KR20230030873A - An Apparatus For Measuring Optic Inteference Intensity For Blank Phase Shift Mask - Google Patents

Abstract

The present invention relates to an apparatus for measuring an optical interference size of a blank phase shift mask. The apparatus includes: a sample having a phase shift film formed on the lower surface of a quartz substrate; a light source radiating light in a vertical direction to the sample; a light detector located in a lower part of the sample and detecting the light transmitted through the phase shift film; a first beam splitter disposed between the sample and the light source to transmit a part of the light inputted from the light source and input the light into the sample while reflecting the remaining part of the light; a reference device installed to be slightly movable and having a reference quartz substrate into which the light reflected from the first beam splitter is inputted and which transmits the inputted light; a light detector located in the lower part of the sample and detecting the light transmitted through the phase shift film and the light transmitted through a reference surface; a second beam splitter disposed between the sample and the light detector to transmit the light transmitted through the sample and input the light into the light detector, and reflect the light inputted after being transmitted through the reference quartz substrate and input the light into the light detector; and a calculation unit slightly moving the reference quartz substrate and adjusting the reference quartz substrate to extinction interference or constructive interference defined by a reference phase, and then calculating the size of a shifted phase. Therefore, the present invention is capable of improving patterning reliability and productivity.

Description

Optical interference size measuring device of blank phase shift mask {An Apparatus For Measuring Optic Inteference Intensity For Blank Phase Shift Mask}

The present invention relates to an apparatus for measuring the size of optical interference of a phase shift film formed on a photomask used in an exposure process, and more particularly, by measuring interference between light passing through a phase shift film and light passing through a reference quartz, It relates to a technique for measuring the size of interference.

A semiconductor device is manufactured by repeatedly using a photolithography technique in which exposure light is applied to a pattern transfer mask on which a circuit pattern is drawn, and the circuit pattern formed on the mask is transferred onto a semiconductor substrate (semiconductor wafer) via a reduction optical system. .

As circuit patterns of semiconductor devices continue to be miniaturized, the wavelength of exposure light has become mainstream at 193 nm using argon fluoride (ArF) excimer laser light. By employing it, it is possible to finally form a pattern having a sufficiently small dimension compared to the exposure wavelength.

A mask for pattern transfer is manufactured by forming a circuit pattern on a substrate (blank mask) on which an optical film is formed.

As the circuit line width decreases in the semiconductor manufacturing process, light sources with very short wavelengths such as EUV are used. If you want to draw a fine pattern that exceeds the resolution limit, interference occurs due to diffraction and scattering of light. This causes a problem that a distorted image different from the original mask pattern is formed on the wafer.

In order to solve this problem, a phase shift film is formed on the quartz substrate to invert the phase of the light to be exposed by 180 degrees, thereby generating vanishing interference with adjacent transmitted light to clarify the intensity (Contrast) of light at the interface between the exposed part and the non-exposed part. Through this, a technology with increased pattern resolution is being applied.

In order to expose a fine pattern using a phase shift mask, it is important that the phase shift accurately matches the design data. For this reason, in recent years, a defect detection technique in a photomask using the interference effect of light, such as a phase shift mask, has emerged as an important technique.

The combined detection technology of the phase shift mask is a technique using the interference of light, a method using the analysis of the Fourier transform image of the uniformly irradiated phase shift pattern, scattering from the phase shift pattern irradiated in an oblique direction, and only diffracted light on the Fourier transform surface. There are various methods such as a method using diffraction and scattering of light, such as a method of detecting through a spatial filter, and a method using a scanning microscope method.

There are several documents such as Japanese Registered Patent No. 3247736 and Japanese Unexamined Patent Publication No. 2014-199361 as prior literature for inspecting a phase shift mask using light interference.

However, most of these prior literatures are techniques for inspecting a mask in a state where an exposure pattern is formed, and there is almost no technique for effectively inspecting defects of a phase shift film in a blank mask step.

