Protective film forming film and method for manufacturing singulated workpiece with protective film

Abstract

To provide a protective film forming film that can sufficiently dissipate heat generated in a singulated workpiece such as a semiconductor chip or the like and that can form a protective film with sufficiently high adhesive reliability in an environment with large temperature changes, and a method for manufacturing the singulated workpiece with the protective film, such as a semiconductor chip or the like with the protective film, using the protective film forming film.SOLUTION: A curable protective film forming film containing a filler, in which, when a rectangular region having a side which has the same length as the thickness in a thickness direction and an area of 625 μm2 is observed in a cross section of the cured protective film forming film parallel to the thickness direction, the ratio of the cross-sectional area of the filler to the area of the smallest encompassing circle that contains all of the outer peripheries of the cross section of the filler is 0.6 to 0.9 inclusive, and the number of fillers whose maximum cross-sectional length exceeds 0.5 μm is 0.08 to 0.80 inclusive per μm2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a protective film-forming film and a method for manufacturing a protective film-coated individual workpiece, and more particularly to a protective film-coated film capable of forming a protective film having excellent heat dissipation characteristics and adhesive reliability, and a method for manufacturing a protective film-coated individual workpiece such as a protective film-coated semiconductor chip using the protective film-coated film. [Background technology]

[0002] Semiconductor chips are obtained as singulated workpieces obtained by singulating a workpiece such as a wafer on which a circuit is formed. In recent years, semiconductor devices have been manufactured using a mounting method called flip-chip bonding, which uses semiconductor chips having circuit surfaces on which convex electrodes such as bumps are formed. In this mounting method, when mounting the semiconductor chip, the circuit surface of the semiconductor chip is inverted (face down) and bonded to the chip mounting section. This results in a structure in which the back side of the semiconductor chip, on which no circuit is formed, is exposed.

[0003] For this reason, a hard protective film made of an organic material is often formed on the back side of the semiconductor chip to protect the semiconductor chip from shocks during transportation, etc. The protective film is formed, for example, by attaching a protective film-forming film to the back side of the semiconductor wafer and then hardening it. The semiconductor chip with the protective film formed thereon is mounted on a substrate or the like as an electronic component.

[0004] As semiconductor chips become smaller and their performance improves, the heat generated by the semiconductor chips during operation increases. Overheating due to the heat generated by the semiconductor chip can cause malfunctions and deformation of the semiconductor chip, reducing its reliability. To eliminate the heat generated by the semiconductor chip, a protective film in contact with the semiconductor chip contains a thermally conductive filler, which dissipates the heat generated by the semiconductor chip through the filler in the protective film. However, if the amount of filler in the protective film is large, there is a problem of reduced adhesion between the protective film and the semiconductor chip.

[0005] Patent Document 1 discloses a resin film-forming layer containing nitride particles as an inorganic filler, and discloses that the resin film-forming layer can improve adhesion to an adherend and the heat dissipation characteristics of a semiconductor device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 083872 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, the range of temperature changes that can be applied is not very wide in terms of the adhesion of the resin film to the adherend, and there is a problem that the adhesive reliability of the resin film is not sufficient in environments with large temperature changes.

[0008] The present invention has been made in consideration of the above-described situation, and aims to provide a protective film-forming film that can sufficiently dissipate heat generated in individual workpieces such as semiconductor chips, and that can form a protective film with sufficiently high adhesive reliability in environments with large temperature changes, and a method for manufacturing individual workpieces with protective films, such as semiconductor chips with protective films, using the protective film-forming film. [Means for solving the problem]

[0009] The aspects of the present invention are as follows.

[0010] [1] A curable protective film-forming film containing a filler, In a cross section parallel to the thickness direction of the cured protective film-forming film, the length of one side is the same as the thickness in the thickness direction, and the area is 625 μm 2When observing a rectangular area in which the ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle that contains all of the outer peripheries of the cross section of the filler is 0.6 to 0.9, and the number of fillers whose maximum cross-sectional length exceeds 0.5 μm is 0.08 / μm 2 More than 0.80 pieces / μm 2 The following are the protective film-forming films that exist.

[0011] [2] The protective film-forming film according to [1], wherein the protective film-forming film has a curable component and a polymer component.

[0012] [3] The protective film-forming film according to [1] or [2], wherein the average particle size of the filler is 0.8 μm or more and 5 μm or less.

[0013] [4] The protective film-forming film according to any one of [1] to [3], wherein the particle size distribution of the filler is a unimodal distribution.

[0014] [5] The protective film-forming film according to any one of [1] to [4], wherein the thickness of the protective film-forming film is less than 50 μm.

[0015] [6] The protective film-forming film according to any one of [1] to [5], wherein the filler material is alumina.

[0016] [7] A protective film-forming film according to any one of [1] to [6], wherein when the area of ​​the rectangular region is 100%, the ratio of the total area occupied by the cross section of the filler in the rectangular region is 30% or more and 70% or less.

[0017] [8] A step of attaching the protective film-forming film according to any one of [1] to [7] to a workpiece; a step of curing the protective film-forming film after the step of attaching it to the workpiece; This is a method for manufacturing individual workpieces with a protective film, which includes a step of singulating the workpiece to which the protective film or protective film-forming film has been attached after the step of attaching the protective film or protective film-forming film to the workpiece, thereby obtaining multiple individual workpieces with the protective film or protective film-forming film. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a protective film-forming film that can sufficiently dissipate heat generated in a workpiece singulated with a semiconductor chip or the like and that can form a protective film with sufficiently high adhesive reliability in an environment with large temperature changes, and a method for manufacturing a workpiece singulated with a protective film, such as a semiconductor chip with a protective film, using the protective film-forming film. [Brief explanation of the drawings]

[0019] [Figure 1A] FIG. 1A is a schematic diagram illustrating the maximum length of the cross section of a filler. [Figure 1B] FIG. 1B is a schematic diagram for explaining the smallest inclusive circle that includes all of the outer peripheries of the cross section of the filler. [Figure 1C] FIG. 1C is a schematic diagram showing an example of a cross section of a filler in which polyhedrons are composed of flat surfaces. [Figure 1D] FIG. 1D is a schematic diagram showing an example of a cross section of a filler in which a polyhedron is composed of curved surfaces. [Figure 2] FIG. 2 is a schematic diagram for explaining a method for identifying a filler in which the ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle that contains all of the outer peripheries of the cross section of the filler is 0.6 or more and 0.9 or less, and the maximum length of the cross section of the filler is more than 0.5 μm. [Figure 3] FIG. 3 is a cross-sectional schematic diagram of an example of the sheet for forming a protective film according to this embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the composite sheet for forming a protective film according to this embodiment. [Figure 5A] FIG. 5A is a schematic cross-sectional view illustrating a step of attaching the sheet for forming a protective film according to this embodiment to a wafer. [Figure 5B] FIG. 5B is a cross-sectional view illustrating a process of attaching the composite sheet for forming a protective film according to this embodiment to a wafer. [Figure 6] FIG. 6 is a schematic cross-sectional view for explaining the step of dividing the wafer with the protective film into individual pieces. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, the present invention will be described in detail based on specific embodiments with reference to the drawings.

[0021] First, the main terms used in this specification will be explained.

[0022] The workpiece refers to a plate-shaped body to which the protective film-forming film according to this embodiment is attached and then singulated. The protective film-forming film is attached to the back surface of the workpiece. Examples of workpieces include circular wafers (including those having an orientation flat), rectangular panel-level packages, and strips (rectangular substrates) sealed with molded resin. Among these, wafers made of inorganic materials are preferred from the viewpoint of easily achieving the effects of the present invention. Examples of wafers include semiconductor wafers such as silicon wafers, gallium arsenide wafers, silicon carbide wafers, gallium nitride wafers, and indium phosphide wafers, as well as insulator wafers such as glass wafers, lithium tantalate wafers, and lithium niobate wafers. They may also be reconstructed wafers made of a semiconductor and a resin used in the manufacture of fan-out packages, etc. From the viewpoint of easily achieving the effects of the present invention, semiconductor wafers or insulator wafers are preferred.

