TWI767053B - Mask blank, phase-shifting mask, method of manufacturing mask blank, and method of manufacturing phase-shifting mask - Google Patents

Abstract

A mask blank of the invention includes a layer that becomes a phase-shifting mask. The mask blank includes: a phase-shifting layer and a low reflective layer which are stacked on a transparent substrate; and a chemical resistance layer that is provided at a position away from the transparent substrate further than those of the phase-shifting layer and the low reflective layer and has a high degree of chemical resistance. A nitrogen content rate of the chemical resistance layer is higher than a nitrogen content rate of the low reflective layer.

Description

Photomask substrate, phase shift photomask, manufacturing method of photomask substrate, and manufacturing method of phase shift photomask

The present invention relates to a preferred technique for a mask substrate, a phase shift mask, a method for manufacturing a mask substrate, and a method for manufacturing a phase shift mask.

With the high definition of FPD (flat panel display, flat panel display), it is more necessary to form fine patterns. Therefore, not only the photomask of the light-shielding film used in the past, but also the edge-enhanced phase shift photomask (PSM photomask) is gradually used (for example, refer to the republication table WO2004/070472).

For such phase shift masks, it is desirable to reduce reflectivity.

In these phase shift masks, it is preferable to reduce the reflectance during exposure, and for this purpose, a film with a lower refractive index needs to be formed on the surface. In the phase shift mask, in order to obtain a film with a lower refractive index, it is desirable to use an oxide film containing an oxidized metal.

On the other hand, in order to remove contaminants from the photomask that may affect the optical properties, the photomask needs to be cleaned with an acidic or alkaline chemical solution. It is known that during this cleaning step, the oxidized metallic film is less resistant to alkaline solutions.

However, as a metallic film used for a phase shift mask, it is known that the progress of oxidation of the film and the resistance to an alkaline solution (chemical solution resistance) are in a trade-off relationship.

For the phase shift mask, a phase shift film with low reflectivity and strong chemical resistance is required.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to realize a phase shift film having both low reflectance and strong chemical resistance.

The above-mentioned problem is solved by the following means, the mask base of the 1st aspect of this invention has the layer which becomes the phase shift mask, and has the phase shift layer and the low reflectance layer, which are laminated on the transparent a substrate; and a chemical-resistant layer, which is disposed at a position farther from the transparent substrate than the phase shift layer and the low-reflection layer, and improves chemical resistance; the nitrogen content in the chemical-resistant layer is set It is higher than the nitrogen content rate of the said low reflectance layer.

In the photomask substrate of the first aspect of the present invention, it is more preferable that the oxygen content of the low reflectance layer is set higher than the oxygen content of the chemical-resistant layer.

Regarding the photomask substrate of the first aspect of the present invention, in the chemical-resistant layer and the low-reflectance layer, the spectral reflectance may have a profile that is convex downward in the vicinity of 400 nm.

Moreover, in the mask base of the 1st aspect of this invention, in the said low reflectivity layer, the refractive index at wavelength 405 nm can be set to 2.2 or less.

Moreover, in the photomask substrate of the first aspect of the present invention, in the chemical-resistant layer, the refractive index at a wavelength of 405 nm can be set to 2.4 or more.

Moreover, in the photomask substrate of the first aspect of the present invention, the chemical-resistant layer and the low-reflectance layer may contain silicide.

Moreover, in the photomask base of the 1st aspect of this invention, the nitrogen content rate of the said chemical-resistant layer can be made into 36 atm% or more.

Moreover, in the photomask substrate of the first aspect of the present invention, the nitrogen content of the low reflectivity layer can be set to 35 atm% or less, and the oxygen content can be set to 30 atm% or more.

Moreover, in the photomask base of the 1st aspect of this invention, the film thickness of the said chemical-resistant layer can be made into 15 nm or less.

Moreover, in the mask substrate of the first aspect of the present invention, in the phase shift layer, the refractive index at a wavelength of 405 nm can be set to be 2.4 or more.

Moreover, in the photomask substrate of the first aspect of the present invention, the nitrogen content of the phase shift layer can be set to 36 atm% or more.

Moreover, the phase shift mask of the 2nd aspect of this invention is manufactured using the mask base of the said 1st aspect.

In addition, the method of manufacturing a photomask substrate of a third aspect of the present invention is the method of manufacturing a photomask substrate of the above-mentioned first aspect, wherein the chemical resistant layer and the low reflectance layer are formed by using nitrogen gas as a film. Differential pressure.

Moreover, in the manufacturing method of the photomask base of the 3rd aspect of this invention, the partial pressure of the oxygen-containing gas can be made different when forming the said chemical-resistant layer and the said low reflectance layer.

In addition, the method of manufacturing a phase shift mask of the fourth aspect of the present invention is the method of manufacturing a phase shift mask of the second aspect described above, when the chemical resistant layer and the low reflectance layer are formed into films. , which can make the partial pressure of nitrogen different.

In the manufacturing method of the phase shift mask of the fourth aspect of the present invention, the partial pressure of the oxygen-containing gas can be made different when the chemical resistant layer and the low reflectance layer are formed.

The mask base of the first aspect of the present invention has a layer to be a phase shift mask, and has: a phase shift layer and a low reflectivity layer, which are laminated on a transparent substrate; and a chemical-resistant layer, which is It is arranged at a position farther from the transparent substrate than the phase shift layer and the low reflectivity layer, and improves chemical resistance; the nitrogen content in the chemical resistance layer is set higher than that of the low reflectivity layer. Thereby, it is possible to provide a photomask substrate that can be made into a phase shift photomask, which has a reflectivity reduced to a specific range, and which is resistant to chemicals used in steps such as cleaning and the like. A mask layer for the desired phase shift effect.

Here, as the chemical, an alkaline chemical or an acidic chemical can be used. As an example, a developing solution, a peeling solution, a cleaning solution, etc. may be mentioned, for example, sodium hydroxide (NaOH), potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), sulfuric acid (H ₂ SO ₄ ), a mixed solution of sulfuric acid and hydrogen peroxide (H ₂ O ₂ ), and the like, especially sodium hydroxide solution.

Moreover, as the mask base of the 1st aspect of this invention, the large-scale mask used for the polychromatic wave exposure of FPD manufacture is conceivable.

In the mask substrate of the first aspect of the present invention, the oxygen content of the low-reflectivity layer is set higher than that of the chemical-resistant layer and the phase shift layer. Reduced reflectance, in a state where the reduction of film thickness due to chemicals is prevented by the chemical-resistant layer, as a mask layer, for example, at wavelengths from g-line (436 nm) to i-line (365 nm) In the frequency band, it can have low reflectivity and phase shift energy.

