JP3335092B2 - Photomask 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 method for manufacturing a photomask.

[0002]

2. Description of the Related Art Conventionally, quartz is mainly used as a transparent substrate material used for a photomask, and chromium is mainly used as a light shielding film material. Chromium film thickness is about 110n
m and formed by vacuum evaporation or sputtering. There are a wet etching method and a dry etching method for etching the light shielding film.

The wet etching method includes an immersion method and a spray method.
m or more, and the chrome pattern line width becomes smaller than the resist pattern line width. In addition, due to the undercut, foreign matter easily adheres and remains on the chrome pattern edge portion.

In recent years, dry etching methods such as plasma and sputtering have been used. The dry etching method is characterized in that an undercut of 0.05 μm or less is suppressed and a pattern corresponding to a resist image is formed, and is superior to the wet etching method. The photomask manufactured in this manner is cleaned using various methods.

[0005] This cleaning is performed by chemical cleaning (acid, alkali,
Surfactants, etc.) and physical cleaning (scrubbing, showering, ultrasonic waves, etc.), both of which are used in combination depending on the degree of cleaning. In chemical cleaning, cleaning is performed by utilizing the chemical reaction force to foreign substances or the cleaning body itself. However, there is a danger that the light-shielding film will be corroded by immersion in the chemical solution for a long time, and it cannot be used frequently. In the physical cleaning, cleaning is performed using physical energy (pressure, frictional force, ultrasonic waves, etc.) applied to the photomask surface.

However, in the physical cleaning, due to an increase in physical energy and a long cleaning time, defects such as cracks and cracks occur in a portion of the photomask where the adhesive strength between the transparent substrate material and the light shielding film material is weak. Let it.

A technique for solving this problem is disclosed in Japanese Unexamined Patent Publication No.
No. 24445. Hereinafter, this technique will be described with reference to FIGS.

First, a first prior art will be described with reference to FIG. First, as shown in FIG.
A photoresist film 12 is applied thereon with a thickness of 1 μm, and is patterned using an electron beam exposure apparatus. Next, FIG.
As shown in FIG. 2B, the glass substrate 11 is etched to a depth of about 0.1 μm by dry etching using the photoresist film 12 as a mask to form a groove 13.

Next, as shown in FIG. 3C, a chromium film 14 is deposited on the entire surface to a thickness of 0.15 μm by a sputtering method or the like. Next, as shown in FIG. 3D, the photoresist film 12 is peeled off from the glass substrate 11, and at the same time, the excess chromium film 14 is removed. Further, the chromium film 14 is etched so that the surface of the chromium film 14 and the surface of the glass substrate 11 are almost equal to each other, thereby completing a mask having no steps.

Next, a second prior art will be described with reference to FIG. First, as shown in FIG.
A photoresist film 12 is applied thereon with a thickness of 1 μm, and is patterned using an electron beam exposure apparatus. Next, using the photoresist film 12 as a mask, the glass substrate 11 is etched by a depth of about 0.1 μm by a dry etching method.
Form 3

Next, as shown in FIG. 4B, after the photoresist film 12 is peeled off, a chromium film 14 is deposited on the entire surface to a thickness of 0.15 μm by a sputtering method or the like. next,
As shown in FIG. 4C, the silica film 1 is formed on the chromium film 14.
5 is formed by a coating method to smooth the surface. Next, the silica film 15 and the chromium film 14 are etched back until the upper surface of the glass substrate 11 is completely exposed,
A stepless mask having the pattern of the chromium film 14 is completed.

[0012]

However, with the above-mentioned prior art, the substrate surface cannot be made completely flat.
That is, in the first prior art, when a sputtering method is used when depositing a chromium film, the chromium film is formed in the central portion of the chromium film pattern because the chromium film is easily deposited in the vertical direction and difficult to be deposited in the lateral direction. growing.

In the second prior art, the flattening by application of a silica film or the like can be performed to some extent, but the thickness of the chrome film near the center of the groove is reduced due to the influence of the concave portion of the base. . When this is etched back, the whole is uniformly etched, so that the center portion of the chromium film pattern becomes thinner than the peripheral portion as shown in FIG. FIG. 5 is a partially enlarged view of FIG.

Therefore, the transmittance of the light shielding film cannot be made uniform on the surface of the photomask substrate.

Further, as shown in FIG. 2 showing the dependency of the transmittance at each exposure wavelength on the chromium film thickness, the transmittance changes with the change in the thickness of the chromium which is the light shielding film. In particular, when the chromium film thickness is 100 nm or less, the change in transmittance is remarkable. For example, when KrF excimer light is used as the exposure light source, the chromium film thickness is in the range of 60 to 70 nm. Otherwise, the transmittance of the light-shielding film cannot be made uniform, and the contrast deteriorates.

