JP2004045043A - Phase measurement device, and optical element, exposure apparatus and device manufacturing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase measurement device which can easily measure phase characteristics corresponding to an EUV wavelength of a reflective coating film applied on a curved mirror or a flat mirror with a high degree of precision. <P>SOLUTION: The phase measurement device comprises an optical system for illumination in which a light flux including EUV light and light with a wavelength of 248 nm is emitted to an inspection surface within a predetermined angle range, and an optical system for detection in which interference fringes of the EUV light and the light with a wavelength of 248 nm are formed on a detection means due to the reflected light from the inspection surface. In addition, by measuring the interference fringes detected by the detection means, the dependence of the phase of the EUV light due to the inspection surface on an incident angle of the EUV light to the inspection surface is measured. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a phase measuring device for an optical thin film, for example, a step-and-repeat method or a step-and-scan method for manufacturing devices such as semiconductor devices such as ICs and LSIs, photographing devices such as CCDs, and display devices such as liquid crystal panels. This method is suitable for measuring the phase of an optical thin film provided on a reflection surface or a transmission surface of an optical system used in an exposure apparatus such as a system.
[0002]
[Prior art]
With the miniaturization of device patterns, the wavelength of exposure light when projecting and exposing device patterns on photosensitive materials such as wafers is becoming shorter and shorter. For example, as exposure wavelengths, KrF having a wavelength of about 248 nm, ArF having a wavelength of about 193 nm, F2 laser having a wavelength of about 157 nm, and even EUV light having a wavelength of 10 to 15 nm have been used.
[0003]
The miniaturization of device patterns is the largest factor that supports the dynamics of the semiconductor industry, and since the era of demanding the resolution of a pattern with a line width of 0.25 micron when creating a 256M DRAM, the required resolvable lines have been required. The width has been rapidly reduced to 180 nm, 130 nm, and 100 nm. In lithography using i-rays (wavelength: about 365 nm) as exposure light, resolution with a line width smaller than the wavelength has not been used.
[0004]
On the other hand, an exposure apparatus using KrF as a light source is applied to lithography for a line width of 180 nm or 150 nm even though the wavelength of the exposure light is about 248 nm. Utilizing the results of improvements in resists, super-resolution techniques, and the like, resolution with a line width equal to or less than the wavelength is being put to practical use. If various super-resolution techniques are used, pattern resolution with a line width of 波長 wavelength in lines and spaces has come into practical use.
[0005]
However, the super-resolution technique often involves restrictions on the production of patterns, and the royal road to improving the resolution is to shorten the wavelength of exposure light and improve the NA of the projection optical system. The above fact is a great motivation for shortening the wavelength of exposure light, which is the reason why EUV lithography using light having a wavelength of 10 to 15 nm (13 to 14 nm) as exposure light is developed.
[0006]
[Problems to be solved by the invention]
When EUV light is used as the exposure light, there is no substance that is transparent in the EUV wavelength range (transmits EUV light at a high transmittance) at present, so there is a great limitation on the materials that can be used in an optical system targeting the EUV range. Joins. In particular, transmission-type (refraction-type) optical elements as conventionally used can no longer be used, and almost all optical systems must be configured as reflection systems. In such an exposure apparatus using EUV light, the optical constant (refractive index) of the optical material with respect to EUV light is close to 1, so that the reflectivity of the mirror surface is low, and the absorptance of each mirror is low. There is a problem that it becomes high. In other words, the characteristics (reflectance and the like) of the reflection enhancing film attached to the reflecting mirror (mirror) in order to obtain a predetermined reflectance have become a major issue.
[0007]
Unlike the case of using laser light such as KrF, ArF, F2, etc., a characteristic of the reflective film for short-wavelength light in the EUV region is that it is required to manage the phase (phase distribution) of the film together with the reflectance. That is. When the EUV light is reflected by the reflection film, the phase of the EUV light changes. If the incident angle of the EUV light to the reflection film is not uniform, the phase length of the reflection film is shifted depending on the incident angle, so that the phase difference of the EUV light reflected by the reflection film is incident on the mirror surface (reflection film). The wavefront is distorted, and as a result, an aberration (wavefront aberration) is caused.
[0008]
For this reason, it has become necessary to measure the phase characteristic (phase distribution of reflected light) of the reflection film when the film is formed on the reflection surface. In particular, it is desirable to measure the angular characteristics (incident angle dependence) when EUV light enters the reflective film at various angles at each position where the reflective film is applied.
[0009]
In addition, in order to correct the aberration of the reflection imaging system, in addition to manufacturing the shape of the substrate such as the curvature of the substrate of the mirror (reflection surface) and the amount of aspherical surface with high accuracy, the performance of the multilayer film for enhancing reflection is also required. Also need to be managed with high accuracy. At this time, the multilayer film must be accurately controlled so that the phase given to light at the time of reflection does not greatly differ depending on the position of reflection within one mirror surface (reflection surface). Therefore, before assembling the reflection imaging system, it is necessary to finish the shape of the mirror and inspect whether the reflection phase at each position where the multilayer film is laminated on the mirror surface is the same as the design value.
[0010]
According to the present invention, a phase characteristic of a film which depends on an incident angle at each position of a film formed on a reflecting mirror, that is, a reflecting mirror (reflecting surface) as a test surface is in an EUV wavelength region (10 nm to 15 nm, preferably 13 nm to 15 nm). It is an object of the present invention to provide a phase measuring apparatus capable of easily and highly accurately measuring the dependence of the phase given to the light of (1) on the angle of incidence of the light of the first wavelength on the surface to be measured.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a phase measuring device according to the present invention includes: an illumination optical system that causes a light beam including light of a first wavelength and light of a second wavelength to enter a test surface with a predetermined angle range; A detection optical system for forming an interference fringe of the light of the first wavelength and an interference fringe of the light of the second wavelength on detection means by reflected light from the surface to be detected, and detected by the detection means; By measuring the interference fringes, the dependence of the phase given to the light of the first wavelength by the test surface on the angle of incidence of the light of the first wavelength on the test surface is measured. And
[0012]
Here, with respect to the angle of incidence of the light of the first wavelength on the surface to be inspected, a phase change given to the light of the first wavelength by the surface to be inspected, and a change in the light of the second wavelength to the surface to be inspected. From the phase change of the light of the second wavelength with respect to the incident angle, the dependence of the phase given to the light of the first wavelength by the test surface on the angle of incidence of the light of the first wavelength on the test surface The property may be measured.
[0013]
Further, by shifting the reflected light from the surface to be measured laterally, an interference fringe of the light of the first wavelength and an interference fringe of the light of the second wavelength are formed. The amount of change is obtained from the interference fringes of the light of the second wavelength, and the surface to be detected gives the light of the first wavelength from the interference fringes of the light of the first wavelength and the amount of change in phase caused by the lateral shift. The dependence of the phase on the angle of incidence of the light of the first wavelength on the surface to be measured may be measured.
