JP6904234B2 - Mask blank substrate and mask blank - Google Patents

Description

The present invention relates to a mask blank substrate and a mask blank, and more particularly to a mask blank substrate and a mask blank applied to a reflective mask used for EUV (Extreme Ultra Violet) lithography in a semiconductor manufacturing process.

Conventionally, an exposure apparatus has been used in a lithography process for manufacturing an integrated circuit by transferring a circuit pattern onto a wafer. With the recent increase in integration, speed, and functionality of integrated circuits, such exposure equipment is required to form a high-resolution circuit pattern on a wafer at a deep depth of focus. I came. In order to meet this demand, the wavelength of the exposure light source is being shortened.

As the exposure light source, g-ray (wavelength 436 nm), i-line (wavelength 365 nm), KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm) and the like have been used so far. Further, by using an ArF excimer laser, an immersion technique, and a multiple exposure technique, a lithography technique having a theoretical resolution of 15 nm has been put into practical use.

Further, as a next-generation exposure light source, a lithography technique using EUV light (extreme ultraviolet light) is drawing attention. EUV light means light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, and specifically represents light having a wavelength of about 0.2 nm to 100 nm. At present, the use of 13.5 nm as a lithography light source is being considered. In the energy region of EUV light, there is no material that transmits light, and a refraction optical system cannot be used. Therefore, in EUV lithography (hereinafter, abbreviated as "EUVL"), a catadioptric system is used (Patent Document 1).

Special Table 2003-505891

The mask used for EUV as described above is manufactured from a mask blank having a glass substrate and an unpatterned laminated film formed on the glass substrate. That is, a mask for EUV is manufactured by patterning the laminated film in the mask blank.

Since the mask is a relatively expensive part, it is cleaned by cleaning or the like after use and is used repeatedly. However, when the mask is used repeatedly, the adhesion between the laminated film and the glass substrate is lowered, and the laminated film may be peeled off.

Therefore, in the future, it is expected that there will be a need for improving the adhesion between the glass substrate and the laminated film in the EUV mask.

The present invention has been made in view of such a background, and an object of the present invention is to provide a mask blank substrate capable of enhancing adhesion with a laminated film. Another object of the present invention is to provide a mask blank capable of enhancing the adhesion between the substrate and the laminated film.

In the present invention, it is a mask blank substrate.
The mask blank substrate has a first main surface and a second main surface facing each other, and is composed of synthetic quartz glass containing _{TiO 2.}
^{When the ratio of monovalent H ions to monovalent Si ions (1} H / ³⁰ Si) is measured from the side of the first main surface by the secondary ion mass spectrometry method, from the first main surface. The ^{average value of 1} H / ³⁰ Si with a depth of 0 to 200 nm is 5 times or more the average value ^{of 1} H / ³⁰ Si with a depth of 2 μm to 4 μm from the first main surface. A large mask blank substrate is provided.

In the present invention, it is possible to provide a mask blank substrate capable of improving adhesion with a laminated film. Further, the present invention can provide a mask blank capable of enhancing the adhesion between the substrate and the laminated film.

It is sectional drawing which shows typically an example of the substrate for a mask blank by one Embodiment of this invention. It is a graph which shows typically an example of the depth profile of ¹ H / ³⁰ Si obtained by the secondary ion mass spectrometry in the mask blank substrate according to one Embodiment of this invention. It is sectional drawing which shows typically an example of the mask blank by one Embodiment of this invention. It is a flow figure which shows typically an example of the manufacturing method of the mask blank by one Embodiment of this invention. It is a flow figure which shows typically an example of the manufacturing method of the substrate for a mask blank by one Embodiment of this invention. It is a graph showing an example of a ^{1 H} / 30 ^Si profile measurements at the first major surface of the substrate for a mask blank. It is a graph showing an example of a ^{1 H} / 30 ^Si profile measurements at the substrate / reflective film interface of the mask blank.

In the present application, a "mask blank" is a substrate having a layer before being patterned into a desired pattern on one main surface, unlike a mask having a patterned layer (laminated film) on one main surface. Means. Therefore, in the usual case, at the "mask blank" stage, the layers are placed over the entire main surface of the substrate. Further, the “mask blank substrate” means a substrate before the above-mentioned layer is installed on the main surface.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Substrate for mask blank according to one embodiment of the present invention)
An embodiment of the present invention will be described with reference to FIG. FIG. 1 schematically shows an example of a cross section of a mask blank substrate according to an embodiment of the present invention.

As shown in FIG. 1, the mask blank substrate 110 according to the embodiment of the present invention has a first main surface 112 and a second main surface 114 facing each other. The mask blank substrate 110 may have a substantially rectangular shape.

The mask blank substrate 110 is made of synthetic quartz glass containing _{TiO 2.} Hereinafter, the mask blank substrate 110 is also referred to as a “first substrate 110”.

Here, the first substrate 110 is subjected to the ratio of monovalent H ions to monovalent Si ions (hereinafter, " ¹ H / ³⁰ Si") from the side of the first main surface 112 by the secondary ion mass spectrometry method. (Represented by), the average value ^{of 1} H / ³⁰ Si (hereinafter referred to as _{“Ave 1} ”) having a depth from the first main surface 112 between 0 and 200 nm is the first main surface. It is characterized in that the depth from the surface 112 is 5 times or more larger than the average value ^{of 1} H / ³⁰ _{Si (hereinafter referred to as “Ave 2”) between 2 μm and 4 μm.}

FIG. 2 schematically shows an example of a depth profile of ¹ H / ³⁰ Si obtained by secondary ion mass spectrometry on the first substrate 110.

In FIG. 2, the horizontal axis represents the distance d in the depth direction from the first main surface 112, and “0 (zero)” represents the first main surface 112. The vertical axis is the value of ¹ H / ^{30 Si.}

As shown in FIG. 2, in this example, ^{the profile of 1} H / ³⁰ _{Si shows a maximum value of M max} on the outermost surface of the first substrate 110, i.e. the first main surface 112, followed by an increase in distance d. It shows a behavior that gradually decreases with. Further, ^{the profile of 1} H / ³⁰ Si becomes almost constant when the distance d is 4 μm or more, and shows _{a minimum value of M min.}

In this example, the average value Ave ₁ / average value Ave ₂ is about 10.

^{The 1} H / ³⁰ Si profile shown in FIG. 2 is merely an example, and the first substrate 110 may have another ¹ H / ³⁰ Si profile. For example, in FIG. 2, the value of ¹ H / ³⁰ Si starts to decrease sharply when the distance d is about 0.5 μm or more, and becomes a _{constant value (M min) when the distance d is about 3 μm or more.} However, the position of the distance d where the value of ¹ H / ³⁰ Si starts to decrease and the position of the distance d showing the _{minimum value M min are not particularly limited.} Further, the _{distance d indicating the maximum value M max} may be slightly deviated from 0 (zero). Such profiles are often found due to the effects of analytical variability and the like.