[0023] Singulation of a workpiece refers to dividing the workpiece into individual circuits to obtain individual workpieces. For example, if the workpiece is a wafer, the individual workpieces are chips, and if the workpiece is a panel-level package or a strip (rectangular substrate) sealed with molded resin, the individual workpieces are semiconductor packages.

[0024] The "surface" of a workpiece refers to the surface on which circuits, electrodes, etc. are formed, and the "back" of a workpiece refers to the surface on which no circuits, etc. are formed. The electrodes may be convex electrodes such as bumps.

[0025] The term "main surface" refers to a surface that is larger in area than the other surfaces of a plate-like body. A plate-like body usually has two main surfaces and other side surfaces, and the two main surfaces face each other. In a workpiece, the "front surface" and the "back surface" are the main surfaces.

[0026] The term "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and similar terms.

[0027] "Energy rays" refers to ultraviolet rays, electron beams, etc., and is preferably ultraviolet rays.

[0028] Unless otherwise specified, "weight-average molecular weight" is a polystyrene-equivalent value measured by gel permeation chromatography (GPC). Measurements using this method are performed using, for example, a Tosoh high-speed GPC system (HLC-8120GPC) connected in this order with high-speed columns (TSK guard column HXL-H, TSK Gel GMHXL, and TSK Gel G2000 HXL) at a column temperature of 40°C and a flow rate of 1.0 mL / min, using a differential refractometer as the detector.

[0029] The release film is a film that supports the protective film-forming film in a releasable manner. The term "film" is not limited to a specific thickness, and is used to include a sheet.

[0030] The mass ratios in the descriptions of compositions such as the composition for the protective film-forming film are based on the active ingredient (solid content), and do not include the solvent unless otherwise specified.

[0031] (1. Protective film forming film) The protective film-forming film according to the present embodiment is used to form a protective film on the workpiece or a workpiece singulated therefrom after being attached to the workpiece. After the protective film is formed, a workpiece with a protective film or a workpiece singulated therefrom is obtained.

[0032] As mentioned above, workpieces such as semiconductor chips generate a lot of heat when in operation, so the protective film in contact with the workpiece is required to not only protect the workpiece, but also to quickly dissipate the heat generated in the workpiece (heat dissipation properties).

[0033] The heat dissipation properties of a protective film are generally achieved by incorporating a large amount of filler made of a material with high thermal conductivity into the protective film, thereby forming a path for heat conduction.

[0034] However, if the protective film contains a large amount of filler, the amount of components responsible for adhesion to the workpiece singulation becomes relatively small, resulting in a decrease in the reliability of the adhesion between the workpiece singulation and the protective film, especially in harsh environments such as those with large temperature changes.

[0035] Therefore, in this embodiment, by using a protective film-forming film containing a specific filler described later at a predetermined ratio, the protective film-forming film (protective film) after curing can achieve both heat dissipation properties and adhesive reliability. The protective film-forming film according to this embodiment will be described below.

[0036] The protective film-forming film according to this embodiment is curable. Therefore, the protective film is obtained as a cured product by curing the uncured protective film-forming film. Therefore, the protective film-forming film after curing is different from the protective film-forming film. The protective film-forming film after curing (protective film) imparts a predetermined function to the workpiece or individual pieces of the workpiece.

[0037] The curable protective film-forming film can be laminated on the workpiece and then cured, thereby firmly adhering the protective film to the workpiece and forming a durable protective film.

[0038] Examples of the cured product include a thermosetting product and an energy ray-cured product. That is, examples of the curable protective film-forming film include a thermosetting protective film-forming film and an energy ray-curable protective film-forming film.

[0039] The protective film-forming film tends to have low light transmittance because it contains a filler described below and preferably further contains a colorant, etc. Therefore, when the protective film-forming film is cured by irradiation with energy rays to obtain an energy ray-cured product, the energy ray curing tends to be insufficient, particularly when the thickness of the protective film-forming film is large.

[0040] On the other hand, a thermosetting protective film-forming film can be sufficiently cured by heating even if it is thick, so that it is easy to form a protective film that can fully exhibit the desired performance. Furthermore, by using a normal heating means such as a heating oven, a large number of protective film-forming films can be heated and thermally cured all at once. Therefore, in this embodiment, it is preferable that the protective film-forming film is thermosetting.

[0041] Whether or not a protective film-forming film is thermosetting can be determined as follows. First, a protective film-forming film at room temperature (23°C) is heated to a temperature above room temperature, and then cooled to room temperature to obtain a protective film-forming film after heating and cooling. Next, when the hardness of the protective film-forming film after heating and cooling is compared with the hardness of the protective film-forming film before heating at the same temperature, if the protective film-forming film after heating and cooling is harder, the protective film-forming film is determined to be thermosetting.

[0042] In addition, it is preferable that the protective film-forming film has adhesiveness at room temperature (23°C) or exhibits adhesiveness when heated. This allows the workpiece to be laminated to the protective film-forming film when it is placed on top of the film. Therefore, positioning can be reliably performed before the protective film-forming film is cured.

[0043] The protective film-forming film may be composed of one layer (single layer) or may be composed of two or more layers. When the protective film-forming film has multiple layers, these multiple layers may be the same or different from each other, and the combination of layers constituting these multiple layers is not particularly limited.

[0044] In this embodiment, the protective film-forming film is preferably one layer (single layer). A one-layer protective film-forming film can be easily produced because it can achieve high precision in terms of thickness. Furthermore, if the protective film-forming film is composed of multiple layers, it is necessary to consider the adhesion between the layers and the stretchability of each layer, which may result in the risk of peeling from the adherend. If the protective film-forming film is one layer, the above risks can be reduced and the degree of freedom in design is increased.

[0045] The thickness of the protective film-forming film may be less than 50 μm, may be 40 μm or less, or may be 30 μm or less. The thickness of the protective film-forming film may be 3 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more.

[0046] The thickness of the protective film-forming film means the thickness of the entire protective film-forming film. For example, the thickness of a protective film-forming film composed of multiple layers means the total thickness of all layers constituting the protective film-forming film.

[0047] The protective film-forming film according to this embodiment contains at least a filler (C). By controlling the number of fillers (C) that have a predetermined shape and dimensions when observing a cross section parallel to the thickness direction of the cured protective film-forming film, heat conduction via the filler is efficiently carried out in the cured protective film-forming film (protective film). As a result, high heat dissipation properties can be exhibited without increasing the amount of filler in the protective film. Therefore, the effect of the amount of filler on the adhesive reliability of the protective film can be suppressed, and the heat dissipation properties and adhesive reliability of the protective film can be both achieved.

[0048] (1.2. Filler) In this embodiment, the number of fillers having a predetermined shape and dimensions is controlled when observing a cross section parallel to the thickness direction in the protective film-forming film (protective film) after curing. Hereinafter, a specific description will be given with reference to Figures 1A to 2.

[0049] In this embodiment, as shown in Fig. 1A, the maximum length is the longest diameter of the filler in the cross section of the filler 3. In Fig. 1A, the diameter L3 is the maximum length.

[0050] Also, a circle is assumed to include all of the perimeter lines that make up the perimeter of the cross section of the filler. Any circle like this can be assumed. As shown in FIG. 1B, the circle with the smallest diameter among such circles is defined as the minimum enclosing circle SEC. The minimum enclosing circle has the smallest diameter among the circles that include the entire cross section of the filler.

[0051] In this embodiment, the cured protective film-forming film is cut along a plane parallel to the thickness direction. As shown in Fig. 2, in the cross section obtained after cutting, a rectangular region RA having one side parallel to the thickness direction is formed, and the length of the side parallel to the thickness direction is the same as the thickness of the cured protective film-forming film 2, and the area of ​​the rectangular region RA is 625 μm 2 For example, if the thickness of the protective film-forming film after curing is 25 μm, a square area of ​​25 μm × 25 μm is set on the cross section of the protective film-forming film after curing. By using a cross section parallel to the thickness direction as the observation area, it is possible to average out any bias in the state of the filler due to settling of the filler that may occur during production of the protective film-forming film.

