JP3037763B2 - Photomask blank and its manufacturing method, and photomask and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used as a master of a photolithography method in microfabrication of a semiconductor integrated circuit and the like, a method of manufacturing the same, and a photomask blank as a material of the photomask and a method of manufacturing the same. About the method.

[0002]

2. Description of the Related Art A photomask blank of this type has a basic structure in which a light-shielding film is formed on a transparent substrate, or a photomask blank having a basic structure in which exposure light is prevented from being reflected on the front and back surfaces of the light-shielding film. An antireflection film is conventionally known. Chromium has been widely used as a material for the light-shielding film of these photomask blanks because of its excellent light-shielding properties. However, when this chromium is used as a light-shielding film material, if dry etching is used instead of wet etching in order to cope with high integration of patterns, carbon tetrachloride, which has difficulty in safety, is used as an atmosphere gas. I had no choice. Therefore, from the viewpoint of safety, MoSi ₂ (molybdenum silicon compound) that can be dry-etched with a mixed gas of carbon tetrafluoride and oxygen has been proposed as an alternative to chromium. For example, the photomask blank described in JP-A-63-214754 has a light-shielding film made of MoSi _2.
The film configuration is such that MoS containing oxygen is provided between the light shielding film and the transparent substrate and on the light shielding film, respectively.
An anti-reflection film made of i ₂ is provided.

[0003]

However, using a photomask blank as a conventional technique 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 composed of the light-shielding film pattern and the anti-reflection film pattern, the light-shielding film pattern width is larger than the anti-reflection film pattern width. It was not possible to prevent the cross-sectional shape of the low-reflection light-shielding film pattern from becoming narrow at the central portion. The reason is that the composition of the antireflection film of this photomask blank is obtained by adding oxygen to the composition (MoSi ₂ ) of the light shielding film.
This is because the oxygen contained causes the etching rate to be lower than that of the light shielding film.

As described above, when a pattern width difference occurs between the antireflection 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. But not
There is a problem that the low-reflection light-shielding film pattern is lost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems. And a method for producing the same. It is another object of the present invention to provide a photomask in which a defect in a low reflection light-shielding film pattern is prevented and a method for manufacturing the same. Still another object of the present invention is to provide a photomask blank which is a suitable material for manufacturing the above-described photomask and a method for manufacturing the same. Still another object of the present invention is to provide a photomask blank in which the width of a low-reflection light-shielding film pattern can be easily controlled.

[0006]

Means for Solving the Problems As means for solving the above problems, a first means is a photomask blank comprising a transparent substrate and a light-shielding film provided on the transparent substrate. A metal silicon compound between the light-shielding film and the transparent substrate, and at least one of above the light-shielding film,
An anti-reflection film containing oxygen and nitrogen is formed, and the anti-reflection film is composed of 85 mol% to 20 mol% of a metal silicon compound, 5 mol% to 30 mol% of oxygen, and 10 mol% of nitrogen.
It is a photomask blank characterized by being 50 mol%. The second means is a transparent substrate, a light-shielding film provided on the transparent substrate, and a light-shielding film between the light-shielding film and the transparent substrate.
And an antireflection film provided on at least one of the upper portions of the light-shielding film, wherein the antireflection film contains a metal silicon compound, oxygen, and nitrogen, and a metal in the metal silicon compound. A photomask blank characterized in that a molar ratio n of / silicon is selected in a range of 70/30 ≦ n ≦ 40/60.
The third means is provided on at least one of a transparent substrate, a light shielding film made of a metal silicon compound provided on the transparent substrate, between the light shielding film and the transparent substrate, and above the light shielding film. The antireflection film contains a metal silicon compound, oxygen, and nitrogen, and has a metal / silicon molar ratio n of 90/10 ≦ in the metal silicon compound. n <33/6
7 is a photomask blank selected in the range of 7. The fourth means includes a transparent substrate, a light shielding film provided on the transparent substrate, an antireflection film provided between the light shielding film and the transparent substrate, and at least one of above the light shielding film. In a photomask blank with
The antireflection film contains a metal silicon compound, oxygen, and nitrogen, and has an antireflection function by adjusting the oxygen content. The metal / silicon in the metal silicon compound also has a molar ratio n, A photomask blank characterized by being selected in the range of 90/10 ≦ n <33/67. A fifth means is the photomask blank according to the fourth means, wherein the reflectance of the antireflection film is 20% or less. The sixth means is according to any one of the first to fifth means, wherein the metal of the metal silicon compound is a kind of metal selected from molybdenum, tantalum, tungsten and nickel. It is a photomask blank. A seventh means is that the light-shielding film is made of the same kind of metal silicon compound as the antireflection film, and the metal / silicon molar ratio n in the metal silicon compound is in the range of 90/10 ≦ n <33/67. The photomask blank according to claim 1, wherein the photomask blank is selected from the group consisting of: The eighth means is the first
A photomask in which a light-shielding film and a thin film or an anti-reflection film are selectively removed from the photomask blank according to any one of the first to seventh means. Ninth
Means, on a transparent substrate, in a method for manufacturing a photomask blank for forming a light-shielding film and an anti-reflection film, the anti-reflection film, in an atmosphere gas containing oxygen and nitrogen,
When forming a film by sputtering a sputter target made of a metal silicon compound, the metal / silicon molar ratio n of the sputter target is set to 90/10 ≦ n <3.
A photomask blank selected in advance within a range of 3/67, and adjusting the amounts of oxygen and nitrogen in the atmospheric gas so that the antireflection film has a predetermined reflectance and a predetermined etching rate. It is a manufacturing method of. A tenth means is a method for manufacturing a photomask blank in which a light-shielding film and an anti-reflection film are formed on a transparent substrate, wherein the anti-reflection film is formed from a metal silicon compound in an atmosphere gas containing oxygen and nitrogen. When a sputter target is formed by sputtering, the molar ratio n of metal / silicon in the sputter target is set to 70/30 ≦ n ≦ 40 /
60 is a method for producing a photomask blank, wherein the photomask blank is selected in the range of 60. An eleventh means is to selectively remove an antireflection film and a light-shielding film from the photomask blank, using a photomask blank obtained by the photomask blank manufacturing method according to the ninth or tenth means as a material. And a method for manufacturing a photomask.

