JPH11257919A - Measuring apparatus and measuring method and exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus and measuring method using a light wave interference measurement capable of a high accuracy displacement measurement by avoiding occurrence of error light due to the retardation on a reflective plane of a reflection mirror or because of a low quenching ratio of a polarization separator element. SOLUTION: In the measuring apparatus wherein a polarization separator element 46 separates a light from a light source 1, a moving mirror 12 movable on a measuring light path reflects a P-polarized light as a measuring light, a fixed mirror 11 fixed to a reference light path reflects an S-polarized light as a reference light, a photoelectric element 6 detects the interference of the measuring light passed over the measuring light path with the reference light passed over the reference light path, and the displacement of the moving mirror 12 is measured, a light separator element 56 having a refractive angle different depending on the polarizing orientation is at least on either the measuring or reference light path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method and apparatus using light wave interference measurement capable of measuring a displacement amount of a displaced object with high accuracy. Further, the present invention relates to an exposure apparatus including a light-wave interference type measuring apparatus for measuring the amount of movement of a stage on which a substrate is mounted and moving, and used in a photolithography step when manufacturing a semiconductor device or a liquid crystal display device.

[0002]

2. Description of the Related Art As a typical example of a measuring device for measuring displacement of an object, a conventional light wave interference measuring device will be described with reference to FIG. In FIG. 7, a light source 1 emits light having a frequency f1 and light having a frequency f1 ′, which have slightly different frequencies. The emitted light of the frequency f1 and the light of the frequency f1 ′ are
It is linearly polarized light whose polarization directions are orthogonal to each other, and the frequency f1
7 has a polarization direction parallel to the plane of FIG. 7, and the light of frequency f1 'has a polarization direction perpendicular to the plane of FIG. The light having the frequencies f1 and f1 ′ emitted from the light source 1 is incident on the polarization separation element 46, and the light having the frequency f1 is transmitted through the polarization separation element 46 and becomes measurement light traveling as P-polarized light to the measurement optical path. Is reflected by the polarization separation element 46,
The reference light travels to the reference light path as S-polarized light.

The frequency f1 'reflected by the polarization separation element 46
Is transmitted through the wave plate (1/4 wavelength plate) 31 and reaches the fixed mirror 11, reflected at the fixed boundary 11, and transmitted through the wave plate 31 again. Since the light having the frequency f1 ′ passes through the wave plate 31 twice, the polarization direction is rotated by 90 degrees, and the light becomes P-polarized light and passes through the polarization separation element 46. The light having the frequency f1 ′ transmitted through the polarization separating element 46 is reflected by the reflecting mirror (corner cube prism) 41 with its optical path shifted, and transmitted through the polarization separating element 46 again. The light of the frequency f1 ′ transmitted through the polarization separation element 46 is transmitted through the wave plate 31 and
And the light is reflected at the fixed boundary 11 and transmitted through the wave plate 31 again. Here also, the light of frequency f1 'is transmitted through the wave plate 31 twice, so that the polarization direction is rotated by 90 degrees to become S-polarized light.
Head for.

On the other hand, the light of the frequency f1 transmitted through the polarization separating element 46 passes through a wavelength plate (1/4 wavelength plate) 32, reaches the movable mirror 12, is reflected at the movable boundary 12, and is again reflected by the wavelength plate 32.
Through. Since the P-polarized light having the frequency f1 is transmitted twice through the wave plate 32, the polarization azimuth is rotated by 90 degrees, and the S-polarized light is reflected by the polarization separation element 46. The light of frequency f1 reflected by the polarization separation element 46 is reflected by the reflection mirror 41 with its optical path shifted, and is reflected again by the polarization separation element 46. The light of the frequency f1 reflected by the polarization separation element 46 passes through the wave plate 32 again, reaches the movable mirror 12, reflects at the moving boundary 12, and transmits through the wave plate 32 again. Also here, since the light of the frequency f1 is transmitted twice through the wave plate 32, the polarization direction is rotated by 90 degrees to become P-polarized light. Therefore, the light having the frequency f1 is again transmitted to the polarization separation element 46.
, Then passes through the polarization splitting element 46. The light having the frequency f1 transmitted through the frequency separation element 46 is coaxial with the light having the frequency f1 ′ and travels toward the polarization element 51.

The lights of frequencies f1 and f1 'which have exited the polarization separation element 46 and become coaxial and have reached the polarization element 51 interfere with each other at the polarization element 51, and the interference light is converted into an electric signal at the light receiving element 6. Is output to the phase meter 21 as a measurement beat signal. From the light source 1, light having a frequency f1 and frequency f1 ′
Is output to the phase meter 21 as a reference beat signal. The phase meter 21 detects a phase change of the measured beat signal with respect to the reference beat signal, and obtains a change in the optical path length of the movable mirror 12 in the direction of the arrow in FIG.

The light wave interference measuring apparatus is mainly used as a position detecting system of a stage apparatus which moves two-dimensionally in an XY plane. In particular, light wave interference measurement devices are widely used as positioning devices for stage devices of machine tools requiring ultra-precision processing, and stage devices of exposure devices used in photolithography processes when manufacturing semiconductor devices or liquid crystal display devices. Used. In particular, in a manufacturing process of a semiconductor device or a manufacturing process of a liquid crystal display device in which elements are formed by accurately superimposing fine patterns, a stage device on which a semiconductor wafer or a glass substrate (hereinafter, referred to as a wafer) is placed and two-dimensionally moved. Since it is necessary to measure the amount of movement of the sample with a measurement resolution of the order of nm (nanometers), an optical interferometer capable of measuring the length with high accuracy in principle has been used as a stage positioning device.

As an exposure apparatus equipped with this light wave interference measuring apparatus as a stage positioning apparatus, a projection exposure for projecting and exposing a circuit pattern formed on a reticle or mask (hereinafter referred to as a reticle) onto a wafer through a projection optical system. There is a device. There are various types of projection exposure apparatuses. For example, in the case of manufacturing a semiconductor device, a wafer is step-and-stepped through a projection optical system having an image field capable of projecting the entire reticle circuit pattern at one time. There are a projection exposure apparatus that performs exposure by a repeat method, and a projection exposure apparatus that employs a so-called step-and-scan method that scans a wafer one-dimensionally at a speed synchronized with that while scanning a reticle one-dimensionally.

[0008]

As described above, an optical interference measuring apparatus is often used for ultra-precision positioning such as a stage apparatus of an exposure apparatus, but has the following problems. I have. That is, in the conventional light wave interference measurement apparatus shown in FIG. 7, the reflection surface of the reflection mirror 41 composed of, for example, a corner cube prism is made of metal such as Al (aluminum) in order to reduce retardation (phase lag). Coated. However, in reality, even if a metal coat is applied, the reflecting mirror 41
Cannot be completely eliminated, and when an attempt is made to measure displacement with high accuracy, an error based on the retardation at the reflecting mirror 41 cannot be ignored.

As described above, the measurement light reflected by the movable mirror 12 becomes S-polarized light when entering the reflection mirror 41,
The reference light reflected by the fixed mirror 11 becomes P-polarized light when entering the reflecting mirror 41. However, these lights reflected by the reflecting surface of the reflecting mirror 41 become elliptically polarized light due to the retardation on the reflecting surface, the reflected light of the reference light includes P-polarized light and weak S-polarized light, and the reflected light of the measurement light is The reflection mirror 41 emits light including S-polarized light and weak P-polarized light. The light of the weak S-polarized component and the light of the weak P-polarized component generated by the retardation at the reflecting mirror 41 are coaxially incident on the measurement optical path and the reference optical path as they are, and become error light, and this error light is detected by the phase meter 21. This causes a problem that an error is superimposed on the measured displacement amount.

