Method for manufacturing protective sheet, electronic component, and glass piece constituting display surface of display device

Abstract

This protective sheet is to be bonded to: a surface to be protected of an electronic component having the surface to be protected; one surface of a piece of glass constituting a display surface of a display device; or one surface of a glass plate for obtaining the piece of glass. The protective sheet comprises a protective layer that is to be bonded to: the surface to be protected of the electronic component; the one surface of the piece of glass; or the one surface of the glass plate. The protective layer is constituted from either a water-soluble resin composition or a curable resin composition the adhesive strength of which is reduced via a curing reaction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2021-164163 and Japanese Patent Application No. 2022-063384, the disclosures of which are incorporated herein by reference. [Technical Field]

[0002] The present invention relates to a protective sheet. More specifically, the present invention relates to a protective sheet that is attached to a surface to be protected of an electronic component having the surface to be protected, a protective sheet that is attached to one surface of a glass piece that constitutes the display surface of a display device, and a protective sheet that is attached to a glass plate from which the glass piece is obtained. The present invention also relates to a method for manufacturing an electronic component and a method for manufacturing a glass piece that constitutes a display surface of a display device. [Background technology]

[0003] 2. Description of the Related Art Semiconductor chips are conventionally known as electronic components. Such semiconductor chips are usually obtained by dicing a semiconductor wafer into individual pieces (for example, Patent Document 1 below). The following Patent Document 1 discloses a semiconductor wafer that includes a semiconductor wafer body and a plurality of paired electrode portions on both sides of the semiconductor wafer body, and both sides of the semiconductor wafer body are circuit formation surfaces. The circuit formation surface typically has multiple circuits formed thereon, each including elements such as transistors and wiring, and the semiconductor wafer body is provided with at least one pair of electrode portions for each circuit on the circuit formation surface. Then, by dicing such a semiconductor wafer, a plurality of semiconductor chips are obtained, each of which includes a semiconductor chip body and at least one circuit and at least one pair of electrodes on both sides of the semiconductor chip body.

[0004] As shown in Patent Document 1 below, the above-mentioned semiconductor chip is used by attaching the electrode portion attached to one surface (hereinafter also referred to as the first semiconductor chip electrode portion) to the electrode portion of a circuit board (hereinafter also referred to as the circuit board electrode portion), and attaching the electrode portion attached to the other surface (hereinafter also referred to as the second semiconductor chip electrode portion) to the first semiconductor chip electrode portion of another semiconductor chip.

[0005] Also known as electronic components are wafer level packages (WLPs) and image sensor packages. The wafer level package includes a circuit board and a plurality of semiconductor packages mounted on the circuit board. The wafer-level package described above is usually diced or otherwise separated into individual semiconductor packages. The image sensor package also includes a sensor chip body having a circuit formed on one surface thereof, and a piece of glass (cover glass) laminated on one surface (the surface on which the circuit is formed) of the sensor chip body via an adhesive layer made of adhesive, glass frit, or the like. The image sensor package is typically obtained by dicing an image sensor package laminate comprising a sensor wafer body having a plurality of circuits formed on one surface thereof, and a glass plate having approximately the same dimensions as the sensor wafer body in a planar view and laminated on one surface (the surface on which the plurality of circuits are formed) of the sensor wafer body via an adhesive layer made of adhesive, glass frit, or the like, into individual image sensor packages each including at least one circuit.

[0006] Furthermore, it is also known to divide a single glass plate into a plurality of glass pieces by dicing or the like in order to obtain glass pieces for forming the display surface of a display device. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-170754 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, when a semiconductor wafer is diced to be cut into a plurality of individual semiconductor chips as described above, a portion of the semiconductor wafer near the cut portion may be pulverized, resulting in the generation of minute foreign matter. In addition, such minute foreign matter may also be generated when the wafer-level package is diced into individual semiconductor packages, when the image sensor package laminate is diced into individual image sensor packages, and when a single glass plate is diced into multiple glass plates.

[0009] When such minute foreign matter is generated, it may adhere to the surfaces of electronic components such as multiple semiconductor chips, multiple semiconductor packages, multiple image sensor packages, or the surfaces of multiple pieces of glass, and remain on these surfaces in large numbers.

[0010] Furthermore, if a large number of such minute foreign particles remain on the surfaces of the plurality of semiconductor chips, this is undesirable because it may reduce the operational reliability of the circuits formed on the surfaces of each of the plurality of semiconductor chips.

[0011] Furthermore, when each of the surfaces of the multiple semiconductor packages is composed of one surface of a glass piece, if a large number of the microscopic foreign matter remains on the surface of each of the multiple semiconductor packages, the remaining microscopic foreign matter will cause the transmittance of the glass piece to change in each of the multiple semiconductor packages. Furthermore, even if a large number of such minute foreign matter remains on the surfaces of the multiple image sensor packages (surfaces of the glass pieces) and the surfaces of the multiple glass pieces, the transmittance of the glass pieces will change due to the remaining minute foreign matter.

[0012] Here, it is necessary to inspect the internal wiring connections of a plurality of semiconductor packages before shipping. For this inspection, it is necessary to capture an image of the inside of the semiconductor package through a piece of glass using a camera or the like. However, if the transmittance of the glass piece changes as described above, there is a concern that it will not be possible to obtain images of multiple semiconductor packages that are clear enough to check the internal wiring connections.

[0013] Furthermore, although the image sensor package is used as an imaging element in a camera or the like, if the transmittance of the glass piece changes as described above, there is a concern that the object to be imaged may not be captured clearly enough.

[0014] Furthermore, when the display surface of a display device is constructed using glass pieces whose transmittance has changed as described above, there is a concern that a clear image may not be displayed on the display surface of the display device.

[0015] Furthermore, in a semiconductor chip such as that described in Patent Document 1, when the first semiconductor chip electrode portion and the second semiconductor chip electrode portion are attached, for example, so as to be flush with the respective surfaces of the semiconductor chip, if a large number of such minute foreign matter remains on the surface as described above, the presence of such minute foreign matter may cause insufficient adhesion of the first semiconductor chip electrode portion of one semiconductor chip to the circuit board electrode portion, or insufficient adhesion of the second semiconductor chip electrode portion of one semiconductor chip to the first semiconductor chip electrode portion of another semiconductor chip. In such a case, poor bonding occurs between the electrodes, and sufficient electrical reliability cannot be obtained, which is undesirable.

[0016] The above-mentioned problems are not limited to specific semiconductor chips, but are common to all semiconductor chips. The above-mentioned problems also occur in electronic components other than semiconductor chips that are obtained by processes involving cutting, such as dicing. For example, the same problem as above occurs when a connected circuit board formed by connecting a plurality of circuit boards is divided into individual circuit boards.

[0017] However, it is difficult to say that sufficient research has been done yet on how to prevent a large number of minute foreign particles from remaining on the surface of an electronic component that should be protected (hereinafter also referred to as the surface to be protected). Furthermore, it is difficult to say that sufficient research has been conducted yet on how to prevent a large number of minute foreign particles from remaining on one surface of a glass piece that constitutes the display screen of a display device.

[0018] Therefore, an object of the present invention is to provide a protective sheet that can prevent a large number of fine foreign objects from remaining on the surface to be protected of an electronic component having such a surface, and on one surface of a piece of glass that constitutes the display surface of a display device. Another object of the present invention is to provide a method for manufacturing an electronic component and a method for manufacturing a glass piece that constitutes the display surface of a display device, using the above-mentioned protective sheet. [Means for solving the problem]

[0019] The protective sheet according to the present invention comprises: A protective sheet that is attached to a surface to be protected of an electronic component having a surface to be protected, one surface of a glass piece that constitutes a display surface of a display device, or one surface of a glass plate from which the glass piece is obtained, a protective layer attached to the surface to be protected of the electronic component, one surface of the glass piece, or one surface of the glass plate; The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesiveness decreases upon curing reaction.

[0020] The method for manufacturing an electronic component according to the present invention includes the steps of: a protective sheet attachment step of attaching a protective sheet to a connected assembly of electronic components in which a plurality of electronic components each having a surface to be protected are connected with the surfaces to be protected facing in the same direction, so as to protect the surfaces to be protected of each of the plurality of electronic components; a connecting body dividing step of dividing the connecting body of electronic components to which the protective sheet is attached at intervals in a planar direction to obtain a plurality of the divided electronic components to which the protective sheet is attached; a protective sheet removing step of removing the protective sheet separated from each of the plurality of electronic components, the protective sheet includes a protective layer attached to the surface to be protected, The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesive strength decreases upon curing reaction.

[0021] A method for manufacturing a glass piece constituting a display surface of a display device according to the present invention includes the steps of: a protective sheet attachment step of attaching a protective sheet to protect one surface of the glass plate from which the glass pieces constituting the display surface of the display device are obtained; a glass plate dividing step of dividing the glass plate with the protective sheet attached thereto at intervals in the surface direction to obtain a plurality of glass pieces with the protective sheet attached thereto; a protective sheet removing step of removing the protective sheet separated from each of the plurality of glass pieces, the protective sheet includes a protective layer attached to one surface of the glass plate or one surface of the glass piece, The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesive strength decreases upon curing reaction. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of a wafer-level package. [Figure 2A] FIG. 2 is a schematic cross-sectional view showing the configuration of an image sensor package. [Figure 2B]FIG. 2 is a schematic cross-sectional view showing the configuration of a laminate for an image sensor package. [Figure 3] 1 is a schematic cross-sectional view showing the configuration of a protective sheet according to one embodiment of the present invention. [Figure 4A] FIG. 2 is a cross-sectional view schematically showing an example of a mode in which the protective sheet according to the present embodiment is attached to the surface of a semiconductor chip. [Figure 4B] FIG. 10 is a cross-sectional view schematically showing another example of the manner in which the protective sheet according to the present embodiment is attached to the surface of a semiconductor chip. [Figure 4C] FIG. 10 is a cross-sectional view schematically showing yet another example of the manner in which the protective sheet according to the present embodiment is attached to the surface of a semiconductor chip. [Figure 4D] FIG. 10 is a cross-sectional view schematically showing yet another example of the manner in which the protective sheet according to the present embodiment is attached to the surface of a semiconductor chip. [Figure 4E] FIG. 10 is a cross-sectional view schematically showing yet another example of the manner in which the protective sheet according to the present embodiment is attached to the surface of a semiconductor chip. [Figure 5] FIG. 1 is a schematic cross-sectional view showing an example of a semiconductor wafer having electrode portions on both sides. [Figure 6A] 1A to 1C are cross-sectional views schematically illustrating an example of a preparation step in a method for manufacturing a semiconductor device. [Figure 6B] 1A to 1C are cross-sectional views schematically illustrating an example of a preparation step in a method for manufacturing a semiconductor device. [Figure 6C] 1A to 1C are cross-sectional views schematically illustrating an example of a preparation step in a method for manufacturing a semiconductor device. [Figure 6D] 10A to 10C are cross-sectional views schematically illustrating an example of a protective sheet attaching step in the method for manufacturing a semiconductor device. [Figure 6E] 10A to 10C are cross-sectional views schematically illustrating an example of a weakened portion forming step in the method for manufacturing a semiconductor device. [Figure 6F] 5A to 5C are cross-sectional views schematically illustrating an example of a semiconductor wafer cleaving step in the method for manufacturing a semiconductor device. [Figure 6G] 5A to 5C are cross-sectional views schematically illustrating an example of a semiconductor wafer cleaving step in the method for manufacturing a semiconductor device. [Figure 6H]5A to 5C are cross-sectional views schematically illustrating an example of a protective sheet removing step in the method for manufacturing a semiconductor device. [Figure 7] FIG. 1 is a cross-sectional view schematically showing an example of a bonding mode of a semiconductor chip. [Figure 8A] 10A and 10B are cross-sectional views schematically illustrating another example of a protective sheet attaching step in the method for manufacturing a semiconductor device. [Figure 8B] 10A and 10B are cross-sectional views schematically illustrating another example of the weakened portion forming step in the semiconductor device manufacturing method. [Figure 8C] 5A to 5C are cross-sectional views schematically illustrating an example of a protective layer hardening step in the method for manufacturing a semiconductor device. [Figure 8D] 5A to 5C are cross-sectional views schematically illustrating an example of a release liner removing step in the method for manufacturing a semiconductor device. [Figure 8E] 10A and 10B are cross-sectional views schematically illustrating another example of the protective sheet removing step in the method for manufacturing a semiconductor device. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the present invention will be described below.

[0024] [Protection sheet] The protective sheet 10 of this embodiment is a protective sheet that is attached to the surface to be protected of an electronic component having such a surface, one surface of a piece of glass that constitutes the display surface of a display device, or one surface of a glass plate from which the glass piece is obtained. The protective sheet 10 according to this embodiment includes a protective layer that is attached to the surface of the electronic component to be protected, one surface of the glass piece, or one surface of the glass plate. In the protective sheet 10 according to this embodiment, the protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesiveness decreases upon curing reaction. Examples of the electronic components include semiconductor wafers, semiconductor chips, circuit boards, and interconnected circuit boards formed by interconnecting a plurality of the circuit boards.

[0025] Examples of the electronic component include a pseudo wafer including a support substrate and a package formed by collectively sealing a plurality of semiconductor chips with resin in a state where the plurality of semiconductor chips are arranged on the support substrate. The pseudo wafer may be the package removed from the support substrate. Furthermore, a rewiring layer may be formed on at least one surface of the pseudo wafer, and in such a case, the protective layer may be used to protect the rewiring layer. Furthermore, examples of the electronic component include divided pseudo wafers obtained by dividing the pseudo wafer into constituent units each including at least one semiconductor chip.

[0026] Examples of the electronic component include a wafer level package (WLP) as shown in FIG. 1 and an image sensor package as shown in FIG. 2A.

[0027] As shown in FIG. 1, a wafer-level package 100 includes a circuit board 110 and a plurality of semiconductor packages 120 mounted on the circuit board 110 . That is, in the wafer level package 10, a plurality of semiconductor chips 120 are individually sealed with resin on the circuit board 110. In the wafer-level package 100, each of the surfaces of the semiconductor packages 120 (the surface opposite to the surface attached to the circuit board 110) may be formed from one surface of the glass piece 120a. That is, in the wafer level package 100, the plurality of semiconductor packages 120 may each have a glass piece 120a on the front surface side (the surface opposite to the surface attached to the circuit board 110). When the wafer level package 100 is configured in this manner, the protective layer is used to protect one surface of the glass piece 120 a for each of the plurality of semiconductor packages 120 . The wafer level package 100 is separated (cut) into individual semiconductor packages by dicing or the like along the cutting lines L as shown in FIG.

[0028] As shown in FIG. 2A, the image sensor package 200 includes a sensor chip body 210 having a circuit formed on one surface thereof, and a piece of glass 230 (cover glass) laminated on one surface (the surface on which the circuit is formed) of the sensor chip body 210 via an adhesive layer 220 made of adhesive, glass frit, or the like. The image sensor package 200 is used as an image pickup element for a camera or the like, for example. In the image sensor package 200 configured as described above, the protective layer is used to protect the surface of the glass piece 230 stacked on the sensor chip body 210 (the surface opposite to the sensor chip body 210 side). The image sensor package 200 is typically obtained by dicing an image sensor package laminate 200', which includes a sensor wafer main body 210' having multiple circuits formed on one surface, as shown in Figure 2B, and a glass plate 230' which has approximately the same dimensions as the sensor wafer main body 210' in a planar view and is laminated on one surface (the surface on which multiple circuits are formed) of the sensor wafer main body 210' via an adhesive layer 220' made of adhesive, glass frit, or the like, into individual image sensor packages 200 each including at least one circuit. Specifically, the image sensor package 200 is obtained by being separated into individual pieces by dicing along the cutting line L' as shown in FIG. 2B.

