JP7062480B2 - Mask blanks and photomasks, their manufacturing methods - Google Patents

Description

The present invention relates to mask blanks and photomasks, methods for producing the same, and particularly to techniques suitable for use in antistatic.

As described in Patent Document 1, a photomask for a large plate used for an FPD (flat panel display) forms a light-shielding film or a semi-transmissive film containing a metal such as chromium on a glass substrate. In the filmed mask blanks, a desired pattern is formed through a patterning process to form a binary mask.
As a result, a mask is manufactured in which a translucent region in which the exposed light-shielding pattern of the transparent substrate is not arranged and a light-shielding region in which a light-shielding layer containing chromium is laminated on the transparent substrate are arranged adjacent to each other in order.

In such a photomask, static electricity may be accumulated in the photomask during the manufacturing process of the photomask, cleaning of the photomask, transportation of the mask, etc., and the photomask may be partially electrostatically destroyed, which is a problem. It has become.

In recent years, the miniaturization of panels for both liquid crystal displays and organic EL displays has greatly progressed, and along with this, the miniaturization of photomasks has also progressed. As a result, the miniaturization of the photomask reduces the distance between isolated patterns, which raises the problem of increasing the probability of electrostatic breakdown.

Further, as the size of the FPD or the like increases, the photomask becomes larger and its area becomes larger, which causes a problem that the number of electrostatic fractures itself increases.

In order to solve this problem, in order not to form an isolated pattern in a photomask, a technique of forming a transparent conductive film on the lower or upper part of a light-shielding film or a semi-transmissive film constituting the photomask is described in Patent Document 2 and Patent Document. It is described in 3.

Japanese Unexamined Patent Publication No. 2007-21738 Japanese Unexamined Patent Publication No. 2008-241921 Japanese Unexamined Patent Publication No. 2009-86383

However, the techniques described in Patent Document 2 and Patent Document 3 have a problem that the transmittance is lowered in the exposure process due to the formed transparent conductive film. Further, these techniques have a problem that the transparent conductive film is not etched in the photomask forming step or the cleaning step, so that the conductivity is lowered and electrostatic fracture occurs.

The present invention has been made in view of the above circumstances, and is intended to achieve the following object.
1. 1. To prevent the occurrence of electrostatic destruction in photomasks.
2. 2. At the same time, prevent deterioration of the optical characteristics of the photomask.

As a result of diligent studies, the inventors of the present application have found that the occurrence rate of electrostatic breakdown can be suppressed by reducing the resistance value of the light-shielding film itself forming the photomask.

It was found that the occurrence rate of electrostatic breakdown can be greatly suppressed by setting the sheet resistance value of the light-shielding film to 10 Ω / sq or less. By setting the sheet resistance value of the light-shielding film to 10 Ω / sq or less in this way, it is possible to form a photomask capable of preventing the occurrence of electrostatic breakdown.

When forming a photomask, it is common to have a two-layer structure in which a chromium oxide film as an antireflection layer is usually formed on the upper side (surface side) and a chromium film is formed on the lower side (side surface side of the glass substrate).
Here, when the light-shielding film is formed of chromium, the film thickness of the light-shielding film is preferably 100 nm or more in order to set the resistance value of the light-shielding film in the above range.
In this case, it is desirable that the chromium oxide film as the antireflection layer provided on the upper side (surface side) has a film thickness range of 20 to 30 nm to reduce the reflection on the film surface.

However, when a photomask is formed using a chrome mask blank having a two-layer structure consisting of an antireflection layer on the surface side and a light-shielding layer on the glass substrate side, when the film thickness of these chrome layers becomes 100 nm or more, it gets wet. It was found that during etching, there is a problem that tailing occurs in the cross-sectional shape when patterning.

In addition, hemming means that the side surface of the light-shielding layer is inclined and the lower side (glass substrate side) is larger than the upper side (front surface side), that is, the cross-sectional shape of the light-shielding layer pattern becomes substantially trapezoidal. Means that. When hemming occurs in this way, when the surface of the photomask is visually observed, the antireflection layer, which is an oxide, has a black color, and the light-shielding layer under the light-shielding layer has a metallic luster, so that the edges of the light-shielding pattern have a luster. It will be. Therefore, the occurrence of tailing can be visually recognized, and it can be seen that the pattern size is not accurate and defective as a photomask.

From these facts, the inventors of the present application have realized mask blanks capable of manufacturing a photomask capable of preventing the occurrence of hemming while the resistance value of the light-shielding film is in a low range as follows. ..