[0052] In this embodiment, the set rectangular area RA is observed, and among the observed fillers 3 (3a, 3b, 3c), fillers in which the ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle (cross-sectional area of ​​the filler / area of ​​the smallest encompassing circle that includes all the peripheries of the cross-section of the filler) is 0.6 or more and 0.9 or less, and the maximum length of the cross-section of the filler is more than 0.5 μm (fillers 3a that are not hatched in FIG. 2) are found to be smaller than 1 μm per unit area (1 μm2 ) is controlled to between 0.08 and 0.80.

[0053] Fillers with a ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle of 0.6 to 0.9 are not spherical particles, nor are they highly anisotropic particles like amorphous particles. This shape allows nearby fillers to come into contact over a larger area than the point contact that occurs between spheres, making it easier to form thicker heat conduction paths through the filler and conduct more heat. Furthermore, because the surface area per unit mass is not as large as that of amorphous particles (anisotropic particles), the amount of filler required to ensure heat conduction paths can be reduced, ensuring the content of components that provide adhesive properties in the protective film.

[0054] Furthermore, fillers with a maximum cross-sectional length of 0.5 μm or less tend to have a large surface area due to their small particle diameter. Therefore, even if a filler has the above-mentioned shape, if a large number of fillers with a maximum cross-sectional length of 0.5 μm or less are observed, the volume occupied by the filler in the protective film tends to be large, and the adhesive reliability of the protective film tends to be poor. Furthermore, voids are likely to be formed in the protective film, which also tends to further poor the adhesive reliability of the protective film. Therefore, fillers with a maximum cross-sectional length of 0.5 μm or less are not counted regardless of their cross-sectional area ratio.

[0055] From the above, by keeping the number of fillers having the above-mentioned specified shapes and dimensions within the above ranges, heat conduction through the fillers is carried out efficiently, ensuring the heat dissipation properties of the protective film and achieving sufficient adhesive reliability.

[0056] On the other hand, when the protective film-forming film contains spherical fillers, the cross-sectional shape of the fillers is close to a circle, and the ratio of the cross-sectional area of ​​the fillers to the area of ​​the smallest encompassing circle is close to 1. Therefore, when the protective film-forming film contains spherical fillers, the number of fillers having the above-mentioned predetermined shape and dimensions is 0.08 pieces / μm 2Since the thickness of the filler is likely to be smaller than the thickness of the filler, it is difficult to form a thick heat conduction path through the filler, and therefore heat conduction is difficult to achieve sufficiently.

[0057] In addition, when the protective film-forming film contains a filler of irregular particles, for example, a plate-shaped filler, the ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle is less than 0.6. Therefore, even if the protective film-forming film contains a filler of irregular particles, the number of fillers having the above-mentioned predetermined shape and dimensions is 0.08 pieces / μm 2 In order to ensure a heat conduction path, the content of irregular particle filler becomes large, which tends to result in poor adhesion reliability.

[0058] In this embodiment, the ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle is 0.6 or more and 0.9 or less, and the number of fillers whose maximum cross-sectional length exceeds 0.5 μm is 0.10 pieces / μm 2 More than 0.70 pieces / μm 2 It may be 0.11 particles / μm or less. 2 More than 0.50 pieces / μm 2 It may be the following:

[0059] Furthermore, when the area of ​​the rectangular region RA is taken as 100%, it is preferable that the ratio of the cross section of the filler (C) to the total area of ​​the rectangular region RA is 30% to 70%. The ratio of the total area occupied by the cross section of the filler (C) (cross-sectional area ratio) reflects the content of the filler (C) in the protective film. Note that the "filler (C)" in the total area occupied by the cross section of the filler (C) is not limited to the filler constituting the filler having the above-mentioned specified shape and dimensions, but also includes fillers whose shape or dimensions differ from the above-mentioned specified ones when observing a cross section parallel to the thickness direction of the cured protective film-forming film. In Figure 2, "filler (C)" refers to filler 3a, filler 3b, and filler 3c.

[0060] When the ratio of the total area occupied by the filler (C) is within the above range, it is easier to achieve both the heat dissipation property and the adhesive reliability of the protective film-forming film after curing.

[0061] The proportion of the total area occupied by the filler (C) may be 35% or more and 65% or less, or may be 40% or more and 60% or less.

[0062] (1.2.1. How to Identify Filler Materials) As a method for observing the filler (C) containing the filler having the above-mentioned predetermined shape and dimensions, and a method for identifying the filler having the above-mentioned predetermined shape and dimensions, any method can be used as long as it can observe and identify the filler in the cross section of the protective film-forming film after curing. In this embodiment, a method for observing the cross section of the protective film-forming film after curing using a scanning electron microscope (SEM) is exemplified.

[0063] A cross-sectional sample of the cured protective film-forming film can be prepared using a known polishing device. In this embodiment, the cross-sectional sample is prepared by ion milling in order to observe the cross-section with an SEM. In ion milling, an argon ion beam is irradiated onto the sample, and the sample is processed by the sputtering phenomenon.

[0064] A cross-sectional sample of the obtained cured protective film-forming film is observed using an SEM, and a still image of the SEM is taken. The SEM image shows the boundary between the filler and materials other than the filler. The observation magnification can be any magnification that allows the rectangular area RA described above to be set in the observation field. In the observation field, an energy dispersive X-ray spectrometer (EDX) is used to detect elements that are contained in large amounts in the filler and are not contained in or are present in small amounts in other components (such as components responsible for adhesiveness). For example, if the filler is made of alumina, aluminum is detected.

[0065] In the mapping image of the element acquired by EDX, a group of pixels with a high content of the element (e.g., aluminum) indicates that the location is the cross-section of the filler. By applying the information of the mapping image acquired by EDX to the boundary information in the SEM image captured above, the positional relationship and boundary between the cross-section of the filler and materials other than the filler in the SEM image can be identified. This makes it possible to create an SEM image in which the shape and dimensions of the cross-section of the filler can be identified. Image processing such as anti-aliasing may be performed on the SEM image in which the shape and dimensions of the cross-section of the filler can be identified to create an SEM image in which the positional relationship and boundaries between the cross-section of the filler and materials other than the filler are more clearly defined.

[0066] Using an SEM image that can identify the cross-sectional shape and dimensions of the filler, the rectangular region RA described above is extracted, and the maximum cross-sectional length of each filler present within the rectangular region RA is measured. The maximum length may be measured manually or by image processing, etc. Fillers with a maximum length of 0.5 μm or less (hatched filler 3b in Figure 2) are excluded from subsequent measurements.

[0067] After measuring the maximum length, for each filler whose maximum cross-sectional length exceeds 0.5 μm, a minimum inclusive circle that includes all of the perimeter lines of the filler's cross section is created. From the area of ​​the created minimum inclusive circle and the cross-sectional area of ​​the filler, the ratio of the filler's cross-sectional area to the area of ​​the minimum inclusive circle (cross-sectional area of ​​the filler / area of ​​the minimum inclusive circle that includes all of the perimeter lines of the filler's cross section) is calculated. Fillers whose calculated ratio is outside the range of 0.6 to 0.9 (cross-hatched filler 3c in Figure 2) are excluded, and the number of fillers whose ratio is within the range of 0.6 to 0.9 is counted, and the number of fillers whose unit area (1 μm ) is calculated in the rectangular area RA. 2 ) to calculate the number of pieces per

[0068] In this embodiment, the filler (C) preferably has a polyhedral shape. The polyhedral shape is a shape obtained by cutting the surface of a sphere along a predetermined plane, and the polyhedron may be composed of flat or curved surfaces, and the vertices may be rounded. An example of a cross section of a filler 3 in which the polyhedron is composed of flat surfaces is shown in FIG. 1C. Also, an example of a cross section of a filler 3 in which the polyhedron is composed of curved surfaces is shown in FIG. 1D. When the filler (C) has a polyhedral shape, it is easier to satisfy the requirement that the number of fillers having the above-mentioned predetermined shape and dimensions be within the above-mentioned range.

[0069] The material of the filler (C) is not particularly limited as long as it improves thermal conductivity, and examples thereof include metals, metal oxides, carbides, and nitrides.

