CN111258175A

CN111258175A - Photomask blank, method for manufacturing photomask, and method for manufacturing display device

Info

Publication number: CN111258175A
Application number: CN201911179769.3A
Authority: CN
Inventors: 田边胜; 浅川敬司; 安森顺一; 石原重德; 花冈修
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2018-11-30
Filing date: 2019-11-27
Publication date: 2020-06-09
Also published as: KR20200066178A; TW202349107A; TW202303262A; KR20240017031A; KR102630136B1; KR102527313B1; TWI816568B; KR20230065208A

Abstract

The invention provides a photomask blank which can shorten the over-etching time and form a transfer pattern with a good cross-sectional shape when the transfer pattern is formed by performing wet etching on a thin film for pattern formation. The photomask blank is a master for forming a photomask, the photomask blank has a transfer pattern on a transparent substrate by wet etching the film for forming a pattern, the film for forming a pattern contains a transition metal and silicon, and the film for forming a pattern has a columnar structure.

Description

Photomask blank, method for manufacturing photomask, and method for manufacturing display device

Technical Field

The invention relates to a photomask blank, a method for manufacturing the photomask blank, a method for manufacturing a photomask and a display device.

Background

In recent years, not only large screens and wide viewing angles but also high definition and high speed Display have been rapidly performed on Display devices such as FPDs (Flat Panel displays) represented by LCDs (Liquid Crystal displays). In order to achieve high definition and high speed display, one of the necessary elements is to manufacture electronic circuit patterns such as fine and highly dimensionally accurate elements and wirings. Photolithography is often used for patterning electronic circuits for display devices. Therefore, a photomask such as a phase shift mask or a binary mask for manufacturing a display device having a fine and highly precise pattern formed thereon is required.

For example, patent document 1 discloses a phase reversal mask blank having a phase reversal film on a transparent substrate. In the mask blank, the phase reversal film is composed of a multilayer film with more than 2 layers formed by a metal silicide compound containing at least 1 light element substance of oxygen (O), nitrogen (N) and carbon (C), the phase reversal film has a reflectivity of less than 35% and a transmissivity of 1% -40% to exposure light with composite wavelength of i line (365nm), h line (405nm) and g line (436nm), and a gradient of a pattern section is formed rapidly when forming a pattern, and the metal silicide compound is formed by injecting a reactive gas containing the light element substance and an inactive gas with a ratio of 0.5: 9.5-4: 6.

Patent document 2 discloses a phase shift mask blank including a transparent substrate, a semi-transmissive light film made of a metal silicide material having a property of changing the phase of exposure light, and an etching mask film made of a chromium-based material. In the phase shift mask blank, a composition gradient region is formed at the interface between the semi-transmissive film and the etching mask film. In the composition gradient region, the proportion of a component that slows down the wet etching rate of the light semi-transmissive film increases in the depth direction. The content of oxygen in the composition gradient region is 10 atomic% or less.

Documents of the prior art

Patent document

Patent document 1: korean granted patent No. 1801101

Patent document 2: japanese patent No. 6101646

Disclosure of Invention

Problems to be solved by the invention

As a phase shift mask used for manufacturing a high-definition (1000ppi or more) panel in recent years, a phase shift mask having a fine phase shift film pattern with an aperture diameter of 6 μm or less and a line width of 4 μm or less is required for transferring a high-resolution pattern. Specifically, a phase shift mask having a fine phase shift film pattern with an aperture of 1.5 μm is required.

In order to realize pattern transfer with higher resolution, a phase shift mask blank having a phase shift film with a transmittance of 15% or more with respect to exposure light and a phase shift mask having a phase shift film pattern with a transmittance of 15% or more with respect to exposure light are required. In terms of the cleaning resistance (chemical properties) of the phase shift mask blank on which the phase shift film having cleaning resistance is formed and the phase shift mask on which the phase shift film pattern having cleaning resistance is formed, the phase shift mask blank and the phase shift mask in which the change in optical properties due to the reduction in the film thickness of the phase shift film pattern and the change in the surface composition is suppressed are required.

In order to satisfy the requirements for transmittance of exposure light and cleaning resistance, it is effective to increase the ratio of silicon in the atomic ratio of metal to silicon in the metal silicide compound (metal silicide-based material) constituting the phase shift film, but there are problems such as a large retardation in wet etching rate (long wet etching time), damage to the substrate by the wet etching solution, and a decrease in transmittance of the transparent substrate.

Further, in the binary mask blank having the light-shielding film containing the transition metal and silicon, there is a need for cleaning resistance even when the light-shielding pattern is formed on the light-shielding film by wet etching, and there is a problem similar to the above.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a photomask blank, a method for manufacturing the photomask, and a method for manufacturing the display device, which are capable of forming a transfer pattern having a good cross-sectional shape by reducing a wet etching time when forming the transfer pattern by wet etching on a thin film for pattern formation such as a phase shift film and a light shielding film containing a transition metal and silicon.

Means for solving the problems

The present inventors have conducted intensive studies on countermeasures for solving these problems. First, a material in which the atomic ratio of the transition metal to silicon in the thin film for pattern formation is 1:3 or more is prepared, and in order to shorten the time for wet etching of the thin film for pattern formation by the wet etching solution, the oxygen gas contained in the sputtering gas introduced into the film forming chamber is adjusted so that a large amount of oxygen (O) is contained in the thin film for pattern formation, thereby forming the thin film for pattern formation. As a result, although the wet etching rate for forming the transfer pattern is increased, the refractive index of the phase shift film in the phase shift mask blank with respect to the exposure light is decreased, and thus the film thickness required for obtaining a desired phase difference (for example, 180 °) is increased. In addition, the light-shielding film in the binary mask blank has a thick film thickness required for obtaining a desired light-shielding performance (for example, an Optical Density (OD) of 3 or more) in order to reduce an extinction coefficient against exposure light. The increase in the film thickness of the thin film for pattern formation is disadvantageous for pattern formation by wet etching, and the effect of shortening the wet etching time is limited due to the increase in the film thickness. On the other hand, when the atomic ratio of the transition metal to silicon is set to 1:3 or more, there is an advantage that the cleaning resistance of the pattern forming thin film can be improved, and therefore, it is not preferable to deviate from the above-mentioned composition ratio of the transition metal to silicon from this viewpoint.

Therefore, the present inventors have made a change of idea and studied to change the film structure by adjusting the pressure of the sputtering gas in the film forming chamber. When forming a thin film for pattern formation on a substrate, the pressure of a sputtering gas in a film forming chamber is usually set to 0.1 to 0.5 Pa. However, the present inventors intentionally set the sputtering gas pressure to be higher than 0.5Pa, and formed a thin film for pattern formation. Then, it was found that a thin film for pattern formation was formed at a sputtering pressure of 0.7Pa or more and 3.0Pa or less, preferably at a sputtering gas pressure of 0.8Pa or more and 3.0Pa or less, and as a result, the film had suitable properties as a thin film, and that an etching time could be significantly shortened when a transfer pattern was formed on the thin film for pattern formation by wet etching, and a transfer pattern having a good cross-sectional shape could be formed. The pattern forming thin film thus formed has a columnar structure which is not present in a typical pattern forming thin film. As a result of the above intensive studies, the present invention has the following configurations.

(embodiment 1) A photomask blank having a thin film for pattern formation on a transparent substrate, wherein,

the photomask blank is a master for forming a photomask having a transferred pattern on the transparent substrate obtained by wet etching the thin film for pattern formation,

the pattern-forming thin film contains a transition metal and silicon,

the pattern-forming thin film has a columnar structure.

(means 2) the photomask blank according to means 1, wherein the pattern-forming film has a spatial spectrum distribution in which a signal intensity of 1.0% or more is present with respect to a maximum signal intensity corresponding to an origin of a spatial frequency,

the spatial frequency spectrum distribution is obtained as follows: in an image obtained by observing a cross section of the photomask blank with a scanning electron microscope at a magnification of 80000 times, image data of 64 pixels in vertical direction × 256 pixels in horizontal direction is extracted from a region including a center portion in a thickness direction of the pattern forming film, and fourier transform is performed on the image data.

(embodiment 3) the photomask blank according to embodiment 2, wherein the signal having a signal intensity of 1.0% or more is located at a spatial frequency of 2.0% or more from an origin of the spatial frequency, when the maximum spatial frequency of the thin film for pattern formation is 100%.

(embodiment 4) the photomask blank according to any one of embodiments 1 to 3, wherein an atomic ratio of the transition metal to the silicon contained in the thin film for pattern formation is 1:3 or more and 1:15 or less.

(embodiment 5) the photomask blank according to any one of embodiments 1 to 4, wherein the thin film for pattern formation contains at least nitrogen or oxygen.

(embodiment 6) the photomask blank according to embodiment 5, wherein the thin film for pattern formation contains nitrogen, and the atomic ratio of the transition metal to the silicon contained in the thin film for pattern formation is 1:3 or more and 1:15 or less,

the indentation hardness of the thin film for forming a pattern obtained by the nano indentation method is more than 18GPa and less than 23 GPa.

(embodiment 7) the photomask blank according to embodiment 6, wherein the nitrogen content is 35 atomic% or more and 60 atomic% or less.

(embodiment 8) the photomask blank according to any one of embodiments 1 to 7, wherein the transition metal is molybdenum.

(embodiment 9) the photomask blank according to any one of embodiments 1 to 8, wherein the thin film for pattern formation is a phase shift film having the following optical properties: the transmittance of the light to a representative wavelength of the exposure light is 1% or more and 80% or less, and the phase difference is 160 ° or more and 200 ° or less.

(embodiment 10) the photomask blank according to any one of embodiments 1 to 9, which comprises an etching mask film having different etching selectivity to the thin film for pattern formation on the thin film for pattern formation.

(embodiment 11) the photomask blank according to embodiment 10, wherein the etching mask film is formed of a material containing chromium but substantially no silicon.

(embodiment 12) a method for manufacturing a photomask blank by forming a thin film for pattern formation containing a transition metal and silicon on a transparent substrate by a sputtering method, comprising:

the thin film for pattern formation is formed in a film formation chamber using a transition metal silicide target containing a transition metal and silicon, and the sputtering gas pressure in the film formation chamber to which a sputtering gas is supplied is 0.7Pa to 3.0 Pa.

(embodiment 13) the method of manufacturing a photomask blank according to embodiment 12, wherein an atomic ratio of the transition metal to silicon in the transition metal silicide target is 1:3 or more and 1:15 or less.

(embodiment 14) the method of manufacturing a photomask blank according to embodiment 12 or 13, wherein an etching mask film is formed on the thin film for pattern formation using a sputtering target formed of a material having a different etching selectivity to the thin film for pattern formation.

(embodiment 15) the method of manufacturing a photomask blank according to embodiment 14, wherein the thin film for pattern formation and the etching mask film are formed using an in-line type sputtering apparatus.

(embodiment 16) a method of manufacturing a photomask, the method comprising:

preparing a photomask blank according to any one of claims 1 to 9 or a photomask blank produced by the method for producing a photomask blank according to claim 12 or 13; and

and a step of forming a resist film on the thin film for pattern formation, and wet-etching the thin film for pattern formation using a resist film pattern formed from the resist film as a mask to form a transfer pattern on the transparent substrate.

(embodiment 17) a method of manufacturing a photomask, the method comprising:

preparing the photomask blank described in claim 10 or 11 or the photomask blank manufactured by the method for manufacturing a photomask blank described in claim 14 or 15;

forming a resist film on the etching mask film, and performing wet etching on the etching mask film using a resist film pattern formed from the resist film as a mask to form an etching mask film pattern on the thin film for pattern formation; and

and a step of forming a transfer pattern on the transparent substrate by wet etching the thin film for pattern formation using the etching mask film pattern as a mask.

(embodiment 18) a method for manufacturing a display device, the method comprising:

and an exposure step of placing the photomask obtained by the method for manufacturing a photomask according to claim 16 or 17 on a mask stage of an exposure apparatus, and exposing and transferring the transfer pattern formed on the photomask to a resist formed on a substrate of a display device.

The present inventors have also studied to change the film structure by adjusting the pressure of the sputtering gas in the film forming chamber, and have found another mode described below. As described above, the present inventors intentionally set the sputtering gas pressure to be higher than 0.5Pa, and formed a thin film for pattern formation. Further, it was found that as a result of forming a thin film for pattern formation at a sputtering gas pressure of 0.7Pa or more, the etching time can be significantly shortened, a transfer pattern having a good cross-sectional shape can be formed, and surface roughness of the transparent substrate can be suppressed. On the other hand, it is found that when the sputtering gas pressure during film formation is set too high, the pattern-forming thin film cannot obtain sufficient cleaning resistance. As a result of intensive studies, the present inventors have found that a film for pattern formation formed by a sputtering gas pressure of 0.7Pa to 2.4Pa can form a transfer pattern having a favorable cross-sectional shape while having favorable properties as a film for pattern formation, and can suppress surface roughness of a transparent substrate and improve the cleaning resistance of the film for pattern formation.

