KR100888933B1 - Apparatus and method for measuring hazes of photomask surface using euv - Google Patents

Abstract

An EUV haze measurement apparatus and a method of measurement are provided to analyze the cause of generation of the haze defect by forming the haze which is the growing deformity on the surface of photomask in a short time. An EUV haze measurement apparatus(100) generates the haze which is the growing deformity on the surface of the photomask(M) and finds the cause of haze generation. The measurement system comprises an optical source section(110), a lighting system(120) and a haze measurement part(130). The optical source section provides the EUV beam. The EUV beam injected from the optical source section is induced to the photomask by the lighting system. The photomask is mounted on the haze measurement part. The haze measurement part generates the haze on the photomask, and detects the generation of haze and analyzes the cause of haze generation.

Description

Y-V haze measuring apparatus and its measuring method {Apparatus and method for measuring hazes of photomask surface using EUV}

The present invention relates to an apparatus and method for finding the cause of haze by generating haze, a growth defect, on a surface of a photomask, and more particularly, extreme ultraviolet (hereinafter, referred to as EUV). A light source unit for providing a beam, an illumination system for guiding an EUV beam emitted from the light source unit to a photomask, and a chamber in which the photomask is mounted, wherein a haze is generated on the surface of the photomask in real time. The present invention relates to an EUV haze measuring device comprising a haze measuring unit having an EUV detector for detecting the same, and a measuring method thereof.

Recently, as the integration degree of semiconductor devices increases, a higher resolution is required for a circuit pattern formed on a wafer. For this purpose, a wavelength of an exposure source used in a photolithography process for forming a pattern becomes shorter.

In general, photolithography is a photolithography process that is widely used to form a desired pattern on a substrate such as a silicon wafer or glass by using a light sensitive photoresist (abbreviated as PR). As one of these processes, it is regarded as one of the indispensable steps in semiconductor manufacturing.

The line width of the pattern that can be realized by the photolithography process is largely determined by the wavelength of the light source used for ultraviolet exposure, and 0.3 in the case of using a G-line (435 nm) or I-line (365 nm) light source. While it is difficult to obtain a pattern having a fine line width of less than or equal to μm, when using a light source having a KrF (248 nm) wavelength or an ArF (193 nm) wavelength, it is possible to form a pattern having a fine line width of 0.15 μm or less.

However, when the exposure process is performed using a KrF or ArF wavelength light source, since the micro-contaminants adsorbed to the microcircuit pattern on the photomask surface may not reproduce the shape of the desired microcircuit pattern as it is. When using the reticle (reticle) to proceed with the etching process there was a problem that a large amount of pattern defects occur.

Contaminants adsorbed on the microcircuit pattern on the photomask surface are photochemically activated by using a light source (ultraviolet rays) irradiated during the photolithography process after nanometer (nm) -sized molecular contaminants remain or adsorb on the mask surface. The problem is serious because it is known to grow through the reaction, and because it grows over several months, it is not detected in the initial photomask inspection process.

Such contaminants are generally classified as haze defects. When haze defects occur on the surface of a photomask, it is difficult to detect them, and a large accident occurs in which the same pattern defect occurs on a large number of wafers.

In particular, serious haze defects have already been reported when using deep ultra-violet (DUV) beams from ArF excimer lasers, and extreme ultraviolet lithography, the next-generation technology to achieve 30 nm line width, has an extreme EUV near 13 nm. With the use of Ultra-Violet beams, very serious haze generation is a concern.

Therefore, there is a need to artificially generate haze defects in the photomask, to identify the cause thereof, and to find solutions. For example, there is a method of performing a photolithography process in a vacuum state, but since this is very difficult in reality, it is necessary to provide quantified exposure energy, ions, temperature, and humidity to the photomask.

To this end, the haze measuring apparatus has been proposed to analyze the cause of the haze in a short time by using the ArF excimer laser as a light source, but the haze by the EUV beam is applied to the conventional haze measuring apparatus by applying the EUV light source as it is. There was a problem that it was unsuitable to measure and analyze the cause of haze generation accordingly. This is why EUV beams are absorbed well by almost all materials, including air, so that even if EUV light sources are used in conventional haze measuring devices, EUV beams are almost lost before they reach the photomask. This is because it is difficult to prepare a projection optical system such as a beam splitter that is separated by a detector.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, so that haze, which is a growth defect generated by repeating photolithography processes on a photomask surface using an EUV beam, is generated in a short time. At the same time, an object of the present invention is to provide an EUV haze measuring apparatus capable of quantitatively analyzing the cause of generation of haze defects and a method of measuring the same.

