Hot-melt resin composition and method for forming surface protective film using hot-melt resin composition

Abstract

To provide a resin composition capable of forming a surface protective film which has flexibility, can prevent the occurrence of a residue of the protective film on the surface of a workpiece without cleaning with an organic solvent, and can reduce an environmental load by preventing the occurrence of an unused portion of the protective film.SOLUTION: The hot-melt resin composition contains (A) polyethylene glycol and (B) a polyvinylpyrrolidone-vinyl acetate copolymer, wherein the number average molecular weight of the polyethylene glycol (A) is 700 or more and 45000 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hot melt resin composition and a method for forming a surface protective film using the hot melt resin composition, and in particular to a hot melt resin composition that is in a solid state at room temperature, that changes phase from the solid state to a liquid state when heated, and that has excellent solubility in hot water even in the solidified state, and a method for forming a surface protective film using the hot melt resin composition. [Background technology]

[0002] In recent years, the demand for smaller and more sophisticated devices has increased, necessitating further improvements in stackability when assembling chips cut from semiconductor wafers into packages. To address this issue, efforts are being made to improve stackability by thinning semiconductor wafers to sufficiently reduce their thickness.

[0003] In thinning a semiconductor wafer, the backside of the semiconductor wafer, on whose front surface a device circuit pattern is formed, is ground, but during thinning, it is necessary to protect the front surface of the semiconductor wafer.

[0004] Conventionally, to protect the surface of a semiconductor wafer, for example, a pressure-sensitive adhesive surface protection sheet has been laminated to the surface of the semiconductor wafer. The pressure-sensitive adhesive surface protection sheet is composed of an olefin substrate, an acrylic adhesive, and a separator. During thinning of the semiconductor wafer, the separator is peeled off from the pressure-sensitive adhesive surface protection sheet, and the surface protection sheet is laminated to the surface of the semiconductor wafer. The surface protection sheet is then cut to fit the shape of the semiconductor wafer, and the remaining portion (unused portion) of the surface protection sheet is discarded. As a result, with surface protection sheets using acrylic adhesives, the unused portion is discarded, which poses a problem of not being able to reduce the environmental impact. Furthermore, after thinning, the surface protection sheet that was laminated to the surface of the semiconductor wafer is peeled off from the surface of the semiconductor wafer and discarded.

[0005] Furthermore, in surface protection sheets using acrylic adhesives, the acrylic adhesive needs to be designed to be soft in order to conform to the unevenness of the circuits on the semiconductor wafer. Furthermore, when the surface protection sheet is peeled off from the surface of the semiconductor wafer, the acrylic adhesive breaks off and remains on the circuits of the semiconductor wafer, which is a problem known as adhesive residue.

[0006] Therefore, a method has been proposed in which a surface protection sheet made of a water-soluble resin such as gelatin is used to remove the surface protection sheet from the surface of the semiconductor wafer by washing with warm water after thinning (Patent Document 1).However, with a sheet-like form, the unused portion of the surface protection sheet is still discarded, which poses a problem of not being able to reduce the environmental impact.

[0007] Therefore, in order to reduce the environmental impact, a method has been considered in which wax is applied only to the necessary areas of the semiconductor wafer according to its shape. However, when a liquid surface protection material in which wax is dissolved in an organic solvent is used, a separate drying process is required to remove the organic solvent, which results in poor production efficiency of the surface protection film. In addition, the drying process generates emissions of volatile organic solvents, which makes it difficult to sufficiently reduce the environmental impact. In addition, the wax adhering to the surface of the semiconductor wafer must be washed with an organic solvent after thinning, which also results in an insufficient reduction in the environmental impact. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-60255 Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above circumstances, the present invention aims to provide a resin composition capable of forming a surface protective film that is flexible, can prevent the generation of residue of the protective film on the surface of a workpiece without washing with an organic solvent, and can prevent the generation of unused portions of the protective film, thereby reducing the environmental load. [Means for solving the problem]

[0010] The gist of the configuration of the present invention is as follows. [1] A hot melt resin composition containing (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, The hot melt resin composition, wherein the polyethylene glycol (A) has a number average molecular weight of 700 or more and 45,000 or less. [2] The hot melt resin composition according to [1], which is in a solid state at 25°C and in a liquid state at 90°C. [3] The hot melt resin composition according to [1] or [2], containing 10 parts by mass or more and 400 parts by mass or less of the polyvinylpyrrolidone-vinyl acetate copolymer (B) per 100 parts by mass of the polyethylene glycol (A). [4] The hot melt resin composition according to [1] or [2], wherein the polyethylene glycol (A) is in a solid state at 25°C. [5] The hot melt resin composition according to [1] or [2], wherein the freezing point of the polyethylene glycol (A) is 30°C or higher and 80°C or lower. [6] The hot melt resin composition according to [1] or [2], wherein the freezing point of the polyethylene glycol (A) is 45°C or higher and 60°C or lower. [7] The hot melt resin composition according to [1] or [2], wherein the weight average molecular weight of the polyvinylpyrrolidone-vinyl acetate copolymer (B) is 10,000 or more and 70,000 or less. [8] The hot melt resin composition according to [1] or [2], further comprising (C) water or an alcohol-based solvent. [9] The hot melt resin composition according to [8], which contains 15 parts by mass or less of the water or alcohol-based solvent per 100 parts by mass of the polyethylene glycol (A).

