Optical member and manufacturing method thereof

Abstract

Provided are a lightweight optical member that can be manufactured at relatively low cost, the optical member having minimal distortion due to temperature increase and having excellent low dust generation and low outgassing properties. A pellicle frame (1) of the present invention is characterized by having a base material (4) composed of titanium or a titanium alloy and a TiO2 coating layer (2) formed on the surface of the base material (4). The TiO2 coating layer (2) preferably contains nitrogen.

Description

[Technical Field]

[0001] The present invention relates to an optical member such as a pellicle frame for a dustproof cover in an exposure process, which is essential in the manufacture of semiconductors, and a method for manufacturing the same. [Background technology]

[0002] In semiconductor devices such as LSIs and VLSIs, and liquid crystal panels, patterns are formed by irradiating light onto semiconductor wafers or liquid crystal masters (lithographic pattern formation). However, if dust or other foreign matter is used as the exposure master, the dust will absorb and / or invert the light, resulting in poor pattern transfer (e.g., pattern deformation or unclear edges). This can result in problems such as impaired quality and appearance of the semiconductor devices and liquid crystal panels, leading to reduced performance and manufacturing yields.

[0003] For this reason, lithography processes are usually performed in clean rooms, but even in such an environment, it is not possible to completely prevent dust from adhering to the exposure master, so a Pecryl film is generally provided on the surface of the exposure master to protect it from dust. The Pecryl film is composed of a Pecryl frame and a Pecryl film stretched over the frame, and is installed so as to surround the pattern area formed on the surface of the exposure master. If the focus is aligned on the pattern of the exposure master during lithography, even if dust adheres to the Pecryl film, the dust will not affect the transfer.

[0004] In recent years, LSI patterns have become increasingly finer, and accordingly, exposure light sources are becoming shorter in wavelength. Specifically, there is a shift from the previously mainstream g-line (wavelength: 436 nm) and i-line (wavelength: 365 nm) emitted by mercury lamps to KrF excimer lasers (wavelength: 248 nm), ArF excimer lasers (wavelength: 193 nm), and F2 excimer lasers (wavelength: 157 nm), etc.

[0005] These short-wavelength exposure light sources have high output and high light energy, so if inorganic acids such as sulfuric acid or phosphoric acid remain in the anodized film on the surface of the aluminum material that forms the pellicle, they will react with basic substances such as ammonia that remain in the exposure atmosphere to form reaction products (haze) such as ammonium sulfate, which can cause the pellicle to become cloudy and affect the pattern transfer image.

[0006] In response to this, for example, Patent Document 1 (JP 2010-237282 A) discloses a method for manufacturing a pellicle support frame formed from an aluminum material made of aluminum or an aluminum alloy, equipped with an optical thin film, and used as a pellicle, characterized in that an anodized film is formed on the surface of the aluminum material by anodizing treatment using an alkaline aqueous solution containing tartaric acid, followed by dyeing treatment using an organic dye, and then sealing treatment using water vapor.

[0007] In the manufacturing method of a pellicle support frame described in Patent Document 1, it is said that by anodizing an aluminum material using an alkaline aqueous solution containing tartaric acid without using sulfuric acid, which is the main cause of haze, it is possible to obtain a pellicle support frame that has excellent corrosion resistance and durability while minimizing the generation of haze.

[0008] Furthermore, pellicle frames also present another problem: if the pellicle frame is distorted significantly due to thermal expansion, the exposure process cannot be carried out precisely. In particular, with regard to exposure devices, the demand for improved productivity (throughput) has led to increased light source output and finer circuit line widths, and exposure light sources have become shorter in wavelength, which has led to problems with distortion due to temperature increases in pellicle frames placed in the optical path.

[0009] Traditionally, aluminum has been used for pellicle frames because of its low specific gravity and good machinability, but aluminum has a high linear expansion coefficient, making aluminum pellicle frames susceptible to distortion due to temperature rise. Therefore, the material for pellicle frames is not limited to aluminum, and studies are underway to consider using ceramics, steel, and other materials.

