KR102743876B1 - Etching solution and photomask deformed by etching solution - Google Patents

Abstract

[Problem] In the manufacture of a photomask for lithography, an etching solution capable of precisely controlling the light transmittance of a semi-transparent portion of a photomask, a method for manufacturing a gradation mask using the etching solution, and a gradation mask manufactured by the method are provided.
[Solution] An etching solution containing ammonium cerium (IV) nitrate or ammonium cerium (IV) sulfate.

Description

ETCHING SOLUTION AND PHOTOMASK DEFORMED BY ETCHING SOLUTION

The present invention relates to an etching solution used for pattern processing of an optical film of a photomask and a photomask processed by the etching solution.

Recently, in the manufacture of TFT liquid crystal displays, a gradation mask is used to simplify the manufacturing process. A typical photomask is composed of a light-transmitting portion and a light-shielding portion, and the intensity of the exposure light projecting through the mask is essentially two values: light-shielding and light-transmitting, but a gradation mask is composed of a light-transmitting portion, a semi-transmitting portion, and a light-shielding portion, and the intensity of the exposure light projected through each portion is changed to three values: light-shielding, semi-transmitting, and light-transmitting. Exposure using halftones is a process that uses a gradation mask to perform a process that requires several normal photomasks on a single photomask.

As one of such methods for manufacturing a gradation mask, a method has been proposed in which a chromium compound is used as a light-shielding film, and the semitransparent portion is partially etched to reduce the thickness of the light-shielding film and obtain a predetermined transmittance (Patent Document 1). On the other hand, since it is difficult to uniformly etch the semitransparent portion over the entire surface of the photomask with this partial etching method, a method has been proposed in which a photomask blank is used in which a two-layer structure of a light-shielding film and a semitransparent film are each formed into a film.

In order to form a gradation mask of three or more gradations, a plurality of semitransparent films, each having a predetermined light transmittance, are prepared and etched sequentially. Not only is it necessary to perform a complicated film formation process by setting the composition or thickness of a plurality of semitransparent films according to the desired combination of light transmittances, but there is also a restriction that only films having a predetermined light transmittance can be formed before film formation.

In addition, since the light transmittance of the formed laminate is substantially determined by each single film that constitutes it, fine adjustment of the light transmittance is not possible. In addition, since the light is affected by the same interface of the laminated semi-transparent films, the burden of verifying the resulting light transmittance calculation by conducting preliminary experiments in advance arises.

Here, as a method for manufacturing a gradation mask with different transmittance, a method of providing a difference in the thickness of a molybdenum silylside (MoSix) film is disclosed (Patent Document 2). The method is to adjust the thickness so that a desired light transmittance is achieved by reducing the thickness of a semi-transparent film formed by MoSix, thereby forming a desired difference in light transmittance for the first and second semi-transparent portions having a small difference in light transmittance. In Patent Document 2, it is described that MoSix is more effective than MoSiON and MoSiN, because fine adjustment is easy when the thickness is manufactured using a chemical solution such as an alkaline solution. On the other hand, a chromium compound film that is generally used as a light-shielding film and a semi-transparent film is thin, and the surface treatment method using an acid or alkaline chemical solution disclosed in Patent Document 2 has the problem that fine adjustment of the thickness is difficult and the uniformity of the thickness after etching is insufficient. For this reason, it is not easy to achieve a match with the desired light transmittance depending on how the end point of the film-cutting process is determined.

Special Publication No. 07-049410 Special Public Notice No. 2009-230126

In this way, in adjusting the light transmittance of the semi-transparent portion of the photomask, it is ideal to accurately measure the light transmittance during the film-detection process so that the film-detection time until the target value can be accurately determined. In particular, in display devices such as liquid crystal displays and organic EL display devices, higher quality is required in terms of brightness, operation speed, power consumption, resolution, etc.

