Photomask blank and method for manufacturing a photomask

Abstract

To provide a photomask blank that simplifies the process for removing hard mask films, and consequently simplifies the mask manufacturing process. [Solution] The device comprises a substrate, a single or multiple pattern-forming layer on the substrate, and a hard mask film on the pattern-forming layer. The hard mask film is made of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen, and the film density of the hard mask film is 6.0 g / cm³. 3 The photomask blank is characterized in that the hard mask film has resistance to dry etching using a gas containing fluorine and not containing oxygen, and resistance to dry etching using a gas containing chlorine and not containing oxygen, and when the film thickness reduction per minute when the hard mask film is treated with sulfuric acid peroxide is v [nm / min] and the film thickness of the hard mask film is d [nm], the following formula (1) d / v ≤ 60 [min] (1) is satisfied.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a photomask used in the manufacture of semiconductor integrated circuits and the like, and to a photomask blank preferably used in this method. [Background technology]

[0002] In the manufacturing process of semiconductor devices (semiconductor devices), photolithography is repeatedly used, which involves irradiating a transfer mask with exposure light to transfer the circuit pattern formed on the mask onto a semiconductor substrate (semiconductor wafer).

[0003] Traditionally, the exposure light wavelength was mainly 193 nm using argon fluoride (ArF) excimer laser light. However, in recent years, with the continuous miniaturization of device patterns, the formation of even finer patterns has become necessary. As a result, EUV lithography technology, which uses extreme ultraviolet (EUV) light with an even shorter wavelength than ArF excimer laser light as the exposure light, has come into use.

[0004] In lithography using excimer laser light with a wavelength of 193 nm, a transmission-type projection optical system and a transmission-type mask for pattern transfer are used. However, EUV light, with a wavelength of approximately 0.2 to 100 nm, more specifically around 13.5 nm, is characterized by extremely low transparency to materials. Because conventional transmission-type projection optical systems and masks cannot be used, EUV lithography uses a reflection-type optical system and a reflection-type mask for pattern transfer. EUV lithography has a shorter exposure wavelength and allows for the transfer of finer patterns. However, the exposure equipment is expensive, and changing equipment from conventional transmission-type to reflection-type systems is difficult. Therefore, transmission-type and reflection-type photomasks are selectively used depending on each step of the lithography process, which is repeated many times.

[0005] When fabricating a photomask, a resist film is formed on a photomask blank, a pattern is drawn using an electron beam, and a resist pattern is obtained through development. The pattern-forming layer is then dry-etched using the obtained resist pattern as a mask. In a transmissive photomask, the pattern-forming layer is a film that includes a light-shielding film that blocks the excimer laser light used for exposure. In a reflective photomask, the pattern-forming layer is a light-absorbing film that absorbs the exposure light, which is in the extreme ultraviolet region.

[0006] When processing a pattern-forming layer, if an attempt is made to process a finer photomask pattern while maintaining the same film thickness as the resist film, the ratio of film thickness to pattern width, or aspect ratio, becomes high. This degrades the shape of the resist pattern, leading to unsuccessful pattern transfer, and in some cases, causing the resist pattern to collapse or peel off. Therefore, as the photomask pattern becomes finer, it is necessary to reduce the burden on the resist pattern.

[0007] To solve such problems in permeable masks, molybdenum silicide films are used, which can be easily etched by fluorine-based dry etching, which is less damaging to the resist film compared to general chromium (Cr) compound films.

[0008] Furthermore, methods have also been developed that include a hard mask film between the resist and the pattern formation layer. For example, Patent Document 1 describes forming an SiO2 film on a MoSi2 film and using the pattern of the SiO2 film as an etching mask when dry etching the MoSi2 film using a chlorine-containing gas. Also, for example, Patent Document 2 describes forming a chromium film as a light-shielding film on a phase-shift film and forming an SiO2 film as a hard mask film on the chromium film, and using the pattern of the SiO2 film as a hard mask when etching the chromium film.

[0009] The material for the hard mask film can be any material that ensures an etching selectivity ratio between the hard mask film and the pattern formation layer when the hard mask pattern is used as a mask for dry etching of the pattern formation layer. When forming light-shielding film patterns containing silicon or absorption film patterns made of tantalum (Ta) or ruthenium (Ru), a hard mask film containing chromium (Cr) that is resistant to etching with a gas containing fluorine or a gas containing chlorine but not oxygen is used. For example, Patent Document 3 proposes a method to obtain high-precision processability by processing a light-shielding film containing silicon using a thin film made of a chromium-based material as an etching mask film.