[0010] For example, Patent Document 2 (JP 2016-177120 A) discloses a pellicle frame formed in a frame shape, made of a sintered body having a Young's modulus of 150 GPa or more and a Vickers hardness of 800 or more, with the corner portions of the frame shape having a width equal to or greater than the width of the straight portions, and at least one of the corner portions having a width wider than the width of the straight portions, and the pellicle frame being made of ceramics, cemented carbide, or cermet.

[0011] The pellicle frame described in Patent Document 2 uses a sintered body with a high Young's modulus and Vickers hardness, which prevents the pellicle frame from being deformed by the tension of the pellicle film that occurs when the pellicle film is stretched over the pellicle frame. Moreover, the width of at least one corner portion is wider than the width of the straight portion, which increases the strength of the corner portion and further prevents deformation and damage to the pellicle frame.

[0012] Furthermore, Patent Document 3 (JP 2014-085435 A) discloses a pellicle frame manufactured by pressing a single metal plate, which has an L-shaped cross section, a pellicle membrane adhesive surface on the outer surface bent at a right angle from the inner wall surface of the pellicle frame outward, and a mask adhesive surface on the end surface that contacts the inner wall surface, and which is made of carbon steel or stainless steel.

[0013] The pellicle frame described in Patent Document 3 above is manufactured by press processing, which is highly suitable for mass production, so the manufacturing costs are extremely low, and because it is molded into an L-shaped or U-shaped cross section, it is said to be able to ensure the necessary and sufficient rigidity for a pellicle frame. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-237282 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-177120 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-085435 Summary of the Invention [Problem to be solved by the invention]

[0015] However, the pellicle frame described in Patent Document 1 is made of aluminum, and when an exposure light source with a shorter wavelength is used (when irradiating with extreme ultraviolet light), distortion due to temperature rise becomes a serious problem.

[0016] Furthermore, the pellicle frame described in Patent Document 2 is made of a material with poor toughness, making it very brittle and difficult to handle. It also has poor workability, resulting in high manufacturing costs. Additionally, the high specific gravity of cemented carbide and cermet increases the weight of the pellicle frame.

[0017] In addition, although the pellicle frame described in Patent Document 3 can be manufactured inexpensively, carbon steel and stainless steel have high specific gravities, which increases the weight of the pellicle frame.

[0018] Furthermore, pellicle frames are required to have low dust generation and low outgassing when irradiated with extreme ultraviolet rays, but it is difficult to say that the pellicle frames described in the above Patent Documents 1 to 3 fully meet these requirements.

[0019] In view of the problems in the prior art as described above, an object of the present invention is to provide an optical component such as a lightweight pellicle frame that can be manufactured relatively inexpensively, in which distortion due to temperature rise is suppressed and which has excellent low dust generation and low outgassing properties, and to provide an efficient method for manufacturing the same. [Means for solving the problem]

[0020] In order to achieve the above object, the inventors conducted extensive research into the materials and surface conditions of optical components, and discovered that using titanium or a titanium alloy as the material and forming a TiO2 coating layer on the surface by a sol-gel method is extremely effective, leading to the completion of the present invention.

[0021] That is, the present invention provides: a substrate made of titanium or a titanium alloy; a TiO2 coating layer formed on the surface of the substrate; The present invention provides an optical member characterized by the above.

[0022] The optical member of the present invention has a substrate made of titanium or a titanium alloy, which makes it lightweight and low thermal expansion. Furthermore, a TiO2 coating layer is formed on the entire surface of the substrate, which provides excellent low dust generation and low outgassing. Additionally, the TiO2 coating layer provides the optical member of the present invention with excellent hydrogen plasma resistance.

[0023] The TiO2 coating layer not only has the effect of trapping foreign matter present on the surface of the substrate and preventing it from falling off, but also, because it is a dense and stable ceramic layer, it generates almost no outgassing even when exposed to extreme ultraviolet rays.

[0024] In the optical element of the present invention, the TiO2 coating layer preferably contains nitrogen. The nitrogen originates from a salt catalyst used when forming the TiO2 coating layer using a sol-gel method. The use of a salt catalyst effectively promotes the polycondensation reaction of Ti alkoxide, the raw material for the TiO2 coating layer, and forms a dense and homogeneous TiO2 coating layer, thereby more reliably ensuring the trapping effect of foreign materials and low outgassing.