[0070] In this specification, the term "metal" refers to an element belonging to Group 1 (excluding H), Groups 2 to 11, Group 12 (excluding Hg), Group 13 (excluding B), Group 14 (excluding C and Si), Group 15 (excluding N, P, As, and Sb), or Group 16 (excluding O, S, Se, Te, and Po) in the periodic table. Examples of metal oxides include magnesium oxide, titanium oxide, zinc oxide, alumina, boehmite, chromium oxide, nickel oxide, copper oxide, zirconium oxide, indium oxide, and composite oxides thereof. Examples of carbides include magnesium carbonate, silicon carbide, and calcium carbonate, and examples of nitrides include boron nitride and aluminum nitride. Among the above materials, titanium oxide, alumina, and aluminum nitride are preferred, with alumina being more preferred. Therefore, alumina having a polyhedral shape is preferred as the filler (C).

[0071] Furthermore, the filler contained in the filler (C) and having the above-mentioned predetermined shape and dimensions may be made of the same metals, metal oxides, carbides, nitrides, etc. as described above, with titanium oxide, alumina, and aluminum nitride being preferred, and alumina being more preferred.

[0072] In this embodiment, the thermal conductivity of the filler (C) is preferably 10 W / (m·K) or more. A thermal conductivity within the above range improves the heat dissipation properties of the protective film. The thermal conductivity of the filler may be 15 W / (m·K) or more, 20 W / (m·K) or more, or even 25 W / (m·K) or more. The upper limit of the thermal conductivity of the filler is, for example, 300 W / (m·K). The thermal conductivity of the filler (C) can be measured, for example, by a laser flash method using a laser flash method thermal constant measurement device (e.g., LFA477 Nanoflash, manufactured by NETZSCH-Geratebau GmbH). The thermal conductivity of the filler (C) is approximately 10 W / (m·K) for titanium oxide, approximately 30 W / (m·K) for alumina, and approximately 285 W / (m·K) for aluminum nitride.

[0073] In this embodiment, the average particle size of the filler (C) is preferably 0.8 μm or more and 5 μm or less. By having the average particle size within the above range, it is easy to satisfy the requirement that the number of fillers having the above-mentioned predetermined shape and dimensions be within the above range.

[0074] The average particle size of the filler (C) may be 1 μm or more and 4 μm or less, 1.3 μm or more and 3.6 μm or less, or 1.6 μm or more and 3 μm or less.

[0075] In this specification, unless otherwise specified, the term "average particle size" refers to the particle size (D50) at an integrated value of 50% in a particle size distribution curve determined by a laser diffraction scattering method.

[0076] Furthermore, in the particle size distribution, which indicates the relationship between frequency and particle size, the particle size distribution of the filler (C) is preferably a unimodal distribution. When multiple powders with different average particle sizes are contained, the particle size distribution is usually a multimodal distribution. Therefore, when the particle size distribution of the filler (C) is a multimodal distribution, multiple fillers with different average particle sizes are contained in the protective film. When multiple fillers with different average particle sizes are contained in the protective film, one filler may hinder contact between the other fillers, making it difficult to form a thick heat conduction path. Therefore, it is preferable that the particle size distribution of the filler (C) be a unimodal distribution so that contact between fillers with similar particle sizes is not hindered. Note that when two or more fillers (e.g., two or more fillers made of different materials) are used as the filler (C), the term "particle size distribution of the filler (C)" used in this specification refers to the particle size distribution of a mixed filler formed by mixing all of the fillers used.

[0077] When the total weight of the composition for the protective film-forming film described below (i.e., the mass of the protective film-forming film) is taken as 100 parts by mass, the content of filler (C) may be 65 parts by mass or more and 85 parts by mass or less, 70 parts by mass or more and 83 parts by mass or less, or 72 parts by mass or more and 82 parts by mass or less.

[0078] By setting the content of the filler within the above range, it is easy to satisfy the requirement that the number of fillers having the above-mentioned predetermined shape and dimensions be within the above range.

[0079] (1.3. Composition for Protective Film-Forming Film) The protective film-forming film is formed using a composition constituting the protective film-forming film (composition for protective film-forming film). That is, the protective film-forming film contains the active ingredient constituting the composition for protective film-forming film. Therefore, the composition for protective film-forming film contains the above-mentioned filler (C).

[0080] In this embodiment, the composition for the protective film-forming film preferably contains, in addition to the above-mentioned filler (C), a polymer component (A) and a curable component (B). By containing such components, the protective film-forming film can be given film-forming properties (film-forming properties) while also being given appropriate tack, and the suitability for attaching the protective film-forming film to the workpiece can be further improved, making it easier to form a protective film with high adhesive reliability.

[0081] The polymer component is a component that can be considered to be formed by a polymerization reaction of a polymerizable compound. The curable component is a component that can undergo a curing (polymerization) reaction. In the present invention, the polymerization reaction also includes a polycondensation reaction.

[0082] In addition, a component contained in the polymer component may also be a curable component. In this embodiment, when the composition for a protective film-forming film contains a component that corresponds to both a polymer component and a curable component, the composition for a protective film-forming film is considered to contain both a polymer component and a curable component.

[0083] (1.3.1. Polymer Component) The polymer component (A) provides the protective film-forming film with film-forming properties (film-forming properties) while imparting appropriate tack, ensuring uniform application of the protective film-forming film to the workpiece. The weight-average molecular weight of the polymer component is usually in the range of 50,000 to 2,000,000, preferably 100,000 to 1,500,000, and particularly preferably 200,000 to 1,000,000. Examples of such polymer components include acrylic resins, urethane resins, phenoxy resins, silicone resins, and saturated polyester resins, with acrylic resins being particularly preferred.

[0084] Examples of acrylic resins include (meth)acrylic acid ester copolymers composed of structural units derived from (meth)acrylic acid ester monomers and (meth)acrylic acid derivatives. The (meth)acrylic acid ester monomers are preferably (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 18 carbon atoms, specifically methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, etc. Examples of (meth)acrylic acid derivatives include (meth)acrylic acid, glycidyl (meth)acrylate, hydroxyethyl (meth)acrylate, etc.

[0085] In this embodiment, it is preferable to introduce a glycidyl group into the acrylic resin using glycidyl methacrylate or the like. The compatibility of the acrylic resin into which the glycidyl group has been introduced with the epoxy resin as the thermosetting component described below is improved, making it easier to form a uniform film, and there is a tendency to more easily obtain a protective film-forming film with stable performance. Furthermore, in this embodiment, it is preferable to introduce a hydroxyl group into the acrylic resin using hydroxyethyl acrylate or the like in order to control the adhesion to the workpiece and the adhesive properties.

[0086] The glass transition temperature of the acrylic resin is preferably −70 to 40° C., −35 to 35° C., −20 to 30° C., −10 to 25° C., or −5 to 20° C. By setting the glass transition temperature of the acrylic resin within the above range, the tack of the protective film-forming film is appropriately increased and the suitability of the protective film-forming film for attachment to a workpiece is improved.

[0087] When an acrylic resin has m types of structural units (m is an integer of 2 or more), the glass transition temperature of the acrylic resin can be calculated as follows: That is, when m types of monomers that derive the structural units in the acrylic resin are each sequentially assigned a unique number from 1 to m and named "monomer m," the glass transition temperature (Tg) of the acrylic resin can be calculated using the Fox formula shown below.

[0088]

number

[0089]

number

[0090] For Tgk, values ​​listed in the Polymer Data Handbook, Adhesive Handbook, or Polymer Handbook can be used. For example, the Tgk of a homopolymer of methyl acrylate is 10°C, that of a homopolymer of n-butyl acrylate is -54°C, that of a homopolymer of 2-hydroxyethyl acrylate is -15°C, and that of a homopolymer of glycidyl methacrylate is 41°C.

[0091] When the total weight of the composition for the protective film-forming film (i.e., the mass of the protective film-forming film) is taken as 100 parts by mass, the content of the polymer component may be 3 to 50 parts by mass, 5 to 40 parts by mass, 8 to 30 parts by mass, 10 to 25 parts by mass, or 11 to 20 parts by mass. By setting the content of the polymer component within the above range, the protective film-forming film is given film-forming properties (film-forming properties) while also being given appropriate tack, making it easier to adjust the suitability for attachment of the protective film-forming film to the workpiece.