With regard to the mask base of the first aspect of the present invention, in the chemical-resistant layer and the low-reflectance layer, the spectral reflectance has a profile that is convex downward in the vicinity of 400 nm. Thereby, in the wavelength region of the exposure light used in exposure apparatuses, such as a stepper, the low reflectivity required as a photomask can be achieved.

Furthermore, in the mask base of the first aspect of the present invention, in the low reflectivity layer, the refractive index at a wavelength of 405 nm is set to be 2.2 or less, whereby the low reflectivity can be realized.

Moreover, in the photomask base of the 1st aspect of this invention, in the said chemical-resistant layer, the refractive index in wavelength 405 nm is set to 2.4 or more. Thereby, as a film used as a phase shift mask, the desired low reflectivity and chemical resistance can be provided.

Moreover, in the photomask base of the 1st aspect of this invention, the said chemical-resistant layer and the said low reflectance layer contain a silicide. Thereby, a film with a specific phase shift energy and strong resistance to a chemical solution can be obtained.

Here, the silicide film that can be used as a mask and a phase is not limited to MoSi-based materials including Mo and Si, and examples include metals and silicon (MSi, M: Mo, Ni, W, Zr, Ti, Cr and other transition metals), oxynitride metals and silicon (MSiON), carbon oxidised metals and silicon (MSiCO), carbonitride oxidised metals and silicon (MSiCON), oxidized metals and silicon (MSiO), Nitrided metals and silicon (MSiN), etc., also include metals such as Ta, Ti, W, Mo, Zr, or alloys of these metals or alloys of these metals and other metals (as other metals, Examples include Cr, Ni), or materials containing these metals or alloys and silicon. In particular, a MoSi film can be cited.

Furthermore, in the photomask substrate of the first aspect of the present invention, the nitrogen content of the chemical-resistant layer is set to 36 atm% or more, whereby desired chemical resistance can be achieved, for example, washing can be suppressed. The variation of the film thickness in the net step prevents the reflectivity and phase shift from deviating from the initially set ranges.

In addition, in the mask substrate according to the first aspect of the present invention, the nitrogen content of the low reflectivity layer is set to 35 atm% or less, and the oxygen content is set to 30 atm% or more, whereby the reflectance can be relatively high. Low ground is set to a specific range.

In addition, in the photomask substrate of the first aspect of the present invention, the film thickness of the chemical-resistant layer is set to 15 nm or less, whereby the desired chemical resistance can be achieved while preventing the low reflection caused by the above-mentioned low reflection The reflectivity set by the rate layer deviates from the initially set range.

Furthermore, in the mask substrate of the first aspect of the present invention, in the above-mentioned phase shift layer, the refractive index at a wavelength of 405 nm is set to be 2.4 or more, whereby a desired phase shift energy can be obtained.

Furthermore, in the photomask substrate of the first aspect of the present invention, the nitrogen content of the phase shift layer is set to 36 atm% or more, whereby a desired phase shift energy can be obtained.

In addition, the phase shift mask of the second aspect of the present invention is manufactured using the mask substrate of the first aspect described above, whereby the phase shift mask required for chemical resistance and low reflectivity can be provided can.

In addition, the method of manufacturing a photomask substrate of a third aspect of the present invention is the method of manufacturing a photomask substrate of the above-mentioned first aspect, wherein the chemical resistant layer and the low reflectance layer are formed by using nitrogen gas as a film. Differential pressure. Thereby, a chemical-resistant layer and a low-reflectance layer can be formed into a film with a specific nitrogen content, and a photomask substrate having specific film characteristics can be produced.

Moreover, in the manufacturing method of the photomask base of the 3rd aspect of this invention, the partial pressure of the oxygen-containing gas is made different when the said chemical-resistant layer and the said low reflectance layer are formed into films. Thereby, a chemical-resistant layer and a low-reflectance layer can be formed into a film with a specific oxygen content, and a photomask substrate having specific film characteristics can be produced.

In addition, the method of manufacturing a phase shift mask of the fourth aspect of the present invention is the method of manufacturing a phase shift mask of the second aspect described above, when the chemical resistant layer and the low reflectance layer are formed into films. , so that the partial pressure of nitrogen is different. Thereby, a phase shift mask having desired film properties in each layer can be produced.

In the manufacturing method of the phase shift mask of the 4th aspect of this invention, the partial pressure of the oxygen-containing gas is made to differ during film-forming of the said chemical-resistant layer and the said low reflectance layer. Thereby, a phase shift mask having desired film properties in each layer can be produced. [Effect of invention]

According to the aspect of the present invention, the following effects can be obtained: a photomask substrate and a phase-shift photomask having chemical resistance and low reflectivity and having specific phase-shift performance can be provided.

Hereinafter, the mask base, the phase shift mask, the manufacturing method of the mask base, and the manufacturing method of the phase shift mask of 1st Embodiment of this invention are demonstrated based on drawing.

FIG. 1 is a cross-sectional view showing a mask base in this embodiment, and FIG. 2 is a cross-sectional view showing a phase shift mask in this embodiment. In the drawings, reference numeral 10B denotes a mask base.

The photomask substrate 10B of the present embodiment is used for a phase shift photomask used in a wavelength range of about 365 nm to 436 nm for exposure light. As shown in FIG. 1 , the mask base 10B includes: a glass substrate 11 (transparent substrate); a phase shift layer 12 formed on the glass substrate 11 ; a low reflectivity layer 13 formed on the phase shift layer 12 ; and a chemical resistant layer 14 formed on the low reflectivity layer 13 . The phase shift layer 12 , the low reflectance layer 13 and the chemical resistance layer 14 constitute a low reflection phase shift film as a mask layer.

Furthermore, the mask substrate 10B of the present embodiment may also be configured to include a protective layer, a light shielding layer, an etch stop layer, etc., in addition to the phase shift layer 12 , the low reflectance layer 13 , and the chemical-resistant layer 14 .

As the transparent substrate 11, a material excellent in transparency and optical isotropy is used, for example, a quartz glass substrate can be used. The size of the transparent substrate 11 is not particularly limited, and it depends on the substrate to be exposed using the mask (for example, an LCD (Liquid Crystal Display, liquid crystal display), a plasma display, an organic EL (Electroluminescence, electroluminescence) display and other FPD substrates etc.) and appropriately selected.

Examples of the phase shift layer 12 and the chemical-resistant layer 14 include: a silicide film containing nitrogen, for example, a film containing metals such as Ta, Ti, W, Mo, Zr, or an alloy of these metals and silicon, In particular, a MoSi _X (X≧2) film (for example, a MoSi ₂ film, a MoSi ₃ film, or a MoSi ₄ film, etc.) can be mentioned.

