JP2010192503A - Photomask and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein atom-like hydrogen enters a light-shielding film, metal including tantalum having hydrogen brittleness, niobium, and vanadium, or at least two of tantalum, niobium, and vanadium is embrittled for deformation when a photomask using metal comprising tantalum, niobium, and vanadium, or at least two of tantalum, niobium, and vanadium as a light-shielding film is cleaned by acid cleaning or hydrogen plasma. <P>SOLUTION: The light-shielding film 23 as a metal film is airtightly sealed by using a metal oxide obtained by oxidizing the light-shielding film 23 as a hydrogen stop film 24. The hydrogen stop film 24 is arranged so that it covers the light-shielding film 23, and has a function of preventing hydrogen atoms generated when performing acid cleaning or hydrogen plasma cleaning from entering the light-shielding film 23, thus preventing deformation of the light-shielding film 23 caused by hydrogen brittleness of the light-shielding film 23 because of entering of atom-like hydrogen in the cleaning process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photomask and a photomask manufacturing method.

  Tantalum has been used as a light-shielding material for a photomask because it has superior adhesion to tantalum pentoxide used for a phase shift mask compared to chromium, which has been the mainstay in the past. In addition, tantalum has recently been developed as an absorption film because it has a higher absorption coefficient than chromium and is excellent in fine workability when used as an absorption film for EUV (Extreme, Ultra, and Violet) exposure. Has been promoted. In addition, the use of niobium or vanadium having the same characteristics as tantalum, or a metal composed of at least two of tantalum, niobium, and vanadium has been studied.

  When a photomask is used, for example, when dust existing in the atmosphere adheres to the photomask, the light pattern on the substrate to be exposed is deformed, resulting in a disadvantage that the resist pattern becomes defective. As an example of a photomask using a tantalum film, for example, Patent Document 1 can be cited.

  For this reason, it is necessary to periodically perform a photomask cleaning process for removing the attached dust or when dust adheres to the photomask. For cleaning, cleaning in a dry atmosphere in which dust is removed using hydrogen plasma or plasma in which hydrogen is added to a rare gas, or cleaning in a wet atmosphere using an acid is preferably used. As an example of cleaning in a wet atmosphere using an acid, for example, Patent Document 2 can be cited.

JP 2002-82423 A JP 2007-233179 A

  When cleaning a photomask using acid cleaning or hydrogen plasma and using a metal composed of at least two of tantalum, niobium, vanadium or tantalum, niobium, and vanadium as a light-shielding film, a phenomenon that the light-shielding film is deformed is observed. It has become an issue. This is because atomic hydrogen is not suitable for cleaning using a mixed solution of sulfuric acid and hydrogen peroxide (also called a piranha solution) that is preferably used for acid cleaning, or when cleaning using hydrogen plasma. It has been found that a metal including at least two of tantalum, niobium, vanadium or tantalum, niobium, and vanadium having hydrogen embrittlement enters the light shielding film and becomes brittle and deformed. If the light-shielding film is deformed, the pattern transferred by the photomask is also deformed and cannot perform as designed, so it must be discarded, but the photomask is expensive and the photomask is not cleaned. Since this is an indispensable process for maintaining pattern accuracy, a photomask that can withstand cleaning and a manufacturing method for obtaining a photomask that can withstand cleaning are required.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples. Here, “upper” is defined as indicating the normal direction of the substrate from the substrate toward the metal film.

  Application Example 1 A photomask according to this application example includes a substrate, a metal film having a pattern shape on the substrate, and a hydrogen blocking film that hermetically covers an upper surface and side surfaces of the metal film. And

  According to this, the metal film is hermetically covered with the hydrogen blocking film. By covering the metal film hermetically with the hydrogen blocking film, it becomes possible to prevent the deformation of the pattern shape due to hydrogen embrittlement caused by the penetration of hydrogen into the metal film. Therefore, even when acid cleaning in which the metal film is in contact with atomic hydrogen or hydrogen plasma cleaning is performed, generation of hydrogen embrittlement can be suppressed and the pattern shape can be maintained.

  Application Example 2 A photomask according to this application example includes a substrate, a reflective film positioned on the substrate, a multilayer film having a pattern shape on the reflective film and including a metal film, and the metal film And a hydrogen blocking film that hermetically covers an upper surface and a side surface.

