JPH11230712A - Optical wave modulator, optical wave interference measuring equipment and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical wave modulator generating a linearly polarized light of a high degree of polarization, an optical interference measuring equipment provided with the modulator, and an aligner provided with the measuring equipment. SOLUTION: This optical wave modulator 401 is equipped with a ray supply equipment 300 supplying a plurality of lights, frequency modulation elements 190, 191 modulating the respective frequencies fl, f2 of a plurality of rays supplied from the equipment 300, polarizers 200, 201 which are arranged in optical paths on the output side of the frequency modulation elements 190, 191 and turn transmitting lights into linearly polarized lights, and a coupling means 130 coupling a plurality of lights modulated by the frequency modulation elements 190, 191 with almost the same optical path. Since the polarizers 200, 201 are installed, the light outputted from the optical wave modulation equipment 401 turns to a linearly polarized light of high degree of polarization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light wave modulation device and a light wave interference measuring device and an exposure device provided with the light wave modulation device. The present invention relates to a light wave interference measurement device provided with a light wave modulation device and an exposure device provided with such a light wave interference measurement device.

[0002]

2. Description of the Related Art As a light wave modulation device, a structure as shown in FIG. 7 has been conventionally known. 7, the light wave modulator 400 has two types of light, that is, polarized light L (f1, H) parallel to the plane of FIG. 7 at a frequency f1 (hereinafter referred to as “light at a frequency f1” to distinguish the types of light). In addition to
A light source 300 that emits light of a polarization parallel to the paper surface at a frequency f2 and light of a polarization L (f2, H) parallel to the paper surface at a frequency f2 is provided in parentheses. I have. Here, the frequency f2 is the second harmonic of the frequency f1 (f2 = 2 · f1).

A frequency shifter 190 is provided in the optical path of light L (f1, H), and a frequency shifter 19 is provided in the optical path of light L (f2, H).
1 is provided, and a mirror is provided after the frequency shifter 191 so that the optical path of the light L (f2, H) intersects with the optical path of the light L (f1, H). A dichroic mirror 130 is provided which transmits the light L (f1, H) and reflects the light L (f2, H).

An acousto-optic device (AOM) or the like is used as the frequency shifters 190 and 191. The frequency shifters slightly shift the frequency of light passing therethrough, and
(= F1 + Δf1) light L (f10, H) and frequency f2
It is assumed that light L (f20, H) of 0 (= f2 + Δf2). Next, the light L (f10, H) and the light L (f20, H) are substantially coaxially coupled by the dichroic mirror 130 and exit from the light wave modulator 400.

[0005]

However, according to the above-mentioned conventional light wave modulator, the extinction ratio of the light source and the A
Light that has been frequency-shifted due to OM distortion or the like becomes elliptically polarized light. The light wave modulator shown in FIG. 7 is used, for example, as a light source of a correction system for refractive index fluctuation using heterodyne interferometry. Light having a polarization direction component perpendicular to the direction causes a non-linear error, which affects measurement accuracy. In other words, this has a significant effect on the measurement accuracy of the displacement measurement of the movable mirror attached to a stage or the like where the displacement is to be measured by the heterodyne interferometer.

Accordingly, the present invention provides a light wave modulation device that generates linearly polarized light having a high degree of polarization, a light wave interference measurement device provided with such a light wave modulation device, and an exposure device provided with such a light wave interference measurement device. The purpose is to do.

[0007]

According to a first aspect of the present invention, there is provided a light wave modulation device for supplying a plurality of lights, as shown in FIG.
The frequency f of the plurality of lights supplied from the light supply device 300
Frequency modulating elements 190, 1
91; a polarizer 2 provided in an optical path on the emission side of the frequency modulation elements 190 and 191 and configured to linearly polarize transmitted light.
00, 201; and coupling means 130 for coupling a plurality of lights modulated by the frequency modulation elements 190, 191 to substantially the same optical path. The polarizer may be provided after the combining means 130 as one polarizer.

With this configuration, the polarizers 200, 2
01, the light emitted from the light wave modulator becomes linearly polarized light having a high degree of polarization.

In this light wave modulation device, as described in claim 2, with reference to FIG. 3, the light supply device separates the light source 351 for emitting light and the light emitted from the light source 351. Light separating means 141 for generating the plurality of lights
May be provided. With this configuration,
Two light beams with high coherency can be obtained from one light source.

In the above-described light wave modulation device, it is preferable that the frequency modulation elements 190 and 191 are acousto-optic elements AOM.

[0011] In the above-mentioned light wave modulation device, a fourth aspect of the present invention is provided.
As described in the above, it is preferable that the frequencies f1 and f2 of the plurality of lights are different from each other. With this configuration, the light wave modulation device can be used as a light source of a correction system of a refractive index fluctuation of a heterodyne interferometer, for example.

In order to achieve the above object, a light wave interference measuring apparatus according to a fifth aspect of the present invention, as shown in FIG.
The light wave modulator 401 or 402 according to any one of claims 1 to 3, a beam splitter 120 provided on the substantially same light path, and separating the light path into a measurement light path MP1 and a reference light path RP1; A fixed mirror 170 provided on the reference light path RP1; a moving mirror 160 provided on the measurement light path MP1 and moving relatively to the fixed mirror 170; passing through the reference light path RP1 and the length measurement light path A light receiving unit 602 for receiving the plurality of lights by interfering with each other;
603.

According to a sixth aspect of the present invention, there is provided a light wave interference measuring apparatus comprising: a light wave modulating device 401 or 402 according to the fourth aspect; and a length measuring light supplying device for supplying length measuring light. 360; the length measuring light supplied by the length measuring light supply device 360, and the length measuring light and the light coupled to the same optical path by the coupling means 130 in the light wave modulators 401 and 402 are common. The light wave modulators 401 and 402 and the length measuring light supply device 360 are arranged so as to be on the same optical path, and the beam splitter 120 separates the common optical path into a measurement optical path MP1 and a reference optical path RP1; A fixed mirror 170 provided on the RP1; a movable mirror 160 provided on the measurement optical path MP1 and relatively moved with respect to the fixed mirror 170; and a reference optical path RP1 and the measurement optical path MP1. A first light receiving unit 601 for interfering and receiving the measured light for measurement; and a light receiving unit for interfering with the plurality of lights passing through the measuring optical path MP1 coupled to the same optical path by the coupling unit 130. The second light receiving unit 60
2 and 603; an error component of the length measurement signal from the first light receiving unit 601 based on the change in the refractive index of the gas is corrected using the measurement signal from the second light receiving units 602 and 603. ing. Here, the gas is typically air that fills the measurement optical path MP1 and the reference optical path RP1.

With this configuration, the second light receiving section 60
2 and 603, the length measurement signal from the first light receiving unit 601 is corrected using the measurement signal from the second light receiving unit, and the refractive index of the gas in the measurement light path MP1 and the reference light path RP1. The influence on the measurement accuracy due to the fluctuation can be eliminated.

The light wave interference measuring device according to claim 7 is the light wave modulation device 401 or 402 according to claim 4.
Light emitted from the light wave modulators 401 and 402 and having different frequencies and having passed through an optical path for detecting a change in the refractive index of a gas, and at least one of the different lights f10
Frequency conversion members 230 and 231 for converting the light into the same frequency f10 ′ as the other light;
Second light receiving units 602 and 603 for receiving the light f10 'converted by the light 31 and the other light f20 by interfering with each other; calculating means for calculating a change in the refractive index of gas in the reference light path RP1 and the measurement light path MP1. 700.

