Pellicle membranes, pellicles, and methods for manufacturing the same.

Abstract

For example, even in lithography processes under a monochromatic exposure light source, the pellicle film is designed to suppress film thickness variations associated with localized surface protrusions, thereby enabling more uniform transmission of exposure light than conventional methods. [Solution] A pellicle film, wherein the surface of the pellicle film satisfies one or more of the following conditions: (A) - the diameter of the circumscribing circle is 5 mm or more, (B) - the height is 2.5 μm or more, and the number of protrusions made of the same composition as the pellicle film is 5 per square meter. 2 A pellicle membrane characterized by the following:

Description

[Technical Field]

[0001] The present invention relates to a pellicle film and pellicle used in the lithography process when manufacturing semiconductor devices, printed circuit boards, or flat panel displays, as well as to a method for manufacturing the same. [Background technology]

[0002] In the manufacturing of semiconductors such as LSIs or flat panel displays, patterns are created by irradiating semiconductor wafers or flat panel display base glass with light (Patent Document 1). If foreign matter adheres to the surface of the photomask or reticle (hereinafter simply referred to as the photomask) used at this time, this foreign matter will absorb or scatter the light. As a result, problems such as distortion of the transferred pattern, blurred edges, and other defects in dimensions and quality have occurred.

[0003] Therefore, these operations are usually performed in a cleanroom, but even then, it is difficult to keep the photomask clean at all times. To address this, a pellicle is attached to the photomask surface for dust protection before exposure. In this case, foreign matter does not directly adhere to the photomask surface but adheres to the pellicle. Consequently, if the lens focus during lithography is aligned with the pattern surface on the photomask, the foreign matter on the pellicle is defocused and irrelevant to the transfer.

[0004] Generally, a pellicle is formed by attaching a transparent pellicle film made of nitrocellulose, cellulose acetate, or fluororesin, which has excellent light transmittance, to the upper surface of a pellicle frame made of aluminum, stainless steel, polyethylene, or the like. Furthermore, an adhesive layer made of silicone resin, acrylic resin, or the like for attaching to a photomask, and a release layer (separator) for protecting this adhesive layer are provided on the lower surface of the pellicle frame.

[0005] Traditionally, the light sources used in lithography processes, such as those in the manufacturing of flat panel displays, have been the g-line (436 nm) and i-line (365 nm) of high-pressure mercury lamps. In the manufacturing process of flat panel displays, compared to semiconductor manufacturing processes, the line width and pitch of the mask pattern are larger, eliminating the need for short-wavelength exposure light. Furthermore, because the exposure area is large and a large amount of exposure light is required, broadband exposure light with wavelengths ranging from i-line to g-line is used.

[0006] In the future, to further increase the resolution of flat panel displays or to accommodate new types of lithography, it will be necessary to support monochromatic light of the i-line mentioned above, as well as lithography using short wavelengths such as KrF (248nm) and ArF (193nm), which are used in semiconductor lithography processes. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-160364 [Overview of the project] [Problems that the invention aims to solve]

[0008] Currently, the pellicle film, a component of the large pellicle used in the lithography process for manufacturing flat panel displays, has sufficient transmittance under broadband exposure light sources, but its area is, for example, 1000 cm². 2 As described above, the film is large. For this reason, the manufacturing method for mass production is limited, and the inventors have now discovered for the first time that the film surface has minute protrusions that affect the transmission of the exposure light in lithography under the aforementioned monochromatic light source.

[0009] Incidentally, in the case of broadband exposure having a wavelength range from the i-line to the g-line, even if the aforementioned fine projections are present on the pellicle film surface of a large-sized pellicle used and exposure light of a specific wavelength is reflected or attenuated, exposure is performed without problem because a large amount of exposure light of other wavelengths exists. Further, in the case of broadband exposure having a wavelength range from the i-line to the g-line, even when there is unevenness in the film thickness distribution of the pellicle film of the large-sized pellicle used, exposure is performed without problem similarly to the above reason.

[0010] On the other hand, in lithography using monochromatic light, there is a high possibility that these projections exert adverse effects such as causing unintended reflection of exposure light or change of the optical path. In fact, the pellicle film of a semiconductor pellicle used in a monochromatic exposure environment requires high in-plane uniformity of film thickness distribution and transmittance. At the projection site of the pellicle film (particularly a large-sized pellicle film) which is the problem to be solved by the present invention, the pellicle film thickness locally changes, and the monochromatic exposure light transmittance also changes in accordance with the change in film thickness, which causes problems such as inducing an abnormality in the exposure light amount at the relevant site.

[0011] An object of the present invention is to provide a pellicle film, a pellicle, and production methods thereof, which can transmit exposure light more uniformly than before by suppressing film thickness unevenness associated with local surface projections, even in, for example, a lithography process under a monochromatic exposure light source. [MEANS FOR SOLVING THE PROBLEM]

[0012] To achieve the above object, the present invention is a pellicle film, wherein On the surface of the pellicle film, the number of projections composed of the same composition as the pellicle film that satisfy any one or more of the following conditions (A) to (B) is 5 or less per m 2 The pellicle film is provided. Condition (A): The diameter of a circumscribed circle is 5 mm or more Condition (B): The height is 2.5 μm or more

[0013] With such a pellicle film of the present invention, the generation of relatively large-sized fine protrusions as described above on the surface of the pellicle film is suppressed, and the pellicle film can be made excellent in smoothness with little film thickness unevenness caused by the protrusions. Therefore, it is possible to transmit exposure light uniformly. In particular, the pellicle film can be adapted to high-definition lithography under a monochromatic light source such as single exposure of ArF, KrF and i-line. The "protrusions formed from the same composition as the pellicle film" as referred to herein do not mean protrusions caused by foreign matter adhering to the surface of the pellicle film, but mean surface bulges formed on the pellicle film itself.

