Photomask blank, method for manufacturing photomask, and photomask

Abstract

To provide a photomask blank excellent in surface roughness of a chromium containing film, capable of detecting a defect of 50 nm, small in value of resistance, capable of adsorbing foreign matters, and capable of reading a bar code pattern.SOLUTION: A photomask blank includes a substrate and a chromium containing film. The chromium containing film has first to third layers from the side away from the substrate, all layers contain chromium. The first layer further contains oxygen and nitrogen and has a content of Cr: 44 atom% or less, O: 30 atom% or more, and N: 26 atom% or less, and a thickness of 8-20 nm. The second layer further contains nitrogen and has a content of Cr: 66-92 atom%, and N: 8-34 atom%, and a thickness of 40-70 or less nm. The third layer further contains oxygen and nitrogen and has a content of Cr: 44 atom% or less, O: 30 atom% or more, and N: 26 atom% or less, and a thickness of 10 nm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a photomask blank (particularly a photomask blank used in the manufacture of semiconductor devices and the like and the management of manufacturing apparatuses), a method for manufacturing a photomask using the same, and a photomask.

Background Art

[0002] In recent years, with the miniaturization of semiconductor devices, particularly due to the high integration of large-scale integrated circuits, high pattern resolution has been required for projection lithography. Therefore, as a technique for improving the resolution of transferred patterns in photomasks, a phase shift mask has been developed. The principle of the phase shift method is to adjust the phase of the transmitted light passing through the aperture of the photomask so that it is inverted by approximately 180 degrees with respect to the phase of the transmitted light passing through the portion adjacent to the aperture. By doing so, when the transmitted lights interfere with each other, the light intensity at the boundary is weakened. As a result, the resolution and depth of focus of the transferred pattern are improved. A photomask using this principle is generally called a phase shift mask.

[0003] The phase shift mask blank used for a phase shift mask generally has a structure in which a phase shift film is laminated on a transparent substrate such as a glass substrate, and a film containing chromium (Cr) is laminated on the phase shift film. The phase shift film usually has a phase difference of 175 to 185 degrees and a transmittance of about 6 to 30% with respect to the exposure light, and is mainly formed of a film containing molybdenum (Mo) and silicon (Si). Further, the film containing chromium is adjusted to a film thickness that provides a desired optical density in combination with the phase shift film. The film containing chromium is used as a light-shielding film and is generally used as a hard mask film for etching the phase shift film.

[0004] As a method of forming a pattern of a phase shift mask from this phase shift mask blank, more specifically, a resist film is formed on a chromium-containing film of the phase shift mask blank, a pattern is drawn on this resist film by light or an electron beam, developed to form a resist pattern, and this resist pattern is used as an etching mask to etch the chromium-containing film to form a pattern. Further, the phase shift film is etched using the pattern of the chromium-containing film as an etching mask to form a phase shift film pattern, and then the resist pattern and the pattern of the chromium-containing film are removed.

[0005] Here, a light-shielding film is left outside the portion where the circuit pattern of the phase shift film pattern is formed, and the light-shielding portion (light-shielding film pattern) of the outer peripheral edge of the phase shift mask is formed so that the optical density of the combined phase shift film and light-shielding film is 3 or more. This is to prevent unnecessary exposure light from leaking when transferring the circuit pattern to the wafer using a wafer exposure apparatus and irradiating the resist film on an adjacent chip located outside the circuit pattern. As a method of forming such a light-shielding film pattern, after forming the phase shift film pattern and removing the resist pattern, a resist film is newly formed, and the chromium-containing film is etched using the resist pattern formed by pattern drawing and development as an etching mask to form a light-shielding film pattern at the outer peripheral edge portion.

[0006] In a phase shift mask that requires high-precision pattern formation, dry etching using gas plasma is the mainstream. For dry etching of a chromium-containing film, dry etching using a chlorine-based gas containing oxygen (chlorine-based dry etching) is used, and for dry etching of a film containing molybdenum and silicon, dry etching using a fluorine-based gas (fluorine-based dry etching) is used. In particular, in the dry etching of a chromium-containing film, it is known that by using an etching gas in which 10 to 25% by volume of oxygen gas is mixed with the chlorine-based gas, the chemical reactivity is increased and the etching rate is improved.

[0007] With the miniaturization of circuit patterns, technologies for finely forming phase shift mask patterns are also required. In particular, assist patterns for line patterns that assist the resolution of the main pattern of a phase shift mask need to be formed smaller than the main pattern so that they are not transferred to the wafer when transferring the circuit pattern to the wafer using a wafer exposure apparatus. In the case of a phase shift mask for a generation where the pitch of the line and space pattern of the circuit on the wafer is 10 nm, the line width of the assist pattern of the line pattern on the phase shift mask is required to be about 40 nm.

[0008] Furthermore, with the miniaturization of semiconductor devices, especially due to the high integration of large-scale integrated circuits, high pattern resolution is required for projection lithography, and the above-mentioned phase shift mask can no longer obtain the desired pattern resolution. Therefore, EUV lithography using light in the extreme ultraviolet region has come to be used for the exposure light.

[0009] Light in the extreme ultraviolet region is easily absorbed by all substances, and transmissive lithography such as conventional photolithography using ArF light cannot be used. For this reason, a reflective optical system is used in EUV lithography.

[0010] The photomask used in EUV lithography has a structure in which a reflective layer that reflects light in the extreme ultraviolet region and an absorber layer that absorbs light in the extreme ultraviolet region are formed in this order on a substrate such as made of glass. As the reflective layer, a multilayer reflective film in which a low refractive index film and a high refractive index film are alternately laminated to increase the reflectivity when the surface of the layer is irradiated with light in the extreme ultraviolet region is used. As the low refractive index film of the multilayer reflective film, a molybdenum (Mo) layer is usually used, and as the high refractive index film, a silicon (Si) layer is usually used. For the absorber layer, a material with a high absorption coefficient for EUV light, specifically, for example, a material mainly composed of chromium (Cr) or tantalum (Ta) is used.

[0011] In addition, the light in the extreme ultraviolet region used in EUV lithography has a wavelength of 13.5 nm, while the conventional ArF light has a wavelength of 193 nm. The exposure wavelength is shorter than that of conventional photolithography, enabling the transfer of finer patterns on the photomask.

[0012] On the other hand, in EUV lithography, minute foreign substances on the photomask that are not transferred in ArF lithography will also be transferred, hindering the production of the desired pattern. Therefore, in EUV lithography, a guarantee of finer defects is required compared to conventional photolithography. For this purpose, it is necessary not to generate foreign substances in the photomask manufacturing process, and a photomask blank that can detect finer defects than the equipment management in conventional photolithography is required.

[0013] In the equipment management of the photomask manufacturing equipment, for example, in a dry etcher, after placing the photomask to be processed on the loader, it is transported to the transfer chamber and then to the plasma processing chamber. If dust is generated from the side walls or the stage in the plasma processing chamber and foreign substances adhere to the circuit pattern of the photomask, these foreign substances will become masks that hinder etching, preventing the production of the desired photomask pattern. Therefore, in order to confirm that no dust is generated in the transfer chamber and the plasma processing chamber, a photomask blank or a transparent substrate is transported to the transfer chamber, then to the plasma processing chamber, plasma processing is not performed, it is transported back to the transfer chamber, then returned to the loader, and then the increase and increase position of foreign substances on the surface layer of the photomask blank or transparent substrate are investigated by a photomask blank inspection device. Not only for the dry etcher described above, but also when manufacturing a photomask, it is necessary to manage foreign substances in the apparatus in a resist coating apparatus, an electron beam lithography apparatus, a developing apparatus, a cleaning apparatus, a photomask pattern appearance inspection apparatus, and a correction apparatus. Furthermore, in an exposure apparatus used in a wafer exposure process, it is also necessary to manage foreign substances in the apparatus. Particularly in EUV lithography, a pellicle for protecting a photomask that prevents foreign substances from adhering to the circuit pattern of the photomask has not been put into practical use, and apparatus management in the wafer exposure apparatus is required.