[0029] The semiconductor chip generally has a semiconductor chip body and electrode portions disposed on at least one surface of the semiconductor chip body and electrically connected to electrode portions of other members. In addition, at least one surface of the semiconductor chip is a circuit formation surface on which a circuit is formed. The other members may include a circuit board and another semiconductor chip configured in the same manner as the semiconductor chip. The semiconductor chip may be of the TSV (Through Silicon Via) type, which has a pair of electrode portions arranged on both sides of the semiconductor chip body and electrically connected to other components, and a conductive portion that penetrates the semiconductor chip body in the thickness direction to electrically connect the pair of electrode portions. In the case of a TSV type semiconductor chip, only one side may be a circuit formation surface, or both sides may be circuit formation surfaces. The semiconductor chip also includes a sensor chip in which the circuit includes a sensor element (for example, a light receiving element or a vibration element) as an element. Examples of the sensor chip include a CMOS (Complementary Metal-Oxide Semiconductor) chip and a MEMS (Micro Electro Systems) chip.

[0030] Examples of the display device include a liquid crystal display device, a plasma display device, and an organic EL display device. The liquid crystal display device, the plasma display device, and the organic EL display device may be a color display device, a character display device, or a graphic display device.

[0031] As shown in FIG. 3, the protective sheet 10 according to this embodiment comprises a protective layer 10a, a first release liner 10b on one surface of the protective layer 10a, and a second release liner 10c on the other surface of the protective layer 10a (the surface opposite the first surface). That is, protective sheet 10 according to this embodiment is constructed by sandwiching protective layer 10a on both sides between a pair of release liners (first release liner 10b and second release liner 10c). In the protective sheet 10 according to this embodiment, the protective layer 10a is attached to the surface to be protected of an electronic component having the surface to be protected, one surface of a glass piece constituting the display surface of a display device, or one surface of a glass plate from which the glass piece is obtained.

[0032] The protective sheet 10 can be produced, for example, by using an applicator to apply a water-soluble resin composition containing excess liquid or a curable resin composition containing excess liquid whose adhesive properties decrease due to a curing reaction to a predetermined thickness (e.g., 10 μm) onto the first release liner 10b, and drying it at a predetermined temperature for a predetermined time (e.g., 110°C for 2 minutes) to form a protective layer 10a on the first release liner 10b, and then laminating the second release liner 10c to the side of the protective layer 10a opposite to the side to which the first release liner 10b is attached.

[0033] In the example shown in FIG. 1, the protective sheet 10 is configured such that the protective layer 10a is sandwiched between a pair of release liners (first release liner 10b and second release liner 10c) on both sides, but the configuration of the protective sheet 10 is not limited to this. Protective sheet 10 may be composed of only protective layer 10a, or may have either first release liner 10b or second release liner 10c on only one surface of protective layer 10a. In short, protective sheet 10 only needs to include at least protective layer 10a.

[0034] In the following, the protective sheet 10 according to the first embodiment will be described using an example in which the protective layer 10a is made of a water-soluble resin composition, and the protective sheet 10 according to the second embodiment will be described using an example in which the protective layer 10a is made of a curable resin composition whose adhesiveness decreases due to a curing reaction.

[0035] (First embodiment) In the protective sheet 10 according to the first embodiment, the protective layer 10a is made of a water-soluble resin composition. The water-soluble resin composition contains a water-soluble polymer compound. In the protective sheet 10 according to the first embodiment, the protective layer 10a is formed, for example, by applying a water-soluble resin composition containing excess liquid onto a release liner and then drying it. In the protective sheet 10 according to the first embodiment, it is preferable to use a water-soluble resin composition containing excess liquid, in which the water-soluble polymer compound is dispersed in water (hereinafter referred to as the first protective layer-forming composition). In the first protective layer-forming composition, the water-soluble polymer compound is preferably contained in an amount of 5 to 80 parts by weight, more preferably 10 to 70 parts by weight, and even more preferably 15 to 60 parts by weight, per 100 parts by weight of water. In addition, the first protective layer-forming composition preferably contains the water-soluble polymer dissolved in water. In the first protective layer-forming composition, the water-soluble polymer compound can be dissolved in water by heating at a temperature of 20°C to 90°C. Furthermore, the viscosity of the first protective layer-forming composition at 25° C. is preferably 0.03 Pa·s or more, more preferably 0.05 Pa·s or more, and even more preferably 0.1 Pa·s or more. By having a viscosity at 25°C that is equal to or greater than the above-mentioned lower limit, when the first protective layer-forming composition is applied to a release liner to form a protective layer 10a on the release liner, the thickness of the protective layer 10a can be relatively prevented from fluctuating. The viscosity of the first protective layer-forming composition at 25° C. is preferably 15 Pa·s or less, more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less. When the viscosity at 25° C. is equal to or less than the upper limit described above, the coating properties of the first protective layer-forming composition can be improved when the composition is applied onto a release liner. The viscosity of the first protective layer forming composition at 25°C can be measured using a digital viscometer (product name "DV-I Prime") manufactured by Eiko Seiki Co., Ltd. as the measuring device, using an LV-3 spindle and adopting conditions of a rotation speed of 50 rpm.

[0036] Examples of the water-soluble polymer compound include polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), water-soluble polyester (PES), and polyethylene oxide (PEO). The water-soluble polymer compound may be polyvinyl alcohol, polyvinylpyrrolidone, water-soluble polyester, polyethylene oxide, or the like, which may be used alone or in combination. As the water-soluble polymer compound, it is preferable to use at least one selected from the group consisting of polyvinyl alcohol, water-soluble polyester, and polyethylene oxide.

[0037] The polyvinyl alcohol preferably has a degree of saponification of 50 or more and 98 or less, more preferably 60 or more and 90 or less. By having a degree of saponification within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and when the polyvinyl alcohol is contained in the first protective layer-forming composition, the first protective layer-forming composition can be applied to a release liner with good workability. The degree of saponification of the polyvinyl alcohol was determined by proton magnetic resonance spectroscopy ( 1 It can be measured by H-NMR measurement. In addition, when the measurement sample contains an additive and the peak derived from the additive overlaps with the peak used for calculating the degree of saponification, the measurement sample is subjected to methanol extraction or the like to separate the additive, and then the degree of saponification of the polyvinyl alcohol is measured. The degree of saponification of the polyvinyl alcohol can be measured under the following conditions. <Measurement conditions> ·Analyzer FT-NMR: Bruker Biospin, AVANCE III-400 Observation frequency: 400MHz (1H) Measurement solvent: deuterated water or deuterated dimethyl sulfoxide (deuterated DMSO) ·Measurement temperature 80℃ ·Chemical shift standard External standard TSP-d4 (0.00ppm) (when measuring heavy water) Measurement solvent (2.50 ppm) (when measuring deuterated DMSO) The degree of saponification of the polyvinyl alcohol is calculated based on the following formula using the peaks derived from the methylene groups of the vinyl alcohol unit (VOH) (heavy water: 2.0 to 1.0 ppm, deuterated DMSO: 1.9 to 1.0 ppm) and the peaks derived from the acetyl groups of the vinyl acetate unit (VAc) (heavy water: around 2.1 ppm, deuterated DMSO: around 2.0 ppm). In the following formula, [VOH(-CH2)-] means the intensity of the peak derived from -CH2- in the vinyl alcohol unit, and [VAc(CH3CO-)] means the intensity of the peak derived from CH3CO- in the vinyl acetate unit.

[0038]

number

[0039] The polyvinyl alcohol preferably has an average degree of polymerization of 100 or more and 1,000 or less, and more preferably 100 or more and 800 or less. By having an average degree of polymerization within the above numerical range, the polyvinyl alcohol can exhibit sufficient water solubility, and when the polyvinyl alcohol is contained in the first protective layer forming composition, the first protective layer forming composition can be applied onto a release liner with good workability. The average degree of polymerization of the polyvinyl alcohol can be measured by aqueous GPC. The average degree of polymerization of the polyvinyl alcohol can be measured under the following conditions. <Measurement conditions> ·Analyzer Agilent, 1260Infinity Columns: TSKgel G6000PWXL (Tosoh Corporation) and TSKgel G3000PWXL (Tosoh Corporation) The two columns are connected in series. Column temperature: 40℃ Eluent: 0.2M aqueous sodium nitrate solution ·Injection volume 100μL Detector: Differential refractometer (RI) Standard samples: PEG standard sample and PVA standard sample The specific measurement is carried out as follows. (1) The mass-average molecular weights Mw of the sample (PVA) and the PVA standard sample are calculated by GPC measurement using a PEG standard sample. The PVA standard sample has a known average degree of polymerization. (2) A calibration curve is prepared using the average degree of polymerization of the PVA standard sample and the calculated mass average molecular weight Mw of the PVA standard sample. (3) Using the created calibration curve, the average degree of polymerization of the sample (PVA) to be measured is determined from the mass average molecular weight Mw of the sample (PVA).

[0040] When polyvinyl alcohol is used as the water-soluble polymer, a plurality of polyvinyl alcohols having different degrees of saponification may be used in combination, or a plurality of polyvinyl alcohols having different average degrees of polymerization may be used in combination.

[0041] The water-soluble polyester has a residue of a polycarboxylic acid and a residue of a polyol. The water-soluble polyester is, for example, a polymerization product of a monomer component including a polycarboxylic acid component and a polyol component. Whether the water-soluble polyester has water solubility can be determined based on common technical knowledge.

[0042] The water-soluble polyester preferably satisfies at least one of the following (1) to (4). (1) When water at room temperature (23±2°C) is sprayed onto the entire surface of a 20 μm-thick thin film formed from the water-soluble polyester at a spray pressure of 0.005 MPa for 20 minutes, the entire thin film dissolves in water. (2) When water at 50° C. is sprayed onto the entire surface of a 20 μm-thick thin film formed from the water-soluble polyester at a spray pressure of 0.005 MPa for 10 minutes, the thin film dissolves completely in water. (3) The water-soluble polyester and room temperature water are mixed in a mass ratio of water-soluble polyester:room temperature water=1:5 to obtain a mixed solution, and when the mixed solution is irradiated with ultrasound for 20 minutes, the water-soluble polyester is completely dissolved in the water. (4) The water-soluble polyester and 50°C water are mixed in a mass ratio of water-soluble polyester:50°C water=1:5 to obtain a mixed solution, and when the mixed solution is irradiated with ultrasound for 10 minutes, the water-soluble polyester is completely dissolved in the water.

[0043] The water-soluble polyester preferably has a mass average molecular weight Mw of 40,000 (40,000) or less. When the first protective layer-forming composition contains a water-soluble polyester having a mass average molecular weight Mw within the above range, the protective layer 10a can be easily formed into a film. When such a film-like protective layer 10a is disposed on one surface of a glass piece that constitutes the surface to be protected of an electronic component or the display surface of a display device, the protective layer 10a sufficiently prevents fine foreign matter from adhering to the surface to be protected or the surface of the glass piece. By including a water-soluble polyester having a mass average molecular weight Mw within the above range, the protective layer 10a has excellent water solubility. Furthermore, from the viewpoint of making the protective layer 10a excellent in durability to water at relatively low temperatures such as 30°C or less (hereinafter also referred to as low-temperature water durability), it is preferable that the water-soluble polyester has a mass average molecular weight Mw of 15,000 (15,000) or more. Since the protective layer 10a contains a water-soluble polyester having a mass-average molecular weight Mw within the above numerical range, the protective layer 10a has excellent water durability at low temperatures, and is therefore difficult to remove from the surface to be protected of the electronic component or one surface of the glass piece constituting the display surface of the display device when it comes into contact with water at a relatively low temperature, such as 30°C or below. On the other hand, when the protective layer 10a comes into contact with relatively high-temperature water (warm water), such as water at 40°C or higher, the protective layer 10a becomes easily removed from the surface to be protected of the electronic component or one surface of the glass piece constituting the display surface of the display device (resulting in reduced water durability at high temperatures). Therefore, for example, when protective layer 10a is attached to one surface of a semiconductor wafer and the semiconductor wafer with protective layer 10a is blade diced while being washed with water at a relatively low temperature of 30°C or less, protective layer 10a is sufficiently fixed to one surface of the semiconductor wafer and can sufficiently protect that surface. On the other hand, by washing the multiple semiconductor chips obtained by dividing the semiconductor wafer by blade dicing with warm water of 40°C or higher, the divided protective layer 10a can be easily removed from each of the multiple semiconductor chips. In addition, the same effect as above can be obtained when dicing a connected circuit board to obtain a circuit board, when dicing a pseudo wafer to obtain divided pseudo wafers, when dividing a wafer-level package into individual semiconductor packages, or when dicing a laminate for an image sensor package to divide it into individual image sensor packages. Furthermore, the same effect as above can be obtained when a glass plate from which the glass fragments are to be obtained is diced into multiple glass fragments to obtain the glass fragments that form the display surface of a display device.

[0044] Furthermore, by using a water-soluble polyester having a high acid value (high acid value), the protective layer 10a can be made to have excellent water resistance at low temperatures and low water resistance at high temperatures. In such cases, the acid value of the water-soluble ester is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, even more preferably 30 mgKOH / g or more, and even more preferably 40 mgKOH / g or more. The upper limit of the acid value of the water-soluble polyester is usually 70 mgKOH / g. The acid value can be determined by the neutralization titration method specified in JIS K 0070-1992. Furthermore, when the water-soluble polyester has a high acid value as described above, the mass average molecular weight Mw of the water-soluble polyester is preferably 10,000 (10,000) or less, more preferably 7,000 or less, and even more preferably 4,000 or less. When the water-soluble polyester has a high acid value and a mass-average molecular weight Mw within the above numerical range, the protective layer 10a has better water resistance at low temperatures and lower water resistance at high temperatures. In addition, when ammonia water of about 0.1 mol / L is used as a cleaning liquid for the protective layer 10a, even if the temperature of the ammonia water is low (below 30°C), the protective layer 10a can be relatively easily removed from the surface to be protected or one surface of the glass piece that constitutes the display surface of the display device.

[0045] The polyethylene oxide preferably has a mass average molecular weight Mw of 1,000,000 (1 million) or less. The polyethylene oxide preferably has a mass average molecular weight Mw of 20,000 (20,000) or more. By including polyethylene oxide having a mass average molecular weight Mw within the above numerical range in the first protective layer-forming composition for forming the protective layer 10a, the first protective layer-forming composition can have suitable viscosity. This makes it easier to form the protective layer 10a (improves film formability) when forming the protective layer 10a using the first protective layer-forming composition. If the mass average molecular weight of the first protective layer-forming composition exceeds 1,000,000, the viscosity of the first protective layer-forming composition becomes relatively high, which often makes it difficult to spread the first protective layer-forming composition when forming the protective layer 10a, whereas if the mass average molecular weight Mw of the first protective layer-forming composition is less than 20,000, the viscosity of the first protective layer-forming composition becomes relatively low, which often makes it difficult to form the protective layer 10a to a desired thickness when forming the protective layer 10a. In other words, film formability often becomes poor. Furthermore, since the protective layer 10a contains polyethylene oxide having a mass average molecular weight Mw within the above numerical range, the protective layer 10a can be relatively easily removed from the surface to be protected of the electronic component or one surface of the glass piece constituting the display surface of the display device by washing with water.

[0046] The weight average molecular weight Mw of the water-soluble polyester and the polyethylene oxide can be measured by GPC in the same manner as described for the average degree of polymerization of polyvinyl alcohol. However, the eluent is selected appropriately from 0.2 M aqueous sodium nitrate solution or DMF (dimethylformamide) depending on the composition of the object to be measured. Specifically, the eluent is appropriately selected so that it can dissolve the object to be measured.

