JP2020074053A - Photo mask, photo mask blank, and method for manufacturing photo mask - Google Patents

Abstract

To provide a photo mask capable of suppressing occurrence of growable foreign substances on the surface of a light shielding film pattern.SOLUTION: A photo mask has a transparent substrate and a light shielding film pattern formed on the transparent substrate, the light shielding film pattern being made of a light shielding film having a desired optical density (OD value). The surface of the light shielding film pattern has an arithmetic average roughness (Ra) of 0.4 nm or less and a nitrogen content of 13 atm% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photomask, a photomask blank, and a photomask manufacturing method.

  In semiconductor LSI manufacturing and the like, a binary mask or a phase shift mask is used as a photomask that is a mask for transferring an LSI pattern. In recent years, with the miniaturization and high integration of LSI patterns, in the photolithography technology used for pattern formation, the light source of the exposure apparatus is changed from the g-line (436 nm) and i-line (365 nm) of the high-pressure mercury lamp to the KrF excimer laser ( 248 nm) and ArF excimer laser (193 nm) are becoming shorter wavelengths. Since such an exposure light source with a short wavelength has a high output at a short wavelength, the energy of light is high, and a foreign substance that grows over time is generated on the photomask used for exposure, which contaminates the photomask. It has been pointed out that there is a phenomenon, and this growing foreign substance (also called haze or cloudiness) becomes more remarkable as the exposure light has a shorter wavelength. In addition, if the growing foreign matter generated on the photomask becomes large enough to be transferred to the wafer, it may cause disconnection or short circuit of the circuit of the semiconductor element.

The generation of growing foreign matter that contaminates the exposure photomask when using this short-wavelength exposure light source is one of the major factors used for cleaning the photomask that remains on the photomask surface after manufacturing the photomask. It is said that sulfuric acid ions, which are acidic substances, and basic substances such as ammonia, which exist in the environment where the photomask is used, react by excimer laser irradiation during pattern transfer to generate ammonium sulfate, etc., and become growth foreign substances. ing.
In addition, it is said that ions and organic substances generated from the members constituting the pellicle and the exposure or storage environment are adsorbed on the photomask to generate growing foreign substances. Further, it is considered that the growing foreign matter is generated not only by direct irradiation of the excimer laser but also by receiving scattered light of the excimer laser. Therefore, the growing foreign matter can be generated from the sulfate ions adsorbed on the surface of the light-shielding film pattern in the photomask.

  As a result, for example, in a line-and-space pattern in a binary mask, a growing foreign substance is generated on the surface of a light-shielding film pattern that constitutes a light-shielding portion, and grows until it covers the light-transmitting portion. Is occurring. In particular, in a photomask of an advanced product in which the dimensions of the pattern are thin and dense, a problem easily occurs up to the portion where the foreign matter generated on the surface of the light shielding film pattern transmits light. From this, even if the inspection after the photomask is manufactured is in a good quality state with no defects, a growing foreign substance is generated on the photomask during repeated excimer laser irradiation in the exposure apparatus and the photomask is not removed. There is a problem that it is contaminated and a good pattern transfer image cannot be obtained on the wafer. The photomask needs to be cleaned to remove the growing foreign matter, but the photomask needs to be cleaned, which increases the cost for manufacturing the product and causes the photomask pattern to wear. There are problems such as doing.

  As a technique for avoiding such a problem, for example, a management method of an exposure photomask described in Patent Document 1 is known (for example, Patent Document 1). In the exposure photomask management method described in Patent Document 1, when the adsorption amount of sulfate ions existing on the surface of the photomask to which ArF excimer laser exposure light is applied exceeds a threshold value, growing foreign matter is generated on the photomask surface. Then, after the specification, the expiration date of the photomask in which the growing foreign matter is not generated is set.

  However, in the exposure photomask management method described in Patent Document 1, the photomask is performed by a method of setting the expiration date of the photomask in which growing foreign matter does not occur and then cleaning the photomask before the expiration date. Management is troublesome and troublesome. In addition, in order to avoid generation of growing foreign matter on the surface of the photomask, it is necessary to clean the photomask.

Japanese Patent No. 4863064

The present invention has been made in view of the above problems, by controlling the surface roughness of the light-shielding film pattern in the photomask, by reducing the adsorption amount of sulfate ions adsorbed on the surface of the light-shielding film pattern, The main object of the present invention is to provide a photomask capable of suppressing the generation of growing foreign matter on the surface of the light shielding film pattern.
Further, by reducing the adsorption amount of the organic material derived from the adhesive material used for sticking the pellicle on the surface of the light-shielding film pattern and the organic matter existing in the exposure environment and the storage environment, the light-shielding film pattern can be formed. The main object of the present invention is to provide a photomask capable of suppressing the generation of growing foreign matter on the surface.

As a result of repeated studies to solve the above problems, the present inventors have found that the surface roughness of the light-shielding film pattern can be reduced to a predetermined range or less to significantly reduce the amount of sulfate ion adsorption. It was newly discovered that the surface composition of the pattern can significantly reduce the amount of adsorbed organic matter, and in particular, can reduce the adsorbed amount of organic matter by reducing the nitrogen content.
That is, the present inventors have found that by simultaneously controlling the surface roughness and the surface composition of the light-shielding film pattern, the generation of growing foreign matter on the surface of the light-shielding film pattern can be greatly reduced, and the present invention has been completed. It was.

  That is, the present invention has a light-shielding film pattern formed of a transparent substrate and a light-shielding film formed on the transparent substrate and having a desired optical density (OD value), and the arithmetic mean roughness of the surface of the light-shielding film pattern. (Ra) is 0.4 nm or less, and the content ratio of nitrogen on the surface of the light-shielding film pattern is 13 atm% or less.

  According to the present invention, it is possible to suppress the growth foreign matter from being generated on the surface of the light shielding film pattern. Therefore, it is possible to suppress the failure to obtain a good pattern transfer image on the wafer.

  In the above invention, the light-transmitting film pattern may further be formed on the transparent substrate, and the light-shielding film pattern may be formed on the light-transmitting film pattern.

  In the above invention, the above-mentioned transparent substrate further has an outer frame light-shielding film formed of the light-shielding film, which is formed in an outer frame region outside a pattern forming region where a pattern transferred to a wafer is formed, The arithmetic mean roughness (Ra) of the surface of the outer frame light-shielding film is preferably 0.4 nm or less. This is because it becomes easy to remove the adhesive material of the pellicle from the surface of the outer frame light-shielding film.

  In the present invention, it is preferable that the material of the light shielding film is a molybdenum silicide-based material, and the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.1 nm or less. This is because it is possible to suppress the growth foreign matter from being generated on the surface of the light shielding film pattern.

  Further, the present invention includes a transparent substrate and a light-shielding film formed on the transparent substrate and having a desired optical density (OD value), and the arithmetic average roughness (Ra) of the surface of the light-shielding film is 0. Provided is a photomask blank having a thickness of 4 nm or less and having a nitrogen content of 13 atm% or less on the surface of the light shielding film.

  According to the present invention, it is possible to suppress the growth foreign matter from being generated on the surface of the light shielding film. Therefore, it is possible to suppress the failure to obtain a good pattern transfer image on the wafer.

  Further, the present invention provides a photomask blanks preparing step of preparing a photomask blank having a transparent substrate and a light shielding film having a desired optical density (OD value) formed on the transparent substrate, and etching the light shielding film. Thus, there is provided a photomask manufacturing method characterized by comprising a light-shielding film pattern forming step of forming a light-shielding film pattern and a smoothing treatment step of smoothing the surface of the light-shielding film pattern.

  According to the present invention, it is possible to obtain a photomask in which growing foreign matter is unlikely to occur on the surface of the light shielding film pattern. Therefore, it is possible to suppress the failure to obtain a good pattern transfer image on the wafer.

  The present invention has an effect that it is possible to suppress the growth foreign matter from being generated on the surface of the light shielding film pattern.

It is a schematic sectional drawing which shows an example of the photomask of this invention. 6 is a graph showing the relationship between the arithmetic average roughness (Ra) of the surface of the light shielding film pattern and the adsorption amount of sulfate ions on the surface of the light shielding film pattern. 5 is a graph showing the relationship between the amount of sulfate ions adsorbed on the surface of the light-shielding film pattern and the number of growing foreign substances generated on the surface of the light-shielding film pattern. 6 is a graph showing the relationship between the surface area of the light shielding film pattern and the adsorption amount of sulfate ions on the surface of the light shielding film pattern. It is a schematic sectional drawing which shows the other example of the photomask of this invention. It is a schematic sectional drawing which shows an example of the photomask blank of this invention. It is a schematic sectional drawing which shows the other example of the photomask blank of this invention. FIG. 6 is a schematic process cross-sectional view showing an example of the method for manufacturing a photomask of the present invention. FIG. 6 is a schematic process cross-sectional view showing an example of the method for manufacturing a photomask of the present invention. FIG. 6 is a schematic process sectional view showing another example of the method for manufacturing the photomask of the present invention. FIG. 6 is a schematic process sectional view showing another example of the method for manufacturing the photomask of the present invention. It is an AFM image of the surface of a light semi-transmissive film pattern. 3 is an AFM image of the light-shielding film pattern and the surface of the light-shielding film. It is a figure which shows the result of irradiating ArF excimer laser with respect to the surface of a light semi-transmissive film pattern after a sulfuric acid cleaning. It is a SEM image which evaluated the generation | occurrence | production of the growth foreign material (Haze) after ArF excimer laser irradiation. It is a figure which shows the result of having evaluated the foreign material removal force of the surface of a light semi-transmissive film pattern. It is a figure which shows the adhesive material of the pellicle which remains on the surface of the synthetic quartz substrate and light-shielding film in a photomask.

  Hereinafter, the photomask, the photomask blank, and the method for manufacturing the photomask of the present invention will be described in detail.

A. Photomask The photomask of the present invention has a transparent substrate and a light-shielding film pattern formed on the transparent substrate, the light-shielding film having a desired optical density (OD value), and the arithmetic mean of the surfaces of the light-shielding film pattern. The roughness (Ra) is 0.4 nm or less.
Here, in the present invention, the arithmetic mean roughness (Ra) is measured by using an atomic force microscope (AFM) <L-trace manufactured by Hitachi High-Tech Science Co., Ltd.> to obtain height data in a 1 μm square range. It refers to Ra (center line surface roughness) originally obtained.

  FIG. 1 is a schematic sectional view showing an example of the photomask of the present invention. The photomask 100 shown in FIG. 1 is a binary mask. The photomask 100 shown in FIG. 1 has a transparent substrate 101 and a light shielding film pattern 102 formed on the transparent substrate 101. The light-shielding film pattern 102 is independently adjusted to have an optical density (OD value) of 3.0 or more. The light-shielding film pattern 102 is a light-shielding film pattern formed on the transparent substrate 101 in a pattern formation region where a pattern to be transferred to a wafer is formed. Here, in the present invention, the “binary mask” is a binary type having the transparent substrate and the light shielding film pattern formed on the transparent substrate, and forming a pattern with a light transmitting portion and a light shielding portion. Means photomask of.

  The arithmetic average roughness (Ra) of the upper surface 101a of the transparent substrate 101 and the upper surfaces 102a and the side surfaces 102b of the light shielding film pattern 102 is 0.4 nm or less.