Japanese Patent Registration No. 3247736 “Inspection method of phase shift photomask” Japanese Patent Publication No. 2014-199361 “Inspection device and laser processing device*

An object of the present invention to solve the disadvantages of the background art is to finely move the reference quartz substrate in the absence of a phase shift film to define a reference phase so that it becomes destructive interference or constructive interference, and light transmitted through the phase shift film and the reference quartz substrate An optical interference size measurement device for a blank phase shift mask that enables sample inspection with a simple configuration by measuring the size of the displaced phase after finely moving the reference quartz so that the transmitted light becomes destructive interference or constructive interference defined by the reference phase. is in providing

The apparatus for measuring the size of optical interference of a blank phase shift mask of the present invention includes a sample having a phase shift film formed on the lower surface of a quartz substrate, a light source for irradiating light in a direction perpendicular to the sample, and a light source positioned below the sample and passing through the phase shift film. An optical detector for detecting light, a first beam splitter disposed between the sample and the light source to transmit a part of the light incident from the light source to the sample and reflect the remaining light, and a first beam splitter installed to enable micro-movement A reference device having a reference quartz substrate for transmitting the light reflected from the incident light, a photodetector positioned below the sample and detecting the light transmitted through the phase shift film and the light transmitted through the reference surface, and the sample A second beam splitter disposed between the and the photodetector to transmit the light transmitted through the sample to the photodetector, and to reflect the incident light after passing through the reference quartz substrate to enter the photodetector and reference quartz and a calculation unit for calculating the size of the displaced phase after finely moving the substrate to adjust the destructive interference or constructive interference defined in the reference phase.

At this time, the reference device of the present invention further comprises a first prism for refracting the light reflected from the first beam splitter and incident on the reference plane, and a second prism for refracting the light transmitted from the reference plane and making it incident on the second beam splitter. can include

According to the present invention, the reliability of the phase shift mask can be improved by more accurately detecting the light interference characteristics and defects of the phase shift mask, and as a result, patterning reliability and productivity using the phase shift mask can be improved.

1 is an apparatus for measuring optical interference magnitude of a blank phase shift mask according to an embodiment of the present invention.
2 is a diagram for explaining a method for measuring a reference phase size of a blank phase shift mask according to an embodiment of the present invention;

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

1 is an apparatus for measuring optical interference magnitude of a blank phase shift mask according to an embodiment of the present invention, including a sample 10, a light source 20, an optical detector 30, a first beam splitter 40, a reference device ( 50), a second beam splitter 60 and a calculator 70.

The sample 10 includes a quartz substrate 12 and a phase shift film 14 formed on a lower surface of the quartz substrate 12 .

The light source 20 is for irradiating light in a vertical direction to the sample, for example, EUV (Extreme Ultraviolet) light in a 13.5 nm wavelength range, DUV light in a wavelength range of about 193 nm using argon fluoride (ArF) plasma, or the like. Ultraviolet light of 248 nm and 365 nm wavelengths using krypton fluoride (KrF) plasma or the like can be irradiated.

The photodetector 30 is positioned below the sample to detect light passing through the phase shift film 14 and incident on the photodetector and light passing through the reference surface 50 and incident on the photodetector.

The first beam splitter 40 is disposed between the sample 10 and the light source 20 to transmit a portion of light incident from the light source 10 to the sample 10 and reflect the remaining light.

Although the device configuration is not shown in the drawing, the reference device 50 is installed to be able to move in a horizontal direction, is installed to be able to move in a small way, and the reference device 50 receives light reflected from the first beam splitter and transmits the incident light. A quartz substrate 52 is included.

The second beam splitter 60 is disposed between the sample 10 and the photodetector 30 to transmit the light transmitted through the sample 10 to the photodetector 30, and the reference quartz substrate 52 After passing through, the incident light is reflected and entered into the photodetector 30 .

