KR100805973B1 - Lithography mask blank - Google Patents

Abstract

The present invention is a lithographic mask blank used as a material for manufacturing a lithographic mask, wherein the lithographic mask blank includes at least one layer of a thin film having a desired function on a substrate, wherein the blank is a thin film containing nitrogen as the thin film; And an ammonium ion generation preventing layer formed on at least a surface portion of the thin film containing nitrogen or at least a surface portion of the thin film containing nitrogen to prevent the production of ammonium ions exposed to the surface when the lithographic mask is manufactured.

Description

Lithography Mask Blank {LITHOGRAPHY MASK BLANK}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic mask blank and a lithographic mask that are used as a material for a lithography mask such as a photomask, an electron beam mask, and an X-ray mask for use in the manufacture of a semiconductor device. The present invention relates to a halftone phase shift mask blank and a halftone phase shift mask which are materials of the present invention.

In the manufacture of a semiconductor device, a transfer pattern is formed by, for example, irradiating exposure light with a photomask (reticle) interposed therebetween.

As such a photomask, one in which a light shielding film pattern is formed on a transparent substrate is conventionally used. As the material of the light shielding film, a chromium-based material (chromium alone, one containing chromium, nitrogen, oxygen, or the like, or a laminated film of these material films) is generally used.

Moreover, as a thing which can improve the resolution of a transfer pattern, the phase shift mask is put to practical use in recent years. As the phase shift mask, various types (Levison type, auxiliary pattern type, self-aligning type, etc.) are known. One of them is a halftone phase shift mask suitable for high resolution pattern transfer of holes and dots.

Such a halftone phase shift mask is one in which a light semitransmissive film pattern having a phase shift amount of about 180 ° is formed on a transparent substrate, and a light semitransmissive film is formed in a single layer or formed in multiple layers. For example, Japanese Patent Laid-Open No. 2966369 discloses that the light semitransmissive film pattern is constituted by a thin film made of a metal such as molybdenum, silicon and nitrogen as main components.

The light semitransmissive film of such a material is able to control a predetermined amount of phase shift and transmittance in a single layer, and is excellent in resistance to acid and light.

As described above, as a film material to be used in a photomask, many things containing nitrogen in the film have been developed for various reasons.

By the way, when performing pattern transfer using a photomask (reticle), high energy laser light is irradiated to the photomask. For this reason, the chemical reaction of the photomask surface is encouraged by laser irradiation. For this reason, the formation of any precipitate is promoted, and there is a problem that the precipitate is generated and adhered on the photomask as foreign matter. It is confirmed that ammonium sulfate exists as one of such precipitates.

Generally, a photomask is wash | cleaned using a sulfuric acid type detergent in the last process. It is considered that sulfuric acid or sulfate ions derived from the sulfuric acid-based cleaner used in such a washing step are often left in the photomask after washing. For this reason, it is thought that the precipitate generate | occur | produces that reaction of the sulfate ion and the ammonium ion generated by any cause is accelerated | stimulated by laser irradiation.

In particular, with the recent miniaturization of the LSI pattern, the wavelength (exposure light wavelength) of the exposure light source has been shortened from an existing KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). Under such a situation, when using a short wavelength exposure light source such as an ArF excimer laser, the laser output is further increased. For this reason, there exists a problem that formation of a precipitate becomes easier to accelerate | stimulate, and generation | occurrence | production of a foreign material becomes more remarkable.

The source of ammonium ions is considered to be a substance or a deposit derived from the atmosphere or pellicle. However, research on a thin film to be used for the photomask as described above with respect to using a material containing nitrogen results, but containing nitrogen in the thin film, an ammonium ion, the film surface than the films that do not contain nitrogen (NH ₄ + ) Was found to exist a lot. Therefore, it is thought that the inclusion of nitrogen in the thin film may contribute to the precipitation of ammonium sulfate which may be a foreign matter defect.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a lithographic mask capable of reducing the production of ammonium ions caused by a constituent of a thin film, and a lithographic mask blank capable of manufacturing such a lithographic mask. To provide.

Furthermore, another object of the present invention is to provide a halftone phase shift mask capable of reducing the production of ammonium ions due to the components of the thin film, and a halftone phase shift mask blank capable of manufacturing such a halftone phase shift mask. There is.