The mask blanks of the present invention have a transparent substrate and
A light-shielding layer containing chromium as a main component formed on the surface of the transparent substrate,
The intermediate layer laminated on the light-shielding layer and
The antireflection layer laminated on the intermediate layer and
Have,
The antireflection layer contains chromium and contains a large amount of oxygen as compared with the light shielding layer .
The intermediate layer contains chromium and contains a large amount of carbon as compared with the antireflection layer and the light shielding layer .
The carbon content in the intermediate layer is set to 14.5 atm% or more, and the carbon content is set to 14.5 atm% or more.
The above problem was solved by setting the sheet resistance to be smaller than 10Ω / sq.
In the present invention, it is more preferable that the carbon content in the intermediate layer is set to twice or more that of the light-shielding layer .
The photomask of the present invention is a photomask manufactured from the mask blanks according to any one of the above.
It is also possible to adopt a means in which the wall surface of the light-transmitting region formed by removing the light-transmitting region from the light-shielding layer has an angle of 80 ° or more in contact with the surface of the glass substrate.
In the method for producing a mask blank of the present invention, the method for producing a mask blank according to any one of the above.
When the intermediate layer is formed, the partial pressure of the carbon-containing gas can be set higher than that when the antireflection layer and the light-shielding layer are formed.

The mask blanks of the present invention have a transparent substrate and
A light-shielding layer containing chromium as a main component formed on the surface of the transparent substrate,
An antireflection layer containing a large amount of oxygen as compared with the light-shielding layer,
An intermediate layer containing a large amount of carbon as compared with the antireflection layer and the light shielding layer,
Have,
By setting the sheet resistance to be smaller than 10Ω / sq, optics equivalent to a two-layer photomask having a chromium oxide film as an antireflection layer on the surface side (upper side) and a chromium film as a light-shielding layer on the lower layer. It has characteristics and can exhibit low resistivity to reduce the occurrence of electrostatic breakdown. Furthermore, by using a three-layer structure and using a chromium film with high carbon concentration and oxygen concentration for the intermediate layer, it is intermediate. The etching rate of the chromium film in the layer can be made smaller than the etching rate of the chromium film located on the transparent substrate side. As a result, it is possible to provide mask blanks capable of producing a photomask with less tailing even when the chromium film thickness, which is a low sheet resistance that can reduce the influence of electrostatic fracture, is 100 nm or more. As a result, it is possible to reduce the variation in the pattern line width in the photomask mask.
Here, the chromium film thickness is a portion that contributes to sheet resistance except for the chromium oxide film that is the antireflection layer, and means, for example, a portion that includes an intermediate layer and a light-shielding layer.

In the present invention, the carbon content in the intermediate layer is set to be at least twice that of the light-shielding layer, so that the etching rate of the chrome film in the intermediate layer is made smaller than the etching rate of the chrome film on the glass substrate side. Therefore, in the etching at the time of pattern formation, the etching amount in the intermediate layer is smaller than that in the light-shielding layer, and since it is located on the upper side (surface side / outside) of the light-shielding layer, the time exposed to the etchant becomes longer. In the intermediate layer, the amount of side etching can be reduced to form an inclination of the boundary side surface with the region removed by etching in the light-shielding pattern in a state close to vertical.

Further, in the present invention, by setting the carbon content in the intermediate layer to 14.5 atm% or more, the etching rate of the chrome film in the intermediate layer is made smaller than the etching rate of the chrome film on the glass substrate side. In etching during pattern formation, the amount of etching in the intermediate layer is smaller than that in the light-shielding layer, and since it is located on the upper side (surface side / outside) of the light-shielding layer, the time exposed to the etchant becomes longer. In the layer, the amount of side etching is controlled to a predetermined state so that the inclination of the boundary side surface between the light-shielding region and the translucent region, that is, the interface side surface with the translucent region removed by etching in the light-shielding pattern is close to vertical. It is possible to form it without a hem.

The photomask of the present invention is a photomask manufactured from the mask blanks according to any one of the above.
In the light-shielding pattern formed by removing the light-transmitting region from the light-shielding layer, the wall surface with the light-transmitting region has an angle of 80 ° or more in contact with the surface of the glass substrate, so that the line width in the light-shielding pattern varies. Can be reduced.

In the method for producing a mask blank of the present invention, the method for producing a mask blank according to any one of the above.
At the time of forming the intermediate layer, the carbon content of the intermediate layer can be set to a predetermined state by setting the partial pressure of the carbon-containing gas higher than that at the time of forming the antireflection layer and the light-shielding layer. As a result, the carbon content in the intermediate layer is set to be higher than that in the antireflection layer and the light-shielding layer, and the etching rate of the chrome film in the intermediate layer is compared with the etching rate of the chrome film on the glass substrate side. In the etching at the time of pattern formation, the etching amount in the intermediate layer is smaller than that in the light-shielding layer, and since it is located on the upper side (surface side / outside) of the light-shielding layer, it takes a long time to be exposed to the etchant. In the intermediate layer, the amount of side etching can be reduced to form an inclination of the boundary side surface with the region removed by etching in the light-shielding pattern in a state close to vertical.

