Photomask blank and method of manufacturing a photomask

Abstract

The present invention relates to a photomask blank capable of simplifying a process for removing a hard mask film, and further capable of simplifying a mask manufacturing process. The photomask blank is characterized by comprising a substrate, a pattern forming layer on the substrate, and a hard mask film on the pattern forming layer, wherein the hard mask film is formed of a material containing chromium and at least one element selected from the group consisting of nitrogen, carbon, and oxygen, and the film density of the hard mask film is 6.0 g / cm 3 Hereinafter, 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 of the hard mask film when treated with a hydrogen peroxide sulfuric acid mixture is set as v [nm / minute], and the film thickness of the hard mask film is set as d [nm], the following formula (1) is satisfied:

Description

Technical Field

[0001] This invention relates to a method for manufacturing a photomask used in the manufacture of semiconductor integrated circuits, and a photomask blank suitable for use in this method. Background Technology

[0002] In the manufacturing process of semiconductor devices (semiconductor equipment), photolithography is a technique that repeatedly uses exposure light to irradiate a transfer mask to transfer the circuit pattern formed on the mask onto a semiconductor substrate (semiconductor wafer).

[0003] Previously, the mainstream wavelength for exposure light was 193nm, which used argon fluoride (ArF) excimer lasers. However, in recent years, with the continuous miniaturization of device patterns, it is necessary to form even finer patterns. Therefore, EUV lithography technology, which uses extreme ultraviolet (EUV) light with a wavelength shorter than ArF excimer lasers as the exposure light, has begun to be used.

[0004] In photolithography using excimer lasers with a wavelength of 193 nm, transmissive projection optics or transmissive masks for pattern transfer are used. However, EUV light, with wavelengths of approximately 0.2–100 nm, and more specifically around 13.5 nm, is characterized by extremely low transmittance to materials. Since existing transmissive projection optics or masks cannot be used, reflective optics and reflective masks for pattern transfer are used in EUV lithography. EUV lithography has a short exposure wavelength, allowing for the transfer of finer patterns. However, due to the high cost of exposure equipment and the difficulty of converting from existing transmissive to reflective equipment, transmissive and reflective photomasks can be selectively used depending on the repeated lithography steps.

[0005] In photomask fabrication, a resist film is formed on the photomask blank, a pattern is drawn using an electron beam, and the resist pattern is obtained after development. This resist pattern is then used as a mask to dry-etch the patterned layer, thus performing the processing. In transmissive photomasks, the patterned layer is a film containing a light-shielding film that blocks the excimer laser used as exposure light. In reflective photomasks, the patterned layer is a light-absorbing film that absorbs the exposure light, which is in the extreme ultraviolet region.

[0006] When processing the patterning layer, if a finer photomask pattern is to be processed while maintaining the thickness of the resist film without alteration, the ratio of film thickness to pattern width, i.e., the aspect ratio, will increase. This will degrade the shape of the resist pattern, leading to difficulties in pattern transfer or, in some cases, the collapse or peeling of the resist pattern. Therefore, as photomask patterns become finer, it is necessary to reduce the load on the resist pattern.

[0007] To address this issue, molybdenum silicide films are used in transmissive masks. Compared to conventional chromium (Cr) compound films, molybdenum silicide films are more easily etched using fluorine-based dry etching, which is less likely to damage the anti-etching film.

[0008] In addition, methods have been implemented that include a hard mask film between the resist and the patterning layer. For example, Patent Document 1 describes forming a SiO2 film on a MoSi2 film and using the pattern of the SiO2 film as an etching mask when dry etching the MoSi2 film with a chlorine-containing gas. Furthermore, Patent Document 2 describes forming a chromium film as a light-shielding film on a phase-shifting film, forming a SiO2 film on the chromium film as a hard mask film, and using the pattern of the SiO2 film as a hard mask when etching the chromium film.

[0009] The material of the hard mask film is simply a material that ensures an etch selectivity between the hard mask film and the pattern forming layer when the hard mask pattern is used as a mask for dry etching of the pattern forming layer. When forming a light-shielding film pattern containing silicon or an absorption film pattern made of tantalum (Ta) or ruthenium (Ru), a chromium-containing (Cr) hard mask film that is resistant to etching using gases containing fluorine or gases containing chlorine but without oxygen can be used. For example, Patent Document 3 describes a method for processing a light-shielding film containing silicon by using a thin film formed of a chromium-based material as an etching mask film, thereby obtaining high-precision processing capability.