[10] The hot melt resin composition according to [1] or [2], wherein the hot melt resin composition is soluble in warm water at a temperature of 40°C or higher and 90°C or lower.

[11] The hot melt resin composition according to [1] or [2], which is used for forming a surface protective film.

[12] A hot-melt resin composition comprising (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, wherein the number average molecular weight of the (A) polyethylene glycol is 700 or more and 45,000 or less, and a melting step of heating and melting the hot-melt resin composition; a coating step of coating the molten hot melt resin composition on a surface of a workpiece; a solidification step of cooling and solidifying the hot melt resin composition applied to the surface of the workpiece; A method for forming a surface protective film, comprising:

[13] The method for forming a surface protective film according to

[12] , wherein the temperature of the heat treatment is 40°C or higher and 100°C or lower.

[14] The method for forming a surface protective film according to

[12] or

[13] , wherein the temperature of the cooling treatment is 10°C or higher and 35°C or lower.

[15] The method for forming a surface protection film according to

[12] or

[13] , wherein the workpiece is a semiconductor wafer.

[0011] In this specification, the term "hot melt resin composition" refers to a resin composition that is in a solidified state with no fluidity at 25°C, i.e., in a solid state, that becomes fluid when heated to a predetermined temperature, and that returns to a solidified state with no fluidity when cooled from the predetermined temperature to 25°C. In other words, the term refers to a resin composition that reversibly changes between a solidified state and a fluid state between 25°C and the predetermined temperature. [Effects of the Invention]

[0012] According to an embodiment of the hot melt resin composition of the present invention, the resin composition contains (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, and the number average molecular weight of the polyethylene glycol (A) is 700 or more and 45,000 or less. This makes it possible to obtain a resin composition that is flexible and can prevent the generation of residues of a protective film on the surface of a workpiece to which the hot melt resin composition is applied by washing with warm water without washing with an organic solvent, and can also prevent the generation of unused portions of the protective film, thereby reducing the environmental load.

[0013] According to an embodiment of the hot melt resin composition of the present invention, since the hot melt resin composition is liquid at 90°C, it changes to a fluid state at temperatures below 100°C, thereby reducing the amount of energy consumed when cleaning and removing a surface protection film formed from the hot melt resin composition from the surface of a workpiece.

[0014] According to an embodiment of the hot melt resin composition of the present invention, the (B) polyvinylpyrrolidone-vinyl acetate copolymer is contained in an amount of 10 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the (A) polyethylene glycol. This optimizes the viscosity of the hot melt resin composition, improving its coatability, and also improving the water resistance and flexibility of the surface protection film formed from the hot melt resin composition in a balanced manner.

[0015] According to an embodiment of the hot melt resin composition of the present invention, the (A) polyethylene glycol is in a solidified state at 25° C., so that a surface protection film can be more reliably formed at room temperature.

[0016] According to an embodiment of the hot melt resin composition of the present invention, the freezing point of the polyethylene glycol (A) is 30°C or higher and 80°C or lower, and therefore the polyethylene glycol changes to a fluid state more reliably at temperatures below 100°C, thereby making it possible to more reliably reduce the amount of energy consumed when cleaning and removing a surface protection film formed from the hot melt resin composition from the surface of a workpiece.

[0017] According to an embodiment of the hot melt resin composition of the present invention, the freezing point of the (A) polyethylene glycol is 45°C or higher and 60°C or lower, so that the hydroxyl value of the (A) polyethylene glycol tends to be low, and the moisture absorption is small even when the composition is left for a long period of time under high humidity conditions, thereby further improving storage stability.

[0018] According to an embodiment of the hot melt resin composition of the present invention, the weight average molecular weight of the (B) polyvinylpyrrolidone-vinyl acetate copolymer is 10,000 or more and 70,000 or less, thereby more reliably forming a surface protective film that is flexible and can prevent the formation of protective film residue on the surface of a workpiece to which the hot melt resin composition has been applied when washed with warm water.

[0019] According to an embodiment of the hot melt resin composition of the present invention, the hot melt resin composition is soluble in hot water of 40°C or higher and 90°C or lower, and therefore the surface protection film formed from the hot melt resin composition can be washed and removed from the surface of the workpiece using hot water of less than 100°C, thereby reducing energy consumption. DETAILED DESCRIPTION OF THE INVENTION

[0020] The hot melt resin composition of the present invention and its constituent components will be described in detail below.