[0010] Furthermore, it is known that films containing chromium (Cr) generally have better adhesion to resists than films containing silicon, and that peeling of the resist pattern during the development process is less likely to occur. Patent Document 4 describes a method for improving resist resolution and forming a high-precision pattern by providing a chromium-containing film between the silicon-containing hard mask film and the resist when creating a photomask.

[0011] As described above, hard mask films containing chromium (Cr) are sometimes formed to obtain higher precision in pattern formation of photomasks. However, chromium hard mask films usually need to be removed by dry etching using a gas containing chlorine (Cl) and oxygen (O) after processing the pattern formation layer. Therefore, when fabricating a photomask using a mask blank with a chromium (Cr) hard mask film, an additional dry etching step for hard mask removal is required in addition to the conventional manufacturing process. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 63-85553 [Patent Document 2] Japanese Patent Application Publication No. 7-49558 [Patent Document 3] Japanese Patent Publication No. 2007-241060 [Patent Document 4] Japanese Patent Publication No. 2022-011477 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention has been made to solve the above problems and aims to provide a photomask blank that can simplify the process for removing the hard mask film, and consequently the photomask manufacturing process, and a method for manufacturing a photomask using the same. [Means for solving the problem]

[0014] To solve the above problems, the present invention provides a photomask blank, circuit board and A pattern-forming layer consisting of one or more layers on the substrate, The hard mask film on the pattern formation layer and It has, The hard mask film is made of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen. The film density of the hard mask film is 6.0 g / cm³. 3 The following: The hard mask film has resistance to dry etching using a fluorine-containing, oxygen-free gas and resistance to dry etching using a chlorine-containing, oxygen-free gas. When the hard mask film is treated with sulfuric acid peroxide, the rate of film thickness reduction per minute is v [nm / min], and the film thickness of the hard mask film is d [nm], then the following formula (1) d / v ≤ 60 [min] (1) The present invention provides a photomask blank characterized by satisfying the following conditions.

[0015] In the method for manufacturing a photomask using such a photomask blank of the present invention, it is possible to remove the hard mask film in the resist stripping step (resist pattern removal) after processing the pattern forming layer. Therefore, according to the photomask blank of the present invention, the process for removing the hard mask film can be simplified, and thus the photomask manufacturing process can be simplified.

[0016] For example, it is preferable that the hard mask film has a chromium content of 60 atomic% or less, a nitrogen content of 40 atomic% or more, and a thickness of 10 nm or less.

[0017] According to the photomask blank including the hard mask film in such a preferable embodiment, the process for removing the hard mask film can be more reliably simplified.

[0018] Alternatively, it is also preferable that the hard mask film has a chromium content of 40 atomic% or less, an oxygen content of 60 atomic% or more, and a thickness of 10 nm or less.

[0019] Also, according to the photomask blank including the hard mask film in such another preferable embodiment, the process for removing the hard mask film can be more reliably simplified.

[0020] Alternatively, it is also preferable that the hard mask film has a chromium content of 40 atomic% or less, a nitrogen content of 15 atomic% or more and 25 atomic% or less, an oxygen content of 30 atomic% or more and 40 atomic% or less, a carbon content of 15 atomic% or less, and a thickness of 10 nm or less.

[0021] Also, according to the photomask blank including the hard mask film in such yet another preferable embodiment, the process for removing the hard mask film can be more reliably simplified.

[0022] For example, the pattern forming layer may be a film including a light shielding film that shields excimer laser light, the light shielding film may be made of a material containing silicon, and the thickness may be 30 nm or more and 180 nm or less.

[0023] Using such photomask blanks, it is possible to manufacture excellent transmissive photomasks.

[0024] Alternatively, the pattern-forming layer is a film containing an absorption film that absorbs exposure light, which is in the extreme ultraviolet region. The substrate and the absorption film may further include a multilayer reflective film that reflects exposure light, and a protective film for protecting the multilayer reflective film.

[0025] Using such photomask blanks, it is possible to manufacture excellent reflective photomasks.

[0026] In this case, the absorption film may be made of a material containing at least one element among Ru and Ta.

[0027] The absorption film may be made of a material containing at least one element from Ru and Ta.

[0028] Furthermore, the present invention provides a method for manufacturing a photomask, Using the photomask blank of the present invention, The present invention provides a method for manufacturing a photomask, characterized by removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

[0029] With this method of manufacturing a photomask according to the present invention, the process for removing the hard mask film can be simplified, and consequently, the photomask manufacturing process can be simplified.

