Method for forming resist film and resist film

Abstract

To provide: a resist film forming method employing a resist with viscosity which is high at normal temperature but decreases upon heating, where the method enables formation of a resist film whose film thickness is 300 μm or more and in-plane film thickness variation is within 10%; and a resist film formed by the resist film forming method.SOLUTION: A resist film forming method comprises: a step A of applying onto a substrate a resist whose viscosity at 23°C is 1000 mPa s to 30000 mPa s, thereby forming a film of the resist; a step B of applying heat treatment to the film of the resist disposed in a region surrounded by a restriction member to restrict efflux of the resist; and a step C of applying hot pressing, via a sheet, to the film of the resist after the heat treatment disposed in a region formed by installation of an adjustment member to adjust the thickness of the film of the resist to a desired thickness. There is also provided a resist film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for forming a resist film and a resist film. [Background technology]

[0002] Conventionally, a method for forming a thick resist film has been known. For example, Patent Document 1 discloses a method for forming a thick resist film, which includes applying a resist solution onto a substrate by spin coating to form a coating film, heating the coating film to remove the solvent and obtain a resist film, arranging spacers having the same thickness as the required resist film thickness around the periphery of the substrate, and then heating the resist film again, and pressing the heated and softened resist film using a glass substrate. Patent Document 1 describes that a thick negative resist having a film thickness of 250 μm was formed by the method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-207969 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, resist films have been formed using resists that have high viscosity at room temperature and that decrease in viscosity when heated. Patent Document 1 also uses a resist solution that has a glass transition temperature of 40°C to 50°C and becomes soft when slightly heated. A representative resist having the above-described properties is SU-8 (product series name) manufactured by Nippon Kayaku Co., Ltd. SU-8 is said to be capable of forming a thick resist film. However, when a resist film is formed using SU-8, the resist flows due to heating during pre-baking (a heat treatment for removing the solvent), which can cause problems such as the final resist film being thinner than expected and large in-plane film thickness variations.

[0005] An object of one embodiment of the present disclosure is to provide a method for forming a resist film using a resist that has high viscosity at room temperature and that decreases in viscosity upon heating, and that can form a resist film having a thickness of 300 μm or more and an in-plane film thickness variation of 10% or less. Another problem to be solved by another embodiment of the present disclosure is to provide a resist film formed by the above-described method for forming a resist film. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following embodiments. [1] A step A of applying a resist having a viscosity of 1000 mPa·s to 30000 mPa·s at 23°C onto a substrate to form a film of the resist; a step B of performing a heat treatment on the resist film disposed in an area surrounded by a restricting member that restricts the outflow of the resist; A step C of heat-pressing the resist film after the heat treatment, which is placed in an area formed by the installation of an adjusting member that adjusts the resist film to a desired thickness, via a sheet; A method for forming a resist film comprising: [2] The method for forming a resist film according to [1], wherein the arithmetic mean roughness Ra of the surface of the sheet on the side of the resist film in step C is 10 μm or less. [3] The method for forming a resist film according to [1] or [2], wherein the Young's modulus of the sheet in step C is 40 MPa to 5500 MPa. [4] The method for forming a resist film according to any one of [1] to [3], wherein the adjusting member in step C and the resist film after the heat treatment are arranged with a gap in the in-plane direction. [5] The method for forming a resist film according to any one of [1] to [4], wherein in step B, the temperature of the resist film is increased stepwise or continuously to set the viscosity of the resist to 5000 mPa·s or less. [6] The method for forming a resist film according to any one of [1] to [5], wherein in step B, the resist film having a viscosity of 5000 mPa·s or less is subjected to a heat treatment in a vacuum environment. [7] The method for forming a resist film according to any one of [1] to [6], wherein the temperature of the heat press in the step C is lower than the temperature of the heat treatment in the step B. [8] A resist film formed by the method for forming a resist film according to any one of [1] to [7], wherein the resist film has a thickness of 300 μm or more and an in-plane thickness variation of 10% or less. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, there is provided a method for forming a resist film using a resist that has high viscosity at room temperature and that decreases in viscosity upon heating, and that can form a resist film with a film thickness of 300 μm or more and an in-plane film thickness variation of 10% or less. According to another embodiment of the present disclosure, there is provided a resist film formed by the above-described method for forming a resist film. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 10 is a schematic cross-sectional view showing one embodiment in which a film of a specific resist is disposed in a region surrounded by a regulating member. [Figure 2A]2 is a schematic plan view for explaining the layer structure of the regulating member shown in FIG. 1. FIG. [Figure 2B] 2 is a schematic plan view for explaining the layer structure of the regulating member shown in FIG. 1. FIG. [Figure 2C] 2 is a schematic plan view for explaining the layer structure of the regulating member shown in FIG. 1. FIG. [Figure 3] FIG. 10 is a schematic plan view showing one embodiment of a state in which a film of a specific resist after heat treatment is disposed in a region formed by the installation of an adjustment member. [Figure 4] FIG. 10 is a schematic plan view showing another embodiment in which a film of a specific resist after heat treatment is disposed in a region formed by the installation of an adjusting member. [Figure 5] FIG. 10 is a schematic plan view showing another embodiment in which a film of a specific resist after heat treatment is disposed in a region formed by the installation of an adjusting member. DETAILED DESCRIPTION OF THE INVENTION

[0009] The resist film forming method and the resist film of the present disclosure will be described in detail below. The following description of the requirements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the present disclosure.

[0010] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0011] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0013] The elements in the drawings shown in this disclosure are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. In each drawing, components having the same function are given the same reference numerals, and duplicated explanations will be omitted.

[0014] In this disclosure, "room temperature" means 23°C. In this disclosure, "high viscosity" means a viscosity of 1000 mPa·s or greater.