[0014] For defect inspection of a photomask blank, a photomask blank inspection apparatus that uses light in the ultraviolet region is used. The photomask blank defect inspection apparatus includes a light emitting means that emits light in a specific wavelength range, and a detector that irradiates the surface of the photomask blank with the light emitted from the light emitting means and receives the reflected light. In a photomask blank defect inspection apparatus, the lower the surface reflectivity of the photomask blank to be inspected, the more light can be irradiated onto the photomask, and a more sensitive inspection can be performed. This is because when the reflectivity of the photomask blank is high, the light from the light emitting means collides with the foreign substance and the surrounding film, and when the reflected light is detected by the detector, the contrast between the reflected light from the foreign substance and the reflected light from the surrounding film becomes small, making it difficult to distinguish the difference between the reflected light from the foreign substance and the reflected light from the film, and thus it is not possible to irradiate the photomask with a large amount of light from the light emitting means. Irradiating the photomask with a larger amount of light from the light emitting means makes it possible to detect smaller defects.

[0015] In the 7nm and 5nm generations of logic devices, it is required that there are no defects of 50nm on the photomask blank, and it is also required that there are no defects of 50nm inside the photomask manufacturing apparatus. Therefore, it is required that the photomask blank for confirming the state of the above-described photomask manufacturing apparatus detects no defects of 50nm. The inspection wavelength of the photomask blank defect inspection apparatus for the 7nm and 5nm generations of logic devices is in the ultraviolet region of about 200nm to 400nm.

[0016] In the exposure apparatus used in the wafer exposure process, it is common to fabricate and manage a barcode pattern at the mask edge on the photomask by lithography in order to manage the photomask. The barcode pattern is read by a means including a light emitting means with a wavelength of 400 nm or more and a detector for receiving the reflected light thereof. Since the wafer exposure machine used in EUV lithography uses a reflective optical system, the means for reading the barcode pattern also becomes a reflective optical system. In the case of an optical system for receiving reflected light, a reflectance of 27% or more at a wavelength of 400 nm or more is required.

[0017] For example, in the method described in Patent Document 1, a chromium oxide layer with a relatively low oxygen content is formed on a transparent substrate in contact with the transparent substrate, and then a thick chromium oxide film with a low oxygen content is formed in contact therewith, and then a thin oxygen-rich chromium oxide film with a high oxygen content is formed in contact therewith, thereby reducing the surface reflectance of the film composed of a material containing chromium. This enables highly sensitive inspection.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0019] As a factor that inhibits defect inspection by the photomask blank inspection apparatus, there are also problems caused by the chromium film. When the roughness of the film surface of the chromium film is poor, the unevenness on the surface layer of the chromium film is determined as a defect, and a large number of pseudo-defects are detected. In that case, it is difficult to distinguish between the defects to be removed and the unevenness of the chromium film, and it is necessary to reduce the inspection sensitivity, resulting in insufficient inspection ability.

[0020] For example, in the method described in Patent Document 1 mentioned above, a chromium oxide layer with a relatively low oxygen content is formed in contact with a transparent substrate, and then a thick chromium oxide film with a low oxygen content is formed in contact with it, and then a thin oxygen-rich chromium oxide film with a high oxygen content is formed in contact with that. However, due to the poor surface roughness Rq of the film composed of a chromium-containing material, the inspection sensitivity for a wavelength of 355 nm of the photomask blank defect inspection apparatus cannot be sufficiently increased, and it has been found that defects of 50 nm cannot be stably detected.

[0021] In addition, since the resistance value of the film composed of a chromium-containing material is high, it is easy to accumulate charges on the surface layer of the film, and foreign substances with negative charges generated in the photomask manufacturing apparatus are repelled by Coulomb force away from the film composed of a chromium-containing material, and foreign substances are not adsorbed on the surface layer of the film composed of a chromium-containing material. When used for the device management of the photomask manufacturing apparatus, the true device state cannot be investigated.

[0022] Furthermore, in an exposure apparatus used in the wafer exposure process, when reading the barcode pattern of a photomask with a reflection optical system, a reflectivity of 27% or more at a wavelength of 400 nm or more is required, but the method described in Patent Document 1 mentioned above cannot meet this requirement.

[0023] The present invention has been made to solve the above problems, and has a good surface roughness Rq of a film composed of a chromium-containing material, can sufficiently increase the inspection sensitivity of a photomask blank defect inspection apparatus, can detect defects of 50 nm, and also has a small resistance value of the film, so that it is possible to adsorb foreign substances around in the photomask manufacturing apparatus and is useful for manufacturing apparatus management. Furthermore, in an exposure apparatus used in the wafer exposure process, it is possible to read the barcode pattern of a photomask with a reflection optical system, and also to provide a photomask blank capable of manufacturing a photomask pattern using a known photomask process. Another object is to provide a method for manufacturing a photomask using the same and a photomask.

Means for Solving the Problems

[0024] The present invention is made to achieve the above object, a substrate, a film composed of a material containing chromium and comprising: the film composed of the material containing chromium has a first layer, a second layer, and a third layer from the side spaced apart from the substrate, the first layer, the second layer, and the third layer all contain chromium, the first layer further contains oxygen and nitrogen, has a chromium content of 44 atomic% or less, an oxygen content of 30 atomic% or more, a nitrogen content of 26 atomic% or less, and a thickness of 8 nm or more and 20 nm or less, the second layer further contains nitrogen, has a chromium content of 66 atomic% or more and 92 atomic% or less, a nitrogen content of 8 atomic% or more and 34 atomic% or less, and a thickness of 40 nm or more and 70 nm or less, the third layer further contains oxygen and nitrogen, has a chromium content of 44 atomic% or less, an oxygen content of 30 atomic% or more, a nitrogen content of 26 atomic% or less, and a thickness of 10 nm or less, and provides a photomask blank.

[0025] Regarding the film composed of the above material containing chromium (hereinafter, also simply referred to as the film containing chromium), first, if the contents of oxygen and nitrogen in the first layer are within the above ranges, it is beneficial for improving the surface roughness (especially the surface roughness Rq) of the film containing chromium. Also, it is beneficial for adjusting the reflectance of the film containing chromium (in particular, making the reflectance of the exposure light with a wavelength of 355 nm 32% or less, and making the reflectance of the exposure light with a wavelength of 400 nm 27% or more. Hereinafter, the exposure light is also simply referred to as light. Also, the exposure light includes the inspection light in the inspection device.). Also, if the thickness of the first layer is within the above range, it is possible to appropriately make the first layer easily affected by the second layer (effects on surface roughness, reflectance, and conductivity).

[0026] If the nitrogen content in the second layer is within the above range, it is beneficial for improving the surface roughness of the chromium-containing film and is also beneficial for adjusting the reflectivity. In addition, the chromium content is higher than that in the first and third layers, and the conductivity of the second layer can be increased. Also, if the thickness of the second layer is within the above range, it is beneficial for making the reflectivity of light with a wavelength of 400 nm in the chromium-containing film 27% or more.

[0027] If the oxygen and nitrogen contents in the third layer are within the above range, it is beneficial for adjusting the reflectivity. Also, if the thickness of the third layer is within the above range, it is beneficial for adjusting the reflectivity.

[0028] If the chromium-containing film is only in the first layer, for example, good surface roughness and adjustment of the target reflectivity as described above cannot be achieved. However, since the thickness of the first layer is within the above range, it can also be affected by the second layer (and the third layer) as described above, and good surface roughness and adjustment of the reflectivity can be achieved. Because the surface roughness is good, in the defect inspection of the photomask blank, it is possible to suppress the situation where the unevenness on the surface layer of the chromium-containing film is determined as a defect and a large number of such pseudo-defects are detected. Therefore, since it is not necessary to reduce the inspection sensitivity to light with a wavelength of 355 nm for distinguishing between defects to be removed and pseudo-defects, in particular, defects with a size of 50 nm level can be detected. Also, regarding the adjustment of the reflectivity, since the reflectivity of light with a wavelength of 355 nm can be adjusted to 32% or less, more light can be irradiated in the defect inspection, a higher-sensitivity inspection can be carried out, and defects with a smaller size can be detected. Also, since the reflectivity of light with a wavelength of 400 nm can be adjusted to 27% or more, when it is made into a photomask, the barcode pattern fabricated for management at the mask edge can be read by the reflection optical system.