[0047] In the protective sheet 10 according to the first embodiment, the adhesive strength of the protective layer 10a to the bare wafer is preferably 0.05 N / 100 mm or more, more preferably 0.5 N / 100 mm or more, and even more preferably 5.0 N / 100 mm or more. By ensuring that the adhesion strength of the protective layer 10a to the bare wafer is equal to or greater than the above-mentioned lower limit, the protective sheet 10 can be sufficiently adhered even when the object to which the protective sheet 10 is to be attached is a semiconductor wafer having electrode portions on both sides or a semiconductor chip obtained by cleaving the semiconductor wafer (more specifically, a semiconductor chip having electrode portions on both sides). In addition, the protective sheet 10 can be prevented from peeling off from the semiconductor wafer or semiconductor chip to which it is to be attached during the fragile portion formation process and semiconductor wafer cleaving process described below. As described below, in the fragile portion forming step, the semiconductor wafer to which protective sheet 10 is attached is irradiated with laser light from the protective sheet 10 side to form fragile portions in the semiconductor wafer, but as described above, peeling of protective sheet 10 from the semiconductor wafer can be prevented, so the surface of protective sheet 10 that is irradiated with laser light can be maintained in a relatively flat state. This allows the laser light to be irradiated toward a relatively smooth surface. Furthermore, by preventing the protective sheet 10 from peeling off from the semiconductor wafer, defects in the protective sheet 10 can be prevented from occurring at the peeled portion of the protective sheet 10 from the semiconductor wafer, and foreign matter can be prevented from reaching the surface of the semiconductor wafer from outside the protective sheet 10 through these defects and adhering to the surface of the semiconductor wafer. Furthermore, in the protective sheet 10 according to the first embodiment, the adhesion strength of the protective layer 10a to the bare wafer is preferably 200 N / 100 mm or less, more preferably 150 N / 100 mm or less, and even more preferably 100 N / 100 mm or less.

[0048] The adhesive strength of the protective layer 10a to the bare wafer can be measured as follows: The measurement method will be explained below using the protective sheet 10 configured as shown in FIG. (1) One release liner (first release liner 10b) is peeled off from protective layer 10a to expose one side of protective layer 10a, and a backing tape is attached to the exposed surface (first exposed surface) to obtain a first test piece. The backing tape is attached to the first exposed surface using a hand roller at a temperature of 25°C. (2) After cutting the first test piece to a width of 100 mm, the other release liner (second release liner 10c) of the protective layer 10a is peeled off to expose the other side of the protective layer 10a, and the exposed surface (second exposed surface) is bonded to a bare wafer to obtain a second test piece (measurement sample). The second exposed surface is bonded to the bare wafer using a 2 kg standard roller (manual adhesion test press wheel adhesive tape adhesion tester) at a temperature of 90°C and a speed of 10 mm / sec. After bonding, the test piece is allowed to cool naturally (cool) for at least 20 minutes. (3) In an atmosphere at 23°C, the peel force of the measurement sample is measured at a peel angle of 180° and a peel rate of 300 mm / min. The measured peel force is defined as the adhesion force. An Autograph (manufactured by Shimadzu Corporation) can be used as the measurement device.

[0049] In the protective sheet 10 according to the first embodiment, the protective layer 10a preferably has a breaking strength at -15°C of 200 MPa or less, more preferably 100 MPa or less, and even more preferably 50 MPa or less. Furthermore, in the protective sheet 10 according to the first embodiment, the protective layer 10a preferably has a breaking strength at -15°C of 0.01 MPa or more, more preferably 0.05 MPa or more, and even more preferably 0.1 MPa or more. Furthermore, in the protective sheet 10 according to the first embodiment, the protective layer 10a preferably has a breaking elongation at -15°C of 100% or less, more preferably 80% or less, and even more preferably 50% or less. Furthermore, in the protective sheet 10 according to the first embodiment, the protective layer 10a preferably has a breaking elongation at -15°C of 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. By having the breaking strength and breaking elongation of the protective layer 10a at -15°C within the above numerical range, when the protective layer 10a is attached to the surface of a semiconductor wafer and the protective layer 10a is fractured and divided into individual pieces together with the semiconductor wafer under low-temperature conditions (e.g., by cool expansion), the protective layer 10a can be fractured more satisfactorily.

[0050] The breaking strength at -15°C and the breaking elongation at -15°C can be measured as follows. Specifically, for the breaking elongation at -15°C, a protective layer 10a having a length of 50 mm, a width of 10 mm, and a thickness of 30 μm was used as a test specimen, and the test specimen was pulled in the longitudinal direction using a tensile testing machine (Autograph AG-IS, manufactured by Shimadzu Corporation) under conditions of a temperature of -15°C, a chuck distance of 20 mm (measurement length: L0), and a pulling speed of 10 mm / sec, and the length at which the test specimen broke (the value obtained by adding the amount of elongation to the measurement length: L1) was measured. Then, the breaking elongation E at −15° C. is calculated based on the following formula. Breaking elongation E = (L1 - L0) / L0 x 100 The breaking strength at -15°C can be determined by measuring the force applied when the test piece breaks when a tensile test is carried out using the test piece and the tensile tester under the same conditions as above.

[0051] In the protective sheet 10 according to the first embodiment, the protective layer 10a preferably has a tensile storage modulus at -15°C of 1 GPa or more and 30 GPa or less, more preferably 2 GPa or more and 20 GPa or less, and even more preferably 3 GPa or more and 15 GPa or less. By having the tensile storage modulus at -15°C within the above numerical range, when the protective layer 10a is attached to the surface of a semiconductor wafer and the protective layer 10a is fractured together with the semiconductor wafer under low-temperature conditions to separate the protective layer 10a into individual pieces (e.g., by cool expansion), the protective layer 10a can be fractured more satisfactorily. Furthermore, in the protective sheet 10 according to the first embodiment, the protective layer 10a preferably has a tensile storage modulus at 25°C of 0.1 MPa or more and 20 GPa or less, more preferably 0.5 MPa or more and 15 GPa or less, and even more preferably 1 MPa or more and 10 GPa or less. Here, since the attachment of the protective sheet 10 to the semiconductor wafer is usually performed at a temperature of about 25°C, if the tensile storage modulus at 25°C is within the above numerical range, it is relatively easy to attach the protective layer 10a to the semiconductor wafer, and if slitting is required in the protective layer 10a, it becomes easier to perform the slitting. Furthermore, since the tensile storage modulus at 25°C is within the above numerical range, when a semiconductor wafer with protective sheet 10 attached is used to manufacture multiple individual semiconductor chips, excessive deformation of protective layer 10a at temperatures of around 25°C can be suppressed. Furthermore, since the tensile storage modulus at 25°C is within the above numerical range, when the protective sheet 10 is attached to a semiconductor wafer or semiconductor chip, the semiconductor wafer or semiconductor chip can be adequately protected from external impacts. In addition, the same effect as above can be obtained when dicing a connected circuit board to obtain a circuit board, when dicing a pseudo wafer to obtain divided pseudo wafers, when dividing a wafer-level package into individual semiconductor packages, or when dicing a laminate for an image sensor package to divide it into individual image sensor packages. Furthermore, the same effect as above can be obtained when a glass plate from which the glass fragments are to be obtained is diced into multiple glass fragments to obtain the glass fragments that form the display surface of a display device.

[0052] The tensile storage modulus at -15°C and 25°C refers to a value measured as follows. Specifically, a protective layer 10a having a length of 40 mm, a width of 10 mm, and a thickness of 50 μm is used as a test piece, and the tensile storage modulus of the test piece is measured in the temperature range of -40°C to 80°C using a solid viscoelasticity measuring device (e.g., Model RSAIII, manufactured by TA Instruments) under conditions of a frequency of 1 Hz, a strain of 0.1%, a heating rate of 10°C / min, and a chuck distance of 20 mm. At this time, the tensile storage modulus at -15°C can be determined by reading the value at -15°C, and the tensile storage modulus at 25°C can be determined by reading the value at 25°C. The measurement is carried out by pulling the test piece in the length direction.

[0053] In the protective sheet 10 according to the first embodiment, the protective layer 10a has a surface free energy of 25 mJ / m 2 More than 85mJ / m 2 Preferably, it is 35 mJ / m or less. 2 More than 75mJ / m 2 More preferably, it is: It is preferable that the surface free energy of protective layer 10a be within the above range for both the surface that contacts first release liner 10b and the surface that contacts second release liner 10c. By ensuring that the surface free energy on both sides of protective layer 10a is within the above range, it becomes easier to control the adhesive strength between first release liner 10b and second release liner 10c. Furthermore, by ensuring that the surface free energy of at least the surface that is attached to the semiconductor wafer (e.g., the surface that abuts first release liner 10b) is within the above range, adhesion to the semiconductor wafer can be relatively high. This makes it difficult for protective sheet 10 to peel off from the surface of the semiconductor wafer when a semiconductor wafer with protective sheet 10 attached is used to manufacture multiple individual semiconductor chips, thereby improving process stability.

[0054] The surface free energy can be measured as follows. First, under conditions of a temperature of 20° C. and a relative humidity of 65% RH, the contact angles of a water droplet (H 2 O) and a droplet of methylene iodide (CH 2 I 2 ) brought into contact with the surface of the protective layer 10a are measured using a contact angle meter. Next, the surface free energy is calculated from the measured value of the contact angle θw of the water droplet and the measured value of the contact angle θi of the methylene iodide droplet as follows. In detail, γs is calculated according to the method of Owens et al. described in Journal of Applied Polymer Science, vol. 13, pp. 1741-1747 (1969). d (dispersion component of surface free energy) and γs h (polar component of surface free energy). And γs d and γs h The value γs (=γs d +γs h ) is the surface free energy of the protective layer 10a. γs d (variance components) and γs h The values ​​of each (polar component) are obtained as solutions to the simultaneous equations with two unknowns shown below in (1) and (2).

[0055]

number

[0056] In equations (1) and (2), γw is the surface free energy of water, d is the dispersion component of the surface free energy of water, γw h is the polar component of the surface free energy of water, γi is the surface free energy of methylene iodide, γi d is the dispersive component of the surface free energy of methylene iodide, γi h is the polar component of the surface free energy of methylene iodide, and is a known value as follows: γw=72.8[mJ / m 2 ] γw d =21.8 [mJ / m 2 ] γw h =51.0[mJ / m 2 ] γi=50.8[mJ / m 2 ] γi d =48.5 [mJ / m 2 ] γi h =2.3 [mJ / m 2 ]

[0057] Specifically, the surface free energy of one surface (the surface that is attached to the semiconductor wafer) of the protective layer 10a is measured. The contact angles of the water droplet and the methylene iodide droplet are measured, and the average value of five measurements is used. The contact angle is measured by dropping 1 mL of the liquid onto one of the surfaces and measuring the contact angle within 5 seconds. The dispersive component and polar component are calculated from each measured value of the contact angle, and the surface free energy is determined by adding them together. The surface free energy of the other surface (the surface opposite to the surface attached to the semiconductor wafer) of the protective layer 10a can also be determined in the same manner as above.

[0058] The thickness of the protective layer 10a is preferably 2 μm or more and 70 μm or less, more preferably 3 μm or more and 50 μm or less, and even more preferably 5 μm or more and 40 μm or less. The thickness of the protective layer 10a can be determined, for example, by measuring the thickness at five randomly selected points using a dial gauge (manufactured by PEACOCK, model R-205) and calculating the arithmetic mean of these thicknesses.

[0059] As will be described later, after first release liner 10b is peeled off from protective layer 10a to expose one side of protective layer 10a, the exposed side of protective layer 10a is attached to at least one circuit-forming side of a semiconductor wafer having a plurality of electrode portions on both sides and at least one side serving as a circuit-forming side on which circuits are formed, and further, with second release liner 10c peeled off from protective layer 10a, i.e., with only protective layer 10a attached to one side of the semiconductor wafer, protective sheet 10 is subjected to a dicing process such as stealth dicing. Therefore, it is preferable that the protective layer 10a can be broken by a dicing process such as stealth dicing. The dicing process may be performed by blade dicing or laser dicing, or may be performed by DBG (Dicing Before Grinding) method. Furthermore, the laser dicing is preferably performed by laser ablation. In addition, when the protective layer 10a contains the polyethylene oxide, the semiconductor wafer having the protective layer 10a removed does not necessarily have excellent breaking properties. In such cases, it is preferable to perform the dicing process by a method other than stealth dicing. As will be described later, protective layer 10a of protective sheet 10 is subjected to an expanding process at a low temperature (-20°C to 5°C) after dicing, and therefore protective layer 10a preferably has a breaking elongation of 100% or less at -15°C. Since the breaking elongation at -15°C is 100% or less, when the protective layer 10a is subjected to an expanding process at low temperature, the protective layer 10a can be easily divided into individual pieces having a size equivalent to the chip size of the semiconductor chip obtained after cleaving.

[0060] An example of the first release liner 10b is a base sheet made of a resin such as polyethylene terephthalate (PET) that has been subjected to a release treatment. The release treatment may include silicone release treatment. An example of such a release liner is MRA50, a product of Mitsubishi Chemical Corporation. The second release liner 10c may be the same as the first release liner 10b.

[0061] The thickness of the first release liner 10b and the second release liner 10c is preferably 15 μm or more and 75 μm or less, and more preferably 20 μm or more and 60 μm or less. The thickness of the first release liner 10b and the thickness of the second release liner 10c may be the same or different. The thickness of the first release liner 10b and the second release liner 10c can be determined in the same manner as the thickness of the protective layer 10a.

[0062] (Second embodiment) In the protective sheet 10 according to the second embodiment, the protective layer 10a is composed of a curable resin composition whose adhesiveness decreases upon curing reaction. In the protective sheet 10 according to the second embodiment, the curable resin composition whose adhesiveness decreases upon curing reaction preferably contains a curable resin such as an acrylic resin, a polyurethane resin, an epoxy resin, or a silicone resin. These curable resins may be used alone or in combination of two or more kinds. The curable resin is preferably an acrylic resin. In the protective sheet 10 according to the second embodiment, the protective layer 10a is formed, for example, by applying a curable resin composition (hereinafter referred to as the second protective layer-forming composition) containing excess liquid that reduces adhesiveness through a curing reaction onto a release liner and then drying it.

[0063] When the curable resin is an acrylic resin, the protective layer 10a preferably contains 40% by mass or more of the acrylic resin, more preferably 60% by mass or more, and even more preferably 80% by mass or more. Moreover, the protective layer 10a preferably contains 98% by mass or less of the acrylic resin, and more preferably 95% by mass or less.

[0064] The acrylic resin preferably has a mass average molecular weight Mw of 50,000 or more and 2,000,000 or less. When the mass average molecular weight Mw of the acrylic resin is within the above range, the protective layer 10a can be more sufficiently adhered to one side of the semiconductor wafer, and as described above, when the semiconductor wafer is subjected to a dicing process such as stealth dicing with only the protective layer 10a attached to one side of the semiconductor wafer, the protective layer 10a can be more sufficiently cleaved. In addition, when forming the protective layer 10a by applying a second protective layer forming composition containing an acrylic resin onto a release liner, it is possible to suppress a decrease in film formability, and it is also possible to suppress the occurrence of cohesive failure in the protective layer 10a. Furthermore, by suppressing the occurrence of cohesive failure, it is possible to suppress the protective layer 10a from becoming brittle and the likelihood of adhesive residue remaining on one surface of the semiconductor wafer. The mass average molecular weight Mw of the acrylic resin is a value measured by the following method. <Measurement of mass average molecular weight Mw of acrylic resin> The mass average molecular weight Mw of the acrylic resin is measured by GPC (gel permeation chromatography). The measurement conditions are as follows. The mass average molecular weight Mw is calculated in terms of polystyrene. Measuring device: Product name HLC-8120GPC (manufactured by Tosoh Corporation) Column: Two TSKgel GMH-H(S) columns (manufactured by Tosoh Corporation) connected in series ·Flow rate: 0.5mL / min Eluent: tetrahydrofuran (THF) Injected sample concentration: 0.1% by mass Detector: Differential refractometer

[0065] The acrylic resin preferably contains an acrylic polymer as a base polymer, which is the main component, and also contains a polymerizable monomer component or a polymerizable oligomer component having a functional group such as a carbon-carbon double bond that is polymerized by active energy rays. Such acrylic resin has relatively high adhesiveness (is in a high adhesive state) before irradiation with active energy rays, and therefore, when the protective layer 10a contains the acrylic resin, the protective layer 10a can be sufficiently adhered to the semiconductor chip. On the other hand, such acrylic resin loses its adhesiveness (becomes in a low adhesive state) after being cured by irradiation with active energy rays, and can be removed from the semiconductor chip relatively easily. Examples of active energy rays include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X rays.

