JP2004134444A - Method and instrument for measuring optical characteristic of optical system for extremely-short ultraviolet ray and method of manufacturing the optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which the optical characteristic of an optical system for extremely-short ultraviolet rays can be measured easily as compared with the conventional method without increasing the size of an instrument. <P>SOLUTION: The light 2 emitted from an optical illumination system 1 having a prescribed light source which emits light rays having wavelengths other than the EUV wavelength region illuminates a mask 4 placed on a mask stage 3. On the mask 4, a prescribed standard pattern is preformed. After passing through the standard pattern, the light 2 is made incident to the optical system 5 for extremely-short ultraviolet rays which is an object to be inspected. The light 6 emitted from the optical system 5 forms the image of the standard pattern formed on the mask 4 on the surface of a wafer 8 placed on a wafer stage 7. Since a resist is applied to the surface of the wafer 8, the distortion of the optical system 5 can be measured by measuring the shape of the image of the standard pattern of the mask by reproducing the image through the well-known process of developing the resist and etching the wafer 8 by using the remaining resist as a mask. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method, a measuring apparatus, and a measuring method for optical characteristics of an ultra-short ultraviolet (EUV: light having a wavelength of 4.5 to 30 nm) optical system such as a projection optical system used in an ultra-short ultraviolet exposure apparatus (EUVL). The present invention relates to a method for manufacturing an optical system.
[0002]
[Prior art]
In an exposure apparatus for manufacturing a semiconductor, a circuit pattern formed on a mask surface as an object surface is projected and transferred onto a substrate such as a wafer via an imaging optical system. A resist is applied to the substrate, and the resist is exposed by exposure to light, and a resist pattern is obtained.
[0003]
The resolution w of the exposure apparatus is determined mainly by the exposure wavelength λ and the numerical aperture NA of the imaging optical system, and is expressed by the following equation.
w = kλ / NA k: constant
Therefore, in order to improve the resolution, it is necessary to shorten the wavelength or increase the numerical aperture. At present, an exposure apparatus used for manufacturing a semiconductor mainly uses i-rays having a wavelength of 365 nm, and a resolution of 0.5 μm is obtained with a numerical aperture of about 0.5. Since it is difficult to increase the numerical aperture in terms of optical design, it is necessary to shorten the wavelength of exposure light in order to further improve the resolution in the future. The exposure light having a wavelength shorter than the i-line is, for example, an excimer laser. The wavelength of the exposure light is 248 nm for a KrF excimer laser and 193 nm for an ArF excimer laser. With a 0.25 μm ArF excimer laser, a resolution of 0.18 μm can be obtained. When ultra-short ultraviolet light (EUV) having a shorter wavelength is used as exposure light, a resolution of, for example, 0.1 μm or less can be obtained at a wavelength of 13 nm.
[0004]
A conventional exposure apparatus mainly includes a light source, an illumination optical system, and a projection imaging optical system. The projection image forming optical system includes a plurality of lenses or reflecting mirrors, and forms a pattern on a mask on a wafer.
[0005]
On the other hand, if an attempt is made to design a projection optical system for EUV in order to obtain higher resolution, the field of view becomes small, and a desired region cannot be exposed at a time. Therefore, a method of exposing a semiconductor chip of 20 mm square or more with a projection optical system having a small visual field by scanning a mask and a wafer at the time of exposure has been adopted. By doing so, a desired exposure area can be exposed even with an ultra-short ultraviolet projection exposure apparatus. For example, when exposing with EUV light having a wavelength of 13 nm, high resolution can be obtained by making the exposure field of the projection optical system annular.
[0006]
FIG. 6 shows a schematic view of a part of the ultrashort ultraviolet projection exposure apparatus. The apparatus mainly includes an EUV light source 21, an illumination optical system 22, a stage 25 of a mask 24, a projection optical system 23, and a stage 27 of a wafer 26. The mask 24 is formed with a pattern of the same size or an enlarged size as the pattern to be drawn. The projection optical system 23 includes a plurality of reflection mirrors 23a to 23d and the like, and forms a pattern on the mask 24 on the wafer 26. On the surfaces of the reflecting mirrors 23a to 23d, a multilayer film for increasing the reflectance is formed.
[0007]
The projection optical system 23 has a ring-shaped field of view, and transfers the pattern of the ring-shaped region forming a part of the mask 24 onto the wafer 26. As the mask 24, a reflection type is used. At the time of exposure, the EUV light 28a from the EUV light source 21 is used as the illumination EUV light 28b by the illumination optical system 22, the mask 24 is irradiated with the EUV light 28b for illumination, and the reflected EUV light 28c is converted into the projection optical system 23. And is incident on the wafer 26. By synchronously scanning the mask 24 and the wafer 26 at a constant speed, a desired region (for example, a region for one semiconductor chip) is exposed.
[0008]
As described above, in the ultra-short ultraviolet optical system including the ultra-short ultraviolet projection optical system, since a transparent glass material cannot be obtained, the optical system is configured around a mirror. At present, in the projection optical system of the ultrashort ultraviolet projection exposure apparatus, six mirrors are being used, unlike the one shown in FIG.
[0009]
[Problems to be solved by the invention]
In such an ultra-short ultraviolet optical system, it is necessary to set optical characteristics (for example, wavefront aberration, distortion, field curvature) within a predetermined range. To this end, these characteristics are measured in such an optical system, and if they do not fall within a predetermined value, the shape of each optical element (mirror, etc.) is corrected, It is necessary to change the mounting method. Therefore, it is required to measure the characteristics of some ultrashort ultraviolet optical system.
[0010]
As a method for measuring the wavefront aberration, distortion, and field curvature of an extremely short ultraviolet optical system, a method using an interferometer is generally employed. In addition, for distortion, image the reference pattern on the image plane, and for field curvature, image the reference pattern on the image plane by changing the position of the image plane, and compare them. Also required by
[0011]
Conventionally, in these measurements, EUV actually used is used as light for measurement. However, since EUV can generally be used only in a vacuum, there has been a problem that at least a part of the measuring device must be placed in a vacuum.