[0014]
Here, it is preferable that the first wavelength is shorter than the second wavelength, and it is further preferable that the second wavelength is longer than 10 times the first wavelength. More specifically, the first wavelength may be a wavelength of 10 nm or more and 15 nm or less, more preferably, a wavelength of 13 nm or more and 14 nm or less, and the second wavelength may be a wavelength of 150 nm or more.
[0015]
Further, it is preferable that the surface to be inspected has a reflective multilayer film formed using Mo and Si. Of course, a Be-Si or Rh-Si film may be used. When a Be-Si film is used, the wavelength is preferably in the range of 10 nm to 12 nm.
[0016]
Here, an interference fringe of the light of the first wavelength is provided by having a branching optical element for branching the reflected light from the surface to be inspected into a plurality of light beams and causing at least two of the plurality of light beams to interfere with each other. And the interference fringes of the light of the second wavelength may be formed on the detecting means.
[0017]
Further, it is preferable that the branch optical element is a branch diffraction grating (diffraction grating). Further, it is more preferable that the detection optical system includes a light blocking member that selectively transmits two light beams among a plurality of light beams branched by the branch optical element. Further, the light shielding member may be formed such that one light beam of the two light beams is an ideal spherical wave on the detection unit side with respect to the light shielding member. Having a first opening for transmitting the light of the first wavelength and a second opening for transmitting the light of the second wavelength, of the light emitted from the branching optical element, The first opening and the second opening may be different in size, and the first opening and the second opening may be configured so that at least a part thereof overlaps with each other. Here, it is more preferable that the first opening and the second opening have substantially the same centers. Further, the branching optical element may be a branching diffraction grating, and a region where the first opening and the second opening overlap each other may be configured to transmit the 0th-order diffracted light emitted from the branching diffraction grating. Still preferred.
[0018]
Further, the second wavelength of the second wavelength, which is obtained by photoelectrically converting an interference fringe of the second wavelength of light detected by the detection unit with respect to a second incident angle at which the second wavelength of light is incident on the surface to be measured, Using a tilt component (tilt component) of a phase change amount received by the light being reflected by the test surface,
The light of the first wavelength is obtained by photoelectrically converting interference fringes of the light of the first wavelength detected by the detection means with respect to a first incident angle at which the light of the first wavelength is incident on the surface to be measured. It is more preferable that the tilt component (tilt component) is removed from the amount of phase change received by the reflection on the test surface.
[0019]
Further, the illumination optical system may include a diffraction grating for superimposing the light of the first wavelength and the light of the second wavelength. Of course, both lights may be superimposed using a member such as a half mirror. Further, it is preferable that the light of the first wavelength and the light of the second wavelength are made to enter the surface to be measured with the same width of the incident angle.
[0020]
Further, the light shielding member may be configured to selectively transmit two diffracted lights out of a plurality of diffracted lights emitted from the branching diffraction grating, or the two diffracted lights may be converted into a plus first-order diffracted light. And minus first-order diffracted light, or one of the two diffracted lights may be zero-order diffracted light.
[0021]
Further, the present invention is not limited to the phase measuring device, but may be a phase measuring method. A phase measuring apparatus according to the present invention includes a step of causing a light beam including light of a first wavelength and light of a second wavelength to enter a test surface with a predetermined angle range in an illumination optical system; Forming interference fringes of the light of the first wavelength and interference fringes of the light of the second wavelength on detection means by light reflected from a surface, and measuring the interference fringes detected by the detection means Measuring the dependence of the phase given to the light of the first wavelength by the test surface on the angle of incidence of the light of the first wavelength on the test surface.
[0022]
Here, an optical element whose phase has been measured by the phase measuring device of the present invention, an exposure apparatus having the optical element, a step of exposing an object to be exposed using the exposure apparatus, and a step of developing the object to be exposed The present invention also includes a method for manufacturing a device having the following.
[0023]
Further, as the interferometer of the present invention, the light from the surface to be inspected is divided into a plurality of lights, and the wavefronts of the plurality of lights are caused to interfere with each other while being shifted laterally from each other to form an interference fringe. In an interferometer for measuring the state of the wavefront of light from the surface to be detected based on the obtained phase distribution, the light includes first and second lights having different wavelengths from each other, and the first and second lights Forming the interference fringes every time, determining a phase change component from a phase distribution obtained from the interference fringes by the second light having a longer wavelength among the first and second lights, It is preferable that the state of the wavefront of the first light be measured using a phase distribution obtained from the interference fringes and the phase change component.
[0024]
Here, it is preferable that the phase change component is caused by the lateral shift and / or the surface shape of the test surface.
[0025]
More preferably, the wavelength of the second light is longer than 10 times the wavelength of the first light. More specifically, the wavelength of the first light is preferably 10 nm or more and 15 nm or less, more preferably 13 nm or more and 14 nm or less, and the second wavelength is preferably 150 nm or more.
[0026]
Here, a step of exposing an object to be exposed using an optical device having the surface to be measured and an optical device having the optical device and an optical device having the optical device measured by the interferometer of the present invention, A method for manufacturing a device, comprising a step of developing the object to be exposed, is also a part of the present invention.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
In the measurement of the reflection phase distribution of the reflection film (multilayer film) of the present embodiment, the phase of the reflected light (dependence on the angle of incidence of the EUV light of the reflection film) due to the difference in the incident angle of the EUV light to the reflection film is measured. ing. The phase measuring apparatus (interferometer) according to the present embodiment is an object to be measured in which convergent light is converted into an almost ideal spherical wave having wavelengths of, for example, 248 nm and 13.5 nm, and a film is formed on the surface in front of the converging point. Irradiate on top. The wavefronts of the light having the wavelengths of 248 nm and 13.5 nm are coaxial and the light-condensing points are made to coincide. Although the wavelength to be originally measured is 13.5 nm, when calculating the wavefront from the interference fringes, the inclination component of the reflected wavefront with respect to the incident wavefront must be removed. In some cases, the interference fringes cannot be obtained because the reflectance of 13.5 nm light is low. When calculating the change in phase using the phase obtained from the interference fringes, the inclination of the phase with respect to the incident angle cannot be obtained unless there is a reference. The present invention uses a wavefront having a wavelength of 248 nm, which is visible light or UV light, which is reflected on the surface of the test surface of the film, as a reference.