[0066] The acrylic polymer may include a polymer containing a monomer unit derived from a (meth)acrylic acid ester, such as a (meth)acrylic acid alkyl ester, a (meth)acrylic acid cycloalkyl ester, or a (meth)acrylic acid aryl ester. As the acrylic polymer, for example, 2-hydroxyethyl acrylate (HEA), ethyl acrylate (EA), butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isononyl acrylate (INA), lauryl acrylate (LA), 4-acryloylmorpholine (AMCO), 2-isocyanatoethyl methacrylate (MOI), or the like is preferably used as a structural unit. These acrylic polymers may be used alone containing a monomer unit derived from the above-mentioned (meth)acrylic acid ester, or two or more of them may be used in combination containing a monomer unit derived from the above-mentioned (meth)acrylic acid ester.

[0067] Examples of the polymerizable monomer component include urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 1,4-butanediol di(meth)acrylate. Examples of the polymerizable oligomer component include various oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based oligomers. The content of the polymerizable monomer component or polymerizable oligomer component in the second protective layer-forming composition is selected within a range that appropriately reduces the adhesiveness of the protective layer 10a.

[0068] The protective layer 10a may contain an external crosslinking agent. Any external crosslinking agent can be used as long as it can react with a base polymer (e.g., an acrylic polymer) to form a crosslinked structure. Examples of such external crosslinking agents include polyisocyanate compounds, epoxy compounds, polyol compounds, aziridine compounds, and melamine-based crosslinking agents.

[0069] When the protective layer 10a contains an external crosslinking agent, the protective layer 10a preferably contains 0.1 parts by mass or more and 10 parts by mass or less of the external crosslinking agent per 100 parts by mass of the acrylic resin, and more preferably 0.5 parts by mass or more and 8 parts by mass or less.

[0070] The protective layer 10a preferably contains a photopolymerization initiator, such as an α-ketol compound, an acetophenone compound, a benzoin ether compound, a ketal compound, an aromatic sulfonyl chloride compound, a photoactive oxime compound, a benzophenone compound, a thioxanthone compound, camphorquinone, a halogenated ketone, an acylphosphinoxide, or an acylphosphonate.

[0071] Examples of α-ketol compounds include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone. Examples of acetophenone compounds include methoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,2-diethoxyacetophenone, 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzoyl)phenyl)-2-methylpropan-1-one. Examples of benzoin ether compounds include benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether. An example of the ketal compound is a benzyl dimethyl ketal compound. An example of the aromatic sulfonyl chloride compound is 2-naphthalenesulfonyl chloride. An example of a photoactive oxime compound is 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)oxime. Examples of benzophenone compounds include benzophenone, benzoin benzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone. Examples of thioxanthone compounds include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone. Among these, it is preferable to use 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzoyl)phenyl)-2-methylpropan-1-one (commercially available product: Omnirad 127 manufactured by IGM Resins).

[0072] The protective layer 10a preferably contains 0.1 parts by mass or more and 10 parts by mass or less of the photopolymerization initiator relative to 100 parts by mass of the acrylic resin, more preferably 0.5 parts by mass or more and 7 parts by mass or less, and even more preferably 0.75 parts by mass or more and 5 parts by mass or less.

[0073] The protective layer 10a may contain components other than those mentioned above. Examples of the other components include plasticizers, fillers, antioxidants, antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, antistatic agents, surfactants, and light release agents.

[0074] The polyurethane resin may be one that is cured by active energy rays (for example, ultraviolet rays). Such polyurethane resins include those having a urethane polymer as the main chain and unsaturated groups such as methacryloyl groups introduced into the side chains. Specific examples of such polyurethane resins include those available from Taisei Fine Chemical Co., Ltd. under the trade names 8UH-1094, 8UH-4005A, and 8UH-4025A. When a polyurethane resin is used, the protective layer 10a preferably contains the polyurethane resin in a proportion similar to the proportion of the acrylic resin described above.

[0075] Examples of epoxy resins include bisphenol A type, bisphenol F type, bisphenol S type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol AF type, biphenyl type, naphthalene type, fluorene type, phenol novolac type, orthocresol novolac type, trishydroxyphenylmethane type, tetraphenylolethane type, hydantoin type, trisglycidyl isocyanurate type, and glycidylamine type epoxy resins. Here, since the epoxy resin is used after being thermally cured, when the second protective layer-forming composition and the protective layer 10a contain an epoxy resin, it is preferable that they further contain a curing agent for the epoxy resin. The curing agent for the epoxy resin preferably contains a phenol resin. Examples of the phenolic resin include novolac-type phenolic resins, resol-type phenolic resins, and polyoxystyrenes such as polyparaoxystyrene. When an epoxy resin is used, the protective layer 10a preferably contains 5% by mass or more and 70% by mass or less of the epoxy resin, and preferably contains 10% by mass or more and 80% by mass or less of the phenol resin.

[0076] Examples of silicone resins include addition type silicone resins and condensation type silicone resins. The silicone resin is usually used after being thermally cured. Examples of the addition type silicone resin include those obtained by curing an alkenyl group-containing polydialkylcyclohexane and a polydialkylhydrogenpolysiloxane through an addition reaction using a platinum compound as a catalyst. The condensation type silicone resin may be obtained by reacting a methylol group-containing polydialkylsiloxane with a polydialkylhydrogenpolysiloxane using a tin catalyst. Examples of the addition type silicone resin include "KS-776A" and "KS-839L" manufactured by Shin-Etsu Chemical Co., Ltd., and examples of the condensation type silicone resin include "KS-723A" and "KS-723B" manufactured by Shin-Etsu Chemical Co., Ltd. When a silicone resin is used, the protective layer 10a preferably contains the silicone resin in a proportion similar to the proportion of the acrylic resin described above.

[0077] In the protective sheet 10 according to the second embodiment, the adhesion strength of the protective layer 10a to the bare wafer before curing is preferably 0.1 N / 100 mm or more and 50 N / 100 mm or less, more preferably 0.5 N / 100 mm or more and 40 N / 100 mm or less, and even more preferably 1 N / 100 mm or more and 30 N / 100 mm or less. Furthermore, the adhesion strength of the protective layer 10a to the bare wafer after curing is preferably 0.01 N / 100 mm or more and 10 N / 100 mm or less, more preferably 0.03 N / 100 mm or more and 6 N / 100 mm or less, and even more preferably 0.05 N / 100 mm or more and 3 N / 100 mm or less. The adhesion of the protective layer 10a to the bare wafer before curing can be measured by the same method as described in the first embodiment. The adhesion of the protective layer 10a to the bare wafer after curing can be measured in the same manner as described in the first embodiment, except that the measurement is carried out after the protective layer 10a has been cured. When ultraviolet (UV) rays are used as active energy rays, the cumulative UV irradiation dose is 200 mJ / cm 2 ~500mJ / cm 2 The protective layer 10a is cured by irradiating it with ultraviolet light so that the protective layer 10a becomes In the case of thermal curing, the protective layer 10a is cured by heat treatment at a temperature at which the curable resin hardens (for example, 170° C. for epoxy resin) for a predetermined time (for example, 1 hour for epoxy resin).

[0078] In the protective sheet 10 according to the second embodiment, the protective layer 10a also preferably has a breaking strength at -15°C of 200 MPa or less, more preferably 100 MPa or less, and even more preferably 50 MPa or less. Furthermore, in the protective sheet 10 according to the second embodiment, the protective layer 10a also preferably has a breaking strength at -15°C of 0.01 MPa or more, more preferably 0.05 MPa or more, and even more preferably 0.1 MPa or more. Furthermore, in the protective sheet 10 according to the second embodiment, the protective layer 10a also has a breaking elongation at -15°C of preferably 100% or less, more preferably 80% or less, and even more preferably 50% or less. Furthermore, in the protective sheet 10 according to the second embodiment, the protective layer 10a also has a breaking elongation at -15°C of preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. Furthermore, in the protective sheet 10 according to the second embodiment, the breaking strength at −15° C. and breaking elongation at −15° C. preferably fall within the above numerical ranges both before and after curing. The breaking strength at -15°C and the breaking elongation at -15°C can be measured by the same method as described in the first embodiment.

[0079] In the protective sheet 10 according to the second embodiment, the protective layer 10a, after curing, preferably has a tensile storage modulus at −15° C. of 1 MPa or more and 30 GPa or less, more preferably 10 MPa or more and 20 GPa or less, and even more preferably 100 MPa or more and 15 GPa or less. Furthermore, in the protective sheet 10 according to the second embodiment, the protective layer 10a, after curing, preferably has a tensile storage modulus at 25°C of 1 MPa or more and 20 GPa or less, more preferably 5 MPa or more and 15 GPa or less, and even more preferably 10 MPa or more and 10 GPa or less. The tensile storage modulus of the cured protective layer 10a at -15°C and the tensile storage modulus of the cured protective layer 10a at 25°C can be measured in the same manner as described in the first embodiment, except that the measurements are performed after the protective layer 10a has been cured. The protective layer 10a can be cured in the same manner as above. Furthermore, in the protective sheet 10 according to the second embodiment, the protective layer 10a preferably has a tensile storage modulus at 25° C. of 10 GPa or less, and more preferably 1 GPa or less, before curing. The tensile storage modulus at 25° C. of the protective layer 10a before curing can be measured by the same method as described in the first embodiment.

[0080] Furthermore, in the protective sheet 10 according to the second embodiment, the thickness of the protective layer 10a is preferably the same as that of the protective layer 10a of the protective sheet 10 according to the first embodiment. Furthermore, in the protective sheet 10 according to the second embodiment, the first release liner 10b and second release liner 10c can be the same as those described for the protective sheet 10 according to the first embodiment.

[0081] [Attachment of protective sheet to surface to be protected] Hereinafter, with reference to FIGS. 4A to 4E, the manner in which protective sheet 10 according to this embodiment is attached to a surface to be protected will be described, taking as an example a case in which the electronic component having a surface to be protected is a semiconductor chip. 4A and 4B show the semiconductor chip 50 including a semiconductor chip body 50a and two paired electrode portions 50b on both sides of the semiconductor chip body 50a. 4A and 4B, one surface of the semiconductor chip body 50a is a circuit formation surface on which circuits are formed. In FIG. 4A and 4B, the region on the circuit formation surface on which circuits are formed is shown as a circuit formation region 50c. 4C to 4E, the semiconductor chip 50 includes a semiconductor chip body 50a and one electrode portion 50b on one surface of the semiconductor chip body. In Figure 4C, one electrode portion 50b is provided on the circuit formation surface (the surface included in the circuit formation area 50c), and in Figures 4D and 4E, one electrode portion 50b is provided on the surface opposite to the circuit formation surface.

[0082] As shown in Figure 4A, the protective layer 10a of the protective sheet 10 of this embodiment has two paired electrode portions 50b on both sides of the semiconductor chip body 50a, and can be attached to a semiconductor chip 50 having one side as a circuit formation surface so as to protect the circuit formation surface. That is, in the example shown in FIG. 4A, the circuit-forming surface having the electrode portion 50b is the surface to be protected. By laminating the protective layer 10a of the protective sheet 10 according to this embodiment in this manner, the circuit-formation surface and the electrode portions 50b provided on the circuit-formation surface can be protected by the protective layer 10a. This type of bonding mode is particularly useful when the semiconductor wafer comprises a semiconductor wafer body and a plurality of paired electrode portions on both sides of the semiconductor wafer body, and both sides of the semiconductor wafer body are circuit formation surfaces, and the surface opposite to the circuit formation surface of the semiconductor wafer is abutted against the stage of a dicing device so that the semiconductor wafer is placed on the stage, and the semiconductor wafer placed on the stage is diced into a plurality of semiconductor chips. Specifically, when the semiconductor wafer is cut and separated into a plurality of semiconductor chips, even if a portion of the semiconductor wafer near the cut portion is powdered and minute foreign matter is generated, it is possible to prevent the minute foreign matter from adhering to and remaining in large numbers on the circuit formation surface.

[0083] Furthermore, as shown in Figure 4B, the protective layer 10a of the protective sheet 10 according to this embodiment can be attached to a semiconductor chip 50 having two paired electrode portions 50b on both sides of the semiconductor chip body 50a, one side of which is a circuit formation surface, to protect the surface opposite the circuit formation surface. That is, in the example shown in FIG. 4B, the surface to be protected is the surface opposite to the circuit formation surface, which has the electrode portion 50b. By laminating the protective layer 10a of the protective sheet 10 according to this embodiment in this manner, the protective layer 10a can protect the surface opposite the circuit-forming surface and the electrode portions 50b provided on that surface. This type of bonding mode is particularly useful when the semiconductor wafer comprises a semiconductor wafer body and a plurality of paired electrode portions on both sides of the semiconductor wafer body, and both sides of the semiconductor wafer body are circuit formation surfaces, and the circuit formation surface side of the semiconductor wafer is abutted against the stage of a dicing device so that the semiconductor wafer is placed on the stage, and the semiconductor wafer placed on the stage is diced into a plurality of semiconductor chips. Specifically, even if minute foreign matter such as that described above occurs when the semiconductor wafer is cut and separated into a plurality of semiconductor chips, it is possible to prevent the minute foreign matter from adhering to and remaining in large numbers on the surface opposite the circuit formation surface.

[0084] Furthermore, as shown in Figure 4C, the protective layer 10a of the protective sheet 10 of this embodiment can also be attached to a semiconductor chip 50 in which one side of the semiconductor chip body 50a is a circuit formation surface and in which a single electrode portion 50b is provided only on the circuit formation surface, so as to protect the circuit formation surface. That is, in the example shown in FIG. 4C, the circuit-forming surface having the electrode portion 50b is the surface to be protected. By laminating the protective layer 10a of the protective sheet 10 according to this embodiment in this manner, the circuit-formation surface and the electrode portions 50b provided on the circuit-formation surface can be protected by the protective layer 10a. Such a bonding mode is particularly useful when a semiconductor wafer has a semiconductor wafer body, one side of which is a circuit formation surface, and the semiconductor wafer has a plurality of electrode portions only on the circuit formation surface.The surface opposite the circuit formation surface of the semiconductor wafer is abutted against a stage of a dicing device, and the semiconductor wafer is placed on the stage, and the semiconductor wafer placed on the stage is diced into a plurality of semiconductor chips. Specifically, even if minute foreign matter such as that described above occurs when the semiconductor wafer is cut and separated into a plurality of semiconductor chips, it is possible to prevent the minute foreign matter from adhering to and remaining on the circuit formation surface in large numbers.

