JP2000111311A - Photo-interference length-measuring device and exposing device using the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-interference length-measuring device capable of continuing measurement without returning a stage to the reference position of a moving device. SOLUTION: The photointerference length-measuring device is constituted by providing a first photointerference length-measuring device having a first photo-interferometer measuring the moving length of a moving reflection mirror 52 from an interference light between the first measurement light reflected by the moving reflection mirror 52 and the first reference light reflected by a fixed reflection mirror 51, and a second photointerference length-measuring device measuring the absolute position of a body to be measured. The second photointerferometer length measuring device varies the wave length and makes interfere the second measurement light reflected by the moving reflection mirror 52 among the light from the light source 80 of variable wavelength, and the second reference light reflected by the fixed reflection mirror 51. Based on the interference light, the absolute position of the moving mirror 52 is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical interferometer having an optical interferometer for accurately measuring the amount of movement of an object to be measured, and more particularly to an exposure apparatus for positioning a stage with high accuracy. The present invention relates to a suitable optical interference measuring device.

[0002]

2. Description of the Related Art Such an optical interferometer measures an amount of movement of a movable reflecting mirror from an interference light between a first measuring light reflected by a moving reflecting mirror and a first reference light reflected by a fixed reflecting mirror. Is provided with an interferometer for measuring. This interferometer
Because the number of passes (relative displacement) of the interference fringes observed on the light receiving element by moving the movable reflector from one position to another is measured as the amount of movement of the movable reflector, the position before movement is determined. Is obtained after the movement with respect to.

[0003]

Therefore, in such an optical interferometer, the absolute position of the movable reflecting mirror cannot be ascertained. Therefore, if the measuring light or reference light is interrupted during the measurement, if the measuring light source stops momentarily, or if the reading error of the interference fringes occurs due to the high-speed movement of the movable reflecting mirror, etc., the measurement of the process and the processing based on the measurement Cannot be continued. In such a case, it is necessary to once return the stage to the reference point of the moving device (for example, the mechanical origin of the moving device) to perform the positioning, and then to start the measurement again, which is a factor that causes the deterioration of productivity.

The present invention has been made in view of such a problem, and has as its object to provide an optical interferometer that can continue measurement without returning a stage to a reference point of a moving device.

[0005]

In order to achieve the above object, an optical interferometer according to the present invention comprises an optical interferometer for detecting a relative displacement between a fixed reflecting mirror and a movable reflecting mirror (a first interferometer). Optical interferometer), the measurement light emitted from the variable-wavelength light source and reflected by the movable reflecting mirror, and the reference light emitted from the variable-wavelength light source and reflected by the fixed reflecting mirror. There is provided a second optical interferometer for causing interference while changing the wavelength of the emitted light and measuring the absolute position of the movable reflecting mirror based on the interference light. When the relative displacement obtained by the first optical interferometer thereby becomes unknown, the absolute position of the movable reflecting mirror is measured by the second optical interferometer, and then the first optical interference is measured. Continue measurement with meter.

[0006] The position of the stage which becomes unclear when the measuring light or the reference light is interrupted (the relative position of the movable reflecting mirror with respect to the fixed reflecting mirror) depends on the second light interference after the interrupted measuring light or the reference light returns. The absolute position data calculated by the meter and the phase data obtained from the first optical interferometer capable of measuring a detailed position (within a range smaller than one fringe) near the absolute position can be determined.

[0007] The optical interferometer measures the position data measured by the second optical interferometer as described above with the first optical interferometer data. It is desirable to replace the data with the stage position determined from the total phase data. With this configuration, the function of the stage can be returned to its original state without returning the stage to the reference point of the moving device.

[0008] The wavelength of the variable wavelength light source is preferably different from the wavelength of the length measuring light source of the first optical interferometer.
In particular, it is preferable to use a wavelength variable laser. Such a light source has good wavelength uniformity and good coherence, and can easily separate two lights by different wavelengths.

The optical paths of the first and second optical interferometers can have a so-called double-pass configuration. With such a configuration, the length measurement sensitivity of the optical interference length measurement device can be doubled.