That is, the profile of the average value Ave ₁ is greater than 5 times higher than the average value Ave _2, that is, if the profile that meets the average value Ave ₁ / average value Ave ₂ ≧ ^5, the profile of 1 ^{H /} 30 Si is particularly limited I can't.

Further, the average value Ave ₁ / average value Ave ₂ is preferably 10 or more, and more preferably 15 or more.

When a first substrate 110 having such characteristics is used and a laminated film is formed on the first main surface 112 to form a mask blank, between the first substrate 110 and the laminated film, It is possible to obtain good adhesion.

The reason why good adhesion between the first substrate 110 and the laminated film can be obtained by using the first substrate 110 having the above-mentioned characteristics is not sufficiently clear at present. .. However, the following can be considered.

As is clear from FIG. 2, many hydrogen atoms (H) are present on the first main surface 112 of the first substrate 110 before the laminated film is formed. It is considered that these hydrogen atoms are present on the first main surface 112 as OH groups and / or adsorbed water (H ₂ O), that is, in a form coexisting with oxygen atoms (O).

When manufacturing a mask blank, a laminated film is installed on the first main surface 112 of such a first substrate 110. Of the laminated films formed on the side of the first main surface 112, the first layer formed is a reflective film. This reflective film is usually formed by a sputtering method.

When the reflective film is formed, the oxygen atoms present on the first main surface 112 of the first substrate 110 are heated together with the hydrogen atoms on both sides, that is, on the side of the reflective film and inside the first substrate 110. Spread to the side. Oxygen diffused on the side of the reflective film reacts with the metal (usually silicon (Si)) that constitutes the reflective film to form an oxide. This oxide plays a role of connecting the first main surface 112 and the reflective film at the interface, like a "glue".

As a result, it is considered that good adhesion can be obtained between the first substrate 110 and the reflective film.

In particular, the first substrate 110 contains _{TiO 2.} It is expected that TiO ₂ has a strong tendency to break the Si—O—Ti bond easily by contact with an acid and separate into Si—OH and a Ti salt.

Therefore, due to the washing process, the first substrate 110 is in contact with the acid solution, the first major surface 112, relatively easily OH groups is formed, thereby, ¹ at the first major surface 112 It is considered that H / ^{30 Si rises.}

However, according to the inventors of the present application _{, the average value Ave 1} becomes 5 times or more larger than the average value Ave ₂ simply by using synthetic quartz glass containing _{TiO 2 as a mask blank substrate.} Has been confirmed not to be obtained. ^{In order to obtain a profile of 1} H / ³⁰ Si as shown in FIG. 2, a treatment for significantly increasing ¹ H / ³⁰ Si on the first main surface 112 as shown below with respect to the mask blank substrate. Is considered necessary.

In any case, ^{by using the first substrate 110 having the profile behavior of 1} H / ³⁰ Si as described above as the substrate for the mask blank, it can be combined with the laminated film installed on the upper part of the first main surface 112. It is possible to obtain good adhesion between them.

(Other features of the first substrate 110)
Next, other features of the first substrate 110 will be described.

As described above, the first substrate 110 is made of synthetic quartz glass containing _{TiO 2.}

_{The content of TiO 2} contained in the first substrate 110 is not particularly limited, but is, for example, in the range of 5% to 10%. The content of TiO ₂ is preferably in the range of 6% to 8% by mass ratio.

The shape of the first substrate 110 is not particularly limited. The first substrate 110 may have a rectangular shape such as a square shape or a disc shape, for example.

The first substrate 110 may have a thickness in the range of, for example, 5 mm to 8 mm.

(Mask blank according to one embodiment of the present invention)
Next, an example of a mask blank according to an embodiment of the present invention will be described with reference to FIG.

FIG. 3 schematically shows a cross section of a mask blank according to an embodiment of the present invention. The mask blank 200 shown in FIG. 3 is a mask blank for EUV, and is therefore a mask blank for a reflective mask.

The mask blank 200 has a substrate 210. In addition, in order to distinguish the substrate 210 of the mask blank 200 from the above-mentioned mask blank substrate 110, it is also referred to as a "second substrate 210" below.

The mask blank 200 further has a laminated film 220 installed on one side of the second substrate 210 and a second layer 280 installed on the other side of the second substrate 210.

The second substrate 210 has a first main surface 212 and a second main surface 214 facing each other. The laminated film 220 is installed on the first main surface 212 of the second substrate 210, and the second layer 280 is installed on the second main surface 214 of the second substrate 210.

The laminated film 220 is composed of a plurality of films. For example, the laminated film 220 has a reflective film 230, a protective film 240, an absorbing film 250, and a low reflective film 260 in this order from the side closer to the second substrate 210.

Of these, the reflective film 230 has a function of reflecting EUV exposure light.

The protective film 240 has a role of protecting the reflective film 230. That is, when manufacturing a mask from the mask blank 200, it is necessary to pattern the absorption film 250 on the upper part of the reflection film 230. The protective film 240 functions as a barrier that protects the reflective film 230 during this treatment.

However, the protective film 240 is not an essential configuration and may be omitted.

The absorption film 250 is made of a material that absorbs exposure light. The absorbent film 250 is processed to have a patterned structure when the mask is manufactured from the mask blank 200. During the EUVL process, the pattern of the absorption film 250 is transferred to the substrate to be processed.

The low-reflection film 260, like the absorption film 250, is a film that is patterned when a mask is manufactured from the mask blank 200. The patterned low-reflection film 260 is used in the pattern inspection of the absorption film 250. That is, when confirming whether or not the pattern of the absorption film 250 is formed as designed, the mask is irradiated with inspection light having a wavelength of 190 nm to 260 nm, and the inspection is performed by this. This inspection is performed by utilizing the difference in the reflectance of the inspection light between the existing portion and the non-existing portion of the absorption film 250. When the low-reflection film 260 is installed on the absorption film 250, the difference in reflectance of the inspection light becomes large between the existing portion and the non-existing portion of the absorption film 250. Therefore, by providing the low-reflection film 260, the accuracy of the pattern inspection of the absorption film 250 can be improved.

However, the low-reflection film 260 is not an essential configuration and may be omitted.

On the other hand, the second layer 280 is made of a conductive material. The second layer 280 is provided to fix the position of the mask blank 200 attached to the exposure apparatus in the EUVL process. That is, by using the second layer 280, the mask blank 200 can be fixed to the stage by the electrostatic chuck method.