[0092] (1.3.2. Thermosetting component) The curable component (B) cures the protective film-forming film to form a hard protective film. As the curable component, a thermosetting component, an energy ray-curable component, or a mixture thereof can be used. As described above, the protective film-forming film is preferably thermosetting, and therefore the curable component is preferably a thermosetting component.

[0093] Preferred examples of thermosetting components include epoxy resins, thermosetting polyimide resins, unsaturated polyester resins, and mixtures thereof. Thermosetting polyimide resin is a general term for low-molecular-weight, low-viscosity monomers or precursor polymers that form polyimide resins by thermal curing. Non-limiting examples of thermosetting polyimide resins are described in, for example, Sen'i Gakkaishi Journal, "Sen'i to Kogyo," Vol. 50, No. 3 (1994), pp. 106-118.

[0094] Epoxy resins as thermosetting components have the property of forming a three-dimensional network structure and a strong coating when heated. Various known epoxy resins are used as such epoxy resins. In this embodiment, the molecular weight (formula weight) of the epoxy resin is preferably 300 or more and less than 50,000, 300 or more and less than 10,000, 300 or more and less than 5,000, or 300 or more and less than 3,000. The epoxy equivalent of the epoxy resin is preferably 50 to 5,000 g / eq, more preferably 100 to 2,000 g / eq, and even more preferably 150 to 1,000 g / eq.

[0095] Specific examples of such epoxy resins include glycidyl ethers of phenols such as bisphenol A, bisphenol F, resorcinol, phenyl novolac, and cresol novolac; glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; glycidyl ethers of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; glycidyl or alkylglycidyl epoxy resins in which the active hydrogen bonded to the nitrogen atom is substituted with a glycidyl group, such as aniline isocyanurate; and so-called alicyclic epoxides in which epoxy groups are introduced by, for example, oxidizing carbon-carbon double bonds within the molecule, such as vinylcyclohexane diepoxide, 3,4-epoxycyclohexylmethyl-3,4-dicyclohexanecarboxylate, and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane. Other epoxy resins that can be used include those having a biphenyl skeleton, a dicyclohexadiene skeleton, a naphthalene skeleton, and the like.

[0096] When a thermosetting component is used as the curing component (B), it is preferable to use a curing agent (D) as an auxiliary. For example, a heat-activated latent epoxy resin curing agent is preferred as a curing agent for epoxy resins. A "heat-activated latent epoxy resin curing agent" is a type of curing agent that is difficult to react with epoxy resins at room temperature (23°C) but becomes activated and reacts with epoxy resins when heated above a certain temperature. Methods for activating heat-activated latent epoxy resin curing agents include generating active species (anions and cations) through a chemical reaction caused by heating; stably dispersing the curing agent in the epoxy resin at room temperature and becoming compatible and dissolved with the epoxy resin at high temperatures to initiate the curing reaction; using a molecular sieve-encapsulated curing agent that dissolves at high temperatures to initiate the curing reaction; and using microcapsules.

[0097] Of the methods exemplified above, a method in which the compound is stably dispersed in the epoxy resin at around room temperature, becomes compatible and dissolved with the epoxy resin at high temperatures, and initiates a curing reaction is preferred.

[0098] Specific examples of heat-activated latent epoxy resin curing agents include various onium salts, dibasic acid dihydrazide compounds, dicyandiamide, amine adduct curing agents, and high-melting-point active hydrogen compounds such as imidazole compounds. These heat-activated latent epoxy resin curing agents can be used alone or in combination of two or more. In this embodiment, dicyandiamide is particularly preferred.

[0099] Phenol resins are also preferred as curing agents for epoxy resins. Examples of phenolic resins that can be used include, but are not limited to, condensates of phenols such as alkylphenols, polyphenols, and naphthol with aldehydes. Specific examples include phenol novolac resins, o-cresol novolac resins, p-cresol novolac resins, t-butylphenol novolac resins, dicyclopentadiene cresol resins, polyparavinylphenol resins, bisphenol A novolac resins, and modified versions of these resins.

[0100] The phenolic hydroxyl groups contained in these phenolic resins can easily undergo addition reaction with the epoxy groups of the epoxy resins by heating to form a cured product with high impact resistance.

[0101] The content of the curing agent (D) may be 0.5 to 100 parts by mass, 1 to 30 parts by mass, 2 to 15 parts by mass, or 2.5 to 10 parts by mass relative to 100 parts by mass of the curable component (B). By setting the content of the curing agent (D) within the above range, it is easy to obtain the performance of protecting the workpiece as a protective film.

[0102] When dicyandiamide is used as the curing agent (D), it is preferable to use a curing accelerator (E) in combination. Examples of the curing accelerator include imidazoles (imidazoles in which one or more hydrogen atoms are substituted with groups other than hydrogen atoms), such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Among these, 2-phenyl-4,5-dihydroxymethylimidazole is particularly preferable.

[0103] The content of the curing accelerator (E) may be 0.5 to 20 parts by mass, 1 to 15 parts by mass, or 2 to 10 parts by mass relative to 100 parts by mass of the curable component (B). By setting the content of the curing accelerator (E) within the above range, it is easy to obtain the performance of protecting the workpiece as a protective film.

[0104] When the total weight of the composition for the protective film-forming film (i.e., the mass of the protective film-forming film) is taken as 100 parts by mass, the total content of the thermosetting component and the curing agent may be 3 to 50 parts by mass, 5 to 40 parts by mass, 8 to 30 parts by mass, 10 to 25 parts by mass, or 11 to 20 parts by mass. When the thermosetting component and the curing agent are blended in such a ratio, the protective film is likely to have the ability to protect the workpiece.

[0105] In particular, when the thermosetting component is an epoxy resin, the content of the epoxy resin may be 3 parts by mass or more, 5 parts by mass or more, or 8 parts by mass or more when the total weight of the composition for the protective film-forming film (i.e., the mass of the protective film-forming film) is 100 parts by mass. By including a predetermined amount or more of the epoxy resin, good curability is likely to be obtained.

[0106] (1.3.3. Energy ray-curable component) When the curable component (B) is an energy ray-curable component, the energy ray-curable component is preferably uncured and has adhesive properties, and more preferably uncured and has adhesive properties.

[0107] The energy ray curable component is a component that is cured by irradiation with energy rays, and is also a component that imparts film-forming properties, flexibility, and the like to the protective film-forming film.

[0108] The energy ray-curable component is preferably, for example, a compound having an energy ray-curable group, and examples of such compounds include known compounds.

[0109] (1.3.4. Colorants) The protective film-forming film may contain a colorant (F), which conceals the back surface of the workpiece singulated, such as a chip, thereby blocking various electromagnetic waves generated within electronic devices and reducing malfunction of the workpiece singulated.

[0110] As the colorant (F), for example, known colorants such as inorganic pigments, organic pigments, organic dyes, etc. In this embodiment, inorganic pigments are preferred.

[0111] Examples of inorganic pigments include carbon black, cobalt-based pigments, iron-based pigments, chromium-based pigments, titanium-based pigments, vanadium-based pigments, zirconium-based pigments, molybdenum-based pigments, ruthenium-based pigments, platinum-based pigments, ITO (indium tin oxide)-based pigments, and ATO (antimony tin oxide)-based pigments. Among these, carbon black is particularly preferred. Carbon black can block electromagnetic waves over a wide wavelength range.

[0112] The amount of the colorant blended in the protective film-forming film also varies depending on the thickness of the protective film-forming film. For example, when the thickness of the protective film-forming film is 25 μm, the content of the colorant may be 0.2 to 5 parts by mass or 0.5 to 3 parts by mass when the total weight of the composition for the protective film-forming film (i.e., the mass of the protective film-forming film) is 100 parts by mass.

[0113] The average particle size of the inorganic pigment is preferably 1 to 500 nm, particularly preferably 3 to 100 nm, and further preferably 5 to 50 nm. When the average particle size of the inorganic pigment is within the above range, it is easy to control the light transmittance within the desired range.