[0014] In this case, the number of the protrusions satisfying both of the above conditions (A) to (B) can be 3 pieces / m 2 or less. In addition, the number of the protrusions that satisfy the above condition (A) and do not satisfy the above condition (B) can be 1 piece / m 2 or less. Further, the number of the protrusions that satisfy the above condition (B) and do not satisfy the above condition (A) can be 1 piece / m 2 or less.

[0015] Such a pellicle film is even more excellent in terms of suppressing film thickness unevenness, and further in the in-plane uniformity of the transmittance of exposure light (particularly monochromatic exposure light).

[0016] In addition, the pellicle film can be a large-sized one with an area of 1000 cm 2 or more.

[0017] Such a pellicle film can be suitably used particularly in the manufacture of flat panel displays.

[0018] Further, the pellicle film may have a film thickness of 2 to 10 μm.

[0019] If the film thickness is 2 μm or more, the physical strength is more sufficient, and problems such as the film tearing when removing foreign matter adhering to the surface by air blowing can be more effectively prevented. Also, if the film thickness is 10 μm or less, the amount of film deflection due to the film's own weight can be suppressed, and the price can be kept down, making it cost-effective.

[0020] Furthermore, the pellicle film can have a film thickness variation of 20 nm or less within any localized area of ​​1.5 mm × 1.5 mm.

[0021] With this type of material, film thickness variations are sufficiently suppressed.

[0022] The present invention also relates to a pellicle comprising a pellicle frame, an adhesive layer provided on the surface of the pellicle frame, and a pellicle film stretched on the surface of the pellicle frame via the adhesive layer, The present invention provides a pellicle characterized in that the pellicle membrane is the pellicle membrane of the present invention described above.

[0023] With the pellicle of the present invention, there are fewer fine protrusions on the surface of the pellicle film, and thickness variations caused by these protrusions are suppressed, making it excellent in that even monochromatic exposure light can pass through with high uniformity within the plane.

[0024] The present invention also relates to a method for producing a pellicle film by forming a coating film of a polymer solution, which is the material for a pellicle film, on a substrate, drying the coating film, and then peeling the dried coating film off the substrate. The present invention provides a method for producing a pellicle film, characterized by subjecting the polymer solution to one or more of the following treatments (i) to (iii) as a pretreatment before forming a coated film of the polymer solution. (i) Adsorption and removal of dissolved substances using an adsorbent (ii) Treatment to remove dissolved substances by evaporation through heating (iii) Separation and removal of dissolved substances by flowing inert gas

[0025] With this method for manufacturing a pellicle film according to the present invention, there are fewer fine protrusions on the surface, and thickness variations caused by these protrusions are suppressed. This makes it possible to manufacture an excellent pellicle film that can pass even monochromatic exposure light with high uniformity across the surface.

[0026] In this case, at least the processes (ii) and (iii) can be performed as the pretreatment.

[0027] In this way, a pellicle film with even greater advantages can be obtained in terms of suppressing film thickness unevenness and, consequently, in-plane uniformity of the transmittance of exposure light (especially monochromatic exposure light).

[0028] Furthermore, the pellicle membrane has an area of ​​1000 cm². 2 We can manufacture items of this size.

[0029] In this way, we can provide a product that is particularly suitable for use in the manufacture of flat panel displays.

[0030] Furthermore, the pellicle film can be manufactured with a thickness of 2 to 10 μm.

[0031] By increasing the film thickness to 2 μm or more, the physical strength is more sufficient, and problems such as the film tearing when removing foreign matter adhering to the surface with air blowing can be more effectively prevented. On the other hand, by keeping the film thickness to 10 μm or less, the amount of film deflection due to the film's own weight can be suppressed, and the price can be kept down, making it cost-effective.

[0032] The present invention also relates to a method for manufacturing a pellicle, comprising a pellicle frame, an adhesive layer provided on the surface of the pellicle frame, and a pellicle film stretched on the surface of the pellicle frame via the adhesive layer, The present invention provides a method for manufacturing a pellicle, characterized in that the pellicle membrane used is one manufactured by the method for manufacturing a pellicle membrane according to the present invention.