In the case of a halftone mask using a translucent film instead of a light-shielding film, variations in the translucent film affect not only the transmittance but also the phase difference. Note that the thickness d for inverting the phase of the halftone film (semi-transparent film) by 180 degrees is determined by the following equation (1).

D = λ / 2 (n−1) (1) where λ = exposure wavelength (248 n for KrF excimer)
m), n = refractive index (2 for MoSi).

[0018]

According to the present invention, there is provided a method for manufacturing a photomask having a transparent substrate and a pattern comprising a light-shielding film formed on the transparent substrate. Selectively etching a portion to form a groove, depositing a light-shielding film on the entire surface of the transparent substrate in which the groove is formed, and removing the light-shielding film by chemical mechanical treatment until the light-shielding film surface becomes flat. The method includes a step of polishing by a polishing method, and a step of leaving a light-shielding film only inside the groove by etching back until the surface of the transparent substrate is exposed.

Further, characterized by using a semi-transparent film in place of the upper Symbol shielding film, a method for producing a full Otomasuku.

With the above structure, the surface of the photomask can be flattened, foreign matter remains at the edge of the pattern of the light-shielding film and the translucent film, the generation rate of defects is reduced, and the ability to remove foreign matter is greatly improved. Can be simplified. Further, by making the thickness of the light shielding portion uniform by using CMP, the transmittance of the light shielding film and the translucent film is made uniform,
In the case of a halftone mask, the phase difference can be made uniform.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, based on one embodiment,
The present invention will be described in detail.

FIG. 1 shows a photomask manufacturing process according to an embodiment of the present invention. In FIG. 1, 1 is a transparent substrate, 2
Denotes a chromium film, 3 denotes an EB resist, 4 denotes a groove, and 5 denotes a light shielding film.

Hereinafter, a manufacturing process of a photomask according to one embodiment of the present invention will be described with reference to FIG.

First, a chromium film 2 having a thickness of 60 to 70 nm is formed on a transparent substrate 1 by sputtering, vacuum evaporation, or the like.
A B resist film 3 is applied in a thickness of about 300 to 350 nm (FIG. 1)
(A)). It should be noted that the chromium film 2 must be able to obtain a sufficient selectivity when the transparent substrate 1 is etched. The EB resist film 3 includes a chrome film 2
Must be excellent in etching resistance at the time of etching. In the drawing process, the transparent area is not drawn,
The light-shielding region is set to a necessary charge amount capable of completely removing the EB resist film 3, and is irradiated with an electron beam.

The EB resist film 3 is classified into a negative type and a positive type. FIG. 1 shows a case where a positive type EB resist is used. The portion which remains as a resist pattern and is exposed to the electron beam is dissolved in a developing solution, and the chromium film 2 is partially exposed (FIG. 1B).

After the development, the exposed chromium film 2 is dry-etched. The EB resist film 3 functions as a protective film against etching, and only the portion of the chrome film 2 not covered with the resist is removed, and the transparent substrate 1 is partially exposed (FIG. 1C). When CH ₂ Cl ₂ and O ₂ are used as the dry etching gas for the chromium film 2, the dry etching resistance of the EB resist film 3 is sufficient. Also, when wet etching is used, the undercut is as large as 0.1 μm or more, so that high-precision patterning cannot be performed during the next etching of the transparent substrate 1, which is not preferable.

Next, after the chromium film 2 is etched,
The entire surface of the B resist film 3 is removed (FIG. 1D). For removing the resist, a chemical solution such as acetone or sulfuric acid-hydrogen peroxide is used.
In this case, the resistance of the transparent substrate 1 and the chromium film 2 to the chemical must be sufficient.

Next, after removing the EB resist film 3, the transparent substrate 1 is dry-etched using the chromium film 2 as a mask. In this case, when the transparent substrate 1 is etched using the resist as a mask, there is a problem that sufficient dimensional accuracy of the light-shielding film cannot be obtained due to insufficient dry etching resistance. Therefore, by using the chromium film 2 as a protective film against etching, the surface of the transparent substrate 1 not covered by the chromium film 2 is removed (FIG. 1E).

When quartz is used for the transparent substrate 1 and CF ₄ and O ₂ are used as the dry etching gas, the chromium film 2
Has sufficient dry etching resistance. The etching depth of the transparent substrate 1 needs to be 60 nm or more when chromium is used for the light shielding film 5. In the case of chromium, the film thickness is 60
This is because the transmittance of KrF excimer light at 0.5 nm or more is 0.5% or less, and light shielding properties can be obtained. Also,
The etching depth can be controlled by the etching time. After etching the transparent substrate 1, the entire surface of the chromium film 2 is removed by etching (FIG. 1F).

