JPH04246649A - Photomask blank, production thereof, photomask and production thereof - Google Patents

Abstract

PURPOSE:To prevent a change of the cross-sectional shape of a pattern of a light shielding film having low reflectance when a photomask is produced from a photomask blank having antireflection films each contg. a metallic silicon compd. and a light shielding film. CONSTITUTION:When a first antireflection film 2, a light shielding film 3 and a second antireflection film 4 are successively laminated on a transparent substrate 1 to obtain a photomask blank 10, the films 2, 4 are made of a molybdenum-silicon compd. contg. oxygen and nitrogen and the photomask blank has 90:10-33:67 molar ratio of molybdenum:silicon.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a photomask used as an original plate for photolithography during microfabrication of semiconductor integrated circuits, etc., and a method for manufacturing the same, as well as a photomask blank, which is a material for the photomask, and the manufacturing method thereof. Regarding the method.

0002

[Prior Art] This type of photomask blank has a basic structure in which a light-shielding film is formed on a transparent substrate, or an additional layer is added to this basic structure to prevent reflection of exposure light on the front and back surfaces of the light-shielding film. Types with an anti-reflection film added are conventionally known. Furthermore, as a material for the light-shielding film of these photomask blanks, chromium has been widely used due to its excellent light-shielding properties. However, when using chromium as a light-shielding film material, if dry etching is used instead of wet etching to accommodate higher pattern integration, carbon tetrachloride, which has safety issues, must be used as an atmospheric gas. I had no choice. Therefore, from the viewpoint of safety, MoSi2 (molybdenum silicon compound), which can be dry etched with a mixed gas of carbon tetrafluoride, oxygen, etc., has been proposed as a substitute for chromium. For example, the photomask blank described in Japanese Patent Application Laid-Open No. 63-214754 has a light-shielding film made of MoSi2.
The film structure is such that Mo containing oxygen is formed between the light shielding film and the transparent substrate, and on the light shielding film.
An antireflection film made of Si2 is provided.

0003

[Problem to be solved by the invention] However, using the photomask blank listed as the conventional technology as a material,
When the light-shielding film and the anti-reflection film are selectively removed to produce a photomask having a low-reflection light-shielding film pattern consisting of the light-shielding film pattern and the anti-reflection film pattern, the width of the light-shielding film pattern is wider than the width of the anti-reflection film pattern. This makes it impossible to avoid the cross-sectional shape of the low-reflection light-shielding film pattern becoming constricted in the center. This is because the composition of the anti-reflection film of this photomask blank is the composition of the light-shielding film (MoSi2) containing oxygen, so the included oxygen causes the etching rate to be slower than that of the light-shielding film. It's for a reason.

[0004] As described above, when a difference in pattern width occurs between the anti-reflection film pattern and the light-shielding film pattern, it becomes difficult to control the pattern width of the low-reflection light-shielding film pattern when manufacturing a photomask from a photomask blank. Not, but
There was a problem in that the low reflection light shielding film pattern was damaged.

The present invention has been made in view of the above-mentioned problems, and provides a photomask that prevents deterioration of the cross-sectional shape of a low-reflection light-shielding film pattern due to the difference in etching rate between the light-shielding film and the anti-reflection film. The purpose is to provide a method for producing the same. Another object of the present invention is to provide a photomask that prevents damage to the low-reflection light-shielding film pattern and a method for manufacturing the same. Still another object of the present invention is to provide a photomask blank that is a suitable material for manufacturing the above-mentioned photomask, and a method for manufacturing the same. Still another object of the present invention is to provide a photomask blank in which the pattern width of a low-reflection light-shielding film can be easily controlled.

[0006]

[Means for Solving the Problems] A first photomask blank of the present invention includes a transparent substrate, a light-shielding film provided on the transparent substrate, a space between the light-shielding film and the transparent substrate, and a space between the light-shielding film and the transparent substrate. In a photomask blank comprising an anti-reflection film provided on at least one of the upper sides, the anti-reflection film contains a metal silicon compound, oxygen, and nitrogen, and the metal/silicon molar ratio in the metal silicon compound is ratio n
is selected within the range of 90/10≦n<33/67.