[0033] With this pellicle manufacturing method of the present invention, there are fewer fine protrusions on the surface of the pellicle film, and thickness variations caused by these protrusions are suppressed. This makes it possible to manufacture an excellent pellicle that can pass even monochromatic exposure light with high uniformity across the surface. [Effects of the Invention]

[0034] The pellicle film and pellicle of the present invention, as well as the methods for manufacturing them, can suppress the generation of fine protrusions on the surface of the pellicle film and provide a pellicle film with excellent smoothness and minimal thickness unevenness. Consequently, it is possible to provide a pellicle that can support high-definition lithography under monochromatic light sources such as ArF, KrF, and i-line single exposure. [Brief explanation of the drawing]

[0035] [Figure 1] This is an explanatory diagram showing an example of the pellicle (including the pellicle membrane of the present invention) of the present invention. [Figure 2] This is an observation diagram showing an example of a visual image of a protrusion under monochromatic inspection light irradiation. [Figure 3] This is an analytical diagram showing an example of the results of height analysis of protrusions using a laser microscope. [Figure 4] This is a flowchart showing an example of the steps in the method for manufacturing the pellicle film of the present invention. [Figure 5] This is a microscopic view of the fine protrusions on the surface of the pellicle film in Comparative Example 1. [Figure 6] This is an analytical diagram showing the results of laser microscopy height analysis of the fine protrusions on the surface of the pellicle film in Comparative Example 1. [Figure 7] This is an explanatory diagram showing the measurement locations for film thickness around fine protrusions on the surface of the pellicle film. [Modes for carrying out the invention]

[0036] The present invention will be described in detail below with reference to the figures as an example of an embodiment, but the present invention is not limited to these. As mentioned above, the pellicle film sometimes had fine protrusions on its surface. While this was not a problem in broadband exposure, in lithography processes under monochromatic exposure light, the transmittance of the monochromatic exposure light changed in accordance with the localized changes in the pellicle film thickness caused by these protrusions, which could lead to abnormal exposure light levels near the protrusions.

[0037] Therefore, the inventors conducted diligent research and found that a pellicle film has a pellicle film on its surface that satisfies one or more of the following conditions (A) and (B) [condition (A) the diameter of the circumscribing circle is 5 mm or more, condition (B) the height is 2.5 μm or more], and has 5 protrusions / m made of the same composition as the pellicle film. 2 We have discovered that the following pellicle film has fewer surface protrusions, less film thickness unevenness caused by these protrusions, and excellent smoothness, and allows for uniform transmission of exposure light even under monochromatic light sources such as single exposure (especially ArF, KrF, and i-lines), and can be used for high-resolution lithography, thus completing the present invention.

[0038] Furthermore, we have discovered that if a method for producing a pellicle film is provided in which a polymer solution, which is the material for the pellicle film, is formed on a substrate, the coating film is dried, and the dried coating film is peeled off from the substrate, and the method involves applying one or more of the following treatments to the polymer solution as a pretreatment before forming the coating film of the polymer solution: (i) adsorption and removal of dissolved substances by an adsorbent, (ii) evaporation and removal of dissolved substances by heating, and (iii) separation and removal of dissolved substances by flowing an inert gas, then such an excellent pellicle film as described above can be provided, and thus the present invention has been completed.

[0039] Figure 1 shows an example of the pellicle of the present invention (including the pellicle film of the present invention), along with the exposure master plate. Figure 1 as a whole is an exposure master plate with a pellicle. First, let's explain the overall structure. A membrane-side adhesive layer 2 is provided on the upper surface (upper end surface) of the pellicle frame (hereinafter sometimes simply referred to as the frame) 1, while a mask-side adhesive layer 3 is provided on the lower surface (lower end surface). The pellicle film 4 of the present invention is stretched over the pellicle frame 1 via the membrane-side adhesive layer 2, thereby forming the pellicle 5 of the present invention. Furthermore, in Figure 1, the pellicle 5 is attached to the exposure master (photomask or reticle) 6 via the mask-side adhesive layer 3 of the pellicle frame 1, forming an exposure master 7 with a pellicle.

[0040] The following provides a detailed description of each part. Frame 1 can be any shape that resembles a frame, and its shape corresponds to the shape of the photomask on which Pellicle 5 is attached. Generally, it is a rectangular (or square) frame. Furthermore, as mentioned above, frame 1 has a surface for attaching the pellicle film 4 (in this case, the upper end surface) and a surface that faces the photomask when the photomask is attached (in this case, the lower end surface). The material of frame 1 is not particularly limited and can be the same as in the past, for example, aluminum, stainless steel, polyethylene, titanium, or titanium alloy.

[0041] Additionally, the sides of frame 1 are typically provided with jig holes (not shown) used for handling and detaching pellicle 5 from the photomask. Furthermore, the frame 1 is provided with ventilation sections 8 to mitigate pressure changes inside and outside the pellicle 5. There are no restrictions on the shape or number of ventilation sections 8. Notches may also be provided on the upper or lower end surfaces of the frame 1 to serve as ventilation sections. A filter 9 can be installed in the ventilation section 8 to prevent foreign matter from entering the pellicle 5. There are no restrictions on where the filter 9 can be installed; it can be on the inside of the frame 1, inside the ventilation section 8, or on the outside of the frame 1. In Figure 1, it is installed on the outside of the frame 1.

[0042] Further, the materials for the film-side adhesive layer 2 and the mask-side adhesive layer 3 are not limited, and known adhesives such as those made of silicone resin, acrylic resin, etc. can be used. In order to strongly hold the pellicle film 4, a pressure-sensitive adhesive with strong adhesive force is preferred.