In the present invention, if the etching rate of the lower (transparent substrate side) chromium layer is controlled so as to change in the film thickness direction, it is possible to obtain a good cross-sectional shape in which the occurrence of tailing in the light-shielding pattern cross-sectional shape is suppressed. It will be possible. Specifically, the intermediate layer, which is the upper side (surface side) of the light-shielding layer (chromium layer), is controlled so that the concentrations of carbon and oxygen in the intermediate layer containing chromium or both carbon and oxygen change in the film thickness direction. By making the carbon concentration and oxygen concentration of the layer higher than that of the light-shielding layer, it is possible to make the etching rate of the intermediate layer on the antireflection layer side slower than the etching rate of the light-shielding layer on the transparent substrate side. In this way, by controlling the carbon concentration and oxygen concentration in the chromium film, it is possible to obtain a cross-sectional shape with less tailing.

In the present invention, the intermediate layer may be a single layer, but it is also possible to have a structure in which a large number of layers are laminated. Further, the carbon content can be made different in each of the intermediate layers having a large number of layers.

INDUSTRIAL APPLICABILITY The present invention can be applied to a mask having a layer containing chromium as a light-shielding film as a binary mask in mask blanks for large plates used in the manufacture of FPDs and the like.
In the present invention, as a method for controlling the carbon concentration of the chromium layer, the chromium layer can be used as a laminated structure, and the carbon concentration can be changed for each layer as the lamination progresses from the lower side to the upper side. Alternatively, it is also possible to control the carbon concentration (carbon concentration) by changing the partial pressure of the carbon-containing gas in the reactive gas so as to increase by using the flow of the reactive gas at the time of film formation.

Further, in the present invention, it is also possible to have a low reflectance layer, an antireflection layer, a protective layer and the like. Further, the stacking order of these layers can be appropriately set.

According to the present invention, it is possible to achieve the effect that the influence of electrostatic fracture can be reduced and mask blanks capable of producing a photomask with less hemming can be provided.

It is sectional drawing which shows 1st Embodiment of the mask blanks which concerns on this invention. It is sectional drawing which shows 1st Embodiment of Photomasks which concerns on this invention. It is a schematic diagram which shows the film forming apparatus in 1st Embodiment of the manufacturing method of the mask blanks which concerns on this invention. It is sectional drawing for demonstrating the side etch in 1st Embodiment of the manufacturing method of the photomasks which concerns on this invention. It is sectional drawing for demonstrating the tailing in the manufacturing method of the conventional photomask. It is a graph which shows the relationship between the chromium film thickness and the taper angle in the 1st Embodiment of the manufacturing method of the mask blanks which concerns on this invention. It is a graph which shows the relationship between the sheet resistance and the chrome layer film thickness in 1st Embodiment of the manufacturing method of the mask blanks which concerns on this invention. It is a graph which shows the relationship between the sheet resistance and the electrostatic breakdown occurrence rate in 1st Embodiment of the manufacturing method of the mask blanks which concerns on this invention.

Hereinafter, a mask blank and a photomask according to the present invention, and a first embodiment of a method for manufacturing the same will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a mask blank in the present embodiment, in which reference numeral 1B is a mask blank.

As shown in FIG. 1, the mask blanks 1B according to the present embodiment are laminated on the light-shielding layer 3B laminated on the glass substrate (transparent substrate) 2, the intermediate layer 4B laminated on the light-shielding layer 3B, and the intermediate layer 4B. It has an antireflection layer 5B and the like.

As the transparent substrate 2, a material having excellent transparency and optical isotropic properties is used, and for example, a quartz glass substrate can be used. The size of the transparent substrate 2 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 an LCD (liquid crystal display), a plasma display, or an organic EL (electroluminescence) display). Will be done. In this embodiment, it can be applied to a rectangular substrate having a side of about 100 mm to a side of 2000 mm or more, and a substrate having a thickness of several mm or a substrate having a thickness of 10 mm or more can also be used.

Further, the flatness of the transparent substrate 2 may be reduced by polishing the surface of the transparent substrate S. The flatness of the transparent substrate 2 can be, for example, 20 μm or less. As a result, the depth of focus of the mask becomes deeper, and it becomes possible to greatly contribute to the formation of fine and highly accurate patterns. Further, the flatness is 10 μm or less, and the smaller the better.

The light-shielding layer 3B contains Cr (chromium) as a main component, and further contains C (carbon) and N (nitrogen). Further, the light-shielding layer 2B may have a composition different in the thickness direction, and in this case, as the light-shielding layer 2B, Cr alone and Cr oxides, nitrides, carbides, oxide nitrides, carbides and oxide carbides are used. It is also possible to stack one or two or more selected from the objects.
As will be described later, the thickness of the light-shielding layer 3B and the composition ratio (atm%) of Cr, N, C, O, etc. are set so as to obtain predetermined optical characteristics and resistivity.

Like the light-shielding layer 3B, the intermediate layer 4B contains Cr (chromium) and further contains C (carbon). As will be described later, the intermediate layer 4B is set to have a higher carbon content (carbon concentration) than the light-shielding layer 3B and the antireflection layer 4B. Specifically, the carbon content (carbon concentration) may be 14.5 atm% or more, and may be twice or more the carbon content (carbon concentration) in the light-shielding layer 3B and the antireflection layer 5B.