As a technical configuration for achieving the above object, the EUV haze measuring device according to the present invention artificially generates a haze that is a growth defect on the surface of the photomask to find the cause of the haze, the EUV haze A light source unit including an emitting EUV light source and a condensing optical system for focusing the EUV beam, an optical integrator for equalizing the intensity of the EUV beam and an EUV beam uniformized by the optical integrator, and determining the size of the EUV beam An illumination system for inducing an EUV beam emitted from the light source unit to a photomask having a parabolic mirror, and a chamber in which the photomask is mounted, EUV for detecting in real time whether haze is generated on the surface of the photomask. A sensor to measure the temperature and humidity of the detector and the chamber, and a control to control the amount of injected gas It made a part having jidoe haze measurement, characterized in that the traveling path of the EUV beam from the EUV detector from the EUV light source is one to be placed under vacuum.

The EUV light source is characterized in that the plasma light source or SR (syntron radiation light) light source.

Here, the plasma light source is characterized in that the laser produced plasma (LPP) or discharge produced plasma (DPP).

The condensing optical system includes a condensing mirror comprising a rotating ellipsoid having a first focus on the EUV light source, a spherical auxiliary condensing mirror which reflects the EUV beam not reflected by the condensing mirror, and the condensing mirror. 2 is characterized by consisting of an aperture that shields the incoming light beam out of focus.

The EUV detector is characterized by consisting of a charge coupled device (CCD).

The haze measurement unit may further include a reflection optical system that reflects the EUV beam reflected by the photomask to the EUV detector.

In this case, the reflective optical system is characterized in that the EUV reflector.

In addition, as a technical configuration for achieving the above object, the EUV haze measurement method according to the present invention in the method of artificially generating a haze that is a growth defect on the surface of the photomask to find the cause of the haze, to emit the EUV beam A first step, a second step of focusing the EUV beam via the condensing optical system, a third step of uniformly forming the intensity of the EUV beam via the optical integrator, and an EUV to reach the photomask surface via a parabolic mirror A fourth step of focusing the beam and determining the size of the EUV beam, and a fifth step of determining whether the haze is generated by measuring the EUV beam reflected by the photomask with the EUV detector, wherein the first to second It is characterized in that the traveling path of the five-step EUV beam is placed under vacuum.

In addition, the EUV haze measuring method according to the present invention further comprises a sixth step of quantitatively measuring the amount of temperature, humidity, injection gas in the chamber to analyze the exact cause of the haze by the EUV beam; do.

In the EUV haze measuring method according to the present invention, the fifth step includes determining an image size, an image storage interval, a storage interval and a storage time of the EUV detector after initializing the equipment, and a constant interval after the laser is operated. And storing the values of the image and energy, and quantitatively measuring whether the haze is generated and the energy value.

As described above, in the EUV haze measuring apparatus and the measuring method according to the present invention, in order to artificially generate haze in the photomask in order to analyze the cause of the haze generation by the EUV beam, the EUV haze measuring path is under vacuum. By measuring the EUV beam reflected from the photomask by placing it, the amount of loss of the EUV beam on the traveling path to the photomask and the EUV detector can be significantly reduced, producing haze by the EUV beam in a few hours and immediately detecting it. Of course, there is an effect that can quantitatively analyze the cause of the haze by controlling the environment inside the chamber in which the photomask is mounted.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention in more detail as follows.

1 is a view schematically showing an EUV haze measuring apparatus according to the present invention. In the drawing, the direction of travel is shown based on the optical axis OA of the EUV beam, but the direction of the light beam is shown in detail only in the light source unit to help understand the description.

As shown in the figure, the EUV (EUV) extreme haze (HAV) measuring apparatus 100 according to the present invention generates a haze that is a growth defect on the surface of the photomask (M) to find the cause of the haze generation. A light source unit 110 for providing an EUV beam, an illumination system 120 for guiding the EUV beam emitted from the light source unit 110 to the photomask M, and a photo for artificially generating haze therein. The mask M is mounted and classified into a haze measuring unit 130 for detecting whether the haze is generated and analyzing the cause of the haze.

Here, it should be noted that the light source unit 110, the illumination system 120, and the haze measurement unit 130 have a traveling path of the EUV beam under the vacuum inside each of them. This is to irradiate a larger amount of EUV beams to the photomask M by minimizing the amount of EUV beams lost on the traveling path since the EUV beams are well absorbed by most materials including air.

The light source unit 110 includes an EUV light source 113 for emitting an EUV beam and a condensing optical system 114 for focusing the EUV beam emitted radially from the EUV light source 113.