The amount of movement measured by the optical interferometer is defined by the amount of movement of the movable reflecting mirror relative to the fixed reflecting mirror. For this reason, the installation position of the fixed reflecting mirror differs depending on the purpose of length measurement. Of these, when measuring the movement locus of the stage with the moving device, or when measuring a plurality of positions on the stage, it is preferable to provide the moving device or the length measuring device with a reference fixed portion. For example, this case corresponds to a case where the optical interference measuring device is used for a laser processing device, a three-dimensional measuring device, or the like.

On the other hand, when measuring the relative position between the stage and another component, it is preferable to dispose the fixed reflecting mirror on the other component. By arranging the fixed reflecting mirror in this way, it is possible to realize relative position measurement that meets the purpose with high accuracy. For example, when such an optical interferometer is applied to a semiconductor exposure apparatus, a movable reflecting mirror is provided on a moving stage of a mask or a wafer, and a fixed reflecting mirror is provided on a lens barrel of the exposing machine. The relative position between the light and the wafer can be controlled with high accuracy.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a first preferred embodiment of an optical interference measuring apparatus according to the present invention. In the optical interferometer shown in FIG. 1, a general Michelson interferometer is provided with a variable wavelength light source (hereinafter, referred to as a second light source) 80 and a light from the light source 80 moved by a movable reflecting mirror 52.
A light-receiving element (hereinafter, referred to as a second light-receiving unit) 85 for measuring an interference fringe of light between the measurement light reflected by the light source and the reference light reflected by the fixed reflecting mirror 51, and a signal from the second light-receiving unit 85. , The absolute position of the movable reflecting mirror 52 is obtained.

Hereinafter, the optical interference measuring apparatus will be described in more detail. A first optical interferometer constituting a general Michelson interferometer includes a light source 10 that emits light having a frequency ω1 having a linear polarization plane and light having a frequency ω1 ′ having a linear polarization plane orthogonal thereto. Light at frequency ω1 and frequency ω
A polarizing beam splitter 22 for splitting the 1 ′ light, and a movable reflecting mirror 5 provided on a stage 90 for measuring a moving amount.
2, the fixed reflecting mirror 51 provided in the reference unit 91 of the interferometer, and the light of the frequency ω1 ′ reflected by the fixed reflecting mirror 51 and the light of the frequency ω1 reflected by the moving reflecting mirror interfere with each other,
A first light receiving unit 60 that receives the interference light, a polarizing beam splitter 22, a quarter-wave plate 32 disposed between the polarizing beam splitter 22 and the movable reflecting mirror 52, and a fixed light source fixed to the polarizing beam splitter 22; The reflecting mirror 21 and the quarter-wave plate 31 are disposed between the reflecting mirror 51 and the reflecting mirror 51.

The polarization beam splitter 22 is set so that the polarization plane of the light of frequency ω 1 emitted from the light source 10 becomes P-polarized light with respect to the incidence plane of the polarization beam splitter 22. Therefore, the light having the frequency ω <b> 1 is transmitted through the polarization beam splitter 22, transmitted through the 波長 wavelength plate 32, and reflected by the movable reflecting mirror 52. Then, after passing through the quarter-wave plate 32 again, the light enters the polarization beam splitter 22 again. Here, the light of the frequency ω1 re-entering the polarization beam splitter 22 passes through the quarter-wave plate 32 twice, so that the polarization direction is rotated by 90 degrees. Therefore, this light is reflected by the polarization beam splitter 22 and enters the first light receiving unit 60.

The light of frequency ω 1 ′ having a polarization plane orthogonal to the light of frequency ω 1 is transmitted to the polarization beam splitter 22.
After being reflected by the fixed reflecting mirror 51, the light enters the polarization beam splitter 22 again. here,
The light of the frequency ω1 ′ re-entering the polarization beam splitter 22 also passes through the quarter-wave plate 31 twice, so that the polarization direction is rotated by 90 degrees. Therefore, the light passes through the polarization beam splitter 22 and enters the first light receiving unit 60. Then, the first light receiving section 60 outputs a beat signal obtained by photoelectrically converting the interference light to the controller 71.

