KR100930381B1 - Manufacturing method of photo mask - Google Patents

Abstract

A method of manufacturing a photomask capable of implementing a pattern having a desired size relatively accurately and shortening a process time includes forming a light shielding film on a substrate, forming a resist pattern on the light shielding film, and masking the resist pattern Etching the light shielding film, measuring the size (CD) of the light shielding film pattern with an optical pattern measuring device (CD), and obtaining a deviation from the target CD (target CD); and correcting the light shielding film Etching, and removing the resist pattern.

Phase inversion mask, pattern size (CD), optical measurement, correction

Description

Method for fabricating photomask

1 to 3 are views for explaining a method of manufacturing a photomask according to an embodiment of the present invention.

4 is a diagram illustrating a method of correcting a pattern size (CD) of a binary mask.

FIG. 5 is a graph showing reflectance for each wavelength band measured after primary etching of a chromium light shielding film for pattern size (CD) correction using a spectrophotometer.

The present invention relates to a method of manufacturing a photomask, and more particularly to a method of manufacturing a photomask that can be used as an optical pattern line width (CD) measuring equipment to implement a pattern of a desired size relatively accurately.

As the degree of integration of semiconductor devices increases, the size of the pattern to be implemented is also getting smaller. According to the trend of high integration and high density of semiconductor devices, various technologies for forming finer patterns have been developed. Among them, a method of forming a pattern using a phase inversion mask including a phase shifter is used as a method of increasing the resolution using a pattern of a mask.

Such a phase inversion mask is generally performed in-situ in an etching process for a light shielding film made of chromium (Cr) and a phase inversion film made of molybdenum silicon nitride (MoSiN). Therefore, the accuracy of the light blocking film or the phase inversion film pattern implemented on the mask depends on the accuracy and reproducibility of the exposure process, the development process, and the dry etching process using the electron beam. If the problem of accuracy or reproducibility occurs in either of the exposure process and the development process, the size of the pattern (Critical Demension) is greatly affected.

As a method of correcting the CD of the pattern embodied in the mask, a method of realizing the correct CD by setting the conditions of the dry etching process using the CD result of the Development-Inspection (DI) step after the development process is used. . The limitation of this method, however, is the lack of reproducibility when measuring CD at the DI stage. When using a CD SEM, which is a general tool for measuring CD, the resist pattern formed after the development process is damaged by the energy of the electron beam, so the reproducibility of the CD measurement is 3-4 nm or more, Particles generated in the vacuum chamber act as a cause of the pattern defect in the subsequent etching step.

As another method of correcting the CD of the pattern, the chromium (Cr) light shielding film is etched and the resist is removed, followed by etching for the CD correction of the chromium light shielding film based on the CD of the chromium light shielding film measured through SEM. There is a method of etching the phase inversion film (MoSiN) using a chromium light shielding film as a mask. However, in this case, since the sidewall protection effect by the polymer is not achieved, the sidewall profile of the MoSiN pattern is etched using the resist pattern as a mask. There is a problem that tends to be lower than the profile of.

The technical problem to be achieved by the present invention is to provide a method of manufacturing a photomask that can implement a pattern of a desired size relatively accurately, and can shorten the process time.

In order to achieve the above technical problem, a method of manufacturing a photomask according to the present invention includes forming a light shielding film on a substrate, forming a resist pattern on the light shielding film, and etching the light shielding film using the resist pattern as a mask. Forming a light source and measuring a light shielding film pattern size (CD) with an optical pattern size (CD) measuring device having a wavelength in the range of 450 to 1000 nm to obtain a deviation from the target size (CD), and correcting the deviation. And etching the light shielding film pattern.

Before forming the resist pattern, the method may further include forming an anti-reflection film on the light blocking film.

A spectrophotometer may be used as the optical pattern size (CD) measuring device.

In the etching of the light blocking film using the resist pattern as a mask, the light blocking film may be etched less than 10 nm thick in consideration of the subsequent correction process for the pattern size CD.

The method may further include forming a phase inversion film on the substrate before the forming of the light blocking film, and after etching the light blocking film to correct the deviation, etching the phase inversion film.