Here, the mask blank 200 passes through the interface between the first main surface 212 of the second substrate 210 and the laminated film 220 from the side of the laminated film 220 by the secondary ion mass spectrometry method, and the mask blank 200 passes through the interface between the laminated film 220 and the second substrate 210. When the ratio of monovalent H ions to monovalent Si ions ( ¹ H / ³⁰ Si) is measured up to the inside, the average value ^{of 1} H / ³⁰ Si between 0 and 200 nm in depth from the interface is , The depth from the interface is 5 times or more larger than the average value ^{of 1} H / ^{30 Si between 2 μm and 4 μm.}

In the mask blank 200 having such characteristics, good adhesion can be obtained between the second substrate 210 and the laminated film 220.

(Other features of Mask Blank 200)
Next, other features of the mask blank 200 will be described.

(Second substrate 210)
As the second substrate 210, the first substrate 110 as described above can be used.

The specifications of the second substrate 210 and the like are the same as those of the first substrate 110 described above, and details thereof will be omitted here.

However, usually, a profile of ¹ H / ³⁰ Si along the depth direction (the second substrate 210 side) from the interface between the first main surface 212 of the second substrate 210 and the reflective film 230 in the mask blank 200. It should be noted that is different from the profile of ¹ H / ³⁰ Si along the depth direction from the first main surface 112 of the first substrate 110.

This is because, as described above, when the reflective film 230 is formed, the hydrogen atoms present on the first main surface 212 of the second substrate 210 are externally (side of the reflective film 230) and inward (on the side of the reflective film 230). This is because it diffuses to the side of the second substrate 210).

Generally, when the mask blank substrate 110 has a profile as shown in FIG. 2, the maximum value M _max ^{of 1} H / ³⁰ Si decreases in the second substrate 210 of the mask blank 200, and the distance in the depth direction is reduced. As d increases, ^{the behavior of 1} H / ³⁰ Si decreasing more gently is obtained.

(Laminated film 220)
Next, the laminated film will be described in detail.

(Reflective film 230)
The reflective film 230 preferably has a high EUV ray reflectance. The reflective film 230 may have, for example, a repeating structure of a high refractive index layer and a low refractive index layer. For example, the high refractive index layer includes silicon (Si), and the low refractive index layer includes molybdenum (Mo). When the reflective film 230 is composed of a multi-layer structure of Mo / Si, it is preferable that the lowermost layer (the second substrate 210 side) is Si.

The reflective film 230 may be formed by a film forming method such as an ion beam sputtering method or a magnetron sputtering method.

The total thickness of the reflective film 230 is, for example, in the range of 200 nm to 400 nm.

(Protective film 240)
The protective film 240 is installed to protect the underlying reflective film 230. For example, the protective film 240 may function as an etching stop layer when the absorption film 250 arranged on the upper portion is etched.

The protective film 240 may be formed of ruthenium (Ru), Si, TiO _2, or the like.

The protective film 240 may be formed on the reflective film 230 by, for example, a sputtering method. The thickness of the protective film 240 is, for example, in the range of 1 nm to 60 nm.

As described above, the protective film 240 may be omitted.

(Absorption membrane 250)
The absorption film 250 preferably has a high EUV light absorption rate, that is, a low EUV light reflectance.

The absorption membrane 250 may contain, for example, at least one or more elements of tantalum (Ta), chromium (Cr), and palladium (Pd). The absorption membrane 250 may be in the form of a metal, alloy, nitride, oxide, oxynitride or the like containing these elements.

The absorption film 250 may be formed on the protective film 240 by, for example, a sputtering method.

The absorption membrane 250 has a thickness in the range of, for example, 30 nm to 90 nm.

(Low reflective film 260)
The low-reflection film 260 may be formed of a material containing Ta, for example, TaO and TaON. The low-reflection film 260 may be formed by, for example, a sputtering method. The thickness of the low-reflection film 260 is, for example, 10 nm to 65 nm.

As described above, the low reflection film 260 may be omitted.

(Second layer 280)
The second layer 280 is made of a conductive material as described above. The second layer 280 may be made of, for example, chromium nitride (CrN) or the like.

The second layer 280 may be formed by, for example, a sputtering method. The second layer 280 has a thickness in the range of, for example, 10 nm to 1000 nm.

The mask blank 200 having the above-described configuration is used as a mask for the EUVL process after the absorption film 250 and the low-reflection film 260 are patterned into a predetermined shape.

When the mask blank 200 is actually used as a mask, the side of the laminated film 220 is the irradiation side of the EUV exposure light.

(Method for manufacturing a mask blank according to an embodiment of the present invention)
Next, a method for producing a mask blank according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

As shown in FIG. 4, the method for producing a mask blank according to the embodiment of the present invention is as follows.
(I) A step of preparing a substrate for a mask blank (step S110) and
(Ii) A step of installing a laminated film on the first main surface of the mask blank substrate (step S120).
(Iii) A step of installing the second layer on the second main surface of the mask blank substrate (step S130).
Have.

The order of steps S120 and S130 may be reversed.

Hereinafter, each step will be described. Here, as an example, a method of manufacturing the mask blank 200 as shown in FIG. 3 from the mask blank substrate 110 as shown in FIG. 1 will be described. Therefore, when referring to each member, layer, portion, etc., the reference numerals shown in FIGS. 1 and 3 are used.

(Step S110)
First, a glass substrate is prepared. As described above, the glass substrate is composed of synthetic quartz glass containing _{TiO 2.}

Next, various treatments (processing, polishing, cleaning, etc.) are performed on the glass substrate so that the glass substrate can be used as the mask blank substrate (first substrate) 110.

Hereinafter, such a process applied to a glass substrate (hereinafter, referred to as “method for manufacturing a mask blank substrate”) will be described with reference to FIG.

As shown in FIG. 5, the method for manufacturing the mask blank substrate is as follows.
Pre-polishing process (process S111) and
Local polishing step (step S112) and
Secondary polishing step (step S113) and
Finish polishing process (process S114) and
Cleaning step (step S115) and
Have.

Hereinafter, each step will be described.

(Step S111)
First, both main surfaces of the accepted glass substrate are pre-polished.

In this pre-polishing step, a polishing slurry is supplied between the first main surface of the glass substrate and the polishing pad, and the entire first main surface is polished. Further, a polishing slurry is supplied between the second main surface of the glass substrate and the polishing pad, and the entire second main surface is polished.

As the polishing pad, for example, a urethane-based polishing pad, a non-woven fabric-based polishing pad, a suede-based polishing pad, or the like is used. As the polishing pad, a pad in which a porous resin layer called a nap layer (NAP layer) is provided on the base material may be used.