Also, as the low reflectance layer 13, a silicide film containing nitrogen is used in the same manner as the phase shift layer 12 and the chemical resistant layer 14, but a film containing oxygen may be further used.

The present inventors have studied hard and found that, regarding the composition of the MoSi film, in the composition ratio of Mo to Si, the higher the Mo ratio, the higher the metallic properties of the MoSi film, and the lower the wavelength dependence of transmittance. Therefore, it was found that the value of X in the MoSi _X film is preferably 3 or less, and it is further desirable that the value of X is 2.5 or less. Therefore, in this study, a target with an X value of 2.3 was used.

In this embodiment, the nitrogen content (nitrogen concentration) of the phase shift layer 12 can be set to 36 atm% or more, and the nitrogen concentration of the phase shift layer 12 is more preferably 40 atm% or more.

In addition, the nitrogen concentration of the low reflectance layer 13 can be set to 35 atm% or less, and the nitrogen concentration of the low reflectance layer 13 is more preferably 30 atm% or less.

In addition, the nitrogen concentration of the chemical-resistant layer 14 can be set to 36 atm% or more, the nitrogen concentration of the chemical-resistant layer 14 is more preferably 40 atm% or more, and the film thickness of the chemical-resistant layer 14 can be set to be less than 20 nm. It is preferable to set it as 15 nm or less. In addition, the film thickness of the chemical-resistant layer 14 may be 0 nm or more, and preferably 5 nm or more.

Meanwhile, in this embodiment, the oxygen content (oxygen concentration) of the low reflectivity layer 13 can be set to 25 atm% or more, and the oxygen concentration of the low reflectivity layer 13 is more preferably 30 atm% or more.

At this time, the oxygen concentration of the phase shift layer 12 may be set to 7.0˜10 atm%, and the oxygen concentration of the chemical resistant layer 14 may be set to 7.0˜10 atm%.

The manufacturing method of the photomask base in this embodiment is to form the phase shift layer 12 on the glass substrate 11 (transparent substrate), and then form the low reflectance layer 13 and the chemical resistance layer 14 into the film.

In the photomask substrate manufacturing method, in addition to the phase shift layer 12, the low reflectivity layer 13 and the chemical resistance layer 14, a protective layer, a light shielding layer, an anti-reflection layer, an etching stop layer, etc. these layering steps.

As an example, the light shielding layer containing chromium is mentioned, for example.

As shown in FIG. 2 , the phase shift mask 10 in this embodiment is obtained by patterning the phase shift layer 12 , the low reflectivity layer 13 and the chemical resistance layer 14 on the mask substrate 10B.

Hereinafter, the manufacturing method of the phase shift mask 10 from the mask base 10B of this embodiment is demonstrated.

A photoresist layer is formed on the outermost surface of the photomask substrate 10B. The photoresist layer can be positive type, or can also be negative type. As the photoresist layer, a liquid resist was used.

Then, by exposing and developing the photoresist layer, a resist pattern is formed on the outer side of the chemical resistant layer 14 . The resist pattern functions as an etching mask for the phase shift layer 12 , the low reflectivity layer 13 and the chemical resistant layer 14 An appropriate shape is determined by etching the pattern. As an example, the phase shift region is set to have a shape having an opening width corresponding to the opening width dimension of the phase shift pattern to be formed.

Next, the phase shift layer 12 , the low reflectance layer 13 , and the chemical-resistant layer 14 are wet-etched using an etching solution through the resist pattern, thereby forming the phase shift patterns 12P, 13P, and 14P. When the phase shift layer 12, the low reflectivity layer 13, and the chemical resistance layer 14 are MoSi, as the etching solution, it is preferable to use at least one fluorine selected from the group consisting of hydrofluoric acid, silicic acid, and ammonium hydrogen fluoride. A compound, and an etching solution of at least one oxidant selected from hydrogen peroxide, nitric acid, and sulfuric acid.

Furthermore, in the case of forming the mask substrate 10B having other films such as a light shielding layer, the film is patterned into the phase shift pattern 12P, 13P and 14P correspond to specific shapes. The patterning of other films such as the light shielding layer can be performed as a specific step before and after the patterning of the phase shift layer 12 , the low reflectivity layer 13 and the chemical resistant layer 14 corresponding to the lamination order.

Through the above steps, as shown in FIG. 2 , the phase shift mask 10 having the phase shift patterns 12P, 13P and 14P can be obtained.

Hereinafter, the manufacturing method of the photomask base in this embodiment is demonstrated based on drawing.

FIG. 3 is a schematic view showing an apparatus for manufacturing a photomask substrate in this embodiment, and FIG. 4 is a schematic view showing an apparatus for manufacturing a photomask substrate in this embodiment.

The photomask substrate 10B in this embodiment is manufactured by the manufacturing apparatus shown in FIG. 3 or FIG. 4 .

The manufacturing apparatus S10 shown in FIG. 3 is an inner-back type sputtering apparatus, and includes: a loading and unloading chamber S11; S11.

The loading and unloading chamber S11 is provided with: a transfer device S11a that transfers the glass substrate 11 carried in from the outside to the film forming chamber S12 or transfers the film forming chamber S12 to the outside; and an exhaust device S11b such as a rotary pump, which The inside of the loading and unloading chamber S11 is roughly evacuated.

The film-forming chamber S12 is provided with: a substrate holding device S12a; a cathode electrode S12c (backing plate) having a target S12b functioning as a supply portion for supplying a film-forming material; and a power source S12d for applying negative pressure to the backing plate S12c. The sputtering voltage of the potential; the gas introduction device S12e, which introduces the gas into the film forming chamber S12; and the high vacuum exhaust device S12f such as a turbo molecular pump, which highly evacuates the interior of the film forming chamber S12.

The substrate holding device S12a holds the glass substrate 11 so as to face the target S12b during film formation with respect to the glass substrate 11 conveyed by the conveying device S11a, and can carry the glass substrate 11 into and out of the loading and unloading chamber S11 to the loading and unloading chamber S11. Unloading chamber S11.

The target S12b contains a material having a composition required to form a film on the glass substrate 11 .

In the manufacturing apparatus S10 shown in FIG. 3, the glass substrate 11 is carried into the inside of the manufacturing apparatus S10 by the loading/unloading chamber S11. After that, in the film-forming chamber S12 (vacuum processing chamber), the glass substrate 11 is formed into a film by sputtering. Then, the glass substrate 11 whose film formation is completed is carried out from the loading and unloading chamber S11 to the outside of the manufacturing apparatus S10.