For these devices, lithography using a photomask is usefully applied to form three-dimensional structures such as contact holes using a photosensitive resin such as an organic insulating film, for example. In particular, as the three-dimensional structure to be formed becomes complex, such as an insulating film having a portion with a different height or a plurality of photo spacers having different heights, a demand arises for a photomask with three or more gradations, and in order to precisely form the three-dimensional structure, it is important to manage the light transmittance of the photomask used.

In particular, it is estimated that a gradation mask having a plurality of semi-transparent parts with different exposure light transmittances in addition to a light-transmitting part and a light-shielding part, for example, those with four or more gradations, can be advantageously utilized. Control of light transmittance is important for precisely forming each of these light-transmitting parts with different light transmittances. In other words, if the light transmittance of each of the plurality of light-transmitting parts is not formed exactly according to the design value, satisfactory function cannot be exhibited in the final device, such as a display device.

Therefore, the object of the present invention is to solve these problems, provide an etching solution having a low etching rate for finely adjusting the thickness and realizing a uniform thickness, and a method for manufacturing a gradation mask using the etching solution.

The present inventors, while diligently examining to solve these problems, discovered that an etching solution of ammonium cerium(IV) nitrate or ammonium cerium(IV) tetrasulfate can realize fine adjustment of the thickness of an optical film and uniform thickness in a pattern processing process of an optical film of a photomask, and furthermore, discovered that a combination of ammonium cerium(IV) nitrate or ammonium cerium(IV) tetrasulfate and an acid can realize even more advanced fine adjustment of the thickness of an optical film and uniform thickness, and as a result of conducting research, they completed the present invention.

That is, the present invention relates to the following.

[1] An etching solution used for processing an optical film pattern of a photomask, wherein the photomask is for photolithography with three or more gradations, and contains ammonium cerium (IV) nitrate or ammonium cerium (IV) sulfate.

[2] [1] An etching solution characterized in that the photomask has a first semi-transparent portion and a second semi-transparent portion having different exposure light transmittances.

[3] In [1] or [2], the etching solution further contains an acid.

[4] [3], the etching solution is one or more selected from the group consisting of sulfuric acid, methane sulfonic acid, nitric acid, acetic acid, and perchloric acid.

[5] An etching solution according to any one of [1] to [4], wherein the optical film is a film containing chromium and/or a chromium compound.

[6] [5] An etching solution in which the chromium compound is one or more selected from the group consisting of chromium oxide, chromium nitride, chromium oxynitride, or chromium oxynitride carbide.

[7] An etching solution having an etching rate of 0.1 nm/min. or more and 100.0 nm/min. or less in any one of [1] to [6].

[8] An etching solution having an etching rate of 0.1 nm/min. or more and 5.0 nm/min. or less in any one of [1] to [6].

[9] A method for manufacturing a gradation mask having a transfer pattern having a plurality of areas with different exposure light transmittance, wherein the method comprises pattern processing an optical film using an etching solution according to any one of [1] to [8].

[10] [9], the optical film before the pattern processing is a light-blocking film and/or a semi-transparent film.

[11] [9] or [10], a method having a plurality of semi-transparent parts with different exposure light transmittances of 10 to 70% in the semi-transparent area and having at least three gradations.

[12] A tone mask manufactured by any one of the manufacturing methods of [9] to [11].

According to the etching solution of the present invention, in the manufacture of a photomask having a chromium series compound film, which is generally used as an optical film, particularly a light-shielding film and a semi-transparent film, which has been difficult to finely adjust in thickness in the past, the light transmittance of the semi-transparent part of the photomask can be precisely controlled according to the complex design of a desired device. In particular, in the process of forming the semi-transparent part, the transmittance can be measured and the required additional etching time can be accurately determined.

In addition, since such fine adjustment is possible, the type of photomask blank to be prepared can be limited. In a situation where a plurality of desired devices each require different gradation numbers or different transmittance values, if the photomask blanks to be prepared are of various kinds, there will be inconveniences in terms of lead time and cost, but if the photomask manufactured by the present invention is used, the process for several photomasks can be performed with one photomask. Meanwhile, if the present invention is applied, the type of photomask blank to be prepared in advance can be limited, and the transmittance can be adjusted to a desired value during the process, thereby providing a variety of display devices with high production efficiency.