The polishing slurry contains polishing particles and a dispersion medium. Abrasive particles are formed of, for example, colloidal silica, cerium oxide, or the like. As the dispersion medium, water, an organic solvent, or the like is used.

(Step S112)
Next, the glass substrate is locally polished.

In this step, the first main surface and the second main surface of the glass substrate are locally processed (polished).

In this step, the first main surface and the second main surface may be polished in order.

The method of local processing is not particularly limited, and for example, an ion beam etching method, a gas cluster ion beam (GCIB) etching method, a plasma etching method, a wet etching method, a polishing method using a magnetic fluid, or a polishing method using a rotary polishing tool, etc. Is used. In particular, the GCIB etching method is suitable.

In the GCIB etching method, a small region is processed by ionizing a mass of gaseous atoms or molecules (gas cluster) and accelerating this to irradiate the surface. The source gas of the gas cluster includes SF ₆ , Ar, O ₂ , N ₂ , NF ₃ , N ₂ O, CHF ₃ , CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₆ , SiF ₄ , And _{gases such as COF 2} can be used alone or in admixture. Of these, SF ₆ and NF ₃ are preferred.

On the other hand, in the polishing method using a magnetic fluid, a magnetic fluid containing polishing particles is used. As the magnetic fluid, for example, a fluid in which a non-colloidal magnetic substance is dispersed is used. Such ferrofluids change their rheological properties (viscosity, elasticity and plasticity) when placed in a magnetic field. Abrasive particles are composed of, for example, silica, cerium oxide or diamond.

Further, in the polishing method using the rotary polishing tool, the first main surface and the second main surface are locally polished by bringing the rotary polishing tool into contact with the surface of the glass substrate. The polished surface of the rotary polishing tool is selected to be smaller than the first and second main surfaces of the glass substrate. The rotary polishing tool is supplied with a slurry containing polishing particles. Abrasive particles are composed of, for example, silica, cerium oxide, alumina, zirconia, silicon carbide, diamond, titania, germania and the like.

By locally polishing the first main surface and the second main surface of the glass substrate, relatively large irregularities can be removed and the flatness of the glass substrate can be significantly improved.

(Step S113)
Next, the glass substrate is secondarily polished.

This step S113 is carried out for the purpose of removing deposits adhering to the first main surface and the second main surface of the glass substrate. Further, in the method for manufacturing the mask blank substrate, this step S113 is further carried out in order to allow (express) a component containing a hydrogen atom on the first main surface of the glass substrate.

In step S113, the glass substrate is polished by the polishing slurry using a double-sided polishing machine.

The polishing slurry contains colloidal silica (silica particles) as an abrasive and water, and the pH is adjusted to be in the range of 1 to 4, preferably 1 to 3.

The average primary particle size of colloidal silica is, for example, 60 nm or less, preferably less than 30 nm. Further, the lower limit of the average primary particle size of colloidal silica is preferably 10 nm or more, and more preferably 15 nm or more from the viewpoint of improving polishing efficiency.

Further, from the viewpoint of finely controlling the particle size, colloidal silica preferably does not contain secondary particles formed by aggregation of primary particles as much as possible. If the colloidal silica contains secondary particles, the average particle size thereof is preferably 70 nm or less.

The particle size of colloidal silica can be determined from a 50,000 to 105,000 times image taken by a scanning electron microscope (SEM).

The content of colloidal silica in the polishing slurry is preferably in the range of 10% by mass to 35% by mass, more preferably in the range of 18% by mass to 30% by mass, and particularly preferably in the range of 20% by mass to 28% by mass.

The polishing slurry has a pH in the range of 1-4. The pH is preferably in the range of 1-3.

The pH of the polishing slurry is preferably as low as possible in order for a component containing a hydrogen atom to be present (expressed) on the first main surface of the glass substrate. However, if the pH is less than 1, corrosion of the polishing machine becomes a problem. Therefore, the pH of the polishing slurry is in the range of 1 to 4.

The pH of the polishing slurry can be adjusted by using an acid selected from inorganic or organic acids alone or in combination.

Examples of the inorganic acid include nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, and amide sulfuric acid. In particular, nitric acid and sulfuric acid are preferable in terms of ease of handling.

Organic acids include citric acid, acetic acid, glycolic acid (hydroxyacetic acid), methoxyacetic acid, cyanate acetic acid, malonic acid, methylmalonic acid, malic acid, maleic acid, fumaric acid, benzoic acid, ascorbic acid, phthalic acid, and succinic acid. , Aspartic acid, lactic acid, tartaric acid, gluconic acid, glutaric acid, adipic acid, glutamic acid, iminonic acid and the like.

Polishing of the glass substrate can be performed by supplying a polishing slurry in which the average primary particle size and concentration of colloidal silica and the pH are adjusted to the polishing apparatus.

A known polishing device can be used. For example, the glass substrate may be sandwiched from above and below with a predetermined load by two polishing machines equipped with polishing pads. In this case, the glass substrate is polished by rotating each polishing machine relative to the glass substrate while supplying a predetermined amount of polishing slurry to the upper and lower polishing pads.

The supply amount of the polishing slurry, the polishing load, the rotation speed of the polishing machine, and the like can be appropriately determined in consideration of the polishing speed, the polishing finish accuracy, and the like. Generally, as the polishing rate increases, the polishing finish accuracy decreases. Therefore, the polishing rate is preferably 0.1 μm / min or less, for example, 0.05 μm / min or less. The amount of polishing is, for example, 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more.

The polishing time is preferably as long as possible so that more components containing hydrogen atoms are present (expressed) on the first main surface of the glass substrate.

The polishing pad is constructed by attaching a nap layer to a base material. The base material is made of, for example, a non-woven fabric or a sheet-like resin such as PET (polyethylene terephthalate). Alternatively, the nap layer can be directly attached to the polishing machine of the polishing apparatus without using a base material.

The nap layer contacts the main surface of the glass substrate at a predetermined polishing pressure, and while supplying a slurry between the nap layer and the glass substrate, the polishing pad rotates relative to the glass substrate (revolution, rotation). It is a polishing member that finish-polishs the main surface of a glass substrate.

Pads with a nap layer are classified as suede-based pads. The thickness of the nap layer is not particularly limited, but for suede pads, it is preferably about 0.3 mm to 1.0 mm. For the suede-based pad, a soft resin foam having appropriate elasticity, for example, a urethane resin foam such as an ether-based, ester-based, or carbonate-based foam is used.

(Step S114)
Next, in step S114, the glass substrate is finish-polished.