This invention has the following aspects.

(1st aspect)

A lithographic mask blank used as a material for manufacturing a lithographic mask, wherein the lithographic mask blank includes at least one thin film having a desired function on a substrate, wherein the blank is a thin film containing nitrogen as the thin film and the nitrogen. At least an ammonium ion generation prevention layer formed on at least a surface portion of the thin film containing or in the nitrogen-containing thin film to prevent the production of ammonium ions exposed to the surface when the lithographic mask is manufactured.

(2nd aspect)

In the lithographic mask blank of the first aspect, the ammonium ion generation prevention layer is a thin film containing less nitrogen than the thin film containing nitrogen.

(Third aspect)

In the lithographic mask blank of the first aspect, the ammonium ion generation prevention layer is formed by heat treatment of the thin film containing nitrogen.

(Fourth aspect)

The photomask is manufactured using the photomask blank in any one of said 1st-3rd aspect.

(Fifth aspect)

A halftone phase shift mask blank used as a material for producing a halftone phase mask, comprising: a halftone phase shift mask blank having a light semitransmissive film composed of one layer or multiple layers having at least a desired transmittance and a phase shift amount on a substrate. The blank according to claim 1, wherein the blank is a thin film constituting the light semitransmissive film, and is formed on at least a surface portion of the thin film containing nitrogen, the thin film containing nitrogen, or the thin film containing nitrogen. At least a ammonium ion generation layer for preventing the production of ammonium ions exposed to the surface is provided.

(Sixth aspect)

In the halftone phase shift mask blank of the fifth aspect, the ammonium ion generation prevention layer is a thin film containing less nitrogen than the thin film containing nitrogen.

(7th aspect)

In the halftone phase shift mask blank of the fifth aspect, the thin film containing nitrogen contains at least silicon and nitrogen, and the ammonium ion generation prevention layer contains at least silicon and oxygen.

(Eighth aspect)

In the halftone phase shift mask blank of the fifth aspect, the ammonium ion generation prevention layer is formed by heat treatment of the thin film containing nitrogen.

(Ninth aspect)

A halftone phase shift mask is manufactured using the halftone phase shift mask blank according to any one of the fifth to eighth aspects.

1 is a cross-sectional view for explaining a halftone phase shift mask blank according to the first embodiment of the present invention.

2 is a cross-sectional view for explaining a method for manufacturing a halftone phase shift mask blank according to the third and fourth embodiments of the present invention.

Fig. 3 is a diagram showing the relationship between the presence or absence of an ammonium production prevention film and the ammonium ion concentration on the film surface in Example 1;

4 is a graph showing the relationship between the heat treatment time performed in Example 3 and the concentration of ammonium ions on the membrane surface.

Fig. 5 is a graph showing the relationship between the heat treatment time performed in Example 4 and the concentration of ammonium ions on the membrane surface.

Hereinafter, the present invention will be described in detail.

In the lithographic mask blank, such as a photomask blank, the inventors have found that ammonium ions are extracted from nitrogen in a film based on the fact that ammonium ions are extracted from a thin film containing nitrogen to which the surface is exposed when the mask is manufactured. Presumed to be due. That is, even in the case of a film containing nitrogen, since it was found that almost no ammonium ions exist in the inside of the film, it is considered that the nitrogen component in the thin film is accompanied by some alteration on the surface of the film to produce ammonium ions.                 

In the present invention, in order to prevent the production of ammonium ions on the surface of the membrane which is believed to be due to nitrogen in the membrane, the formation of ammonium ions on the thin film containing nitrogen or at least the surface portion of the thin film containing nitrogen is prevented. To form an ammonium ion generation prevention layer. This reduces the production of ammonium ions, which are thought to be due to nitrogen in the film, in the layer where the surface is exposed when the mask is manufactured.

As a result, the concentration of ammonium ions on the surface of the film decreases, and even after sulfuric acid or sulfate ions, etc. remain in sulfuric acid cleaning of a mask blank or sulfuric acid cleaning of a photomask manufactured using the mask blank, the laser irradiation during exposure is performed. As a result, generation of foreign matters due to ammonium ions such as ammonium sulfate can be suppressed.

