Protective film and protector, and method for manufacturing the same

Abstract

The present application provides a protective film which can suppress film thickness unevenness accompanying local surface protrusions even in a photolithography process under, for example, a monochromatic exposure light source, and thus can transmit exposure light more uniformly than before, the protective film being characterized in that, on the surface of the protective film, the number of protrusions formed of the same composition as the protective film and satisfying any one or more of the conditions (A) to (B) [condition (A) circumscribed circle diameter of 5 mm or more, condition (B) height of 2.5 μm or more] is 5 / m 2 The following.

Description

Technical Field

[0001] This invention relates to a dustproof protective film and protective component used in the photolithography process of manufacturing semiconductor devices, printed circuit boards, or flat panel displays, and a method for manufacturing the protective film and protective component. Background Technology

[0002] In the manufacture of semiconductors such as large-scale integrated circuits (LSI) or flat panel displays, patterns are created by irradiating the semiconductor wafer or the flat panel display substrate with light (Patent Document 1). If foreign matter adheres to the surface of the photomask or photomask used in this process, the foreign matter will absorb or scatter the light. Therefore, there are problems such as distorted transferred patterns and unclear edges, resulting in damage to dimensions and quality.

[0003] Therefore, even though the above operations are usually performed in a cleanroom, it is still difficult to keep the photomask clean at all times. To address this, a protective dust cover is attached to the photomask surface before exposure. In this case, foreign objects do not adhere directly to the photomask surface, but rather to the protective cover. Therefore, as long as the lens focus during photolithography is aligned with the patterned surface on the photomask beforehand, foreign objects on the protective cover will be out of focus and will not affect the transfer.

[0004] Generally, the protective component is formed by attaching a transparent protective film with excellent light transmittance, made of nitrocellulose, cellulose acetate, or fluoropolymer, to the upper surface of a protective frame made of aluminum, stainless steel, polyethylene, etc. Furthermore, an adhesive layer (adhesive layer) made of silicone resin, acrylic resin, etc., for mounting to a photomask, and a release layer (diaphragm) for protecting the adhesive layer are provided on the lower surface of the protective frame.

[0005] Previously, the light source used in the photolithography process, such as in the manufacture of flat panel displays, was a high-pressure mercury lamp with g-line (436nm) and i-line (365nm) wavelengths. In the manufacturing process of flat panel displays, compared to semiconductor manufacturing processes, the linewidth and spacing of the mask pattern are larger, so there is no need to use short-wavelength exposure light. Furthermore, due to the larger exposure area and the required amount of exposure light, broadband exposure light with wavelengths from i-line to g-line is used.

[0006] In the future, in order to cope with the higher precision of flat panel displays and new types of lithography, it will be necessary to deal with lithography using the aforementioned i-line monochromatic light or short wavelengths such as KrF (248nm) and ArF (193nm) used in semiconductor lithography processes.

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2022-160364 Summary of the Invention

[0008] (a) Technical problems to be solved Currently, the protective film, a component of the large protective parts used in the photolithography process of flat panel displays, can adequately ensure transmittance under broadband exposure light sources, but its area is, for example, as large as 1000 cm². 2 Therefore, the manufacturing method is limited during mass production. However, for photolithography under the aforementioned monochromatic light source, the inventors of this invention have for the first time discovered that the film surface has fine protrusions that affect the transmission of the exposure light.

[0009] Furthermore, in the case of broadband exposure covering the wavelength range from the i-line to the g-line, even assuming the presence of the aforementioned micro-protrusions on the surface of the protective film of the large protective component, which would cause the exposure light of a specific wavelength to be reflected and weakened, exposure can still be performed smoothly due to the presence of a large number of other wavelengths of exposure light. Moreover, in the case of broadband exposure covering the wavelength range from the i-line to the g-line, even if the film thickness distribution of the protective film of the large protective component is uneven, exposure can still be performed smoothly for the same reasons mentioned above.

[0010] However, when using monochromatic light for photolithography, these protrusions can unexpectedly cause reflection of the exposed light, alter the optical path, and potentially lead to adverse effects. In fact, for protective films used in semiconductor protective components under monochromatic exposure environments, high in-plane uniformity in film thickness distribution and transmittance is required. Regarding the protruding portions of the protective films (especially large protective films), which pose a technical problem in this invention, the thickness of the protective film varies locally, and the transmittance of monochromatic exposure light also changes due to the thickness variation. Therefore, problems such as abnormal exposure light levels at these locations may occur.

[0011] The present invention aims to provide a protective film and a protective element that can suppress uneven film thickness caused by local surface protrusions even in a photolithography process under a monochromatic exposure light source, thereby enabling exposure light to pass through more uniformly than before, and a method for manufacturing the protective film and the protective element.

[0012] (II) Technical Solution To achieve the above objectives, the present invention provides a protective film, characterized in that, On the surface of the protective film, the number of protrusions formed from the same composition as the protective film, satisfying one or more of the following conditions (A) to (B), is 5 per m. 2 the following, Condition (A): The diameter of the circumscribed circle is 5mm or more; Condition (B): Height is 2.5 μm or more.

[0013] According to the protective film of the present invention, the formation of such large-sized micro-protrusions on the surface of the protective film can be suppressed, and a smooth protective film with less uneven film thickness caused by such protrusions can be produced. Therefore, exposure light can be transmitted uniformly. In particular, a protective film that can also withstand high-precision photolithography under monochromatic light sources such as ArF, KrF and i-line single exposure can be produced.