[0012]
When measuring optical characteristics using an interferometer, it is desirable to use laser light having the same wavelength and phase as the measurement light. However, those commonly used as EUV light sources are emitted from plasma. Light, and it is difficult to obtain such characteristics. If synchrotron radiation is used as the light source, a light close to laser light can be obtained to some extent, but there is a problem that the apparatus becomes very expensive.
[0013]
The present invention has been made in view of such circumstances, and a method and a method for easily measuring the optical characteristics of an ultra-short ultraviolet optical system as compared with the related art without increasing the size of the apparatus. It is an object of the present invention to provide an apparatus, and a method for manufacturing an ultrashort ultraviolet optical system using the apparatus and the method.
[0014]
[Means for Solving the Problems]
A first means for solving the above-mentioned problem is a method for measuring optical characteristics of an ultra-short ultraviolet optical system, wherein measurement is performed using light other than ultra-short ultraviolet light as light used for measuring the optical characteristics. A method for measuring optical characteristics of an ultra-short ultraviolet optical system, wherein the wavelength of light used for measuring the optical characteristics is in a range of 150 nm to 250 nm. (Claim 1).
[0015]
As described above, in the ultrashort ultraviolet optical system, a mirror is mainly used as an optical element, and a refractive optical element such as a lens is not used. Therefore, it can be said that the ultrashort ultraviolet optical system is an optical system having essentially no chromatic aberration. This means takes advantage of this. That is, even if the measurement is performed using light having a wavelength different from that of the actually used EUV, the same measurement result as in the case of using the actually used EUV is obtained without being affected by the difference in wavelength.
[0016]
If the optical characteristics are measured using light having a wavelength different from that of EUV, for example, the measurement can be performed even in a state other than in a vacuum, so that the apparatus configuration can be simplified. In addition, since measurement can be performed using laser light, accurate measurement of optical characteristics can be performed.
[0017]
Further, a multilayer optical thin film is formed as a reflector on the surface of a mirror generally used in an ultrashort ultraviolet optical system. This multilayer optical thin film is generally obtained by alternately laminating Si and Mo. The reflectivity of such a multilayer optical thin film decreases to about 40% in the visible light region, but remains high in the wavelength region of 150 nm to 250 nm (50.3% at a wavelength of 150 nm, 53.8% at a wavelength of 198 nm, (About 54.1% at a wavelength of 248 nm). In this wavelength range, F ₂ Since a laser (wavelength: 150 nm), an ArF laser (wavelength: 198 nm), and a KrF laser (wavelength: 248 nm) can be used as a light source, measurement can be performed by an interferometer or the like using an existing light source.
[0018]
In many cases, the multilayer optical thin film is formed by alternately laminating Si and Mo, but instead of Mo, Ru, Rh, or the like is used, or a compound such as Mo, Ru, Rh, or the like is used. May be done. In addition, Be, B, C, or the like may be used instead of Si, or a compound such as Si, Be, B, or C may be used. Even in such a case, the present means works effectively.
[0019]
A second means for solving the above-mentioned problem is a method of measuring the optical characteristics of an ultra-short ultraviolet optical system, and performing measurement using light other than the ultra-short ultraviolet light as light used for measuring the optical characteristics. In the method for measuring the optical characteristics of an ultra-short ultraviolet optical system, the optical thin film for measurement is formed instead of the multilayer optical thin film formed on the surface of the mirror used in the ultra-short ultraviolet optical system. And measuring the optical characteristics of the ultrashort ultraviolet optical system (claim 2).
[0020]
The thickness of the multilayer optical thin film formed on the surface of the mirror hardly contributes to the optical characteristics of the ultrashort ultraviolet optical system, and most of the optical characteristics are determined by the shape of the substrate constituting the mirror. This means focuses on such a property, and performs measurement by forming an optical thin film for measurement instead of a multilayer optical thin film actually used. In this way, for example, a material having a high reflectance in the ultraviolet or visible light region can be used as the optical thin film for measurement, and a light source ordinarily used such as an excimer laser or a He-Ne laser can be used. The optical characteristics of the ultrashort ultraviolet optical system can be detected using an extremely commonly used detector such as a CCD.
[0021]
A third means for solving the problem is the second means, wherein the optical thin film for measurement is formed using a material which can be etched by an etching method in which the substrate has a resistance. (Claim 3).
[0022]
In this means, since the optical thin film for measurement is formed using a material which can be etched with respect to the etching method in which the substrate has resistance, if this etching method is used, the optical film for measurement can be used without affecting the substrate. It becomes easy to peel off the optical thin film.
[0023]
A fourth means for solving the above-mentioned problem is the third means, wherein a material forming the mirror is made of a material having etching resistance to nitric acid, and the optical thin film for measurement is made of nitric acid. It is characterized in that it is composed of an etchable material (claim 4).
[0024]
In this means, since the optical thin film for measurement can be dissolved and removed using nitric acid as an etchant, the optical thin film for measurement can be easily peeled off without affecting the substrate by a simple method.
[0025]
A fifth means for solving the above-mentioned problem is the third means or the fourth means, wherein the substrate constituting the mirror is made of at least one of glass, quartz, or ceramics, The optical thin film for use is made of silver or aluminum or a material containing these as a main component (claim 5).
[0026]
Silver has a high reflectance (about 50-98%) for visible light having a wavelength of 330-650 nm, and aluminum has a high reflectance (about 90%) for visible or ultraviolet light having a wavelength of 150-650 nm. ), Measurement using light in this wavelength range is possible. Note that these reflectivities are calculated values and may actually decrease depending on the state of the film or the like. Therefore, it is preferable to check whether a desired reflectivity is obtained by experiments or the like when actually using the reflectivity.
[0027]
Moreover, silver and aluminum are easily dissolved in nitric acid. On the other hand, when the substrate is made of a material that does not dissolve in nitric acid such as glass, quartz or ceramics, after the measurement is completed, a thin film of silver or aluminum or a material containing these as a main component formed on the surface is dissolved with nitric acid. Thus, the optical thin film for measurement can be easily removed without affecting the substrate constituting the mirror.