[0015] [Method for forming resist film] The method for forming a resist film of the present disclosure includes: Step A of applying a resist having a viscosity of 1000 mPa·s to 30000 mPa·s at 23°C onto a substrate to form the resist film; Step B of performing a heat treatment on the resist film, which is disposed within an area surrounded by a control member that controls the outflow of the resist; and Step C of performing a heat press, via a sheet, on the heat-treated resist film, which is disposed within an area formed by the installation of an adjustment member that adjusts the resist film to a desired thickness. According to the resist film forming method of the present disclosure, even when using a resist that has high viscosity at room temperature and whose viscosity decreases when heated, it is possible to form a resist film that has a film thickness of 300 μm or more and an in-plane film thickness variation of 10% or less. Although it is unclear why the resist film forming method of the present disclosure can achieve such an effect, the present inventors speculate as follows: However, the following speculation is not intended to limit the resist film forming method of the present disclosure, but is merely an example.

[0016] When a resist film is formed using a resist that has a high viscosity at room temperature and whose viscosity decreases when heated, the resist flows when heated during pre-baking, which can result in problems such as the thickness of the final resist film being thinner than expected and large variations in film thickness within the surface. In contrast, in the resist film forming method of the present disclosure, by performing a heat treatment on a resist film arranged within an area surrounded by a regulating member that regulates the outflow of the resist, the flow of the resist due to heating during pre-baking, for example, is prevented, and therefore the thickness of the resist film is prevented from becoming thin.Furthermore, by performing a heat press via a sheet on the heat-treated resist film arranged within an area formed by the installation of an adjusting member that adjusts the resist film to a desired thickness, the resist film surface is smoothed and the film thickness is made uniform.Therefore, it is estimated that even when using a resist that has a high viscosity at room temperature and whose viscosity decreases when heated, it is possible to form a resist film with a film thickness of 300 μm or more and an in-plane film thickness variation of 10% or less.

[0017] In contrast to the resist film forming method of the present disclosure, the resist film forming method described in Patent Document 1 (JP 2007-207969 A; the same applies hereinafter) does not position the resist film within an area surrounded by a restricting member that restricts the outflow of the resist when pre-baking the resist film. Therefore, the resist film flows due to heating during pre-baking, making it difficult to form a resist film with a thickness of 300 μm or more. Furthermore, in the resist film forming method described in Patent Document 1, when heating and pressing the resist film, the resist film is not positioned within an area formed by the installation of an adjusting member that adjusts the resist film to a desired thickness. Therefore, it is difficult to form a resist film with an in-plane film thickness variation of 10% or less.

[0018] The method for forming a resist film according to the present disclosure will be described in detail below.

[0019] [Process A] Step A is a step of applying a resist having a viscosity of 1000 mPa·s to 30000 mPa·s at 23° C. onto a substrate to form a film of the specific resist. In the present disclosure, "a resist having a viscosity of 1000 mPa·s to 30000 mPa·s at 23° C." is also referred to as "specific resist."

[0020] The material of the substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples of substrates include glass substrates, resin substrates (e.g., polyethylene terephthalate (PET) substrates, polyethylene naphthalate (PEN) substrates, polycarbonate (PC) substrates, polyimide (PI) substrates, and triacetyl cellulose (TAC) substrates), metal substrates (e.g., aluminum substrates and stainless steel substrates), and semiconductor substrates (e.g., silicon substrates). The shape and thickness of the substrate are not particularly limited and can be appropriately selected depending on the purpose.

[0021] When the specific resist is applied directly to the surface of the substrate, the surface of the substrate on which the specific resist is applied (hereinafter also referred to as "substrate surface") preferably has high flatness. Specifically, the arithmetic mean roughness Ra of the substrate surface is, for example, preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 1 μm or less. When the arithmetic mean roughness Ra of the substrate surface is 10 μm or less, a resist film with smaller in-plane film thickness variations tends to be formed.

[0022] In the present disclosure, the arithmetic mean roughness Ra of a substrate surface is a value measured using a surface roughness measuring instrument. As the surface roughness measuring instrument, for example, a one-shot 3D shape measuring instrument (type: head, model: VR-5100) manufactured by Keyence Corporation can be used. However, the surface roughness measuring instrument is not limited to this.

[0023] In step A, a resist having a viscosity of 1000 mPa·s to 30000 mPa·s at 23° C. (ie, a specific resist) is applied onto a substrate. The specific resist of the present disclosure is not particularly limited as long as it has a viscosity at 23° C. of 1000 mPa·s to 30000 mPa·s and the viscosity decreases when heated. Examples of the specific resist include SU-8 3050 (trade name, viscosity at 23°C: 12000 mPa·s) and KMPR-1035 (trade name, viscosity at 23°C: 8300 mPa·s) manufactured by Nippon Kayaku Co., Ltd. These commercially available products can be used as the specific resist as is. These commercially available products may be used as specific resists by diluting them with a solvent and / or adding various additives, as long as the viscosity at 23°C is 1000 mPa·s to 30000 mPa·s and the property of decreasing viscosity upon heating is not impaired.

[0024] The viscosity of the specific resist at 23° C. is, for example, preferably 5000 mPa·s to 30000 mPa·s, more preferably 8000 mPa·s to 25000 mPa·s, and even more preferably 10000 mPa·s to 20000 mPa·s.

[0025] In the present disclosure, the viscosity of a resist at 23°C is a value measured using a viscometer (including a rheometer; the same applies hereinafter). For example, the viscosity of a resist at 23°C is measured using a viscometer after adjusting the temperature of the resist to 23°C. As the viscometer, for example, a rheometer (product name: HAAKE RheoStress 6000) manufactured by Thermo Fisher Scientific K.K. can be used. However, the viscometer is not limited to this.

