KR20080095153A - Method for fabricating in photo mask - Google Patents

Abstract

A method for manufacturing photomasks is provided to improve critical dimension uniformity of phase shift film patterns by compensating for critical dimension of light shield film patterns in the manufacturing of the photomasks. A resist pattern(131) is formed on a transparent substrate(100) including a light shield film. By using the resist pattern as an etch mask, a light shield film pattern(121) is formed. By radiating ultraviolet ray on the resist pattern, the resist pattern is shrunk. By etching a light shield film pattern exposed by the shrunk resist pattern, critical dimension of the light shield film pattern is compensated. Then the resist pattern is removed.

Description

Method for fabricating in photo mask

1 to 8 are cross-sectional views illustrating a method of manufacturing a photomask according to the present invention.

9 and 10 are SEM photographs for comparing the CD of the pattern corrected in the manufacturing method of the photomask according to the present invention.

The present invention relates to a manufacturing method of a photomask, and more particularly, to a method of manufacturing a photomask capable of correcting a pattern CD on a photomask.

Photomasks are used to implement patterns to be formed on wafers during semiconductor device manufacturing. As the degree of integration of semiconductor devices increases, the patterns constituting the semiconductor devices also become finer. For example, in order to transfer a pattern of a critical dimension (CD) smaller than 100 nm to a wafer, a pattern having a CD smaller than 400 nm must be formed on the photomask. Recently, design rules for forming fine patterns require CD 4 nm and MTT 8 nm, and it is difficult to accurately implement the required design rules in the current mass production process. In addition, it is difficult to implement a pattern having a desired CD on the photomask due to various causes in the photomask manufacturing process.

Accordingly, a method of correcting the CD of the pattern during the photomask manufacturing process is used. Referring to the conventional CD correction process, a photoresist pattern is formed using a resist pattern formed through a photolithography process on an transparent substrate on which a phase inversion film is formed, and then the resist pattern is removed. Next, the CD of the light blocking film pattern is measured by using a measuring device, and a region that needs to be corrected is exposed using a separate photo mask, and then the CD of the light blocking film pattern is corrected using various correction methods. Next, a phase inversion film pattern is formed using the corrected light blocking film pattern as an etching mask.

In general, when the final inspection critical dimension (FICD) of the resist pattern is measured through a scanning electron microscope (SEM), the resist pattern may be damaged at every measurement by the secondary electrons generated during the CD measurement. In addition, if the CD measurement of the resist pattern is repeated several times, an accurate CD value cannot be obtained. Thus, the CD of the light blocking film pattern is measured after removing the resist pattern.

Accordingly, since a separate photo mask is used by performing an exposure process and a developing process, process time and manufacturing cost increase. In addition, foreign matters generated during the separate exposure process, development process, and correction process may remain on some surfaces of the phase shift film. Accordingly, when an etching process is performed to form a subsequent phase inversion film pattern, a bridge may be generated between the phase inversion film patterns due to the remaining foreign matter, thereby forming a bad pattern.

An object of the present invention is to provide a method of manufacturing a photomask that can simplify the CD correction of the pattern in the photomask manufacturing process.

In order to achieve the above technical problem, a method of manufacturing a photomask according to the present invention comprises the steps of: forming a resist pattern on a transparent substrate on which a light blocking film is formed; Forming a light blocking layer pattern using the resist pattern as an etching mask; Irradiating the resist pattern with ultraviolet light to reduce the resist pattern; Correcting the line width of the light blocking layer pattern by etching the light blocking layer pattern exposed by the reduced resist pattern; And removing the resist pattern.

Forming a phase inversion layer under the light blocking layer, and after correcting the line width of the light blocking layer pattern, using the corrected line width of the light blocking layer pattern as an etching mask to form a phase inversion layer pattern; Can be.

After removing the resist pattern, the method may further include removing a portion of the light blocking layer pattern by using a mask pattern exposing a portion of the light blocking layer pattern and the phase inversion layer pattern.