In the film forming step, the sputtering gas and the reaction gas are supplied from the gas introduction device S12e to the film forming chamber S12, and a sputtering voltage is applied to the backing plate S12c (cathode electrode) from an external power source. In addition, a specific magnetic field may be formed on the target S12b by a magnetron magnetic circuit. In the film-forming chamber S12, the ions of the sputtering gas excited by the plasma collide with the target S12b of the cathode electrode S12c, and the particles of the film-forming material are ejected. Then, after the particles that fly out are combined with the reaction gas, they adhere to the glass substrate 11 , whereby a specific film is formed on the surface of the glass substrate 11 .

At this time, in the film forming step of the phase shift layer 12, the chemical resistant layer 14 and the low reflectivity layer 13, different amounts of nitrogen gas and oxygen-containing gas are supplied from the gas introduction device S12e to control the partial pressure of the gas. The amount of the gas is switched so that the composition of the phase shift layer 12 , the chemical resistant layer 14 , and the low reflectivity layer 13 is within the set range.

Here, as an oxygen-containing gas, _CO2 (carbon dioxide), _O2 (oxygen), _N2O (nitrous oxide), NO (nitrogen monoxide), etc. are mentioned.

Furthermore, in the film forming steps of the phase shift layer 12 , the chemical resistant layer 14 and the low reflectivity layer 13 , if necessary, the target S12 b can also be replaced.

Furthermore, in addition to the film formation of the phase shift layer 12 , the chemical-resistant layer 14 , and the low reflectance layer 13 , a laminate film laminated on these layers may also be formed into a film. In this case, sputtering conditions such as a target and a gas used for film formation of the laminated film can be adjusted, and the laminated film can be formed by sputtering, or another film forming method can be used. By forming the laminated film in this way, the mask base 10B of the present embodiment can be obtained.

Moreover, the manufacturing apparatus S20 shown in FIG. 4 is an in-line sputtering apparatus. The sputtering apparatus includes a loading chamber S21, a film forming chamber S22 (vacuum processing chamber) connected to the loading chamber S21 via a sealing portion S23, and an unloading chamber S25 connected to the film forming chamber S22 via a sealing portion S24.

The load chamber S21 is provided with a transfer device S21a that transfers the glass substrate 11 carried in from the outside to the film formation chamber S22, and an exhaust device S21b such as a rotary pump that roughly evacuates the inside of the load chamber S21.

The film-forming chamber S22 is provided with: a substrate holding device S22a; a cathode electrode S22c (backing plate) having a target S22b functioning as a supply portion for supplying a film-forming material; and a power source S22d for applying negative pressure to the backing plate S22c. The sputtering voltage of the potential; the gas introduction device S22e, which introduces the gas into the film formation chamber S22; and the high vacuum exhaust device S22f such as a turbo molecular pump, which highly evacuates the interior of the film formation chamber S22.

The substrate holding device S22a holds the glass substrate 11 so as to face the target S22b during film formation with respect to the glass substrate 11 conveyed by the conveying device S21a. Furthermore, the board|substrate holding apparatus S22a can carry in and carry out the glass substrate 11 from the loading chamber S21 to the unloading chamber S25.

The target S22b contains a material having a composition required to form a film on the glass substrate 11 .

The unloading chamber S25 is provided with: a transfer device S25a that transfers the glass substrate 11 carried in from the film forming chamber S22 to the outside; and an exhaust device S25b such as a rotary pump that roughly evacuates the inside of the unloading chamber S25.

In the manufacturing apparatus S20 shown in FIG. 4, the glass substrate 11 is carried into the inside of the manufacturing apparatus S20 through the loading chamber S21. After that, in the film-forming chamber S22 (vacuum processing chamber), the glass substrate 11 is formed into a film by sputtering. Then, the glass substrate 11 whose film formation is completed is carried out from the unloading chamber S25 to the outside of the manufacturing apparatus S20.

In the film forming step, the sputtering gas and the reaction gas are supplied from the gas introduction device S22e to the film forming chamber S22, and a sputtering voltage is applied to the backing plate S22c (cathode electrode) from an external power source. In addition, a specific magnetic field may be formed on the target S22b by a magnetron magnetic circuit. In the film-forming chamber S22, the ions of the sputtering gas excited by the plasma collide with the target S22b of the cathode electrode S22c, and the particles of the film-forming material are ejected. Then, after the particles that fly out are combined with the reaction gas, they adhere to the glass substrate 11 , whereby a specific film is formed on the surface of the glass substrate 11 .

At this time, in the film forming step of the phase shift layer 12, the chemical resistant layer 14 and the low reflectivity layer 13, different amounts of nitrogen gas and oxygen-containing gas are supplied from the gas introduction device S22e to control the partial pressure of the gas. The amount of the gas is switched so that the composition of the phase shift layer 12 , the chemical resistant layer 14 , and the low reflectivity layer 13 is within the set range.

Here, as an oxygen-containing gas, _CO2 (carbon dioxide), _O2 (oxygen), _N2O (nitrous oxide), NO (nitrogen monoxide), etc. are mentioned.

Furthermore, in the film forming steps of the phase shift layer 12 , the chemical resistant layer 14 , and the low reflectivity layer 13 , if necessary, the target S22 b can also be replaced.

Furthermore, in addition to the film formation of the phase shift layer 12 , the chemical-resistant layer 14 , and the low reflectance layer 13 , a laminate film laminated on these layers may also be formed into a film. In this case, sputtering conditions such as a target and a gas used for film formation of the laminated film can be adjusted, and the laminated film can be formed by sputtering, or another film forming method can be used. By forming the laminated film in this way, the mask base 10B of the present embodiment can be obtained.

Hereinafter, the film properties of the phase shift layer 12, the low reflectance layer 13, and the chemical-resistant layer 14 in this embodiment will be described.

Here, for the sake of explanation, the phase shift layer 12 , the low reflectance layer 13 and the chemical resistant layer 14 are made of films containing MoSi, but the present invention is not limited thereto.

In the phase shift layer 12 , the low reflectivity layer 13 and the chemical resistant layer 14 which are the low reflection phase shift films of the present embodiment, the nitrogen concentration in the low reflectivity layer 13 is set lower than that in the phase shift layers 12 and 14 . The nitrogen concentration of the chemical resistant layer 14 .

Specifically, the low reflectance layer 13 is formed by changing the N ₂ partial pressure during film formation by sputtering, for example, forming a MoSi film with a nitrogen concentration of 30% or less.

The chemical-resistant layer 14 is formed by changing the N ₂ partial pressure during film formation by sputtering, for example, forming a MoSi film with a nitrogen concentration of 40% or more.