Then, the present inventors have further searched for physical indicators of a film for pattern formation having such excellent characteristics. As a result, it was found that the indentation hardness of the thin film for pattern formation correlated with the wet etching rate. As a result of intensive studies, it has been found that when the indentation hardness obtained by the nanoindentation method is 18GPa or more and 23GPa or less, not only is a suitable characteristic as a pattern-forming thin film obtained, but also a transfer pattern having a good cross-sectional shape can be formed when the transfer pattern is formed on the pattern-forming thin film by wet etching, and that the surface roughness of the transparent substrate can be suppressed and the cleaning resistance of the pattern-forming thin film can be improved.

(other means 1) A photomask blank having a thin film for pattern formation on a transparent substrate, wherein,

the photomask blank is a master for forming a photomask having a transfer pattern on the transparent substrate by wet etching the thin film for pattern formation,

the thin film for pattern formation contains a transition metal, silicon and nitrogen, and the atomic ratio of the transition metal to the silicon contained in the thin film for pattern formation is 1:3 or more and 1:15 or less,

(other embodiment 2) the photomask blank according to the other embodiment 1, wherein the transition metal is molybdenum.

(other embodiment 3) the photomask blank according to the other embodiment 1 or 2, wherein the nitrogen content is 35 atomic% or more and 60 atomic% or less.

(other embodiment 4) the photomask blank according to any one of embodiments 1 to 3, wherein the thin film for pattern formation is a phase shift film having the following optical characteristics: the transmittance of the light to a representative wavelength of the exposure light is 1% or more and 80% or less, and the phase difference is 160 ° or more and 200 ° or less.

(other embodiment 5) the photomask blank according to any one of embodiments 1 to 4, which comprises an etching mask film having different etching selectivity to the thin film for pattern formation on the thin film for pattern formation.

(other embodiment 6) the photomask blank according to other embodiment 5, wherein the etching mask film is formed of a material containing chromium but substantially not containing silicon.

(other embodiment 7) a method for manufacturing a photomask, the method comprising:

preparing a photomask blank according to any one of claims 1 to 4; and

(other aspect 8) a method for manufacturing a photomask, the method comprising:

preparing a photomask blank according to any one of claims 5 to 6;

(other aspect 9) a method for manufacturing a display device, the method comprising:

and an exposure step of placing the photomask obtained by the method for manufacturing a photomask described in any one of claims 7 and 8 on a mask stage of an exposure apparatus, and exposing and transferring the transfer pattern formed on the photomask to a resist formed on a substrate of a display device.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the photomask blank or the method for manufacturing a photomask blank of the present invention, when a thin film for transfer pattern formation is wet-etched to form a desired fine transfer pattern, in view of cleaning resistance and the like, when the thin film for pattern formation is made of a silicon-rich metal silicide compound, it is possible to obtain a photomask blank capable of forming a transfer pattern having a good cross-sectional shape in a short etching time without causing a decrease in transmittance of a transparent substrate due to damage to the substrate by a wet etching solution. Further, according to the photomask blank according to another aspect of the present invention, when a desired fine transfer pattern is formed by wet etching the thin film for transfer pattern, a photomask blank capable of forming a transfer pattern having a good cross-sectional shape, suppressing surface roughness of the transparent substrate, and improving the cleaning resistance of the thin film for transfer pattern can be obtained.

In addition, according to the method for manufacturing a photomask of the present invention, a photomask is manufactured using the photomask blank described above. Therefore, in the case where the pattern forming thin film is made of a silicon-rich metal silicide compound from the viewpoint of cleaning resistance or the like, a photomask can be manufactured which has a transfer pattern with good transfer accuracy and in which the decrease in transmittance of the transparent substrate due to damage to the substrate by the wet etching solution does not occur. The photomask can cope with the miniaturization of line, gap pattern and contact hole. Further, according to the method for manufacturing a photomask of another aspect of the present invention, a photomask can be manufactured which can form a transfer pattern having a good cross-sectional shape, can suppress surface roughness of a transparent substrate, and can improve the cleaning resistance of a transfer pattern film.

In addition, according to the method for manufacturing a display device of the present invention, a display device is manufactured using a photomask manufactured using the photomask blank described above or obtained by the method for manufacturing a photomask described above. Therefore, a display device having fine line and space patterns and contact holes can be manufactured.

Drawings

Fig. 1 is an explanatory diagram illustrating a film structure of a phase shift mask blank according to embodiment 1.

Fig. 2 is an explanatory diagram illustrating a film structure of a phase shift mask blank according to embodiment 2.

Fig. 3(a) to (e) are explanatory views showing steps of manufacturing the phase shift mask according to embodiment 3.

Fig. 4(a) to (c) are explanatory views showing steps of manufacturing the phase shift mask of embodiment 4.

Fig. 5 a is an enlarged photograph (image data) of the central portion in the thickness direction of the phase shift film in the cross-sectional SEM image of the phase shift mask blank of example 1, and fig. 5 b is a result of fourier transform of the enlarged photograph (image data) of (a).

Fig. 6 is a dark field top view STEM photograph of the phase shift film in the phase shift mask blank of example 1.

FIG. 7 is a photograph of a cross section of a phase shift mask of example 1.

Fig. 8 a is an enlarged photograph (image data) of the central portion in the thickness direction of the phase shift film in the cross-sectional SEM image of the phase shift mask blank of example 2, and fig. 8 b is a result of fourier transform of the enlarged photograph (image data) of fig. 8 a.

FIG. 9 is a photograph of a cross section of a phase shift mask of example 2.

Fig. 10 a is an enlarged photograph (image data) of the central portion in the thickness direction of the phase shift film in the cross-sectional SEM image of the phase shift mask blank of example 3, and fig. 10 b is a result of fourier transform of the enlarged photograph (image data) of fig. 10 a.

FIG. 11 is a photograph of a cross section of a phase shift mask of example 3.

Fig. 12 a is an enlarged photograph (image data) of the central portion in the thickness direction of the phase shift film in the cross-sectional SEM image of the phase shift mask blank of comparative example 1, and fig. 12 b is a result of fourier transform of the enlarged photograph (image data) of fig. 12 a.

Fig. 13 is a cross-sectional photograph of the phase shift mask of comparative example 1.

FIG. 14 is a graph showing the relationship among the etching rate, sputtering gas pressure, and indentation hardness of the phase shift films of the phase shift masks of other examples 1 to 4 and other comparative examples 1 and 2.

Description of the symbols

10 … phase shift mask blank

20 … transparent substrate

30 … phase shift film

30a … phase shift film pattern

40 … etching mask film

40a … 1 st etch mask film pattern

40b … 2 nd etch mask film pattern

50 … No. 1 resist film Pattern

60 … No. 2 resist film Pattern

100 … phase shift mask

Detailed Description

Embodiment 1.2.

In embodiments 1 and 2, a phase shift mask blank will be described. The phase shift mask blank according to embodiment 1 is a master for forming a phase shift mask having a phase shift film pattern on a transparent substrate by wet etching a phase shift film using, as a mask, an etching mask film pattern in which a desired pattern is formed on an etching mask film. The phase shift mask blank according to embodiment 2 is a master for forming a phase shift film having a phase shift film pattern on a transparent substrate by wet etching the phase shift film using a resist pattern in which a desired pattern is formed on the resist as a mask.

Fig. 1 is an explanatory diagram illustrating a film structure of a phase shift mask blank 10 according to embodiment 1.

The phase shift mask blank 10 shown in fig. 1 includes: a transparent substrate 20, a phase shift film 30 formed on the transparent substrate 20, and an etching mask film 40 formed on the phase shift film 30.

Fig. 2 is an explanatory diagram illustrating a film structure of the phase shift mask blank 10 of embodiment 2.

The phase shift mask blank 10 shown in fig. 2 includes: a transparent substrate 20, and a phase shift film 30 formed on the transparent substrate 20.

The transparent substrate 20, the phase shift film 30, and the etching mask film 40 constituting the phase shift mask blank 10 according to embodiments 1 and 2 will be described below.

The transparent substrate 20 is transparent to the exposure light. When there is no surface reflection loss, the transparent substrate 20 has a transmittance of 85% or more, preferably 90% or more, with respect to the exposure light. The transparent substrate 20 is made of a material containing silicon and oxygen, and may be made of synthetic quartz glass, aluminosilicate glass, soda-lime glass, low thermal expansion glass (SiO)₂-TiO₂Glass, etc.). On a transparent substrateWhen the transparent substrate 20 is made of low thermal expansion glass, the position change of the phase shift film pattern due to the thermal deformation of the transparent substrate 20 can be suppressed. The transparent substrate 20 used for the display device is usually a rectangular substrate, and a substrate having a short side of 300mm or more may be used. The present invention provides a phase shift mask blank which can stably transfer a fine phase shift film pattern of, for example, less than 2.0 [ mu ] m formed on a transparent substrate even when the phase shift mask blank has a large size in which the length of the short side of the transparent substrate is 300mm or more.

The phase shift film 30 is made of a transition metal silicide type material containing a transition metal and silicon. As the transition metal, molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), and the like are suitable, and molybdenum (Mo) is particularly preferable.

In addition, the phase shift film 30 preferably contains at least nitrogen or oxygen. In the above-described transition metal silicide-based material, oxygen as a light element component has an effect of reducing an extinction coefficient as compared with nitrogen as a light element component, and the content of other light element components (such as nitrogen) for obtaining a desired transmittance can be reduced, and the reflectance of the front surface and the back surface of the phase shift film 30 can be effectively reduced. In the transition metal silicide-based material, nitrogen as a light element component has an effect of not lowering the refractive index as compared with oxygen as a light element component, and therefore, the thickness of the film for obtaining a desired retardation can be made thin. The total content of light element components including oxygen and nitrogen contained in the phase shift film 30 is preferably 40 atomic% or more, more preferably 40 atomic% or more and 70 atomic% or less, and is preferably 50 atomic% or more and 65 atomic% or less. When oxygen is contained in the phase shift film 30, the content of oxygen is preferably more than 0 atomic% and 40 atomic% or less from the viewpoint of defect quality and chemical resistance.

Examples of the transition metal silicide-based material include: a nitride of a transition metal silicide, an oxide of a transition metal silicide, an oxynitride of a transition metal silicide, a oxycarbonitride of a transition metal silicide. In addition, from the viewpoint of easily obtaining an excellent pattern sectional shape by wet etching, the transition metal silicide-based material is preferably a molybdenum silicide-based material (MoSi-based material), a zirconium silicide-based material (ZrSi-based material), a molybdenum zirconium silicide-based material (MoZrSi-based material), and particularly preferably a molybdenum silicide-based material (MoSi-based material).

In addition, the phase shift film 30 may contain other light element components such as carbon and helium in addition to the above-described oxygen and nitrogen in order to reduce the film stress and control the wet etching rate.

The phase shift film 30 has a function of adjusting the reflectance with respect to light incident from the transparent substrate 20 side (hereinafter, sometimes referred to as back surface reflectance) and a function of adjusting the transmittance and phase difference with respect to exposure light.

The phase shift film 30 may be formed by a sputtering method.