[0026] The application of the specific resist onto the substrate is not limited to direct application onto the surface of the substrate. The particular resist may be applied, for example, onto a film base that is disposed on a substrate. When the film substrate is disposed on the substrate, it is preferable that the film substrate is fixed on the substrate. The means for fixing the film substrate on the substrate is not particularly limited, but it is preferable that the means be one that allows the film substrate to be removed from the substrate when the fixing of the film substrate is no longer necessary. From this viewpoint, examples of the means for fixing the film substrate on the substrate include peelable fixing means such as an adhesive, a double-sided adhesive sheet, etc. When fixing the film base on the substrate, it is preferable to prevent air bubbles from getting between the substrate and the film base, for example, from the viewpoint of easily realizing the formation of a resist film with an in-plane film thickness variation of 10% or less.

[0027] Examples of materials for the film substrate include resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), and triacetyl cellulose (TAC). The film substrate may constitute at least a part of the regulating member in step B described below.

[0028] The surface of the film substrate on which the specific resist is applied (hereinafter also referred to as the "film substrate surface") preferably has high flatness. Specifically, the arithmetic mean roughness Ra of the film substrate surface is, for example, preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 1 μm or less. When the arithmetic mean roughness Ra of the film substrate surface is 10 μm or less, it tends to be possible to form a resist film with smaller in-plane film thickness variations.

[0029] In the present disclosure, the arithmetic mean roughness Ra of the surface of the film substrate is a value measured using a surface roughness measuring instrument. As the surface roughness measuring instrument, for example, a one-shot 3D shape measuring instrument (type: head, model: VR-5100) manufactured by Keyence Corporation can be used. However, the surface roughness measuring instrument is not limited to this.

[0030] The method for applying the specific resist onto the substrate is not particularly limited. Examples of methods for applying the specific resist onto the substrate include coating methods (for example, slit coating, spin coating, and curtain coating) and inkjet methods. When the specific resist is applied to an area surrounded by a regulating member installed on the substrate, i.e., a regulating member that regulates the outflow of the specific resist, which will be described in step B below, the specific resist may be applied to the substrate by injecting it into the area.

[0031] The amount of the specific resist to be applied is not particularly limited, and is set appropriately depending on, for example, the desired thickness of the resist film to be finally obtained. When the specific resist is applied to a region surrounded by a regulating member installed on a substrate, i.e., a regulating member that regulates the outflow of the specific resist, which will be described in step B below, it is preferable that the amount does not exceed the height of the regulating member.

[0032] [Process B] Step B is a step of performing a heat treatment on a film of the specific resist arranged in an area surrounded by a restricting member that restricts the outflow of the specific resist. Hereinafter, the "control member that controls the outflow of the specific resist" will also be simply referred to as the "control member."

[0033] In step B, the specific resist film is disposed within an area surrounded by a regulating member. The regulating member may be disposed on the substrate so as to surround the specific resist film at the time when the specific resist film is subjected to heat treatment. The regulating member may be provided on the substrate before applying the specific resist onto the substrate in step A, or may be provided on the substrate after forming a film of the specific resist in step A. A preferred embodiment is one in which the regulating member is provided on the substrate before applying the specific resist onto the substrate in step A. This embodiment tends to make it easier to form a resist film with a film thickness of 300 μm or more.

[0034] The material of the restricting member is not particularly limited. Examples of materials for the restricting member include resin, glass, and metal. Among these, resin is preferable as the material for the restricting member. Examples of resins include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), and triacetyl cellulose (TAC). Among these, polyethylene terephthalate (PET) is preferred as the resin.

[0035] Commercially available materials can be used for the restricting member. An example of a commercially available product is the Lumirror (registered trademark) series manufactured by Toray Industries, Inc. (material: biaxially stretched PET film).

[0036] The shape of the restricting member is not particularly limited as long as it can restrict the outflow of the specific resist. The shape of the restricting member is preferably, for example, a frame shape, a concave shape, or the like.

[0037] The regulating member is preferably fixed onto the substrate. The means for fixing the regulating member to the substrate is not particularly limited, but is preferably a means that allows the regulating member to be removed from the substrate when the fixing of the regulating member is no longer necessary. From this perspective, examples of the means for fixing the regulating member to the substrate include peelable fixing means such as an adhesive or a double-sided adhesive sheet.

[0038] A preferred embodiment of the restricting member will be described with reference to FIGS. 1, 2A, 2B, and 2C. FIG. 1 is a schematic cross-sectional view showing one embodiment in which a film of a specific resist is disposed within an area surrounded by a regulating member, and FIGS. 2A, 2B, and 2C are schematic plan views for explaining the layer structure of the regulating member shown in FIG. As shown in FIG. 1, a film of specific resist 100 is disposed within an area surrounded by a regulating member 2 provided on the surface of substrate 1. Regulating member 2 is fixed to the surface of substrate 1 via a double-sided adhesive sheet 3. Regulating member 2 is formed by laminating, in this order, a PET sheet 10 shown in FIG. 2A, a frame-shaped double-sided adhesive sheet 20 shown in FIG. 2B, and a frame-shaped PET sheet 30 shown in FIG. 2C. The combined film thickness of the frame-shaped double-sided adhesive sheet 20 and the frame-shaped PET sheet 30 is greater than the film thickness of specific resist 100. This prevents specific resist 100 from flowing out. The frame-shaped double-sided adhesive sheet 20 and the frame-shaped PET sheet 30 are peeled off after step B and before the heat pressing in step C. For example, when forming a resist film having dimensions of 65 mm x 48 mm and a thickness of 300 μm, one embodiment of PET sheet 10 has dimensions of 150 mm x 100 mm and a thickness of 250 μm, one embodiment of double-sided adhesive sheet 20 has an outer diameter of 110 mm x 80 mm, an inner diameter of 80 mm x 60 mm, and a thickness of 210 μm, and one embodiment of PET sheet 30 has an outer diameter of 110 mm x 80 mm, an inner diameter of 80 mm x 60 mm, and a thickness of 250 μm.

