JP2004153064A - Aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner equipped with a cooling mechanism which can stably and efficiently cool an optical element. <P>SOLUTION: In an exposure chamber 120, a reflector 122 is arranged in a barrel 131. The reflector 122 is cooled by a heat pipe 10. The endothermic portion 11 of the heat pipe is fixed to the reflector 122, and the radiating portion 13 is fixed to an external radiating mechanism 133 in the exposure chamber 120. The vertical position of the radiating mechanism 133 is relatively higher than that of the reflector 122 by a difference H. By arranging the endothermic portion 11 in a lower position and the radiating portion 13 in an upper position, heat transport efficiency by the heat pipe 10 is enhanced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exposure apparatus using EUV light (soft X-ray). In particular, the present invention relates to an exposure apparatus that can effectively cool an optical element in the apparatus.
[0002]
[Prior art]
In recent years, with the miniaturization of semiconductor integrated circuits, reduction projection lithography technology using EUV light (soft X-ray) has been developed in order to improve the resolution of an optical system limited by the diffraction limit of light.
[0003]
An EUV lithography apparatus mainly includes a soft X-ray light source, an illumination optical system, a mask stage, an imaging optical system, a wafer stage, and the like. Since the EUV light has a wavelength of 5 to 20 nm and is absorbed by the atmosphere and attenuated, the apparatus is arranged in a vacuum chamber, and the optical path of the light is maintained in a vacuum atmosphere. Further, since the refractive index of the substance is very close to 1 in the wavelength region of EUV light (especially, 11 to 14 nm), an optical element utilizing refraction or reflection cannot be used. Therefore, an oblique incidence mirror utilizing total reflection due to the refractive index being slightly smaller than 1, or a multilayer reflector which obtains a high reflectance as a whole by superimposing a large number of weak reflected lights at the interface in phase. Etc. are used.
[0004]
When a Mo / Si multilayer film in which a molybdenum (Mo) layer and a silicon (Si) layer are alternately laminated on a substrate is used as the multilayer film, 67.5% of the direct incident light has a wavelength range around 13.4 nm. The reflectance can be obtained. When a Mo / Be multilayer film in which Mo layers and beryllium (Be) layers are alternately stacked on a substrate is used, in the wavelength region of 11.3 nm, a reflectance of 70.2% can be obtained at a direct incidence. it can.
[0005]
[Problems to be solved by the invention]
As described above, since the reflectivity of the multilayer film formed on the reflector constituting the optical system of the EUV exposure apparatus is about 70%, about 30% of the irradiated energy is absorbed by the multilayer film and The temperature rises. Since the inside of the EUV exposure apparatus is maintained in a vacuum atmosphere as described above, heat generated on the substrate is exhausted only by the thermal conductance flowing from the substrate to the exposure chamber, and the cooling rate is reduced.
[0006]
When the temperature rises, the substrate is thermally expanded and deformed. When the shape of the optical element is deformed in this way, it is finally impossible to transfer the pattern with high accuracy.
[0007]
The present invention has been made in view of the above problems, and has as its object to provide an exposure apparatus including a cooling mechanism that can stably and efficiently cool an optical element.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, an exposure apparatus according to the present invention includes: an X light source that generates EUV light; an illumination optical system that guides EUV light from the light source to a reflective reticle; and an EUV light reflected by the reflective reticle. A projection optical system for guiding to a sensitive substrate, and a vacuum chamber for accommodating the above-mentioned components; and an exposure apparatus for transferring a device pattern formed on the reflective reticle to the sensitive substrate, further comprising: Alternatively, a heat pipe for cooling an optical element constituting the illumination optical system or the projection optical system is provided, and a heat radiation side of the heat pipe is located at a position relatively higher than a heat absorption side connected to the reticle or the optical element. It is characterized by.
By using a heat pipe having a good heat radiation function, the optical element can be cooled quickly. By setting the heat absorbing side (heat source, that is, the element to be cooled) of the heat pipe downward and the heat radiating side (cooling source, that is, a portion that takes away the heat transferred by the heat pipe) upward, the heat pipe is used. Heat transport efficiency is increased. For this reason, a smaller and cheaper heat pipe can be used, and the cost is reduced.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, description will be made with reference to the drawings.
First, the exposure apparatus will be described.
FIG. 2 is a diagram showing a configuration of an example of the X-ray EUV light exposure apparatus according to the embodiment of the present invention. This X-ray exposure apparatus uses light in the soft X-ray region near a wavelength of 13 nm as exposure illumination light.