Next, the second optical interferometer will be described.
The variable wavelength second light source 80 is a laser light source having a wavelength different from that of the length measuring light source 10, and can be configured using, for example, a variable wavelength semiconductor laser or solid-state laser. Also,
As a method of modulating the oscillation wavelength of the semiconductor laser, for example, current modulation or operating temperature modulation can be performed.
Examples of the method of modulating the wavelength of the solid-state laser include operating temperature modulation and resonator length modulation. In this embodiment, the fundamental wavelength is 660n.
An example in which wavelength modulation is performed by current modulation using a semiconductor laser having a linearly polarized light output of m will be described.

The optical coupling element 81 superimposes the linearly polarized laser light emitted from the light source 80 on the same optical axis as the laser light emitted from the first light source 10. At this time, the polarization direction after the superimposition is the same as the polarization plane (S-polarized light and P-polarized light) of the first light source 10.
For example, an adjustment mechanism (not shown) or the like is provided so as to form an angle of 5 degrees. The optical coupling element 81 can be configured by using, for example, a partial reflecting mirror having wavelength selectivity.

The two laser beams having different wavelengths superimposed in this way are supplied to a polarization beam splitter (optical splitter) 2.
2 is incident. As described above, since the polarization plane of the light emitted from the second light source 80 is inclined by 45 degrees with respect to the S polarization plane and the P polarization plane of the first light source 10, the polarization beam splitter 2
The light is incident with the incident angle shifted by 45 degrees with respect to the two polarization axes. For this reason, the light emitted from the second light source 80 is split by the polarization beam splitter 22 into S-polarized light and P-polarized light. The S-polarized light component is reflected by the polarization beam splitter 22 and travels to the fixed reflecting mirror 51 as reference light. The light of the P polarization component passes through the polarization beam splitter 22 and travels to the movable reflecting mirror 52 as measurement light.

Light from the second light source 80 toward the fixed reflecting mirror 51 and the moving reflecting mirror 52 is transmitted to the quarter-wave plates 31 and 3.
2, the polarization direction is rotated by 90 degrees, transmitted through or reflected by the polarization beam splitter 22, and enters the second light receiving unit 85. A light separating element 82 is provided in the superimposed optical path in order to make the former of the light emitted from the first light source 10 and the second light source 80 incident on the first light receiving part 60 and the latter on the second light receiving part 85. The light separating element 82 includes an optical coupling element 8.
A partial reflecting mirror having wavelength selectivity is used as in the case of 1. The light separating element 82 transmits the light emitted from the first light source 10 and makes the light incident on the first light receiving unit 60, and reflects the light emitted from the second light source 80 and makes the light incident on the second light receiving unit 85.

Each of the first light receiving section 60 and the second light receiving section 85 comprises a polarizer and a light receiving element. The light receiving elements of these two light receiving units 60 and 85 output measurement data of an interference image between the measurement light and the reference light observed on the polarizer to the controller 71. Controller 7
1 calculates the amount of movement of the movable reflecting mirror 52 from the signals output from the light receiving units 60 and 85, and calculates the relative position of the moving reflecting mirror 52 with respect to the fixed reflecting mirror 51.

The displacement observation by the first optical interferometer is based on the number of interference fringes passing through the light receiving element of the first light receiving section 60 during the movement of the stage 90 and the interpolated value in the interference fringes. Convert to Therefore, in the first optical interferometer having the same configuration as that of the related art, if the measurement light or the reference light is interrupted during the measurement, or if an instantaneous stop of the length measuring light source or the like occurs, the stage 90
Position becomes unknown.

In such a situation, the second optical interferometer modulates the emission wavelength of the second light source 80,
The position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 51, which is unknown from the phase change of the interference light of the light emitted from 0, is calculated.

A case will be described in which a laser whose oscillation wavelength is variable is used as the second light source. First, the controller 71 controls the second light source 80 to change its fundamental oscillation wavelength λ by δλ. Specifically, the current supplied to the second light source 80 may be modulated. When performing current modulation, it is possible to use change data of the oscillation wavelength with respect to the injection current value that is known in advance. However, in more detail, a wavelength measuring unit (for example, an optical spectrum analyzer or an etalon), not shown, is used. Preferably, λ and δλ are used to monitor.