[0039] In step B, the specific resist film is subjected to a heat treatment. The heat treatment method is not particularly limited. Examples of the heat treatment means include a hot plate and a convection oven (a so-called hot air circulation dryer), and examples of the heat treatment means in a vacuum environment include a vacuum heating dryer.

[0040] The heat treatment temperature is not particularly limited and is set appropriately depending on the type of specific resist, for example. For example, in the case of a specific resist having a viscosity of 5000 mPa s or less at 23°C, the heat treatment temperature is set to a temperature at which the viscosity of the specific resist decreases due to the heat treatment. The heat treatment temperature is, for example, preferably 50° C. or higher, more preferably 55° C. or higher, even more preferably 60° C. or higher, and particularly preferably 65° C. or higher. The heat treatment temperature is, for example, preferably 130° C. or lower, more preferably 120° C. or lower, and even more preferably 110° C. or lower.

[0041] If the viscosity of the specific resist at 23°C exceeds 5000 mPa·s, it is preferable in step B to increase the temperature of the specific resist film stepwise or continuously to make the viscosity of the specific resist 5000 mPa·s or less. Increasing the temperature of the specific resist film stepwise or continuously can prevent bubbles from forming in the film due to a sudden temperature rise. In addition, keeping the viscosity of the specific resist below 5000 mPa·s makes it easier to remove bubbles from the film. The temperature of the specific resist film may be increased stepwise or continuously, but it is more preferable to increase it stepwise. When the temperature of the specific resist film is increased stepwise, the number of steps is not particularly limited as long as it is at least 2. For example, from the viewpoint of reducing the complexity of the operation, the number of steps is preferably 5 steps or less, and particularly preferably 2 steps. When the temperature of the specific resist film is increased in stages, for example, the temperature of the specific resist film is preferably increased to 50°C to 70°C and then to 90°C to 130°C, more preferably increased to 55°C to 70°C and then to 90°C to 120°C, and even more preferably increased to 60°C to 70°C and then to 90°C to 110°C. The heating time in each stage is not particularly limited, but it is preferable that the heating time in the final stage is the longest.

[0042] When the temperature of the specific resist film is continuously increased, the temperature increase rate is not particularly limited, but is preferably, for example, 70°C / min or less, more preferably 50°C / min or less, and even more preferably 30°C / min or less. The lower limit of the temperature rise rate is preferably, for example, 5° C. / min or more.

[0043] In the present disclosure, the temperature of the resist film refers to the temperature of the resist film surface measured using a radiation thermometer. The radiation thermometer may be, for example, a radiation thermometer (model number: IT-314) manufactured by AS ONE Corporation. However, the radiation thermometer is not limited to this.

[0044] In the present disclosure, the viscosity of the resist forming the film is determined according to the following procedures (1) to (3). (1) In advance, a calibration curve (also called a "temperature-viscosity curve") is created that shows the relationship between the temperature and viscosity of the resist to be applied to the substrate in step A. Specifically, the temperature of the resist is changed in steps of 10°C from 23°C to 153°C, and the viscosity of the resist at each temperature step is measured using a viscometer, and a temperature-viscosity curve is created based on the values ​​obtained. (2) The temperature of the resist film is measured using a radiation thermometer. (3) The viscosity of the resist film is determined by applying the measured temperature of the resist film to the temperature-viscosity curve prepared in advance.

[0045] As the viscometer in (1) above, for example, a rheometer (product name: HAAKE RheoStress 6000) manufactured by Thermo Fisher Scientific Co., Ltd. can be used, but the viscometer is not limited to this.

[0046] The time for the heat treatment is not particularly limited and may be set appropriately depending on, for example, the type of specific resist and the temperature for the heat treatment. The heat treatment time is, for example, preferably 4 to 9 hours, more preferably 4 to 8 hours, further preferably 5 to 8 hours, and particularly preferably 5 to 7 hours.

[0047] In step B, it is preferable to perform a heat treatment in a vacuum environment on a film of the specific resist having a viscosity of 5000 mPa·s or less. In this disclosure, "vacuum" refers to a state in which the degree of vacuum is 0.1 MPa or less.

[0048] In a resist film with high viscosity, once air bubbles are mixed into the film, they tend to be difficult to remove. In contrast, if the viscosity of the resist is 5000 mPa·s or less, the air bubbles in the film tend to move more easily, making them easier to remove from the film. Also, in general, in a vacuum environment, the volume of the bubbles increases and they expand, increasing the buoyancy of the bubbles, making it easier for the bubbles to remove from the film than under atmospheric pressure. When a specific resist film with a viscosity of 5000 mPa·s or less is subjected to a heat treatment in a vacuum environment, the specific resist is vacuum degassed in a state in which air bubbles can be easily removed, thereby enabling the formation of a resist film with even fewer air bubbles. From this perspective, in step B, it is desirable to perform a heat treatment in a vacuum environment on a specific resist film having a viscosity of 5000 mPa·s or less, preferably 4000 mPa·s or less, more preferably 3000 mPa·s or less, even more preferably 2000 mPa·s or less, and particularly preferably 1000 mPa·s or less.

[0049] When the heat treatment is performed in a vacuum environment, the temperature of the heat treatment is not particularly limited as long as the viscosity of the specific resist can be maintained at 5000 mPa·s or less. When heat treatment is performed in a vacuum environment, the heat treatment temperature is, for example, preferably 70°C to 130°C, more preferably 90°C to 130°C, even more preferably 90°C to 120°C, and particularly preferably 90°C to 110°C.