In this step, one main surface (first main surface) of the glass substrate is polished by using the polishing pad used in the above-mentioned secondary polishing step and the single-sided single-wafer polishing machine. The main surface to be polished is the surface on which the multilayer film is formed in the subsequent film forming step.

In this step S114, scratches having a diameter of 100 nm or less can be removed.

Further, also in this step S114, a component containing a hydrogen atom can be present (expressed) on the first main surface of the glass substrate.

The glass substrate is polished using a double-sided grinding machine. For polishing, a polishing slurry containing colloidal silica (silica particles) and water and whose pH is adjusted to be in the range of 1 to 3 is used. That is, the polishing slurry contains colloidal silica as an abrasive, an acid for adjusting the pH, and water for making a slurry.

Here, the average primary particle size of colloidal silica is 40 nm or less, preferably less than 30 nm. The lower limit of the average primary particle size of colloidal silica is preferably 10 nm or more, more preferably 15 nm or more, from the viewpoint of improving polishing efficiency.

If the average primary particle size of colloidal silica is more than 40 nm, it becomes difficult to polish the glass substrate to a desired surface roughness. When the particle size of colloidal silica is reduced, the polishing efficiency is lowered and the specific surface area is increased. This is not preferable because it leads to an increase in the surface activity of colloidal silica and further, colloidal silica easily adheres to the glass substrate.

Further, from the viewpoint of finely controlling the particle size, it is preferable that the colloidal silica does not contain secondary particles formed by agglomeration of primary particles as much as possible. When secondary particles are contained, the average particle size thereof is preferably 70 nm or less. The particle size of colloidal silica can be obtained by measuring an image of 50,000 to 105,000 times using an SEM (scanning electron microscope).

The content of colloidal silica contained in the polishing slurry is preferably 10 to 35% by mass, more preferably 18 to 30% by mass, and particularly preferably 20 to 28% by mass. If the content of colloidal silica is less than 10% by mass, the polishing efficiency is lowered. On the other hand, if the content of colloidal silica exceeds 35% by mass, colloidal silica tends to aggregate, which is not preferable.

The pH of the polishing slurry is adjusted to 1-3 for the reasons described above. The pH is preferably in the range of 1.2 to 2.5.

The pH of the polishing slurry can be adjusted by using an acid selected from inorganic acids alone or in combination. For example, a conventional inorganic acid or organic acid known as a pH adjuster for a polishing slurry can be appropriately selected and used.

Examples of the inorganic acid include nitric acid, sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, and amide sulfuric acid. In particular, nitric acid and sulfuric acid are preferable in terms of ease of handling.

Examples of organic acids include citric acid, acetic acid, glycolic acid (hydroxyacetic acid), methoxyacetic acid, cyanate acetic acid, malonic acid, methylmalonic acid, malic acid, maleic acid, fumaric acid, benzoic acid, ascorbic acid, and phthalic acid. Examples thereof include succinic acid, aspartic acid, lactic acid, tartaric acid, gluconic acid, glutaric acid, adipic acid, glutamic acid, and iminoniacetic acid.

A known polishing device can be used. For example, the first main surface of the glass substrate may be finish-polished by using a polishing apparatus such as that used in the above-mentioned secondary polishing step.

The supply amount of the polishing slurry, the polishing load, the rotation speed, etc. are appropriately determined in consideration of the polishing speed, the polishing finish accuracy, and the like. For example, the polishing rate is set to 0.05 μm / min or less.

The polishing time is preferably as long as possible from the viewpoint of allowing a component containing more hydrogen atoms to be present (expressed) on the first main surface of the glass substrate. For example, the total of the polishing time in the main step S114 and the polishing time in the previous step S113 may be in the range of 10 minutes to 60 minutes, preferably in the range of 20 minutes to 50 minutes.

The amount of polishing is, for example, 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more.

(Step S115)
Next, the glass substrate is washed.

One object of this cleaning step S115 is to remove foreign substances such as abrasives remaining on the glass substrate. Further, the cleaning step S115 is carried out in order to make (express) a component containing more hydrogen atoms on the first main surface.

For these purposes, the cleaning step S115 has, for example, the following steps:
First alkaline cleaning step (S115-A),
An acid cleaning step (S115-B) and a second alkaline cleaning step (S115-C).

Hereinafter, each step will be described.

(S115-A)
First, in the first alkaline cleaning step (S115-A), the glass substrate is cleaned using an alkaline cleaning liquid (hereinafter, referred to as "first cleaning liquid").

In this step, a first cleaning solution having a pH in the range of 8 to 14 is used. The pH is preferably 9 to 13, more preferably 10 to 12.

The first cleaning solution contains a pH adjuster. The pH regulator may include inorganic and / or organic alkalis.

Examples of the inorganic alkali include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate and the like. These inorganic alkalis may be used alone or in two or more kinds.

Examples of the organic alkali include alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine, alkylamines such as ethylamine, n-butylamine, ethylenediamine, and hexamethylenediamine, tetramethylammonium hydroxide, and methyltrihydroxy hydroxide. Examples thereof include ethylammonium and quaternary ammonium hydroxides such as tetrabutylammonium hydroxide. These organic alkalis may be used alone or in two or more types.

The first cleaning solution may further contain a chelating agent for an organic acid salt such as sodium citrate, a surfactant, a builder, and the like.

The cleaning tank for cleaning the glass substrate may be a batch type cleaning tank or a single-wafer type cleaning tank. Alternatively, the glass substrate may be cleaned using an ultrasonic cleaner. However, in that case, the frequency of the ultrasonic waves is preferably 100 kHz or higher in order to suppress damage caused by the ultrasonic waves.

Abrasive particles and the like are removed by the first alkaline cleaning step. However, in this step S115-A, it is difficult to make (express) a component containing a hydrogen atom on the first main surface of the glass substrate.

(S115-B)
Next, in the acid cleaning step (S115-B), the glass substrate is cleaned with an acidic cleaning solution.

In this step, a cleaning solution having a pH in the range of 1 to 6 is used. The pH is preferably in the range of 1.5 to 5, more preferably in the range of 1.5 to 4.

The cleaning solution preferably contains a pH adjuster and a chelating agent. As the pH adjuster, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and amide sulfuric acid, and organic acids such as maleic acid, fumaric acid, benzoic acid, acetic acid, hydroxyacetic acid, methoxyacetic acid, and glutaric acid can be used. Is. These acids may be used alone or in admixture of two or more. Examples of the chelating agent include phosphoric acid compounds such as phosphoric acid and phosphonic acid, citric acid, oxalic acid, alcorbic acid, malonic acid, malonic acid, phthalic acid, succinic acid, lactic acid, tartrate acid, gluconic acid, and formic acid. Condensed sodium phosphates such as organic acids, sodium orthorate, sodium picolinate, and sodium tripolyphosphate, aminocarboxylic acid chelating agents such as ethylenediamine tetraacetic acid, and N- (2-hydroxyethyl) -iminodiacetic acid, and polyacrylics. High molecular weight chelating agents such as acids and poly (ethylene-maleic acid) copolymers may be used.