[0028]
A sixth means for solving the above-mentioned problem is a method for measuring the optical characteristics of an ultra-short ultraviolet optical system, wherein the measurement is performed using light other than the ultra-short ultraviolet light as light used for measuring the optical characteristics. In the method for measuring the optical characteristics of an ultra-short ultraviolet optical system, the optical thin film for measurement is formed on a multilayer optical thin film formed on the surface of a mirror used in the ultra-short ultraviolet optical system. A method for measuring optical characteristics of an ultra-short ultraviolet optical system, wherein the measurement is performed.
[0029]
The principle of this means is basically the same as that of the second means. However, in the second means, an optical thin film for measurement is formed on a substrate constituting a mirror. In the means, an optical thin film for measurement is formed on the multilayer optical thin film. Therefore, it is suitable for measuring the optical characteristics of the ultrashort ultraviolet optical system using the completed mirror. However, in this case, after the measurement is completed, it is necessary that the optical thin film for measurement can be removed without affecting the multilayer optical thin film.
[0030]
A seventh means for solving the above problem is the seventh means, wherein the optical thin film for measurement uses a material which can be etched by an etching method in which the substrate and the multilayer optical thin film have resistance. It is characterized by being formed (claim 7).
[0031]
In this means, since the optical thin film for measurement is formed using a material which can be etched with respect to the etching method in which the substrate has resistance, if this etching method is used, the optical film for measurement can be used without affecting the substrate. It becomes easy to peel off the optical thin film.
[0032]
An eighth means for solving the above-mentioned problem is the seventh means, wherein the material forming the mirror and the material forming the surface of the multilayer optical thin film are made of a material having etching resistance to nitric acid. The optical thin film for measurement is made of a material that can be etched with nitric acid (claim 8).
[0033]
In this means, since the optical thin film for measurement can be dissolved and removed using nitric acid as an etchant, the optical thin film for measurement can be easily peeled off without affecting the substrate by a simple method.
[0034]
A ninth means for solving the above problem is the seventh means or the eighth means, wherein a substrate constituting the mirror is made of at least one of glass, quartz, and ceramics, and The surface of a multilayer optical thin film is made of Si, and the optical thin film for measurement is made of silver or aluminum, or a material containing these as a main component. ).
[0035]
As described above, silver and aluminum have high reflectance in the ultraviolet or visible light range, and it is easy to form a thin film on a substrate. It is easy to dissolve in nitric acid. On the other hand, if the substrate is made of a material that does not dissolve in nitric acid such as glass, quartz or ceramics, and the surface of the multilayer optical thin film is made of a material that does not dissolve in nitric acid such as Si, it is formed on the surface after the measurement is completed. By dissolving the thin film of silver or aluminum or a material containing these as a main component with nitric acid, the optical thin film for measurement can be easily removed without affecting the substrate constituting the mirror or the multilayer optical thin film. it can.
[0036]
A tenth means for solving the above-mentioned problems is any one of the second means to the ninth means, wherein a film thickness distribution of the optical thin film for measurement is determined by using ultra-short ultraviolet light in the multilayer optical thin film. The film thickness distribution is such that a phase change equivalent to a phase change received when light is reflected is obtained (claim 10).
[0037]
As described above, the optical characteristics of a mirror are almost determined by the shape of the substrate that constitutes the mirror, and the thickness of the multilayer optical thin film and other effects are small, but strictly speaking, the incident direction of light at each part of the multilayer optical thin film Are different, the phase of the reflected light changes in each part accordingly. The degree of this phase change can be determined by simulation calculation or the like. In this means, when forming the optical thin film for measurement, the phase change of the measurement light reflected at each part thereof is equivalent to the phase change received when the ultra-short ultraviolet light is reflected on the multilayer optical thin film. First, the film thickness and the like are changed. Therefore, the measurement can be performed under conditions similar to those in the case where actual ultrashort ultraviolet light is used.
[0038]
An eleventh means for solving the above problem is any one of the second means to the tenth means, wherein a reflectance of light used for measuring the optical characteristics in the optical thin film for measurement is determined. The reflectance is made substantially equal to the reflectance of the ultra-short ultraviolet ray in the multilayer optical thin film (claim 11).
[0039]
Light not reflected by the mirror is absorbed by the mirror and becomes heat, raising the temperature of the mirror. As a result, the mirror deforms and changes the optical characteristics of the ultrashort ultraviolet optical system. In this means, the reflectivity of light used for measuring optical properties in the optical thin film for measurement is set to be substantially equal to the reflectivity of ultra-short ultraviolet rays in the multilayer optical thin film. And the temperature rise of the mirror in the actual use state become substantially equal, and the optical characteristics can be measured in a state close to the actual use state. At this time, it is preferable that the amount of light incident on the projection system in the exposure and the amount of light incident on the projection system in the measurement be approximately the same.
[0040]
Note that `` substantially equal '' means that the difference in optical characteristics caused by the difference between the temperature rise of the mirror at the time of measuring the optical characteristics and the temperature rise of the mirror in an actual use state is a problem in required measurement accuracy. If it does not fall within the range, it does not need to exactly match.
[0041]
A twelfth means for solving the above problem is any of the second means to the eleventh means, wherein a wavelength of light used for measuring the optical characteristics is in a range of 150 nm to 250 nm. (Claim 12).
[0042]
In this means, as in the first means, F ₂ Even when a laser (wavelength 150 nm), an ArF laser (wavelength 198 nm), or a KrF laser (wavelength 248 nm) is used as a light source, the reflectivity of the multilayer optical thin film does not decrease so much. A measurement can be made.
[0043]
A thirteenth means for solving the above problem is an apparatus for measuring the optical characteristics of an ultra-short ultraviolet optical system, wherein a light source that emits light having a wavelength other than an ultra-short ultraviolet ray and a predetermined standard pattern are provided. A formed mask, and an illumination optical system that irradiates the mask with light from the light source and guides light transmitted through the mask or light reflected by the mask to an ultra-short ultraviolet optical system to be measured. An optical characteristic measuring apparatus for an ultra-short ultraviolet optical system, comprising: a light-receiving substrate provided on an image forming surface of the ultra-short ultraviolet optical system to be measured and having a photosensitive member applied to the surface thereof. Claim 13).