[0050] The time for heat treatment when heat treatment is performed in a vacuum environment is not particularly limited, but is preferably, for example, 1 minute or more, more preferably 2 minutes or more, even more preferably 3 minutes or more, and particularly preferably 4 minutes or more. The upper limit is not particularly limited, but is preferably, for example, 10 minutes or less.

[0051] In step B, it is preferable to subject the specific resist film that has been heat-treated in a vacuum environment to a heat treatment under atmospheric pressure. In the present disclosure, "under atmospheric pressure" means a range of more than 0.1 MPa to 0.12 MPa. When a specific resist film is heat-treated in a vacuum environment, the viscosity of the specific resist is relatively high, and therefore, when bubbles are released, marks caused by the bubbles popping may remain on the surface of the film. When a specific resist film that has been heat-treated in a vacuum environment is heat-treated under atmospheric pressure, the surface of the film is leveled and flattened. Furthermore, when a specific resist film that has been heat-treated in a vacuum environment is heat-treated under atmospheric pressure, residual solvent in the specific resist film can also be removed.

[0052] When heat treatment is performed under atmospheric pressure after heat treatment in a vacuum environment, the heat treatment temperature is not particularly limited, but is preferably, for example, 70°C to 130°C, more preferably 90°C to 130°C, even more preferably 90°C to 120°C, and particularly preferably 90°C to 110°C. When heat treatment is performed under atmospheric pressure after heat treatment under a vacuum environment, the temperature of the heat treatment is preferably equal to or higher than the temperature of the heat treatment performed under a vacuum environment, and more preferably the same as the temperature of the heat treatment performed under a vacuum environment.

[0053] The time for which heat treatment is performed under atmospheric pressure after heat treatment under a vacuum environment is not particularly limited, but is preferably, for example, 3 hours or more, more preferably 3 to 8 hours, even more preferably 4 to 7 hours, and particularly preferably 4 to 6 hours.

[0054] [Process C] Step C is a step of performing heat pressing via a sheet on the heat-treated specific resist film, which is placed in an area formed by installing an adjustment member that adjusts the specific resist film to the desired thickness. Hereinafter, the "adjusting member for adjusting the thickness of a specific resist film to a desired thickness" will also be simply referred to as the "adjusting member."

[0055] In step C, the film of the specific resist after the heat treatment in step B is placed in the region formed by the placement of the adjusting member. The adjusting member may be placed on the substrate at the time when the heat-pressing is performed on the specific resist film after the heat treatment.

[0056] The material of the adjustment member is not particularly limited. Examples of materials for the adjustment member include metal, glass, and resin. Among these, metal is preferable as the material for the adjustment member, for example, from the viewpoint of being less susceptible to breakage or deformation. Examples of metals include stainless steel (SUS), iron, copper, and aluminum. Among these, stainless steel (SUS) is preferred as the metal.

[0057] The shape of the adjustment member is not particularly limited, but it is preferable that the shape allows the sheet to be stably positioned, specifically, that the shape allows the sheet to be stably supported in a state parallel to the film of the specific resist after heat treatment. The shape of the adjustment member may be, for example, a columnar shape (for example, a cylindrical shape or a rectangular columnar shape), a horseshoe shape, or the like.

[0058] The height of the adjusting member is preferably lower than the film thickness of the specific resist film after heat treatment. When the height of the adjusting member is lower than the film thickness of the specific resist film after heat treatment, a resist film with smaller in-plane film thickness variation tends to be formed.

[0059] The adjusting member and the film of the specific resist after heat treatment are preferably disposed with a gap therebetween in the in-plane direction. The interval is not particularly limited, but is preferably 5 mm to 30 mm, and more preferably 10 mm to 20 mm, for example. If the gap is 5 mm or more, there is a tendency that problems such as the specific resist having its viscosity reduced by heat pressing entering the gap between the substrate or base material and the adjusting member are less likely to occur. If the distance is 30 mm or less, for example, there is a tendency that fluctuations in the in-plane film thickness of the resist film due to bending of the center of the sheet used during hot pressing are less likely to occur.

[0060] It is preferable that the region formed by the installation of the adjusting member is not a region that is completely closed by the installation of the adjusting member, but a region that is at least partially open. If at least a portion of the region formed by the installation of the adjusting member is open, excess specific resist can flow out from the open portion when hot pressing is performed. This tends to make it easier to adjust the thickness of the specific resist film to the desired thickness.

[0061] The adjustment member is preferably fixed on a substrate. The means for fixing the adjusting member to the substrate is not particularly limited, but is preferably a means that allows the adjusting member to be removed from the substrate when the fixing of the adjusting member is no longer necessary. From this perspective, examples of the means for fixing the adjusting member to the substrate include releasable fixing means such as an adhesive or a double-sided adhesive sheet.

[0062] A preferred embodiment of the adjustment member will be described with reference to FIGS. Figure 3 is a schematic plan view showing one embodiment of the state in which a specific resist film after heat treatment is arranged within an area formed by the installation of an adjustment member when a stainless steel material (SUS) having a rectangular columnar (more specifically, rectangular parallelepiped) shape is used as the adjustment member 40; Figure 4 is a schematic plan view showing another embodiment of the state in which a specific resist film after heat treatment is arranged within an area formed by the installation of the adjustment member when a stainless steel material (SUS) having a horseshoe shape is used as the adjustment member 40; and Figure 5 is a schematic plan view showing another embodiment of the state in which a specific resist film after heat treatment is arranged within an area formed by the installation of the adjustment member when a stainless steel material (SUS) having a cylindrical shape is used as the adjustment member 40. 3, 4, and 5, the adjusting member 40 is placed on the surface of a PET sheet 10 (i.e., a member forming part of the restricting member 2 shown in FIG. 1) provided on the surface of the substrate 1, and a film of the specific resist 100 after heat treatment is disposed in the area formed by the placement of the adjusting member 40. The "area formed by the placement of the adjusting member 40" refers to an area surrounded by one adjusting member 40 or an area sandwiched between multiple adjusting members 40, and may also be an area surrounded by imaginary lines (dash-two-dot lines), such as area 50A sandwiched between two adjusting members 40 shown in FIG. 3, area 50B surrounded by one adjusting member 40 shown in FIG. 4, and area 50C sandwiched between four adjusting members 40 shown in FIG. 5. 3, 4, and 5, the adjusting member 40 and the film of the specific resist 100 after heat treatment are installed with a gap in the in-plane direction. This type of installation tends to prevent problems such as the specific resist 100, whose viscosity has been reduced by heat pressing, entering the gap between the substrate 1 or PET sheet 10 and the adjusting member 40. Also, in FIGS. 3, 4, and 5, the region formed by the installation of the adjusting member 40 is not a completely closed region, but has at least a partial opening. This type of installation tends to make it easier to adjust the thickness of the film of the specific resist 100 to a desired thickness, since excess specific resist 100 can flow out from the opening.