[0021] Hot melt resin composition The hot melt resin composition of the present invention is a hot melt resin composition containing (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, and the number average molecular weight of (A) polyethylene glycol is 700 or more and 45,000 or less. The hot melt resin composition of the present invention is flexible, and can prevent the generation of protective film residue on the surface of a workpiece to which the hot melt resin composition is applied by washing with warm water without washing with an organic solvent, and can form a surface protective film that prevents the generation of unused portions of the protective film and reduces the environmental load.

[0022] The hot-melt resin composition of the present invention is in a solidified state with no fluidity at 25°C, but changes to a fluid state when heated from 25°C to a predetermined temperature. Furthermore, when cooled from the predetermined temperature to 25°C, the resin composition changes from a fluid state to a solidified state with no fluidity again. In other words, the hot-melt resin composition of the present invention is a temperature-responsive resin composition that reversibly changes between a solidified state and a fluid state between 25°C and the predetermined temperature. The predetermined temperature can be, for example, 40°C or higher and 90°C or lower.

[0023] The hot-melt resin composition of the present invention can be heat-treated to make it fluid, and then applied in only the required amount to the surface of a workpiece. The applied hot-melt resin composition can then be cooled (for example, to a temperature in the range of 10°C to 35°C) to solidify it, thereby preparing a surface protective film formed from the hot-melt resin composition of the present invention on the surface of the workpiece. As described above, when preparing a surface protective film from the hot-melt resin composition of the present invention, it is possible to prevent unused portions of the protective film. The surface protective film is, for example, a coating of the hot-melt resin composition that covers the surface of the workpiece.

[0024] Furthermore, since the hot melt resin composition of the present invention has a fluidity at a predetermined temperature, applying hot water to the surface protection film changes the hot melt resin composition of the present invention from a solidified state to a fluidity, i.e., the hot melt resin composition of the present invention has solubility in hot water, and as a result, applying hot water to the surface protection film allows the surface protection film to be washed and removed from the surface of the workpiece.

[0025] The hot melt resin composition of the present invention is preferably liquid at 90°C, and particularly preferably liquid at 80°C, because it changes to a fluid state at temperatures below 100°C, thereby reducing the amount of energy consumed when cleaning and removing a surface protection film formed from the hot melt resin composition from the surface of a workpiece.

[0026] Furthermore, the hot melt resin composition of the present invention is preferably soluble in hot water of 40°C or higher and 90°C or lower, since the surface protection film formed from the hot melt resin composition can be washed and removed from the surface of the workpiece using hot water of less than 100°C, thereby reducing energy consumption.

[0027] As described above, the hot melt resin composition of the present invention can be used for forming a surface protective film, and in particular, can be used for forming a surface protective film that can be appropriately washed away.

[0028] (A) Polyethylene glycol The polyethylene glycol, which is component (A), is a component that promotes the solidification of the hot melt resin composition of the present invention at room temperature (25°C) and imparts mechanical strength to the solidified hot melt resin composition.

[0029] The number-average molecular weight of the polyethylene glycol is 700 or more and 45,000 or less. By setting the lower limit of the number-average molecular weight of the polyethylene glycol to 700, the hot-melt resin composition maintains its solidified state at room temperature (25°C), contributing to improved solubility of the hot-melt resin composition in warm water, and preventing the formation of protective film residue on the surface of a workpiece to which the hot-melt resin composition has been applied by washing with warm water, even without washing with an organic solvent. Furthermore, by setting the upper limit of the number-average molecular weight of the polyethylene glycol to 45,000, an increase in the viscosity of the hot-melt resin composition can be prevented, resulting in excellent applicability to the surface of the workpiece.

[0030] The number-average molecular weight of polyethylene glycol is not particularly limited as long as it is in the range of 700 to 45,000, but the lower limit is preferably 800, which contributes to preventing the formation of protective film residue on the surface of the workpiece to which the hot-melt resin composition is applied when washed with warm water, while ensuring that the hot-melt resin composition can maintain a solidified state at room temperature (25°C). For example, when room-temperature water is supplied to the backside of a semiconductor wafer as grinding water when grinding the backside of the semiconductor wafer, 900 is more preferred, which provides excellent water resistance to water at room temperature (25°C). 1000 is particularly preferred, which allows the hot-melt resin composition to maintain a solidified state at room temperature (25°C) more reliably, while further improving water resistance to water at room temperature (25°C). From the viewpoint of storage stability, the lower limit of the number-average molecular weight of polyethylene glycol is preferably 1500, more preferably 2000.

[0031] On the other hand, the upper limit of the number average molecular weight of polyethylene glycol is preferably 15,000 in order to reliably obtain excellent applicability, more preferably 8,000 in order to reliably prevent the formation of residue of the protective film on the surface of the workpiece to which the hot melt resin composition has been applied when washed with warm water, and even more preferably 3,500, particularly preferably 3,100, and most preferably 3,000 in order to reliably prevent the formation of residue of the protective film on the surface of the workpiece to which the hot melt resin composition has been applied when washed with warm water.

[0032] Furthermore, since the hot-melt resin composition solidifies more reliably at room temperature, thereby enabling the surface protection film to be formed more reliably, it is preferable that the polyethylene glycol is in a solidified state at 25° C. The phase of the polyethylene glycol at 25° C. can be adjusted by the number-average molecular weight of the polyethylene glycol.