In order to achieve the above object, a light wave modulation device according to the invention according to claim 8 comprises a first light wave modulation device as shown in FIG.
A light supply device 300 for supplying a first light L (f1, H) having a frequency f1 and a second light L (f2, H) having a second frequency f2; and the first light L (f1, H). ) To the third
The light L (f1, H) to L (f10, H) and the fourth light L
(F1, V) to L (f11, V)
A first frequency modulating element 192 for modulating the frequency of the third light; a second frequency modulating element 193 for modulating the frequency of the fourth light; the first and second frequency modulating elements Polarizers 202 and 203 provided in the light paths on the emission side of 192 and 193, respectively, to convert transmitted light into linearly polarized light; and to convert the second light L (f2, H) into a fifth light L (f2, H). H) to L (f20, H) and the sixth light L (f
(2, V) to L (f21, V); second light separating means 124; and third light modulating means for modulating the frequency of the fifth light.
A frequency modulating element 194; a fourth frequency modulating element 195 for modulating the frequency of the sixth light; and transmitted light provided in the light paths on the emission side of the third and fourth frequency modulating elements 194 and 195, respectively. Polarizer 20 that converts light into linearly polarized light
4, 205; first coupling means 123 for coupling the light modulated by the first frequency modulation element 192 and the light modulated by the second frequency modulation element 193 into substantially the same optical path; A second coupling means 125 for coupling the light modulated by the frequency modulation element 194 and the light modulated by the fourth frequency modulation element 195 into substantially the same optical path; and the first coupling means 12
Third coupling means 132 for coupling the light coupled by the third and the light coupled by the second coupling means 125 into substantially the same optical path.
And

With this configuration, four types of light L (f20, H), L (f21, V) and L (f10,
H) and L (f11, V) are obtained.

A light wave interference measuring device 502 according to a ninth aspect of the present invention is provided, as shown in FIG. 6, with the light wave modulating device 403 according to the eighth aspect and on the optical path of light emitted from the light wave modulating device 403. A beam splitter 126 for separating the optical path into a measurement optical path MP2 and a reference optical path RP2; a fixed mirror 171 provided on the reference optical path RP2; and a fixed mirror 171 provided on the measurement optical path MP2. A movable mirror 161 that moves relatively; the fifth light L (f20, H) passing through the measurement optical path MP2 and the sixth light L (f21, V) passing through the reference optical path RP2 interfere with light reception A first light receiving unit 605 that performs at least one of the third light L (f10, H) passing through the measurement optical path MP2 or the fifth light L (f20, H) passing through the measurement optical path MP2. light The second light receiving portion 603 for receiving the light interference at the first frequency converter; substantially the same frequency as the first frequency conversion unit 231 to interfere with the frequency conversion
And at least the fourth light L (f passing through the reference light path RP2
11, V) or the sixth light L passing through the reference light path RP2
(F21, V) A second frequency conversion unit 2 that frequency-converts one light to substantially the same frequency as the other light and causes interference.
30; a third light receiving unit 602 for receiving light that has interfered with the second frequency conversion unit; a measurement signal from the first light receiving unit 605; and second and third light receiving units 603 and 602.
Is used to correct the fluctuation of the refractive index of the gas in the measurement optical path MP2 and the reference optical path RP2 using the measurement signal obtained from
1 is detected.

An exposure apparatus 80 according to a tenth aspect of the present invention.
0 is a light wave interference measurement device 501 according to any one of claims 5 to 7 and 9, as shown in FIG.
A substrate stage 2 on which a substrate for exposing a pattern is placed
The movable mirror 160 is attached to the substrate stage 250.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same reference numerals, and redundant description will be omitted. 1 to 3 are diagrams showing a configuration of an embodiment of a light wave modulation device according to the present invention.

FIG. 1 shows the configuration of a first embodiment of the light wave modulator according to the present invention. The light wave modulation device 401 shown in FIG. 1 includes two types of light: light L (f1, H) having a polarization direction parallel to the plane of FIG. 1 at a frequency f1 and light L having a polarization direction parallel to the plane at a frequency f2. The light source 300 emitting (f2, H) is provided. Here, the frequency f2 is the frequency f1
And the relation of f2 = 2 · f1 is satisfied.

A frequency shifter 190 is arranged in the optical path of the light L (f1, H), and a frequency shifter 191 is arranged in the optical path of the light L (f2, H). A mirror is provided after the frequency shifter 191 and will be described later. The optical path of the light L (f20, H) is intersected with the optical path of the light L (f10, H) described later, and the light from the light L (f1, H) is selectively placed at the intersection. A dichroic mirror (hereinafter, appropriately referred to as “DM”) 130 that transmits and reflects light from the light L (f2, H) is provided.

An acousto-optic device (AOM) or the like is used as the frequency shifters 190 and 191. The frequency shifters slightly shift the frequency of light passing therethrough, and
(= F1 + Δf1) light L (f10, H) and frequency f2
It is assumed that light L (f20, H) of 0 (= f2 + Δf2).

Further, a polarizer 200 having a good extinction ratio is disposed between the frequency shifter 190 and the DM 130 in the optical path of the light L (f10, H), and the frequency shifter in the optical path of the light L (f20, H) is provided. A polarizer 201 having a good extinction ratio is disposed between the mirror 191 and the DM 130, and between the frequency shifter 191 and the mirror in FIG.

The operation of the light wave modulator according to the first embodiment configured as described above will be described. Light having a frequency f1 and a frequency f2 emitted from the light source 300 and having a polarization direction parallel to the sheet of paper, ie, light L (f1, H) and light L (f2, H).
Enter the AOMs 190 and 191 respectively. The respective lights are slightly frequency-shifted by the AOMs 190 and 191, and the light L (f10, の) having the frequency f10 (= f1 + Δf1) is obtained.
H) and light L (f2) having a frequency f20 (= f2 + Δf2)
0, H).

At this time, the two lights are mostly lights having a polarization direction parallel to the paper surface, but the extinction ratio of the light source 300 and the AO
Due to the distortion of M190 and 191, the light is elliptically polarized light having a component of the polarization direction slightly perpendicular to the paper surface. Each of the elliptically polarized lights is a polarizer 200, 2 having a good extinction ratio.
01 is incident.

The polarizers 200 and 201 are installed so as to transmit only light having a polarization direction parallel to the plane of the paper. Light transmitted through the polarizers 200 and 201 is a straight line having only a component of the polarization direction parallel to the plane of the paper. It becomes polarized light.

As the polarizers 200 and 201, an element having a good extinction ratio such as a Glan-Thompson prism or a Glan-Taylor prism (PBS using a calcite crystal) is installed and used so as to transmit only a predetermined polarization direction. You can do it.

The light L (f10, H) and the light L (f20, H) transmitted through the polarizers 200 and 201, respectively, are linearly polarized light, and are DM130 which is a frequency coupling element.
And the light wave modulator 401 is emitted. Thus, the light wave modulator can supply linearly polarized light having a high degree of polarization. As a result, non-linear errors are reduced when this device is used in a light wave interference measurement device.

Here, instead of providing the two polarizers 200 and 201 in each optical path, one polarizer (not shown) may be provided in the optical path after being combined by the DM 130.
This is the same in the embodiment shown in FIG. 2 described later.

Referring to FIG. 2, a light wave modulation device according to a second embodiment of the present invention will be described. The light wave modulation device 402 shown in FIG. 2 includes wave plates 155 and 156 in the light path behind the polarizers 200 and 201 in the light wave modulation device 401 (between the frequency shifters 190 and 191 and the DM 130, respectively). Has been inserted.