[0025] In the optical member of the present invention, it is also preferable that the substrate has through holes, and the TiO2 coating layer is also formed on the inner surface of the through holes. When through holes are present in the substrate, it is extremely difficult to completely remove foreign matter adhering to the inner surface of the through holes. However, in the optical member of the present invention, a dense and uniform TiO2 coating layer is formed on the inner surface of the through holes by a sol-gel method, thereby ensuring excellent low dust generation properties.

[0026] Furthermore, in the optical component of the present invention, it is preferable that the amount of hydrogen gas generated by irradiation with extreme ultraviolet rays is 1.2 times or less than the amount of hydrogen gas generated when the substrate is irradiated with extreme ultraviolet rays under the same conditions. The TiO2 coating layer formed on the surface of the optical component of the present invention is a dense, homogeneous, and chemically stable ceramic layer, and even when irradiated with extreme ultraviolet rays, the amount of outgassing generated from the TiO2 coating layer is extremely small. As a result, the amount of hydrogen gas generated by irradiation with extreme ultraviolet rays can be reduced to 1.2 times or less than the amount of hydrogen gas generated when the substrate is irradiated with extreme ultraviolet rays under the same conditions. A more preferable amount of hydrogen gas generated is 1.1 times or less, and a most preferable amount of hydrogen gas generated is 1.05 times or less.

[0027] Furthermore, when the optical member of the present invention is immersed in 3 L of pure water and subjected to ultrasonic irradiation for 1 minute, the number of particles having a particle size of 1 to 15 μm present in 50 ml of the pure water is 600 particles / 68 cm 2In the optical element of the present invention, foreign matter is trapped by the dense and uniform TiO2 coating layer formed on the surface of the substrate, so that even under harsh conditions such as when the optical element is immersed in pure water and irradiated with ultrasonic waves, the detachment of foreign matter (particles) is extremely effectively suppressed.

[0028] Furthermore, when the optical member of the present invention is immersed in 3 L of pure water and subjected to ultrasonic irradiation for 1 minute, the number of particles having a particle size of 0.5 to 1 μm present in 50 ml of the pure water is 2000 particles / 68 cm 2 In the optical element of the present invention, foreign matter is trapped by the dense and uniform TiO2 coating layer formed on the surface of the substrate, so that even under harsh conditions such as when the optical element is immersed in pure water and irradiated with ultrasonic waves, the detachment of foreign matter (particles) is extremely effectively suppressed.

[0029] The optical element of the present invention is preferably a pellicle frame, but is not particularly limited as long as the effects of the present invention are not impaired. For example, it can be any of various conventionally known optical components (such as the housing, various support parts inside the housing, shutter blades, and apertures) that constitute optical devices such as digital cameras, digital video cameras, and camera-equipped mobile phones.

[0030] The present invention also provides a process for preparing a substrate for an optical member, in which a substrate made of titanium or a titanium alloy is processed into the shape of a substrate for an optical member; a coating step of forming a TiO2 coating layer on the surface of the substrate for optical members using a sol-gel method, using a nitrogen-containing salt catalyst in the coating step; Also provided is a method for producing an optical member, characterized by:

[0031] The method for manufacturing an optical member of the present invention is characterized by (1) using a titanium or titanium alloy substrate for the optical member, (2) using a sol-gel process, and (3) using a nitrogen-containing salt catalyst in the sol-gel process. In particular, the use of the salt catalyst allows for the efficient formation of a dense and uniform TiO2 coating layer over the entire surface of the substrate.

[0032] In the method for producing an optical member of the present invention, it is preferable that through holes are formed in the substrate for optical members in the optical member substrate preparation step, and that the TiO2 coating layer is also formed on the inner surface of the through holes in the coating step. Since the method for producing an optical member of the present invention uses a sol-gel method, the TiO2 coating layer can be easily formed inside the through holes. In particular, by applying dip coating, the TiO2 coating layer can be easily and efficiently formed inside the through holes.