  According to this, the multilayer film is hermetically covered with the hydrogen blocking film. By covering the multilayer film hermetically with a hydrogen blocking film, it becomes possible to prevent deformation of the pattern shape due to hydrogen embrittlement due to hydrogen intrusion into the multilayer film. Even when cleaning is performed, the occurrence of hydrogen embrittlement can be suppressed and the pattern shape can be maintained. In addition, by providing a multilayer film structure, when applied to a reflective photomask capable of dealing with extreme ultraviolet (EUV) light, the film thickness of the multilayer film can be adjusted to the wavelength of EUV light to increase the absorption rate. By matching the film thickness, higher contrast can be obtained.

  Application Example 3 In the photomask according to the application example described above, the hydrogen blocking film is an oxide film derived from the metal film.

  According to the application example described above, a denser film than the hydrogen blocking film formed by the deposition method can be obtained. Therefore, higher hydrogen blocking performance can be obtained. Further, by forming the hydrogen blocking film by oxidation, it is possible to form the hydrogen blocking film with high uniformity, for example, on the pattern side surface of the metal film. In addition, the hydrogen blocking film obtained by oxidation has higher adhesion than the film formed by the deposition method, so that it is difficult for the film to peel off and a photomask with higher durability is obtained. It becomes possible to provide.

  Application Example 4 In the photomask according to the application example described above, the thickness of the hydrogen blocking film is 5 nm or more and 100 nm or less.

  According to the application example described above, when the thickness of the hydrogen blocking film is 5 nm or more, it is possible to suppress the intrusion of hydrogen even when the metal film is subjected to acid cleaning or hydrogen plasma cleaning in contact with atomic hydrogen. It becomes. Further, if the thickness of the hydrogen blocking film is 100 nm or less, it is possible to suppress the penetration of hydrogen by suppressing a decrease in pattern shape accuracy.

  Application Example 5 A photomask according to the application example described above, wherein the optical length of the hydrogen blocking film in the normal direction of the substrate is matched with the wavelength of exposure light.

  According to the application example described above, the phase of the exposure light in the hydrogen blocking film is approximately 360 °. That is, it becomes optically transparent with respect to the exposure wavelength. Therefore, the influence on the light distribution near the edge of the photomask can be avoided. For example, when ArF excimer laser light having a wavelength of 193 nm is used and tantalum oxide is used as the hydrogen blocking film, optical interference can be avoided by setting the film thickness to about 80 nm.

  Application Example 6 In the photomask according to the application example described above, the optical length of the hydrogen blocking film in the normal direction of the substrate is adjusted to an integral multiple of half the wavelength of the exposure light. It is characterized by.

  According to the application example described above, the phase of the exposure light in the hydrogen blocking film is approximately 180 °. This film thickness is substantially equal to the amount of phase modulation in the phase shift pattern. Therefore, it can be shared with the phase shift portion of the photomask. For example, when ArF excimer laser light having a wavelength of 193 nm is used and tantalum oxide is used as the hydrogen blocking film, the thickness is matched to this condition if the film thickness is about 40 nm.

  Application Example 7 In the photomask according to the application example described above, the metal film is a metal composed of tantalum, niobium, vanadium, or at least two of tantalum, niobium, and vanadium.

  According to the application example described above, a metal composed of at least two of tantalum, niobium, vanadium, or tantalum, niobium, and vanadium has a high absorption rate of extreme ultraviolet (EUV) light when used as a reflective photomask, for example. Compared with the case of using a metal such as chromium, a photomask with higher contrast can be obtained.

  Moreover, it is excellent in workability, and a particularly fine pattern shape can be obtained. Furthermore, since the adhesiveness between the above-described metal and the above-described metal oxide is high, it is possible to provide a photomask with excellent film durability in which film peeling is suppressed. Note that “a metal composed of at least two of tantalum, niobium, and vanadium” includes a state in which a mixture, a laminate, and the like are exhibited in addition to the alloy.