The light source unit 300 emits light having a polarization direction parallel to the plane of the paper at the frequency f1 and the frequency f2, that is, the light L (f1,
H) and light L (f2, H). As such a light source unit 300, a light source that directly emits light of frequency f1 and light of frequency f2 can be used.

As the light source unit 300, a light source unit 350 as shown in FIG. 3 may be used. Light source section 350
Has a built-in light source 351 that emits only light having the frequency f1, and a second harmonic conversion element (hereinafter, referred to as “SHG conversion element”) 232 and a frequency such as a dichroic mirror in the optical path of the light emitted from the light source 351. A configuration may be adopted in which the separation element 141 is provided, a mirror is arranged in the direction reflected by the frequency separation element 141, and the optical path bent by the mirror is parallel to the optical path of the light of frequency f1.

The light source unit 350 shown in FIG. 3 causes the light of the frequency f1 from the light source 351 to enter the SHG conversion element 232, and a part of the light is the frequency f2 (= 2 · f1) which is the second harmonic.
Is converted to light. The SHG-converted light having the frequency f2 and the SHG-unconverted light having the frequency f1 are separated by the frequency separating element 141 that transmits the light having the frequency f1 and reflects the light having the frequency f2. The light having the frequency f2 is transmitted as it is, reflected by the frequency separation element 141, further reflected by the mirror, and emitted from the light source unit 350 in parallel with each other.

Returning to FIG. 2, the operation of the light wave modulator will be described. The light of frequency f1 emitted from the light source unit 300 and the frequency f
2 pass through the frequency shifters 190 and 191 and the polarizers 200 and 201 having a good extinction ratio, respectively, and
Light having a polarization direction parallel to the plane of paper at 10 and frequency f20,
That is, light L (f10, H) and light L (f20, H) are obtained.

As the polarizer, an element having a good extinction ratio, such as a Glan-Thompson prism or a Glan-Taylor prism, can be used by setting it so that light transmits only in a predetermined polarization direction.

These two lights pass through the half-wave plates 155 and 156, respectively. At this time, the half-wave plate 15
5 and 156 are rotated around the optical axis, the light L
(F10, H) and the polarization direction of the light L (f20, H) can be arbitrarily changed.

The two lights that have passed through the half-wave plates 155 and 156, respectively, are made substantially coaxial with each other by the DM 130, which is a frequency coupling element, and exit the light wave modulator 402. This realizes a light wave modulation device that supplies linearly polarized light with a high degree of polarization and that can freely set each polarization direction.

Next, an optical interference measuring apparatus according to a third embodiment of the present invention will be described with reference to FIG. This light wave interference measuring device is a device for measuring the length, displacement, density, etc. of an object. FIG. 4 shows a schematic configuration of a heterodyne interferometer as a typical example. is there.

A heterodyne interferometer 501 shown in FIG. 4 is a first optical system for measuring a displacement of a stage 250 such as a substrate stage for holding a substrate of an exposure apparatus in an optical axis direction of a length measuring optical path MP1. And a second optical system that monitors a refractive index variation of a gas (hereinafter, appropriately referred to as “air”) through which light passes through the length measurement optical path MP1.

First, the first optical system will be described with reference to FIG. In FIG. 4, a light source 360 emits light including light L (f00, H) having a frequency f00 in a polarization direction parallel to the paper surface and light L (f01, V) having a frequency f01 in a polarization direction perpendicular to the paper surface. Light source. The two lights have slightly different frequencies and orthogonal polarization directions.

In the present embodiment, the split surface is set at about 4 ft with respect to the optical path of the light emitted from the light source 360.
With a 5 degree angle, the beam splitter (hereinafter referred to as “B
S ”). A part of the incident light is reflected by the BS 110, and the polarizer 210 is disposed on the optical path in the reflection direction, and the detector 600 is disposed ahead of the polarizer 210. The polarization direction of the polarizer 210 is inclined 45 degrees with respect to the polarization directions of the two lights. The detector 600 is electrically connected to the arithmetic device 700.

On the optical path of the light transmitted through the BS 110, a polarizing beam splitter (hereinafter, appropriately referred to as “PBS”) 120 for separating incident light according to the polarization direction is disposed. In the present embodiment, the PBS 120 is arranged with the split surface at an angle of about 45 degrees with respect to the optical path. The PBS 120 transmits light having a polarization direction parallel to the paper surface and reflects light having a polarization direction perpendicular to the paper surface.

Further, on the optical path of the light transmitted through the PBS 120, a movable mirror 160 of the length measuring optical path MP1 is placed.
The fixed mirror 1 of the reference optical path RP1
70 are arranged. The moving mirror 160 is mounted on the stage 25
0, and is displaced in the optical axis direction of the length measuring optical path MP1. In the present embodiment, the fixed mirror 170 and the movable mirror 160 are illustrated as corner cubes (hereinafter appropriately referred to as “CCP”). If a corner cube or a cat's eye is used as the movable mirror 160, the incident light can be returned to the original direction even if the attitude of the movable mirror 160 slightly changes as the stage moves.

The light reflected on the reference light path RP1 is incident on the fixed mirror 170, and the light reflected there is again reflected on the PBS1.
These optical elements are arranged so as to be incident on 20. On the optical path in the direction in which the light incident on the PBS 120 is reflected again, the DM 140 is disposed with its reflection surface at an angle of about 45 degrees with respect to the optical path.

The DM 140 is located in the transmission direction of the light that enters the length measuring optical path MP 1, is reflected by the moving mirror 160, and again enters the PBS 120. Further, a PBS 121 is arranged on an optical path that enters from the PBS 120 and passes through the DM 140. In the present embodiment, a mirror is disposed in the optical path of the light passing through the fixed mirror 170 among the light transmitted through the DM 140 in this manner, and the light is configured to be incident on the PBS 121. .

The PBS 121 reflects light having a polarization direction perpendicular to the plane of FIG. 4 and transmits light having a polarization direction parallel to the plane of FIG. Further, the polarizer 211 is disposed on the optical path of the light transmitted through the PBS 121, and the detector 601 is disposed on the optical path of the light transmitted through the polarizer 211. The polarizer 211 is disposed at an angle of 45 degrees with respect to the polarization directions of the two lights that enter the polarization directions.

The detector 601 converts the energy of the incident light into electricity. The detector 601 is provided by the arithmetic unit 700
Is electrically connected to

Referring to FIG. 4, the operation of the first optical system having the above configuration will be described. The light emitted from the light source 360, that is, the light whose frequency is slightly different and whose polarization direction is orthogonal
The two lights L (f00, H) and L (f01, V) are partially reflected by the beam splitter 110. The reflected light passes through the polarizer 210 and then enters the detector 600.

Since the polarization direction of the polarizer 210 is inclined by 45 degrees with respect to the polarization directions of the two lights, the two lights transmitted through the polarizer 210 interfere with each other. This interference light is detected by the detector 60.
0, the signal is converted into a beat signal having a difference (f00-f01) between the frequency f00 and the frequency f01.
It is input to the arithmetic unit 700 as a reference signal for 60 displacement measurement.