[Figure 1] Figure 1 is an explanatory drawing explaining a first embodiment of a photomask manufacturing method of the present invention.
[Figure 2] Figure 2 is an explanatory diagram illustrating a method for manufacturing a gradation mask by applying a laminate composed of a semitransparent film, an etching stopper film, and a light-shielding film as an optical film formed on a transparent substrate.
[Figure 3] Figure 3 is a diagram showing the relationship between the etching solution and the etching rate with varying sulfuric acid concentration in the case of 2.0 mass% of ammonium cerium(IV) nitrate or ammonium cerium(IV) sulfate.
[Figure 4] Figure 4 is a diagram showing the relationship between the etching rate and the nitric acid concentration of 2.0 mass% of ammonium cerium(IV) nitrate or ammonium cerium(IV) sulfate.
[Figure 5] Figure 5 is a diagram showing the relationship between the etching rate and the concentration of methane sulfonic acid in an etching solution containing 2.0 mass% of ammonium cerium (IV) nitrate or ammonium cerium (IV) sulfate.
[Figure 6] Figure 6 is a diagram showing the relationship between the etching solution with changed concentration of ammonium cerium (IV) nitrate and the etching rate.
[Figure 7] Figure 7 is a diagram showing the relationship between the etching solution and the etching rate in which the concentrations of diammonium cerium (IV) nitrate and diammonium cerium (IV) sulfate are changed in the case of 40 mass% sulfuric acid.
[Figure 8] Figure 8 is a diagram showing the relationship between the processing time and the film reduction amount when etching the surface of a glass substrate, each of which is a film formation evaluation substrate c, using an etching solution containing 2.0 mass% of ammonium cerium (IV) nitrate and 40 mass% of sulfuric acid.

Hereinafter, embodiments of the present invention will be described in detail.

FIG. 1 is an explanatory drawing illustrating a first embodiment of a photomask manufacturing method of the present invention.

Process 1: As shown in Fig. 1(a), an optical film is formed on a transparent substrate, and a photomask substrate is prepared by further forming a first resist film on the surface. Here, the photomask substrate is a photomask blank, but the photomask substrate may already be partially patterned.

In addition, the first resist film of the photomask substrate may be formed directly on the surface of the optical film, and another film may be interposed between the first resist film and the optical film as long as it does not interfere with the effect of the present invention. The optical film may be a light-shielding film or a semi-transparent film, and may have a function such as shifting the phase of exposure light by a predetermined amount (phase shift film). In addition, the film surface portion may have an antireflection layer that prevents reflection of light. Furthermore, the optical film may be a plurality of films laminated together. For example, FIG. 1 exemplifies a case where the optical film is a light-shielding film.

The method for forming an optical film can be performed using a known film forming method, such as a sputtering method.

There are no particular restrictions on the material of the optical film. Here, a light-shielding film is exemplified, but as a light-shielding film material, a light-shielding film containing Cr as its main component can be exemplified. It is preferable to have an antireflection layer such as Cr oxide on the surface.

Process 2: A drawing pattern (first drawing pattern) for forming a light-transmitting portion is drawn using a drawing device. After drawing, a first development is performed to form a first resist pattern (Fig. 1(b)). Since a positive photoresist is used as the resist here, the resist in the drawing portion is removed.

Process 3: Using the first resist pattern formed in Process 1 as an etching mask, the optical film (shielding film) is etched away (Fig. 1(c)). Here, wet etching is performed using a known etching solution. As a result, the light-transmitting portion is determined (first forming process).

Process 4: The first resist pattern (resist film) is peeled off (Fig. 1(d)).

Process 5: A new second resist film is formed by applying it to the surface (Fig. 1(e)).

