JPS63210930A - Production of photomask blank - Google Patents

Abstract

PURPOSE:To surely form a pattern having a prescribed line width by forming a light shielding film in a mixed gas atmosphere of an inactive gas such as argon, etc., a gas contg. nitrogen atom and a gap incorporating at least one selected from alcohol, carboxylic acid and aldehyde. CONSTITUTION:The light shielding film is formed on one of the main surfaces of a light transmittable film in the mixed gas atmosphere of the inactive gas such as argon, etc., the gas contg. the nitrogen atom and gas incorporating at least one selected from the alcohol, the carboxylic acid and the aldehyde. The formed light shielding film is composed of chromium carbide and chromium nitride. And, the etching velocity of the light shielding film composed from the chromium carbide and chromium nitride is slower than that composed of the chromium nitride by incorporating the chromium carbide in the light shielding film. Thus, the pattern having the prescribed line width is surely formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a photomask blank, which is a material for manufacturing a photomask used in the manufacturing process of semiconductor integrated circuits such as ICs and LSIs. Regarding.

(Prior art) Conventionally, photomask blanks have been manufactured by, for example, Japanese Patent Application Laid-Open No. 57-1
As proposed in No. 47634, a light-shielding film made of chromium nitride is formed on a transparent substrate by vacuum evaporation, sputtering, or ion blating in an atmosphere containing nitrogen. Ta. Note that the above-mentioned light-shielding film has a light-shielding property against ultraviolet light, but has transparency against visible light.

When manufacturing a photomask from the above-mentioned photomask blank, first, a fore resist is coated on a light-shielding film made of chromium nitride. Next, the photoresist is exposed to ultraviolet light through an exposure mask having a predetermined light-shielding pattern, and then the photoresist is developed to form a resist pattern on the light-shielding film made of glazed chromium nitride. Next, using the resist pattern as a mask, the light-shielding film made of chromium nitride is selectively etched with an etching solution, and then the resist pattern is peeled off to leave the light-shielding film pattern made of chromium nitride on the transparent substrate. A photomask is manufactured by forming a photomask.

[Problem that the invention seeks to solve]

However, when manufacturing a photomask through the process of selectively etching a light-shielding film made of chromium nitride as described above, the etching speed of the light-shielding film made of chromium nitride is very fast, so the desired line width is It is difficult to form a light-shielding film pattern made of chromium nitride with It is difficult to control the line width of the light-shielding film pattern to be formed due to minute fluctuations in etching conditions such as the amount of liquid and the fact that etching is mistakenly etched longer than it should be during the etching process. Because it will be.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a photomask blank that can reliably form a pattern with a desired line width and manufacture a photomask. do.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a photomask characterized in that a light-shielding film is formed on the surface of a light-transmitting substrate in a mixed gas atmosphere with a necessary gas. This is a blank manufacturing method.

Note that methods for forming the light-shielding film in the above-mentioned mixed gas atmosphere include sputtering method, vacuum evaporation method, and CVD method.
A film forming method such as a method or an ion blating method can be adopted. Generally speaking, in the present invention, the light-shielding film is not necessarily formed directly on the surface of the light-transmitting substrate, but a thin film is interposed between the light-shielding film and the surface of the light-transmitting substrate. Good too.

[Effect]

A light-shielding film formed in a mixed gas atmosphere of an inert gas such as argon, a gas containing nitrogen atoms, and a gas containing at least one of alcohol, carboxylic acid, and aldehyde. contains chromium carbide and chromium nitride.

The etching rate of the light-shielding film containing chromium carbide and chromium nitride is slower than that of the light-shielding film containing chromium nitride due to the inclusion of chromium carbide in the light-shielding film. Become.

〔Example〕

Hereinafter, a method for manufacturing a photomask blank according to an embodiment of the present invention will be described in detail.

