror wafer, measuring at any five points (approximately 5 mm long x 5 points) on the rear surface of the substrate film, and the average value was taken as the surface roughness Ra of the rear surface. For the measurement, a measuring device "Surftest SJ-310" (manufactured by Mitutoyo Corporation) according to JIS B0601 was used. The measurement conditions were as follows. - Measurement conditions - Curve: R Parameter: 2 Filter: GAUSS λc: 0.8 mm λs: 2.5 μm Number of sections: 5

[0062] (Yield point up to 50% elongation when tensile at -15°C) A stress-elongation curve at -15°C was obtained as follows, and the presence or absence of a yield point up to an elongation of 50% (1.5 times the initial length) was confirmed. Using a tensile testing device conforming to JIS B7721:2018, the stress and elongation of each substrate film were measured by a tensile test under the following measurement conditions, and a stress-elongation curve was obtained using these results. From the obtained stress-elongation curve, the presence or absence of a yield point up to an elongation of 50% (elongation range of 0 to 50%) was confirmed. A specimen 5 mm wide (MD direction) and 60 mm long (TD direction) was cut out from each substrate film to prepare a test piece. - Measurement conditions - Measurement temperature: -15°C A low-temperature thermostatic chamber was used, and the sample was placed therein, and measurement was started 5 minutes after the temperature reached -15°C Chuck distance: 20 mm Tensile speed: 300 mm / min

[0063] (Stress) A stress-elongation curve was created under the same measurement conditions as in the yield point test described above, and the stress value (MPa) at 30% tension (elongation 30%) was determined. The following test specimens were used. Test specimen A: A test specimen with a width of 5 mm in the MD direction and a length of 60 mm in the TD direction. Test specimen B: A test specimen with a width of 5 mm in the TD direction and a length of 60 mm in the MD direction. The stress value of test specimen A was defined as the TD stress (S2), and the stress of test specimen B was defined as the MD stress (S1), and S1 - S2 was calculated.

[0064] The pressure-sensitive adhesive tapes of the Examples and Comparative Examples were evaluated for transmittance after heat adsorption, meandering of the modified region during stealth dicing, tape breakage during cool expansion, and kerf width as follows.

[0065] (Transmittance after heat adsorption) Each adhesive tape obtained in the examples and comparative examples was attached to a ring frame (inner diameter: 350 mm). Then, each adhesive tape was placed on a porous chuck table (Porous Chuck (trade name), manufactured by Yoshioka Seiko Co., Ltd., material: alumina, 12-inch wafer size, average porous pore diameter: 55 μm) heated to 80 ° C., with the back surface (the surface not coated with adhesive) facing the chuck table, and adsorbed and fixed at a vacuum pressure of 90 kPa. This state was maintained for 5 minutes. Thereafter, each adhesive tape was removed from the chuck table, and light was irradiated from the back side of each adhesive tape. The transmittance was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, trade name: UV-1800). Measurements were performed at any five points on each adhesive tape, and the average transmittance at 650 nm was calculated and used as the transmittance after heat adsorption. Photometry mode: %T Scan range: 1100 to 200 nm Recording range: 0.0 to 100.0% Scan speed: High speed Scan pitch: AUTO Number of scans: 1 In the above test, the chuck table was heated to 80°C, which is the temperature normally used when bonding an adhesive film to a wafer. 650 nm is the typical wavelength of the laser provided in the autofocus unit of a dicing machine, which is used to determine the processing depth of the modified area by laser irradiation.

