Protective film forming agent, protective film, method for producing protective film, and method for producing semiconductor chip

Abstract

The invention provides a protective film forming agent and a manufacturing method thereof, a protective film obtained by the protective film forming agent, and a manufacturing method of a semiconductor chip. The protective film forming agent has excellent film forming performance when forming a protective film and can obtain a protective film with excellent plasma etching resistance. Provided is a protective film-forming agent which contains: a first resin that does not have an aromatic ring; a metal salt having a boiling point of 900 DEG C or higher when the metal salt is a metal fluoride; and a solvent.

Description

Technical Field

[0001] The present invention relates to a protective film forming agent, a protective film, a method for manufacturing a protective film, and a method for manufacturing a semiconductor chip. Background Art

[0002] A wafer formed in a semiconductor device manufacturing process is obtained by dividing a laminate in which an insulating film and a functional film are laminated on the surface of a semiconductor substrate such as a silicon substrate by a lattice-shaped predetermined dividing line called a scribe line. By cutting the wafer along the scribe line, a plurality of semiconductor chips (chip separation) are obtained. That is, each region divided by the scribe line becomes a semiconductor chip such as an IC or an LCI.

[0003] A plurality of semiconductor chips are obtained by cutting the wafer along the scribe line. For example, in an optical device wafer, a laminate including a gallium nitride-based compound semiconductor or the like is divided into a plurality of regions by a scribe line. By cutting along the scribe line, the optical device wafer is divided into optical devices such as light-emitting diodes and laser diodes. These optical devices are widely used in electrical equipment.

[0004] Cutting of such a wafer is performed, for example, by plasma cutting. Plasma cutting is a processing technique in which a wafer is cut and chip-separated by performing dry etching under vacuum or reduced pressure. In plasma cutting, for example, the Bosch process or the like capable of deeply etching the wafer is used.

[0005] Patent Document 1 discloses a method for cutting a substrate including a plurality of ICs, including: a step of forming a mask on the substrate that covers and protects the ICs, the mask including a water-soluble material layer in contact with the upper surface of the ICs; a step of patterning the mask using a laser scribing process to provide a patterned mask having gaps, exposing the regions of the substrate between the ICs; and a step of performing plasma etching on the substrate through the gaps in the patterned mask to singulate the ICs.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-523112 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] When cutting a wafer by plasma cutting, in order to protect the wafer, an operation of providing a protective film on the surface of the wafer is performed. The protective film is a film that prevents impurities such as cutting debris and other particles generated during cutting from adhering to the surface of the wafer, but there is still room for improvement in the performance of the protective film.

[0011] Generally, a protective film is formed by applying a protective film forming agent to a wafer and forming a film. However, if cracks are generated in the protective film, impurities such as cutting chips and other particles adhere to the wafer, contaminating the wafer or causing damage to the wafer. In addition, when performing plasma cutting on a device with a step difference, it is impossible to sufficiently ensure the thickness of the protective film at the upper part of the step difference, and an undesired thinning occurs. Therefore, for the protective film forming agent, excellent film forming properties capable of suppressing crack generation are required.

[0012] In addition, in plasma cutting, an etching gas such as a fluorine-based gas is used to etch the wafer. At this time, free radicals generated by such an etching gas (for example, fluorine free radicals generated by a fluorine-based gas) may also cause unnecessary etching or damage to the wafer. If such an undesired etching occurs, the film loss of the protective film will be aggravated. Therefore, for the protective film forming agent, excellent plasma etching tolerance is required.

[0013] The present invention has been made in view of the above circumstances, and the main object thereof is to provide a protective film forming agent, a method for manufacturing the same, a protective film obtained from the protective film forming agent, and a method for manufacturing a semiconductor chip, wherein the protective film forming agent has excellent film forming properties when forming a protective film and can obtain a protective film with excellent plasma etching tolerance.

[0014] Means for Solving the Problem

[0015] The inventors of the present application conducted in-depth research to solve the above object, and as a result, they found that a protective film forming agent containing a metal salt having a boiling point of 900 °C or higher when it is a metal fluoride, a first resin having no aromatic ring, and a solvent was prepared, thereby completing the present invention.

[0016] That is, the present invention is as follows.

[0017] <1> A protective film forming agent, comprising:

[0018] A metal salt having a boiling point of 900 °C or higher when it is a metal fluoride;

[0019] A first resin having no aromatic ring; and

[0020] A solvent.

[0021] <2> The protective film forming agent according to <1>, further comprising a second resin having an aromatic ring.

[0022] <3> The protective film forming agent according to <1> or <2>, wherein the content ratio of the metal of the metal salt is 0.15% by mass or more in the total amount of the components obtained by removing the solvent from the protective film forming agent.

[0023] <4>The protective film forming agent according to any one of <1> to <3>, wherein the metal of the metal salt includes at least one selected from the group consisting of Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce.

[0024] <5>The protective film forming agent according to any one of <1> to <4>, wherein the metal salt includes at least one selected from the group consisting of sulfates, nitrates, nitrites, and their hydrates.

[0025] <6>The protective film forming agent according to any one of <1> to <5>, wherein the first resin includes at least one selected from the group consisting of cellulose-based resins and vinyl-based resins.

[0026] <7>The protective film forming agent according to any one of <1> to <6>, wherein the first resin includes at least one selected from the group consisting of a resin (1A) containing a repeating unit represented by the following formula (1a), a resin (1B) containing a repeating unit represented by the following formula (1b-1) and a repeating unit represented by the following formula (1b-2), a resin (1C) containing a repeating unit represented by the following formula (1c), and a resin (1D) containing a repeating unit represented by the following formula (1d).

[0027] [Chemical formula 1]

[0028]

[0029] (In the formula, R 1 , R 2 and R 3 are each independently a substituent represented by -H, -CH3, -CH2CH3, or -CH2CH(OH)CH3, and all R 1 , R 2 and R 3 at least one of them is a substituent other than -H.)

[0030] [Chemical formula 2]

[0031]

[0032] [Chemical formula 3]

[0033]

[0034] [Chemical formula 4]

[0035]

[0036] <8>The protective film forming agent according to any one of <2> to <7>, wherein the second resin contains at least one selected from the group consisting of a resin (2A) containing a repeating unit represented by the following formula (2a-1) and a repeating unit represented by the following formula (2a-2), a resin (2B) containing a repeating unit represented by the following formula (2b-1) and a repeating unit represented by the following formula (2b-2), and a resin (2C) containing a repeating unit represented by the following formula (2c).

[0037] [Chemical formula 5]

[0038]

[0039] (In the formula, X + is an alkali metal cation, a proton or N + R 4 4, R 4 is a hydrogen atom, an alkyl group or a hydroxyalkyl group.)

[0040] [Chemical formula 6]

[0041]

[0042] (In the formula, M 1+ and M 2+ are each independently an alkali metal cation, a proton or N + R 5 4, R 5 is a hydrogen atom, an alkyl group or a hydroxyalkyl group.)

[0043] [Chemical formula 7]

[0044]

[0045] <9>The protective film contains: a metal salt having a boiling point of 900 °C or higher when it is a metal fluoride; and a first resin having no aromatic ring.

[0046] <10>The protective film according to <9>, further containing a second resin having an aromatic ring.

[0047] <11>The protective film according to <9> or <10>, wherein the content of the metal of the metal salt in the protective film is 0.15% by mass or more.

[0048] <12>The protective film according to any one of <9> to <11>, wherein the metal of the metal salt contains at least one selected from the group consisting of Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce.

[0049] <13>The protective film according to any one of <9> to <12> has a film thickness of 0.1 μm or more and 100 μm or less.

[0050] <14>A method for manufacturing a protective film, which includes a step of forming a protective film by coating a protective film forming agent according to any one of <1> to <7> on a substrate.

[0051] <15>A method for manufacturing a semiconductor chip, which is a method for manufacturing a semiconductor chip by cutting a semiconductor wafer by plasma cutting. The method for manufacturing a semiconductor chip includes: a step of forming a protective film by coating a protective film forming agent according to any one of <1> to <7> on the semiconductor wafer; a step of irradiating a laser to a predetermined position of one or more layers including the protective film on the semiconductor wafer to form a processing groove that exposes the surface of the semiconductor wafer and has a pattern corresponding to the shape of the semiconductor chip; and a step of irradiating the semiconductor wafer having the processing groove with plasma to cut the semiconductor wafer at the position of the processing groove, thereby obtaining a semiconductor chip.

[0052] Effects of the Invention

[0053] According to the present invention, it is possible to provide a protective film forming agent, a method for manufacturing the same, a protective film obtained from the protective film forming agent, and a method for manufacturing a semiconductor chip. The protective film forming agent has excellent film-forming properties when forming a protective film and can obtain a protective film with excellent plasma etching tolerance. Detailed Embodiments

[0054] Hereinafter, the mode for carrying out the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and the gist is not to limit the present invention to the following content. The present invention can be appropriately modified and implemented within the scope of its gist.

[0055] <Protective Film Forming Agent>

[0056] The protective film forming agent according to the present embodiment is a protective film forming agent containing a metal salt having a boiling point of 900 °C or higher when it is a metal fluoride, a first resin having no aromatic ring, and a solvent. The protective film forming agent can be used, for example, to form a protective film on the surface of a semiconductor wafer when cutting the semiconductor wafer. The inventors of the present application conducted in-depth research and unexpectedly found that by using a resin having no aromatic ring in combination with a metal salt having a boiling point of 900 °C or higher when it is a metal fluoride, the film-forming properties when forming a protective film are excellent, and a protective film with excellent plasma etching tolerance can be obtained.

[0057] (Metal Salt, Metal)

[0058] The protective film forming agent according to this embodiment contains a metal salt having a boiling point of 900 °C or higher when it is a metal fluoride.

[0059] The type of metal (metal species) of the metal salt may be any metal having a boiling point of 900 °C or higher when it is a metal fluoride, and the type of metal is not particularly limited. From the viewpoint of further improving film formability and plasma etching tolerance, the metal of the metal salt preferably contains at least one selected from the group consisting of Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce.