  Here, in the present invention, the surface of the light-shielding film pattern means the upper surface of the light-shielding film pattern, such as the upper surface 102a of the light-shielding film pattern 102 shown in FIGS. The upper surface of the light-shielding film pattern is a surface opposite to the lower surface of the light-shielding film pattern, which is in contact with the transparent substrate or a light semi-transmissive film pattern described later. Further, the surface of the transparent substrate means the upper surface of the transparent substrate such as the upper surface 101a of the transparent substrate 101 shown in FIGS. 1 and 5. The upper surface of the transparent substrate is the surface of the transparent substrate on which the light shielding film pattern or the light semitransmissive film pattern described later is formed.

  According to the present invention, the surface area of the light-shielding film pattern is reduced by the arithmetic average roughness (Ra) of the surface of the light-shielding film pattern being 0.4 nm or less. Therefore, the amount of sulfate ions adsorbed on the surface of the light shielding film pattern can be reduced. Accordingly, it is possible to suppress the growth foreign matter from being generated on the surface of the light shielding film pattern. As a result, it is possible to prevent the growing foreign matter generated on the surface of the light-shielding film pattern from growing until it covers the light-transmitting portion of the photomask. As a result, it is possible to prevent the failure to obtain a good pattern transfer image on the wafer.

  Further, in the photomask of the present invention, the surface of the light shielding film pattern has an arithmetic average roughness (Ra) of 0.4 nm or less, and the surface of the light shielding film pattern is smooth. Therefore, when cleaning the photomask with the miniaturization of the pattern transferred to the wafer, a physical cleaning tool such as megasonic is used to prevent damage from occurring in the pattern transferred to the wafer. Even if the output is weakened, the surface of the light-shielding film pattern is smooth, so that the foreign matter can be easily removed from the surface of the light-shielding film pattern. The structure of the photomask of the present invention will be described below.

1. Light-shielding film pattern The light-shielding film pattern in the present invention is a light-shielding film formed on the transparent substrate and having a desired optical density (OD value). The light-shielding film pattern in the present invention has an arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern of 0.4 nm or less.

(1) Surface of light-shielding film pattern a. Arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern
FIG. 2 is a graph showing the relationship between the arithmetic mean roughness (Ra) of the surface of the light shielding film pattern and the adsorption amount of sulfate ions on the surface of the light shielding film pattern. The sulfate ion adsorption amount (SO ₄ adsorption amount) shown in the graph shown in FIG. 2 changes depending on the arithmetic mean roughness (Ra), and is shown in the graph shown in FIG. The relationship between the arithmetic mean roughness (Ra) and the adsorption amount of sulfate ions is established on the surface and side surface of the light shielding film pattern, the surface of the transparent substrate, and the surface and side surface of the light semitransmissive film pattern. The relationship shown in the graph shown in FIG. 2 was evaluated under the following evaluation conditions.
<Cleaning conditions>
・ Sulfuric acid cleaning <Ion chromatography conditions>
・ DIW 100ml 90 ℃ 2h extraction

  Then, Table 1 shows the adsorption amount of sulfate ions on the surface of the light shielding film pattern with respect to the arithmetic average roughness (Ra) of the surface of the light shielding film pattern shown in the graph shown in FIG.

FIG. 3 is a graph showing the relationship between the adsorption amount of sulfate ions on the surface of the light shielding film pattern and the number of growing foreign substances generated on the surface of the light shielding film pattern. The graph shown in FIG. 3 shows that when the cumulative exposure amount of ArF excimer laser exposure light to the photomask is changed from 800 J / cm ^{2 to} 3000 J / cm ² , the adsorption amount of sulfate ions on the surface of the light shielding film pattern and the light shielding It shows the relationship with the number of growing foreign substances generated on the surface of the film pattern. As shown in FIG. 3, when the sulfate ion adsorption amount on the surface of the light-shielding film pattern is 0.9 ng / cm ² or less, the integrated exposure amount is 800 J / cm ² , 1500 J / cm ² , and 3000 J / cm ² . In any case of cm ^2, no growing foreign matter is generated. Then, the number of the growing foreign matter that is shown in the graph shown in FIG. 3 changes depending on the adsorption amount of sulfate ions, and the adsorption of sulfate ions shown in the graph shown in FIG. The relationship between the amount and the number of growing foreign matter generated is established on the surface and side surface of the light shielding film pattern, the surface of the transparent substrate, and the surface and side surface of the light semitransmissive film pattern.

On the other hand, as shown in FIG. 2 and Table 1, when the arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern is 0.4 nm or less, the adsorption amount of sulfate ions on the surface of the light-shielding film pattern. Is 4.5 ppb (0.9 ng / cm ² ) or less. Therefore, as shown in FIG. 2 and Table 1, when the arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern is 0.4 nm or less, the adsorption amount of sulfate ions on the surface of the light-shielding film pattern. Is 4.5 ppb (0.9 ng / cm ² ) or less, so that it is possible to prevent the growth foreign matter from being generated on the surface of the light shielding film pattern.

The arithmetic average roughness (Ra) of the surface of the light-shielding film pattern is not particularly limited as long as it is 0.4 nm or less, but is preferably 0.3 nm or less, and particularly preferably 0.2 nm or less. This is because the adsorption amount of sulfate ions is smaller.
More specifically, the arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern is 0.2 nm or less when the material of the light-shielding film forming the light-shielding film pattern is a molybdenum silicide-based material, for example. Is preferable, and 0.1 nm or less is particularly preferable.
This is because the adsorption amount of sulfate ions is smaller.
The arithmetic mean roughness (Ra) of the surface of the light shielding film pattern is preferably 0.3 nm or less when the material of the light shielding film forming the light shielding film pattern is a chromium-based material. .. This is because the adsorption amount of sulfate ions is smaller.

b. Surface Area of Light-Shielding Film Pattern When the arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern is 0.4 nm or less, the surface area of the light-shielding film pattern is 99800 nm ² or less. In the present invention, the surface area of the light-shielding film pattern means one obtained by a method such as image analysis from the arithmetic average roughness (Ra) of the surface of the light-shielding film pattern, and, for example, according to the following evaluation conditions. Refers to what has been evaluated. Specifically, for example, Ra (center line surface) obtained by measuring using an atomic force microscope (AFM) <L-trace manufactured by Hitachi High-Tech Science Co., Ltd.> based on height data in a 1 μm square range Roughness) means that determined by image analysis.

FIG. 4 is a graph showing the relationship between the surface area of the light shielding film pattern and the adsorption amount of sulfate ions on the surface of the light shielding film pattern. The sulfate ion adsorption amount (SO ₄ adsorption amount) shown in the graph shown in FIG. 4 changes depending on the surface area, and the surface area and sulfate ion shown in the graph shown in FIG. The relationship of the adsorption amount of is established on the surface and the side surface of the light shielding film pattern, the surface of the transparent substrate, and the surface and the side surface of the light semi-transmissive film pattern. Note that the relationship represented by the graph shown in FIG. 4 is evaluated under the above-described evaluation conditions, similarly to the relationship represented by the graph shown in FIG.

As shown in FIG. 4, when the surface area of the light shielding film pattern is 99800 nm ² or less, the adsorption amount of sulfate ions on the surface of the light shielding film pattern is 4.5 ppb (0.9 ng / cm ² ) or less. Therefore, it is possible to suppress the growth foreign matter from being generated on the surface of the light shielding film pattern. This means that, as described above, when the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less, as shown in FIG. 2, the light shielding film pattern grows on the surface of the light shielding film pattern. It is possible to suppress the generation of foreign matter.

Further, the surface area of the light shielding film pattern is not particularly limited, among others, 99700Nm ² or less, particularly, 99600Nm ² or less. This is because the adsorption amount of sulfate ions is smaller.

c. Component composition of the surface of the light-shielding film pattern The component composition of the surface of the light-shielding film pattern may be any as long as it can suppress the generation of growing foreign matter, and varies depending on the material of the light-shielding film forming the light-shielding film pattern.
The nitrogen content on the surface of such a light-shielding film pattern is preferably 13 atm% or less, and more preferably 6 atm% or less, from the viewpoint of reducing the adhesion of organic substances that cause the growth of foreign matter. It is preferable that the amount is 5 atm% or less.
Here, it is not clear why reducing the content ratio of nitrogen can reduce, for example, the adhesion of organic substances that are considered to be caused by the adhesive material of the pellicle or the organic substances existing in the exposure environment and the storage environment. However, if nitrogen atoms are present on the surface, it is presumed that the nitrogen atoms serve as nuclei and organic substances are likely to aggregate. Therefore, by reducing the content ratio of nitrogen that causes the aggregation of organic substances, it is possible to suppress the generation of growth foreign substances that are caused by the adhesion of organic substances that are considered to be due to the adhesive material of the pellicle on the surface of the light-shielding film pattern. It is speculated that it can be done.
Further, the oxygen content rate on the surface of the light-shielding film pattern is preferably 50 atm% or more, and more preferably 55 atm% or more, from the viewpoint of reducing the adhesion of organic substances that cause growth foreign matter. It is preferably at least 60 atm%.
Here, it is not clear why increasing the oxygen content ratio can reduce, for example, the adhesion of organic substances that are considered to be caused by the adhesive material of the pellicle or the like, and organic substances existing in the exposure environment and the storage environment. However, it is speculated that the higher the oxygen content on the surface, the more stable the chemical properties of the surface and the less likely it is that organic substances will be adsorbed. Therefore, by increasing the oxygen content ratio, it is possible to suppress the adhesion of organic substances and the like, which are considered to be caused by the adhesive material of the pellicle, etc., to the surface of the light-shielding film pattern, and as a result, it is possible to suppress the generation of growing foreign substances. To be done.
Furthermore, when the material of the light-shielding film forming the light-shielding film pattern is a molybdenum silicide-based material, the content ratio of molybdenum on the surface of the light-shielding film pattern is to reduce the adhesion of organic substances that cause growth foreign matter. From the viewpoint of the above, it is preferably 1.2 atm% or less, more preferably 1.0 atm% or less, and particularly preferably 0.5 atm% or less.
Here, it is not clear why reducing the content ratio of molybdenum can reduce, for example, the adhesion of organic substances that are considered to be caused by the adhesive material of the pellicle or the organic substances existing in the exposure environment and the storage environment. However, it is presumed that this is because molybdenum acts as a catalyst for the growth of foreign substances due to organic substances. Therefore, by reducing the content ratio of molybdenum on the surface, even if an organic substance that causes a growing foreign substance is attached to the surface, it can be suppressed from increasing until it is recognized as a growing foreign substance, and as a result, It is presumed that the generation of growing foreign substances can be suppressed.

In addition, atm% refers to the ratio of each element when the total of the elements detected from the surface of the light-shielding film pattern is 100%.
Further, the above-described method for measuring the component composition of the light-shielding film pattern surface may be any method capable of accurately measuring the surface component composition, and for example, an average value within a range of 5 nm from the outermost surface of the light-shielding film pattern in the thickness direction A method of measuring the component composition can be used.
As such measurement conditions, the following X-ray conditions, X-ray uptake angles, and neutralization conditions can be used, for example.
In addition, as such a device for measuring the surface composition, for example, Quantum 2000 manufactured by ULVAC-PHI can be used.

