JPH0434436A - Photomask blank and photomask - Google Patents

Abstract

PURPOSE:To prevent the annihilation of the upper layer parts of antireflection film patterns by forming an antireflection film of a chromium/molybdenum alloy contg. oxygen and/or nitrogen. CONSTITUTION:The antireflection film 4 of the photomask blank having a light transparent substrate 2 and a light shielding film 3 and antireflection film 4 formed successively on the main surface of this light transparent substrate 2 is formed of the chromium/molybdenum alloy contg. the oxygen and/or nitrogen. The photomask is formed by selectively etching the light shielding film and the reflecting film of this photomask blank. The antireflection film 4 and antireflection film patterns which are the substrate for resist patterns are constituted of the compsn. having high plasma resistance in such a manner, by which the annihilation of the upper layer part of the antireflection film patters is prevented and a sufficient antireflection effect is exhibited.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a photomask used as an exposure mask in photolithography technology used in the production of ICs, LSIs, etc., and materials for the photomask. Regarding the photomask blank.

[Conventional technology]

Generally, when a resist on a predetermined substrate is fogged using a photomask consisting of a transparent substrate coated with an edge film pattern of chromium or the like, the ultraviolet light used for exposure is applied to the edge film pattern. It is widely known that the reflection on the surface of the photomask causes misalignment of the photomask, and as a result, the pattern accuracy of the substrate to be exposed is reduced. In order to solve these problems, for example, an antireflection film is further formed on a continuous light film formed on a transparent substrate, as in the photomask blank described in Japanese Patent Publication No. 62-32782. Photomask blanks have been proposed.

The photomask blank described in this publication has a high antireflection effect on the surface of the edge film by forming the antireflection film from chromium oxide containing chromium nitride.

By the way, in order to manufacture a photomask from this type of photomask blank, the following known steps are followed.

(1) First, a photomask blank is prepared by sequentially forming an edge-light film and an anti-reflection film on a transparent substrate, a resist solution is dropped onto the anti-reflection film of this photomask blank, and it is centrifuged. A resist film is formed on the surface of the anti-reflection film using force.

(2) Next, the resist film formed in the above step is selectively exposed using a master mask on which a predetermined pattern is formed. During this exposure, direct drawing may be performed using an electron beam.

(3) Next, the resist film of the exposure method is developed with a predetermined developer to form a resist pattern.

(4) Next, the backlight film and antireflection film are etched using the resist pattern as a mask.

(5) Next, the resist pattern used as a mask in the etching process described above is peeled off.

(Problems to be Solved by the Invention) By the way, the above-mentioned resist pattern peeling process involves the following steps:
A wet stripping method in which a processed substrate is immersed in a processing liquid made of an organic solvent, or a plasma gas discharge stripping method in which a reactive gas such as oxygen is caused to be plasma discharged to strip the resist pattern is used. This plasma gas discharge stripping method has advantages over the wet stripping method in terms of cleanliness, safety, and ease of operation, and has attracted much attention in recent years. In particular, when an electron beam resist film is used as the resist, the cleaning quality is remarkable.

However, when manufacturing a photomask from the photomask blank described in the above-mentioned Japanese Patent Publication No. 62-32782, when the resist pattern is removed by the above-mentioned plasma gas discharge peeling method, the anti-reflection film has a composition with poor plasma resistance. The following problems arise due to the fact that the film is composed of a chromium oxide film containing chromium nitride.

Generally, it is extremely difficult to determine the point at which resist pattern stripping is completed, so that excessive plasma gas discharge tends to be performed by mistake even after stripping is completed. When such a situation occurs, the antireflection film underlying the resist pattern is also exposed to the plasma gas discharge, and the upper layer thereof disappears. As a result, the desired effect of the antireflection liquid is reduced, resulting in a problem of deterioration of pattern accuracy when performing transfer using this photomask.

In order to solve the above-mentioned problems, the present invention prevents the disappearance of the upper layer of the anti-reflective film pattern by composing the anti-reflective film and the anti-reflective film pattern that serve as the base of the resist pattern from a composition having high plasma resistance. It is an object of the present invention to provide a photomask blank and a photomask that can fully exhibit an antireflection effect. Furthermore, another object of the present invention is to provide a photomask blank and a photomask from which a resist pattern can be quickly removed by plasma gas discharge.

[Means to solve the problem]

The photomask blank of the present invention includes a light-transmitting substrate, and a backlight film and an anti-reflection film sequentially formed on the main surface of the light-transmitting substrate, wherein the anti-reflection film contains oxygen and It is characterized by being made of a chromium-molybdenum alloy containing/or nitrogen.