Also, the extinction ratio of the polarization splitting element 46 is not actually perfect, and it is not possible to completely separate the P-polarized light and the S-polarized light. Therefore, an error light that reciprocates a large number of times in the measurement optical path between the polarization separation element 46 and the movable mirror 12 occurs due to the extinction ratio of the polarization separation element 46, and it is impossible to measure displacement with high accuracy. Occurs.

It is an object of the present invention to provide a measuring method and apparatus using light wave interference measurement capable of preventing displacement of error light due to retardation on a reflecting surface of a reflecting mirror and measuring displacement with high accuracy. Further, an object of the present invention is to provide a measurement method and apparatus using light wave interference measurement capable of preventing occurrence of error light due to a low extinction ratio in a polarization separation element and performing highly accurate displacement measurement. It is in. further,
SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus provided with a light wave interference type measurement device capable of measuring displacement with high accuracy.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to reflect one of two lights whose polarization directions are orthogonal to each other as a measuring light by a movable mirror movably provided on a measuring optical path and refer to the other as a reference light. A measuring device that reflects the light with a fixed mirror fixed to the optical path, interferes the measuring light passing through the measuring optical path with the reference light passing through the reference optical path, performs photoelectric detection, and measures the displacement of the moving mirror. This is achieved by a measuring apparatus characterized in that light separating elements having different refraction angles are provided in at least one of the measurement light path and the reference light path.

The measuring apparatus of the present invention includes a light source for emitting linearly polarized light and a polarization separating element for separating linearly polarized light into measuring light and reference light, wherein the light separating element includes a movable mirror and a fixed mirror. It is characterized by being arranged between at least one of the mirrors and the polarization splitting element. Further, the light separating element separates the error light based on the extinction ratio of the polarization separating element. Further, in the measurement device of the present invention, the measurement device has a wavelength plate provided in at least one of the measurement light path and the reference light path, and the light separation element is disposed between the wave plate and the polarization separation element. Features.

Further, the measuring apparatus of the present invention includes a reflecting mirror provided in the measuring optical path so that at least the measuring light is reflected a plurality of times by the moving mirror, and the light separating element is a light separating element between the reflecting mirror and the polarization separating element. It is characterized by being provided between them. The light separating element separates the error light generated by the retardation by the reflecting mirror. Further, in the measuring device of the present invention, two lights whose polarization directions are orthogonal to each other have different frequencies. Further, the light source emits light for refractive index fluctuation measurement for measuring at least the refractive index fluctuation of the gas in the measurement optical path and correcting the displacement of the movable mirror.

In the measuring apparatus according to the present invention, the light separating element is a crystal having anisotropy, for example, a Wollaston prism. Further, the measuring device of the present invention is characterized in that a light shielding means for shielding the error light separated by the light separating element is provided.

The above object is also achieved by fixing one of two lights having polarization directions orthogonal to each other as a measuring light by a movable mirror movably provided on a measuring optical path, and fixing the other as a reference light to the reference optical path. In the measurement method, the reflected light is reflected by a fixed mirror, the measurement light passing through the measurement optical path and the reference light passing through the reference optical path interfere with each other, photoelectrically detected, and the displacement of the movable mirror is measured. This is achieved by a measuring method characterized in that different light separating elements are arranged in at least one of the measurement light path and the reference light path, and error light generated in the light path is separated.

As described above, according to the measuring method and apparatus of the present invention, a light separating element having anisotropy that emits ordinary light and extraordinary light in different directions is inserted into a predetermined optical path. Therefore, for example, when a light separating element is inserted between the polarization separating element and the reflecting mirror, unnecessary polarization included in the measurement light or the reference light that has become elliptically polarized light due to the retardation by the reflecting mirror is taken as an example. The component light (error light) can be separated by the light separation element. Further, the optical path of the separated error light is not coaxial with the measurement optical path and the reference optical path, so that the original measurement light and the reference light can interfere with each other to perform highly accurate displacement measurement.

Further, the object is to provide a reticle stage on which a reticle on which a pattern is formed can be mounted and movable,
A reticle stage-side measuring unit for measuring the position of the reticle stage, a substrate stage on which the substrate can be placed and movable, and a substrate stage-side measuring unit for measuring the position of the substrate stage; In the transfer exposure apparatus, at least one of the reticle stage-side measurement unit and the substrate stage-side measurement unit is achieved by an exposure apparatus including the above-described measurement apparatus of the present invention. In addition, by electrically, mechanically, or optically connecting the above-described components, an exposure apparatus according to the present invention is assembled.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A measuring method and apparatus in light wave interference measurement according to a first embodiment of the present invention will be described with reference to FIGS. First, the overall configuration of the optical interference measuring apparatus according to the present embodiment will be described with reference to FIG. FIG.
In, the light source 1 emits light having a frequency f1 and light having a frequency f1 ′ whose frequencies are slightly different from each other. The emitted light having the frequency f1 and the light having the frequency f1 ′ are linearly polarized lights whose polarization directions are orthogonal to each other.
Has a polarization direction parallel to the plane of the drawing, and the light of frequency f1 'has a polarization direction perpendicular to the plane of the drawing. The light of frequencies f1 and f1 ′ emitted from the light source 1 is incident on the polarization separation element 46, and the light of frequency f1 is transmitted through the polarization separation element 46 and
The measurement light travels to the measurement optical path as polarized light and has a frequency f
The light 1 ′ is reflected by the polarization separation element 46 and becomes reference light that travels to the reference light path as S-polarized light.

Here, the configuration and the optical path in the block indicated by the broken line 101 in FIG. 1 will be described with reference to FIG. The light having the frequency f1 ′ reflected by the polarization separation element 46 passes through the wave plate 31 and reaches the fixed mirror (plane mirror) 11, is reflected by the fixed boundary 11 and passes through the wave plate 31 again.
The S-polarized light having the frequency f1 ′ passes through the wave plate 31 twice, and its polarization direction is rotated by 90 degrees, becomes P-polarized light, and passes through the polarization splitter 46. The light having the frequency f1 ′ transmitted through the polarization separation element 46 enters a light separation element 56 provided between the polarization separation element 46 and the reflecting mirror 41. The light separating element 56 is a crystal having anisotropy that emits ordinary light and extraordinary light in different directions. For example, a Wollaston prism is used. Also, the light separating element 56
Are arranged so that S-polarized incident light is transmitted almost as it is and P-polarized light is emitted obliquely.

Accordingly, the P-polarized light having the frequency f1 'incident on the light separating element 56 is obliquely emitted from the light separating element 56, enters the reflecting mirror 41, and is reflected with its optical path shifted. Here, the light of the frequency f1 ′ becomes elliptically polarized light including a weak S-polarized component (error light 201) due to the retardation by the reflecting mirror 41. When the light is incident on the light separating element 56 again obliquely, the original P-polarized light is emitted. S is emitted obliquely to the incident direction and travels toward the polarization separation element 46 to become the error light 201.
The light of the polarization component passes through the light separation element 56 as it is and is separated from the light of the P polarization. The error light 201 is shielded by a light shielding plate 110 provided between the light separation element 56 and the polarization separation element 46. As described above, since the light separating element 56 is arranged between the polarization separating element 46 and the reflecting mirror 41, the error light 201 of the P-polarized light having the frequency f1 ′ generated by the retardation of the reflecting mirror 41 is generated. It can be separated from the reference light path.