Further, as the cleaning liquid, a cleaning liquid in which sulfuric acid and hydrogen peroxide solution are mixed may be used. In this case, the cleaning solution may be adjusted by using sulfuric acid as an aqueous solution of 0.1% by weight or more and 10% by weight or less and hydrogen peroxide solution as an aqueous solution of 1% by weight or more and 15% by weight or less, or sulfuric acid as 50% by weight or more and water. Concentrated sulfuric acid having a content of 50% by weight or less may be used.

After that, the glass substrate is rinsed with pure water.

By this acid cleaning step, a component containing a hydrogen atom can be present (expressed) on the first main surface of the glass substrate.

Although it depends on the dimensions of the glass substrate, the acid cleaning time is preferably in the range of 1 minute to 10 minutes, and more preferably in the range of 1 minute to 8 minutes. By carrying out acid cleaning for 1 minute or more, the amount of hydrogen atoms present on the first main surface of the glass substrate can be increased.

(S115-C)
Next, the second alkaline cleaning step (S115-C) is carried out.

By carrying out this step, the acid that may remain on the glass substrate in the previous step (S115-B) can be sufficiently removed. In addition, the activity of the main surface of the glass substrate can be reduced.

The above-mentioned first cleaning liquid may be used in the second alkaline cleaning step. Further, in the second alkaline cleaning step, the apparatus used in the above-mentioned step S115-A may be used.

After the second alkaline cleaning step, the glass substrate is sufficiently dried.

Through the above steps, the mask blank substrate 110 is prepared. That is, a mask blank substrate 110 in which the first main surface 112 has ^{a depth profile of 1} H / ^{30 Si as shown in FIG. 2 is manufactured.}

(Step S120)
Next, the laminated film 220 is formed on the mask blank substrate 110 manufactured in step S110. Specifically, the reflective film 230, the protective film 240, the absorbing film 250, and the low reflective film 260 are deposited on the first main surface 112 of the mask blank substrate 110 in this order.

However, as described above, the protective film 240 and / or the low-reflection film 260 may be omitted.

The reflective film 230 is formed by, for example, alternately laminating Si layers and Mo layers by using a sputtering method. The total number of layers is, for example, 20-50.

Here, when the reflective film 230 is formed on the first main surface 112 of the mask blank substrate 110, the depth profile of ¹ H / ^{30 Si at the interface between the reflective film 230 and the first main surface 212 is determined.} It changes compared to before film formation.

Specifically, after the film formation of the reflective film 230, the maximum value M _max ^{of 1} H / ³⁰ Si in the vicinity of the first main surface 212 is lower and the depth is lower than that of the mask blank substrate 110. The decreasing curve of ¹ H / ³⁰ Si along the direction becomes gentler.

This is because when the reflective film 230 is formed, hydrogen atoms existing on the first main surface 112 of the mask blank substrate 110 are caused by heat on both sides, that is, on the side of the reflective film 230 and on the first substrate 110. This is because it diffuses to the inside.

With the spread of such a hydrogen atom, an oxygen atom present on the first major surface 112 in the form of OH groups or a water molecule (H 2 _O) is also diffused from the interface on both sides. As a result, Si is oxidized and an oxide is formed in the silicon (Si) layer forming the lowermost layer of the reflective film 230. This oxide can bind the first main surface 212 and the reflective film 230 together like a "glue" at the interface.

As a result, good adhesion can be obtained between the second substrate 210 and the reflective film 230.

Next, the protective film 240 is formed on the reflective film 230. The protective film 240 is made of ruthenium (Ru), Si, TiO ₂ , or the like, and may be formed by, for example, a sputtering method.

Next, the absorption film 250 is formed on the protective film 240. The absorption film 250 is made of TaN or the like, and may be formed by, for example, a sputtering method.

Next, the low reflection film 260 is formed on the absorption film 250. The low-reflection film 260 is formed of TaO, TaON, or the like, and may be formed by, for example, a sputtering method.

(Step S130)
Next, the second layer 280 is installed on the second main surface 114 of the mask blank substrate 110, that is, the second main surface 214 of the second substrate 210.

As described above, the second layer 280 may be made of chromium nitride (CrN) or the like. The second layer 280 may be formed on the second main surface 214 by, for example, a sputtering method.

Note that this step S130 may be performed before the above-mentioned step S120.

Through the above steps, the mask blank 200 as shown in FIG. 3 can be manufactured.

As described above, an example of a method for manufacturing a mask blank according to an embodiment of the present invention has been described with reference to FIGS. 4 and 5. However, such description is merely an example. The mask blank according to the embodiment of the present invention is manufactured by any manufacturing method as long as the depth profile of ¹ H / ³⁰ Si as described above can be obtained at the interface between the second substrate 210 and the reflective film 230. May be done.

(Example 1)
A substrate for a mask blank was manufactured by the following method.

(Manufacturing of substrates for mask blanks)
A rectangular glass substrate was prepared. As the glass substrate, synthetic quartz glass containing 7% by mass of _{TiO 2 was used.}

The four sides of the glass substrate were chamfered using a # 120 diamond grindstone. As a result, a glass substrate having a shape of 152 mm in length × 152 mm in width × 6.75 mm in thickness was obtained.

Next, a substrate for mask blanks was manufactured from this glass substrate by using the above-mentioned "method for manufacturing a substrate for mask blanks".

(Preliminary polishing)
First, the glass substrate was pre-polished. As pre-polishing, primary pre-polishing to fifth pre-polishing were carried out.

As the primary pre-polishing, both main surfaces of the glass substrate were polished.

A 20B double-sided lapping machine (manufactured by Speedfam) was used for the primary pre-polishing. Both main surfaces of the glass substrate were polished by supplying a slurry containing an abrasive. SiC particles (GC # 400; manufactured by Fujimi Incorporated) were used as the abrasive. This abrasive was suspended in 18 to 20% by mass in filtered water to prepare a slurry.

The primary pre-polishing was carried out until the thickness of the glass substrate was about 6.63 mm.

Next, as secondary pre-polishing, both main surfaces of the glass substrate were polished.

