JP7303077B2 - Method for manufacturing mask blanks, method for manufacturing photomask, mask blanks and photomask - Google Patents

Description

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

2. Description of the Related Art As FPDs (flat panel displays) become more precise, there is an increasing need to form fine patterns. Therefore, not only the conventionally used mask using a light-shielding film but also an edge-emphasized phase-shifting mask (PSM mask; Phase-Shifting Mask) has come to be used.

These phase shift masks often have a high reflectance, and in such cases, the influence of standing waves increases during the exposure of the resist during mask fabrication, resulting in large variations in the line width of the mask pattern. . Therefore, it is desired to reduce the reflectance of the phase shift mask (Patent Document 1).

In order to reduce the reflectance of the phase shift mask, it is necessary to form a layer having a lower refractive index than the lower layer of the phase shift mask and reduce the reflectance using the optical interference effect.
A chromium material is generally used as a phase shift layer in mask blanks. In this case, an oxidized chromium oxide film can be used to obtain a film with a low refractive index as the antireflection layer.

WO2004/070472

However, a chromium oxide film with a high oxygen concentration has a low etching rate. As a result, when a chromium oxide film having a high oxygen concentration is used as the antireflection layer, the antireflection layer has a lower etching rate than the phase shift layer, so that the antireflection layer may not be etched.

Therefore, when a mask pattern is produced, etching of the phase shift layer progresses more than that of the antireflection layer, and there is a problem that a cross-sectional shape with an eaves is generated. I understand.

As a method for achieving both a low reflectance and a favorable cross-sectional shape, it is conceivable to use a metal silicide film such as a molybdenum silicide film for the antireflection layer when the phase shift layer is formed of a material containing chromium as a main component. . By forming the phase shift layer and the antireflection layer using different materials in this manner, etching can be performed selectively because one material is not etched when the other material is etched. As a result, it becomes possible to obtain a favorable cross-sectional shape.

However, since a silicide film such as a molybdenum silicide film has hydrophilic properties, it has been found that when a resist is applied thereon for pattern formation, the adhesion to the resist deteriorates. .

The present invention has been made in view of the above circumstances, and has an antireflection layer that achieves both a low reflectance and the ability to suppress etching of other layers with a high selection ratio, and has adhesion to the resist. An object of the present invention is to realize mask blanks and photomasks which are good and which allow reliable pattern formation.

The mask blanks of the present invention are mask blanks having a layer to be a phase shift mask,
a phase shift layer laminated on a transparent substrate;
an antireflection layer provided at a position further away from the transparent substrate than the phase shift layer;
an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer;
has
the phase shift layer contains chromium,
the antireflection layer contains molybdenum silicide and oxygen,
the adhesion layer contains chromium and oxygen,
The above problem is solved by setting the oxygen content in the adhesive layer so as to have adhesiveness that enables patterning to the photoresist layer.
In the mask blank of the present invention, the oxygen content in the adhesion layer can be set within the range of 8.4 atm % to 65.7 atm %.
In the present invention, it is preferable that the adhesion layer contains nitrogen, and the nitrogen content is set in the range of 3.7 atm % to 42.3 atm %.
In the mask blank of the present invention, the adhesion layer contains carbon, and the carbon content can be set in the range of 2.2 atm % to 2.3 atm %.
In the mask blanks of the present invention, it is also possible to employ means for setting the content of chromium in the range of 25.2 atm % to 42.4 atm % in the adhesion layer.
In the mask blank of the present invention, the adhesive layer may have a film thickness in the range of 5 nm to 15 nm.
In the mask blank of the present invention, the antireflection layer may have an oxygen content in the range of 6.7 atm % to 63.2 atm %.
In the mask blank of the present invention, the antireflection layer contains nitrogen, and the nitrogen content can be set in the range of 4.6 atm % to 39.3 atm %.
The mask blanks of the present invention can have a photoresist layer provided at a position spaced apart from the transparent substrate more than the adhesion layer.
A method for manufacturing a mask blank of the present invention is the method for manufacturing a mask blank according to any one of the above,
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;
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;
has
In the adhesion layer forming step,
By setting the partial pressure of the oxygen-containing gas as the supply gas in the sputtering, the adhesion layer can be formed so as to have adhesion that enables patterning formation with respect to the photoresist layer.
In the mask blank manufacturing method of the present invention, in the adhesion layer forming step,
By setting the partial pressure of the oxygen-containing gas, the adhesion of the adhesion layer can be increased as the oxygen content increases.
In the mask blank manufacturing method of the present invention, in the adhesion layer forming step,
It is preferable to set the partial pressure ratio of the oxygen-containing gas in the range of 0.00 to 0.30.
In the mask blank manufacturing method of the present invention, in the adhesion layer forming step,
The oxygen-containing gas can be NO.
The photomask of the present invention can be manufactured from any of the mask blanks described above.
In the method for manufacturing a photomask of 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;
an adhesion pattern forming step of forming a pattern on the adhesion layer;
has
The etchant used in the phase shift pattern forming step and the adhesion pattern forming step may be different from the etchant used in the antireflection pattern forming step.

The mask blanks of the present invention are mask blanks having a layer to be a phase shift mask,
a phase shift layer laminated on a transparent substrate;
an antireflection layer provided at a position further away from the transparent substrate than the phase shift layer;
an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer;
has
the phase shift layer contains chromium,
the antireflection layer contains molybdenum silicide and oxygen,
the adhesion layer contains chromium and oxygen,
In the adhesion layer, the oxygen content is set so as to have adhesion that enables patterning to the photoresist layer.
As a result, a mask blank having an antireflection layer containing molybdenum silicide, which originally has poor adhesion to the photoresist layer, has sufficient adhesion to the photoresist layer by having the adhesion layer in contact with the photoresist layer. to allow the required patterning. At this time, at the same time, in the antireflection layer, the oxygen content in the antireflection layer set according to the profile in which the refractive index value in the antireflection layer decreases as the oxygen content increases, the antireflection layer can set the value of the refractive index in
Here, it is desirable to use a chromium compound as the adhesion layer. A chromium compound is suitable for use at the interface that comes into contact with the resist because it has the property of being highly resistant to acid and alkaline solutions and the property of being hydrophobic.

Among metal silicides, molybdenum silicide is preferably used as the antireflection layer. This is because molybdenum silicide is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide, which is commonly used for mask cleaning, and optical properties can be greatly controlled by controlling the concentrations of nitrogen and oxygen contained in molybdenum silicide. Because it is possible.
Further, the refractive index and extinction coefficient of the antireflection layer can be set by the oxygen content of the antireflection layer.
Moreover, it is desirable to use a chromium compound as the phase shift layer. It is possible to form a phase shift film (mask layer) with two kinds of materials, ie, a chromium compound and a metal silicide, which are highly resistant to chemicals.

As a result, the refractive index of the antireflection layer can be set to a predetermined value while maintaining the necessary adhesion, and the antireflection layer can have a lower refractive index than the phase shift layer. can be reduced. At the same time, since the adhesion layer and the phase shift layer contain chromium, and the antireflection layer contains molybdenum silicide, different etchants (etching liquids) are used for patterning them by etching. As a rate, it becomes possible to exhibit high selectivity. Therefore, it is possible to provide a mask blank capable of manufacturing a phase shift mask having a desired cross-sectional shape without affecting each other in etching the phase shift layer, the antireflection layer, and the adhesion layer.

Here, in the mask blanks of the present invention, the reflectance as mask blanks is reduced. For this purpose, it is important to make the optical constants of the adhesion layer and the antireflection layer close to each other, and then increase the difference in the values of the refractive index and the extinction coefficient between the antireflection layer and the phase shift layer. is. Therefore, in order to reduce the reflectance of the mask blank, it is desirable to reduce the values of the refractive index and the extinction coefficient of the adhesion layer and the antireflection layer.