[0043] Further, on the surface of the pellicle film 4, the number of protrusions (raised portions on the surface of the pellicle film itself) made of the same composition as the pellicle film that satisfy one or more of the following conditions (A) to (B) is 5 per m 2 or less (0 per m 2 or more). Condition (A): The diameter of the circumscribed circle is 5 mm or more Condition (B): The height is 2.5 μm or more

[0044] As described above, in the pellicle film 4 of the pellicle 5 of the present invention, among the protrusions formed on the surface, the number of relatively large-sized protrusions as described above is sufficiently suppressed, so that the film thickness unevenness is small. Therefore, the surface smoothness is excellent. For this reason, in the lithography process, exposure light can be uniformly transmitted through the entire in-plane area of the pellicle film. Even when monochromatic exposure light (in particular, short-wavelength monochromatic light such as ArF, KrF, and i-line) is used, the pellicle film of the present invention can achieve in-plane uniform transmittance, which is extremely excellent. On the other hand, in conventional products, since the number of surface protrusions is large, there are many locations with uneven film thickness, and it is difficult to achieve the above effects as in the present invention.

[0045] Note that the upper limits of the numerical values for the diameter of the circumscribed circle in condition (A) and the height in condition (B) cannot be limited. The present invention aims to improve the transmittance of exposure light and the like, and the larger these sizes are, the more adversely they may affect the transmittance of exposure light and the like.

[0046] Further, in this case, the number of protrusions that satisfy both conditions (A) to (B) can be 3 per m 2 or less. Also, the number of protrusions that satisfy condition (A) and do not satisfy condition (B) is 1 per m 2The following conditions may apply. Furthermore, the number of protrusions that satisfy condition (B) but do not satisfy condition (A) is 1 per meter. 2 The following may be used: These types of materials are even more preferable because they offer superior suppression of film thickness unevenness and, consequently, greater uniformity of in-plane transmittance of exposed light.

[0047] In this case, the pellicle film 4 is preferably one in which the film thickness variation within any 1.5 mm × 1.5 mm local region is 20 nm or less (0 nm or more). A film thickness variation within this numerical range can be said to be sufficiently suppressed, and in-plane uniformity of transmittance is more preferable.

[0048] Furthermore, the pellicle membrane 4 has an area of ​​1000 cm². 2 These can be made to be even larger. Such large-area designs are particularly suitable for use in the manufacture of flat panel displays.

[0049] In the present invention, amorphous fluoropolymers such as CYTOP from AGC, Teflon® AF from DuPont, and Algoflon AD from Solvay can be used as materials for the pellicle film 4. The pellicle film 4 may be a single layer film using these fluoropolymers, or a multilayer film in which it is coated as an anti-reflective film on another transparent resin film such as nitrocellulose or cellulose acetate.

[0050] In pellicle membranes 4 (especially large pellicle membranes), the film thickness is preferably 2 to 10 μm. A thickness of 2 μm or more provides higher physical strength, and more effectively suppresses problems such as the membrane tearing during air blowing to remove foreign matter. On the other hand, a thinner film of 10 μm or less can more reliably suppress the increase in membrane deflection due to the membrane's own weight and prevent the cost from increasing.

[0051] Furthermore, since the pellicle 5 of the present invention is equipped with the pellicle film 4 described above, unevenness in film thickness caused by surface protrusions of the pellicle film 4 is suppressed, and even in the case of monochromatic exposure light, it is possible to pass through with high uniformity within the plane.

[0052] [Regarding observation and measurement of film thickness variations, protrusions, and film thickness] Here, we will explain the observation and measurement of the pellicle film thickness variations, surface protrusions, and film thickness mentioned earlier. The pellicle film can be visually inspected under monochromatic inspection light irradiation to confirm its appearance. In this case, if there are film thickness variations within the film surface, the degree of these variations can be observed by the difference in the degree of interference of the inspection light with the surrounding area. For example, when observing using the D line of a low-pressure sodium lamp as the inspection light, film thickness variations associated with localized surface protrusions in this invention can be sufficiently observed.

[0053] Furthermore, foreign matter inspection can be performed on the pellicle film using scattered and reflected light from a high-intensity focusing lamp. For example, white light from a halogen lamp or LED can be used as the light source. If foreign matter is present on the film surface, the light emitted from the light source will be scattered or reflected by the foreign matter and observed. However, as mentioned above, the localized surface protrusions in this invention are not caused by foreign matter, and since there is almost no difference in transmittance to white light around them, they cannot be observed during inspection under white light.

[0054] Generally, regarding localized surface protrusions (raised areas on the film surface itself), the diameter of the circumscribed circle surrounding these protrusions varies depending on the film material and its dissolved substances, but is often approximately 100 μm or larger. Furthermore, the height of the protrusions from the surrounding flat area is often approximately 0.4 μm or larger. Of these, those with a relatively large size, such as those with a circumscribed circle diameter of 5 mm or more, or a height of 2.5 μm or more, tend to particularly affect film thickness unevenness and, consequently, the in-plane uniformity of light transmittance. As mentioned above, in the pellicle film of the present invention, these relatively large sizes are reduced, resulting in excellent in-plane uniformity of transmittance.

[0055] The size of localized surface protrusions can be measured simply by observing the diameter of the circumscribed circle under monochromatic inspection light. More detailed measurements, including height, can be performed using techniques such as laser microscopy or AFM. For example, Figure 2 is an example of a visual image of a protrusion under monochromatic inspection light (low-pressure sodium lamp) irradiation. The difference between the protrusion located near the center of Figure 2 and the surrounding flat area can be easily observed, and the diameter of the circumscribed circle of the protrusion can be easily measured (width indicated by the arrow). Figure 3 shows an example of the results of a laser microscope analysis of the protrusion height. The upper figure is a plan view of the protrusion, and the lower figure shows the maximum height difference (protrusion height) between the peak of the protrusion in the height direction (position A) and the flat area around the protrusion (position B). The lower figure also shows the height change along the line connecting A and B.