[0033] Furthermore, in the method for producing an optical member of the present invention, the polycondensation reaction of the coating raw material is accelerated using a nitrogen-containing salt catalyst, and the crystallization of TiO2 is accelerated even when the TiO2 coating layer is formed by low-temperature firing at about 200 to 300°C. As a result, the TiO2 coating layer obtained can be a good ceramic layer with a high degree of crystallinity. [Effects of the Invention]

[0034] According to the present invention, it is possible to provide a lightweight optical component that can be manufactured relatively inexpensively, in which distortion due to temperature rise is suppressed, and which has excellent low dust generation and low outgassing properties, and an efficient method for manufacturing the same. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 2 is a perspective view of a pellicle frame according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the pellicle frame taken along the line CC′ of the embodiment. [Figure 3]1A to 1C are process diagrams illustrating a method for manufacturing a pellicle frame according to an embodiment. [Figure 4] 1 is an SEM photograph of an example pellicle frame 1. [Figure 5] 1 is an SEM photograph of an example pellicle frame 2. [Figure 6] 1 is an SEM photograph of a comparative pellicle frame 1. [Figure 7] 1 is an SEM photograph of a comparative pellicle frame 2. [Figure 8] 1 is an SEM photograph of a comparative pellicle frame 4. [Figure 9] 1 is an IR spectrum of an example pellicle frame 1. [Figure 10] 1 is an IR spectrum of an example pellicle frame 2. [Figure 11] IR spectrum of comparative pellicle frame 1. [Figure 12] IR spectrum of comparative pellicle frame 2. [Figure 13] IR spectrum of comparative pellicle frame 4. [Figure 14] This is the measurement result of hydrogen gas. [Figure 15] These are the measurement results for water and ammonia. [Figure 16] This is the measurement result of hydrocarbons. DETAILED DESCRIPTION OF THE INVENTION

[0036] Representative embodiments of the optical element and its manufacturing method of the present invention will be described in detail below with reference to the drawings, using a pellicle frame as a representative example, but the present invention is not limited to these. Furthermore, some or all of the components in the embodiments can be combined as appropriate. In the following description, identical or equivalent parts are designated by the same reference numerals, and redundant explanations may be omitted. Furthermore, since the drawings are intended to conceptually explain the present invention, the dimensions and ratios of the components shown may differ from the actual dimensions.

[0037] 1. Pellicle frame As shown in FIGS. 1 and 2, the pellicle frame 1 is composed of a frame 4 made of titanium or a titanium alloy and having a TiO2 coating layer 2 on its surface.

[0038] Because the frame 4 is made of titanium or a titanium alloy, it has higher strength and Young's modulus than the pellicle frame made of aluminum alloy, which has been commonly used in the past. In addition, titanium and titanium alloys are relatively light, with a specific gravity of about 4.5, which makes it possible to suppress an increase in the weight of the pellicle frame 1.

[0039] The titanium alloy used for the frame 4 is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known titanium alloys can be used. Examples of titanium alloys include Ti-6Al-4V alloy, Ti-6Al-6V-2Sn alloy, Ti-6Al-2Sn-4Zr-6Mo alloy, Ti-10V-2Fe-3Al alloy, Ti-7Al-4Mo alloy, Ti-5Al-2.5Sn alloy, Ti-6Al-5Zr-0.5Mo-0.2Si alloy, Ti-5.5Al-3.5Sn-3Zr-0.3Mo-1Nb-0.3Si alloy, Ti-8Al-1Mo-1 Examples of such alloys include V alloy, Ti-6Al-2Sn-4Zr-2Mo alloy, Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy, Ti-11.5Mo-6Zr-4.5Sn alloy, Ti-15V-3Cr-3Al-3Sn alloy, Ti-15Mo-5Zr-3Al alloy, Ti-15Mo-5Zr alloy, and Ti-13V-11Cr-3Al alloy.

[0040] From the viewpoint of ensuring good workability and purity, it is preferable to use titanium (pure titanium), from the viewpoint of achieving both high strength and good workability, it is preferable to use an α+β type alloy, and from the viewpoint of material price and ease of availability, it is preferable to use a Ti-6Al-4V alloy.

[0041] The shape of the pellicle frame 1 is not particularly limited as long as it does not impair the effects of the present invention, and can be any of a variety of conventionally known shapes depending on the shape of the exposure master, but generally the planar shape of the pellicle frame 1 is ring-shaped, rectangular or square, and has a size and shape that covers the circuit pattern portion provided on the exposure master.