As shown in FIG. 2, the X-ray exposure apparatus 100 includes an X-ray generator 101 and an exposure chamber 120. The vacuum vessel 102 of the X-ray generator 101 is installed above the exposure chamber 120. In the container, a target material 103 and a multilayer elliptical mirror 104 are arranged. The target material 103 is irradiated with a pulse laser beam 105 for excitation from outside the vacuum vessel (right side in the figure). When the laser light 105 is condensed by the lens 106 and is irradiated on the target material 103 through the window 108 opened in the vacuum vessel 102, the target material 103 generates a plasma 107. EUV light 109 of soft X-ray having a wavelength of 13 nm is radiated from the plasma 107. The EUV light 109 is reflected by the multilayer elliptical mirror 104, and is irradiated into the exposure chamber 120 via the visible light cut X-ray filter 110.
Note that a discharge plasma X-ray source may be used instead of a laser plasma X-ray source as the X-ray generator. The discharge plasma X-ray source generates a discharge by applying a pulsed high voltage to an electrode, ionizes an operating gas by the discharge to generate plasma, and radiates soft X-rays from the plasma.
[0010]
An illumination optical system 121 that receives irradiation of the EUV light 109 from the X-ray generator 101 is disposed in the exposure chamber 120. The illumination optical system 121 is composed of a condenser-type reflecting mirror, a fly-eye optical-system reflecting mirror, and the like. The X-ray reflected by the mirror 104 is shaped into an arc shape and emitted toward the left in FIG. .
[0011]
An X-ray reflecting mirror 122 is arranged on a side (left side in FIG. 2) of the illumination optical system 121. The X-ray reflecting mirror 122 has a circular shape with a concave reflecting surface 122a (the surface on the right side in FIG. 2) and is held vertically. On the side of the X-ray reflecting mirror 122 (to the right in FIG. 2), an optical path bending reflecting mirror 123 is disposed obliquely. Above the optical path bending reflecting mirror 123, a reflective mask 124 is mounted on a stage device 125, and is arranged horizontally so that the reflective surface faces down. The X-rays emitted from the illumination optical system 121 are reflected and condensed by the X-ray reflecting mirror 122, and then reach the reflecting surface of the reflective mask 124 via the optical path bending reflecting mirror 123.
[0012]
The bases of the reflecting mirrors 122 and 123 are made of a quartz substrate whose reflecting surface is processed with high precision. On this reflection surface, a Mo / Si multilayer film is formed similarly to the reflection surface of the mirror 104 of the X-ray generator 101. When X-rays having a wavelength of 10 to 15 nm are used, a material such as Ru (ruthenium) and Rh (rhodium) and a material such as Si, Be (beryllium), and B ₄ C (carbon tetraboride) are used. May be used as a multilayer film.
[0013]
A reflective film made of a multilayer film is also formed on the reflective surface of the reflective mask 124. A mask pattern corresponding to the pattern to be transferred to the wafer 127 is formed on the reflection film. The mask 124 is fixed on a mask stage device 125 movable at least in the X and Y directions by suction or the like. The X-rays reflected by the optical path bending reflecting mirror 123 are sequentially irradiated onto the mask 124.
[0014]
Below the reflective mask 124, a projection optical system 126 and a wafer 127 are sequentially arranged. The projection optical system 126 includes a plurality of reflecting mirrors and the like, reduces the X-rays reflected by the reflective mask 124 to a predetermined reduction magnification (for example, １ ／), and forms an image on the wafer 127. The wafer 127 is fixed to the wafer stage device 128 movable in the XYZ directions by suction or the like.
[0015]
When performing the exposure operation, the illumination optical system 121 irradiates the reflective surface of the reflective mask 124 with X-rays. At this time, the reflective mask 124 and the wafer 127 are relatively synchronously scanned with respect to the projection optical system 126 at a predetermined speed ratio determined by the reduction magnification of the projection optical system. As a result, the entire circuit pattern of the reflective mask 124 is transferred to each of the plurality of shot areas on the wafer 127 by the step-and-scan method. Note that the chips of the wafer 127 are, for example, 25 × 25 mm square, and an IC pattern of 0.07 μmL / S can be exposed on the resist.
[0016]
Next, a mirror cooling mechanism in the exposure apparatus will be described in detail.