The etching of the phase inversion film may be performed in-situ in the equipment in which the light shielding film etching for correcting the deviation is performed.

In the step of measuring the size (CD) of the light shielding film pattern, a wavelength of less than 450nm can be blocked using an ultraviolet filter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below.

1 to 3 are views for explaining a method of manufacturing a photomask according to an embodiment of the present invention.

Referring to FIG. 1, a phase inversion film 102 is formed by depositing molybdenum silicon nitride (MoSiN) on the transparent mask substrate 100, and then a light shielding material such as chromium (Cr) is deposited to shield the light shielding film 104. ). An electron beam resist is applied on the light shielding film 104 and then exposed using an electron beam to form a resist pattern 108. An anti-reflection film 106 may be formed below the resist pattern 108 to prevent reflection during an exposure process using an electron beam. Next, the light shielding pattern is formed by dry etching the chromium (Cr) light shielding film 104 using the resist pattern 108 as a mask. Etching of the chromium light shielding film is performed using chlorine gas (Cl ₂ ) plasma. At this time, in consideration of the subsequent CD correction step, the etching is adjusted by adjusting the etching conditions to be about 10 nm under etch compared to the initial target (target) CD.

In the mask after the first etching of the chromium (Cr) light shielding film, the first region and the phase inversion film 102 in which the resist pattern 108, the antireflection film 106, and the chromium (Cr) light shielding film 104 exist are present. ) Is divided into the second region where only. Optical CD measurements are performed on these two areas. Optical CD measurements can be made using a spectrophotometer. Optical CD measurements are made using only the spectrophotometer's reflected light source, and block certain wavelength bands because they cause damage to the resist pattern 108 by Deep Ultra Violet (DUV). To this end, a wavelength of less than 450nm is blocked through an ultraviolet filter and a wavelength of about 450 to 1000nm is used. This is because measurement reproducibility cannot be ensured when resist loss due to the DUV wavelength band occurs, and accuracy and reproducibility within an error range of 2 nm can be ensured even through a wavelength band of 450 nm or more. A detailed description of optical CD measurement using a spectrophotometer will be given later.

After the optical CD measurement is completed in the first etching process on the chromium (Cr) light shielding film 104, the amount of additional etching is compared by comparing the measurement result with the target CD, and the etching conditions are calculated accordingly. . Since the etching amount of the chromium (Cr) shading film is proportional to time, it is possible to set an additional etching time according to the required CD correction amount.

Referring to FIG. 2, the additional etching corresponding to the target CD is performed based on the optical CD measurement result of the first etched chromium (Cr) light shielding film 104. Since the etching amount for the chromium (Cr) light shielding film is proportional to time, the etching time is appropriately adjusted according to the required CD correction amount.

Referring to FIG. 3, the chromium (Cr) light shielding film 104 whose pattern size (CD) is corrected is used as an etching mask to etch the phase inversion film 102. ) It proceeds immediately following the additional etching process for CD correction of light shielding film.

The pattern CD correction method of the phase inversion mask can also be applied to a binary mask.

Referring to FIG. 4, the binary mask is a mask in which a chromium (Cr) light shielding film 204 and a resist 208 for light shielding are uniformly coated on the transparent substrate 200. 206 may be disposed. Even when the pattern size of the chromium (Cr) light shielding film 204 of the binary mask is corrected, the optical CD is measured using a spectrophotometer after the first etching on the chromium light shielding film, and the measured value and the target CD are measured. The size of the chromium light shielding pattern may be corrected by performing additional etching on the chromium (Cr) shielding film according to the deviation from and.

Next, an optical CD measuring method using a spectrophotometer will be described.

Optical CD measurements using spectrophotometers begin with modeling the structure of the film. Refractive index (n) and extinction coefficient (k) of each quartz (Qz) substrate, phase inversion film (MoSiN), light shielding film (Cr), antireflection film, and resist film constituting a phase inversion mask using ArF and KrF as a light source After inputting unique information about, enter the thickness information of each film. The thickness of each film starts from the expected information and after measurement the actual value measured from the measuring device is obtained. After the input of such information on the multilayer film is completed, the pattern to be measured is defined by region. For example, as shown in Figure 1, it is divided into two areas. That is, the first region has a five-layer structure composed of a substrate (Qz) -phase inversion film (MoSiN) -shielding film (Cr) -anti-reflection film-resist, and the second region is a substrate (Qz) -phase inversion film (MoSiN). It is a two-layer structure composed of. The third to fifth layers of the second region may be defined as an air region.