(Measurement condition)
X-ray condition: Al mono 200 μmφ × 30 W 15 kV
X-ray acquisition angle: 45 °
Neutralization conditions: ION / Electron 20 μA

(2) Side surface of light-shielding film pattern The light-shielding film pattern is not particularly limited, but as in the light-shielding film pattern 102 shown in FIG. 1, the arithmetic average roughness (Ra) of the side surface of the light-shielding film pattern. Is preferably 0.4 nm or less. This is because the same effect as when the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less can be obtained. Specifically, it is possible to suppress the growth foreign matter from being generated on the side surface of the light shielding film pattern. Further, even if the output of a physical cleaning tool or the like is weakened when cleaning the photomask, foreign matter can be easily removed from the side surface of the light shielding film pattern. Further, when the growing foreign matter is generated on the side surface of the light shielding film pattern, unlike the case where the growing foreign matter is generated on the surface of the light shielding film pattern, even if the growing foreign matter does not grow so much, To cover the part that penetrates. Therefore, since the arithmetic mean roughness (Ra) of the side surface of the light shielding film pattern is 0.4 nm or less, the arithmetic mean roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less. This is also because it is possible to remarkably suppress the failure to obtain a good pattern transfer image on the wafer.

Here, in the present invention, the side surface of the light-shielding film pattern means a surface between the surface of the light-shielding film pattern and the surface of the transparent substrate or the surface of the light-semitransmissive film pattern described later.
More specifically, the side surface of the light-shielding film pattern may be the upper surface of the light-shielding film pattern such as the side surface 102b of the light-shielding film pattern 102 shown in FIGS. The surface between the upper surfaces of the film pattern is meant.

  The arithmetic mean roughness (Ra) of the side surface of the light-shielding film pattern is not particularly limited, but is preferably 0.3 nm or less, and particularly preferably 0.2 nm or less. This is because the adsorption amount of sulfate ions is smaller.

When the arithmetic mean roughness (Ra) of the side surface of the light shielding film pattern is 0.4 nm or less, the side area of the light shielding film pattern is 99800 nm ² or less. In the present invention, the side area of the light-shielding film pattern means that calculated from the arithmetic average roughness (Ra) of the side surface of the light-shielding film pattern by the same method and evaluation conditions as the surface area of the light-shielding film pattern. To do.
The arithmetic mean roughness (Ra) of the side surface of the light-shielding film pattern and the component composition of the side surface are more specifically the same as those described in the above section “(1) Surface of light-shielding film pattern”. You can

Further, the side area of the light-shielding film pattern is not particularly limited, among others, 99700Nm ² or less, particularly, 99600Nm ² or less. This is because the adsorption amount of sulfate ions is smaller.

(3) Light-shielding film pattern In the present invention, the light-shielding film pattern has a pattern formation region (hereinafter referred to as a light-shielding film pattern 102 shown in FIG. 1) in which a pattern to be transferred to a wafer is formed on the transparent substrate. , Abbreviated as “pattern formation region”).

  The light-shielding film pattern is not limited to the light-shielding film pattern in the binary mask such as the light-shielding film pattern 102 shown in FIG. 1, and for example, the light-shielding film formed on the light semi-transmissive film pattern described later. It may be a pattern.

2. Outer Frame Light-Shielding Film The photomask of the present invention is not particularly limited, but is formed on an outer frame region (hereinafter, abbreviated as “outer frame region”) outside the pattern formation region on the transparent substrate. It may further have an outer frame light-shielding film formed and made of the above-mentioned light-shielding film. In this case, it is preferable that the arithmetic mean roughness (Ra) of the surface of the outer frame light-shielding film is 0.4 nm or less. This is for the following reason.

  Since the pellicle deteriorates when the photomask is continuously used, it is necessary to remove the pellicle from the photomask once, wash the photomask, and attach the pellicle to the photomask again. Then, the pellicle is attached to the outer frame region of the photomask by being bonded to the outer frame region with an adhesive. Therefore, when the photomask is formed in the outer frame region and further has an outer frame light-shielding film made of a light-shielding film, the pellicle adheres to the surface of the outer frame light-shielding film formed in the outer frame region. It is bonded through the agent. As a result, when the pellicle is peeled off from the photomask, a large amount of the adhesive material of the pellicle remains on the surface of the outer frame light-shielding film. Further, it is difficult to remove the adhesive material of the pellicle remaining on the surface of the outer frame light-shielding film. For this reason, the photomask must be washed many times in order to remove the adhesive material of the pellicle. Further, a large amount of the adhesive material of the pellicle remaining on the surface of the outer frame light-shielding film is scattered in the pattern formation region of the photomask due to cleaning of the photomask or the like, and becomes defective. Further, since the adhesive material of the pellicle is an organic substance, a large amount of the adhesive material of the pellicle remaining on the surface of the outer frame light-shielding film may generate gas or the like, which may cause growth foreign matter.

  On the other hand, according to the present invention, the arithmetic mean roughness (Ra) of the surface of the outer frame light-shielding film is 0.4 nm or less, and the surface of the outer frame light-shielding film is smooth. It becomes easy to remove the adhesive material from the surface of the outer frame light-shielding film. As a result, the number of times the photomask is washed to remove the adhesive material of the pellicle from the surface of the outer frame light-shielding film can be reduced. Further, it is possible to prevent a large amount of the adhesive material of the pellicle remaining on the surface of the outer frame light-shielding film from being scattered and defective in the pattern formation region of the photomask due to cleaning of the photomask or the like. Furthermore, it is possible to prevent the adhesive material of the pellicle that remains on the surface of the outer frame light-shielding film in a large amount from causing growth foreign matter. As a result, it is possible to prevent the growing foreign matter from growing and failing to obtain a good pattern transfer image on the wafer. Therefore, the photomask preferably has the outer frame light-shielding film.

3. Light-shielding film The light-shielding film is not particularly limited, but when the photomask of the present invention is a binary mask such as the photomask 100 shown in FIG. 1, the optical density (OD value) alone is used. However, it is preferably adjusted to be 3.0 or more. This is because it is possible to obtain the necessary light-shielding property in a desired portion during exposure. Further, when the photomask of the present invention is a phase shift mask described later, the light shielding film has an optical density (OD value) of 3.0 or more together with a light semitransmissive film pattern described later. It is preferably adjusted to. This is because it is possible to obtain the necessary light-shielding property in a desired portion during exposure.

  The material of the light-shielding film is not particularly limited, but examples of the material of the light-shielding film include molybdenum silicide (MoSi) -based material and chromium (Cr) -based material. The molybdenum silicide (MoSi) -based material may be MoSiO, MoSiN, MoSiON, or the like. Examples of the chromium (Cr) -based material include Cr, CrO, CrN, CrON and the like.

Further, the thickness of the light-shielding film varies depending on the kind of the material and is not particularly limited, but is preferably within the range of 10 nm to 500 nm, and more preferably within the range of 10 nm to 300 nm. It is preferable that it exists, and it is particularly preferable that it is in the range of 10 nm to 200 nm. This is because if it has the above-mentioned thickness, an optical density (OD value) of 3.0 or more can be secured alone or in combination with a light semi-transmissive film pattern described later.
In the present invention, from the viewpoint that the surface area of the light shielding film pattern can be reduced, the thickness of the light shielding film is preferably 65 nm or less.

4. Transparent Substrate The transparent substrate in the present invention is not particularly limited, but examples of the transparent substrate in the present invention include optically polished synthetic quartz glass, fluorite, and fluorinated that transmit exposure light with high transmittance. Examples thereof include calcium. Of these, synthetic quartz glass is preferable. This is because it is widely used, the quality is stable, and the transmittance of short-wavelength exposure light is high.

  The transparent substrate is not particularly limited, but a transparent substrate having an arithmetic mean roughness (Ra) of 0.4 nm or less on the surface of the transparent substrate, such as the transparent substrate 101 shown in FIG. 1, is preferable. This is because the same effect as when the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less can be obtained. Specifically, since the surface area of the transparent substrate is small, it is possible to suppress the growth foreign matter from being generated on the surface of the transparent substrate. Further, even when the output of a physical cleaning tool or the like is weakened when cleaning the photomask, foreign matter can be easily removed from the transparent substrate. Furthermore, when a growing foreign substance is generated on the surface of the transparent substrate, unlike the case where the growing foreign substance is generated on the surface of the light-shielding film pattern, light is generated even if the growing foreign substance does not grow so much. It covers the transparent part. Therefore, since the surface of the transparent substrate has an arithmetic average roughness (Ra) of 0.4 nm or less, the surface of the light shielding film pattern has an arithmetic average roughness (Ra) of 0.4 nm or less. This is because it is possible to remarkably suppress the failure to obtain a good pattern transfer image on the wafer.

  Further, when the light-shielding film pattern and the light-semitransmissive film pattern described later are not formed in the outer frame region and the transparent substrate is exposed in the outer frame region, the transparent film in the outer frame region is transparent. The smooth surface of the substrate facilitates removal of the pellicle adhesive from the surface of the transparent substrate in the outer frame region. This makes it possible to reduce the number of times the photomask is washed to remove the adhesive material of the pellicle from the surface of the transparent substrate. Further, in this case, it is possible to prevent a large amount of the adhesive material of the pellicle remaining on the surface of the transparent substrate from being scattered and defective in the pattern formation region of the photomask. Further, in this case, it is possible to prevent the adhesive material of the pellicle that remains on the surface of the transparent substrate in a large amount from causing growth foreign matter. This is because it is possible to prevent the growing foreign matter from growing and preventing a good pattern transfer image from being obtained on the wafer.

  The arithmetic average roughness (Ra) of the surface of the transparent substrate is not particularly limited, but is preferably 0.3 nm or less, particularly preferably 0.2 nm or less, and particularly preferably 0.13 nm or less. preferable. This is because the adsorption amount of sulfate ions is smaller.

The content ratio of nitrogen on the surface of the transparent substrate is preferably as low as possible from the viewpoint of reducing the adhesion of organic substances that cause the growth foreign matter, and is preferably 5.0 atm% or less.
In addition, the oxygen content rate on the surface of the transparent substrate is preferably 60.0 atm% or more from the viewpoint of reducing the adhesion of organic substances that cause the growth foreign matter.

5. Phase Shift Mask The photomask of the present invention is not limited to a binary mask like the photomask 100 shown in FIG. 1, but may be, for example, a phase shift mask having a tritone structure.

  The phase shift mask having a tritone structure of the present invention is the photomask, further comprising a light semi-transmissive film pattern formed on the transparent substrate, wherein the light shielding film pattern is on the light semi-transmissive film pattern. It was formed in. Here, in the present invention, the “tritone structure” means a structure in which the light-semitransmissive film pattern is formed in the pattern formation region and the light-shielding film pattern is formed on the light-semitransmissive film pattern. ..