In the mask blanks of the present invention, the oxygen content in the adhesion layer is set within the range of 8.4 atm % to 65.7 atm %.
As a result, the adhesion layer can have sufficient adhesion to the photoresist layer, and can maintain the state of having the optical properties necessary for the mask layer. In particular, by increasing the oxygen content in the adhesive layer, it is possible to decrease the hydrophilicity and improve the hydrophobicity, thereby improving the adhesion to the photoresist. Furthermore, by increasing the oxygen content in the adhesion layer, it is possible to lower the values of the refractive index and the extinction coefficient.

In the present invention, the adhesion layer contains nitrogen, and the nitrogen content is set in the range of 3.7 atomic % to 42.3 atomic %.
As a result, the adhesion layer can have sufficient adhesion to the photoresist layer, has a predetermined etching rate, and at the same time has optical properties as a mask layer set together with other layers. Desired mask blanks can be obtained while maintaining a state in which they do not affect the In particular, by increasing the nitrogen content in the adhesion layer, it is possible to lower the values of the refractive index and the extinction coefficient.
Furthermore, in the chromium compound used for the adhesion layer, it is possible to lower the refractive index and the extinction coefficient 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 can be set in the range of 2.2 atm % to 2.3 atm %.
As a result, the adhesion layer can have sufficient adhesion to the photoresist layer, has a predetermined etching rate, and at the same time has optical properties as a mask layer set together with other layers. Desired mask blanks can be obtained while maintaining a state in which they do not affect the

In the mask blanks of the present invention, it is also possible to employ means for setting the content of chromium in the range of 25.2 atm % to 42.4 atm % in the adhesion layer.
As a result, the adhesion layer can have sufficient adhesion to the photoresist layer, has a predetermined etching rate, and at the same time has optical properties as a mask layer set together with other layers. Desired mask blanks can be obtained while maintaining a state in which they do not affect the
It is desirable to use a chromium compound as the adhesion layer. A chromium compound is suitable for use at the interface that comes into contact with the resist because it has the property of being highly resistant to acid and alkaline solutions and the property of being hydrophobic.

In the mask blank of the present invention, the adhesive layer may have a film thickness in the range of 5 nm to 15 nm.
As a result, the adhesion layer can have sufficient adhesion to the photoresist layer, has a predetermined etching rate, and at the same time has optical properties as a mask layer set together with other layers. Desired mask blanks can be obtained while maintaining a state in which they do not affect the

In the mask blank of the present invention, the oxygen content in the antireflection layer is set within the range of 6.7 atm % to 63.2 atm %.
As a result, the antireflection layer can have a refractive index within the range of 2.5 to 1.8 at wavelengths of 365 nm to 436 nm.
As a result, the antireflection layer can have a lower refractive index than the phase shift layer containing chromium, and the reflectance of the mask blank can be reduced.
Therefore, the reflectance of the antireflection layer can be lowered, and while the cross-sectional shape in patterning is maintained in a predetermined state, as a mask layer, for example, in the wavelength band from g-line (436 nm) to i-line (365 nm) It is possible to have a low reflective transmittance.
This makes it possible to provide blanks having a predetermined reflectance even in patterning using laser light in FPD manufacturing.

By containing molybdenum silicide in the antireflection layer, molybdenum silicide is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide, which is commonly used for mask cleaning. can be largely controlled.
In addition, in the antireflection layer, the oxygen content in the antireflection layer set according to the profile in which the refractive index value in the antireflection layer decreases as the oxygen content increases, the refractive index in the antireflection layer A rate value can be set.
As a result, the refractive index of the antireflection layer can be set to a predetermined value to form an antireflection layer having a lower refractive index than that of the phase shift layer, and the reflectance of the mask blank can be reduced.

Further, in the antireflection layer, the oxygen content can be set within the above range, and the value of the extinction coefficient at wavelengths of 365 nm to 436 nm can be set within the range of 0.6 to 0.1.
As a result, an antireflection layer having a predetermined refractive index and extinction coefficient can be formed with respect to the chromium-containing phase shift layer, and the reflectance of the mask blank can be set to a predetermined value. .

In the mask blank of the present invention, the antireflection layer contains nitrogen, and the nitrogen content is set in the range of 4.6 atm % to 39.3 atm %.
As a result, an antireflection layer having a predetermined refractive index and extinction coefficient can be formed with respect to the chromium-containing phase shift layer, and the reflectance of the mask blank can be set to a predetermined value. .
By using molybdenum silicide as the metal silicide used in the antireflection layer and increasing the nitrogen concentration and oxygen concentration in the antireflection layer, it is possible to lower the refractive index and the extinction coefficient. 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.

In addition, by providing the antireflection layer, the reflectance ratio at a wavelength of 365 nm to 436 nm is reduced to a range of 1 (25%) to 1/5 (5%) compared to the case where the antireflection layer is not provided. be able to.
As a result, an antireflection layer having a predetermined refractive index and extinction coefficient can be formed with respect to the chromium-containing phase shift layer, and the reflectance of the mask blank can be set to a predetermined value. .

The mask blank of the present invention has a photoresist layer provided at a position spaced apart from the transparent substrate more than the adhesion layer.
As a result, the mask blank has sufficient adhesion between the photoresist layer and the mask layer when patterning is performed by photolithography, and the etchant does not enter the interface of the photoresist layer on the transparent substrate side. can do.

A method for manufacturing a mask blank of the present invention is the method for manufacturing a mask blank according to any one of the above,
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;
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;
has
In the adhesion layer forming step,
By setting the partial pressure of the oxygen-containing gas as the supply gas in the sputtering, the adhesion layer is formed so as to have adhesion that enables patterning to the photoresist layer.
As a result, in the adhesion layer forming step, the adhesion layer containing chromium is laminated on the antireflection layer by sputtering while the partial pressure of the oxygen-containing gas is set within a predetermined range, thereby reducing the hydrophobicity of the adhesion layer. As a result, 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, while maintaining the required adhesion and maintaining the cross-sectional shape in patterning in a predetermined state, the mask layer has a low wavelength band from the g-line (436 nm) to the i-line (365 nm), for example. It becomes possible to have a reflective transmittance.

Specifically, first, a chromium compound film, which is the main component film of the phase shift layer, is formed on a glass substrate (transparent substrate) used as a mask blank by sputtering 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, it is possible to form a phase shift layer having desired transmittance and phase.

At this time, if the phase shift layer is formed only from a chromium compound, the reflectance will be as high as about 25%. Therefore, it is desirable to reduce the reflectance by forming a low-reflection layer on the surface of the phase shift layer.

Therefore, by adjusting the film thickness and optical constants of the antireflection layer in addition to adjusting the film thickness and optical constants of the chromium film forming the phase shift layer, It is necessary to control phase difference and transmittance and reflectance.

Here, by forming the antireflection layer with a different material from the phase shift layer, when wet etching is used in the etching process, it is possible to selectively etch by changing the etchant as a different etching process. is.

In order to reduce the reflectance of the phase shift mask, it is important to increase the difference in refractive index and extinction coefficient between the antireflection layer and the phase shift layer. Therefore, in order to reduce the reflectance of the phase shift mask, it is desirable to reduce the refractive index and extinction coefficient of the antireflection layer.

As a result of intensive studies, the present inventors have found that a chromium compound is used as an adhesion layer for improving the adhesion to the photoresist on the outermost surface of the mask layer, and a metal silicide such as molybdenum silicide is used as an antireflection layer below it. By using a three-layer structure using a chromium compound as the bottom layer as a phase shift layer, the adhesiveness with the photoresist layer is improved, and during etching, each layer has a high selectivity to other layers. We have found that it is desirable to use a process that can suppress the etching of .