[0030] Furthermore, the present invention provides a method for manufacturing a transmissive photomask, Using the photomask blank of the present invention, The present invention provides a method for manufacturing a transmissive photomask, characterized by removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

[0031] With this method for manufacturing a transmissive photomask according to the present invention, the process for removing the hard mask film can be simplified, and consequently, the photomask manufacturing process can be simplified.

[0032] Furthermore, the present invention provides a method for manufacturing a reflective photomask, Using the photomask blank of the present invention, The present invention provides a method for manufacturing a reflective photomask, characterized by removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

[0033] With this method for manufacturing a reflective photomask according to the present invention, the process for removing the hard mask film can be simplified, and consequently, the photomask manufacturing process can be simplified. [Effects of the Invention]

[0034] As described above, the photomask blank of the present invention allows for the removal of a chromium-containing hard mask film in conjunction with the removal of the resist pattern, and eliminates the need to add a new step after cleaning during resist stripping. Therefore, the process of manufacturing a photomask from a mask blank with high-precision processability can be simplified. In other words, the photomask blank of the present invention simplifies the process for removing the hard mask film, and consequently simplifies the photomask manufacturing process. [Brief explanation of the drawing]

[0035] [Figure 1] This is a schematic diagram showing an example of a photo blank of the present invention. [Figure 2] This flowchart shows an example of a method for manufacturing a photomask according to the present invention. [Modes for carrying out the invention]

[0036] As mentioned above, there was a need to develop a photomask blank that could simplify the process for removing the hard mask film, and consequently, the photomask manufacturing process.

[0037] The inventors of this invention have conducted extensive research on the above problem and have found that the film density is 6.0 g / cm³. 3 The present invention was discovered to solve the above problem by providing a hard mask film that has resistance to dry etching using a gas containing fluorine but not oxygen, and resistance to dry etching using a gas containing chlorine but not oxygen, and that can be removed by cleaning with sulfuric acid peroxide (SPM cleaning), thereby enabling the removal of the hard mask film in the resist peeling process after processing the pattern formation layer.

[0038] In other words, the present invention is a photomask blank, circuit board and A pattern-forming layer consisting of one or more layers on the substrate, The hard mask film on the pattern formation layer and It has, The hard mask film is made of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen. The film density of the hard mask film is 6.0 g / cm³. 3 The following: The hard mask film has resistance to dry etching using a fluorine-containing, oxygen-free gas and resistance to dry etching using a chlorine-containing, oxygen-free gas. When the hard mask film is treated with sulfuric acid peroxide, the rate of film thickness reduction per minute is v [nm / min], and the film thickness of the hard mask film is d [nm], then the following formula (1) d / v ≤ 60 [min] (1) This is a photomask blank characterized by satisfying the following conditions.

[0039] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0040] [Photomask blank] The photomask blank of the present invention is circuit board and A pattern-forming layer consisting of one or more layers on the substrate, The hard mask film on the pattern formation layer and It has, The hard mask film is made of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen. The film density of the hard mask film is 6.0 g / cm³. 3 The following: The hard mask film has resistance to dry etching using a fluorine-containing, oxygen-free gas and resistance to dry etching using a chlorine-containing, oxygen-free gas. When the hard mask film is treated with sulfuric acid peroxide, the rate of film thickness reduction per minute is v [nm / min], and the film thickness of the hard mask film is d [nm], then the following formula (1) d / v ≤ 60 [min] (1) It satisfies the condition.

[0041] Figure 1 shows a schematic diagram of an example of a photo blank of the present invention. The photo mask blank 10 in Figure 1 has a substrate 1, a pattern forming layer 2 on the substrate 1, and a hard mask film 3 on the pattern forming layer 2. In Figure 1, the pattern forming layer 2 is shown as one layer as an example, but it may be a single layer or may consist of multiple layers.

[0042] The photomask blank of the present invention may be a transmissive mask blank or a reflective mask blank.

[0043] The transparent mask blank of the present invention may have a substrate which is a transparent substrate, a pattern forming layer which is a film that includes a light-shielding film that blocks exposure light and is formed on one of the main surfaces (surfaces) of the substrate, and a hard mask film formed on the light-shielding film.

[0044] As for the transparent substrate, there are no particular restrictions as long as it is a material that is transparent to exposure light and does not deform much during the heat treatment in the manufacturing of the photomask blank and photomask. One example is a quartz substrate.

[0045] The reflective mask blank of the present invention may have a substrate, a pattern-forming layer which is a multilayer reflective film that reflects exposure light and is formed on one main surface (surface) of the substrate, an absorption film that absorbs exposure light and is formed on the multilayer reflective film, and a hard mask film on the absorption film.