[0029] Furthermore, it has a three-layer structure in which the first layer and the third layer are positioned so as to sandwich the second layer having a high conductivity as described above, and the resistance value of the chromium-containing film can be reduced. Since the film resistance value can be made small, it is possible to adsorb foreign matter around in a photomask manufacturing apparatus, and it can be made useful for management of the manufacturing apparatus.

[0030] Also, a photomask pattern can be sufficiently manufactured from a photomask blank having such a chromium-containing film by a known photomask process.

[0031] At this time, the film made of the chromium-containing material is a light-shielding film, and the reflectance with respect to exposure light having a wavelength of 355 nm is 32% or less, and the reflectance with respect to exposure light having a wavelength of 400 nm is 27% or more.

[0032] If it is such a thing, in defect inspection, more light quantity can be irradiated, and it becomes a photomask blank having a light-shielding film capable of more sensitive inspection and thus detection of smaller size defects. Also, a barcode pattern for management of the photomask can be read.

[0033] Also, the film thickness of the film made of the chromium-containing material can be 53 nm or more and 100 nm or less.

[0034] If it is such a thing, adjustment of the reflectance can be performed more reliably.

[0035] Also, the resistance value of the film made of the chromium-containing material can be 20 ohms / square or less.

[0036] If it is such a thing, since the resistance value is small, in a photomask manufacturing apparatus, adsorption of foreign matter around can be performed more reliably, and it becomes more useful for management of the manufacturing apparatus.

[0037] Further, the substrate is further provided with a backside film on the side opposite to the side having the film made of the material containing chromium with respect to the substrate. The backside film can have the same first layer, second layer, and third layer as the film made of the material containing chromium from the side separated from the substrate.

[0038] When the substrate is made of, for example, quartz, it is easy to accumulate charges on the surface layer of the substrate and difficult to adsorb foreign substances generated in the photomask manufacturing apparatus. However, if, in addition to the film made of the material containing chromium as described above, the backside film is provided on the opposite side thereof, it is possible to easily adsorb foreign substances also on the side having the backside film, and it can be made more useful for the management of the manufacturing apparatus.

[0039] The present invention is also a method for manufacturing a photomask having a circuit pattern of a film made of the material containing chromium from the above-described photomask blank, (A) A step of forming a resist film on the side separated from the substrate of the film made of the material containing chromium; (B) A step of patterning the resist film to form a resist pattern; (C) A step of patterning the film made of the material containing chromium by dry etching using a chlorine-based gas containing oxygen with the resist pattern as an etching mask to form a pattern of the film made of the material containing chromium; (D) A step of removing the resist pattern is provided, and a method for manufacturing a photomask is provided.

[0040] In this way, it is possible to manufacture a photomask having good surface roughness, capable of detecting defects with a size of 50 nm in defect inspection, capable of adsorbing foreign substances in the manufacturing apparatus, and capable of reading a barcode pattern.

[0041] The present invention also relates to a substrate, A film made of a chromium-containing material provided on the substrate and having an active region which is a circuit pattern comprising the film made of the chromium-containing material has a first layer, a second layer, and a third layer on the side separated from the substrate, the first layer, the second layer, and the third layer all contain chromium, the first layer further contains oxygen and nitrogen, has a chromium content of 44 atomic% or less, an oxygen content of 30 atomic% or more, a nitrogen content of 26 atomic% or less, and a thickness of 8 nm or more and 20 nm or less, the second layer further contains nitrogen, has a chromium content of 66 atomic% or more and 92 atomic% or less, a nitrogen content of 8 atomic% or more and 34 atomic% or less, and a thickness of 40 nm or more and 70 nm or less, the third layer further contains oxygen and nitrogen, has a chromium content of 44 atomic% or less, an oxygen content of 30 atomic% or more, a nitrogen content of 26 atomic% or less, and a thickness of 10 nm or less, and provides a photomask characterized by this.

[0042] If it is such a thing, the surface roughness is good, defects with a size of 50 nm can be detected in defect inspection, foreign matter in the manufacturing apparatus can be adsorbed, and a barcode pattern can be read. Moreover, a photomask pattern can be manufactured from a photomask blank by a known photomask process.

Effects of the Invention

[0043] The photomask blank of the present invention has good surface roughness of the film made of a chromium-containing material, can detect defects of 50 nm without detecting pseudo-defects even when the inspection sensitivity of the photomask blank inspection apparatus is increased. Also, in particular, the reflectance with respect to inspection light having a wavelength of 400 nm is 27% or more and it is possible to read a barcode pattern. Also, since the resistance value of the film is small, it is possible to adsorb foreign matter around it. In particular, since the film made of the above chromium-containing material is laminated on both sides of the substrate, it is possible to adsorb foreign matter on the upper surface and the lower surface of the photomask blank.

Brief Description of the Drawings

[0044]

Figure 1

Figure 2

Figure 3

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Figure 8

Embodiments for Carrying Out the Invention

[0045] As described above, regarding the photomask blank, there have been problems caused by surface roughness, reflectance with respect to light having a wavelength of 355 nm or light having a wavelength of 400 nm, and resistance value. Therefore, in order to solve the above problems, the inventors of the present invention have intensively studied a photomask blank including a substrate such as a transparent substrate and a film formed of a material containing chromium on the substrate. As a result, it has been found that a layer containing oxygen and nitrogen with a high oxygen content is favorable because the surface roughness of the film is good, especially the surface reflectance with respect to inspection light having a wavelength of 355 nm is low, and the reflectance with respect to inspection light having a wavelength of 400 nm satisfies 27% or more. Furthermore, when the resistance value of the film formed of the material containing chromium is a small value such as 20 ohms / square or less, it can adsorb foreign substances in the surroundings. Therefore, instead of a single layer of the film containing chromium, a chromium nitride layer with good conductivity is inserted in between, and from the side separated from the substrate, for example, a three-layer structure of a chromium oxynitride layer, a chromium nitride layer, and a chromium oxynitride layer can reduce the resistance value of the film.

[0046] Based on these findings, as a photomask blank, it includes a substrate and a film formed of a material containing chromium. The film formed of the material containing chromium has a first layer, a second layer, and a third layer from the side separated from the substrate. The first layer, the second layer, and the third layer all contain chromium. The first layer further contains oxygen and nitrogen, the chromium content is 44 atomic% or less, the oxygen content is 30 atomic% or more, the nitrogen content is 26 atomic% or less, and the thickness is 8 nm or more and 20 nm or less. The second layer further contains nitrogen, the chromium content is 66 atomic% or more and 92 atomic% or less, the nitrogen content is 8 atomic% or more and 34 atomic% or less, and the thickness is 40 nm or more and 70 nm or less. The third layer further contains oxygen and nitrogen, the chromium content is 44 atomic% or less, the oxygen content is 30 atomic% or more, the nitrogen content is 26 atomic% or less, and the thickness is 10 nm or less. It has been found that such a structure is effective, and the present invention has been completed.

[0047] Hereinafter, the present embodiment will be described. The photomask blank of the present embodiment has a substrate and a film formed of a chromium-containing material on the substrate. In the present embodiment, the film formed of the chromium-containing material is a laminated film having a three-layer structure including a first layer, a second layer, and a third layer from the side separated from the substrate. Note that the film formed of the chromium-containing material may be composed of four or more layers, for example, five or six layers. Also, as will be described in detail later, the film formed of the chromium-containing material may be laminated not only on one side but also on both sides of the substrate.

[0048] (Regarding the substrate) There is no particular limitation on the type of the substrate and the substrate size. In the case of a reflective photomask blank and a photomask, it is not necessarily required to be transparent at the wavelength used as the exposure wavelength. In the case of a transmissive photomask blank and a photomask, a transparent substrate such as a quartz substrate that is transparent at the wavelength used as the exposure wavelength is applied. For example, a substrate called a 6025 substrate having a size of 6 inches square and a thickness of 0.25 inches defined in the SEMI standard is suitable. The 6025 substrate is usually expressed as a substrate having a size of 152 mm square and a thickness of 6.35 mm when using the SI unit system.