[0114] (1.3.5. Coupling Agents) The protective film-forming film preferably contains a coupling agent (G). By containing a coupling agent, after the protective film-forming film is cured, the adhesion between the protective film and the workpiece can be further improved without impairing the heat resistance of the protective film, and the water resistance (moist heat resistance) can be improved. As the coupling agent, a silane coupling agent is preferred from the viewpoint of its versatility and cost benefits.

[0115] Examples of silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-(methacryloxypropyl)trimethoxysilane, γ-aminopropyltrimethoxysilane, N-6-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-6-(aminoethyl)-γ-aminopropylmethyldiethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfane, methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriacetoxysilane, and imidazolesilane. These may be used alone or in combination of two or more.

[0116] When the total weight of the composition for the protective film-forming film (i.e., the mass of the protective film-forming film) is 100 parts by mass, the content of the coupling agent is preferably 0.005 to 1 part by mass, 0.01 to 0.5 parts by mass, 0.015 to 0.3 parts by mass, or 0.02 to 0.1 parts by mass.

[0117] (1.3.6. Other Additives) The composition for a protective film-forming film may contain, as other additives, for example, a photopolymerization initiator, an ultraviolet absorber, a crosslinking agent, a plasticizer, an antistatic agent, an antioxidant, a gettering agent, a tackifier, a release agent, etc., within a range that does not impair the effects of the present invention. When the total weight of the composition for a protective film-forming film (i.e., the mass of the protective film-forming film) is taken as 100 parts by mass, the content of other additives may be less than 4 parts by mass or less than 2 parts by mass.

[0118] (2. Protective film forming sheet and protective film forming composite sheet) The protective film-forming film is usually used in the form of a protective film-forming sheet or a protective film-forming composite sheet. The protective film-forming sheet is used to form a protective film on the workpiece or an individual piece of the workpiece (singular workpiece) by attaching the protective film-forming film to the workpiece. The protective film-forming composite sheet is attached to the workpiece to hold the workpiece when processing the workpiece, and is also used to form a protective film on the workpiece or an individual piece of the workpiece (singular workpiece) by attaching the protective film-forming film to the workpiece.

[0119] The protective film-forming sheet 10 has the configuration shown in Fig. 3. The protective film-forming film 1 has two opposing main surfaces 1a and 1b. A first release film 21 that supports the protective film-forming film 1 is disposed on the main surface 1a, and a second release film 22 that supports the protective film-forming film 10 is disposed on the main surface 1b.

[0120] When release films are formed on both main surfaces of the protective film-forming film as shown in Figure 3, it is preferable to increase the release strength of one release film to make it a heavy release type release film, and to decrease the release strength of the other release film to make it a light release type release film.

[0121] The protective film forming sheet is preferably a long sheet capable of forming a plurality of protective film forming films to be attached to the workpiece. The protective film forming sheet is also preferably a sheet roll obtained by winding up the long sheet. The protective film forming sheet may also be a single sheet obtained by cutting the long protective film forming sheet to form a single protective film forming film to be attached to the workpiece. The protective film forming sheet may also be configured to not have either the first release film or the second release film.

[0122] The composite sheet for forming a protective film has a protective film-forming film and a support sheet that supports the protective film-forming film. The support sheet is other than a release film and has a configuration that can support the protective film-forming film. An example of the support sheet is a pressure-sensitive adhesive sheet having a substrate and a pressure-sensitive adhesive layer.

[0123] Specifically, as shown in Fig. 4, the composite sheet 11 for forming a protective film has a configuration including an adhesive sheet 40 formed by laminating an adhesive layer 42 on one surface of a substrate 41 as a support sheet, a protective film-forming film 1 laminated so that its main surface 1a is in contact with the adhesive layer 42 of the adhesive sheet 40, and a release film 23 arranged on the main surface 1b of the protective film-forming film 1. Furthermore, a jig adhesive layer (not shown) may be arranged on the peripheral edge of the protective film-forming film 1. The jig adhesive layer is a layer for adhering the composite sheet for forming a protective film to a jig such as a ring frame.

[0124] It is preferable that first release film 21, second release film 22, and release film 23 are all release films formed by forming a silicone-based release agent layer on one side of a polyethylene terephthalate (PET) film.

[0125] (3. Production of protective film-forming film) The protective film-forming film can be produced by a known method. For example, the protective film-forming film can be produced using the above-mentioned composition for a protective film-forming film or a composition obtained by diluting the composition for a protective film-forming film with a solvent (these compositions are referred to as "coating agents"). The coating agent is prepared by mixing the components constituting the composition for a protective film-forming film by a known method.

[0126] The obtained coating agent is applied to the release surface of the first release film using a coating machine such as a roll coater, a knife coater, a roll knife coater, an air knife coater, a die coater, a bar coater, a gravure coater, a curtain coater, etc. If necessary, the solvent in the coating agent is removed by drying to form a protective film-forming film on the first release film.

[0127] When producing a sheet for forming a protective film, it is obtained by further laminating the release surface of a second release film to the exposed surface of the protective film-forming film formed on the first release film.

[0128] Furthermore, when manufacturing a composite sheet for forming a protective film, a laminate including a pressure-sensitive adhesive sheet and the above-mentioned sheet for forming a protective film can be used. The pressure-sensitive adhesive sheet can be manufactured by a known method. For example, a composition constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is prepared, applied to the release surface of a third release film, and dried as necessary to form a pressure-sensitive adhesive layer on the third release film. Next, a substrate is attached to the exposed pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive sheet in which the third release film is disposed on the pressure-sensitive adhesive layer.

[0129] Next, the second release film of the sheet for forming a protective film is peeled off, and the third release film of the pressure-sensitive adhesive sheet is peeled off, and the protective film-forming film and the pressure-sensitive adhesive layer are bonded together to obtain a composite sheet for forming a protective film. If necessary, after peeling off the first release film, a jig pressure-sensitive adhesive layer is formed on the peripheral portion of the exposed pressure-sensitive adhesive layer.

[0130] The protective film-forming film may be cut out to the size of the adherend (for example, a wafer) to which it is to be attached or to a size close to the size of the adherend, as needed.

[0131] (4. Method for manufacturing individual workpieces with protective film) The method for manufacturing individual workpieces with protective films according to this embodiment includes at least the following steps 1 to 3. Step 1: A step of attaching the above-mentioned protective film-forming film to the workpiece Process 2: A process of hardening the protective film that has been applied after the process of applying it to the workpiece. Step 3: A step of obtaining a plurality of individual workpieces with the protective film or protective film-forming film attached thereto after the step of attaching the protective film or protective film-forming film to the workpiece.

[0132] As is clear from the above, step 2 may be performed before step 3 or after step 3, provided that it is performed after step 1.

[0133] The method for producing the individual workpieces with the protective film, which includes the above steps 1 to 3, will be described with reference to FIGS. 5A, 5B and 6. FIG.

[0134] Below, as an example of a method for manufacturing a protective film-coated workpiece using a protective film-forming sheet or a protective film-forming composite sheet according to this embodiment, a method for manufacturing a protective film-coated chip obtained by processing a wafer to which a protective film-forming film is attached will be described.

[0135] 5A, the protective film-forming film 1 of the sheet 10 for forming a protective film from which the second release film 22 has been removed is attached to the back surface of the wafer 100 (step 1). The first release film 21 may be peeled off after step 1, if necessary.

[0136] 5B, the protective film-forming film 1 of the composite sheet 11 for forming a protective film is attached to the back surface of the wafer 100 (step 1). At this time, the jig adhesive layer 50 provided on the outer periphery of the protective film-forming film 1 may be attached and fixed to a ring frame 150. The surface of the protective film-forming film 1 opposite to the surface in contact with the adhesive layer 42 is attached to the back surface of the wafer 100. When attaching the protective film-forming film 1 to the wafer 100, the protective film-forming film 1 may be heated, if desired, to exhibit adhesiveness.