The controller 71 calculates the relative position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 51 from the relationship with the phase change δφ of the interference light observed when the oscillation wavelength is changed. In this calculation, the fundamental wavelength of the light source 80 is λ,
When the modulation width is δλ, and the phase change measured by the optical interferometer 85 with the change in the light source wavelength is δφ,
The following relational expression derived from the light interference expression and the approximate expression is used.

[0025]

Δφ = 2πn (Lr−Lm) δλ / λ ² (1) where n: refractive index of medium Lr: optical path length of reference light Lm: optical path length of measurement light

Here, the refractive index n of the medium refers to the refractive index of the measurement environment, and is the refractive index of air in a normal measurement environment. Further, the optical path lengths Lr and Lm of the reference light and the measurement light are branched by the polarization beam splitter 22, reflected by the fixed reflecting mirror 51 or the moving reflecting mirror 52, and returned to the polarization beam splitter 2 again.
2 are the optical path lengths after being superimposed on each other and entering the polarizer of the second light receiving unit 85.

From this relational expression, by modulating the wavelength λ of the light emitted from the second light source 80 and moving the movable reflecting mirror 52 (stage 90) so that δφ becomes zero even if it is changed by δλ. , The movable reflecting mirror 52 can be positioned at the position of Lr-Lm = 0 (absolute position).

For example, when this length measuring device is used as a positioning device of an exposure apparatus, a fixed reflecting mirror 51 is disposed on a lens barrel serving as a reference of the exposure apparatus, and a moving reflecting mirror 52 is mounted on a moving stage of the wafer. By adjusting the optical path so that Lr−Lm = 0 at the stage position serving as a reference at the time of exposure, positioning can be performed efficiently.

From the above relational expression, the proportional coefficient (L
(r−Lm) increases as the difference in optical path length between the reference light and the measurement light increases, and decreases as the difference in optical path length decreases. That is, the position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 51 can be found by changing the wavelength of the second light source 80 by δλ at an arbitrary position and measuring the phase change δφ at this time. .

Therefore, in the second optical interferometer, the position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 51 can be calculated by the above method. Note that the resolution of the position of the movable reflecting mirror calculated by such a method may be smaller than the distance corresponding to one cycle of interference fringes obtained by the first optical interferometer.

Then, the measuring light or the reference light is blocked,
The position of the stage (relative position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 51) determined by the first optical interferometer is determined by the moving reflecting mirror 52 with respect to the fixed reflecting mirror 51 calculated by the second optical interferometer. Relative position data (position data)
And the phase data obtained from the first optical interferometer from which the interrupted measurement light or reference light is restored and measurement is started again.

The optical interferometer measures the data of the stage position, which is unknown because the light is blocked or the light source temporarily stops emitting light, with the second optical interferometer as described above. It is preferable to replace the stage position data determined from the obtained position data and the phase data of the first optical interferometer with the stage position data. With this configuration, the function of the stage can be returned to its original state without returning the stage to the reference point before the movement of the moving device.

Next, the optical paths of the measurement light and the reference light of the first optical interferometer and the second optical interferometer may be of a so-called double-path configuration. That is, in the conventional configuration in which the first optical interferometer employs the double-pass configuration, the optical path of the second optical interferometer is superimposed on the first optical interferometer by the optical coupling element 81, and the second optical interference The optical path of the meter may be separated from the first optical interferometer by the light separating element 82.

It is known that such a double-pass interferometer can double the measurement sensitivity. Further, in the interferometer having such a double-pass configuration, even when the movable reflecting mirror 52 or the fixed reflecting mirror 51 is slightly inclined, the light receiving elements of the first light receiving section 60 and the second light receiving section 85 have Since the inclination of the measurement light or the reference light is shifted instead of the inclination, the visibility of the interference light is not easily reduced.

Next, a second preferred embodiment of the optical interference measuring apparatus according to the present invention will be described with reference to FIG. This embodiment is an embodiment in which the present invention is applied to a length measuring device that measures an inclination angle of a movable reflecting mirror provided on a stage.