The phase shift layer 12 is formed into a MoSi film with a nitrogen concentration of 40% or more by changing the N ₂ partial pressure during film formation by sputtering. In addition, in order to function as a desired phase shifter, the phase shift layer 12 can be set to a nitrogen partial pressure different from that of the chemical resistant layer 14 .

In addition, in the phase shift layer 12 , the low reflectivity layer 13 and the chemical resistant layer 14 which are the low reflection phase shift films of the present embodiment, the oxygen concentration in the low reflectivity layer 13 is set higher than that in the phase shift layer 12 and the nitrogen concentration of the chemical resistant layer 14.

Specifically, the low reflectance layer 13 is formed by changing the partial pressure of CO ₂ as an oxygen-containing gas during film formation by sputtering, for example, forming a MoSi film with an oxygen concentration of 30% or more.

The chemical-resistant layer 14 is formed by changing the partial pressure of CO ₂ , which is an oxygen-containing gas, during film formation by sputtering, for example, forming a MoSi film with an oxygen concentration of 30% or less.

The phase shift layer 12 is formed by changing the partial pressure of CO ₂ , which is an oxygen-containing gas, during film formation by sputtering, for example, forming a MoSi film with an oxygen concentration of 30% or less. In addition, in order to function as a desired phase shifter, the phase shift layer 12 can be set to a different oxygen-containing gas partial pressure from the chemical resistant layer 14 .

Here, changes in film properties due to changes in the contents of nitrogen and oxygen were verified.

First, the change in transmittance caused by the change in nitrogen content was verified. As an example, the composition ratio change of the MoSi film monolayer when the N ₂ partial pressure during film formation by sputtering is changed is shown in Table 1. (Table 1)

As shown in Table 1, it can be seen that when the composition ratio of nitrogen is changed, the transmittance is changed accordingly. In the phase shift layer 12 , the low reflectance layer 13 , and the chemical-resistant layer 14 which are the low-reflection phase shift films of the present embodiment, the phase shift films can be set so as to have specific transmittances by taking advantage of this.

Next, the chemical resistance resulting from changes in nitrogen content was verified.

FIG. 5 is a graph showing the N ₂ /Ar gas ratio dependence of transmittance change after NaOH treatment in the low-reflection phase shift film of the present embodiment, and FIG. 6 is a graph of the low-reflection phase shift film of the present embodiment. Fig. 7 is a graph showing the _CO2 concentration dependence of transmittance change after NaOH treatment in the low reflection phase shift film of the present embodiment.

As an example, in the MoSi film monolayer when the partial pressure of N ₂ gas by sputtering was changed as described above, the change in transmittance at 405 nm before and after the alkaline solution treatment was examined.

Here, the treatment conditions were changed to NaOH concentration of 5%, temperature of 40°C, and immersion time of 15 to 60 minutes. In addition, the gas conditions at the time of film formation were represented by the flow ratio of N ₂ : Ar corresponding to the N ₂ partial pressure in Table 1.

From this result, as shown in Fig. 5 and Fig. 6 , when the nitrogen partial pressure changes from 100% to 0%, the nitrogen partial pressure dependence is as follows: the change in the film thickness after the NaOH treatment As the nitrogen partial pressure becomes smaller, the transmittance change at 405 nm becomes larger.

Therefore, it can be seen that when the nitrogen concentration is 40 atm% or more, the change in film thickness and the nitrogen concentration dependence can be almost ignored in the transmittance change at 405 nm.

Next, the chemical resistance caused by the change in the partial pressure of CO ₂ gas was verified.

As an example, the composition ratio change of the MoSi film monolayer when the CO ₂ partial pressure during film formation by sputtering is changed is shown in Table 2. Here, the N ₂ partial pressure and the Ar partial pressure were set to 10:0, and only the CO ₂ partial pressure was changed to a flow rate of 1 to 10 sccm. (Table 2)

Next, in the MoSi film monolayer when the partial pressure of the CO ₂ gas by sputtering was changed as described above, the change of the transmittance at 405 nm before and after the alkaline solution treatment was examined.

Here, the treatment conditions were changed to NaOH concentration of 5%, temperature of 40°C, and immersion time of 15 to 60 minutes.

From this result, as shown in FIG. 7 , when the partial pressure of CO ₂ gas was changed only to a flow rate of 1 to 10 sccm, it was found that the oxygen dependence was as follows _: As the flow rate becomes larger, the transmittance change at 405 nm becomes larger.

Therefore, when the oxygen concentration in the chemical-resistant layer 14 is low, it can be seen that there is a film thickness change and oxygen concentration dependence that can substantially ignore the transmittance change at 405 nm.

Next, the wavelength dependence is verified.

FIG. 8 is a graph showing the wavelength dependence of the refractive index in the phase shift film of the present embodiment, and FIG. 9 is a graph showing the wavelength dependence of the extinction coefficient in the phase shift film of the present embodiment.

As an example, the wavelength dependence of the refractive index and the extinction coefficient was examined in the MoSi film monolayer when the partial pressure of the CO ₂ gas by sputtering was changed as described above.

From this result, as shown in Fig. 8, when the CO ₂ gas flow rate is changed from 1 sccm to 10 sccm, the CO ₂ gas flow rate dependence is as follows: as the CO ₂ gas flow rate increases, the refraction at each wavelength increases. The rate change becomes smaller, and, as shown in FIG. 9, the extinction coefficient becomes smaller.

Next, verify the spectral reflectance change.

FIG. 10 is a graph showing the relationship between the spectral reflectance and the film thickness characteristics of the chemical resistant layer/low reflectance layer in the phase shift film of the present embodiment, and FIG. 11 is a graph showing the phase shift film of the present embodiment. A graph of the relationship between the spectral reflectance and the film thickness characteristics of the chemical resistant layer/low reflectance layer.

As an example, in the low reflectivity layer 13 and the chemical-resistant layer 14 including MoSi, it was checked that the film thickness of the chemical-resistant layer 14 was changed to 0 nm to 20 nm and the film thickness of the low reflectivity layer 13 was changed to 0 Film thickness dependence of spectral reflectance at 405 nm at nm or 40 nm.

The results are shown in FIG. 10 .

In the figure, A: the thickness of the chemical-resistant layer/B: the thickness of the low-reflectance layer is shown.