[0046] In this case, the substrate is preferably one that has low thermal expansion characteristics for use with EUV light exposure, for example, a thermal expansion coefficient of ±2 × 10 -8 Within / ℃, preferably ±5 × 10 -9 It is preferable that the material be formed within a range of / ℃ or less. Examples of such materials include titania-doped quartz glass (SiO2-TiO2 glass).

[0047] The substrate size is preferably 152 mm square for the main surface area and 6.35 mm for the thickness. A substrate of this size is what is known as a 6025 substrate (a substrate with a main surface area of ​​6 inches square and a thickness of 0.25 inches).

[0048] The exposure light used in the photomask blank and photomask of the present invention (the light used in exposure using the photomask) is preferably ArF excimer laser light (wavelength 193 nm) and extreme ultraviolet light (EUV) around 13.5 nm.

[0049] In the present invention, the pattern-forming layer is a layer that forms a mask pattern. When the exposure light is excimer laser light, it is a light-shielding film or a phase-shifting film, and when the exposure light is in the extreme ultraviolet region, it is an absorbing film that absorbs the exposure light. The pattern-forming layer may be a single layer or may consist of multiple layers. The hard mask film is a film that acts as an etching mask when the pattern-forming layer is a single layer and when the pattern-forming layer consists of multiple layers, it is at least the hard mask-side film of the pattern-forming layer that acts as an etching mask when patterning.

[0050] The hard mask film is preferably in contact with the pattern-forming layer.

[0051] When the exposure light is excimer laser light, the pattern-forming layer is, in the case of a single layer, for example, a light-shielding film or a phase-shifting film, and when it consists of multiple layers, it is a layer having multiple films selected from the group consisting of, for example, a light-shielding film, a phase-shifting film, an etching stopper film, etc.

[0052] In a transmissive mask blank, if the pattern-forming layer is a single layer, it is preferable that the entire pattern-forming layer is a light-shielding layer. If the pattern-forming layer consists of multiple layers, it is preferable that the layer in contact with the hard mask film, or the layer that forms the pattern using the hard mask film as a mask, is a light-shielding layer.

[0053] The above-mentioned light-shielding film is preferably made of a silicon-containing material, for example, preferably containing molybdenum, silicon, and nitrogen. Specifically, as a material for the light-shielding film, examples include molybdenum-silicon nitride (MoSiN), which consists of molybdenum, silicon, and nitrogen, as well as molybdenum-silicon nitrogen compounds containing one or more elements from molybdenum, silicon, nitrogen, oxygen, and carbon, such as molybdenum-silicon oxide (MoSiNO), molybdenum-silicon carbide (MoSiNC), and transition metal silicon nitride oxide carbide (MoSiNOC). The light-shielding film needs to have sufficient light-shielding properties for the exposure wavelength of ArF, and the film thickness of the light-shielding film is usually between 30 nm and 180 nm.

[0054] A transmissive mask blank, which is an example of a photomask blank of the present invention, may have an etching prevention film between the substrate and the light-shielding film, and may also have a phase-shift film between the etching prevention film and the substrate. The etching prevention film is made of a chromium-containing material and functions as an etching stopper during dry etching of the light-shielding film, thereby preventing the substrate provided in the underlying layer, or the phase-shift film if one is present, from being excessively etched. The phase-shift film is a film that changes the phase of the exposure light transmitted through the film by, for example, about 180° compared to when there is no film, and is usually formed of a silicon-containing material with a film thickness of 40 nm to 100 nm. Furthermore, in the transmissive mask blank of the present invention, the pattern-forming layer may include the substrate surface to be processed.

[0055] A reflective mask blank generally has a basic structure comprising a substrate with low thermal expansion, a multilayer reflective film that reflects EUV light formed on one of the two main surfaces of the substrate, and an absorption film pattern that absorbs EUV light formed on the same. When the exposure light is in the extreme ultraviolet region, the pattern-forming layer is an absorption film or a phase-shift film if it is a single layer, and a layer having multiple films selected from an absorption film, a phase-shift film, an etching stopper film, etc. if it is a multilayer layer. When the pattern-forming layer is a single layer, it is preferable that the entire pattern-forming layer is an absorption film, and when the pattern-forming layer consists of multiple layers, it is preferable that the layer in contact with the hard mask film, or the layer that forms the pattern using the hard mask film as a mask, is an absorption film. The above absorption film may be a film that has a phase-shift effect, changing the phase by about 170-240° compared to when there is no absorption film.

[0056] The absorption film may be a single layer or a multilayer, and an anti-reflective layer or the like may be formed on its surface. The absorption film is a film that absorbs EUV light, and in the present invention, it is preferably a material that is dry-etched with a gas that contains fluorine and does not contain oxygen, or a gas that contains chlorine and does not contain oxygen. Specifically, as a material for the absorption film, a material containing at least one element from Ru, Ta, Ir, Pt, Rh, and Si, more preferably at least one from Ru and Ta, is mentioned.