[0033] The lower limit of the freezing point of polyethylene glycol is preferably 30°C, and particularly preferably 35°C, from the viewpoint of ensuring that the hot melt resin composition can maintain a solidified state at room temperature (25°C) while improving water resistance to water at room temperature (25°C). From the viewpoint of the storage stability of the hot melt resin composition, the lower limit of the freezing point of polyethylene glycol is even more preferably 45°C. On the other hand, the upper limit of the freezing point of polyethylene glycol is preferably 80°C, more preferably 70°C, and particularly preferably 60°C, from the viewpoint of ensuring that the hot melt resin composition changes to a fluid state at temperatures below 100°C, and further reducing the amount of energy consumed when cleaning and removing a surface protection film formed from the hot melt resin composition from the surface of a workpiece.

[0034] The freezing point of polyethylene glycol can be adjusted by the number average molecular weight of polyethylene glycol, and by setting the number average molecular weight of polyethylene glycol in the range of about 700 to about 40,000, the freezing point of polyethylene glycol will be in the range of 30°C to 80°C.

[0035] The lower limit of the hydroxyl value of polyethylene glycol is preferably 5 KOHmg / g, more preferably 10 KOHmg / g, and even more preferably 20 KOHmg / g, from the viewpoint of reliably obtaining excellent coatability and contributing to reliably preventing the formation of residue of the protective film on the surface of the workpiece to which the hot-melt resin composition is applied when washed with warm water. The upper limit of the hydroxyl value of polyethylene glycol is preferably 120 KOHmg / g, more preferably 80 KOHmg / g, and even more preferably 60 KOHmg / g, from the viewpoint of reducing hygroscopicity and improving storage stability.

[0036] In this specification, "warm water" means water at a temperature of 40° C. or higher. Furthermore, "number average molecular weight" means the number average molecular weight calculated as polystyrene by gel permeation chromatography.

[0037] (B) Polyvinylpyrrolidone-vinyl acetate copolymer The polyvinylpyrrolidone-vinyl acetate copolymer, component (B), is a component that imparts the property of dissolving in warm water to the solidified hot-melt resin composition. The polyvinylpyrrolidone structural unit in the polyvinylpyrrolidone-vinyl acetate copolymer primarily imparts the property of dissolving in warm water to the solidified hot-melt resin composition. That is, the polyvinylpyrrolidone structural unit primarily imparts the property of preventing the formation of a protective film residue on the surface of a workpiece to which the hot-melt resin composition has been applied when washed with warm water. Furthermore, the vinyl acetate structural unit primarily imparts film-forming properties to the hot-melt resin composition upon solidification. Furthermore, the vinyl acetate structural unit primarily imparts compatibility with polyethylene glycol, component (A).

[0038] The polyvinylpyrrolidone-vinyl acetate copolymer is a water-soluble resin, and is, for example, a copolymer made of a polyvinylpyrrolidone monomer and a vinyl acetate monomer.

[0039] The weight-average molecular weight of the polyvinylpyrrolidone-vinyl acetate copolymer is not particularly limited, but the lower limit thereof is preferably 10,000, more preferably 20,000, and particularly preferably 30,000, from the viewpoints of more reliably forming a flexible surface protective film and more reliably preventing the formation of protective film residue on the surface of a workpiece to which the hot-melt resin composition has been applied by washing with warm water. On the other hand, the upper limit of the weight-average molecular weight of the polyvinylpyrrolidone-vinyl acetate copolymer is preferably 70,000, more preferably 65,000, and particularly preferably 60,000, from the viewpoints of more reliably preventing an increase in the viscosity of the hot-melt resin composition and more reliably obtaining excellent applicability to the surface of the workpiece.

[0040] In this specification, the term "weight average molecular weight" refers to the weight average molecular weight calculated as polystyrene by gel permeation chromatography.

[0041] The molar ratio of polyvinylpyrrolidone structural units to vinyl acetate structural units in the polyvinylpyrrolidone-vinyl acetate copolymer is not particularly limited, but from the viewpoint of achieving a well-balanced improvement in the dissolution properties of the solidified hot-melt resin composition in warm water, the film-forming properties upon solidification of the hot-melt resin composition, and the compatibility with polyethylene glycol, the ratio of the number of moles of vinyl acetate structural units to the number of moles of polyvinylpyrrolidone structural units is preferably 0.25 or more and 4.0 or less, more preferably 0.30 or more and 2.0 or less, even more preferably 0.40 or more and 1.0 or less, and particularly preferably 0.50 or more and 0.80 or less.

[0042] The glass transition temperature of the polyvinylpyrrolidone-vinyl acetate copolymer is not particularly limited, but the lower limit is preferably 50° C., and particularly preferably 60° C., from the viewpoint of ensuring that the hot-melt resin composition can be maintained in a solidified state at 25° C. On the other hand, the upper limit of the glass transition temperature of the polyvinylpyrrolidone-vinyl acetate copolymer is preferably 130° C., and particularly preferably 120° C., from the viewpoint of improving the handleability of the hot-melt resin composition.