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

According to the photomask blank of the present invention, the molar ratio n of metal / silicon in the antireflection film is 90/10 ≦ n <33 /.
Since the thickness is selected within the range of 67, it is possible to maintain a favorable film adhesion and reduce the film thickness without impairing a predetermined antireflection effect. As described above, the antireflection film is further thinned to reduce the difference in the side etching amount, and the etching rate slowed down by oxygen contained therein is increased by containing nitrogen. Thereby, the pattern width difference between the light shielding film pattern and the antireflection film pattern can be suppressed. Also, by suppressing the pattern width difference in this manner, the control of the pattern width of the low-reflection light-shielding film becomes accurate and easy.

In addition, by selecting not only the antireflection film but also the metal / silicon molar ratio n of the light-shielding film in the range of 90/10 ≦ n <33/67, the light-shielding film can be further thinned.
The difference in the side etching amount between the light shielding film and the antireflection film can be further reduced. Further, the adhesive strength between the light shielding film and the antireflection film can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A photomask blank and a method of manufacturing the same according to an embodiment of the present invention, and a photomask and a method of manufacturing the same will be described below with reference to the drawings. First, the photomask blank 10 of the first embodiment will be described with reference to FIG. Photomask blank 1 of this embodiment
0 denotes a first antireflection film 2, a light shielding film 3,
And the second antireflection film 4 are sequentially formed.

First antireflection film 2 and second antireflection film 4
Are composed of a molybdenum silicon compound containing 15 mol% of oxygen, 30 mol% of nitrogen, and 55 mol%, and the molar ratio n of molybdenum / silicon in the molybdenum silicon compound is selected to be 50/50. The thickness of each film is 330 Å for the first anti-reflection film 2 and 490 Å for the second anti-reflection film. The light-shielding film 3 includes the first antireflection film 2 and the second antireflection film 4 and a molybdenum / antireflection film.
The molar ratio n with silicon is equal, the molar ratio n = 50/50
Of molybdenum silicon compound having a thickness of 830 angstroms. The transparent substrate 1 is composed of a main surface on which the first antireflection film 2 is formed and a quartz glass substrate whose opposing surface facing the main surface is precisely polished, and has an outer shape of 5 inches long × 5 inches wide × thickness. 0.09 inches. The optical density of the photomask blank 10 having the above configuration was 3.0, and the reflectance for light having a wavelength of 436 nm was 15% on the front surface and 20% or less on the back surface.