When a in the present invention, a foreign substance generation-resistant due to the ammonium ions such as ammonium sulfate, is carried out the surface, as measured for the ammonium ion (NH ₄ +) concentration, such as pure water (純水) ions by extraction chromatography, was NH ₄ + concentration is reduced compared to before treatment, for example, is a NH ₄ + concentration measured by the ion chromatography method, so that the 20ng / ㎠ or less, preferably such that the 10ng / ㎠ or less, and more preferably not more than 5ng / ㎠ Processing takes place.

In the present invention, the ammonium ion generation prevention layer is formed so as not to impair the original function of the thin film. Or when an ammonium ion production | generation prevention layer is formed, it adjusts to have an original function.

In the present invention, the ammonium ion generation layer may be formed during or after the preparation of the mask blank, or may be formed during or after the preparation of the mask.                 

The following two methods can be considered as a typical formation method of an ammonium ion generation prevention layer.

(1) On the outermost surface, a layer containing few substances due to the production of ammonium ions is formed.

(2) At least the outermost surface is a layer which is hard to elute, even if a substance resulting from the production of ammonium ions is present, or a layer which suppresses the production of ammonium ions.

Regarding the method of (1), specifically, there is a method of forming a thin film (ammonium ion generation prevention layer) having a lower nitrogen content than a thin film containing nitrogen. Such an ammonium ion generation prevention layer includes a method of newly forming a film on a thin film containing nitrogen by forming a film. By covering the thin film containing nitrogen with a thin film containing less nitrogen than the thin film containing nitrogen, there is no less nitrogen present on the exposed surface when the mask is used. Accordingly, it is possible to prevent the formation of ammonium ions on the surface of the thin film due to nitrogen in the thin film. Moreover, the thin film with little nitrogen content includes the thin film which does not contain nitrogen substantially.

As for the method of (2), specifically, the heat treatment of the thin film containing nitrogen is mentioned, for example. By performing heat treatment in the atmosphere or in an atmosphere containing oxygen such as O ₂ , CO ₂ , inert gas atmosphere such as nitrogen or Ar, vacuum, or the like, the thin film containing nitrogen of the mask blank and its surface layer portion are subjected to thermal perturbation ( Perturbation).

As a result, rearrangement of the film structure is encouraged. For example, in the film surface layer portion, a dangling bond of silicon or nitrogen, which is a thin film constituent element, forms a bond more efficiently and changes to a stable state.

On the other hand, depending on the atmosphere in which heat treatment is performed, a dense ultra thin oxide film is formed by the reaction between the film surface subjected to thermal perturbation and the atmosphere in the same manner, and the above-described method (1) can also be provided.

That is, by appropriately applying thermal energy, the photomask surface is modified to a more stable state chemically. As a result, the generation of ammonium ions on the surface of the thin film can be suppressed.

Thus, the heat processing temperature for obtaining a preferable effect is 180 degreeC or more, and 250 degreeC or more is preferable.

In addition, the heat treatment time varies depending on the treatment temperature or the treatment atmosphere, but at least 5 minutes or more, preferably considering the fact that the alteration of the inside of the thin film can be stably controlled while giving thermal perturbation uniformly to the photomask blank. Is preferably at least 10 minutes.

In addition, when the heat treatment temperature exceeds 400 ° C., it is necessary to be careful because the reaction with the surface of the thin film may proceed radically in an active atmosphere containing oxygen, which may impair the function of the thin film.

In the case of high temperature heat treatment, it is preferable to heat-process in the atmosphere which does not contain oxygen preferably or fully controlled oxygen concentration.                 

As a method other than the above heat treatment, a method of allowing a substance which suppresses the production of ammonium ions by nitrogen to coexist in the membrane with nitrogen. Oxygen is mentioned as a substance which suppresses generation | occurrence | production of ammonium ion, As a formation method of this ammonium ion generation | generation prevention layer, the method of injecting oxygen ion etc. in the film surface with respect to the thin film containing nitrogen, heat, a plasma, etc. There is a method of forming by surface treatment, such as surface oxidation treatment using such.

In the present invention, examples of the foreign matter resulting from ammonium ions include ammonium sulfate, ammonium salt mainly containing ammonium sulfate, and other ammonium salts.