The irradiating the resist pattern with ultraviolet rays may further include performing a cleaning process using ozone water on the substrate on which the resist pattern is reduced.

Reducing the resist pattern is preferably performed about four times during the same time while rotating the transparent substrate on which the resist pattern is formed at an angle of 90 °.

Correcting the line width of the pattern of the light blocking film is preferably performed by a dry etching process.

1 to 8 are cross-sectional views illustrating a method of manufacturing a photomask according to the present invention.

Referring to FIG. 1, a phase inversion film 110 and a light blocking film 120 are formed on a transparent substrate 100 such as quartz. The phase inversion film 110 may be formed of a material capable of inverting the phase of transmitted light, for example, a molybdenum silicon nitride (MoSiN) film. The light blocking layer 120 may be formed of a material capable of blocking transmitted light, for example, a chromium (Cr) film.

The first resist pattern 131 is formed on the light blocking layer 120. Specifically, the first resist film is formed on the transparent substrate 100 on which the light blocking film 120 and the phase inversion film 110 are formed, and the first resist film has the same CD as the design rule designed by the electron beam. After the pattern is transferred, the pattern is developed to form the first resist pattern 131.

Referring to FIG. 2, the exposed light blocking layer is etched using the first resist pattern 131 as an etching mask to form the light blocking layer pattern 121.

However, a light blocking film pattern having a CD that is relatively larger than a pattern CD of a design rule designed for various reasons may be formed while performing an exposure process, a developing process, and an etching process.

Accordingly, in the embodiment of the present invention, the CD of the light blocking layer pattern may be corrected by performing the following process.

Referring to FIG. 3, the first resist pattern 131 is irradiated with ultraviolet light for a predetermined time to shrink the resist pattern. In this case, excimer light having a wavelength of 172 nm may be used as ultraviolet rays.

Specifically, after loading the transparent substrate 100 on which the first resist pattern 131 and the light blocking film pattern 121 are formed in the ultraviolet irradiation device, ultraviolet rays are applied to the first resist pattern 131 using an ultraviolet lamp. Irradiate for a predetermined time. Then, the resist pattern 131 is disassembled and removed to expose the edge region of the light blocking layer pattern 121.

In general, when irradiating the resist pattern with ultraviolet rays, since the resist pattern of about 4-5 nm is removed per minute, the irradiation time and conditions of the resist pattern may be arbitrarily adjusted to expose the edge region of the light blocking layer pattern. In addition, in order to improve uniformity of the reduced resist pattern, the transparent substrate on which the resist pattern is formed may be rotated at an angle of 90 °, respectively, for about four times during the same time.

On the other hand, after irradiating the resist pattern with ultraviolet rays for a predetermined time, a cleaning process using ozone water is performed to remove contaminants caused in the ultraviolet irradiation process.

In this way, when the ultraviolet rays of the appropriate wavelength are irradiated to the resist pattern, the resist pattern is reduced over time. In particular, since the width is significantly reduced rather than the height of the resist pattern, the thickness margin of the resist pattern may be secured in a subsequent process.

In addition, since the resist pattern is decomposed and removed by ultraviolet rays, the foreign matters generated can be easily cleaned with ozone water, thereby suppressing a phenomenon in which subsequent phase inversion film patterns are bridged to each other.

Referring to FIG. 4, the CD of the light blocking layer pattern 121 exposed by the reduced first resist pattern 131a is measured through a measuring device such as an SEM.

As such, when the resist pattern is reduced to expose the edge region of the light blocking film pattern, the CD of the light blocking film pattern can be reliably measured without removing the resist pattern. In addition, since the light blocking layer pattern is not damaged by the induced secondary electrons, the measurement error may be reduced even if the CD of the light blocking layer pattern is repeatedly measured. Therefore, since a separate photo mask is not required, the correction process can be simplified.