  FIG. 5 is a schematic sectional view showing another example of the photomask of the present invention. The photomask 100 shown in FIG. 5 is a phase shift mask having a tritone structure. The photomask 100 shown in FIG. 5 includes a transparent substrate 101, a light-semitransmissive film pattern 103 formed on the transparent substrate 101, and a light-shielding film pattern 102 formed on the light-semitransmissive film pattern 103. .. The light shielding film pattern 102 is partially formed on the upper surface 103a of the light semi-transmissive film pattern 103. The light-shielding film pattern 102 is adjusted to have an optical density (OD value) of 3.0 or more together with the light-semitransmissive film pattern 103. The light semi-transmissive film pattern 103 is a light semi-transmissive film pattern formed in the pattern formation region. The structure in which the light-semitransmissive film pattern 103 is formed in the pattern formation region and the light-shielding film pattern 102 is formed on the light-semitransmissive film pattern 103 is a tritone structure.

  The arithmetic mean roughness (Ra) of all of the upper surface 101a of the transparent substrate 101, the upper surface 103a and the side surface 103b of the light semi-transmissive film pattern 103, and the upper surface 102a and the side surface 102b of the light shielding film pattern 102 is 0.4 nm or less. ..

  Here, in the present invention, the light-semitransmissive film pattern means a light-semitransmissive film pattern formed in the pattern formation region, like the light-semitransmissive film pattern 103 shown in FIG. Further, in the present invention, the surface of the light semi-transmissive film pattern means the upper surface of the light semi-transmissive film pattern such as the upper surface 103a of the light semi-transmissive film pattern 103 shown in FIG. The upper surface of the light-semitransmissive film pattern is a surface opposite to the lower surface of the light-semitransmissive film pattern, which is in contact with the transparent substrate.

  The phase shift mask having the tritone structure is not particularly limited as long as the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less, but the light semitransmissive film pattern is Like the light-semitransmissive film pattern 103 shown in FIG. 5, it is preferable that the surface of the light-semitransmissive film pattern has an arithmetic average roughness (Ra) of 0.4 nm or less. This is because the same effect as when the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less can be obtained. Specifically, it is possible to suppress the growth foreign matter from being generated on the surface of the light semi-transmissive film pattern. Further, even if the output of a physical cleaning tool or the like is weakened when cleaning the photomask, foreign matter can be easily removed from the surface of the light semitransmissive film pattern.

  The arithmetic average roughness (Ra) of the surface of the light-semitransmissive film pattern is not particularly limited, but is preferably 0.3 nm or less, and particularly preferably 0.2 nm or less. This is because the adsorption amount of sulfate ions is smaller.

When the arithmetic mean roughness (Ra) of the surface of the light semi-transmissive film pattern is 0.4 nm or less, the surface area of the light semi-transmissive film pattern is 99800 nm ² or less. In the present invention, the surface area of the light-semitransmissive film pattern is obtained from the arithmetic mean roughness (Ra) of the surface of the light-semitransmissive film pattern by the same method and evaluation conditions as the surface area of the light-shielding film pattern. Means something.

Further, the surface area of the light semi-transmitting film pattern is not particularly limited, among others, 99700Nm ² or less, particularly, 99600Nm ² or less. This is because the adsorption amount of sulfate ions is smaller.

  Further, the light-semitransmissive film pattern is not particularly limited, but like the light-semitransmissive film pattern 103 shown in FIG. 5, the arithmetic mean roughness (Ra) of the side surface of the light-semitransmissive film pattern is increased. Is preferably 0.4 nm or less. This is because the same effect as when the arithmetic average roughness (Ra) of the surface of the light shielding film pattern is 0.4 nm or less can be obtained. Specifically, it is possible to suppress the growth foreign matter from being generated on the side surface of the light semi-transmissive film pattern. Further, even if the output of a physical cleaning tool or the like is weakened when cleaning the photomask, foreign matter can be easily removed from the side surface of the light semitransmissive film pattern. Further, when a growing foreign substance occurs on the side surface of the light-semitransmissive film pattern, unlike the case where a growing foreign substance occurs on the surface of the light-semitransmissive film pattern, the growing foreign substance grows so much. Even if it does not exist, it will cover the part that transmits light. Therefore, the arithmetic mean roughness (Ra) of the side surface of the light-semitransmissive film pattern is 0.4 nm or less, so that the arithmetic mean roughness (Ra) of the surface of the light-semitransmissive film pattern is 0.4 nm or less. It is possible to remarkably suppress that a good pattern transfer image cannot be obtained on the wafer, as compared with the above case.

  Here, in the present invention, the side surface of the light-semitransmissive film pattern means a surface between the surface of the light-semitransmissive film pattern and the surface of the transparent substrate. More specifically, the side surface of the light-semitransmissive film pattern is between the upper surface of the light-semitransmissive film pattern and the upper surface of the transparent substrate, such as the side surface 103b of the light-semitransmissive film pattern 103 shown in FIG. Means a face.

  The arithmetic average roughness (Ra) of the side surface of the light-semitransmissive film pattern is not particularly limited, but is preferably 0.3 nm or less, and particularly preferably 0.2 nm or less. This is because the adsorption amount of sulfate ions is smaller.

When the arithmetic mean roughness (Ra) of the side surface of the light semi-transmissive film pattern is 0.4 nm or less, the side area of the light semi-transmissive film pattern is 99800 nm ² or less. In the present invention, the side area of the light-semitransmissive film pattern is determined from the arithmetic mean roughness (Ra) of the side surface of the light-semitransmissive film pattern by the same method and evaluation conditions as the surface area of the light-shielding film pattern. Means something that can be done.

Further, the side area of the light semi-transmitting film pattern is not particularly limited, among others, 99700Nm ² or less, particularly, 99600Nm ² or less. This is because the adsorption amount of sulfate ions is smaller.

  The material of the light-semitransmissive film pattern is not particularly limited, but examples of the material of the light-semitransmissive film pattern include molybdenum silicide (MoSi) -based material and silicon nitride (SiN) -based material. Is mentioned. Then, examples of the molybdenum silicide (MoSi) -based material include MoSiO, MoSiN, and MoSiON. Examples of the silicon nitride (SiN) -based material include SiN and SiON.

  Furthermore, the thickness of the light-semitransmissive film pattern varies depending on the type of the material, and is not particularly limited, but it is preferably in the range of 10 nm to 500 nm, and particularly 10 nm to 300 nm. It is preferably in the range, and particularly preferably in the range of 10 nm to 200 nm. The thickness required to form the fine pattern of the light-semitransmissive film used to form a fine pattern of a semiconductor on a photomask, and the thickness necessary to make the light-semitransmissive film pattern have a desired transmittance. This is because the thickness is in such a range, and further, it is advantageous that the thickness of the light semi-transmissive film pattern is thinner in forming the fine pattern of the light semi-transmissive film on the photomask. Is.

B. Photomask Blanks A photomask blank of the present invention has a transparent substrate and a light-shielding film having a desired optical density (OD value) formed on the transparent substrate, and the arithmetic mean roughness ( Ra) is 0.4 nm or less.

  FIG. 6 is a schematic sectional view showing an example of the photomask blank of the present invention. A photomask blank 200 shown in FIG. 6 is a photomask blank used for manufacturing a binary mask. The photomask blank 200 shown in FIG. 6 includes a transparent substrate 101, a light shielding film 202 formed on the transparent substrate 101, and a hard mask layer 204 formed on the light shielding film 202. The light-shielding film 202 is individually adjusted so that the optical density (OD value) is 3.0 or more. The light shielding film 202 is made of molybdenum silicide (MoSi) -based material. The hard mask layer 204 is made of a chromium (Cr) -based material. The photomask blank of the present invention has a transparent substrate and a light-shielding film having a desired optical density (OD value) formed on the transparent substrate, and has an arithmetic mean roughness (Ra) of the surface of the light-shielding film. Is 0.4 nm or less, the hard mask layer such as the hard mask layer 204 shown in FIG. 6 may not be provided.

  The arithmetic average roughness (Ra) of the upper surface 202a of the light shielding film 202 is 0.4 nm or less.

  Here, in the present invention, the surface of the light shielding film means the upper surface of the light shielding film such as the upper surface 202a of the light shielding film 202 shown in FIGS. 6 and 7. The upper surface of the light shielding film is a surface opposite to the lower surface of the light shielding film which is in contact with the transparent substrate or a light semi-transmissive film described later. Further, the surface of the transparent substrate means the upper surface of the transparent substrate such as the upper surface 101a of the transparent substrate 101 shown in FIGS. 6 and 7. The upper surface of the transparent substrate is the surface of the transparent substrate on which the light-shielding film or the light semi-transmissive film described later is formed.

  According to the present invention, the arithmetic mean roughness (Ra) of the surface of the light-shielding film is 0.4 nm or less, and the surface of the light-shielding film is smooth, so that the same effect as that of the photomask of the present invention can be obtained. Be done.

  The photomask blank of the present invention is not limited to the photomask blank used for manufacturing a binary mask such as the photomask blank 200 shown in FIG. 6, and may have a structure without a hard mask layer, for example. Further, it may be a photomask blank used for manufacturing a phase shift mask having a tritone structure.

  A photomask blank used for manufacturing a phase shift mask having a tritone structure of the present invention is the photomask blank, further comprising a light semi-transmissive film formed on the transparent substrate, and the light shielding film is It is formed on the above-mentioned light semi-transmissive film.

  FIG. 7 is a schematic cross-sectional view showing another example of the photomask blank of the present invention. The photomask blank 200 shown in FIG. 7 is a photomask blank used for manufacturing a phase shift mask having a tritone structure. The photomask blank 200 shown in FIG. 7 includes a transparent substrate 101, a light semi-transmissive film 203 formed on the transparent substrate 101, and a light shielding film 202 formed on the light semi-transmissive film 203. The light-shielding film 202 is adjusted so that the optical density (OD value) is 3.0 or more together with the light-semitransmissive film 203.

  The arithmetic average roughness (Ra) of the upper surface 202a of the light shielding film 202 is 0.4 nm or less.

  Here, in the present invention, the surface of the light-semitransmissive film means the upper surface of the light-semitransmissive film, such as the upper surface 203a of the light-semitransmissive film 203 shown in FIG. The upper surface of the light semi-transmissive film is the surface of the light semi-transmissive film opposite to the lower surface in contact with the transparent substrate.

  The method of making the arithmetic average roughness (Ra) of the surface of the light-shielding film 0.4 nm or less is not particularly limited, but it will be described later in “C. Photomask manufacturing method 3. Smoothing treatment step”. In addition to the method of smoothing the surface of the light-shielding film pattern described in the item, a method of forming the light-shielding film from an element having a small mass and the like can be mentioned. The method of forming the light-shielding film from an element having a small mass is not particularly limited, and examples thereof include a method of forming from Si, SiON, SiN or the like.

The structure of the photomask blank of the present invention has the above-mentioned points, and the light-shielding film used for forming them instead of the light-shielding film pattern, the outer frame light-shielding film, and the light semi-transmissive film pattern. The photomask has the same configuration as that of the photomask of the present invention described in the item "A. Photomask" except that it has the above-mentioned light semi-transmissive film. Therefore, the description here is omitted.
Moreover, when manufacturing a photomask using the said photomask blanks, as a method of maintaining the arithmetic mean roughness (Ra) of the surface of the light shielding film in a photomask blank, for example, among the light shielding films of the said photomask blanks, A method of covering the surface of the portion used as the light shielding film of the photomask with a resist can be used. As the resist for covering the light-shielding film and the method for forming the resist, a resist and a method for forming the resist that are generally used when forming a photomask from a photomask blank can be used.