Furthermore, the nitrogen concentration in the low reflectivity layer 13 at this time was 29.5 atm% (the partial pressure of N ₂ gas during film formation was 30%), and the oxygen concentration in the low reflectivity layer 13 was 23.0 atm% (CO during film formation). ₂ Gas flow rate 5 sccm), the nitrogen concentration in the chemical-resistant layer 14 is 49.9 atm% ( _N2 partial pressure during film formation is 100%), and the oxygen concentration in the chemical-resistant layer 14 is 9.9 atm% (CO during film formation). ₂ gas flow 0 sccm).

In the lamination of these MoSi films, only the nitrogen concentration can be switched, and the gas can be continuously supplied, or as a different sputtering step, the partial pressure of nitrogen gas and CO ₂ gas can be switched when the lamination reaches a specific film thickness. flow.

From this result, in the chemical-resistant layer 14 and the low-reflectance layer 13, the spectral reflectance has the profile which becomes convex downward in the vicinity of 400 nm at each film thickness.

Here, by changing the film thicknesses of the chemical-resistant layer 14 and the low-reflectance layer 13, the wavelength at which the reflectance profile becomes convex downward can be set to a range from around 400 nm to around 500 nm.

Similarly, in the low reflectivity layer 13 and the chemical-resistant layer 14 including MoSi, it was checked that the film thickness of the chemical-resistant layer 14 was changed to 0 nm to 20 nm and the film thickness of the low reflectivity layer 13 was changed to 0. Film thickness dependence of spectral reflectance at 405 nm from nm to 55 nm.

The results are shown in FIG. 11 .

In the figure, A: the thickness of the chemical-resistant layer/B: the thickness of the low-reflectance layer is shown.

Furthermore, the nitrogen concentration in the low reflectivity layer 13 at this time was 29.5 atm% (the partial pressure of N ₂ gas during film formation was 30%), and the oxygen concentration in the low reflectivity layer 13 was 23.0 atm% (CO during film formation). ₂ Gas flow rate 5 sccm), the nitrogen concentration in the chemical-resistant layer 14 is 49.9 atm% ( _N2 partial pressure during film formation is 100%), and the oxygen concentration in the chemical-resistant layer 14 is 9.9 atm% (CO during film formation). ₂ gas flow 0 sccm).

From this result, it can be seen that in the chemical-resistant layer 14 and the low-reflectance layer 13, at each film thickness, the spectral reflectance has a convex profile around 400 nm. The thickness of the reflectance layer 13 can be set so that the wavelengths that are convex under the reflectance profile are concentrated in the vicinity of 400 nm.

In this way, it can be seen that the reflectance can be reduced in a desired wavelength region by using the embodiment of the present invention.

In the present embodiment, the N ₂ partial pressure and the CO ₂ partial pressure can be controlled during the film formation of the MoSi-containing phase shift layer 12 , the low reflectivity layer 13 and the chemical resistant layer 14 , and the film thickness thereof can be controlled. Then, a photomask substrate 10B and a phase-shift photomask 10 having a low-reflection phase-shift film with low reflectivity and high chemical resistance are manufactured.

In addition, the photomask substrate 10B and the phase shift photomask 10 can be manufactured as follows. In the cleaning step, the photomask substrate 10B, the phase shift mask 10B and the phase shift mask 10 are decomposed with an acidic or alkaline chemical solution in order to remove contaminants that affect the optical characteristics. When the photomask 10 is cleaned, the tolerance is high, and the variation of the film thickness and the variation of the reflectance and transmittance associated therewith are small.

In the mask substrate 10B and the phase shift mask 10 used to manufacture the FPD element of the present embodiment, the phase shift layer 12 including MoSi, the low reflectivity layer 13 and the chemical resistance are formed into the low reflection phase shift film. The product layer 14 is switched to control the N ₂ partial pressure, the CO ₂ partial pressure, and the film thickness during film formation. Only by performing such control, the phase shift layer 12, the low reflectance layer 13 and the chemical resistance layer including MoSi can be used in the wavelength band and its vicinity from at least the i-line to the g-line radiated from the ultra-high pressure mercury lamp. In 14, the peak that can reduce the reflectivity the most (the convex profile in Fig. 10 and Fig. 11) is controlled so that it is near 405 nm. Thereby, it becomes a phase shifter which has the phase shift energy which can reduce a reflectance in a specific wavelength band.

In the mask substrate 10B and the phase shift mask 10 used to manufacture the FPD element of the present embodiment, the phase shift layer 12 including MoSi, the low reflectivity layer 13 and the chemical resistance are formed into the low reflection phase shift film. The material of the product layer 14 is not limited to MoSi-based materials including Mo and Si. Examples of the material include metals and silicon (MSi, M: transition metals such as Mo, Ni, W, Zr, Ti, Cr, etc.), oxynitride metals and silicon (MSiON), and carbon-oxygenated metals and silicon ( MSiCO), metal and silicon oxycarbonitride (MSiCON), metal and silicon oxide (MSiO), metal and silicon nitride (MSiN), etc. In addition, metals such as Ta, Ti, W, Mo, and Zr, or alloys of these metals, or alloys of these metals and other metals (as other metals, Cr and Ni are exemplified), or those containing metals or alloys and silicon materials.

The mask substrate 10B and the phase shift mask 10 for manufacturing the FPD element of this embodiment may have a light shielding layer. In this case, the material of the light-shielding layer may be, for example, a material having a different etching property from that of the low-reflection phase shift film, and when the metal constituting the low-reflection phase shift film is molybdenum, it is preferably chromium or chromium Oxides of chromium, nitrides of chromium, carbides of chromium, fluorides of chromium, and materials containing at least one of these. Similarly, when the translucent film includes a chromium nitride film-based material, it is preferably chromium, or chromium oxide, chromium carbide, chromium fluoride, or a material containing at least one of these. .

As the structure of the light-shielding layer, a type of placing the light-shielding layer on the outer side of the low-reflection phase shift film relative to the glass substrate 11 can be adopted, or the light-shielding layer can be placed on the inner side and below the low-reflection phase shift film. type. Furthermore, at this time, an etching stopper layer may also be provided between the light shielding layer and the low reflection phase shift film.

The mask substrate 10B and the phase shift mask 10 used to manufacture the FPD element of the present embodiment can be changed into the phase shift layer 12 , the low reflectivity layer 13 and the chemical resistance layer 14 of the low reflection phase shift film only by changing Manufactured with the nitrogen concentration and oxygen concentration. Therefore, the photomask substrate 10B and the phase shift photomask 10 can be manufactured only by supplying the atmosphere gas with a predetermined concentration (specific flow rate ratio) during sputtering. Thereby, the nitrogen concentration and the oxygen concentration in the in-plane direction in the low-reflection phase shift film can be easily made uniform, and the variation in the in-plane direction of reflectance, transmittance, and phase shift energy can be suppressed.