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

[0011] As mentioned above, sometimes a hard mask film containing chromium (Cr) is formed in order to obtain high-precision processability when patterning a photomask. However, the chromium hard mask film usually needs to be removed by dry etching using a gas containing chlorine (Cl) and oxygen (O) after the patterning layer is processed. When making a photomask using a mask blank containing a hard mask film containing chromium (Cr), in addition to the existing manufacturing process, a dry etching process for hard mask removal is required.

[0012] Existing technical documents Patent documents 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 Application Publication No. 2007-241060 Patent Document 4: Japanese Patent Application Publication No. 2022-011477 Summary of the Invention

[0013] (a) Technical problems to be solved The present invention was made to solve the above-mentioned problems, and its purpose is to provide a photomask blank and a method for manufacturing a photomask using the photomask blank. The photomask blank can simplify the process of removing the hard mask film, thereby simplifying the photomask manufacturing process.

[0014] (II) Technical Solution To solve the above-mentioned technical problems, the present invention provides a photomask blank, characterized in that the photomask blank has: substrate; The patterning layer on the substrate, consisting of a single layer or multiple layers; and The hard mask film on the pattern forming layer The hard mask is composed of a material containing chromium and at least one element selected from nitrogen, carbon, and oxygen. The density of the hard mask film is 6.0 g / cm³. 3 the following, The hard mask film is resistant to dry etching using gases containing fluorine but not oxygen, and also resistant to dry etching using gases containing chlorine but not oxygen. When the thickness reduction per minute of the hard mask film during treatment with the sulfuric acid-hydrogen peroxide mixture is defined as v [nm / min], and the thickness of the hard mask film is defined as d [nm], the following equation (1) is satisfied: .

[0015] In the photomask manufacturing method using this photomask preform of the present invention, the hard mask film can be removed by a resist stripping process (resist pattern removal) after processing the pattern forming layer. Therefore, the photomask preform of the present invention simplifies the process for removing the hard mask film, thereby simplifying the photomask manufacturing process.

[0016] For example, preferably, the hard mask film has a chromium content of less than 60 atomic% and a nitrogen content of more than 40 atomic% and a thickness of less than 10 nm.

[0017] Based on the photomask blank containing this preferred solution for the hard mask film, the process for removing the hard mask film can be simplified more reliably.

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

[0019] The photomask blank containing this alternative preferred solution of hard mask film can also more reliably simplify the process for removing the hard mask film.

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

[0021] Based on the photomask blank containing this alternative preferred solution of hard mask film, the process for removing the hard mask film can also be simplified more reliably.

[0022] For example, the pattern forming layer may be a film containing a light-shielding film for shielding the excimer laser, the light-shielding film being formed of a silicon-containing material, and the thickness of the light-shielding film being 30 nm to 180 nm.

[0023] If this photomask blank is used, it is possible to manufacture excellent transmissive photomasks.

[0024] Alternatively, the pattern forming layer may be a film containing an absorption film that absorbs exposure light as extreme ultraviolet light, and the photomask blank may further have a multilayer reflective film for reflecting exposure light and a protective film for protecting the multilayer reflective film between the substrate and the absorption film.

[0025] If this photomask blank is used, it is possible to manufacture excellent reflective photomasks.

[0026] In this case, the absorbent membrane may also be made of a material containing at least one element from Ru and Ta.

[0027] The absorber membrane can be made of a material containing at least one of Ru and Ta.

[0028] Furthermore, the present invention provides a method for manufacturing a photomask, characterized in that the photomask blank of the present invention is used, and the hard mask film is removed using a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide.

[0029] If the photomask manufacturing method of this invention is adopted, the process for removing the hard mask film can be simplified, thereby simplifying the photomask manufacturing process.

[0030] Furthermore, the present invention provides a method for manufacturing a transmissive photomask, characterized in that the photomask blank of the present invention is used, and the hard mask film is removed using a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide.

[0031] If the method for manufacturing the transmissive photomask of this invention is adopted, the process for removing the hard mask film can be simplified, thereby simplifying the photomask manufacturing process.

