CN112558408A

CN112558408A - Mask blank, method for manufacturing mask blank, photomask, and method for manufacturing photomask

Info

Publication number: CN112558408A
Application number: CN202010933261.4A
Authority: CN
Inventors: 诸沢成浩
Original assignee: Afac Film Co ltd
Current assignee: Afac Film Co ltd
Priority date: 2019-09-10
Filing date: 2020-09-08
Publication date: 2021-03-26
Also published as: TW202115484A; JP2021043307A; TWI761942B; KR20210030881A; KR102503133B1; JP7303077B2

Abstract

The present invention relates to a mask blank, a method for manufacturing the mask blank, a photomask, and a method for manufacturing the photomask. The mask blank of the present invention has a layer as a phase shift mask, and the mask blank has: a phase shift layer laminated on the transparent substrate; an antireflection layer provided at a position farther from the transparent substrate than the phase shift layer; and an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer. The phase shift layer contains chromium, the antireflection layer contains molybdenum silicide and oxygen, and the adhesion layer contains chromium and oxygen, and the oxygen content is set so as to have adhesion to the photoresist layer that can be patterned.

Description

Mask blank, method for manufacturing mask blank, photomask, and method for manufacturing photomask

Technical Field

The present invention relates to a mask blank, a method for manufacturing a mask blank, a photomask and a method for manufacturing a photomask, and particularly to a technique suitable for use in a phase shift mask.

Background

With high definition of FPDs (flat panel displays), demand for forming fine patterns is increasing. Therefore, not only a Mask of a light-shielding film that has been used conventionally but also a Phase-shift Mask (PSM Mask) of an edge enhancement type is used.

In these phase shift masks, the reflectivity is generally high. In this case, since the influence of standing waves becomes large at the time of resist exposure at the time of mask formation, the variation in line width of the mask pattern becomes large. Therefore, it is preferable to reduce the reflectance of the phase shift mask (patent document 1).

In order to reduce the reflectivity of the phase shift mask, it is necessary to form a layer having a lower refractive index than the mask lower layer on the upper layer of the phase shift mask and to reduce the reflectivity using an optical interference effect.

In addition, a chromium material is generally used as the phase shift layer in the mask blank. In this case, an oxidized chromium oxide film may be used to obtain a film having a low refractive index as an antireflection layer.

Patent document 1: international publication No. 2004/070472

However, the etching rate of the chromium oxide film having a high oxygen concentration is lowered. As a result, when a chromium oxide film having a high oxygen concentration is used as the anti-reflective layer, the anti-reflective layer is not etched because the etch rate is lower than that of the phase shift layer.

Therefore, when a mask pattern is formed, there is a problem that etching of the phase shift layer proceeds as compared with the anti-reflection layer, and the sectional shape of the overhang is formed.

As a method of achieving both low reflectance and a good cross-sectional shape, a method of using an antireflection layer, for example, a metal silicide film such as a molybdenum silicide film, when the phase shift layer is formed of a material containing chromium as a main component is conceivable. By forming the phase shift layer and the antireflection layer using different materials, respectively, when etching one material, the other material is not etched, so that the etching process can be selectively performed, and as a result, a favorable cross-sectional shape can be obtained.

However, a silicide film such as a molybdenum silicide film has a hydrophilic property. Therefore, when a resist is applied to form a pattern, a problem is found that adhesion between the silicide film and the resist is deteriorated.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and achieves the following objects: a mask blank and a photomask are provided which have an antireflection layer capable of suppressing etching of other layers with a high selectivity ratio while achieving a low reflectance, and which have good adhesion to a resist and can form a reliable pattern.

The mask blank of the present invention is a mask blank having a layer as a phase shift mask, and has: a phase shift layer laminated on the transparent substrate; an antireflection layer provided at a position farther from the transparent substrate than the phase shift layer; and an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer. The phase shift layer contains chromium, the antireflection layer contains molybdenum silicide and oxygen, and the adhesion layer contains chromium and oxygen, and the oxygen content of the adhesion layer is set so as to have adhesion to the photoresist layer in which a pattern can be formed. Thus, the above problems are solved.

In the mask blank of the present invention, the oxygen content of the adhesion layer is set to be in a range of 8.4 atomic% to 65.7 atomic%.

In the present invention, it is preferable that the adhesion layer contains nitrogen, and the nitrogen content of the adhesion layer is set to be in a range of 3.7 atomic% to 42.3 atomic%.

The mask blank of the present invention is characterized in that the adhesion layer contains carbon, and the carbon content of the adhesion layer is set in the range of 2.2 atomic% to 2.3 atomic%.

In the mask blank of the present invention, the chromium content of the adhesion layer is set in a range of 25.2 atomic% to 42.4 atomic%.

In the mask blank of the present invention, the thickness of the adhesion layer is set to be in the range of 5nm to 15 nm.

In the mask blank of the present invention, the oxygen content of the antireflective layer is set in a range of 6.7 atomic% to 63.2 atomic%.

The mask blank of the present invention is characterized in that the anti-reflection layer contains nitrogen, and the nitrogen content of the anti-reflection layer is set to be in the range of 4.6 atomic% to 39.3 atomic%.

The mask blank of the present invention has a photoresist layer provided at a position farther from the transparent substrate than the bonding layer.

A method for manufacturing a mask blank according to the present invention is a method for manufacturing a mask blank according to any one of the above methods, including: a phase shift layer forming step of laminating the phase shift layer containing chromium on the transparent substrate; an antireflection layer forming step of laminating the antireflection layer containing molybdenum silicide and oxygen at a position farther from the transparent substrate than the phase shift layer; and an adhesion layer forming step of laminating the adhesion layer containing chromium and oxygen at a position farther from the transparent substrate than the antireflection layer, wherein the adhesion layer is formed so as to have adhesion to the photoresist layer so as to be able to form a pattern by setting a partial pressure of an oxygen-containing gas as a supply gas during sputtering.

In the method for producing a mask blank according to the present invention, in the adhesion layer forming step, the partial pressure of the oxygen-containing gas is set so that the adhesion in the adhesion layer increases with an increase in the oxygen content.

In the method for producing a mask blank according to the present invention, it is preferable that the partial pressure ratio of the oxygen-containing gas in the adhesion layer forming step is set to be in the range of 0.00 to 0.30.

In the method for manufacturing a mask blank according to the present invention, in the adhesion layer forming step, the oxygen-containing gas is set to NO.

The photomask of the present invention is produced from the mask blank according to any one of the above.

The method for manufacturing a photomask of the present invention is a method for manufacturing the photomask, and includes: a phase shift pattern forming step of forming a pattern on the phase shift layer; an antireflection pattern forming step of forming a pattern on the antireflection layer; and a bonding pattern forming step of forming a pattern on the bonding layer, wherein an etching solution in the phase shift pattern forming step and the bonding pattern forming step is different from an etching solution in the antireflection pattern forming step.

The mask blank of the present invention is a mask blank having a layer as a phase shift mask, and has: a phase shift layer laminated on the transparent substrate; an antireflection layer provided at a position farther from the transparent substrate than the phase shift layer; and an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer. The phase shift layer contains chromium, the antireflection layer contains molybdenum silicide and oxygen, and the adhesion layer contains chromium and oxygen, and the oxygen content of the adhesion layer is set so as to have adhesion to the photoresist layer in which a pattern can be formed.

Thus, in a mask blank having an antireflection layer originally containing molybdenum silicide having poor adhesion to a photoresist layer, the mask blank has sufficient adhesion to the photoresist layer by having an adhesion layer in contact with the photoresist layer, and can realize desired patterning. In this case, the value of the refractive index in the antireflection layer can be set by the set oxygen content in the antireflection layer, based on a curve in which the value of the refractive index in the antireflection layer decreases with an increase in the oxygen content in the antireflection layer.

Here, as the adhesion layer, a chromium compound is preferably used. The chromium compound has a strong chemical resistance to acid and alkali solutions and a hydrophobic property. Therefore, a chromium compound is suitably used at the interface of the adhesion layer and the resist.

As the antireflection layer, molybdenum silicide is preferably used among metal silicides. This is because molybdenum silicide is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide water which is generally used for mask cleaning, and optical characteristics can be controlled greatly by controlling the nitrogen and oxygen concentrations contained in molybdenum silicide.

In addition, the refractive index and extinction coefficient in the antireflection layer can be set according to the oxygen content in the antireflection layer.

In addition, as the phase shift layer, a chromium compound is preferably used. The phase shift film (mask layer) can be formed using two materials, a chromium compound and a metal silicide, which have high chemical resistance.