  Application Example 8 A photomask manufacturing method according to this application example includes a substrate, a metal film having a pattern shape on the substrate, and a hydrogen blocking film that hermetically covers an upper surface and side surfaces of the metal film. A method of manufacturing a photomask, wherein the metal film is oxidized by an anodic oxidation method, a thermal oxidation method in an oxidizing atmosphere, a plasma oxidation method using gas plasma in an oxidizing atmosphere, or an oxidation process combining these, and the hydrogen It is characterized by obtaining a blocking film.

  According to this, it becomes possible to obtain a hydrogen blocking film having excellent coverage. Specifically, a hydrogen blocking film having a high film thickness uniformity can be obtained even in a portion that tends to be shaded such as a pattern side surface. In addition, when the anodic oxidation method is used, a thick oxide film is formed at the electrical weak point. Since a dense metal oxide film obtained by the anodic oxidation method can be obtained, a method for manufacturing a photomask with higher reliability can be provided.

  In addition, when the anodizing method is used, it is once exposed from the vacuum atmosphere to the air atmosphere, and there is a possibility that the hydrogen in the air is occluded when it is exposed to the air. The phenomenon of hydrogen in the atmosphere entering into the metal film is avoided by using an anodic oxidation method (combined oxidation process) after forming a thin hydrogen blocking film after exposure to oxygen atmosphere It is also possible.

  Application Example 9 A photomask manufacturing method according to this application example includes a substrate, a reflective film disposed on the substrate, a multilayer film having a pattern shape and including a metal film located on the reflective film, And a hydrogen blocking film that hermetically covers an upper surface and side surfaces of the metal film, wherein the hydrogen blocking film is formed by using an anodic oxidation method, a thermal oxidation method in an oxidizing atmosphere, and an oxidizing atmosphere gas. It is characterized by being obtained by oxidizing the metal film by a plasma oxidation method using plasma or an oxidation process combining these.

  According to this, it becomes possible to obtain a hydrogen blocking film having excellent coverage. Specifically, a hydrogen blocking film having high uniformity can be obtained even in a portion that tends to be shaded, such as a pattern side surface. In addition, when the anodic oxidation method is used, a thick oxide film is formed at the electrical weak point. Since a dense metal oxide film obtained by the anodic oxidation method can be obtained, a method for manufacturing a photomask with higher reliability can be provided.

  In addition, when the anodizing method is used, it is once exposed from the vacuum atmosphere to the air atmosphere, and there is a possibility that the hydrogen in the air is occluded when it is exposed to the air. The phenomenon of hydrogen in the atmosphere entering into the metal film is avoided by using an anodic oxidation method (combined oxidation process) after forming a thin hydrogen blocking film after exposure to oxygen atmosphere It is possible.

  Moreover, when it is applied to a reflective photomask capable of dealing with extreme ultraviolet (EUV) light by providing a multilayer film structure, the film thickness of each layer can be adjusted to the wavelength of EUV light to increase the absorption rate. By providing the distribution, a higher light absorption rate can be obtained. The “reflective film” includes a protective film for the reflective film and a buffer film.

  Application Example 10 In the photomask manufacturing method according to the application example described above, the metal film is formed using tantalum, niobium, vanadium, or a metal composed of at least two of tantalum, niobium, and vanadium. It is characterized by that.

  According to the application example described above, when a metal composed of at least two of tantalum, niobium, vanadium, or tantalum, niobium, and vanadium is used, for example, when used as a reflective photomask, the above-described metal is extreme ultraviolet (EUV). ) It is possible to obtain a photomask having a high light absorption rate and higher contrast than the case of using a metal such as chromium.

  Moreover, it is excellent in workability, and a particularly fine pattern shape can be obtained. Furthermore, when used as a transmission type photomask, since the adhesion between the above-described metal and the above-described metal oxide is high, it is possible to provide a photomask with excellent film durability, in which film peeling is suppressed. Become. Note that “a metal composed of at least two of tantalum, niobium, and vanadium” includes a state in which a mixture, a laminate, and the like are exhibited in addition to the alloy.

  Application Example 11 In the photomask manufacturing method according to the application example described above, when the metal film or the multilayer film is in a state before the oxidation process, a decrease in the metal film due to the oxidation process is corrected in advance. It is characterized by having a pattern shape.

  According to the application example described above, it is possible to form the pattern shape with high accuracy by correcting the loss due to the oxidation process.