As a result, the etching of the adhesion layer, the antireflection layer, and the phase shift layer can be independently controlled, so that the cross-sectional shape suitable for use as a mask while sufficiently reducing the reflectance can be obtained. It is possible to obtain

Further, the inventors have found that it is desirable to use molybdenum silicide among metal silicides as the antireflection layer.
This is based on the knowledge that it is possible to greatly control the optical properties by controlling the concentrations of nitrogen and oxygen contained in molybdenum silicide. This is because the optical constant of the molybdenum silicide film can be greatly controlled by controlling the concentrations of molybdenum, silicon, oxygen, and nitrogen contained in the molybdenum silicide film.

In particular, the inventors have found that molybdenum silicide can lower the refractive index and extinction coefficient by increasing the nitrogen and oxygen concentrations in the film.
In particular, it was 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, by using a chromium compound as the phase shift layer and using a molybdenum silicide film as the antireflection layer, it is possible to lower the reflectance of the phase shift mask.

In addition, high selectivity in etching can be provided as compared with the case where a chromium compound is used as the phase shift layer.
Furthermore, molybdenum silicide is highly resistant to a mixture of sulfuric acid and hydrogen peroxide, which is commonly used in mask cleaning.

In the mask blank manufacturing method of the present invention, in the adhesion layer forming step,
By setting the partial pressure of the oxygen-containing gas, the adhesion of the adhesion layer increases as the oxygen content increases.
As a result, in the adhesion layer forming step, by laminating the adhesion layer on the antireflection layer while setting the partial pressure of the oxygen-containing gas within a predetermined range, the photoresist layer depends on the hydrophobicity and water repellency of the adhesion layer. It is possible to set the values of the adhesion to the film and the values of the refractive index and the extinction coefficient to predetermined values.
Here, by setting the partial pressure of the oxygen-containing gas in sputtering to a predetermined value, the values of the refractive index and the extinction coefficient in the adhesive layer can be set.
Specifically, in the adhesion layer forming step, the partial pressure of the oxygen-containing gas is increased to increase the adhesion of the adhesion layer to the photoresist layer, and the values of the refractive index and the extinction coefficient of the adhesion layer can be decreased, and the partial pressure of the oxygen-containing gas can be decreased to increase the values of the refractive index and the extinction coefficient in the adhesion layer.

In the mask blank manufacturing method of the present invention, in the adhesion layer forming step,
A partial pressure ratio of the oxygen-containing gas is set within a range of 0.00 to 0.30.
As a result, the adhesion layer can be laminated on the antireflection layer with a predetermined oxygen content. Therefore, it is possible to set the adhesion of the adhesion layer to the photoresist layer, the refractive index, and the extinction coefficient to predetermined values.

In the mask blank manufacturing method of the present invention, in the adhesion layer forming step,
The oxygen-containing gas can be NO.
In addition, _O2 , CO, _NOx , etc. can also be used as oxygen-containing gas.
Furthermore, in the adhesion layer forming step, a gas different from the oxygen-containing gas used when forming the same chromium-containing phase shift layer can be employed.

The photomask of the present invention can be manufactured from any of the mask blanks described above.

In the method for manufacturing a photomask of 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;
an adhesion pattern forming step of forming a pattern on the adhesion layer;
has
The etchant used in the phase shift pattern forming step and the adhesion pattern forming step is different from the etchant used in the antireflection pattern forming step.
This makes it possible to exhibit high selectivity as different etchants. Therefore, it is possible to provide a mask blank that can manufacture a photomask having a desired cross-sectional shape without affecting each other in the respective etchings of the adhesive layer, the phase shift layer, and the antireflection layer.
Thereby, a photomask having desired film properties can be manufactured for each layer.

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

According to the present invention, it has an antireflection layer that achieves both a low reflectance and the ability to suppress etching of other layers with a high selectivity, and has good adhesion to the resist, enabling reliable pattern formation. It is possible to obtain the effect of being able to provide mask blanks and photomasks of high quality.

1 is a cross-sectional view showing a first embodiment of mask blanks according to the present invention; FIG. 1 is a cross-sectional view showing a first embodiment of mask blanks according to the present invention; FIG. 1 is a cross-sectional view showing a first embodiment of a photomask according to the present invention; FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a film forming apparatus in a first embodiment of a method for manufacturing mask blanks and photomasks according to the present invention; 2 is a graph showing the CO ₂ partial pressure ratio dependence of the refractive index of the MoSi compound applied to the antireflection layer of the first embodiment of the mask blank and photomask manufacturing method according to the present invention. 2 is a graph showing the dependence of the extinction coefficient of the MoSi compound applied to the antireflection layer of the first embodiment of the mask blank and photomask manufacturing method according to the present invention on the CO ₂ partial pressure ratio. 4 is a graph showing NO partial pressure ratio dependence of the refractive index of the Cr compound applied to the adhesion layer of the first embodiment of the mask blanks and photomask manufacturing method according to the present invention. 4 is a graph showing the NO partial pressure ratio dependency of the extinction coefficient of the Cr compound applied to the adhesion layer of the first embodiment of the mask blanks and photomask manufacturing method according to the present invention. 4 is a graph showing the CO ₂ partial pressure ratio dependence of the refractive index of a Cr compound applied to the phase shift layer of the first embodiment of the mask blank and photomask manufacturing method according to the present invention. 4 is a graph showing the dependence of the extinction coefficient of the Cr compound applied to the phase shift layer of the first embodiment of the mask blank and photomask manufacturing method of the present invention on the CO ₂ partial pressure ratio. 4 is a graph showing the film thickness dependence of the antireflection layer of the reflectance characteristics in the first embodiment of the mask blank and photomask manufacturing method according to the present invention. 5 is a graph showing the transmittance characteristics and film thickness dependence of the antireflection layer in the first embodiment of the mask blank and photomask manufacturing method according to the present invention. 4 is a graph showing the film thickness dependence of the adhesive layer of the reflectance characteristics in the first embodiment of the mask blank and photomask manufacturing method according to the present invention. 5 is a graph showing the film thickness dependence of the adhesion layer of the transmittance characteristics in the first embodiment of the mask blanks and photomask manufacturing method according to the present invention.

A first embodiment of mask blanks, a phase shift mask, and a method for manufacturing the same according to the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view showing the mask blanks in this embodiment, FIG. 2 is a cross-sectional view showing the mask blanks in this embodiment, and reference numeral 10B denotes the mask blanks.

The mask blank 10B according to the present embodiment is intended to be used for a phase shift mask (photomask) used with exposure light having a wavelength in the range of about 365 nm 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, and a It is composed of an antireflection layer 13 and an adhesion 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 is. Also, the adhesion layer 14 is provided at a position spaced apart from the glass substrate 11 more than the antireflection layer 13 .
The phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 constitute a mask layer, which is a phase shift film having optical characteristics necessary for a photomask and low reflection.

Furthermore, the mask blank 10B according to the present embodiment has, as shown in FIG. A configuration in which the photoresist layer 15 is formed in advance may also be used.

Note that the mask blank 10B according to the present embodiment may be configured by laminating a chemical-resistant layer, a protective layer, a light-shielding layer, an etching stopper layer, etc., in addition to the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14. good. Furthermore, a photoresist layer 15 may be formed on these laminated films as shown in FIG.

As the glass substrate (transparent substrate) 11, a material having excellent transparency and optical isotropy is 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 the substrate to be exposed using the mask (for example, a substrate for FPD such as LCD (liquid crystal display), plasma display, organic EL (electroluminescence) display, etc.). be done.

In this embodiment, as the glass substrate (transparent substrate) 11, a rectangular substrate having a side of about 100 mm to 2000 mm or more can be applied. Substrates can also be used.

Further, 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 can be set to 20 μm or less, for example. As a result, the depth of focus of the mask is increased, making it possible to greatly contribute to fine and highly accurate pattern formation. Furthermore, the flatness is 10 μm or less, and the smaller the better.

