KR20090112465A - Method for detecting haze of photo mask - Google Patents

Abstract

PURPOSE: A haze detecting method of a photomask is provided to increase the reliability of mask and the productivity of the mask manufacture process. CONSTITUTION: A haze detecting method of a photomask is as follows. The sample mask is prepared(110). In the sample mask, the exposure area which performs the acceleration of the light source is set up(120). The standard value is set up by measuring the reflectivity of the exposure area which is set up(130). The acceleration exposure to the exposure area using a light source and the measurement of the reflectivity of the exposure area are repeatedly performed(150). The changed amount of the reflectivity by the haze is calculated by removing the change amount of the reflectivity by the damage of the pellicle membrane(160).

Description

Method for detecting haze of photo mask

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a photomask, and more particularly, to a method of detecting a haze of a photomask capable of relatively accurately detecting the occurrence of haze.

A photolithography process in a semiconductor manufacturing process involves exposing a photoresist applied on a wafer to a reticle or mask that includes a circuit pattern designed to be implemented on the wafer to expose a desired pattern onto the wafer. It is a process to implement. That is, after the photosensitive agent is applied onto the wafer and the wafer is exposed to the light passing through the reticle containing the pattern information so that only the light in the desired direction passes, the photosensitive agent is exposed only to the desired area according to the pattern contained in the reticle, and thus the desired surface is exposed on the wafer surface. A pattern is formed.

As such, the reticle is a very important factor for implementing circuit patterns on the wafer. Although such a reticle can be manufactured without defects using techniques such as a repair technique, the possibility of contamination of the reticle by manipulation and atmospheric contaminants cannot be completely excluded. Therefore, in order to protect the reticle from contaminants such as particles during the exposure process, a pellicle is used to prevent particles from being attached to the reticle to block or scatter light.

On the other hand, with the higher integration of semiconductor devices, the wavelength of the light source used in the exposure process is gradually shorter and the exposure energy is increasing. Accordingly, the frequency of haze is gradually increasing, and development of a haze detection method as well as a haze control process has become an important problem.

Haze (haze) detection method has a cumulative exposure and inspection of the wafer, but there is a disadvantage that takes time and cost. Therefore, cumulative evaluation is performed using a detection tool called an ArF haze accelerator to detect the presence or absence of a haze or a reticle replacement time. There are two methods for verifying haze generation using an ArF accelerator.

First, it is a method of visual detection using an electron microscope (microscope). In this method, a sample is prepared by setting a scribe area in which a substrate, a phase inversion film and a chromium (Cr) light shielding film are stacked in a patterned photomask to a size of about 5 mm by 5 mm, and irradiating the prepared sample with ArF rays. Proceed with acceleration. After the acceleration process, the exposure area is observed as a dark image using an electron microscope. This method takes less time to check the occurrence of haze, and when observed at a magnification of 400 times, there is an advantage of observing at least about 2㎛ size. On the other hand, since the observer observes with the naked eye, there is a significant difference according to the observer, and it is difficult to grasp the progress of haze diffusion.

Second, a die-to-die inspection is performed using an inspection tool, and a certain region including an exposure region to perform ArF acceleration is set as an inspection region to cause haze to die-to-die. How to check for occurrence. This method has the advantage of being able to detect the haze relatively accurately and easily determine the degree of diffusion of the haze, but has the disadvantage of taking a long inspection time.

Such conventional haze inspection methods have a disadvantage in that accurate detection is difficult or takes a long time for inspection, and thus a more useful haze detection method is required.

The technical problem to be achieved by the present invention is to provide a haze detection method of a photomask that can accurately detect the occurrence of haze in the reticle and does not take a long time to inspect.

In order to achieve the above technical problem, the haze detection method of a photomask according to the present invention comprises the steps of preparing a sample mask, setting an exposure area to accelerate the light source in the sample mask, and setting the reflectance of the set exposure area. Measuring and setting a reference value, repeatedly performing accelerated exposure to the exposure area using a light source, reflectance measurement to the exposure area where the accelerated exposure has been performed, and damage to the pellicle membrane at the measured reflectance And calculating a change amount of the reflectance due to the haze by removing the change amount of the reflectance.

In the preparing of the sample mask, a sample mask for measuring a reflectance and a sample mask for acceleration evaluation may be prepared, respectively.

The said exposure area can set the area | region in which the mask substrate, the phase inversion film, and the light shielding film are laminated | stacked to the magnitude | size of 5 mm x 5 mm.

The amount of change in reflectance due to damage of the pellicle membrane may be calculated by subtracting the reflectance of the initial pellicle membrane from the reflectance of the pellicle membrane measured after the accelerated exposure.

According to the haze detection method of the photomask according to the present invention, it is possible to secure a change in reflectance caused by haze generation, to enable early detection of haze, and to secure accurate data. In addition, by applying this to the actual mask manufacturing process it is possible to increase the productivity of the mask manufacturing process and improve the reliability of the mask.