[0014] In addition, the "protrusions formed by the same composition as the protective film" here refers to surface bulges formed by the protective film itself, and not protrusions formed by foreign matter attached to the surface of the protective film.

[0015] At this point, it can be set that the number of protrusions satisfying both conditions (A) and (B) is 3 per m. 2 the following.

[0016] Furthermore, it can be set that the number of protrusions satisfying condition (A) but not condition (B) is 1 per m. 2 the following.

[0017] Furthermore, it can be set that the number of protrusions satisfying condition (B) but not condition (A) is 1 per m. 2 the following.

[0018] If the protective film is as described above, it becomes even more superior in suppressing film thickness unevenness and in-plane uniformity of the transmittance of exposed light (especially monochromatic exposure light).

[0019] Furthermore, the protective film can be configured to have an area of ​​1000 cm². 2 The above are large protective films.

[0020] If it is the protective film described above, it is particularly suitable for use in the manufacture of flat panel displays.

[0021] In addition, the thickness of the protective film can be set to 2~10μm.

[0022] If the film thickness is 2 μm or more, the physical strength is sufficient, which can more effectively prevent problems such as film rupture when removing foreign matter attached to the surface by blowing air. In addition, if the film thickness is less than 10 μm, the amount of film deflection caused by the film's own weight can be suppressed, and the price increase can be suppressed, which is advantageous in terms of cost.

[0023] Furthermore, the thickness deviation of the protective film within any 1.5mm × 1.5mm local area can be set to less than 20nm.

[0024] If the protective film is as described above, it can effectively suppress uneven film thickness (film thickness deviation).

[0025] Furthermore, the present invention provides a protective member having a protective frame, an adhesive layer disposed on the surface of the protective frame, and a protective film tightly disposed on the surface of the protective frame through the adhesive layer, wherein the protective film is the protective film described above in the present invention.

[0026] According to the above-described protective component of the present invention, the protective film surface has fewer micro-protrusions, and the film thickness unevenness caused by these protrusions is suppressed. Even monochromatic exposure light can pass through the surface with high uniformity, making it an excellent protective component.

[0027] Furthermore, the present invention provides a method for manufacturing a protective film, which involves forming a coating of a polymer solution serving as a protective film material on a substrate, drying the coating, and then peeling the dried coating off the substrate to manufacture the protective film. The method is characterized in that... Before forming the coating film of the polymer solution, the polymer solution is subjected to any one or more of the following treatments (i) to (iii) as a pretreatment: (i) Removal treatment by adsorption of dissolved substances in the adsorbent; (ii) Remove the dissolved substances by evaporation under heating; (iii) Separation and removal of dissolved substances using inactive gas flow.

[0028] According to the above-described method for manufacturing a protective film based on the present invention, an excellent protective film with fewer micro-protrusions on its surface, where uneven film thickness caused by these protrusions is suppressed, and where even monochromatic exposure light can pass through the surface with high uniformity, can be manufactured.

[0029] At this point, as the preprocessing, at least the processes (ii) and (iii) can be performed.

[0030] In this way, a protective film with superior performance in suppressing film thickness unevenness and in-plane uniformity of transmittance of exposed light (especially monochromatic exposure light) can be obtained.

[0031] Furthermore, the protective film can be manufactured with an area of ​​1000 cm². 2 The above are large protective films.

[0032] This allows for the provision of protective films that are particularly suitable for the manufacture of flat panel displays.

[0033] Furthermore, the protective film can be manufactured with a thickness of 2 to 10 μm.

[0034] If the film thickness is set to 2 μm or more as described above, the physical strength is sufficient, and problems such as film rupture when removing foreign matter attached to the surface by blowing air can be more effectively prevented. In addition, if the film thickness is set to 10 μm or less, the amount of film deflection caused by the film's own weight can be suppressed, and the price increase can be suppressed, thus being advantageous in terms of cost.

[0035] Furthermore, the present invention provides a method for manufacturing a protective component, which is a method for manufacturing a protective component having a protective frame, an adhesive layer disposed on the surface of the protective frame, and a protective film tightly disposed on the surface of the protective frame through the adhesive layer. The method is characterized in that the protective film is a protective film manufactured by the above-described method for manufacturing a protective film according to the present invention.

[0036] According to the above-described method for manufacturing a protective component based on the present invention, an excellent protective component can be manufactured with fewer micro-protrusions on the surface of the protective film, thereby suppressing film thickness unevenness caused by the protrusions, and allowing monochromatic exposure light to pass through the surface with high uniformity.

[0037] (III) Beneficial Effects If the protective film and protective component, and the method for manufacturing the protective film and protective component of the present invention are described, a protective film with excellent smoothness that can suppress the formation of micro-protrusions on the surface of the protective film and has less uneven film thickness can be provided. Furthermore, a protective component capable of withstanding high-precision photolithography under monochromatic light sources such as ArF, KrF, and i-rays under single exposure can also be provided. Attached Figure Description

[0038] Figure 1 An illustrative diagram showing an example of the protective element (including the protective film of the present invention).

[0039] Figure 2 An observation diagram showing an example of an eye-view image of a protrusion illuminated by monochromatic detection light.

[0040] Figure 3 An analytical diagram illustrating an example of protrusion height analysis results obtained using a laser microscope.