[0049] Hereinafter, the structure of the photomask blank and the photomask according to the present embodiment, and a method for manufacturing a photomask from the photomask blank will be described with reference to the drawings. For the same components, the same reference numerals may be given, and duplicate explanations may be omitted. Also, the drawings may be shown enlarged for convenience, and the dimensional ratios of the respective components are not necessarily the same as the actual ones.

[0050] FIG. 1 is a cross-sectional view showing an example of a first aspect of a photomask blank according to the present embodiment. This photomask blank 511 has a film (also referred to as a chromium-containing film or a film to be processed) (e.g., a light-shielding film) 21 made of a chromium-containing material formed in contact with a transparent substrate 1 on the transparent substrate 1. The film 21 made of a chromium-containing material is composed of a first layer 211, a second layer 212, and a third layer 213 from the side spaced apart from the transparent substrate. In other words, the third layer 213, the second layer 212, and the first layer 211 are laminated from the transparent substrate 1 side.

[0051] FIG. 2 is a cross-sectional view showing an example of a first aspect of a photomask according to the present embodiment. This photomask 513 has a pattern of a film (light-shielding film pattern) 21a made of a chromium-containing material formed in contact with a transparent substrate 1 on the transparent substrate 1. The light-shielding film pattern 21a is composed of a first layer 211, a second layer 212, and a third layer 213 from the side spaced apart from the transparent substrate 1 (the third layer 213, the second layer 212, and the first layer 211 from the transparent substrate 1 side). The photomask 513 shown in FIG. 2 can be manufactured from the photomask blank 511 shown in FIG. 1. In the photomask 513, the region where the circuit pattern is drawn is the effective region 5, and the region located around the effective region 5 where the circuit pattern is not drawn is the light-shielding film region 6.

[0052] FIG. 3 is a cross-sectional view showing an example of a second aspect of a photomask blank according to the present embodiment. This photomask blank 521 first has a film 21 (film to be processed) made of a chromium-containing material on the upper surface side of the transparent substrate 1, and is composed of a first layer 211, a second layer 212, and a third layer 213 from the side spaced apart from the transparent substrate. Further, a backside film 21' is provided on the opposite side (lower surface side). This backside film 21' has the same first layer 211, second layer 212, and third layer 213 as the film 21 made of a chromium-containing material on the upper surface side from the side spaced apart from the transparent substrate 1. That is, in this aspect, films made of the same chromium-containing material are provided on both sides in contact with the transparent substrate 1.

[0053] FIG. 4 is a cross-sectional view showing an example of a second aspect of the photomask of the present embodiment. This photomask 523 has a pattern (light-shielding film pattern) 21a of a film made of a chromium-containing material formed in contact with the transparent substrate 1 on the upper surface side of the transparent substrate 1, and is composed of a first layer 211, a second layer 212, and a third layer 213 from the side spaced apart from the transparent substrate. Further, a backside film 21' is provided on the opposite side (lower surface side). This backside film 21' has the same first layer 211, second layer 212, and third layer 213 as the film 21 made of a chromium-containing material on the upper surface side from the side spaced apart from the transparent substrate 1.

[0054] In the present embodiment, the film made of a chromium-containing material is a laminated film having a three-layer structure composed of a first layer, a second layer, and a third layer from the side spaced apart from the substrate. The first layer and the third layer are each made of a material containing chromium, oxygen, and nitrogen, and the second layer is made of a material containing chromium and nitrogen. The chromium-containing material is preferably a material having resistance to fluorine-based dry etching and removable by chlorine-based dry etching. The materials containing chromium, oxygen, and nitrogen in the first layer and the third layer preferably do not contain silicon. As the materials containing chromium, oxygen, and nitrogen in the first layer and the third layer, a material (CrON) composed of chromium (Cr), oxygen (O), and nitrogen (N) is suitable. On the other hand, the material containing chromium and nitrogen in the second layer also preferably does not contain silicon. As the material containing chromium and nitrogen in the second layer, a material (CrN) composed of chromium (Cr) and nitrogen (N) is suitable.

[0055] Hereinafter, each layer will be described in more detail. Basically, the content ratio, thickness, and effects of each atom for each layer will be described, but since there is also an influence between layers, in the part where one layer is described, the description of another layer and the relationship with the other layer may also be described together. (Regarding the first layer) In the film composed of the chromium-containing material of the present embodiment, the composition of the first layer (upper layer), which is the layer on the side separated from the substrate, has a chromium content of 44 atomic% or less, an oxygen content of 30 atomic% or more, and a nitrogen content of 26 atomic% or less, and a thickness of 8 nm or more and 20 nm or less. The chromium content of the first layer is preferably 43 atomic% or less, and preferably 30 atomic% or more, particularly preferably 38 atomic% or more. The oxygen content of the first layer is preferably 32 atomic% or more, and preferably 60 atomic% or less, particularly preferably 54 atomic% or less. The nitrogen content of the first layer is preferably 25 atomic% or less, and preferably 5 atomic% or more, particularly preferably 8 atomic% or more. The thickness of the first layer is preferably 18 nm or less, and preferably 10 nm or more.

[0056] When manufacturing a photomask from a photomask blank, the first layer is a layer that comes into direct contact with the cleaning liquid and is a layer that contacts the resist film. When inspected with a photomask blank inspection apparatus, it is a layer located on the side separated from the substrate where the light emitted from the light emission means is incident. Therefore, the first layer is required to have high chemical resistance to the cleaning liquid, and also, when the first layer, the second layer, and the third layer are combined, the reflectance with respect to the inspection light with a wavelength of 355 nm is 32% or less, and the reflectance with respect to the inspection light with a wavelength of 400 nm is 27% or more (hereinafter, also referred to as adjustment of reflectance).

[0057] Chromium oxynitride (CrON) is not dissolved in a mixed solution of sulfuric acid and hydrogen peroxide water or ammonia-added water (ammonia-added hydrogen peroxide water, APM) compared to chromium oxide (CrO), and it is possible to stably maintain optical properties. In addition, chromium oxynitride (CrON) has a lower reflectance with respect to exposure light compared to chromium nitride (CrN). Therefore, it is advantageous when the reflectance of the film composed of the chromium-containing material with respect to the inspection light with a wavelength of 355 nm is 32% or less. From such a perspective, it is beneficial to configure the first layer with a material containing chromium, oxygen, and nitrogen, and to have the above-described predetermined composition (chromium content of 44 atomic % or less, oxygen content of 30 atomic % or more, nitrogen content of 26 atomic % or less) which is an oxygen-rich composition with a relatively high oxygen content.

[0058] Also, chromium oxynitride (CrON) has a better surface roughness Rq of the film compared to chromium oxide (CrO). From such a perspective, it is beneficial to make the first layer have the above-described predetermined composition (chromium content of 44 atomic % or less, oxygen content of 30 atomic % or more, nitrogen content of 26 atomic % or less) which is an oxygen-nitrogen-rich composition with a relatively high oxygen content and nitrogen content.

[0059] Also, as will be described later, from the perspectives of the surface roughness Rq, reflectance, and resistance value of the film composed of a material containing chromium, the thickness of the first layer is set to 20 nm or less as described above. On the other hand, if the thickness is too thin, there is a risk of being overly affected by the second layer, so it is set to 8 nm or more as described above. With the first layer as described above, it is possible to appropriately receive the influence from the second layer (and the third layer), which is beneficial for obtaining a chromium-containing film with good surface roughness, appropriate adjustment of reflectance, and reduction of resistance value.

[0060] (Regarding the second layer) In the film composed of the chromium-containing material of the present embodiment, the composition of the second layer, which is the layer sandwiched between the first layer and the third layer, has a chromium content of 66 atomic % or more and 92 atomic % or less, a nitrogen content of 8 atomic % or more and 34 atomic % or less, and a thickness of 40 nm or more and 70 nm or less. The chromium content of the second layer is preferably particularly 70 atomic % or more and 90 atomic % or less. The nitrogen content of the second layer is preferably 30 atomic % or less, and particularly preferably 10 atomic % or more.