For example, the light converging optical system 114 may collect a spheroid condensing mirror 114a having a first focus on the EUV light source 113 and an EUV beam not reflected by the condensing mirror 114a. A second focusing mirror 114b of a spherical surface to be reflected by the condensing mirror 114a, and a second focal point of the condensing mirror 114a, which is installed perpendicular to the optical axis OA of the EUV beam focused by the condensing mirror 114a The diaphragm 114c is formed of an aperture 114c that shields the luminous flux incident directly from the EUV light source 113. In addition, the illumination system 120 is provided downstream of the diaphragm 114c to introduce a luminous flux emitted from the light source image OF.

Here, the EUV light source 113 is currently proposed as a light source for supplying an EUV beam, and three types of light sources shown below are used.

(1) a light source for supplying SR (Synchrotron Radiation);

(2) a laser-produced plasma light source (LPP) for condensing laser light on a target and converting the target into plasma to obtain EUV light;

(3) A DPP (Discharge Produced Plasma) light source that applies a voltage between the electrodes on the electrode made of the target material or between the electrodes, and converts the target material into plasma to obtain EUV light.

Here, the target of the LPP light source may be formed such that a high pressure gas, for example, made of xenon (Xe) is injected from the nozzle at the first focal point of the condensing mirror 114a. Such a gas target is plasma-charged by generating energy by laser light collected by the lens 112 to generate an EUV beam. On the other hand, the gas which has emitted light is sucked through the recovery means and guided to the outside.

Hereinafter, the LPP light source and the DPP light source will be collectively referred to as a plasma light source, and in the following description, an example in which an LPP type light source is applied as the plasma light source will be described.

In the plasma light source 113 disposed at the first focal point of the condensing mirror 114a, non-EUV, which is light generated from the laser light source 111, is focused by the lens 112 and then the condensing mirror 114a. The light is collected through a through hole (not shown).

Here, the laser light source 111 is preferably disposed at a slight inclination with respect to the optical axis OA such that a laser, that is, a non-EUV, does not directly enter the second focal point of the condensing mirror 114a.

A portion of the EUV beam isotropically emitted from the plasma light source 113 is reflected by the condensing mirror 114a to form a light source image OF at a second focal point of the condensing mirror 114a, and the other part is After being reflected by the auxiliary condensing mirror 114b, it is again reflected by the condensing mirror 114a and imaged at the same position as the light source image OF.

The illumination system 120 is to guide the EUV beam emitted from the light source unit 110 to the photomask M, and an optical integrator for uniformly forming the intensity of the EUV beam provided from the light source unit 110. the intensity of energy per unit area of the EUV beam to reach the photomask M by focusing the integrator 121 and the EUV beam uniformized by the optical integrator 121 and determining the size of the EUV beam. It is desirable to include a parabolic mirror 122.

In the drawing, the optical integrator 121 is shown as a reflection type, but the optical integrator 121 is not limited thereto but may be applied to any type of optical integrator within a range capable of uniformly forming the intensity of the EUV beam. Of course.

In addition, the illumination system 120 is a light source image (OF) of the light source unit 110 therein through the integrator 121 and the parabolic mirror 122 to the target point in the haze measuring unit 130 therein. It is preferable to have a plurality of mirrors including a collimator as an auxiliary device for closely connecting the EUV beams.

Here, the collimator is preferably arranged so that the EUV beam provided from the light source image (OF) reaches before passing through the mirror and integrator 121 and the parabolic mirror 122 as the auxiliary device.

On the other hand, the number of mirrors used as the auxiliary device is not limited to one as shown in the figure, of course, can be adjusted as needed.

The haze measurement unit 130 is a chamber in which the photomask M is mounted, as well as the EUV detector 131 for detecting in real time whether haze is generated on the surface of the photomask M, as well as the temperature inside the chamber, Sensors 134 and 135 for measuring the humidity, respectively, and a controller 136 for controlling the amount of injected gas.

The haze measurement unit 130 continuously exposes the photomask M with the EUV beam emitted from the illumination system 120 when the stage 133 having the photomask M fixed therein is moved and positioned. Let's do it.

Here, the EUV detector 131 may be configured as a charge-coupled device (CCD) as an example. In this case, unless the CCD can detect the EUV beam directly, the CCD further includes an element for converting the EUV beam into visible light. In addition, it is obvious that the EUV detector 131 may be replaced with a detection system different from the CCD as long as it conforms to a principle capable of measuring haze.

In addition, the haze measuring unit 130 may further include a reflection optical system 132 reflecting the EUV beam reflected by the photomask M to the EUV detector 131. In this case, the reflective optical system 132 may be configured as, for example, an EUV reflector capable of reflecting an EUV beam.

2 is a flowchart illustrating an operation procedure of the EUV haze measurement apparatus according to the present invention.

