KR19980014177A - Method of defect inspection of phase inversion mask - Google Patents

Abstract

A defect inspection method of a new type of phase shift mask is disclosed. The present invention relates to a method for inspecting defects on a phase inversion mask, the method comprising the steps of: detecting a defect having a wavelength at which the phase inversion mask can be transmitted, in order to accurately detect a defect even at a certain position on the mask, The light of a short wavelength is incident at a predetermined angle from a light source positioned on the rear side of the mask and the light is accurately detected through a detector located on the upper side of the mask using the light scattering effect at the defective portion.

Description

Method of defect inspection of phase inversion mask

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask (hereinafter referred to as PSM) used in a semiconductor manufacturing process, and more particularly, to a defect inspection method of PSM.

In the process of manufacturing a highly integrated semiconductor device, particles may cause a lot of problems.

In particular, particles present on phase inversion masks are considered to be very important for semiconductor fabrication.

Most conventional particle inspection apparatuses use a method of detecting a difference in intensity of transmitted light to inspect defects.

FIG. 1 is a view for explaining a particle inspecting method of a conventional phase inversion mask, in which light irradiated from above the mask is scattered by particles 10 on the surface of the measurement sample 11, By means of detection means 13 in the same direction as the light source to be scanned.

That is, the detection means 13 detects the difference between the intensity of the scanned light scattered by the particle 11 on the surface of the mask 11 and the particle 10 on the mask surface to check presence or absence of the particle 10.

However, such a defect detection method has a problem in that detection failure (false) occurs when the step difference of the surface of the measurement sample is severe.

FIG. 2 is a view for explaining a problem caused by a conventional particle inspection method, wherein FIG. 2A shows a case where roughness of the surface is severe, and FIG. 2B shows an example of a case with a step.

As described above, when there is a roughness or level difference, defects may occur in the backward scattering method using the intensity difference of the above-described scattered light.

Moreover, backward scattering is difficult to use because it is not possible to detect the exact pixel if the level difference is very severe, such as the Levenson type PSM. In addition, the transparent defects present in the shifter region of the Levenson PSM are transparent and thus can not be detected.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made under such circumstances, and it is an object of the present invention to provide a defect inspection method capable of accurately detecting a particle at a certain position on a mask even when the level difference is severe.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view for explaining a particle inspection method of a conventional phase inversion mask. Fig.

FIGS. 2A and 2B are diagrams for explaining a problem caused by a conventional particle inspection method. FIG.

3A and 3B are views for explaining a defect inspection method of the Levenson phase inversion mask according to the present invention.

According to another aspect of the present invention, there is provided a method of inspecting defects on a phase shift mask, the method comprising the steps of: (a) detecting a defect on a phase shift mask, Light of a short wavelength having a wavelength enough to be incident is incident at a predetermined angle from a light source located on the rear side of the mask and is detected through a detector located on the upper side of the mask using the scattering effect of the light at the defective portion.

Preferably, the light source uses any one of KrF and ArF lasers capable of emitting light having a short wavelength shorter than the i-line (365 nm).

More preferably, the detectors are arranged at a plurality of positions at an angle of 5 DEG or more in a direction perpendicular to the incident light.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention is a method of scanning light on the back surface of a mask and detecting light scattered by the defect on the upper surface of the mask.

FIG. 3 is a view for explaining a defect inspection method of a phase inversion mask according to the present invention. In FIG. 3 (A), the quartz portion is etched, and FIG. silicon on glass (SOG top).

3, in order to implement the present invention, it is necessary to use a light source 33 capable of scanning light to such a degree that it can transmit the pattern of the crone portion (Cr) on the mask. In this embodiment, as a preferable example, any one of KrF and ArF which can emit light having a short wavelength shorter than the i-line (365 nm) is used. Alternatively, a method of scanning light of a short wavelength through filtering may be used.

The light source 33 that scans light of the above-described short wavelength is located on the back side of the mask and allows light to be incident at a vertical or specific angle. The incident light passes through the chrome pattern (Cr) of the mask.

At this time, as shown in Fig. 3, the portion free of defects such as particles transmits through the same optical axis with respect to the incident direction. On the other hand, as shown in FIG. 3A, when the defect 30a exists in the quartz (Qz) etching region or when the defect 30b exists in the SOG region as shown in FIG. 3B, scattering occurs By scattering light in all directions, light can be detected at a part away from the optical axis.

Using this principle, the intensity of light scattered by a defect can be checked by arranging the detectors 36, for example, uniformly on top of a mask having an angle of about 5 degrees or more in a direction perpendicular to the incident light .

At this time, the mask may be scanned by continuously moving in one direction, or by rotating at a constant speed, and performing twisting or the like.

Furthermore, by using the linear light source 33 so as to increase the scanning speed, defects can be inspected in a shorter time in a wider area.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

As described above, according to the defect inspection method of the PSM according to the present invention, it is possible to accurately detect defects such as particles even when the position is on a mask or a step between patterns is very severe .

Claims (3)

A method for inspecting defects on a phase inversion mask, In order to accurately detect defects even when the mask is located at a certain position on the mask or when the step between the patterns is very severe, light of a short wavelength having a wavelength enough to transmit the phase inversion mask is irradiated onto the mask at a predetermined angle And detecting the light through a detector located on the upper side of the mask using the scattering effect of the light at the defective portion. The method according to claim 1, Wherein the light source uses any one of KrF and ArF lasers capable of emitting light having a short wavelength shorter than the I-line (365 nm). The method according to claim 1, Wherein the plurality of detectors are arranged in a plurality of locations at an angle of 5 DEG or more in a direction perpendicular to the incident light.