[0042] The height (thickness) of the pellicle frame 1 is preferably 0.5 to 10 mm, more preferably 1 to 7 mm, and most preferably 1.0 to 3.0 mm. By setting the height (thickness) of the pellicle frame 1 to these values, deformation of the pellicle frame 1 can be suppressed and good handleability can be ensured.

[0043] The cross-sectional shape of the pellicle frame 1 is not particularly limited as long as it does not impair the effects of the present invention, and can be any of a variety of conventionally known shapes, but is preferably a quadrilateral with parallel upper and lower edges. The upper edge of the pellicle frame 1 must be wide enough to stretch the pellicle membrane, and the lower edge must be wide enough to provide an adhesive layer for bonding to the exposure master. For this reason, the width (W) of the upper and lower edges of the pellicle frame 1 is preferably about 1 to 3 mm.

[0044] The flatness of the pellicle frame 1 is preferably 30 μm or less, and more preferably 20 μm or less. By improving the flatness of the pellicle frame 1, it is possible to reduce the amount of deformation of the exposure master when the pellicle is attached to the exposure master. The flatness of the pellicle frame 1 can be calculated by measuring the height at a total of eight points, four points at each corner of the pellicle frame 1 and four points at the centers of the four sides, to calculate an imaginary plane, and then calculating the difference between the highest and lowest distances of each point from the imaginary plane.

[0045] The TiO2 coating layer 2 is formed by a sol-gel method, and preferably contains nitrogen. The nitrogen originates from the salt catalyst used when forming the TiO2 coating layer 2 using the sol-gel method. The use of a salt catalyst effectively promotes the polycondensation reaction of Ti alkoxide, the raw material for the TiO2 coating layer 2, resulting in the formation of a dense and homogeneous TiO2 coating layer 2, which more reliably ensures the trapping effect of foreign materials and low outgassing. The method for detecting nitrogen is not particularly limited, and various conventional elemental analysis methods can be used.

[0046] The TiO2 coating layer 2 is formed on the entire surface of the frame 4, and although there are no particular limitations on the thickness as long as it does not impair the effects of the present invention, it is preferably 10 nm to 50 μm.

[0047] Furthermore, it is preferable that a through-hole (not shown) is present in the pellicle frame 1, and that the inner surface of the through-hole is also formed with a TiO2 coating layer 2. When a through-hole is present in the frame 4, it is extremely difficult to completely remove foreign matter adhering to the inner surface of the through-hole, but by forming a dense and uniform TiO2 coating layer 2 also on the inner surface of the through-hole, excellent low dust generation properties can be ensured.

[0048] In the pellicle frame 1, the amount of hydrogen gas generated by extreme ultraviolet irradiation is preferably 1.2 times or less than the amount of hydrogen gas generated when the frame 4 is irradiated with extreme ultraviolet rays under the same conditions. The TiO2 coating layer 2 is a dense, homogeneous, and chemically stable ceramic layer, and even when irradiated with extreme ultraviolet rays, the amount of outgassing generated from the TiO2 coating layer 2 is extremely small. As a result, the amount of hydrogen gas generated by extreme ultraviolet irradiation can be made 1.2 times or less than the amount of hydrogen gas generated when the frame 4 is irradiated with extreme ultraviolet rays under the same conditions. A more preferable amount of hydrogen gas generated is 1.1 times or less, and most preferable amount of hydrogen gas generated is 1.05 times or less.

[0049] Furthermore, with regard to outgassing during extreme ultraviolet irradiation, not only hydrogen gas but also hydrocarbon gases such as C3H5 are effectively suppressed from being generated. Note that the method for measuring the amount of outgassing is not particularly limited, and various conventionally known gas analysis methods can be used.

[0050] In addition, when the pellicle frame 1 is immersed in 3 L of pure water and subjected to ultrasonic irradiation for 1 minute, the number of particles having a particle size of 1 to 15 μm present in 50 ml of the pure water is 600 particles / 68 cm 2 In the pellicle frame 1, foreign matter is trapped by the dense and uniform TiO2 coating layer 2 formed on the surface of the frame 4, so that even under harsh conditions such as when the pellicle frame 1 is immersed in pure water and irradiated with ultrasonic waves, the detachment of foreign matter (particles) is extremely effectively suppressed.