[0041] Figure 4 A flowchart illustrating an example of the steps in the manufacturing method of the protective film of the present invention.

[0042] Figure 5 Microscopic observation of the fine protrusions on the surface of the protective film in Comparative Example 1.

[0043] Figure 6 An analytical diagram showing the height analysis results of the micro-protrusions on the surface of the protective film in Comparative Example 1, obtained using a laser microscope.

[0044] Figure 7An explanatory diagram showing the location of film thickness measurement around the micro-protrusions on the surface of the protective film. Detailed Implementation

[0045] Hereinafter, with reference to the accompanying drawings, an example of an embodiment of the present invention will be described in detail, but the present invention is not limited thereto.

[0046] As mentioned above, protective films sometimes have micro-protrusions on their surface. While this is not a problem in broadband exposure, in photolithography processes under monochromatic exposure light sources, the localized changes in the thickness of the protective film caused by these protrusions can alter the transmittance of the monochromatic exposure light, sometimes resulting in abnormal exposure light levels near the protrusions.

[0047] In response, the inventors of this invention, after in-depth research, discovered that if the number of protrusions on the surface of the protective film meets one or more of the following conditions (A) to (B) [Condition (A): the diameter of the circumscribed circle is 5 mm or more, Condition (B): the height is 2.5 μm or more] and is formed from the same composition as the protective film, the number of protrusions is 5 per m. 2 The protective film described below has fewer surface protrusions, resulting in less uneven film thickness and thus excellent smoothness. Even under a single exposure (especially a monochromatic light source such as ArF, KrF, and i-line), the exposure light can be transmitted uniformly, and it can also handle high-precision lithography, thereby completing the present invention.

[0048] Furthermore, it has been found that the above-mentioned excellent protective film can be provided by the following manufacturing method, thereby completing the present invention. The manufacturing method is to form a coating of a polymer solution as a protective film material on a substrate, and to peel off the dried coating from the substrate to manufacture a protective film. In this method, before forming the coating of the polymer solution, the polymer solution is subjected to one or more of the following pretreatments: (i) adsorption removal treatment using an adsorbent, (ii) evaporation removal treatment using heated solutes, and (iii) separation removal treatment using inactive gas flow.

[0049] Figure 1 An example of the protective element of the present invention (including the protective film of the present invention) is shown, and the original exposure is also illustrated. Figure 1 The entire image is an original exposure with protective components.

[0050] First, the overall structure will be described. A film-side adhesive layer 2 is provided on the upper surface (upper end surface) of the protective frame (hereinafter sometimes simply referred to as the frame) 1, and a mask-side adhesive layer 3 is provided on the lower surface (lower end surface). Furthermore, the protective film 4 of the present invention is tautly provided on the protective frame 1 through the film-side adhesive layer 2, thereby constituting the protective member 5 of the present invention.

[0051] also, Figure 1 In this process, the aforementioned protective component 5 is installed on the exposure master (photomask, mask plate) 6 through the mask-side adhesive layer 3 of the protective frame 1, thereby forming an exposure master 7 with protective components.

[0052] The following is a detailed explanation of each part.

[0053] Frame 1 can be frame-shaped, and its shape corresponds to the shape of the photomask on which the protective component 5 is installed. Generally, it is a quadrilateral (rectangular or square) frame.

[0054] In addition, as described above, the frame 1 has a surface for setting the protective film 4 (the upper surface here) and a surface facing the photomask when installing the photomask (the lower surface here).

[0055] There are no special restrictions on the material of frame 1. It can be the same material as before, such as aluminum, stainless steel, polyethylene, titanium or titanium alloy.

[0056] In addition, clamping holes (not shown) are usually provided on the side of the frame 1 for use during operation or when peeling off the photomask protector 5.

[0057] Furthermore, a vent 8 is provided on the frame 1 to alleviate pressure changes inside and outside the protective component 5. The shape and number of vent 8 are not limited. A notch may also be provided on the upper or lower end face of the frame 1 as a vent.

[0058] A filter 9 can be installed on the vent 8 to prevent foreign objects from entering the protective component 5. There are no restrictions on the location of the filter 9; it can be installed on the inside of the frame 1, inside the vent 8, or on the outside of the frame 1. Figure 1 It is positioned on the outside of frame 1.

[0059] Furthermore, there are no restrictions on the materials of the film-side adhesive layer 2 and the mask-side adhesive layer 3; known adhesive materials such as adhesives made of silicone resin or acrylic resin can be used. To strongly maintain the protective film 4, an adhesive with strong adhesion is preferred.

[0060] Furthermore, the protective film 4 satisfies one or more of the following conditions (A) to (B) on its surface, and the number of protrusions (surface ridges of the protective film itself) formed by the same composition as the protective film is 5 per m. 2 The following (0 / m)2 above).

[0061] Condition (A): The diameter of the circumscribed circle is 5mm or more; Condition (B): Height is 2.5 μm or more.

[0062] Thus, for the protective film 4 of the protective member 5 of the present invention, the number of such large protrusions formed on the surface is sufficiently suppressed, resulting in less uneven film thickness. Therefore, the surface smoothness is excellent. Consequently, during the photolithography process, exposure light can be uniformly transmitted throughout the entire surface of the protective film. Even when using monochromatic exposure light (especially short-wavelength monochromatic light such as ArF, KrF, and i-rays), the protective film of the present invention still achieves uniform in-plane transmittance, making it an extremely superior protective film.