At this time, the reference device 50 further includes a first prism 54 and a second prism 56 .

The first prism 54 is installed between the first beam splitter 40 and the reference quartz substrate 52, and refracts the light reflected from the first beam splitter 40 to form the reference quartz substrate 52. put into

The second prism 56 is installed on the reference quartz substrate 52 and the second beam splitter 60, and refracts the light transmitted through the reference quartz substrate 52 to pass the light to the second beam splitter 60. put in

The calculation unit 50 calculates the size of the interference caused by the phase shift film by using the interference between the two lights detected by the photodetector 40 .

2 is a diagram for explaining a method for measuring the size of a reference phase of a blank phase shift mask according to an embodiment of the present invention.

First, as shown in FIG. 2, after placing the quartz substrate 12 having no phase shift film under the light source, the reference device 50 is set so that light incident on the photodetector 30 becomes destructive interference or constructive interference. Finely move to define the reference phase.

Subsequently, the light transmitted through the sample 10 and the light transmitted through the reference quartz substrate 52 are incident on the photodetector 30 using the apparatus shown in FIG. 1 .

More specifically, the light generated from the light source 20 is split in the first beam splitter 40, a portion of the light is incident on the sample 10, and the remaining light is reflected and refracted by the first prism 54, and then a reference quartz substrate (52) is entered.

The light incident on the sample 10 passes through the quartz substrate 12 and the phase shift film 14, passes through the second beam splitter 60, and is incident on the photodetector 30.

The light incident on the reference quartz substrate 52 passes through the reference quartz substrate 52, is refracted by the second prism 56, and is incident on the second beam splitter 60. The incident light is reflected internally and finally enters the photodetector 30 .

At this time, the calculation unit 70 slightly moves the reference quartz substrate 50 so that the light incident from the photodetector 30 causes destructive interference or constructive interference defined in the reference phase.

Finally, the calculation unit 70 measures the magnitude of the phase displaced by the phase shift film by measuring the magnitude of the phase that causes destructive interference or constructive interference defined in the reference phase.

The apparatus for measuring the size of optical interference of a blank phase shift mask according to an embodiment of the present invention defines a reference phase that is destructive interference or constructive interference, and measures the difference between light transmitted through the phase shift film of the sample and light transmitted through the reference quartz substrate. It is possible to increase the precision of measuring the phase shift magnitude of the phase shift film with a simple device structure using the interference magnitude.

Although the present invention has been described with respect to the preferred embodiments mentioned above, various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the scope of the appended claims will include such modifications and variations as fall within the scope of this invention.

10: sample 12: quartz substrate
14: phase shift film 20: light source
30: photodetector 40: first beam splitter
50: reference device 60: second beam splitter
70: calculation unit

Claims (2)

A sample having a phase shift film formed on the lower surface of the quartz substrate;
a light source for radiating light in a vertical direction to the sample;
a first beam splitter disposed between the sample and the light source to transmit a portion of the light incident from the light source to the sample and reflect the remaining light;
a reference device having a reference quartz substrate which is installed to enable micro-movement and transmits light reflected from the first beam splitter;
an optical detector positioned below the sample and detecting light transmitted through the phase shift film and light transmitted through the reference quartz substrate;
a second beam splitter disposed between the sample and the photodetector to transmit the light passing through the sample to the photodetector, and to reflect the incident light after passing through the reference surface to be incident on the photodetector; and
Optical interference size measuring device of a blank phase shift mask, characterized in that it comprises a calculator for finely moving the reference quartz substrate to adjust it to be destructive interference or constructive interference defined in the reference phase, and then calculating the size of the displaced phase.
According to claim 1,
The reference device includes a first prism that refracts the light reflected from the first beam splitter and makes it incident to a reference surface;
The optical interference size measuring device of the blank phase shift mask, characterized in that it further comprises a second prism for refracting the light transmitted through the reference plane and entering the second beam splitter.

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