[0063] After the heat treatment, the specific resist film is heat-pressed via a sheet. When a specific resist film after heat treatment is subjected to heat pressing via a sheet, the specific resist film is easier to peel off after heat pressing compared to when a sheet is not used, and therefore fluctuations in the in-plane film thickness due to peeling tend to be less likely to occur. The material of the sheet is not particularly limited, but is preferably, for example, a resin. Examples of resins include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), and triacetyl cellulose (TAC). Among these, polyethylene terephthalate (PET) is preferred as the resin.

[0064] As the sheet, a commercially available product can be used. An example of a commercially available product is the Lumirror (registered trademark) series manufactured by Toray Industries, Inc. (material: biaxially stretched PET film).

[0065] The shape of the sheet is not particularly limited and can be appropriately selected depending on the shape of the specific resist film, for example.

[0066] The thickness of the sheet is not particularly limited, but is preferably 100 μm to 400 μm, and more preferably 200 μm to 250 μm, for example. When the film thickness of the sheet is within the above range, the specific resist tends to be more easily peeled off from the film after heat pressing.

[0067] In the present disclosure, the thickness of a sheet means the average thickness of the sheet. The average thickness of the sheet is a value determined by the following method. The arithmetic mean value of the film thickness of the sheet measured at 10 randomly selected points in the thickness direction of the sheet is calculated, and the obtained value is regarded as the average film thickness of the sheet. A micrometer is used to measure the film thickness of the sheet. An example of the micrometer is a micrometer manufactured by Mitutoyo Corporation (product name: Crimp Height Micrometer). However, the micrometer is not limited to this.

[0068] It is preferable that the surface of the sheet on the side of the specific resist film after heat treatment (hereinafter also referred to as the "sheet surface") has high flatness. Specifically, the arithmetic mean roughness Ra of the sheet surface is, for example, preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 1 μm or less. When the arithmetic mean roughness Ra of the sheet surface is 10 μm or less, it tends to be possible to form a resist film with smaller in-plane film thickness variations.

[0069] In the present disclosure, the arithmetic mean roughness Ra of the sheet surface is a value measured using a surface roughness measuring instrument. As the surface roughness measuring instrument, for example, a one-shot 3D shape measuring instrument (type: head, model: VR-5100) manufactured by Keyence Corporation can be used. However, the surface roughness measuring instrument is not limited to this.

[0070] The sheet preferably has a suitable degree of elasticity. Specifically, the Young's modulus of the sheet is, for example, preferably 40 MPa to 5500 MPa, more preferably 200 MPa to 5500 MPa, further preferably 1000 MPa to 5000 MPa, and particularly preferably 4000 MPa to 5000 MPa. When the Young's modulus of the sheet is 40 MPa or more, the sheet is appropriately soft, and therefore tends to be more easily peeled off from the specific resist film after heat pressing. When the Young's modulus of the sheet is 5500 MPa or less, the sheet is appropriately hard, and therefore tends to be more easily peeled off from the specific resist film after heat pressing.

[0071] In the present disclosure, the Young's modulus of a sheet is a value determined by a tensile test based on JIS K 7161-1:2014 and JIS K 7127:1999.

[0072] For example, from the viewpoint of realizing the formation of a resist film with smaller in-plane film thickness variations, it is preferable to perform the heat pressing after the surface of the specific resist film and the surface of the sheet are brought into close contact with each other so as to prevent air bubbles from being trapped between the specific resist film and the sheet. The means for bringing the surface of the specific resist film and the surface of the sheet into close contact is not particularly limited, and examples thereof include means using a pressure roller, a vacuum suction machine, or the like.

[0073] The means for heat pressing is not particularly limited. Examples of the heat pressing means include a combination of a hot plate and a weight, and a heat pressing machine. The load condition is not particularly limited, but for example, 1.0 N / cm 2 It is preferable that the resistance is 1.0 N / cm or more. 2 ~2.0N / cm 2 It is more preferable that:

[0074] The temperature of the heat press is not particularly limited, but is preferably 60°C to 120°C, more preferably 60°C to 110°C, even more preferably 60°C to 100°C, and particularly preferably 60°C to 90°C.

[0075] The temperature of the heat press is preferably lower than the temperature of the heat treatment in step B. If the temperature of the heat press is too high, bubbles may be generated in the specific resist film after the heat treatment. If the temperature of the heat press is lower than the temperature of the heat treatment in step B, the generation of bubbles due to the temperature of the heat press can be suppressed.

[0076] The time for the heat pressing is not particularly limited, but is preferably 10 to 60 minutes, more preferably 15 to 50 minutes, and even more preferably 20 to 40 minutes.

[0077] [Other steps] The method for forming a resist film according to the present disclosure may include steps other than Step A, Step B, and Step C (so-called other steps) as needed, provided that the effects of the present disclosure are not impaired.