(A) is a top view which shows the structure of the photomask concerning this embodiment, (b) is sectional drawing in the A-A 'line of (a). Sectional drawing which shows the example of the exposure optical system which used the photomask. (A) is a top view which shows the structure of the photomask concerning this embodiment, (b) is sectional drawing in the A-A 'line of (a). (A)-(c) is process sectional drawing which shows the manufacturing process of a photomask. (A)-(c) is process sectional drawing which shows the manufacturing process of a photomask.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

(First embodiment: reflective photomask)
Hereinafter, the structure of the photomask will be described with reference to the drawings. FIG. 1A is a plan view showing the configuration of the photomask according to the present embodiment, and FIG. 1B is a cross-sectional view taken along the line AA ′ in FIG. The photomask 10 includes a substrate 11, a reflection film 12, a light absorption film 13 as a metal film or a multilayer film, and a hydrogen blocking film 14. The photomask 10 functions as a reflective photomask that reflects incident light and transfers a mask pattern.

  The substrate 11 is formed using, for example, quartz or glass having a small thermal expansion coefficient, and has a function of supporting a reflection film 12, a light absorption film 13, and a hydrogen blocking film 14, which will be described later.

  The reflection film 12 is formed using, for example, a multilayer film and has a function of reflecting EUV light. As a typical example, a molybdenum film having a film thickness of 2.6 nm and a silicon film having a film thickness of 4.1 nm alternately deposited by about 50 layers can be used. Note that it is also preferable to provide a protective film on the reflective film 12 in order to prevent a decrease in reflectance due to damage in the manufacturing process. In addition, when a stress or the like is generated between the substrate 11 and the reflective film 12, a buffer film may be provided.

  The light absorption film 13 absorbs the incident EUV light and generates “black” information. As the light absorption film 13, it is preferable to use a film in which tantalum is formed with a film thickness of about 100 nm. Instead of tantalum, niobium, vanadium, or a metal containing at least two of tantalum, niobium, and vanadium may be used. Alternatively, a multilayer film structure including the metal film made of the metal described above and a metal oxide film, a dielectric film, a silicon film, a silicon oxide film, or the like may be used.

  The hydrogen blocking film 14 is disposed so as to cover the light absorption film 13 and has a function of preventing intrusion of hydrogen atoms generated when performing acid cleaning or hydrogen plasma cleaning into the light absorption film 13. The hydrogen blocking film 14 is preferably a film obtained by oxidizing the light absorption film 13 from the viewpoint of adhesion and the like, and preferably has a thickness of about 5 nm to 100 nm. . If the thickness is 5 nm or more, it is possible to suppress the transmission of hydrogen atoms. Further, by setting the thickness to 100 nm or less, it is possible to suppress the attenuation of EUV light and reach the reflective film 12. The hydrogen blocking film 14 is disposed including the upper and side surfaces of the light absorption film 13 and is kept airtight. Therefore, it is possible to suppress the occurrence of hydrogen embrittlement associated with hydrogen absorption.

  FIG. 2 is a sectional view showing an example of an exposure optical system using a photomask. The EUV light source 100 is used as an exposure light source, and the photomask 10 is illuminated by being incident obliquely at an incident angle θ. Although the incident angle θ is different in various optical systems, it is about 1 ° to 15 °. As shown in FIG. 1, the photomask 10 includes a reflection film 12 and a light absorption film 13 as a pattern having a predetermined shape. The EUV light reflected by the photomask 10 is reflected by the convex mirror 101, further reflected by the concave mirror 102, and forms an image on the wafer 103. A multilayer film is formed on the convex mirror 101 and the concave mirror 102 to reflect EUV light. Here, a region drawn by a dotted line of the concave mirror 102 is opened, and has a configuration that allows light reflected from the photomask 10 to pass therethrough.

  In the photomask 10 in this embodiment, a metal film containing at least two of tantalum, niobium, vanadium, tantalum, niobium, and vanadium, a multilayer film with an oxide film of the metal, or the like is used as the light absorption film 13. Therefore, EUV light can be absorbed efficiently. In addition, since the hydrogen blocking film 14 including the side surface of the light absorption film 13 is provided, the cleaning is performed using a mixed solution of sulfuric acid and hydrogen peroxide, or cleaning using hydrogen plasma. Intrusion of atomic hydrogen can be suppressed. Therefore, it is possible to provide a photomask in which deterioration due to the cleaning process is suppressed.