Furthermore, in this embodiment, the nitrogen concentration and the oxygen concentration of the phase shift layer 12 , the low reflectance layer 13 , and the chemical resistant layer 14 may be changed in the film thickness direction. In this case, if a high nitrogen concentration is maintained on the outermost surface (outer position) in order to maintain chemical resistance, the film thickness, nitrogen concentration, and oxygen concentration can maintain specific reflectance, transmittance, and phase shift. Appropriate changes can be made. Example

Hereinafter, examples of the present invention will be described.

<Example 1> On a large glass substrate (synthetic quartz (QZ) 10 mm thick, size 850 mm×1200 mm), a low reflection phase shift mask film was formed using a large inline sputtering apparatus. Specifically, a MoSi film was formed by using a MoSi _X target with an X value of 2.3, and using Ar gas and N ₂ gas as sputtering gases. At this time, the nitrogen partial pressure was changed as shown in Table 1, and the nitrogen concentration was changed stepwise to 44.9 atm% (Experiment 1), 40.8 atm% (Experiment 2), 29.5 atm% (Experiment 3), 7.2 atm% (Experimental Example 4), and a plurality of samples were produced.

The results of the change in transmittance at 405 nm before and after the NaOH solution treatment for the membrane inspection of the above-mentioned Experimental Examples 1 to 4 are shown in FIGS. 5 and 6 .

Here, the treatment conditions were changed to NaOH concentration of 5%, temperature of 40°C, and immersion time of 15 to 60 minutes. In addition, the gas conditions at the time of film formation were represented by the flow ratio of N ₂ : Ar corresponding to the N ₂ partial pressure in Table 1.

<Example 2> Next, in the same manner as in the above-mentioned Experimental Examples 1 to 4, a MoSi film was formed using Ar gas, N ₂ gas, and CO ₂ gas as sputtering gases. At this time, the flow rate of CO ₂ gas was changed as shown in Fig. 7, and the oxygen concentration was changed stepwise to 9.9 atm% (Experimental Example 5), 12.7 atm% (Experimental Example 6), 18.0 atm% (Experimental Example 7), 34.7 atm% (Experimental Example 8) and 47.1 atm% (Experimental Example 9), and a plurality of samples were produced.

FIG. 7 shows the results of the change in transmittance at 405 nm before and after the NaOH solution treatment for the membrane inspection of the above-mentioned Experimental Examples 5 to 9.

Here, the treatment conditions were changed to NaOH concentration of 5%, temperature of 40° C., and immersion time of 15 to 60 minutes in the same manner as in the above-mentioned Experimental Examples 1 to 4. In addition, the gas conditions at the time of film formation were represented by the flow ratio of N ₂ : Ar corresponding to the N ₂ partial pressure in Table 1.

Furthermore, the results of examining the wavelength dependence of the refractive index and the extinction coefficient for the films of the above-mentioned Experimental Examples 5 to 9 are shown in FIGS. 8 and 9 .

From these results, it can be seen that the chemical resistance, transmittance, and refractive index change depending on the oxygen concentration in the MoSi film.

Next, in order to examine the influence of C (carbon) in the CO ₂ gas as the oxygen-containing film-forming gas, the films of the above-mentioned Experimental Examples 5 to 9 were analyzed for the composition ratios containing C. The results are shown in Table 3. (table 3)

From these results, it appears from the data that the carbon concentration does not have a significant effect on the chemical resistance properties. Moreover, even if it contains carbon, it turns out that it can function as an antireflection film.

<Example 3> Next, as in Example 2, a MoSi film having a nitrogen concentration of 49.5 atm% and an oxygen concentration of 6.69 atm%, and a nitrogen concentration of 29.5 atm% and an oxygen concentration of 36.77 atm% were laminated in the film thickness direction. MoSi film and three layers of MoSi film with nitrogen concentration of 49.5 atm% and oxygen concentration of 6.69 atm%. At this time, the nitrogen concentration of the layer on the glass substrate side is increased and the oxygen concentration is decreased, after the start of film formation, after the MoSi film becomes a specific film thickness, the N ₂ gas partial pressure and the CO ₂ gas partial pressure of the introduced gas are switched. The nitrogen partial pressure was increased in such a way that the N ₂ gas partial pressure concentration of the uppermost layer had the chemical resistance in Example 2 to form a film.

In addition, in the state where MoSi films having different nitrogen and oxygen concentrations are stacked, the film thickness of the uppermost high nitrogen concentration film is A, and the film thickness of the second high oxygen concentration MoSi film is B, A/B was changed to 0 nm/0 nm (Experimental Example 10), 0 nm/40 nm (Experimental Example 11), 5 nm/40 nm (Experimental Example 12), 10 nm/40 nm (Experimental Example 13), 15 nm/40 nm (Experimental Example 14), 20 nm/40 nm (Experimental Example 15).

FIG. 10 shows the results of examining the wavelength dependence of spectral reflectance for the films of Experimental Examples 10 to 15 described above.

Similarly, when MoSi films having different nitrogen and oxygen concentrations are stacked, and the film thickness of the uppermost high nitrogen concentration film is A, and the film thickness of the second high oxygen concentration MoSi film is B , change A/B to 0 nm/0 nm (Experimental Example 10), 0 nm/40 nm (Experimental Example 11), 5 nm/35 nm (Experimental Example 16), 10 nm/30 nm (Experimental Example 17) , 15 nm/15 nm (Experimental Example 18), 20 nm/10 nm (Experimental Example 19).

FIG. 11 shows the results of examining the wavelength dependence of spectral reflectance for the films of Experimental Examples 10 to 15 described above.

From these results, it can be seen that by changing the nitrogen concentration and oxygen concentration in the MoSi film in the thickness direction and adjusting the film thickness, the spectral reflectance profile in the laminated film relative to the film thickness of the uppermost high nitrogen concentration film become convex.

Here, by changing the nitrogen concentration and the oxygen concentration in the MoSi film in the thickness direction, the wavelength at which the reflectance profile becomes convex downward can be set to a range from around 400 nm to around 500 nm.

In addition, by changing the nitrogen concentration and oxygen concentration in the MoSi film in the thickness direction, and adjusting the film thickness, it can be set so that the wavelength that becomes convex under the reflectance profile is concentrated in the vicinity of 400 nm.

In this way, it can be seen that by using the phase shift mask of the present invention, the reflectance can be reduced in a desired wavelength region. [Industrial Availability]

As an application example of the present invention, it can be used for all masks required for the manufacture of LCD or organic EL displays. For example, it can be applied to a photomask for manufacturing a TFT (Thin-film Transistor, thin film transistor) or a color filter.