The phase shift film 30 preferably has a columnar structure. The columnar structure can be confirmed by observing the phase shift film 30 with a cross-sectional SEM. That is, the columnar structure of the present invention is a state in which the particles of the transition metal silicide compound containing the transition metal and silicon constituting the phase shift film 30 have a columnar particle structure extending in the film thickness direction of the phase shift film 30 (the direction in which the particles are deposited). In the present application, particles having a length in the film thickness direction longer than a length in the perpendicular direction are referred to as columnar particles. That is, the phase shift film 30 has columnar particles extending in the film thickness direction formed on the entire surface of the transparent substrate 20. In the phase shift film 30, by adjusting the film formation conditions (sputtering pressure, etc.), sparse portions having a relatively low density as compared with columnar particles (hereinafter, also simply referred to as "sparse portions") are formed. In order to effectively suppress side etching during wet etching and to improve the pattern cross-sectional shape of the phase shift film 30, it is preferable that columnar particles extending in the film thickness direction are irregularly formed in the film thickness direction as a preferable form of the columnar structure of the phase shift film 30. It is further preferable that the columnar particles of the phase shift film 30 are in a state where the lengths in the film thickness direction are not aligned. It is preferable that the sparse portion of the phase shift film 30 is formed continuously in the film thickness direction. It is preferable that the sparse portions of the phase shift film 30 are formed intermittently in a direction perpendicular to the film thickness direction. As a preferred form of the columnar structure of the phase shift film 30, an index obtained by fourier transforming an image obtained by the above cross-sectional SEM observation can be used as follows. That is, the columnar structure of the phase shift film 30 is preferably in the following state: in an image obtained by observing a cross section of a phase shift mask blank by a cross-sectional SEM at a magnification of 80000 times, image data of 64 pixels in the vertical direction × 256 pixels in the horizontal direction is extracted from a region including the center portion in the thickness direction of the phase shift film 30, and a spatial spectrum obtained by fourier-transforming the image data has a signal intensity of 1.0% or more with respect to the maximum signal intensity corresponding to the origin of the spatial frequency. By forming the phase shift film 30 into the columnar structure as described above, the wet etching liquid is likely to penetrate in the film thickness direction of the phase shift film 30 during wet etching using the wet etching liquid, and therefore, the wet etching rate can be increased, and the wet etching time can be greatly shortened. Therefore, even if the phase shift film 30 is a silicon-rich metal silicide compound, the transmittance of the transparent substrate does not decrease due to damage to the substrate by the wet etching solution. Further, since the phase shift film 30 has a columnar structure extending in the film thickness direction, side etching during wet etching can be suppressed, and the pattern cross-sectional shape can be made favorable.

In the phase shift film 30, when the maximum spatial frequency is 100%, a signal having a signal intensity of 1.0% or more with respect to the maximum signal intensity of the spatial spectrum distribution obtained by fourier transform is preferably located at a spatial frequency 2.0% or more apart from the origin of the spatial frequency. A signal distance of 2.0% or more, which has a signal intensity of 1.0% or more with respect to the maximum signal intensity, indicates that a certain or more high spatial frequency component is included. That is, it is preferable that the phase shift film 30 has a fine columnar structure and the line edge roughness of the phase shift film pattern 30a formed by wet etching the phase shift film 30 is smaller as the spatial frequency is located farther from the origin.

The indentation hardness of the phase shift film 30 is preferably 18GPa or more and 23GPa or less. The indentation hardness is a hardness measured using the principle of the nanoindentation method established in accordance with ISO 14577.

By setting the indentation hardness of the phase shift film 30 to 18GPa or more and 23GPa or less, the wet etching liquid is likely to penetrate in the film thickness direction of the phase shift film 30 during wet etching using the wet etching liquid, and thus the wet etching speed can be increased and the wet etching time can be shortened. In addition, the phase shift film pattern 30a having not only suitable characteristics as the phase shift film 30 but also a good cross-sectional shape can be formed, and the surface roughness of the transparent substrate 20 can be suppressed, and the cleaning resistance of the phase shift film 30 can be improved.

The atomic ratio of the transition metal to silicon contained in the phase shift film 30 is preferably 1:3 or more and 1:15 or less. In this range, the effect of suppressing the decrease in the wet etching rate of the phase shift film 30 at the time of patterning by the columnar structure can be increased. In addition, the resistance to cleaning of the phase shift film 30 can be improved, and the transmittance can be easily improved. In addition, in this range, the indentation hardness is set to 18GPa or more and 23GPa or less, whereby the effect of suppressing the decrease in the wet etching rate of the phase shift film 30 during the pattern formation can be increased. From the viewpoint of improving the cleaning resistance of the phase shift film 30, the atomic ratio of the transition metal and silicon contained in the phase shift film 30 is preferably 1:4 or more and 1:15 or less, and more preferably 1:5 or more and 1:15 or less.

The transmittance of the phase shift film 30 with respect to the exposure light satisfies a value necessary as the phase shift film 30. The transmittance of the phase shift film 30 with respect to light of a given wavelength (hereinafter, referred to as a representative wavelength) included in the exposure light is preferably 1% or more and 80% or less, more preferably 15% or more and 65% or less, and further preferably 20% or more and 60% or less. That is, when the exposure light is composite light including light having a wavelength range of 313nm to 436nm, the phase shift film 30 has the transmittance described above with respect to light having a representative wavelength included in the wavelength range. For example, when the exposure light is composite light including i-line, h-line, and g-line, the phase shift film 30 has the transmittance described above with respect to any one of the i-line, h-line, and g-line.

The transmittance can be measured using a phase shift amount measuring device or the like.

The phase difference of the phase shift film 30 with respect to the exposure light satisfies a value necessary as the phase shift film 30. The phase difference of the phase shift film 30 is preferably 160 ° or more and 200 ° or less, and more preferably 170 ° or more and 190 ° or less, with respect to light of a representative wavelength included in the exposure light. By utilizing this property, the phase of light having a representative wavelength included in the exposure light can be changed to 160 ° or more and 200 ° or less. Therefore, a phase difference of 160 ° or more and 200 ° or less is generated between the light having the representative wavelength transmitted through the phase shift film 30 and the light having the representative wavelength transmitted only through the transparent substrate 20. That is, when the exposure light is the composite light including the light having the wavelength range of 313nm to 436nm, the phase shift film 30 has the above-described phase difference with respect to the light having the representative wavelength included in the wavelength range. For example, when the exposure light is composite light including i-line, h-line, and g-line, the phase shift film 30 has the above-described phase difference with respect to any one of the i-line, the h-line, and the g-line.

The phase difference can be measured using a phase shift amount measuring device or the like.

The back surface reflectance of the phase shift film 30 is 15% or less, preferably 10% or less in the wavelength range of 365nm to 436 nm. When the exposure light includes j lines, the back surface reflectance of the phase shift film 30 is preferably 20% or less, more preferably 17% or less, and still more preferably 15% or less with respect to light having a wavelength ranging from 313nm to 436 nm. The back surface reflectance of the phase shift film 30 is 0.2% or more in the wavelength range of 365nm to 436nm, and preferably 0.2% or more with respect to light in the wavelength range of 313nm to 436 nm.

The back surface reflectance can be measured using a spectrophotometer or the like.

The phase shift film 30 may be formed of a plurality of layers or a single layer. The phase shift film 30 formed of a single layer is not likely to form an interface in the phase shift film 30, and is preferable in terms of easy control of the cross-sectional shape. On the other hand, the phase shift film 30 composed of a plurality of layers is preferable from the viewpoint of ease of film formation.

The etching mask film 40 is disposed on the upper side of the phase shift film 30, and is formed of a material having etching resistance (different from the etching selectivity of the phase shift film 30) to an etching solution for etching the phase shift film 30. The etching mask film 40 may have a function of blocking the transmission of the exposure light, and may have a function of reducing the film-surface reflectance so that the film-surface reflectance of the phase shift film 30 is 15% or less in a wavelength range of 350nm to 436nm with respect to the light incident from the phase shift film 30 side. The etching mask film 40 is made of a chromium-based material containing chromium (Cr). More specific examples of the chromium-based material include: chromium (Cr), or a material containing chromium (Cr) and at least one of oxygen (O), nitrogen (N), and carbon (C). Or, there may be mentioned: a material containing chromium (Cr) and at least one of oxygen (O), nitrogen (N) and carbon (C), and further containing fluorine (F). For example, as materials constituting the etching mask film 40, there can be mentioned: cr, CrO, CrN, CrF, CrCO, CrCN, CrON, CrCON, CrCONF.

The etching mask film 40 may be formed by a sputtering method.

When the etching mask film 40 has a function of blocking the transmission of the exposure light, the optical density with respect to the exposure light is preferably 3 or more, more preferably 3.5 or more, and further preferably 4 or more in a portion where the phase shift film 30 and the etching mask film 40 are laminated.

The optical density can be measured using a spectrophotometer, an OD meter, or the like.

Depending on the function, the etching mask film 40 may be formed of a single film having a uniform composition, may be formed of a plurality of films having different compositions, or may be formed of a single film having a composition continuously changing in the thickness direction.

The phase shift mask blank 10 shown in fig. 1 includes the etching mask film 40 on the phase shift film 30, and the present invention is also applicable to a phase shift mask blank that includes the etching mask film 40 on the phase shift film 30 and a resist film on the etching mask film 40.

Next, a method for manufacturing the phase shift mask blank 10 according to embodiments 1 and 2 will be described. The phase shift mask blank 10 shown in fig. 1 can be manufactured by performing the following phase shift film forming step and etching mask film forming step. The phase shift mask blank 10 shown in fig. 2 can be manufactured by a phase shift film forming process.

Hereinafter, each step will be described in detail.

1. Phase shift film formation step

First, the transparent substrate 20 is prepared. The transparent substrate 20 may be made of synthetic quartz glass, aluminosilicate glass, soda-lime glass, or low thermal expansion glass (SiO) as long as it is transparent to exposure light₂-TiO₂Glass, etc.) and the like.

Next, the phase shift film 30 is formed on the transparent substrate 20 by a sputtering method.

A transition metal silicide target containing a transition metal and silicon or a transition metal silicide target containing a transition metal, silicon, oxygen, and/or nitrogen, which is a main component of a material constituting the phase shift film 30, is used as the sputtering target, and the phase shift film 30 is formed in a sputtering gas atmosphere, for example, a sputtering gas atmosphere formed of an inert gas containing at least one selected from helium, neon, argon, krypton, and xenon, or a mixed gas of the inert gas and an active gas containing at least oxygen and nitrogen selected from oxygen, nitrogen, carbon dioxide, nitric oxide, and nitrogen dioxide. Then, the gas pressure in the film forming chamber during sputtering is set to 0.7Pa to 3.0Pa, thereby forming the phase shift film 30. The phase shift film 30 is preferably formed so that the gas pressure in the film forming chamber during sputtering is 0.8Pa to 3.0 Pa. By setting the range of the gas pressure in this way, a columnar structure can be formed in the phase shift film 30. With this columnar structure, not only can side etching at the time of pattern formation described later be suppressed, but also a high etching rate can be achieved. Here, from the viewpoint of having a large effect of suppressing a decrease in wet etching rate due to the columnar structure, being able to improve the cleaning resistance of the phase shift film 30, being easy to improve the transmittance, and the like, the atomic ratio of the transition metal and silicon in the transition metal silicide target is preferably 1:3 or more and 1:15 or less.

The composition and thickness of the phase shift film 30 may be adjusted so that the phase shift film 30 has the above-described phase difference and transmittance. The composition of the phase shift film 30 can be controlled by the content ratio of the elements constituting the sputtering target (for example, the ratio of the content ratio of the transition metal to the content ratio of silicon), the composition and flow rate of the sputtering gas, and the like. The thickness of the phase shift film 30 can be controlled by sputtering power, sputtering time, and the like. The phase shift film 30 is preferably formed by using an in-line sputtering apparatus. In the case where the sputtering apparatus is an in-line type sputtering apparatus, the thickness of the phase shift film 30 can be controlled by the conveyance speed of the substrate. Thereby, the content of the light element component including oxygen and nitrogen in the phase shift film 30 can be controlled to 40 atomic% or more and 70 atomic% or less.

When the phase shift film 30 is formed of a single film, the above-described film formation process is performed only 1 time by appropriately adjusting the composition and flow rate of the sputtering gas. When the phase shift film 30 is formed of a plurality of films having different compositions, the above-described film formation process is performed a plurality of times by appropriately adjusting the composition and flow rate of the sputtering gas. The phase shift film 30 can be formed using targets having different content ratios of elements constituting the sputtering target. When the film formation process is performed a plurality of times, the sputtering power applied to the sputtering target can be changed according to the film formation process.

2. Surface treatment step

When the phase shift film 30 is formed of an oxygen-containing transition metal silicide material such as a transition metal silicide oxide containing a transition metal, silicon, and oxygen, or a transition metal silicide oxynitride containing a transition metal, silicon, oxygen, and nitrogen, a surface treatment step of adjusting the surface oxidation state of the phase shift film 30 may be performed on the surface of the phase shift film 30 in order to suppress permeation of an etching solution due to the presence of the transition metal oxide. When the phase shift film 30 is formed of a transition metal silicide nitride containing a transition metal, silicon, and nitrogen, the content of the transition metal oxide is lower than that of the transition metal silicide material containing oxygen. Therefore, when the material of the phase shift film 30 is a transition metal silicide nitride, the surface treatment step may be performed or may not be performed.