[0044]
In this means, light having a wavelength other than the ultra-short ultraviolet light emitted from the light source is applied to the mask on which the standard pattern is formed, and the light transmitted through the mask (in the case of a transmission mask) or reflected by the mask The reflected light (in the case of a reflective mask) is guided to an ultra-short ultraviolet optical system to be measured, and an image of the standard pattern of the mask is formed on an imaging plane by the ultra-short ultraviolet optical system. Then, a light receiving substrate having a surface coated with a photosensitive member is exposed to light, and the photosensitive member is developed to obtain an image of a standard pattern, and then optical characteristics such as distortion are measured.
[0045]
When measuring the curvature of field, the light-receiving substrate is placed not only on the actual imaging plane but also in various places near the actual imaging plane, and the standard pattern at that position is placed. It goes without saying that the field curvature is obtained by comparing the images.
[0046]
A fourteenth means for solving the above-mentioned problem is that, in place of the light-receiving substrate in the thirteenth means, the intensity of light on the imaging surface of the ultrashort ultraviolet optical system to be measured is two-dimensionally measured. An optical characteristic measuring apparatus for an ultra-short ultraviolet optical system, wherein an optical sensor mechanism capable of measurement is provided.
[0047]
In this means, since the two-dimensional light intensity on the image plane is measured by an optical sensor mechanism instead of the light receiving substrate, a step of developing the light receiving substrate becomes unnecessary, and automation is easy. It is. Also in this case, it is preferable that the wavelength of the light used for measuring the optical characteristics be in the range of 150 nm to 250 nm for the reason described in the description of the first means.
[0048]
A fifteenth means for solving the above problem is a method for measuring an optical characteristic of an ultra-short ultraviolet optical system, which is one of the first means to the twelfth means, or a thirteenth means, a fourteenth means Using an optical characteristic measuring device for an ultra-short ultraviolet optical system, the optical characteristics of the ultra-short ultraviolet optical system are measured, and according to the result, an optical element constituting the ultra-short ultraviolet optical system is measured. A method of manufacturing an ultra-short ultraviolet optical system, comprising a step of performing at least one of correcting a surface shape and adjusting an installation position of the optical element (claim 16).
[0049]
In this means, the optical characteristics of the ultra-short ultraviolet optical system are measured using the optical characteristics measuring method or apparatus of the ultra-short ultraviolet optical system according to the present invention, and the ultra-short ultraviolet optical system is configured according to the result. Since the surface shape of the optical element to be performed, and at least one of the adjustment of the installation position of the optical element is performed, without performing a complicated measurement such as measurement in a vacuum, it is possible to measure, It becomes easy to manufacture an ultra-short ultraviolet optical system. In addition, since measurement using laser light becomes possible, in this case, optical characteristics can be measured accurately, and a very short ultraviolet optical system with high accuracy can be manufactured.
[0050]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of an optical characteristic measuring device of an ultrashort ultraviolet optical system which is a first example of an embodiment of the present invention.
[0051]
Illumination light 2 emitted from an illumination optical system 1 having a predetermined light source illuminates a mask 4 mounted on a mask stage 3. A predetermined standard pattern is formed on the mask 4 in advance. The illumination light 2 that has passed through the standard pattern is incident on an ultrashort ultraviolet optical system 5 that is an object to be inspected. The very short ultraviolet optical system 5 is similar to the projection optical system 43 in FIG. The emitted light 6 from the ultrashort ultraviolet optical system 5 forms an image of the standard pattern of the mask 4 on the surface of the wafer 8 placed on the wafer stage 7.
[0052]
A resist is applied to the surface of the wafer 8, and the resist is developed, and the image of the standard pattern of the mask 4 is reproduced by a well-known process of etching the wafer 8 using the remaining resist as a mask. By measuring, the distortion of the ultrashort ultraviolet optical system can be measured, and the field curvature can be measured by repeatedly performing this measurement while changing the height of the wafer stage 7. If the entire standard pattern cannot be exposed and transferred by a single exposure, the mask stage 3 and the wafer stage 7 are moved in synchronization and the exposure and transfer are performed a plurality of times in the same manner as a normal stepper.
[0053]
In the present embodiment, in order to measure the optical characteristics of the ultrashort ultraviolet optical system 5, a light source F ₂ A laser (wavelength 150 nm), an ArF laser (wavelength 198 nm), and a KrF laser (wavelength 248 nm) are used. Thus, a lens made of fluorite or the like can be used for the illumination optical system 1, and light loss can be reduced as compared with the case where a mirror is used. In addition, it is conceivable to purge the projection system with an inert gas such as He due to problems such as contamination. The measurement becomes simple and the measurement time can be shortened.
[0054]
In addition, since light in these wavelength bands can pass through the air without a large loss, it is not necessary to place the measuring apparatus and the ultra-short ultraviolet optical system 5 as an object to be inspected in a vacuum. Further, a mirror which is a main optical element in the ultrashort ultraviolet optical system 5 is provided with a multilayer optical thin film in which Si and Mo are alternately laminated on the surface thereof. Has a high reflectance with respect to the light, the measurement can be performed in a state where the loss of light is small.
[0055]
As a modified example of this embodiment, visible light, for example, a laser in a visible region such as a He-Ne laser can be used as a light source. However, in this case, the multilayer optical thin film designed for the ultrashort ultraviolet optical system 5 often shows only a low reflectance with respect to visible light. Therefore, in such a case, it is necessary to coat a material having a high reflectance to visible light to be used on the multilayer optical thin film of the mirror.
[0056]
As such a coating material, silver, aluminum or a material containing these as a main component is preferable. These materials exhibit high reflectivity to visible light and can be uniformly deposited as thin films on Si that constitutes multilayer optical thin films by vapor phase epitaxy, especially ion beam sputtering and magnetron sputtering. It is. Therefore, even if the film is formed on the multilayer optical thin film, it hardly affects the measurement of the optical characteristics.