[0060] Here, as an example, the boiling points of fluorides of various metals are shown in the following table. It should be noted that the so-called "boiling point of 900 °C or higher when it is a metal fluoride" means that at least one of the fluorides obtainable for the metal is 900 °C or higher. For example, in the case of Ag, various fluorides such as Ag2F, AgF, AgF2, and AgF3 can be considered, and at least one of them (for example, AgF) having a boiling point of 900 °C or higher is sufficient.

[0061] [Table 1]

[0062]

[0063] The content rate of the metal having a boiling point of 900 °C or higher when it is a metal fluoride is not particularly limited. From the viewpoint of having excellent film formability and being able to further improve the selectivity, the content ratio of the metal of the metal salt ((metal of the metal salt) / (total amount of the components obtained by removing the solvent from the protective film forming agent)) in the total amount of the components obtained by removing the solvent from the protective film forming agent is preferably 0.15% by mass or more. The lower limit of this content ratio is more preferably 1.0% by mass or more, and further preferably 1.5% by mass or more. The upper limit of this content ratio is preferably 3.5% by mass or less, more preferably 3.0% by mass or less, and further preferably 2.5% by mass or less.

[0064] The protective film forming agent according to this embodiment may contain not only a salt of a metal having a boiling point of 900 °C or higher when it is a metal fluoride but also a salt of a metal having a boiling point of less than 900 °C when it is a metal fluoride as the metal salt. From the viewpoint of achieving film formability and plasma etching tolerance at a higher level simultaneously, the protective film forming agent according to this embodiment preferably contains only a salt of a metal having a boiling point of 900 °C or higher when it is a metal fluoride as the metal salt. That is, the metal of the metal salt contained in the protective film forming agent is preferably only a metal having a boiling point of 900 °C or higher when it is a metal fluoride.

[0065] Moreover, from the viewpoint of simultaneously achieving film-forming properties and plasma etching resistance at a higher level, the protective film-forming agent according to the present embodiment preferably substantially does not contain salts (metal salts) of metals other than Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce. In addition, the content rate of salts (metal salts) of metals other than Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce is more preferably 0 mass%. It should be noted that "substantially does not contain" in this specification means that the component is not actively added or mixed, and does not exclude the case of inevitably containing or mixing.

[0066] In addition, the type of the salt of the metal salt contained in the protective film-forming agent according to the present embodiment is not particularly limited. As the type of the salt of the metal salt, it is preferably at least one selected from the group consisting of sulfates, nitrates, nitrites, and hydrates thereof. These salts tend to have high water solubility, so the compatibility with other components in the protective film-forming agent is further improved, and the film-forming properties can also be further improved.

[0067] The protective film-forming agent according to the present embodiment may contain not only sulfates, nitrates, nitrites, and hydrates thereof, but also metal salts other than these as metal salts, or may not contain metal salts other than sulfates, nitrates, nitrites, and hydrates thereof.

[0068] In the protective film-forming agent according to the present embodiment, the content of the metal salt is not particularly limited. The total content of the metal salt relative to 100 parts by mass of the solid components in the protective film-forming agent is preferably 15.0 parts by mass or less, more preferably 9.4 parts by mass or less, further preferably 9.3 parts by mass or less, and still more preferably 9.0 parts by mass or less. In addition, the total content of the metal salt relative to 100 parts by mass of the solid components in the protective film-forming agent is preferably 0.15 parts by mass or more, more preferably 0.3 parts by mass or more, and further preferably 0.4 parts by mass or more.

[0069] (First resin)

[0070] The first resin is a resin that does not have an aromatic ring (sometimes referred to as a "non-aromatic resin"). The first resin is preferably water-soluble (sometimes referred to as a "water-soluble resin"). If it is water-soluble, the protective film can be effectively formed by dissolving it in a solvent such as water or an aqueous medium and then coating and drying. In addition, after plasma etching, the protective film can be easily removed by washing with water. It should be noted that in this specification, the so-called "water-soluble" means that 0.5 g or more of the solute (this resin) is dissolved in 100 g of water at 25 °C.

[0071] Regarding this point, in the past, when a water-soluble material was used to form a protective film, there was a problem that cracks were likely to occur. Especially when the protective film was thick, there was a tendency for cracks to easily occur. In addition, there was a tendency for the plasma etching resistance to be easily reduced due to the use of a water-soluble material. However, according to this embodiment, unexpectedly, by using the above metal salt in combination with the first resin, such problems can be effectively suppressed from occurring.

[0072] It should be noted that water-soluble resins also include resins that can be solubilized in water by performing a hydrolysis reaction and an alkali-based treatment in an aqueous medium. For example, resins that can dissolve 0.5 g or more of the solute (this resin) in 100 g of water at 25 °C as a result of performing such reactions and treatments also belong to the "water-soluble resins" referred to in this specification.

[0073] The first resin preferably contains at least one selected from the group consisting of a cellulose-based resin, a vinyl-based resin, a polyalkylene oxide (for example, polyethylene oxide such as polyethylene glycol, polypropylene oxide such as polypropylene glycol, etc.), polyglycerol, and water-soluble nylon, and more preferably contains at least one selected from the group consisting of a cellulose-based resin and a vinyl-based resin. These are preferably water-soluble.

[0074] The weight average molecular weight of the first resin is not particularly limited, and is usually preferably 100 or more and 300,000 or less. The lower limit of this weight average molecular weight is more preferably 1,000 or more, and further preferably 10,000 or more. In addition, the upper limit of this weight average molecular weight is more preferably 200,000 or less, and further preferably 150,000 or less.

[0075] It should be noted that unless otherwise specified, the weight average molecular weight in this specification refers to the weight average molecular weight (M w ) obtained by gel permeation chromatography (GPC) analysis and converted to polystyrene.

[0076] As the cellulose-based resin, it is cellulose or a cellulose derivative, preferably having water solubility. As the cellulose derivative, for example, substances obtained by modifying cellulose with an alkyl group (such as methyl, ethyl, etc.), substances obtained by modifying cellulose with a hydroxyalkyl group (such as hydroxymethyl, hydroxyethyl, hydroxypropyl, etc.), etc. can be cited. As specific examples of the cellulose derivative, at least one selected from the group consisting of methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. can be cited.

[0077] The weight average molecular weight of the cellulose-based resin is not particularly limited, and is preferably 1000 or more and 300000 or less. The lower limit of this weight average molecular weight is more preferably 10000 or more. In addition, the upper limit of this weight average molecular weight is more preferably 200000 or less, and further preferably 150000 or less.

[0078] As the vinyl-based resin, a homopolymer of a monomer having a vinyl group or a copolymer of a monomer having a vinyl group, and a water-soluble resin are preferred. As specific examples of the vinyl-based resin, for example, at least one selected from the group consisting of polyvinyl alcohol-based resins, poly-N-vinylacetamide, polyvinylpyrrolidone, polyacrylamide, poly(N-alkylacrylamide), polyallylamine, poly(N-alkylallylamine), partially amidated polyallylamine, poly(diallylamine), allylamine·diallylamine copolymer, and polyacrylic acid can be cited.

[0079] As specific examples of the polyvinyl alcohol-based resin, for example, polyvinyl alcohol, polyvinyl acetal (including vinyl acetate copolymers), butanediol·vinyl alcohol copolymer, polyvinyl alcohol-polyacrylic acid block copolymer, polyvinyl alcohol-polyacrylate block copolymer, etc. can be cited. Among these, polyvinyl alcohol is also preferred.

[0080] The protective film formed on the surface of the semiconductor wafer is usually removed from the surface of the semiconductor wafer or semiconductor chip by water washing at an appropriate time point after forming the processing groove. Therefore, from the viewpoint of the water washability of the protective film, a water-soluble resin having a high affinity for water is preferred. As the water-soluble resin having a high affinity for water among the above resins, a resin having only a hydroxy group, an amide bond, and / or an ether bond as a polar group is preferred, such as hydroxypropyl cellulose, polyvinyl alcohol, poly-N-vinylacetamide, polyvinylpyrrolidone, polyethylene glycol, etc.

[0081] In addition, from the viewpoint of expecting to be able to more effectively suppress the deterioration of the shape of the processing groove caused by the thermal collapse of the protective film, etc., a cellulose-based resin and a vinyl-based resin are preferred, and hydroxypropyl cellulose, polyvinyl alcohol, poly-N-vinylacetamide, polyvinylpyrrolidone, etc. are more preferred.

[0082] These can be used alone or in combination of two or more.

[0083] A more specific suitable example of the first resin will be described. The first resin preferably contains at least one selected from the group consisting of a resin (1A) containing a repeating unit represented by the following formula (1a), a resin (1B) containing a repeating unit represented by the following formula (1b-1) and a repeating unit represented by the following formula (1b-2), a resin (1C) containing a repeating unit represented by the following formula (1c), and a resin (1D) containing a repeating unit represented by the following formula (1d).

[0084] [Chemical formula 8]

[0085]

[0086] (In the formula, R 1 , R 2 and R 3 are each independently a substituent represented by -H, -CH3, -CH2CH3 or -CH2CH(OH)CH3, and all of R 1 , R 2 and R 3 are at least one substituent other than -H.)

[0087] [Chemical formula 9]

[0088]

[0089] [Chemical formula 10]

[0090]

[0091] [Chemical formula 11]

[0092]

[0093] The resin (1A) only needs to be a resin containing the repeating unit represented by the formula (1a), and may also have other repeating units. From the viewpoints of film-forming properties of the protective film, plasma etching resistance, water washability, precision of the shape of the processing tank, etc., the resin (1A) is preferably a resin having only the repeating unit represented by the formula (1a). Specific examples of the resin (1A) include cellulose derivatives. Suitable examples of the resin (1A) include the above-mentioned methyl cellulose, ethyl cellulose, and propylene cellulose, etc.

[0094] R 1 , R 2 and R 3 in the formula (1a) may each independently be a substituent represented by -H, -CH3, -CH2CH3 or -CH2CH(OH)CH3, and R 1 , R 2and R 3 Each independently represents a substituent represented by -H or -CH2CH(OH)CH3, and preferably all of R 1 、R 2 and R 3 At least one of them is -CH2CH(OH)CH3.