The P-polarized light having the frequency f1 'from which the error light 201 has been removed passes through the polarization separating element 46, passes through the wave plate 31, reaches the fixed mirror 11, is reflected by the fixed boundary 11, and is again reflected. The light passes through the wave plate 31. Here, since the light having the frequency f1 ′ passes through the wave plate 31 twice, the polarization direction is rotated by 90 degrees, becomes S-polarized light, and is reflected by the polarization separation element 46. The light of the frequency f1 ′ reflected by the polarization separation element 46 is reflected by the reflection mirror 13 and the polarization coupling element 47 and travels to the polarization element 51.

On the other hand, the light having the frequency f1 transmitted through the polarization splitting element 46 is transmitted through the wave plate 32, and the movable mirror (plane mirror) 1
2, the light is reflected at the moving boundary 12 and passes through the wave plate 32 again. Since the P-polarized light having the frequency f1 is transmitted twice through the wave plate 32, the polarization direction is rotated by 90 degrees to be S-polarized light and reflected by the polarization splitting element. The light of the frequency f1 reflected by the polarization separation element 46 is
The light is incident on a light separating element 56 provided between the reflector 41. As described above, the light separating element 56 is arranged so as to transmit the S-polarized light almost as it is and to emit the P-polarized light obliquely. Therefore, the S-polarized light having the frequency f1 which is the measurement light incident on the light separating element 56 passes through the light separating element 56 as it is, is separated from the P-polarized light having the frequency f1 ′ which is the reference light, and is reflected by the reflecting mirror 41. The light is incident and the optical path is shifted and reflected.

Here, the light of the frequency f1 is weak P-polarized light component (error light 202) due to the retardation by the reflecting mirror 41.
However, the s-polarized light enters the light separation element 56 again, and the original S-polarized light is transmitted as it is and the polarization separation element 4
6, the P-polarized light component, which is the error light 202, is separated by the light separating element 56 and emitted obliquely. This error light 2
02 is also shielded from light by a light shielding plate 110 provided between the light separation element 56 and the polarization separation element 46. As described above, by disposing the light separating element 56 between the polarization separating element 46 and the reflecting mirror 41, the error light 202 of the S-polarized light having the frequency f1 generated by the retardation in the reflecting mirror 41 is transmitted from the measurement optical path. Be able to separate.

The light of the frequency f1 of the S-polarized light from which the error light 202 has been removed is reflected by the polarization separating element 46, passes through the wave plate 32, reaches the movable mirror 12, is reflected by the moving boundary 12, and is again reflected by the wave plate. 32. Here, since the light of the frequency f1 is transmitted twice through the wave plate 32, the polarization direction is rotated by 90 degrees to be P-polarized light and transmitted through the polarization separation element 46.
The light of frequency f1 that has passed through the polarization separation element 46 passes through the polarization coupling element 47 and is coaxial with the light of frequency f1 ′, and travels toward the polarization element 51.

Returning to FIG. 1, the frequencies f1 and f1, which are emitted from the polarization coupling element 47 and become coaxial and reach the polarization element 51,
The light 1 ′ interferes with the polarization element 51, and the interference light is converted into an electric signal by the light receiving element 6 and output to the phase meter 21 as a measurement beat signal. From the light source 1, an interference signal between the light having the frequency f1 and the light having the frequency f1 ′ is output to the phase meter 21 as a reference beat signal. The phase meter 21 detects the phase change of the measured beat signal with respect to the reference beat signal, and obtains the optical path length change of the movable mirror 12 in the direction of the arrow in FIG.

As described above, in the measuring method and apparatus according to the present embodiment, the light separating element 56 having a different refraction angle according to the polarization direction is arranged in the common optical path of the measuring optical path and the reference optical path, and the original polarization is obtained. Light of a component different from the azimuth is separated from each optical path. in this way,
Since the light separating element 56 having anisotropy is inserted between the polarization separating element 46 and the reflecting mirror 41, the error light 201 included in the measurement light or the reference light that has become elliptically polarized light due to the retardation by the reflecting mirror 41. , 202 to the light separating element 5
6 to allow separation. Furthermore, in the present embodiment, since the light shielding plate 110 that blocks the separated error light is provided, the error light 201 and 202 can be reliably removed.

Next, a description will be given of a measuring method and apparatus in lightwave interference measurement according to a second embodiment of the present invention with reference to FIG. FIG. 3 shows a schematic configuration of the light wave interference measuring apparatus according to the present embodiment. The measurement method and apparatus by light wave interference according to the present embodiment are designed to measure the refractive index fluctuation amount of gas such as air on the measurement light path and the reference light path in the light wave interference measurement apparatus according to the first embodiment by using two different frequencies. It is characterized in that a very accurate displacement amount of the movable mirror can be measured by measuring and correcting using light.

In this embodiment, a configuration in which a refractive index fluctuation measuring system is added to the optical interference measuring apparatus according to the first embodiment described with reference to FIGS. 1 and 2 will be described.
In FIG. 3, a light source 1 emits light of a frequency f1 having a polarization direction parallel to the paper surface of FIG. 3 and light of a frequency f1 ′ (= f1 + Δf) having a polarization direction perpendicular to the paper surface of FIG. The light of the frequencies f1 and f1 ′ emitted from the light source 1 is
The light enters the frequency coupling element 67.

The light source 2 emits light having a frequency f2 and light having a frequency f3 (= 2 · f2) obtained by converting the light having the frequency f2 into a second harmonic. The light of frequency f2 and the light of frequency f3 are:
The polarization directions are adjusted to be the same, and to be inclined by 45 ° with respect to the polarization direction of the light of frequency f1. Frequency f
The light of No. 2 is bent in the optical path by the reflecting mirror 14 and made coaxial with the light of frequency f3 by the frequency coupling element 66, and the frequency f
2 and f3 are incident on the frequency coupling element 67 and
1. The light is coupled coaxially with the light of f1 ′ and is incident on the polarization beam splitter 48. The polarization splitter 48 transmits the P-polarized light component and reflects the S-polarized light component. Therefore, the light of frequency f1 having the polarization direction parallel to the paper surface is transmitted as the P-polarized light through the polarization separating element 48 to the measurement optical path, and the light of frequency f1 ′ having the polarization direction perpendicular to the paper surface is polarized light. The light is reflected at 48 toward the reference light path. Further, both the light of frequency f2 and the light of frequency f3 are 45
Since the polarization direction is inclined, the polarized light is split by the polarization splitting element 48 into transmitted light and reflected light.

The frequencies f1 and f of the P-polarized light traveling to the measurement optical path
The lights of f 2, f 3 pass through the wave plate 34 functioning as a 波長 wave plate for the lights of the frequencies f 1, f 2, f 3, and enter the movable mirror 12. The light of the frequencies f1, f2, and f3 of the circularly polarized light reflected by the movable mirror 12 passes through the wave plate 34 again and enters the polarization splitter 48. Here, the lights of the frequencies f1, f2, and f3 are transmitted through the wave plate 34 twice, so that the polarization azimuth is rotated by 90 °, becomes S-polarized light, and is reflected by the polarization separation element 48. Thereafter, the light enters a light separating element 57 provided between the polarization separating element 48 and the reflecting mirror 42. The light separating element 57 is a crystal having anisotropy that emits ordinary light and extraordinary light in different directions. For example, a Wollaston prism is used.