[0061] In addition, in a photomask blank inspection apparatus, since a larger reflectance of a film made of a chromium-containing material with respect to the inspection light emitted from the light emitting means means that less light can be irradiated, it is necessary to reduce the inspection sensitivity. From this perspective, it is desirable that the reflectance with respect to the inspection light having a wavelength of 355 nm is 32% or less, particularly 30% or less. In addition, in an exposure apparatus used in a wafer exposure process, in order to manage a photomask, it is common to fabricate a barcode pattern at the mask edge on the photomask by photolithography and manage the photomask using the information of the barcode. The barcode pattern is read by a device including a light emitting means that emits light with a wavelength of 400 nm or more and a detector that receives the reflected light. When receiving the reflected light, a reflectance of 27% is required for a film made of a chromium-containing material with respect to the inspection light having a wavelength of 400 nm or more. From this perspective, it is desirable that the reflectance with respect to the inspection light having a wavelength of 400 nm is 27% or more. In addition, in order to satisfy the above-described reflectance (particularly the reflectance of light with a wavelength of 400 nm), the thickness of the second layer is preferably 40 nm or more and 70 nm or less, particularly 44 nm or more and 68 nm or less.

[0062] Chromium nitride becomes a nitrogen-rich chromium nitride with a high nitrogen content, resulting in good surface roughness Rq of the film. From this perspective, it is beneficial to make the second layer have the above-described predetermined composition (chromium content of 66 atomic% or more and 92 atomic% or less, nitrogen content of 8 atomic% or more and 34 atomic% or less) which is a nitrogen-rich composition with a relatively high nitrogen content. And if it is within the more preferable content range described above, it will more surely have good surface roughness.

[0063] In addition, since the second layer is in contact with the first layer, a thinner thickness of the first layer is more affected by the surface roughness Rq of the second layer. Therefore, it is beneficial to make the thickness of the first layer 20 nm or less as described above (however, 8 nm or more). In addition, chromium nitride becomes nitrogen-rich, resulting in a lower reflectivity for inspection light with a wavelength of 355 nm. Since the second layer is formed in contact with the first layer, the second layer affects the reflectivity of the inspection light with a wavelength of 355 nm. From such a perspective alone, it is beneficial to set the second layer to the above-described predetermined composition that is relatively nitrogen-rich. However, on the other hand, chromium nitride has a higher reflectivity for inspection light with a wavelength of 400 nm when it contains less nitrogen. Since the second layer is formed in contact with the first layer, the second layer affects the reflectivity of the inspection light with a wavelength of 400 nm. From these perspectives regarding light with wavelengths of 355 nm and 400 nm, it is beneficial to set the second layer to the above-described predetermined composition (chromium content of 66 atomic % or more and 92 atomic % or less, nitrogen content of 8 atomic % or more and 34 atomic % or less).

[0064] When a film made of a material containing chromium is transported into a photomask manufacturing apparatus, it is exposed to the atmosphere inside the photomask manufacturing apparatus. When the resistance value of the film made of a material containing chromium is high, charges tend to accumulate on the surface layer of the film made of a material containing chromium, and foreign objects with negative charges generated inside the photomask manufacturing apparatus are repelled by Coulomb force away from the film made of a material containing chromium. Therefore, it is difficult to adsorb foreign objects generated inside the photomask manufacturing apparatus, and when used for the purpose of investigating foreign objects inside the photomask manufacturing apparatus, the true state of the apparatus cannot be investigated. Therefore, as described above, a low resistance value of the film made of a material containing chromium has been cited as an issue.

[0065] For the reasons described above, the first layer is made of a material containing chromium, oxygen, and nitrogen, and has an oxygen-rich composition with a relatively high oxygen content. However, chromium oxide (CrO) has a higher resistance value than chromium nitride (CrN), and the first layer, which is chromium oxynitride (CrON) with an oxygen-rich composition, has a relatively high resistance value. In addition, due to the reasons described above, the second layer is composed of a material containing chromium and nitrogen, and has a nitrogen-rich composition with a relatively high nitrogen content rate. However, the chromium content rate is also relatively high (66 atomic % or more and 92 atomic % or less), and the sheet resistance value is low. Therefore, as described above, it is beneficial to reduce the film thickness of the first layer and set the second layer to the above-described predetermined composition with a relatively high nitrogen content.

[0066] The resistance value of the film composed of the material containing chromium is preferably such that the combined resistance value of the first layer, the second layer, and the third layer is, for example, 20 kΩ / sq or less, and particularly preferably 18 kΩ / sq or less. Due to the above-described characteristics of the first layer and the second layer, it is possible to form a film composed of a material containing chromium having such a resistance value. Further, since the second layer is in contact with the first layer, when the film thickness of the first layer is small, the first layer is easily affected by the highly conductive second layer during the formation of the first layer, so that it is easy to set the first layer to a composition with low conductivity. Therefore, from this viewpoint, it is beneficial to set the thickness of the first layer to 20 nm or less (however, 8 nm or more).

[0067] (Regarding the third layer) In the film composed of the material containing chromium according to the present embodiment, the composition of the third layer, which is the layer on the substrate side, has a chromium content rate of 44 atomic % or less, an oxygen content rate of 30 atomic % or more, a nitrogen content rate of 26 atomic % or less, and a thickness of 10 nm or less. The chromium content rate of the third layer is preferably 43 atomic % or less, and is preferably 30 atomic % or more, particularly preferably 38 atomic % or more. The oxygen content rate of the third layer is preferably 32 atomic % or more, and is preferably 60 atomic % or less, particularly preferably 54 atomic % or less. The nitrogen content rate of the third layer is preferably 25 atomic % or less, and is preferably 5 atomic % or more, particularly preferably 8 atomic % or more. The thickness of the third layer is preferably 1 nm or more, and particularly preferably 3 nm or more.

[0068] In the third layer, if the oxygen and nitrogen content rates are within the above ranges (oxygen content rate is 30 atomic % or more and nitrogen content rate is 26 atomic % or less), it is beneficial for adjusting the reflectance of the chromium-containing film.

[0069] The first layer and the second layer have the above-described constraints. Since the inspection lights with wavelengths of 355 nm and 400 nm reach the third layer after passing through the first layer and the second layer, the structure of the third layer affects the reflectance of the film composed of a chromium-containing material. In order to satisfy that the reflectance with respect to the inspection light with a wavelength of 355 nm is 32% or less and the reflectance with respect to the inspection light with a wavelength of 400 nm is 27% or more, the thickness of the third layer is set to 10 nm or less.

[0070] If it is the photomask blank of the present invention as described above, the surface roughness of the chromium-containing film can be made good. And because it has good surface roughness, it is possible to prevent a large amount of pseudo defect detection in defect inspection. Therefore, it is not necessary to reduce the inspection sensitivity with respect to the light with a wavelength of 355 nm, the inspection ability can be made sufficient, and it becomes possible to sufficiently detect even small defects with a size of 50 nm or less. Also, particularly, since the reflectance of the inspection light with a wavelength of 355 nm can be made 32% or less, high-sensitivity defect inspection becomes possible. At the same time, since the reflectance of the inspection light with a wavelength of 400 nm can also be made 27% or more, when it is used as a photomask, the barcode pattern for its management can be read.

[0071] And the resistance value of the chromium-containing film can be made small. For this reason, in a photomask manufacturing apparatus, it is possible to adsorb foreign matters, which is useful for investigating the true state of the apparatus. Particularly, if the resistance value of the chromium-containing film is as small as 20 ohms / square or less, the adsorption of foreign matters can be made more reliable, which is more useful for the management of the manufacturing apparatus.

[0072] Moreover, it is also possible to manufacture a photomask pattern by a known photomask process.

[0073] When the film made of a chromium-containing material is a light-shielding film, particularly when used as a photomask, in the portion located at the outer peripheral edge of the substrate, which is the region where the barcode pattern of the film made of a chromium-containing material is formed, if it is to be left as a light-shielding film, and when the detector for reading the barcode receives the reflected light after the light emitted from the light-emitting means irradiates the photomask, the reflectivity of the film made of a chromium-containing material, which is the light-shielding film, can be 27% or more, particularly preferably 28% or more, with respect to inspection light, for example, inspection light with a wavelength of 400 nm, light with a wavelength such as a gallium nitride-based laser.