Like the light-shielding layer 3B, the antireflection layer 5B is a chromium oxide film containing O (oxygen), but can further contain N (nitrogen). The film thickness of the antireflection layer 5B is set by the exposure wavelength when used as a mask in the exposure process, the necessary optical characteristics defined by the exposure wavelength, the reflectance, and the like. For example, the thickness can be set to about 25 nm. At the same time, in order to set the reflectance, it is necessary that the oxygen content is also within a predetermined range. Specifically, the oxygen content is set to be about 30 atm% or more.

The mask blanks 1B of the present embodiment can be applied, for example, when manufacturing a patterning mask for an FPD glass substrate.
Further, in the mask blanks 1B of the present embodiment, the total film thickness of the light-shielding layer 3B, the intermediate layer 4B and the antireflection layer 5B is 100 nm or more, preferably 150 nm or more, and more preferably 200 nm or more.
Further, the mask blanks 1B of the present embodiment are set so that the combined sheet resistance of the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B is 10Ω / sq. This sheet resistance is set by the film thickness of the light-shielding layer 3B and the intermediate layer 4B.

In the method for manufacturing the mask blank 1B in the present embodiment, the light-shielding layer 3B and the intermediate layer 4B are formed on the glass substrate (transparent substrate) 2, and then the antireflection layer 5B is formed. Further, in the mask blank manufacturing method, when a protective layer, a low reflection layer, an antireflection layer, an etching stopper layer, etc. are laminated in addition to the light shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B, these are laminated. Can have a process.

Hereinafter, a method for manufacturing a mask blank in the present embodiment will be described with reference to the drawings.
FIG. 2 is a schematic view showing a mask blank manufacturing apparatus according to the present embodiment.

The mask blank 1B in the present embodiment is manufactured by the manufacturing apparatus shown in FIG.

The manufacturing apparatus S10 shown in FIG. 2 is an inter-back type sputtering apparatus, and is connected to the load chamber S11, the unload chamber S16, and the load chamber S11 via the sealing means S17, and is connected to the unloading chamber S11 by the sealing means. It is assumed to have a film forming chamber (vacuum processing chamber) S12 connected via S18.

The load chamber S11 is provided with a transport means S11a for transporting the glass substrate 1 carried in from the outside to the film forming chamber S12, and an exhaust means S11f such as a rotary pump for drawing a rough vacuum in the chamber, and also an unload chamber. The S16 is provided with a transport means S16a for transporting the glass substrate 1 having a film formation completed from the film formation chamber S12 to the outside, and an exhaust means S16f such as a rotary pump that draws a rough vacuum in the chamber.

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

The substrate holding means S12a holds the glass substrate 11 conveyed by the conveying means S11a so as to face the target S12b during film formation, and loads the glass substrate 11 from the load / unload chamber S11. It is possible to carry in and carry out to the load / unload room S11.

At the position on the load chamber S11 side of the film forming chamber S12, a cathode electrode (backing) having a target S13b as a film forming means S13 for supplying the film forming material of the first stage among the three stages of film forming means S13, S14, S15. Plate) S13c, power supply S13d that applies a negative potential sputter voltage to the backing plate S13c, and gas introduction means S13e that mainly introduces gas near the cathode electrode (backing plate) S13c in the film forming chamber S12. A high vacuum exhaust means S13f such as a turbo molecular pump that intensively draws a high vacuum in the vicinity of the cathode electrode (backing plate) S13c in the membrane chamber S12 is provided.

Further, at an intermediate position between the load chamber S11 and the unload chamber S16 of the film forming chamber S12, as the film forming means 1S4 for supplying the second stage film forming material among the three steps of the film forming means 13, S14, S15. , A cathode electrode (backing plate) S14c having a target S14b, a power supply S14d for applying a negative potential sputter voltage to the backing plate S14c, and a gas focused on the vicinity of the cathode electrode (backing plate) S14c in the film forming chamber S12. A gas introducing means S14e to be introduced and a high vacuum exhausting means S14f such as a turbo molecular pump that intensively draws a high vacuum in the vicinity of the cathode electrode (backing plate) S14c in the film forming chamber S12 are provided.

Further, at the position on the unload chamber S16 side of the film forming chamber S12, a cathode having a target S15b as a film forming means S15 for supplying the film forming material of the third stage among the three stages of the film forming means S13, S14, S15. The electrode (backing plate) S15c, the power supply S15d that applies a negative potential sputter voltage to the backing plate S15c, and the gas introduction means S15e that mainly introduces gas in the vicinity of the cathode electrode (backing plate) S15c in the film forming chamber S12. And a high vacuum exhaust means S15f such as a turbo molecular pump that intensively draws a high vacuum in the vicinity of the cathode electrode (backing plate) S15c in the film forming chamber S12.

In the film forming chamber S12, the gas supplied from the gas introducing means S13e, S14e, S15e does not mix with the adjacent film forming means S13, S14, S15 in the vicinity of the cathode electrodes (backing plates) S13c, S14, S15c. As described above, the gas barrier S12g that suppresses the gas flow is provided. These gas barriers S12g are configured so that the substrate holding means S12a can move between the film forming means S13, S14, and S15 adjacent to each other.