[0095] The weight average molecular weight of the resin (1A) is not particularly limited, and is preferably 10,000 or more and 300,000 or less. The lower limit of the weight average molecular weight is more preferably 15,000 or more, and further preferably 20,000 or more. In addition, the upper limit of the weight average molecular weight is more preferably 200,000 or less, further preferably 100,000 or less, and even more preferably 50,000 or less.

[0096] The resin (1B) may be a resin containing the repeating unit represented by the formula (1b-1) and the repeating unit represented by the formula (1b-2) (see the formula (1b)), and may also contain other repeating units. From the viewpoints of the film-forming property of the protective film, plasma etching resistance, water washability, precision of the shape of the processing tank, etc., the resin (1B) is preferably a resin having only the repeating unit represented by the formula (1b-1) and the repeating unit represented by the formula (1b-2) (see the formula (1b)).

[0097] The water solubility of the resin (1B) can be increased, for example, by adjusting the content of the repeating unit represented by the formula (1b-1), the content of the repeating unit represented by the formula (1b-2), and the molar ratio of the repeating unit represented by the formula (1b-1) to the repeating unit represented by the formula (1b-2).

[0098] The ratio of the repeating unit represented by the formula (1b-1) to the repeating unit represented by the formula (1b-2) is not particularly limited. From the above viewpoints, the upper limit of the molar ratio of the repeating unit represented by the formula (1b-1) in the total of the repeating unit represented by the formula (1b-1) and the repeating unit represented by the formula (1b-2) (formula (1b-1) / (formula (1b-1)+formula (1b-2))) is preferably 0.965 or less, and preferably 0.890 or less. The lower limit of this molar ratio is not particularly limited, and is preferably 0.500 or more, and more preferably 0.695 or more.

[0099] As a suitable example of the resin (1B), the above-mentioned polyvinyl alcohol etc. can be cited. Polyvinyl alcohol can be obtained, for example, by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate monomers. In this case, a resin having both the repeating unit represented by the formula (1b-1) and the repeating unit represented by the formula (1b-2) as represented by the formula (1b) can be obtained.

[0100] The degree of polymerization of the resin (1B) is not particularly limited, and is preferably 300 or more and 2500 or less. The lower limit of the degree of polymerization is more preferably 500 or more. In addition, the upper limit of the degree of polymerization is more preferably 2000 or less.

[0101] The resin (1C) may be a resin containing the repeating unit represented by the formula (1c), and may also contain other repeating units. From the viewpoints of film-forming properties of the protective film, plasma etching resistance, water washability, precision of the shape of the processing tank, etc., the resin (1C) is preferably a resin having only the repeating unit represented by the formula (1c). Suitable examples of the resin (1C) include the above-mentioned poly-N-vinylacetamide and the like.

[0102] The weight-average molecular weight of the resin (1C) is not particularly limited, and is preferably 200000 or more and 1500000 or less. The lower limit of the weight-average molecular weight is more preferably 250000 or more, and further preferably 500000 or more. In addition, from the viewpoints of film-forming properties, etc., the upper limit of the weight-average molecular weight is more preferably 1000000 or less.

[0103] The resin (1D) may be a resin containing the repeating unit represented by the formula (1d), and may also have other repeating units. From the viewpoints of film-forming properties of the protective film, plasma etching resistance, water washability, precision of the shape of the processing tank, etc., the resin (1D) is preferably a resin having only the repeating unit represented by the formula (1d). Suitable examples of the resin (1D) include the above-mentioned polyvinylpyrrolidone and the like.

[0104] The weight-average molecular weight of the resin (1D) is not particularly limited, and is preferably 10000 or more and 1500000 or less. The lower limit of the weight-average molecular weight is more preferably 40000 or more, further preferably 50000 or more, and still further preferably 100000 or more. In addition, the upper limit of the weight-average molecular weight is more preferably 1200000 or less.

[0105] (Second resin)

[0106] The second resin is a resin having an aromatic ring (sometimes referred to as an "aromatic resin"). As the aromatic ring having a monocyclic structure, a benzene ring can be cited. As the aromatic ring having a polycyclic structure, a naphthalene ring, a biphenyl ring, an anthracene ring, a phenanthrene ring, etc. can be cited.

[0107] The second resin is preferably water-soluble. When the second resin is a water-soluble resin, it is more preferably a water-soluble resin having an aromatic ring and a water-soluble group. Among the water-soluble resins referred to here, as described above, resins that can be solubilized in water by performing a hydrolysis reaction or an alkali-based treatment in an aqueous medium are also included. As the water-soluble group, for example, -SO3 - A + (A +is an alkali metal cation, a proton or N + R4. R is a hydrogen atom, an alkyl group or a hydroxyalkyl group.), -COO - A + (A + is an alkali metal cation, a proton or N + R4. R is a hydrogen atom, an alkyl group or a hydroxyalkyl group.), a carboxylic anhydride group (-CO-O-CO-), a hydroxyl group, an ether bond (-O-), etc.

[0108] It should be noted that, as the above-mentioned alkali metal cation, for example, a sodium cation (Na + ), a potassium cation (K + ), a strontium cation (Sr + ) etc. can be cited. As the above-mentioned alkyl group, for example, a methyl group, an ethyl group, a propyl group (for example, a n-propyl group, an isopropyl group), etc. can be cited. As the hydroxyalkyl group, for example, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, etc. can be cited. In addition, the carboxylic anhydride group (-CO-O-CO-) provides -COO - X + through hydrolysis or base-based treatment in water.

[0109] As the second resin, for example, a resin containing a styrene-based unit, a resin containing a phenol-based unit, etc. can be cited. As the styrene-based unit, for example, a structural unit derived from styrene or a styrene derivative having a substituent at the α-position or on the benzene ring, etc. can be cited. As the phenol-based unit, for example, a resin containing a phenolic hydroxyl group, etc. can be cited.

[0110] The resin having a phenolic hydroxyl group exists as a water-soluble case and a water-insoluble case (non-water-soluble case) depending on its structure. When the resin having a phenolic hydroxyl group is water-insoluble, the resin can be made water-soluble by treating the resin in an alkaline aqueous medium and converting the phenolic hydroxyl group into a salt.

[0111] The weight average molecular weight of the second resin is not particularly limited, and usually, it is preferably 100 or more and 300000 or less. The lower limit of this weight average molecular weight is more preferably 1000 or more, and further preferably 10000 or more. In addition, the upper limit of this weight average molecular weight is more preferably 200000 or less, and further preferably 150000 or less.

[0112] A more specific suitable example of the second resin will be described. The second resin preferably contains at least one selected from the group consisting of a resin (2A) containing a repeating unit represented by the following formula (2a-1) and a repeating unit represented by the following formula (2a-2), a resin (2B) containing a repeating unit represented by the following formula (2b-1) and a repeating unit represented by the following formula (2b-2), and a resin (2C) containing a repeating unit represented by the following formula (2c). By using these resins in combination with the above-mentioned metal salt and the first resin, at least the film-forming property and the plasma etching resistance can be further improved.

[0113] [Chemical formula 12]

[0114]

[0115] (In the formula, X + is an alkali metal cation, a proton or N + R 4 4, R 4 is a hydrogen atom, an alkyl group or a hydroxyalkyl group.)

[0116] [Chemical formula 13]

[0117]

[0118] (In the formula, M 1+ and M 2+ are each independently an alkali metal cation, a proton or N + R 5 4, R 5 is a hydrogen atom, an alkyl group or a hydroxyalkyl group.)

[0119] [Chemical formula 14]

[0120]

[0121] The resin (2A) may be a resin containing a repeating unit represented by the formula (2a-1) and a repeating unit represented by the formula (2a-2) (see the formula (2a)), and may also have other repeating units. From the viewpoints of the film-forming property of the protective film, the plasma etching resistance, the water washability, the precision of the shape of the processing tank, etc., the resin (2A) is preferably a resin that only has a repeating unit represented by the formula (2a-1) and a repeating unit represented by the formula (2a-2) (see the formula (2a)).

[0122] In the formula (2a-2), X + is an alkali metal cation, a proton or N + R 4 4, R 4 being a hydrogen atom, an alkyl group or a hydroxyalkyl group is sufficient. As the alkali metal cation, for example, a sodium cation (Na +) Potassium cation (K + ) Strontium cation (Sr + ) etc. As the alkyl group, for example, methyl group, ethyl group, propyl group (e.g., n-propyl group, isopropyl group), etc. can be mentioned. As the hydroxyalkyl group, for example, hydroxymethyl group, hydroxyethyl group, hydroxypropyl group, etc. can be mentioned.

[0123] Among the above, X + is preferably N + R 4 4, R 4 is more preferably a hydrogen atom. As a specific example of X + , for example, X + is preferably NH4 + .

[0124] The water solubility of the resin (2A) can be improved, for example, by increasing the content of the repeating unit represented by the formula (2a-2) having high hydrophilicity.

[0125] The ratio of the repeating unit represented by the formula (2a-1) and the repeating unit represented by the formula (2a-2) is not particularly limited. From the above viewpoints, the molar ratio of the repeating unit represented by the formula (2a-1) to the repeating unit represented by the formula (2a-2) (formula (2a-1) / (formula (2a-2))) is preferably 0.1 or more and 9 or less from the viewpoint of easily imparting water solubility. The lower limit of this molar ratio is more preferably 0.25 or more. In addition, the upper limit of this molar ratio is more preferably 7 or less, and further preferably 4 or less.

[0126] As a suitable example of the resin (2A), a resin in which X + in the formula (2a-2) is NH4 + can be mentioned. This resin can be obtained, for example, by the following method: treating a copolymer containing a dihydroxydiphenylsulfone type repeating unit (see the formula (2a-1)) and a phenolic repeating unit of sodium sulfonate (see the case where X + in the formula (2a-2) is Na + ) with hydrochloric acid to remove metal (demetalize), and then diluting with ammonia water.