[0032] Furthermore, the present invention provides a method for manufacturing a reflective photomask, characterized in that the photomask blank of the present invention is used, and the hard mask film is removed using sulfuric acid or a mixture of sulfuric acid and hydrogen peroxide.

[0033] If the method for manufacturing the reflective photomask of this invention is adopted, the process for removing the hard mask film can be simplified, thereby simplifying the photomask manufacturing process.

[0034] (III) Beneficial Effects As described above, the photomask blank according to the present invention allows for the continuous removal of the chromium-containing hard mask film along with the removal of the resist pattern, eliminating the need for additional steps after cleaning during resist stripping. This simplifies the process of manufacturing photomasks from a photomask blank with high-precision machinability. In other words, the photomask blank according to the present invention simplifies the process for removing the hard mask film, thereby simplifying the photomask manufacturing process. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating an example of the photomask blank of the present invention.

[0036] Figure 2 A flowchart illustrating an example of a method for manufacturing a photomask according to the present invention.

[0037] Explanation of reference numerals in the attached figures 1: Substrate; 2: Pattern forming layer; 2A: Pattern forming layer with pattern; 3: Hard mask film; 3A: Hard mask pattern; 4: Resist pattern; 10: Photomask blank; 20: Photomask. Detailed Implementation

[0038] As mentioned above, the aim is to develop a photomask blank that simplifies the process of removing the hard mask film, thereby simplifying the photomask manufacturing process.

[0039] The inventors of this application conducted in-depth research on the aforementioned technical problems and discovered that by setting a hard mask film, the hard mask film can be removed through the resist stripping process after processing the pattern forming layer, thus solving the above-mentioned technical problems and completing the present invention. The film density of the hard mask film is 6.0 g / cm³. 3The following describes a method that is resistant to dry etching using gases containing fluorine but not oxygen, and also resistant to dry etching using gases containing chlorine but not oxygen. The hard mask film can be removed by cleaning with a mixture of sulfuric acid and hydrogen peroxide (SPM cleaning).

[0040] That is, the present invention is a photomask blank, characterized in that the photomask blank has: substrate; The patterning layer on the substrate, consisting of a single layer or multiple layers; and The hard mask film on the pattern forming layer The hard mask is formed of a material comprising chromium and at least one element selected from nitrogen, carbon, and oxygen. The density of the hard mask film is 6.0 g / cm³. 3 the following, The hard mask film is resistant to dry etching using gases containing fluorine but not oxygen, and also resistant to dry etching using gases containing chlorine but not oxygen. When the thickness reduction per minute of the hard mask film during treatment with the sulfuric acid-hydrogen peroxide mixture is set as v [nm / min], and the thickness of the hard mask film is set as d [nm], the following equation (1) is satisfied: .

[0041] The present invention will now be described in detail, but it is not limited thereto.

[0042] [Photomask preform] The photomask blank of the present invention has the following characteristics: substrate; The patterning layer on the substrate, consisting of a single layer or multiple layers; and The hard mask film on the pattern forming layer The hard mask is formed of a material comprising chromium and at least one element selected from nitrogen, carbon, and oxygen. The density of the hard mask film is 6.0 g / cm³. 3 the following, The hard mask film is resistant to dry etching using gases containing fluorine but not oxygen, and also resistant to dry etching using gases containing chlorine but not oxygen. When the thickness reduction per minute of the hard mask film during treatment with the sulfuric acid-hydrogen peroxide mixture is set as v [nm / min], and the thickness of the hard mask film is set as d [nm], the following equation (1) is satisfied: .

[0043] Figure 1A schematic diagram showing an example of the photomask blank of the present invention is shown. Figure 1 The photomask blank 10 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. Although the pattern forming layer 2... Figure 1 The middle layer is recorded as a single layer, but it can be a single layer or composed of multiple layers.

[0044] The photomask blank of the present invention can be a transmissive photomask blank or a reflective photomask blank.

[0045] The transmissive mask blank of the present invention may have: a substrate as a transparent substrate, a pattern forming layer formed on a main surface (surface) of the substrate as a film containing a light-shielding film for blocking exposure light, and a hard mask film formed on the light-shielding film.

[0046] As a transparent substrate, there are no particular restrictions as long as it is a material that is transparent to the exposure light and has minimal deformation during heat treatment in the manufacturing of the photomask blank and the photomask. Quartz substrates can be cited as an example.