[0074] The film thickness (total thickness of the first layer, the second layer, and the third layer) of the film made of a chromium-containing material is preferably 53 nm or more and 100 nm or less. With such a film thickness, the film made of a chromium-containing material can be more reliably adjusted so that the reflectivity with respect to inspection light with a wavelength of 355 nm is 32% or less and the reflectivity with respect to inspection light with a wavelength of 400 nm is 27% or more. Furthermore, it is more preferable that the film thickness of the film made of a chromium-containing material is 70 nm or more and 87 nm or less, as the adjustment of the above reflectivity can be performed more reliably.

[0075] As shown in FIG. 3, when the substrate has chromium-containing films on both sides (that is, the chromium-containing film 21 on the upper surface side and the back film 21' on the lower surface side), foreign matters can be adsorbed not only on the upper surface side but also on the lower surface side, which is more preferable for the management of the photomask manufacturing apparatus.

[0076] The photomask blank of the present embodiment may further have a resist film in contact with the side spaced apart from the substrate of the film made of a material containing chromium. The resist film may be an electron beam resist drawn with an electron beam, and particularly preferably a photoresist drawn with light. The photoresist drawn with light may be a negative type, but a positive type is desirable in order to leave a larger area of the film made of a material containing chromium. During fine pattern formation, in the dry etching process, although the resist film also disappears by etching simultaneously with the film made of a material containing chromium, it is preferable to increase the film thickness of the resist film so that the resist film does not disappear by etching before the processed portion of the film made of a material containing chromium disappears by etching. 300 nm or more, particularly preferably 400 nm or more.

[0077] FIG. 5 is a cross-sectional view showing another example of the first aspect of the photomask blank of the present embodiment. In this photomask blank 512, a resist film 3 is formed in contact with the film (film to be processed) 21 made of a material containing chromium of the photomask blank shown in FIG. 1. The photomask 513 shown in FIG. 2 can also be manufactured from the photomask blank 512 shown in FIG. 5.

[0078] FIG. 6 is a cross-sectional view showing another example of the second aspect of the photomask blank of the present embodiment. In this photomask blank 522, a resist film 3 is formed in contact with the film (film to be processed) 21 made of a material containing chromium of the photomask blank shown in FIG. 3. The photomask 523 shown in FIG. 4 can also be manufactured from the photomask blank 522 shown in FIG. 6.

[0079] In addition, as shown in FIGS. 2 and 4, the photomask of the present invention has a film composed of a chromium-containing material, and its composition (chromium, oxygen, nitrogen) is the same as that of the photomask blank of the present invention, and it can achieve the same effects as those in the above-mentioned photomask blank of the present invention. That is, it has good surface roughness and can detect defects with a size of 50 nm, adsorb foreign substances, and read bar code patterns.

[0080] Hereinafter, the procedure for manufacturing the photomask blank of the present invention will be described. The formation of the film composed of the chromium-containing material of the present embodiment on the substrate is not particularly limited, but sputtering is preferably used because of its good controllability and the ease of forming a film having predetermined characteristics. As the sputtering method, DC sputtering, RF sputtering, etc. can be applied, and there is no particular limitation.

[0081] When forming a film containing chromium and not containing silicon as the film composed of the chromium-containing material, a chromium target can be used as the sputter target.

[0082] The power input to the sputter target may be appropriately set according to the size of the sputter target, the cooling efficiency, the ease of controlling film formation, etc. Usually, as the power per unit area of the sputter surface of the sputter target, 0.1 to 10 W / cm 2 is sufficient.

[0083] When forming a film of a material containing oxygen or nitrogen, reactive sputtering is preferably used for sputtering. As the sputtering gas, noble gases such as helium gas (He), neon gas (Ne), and argon gas (Ar) and a reactive gas are used. For example, when forming a film of a material containing oxygen, oxygen gas (O2 gas) may be used as the reactive gas, and when forming a film of a material containing nitrogen, nitrogen gas (N2 gas) may be used as the reactive gas. Further, when forming a film of a material containing both nitrogen and oxygen, oxygen gas (O2 gas) and nitrogen gas (N2 gas) may be used simultaneously as the reactive gas, or nitrogen oxide gases such as nitric oxide gas (NO gas), nitrogen dioxide gas (NO2 gas), and nitrous oxide gas (N2O gas) may be used.

[0084] The pressure during film formation may be appropriately set in consideration of film stress, chemical resistance, cleaning resistance, etc. Usually, by setting it to 0.01 Pa or more, particularly 0.03 Pa or more, and 1 Pa or less, particularly 0.3 Pa or less, the chemical resistance is improved. Further, each gas flow rate may be appropriately set so as to obtain a desired composition, and usually 0.1 to 100 sccm may be used.

[0085] In the process of manufacturing a photomask blank, heat treatment may be performed on the substrate or the film formed on the substrate and the substrate. As the heat treatment method, infrared heating, resistance heating, etc. can be applied, and the treatment conditions are not particularly limited. The heat treatment can be carried out, for example, in a gas atmosphere containing oxygen. The concentration of the gas containing oxygen is not particularly limited. For example, in the case of oxygen gas (O2 gas), it can be 1 to 100% by volume. The heat treatment temperature is preferably 200°C or higher, particularly 400°C or higher. Further, in the process of manufacturing a photomask blank, ozone treatment, plasma treatment, etc. may be performed on the film formed on the substrate, particularly the film composed of a material containing chromium, and the treatment conditions are not particularly limited. Any treatment can be carried out for the purpose of increasing the oxygen concentration in the surface portion of the film. In that case, the treatment conditions may be appropriately adjusted so as to obtain a predetermined oxygen concentration. When the film is formed by sputtering, it is also possible to increase the oxygen concentration in the surface portion of the film by adjusting the ratio of the rare gas in the sputtering gas and the gas containing oxygen (oxidizing gas) such as oxygen gas (O2 gas), carbon monoxide gas (CO gas), and carbon dioxide gas (CO2 gas).

[0086] In the process of manufacturing a photomask blank, a cleaning treatment may be performed to remove defects existing on the surface of the substrate or the film formed on the substrate. The cleaning can be carried out using one or both of ultrapure water and functional water which is ultrapure water containing ozone gas, hydrogen gas, etc. Further, after cleaning with ultrapure water containing a surfactant, cleaning may be further performed using one or both of ultrapure water and functional water. The cleaning can be carried out while irradiating ultrasonic waves as necessary, and further, UV light irradiation can also be combined.

[0087] When forming a resist film on the photomask blank of the present embodiment, the coating method of the resist film is not particularly limited, and known techniques can be applied.

[0088] Next, the method for manufacturing a photomask of the present invention will be described. A photomask is manufactured from the photomask blank of the present embodiment. FIG. 7 is a cross-sectional view for explaining a process of manufacturing a phase shift mask from the phase shift mask blank of the first aspect of the present embodiment. In this case, first, as shown in FIG. 7(a), a resist film (the film thickness is 300 nm or more, particularly preferably 400 nm or more) 3 is formed in contact with the side of the transparent substrate 1 separated from the film (light-shielding film 21) made of a chromium-containing material (step A). Next, as shown in FIG. 7(b), the resist film 3 is patterned to form a resist pattern 31 (step B).

[0089] Next, as shown in FIG. 7(c), using the resist pattern 31 as an etching mask, a film (light-shielding film 21) made of a chromium-containing material composed of a first layer 211, a second layer 212, and a third layer 213 is patterned by chlorine-based dry etching (dry etching using a chlorine-based gas containing oxygen) to form a pattern of the film made of a chromium-containing material (light-shielding film pattern 21a) (step C). Next, as shown in FIG. 7(d), by removing the remaining resist pattern 31, a photomask (phase shift mask) can be obtained (step D).

[0090] FIG. 8 is a cross-sectional view for explaining a process of manufacturing a phase shift mask from the phase shift mask blank of the second aspect of the present embodiment. In this case, first, as shown in FIG. 8(a), a resist film (the film thickness is 300 nm or more, particularly preferably 400 nm or more) 3 is formed in contact with the side of the transparent substrate 1 separated from the film (light-shielding film 21) made of a chromium-containing material on the upper surface side (step A). Next, as shown in FIG. 8(b), the resist film 3 is patterned to form a resist pattern 31 (step B).