The phase shift layer 12 is mainly composed of Cr (chromium) and further contains C (carbon), O (oxygen) and N (nitrogen).
Furthermore, the phase shift layer 12 can have different compositions in the thickness direction. One or two or more selected from carbonitrides can also be laminated.
As will be described later, the thickness of the phase shift layer 12 and the composition ratio (atm %) of Cr, N, C, O, etc. are set so as to obtain predetermined optical characteristics and resistivity.

The film thickness of the phase shift layer 12 is set according to the optical properties required for the phase shift layer 12, and changes according to the composition ratio of Cr, N, C, O, and the like. The film thickness of the phase shift layer 12 can be 50 nm to 150 nm.

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

As a result, when the phase shift layer 12 has a refractive index of about 2.4 to 3.1 and an extinction coefficient of about 0.3 to 2.1 in a wavelength range of about 365 nm to 436 nm, the film thickness is about 90 nm. can be set.

As the antireflection layer 13, a metal silicide film such as a metal such as Ta, Ti, W, Mo, Zr, or a film containing silicon and an alloy of these metals is used as a material different from that of the phase shift layer 12. can do. In particular, among metal silicides, molybdenum silicide is preferably used, and examples thereof include MoSi _x (X≧2) films (eg, MoSi ₂ film, MoSi ₃ film, MoSi ₄ film, etc.).

The antireflection layer 13 is preferably a molybdenum silicide film containing O (oxygen) and N (nitrogen).
Furthermore, the antireflection layer 13 preferably contains C (carbon).
In the antireflection layer 13, the oxygen content (oxygen concentration) is set in the range of 6.7 atm% to 63.2 atm%, and the nitrogen content (nitrogen concentration) is set in the range of 4.6 atm% to 39.3 atm%. However, the carbon content (carbon concentration) can be set in the range of 4.0 atm % to 13.5 atm %.

In the antireflection layer 13, it is desirable to use a molybdenum silicide compound containing 36 atm % or more of oxygen content (oxygen concentration) and 10 atm % or more of nitrogen content (nitrogen concentration).
In the antireflection layer 13, it is possible to increase the nitrogen concentration and oxygen concentration in the film to lower the values of the refractive index and the extinction coefficient. In particular, by increasing the oxygen concentration in the film, the values of the refractive index and the extinction coefficient are greatly reduced.
Also, by setting the film thickness of the antireflection layer 13 to 30 nm or more and 60 nm or less, the reflectance at wavelengths of 365 to 436 nm can be reduced.

At this time, in the antireflection layer 13, the silicon content (silicon concentration) is set in the range of 11.1 atomic % to 21.7 atomic %, and the molybdenum content (molybdenum concentration) is set in the range of 14.9 atomic % to 28.3 atomic %. A range can be set.

Thereby, in the antireflection layer 13, the value of the refractive index at wavelengths of 365 nm to 436 nm can be set in the range of 2.5 to 1.8.
Further, in the antireflection layer 13, the value of the extinction coefficient at wavelengths of 365 nm to 436 nm can be set within the range of 0.7 to 0.1.

Therefore, in the mask blank 10B of the present embodiment, by having the phase shift layer 12 and the antireflection layer 13, the reflectance ratio at a wavelength of 365 nm to 436 nm is 1 ( 25%) to 1/5 (5%).

The adhesion layer 14 is mainly composed of Cr (chromium) and O (oxygen), and further contains C (carbon) and N (nitrogen).
In this case, the adhesion layer 14 may be formed by laminating one or more selected from Cr oxides, nitrides, carbides, oxynitrides, carbonitrides, and oxycarbonitrides. can. Furthermore, the adhesion layer 14 can have different compositions in the thickness direction.
As will be described later, the adhesion layer 14 has a predetermined adhesion (hydrophobicity), a thickness so as to obtain predetermined optical characteristics, and a composition ratio (atm %) of Cr, N, C, O, Si, etc. is set.

For example, the composition ratio of the adhesion layer 14 is as follows: oxygen content (oxygen concentration) is 8.4 atomic % to 65.7 atomic %, nitrogen content (nitrogen concentration) is 3.7 atomic % to 42.3 atomic %, and chromium is 25.5 atomic %. It can be set to be 2 atm % to 42.4 atm %, carbon content (carbon concentration) is 2.2 atm % to 2.3 atm %, and silicon is 3.3 atm % to 4.7 atm %.

The film thickness of the adhesion layer 14 is set according to the adhesion (hydrophobicity) and optical characteristics required for the adhesion layer 14, and changes according to the composition ratio of Cr, N, C, O, and the like. The film thickness of the adhesion layer 14 can be 5 nm to 20 nm, further 10 nm to 15 nm.
By setting the film thickness of the adhesive layer 14 within the above range, the adhesiveness to the photoresist layer 15 used for chromium-based materials, for example, can be improved during patterning formation in the photolithography method, and the interface with the photoresist layer 15 can be improved. Since the penetration of the etchant does not occur in , a good pattern shape can be obtained and a desired pattern can be formed.

If the film thickness of the adhesion layer 14 is smaller than the above range, the adhesion with the photoresist layer 15 will not be in a predetermined state, the photoresist layer 15 will peel off, and the etchant will enter the interface. is not preferable because pattern formation cannot be performed. If the adhesion layer 14 has a thickness greater than the above range, it may be difficult to set the optical characteristics of the photomask to desired conditions, or the cross-sectional shape of the mask pattern may not be in a desired state. It is not preferred because of its volatility.

By increasing the concentration of oxygen and nitrogen in the chromium compound, the adhesion layer 14 can reduce hydrophilicity, improve hydrophobicity, and increase adhesion.
At the same time, the adhesion layer 14 can have a low refractive index and a low extinction coefficient by increasing the oxygen concentration and nitrogen concentration in the chromium compound.

In the method of manufacturing the mask blanks in this embodiment, after forming the phase shift layer 12 on the glass substrate (transparent substrate) 11, the antireflection layer 13 is formed, and then the adhesion layer 14 is formed. be.

The manufacturing method of the mask blanks includes a lamination step of a protective layer, a light-shielding layer, a chemical-resistant layer, an etching stopper layer, etc., in addition to the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, if they are laminated. be able to.
As an example, for example, a light shielding layer containing chromium can be mentioned.

FIG. 3 is a cross-sectional view showing a photomask in this embodiment.
As shown in FIG. 3, the phase shift mask (photomask) 10 in this embodiment is formed by forming a pattern on the phase shift layer 12, the antireflection layer 13 and the adhesion layer 14 which are laminated as the mask blanks 10B. be.

A manufacturing method for manufacturing the phase shift mask 10 from the mask blank 10B of this embodiment will be described below.

As a resist pattern forming step, as shown in FIG. 2, a photoresist layer 15 is formed on the outermost surface of the mask blanks 10B. Alternatively, the mask blanks 10B having the photoresist layer 15 formed on the outermost surface in advance may be prepared. The photoresist layer 15 may be positive or negative. The photoresist layer 15 is made to be compatible with etching of so-called chromium-based materials and etching of molybdenum silicide-based materials. A liquid resist is used as the photoresist layer 15 .

Subsequently, a resist pattern is formed outside the adhesion layer 14 by exposing and developing the photoresist layer 15 . The resist pattern functions as an etching mask for the phase shift layer 12 , the antireflection layer 13 and the adhesion layer 14 .

The shape of the resist pattern is appropriately determined according to the etching pattern of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14. FIG. As an example, the phase shift region is set to have a shape having an aperture width corresponding to the aperture width dimension of the phase shift pattern to be formed.

Next, in the adhesion pattern forming step, the adhesion layer 14 is wet-etched using an etchant through the resist pattern to form an adhesion pattern 14P.

As the etching solution in the adhesion pattern forming step, an etching solution containing ceric ammonium nitrate can be used. For example, it is preferable to use cerium nitrate ammonium containing an acid such as nitric acid or perchloric acid.