C. Method for producing photomask The method for producing a photomask according to the present invention is to prepare a photomask blank having a transparent substrate and a light-shielding film having a desired optical density (OD value) formed on the transparent substrate. A light-shielding film pattern forming step of forming the light-shielding film pattern by etching the light-shielding film, and a smoothing treatment step of smoothing the surface of the light-shielding film pattern. is there.

  8 and 9 are schematic process sectional views showing an example of the method for manufacturing a photomask of the present invention. The photomask manufacturing method shown in FIGS. 8 and 9 is a binary mask manufacturing method. Hereinafter, a method for manufacturing the photomask shown in FIGS. 8 and 9 will be described.

  First, as shown in FIG. 8A, a photomask blank 200 having a transparent substrate 101, a light shielding film 202 formed on the transparent substrate 101, and a hard mask layer 204 formed on the light shielding film 202. To prepare. The light-shielding film 202 is individually adjusted so that the optical density (OD value) is 3.0 or more. The light shielding film 202 is made of molybdenum silicide (MoSi) -based material. The hard mask layer 204 is made of a chromium (Cr) -based material.

  Next, as shown in FIG. 8B, an electron beam resist is applied on the hard mask layer 204 to form a resist layer 205. Next, as shown in FIG. 8C, the resist layer 205 is pattern-exposed by an electron beam drawing apparatus and developed with a resist-dedicated developing solution to form a resist pattern 105 having a desired shape.

  Next, as shown in FIG. 8D, the hard mask layer 204 is dry-etched using a reactive etching gas by a dry etching apparatus using the resist pattern 105 having a desired shape as an etching mask. Is etched into the shape of the light shielding film pattern 102 described later. Thereby, the hard mask layer pattern 104 is formed.

Next, as shown in FIG. 8E, the resist pattern 105 having a desired shape is removed. Next, as shown in FIG. 9A, the light shielding film 202 is dry-etched using a reactive etching gas by a dry etching apparatus using the hard mask layer pattern 104 as an etching mask. Thereby, the light shielding film pattern 102 is formed in the pattern formation region.
Next, as shown in FIG. 9B, the hard mask layer pattern 104 is dry-etched and removed by a dry etching apparatus using a reactive etching gas.

  Next, as shown in FIG. 9C, a smoothing process is performed to reduce the arithmetic average roughness (Ra) of the upper surface 101a of the transparent substrate 101 and the upper surface 102a of the light shielding film pattern 102 to 0.4 nm or less. Thereby, the photomask 100 in which the arithmetic average roughness (Ra) of the upper surface 101a of the transparent substrate 101 and the upper surface 102a of the light shielding film pattern 102 is 0.4 nm or less is obtained. The photomask 100 is a binary mask. Here, in the present invention, the surface of the light shielding film pattern and the surface of the transparent substrate have the same contents as those described in the item “A. Photomask”.

According to the present invention, a photomask in which the surface of the light shielding film pattern is smoothed can be obtained.
As a result, the amount of sulfate ions adsorbed on the surface of the light-shielding film pattern can be reduced, so that it is possible to obtain a photomask in which growing foreign matter is unlikely to occur on the surface of the light-shielding film pattern. Further, since the surface of the light-shielding film pattern can be made smooth, foreign matter can be easily removed from the surface of the light-shielding film pattern even when the output of a physical cleaning tool or the like is weakened when cleaning the photomask. A photomask that can be obtained can be obtained. As a result of these, it is possible to suppress the failure to obtain a good pattern transfer image on the wafer. The configuration of the photomask manufacturing method of the present invention will be described below.

1. Photomask blanks preparation step The photomask blanks preparation step in the present invention is a step of preparing a photomask blank having a transparent substrate and a light-shielding film having a desired optical density (OD value) formed on the transparent substrate.

  The configuration of the transparent substrate is the same as the configuration of the transparent substrate described in the item “A. Photomask 4. Transparent substrate”. Therefore, the description here is omitted.

  The configuration of the light shielding film is the same as the configuration of the light shielding film described in the item “A. Photomask 3. Light shielding film”. Therefore, the description here is omitted.

  The photomask blanks preparation step is not particularly limited, but as the photomask blanks, the transparent substrate, a light semi-transmissive film formed between the transparent substrate and the light-shielding film, the optical half A step of preparing a photomask blank having the above-mentioned light-shielding film formed on the transparent film is preferable. This is because the surfaces of both the light-shielding film pattern and the light-semitransmissive film pattern described later can be smoothed in the smoothing process step.

  The material and the thickness of the light semi-transmissive film are the same as the material and the thickness of the light semi-transmissive film pattern described in the item of “A. Photomask 5. Phase shift mask”. Therefore, the description here is omitted.

2. Light-Shielding Film Pattern Forming Step The light-shielding film pattern forming step in the present invention is a step of forming the light-shielding film pattern by etching the light-shielding film. In the present invention, the light shielding film pattern is formed in the pattern forming region as shown in FIG.

The light-shielding film pattern forming step is not particularly limited, but as a method of etching the light-shielding film, when the light-shielding film is made of a molybdenum silicide (MoSi) -based material, for example, a fluorine-based material is used. Examples of the method include dry etching using a gas, for example, SF ₆ , CF ₄ , CHF ₃ , C ₂ F ₆ , a mixed gas thereof, or a gas obtained by mixing oxygen in these gases as an etching gas. When the light-shielding film is made of a chromium (Cr) -based material, for example, a dry etching method using a mixed gas of chlorine-based gas and oxygen gas as an etching gas can be used.

3. Smoothing Treatment Step The smoothing treatment step in the present invention is a step of smoothing the surface of the light shielding film pattern.

  The smoothing treatment step is not particularly limited, but a step of smoothing both the surface and the side surface of the light shielding film pattern is preferable. This is because it is possible to obtain a photomask in which growing foreign matter is unlikely to occur on both the surface and the side surface of the light shielding film pattern. Further, when cleaning the photomask, even if the output of a physical cleaning tool or the like is weakened, it is possible to obtain a photomask that can easily remove foreign matter from both the front surface and the side surface of the light-shielding film pattern. Is. Further, when the growing foreign matter is generated on the side surface of the light shielding film pattern, unlike the case where the growing foreign matter is generated on the surface of the light shielding film pattern, even if the growing foreign matter does not grow so much, To cover the part that penetrates. Therefore, by smoothing both the surface and the side surface of the light-shielding film pattern, it is remarkable that a good pattern transfer image to the wafer cannot be obtained, as compared with the case where only the surface of the light-shielding film pattern is smoothed. It is because it can be suppressed to.

  The smoothing treatment step is not particularly limited, but a step of smoothing the surface of the light shielding film pattern and the surface of the transparent substrate is preferable. This is because it is possible to obtain a photomask in which growing foreign matter is unlikely to occur on the surface of the transparent substrate. Further, it is possible to obtain a photomask which can easily remove foreign matters from the surface of the transparent substrate even when the output of a physical cleaning tool or the like is weakened when the photomask is cleaned. Furthermore, when a growing foreign substance is generated on the surface of the transparent substrate, unlike the case where the growing foreign substance is generated on the surface of the light-shielding film pattern, light is generated even if the growing foreign substance does not grow so much. It covers the transparent part. Therefore, by smoothing the surface of the transparent substrate, it is possible to remarkably suppress the situation where a good pattern transfer image on the wafer cannot be obtained, as compared with the case where only the surface of the light shielding film pattern is smoothed. Because you can. Further, since the surface of the transparent substrate is smooth in the outer frame region, it is possible to obtain a photomask in which the adhesive material of the pellicle can be easily removed from the surface of the transparent substrate in the outer frame region. Accordingly, it is possible to obtain a photomask in which it is easy to reduce the number of times of cleaning the photomask in order to remove the adhesive material of the pellicle from the surface of the transparent substrate in the outer frame region. Further, a large amount of the adhesive material of the pellicle remaining on the surface of the transparent substrate in the outer frame region can be scattered in the pattern forming region of the photomask by cleaning the photomask or the like to obtain a photomask that is less likely to become defective. it can. Further, it is possible to obtain a photomask in which a large amount of the adhesive material of the pellicle remaining on the surface of the transparent substrate in the outer frame region is unlikely to cause growth foreign matter.

  The smoothing treatment step is not particularly limited, but a step of making the arithmetic average roughness (Ra) of the surface or the side surface of the light shielding film pattern or the surface of the transparent substrate 0.4 nm or less is preferable. This is because it is possible to obtain a photomask in which no growing foreign matter is generated on the surface or the side surface of the light shielding film pattern or the surface of the transparent substrate. The smoothing treatment step is preferably a step of making the arithmetic average roughness (Ra) of the surface or the side surface of the light-shielding film pattern or the surface of the transparent substrate 0.3 nm or less, and particularly, the light-shielding film pattern. The step of making the arithmetic average roughness (Ra) of the surface or side surface of the above or the surface of the transparent substrate 0.2 nm or less is preferable. This is because the adsorption amount of sulfate ions is smaller.

  The method of smoothing the surface of the light-shielding film pattern is not particularly limited, and examples thereof include a method of smoothing by dry etching, a method of smoothing by wet etching, and a method of irradiating light such as UV. And a method of smoothing by heating.

The method of smoothing by the dry etching is not particularly limited, and examples thereof include a method of performing plasma treatment using a chlorine-based gas, a fluorine-based gas, an oxygen-based gas, or the like. Above all, when the light-shielding film pattern is made of a chromium (Cr) -based material, a method of performing plasma treatment using a fluorine-based gas or an oxygen-based gas is preferable. When it is composed of a MoSi) -based material, a method of performing plasma treatment using a chlorine-based gas or an oxygen-based gas is preferable.
In the method of smoothing by dry etching, it is possible to equally smooth both the surface and the side surface of the light shielding film pattern by performing isotropic plasma treatment.

The method of smoothing by wet etching is not particularly limited, and examples thereof include a method of performing wet etching using a solution having an adjusted concentration such as an alkali cleaning solution or an acidic cleaning solution. Above all, for a light-shielding film pattern made of a Si-based material such as molybdenum silicide (MoSi) -based material, an alkaline cleaning solution, a hydrofluoric acid aqueous solution (HF, NH ₄ F, etc.), or a phosphoric acid solution (H ₃ PO) is used. ₄ : HNO ₃ ) and the like, wet etching using an acidic cleaning solution or the like is preferable. For a light-shielding film pattern made of a chromium (Cr) -based material, an alkaline cleaning solution or ceric nitrate is used. A method of performing wet etching using an acidic cleaning liquid such as ammonium or perchloric acid is preferable.
In the method of smoothing by the wet etching, the wet etching is generally an isotropic process, and therefore both the surface and the side surface of the light shielding film pattern can be equally smoothed.

  According to the above-described method of smoothing the surface, not only the surface and the side surface of the light shielding film pattern but also the surface of the transparent substrate can be smoothed in the smoothing step. In addition, according to the above-described method for smoothing the surface, the surface of the outer frame light-shielding film described in “A. Photomask 2. Outer frame light-shielding film” has an arithmetic average roughness (Ra) of 0. It can also be smoothed so as to be 0.4 nm or less.