In this embodiment, two measurement optical paths are arranged in the vertical direction in the figure with respect to the movable reflecting mirror 52. Light from the length measuring light source 10 passes through the optical coupling element 81 and is split into two by the beam splitter 24. As a result, two measurement optical paths are formed.

The P-polarized light and the S-polarized laser light emitted from the first light source 10 are split by the beam splitter 24 into a first measurement optical path and a second measurement optical path. An optical splitting element (polarizing beam splitter) 22 is provided on a first measurement optical path that passes through the beam splitter 24. A quarter-wave plate 31 is provided on the reflection light path and the transmission light path of the light branching element 22.
And a quarter-wave plate 32 are arranged, and by passing twice, the polarization plane thereof is rotated by 90 degrees. As a result, S polarized light is converted to P polarized light, and P polarized light is converted to S polarized light.

The P-polarized light of the laser light incident on the light splitting element 22 is transmitted, and after passing through the quarter-wave plate 32,
The light is reflected by the movable reflecting mirror 52, passes through the 波長 wavelength plate 32 again, and returns to the optical branching element 22. Then, the light is reflected by the light branching element 22 and travels to the light receiving section 61. This light traveling to the movable reflecting mirror 52 is the measuring light.

On the other hand, the S-polarized light of the laser light incident on the light splitting element 22 is reflected and passes through the quarter-wave plate 31, then reflected by the fixed reflecting mirror 53, and again reflected by the quarter-wave plate 31.
And returns to the optical branching element 22. Then, the light is transmitted to the light branching element 22 and superimposed on the measurement light reflected by the movable reflecting mirror 52, and travels toward the light receiving unit 61. This light traveling toward the fixed reflecting mirror 53 is reference light.

A partial reflecting mirror 86 having wavelength selectivity is provided in front of the light receiving section 61. The partial reflecting mirror 86 transmits light having the wavelength of the first light source 10 and reflects light having the wavelength of the second light source 80. The light receiving unit 61 includes a polarizer and a light receiving element, and the light receiving element outputs measurement data of an interference image between the measurement light generated on the polarizer and the reference light to the controller 72. The controller 72 converts the input measurement data into a moving distance (amount of displacement) of the movable reflecting mirror 52.

The laser light emitted from the first light source 10 and reflected by the beam splitter 24 passes through a wavelength plate 35 and enters a light splitting element 25 constituted by a polarizing beam splitter. The wavelength plate 35 is for adjusting the polarization plane so as to be oriented optimally with respect to the reflection plane of the light branching element 25.

Of the laser light reflected by the beam splitter 24, S-polarized light is reflected by the light splitting element 25, passes through the 波長 wavelength plate 33, is reflected by the movable reflecting mirror 52, and is 再 び again.
After passing through the wave plate 33, the light returns to the light branching element 25. The S-polarized light that has passed through the quarter-wave plate 33 twice has its polarization plane rotated by 90 degrees, passes through the light branching element 25, and travels toward the light receiving unit 62. This light traveling to the movable reflecting mirror 52 is the measuring light.

The P-polarized light of the laser light reflected by the beam splitter 24 passes through the light splitting element 25 and
After passing through the wave plate 34, it is reflected by the fixed reflecting mirror 54,
The light returns to the light splitting element 25 after passing through the four-wavelength plate 34. This light going to the fixed mirror is the reference light. 1/4 wavelength plate 34
The P-polarized light that has passed through twice is rotated by 90 degrees in the plane of polarization.
The light is reflected by the light splitting element 25, is superimposed on the P-polarized measurement light that is reflected by the movable reflecting mirror 52, and passes through the light splitting element 25, and travels toward the light receiving section 62.

In front of the light receiving section 62, a partial reflecting mirror 87 having wavelength selectivity is provided. The partial reflecting mirror 87 transmits light having the wavelength of the first light source 10 and reflects light having the wavelength of the second light source 80, similarly to the partial reflecting mirror 86. Therefore, as for the light from the first light source 10, the measurement light reflected by the movable reflecting mirror 52 and the light reflected by the fixed reflecting mirror 54 pass through the partial reflecting mirror 86 and enter the light receiving section 62.