Next, as an antireflection pattern forming step, the antireflection layer 13 is wet-etched using an etchant through the adhesion pattern 14P to form an antireflection pattern 13P.

When the antireflection layer 13 is MoSi, the etchant used in the antireflection pattern formation step is at least one fluorine compound selected from hydrofluoric acid, hydrosilicofluoric acid, and ammonium hydrogen fluoride. and at least one oxidizing agent selected from hydrogen peroxide, nitric acid and sulfuric acid.

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

As the etching solution in the phase shift pattern forming step, an etching solution containing ceric ammonium nitrate can be used. For example, it is preferable to use ceric ammonium nitrate containing an acid such as nitric acid or perchloric acid.

The molybdenum silicide compound forming the antireflection layer 13 can be etched with, for example, a mixed solution of ammonium hydrogen fluoride and hydrogen peroxide. On the other hand, the chromium compound forming the adhesion layer 14 and the phase shift layer 12 can be etched with, for example, a mixed solution of ceric ammonium nitrate and perchloric acid.

Therefore, the selectivity in each wet etching becomes very large. Therefore, after the adhesion pattern 14P, the antireflection pattern 13P, and the phase shift pattern 12P are formed by etching, it is possible to obtain a favorable cross-sectional shape of the phase shift mask 10 that is nearly vertical. .

Further, in the phase shift pattern forming process, the oxygen concentration of the adhesion layer 14 is set higher than that of the phase shift layer 12, so the etching rate is lowered. Therefore, the etching of the adhesion pattern 14</b>P progresses slower than the etching of the phase shift layer 12 .

That is, the angle (taper angle) θ between the contact pattern 14P, the antireflection pattern 13P, and the phase shift pattern 12P and the surface of the glass substrate 11 becomes close to a right angle, for example, about 90°.

Moreover, since the adhesion pattern 14P is formed from the adhesion layer 14, the adhesion between the adhesion pattern 14P and the resist pattern is improved. This prevents the etchant from entering the interface between the contact pattern 14P and the resist pattern. Therefore, reliable pattern formation can be performed.

Furthermore, in the case of the mask blank 10B on which other films such as a light-shielding layer are formed, the adhesion pattern 14P, the antireflection pattern 13P and the phase shift pattern 12P are etched by wet etching or the like using a corresponding etchant. is patterned into a predetermined shape corresponding to the Patterning of other films such as the light-shielding layer can be performed as a predetermined process before and after patterning of the phase shift layer 12, the antireflection layer 13 and the adhesion layer 14 corresponding to the stacking order.

Further, by changing the oxygen concentration in the film thickness direction of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, it is possible to improve the cross-sectional shape after patterning.
Specifically, it is known that the etching rate of the antireflection layer 13, that is, the MoSi film, increases as the oxygen concentration in the film increases. Therefore, by setting the oxygen concentration on the upper layer side of the antireflection layer 13 to be lower than that on the lower layer side, the etching rate on the upper layer side can be made lower than that on the lower layer side. As a result, the cross-sectional shape after etching can be made nearly vertical.
On the other hand, in the phase shift layer 12 and the adhesion layer 14, that is, the Cr film, the higher the oxygen concentration in the film, the lower the etching rate. Therefore, for the phase shift layer 12 and the adhesion layer 14, by making the oxygen concentration on the upper layer side higher than the oxygen concentration on the lower layer side, the etching rate on the upper layer side can be made lower than the etching rate on the lower layer side. .

As a result, phase shift mask 10 having adhesion pattern 14P, antireflection pattern 13P and phase shift pattern 12P is obtained as shown in FIG.

A method for manufacturing mask blanks according to the present embodiment will be described below with reference to the drawings.

FIG. 4 is a schematic diagram showing a mask blank manufacturing apparatus according to this embodiment.
The mask blanks 10B in this embodiment are manufactured by the manufacturing apparatus shown in FIG.

The manufacturing apparatus S10 shown in FIG. 4 is an inter-back type sputtering apparatus, and is connected to the load chamber S11 and the unload chamber S16 via a sealing mechanism S187. and a film forming chamber (vacuum processing chamber) S12 connected via S18.

The load chamber S11 is provided with a transport mechanism S11a for transporting the glass substrate 11 loaded from the outside to the film forming chamber S12, and an exhaust mechanism S11f such as a rotary pump for roughly evacuating the interior of the chamber.

The unload chamber S16 is provided with a transfer mechanism S16a for transferring the glass substrate 11 on which film formation has been completed from the film formation chamber S12 to the outside, and an exhaust mechanism S16f such as a rotary pump for roughly evacuating the chamber.

The film formation chamber S12 is provided with a substrate holding mechanism S12a and two-stage film formation mechanisms S13, S14, and S15 as mechanisms corresponding to three film formation processes.

The substrate holding mechanism S12a holds the glass substrate 11 transported by the transport mechanism S11a so as to face the targets S13b, S14b, and S15b during film formation, and moves the glass substrate 11 from the load chamber S11. can be carried in and out to the unloading chamber S16.

A film formation mechanism S13 for supplying a first-stage film formation material among the three-stage film formation mechanisms S13, S14, and S15 is provided at the load chamber S11 side position of the film formation chamber S12.
The film forming mechanism S13 has a cathode electrode (backing plate) S13c having a target S13b, and a power source S13d for applying a negative sputtering voltage to the backing plate S13c.

The film formation mechanism S13 includes a gas introduction mechanism S13e that introduces gas mainly in the vicinity of the cathode electrode (backing plate) S13c in the film formation chamber S12, and a gas introduction mechanism S13e that mainly introduces gas in the vicinity of the cathode electrode (backing plate) S13c in the film formation chamber S12. and a high vacuum pumping mechanism S13f such as a turbo-molecular pump for drawing a high vacuum.

Further, in the film forming chamber S12, a film forming mechanism S14 for supplying the second film forming material among the two film forming mechanisms S13, S14, and S15 is provided at an intermediate position between the load chamber S11 and the unload chamber S16. is provided.
The film forming mechanism S14 has a cathode electrode (backing plate) S14c having a target S14b, and a power source S14d for applying a negative sputtering voltage to the backing plate S14c.

The film formation mechanism S14 includes a gas introduction mechanism S14e that introduces gas mainly in the vicinity of the cathode electrode (backing plate) S14c in the film formation chamber S12, and a gas introduction mechanism S14e that mainly introduces gas in the vicinity of the cathode electrode (backing plate) S14c in the film formation chamber S12. and a high vacuum pumping mechanism S14f such as a turbomolecular pump for drawing a high vacuum.

Furthermore, a film forming mechanism S15 for supplying the third stage film forming material among the three stage film forming mechanisms S13, S14, and S15 is provided at the position of the film forming chamber S12 on the side of the unloading chamber S16.
The film forming mechanism S15 has a cathode electrode (backing plate) S15c having a target S15b, and a power source S15d for applying a negative sputtering voltage to the backing plate S15c.

The film formation mechanism S15 includes a gas introduction mechanism S15e that introduces gas mainly in the vicinity of the cathode electrode (backing plate) S15c in the film formation chamber S12, and a gas introduction mechanism S15e that mainly introduces gas in the vicinity of the cathode electrode (backing plate) S15c in the film formation chamber S12. and a high vacuum pumping mechanism S15f such as a turbo-molecular pump for drawing a high vacuum.

In the deposition chamber S12, the gases supplied from the gas introduction mechanisms S13e, S14e, and S15e are mixed into the adjacent deposition mechanisms S13, S14, and S15 in the vicinity of the cathode electrodes (backing plates) S13c, S14c, and S15c. A gas barrier S12g is provided to restrain the gas flow so that it does not occur. These gas barriers S12g are configured so that the substrate holding mechanism S12a can move between the adjacent film forming mechanisms S13, S14, and S15.