[0051] Here, when the pellicle frame 1 is immersed in 3 L of pure water and subjected to ultrasonic irradiation for 1 minute, the particles that are prevented from being released are not limited to those having a particle diameter of 1 to 15 μm. For example, the number of particles present in 50 ml of pure water is 2000 particles / 68 cm when the particle diameter is 0.5 to 1 μm. 2 It is preferable to do the following:

[0052] 2. Manufacturing method of pellicle frame 3, the method for manufacturing a pellicle frame of this embodiment includes a frame (substrate for optical component) fabrication step (S01) in which a substrate made of titanium or a titanium alloy is processed into the shape of the frame 4, and a coating step (S02) in which a TiO2 coating layer 2 is formed on the surface of the frame 4 by a sol-gel method. Each step will be described in detail below.

[0053] (1) Frame manufacturing process (S01) The frame body fabrication process (S01) is a process for obtaining the frame body 4, and is a process for obtaining the frame body 4 of the pellicle frame body 1 with high dimensional accuracy by performing joining, cutting, etc. on the titanium or titanium alloy material as necessary.

[0054] If the titanium or titanium alloy material has a sufficient size, the frame body 4 can be cut out from the material. On the other hand, the frame body 4 can also be obtained by joining titanium or titanium alloy materials, which can increase the yield of the titanium or titanium alloy material. Here, solid-state welding is preferably used to join titanium or titanium alloy materials. By using solid-state welding, it is possible to suppress distortion that occurs at the joint and to reduce the difference in mechanical properties between the joint and the base material. The frame body 4 obtained by cutting or joining may be further subjected to cutting processing.

[0055] It is also preferable to form a through-hole in the frame 4 and form the TiO2 coating layer 2 on the inner surface of the through-hole in the coating step (S02). Since the sol-gel method is used in the coating step (S02), the TiO2 coating layer 2 can be easily formed inside the through-hole.

[0056] (2) Coating process (S02) The coating step (S02) is a step for forming a TiO2 coating layer 2 on the surface of the frame body 4 obtained in the base material preparation step (S01).

[0057] As a pretreatment for the coating step (S02), it is preferable to degrease the frame 4. Specifically, oil can be removed by washing the frame 4 with acetone or the like, then washing it with pure water, and drying it. It is also preferable to chemically polish the frame 4 to smooth the surface.

[0058] Next, Ti alkoxide is used as the raw material for the TiO coating layer 2, and the TiO coating layer 2 can be formed on the surface of the frame 4 by hydrolysis and polycondensation of the Ti alkoxide. The method for applying the Ti alkoxide to the surface of the frame 4 is not particularly limited as long as it does not impair the effects of the present invention, but immersing the frame 4 (dip coating) is preferred. By applying dip coating, the TiO coating layer 2 can be formed simply and efficiently.

[0059] The morphology of the TiO2 coating layer 2 varies depending on the extent to which the Ti alkoxide undergoes hydrolysis before polymerization. Specifically, suppressing hydrolysis and promoting polycondensation results in low-dimensional growth, while promoting hydrolysis and suppressing polycondensation results in high-dimensional growth. Because low-dimensional growth can lead to gelation, promoting polycondensation is preferred when using Ti alkoxides with slow polycondensation rates as raw materials.

[0060] Furthermore, a nitrogen-containing salt catalyst is used in the process of forming the TiO2 coating layer 2 using the sol-gel method. The use of the nitrogen-containing salt catalyst can promote the polycondensation reaction.

[0061] Furthermore, a dense and uniform TiO2 coating layer 2 can be obtained by low-temperature heating of the Ti alkoxide gelled on the surface of the frame 4. The heating temperature is not particularly limited as long as it does not impair the effects of the present invention and can be adjusted appropriately depending on the desired state of the TiO2 coating layer 2, but low-temperature heating at 200 to 300°C is preferred. The polycondensation reaction of Ti alkoxide is promoted using a salt catalyst, and even when the TiO2 coating layer is formed by low-temperature firing at approximately 200 to 300°C, the crystallization of TiO2 is promoted. As a result, the finally obtained TiO2 coating layer 2 can be a good ceramic layer with a high degree of crystallinity.