The light receiving section 62 includes a polarizer and a light receiving element. The light receiving element outputs measurement data of an interference image between the measurement light generated on the polarizer and the reference light to the controller 72. Then, the controller 72 converts the input measurement data into a moving distance (amount of displacement). In this way, the light of the first light source 10 is split into two by the beam splitter 24, and then becomes light for two interferometers for measuring different positions of the movable reflecting mirror 52.

The light from the second light source 80 superimposed on the light from the first light source 10 by the optical coupling element 81 is split into two by the beam splitter 24. The light transmitted through the beam splitter 24 is incident on the light splitting element 22. Since this incident light is P-polarized light, the light splitting element 22 and the 波長 wavelength plate 32
And travels toward the movable reflecting mirror 52 as measurement light.

The P-polarized light reflected by the movable reflecting mirror 52 passes through the quarter-wave plate 32 again to become S-polarized light, is reflected by the light branching element 22, and enters the partial reflecting mirror 86. The S-polarized light that has entered the partial reflecting mirror 86 is reflected by the partial reflecting mirror 86 and enters the optical coupling element 88. The optical coupling element 88 is a polarization beam splitter that reflects S-polarized light and transmits P-polarized light. Therefore, S reflected by the partial reflecting mirror 86
The polarized light is reflected by the optical coupling element 88, and the third light receiving portion 8
5 is incident.

On the other hand, a beam splitter (light splitting element) 2
The reflected light of the P-polarized light from the second light source 80 split into two at 4 passes through the wave plate 35 and the light splitting element 25.
Incident on. Then, the light splitting element 25 and the partial reflecting mirror 87
And is incident on the optical coupling element 88. Optical coupling element 88
Is a polarizing beam splitter that transmits a P-polarized component. Accordingly, the P-polarized light reflected by the fixed reflecting mirror 54 is superimposed on the S-polarized light reflected by the moving reflecting mirror 52 and enters the third light receiving unit 85. The third light receiving unit 85 outputs the phase data of the measured interference light to the controller 72.

In the present embodiment configured as described above, the direction of the measurement optical path of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 53 is first determined with respect to the first measuring optical path based on the phase information of the interference fringes obtained from the light receiving unit 61. Is measured, and the relative position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 53 is calculated from the sum of the moving amounts.

Further, regarding the second measurement optical path, the light receiving section 62
Fixed mirror 54 based on the interference fringe phase information obtained from
Is measured in the measurement axis direction with respect to, and the relative position of the movable reflecting mirror 52 with respect to the fixed reflecting mirror 54 is calculated from the sum of the moving amounts. The inclination of the reflecting mirror can be calculated from the relative positions of the moving reflecting mirror at the two locations calculated as described above.

However, when the measuring light is blocked, the inclination angle becomes unknown. Therefore, when the first measurement optical path is interrupted, the controller 72 sets the oscillation wavelength of the second light source 80 to δλ in the measurement system using the second light source 80, as already described in the first embodiment. And the phase change δφ of the light observed by the third light receiving unit 85 at this time is measured, whereby the relative position (region position) of the movable reflecting mirror 52 to the fixed reflecting mirror 53 in the first measurement optical path is measured. Can be calculated.

Since the calculated position data has a position accuracy capable of specifying the position of the light receiving portion 61 in the field of view, the measurement light on the first measurement light path returns and interference fringes are observed again. When the operation is started, the controller 7
Reference numeral 2 can determine the stage position from the area position data calculated by the wavelength variable optical interferometer and the detailed phase data observed by the optical interferometer on the returned first measurement optical path. .

When the position is determined in this way, the position data of the first measurement optical path that has become unknown is replaced with the determined position data, so that the optical interferometer for measuring the inclination angle is obtained. The device can self-reset.

In the embodiment shown in FIG. 2,
It is also possible to provide a half-wave plate as the wave plate 35. This half-wave plate has a function of rotating the polarization plane by 90 degrees by passing once. Therefore, the light from the first light source 10 has its S-polarized light turned into P-polarized light and its P-polarized light turned into S-polarized light.
Although the light is converted into polarized light, the light path after this conversion enters the light receiving unit 62 through the same path as described above.