The light transmitted through the BS 110 is separated by the PBS 120 according to the respective polarization directions. That is, light having a polarization direction parallel to the paper surface is transmitted, and light having a polarization direction perpendicular to the paper surface is reflected. Since the light L (f00, H) is light having a polarization direction parallel to the paper surface, the moving mirror 160 of the length measuring optical path MP1 is used.
Since the light L (f01, V) is light having a polarization direction perpendicular to the plane of the paper, the light L (f01, V) is emitted to the fixed mirror 170 on the reference optical path RP1.

The light L (f0) reflected on the reference light path RP1
1, V) is reflected by the fixed mirror 170 and again
Incident on. This light L (f01, V) is reflected by the PBS 120 and enters the DM 140. The DM 140 has a property of transmitting light of the frequency f00 and the frequency f01 and light of a frequency near the light, and reflecting light of the frequency f10 and the frequency f20 and light of the frequency near the light.

The light L (f00,
H) is reflected by the moving mirror 160 and again
The light is parallel to the plane of the paper, so that it passes through the PBS 120 and enters the DM 140.

Each of the length measuring optical path MP1 and the reference optical path RP
Light L (f00, H) and light L (f01, V) that have reciprocated 1
Pass through the DM 140 and enter the PBS 121. PB
In step S121, light having a polarization direction perpendicular to the paper surface is reflected, and light having a polarization direction parallel to the paper surface is transmitted.
H) is transmitted and the light L (f01, V) is reflected, and these two lights are emitted coaxially through the PBS 121 toward the polarizer 211.

In this way, the two lights are polarized by the polarizer 211.
And enters the detector 601. Since the polarization direction of the polarizer 211 is inclined by 45 degrees with respect to the polarization directions of the two lights, the light L (f01,
V) and the light L (f00,
H) interfere after passing through this polarizer 211.

This interference light is photoelectrically converted by the detector 601 and the difference between the frequency f00 and the frequency f01 (f00−f0)
It becomes the beat signal of 1) and is input to the arithmetic unit 700 as a length measurement signal for the displacement measurement of the moving mirror. Arithmetic unit 700
Measures the phase change of the length measurement signal with respect to the reference signal, and determines the displacement of the stage 250 in the direction of the arrow in the figure, that is, the direction along the optical path of the light L (f00, H) from the change amount.

The second optical system will be described with reference to FIG. BS1 on the optical path of the light emitted from the light source 360
DM 131, which is a frequency coupling element, is disposed between the optical path 10 and the PBS 120 so that its reflection surface is at an angle of about 45 degrees with respect to the optical path. And this DM131
The light wave modulator 401 described in the first embodiment is arranged such that the reflected light of the light wave travels toward the PBS 120. Hereinafter, in the present embodiment, the light wave modulation device 401 will be described, but the light wave modulation device 4 is used instead.
02 may be used.

Further, the reference light paths RP1 to RP
DM1 of light incident on DM140 via BS120
An SHG conversion element 230 as a frequency conversion member is provided on the optical path in the reflection direction at 40, and a detector 602 as a light receiving unit is provided ahead of the SHG conversion element 230. The detector 602 is electrically connected to the arithmetic device 700 so as to transmit the reference signal.

Similarly, the DM of the light that enters the DM 140 via the PBS 120 from the length measuring optical path MP 1 described above
An SHG conversion element 231 serving as a frequency conversion member is provided on the optical path in the reflection direction at 140, and a detector 603 serving as a light receiving unit is provided beyond the SHG conversion element 231. The detector 603 is
It is electrically connected to the arithmetic unit 700 so as to transmit a reference signal.

Referring to FIG. 4, the operation of the second optical system in the light wave interference measuring apparatus having the above configuration will be described. The light L (f1) having the frequency f10 emitted from the lightwave modulator 401
0, H) and the light L (f20, H) having the frequency f20 have their polarization directions rotated by the wave plate 150, and have a polarization direction inclined by 45 degrees with respect to the paper surface. The frequency coupling element DM131 is
Since the light having the frequency f10 and f20 and the light having the frequency close thereto are reflected, and the light having the frequency f00 and f10 and the light having the frequency close thereto are DMs having a characteristic of transmitting, these two lights are reflected by the DM 131. , Light L (f00, H) and light L (f01, V) passing therethrough
Are reflected substantially coaxially and enter the PBS 120.

The frequencies f10 and f reflected by the DM 131
Since the polarization direction of the light 20 is inclined 45 degrees with respect to the plane of the paper, the light is incident on the reference light path RP1 and the length measurement light path MP1 by the PBS 120, respectively.

The light L (f10, V) and the light L (f20, V) having a polarization direction perpendicular to the paper surface reflected by the reference light path RP1.
Is reflected by the fixed mirror 170 in the same manner as the light L (f01, V) described above, then re-enters the PBS 120,
It is ejected toward.

On the other hand, the light L (f10, H) and the light L (f20, H) having a polarization direction parallel to the paper and entering the length measuring optical path MP1.
Is reflected by the moving mirror 160 in the same manner as the light L (f00, H) described above, then re-enters the PBS 120,
0 is transmitted as it is and enters DM 140.

The DM 140 is composed of light of frequency f10 and frequency f10.
The light L (f10, V) and the light L (f
20, V), light L (f10, H), light L (f20, H)
Are all reflected.

The light L (f10, V) and the light L (f20, V) having a polarization direction perpendicular to the plane of the paper passing through the reference light path RP1 are
Light L incident on the SHG conversion element 230 and having a frequency f10
A part of (f10, V) is converted to the second harmonic and the frequency f
The light becomes 10a (= 2 · f10).

At this time, the light L (f20,
V) passes through the SHG conversion element 230 as it is. The light having the frequency f10a and the light L (f20, V) are detected by the detector 602.
And the interference light is photoelectrically converted by the detector 602,
A beat signal equal to the frequency difference (= 2 × Δf1−Δf2) is input to the arithmetic unit 700 as a reference signal for measuring the refractive index fluctuation of air.

On the other hand, the light L (f10, H) and the light L (f20,
H) enters the SHG conversion element 231 and has a frequency f10
A part of the light L (f10, H) is converted into a second harmonic and becomes light having a frequency f10a (= 2 · f10).

At this time, the light L (f20,
H) passes through the SHG conversion element 231 as it is. The light having the frequency f10a and the light L (f20, H) are incident on the detector 603, the interference light thereof is photoelectrically converted by the detector 603, and a beat signal equal to the frequency difference (= 2 × Δf1-Δf2) is converted into the air. The measurement signal is input to the arithmetic unit 700 as a measurement signal of the refractive index fluctuation measurement.

The arithmetic unit 700 compares the reference signal of the refractive index fluctuation measurement from the detector 602 with the measurement signal of the refractive index fluctuation measurement from the detector 603, and obtains the phase change amount.

As described above, the arithmetic unit 700 calculates the amount of movement of the stage 250 measured by the first optical system by using the measured amount of fluctuation of the refractive index of air measured by the second optical system. After the correction, the geometric displacement of the stage 250 is obtained.

Here, a method for correcting the refractive index fluctuation of air will be described. The optical path lengths measured with light of frequencies fa, fb, and fc are D (fa), D (fb), and D (fa), respectively.
(Fc). At this time, these optical path lengths are represented by the following equations.

[0072] Where D is the geometric distance, N is the density of air, F
(F) is a function determined by the frequency f of light without depending on the density of air unless the composition ratio of air changes.

From the above equation, the geometric distance D is expressed by the following equation.

[0074] Here, A = F (fa) / {F (fc) -F (fb)}.

From the above, the displacement of the geometric distance desired by this interferometer, that is, the true displacement ΔD can be calculated by the following equation (5).