Process 6: A second drawing pattern is drawn using a re-drawing device and a second development is performed. As a result, the second resist film of the portion corresponding to the light-transmitting portion and the portion corresponding to the semi-light-transmitting portion is removed, and a second resist pattern is formed in which a portion of the transparent substrate and the optical film surface are each exposed to light (Fig. 1(f)).

Process 7: Using the second resist pattern as a mask, the optical film of the exposed portion is etched using an etching solution according to the present invention (second patterning process). As a result, a transparent portion having a desired exposure light transmittance is formed (Fig. 1(g)).

The present invention relates to an etching solution used for pattern processing of an optical film of a photomask, wherein the photomask is a photolithography having three or more gradations, and an etching solution composition containing ammonium cerium (IV) nitrate or ammonium cerium (IV) sulfate.

Here, the etching solution is an etching composition containing ammonium cerium (IV) nitrate or ammonium cerium (IV) sulfate for etching an optical film forming a gradation mask, for example, a chromium film or a chromium compound.

The above etching solution may contain an acid. The acid is not particularly limited, and examples thereof include sulfuric acid, methane sulfonic acid, nitric acid, acetic acid, perchloric acid, etc. From the viewpoints of the etching rate for a chromium film or a chromium compound film and the stability of the chemical solution, sulfuric acid, methane sulfonic acid, acetic acid, and nitric acid are preferable, sulfuric acid, methane sulfonic acid, and acetic acid are more preferable, and sulfuric acid and methane sulfonic acid are particularly preferable.

The content of ammonium cerium(IV) nitrate or ammonium cerium(IV) sulfate used in the present invention varies depending on the type of acid and the chromium film or chromium compound film, and is not particularly limited. However, when the etching solution composition is 100 mass%, it is preferably 0.1 mass% to 10 mass%, more preferably 0.5 mass% to 8.0 mass%, and most preferably 1.0 mass% to 6.0 mass%.

For the above etching rate, for a substrate having a layer (or film) made of chromium or a chromium compound on its surface, the etching rate is preferably 0.1 nm/min. or more and 100.0 nm/min. or less in the thickness direction of the layer (or film), more preferably 0.1 nm/min. or more and 10.0 nm/min. or less, more preferably 0.1 nm/min. or more and 5.0 nm/min. or less, and most preferably 0.3 nm/min. or more and 1.0 nm/min. or less.

Those skilled in the art can appropriately optimize the temperature, time, flow conditions of the etchant during etching, and swing conditions of the substrate (including conditions for spraying the etchant composition as a shower onto the substrate), but in particular, the temperature is preferably 20.0 to 25.0°C. If the temperature is within the above range, it is preferable because it can be used at room temperature and the temperature is stable. In addition, the immersion time is preferably 30.0 to 180.0 seconds. If the immersion time is within the above range, it is preferable from the viewpoint of easy acquisition of on-surface uniformity in device processing and the amount of etchant required for processing.

The optical film refers to a semi-transparent film, an etching stopper film, and a light-shielding film, and pattern processing refers to pattern processing in the photomask manufacturing process.

Process 8: The second resist pattern is peeled off to complete a three-level photomask having a light-transmitting portion, a light-shielding portion, and a semi-transmitting portion (Fig. 1(h)).

The photomask manufacturing method shown in Fig. 2 exemplifies a method for manufacturing a gradation mask by applying a laminate composed of a semi-transparent film, an etching stopper film, and a light-shielding film as optical films formed on a transparent substrate.

Process 1: A photomask substrate having an optical film formed by laminating a semitransparent film, an etching stopper film, and a light-shielding film on a transparent substrate and having a first resist film formed on the surface is prepared (Fig. 2(a)). Since the semitransparent film is a film having a predetermined exposure light transmittance that transmits a portion of exposure light, in this embodiment, for example, the exposure light transmittance is set to be 50 to 60%.

In addition, the light-shielding film and the etching stopper film have etching selectivity, and are made of materials that are etching resistant to each other's etchant (an etchant here since wet etching is applied). Furthermore, the semi-transparent film and the etching stopper film are also made of materials that are resistant to each other's etchants. The light-shielding film and the semi-transparent film may or may not have etching selectivity to each other. Therefore, here, the materials of the light-shielding film and the semi-transparent film are assumed to have in common an etching characteristic that includes Cr.