[0056] Furthermore, the thickness of the pellicle film can be measured at any point using a transmittance meter, allowing for the measurement of both the optical film thickness and light transmittance.

[0057] The film thickness is the transmittance of light of a certain wavelength I T The effect of can be calculated using Airy's equation (Equation 1). The constant F in Equation 1 is defined by the reflectance R obtained from Fresnel's equation (Equation 2). The multiple reflection phase difference φ of a thin film can be determined using Equation 3, based on the film thickness and the angle of refraction between the medium. The relationship between the angle of refraction and the angle of incidence follows Snell's law (Equation 4).

[0058]

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[0059]

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[0060]

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[0061]

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[0062] Next, a method for manufacturing the pellicle membrane of the present invention as described above will be explained. Figure 4 is a flowchart showing an example of the steps of the manufacturing method of the present invention. The pellicle film in the present invention is manufactured by the following steps: preparing a polymer solution by dissolving a pellicle film material polymer in a solvent; pre-treating the polymer solution; uniformly coating the pre-treated polymer solution onto a film-forming substrate (hereinafter also simply referred to as the substrate) to form a coating film; and heating and drying the substrate coated with the polymer solution, followed by peeling the dried coating film from the substrate. The above preprocessing includes one or more of the following processes (i) to (iii). (i) Adsorption and removal of dissolved substances using an adsorbent (ii) Treatment to remove dissolved substances by evaporation through heating (iii) Separation and removal of dissolved substances by flowing inert gas

[0063] <Coating liquid preparation process> First, the preparation process for the coating solution (polymer solution) will be explained. The pellicle film material polymer is dissolved in a solvent before use. Due to the product properties of the pellicle film, it is necessary to control the adhesion of foreign matter, so it is preferable to remove foreign matter from the coating solution by performing precision filtration using a depth filter or membrane filter.

[0064] <Pre-treatment process> Furthermore, dissolved substances may be present in the solvent during the preparation of the coating solution. For example, when a non-aqueous solvent is used, dissolved water vapor originating from the storage and usage environment of the polymer solution may be present in the polymer solution. If this is not removed, condensed water may be locally present on the wet film after coating, and depending on the affinity between the solvent and water, a phenomenon may occur in subsequent processes where the wet film is repelled by water.

[0065] On the other hand, other dissolved substances that may solidify after heating and drying the polymer solution are also conceivable. However, in this case, foreign substances will remain on the film as foreign components, which are different from the aforementioned protrusions and are not what is intended by the present invention.

[0066] The condensed water mentioned above evaporates during the subsequent heating and drying process and does not usually remain on the pellicle film. However, because the polymer solution dries on the film surface while retaining a local structure where it has been repelled by water, the aforementioned fine protrusions may form on the film surface after heating and drying. These protrusions cause localized film thickness variations within the pellicle film surface.

[0067] The degree of film thickness unevenness, that is, the size of the protrusions formed by repulsion, is thought to depend on the amount of dissolved substances in the polymer solution, the coating method, and the drying method after coating. However, the inventors investigated a pretreatment of the polymer solution before coating as a method to reduce the amount of dissolved substances in the polymer solution before coating, and succeeded in obtaining a pellicle film (especially a large pellicle film) without localized film thickness unevenness.

[0068] In order to suppress the surface protrusions of the coating film induced by the repulsion of the polymer solution mentioned above, the following treatments can be specifically performed as pretreatment before coating. (i) Adsorption and removal of dissolved substances using an adsorbent By adding an adsorbent to a polymer solution, dissolved substances can be adsorbed and removed. Examples of adsorbents include molecular sieves and silica gel, which can be appropriately selected depending on the type of polymer and solvent.

[0069] Specific methods include the static method, which involves adding an appropriate amount of the adsorbent to the polymer solution, stirring, and then letting it stand repeatedly, and the column method, which involves packing the adsorbent into a column and flowing the polymer solution through it at a certain flow rate. The removal of dissolved substances using adsorbents is effective for low-viscosity polymer solutions because adsorption occurs at the interface between the liquid and the adsorbent.

[0070] (ii) Treatment to remove dissolved substances by evaporation through heating Generally, the solubility of dissolved gases in a liquid decreases as the temperature rises, so dissolved substances can also be removed by heating the polymer solution. Furthermore, heating tends to decrease the viscosity of the solution, so by adding the adsorbent to the heated solution, interfacial contact between the adsorbent and the polymer solution is promoted, allowing for more efficient removal of dissolved substances. Thus, pretreatment by heating is effective for polymer solutions with high viscosity. The heating temperature should preferably be within a range that does not significantly change the concentration of the polymer solution, taking into consideration the boiling point of the solvent.

[0071] (iii) Separation and removal of dissolved substances by flowing inert gas In addition to the removal of dissolved substances by adsorbents and heating as described above, separation and removal of dissolved substances is also possible by circulating an inert gas. If the solubility of the dissolved substance in the polymer solution is greater in the inert gas than in the solvent, it will be removed from the system by bubbling along with the inert gas. Furthermore, in the case of dissolved gases, due to their diffusion and partial pressure, they tend to mix with the circulating gas, and the removal effect of the dissolved gas is desirable.