In the film forming chamber S12, the three-stage film forming means S13, S14, and S15 are assumed to have the composition and conditions necessary for sequentially forming a film on the glass substrate 1.
In the present embodiment, the film forming means S13 corresponds to the film formation of the light shielding layer 3B, the film forming means S14 corresponds to the film forming of the intermediate layer 4B, and the film forming means S15 forms the antireflection layer 5B. Corresponds to the membrane.

Specifically, in the film forming means S13, the target S13b is made of a material having chromium as a composition necessary for forming the light-shielding layer 3B on the glass substrate 1.
At the same time, in the film forming means S13, as the gas supplied from the gas introducing means S13e, the process gas contains carbon, nitrogen, oxygen and the like corresponding to the film formation of the light-shielding layer 3B, and together with the sputter gas such as argon. The conditions are set as predetermined gas partial pressures, and exhaust from the high vacuum exhaust means S13f is performed according to the film forming conditions.
Further, in the film forming means S13, the sputter voltage applied from the power supply S13d to the backing plate S13c is set corresponding to the film formation of the light shielding layer 3B.

Further, in the film forming means S14, the target S14b is made of a material having chromium as a composition necessary for forming the intermediate layer 4B on the light shielding layer 3B.
At the same time, in the film forming means S14, as the gas supplied from the gas introducing means S14e, the process gas contains carbon, nitrogen, oxygen and the like corresponding to the film formation of the intermediate layer 4B, and together with the sputter gas such as argon. , It is set as a predetermined gas partial pressure, and is exhausted from the high vacuum exhaust means S14f according to the film forming conditions.
Further, in the film forming means S14, the sputtering voltage applied from the power supply S14d to the backing plate S14c is set corresponding to the film forming of the intermediate layer 4B.

Further, in the film forming means S15, the target S15b is made of a material having chromium as a composition necessary for forming the antireflection layer 5B on the intermediate layer 4B.
At the same time, in the film forming means S15, as the gas supplied from the gas introducing means S15e, the process gas contains carbon, nitrogen, oxygen and the like corresponding to the film formation of the antireflection layer 5B, and a sputter gas such as argon is used. At the same time, it is set as a predetermined gas partial pressure, and exhaust is performed from the high vacuum exhaust means S15f according to the film forming conditions.
Further, in the film forming means S15, the sputter voltage applied from the power supply S15d to the backing plate S15c is set corresponding to the film formation of the antireflection layer 5B.

In the manufacturing apparatus S10 shown in FIG. 4, the glass substrate 1 carried in from the load chamber S11 by the conveying means S11a is conveyed by the conveying means S12a in the film forming chamber (vacuum processing chamber) S12, and three-stage sputtering film formation is performed. After that, the glass substrate 1 whose film formation has been completed is carried out from the unload chamber S16 to the outside by the transport means S16a.

In the film forming step, in the film forming means S13, the sputter gas and the reaction gas are supplied from the gas introducing means S13e to the vicinity of the backing plate S13c of the film forming chamber S12, and sputtered from an external power source to the backing plate (cathode electrode) S13c. Apply voltage. Further, a predetermined magnetic field may be formed on the target S13b by the magnetron magnetic circuit. Ions of the spatter gas excited by plasma near the backing plate S13c in the film forming chamber S12 collide with the target S13b of the cathode electrode S13c and eject the particles of the film forming material. Then, after the ejected particles and the reaction gas are combined and then adhered to the glass substrate 1, the light-shielding layer 3B is formed on the surface of the glass substrate 1 with a predetermined composition.

Similarly, in the film forming means S14, the sputter gas and the reaction gas are supplied from the gas introducing means S14e to the vicinity of the backing plate S14c of the film forming chamber S12, and the sputtering voltage is applied to the backing plate (cathode electrode) S14c from an external power source. do. Further, a predetermined magnetic field may be formed on the target S14b by the magnetron magnetic circuit. Ions of the spatter gas excited by plasma near the backing plate S14c in the film forming chamber S12 collide with the target S14b of the cathode electrode S14c and eject the particles of the film forming material. Then, after the ejected particles and the reaction gas are combined and then adhered to the glass substrate 1, the intermediate layer 4B is formed on the surface of the glass substrate 1 with a predetermined composition.

Similarly, in the film forming means S15, the sputter gas and the reaction gas are supplied from the gas introducing means S15e to the vicinity of the backing plate S15c of the film forming chamber S12, and the sputtering voltage is applied to the backing plate (cathode electrode) S15c from an external power source. do. Further, a predetermined magnetic field may be formed on the target S15b by a magnetron magnetic circuit. Ions of the spatter gas excited by plasma near the backing plate S15c in the film forming chamber S12 collide with the target S15b of the cathode electrode S15c and eject the particles of the film forming material. Then, after the ejected particles and the reaction gas are combined and then adhered to the glass substrate 1, the antireflection layer 5B is formed on the surface of the glass substrate 1 with a predetermined composition.