(Second Embodiment: Transmission Photomask)
Hereinafter, a transmission type photomask will be described as a second embodiment. FIG. 3A is a plan view showing the configuration of the photomask according to the present embodiment, and FIG. 3B is a cross-sectional view taken along the line AA ′ in FIG. The photomask 20 includes a substrate 21, a light shielding film 23 as a metal film, and a hydrogen blocking film 24.

  The substrate 21 is formed using, for example, quartz or glass having a small thermal expansion coefficient, and has a function of supporting a light shielding film 23 and a hydrogen blocking film 24 described later.

  The light shielding film 23 shields incident ultraviolet light and generates “black” information. As the light shielding film 23, it is preferable to use a film in which tantalum is formed with a film thickness of about 100 nm. Further, instead of tantalum, a metal composed of niobium, vanadium, or at least two of tantalum, niobium, and vanadium may be used. As the film thickness, for example, it is necessary to increase the thickness of the photoresist used in the process of manufacturing the photomask when the thickness is about 100 nm. (Accuracy decreases), which is preferable.

  The hydrogen blocking film 24 is disposed so as to cover the light shielding film 23, and has a function of preventing the entry of hydrogen atoms generated when performing acid cleaning or hydrogen plasma cleaning into the light shielding film 23. The hydrogen blocking film 24 is preferably a film obtained by oxidizing the light shielding film 23 from the viewpoint of adhesion and the like, and preferably has a thickness of about 5 nm to 100 nm. If the thickness is 5 nm or more, it is possible to suppress the transmission of hydrogen atoms. In addition, by setting the thickness to 100 nm or less, it is possible to transmit ultraviolet light while suppressing attenuation of ultraviolet light.

  It is also preferable to match the optical length of the hydrogen blocking film 24 in the normal direction of the substrate 21 with an integral multiple of the exposure light wavelength. In this case, the hydrogen blocking film 24 is optically transparent, It does not affect the light transmitting portion of the photomask 20. For example, when ArF excimer laser light having a wavelength of 193 nm is used and tantalum oxide is used as the hydrogen blocking film 24, optical interference can be avoided if the film thickness is about 80 nm. In this case, the thickness of the light shielding film 23 may be reduced to the thickness of the tantalum oxide (hydrogen blocking film 24) in the normal direction of the substrate 21. The thickness of the light shielding film 23 is increased to about 160 nm ( The thickness may be twice the wavelength).

  It is also preferable to match the optical length of the hydrogen blocking film 24 in the normal direction of the substrate 21 with an integral multiple of half the exposure light wavelength. The phase changes by π. Therefore, the hydrogen blocking film 24 can be used as a phase shift region. For example, when ArF excimer laser light having a wavelength of 193 nm is used and tantalum oxide is used as the hydrogen blocking film, the film can be used as a phase shift region by setting the film thickness to about 40 nm. In this case, it is also preferable to control the light transmission amount using a metal composed of at least two of tantalum, niobium, and vanadium, or tantalum, niobium, and vanadium.

(Third Embodiment: Manufacturing Method of Reflective Photomask)
Hereinafter, a photomask manufacturing method will be described with reference to the drawings. Here, a manufacturing method of the reflective photomask shown in FIG. 1 will be described. 4A to 4C are process cross-sectional views illustrating the photomask manufacturing process according to the present embodiment.

  First, quartz, heat resistant glass having a small thermal expansion coefficient, or the like is prepared as the substrate 11.

  Next, the reflective film 12 is formed using a sputtering method or the like. As the reflective film 12, a film in which about 50 layers of a molybdenum film having a film thickness of 2.6 nm and a silicon film having a film thickness of 4.1 nm are alternately deposited can be used.

  Next, the light absorption film 13 is formed using a sputtering method or the like. As the light absorption film 13, it is preferable to use a film in which tantalum is formed with a film thickness of about 100 nm. Instead of tantalum, niobium, vanadium, or a metal containing at least two of tantalum, niobium, and vanadium may be used. Further, a multilayer film structure including the metal described above and a metal oxide film, a dielectric, silicon, silicon oxide, or the like may be used.