[0057]
In addition, silver, aluminum or a material containing these as a main component is easily dissolved in nitric acid, whereas glass, quartz, and ceramics, which are substrates of Si constituting a multilayer optical thin film and a mirror, are hardly dissolved in nitric acid. Therefore, by performing a design so that Si comes to the surface of the multilayer optical thin film, after the measurement is completed, a thin film made of silver, aluminum or a material containing these as a main component is dissolved in nitric acid, and the The thin film for measurement formed later can be removed with little effect on the multilayer optical thin film or the mirror substrate.
[0058]
In actual manufacturing of an ultra-short ultraviolet optical system, it may be necessary to measure optical characteristics after assembly and as a result rework the surface of the mirror. In such a case, it is necessary to peel off the formed multilayer optical thin film and perform processing, and form a multilayer optical thin film again. In order to avoid this, first, a multilayer optical thin film is not formed on the surface of the mirror, but a thin film of silver, aluminum, etc. is formed, and in that state, the ultrashort ultraviolet optical system is assembled, and visible light is applied as described above. It is preferable to measure the optical characteristics and to process the mirror as necessary based on the result. Then, if the multilayer optical thin film is formed on the mirror substrate after the optical characteristics measured using visible light fall within a predetermined range, the process of forming the multilayer optical thin film can be performed only once.
[0059]
Also in this case, a thin film made of silver, aluminum, or a material containing these as a main component is dissolved in nitric acid, so that the thin film for measurement has almost no effect on the original mirror substrate (glass, quartz, ceramics). Can be removed.
[0060]
When such a process is adopted, it is preferable that measurement can be performed with the same measuring device for both the case where the multilayer optical thin film is formed on the surface of the mirror substrate and the case where the thin film of silver or aluminum is formed. . For this purpose, it is preferable that the light source can be changed according to the type of the thin film as the reflection film. For example, when a multilayer optical thin film is formed on the surface of a mirror substrate, F ₂ Any one of a laser (wavelength 150 nm), an ArF laser (wavelength 198 nm), and a KrF laser (wavelength 248 nm). When a thin film such as silver or aluminum is formed, a He-Ne laser is used. . Such switching can be easily realized by preparing a plurality of types of light sources and switching them by a mirror.
[0061]
In a mirror in an actual ultrashort ultraviolet optical system, the thickness of the multilayer optical thin film formed on the surface thereof hardly contributes to the characteristics of the ultrashort ultraviolet optical system. However, since most mirrors are concave mirrors or convex mirrors, the incident angle of light actually used may be different in each part of the mirror. In this case, the phase of the reflected light differs depending on each part of the mirror.
[0062]
Therefore, when a special thin film is formed for measuring optical characteristics, it is preferable to consider a change in the phase of the reflected light. That is, the phase characteristics of the reflected light in the state of actual use can be obtained by calculation or simulation if the formed thin film and the incident angle are known. Therefore, it is preferable to form a thin film for measuring optical characteristics in consideration of the phase characteristics of the reflected light. For example, when a thin film for measuring optical characteristics is formed of silver or aluminum, the phase of reflected light can be changed according to the reflection position of the mirror by changing the thickness at the position of the mirror.
[0063]
When a thin film for measuring optical properties is formed of silver or aluminum, sputtering is often used as described above.However, a shield plate prevents silver or aluminum from reaching the mirror, and the mirror is prevented from forming. By controlling the shielding time according to the location, the thickness of the thin film can be changed according to the location of the mirror.
[0064]
Further, it is preferable to perform the measurement in consideration of the thermal deformation of these mirrors when the ultrashort ultraviolet optical system is used. That is, in the use state of the ultrashort ultraviolet optical system, EUV not reflected by the mirror is absorbed by the mirror, and the temperature of the mirror increases. As a result, the mirror undergoes thermal deformation, which changes the optical characteristics of the ultrashort ultraviolet optical system. Usually, in the design of the ultrashort ultraviolet optical system, the design is performed in consideration of the thermal deformation of the mirror.
[0065]
Therefore, when light other than EUV is used for the measurement of optical characteristics, or when a reflection film other than a multilayer optical thin film is provided on a mirror to measure the optical characteristics, the difference between the wavelength of light and the reflectance of the reflection film is measured. As a result, the temperature rise and thermal deformation of the mirror may differ from the actual use conditions, and the optical characteristics in the actual use conditions may not be measured.
[0066]
In such a case, it is preferable that the reflectance of light used for measuring optical characteristics in the optical thin film for measurement is substantially equal to the reflectance of ultrashort ultraviolet rays in the actually used multilayer optical thin film. . Then, it is preferable that the light amount of the measurement light to be incident on the projection system and the light amount of the exposure light incident on the projection system at the time of exposure are made substantially the same. As a result, the temperature rise and thermal deformation of the mirror in the measurement state of the optical characteristics can be made substantially equal to those in the actual use state, and the above-mentioned problems can be avoided.
In this embodiment, a transmission type mask is used as a mask, but it goes without saying that measurement can be performed using a reflection type mask.
[0067]
FIG. 2 is a diagram showing an outline of an optical characteristic measuring device for an ultra-short ultraviolet optical system according to a second embodiment of the present invention. Since the device shown in FIG. 2 is mostly the same as the device shown in FIG. 1, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0068]
The light emitted from the ultrashort ultraviolet optical system 5, which is the object to be inspected, forms an image of the standard pattern of the mask 4 on the pinhole plate 10 mounted on the pinhole plate stage 9. One pinhole is opened in the pinhole plate 10, and light passing therethrough is incident on the light detector 11 and detected.
[0069]
By moving the pinhole plate stage 9 two-dimensionally, the position of the pinhole can be changed two-dimensionally, and the two-dimensional light quantity distribution on the imaging plane can be measured. From the light quantity distribution measured in this way, an image of the pattern of the mask 4 formed on the image forming plane can be reproduced. If it is not possible to illuminate the entire standard pattern of the mask 4 at one time, the mask stage 3 may be driven to change the illumination position and measure sequentially. The measurement of the field curvature can be performed by sequentially changing the position of the pinhole plate stage 9 in the optical axis direction, which is the same as the apparatus shown in FIG.