The second photomask blank of the present invention is
The first photomask blank is characterized in that the metal of the metal silicon compound is a metal selected from molybdenum, tantalum, tungsten, and nickel.

In the third photomask blank of the present invention, the light-shielding films of the first and second photomask blanks are made of the same type of metal silicon compound as the antireflection film, and the metal/silicon content in the metal silicon compound is Molar ratio n is 90
/10≦n<33/67.

The method for producing a photomask blank of the present invention is a method for producing a photomask blank in which a light shielding film and an antireflection film are formed on a transparent substrate. When forming a film by sputtering a sputter target made of a metal silicon compound, the sputter target is made of a metal/silicon compound.
It is characterized in that the molar ratio n of silicon is selected in advance within the range of 90/10≦n<33/67.

The photomask manufacturing method of the present invention uses the photomask blank obtained by the photomask blank manufacturing method as a material, and selectively removes an antireflection film and a light shielding film in the photomask blank. Features.

In addition, in the first photomask blank, the third photomask blank, and the method for manufacturing the photomask blank described above, the reason why the molar ratio n is selected within the above range is that it is smaller than 33/67. This is because the anti-reflection film can be made thinner, and by setting the ratio to 90/10 or more, good adhesion of the anti-reflection film (to a transparent substrate or a light-shielding film) can be obtained. Further, the preferable range of the molar ratio n is 70/30 to 40/60, and by setting it within this range, the adhesion force of the film and the effect of thinning the film become remarkable.

0012

[Function] The photomask blank of the present invention has a metal/silicon molar ratio n of the antireflection film of 90/10≦n<33/
Since it is selected within the range of 67, it is possible to maintain good film adhesion and reduce the film thickness without impairing the predetermined antireflection effect. In this way, the antireflection film is made thinner to reduce the side etching amount difference, and the etching rate, which was slowed down by the oxygen contained, is increased by containing nitrogen. Thereby, the pattern width difference between the light shielding film pattern and the antireflection film pattern can be suppressed. Furthermore, by suppressing the pattern width difference in this manner, the low reflection light shielding film pattern width can be controlled accurately and easily.

In addition, by selecting not only the antireflection film but also the metal/silicon molar ratio n of the light shielding film within the range of 90/10≦n<33/67, the light shielding film can be made even thinner.
The difference in side etching amount between the light shielding film and the antireflection film can be further reduced. Furthermore, the adhesion between the light shielding film and the antireflection film can also be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A photomask blank and a method for manufacturing the same, and a photomask and a method for manufacturing the same according to embodiments of the present invention will be described below with reference to the drawings. First of all, referring to FIG. 1, a photomask blank 1 of the first embodiment will be explained.
Explain 0. Photomask blank 10 of this example
is constructed by sequentially forming a first antireflection film 2, a light shielding film 3, and a second antireflection film 4 on a transparent substrate 1.

Both the first antireflection film 2 and the second antireflection film 4 are made of a molybdenum silicon compound containing 15 mol% of oxygen, 30 mol% of nitrogen, and 55 mol% of molybdenum/silicon in the molybdenum silicon compound. molar ratio n is 5
It is selected as 0/50. The thickness of each film is 330 angstroms for the first antireflection film 2 and 490 angstroms for the second antireflection film. The light shielding film 3 is
The antireflection film 2 and the second antireflection film 4 are made of a molybdenum silicon compound having the same molar ratio n of molybdenum/silicon, n=50/50, and have a film thickness of 830 angstroms. The transparent substrate 1 is made of a quartz glass substrate whose main surface on which the first antireflection film 2 is deposited and the opposite surface facing the main surface are precisely polished, and its external dimensions are 5 inches long x 5 inches wide x thick. It is 0.09 inch. The optical density of the photomask blank 10 having the above configuration was 3.0, and the reflectance for light with a wavelength of 436 nm was 15% on the front surface and 20% or less on the back surface.