In the film-forming chamber S12, each of the three-stage film-forming mechanisms S13, S14, and S15 has the necessary composition and conditions for forming films on the glass substrate 11 in order.
In this embodiment, the film forming mechanism S13 corresponds to film formation of the phase shift layer 12, the film forming mechanism S14 corresponds to film formation of the antireflection layer 13, and the film forming mechanism S15 corresponds to film formation of the adhesion layer 14. Suitable for film deposition.

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

At the same time, in the film forming mechanism S13, the gas supplied from the gas introduction mechanism S13e is a process gas containing carbon, nitrogen, oxygen, etc., corresponding to the film formation of the phase shift layer 12, and argon, nitrogen gas, etc. is set as a predetermined gas partial pressure together with the sputtering gas of .

In addition, exhaust is performed from the high vacuum exhaust mechanism S13f in accordance with film forming conditions.
Further, in the film forming mechanism S13, the sputtering voltage applied from the power source S13d to the backing plate S13c is set corresponding to the film formation of the phase shift layer 12. FIG.

In the deposition mechanism S14, the target S14b is made of a material containing molybdenum silicide as a composition necessary for depositing the antireflection layer 13 on the phase shift layer 12. FIG.

At the same time, in the film-forming mechanism S14, the gas supplied from the gas introduction mechanism S14e is a process gas containing carbon, nitrogen, oxygen, etc., corresponding to the film-forming of the antireflection layer 13, and argon, nitrogen gas, etc. is set as a predetermined gas partial pressure together with the sputtering gas of .

Further, the high-vacuum exhaust mechanism S14f performs exhaust according to film forming conditions.
Further, in the film forming mechanism S14, the sputtering voltage applied from the power source S14d to the backing plate S14c is set corresponding to the film formation of the antireflection layer 13. FIG.

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

At the same time, in the film-forming mechanism S15, as the gas supplied from the gas introduction mechanism S15e, the process gas contains carbon, nitrogen, oxygen, etc., corresponding to the film-forming of the adhesion layer 14, and argon, nitrogen gas, etc. The condition is set as a predetermined gas partial pressure together with the sputtering gas.

Further, the high-vacuum exhaust mechanism S15f performs exhaust according to film forming conditions.
Further, in the film forming mechanism S15, the sputtering voltage applied from the power source S15d to the backing plate S15c is set corresponding to the film formation of the adhesion layer 14. FIG.

In the manufacturing apparatus S10 shown in FIG. 4, the glass substrate 11 loaded by the transport mechanism S11a from the load chamber S11 is transported by the substrate holding mechanism S12a in the film deposition chamber (vacuum processing chamber) S12 while being transported by the substrate holding mechanism S12a. After the film formation, the glass substrate 11 on which the film formation has been completed is carried out from the unload chamber S16 to the outside by the transport mechanism S16a.

In the phase shift layer forming step, in the film forming mechanism S13, a sputtering gas and a reaction gas are supplied as supply gases from the gas introduction mechanism S13e to the vicinity of the backing 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 source. Alternatively, a predetermined magnetic field may be formed on the target S13b by a magnetron magnetic circuit.

Ions of the sputtering gas excited by the plasma near the backing plate S13c in the film forming chamber S12 collide with the target S13b of the cathode electrode S13c to eject particles of the film forming material. Then, after the ejected particles are combined with the reaction gas, they are attached 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 mechanism S14, a sputtering gas and a reaction gas are supplied as supply gases from the gas introducing mechanism S14e to the vicinity of the backing 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. Alternatively, a predetermined magnetic field may be formed on the target S14b by a magnetron magnetic circuit.

Ions of the sputtering gas excited by the plasma near the backing plate S14c in the film forming chamber S12 collide with the target S14b of the cathode electrode S14c to eject particles of the film forming material. Then, after the ejected particles are combined with the reaction gas, they 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 formation mechanism S15, the sputtering gas and the reaction gas are supplied as supply gases from the gas introduction mechanism S15e to the vicinity of the backing plate S15c of the film formation chamber S12. In this state, a sputtering voltage is applied to the backing plate (cathode electrode) S15c from an external power source. Alternatively, a predetermined magnetic field may be formed on the target S15b by a magnetron magnetic circuit.

Ions of the sputtering gas excited by the plasma near the backing plate S15c in the film forming chamber S12 collide with the target S14b of the cathode electrode S15c to eject particles of the film forming material. After the ejected particles are combined with the reaction gas, they adhere to the glass substrate 11 , forming an adhesion layer 14 with a predetermined composition on the surface of the glass substrate 11 .

At this time, in forming the phase shift layer 12, the gas introduction mechanism S13e supplies a nitrogen gas, an oxygen-containing gas, or the like having a predetermined partial pressure, and switches to control the partial pressure to set the composition. be within range.

Further, in the film formation of the antireflection layer 13, a nitrogen gas, an oxygen-containing gas, or the like having a predetermined partial pressure is supplied from the gas introduction mechanism S14e, and the partial pressure is switched to control the composition within a set range. inside.

Further, in forming the adhesion layer 14, the gas introduction mechanism S15e supplies nitrogen gas, oxygen-containing gas, etc., at a predetermined partial pressure, and switches to control the partial pressure, thereby setting the composition within the set range. to

Here, examples of the oxygen-containing gas include CO ₂ (carbon dioxide), O ₂ (oxygen), N ₂ O (dinitrogen monoxide), NO (nitrogen monoxide), CO (carbon monoxide), and the like. can.
Carbon-containing gases include CO ₂ (carbon dioxide), CH ₄ (methane), C ₂ H ₆ (ethane), CO (carbon monoxide), and the like.
It should be noted that the targets S13b, S14b, and S15b can be exchanged for the film formation of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, if necessary.

Furthermore, in addition to the film formation of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14, in the case of laminating other films, the films may be formed by sputtering under sputtering conditions such as corresponding targets and gases. The corresponding films are laminated by the film forming method of 1 to form the mask blank 10B of the present embodiment.

Film properties of the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 in this embodiment will be described below.

First, a chromium compound film, which is the main component film of the phase shift layer 12, is formed by sputtering or the like on the glass substrate 11 for forming a mask. 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 the phase shift layer 12, it is possible to form the phase shift layer 12 having desired transmittance and phase. .

Here, if the phase shift layer 12 is formed only with a chromium compound and no other films are used, the reflectance will be as high as about 25%. Therefore, it is desirable to reduce the reflectance by forming the antireflection layer 13, which is a low-reflection layer, on the surface of the phase shift layer 12. FIG.

Among metal silicides, molybdenum silicide is preferably used as the antireflection layer 13 . Molybdenum silicide is highly resistant to a mixed solution of sulfuric acid and hydrogen peroxide, which is commonly used for mask cleaning, and it is possible to greatly control optical properties by controlling the concentration of nitrogen and oxygen contained in molybdenum silicide. .

Here, since molybdenum silicide has hydrophilicity, it may have poor adhesion to a photoresist. In order to improve this, the adhesion is improved by forming the adhesion layer 14 having water repellency.
As the adhesion layer 14, it is desirable to use a chromium compound. A chromium compound is suitable for use at the interface that comes into contact with the photoresist because it has the property of being highly resistant to acid and alkaline solutions and the property of being hydrophobic.

By laminating the phase shift layer 12, the antireflection layer 13, and the adhesion layer 14 in this manner, two kinds of materials, namely, a chromium compound and a metal silicide, which are highly resistant to chemicals, can be used to obtain the optical properties required for the photomask 10. It becomes possible to form a phase shift film.

In order to reduce the reflectance of the phase shift mask 10, the optical constants of the adhesion layer 14 and the antireflection layer 13 are made close to each other, and further, between the antireflection layer 13 and the phase shift layer 12, It is important to increase the difference in refractive index and the difference in extinction coefficient. Thus, in order to reduce the reflectance of the phase shift mask 10, it is desirable to reduce the values of the refractive index and the extinction coefficient of the adhesion layer 14 and the antireflection layer 13. FIG.