[0043] The content of polyvinylpyrrolidone-vinyl acetate copolymer is not particularly limited, but the lower limit is preferably 10 parts by mass, more preferably 15 parts by mass, and particularly preferably 20 parts by mass per 100 parts by mass of polyethylene glycol, from the viewpoint of further improving the warm water solubility and flexibility of the surface protective film formed from the hot melt resin composition. On the other hand, the upper limit of the content of polyvinylpyrrolidone-vinyl acetate copolymer is preferably 400 parts by mass, more preferably 300 parts by mass, and particularly preferably 250 parts by mass per 100 parts by mass of polyethylene glycol, from the viewpoint of optimizing the viscosity of the hot melt resin composition and improving its coatability, and also improving the water resistance of the surface protective film formed from the hot melt resin composition.

[0044] (C) Water or alcohol-based solvent Although the hot melt resin composition is usually solvent-free, the water or alcohol-based solvent (C) is an optional component that can be added as needed, and functions as a solvent for the polyethylene glycol and polyvinylpyrrolidone-vinyl acetate copolymer that are added to the hot melt resin composition. By adding water (c1) or an alcohol-based solvent (c2), the dissolution of the polyethylene glycol and polyvinylpyrrolidone-vinyl acetate copolymer in the hot melt resin composition can be promoted.

[0045] Examples of the alcohol-based solvent (c2) include methanol, ethanol, n-propanol, and isopropanol.

[0046] When water or an alcohol-based solvent is added, the content of the water or alcohol-based solvent is not particularly limited, but the lower limit is preferably 1.0 part by mass, and more preferably 3.0 parts by mass, per 100 parts by mass of polyethylene glycol, from the viewpoint of reliably promoting dissolution of polyethylene glycol and polyvinylpyrrolidone-vinyl acetate copolymer in the hot-melt resin composition. On the other hand, the upper limit of the content of the water or alcohol-based solvent is preferably 15 parts by mass, and more preferably 10 parts by mass, from the viewpoint of facilitating removal of water or organic solvent during film formation by solidification of the hot-melt resin composition.

[0047] The hot-melt resin composition of the present invention may contain other water-soluble resin components as optional components within the range that does not impair the performance of the composition. Examples of other water-soluble resins include water-soluble plasticizers and water-soluble polymers. The hot-melt resin composition of the present invention may also contain other optional components, such as plasticizers, thixotropy-imparting agents, surface conditioners (antifoaming agents, leveling agents, etc.), fillers, pigments, dyes, and heat stabilizers.

[0048] Next, a method for forming a surface protective film using the hot melt resin composition of the present invention will be described.

[0049] The method for forming a surface protection film using the hot melt resin composition of the present invention is a hot melt resin composition containing (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, and includes the following steps: a melting step of melting the hot melt resin composition of the present invention by heat treatment, wherein the hot melt resin composition contains (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, and wherein the number average molecular weight of (A) polyethylene glycol is 700 or more and 45,000 or less; an application step of applying the molten hot melt resin composition to the surface of a workpiece; and a solidification step of cooling and solidifying the hot melt resin composition applied to the surface of the workpiece.

[0050] Melting process By heating the storage tank in which the hot melt resin composition of the present invention is stored, the entire stored hot melt resin composition may be melted, or only a necessary amount of the stored hot melt resin composition may be heated and melted.

[0051] The temperature of the heat treatment is not particularly limited as long as it is a temperature at which the hot-melt resin composition changes from a solidified state at room temperature to a melted state having flowability. However, from the viewpoint of reducing the environmental load while preventing an increase in the viscosity of the hot-melt resin composition and achieving excellent coatability, the temperature is preferably 40°C or higher and 100°C or lower, and particularly preferably 60°C or higher and 80°C or lower.

[0052] Coating process In the coating step, only the required amount of the molten hot-melt resin composition is coated on the surface of the workpiece. By coating the molten hot-melt resin composition on the surface of the workpiece, a coating film of the hot-melt resin composition is formed on the surface of the workpiece. The method for coating the molten hot-melt resin composition is not particularly limited, and examples thereof include bar coating, spray coating, dispenser coating, and die coater coating.

[0053] Solidification process By cooling the molten hot-melt resin composition applied to the surface of the workpiece, the molten hot-melt resin composition solidifies to form a surface protective film on the surface of the workpiece. The temperature for the cooling treatment is not particularly limited as long as it is a temperature at which the hot-melt resin composition changes from a molten, fluid state to a solid state, but a temperature of 10°C or higher and 35°C or lower is preferred to ensure smooth solidification.