Next, the above-mentioned photomask blank 20
The manufacturing method will be explained. First, a quartz glass substrate (external size: 5 inches long x
Transparent substrate 1 consisting of 5 inches wide x 0.09 inches thick
A transparent substrate 1 is prepared and carried into a chamber of a reactive sputtering apparatus. Next, a mixed gas of argon and nitrous oxide is introduced into this chamber, and in this mixed gas atmosphere, molybdenum/silicon molar ratio n
A first antireflection film 2 (thickness: 330 angstroms) is formed on the main surface of the transparent substrate 1 by sputtering a sputter target made of a molybdenum silicon compound having a ratio of 50 (mol %)/50 (mol %). Furthermore, the molar ratio of argon and nitrous oxide (N2O) in the mixed gas in the chamber mentioned above is 80% argon and 20% nitrous oxide.
The mixed gas pressure was 1.5×10 −3 Torr.

[0017] Next, the mixed gas of argon and nitrous oxide in the chamber was evacuated, and argon gas was newly introduced. A light shielding film 3 (thickness: 830 angstroms) was formed on the first antireflection film 2 by sputtering using a sputtering target made of the same molybdenum silicon compound. Note that the pressure of argon gas in the chamber was 2×10 −3 Torr. Next, nitrous oxide was introduced into the chamber again, and the atmosphere was made into a mixed gas with a molar ratio of argon/nitrous oxide = 80%/20% (mixed gas pressure: 1.5 x 10-3 Torr). Then, the second anti-reflection film 4 (thickness:
90 angstroms) was formed on the light shielding film 3.

Now, the above-mentioned photomask blank 10
A photomask 20 manufactured using the material will be described with reference to FIG. The photomask 20 shown in FIG. 2 includes the first antireflection film 2 and the light shielding film 3 of the photomask 10 shown in FIG.
, and the second antireflective film 4 are selectively removed and patterned to form a first reflective film pattern 2a, a light shielding film pattern 3a,
A low-reflection light-shielding film pattern 5 consisting of a second anti-reflection film pattern 4a is formed.

Next, the photomask 20 shown in FIG.
The manufacturing method will be explained. First, a positive photoresist (for example, AZ1350 manufactured by Hoechst) is dropped onto the second antireflection film 4 of the photomask blank 10 shown in FIG. 1, and a resist film with a thickness of 5000 angstroms is formed by spin coating. . Next, the pattern width is 2μ
The resist film is selectively exposed to ultraviolet light through a master mask having a pattern of m, and then the resist film is developed with a predetermined developer to dissolve the exposed portion of the resist film and form the pattern. turned into
Form a resist pattern. Next, this photomask blank 10 with a resist pattern is carried into a chamber of a parallel plate type plasma etching apparatus, and the photomask blank 10 is carried in using the resist pattern as a mask.
A first anti-reflection film 2, a light shielding film 3, and a second anti-reflection film 4
Each exposed portion of the substrate was selectively and sequentially dry etched. This dry etching is reactive ion etching under the following etching conditions.

*Etching atmosphere gas...(CF4
; 80 mol% + O2 ; 20 mol%) mixed gas * Etching atmosphere gas pressure... 0.1 Torr * High frequency output... 100 W Through this dry etching process, the first An antireflection film pattern 2a, a light shielding film pattern 3a, a second antireflection film pattern 4a, and a resist pattern were formed. Finally, the unnecessary resist pattern is removed by contacting it with concentrated sulfuric acid, and then ultrasonic cleaning (ultrasonic output: 600W, frequency 28KHz)
A photomask 20 shown in FIG. 2 was obtained.