Process 2: A drawing pattern (first drawing pattern) for forming a light-transmitting portion is drawn using a drawing device. After drawing, a first development is performed to form a first resist pattern (Fig. 2(b)).

Process 3: The first resist pattern formed in Process 2 is etched to remove the light-shielding film using an etching mask (Figure 2(c)).

Process 4: Change to an etchant for the etching stopper film, and etch away the etching stopper film (Fig. 2(d)).

Process 5: The etchant is changed again, and the semi-transparent film is etched away by the etchant for the semi-transparent film. Then, the first resist pattern (first resist film) is peeled off (Fig. 2(e)).

Process 6: A new second resist film is formed on the surface (Fig. 2(f)).

Process 7: Using a re-drawing device, a second drawing pattern is drawn and a second development is performed. As a result, the second resist film of the portion corresponding to the transparent portion and the portion corresponding to the semi-transparent portion (the first semi-transparent portion) is removed, and a second resist pattern is formed in which a portion of the transparent substrate and the light-shielding film surface are each exposed (Fig. 2(g)).

Process 8: The light-shielding film of the portion that exposes the second resist pattern as a mask is etched away. In addition, the etchant is changed and the etching stopper film is etched away (Fig. 2(h)).

Process 9: Next, by changing the etchant, the exposed semi-transparent film is etched using an etchant according to the present invention (second patterning process). As a result, a semi-transparent portion (first semi-transparent portion) having a desired exposure light transmittance is formed (Fig. 2(i)).

Process 10: The second resist pattern (second resist film) is peeled off to complete a three-level photomask having a light-transmitting portion, a light-shielding portion, and a semi-light-transmitting portion (Fig. 2(j)).

In addition, in the case of manufacturing a 4-level photomask having a transfer pattern having two types of semi-transparent parts (first and second semi-transparent parts) with different exposure light transmittances in addition to a light-transmitting part and a light-shielding part, the following process can be further performed on the photomask of Fig. 2(j).

Process 11: A new third resist film is formed on the surface (Fig. 2(k)).

Process 12: A drawing pattern (third drawing pattern) for forming an additional semi-transparent portion (second semi-transparent portion) using a drawing device is drawn and developed a third time to form a third resist pattern (Fig. 2(l)).

Process 13: Using the third resist pattern as a mask, the light-shielding film and the etching stopper film are etched away to form a second semi-transparent portion (Fig. 2(m)).

Process 14: The third resist pattern (third resist film) is peeled off, and a four-level photomask having a light-transmitting portion, a light-shielding portion, a first semi-transmitting portion, and a second semi-transmitting portion is completed (Fig. 2(n)).

Through the above process, first and second semi-transparent sections having different exposure light transmittances can be formed by a single semi-transparent film.

Above, the embodiments of the present invention have been described using FIGS. 1 and 2, but the present invention is not limited to these embodiments and includes various embodiments as long as the effects of the invention are not impaired. In addition, the process in each embodiment described above may be changed or another process may be added as long as the operational effects of the present invention are not impaired.

In addition, in the description of these embodiments, the expressions “first” and “second” conveniently indicate the order of the processes, and can be appropriately understood when other processes are performed before, after, or between them.

In all of these forms, it is more preferable to apply wet etching for etching. In particular, in the case of photomasks for device manufacturing, since it is necessary to produce a variety of photomask substrates having a large size of 300 mm or more on one side and having various aspect ratios and areas, the effect of applying wet etching is significant.

In addition, it is also possible to use a photomask blank on which an optical film and a resist film are formed on a transparent substrate as a starting material, and it goes without saying that any patterned or otherwise processed photomask intermediate can be applied as a starting material.

There is no particular limitation on the use of the photomask of the present invention.