[0054] Next, a method for removing a surface protective film formed on the surface of a workpiece will be described. The hot-melt resin composition of the present invention is temperature responsive, so that by applying hot water to the surface protective film, the hot-melt resin composition changes from a solidified state, i.e., the state of a surface protective film, to a state having fluidity. The surface protective film changes to a state having fluidity by the hot water, and the surface protective film is washed and removed from the surface of the workpiece. The temperature of the hot water is 40°C or higher, for example, preferably 40°C or higher and 100°C or lower, and particularly preferably 40°C or higher and 90°C or lower.

[0055] The workpiece on which the surface protection film is formed is not particularly limited, and examples thereof include semiconductor wafers. When the workpiece is a semiconductor wafer, the hot melt resin composition of the present invention can be used in thinning the semiconductor wafer, i.e., in a method for grinding the semiconductor wafer.

[0056] Specifically, for example, a surface protective film is formed on the surface of a semiconductor wafer on which a device circuit pattern has been formed, in accordance with the method for forming a surface protective film using the hot melt resin composition of the present invention described above, to protect the surface of the semiconductor wafer. Next, the back surface of the semiconductor wafer is ground to thin the semiconductor wafer. When grinding the back surface of the semiconductor wafer, room temperature water is supplied to the back surface of the semiconductor wafer as grinding water, if necessary. After grinding the back surface of the semiconductor wafer, the surface protective film is washed and removed from the front surface of the semiconductor wafer with warm water in accordance with the method for removing the surface protective film described above. [Example]

[0057] Next, examples of the hot melt resin composition of the present invention will be described, but the present invention is not limited to these examples as long as they do not depart from the spirit of the invention.

[0058] Preparation of hot melt resin compositions of examples and comparative examples Example 1 100 parts by mass of polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product name "PEG-1000", freezing point 37°C, number average molecular weight 1000, hydroxyl value 113 KOHmg / g) melted in a Kolben at 80°C was added to 33 parts by mass of polyvinylpyrrolidone-vinyl acetate copolymer (manufactured by Ashland, product name "S630", copolymerization ratio of polyvinylpyrrolidone 60 mol%, glass transition temperature: 110°C, weight average molecular weight 51000) without forming lumps, and the mixture was stirred while maintaining the temperature at 80°C until all solids were removed, thereby preparing the hot melt resin composition of Example 1.

[0059] <Example 2> A hot melt resin composition of Example 2 was prepared in the same manner as in Example 1, except that the blending amount of polyvinylpyrrolidone-vinyl acetate copolymer was 50 parts by mass.

[0060] Example 3 A hot melt resin composition of Example 3 was prepared in the same manner as in Example 1, except that the blending amount of polyvinylpyrrolidone-vinyl acetate copolymer was 25 parts by mass.

[0061] Example 4 A hot melt resin composition of Example 4 was prepared in the same manner as in Example 1, except that the amount of polyvinylpyrrolidone-vinyl acetate copolymer was changed to 200 parts by mass.

[0062] <Example 5> The hot-melt resin composition of Example 5 was prepared in the same manner as in Example 1, except that 80 parts by mass of PEG-1000 and 20 parts by mass of polyethylene glycol with the product name "PEG-10000" (manufactured by Sanyo Chemical Industries, Ltd., freezing point 62°C, number average molecular weight 11000, hydroxyl value 6.5 KOHmg / g) were used as the polyethylene glycol.

[0063] Example 6 The hot-melt resin composition of Example 6 was prepared in the same manner as in Example 3, except that 80 parts by mass of PEG-1000 and 20 parts by mass of polyethylene glycol with the product name "PEG-4000S" (manufactured by Sanyo Chemical Industries, Ltd., freezing point 56°C, number average molecular weight 3100, hydroxyl value 33 KOHmg / g) were used as the polyethylene glycol.

[0064] Example 7 A hot-melt resin composition of Example 7 was prepared in the same manner as in Example 3, except that polyethylene glycol "PEG-1000" was replaced with polyethylene glycol with the product name "PEG-2000" (manufactured by Sanyo Chemical Industries, Ltd., freezing point 51°C, number average molecular weight 2000, hydroxyl value 56 KOHmg / g).

[0065] Example 8 A hot-melt resin composition of Example 8 was prepared in the same manner as in Example 3, except that 80 parts by mass of PEG-2000 and 20 parts by mass of PEG-4000S were used as the polyethylene glycol.

[0066] <Comparative Example 1> A hot melt resin composition of Comparative Example 1 was prepared in the same manner as in Example 1, except that the polyvinylpyrrolidone-vinyl acetate copolymer was not blended.

[0067] <Comparative Example 2> A hot-melt resin composition of Comparative Example 2 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "Pitzcol K30", weight-average molecular weight 45,000) was used instead of the polyvinylpyrrolidone-vinyl acetate copolymer.

[0068] <Comparative Example 3> A hot-melt resin composition of Comparative Example 3 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "Pitzcol K50", weight-average molecular weight 250,000) was used instead of the polyvinylpyrrolidone-vinyl acetate copolymer.

[0069] <Comparative Example 4> A hot-melt resin composition of Comparative Example 4 was prepared in the same manner as in Example 1, except that polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product name "PEG-400", freezing point 7°C, number average molecular weight 400, hydroxyl value 281 KOHmg / g) was used instead of polyethylene glycol "PEG-1000".