[0028]
Specifically, a branch diffraction grating for shifting the wavefront reflected by the surface to be measured laterally (of course, not limited to the branch diffraction grating, but if it is a device for splitting and shifting the light beam, it is formed in a half mirror or lattice shape). Any branching optical element such as a mirror may be used.) At the light-converging point, for example, + 1st-order and -1st-order light are selected by an aperture and the like, and are detected on detection means such as a CCD (detection surface). ), A shearing interference fringe or a point diffraction interference fringe is generated, and the phase of the wavefront is determined from the interference fringes. Here, the wavelength of 13.5 nm and the wavelength of 248 nm divide the branch grating, and the pitch of the diffraction grating is determined so that each wavelength has the same diffraction angle. Even if a 13.5 nm wavefront enters the 248 nm diffraction grating, it is cut by the above-mentioned aperture, and conversely, if a 248 nm wavefront enters the 13.5 nm diffraction grating, it is also cut by the aperture.
[0029]
As described so far, the wavefront of the 248 nm light has the wavefront having the information of the surface shape of the surface to be measured and / or the information of the phase change component caused by laterally shifting the reflected light from the surface to be measured. The wavefront of 13.5 nm light is a wavefront having information inside the film (test surface, test film). Of course, the wavefront of 13.5 nm light also has information that the wavefront of 248 nm light has. Therefore, the phase of the reflected light due to the difference in the incident angle to the reflective film (the incident angle of the EUV light of the reflective film) is based on the information of the wavefront of the light of 248 nm having the wavelength of 13.5 nm and the wavefront of 13.5 nm. Dependence) can be measured. As means for obtaining the wavefront information, there is a means for measuring interference fringes of light of each wavelength.
[0030]
Although the shearing interferometer has been described as an interferometer for detecting a wavefront, a point diffraction interferometer (PDI) is also possible. In the case of PDI, one aperture in the aperture for selecting the diffracted light after the branch diffraction grating has an aperture large enough to reflect the wavefront aberration and a pinhole small enough to generate an ideal spherical wave (about twice the wavelength). , 1.5 times or more and 3 times or less. As clearly shown in the second embodiment, the pinhole is configured to generate a spherical wave with respect to both visible light or UV light and EUV light.
[0031]
Hereinafter, specific examples will be described with reference to the drawings.
[0032]
(First embodiment)
FIGS. 1 to 5 are schematic views of a main part of a first embodiment of a phase measuring apparatus according to the present invention, and show a case where phase information of a reflection film on a reflection surface for EUV wavelength region light is measured. .
[0033]
FIG. 1 will be described. A light beam L1 from a light source 1 for EUV that emits light having a wavelength of 13.5 nm (the wavelength is not limited to 13.5 nm, but may be 13.4 nm, or any light having a wavelength of 10 nm to 15 nm) is a reflecting mirror. The wavefront is adjusted by reflecting the light at 2 and making the light beam L4 substantially emitted from the point light source through the pinhole 3a provided on the member 3. The light beam L4 spread from the pinhole 3a is transmitted from the first incident angle θ1 to the second incident angle θ1 on the reflecting film (test surface) 5 via the reflecting mirror 9 such as an ellipsoid, a paraboloid, or a rotationally asymmetric aspheric surface. The measurement point 5c on the reflection film 5 is irradiated as a light beam L5 having a width (range) up to the incident angle θ2. On the other hand, the light source 21 having a wavelength of 248 nm is superimposed on the light beam L5 through the condensing optical system 19 and the multiplexing grating 22, and similarly to the light beam L5, the width (range) from the first incident angle θ1 to the second incident angle θ2. ) Is irradiated on the measurement point 5c on the reflection film 5 as a light beam L5.
[0034]
The light beam L6 reflected at the measurement point 5c on the reflection film 5 travels toward the condensing point 8, but the light of each wavelength is diffracted by the branch diffraction grating (light beam splitting means) G1 on the way. The light beam L6 is sheared and separated into two light beams. Then, only the + 1st-order and -1st-order diffracted lights selectively pass through the aperture by the aperture A1 having a plurality of openings. The + 1st-order and -1st-order diffracted lights are caused to interfere with each other, and the interference information is detected by detecting means 7 using a photoelectric converter such as a CCD. In FIG. 1, the light beam emitted from the branch diffraction grating G1 does not seem to be split, but the light beam is actually diffracted as shown in FIG. 5, and the 0th-order light, the + 1st-order light, the -1st-order light, and the + 2nd-order light. .. Etc.
[0035]
Then, the arithmetic means 10 obtains the incident angle distribution (incident angle dependency) of the phase of the reflected light reflected at the measurement point 5c at the incident angles θ1θ1 and θ2 using the signal from the detecting means 7. The incident angle distribution is
φ (x, θ + Δθ) -φ (x, θ)
Is obtained as the intensity of the interference signal.
[0036]
Δθ is a deviation (shift angle) of the angle of incidence of light on the reflection film 5 from θ. The above equation represents the phase shift of the reflected light when the incident angle is shifted by a predetermined angle Δθ from θ with respect to the incident angle θ, where the incident angle θ is the first incident angle. This is a predetermined angle within a range from the angle θ1 to the second incident angle θ2. Here, dφ (x1, θ) / dθ is measured by making Δθ very small at the first position x1 on the reflective film.
[0037]
The light beam L5 scans the entire surface of the multilayer film by the relative movement of the reflection film 5 (test object 6) and the measurement system, thereby obtaining the incident angle characteristics (incident angle dependence) of the reflected light on the entire reflection film 5. ing. By differentiating this integral value, the position x ₁ Angle distribution φ (x ₁ , Θ) can be obtained.
[0038]
As described above, in the first embodiment, light having a width (range) at an incident angle is incident on the film 5 by the condensing optical system (reflecting mirror) 9 having a constant NA. The reflected light is sheared at the wavefront by a branching diffraction grating (light beam splitting means) G1 to cause interference, and the detecting means 7 obtains this interference information, thereby obtaining phase information (incident angle dependency) based on the incident angle of the reflective film 5. ing.
[0039]
FIG. 2 shows the positional relationship among the test surface, the branch diffraction grating G1, and the aperture (aperture) A1 in FIG. Here, a direction perpendicular to the Z axis, which is the direction in which the light wave travels, and parallel to the paper surface is defined as an X axis, and a direction perpendicular to the paper surface is defined as a Y axis. The light beam L6 is diffracted by the branch diffraction grating G1 and is separated into light beams of the 0th order, ± 1st order, ± 2nd order,... FIG. 5 shows the state of this separation, and FIGS. 3 to 6 show the state near the branch diffraction grating G1. Here, the branch diffraction grating G1 has a moving mechanism for moving in the X direction.