In the chromium compound used for the adhesion layer 14, the values of the refractive index and the extinction coefficient can be lowered 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.

Further, when molybdenum silicide is used as the metal silicide used in the antireflection layer 13, the values of the refractive index and the extinction coefficient can be lowered by increasing the nitrogen concentration and 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 adhesion Although the layer 14 is mainly composed of a chromium compound containing oxygen and nitrogen, it is not limited to this.

Thus, 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 phase shift layer 12 has an oxygen concentration, a carbon concentration, and a nitrogen concentration within the ranges described above. is set, the oxygen concentration, carbon concentration, and nitrogen concentration are set within the ranges described above in the antireflection layer 13, and the oxygen concentration, carbon concentration, and nitrogen concentration are set within the ranges described above in the adhesive layer 14.

First, the change in adhesion of 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 adhesion evaluation between the chromium compound and the photoresist in that case was investigated.
For evaluation of resist adhesion, a resist pattern is formed on the mask blank 10B having a three-layer structure in this embodiment, and then wet etching is performed.
As the photoresist layer 15, for example, novolac resin or the like can be applied.

In this case, when the etchant permeated the interface between the photoresist layer 15 and the mask layer, it was judged as NG, and when the etchant did not permeate, it was judged as OK.
If the etchant penetrates into the interface between the photoresist layer and the mask layer, the phase shift layer 12, which is a low-reflection phase shift film (mask layer), and the antireflection layer 13 are in close contact with each other. A pattern in layer 14 is not formed.
The results are shown in Table 1.

From this result, it was found that when the film thickness of the adhesion layer (adhesion improving layer) 14 is 10 nm or more, a favorable cross-sectional shape in which the etchant does not permeate can be obtained.

Next, the composition of the antireflection layer 13, that is, changes in film characteristics due to changes in the content of oxygen, nitrogen, etc. will be verified.

A film of a molybdenum silicide compound was formed using a sputtering method.
The composition of the molybdenum silicide target used here is Mo:Si=1:2.3. A mixed gas of N ₂ and CO ₂ was used during sputtering.
The _CO2 partial pressure was varied during the deposition of the molybdenum silicide compound.
FIG. 5 shows the wavelength dependence of the refractive index when the CO ₂ partial pressure is changed during the MoSi compound film formation. FIG. 6 shows the wavelength dependence of the extinction coefficient when the CO ₂ partial pressure is changed during the MoSi compound film formation.

When the CO ₂ partial pressure changes during the film formation of the molybdenum silicide compound, the composition ratio of carbon, nitrogen, and oxygen changes accordingly. At the same time, the composition ratio of molybdenum and silicon also changes. By increasing the _CO2 partial pressure during film formation, the oxygen concentration and carbon concentration increase, and the nitrogen concentration, silicon concentration and molybdenum concentration decrease.
As shown in FIGS. 5 and 6, it can be seen that the refractive index and the extinction coefficient can be reduced by increasing the CO ₂ partial pressure during film formation of the molybdenum silicide compound.

Also, the composition of the molybdenum silicide compound was determined by Auger electron spectroscopy.
The results are shown in Table 2.

It can be seen that the oxygen concentration increases and the nitrogen concentration, silicon concentration, and molybdenum concentration decrease by increasing the CO ₂ partial pressure during film formation.

In order to etch a molybdenum silicide film using wet etching, it is usually necessary to etch using a chemical solution containing hydrogen fluoride. However, hydrogen fluoride also etches substrates such as quartz. Therefore, it is desirable to use a material with a low silicon concentration in molybdenum silicide. Therefore, it is desirable to use a target composition of Mo and Si as described above when forming molybdenum silicide. If the Si concentration is further lowered, 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, changes in film characteristics due to changes in the content of oxygen, nitrogen, etc., will be verified.

Adhesion layer 14 and phase shift layer 12 are made of a chromium compound.
A film of a chromium compound was formed using a sputtering method.
_CO2 gas and NO gas are selected as oxidizing gases when forming a chromium compound, and the graph of the wavelength dependence of the refractive index and the extinction coefficient when the partial pressure of each gas is changed. indicates

FIG. 7 shows the wavelength dependence of the refractive index when the NO gas partial pressure during Cr compound film formation is varied from 0% to 30% in gas flow ratio. FIG. 8 shows the wavelength dependence of the extinction coefficient when the NO gas partial pressure is changed during Cr compound film formation.
Chromium compounds can greatly change their optical properties by adjusting the partial pressure of the oxidizing gas during formation.
As shown in FIGS. 7 and 8, it can be seen that the refractive index and the extinction coefficient can be lowered by increasing the NO gas partial pressure during film formation.

The composition of the chromium compound formed by selecting NO gas as the oxidizing gas was determined by Auger electron spectroscopy. Table 3 shows the results.

FIG. 9 shows the wavelength dependence of the refractive index when the CO ₂ gas partial pressure during Cr compound film formation is varied from 0% to 30% in gas flow ratio. FIG. 10 shows the wavelength dependence of the extinction coefficient when the CO ₂ gas partial pressure is changed during Cr compound film formation.
In addition, the composition of the chromium compound formed by selecting CO ₂ gas as the oxidizing gas was determined by Auger electron spectroscopy. Table 4 shows the results.

It can be seen that the oxygen concentration increases and the nitrogen concentration and the chromium concentration decrease by increasing the CO ₂ partial pressure or the NO partial pressure during Cr compound film formation.
By adjusting the gas partial pressure during film formation for both the molybdenum silicide compound and the chromium compound in this manner, a film having a desired optical constant can be obtained.

The phase shift mask 10 is set to have a transmittance of about 5% for the i-ray (wavelength of 365 nm) and a phase difference of about 180° between the phase shift portion and the transmission portion. Therefore, by adjusting the film thicknesses and optical constants of 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, It is possible to control phase difference and transmittance and reflectance.

The phase shift mask 10 is required to reduce reflectance. For this reason, the refractive index and the extinction coefficient of the adhesion layer 14 and the antireflection layer 13 are decreased, and the refractive index and the extinction coefficient of the phase shift layer 12 are increased. In other words, it is desirable to increase the difference in refractive index between the antireflection layer 13 and the phase shift layer 12 and at the same time increase the difference in extinction coefficient between the antireflection layer 13 and the phase shift layer 12. .

For this reason, it is desirable to increase the oxygen concentration in the adhesion layer 14 by increasing the NO gas partial pressure during film formation.
In order to improve adhesion using a chromium film with a high oxygen concentration, it is possible to improve adhesion to the resist by oxidation using NO gas rather than CO ₂ gas. Therefore, the chromium film used for the adhesion layer is preferably formed using NO gas.

Also, for the antireflection layer 13, it is desirable to increase the oxygen concentration in the film by increasing the partial pressure of the oxygen-containing gas during film formation. When the oxygen concentration of the antireflection layer 13 is increased, the hydrophilicity may increase, so it is desirable to increase the hydrophobicity of the adhesion layer 14 .

Furthermore, the phase shift layer 12 is formed of a chromium film formed by adding CO ₂ gas, and the optical constant of the phase shift layer 12 is controlled by changing the amount of CO ₂ gas added during film formation. , it becomes possible to obtain the set transmittance and phase difference of the phase shift mask 10 .

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

For example, when the phase shift layer 12 is formed, the CO ₂ gas partial pressure is set to 15% to 25%, and when the antireflection layer 13 is formed, the NO gas partial pressure is set to 25% to 35%, and the adhesion layer 14 is formed. The NO gas partial pressure may be 25% to 35% during film formation.