The light separating element 57 is arranged to transmit the S-polarized light almost as it is and to emit the P-polarized light obliquely. Accordingly, the S-polarized light having the frequencies f1, f2, and f3, which are the measurement lights incident on the light separating element 57, pass through the light separating element 57 as it is, enter the reflecting mirror 42, and are reflected with a shifted optical path. Where the frequency f
The light of f1, f2, and f3 becomes elliptically polarized light including a weak P-polarized component (error light) due to the retardation by the reflecting mirror 42, but re-enters the light separating element 57 and transmits the original S-polarized light as it is. Then, the light of the P polarization component, which becomes error light, is separated by the light separation element 57 and is emitted obliquely (not shown). Thus, the light separating element 5
7 is disposed between the polarization splitting element 48 and the reflecting mirror 42, thereby separating the error light of the S-polarized light having the frequencies f1, f2, and f3 generated by the retardation in the reflecting mirror 42 from the measurement optical path. Will be able to do it.

The frequency f1 of the S-polarized light from which the error light has been removed,
The light beams f2 and f3 are reflected by the polarization separation element 48, pass through the wave plate 34, reach the movable mirror 12, are reflected at the moving boundary 12, and pass through the wave plate 34 again. Where the frequencies f1, f
Since the light of f2 and the light of f3 are transmitted twice through the wave plate 34, the polarization direction is rotated by 90 degrees to be P-polarized light and transmitted through the polarization splitter 48. Light having frequencies f1, f2, and f3 transmitted through the polarization separation element 48 enters the frequency separation element 68.

The frequency separating element 68 has a property of transmitting light near the frequency f1 and reflecting light of the frequencies f2 and f3. Therefore, the light of the frequency f1 is transmitted through the frequency separating element 68 and transmitted. The light having frequencies f2 and f3 is separated toward the polarization coupling element 47 so as to be directed toward the wave plate 35.

Of the light having the frequencies f2 and f3 reflected by the frequency separation element 68 and having passed through the measurement optical path, the light having the low frequency f2 is transmitted by the frequency conversion element 61 to the frequency f2.
The light is converted into 3 ′ (= 2 · f2) light, interferes with light having a frequency f3 passing through the measurement optical path, and the interference light is received by the light receiving element 7 and input to the phase meter 22 as a measurement signal of the refractive index fluctuation. Is done.

On the other hand, the lights of the frequencies f1 ', f2, and f3 reflected by the polarization separating element 48 pass through the wave plate 33 and reach the fixed mirror 11, are reflected by the fixed boundary 11, and pass through the wave plate 33 again. . Light of frequencies f1 ', f2, and f3 is
3 is transmitted twice, so that the polarization direction is rotated by 90 degrees to become P-polarized light and transmitted through the polarization splitting element 48. The light having the frequencies f1 ′, f2, and f3 transmitted through the polarization splitter 48 enters the light splitter 57. The light separating element 57 is
Since the light is arranged so as to transmit the polarized light almost as it is and emit the P-polarized light obliquely, the P-polarized light having entered the light separating element 57 at the frequencies f1 ′, f2, and f3 is separated by the light separating element. The light exits obliquely from 57 and enters the reflecting mirror 42 to be reflected with its optical path shifted.

Here, the light having the frequencies f1 ', f2, and f3 becomes elliptically polarized light including a weak S-polarized component (error light) due to the retardation by the reflecting mirror 42.
7, the original P-polarized light is emitted obliquely with respect to the incident direction and travels to the polarization splitter 46, and the S-polarized component light, which is error light, passes through the light splitter 57 almost as it is, and It is separated from P-polarized light (not shown). As described above, since the light separating element 57 is disposed between the polarization separating element 48 and the reflecting mirror 42, the frequency f1 ′ of the P-polarized light generated by the retardation at the reflecting mirror 42,
The error light of the light of f2 and f3 can be separated from the reference light path.

Frequency f of P-polarized light from which error light has been removed
The light beams 1 ′, f2, and f3 pass through the polarization splitter 48, pass through the wave plate 33, reach the fixed mirror 11, reflect at the fixed boundary 11, and pass through the wave plate 33 again. Where frequency f
Since the light of 1 ', f2, and f3 are transmitted through the wave plate 33 twice, the polarization direction is rotated by 90 degrees to be S-polarized light and reflected by the polarization splitting element 48. The lights of the frequencies f1 ′, f2, and f3 reflected by the polarization separation element 48 travel to the frequency separation element 69.

The frequency separating element 69 has a property of transmitting light near the frequency f1 'and reflecting light of the frequencies f2 and f3. Therefore, the light of the frequency f1' transmits through the frequency separating element 69. Then, the light is directed to the polarization coupling element 47 via the reflection mirror 13, is made coaxial with the light having the frequency f <b> 1, and is incident on the polarization element 51. The lights of the frequencies f2 and f3 reflected by the frequency separation element 69 are separated so as to travel toward the wave plate. Of the light of frequencies f2 and f3 that have passed through the reference optical path and are reflected by the frequency separation element 69, the light of the low frequency f2 is transmitted to the frequency f3 ′ by the frequency conversion element 62.
(= 2 · f2), which interferes with light of frequency f3 that has passed through the reference optical path. The interference light is received by the light receiving element 8 and input to the phase meter 22 as a reference signal for refractive index fluctuation. .

On the other hand, the light of the frequency f1 and the light of the frequency f1 'made coaxial by the polarization coupling element 47 pass through the polarization element 51 and interfere with each other, and the interference light is received by the light receiving element 6 and becomes a measurement beat signal. It is input to the phase meter 21. In addition, a reference beat signal that causes a part of light having the frequencies f1 and f1 ′ to interfere with each other is input from the light source 1 to the phase meter 21. The phase meter 21 calculates the displacement of the movable mirror 12 from the measured beat signal and the reference beat signal, and outputs the displacement to the calculator 23. The phase meter 22
Calculates the refractive index variation of gas such as air generated in the measurement optical path and the reference optical path from the measurement signal and the reference signal.
Output to In the arithmetic unit 23, the moving mirror 1 from the phase meter 21
The true displacement of the movable mirror 12 is obtained by calculating the displacement of No. 2 and the refractive index variation from the phase meter 22.

As described above, according to the measuring method and apparatus according to the present embodiment, it is possible to perform high-precision displacement measurement in which the refractive index fluctuation of the gas generated in the measuring optical path and the reference optical path is corrected, and the light separating element is used. By locating 57 in the common optical path of the measurement optical path and the reference optical path, the frequencies f1, f
Frequency f used to measure refractive index fluctuations as well as 1 'light
Error light generated in the light of 2, f3 can also be removed.

Next, a measuring method and apparatus in light wave interference measurement according to a third embodiment of the present invention will be described with reference to FIG. This embodiment is a modification of the configuration and the optical path in the block indicated by the broken line 101 shown in FIGS. 1 and 2 in the first embodiment. And polarization splitter 46 and fixed mirror 1
It is characterized in that a light separating element is disposed between the light-emitting device and the light-emitting device. FIG. 4 shows a dashed line 102 corresponding to the dashed line 101 in FIG. 1. Components having the same functions and operations as those described with reference to FIG. 1 and FIG. Omitted.

As shown in FIG. 4, the S-polarized light having the frequency f1 'reflected by the polarization separation element
The light is incident on a light separating element 58 provided between the light source and the wavelength plate 31. The light separating element 58 is a crystal having anisotropy that emits ordinary light and extraordinary light in different directions, similarly to the light separating element 56 in the first embodiment. For example, a Wollaston prism is used. I have. Also, the light separating element 5
Reference numeral 8 is arranged so as to transmit the S-polarized light almost as it is and to emit the P-polarized light obliquely. Therefore, the S-polarized light having the frequency f1 ′ incident on the light separating element 58 travels straight through the light separating element 58, exits, passes through the wave plate 31, and is reflected by the fixed mirror 11. The light of the frequency f1 ′ reflected by the fixed mirror 11 and transmitted through the wavelength plate 31 becomes P-polarized light, reenters the light separating element 58, and exits obliquely from the light separating element 58. The light having the frequency f1 ′ emitted obliquely passes through the polarization separation element 46, enters the reflection mirror 41, is shifted in optical path, and transmits through the polarization separation element 46 again to enter the light separation element 58.