[0072] Furthermore, it is particularly preferable to apply treatments (ii) and (iii). By applying at least these treatments, the number of protrusions can be more effectively suppressed, film thickness unevenness can be suppressed, and consequently, the in-plane transmittance of exposure light can be made more reliable.

[0073] <Coating Process> Next, the polymer solution prepared using the coating solution and the pre-treated polymer solution after preparation is applied to a substrate (such as a quartz glass substrate) using a slit coating method, spin coating method, or the like to form a coated film (coating solution film). There are no particular restrictions on the type of coater, but in this case, it is preferable to have high thickness uniformity of the coating solution film.

[0074] <Heat drying and peeling process> Next, the coating liquid film is first air-dried in a cleanroom environment to evaporate a certain amount of the solvent. At this stage, the coating liquid film may develop uneven film thickness due to the downward airflow in the cleanroom and the horizontality of the air-drying area. Therefore, air-drying is performed as horizontally as possible and under appropriate airflow conditions. After that, the pellicle film is obtained as a solid polymer film by heat drying at an appropriate temperature. The pellicle film obtained in this way as a solid film is peeled from the substrate using a known method to obtain a pellicle film as a self-supporting film.

[0075] As described above, the pellicle film 4 of the present invention can be manufactured. Then, by attaching the pellicle film 4 to the upper end surface of a separately prepared pellicle frame 1 (upper end surface: film-side adhesive layer 2, lower end surface: mask-side adhesive layer 3) via the film-side adhesive layer 2, the pellicle 5 of the present invention as shown in Figure 1 can be manufactured. Furthermore, by attaching the pellicle 5 to the exposure master 6 via the mask-side adhesive layer 3, an exposure master 7 with a pellicle can be obtained. [Examples]

[0076] The present invention will be described more specifically below with reference to examples of the present invention, but the present invention is not limited to these examples. (Examples 1-7, Comparative Example 1) A rectangular piece of synthetic quartz glass measuring 850mm x 1200mm and 10mm thick (approximately 10,000cm²) 2 A material was prepared, its surface was cleaned by dry cleaning, and this was used as the film-forming substrate. We also prepared a polymer solution by dissolving CYTOP (CTX-809SP2, manufactured by AGC) in perfluorotributylamine (FC-43, manufactured by 3M). As shown in Table 1, one or more of the following treatments (i) to (iii) were performed on this polymer solution as a pretreatment in Examples 1-7. On the other hand, in Comparative Example 1, none of the pretreatment steps (i) to (iii) were performed.

[0077] [Table 1]

[0078] The processing details in Table 1 will be explained in detail. In pretreatment (i), molecular sieves 13X (manufactured by Kanto Chemical Co., Ltd.) were added as an adsorbent in an amount equivalent to 10% by weight of the polymer solution, and dissolved substances were removed over 6 hours by a static method in which stirring and standing were repeated at a frequency of once per hour.

[0079] In pretreatment (ii), the polymer solution was heated on a hot plate at 100°C for 24 hours to remove dissolved gases.

[0080] In pretreatment (iii), the polymer solution was gas-purged by stirring it for 24 hours while circulating nitrogen gas as an inert gas at a flow rate of 0.5 L / min through a tank equipped with a stirring blade.

[0081] When multiple pretreatments (i), (ii), and (iii) described above were used in combination, the first step was heating (ii), followed by the addition of the adsorbent (i), and finally, gas replacement with an inert gas (iii).

[0082] The polymer solutions of Examples 1-7, each subjected to the respective pretreatments shown in Table 1, and the polymer solution of Comparative Example 1, which was not pretreated, were each pumped into a 0.2 μm diameter membrane filter and filtered. The filtered liquids were uniformly coated onto the film-forming substrate using the slit-coating method to achieve a dry film thickness of 4 μm. After air drying for more than 2 hours, drying was performed by far-infrared heating (180°C, 30 min). Subsequently, the pellicle film was peeled off using a temporary frame. In this way, the pellicle films of Examples 1-7 and Comparative Example 1 were obtained.

[0083] The pellicle films prepared as described above were visually inspected under irradiation with a low-pressure sodium lamp (Iwasaki Electric, NX180) to observe for film thickness variations. As a result of this observation, localized film thickness variations were first identified in Comparative Example 1. Furthermore, when the areas observed in Comparative Example 1 were examined using a laser microscope (OLYMPUS, LEXT OLS4100), protrusions (raised areas on the surface of the film itself) were observed under 405nm laser irradiation as shown in Figure 5 (middle image in Figure 5). At this time, the diameter of the circumscribed circle of the protrusion was approximately 5 mm, which was the same as the result of visual observation under sodium lamp mentioned above.

[0084] Furthermore, under white LED illumination, no such protrusions were observed in the same field of view under the microscope (left panel of Figure 5). This is consistent with the observation that scattered and reflected light from high-intensity focusing lamps was not observed under fluorescent lighting or in a darkroom.