When quartz is used for the transparent substrate 1 and ceric ammonium nitrate is used for the etchant, the selectivity with the transparent substrate 1 is sufficient, and the transparent substrate 1 does not deteriorate at all. After removing the chromium film 2, a light-shielding film 5 is formed (FIG. 1G).

When chromium is used for the light-shielding film 5 and quartz is used for the transparent substrate 1 and the light-shielding film 5 is formed by a sputtering method, sufficient adhesion to the transparent substrate 1 must be obtained. In this case, the amount of chromium embedded in the quartz substrate is at least 60 so that sufficient light-shielding properties can be obtained.
７０70 nm or more is required. For example, if the depth of the groove is 60-
In the case of 70 nm, after forming the light shielding film 5 (150 nm), the light shielding film 5 is flattened (FIG. 1H). Using chromium for the light shielding film 5 and quartz for the transparent substrate 1, chemical mechanical polishing (CMP: chemical mechanical polishing)
The thickness of the chromium is reduced to 110 to 120 n by flattening the surface of the light-shielding film by an al polishing method.
m. Chromium film thickness to obtain light-shielding property is 60 nm
However, in order to prevent the occurrence of scratches by the CMP method, a preliminary film thickness of 50 nm or more is required. After the light-shielding film 5 is flattened, the thickness of the light-shielding film 5 is adjusted by dry etching (etching 50 nm to make the final film thickness 60 to 70 nm) (FIG. 1 (i)).

When chromium is used for the light-shielding film 5, quartz is used for the transparent substrate 1, and CH ₂ Cl ₂ and O ₂ are used for the dry etching gas, the etching rate of chrome is higher than that of quartz. The amount of etching must be adjusted. The chromium etching amount is controlled by the pressure of 33.
The etching is performed by adjusting the etching time at 2 Pa, a low RF power of about 50 W, a flow rate of CH ₂ Cl ₂ of 25 SCCM, and a flow rate of O ₂ of 75 SCCM. By performing etching under these conditions, the etching rate of quartz can be suppressed to 1/20 or less of the etching rate of chromium, and the etching amount of quartz can be virtually ignored.

Through the above steps, the light-shielding film pattern is buried in the transparent substrate of the photomask, and the damage of the light-shielding film pattern due to cleaning is reduced. As a result, the photomask can be manufactured stably. By flattening the mask surface, it is possible to stably manufacture a photomask capable of eliminating foreign matter remaining at the edge of the light-shielding film pattern and simplifying the removal of minute foreign matter.

In this embodiment, the case where a chromium film is used as the light-shielding film has been described. However, a half-tone mask using a translucent film instead of the light-shielding film can be manufactured by the same manufacturing process. An oxynitride film such as MoSiON or CrON can be used as the translucent (halftone) film. For example, when an i-line is used as a light source, a necessary transmittance is about 6 to 8% and a phase shift effect is obtained. For this purpose, a thickness of 165 nm is required, so that the depth of the groove formed in the transparent substrate is also required to be about 165 nm. Also,
When a KrF excimer laser is used as a light source, a required transmittance is about 5% and a thickness of 110 nm is required to obtain a phase shift effect.
nm.

[0035]

As described above in detail, by using the present invention, a light-shielding film pattern is buried in a transparent substrate of a mask and the surface of the mask is flattened to thereby form a light-shielding film pattern by cleaning. Can be reduced, and as a result, mask defects can be prevented. In addition, the foreign matter remains at the light shielding film and the translucent film pattern edge portion, the defect occurrence rate is reduced, and
Removal of foreign matter can be simplified, the number of cleaning and line difference steps that currently occupy half of the photomask manufacturing process can be reduced, and mass productivity can be dramatically improved. Also,
Since the light-shielding film and the translucent film are uniform in film thickness, the transmittance can be made uniform, so that the variation in contrast due to the variation in the transmittance can be drastically reduced. Further, in the case of a halftone mask using a translucent film, it is possible to suppress the phase difference variation.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a photomask according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a first conventional photomask.

FIG. 3 is a manufacturing process diagram of a second conventional photomask.

FIG. 4 is a diagram showing the dependency of transmittance on the chromium film thickness at each exposure wavelength.

FIG. 5 is a partially enlarged view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Chromium film 3 EB resist 4 Groove 5 Light shielding film

Claims (2)

(57) [Claims] 1. A method of manufacturing a photomask having a transparent substrate and a pattern comprising a light-shielding film formed on the transparent substrate, wherein a portion of the transparent substrate is selectively etched to form a groove.
After that, a light shielding film is formed on the entire surface of the transparent substrate on which the groove is formed.
And the product, then, is it a flat light shielding film surface by chemical mechanical polishing
After polishing the light shielding film to that, by etching back until the surface of the transparent substrate is exposed, and wherein the score residual light-shielding film only inside the trench, the manufacturing method of the photomask. 2. The method according to claim 1, wherein a translucent film is used instead of the light-shielding film.