[0070]
In particular, it is preferable to use ultraviolet light or visible light as a light source, since a light detector 11 developed for ultraviolet light or visible light such as a photomultiplier can be used as it is. The items described in the description of the apparatus shown in FIG. 1, such as the light source used and the reflection film of the mirror in the ultrashort ultraviolet optical system 5, can be applied to the apparatus shown in FIG.
[0071]
FIG. 3 is a diagram showing an outline of an optical characteristic measuring device for an ultra-short ultraviolet optical system according to a third embodiment of the present invention. Since the device shown in FIG. 3 is also substantially the same as the device shown in FIG. 1, the same components as those shown in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
[0072]
The light emitted from the ultrashort ultraviolet optical system 5 which is the object to be inspected enters the relay optical system 12. The relay optical system 12 forms an image formed on the image plane of the ultrashort ultraviolet optical system 5 on the two-dimensional optical sensor 13 at an enlarged magnification. As the two-dimensional optical sensor 13, a two-dimensional CCD or the like can be used. In particular, it is preferable to use visible light as the light source, since the relay optical system 12 and the two-dimensional light sensor 13 can be used as they are as developed for ultraviolet light or visible light.
[0073]
According to the apparatus shown in FIG. 3, the image of the standard pattern formed on the mask 4 can be measured two-dimensionally. The relay optical system 12 is used because the image formed on the image plane of the ultrashort ultraviolet optical system 5 has a fine line width. This is because it is not possible to detect at the intended resolution. Therefore, the relay optical system 12 enlarges the image to such an extent that the image can be detected with the resolution of the two-dimensional sensor 13.
[0074]
If it is not possible to illuminate the entire standard pattern of the mask 4 at one time, the mask stage 3 may be driven to change the illumination position and measurement may be performed sequentially. Changing the position of the two-dimensional sensor 13 in the direction of the optical axis and sequentially performing the measurement enables measurement of the field curvature, which is the same as the apparatus shown in FIG. The items described in the description of the apparatus shown in FIG. 1, such as the light source used and the reflection film of the mirror in the ultrashort ultraviolet optical system 5, can be applied to the apparatus shown in FIG.
[0075]
As the “optical sensor mechanism” according to claim 15, various valuations can be considered as described above, but any configuration is possible as long as an image formed on an image forming surface can be converted into an electric signal with a desired resolution. May be adopted.
[0076]
In each of the above-described devices, it is preferable that the light emitted from the illumination optical system 1 has a property similar to the illumination light actually used as much as possible. For example, when two-dimensional uniform illumination light is formed by an integrator or the like in a light source actually used, light emitted from the illumination optical system 1 is also two-dimensional uniform illumination light. If light having telecentricity is used, it is preferable that light emitted from the illumination optical system 1 also has telecentricity.
[0077]
Further, depending on the light used for the measurement, contamination may occur in the apparatus during the measurement. In such a case, it is preferable to provide the device with a function of suppressing contamination of the optical system or a function of removing contamination attached to the optical element. The function of suppressing the contamination can be realized by, for example, flowing an inert gas or an organic gas containing little impurity gas around the projection optical system. The function of removing contamination can be realized, for example, by flowing ozone around the projection optical system.
[0078]
The example of the method of forming an image of the standard pattern formed on the mask on the image forming surface through the ultrashort ultraviolet optical system 5 as an object to be inspected and measuring distortion and field curvature from the pattern has been described. On the other hand, if an interferometer is used, wavefront aberration, distortion, and field curvature can be measured.
[0079]
FIG. 4 is a diagram showing an outline of an optical characteristic measuring device for an ultra-short ultraviolet optical system according to a fourth embodiment of the present invention. In this example, wavefront aberration is measured as an optical characteristic. 14 is a laser light source, F ₂ , KrF, Arf, He-Ne, etc., the measurement light source used in FIGS. 1 to 3 can be used. From the light source 14, a laser beam in a predetermined wavelength range is emitted in a substantially plane wave state.
[0080]
After passing through the beam splitter 15, the laser light travels to the focusing optical system 16. The condensing optical system 16 is a substantially aberration-free optical system in which the spherical aberration and the sine condition are suppressed to a negligible level with respect to the measurement accuracy of the wavefront aberration measuring instrument. Here, the incident surface 16a of the condensing optical system 16 has the same shape (that is, a plane) as the incident plane wave, and the incident surface 16a is a half mirror surface. Accordingly, the plane wave incident on the incident surface 16a is amplitude-divided here, and the reflected light is returned to the beam splitter 15 as the reference light as the plane wave.
[0081]
On the other hand, the transmitted light that has passed through the incident surface 16a is condensed by the condensing optical system 16 as measurement light, is converted into a spherical wave, and travels to the ultrashort ultraviolet optical system 5, which is the object to be inspected. Needless to say, the last surface (the lens surface closest to the exit side) of the light collecting optical system 16 may be used as the reference surface.
[0082]
The ultrashort ultraviolet optical system 5 is positioned in the wavefront aberration measuring device so that the position of the object plane (mask surface) coincides with the position of the focal point of the spherical wave. Will be incident. Here, if there is no wavefront aberration in the ultrashort ultraviolet optical system 5 (if the ultrashort ultraviolet optical system 5 is an ideal optical system), the ultrashort ultraviolet optical system 5 converges at an image plane position. A spherical wave will be emitted.
[0083]
A spherical mirror 17 is disposed on the emission side of the ultrashort ultraviolet optical system 5 on the opposite side of the projection system with respect to the image plane. The surface shape of the spherical mirror 17 is formed in the same shape as the spherical wave emitted from the ultrashort ultraviolet optical system 5 when the ultrashort ultraviolet optical system 5 is an ideal optical system. Therefore, when the ultrashort ultraviolet optical system 5 is an ideal optical system, a spherical wave having the same shape as the spherical wave emitted from the ultrashort ultraviolet optical system 5 is returned to the ultrashort ultraviolet optical system 5 again. If the ultrashort ultraviolet optical system 5 has a wavefront aberration, a wavefront having a shape corresponding to the wavefront aberration is returned to the ultrashort ultraviolet optical system 5.