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 is a flowchart illustrating a haze detection method of a photomask according to the present invention, and FIG. 2 is a view illustrating an exposure area of a mask sample.

1 and 2, samples are first prepared to detect the occurrence of haze (step 110). The sample prepares a mask sample for measuring reflectance and a mask sample for ArF acceleration evaluation, respectively. Both the sample for reflectivity measurement and the sample for ArF acceleration evaluation can be prepared with a phase inversion mask (PSM) or a halftone phase inversion mask (half tone PSM) using an ArF light source.

After the mask sample is prepared, an exposure area for ArF acceleration is set in the prepared sample (step 120). The exposure area 210 of FIG. 2 sets a region in which a mask substrate, a phase inversion film, and a chromium (Cr) light shielding film are stacked, for example, to a size of, for example, about 5 mm x 5 mm. .

After the exposure area is set, a reference value is set by measuring a reflectance at the same position as the set exposure area (step 130). In this case, reflectances of the mask substrate, the phase inversion film, and the chromium (Cr) light shielding film are respectively measured to set reference values.

After setting the reference value, ArF acceleration is performed (step 140). After the ArF light source is set to a constant energy, ArF acceleration is performed on the exposed area of the prepared mask sample.

After the ArF acceleration is performed for a predetermined time, the reflectance of each material of the exposed region where the ArF acceleration is performed is measured (step 150). This ArF acceleration step (step 140) and reflectance measurement step (step 150) are repeated several times. That is, the ArF acceleration and reflectance measurement processes are repeatedly performed for the exposure area at regular intervals.

3 is a graph showing the reflectance of the molybdenum (Mo) film according to the wavelength of the light source. 4 is a graph showing the reflectance of the molybdenum (Mo) film according to the accumulation of exposure energy, and shows the reflectance when the cumulative exposure energy is 10 kJ, 15 kJ, 20 kJ and 35 kJ, respectively.

Next, the amount of change in reflectance due to membrane damage of the pellicle is calculated from the measured reflectance (step 160). Since the membrane thin film is made of a thin light-transmissive thin film, if the ArF acceleration is repeated repeatedly, the membrane thin film also changes. Therefore, a change also occurs in the reflectance of the mask. In order to detect only the change in reflectance caused by the haze, the amount of change in reflectance by the membrane thin film must be calculated. The amount of change in reflectance by the membrane thin film can be obtained by measuring the reflectance of the membrane thin film after the acceleration process and calculating the difference from the initial reflectance.

After calculating the reflectance change due to the membrane thin film, the reflectance change due to the damage of the membrane thin film is removed from the reflectance according to the ArF acceleration, and the reflectance change due to the generation of haze is calculated and applied to the mask manufacturing process. (Step 170).

5 is a graph showing the reflectance of the molybdenum (Mo) film, including the change in reflectance caused by damage to the membrane thin film, Figure 6 is a graph of the molybdenum (Mo) film according to the cumulative energy of the state removed by the damage of the membrane thin film It is a graph showing reflectance. In FIG. 6, it can be seen that haze occurs when the cumulative energy is 20 kJ.

As described above, when the method of the present invention is used, it is possible to secure a change in reflectance due to haze generation, to enable early detection of haze, and to secure accurate data. In addition, by applying this to the actual mask manufacturing process it is possible to increase the productivity of the mask manufacturing process and improve the reliability of the mask.

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.

1 is a flowchart illustrating a haze detection method according to the present invention.

2 illustrates a mask sample and an exposure area.

3 is a graph showing the reflectance of the molybdenum (Mo) film according to the wavelength of the light source.

4 is a graph showing the reflectance of the molybdenum (Mo) film according to the accumulation of the exposure energy.

5 is a graph showing the reflectance of the molybdenum (Mo) film, including the change in reflectance caused by damage to the membrane thin film.

6 is a graph showing the reflectance of the molybdenum (Mo) film according to the cumulative energy in a state in which the effect of damage to the membrane thin film is removed.

Claims (4)

Preparing a sample mask; Setting an exposure area to accelerate the light source in the sample mask; Setting a reference value by measuring a reflectance of the set exposure area; Repeatedly performing accelerated exposure on the exposure area and reflectance measurement on the exposure area on which the accelerated exposure is performed using a light source; And And calculating a change amount of the reflectance caused by the haze by removing the change amount of the reflectance caused by the damage of the pellicle membrane from the measured reflectance. The method of claim 1, In the step of preparing the sample mask, A sample mask for measuring reflectance, A haze detection method of a photomask, characterized by preparing a sample mask for acceleration evaluation, respectively. The method of claim 1, The exposure area is a haze detection method for a photomask, characterized in that the area in which the mask substrate, the phase inversion film and the light shielding film are laminated is set to a size of 5 mm x 5 mm. The method of claim 1, The amount of change in reflectance due to damage of the pellicle membrane, The haze detection method of a photomask, characterized in that it is calculated by subtracting the reflectance of the initial pellicle membrane from the reflectance of the pellicle membrane film measured after the accelerated exposure.

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