[0076] Equation 5 is based on the displacement of the movable mirror measured with the light of frequency fa.
This means that the true displacement can be obtained by correcting the influence of the change in the refractive index obtained with light having the frequencies fb and fc.

The arithmetic unit 700 calculates ΔD (fa) in the above equation from the phase change amount of the displacement measurement reference signal and the length measurement signal in the first optical system, and calculates the refractive index fluctuation reference signal and the measurement signal of the second optical system. From the amount of phase change, ｛ΔD (fc) -ΔD
(Fb)｝ is calculated, and the true displacement ΔD of the movable mirror is calculated by (Equation 5).

As described above, in the third embodiment, since the light wave modulator 401 or 402 which emits light of frequencies f10 and f20 of substantially only linearly polarized light substantially coaxially is used, the nonlinear error is reduced. Accurate refractive index fluctuation measurement can be performed. Therefore, it is possible to correct the error due to the refractive index fluctuation and measure the displacement of the movable mirror with high accuracy. Therefore, a light wave interference measurement device capable of performing highly accurate measurement with reduced non-linear errors is realized.

A light wave modulator according to a fourth embodiment will be described with reference to FIG. 5, and a light wave modulator according to a fifth embodiment using the light wave modulator of FIG. 5 with reference to FIG. The interference measurement device will be described.

FIG. 5 is a diagram showing a configuration of the light wave modulation device 403. In FIG. 5, as described above, the light source unit 300 includes two types of light having polarization directions parallel to the paper surface of the frequency f1 and the frequency f2, that is, light L (f1, H) and light L.
Inject (f2, H).

The light source unit 300 is a light source unit 35 shown in FIG.
It may be replaced with 0. In any case, the light L (f2,
H) is the second harmonic of the light L (f1, H). That is,
There is a relationship of frequency f2 = 2 · f1.

Light L of frequency f1 emitted from light source unit 300
On the optical path of (f1, H), １ ／ from the light source unit 300 side
The wavelength plate 151 and the PBS 122 as the second light separating means are arranged, and on the optical path in the direction of transmitting the PBS 122,
The AOM 192, which is the third frequency modulation means, is connected to the PBS 12
An AOM 193, which is a fourth frequency modulating means, is arranged on the optical path in the direction in which the light reflected from the light source 2 is reflected. In the present embodiment,
Between the PBS 122 and the AOM 193, a mirror having a reflecting surface making an angle of approximately 45 degrees is placed between the PBS 122 and the AOM 193 so that the light paths of the light passing through the AOMs 192 and 193 are parallel.

Further, a polarizer 202 having a good extinction ratio is provided at the end of the AOM 192 on the optical path so as to transmit only light having a polarization direction parallel to the plane of the drawing. The sub-element 203 is installed so as to transmit only light having a polarization direction perpendicular to the plane of the drawing.

On the optical path of the light parallel to the paper surface via the polarizer 202, a PBS 123 as a second coupling means is disposed. In addition, a mirror that directs the optical path in a direction intersecting the PBS 123 is arranged on the optical path of the light perpendicular to the paper surface via the polarizer 203. That is, PBS123
Are arranged to couple the two types of light substantially coaxially.

Further, on the optical path of the light coupled by the PBS 123, a frequency coupling element DM1 as a third coupling means is provided.
32 are arranged. The DM 132 outputs the light L (f10, L10) having the frequency combined with the PBS 123, that is, the light having the frequency f1 modulated by the AOM 192 or the AOM 193.
H), light L (f11, V) and light having a frequency in the vicinity thereof are transmitted, and a frequency f2 described later is changed to an AOM 194 described later.
The light L (f20, H) of the frequency modulated at 195, the light L
(F21, V) and have a characteristic of reflecting light having a frequency in the vicinity thereof.

On the optical path of the light L (f2, H) having the frequency f2 emitted from the light source unit 300,
/ 2 wavelength plate 152 and PBS12 as the first light separating means
AOM 194, which is a first frequency modulation element, is provided on the optical path in the direction in which the
A second frequency modulation element AOM195 is arranged on the optical path in the direction reflecting S124. In the present embodiment, a mirror having a reflection surface making an angle of about 45 degrees with the optical path is placed between the PBS 124 and the AOM 195 so that the optical paths of the light passing through the AOMs 194 and 195 are parallel.

Further, a polarizer 204 having a good extinction ratio is installed at the end of the AOM 194 on the optical path so as to transmit only light having a polarization direction parallel to the plane of the drawing. The sub-element 205 is installed so as to transmit only light having a polarization direction perpendicular to the plane of the drawing.

On the optical path of light parallel to the plane of the paper via the polarizer 204, a PBS 125, which is a first coupling means, is disposed. In addition, a mirror that directs the light path toward the PBS 125 is disposed on the light path of the light perpendicular to the paper surface via the polarizer 205. That is, the PBS 125 is arranged to couple the two types of light substantially coaxially.

Further, a mirror is arranged on the optical path of the light combined by the PBS 125 so that the optical path intersects the DM 132 described above.

A beam splitter BS111 is arranged between the PBS 125 and the DM132.
The polarizer 212 is disposed on the optical path of the light reflected by the polarizer 212 with the polarization directions inclined at 45 degrees with respect to the polarization directions of the two incident lights, and the detector 604 as a light receiving unit is disposed on the optical path ahead of the polarizer 212. Has been.

For the polarizers 202, 203, 204, and 205, an element having a high extinction ratio, such as a Glan-Thompson prism or a Glan-Taylor prism, may be installed and used so as to transmit only a predetermined polarization direction. I can do it.

The calcite PBS was replaced with PBS123,
When used in the PBS 125, polarized light having a sufficiently high extinction ratio can be obtained through this, so in this case, the polarizers 202 to 205 may be regarded as being incorporated in the PBS, and the polarizers are separately provided. No need.

The operation of the light wave modulator 403 having the above configuration will be described with reference to the drawings. In FIG. 5, light L (f1, H) of frequency f1 emitted from light source unit 300 is:
The half-wave plate 151 and the PBS 122 cause the light having a polarization direction parallel to the paper surface and the light L (f
1, V). By rotating the half-wave plate 151 around the optical axis, the light L (f1, H) and the light L (f1,
The intensity ratio V) can be freely changed.

Light L (f1, H) transmitted through PBS 122
The frequency f1 is slightly shifted by Δf1 in the AOM 192 to become light L (f10, H) at the frequency f10 (= f1 + Δf1).

The light L (f1, f1,
V), the frequency f1 is slightly shifted by Δf1a in the AOM 193, and the frequency f11 (= f1 + Δf)
It becomes light L (f11, V) of 1a).

At this time, the two frequency-shifted lights, light L (f10, H) and light L (f11, V), are
The light is slightly elliptically polarized light due to the extinction ratio of 2 and AOM distortion.

The polarizer 202 having a good extinction ratio is installed so as to transmit only light having a polarization direction parallel to the plane of the drawing, and the polarizer 203 having a good extinction ratio transmits only light having a polarization direction perpendicular to the drawing. , The light transmitted through the polarizers 202 and 203 becomes linearly polarized light having a good degree of polarization, and the light having the polarization direction parallel to the paper of frequency f10 and the polarization azimuth perpendicular to the paper of frequency f11. , Light L (f10, H) and light L (f11, V), respectively. 2
The two lights are made substantially coaxial by the PBS 123 and pass through the frequency coupling element 132.