[0127] The weight average molecular weight of the resin (2A) is not particularly limited, and is preferably 5000 or more and 300000 or less. The lower limit of the weight average molecular weight is more preferably 10000 or more, further preferably 15000 or more, and still further preferably 20000 or more. In addition, the upper limit of the weight average molecular weight is more preferably 200000 or less, further preferably 100000 or less, still further preferably 50000 or less, and even further preferably 25000 or less.

[0128] The resin (2B) may be a resin containing the repeating unit represented by formula (2b-1) and the repeating unit represented by formula (2b-2) (see formula (2b)), and may also have other repeating units. From the viewpoints of film-forming properties of the protective film, plasma etching resistance, water washability, precision of the shape of the processing tank, etc., the resin (2B) is preferably a resin that only has the repeating unit represented by formula (2b-1) and the repeating unit represented by formula (2b-2) (see formula (2b)).

[0129] In formula (2b-2), M 1+ and M 2+ are, for example, monovalent cations, each independently being an alkali metal cation, a proton, or N + R 5 4, and R 5 may be a hydrogen atom, an alkyl group, or a hydroxyalkyl group. As the alkali metal cation, for example, a sodium cation (Na + ), a potassium cation (K + ), a strontium cation (Sr + ), etc. may be mentioned. As the alkyl group, for example, a methyl group, an ethyl group, a propyl group (e.g., n-propyl group, isopropyl group), etc. may be mentioned. As the hydroxyalkyl group, for example, a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, etc. may be mentioned.

[0130] Among the above, it is preferable that at least one of M 1+ and M 2+ is N + R 5 4, and more preferably R 5 is a hydrogen atom. In addition, it is further preferable that M 1+ and M 2+ are the same. As specific examples of M 1+ and M 2+ , it is preferable that at least one is NH4 + , and it is preferable that M 1+ and M 2+ are both NH4 + .

[0131] The water solubility of the resin (2B) can be increased, for example, by increasing the content of the repeating unit represented by formula (2b-2) having high hydrophilicity.

[0132] The ratio of the repeating unit represented by the formula (2b-1) and the repeating unit represented by the formula (2b-2) is not particularly limited. From the above viewpoints, the molar ratio of the repeating unit represented by the formula (2b-1) to the repeating unit represented by the formula (2b-2) (formula (2b-1) / (formula (2b-2))) is preferably 1 or more and 8 or less from the viewpoint of ease of imparting water solubility. The lower limit of this molar ratio is more preferably 2 or more. In addition, the upper limit of this molar ratio is more preferably 6 or less, further preferably 5 or less, and even more preferably 4 or less.

[0133] As a suitable example of the resin (2B), M of the formula (2b-2) as described above can be cited 1+ and M 2+ are both NH4 + resin. This resin can be obtained, for example, by diluting a styrene-maleic anhydride copolymer with ammonia water.

[0134] The weight average molecular weight of the resin (2B) is not particularly limited, and is preferably 5000 or more and 200000 or less. The lower limit of the weight average molecular weight is more preferably 7000 or more, and further preferably 8000 or more. In addition, the upper limit of the weight average molecular weight is more preferably 100000 or less, further preferably 50000 or less, even more preferably 40000 or less, and further more preferably 30000 or less.

[0135] The resin (2C) may be a resin containing the repeating unit represented by the formula (2c), and may also contain other repeating units. From the viewpoints of film formability of the protective film, plasma etching resistance, water washability, precision of the shape of the processing tank, etc., the resin (2C) is preferably a resin having only the repeating unit represented by the formula (2c). As a suitable example of the resin (2C), polystyrene sulfonic acid can be cited.

[0136] The weight average molecular weight of the resin (2C) is not particularly limited, and is preferably 5000 or more and 1200000 or less. The lower limit of the weight average molecular weight is more preferably 10000 or more, further preferably 15000 or more, and even more preferably 20000 or more. In addition, the upper limit of the weight average molecular weight is more preferably 500000 or less, more preferably 300000 or less, further preferably 100000 or less, even more preferably 50000 or less, and even more preferably 30000 or less.

[0137] It should be noted that the protective film forming agent involved in this embodiment preferably contains only a water-soluble resin as the resin. In this case, the protective film forming agent involved in this embodiment may further contain other resins in addition to the above-mentioned first resin and second resin. For example, when the protective film forming agent involved in this embodiment contains only the first resin as the resin, the first resin is preferably a water-soluble resin. When the protective film forming agent involved in this embodiment contains only the first resin and the second resin as the resins, the first resin and the second resin are preferably water-soluble resins. When the protective film forming agent involved in this embodiment contains the first resin, the second resin, and other resins in addition to the first resin and the second resin as the resins, the first resin, the second resin, and the other resins are preferably all water-soluble resins.

[0138] In the protective film forming agent involved in this embodiment, the content ratios of the first resin and the second resin are not particularly limited. The total content of the first resin and the second resin, relative to 100 parts by mass of the solid components in the protective film forming agent, is preferably 99.8 parts by mass or less, more preferably 99.6 parts by mass or less. In addition, the total content of the first resin and the second resin, relative to 100 parts by mass of the solid components in the protective film forming agent, is preferably 80.0 parts by mass or more, more preferably 90.0 parts by mass or more.

[0139] (Additives, etc.)

[0140] The protective film forming agent involved in this embodiment may contain other additives as needed. Examples of other additives include light absorbents, basic compounds, dyes, pigments, plasticizers, preservatives, and surfactants.

[0141] (Light absorbent)

[0142] As the light absorbent, light absorbents commonly used in protective film forming agents can be used. Examples of light absorbents include organic acids having a carboxyl group and / or a sulfonic acid group; sodium salts, potassium salts, ammonium salts, and quaternary ammonium salts of these organic acids; compounds having a hydroxyl group, etc.

[0143] Specific examples of light absorbents include benzophenone-based compounds, cinnamic acid-based compounds, anthraquinone-based compounds, naphthalene-based compounds, biphenyl-based compounds, water-soluble amines, etc.

[0144] Specific examples of benzophenone-based compounds include benzophenone, 4,4'-dicarboxybenzophenone, benzophenone-4-carboxylic acid, tetrahydroxybenzophenone, 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (DHBA), EAB-F (4,4'-bis(diethylamino)benzophenone), etc.

[0145] As specific examples of the cinnamic acid-based compounds, for example, cinnamic acid, 4-aminocinnamic acid, 3-aminocinnamic acid, 2-aminocinnamic acid, sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid), ferulic acid, caffeic acid, etc. can be cited. Among these, 4-aminocinnamic acid, 3-aminocinnamic acid, 2-aminocinnamic acid, and ferulic acid are preferred, 4-aminocinnamic acid and ferulic acid are more preferred, and 4-aminocinnamic acid is further preferred.

[0146] As specific examples of the anthraquinone-based compounds, for example, anthraquinone, 2-carboxyanthraquinone, 2,6-anthraquinonedisulfonic acid, 2,7-anthraquinonedisulfonic acid, etc. can be cited.

[0147] As specific examples of the naphthalene-based compounds, for example, naphthalene, 1,2-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, etc. can be cited.

[0148] As specific examples of the biphenyl-based compounds, for example, biphenyl, biphenyl-4-sulfonic acid, etc. can be cited.

[0149] As specific examples of the water-soluble amines, for example, curcumin, etc. can be cited.

[0150] Among the above, benzophenone-based compounds, cinnamic acid-based compounds, etc. are preferred, and tetrahydroxybenzophenone, 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (DHBA), 4-aminocinnamic acid, etc. are more preferred.

[0151] The content ratio of the light absorber in the protective film-forming agent according to the present embodiment is not particularly limited as long as it is within the range that does not impair the object of the present embodiment. The content of the light absorber relative to 100 parts by mass of the solid components in the protective film-forming agent is preferably 1 part by mass or more and 10 parts by mass or less. The lower limit of the content of the light absorber relative to 100 parts by mass of the solid components in the protective film-forming agent is more preferably 1.5 parts by mass or more. In addition, the upper limit of the content of the light absorber relative to 100 parts by mass of the solid components in the protective film-forming agent is more preferably 7 parts by mass or less, further preferably 5 parts by mass or less, and still further preferably 3 parts by mass or less.

[0152] (Basic compound)

[0153] The protective film-forming agent according to the present embodiment may contain a basic compound for the purpose of making the solid components more easily soluble. As the basic compound, both inorganic compounds and organic compounds can be used. As the basic compound, organic compounds are preferred.

[0154] Specific examples of the basic compound include, for example, basic inorganic compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, ammonia, etc.; basic organic compounds such as ethylamine, n-propylamine, monoethanolamine (MEA), diethylamine, di-n-propylamine, diethanolamine, triethylamine, methyldiethylamine, dimethylethanolamine, triethanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, pyrrole, piperidine, 1,8-diazabicyclo[5,4,0]-7-undecene, 1,5-diazabicyclo[4,3,0]-5-nonane, etc. Among these, basic organic compounds are preferred, and monoethanolamine (MEA), ammonia, etc. are more preferred.

[0155] The content rate of the basic compound in the protective film forming agent according to this embodiment is not particularly limited as long as it is within the range that does not impair the purpose of this embodiment. The content of the basic compound relative to 100 parts by mass of the solid components in the protective film forming agent is preferably 0.1 part by mass or more and 3.0 parts by mass or less. The upper limit of the content of the basic compound relative to 100 parts by mass of the solid components in the protective film forming agent is more preferably 1.5 parts by mass or less, and further preferably 1.0 part by mass or less. In addition, the lower limit of the content of the basic compound relative to 100 parts by mass of the solid components in the protective film forming agent is more preferably 0.3 part by mass or more.

[0156] In addition, the molar ratio of the basic compound to the light absorber (basic compound / light absorber) is preferably 1 or more, and more preferably 1 or more and 20 or less. The lower limit of the molar ratio of the basic compound to the light absorber can be 1.5 or more, can be 2 or more, can be 3 or more. The upper limit of the molar ratio of the basic compound to the light absorber can be 15 or less, can be 10 or less, can be 5 or less.