Further, the photomask of the present invention is characterized in that the backlight film and the antireflection film are selectively etched in the photomask blank described above.

[Effect]

The photomask blank and photomask of the present invention each have an anti-reflective film and an anti-reflective film pattern formed of oxygen and/or anti-reflective film.
Alternatively, it is made of a chromium-molybdenum alloy containing nitrogen. As a result, the anti-reflective film and the anti-reflective film pattern have high plasma resistance, so when the resist pattern formed on the anti-reflective film pattern is peeled off by plasma gas discharge, the upper layer of the anti-reflective film pattern is Parts can be prevented from disappearing. Also, the threshold power (
Since the power at which the upper layer of the anti-reflection coating starts to disappear) is relatively high, the power supplied to cause the plasma gas discharge can be set to a high value. This makes it possible to shorten the time required to peel off the resist pattern.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of a photomask blank according to the present invention. This photomask blank
A luminescent film 3 made of chromium is deposited on one main surface of a translucent substrate 2 made of quartz glass, and an antireflection film made of a chromium-molybdenum alloy containing oxygen and nitrogen is deposited on the luminescent film 3. 4 are sequentially laminated.

Next, a method for manufacturing this photomask blank 1 will be explained.

First, quartz glass (dimensions:
A translucent substrate 2 having a size of 5 inches x 5 inches x 0.09 inches is prepared. Next, using a chrome target,
By reactive sputtering method, in Ar gas atmosphere (2
Backlit ml!3 is deposited on the transparent substrate 2 at a film thickness of 650 at x 10-” Torr).Next, the weight ratio of chromium to molybdenum (WtX) 87:I 30
Using an alloy target, the anti-reflection film 4 is deposited on the Liaoguang film 3 in a mixed gas atmosphere (1.3 x 10-'' Torr) with a molar ratio of 80% Ar and 20% N0 by the sputtering method described above. : 250 people stacked the layers to produce photomask blank 1. The thus produced photomask blank! had an optical density of 3.0 and a surface reflectance at a wavelength of 436 nm of about 10°596.

Next, a method for manufacturing a photomask from this photomask blank 1 will be explained with reference to the process diagrams of FIGS. 2(a) to 2(d).

(1) First, apply a negative electron beam resist solution (for example, CM manufactured by Tosoh Corporation) onto the antireflection M4 of the photomask blank l.
S-EX<S>) is dropped and spread over the entire surface of the anti-reflection film 40 using a spin code method to form a resist film 6 with a thickness of 3500 mm (see FIG. 2(a)).

(2) Next, the resist film 6 is selectively exposed by drawing an electron beam (beam diameter: 2 μm) in a predetermined trajectory using an electron beam drawing device. After bonding, this resist film 6
Immerse the attached photomask blank 1 in a prescribed developer,
A resist pattern 6b is formed by dissolving the unexposed region of the resist film 6 (see FIG. 2(b)).

(3) Next, the photomask blank 1 with the resist pattern 6b obtained in step (2) is post-baked to solidify the adhesion between the antireflection film 4 and the resist pattern 6b. Thereafter, the side wall 6b1 of the resist pattern 6b is smoothed by applying plasma gas discharge (active gas-oxygen) using a barrel type gas plasma device.

The conditions for plasma gas discharge at this time are as follows. In particular, the value of the discharge high-frequency power is set to a threshold electric crab 5 determined in advance.
300W smaller than 50W (sputter target chromium to molybdenum weight ratio (11%) is 87; 13)
And so.

*Discharge atmosphere...Saturated water vapor (1.0 Torr) flowing in at 600cc/inch *Discharge high frequency power...300W *Discharge time...7 minutes (4) Next, the The resist pattern 6b is etched by immersing the photomask blank l with the resist pattern 6b in an etching solution (for example, a mixed solution of ceric ammonium nitrate, an oxygenable acid, and pure water).
Using b as a mask, selectively apply anti-reflection II 4 and smoker film 3.
are sequentially etched to form an antireflection film pattern 4a and a phosphorescent film pattern 3a (see FIG. 2(c)).

(5) Next, the photomask blank I obtained in the step (4), in which the phosphor film 3 and the antireflection film 4 have been selectively etched, is placed in the barrel-type gas plasma apparatus used in the step (3). The photomask 5 shown in FIG. 2(d) was obtained by reintroducing the resist pattern 6b and separating it by H by applying plasma gas discharge (active gas oxygen).

The plasma gas discharge conditions at this time were selected as follows.