According to these, the refractive index of the anti-reflection layer can be set to a predetermined value while maintaining the necessary adhesiveness, and the anti-reflection layer having a lower refractive index than the phase shift layer can be used, so that the reflectance of the mask blank can be reduced. Meanwhile, since the adhesion layer and the phase shift layer contain chromium and the antireflection layer contains molybdenum silicide, when they are patterned by etching, different etchants (etching solutions) can be used, respectively, as etching rates different from each other, and high selectivity is exhibited. Therefore, it is possible to provide a mask blank capable of manufacturing a phase shift mask having a preferable cross-sectional shape without affecting each other in etching of the phase shift layer, the antireflection layer, and the adhesion layer.

Here, in the mask blank of the present invention, the reflectance as the mask blank is reduced. For this reason, it is important to increase the difference between the refractive index and the extinction coefficient between the anti-reflection layer and the phase shift layer, while setting the optical constants of the adhesion layer and the anti-reflection layer to be close to each other. Therefore, in order to reduce the reflectance of the mask blank, it is preferable to reduce the values of the refractive index and extinction coefficient of the adhesion layer and the antireflection layer.

This makes it possible to provide the adhesion layer with sufficient adhesion to the photoresist layer and maintain the state of having optical characteristics required as a mask layer. In particular, in the adhesion layer, increasing the oxygen content can reduce the hydrophilicity and improve the hydrophobicity, thereby improving the adhesion to the photoresist. In addition, in the adhesion layer, the values of the refractive index and the extinction coefficient can be reduced by increasing the oxygen content.

In the present invention, the adhesion layer contains nitrogen, and the nitrogen content of the adhesion layer is set to be in a range of 3.7 atomic% to 42.3 atomic%.

This makes it possible to provide the adhesion layer with sufficient adhesion to the photoresist layer. In addition, a preferable mask blank can be set to have a predetermined etching rate while maintaining a state in which the optical characteristics as a mask layer set together with other layers are not affected. In particular, by increasing the nitrogen content of the adhesion layer, the values of the refractive index and the extinction coefficient can be reduced.

Further, in the chromium compound used in the adhesion layer, the values of the refractive index and the extinction coefficient can be further reduced by increasing both the oxygen concentration and the nitrogen concentration in the chromium compound.

In the mask blank of the present invention, the adhesion layer contains carbon, and the carbon content of the adhesion layer is set in a range of 2.2 atomic% to 2.3 atomic%.

This makes it possible to provide the adhesion layer with sufficient adhesion to the photoresist layer. In addition, a desired mask blank can be set, which has a predetermined etching rate while maintaining a state that does not affect the optical characteristics of the mask layer set together with the other layers.

As the adhesion layer, a chromium compound is preferably used. The chromium compound has a strong chemical resistance to acid and alkali solutions and a hydrophobic property. Therefore, a chromium compound is suitably used at the interface of the adhesion layer and the resist.

Thus, in the antireflection layer, the refractive index at a wavelength of 365nm to 436nm can be set to a value in the range of 2.5 to 1.8.

This makes it possible to provide an antireflection layer having a refractive index lower than that of the phase shift layer containing chromium, and to reduce the reflectance of the mask blank.

Therefore, the reflectance of the antireflection layer can be reduced, and the mask layer can have a low reflectance in a wavelength band from g-line (436nm) to i-line (365nm), for example, while maintaining the cross-sectional shape in patterning in a predetermined state.

Thus, in patterning using a laser in the manufacture of an FPD, a blank having a predetermined reflectance can also be provided.

By containing molybdenum silicide in the anti-reflective layer, the optical characteristics can be controlled greatly by controlling the concentrations of nitrogen and oxygen contained in molybdenum silicide which is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide water which is generally used for mask cleaning.

In the antireflection layer, the value of the refractive index of the antireflection layer can be set by the set oxygen content in the antireflection layer on the basis of a curve in which the value of the refractive index of the antireflection layer decreases as the oxygen content increases.

This makes it possible to set the refractive index of the anti-reflection layer to a predetermined value and to set the anti-reflection layer to have a lower refractive index than the phase shift layer, thereby reducing the reflectance of the mask blank.

In the antireflection layer, the oxygen content may be set in the above range, and the value of the extinction coefficient at a wavelength of 365nm to 436nm may be set in a range of 0.6 to 0.1.

Thus, the phase shift layer containing chromium can be provided as an antireflection layer having a predetermined refractive index and extinction coefficient, and the reflectance of the mask blank can be set to a predetermined value.

By using molybdenum silicide for the metal silicide used for the antireflection layer and increasing the nitrogen concentration and the oxygen concentration in the antireflection layer, the values of the refractive index and the extinction coefficient can be reduced. In particular, by increasing the oxygen concentration in the antireflection layer, the values of the refractive index and the extinction coefficient can be greatly reduced.

Further, by providing the antireflection layer, the reflectance ratio at a wavelength of 365nm to 436nm can be reduced to a range of 1 (25%) to 1/5 (5%) as compared with the case where the antireflection layer is not provided.

The mask blank of the present invention has a photoresist layer disposed at a position farther from the transparent substrate than the adhesion layer.

Thus, when patterning is performed by photolithography, the photoresist layer and the mask layer have sufficient adhesion, and the mask blank can be used without the etching solution penetrating into the interface on the transparent substrate side of the photoresist layer.

A method for manufacturing a mask blank according to the present invention is a method for manufacturing a mask blank according to any one of the above methods, including: a phase shift layer forming step of laminating the phase shift layer containing chromium on the transparent substrate; an antireflection layer forming step of laminating the antireflection layer containing molybdenum silicide and oxygen at a position farther from the transparent substrate than the phase shift layer; and an adhesion layer forming step of laminating the adhesion layer containing chromium and oxygen at a position farther from the transparent substrate than the antireflection layer, wherein the adhesion layer is formed with adhesion to the photoresist layer so as to be capable of forming a pattern by setting a partial pressure of an oxygen-containing gas as a supply gas during sputtering.

In this way, in the adhesion layer forming step, the adhesion layer containing chromium is laminated on the antireflection layer by sputtering in a state where the partial pressure of the oxygen-containing gas is set within a predetermined range, so that the water repellency of the adhesion layer is reduced, the water repellency is increased, the adhesion to the photoresist layer is improved, and the values of the refractive index and the extinction coefficient can be set to predetermined values.

Therefore, the mask layer can have a low reflectance in a wavelength band from g-line (436nm) to i-line (365nm), for example, while maintaining a predetermined cross-sectional shape during patterning with necessary adhesion.

Specifically, first, a chromium compound film as a main component film of the phase shift layer is formed on a glass substrate (transparent substrate) as a mask blank by a sputtering method or the like. The chromium compound formed at this time is preferably a film containing chromium, oxygen, nitrogen, carbon, or the like. By controlling the composition and film thickness of chromium, oxygen, nitrogen, and carbon contained in the film, a phase shift layer having preferable transmittance and phase can be formed.

At this time, in the case of forming the phase shift layer using only the chromium compound, the reflectance is improved by about 25%. Therefore, it is preferable to reduce the reflectance by forming a low reflection layer on the surface of the phase shift layer.

Therefore, for the chromium film forming the phase shift layer, it is necessary to control the phase difference, the transmittance, and the reflectance by adjusting the film thickness and the optical constant of the anti-reflection layer in addition to the film thickness and the optical constant of the phase shift layer.

Here, when wet etching is used in the etching step by forming the anti-reflection layer of another material for the phase shift layer, the etching solution can be changed to selectively etch the phase shift layer in a different etching step.

In addition, in order to reduce the reflectance of the phase shift mask, it is important to increase the difference between the refractive index and the extinction coefficient between the anti-reflection layer and the phase shift layer. Therefore, in order to reduce the reflectance of the phase shift mask, it is preferable to further reduce the values of the refractive index and the extinction coefficient of the antireflection layer.

As a result of intensive studies conducted by the present inventors, it was found that by using a three-layer structure as follows: in the case where a chromium compound is used as an adhesion layer for improving adhesion to a photoresist on the outermost surface of the mask layer, a metal silicide such as molybdenum silicide is used as an antireflection layer under the adhesion layer, and a chromium compound is used as a phase shift layer on the lowermost layer, it is preferable to use a process in which each layer can be prevented from being etched at a high selectivity in etching while improving adhesion to the photoresist layer.

Therefore, since the etching of the adhesion layer, the antireflection layer, and the phase shift layer can be controlled independently of each other, the cross-sectional shape suitable for use as a mask can be obtained while sufficiently reducing the reflectance.

Further, it has been found that molybdenum silicide is preferably used among metal silicides as an antireflection layer.