On the other hand, the frequency f2 at which the light source 300 is emitted
Of light L (f2, H) are transmitted to the half-wave plate 152 and PB
By S124, the light L (f2,
H) and light L (f2, V) having a polarization direction perpendicular to the paper surface. By rotating the half-wave plate 152 around the optical axis, the intensity ratio between the light L (f2, H) and the light L (f2, V) can be freely changed.

Light L (f2, H) transmitted through PBS 124
Is the light L having the frequency f2 slightly shifted by Δf2 in the AOM 194 and having the frequency f20 (= f2 + Δf2).
(F20, H).

The light L (f2,
V), the frequency f2 is slightly shifted by Δf2a in the AOM 193, and the frequency f21 (= f2 + Δf2
The light L of (a) becomes (f21, V).

At this time, the two lights L frequency-shifted
(F20, H) and the light L (f21, V)
The light is slightly elliptically polarized light due to the extinction ratio and AOM distortion.

The polarizer 204 having a good extinction ratio is installed so as to transmit only light having a polarization direction parallel to the plane of the drawing, and the polarizer 205 having a good extinction ratio transmits only light having a polarization direction perpendicular to the drawing. The light transmitted through the polarizers 204 and 205 becomes linearly polarized light having a good degree of polarization, and has a polarization direction parallel to the plane of the frequency f20 and a polarization direction perpendicular to the plane of the frequency f21. , Light L (f20, H) and light L (f21, V), respectively. 2
The two lights are made substantially coaxial by the PBS 125 and a part of the light is reflected by the BS 111.

The light reflected by BS 111 is a polarizer 212
And enters the detector 604. Since the polarization direction of the polarizer 212 is inclined by 45 degrees with respect to the polarization directions of the two lights, the light transmitted through the polarizer 212 interferes with the detector 604.
And outputs a beat signal equal to the frequency difference (= Δf2−Δf2a) as a reference signal.

The light transmitted through the BS 111 enters the DM 132 after the optical path is bent by a mirror. DM132
Has the characteristic of reflecting the light of the frequencies f20 and f21, and is reflected there, and the light of the frequencies f10 and f11 described above, that is, the light L (f10, H) and the light L (f
11, V) and substantially coaxially with the lightwave modulator 403.
Inject

In this way, a light wave modulator which supplies linearly polarized light having a high degree of polarization and generates light having two orthogonal two frequencies is realized.

Referring to FIG. 6, a description will be given of an optical interference measuring apparatus according to a fifth embodiment of the present invention. This light wave interference measuring device 502 is a heterodyne interferometer as in the embodiment of FIG. 4, and the light wave modulator 403 of FIG. 5 is used for this device.

Lightwave interference measuring apparatus 502 of the present embodiment
The third embodiment is different from the third embodiment in that the displacement of the movable mirror is measured with light having a frequency f2, the PBS has a three-stage configuration, and the light travels twice in each optical path.

In FIG. 6, the light wave interference measuring apparatus 502 of the present embodiment has the third light frequency f1 as described above.
Light waves that coaxially emit 0 and fifth light having a polarization direction parallel to the paper surface of a frequency f20, and fourth light being a light having a polarization direction perpendicular to the paper surface of a frequency f11 and a sixth light being a frequency f21. A modulation device 403 is provided.

On the optical path of these lights emitted from the light wave modulator 403, a PBS 126 for separating the light in accordance with the incident polarization direction is disposed with the reflection surface at an angle of approximately 45 degrees in the optical path, and is parallel to the paper. The light of the polarization direction is transmitted and guided to the length measuring optical path MP2, and the light of the polarization direction perpendicular to the paper is reflected and incident on the reference optical path RP2.

A wavelength plate 153 is disposed on the optical path of the light incident on the reference optical path RP2, and a fixed mirror 171 is disposed on the optical path beyond the wavelength plate 153. In the present embodiment,
The fixed mirror 171 is a plane mirror. Here, the fixed mirror 1 is set so that the light reflected substantially coaxially passes through the wave plate 153 again.
The reflection surface 71 is disposed so as to be orthogonal to the optical path.
Here, the wave plate 153 is a quarter wave plate.

The above components operate as follows. The light L (f10, H) and the light L
(F20, H), and light L (f11, V) and light L (f2
1, V) are emitted coaxially. These lights are separated by the PBS 126 according to the respective polarization directions. That is,
The light L (f10, H) and the light L (f20, H) having the polarization direction parallel to the paper surface of the frequency f10 and the frequency f20 are PBS.
The light L (f11, V) and the light L (f21, V) having the polarization direction perpendicular to the plane of the drawing at the frequency f11 and the frequency f21 are transmitted through the PBS 1
The light is reflected by 26 and enters the reference optical path RP2.

The light having a polarization direction perpendicular to the plane of the drawing, which has entered the reference optical path RP2, passes through the wave plate 153, is reflected almost coaxially by the fixed mirror 171 and passes through the wave plate 153 again. Here, since the wave plate 153 is a 波長 wave plate, the wave plate
The light passes through the light once, and the polarization direction is rotated, so that the light is polarized in a direction parallel to the plane of the drawing.

The structure will be further described. In this way,
Light of frequency f11 and light of frequency f21 having polarization directions parallel to the paper, light L (f11, H) and light L (f
21, H) in the direction in which PBS1 passes through PBS126.
27 is arranged such that its reflection surface forms an angle of approximately 45 degrees with the optical path, and transmits light having a polarization direction parallel to the paper surface.

Thus, on the optical path in the direction of transmission through the PBS 127, the CCP 180, which is a corner cube,
The optical path is shifted so that the light is reflected in the original direction.

The operation of the above configuration is as follows. The light L (f11, H) and the light L (f2) having polarization directions parallel to the paper surface are shown.
1, H) penetrates PBS 126, 127 and CCP1
The optical path is shifted at 80 and again passes through the PBS 127 and 126 and enters the reference optical path RP2. Then the wave plate 15
3, the polarization direction is rotated again by the action of the fixed mirror 171 and the wave plate 153, and the light L (f1
1, V) and L (f21, V). The light having the polarization direction perpendicular to the paper is reflected by the PBS 126.

On the optical path of the reflected light, the DM 142
The reflecting surface is arranged at an angle of about 45 degrees with respect to the optical path, and the reflected light enters the DM 142. The DM 142 has a characteristic of reflecting all the light having the frequency f10 and the frequency f11 and the light having the frequency in the vicinity thereof, and reflecting the light having the frequency f20 and the frequency f21 and a part of the light having the frequency in the vicinity thereof. A mirror is arranged on the optical path of the transmitted light of the DM 142, and the optical path is changed to a PBS described later.
129. Also, DM1
An SHG conversion element 230 and a detector 602 are arranged on the optical path of the reflected light at 42.

On the other hand, a wavelength plate 154 is arranged on the optical path of light having a polarization direction parallel to the plane of the paper incident on the length measuring optical path MP2. A movable mirror 161 attached to the stage 251 whose position is to be measured is located ahead of the movable mirror 161. The movable mirror 161 is a plane mirror in the present embodiment, and reflects reflected light substantially coaxially with the incident light in the same direction. , And the light is arranged to pass through the wave plate 154 again. Here, the wave plate 154 is a quarter wave plate.

The above components operate as follows. Light having a polarization direction parallel to the paper surface, that is, light L (f10, H) and light L (f20, H) incident on the length measurement optical path MP2 are
The light passes through the wave plate 154, is substantially coaxially reflected by the movable mirror 161, and passes through the wave plate 154 again. Wave plate 154 is 1 /
Since it is a four-wavelength plate, the light passes through this plate twice to rotate the polarization direction, and becomes light with a polarization direction perpendicular to the paper surface.