At this time, the light of the frequency f1 'is reflected by the reflecting mirror 41.
S-polarized light component (error light 20)
The light becomes elliptically polarized light including (1).
, The original P-polarized light is emitted obliquely to the incident direction and goes to the wave plate 31, and the S-polarized component light, which is error light, passes through the light separation element 58 almost as it is and Separated from polarized light. As described above, since the light separating element 58 is disposed between the polarization separating element 46 and the wavelength plate 31, the error light 201 of the P-polarized light having the frequency f1 ′ generated by the retardation of the reflecting mirror 41 is generated. It can be separated from the reference light path.

On the other hand, the light having the frequency f1 of the P-polarized light transmitted through the polarization separation element 46 enters a light separation element 59 provided between the polarization separation element 46 and the wavelength plate 32. Similarly to the light separating element 58, the light separating element 59 is a crystal having anisotropy that emits ordinary light and extraordinary light in different directions. For example, a Wollaston prism is used. The light separating element 59 is disposed so as to transmit the P-polarized light almost as it is and to emit the S-polarized light obliquely. Accordingly, the P-polarized light having a frequency of f1 incident on the light separating element 59 travels straight through the light separating element 59 and exits therefrom.
2 and is reflected by the movable mirror 12. The light of the frequency f1 reflected by the movable mirror 12 and transmitted through the wavelength plate 32 becomes S-polarized light, and is incident on the light separating element 59 again to be separated by the light separating element 5.
The light exits obliquely from 9, is reflected by the polarization separation element 46, enters the reflection mirror 41, is shifted in optical path, is reflected by the polarization separation element 46 again, and enters the light separation element 59.

At this time, the light of frequency f1 is weakly P-polarized light component (error light 20) due to the retardation by the reflecting mirror 41.
Although the light becomes elliptically polarized light including 2), when the light enters the light separation element 59 obliquely, the original S-polarized light is emitted obliquely with respect to the direction of incidence on the light separation element 59, and travels toward the wave plate 32 to generate an error. The light of the P-polarized component, which becomes light, passes through the light separating element 59 as it is and is separated from the light of the S-polarized light. As described above, since the light separating element 59 is disposed between the polarization separating element 46 and the wavelength plate 32, the error light 202 of the S-polarized light having the frequency f1 caused by the retardation by the reflecting mirror 41 is measured. It can be separated from the optical path.

As described above, also in the present embodiment, the light separating element 58 is disposed on the reference light path and the light separating element 59 is disposed on the measuring light path, so that light having a component different from the original polarization direction is separated from each light path. I am trying to do it. By doing so, the error light 2 included in the reference light or the measurement light that has become elliptically polarized light due to the retardation by the reflecting mirror 41.
01 and 202 can be separated and removed by the light separating elements 58 and 59. In the present embodiment, the error light 20
Although the light separating elements 1 and 202 are removed by the light separating elements 58 and 59, they can also be removed by the polarization separating element 46.

Next, a measuring method and apparatus in lightwave interference measurement according to a fourth embodiment of the present invention will be described with reference to FIG. In the present embodiment, a description will be given of a measurement method and apparatus in which error light generated due to an extinction ratio of a polarization separation element that separates light from a light source into reference light and measurement light is reduced. As shown in FIG. 5, the light source 3 emits light of a frequency f1 having a polarization direction parallel to the plane of FIG. 5 and light of a frequency f1 ′ (= f1 + Δf) having a polarization direction perpendicular to the plane of FIG. . Frequency f1, f emitted from light source 3
The light 1 ′ is incident on the polarization beam splitter 49. Frequency f1
Is transmitted through the polarization splitting element 49 as P-polarized light and goes to the measurement optical path, and the light of frequency f1 'is reflected by the polarization splitting element 49 as S-polarized light and goes to the reference optical path. At this time, the extinction ratio of the polarization separation element 49 is not perfect, and P-polarized light and S-polarized light cannot be completely separated.
Therefore, due to the extinction ratio of the polarization splitting element 49, the light having the frequency f1 traveling toward the measurement optical path is reduced to the frequency f of the weak S-polarized light.
1 ′ light (error light). On the other hand, the light having the frequency f1 ′ traveling toward the reference light path includes light (error light) having the frequency f1 of weak P-polarized light.

The light having the frequency f1 and the light having the frequency f1 ′ transmitted through the polarization splitting element 49 are
8 and is incident on a light separation element 61 provided between the light separation element 8 and the light separation element 8. The light separating element 61 is a light separating element 5 according to the first embodiment.
Similar to 6, the crystal is anisotropic and emits ordinary and extraordinary rays in different directions. For example, a Wollaston prism is used. Further, the light separating element 61 is arranged so as to transmit the P-polarized light almost as it is and to emit the S-polarized light obliquely. Accordingly, the P-polarized light having the frequency f1 incident on the light separating element 61 travels straight through the light separating element 61, exits, passes through the wave plate 38, and travels through the movable mirror 1
The light is reflected at 6. On the other hand, the light having the frequency f1 ′ of the weak S-polarized light, which becomes the error light, is obliquely bent by the light separating element 61 and separated from the measuring light path and removed. The light of the frequency f1 that has been reflected by the movable mirror 16 and transmitted through the wavelength plate 38 becomes S-polarized light and is incident again on the light separating element 61 to be separated by the light separating element 6.
The light exits obliquely from 1 and is reflected by the polarization separation element 49 and enters the polarization element 52.

On the other hand, the light of the frequency f1 ′ and the light of the frequency f1 reflected by the polarization separation element 49 enter a light separation element 60 provided between the polarization separation element 49 and the wavelength plate 37. The light separating element 60 is a crystal having anisotropy that emits ordinary light and extraordinary light in different directions, like the light separating element 61. For example, a Wollaston prism is used. The light separating element 60 is disposed so as to transmit the S-polarized light almost as it is and to emit the P-polarized light obliquely. Therefore, the S-polarized light having the frequency f1 ′ incident on the light separating element 60 travels straight through the light separating element 60, exits, passes through the wave plate 37, and is reflected by the fixed mirror 15.
On the other hand, the light having the frequency f1 of the weak P-polarized light, which becomes the error light, is obliquely bent by the light separating element 60, separated from the reference light path, and removed.

The light of the frequency f1 ′ reflected by the fixed mirror 15 and transmitted through the wavelength plate 37 becomes P-polarized light, reenters the light separating element 60, and exits obliquely from the light separating element 60.
The light passes through the polarization splitting element 49 and becomes coaxial with the light of the frequency f1 and enters the polarization element 52. The light having the frequencies f1 and f1 ′ that has reached the polarizing element 52 interferes with the polarizing element 52, is converted into an electric signal by the light receiving element 9 and is output to the phase meter 23 as a measurement beat signal. From the light source 3, an interference signal between the light having the frequency f 1 and the light having the frequency f 1 ′ is output to the phase meter 23 as a reference beat signal. The phase meter 23 detects a phase change of the measured beat signal with respect to the reference beat signal, and obtains a change in the optical path length of the movable mirror 16 in the direction of the arrow in FIG. As described above, according to the present embodiment, by arranging the light separation element 60 in the reference light path and the light separation element 61 in the measurement light path, the polarization separation element 4
Light having a component different from the original polarization direction due to the extinction ratio of 9 can be separated and removed from each optical path.