[0078] Other steps include, for example, a step of gradually or continuously lowering the temperature of the specific resist film after heat pressing (a so-called cooling step). If the temperature of the specific resist film after heat pressing is suddenly reduced, stress will be generated inside the specific resist film, which may affect the in-plane film thickness variation of the resist film. Therefore, the temperature of the specific resist film after heat pressing is preferably reduced stepwise or continuously (so-called gradual cooling), and more preferably reduced continuously. When the temperature of the specific resist film after heat pressing is continuously reduced, the temperature reduction rate is not particularly limited, but is preferably, for example, 5°C / min or less, more preferably 4°C / min or less, and even more preferably 3°C / min or less. The lower limit of the temperature drop rate is preferably, for example, 0.1° C. / min or more. The temperature of the specific resist film after cooling is not particularly limited, but is preferably from 5°C to 30°C, more preferably from 10°C to 25°C, and even more preferably from 15°C to 23°C.

[0079] Furthermore, for example, when the specific resist is photocurable, the other step may be a step of irradiating the specific resist film with light after the cooling step (a so-called exposure step). Specific examples of the light source include various lasers, light-emitting diodes (LEDs), ultra-high pressure mercury lamps, high pressure mercury lamps, and metal halide lamps. The exposure amount (so-called cumulative light amount) is not particularly limited and can be set appropriately depending on, for example, the type of specific resist. Other steps include, for example, a development step, a post-baking step, and the like.

[0080] [Resist film] The resist film of the present disclosure is a resist film formed by the method for forming a resist film of the present disclosure, and has a film thickness of 300 μm or more and an in-plane film thickness variation of 10% or less. The method for forming a resist film according to the present disclosure is as described above. The resist film of the present disclosure preferably has a thickness of 300 μm or more and an in-plane thickness variation of 8% or less, more preferably has a thickness of 300 μm or more and an in-plane thickness variation of 6% or less, even more preferably has a thickness of 300 μm or more and an in-plane thickness variation of 4% or less, and particularly preferably has a thickness of 300 μm or more and an in-plane thickness variation of 2% or less.

[0081] In the present disclosure, the film thickness of the resist film means the average film thickness of the resist film. The average film thickness of the resist film is a value determined by the following method. The arithmetic mean value of the film thickness of the resist film measured at 10 randomly selected points in the thickness direction of the resist film is calculated, and the obtained value is regarded as the average film thickness of the resist film. A laser displacement meter is used to measure the film thickness of the resist film. An example of the laser displacement meter is a spectral interference laser displacement meter (model: SI-F10) manufactured by Keyence Corporation. However, the laser displacement meter is not limited to this.

[0082] The in-plane film thickness variation of the resist film is a value calculated using the maximum and minimum film thickness values ​​of the resist film measured at 10 randomly selected points in the thickness direction of the resist film, and the average film thickness of the resist film calculated above, using the following calculation formula. In-plane thickness variation of resist film (unit: %) = [maximum resist film thickness (unit: μm) - minimum resist film thickness (unit: μm)] / average resist film thickness (unit: μm) × 100 For example, if the film thicknesses of a resist film measured at 10 randomly selected locations are 300 μm, 300 μm, 305 μm, 305 μm, 310 μm, 310 μm, 315 μm, 315 μm, 320 μm, and 320 μm, respectively, the average film thickness of the resist film is 310 μm and the in-plane film thickness variation of the resist film is approximately 6.5%. [Example]

[0083] The method for forming a resist film and the resist film of the present disclosure will be described in more detail below using examples. However, the method for forming a resist film and the resist film of the present disclosure are not limited to the following examples as long as they do not deviate from the gist of the disclosure.

[0084] In the following examples, the film thickness and in-plane film thickness variation of the resist film were determined by the methods described above. The measurement device used was a spectral interference laser displacement meter (model: SI-F10) manufactured by Keyence Corporation.

[0085] The viscosity of the resist was measured using a rheometer manufactured by Thermo Fisher Scientific (trade name: HAAKE RheoStress 6000).

[0086] The temperature of the resist film was measured using a radiation thermometer (model number: IT-314) manufactured by AS ONE Corporation. The viscosity of the resist forming the film was determined by the method described above. That is, a calibration curve (i.e., a temperature-viscosity curve) showing the relationship between the temperature and viscosity of the resist used in the following examples was prepared in advance, and the temperature of the resist film measured using the radiation thermometer was applied to the temperature-viscosity curve to determine the viscosity of the resist forming the film.

[0087] [Resist film formation] Example 1 -Process A- A three-layered PET sheet serving as a regulating member, specifically, a concave-shaped regulating member 2 having a laminated structure of PET sheet 10 / double-sided adhesive sheet 20 / PET sheet 30 shown in Figures 1 and 2, was attached to one surface of a substrate (product name: SMS6025E2, size: 6025 (dimensions: 152 mm × 152 mm, thickness: 6.35 mm), material: synthetic quartz glass, manufactured by Shin-Etsu Chemical Co., Ltd.) using a double-sided adhesive sheet. PET sheet 10 measured 150 mm × 100 mm and had a film thickness of 250 μm. Double-sided adhesive sheet 20 had an outer diameter of 110 mm × 80 mm, an inner diameter of 80 mm × 60 mm, and a film thickness of 210 μm. PET sheet 30 had an outer diameter of 110 mm × 80 mm, an inner diameter of 80 mm × 60 mm, and a film thickness of 250 μm. Next, a specific resist, SU-8 3050 (trade name, viscosity at 23°C: 12000 mPa s, manufactured by Nippon Kayaku Co., Ltd.) was applied in a slit coating manner to a thickness of 460 μm into the recesses of the PET sheet to form a specific resist film. The formed specific resist film was positioned within the area surrounded by the regulating member.