[0085] Furthermore, as shown in Figure 4D, the protective layer 10a of the protective sheet 10 of this embodiment can also be attached to a semiconductor chip 50 in which one side of the semiconductor chip body 50a is a circuit formation surface and in which a single electrode portion 50b is provided only on the surface opposite the circuit formation surface, so as to protect the surface opposite the circuit formation surface. That is, in the example shown in FIG. 4D, the surface opposite to the circuit formation surface, which is provided with electrode portion 50b, is the surface to be protected. By laminating the protective layer 10a of the protective sheet 10 according to this embodiment in this manner, the protective layer 10a can protect the surface opposite the circuit-forming surface and the electrode portions 50b provided on that surface. Such a bonding mode is particularly useful when the circuit formation surface side of a semiconductor wafer having a semiconductor wafer body, one side of which is a circuit formation surface and having a plurality of electrode portions only on the surface opposite to the circuit formation surface, is abutted against a stage of a dicing device so that the semiconductor wafer is placed on the stage, and the semiconductor wafer placed on the stage is diced into a plurality of semiconductor chips. Specifically, even if minute foreign matter such as that described above occurs when the semiconductor wafer is cut and separated into a plurality of semiconductor chips, it is possible to prevent the minute foreign matter from adhering to and remaining in large numbers on the surface opposite the circuit formation surface.

[0086] Furthermore, as shown in Figure 4E, the protective layer 10a of the protective sheet 10 of this embodiment can also be attached to a semiconductor chip 50 in which one side of the semiconductor chip body 50a is a circuit formation surface and in which a single electrode portion 50b is provided only on the surface opposite to the circuit formation surface, so as to protect the circuit formation surface. That is, in the example shown in FIG. 4E, the circuit formation surface that does not have the electrode portion 50b is the surface to be protected. By laminating the protective layer 10a of the protective sheet 10 according to this embodiment in this manner, the circuit-forming surface can be protected by the protective layer 10a. This type of bonding mode is particularly useful for placing a semiconductor wafer on a stage of a dicing device, the surface opposite to the circuit formation surface of the semiconductor wafer having a semiconductor wafer body, one side of which is a circuit formation surface, and a plurality of electrode portions only on the surface opposite to the circuit formation surface, and then dicing the semiconductor wafer placed on the stage into a plurality of semiconductor chips. Specifically, even if minute foreign matter such as that described above occurs when the semiconductor wafer is cut and separated into a plurality of semiconductor chips, it is possible to prevent the minute foreign matter from adhering to and remaining on the circuit formation surface in large numbers.

[0087] 4A to 4E show an example in which the protective layer 10a of the protective sheet 10 according to this embodiment is attached to only one side of the semiconductor chip, but if necessary, the protective layer 10a may be attached to both sides of the semiconductor chip.

[0088] 4A to 4E show an example in which the surface to be protected is one surface of a semiconductor chip, but the surface to be protected may be the surface to be protected of another electronic component. For example, it may be at least one side of a semiconductor wafer from which semiconductor chips are obtained, or it may be at least one side of a pseudo wafer comprising a support substrate and a package body formed by arranging multiple semiconductor chips on the support substrate and resin-sealing the multiple semiconductor chips together, i.e., at least one side of a pseudo wafer in which the support substrate and the package body are integrated, or it may be at least one side of a pseudo wafer formed by removing the support substrate from the package body, i.e., at least one side of a pseudo wafer formed only by the package body, or it may be at least one side of a divided body of a pseudo wafer formed by dividing the pseudo wafer into each constituent unit including at least one semiconductor chip, or it may be at least one side of a circuit board, or it may be at least one side of a connected circuit board formed by connecting multiple circuit boards. In addition, when the pseudo wafer has a rewiring layer on at least one side, the protective layer 10a of the protective sheet 10 of this embodiment is attached to the pseudo wafer or a divided body of the pseudo wafer to protect the rewiring layer and the like formed thereon. In this way, by attaching the protective layer 10a of the protective sheet 10 of this embodiment to the pseudo wafer so as to protect the rewiring layer, etc., even if part of the sealing resin near the cleavage portion turns into powder and generates fine foreign matter when the pseudo wafer is cleaved to obtain divided pseudo wafer bodies, it is possible to prevent the fine foreign matter from adhering to and remaining in large numbers on the rewiring layer, etc. Furthermore, the protective layer 10a of the protective sheet 10 according to this embodiment is attached to the circuit board or the interconnected circuit board to protect the circuits and the like formed thereon. In this way, by laminating the protective layer 10a of the protective sheet 10 according to this embodiment to the interconnected circuit board so as to protect the circuits and the like, even if the resin constituting the support substrate of the interconnected circuit board turns into powder and generates fine foreign matter when the interconnected circuit board is cut to obtain a plurality of the circuit boards, it is possible to prevent the fine foreign matter from adhering to and remaining in large numbers on the circuits and the like.

[0089] In addition, the surface to be protected of the other electronic component may be at least one surface of a wafer-level package comprising a circuit board and a plurality of semiconductor packages mounted on the circuit board, or at least one surface of a semiconductor package obtained by dividing the wafer-level package. In the wafer level package, one surface of each of the plurality of semiconductor packages may be formed from one surface of a glass piece. In the wafer-level package, when one side of each of the multiple semiconductor packages is made up of one surface of a glass piece, the protective layer 10a of the protective sheet 10 of this embodiment is attached to protect one surface of the glass piece that constitutes one side of the multiple semiconductor packages. In this way, by attaching the protective layer 10a of the protective sheet 10 of this embodiment to the wafer-level package so as to protect one surface of the glass plate, even if a part of the circuit board near the cutting portion is powdered and fine foreign matter is generated when the circuit board portion of the wafer-level package is cut to obtain the semiconductor package, it is possible to prevent the fine foreign matter from adhering to and remaining in large numbers on one surface of the glass plate.

[0090] Furthermore, the surface to be protected of the other electronic component may be at least one surface of a laminate for an image sensor package, which comprises a sensor wafer body having a plurality of circuits formed on one surface thereof and a glass plate having approximately the same dimensions as the sensor wafer body in a planar view and laminated on one surface (the surface on which the plurality of circuits are formed) of the sensor wafer body via an adhesive layer made of adhesive, glass frit, or the like, or may be at least one surface of an image sensor package obtained by singulating the laminate for the image sensor package. In the laminate for an image sensor package, the protective layer 10a of the protective sheet 10 according to this embodiment is attached to, for example, one surface of the glass plate to protect it. In the image sensor package, the protective layer 10a of the protective sheet 10 according to this embodiment is attached to protect one surface of the glass piece obtained by cleaving the glass plate, for example. In this way, by attaching the protective layer 10a of the protective sheet 10 of this embodiment to the laminate for the image sensor package so as to protect one surface of the glass plate, even if a part of the sensor wafer body near the cutting portion is powdered and fine foreign matter is generated when the laminate for the image sensor package is cut to obtain the image sensor package, it is possible to prevent the fine foreign matter from adhering to and remaining on one surface of the glass piece of the image sensor package.

[0091] Furthermore, as described above, the object to be protected by the protective layer 10a of the protective sheet 10 according to this embodiment may not be the surface to be protected of an electronic component, but may be one surface of a glass piece constituting the display surface of a display device, or one surface of a glass plate from which the glass piece is obtained. In this way, by attaching the protective layer 10a of the protective sheet 10 of this embodiment to one surface of the glass plate from which the glass fragments are obtained, even if a portion of the glass plate near the fractured portion is powdered and fine foreign matter is generated when the glass plate is fractured to obtain multiple glass fragments, the fine foreign matter can be prevented from adhering to and remaining on one surface of the glass fragments (the display surface of the display device).

[0092] [How to use the protective sheet] The protective sheet 10 according to this embodiment is used as an auxiliary tool for manufacturing electronic component devices. Hereinafter, a specific example of the use of the protective sheet 10 according to this embodiment in the case of manufacturing a semiconductor device as an electronic component device will be described. In the following, an example will be described in which a TSV type semiconductor chip is obtained using the protective sheet 10 according to this embodiment.

[0093] In the manufacture of the semiconductor device according to this embodiment, the protective sheet 10 according to this embodiment is attached to a semiconductor wafer having electrode portions so as to protect the electrode portions. The semiconductor wafer includes a semiconductor wafer body and a plurality of electrode portions arranged on each of both surfaces of the semiconductor wafer body and electrically connected to electrode portions of other members. In a semiconductor wafer, the semiconductor wafer body usually has a disk shape, and the dimensions of the semiconductor wafer body include, for example, an outer diameter of 12 inches (300 mm) and a thickness of 40 μm to 50 μm. In addition, in the semiconductor wafer, at least one surface of the semiconductor wafer body is a circuit formation surface on which a circuit is formed. More specifically, the semiconductor wafer has at least one pair of electrode portions electrically connected to other members on both surfaces of each semiconductor wafer body portion that is cut and separated into semiconductor chips. Furthermore, in the semiconductor wafer, circuits corresponding to each semiconductor chip are formed on at least one surface of each semiconductor wafer body portion that is cut and separated into individual semiconductor chips.

[0094] An example of such a semiconductor wafer is shown in FIG. The semiconductor wafer 20 shown in Figure 5 is of a TSV (Through Silicon Via) type, and includes a semiconductor wafer main body 20a, a pair of electrode portions 20b, 20c arranged on both sides of the semiconductor wafer main body 20a and electrically connected to other components, and a conductive portion 20d that penetrates the semiconductor wafer main body 20a in the thickness direction so as to electrically connect the pair of electrode portions 20b, 20c. In the semiconductor wafer 20 shown in FIG. 5, only one surface (the surface on which the electrode portions 20b are provided) is the circuit formation surface.

[0095] In the semiconductor wafer 20 shown in FIG. 5, the conductive portion 20d is made of a solid conductor. However, the conductive portion 20d only needs to be configured to be in contact with at least a portion of the pair of electrode portions 20b, 20c and to be able to electrically connect the pair of electrode portions 20b, 20c, and may be configured, for example, as a hollow conductor. In addition, in the semiconductor wafer 20 shown in Figure 5, an insulating layer 20e is formed on each side of the semiconductor wafer body 20a to prevent conduction between adjacent electrode portions, specifically, between adjacent electrode portions 20b and between adjacent electrode portions 20c. In the semiconductor wafer 20 shown in Figure 5, the outermost surface of one insulating layer 20e is flush with the outermost surface of each electrode portion 20b, and the outermost surface of the other insulating layer 20e is flush with the outermost surface of each electrode portion 20c. That is, in the semiconductor wafer 20 shown in FIG. 5, each electrode portion 20b is provided on the semiconductor wafer main body 20a so that only its outermost surface is exposed from one insulating layer 20e, and each electrode portion 20c is provided on the semiconductor wafer main body 20a so that only its outermost surface is exposed from the other insulating layer 20e. On the other hand, each electrode portion 20b may be provided on the semiconductor wafer body 20a so as to be entirely covered by one insulating layer 20e, and each electrode portion 20c may be provided on the semiconductor wafer body 20a so as to be entirely covered by the other insulating layer 20e. That is, each electrode portion 20b may be provided on the semiconductor wafer body 20a so as to be embedded in one insulating layer 20e, and each electrode portion 20c may be provided on the semiconductor wafer body 20a so as to be embedded in the other insulating layer 20e.

[0096] The electrode portions 20b and 20c and the conductive portion 20d may be integrally formed or may be formed separately. The electrode portions 20b, 20c and the conductive portion 20d are inserted, in an integrated state, into conductive portion through-holes formed so as to penetrate the semiconductor wafer body 20a. The electrode portions 20b, 20c and the conductive portion 20d may be made of copper, aluminum, or the like. The electrode portions 20b and 20c are provided on the semiconductor wafer body 20a so as to have a thickness of 5 nm to 10 μm from the outermost surface of the semiconductor wafer body 20a. The length of the conductive portion 20d is set to be approximately the same as the length of the conductive portion through-hole (that is, the thickness of the semiconductor wafer body 20a). The dimensions and shape of the conductive portion 20d are appropriately selected depending on the shape of the conductive portion through hole. For example, if the conductive portion through hole is cylindrical, the dimensions and shape of the conductive portion 20d are selected to be cylindrical with an outer diameter slightly smaller than that of the conductive portion through hole.

[0097] The insulating layer 20e is made of materials such as silicon dioxide (SiO2) and silicon nitride (SiN). The insulating layer 20e can be formed on both sides of the semiconductor wafer body 20a by a CVD method or the like. The thickness of the insulating layer 20e is appropriately selected depending on the thickness of the electrode portions 20b and 20c.

[0098] [Electronic component manufacturing method] The method for manufacturing an electronic component according to this embodiment includes the steps of: a protective sheet attachment step S1 of attaching a protective sheet to a connected body of electronic components in which a plurality of electronic components having surfaces to be protected are connected with the surfaces to be protected facing in the same direction, so as to protect the surfaces to be protected of each of the plurality of electronic components; an electronic component linked body dividing step S2 of dividing the electronic component linked body with the protective sheet attached at intervals in a planar direction to obtain a plurality of divided electronic components with the protective sheet attached; and a protective sheet removing step S3 of removing the protective sheet separated from each of the plurality of electronic components. In the method for manufacturing an electronic component according to this embodiment, the protective sheet includes a protective layer that is attached to the surface to be protected. In the method for manufacturing an electronic component according to this embodiment, the protective layer is made of either a water-soluble resin composition or a curable resin composition whose adhesive strength decreases upon curing.

[0099] [Method of manufacturing semiconductor device] Next, as an example of a method for manufacturing an electronic component, a method for manufacturing a semiconductor device using a semiconductor wafer having electrodes on both sides and the protective sheet 10 according to this embodiment will be described. In the method for manufacturing a semiconductor device, the "semiconductor wafer" corresponds to the "connection of electronic components" in the above-mentioned method for manufacturing electronic components, and the "semiconductor chip" corresponds to the "electronic component" in the above-mentioned method for manufacturing electronic components. In addition, in the method of manufacturing a semiconductor device, "cutting into individual pieces" is a concept that is included in "dividing."

[0100] A method for manufacturing a semiconductor device includes: a step of attaching a protective sheet 10 to at least one circuit-forming surface of a semiconductor wafer, the semiconductor wafer comprising a semiconductor wafer body and electrode portions disposed on both surfaces of the semiconductor wafer body and electrically connected to electrode portions of other members, at least one surface of the semiconductor wafer body being a circuit-forming surface on which circuits are formed (protective sheet attaching step S1a); a step of cutting the semiconductor wafer (more specifically, the semiconductor wafer body) to which the protective sheet 10 is attached into individual pieces (semiconductor wafer cutting step S2a); and removing the protective sheet 10 from the semiconductor wafer (protective sheet removing step S3a). Hereinafter, the method for manufacturing the semiconductor device according to this embodiment will be described in more detail, taking the first and second embodiments as examples. In the first' and second' embodiments, the method for manufacturing a semiconductor device is carried out using the semiconductor wafer 20 shown in FIG. 5 and the protective sheet 10 according to this embodiment.

[0101] (First embodiment) First, a method for manufacturing a semiconductor device according to the first embodiment will be described with reference to FIGS. 6A to 6H. In the method for manufacturing a semiconductor device according to the first embodiment, the protective sheet 10 used is the protective sheet 10 according to the first embodiment described above. That is, protective layer 10a of protective sheet 10 contains a water-soluble polymer compound.