Examples of the surface treatment step for adjusting the surface oxidation state of the phase shift film 30 include: a method of surface treatment with an acidic aqueous solution, a method of surface treatment with an alkaline aqueous solution, a method of surface treatment by dry treatment such as ashing, and the like.

Thereby, the phase shift mask blank 10 of embodiment 2 can be obtained. The following etching mask film forming step may be performed in the production of the phase shift mask blank 10 according to embodiment 1.

3. Etching mask film formation process

After the phase shift film formation step, a surface treatment for adjusting the surface oxidation state of the surface of the phase shift film 30 may be performed as necessary, and then the etching mask film 40 may be formed on the phase shift film 30 by a sputtering method. The etching mask film 40 is preferably formed using an in-line type sputtering apparatus. In the case where the sputtering apparatus is an in-line type sputtering apparatus, the thickness of the etching mask film 40 can be controlled by the transport speed of the transparent substrate 20.

The etching mask film 40 is formed using a sputtering target containing chromium or a chromium compound (chromium oxide, chromium nitride, chromium carbide, chromium oxynitride, chromium oxycarbonitride, etc.) in a sputtering gas atmosphere containing at least one inert gas selected from helium, neon, argon, krypton, and xenon, or a mixed gas of an inert gas containing at least one selected from helium, neon, argon, krypton, and xenon and an active gas containing at least one selected from oxygen, nitrogen, nitric oxide gas, nitrogen dioxide gas, carbon dioxide gas, hydrocarbon gas, and fluorine-based gas. As the hydrocarbon gas, for example: methane gas, butane gas, propane gas, styrene gas, etc. Then, by adjusting the gas pressure in the film forming chamber when sputtering is performed, the etching mask film 40 can be formed into a columnar structure in the same manner as the phase shift film 30. This makes it possible to suppress side etching in patterning described later and to realize a high etching rate.

In the case where the etching mask film 40 is formed of a single film having a uniform composition, the above-described film formation process is performed only 1 time without changing the composition and flow rate of the sputtering gas. In the case where the etching mask film 40 is formed of a plurality of films having different compositions, the above-described film formation process is performed a plurality of times while changing the composition and flow rate of the sputtering gas in accordance with the film formation process. In the case where the etching mask film 40 is formed of a single film whose composition continuously changes in the thickness direction, the composition and flow rate of the sputtering gas are changed together with the elapsed time of the film formation process, and the above-described film formation process is performed only 1 time.

Thereby, the phase shift mask blank 10 of embodiment 1 can be obtained.

Since the phase shift mask blank 10 shown in fig. 1 includes the etching mask film 40 on the phase shift film 30, the etching mask film forming step is performed when manufacturing the phase shift mask blank 10. In the case of manufacturing a phase shift mask blank having the etching mask film 40 on the phase shift film 30 and the resist film on the etching mask film 40, the resist film is formed on the etching mask film 40 after the etching mask film forming step. In the phase shift mask blank 10 shown in fig. 2, when a phase shift mask blank having a resist film on the phase shift film 30 is manufactured, the resist film is formed after the phase shift film forming step.

In the phase shift mask blank 10 according to embodiment 1, the etching mask film 40 is formed on the phase shift film 30, and at least the phase shift film 30 has a columnar structure. In addition, the phase shift mask blank 10 of embodiment 2 has the phase shift film 30 formed thereon, and the phase shift film 30 has a columnar structure.

In the phase shift mask blank 10 according to embodiments 1 and 2, when the phase shift film 30 is patterned by wet etching, etching in the film thickness direction is promoted and side etching is suppressed, so that the cross-sectional shape is good and a phase shift film pattern having a desired transmittance (for example, a high transmittance) can be formed in a short etching time. Accordingly, a phase shift mask blank capable of manufacturing a phase shift mask capable of accurately transferring a high-definition phase shift film pattern without reducing the transmittance of a transparent substrate due to damage to the substrate by a wet etching solution can be obtained.

In the case of forming the phase shift film 30 on the transparent substrate 20, the gas pressure in the film forming chamber during sputtering may be 0.7Pa to 2.4 Pa. By setting the gas pressure range in this manner, the phase-shift film 30 having the indentation hardness of 18GPa to 23GPa can be formed by the nanoindentation method. By setting the indentation hardness of the phase shift film 30 to 18GPa or more and 23GPa or less, not only the side etching at the time of pattern formation described later can be suppressed, but also a high etching rate can be achieved, and the surface roughness of the transparent substrate 20 can be suppressed. Here, from the viewpoints that the indentation hardness is 18GPa or more and 23GPa or less, thereby suppressing an increase in the effect of reducing the wet etching rate, improving the cleaning resistance of the phase-shift film 30, and easily improving the transmittance, it is preferable that the atomic ratio of the transition metal and silicon in the transition metal silicide target is 1:3 or more and 1:15 or less as described above.

Embodiment 3.4.

In embodiments 3 and 4, a method for manufacturing a phase shift mask will be described.

Fig. 3 is an explanatory diagram illustrating a method of manufacturing the phase shift mask of embodiment 3. Fig. 4 is an explanatory diagram illustrating a method of manufacturing the phase shift mask of embodiment 4.

The method of manufacturing a phase shift mask shown in fig. 3 is a method of manufacturing a phase shift mask using the phase shift mask blank 10 shown in fig. 1, the method including: a step of forming a resist film on the etching mask film 40 of the phase shift mask blank 10; a step (1 st resist pattern forming step) of forming a resist pattern 50 by drawing and developing a desired pattern into a resist film (1 st resist pattern forming step), and wet-etching the etching mask film 40 using the resist pattern 50 as a mask to form an etching mask film pattern 40a on the phase shift film 30; and a step (phase shift film pattern forming step) of wet-etching the phase shift film 30 using the etching mask film pattern 40a as a mask to form a phase shift film pattern 30a on the transparent substrate 20. Further, the method includes a 2 nd resist film pattern forming step and a 2 nd etching mask film pattern forming step.

The method of manufacturing a phase shift mask shown in fig. 4 is a method of manufacturing a phase shift mask using the phase shift mask blank 10 shown in fig. 2, the method including: a step of forming a resist film on the phase shift mask blank 10; a step (phase shift film pattern forming step) of forming a resist pattern 50 by drawing and developing a desired pattern on a resist (step 1 resist pattern forming step), and wet etching the phase shift film 30 using the resist pattern 50 as a mask to form a phase shift film pattern 30a on the transparent substrate 20.

Hereinafter, each step of the phase shift mask manufacturing steps of embodiments 3 and 4 will be described in detail.

Process for manufacturing phase Shift mask according to embodiment 3

1. 1 st resist film Pattern Forming Process

In the 1 st resist pattern forming step, first, a resist film is formed on the etching mask film 40 of the phase shift mask blank 10 of embodiment 1. The resist film material used is not particularly limited. For example, the material may be any material that can be exposed to laser light having any wavelength selected from the wavelength range of 350nm to 436nm, which will be described later. The resist film may be either a positive type or a negative type.

Then, a desired pattern is drawn on the resist film using a laser having an arbitrary wavelength selected from a wavelength range of 350nm to 436 nm. The pattern drawn on the resist film is the pattern formed on the phase shift film 30. Examples of the pattern drawn on the resist film include: line and space patterns, hole patterns.

Then, the resist film is developed with a given developing solution, and a 1 st resist film pattern 50 is formed on the etching mask film 40 as shown in fig. 3 (a).

2.1 st etching mask film pattern forming process

In the 1 st etching mask film pattern forming step, first, the etching mask film 40 is etched using the 1 st resist film pattern 50 as a mask to form a 1 st etching mask film pattern 40 a. The etching mask film 40 is formed of chromium-based material containing chromium (Cr). From the viewpoint of increasing the etching rate and suppressing the side etching, it is preferable that the etching mask film 40 has a columnar structure. The etching solution for etching the etching mask film 40 is not particularly limited as long as it can selectively etch the etching mask film 40. Specifically, an etching solution containing cerium ammonium nitrate and perchloric acid may be mentioned.

Then, the 1 st resist film pattern 50 is stripped as shown in fig. 3(b) using a resist stripping solution or by ashing. In some cases, the following phase shift film pattern forming step may be performed without peeling the 1 st resist pattern 50.

3. Phase shift film pattern formation process

In the phase shift film pattern forming step 1, the phase shift film 30 is wet-etched using the 1 st etching mask film pattern 40a as a mask, thereby forming a phase shift film pattern 30a as shown in fig. 3 (c). As the phase shift film pattern 30a, there can be mentioned: line and space patterns, hole patterns. The etching solution for etching the phase shift film 30 is not particularly limited as long as it can selectively etch the phase shift film 30. For example, there may be mentioned: the etching solution comprises ammonium fluoride, phosphoric acid and hydrogen peroxide, and the etching solution comprises ammonium hydrofluoride and hydrogen peroxide.

In order to improve the cross-sectional shape of the phase shift film pattern 30a, it is preferable to perform wet etching for a time (over-etching time) longer than the time (appropriate etching time) until the transparent substrate 20 is exposed in the phase shift film pattern 30 a. In consideration of the influence on the transparent substrate 20, the overetching time is preferably set to a time obtained by adding 20% of the proper etching time to the proper etching time, and more preferably set to a time obtained by adding 10% of the proper etching time.

4. 2 nd resist film Pattern Forming Process

In the 2 nd resist pattern forming step, first, a resist film is formed to cover the 1 st etching mask film pattern 40 a. The resist film material used is not particularly limited. For example, the material may be any material that can be exposed to laser light having any wavelength selected from the wavelength range of 350nm to 436nm, which will be described later. The resist film may be either a positive type or a negative type.

Then, a desired pattern is drawn on the resist film using a laser having an arbitrary wavelength selected from a wavelength range of 350nm to 436 nm. The pattern drawn on the resist film is a light shielding stripe pattern for shielding the outer peripheral region of the region where the pattern is formed on the phase shift film 30, a light shielding stripe pattern for shielding the central portion of the phase shift film pattern, or the like. The pattern drawn on the resist film also includes a pattern of a light shielding band pattern that does not shield the central portion of the phase shift film pattern 30a from light, depending on the transmittance of the phase shift film 30 to the exposure light.

Then, the resist film is developed with a given developing solution, and as shown in fig. 3(d), a 2 nd resist film pattern 60 is formed on the 1 st etching mask film pattern 40 a.

5. 2 nd etching mask film patterning process

In the 2 nd etching mask film pattern forming step, the 1 st etching mask film pattern 40a is etched using the 2 nd resist film pattern 60 as a mask, and a 2 nd etching mask film pattern 40b is formed as shown in fig. 3 (e). The 1 st etching mask film pattern 40a is formed of chromium-based material containing chromium (Cr). The etching solution for etching the 1 st etching mask film pattern 40a is not particularly limited as long as it can selectively etch the 1 st etching mask film pattern 40 a. For example, an etching solution containing cerium ammonium nitrate and perchloric acid may be mentioned.

Then, the 2 nd resist film pattern 60 is peeled off using a resist peeling liquid or by ashing.

Thereby, the phase shift mask 100 can be obtained.

In the above description, although the case where the etching mask film 40 has the function of blocking the transmission of the exposure light has been described, in the case where the etching mask film 40 has only the function of a hard mask in etching the phase shift film 30, the phase shift mask 100 is produced by removing the 1 st etching mask film pattern after the phase shift film pattern forming step without performing the 2 nd resist pattern forming step and the 2 nd etching mask film pattern forming step in the above description.

According to the method of manufacturing a phase shift mask of embodiment 3, since the phase shift mask blank of embodiment 1 is used, the etching time can be shortened, and a phase shift film pattern having a good cross-sectional shape can be formed. Therefore, a phase shift mask capable of transferring a high-definition phase shift film pattern with good accuracy can be manufactured. The phase shift mask manufactured in this way can cope with the miniaturization of the line, gap pattern, and contact hole.

Process for manufacturing phase Shift mask according to embodiment 4

1. Resist film pattern formation step

In the resist pattern forming step, first, a resist film is formed on the phase shift film 30 of the phase shift mask blank 10 of embodiment 2. The resist film material used is the same as that described in embodiment 3. In order to improve the adhesion to the phase shift film 30, the phase shift film 30 may be subjected to a surface modification treatment before the resist film is formed, if necessary. After the resist film is formed in the same manner as described above, a desired pattern is drawn on the resist film using a laser beam having an arbitrary wavelength selected from the wavelength range of 350nm to 436 nm. Then, the resist film is developed with a given developing solution, and a resist film pattern 50 is formed on the phase shift film 30 as shown in fig. 4 (a).