For the secondary pre-polishing, a 20B double-sided lapping machine (manufactured by Speedfam Co., Ltd.) was used, and another slurry was supplied. The slurry was prepared by suspending 18 to 20% by mass of an abrasive (FO # 1000; manufactured by Fujimi Incorporated) mainly composed of _{Al 2} O _{3 in filtered water.}

The secondary pre-polishing was carried out until the thickness of the glass substrate became about 6.51 mm.

Next, a secondary pre-polishing was performed using a 20B double-sided polishing machine (manufactured by Speedfam). As the slurry, an abrasive material (Millake 801A; manufactured by Mitsui Mining & Smelting Co., Ltd.) suspended in 10 to 12% by mass was used in filtered water.

The tertiary pre-polishing was carried out until both main surfaces were polished by a total of 50 μm.

Next, the polishing pad was replaced with a polishing pad (Seagull 7355; manufactured by Toray Cortex), and a 20B double-sided polishing machine (manufactured by Speedfam) was used to perform the fourth pre-polishing.

The fourth pre-polishing was carried out until both main surfaces were polished by a total of 10 μm. The flatness (Rms) of the glass substrate was about 0.8 nm.

Finally, the fifth pre-polishing was performed under the following conditions:
Polishing tester: Double-sided 24B polishing machine (manufactured by Hamai Co., Ltd.)
Polishing pad: Bellatrix K7512 (manufactured by Kanebo)
Polishing slurry: Colloidal silica slurry (pH 2) having an average particle size of 20 nm adjusted with nitric acid.
Polishing surface plate rotation speed: 35 rpm
Polishing time: 50 minutes Polishing load: 80 g / cm ²
Slurry flow rate: 10 L / min.

(Local polishing)
Next, the glass substrate was locally polished. A single-sided polishing machine was used for local polishing, and both main surfaces of the glass substrate were processed in order.

A soft polisher was used for the polishing pad, and an aqueous solution containing cerium oxide and polishing particles having an average particle size of 1.0 μm was used as the polishing slurry.

Local polishing was performed for about 60 minutes.

Then, the glass substrate was washed.

(Secondary polishing)
Next, the glass substrate was secondarily polished.

In the secondary polishing, both main surfaces of the glass substrate were polished at the same time. As the slurry, an aqueous nitric acid solution containing abrasive particles made of colloidal silica and having an average particle size of 20 nm was used. The pH is 1.5. In addition, an ultra-soft polisher was used as the polishing pad.

The polishing time was 30 minutes. The amount of polishing was about 1 μm for both main surfaces combined.

(Finish polishing)
Next, the glass substrate was finish-polished.

For finish polishing, a single-wafer single-sided polishing machine was used to polish the first main surface of the glass substrate.

As the slurry and the polishing pad, those used in the above-mentioned secondary polishing step were used, respectively.

The polishing time was 15 minutes. The amount of polishing was about 0.5 μm.

(Washing)
The polished glass substrate was washed. The cleaning treatment was carried out in the order of alkaline cleaning, acid cleaning, and alkaline cleaning.

In the first alkaline cleaning step, the glass substrate was immersed in a bathtub containing an alkaline cleaning solution (pH 12) containing KOH, and then scrub cleaning was performed. For scrub cleaning, a scrub cleaning solution having a pH of 10 containing KOH and a surfactant was used.

Next, in the acid cleaning step, the glass substrate was immersed in a bathtub containing an acid cleaning solution (pH 1) containing sulfuric acid and hydrogen peroxide solution for 5 minutes.

Then, the above-mentioned alkaline cleaning step was carried out again.

Finally, the glass substrate was rinsed with ultrapure water and spin-dried.

As a result, a substrate for a mask blank was manufactured.

( ^{Measurement of 1} H / ³⁰ Si profile)
Using the obtained mask blank substrate, ^{the profile of 1} H / ³⁰ Si on the first main surface was measured. Secondary ion mass spectrometry (SIMS) was used for the measurement.

The measurement was performed according to the following procedure:
(1) A part of the mask blank substrate is cut out to prepare a sample.
(2) Fix the sample on the sample table.
(3) Obtain the depth profile of the respective intensities of ¹ H and ^{30 Si.}
(4) Obtain a profile of ¹ H / ^{30 Si.}

The measurement conditions in (3) are as follows:
Equipment: ADEPT1010 (manufactured by ULVAC-PHI)
Primary ion species; Cs ⁺
Acceleration voltage of primary ion; 5 kV
Primary ion current value; 500 nA
Angle of incidence of primary ions; 60 ° with respect to the normal of the sample surface
Raster size of primary ion; 300 x 300 μm ²
Secondary ion polarity; Negative secondary ion detection region; 60 x 60 μm ² (4% of primary ion raster size)
ESA Input Lens; 0
Use of neutralizing gun: Yes How to convert the horizontal axis from sputtering time to depth: Measure the depth of the analytical crater with a stylus type surface shape measuring instrument (Dektake 150 manufactured by Veeco) to determine the sputtering rate of primary ions. .. Using this sputtering rate, the horizontal axis is converted from the sputtering time to the depth.

FIG. 6 shows an example of the measurement result of the profile of ¹ H / ^{30 Si.}

In FIG. 6, the horizontal axis is the depth from the first main surface, and the vertical axis is the value of ¹ H / ^{30 Si.}

As shown in FIG. 6, ^{the profile of 1} H / ³⁰ Si showed a tendency to reach a maximum near the depth of 0 (zero) and then gradually decrease to about 1200 nm. The average value Ave ₁ ^{of 1} H / ³⁰ Si between 0 and 200 nm in depth from the first main surface was 1.13. On the other hand, the average value Ave ₂ ^{of 1} H / ³⁰ Si between 2 μm and 4 μm in depth from the first main surface was 0.00377. Therefore, the average value Ave ₁ / average value Ave ₂ was about 300.

As described above, it was confirmed that a region in which hydrogen atoms were concentrated existed on the first main surface of the mask blank substrate. Such enrichment of hydrogen atoms suggests the presence of oxygen bound to hydrogen atoms.

(Example 2)
A mask blank was produced from the mask blank substrate produced by the method of Example 1. Specifically, the following steps were carried out.

(Formation of conductive layer)
A conductive layer was formed on the second main surface of the mask blank substrate.

The conductive layer was a CrN layer and was formed on the second main surface by using a magnetron sputtering method.

The film formation conditions for the conductive layer are shown below:
Target; Cr target Sputtering gas; Ar + N ₂ + H ₂ mixed gas (Ar = 58.2 _{vol%, N 2} = 40 vol%, H ₂ = 1.8 vol%, gas pressure = 0.1 Pa)
Input power; 1500W
Film formation rate: 0.18 nm / sec
Target film thickness; 185 nm.

The sheet resistance of the obtained conductive layer was 100 Ω / □.