[0102] <Preparation process S0a> In the first' method of manufacturing a semiconductor device, as shown in Figure 6A, in the preparation step S0a, a semiconductor chip is provided with a semiconductor wafer main body 20a and electrode portions 20b, 20c arranged on both sides of the semiconductor wafer main body 20a and electrically connected to electrode portions of other components, and the semiconductor chip is provided with a circuit formation surface on one side of the semiconductor wafer main body 20a (the surface on which the electrode portions 20b are provided) on which a circuit is formed.A glass carrier 30 serving as a support is attached to the circuit formation surface (the surface on which the electrode portions 20b are provided) of the semiconductor wafer main body 20a. The semiconductor wafer 20 generally used has a semiconductor wafer body 20a with an outer diameter of 12 inches (300 mm) and a thickness of 40 μm to 50 μm. The glass carrier 30 generally used has planar dimensions and a planar shape that are substantially the same as the planar shape of the semiconductor wafer 20 and a thickness of 0.5 mm to 5 mm. Next, as shown in FIG. 6B, the semiconductor wafer 20 with the glass carrier 30 attached thereto is attached onto the adhesive layer 40b of the dicing tape 40, which has an adhesive layer 40b laminated on a base layer 40a. In detail, after attaching the dicing ring R to the adhesive layer 40b of the dicing tape 40, the side of the semiconductor wafer 20 to which the glass carrier 30 is attached, on which the electrode portion 20c is provided (the side opposite to the side to which the glass carrier 30 is attached), is attached to the adhesive layer 40b of the dicing tape 40. The semiconductor wafer 20 does not necessarily have sufficient strength on its own because the thickness of the semiconductor wafer body 20a is relatively thin, at 20 μm to 100 μm. However, by attaching it to the glass carrier 30, it can be attached onto the adhesive layer 40b of the dicing tape 40 in a state of sufficient strength. Therefore, when the dicing tape 40 is attached onto the adhesive layer 40b, damage to the semiconductor wafer body 20a can be suppressed. Next, as shown in FIG. 6C, the glass carrier 30 is removed from the semiconductor wafer 20.

[0103] <Protective sheet attachment process S1a> In the first' method of manufacturing a semiconductor device, as shown in FIG. 6D, a protective sheet 10 is attached onto a semiconductor wafer 20 in a protective sheet attaching step S1a. Specifically, the first release liner 10b is peeled off from the protective sheet 10 to expose one side of the protective layer 10a, and the exposed side is attached to one side of the semiconductor wafer 20 (the side on which the electrode portion 20b is provided), and then the second release liner 10c is peeled off from the protective sheet 10 to expose the other side of the protective layer 10a, and the protective sheet 10 is attached onto the semiconductor wafer 20. In the example shown in Figure 6D, the second release liner 10c is peeled off from the protective sheet 10 to expose the other side of the protective layer 10a, but it is not necessarily necessary to peel off the second release liner 10c in the protective sheet attachment step S1. The steps up to the fragile portion forming step described below may be carried out with second release liner 10c attached, and after the fragile portion forming step, second release liner 10c may be released and the semiconductor wafer cleaving step S2a may be carried out.

[0104] Next, as shown in Figure 6E, the semiconductor wafer 20, one side of which is attached to the protective sheet 10 (more specifically, the protective layer 10a) and the other side of which is attached to the adhesive layer 40b of the dicing tape 40, is placed on the stage S of the stealth dicing device. Specifically, the semiconductor wafer 20 is placed on the stage S so that the protective sheet 10 abuts against the stage S. Next, a laser beam focused on the interior of the semiconductor wafer 20 (i.e., the semiconductor wafer main body 20a) is emitted from a laser irradiation light source of the stealth dicing device along a pre-determined dicing position (planned dividing line), and a weak portion WP is formed inside the semiconductor wafer 20 (i.e., the semiconductor wafer main body 20a) by ablation due to multiphoton absorption (weak portion forming step). The weak portion WP is a modified region for dividing the semiconductor wafer 20 into individual semiconductor chips. A method for forming a fragile portion WP on a planned dividing line by irradiating a semiconductor wafer 20 with laser light is described in detail, for example, in Japanese Patent Application Laid-Open No. 2002-192370. In this embodiment, the irradiation conditions of the laser light are appropriately adjusted, for example, within the range of the following conditions. <Laser light irradiation conditions> (A) Laser light Laser light source: Diode-pumped Nd:YAG laser Wavelength: 1064nm, 1088nm, 1099nm, or 1342nm Laser beam spot cross-sectional area: 3.14×10 -8 cm 2 Oscillation mode: Q-switched pulse Repetition frequency: 100kHz or less Pulse width: 1 μs or less Output; 1mJ or less Laser light quality; TEM00 Polarization characteristics: Linear polarization (B) Condenser lens Magnification: 100x or less NA;0.55 Transmittance to laser light wavelength: 100% or less (C) Stage movement speed: 280 mm / sec or less

[0105] <Semiconductor wafer cleaving process S2a> Next, after removing the semiconductor wafer 20 from the stage S of the stealth dicing device, the dicing ring R is fixed to the holder H of the expanding device, and both end edge sides of the base layer 40a of the dicing tape 40 are fixed to the holder H, as shown in Figure 6F. Then, a push-up member U provided in the expanding device is used to push up the dicing tape 40 from below, thereby stretching the dicing tape 40 so as to spread it in the planar direction. As a result, under specific temperature conditions, the semiconductor wafer body 20a having the fragile parts WP therein is cleaved along the fragile parts WP and singulated into a plurality of semiconductor chips. At this time, the protective layer 10a is also cut into individual pieces having a size corresponding to a chip together with the semiconductor wafer. The temperature condition is, for example, -30°C to 5°C, preferably -25°C to 0°C, and more preferably -20°C to -5°C. Next, as shown in FIG. 6G, the push-up member U is lowered to release the expanded state.

[0106] <Protective sheet removal step S3a> In the method for manufacturing a semiconductor device according to the first' embodiment, in the protective sheet removing step S3a, water is applied to the protective layer 10a using a water washing mechanism provided in the expanding device. Specifically, water is applied (specifically, sprayed) from the water cleaning mechanism of the expanding device toward the individualized protective layer 10a, and the individualized protective layer 10a is removed from the surface of each semiconductor chip, thereby exposing one surface of each semiconductor chip (the surface not attached to the dicing tape 40) (see Figure 6H). An example of an expanding device equipped with a water washing mechanism is the cleaving device DDS2300 manufactured by Disco Corporation. The expanding device includes a rotatable stage, and the water cleaning mechanism includes a water jetting unit that jets water toward the individual protective layers 10a. Then, while the stage is rotated, water is sprayed from the water spraying unit toward the individualized protective layer 10a, whereby the protective layer 10a dissolved by the water is discharged outside the stage. In such an apparatus, the rotation speed of the stage is preferably 500 rpm to 4000 rpm, the amount of water sprayed (water volume) is preferably 0.05 L / min to 5.0 L / min, and the water spray time is preferably 5 seconds to 300 seconds. The protective sheet removal step S3a may be performed by spraying water at high pressure. The pressure at which water is sprayed can be appropriately set in consideration of the size of the semiconductor chips to be sprayed and the balance of adhesive strength between the semiconductor chips and the protective sheet (individualized protective sheet).

[0107] As described above, each semiconductor chip with one surface exposed can be collected by a pickup device equipped with a pin member and a suction jig. Specifically, a pin member is raised from the dicing tape 40 side, pushing up the semiconductor chip to be picked up through the dicing tape 40, and the pushed-up semiconductor chip is held by a suction jig, thereby recovering each semiconductor chip. As shown in Figure 7, the electrode portion 20c on one side of one semiconductor chip 20aa is joined to the electrode portion CBa of the circuit board CB, and the electrode portion 20b on the other side of one semiconductor chip 20aa is joined to the electrode portion 20c on one side of another semiconductor chip, and so on, until the semiconductor chips are stacked in multiple layers, and then molded and packaged to form a semiconductor device. In addition, the bonding between the electrode portion CBa of the circuit board CB and the electrode portion 20c on one side of one semiconductor chip 20aa, and the bonding between the electrode portion 20b on the other side of one semiconductor chip 20aa and the electrode portion 20c on one side of another semiconductor chip 20aa can be performed by atomic diffusion bonding or the like. That is, the protective sheet 10 is used to protect the electrode portions of the semiconductor chip that are directly bonded to the electrode portions of another member.

[0108] (Second' embodiment) Next, a method for manufacturing a semiconductor device according to a second embodiment will be described with reference to FIGS. 6A to 6C, 6F, and 6G, as well as with reference to FIGS. 8A to 8E. In the method for manufacturing a semiconductor device according to the second embodiment, the protective sheet according to the second embodiment described above is used as the protective sheet 10. That is, protective layer 10a of protective sheet 10 contains a resin, more specifically, an acrylic resin.

[0109] <Preparation process S0b> In the semiconductor device manufacturing method according to the second embodiment, the preparation step S0b is carried out in the same manner as in the semiconductor device manufacturing method according to the first embodiment. Specifically, as shown in FIGS. 6A to 6C, a preparation step S0b is performed.

[0110] <Protective sheet attachment process S1b> In the method for manufacturing a semiconductor device according to the second' embodiment, in the protective sheet attaching step S1b, a protective sheet 10 is attached onto the semiconductor wafer 20 as shown in FIG. 8A. Specifically, the first release liner 10b is peeled off from the protective sheet 10 to expose one side of the protective layer 10a, and the exposed side is attached to one side of the semiconductor wafer 20 (the side on which the electrode portion 20b is provided), thereby attaching the protective sheet 10 to the semiconductor wafer 20 without exposing the other side of the protective layer 10a. The method for manufacturing a semiconductor device according to the second embodiment differs from the protective sheet attachment step S1a in the method for manufacturing a semiconductor device according to the first embodiment in that in the protective sheet attachment step S1b, the protective sheet 10 is attached to the semiconductor wafer 20 in a state in which the other side of the protective layer 10a is not exposed. In the example shown in Figure 6A, the second release liner 10c is not peeled off from the protective sheet 10, and the second release liner 10c covers the other side of the protective layer 10a, but it is not necessarily necessary to cover the other side of the protective layer 10a with the second release liner 10c in the protective sheet attachment step S1b. In the protective sheet attachment step S1b, second release liner 10c may be peeled off from protective sheet 10 to expose the other side of protective layer 10a, and the subsequent weakened portion formation step may be carried out.

[0111] Next, as shown in Figure 8B, the semiconductor wafer 20 is placed on the stage S of the stealth dicing device with the second release liner 10c of the protective sheet 10 abutted against it (with the other side of the protective layer 10a covered by the second release liner 10c), and a fragile portion WP is formed inside the semiconductor wafer main body 20a in the same manner as in the semiconductor device manufacturing method of embodiment 1' (fragile portion formation process).

[0112] Next, after removing the semiconductor wafer 20 from the stage S of the stealth dicing device, as shown in FIG. 8C, a UV (ultraviolet) irradiation light source (for example, a product name "UM-810" manufactured by Nitto Seiki Co., Ltd. (high pressure mercury lamp, 60 mW / cm 2)) is used, and UV is irradiated from the second release liner 10c side to cure the protective layer 10a (protective layer curing step). When the resin contained in the protective layer 10a is an acrylic resin, the cumulative dose of UV is 200 mJ / cm 2 2 ~500mJ / cm 2 It is preferable that: Then, as shown in FIG. 6D, the second release liner 10c is removed from the cured protective layer 10a (release liner removing step).

[0113] <Semiconductor wafer cleaving process S2b> In the semiconductor device manufacturing method according to the second' embodiment, as shown in FIGS. 6F and 6G, the semiconductor wafer cleaving step S2b is carried out in the same manner as described in the semiconductor device manufacturing method according to the first' embodiment.

[0114] <Protective sheet removal step S3b> In the manufacturing method of the semiconductor device according to the second' embodiment, in the protective sheet removal process S3b, as shown in FIG. 8E, a release tape T is attached to the individual protective layer 10a, and then the release tape T is pulled upward to remove the individual protective layer 10a from each semiconductor chip, thereby exposing one surface of each semiconductor chip (the surface not attached to the dicing tape 40).

[0115] As described above, each semiconductor chip with one surface exposed can be collected by a pickup device equipped with a pin member and a suction jig, as described in the semiconductor device manufacturing method of the first embodiment. As shown in Figure 7, the electrode portion 20c on one side of one semiconductor chip 20aa is joined to the electrode portion CBa of the circuit board CB, and the electrode portion 20b on the other side of one semiconductor chip 20aa is joined to the electrode portion 20c on one side of another semiconductor chip 20aa, and so on, until the semiconductor chips are stacked in multiple layers, and then molded and packaged to form a semiconductor device.

[0116] Although the above describes the manufacturing method of a semiconductor device using the protective sheet 10 using the first and second embodiments, the manufacturing method of a semiconductor device using the protective sheet 10 is not limited to these and various modifications are possible.

[0117] [Method of manufacturing glass pieces constituting the display surface of a display device] The method for manufacturing the glass piece that constitutes the display surface of the display device according to this embodiment is as follows: a protective sheet attachment step S1' of attaching a protective sheet to protect one surface of a glass plate from which glass pieces constituting a display surface of the display device are obtained; a glass plate dividing step S2' in which the glass plate with the protective sheet attached is divided at intervals in the surface direction to obtain a plurality of glass pieces with the divided protective sheet attached; a protective sheet removing step S3′ of removing the protective sheet separated from each of the plurality of glass pieces, the protective sheet includes a protective layer attached to one surface of the glass plate or one surface of the glass piece, The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesive strength decreases upon curing reaction.

[0118] The protective sheet attaching step S1' can be carried out in the same manner as described in the "protective sheet attaching step S1a" or "protective sheet attaching step S1b" in the section on the method for manufacturing a semiconductor device above. The glass plate dividing step S2' can be carried out in the same manner as described in the "semiconductor wafer dividing step S2a" or "semiconductor wafer dividing step S2b" in the section on the method for manufacturing a semiconductor device above. Furthermore, the protective sheet removing step S3' can be carried out in the same manner as described in the "protective sheet removing step S3a" or "protective sheet removing step S3b" in the section on the manufacturing direction of the semiconductor device above.

[0119] The matters disclosed by this specification include the following.

[0120] (1) A protective sheet that is attached to a surface to be protected of an electronic component having a surface to be protected, one surface of a glass piece that constitutes a display surface of a display device, or one surface of a glass plate from which the glass piece is obtained, a protective layer attached to the surface to be protected of the electronic component, one surface of the glass piece, or one surface of the glass plate; The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesiveness decreases upon curing reaction. Protective sheet.

[0121] According to this configuration, the protective layer of the protective sheet can protect the surface to be protected of the electronic component, one surface of the glass piece that constitutes the display surface of the display device, or one surface of the glass plate from which the glass piece is obtained. Therefore, even if minute foreign matter is generated during a dicing process or the like, it is possible to prevent a large number of minute foreign matter from adhering to the surface to be protected of the electronic component or one surface of the glass piece. As a result, it is possible to prevent a large number of minute foreign matters from remaining on the surface of the electronic component to be protected or on one surface of the glass piece.

[0122] (2) the protective layer is made of the water-soluble resin composition, The water-soluble resin composition contains at least one water-soluble polymer compound selected from the group consisting of polyvinyl alcohol, water-soluble polyester, and polyethylene oxide. The protective sheet according to (1) above.

[0123] According to this configuration, when removing the protective layer from the surface of the electronic component to be protected or one surface of the glass piece, adding water to the protective layer makes it even easier to remove the protective layer from the surface of the electronic component to be protected or one surface of the glass piece. That is, the protective layer can be easily removed from the surface of the electronic component to be protected or from one surface of the glass piece.

[0124] (3) the protective layer is made of the curable resin composition whose adhesiveness decreases by a curing reaction, The curable resin composition contains an acrylic resin and is cured by heat or active energy rays. The protective sheet according to (1) above.

[0125] With this configuration, the hardening reaction of the protective layer can be accelerated, so that the protective layer has moderate hardening properties, and the protective layer can be relatively easily removed from the surface to be protected of the electronic component or one surface of the glass piece. That is, the protective layer can be removed relatively easily from the surface of the electronic component to be protected or from one surface of the glass piece.