[0088] -Process B- Next, the specific resist film formed as described above was subjected to a heat treatment. Specifically, the following procedure was performed: The PET sheet-attached substrate with the specific resist film disposed in the recesses was placed on a hot plate with a heating temperature set to 70°C, heated for 30 seconds (the so-called first stage heating), and then moved onto a hot plate with a heating temperature set to 100°C, and heated for another hour (the so-called second stage heating), thereby gradually increasing the temperature of the specific resist film. The temperature of the specific resist film after the first heating stage was 65°C, the temperature of the specific resist film after the second heating stage was 95°C, and the viscosity of the specific resist after the second heating stage was 4000 mPa·s. Next, the PET sheet-attached substrate X was placed in a vacuum dryer (product name: ETTAS vacuum dryer, model number: AVO-200NS-D, manufactured by AS ONE Corporation) with the temperature inside the dryer set to 100°C, and vacuum-heated for 5 minutes. The degree of vacuum inside the dryer was 0.1 MPa. Next, the PET sheet-attached substrate was removed from the vacuum dryer, placed on a hot plate with the heating temperature set to 100°C, and heated for an additional 5 hours under atmospheric pressure. Next, the double-sided pressure-sensitive adhesive sheet 20 and the PET sheet 30 were peeled off from the PET sheet-attached substrate.

[0089] -Process C- Next, the specific resist film that had been subjected to the heat treatment described above was subjected to heat pressing. Specifically, the following operations were carried out. A shim plate (material: SUS, size: 10 mm x 110 mm, height: 300 μm, shape: rectangular parallelepiped) of the same height as the target resist film thickness was placed on the surface of the PET sheet 10 on which the heat-treated specific resist film was placed, specifically, the adjustment member 40 shown in FIG. 3, so as to be spaced apart (spacing: 20 mm) in the in-plane direction from the specific resist film, as shown in FIG. 3. Next, a sheet (material: PET, size: 150 mm x 210 mm, thickness: 250 μm, arithmetic mean roughness Ra of the sheet surface: 0.6 μm, Young's modulus of the sheet: 5000 MPa) was placed on the surface of the specific resist film, and the specific resist film and the sheet were then tightly attached using a hand roller. Next, a weight weighing 6000 g was placed on the sheet that had been attached to the specific resist film, and a pressure of 1.2 N / cm was applied to the specific resist film. 2 After applying the load, the substrate was placed on a hot plate heated to 80° C. and heated for 30 minutes. The temperature of the specific resist film after heating was 75°C.

[0090] -Other processes- Next, the substrate was removed from the hot plate, and the specific resist film after heat pressing was cooled to 23°C over 6 hours at a temperature drop rate of 0.14°C / min. After cooling, the weight, sheet, and shim plate were removed. In this manner, a resist film was formed.

[0091] The resist film formed by the method of Example 1 had a film thickness of 300 μm and an in-plane film thickness variation of 5%. Furthermore, when the resist film formed by the method of Example 1 was visually observed, no bubbles were found.

[0092] Example 2 A resist film was formed by the same procedure as in Example 1, except that KMPR-1035 (trade name, viscosity at 23°C: 8300 mPa s, manufactured by Nippon Kayaku Co., Ltd.) was used as the specific resist instead of SU-8 3050 (trade name, viscosity at 23°C: 12000 mPa s, manufactured by Nippon Kayaku Co., Ltd.).

[0093] The resist film formed by the method of Example 2 had a film thickness of 300 μm and an in-plane film thickness variation of 5%. Furthermore, when the resist film formed by the method of Example 2 was visually observed, no air bubbles were found.

[0094] Comparative Example 1 A resist film was formed in the same manner as in Example 1, except that step C in Example 1 was not performed.

[0095] The resist film formed by the method of Comparative Example 1 had a film thickness of 250 μm and an in-plane film thickness variation of 40%. [Explanation of symbols]

[0096] 1: Circuit board 2: Regulating member 3: Double-sided adhesive sheet 10: PET sheet (base material) 20: Double-sided adhesive sheet 30:PET sheet 40: Adjustment member 50A: Area formed by installing the adjustment member 50B: Area formed by installing the adjustment member 50C: Area formed by installing the adjustment member 100: Specific Resist

Claims

1. a step A of applying a resist having a viscosity of 1,000 mPa·s to 30,000 mPa·s at 23°C and a viscosity that decreases upon heat treatment at 50°C or higher onto a substrate to form a film of the resist; a step B of performing a heat treatment on the resist film disposed in an area surrounded by a restricting member that restricts the outflow of the resist; a step C of removing the regulating member from the substrate, and then performing a heat press via a sheet on the resist film after the heat treatment, the resist film being disposed in a region formed by the installation of an adjusting member that adjusts the resist film to a desired thickness; Including, The adjusting member in the step C and the resist film after the heat treatment are respectively arranged on the substrate with a gap therebetween. A method for forming a resist film.

2. 2. The method for forming a resist film according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the sheet on the side of the resist film in step C is 10 μm or less.

3. 3. The method for forming a resist film according to claim 1, wherein the Young's modulus of the sheet in step C is 40 MPa to 5500 MPa.

4. 4. The method for forming a resist film according to claim 1, wherein in step B, the temperature of the resist film having a viscosity of more than 5000 mPa s at 23° C. is increased stepwise or continuously to reduce the viscosity of the resist to 5000 mPa s or less.

5. 5. The method for forming a resist film according to claim 1, wherein in the step B, the resist film having a viscosity of 5000 mPa·s or less is subjected to a heat treatment in a vacuum environment.

6. The temperature of the heat press in the step C is set to be higher than the temperature of the heat treatment in the step B. The method for forming a resist film according to any one of claims 1 to 5, wherein the resistivity is also low.

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