Next, the photomask blank 20 described above is used.
A method of manufacturing the device will be described. First, a quartz glass substrate whose main surface and opposing surface are precisely polished (outer size: 5 inches long x
Transparent substrate 1 consisting of 5 inches wide x 0.09 inches thick)
Is prepared, and the transparent substrate 1 is carried into the chamber of the reactive sputtering apparatus. Next, a mixed gas of argon and nitrous oxide is introduced into the chamber, and in this mixed gas atmosphere, a molybdenum / silicon molar ratio n
The first antireflection film 2 (having a thickness of 330 Å) is formed on the main surface of the transparent substrate 1 by sputtering a sputtering target made of a molybdenum silicon compound of 50 (mol%) / 50 (mol%). The molar ratio of argon and nitrous oxide (N ₂ O) in the mixed gas in the above-mentioned chamber was 20% for nitrous oxide with respect to 80% for argon.
The mixed gas pressure was 1.5 × 10 ⁻³ Torr.

Next, the mixed gas of argon and nitrous oxide in the chamber was evacuated, and argon gas was newly introduced. In the argon gas atmosphere, the mixed gas was used when the first antireflection film was formed. A light-shielding film 3 (830 angstrom thick) was formed on the first antireflection film 2 by sputtering a sputtering target made of the same molybdenum silicon compound. The pressure of the argon gas in the chamber was 2 × 10 ⁻³ Torr. Next, nitrous oxide was again introduced into the chamber, and the atmosphere was changed to a mixed gas (mixed gas pressure: 1.5 × 10 ⁻³ Torr) with a molar ratio of argon / nitrous oxide = 80% / 20%. Then, the second antireflection film 4 (thickness 4) is again sputtered with the same sputtering target made of the same molybdenum silicon compound as used for forming the first antireflection film 2 and the light shielding film 3.
90 Å) was formed on the light shielding film 3.

Now, the above-described photomask blank 10
Referring to FIG. 2, a photomask 20 manufactured by using as a material will be described. The photomask 20 shown in FIG. 2 is patterned by selectively removing the first antireflection film 2, the light-shielding film 3, and the second antireflection film 4 of the photomask 10 shown in FIG. Reflective film pattern 2a, light shielding film pattern 3
a and a low-reflection light-shielding film pattern 5 composed of a second antireflection film pattern 4a.

Next, the photomask 20 shown in FIG.
A method of manufacturing the device will be described. First, a positive photoresist (for example, AZ1350 manufactured by Hoechst) is dropped on the second antireflection film 4 of the photomask blank 10 shown in FIG. 1, and a 5000-Å-thick resist film is formed by spin coating. . Next, the pattern width 2μ
m, selectively exposing the resist film with ultraviolet light through a master mask having a pattern, and then developing the resist film with a predetermined developing solution, thereby dissolving the exposed portion of the resist film to form a pattern. And a resist pattern is formed. Next, the photomask blank 10 with the resist pattern is carried into a chamber of a parallel plate type plasma etching apparatus, and the first antireflection film 2, the light shielding film 3, and the second Each exposed portion of the antireflection film 4 was selectively and sequentially dry-etched. This dry etching is reactive ion etching under the following etching conditions.

* Etching atmosphere gas (CF ₄ ;
80 mol% + O ₂ ; 20 mol%) mixed gas * Etching atmosphere gas pressure: 0.1 Torr * High frequency output: 100 W By this dry etching process, the first layer was sequentially laminated on the transparent substrate 1. An anti-reflection film pattern 2a, a light-shielding film pattern 3a, a second anti-reflection film pattern 4a, and a resist pattern were formed. Finally, the unnecessary resist pattern is removed by contacting with concentrated sulfuric acid, and thereafter, ultrasonic cleaning (ultrasonic output: 600 W, frequency 28 K)
Hz) to obtain a photomask 20 shown in FIG.

Observation of the low-reflection light-shielding film pattern 5 of the photomask 20 obtained by the photomask manufacturing method of this embodiment revealed that the master mask pattern (pattern width 2 μm) was faithfully reproduced, Pattern width (2
μm) were confirmed to have substantially the same rectangular cross section. Also, no pattern defect due to ultrasonic cleaning was observed. This is because the first anti-reflection film 2, the light-shielding film 3,
Each of the second antireflection films 4 is selected to have a molar ratio n of molybdenum / silicon of 50/50 so as to further reduce the thickness without deteriorating the predetermined reflectance and to exhibit the antireflection effect. The side etching rate of the light-shielding film is substantially the same as that of the first and second antireflection films by increasing the etching rate slowed by the oxygen contained in mol% by adding 30 mol% of nitrogen. It depends on having done. The fact that the side etching rates are substantially the same is supported by the fact that the widths of the respective patterns are uniformly reduced even when overetching is performed. As a result, the pattern widths of the first anti-reflection film pattern 2a, the light-shielding film pattern 3a, and the second anti-reflection film pattern 4a could be made substantially uniform. Also, after contacting with concentrated sulfuric acid to remove the resist pattern,
When the antireflection film was examined, 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. Further, according to the present embodiment, the first antireflection film 2, the light shielding film 3, and the second
Since each of the anti-reflection films is made thin, the productivity is also improved.