First, a quartz glass plate is ground to predetermined dimensions, and then the amphibatic surface of the ground quartz glass plate is polished to prepare a transparent substrate made of quartz glass (dimensions: 5 x 5 x 0.09 inches). .

Next, using a DC magnetron sputtering device, firstly in a mixed gas atmosphere of argon (Ar) gas, nitrogen (N2) gas, and methyl alcohol (CH30H) gas, and secondly in a mixed gas atmosphere of argon (Ar) gas, nitrogen (N2) gas, and methyl alcohol (CH30H) gas; (N2) gas and ethyl alcohol (C2N50H) gas by a sputtering method in a mixed gas atmosphere of ethyl alcohol (C2N50H) gas so that the transmittance of ultraviolet light with a wavelength of 450 nm is 3.5%. Each film was deposited on the surface of the substrate to produce a photomask blank.

Here, in each case where a photomask blank was manufactured by forming a light-shielding film so that the transmittance of ultraviolet light with a wavelength of 450 nm was 3.5%, the introduced gas, each of the above-mentioned mixed gases, etc. gas mixture ratio (molar ratio), gas pressure,
The thickness of the light-shielding film, just etching time, and etching rate are shown in the table below.

In addition, as a comparative example, the transmittance of ultraviolet light with a wavelength of 450 nm was 3.5% by sputtering in a mixed gas atmosphere of argon gas and nitrogen gas without introducing either methyl alcohol or ethyl alcohol gas. A photomask blank was manufactured by forming a light-shielding film on the entire surface of a light-transmitting substrate so as to have the following properties. The mixing ratio (molar ratio) of argon gas and nitrogen gas in this case is also shown in the table below.

When etching each of the above-mentioned light-shielding films, pure water was added to 165 g of ceric ammonium nitrate and 42 rIJfl of perchloric acid (70%) as an etching solution.
00Id! A solution (liquid temperature: 20°C) was used.

Examples 1, 2, 3 and 4 shown in the table above
As a result of examining the composition of each light-shielding film formed in the above by Auger electron spectroscopy, it was confirmed that each light-shielding film contained chromium carbide and chromium nitride. Further, the light-shielding film formed in the comparative example shown in the table above is made of chromium nitride.

As shown in the table above, when comparing the etching rates in each case of Examples 1 to 4 and the case of the comparative example, each of the light-shielding films formed in each case of Examples 1 to 4 was The etching speed is slower than that of the light-shielding film formed in the comparative example. The reason for this is that each light-shielding film formed in each case of Examples 1 to 4
This is because it contains not only chromium nitride but also chromium carbide.

Furthermore, when comparing the etching rates of the light shielding films formed in Examples 1 and 2, the etching rate in Example 2 is slower than that in Example 1. The reason for this is that in the case of Example 2, the ratio of methyl alcohol gas in the mixed gas is higher than in the case of Example 1. This is because the carbide content is higher than the chromium carbide content in the light-shielding film formed in Example 1.

Furthermore, when comparing the etching rates of the light shielding films formed in Examples 3 and 4, the etching rate in Example 4 is slower than that in Example 3. The reason for this is that in the case of Example 4, the ratio of ethyl alcohol gas in the mixed gas is higher than in the case of Example 3, so that the same thing as described above occurs.

Furthermore, when comparing the etching rates of the light shielding films formed in Examples 1 and 3, the etching rate in Example 3 is slower than that in Example 1. The reason for this is that in the case of Example 3, compared to the case of Example 1, carbon (
C) Since the concentration of atoms increases, the content of chromium carbide in the light-shielding film formed in Example 3 is lower than that in Example 1.
This is because the content of chromium carbide in the light-shielding film formed in the case of Furthermore, for the same reason, the etching rate in Example 4 is slower than that in Example 2.

In addition, as described above, the wavelength/150 nm of each light shielding film formed in Example 2 and Comparative Example, respectively.
Both have ultraviolet light transmittances of 3.5%.