[0157] (Dye)

[0158] As the dye, a water-soluble dye is preferred. Specific examples of the water-soluble dye include, for example, azo dyes (monoazo and polyazo dyes, metal complex azo dyes, pyrazolone azo dyes, stilbene azo dyes, thiazole azo dyes), anthraquinone dyes (anthraquinone derivatives, anthrone derivatives), indigo dyes (indigo derivatives, thioindigo derivatives), phthalocyanine dyes, carbonium dyes (diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, acridine dyes), quinoneimine dyes (azine dyes, oxazine dyes, thiazine dyes), methine dyes (cyanine dyes, azomethine dyes), quinoline dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, naphthalenedicarboximide dyes, violanthrone dyes, other dyes, etc.

[0159] (Pigment)

[0160] As the pigment, a water-soluble pigment is preferred. Specific examples of the water-soluble pigment include, for example, Food Red No. 2, Food Red No. 40, Food Red No. 102, Food Red No. 104, Food Red No. 105, Food Red No. 106, Food Yellow NY, Food Yellow No. 4 Lemon Yellow, Food Yellow No. 5, Food Yellow No. 5 Sunset Yellow FCF, Food Orange AM, Food Vermilion No. 1, Food Vermilion No. 4, Food Vermilion No. 101, Food Blue No. 1, Food Blue No. 2, Food Green No. 3, Food Melon Color B, Food Egg Color No. 3 and other food additive pigments. From the viewpoint of low environmental load, etc., food additive pigments are suitable.

[0161] (Plasticizer)

[0162] By using a plasticizer, it is possible to more effectively suppress the generation of cracks in the protective film and more effectively improve the flexibility, elasticity, laser processability, etc. of the protective film. Specific examples of the plasticizer include, for example, monosaccharides, disaccharides, etc.

[0163] Specific examples of the monosaccharides include, for example, aldoses (monosaccharides having a formyl group), ketoses (monosaccharides having a carbonyl group), and their derivatives. As the derivatives, there are aldonic acids (carboxylic acids formed by converting the formyl group at the 1-position of aldoses into a carboxyl group), uronic acids (carboxylic acids formed by converting the hydroxymethyl group at the end of the main chain of monosaccharides into a carboxyl group), aldaric acids (dicarboxylic acids formed by changing both the formyl group at the 1-position of aldoses and the hydroxymethyl group at the end of the main chain into carboxyl groups), etc.

[0164] Specific examples of the aldoses include, for example, D-glyceraldehyde, D-erythrose, D-threose, D-ribose, D-arabinose, D-xylose, D-lyxose, D-glucose, D-galactose, D-allose, D-altrose, D-mannose, D-gulose, D-idose, D-talose, etc.

[0165] Specific examples of the ketoses include, for example, dihydroxyacetone, D-erythrulose, D-xylulose, D-ribulose, D-fructose, D-psicose, D-sorbose, D-tagatose, D-sedoheptulose, etc.

[0166] Specific examples of the derivatives include, for example, gluconic acid, glucuronic acid, glucaric acid, inositol, etc.

[0167] As the disaccharides, there are disaccharides formed from the above-mentioned monosaccharides described as monosaccharides. Specific examples of the disaccharides include, for example, maltose, sucrose, lactose, lactulose, trehalose, cellobiose.

[0168] Among the above, D-ribose, D-xylose, D-glucose, D-galactose, D-fructose, inositol, and maltose are preferred, and D-ribose, D-glucose, D-galactose, D-fructose, inositol, and maltose are more preferred.

[0169] (Preservative)

[0170] From the viewpoints of further improving the antiseptic effect of the protective film forming agent according to the present embodiment and further reducing the treatment load of the waste liquid after semiconductor wafer cleaning, it is preferable to use a preservative. As the preservative, for example, benzoic acid, butyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, sodium benzoate, sodium propionate, benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenethyl alcohol, 2-phenoxyethanol, phenylmercuric nitrate, thimerosal, m-cresol, lauryldimethylamine oxide, etc. can be cited. These can be used alone or in combination of two or more.

[0171] (Surfactant)

[0172] The surfactant is used to improve, for example, the defoaming property during the manufacture of the protective film forming agent, the stability of the protective film forming agent, and the coating property of the protective film forming agent. From the viewpoint of the defoaming property during the manufacture of the protective film forming agent, it is preferable to use a surfactant.

[0173] The protective film is formed, for example, by spin-coating the protective film forming agent. However, when forming the protective film, unevenness caused by bubbles sometimes occurs. In order to suppress the generation of such unevenness, it is preferable to use a defoaming agent such as a surfactant.

[0174] As the surfactant, a water-soluble surfactant can be preferably used. As the surfactant, any of a nonionic surfactant, a cationic surfactant, an anionic surfactant, and an amphoteric surfactant can be used. The surfactant can be a silicone-based one. From the aspect of cleanability, a nonionic surfactant is preferred.

[0175] (Solvent)

[0176] In order to dissolve the above solid components, the protective film forming agent according to the present embodiment contains a solvent. As the solvent, water (for example, pure water, ultrapure water (DIW), ion water, distilled water, purified water, etc.), an organic solvent, or both can be used. From the viewpoints of less danger such as ignition during use and cost, etc., the solvent preferably contains water. Specifically, the solvent is preferably water and an aqueous solution of an organic solvent, and more preferably a combination of water and an organic solvent.

[0177] Specific examples of the organic solvent are not particularly limited, and examples thereof include methanol, ethanol, alkylene glycol, alkylene glycol monoalkyl ether, alkylene glycol monoalkyl ether acetate, and the like.

[0178] Examples of the alkylene glycol include ethylene glycol, propylene glycol, and the like. Examples of the alkylene glycol monoalkyl ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like. Examples of the alkylene glycol monoalkyl ether acetate include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and the like.

[0179] The organic solvent may be used alone or in combination of two or more.

[0180] The protective film forming agent according to the present embodiment may use water and an organic solvent in combination. As a combination of water and an organic solvent, for example, a mixed solvent of water and an alkylene glycol monoalkyl ether is preferably used, and a mixed solvent of water and propylene glycol monomethyl ether is more preferably used.

[0181] When using a mixed solvent in which water and an organic solvent are used in combination, the content ratio of the organic solvent in the mixed solvent (the content ratio of the organic solvent relative to the total of water and the organic solvent; (organic solvent / (water + organic solvent))) is not particularly limited. From the viewpoint of flammability, the upper limit of the content ratio of the organic solvent in the mixed solvent is preferably less than 50% by mass, more preferably 30% by mass or less, further preferably 20% by mass or less, and still further preferably 15% by mass or less.

[0182] In addition, from the viewpoint of flammability, it is desirable to reduce the content ratio of the organic solvent in the mixed solvent. According to the present embodiment, when only a water-soluble resin is used as the resin, the content ratio of the organic solvent can be sufficiently reduced. From such a viewpoint, as a suitable mode achievable in the present embodiment, it is preferable that the lower limit of the content ratio of the organic solvent in the mixed solvent can be reduced to 5% by mass (5% by mass or more), more preferably to 3% by mass (3% by mass or more), further preferably to 0% by mass (0% by mass or more).

[0183] In the present embodiment, when only a water-soluble resin is used as the resin, even if the content ratio of the organic solvent is reduced to the above range, the solid components in the protective film forming agent can be effectively dissolved, which is preferable.

[0184] The solvent is preferably selected such that the protective film forming agent does not have a flash point at 1 atmosphere. Specifically, by adjusting the water content in the protective film forming agent, the flash point and the presence or absence of a flash point of the protective film can be adjusted.

[0185] A protective film forming agent without a flash point can ensure higher safety. For example, the protective film forming agent can be placed in a non-explosion-proof environment. Specifically, operations such as storage, transportation, and use of the protective film forming agent can be carried out in a non-explosion-proof environment. For example, not only can the protective film forming agent be introduced into a semiconductor factory in a non-explosion-proof environment, but also the formation of the protective film can be carried out in a non-explosion-proof environment. Therefore, considering the aspect of not requiring an explosion-proof environment such as usually expensive explosion-proof equipment, the protective film forming agent without a flash point is very advantageous industrially.

[0186] Regarding the flash point, at 1 atmospheric pressure, when the liquid temperature is 80 °C or lower, it is obtained by measuring with the Tag closed cup method, and when the liquid temperature exceeds 80 °C, it is obtained by measuring with the Cleveland open cup method. In this specification, the case where the flash point cannot be measured even by the Cleveland open cup method is regarded as having no flash point.

[0187] <Method for manufacturing a protective film, protective film>

[0188] According to the present embodiment, a protective film can be obtained by coating the above-mentioned protective film forming agent on a substrate or the like to be protected. Specifically, the method for manufacturing a protective film according to the present embodiment preferably includes a step of forming a protective film by coating the above-mentioned protective film forming agent on a substrate. The coating method is not particularly limited, and spin coating, spraying, die coating, roll coating, curtain coating, etc. can be adopted according to the shape, material, etc. of the object to be protected. Further, after coating, post-treatments such as natural drying, hot air drying, and light irradiation such as ultraviolet irradiation can be carried out.

[0189] Generally, in the case of manufacturing a protective film for a semiconductor wafer, spin coating or the like is adopted. Spin coating, for example, performs the following steps: (i) a step of coating a protective film forming agent on a coating object (such as a semiconductor wafer) fixed on a spin coater platform (spraying step); (ii) a step of removing the excess protective film forming agent by centrifugal force by rotating the platform to form a thin film (rotating treatment step); (iii) a step of removing the workpiece from the spin coater and producing a thin film by natural drying, hot air drying, etc. (drying step). Spin coating has advantages such as enabling film formation with less film thickness deviation and excellent film formation cost and film formation speed even without a vacuum, and is therefore suitable as a protective film for semiconductor wafers and even for protective films for plasma cutting.