As a thin film which has a desired function in a photomask blank in this invention, a light-shielding film, an antireflective film, the light semitransmissive film for halftone type phase shift masks, etc. are mentioned, for example. These thin films often correspond to thin films whose surfaces are exposed when a photomask is manufactured.

Further, in the halftone phase shift mask blank of the present invention, the mask formed on at least a surface portion of the thin film containing nitrogen, the thin film containing nitrogen, or the thin film containing nitrogen as a thin film constituting the light semitransmissive film. At least a ammonium ion generation prevention layer for preventing the production of ammonium ions exposed to the surface when prepared.

As described above, when the thin film containing nitrogen is a light semitransmissive film having a desired transmittance and a phase shift amount of the halftone phase shift mask blank, the thin film containing nitrogen is a single layer composed of a thin film containing nitrogen. In the structure of the light semitransmissive film having a structure or a multilayer structure, a thin film containing nitrogen is formed in the layer immediately below the ammonium ion generation prevention layer.

Here, the material of the light semitransmissive film having a single layer structure is, for example, one containing silicon and nitrogen, or one containing metal, silicon, and nitrogen, or these selected from oxygen, fluorine, carbon, and hydrogen. The material containing 1 type or 2 or more types is mentioned. Moreover, as a metal, what contains 1 type, or 2 or more types chosen from molybdenum, tantalum, tungsten, chromium, titanium, nickel, palladium, hafnium, zirconium, etc. are mentioned.

The material film may be formed by performing reactive sputtering in an atmosphere using a reactive gas such as nitrogen using a silicon or a target made of metal and silicon, but may be formed using a target containing nitrogen. .

As the multi-layered light semitransmissive film, two or more layers of the material film of the single-layered light semitransmissive film are laminated, chromium, tantalum, hafnium, magnesium, aluminum, titanium, vanadium, yttrium, zirconium, niobium, molybdenum, tin, The lamination | stacking of the transmittance | permeability adjustment layer, such as a metal film containing 1 type, or 2 or more types chosen from lanthanum, tungsten, silicon, etc., and the material (halftone film) of the said single layer, etc. are mentioned. Moreover, in order to acquire the effect as a halftone type phase shift film, a light semitransmissive film has a phase difference set to about 180 degrees, and the transmittance | permeability is set to the transmittance | permeability selected in the range of 3-40%.

In particular, when an ammonium formation preventing layer is formed on a material layer containing a metal, silicon and nitrogen, or a material layer containing one or two or more selected from oxygen, fluorine, carbon, and hydrogen, ammonium is produced. As the material of the barrier layer, it is possible to use a material containing oxygen in silicon, a material containing one selected from metals, nitrogen (having less nitrogen than the nitrogen-containing layer) and carbon.

Hereinafter, the present invention will be described in more detail with reference to examples.

(Example 1)

A mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) using a mixed target of molybdenum (Mo) and silicon (Si) (Mo: Si = 20: 80 mol%) (Ar: N ₂ = 10%: 90 %, Pressure: 0.2 Pa) to form a light semitransmissive film (2, film thickness of about 935 angstroms) of molybdenum and silicon (MoSiN) on the transparent substrate 1 by reactive sputtering (DC sputtering). Three halftone phase shift mask blanks were prepared (see FIG. 1 (1)). In the halftone phase shift mask blank, the transmittance was 5.5% and the phase shift amount was about 180 ° in a KrF excimer laser (wavelength 248 nm), respectively.

On the light semitransmissive film 2 of the above two phase shift blanks, using a target as described above, a mixed gas atmosphere of argon (Ar) and oxygen (O ₂ ) (Ar: O ₂ = 60%: 40% , Pressure: 0.2 Pa), by reactive sputtering (DC sputtering), an ammonium ion generating layer 3 consisting of a thin film of molybdenum and silicon (MoSiO) oxidized on the transparent substrate 1 (film thickness of about 30 angstroms and 100 angstroms) was formed to produce a halftone phase shift mask blank (see Fig. 1 (2)).

The halftone phase shift mask blank may use a MoSiN film + MoSiO film as a light semitransmissive film of a halftone phase shift mask blank.