[0047] The reflective mask blank of the present invention may include: a substrate, a pattern forming layer of a multilayer reflective film formed on a main surface (surface) of the substrate as a reflective exposure light, an absorbing film formed on the multilayer reflective film to absorb the exposure light, and a hard mask film on the absorbing film.

[0048] At this point, a substrate with low thermal expansion characteristics is preferred as the substrate used for EUV light exposure, for example, a substrate with a thermal expansion coefficient of ±2×10⁻⁶. -8 Within / ℃, preferably ±5×10 -9 Materials formed within a temperature range of / ℃. Examples of such materials include titanium dioxide-doped quartz glass (SiO2-TiO2 type glass).

[0049] Regarding the substrate size, it is preferred that the main surface area of ​​the substrate is 152 mm square and the substrate thickness is 6.35 mm. This size substrate 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).

[0050] The photomask blank and the exposure light used in the photomask of the present invention (the light used in the exposure using the photomask) are preferably ArF excimer laser (wavelength of 193nm) and extreme ultraviolet (hereinafter referred to as "EUV") with a wavelength of around 13.5nm.

[0051] In this invention, the pattern forming layer refers to the layer that forms the mask pattern. When the exposure light is an excimer laser, the pattern forming layer is a light-shielding film or a phase-shifting film, etc.; when the exposure light is extreme ultraviolet light, the pattern forming layer is an absorption film that absorbs the exposure light, etc. The pattern forming layer can be a single layer or can be composed of multiple layers. For the hard mask film, when the pattern forming layer is a single layer, the hard mask film is the film that becomes the etching mask when the entire pattern forming layer is patterned; when the pattern forming layer is multilayer, the hard mask film is at least the film of the pattern forming layer closest to the hard mask side and becomes the etching mask during patterning.

[0052] The hard mask film is preferably in contact with the pattern forming layer.

[0053] When the exposure light is an excimer laser, the pattern forming layer is a single layer, such as a light-shielding film or a phase-shifting film, or the pattern forming layer is composed of multiple layers, such as a layer having multiple films selected from the group consisting of a light-shielding film, a phase-shifting film, an etching stopper film, etc.

[0054] In a transmissive mask blank, when the pattern forming layer is a single layer, it is preferable that the entire pattern forming layer is a light-shielding layer. When the pattern forming layer is composed 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 film.

[0055] The aforementioned light-shielding film is preferably formed from a silicon-containing material, such as a material containing molybdenum, silicon, and nitrogen. Specifically, in addition to molybdenum silicon nitride (MoSiN), which is composed of molybdenum, silicon, and nitrogen, other molybdenum silicon nitride compounds containing one or more of molybdenum, silicon, nitrogen, oxygen, and carbon can be listed, such as molybdenum silicon nitride oxide (MoSiNO), molybdenum silicon nitride 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 is typically 30 nm to 180 nm.

[0056] As an example of the photomask blank of the present invention, the transmissive photomask blank may have an etch-resistant film between the substrate and the light-shielding film, and may further have a phase-shifting film between the etch-resistant film and the substrate. The etch-resistant film is formed of a chromium-containing material and functions as an etch stop film during dry etching of the light-shielding film, thereby preventing over-etching of the substrate underneath, or, if a phase-shifting film is present. The phase-shifting film is a film that causes a phase change of, for example, about 180° in the phase of the exposure light transmitted through the film compared to when there is no film, and is typically 40 nm to 100 nm thick and mainly formed of a silicon-containing material. Furthermore, the transmissive photomask blank of the present invention may include a substrate surface processed with a patterning layer.

[0057] Reflective mask blanks typically have the following basic structure: a substrate with low thermal expansion, a multilayer reflective film formed on one of the two main surfaces of the substrate to reflect EUV light, and an absorbent film pattern formed on the multilayer reflective film to absorb EUV light. When the exposure light is extreme ultraviolet light, if the pattern forming layer is a single layer, it is an absorbent film or a phase-shifting film; if the pattern forming layer is multilayer, it is a layer containing multiple films such as an absorbent film, a phase-shifting film, and an etch stop film. When the pattern forming layer is a single layer, it is preferable that the entire pattern forming layer is an absorbent film; when the pattern forming layer is composed of multiple layers, it is preferable that the layer in contact with the hard mask film, or the layer in which the pattern is formed using the hard mask film, is an absorbent film. The aforementioned absorbent film can be a film that causes a phase shift of approximately 170-240° compared to when there is no absorbent film and has a phase-shifting effect.