  Next, a photoresist precursor 17a is applied using a spin coat method or the like. FIG. 4A shows a process cross-sectional view after the steps so far.

  Then, after application, heat treatment is performed to form a photoresist 17. The photoresist 17 preferably has a thickness of about 400 nm. When it is too thick, the dimensional accuracy in electron beam exposure described later is lowered, and the pattern accuracy is lowered. If it is too thin, the photoresist 17 will be reduced or disappeared when the light absorbing film 13 is etched, making it difficult to pattern. Here, the value of 400 nm is one suitable value. However, the thickness may be reduced if the selection ratio in etching can be increased, and the thickness needs to be increased if the selection ratio cannot be obtained.

  Next, the photoresist 17 is irradiated with an electron beam based on the CAD data to be exposed and developed. In this case, in the CAD data, the amount of reduction due to the reduction in proximity effect or the like that occurs when performing electron beam exposure may be corrected. In addition, it is preferable to include in advance a dimensional variation associated with an oxidation step of the light absorption film 13 described later. FIG. 4B shows a process cross-sectional view after the steps so far are completed.

  Next, dry etching is performed using the photoresist 17 as a mask. For example, parallel plate type reactive ion etching (RIE) can be used for dry etching, and a mixed gas of tetrachloromethane and oxygen or a mixed gas of dichloromethane and oxygen can be used as an etching gas. FIG. 4C shows a process cross-sectional view after the steps so far are completed.

  Next, the photoresist 17 is removed by ashing using a gas such as argon. This step may be removed by wet treatment in order to reduce damage to the base. After this step, it is also preferable to take a step of inspecting, investigating and correcting dust and defects. Next, a hydrogen blocking film 14 is formed on the light absorption film 13 by using an anodic oxidation method. Here, it is preferable that the film thickness of the hydrogen blocking film 14 formed by using the anodic oxidation method has a value of about 5 nm or more and 100 nm or less. If the thickness is 5 nm or more, it is possible to suppress the transmission of hydrogen atoms. Further, by setting the thickness to 100 nm or less, it is possible to suppress the attenuation of EUV light and reach the reflective film 12. Here, instead of the anodic oxidation method, the oxide film may be formed by a thermal oxidation method in an oxidizing atmosphere, a plasma oxidation method using gas plasma in an oxidizing atmosphere, or an oxidation process combining these. Further, since a substrate 11 having high heat resistance is used, it is also preferable to perform thermal oxidation or plasma oxidation, and the pattern is free as compared with the anodic oxidation method in which the pattern needs to be electrically connected. The degree becomes higher.

  Before using the anodic oxidation method, the substrate 11 from which the photoresist 17 has been removed is exposed to argon plasma or the like in an oxygen-free atmosphere to remove the natural oxide film, and then the substrate 11 is placed in a vacuum atmosphere to release hydrogen. Thereafter, an oxidizing atmosphere may be introduced without exposing to the air to form an oxide film that covers the light absorption film 13, and then exposed to the air to perform anodic oxidation. In this case, since this oxide film functions as a hydrogen blocking film, it is possible to suppress the intrusion of hydrogen in the atmosphere and to realize a state where hydrogen is removed in the initial state when anodizing is performed. Thus, the light absorption film 13 with higher reliability can be formed. Further, instead of the anodic oxidation method, the substrate 11 from which the photoresist 17 has been removed is exposed to argon plasma or the like in an oxygen-free atmosphere to remove the natural oxide film, and then the substrate 11 is placed in a vacuum atmosphere to release hydrogen. Alternatively, the hydrogen blocking film 14 made of an oxide film covering the light absorption film 13 may be formed by introducing an oxidizing atmosphere without being exposed to the air and further raising the temperature of the substrate 11. Even in this case, a state in which hydrogen is removed in the initial state can be realized. Furthermore, compared to the anodic oxidation method, it is not necessary to connect the patterns electrically, so that the degree of freedom of pattern becomes higher. Here, oxygen, laughing gas, ozone, oxygen plasma, or the like can be used as the oxidizing atmosphere.