[0063] However, existing products have a large number of surface protrusions, resulting in many areas of uneven film thickness, making it difficult to achieve the above-mentioned effects of the present invention.

[0064] Furthermore, the upper limit of the circumscribed circle diameter in condition (A) and the height in condition (B) cannot be limited. This is because the present invention aims to improve the transmittance of exposed light, and the larger the aforementioned dimensions are, the more likely they are to have an adverse effect on the transmittance of exposed light.

[0065] Furthermore, at this point, it can be set that the number of protrusions satisfying conditions (A) to (B) is 3 per m. 2 The following (0 / m) 2 (Above). Furthermore, it can be set that the number of protrusions satisfying condition (A) but not condition (B) is 1 per m. 2 The following (0 / m) 2 (Above). Furthermore, it can be set that the number of protrusions satisfying condition (B) but not condition (A) is 1 per m. 2 The following (0 / m) 2 above).

[0066] If the protective film is as described above, it is superior in suppressing uneven film thickness and in-plane uniformity of the transmittance of exposed light, and is therefore preferred.

[0067] At this point, as the protective film 4, it is preferable that the film thickness deviation in any local area of ​​1.5mm × 1.5mm is less than 20nm (more than 0nm). If the film thickness deviation is within this range, it can be considered that it has been sufficiently suppressed, and the in-plane uniformity of transmittance is better.

[0068] In addition, the protective film 4 can be set to have an area of ​​1000 cm². 2 The above refers to large-area protective films. Such large-area protective films are particularly suitable for the manufacture of flat panel displays.

[0069] Furthermore, in this invention, which is able to achieve in-plane uniformity of the transmittance of the exposed light, it can be said that the larger the area of ​​the protective film 4, the better, so its upper limit cannot be limited.

[0070] The material used for the protective film 4 in this invention includes, for example, amorphous fluoropolymers such as CYTOP manufactured by AGC, Teflon AF (registered trademark) manufactured by DuPont, and Algoflon AD manufactured by Solvay. Alternatively, the protective film 4 may be a single-layer film using these fluoropolymers, or a multilayer film formed by coating these fluoropolymers onto other transparent resin films such as nitrocellulose or cellulose acetate as an anti-reflective film.

[0071] The thickness of the protective film 4 (especially large protective films) is preferably 2 to 10 μm. By setting the thickness to 2 μm or more, the physical strength can be increased, and the tendency for problems such as film rupture when removing foreign objects by blowing air can be more effectively suppressed. On the other hand, by setting the thickness to 10 μm or less, the increase in film deflection due to the film's own weight can be more reliably suppressed, and the price increase can be prevented.

[0072] Furthermore, since the protective member 5 of the present invention is equipped with the aforementioned protective film 4, the uneven film thickness caused by the surface protrusions of the protective film 4 is suppressed, and it can pass through the surface with high uniformity even under monochromatic exposure light.

[0073] [Observation and measurement of film thickness unevenness, protrusions, and film thickness] Here, the observation and measurement of the uneven film thickness, surface protrusions, and film thickness of the aforementioned protective film are explained.

[0074] The appearance of the protective film can be confirmed by visual inspection under monochromatic detection light. If uneven film thickness exists on the film surface, the degree of this unevenness can be observed by the difference in interference with the surrounding detection light. For example, when using the D-line of a low-pressure sodium lamp as the detection light, the uneven film thickness caused by local surface protrusions in this invention can be fully observed.

[0075] In addition, the diffused / reflected light from a high-brightness spotlight can be used to detect foreign objects on the protective film. Light sources such as halogen lamps or light-emitting diodes (LEDs) can be used for white light. When a foreign object is attached to the film surface, the light emitted from the light source will be scattered or reflected at the foreign object and thus observed.

[0076] However, as mentioned above, the local surface protrusions in this invention are not formed by foreign matter, and there is almost no difference in transmittance to white light around them, so they cannot be observed in detection under white light.

[0077] Generally speaking, regarding the formed local surface protrusions (surface bulges of the membrane itself), the diameter of the circumscribed circle surrounding the protrusion, although varying depending on the membrane material and its dissolved substances, is mostly approximately 100 μm or more. Furthermore, the height of the protrusion, measured from the flat portion surrounding it, is mostly approximately 0.4 μm or more.

[0078] In cases where the circumscribed circle diameter is 5 mm or more, or the height is 2.5 μm or more, the larger dimensions can easily affect film thickness uniformity and even the in-plane uniformity of light transmittance. As described above, the protective film of the present invention reduces the aforementioned large dimensions, thus achieving excellent in-plane uniformity of transmittance.

[0079] Regarding the measurement of the size of local surface protrusions, the circumscribed circle diameter can be observed under monochromatic detection light and is easily measured. Furthermore, more detailed information, including height, can be measured using methods such as laser microscopy or atomic force microscopy (AFM).

[0080] For example, Figure 2 This is an example of a visual image of a protrusion under monochromatic detection light (low-pressure sodium lamp). It is easily observable. Figure 2 The difference between the protrusion at approximately the center and the surrounding flat area allows for easy measurement of the protrusion's circumscribed circle diameter (width indicated by the arrow).

[0081] also, Figure 3 This is an example of the height analysis results of a protrusion obtained using a laser microscope. The top image is a top view of the protrusion, and the bottom image shows the maximum height difference (protrusion height) between the peak (position A) and the flat area around the protrusion (position B) in the height direction. Additionally, the bottom image shows the height variation at the line segment connecting A and B.