On the other hand, the light from the second light source 80 is
Since the P-polarized light is converted to S-polarized light by the half-wave plate 35, the P-polarized light is reflected by the polarization beam splitter 25, passes through the quarter-wave plate 33, passes through the first measurement optical path, and moves.
And again passes through the quarter-wave plate 33 to become P-polarized light. This time, the light passes through the polarizing beam splitter 25, is reflected by the partial reflecting mirror 87, and is first reflected by the polarizing beam splitter (optical coupling element) 88. The light is superimposed on the S-polarized light that has passed through the measurement optical path, enters the third light receiving unit 85, and interferes on the polarizer in the optical interferometer.

In other words, with such a configuration, the optical interferometer using this variable wavelength light source can move the movable reflecting mirror 52.
By measuring the change in the optical path length between the first measurement optical path and the second measurement optical path, the inclination of the movable reflecting mirror 52 can be measured. And in such a system, the first light source 1
0, the optical path of either the first measurement optical path or the second measurement optical path is blocked, and even when the relative position on the measurement optical path and the tilt of the movable reflecting mirror become unknown, the first execution According to the method shown in the embodiment, the optical path length difference between the first measurement optical path and the second measurement optical path of this movable reflecting mirror is calculated, and it becomes unknown from the calculated data and the detailed phase data of the restored interferometer. Position data can be determined.

Further, in this embodiment, the polarization direction of the incident light of the second light source 80 is set to 45 degrees as in the first embodiment, and the light is moved and reflected for each of the first measurement optical path and the second measurement optical path. By providing a light receiving unit that receives the interference light between the reflected light of the mirror 52 and the reflected light of the fixed reflecting mirror 54, and a light receiving unit that receives the reflected light of the moving reflecting mirror 52 and the reflected light of the fixed reflecting mirror 53, Even if the first and second optical paths of the movable reflecting mirror 52 are interrupted (even if they are interrupted at the same time), the optical interferometer can be made self-recoverable.

Next, a third preferred embodiment of the optical interference device according to the present invention shown in FIG. 3 is, for example, an optical interference measurement device having the configuration of any of the first and second embodiments described above. In the apparatus, a plurality of stages 90 each having a movable reflecting mirror 52 are prepared, and these are sequentially loaded into an optical interferometer and unloaded after a series of measurement or processing is completed. . Here, an example to which the above-described first embodiment is applied will be described with reference to FIGS.

First, in FIG. 3, a stage 90A as a first stage has a movable reflecting mirror 52A, and an optical interferometer has, for example, first and second optical interferometers shown in FIG. ing. When the measurement or processing of the stage 90A is completed, the stage 90A is unloaded in the moving device 100, and the stage 90B, which is the second stage, is loaded instead.

At this time, since the reflected light of the measuring light disappears in the optical interferometer, a state occurs in which the length cannot be measured thereafter. Meanwhile, the newly loaded stage 90B
Is provided with a movable reflecting mirror 52B, and when set in a length measuring device, the measuring light of the first optical interferometer using the first light source 10 and the second optical interference using the second light source 80. The measurement light of the meter is detected.

Here, the controller 71 modulates the wavelength of the light source 80 of the second optical interferometer by δλ and measures the phase change δφ observed at this time. Then, even if the light source wavelength λ is modulated and changed by δλ, δφ does not change (or so as to have a predetermined proportional coefficient).
By moving the stage 2B (stage), the relative position of the movable reflecting mirror 52B with respect to the fixed reflecting mirror 51 is changed to the stage 9
The position can be adjusted to the same position where the movable reflecting mirror 52A disposed at 0A was located.

The controller 71 outputs the position data of the stage 90B output from the second optical interferometer and calculated as described above, and the detailed phase data output from the first optical interferometer. , The position of the stage 90B is determined.