As shown in the figure, the EUV haze measuring method according to the present invention is a method for measuring by generating a haze that is a growth defect on the surface of the photomask (M), the first step (S101) for emitting the EUV beam and condensing A second step S102 of focusing the EUV beam via the optical system 114, a third step S103 of uniformly forming the intensity of the EUV beam via the optical integrator 121, and a parabolic mirror 122 A fourth step S104 of focusing the EUV beam to reach the surface of the photomask M and determining the size of the EUV beam, and measuring the EUV beam reflected from the photomask M with the EUV detector 131. A fifth step (S105) of determining whether the haze is generated, so that the traveling path of the EUV beam of the first to fifth steps (S101 to S105) is placed under vacuum.

The fifth step (S105) is a step of determining the image size, the image storage interval, the storage interval and the storage time of the EUV detector 131 after initializing the equipment, and the image and energy at a constant interval after the laser operation Storing the values, and quantitatively measuring the generation of the haze and the energy value.

In addition, the EUV haze measuring method according to the present invention further comprises a sixth step (S106) of quantitatively measuring the temperature, humidity, and the amount of injection gas in the chamber in which the photomask is mounted in order to analyze the cause of the exact generation of the haze. It is preferable to include.

As described above, in the detailed description of the present invention has been described with respect to preferred embodiments of the present invention, those skilled in the art to which the present invention pertains various modifications without departing from the scope of the invention Of course it is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the equivalents as well as the claims to be described later.

1 is a view showing the EUV haze measuring apparatus according to the present invention,

2 is a flowchart illustrating an operation procedure of the EUV haze measurement apparatus according to the present invention.

<Code Description of Main Parts of Drawing>

100: EUV haze measuring device 110: light source unit

111: laser (LS) 112: lens

113: EUV light source (plasma light source) 114: condensing optical system

114a: condenser mirror 114b: auxiliary condenser mirror

114c: Aperture 120: Lighting system

121: optical integrator 122: parabolic mirror

130: haze measuring unit 131: EUV detector

132: reflection optical system 133: stage

134: temperature sensor 135: humidity sensor

136: controller M: photomask

OA: optical axis

Claims (10)

In the device for artificially generating a haze that is a growth defect on the surface of the photomask to find the cause of generation of haze, A light source unit including an EUV light source for emitting an EUV beam and a condensing optical system for focusing the EUV beam; An optical integrator for equalizing the intensity of the EUV beam and a parabolic mirror for focusing the EUV beam uniformized by the optical integrator and determining the size of the EUV beam are provided to guide the EUV beam emitted from the light source to the photomask. Lighting system for; And A chamber in which the photomask is mounted, comprising: an EUV detector for detecting in real time whether haze is generated on the surface of the photomask, a sensor for measuring temperature and humidity in the chamber, and a controller for controlling the amount of injected gas; Haze measuring unit; consisting of, EUV haze measuring device characterized in that the traveling path of the EUV beam from the EUV light source to the EUV detector under vacuum. The method of claim 1, The EUV haze measuring apparatus, wherein the EUV light source is a plasma light source or a SR (synchronotron radiation) light source. The method of claim 2, The plasma light source is EUV haze measuring apparatus, characterized in that using the laser produced plasma (LPP) or discharge produced plasma (DPP). The method of claim 1, The condensing optical system includes a condensing mirror comprising a rotating ellipsoid having a first focus on the EUV light source, a spherical auxiliary condensing mirror which reflects the EUV beam not reflected by the condensing mirror, and the condensing mirror. 2 EUV haze measuring device, characterized in that consisting of an aperture shielding the incoming light beam out of focus. The method of claim 1, Measuring apparatus, characterized in that the EUV detector is composed of a CCD. The method of claim 1, The haze measuring unit further comprises a reflection optical system for reflecting the EUV beam reflected by the photomask to the EUV detector. The method of claim 6, EUV haze measuring apparatus, characterized in that the reflective optical system consists of an EUV reflector. In the method of artificially generating a haze that is a growth defect on the surface of the photomask to find the cause of the haze, Emitting a EUV beam; A second step of focusing the EUV beam via a condensing optical system; A third step of uniformly forming the intensity of the EUV beam via the optical integrator; A fourth step of focusing the EUV beam to reach the photomask surface via the parabolic mirror and determining the size of the EUV beam; And And a fifth step of determining whether haze is generated by measuring the EUV beam reflected by the photomask with an EUV detector. EUV haze measuring method characterized in that the traveling path of the EUV beam of the first to fifth steps to be placed under vacuum. The method of claim 8, And a sixth step of quantitatively measuring the amount of temperature, humidity, and injected gas in the chamber in order to analyze the exact cause of the haze caused by the EUV beam. The method according to claim 8 or 9, The fifth step includes determining an image size, an image storage interval, a storage interval and a storage time of the EUV detector after initializing the equipment, storing the values of the image and energy at regular intervals after the laser is operated; And quantitatively measuring whether the haze is generated and the energy value.

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