[0085] Furthermore, Figure 6 shows the results of an analysis performed in the height direction on the line connecting the two locations shown in the right-hand diagram of Figure 5 (near the peak of the protrusion and the flat area). As shown in Figure 6, the film thickness variation in question has protrusions, and the maximum height difference of the protrusions was approximately 2.5 μm.

[0086] As described above, the film thickness around the observed protrusions was investigated. A transmittance meter (Spectra Corp., Handy Lambda II Thickness) was used for the measurements. Figure 7 is an explanatory diagram showing the film thickness measurement locations around the fine protrusions on the pellicle film surface. As shown in Figure 7, within the plane of the observation diagram, the film thickness was measured at four points at 0.5 mm intervals horizontally (in-plane transverse direction) and four points at 0.5 mm intervals vertically (in-plane longitudinal direction) (M1 to M8 in Figure 7), centered around the peak of the protrusion. That is, this measurement range is a square with two diagonal lengths of 1.5 mm each, and is here also referred to as a "1.5 mm × 1.5 mm" local area (measurement range). Similar measurements were also performed on the normal area (flat area where no protrusions were observed) within the same film plane.

[0087] From the film thickness measurements obtained in the above measurements, the transmittance at a single wavelength of i-line (365 nm) was calculated using Airy's formula (Equation 1) mentioned above. The results are summarized in Table 2.

[0088] [Table 2]

[0089] As is clear from Table 2, at the protruding area, there is a localized film thickness variation of 0.02 μm within a measurement range of 1.5 mm × 1.5 mm, which results in a localized reduction of approximately 3.62% compared to the normal area when irradiated with i-line monochromatic light. In fact, in semiconductor lithography processes where monochromatic exposure is performed, the light transmittance of the pellicle film is required to be, for example, 99% or higher. Therefore, this level of transmittance reduction could become a problem when considering further miniaturization of lithography processes using large pellicles (i.e., in monochromatic exposure of even shorter wavelengths).

[0090] The film deposition process for Examples 1-7 and Comparative Example 1 was repeated 10 times each to obtain 10 pellicle films. Then, for each example, the total number of film thickness variations associated with localized surface protrusions confirmed by the visual inspection of the pellicle film was used to determine the film area per 1 m². 2Table 3 shows the results of the calculation of the number of occurrences per unit. The area per membrane is 1.037 m². 2 It is (a large pellicle membrane). Furthermore, the protrusions summarized in Table 3 must satisfy one or more of the following conditions (A) to (B). Condition (A) The diameter of the circumscribed circle (also called the outer diameter of the projection) is 5 mm or larger. Condition (B) Height is 2.5 μm or more

[0091] [Table 3]

[0092] Table 3 shows the "Total number of protrusions" and "1m 2 As is clear from the "number per square meter," Examples 1-7 show that the generation of localized protrusions is suppressed compared to Comparative Example 1. Comparative Example 1 had 6.5 protrusions / m². 2 In Examples 1-7, where a polymer solution pre-treated before coating was used, the number of protrusions observed was 5 per square meter. 2 The following (more specifically, 4.1 pieces / m) 2 The following high-quality, large-scale pellicle membranes were obtained. In other words, in the present invention products of Examples 1 to 7, the number of relatively large protrusions as described above can be suppressed compared to conventional products such as Comparative Example 1, thereby reducing the occurrence of film thickness unevenness. As a result, it was possible to obtain products with excellent in-plane uniformity with respect to the transmission of exposure light (especially monochromatic light of shorter wavelengths).

[0093] Furthermore, focusing on the classification of the observed protrusions, the following can be said: 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)), the number of protrusions is 3 per meter in all embodiments. 2 The following (more specifically, 2.1 pieces / m) 2 The levels were reduced to the following, and were lower than in Comparative Example 1. 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)), the count is 1 per meter in all embodiments. 2 The following (more specifically, 0.8 pieces / m) 2 The levels were reduced to the following, and were lower than in Comparative Example 1. 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)), in particular in Examples 6 and 7, the limit was 1 piece / m 2 Less than (more specifically, 0.7 pieces / m) 2 The occurrence could be suppressed to the following extent, which was less than in Comparative Example 1.

[0094] As can be seen from Table 3, by performing both (ii) and (iii) treatments as in Example 6, a better pellicle film than that in Examples 1-5 can be obtained. Furthermore, as shown in Example 7, by performing more appropriate pretreatment (all of the treatments (i) to (iii)) on the polymer solution before coating, it can be seen that the generation of these localized protrusions (and the generation of film thickness unevenness caused by these protrusions) can be completely suppressed. Therefore, the in-plane uniformity of the transmittance of exposed light can be made extremely excellent.