2. Phase shift film pattern formation process

In the phase shift film pattern forming step, the phase shift film 30 is etched using the resist pattern as a mask, thereby forming a phase shift film pattern 30a as shown in fig. 4 (b). The etching solution and the over-etching time for etching the phase shift film pattern 30a and the phase shift film 30 are the same as those described in embodiment 3.

Then, the resist film pattern 50 is peeled off by using a resist stripping liquid or by ashing (fig. 4 (c)).

Thereby, the phase shift mask 100 can be obtained.

According to the method of manufacturing a phase shift mask of embodiment 4, since the phase shift mask blank of embodiment 2 is used, the etching time can be shortened, and a phase shift film pattern having a good cross-sectional shape can be formed without causing a decrease in the transmittance of the transparent substrate due to damage to the substrate by the wet etching solution. Therefore, a phase shift mask capable of transferring a high-definition phase shift film pattern with good accuracy can be manufactured. The phase shift mask manufactured in this way can cope with the miniaturization of the line, gap pattern, and contact hole. In addition, when a phase shift mask is manufactured using a phase shift mask blank having a phase shift film 30 with an indentation hardness of 18GPa or more and 23GPa or less obtained by the nanoindentation method, in addition to the above-described effects, surface roughness of the transparent substrate 20 can be suppressed, and the cleaning resistance of the phase shift film 30 can be improved.

Embodiment 5.

In embodiment 5, a method for manufacturing a display device will be described. The display device can be manufactured by a process (mask placing process) using the phase shift mask 100 and a process (exposure process) of exposing and transferring a transfer pattern to a resist film on the display device, the phase shift mask 100 being manufactured using the above-described phase shift mask blank 10 or the above-described method of manufacturing the phase shift mask 100.

Hereinafter, each step will be described in detail.

1. Placing procedure

In the placing step, the phase shift mask manufactured in embodiment 3 is placed on a mask stage of an exposure apparatus. Here, the phase shift mask is disposed so as to face the resist film formed on the display device substrate with the projection optical system of the exposure apparatus interposed therebetween.

2. Pattern transfer process

In the pattern transfer step, the phase shift mask 100 is irradiated with exposure light to transfer a phase shift film pattern to a resist film formed on a display device substrate. The exposure light may be a composite light including light having a plurality of wavelengths selected from a wavelength range of 365nm to 436nm, or a monochromatic light selected by removing a certain wavelength range from the wavelength range of 365nm to 436nm by an optical filter. For example, the exposure light is a composite light including i-line, h-line, and g-line, or an i-line monochromatic light. When the composite light is used as the exposure light, the exposure light intensity can be increased to increase the light flux, so that the manufacturing cost of the display device can be reduced.

According to the method for manufacturing a display device of embodiment 3, a high-resolution, high-definition display device having fine line and space patterns and contact holes can be manufactured.

In the above embodiments, the case of using a phase shift mask blank having a phase shift mask film and a phase shift mask having a phase shift mask film pattern as a photomask blank having a thin film for pattern formation and a photomask having a transfer pattern has been described, but the present invention is not limited thereto. For example, the present invention can be applied to a binary mask blank having a light-shielding film as a pattern-forming thin film and a binary mask having a light-shielding film pattern.

Examples

Example 1.

A. Phase shift mask blank and method of manufacturing the same

To manufacture the phase shift mask blank of example 1, first, a synthetic quartz glass substrate of 1214 size (1220mm × 1400mm) was prepared as the transparent substrate 20.

Then, the synthetic quartz glass substrate was placed on a tray (not shown) with the main surface facing downward, and was transported into a chamber of the in-line sputtering apparatus.

In order to form the phase shift film 30 on the main surface of the transparent substrate 20, first, argon (Ar) and nitrogen (N) were introduced under a sputtering gas pressure of 1.6Pa in the 1 st chamber₂) And an inert gas (Ar: 18sccm, N₂: 13sccm, He: 50 sccm). Then, a sputtering power of 7.6kW was applied to a 1 st sputtering target (molybdenum: silicon ═ 1:9) containing molybdenum and silicon, and a nitride of molybdenum silicide containing molybdenum, silicon, and nitrogen was deposited on the main surface of the transparent substrate 20 by reactive sputtering. Then, a phase shift film 30 having a film thickness of 150nm was formed.

Subsequently, the transparent substrate 20 with the phase shift film 30 is transferred into the 2 nd chamber, and argon (Ar) and nitrogen (N) are introduced₂) The mixed gas (Ar: 65sccm, N₂:15 sccm) was introduced into the 2 nd chamber. Then, a sputtering power of 1.5kW was applied to the 2 nd sputtering target including chromium, and chromium nitride (CrN) including chromium and nitrogen was formed on the phase shift film 30 by reactive sputtering (film thickness 15 nm). Then, argon (Ar) gas and methane (CH) were introduced into the 3 rd chamber in a predetermined degree of vacuum₄: 4.9%) of the mixed gas (30sccm), a sputtering power of 8.5kW was applied to the 3 rd sputtering target containing chromium, and chromium carbide (CrC) containing chromium and carbon was formed on CrN by reactive sputtering (film thickness 60 nm). Finally, argon (Ar) and methane (CH) were introduced into the 4 th chamber under a predetermined degree of vacuum₄: 5.5%) gas mixture and nitrogen (N)₂) With oxygen (O)₂) Mixed gas of (Ar + CH)₄：30sccm、N₂：8sccm、O₂: 3sccm), 2.0kW of sputtering was applied to the 4 th sputtering target containing chromiumThe chromium oxycarbonitride (CrCON) (film thickness 30nm) containing chromium, carbon, oxygen and nitrogen was formed on CrC by reactive sputtering. As described above, the etching mask film 40 having a laminated structure of the CrN layer, the CrC layer, and the CrCON layer is formed on the phase shift film 30.

Thus, a phase shift mask blank 10 in which the phase shift film 30 and the etching mask film 40 are formed on the transparent substrate 20 is obtained.

The transmittance and the phase difference of the phase shift film 30 (surface of the phase shift film 30) of the obtained phase shift mask blank 10 were measured by using MPM-100 manufactured by Lasertec corporation. For the measurement of the transmittance and the phase difference of the phase shift film 30, a phase shift film-attached substrate (dummy substrate) in which the phase shift film 30 is formed on the main surface of a synthetic quartz glass substrate is used, and the phase shift film-attached substrate is mounted on the same tray. Before the etching mask film 40 was formed, the substrate with the phase shift film (dummy substrate) was taken out from the chamber, and the transmittance and the phase difference of the phase shift film 30 were measured. As a result, the transmittance was 27% (wavelength: 405nm), and the phase difference was 178 ° (wavelength: 405 nm).

The obtained phase shift mask blank 10 was subjected to composition analysis in the depth direction by X-ray photoelectron spectroscopy (XPS).

As a result of analyzing the composition of the phase shift mask blank 10 in the depth direction by XPS, the content of each constituent element in the phase shift film 30 in the depth direction was substantially constant, with the exception of the composition gradient region of the interface between the transparent substrate 20 and the phase shift film 30 and the composition gradient region of the interface between the phase shift film 30 and the etching mask film 40, and the content of Mo was 8 atomic%, Si was 40 atomic%, N was 48 atomic%, and O was 4 atomic%. The atomic ratio of molybdenum to silicon is 1:5, which is in the range of 1:3 to 1: 15. The total content of oxygen and nitrogen as light elements is 52 atomic% or more and 65 atomic% or less. It is considered that the presence of oxygen in the phase shift film 30 is such that the sputtering gas pressure is as high as 0.8Pa or more and a slight amount of oxygen is present in the chamber during film formation.

The indentation hardness of the obtained phase shift film 30 was measured (the measurement method is described later), and as a result, the indentation hardness satisfied 18GPa to 23 GPa.

Next, cross-sectional SEM (scanning electron microscope) observation was performed at 80000 magnifications at the center position of the transfer pattern formation region of the obtained phase shift mask blank 10, and it was confirmed that the phase shift film 30 had a columnar structure. That is, it was confirmed that the particles of the molybdenum silicide compound constituting the phase shift film 30 had a columnar particle structure extending in the film thickness direction of the phase shift film 30. It was confirmed that columnar particles in the film thickness direction were formed irregularly in the columnar particle structure of the phase shift film 30, and the lengths of the columnar particles in the film thickness direction were not uniform. It was also confirmed that the sparse portions of the phase shift film 30 were continuously formed in the film thickness direction. In addition, for the image obtained by the cross-sectional SEM observation, image data of 64 pixels in the vertical direction × 256 pixels in the horizontal direction was extracted for the region including the center portion in the thickness direction of the phase shift film 30 (fig. 5 (a)). Further, the image data shown in fig. 5 is fourier-transformed (fig. 5 (b)). It was confirmed that in the spatial frequency distribution obtained by fourier transform, the signal intensity of the origin of the spatial frequency (maximum signal intensity) was 3136000, and a spatial frequency spectrum having a signal intensity of 66150 was present in addition to the maximum signal intensity. The maximum signal intensity corresponding to the origin of the spatial frequency is 66150/3136000 ═ 0.021 (i.e., 2.1%), and the phase shift film 30 has a columnar structure having a signal intensity of 1.0% or more.

In the fourier-transformed image of fig. 5(b), when the origin of the spatial frequency, that is, the center of the image of fig. 5(b) is set as the origin (0) and the maximum spatial frequency corresponding to both ends of 256 pixels on the horizontal axis is set as 1 (100%), a signal having a signal intensity of 2.1% with respect to the maximum signal intensity corresponding to the origin of the spatial frequency is the phase shift film 30 having a columnar structure having a signal at a position 0.055%, that is, 5.5% away from the origin. The same applies to fourier transform images of the following examples and comparative examples.

In addition, a plate-like sample of 100nm in the direction perpendicular to the film thickness direction (in-plane direction of the substrate) was collected in the vicinity of the film thickness center of the phase shift film 30, and dark field planar STEM observation was performed. Fig. 6 shows the results of dark field planar STEM (scanning transmission electron microscope) observation. As shown in fig. 6, patches of gray-white and gray-black that are considered to be columnar particle portions (gray-white portions) and between particles (gray-black portions) are observed. The gray-white and gray-black portions were quantitatively analyzed for the elements (Mo, Si, N, O) constituting the phase shift film 30 by EDX analysis (energy dispersive X-ray analysis) (not shown). As a result, it was confirmed that the detected amount (count) of Si is higher than that of Mo in the gray-black portion and the gray-white portion, and the detected amount (count) of the phase shift film 30 constituent element in the gray-black portion is lower than that of the phase shift film 30 constituent element in the gray-white portion. In particular, the detected amount (count) of Si in the gray-black portion was 600(Counts), and the detected amount (count) of Si in the gray-white portion was 400(Counts), and the difference between the detected amounts (Counts) was large compared to other elements. From the results, it was confirmed that the phase shift film 30 formed a particle portion (gray-white portion) having a relatively high density and a sparse portion (gray-black portion) having a relatively low density. The particle portion corresponds to the columnar particles shown in fig. 5 and 7. The film density of the entire phase shift film 30 is lower than that of the conventional phase shift film.

B. Phase shift mask and method of manufacturing the same

To manufacture the phase shift mask 100 using the phase shift mask blank 10 manufactured as described above, first, a photoresist film is coated on the etching mask film 40 of the phase shift mask blank 10 using a resist coating apparatus.

Then, a photoresist film having a film thickness of 520nm was formed through the heating/cooling process.

Then, a photoresist film was drawn using a laser drawing device, and a resist film pattern having a hole pattern with a hole diameter of 1.5 μm was formed on the etching mask film through a developing/rinsing process.

Then, the etching mask film was wet-etched using a chromium etching solution containing ammonium cerium nitrate and perchloric acid with the resist film pattern as a mask, to form a 1 st etching mask film pattern 40 a.

Then, the phase shift film 30 was wet-etched using a molybdenum silicide etching solution in which a mixed solution of ammonium hydrofluoride and hydrogen peroxide was diluted with pure water, using the 1 st etching mask film pattern 40a as a mask, to form a phase shift film pattern 30 a. The wet etching was performed with an over-etching time of 110% in order to make the cross-sectional shape vertical and to form a desired fine pattern. The etching time in example 1 is 0.15 times as long as that in the comparative example described later, and the etching time can be significantly shortened.

Then, the resist pattern is peeled off.

Then, a photoresist film is coated using a resist coating apparatus in such a manner as to cover the 1 st etching mask film pattern 40 a.

Then, a photoresist film is drawn using a laser drawing device, and a 2 nd resist film pattern 60 for forming a light shielding tape is formed on the 1 st etching mask film pattern 40a through a developing/rinsing process.