[0062] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. [Example]

[0063] Example 1 A 50mm x 50mm x 1.5mm optical component substrate was cut out from a 2mm thick pure titanium plate (optical component substrate production process), and the surface was smoothed by chemical polishing. Next, a TiO2 coating layer was formed over the entire surface of the frame using a sol-gel method with Ti alkoxide as the raw material (coating process). A nitrogen-containing salt catalyst was used in the coating process, and a gelled Ti alkoxide layer was formed over the entire surface of the frame using dip coating. The frame was immersed in the raw material at a speed of 5mm / s and pulled out at a speed of 1mm / s.

[0064] Next, the frame with the gelled Ti alkoxide layer formed on the entire surface was baked at 300°C for 2 hours to form a TiO2 coating layer, thereby obtaining an example pellicle frame 1, which is an example of the present invention. When the film thickness of the TiO2 coating layer was observed by cross-sectional observation, it was found to be 20 to 30 nm.

[0065] Example 2 An example pellicle frame 2 was obtained in the same manner as in Example 1, except that the firing temperature was set to 200°C.

[0066] Comparative Example 1 A comparative pellicle frame 1 was obtained in the same manner as in Example 1, except that the entire surface of the frame was dip-coated with HoneyCeran PI-20 manufactured by Honey Chemical Co., Ltd. and the baking conditions were 150°C and 1 hour.

[0067] "Honeyceran PI-20" is a one-component baking paint for glass materials whose main component is polysiloxane resin, and an SiO2 coating layer is formed on the surface of the frame by baking.

[0068] Comparative Example 2 Comparative pellicle frame 2 was obtained in the same manner as in Example 1, except that the entire surface of the frame was dip-coated with "Sancerazane #200-1" manufactured by Sanwa Chemical Co., Ltd. and the baking conditions were 150°C and 1 hour.

[0069] "Suncelazane #200-1" is a mixture of 1% inorganic polysilazane and 90-99% dibutyl ether, and upon firing, an SiO2 coating layer is formed on the surface of the frame.

[0070] Comparative Example 3 A comparative pellicle frame 3 was obtained in the same manner as in Example 1, except that chemical polishing and coating treatment were not carried out.

[0071] Comparative Example 4 A comparative pellicle frame 4 was obtained in the same manner as in Example 1, except that no coating treatment was performed.

[0072] [evaluation] (1) Surface morphology changes due to extreme ultraviolet irradiation 4W / cm 2 The surface of each pellicle frame was irradiated with extreme ultraviolet light for 30 minutes, and the surface conditions before and after irradiation were observed using a scanning electron microscope (ULTRA PLUS, manufactured by Carl Zeiss). SEM photographs of Example Pellicle Frame 1, Example Pellicle Frame 2, Comparative Pellicle Frame 1, Comparative Pellicle Frame 2, and Comparative Pellicle Frame 4 are shown in Figures 4, 5, 6, 7, and 8, respectively.

[0073] In the example pellicle frame 1 and the example pellicle frame 2, no cracks or the like were generated by irradiation with extreme ultraviolet light, and a good surface condition was maintained. On the other hand, in the comparative pellicle frame, the coating layer was uneven even before irradiation, and it was found that the film formation properties were poor. In addition, peeling of the coating layer due to irradiation was also observed in the comparative pellicle frame 2.

[0074] The IR spectra of the surface before and after irradiation with extreme ultraviolet light were measured. An Agilent Technologies FT-IR 660-IR / 620-IR was used for the measurements. The IR spectra of Example Pellicle Frame 1, Example Pellicle Frame 2, Comparative Pellicle Frame 1, Comparative Pellicle Frame 2, and Comparative Pellicle Frame 4 are shown in Figures 9, 10, 11, 12, and 13, respectively.

[0075] In the example pellicle frame 1 and the example pellicle frame 2, no significant change was observed in the IR spectrum due to irradiation with extreme ultraviolet light, and it is clear that a good surface condition was maintained.

[0076] (2) Measurement of outgassing due to extreme ultraviolet radiation Each pellicle frame was placed in a vacuum chamber and evacuated. Next, measurements were taken in the range of 1 to 200 amu before extreme ultraviolet irradiation. Next, at 4 W / cm 2 After irradiation with extreme ultraviolet light, mass peaks were measured for 12 minutes in the range of 1 to 200 amu. Next, after irradiating different areas with extreme ultraviolet light, time-dependent changes were measured at specific amu (0 to 30 minutes).