[0040]
FIG. 3 shows the branch diffraction grating G1 in the XY plane, and the X direction is the periodic direction of the diffraction grating. In the Y direction, a diffraction grating for a wavelength of 13.5 nm is formed in the central portion G10, and a diffraction grating for 248 nm is formed on both sides G11 and G12, and the pitch of the diffraction grating of G10 and that of G11 and G12 are different. It is different from the pitch of the diffraction grating. The diffraction grating G10 has a pitch of 13 such that the diffraction angles of the 13.5 nm light and the 248 nm light (especially the diffraction angle of the plus first order light and the minus 1st order light) are equal. For light having a wavelength of 0.5 nm, the diffraction gratings G11 and G12 are formed for light having a wavelength of 248 nm.
[0041]
FIG. 4 shows the aperture A1 in the XY plane. In the drawing, black portions are regions that block light having a wavelength of 13.5 nm and light having a wavelength of 248 nm, and two white portions A11 and A12 in the black portions are openings. The + 1st-order diffracted light of the light having the wavelength of 13.5 nm and the light having the wavelength of 248 nm transmits through the opening A11, and the −1st-order light transmits through the opening A12.
[0042]
FIG. 5 shows the relationship between the diffracted light and the aperture A1 as viewed in the XZ plane. The zero-order light is blocked, and only the ± first-order light passes through the opening. On the other hand, the zero-order light is cut by the light-shielding portion of the aperture A1 and is not transmitted. Further, diffracted light of ± second order light or more (not shown) is similarly cut. Therefore, only the ± 1st order light of the light having the wavelength of 13.5 nm and the light having the wavelength of 248 nm is transmitted through the aperture A1 by the aperture A1.
[0043]
FIG. 6 shows the branch diffraction grating G1 and the aperture A1 in the YZ plane. Of the two wavelength light beams transmitted through G1, the light beam having a wavelength of 248 nm is diffracted by the branch diffraction gratings G11 and G12, and the light beams emitted therefrom become L61 and L62 and are condensed on the aperture A1. The light beam having a wavelength of 13.5 nm is branched by the branch diffraction grating G10, becomes a light beam L60, and is condensed on the aperture A1. As described above, the periods of these diffraction gratings are configured such that ± first-order diffracted lights of the respective wavelengths pass through the apertures A11 and A12 of the aperture. Therefore, of the light beam having a wavelength of 248 nm, the light beam diffracted by the G10 branch diffraction grating passes through the diffraction grating cut for the wavelength of 13.5 nm, so that the zero-order light travels straight, and is naturally cut by the aperture. Since the first-order or higher light beam has a wavelength longer than 13.5 nm, the light travels considerably outward from the openings A11 and A12, and is similarly cut by the aperture. On the other hand, when a light beam having a wavelength of 13.5 nm is diffracted at G11 and G12, the 0th-order light is cut because it goes straight, and the diffracted light of ± 1st order or more travels considerably inside the openings A11 and A12, so that the aperture is similarly increased. Is cut at Normally, a considerable amount of incident light is converted into zero-order light and primary light, and in the case of the present embodiment, the wavelength is considerably wide at 13.5 nm and 248 nm. Even if there is light passing through A12, it is considered that the amount of light is small because it is a diffracted light of a considerably high order, and has little effect on the detection result. Here, the diffraction gratings G10 and G10 are arranged so that the positions of the openings A11 and A12 are between the n-th order diffracted light and the (n + 1) th order diffracted light when the light having the wavelength of 13.5 nm is diffracted by the G11 and G12. It is also possible by setting the periods of G11 and G12. It is also possible to install a short-wavelength cut filter at a portion where a 248 nm interference fringe of a two-dimensional sensor (such as a CCD) is formed to cut a 13.5 nm light beam.
[0044]
FIG. 7 schematically shows the shape of interference fringes on the two-dimensional sensor on the XY plane. Reference numerals 71 and 72 represent light beams of 248 nm, and reference numeral 70 represents interference fringes of 13.5 nm. In the figure, for ease of understanding, the reference numeral 70 shows the 13.5 nm interference fringe equivalently converted to a 248 nm interference fringe. The interference fringes are phase-modulated by moving the branch diffraction grating G1 in the X direction by at least one pitch of the diffraction gratings G11 and G12 for 248 nm.
[0045]
FIG. 8 shows the result of photoelectrically converting the interference fringes of FIG. 7 and converting the intensity signal of the interference fringes into a phase difference by the processing system 10. 4) is a graph showing the incident angle (corresponding to the X coordinate on the detecting means) with respect to the angle. As is well known, this processing system moves the branch diffraction grating G1 in the X direction and obtains a plurality of interference fringe images to accurately determine the phase difference. In the figure, reference numerals 81 and 82 denote phase shapes by light having a wavelength of 248 nm, and reference numeral 80 denotes a phase difference shape by light having a wavelength of 13.5 nm. Since the light having the wavelength of 248 nm and the light having the wavelength of 13.5 nm have the same tilt component, the tilt component of the phase shape due to the light having the wavelength of 13.5 nm is removed based on the tilt component of 248 nm. That is, with respect to the incident angle of the light of 13.5 nm (light of the first wavelength) to the surface to be measured, the inclination component of the phase given to the light of the first wavelength by the surface to be measured is determined by the interference fringe of the light of the second wavelength It is removed using information (tilt component, tilt component) obtained from the interference fringes. Specifically, the tilt component can be removed by averaging the phase difference between 81 and 82 with respect to the X axis and subtracting the average with respect to 80. In other words, the tilt component obtained from the phase distribution (distribution of the phase difference with respect to the incident angle of the 248 nm light to the surface to be measured) derived from the interference fringes of the 248 nm light by a method such as an arithmetic operation is the EUV wavelength light 13 By removing from the phase distribution (distribution of the phase difference with respect to the incident angle of the 13.5 nm light to the surface to be measured) obtained from the interference fringe of the light having the wavelength of 0.5 nm, the light having the wavelength of 13.5 nm can be reduced. The phase of the 13.5 nm light reflected from the test surface with respect to the incident angle at which the light is incident can be obtained.
[0046]
FIG. 9 shows the phase (distribution) shape of the 13.5 nm wavelength light after removing the tilt component in the phase distribution of the 13.5 nm wavelength light. The horizontal axis is the angle of incidence (corresponding to the X coordinate on the detection means) with respect to the surface to be measured (reflection film). Since this phase difference is a phase distribution due to shearing interference, a reflection phase shape to be obtained can be obtained by integrating the phase difference with dX, that is, dθ.
[0047]
FIG. 10 is a graph showing the relationship (incident angle dependency) between the phase of the reflected light reflected on the test surface (reflection film) and the incident angle on the test surface (reflection film) by performing the above-described integration. It is.
[0048]
The above is the description of the main part of the present embodiment.
[0049]
Here, in the present embodiment, the reflecting mirror 9 converts the light beam L4 into a condensed light beam L5, but the reflecting mirror 9 does not have to have a positive power. That is, the light beam incident on the reflection film 5 does not need to be a converged light beam, and may be a divergent light beam if the incident angle is configured to have a predetermined width (range). In this case, after being reflected by the reflection film 5, the light is converted into a condensed light beam by a reflecting mirror or the like, and then condensed at a plurality of points via a demultiplexing diffraction grating (light beam splitting means) or the like as in the present invention. Just do it.