At this time, in the film formation of the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B, different amounts of carbon-containing gas, nitrogen gas, and oxygen-containing gas are supplied from the gas introducing means S13e, 14e, and 15e to divide the pressure. Switch to control and keep its composition within the set range.

Here, examples of the carbon-containing gas include CO ₂ (carbon dioxide), CH ₄ (methane), C ₂ H ₆ (ethane), and CO (carbon monoxide). Examples of the oxygen-containing gas include CO ₂ (carbon dioxide), O ₂ (oxygen), N ₂ O (nitrous oxide), NO (nitrous oxide) and the like.
The targets S13b, S14b, and S15b can be replaced if necessary in the film formation of the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B.

Further, in addition to the film formation of the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B, when another film is laminated, the film formation may be performed by sputtering as the sputtering conditions of the corresponding target, gas, etc. The corresponding films are laminated according to the film forming method to obtain the mask blank 1B of the present embodiment.

In the mask blank 1B for the antistatic binary chrome mask of the present embodiment, the carbon concentration in the intermediate layer 4B is set to be higher than the carbon concentration in the light shielding layer 3B and the antireflection layer 5B. Specifically, the carbon concentration in the intermediate layer 4B is set to be about twice as high as or higher than the carbon concentration in the light-shielding layer 3B and the antireflection layer 5B.

That is, it is supplied from the gas introducing means S14e at the time of forming the intermediate layer 4B as compared with the partial pressure of the carbon-containing gas supplied from the gas introducing means S13e and S15e at the time of forming the film of the light shielding layer 3B and the antireflection layer 5B. The above composition ratio is realized by increasing the partial pressure of the carbon-containing gas that can be obtained.
Alternatively, it is supplied from the gas introducing means S14e at the time of forming the intermediate layer 4B as compared with the gas flow rate of the carbon-containing gas supplied from the gas introducing means S13e and S15e at the time of forming the film of the light shielding layer 3B and the antireflection layer 5B. The above composition ratio can also be realized by increasing the gas flow rate of the carbon-containing gas.

As a result, the intermediate layer 4B is formed so as to have a small side etch rate at the time of wet etching which is a subsequent step.

Further, the partial pressure of each gas is set according to the composition ratio in the film such as nitrogen and oxygen, and a predetermined film is formed.

FIG. 3 is a cross-sectional view showing a photomask in the present embodiment.
As shown in FIG. 3, the photomask 1 in the present embodiment is assumed to have a pattern formed on the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B of the mask blank 1B.

Hereinafter, a manufacturing method for manufacturing a photomask (binary mask) 1 from the mask blank 1B of the present embodiment will be described.

A photoresist layer is formed on the outermost surface of the mask blanks 1B. The photoresist layer may be a positive type or a negative type. A liquid resist is used as the photoresist layer.

Subsequently, by exposing and developing the photoresist layer, a resist pattern is formed on the outer side of the antireflection layer 5B. The resist pattern functions as an etching mask between the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B, and its shape is appropriately determined according to the etching pattern between the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B. As an example, in the translucent region 2A, a shape having an opening width corresponding to the opening width dimension of the light-shielding pattern to be formed is set.

Next, the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B are wet-etched through the resist pattern using an etching solution to form light-shielding patterns 3, 4, and 5. As the etching solution, an etching solution containing diammonium cerium nitrate can be used, and for example, it is preferable to use diammonium cerium nitrate containing an acid such as nitric acid or perchloric acid.

Here, the etching in the light-shielding layer 3B, the intermediate layer 4B, and the antireflection layer 5B will be considered.
FIG. 4 is a cross-sectional view for explaining the etching state in the present embodiment, and FIG. 5 is a cross-sectional view for explaining the etching state.

In this embodiment, it is assumed that the thickness of the chromium film to be etched is about 200 nm, which exceeds 100 nm. This is to obtain the low sheet resistance value required for preventing the occurrence of electrostatic fracture.

Here, first, in the case of a two-layer structure in which there is no intermediate layer 4B and the antireflection layer 5B and the light shielding layer 3B are used, a state in which an exposed region of the glass substrate 1 is secured as a dimension required for a pattern opening is considered.

In this case, since the etching rate in the film thickness direction in the light-shielding layer 3B is constant, the corresponding lateral side etching progresses to a predetermined amount or more as the etching in the film thickness direction in the light-shielding layer 3B progresses. It will be. Therefore, when the exposed translucent region 2A of the glass substrate 1 is secured as a dimension required for the pattern opening, the lateral side etching amount on the outer side (upper side) in the film thickness direction is on the inner side (lower side) in the film thickness direction. It is larger than the amount of side etching in the lateral direction.

As a result, as shown in FIG. 5, the side surfaces of the light-shielding patterns 3, 4, and 5 on the translucent region 2A side are inclined so as to recede from the glass substrate 1 side toward the outside (upper side). In this hemming state, the angle (taper angle) θ formed by the light-shielding patterns 3, 4, and 5 and the surface of the glass substrate 2 becomes sharp, and may be, for example, about 40 °.