[0084]
The measurement light reflected by the spherical mirror 17 and returned to the ultra-short ultraviolet optical system 5 is emitted from the ultra-short ultraviolet optical system 5, passes through the condenser optical system 16, and travels to the beam splitter 15. As described above, the reference light reflected on the incident surface 16a of the light-converging optical system 16 also travels to the beam splitter 15, and the measurement light and the reference light are reflected on the beam splitter 15, and are reflected by a photoelectric conversion device such as a CCD. The light reaches the light receiving surface of the light receiver 18 composed of a conversion element. Here, when the extremely short ultraviolet optical system 5 has a wavefront aberration, interference fringes corresponding to the wavefront aberration are generated on the light receiving surface. This interference fringe has a shape corresponding to the difference between the reference wavefront and the wavefront of the light beam that has reciprocated through the projection system 9. You can ask.
[0085]
Here, the measurement is performed while relatively moving the ultra-short ultraviolet optical system 5, the condensing optical system 16 and the spherical mirror 17, so that a plurality of positions in the field of view (or exposure area) of the ultra-short ultraviolet optical system 5 are obtained. Measurement of wavefront aberration.
[0086]
The details of this apparatus are disclosed in Japanese Patent Application Laid-Open No. 2000-91209. From the wavefront aberration obtained in this way, it becomes possible to correct the surface shape of each mirror constituting the projection optical system by the method disclosed in JP-A-2000-91209 or the like.
[0087]
FIG. 5 shows an example of a procedure for assembling and adjusting the ultra-short ultraviolet optical system in the manufacturing process of the ultra-short ultraviolet optical system using the measuring apparatus described in each of the embodiments.
[0088]
First, the mirror substrate is polished based on the design specifications (step S11). Subsequently, an optical property measuring reflection film is formed on the polished surface of the mirror substrate instead of the multilayer film (Step S12). For example, when ultraviolet light or visible light is used as a light source for measuring optical characteristics, a silver or aluminum thin film is formed by sputtering as described above. Then, the optical system is assembled using the mirror in this state (step S13). After the assembly is completed, optical characteristics such as wavefront aberration, distortion, and curvature of field are evaluated (step S14). As the measuring device, for example, the one described in the section of the present embodiment is used. Then, it is determined whether or not the measurement result satisfies the specifications required for the ultrashort ultraviolet optical system (step S15).
[0089]
If the specifications are satisfied, the reflection film for measuring optical characteristics is peeled off (step S16), and a multilayer film (multilayer optical thin film) actually used is coated instead (step S17). Then, the optical system is reassembled using this mirror (step S18).
[0090]
If it is determined in step S15 that the specifications are not satisfied, a required correction value of the mirror shape and a required correction value of the assembly position are obtained based on the measurement data. Normally, the assembling position correction value is obtained first, and if the optical characteristic is within the specification value only by correcting the assembling position, the process proceeds to step S19, and the optical system is reassembled based on this correction value. After the assembly, the process returns to step S14.
[0091]
If the optical characteristics do not fall within the specification values only by correcting the assembly position, the process proceeds to step S20, and the mirror shape is corrected based on the mirror shape correction value. At this time, prior to reworking the mirror substrate, it goes without saying that the reflection film for measuring optical characteristics formed on the mirror surface is peeled off. After the rework of the mirror substrate is completed, the process returns to step S12. If it is necessary to adjust the assembling position at the time of assembling the optical system in step S13, it goes without saying that this adjustment is performed. No.
[0092]
Normally, the assembly and adjustment of the ultra-short ultraviolet optical system can be performed by the above-described steps. However, after step S18, the optical characteristics when an actual multilayer film is used are measured to confirm the result. If it does not fall within one specification, the process may shift to step S18 again. In this case, it is difficult to perform the optical characteristics in the visible light range when the multilayer film is used. ₂ It is preferable to use a laser (wavelength 150 nm), an ArF laser (wavelength 198 nm), a KrF laser (wavelength 248 nm), or the like as a light source.
[0093]
The example shown in FIG. 5 is an example in which a thin film for measuring optical characteristics is formed and measured before forming a multilayer optical thin film on the mirror substrate surface. The measurement may be performed by forming a measurement thin film. Also, F ₂ A laser (wavelength: 150 nm), an ArF laser (wavelength: 198 nm), a KrF laser (wavelength: 248 nm), or the like may be used as a light source, and the measurement may be performed by using reflection from a multilayer optical thin film. However, in these cases, there is a demerit that the multilayer optical thin film formed must be peeled off when processing the mirror.
[0094]
Note that it is preferable to perform measurement using exposure light to evaluate the final performance of the optical system. Since the almost final surface shape can be formed by the measurement using the non-exposure light having a relatively short measurement time, the time required for the entire measurement can be significantly reduced.
[0095]
【The invention's effect】
As described above, according to the present invention, a method and an apparatus for easily measuring the optical characteristics of an ultra-short ultraviolet optical system as compared with the related art without increasing the size of the apparatus, Can provide a method for manufacturing an ultrashort ultraviolet optical system using these methods and apparatuses.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an optical characteristic measuring device for an ultrashort ultraviolet optical system which is a first example of an embodiment of the present invention.
FIG. 2 is a diagram showing an outline of an optical characteristic measuring device of an ultrashort ultraviolet optical system which is a second example of an embodiment of the present invention.
FIG. 3 is a diagram illustrating an outline of an optical characteristic measuring device of an ultrashort ultraviolet optical system according to a third embodiment of the present invention.
FIG. 4 is a diagram showing an outline of an optical characteristic measuring device for an ultra-short ultraviolet optical system according to a fourth embodiment of the present invention.
FIG. 5 is a diagram illustrating an example of a procedure for assembling and adjusting the ultra-short ultraviolet optical system in the manufacturing process of the ultra-short ultraviolet optical system using the measuring apparatus described in each of the embodiments. .