[0058] The absorption film can be a single layer or multiple layers, and an anti-reflective layer can also be formed on the surface. The absorption film is a film that absorbs EUV light. In this invention, it is preferable to use a material that is dry-etched using a gas containing fluorine but not oxygen or containing chlorine but not oxygen as the material of the absorption film. Specifically, materials containing at least one element selected from Ru, Ta, Ir, Pt, Rh and Si can be listed, and materials containing at least one element selected from Ru and Ta can be more preferred.

[0059] As an example of the photomask blank of the present invention, the reflective photomask blank may have a protective film between the multilayer reflective film and the absorber film to protect the multilayer reflective film. The protective film is also called a capping film. The protective film is a film used to protect the multilayer reflective film. The protective film is typically disposed in contact with the multilayer reflective film. Ruthenium (Ru) compounds can be listed as materials for forming the protective film.

[0060] Hard mask film is a film that functions as an etching mask when dry etching patterning layers, such as light-shielding films (in the case of transmissive mask blanks) or absorption films (in the case of reflective mask blanks).

[0061] The hard mask film formed from a chromium (Cr)-containing material included in the photomask blank of the present invention 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 but not oxygen, and resistance to dry etching using a gas containing chlorine but not oxygen.

[0062] From the perspective 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.

[0063] Furthermore, in dry etching used for processing patterned layers, a hard mask film with high etch resistance, i.e., a slow etching rate, is generally preferred. When using a hard mask film with a thickness of 5 nm to 10 nm, the etching rate under 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. Additionally, when using a hard mask film with a thickness of 5 nm to 10 nm, the etching rate under 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.

[0064] In the photomask blank of the present invention, the hard mask film can be easily removed by SPM cleaning. More specifically, when the thickness reduction per minute of the hard mask film during treatment with the sulfuric acid-hydrogen peroxide mixture is set as v [nm / min] and the thickness of the hard mask film is set as d [nm], the following equation (1) is satisfied: .

[0065] To facilitate the removal of the chromium (Cr)-containing hard mask film in the photomask preform of this invention by SPM cleaning, the film density is 6.0 g / cm³. 3 the following.

[0066] In addition, in this invention, SPM refers to a solution containing sulfuric acid and hydrogen peroxide water, for example, a solution prepared by mixing 96% sulfuric acid and 30% hydrogen peroxide water in a volume ratio of 3 to 1. Cleaning using SPM is called SPM cleaning.

[0067] 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 formed of a material containing chromium (Cr) and at least one element selected from the group consisting of oxygen (O), nitrogen (N), and carbon (C). Specifically, chromium (Cr) compounds such as CrO, CrN, CrON, and CrCON can be listed as materials containing chromium (Cr). When the hard mask film is a film formed from 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 from 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% or more but less than 25 atomic%, the oxygen content is preferably 30 atomic% or more but less than 40 atomic% and the carbon content is preferably 15 atomic% or less.

[0068] Furthermore, in the photomask blank of the present invention, a resist film can be formed in such a way that it contacts the side of the hard mask film away from the substrate (the main surface opposite to the substrate).

[0069] The layers constituting the photomask blank of the present invention are preferably formed by sputtering, which readily yields films with excellent uniformity. Any method, such as DC sputtering or RF sputtering, can also be used. The target material and sputtering gas can be appropriately selected based on the layer composition. Films composed of chromium-containing materials can be formed by reactive sputtering, using a chromium target, a target material in which one or more of oxygen, nitrogen, and carbon are added, and a sputtering gas in which a reactive gas selected from oxygen-containing gases, nitrogen-containing gases, and carbon-containing gases is appropriately added to a rare gas (inactive gas) such as helium, neon, or argon, depending on the film to be formed.

[0070] Especially in the formation of the hard mask film described above (film density 6.0 g / cm³). 3 Hereinafter, when the material exhibits 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 satisfies d / v ≤ 60 [minutes] (1), it is preferable to set the pressure during film formation to 0.10 Pa or more, and particularly preferably to 0.12 Pa or more. However, the method for fabricating the hard mask film of the photomask blank of the present invention is not limited to this method.