On the other hand, as in the present embodiment, the etching rate of the intermediate layer 4B is set to be smaller than the etching rate of the light-shielding layer 3B, so that the etching in the film thickness direction of the light-shielding layer 3B proceeds. Even in this case, the corresponding lateral side etching does not proceed more than the specified amount in the intermediate layer 4B.

As a result, as shown in FIG. 4, the side surfaces of the light-shielding patterns 3, 4, and 5 on the translucent region 2A side do not retreat so much from the glass substrate 1 side toward the outside (upper side), and are formed substantially vertically. In this state, the angle θ formed by the light-shielding patterns 3, 4, and 5 and the surface of the glass substrate 2 becomes large. Here, for example, it is preferable that the angle θ formed by the light-shielding patterns 3, 4, and 5 and the surface of the glass substrate 2 is closer to vertical than about 80 °.

In the light-shielding layer 2B in the portion close to the intermediate layer 3B, the carbon concentration in the composition remains low, so that the etching rate in the lateral direction in this portion is the same as that in the light-shielding layer 2B on the glass substrate 1 side. However, since the carbon concentration in the composition of the intermediate layer 3B in contact is high and the etching rate in the lateral direction is low, etching is not performed. Therefore, the light-shielding layer 2B in the portion in contact with the intermediate layer 3B also has a small side etching amount. .. As a result, as shown in FIG. 4, the angle θ formed by the light-shielding patterns 3, 4, and 5 and the surface of the glass substrate 2 can be set to a state closer to vertical than about 80 °.

In the present embodiment, the etching rate of the chromium layer on the glass substrate 1 side is controlled to change in the film thickness direction as the light-shielding layer 3B and the intermediate layer 4B. This makes it possible to suppress the occurrence of tailing in the cross-sectional shapes of the light-shielding patterns 3, 4, and 5, and to obtain a good cross-sectional shape.

Specifically, as the light-shielding layer 3B and the intermediate layer 4B, the concentrations of carbon and oxygen contained in the chromium layer or both carbon and oxygen are controlled in the film thickness direction, and the carbon of the intermediate layer 4B which is the upper chromium layer is controlled. By making the concentration and oxygen concentration higher than that of the light-shielding layer 3B, which is the lower chromium layer, the etching rate of the intermediate layer 4B, which is the upper chromium layer, is slower than the etching rate of the light-shielding layer 3B, which is the lower chromium layer. It is possible to control so as to be.
By controlling the carbon concentration and the oxygen concentration in the chromium film in this way, it is possible to obtain a cross-sectional shape with less tailing.

Thereby, in the present embodiment, the mask blanks 1B capable of preventing the occurrence of tailing even when the chromium film thickness, which is a low sheet resistance capable of reducing the influence of electrostatic fracture, is 100 nm or more, preferably 200 nm or more, is provided. It becomes possible to form. As a result, it is possible to reduce the variation in the pattern line width in the photomask 1.

In the present embodiment, the intermediate layer 4B is exemplified as a single layer with respect to the light-shielding layer 3B which is a chrome film, but the present invention is not limited to this configuration, and it is intended to reduce electrostatic breakdown and prevent the occurrence of tailing. If the configuration is such that the above can be simultaneously performed, a plurality of laminated intermediate layers may be formed.

In the present embodiment, the film forming chamber S12 is provided with the three-stage film forming means S13, S14, and S15, and the film is formed on the glass substrate 2 in order, but the film forming means has a smaller number of steps. In this case, the glass substrate 1 can be returned to any of the film forming means, and the corresponding film can be formed under different film forming conditions.

Hereinafter, examples of the present invention will be described.

<Composition measurement>
First, Cr (chromium), N (nitrogen), C (carbon), and O (oxygen) are applied to each of the antireflection layer, the intermediate layer, and the light-shielding layer in the mask blanks of the present invention by using Auger electron spectroscopy. The results of the composition analysis of) are shown in Table 1. In Table 1, the layer A shows an antireflection layer, the layer B shows an intermediate layer, and the layer C shows a light-shielding layer.

Similarly, Table 2 shows the results of composition analysis using Auger electron spectroscopy for each of the antireflection layer and the light-shielding layer in the mask blanks without an intermediate layer. In Table 2, the layer A shows an antireflection layer, and the layer B shows a light-shielding layer.

From these results, in the three-layer structure shown in Table 1, the carbon concentration in the B layer (intermediate layer) is about twice as high as that in the C layer (light-shielding layer) and the A layer (antireflection layer). You can see that.

<Confirmation of hemming>
Next, a pattern was formed on the mask blanks having a three-layer structure in which the antireflection layer, the intermediate layer, and the light-shielding layer were formed in the present invention, and the occurrence of tailing in the pattern was confirmed.
The results are shown in FIG. In the figure, only the outline is emphasized in order to clarify the SEM image of the cross section.

The film thickness of each layer is as follows.
Chromium layer (intermediate layer, light-shielding layer); film thickness 200 nm
Layer A (antireflection layer); 25 nm
B layer (intermediate layer); 150 nm
C layer (light-shielding layer); 50 nm
Is said to be.