Then, the 1 st etching mask film pattern 40a formed in the transfer pattern forming region was wet-etched using a chromium etching solution containing cerium ammonium nitrate and perchloric acid with the 2 nd resist film pattern 60 as a mask.

Then, the 2 nd resist film pattern 60 is peeled off.

Thus, a phase shift mask 100 was obtained in which a phase shift film pattern 30a having an aperture diameter of 1.5 μm was provided on the transparent substrate 20 in the transfer pattern formation region, and a light-shielding film having a laminated structure of the phase shift film pattern 30a and the etching mask film pattern 40b was formed on the transparent substrate 20.

The cross section of the resulting phase shift mask was observed with a scanning electron microscope. The cross section of the phase shift film pattern is composed of the upper surface, the lower surface and the side surface of the phase shift film pattern. The angle of the cross section of the phase shift film pattern is an angle formed by a portion (upper side) where the upper surface of the phase shift film pattern is in contact with the side surface and a portion (lower side) where the side surface is in contact with the lower surface. The phase shift film pattern 30a of the resulting phase shift mask had a cross-sectional angle of 74 ° and a cross-sectional shape close to vertical. The phase shift film pattern 30a formed in the phase shift mask of example 1 has a cross-sectional shape capable of sufficiently exerting a phase shift effect. The phase shift film pattern 30a has a good cross-sectional shape by providing the phase shift film 30 with a columnar structure, and this is considered to be due to the following mechanism. As a result of observation of the cross-sectional SEM photograph of fig. 7, the phase shift film 30 had a columnar particle structure (columnar structure) in which columnar particles extending in the film thickness direction were irregularly formed. In addition, from the observation result of the dark field plane STEM photograph of fig. 6 and the observation result of the cross-sectional SEM photograph of fig. 7, the phase shift film 30 forms each columnar particle portion having a relatively high density and a sparse portion having a relatively low density. From these facts, it is considered that, when the phase shift film 30 is patterned by wet etching, the etching liquid penetrates into the sparse portions in the phase shift film 30 and is easily etched in the film thickness direction, and on the other hand, columnar particles are irregularly formed in the direction perpendicular to the film thickness direction (direction in the substrate surface) and the sparse portions in the direction are intermittently formed, so that it is difficult to perform etching in the direction and side etching is suppressed, and therefore, the phase shift film pattern 30a has a good cross-sectional shape close to the perpendicular. In addition, in the phase shift film pattern, no penetration was observed at the interface with the etching mask film pattern and the interface with the substrate. Therefore, a phase shift mask having an excellent phase shift effect is obtained for exposure light including light in a wavelength range of 300nm or more and 500nm or less, more specifically, for exposure light including composite light of i-line, h-line, and g-line.

Therefore, when the phase shift mask of example 1 was set on the mask stage of the exposure apparatus and exposed to light and transferred to the resist film on the display device, a fine pattern smaller than 2.0 μm could be transferred with high precision.

The cross-sectional SEM photograph of fig. 7 is a cross-sectional SEM photograph of the phase shift mask in example 1, which was obtained by wet etching (110% over-etching) the phase shift film 30 with a molybdenum silicide etching solution using the 1 st etching mask film pattern 40a as a mask to form the phase shift film pattern 30a and then stripping off the resist pattern. As shown in fig. 7, the phase shift film pattern 30a maintains the columnar structure of the phase shift film 30, and the surface of the transparent substrate 20 exposed after the phase shift film 30 is removed is smooth in a state where the transmittance is negligibly decreased due to the surface roughness of the transparent substrate 20.

Example 2.

A. Phase shift mask blank and method of manufacturing the same

In order to manufacture the phase shift mask blank of example 2, a synthetic quartz glass substrate of 1214 size (1220mm × 1400mm) was prepared as a transparent substrate in the same manner as in example 1.

A synthetic quartz glass substrate was conveyed into a chamber of an in-line type sputtering apparatus by the same method as in example 1. The same sputtering target materials as in example 1 were used as the 1 st, 2 nd, 3 rd, and 4 th sputtering targets. Then, argon (Ar), helium (He), and nitrogen (N) were introduced while the sputtering gas pressure in the 1 st chamber was set to 1.6Pa₂) The mixed gas (Ar: 18sccm, N₂:15 sccm, He: 50sccm, NO: 4 sccm). Then, a sputtering power of 7.6kW was applied to the 1 st sputtering target (molybdenum: silicon ═ 1:9) containing molybdenum and silicon, and oxynitride of molybdenum silicide containing molybdenum, silicon, oxygen, and nitrogen was deposited on the main surface of the transparent substrate 20 by reactive sputtering. Then, a phase shift film 30 having a film thickness of 140nm was formed.

Then, after the phase shift film was formed on the transparent substrate, the substrate was taken out from the chamber, and the surface of the phase shift film was cleaned with pure water. The pure water cleaning conditions were a temperature of 30 ℃ and a cleaning time of 60 seconds.

Then, the etching mask film 40 was formed by the same method as in example 1.

The transmittance and the phase difference of the phase shift film (phase shift film obtained by washing the surface of the phase shift film with pure water) of the obtained phase shift mask blank 10 were measured by using MPM-100 manufactured by Lasertec corporation. For the measurement of the transmittance and the phase difference of the phase shift film, a phase shift film-attached substrate (dummy substrate) in which a phase shift film 30 is formed on the main surface of a synthetic quartz glass substrate was used, and the phase shift film-attached substrate was mounted on the same tray. The substrate with the phase shift film (dummy substrate) was taken out from the chamber before the etching mask film was formed, and the transmittance and the phase difference of the phase shift film 30 were measured. As a result, the transmittance was 33% (wavelength: 365nm), and the phase difference was 169 degrees (wavelength: 365 nm).

The obtained phase shift mask blank was subjected to composition analysis in the depth direction by X-ray photoelectron spectroscopy (XPS).

As a result, in the phase shift film 30, the content of each constituent element was substantially constant in the depth direction, with 7 atomic% of Mo, 38 atomic% of Si, 45 atomic% of N, and 10 atomic% of O, except for the composition gradient region of the interface between the transparent substrate 20 and the phase shift film 30 and the composition gradient region of the interface between the phase shift film 30 and the etching mask film 40, as in example 1. The atomic ratio of molybdenum to silicon is 1:5.4, which is in the range of 1:3 to 1: 15. The total content of oxygen, nitrogen, and carbon as light elements is 55 atomic% or more and 65 atomic% or less.

Next, cross-sectional SEM observation was performed at 80000 times magnification at the center position of the transfer pattern formation region of the obtained phase shift mask blank 10, and it was confirmed that the phase shift film 30 had a columnar structure. That is, it was confirmed that the particles of the molybdenum silicide compound constituting the phase shift film 30 had a columnar particle structure extending in the film thickness direction of the phase shift film 30. It was confirmed that columnar particles in the film thickness direction were formed irregularly in the columnar particle structure of the phase shift film 30, and the lengths of the columnar particles in the film thickness direction were not uniform. It was also confirmed that the sparse portions of the phase shift film 30 were continuously formed in the film thickness direction. In addition, for the image obtained by the cross-sectional SEM observation, image data of 64 pixels in the vertical direction × 256 pixels in the horizontal direction was extracted for the region including the center portion in the thickness direction of the phase shift film 30 (fig. 8 (a)). Further, the image data shown in fig. 8(a) is fourier-transformed (fig. 8 (b)). It was confirmed that in the spatial frequency distribution obtained by fourier transform, the signal intensity at the origin of the spatial frequency (maximum signal intensity) was 2406000, and a spatial frequency spectrum having a signal intensity of 39240 was present in addition to the maximum signal intensity. The maximum signal intensity corresponding to the origin of the spatial frequency is 39240/2406000 ═ 0.016 (i.e., 1.6%), and the phase shift film 30 has a columnar structure having a signal intensity of 1.0% or more.

In the fourier-transformed image of fig. 8(b), when the origin of the spatial frequency, that is, the center of the image of fig. 8(b) is set as the origin (0) and both ends of 256 pixels on the horizontal axis are set as 1 (100%), a signal having a signal intensity of 1.6% with respect to the maximum signal intensity corresponding to the origin of the spatial frequency is the phase shift film 30 having a columnar structure having a signal at a position 0.023% or 2.3% away from the origin.

In addition, in the same manner as in example 1, dark field plane STEM observation was performed in the vicinity of the film thickness center of the phase shift film 30. As a result, it was confirmed that each columnar particle portion and the sparse portion were formed in the phase shift film 30 as in example 1.

B. Phase shift mask and method of manufacturing the same

Using the phase shift mask blank manufactured as described above, a phase shift mask having a phase shift film pattern with an aperture of 1.5 μm was manufactured by the same method as in example 1. The wet etching of the phase shift film 30 is performed with an over-etching time of 110% in order to make the cross-sectional shape vertical and to form a desired fine pattern. The etching time appropriate for example 2 was 0.07 times the etching time appropriate for the comparative example described later, and the etching time was significantly shortened.

The cross section of the resulting phase shift mask was observed with a scanning electron microscope. The phase shift film pattern 30a of the phase shift mask has a cross-section with an angle of 74 deg., and has a nearly vertical cross-sectional shape. In addition, in the phase shift film pattern, no penetration was observed at the interface with the etching mask film pattern and the interface with the substrate. Therefore, a phase shift mask having an excellent phase shift effect is obtained for exposure light including light in a wavelength range of 300nm or more and 500nm or less, more specifically, for exposure light including composite light of i-line, h-line, and g-line.

Therefore, when the phase shift mask of example 2 was set on the mask stage of the exposure apparatus and exposed to light and transferred to the resist film on the display device, a fine pattern smaller than 2.0 μm could be transferred with high precision.

In the phase shift mask manufacturing process of example 2, the cross-sectional SEM photograph of fig. 9 is a cross-sectional SEM photograph of the phase shift film 30 that was formed by wet etching (110% over-etching) the phase shift film 30 with a molybdenum silicide etching solution using the 1 st etching mask film pattern 40a as a mask and the resist pattern was peeled off. As shown in fig. 9, the phase shift film pattern 30a maintains the columnar structure of the phase shift film 30, and the surface of the transparent substrate 20 exposed after the phase shift film 30 is removed is smooth in a state where the transmittance is negligibly decreased due to the surface roughness of the transparent substrate 20.

Example 3.

A. Phase shift mask blank and method of manufacturing the same

The phase shift mask blank of example 3 is a phase shift mask blank without the etching mask film in the phase shift mask blank of example 1.

In order to manufacture the phase shift mask blank of example 3, a synthetic quartz glass substrate of 1214 size (1220mm × 1400mm) was prepared as the transparent substrate 20 in the same manner as in example 1.

In order to form the phase shift film 30 on the main surface of the transparent substrate 20 by the same film formation method as in example 1, first, argon (Ar) and nitrogen (N) were introduced while the sputtering gas pressure in the 1 st chamber was set to 1.4Pa₂) And an inert gas (Ar: 18sccm, N₂: 13.5sccm, He: 50 sccm). Under these film formation conditions, a phase shift film 30 (film thickness: 150nm) composed of an oxynitride of molybdenum silicide was formed on the transparent substrate 20.

Thus, a phase shift mask blank 10 having the phase shift film 30 formed on the transparent substrate 20 was obtained.

The transmittance and the phase difference were measured with respect to the phase shift film of the obtained phase shift mask blank 10 by using MPM-100 manufactured by Lasertec corporation. For the measurement of the transmittance and the phase difference of the phase shift film, a phase shift film-attached substrate (dummy substrate) in which a phase shift film 30 is formed on the main surface of a synthetic quartz glass substrate was used, and the phase shift film-attached substrate was mounted on the same tray. As a result, the transmittance was 24% (wavelength: 405nm) and the phase difference was 183 degrees (wavelength: 405 nm).

As a result of analyzing the composition of the phase shift film 30 of the phase shift mask blank 10 obtained in the depth direction by X-ray photoelectron spectroscopy (XPS), the content of each constituent element in the phase shift film 30 in the depth direction was substantially constant as in example 1. The atomic ratio of molybdenum to silicon is 1:5, which is in the range of 1:3 to 1: 15. The total content of oxygen, nitrogen, and carbon as light elements is 52 atomic% or more and 65 atomic% or less. The oxygen content is 0.3 atomic% or more and 40 atomic% or less.