[0050]
Further, in this embodiment, the diffraction grating 3 is formed by dividing the central portion into three regions, that is, 13.5 nm at the center portion and 248 nm at both sides. One part may be used for 13.5 nm and the other may be used for 248 nm, or four or more regions may be used and the ones for 13.5 nm and the one for 248 nm may be arranged appropriately (preferably alternately). In addition to the division in the Y direction, it may be divided into several regions in the X direction, and diffraction gratings for 13.5 nm and 248 nm may be provided. Further, in the aperture A1 at the subsequent stage, the + 1st-order light and the -1st-order light of the light of both wavelengths do not need to pass through the opening, and the + 1st-order light and the -secondary light or the 0th-order light and -1st light The next light may be selectively transmitted. Needless to say, the branch diffraction grating is not limited to the diffraction grating, but may be another optical element that performs the same function. If a wavelength other than 248 nm is used as a wavelength other than EUV light, the wavelength is 248 nm. It is necessary to appropriately design the pitch of the diffraction grating in the portion described as the diffraction grating for the light according to the wavelength of the light.
[0051]
FIG. 11 shows a method of removing the aberration of the original measurement system (the optical system for guiding light from the light source to the surface to be measured) when the focusing optical system 9 is not aberration-free in this method. Until FIG. 10, the wavefront shape after reflection of the test surface (reflection surface) was measured using the detection means. Here, the interference fringe is measured using the detecting means 7 'using the branch diffraction grating G1' and the aperture A1 'without removing the surface to be measured and reflecting the light on the surface to be measured (reflection surface). Find the phase. Since the phase obtained here is a phase provided by the measurement system, the phase dependence of the reflected light on the surface to be measured (reflection surface) is determined from the phase obtained here and the phase of the reflected light obtained in FIG. Sex can be accurately determined. Incidentally, the measurement of the phase of light that does not pass through the test surface in this way is preferably performed before and after measuring the test surface, but by performing at least either immediately before or immediately after the measurement of the test surface, Errors due to aging can be minimized. In the measurement of the phase of light without passing through the surface to be measured, conditions such as temperature, humidity, and atmosphere inside the phase measuring device are set to be substantially the same as when measuring the phase of light through the surface to be measured. Is preferred.
[0052]
Also, as shown in FIG. 12, the test surface (reflection surface) can be rotated in the XZ plane so that the incident angle range (θ1 to θ2) on the test surface (reflection surface) can be changed. It is good. FIG. 12 is a drawing simply showing the positional relationship between the light beam L5 incident on the test surface, the test surface (reflection film) 5, the light beam L6 emitted from the test surface, and the detecting means 7. In FIG. 12, the angle of incidence of the incident light L5 on the surface to be inspected can be adjusted by rotating the surface to be inspected, and the position of the detecting means 7 where the light beam L6 emitted from the surface to be inspected is incident. Is adjusted so that the outgoing light L6 from the test surface can be made incident on the detection means 7 even when the test surface rotates. The arrows indicate the directions in which the inspection surface 5 and the detection means 7 are movable. FIG. 12 shows that the angle of incidence of light on the reflective film 5 is variable in the measurement apparatus of the present embodiment, and measurement is performed by changing the angle of incidence θ1 and the angle of incidence θ2.
[0053]
In the first embodiment, the phase characteristic of the light reflected at one point on the surface to be inspected (reflection surface) is measured. The uniformity of the reflective film characteristics over the entire inspection surface may also be measured.
[0054]
Here, the light from the surface to be measured is divided into a plurality of lights, and the wavefronts of the plurality of lights are shifted laterally from each other.
Forming an interference fringe by causing interference, an interferometer for measuring a state of a wavefront of light from the test surface based on a phase distribution obtained from the interference fringe,
The light includes first and second lights having different wavelengths from each other, forms the interference fringes for each of the first and second lights, and includes a second light having a longer wavelength among the first and second lights. A phase change component due to the lateral shift is obtained from a phase distribution obtained from the interference fringe of the first light, and the first and second phase distributions are obtained using the phase distribution obtained from the interference fringe of the first light and the phase change component. An interferometer for measuring a state of the wavefront of the light.
[0055]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. While the first embodiment is a shearing interferometer system, the present embodiment is a point diffraction interferometer system. The description will be made with reference to the drawings. The same number or the same function is denoted by the same number in the figures with different numbers.
[0056]
FIG. 13 is an overall configuration diagram of the present embodiment. Unlike the second embodiment and the first embodiment described above, the reference light is generated by using the zero-order diffracted light emitted from the branch diffraction grating G1. Other parts not specifically described are the same as in the first embodiment. Hereinafter, a brief description will be given with reference to FIG. The light beam L1 from the light source 1 is reflected by the reflecting mirror 2 and passes through a pinhole 3a provided in the member 3 to make the wavefront substantially equal to the light beam emitted from the point light source. The light beam L4 spread from the pinhole 3a is transmitted from the first incident angle θ1 to the second light on the film (test light surface) 5 via the reflecting mirror 9 such as an ellipsoid, a paraboloid, or a rotationally asymmetric aspheric surface. The measurement point 5c on the test surface (reflection film) 5 is irradiated as a light beam L5 having a width (range) up to the incident angle θ2. The light beam L6 reflected at the measurement point 5c on the reflective film 5 is split into two light beams by the branch diffraction grating G1, and is irradiated on the aperture A2.
[0057]
FIG. 14 is a diagram of the aperture A2 in the XY plane. The aperture A2 has two openings A21 and A22. A21 is arranged at a position where the 0th-order diffracted light for forming the reference light is incident, and A22 is arranged at a position where the + 1st-order light is incident. Of course, this combination may use other orders of diffracted light, but the order of the diffracted light incident on the aperture for forming the reference light is the same or higher than the order of the diffracted light incident on the other aperture. It is preferable that the diffracted light has a lower order than that of the diffracted light. As described above, in the second embodiment, unlike the first embodiment, the reference light is generated using the zero-order diffracted light emitted from the branch diffraction grating G1. Here, in order to generate the reference light using the stronger zero-order light, the zero-order diffracted light is guided to a minute pinhole A21 having a diameter of about twice the wavelength. On the other hand, the + 1st-order light is guided to a larger aperture A22 so as to directly reflect the disturbance of the wavefront shape due to the surface to be measured. The light wave that has passed through A21 becomes an ideal spherical wave and becomes reference light. On the other hand, the wavefront transmitted through A22 is transmitted while retaining the information of the surface to be detected as it is, and interferes with the reference wave.