In this step, the method of smoothing the surface is preferably a method of smoothing the surface and adjusting the component composition of the surface of the light-shielding film pattern.
In this step, the smoothing method may be, for example, a method of reducing the nitrogen content rate on the surface of the light-shielding film pattern, and is preferably a method of reducing the nitrogen content rate by 5 atm% or more. Particularly, a method of reducing by 7 atm% or more is preferable, and a method of reducing by 15 atm% or more is particularly preferable. This is because the light-shielding film pattern formed in this step can reduce the adhesion of organic substances that cause the growth of foreign matter by using the above smoothing method.
In this step, the smoothing method may be a method of increasing the oxygen content rate of the light-shielding film pattern surface, and is preferably a method of increasing the oxygen content rate of 5 atm% or more, and particularly preferably It is preferably a method of increasing by 13 atm% or more, and particularly preferably a method of increasing by 14 atm% or more. This is because the light-shielding film pattern formed in this step can reduce the adhesion of organic substances that cause the growth of foreign matter by using the above smoothing method.
In this step, when the material of the light-shielding film forming the light-shielding film pattern is a molybdenum silicide-based material, it is possible to reduce the content ratio of molybdenum on the surface of the light-shielding film pattern. A method of decreasing the content ratio by 0.4 atm% or more is preferable, and a method of decreasing by 1 atm% or more is particularly preferable. This is because the light-shielding film pattern formed in this step can reduce the adhesion of organic substances that cause the growth of foreign matter by using the above smoothing method.

As a smoothing method capable of smoothing such a surface and adjusting the component composition of the surface of the light-shielding film pattern, specifically, a method of smoothing by dry etching is preferable. This is because the above-described smoothing method can easily adjust the surface component composition by adjusting the type of gas used for plasma treatment and the number of plasma treatments.
As a combination of the type of gas and the number of times of plasma treatment, for example, the material of the light-shielding film forming the light-shielding film pattern is a molybdenum silicide-based material, the content ratio of nitrogen is reduced, the content ratio of oxygen is increased, and the molybdenum content is increased. From the viewpoint of reducing the content ratio of silicide, a combination of performing chlorine plasma treatment using a chlorine-based gas, and then performing oxygen plasma treatment using an oxygen-based gas, and the like can be mentioned.

4. Method of Manufacturing Phase Shift Mask The method of manufacturing the photomask of the present invention is not limited to the method of manufacturing a binary mask as shown in FIGS. 8 and 9. For example, a method of manufacturing a phase shift mask having a tritone structure can be used. A manufacturing method may be used.

  A method for manufacturing a phase shift mask having a tritone structure according to the present invention is the method for manufacturing a photomask described above, wherein in the photomask blank preparing step, the transparent substrate, the transparent substrate, and the transparent substrate are used as the photomask blanks. A photomask blank having a light-semitransmissive film formed between light-shielding films, and the light-shielding film formed on the light-semitransmissive film is prepared, and the light is obtained by etching the light-semitransmissive film. The method further comprises a light semi-transmissive film pattern forming step of forming a semi-transmissive film pattern.

  10 and 11 are schematic process cross-sectional views showing another example of the method for manufacturing a photomask of the present invention. The photomask manufacturing method shown in FIGS. 10 and 11 is a method of manufacturing a phase shift mask having a tritone structure. Hereinafter, a method of manufacturing the phase shift mask having the tritone structure shown in FIGS. 10 and 11 will be described.

  First, as shown in FIG. 10A, the transparent substrate 101, the light semitransmissive film 203 formed between the transparent substrate 101 and the light shielding film 202, and the light shielding film 202 formed on the light semitransmissive film 203. A photomask blank 200 having the following is prepared. The light-shielding film 202 is adjusted so that the optical density (OD value) is 3.0 or more together with the light-semitransmissive film 203. The light shielding film 202 is made of a chromium (Cr) based material. The light semi-transmissive film 203 is made of molybdenum silicide (MoSi) -based material.

  Next, as shown in FIG. 10B, an electron beam resist is applied on the light shielding film 202 to form a resist layer 205. Next, as shown in FIG. 10C, the resist layer 205 is pattern-exposed by an electron beam drawing apparatus and developed with a resist-dedicated developing solution to form a resist pattern 105 having a desired shape.

  Next, as shown in FIG. 10D, the light-shielding film 202 is dry-etched by using a reactive etching gas with a resist pattern 105 having a desired shape as an etching mask and using a reactive etching gas. The shape of the light-semitransmissive film pattern 103 is etched.

  Next, as shown in FIG. 10E, the resist pattern 105 having a desired shape is removed. Next, as shown in FIG. 10F, the light-semitransmissive film is formed by a dry etching apparatus using a reactive etching gas with the light-shielding film 202 etched into the shape of the light-semitransmissive film pattern 103 as an etching mask. 203 is dry-etched. As a result, the light semi-transmissive film pattern 103 is formed in the pattern formation region.

  Next, as shown in FIG. 11A, an electron beam resist is applied on the light shielding film 202 to form a resist layer 205. Next, as shown in FIG. 11B, the resist layer 205 is pattern-exposed by an electron beam drawing apparatus and developed with a resist-dedicated developing solution to form a resist pattern 105 having a desired shape.

  Next, as shown in FIG. 11C, the light shielding film 202 is dry-etched using a reactive etching gas by a dry etching apparatus using the resist pattern 105 having a desired shape as an etching mask. Thereby, the light shielding film pattern 102 is formed in the pattern formation region.

  Next, as shown in FIG. 11D, the resist pattern 105 having a desired shape is removed. Next, as shown in FIG. 11E, all the arithmetic mean roughness (Ra) of the upper surface 101a of the transparent substrate 101, the upper surface 103a of the light semi-transmissive film pattern 103, and the upper surface 102a of the light shielding film pattern 102 are set to 0. A smoothing process is performed to reduce the thickness to 0.4 nm or less. As a result, the photomask 100 in which the arithmetic average roughness (Ra) of all of the upper surface 101a of the transparent substrate 101, the upper surface 103a of the light semi-transmissive film pattern 103, and the upper surface 102a of the light shielding film pattern 102 is 0.4 nm or less is obtained. Be done. The photomask 100 is a phase shift mask having a tritone structure. Here, in the present invention, the surface of the light-semitransmissive film pattern has the same content as that described in the item “A. Photomask 5. Phase shift mask”.

  The light-semitransmissive film pattern forming step in the present invention is a step of forming the light-semitransmissive film pattern by etching the light-semitransmissive film. In the present invention, the light semi-transmissive film pattern is formed in the pattern formation region as shown in FIG.

The light-semitransmissive film pattern forming step is not particularly limited, but as a method of etching the light-semitransmissive film, the light-semitransmissive film is formed of a molybdenum silicide (MoSi) -based material. Is dry-etched using, for example, a fluorine-based gas such as SF ₆ , CF ₄ , CHF ₃ , C ₂ F ₆ , a mixed gas thereof, or a gas obtained by mixing these gases with oxygen as an etching gas. Methods and the like. When the light-semitransmissive film is made of a silicon nitride (SiN) -based material, for example, a fluorine-based gas such as SF ₆ , CF ₄ , CHF ₃ , C ₂ F _6, or a mixed gas thereof is used. Alternatively, a method of dry etching using a gas obtained by mixing these gases with oxygen as an etching gas can be used.

  The method for producing the phase shift mask is not particularly limited, but it is preferable that the smoothing treatment step is a step of smoothing the surfaces of both the light shielding film pattern and the light semi-transmissive film pattern. .. Since it is possible to reduce the adsorption amount of sulfate ions adsorbed on the surfaces of both the light-shielding film pattern and the light-semitransmissive film pattern, it is possible to grow foreign substances on the surfaces of both the light-shielding film pattern and the light-semitransmissive film pattern. This is because it is possible to obtain a phase shift mask that is less likely to occur. Further, since the surfaces of both the light-shielding film pattern and the light-semitransmissive film pattern can be made smooth, even when the output of a physical cleaning tool or the like is weakened when cleaning the phase shift mask, the light-shielding film This is because it is possible to obtain a phase shift mask that can easily remove foreign matter from both surfaces of the pattern and the light-semitransmissive film pattern. As a result, it is possible to suppress the failure to obtain a good pattern transfer image on the wafer.

The method for manufacturing the phase shift mask is not particularly limited, but the smoothing step is preferably a step of smoothing both the surface and the side surface of the light semitransmissive film pattern.
This is because it is possible to obtain a photomask in which growing foreign matter is unlikely to occur on both the surface and the side surface of the light semi-transmissive film pattern. Further, it is possible to obtain a photomask that can easily remove foreign matter from both the front surface and the side surface of the light semi-transmissive film pattern even when the output of a physical cleaning tool or the like is weakened when cleaning the photomask. Because you can. Furthermore, when a growing foreign substance occurs on the side surface of the light semi-transmissive film pattern, unlike the case where the growing foreign substance occurs on the surface of the light semi-transmissive film pattern, the growing foreign substance grows so much. Even if it does not exist, it will cover the part that transmits light. Therefore, by smoothing both the surface and the side surface of the light-semitransmissive film pattern, a better pattern transfer image to the wafer can be obtained as compared with the case where only the surface of the light-semitransmissive film pattern is smoothed. This is because it can be suppressed significantly.

  The smoothing treatment step is not particularly limited, but a step of making the arithmetic average roughness (Ra) of the surface or the side surface of the light semitransmissive film pattern 0.4 nm or less is preferable. This is because it is possible to obtain a photomask in which growing foreign matter does not occur on the surface or the side surface of the light semi-transmissive film pattern. As the smoothing treatment step, among others, a step of making the arithmetic mean roughness (Ra) of the surface or side surface of the light semi-transmissive film pattern 0.3 nm or less is preferable, and particularly, the surface of the light semi-transmissive film pattern or A step of setting the arithmetic average roughness (Ra) of the side surface to 0.2 nm or less is preferable. This is because the adsorption amount of sulfate ions is smaller.

The method for smoothing the surface of the light-semitransmissive film pattern is not particularly limited, but for example, the method for smoothing the surface of the light-shielding film pattern described in the item “3. Smoothing treatment step”. The method similar to is mentioned. As a method of smoothing by the dry etching, a chlorine-based gas or a gas of chlorine-based is used when the light-semitransmissive film pattern is composed of molybdenum silicide (MoSi) -based material and silicon nitride (SiN) -based material. A method of performing plasma treatment using an oxygen-based gas is preferable. In addition, as a method of smoothing by the above wet etching, among others, for a light semi-transmissive film pattern composed of a Si-based material such as a molybdenum silicide (MoSi) -based material and a silicon nitride (SiN) -based material, A wet etching method using an alkaline cleaning solution, an acidic cleaning solution such as an aqueous solution of hydrofluoric acid (HF, NH ₄ F, etc.), a phosphoric acid solution (H ₃ PO ₄ : HNO ₃ ) or the like is preferable.

  Further, the method of smoothing the side surface of the light-semitransmissive film pattern is not particularly limited, but for example, the side surface of the light-shielding film pattern described in “3. Smoothing process step” is dry-etched. And a method similar to the method of smoothing the side surface of the light shielding film pattern by wet etching.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has the same operational effect It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[Example 1]
First, an optically polished 6-inch square 0.25-inch thick synthetic quartz substrate (transparent substrate), a light-semitransmissive film made of a molybdenum silicide (MoSi) -based material formed on the synthetic quartz substrate, and A photomask blank (A61A-TFC manufactured by HOYA) having a hard mask layer (light-shielding film) formed on the semi-transmissive film was prepared.