[0071] In the photomask blank of the present invention described above, the hard mask film exhibits excellent etch resistance to dry etching used in the processing of the patterning layer, and therefore can be effectively used as an etching mask for the patterning layer. Furthermore, since the hard mask film can be easily removed by cleaning with a sulfuric acid-hydrogen peroxide mixture (SPM cleaning), it can be removed during the resist stripping process after processing the patterning layer. Therefore, no additional process is required after the cleaning during resist stripping, thus simplifying the process of manufacturing photomasks from a mask blank with high-precision processability. In other words, the photomask blank according to the present invention simplifies the process for removing the hard mask film, thereby simplifying the photomask manufacturing process.

[0072] [Methods for manufacturing photomasks] The method for manufacturing a photomask of the present invention uses the photomask blank of the present invention and removes the hard mask film using a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide.

[0073] The following is for reference Figure 2 An example of the method for manufacturing the photomask of the present invention will be described. However, the method for manufacturing the photomask of the present invention is not limited to... Figure 2 The example shown.

[0074] First, such as Figure 2 As shown in (A), the photomask blank of the present invention is prepared. In this example, using... Figure 1 The photomask blank 10 shown.

[0075] Next, a resist film (not shown) is coated onto the hard mask film 3 of the photomask blank 10. Then, the resist film is exposed and developed to form a resist pattern.

[0076] Next, the resist pattern is used as an etching mask, for example, by dry etching to process the hard mask film 3. This yields, for example, as shown... Figure 2 The hard mask pattern 3A shown in (B) has a resist pattern 4 remaining on the hard mask pattern 3A.

[0077] Next, the hard mask pattern 3A is used as an etching mask to process the pattern forming layer 2. Thus, as... Figure 2 As shown in (C), a pattern forming layer 2A with a pattern is obtained.

[0078] In addition, during this stage, the hard mask pattern 3A and the resist pattern 4 remain on the pattern forming layer 2A.

[0079] Next, the resist pattern 4 is removed by cleaning with a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide. By simultaneously or subsequently cleaning with a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide, the hard mask film 3 can be removed, and more specifically, the hard mask pattern 3A can be removed.

[0080] By removing the hard mask film 3, such as Figure 2 As shown in (D), a photomask 20 having a substrate 1 and a pattern forming layer 2A formed on the substrate 1 is obtained.

[0081] Thus, in the photomask manufacturing method of the present invention, since the hard mask film can be easily removed by cleaning with a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide (SPM cleaning), the hard mask film can be removed by the resist stripping step after processing the patterning layer. Therefore, no additional step is required after the cleaning during resist stripping, thereby simplifying the process of manufacturing a photomask from a mask blank with high-precision machinability. That is, the photomask manufacturing method according to the present invention simplifies the process for removing the hard mask film, thereby simplifying the photomask manufacturing process.

[0082] Transmissive photomasks can be manufactured by using transmissive photomask blanks. Alternatively, reflective photomasks can be manufactured by using reflective photomask blanks.

[0083] Example The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited thereto.

[0084] (Example 1) Using a chromium target as the target material and argon and nitrogen as sputtering gases, the sputtering gas flow rate was adjusted to achieve a film formation pressure of 0.12 Pa. 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 on a 152 mm square, approximately 6 mm thick, transparent quartz substrate. The composition of the hard mask film was determined using X-ray photoelectron spectroscopy, the thickness was measured using a stylus-type film thickness gauge, and the film density was calculated using X-ray reflectance (XRR) measurement.

[0085] For this hard mask film, 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 sample for 6 minutes. Then, the hard mask film was rinsed with pure water for 1 minute. After repeating the above operation three times, the film thickness of the hard mask film was measured, and the reduction in film thickness was calculated. The results showed that the reduction in film thickness of the hard mask film relative to the sulfuric acid-hydrogen peroxide mixture SPM was 0.30 nm / min.

[0086] (Example 2) Except that argon, nitrogen, and oxygen were used as sputtering gases and the pressure during film formation was set to 0.17 Pa, an oxygen-containing chromium film with a chromium content of 35 atomic%, an oxygen content of 65 atomic%, and a thickness of 10 nm was formed as a hard mask film in the same manner as in Example 1. Furthermore, although nitrogen was used in the formation of the hard mask film, almost no nitrogen was detected in the compositional analysis (less than 1 atomic%).