[0058]
Here, in order to form reference light (light that generates a spherical wave) by the 0th-order diffracted light incident on the opening A21 of the aperture A2, the size of the opening A21 is about twice the wavelength. There is a need. However, the light incident on the opening A21 is difficult because it includes two types of light having different wavelengths from light having a wavelength of 13.5 nm and light having a wavelength of 248 nm. Therefore, in this embodiment, the vicinity of the aperture A21 of the aperture is configured as shown in FIG. The opening A22 is a normal opening.
[0059]
FIG. 15 is an enlarged view of the opening A21 of the aperture of FIG. The opening (pinhole) is a double pinhole sharing the center. This is so that both light having a wavelength of 13.5 nm and light having a wavelength of 248 nm generate ideal spherical waves, and are constituted by two light shielding members. One of the two light blocking members is provided with a pinhole having a diameter of about twice the wavelength of 248 nm in the non-exposure light blocking member A24 that blocks light having a wavelength of 248 nm (hereinafter, referred to as non-exposure light). And the other is provided with a pinhole having a diameter about twice as large as the wavelength of 13.5 nm in the exposure light shielding member A23 for transmitting light of the wavelength of 248 nm and shielding the light of the wavelength of 13.5 nm. Are combined to form a double structure, whereby light of two different wavelengths generates an almost ideal spherical wave. Of course, the size of the diameter of the opening provided in the light-shielding member is not limited to twice the wavelength, and it is possible to substitute another means for generating reference light having an ideal spherical wave.
[0060]
In this way, the light beam interference information can be detected by the detecting means 7 such as a two-dimensional CCD. Here, a short wavelength cut filter may be used on the two-dimensional CCD so as to separate the interference fringes of the light having the wavelength of 248 nm and the light having the wavelength of 13.5 nm in place as in the first embodiment.
[0061]
In the first embodiment, the phase characteristic of the light reflected at one point on the surface to be inspected (reflection surface) is measured. The uniformity of the reflective film characteristics over the entire inspection surface may also be measured.
[0062]
(Third embodiment)
A third embodiment will be described with reference to FIG. The third embodiment is an example using one half of a Schwarzchild optical system. Since the vicinity of the light source is the same as in the first and second embodiments, the description is omitted. First, light from a light source is emitted from a pinhole 3a provided in the member 3, and EUV light (wavelength of about 13.5 nm) emitted from the pinhole 3a is combined with light of another wavelength (for example, light of a wavelength of about 248 nm). A multiplexing grating (not shown) for multiplexing is used. Thereafter, the multiplexed light is reflected by the reflecting mirror 9 ″ and the reflecting mirror 9 ′ and is incident on the surface to be measured (reflecting surface) 5, and then passes through the branch diffraction grating G 1 and the aperture A 1 to the detecting means 7. Incident. Here, the interference fringes are measured, and the phase of the light reflected on the surface to be measured is measured from the measurement result. Other parts not specifically described are the same as in the first embodiment.
[0063]
(Fourth embodiment)
A fourth embodiment will be described with reference to FIG. This fourth embodiment is an example using a Zernnitana optical system. This also multiplexes the second wavelength (not shown) coaxially. Since the vicinity of the light source is the same as in the first and second embodiments, the description is omitted. First, light from a light source is emitted from a pinhole 3a provided in the member 3, and EUV light (wavelength: about 13.5 nm) emitted from the pinhole 3a is combined with light of another wavelength (for example, light having a wavelength of about 248 nm). A multiplexing grating (not shown) for multiplexing is used. Thereafter, the multiplexed light is reflected by the reflecting mirror 9 ′ and is incident on the surface to be measured (reflecting surface) 5, and then is incident on the detecting means 7 via the reflecting mirror 9 ″, the branch diffraction grating G 1, and the aperture A 1. I do. Here, the interference fringes are measured, and the phase of the light reflected on the surface to be measured is measured from the measurement result. Other parts not specifically described are the same as in the first embodiment. As in the above embodiment, in order to measure the angle characteristic of the phase of the reflective film as the surface to be measured, the first wavelength of at wavelength is the wavelength of the visible light or the UV light that is reflected by the surface of the surface to be measured. By using the wavelength, it can be determined correctly. Other parts not specifically described are the same as in the first embodiment.
[0064]
(Fifth embodiment)
In the fifth embodiment, the reflection surface obtained by measuring the incident angle dependence of the reflection film (the incident angle dependence of the phase of the reflected light reflected on the surface to be measured) by the method of the first to fourth embodiments is used. This is an example in which an EUV exposure apparatus is configured.
[0065]
A laser plasma light source is used as the EUV light source having a wavelength of 13.5 nm in the present embodiment. In this method, high-intensity pulsed laser light is applied to the target material TA supplied into the vacuum chamber 701 to generate high-temperature plasma 705, and EUV light with a wavelength of, for example, about 13 nm emitted from this is used. . As the target material, a metal thin film, an inert gas, a droplet, or the like is used, and the target material is supplied into the vacuum vessel 701 by a target supply device 702 having a means such as a gas jet. Further, the pulse laser light is output from the excitation pulse laser 703 and is irradiated on the target material TA via the condenser lens 704. In order to increase the average intensity of the emitted EUV light, the higher the repetition frequency of the pulse laser, the better. The excitation pulse laser 703 is usually operated at a repetition frequency of several kHz.
[0066]
Note that a discharge plasma light source can be used as the EUV light source. A discharge plasma light source emits gas around an electrode placed in a vacuum vessel, applies a pulse voltage to the electrode to cause a discharge to generate high-temperature plasma, and emits EUV light having a wavelength of, for example, about 13 nm emitted from the electrode. To use. In order to increase the average intensity of the emitted EUV light, the higher the repetition frequency of the discharge, the better, and it is usually operated at a repetition frequency of several kHz.
[0067]
The illumination optical system has a plurality of multilayer films or oblique incidence mirrors and an optical integrator. The illumination optical system according to the present embodiment includes an illumination system first mirror 706, an optical integrator 707, an illumination system second mirror 708, and an illumination system third mirror 709, and EUV emitted from the plasma 705 by these members. The light is guided to a reticle (mask) 711.
[0068]
The first-stage condenser mirror (illumination system first mirror) 706 of the illumination optical system plays a role of collecting EUV light emitted almost isotropically from the laser plasma 705. The optical integrator 707 has a role of uniformly illuminating the reticle 711 with a predetermined numerical aperture. An aperture 710 having an arc opening is provided at a position conjugate with the reticle 711 of the illumination optical system to limit an area illuminated on the reticle surface to an arc shape.