[0091] Next, as shown in FIG. 8(c), using the resist pattern 31 as an etching mask, a film (light-shielding film 21) made of a chromium-containing material composed of the first layer 211, the second layer 212, and the third layer 213 is patterned by chlorine-based dry etching (dry etching using a chlorine-based gas containing oxygen) to form a pattern of the film made of the chromium-containing material (light-shielding film pattern 21a) (Step C). Next, as shown in FIG. 8(d), by removing the remaining resist pattern 31, a photomask (phase shift mask) can be obtained (Step D).

[0092] When inspecting the photomask with a photomask pattern appearance inspection device, an alignment mark is required. However, the photomask of the present embodiment is particularly effective in exposure for transferring a pattern as exposure light to a photoresist film formed on a substrate to be processed with exposure light having a wavelength of 300 nm or more, such as an ArF excimer laser (wavelength: 193 nm), in photolithography for forming an alignment pattern of 500 nm to 50,000 nm on the substrate to be processed.

[0093] The exposure apparatus used in the wafer exposure process produces and manages a barcode pattern at the mask edge by lithography in order to manage the photomask. The photomask of the present embodiment is particularly effective in exposure for transferring a pattern as exposure light to a photoresist film formed on a substrate to be processed with exposure light having a wavelength of 300 nm or more, such as an ArF excimer laser (wavelength: 193 nm), in photolithography for forming a barcode pattern of 100 μm or more on the substrate to be processed.

Example

[0094] Hereinafter, the present embodiment will be specifically described by showing examples and comparative examples, but the present embodiment is not limited to the following examples.

[0095] [Example 1] A photomask blank was manufactured by laminating a film made of a chromium-containing material on a transparent quartz substrate with a 152 mm angle and a thickness of about 6 mm.

[0096] First, using a chromium target as a target on the transparent substrate, while adjusting the applied power to the target and using argon gas, nitrogen gas, and oxygen gas as sputtering gases, a third layer composed of CrON was manufactured. Next, using a chromium target as a target, while adjusting the applied power to the target and using argon gas and nitrogen gas as sputtering gases, a second layer composed of CrN was manufactured. Then, using a chromium target, while adjusting the applied power to the target and using argon gas, nitrogen gas, and oxygen gas as sputtering gases, a first layer composed of CrON was manufactured, and a photomask blank without a resist film as shown in FIG. 1 was obtained. Table 1 shows the compositions of the first, second, and third layers and the thicknesses of the first, second, and third layers.

[0097] The composition was measured using an X-ray photoelectron spectrometer K-Alpha manufactured by Thermo Fisher Scientific Co., Ltd., and the thickness of the film (layer) was measured using a contact stylus profilometer P-16+ manufactured by KLA-Tencor Corporation (the same applies hereinafter).

[0098] [Example 2] In the second layer, the chromium content (atomic %) was reduced and the nitrogen content (atomic %) was increased compared to Example 1, and in other respects, in the same manner as in Example 1, a film made of a chromium-containing material was formed on the transparent substrate to obtain a photomask blank without a resist film. Table 1 shows the compositions of the first, second, and third layers and the thicknesses of the first, second, and third layers.

[0099] [Example 3] In the second layer, the chromium content (atomic %) was reduced and the nitrogen content (atomic %) was increased compared to Example 1, and in other respects, in the same manner as in Example 1, a film made of a chromium-containing material was formed on the transparent substrate to obtain a photomask blank without a resist film. The compositions of the first layer, the second layer, and the third layer, and the thicknesses of the first layer, the second layer, and the third layer are shown in Table 1.

[0100] [Example 4] In the second layer, the chromium content (atomic %) was decreased and the nitrogen content (atomic %) was increased compared to Example 1, and in other respects, in the same manner as in Example 1, a film made of a chromium-containing material was formed on a transparent substrate to obtain a photomask blank without a resist film. The compositions of the first layer, the second layer, and the third layer, and the thicknesses of the first layer, the second layer, and the third layer are shown in Table 1.

[0101] [Example 5] The first layer was made thicker than in Example 4, and in other respects, in the same manner as in Example 4, a film made of a chromium-containing material was formed on a transparent substrate to obtain photomask blanks without a resist film. The compositions of the first layer, the second layer, and the third layer, and the thicknesses of the first layer, the second layer, and the third layer are shown in Table 1.

[0102] [Comparative Example 1] The first layer and the third layer were made of chromium oxide (CrO) instead of chromium oxynitride (CrON), and the second layer was made of chromium oxide (CrO) instead of chromium nitride (CrN). In other respects except for the compositions of the respective layers of the first layer, the second layer, and the third layer, in the same manner as in Example 1, a film made of a chromium-containing material was formed on a transparent substrate to obtain a photomask blank without a resist film. The compositions of the first layer, the second layer, and the third layer, and the thicknesses of the first layer, the second layer, and the third layer are shown in Table 1.

[0103] [Comparative Example 2] In the second layer, the chromium content (atomic %) was increased and the nitrogen content (atomic %) was decreased compared to Example 1, and in other respects, in the same manner as in Example 1, a film made of a chromium-containing material was formed on a transparent substrate to obtain a photomask blank without a resist film. The compositions of the first layer, the second layer, and the third layer, and the thicknesses of the first layer, the second layer, and the third layer are shown in Table 1.

[0104] [Comparative Example 3] In the second layer, the chromium content (atomic %) was reduced and the nitrogen content (atomic %) was increased compared to Example 1, and in other respects, in the same manner as in Example 1, a film made of a chromium-containing material was formed on a transparent substrate to obtain a photomask blank without a resist film. The compositions of the first, second, and third layers and the thicknesses of the first, second, and third layers are shown in Table 1.

[0105] [Comparative Example 4] The first layer was made thicker than in Example 4, and in other respects, in the same manner as in Example 4, a film made of a chromium-containing material was formed on a transparent substrate to obtain a photomask blank without a resist film. The compositions of the first, second, and third layers and the thicknesses of the first, second, and third layers are shown in Table 1.

[0106] [Comparative Example 5] The first layer was made thinner than in Example 4, and in other respects, in the same manner as in Example 4, a film made of a chromium-containing material was formed on a transparent substrate to obtain a photomask blank without a resist film. The compositions of the first, second, and third layers and the thicknesses of the first, second, and third layers are shown in Table 1.

[0107] (Regarding surface roughness) Next, in order to evaluate the surface roughness Rq of the film made of a chromium-containing material, evaluation was performed using the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. The surface roughness Rq of the film made of a chromium-containing material was evaluated using a NanoScope V / Dimension Icon manufactured by Bruker AXS. The results are shown in Table 2.

[0108] As shown in Table 2, for the photomask blanks of Comparative Example 1 and Comparative Example 2, it was confirmed that the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5, which are the photomask blanks of the present embodiment, have good surface roughness Rq. This is presumably because, for Comparative Example 1, the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 had chromium oxynitride with good surface roughness Rq formed on the surface. Also, for Comparative Example 2, it is presumably because the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 had chromium nitride, which is relatively nitrogen-rich and has good surface roughness Rq, formed in the second layer.

[0109] (Regarding reflectance) Next, in order to evaluate the reflectance of the films composed of materials containing chromium at wavelengths of 355 nm and 400 nm, evaluations were made using the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. The reflectance at wavelengths of 355 nm and 400 nm was measured using a UV-visible near-infrared spectrophotometer SolidSpec-3700 manufactured by Shimadzu Corporation. The results are shown in Table 3.