[0066] (Meandering of Modified Regions During Stealth Dicing) 1) Stealth Dicing A silicon mirror wafer (diameter: 12 inches, thickness: 100 μm) and a ring frame were attached to the adhesive layer of an adhesive tape to obtain a laminated structure. The resulting laminated structure was fixed by suction from the backside (the side not coated with adhesive) of each adhesive tape using a porous chuck table heated to 80°C, as in the transmittance test after thermal adsorption, at a vacuum pressure of 90 kPa, and this state was maintained for 5 minutes. The laminated structure was then set in a laser dicer (manufactured by DISCO Corporation, product name "DF-7362"), and a stealth dicing laser beam was irradiated onto the laminated structure from the backside of the adhesive tape to form regularly spaced modified regions within the silicon mirror wafer. More specifically, the laser was irradiated so that dot-like modified regions were formed in a straight line along the planned line A in the cross section of the wafer chip obtained by stealth dicing. The width of the planned line A in the thickness direction of the wafer chip corresponds to the length of the modified region 32 in the thickness direction in the cross section of the wafer 30 shown in Figure 5. In this evaluation, the width of the planned line A was 20 µm. The laminated structure was then placed in a die separator (manufactured by Disco Corporation, product name "DDS2300") and expanded (cool expanded) at -15°C under conditions of an expansion speed (pull-down speed) of 300 mm / sec and an expansion amount of 12 mm, resulting in an 8 mm x 8 mm chip. Further expansion was then performed at room temperature under conditions of an expansion speed of 5 mm / sec and an expansion amount of 10 mm. A heat shrink treatment was then performed under the following conditions. Here, the expansion amount refers to the amount of change in the relative position of the ring frame and the push-up member before and after pressing down. In this way, wafer chips were obtained on the adhesive tape attached to the ring frame by cool expansion separation and heat shrinking, and then picked up.[Conditions] Heater set temperature: 220°C, Hot air flow rate: 40 L / min, Distance between heater and adhesive tape: 20 mm, Heater rotation speed: 7° / sec. 2) Meandering of modified regions during stealth dicing. The cross section of the wafer chip obtained by the stealth dicing (the side surface formed by the above-mentioned division) (any one surface) was observed with a digital microscope (Keyence Corporation, VHX-5000 (product name)) to confirm the modified regions in the wafer chip cross section. In this cross section, the modified regions were observed as dots spaced apart along the length of the wafer chip. In the cross section, the width a1 (length in the thickness direction of the wafer chip) of the rectangle with the smallest area including all modified regions formed above the upper end of the wafer chip in the thickness direction of the planned line A, and the width a2 of the rectangle with the smallest area including all modified regions formed below the lower end of the wafer chip in the thickness direction of the planned line A were measured, and the larger of a1 and a2 was taken as the amount of meandering of the modified region in the cross section. If the amount of meandering is zero, the widths a1 and a2 of the rectangles will be zero. The obtained meandering amount was evaluated according to the following evaluation ranks. If the meandering amount of the modified region is large in the upper and lower thickness directions of the wafer chip, it may not be possible to separate the chips with good processing accuracy. -Evaluation rank- ◎: Less than 10 μm ◯: 10 μm or more but less than 20 μm △: 20 μm or more but less than 30 μm ×: 30 μm or more.

[0067] (Tape breakage during cool expansion) The above 1) stealth dicing was performed on 10 sheets of each adhesive tape. The presence or absence of breakage of the adhesive tape during cool expansion was checked and rated using the following evaluation rank. If the adhesive tape breaks during cool expansion, the next step cannot be carried out, which is undesirable as it reduces the yield. -Evaluation rank- x: Breakage of the adhesive tape occurred in any of the 10 adhesive tapes ◯: Breakage of the adhesive tape did not occur in any of the 10 adhesive tapes

[0068] (Kerf Width) As shown in Figure 7, the kerf width X (MD kerf width) between the rightmost chip 50a in Figure 7, which is free of chips in the MD direction of the adhesive tape, and the kerf width Y (TD kerf width) between the chip 50a and the adjacent chip closer to the TD center are measured. Similarly, the MD kerf width and TD kerf width are also measured for the leftmost chip 50b in Figure 7, which is free of chips in the MD direction of the adhesive tape. In addition, the MD kerf width and TD kerf width are also measured for the outermost chips 51 and the central chip 52 in the TD direction of the adhesive tape, which are free of chips. The average value of the MD kerf widths at the above five points and the average value of the TD kerf widths at the above five points are calculated. The obtained kerf widths (µm) were evaluated according to the following evaluation ranks. - Evaluation rank - ◎: 30 μm or more 〇: 20 to 29 μm △: 9 to 19 μm ×: 8 μm or less

[0069] The results obtained are summarized in Table 1 below.