  Further, as described above, it is also preferable to use the dimension corrected for the dimensional variation due to the oxidation process in the CAD data in advance or by correcting the CAD data with a post processor. As a final structure, the photomask shown in FIG. 1 is manufactured. By following the above-described steps, it is possible to provide a photomask manufacturing method having high resistance to acid cleaning and hydrogen plasma cleaning.

(Fourth embodiment: transmissive photomask)
Hereinafter, a method for manufacturing a transmissive photomask will be described with reference to the drawings. Here, a manufacturing method of the transmission type photomask shown in FIG. 3 will be described. 5A to 5C are process cross-sectional views illustrating the photomask manufacturing process according to the present embodiment.

  First, quartz, heat resistant glass having a small thermal expansion coefficient, or the like is prepared as the substrate 21.

  Next, the light shielding film 23 is formed using a sputtering method or the like. As the light shielding film 23, it is preferable to use a film in which tantalum is formed with a film thickness of about 100 nm. Instead of tantalum, niobium, vanadium, or a metal containing at least two of tantalum, niobium, and vanadium may be used.

  Next, a photoresist precursor 27a is applied using a spin coat method or the like. FIG. 5A shows a process cross-sectional view after the steps so far. Then, after application, heat treatment is performed to form a photoresist 27. FIG. 5B shows a process cross-sectional view after the steps so far are completed. The photoresist 27 preferably has a thickness of about 400 nm. When it is too thick, the dimensional accuracy in electron beam exposure described later is lowered, and the pattern accuracy is lowered. If it is too thin, the photoresist 27 will be lost or disappeared when the light shielding film 23 is etched, making it difficult to pattern accurately.

  Next, based on the CAD data, the photoresist 27 is exposed to an electron beam for exposure and development. In this case, in the CAD data, the amount of reduction due to the reduction in proximity effect or the like that occurs when performing electron beam exposure may be corrected. In addition, it is preferable to include in advance a dimensional variation associated with an oxidation process of the light shielding film 23 described later.

  Next, dry etching is performed using the photoresist 27 as a mask. For example, parallel plate type reactive ion etching (RIE) can be used for dry etching, and a mixed gas of tetrachloromethane and oxygen or a mixed gas of dichloromethane and oxygen can be used as an etching gas. FIG. 5C shows a process cross-sectional view after the steps so far are completed.

  Next, the photoresist 27 is removed by ashing using a gas such as argon. This step may be removed by wet treatment in order to reduce damage to the base. After this step, it is also preferable to take a step of inspecting, investigating and correcting dust and defects.

  Next, the hydrogen blocking film 24 is formed on the light shielding film 23 by using an anodic oxidation method. Here, it is preferable that the film thickness of the hydrogen blocking film 24 formed by using the anodic oxidation method has a value of about 5 nm or more and 100 nm or less. If the thickness is 5 nm or more, it is possible to suppress the transmission of hydrogen atoms. In addition, by setting the thickness to 100 nm or less, it is possible to suppress the attenuation of EUV light and reach the substrate 21. Here, instead of the anodic oxidation method, the oxide film may be formed by a thermal oxidation method in an oxidizing atmosphere, a plasma oxidation method using gas plasma in an oxidizing atmosphere, or an oxidation process combining these. Further, since a substrate 21 having high heat resistance is used, it is also preferable to perform thermal oxidation or plasma oxidation, and the pattern is free as compared with the anodic oxidation method in which the pattern needs to be electrically connected. The degree becomes higher.

  Before using the anodic oxidation method, the substrate 21 from which the photoresist 27 has been removed is exposed to argon plasma or the like in an oxygen-free atmosphere to remove the natural oxide film, and then the substrate 21 is placed in a vacuum atmosphere to release hydrogen. Thereafter, an oxidizing atmosphere may be introduced without exposing to the air to form an oxide film that covers the light-shielding film 23, and then exposing to the air to perform anodization. In this case, since this oxide film functions as a hydrogen blocking film, it is possible to suppress the intrusion of hydrogen in the atmosphere and to realize a state where hydrogen is removed in the initial state when anodizing is performed. Thus, the light-shielding film 23 with higher reliability can be formed. Further, instead of the anodic oxidation method, the substrate 21 from which the photoresist 27 has been removed is exposed to argon plasma or the like in an oxygen-free atmosphere to remove the natural oxide film, and then the substrate 21 is placed in a vacuum atmosphere to release hydrogen. Alternatively, the hydrogen blocking film 24 made of an oxide film covering the light shielding film 23 may be formed by introducing an oxidizing atmosphere without being exposed to the air and further raising the temperature of the substrate 21. Even in this case, a state in which hydrogen is removed in the initial state can be realized. Furthermore, compared to the anodic oxidation method, it is not necessary to connect the patterns electrically, so that the degree of freedom of pattern becomes higher. Here, oxygen, laughing gas, ozone, oxygen plasma, or the like can be used as the oxidizing atmosphere.