[0126] (4) a protective sheet attachment step of attaching a protective sheet to a connected assembly of electronic components in which a plurality of electronic components each having a surface to be protected are connected with the surfaces to be protected facing in the same direction, so as to protect the surfaces to be protected of each of the plurality of electronic components; a connecting body dividing step of dividing the connecting body of electronic components to which the protective sheet is attached at intervals in a planar direction to obtain a plurality of the divided electronic components to which the protective sheet is attached; a protective sheet removing step of removing the protective sheet separated from each of the plurality of electronic components, the protective sheet includes a protective layer attached to the surface to be protected, The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesive strength decreases upon curing reaction. Manufacturing methods for electronic components.

[0127] With this configuration, even if minute foreign matter is generated during the manufacturing of the electronic component, it is possible to prevent the minute foreign matter from adhering in large numbers to the surface of the electronic component to be protected. As a result, it is possible to prevent a large number of minute foreign particles from remaining on the surface of the electronic component to be protected.

[0128] (5) a protective sheet attachment step of attaching a protective sheet to protect one surface of the glass plate from which the glass pieces constituting the display surface of the display device are obtained; a glass plate dividing step of dividing the glass plate with the protective sheet attached thereto at intervals in the surface direction to obtain a plurality of glass pieces with the protective sheet attached thereto; a protective sheet removing step of removing the protective sheet separated from each of the plurality of glass pieces, the protective sheet includes a protective layer attached to one surface of the glass plate or one surface of the glass piece, The protective layer is composed of either a water-soluble resin composition or a curable resin composition whose adhesive strength decreases upon curing reaction. A method for manufacturing glass pieces that make up the display surface of a display device.

[0129] With this configuration, even if minute foreign matter is generated during the manufacturing of the glass pieces that make up the display surface, it is possible to prevent the minute foreign matter from adhering in large numbers to one surface of the glass pieces that make up the display surface. As a result, it is possible to prevent a large number of minute foreign matters from remaining on one surface of the glass piece that constitutes the display surface.

[0130] It should be noted that the protective sheet, the method for manufacturing electronic components, and the method for manufacturing glass pieces that constitute the display surface of a display device according to the present invention are not limited to the above-described embodiments. Furthermore, the protective sheet, the method for manufacturing electronic components, and the method for manufacturing glass pieces that constitute the display surface of a display device according to the present invention are not limited by the above-described effects. The protective sheet, the method for manufacturing electronic components, and the method for manufacturing glass pieces that constitute the display surface of a display device according to the present invention can be modified in various ways without departing from the spirit of the present invention.

[0131] In the above embodiment, an example has been described in which, in the semiconductor wafer 20, the outermost surface of one insulating layer 20e is flush with the outermost surface of each electrode portion 20b, and the outermost surface of the other insulating layer 20e is flush with the outermost surface of each electrode portion 20c, but the mounting manner of each electrode portion 20b, 20c in the semiconductor wafer 20 is not limited to this. For example, in the semiconductor wafer 20, the outermost surface of each electrode portion 20b may protrude from the outermost surface of one insulating layer 20e, and the outermost surface of each electrode portion 20c may protrude from the outermost surface of the other insulating layer 20e. Furthermore, each of the electrode portions 20b and each of the electrode portions 20c may be formed of a solder ball. [Example]

[0132] The present invention will now be described in more detail with reference to examples. The following examples are intended to explain the present invention in more detail, but are not intended to limit the scope of the present invention.

[0133] [Example 1] In a container, polyvinyl alcohol (saponification degree 65, average polymerization degree 240) was dispersed in water to prepare an aqueous dispersion. Next, the container containing the aqueous dispersion was placed in a water bath at 90° C., and the aqueous dispersion container was stirred to dissolve the polyvinyl alcohol in the water, thereby obtaining a first protective layer composition. Next, the first protective layer composition was applied to a thickness of 10 μm using an applicator onto the release-treated surface of a first PET release liner (product name MRA50, manufactured by Mitsubishi Chemical Corporation, thickness 50 μm) having a surface treated with silicone release. Next, the first PET release liner coated with the first protective layer composition was dried at 110° C. for 2 minutes to form a protective layer on the first PET release liner. Next, the release-treated surface of a second PET release liner (product name MRA25, manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) having a surface that had been subjected to a silicone release treatment was attached to the protective layer to obtain the protective sheet of Example 1.

[0134] The saponification degree and average polymerization degree of the polyvinyl alcohol were measured in accordance with the method described in the above embodiment section.

[0135] [Example 2] A protective sheet according to Example 2 was obtained in the same manner as in Example 1, except that polyvinyl alcohol with a hydrolysis value of 80 and an average degree of polymerization of 240 was used. In Example 2, the saponification degree of polyvinyl alcohol and the average polymerization degree of polyvinyl alcohol were determined in the same manner as in Example 1.

[0136] [Example 3] A protective sheet according to Example 3 was obtained in the same manner as in Example 1, except that polyvinyl alcohol with a hydrolysis value of 74 and an average degree of polymerization of 500 was used. In Example 3, the saponification degree of polyvinyl alcohol and the average polymerization degree of polyvinyl alcohol were determined in the same manner as in Example 1.

[0137] [Example 4] The protective sheet of Example 4 was obtained in the same manner as Example 1, except that polyvinyl alcohol with a hydrolysis value of 88 and an average degree of polymerization of 500 was used. In Example 4, the saponification degree of polyvinyl alcohol and the average polymerization degree of polyvinyl alcohol were determined in the same manner as in Example 1.

[0138] [Example 5] The protective sheet of Example 5 was obtained in the same manner as Example 1, except that polyvinyl alcohol with a hydrolysis value of 65 and an average degree of polymerization of 100 was used. In Example 5, the saponification degree of polyvinyl alcohol and the average polymerization degree of polyvinyl alcohol were determined in the same manner as in Example 1.

[0139] [Example 7] A protective sheet according to Example 7 was obtained in the same manner as in Example 1, using a water-soluble polyester (trade name "Z-221", manufactured by GOO Chemical Co., Ltd.) instead of polyvinyl alcohol. The water-soluble polyester had a mass average molecular weight Mw of 14,000. The mass average molecular weight Mw was measured according to the method described above in the embodiment section. The acid value of the water-soluble polyester was less than 5 mgKOH / g.

[0140] [Example 8] A protective sheet according to Example 8 was obtained in the same manner as in Example 1, using a water-soluble polyester (trade name "Z-592", manufactured by GOO Chemical Co., Ltd.) instead of polyvinyl alcohol. The water-soluble polyester had a mass average molecular weight Mw of 30,000. The mass average molecular weight Mw was measured according to the method described above in the embodiment section. The acid value of the water-soluble polyester was less than 5 mgKOH / g.

[0141] [Example 9] A protective sheet according to Example 9 was obtained in the same manner as in Example 1, except that a water-soluble polyester (trade name "Z-730", manufactured by GOO Chemical Co., Ltd.) was used instead of polyvinyl alcohol. The water-soluble polyester had a mass average molecular weight Mw of 3,000. The mass average molecular weight Mw was measured according to the method described above in the embodiment section. The acid value of the water-soluble polyester was about 50 mgKOH / g.

[0142] [Example 10] The protective sheet of Example 10 was obtained in the same manner as Example 1, except that polyethylene oxide (product name "PEO-3", manufactured by Sumitomo Seika Chemicals Co., Ltd.) was used instead of polyvinyl alcohol and the polyethylene oxide was dissolved in water without heating the aqueous dispersion. The mass average molecular weight Mw of the polyethylene oxide was 600,000 (six hundred thousand). The mass average molecular weight Mw was measured according to the method described above in the embodiment section.

[0143] [Example 11] The protective sheet of Example 11 was obtained in the same manner as Example 1, except that polyethylene oxide (product name "PEO-8", manufactured by Sumitomo Seika Chemicals Co., Ltd.) was used instead of polyvinyl alcohol and the polyethylene oxide was dissolved in water without heating the aqueous dispersion. The mass average molecular weight Mw of the polyethylene oxide was 2,000,000 (2 million). The mass average molecular weight Mw was measured according to the method described above in the embodiment section.

[0144] <Evaluation of minute foreign particles> With the protective sheets according to Examples 1 to 5 and Examples 8 to 11 attached to the surface of a bare wafer, the bare wafer was cleaved into multiple semiconductor chips, and then the microscopic foreign matter remaining on the surface of the multiple semiconductor chips was evaluated. The evaluation of fine foreign matter was carried out as follows. (1) The second PET release liner is removed from the prepared protective sheet to expose one side of the protective layer of the protective sheet. (2) A bare wafer (outer diameter 12 inches (300 mm), thickness 40 μm) is prepared with a glass carrier attached to one side and a dicing tape attached to the other side (specifically, attached to the adhesive layer of the dicing tape), and the glass carrier is removed from one side of the bare wafer to obtain a bare wafer with dicing tape. Then, the protective sheet is attached to the surface of the bare wafer from which the glass carrier has been removed. A dicing ring is attached to the edge of the adhesive layer of the dicing tape. (3) The bare wafer with the protective sheet attached is placed on the stage of a vacuum mounter (model MV3000, manufactured by Nitto Seiki Co., Ltd.), and the stage temperature is then raised to 90°C to adhere the protective sheet to the bare wafer (hereinafter referred to as a bare wafer with a protective sheet). (4) A bare wafer with a protective sheet is placed on the stage of a stealth dicing machine (model DFL7361, manufactured by Disco Corporation) so that the first PET release liner is in contact with the stage. Then, laser light is irradiated from the laser irradiation light source of the stealth dicing machine along a predetermined dicing line to form a fragile portion inside the bare wafer. Specifically, fragile portions are formed in a lattice pattern inside the bare wafer so that after cutting, a plurality of bare chips having planar dimensions of 10 mm×10 mm are obtained. The laser light emitted from the laser irradiation light source is irradiated under the conditions described in the embodiment section. After forming a fragile portion inside the bare wafer, the first PET release liner is removed from the other side of the protective layer of the protective sheet to expose the other side of the protective layer of the protective sheet (hereinafter referred to as a bare wafer with a fragile portion formed therein). (5) After removing the bare wafer with the fragile portions formed thereon from the stage of the stealth dicing device, an expanding device (model DDS2300, manufactured by Disco Corporation) is used to expand (expand) the bare wafer with the fragile portions formed thereon in the surface direction, thereby fracturing the bare wafer with the fragile portions formed thereon into individual pieces of semiconductor chips, and also fracturing the protective layer of the protective sheet into pieces of chip-sized pieces. The expansion by the expanding device is carried out under the conditions of a temperature of -15°C and an expansion speed of 200 mm / s. (6) While rotating the stage of the expanding device at 1000 rpm, water is applied (sprayed) from the water spraying section of the water cleaning mechanism of the expanding device toward the diced protective layer, and the diced protective layer is removed from the surface of each semiconductor chip toward the outside of the stage, thereby exposing one surface of each semiconductor chip (the side on which the dicing tape is not attached). The amount of water sprayed (water volume) is set to a value within the range of 100 L / min to 300 L / min, and the water spray time is set to a value within the range of 60 seconds to 90 seconds. Furthermore, low-temperature water (23±2°C) is first used, and if the individualized protective layer cannot be removed with low-temperature water, high-temperature water (40±2°C) is used to remove the individualized protective layer. In Example 9, the protective layer was removed from the individual pieces using 0.1 mol / L ammonia water (temperature: 23±2° C.) instead of water. (7) After each semiconductor chip with one exposed surface was picked up using a pickup device, the surface of the semiconductor chip from which the individual protective layer had been removed was observed using a digital microscope (model VHX-5000, manufactured by Keyence Corporation). The observation of the surface of the semiconductor chip using a digital microscope was carried out on a randomly selected 10 mm×10 mm area on the surface, with an observation magnification of 50 times. Then, the number of minute foreign particles remaining on the surface was counted. In addition, observation using a digital microscope was performed on five semiconductor chips, and the number of minute foreign particles was calculated by arithmetic averaging. The figures below the decimal point were rounded off. (8) The presence or absence of minute foreign matter was evaluated according to the following criteria. Excellent: The number of remaining fine foreign objects is less than 10. Unacceptable: There are 10 or more tiny foreign objects remaining. The results are shown in Table 1 below.

[0145] <Evaluation of semiconductor wafer cleavability and protective layer removability> While the evaluation of minute foreign matters was being carried out as described above, the cleavability of the semiconductor wafer and the removability of the protective layer were also evaluated for Examples 1 to 5 and Examples 7 to 11 at the same time. The cleavability of the semiconductor wafer was evaluated by observing all of the 10 mm × 10 mm bare chips obtained after cleaving and assessing whether the kerf width (the distance between paired chips) was sufficient (10 μm or more) and whether there were any connected portions in the protective layer. In addition, the removability of the protective layer was evaluated by analyzing all surfaces of multiple 10 mm x 10 mm bare chips obtained after water spraying using a Fourier transform infrared spectrophotometer (FT-IR) to evaluate the presence or absence of residual organic matter. The evaluation criteria for the breakability of the semiconductor wafer and the removability of the protective layer were as follows: -Semiconductor wafer cleavability Excellent: For all of the bare chips, the kerf width is sufficient and no connecting portions are observed in the protective layer. Unacceptable: Even among multiple bare chips, there is one in which the curve width is not sufficiently recognized, or there is a connection part in the protective layer. -Removability of the protective layer Excellent: No residual organic matter was found on any of the bare chips (800-4000 cm -1 Maximum absorption at ≦0.05 Not permitted: Even if one of the bare chips has residual organic matter (800-400cm -1 Maximum absorption at >0.05 The results are shown in Table 1 below.

[0146] <Low temperature water resistance> The protective layer (containing water-soluble polyester) according to Example 7, the protective layer (containing water-soluble polyester) according to Example 8, the protective layer (containing water-soluble polyester) according to Example 9, the protective layer (containing polyethylene oxide) according to Example 10, and the protective layer (containing polyethylene oxide) according to Example 11 were evaluated for durability when washed with water at low temperature (23±2°C), i.e., water durability at low temperature. Specifically, in (6) of the above <Evaluation of Fine Foreign Matter>, if the protective layer could not be removed with low-temperature water, it was judged as "excellent," and if the protective layer could be removed with low-temperature water, it was judged as "unacceptable." The results are shown in Table 1 below.

[0147] <Film forming properties> The protective layers according to Examples 7 to 11 were evaluated for film formability when forming the protective layer. Specifically, when the first protective composition was applied to a predetermined thickness on the release-treated surface of the first PET release liner using an applicator, if it could be spread sufficiently or applied to the desired thickness, it was rated as "excellent," and if not, it was judged as "unacceptable." The results are shown in Table 1 below.

[0148] [ reference Example 6] (Preparation of acrylic polymer) A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer was charged with 11 parts by mass of hydroxyethyl acrylate (HEA) and 89 parts by mass of 2-ethylhexyl acrylate (2EHA) as monomers, as well as 2,2'-azobisbutyronitrile (AIBN) as a thermal polymerization initiator, and further, butyl acetate was added as a reaction solvent so that the concentration of the monomers became 36% by mass, thereby preparing a first reaction solution. The first reaction solution was subjected to a polymerization treatment under a nitrogen gas flow to obtain a first acrylic polymer A as an intermediate. In the polymerization treatment, the first polymerization treatment was carried out at a temperature of 62°C for 4 hours, and then the second polymerization treatment was carried out at a temperature of 75°C for 2 hours. To the first reaction solution containing this first acrylic polymer A, 13 parts by mass of 2-isocyanatoethyl methacrylate (MOI) was added as a monomer, and 0.07 parts by mass of dibutyltin dilaurate was added per 100 parts by mass of the first acrylic polymer A to prepare a second reaction solution. The second reaction solution is subjected to an addition reaction treatment at 50°C for 12 hours under an air flow, referenceAn acrylic polymer A' (acrylic resin) according to Example 6 was obtained. The MOI used was Karenz MOI (registered trademark) manufactured by Showa Denko K.K. Karenz MOI (registered trademark) is a polymerizable group-containing (meth)acrylate having an isocyanate group, and has a vinyl group as the polymerizable group.