[0069]
The reticle 711 is irradiated with an arc-shaped light beam that has passed through the aperture 710, and the reflected light is irradiated on the wafer 731 via a projection optical system including reflecting mirrors 721 to 724. A mirror with a multilayer film (multilayer mirror) used in the EUV region has a large loss of light as compared with a visible light mirror, and therefore, it is necessary to minimize the number of mirrors. Reference numeral 725 denotes an aperture limiting aperture.
[0070]
In the present embodiment, in order to realize a projection optical system having a wide exposure area with a small number of mirrors, a ring field optical system using only a thin arc-shaped area (ring field) separated by a certain distance from the optical axis is used. We are using. Then, a method (scan exposure) in which the reticle 711 and the wafer 731 are simultaneously scanned synchronously and transferred with a wide exposure area is used. An arc-shaped illumination area on the reticle 711 surface is formed by an optical integrator 707 and front and rear mirrors 708 and 709 in the illumination optical system.
[0071]
A plurality of mirrors are also used for the projection optical system. In FIG. 3, the reflected light from the reticle 711 is guided onto the wafer 731 mounted on the wafer chuck 733 by the projection system first to fourth mirrors (721 to 724). The smaller the number of mirrors, the higher the utilization efficiency of EUV light, but it becomes difficult to correct aberrations. In order to perform good aberration correction, the number of mirrors is set to about four to six. The reflecting surface of the mirror has a convex or concave spherical surface, an aspherical surface, a rotationally asymmetrical aspherical surface, or the like. The numerical aperture NA of the projection optical system is about 0.1 to 0.3.
[0072]
Each mirror is ground and polished on a substrate made of a material having a high rigidity and a high hardness such as a low expansion coefficient glass or silicon carbide and a low coefficient of thermal expansion to create a predetermined reflection surface shape. -An Si film (a multilayer film of molybdenum / silicon or the like) is used. Of course, a Be-Si film or a Rh-Si film may be used as another configuration of the reflection film. If the angle of incidence is not constant depending on the location within the mirror surface, as is apparent from the Bragg equation, the wavelength of EUV light whose reflectance increases in a multilayer film having a constant film period shifts depending on the location. Therefore, a film period distribution is provided so that EUV light of the same wavelength is efficiently reflected within the mirror surface.
[0073]
The reticle stage 712 and the wafer stage 732 have a mechanism that scans synchronously at a speed ratio proportional to the reduction magnification of the projection optical system. Here, as the coordinate system, the scanning direction in the plane of the reticle 711 or the wafer 732 is the X axis, the direction perpendicular thereto is the Y axis, and the direction perpendicular to the reticle or wafer surface is the Z axis.
[0074]
Reticle 711 is held by reticle chuck 713 on reticle stage 712. The reticle stage 712 has a mechanism for moving at high speed in the X direction. The reticle 711 has a fine movement mechanism in the X direction, the Y direction, the Z direction, and the rotation direction around each axis, so that the reticle 711 can be positioned. The position and orientation of the reticle stage 712 are measured by a known method using a laser interferometer (not shown), and the position and orientation are controlled based on the result.
[0075]
Wafer 731 is held on wafer stage 732 by wafer chuck 733. The wafer stage 732 has a mechanism that moves at a high speed in the X direction, like the reticle stage 712. Further, a fine movement mechanism is provided in the X direction, the Y direction, the Z direction, and the rotation direction around each axis so that the wafer can be positioned. The position and orientation of wafer stage 732 are measured by a known method using a laser interferometer (not shown), and the position and orientation are controlled based on the results.
[0076]
In order to detect the relative positional relationship between the reticle 711 and the wafer 731, the alignment detecting mechanisms 714 and 734 detect the positional relationship between the position of the reticle 711 and the optical axis of the projection optical system, and the position of the wafer 731 and the light of the projection optical system. The positional relationship with the axis is measured, and the positions and angles of the reticle stage 712 and the wafer stage 732 are set so that the projected image of the reticle 711 matches a predetermined position on the wafer 731.
[0077]
The focus position in the Z direction is measured on the wafer surface by a focus position detection mechanism 735 that detects the best image forming position of the projection optical system, and the position and angle of the wafer stage 732 are controlled. At the best imaging position by the projection optical system.
[0078]
After one scan exposure on the wafer 731 is completed, the wafer stage 732 moves stepwise in the X and Y directions to move to the next scanning exposure start position, and the reticle stage 712 and the wafer stage 732 reduce the size of the projection optical system again. The pattern of the reticle 711 is exposed on the wafer 731 by performing synchronous scanning in the X direction at a speed ratio proportional to the magnification.
[0079]
In this way, the operation of synchronously scanning the reduced projection image of the reticle 711 and the image formed on the wafer 731 is repeated (step-and-scan), and the transfer pattern of the reticle is transferred to the entire surface of the wafer. You.
[0080]
As described above, according to each embodiment, the phase of the optical thin film formed on the optical element surface can be accurately measured with a simple configuration. In addition, since the configuration of each embodiment does not depend on the wavelength, it can be applied to a system in which the types of optical elements used extremely are limited, such as EUV.
[0081]
In addition, an optical element that has been measured using the phase measurement device or the interferometer described above, or an exposure apparatus that incorporates the optical element and uses an EUV wavelength light, or another optical device that uses light in the EUV wavelength region Devices and the like are also part of the embodiments of the present invention.
[0082]
In addition, a step of exposing an object to be exposed (a wafer or the like) by an exposure apparatus having an optical element that has been measured using the phase measurement method, the phase measurement apparatus, or the interferometer described above; The device may be manufactured through the step of developing the object to be exposed. The method for manufacturing the device includes various known steps in addition to the above steps.
[0083]
Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the gist.
[0084]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the phase characteristic in each position of the film | membrane applied to the reflecting mirror with a curvature or a plane reflecting mirror and / or the phase characteristic of the film depending on an incident angle can be measured easily and with high precision. A phase measurement device can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic view of a main part of a phase measuring apparatus according to a first embodiment of the present invention.
FIG. 2 is an enlarged view of the vicinity of a test surface (reflection surface) according to the first embodiment of the present invention.
FIG. 3 is a schematic view of a branch diffraction grating according to the first embodiment of the present invention.
FIG. 4 is a schematic view of an aperture according to the first embodiment of the present invention.
FIG. 5 is an XZ plan view near a branch diffraction grating according to the first embodiment of the present invention.
FIG. 6 is a YZ plan view showing the vicinity of the branch diffraction grating according to the first embodiment of the present invention.
FIG. 7 is a schematic diagram of interference fringes detected by the detection unit according to the first embodiment of the present invention.
FIG. 8 shows a detection result of a phase difference by the detection means 7 in the first embodiment of the present invention.
FIG. 9 shows a phase difference of EUV light reflected on the surface to be measured in the first embodiment of the present invention.
FIG. 10 shows a phase given to EUV light by the surface to be measured in the first embodiment of the present invention.