This is because it was recognized that by controlling the nitrogen and oxygen concentrations contained in the molybdenum silicide, the optical characteristics can be controlled greatly. This is because the optical constants of the molybdenum silicide film can be controlled greatly by controlling the concentrations of molybdenum, silicon, oxygen, and nitrogen contained in the molybdenum silicide film.

In particular, the present inventors have found that molybdenum silicide can reduce the values of the refractive index and the extinction coefficient by increasing the nitrogen concentration and the oxygen concentration in the film.

In particular, it has been found that the values of the refractive index and the extinction coefficient can be greatly reduced by increasing the oxygen concentration in the film.

Therefore, the reflectance of the phase shift mask can be reduced by using a chromium compound as the phase shift layer and a molybdenum silicide film as the antireflection layer.

In addition, in the case of using a chromium compound as a phase shift layer, high selectivity in etching can be brought about.

Further, molybdenum silicide is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide water which is generally used for mask cleaning.

In the method for producing a mask blank according to the present invention, the partial pressure of the oxygen-containing gas is set in the adhesion layer forming step, whereby the adhesion in the adhesion layer increases with an increase in the oxygen content.

In this way, in the adhesion layer forming step, the adhesion layer is laminated on the antireflection layer in a state where the partial pressure of the oxygen-containing gas is set within a predetermined range, whereby the adhesion of the photoresist layer with respect to the water repellency and water repellency in the adhesion layer and the values of the refractive index and the extinction coefficient can be set to predetermined values.

Here, by setting the partial pressure of the oxygen-containing gas during sputtering to a predetermined value, the values of the refractive index and the extinction coefficient in the adhesion layer can be set.

Specifically, in the adhesion layer forming step, the partial pressure of the oxygen-containing gas can be increased to increase the adhesion between the adhesion layer and the photoresist layer, and the values of the refractive index and the extinction coefficient of the adhesion layer can be decreased to decrease the partial pressure of the oxygen-containing gas to increase the values of the refractive index and the extinction coefficient of the adhesion layer.

In the method for producing a mask blank according to the present invention, in the adhesion layer forming step, the partial pressure ratio of the oxygen-containing gas is set in the range of 0.00 to 0.30.

Thus, the adhesive layer can be laminated on the antireflection layer as a predetermined oxygen content. Therefore, the adhesion of the adhesion layer to the photoresist layer and the values of the refractive index and the extinction coefficient can be set to predetermined values.

In the method for manufacturing a mask blank according to the present invention, the oxygen-containing gas may be NO in the adhesion layer forming step.

Further, as the oxygen-containing gas, O may be used₂、CO、NO_XAnd the like.

Further, in the adhesion layer forming step, a gas different from the oxygen-containing gas used in the formation of the phase shift layer containing the same chromium may be used.

The photomask of the present invention may be produced from any of the mask blanks described above.

In the method for manufacturing a photomask according to the present invention, the method for manufacturing a photomask includes: a phase shift pattern forming step of forming a pattern on the phase shift layer; an antireflection pattern forming step of forming a pattern on the antireflection layer; and a bonding pattern forming step of forming a pattern on the bonding layer, wherein an etching solution in the phase shift pattern forming step and the bonding pattern forming step is different from an etching solution in the antireflection pattern forming step.

Thus, high selectivity can be exhibited as etching rates different from each other. Accordingly, it is possible to provide a mask blank capable of manufacturing a photomask having a desired cross-sectional shape without affecting each other in the etching of the adhesion layer, the phase shift layer, and the antireflection layer.

This enables production of a photomask having desired film characteristics in each layer.

Here, a general phase shift mask has a transmittance of about 5% at i-line (wavelength 365nm), and a phase difference between the phase shift portion and the transmission portion is set to 180 °.

According to the present invention, the following effects are achieved, and a mask blank and a photomask having an antireflection layer that can suppress etching of other layers with a high selectivity ratio while achieving a low reflectance, having good adhesion to a resist, and capable of forming a reliable pattern can be provided.

Drawings

Fig. 1 is a sectional view showing a mask blank according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view showing a mask blank according to an embodiment of the present invention.

Fig. 3 is a sectional view showing a photomask according to an embodiment of the present invention.

Fig. 4 is a schematic view showing a film deposition apparatus in the method for manufacturing a mask blank or a photomask according to the embodiment of the present invention.

FIG. 5 shows CO showing refractive index of MoSi compound used for an antireflection layer in a mask blank and a photomask manufacturing method according to an embodiment of the present invention₂Graph of partial pressure ratio dependence.

FIG. 6 shows CO showing extinction coefficient of MoSi compound applied to an antireflection layer in a mask blank and a photomask manufacturing method according to an embodiment of the present invention₂Graph of partial pressure ratio dependence.

Fig. 7 is a graph showing the NO partial pressure ratio dependency of the refractive index of the Cr compound in the adhesion layer applied to the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention.

Fig. 8 is a graph showing NO partial pressure ratio dependency of extinction coefficient in Cr compound applied to the bonding layer in the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention.

FIG. 9 shows CO showing the refractive index of Cr compounds in the phase shift layer applied to the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention₂Graph of partial pressure ratio dependence.

FIG. 10 shows CO showing extinction coefficients of Cr compounds in a phase shift layer applied to a mask blank and a method for manufacturing a photomask according to an embodiment of the present invention₂Graph of partial pressure ratio dependence.

Fig. 11 is a graph showing the film thickness dependence in the antireflection layer of the reflectance characteristics in the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention.

Fig. 12 is a graph showing the transmittance characteristics and the film thickness dependence in the antireflection layer in the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention.

Fig. 13 is a graph showing the film thickness dependence in the adhesion layer of the reflectance characteristics in the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention.

Fig. 14 is a graph showing the dependency of the film thickness in the adhesion layer on the transmittance characteristics in the mask blank and the method for manufacturing a photomask according to the embodiment of the present invention.

Detailed Description

Embodiments of a mask blank, a phase shift mask, and a method for manufacturing the same according to the present invention will be described below with reference to the accompanying drawings.

Fig. 1 is a sectional view showing a mask blank in the present embodiment, fig. 2 is a sectional view showing a mask blank in the present embodiment, and reference numeral 10B in the drawing denotes a mask blank.

The mask blank 10B according to the present embodiment is provided to a phase shift mask (photomask) used in a range where the wavelength of exposure light is approximately 365nm to 436 nm.

As shown in fig. 1, the mask blank 10B according to the present embodiment includes a glass substrate (transparent substrate) 11, a phase shift layer 12 formed on the glass substrate 11, an antireflection layer 13 formed on the phase shift layer 12, and a bonding layer 14 formed on the antireflection layer 13.

That is, the antireflection layer 13 is provided at a position farther from the glass substrate 11 than the phase shift layer 12. The adhesion layer 14 is provided at a position farther from the glass substrate 11 than the antireflection layer 13.

These phase shift layer 12, antireflection layer 13, and adhesion layer 14 constitute a mask layer having optical characteristics required as a photomask and being a low-reflection phase shift film.

Furthermore, the mask blank 10B according to the present embodiment may have a structure in which a photoresist layer 15 is formed in advance as shown in fig. 2 with respect to a mask layer in which the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 are stacked as shown in fig. 1.

The mask blank 10B according to the present embodiment may be configured such that a chemical-resistant layer, a protective layer, a light-shielding layer, an etching stopper layer, and the like are laminated in addition to the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14. Further, as shown in fig. 2, a photoresist layer 15 may be formed on these laminated films.

As the glass substrate (transparent substrate) 11, a material excellent in transparency and optical isotropy can be used, and for example, a quartz glass substrate can be used. The size of the glass substrate 11 is not particularly limited, and is appropriately selected according to a substrate to be exposed using the mask (for example, a substrate for an FPD such as an LCD (liquid crystal display), a plasma display, or an organic EL (electroluminescence) display).

In the present embodiment, as the glass substrate (transparent substrate) 11, a rectangular substrate having a side of about 100mm to 2000mm or more can be applied, and further, a substrate having a thickness of 1mm or less, a substrate having a thickness of several millimeters, or a substrate having a thickness of 10mm or more can be used.

In addition, the flatness of the glass substrate 11 may be reduced by polishing the surface of the glass substrate 11. The flatness of the glass substrate 11 may be set to 20 μm or less, for example. This makes it possible to increase the depth of focus of the mask, and to contribute significantly to fine and highly accurate pattern formation. Further, the flatness is preferably a small value of 10 μm or less.

The phase shift layer 12 contains Cr (chromium) as a main component, and further contains C (carbon), O (oxygen), and N (nitrogen).

In this case, the phase shift layer 12 may be formed by laminating one or more kinds selected from the group consisting of Cr alone and Cr oxide, nitride, carbide, oxynitride, carbonitride, and oxycarbonitride.