[0137] Thereafter, the attached protective film-forming film 1 is cured to form a protective film (step 2), thereby obtaining a wafer with a protective film. When the protective film-forming film is thermosetting, the protective film-forming film may be heated at a predetermined temperature for an appropriate time. For example, the heating temperature during thermal curing of the protective film-forming film may be 100 to 200°C, 110 to 170°C, or 120 to 150°C. The heating time during thermal curing may be 0.5 to 5 hours, 0.5 to 4 hours, or 1 to 3 hours. The protective film obtained by thermal curing is preferably slowly cooled to room temperature. The method of slow cooling is not particularly limited, and the film may be allowed to cool naturally. When the protective film-forming film is energy ray-curable, energy rays may be incident from the pressure-sensitive adhesive sheet or release film side.

[0138] The protective film-forming film may be cured after the singulation (for example, dicing) step, or the chip with the protective film-forming film may be picked up from the adhesive sheet and then the protective film-forming film may be cured.

[0139] Next, if necessary, the protective film-formed wafer 100 and ring frame 150 obtained by curing the protective film-formed film 1 shown in Fig. 5A are attached to a known dicing sheet 80, and the protective film-formed wafer 100 is divided into individual pieces (for example, diced) to obtain chips (protective film-formed chips 101) having the protective film 2 shown in Fig. 6. Alternatively, the wafer 100 with the protective film-formed film 1 and ring frame 150 shown in Fig. 5A are attached to a known dicing sheet 80, and the protective film-formed wafer 100 is divided into individual pieces (for example, diced) to obtain chips having the protective film-formed film 1 (chips with the protective film-formed film) (step 3).

[0140] Furthermore, the protective film-containing wafer 100 obtained by curing the protective film-forming film 1 shown in Fig. 5B is divided into individual pieces (e.g., diced) by a known method to obtain chips (protective film-containing chips 101) having the protective film 2 shown in Fig. 6. Alternatively, the wafer 100 with the protective film-forming film 1 shown in Fig. 5B is divided into individual pieces (e.g., diced) to obtain chips having the protective film-forming film (chips with the protective film-forming film) (step 3).

[0141] The obtained chip with the protective film is picked up and mounted on a substrate, etc. The chip with the protective film-forming film is mounted on a substrate, etc. after the protective film-forming film is cured.

[0142] The chip with the protective film thus obtained has the number of fillers in the protective film having the above-mentioned predetermined shape and dimensions satisfying the above-mentioned relationship, thereby achieving both the heat dissipation properties and adhesive reliability of the protective film.

[0143] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified in various ways within the scope of the present invention. [Example]

[0144] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0145] (Preparation of protective film forming sheet) A sheet for forming a protective film including a thermosetting protective film-forming film was prepared as follows using a coating agent including the composition for forming a protective film described below.

[0146] (Coating agent containing composition for protective film-forming film) The following components were mixed in the mass blending ratio (solid content equivalent) shown in Table 1 and diluted with methyl ethyl ketone to a solid content concentration of 65 mass % to prepare a coating agent containing a composition for a protective film-forming film. (A) Polymer component (A-1) A (meth)acrylic acid ester copolymer obtained by copolymerizing 10 parts by mass of n-butyl acrylate, 70 parts by mass of methyl acrylate, 5 parts by mass of glycidyl methacrylate, and 15 parts by mass of 2-hydroxyethyl acrylate (weight average molecular weight: 400,000, glass transition temperature: -1°C). (A-2) (Meth)acrylic acid ester copolymer obtained by copolymerizing 85 parts by mass of methyl acrylate and 15 parts by mass of 2-hydroxyethyl acrylate (weight average molecular weight: 400,000, glass transition temperature: 6°C) (B) Curing component (thermosetting component) (B-1) Bisphenol A epoxy resin (Mitsubishi Chemical Corporation, jER828, epoxy equivalent 184-194g / eq) (B-2) Dicyclopentadiene epoxy resin (DIC Corporation, Epicron HP-7200HH, epoxy equivalent 274-286g / eq) (C) Filler (C-1) Alumina filler (Sumitomo Chemical Co., Ltd., AA-1.5, polyhedral shape, average particle size 1.7 μm) (C-2) Alumina filler (Sumitomo Chemical Co., Ltd., AA-2, polyhedral shape, average particle size 2.2 μm) (C-3) Alumina filler (Sumitomo Chemical Co., Ltd., AA-3, polyhedral shape, average particle size 3.5 μm) (C-4) Alumina filler (Sumitomo Chemical Co., Ltd., AA-10, polyhedral shape, average particle size 13.5 μm) (C-5) Alumina filler (Sumitomo Chemical Co., Ltd., AA-03F, polyhedral shape, average particle size 0.26 μm) (C-6) Alumina filler (Resonac, CB-P02, spherical, average particle size 3 μm) (D) Hardener (D-1) Dicyandiamide (DICY7, manufactured by Mitsubishi Chemical Corporation) (E) Curing accelerator (E-1) 2-phenyl-4,5-dihydroxymethylimidazole (Curezol 2PHZ, manufactured by Shikoku Chemicals Corporation) (F) Colorant (F-1) Carbon black (Mitsubishi Chemical Corporation, MA-600B, average particle size 28 nm) (G) Coupling agent (G-1) Silane coupling agent (Shinetetsu Chemical Co., Ltd., KBM-403)

[0147] [Table 1]

[0148] A first release film (SP-PET502150, manufactured by Lintec Corporation) was prepared, which consisted of a 50 μm-thick polyethylene terephthalate (PET) film with a silicone-based release agent layer formed on one side. Also, a second release film (SP-PET381031, manufactured by Lintec Corporation) was prepared, which consisted of a 38 μm-thick polyethylene terephthalate (PET) film with a silicone-based release agent layer formed on one side.

[0149] The coating agent containing each prepared protective film-forming film composition was applied to the release-treated surface of a first release film and dried at 100°C for 2 minutes to form a protective film-forming film with a thickness of 25 μm. Subsequently, the release-treated surface of the prepared second release film was attached to the surface of the protective film-forming film to obtain a protective film-forming sheet in which release films were arranged on both sides of the protective film-forming film. The attachment conditions were a temperature of 60°C, a pressure of 0.4 MPa, and a speed of 1 m / min.

[0150] The obtained sheet for forming a protective film was subjected to the following measurements and evaluations.

[0151] (Number of fillers having the above-mentioned predetermined shape and dimensions) The resulting protective film-forming sheet was placed in a 140°C environment for 2 hours to completely cure the protective film-forming film, and the first and second release films were removed. To prepare a sample with a cross section parallel to the thickness direction of the cured protective film-forming film, a cover glass, adhesive, cured protective film-forming film, adhesive, and cover glass were stacked in this order on a tungsten sample stage and allowed to stand for 24 hours to completely cure the adhesive (a sample for ion milling). To facilitate obtaining a cross section suitable for observation by ion milling, the edge of the ion milling sample was placed so that it protruded 1 mm from the tungsten sample stage. The adhesive used was "Bondquick 5" manufactured by Konishi Co., Ltd., and the cover glass was "Square Cover Glass 18 x 18 No. 1" manufactured by Matsunami Glass Industry Co., Ltd.

[0152] The prepared sample was placed in a cross-section polisher (manufactured by JEOL Ltd., product name "SM-09010 Cross-Section Polisher"), and a sample having a cross section parallel to the thickness direction of the cured protective film-forming film was prepared by ion milling under the following processing conditions. (Processing conditions) Inlet gas: Argon (adjust the amount introduced so that the current is 80% of the maximum output) Ion acceleration voltage: 4.1 kV Sample swing: ±30° Processing time: 48 hours (intermittent processing at 10-second intervals)

[0153] Cross-sectional specimens of the obtained samples were observed using an SEM (ZEISS Microscopy, product name "ZEISS GeminiSEM 560") and still images were taken to obtain information on the boundaries between the filler and materials other than the filler. Furthermore, because the filler was made of alumina, a mapping image of aluminum was obtained using an energy dispersive X-ray spectrometer (EDX). Note that EDX mapping was performed by applying a voltage of 15 kV for a period of time (5 to 40 minutes) that was sufficient to determine whether each region represented by the boundaries in the SEM image was a region indicating the filler (alumina).