When the low-reflection light-shielding film pattern 5 of the photomask 20 obtained by the photomask manufacturing method of this example was observed, it was found that the pattern of the master mask (pattern width 2 μm) was faithfully reproduced; Pattern width (2
It was confirmed that the cross section had a rectangular cross section with substantially equal diameters (μm). Furthermore, no damage to the pattern was observed due to ultrasonic cleaning. This includes a first antireflection film 2, a light shielding film 3,
The molybdenum/silicon molar ratio n of each of the second antireflection coatings 4 is selected to be 50/50 to make the film even thinner and to exhibit the antireflection effect without impairing the predetermined reflectance. The side etching rate of the light-shielding film and the first and second antireflection films is substantially the same by increasing the etching rate, which was slowed down by the mol% oxygen content, by adding 30 mol% nitrogen. It depends on what you did. The fact that the side etching rates became substantially the same is also supported by the fact that the widths of each pattern uniformly decreased even after overetching. As a result, each pattern width of the first antireflection film pattern 2a, the light shielding film pattern 3a, and the second antireflection film pattern 4a could be made substantially uniform. Furthermore, when the antireflection film was examined after being brought into contact with concentrated sulfuric acid to remove the resist pattern, neither film peeling nor film reduction occurred. From this, it was found that the antireflection film of this example had sufficient film adhesion and acid resistance. Furthermore, according to this embodiment, since the first antireflection film 2, the light shielding film 3, and the second antireflection film are all made thinner, productivity is also improved.

Molybdenum/silicon molar ratio n is 33/6
In the comparative example No. 7 (stoichiometrically stable), each film of the first antireflection film and the second antireflection film required to obtain the same reflectance as the photomask 20 of the first example described above. Table 1 shows the thickness and the etching time required for just etching. Table 1 also shows a second example in which the molar ratio n of molybdenum and silicon was 85/15, a third example in which it was 67/33, a fourth example in which it was 40/60, and 3.
A fifth example set on 7/63 will also be shown. Note that these comparative examples and the second to fourth examples were all under the same conditions except that the molar ratio of molybdenum to silicon was changed. Further, the molar ratio was changed by changing the ratio of molybdenum to silicon in the sputter target.

[0023]

[Table 1]

As is clear from Table 1, the molar ratio of molybdenum to silicon in the first and second antireflection films is such that the molar percentage of molybdenum is increased from the molar ratio that is stoichiometrically stable as in the comparative example. It can be seen that the film thicknesses of the first and second antireflection films are thinner in the first to fifth embodiments, which are shifted in the direction shown in FIG. Also, due to the thinning of the first and second antireflection films and the action of nitrogen contained in each antireflection film,
The photomasks of the second and third examples also had the same effect of preventing deterioration of the pattern cross section as the first example. Furthermore, in the second to fifth examples, it was confirmed that the antireflection films had good film adhesion and acid resistance, as in the first example. Although not listed in Table 1 above, the molar ratio n
When the ratio was 95/5, the antireflection film was reduced by about 5% due to contact with concentrated sulfuric acid, and as a result, the reflectance also changed. In addition, peeling of the film was also observed. The overall effect of the film adhesion, acid resistance, and film thinning effect of the antireflection film mentioned above became remarkable when the molar ratio n was in the range of 70/30 to 40/60. This was the fourth example.

Furthermore, in the first to fifth embodiments described above, the molybdenum/silicon molar ratio n is set to 90/10≧n
By selecting within the range of >33/67, the effect of improving the adhesion between the resist and the second antireflection film was also obtained. This eliminates the need for the conventionally required step of applying an adhesion promoter to the second antireflection film before applying the resist.

Next, aspects of the present invention other than the first to fifth embodiments described above will be explained. The above-mentioned 1st to 5th
In the embodiment, the film structure is such that the light-shielding film is sandwiched between the first and second anti-reflection films, but the film structure may be such that only one of the first and second anti-reflection films and the light-shielding film are used. Furthermore, by setting the molybdenum/silicon molar ratio in the light-shielding film to the same value as that of the first anti-reflection film and the second anti-reflection film, the first
Although the effect of improving the adhesion between the anti-reflective film and the second anti-reflective film was achieved and the effect of preventing deterioration of the cross-sectional shape of the pattern was achieved, the bond between the light shielding film and the first and second anti-reflective films The molar ratios do not necessarily have to match. Further, the light shielding film is not limited to a metal silicon compound. Furthermore, the preferred ranges of mol% of the metal silicon compound, oxygen, and nitrogen in the antireflection film are 85 mol% to 20 mol%, 5 mol% to 30 mol%, and 10 mol% to 50 mol%, respectively.
It is. Further, in order to obtain a predetermined antireflection effect and eliminate the difference in etching rate with the light shielding film, it is preferable to set the oxygen/nitrogen molar ratio to around 1/2. Also, at the appropriate time,
Depending on the purpose, the antireflection film may contain carbon or the like. Further, the metal of the metal silicon compound may be tungsten, tantalum, nickel, etc. in addition to molybdenum.