FIG. 1 is a diagram schematically illustrating a mirror cooling mechanism in an exposure apparatus according to an embodiment of the present invention.
In this example, a cooling mechanism of the reflecting mirror 122 will be described. As shown in FIG. 1, the reflecting mirror 122 is actually arranged inside the lens barrel 131. The reflecting mirror 122 is cooled by the heat pipe 10. As described later in detail, the heat pipe 10 has a heat absorbing part 11 and a heat radiating part 13. The heat absorbing section 11 is fixed to a reflecting mirror 122 to be cooled, and the heat radiating section 13 is fixed to a heat radiating mechanism 133 outside the exposure chamber 120. The heat radiation mechanism 133 is, for example, a portion of the outer wall of the chamber 120 that is easily cooled. Here, the height position of the heat radiation mechanism 133 is relatively higher than the height position of the reflection mirror 122 by the difference H.
[0017]
Here, the heat pipe 10 will be described.
FIG. 3 is a diagram illustrating the operation principle of the heat pipe.
The heat pipe 10 is one in which a small amount of hydraulic fluid 15 is sealed in a closed space that is decompressed. As the working fluid 15, pure water or the like can be used. When one end 11 of the heat pipe 10 comes into contact with a heating element or the like, the part becomes a heat absorbing portion, and the working fluid 15 boils at a low temperature, and at that time, absorbs latent heat of evaporation. The steam moves to the other end 13 of the heat pipe 10 at a speed close to the speed of sound. Then, the part becomes a heat radiating part, and the vapor condenses and returns to a liquid state again, and at this time, the latent heat of condensation is released. The working fluid that has returned to the liquid travels along the inner wall surface of the pipe and returns to the heat absorbing section 11 again. By repeating this cycle, the amount of heat is moved from the heat absorbing section 11 to the heat radiating section 13. In addition, in the actual heat pipe, since the movement efficiency is enhanced by utilizing the capillary phenomenon, a fine mesh is disposed inside, or a fine groove is formed in the inner wall surface.
[0018]
With such a mechanism, the heat absorbed by the heat absorbing section 11 of the heat pipe 10 efficiently moves to the heat radiating section 13 at a very high speed, so that the heat can be quickly moved to a remote position.
[0019]
Such a heat pipe is commonly used for cooling a CPU in a notebook PC. In this case, the heat-absorbing part of the heat pipe is attached to the heat-dissipating surface of the Peltier element attached to the CPU, and the heat-dissipating part is attached to an easily cooled surface (heat dissipating mechanism) such as the back surface of the PC. Then, the heat absorbed by the heat absorbing section is transferred to the heat radiating section, and radiated from the section to the heat radiating mechanism.
[0020]
Further, the heat pipe has a property that it can be used at any inclination angle. This is because the vapor generated at one end can freely reach the other end at a speed close to the speed of sound, and the structure utilizing the capillary phenomenon can move the liquid. Further, the heat pipe is usually a structure that is easy to bend, and can be freely arranged even when it is necessary to bend midway due to other structural restrictions.
[0021]
However, in practice, heat pipes have some degree of angle dependence.
FIG. 4 is a graph illustrating the installation angle dependence of the heat pipe. The vertical axis in the figure shows the maximum heat transport amount (W), and the horizontal axis in the figure shows the inclination angle (°) of the heat pipe. As for the inclination angle, + indicates an inclination in which the heat absorbing portion is lower and the heat radiating portion is upper, and-indicates a tilt in which the heat absorbing portion is upper and the heat radiating portion is lower. The heat pipe used was 200 mm in length, 4 mm in diameter and in a straight line. In the figure, ● indicates a case where the operating temperature is 60 ° C., ▲ indicates a case where the operating temperature is 50 ° C., and Δ indicates a case where the operating temperature is 40 ° C.
[0022]
As can be seen from FIG. 4, at all operating temperatures, the heat pipe has a larger heat transport amount as the inclination angle is larger (the heat absorbing portion is located at a position lower than the heat radiating portion). For example, when the operating temperature is 40 ° C., the heat transport amount is 10 W in a horizontal state (inclination angle 0 °), but when the operating temperature is inclined to 10 °, the maximum heat transport amount increases to 17 W and increases by about 70%. . On the other hand, when inclined to -10 [deg.], The heat transport amount decreases to 6W and decreases by about 40%.