Fig. 3 shows a sample (not shown in the drawing) that has not been subjected to foreign matter generation prevention treatment due to ammonium ions such as ammonium sulfate and the foreign matter generation prevention treatment due to ammonium ions such as ammonium sulfate. It is the result of measuring the ammonium ion density | concentration of the membrane surface by the ion chromatography method in the sample (it is expressed by membrane thickness in drawing). As is apparent from the above figure, it can be seen that ammonium ions on the surface of the membrane are drastically reduced when the ammonium sulfate generation prevention treatment is performed.

Next, a chromium-based light shielding film was formed on a thin film made of MoSiO film, then a resist film was formed, and a resist pattern was formed by pattern exposure and development. Subsequently, the MoSiO film and the MoSiN film are etched by dry etching with CF ₄ + O ₂ gas, the resist is peeled off, washed with 100% 98% sulfuric acid (H ₂ SO ₄ ) at 100 ° C., and rinsed with pure water to obtain a phase shift mask. Got it.

In the phase shift mask, since the sample subjected to the foreign matter generation prevention treatment due to ammonium ions such as ammonium sulfate has less ammonium ions on the surface of the membrane, when the pattern transfer is performed by laser irradiation such as KrF excimer laser, ammonium sulfate This can reduce the generation of foreign matter defects.

(Example 2)

Mixed gas atmosphere of argon (Ar) and nitrogen (N ₂ ) by using a mixed target of molybdenum (Mo) and silicon (Si) (Mo: Si = 8: 92 mol%) (Ar: N ₂ = 10%: 90 %, Pressure: 0.2 Pa) to form a light semitransmissive film (2, film thickness of about 800 angstroms) of molybdenum nitride and silicon (MoSiN) on the transparent substrate 1 by reactive sputtering (DC sputtering). Three halftone phase shift mask blanks were prepared (see Fig. 1 (1)). In the halftone phase shift mask blank, the transmittance was 5.5% and the phase shift amount was about 180 ° in an ArF excimer laser (wavelength 193 nm), respectively.

Two halftone phase shift mask blanks were formed on the same transparent substrate 1 as in Example 1, on which a light semitransmissive film (2, film thickness of about 800 angstroms) of molybdenum nitride and silicon (MoSiN) was formed.

On the light semitransmissive film 2 of the phase shift blank, a mixed gas atmosphere of argon (Ar), nitrogen (N ₂ ) and oxygen (O ₂ ) using a silicon target (Ar: N ₂ : O ₂ = 20%: 60%: 20%, pressure: 0.1 Pa), by reactive sputtering (DC sputtering), an ammonium ion generation prevention layer (3, each film thickness of about 30 angstroms) consisting of a thin film of SiON on the transparent substrate 1 And about 100 Angstroms) to produce a halftone phase shift mask blank. The composition of the MoSiN layer is Mo: Si: N = 5: 45: 50at% (atomic percent), whereas the composition of the SiON layer is Si: O: N = 42: 43: 15at%. "Ammonia production prevention layer" is less than "layer containing nitrogen".

The said halftone phase shift mask blank can make a MoSiN film + SiON film a light semitransmissive film of a halftone type phase shift mask blank.

In the halftone phase shift mask blank, the concentration of ammonium ions on the surface of the membrane was measured by ion chromatography. As a result, 3.5 ng / cm 2 for a sample having a thickness of 30 angstroms and 2.8 ng / cm 2 for a sample having a thickness of 100 angstroms. It was.

Next, a chromium-based light shielding film was formed on a thin film made of MoSiO film, then a resist film was formed, and a resist pattern was formed by pattern exposure and development. Subsequently, the MoSiO film and the MoSiN film are etched by dry etching with CF ₄ + O ₂ gas, the resist is peeled off, and then washed with 100% 98% sulfuric acid (H ₂ SO ₄ ) at 100 ° C. and rinsed with pure water to obtain a phase shift mask. Got it.

In the phase shift mask, since the sample subjected to the foreign matter generation prevention treatment due to ammonium ions such as ammonium sulfate has less ammonium ions on the surface of the membrane, when the pattern transfer is performed by laser irradiation such as KrF excimer laser, ammonium sulfate This can reduce the generation of foreign matter defects.

In the present invention, the preferred thickness of the ammonium formation preventing layer is preferably 10 angstroms or more, more preferably 30 angstroms or more, from the viewpoint of drastically reducing the ammonium ions on the membrane surface.