Next, as a fifth embodiment of the present invention,
An exposure apparatus equipped with the measuring apparatus in the light wave interference measurement according to the first embodiment will be described with reference to FIG. FIG. 6 shows a schematic configuration of an exposure apparatus according to the present embodiment. In the present embodiment, step-and-
A description will be given of an example of a projection exposure apparatus that employs a scanning exposure operation. The illumination system 300 irradiates illumination light from a light source such as a mercury lamp or a KrF excimer laser or an ArF excimer laser onto the reticle R mounted on the reticle stage 330 via a fly-eye lens, a condenser lens, or the like, so that the illuminance is uniform. Irradiation. The column 332 is integrated with a column (not shown) for fixing the lens barrel of the projection lens PL. Reticle stage 3
30 is a one-dimensional scanning movement in the X direction by the driving system 334;
A minute rotation movement for yawing correction can be performed.

At one end of reticle stage 330, a first
The measuring device using the light wave interference described in the above embodiment is mounted as a positioning and length measuring system of reticle stage 330. In FIG. 6, the light source 1, the polarization coupling element 47, the reflection mirror 13, the polarization element 51, the light receiving element 6, and the phase meter 21 of the light wave interference measurement apparatus described with reference to FIG. 338.
Although not shown, since the yaw correction amount is measured together with the one-dimensional scanning movement amount in the X direction, the interference measurement system 33 is used.
8, light beams of frequencies f1 and f1 'emitted from the light source 1 are split by a beam splitter to form a parallel two-axis interferometer in the XY plane, and each measurement light beam is substantially perpendicular to the moving plane mirror 12r. It is made to enter. By doing so, for example, the measurement optical path of the measurement light of one interferometer is arranged at a position intersecting the optical axis AX of the projection lens PL to measure the one-dimensional scanning movement amount in the X direction, and the other interferometer The yaw correction amount can be calculated by calculating the difference from the measured value. Hereinafter, the projection lens PL
An interferometer having a measurement optical path arranged at a position intersecting the optical axis AX will be described as a representative.

Lights of frequencies f1 and f1 'emitted from the light source 1 of the interference measurement system 338 are coaxially incident on a reticle stage polarization splitting element (hereinafter referred to as PBS) 46r, and light of frequency f1 is transmitted through the PBS 46r. Thus, the measurement light travels to the measurement optical path as P-polarized light, and the light at the frequency f1 ′ is reflected by the PBS 46r and becomes the reference light traveling to the reference optical path as S-polarized light.

The light of the frequency f1 'reflected by the PBS 46r has its optical path bent by the reflecting mirror 18r, passes through the quarter-wave plate 31r, and enters the fixed mirror (plane mirror) 11r almost vertically. The fixed mirror 11r is connected to the optical axis AX of the projection lens PL.
And the relative displacement between the reticle R and the center
The projection lens PL is fixed to the upper end of the lens barrel. The light of the frequency f1 ′ reflected at the fixed boundary 11r is again transmitted to the wave plate 31r.
, And its polarization direction is rotated by 90 degrees to become P-polarized light and transmitted through the PBS 46r. The light having the frequency f1 'transmitted through the PBS 46r is incident on a light separating element 56r provided between the PBS 46r and a reflecting mirror (corner cube prism) 41r. Light separation element 56r
Uses a Wollaston prism. Also,
The light separating element 56r is arranged so as to transmit the S-polarized light almost as it is and emit the P-polarized light obliquely.

Accordingly, the P-polarized light having a frequency of f1 'incident on the light separating element 56r is obliquely emitted from the light separating element 56r, is incident on the reflecting mirror 41r, and is reflected with its optical path shifted. Here, the light of the frequency f1 ′ becomes elliptically polarized light including a weak S-polarized component (error light) due to the retardation by the reflecting mirror 41r. The S-polarized light, which is emitted obliquely with respect to the incident direction and travels toward the PBS 46r and becomes error light, passes through the light separating element 56r almost as it is and is separated from the P-polarized light.

Frequency f1 'of P-polarized light from which error light has been removed
Is transmitted through the PBS 46r, the optical path is bent by the reflecting mirror 18r, passes through the wave plate 31r, reaches the fixed mirror 11r, is reflected at the fixed boundary 11r, and passes through the wave plate 31r again. Here, since the light of the frequency f1 ′ is transmitted twice through the wave plate 31r, the polarization direction is rotated by 90 degrees, becomes S-polarized light, and is reflected by the PBS 46r. The light of the frequency f1 ′ reflected by the PBS 46r is directed to the polarization element 51r in the interference measurement system 338.

On the other hand, the frequency f1 transmitted through the PBS 46r
Is transmitted through the wave plate 32r and travels through the movable mirror (plane mirror) 12
r, and is reflected at the moving boundary 12r and transmitted through the wave plate 32r again. The movable mirror 12r is fixed to the side surface of the reticle stage 330, and can move together with the reticle stage 330 in the direction of the arrow in FIG. Since the P-polarized light having the frequency f1 is transmitted twice through the wavelength plate 32r, the polarization direction is rotated by 90 degrees to become S-polarized light, and PB
The light is reflected at S46r. Frequency f reflected by PBS 46r
The light 1 enters a light separating element 56r provided between the PBS 46r and the reflecting mirror 41r. Light separation element 56r
Is arranged so as to transmit the S-polarized light almost as it is and to emit the P-polarized light obliquely, so that the frequency f of the S-polarized light which is the measurement light incident on the light separating element 56r.
The light 1 passes through the light separating element 56r as it is, is separated from the P-polarized light, which is the reference light, having the frequency f1 ′, and is reflected by the reflecting mirror 41.
and is reflected by the optical path being shifted.

Here, the light of the frequency f1 becomes elliptically polarized light including a weak P-polarized component (error light) due to the retardation by the reflecting mirror 41r. The light of the P-polarized component, which is transmitted as it is and travels to the PBS 46r and becomes error light, is separated by the light separating element 56r.
And separated and ejected diagonally.

The S-polarized light from which the error light has been removed is reflected by the PBS 46r, passes through the wave plate 32r, reaches the movable mirror 12r, is reflected at the moving boundary 12r, and passes through the wave plate 32r again. . Here, the light of the frequency f1 is
Since 2r is transmitted twice, the polarization direction is rotated by 90 degrees to become P-polarized light and transmitted through the PBS 46r. PB
The light of frequency f1 transmitted through S46r is
The light passes through r and becomes coaxial with the light having the frequency f1 ′, and travels toward the polarizing element 51r in the interference measurement system 338.

The frequencies f1, f reaching the polarizing element 51r
The 1 ′ light interferes, a measurement beat signal is detected based on the interference light, a phase change of the measurement beat signal with respect to the reference beat signal is detected, and a movable mirror 12r that moves with the movement of the reticle stage 330; The relative displacement between the projection lens PL and the fixed mirror 11r fixed to the lens barrel is obtained. Even in the light wave interference measurement device that measures the amount of movement of the reticle stage 330 mounted on the exposure apparatus according to the present embodiment, the light separation element 56r having a different refraction angle depending on the polarization direction is used.
Are arranged in a common optical path of the measurement optical path and the reference optical path so that light having a component different from the original polarization direction is separated from each optical path. As described above, by inserting the light separating element 56r having anisotropy between the PBS 46r and the reflecting mirror 41r, the error light included in the elliptically polarized measurement light or the reference light due to the retardation by the reflecting mirror 41r. Can be separated by the light separating element 56r. Therefore, the amount of movement of the reticle stage 330 can be detected with high accuracy by reducing the retardation error caused by the reflecting mirror. The position of the reticle R in the X direction and the amount of yawing are output to the main control unit 310 in real time based on a signal from the light wave interference measurement device configured with such an optical path.