[0149] (Preparation of adhesive solution) reference To the second reaction solution containing the acrylic polymer A′ of Example 6, 0.8 parts by mass of a polyisocyanate compound (trade name “Takenate D-101A”, manufactured by Mitsui Chemicals, Inc.) was added as an external crosslinking agent, and 5 parts by mass of a photopolymerization initiator (trade name “Omnirad127”, manufactured by IGM Resins) was added, reference An adhesive solution A according to Example 6 was prepared. The parts by mass of the external crosslinking agent and the photopolymerization initiator are: reference The values ​​are based on 100 parts by mass of the acrylic polymer A′ of Example 6.

[0150] (Preparation of protective sheet) reference The adhesive solution A of Example 6 was applied using an applicator to the silicone release-treated surface of a first PET release liner (thickness 50 μm) having a surface that had been subjected to a silicone release treatment, and dried for 2 minutes at 120° C. to form an adhesive layer with a thickness of 30 μm. Thereafter, the release-treated surface of a second PET release liner (trade name "MRA25", manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) was laminated onto the adhesive layer, and then stored at a temperature of 50° C. for 24 hours. reference A protective sheet according to Example 6 was obtained.

[0151] <Evaluation of minute foreign particles> On the surface of a bare wafer reference With the protective sheet of Example 6 attached, the bare wafer was cleaved into a plurality of semiconductor chips, and then minute foreign matter remaining on the surfaces of the plurality of semiconductor chips was evaluated. The evaluation of fine foreign matter was carried out as follows. (1) to (3) The same procedures as (1) to (3) above were carried out when the protective sheets of Examples 1 to 5 were used. (4) A bare wafer with a protective sheet is placed on the stage of a stealth dicing machine (model DFL7361, manufactured by Disco Corporation) so that the first PET release liner is in contact with the stage. Then, laser light is irradiated from the laser irradiation light source of the stealth dicing machine along a predetermined dicing line to form a fragile portion inside the bare wafer. Specifically, fragile portions are formed in a lattice pattern inside the bare wafer so that after cutting, a plurality of bare chips having planar dimensions of 10 mm×10 mm are obtained. Then, UV (ultraviolet rays) was irradiated from the first PET release liner side (cumulative irradiation dose 300 mJ / cm 2 ), the protective layer of the protective sheet is cured, and the first PET release liner is peeled off from the protective layer of the protective sheet to expose the other side of the protective layer of the protective sheet. As a result, a bare wafer with a fragile portion formed thereon is obtained. (5) In the same manner as in (5) when the protective sheets of Examples 1 to 5 described above are used, the semiconductor wafer with the fragile portion formed thereon is cut into individual pieces into a plurality of semiconductor chips, and the protective layer of the protective sheet is also cut into pieces of a size equivalent to the chips and cut into individual pieces. (6) Using a laminator, release tape (model number 360UL, manufactured by Nitto Denko) is attached to each of the individual protective layers, and then the release tape is pulled upward to remove each of the individual protective layers from each of the individual semiconductor chips, thereby exposing one surface of each semiconductor chip (the side on which the dicing tape is not attached). (7) In the same manner as in (7) above when the protective sheets of Examples 1 to 5 were used, the surfaces of the five semiconductor chips from which the individual protective layers had been removed were observed using a digital microscope (model VHX-5000, manufactured by Keyence Corporation). (8) In the same manner as in (8) above when the protective sheets of Examples 1 to 5 were used, the presence or absence of fine foreign matter was evaluated. The results are shown in Table 1 below.

[0152] <Evaluation of semiconductor wafer cleavability and protective layer removability> When evaluating minute foreign particles as described above, reference For Example 6, the fracture properties of the semiconductor wafer and the removability of the protective layer were also evaluated at the same time. The cleavability of the semiconductor wafer and the removability of the protective layer were evaluated according to the same criteria as in Examples 1 to 5 above. The results are shown in Table 1 below.

[0153] <Protective layer thickness> Examples 1 to 11 (Including Reference Example 6) The thickness of the protective layer of each of the protective sheets was measured. The thickness of the protective layer was determined by measuring the thickness at five randomly selected locations using a dial gauge (Model R-205, manufactured by PEACOCK) and calculating the arithmetic mean of these thicknesses. The results are shown in Table 1 below.

[0154] <Adhesion of protective layer to bare wafer> Examples 1 to 11 (Including Reference Example 6) For the protective sheets according to the above, the adhesive strength of the protective layer to the bare wafer was measured. The adhesion of the protective layer to the bare wafer was measured as described in the above embodiment. In addition, reference For the protective sheet of Example 6, the adhesive strength of the protective layer to the bare wafer was measured both before and after UV irradiation.

[0155] <Breaking strength at -15°C and breaking elongation at -15°C> Examples 1 to 8 (Including Reference Example 6) The protective sheets according to the above were measured for breaking strength at -15°C and breaking elongation at -15°C. Specifically, for the elongation at break at -15°C, a protective layer having a length of 50 mm, a width of 10 mm, and a thickness of 30 μm was used as a test specimen, and the test specimen was pulled in the longitudinal direction using a tensile testing machine (Autograph AG-IS, manufactured by Shimadzu Corporation) under conditions of a temperature of -15°C, a chuck distance of 20 mm (measurement length, L0), and a tensile speed of 10 mm / sec, and the length at which the test specimen broke (the value obtained by adding the amount of elongation to the measurement length, L0, L1) was measured. Then, the breaking elongation E at −15° C. was calculated based on the following formula. Breaking elongation E = (L1 - L0) / L0 x 100 The breaking strength at -15°C was determined by measuring the force applied when the test piece broke when a tensile test was carried out using the test piece and the tensile tester under the same conditions as above. The results are shown in Table 1 below.

[0156] <Tensile storage modulus at -15°C and 25°C> Examples 1 to 11 (Including Reference Example 6) The tensile storage modulus at -15°C and the tensile storage modulus at 25°C were measured for the protective sheet according to the above. Specifically, a protective layer having a length of 40 mm, a width of 10 mm, and a thickness of 50 μm was used as a test specimen, and the tensile storage modulus of the test specimen was measured in the temperature range of -40°C to 80°C using a solid viscoelasticity measuring device (for example, Model RSAIII, manufactured by TA Instruments) under the conditions of a frequency of 1 Hz, a strain of 0.1%, a heating rate of 10°C / min, and a chuck distance of 20 mm. At that time, the tensile storage modulus at -15°C was determined by reading the value at -15°C, and the tensile storage modulus at 25°C was determined by reading the value at 25°C. The measurement was carried out by pulling the test piece in the length direction. The results are shown in Table 1 below.

[0157] <Surface free energy> The surface free energy of the protective layer of the protective sheets of Examples 1 to 5 and Examples 7 to 11 was measured. The surface free energy of the protective layer was measured as described in the above embodiment. The results are shown in Table 1 below.

[0158] [Comparative Example 1] Comparative Example 1 was an example in which a semiconductor wafer was cleaved and divided into a plurality of semiconductor chips in the same manner as in Example 1, except that a bare wafer with no protective sheet attached was used. In Comparative Example 1, only minute foreign matter was evaluated. The results are shown in Table 1 below.

[0159] Comparative Example 2 A protective sheet according to Comparative Example 2 was obtained in the same manner as in Example 9, except that polyethylene oxide (trade name "PEO-1", manufactured by Sumitomo Seika Chemicals) was replaced with another polyethylene oxide (trade name "PEO-4", manufactured by Sumitomo Seika Chemicals). The weight average molecular weight Mw of the polyethylene oxide contained in the protection sheet of Comparative Example 2 was 1,000,000 (1 million). The mass average molecular weight Mw was measured according to the method described above in the embodiment section. In the protective sheet of Comparative Example 2, the polyethylene oxide contained in the first protective layer-forming composition for forming the protective layer had a high mass average molecular weight Mw of 1,000,000, and therefore the first protective layer-forming composition could not be sufficiently spread over the release-treated surface of the first PET release liner during the formation of the protective layer, making it impossible to evaluate film-formability. Therefore, each evaluation item in Table 1 below is marked as "unmeasurable" or "unassessable."

[0160] Comparative Example 3 A protective sheet according to Comparative Example 3 was obtained in the same manner as in Example 9, except that polyethylene glycol (product name "PEG-20000", manufactured by Sanyo Chemical Industries, Ltd.) was used instead of polyethylene oxide (product name "PEO-1", manufactured by Sumitomo Seika Chemicals Co., Ltd.). The weight average molecular weight Mw of the polyethylene glycol contained in the protection sheet of Comparative Example 3 was 20,000 (20,000). The mass average molecular weight Mw was measured according to the method described above in the embodiment section. In the protective sheet of Comparative Example 3, the polyethylene oxide contained in the first protective layer-forming composition for forming the protective layer had a low mass average molecular weight Mw of 20,000, and therefore could not be applied to achieve the desired thickness when forming the protective layer, making it impossible to evaluate film-formability. Therefore, each evaluation item in Table 1 below is marked as "unmeasurable" or "unassessable."

[0161] [Reference example 1] reference A protective sheet prepared in the same manner as in Example 6 was used, except that the protective layer of the protective sheet was not cured. reference As in Example 6, a semiconductor wafer was cut and divided into a plurality of semiconductor chips, which was used as Reference Example 1. For Reference Example 1, the thickness of the protective layer, the adhesion of the protective layer to the bare wafer before UV irradiation, the breaking strength at -15°C, the breaking elongation at -15°C, the cleavability of the semiconductor wafer, and the removability of the protective layer were evaluated. The results are shown in Table 1 below. Although attempts were made to measure the tensile storage modulus at -15°C and 25°C for Reference Example 1, the measurement itself was difficult. Furthermore, an attempt was made to evaluate minute foreign matter in Reference Example 1, but after removing the individual protective layers from each individual semiconductor chip, glue residue remained on the surface of each semiconductor chip, making it difficult to count minute foreign matter.

[0162] [Table 1]

[0163] From Table 1, Examples 1 to 5, Reference example When the protective sheets according to Examples 6 and 8 to 11 were used, the evaluation of fine foreign matter was "excellent" in all cases. In the evaluation of minute foreign particles, the numbers in parentheses in each example indicate the number of minute foreign particles on the surface of the individual semiconductor chips. In contrast, in Comparative Example 1, in which no protective sheet was used, the evaluation of microscopic foreign matter was "unacceptable," and the number of microscopic foreign matter on the surface of the individual semiconductor chips exceeded 200. In addition, in Comparative Examples 2 and 3, the protective layer of the protective sheet could not be sufficiently formed, and the results were "ineligible for evaluation." In addition, in Reference Example 1, as described above, after the individualized protective layer was removed from each individualized semiconductor chip, glue residue remained on the surface of each semiconductor chip, making it difficult to count minute foreign matter and even difficult to evaluate the minute foreign matter.

[0164] These results show that when a semiconductor wafer is cut and diced into multiple semiconductor chips, using a protective sheet can prevent a large number of tiny foreign objects from remaining on the surface of the diced semiconductor chips.

[0165] Furthermore, when the protective sheet of Example 7 was compared with the protective sheet of Example 8 in terms of water durability at low temperatures, the protective sheet of Example 8 was evaluated as "excellent," while the protective sheet of Example 7 was evaluated as "poor." This is believed to be due to the weight average molecular weight Mw of the water-soluble polyester contained in the protective layer. Furthermore, when the protective sheets of Examples 10 and 11 were compared with the protective sheets of Comparative Examples 2 and 3 in terms of film-forming ability, the protective sheets of Examples 10 and 11 were evaluated as "excellent," whereas the protective sheets of Comparative Examples 2 and 3 were evaluated as "poor." This is also believed to be due to the mass average molecular weight Mw of the polyethylene oxide and polyethylene glycol contained in the protective layer. [Explanation of symbols]

[0166] 10 protective sheet, 10a protective layer, 10b first release liner, 10c second release liner, 20 semiconductor wafers, 20a semiconductor wafer body, 20b electrode portion, 20c electrode portion, 20d conductive portion, 20e insulating layer, 30 glass carriers, 40 dicing tape, 40a base material layer, 40b adhesive layer, 50 semiconductor chips, 50a: semiconductor chip body; 50b: electrode portion; 50c: circuit formation region. 100 wafer level package, 110 circuit board, 120 semiconductor package, 120a Glass fragments, 200 image sensor package, 210 sensor chip body, 220 adhesive layer, 230 glass piece, 200' image sensor package laminate, 210' sensor wafer body, 220' adhesive layer, 230' glass plate.

Claims

1. A protective sheet that is attached to a surface to be protected of an electronic component having a surface to be protected, one surface of a glass piece that constitutes a display surface of a display device, or one surface of a glass plate from which the glass piece is obtained, a protective layer attached to the surface to be protected of the electronic component, one surface of the glass piece, or one surface of the glass plate; the protective layer is made of a water-soluble resin composition, the protective sheet includes a first release liner and a second release liner respectively abutting on both sides of the protective layer; The surface free energy of the surface of the protective layer that contacts the first release liner and the surface that contacts the second release liner are both 25 mJ / m ２ 85mJ / m or more ２ is as follows: The protective layer is configured to be removable by washing with water after being attached to the surface to be protected, one surface of the glass piece, or one surface of the glass plate. Protective sheet.

2. the protective layer is made of the water-soluble resin composition, The water-soluble resin composition contains at least one water-soluble polymer compound selected from the group consisting of polyvinyl alcohol, water-soluble polyester, and polyethylene oxide. The protective sheet according to claim 1 .

3. A method for manufacturing an electronic component by laminating the protective sheet according to claim 1 or 2 to the surface to be protected of the electronic component, a protective sheet attachment step of attaching the protective layer of the protective sheet to a connected body of electronic components in which a plurality of electronic components having surfaces to be protected are connected with the surfaces to be protected facing in the same direction, so as to protect the surfaces to be protected of each of the plurality of electronic components; a coupled body dividing step of dividing the coupled body of electronic components to which the protective layer of the protective sheet is attached at intervals in a planar direction to obtain a plurality of the divided electronic components to which the protective layer of the protective sheet is attached; a protective sheet removing step of removing the protective layer of the divided protective sheet from each of the plurality of electronic components by washing with water, In the protective sheet attaching step, the first release liner is peeled from the protective layer, and the exposed surface of the protective layer exposed by the peeling is attached to the surface to be protected together with the second release liner, and then the second release liner is peeled from the protective layer. Manufacturing methods for electronic components.

4. A method for producing a glass piece for a display surface of a display device, comprising bonding the protective sheet according to claim 1 or 2 to one surface of a glass plate from which the glass piece is obtained, a protective sheet attachment step of attaching the protective layer of the protective sheet so as to protect one surface of a glass plate from which glass pieces constituting a display surface of a display device are obtained; a glass plate dividing step of dividing the glass plate to which the protective layer of the protective sheet is attached at intervals in the surface direction to obtain a plurality of glass pieces to which the protective layer of the protective sheet is attached; a protective sheet removing step of removing the protective layer of the divided protective sheet from each of the plurality of glass pieces by washing with water, In the protective sheet attaching step, the first release liner is peeled from the protective layer, and the exposed surface of the protective layer exposed by the peeling is attached to the surface to be protected together with the second release liner, and then the second release liner is peeled from the protective layer. A method for manufacturing glass pieces for display surfaces of display devices.

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