In particular, the discharge high-frequency power was selected to be 500 W so as to be smaller than the threshold power of 550 W as in step (3).

*Discharge atmosphere: Saturated water vapor (0.7 Torr) flowing in at 250cc/win *Discharge high frequency power: 500W *Discharge time: Obtained through steps (1) to (6) of 15 minutes or more When the optical density of the backlit film pattern 3a of the photomask 5 and the reflectance on its surface were measured, they were almost the same as those of the photomask blank 1. From this measurement result, it was confirmed that the upper layer of the backlight film pattern had not disappeared.

By the way, in the above-described embodiment, when forming the anti-reflection M4 film, the weight ratio of chromium to molybdenum (wt 96>) in the sputtering target was set to 87:13, but the present invention is of course limited to this weight ratio. Therefore,
Table 1 below shows - As an example, antireflection films (thickness: 250) were formed by varying the weight ratio of chromium to molybdenum in the range of 100:DO to 75:25, and the antireflection results at each weight ratio were shown. The results of measuring the threshold power of the film and the time required to peel off the resist pattern 6b with a high frequency power of 91% of the threshold power are described below.

As is clear from Table 1 of the clay figures below, as the weight ratio of molybdenum increases, the threshold power also improves, and the iIJ release time becomes shorter. The weight ratio of molybdenum to chromium is preferably in the range of 2 wt% to 2011 t%. This is because when it is less than 2Wt96, the threshold power increases only slightly, whereas when it exceeds 211Ht%, the smoothness of the etching profile of the antireflection film tends to be gradually impaired.

Although the present invention has been described above with reference to Examples, the present invention includes the following modifications.

First, the antireflection film may contain elements suitably selected depending on various purposes, such as carbon in order to adjust the etching rate.

In addition, in the examples, in order to impart an antireflection effect to the antireflection film, No. 20 was used as one of the sputtering conditions.
% in the atmosphere, but the contents of nitrogen and oxygen may be appropriately selected in consideration of etching, reflectance, and etching rate. Further, the gas does not necessarily have to be a mixture of nitrogen and oxygen (or only one of them may be used).

Also, during plasma gas discharge to remove the resist pattern,
Even when a parallel plate type gas plasma device is used instead of the barrel type gas plasma device, the same effects as in the above embodiment can be obtained.

Furthermore, in the step of etching the photonic film, instead of wet etching, etching by plasma gas discharge using CC1 as a reactive gas may be used.

Furthermore, instead of consisting of only chromium, the backlighting material may contain elements such as oxygen, nitrogen, and carbon in order to impart desired characteristics. As the base metal, nickel, tantalum, tungsten, or an alloy thereof can be used instead of chromium.

Furthermore, the resist film is made of photoresist instead of electron beam.
An X-ray sensitive resist may also be used.

Furthermore, instead of quartz glass, the transparent substrate may be made of glass such as soda lime glass, aluminosilicate glass, aluminoborosilicate glass, or the like.

Furthermore, as a film forming method for the backlight film and the antireflection film, a vacuum evaporation method, an ion blating method, etc. may be used instead of sputtering.

〔Effect of the invention〕

According to the photomask blank and photomask of the present invention, since the anti-reflection film and the anti-reflection false pattern have high plasma resistance, when the resist pattern is peeled off in the process of manufacturing a photomask from the photomask blank, , it is possible to prevent the upper layer portion of the anti-reflection film pattern from disappearing due to plasma gas discharge. Therefore, if the photomask of the present invention is used to expose a resist on a predetermined substrate, the original antireflection effect of the antireflection film is not impaired, so that deterioration of resist pattern accuracy can be prevented. Further, since the antireflection film of the present invention has a relatively high threshold power, the time required to remove the resist pattern can be shortened by setting the supplied power that causes plasma gas discharge to a high value.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of an embodiment of the photomask blank of the present invention, and FIG. 2 is a vertical cross-sectional view of the photomask of the present invention.
2(a) to 2(d) are process diagrams for manufacturing a photomask according to an embodiment of the present invention from the photomask blank shown in FIG. 1. 1... Photomask blank, 2... Transparent substrate 3
...Backlight film, 4...Anti-reflection film

Claims (2)

[Claims] (1) A photomask blank comprising a light-transmitting substrate and a light-shielding film and an anti-reflection film sequentially formed on the main surface of the light-transmitting substrate, wherein the anti-reflection film contains oxygen and/or nitrogen. A photomask blank characterized by being made of a chromium-molybdenum alloy. (2) A photomask blank according to claim (1), characterized in that the light shielding film and the antireflection film are selectively etched.