FIG. 6 is a view schematically showing a part of an extremely short ultraviolet projection exposure apparatus.
[Explanation of symbols]
1: Illumination optical system
2: Illumination light
3: Mask stage
4: Mask
5: Ultra-short ultraviolet optical system
6: Outgoing light
7: Wafer stage
8: Wafer
9: Pinhole plate stage
10: Pinhole plate
11: Optical detector
12: Relay optical system
13: Two-dimensional optical sensor
14: Laser light source
15: Beam splitter
16: Condensing optical system
16a: incident surface
17: Spherical mirror
18: Receiver

Claims (15)

A method for measuring the optical characteristics of an ultrashort ultraviolet optical system, wherein the measurement is performed using light other than the ultrashort ultraviolet light as light used for measuring the optical characteristics. A characteristic measuring method, wherein a wavelength of light used for measuring the optical characteristic is in a range of 150 nm to 250 nm. A method for measuring the optical characteristics of an ultrashort ultraviolet optical system, wherein the measurement is performed using light other than the ultrashort ultraviolet light as light used for measuring the optical characteristics. In the characteristic measuring method, the measurement is performed by forming an optical thin film for measurement instead of the multilayer optical thin film formed on the surface of the mirror used in the ultrashort ultraviolet optical system. A method for measuring the optical characteristics of an optical system. 3. The method for measuring optical characteristics of an ultra-short ultraviolet optical system according to claim 2, wherein the optical thin film for measurement is formed using a material that can be etched by an etching method in which the substrate has resistance. A method for measuring the optical characteristics of an ultra-short ultraviolet optical system. 4. The method for measuring optical properties of an ultra-short ultraviolet optical system according to claim 3, wherein the material forming the mirror is made of a material having etching resistance to nitric acid, and the optical thin film for measurement is etchable with nitric acid. A method for measuring optical characteristics of an ultra-short ultraviolet optical system, comprising: 5. The method for measuring optical characteristics of an extreme ultraviolet optical system according to claim 3, wherein the substrate forming the mirror is made of at least one of glass, quartz, and ceramics, and the optical thin film for measurement is used. Is made of silver or aluminum or a material containing these as a main component. A method for measuring the optical characteristics of an ultrashort ultraviolet optical system, wherein the measurement is performed using light other than the ultrashort ultraviolet light as light used for measuring the optical characteristics. In the characteristic measuring method, an ultra-short ultraviolet ray is formed by forming an optical thin film for measurement on a multilayer optical thin film formed on a surface of a mirror used in the ultra-short ultraviolet optical system and performing measurement. A method for measuring the optical characteristics of an optical system. 7. The method for measuring optical characteristics of an ultra-short ultraviolet optical system according to claim 6, wherein the optical thin film for measurement is formed using a material that can be etched by an etching method in which the substrate and the multilayer optical thin film have resistance. A method for measuring optical characteristics of an ultra-short ultraviolet optical system, comprising: The method for measuring optical characteristics of an ultra-short ultraviolet optical system according to claim 7, wherein the material forming the mirror and the material forming the surface of the multilayer optical thin film are made of a material having etching resistance to nitric acid, The method for measuring optical characteristics of an ultra-short ultraviolet optical system, wherein the optical thin film for measurement is made of a material that can be etched with nitric acid. The method for measuring optical characteristics of an extreme ultraviolet optical system according to claim 7 or 8, wherein the substrate constituting the mirror is made of at least one of glass, quartz, or ceramics, and a multilayer optical thin film. The surface is made of Si, and the optical thin film for measurement is made of silver or aluminum, or a material containing these as a main component. Method. The method for measuring the optical characteristics of an ultra-short ultraviolet optical system according to claim 2, wherein a film thickness distribution of the optical thin film for measurement is measured using an ultra-short ultraviolet light in the multilayer optical thin film. A method for measuring optical characteristics of an ultra-short ultraviolet optical system, wherein a film thickness distribution is such that a phase change equivalent to a phase change received when light is reflected is produced. The method for measuring optical characteristics of an ultra-short ultraviolet optical system according to any one of claims 2 to 10, wherein the reflectance of light used for measuring the optical characteristics in the optical thin film for measurement is determined. A method for measuring the optical characteristics of the ultrashort ultraviolet optical system, wherein the reflectance is substantially equal to the reflectance of the ultrashort ultraviolet light in the multilayer optical thin film. The method for measuring optical characteristics of an ultra-short ultraviolet optical system according to any one of claims 2 to 11, wherein a wavelength of light used for measuring the optical characteristics is in a range of 150 nm to 250 nm. A method for measuring optical characteristics of an ultra-short ultraviolet optical system, characterized in that: A device for measuring the optical characteristics of the ultrashort ultraviolet optical system, a light source that emits light having a wavelength other than ultrashort ultraviolet light, a mask having a predetermined standard pattern, and light from the light source, An illumination optical system that irradiates the mask and transmits light transmitted through the mask or light reflected by the mask to an ultrashort ultraviolet optical system to be measured, and an ultrashort ultraviolet optical system to be measured And a light receiving substrate having a photosensitive member applied to the surface thereof. 14. Instead of the light-receiving substrate in the optical characteristic measuring apparatus for an ultra-short ultraviolet optical system according to claim 13, two-dimensionally measuring the intensity of light on an imaging surface of the ultra-short ultraviolet optical system to be measured is possible. An optical characteristic measuring device for an ultra-short ultraviolet optical system, comprising: an optical sensor mechanism. An optical characteristic measuring method for an ultra-short ultraviolet optical system according to any one of claims 1 to 12, or an optical characteristic measuring apparatus for an ultra-short ultraviolet optical system according to claim 13 or 14. Then, the optical characteristics of the ultrashort ultraviolet optical system are measured, and according to the result, at least one of correction of the surface shape of the optical element constituting the ultrashort ultraviolet optical system and adjustment of the installation position of the optical element A process for producing an ultra-short ultraviolet optical system.

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