[0057] A reflective mask blank, which is an example of a photomask blank of the present invention, may have a protective film between the multilayer reflective film and the absorbing film to protect the multilayer reflective film. The protective film is also called a capping film. The protective film is a film for protecting the multilayer reflective film. The protective film is usually provided in contact with the multilayer reflective film. Examples of materials for forming the protective film include ruthenium (Ru) compounds.

[0058] A hard mask film is a film that functions as an etching mask when dry etching a pattern-forming layer, such as a light-shielding film (in the case of a transmissive mask blank) or an absorption film (in the case of a reflective mask blank).

[0059] The hard mask film included in the photomask blank of the present invention, which is made of a chromium (Cr)-containing material, can be dry-etched using a gas containing chlorine (Cl) and oxygen (O). On the other hand, the hard mask film included in the photomask blank of the present invention has resistance to dry etching using a gas containing fluorine and not oxygen, and resistance to dry etching using a gas containing chlorine and not oxygen.

[0060] From the standpoint of functioning as a mask for dry etching, the thickness of the hard mask film is more preferably 5 nm or more, and more preferably 10 nm or less.

[0061] In general, when dry etching is performed to process a pattern-forming layer, it is preferable that the hard mask film has high etching resistance, i.e., a slow etching rate. When using a hard mask film with a thickness of 5 nm to 10 nm, the etching rate in dry etching using a gas containing fluorine but not oxygen is preferably 0.3 nm / min or less, more preferably 0.2 nm / min or less. Also, when using a hard mask film with a thickness of 5 nm to 10 nm, the etching rate in dry etching using a gas containing chlorine but not oxygen is preferably 0.3 nm / min or less, more preferably 0.2 nm / min or less.

[0062] In the photomask blank of the present invention, the hard mask film can be easily removed by SPM cleaning. More specifically, when the rate of film thickness reduction per minute when the hard mask film is treated with sulfuric acid peroxide is v [nm / min], and the film thickness of the hard mask film is d [nm], then the following formula (1) d / v ≤ 60 [min] (1) It satisfies the condition.

[0063] In the photomask blank of the present invention, the hard mask film containing chromium (Cr) is easily removed by SPM washing, and the film density is 6.0 g / cm³. 3 The following applies:

[0064] In this invention, SPM refers to a solution obtained by mixing sulfuric acid and hydrogen peroxide. For example, it is a solution prepared by mixing 96% sulfuric acid and 30% hydrogen peroxide in a volume ratio of 3:1. Cleaning using SPM is referred to as SPM cleaning.

[0065] Furthermore, the chromium content in the hard mask film is preferably 60 atomic% or less, more preferably 45% or less, and even more preferably 40% or less. The hard mask film is made of a material containing chromium (Cr) and at least one element selected from the group consisting of oxygen (O), nitrogen (N), and carbon (C). Specific examples of chromium (Cr)-containing materials include chromium (Cr) compounds such as CrO, CrN, CrON, and CrCON. When the hard mask film is a film formed of chromium and nitrogen, the chromium content in the hard mask film is preferably 60 atomic% or less, and the nitrogen content is preferably 40 atomic% or more. When the hard mask film is a film formed of chromium and oxygen, the chromium content in the hard mask film is preferably 40 atomic% or less, and the oxygen content is preferably 60 atomic% or more. When the hard mask film is a film formed of chromium, oxygen, nitrogen, and carbon, the chromium content in the hard mask film is preferably 40 atomic% or less, the nitrogen content is preferably 15 atomic% to 25 atomic%, the oxygen content is preferably 30 atomic% to 40 atomic%, and the carbon content is preferably 15 atomic% or less.

[0066] Furthermore, in the photomask blank of the present invention, a resist film may be formed in contact with the side of the hard mask film that is separated from the substrate (the main surface opposite to the substrate).

[0067] Each layer constituting the photomask blank of the present invention is preferably deposited by sputtering, which easily yields a film with excellent homogeneity, and either DC sputtering or RF sputtering can be used. The target and sputtering gas are appropriately selected according to the layer configuration and composition. Films made of chromium-containing materials can be deposited by reactive sputtering using a sputtering gas prepared by adding a reactive gas, such as an oxygen-containing gas, nitrogen-containing gas, or carbon-containing gas, to a noble gas (inert gas) such as helium, neon, or argon, depending on the film to be deposited.