Next, cross-sectional SEM observation was performed at 80000 times magnification at the center position of the transfer pattern formation region of the obtained phase shift mask blank 10, and it was confirmed that the phase shift film 30 had a columnar structure. That is, it was confirmed that the particles of the molybdenum silicide compound constituting the phase shift film 30 had a columnar particle structure extending in the film thickness direction of the phase shift film 30. It was confirmed that columnar particles in the film thickness direction were formed irregularly in the columnar particle structure of the phase shift film 30, and the lengths of the columnar particles in the film thickness direction were not uniform. It was also confirmed that the sparse portions of the phase shift film 30 were continuously formed in the film thickness direction. In addition, for the image obtained by the cross-sectional SEM observation, image data of 64 pixels in the vertical direction × 256 pixels in the horizontal direction was extracted for the region including the center portion in the thickness direction of the phase shift film 30 (fig. 10 (a)). Further, the image data shown in fig. 10(a) is fourier-transformed (fig. 10 (b)). It was confirmed that in the spatial frequency distribution obtained by fourier transform, the signal intensity of the origin of the spatial frequency (maximum signal intensity) was 31590000, and a spatial frequency spectrum having a signal intensity of 47230 was present in addition to the maximum signal intensity. The maximum signal intensity corresponding to the origin of the spatial frequency is 47230/3159000 ═ 0.015 (i.e., 1.5%), and the phase shift film 30 has a columnar structure having a signal intensity of 1.0% or more.

In the fourier-transformed image of fig. 10(b), when the origin of the spatial frequency, that is, the center of the image of fig. 10(b) is set as the origin (0) and both ends of 256 pixels on the horizontal axis are set as 1 (100%), a signal having a signal intensity of 1.5% with respect to the maximum signal intensity corresponding to the origin of the spatial frequency is the phase shift film 30 having a fine columnar structure having a large spatial frequency at a position 0.078% away from the origin, that is, at a position 7.8% away from the origin.

In addition, in the same manner as in example 1, dark field plane STEM observation was performed in the vicinity of the film thickness center of the phase shift film 30. As a result, it was confirmed that each columnar particle and the sparse portion were formed in the phase shift film 30 as in example 1.

B. Phase shift mask and method of manufacturing the same

Using the phase shift mask blank 10 manufactured as described above, a phase shift mask having a phase shift film pattern with an aperture of 1.5 μm was manufactured by the same method as in example 1. The wet etching of the phase shift film 30 is performed with an over-etching time of 110% in order to make the cross-sectional shape vertical and to form a desired fine pattern. The etching time suitable for example 3 is 0.20 times as long as that of comparative example described later, and the etching time can be significantly shortened.

The cross section of the resulting phase shift mask was observed with a scanning electron microscope. The phase shift film pattern 30a of the phase shift mask has a cross-sectional angle of 80 deg., having a nearly vertical cross-sectional shape. In addition, in the phase shift film pattern, no penetration was observed at the interface with the etching mask film pattern and the interface with the substrate. Therefore, a phase shift mask having an excellent phase shift effect is obtained for exposure light including light in a wavelength range of 300nm or more and 500nm or less, more specifically, for exposure light including composite light of i-line, h-line, and g-line.

Therefore, when the phase shift mask of example 3 was set on the mask stage of the exposure apparatus and exposed to light and transferred to the resist film on the display device, a fine pattern smaller than 2.0 μm could be transferred with high precision.

In the phase shift mask manufacturing process of example 3, the cross-sectional SEM photograph of fig. 11 is a cross-sectional SEM photograph of the phase shift film 30 that was formed by wet etching (110% over-etching) the phase shift film 30 with a molybdenum silicide etching solution using the 1 st etching mask film pattern 40a as a mask and the resist pattern was peeled off. As shown in fig. 11, the phase shift film pattern 30a maintains the columnar structure of the phase shift film 30, and the surface of the transparent substrate 20 exposed after the phase shift film 30 is removed is smooth in a state where the transmittance is negligibly decreased due to the surface roughness of the transparent substrate 20. The line edge roughness was much better than in example 1.

In the above-described examples, the case where molybdenum is used as the transition metal is described, but the same effect as described above can be obtained also in the case of other transition metals.

In the above-described embodiments, examples of the phase shift mask blank for manufacturing the display device and the phase shift mask for manufacturing the display device have been described, but the invention is not limited thereto. The phase shift mask blank and the phase shift mask of the present invention can be suitably used for semiconductor device production, MEMS production, printed circuit board production, and the like. The present invention is also applicable to a binary mask blank having a light-shielding film as a pattern-forming thin film and a binary mask having a light-shielding film pattern.

In the above-described embodiment, the example in which the transparent substrate has a size of 1214 (1220mm × 1400mm × 13mm) was described, but the present invention is not limited to this. In the case of a phase shift mask blank for manufacturing a display device, a Large (Large Size) transparent substrate having a side length of 300mm or more can be used. The size of the transparent substrate used for the phase shift mask blank for manufacturing the display device is, for example, 330mm × 450mm or more and 2280mm × 3130mm or less.

In the case of a phase shift mask blank for semiconductor device manufacturing, MEMS manufacturing, or printed circuit board, a Small (Small Size) transparent substrate having a side length of 9 inches or less is used. The size of the transparent substrate used for the phase shift mask blank for the above-described application is, for example, 63.1mm × 63.1mm or more and 228.6mm × 228.6mm or less. Generally, 6025 size (152mm × 152mm) and 5009 size (126.6mm × 126.6mm) are used for semiconductor manufacturing and MEMS manufacturing, and 7012 size (177.4mm × 177.4mm) and 9012 size (228.6mm × 228.6mm) are used for printed circuit board.

Comparative example 1.

A. Phase shift mask blank and method of manufacturing the same

In order to manufacture the phase shift mask blank of comparative example 1, a synthetic quartz glass substrate of 1214 size (1220mm × 1400mm) was prepared as a transparent substrate in the same manner as in example 1.

A synthetic quartz glass substrate was conveyed into a chamber of an in-line type sputtering apparatus by the same method as in example 1. Then, argon (Ar) gas and nitrogen (N) gas were introduced with the sputtering gas pressure in the 1 st chamber set to 0.5Pa₂) Mixed gas of gases (Ar: 30sccm, N₂: 30 sccm). Then, a sputtering power of 7.6kW was applied to a 1 st sputtering target (molybdenum: silicon ═ 1:9) containing molybdenum and silicon, and a nitride of molybdenum silicide containing molybdenum, silicon, and nitrogen was deposited on the main surface of the transparent substrate by reactive sputtering. Thus, a phase-shift film having a thickness of 144nm was formed.

The indentation hardness of the phase shift film of comparative example 1 was not more than 18GPa and not more than 23 GPa.

Then, an etching mask film was formed by the same method as in example 1.

Thus, a phase shift mask blank in which a phase shift film and an etching mask film were formed on a transparent substrate was obtained.

The transmittance and the phase difference of the phase shift film of the obtained phase shift mask blank were measured by using MPM-100 manufactured by Lasertec corporation. For measurement of transmittance and phase difference of the phase shift film, a phase shift film-attached substrate (dummy substrate) in which a phase shift film is formed on a main surface of a synthetic quartz glass substrate was used, and the phase shift film-attached substrate was mounted on the same tray. The substrate (dummy substrate) with the phase shift film was taken out from the chamber before the etching mask film was formed, and the transmittance and the phase difference of the phase shift film were measured. As a result, the transmittance was 30% (wavelength: 405nm) and the phase difference was 177 degrees (wavelength: 405 nm).

The obtained phase shift mask blank was subjected to composition analysis in the depth direction by X-ray photoelectron spectroscopy (XPS). As a result, the content of each constituent element in the phase shift film 30 was substantially constant in the depth direction, except for the composition gradient region at the interface between the transparent substrate 20 and the phase shift film 30 and the composition gradient region at the interface between the phase shift film 30 and the etching mask film 40, and the content of Mo was 8 atomic%, Si was 39 atomic%, N was 52 atomic%, and O was 1 atomic%. The atomic ratio of molybdenum to silicon is 1:4.9, which is in the range of 1:3 to 1: 15. The total content of oxygen, nitrogen, and carbon as light elements is 53 atomic% and is in the range of 50 atomic% to 65 atomic%.

Next, cross-sectional SEM observation was performed at 80000 times magnification at the center position of the transfer pattern formation region of the obtained phase shift mask blank 10, and as a result, a columnar structure was not confirmed in the phase shift film, and an ultrafine crystal structure or an amorphous structure was confirmed. For the image obtained by the cross-sectional SEM observation, image data of 64 pixels in the vertical direction × 256 pixels in the horizontal direction was extracted for the region including the center portion in the thickness direction of the phase shift film 30 (fig. 12 (a)). Further, the image data shown in fig. 12(a) is fourier-transformed (fig. 12 (b)). In the spatial frequency spectrum distribution obtained by fourier transform, the signal intensity of the origin of the spatial frequency (maximum signal intensity) was 2073000, no strong signal was recognized except for the maximum intensity signal, and only a spatial frequency spectrum having a signal intensity of 12600 existed. The maximum signal intensity corresponding to the origin of the spatial frequency is 12600/2073000 ═ 0.006 (i.e., 0.6%), and the phase shift film 30 has an ultrafine crystal structure or an amorphous structure which does not have a signal intensity of 1.0% or more.

B. Phase shift mask and method of manufacturing the same

Using the phase shift mask blank manufactured as described above, a phase shift mask was manufactured by the same method as in example 1. In order to make the cross-sectional shape vertical and to form a desired fine pattern, wet etching of the transferred film was performed with an over-etching time of 110%. The etching time in comparative example 1 was 142 minutes, which is a long time.

The sectional SEM photograph of fig. 13 is a sectional SEM photograph before the phase shift film pattern 30a is formed by wet etching (110% over-etching) the phase shift film 30 with a molybdenum silicide etching solution using the 1 st etching mask film pattern 40a as a mask and the resist film pattern is peeled off in the manufacturing process of the phase shift mask of the comparative example. As shown in fig. 13, the surface of the transparent substrate 20 exposed after the phase shift film 30 is removed is rough and is in a state of white turbidity when observed with naked eyes. Therefore, the transmittance is remarkably reduced due to the surface roughness of the transparent substrate 20.

Therefore, it is predicted that when the phase shift mask of comparative example 1 is set on the mask stage of the exposure apparatus and exposed to the resist film transferred onto the display device, a fine pattern of less than 2.0 μm cannot be transferred.

Other examples 1 to 4 and other comparative examples 1 and 2 (hereinafter, may be simply referred to as "examples") for more specifically describing the embodiment of the present invention will be described below.

A. Phase shift mask blank and method of manufacturing the same

In each of other examples 1 to 4 and other comparative examples 1 and 2, in order to manufacture a phase shift mask blank, first, a synthetic quartz glass substrate having a size of 1214 (1220mm × 1400mm) was prepared as the transparent substrate 20.

In each example, the synthetic quartz glass substrate was placed on a tray (not shown) with the main surface facing downward, and was transported into a chamber of the in-line sputtering apparatus.

In order to form the phase shift film 30 on the main surface of the transparent substrate 20, first, argon (Ar), helium (He), and nitrogen (N) are included₂) The mixed gas of (2) is introduced into the 1 st chamber. The sputtering gas pressure at the time of introduction is adjusted by adjusting argon (Ar), helium (He), and nitrogen (N) in a range where the phase shift film satisfies a predetermined transmittance and phase difference₂) The flow rate of (c) was set to a different value in each example (see table 1 below). As shown in Table 1, the sputtering gas pressure in each of the other examples 1 to 4 was in the range of 0.7Pa to 2.4Pa, and the sputtering gas pressure in each of the other comparative examples 1 and 2 was in the range of 0.7Pa to 2.4 Pa. However, the device is not suitable for use in a kitchenIn each example, a sputtering power of 7.6kW was applied to a 1 st sputtering target (molybdenum: silicon ═ 1:9) containing molybdenum and silicon, and a nitride of molybdenum silicide containing molybdenum, silicon, and nitrogen was deposited on the main surface of the transparent substrate 20 by reactive sputtering, thereby forming a phase shift film 30. In each example, the thickness of the phase shift film 30 is 144nm to 170 nm.