[0070] <Comparative Example 5> A hot-melt resin composition of Comparative Example 5 was prepared in the same manner as in Example 1, except that polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., product name "PEG-600", freezing point 20°C, number average molecular weight 600, hydroxyl value 187 KOHmg / g) was blended in place of polyethylene glycol "PEG-1000".

[0071] Details of the components of the hot melt resin compositions of the Examples and Comparative Examples are shown in Table 1 below, in which the blending amounts are shown in parts by mass.

[0072] [Table 1]

[0073] The evaluation items of the hot melt resin compositions of the Examples and Comparative Examples are as follows. (1) Appearance The appearance of the hot melt type resin composition at 25°C and the hot melt type resin composition at 80°C was visually observed, and a composition that was in a solidified state such as a solid at 25°C and had fluidity such as a liquid at 80°C was evaluated as passing.

[0074] (2) Compatibility The hot-melt resin composition was evaluated for its molten state at 80°C and its solidified state at 25°C according to the following criteria. ◯: No phase separation was observed in the molten state and the material was transparent, and in the solidified state it was uniformly transparent or milky white. ×: Phase separation was observed in the molten state, and liquid or powdery material adhered to the touch, and the material separated when the phase changed to a solid state.

[0075] (3) Spreadability The hot-melt resin composition was heated to 80°C and confirmed to be uniformly melted. Then, the hot-melt resin composition was applied to a polyethylene terephthalate film using a bar coater, and the appearance was evaluated according to the following criteria, with a rating of 0 or higher being considered a pass. ◎: The surface is evenly coated. ◯: Viscosity is slightly high, and slight streaks are observed when applied. ×: The viscosity is high and many streaks are observed when applied.

[0076] (4) Protective film flexibility The hot-melt resin composition was heated to 80°C, and after confirming that it was uniformly melted, it was coated using a bar coater and cooled to 15°C to solidify, producing a sheet piece of 50 mm x 50 mm x 0.3 mm. This was used as a test piece and evaluated according to the following criteria, with a rating of △ or better being considered a pass. Good: No deformation occurs when pressed with a finger, and the film shape is maintained. One side of the test specimen is fixed, and the other opposite side is raised by 10 mm. The film shape is maintained even when the test specimen is bent. △: Deforms when pressed with a finger. ×: Fluid and liquid. Or, when one side of the test piece is fixed and the other opposite side is raised by 10 mm and an attempt is made to bend the test piece, the test piece breaks and cannot maintain its shape.

[0077] (5) Water resistance (25℃ room temperature water) The hot-melt resin composition was heated to 80°C, and after confirming that it was uniformly melted, it was coated using a bar coater and cooled to 15°C to solidify, producing a sheet piece of 50 mm x 50 mm x 0.3 mm. This test piece was immersed in water at 25°C and removed from the water after 60 seconds. The appearance of the sheet piece was visually observed and evaluated according to the following criteria. ◯: The sheet piece retains its shape. ×: Completely dissolved or dissolved at the edge of the sheet piece, and the shape of the sheet piece is not maintained when taken out of water.

[0078] (6) Warm water solubility (cleanability) The hot-melt resin composition was heated to 80°C, and after confirming that it was uniformly melted, it was coated using a bar coater on a 50 mm x 50 mm x 3 mm glass plate as the coating object, and then cooled to 15°C to solidify, producing a 50 mm x 50 mm x 0.3 mm sheet piece. Warm water at 80°C was poured over this test piece at a rate of 2 L / min, and the residue on the glass plate after 60 seconds was visually observed and evaluated according to the following criteria. 〇: Dissolves in warm water and is washed away without leaving any residue. ×: Not dissolved, and some residue remains on the glass.

[0079] (7) Stability during storage The hot-melt resin composition was heated to 80°C, and after confirming that it was uniformly melted, it was coated using a bar coater and cooled to 15°C to solidify, producing a sheet piece of 50 mm x 50 mm x 0.3 mm. The obtained test piece was left to stand in a sealed desiccator maintained at 23°C and 65% humidity for 24 hours, and then evaluated according to the following criteria. ⊚: No change in touch evaluation before and after storage. Good: It feels moist and tacky compared to before storage.

[0080] The evaluation results of the hot melt resin compositions of the Examples and Comparative Examples are shown in Table 2 below.

[0081] [Table 2]

[0082] As shown in Tables 1 and 2 above, the hot-melt resin compositions of Examples 1 to 5, which contained polyethylene glycol and polyvinylpyrrolidone-vinyl acetate copolymer and in which the number-average molecular weight of the polyethylene glycol was 700 to 45,000, were solid at room temperature (25°C) and liquid at high temperatures (80°C), and thus reversibly changed between a solidified state and a fluid state between room temperature and high temperatures, exhibiting excellent temperature responsiveness. Furthermore, the hot-melt resin compositions of Examples 1 to 5 exhibited excellent compatibility of the constituent components and excellent coatability. In particular, Examples 1 to 3 and 5, which contained 25 to 50 parts by mass of polyvinylpyrrolidone-vinyl acetate copolymer per 100 parts by mass of polyethylene glycol, exhibited improved coatability compared to Example 4, which contained 200 parts by mass of polyvinylpyrrolidone-vinyl acetate copolymer per 100 parts by mass of polyethylene glycol.