[0082] Furthermore, the thickness of the protective film can be measured using a transmittance meter to determine the optical film thickness and transmittance at any location.

[0083] Regarding the effect of film thickness on the transmitted light intensity I of a certain wavelength of light T The resulting effect can be calculated using the Airy formula (Equation 1). The constant F in Equation 1 is defined by the reflectivity R obtained from the Fresnel formula (Equation 2). The phase difference of multiple reflections of the thin film... Equation 3 can be used to determine the angle of refraction from the film thickness and the angle of refraction between the media. Furthermore, the relationship between the angle of refraction and the angle of incidence follows Snell's law (Equation 4).

[0084] Multiple reflection phase difference (rad) R: Membrane reflectance (-) n1: Refractive index of the incident medium (-) n2: Refractive index through the medium (-) d: film thickness (m), λ: incident light wavelength (m) θ2: Angle of refraction; n1: Refractive index of the incident medium (-) n1: Refractive index of the incident medium (-), θ1: Angle of incidence n2: Refractive index of the medium (-), θ2: Angle of refraction Next, the method for manufacturing the protective film of the present invention will be described. Figure 4 A flowchart illustrating an example of the steps in the manufacturing method of the present invention.

[0085] The protective film of the present invention is manufactured through the following steps: a step of dissolving the polymer of the protective film material in a solvent to prepare a polymer solution; a step of pretreating the polymer solution; a step of uniformly coating the pretreated polymer solution onto a film-forming substrate (hereinafter also referred to as the substrate) (forming a coating film); and a step of heating and drying the substrate coated with the polymer solution, and then peeling the dried coating film off the substrate.

[0086] In addition, the above preprocessing is any one or more of the following (i) to (iii): (i) Removal treatment by adsorption of dissolved substances in the adsorbent; (ii) Remove the dissolved substances by evaporation under heating; (iii) Separation and removal of dissolved substances using inactive gas flow.

[0087] <Coating Solution Preparation Process> First, the preparation process of the coating solution (polymer solution) will be explained. The protective film material polymer is dissolved in a solvent before use. Since the protective film requires foreign matter adhesion management due to its product properties, it is preferable to use a depth filter or membrane filter to pre-filter the coating solution to remove foreign matter.

[0088] <Pretreatment Process> Furthermore, dissolved substances exist in the solvent during the preparation of the coating solution. For example, when using non-aqueous solvents, dissolved water vapor from the storage and usage environment of the polymer solution may sometimes be present in the polymer solution. If this is not removed, condensation will occur locally on the wet film after coating, which, due to the affinity between the solvent and water, will cause the wet film to be repelled by water in subsequent processes.

[0089] On the other hand, as other solvents, solids formed by heating and drying polymer solutions can also be considered. However, in this case, foreign matter will remain on the membrane as heterogeneous components, which are different substances from the above-mentioned protrusions and are not the substances targeted by this invention.

[0090] The condensate evaporates during the subsequent heating and drying process and usually does not remain on the protective film. However, because the film surface is dried in a localized state where the polymer solution is repelled by water, the aforementioned fine protrusions sometimes form on the heated and dried film surface. These protrusions can cause localized uneven film thickness within the protective film surface.

[0091] The degree of film thickness unevenness, i.e. the size of the protrusions formed due to repulsion, depends on the amount of dissolved substances in the polymer solution, the coating method, and the drying method after coating. However, as a method to reduce the dissolved substances in the polymer solution before coating, the inventors of this invention have studied the pretreatment of the polymer solution before coating and successfully obtained a protective film (especially a large protective film) without local film thickness unevenness.

[0092] To suppress the surface protrusions of the coating film induced by the repulsion of the polymer solution, the following pretreatments can be specifically listed as pretreatments for coating.

[0093] (i) Treatment by adsorption of dissolved substances in the adsorbent By adding an adsorbent to a polymer solution, dissolved substances can be adsorbed and removed. Examples of suitable adsorbents include molecular sieves and silica gel, and the adsorbent can be selected appropriately based on the type of polymer and solvent.

[0094] Specific methods include: the settling method, which involves adding the adsorbent to an appropriate amount of polymer solution and repeatedly stirring and allowing it to stand; and the column method, which involves filling the adsorbent into a column and allowing the polymer solution to flow at a certain flow rate.

[0095] When using adsorbents to remove dissolved substances, adsorption occurs at the interface between the liquid and the adsorbent, making it effective for polymer solutions with low viscosity.

[0096] (ii) Removal of dissolved substances by evaporation under heating Generally, the solubility of dissolved gases in liquids decreases with increasing temperature; therefore, heating the polymer solution can also remove dissolved substances. Furthermore, solution viscosity tends to decrease with heating; therefore, adding the adsorbent to the heated solution promotes interfacial contact between the adsorbent and the polymer liquid, leading to more efficient removal of dissolved substances. This pretreatment with heating is effective, at least for polymer solutions with high viscosity. Regarding the heating temperature, it is preferable to consider a range where the solvent boiling point and other parameters do not significantly change the concentration of the polymer solution.