Referring to FIG. 5, the extracted portion of the light blocking layer pattern 121 is etched to correct the CD of the light blocking layer pattern 121. At this time, the etching process for the CD correction may be performed by dry etching. In this case, since the etch rate of the light blocking layer pattern is about 1 nm per minute, the light blocking layer is removed, so that a correction process may be performed to adjust the etching profile to match the desired CD and Mean to Target (MTT).

Referring to FIG. 6, after removing the first resist pattern (131a of FIG. 5), the phase shift film is selectively etched using the corrected light blocking layer pattern 121 a as an etching mask to form the phase shift film pattern 111. do.

Referring to FIG. 7, a portion of the corrected light blocking layer pattern 121a and the phase inverting layer pattern 111 are formed on the transparent substrate 100 on which the corrected light blocking layer pattern 121a and the phase shifting layer pattern 111 are formed. A second resist pattern 141 to be exposed is formed.

Next, using the second resist pattern 141 as an etching mask, the corrected light blocking layer pattern 121a is selectively etched.

Referring to FIG. 8, the second resist pattern 131a of FIG. 7 is removed. Then, only a phase inversion film pattern 111 is formed in a portion of the transparent substrate 100, and a light blocking film pattern 111 and a phase inversion film pattern 121a are formed in a portion of the transparent substrate 100.

9 and 10 are SEM photographs for comparing the CD of the pattern corrected in the method of manufacturing a photomask according to the present invention. It is an SEM photograph before performing, and FIG. 10 is an SEM photograph after performing ultraviolet irradiation and ozone water washing | cleaning.

When the ultraviolet rays of the appropriate wavelength are irradiated to the resist pattern having a gap 201 between the CD 200 and the pattern shown in FIG. 9, the CD of the resist pattern gradually decreases over time, as shown in FIG. 10. The resist pattern is reduced. In FIG. 10, reference numeral 300 denotes a CD of a reduced resist pattern, and reference numeral 301 denotes a space between the increased patterns as the resist pattern is reduced.

Accordingly, the size of the resist pattern can be adjusted without a separate photo mask, and as a result, the CD of the light blocking film pattern and the phase shift film pattern formed on the photomask can be adjusted.

In some cases, the present invention can be applied to the manufacturing process of the other photomask in addition to the phase inversion mask according to an embodiment of the present invention can simplify the line width correction.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the technical spirit of the present invention. Do.

As described above, according to the manufacturing method of the photomask according to the present invention, the CD uniformity of the phase shift film pattern may be improved by correcting the CD of the light blocking film pattern in the photomask manufacturing step. In addition, the CD of the light blocking film pattern can be measured without removing the first resist pattern.

Accordingly, since a separate correction mask is not required, manufacturing process time and manufacturing cost are saved.

Claims (6)

Forming a resist pattern on the transparent substrate on which the light blocking film is formed; Forming a light blocking layer pattern using the resist pattern as an etching mask; Irradiating the resist pattern with ultraviolet light to reduce the resist pattern; Correcting the line width of the light blocking layer pattern by etching the light blocking layer pattern exposed by the reduced resist pattern; And And removing the resist pattern. The method of claim 1, After forming a phase inversion film under the light blocking film, and correcting the line width of the light blocking film pattern, And forming a phase shift film pattern by using the corrected line width of the light shielding film pattern as an etching mask. The method of claim 2, After removing the resist pattern, And removing a portion of the light blocking layer pattern by using a mask pattern exposing a portion of the light blocking layer pattern and the phase inversion layer pattern. The method of claim 1, Irradiating the resist pattern with ultraviolet light, And performing a cleaning process using ozone water on the substrate on which the resist pattern is reduced. The method of claim 1, Reducing the resist pattern, A method of manufacturing a photomask that is performed about four times during the same time while rotating the transparent substrate on which the resist pattern is formed to each 90 ° angle. The method of claim 1, Compensating the line width of the pattern of the light blocking film is a method of manufacturing a photomask performed by a dry etching process.

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