[0087] The reduction in film thickness per minute of the hard mask film relative to the SPM was determined in the same manner as in Example 1, and the result was 0.19 nm / min.

[0088] (Example 3) Except that argon, nitrogen, oxygen and carbon dioxide are used as sputtering gases and the pressure during film formation is set to 0.16 Pa, a chromium film containing oxygen, nitrogen and carbon 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 is formed as a hard mask film in the same manner as in Example 1.

[0089] The reduction in film thickness per minute of the hard mask film relative to the SPM was determined in the same manner as in Example 1, and the result was 0.25 nm / min.

[0090] (Comparative Example 1) Except that only argon was used as the sputtering gas and the pressure during film formation was set to 0.06 Pa, a chromium film with a thickness of 10 nm and a chromium content of 100 atomic percent was formed as a hard mask film in the same manner as in Example 1.

[0091] The reduction in film thickness per minute of the hard mask film relative to the SPM was determined in the same manner as in Example 1, and the result was 0.05 nm / min.

[0092] (Comparative Example 2) Except that the pressure during film formation was set 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.

[0093] The reduction in film thickness per minute of the chromium film relative to the SPM was determined in the same manner as in Example 1, and the result was 0.13 nm / min.

[0094] Table 1 below shows the pressure and physical properties of the hard mask film during film formation in Examples 1-3, Comparative Examples 1 and 2.

[0095] [Table 1] Generally, the thickness of the chromium hard mask used for resist thinning is more preferably 5 nm or more, and more preferably 10 nm or less. For the hard mask films in Examples 1 to 3, which show the composition, film density and d / v value shown in Table 1, when using a hard mask of 5 nm to 10 nm, the chromium hard mask film can be peeled off by SPM cleaning for less than 60 minutes.

[0096] On the other hand, in Comparative Examples 1 and 2, removing the chromium hard mask film with a thickness of approximately 10 nm by SPM required more than 60 minutes of SPM treatment. During such prolonged cleaning, depending on the composition of the film directly beneath the chromium hard mask, the SPM treatment could cause deterioration or haze. Therefore, removing the hard mask film formed in Comparative Examples 1 or 2 by SPM is impractical.

[0097] (Etching resistance test) The etching rates of the films formed in the same manner as the hard mask films obtained in Examples 1-3 and Comparative Examples 1 and 2 were investigated. As a result, in both dry etching using SF6 and dry etching using Cl2, the etching rate of any film was less than 0.2 nm / min.

[0098] The results show that by forming the film formed in Examples 1 to 3 on the pattern forming layer that can be used in the photomask blank to make the photomask blank, forming a pattern on the hard mask film of the photomask blank using a resist method to obtain a hard mask pattern, and using the hard mask pattern as an etching mask, the pattern forming layer can be processed with good precision.

[0099] Furthermore, as described above, the films formed in Examples 1-3 can be easily removed using SPM, and therefore the hard mask film can be removed via a resist stripping process after processing the patterned layer. In other words, Examples 1-3 demonstrate that the photomask blank according to the present invention simplifies the process for removing the hard mask film, thereby simplifying the photomask manufacturing process.

[0100] The present invention includes the following solutions.

[0101] [1] A photomask blank, characterized in that the photomask blank comprises a substrate, a pattern forming layer composed of a single layer or multiple layers on the substrate, and a hard mask film on the pattern forming layer, the hard mask film being formed of a material comprising chromium and at least one element selected from nitrogen, carbon, and oxygen, and the film density of the hard mask film being 6.0 g / cm³. 3Hereinafter, the hard mask film 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. When the thickness reduction per minute of the hard mask film treated with a sulfuric acid-hydrogen peroxide mixture is set as v [nm / min], and the thickness of the hard mask film is set as d [nm], the following equation (1) is satisfied: .

[0102] [2] According to the photomask blank described in [1], the hard mask film has a chromium content of less than 60 atomic% and a nitrogen content of more than 40 atomic% and a thickness of less than 10 nm.

[0103] [3] According to the photomask blank described in [1], the hard mask film has a chromium content of less than 40 atomic% and an oxygen content of more than 60 atomic% and a thickness of less than 10 nm.