[0190] The protective film obtained by the present embodiment is a protective film containing a metal salt having a boiling point of 900 °C or higher when it is a metal fluoride and a first resin without an aromatic ring. In addition, the protective film preferably further contains a second resin having an aromatic ring. The metal salt (metal salt) having a boiling point of 900 °C or higher when it is a metal fluoride, the first resin, and the second resin can use the above-mentioned substances.

[0191] Moreover, the content rate of the metal salt having a boiling point of 900 °C or higher when it is a metal fluoride in the protective film according to the present embodiment is not particularly limited. From the viewpoints of having excellent film-forming properties and being able to further improve the selectivity, the content ratio of the metal salt in the protective film (metal / protective film) is preferably 0.15% by mass or more. The lower limit of this content ratio is more preferably 1.0% by mass or more, and further preferably 1.5% by mass or more. The upper limit of this content ratio is preferably 3.5% by mass or less, more preferably 3.0% by mass or less, and further preferably 2.5% by mass or less.

[0192] The metal having a boiling point of 900 °C or higher when it is a metal fluoride preferably includes at least one selected from the group consisting of Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce. Regarding this metal, a metal having the above physical properties and characteristics can be appropriately used.

[0193] According to the present embodiment, it is possible to expect to form a protective film having excellent film-forming properties and etching resistance over a wide film thickness range from a thin film thickness to a thick film thickness. As a suitable mode thereof, the film thickness of the protective film is preferably 0.1 μm or more and 100 μm or less. The lower limit of the film thickness is more preferably 1 μm or more, and further preferably 3 μm or more. In addition, the upper limit of the film thickness is more preferably 50 μm or less, further preferably 30 μm or less, still further preferably 20 μm or less, and even more preferably 10 μm or less. In this regard, for example, when forming the protective film by spin coating, for the film thickness within the above range, it is possible to more effectively form a film having excellent film-forming properties and etching resistance.

[0194] <Method for manufacturing a semiconductor chip>

[0195] By using the protective film forming agent according to the present embodiment, a semiconductor wafer based on plasma cutting can be suitably manufactured. Typically, the above method for manufacturing a semiconductor chip includes cutting the position of the processing groove in the semiconductor wafer (the position corresponding to the position of the trace). A suitable example of the method for manufacturing a semiconductor chip according to the present embodiment is a method for manufacturing a semiconductor chip by cutting a semiconductor wafer by plasma cutting. A method for manufacturing a semiconductor chip including the following steps can be cited.

[0196] (1) A step of coating the above protective film forming agent on a semiconductor wafer to form a protective film;

[0197] (2) A step of irradiating a specified position of one or more layers including a protective film on a semiconductor wafer with a laser to form a processing groove that exposes the surface of the semiconductor wafer and has a pattern corresponding to the shape of the semiconductor chip; and

[0198] (3) A step of irradiating the semiconductor wafer with a formed processing groove with plasma to cut the position of the processing groove of the semiconductor wafer, thereby obtaining a semiconductor chip.

[0199] Hereinafter, regarding the step of forming the protective film (see step (1)), it is also referred to as the "protective film forming step". Regarding the step of forming the processing groove (see step (2)), it is also referred to as the "processing groove forming step". Regarding the step of cutting the position of the processing groove in the semiconductor wafer (see step (3)), it is also referred to as the "cutting step".

[0200] (Protective film forming step)

[0201] In the protective film forming step, the above-mentioned protective film forming agent is coated on the semiconductor wafer to form a protective film. The coating of the protective film forming agent is preferably carried out by spin coating.

[0202] The shape of the processing surface of the semiconductor wafer is not particularly limited as long as the desired processing can be performed on the semiconductor wafer. Typically, the processing surface of the semiconductor wafer has a large number of irregularities. In addition, recesses are formed in the area corresponding to the traces. In the processing surface of the semiconductor wafer, a plurality of regions corresponding to the semiconductor chips are divided by the traces.

[0203] From the aspects of being easily removed by water washing after processing and further improving the durability of the protective film against plasma irradiation (such as plasma etching tolerance, etc.) during plasma irradiation in the subsequent cutting step, etc., the film thickness of the protective film is preferably 0.1 μm or more and 100 μm or less. The lower limit of the film thickness is more preferably 1 μm or more, and further preferably 3 μm or more. In addition, the upper limit of the film thickness is more preferably 50 μm or less, further preferably 30 μm or less, still further preferably 20 μm or less, and even more preferably 10 μm or less.

[0204] Hereinafter, a manufacturing method of a semiconductor chip for cutting a semiconductor wafer having a plurality of semiconductor chips divided by lattice-shaped traces using a protective film forming agent will be described as a preferred embodiment of the manufacturing method of the semiconductor chip. It should be noted that the shape and size of the semiconductor chip are not particularly limited and can be appropriately set according to the design of the semiconductor chip.

[0205] In a semiconductor wafer, on the surface of a semiconductor substrate such as silicon (silicon substrate, etc.), a laminate in which functional films (which form insulating films and circuits) are laminated is provided. In this laminate, a plurality of semiconductor chips such as ICs and LSIs are formed in a matrix. Each semiconductor chip is divided by traces formed in a lattice pattern. And, as the insulating film, for example, a low dielectric constant insulator film (Low-k film) etc. can be used, and the low dielectric constant insulator film includes: an inorganic film such as a SiO2 film or SiOF, BSG (SiOB); an organic film such as a polyimide-based, parylene-based polymer film.

[0206] Then, a protective film forming agent is applied on the surface of the laminate on the semiconductor substrate to form a protective film. In the protective film forming process, for example, a protective film forming agent is applied on the surface of the semiconductor wafer using a spin coater. It should be noted that the coating method of the protective film forming agent is not particularly limited as long as a protective film with a desired film thickness can be formed, and the above various coating methods can be used.

[0207] Next, if necessary, the liquid protective film forming agent covering the surface is dried. Thereby, a protective film is formed on the surface of the semiconductor wafer. As described above, the protective film according to this embodiment is a protective film that suppresses crack generation, has no cracks or few cracks, and has excellent plasma etching tolerance. In addition, a protective film with suppressed stickiness can be formed.

[0208] After forming a protective film on the surface of the semiconductor wafer in this way, a protective tape can be attached to the back surface of the semiconductor wafer as needed.

[0209] (Processing groove forming process)

[0210] In the processing groove forming process, a laser is irradiated on a specified position of one or more layers including the protective film on the semiconductor wafer to form a processing groove that exposes the surface of the semiconductor substrate and has a pattern corresponding to the shape of the semiconductor chip. According to the protective film forming agent and the protective film according to this embodiment, not only the film forming property and the plasma etching tolerance are excellent, but also the straightness of the processing groove (the straightness of the side wall of the protective film constituting the processing groove) and the rectangularity of the cross section of the processing groove (the rectangularity of the cross section of the protective film constituting the processing groove) are expected to be improved. If the processability is excellent, when cutting by plasma etching, it is possible to accurately cut without deviating from the desired position, and thus it is also possible to perform cutting with higher positional accuracy.

[0211] Specifically, the laser passes through the protective film and irradiates the surface (trace) on the semiconductor wafer. From the viewpoint of intensity, the laser is preferably an ultraviolet laser with a wavelength of 100 nm or more and 400 nm or less. Additionally, YVO4 lasers, YAG lasers with wavelengths of 266 nm, 355 nm, etc. are preferred.

[0212] The above laser irradiation in the processing groove forming step can be performed under the following processing conditions, for example. It should be noted that the spot diameter can be appropriately selected in consideration of the width of the processing groove.

[0213] Light source of the laser: YVO4 laser or YAG laser

[0214] Wavelength: 355 nm

[0215] Repetition frequency: 50 kHz or more and 100 kHz or less

[0216] Output power: 0.1 W or more and 4.0 W or less

[0217] Processing conveyance speed: 1 mm / second or more and 800 mm / second or less

[0218] By implementing the above processing groove forming step, in the laminate having the traces in the semiconductor wafer, processing grooves are formed along the traces. As described above, the protective film according to the present embodiment can suppress the generation of cracks and has excellent durability (for example, plasma etching tolerance, etc.). Thus, by irradiating the protective film with a laser, grooves (processing grooves) having excellent straightness and rectangular cross-section can be formed in the protective film.

[0219] After performing the irradiation of the laser along the specified traces in the above manner, the semiconductor wafer held on the chuck table is indexed and moved only at the intervals of the traces, and the irradiation of the laser is performed again.

[0220] After performing the irradiation of the laser and the indexing and moving along all the traces extending in the specified direction in the above manner, the semiconductor wafer held on the chuck table is rotated by 90 degrees, and along each trace extending at a right angle to the above specified direction, the irradiation of the laser and the indexing and moving are performed in the same manner as above. In the above manner, processing grooves can be formed along all the traces formed on the laminate on the semiconductor wafer.

[0221] (Cutting step)

[0222] In the cutting step, the semiconductor wafer having the processing grooves formed thereon is irradiated with plasma to cut the positions of the processing grooves of the semiconductor wafer, and semiconductor chips are obtained. Specifically, by plasma etching, the semiconductor wafer having the processing grooves at the positions corresponding to the positions of the traces is cut. Since the protective film according to the present embodiment is suitable as a protective film for plasma etching, its advantages can be exhibited in the manufacturing method of a semiconductor wafer using a cutting method based on plasma etching.

[0223] When irradiating the plasma, the plasma is irradiated to a part or the entire surface of the side of the semiconductor wafer having the protective film in such a manner that the plasma is exposed to the surface of the processing tank. Hereinafter, an example of the cutting method based on plasma irradiation will be described.

[0224] First, the semiconductor wafer having the protective film and the processing tank is irradiated with plasma. In this way, the position of the processing tank in the semiconductor wafer is cut. Specifically, in the semiconductor wafer covered with the protective film, the processing tank is formed as described above, and then the protective film and the surface of the semiconductor substrate exposed from the processing tank are irradiated with plasma. As a result, the semiconductor wafer is cut according to the shape of the semiconductor chip, and the semiconductor wafer is divided into individual semiconductor chips.