[0068] In particular, the membrane density described above is 6.0 g / cm³. 3 The following conditions apply when forming a hard mask film that has resistance to dry etching using a fluorine-containing, oxygen-free gas and resistance to dry etching using a chlorine-containing, oxygen-free gas, and satisfies d / v ≤ 60 [min] (1), it is preferable to set the pressure during film formation to 0.10 Pa or higher, particularly 0.12 Pa or higher. However, the method for producing the hard mask film of the photomask blank of the present invention is not limited to this method.

[0069] In the photomask blank of the present invention described above, the hard mask film has excellent etching resistance to dry etching used in processing the pattern formation layer, and can therefore be usefully used as an etching mask for the pattern formation layer. Furthermore, since this hard mask film can be easily removed by cleaning with sulfuric acid peroxide (SPM) (SPM cleaning), the hard mask film can be removed in the resist stripping process after processing the pattern formation layer. Therefore, since there is no need to add a new step after cleaning during resist stripping, the process of manufacturing a photomask from a mask blank with high-precision processability can be simplified. In other words, the photomask blank of the present invention simplifies the process for removing the hard mask film, and consequently simplifies the photomask manufacturing process.

[0070] [Method for manufacturing photomasks] The method for manufacturing a photomask of the present invention is: Using the photomask blank of the present invention, The hard mask film is removed using sulfuric acid or sulfuric acid peroxide.

[0071] The following describes an example of the method for manufacturing a photomask according to the present invention, with reference to Figure 2. However, the method for manufacturing a photomask according to the present invention is not limited to the example shown in Figure 2.

[0072] First, prepare the photomask blank of the present invention as shown in Figure 2(A). In this example, the photomask blank 10 shown in Figure 1 is used.

[0073] Next, a resist film (not shown) is applied to the hard mask film 3 of the photomask blank 10. Then, the resist film is subjected to exposure and development to form a resist pattern.

[0074] Next, the hard mask film 3 is processed, for example, by dry etching, using the resist pattern as an etching mask. This yields a hard mask pattern 3A, as shown in Figure 2(B). The resist pattern 4 remains on the hard mask pattern 3A.

[0075] Next, the hard mask pattern 3A is used as an etching mask to process the pattern-forming layer 2. This results in a pattern-forming layer 2A with a pattern formed on it, as shown in Figure 2(C).

[0076] At this stage, the hard mask pattern 3A and the resist pattern 4 remain on the pattern formation layer 2A.

[0077] Next, the resist pattern 4 is removed by washing with sulfuric acid or sulfuric acid peroxide. Simultaneously or subsequently, the hard mask film 3, or more specifically the hard mask pattern 3A, can be removed by washing with sulfuric acid or sulfuric acid peroxide.

[0078] By removing the hard mask film 3, a photomask 20 is obtained having a substrate 1 and a pattern-forming layer 2A on which a pattern is formed on the substrate 1, as shown in Figure 2(D).

[0079] Thus, in the photomask manufacturing method of the present invention, the hard mask film can be easily removed by washing with sulfuric acid or sulfuric acid peroxide (SPM) (SPM washing), making it possible to remove the hard mask film in the resist stripping step after processing the pattern formation layer. Therefore, since there is no need to add a new step after washing during resist stripping, the process of manufacturing a photomask from a mask blank with high-precision processability can be simplified. In other words, the photomask manufacturing method of the present invention simplifies the process for removing the hard mask film, and consequently simplifies the photomask manufacturing process.

[0080] By using a transmissive mask blank, a transmissive photomask can be manufactured. Alternatively, by using a reflective mask blank, a reflective photomask can be manufactured. [Examples]

[0081] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0082] (Example 1) On a 152 mm square, approximately 6 mm thick transparent quartz substrate, a chromium target was used as the target, and argon and nitrogen were used as the sputtering gases. The flow rate of the sputtering gases was adjusted, and sputtering was performed at a pressure of 0.12 Pa during film formation. A nitrogen-containing chromium film with a chromium content of 51 atomic%, a nitrogen content of 49 atomic%, and a thickness of 10 nm was formed as a hard mask film. The composition of the hard mask film was measured using an X-ray photoelectron spectroscopy analyzer, the thickness was measured using a stylus-type film thickness gauge, and the film density was calculated by X-ray reflectivity measurement (XRR).

[0083] A solution (SPM) prepared by mixing 96 wt% sulfuric acid and 30 wt% hydrogen peroxide in a 3:1 volume ratio was continuously applied to the hard mask film for 6 minutes. After that, the hard mask film was rinsed with pure water for 1 minute. After repeating the above procedure three times, the film thickness of the hard mask film was measured and the amount of film thickness reduction was determined. As a result, the amount of film thickness reduction per minute for this hard mask film in relation to the sulfuric acid / hydrogen peroxide SPM was 0.30 nm / min.