[0110] As shown in Table 3, the photomask blanks of Comparative Example 2 and Comparative Example 5 had a reflectance at a wavelength of 355 nm higher than 32%, whereas the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 were confirmed to have a reflectance at a wavelength of 355 nm of 32% or less. This is presumably because, for Comparative Example 2, a layer that is relatively nitrogen-rich and has a low reflectance at a wavelength of 355 nm was formed in the second layer of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5. For Comparative Example 5, since the thickness of the first layer of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 was thick, it was not overly affected by the second layer with relatively high reflectance, and thus the reflectance was small. The thickness of the first layer of Comparative Example 5 was too thin and was presumably overly affected. In addition, the reflectance of the photomask blank of Comparative Example 3 was as low as less than 27% with respect to a wavelength of 400 nm, whereas the reflectances of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 were confirmed to be 27% or more with respect to a wavelength of 400 nm. It is considered that this is because the composition of chromium nitride was adjusted so that the reflectance with respect to the film thickness of a wavelength of 400 nm became 27% or more in the second layer of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 as compared with Comparative Example 3.

[0111] (Regarding the resistance value) Next, in order to evaluate the resistance value of a film composed of a material containing chromium, evaluation was performed using the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. The resistance value of the chromium film was evaluated using a resistivity meter MCP-T600 manufactured by Mitsubishi Chemical Corporation. The results are shown in Table 4.

[0112] As shown in Table 4, with respect to the photomask blanks of Comparative Example 1, Comparative Example 3, and Comparative Example 4, it was confirmed that the resistance values of the films of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5, which are the photomask blanks of the present embodiment, were small. It is considered that this is because relatively nitrogen-rich and highly conductive chromium nitride was formed in the second layer of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 as compared with Comparative Example 1 and Comparative Example 3. In addition, with respect to Comparative Example 4, it is considered that this is because the film thickness of the first layer of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 was made as thin as 20 nm or less so as to be affected by the highly conductive second layer.

[0113] (Regarding the detection limit) Next, in order to evaluate the detection limit of a film composed of a chromium-containing material using a photomask blank inspection apparatus, evaluation was performed using the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. On the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5, 1000 PSL (polystyrene latex) standard particles of the same size were arranged at regular intervals in a 1 cm × 1 cm area. The area where the PSL standard particles were arranged was inspected using a photomask blank inspection apparatus having an inspection wavelength of 355 nm. The size of the PSL standard particles was changed from 70 nm to 40 nm in 2 nm increments and placed on the photomask blank. For PSL standard particles of different sizes, the number of defects detected by the photomask blank inspection apparatus was evaluated. If 95% or more of the 1000 arranged PSL standard particles could be detected, the PSL standard particles were considered detectable. If the number of detected particles was less than 95% of the 1000 arranged PSL standard particles, the PSL standard particles were considered undetectable, and the size of the PSL standard particles that did not fall below 95% was taken as the detection limit. The results are shown in Table 5.

[0114] As shown in Table 5, it was confirmed that for the photomask blanks of Comparative Example 1, Comparative Example 2, and Comparative Example 5, the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 had a lower defect detection limit and could detect smaller defects. As shown in Table 2, this is presumably because the surface roughness Rq of the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 is smaller than that of the photomask blanks of Comparative Example 1 and Comparative Example 2. Also, it is considered that the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 have a lower reflectance with respect to the inspection light with a wavelength of 355 nm than Comparative Example 5.

[0115] (Regarding foreign matter adsorption) Next, in order to evaluate the amount of foreign matter adsorption of the photomask blank in the photomask manufacturing apparatus, evaluation was performed using the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5. First, the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 are inspected by a photomask blank inspection apparatus having an inspection wavelength of 355 nm. Next, the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 are transported from the loader of the photomask manufacturing apparatus into the processing chamber, and then returned to the loader again without being processed. This operation is repeated 20 times. Thereafter, again, the photomask blanks obtained in Example 1, Example 2, Example 3, Example 4, Example 5, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 are inspected by the photomask blank inspection apparatus having the inspection wavelength of 355 nm, and the number of increased defects is investigated. The results are shown in Table 6.

[0116] As shown in Table 6, it was confirmed that the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 adsorbed more foreign matter than the photomask blanks of Comparative Example 1, Comparative Example 3, Comparative Example 4, and Comparative Example 5. This is because, as shown in Table 4, the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 have a lower film resistance value than Comparative Example 1, Comparative Example 3, and Comparative Example 4. Also, it is considered that the photomask blanks of Example 1, Example 2, Example 3, Example 4, and Example 5 have a smaller detection limit than the photomask blank of Comparative Example 5, as shown in Table 5.

[0117]

Table 1

[0118]

Table 2

[0119]

Table 3

[0120]

Table 4

[0121]

Table 5

[0122]

Table 6

[0123] Note that the present invention is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Explanation of Reference Numerals

[0124] 1 Substrate (transparent substrate) 21 Film made of a chromium-containing material (light-shielding film) 21’ Backside film 21a Pattern of the film made of a chromium-containing material (light-shielding film pattern) 211 First layer 212 Second layer 213 Third layer 3 Resist film 31 Resist pattern 5 Active region 511, 512, 521, 522 Photomask blank 513, 523 Photomask 6 Light-shielding film area

Claims

1. A substrate; A film made of a material containing chromium Equipped with the film made of a material containing chromium has a first layer, a second layer, and a third layer from a side away from the substrate, the first layer, the second layer, and the third layer all contain chromium; the first layer further contains oxygen and nitrogen, has a chromium content of 30 atomic % or more and less than 38 atomic %, an oxygen content of 30 atomic % or more and 65 atomic % or less, and a nitrogen content of 5 atomic % or more and 26 atomic % or less, and has a thickness of 8 nm or more and 20 nm or less; the second layer further contains nitrogen, has a chromium content of 66 atomic % or more and 92 atomic % or less, a nitrogen content of 8 atomic % or more and 34 atomic % or less, and has a thickness of 40 nm or more and 70 nm or less; the third layer further contains oxygen and nitrogen, has a chromium content of 30 atomic % or more and 44 atomic % or less, an oxygen content of 30 atomic % or more and 65 atomic % or less, and a nitrogen content of 5 atomic % or more and 26 atomic % or less, and has a thickness of 10 nm or less.

2. 2. The photomask blank according to claim 1, wherein the film made of a material containing chromium is a light-shielding film having a reflectance of 32% or less for exposure light having a wavelength of 355 nm and a reflectance of 27% or more for exposure light having a wavelength of 400 nm.

3. 3. The photomask blank according to claim 1, wherein the film made of the chromium-containing material has a thickness of 70 nm or more and 88 nm or less.

4. 4. The photomask blank according to claim 1, wherein the film made of the chromium-containing material has a resistance value of 20 ohms / square or less.

5. The substrate further includes a backside film on the side opposite to the side having the film made of the chromium-containing material, 5. The photomask blank of claim 1, wherein the backside film has, from the side away from the substrate, the first layer, the second layer, and the third layer which are similar to a film composed of a material containing chromium.

6. A method for producing a photomask having a circuit pattern of a film made of a material containing chromium from the photomask blank according to any one of claims 1 to 5, comprising the steps of: (A) forming a resist film on a side of the film made of a material containing chromium that is away from the substrate; (B) patterning the resist film to form a resist pattern; (C) patterning the film made of the chromium-containing material by dry etching using a chlorine-based gas containing oxygen, using the resist pattern as an etching mask, to form a pattern of the film made of the chromium-containing material; (D) Step of removing the resist pattern A method for manufacturing a photomask, comprising:

7. A substrate; A film made of a material containing chromium and provided on the substrate, the film having an effective area that is a circuit pattern. Equipped with the film made of a material containing chromium has a first layer, a second layer, and a third layer from a side away from the substrate, the first layer, the second layer, and the third layer all contain chromium; the first layer further contains oxygen and nitrogen, has a chromium content of 30 atomic % or more and less than 38 atomic %, an oxygen content of 30 atomic % or more and 65 atomic % or less, and a nitrogen content of 5 atomic % or more and 26 atomic % or less, and has a thickness of 8 nm or more and 20 nm or less; the second layer further contains nitrogen, has a chromium content of 66 atomic % or more and 92 atomic % or less, a nitrogen content of 8 atomic % or more and 34 atomic % or less, and has a thickness of 40 nm or more and 70 nm or less; The third layer further contains oxygen and nitrogen, has a chromium content of 30 atomic % or more and 44 atomic % or less, an oxygen content of 30 atomic % or more and 65 atomic % or less, and a nitrogen content of 5 atomic % or more and 26 atomic % or less, and has a thickness of 10 nm or less.

Images