[0225] Regarding the plasma irradiation conditions, there is no particular limitation as long as the semiconductor wafer can be cut well at the position of the processing tank. For the plasma irradiation conditions, the material of the semiconductor wafer, the type of plasma, etc. can be considered, and the conditions suitable for plasma etching of the semiconductor substrate can be selected.

[0226] In plasma irradiation, the gas (etching gas) used to generate plasma can be appropriately selected according to the material of the semiconductor wafer, etc. For example, SF6 gas or the like can be used. In addition, it is preferable to use the Bosch process to alternately perform sidewall protection based on the supply of fluorine-based gases such as C4F6 gas and C4F8 gas and etching of the semiconductor wafer based on plasma irradiation, thereby cutting the semiconductor wafer. The Bosch process has the following advantages: etching can be performed with a high aspect ratio, and even when the semiconductor wafer is thick, it is easy to cut the semiconductor wafer.

[0227] In addition, in the Bosch process, the above-mentioned fluorine-based gas is used as the etching gas under vacuum or reduced pressure, so fluorine radicals are generated in the system. However, since the protective film according to the present embodiment contains a metal having a boiling point of 900 °C or higher when it is a metal fluoride, it is possible to effectively suppress the volatilization of fluorine radicals in the system. As a result, it also has the following advantages: it is possible to effectively suppress adverse conditions such as unnecessary contamination, etching, and damage of the wafer caused by the volatilized fluorine radicals.

[0228] Moreover, the protective film according to the present embodiment at least has excellent plasma etching tolerance. By using this protective film, it is also possible to expect to form a processing tank having excellent straightness and cross-sectional rectangularity. As a result, through plasma irradiation, it is possible to accurately cut the desired position, and it is also possible to obtain a semiconductor chip having excellent straightness.

[0229] In addition, the protective film according to this embodiment can at least suppress the generation of cracks and has excellent film-forming properties. Therefore, it can sufficiently protect positions other than the cut position and can effectively prevent unintended positions (positions other than the processing grooves) from being cut due to plasma irradiation or the like. Also, it can effectively suppress contamination, damage, etc. of the semiconductor substrate by gases such as fluorine-based gases used during plasma irradiation.

[0230] Next, the protective film covering the surface of the semiconductor chip is removed. When the protective film contains a water-soluble resin as described above, the protective film can be efficiently washed away with water.

[0231] As described above, an example of a method for manufacturing a semiconductor chip by processing a semiconductor wafer has been described. Regarding the method for manufacturing a semiconductor chip according to this embodiment, any method that includes forming a protective film on the surface of the semiconductor wafer, forming processing grooves at positions corresponding to traces on the surface of the semiconductor wafer having the protective film, and cutting them by plasma irradiation can be applicable to various methods for manufacturing semiconductor chips.

[0232] In recent years, in order to increase the number of chips taken out per wafer (number of chips), narrow trace formation has been developing. In addition, for small chip devices required for mobile devices and IoT, further improvement in quality and productivity is desired. In the semiconductor manufacturing process of such devices that require high quality and high productivity, the manufacturing method according to this embodiment can solve the above problems of plasma cutting and is particularly suitable.

[0233] Examples

[0234] The present invention will be described in more detail by the following examples and comparative examples, but the present invention is not limited by any of the following examples. It should be noted that hereinafter, unless otherwise specified, the amounts are based on mass, and the experiments are carried out under the conditions of 25°C and atmospheric pressure.

[0235] <Components Used>

[0236] The resins, metal salts, additives, etc. used in this example will be described.

[0237] (1) First water-soluble resin (non-aromatic resin)

[0238] · Resin (1Aa):

[0239] Hydroxypropyl cellulose (resin having a repeating unit represented by the following formula (1Aa), weight average molecular weight 25,000, manufactured by Nippon Soda Co., Ltd., trade name “HPC-SSL”, HPC-SSL)

[0240] [Chemical formula 15]

[0241]

[0242] (In the formula, R 1 , R 2 and R 3 are each independently a substituent represented by -H or -CH2CH(OH)CH3, and at least one of all R 1 , R 2 and R 3 contained in the resin is -CH2CH(OH)CH3.)

[0243] · Resin (1Bb):

[0244] Polyvinyl alcohol (Formula (1b): A resin having a repeating unit represented by the following formula (1b-1) and a repeating unit represented by the following formula (1b-2), estimated degree of polymerization 500, manufactured by Kuraray Co., Ltd., trade name "Kuraray Poval PVA-505C", PVA-505C)

[0245] [Chemical formula 16]

[0246]

[0247] · Resin (1Cc):

[0248] Poly-N-vinylacetamide (A resin having a repeating unit represented by the following formula (1c), weight-average molecular weight 300,000, manufactured by Showa Denko K.K., trade name "PNVA GE191-104", PNVA 104)

[0249] [Chemical formula 17]

[0250]

[0251] · Resin (1Dd):

[0252] Polyvinylpyrrolidone (A resin having a repeating unit represented by the following formula (1d), weight-average molecular weight 1,200,000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name "PITZCOL K-90", PVP K-90)

[0253] [Chemical formula 18]

[0254]

[0255] (2) Second water-soluble resin (aromatic resin)

[0256] · Resin (2Aa):

[0257] Prepare a resin having a repeating unit represented by formula (2a-1) and a repeating unit represented by formula (2a-2) (see formula (2Aa), weight-average molecular weight 22,000), and use this resin.

[0258] [Chemical formula 19]

[0259]

[0260] Resin (2Aa) is obtained by treating a resin (2Aaa) as a raw material (see the following formula (2Aaa), a resin (2Aaa) having a repeating unit represented by formula (2aa-1) and a repeating unit represented by formula (2aa-2) in a molar ratio of 4:1, that is, the molar ratio of the repeating unit represented by formula (2a-1) to the repeating unit represented by formula (2a-2) (formula (2a-1) / (formula (2a-2)) is 4, weight-average molecular weight 22,000, trade name "WSR-SP82" manufactured by Konishi Chemical Industry Co., Ltd.) with hydrochloric acid, and then diluting with an aqueous ammonia solution (WSR-SP82(NH4)).

[0261] [Chemical formula 20]

[0262]

[0263] · Resin (2Bb):

[0264] Prepare a resin having a repeating unit represented by formula (2b-1) and a repeating unit represented by formula (2b-2) (see formula (2Bb), weight-average molecular weight 10,000), and use this resin.

[0265] [Chemical formula 21]

[0266]

[0267] Resin (2Bb) is obtained as follows (XIRAN-3000P(NH4)): For a styrene-maleic anhydride copolymer as a raw material (see the following formula (2Bbb), a resin (2Bbb) having a repeating unit represented by formula (2bb-1) and a repeating unit represented by formula (2bb-2) in a molar ratio of 3:1, that is, the molar ratio of the repeating unit represented by formula (2bb-1) to the repeating unit represented by formula (2bb-2) is 3, weight-average molecular weight 10,000, trade name "XIRAN3000P" manufactured by POLYSCOPE), in a mixed solvent of ultrapure water (DIW) and propylene glycol monomethyl ether (PGME) (mass ratio of DIW / PGME = 85 / 15) so that the resin solid content concentration becomes 14% by mass, dilute with an aqueous ammonia solution (ammonia concentration 5% by mass) to open the ring of maleic anhydride.

[0268] [Chemical formula 22]

[0269]

[0270] · Resin (2Cc):

[0271] Polystyrene sulfonic acid (resin having a repeating unit represented by the following formula (2c), weight average molecular weight 22,000, manufactured by Tosoh Finechem Corporation, trade name “PS-1H”, PS-1H)

[0272] [Chemical formula 23]

[0273]

[0274] It should be noted that both the above-mentioned first water-soluble resin and second water-soluble resin are resins that can dissolve 0.5 g or more of the resin in 100 g of water at 25°C.

[0275] (3) Metal salt

[0276] · Sodium sulfate

[0277] · Sodium nitrate

[0278] · Calcium nitrate tetrahydrate

[0279] · Zirconium nitrate dihydrate

[0280] · Aluminum nitrate nonahydrate

[0281] It should be noted that the mass fraction of the metal salt hydrate recorded in each table is the mass fraction of only the metal salt excluding the water of the hydrate.

[0282] (4) Additive

[0283] · Light absorbent: 2-(4-Diethylamino-2-hydroxybenzoyl)benzoic acid (DHBA)

[0284] · Basic compound: Monoethanolamine (MEA)

[0285] <Example 1>

[0286] First, the components described in Table 2 (99.54 parts by mass of the first resin (a cellulose derivative obtained by reacting propylene oxide with cellulose, manufactured by Nippon Soda Co., Ltd., trade name “NISSO HPC-SSL”) and 0.46 parts by mass of sodium sulfate) were added to a mixed solvent of ultrapure water (DIW: De-ionized water) and propylene glycol monomethyl ether (PGME) (mass ratio of DIW / PGME = 85 / 15, and the content rate of the organic solvent in the mixed solvent was 15% by mass), and diluted to achieve the solid component concentration described in Table 2 (target solid component concentration, solvent mass ratio = DIW / PGME = 85 / 15). Then, it was stirred until the system became a homogeneous system to obtain a protective film forming agent. This protective film forming agent was a protective film forming agent containing 99.54 parts by mass of the first resin (non-aromatic resin) and 0.46 parts by mass of a metal salt as solid components, and having a solid component concentration of 20% by mass).

[0287] Next, using a spin coater, the protective film forming agent was coated on the surface of the silicon substrate and then naturally dried at room temperature for 15 minutes to form a protective film with a film thickness of 5 μm.

[0288] Next, plasma irradiation was performed linearly on the surface of the protective film side of the Si substrate to perform etching for forming a dividing groove. It should be noted that the plasma irradiation was performed under the following laser irradiation conditions using the Bosch process.

[0289] ·Bosch process:

[0290] The following processes were alternately repeated: a sidewall protection process based on the supply of fluorine gas (C4F8 gas) (a process of plasmaizing the fluorine gas and depositing a CF-based protective film on the silicon substrate); and an etching process (an etching process of removing the film on the bottom surface using the ion assist effect and reacting the Si of the silicon substrate exposed by SF6 plasma irradiation with the F atoms generated by plasmaization to remove it in the form of silicon tetrafluoride (SiF4)).