(Example 3)

In the same manner as in Example 1, a light semitransmissive film 2 of molybdenum nitride and silicon (MoSiN) (film thickness of about 935 angstroms) was formed on the transparent substrate 1 (see FIG. 2 (1)).

Subsequently, heat treatment 4 was performed at 280 ° C. in air (see FIG. 2 (2)). 4 is a result of measuring the relationship between the heat treatment time and the concentration of ammonium ions on the membrane surface by ion chromatography.

As is apparent from FIG. 4, it can be seen that by heat treatment, ammonium ions are reduced, and particularly, significantly decreases in the vicinity of the heat treatment time exceeding 15 minutes. This is considered to be because, in this embodiment, heat perturbation imparted to the mask blank from about 15 minutes after heat treatment acted uniformly and effectively on the entire surface of the thin film.

Next, the mask processing similar to Example 1 was performed and the phase shift mask was obtained.

In the phase shift mask, since the sample subjected to the ammonium sulfate generation prevention treatment has less ammonium ions on the surface of the film, foreign matter defects are generated by ammonium sulfate when pattern transfer is performed by laser irradiation such as a KrF excimer laser. Could prevent.

(Example 4)

In the same manner as in Example 1, a light semitransmissive film 2 of molybdenum nitride and silicon (MoSiN) (film thickness of about 935 angstroms) was formed on the transparent substrate 1 (see FIG. 2 (1)).

Subsequently, heat treatment 4 was performed at 400 ° C. in a nitrogen atmosphere (see FIG. 2 (2)). 5 is a result of measuring the heat treatment time and the concentration of ammonium ions on the membrane surface by ion chromatography.

As is apparent from FIG. 5, it can be seen that by the heat treatment, ammonium ions are reduced, and particularly, a significant decrease from the vicinity of the heat treatment time exceeding 20 minutes. This is considered to be because the heat perturbation imparted to the photomask blank from about 20 minutes after the heat treatment acted uniformly and effectively on the entire surface of the thin film.

Next, the mask processing similar to Example 1 was performed and the phase shift mask was obtained.

In the phase shift mask, since the sample subjected to the ammonium sulfate generation prevention treatment has less ammonium ions on the surface of the film, foreign matter defects are generated by ammonium sulfate when pattern transfer is performed by laser irradiation such as a KrF excimer laser. Could prevent.

According to the present invention, when the photomask is manufactured, the thin film on which the surface is exposed is a thin film containing at least nitrogen, and the thin film containing nitrogen has a surface to which foreign matter generation prevention treatment due to ammonium ions such as ammonium sulfate has been performed. By doing so, the photomask blank which can manufacture the photomask in which ammonium sulfate does not precipitate by laser irradiation can be obtained.

Claims (9)

A lithographic mask blank, which is used as a material for producing a lithographic mask and has a wavelength of an exposure light source of KrF excimer laser or an ArF excimer laser, is a lithographic mask blank including at least one thin film having a desired function on a substrate, The blank is formed of a thin film made of molybdenum, silicon, and nitrogen as the thin film, and a heat treatment in an atmosphere containing oxygen in at least a surface portion of the thin film to form ammonium ions exposed to the surface when the lithographic mask is manufactured. Has at least an ammonium ion generation layer to prevent formation, Lithography mask blank, characterized in that the concentration of the ammonium ion is 20ng / cm ² or less. delete delete A photomask manufactured by using the lithographic mask blank according to claim 1. A halftone phase shift mask blank, which is used as a material for producing a halftone phase mask and whose wavelength of an exposure light source is a KrF excimer laser or an ArF excimer laser, is a single layer or a multilayer having at least a desired transmittance and a phase shift amount on a substrate. A halftone phase shift mask blank comprising a light semitransmissive film comprising: The blank is a thin film constituting the light semitransmissive film and formed by performing a heat treatment in an atmosphere containing oxygen in a thin film made of molybdenum, silicon and nitrogen, and at least a surface portion of the thin film, when the lithographic mask is manufactured. Has at least an ammonium ion generation layer to prevent the production of ammonium ions exposed to the Halftone phase shift mask blank, characterized in that the concentration of the ammonium ion is 20ng / cm ² or less. delete delete delete It manufactured using the said halftone phase shift mask blank of Claim 5. The halftone phase shift mask characterized by the above-mentioned.

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