Alternatively, the CO ₂ gas partial pressure is 0% to 5%, the CO ₂ gas partial pressure is 5% to 15%, the CO ₂ gas partial pressure is 10% to 20%, the CO ₂ gas Partial pressures of 20% to 30% and CO ₂ gas partial pressures of 25% to 35% are also possible.
Further, the NO gas partial pressure is set to 5% to 15%, the NO gas partial pressure is set to 10% to 20%, the NO gas partial pressure is set to 15% to 25%, and the NO gas partial pressure is set to 20%. % to 30%. Furthermore, these ranges can be used in combination.
Further, when the sputtering gas contains argon, the partial pressure of the oxygen-containing gas can be set higher.

In the phase shift mask 10 having low reflection characteristics, the adhesion layer 14, the antireflection layer 13, and the phase shift layer 12 are made of different materials. Therefore, when wet etching is used in the etching process for patterning, it is possible to selectively etch by changing the etchant.

A molybdenum silicide compound can be etched with, for example, a mixture of ammonium hydrogen fluoride and hydrogen peroxide. A chromium compound can be etched with, for example, a mixture of ceric ammonium nitrate and perchloric acid.
The selectivity for each different WET etch is very high. Therefore, it is possible to obtain a favorable cross-sectional shape by making the cross-sectional shape of the phase shift mask 10 after etching nearly vertical.

The characteristics of the phase shift mask 10 having low reflection characteristics were verified.
For confirmation, a mask blank 10B was formed as a phase shift mask 10 having a three-layer structure. A phase shift layer 12 was formed on a glass substrate 11 using a chromium compound formed at a CO ₂ gas partial pressure of 20%. An antireflection layer 13 was formed on the phase shift layer 12 using a molybdenum silicide compound formed at a CO ₂ gas partial pressure of 30%. An adhesion layer 14 was formed on the antireflection layer 13 using a chromium compound formed at a NO gas partial pressure of 30%. Here, the film thickness of the phase shift layer 12 was set to 90 nm, the film thickness of the antireflection layer 13 was set to 30 nm, and the film thickness of the adhesion layer 14 was set to 10 nm.

Changes in the characteristics of the phase shift mask 10 were verified by changing the film thickness of the antireflection layer 13 .
FIG. 11 shows reflectance characteristics of the phase shift mask 10 when the film thickness of the antireflection layer 13 of this example is changed.
FIG. 12 shows transmittance characteristics of the phase shift mask 10 when the film thickness of the antireflection layer 13 of this example is changed.
LR indicates the film thickness of the antireflection layer 13 .

According to this, the thickness of the antireflection layer 13 is 30 to 40 nm, and the reflectance is about 5%. That is, when the film thickness of the antireflection layer 13 is around 30 nm, a low reflectance can be obtained around a wavelength of 400 nm, for example, 413 nm.

Next, changes in the characteristics of the phase shift mask 10 were verified by changing the film thickness of the adhesion layer 14 .
FIG. 13 shows reflectance characteristics of the phase shift mask 10 when the film thickness of the adhesion layer 14 of this example is changed.
FIG. 13 shows transmittance characteristics of the phase shift mask 10 when the film thickness of the adhesion layer 14 of this embodiment is changed.
AE indicates the film thickness of the adhesion layer 14 .

The reflectance tends to increase as the thickness of the adhesion layer 14 increases to 10 nm or more, but it can be seen that at 10 nm, the reflectance at a wavelength of around 400 nm is about 5%, which is a sufficiently low reflectance characteristic. When the film thickness of the adhesion layer 14 is changed, the thinner the film, the lower the reflectance. In addition, if the thickness is increased, a component with a high refractive index is formed, so it is considered that the reflectance increases.

From these, it can be seen that the phase shift mask 10 in this embodiment has low reflectance characteristics.

The mask blank 10B and the photomask 10 according to the present embodiment can independently control the etching of the adhesion layer 14, the antireflection layer 13, and the phase shift layer 12. Therefore, the mask blank 10B and the photomask 10 have high chemical resistance and high reflectance. It is possible to obtain a cross-sectional shape suitable for use as a mask while being sufficiently reduced.
In addition, by controlling the gas flow ratio of oxygen-containing gas or the like during film formation, the composition and film thickness of chromium, oxygen, nitrogen, and carbon contained in the film can be controlled, and the desired transmittance and phase can be obtained. The mask blank 10B and the photomask 10 having a low reflectance can be realized by using the adhesion layer 14 and the antireflection layer 13 having a phase shift layer having a low refractive index and a small extinction coefficient.

Although the phase shift mask 10 having the phase shift layer 12 as a mask layer has been described in this embodiment, the present invention is not limited to this configuration.
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 combining these layers including other layers may be used.

DESCRIPTION OF SYMBOLS 10... Phase shift mask 10B... Mask blanks 11... Glass substrate (transparent substrate)
DESCRIPTION OF SYMBOLS 12... Phase shift layer 12P... Phase shift pattern 13... Antireflection layer 13P... Antireflection pattern 14... Adhesion layer 14P... Adhesion pattern 15... Photoresist layer

Claims (15)

A mask blank having a layer to be a phase shift mask,
a phase shift layer laminated on a transparent substrate;
an antireflection layer provided at a position further away from the transparent substrate than the phase shift layer;
an adhesion layer provided at a position farther from the transparent substrate than the antireflection layer;
has
the phase shift layer contains chromium,
the antireflection layer contains molybdenum silicide and oxygen,
the adhesion layer contains chromium and oxygen,
A mask blank, wherein the oxygen content in the adhesive layer is set so as to have adhesiveness enabling patterning to the photoresist layer. 2. The mask blanks according to claim 1, wherein the oxygen content in the adhesion layer is set within a range of 8.4 atm % to 65.7 atm %. 3. The mask blank according to claim 2, wherein the adhesion layer contains nitrogen, and the nitrogen content is set within a range of 3.7 atomic % to 42.3 atomic %. 4. The mask blank according to claim 2, wherein the adhesion layer contains carbon, and the carbon content is set in the range of 2.2 atomic % to 2.3 atomic %. 5. The mask blank according to claim 2, wherein the adhesion layer has a chromium content within a range of 25.2 atm % to 42.4 atm %. 6. The mask blank according to any one of claims 1 to 5, wherein the adhesive layer has a film thickness set within a range of 5 nm to 15 nm. 7. The mask blank according to claim 1, wherein the antireflection layer has an oxygen content within a range of 6.7 atm % to 63.2 atm %. 8. The mask blank according to claim 7, wherein said antireflection layer contains nitrogen, and the nitrogen content is set within a range of 4.6 atm % to 39.3 atm %. 9. The mask blank according to any one of claims 1 to 8, further comprising a photoresist layer provided at a position spaced apart from the transparent substrate more than the adhesion layer. A method for manufacturing a mask blank according to any one of claims 1 to 9,
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;
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;
has
In the adhesion layer forming step,
A method for manufacturing a mask blank, wherein the adhesion layer is formed so as to have adhesion for patterning to a photoresist layer by setting a partial pressure of an oxygen-containing gas as a supply gas in sputtering. In the adhesion layer forming step,
11. The method of manufacturing a mask blank according to claim 10, wherein by setting the partial pressure of the oxygen-containing gas, the adhesion of the adhesion layer increases as the oxygen content increases. In the adhesion layer forming step,
12. The method of manufacturing mask blanks according to claim 11, wherein the partial pressure ratio of the oxygen-containing gas is set in the range of 0.00 to 0.30. In the adhesion layer forming step,
13. The method of manufacturing mask blanks according to claim 12, wherein the oxygen-containing gas is NO. A photomask manufactured from the mask blank according to any one of claims 1 to 9. A method for manufacturing a photomask according to claim 14,
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;
an adhesion pattern forming step of forming a pattern on the adhesion layer;
has
A method of manufacturing a photomask, wherein an etchant used in the phase shift pattern forming step and the adhesion pattern forming step is different from an etchant used in the antireflection pattern forming step.

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