After completing the modeling of the measurement object as described above, CD measurement is performed in earnest. The spot size of the reflective light source is about 40 μm, yielding an average CD for the repetitive pattern present in this spot area. The reflectance for each wavelength which a measurement object has is measured using the wavelength of 450-1000 nm band.

FIG. 5 is a graph showing reflectance for each wavelength band measured after primary etching of a chromium light shielding film for pattern size (CD) correction using a spectrophotometer. Area CD and thickness information of each layer by a scalar calculation method using the measured reflectance and the information of the film for each region input in the initial stage, that is, the refractive index (n) and the extinction coefficient (k) of the film in each region. Is calculated. The optical CD value calculated by this method has a certain linearity, although there is a difference in absolute value due to the difference in measurement method, when compared with the value measured using the CD measurement SEM, it is corrected according to each pattern design The offset setting makes it available for actual CD measurements.

Another advantage of the optical CD measuring equipment is that, unlike the SEM apparatus using the vacuum chamber, since the measurement is performed in the air, the mask can be safely protected from particles or contamination only through environmental management inside and outside the measuring apparatus. Therefore, no additional cleaning process is required, and the etching for the CD correction of the chromium (Cr) film and the subsequent etching of molybdenum silicon nitride (MoSiN) are possible immediately after the measurement.

The present invention is not limited to the above embodiments, and various modifications can be made by those skilled in the art within the technical spirit of the present invention.

As described above, the method for correcting a pattern size (CD) of a photomask according to the present invention is a chromium light-shielding film etched using an optical CD measuring device in a state where a resist pattern exists after the primary etching of the chromium-shielding film is completed. CD is measured, the deviation from the target CD is calculated, the conditions of the etching process for CD correction are set, and then additional etching of the chromium light shielding film for CD correction is performed. Therefore, the resist pattern formed initially may exist until the etching phase of the final phase shift film to protect sidewalls of the phase shift film pattern, thereby realizing a phase shift film pattern that is almost vertical. In addition, since the damage of the resist can be prevented by blocking the wavelength of 450 nm or less by using an ultraviolet filter, it is possible to measure the CD with reproducibility and accuracy.

In addition, since the optical measuring device is measured in the air, the mask can be safely protected from particles or contamination only through environmental management inside and outside the measuring device. Therefore, no additional cleaning process is required, and additional etching for CD correction of the chromium (Cr) light shielding film and subsequent phase inversion film etching are possible immediately after the measurement.

Claims (8)

Forming a light shielding film on the substrate; Forming a resist pattern on the light shielding film; Etching the light blocking film using the resist pattern as a mask to form a light blocking film pattern; Obtaining a deviation from a target CD by measuring the size CD of the light shielding film pattern with an optical pattern size (CD) measuring device having a wavelength in the range of 450 to 1000 nm; And And etching the light shielding pattern in order to correct the deviation. The method of claim 1, Before forming the resist pattern, And forming an anti-reflection film on the light shielding film. The method of claim 1, Method for producing a photomask, characterized in that using a spectrophotometer (CD) as the optical pattern size (CD) measuring equipment. The method of claim 1, Etching the light blocking film using the resist pattern as a mask; A method of manufacturing a photomask, wherein the light shielding film is etched less than a target size (CD) by 10 nm in consideration of a subsequent correction process for the pattern size (CD). The method of claim 1, And forming a phase inversion film on the substrate before forming the light shielding film. And etching the phase inversion film after etching the light shielding film to correct the deviation. The method of claim 5, The etching of the phase inversion film, the method of manufacturing a photomask, characterized in that to proceed in-situ (in-situ) in the equipment that performed the light-shielding film etching to correct the deviation. delete The method of claim 1, wherein in the measuring of the size (CD) of the light shielding film pattern, a wavelength of less than 450 nm is blocked by using an ultraviolet filter.

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