(Formation of laminated film)
Next, a laminated film was formed on the first main surface of the mask blank substrate in the following order.

(Reflective film)
A reflective film was formed on the first main surface by using an ion beam sputtering method.

The reflective film was a Si / Mo multilayer film. The Si layer and the Mo layer were alternately formed 50 times. The thickness of each Si layer was 4.5 nm, the thickness of each Mo layer was 2.3 nm, and the total thickness of the reflective film was 340 nm.

The film formation conditions are shown below:
Film formation conditions for Si layer Target; Si target (boron-doped)
Sputtering gas; Ar gas (gas pressure: 0.02 Pa)
Voltage; 700V
Film formation rate: 0.077 nm / sec
Mo layer film formation conditions Target; Mo target Sputtering gas; Ar gas (gas pressure: 0.02 Pa)
Voltage; 700V
Film formation rate: 0.064 nm / sec.

(Protective film)
Next, a protective film was formed on the reflective film by using the ion beam sputtering method. The protective film was a Ru film. The film formation conditions for the protective film are shown below:
Target; Ru target Sputtering gas; Ar gas (gas pressure: 0.02 Pa)
Voltage; 700V
Film formation rate: 0.052 nm / sec
Film thickness; 2.5 nm.

(Absorption membrane)
Next, an absorption film was formed on the protective film by using the magnetron sputtering method. The absorption film was a TaN film. The film formation conditions for the absorbent film are shown below:
Target; Ta target Sputtering gas; _{mixed gas of Ar and N 2} (Ar = 86 vol%, N ₂ = 14 vol%, gas pressure = 0.3 Pa)
Input power; 150W
Film formation rate; 7.2 nm / min
Film thickness: 60 nm.

(Low reflective film)
Next, a low-reflection film was formed on the absorption film by using a magnetron sputtering method. The low-reflection film was a TaON film. The film formation conditions for the low-reflection film are shown below:
Target; Ta target Sputtering gas; Ar + O ₂ + N ₂ mixed gas (Ar = 49 vol%, O ₂ = 37 vol%, N ₂ = 14 vol%. Gas pressure = 0.3 Pa)
Input power; 250W
Film formation rate: 2.0 nm / min
Film thickness: 8 nm.

As a result, a mask blank having a laminated film on the first main surface of the substrate and a conductive layer on the second main surface of the substrate was produced.

( ^{Measurement of 1} H / ³⁰ Si profile)
Using the obtained mask blank, ^{the profile of 1} H / ³⁰ Si at the substrate / reflective film interface was measured by the above-mentioned method.

FIG. 7 shows an example of the measurement result. In FIG. 7, the horizontal axis is the distance in the depth direction of the mask blank, and the vertical axis is the value of ¹ H / ^{30 Si.} The horizontal axis indicates that the larger the value, the more it enters the inner side through the first main surface of the substrate, and the 0 point represents an arbitrary position in the reflective film.

As shown in FIG. 7, ^{it can be seen that the profile of 1} H / ³⁰ Si in this mask blank exhibits characteristic behavior along the depth direction. That is, ¹ H / ³⁰ Si showed a moderately high value from a depth of 0 to 200 nm (referred to as the “first region”), and showed a maximum value (peak) at a depth of about 200 nm. After that, it gradually decreases and shows a substantially constant value after a depth of 1900 nm.

Of these, the first region is considered to correspond to the reflective film of the mask blank. Further, the ^{position where 1} H / ³⁰ Si shows the maximum value (the position at a depth of about 200 nm) is considered to correspond to the interface between the reflective film and the substrate, that is, the first main surface of the substrate.

As a result of the measurement, the average value Ave ₁ ^{of 1} H / ³⁰ Si between the interface between the substrate and the reflective film, that is, the depth from the position of 200 nm was 0 to 200 nm was 0.305. On the other hand, the average value Ave ₂ ^{of 1} H / ³⁰ Si between 2 μm and 4 μm in depth from the interface between the substrate and the reflective film was 0.0035. Therefore, the average value Ave ₁ / average value Ave ₂ was about 87.

As described above, it was found that there is a region where hydrogen atoms are concentrated at the interface between the reflective film of the mask blank and the substrate.

^{Here, the maximum value of 1} H / ³⁰ Si at the interface is lower than that in FIG. From this, it is presumed that some of the hydrogen atoms present on the first main surface of the mask blank substrate are diffused together with the oxygen atoms on the substrate side and the reflective film side, respectively.

Oxygen diffused on the side of the reflective film reacts with the metal (Si layer) constituting the reflective film to form an oxide. This oxide is expected to play a role of connecting the two at the interface between the substrate and the reflective film.

Therefore, it is expected that the mask blank having the profile of ¹ H / ³⁰ Si shown in FIG. 7 has improved adhesion between the reflective film and the substrate.

110 Mask blank substrate 112 First main surface 114 Second main surface 200 Mask blank 210 substrate (second substrate)
212 First main surface 214 Second main surface 220 Laminated film 230 Reflective film 240 Protective film 250 Absorbent film 260 Low reflective film 280 Second layer

Claims (6)

A substrate for mask blanks
The mask blank substrate has a first main surface and a second main surface facing each other, and is composed of synthetic quartz glass containing _{TiO 2.}
^{When the ratio of monovalent H ions to monovalent Si ions (1} H / ³⁰ Si) is measured from the side of the first main surface by the secondary ion mass spectrometry method, from the first main surface. The ^{average value of 1} H / ³⁰ Si with a depth of 0 to 200 nm is 5 times or more the average value ^{of 1} H / ³⁰ Si with a depth of 2 μm to 4 μm from the first main surface. Large, mask blank substrate. The mask blank substrate according to claim 1, which contains 5% to 10% of TiO _{2 by mass.} A mask blank having a substrate and a laminated film arranged on the substrate.
The substrate is made of synthetic quartz glass containing _{TiO 2.}
An interface exists between the laminated film and the substrate,
^{When the ratio of monovalent H ions to monovalent Si ions (1} H / ³⁰ Si) is measured from the side of the laminated film to the inside of the substrate through the interface by the secondary ion mass spectrometry method. , ^{The average value of 1} H / ³⁰ Si with a depth of 0 to 200 nm from the interface is 5 times or more the average value ^{of 1} H / ^{30 Si with a depth of 2 μm to 4 μm from the interface.} Large, mask blank. The mask blank according to claim 3, wherein the substrate contains 5% to 10% of TiO _{2 by mass.} The mask blank according to claim 3 or 4, wherein the laminated film has a reflective film and an absorbing film. The mask blank according to any one of claims 3 to 5, wherein a layer of a conductive material is arranged on the side of the substrate opposite to the laminated film.

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