Frequency f1 at which the polarization direction is perpendicular to the paper surface
0 and the light of the frequency f20, the light L (f10,
V) and light L (f20, V) are reflected by the PBSs 126 and 127.

On the optical path of the light reflected by the PBS 127 in this way, the PBS 128 is arranged with the reflection surface at an angle of about 45 degrees with respect to the optical path, and the CCP 181 is placed on the optical path of the reflected light. The optical path is shifted so that the light is reflected in the original direction.

As described above, the light L (f10, V) and the light L (f20, V) having the frequency f10 and the frequency f20 in the polarization direction perpendicular to the paper surface reflected by the PBSs 126 and 127.
V) is further reflected by the PBS 128 and the CCP181
The optical path is shifted by, reflected by the PBSs 128, 127 and 126, and enters the length measuring optical path MP2.

Then, the polarization direction is rotated again by the action of the wavelength plate 154, the moving mirror 161, and the wavelength plate 154, and the light L (f10, H) and the light L (f2) having the polarization direction parallel to the paper surface are obtained.
0, H). The light with the polarization direction parallel to this paper is PB
The light passes through S126 and enters the DM 142. DM14
The SHG conversion element 231 and the detector 603 are arranged on the optical path in the reflection direction of No. 2.

The DM 142 reflects all the light L (f10, H) of the frequency f10 according to the characteristic, and
Part 20 of the light L (f20, H) is reflected. On the optical path in the transmission direction, the PBS 129, the polarizer 213, and the detector 605 are arranged in this order. The polarizer 213 is
The polarization direction is set at an angle of 45 degrees with the polarization direction of the incident light.

The operation will be described below. Light L of frequencies f20 and f21 transmitted through DM 142 according to its characteristics
(F20, H) and the light L (f21, V) are made substantially coaxial with the PBS 129, transmitted through the polarizer 213, and detected by the detector 605.
Incident on.

Since the polarizer 213 is installed at an angle of 45 degrees with respect to the polarization direction of the light of the frequency f20 and the frequency f21, the light transmitted through the polarizer 213 interferes, and the interference light is photoelectrically converted by the detector 605. And the frequency difference (= Δf2
The beat signal of -Δf2a) is input to the arithmetic unit 701 as a length measurement signal for moving mirror displacement measurement.

The light of frequency f10 reflected by the DM 142 and the remaining light L (f10, H) and light L (f
20, H) enters the SHG conversion element 231, and a part of the light L (f10, H) having the frequency f10 is SHG-converted by the SHG conversion element 231 to generate the frequency f10a (= 2 · f10).
Of the second harmonic.

The light L (f20, H) having the frequency f20 passes through the SHG conversion element 231 as it is. The SHG-converted light having the frequency f10a and the light having the frequency f20 interfere with each other, the interference light is photoelectrically converted by the detector 603, and a beat signal equal to the frequency difference (= 2 × Δf1-Δf2) is measured as a measurement signal for refractive index fluctuation measurement. Is input to the arithmetic unit 701.

Similarly, the frequency f1 reflected by the DM 142
1 light L (f11, V) and the remaining light L at frequency f21
(F21, V) enters the SHG conversion element 230,
Light L (f11, V) of frequency f11 by G conversion element 230
Is subjected to SHG conversion to obtain a frequency f11a (= 2 · f1).
It becomes the second harmonic light of 1). In addition, light L of frequency f21
(F21, V) passes through the SHG conversion element 230 as it is.

The SHG-converted light having the frequency f11a and the light having the frequency f20 interfere with each other, the interference light is photoelectrically converted by the detector 602, and a beat signal having a frequency difference (= 2 × Δf1a-Δf2a) is measured. And input to the arithmetic unit 701.

The arithmetic unit 701 measures the phase change of the reference signal for measuring the displacement of the moving mirror from the detector 604 (FIG. 5) of the light wave modulator 403 and the phase change of the length measurement signal for measuring the displacement of the moving mirror from the detector 605. , The displacement ΔD (f2) of the moving mirror is calculated.

Further, based on the phase change of the reference signal and the measurement signal of the refractive index fluctuation measurement from the detectors 602 and 603, the difference 移動 ΔD (f2) −ΔD (f
1) Find｝.

Here, since the displacement of the moving mirror is measured with the light of frequencies f20 and f21, (Equation 5) can be expressed as follows.

[0133] Here, A = F (fc) / {F (fb) -F (fc)} In the above equation, the frequency fb corresponds to the frequency f1, and the frequency fc corresponds to the frequency f2. Using this (Equation 6), the true displacement ΔD of the movable mirror is obtained. As a result, light wave interference that can perform high-precision displacement measurement with reduced measurement error of refractive index fluctuation due to non-linear error (caused by the light source unit) caused by polarization of light emitted from the light wave emission device becoming elliptically polarized light. A measuring device is obtained.

In the fifth embodiment of the optical interference measuring apparatus, the displacement of the movable mirror 161 is measured by using light of frequency f2, but may be measured by light of another frequency f1 in principle. .

The above is the embodiment of the light wave modulator of the present invention and the embodiment in which the light wave modulator is applied to a heterodyne interferometer. Further, the present invention can be applied to various light wave interference measuring devices other than the length measuring machine.

Referring to FIG. 8, an exposure apparatus according to a sixth embodiment of the present invention will be described. The exposure apparatus 800 according to the present embodiment includes an interferometer 501, which is the optical interference measuring apparatus described in the above embodiment, and a substrate stage 250 on which a substrate W on which a pattern of a reticle R is projected.
The movable mirror 160 is attached to the substrate stage 250.

More specifically, as shown in FIG. 8, a projection optical system PL, a reticle stage 802 for holding a reticle R on which a pattern is formed, and a substrate W on which the pattern is to be projected are held on the surface. Substrate stage 2
50. The pattern surface of the reticle R and the surface of the substrate W are conjugate with respect to the projection optical system PL. Reticle R is uniformly illuminated by illumination optical system 801.

The substrate stage 250 has an interferometer 50
1 is installed. That is, the movable mirror 160 of the interferometer 501 is attached to the substrate stage 250,
Fixed mirror 170 is provided to be fixed relatively to projection optical system PL.

A driving device 804 for driving the substrate stage 250 is attached to the substrate stage 250.
4 is electrically connected to the driving device 804.

The length measurement signal from the interferometer 501 is sent to the control device 806, and the control signal from the control device 806 is sent to the drive device 804 to control the position of the substrate stage 250.

FIG. 8 shows an interferometer 501 and a driving device 8.
In FIG. 4, only one pair for measuring and driving the substrate stage 250 in one direction is shown, but typically, another pair of interferometers for driving the substrate stage 250 in a direction perpendicular thereto is used. A device is provided.

Similarly, an interferometer 501 ′ having the same structure as the interferometer 501 is installed on the reticle stage 802. That is, the movable mirror 160 ′ of the interferometer 501 ′ is attached to the reticle stage 802,
A fixed mirror 170 'is provided to be fixed relatively to the illumination optical system 801 or the projection optical system PL.

The reticle stage 802 is provided with a driving device 805 for driving the reticle stage 802, and the driving device 805 is electrically connected to the control device 806. The control device 806 also controls the position of the reticle stage 802. The length measurement signal from the interferometer 501 'is sent to the control device 806, and the control signal from the control device 806 is sent to the drive device 805 to control the position of the reticle stage 802.