[0095] This specification includes the following embodiments: [1]: A pellicle membrane, On the surface of the pellicle film, the number of protrusions made of the same composition as the pellicle film is 5 / m, satisfying one or more of the following conditions (A) to (B). 2 The pellicle membrane is as follows: Condition (A) The diameter of the circumscribed circle is 5 mm or larger. Condition (B) Height is 2.5 μm or more [2]: The number of protrusions that satisfy both conditions (A) and (B) above is 3 per meter. 2 The pellicle membrane described above [1] is the following: [3]: The number of protrusions that satisfy condition (A) and do not satisfy condition (B) is 1 per meter. 2The pellicle membrane described above [1] is the following: [4]: The number of protrusions that satisfy condition (B) and do not satisfy condition (A) is 1 per meter. 2 The pellicle membrane described above [1] is the following: [5]: The pellicle membrane has an area of ​​1000 cm² 2 A large pellicle membrane as described in any of the above [1] to [4]. [6]: The pellicle film is the pellicle film according to any one of [1] to [5] above, wherein the film thickness is 2 to 10 μm. [7]: The pellicle film is the pellicle film according to any one of [1] to [6] above, wherein the film thickness variation within any 1.5 mm × 1.5 mm local region is 20 nm or less. [8]: A pellicle comprising a pellicle frame, an adhesive layer provided on the surface of the pellicle frame, and a pellicle film stretched on the surface of the pellicle frame via the adhesive layer, The pellicle is a pellicle film described in any of the above [1] to [7]. [9]: A method for producing a pellicle film by forming a coating film of a polymer solution which is the material for the pellicle film on a substrate, drying the coating film, and then peeling the dried coating film off the substrate, A method for producing a pellicle film, comprising subjecting the polymer solution to one or more of the following treatments (i) to (iii) as a pretreatment before forming a coated film of the polymer solution. (i) Adsorption and removal of dissolved substances using an adsorbent (ii) Treatment to remove dissolved substances by evaporation through heating (iii) Separation and removal of dissolved substances by flowing inert gas

[10] : The method for producing a pellicle film according to [9] above, wherein the pretreatment is performed by at least the treatments (ii) and (iii).

[11] : The pellicle membrane has an area of ​​1000 cm². 2 A method for manufacturing a pellicle membrane as described in [9] or

[10] above, for producing the above-mentioned large-sized ones.

[12] : A method for producing a pellicle film having a thickness of 2 to 10 μm as described in any of [9] to

[11] above.

[13] : A method for manufacturing a pellicle, comprising a pellicle frame, an adhesive layer provided on the surface of the pellicle frame, and a pellicle film stretched on the surface of the pellicle frame via the adhesive layer, A method for manufacturing a pellicle, using a pellicle membrane manufactured by the method for manufacturing a pellicle membrane described in any of [9] to

[12] above as the pellicle membrane.

[0096] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that has substantially the same technical idea as described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0097] 1... Pellicle frame, 2... Adhesive layer on the film side, 3... Adhesive layer on the mask side 4…The pellicle film of the present invention, 5…The pellicle of the present invention, 6... Exposure plate, 7... Exposure plate with pellicle, 8... Ventilation section, 9... Filter, M1~M8... Film thickness measurement points.

Claims

1. It is a pellicle membrane, On the surface of the pellicle film, the number of protrusions made of the same composition as the pellicle film is 5 / m, satisfying one or more of the following conditions (A) to (B). ２ A pellicle membrane characterized by the following: Condition (A) The diameter of the circumscribed circle is 5 mm or larger. Condition (B) Height is 2.5 μm or more

2. The number of protrusions that satisfy both of the above conditions (A) and (B) is 3 per meter. ２ The pellicle membrane according to claim 1, characterized in that it is as follows.

3. The number of protrusions that satisfy condition (A) and do not satisfy condition (B) is 1 per meter. ２ The pellicle membrane according to claim 1, characterized in that it is as follows.

4. The number of protrusions that satisfy condition (B) and do not satisfy condition (A) is 1 per meter. ２ The pellicle membrane according to claim 1, characterized in that it is as follows.

5. The pellicle membrane has an area of ​​1000 cm². ２ The pellicle membrane according to claim 1, characterized in that it is of the above large size.

6. The pellicle film according to claim 1, characterized in that the pellicle film has a film thickness of 2 to 10 μm.

7. The pellicle film according to claim 1, characterized in that the pellicle film has a film thickness variation of 20 nm or less within any local region of 1.5 mm × 1.5 mm.

8. A pellicle comprising a pellicle frame, an adhesive layer provided on the surface of the pellicle frame, and a pellicle film stretched on the surface of the pellicle frame via the adhesive layer, A pellicle characterized in that the pellicle membrane is the pellicle membrane described in any one of claims 1 to 7.

9. A method for producing a pellicle film by forming a coating film of a polymer solution, which is the material for the pellicle film, on a substrate, drying the coating film, and then peeling the dried coating film off the substrate, A method for producing a pellicle film, characterized by subjecting the polymer solution to one or more of the following treatments (i) to (iii) as a pretreatment before forming a coated film of the polymer solution. (i) Adsorption and removal of dissolved substances using an adsorbent (ii) Evaporation and removal of dissolved substances by heating (iii) Separation and removal of dissolved substances by inert gas flow treatment

10. The method for producing a pellicle film according to claim 9, characterized in that at least the treatments (ii) and (iii) are performed as the aforementioned pretreatment.

11. The pellicle membrane has an area of ​​1000 cm². ２ The method for manufacturing a pellicle membrane according to claim 9, characterized in that it manufactures the above-mentioned large size.

12. The method for producing a pellicle film according to claim 9, characterized in that the pellicle film has a thickness of 2 to 10 μm.

13. A method for manufacturing a pellicle, comprising a pellicle frame, an adhesive layer provided on the surface of the pellicle frame, and a pellicle film stretched on the surface of the pellicle frame via the adhesive layer, A method for manufacturing a pellicle, characterized in that the pellicle membrane is manufactured by the method for manufacturing a pellicle membrane described in any one of claims 9 to 12.

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