[0077] The measurement results for hydrogen gas are shown in Figure 14, the measurement results for water and ammonia in Figure 15, and the measurement results for hydrocarbons in Figure 16. It can be seen that the amount of hydrogen gas and hydrocarbons emitted from the example pellicle frame 1 and example pellicle frame 2, on which a TiO2 coating layer was formed, was significantly reduced. Furthermore, for water and ammonia, although the amount of emissions was inferior to when no coating was applied, it was clearly reduced compared to when an SiO2 coating layer was formed.

[0078] (3) Evaluation of dust generation amount The amount of dust generated was evaluated by liquid particle evaluation. Specifically, after ultrasonic cleaning of a glass beaker with pure water, 3 L of pure water was collected in the beaker, and the blank value was measured using a liquid particle counter (NP500T, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0079] Next, the pellicle frame was immersed in pure water and subjected to ultrasonic irradiation for 1 minute. After that, the pellicle frame was removed and the number of particles in 50 ml of pure water was measured using a liquid particle counter. The results are shown in Table 1. The values ​​in Table 1 are converted values ​​(particles / 68 cm 2 )

[0080] [Table 1]

[0081] When an SiO2 coating layer was formed (Comparative Pellicle Frame 1 and Comparative Pellicle Frame 2), no reduction in the amount of dust generated was observed due to the formation of the coating layer, and in fact the amount of dust generated tended to increase compared to the state where only chemical polishing was performed (Comparative Pellicle Frame 4).In contrast, it can be seen that the amount of dust generated by Example Pellicle Frame 1 and Example Pellicle Frame 2, on which a TiO2 coating layer was formed, was significantly reduced.

[0082] (4) Evaluation of ion elution amount The pellicle frame was immersed in 100 ml of pure water in a polyethylene bag, then placed in a 90°C water bath and left to stand for 3 hours. It was then transferred to a room-temperature water bath to cool, after which the amount of ions in the pure water (pellicle frame immersion solution) was measured using ion chromatography (anions) and absorptiometry (NH4). A Thermo Integrion RFIC was used for ion chromatography, and a JASCO Spectrophotometer V-630 was used for absorptiometry. The results are shown in Table 2.

[0083] [Table 2]

[0084] No significant increase in the amount of ion elution was observed in the example pellicle frame 1 and example pellicle frame 2, which had a TiO2 coating layer formed on them, and it can be seen that the pellicle frame of the present invention has good characteristics in terms of the amount of ion elution. [Explanation of symbols]

[0085] 1. Pellicle frame body, 2. TiO2 coating layer, 4...Frame body.

Claims

1. a substrate made of titanium or a titanium alloy; TiO formed on the surface of the substrate 2 a coating layer; The TiO 2 The coating layer contains nitrogen; An optical element characterized by:

2. The substrate has through holes, The TiO 2 A coating layer is formed; The optical member according to claim 1 ,

3. the amount of hydrogen gas generated by irradiation with extreme ultraviolet rays is 1.2 times or less than the amount of hydrogen gas generated when the substrate is irradiated with extreme ultraviolet rays under the same conditions; 3. The optical member according to claim 1 or 2,

4. When immersed in 3 L of pure water and subjected to ultrasonic irradiation for 1 minute, the number of particles having a particle size of 1 to 15 μm present in 50 ml of the pure water was 600 particles / 68 cm 2 That is:

3. The optical member according to claim 1 or 2,

5. When immersed in 3 L of pure water and subjected to ultrasonic irradiation for 1 minute, the number of particles having a particle size of 0.5 to 1 μm present in 50 ml of the pure water was 2000 particles / 68 cm 2 That is:

3. The optical member according to claim 1 or 2,

6. a process for preparing a substrate for an optical member, in which a substrate made of titanium or a titanium alloy is processed into the shape of a substrate for an optical member; The surface of the substrate for optical members is coated with TiO using a sol-gel method. 2 a coating step of forming a coating layer, using a nitrogen-containing salt catalyst in the coating step; A method for manufacturing an optical member, comprising:

7. In the optical member substrate preparation step, a through hole is formed in the optical member substrate, In the coating process, the TiO 2 forming a coating layer; The method for producing an optical member according to claim 6,

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