[0097] (iii) Separation and removal of dissolved substances using inactive gas flow In addition to the methods of removing dissolved substances using adsorbents and heating, the flow of inert gases can also be used to separate and remove dissolved substances. When the solubility of the dissolved substance in the inert gas is greater than its solubility in the solvent in the polymer solution, bubbling can remove the dissolved substance as part of the inert gas and remove it from the system. Furthermore, in the case of gaseous dissolved substances, due to diffusion and partial pressure, there is a tendency for them to mix with the flowing gas; therefore, a good removal effect of the dissolved gas can be expected.

[0098] Furthermore, it is preferable to implement the treatments in (ii) and (iii). By implementing at least these treatments, the number of protrusions generated can be suppressed more effectively, and the suppression of film thickness unevenness and the in-plane uniformity of exposure light transmittance can be achieved more reliably.

[0099] <Coating Process> Next, using methods such as slot coating or spin coating, the polymer solution, after undergoing the preparation and pretreatment of the coating liquid, is coated onto a substrate (such as a quartz glass substrate) to form a coating film (coating liquid film). There are no particular limitations on the type of coating machine, but a type with high uniformity of coating liquid film thickness is preferred.

[0100] <Heating, drying, and peeling processes> Next, the coating liquid film is first dried in a cleanroom environment to allow a certain degree of solvent evaporation. During this process, the film thickness may be uneven due to the downward airflow within the cleanroom and the levelness of the drying position. Therefore, drying is performed under ideally horizontal and appropriate airflow conditions. Afterward, it is heated and dried at an appropriate temperature to obtain a protective film as a solid polymer film.

[0101] Using a known method, the protective film, which is a solid film, obtained in the above manner, is peeled off from the substrate to obtain a protective film that is a self-supporting film.

[0102] The protective film 4 of the present invention can be manufactured in the manner described above.

[0103] Then, the aforementioned protective film 4 is tautly attached to the upper surface of a separately prepared protective frame 1 (upper end face: film-side adhesive layer 2, lower end face: mask-side adhesive layer 3) through the film-side adhesive layer 2, thereby manufacturing... Figure 1 The protective component 5 of the present invention is shown.

[0104] Furthermore, the protective element 5 is installed on the exposure original 6 through the mask-side adhesive layer 3, thereby obtaining the exposure original 7 with the protective element.

[0105] Example The following examples illustrate the invention in more detail, but the invention is not limited thereto.

[0106] (Examples 1-7, Comparative Example 1) Prepare a rectangular piece of synthetic quartz glass measuring 850mm x 1200mm and 10mm thick (approximately 10000cm). 2 The surface is cleaned by dry cleaning, and the quartz glass is used as the film-forming substrate.

[0107] In addition, a polymer solution is prepared by dissolving CYTOP (CTX-809SP2, manufactured by AGC) in perfluorotributylamine (FC-43, manufactured by 3M).

[0108] For the polymer solution, one or more of the treatments (i) to (iii) in Examples 1 to 7 were performed as pretreatments as shown in Table 1.

[0109] On the other hand, none of the preprocessing steps (i) to (iii) were performed in Comparative Example 1.

[0110] [Table 1] The processing details in Table 1 are explained in detail.

[0111] In the pretreatment (i), molecular sieve 13X (manufactured by KANTO CHEMICAL CO.,INC.) was added as an adsorbent in an amount equivalent to 10% by weight of the polymer solution, and dissolved substances were removed by repeated stirring and settling for 6 hours at a frequency of 1 time / hour.

[0112] In pretreatment (ii), the polymer solution is heated at 100°C for 24 hours on a hot plate to remove dissolved gases.

[0113] In pretreatment (iii), nitrogen is used as an inactive gas and circulated in a tank with stirring blades at a flow rate of 0.5 L / min while the polymer solution is stirred for 24 hours, thereby purging the polymer solution of gases.

[0114] When multiple of the above pretreatments (i), (ii), and (iii) are performed simultaneously, the heating of pretreatment (ii) is performed first, followed by the addition of adsorbent to pretreatment (i), and finally the gas replacement of pretreatment (iii) using an inactive gas.

[0115] The polymer solutions of Examples 1-7, which underwent the pretreatments described in Table 1, and the polymer solution of Comparative Example 1, which did not undergo pretreatment, were pumped into a 0.2 μm diameter membrane filter for filtration. The filtered liquid was uniformly coated onto a film-forming substrate using a slot coating method to achieve a film thickness of 4 μm upon drying. The substrate was then air-dried for at least 2 hours, followed by far-infrared heating (180°C, 30 minutes). The protective film was then peeled off using a temporary frame. This yielded the protective films for Examples 1-7 and Comparative Example 1.

[0116] The protective film prepared above was visually inspected under the illumination of a low-pressure sodium lamp (Iwasaki Electric Co., Ltd., NX180) to observe for uneven film thickness. Regarding the results of this observation, localized areas of uneven film thickness were first identified in Comparative Example 1.

[0117] Furthermore, the areas identified in Comparative Example 1 were observed using a laser microscope (Olympus LEXTOLS 4100). The results showed that under 405nm laser irradiation, as... Figure 5 The protrusions observed (surface bulges of the membrane itself) are shown. Figure 5 (The figure is in the very center). At this point, the diameter of the circumscribed circle of the protrusion is approximately 5 mm, which is the same as the visual observation result under the sodium lamp mentioned above.

[0118] Furthermore, the protrusion was not observed at all under white LED illumination in the same field of view under the microscope. Figure 5 (See the left-hand image). This situation is consistent with the observation of scattered / reflected light from high-brightness spotlights under fluorescent lights and in dark rooms.