10‧‧‧Phase Shift Mask 10B‧‧‧ Mask Base 11‧‧‧Glass Substrate (Transparent Substrate) 12‧‧‧Phase Shift Layer 13‧‧‧Low Reflectance Layer 14‧‧‧Chemical Resistant Layer 12P, 13P, 14P‧‧‧phase shift pattern S10‧‧‧film forming device (sputtering device) S11‧‧‧loading and unloading chamber S11a‧‧‧transferring device (transferring robot) S11b‧‧‧exhaust device S12 ‧‧‧Film forming chamber (chamber) S12a‧‧‧Substrate holding device S12b‧‧‧Target S12c‧‧‧Backing plate (cathode electrode) S12d‧‧‧Power supply S12e‧‧‧Gas introduction device S12f‧‧‧High Vacuum Evacuation Device S13‧‧‧Sealed Part S20‧‧‧Film Forming Device (Sputtering Device) S21‧‧‧Loading Chamber S21a‧‧‧Transportation Device (Transfer Robot) S21b‧‧‧Exhaust Device S22‧‧‧Complete Film chamber (chamber) S22a‧‧‧Substrate holding device S22b‧‧‧Target S22c‧‧‧Backing plate (cathode electrode) S22d‧‧‧Power supply S22e‧‧‧Gas introduction device S22f‧‧‧High vacuum exhaust device S23‧‧‧Closed part S24‧‧‧Closed part S25‧‧‧Unloading chamber S25a‧‧‧Transportation device (transport robot) S25b‧‧‧Exhaust device

FIG. 1 is a cross-sectional view showing a mask base according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view showing a phase shift mask according to the first embodiment of the present invention. 3 is a schematic view showing a film-forming apparatus in the method of manufacturing a mask substrate and a phase-shift mask according to the first embodiment of the present invention. FIG. 4 is a schematic view showing a film forming apparatus in a method of manufacturing a mask substrate and a phase shift mask according to the first embodiment of the present invention. 5 is a graph showing the N ₂ change in transmittance after NaOH treatment in the mask substrate, the phase-shift mask, the method for manufacturing the mask substrate, and the method for manufacturing the phase-shift mask according to the first embodiment of the present invention Graph of the dependence of /Ar gas ratio. 6 is a graph showing the nitrogen concentration dependence of transmittance change after NaOH treatment in the mask substrate, the phase shift mask, the method for manufacturing the mask substrate, and the method for manufacturing the phase shift mask according to the first embodiment of the present invention Sex Graph. 7 is a graph showing the CO ₂ concentration of the transmittance change after NaOH treatment in the mask substrate, the phase shift mask, the manufacturing method of the mask substrate, and the manufacturing method of the phase shift mask according to the first embodiment of the present invention Dependency graph. 8 is a graph showing the wavelength dependence of the refractive index in the mask base, the phase-shift mask, the method for manufacturing the mask base, and the method for manufacturing the phase-shift mask according to the first embodiment of the present invention. 9 is a graph showing wavelength dependence of extinction coefficients in a mask base, a phase-shift mask, a method for manufacturing a mask base, and a method for manufacturing a phase-shift mask according to the first embodiment of the present invention. 10 shows the spectral reflectance and chemical resistance layer/low level in the photomask substrate, the phase shift photomask, the method for manufacturing the photomask substrate, and the method for manufacturing the phase shifting photomask according to the first embodiment of the present invention Graph of the relationship between the film thickness characteristics of the reflectivity layer. 11 shows the spectral reflectance and chemical resistance layer/low level in the photomask substrate, the phase shift photomask, the method of manufacturing the photomask substrate, and the method of manufacturing the phase shifted photomask according to the first embodiment of the present invention Graph of the relationship between the film thickness characteristics of the reflectivity layer.

10B‧‧‧Reticle Base

11‧‧‧Glass substrate (transparent substrate)

12‧‧‧Phase Shift Layer

13‧‧‧Low reflectivity layer

14‧‧‧Chemical resistant layer

Claims (15)

A photomask substrate, which has a layer to become a phase shift photomask, and has: a phase shift layer and a low reflectivity layer, which are layered on a transparent substrate; The offset layer and the low reflectivity layer are farther away from the transparent substrate, and the chemical resistance is improved; the nitrogen content in the chemical resistance layer is set to be higher than the nitrogen content in the low reflectivity layer; the above The nitrogen content of the chemical-resistant layer is set to 36 atm% or more. The photomask substrate of claim 1, wherein the oxygen content of the low reflectivity layer is set higher than the oxygen content of the chemical-resistant layer. The photomask substrate according to claim 1 or 2, wherein in the chemical-resistant layer and the low-reflectivity layer, the spectral reflectance has a profile that is convex downward at around 400 nm. The photomask substrate according to claim 1 or 2, wherein, in the low reflectivity layer, the refractive index at a wavelength of 405 nm is set to be 2.2 or less. The photomask substrate according to claim 1 or 2, wherein, in the chemical-resistant layer, the refractive index at a wavelength of 405 nm is set to be 2.4 or more. The photomask substrate according to claim 1 or 2, wherein the chemical-resistant layer and the low-reflectivity layer comprise silicide. The photomask substrate according to claim 1 or 2, wherein the nitrogen content of the low reflectivity layer is set to 35 atm% or less, and the oxygen content is set to 30 atm% or more. The photomask substrate according to claim 1 or 2, wherein the chemical-resistant layer has a film thickness of 15 nm or less. The photomask substrate according to claim 1 or 2, wherein, in the phase shift layer, the refractive index at a wavelength of 405 nm is set to be 2.4 or more. The photomask substrate according to claim 1 or 2, wherein the nitrogen content of the phase shift layer is set to 36 atm% or more. A phase shift reticle fabricated using the reticle substrate of any one of claims 1 to 10. A method for manufacturing a photomask substrate, which is the method for manufacturing a photomask substrate as claimed in any one of claims 1 to 10, wherein the chemical-resistant layer and the low-reflectivity layer are formed by adding nitrogen gas to the film. Can't press same. The method for manufacturing a photomask substrate according to claim 12, wherein the partial pressure of the oxygen-containing gas is different during the film formation of the chemical-resistant layer and the low-reflection layer. A method for manufacturing a phase shift mask, which is the method for manufacturing a phase shift mask as claimed in claim 11, wherein the partial pressure of nitrogen gas is different during film formation of the chemical resistant layer and the low reflectivity layer . The manufacturing method of the phase shift mask of claim 14, wherein the partial pressure of the oxygen-containing gas is made different when the chemical resistant layer and the low reflectance layer are formed.

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