[0084] (Example 2) Except for using argon, nitrogen, and oxygen as sputtering gases and setting the pressure during film formation to 0.17 Pa, an oxygen-containing chromium film with a chromium content of 35 atomic percent, an oxygen content of 65 atomic percent, and a thickness of 10 nm was formed as a hard mask film in the same manner as in Example 1. Although nitrogen was used in the formation of the hard mask film, it was hardly detectable in the compositional analysis (less than 1 atomic percent).

[0085] Similar to Example 1, the rate of film thickness reduction per minute relative to SPM for this hard mask film was determined to be 0.19 nm / min.

[0086] (Example 3) Except for using argon, nitrogen, oxygen, and carbon dioxide as sputtering gases and setting the pressure during film formation to 0.16 Pa, an oxygen, nitrogen, and carbon-containing chromium film with a chromium content of 32 atomic%, an oxygen content of 36%, a nitrogen content of 20 atomic%, a carbon content of 12%, and a thickness of 10 nm was formed as a hard mask film in the same manner as in Example 1.

[0087] Similar to Example 1, the rate of film thickness reduction per minute relative to SPM for this hard mask film was determined to be 0.25 nm / min.

[0088] (Comparative Example 1) Except for using only argon as the sputtering gas and setting the pressure during film formation to 0.06 Pa, a chromium film with a thickness of 10 nm and 100 atomic percent chromium was formed as a hard mask film in the same manner as in Example 1.

[0089] Similar to Example 1, the rate of film thickness reduction per minute relative to SPM for this hard mask film was determined to be 0.05 nm / min.

[0090] (Comparative Example 2) Except for setting the pressure during film formation to 0.08 Pa, a nitrogen-containing chromium film with a chromium content of 79 atomic%, a nitrogen content of 21 atomic%, and a thickness of 10 nm was formed in the same manner as in Example 1.

[0091] Similar to Example 1, the rate of decrease in film thickness per minute relative to SPM of this chromium film was determined to be 0.13 nm / min.

[0092] Table 1 below shows the pressure during film formation and the physical properties of the hard mask films in Examples 1 to 3 and Comparative Examples 1 and 2.

[0093] [Table 1]

[0094] Generally, the thickness of a chromium hard mask film used for thinning resists is more preferably 5 nm or more, and more preferably 10 nm or less. In Examples 1 to 3, which show the composition, film density, and d / v value in Table 1, the chromium hard mask film can be peeled off by SPM cleaning in less than 60 minutes when a hard mask of 5 nm to 10 nm is used.

[0095] On the other hand, in Comparative Examples 1 and 2, removing a chromium hard mask film with a thickness of approximately 10 nm using SPM requires more than 60 minutes of SPM treatment. Such prolonged cleaning raises concerns about potential alteration of the film composition directly beneath the Cr hard mask due to SPM, as well as the generation of haze. Therefore, removing the hard mask films formed in Comparative Examples 1 or 2 using SPM is not practical.

[0096] (Etching resistance test) The etching rates of thin films formed in the same manner as the hard mask films obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were examined. As a result, in dry etching using SF6 and dry etching using Cl2, the etching rate of each film was 0.2 nm / min or less.

[0097] From this result, a film formed in Examples 1 to 3 was formed on a pattern forming layer that can be used as a photomask blank to produce a photomask blank. A pattern was formed on the hard mask film of this photomask blank by a resist method to obtain a hard mask pattern. By using this hard mask pattern as an etching mask, it can be seen that the pattern forming layer can be accurately processed.

[0098] Also, as described above, since the films formed in Examples 1 to 3 can be easily removed by SPM, the hard mask film can be removed in the resist stripping step after processing the pattern forming layer. That is, it was demonstrated that according to the photomask blank of the present invention in Examples 1 to 3, the process for removing the hard mask film can be simplified, and thus the photomask manufacturing process can be simplified.