The molar ratio n of molybdenum / silicon is 33/6
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 embodiment described above. Table 1 shows the thickness and the etching time required for the just etching. In Table 1, the second embodiment in which the molar ratio n between molybdenum and silicon is 85/15, the third embodiment in which the molar ratio n is 67/33, the fourth embodiment in which the molar ratio n is 40/60, and 3
A fifth embodiment of 7/63 is also shown.
Note that these comparative examples and the second to fourth examples are all under the same conditions except that the molar ratio of molybdenum and silicon is changed. 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 higher than that in the stoichiometrically stable molar ratio as in the comparative example. It can be seen that the thicknesses of the first and second antireflection films are thinner in the first to fifth embodiments, which are shifted in the direction in which they are performed. Also, due to the thinning of the first and second anti-reflection films and the function of nitrogen contained in each anti-reflection film, the photomasks of the second and third embodiments are also described in the first embodiment.
The same effect of preventing the pattern cross section from being deteriorated as in the example was obtained. Also in the second to fifth examples, it was confirmed that the antireflection film had good film adhesion and acid resistance as in the first example. Although not listed in Table 1 above, when the molar ratio n 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, film peeling was also observed. The total effect of the above-described anti-reflection coating film adhesion, acid resistance, and thinning effect became remarkable when the molar ratio n was 70/30 to 40 /.
The first, third, and fourth embodiments were within the range of 60.

Further, in the first to fifth embodiments described above, the molar ratio n of molybdenum / silicon is set to 90/10 ≧ n
By selecting a value 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 a step of applying an adhesion promoter to the second antireflection film, which is conventionally required before the resist is applied.

Next, aspects other than the above-described first to fifth embodiments of the present invention will be described. 1st to 5th described above
In the embodiment, the film configuration in which the light shielding film is sandwiched between the first and second antireflection films is used. However, the film configuration may include only one of the first and second antireflection films and the light shielding film. Also, by setting the molar ratio of molybdenum / silicon in the light shielding film to the same value as that of the first antireflection film and the second antireflection film, the first
Although the effect of improving the adhesion to each of the anti-reflection film and the second anti-reflection film is obtained and the effect of preventing the deterioration of the sectional shape of the pattern is promoted, the light-shielding film and the first and second anti-reflection films are not The molar ratios need not necessarily match. Further, the light shielding film is not limited to the metal silicon compound. Furthermore, the preferable range of the mole percent of the metal silicon compound, oxygen, and nitrogen in the antireflection film is 85 mole percent to 20 mole percent, respectively.
Mol%, 5 mol% to 30 mol%, 10 mol% to 50 mol%. Further, in order to obtain a predetermined antireflection effect and to eliminate the difference in etching rate with the light-shielding film, it is preferable to set the molar ratio of oxygen / nitrogen to about 1/2. Further, the antireflection film may contain carbon or the like as appropriate according to the purpose. Further, as the metal of the metal silicon compound, tungsten, tantalum, nickel or the like may be used in addition to molybdenum.

Next, as a gas for oxidizing and nitriding the anti-reflection film, NO, NO ₂ , or a mixed gas of O ₂ and N ₂ may be used in addition to N ₂ O. May be changed according to the desired reflectance and etching rate. Next, the film formation method is not limited to the reactive sputtering method, but may be another sputtering method, a vacuum evaporation method, an ion plating method, or the like. Next, the resist is not limited to the one used in the embodiment, but may be an electron beam or an X-ray resist. As a method for selectively etching the antireflection film and the light-shielding film of the photomask blank, plasma etching, ion milling, ion beam method, or the like may be used in addition to reactive ion etching.