[0070]

[0071] (Notes for Table 1) The column "Rolls used in film formation" indicates the rolls used in producing each substrate film. "MR1" represents mirror-finished roll (1), "MR2" represents mirror-finished roll (2), "ER1" represents textured roll (1), and "ER2" represents textured roll (2).

[0072] The following can be seen from Table 1 above. The adhesive tape of Comparative Example 1 has a base film made of PP with a high melting point (155°C). The adhesive tape of Comparative Example 1 broke during cool expansion. The adhesive tapes of Comparative Examples 2 to 4 have base films with low penetration temperatures on the back surface of the base film. All of the adhesive tapes of Comparative Examples 2 to 4 had a post-heat adsorption transmittance of less than 80% after being vacuum-adsorbed to a chuck table under heating, and a meandering of the modified region of 20 μm or more occurred during stealth dicing. The adhesive tapes of Comparative Examples 5 and 6 have base films with a large surface roughness Ra on the back surface of the base film. All of the adhesive tapes of Comparative Examples 5 and 6 had a post-heat adsorption transmittance of less than 80% and a meandering of the modified region occurred during stealth dicing. Furthermore, the kerf width became too narrow after heat shrinking. In contrast, the adhesive tapes of Examples 1 to 6 have a substrate film with a melting point of 150°C or less, a backside surface roughness Ra of 0.10 μm or less, and a penetration temperature of 80°C or higher. All of the adhesive tapes of Examples 1 to 6 had a transmittance of 84% or more after heat adsorption, allowing sufficient transmission of laser light, and reducing the meandering of the modified region during stealth dicing to less than 20 μm. Furthermore, no breakage occurred during cool expansion. It can be seen that the adhesive tape of the present invention, despite using a resin with a relatively low melting point, exhibits sufficient transmittance to laser light after vacuum adsorption to a chuck table under heating, and also exhibits excellent expansion during expansion and cleavage. Furthermore, it can be seen that by using a substrate film that does not have a yield point up to 50% elongation in the stress-strain curve at -15°C (Examples 3 to 6), the kerf width can be appropriately maintained after heat shrinking.

[0073] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0074] This application claims priority based on Japanese Patent Application No. 2023-053186, filed on March 29, 2023, the contents of which are incorporated herein by reference as part of the present specification.

[0075] REFERENCE SIGNS LIST 10 Dicing adhesive tape 11 Base film 12 Adhesive layer 20 Ring frame 30 Wafer 31 Circuit surface 32 Modified region 33 Chip 40 Adhesive film with release film 41 Adhesive film 42 Release film 60 Laser light 70 Chuck table

Claims

1. A dicing adhesive tape having an adhesive layer on a base film, wherein the melting point of the base film is 150°C or less, the surface roughness Ra of a surface A of the base film opposite the adhesive layer is 0.10 μm or less, and the penetration temperature of this surface A is 80°C or higher.

2. 2. The pressure-sensitive adhesive tape for dicing according to claim 1, wherein the base film has no yield point up to an elongation of 50% in a stress-elongation curve at -15°C.

3. 3. The dicing pressure-sensitive adhesive tape according to claim 1, wherein, in a tensile test at −15° C., the absolute value of the difference between the stress (MD stress, S1) (MPa) at an elongation rate of 30% when stretched in the MD direction and the stress (TD stress, S2) at an elongation rate of 30% when stretched in the TD direction is 4 MPa or less.

4. 3. The pressure-sensitive adhesive tape for dicing according to claim 1, wherein the base film is composed of at least two layers, and the relationship between the penetration temperature (T1) of the surface on which the pressure-sensitive adhesive layer is formed and the penetration temperature (T2) of the surface on which the pressure-sensitive adhesive layer is not formed satisfies [(T2) - (T1)] > 0°C.

5. 3. The pressure-sensitive adhesive tape for dicing according to claim 1, wherein the substrate film contains at least one of an ethylene-(meth)acrylic acid alkyl ester copolymer resin and an ionomer resin.

6. 3. The adhesive tape for dicing according to claim 1, which is an adhesive tape for stealth dicing.