[0083] Furthermore, as shown in Tables 1 and 2, coating films excellent in flexibility and water resistance could be formed using the hot-melt resin compositions of Examples 1 to 5. Furthermore, the coating films formed using the hot-melt resin compositions of Examples 1 to 5 had excellent warm water solubility and could be washed away by applying warm water.

[0084] On the other hand, as shown in Tables 1 and 2 above, the resin composition of Comparative Example 1, which did not contain polyvinylpyrrolidone-vinyl acetate copolymer, was unable to form a coating film with excellent flexibility. Furthermore, the resin compositions of Comparative Examples 2 and 3, which contained polyvinylpyrrolidone instead of polyvinylpyrrolidone-vinyl acetate copolymer, were unable to achieve compatibility and were unable to form a coating film. Furthermore, the resin compositions of Comparative Examples 5 and 6, which used polyethylene glycol with a number-average molecular weight of 400 to 600, appeared liquid at 25°C, did not exhibit temperature responsiveness, and did not produce coating films with flexibility and water resistance.

[0085] Furthermore, as shown in Tables 1 and 2, the hot-melt resin compositions of Examples 7 and 8, which were obtained using polyethylene glycol having a freezing point of 45°C or higher and 60°C or lower and a hydroxyl value within a specific range, showed little change in the film surface before and after storage. Water-soluble resins are hygroscopic and have the property of gradually absorbing moisture in the atmosphere, but by adjusting the freezing point and hydroxyl value, it is possible to improve the storage stability of hot-melt resin compositions. [Industrial Applicability]

[0086] The hot melt resin composition of the present invention has flexibility and water resistance, and can prevent the generation of residue of the protective film on the surface of the workpiece without washing with an organic solvent. Furthermore, it can form a surface protective film that can prevent the generation of unused portions of the protective film. Therefore, the hot melt resin composition of the present invention is highly useful in fields such as protecting the surface of a semiconductor wafer on which a circuit pattern is formed, for example, in thinning processing of semiconductor wafers by grinding the back surface of the semiconductor wafer.

Claims

1. A hot melt resin composition containing (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, The hot melt resin composition (A) is characterized in that the number average molecular weight of the polyethylene glycol is 700 or more and 45,000 or less.

2. 2. The hot melt resin composition according to claim 1, which is in a solid state at 25°C and in a liquid state at 90°C.

3. 3. The hot melt resin composition according to claim 1, wherein the polyvinylpyrrolidone-vinyl acetate copolymer (B) is contained in an amount of 10 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the polyethylene glycol (A).

4. 3. The hot melt resin composition according to claim 1, wherein the polyethylene glycol (A) is in a solid state at 25°C.

5. 3. The hot melt resin composition according to claim 1, wherein the polyethylene glycol (A) has a freezing point of 30°C or higher and 80°C or lower.

6. 3. The hot melt resin composition according to claim 1, wherein the polyethylene glycol (A) has a freezing point of 45°C or higher and 60°C or lower.

7. 3. The hot melt resin composition according to claim 1, wherein the weight average molecular weight of the polyvinylpyrrolidone-vinyl acetate copolymer (B) is 10,000 or more and 70,000 or less.

8. 3. The hot melt resin composition according to claim 1, further comprising (C) water or an alcohol-based solvent.

9. 9. The hot melt resin composition according to claim 8, wherein the water or alcohol solvent is contained in an amount of 15 parts by mass or less per 100 parts by mass of the polyethylene glycol (A).

10. 3. The hot melt resin composition according to claim 1, wherein the hot melt resin composition is soluble in warm water at a temperature of 40°C or higher and 90°C or lower.

11. 3. The hot melt resin composition according to claim 1, which is used for forming a surface protective film.

12. a melting step of heating and melting the hot-melt resin composition, which is a hot-melt resin composition containing (A) polyethylene glycol and (B) polyvinylpyrrolidone-vinyl acetate copolymer, wherein the number average molecular weight of the (A) polyethylene glycol is 700 or more and 45,000 or less; a coating step of coating the molten hot melt resin composition on a surface of a workpiece; a solidification step of cooling and solidifying the hot melt resin composition applied to the surface of the workpiece; A method for forming a surface protective film, comprising:

13. 13. The method for forming a surface protective film according to claim 12, wherein the temperature of the heat treatment is 40° C. or higher and 100° C. or lower.

14. 14. The method for forming a surface protective film according to claim 12, wherein the temperature of the cooling treatment is 10°C or higher and 35°C or lower.

15. 14. The method for forming a surface protection film according to claim 12, wherein the workpiece is a semiconductor wafer.

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