Now, the image of the pattern formed on the reticle R is reduced to 1/4 by the projection lens PL and formed on the wafer W. The wafer W is held together with the fiducial mark plate FM by a micro-rotatable wafer holder 344. The holder 344 is provided on a Z stage 346 that can be finely moved in the direction of the optical axis AX (Z) of the projection lens PL. The Z stage 346 is provided on a wafer stage 348 that moves two-dimensionally in the X and Y directions, and the wafer stage 348 is driven by a drive system 354. Also, the wafer stage 348
The coordinate position and yawing amount in the X direction of the X axis direction measurement system 3
The measurement is performed by a light wave interference measurement device including 50. Although not shown, similarly to the reticle stage 330 described above, the light source 1 of the X-axis direction measurement system 350 is used to measure the coordinate position in the X direction and the yawing correction amount.
The light having the frequencies f1 and f1 ′ emitted from the light source is split by a beam splitter to form a two-axis interferometer parallel in the XY plane, and each measurement light is incident on the moving plane mirror 12w almost perpendicularly. Then, for example, the measurement light of one interferometer is arranged at a position crossing the optical axis AX of the projection lens PL to measure the one-dimensional scanning movement amount in the X direction, and the difference from the measurement value of the other interferometer is measured. , The yaw correction amount is calculated. Similarly, the coordinate position of the wafer stage 348 in the Y direction is indicated by Y (not shown).
The measurement is performed by a light wave interference measurement device including an axial fixed system. Hereinafter, an interferometer for X-axis direction measurement in which a measurement optical path is arranged at a position intersecting with the optical axis AX of the projection lens PL will be described as a representative.

The optical interference measuring apparatus including the X-axis direction measuring system 350 is the same as the optical interference measuring apparatus described in the first embodiment. In FIG. 6, the light source 1, the polarization coupling element 47, and the reflecting mirror 1 of the lightwave interference measuring apparatus described with reference to FIG.
3, the polarizing element 51, the light receiving element 6, and the phase meter 21 are 1
These are collectively shown as an X-axis direction measurement system 350 as one block.

The lights of frequencies f1 and f1 ′ emitted from the light source 1 of the X-axis direction measuring system 350 are coaxially incident on the wafer stage polarization splitting element (PBS) 46w, and the light of frequency f1 is transmitted through the PBS 46w. , P-polarized light becomes measurement light that travels to the measurement optical path, and light of frequency f1 ′ is
The light is reflected by w and becomes reference light that travels to the reference light path as S-polarized light.

The light of the frequency f1 'reflected by the PBS 46w is bent by the reflecting mirror 18w, passes through the quarter-wave plate 31w, and is incident on the fixed mirror (plane mirror) 11w almost perpendicularly. The fixed mirror 11w is connected to the optical axis AX of the projection lens PL.
Is fixed to the lower end of the lens barrel of the projection lens PL so that the relative displacement of the wafer stage 348 with respect to can be measured. The light of the frequency f1 'reflected at the fixed boundary 11w again passes through the wave plate 31w, and its polarization direction is rotated by 90 degrees, becomes P-polarized light, and passes through the PBS 46w. PB
The light of frequency f1 ′ transmitted through S46w is
The light is incident on a light separating element 56w provided between the light source and the reflecting mirror (corner cube prism) 41w. A Wollaston prism is used for the light separating element 56w. The light separating element 56w is arranged so as to transmit the S-polarized light almost as it is and to emit the P-polarized light obliquely.

Accordingly, the P-polarized light having the frequency f1 'incident on the light separating element 56w exits obliquely from the light separating element 56w, enters the reflecting mirror 41w, and is reflected with its optical path shifted. Here, the light of the frequency f1 ′ becomes elliptically polarized light including a weak S-polarized component (error light) due to the retardation by the reflecting mirror 41w. The light of the S-polarized component, which is emitted obliquely with respect to the incident direction and travels toward the PBS 46w and becomes error light, passes through the light separating element 56w almost as it is and is separated from the P-polarized light.

The P-polarized light from which the error light has been removed, having the frequency f1 ', passes through the PBS 46w, the optical path of which is bent by the reflecting mirror 18w, passes through the wave plate 31w, and passes through the fixed plate 11w.
w, reflected at the fixed boundary 11w, and transmitted through the wave plate 31w again. Here, the light of the frequency f1 'is applied to the wave plate 31w by 2
Since the light is transmitted twice, the polarization direction is rotated by 90 degrees to become S-polarized light, which is reflected by the PBS 46w. PBS46w
The light of frequency f1 ′ reflected by the X-axis direction measurement system 350
Toward the polarizing element 51w in the inside.

On the other hand, the frequency f1 transmitted through the PBS 46w
Is transmitted through the wave plate 32w, and the movable mirror (plane mirror) 12
w, and is reflected at the moving boundary 12w and transmitted through the wave plate 32w again. The movable mirror 12w is located on the Z on the wafer stage 348.
It is fixed to the side end of the stage 346 and can move in the X direction together with the wafer stage 348. P
Since the polarized light having the frequency f1 is transmitted twice through the wave plate 32w, the polarization direction is rotated by 90 degrees to become S-polarized light, which is reflected by the PBS 46w. The light having the frequency f1 reflected by the PBS 46w is incident on a light separating element 56w provided between the PBS 46w and the reflecting mirror 41w. The light separating element 56w transmits the S-polarized incident light almost as it is,
Since the P-polarized light is arranged to be emitted obliquely, the S-polarized light having the frequency f1 which is the measurement light incident on the light separating element 56w passes through the light separating element 56w as it is,
The light is separated from the P-polarized light, which is the reference light, having the frequency f1 ', enters the reflecting mirror 41w, and is reflected with its optical path shifted.

Here, the light of the frequency f1 becomes elliptically polarized light including a weak P-polarized component (error light) due to the retardation by the reflecting mirror 41w. The P-polarized component light, which is transmitted as it is and travels to the PBS 46w and becomes error light, is separated by the light separating element 56w.
And separated and ejected diagonally.

The S-polarized light having the frequency f1 from which the error light has been removed is reflected by the PBS 46w, passes through the wave plate 32w, reaches the moving mirror 12w, is reflected at the moving boundary 12w, and passes through the wave plate 32w again. . Here, the light of the frequency f1 is
Since the light passes through 2w twice, the polarization direction is rotated by 90 degrees to become P-polarized light, which is transmitted through the PBS 46w. PB
The light of frequency f1 transmitted through S46w is
The light passes through w and becomes coaxial with the light having the frequency f1 ′ and travels toward the polarizing element 51w in the X-axis direction measurement system 350. Polarizing element 5
The lights of the frequencies f1 and f1 ′ that have reached 1w interfere with each other, a measurement beat signal is detected based on the interference light, a phase change of the measurement beat signal with respect to the reference beat signal is detected, and as the wafer stage 348 moves, The moving mirror 12w that moves and the fixed mirror 1 that is fixed to the lens barrel of the projection lens PL
The relative displacement with respect to 1w is obtained.

In the light wave interference measuring apparatus for measuring the amount of movement of the wafer stage 348 mounted on the exposure apparatus according to the present embodiment, the light separating element 56w having a different refraction angle depending on the polarization direction is used for the measurement light path and the reference light path. By arranging them in a common optical path, light having a component different from the original polarization direction is separated from each optical path. As described above, by inserting the light separating element 56w having anisotropy between the PBS 46w and the reflecting mirror 41w, the measuring light or the error light included in the reference light that has become elliptically polarized light due to the retardation by the reflecting mirror 41w. Can be separated by the light separating element 56w. Therefore, the amount of movement of the wafer stage 348 can be detected with high accuracy by reducing the retardation error caused by the reflecting mirror. The position of the wafer W in the X direction and the amount of yawing are output to the main control unit 310 in real time based on a signal from the lightwave interference measurement device configured with such an optical path.