For example, it is also suitable for so-called photo-PEP (reducing the number of photomasks used when manufacturing display device panels), which is useful as a tone mask.

In addition, it can be used as a photomask for forming a three-dimensional shape of a structural material (made of photosensitive resin, etc.) in a display device. For example, when forming a photo spacer of a liquid crystal display device and an insulating layer of a display device, the effect of the invention is remarkable because the height control of structural materials having a plurality of different heights is each precisely performed. It is particularly advantageous in a photomask with 4 or more gradations.

Furthermore, the present invention includes a method for manufacturing a display device, which includes a process of transferring a transfer pattern onto a transfer target by an exposure device using a photomask manufactured by one of the embodiments.

The following are examples of materials for the optical film used in the photomask of the present invention.

Here, there is no particular limitation on the material of the optical film used, but preferably, a compound containing Cr as a main component can be used. For example, an oxide, a nitride compound, a carbide, an oxynitride, or an oxynitride carbide of Cr can be used, and preferably, an oxide or an oxynitride carbide of Cr can be used. These materials may be used alone or in combination of two or more. It is preferable that the thickness of the portion used as the light-shielding portion obtains sufficient light-shielding properties (optical density OD≥3, preferably OD≥4).

The semi-transparent film may or may not have etching selectivity between the light-shielding films. However, in the case where there is no etching selectivity (i.e., the etching characteristics are common), a common etchant can be used, which improves the production technology efficiency.

Accordingly, it is possible to select from the shade film materials exemplified above. In addition, in the case of etching film, it is more preferable that the thickness is 50 to 2000 Å in order to facilitate control of the etching time up to the target light transmittance.

Since it is desirable for the etching stopper film to have etching selectivity with respect to the light-shielding film and the semi-transparent film, a material selected from among Ta, Mo, W and compounds thereof (e.g., oxides, nitrides, oxynitrides, or TaSi, MoSi, WSi (metal silyl sides) or nitrides, oxynitrides, etc. of these) can be used.

[Example]

Hereinafter, the present invention will be described more specifically by examples and comparative examples, but the present invention is not limited to these examples, and various modifications are possible without departing from the technical spirit of the present invention.

On the surface of a glass substrate, a film evaluation substrate a was produced in which chromium oxide was deposited at a thickness of 19 nm (transmittance of 17%) and 15 nm (transmittance of 35.5%), respectively, and also, the etching compositions shown in Table 1 and Table 2 were produced, respectively. At that time, the presence or absence of crystal precipitation of each etching composition was observed.

Each evaluation substrate a was cut to 2.0 X 2.0 cm, and the thickness of the chromium oxide film was measured using a fluorescence X-ray analyzer (ZSX100e) before etching solution maturation.

Each evaluation substrate b was obtained by stirring and maturing at 25°C for 15 to 1800 seconds in a glass container containing 80 ml of each etching composition, rinsing with ultrapure water for 1 minute, and drying by nitrogen blur.

For each evaluation substrate b, the etching amount of the chromium oxide film was measured using a fluorescence X-ray analyzer, and the etching rate (E.R.) was calculated from the immersion time and the etching amount. The results of the presence or absence of crystal precipitation and the etching rate are shown in Tables 1 and 2, along with the components of the etching solution composition and the concentrations of the components.

[Table 1]

When using ammonium cerium (IV) nitrate and one of perchloric acid, nitric acid, sulfuric acid, acetic acid, and methane sulfonic acid, the target etching rate was obtained. On the other hand, when phosphoric acid was used as the acid, crystals were precipitated regardless of the concentration, and the etching rate could not be measured.

[Table 2]

When ammonium cerium(IV) sulfate and one of nitric acid, sulfuric acid, acetic acid, and methane sulfonic acid were used, the target etching rate was obtained. On the other hand, when perchloric acid or phosphoric acid was used as the acid, crystals were precipitated regardless of the concentration, and the etching rate could not be measured.