Here, the chrome layer indicates a low resistance chrome layer excluding the A layer which is a high resistance antireflection layer, and in the case of a two-layer structure, the film thickness of the B layer is used, and in the case of a three-layer structure. The film thickness of the sum of the B layer and the C layer is shown.

Similarly, a pattern was formed on the mask blanks having a two-layer structure without an intermediate layer, and the occurrence of tailing in the pattern was confirmed.
The results are shown in FIG.

The film thickness of each layer is as follows.
Chromium layer (light-shielding layer); film thickness 200 nm
Layer A (antireflection layer); 25 nm
B layer (light-shielding layer); 200 nm
Is said to be.

Further, these taper angles θ were measured by changing the film thickness of the chromium layer.
The results are shown in FIG.

From these results, it can be seen that it is possible to increase the taper angle θ of the mask as compared with the two-layer structure by adopting the three-layer structure. When the film thickness of the chrome layer is 200 nm, the taper angle θ can be increased to 80 ° by using a three-layer structure, whereas the taper angle θ is 45 ° in the two-layer structure. be.

When the film thickness of the chromium layer is 150 nm, the film thickness of each layer of the three-layer structure can be 25 nm for the A layer, 100 nm for the B layer, and 50 nm for the C layer, and 25 nm for the A layer and 150 nm for the B layer in the two-layer structure. Can be.

<Sheet resistance measurement>
Next, the sheet resistance of the mask blanks having a three-layer structure in which the antireflection layer, the intermediate layer, and the light-shielding layer were formed in the present invention was measured, and the relationship with the chromium layer film thickness was confirmed.

Similarly, the sheet resistance was measured for mask blanks having a two-layer structure without an intermediate layer, and the relationship with the chromium layer film thickness was confirmed.
These results are shown in FIG.

From these results, in the three-layer structure, since a chromium film having a high carbon concentration and oxygen concentration is used for the intermediate layer, the sheet resistance is increased as compared with the mask of the two-layer structure having the same film thickness of the chromium layer. It can be seen that the sheet resistance is 10 Ω / sq or less regardless of whether the thickness of the chromium layer is 150 nm or 200 nm.

<Confirmation of electrostatic destruction>
Next, the relationship between the measured sheet resistance and the occurrence of electrostatic fracture was confirmed for the mask blanks having a three-layer structure in which the antireflection layer, the intermediate layer, and the light-shielding layer were formed in the present invention.
Here, the rate of occurrence of electrostatic breakdown is evaluated by visually confirming the rate at which the mask pattern is broken by electrostatic breakdown by charging the mask formed on the glass substrate under a microscope. ..

Similarly, for mask blanks having a two-layer structure without an intermediate layer, the relationship between the measured sheet resistance and the occurrence of electrostatic fracture was confirmed.
These results are shown in FIG.

From these results, it can be seen that the occurrence rate of electrostatic fracture can be suppressed by setting the sheet resistance to 10 Ω / sq or less even in the three-layer structure.
As a result, by using mask blanks with a three-layer structure with a high carbon concentration in the B layer and a sheet resistance of 10 Ω / sq or less, there is an antistatic effect that is resistant to electrostatic breakdown, and the mask cross-sectional shape is also hemmed. It can be seen that it is possible to form a mask with less variation in line width and less variation in line width.

Examples of utilization of the present invention include masks and mask blanks capable of suppressing electrostatic breakdown.

1 ... Photomask 1B ... Mask blanks 2 ... Glass substrate (transparent substrate)
2A ... Translucent regions 3, 4, 5 ... Light-shielding pattern 3B ... Light-shielding layer 4B ... Intermediate layer 5B ... Antireflection layer

Claims (4)

With a transparent board
A light-shielding layer containing chromium as a main component formed on the surface of the transparent substrate,
The intermediate layer laminated on the light-shielding layer and
The antireflection layer laminated on the intermediate layer and
Have,
The antireflection layer contains chromium and contains a large amount of oxygen as compared with the light shielding layer .
The intermediate layer contains chromium and contains a large amount of carbon as compared with the antireflection layer and the light shielding layer .
The carbon content in the intermediate layer is set to 14.5 atm% or more, and the carbon content is set to 14.5 atm% or more.
Mask blanks characterized in that the sheet resistance is set to be less than 10Ω / sq. The mask blank according to claim 1, wherein the carbon content in the intermediate layer is set to be twice or more that of the light-shielding layer. A photomask manufactured from the mask blanks according to claim 1 or 2 .
A photomask characterized in that the angle at which the wall surface of the light-transmitting region in the light-shielding pattern formed by removing the light-transmitting region from the light-shielding layer is in contact with the surface of the glass substrate is 80 ° or more. The method for manufacturing a mask blank according to claim 1 or 2 .
A method for producing a mask blank, characterized in that the partial pressure of the carbon-containing gas is set higher when the intermediate layer is formed than when the antireflection layer and the light-shielding layer are formed.

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