[0291] ·Laser irradiation conditions:

[0292] Wavelength: 355 nm

[0293] Frequency: 100 kHz

[0294] Output power: 0.1 W

[0295] Defocus amount: -0.1 mm

[0296] Conveyor speed: 100 mm / s

[0297] Pass: 2

[0298] (Determination of Solid Component Concentration)

[0299] First, accurately weigh the aluminum box (tare weight A (g)). Next, accurately weigh 1 g of the protective film forming agent and place it in the aluminum box (measured value: B (g)). Dry it under the conditions of 140 °C for 120 minutes. After drying, cool it to room temperature and then accurately weigh it (measured value: C (g)). Then, calculate the solid component concentration based on the following formula. It should be noted that the electronic balance used for accurate weighing is a balance that can weigh to the unit of 0.0001 g.

[0300] Solid component concentration (mass %) = (C - A) / (B - A) × 100

[0301] A: Mass of tare weight (g)

[0302] B: Total mass of sample and tare weight (g)

[0303] C: Total mass of dried sample and tare weight (g)

[0304] (Determination of Metal Content)

[0305] Use inductively coupled plasma optical emission spectrometry to quantify the metal content in the protective film forming agent. It should be noted that the measurement is carried out using the standard curve method. A standard curve is made with concentrations of 4 gradients or more. For this standard curve, the measurement is carried out under the condition of a correlation coefficient of 0.99 or more. As the metal reagent used in the standard curve method, a mixed solution of 1 mass part of the multi-element mixed standard solution "XSTC-622" (metal element concentration is 10 mg / L) manufactured by SPEX and 99 mass parts of dimethylacetamide (DMAC) (metal element concentration is 100 mass ppb) is used.

[0306] (Evaluation of Film Formability (Cracks in the Protective Film))

[0307] Under the above conditions, use the spin coating method to coat the protective film forming agent on a silicon substrate to obtain a protective film with a film thickness of 5 μm. Dry the obtained protective film under reduced pressure to the measurement environment of SEM (scanning electron microscope) (6.0 Pa). Then, observe the coated film after drying under reduced pressure with a 10-fold optical microscope and evaluate the film formability (presence or absence of cracks in the protective film) based on the following criteria. It should be noted that in the case of cracks occurring ("B" case), the measurement of the selection ratio is not carried out ("-" in each table).

[0308] · "A": No cracks are confirmed to occur.

[0309] · "B": Cracks are confirmed to occur.

[0310] It should be noted that for Examples 1 to 17, the surface of the protective film was touched with a finger to confirm the presence or absence of stickiness (adhesion). As a result, it was confirmed that none of the examples showed stickiness.

[0311] (Measurement of selection ratio)

[0312] Based on the following formula, the selection ratio was calculated.

[0313] Selection ratio = Film loss amount of silicon substrate / Film loss amount of protective film

[0314] · Film loss amount of silicon substrate = Film thickness of silicon substrate before irradiation - Film thickness of silicon substrate after irradiation

[0315] · Film loss amount of protective film = Film thickness of protective film before irradiation - Film thickness of protective film after irradiation

[0316] <Examples 2 to 11>

[0317] Except for changing the components of the protective film forming agent to the components described in Table 2, the protective film forming agent was prepared in accordance with Example 1. It should be noted that the protective film forming agent of Example 7 contains, as solid components, 91.26 parts by mass of the first resin, 5.54 parts by mass of the metal salt, 2.5 parts by mass of 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (DHBA), and 0.7 parts by mass of monoethanolamine (MEA), and has a solid component concentration of 20% by mass. In addition, in the protective film forming agent of Example 7, the molar ratio of MEA / DHBA is 1.1 (= (0.7÷61.08) / (2.5÷246.22)).

[0318] <Examples 12 to 17>

[0319] Except for changing the components of the protective film forming agent to the components described in Table 3, the protective film forming agent was prepared in accordance with Example 1. For example, the protective film forming agent of Example 12 contains, as solid components, 85.01 parts by mass of the first resin (non-aromatic resin), 9.45 parts by mass of the second resin (aromatic resin), and 5.54 parts by mass of the metal salt, and has a solid component concentration of 18% by mass.

[0320] It should be noted that for Examples 1 to 17, the straightness was also evaluated based on the following criteria. If it is at least "B" or above ("B" or "A"), it is evaluated as a level with no practical problems. As a result, it was confirmed that all examples were at least "B" or above ("B" or "A").

[0321] · "A": The cross-section of the protective film (side wall of the processing groove) is flat, and a straight groove (trench) without voids is formed.

[0322] · "B": The cross-section of the protective film is relatively flat, forming a groove (channel) that is slightly porous but relatively straight.

[0323] · "C": The cross-section of the protective film is uneven, forming a groove (channel) with large voids.

[0324] · "D": Poor processing (due to the heat of the laser, the pattern becomes soft, unable to maintain its shape, and unable to form a processed groove).

[0325] <Comparative Examples 1 - 12>

[0326] A protective film forming agent was prepared according to Example 1, except that the composition of the protective film forming agent was changed to the composition described in Table 4. For example, the protective film forming agent of Comparative Example 1 is a protective film forming agent with a solid content concentration of 18% by mass, containing only 100 parts by mass of the first resin (non-aromatic resin) as the solid component.

[0327] The formulations and evaluation results of Examples 1 - 11 are shown in Table 2, the formulations and evaluation results of Examples 12 - 17 are shown in Table 3, and the formulations and evaluation results of Comparative Examples 1 - 12 are shown in Table 4.

[0328] [Table 2]

[0329]

[0330] [Table 3]

[0331]

[0332] [Table 4]

[0333]

[0334] Based on the above, it is at least confirmed that a protective film with excellent film-forming properties and a high selectivity ratio can be produced by the protective film forming agent according to this example.

[0335] This application is based on Japanese Patent Application (Japanese Patent Application No. 2022 - 208225) filed with the Japan Patent Office on December 26, 2022, the content of which is incorporated herein by reference.

Claims

1. A protective film forming agent, comprising: A metal salt having a boiling point of 900 °C or higher when it is a metal fluoride; A first resin having no aromatic ring; and A solvent.

2. The protective film forming agent according to claim 1, further comprising a second resin having an aromatic ring.

3. The protective film forming agent according to claim 1 or 2, wherein In the total amount of the components after removing the solvent from the protective film forming agent, the content ratio of the metal of the metal salt is 0.15% by mass or more.

4. The protective film forming agent according to claim 1 or 2, wherein The metal of the metal salt includes at least one selected from the group consisting of Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce.

5. The protective film forming agent according to claim 1 or 2, wherein, The metal salt includes at least one selected from the group consisting of sulfate, nitrate, nitrite, and their hydrates.

6. The protective film forming agent according to claim 1 or 2, wherein, The first resin includes at least one selected from the group consisting of a cellulose-based resin and a vinyl-based resin.

7. The protective film forming agent according to claim 1 or 2, wherein, The first resin includes at least one selected from the group consisting of a resin (1A) containing a repeating unit represented by the following formula (1a), a resin (1B) containing a repeating unit represented by the following formula (1b-1) and a repeating unit represented by the following formula (1b-2), a resin (1C) containing a repeating unit represented by the following formula (1c), and a resin (1D) containing a repeating unit represented by the following formula (1d). [Chemical formula 1] In formula (1a), R 1 , R 2 and R 3 are each independently a substituent represented by -H, -CH3, -CH2CH3 or -CH2CH(OH)CH3, and all of R 1 , R 2 and R 3 are at least one substituent other than -H, [Chemical formula 2] [Chemical formula 3] [Chemical formula 4] 8. The protective film forming agent according to claim 2, wherein, The second resin includes at least one selected from the group consisting of a resin (2A) containing a repeating unit represented by the following formula (2a-1) and a repeating unit represented by the following formula (2a-2), a resin (2B) containing a repeating unit represented by the following formula (2b-1) and a repeating unit represented by the following formula (2b-2), and a resin (2C) containing a repeating unit represented by the following formula (2c). [Chemical formula 5] In formula (2a-2), X + is an alkali metal cation, a proton, or N + R 4 4, where R 4 is a hydrogen atom, an alkyl group, or a hydroxyalkyl group; [Chemical formula 6] In formula (2b-2), M 1+ and M 2+ each independently represents an alkali metal cation, a proton or N + R 5 4, where R 5 is a hydrogen atom, an alkyl group or a hydroxyalkyl group; [Chemical formula 7] 9. A protective film, comprising: A metal salt having a boiling point of 900 °C or higher when it is a metal fluoride; and A first resin having no aromatic ring.

10. The protective film according to claim 9, further comprising a second resin having an aromatic ring.

11. The protective film according to claim 9 or 10, wherein, The content rate of the metal of the metal salt in the protective film is 0.15% by mass or more.

12. The protective film according to claim 9 or 10, wherein The metal of the metal salt includes at least one selected from the group consisting of Li, Be, Na, Mg, Al, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ag, Cd, In, Cs, Ba, La, and Ce.

13. The protective film according to claim 9 or 10, having a film thickness of 0.1 μm or more and 100 μm or less.

14. A method for manufacturing a protective film, comprising a step of forming a protective film by coating the protective film forming agent according to claim 1 or 2 on a substrate.

15. A method for manufacturing a semiconductor chip, which is a method for manufacturing a semiconductor chip by plasma cutting a semiconductor wafer, the method for manufacturing the semiconductor chip includes: A step of forming a protective film by coating the protective film forming agent according to claim 1 or 2 on a semiconductor wafer; A step of irradiating a laser on a specified position of one or more layers including the protective film on the semiconductor wafer to form a processing groove that exposes the surface of the semiconductor wafer and has a pattern corresponding to the shape of a semiconductor chip; and A step of irradiating the semiconductor wafer having the processing groove with plasma to cut the position of the processing groove of the semiconductor wafer, thereby obtaining a semiconductor chip.

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