  Further, as described above, it is also preferable to use the dimension corrected for the dimensional variation due to the oxidation process in the CAD data in advance or by correcting the CAD data with a post processor. As a final structure, the photomask shown in FIG. 3 is manufactured. By following the above-described steps, it is possible to provide a photomask manufacturing method having high resistance to acid cleaning and hydrogen plasma cleaning.

  DESCRIPTION OF SYMBOLS 10 ... Photomask, 11 ... Substrate, 12 ... Reflective film, 13 ... Light absorption film, 14 ... Hydrogen blocking film, 17 ... Photoresist, 17a ... Photoresist precursor, 20 ... Photomask, 21 ... Substrate, 23 ... Light shielding Membrane, 24 ... hydrogen blocking film, 27 ... photoresist, 27a ... photoresist precursor, 100 ... EUV light source, 101 ... convex mirror, 102 ... concave mirror, 103 ... wafer.

Claims (11)

A substrate,
A metal film having a pattern shape on the substrate;
And a hydrogen blocking film that hermetically covers an upper surface and a side surface of the metal film. A substrate,
A reflective film located on the substrate;
A multilayer film having a pattern shape and including a metal film located on the reflective film;
And a hydrogen blocking film that hermetically covers an upper surface and a side surface of the metal film.   3. The photomask according to claim 1, wherein the hydrogen blocking film is an oxide film derived from the metal film.   4. The photomask according to claim 1, wherein the hydrogen blocking film has a thickness of 5 nm or more and 100 nm or less. 5.   4. The photomask according to claim 1, wherein an optical length of the hydrogen blocking film in a normal direction of the substrate is matched with a wavelength of exposure light. 5. Photo mask to be used.   4. The photomask according to claim 1, wherein an optical length of the hydrogen blocking film in a normal direction of the substrate is adjusted to an integral multiple of a half of a wavelength of exposure light. A photomask characterized by comprising:   7. The photomask according to claim 1, wherein the metal film is made of tantalum, niobium, vanadium, or a metal composed of at least two of tantalum, niobium, and vanadium. mask. A substrate,
A metal film having a pattern shape on the substrate;
A hydrogen blocking film that hermetically covers an upper surface and a side surface of the metal film, and a photomask manufacturing method comprising:
The metal film is oxidized by an anodic oxidation method, a thermal oxidation method in an oxidizing atmosphere, a plasma oxidation method using an oxidizing atmosphere gas plasma, or an oxidation process combining these, to obtain the hydrogen blocking film. Photomask manufacturing method. A substrate,
A reflective film disposed on the substrate;
A multilayer film having a pattern shape and including a metal film located on the reflective film;
A hydrogen blocking film that hermetically covers an upper surface and a side surface of the metal film, and a photomask manufacturing method comprising:
The hydrogen blocking film is obtained by oxidizing the metal film by an anodic oxidation method, a thermal oxidation method in an oxidizing atmosphere, a plasma oxidation method using an oxidizing atmosphere gas plasma, or an oxidation process combining these. A method for manufacturing a photomask.   10. The method for manufacturing a photomask according to claim 8, wherein the metal film is formed using a metal composed of at least two of tantalum, niobium, and vanadium, or tantalum, niobium, and vanadium. A manufacturing method of a photomask.   11. The method of manufacturing a photomask according to claim 8, wherein when the metal film or the multilayer film is in a state before the oxidation process, a decrease in the metal film due to the oxidation process is calculated. A photomask manufacturing method comprising a pattern shape corrected in advance.

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