Next, as a gas for oxidizing and nitriding the antireflection film, in addition to N2O, NO, NO2, and, of course, O
A mixed gas of 2 and N2 may be used, and the mixing ratio with Ar gas may also be changed depending on the desired reflectance, etching rate, etc. Next, the film forming method is not limited to the reactive sputtering method, and other sputtering methods, vacuum evaporation methods, ion plating methods, etc. may be used. Next, the resist is not limited to that used in the embodiments, and may be an electron beam or X-ray resist. Further, as a method for selectively etching the antireflection film and the light shielding film of the photomask blank, in addition to reactive ion etching, plasma etching, ion milling, ion beam method, etc. may be used.

[0028]

[Effects of the Invention] According to the present invention, good film adhesion is maintained and deterioration of the cross-sectional shape of the low-reflection light-shielding film pattern due to the difference in etching speed between the light-shielding film and the anti-reflection film is prevented. be able to. Therefore, the width control of the low reflection light shielding film pattern becomes easy and accurate. Moreover, it is also possible to prevent damage to the low reflection light shielding film pattern. Furthermore, the light shielding film is also composed of the same type of metal silicon compound as the antireflection film, and the metal/silicon molar ratio n is within the range of 90/10≦n<33/67, thereby achieving the above-mentioned effect. The effect of preventing deterioration of the cross-sectional shape of the low-reflection light-shielding film pattern can be further enhanced. In addition to this effect, it is also possible to improve the adhesion between the light shielding film and the antireflection film.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a photomask blank according to an embodiment of the present invention.

FIG. 2 is a sectional view of a photomask according to an embodiment of the present invention.

[Explanation of symbols]

1 Transparent substrate 2 First anti-reflection film 2a First anti-reflection film pattern 3. Light shielding film 3a Light shielding film pattern 4 Second anti-reflection film 4a Second anti-reflection film pattern 5 Low reflection light shielding film pattern 10 Photomask blank 20 Photomask

Claims (6)

[Claims] 1. A transparent substrate, a light-shielding film provided on the transparent substrate, and an antireflection film provided between the light-shielding film and the transparent substrate and at least one above the light-shielding film. In the photomask blank, the antireflection film contains a metal silicon compound, oxygen, and nitrogen, and the metal/silicon molar ratio n in the metal silicon compound is 90/10≦n<33/67. A photomask blank characterized by being selected within the range of. 2. The photomask blank according to claim 1, wherein the metal of the metal silicon compound is a metal selected from molybdenum, tantalum, tungsten, and nickel. 3. The light shielding film is made of the same type of metal silicon compound as the antireflection film, and the metal/silicon molar ratio n in the metal silicon compound is 90/10≦n<33/67.
3. The photomask blank according to claim 1, wherein the photomask blank is selected within the range of . 4. A photomask, characterized in that the light-shielding film and the anti-reflection film of the photomask blank according to any one of claims 1 to 3 are selectively removed. 5. A method for manufacturing a photomask blank in which a light-shielding film and an anti-reflection film are formed on a transparent substrate, comprising:
When forming the antireflection film by sputtering a sputter target made of a metal silicon compound in an atmosphere containing oxygen and nitrogen, the metal/silicon molar ratio n of the sputter target is 90/10≦ n<
1. A method for manufacturing a photomask blank, characterized in that a photomask blank is selected in advance within a range of 33/67. 6. A photomask blank obtained by the method for producing a photomask blank according to claim 5 as a material, and characterized in that antireflection and light shielding films in the photomask blank are selectively removed. How to make a mask.