In this embodiment, the projection magnification is set to 1/4.
Therefore, the moving speed Vws of the wafer stage 348 in the X direction at the time of scan exposure is １ ／ of the speed Vrs of the reticle stage 330. Further, in the present embodiment,
A TTR (through-the-reticle) type alignment system 360 for detecting an alignment mark (or a reference mark FM) on the wafer W via the reticle R and the projection lens PL, and a projection lens PL from the space below the reticle R
And a TTL (through-the-lens) type alignment system 362 for detecting an alignment mark (or a reference mark FM) on the wafer W through the reticle R before starting the step-and-scan exposure or during the scan exposure. And the wafer W are aligned relative to each other.

The exposure sequence and control in the scanning projection exposure apparatus according to the present embodiment are totally managed by the main control section 310. The main control unit 310 receives position information and yaw information from a light wave interference measurement device provided on the X axis side of the reticle stage 330 and the wafer stage 348 and a light wave interference measurement device on the Y axis side (not shown), and a drive system. The pattern formed on the reticle R and the wafer pattern are maintained while maintaining a predetermined speed ratio between the reticle stage 330 and the wafer stage 348 during scan exposure based on the input of speed information or the like from the tachogenerators 334 and 354. Are moved relative to each other while keeping the relative positional relationship within a predetermined alignment error, so that the front surface of the pattern of the reticle R can be accurately transferred to a predetermined shot area on the wafer W. in this way,
According to the exposure apparatus of the present embodiment, since the measuring apparatus of the light wave interference method capable of measuring displacement with high accuracy is provided in the stage length measuring system, the reticle stage or the wafer stage can be positioned very accurately. Become like

The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the first to fourth embodiments, the displacement amount of the movable mirror is obtained by using the heterodyne interferometry. However, the present invention is not limited to this, and is applicable to the case where the homodyne interferometry is used. can do.
Further, for example, in the second embodiment, the homodyne interferometry is used in the measurement of the refractive index fluctuation of the measurement optical path, but the present invention is not limited to this, and it is of course applicable to the case where the heterodyne interferometry is used. it can.

Further, for example, the exposure apparatus of the fifth embodiment performs the exposure operation of the step-and-scan method, but the present invention is not limited to this, and the exposure apparatus of the fifth embodiment can be applied to the exposure apparatus of the step-and-repeat method. Of course, it can be applied. Further, in the fifth embodiment, the example in which the optical interference measuring apparatus according to the first embodiment is mounted has been described. However, the present invention is not limited to this, and has been described in the second to fourth embodiments. Any of the light wave interference measurement devices can be mounted.

[0076]

As described above, according to the present invention, it is possible to prevent the occurrence of error light due to the retardation on the reflecting surface of the reflecting mirror and to perform the light wave interference measurement with high accuracy. Further, according to the present invention, it is possible to prevent the occurrence of error light due to a low extinction ratio in the polarization splitting element, and to perform high-precision light wave interference measurement. According to the present invention,
An exposure apparatus capable of controlling the positioning of the stage device with extremely high accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a light wave interference measurement device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a length measuring portion of the optical interference measuring apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a light wave interference measurement device according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a schematic configuration of an optical interference measurement apparatus according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a light wave interference measurement device according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of an exposure apparatus according to a fifth embodiment of the present invention.

FIG. 7 is a diagram showing a schematic configuration of a conventional light wave interference measurement device.

[Explanation of symbols]

1, 2, 3 Light source 6, 7, 8 Light receiving element 11, 12, 13, 14, 15, 16 Reflecting mirror 21, 22 Phase meter 23 Operation unit 31, 32, 33, 34, 35, 36, 37, 38 Wavelength Plates 41, 42 Reflecting mirrors 46, 48 Polarization separation element 47 Polarization coupling element 51 Polarization element 56, 57, 58, 59, 60 Light separation element 61, 62 Frequency conversion element 66, 67 Frequency coupling element 68, 69 Frequency separation element 201 , 202 Error light 300 Illumination system 310 Main control unit 330 Reticle stage 334 Drive system 338 Interference measurement system 346 Z stage 348 Wafer stage 350 X-axis direction measurement system 354 Drive system R Reticle PL Projection optical system W Wafer AX Light of projection optical system axis

Claims (13)

[Claims] 1. One of two lights whose polarization directions are orthogonal to each other is reflected as a measurement light by a movable mirror movably provided on a measurement optical path, and the other is a fixed mirror fixed to the reference optical path as a reference light. A measuring device that reflects, photoelectrically detects and interferes with the measurement light that has passed through the measurement optical path and the reference light that has passed through the reference optical path, and measures the displacement of the movable mirror. A light separating element provided in at least one of the measurement optical path and the reference optical path. 2. The measuring apparatus according to claim 1, further comprising: a light source that emits linearly polarized light; and a polarization separation element that separates the linearly polarized light into the measurement light and the reference light. The measuring device, wherein the separation element is disposed between at least one of the movable mirror and the fixed mirror and the polarization separation element. 3. The measuring apparatus according to claim 1, wherein the light separating element separates error light based on an extinction ratio of the polarization separating element. 4. The measuring apparatus according to claim 1, further comprising: a wavelength plate provided in at least one of the measurement optical path and the reference optical path, A measuring device, which is arranged between a plate and the polarization splitting element. 5. The measuring device according to claim 1, further comprising: a reflecting mirror provided in the measuring optical path so that at least the measuring light is reflected by the moving mirror a plurality of times. A measuring device, wherein the separation element is provided between the reflection mirror and the polarization separation element. 6. The measuring apparatus according to claim 5, wherein said light separating element separates error light generated by retardation by said reflecting mirror. 7. The measuring device according to claim 1, wherein the two lights whose polarization directions are orthogonal to each other have different frequencies. 8. The measuring apparatus according to claim 2, wherein the light source measures at least a refractive index variation of gas in the measurement optical path and corrects a displacement of the movable mirror. A measuring device that emits light for use. 9. The measuring apparatus according to claim 1, wherein the light separating element is a crystal having anisotropy. 10. The measuring apparatus according to claim 9, wherein said light separating element is a Wollaston prism. 11. The measuring apparatus according to claim 1, further comprising: a light shielding unit that shields the error light separated by the light separating element. 12. One of two lights whose polarization directions are orthogonal to each other is reflected as a measurement light by a movable mirror movably provided on a measurement optical path, and the other is a fixed mirror fixed to the reference optical path as a reference light. A measuring method for reflecting and measuring the displacement of the movable mirror by photoelectrically detecting the interference between the measurement light passing through the measurement optical path and the reference light passing through the reference optical path, and measuring the displacement of the movable mirror, A light separating element, which is different from the above, is disposed in at least one of the measurement light path and the reference light path, and the error light generated in the light path is separated. 13. A reticle stage on which a reticle on which a pattern is formed is placed and movable, a reticle stage-side measuring means for measuring a position of the reticle stage, and a substrate stage on which a substrate is placed and movable. An exposure apparatus having a substrate stage-side measuring means for measuring the position of the substrate stage, wherein at least one of the reticle stage-side measuring means and the substrate stage-side measuring means comprises: An exposure apparatus comprising the measurement apparatus according to any one of claims 1 to 11.