[0023]
When a heat pipe is actually installed in the exposure apparatus, the positional relationship (inclination angle) between the heat absorbing section (the element to be cooled) and the heat radiating section (radiating mechanism) is limited by mechanical restrictions in the exposure apparatus. Will be decided. For example, as described later, if the reflecting mirror is arranged at a position higher than the position of the heat radiating mechanism, a part of the heat pipe will have a negative inclination angle, and transport efficiency will be significantly impaired.
[0024]
Therefore, in the present invention, as shown in FIG. 1, the heat absorbing portion 11 of the heat pipe 10 is always arranged at a position lower than the heat radiating portion 13 by the difference H. That is, the reflecting mirror 122, which is an object to be cooled, is disposed below the heat radiating mechanism 133. Thereby, the inclination angle of the heat pipe 10 becomes +. In this example, a local cooling element such as a Peltier element may be attached to the reflector 122. In this case, the heat absorbing portion 11 of the heat pipe 10 is attached to the heat dissipation surface of the Peltier device. The heat dissipating mechanism 133 is a surface of the chamber 120 that is easily cooled as described above. If fins or fans are provided on this surface, the cooling effect can be enhanced. Attachment of the heat pipe 10, the cooling surface of the reflecting mirror 122 (the cooling surface of the Peltier element), and the heat radiating mechanism 133 may be only a simple contact, and a high heat conductive adhesive material, a heat absorbing portion inside the reflecting mirror. Methods such as plugged-in structures can be used.
[0025]
By connecting the reflecting mirror 122 and the heat radiating mechanism 133 arranged in this way with the heat pipe 10, even when the heat pipe 10 needs to be bent in the middle, a portion having a negative direction is basically generated. Nothing. As a result, the heat pipe can be used with high efficiency, and the heat transport amount can be increased. If a sufficient heat transport amount can be maintained, a smaller or less expensive heat pipe can be used.
[0026]
FIG. 5 is a diagram schematically illustrating a comparative example of a reflector cooling mechanism in the exposure apparatus.
In FIG. 5, the heat radiation mechanism 217 is installed at a position lower than the object to be cooled (reflecting mirror 222) by a difference H due to restrictions by the illumination optical system connection portion 233 and the stage transport system 215. When the heat pipe 210 is used for cooling the reflecting mirror 122, the heat absorbing portion 211 of the heat pipe 210 is located at a position higher than the heat radiating portion 213, and the inclination angle is negative. With such an inclination angle, the heat pipe 210 cannot exhibit high heat transport efficiency, and it is necessary to install a larger heat pipe, which increases costs.
[0027]
【The invention's effect】
As is apparent from the above description, according to the present invention, the heat pipe is used for cooling the optical element, and the heat radiation side of the heat pipe is positioned higher than the heat absorption side connected to the optical element to be cooled. The heat transfer efficiency of the heat pipe can be increased. Therefore, the reticle and the optical element can be efficiently cooled.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a mirror cooling mechanism in an exposure apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of an example of an X-ray EUV light exposure apparatus according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating the operating principle of a heat pipe.
FIG. 4 is a graph illustrating the installation angle dependence of a heat pipe.
FIG. 5 is a diagram schematically illustrating a comparative example of a reflector cooling mechanism in the exposure apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Heat pipe 11 Heat absorption part 13 Heat radiation part 15 Working fluid 100 X-ray exposure apparatus 101 X-ray generation apparatus 102 Vacuum container 103 Target material 104 Multilayer elliptical mirror 105 Pulse laser beam 106 Lens 107 Plasma 108 Window 109 EUV light 110 Visible light cut X-ray filter 120 Exposure chamber 121 Illumination optical system 122 X-ray reflector 123 Optical path bending reflector 124 Reflective mask 125 Stage device 126 Projection optical system 127 Wafer 128 Wafer stage device 131 Lens tube 133 Heat dissipation mechanism

Claims (1)

An X light source that generates EUV light, an illumination optical system that guides EUV light from the light source to a reflective reticle, a projection optical system that guides EUV light reflected by the reflective reticle to a sensitive substrate, and the components are housed. An exposure apparatus, comprising: a vacuum chamber; and transferring a device pattern formed on the reflective reticle to the sensitive substrate.
Further, the reticle, or, comprising a heat pipe for cooling the optical element constituting the illumination optical system or the projection optical system,
An exposure apparatus, wherein a heat radiation side of the heat pipe is located at a position relatively higher than a heat absorption side connected to the reticle or the optical element.

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