FIG. 8 shows the case where the interferometer 501 is used, but it goes without saying that the interferometer 502 may be used.

As described above, according to the embodiment of the present invention, the elliptically polarized light generated by the extinction ratio of the light source or the distortion of the AOM is converted into only the linearly polarized light by the polarizer having a high extinction ratio. A light wave modulator that can be obtained is obtained. In addition, by applying the light wave modulation device according to the embodiment of the present invention to a heterodyne interferometer, measurement errors due to non-linear errors can be reduced, and light wave interference measurement can be performed with higher accuracy. A device is obtained. Further, an exposure apparatus capable of projecting a fine pattern on the reticle R onto a substrate W such as a wafer and manufacturing a highly integrated device can be obtained.

[0146]

As described above, according to the present invention, since a polarizer for converting transmitted light into linearly polarized light is provided, a light wave modulator for generating linearly polarized light having a high degree of polarization, and such a light modulator. It is possible to provide a light wave interference measurement device provided with a simple light wave modulation device and an exposure device provided with such a light wave interference measurement device. In this manner, the influence of the elliptically polarized light on the non-linear error on the measurement accuracy can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of a lightwave modulation device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a configuration of a lightwave modulation device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing an example of a light source unit that can be used in an embodiment of the light wave modulation device of the present invention.

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

FIG. 5 is a schematic configuration diagram illustrating a configuration of a lightwave modulation device according to a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a configuration of a light wave interference measurement device (heterodyne interferometer) according to a fifth embodiment of the present invention using the light wave modulation device of FIG. 5;

FIG. 7 is a schematic configuration diagram showing a configuration of a conventional lightwave modulation device.

FIG. 8 is a schematic configuration diagram showing a configuration of an exposure apparatus according to a sixth embodiment of the present invention.

[Explanation of symbols]

110, 111 Beam splitter 120-128 Polarization beam splitter 130-132 Frequency coupling element 140-142 Frequency separation element 150-156 Wave plate 160, 161 Moving mirror 170, 171 Fixed mirror 180, 181 Corner cube 190-195 Frequency shifter 200- 205, 210-213 Polarizer 230-232 SHG conversion element 250, 251 Stage 300 Light source section 350, 351, 360 Light source 400-403 Light wave modulator 501, 502 Light wave interference measurement device (heterodyne interferometer) 600-605 Detection 700, 701 Computing device 800 Exposure device MP1, MP2 Measurement optical path RP1, RP2 Reference optical path

Claims (10)

[Claims] 1. A light beam supply device that supplies a plurality of lights; a frequency modulation element that modulates a frequency of each of the plurality of lights supplied from the light beam supply device; and a light modulation device provided in an optical path on an emission side of the frequency modulation device. A light polarizer for converting transmitted light into linearly polarized light; and coupling means for coupling a plurality of lights modulated by the frequency modulation element to substantially the same optical path. 2. The light beam supply device comprises: a light source for emitting light; and a light separating unit for separating the light emitted from the light source to generate the plurality of lights.
The light wave modulation device according to claim 1. 3. The light wave modulation device according to claim 1, wherein the frequency modulation device is an acousto-optic device. 4. The light wave modulation device according to claim 1, wherein frequencies of the plurality of lights are different from each other. 5. The light wave modulation device according to claim 1, wherein the light wave modulation device is provided on the substantially same optical path,
A beam splitter for separating the optical path into a measurement optical path and a reference optical path; a fixed mirror provided on the reference optical path; and a movable mirror provided on the measurement optical path and moving relatively to the fixed mirror. A light-receiving unit that interferes with and receives the plurality of lights passing through the reference light path and the length-measuring light path; 6. The light wave modulation device according to claim 4, a length measurement light supply device for supplying a length measurement light, a length measurement light supplied by the length measurement light supply device, and the length measurement. The light wave modulation device and the length measuring light supply device are arranged such that the light for use and the light coupled to the same light path by the coupling means in the light wave modulation device are on a common light path, A beam splitter that separates the optical path into a measurement optical path and a reference optical path; a fixed mirror provided on the reference optical path; a movable mirror provided on the measurement optical path and relatively moved with respect to the fixed mirror; A first light receiving unit that interferes with and receives the length measurement light that has passed through the reference light path and the measurement light path; and the plurality of lights that have passed through the measurement light path and have been coupled to the same light path by the coupling unit. A second light receiving section for receiving light by causing interference with the first light receiving section; An error component of the length measurement signal from the unit based on a change in the refractive index of the gas is corrected using the measurement signal from the second light receiving unit;
Light wave interference measurement device. 7. The light wave modulation device according to claim 4, wherein the light wave light emitted from the light wave modulation device and having a plurality of different frequencies passing through an optical path for detecting a change in the refractive index of gas is selected from among at least the different lights. A frequency converting member for converting one of the two to substantially the same frequency as the other light; a second light receiving portion for receiving the light converted by the frequency converting member and the other light so as to interfere with each other; And a calculating means for calculating a change in the refractive index of the gas in the measurement optical path; a light wave interference measurement device. 8. A light beam supply device for supplying a first light having a first frequency and a second light having a second frequency; and a light source for separating the first light into a third light and a fourth light. A first frequency modulation element for modulating the frequency of the third light; a second frequency modulation element for modulating the frequency of the fourth light; emission of the first and second frequency modulation elements Polarizers respectively provided in the optical paths on the side for converting transmitted light into linearly polarized light; second light separating means for separating the second light into fifth light and sixth light; and the fifth light A third frequency modulating element for modulating the frequency of the third light; a fourth frequency modulating element for modulating the frequency of the sixth light; a transmission element provided in the light path on the emission side of the third and fourth frequency modulating elements. A polarizer that converts light to be linearly polarized; light that has been modulated by the first frequency modulation element; First coupling means for coupling the light modulated by the wave number modulation element to substantially the same optical path; and the light modulated by the third frequency modulation element and the light modulated by the fourth frequency modulation element. Are coupled to almost the same optical path.
And third coupling means for coupling the light coupled by the first coupling means and the light coupled by the second coupling means into substantially the same optical path. ;
Light wave modulator. 9. The light wave modulation device according to claim 8, a beam splitter provided on an optical path of light emitted from the light wave modulation device, and separating the light path into a measurement light path and a reference light path; A fixed mirror provided on the optical path; a movable mirror provided on the measuring optical path and moving relatively to the fixed mirror; a fifth light passing through the measuring optical path, and passing through the reference optical path A first light receiving unit that receives light by causing interference with the sixth light; and a third light receiving unit that has passed at least the measurement light path.
A first frequency conversion unit that frequency-converts one of the light or the fifth light that has passed through the measurement optical path to substantially the same frequency as the other light to cause interference; and the light that has interfered with the first frequency conversion unit. A second light receiving unit for receiving light; at least one of the fourth light passing through the reference light path or the sixth light passing through the reference light path is frequency-converted to substantially the same frequency as the other light to cause interference. A second frequency conversion unit; a third light reception unit for receiving light that has interfered with the second frequency conversion unit; a measurement signal from the first light reception unit; Using the measurement signal obtained from the light receiving unit,
A light wave interference measurement apparatus configured to correct the refractive index fluctuation of gas in the measurement optical path and the reference optical path to detect the displacement of the movable mirror. 10. A light wave interference measuring apparatus according to claim 5, further comprising: a substrate stage on which a substrate for exposing a pattern is placed; and said movable mirror mounted on said substrate stage. The exposure apparatus.