As described later, the phase shift layer 12 has a thickness and a composition ratio (atomic%) of Cr, N, C, O, and the like set so as to obtain predetermined optical characteristics and resistivity.

The film thickness of the phase shift layer 12 is set in accordance with optical characteristics required for the phase shift layer 12, and varies depending on the composition ratio of Cr, N, C, O, and the like. The thickness of the phase shift layer 12 may be 50nm to 150 nm.

For example, the composition ratio in the phase shift layer 12 may be set such that the carbon content (carbon concentration) is 2.3 atomic% to 10.3 atomic%, the oxygen content (oxygen concentration) is 8.4 atomic% to 72.8 atomic%, the nitrogen content (nitrogen concentration) is 1.8 atomic% to 42.3 atomic%, and the chromium content (chromium concentration) is 20.3 atomic% to 42.4 atomic%.

Accordingly, the phase shift layer 12 can be formed to have a thickness of about 90nm when the wavelength is in the range of about 365nm to 436nm, the refractive index is about 2.4 to 3.1, and the extinction coefficient is 0.3 to 2.1.

As the anti-reflection layer 13, a film containing a metal such as Ta, Ti, W, Mo, or Zr, an alloy of these metals, and silicon can be used as a material different from the phase shift layer 12. Among the metal silicides, molybdenum silicide is preferably used, and MoSi may be mentioned_X(X.gtoreq.2) film (e.g., MoSi)₂Film, MoSi₃Film or MoSi₄Films, etc.).

The antireflection layer 13 is preferably a molybdenum silicide film containing O (oxygen) and N (nitrogen).

Further, the antireflection layer 13 preferably contains C (carbon).

In the antireflection layer 13, the oxygen content (oxygen concentration) may be set to a range of 6.7 atomic% to 63.2 atomic%, the nitrogen content (nitrogen concentration) may be set to a range of 4.6 atomic% to 39.3 atomic%, and the carbon content (carbon concentration) may be set to a range of 4.0 atomic% to 13.5 atomic%.

The anti-reflection layer 13 preferably contains a molybdenum silicide compound having an oxygen content (oxygen concentration) of 36 atomic% or more and a nitrogen content (nitrogen concentration) of 10 atomic% or more.

In the antireflection layer 13, the nitrogen concentration and the oxygen concentration in the film can be increased, and the values of the refractive index and the extinction coefficient can be decreased. In particular, the values of the refractive index and the extinction coefficient are greatly reduced by increasing the oxygen concentration in the film.

Further, by setting the thickness of the antireflection layer 13 to be 30nm or more and 60nm or less, the reflectance at a wavelength of 365nm to 436nm can be reduced.

In this case, the anti-reflection layer 13 may have a silicon content (silicon concentration) in a range of 11.1 atomic% to 21.7 atomic% and a molybdenum content (molybdenum concentration) in a range of 14.9 atomic% to 28.3 atomic%.

Thus, in the antireflection layer 13, the value of the refractive index at a wavelength of 365nm to 436nm can be set in the range of 2.5 to 1.8.

In the antireflection layer 13, the value of the extinction coefficient at a wavelength of 365nm to 436nm may be set in a range of 0.7 to 0.1.

Therefore, in the mask blank 10B of the present embodiment, by providing the phase shift layer 12 and the antireflection layer 13, the reflectance ratio at a wavelength of 365nm to 436nm can be reduced to a range of 1 (25%) to 1/5 (5%) as compared with the case where the antireflection layer 13 is not provided.

The adhesion layer 14 contains Cr (chromium) and O (oxygen) as main components, and further contains C (carbon) and N (nitrogen).

In this case, the adhesion layer 14 may be formed by laminating one or more kinds selected from the group consisting of Cr oxide, nitride, carbide, oxynitride, carbonitride, and oxycarbonitride. Further, the adhesion layer 14 may also have a different composition in the thickness direction.

As described later, the thickness of the adhesion layer 14 and the composition ratio (atomic%) of Cr, N, C, O, Si, and the like are set so as to obtain predetermined adhesion (water repellency) and predetermined optical characteristics.

For example, the composition ratio of the sealing layer 14 may be set such that the oxygen content (oxygen concentration) is 8.4 atomic% to 65.7 atomic%, the nitrogen content (nitrogen concentration) is 3.7 atomic% to 42.3 atomic%, the chromium content is 25.2 atomic% to 42.4 atomic%, the carbon content (carbon concentration) is 2.2 atomic% to 2.3 atomic%, and the silicon content is 3.3 atomic% to 4.7 atomic%.

The film thickness of the adhesion layer 14 is set in accordance with adhesion (water repellency) and optical characteristics required for the adhesion layer 14, and the film thickness varies depending on the composition ratio of Cr, N, C, O, and the like. The thickness of the adhesion layer 14 may be 5nm to 20nm, and may be further 10nm to 15 nm.

When the film thickness of the adhesion layer 14 is set to the above range, adhesion to the photoresist layer 15 used in, for example, chromium is improved and the etching solution does not enter into the interface between the adhesion layer 14 and the photoresist layer 15 when patterning is performed by photolithography, and therefore, a favorable pattern shape can be obtained and a preferable pattern can be formed.

Further, if the thickness of the adhesion layer 14 is smaller than the above range, the adhesion to the photoresist layer 15 is not in a predetermined state, but the photoresist layer 15 is peeled off, and the etching solution enters the interface, and the pattern formation is not performed, which is not preferable. In addition, when the thickness of the adhesion layer 14 is larger than the above range, it may be difficult to set the optical characteristics as a photomask to preferable conditions, or the sectional shape of the mask pattern may not be in a desired state, which is not preferable.

The adhesion layer 14 can reduce hydrophilicity, increase hydrophobicity, and improve adhesion by increasing the oxygen concentration and the nitrogen concentration in the chromium compound.

Meanwhile, the adhesion layer 14 can reduce the values of the refractive index and the extinction coefficient by increasing the oxygen concentration and the nitrogen concentration in the chromium compound.

In the method for manufacturing the mask blank according to the present embodiment, the phase shift layer 12 is formed on the glass substrate (transparent substrate) 11, the antireflection layer 13 is formed thereon, and the adhesion layer 14 is formed thereon.

The method of manufacturing the mask blank may include a step of laminating a protective layer, a light-shielding layer, a chemical-resistant layer, an etching stopper layer, and the like in addition to the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14.

For example, a light-shielding layer containing chromium may be mentioned.

Fig. 3 is a sectional view showing a photomask in the present embodiment.

The phase shift mask (photomask) 10 in the present embodiment can be obtained by patterning the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 stacked as the mask blank 10B, as shown in fig. 3.

Next, a method for manufacturing the phase shift mask 10 from the mask blank 10B of the present embodiment will be described.

As a resist pattern forming step, as shown in fig. 2, a photoresist layer 15 is formed on the outermost surface of the mask blank 10B. Alternatively, mask blank 10B having photoresist layer 15 formed on the outermost surface may be prepared in advance. The photoresist layer 15 may be either a positive type or a negative type. As the photoresist layer 15, a material which can be suitably used for etching of a so-called chromium-based material and etching of a molybdenum silicide-based material can be used. As the photoresist layer 15, a liquid resist is used.

Next, the photoresist layer 15 is exposed and developed, whereby a resist pattern is formed on the outer side of the adhesion layer 14. The resist pattern functions as an etching mask between the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14.

The resist pattern is determined to have an appropriate shape according to the etching pattern among the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14. For example, the phase shift region is set to have a shape having an opening width corresponding to the opening width dimension of the formed phase shift pattern.

Next, as an adhesion pattern forming step, the adhesion layer 14 is wet-etched with an etching solution over the resist pattern to form an adhesion pattern 14P.

As the etching solution in the adhesion pattern forming step, an etching solution containing cerous ammonium nitrate (セリウム, 2 アンモニウム) can be used, and for example, cerous ammonium nitrate containing an acid such as nitric acid or perchloric acid is preferably used.

Next, as an antireflection pattern forming step, the antireflection layer 13 is wet-etched with an etching solution over the adhesion pattern 14P to form an antireflection pattern 13P.

When the anti-reflection layer 13 is MoSi as an etching solution in the anti-reflection pattern forming step, it is preferable to use a material containing at least one fluorine compound selected from hydrofluoric acid, hydrogen hydrofluoric acid, and ammonium hydrogen fluoride, and at least one oxidizing agent selected from hydrogen peroxide, nitric acid, and sulfuric acid as the etching solution.

Next, as a phase shift pattern forming step, the phase shift layer 12 is wet-etched across the patterned antireflection pattern 13P, adhesion pattern 14P, and resist pattern, thereby forming a phase shift pattern 12P.