FIG. 11 is a configuration diagram for correcting an error of the apparatus according to the first embodiment of the present invention.
FIG. 12 is a view showing a variable incident angle mechanism according to the first embodiment of the present invention.
FIG. 13 is a schematic diagram of a main part of a phase measuring apparatus according to a second embodiment of the present invention.
FIG. 14 is a plan view of an aperture according to a second embodiment of the present invention.
FIG. 15 is a partial cross-sectional view of an aperture according to a second embodiment of the present invention.
FIG. 16 is a schematic view of a main part of a third embodiment of the present invention.
FIG. 17 is a schematic view of a main part of a fourth embodiment of the present invention.
FIG. 18 is a schematic view of a main part of a fifth embodiment of the present invention.
[Explanation of symbols]
1 Light source member
2 Reflector
3a aperture
5 Test surface (reflective surface, reflective film)
6 Test object
7 Detecting means
9 Reflector
10 arithmetic means
22 Combining (coupling) grating
G1 Branch diffraction grating
A1 aperture

Claims (30)

An illumination optical system for causing a light beam including light of the first wavelength and light of the second wavelength to enter the test surface with a predetermined angle range, and interference of the light of the first wavelength by reflected light from the test surface. A detection optical system that forms a fringe and an interference fringe of the light of the second wavelength on a detection unit, and by measuring the interference fringe detected by the detection unit, the surface to be detected becomes the second surface. A phase measuring device for measuring the dependence of the phase given to one wavelength of light on the angle of incidence of the first wavelength of light on the surface to be measured. The phase change given to the light of the first wavelength by the test surface with respect to the incident angle of the light of the first wavelength to the test surface, and the phase change of the light of the second wavelength to the incident angle to the test surface. Measuring, from the phase change of the light of the second wavelength, the dependence of the phase given to the light of the first wavelength by the test surface on the angle of incidence of the light of the first wavelength on the test surface. The phase measurement device according to claim 1, wherein the phase measurement is performed. By shifting the reflected light from the surface to be measured laterally, an interference fringe of the light of the first wavelength and an interference fringe of the light of the second wavelength are formed, and the amount of phase change caused by the lateral shift Is determined from the interference fringes of the light of the second wavelength, and from the interference fringes of the light of the first wavelength and the amount of phase change caused by the lateral shift, the phase of the phase to be given to the light of the first wavelength 3. The phase measurement apparatus according to claim 1, wherein the dependence of the light of the first wavelength on the incident angle on the surface to be measured is measured. 4. The phase measuring device according to claim 1, wherein the first wavelength is shorter than the second wavelength. The phase measuring device according to claim 1, wherein the second wavelength is longer than ten times the first wavelength. The phase measurement device according to claim 1, wherein the first wavelength is a wavelength of 10 nm or more and 15 nm or less. The phase measurement device according to claim 1, wherein the first wavelength is a wavelength of 13 nm or more and 14 nm or less. The phase measurement device according to claim 1, wherein the second wavelength is a wavelength of 150 nm or more. 9. The phase measuring apparatus according to claim 1, wherein the surface to be inspected has a reflective multilayer film formed using Mo and Si. 10. A branch optical element for branching the reflected light from the surface to be inspected into a plurality of light fluxes, and by causing at least two of the plurality of light fluxes to interfere with each other, the interference fringe of the light of the first wavelength and the second 10. The phase measuring device according to claim 1, wherein interference fringes of light of two wavelengths are formed on the detecting means. The phase measuring device according to claim 10, wherein the branch optical element is a branch diffraction grating. The phase measuring device according to claim 10, wherein the detection optical system includes a light blocking member that selectively transmits two light beams out of the plurality of light beams branched by the branch optical element. 13. The phase according to claim 12, wherein the light shielding member is formed such that one of the two light beams has an ideal spherical wave closer to the detection unit than the light shielding member. measuring device. The light-blocking member includes a first opening for transmitting the light of the first wavelength, and a second opening for transmitting the light of the second wavelength, of the light emitted from the branching optical element. The first opening and the second opening have different sizes, and the first opening and the second opening at least partially overlap each other. Or the phase measurement device according to item 13. The phase measurement device according to claim 14, wherein the first opening and the second opening have substantially the same centers. The branch optical element is a branch diffraction grating, and a zero-order diffracted light emitted from the branch diffraction grating is transmitted through a region where the first opening and the second opening overlap. Item 16. The phase measuring device according to item 14 or 15. The light of the second wavelength is obtained by photoelectrically converting interference fringes of the light of the second wavelength detected by the detection means with respect to a second incident angle at which the light of the second wavelength is incident on the surface to be measured. By using the gradient component of the amount of phase change received by reflecting on the test surface,
The light of the first wavelength is obtained by photoelectrically converting interference fringes of the light of the first wavelength detected by the detection means with respect to a first incident angle at which the light of the first wavelength is incident on the surface to be measured. 17. The phase measurement device according to claim 1, wherein a tilt component is removed from a phase change amount received by being reflected by the test surface. An optical element whose phase has been measured by the phase measuring device according to claim 1. An exposure apparatus comprising the optical element according to claim 18. A method for manufacturing a device, comprising: a step of exposing an object to be exposed using the exposure apparatus according to claim 19; and a step of developing the object to be exposed. The light from the surface to be inspected is divided into a plurality of lights, and the wavefronts of the plurality of lights are caused to interfere with each other while being shifted laterally from each other to form an interference fringe, and the inspection is performed based on a phase distribution obtained from the interference fringe. In an interferometer that measures a state of a wavefront of light from a surface, the light includes first and second lights having different wavelengths from each other, and forms the interference fringes for each of the first and second lights. A phase change component is obtained from a phase distribution obtained from the interference fringe by the second light having a longer wavelength of the first and second lights, and a phase distribution obtained from the interference fringe by the first light and the phase An interferometer for measuring a state of the wavefront of the first light using a change component. The interferometer according to claim 21, wherein the phase change component is caused by the lateral shift. 23. The interferometer according to claim 21, wherein the phase change component is caused by a surface shape of the test surface. 24. The interferometer according to claim 21, wherein a wavelength of the second light is longer than 10 times a wavelength of the first light. 25. The interferometer according to claim 21, wherein a wavelength of the first light is a wavelength of 10 nm or more and 15 nm or less. 26. The interferometer according to claim 21, wherein the first wavelength is a wavelength of 13 nm or more and 14 nm or less. The interferometer according to any one of claims 21 to 26, wherein the second wavelength is a wavelength of 150 nm or more. An optical element whose wavefront state is measured by the interferometer according to any one of claims 21 to 27. An exposure apparatus comprising the optical element according to claim 28. A method for manufacturing a device, comprising: a step of exposing an object to be exposed using the exposure apparatus according to claim 29; and a step of developing the object to be exposed.

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