[0099] The present invention includes the following aspects. [1] A photomask blank having a substrate, a pattern forming layer composed of a single layer or a plurality of layers on the substrate, and a hard mask film on the pattern forming layer, wherein the hard mask film is made of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen, and the film density of the hard mask film is 6.0 g / cm 3 is as follows. The hard mask film has resistance to dry etching using a gas containing fluorine and not containing oxygen, and resistance to dry etching using a gas containing chlorine and not containing oxygen. When the hard mask film is treated with sulfuric acid peroxide, the film thickness reduction amount per minute is v [nm / min], and when the film thickness of the hard mask film is d [nm], the following formula (1) d / v ≦ 60 [min] (1) A photomask blank characterized by satisfying the above. [2] The hard mask film is characterized in that it has a chromium content of 60 atomic% or less, a nitrogen content of 40 atomic% or more, and a thickness of 10 nm or less, as described in [1]. [3] The hard mask film is characterized in that it has a chromium content of 40 atomic% or less, an oxygen content of 60 atomic% or more, and a thickness of 10 nm or less, as described in [1]. [4] The hard mask film is characterized in that it has a chromium content of 40 atomic% or less, a nitrogen content of 15 atomic% to 25 atomic% or less, an oxygen content of 30 atomic% to 40 atomic% or less, a carbon content of 15 atomic% or less, and a thickness of 10 nm or less, as described in [1]. [5] The photomask blank according to any one of [1] to [4], characterized in that the pattern forming layer is a film including a light-shielding film that blocks excimer laser light, the light-shielding film is made of a silicon-containing material and has a thickness of 30 nm to 180 nm. [6] The photomask blank according to any one of [1] to [4], characterized in that the pattern forming layer is a film including an absorption film that absorbs exposure light which is in the extreme ultraviolet region, and further comprises a multilayer reflective film that reflects exposure light and a protective film for protecting the multilayer reflective film between the substrate and the absorption film. [7] The photomask blank according to [6], characterized in that the absorption film is made of a material containing at least one element among Ru and Ta. [8] A method for manufacturing a photomask, characterized by using the photomask blank described in [1] and removing the hard mask film using sulfuric acid or sulfuric acid peroxide. [9] A method for manufacturing a transmissive photomask, characterized by using a photomask blank described in [1] or [5] and removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

[10] A method for manufacturing a reflective photomask, characterized by using a photomask blank described in [1], [6] or [7] and removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

[0100] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0101] 1...Substrate, 2...Pattern formation layer, 2A...Pattern formation layer with pattern formed, 3...Hard mask film, 3A...Hard mask pattern, 4...Resist pattern, 10...Photomask blank, 20...Photomask.

Claims

1. It is a photomask blank, circuit board and A pattern-forming layer consisting of one or more layers on the substrate, The hard mask film on the pattern formation layer and It has, The hard mask film is made of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen. The film density of the hard mask film is 6.0 g / cm³. ３ The following: The hard mask film has resistance to dry etching using a fluorine-containing, oxygen-free gas and resistance to dry etching using a chlorine-containing, oxygen-free gas. When the hard mask film is treated with sulfuric acid peroxide, the rate of film thickness reduction per minute is v [nm / min], and the film thickness of the hard mask film is d [nm], then the following formula (1) d / v≦60 [min] (1) A photomask blank characterized by satisfying the following conditions.

2. The photomask blank according to claim 1, characterized in that the hard mask film has a chromium content of 60 atomic percent or less, a nitrogen content of 40 atomic percent or more, and a thickness of 10 nm or less.

3. The photomask blank according to claim 1, characterized in that the hard mask film has a chromium content of 40 atomic percent or less, an oxygen content of 60 atomic percent or more, and a thickness of 10 nm or less.

4. The hard mask film is characterized in that it has a chromium content of 40 atomic percent or less, a nitrogen content of 15 atomic percent or more and 25 atomic percent or less, an oxygen content of 30 atomic percent or more and 40 atomic percent or less, a carbon content of 15 atomic percent or less, and a thickness of 10 nm or less, as described in claim 1.

5. The photomask blank according to claim 1, characterized in that the pattern-forming layer is a film including a light-shielding film that blocks excimer laser light, the light-shielding film is made of a silicon-containing material and has a thickness of 30 nm or more and 180 nm or less.

6. The pattern-forming layer is a film that includes an absorption film that absorbs exposure light, which is in the extreme ultraviolet region. The photomask blank according to claim 1, further comprising a multilayer reflective film that reflects exposure light between the substrate and the absorption film, and a protective film for protecting the multilayer reflective film.

7. The photomask blank according to claim 6, characterized in that the absorption film is made of a material containing at least one element from Ru and Ta.

8. A method for manufacturing a photomask, Using the photomask blank described in claim 1, A method for manufacturing a photomask, characterized by removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

9. A method for manufacturing a transmissive photomask, Using the photomask blank described in claim 1 or 5, A method for manufacturing a transmissive photomask, characterized by removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

10. A method for manufacturing a reflective photomask, Using the photomask blank described in claim 1, 6, or 7, A method for manufacturing a reflective photomask, characterized by removing the hard mask film using sulfuric acid or sulfuric acid peroxide.

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