As the etching solution in the phase shift pattern forming step, an etching solution containing cerous ammonium nitrate can be used, and for example, cerous ammonium nitrate containing an acid such as nitric acid or perchloric acid is preferably used.

The molybdenum silicide compound constituting the anti-reflection layer 13 can be etched by a mixed solution of ammonium bifluoride and hydrogen peroxide, for example. In contrast, the chromium compound forming the adhesion layer 14 and the phase shift layer 12 can be etched by a mixed solution of cerium ammonium nitrate and perchloric acid, for example.

Therefore, the selection ratio at the time of etching of each wafer becomes very large. Therefore, after the adhesion patterns 14P, the antireflection patterns 13P, and the phase shift patterns 12P are formed by etching, a good cross-sectional shape close to the vertical can be obtained as the cross-sectional shape of the phase shift mask 10.

In the phase shift pattern forming step, the oxygen concentration of the adhesion layer 14 is set higher than the oxygen concentration of the phase shift layer 12, and therefore the etching rate is lowered. Therefore, the etching of the close adhesion pattern 14P is performed slower than the etching of the phase shift layer 12.

That is, the angle (taper angle) θ formed by the close adhesion pattern 14P, the antireflection pattern 13P, and the phase shift pattern 12P with the surface of the glass substrate 11 is close to a right angle, and may be, for example, about 90 °.

Then, by forming the close-contact pattern 14P from the close-contact layer 14, the close-contact pattern 14P and the resist pattern have improved close contact. This prevents the etching solution from entering the interface between the adhesion pattern 14P and the resist pattern. Therefore, the pattern can be formed reliably.

Further, when forming the mask blank 10B of another film such as a light shielding layer, the film is patterned into a predetermined shape corresponding to the close-contact pattern 14P, the antireflection pattern 13P, and the phase shift pattern 12P by wet etching using a corresponding etching solution. Patterning of other films such as the light-shielding layer can be performed as a predetermined step before and after patterning of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, according to the lamination order.

Further, the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 have their respective oxygen concentrations varied in the film thickness direction, thereby improving the cross-sectional shape after patterning.

Specifically, in the anti-reflection layer 13, i.e., the MoSi film, the higher the oxygen concentration in the film, the higher the etching rate. Therefore, in the antireflection layer 13, the etching rate on the upper layer side can be made slower than that on the lower layer side by making the oxygen concentration on the upper layer side lower than that on the lower layer side. This makes it possible to make the cross-sectional shape after etching nearly vertical.

On the other hand, in the phase shift layer 12 and the adhesion layer 14, i.e., the Cr film, the higher the oxygen concentration in the film, the lower the etching rate. Therefore, the etching rate of the upper layer side can be made lower than that of the lower layer side by making the oxygen concentration of the phase shift layer 12 and the adhesion layer 14 higher on the upper layer side than on the lower layer side.

As described above, the phase shift mask 10 having the close-contact pattern 14P, the antireflection pattern 13P, and the phase shift pattern 12P is obtained as shown in fig. 3.

Hereinafter, a method for manufacturing a mask blank according to the present embodiment will be described with reference to the drawings.

Fig. 4 is a schematic diagram showing a mask blank manufacturing apparatus in the present embodiment.

The mask blank 10B in the present embodiment is manufactured by the manufacturing apparatus shown in fig. 4.

The manufacturing apparatus S10 shown in fig. 4 is an interactive (インターバック) sputtering apparatus. The manufacturing apparatus S10 includes: a load chamber S11; an unloading chamber S16; and a film forming chamber (vacuum processing chamber) S12. The film forming chamber S12 is connected to the loading chamber S11 via a sealing device S17, and is connected to the unloading chamber S16 via a sealing device S18.

The load chamber S11 is provided with a transfer device S11a for transferring the glass substrate 11 carried in from the outside to the film forming chamber S12, and an exhaust device S11f such as a rotary pump for evacuating the chamber to a rough vacuum.

The unloading chamber S16 is provided with a transfer device S16a for transferring the glass substrate 11 after film formation from the film forming chamber S12 to the outside, and an exhaust device S16f such as a rotary pump for evacuating the inside of the chamber to a rough vacuum.

The film forming chamber S12 is provided with a substrate holding apparatus S12a and three-stage film forming apparatuses S13, S14, and S15 as apparatuses corresponding to the three film forming processes.

The substrate holding device S12a holds the glass substrate 11 conveyed by the conveyance device S11a so that the glass substrate 11 faces the targets S13b, S14b, and S15b during film formation. The substrate holding device S12a can carry the glass substrate 11 in from the load chamber S11 and can carry the glass substrate 11 out to the unload chamber S16.

In the structure of the film forming chamber S12, a film forming apparatus S13 for supplying a film forming material at the first stage among the three stages of film forming apparatuses S13, S14, and S15 is provided at a position close to the load chamber S11.

The film forming apparatus S13 includes: a cathode electrode (backing plate) S13c having a target S13b, and a power source S13d for applying a sputtering voltage of negative potential to the backing plate S13 c.

The film forming apparatus S13 includes: a gas introduction device S13e for introducing a gas in the film forming chamber S12 with a high degree of focus in the region near the cathode electrode (backing plate) S13c, and a high vacuum exhaust device S13f such as a turbo molecular pump for evacuating the region near the cathode electrode (backing plate) S13c with a high degree of focus in the film forming chamber S12.

Further, a film forming device S14 for supplying a film forming material of the second stage among the three film forming devices S13, S14, and S15 is provided at an intermediate position between the load chamber S11 and the unload chamber S16 in the film forming chamber S12.

The film forming apparatus S14 includes: a cathode electrode (backing plate) S14c having a target S14b, and a power source S14d for applying a sputtering voltage of negative potential to the backing plate S14 c.

The film forming apparatus S14 includes: a gas introduction device S14e for introducing a gas in the film forming chamber S12 with a high degree of focus in the region near the cathode electrode (backing plate) S14c, and a high vacuum exhaust device S14f such as a turbo molecular pump for evacuating the region near the cathode electrode (backing plate) S14c with a high degree of focus in the film forming chamber S12.

Further, in the structure of the film forming chamber S12, a film forming apparatus S15 for supplying a film forming material at the third stage among the three stages of film forming apparatuses S13, S14, and S15 is provided at a position close to the unloading chamber S16.

The film forming apparatus S15 includes: a cathode electrode (backing plate) S15c having a target S15b, and a power source S15d for applying a sputtering voltage of negative potential to the backing plate S15 c.

The film forming apparatus S15 includes: a gas introduction device S15e for intensively introducing a gas into the region near the cathode electrode (backing plate) S15c in the film forming chamber S12, and a high vacuum exhaust device S15f such as a turbo molecular pump for intensively evacuating the region near the cathode electrode (backing plate) S15c in the film forming chamber S12.

In the film forming chamber S12, a gas barrier S12g for suppressing the flow of gas is provided in the vicinity of the cathode electrodes (back plates) S13c, S14c, and S15c so that the gas supplied from the gas introduction devices S13e, S14e, and S15e does not mix into the adjacent film forming devices S13, S14, and S15. The gas barrier S12g is set so that the substrate holding apparatus S12a can move between the adjacent film forming apparatuses S13, S14, and S15.

In the film forming chamber S12, the three-stage film forming apparatuses S13, S14, and S15 each have a composition and conditions necessary for sequentially forming a film on the glass substrate 11.

In the present embodiment, the film formation device S13 corresponds to the film formation of the phase shift layer 12, the film formation device S14 corresponds to the film formation of the antireflection layer 13, and the film formation device S15 corresponds to the film formation of the adhesion layer 14.

Specifically, in the film forming apparatus S13, the target S13b is made of a material containing chromium as a composition required for forming the phase shift layer 12 on the glass substrate 11.

Meanwhile, in the film forming apparatus S13, the process gas supplied from the gas introduction apparatus S13e contains carbon, nitrogen, oxygen, and the like, and is set as a predetermined partial pressure of the gas together with the sputtering gas such as argon, nitrogen, and the like, in accordance with the film formation of the phase shift layer 12.

Further, the high vacuum evacuation apparatus S13f evacuates the film according to the film formation conditions.

In the film formation apparatus S13, the sputtering voltage applied from the power source S13d to the back plate S13c is set in accordance with the film formation of the phase shift layer 12.

In the film forming apparatus S14, the target S14b is made of a material having molybdenum silicide as a composition required for forming the antireflection layer 13 on the phase shift layer 12.