Next, in each example, the transparent substrate 20 with the phase shift film 30 was transferred into the 2 nd chamber, and argon (Ar) and nitrogen (N) were introduced₂) The mixed gas of (2) is introduced into the 2 nd chamber. Then, a sputtering power of 1.5kW was applied to the 2 nd sputtering target made of chromium, and chromium nitride (CrN) (film thickness 15nm) containing chromium and nitrogen was formed on the phase shift film 30 by reactive sputtering. Then, argon (Ar) and methane (CH) were introduced into the 3 rd chamber in a predetermined degree of vacuum₄: 4.9%) of the mixed gas, a sputtering power of 8.5kW was applied to the 3 rd sputtering target made of chromium, and chromium carbide (CrC) containing chromium and carbon was formed on CrN by reactive sputtering (film thickness 60 nm). Finally, argon (Ar) and methane (CH) were introduced in the 4 th chamber under a predetermined degree of vacuum₄: 5.5%) gas mixture and nitrogen (N)₂) With oxygen (O)₂) The mixed gas of (2) was applied to a 4 th sputtering target made of chromium with a sputtering power of 2.0kW, and chromium oxycarbonitride (CrCON) containing chromium, carbon, oxygen and nitrogen was formed on CrC by reactive sputtering (film thickness 30 nm). As described above, in each example, the etching mask film 40 having a laminated structure of the CrN layer, the CrC layer, and the CrCON layer is formed on the phase shift film 30.

Thus, in each example, a phase shift mask blank 10 in which the phase shift film 30 and the etching mask film 40 were formed on the transparent substrate 20 was obtained.

In each example, the transmittance and the phase difference of the phase shift film 30 (the surface of the phase shift film 30) of the obtained phase shift mask blank 10 were measured by using MPM-100 manufactured by Lasertec corporation. For the measurement of the transmittance and the phase difference of the phase shift film 30, a phase shift film-attached substrate (dummy substrate) in which the phase shift film 30 is formed on the main surface of a synthetic quartz glass substrate is used, and the phase shift film-attached substrate is mounted on the same tray. In each example, the substrate with the phase shift film (dummy substrate) was taken out from the chamber before the etching mask film 40 was formed, and the transmittance and the phase difference of the phase shift film 30 were measured. As a result, in each example, the transmittance and the retardation both satisfy the required ranges (transmittance: 10 to 50% at a wavelength of 405nm, and retardation: 160 DEG to 200 DEG at a wavelength of 405 nm).

In each example, the obtained phase shift mask blank 10 was subjected to composition analysis in the depth direction by X-ray photoelectron spectroscopy (XPS).

In each example, as a result of analyzing the composition of the phase shift mask blank 10 in the depth direction by XPS, the content of each constituent element in the phase shift film 30 is substantially constant in the depth direction except for the composition gradient region of the interface between the transparent substrate 20 and the phase shift film 30 and the composition gradient region of the interface between the phase shift film 30 and the etching mask film 40. In each example, the atomic ratio of molybdenum to silicon is in the range of 1:3 or more and 1:15 or less.

Then, in each example, indentation hardness of the obtained phase shift film 30 was measured. Specifically, the phase shift films 30 in each example were measured at measurement positions set at 6 × 6 matrix positions (36 positions) at a pitch of 50um, and a special probe equipped with a diamond indenter was pressed at each position with a maximum of 0.5mN to measure the change in load. The abnormal values, the maximum values and the minimum values were removed from the measured values obtained at the respective positions, and the indentation hardness of each example was calculated (see table 1). By removing the abnormal value, the maximum value, and the minimum value, it was confirmed that the standard deviation was 7% or less of the measured value.

As shown in Table 1, the indentation hardness of the other examples 1 to 4 was 18GPa or more and 23GPa or less, and the indentation hardness of the other comparative examples 1 and 2 was not 18GPa or more and 23GPa or less.

B. Phase shift mask and method of manufacturing the same

In order to manufacture the phase shift mask 100 using the phase shift mask blank 10 manufactured as described above, first, in each example, a photoresist film is coated on the etching mask film 40 of the phase shift mask blank 10 using a resist coating apparatus.

Then, in each example, the etching mask film was wet-etched using a chromium etching solution containing ammonium cerium nitrate and perchloric acid with the resist film pattern as a mask, to form a 1 st etching mask film pattern 40 a.

In each example, the phase shift film 30 was wet-etched using a molybdenum silicide etching solution in which a mixed solution of ammonium hydrofluoride and hydrogen peroxide was diluted with pure water, using the 1 st etching mask film pattern 40a as a mask, to form a phase shift film pattern 30 a.

In each example, the wet etching was performed for an over-etching time of 110% in order to make the cross-sectional shape vertical and to form a desired fine pattern.

The etching rates of the phase shift films 30 in the respective examples are shown in table 1. As shown in Table 1, the etching rates of the other comparative examples 1 were the smallest 1.0 nm/min, and the etching rates of the other comparative examples 2 were the largest 12.0 nm/min.

Then, the resist pattern is peeled off.

Then, the 2 nd resist film pattern 60 is peeled off.

In each example, a cleaning treatment using a reagent (sulfuric acid/hydrogen peroxide water (SPM), ammonia/hydrogen peroxide water (SC1), ozone water) was appropriately performed.

Thus, in each example, a phase shift mask 100 was obtained in which a phase shift film pattern 30a having a pore diameter of 1.5 μm was provided on a transparent substrate 20 in a transfer pattern formation region, and a light-shielding film having a laminated structure of the phase shift film pattern 30a and an etching mask film pattern 40b was formed on the transparent substrate 20.

[ Table 1]

	Other examples 1	Other example 2	Other examples 3	Other example 4	Other comparative example 1	Other comparative example 2
							Pressure [ Pa ]]	1.6	1.9	1.1	0.7	0.5	2.5
Etching Rate [ nm/min ]]	7.4	8.6	5.8	3.3	1.0	12.0
							Indentation hardness [ GPa]	19.3	18.3	21.3	23.0	26.2	17.5
The surface of the substrate is rough	OK	OK	OK	OK	NG	OK
							Resistance to washing	OK	OK	OK	OK	OK	NG

Table 1 shows the following results, respectively: the sputtering gas pressure (Pa) during the film formation of the phase shift film 30, the etching rate (nm/min) of the phase shift film 30, the indentation hardness (GPa) of the phase shift film 30, the presence or absence of surface roughness of the transparent substrate 20 due to wet etching, and the cleaning resistance of the phase shift film 30 in the other examples 1 to 4 and the other comparative examples 1 and 2.

FIG. 14 is a graph showing the relationship among the etching rate, the sputtering gas pressure, and the indentation hardness of the phase shift film 30 of the phase shift mask 100 according to the other examples 1 to 4 and the other comparative examples 1 and 2. Fig. 14 shows the indentation hardness and the sputtering gas pressure of other comparative example 1, other example 4, other example 3, other example 2, other example 1, and other comparative example 2 from the left side to the right side (in order of the etching rate from small to large). As can be seen from fig. 14, a correlation was observed between the etching rate of the phase shift film 30 and the indentation hardness or the sputtering gas pressure.

The cross section of the resulting phase shift mask was observed with a scanning electron microscope. The cross section of the phase shift film pattern is composed of the upper surface, the lower surface and the side surface of the phase shift film pattern. The angle of the cross section of the phase shift film pattern is an angle formed by a portion (upper side) where the upper surface of the phase shift film pattern is in contact with the side surface and a portion (lower side) where the side surface is in contact with the lower surface. As a result, the phase shift film patterns 30a of the phase shift masks of the other examples 1 to 4 and the other comparative example 2 had cross-sectional shapes in the range of 65 ° to 75 °, and the phase shift effect was sufficiently exhibited. The phase shift masks 100 of other examples 1 to 4 exhibited a smooth surface of the transparent substrate 20, and the transmittance was negligibly decreased due to the surface roughness of the transparent substrate 20. Therefore, a phase shift mask having an excellent phase shift effect is obtained for exposure light including light in a wavelength range of 300nm or more and 500nm or less, more specifically, for exposure light including composite light of i-line, h-line, and g-line.

Therefore, when the phase shift mask according to the other embodiments 1 to 4 is set on the mask stage of the exposure apparatus and is exposed and transferred to the resist film on the display device, the fine pattern of less than 2.0 μm can be transferred with high precision.

In the phase shift film patterns 30a of the phase shift masks 100 of the other examples 1 to 4, columnar structures were observed.

In contrast, the transparent substrate 20 exposed by the phase shift mask 100 of the other comparative example 1 had a rough surface and was in a state of white turbidity when observed with the naked eye. Therefore, the transmittance is remarkably reduced due to the surface roughness of the transparent substrate 20.

Therefore, it is predicted that when the phase shift mask 100 of the other comparative example 1 is set on the mask stage of the exposure apparatus and is exposed to the resist film transferred onto the display device, the fine pattern of less than 2.0 μm cannot be transferred.

The phase shift mask 100 of the other comparative example 2 is such that the surface of the transparent substrate 20 exposed is smooth and the decrease in transmittance due to the roughness of the surface of the transparent substrate 20 is negligible. However, the amount of change in transmittance and the amount of change in phase difference caused by the reagents (sulfuric acid/hydrogen peroxide Solution (SPM), ammonia/hydrogen peroxide solution (SC1), and ozone water) used to clean the phase shift mask 100 are large, and do not satisfy the transmittance and phase difference required for the phase shift mask 100.

Therefore, it is predicted that when the phase shift mask of the other comparative example 2 is set on the mask stage of the exposure apparatus and is exposed to the resist film transferred onto the display device, the fine pattern of less than 2.0 μm cannot be transferred.

Note that no columnar structure was observed in the phase shift film pattern 30a of the phase shift mask 100 of the other comparative example 1. The same applies to the phase shift film pattern 30a of the phase shift mask 100 of the other comparative example 2.

Claims

1. A photomask blank having a thin film for pattern formation on a transparent substrate, wherein,

the pattern-forming thin film contains a transition metal and silicon,

the pattern-forming thin film has a columnar structure.

2. The photomask blank according to claim 1, wherein in the spatial spectrum distribution of the pattern-forming thin film, there is a spatial spectrum having a signal intensity of 1.0% or more with respect to a maximum signal intensity corresponding to an origin of a spatial frequency,

3. The photomask blank of claim 2, wherein,

in the thin film for pattern formation, the signal having a signal intensity of 1.0% or more is located at a spatial frequency of 2.0% or more from an origin of the spatial frequency, assuming that a maximum spatial frequency is 100%.

4. The photomask blank according to claim 1 or 2, wherein an atomic ratio of the transition metal to the silicon contained in the thin film for pattern formation is 1:3 or more and 1:15 or less.

5. The photomask blank of claim 1 or 2, wherein,

the pattern-forming thin film contains at least nitrogen or oxygen.

6. The photomask blank of claim 1 or 2, wherein,

the transition metal is molybdenum.

7. The photomask blank of claim 1 or 2, wherein,

the thin film for pattern formation is a phase shift film having the following optical properties: the transmittance of the light to a representative wavelength of the exposure light is 1% or more and 80% or less, and the phase difference is 160 ° or more and 200 ° or less.

8. The photomask blank according to claim 1 or 2, which comprises, on the thin film for pattern formation, an etching mask film having a different etching selectivity to the thin film for pattern formation.

9. The photomask blank of claim 8, wherein,

the etching mask film is formed of a material containing chromium but substantially not containing silicon.

10. A method for manufacturing a photomask blank by forming a thin film for pattern formation containing a transition metal and silicon on a transparent substrate by a sputtering method, comprising:

the thin film for pattern formation is formed in a film formation chamber using a transition metal silicide target containing a transition metal and silicon, and the sputtering gas pressure in the film formation chamber to which a sputtering gas is supplied is 0.8Pa or more and 3.0Pa or less.

11. The method of manufacturing a photomask blank according to claim 10,

the transition metal silicide target has an atomic ratio of the transition metal to silicon of 1:3 or more and 1:15 or less.

12. The method of manufacturing a photomask blank according to claim 10 or 11,

an etching mask film is formed on the thin film for pattern formation using a sputtering target formed of a material having a different etching selectivity to the thin film for pattern formation.

13. The method of manufacturing a photomask blank according to claim 12,

the thin film for pattern formation and the etching mask film are formed using an in-line sputtering apparatus.

14. A method of manufacturing a photomask, the method comprising:

a step of preparing the photomask blank according to any one of claims 1 to 7 or the photomask blank produced by the method for producing a photomask blank according to claim 10 or 11; and

15. A method of manufacturing a photomask, the method comprising:

a step of preparing the photomask blank according to claim 8 or 9 or the photomask blank manufactured by the method for manufacturing a photomask blank according to claim 12 or 13;

16. A method of manufacturing a display device, the method comprising:

an exposure step of placing the photomask obtained by the method for manufacturing a photomask according to claim 14 or 15 on a mask stage of an exposure apparatus, and exposing and transferring the transfer pattern formed on the photomask to a resist formed on a substrate of a display device.