[0119] In addition, for links Figure 5 The line segments of the two regions shown in the right figure (near the protruding peak and the flat area) are analyzed in the height direction, and the analysis results are shown below. Figure 6 .like Figure 6 As shown, the film has uneven thickness with protrusions, and the maximum height difference of the protrusions is about 2.5 μm.

[0120] The film thickness around the observed protrusions was investigated. A transmittance meter (Spectra Coop, Handy Lambda II Thickness) was used for the measurements. Figure 7 This diagram illustrates the location of film thickness measurements around the micro-protrusions on the surface of the protective film. (See diagram for reference.) Figure 7 As shown, taking the area near the protruding peak as the center, the film thickness was measured at four points in the horizontal direction (in-plane transverse) at 0.5 mm intervals, and at four points in the vertical direction (in-plane longitudinal) at 0.5 mm intervals. Figure 7 (M1~M8 in the diagram). That is, the measurement range is a square with two diagonals each 1.5 mm in length, also referred to here as a local area (measurement range) of "1.5 mm × 1.5 mm". The same measurement is also performed on the normal part (flat part where no protrusions are observed) within the same membrane surface.

[0121] Based on the film thickness measurements obtained above, the transmittance at a single wavelength (365nm) of the i-line was calculated using the Airy formula (Equation 1). The results are summarized in Table 2.

[0122] [Table 2] As can be clearly seen from Table 2, for this protruding part, there is a local film thickness unevenness of 0.02μm within a measurement range of 1.5mm×1.5mm. As a result, when irradiated with i-line monochromatic light, the thickness is reduced by about 3.62% in a dotted manner compared to the normal part.

[0123] In fact, in the semiconductor lithography process of monochromatic exposure, the transmittance of the protective film is required to be, for example, above 99%. Therefore, a decrease in this level of transmittance will become a problem in the case of more miniaturized lithography processes that use large protective components (i.e., monochromatic exposure with shorter wavelengths).

[0124] The film-forming process of Examples 1-7 and Comparative Example 1 was repeated 10 times each, yielding 10 protective films in each case. Next, for each example, based on the total number of uneven film thicknesses caused by localized surface protrusions confirmed in the aforementioned appearance inspection of the protective film, the number of films per 1m was counted. 2 The number of cells generated in the membrane area is shown in Table 3.

[0125] In addition, the area of ​​each membrane is 1.037m². 2 (Large protective film).

[0126] In addition, the protrusions counted in Table 3 meet one or more of the following conditions (A) to (B): Condition (A): The circumscribed circle diameter (also known as the circumscribed circle diameter) is 5 mm or more; Condition (B): Height is 2.5 μm or more.

[0127] [Table 3] According to Table 3, "Total number of protrusions" and "per 1m" 2 The number of protrusions clearly shows that, compared to Comparative Example 1, Examples 1-7 have suppressed the formation of local protrusions. Comparative Example 1 confirmed 6.5 protrusions / m². 2 The protrusions were observed, and in Examples 1-7, where the polymer solution was pretreated before coating, the number of protrusions was 5 per m. 2 The following (more specifically 4.1 per m) 2 (The following) High-quality large protective film.

[0128] That is, compared with the existing product such as Comparative Example 1, the products of the present invention in Examples 1 to 7 further suppress the number of such large protrusions, thereby reducing the generation of film thickness unevenness, and thus achieving excellent in-plane uniformity in terms of the transmission of exposed light (especially shorter wavelength monochromatic light).

[0129] Furthermore, by examining the classification of the observed protrusions, we can see that: For protrusions with a circumscribed circle diameter of 5 mm or more and a height of 2.5 μm or more (i.e., protrusions that satisfy both conditions (A) and (B)), in any embodiment, the number can be suppressed to 3 / m. 2 The following (more specifically 2.1 per m) 2 (The following), less than Comparative Example 1.

[0130] Furthermore, for protrusions with a circumscribed circle diameter of 5 mm or more and a height of less than 2.5 μm (i.e., protrusions that satisfy condition (A) but not condition (B), in any embodiment, the number can be suppressed to 1 per m. 2 The following (more specifically 0.8 per m) 2 (The following), less than Comparative Example 1.

[0131] Furthermore, for protrusions with a height of 2.5 μm or more and a circumscribed circle diameter of less than 5 mm (i.e., protrusions that satisfy condition (B) but not condition (A)), especially in Examples 6 and 7, the number of protrusions can be suppressed to less than 1 per m. 2 (More specifically 0.7 per m) 2 (The following), less than Comparative Example 1.

[0132] As shown in Table 3, by performing the treatments (ii) and (iii) as in Example 6, a better protective film than that in Examples 1-5 can be obtained.

[0133] Furthermore, as shown in Example 7, by performing more appropriate pretreatment on the polymer solution before coating (all treatments in (i) to (iii)), the generation of this local protrusion (and the film thickness unevenness caused by this protrusion) can be completely suppressed. Therefore, the in-plane uniformity of the transmittance of the exposed light is excellent.

[0134] This manual includes the following solutions: [1] A protective film, wherein, On the surface of the protective film, the number of protrusions formed from the same composition as the protective film, satisfying one or more of the following conditions (A) to (B), is 5 per m. 2 the following, Condition (A): The diameter of the circumscribed circle is 5mm or more; Condition (B): Height is 2.5 μm or more.