Meanwhile, in the film forming apparatus S14, the process gas contains carbon, nitrogen, oxygen, and the like as the gas supplied from the gas introduction apparatus S14e, and the conditions are set as a predetermined partial pressure of the gas together with the sputtering gas such as argon, nitrogen, and the like in accordance with the formation of the antireflection layer 13.

Further, the high vacuum evacuation apparatus S14f evacuates the film according to the film formation conditions.

In the film formation apparatus S14, the sputtering voltage applied from the power source S14d to the back plate S14c is set in accordance with the formation of the antireflection layer 13.

In the film forming apparatus S15, the target S15b is made of a material containing chromium as a composition required for forming the adhesion layer 14 on the antireflection layer 13.

Meanwhile, in the film forming apparatus S15, the process gas contains carbon, nitrogen, oxygen, and the like as the gas supplied from the gas introduction apparatus S15e, and the conditions are set as a predetermined partial pressure of the gas together with the sputtering gas such as argon, nitrogen, and the like in accordance with the film formation of the adhesion layer 14.

Further, the high vacuum evacuation apparatus S15f evacuates the film according to the film formation conditions.

In the film forming apparatus S15, the sputtering voltage applied from the power source S15d to the backing plate S15c is set in accordance with the formation of the adhesion layer 14.

In the manufacturing apparatus S10 shown in fig. 4, the glass substrate 11 carried in from the load chamber S11 by the carrying apparatus S11a is subjected to sputtering film formation in three stages while being carried by the substrate holding apparatus S12a in the film formation chamber (vacuum processing chamber) S12. Then, the glass substrate 11 on which the film formation has been completed is carried out from the unloading chamber S16 to the outside by the carrying device S16 a.

In the phase shift layer forming step, in the film forming apparatus S13, a sputtering gas and a reaction gas are supplied as supply gases from the gas introduction apparatus S13e to a region near the back plate S13c of the film forming chamber S12. In this state, a sputtering voltage is applied to the backing plate (cathode electrode) S13c from an external power supply. Further, a predetermined magnetic field can be formed on the target S13b by the magnetron magnetic circuit.

In the region near the backing plate S13c in the film forming chamber S12, ions of the sputtering gas excited by the plasma collide with the target S13b of the cathode electrode S13c to fly particles of the film forming material. The ejected particles are combined with the reaction gas and then adhere to the glass substrate 11, thereby forming the phase shift layer 12 with a predetermined composition on the surface of the glass substrate 11.

Similarly, in the antireflection layer forming step, in the film forming apparatus S14, a sputtering gas and a reactive gas are supplied as supply gases from the gas introduction apparatus S14e to a region near the back plate S14c of the film forming chamber S12. In this state, a sputtering voltage is applied to the backing plate (cathode electrode) S14c from an external power supply. Further, a predetermined magnetic field can be formed on the target S14b by the magnetron magnetic circuit.

In the region near the backing plate S14c in the film forming chamber S12, ions of the sputtering gas excited by the plasma collide with the target S14b of the cathode electrode S14c to fly particles of the film forming material. The ejected particles are bonded to the reaction gas and then adhere to the glass substrate 11, thereby forming the antireflection layer 13 with a predetermined composition on the surface of the glass substrate 11.

Similarly, in the adhesion layer forming step, in the film forming apparatus S15, the sputtering gas and the reactive gas are supplied as the supply gases from the gas introduction apparatus S15e to the region near the back plate S15c of the film forming chamber S12. In this state, a sputtering voltage is applied to the backing plate (cathode electrode) S15c from an external power supply. Further, a predetermined magnetic field can be formed on the target S15b by the magnetron magnetic circuit.

In the region near the backing plate S15c in the film forming chamber S12, ions of the sputtering gas excited by the plasma collide with the target S15b of the cathode electrode S15c to fly particles of the film forming material. The ejected particles are bonded to the reaction gas and then adhere to the glass substrate 11, thereby forming the adhesive layer 14 with a predetermined composition on the surface of the glass substrate 11.

At this time, during the deposition of the phase shift layer 12, nitrogen gas, oxygen-containing gas, or the like having a predetermined partial pressure is supplied from the gas introducing device S13e, and the partial pressure is switched so as to control the composition within a predetermined range.

In the formation of the antireflection layer 13, nitrogen gas, oxygen-containing gas, or the like having a predetermined partial pressure is supplied from the gas introducing device S14e, and the partial pressure is switched so as to control the composition within a predetermined range.

During the deposition of the adhesion layer 14, nitrogen gas, oxygen-containing gas, and the like are supplied from the gas introduction device S15e at a predetermined partial pressure, and the partial pressure is controlled so as to be switched to a composition within a predetermined range.

Examples of the oxygen-containing gas include CO₂(carbon dioxide), O₂(oxygen), N₂O (nitrous oxide), NO (nitric oxide), CO (carbon monoxide), and the like.

As the carbon-containing gas, CO may be mentioned₂(carbon dioxide), CH₄(methane), C₂H₆(ethane), CO (carbon monoxide), and the like.

In the formation of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, the targets S13b, S14b, and S15b may be replaced if necessary.

In addition to the deposition of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, when other films are stacked, the films are deposited by sputtering under sputtering conditions such as a target and a gas, or the films are stacked by another film deposition method, thereby manufacturing the mask blank 10B of the present embodiment.

Next, film properties of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 in the present embodiment will be described.

First, a chromium compound film to be a main component film of the phase shift layer 12 is formed on the glass substrate 11 for forming a mask by a sputtering method or the like. The chromium compound formed at this time is preferably a film containing chromium, oxygen, nitrogen, carbon, or the like. By controlling the composition and film thickness of chromium, oxygen, nitrogen, and carbon contained in the film of phase shift layer 12, phase shift layer 12 having a desired transmittance and phase can be formed.

Here, when the phase shift layer 12 is formed only with a chromium compound and no other film is provided, the reflectance becomes high, and is about 25%. Therefore, it is preferable to reduce the reflectance by forming the antireflection layer 13 to be a low reflection layer on the surface of the phase shift layer 12.

As the antireflection layer 13, molybdenum silicide is preferably used as the metal silicide. Molybdenum silicide is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide water generally used for mask cleaning, and optical characteristics can be controlled greatly by controlling the nitrogen and oxygen concentrations contained in molybdenum silicide.

Here, since molybdenum silicide has hydrophilicity, adhesion to a photoresist may not be good. In order to improve this, the adhesion is improved by forming the adhesion layer 14 having water repellency.

As the adhesion layer 14, a chromium compound is preferably used. The chromium compound has a strong chemical resistance to acid and alkali solutions and a hydrophobic property. Therefore, a chromium compound is suitably used at the interface of the adhesion layer 14 in contact with the photoresist.

By laminating the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 in this manner, a phase shift film having optical characteristics and the like required for the photomask 10 can be formed using two materials, i.e., a chromium compound and a metal silicide, which have high chemical resistance.

In order to reduce the reflectance of the phase shift mask 10, it is important to further increase the difference in refractive index and the difference in extinction coefficient between the anti-reflection layer 13 and the phase shift layer 12 in addition to making the optical constants of the adhesion layer 14 and the anti-reflection layer 13 close. In this manner, in order to reduce the reflectance of the phase shift mask 10, it is preferable to reduce the values of the refractive index and the extinction coefficient between the adhesion layer 14 and the antireflection layer 13.

In the chromium compound used in the adhesion layer 14, the values of the refractive index and the extinction coefficient can be reduced by increasing the oxygen concentration and the nitrogen concentration in the chromium compound. In particular, by increasing the oxygen concentration in the film, the values of the refractive index and the extinction coefficient can be greatly reduced.

In addition, in the case of using molybdenum silicide as the metal silicide used for the reflection preventing layer 13, the values of the refractive index and the extinction coefficient can be reduced by increasing the nitrogen concentration and the oxygen concentration in the film. In particular, by increasing the oxygen concentration in the film, the values of the refractive index and the extinction coefficient can be greatly reduced.

Here, for the sake of explanation, the phase shift layer 12 is a film mainly composed of a chromium compound containing nitrogen, oxygen, and carbon, the antireflection layer 13 is a film mainly composed of molybdenum silicide containing oxygen and nitrogen, and the adhesion layer 14 is a film mainly composed of a chromium compound containing oxygen and nitrogen, but the present invention is not limited thereto.

As described above, in the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 which are low-reflection phase shift films (mask layers), the oxygen concentration, the carbon concentration, and the nitrogen concentration are set within the above ranges in the phase shift layer 12, the oxygen concentration, the carbon concentration, and the nitrogen concentration are set within the above ranges in the antireflection layer 13, and the oxygen concentration, the carbon concentration, and the nitrogen concentration are set within the above ranges in the adhesion layer 14.

First, the change in adhesion in the adhesion layer 14 was evaluated.