[0104] [4] According to the photomask blank described in [1], the hard mask film has a chromium content of less than 40 atomic%, a nitrogen content of more than 15 atomic% and less than 25 atomic%, an oxygen content of more than 30 atomic% and less than 40 atomic%, a carbon content of less than 15 atomic%, and a thickness of less than 10 nm.

[0105] [5] The photomask blank according to any one of [1] to [4] is characterized in that the pattern forming layer is a film containing a light-shielding film for shielding the excimer laser, the light-shielding film is formed of a silicon-containing material, and the thickness of the light-shielding film is more than 30 nm and less than 180 nm.

[0106] [6] The photomask blank according to any one of [1] to [4] is characterized in that the pattern forming layer is a film comprising an absorption film that absorbs exposure light as extreme ultraviolet light, and the photomask blank further comprises a multilayer reflective film for reflecting exposure light and a protective film for protecting the multilayer reflective film between the substrate and the absorption film.

[0107] [7] According to the photomask blank of [6], the absorption film is characterized in that it is made of a material containing at least one element of Ru and Ta.

[0108] [8] A method for manufacturing a photomask, characterized in that the photomask blank described in [1] is used and the hard mask film is removed using a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide.

[0109] [9] A method for manufacturing a transmissive photomask, characterized in that the photomask blank described in [1] or [5] is used, and the hard mask film is removed using a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide.

[0110]

[10] A method for manufacturing a reflective photomask, characterized in that the photomask blank described in [1], [6] or [7] is used, and the hard mask film is removed using a mixture of sulfuric acid or sulfuric acid and hydrogen peroxide.

[0111] Furthermore, this invention is not limited to the above-described embodiments. The above embodiments are illustrative examples, and any technical solutions having a substantially identical structure and achieving the same effect as the technical concept described in the claims of this invention are included within the scope of protection of this invention.

Claims

1. A photomask blank, characterized in that, The photomask blank has the following characteristics: substrate; The patterning layer on the substrate, consisting of a single layer or multiple layers; and The hard mask film on the pattern forming layer The hard mask is formed of a material comprising chromium and at least one element selected from nitrogen, carbon, and oxygen. The density of the hard mask film is 6.0 g / cm³. 3 the following, The hard mask film is resistant to dry etching using gases containing fluorine but not oxygen, and also resistant to dry etching using gases containing chlorine but not oxygen. When the thickness reduction per minute of the hard mask film during treatment with the sulfuric acid-hydrogen peroxide mixture is set as v [nm / min], and the thickness of the hard mask film is set as d [nm], the following equation (1) is satisfied: 。 2. The photomask blank according to claim 1, characterized in that, The hard mask film has a chromium content of less than 60 atomic% and a nitrogen content of more than 40 atomic% and a thickness of less than 10 nm.

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

4. The photomask blank according to claim 1, characterized in that, The hard mask film has a chromium content of less than 40 atomic%, a nitrogen content of more than 15 atomic% and less than 25 atomic%, an oxygen content of more than 30 atomic% and less than 40 atomic%, and a carbon content of less than 15 atomic%, and the thickness of the hard mask film is less than 10 nm.

5. The photomask blank according to claim 1, characterized in that, The pattern forming layer is a film containing a light-shielding film for shielding against excimer laser light. The light-shielding film is formed from a silicon-containing material and has a thickness of 30 nm to 180 nm.

6. The photomask blank according to claim 1, characterized in that, The pattern forming layer is a film that includes an absorption film that absorbs exposure light as extreme ultraviolet light. The photomask blank further includes 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 claim 6, characterized in that, The absorbent membrane is made of a material containing at least one element selected from Ru and Ta.

8. A method for manufacturing a photomask, characterized in that, The photomask blank of claim 1 is used, and the hard mask film is removed using sulfuric acid or a mixture of sulfuric acid and hydrogen peroxide.

9. A method for manufacturing a transmissive photomask, characterized in that, The photomask blank as described in claim 1 or 5 is used, and the hard mask film is removed using sulfuric acid or a mixture of sulfuric acid and hydrogen peroxide.

10. A method for manufacturing a reflective photomask, characterized in that, The photomask blank according to claim 1, 6 or 7 is used, and the hard mask film is removed using sulfuric acid or a mixture of sulfuric acid and hydrogen peroxide.

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