However, the transmittance of visible light at a wavelength of 600 nm in the light-shielding film formed in the comparative example was 7%;
The transmittance of visible light at the same wavelength in the light-shielding film formed in Example 2 was 11%, and the transmittance characteristic of visible light at the same wavelength (so-called, the film also had a wavelength of 600 nm).
The visible light transmittance characteristics of 1ll are improved.

As described above, according to the method for manufacturing a photomask blank of this example, the formed light-shielding film contains chromium carbide and chromium nitride, so the etching rate is lower than that of chromium nitride. The etching rate can be made slower than the etching rate of the light-shielding film. Therefore, if the photomask blank manufactured according to this example is used as a material, a photomask having a pattern with a desired line width can be easily manufactured. Furthermore, the etching rate of the light-shielding film can also be controlled by changing the ratio of methyl alcohol or ethyl alcohol in the mixed gas and changing the content of chromium carbide in the light-shielding film. Therefore, it becomes easier to manufacture a photomask having a pattern with a desired line width.

Furthermore, the transmittance characteristics for visible light in the light-shielding film containing chromium carbide and chromium nitride are also improved. Therefore, when using the photomask blank manufactured by Tera-Tera-Tera≠ in this example as a material, a photomask (so-called "see-through mask") that can be easily aligned can be manufactured.

The present invention is not limited to the embodiments described above.

In the above examples, methyl alcohol or ethyl alcohol gas was used when forming the light-shielding film.
Other alcohol gases such as butyl alcohol may also be used. In place of alcohol gas, formic acid (1
A gas containing at least one of carboxylic acid gas such as 1cOOH), acetic acid (CH3COON>, etc.), formaldehyde, alecol gas, carboxylic acid gas, and aldehyde gas, and argon. The light-shielding film may be formed in a mixed gas atmosphere of gas and nitrogen gas.

Further, in place of argon gas, an inert gas such as helium, neon, or xenon may be used. Furthermore, instead of nitrogen gas, a gas containing nitrogen atoms such as -nitrogen oxide, nitrogen dioxide, or dinitrogen monoxide may be used.

Furthermore, it goes without saying that the gas mixture ratio in the mixed gas of argon gas, nitrogen gas, and methyl alcohol or ethyl alcohol gas is not limited to that described in the above examples, and may be selected as appropriate. . Further, the gas pressure may also be selected as appropriate. Furthermore, in the above examples, the light-shielding film was formed by sputtering method, but vacuum evaporation method was used.

The light-shielding film may be formed by a film forming method such as a CVD method or an ion blating method. In general, the thickness of the light-shielding film to be formed can be appropriately selected depending on the desired transmittance of the light-shielding film.

In addition to quartz glass, the translucent substrate is made of soda lime glass and aluminoborosilicate glass.

It may be made of a translucent material such as sapphire or ceramic, and its dimensions may be determined as appropriate.

Generally speaking, in the above examples, a light-shielding film was formed directly on one main surface of a light-transmitting substrate, but on one main surface of a light-transmitting substrate,
A mixture of indium oxide and tin oxide (so-called rlT)
A thin film made of OJ>, tin oxide, or the like may be formed, and then a light-shielding film may be formed on the thin film.

〔Effect of the invention〕

According to the six WA manufacturing methods of the photomask blank of the present invention,
A photomask blank in which the light-shielding film contains chromium carbide and chromium nitride and the etching speed of the light-shielding film is slow, making it possible to reliably form a pattern with a desired line width and manufacturing a photomask. can be manufactured.

Claims (1)

[Claims] (1) In a method for manufacturing a photomask blank in which a light-shielding film is formed on one main surface of a light-transmitting substrate, an inert gas such as argon, a gas containing nitrogen atoms, an alcohol, a carboxylic acid, etc. In a mixed gas atmosphere with a gas containing at least one of the following:
A method for manufacturing a photomask blank, comprising forming the light-shielding film.