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Figure 3 shows the relationship between the etching rate and the sulfuric acid concentration of the etching solution, in the case of 2.0 mass% of ammonium cerium(IV) nitrate or ammonium cerium(IV) sulfate. It was confirmed that the etching rate tends to decrease as the sulfuric acid concentration increases.

Figure 4 shows the relationship between the etching rate and the nitric acid concentration of the etching solution when the nitric acid concentration is 2.0 mass% of ammonium cerium(IV) nitrate or ammonium cerium(IV) tetrasulfate. In the case of ammonium cerium(IV) nitrate, it was confirmed that the etching rate tends to decrease as the nitric acid concentration increases. On the other hand, in the case of ammonium cerium(IV) sulfate, it was confirmed that the etching rate tends to increase as the nitric acid concentration increases in the range of about 40%, and that the etching rate tends to decrease as the nitric acid concentration increases in the range of 40% or more.

Figure 5 shows the relationship between the etching rate and the concentration of methanesulfonic acid in the etching solution when the concentration of ammonium cerium(IV) nitrate or ammonium cerium(IV) sulfate is 2.0 mass%. It was confirmed that the etching rate tends to decrease as the concentration of methanesulfonic acid increases.

Figure 6 shows the relationship between the etching solution and the etching rate with varying concentrations of diammonium cerium (IV) nitrate. It was confirmed that the etching rate tends to decrease as the concentration of diammonium cerium (IV) nitrate decreases.

Figure 7 shows the relationship between the etching solution and the etching rate in which the concentrations of diammonium cerium(IV) nitrate and diammonium cerium(IV) sulfate were changed in the case of 40 mass% sulfuric acid. It was confirmed that the etching rate tended to increase as the concentrations of diammonium cerium(IV) nitrate and diammonium cerium(IV) sulfate increased.

Figure 8 shows the relationship between the processing time and the film reduction amount when etching the surface of a glass substrate, each of which is a film-forming evaluation substrate c, with an etching solution containing 2.0 mass% of ammonium cerium (IV) nitrate and 40 mass% of sulfuric acid. Since the film reduction occurs linearly with respect to the processing time, it was confirmed that the transmittance of chromium oxide can be controlled by the processing time.

Claims (12)

In the etching solution used for processing the optical film pattern of the photomask,
The above photomask is for photolithography with three or more tones.
Ammonium cerium (IV) nitrate further comprising one or more acids selected from the group consisting of sulfuric acid, methanesulfonic acid, acetic acid and nitric acid, or
An etching solution further comprising at least one acid selected from the group consisting of ammonium cerium(IV) sulfate and methanesulfonic acid and nitric acid.
In an etching solution used for processing the optical film pattern of a photomask,
The above photomask is for photolithography with three or more tones.
An etching solution containing 0.1 mass% to 4.0 mass% of ammonium cerium (IV) sulfate and sulfuric acid.
In paragraph 1 or 2,
An etching solution, characterized in that the above photomask has a first semi-transparent portion and a second semi-transparent portion having different exposure light transmittances.
delete In paragraph 1 or 2,
The above optical film is an etching solution containing chromium and/or a chromium compound.
In paragraph 5,
An etching solution wherein the above chromium compound is one or more selected from the group consisting of chromium oxide, chromium nitride, chromium oxynitride, or chromium oxynitride carbide.
In paragraph 1 or 2,
An etching solution having an etching rate of 0.1 nm/min. or more and 100.0 nm/min. or less.
In paragraph 1 or 2,
An etching solution having an etching rate of 0.1 nm/min. or more and 5.0 nm/min. or less.
A method for manufacturing a gradation mask having a transfer pattern having a plurality of semi-transparent areas having different exposure light transmittances, wherein an optical film is pattern-processed using the etching solution of claim 1 or 2.
In Article 9,
A method in which the optical film before the above pattern processing is a light-blocking film and/or a semi-transparent film.
In Article 9,
A method in which the above semi-transparent area has a plurality of semi-transparent portions having different exposure light transmittances of 10 to 70%, and the gradation mask has at least three gradations.
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