  Next, a resist pattern having a desired shape was formed on the hard mask layer, and the hard mask layer was etched into the shape of a light semi-transmissive film pattern described later using the resist pattern as an etching mask. As a result, a hard mask layer pattern was formed.

  Next, the light semi-transmissive film was etched using the hard mask layer pattern as an etching mask to form a light semi-transmissive film pattern. Next, a resist pattern having a desired shape was formed on the hard mask layer pattern, and the hard mask layer pattern was further etched by dry etching using the resist pattern as an etching mask. As a result, a light shielding film pattern was formed, and a photomask (phase shift mask) before the smoothing process was produced.

  Next, a smoothing process was performed to make the arithmetic average roughness (Ra) of the surface of the light semi-transmissive film pattern 0.4 nm or less. Specifically, the smoothing treatment was performed by dry etching which performed isotropic plasma treatment. Thus, a photomask (phase shift mask) was produced.

[Example 2]
First, a 6-inch square and 0.25-inch thick synthetic quartz substrate (transparent substrate) that has been optically polished, a light-semitransmissive film made of a silicon nitride (SiN) -based material formed on the synthetic quartz substrate, and A photomask blank (SiN) having a hard mask layer (light-shielding film) formed on the semi-transmissive film was prepared.

  Next, a resist pattern having a desired shape was formed on the hard mask layer, and the hard mask layer was etched into the shape of a light semi-transmissive film pattern described later using the resist pattern as an etching mask. As a result, a hard mask layer pattern was formed.

Next, the light semi-transmissive film was etched using the hard mask layer pattern as an etching mask to form a light semi-transmissive film pattern. Next, a resist pattern having a desired shape was formed on the hard mask layer pattern, and the hard mask layer pattern was etched by dry etching using the resist pattern as an etching mask. As a result, a light shielding film pattern was formed, and a photomask (phase shift mask) before the smoothing process was produced. Next, a smoothing process was performed to make the arithmetic average roughness (Ra) of the surface of the light semi-transmissive film pattern 0.4 nm or less.
Specifically, the smoothing treatment was performed by dry etching which performed isotropic plasma treatment. Thus, a photomask (phase shift mask) was produced.

[Example 3]
First, an optically polished 6-inch square 0.25-inch thick synthetic quartz substrate (transparent substrate), a light-shielding film made of a molybdenum silicide (MoSi) -based material formed on the synthetic quartz substrate, and a light-shielding film A photomask blank (W0G manufactured by Shin-Etsu Chemical Co., Ltd.) having a hard mask layer formed on the substrate was prepared.

  Next, a resist pattern having a desired shape was formed on the hard mask layer, and the hard mask layer was etched into the shape of a light-shielding film pattern described later using the resist pattern as an etching mask. As a result, a hard mask layer pattern was formed.

  Next, the light-shielding film was etched using the hard mask layer pattern as an etching mask to form a light-shielding film pattern. Next, the hard mask layer pattern was removed by dry etching. As a result, a photomask (binary mask) before the smoothing process was manufactured. Next, a smoothing process was performed to make the arithmetic average roughness (Ra) of the surface of the light shielding film pattern 0.4 nm or less. Specifically, the smoothing treatment was performed by dry etching which performed isotropic plasma treatment. Thereby, a photomask (binary mask) was produced.

[Example 4]
First, an optically polished 6-inch square 0.25-inch thick synthetic quartz substrate (transparent substrate), a light-shielding film made of a molybdenum silicide (MoSi) -based material formed on the synthetic quartz substrate, and a light-shielding film A photomask blank (W0G manufactured by Shin-Etsu Chemical Co., Ltd.) having a hard mask layer formed on the substrate was prepared.

  Next, a resist pattern having a desired shape was formed on the hard mask layer, and the hard mask layer was etched into the shape of a light-shielding film pattern described later using the resist pattern as an etching mask. As a result, a hard mask layer pattern was formed.

  Next, the light-shielding film was etched using the hard mask layer pattern as an etching mask to form a light-shielding film pattern. Next, the hard mask layer pattern was removed by dry etching. As a result, a photomask (binary mask) before the smoothing process was manufactured. Next, a smoothing treatment was performed to make the arithmetic average roughness (Ra) of the surface of the light shielding film pattern 0.4 nm or less. Specifically, the smoothing treatment was performed by dry etching which performed isotropic plasma treatment. Thereby, a photomask (binary mask) was produced.

[Example 5]
First, a 6-inch square and 0.25-inch thick synthetic quartz substrate (transparent substrate) that has been optically polished, a light-shielding film composed of a Cr film formed on the synthetic quartz substrate, and a hardware formed on the light-shielding film. A photomask blank (AR8 manufactured by HOYA) having a mask layer was prepared.

  Next, a resist pattern having a desired shape was formed on the hard mask layer, and the hard mask layer was etched into the shape of a light-shielding film pattern described later using the resist pattern as an etching mask. As a result, a hard mask layer pattern was formed.

  Next, the light-shielding film was etched using the hard mask layer pattern as an etching mask to form a light-shielding film pattern. Next, the hard mask layer pattern was removed by dry etching. As a result, a photomask (binary mask) before the smoothing process was manufactured.

  Next, a smoothing process was performed to make the arithmetic average roughness (Ra) of the surface of the light shielding film pattern 0.4 nm or less. Specifically, the smoothing treatment was performed by dry etching which performed isotropic plasma treatment. Thereby, a photomask (binary mask) was produced.

[Comparative Example 1]
In the same manner as in Example 1, a photomask (phase shift mask) before the smoothing process was manufactured.

[Comparative example 2]
First, a 6-inch square and 0.25-inch thick synthetic quartz substrate (transparent substrate) that has been optically polished, a light-shielding film composed of a Cr film formed on the synthetic quartz substrate, and a hardware formed on the light-shielding film. A photomask blank (AR8 manufactured by HOYA) having a mask layer was prepared. In Comparative Example 2, this photomask blank was evaluated instead of the photomask in the evaluation described below.

[Evaluation 1]
Synthetic quartz substrates that the photomasks of Examples 1 to 5 (all Examples) have in common, light semitransmissive film patterns in the photomasks (phase shift masks) of Examples 1 and 2, photomasks of Examples 3 to 5 The arithmetic average roughness (Ra) of the surface of the light-shielding film pattern in the (binary mask), the light-semitransmissive film pattern in the photomask (phase shift mask) of Comparative Example 1, and the light-shielding film in the photomask blank of Comparative Example 2 were measured. nm], surface area [nm ² ], root mean square roughness (RMS) [nm], maximum height difference (Rmax) [nm], and adsorption amount of sulfate ion [ppb] on the surface after sulfuric acid cleaning and The adsorption amount [ppb] of ammonia ions was evaluated. The arithmetic average roughness (Ra) is measured using an atomic force microscope (AFM) <L-trace manufactured by Hitachi High-Tech Science Co., Ltd.> and is determined based on height data in a 1 μm square range (Ra ( The center line surface roughness) was determined. Specifically, it was evaluated under the following evaluation conditions.
<Surface area evaluation conditions>
-Scan 1 μm square with AFM.
<Cleaning conditions>
・ Sulfuric acid cleaning <Ion chromatography conditions>
・ DIW 100 ml 90 ° C 2h extraction <Sulfate ion adsorption amount evaluation conditions>
-Quantitative analysis of the water extracted above by ion chromatography.
<Ammonia ion adsorption amount evaluation conditions>
-Quantitative analysis of the water extracted above by ion chromatography.

  The evaluation results are shown in Table 2 below.

In addition, FIG. 2 is a graph showing the relationship between the arithmetic average roughness (Ra) [nm] of the surface and the adsorption amount [ppb] of sulfate ions according to Examples 1 to 5 and Comparative Examples 1 and 2 shown in Table 2. Is shown. The amount of sulfate ion adsorption shown in the graph shown in FIG. 2 changes depending on the arithmetic mean roughness (Ra), and the arithmetic mean roughness shown in the graph shown in FIG. The relationship between (Ra) and the adsorption amount of sulfate ions is established on the surface and side surface of the light shielding film pattern, the surface of the transparent substrate, and the surface and side surface of the light semi-transmissive film pattern. Further, FIG. 4 is a graph showing the relationship between the surface area [nm ² ] and the sulfate ion adsorption amount [ppb] according to Examples 1 to 5 and Comparative Examples 1 and 2 shown in Table 2. The adsorbed amount of sulfate ions shown in the graph shown in FIG. 4 changes depending on the surface area, and the relationship between the surface area shown in the graph shown in FIG. 4 and the adsorbed amount of sulfate ions is , The surface and side surface of the light shielding film pattern, the surface of the transparent substrate, and the surface and side surface of the light semi-transmissive film pattern.

  FIG. 12 is an AFM image of the surface of the light semi-transmissive film pattern. 12A and 12B, the surface (Ra = 0.3875 nm) of the light semitransmissive film pattern in the photomask (phase shift mask) of Example 1 and the photomask of Comparative Example 1 ( An AFM image of the surface (Ra = 0.5276 nm) of the light-semitransmissive film pattern in the phase shift mask is shown. 13 is an AFM image of the light-shielding film pattern and the surface of the light-shielding film. FIGS. 13A and 13B show the surface (Ra = 0.2887 nm) of the light-shielding film pattern in the photomask (binary mask) of Example 5 and the light-shielding film in the photomask blank of Comparative Example 2, respectively. The AFM image of the surface (Ra = 0.8566 nm) is shown.

  As shown in FIGS. 12A and 12B, the surface of the light-semitransmissive film pattern in the photomask of Example 1 is more than the surface of the light-semitransmissive film pattern in the photomask of Comparative Example 1. The height difference is small and the surface is smooth. Further, as shown in FIGS. 13A and 13B, the surface of the light shielding film pattern in the photomask of Example 5 is higher and lower than the surface of the light shielding film in the photomask blank of Comparative Example 2. The difference is small and the surface is smooth.

[Evaluation 2]
Surface of the light-semitransmissive film pattern (Ra = 0.3875) in the photomask (phase shift mask) of Example 1 after washing with sulfuric acid under the same conditions and light-semitransmission in the photomask (phase shift mask) of Comparative Example 1 With respect to the surface of the film pattern (Ra = 0.5276), the change after ArF excimer laser irradiation was evaluated. Specifically, it was evaluated under the following evaluation conditions.
<Cleaning conditions>
・ Sulfuric acid cleaning <irradiation conditions>
・ Humidity: 40%
・ Temperature: 25 ℃
・ Total irradiation dose: 1500J

  FIG. 14 is a diagram showing a result of irradiating the surface of the light semitransmissive film pattern with ArF excimer laser after cleaning with sulfuric acid. On the right side of FIG. 14, the result of confirming the change after the ArF excimer laser irradiation on the surface of the light semitransmissive film pattern after the cleaning with sulfuric acid of Example 1 by the SEM image is shown. On the left side of FIG. 14, the result of confirming the change after the ArF excimer laser irradiation on the surface of the light semitransmissive film pattern after cleaning with sulfuric acid in Comparative Example 1 by SEM images is shown. For each of Example 1 and Comparative Example 1, the upper side of FIG. 14 shows the surface of the light semi-transmissive film pattern after cleaning with sulfuric acid and before irradiation of ArF excimer laser, and the lower side of FIG. 14 shows the ArF excimer laser. The surface of the light semi-transmissive film pattern after irradiation is shown. For comparison, the surface irradiated with ArF excimer laser and the surface not irradiated with ArF excimer laser are shown together.