[0154] By applying the information on the mapping image obtained by EDX to the boundary information in the SEM image taken above, the positional relationship and boundaries of the cross section of the filler and other parts in the SEM image taken above were identified, and an SEM image was created in which the shape and dimensions of the cross section of the filler could be identified. Next, using image processing software (GIMP), the created SEM image was anti-aliased to binarize the cross section of the filler and other parts by setting the brightness of pixels belonging to the area that makes up the cross section of the filler to 255 and the brightness of pixels belonging to other parts to 40, and then the thickness of the protective film-forming film after curing was taken as one side, and the area was 625 μm 2 A rectangular area RA was extracted.

[0155] In the extracted rectangular region RA in the SEM image after the anti-aliasing process, the maximum length of the cross section of each filler present within the rectangular region RA was measured. For fillers present within the rectangular region RA whose maximum cross-sectional length exceeded 0.5 μm, a minimum inclusive circle containing all of the perimeter lines of the filler's cross section was drawn for each filler's cross section. The total number of pixels belonging to the region that constitutes the minimum inclusive circle was taken as the area of ​​the minimum inclusive circle, and the total number of pixels belonging to the region that constitutes the filler for which the minimum inclusive circle was drawn was taken as the cross-sectional area of ​​the filler, and "(cross-sectional area of ​​filler) / (area of ​​the minimum inclusive circle containing all of the perimeter lines of the filler's cross section)" was calculated. This operation was performed for all fillers present within the rectangular region RA whose maximum cross-sectional length exceeded 0.5 μm. After that, the number of fillers for which "(cross-sectional area of ​​filler) / (area of ​​the minimum inclusive circle containing all of the perimeter lines of the filler's cross section)" was found to be between 0.6 and 0.9, and the unit area (1 μm 2 ) Number of pieces (pieces / μm 2 The results are shown in Table 2.

[0156] If the area of ​​the minimum inclusive circle of one filler to be calculated includes fillers other than the one filler to be calculated, the lightness of the fillers other than the filler to be calculated is temporarily set to 40, and the area of ​​the minimum inclusive circle is calculated. Also, if the outer periphery of a filler overlaps with any side of the rectangular area RA, that filler is not counted even if it corresponds to a filler having the above-mentioned specified shape and dimensions.

[0157] (Ratio of cross-sectional area occupied by filler (C)) In the extracted rectangular region RA in the SEM image after the above anti-aliasing processing, the total number of pixels belonging to the rectangular region RA was taken as the area of ​​the rectangular region RA, and the total number of pixels belonging to the area constituting the cross-section of all fillers (C) present within the rectangular region RA was taken as the area occupied by the cross-section of the filler (C), and the ratio of the total area occupied by the cross-section of the filler (C) in the rectangular region RA was calculated as (100 x (total area occupied by the cross-section of filler (C)) / (area of ​​rectangular region RA)) (%). The results are shown in Table 2.

[0158] (Thermal conductivity of the protective film after curing) The obtained protective film-forming sheet was placed in a 140°C environment for 2 hours to completely cure the protective film-forming film, and the first and second release films were removed. Next, the thermal diffusivity of the cured protective film-forming film was measured using a thermal diffusivity / thermal conductivity measuring device (manufactured by i-Phase Corporation, product name "ai-Phase Mobile 1u") in an environment of 23°C and 50% relative humidity. Measurements were performed at 10 locations on the surface of the cured protective film-forming film. Of the 10 measurement data obtained, the smallest data point and the five largest data points were excluded, and the average of the remaining four data points was used as the thermal diffusivity of the cured protective film-forming film. Using the obtained thermal diffusivity, the thermal conductivity of the cured protective film-forming film was calculated using the following formula. The specific heat of the cured protective film-forming film alone was calculated using the DSC method, and the density was calculated using the Archimedes method. In this example, samples with a thermal conductivity of 3.0 W / (m·K) or higher were considered to be good. The results are shown in Table 2. Calculation formula: Thermal conductivity (W / (m·K)) = Thermal diffusivity × Density × Specific heat

[0159] (Utilization efficiency of filler (C)) Using the cross-sectional area ratio of the filler (C) obtained above and the thermal conductivity of the protective film-forming film after curing, the utilization efficiency of the filler (C) (thermal conductivity of the protective film-forming film after curing / cross-sectional area ratio of the filler (C)) was calculated. In this example, samples with a utilization efficiency of 0.057 or more were judged to be good. The results are shown in Table 2.

[0160] (Adhesion reliability of protective film after curing) The second release film of the obtained protective film-forming sheet was peeled off, and the silicon wafer was attached to the polished surface of a #2000 polished silicon wafer (diameter: 200 mm, thickness: 280 μm) using a tape mounter (manufactured by Lintec Corporation, product name "Adwill RAD-3600 F / 12") while heated to 70°C, thereby producing a silicon wafer with a protective film-forming film.

[0161] The first release film of the silicon wafer with the protective film-forming film thus prepared was peeled off, and the silicon wafer was placed in an environment of 140°C for 2 hours to completely harden the protective film-forming film, thereby producing a silicon wafer with a protective film (cured protective film-forming film).

[0162] Dicing tape (manufactured by Lintec Corporation, product name "Adwill D-676H") was attached to the exposed protective film side of the prepared silicon wafer with protective film, and the silicon wafer was diced into 3 mm x 3 mm size using a dicing device (manufactured by Disco Corporation, product name "DFD651") to obtain chips with protective film (protective film-forming film after curing).

[0163] The 25 chips with protective film thus prepared were placed in a thermal shock chamber (manufactured by ESPEC, product name "TSE-11A"), and a cycle of "holding at -65°C for 10 minutes, then holding at 150°C for 10 minutes" was repeated 1,000 times.

[0164] The cross section of the protective film-coated chip removed from the thermal shock chamber was then observed using a scanning ultrasonic flaw detector (Hitachi Construction Machinery Finetech Co., Ltd., product name "Hye-Focus") to check for any lifting, peeling, or cracks in the protective film at the joint between the chip and the protective film.

[0165] Chips with protective films in which lifting, peeling, or cracks of the protective film were observed were judged to be "NG." Table 2 shows the number of chips with protective films judged to be "NG" out of 25 chips with protective films observed. In this example, samples in which the number of chips judged to be NG was 10 or less were judged to be good.

[0166] [Table 2]

[0167] From Table 2, it was confirmed that when a filler that satisfies the above-mentioned relationship is used, the heat dissipation properties of the protective film and the adhesive reliability can both be achieved. [Explanation of symbols]

[0168] 1...Protective film forming film 2...Protective film-forming film after hardening (protective film) 3…Filling material 10...Protective film forming sheet 11...Composite sheet for forming protective film

Claims

1. A curable protective film-forming film containing a filler, In a cross section parallel to the thickness direction of the cured protective film-forming film, the length of one side is the same as the thickness in the thickness direction, and the area is 625 μm 2 When observing a rectangular region in which the ratio of the cross-sectional area of ​​the filler to the area of ​​the smallest encompassing circle that contains all of the outer peripheries of the cross section of the filler is 0.6 or more and 0.9 or less, and the number of fillers whose maximum cross-sectional length exceeds 0.5 μm is 0.08 pieces / μm 2 0.80 pieces / μm or more 2 The following protective film-forming films exist:

2. The protective film according to claim 1, wherein the protective film comprises a curable component and a polymer component.

3. 3. The protective film according to claim 1, wherein the filler has an average particle size of 0.8 μm or more and 5 μm or less.

4. 3. The protective film-forming film according to claim 1, wherein the particle size distribution of the filler is a unimodal distribution.

5. The protective film-forming film according to claim 1 or 2, wherein the thickness of the protective film-forming film is less than 50 μm.

6. 3. The protective film according to claim 1, wherein the filler is made of alumina.

7. A protective film-forming film as described in claim 1 or 2, wherein when the area of ​​the rectangular region is 100%, the ratio of the total area occupied by the cross section of the filler in the rectangular region is 30% or more and 70% or less.

8. A step of attaching the protective film-forming film according to claim 1 or 2 to a workpiece; a step of curing the protective film-forming film after the step of attaching it to the workpiece; A method for manufacturing a workpiece with a protective film, comprising: a step of singulating the workpiece with the protective film or protective film-forming film attached thereto after the step of attaching the protective film or protective film-forming film to the workpiece, thereby obtaining a plurality of workpieces with the protective film or protective film-forming film attached thereto.

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