Here, the film thickness of the chromium compound used as the adhesion layer 14 was changed, and the relationship of the evaluation of the adhesion between the chromium compound and the photoresist in this case was examined.

Evaluation of resist adhesion a resist pattern was formed on the mask blank 10B having a three-layer structure in the present embodiment, and then wet etching was performed.

As the photoresist layer 15, for example, a phenol resin or the like can be applied.

At this time, NG is the case where the etching solution enters the interface between the photoresist layer 15 and the mask layer, and OK is the case where the etching solution does not enter the interface.

In addition, when the etching solution enters the interface between the photoresist layer and the mask layer, the patterns of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, which are low-reflection phase shift films (mask layers), are not formed in this portion.

The results are shown in Table 1.

[ Table 1]

Bonding layer (nm)	Evaluation of adhesion
		3	NG
5	OK
		10	OK
15	OK

Relationship between film thickness and adhesion of adhesion layer

From the results, it is understood that when the film thickness of the adhesion layer (adhesion improving layer) 14 is 10nm or more, a good cross-sectional shape without the intrusion of the etching solution can be obtained.

Next, changes in film characteristics due to changes in the composition of the antireflection layer 13, that is, changes in the content of oxygen, nitrogen, and the like, were examined.

The molybdenum silicide compound was formed into a film by a sputtering method.

The composition of the molybdenum silicide target used here is Mo: Si ═ 1: 2.3. In addition, during sputtering, N is used₂And CO₂The mixed gas of (1).

CO in film formation of molybdenum silicide compound₂The partial pressure changes.

Thus, CO in the formation of the MoSi compound₂The wavelength dependence of the refractive index when the partial pressure was varied is shown in fig. 5. CO in the formation of a MoSi compound₂The wavelength dependence of the extinction coefficient when the partial pressure was varied is shown in fig. 6.

CO when film formation of molybdenum silicide compound₂When the partial pressure is changed, the composition ratio of carbon, nitrogen and oxygen is changed. At the same time, the composition ratio of molybdenum and silicon is also changed. By increasing CO during film formation₂The partial pressure, oxygen concentration and carbon concentration are increased, and the nitrogen concentration, silicon concentration and molybdenum concentration are decreased.

As shown in FIGS. 5 and 6, it is understood that CO is increased during the film formation of the molybdenum silicide compound₂Partial pressure can reduce the refractive index and extinction coefficient.

In addition, the composition of the molybdenum silicide compound was determined by auger electron spectroscopy.

The results are shown in Table 2.

[ Table 2]

CO in sputtering of MoSi compounds₂Relationship between gas partial pressure and composition

CO₂Partial pressure of gas	C	N	O	Si	Mo
							0％	4.0	39.3	6.7	21.7	28.3
10％	13.5	12.3	36.1	16.2	22.0
						20％	9.7	9.9	50.7	14.0	15.8
30％	6.2	4.6	63.2	11.1	14.9

It is known that by increasing CO at the time of film formation₂Partial pressure, increased oxygen concentration, nitrogen concentration, siliconThe concentration and the molybdenum concentration are reduced.

In order to etch the molybdenum silicide film by wet etching, it is generally necessary to perform etching using a chemical solution containing hydrogen fluoride. However, hydrogen fluoride also etches a substrate such as quartz. Therefore, a material having a low silicon concentration in molybdenum silicide is preferably used. Therefore, it is preferable to use a composition containing Mo and Si as described above as a target composition in forming molybdenum silicide. If the Si concentration is further decreased, it becomes difficult to maintain the uniformity of the target composition.

Next, the composition of the adhesion layer 14 and the phase shift layer 12, that is, the change in film characteristics due to the change in the content of oxygen, nitrogen, or the like, was examined.

The adhesion layer 14 and the phase shift layer 12 are provided as chromium compounds.

The chromium compound was formed into a film by a sputtering method.

Showing the selection of CO as an oxidizing gas in the formation of chromium compounds₂Graph of wavelength dependence of refractive index and extinction coefficient when the partial pressure of each gas was varied for gas and NO gas.

Fig. 7 shows the wavelength dependence of the refractive index when the partial pressure of NO gas in the film formation of the Cr compound was changed to 0% to 30% in terms of the gas flow ratio. Fig. 8 shows the wavelength dependence of the extinction coefficient when the partial pressure of NO gas is changed during the film formation of the Cr compound.

The optical properties of the chromium compound can be greatly changed by adjusting the partial pressure of the oxidizing gas during formation.

As shown in fig. 7 and 8, it is understood that the refractive index and the extinction coefficient can be decreased by increasing the partial pressure of NO gas at the time of film formation.

The composition of a chromium compound formed as a film by selecting NO gas as an oxidizing gas was determined by auger electron spectroscopy. The results are shown in Table 3.

[ Table 3]

Relationship between NO gas partial pressure and composition during sputtering of Cr compound

Partial pressure of NO gas	C	N	O	Si	Cr
							0％	2.3	42.3	8.4	4.5	42.4
10％	2.3	39.5	11.4	4.7	42.1
						20％	2.2	21.6	38.5	4.0	33.7
30％	2.2	3.7	65.7	3.3	25.2

CO in forming Cr compound film₂Fig. 9 shows the wavelength dependence of the refractive index when the gas partial pressure was varied from 0% to 30% in terms of the gas flow rate ratio. CO in forming Cr compound film₂The wavelength dependence of the extinction coefficient when the gas partial pressure was varied is shown in fig. 10.

Further, the selection of CO as an oxidizing gas was determined by Auger electron spectroscopy₂Composition of chromium compound for film formation by gas. The results are shown in Table 4.

[ Table 4]

CO in sputtering of Cr compound₂Relationship between gas partial pressure and composition

CO₂Partial pressure of gas	C	N	O	Si	Cr
							0％	2.3	42.3	8.4	4.5	42.4
10％	9.8	34.2	12.3	4.4	39.4
						20％	10.3	19.9	32.4	3.6	33.7
30％	2.5	1.8	72.8	2.7	20.3

It is found that CO is increased when a Cr compound is formed into a film₂Partial pressure or NO partial pressure, oxygen concentration increases, and nitrogen concentration and chromium concentration decrease.

In this way, by adjusting the gas partial pressure at the time of film formation for both the molybdenum silicide compound and the chromium compound, a film having a preferable optical constant can be obtained.

The phase shift mask 10 is set to have a transmittance of about 5% at i-line (wavelength 365nm) and a phase difference of about 180 ° between the phase shift portion and the transmission portion. Therefore, in the chromium film forming the phase shift layer 12, the molybdenum silicide film forming the antireflection layer 13, and the chromium film forming the adhesion layer 14, the phase difference, the transmittance, and the reflectance can be controlled by adjusting the film thicknesses and the optical constants, respectively.

The phase shift mask 10 needs to reduce the reflectivity. Therefore, in the adhesion layer 14 and the antireflection layer 13, the refractive index and the extinction coefficient are reduced, and the refractive index and the extinction coefficient are increased in the phase shift layer 12. That is, it is preferable to increase the difference in refractive index between the antireflection layer 13 and the phase shift layer 12, while increasing the difference in extinction coefficient between the antireflection layer 13 and the phase shift layer 12.

Therefore, it is preferable that the oxygen concentration in the adhesion layer 14 be increased by increasing the partial pressure of NO gas at the time of film formation.

In order to improve the adhesion by using a chromium film having a high oxygen concentration, the chromium film is bonded to CO₂The use of NO gas for oxidation can improve the adhesion to the resist more than with a gas. Therefore, the chromium film for the adhesion layer is preferably formed using NO gas.

In addition, the antireflection layer 13 is preferably formed by increasing the oxygen-containing gas partial pressure during film formation to increase the oxygen concentration in the film. When the oxygen concentration of the antireflection layer 13 is increased, the hydrophilicity may increase, and therefore, it is preferable to increase the hydrophobicity of the adhesion layer 14.

Further, with respect to the phase shift layer 12, by adding CO₂Forming a chromium film by gas, by changing CO at the time of film formation₂The amount of gas added can control the optical constants of the phase shift layer 12, and the transmittance and phase difference of the phase shift mask 10 can be set.

In the phase shift mask 10 having a low reflection characteristic, when the adhesion layer 14, the antireflection layer 13, and the phase shift layer 12 are formed, oxygen-containing gas is selected as each sputtering gas, and the gas flow rate (partial pressure ratio) is set so that the composition ratio of oxygen and the like in each film can be set as described above.

For example, CO may be added during the formation of the phase shift layer 12₂The gas partial pressure is set to 15% to 25%, the NO gas partial pressure is set to 25% to 35% when the antireflection layer 13 is formed, and the NO gas partial pressure is set to 25% to 35% when the adhesion layer 14 is formed.