When the position of the stage 90B is determined in this way, the controller 71 is set so as to replace the second stage position data whose position is unknown, with the stage position data thus determined. ing. Therefore, the optical interferometer according to the present invention is capable of newly setting the origin even when the measurement of the optical interferometer or the reference light is interrupted in the process of exchanging a plurality of stages, so that the measurement of the optical interferometer becomes impossible. The stage can be positioned at the same position without performing return or the like, and the stage position can be determined so that length measurement or processing can be performed continuously.

For example, in a conventional semiconductor exposure apparatus or the like, after a wafer on a stage is positioned and exposed, the exposed wafer is taken out, and the exposure apparatus performs exposure while the next wafer is positioned on the stage. Could not do. Further, after positioning on the stage, the stage is again moved to the reference position of the optical interferometer, and the exposure cannot be positioned unless the reference position data of the optical interferometer is input.

However, according to such an embodiment, the exposure apparatus positions the wafer with respect to the first stage, and during the exposure, the wafer can be positioned on the second stage. And the second stage is loaded, and at the same time, the exposure positioning operation of the second stage can be performed.

[0066]

As described above, in the optical interferometer according to the present invention, in addition to the first optical interferometer for detecting the relative displacement between the fixed reflecting mirror and the moving reflecting mirror, the light from the length measuring light source is measured. And a second optical interferometer for detecting the position of the movable reflecting mirror with respect to the fixed reflecting mirror by modulating the wavelength. For this reason, even if the observation light of the first optical interferometer is blocked and the stage position (relative position) becomes unknown in the optical interferometer, the area position of the stage is measured by the second optical interferometer. Therefore, the stage position can be determined from the area position data and the phase data in the field of view of the first optical interferometer.

This second optical interferometer is constructed on the same optical path as the conventional first optical interferometer using a variable wavelength light source, and is observed when the light source wavelength λ is changed by δλ. By measuring the change .delta..phi. Of the phase .phi. (By calculating this proportionality factor), the relative position of the moving mirror with respect to the fixed mirror is calculated. Therefore, the optical interference measuring device can be easily configured without complicating the device.

Then, the optical interferometer as described above is
It is preferably used as a length measuring device or a positioning device for an exposure device. A highly productive exposure apparatus that satisfies the positional accuracy required by the exposure apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an optical interferometer according to the present invention.

FIG. 2 is a configuration diagram illustrating a second embodiment of the optical interference measuring apparatus according to the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the optical interference measuring device according to the present invention.

[Explanation of symbols]

Reference Signs List 10 Measurement light source 22 Light splitting element (polarizing beam splitter) 24 Light splitting element (beam splitter) 51 Fixed reflecting mirror 52 (52A, 52B) Moving reflecting mirror 60 First light receiving unit 61, 62 First light receiving unit ( 71, 72 Processing device (controller) 80 Variable wavelength light source 81 Optical coupling element (partially reflecting mirror with wavelength selectivity) 82 Light separating element (wavelength selectivity) 85) Second light receiving unit (third light receiving unit) 90 (90A, 90B) DUT (stage)

Continuation of the front page F term (reference) 2F064 AA01 EE01 FF01 FF05 FF08 GG12 GG20 GG22 GG23 GG38 GG39 HH01 HH06 JJ05 2F065 AA02 CC17 FF51 GG04 GG06 GG22 GG25 JJ05 JJ15 LL12 LL12 LL10 LL46

Claims (2)

[Claims] 1. A first optical interferometer for measuring a moving amount of a movable reflecting mirror from interference light between a first measuring light reflected by a moving reflecting mirror and a first reference light reflected by a fixed reflecting mirror. In the optical interferometer having, the light from the variable wavelength light source is projected on the movable reflecting mirror as the second measurement light, and the light from the variable wavelength light source is reflected on the fixed reflecting mirror as a second reference light. A second optical interferometer is provided for projecting and causing interference while changing the wavelength of the second measurement light and the second reference light, and measuring the absolute position of the movable reflecting mirror based on the interference light. An optical interferometer that is characterized in that: 2. An exposure apparatus, wherein the optical interference length measurement apparatus according to claim 1 is used as a wafer or mask movement length measurement apparatus or a positioning apparatus.