  As shown in FIG. 14, on the surface of the light-semitransmissive film pattern of Comparative Example 1, growing foreign matter (Haze) was generated after ArF excimer laser irradiation, whereas in the light-semitransmissive film pattern of Example 1, No growing foreign matter was generated on the surface even after irradiation with ArF excimer laser. It is considered that this is because the surface of the light-semitransmissive film pattern of Example 1 was smooth, so that sulfate ions were hard to be adsorbed even if sulfuric acid washing was performed. From the above, it was found that by making the surface of the light-semitransmissive film pattern smooth, it is possible to suppress the growth foreign matter from being generated on the surface of the light-semitransmissive film pattern.

[Evaluation 3]
In the photomask of Example 1 (phase shift mask) and the photomask of Comparative Example 1 (phase shift mask), ArF excimer laser irradiation was performed on both the surface and the side surface of the light semitransmissive film pattern after cleaning with sulfuric acid under the same conditions. The subsequent generation of growing foreign matter (Haze) was evaluated by SEM images. Specifically, it was evaluated under the following evaluation conditions.
<Cleaning conditions>
・ Sulfuric acid cleaning <irradiation conditions>
・ Humidity: 40%
・ Temperature: 25 ℃
・ Total irradiation dose: 1500J

  The evaluation results are shown in Table 3 below together with the arithmetic average roughness (Ra) [nm] of the surface of the light semi-transmissive film pattern. In Table 3, when the growing foreign matter (Haze) is generated after ArF excimer laser irradiation on the surface and the side surface of the light semi-transmissive film pattern in Example 1 and Comparative Example 1, the growing foreign matter (Haze) is generated. The case where it is not shown is indicated by x.

  FIG. 15 is an SEM image that evaluates the generation of growing foreign matter (Haze) after ArF excimer laser irradiation. 15 (a) and 15 (b), a growing foreign matter (surface) and a side surface of the light semitransmissive film pattern after the ArF excimer laser irradiation in the photomask (phase shift mask) of Comparative Example 1 ( The SEM image of Haze) was shown.

  As shown in Table 3, in the photomask (phase shift mask) of Example 1, no growable foreign matter (Haze) was generated after ArF excimer laser irradiation on both the surface and the side surface of the light semitransmissive film pattern. .. Further, in the photomask (phase shift mask) of Comparative Example 1, growing foreign matter (Haze) was generated on both the surface and the side surface of the light semi-transmissive film pattern after ArF excimer laser irradiation. From this, when the photomask (phase shift mask) of Example 1 was manufactured, the arithmetic mean roughness (Ra) of the surface of the light semi-transmissive film pattern was set to 0 by dry etching which performed isotropic plasma treatment. It is considered that by performing the smoothing treatment to 4 nm or less, the arithmetic mean roughness (Ra) of the side surface of the light semi-transmissive film pattern becomes 0.4 nm or less, like the surface. Then, when the photomask (phase shift mask) of Comparative Example 1 was manufactured, the arithmetic average roughness (Ra) of the side surface of the light semi-transmissive film pattern was 0.4 nm or less, like the surface of the light semi-transmissive film pattern. It is believed that it has grown.

  Further, from FIGS. 15A and 15B, in the photomask (phase shift mask) of Comparative Example 1, the growth occurred on the surface of the light semi-transmissive film pattern (the upper surface 103a of the light semi-transmissive film pattern 103). While the foreign substance (Haze) 301 does not cover the exposed region (the portion that transmits light) of the transparent substrate 101, the growing foreign substance (Haze) 301 generated on the side surface 103b of the light-semitransmissive film pattern 103 does not. It was found that the transparent substrate 101 covers the exposed region (the part that transmits light).

[Evaluation 4]
The surface of the light semi-transmissive film pattern (Ra = 0.2075) in the photomask (phase shift mask) of Example 2 and the light semitransmissive film pattern of the photomask (phase shift mask) before the smoothing process of Comparative Example 1 The foreign matter removing power of the surface (Ra = 0.5276) was evaluated. Specifically, it was evaluated under the following evaluation conditions.
<Cleaning conditions>
・ Sulfuric acid free cleaning

FIG. 16 is a diagram showing the results of evaluation of the foreign matter removing force on the surface of the light semi-transmissive film pattern. On the right side of FIG. 16, the distribution of foreign matter on the surface of the light semi-transmissive film pattern before and after cleaning in Example 2 is shown.
The left side of FIG. 16 shows the distribution of foreign matter on the surface of the light semi-transmissive film pattern before and after cleaning in Comparative Example 1.

  As shown in FIG. 16, despite cleaning under the same cleaning conditions, the surface of the light-semitransmissive film pattern of Example 2 has more foreign matter removed than the surface of the light-semitransmissive film pattern of Comparative Example 1. The power was great. Specifically, 99.5% of the foreign matter was removed and most of the foreign matter was removed from the surface of the light-semitransmissive film pattern of Example 2, whereas the light-semitransmissive film pattern of Comparative Example 1 was removed. On the surface, foreign matter was removed by only 83.8%. This is considered to be because the surface of the light-semitransmissive film pattern of Example 2 is smoother than that of Comparative Example 1, and thus foreign matter is more easily removed.

[Evaluation 5]
The surface of the synthetic quartz substrate (Ra = 0.1285) that the photomasks of Examples 1 to 5 (all Examples) have in common and the surface of the light-shielding film (Ra = 0.8566) in the photomask blank of Comparative Example 2 For, the remaining amount of the adhesive material of the pellicle was evaluated. Specifically, when the pellicle was peeled from the surfaces of the synthetic quartz substrate and the light shielding film under the same peeling conditions, it was evaluated how much the adhesive material of the pellicle remained on the surface of the synthetic quartz substrate and the light shielding film.

  FIG. 17 is a diagram showing the adhesive material of the pellicle remaining on the surfaces of the synthetic quartz substrate and the light shielding film in the photomask. FIG. 17A shows the adhesive material of the pellicle remaining on the surface of the synthetic quartz substrate that the photomasks of Examples 1 to 5 (all Examples) have in common. FIG. 17B shows the adhesive material of the pellicle remaining on the surface of the light shielding film of Comparative Example 2.

  As shown in FIG. 17, on the surface of the synthetic quartz substrate which the photomasks of Examples 1 to 5 (all Examples) have in common, the adhesive material of the pellicle hardly remains, whereas On the surface of the light-shielding film of Comparative Example 2, much of the adhesive material of the pellicle remains. It is considered that this is because the surface of the synthetic quartz substrate is smoother than the surface of the light-shielding film of Comparative Example 2, and thus the adhesive material of the pellicle is easily peeled off.

[Example 6]
The photomask after the smoothing treatment obtained in Example 4 was further dry-etched by performing an isotropic plasma treatment as the smoothing treatment.
The arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern was 0.10 nm in the obtained photomask by the same method as described in "Evaluation 1" above.

[Evaluation 6]
With respect to the light-shielding films of the photomasks of Examples 3 to 6 and Comparative Example 2, with the pellicle attached, the light-shielding film covered with the pellicle was irradiated with ArF excimer laser, and the growth property with respect to the accumulated irradiation amount was increased. The presence or absence of foreign matter (Haze) was inspected using an appearance inspection device (manufactured by KLA), and the detected portion was confirmed by SEM observation. The results are shown in Table 4 below.
The pellicle-equipped photomask used in the evaluation had a pellicle size of 149 × 115 mm, and the adhesive material used was a styrene-based polymer with a thickness of 0.65 mm. It was formed using a method in which a pellicle was pressed through a base polymer to bond them together.
Further, the laser irradiation was applied to a 1 cm square area which was the center of the mask with a pellicle.
Further, in Table 4 below, “O” was entered when the occurrence of growing foreign matter (Haze) was observed, and “X” was entered when it was not observed.
The irradiation conditions, except that was varied in the range of integrated irradiation dose of 100kJ ^/ cm ² ~400kJ ^/ cm 2 as shown in Table 4 were the same conditions as above "Evaluation 3".

[Evaluation 7]
The composition of the light-shielding film pattern surface of the photomasks of Examples 3 to 6 and Comparative Example 2 was measured.
Further, the component composition of the surface of the synthetic quartz substrate of Example 5 and Comparative Example 1 was measured.
As a measuring method, Quantum 2000 manufactured by ULVAC-PHI was used and measured under the following measuring conditions. The results are shown in Table 4 below.
In addition, as the component composition of the surface, an average component composition within a range of 5 nm from the surface in the thickness direction was measured.

(Measurement condition)
X-ray condition: Al mono 200 μmφ × 30 W 15 kV
X-ray acquisition angle: 45 °
Neutralization conditions: ION / Electron 20 μA

From Table 4, it was confirmed that the generation of growing foreign matter (Haze) can be suppressed by reducing the nitrogen content on the surface of the light-shielding film pattern.
Specifically, in the light-shielding films using the molybdenum silicide-based materials of Examples 3 to 6, the nitrogen content rate was 13 atm% or less and 5 atm% or less, so that the integrated irradiation amount increased. It was confirmed that the generation of growing foreign matter can be suppressed even in the case.
Further, with respect to the light-shielding film using the chromium-based material of Example 5 and Comparative Example 2, since the nitrogen content ratios are 11 atm% or less and 6 atm% or less, the growth property is increased even when the integrated irradiation amount is increased. It was confirmed that the generation of foreign matter can be suppressed.
Further, in Evaluation 6, the photomask of Example 3 was used as a photomask with a pellicle, and the growth foreign matter (Haze) generated when the ArF excimer laser irradiation was performed so that the integrated irradiation amount was 200 kJ / cm ² was time-of-flight type. When analyzed by secondary ion mass spectrometry (TOF-SIMS), organic amine was detected. From this, it was speculated that the growing foreign matter generated by irradiating the photomask with the pellicle with the excimer laser was derived from the adhesive material used to attach the pellicle to the light-shielding film pattern.
Furthermore, compared with Example 4 and Example 6 based on Example 3, it was possible to reduce the nitrogen content by 7.8 atm% and 15.3 atm% by performing the smoothing treatment. In addition, the oxygen content could be increased by 5.3 atm% and 14.6 atm%. Further, the content ratio of molybdenum could be reduced by 0.4 atm% and 1.1 atm%.
On the other hand, compared with Example 5 based on Comparative Example 2, the nitrogen content could be reduced by 5.8 atm% by performing the smoothing treatment. Further, the oxygen content ratio could be increased by 13.4 atm%.

100 ... Photomask 101 ... Transparent substrate 102 ... Shading film pattern

Claims (1)

A transparent substrate, and a light-shielding film pattern formed on the transparent substrate and comprising a light-shielding film having a desired optical density (OD value),
The arithmetic mean roughness (Ra) of the surface of the light-shielding film pattern is 0.4 nm or less,
The photomask, wherein the nitrogen content on the surface of the light-shielding film pattern is 13 atm% or less.