Alternatively, CO may be introduced₂The gas partial pressure is set to 0 to 5 percent, and CO₂The gas partial pressure is set to 5 to 15 percent, and CO is₂The gas partial pressure is set to 10-20%, CO₂The gas partial pressure is set to 20-30%, CO₂The gas partial pressure is set to 25 to 35%.

Further, the partial pressure of NO gas may be set to 5% to 15%, the partial pressure of NO gas may be set to 10% to 20%, the partial pressure of NO gas may be set to 15% to 25%, and the partial pressure of NO gas may be set to 20% to 30%. Further, these ranges may be used in combination.

In addition, when argon is contained in the sputtering gas, the partial pressure of the oxygen-containing gas can be set high.

In the phase shift mask 10 having a low reflection characteristic, the adhesion layer 14, the antireflection layer 13, and the phase shift layer 12 are formed of different materials, respectively. Therefore, when WET etching is used in the etching step for patterning, the etching solution can be changed to selectively etch the pattern.

For example, the molybdenum silicide compound may be etched by a mixed solution of ammonium bifluoride and hydrogen peroxide. For example, the chromium compound may be etched by a mixed solution of cerous ammonium nitrate and perchloric acid.

The WET etching selectivity is very large when these WET etches are different from each other. Therefore, the cross-sectional shape of the phase shift mask 10 after etching is a nearly vertical shape, and a good cross-sectional shape can be obtained.

The characteristics of the phase shift mask 10 having low reflection characteristics were verified.

For confirmation, the mask blank 10B of the phase shift mask 10 as a three-layer structure was formed. On the glass substrate 11, CO is used₂A chromium compound having a gas partial pressure of 20% was formed as the phase shift layer 12. On the phase shift layer 12, CO is used₂A molybdenum silicide compound having a gas partial pressure of 30% was formed as the antireflection layer 13. On the antireflection layer 13, a chromium compound formed at an NO gas partial pressure of 30% is used as the adhesion layer 14. Here, the film thickness of the phase shift layer 12 is 90nm, the film thickness of the antireflection layer 13 is 30nm, and the film thickness of the adhesion layer 14 is 10 nm.

The characteristic variation of the phase shift mask 10 was verified by changing the film thickness of the antireflection layer 13.

Fig. 11 shows the reflectance characteristics of the phase shift mask 10 when the film thickness of the anti-reflection layer 13 of the present embodiment is changed.

Fig. 12 shows transmittance characteristics of the phase shift mask 10 when the film thickness of the antireflection layer 13 of the present embodiment is changed.

LR represents the film thickness of the antireflection layer 13.

Accordingly, the anti-reflection layer 13 has a film thickness of 30 to 40nm and a reflectance of about 5%. That is, it is found that in the region where the film thickness of the antireflection layer 13 is in the vicinity of 30nm, for example, a low reflectance can be obtained in the vicinity of 400nm, such as 413 nm.

Next, the characteristic variation of the phase shift mask 10 was verified by changing the film thickness of the adhesion layer 14.

Fig. 13 shows the reflection characteristics of phase shift mask 10 when the thickness of adhesion layer 14 of the present example is changed.

Fig. 14 shows transmittance characteristics of the phase shift mask 10 when the thickness of the adhesion layer 14 of the present embodiment is changed.

AE represents the film thickness of the adhesion layer 14.

It is found that the reflectance tends to increase when the film thickness of the adhesion layer 14 is increased to 10nm or more, but the reflectance of the region having a wavelength of 400nm or so is sufficiently low at 10nm to obtain reflectance characteristics of about 5%. When the film thickness of the adhesion layer 14 is changed, the reflectance is reduced when the film thickness is thin. Further, if the thickness is increased, a component having a high refractive index is generated, and thus the reflectance is considered to be improved.

As can be seen from these, the phase shift mask 10 in the present embodiment has low reflectance characteristics.

Since the mask blank 10B and the photomask 10 according to the present embodiment can control the etching of the adhesion layer 14, the antireflection layer 13, and the phase shift layer 12 independently of each other, the sectional shape suitable for use as a mask can be obtained while the chemical resistance is high and the reflectance is sufficiently reduced.

Further, by controlling the gas flow rate ratio of the oxygen-containing gas or the like at the time of film formation, the composition and the film thickness of chromium, oxygen, nitrogen, and carbon contained in the film can be controlled, and a phase shift layer having a preferable transmittance and phase can be obtained, and similarly, a low-reflectance mask blank 10B and a photomask 10 can be realized by the adhesion layer 14 and the antireflection layer 13 having low values of the refractive index and the extinction coefficient.

In the present embodiment, the phase shift mask 10 having the phase shift layer 12 as the mask layer is described, but the present invention is not limited to this structure.

For example, instead of the phase shift layer 12, a light-shielding mask having a light-shielding layer, a halftone mask having a halftone layer, or a photomask including a combination of these layers in addition to other layers may be used.

Description of reference numerals

10 … … phase shift mask

10B … … mask blank

11 … … glass substrate (transparent substrate)

12 … … phase shift layer

12P … … phase shift pattern

13 … … anti-reflection layer

13P … … anti-reflection pattern

14 … … sealing layer

14P … … closed pattern

15 … … Photoresist layer

Claims

1. A mask blank having a layer as a phase shift mask, wherein the mask blank has:

a phase shift layer laminated on the transparent substrate;

an antireflection layer provided at a position farther from the transparent substrate than the phase shift layer; and

an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer,

the phase-shift layer contains chromium and,

the anti-reflective layer contains molybdenum silicide and oxygen,

the adhesion layer contains chromium and oxygen,

the oxygen content of the adhesion layer is set so as to have adhesion to the photoresist layer to enable patterning.

2. The mask blank according to claim 1, wherein the oxygen content of the adhesion layer is in a range of 8.4 atomic% to 65.7 atomic%.

3. The mask blank according to claim 2, wherein the adhesion layer contains nitrogen, and the nitrogen content of the adhesion layer is in a range of 3.7 atomic% to 42.3 atomic%.

4. The mask blank according to claim 2 or claim 3, wherein the adhesion layer contains carbon, and the carbon content of the adhesion layer is in a range of 2.2 atomic% to 2.3 atomic%.

5. The mask blank according to claim 2 or claim 3, wherein the chromium content of the adhesion layer is in the range of 25.2 atomic% to 42.4 atomic%.

6. The mask blank according to claim 1, wherein the film thickness of the adhesion layer is in a range of 5nm to 15 nm.

7. The mask blank according to claim 1, wherein an oxygen content of the antireflection layer is in a range of 6.7 atomic% to 63.2 atomic%.

8. The mask blank according to claim 7, wherein the anti-reflection layer contains nitrogen, and the nitrogen content of the anti-reflection layer is in a range of 4.6 atomic% to 39.3 atomic%.

9. The mask blank according to claim 1, wherein there is a photoresist layer disposed at a position farther from the transparent substrate than the adhesion layer.

10. A method of manufacturing a mask blank, the mask blank of any one of claims 1 to 9 being manufactured, the method comprising:

a phase shift layer forming step of laminating the phase shift layer containing chromium on the transparent substrate;

an antireflection layer forming step of laminating the antireflection layer containing molybdenum silicide and oxygen at a position farther from the transparent substrate than the phase shift layer; and

a bonding layer forming step of laminating the bonding layer containing chromium and oxygen at a position farther from the transparent substrate than the antireflection layer,

in the adhesion layer forming step, the adhesion layer is formed so as to have adhesion to the photoresist layer to enable pattern formation by setting a partial pressure of an oxygen-containing gas as a supply gas during sputtering.

11. The method for manufacturing a mask blank according to claim 10,

in the adhesion layer forming step, the partial pressure of the oxygen-containing gas is set so that the adhesion of the adhesion layer increases as the oxygen content increases.

12. The method for manufacturing a mask blank according to claim 11,

in the step of forming the adhesion layer, the partial pressure ratio of the oxygen-containing gas is set to be in the range of 0.00 to 0.30.

13. The method for manufacturing a mask blank according to claim 12,

in the bonding layer forming step, the oxygen-containing gas is NO.

14. A photomask produced from the mask blank according to any one of claims 1 to 9.

15. A method for manufacturing a photomask according to claim 14, the method comprising:

a phase shift pattern forming step of forming a pattern on the phase shift layer;

an antireflection pattern forming step of forming a pattern on the antireflection layer; and

a bonding pattern forming step of forming a pattern on the bonding layer,

the etching solution in the phase shift pattern forming step and the adhesion pattern forming step is different from the etching solution in the antireflection pattern forming step.