[0028]

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 caused by the difference in etching rate between the light-shielding film and the antireflection film is prevented. be able to. Therefore, the width control of the low-reflection light-shielding film pattern becomes easy and accurate. In addition, it is possible to prevent the loss of the low reflection light shielding film pattern. Further, the light-shielding film is also made of the same kind of metal silicon compound as the anti-reflection film, and the metal / silicon molar ratio n is set to be in the range of 90/10 ≦ n <33/67. The effect of preventing the cross-sectional shape of the low-reflection light-shielding film pattern from deteriorating 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 description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st antireflection film 2a 1st antireflection film pattern 3 Shielding film 3a Shielding film pattern 4 2nd antireflection film 4a 2nd antireflection film pattern 5 Low-reflection light-shielding film pattern 10 Photomask blank 20 Photomask

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03F 1/00-1/16

Claims (11)

(57) [Claims] 1. A transparent substrate and a transparent substrate provided on the transparent substrate
A photomask blank comprising a light-shielding film, wherein the light-shielding film is provided between the light-shielding film and the transparent substrate and on the light-shielding film.
At least one of the metal silicon compound, oxygen, and nitrogen
Contains elementAnti-reflective coatingIs formed, andAnti-reflective coating
Is that the metal silicon compound is 85 mol% to 20 mol%, and the oxygen is
5 mol% to 30 mol%, nitrogen is 10 mol% to 50 mol%
A photomask blank, characterized in that: 2. A transparent substrate, and a transparent substrate provided on the transparent substrate.
A light shielding film, between the light shielding film and the transparent substrate, and the light shielding
An antireflection film provided on at least one of the upper surfaces of the film.
In the photomask blank provided, the antireflection film includes a metal silicon compound, oxygen, and nitrogen.
And the metal / silicon in the metal silicon compoundMolar ratio n
Was selected in the range of 70/30 ≦ n ≦ 40/60.
A photomask blank characterized by the following. 3. A transparent substrate, and a transparent substrate provided on the transparent substrate.
A light-shielding film made of a metal silicon compound;
Between the substrate and the light-shielding film.
Photomask blank with anti-reflective coating
Wherein the anti-reflection film contains a metal silicon compound, oxygen, and nitrogen.
And the metal / silicon in the metal silicon compoundMolar ratio n
Was selected in the range of 90/10 ≦ n <33/67.
A photomask blank characterized by the following. 4. A transparent substrate and a shielding provided on the transparent substrate.
An optical film, between the light shielding film and the transparent substrate, and the light shielding film
An antireflection film provided on at least one of the
In the photomask blank obtained, the anti-reflection film includes a metal silicon compound, oxygen, and nitrogen.
Anti-reflective function by adjusting oxygen content while containing
And the metal / silicon in the metal silicon compound is alsoMolar ratio n
Was selected in the range of 90/10 ≦ n <33/67.
A photomask blank characterized by the following. 5. The reflectance of the antireflection film is 20%.
The photomask blank according to claim 4, wherein: Wherein the metal of said metal silicon compound, according to claim 1, wherein molybdenum, tantalum, tungsten, that is a kind of metal selected from among nickel
The photomask blank according to any one of the above. 7. The light-shielding film is made of the same kind of metal silicon compound as the antireflection film, and the metal / silicon compound has a metal / silicon molar ratio n of 90/10 ≦ n <3.
2. The method according to claim 1 , wherein the value is selected in a range of 3/67.
7. The photomask blank according to any one of Nos. 6 to 6 . 8. A photomask according to claim 1, wherein a light-shielding film and a thin film or an anti-reflection film are selectively removed from the photomask blank according to claim 1. 9. A method for manufacturing a photomask blank in which a light-shielding film and an antireflection film are formed on a transparent substrate, wherein the antireflection film is made of a metal silicon compound in an atmosphere gas containing oxygen and nitrogen. When forming a film by sputtering a sputter target,
The target metal / silicon molar ratio n is set to 90/10 ≦
n is selected in advance in the range of n <33/67, and the amounts of oxygen and nitrogen in the atmosphere gas are adjusted so that the antireflection film has a predetermined reflectance and a predetermined etching rate. Manufacturing method of mask blank. 10. A method of manufacturing a photomask blank for forming a light-shielding film and an antireflection film on a transparent substrate, wherein the antireflection film is made of a metal silicon compound in an atmosphere gas containing oxygen and nitrogen. When forming a film by sputtering a sputter target,
When the target metal / silicon molar ratio n is 70/30 ≦
A method for producing a photomask blank, wherein the photomask blank is selected within a range of n ≦ 40/60. 11. A photomask blank obtained by the method for manufacturing a photomask blank according to claim 9 or 10, wherein an antireflection film and a light-shielding film in the photomask blank are selectively removed. Method of manufacturing a photomask.