[0135] [2] According to the protective film described in [1] above, the number of protrusions satisfying both conditions (A) and (B) is 3 per m. 2 the following.

[0136] [3] According to the protective film described in [1] above, the number of protrusions that satisfy condition (A) but do not satisfy condition (B) is 1 per m. 2 the following.

[0137] [4] According to the protective film described in [1] above, the number of protrusions that satisfy condition (B) but do not satisfy condition (A) is 1 per m. 2 the following.

[0138] [5] The protective film according to any one of [1] to [4] above, wherein the protective film has an area of ​​1000 cm². 2 The above are large protective films.

[0139] [6] The protective film according to any one of [1] to [5] above, wherein the thickness of the protective film is 2 to 10 μm.

[0140] [7] The protective film according to any one of [1] to [6] above, wherein the film thickness deviation in any 1.5mm × 1.5mm local area of ​​the protective film is less than 20nm.

[0141] [8] A protective component comprising a protective frame, an adhesive layer disposed on the surface of the protective frame, and a protective film tautly disposed on the surface of the protective frame through the adhesive layer, wherein, The protective film is any one of the protective films described in [1] to [7] above.

[0142] [9] A method for manufacturing a protective film, comprising forming a coating of a polymer solution as a protective film material on a substrate, drying the coating, and then peeling the dried coating off the substrate to manufacture a protective film, wherein... Before forming the coating film of the polymer solution, the polymer solution is subjected to any one or more of the following treatments (i) to (iii) as a pretreatment: (i) Removal treatment by adsorption of dissolved substances in the adsorbent; (ii) Remove the dissolved substances by evaporation under heating; (iii) Separation and removal of dissolved substances using inactive gas flow.

[0143]

[10] According to the method for manufacturing the protective film described above [9], at least the treatments (ii) and (iii) are performed as the pretreatment.

[0144]

[11] According to the method for manufacturing the protective film described in [9] or

[10] above, wherein the protective film has a manufacturing area of ​​1000 cm². 2 The above are large protective films.

[0145]

[12] The method for manufacturing a protective film according to any one of [9] to

[11] above, wherein the protective film is manufactured with a thickness of 2 to 10 μm.

[0146]

[13] A method for manufacturing a protective component, comprising a protective frame, an adhesive layer disposed on the surface of the protective frame, and a protective film tightly disposed on the surface of the protective frame through the adhesive layer, wherein, The protective film is a protective film manufactured by the method described in any one of [9] to

[12] above.

[0147] Furthermore, this invention is not limited to the above-described embodiments. The above embodiments are merely examples, and any technical solution having a substantially identical structure and achieving the same technical effect as the technical concept described in the claims of this invention is covered within the technical scope of this invention.

Claims

1. A protective film, characterized in that, On the surface of the protective film, the number of protrusions formed from the same composition as the protective film, satisfying one or more of the following conditions (A) to (B), is 5 per m. 2 the following, Condition (A): The diameter of the circumscribed circle is 5 mm or more; Condition (B): Height is 2.5 μm or more.

2. The protective film according to claim 1, characterized in that, The number of protrusions satisfying both conditions (A) and (B) is 3 per m. 2 the following.

3. The protective film according to claim 1, characterized in that, The number of protrusions that satisfy condition (A) but not condition (B) is 1 per m. 2 the following.

4. The protective film according to claim 1, characterized in that, The number of protrusions that satisfy condition (B) but not condition (A) is 1 per m. 2 the following.

5. The protective film according to claim 1, characterized in that, The protective film has an area of ​​1000 cm². 2 The above are large protective films.

6. The protective film according to claim 1, characterized in that, The thickness of the protective film is 2~10μm.

7. The protective film according to claim 1, characterized in that, The thickness deviation of the protective film within any 1.5mm × 1.5mm local area is less than 20nm.

8. A protective member comprising a protective frame, an adhesive layer disposed on the surface of the protective frame, and a protective film tautly disposed on the surface of the protective frame through the adhesive layer, characterized in that, The protective film is the protective film according to any one of claims 1 to 7.

9. A method for manufacturing a protective film, comprising forming a coating of a polymer solution serving as a protective film material on a substrate, drying the coating, and then peeling the dried coating off the substrate to manufacture the protective film, characterized in that... Before forming the coating film of the polymer solution, the polymer solution is subjected to any one or more of the following treatments (i) to (iii) as a pretreatment: (i) Removal treatment by adsorption of dissolved substances in the adsorbent; (ii) Remove the dissolved substances by evaporation under heating; (iii) Separation and removal of dissolved substances using inactive gas flow.

10. The method for manufacturing the protective film according to claim 9, characterized in that, As part of the preprocessing, at least the processes (ii) and (iii) are performed.

11. The method for manufacturing the protective film according to claim 9, characterized in that, The protective film has a manufacturing area of ​​1000 cm². 2 The above are large protective films.

12. The method for manufacturing the protective film according to claim 9, characterized in that, As the protective film, a protective film with a thickness of 2~10μm is manufactured.

13. A method for manufacturing a protective component, comprising a protective frame, an adhesive layer disposed on the surface of the protective frame, and a protective film tautly disposed on the surface of the protective frame through the adhesive layer, characterized in that... The protective film is a protective film manufactured by the method for manufacturing a protective film according to any one of claims 9 to 12.

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