JPH09166415A - Exposure equipment - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To reduce fluctuation of measurement values of an interferometer due to fluctuation of refractive index of air. A beam from a laser light source is divided into a measurement beam and a reference beam, the measurement beam is irradiated toward an object to be measured that is movable in a two-dimensional plane, and the beam from the object to be measured is irradiated. In a device for measuring the position and distance of the object to be measured by photoelectrically detecting the interference beam by superimposing a reflected beam and the reference beam, a temperature-stabilized gas having a predetermined velocity is used. A gas source for generating a flow, and a gas flow from the gas source for guiding the gas flow across the beam into a space through which the measurement beam and the reflected beam pass, in a two-dimensional plane of the object to be measured. An air guide means having a blower port fixedly arranged in a space above the optical path of the beam is provided so as not to spatially interfere with the movement trajectory of the beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring device using a laser interferometer.

[0002]

2. Description of the Related Art A laser interferometer using a frequency-stabilized helium-neon (He-Ne) laser as a light source is used for precise length measurement and coordinate measurement. A typical example is the system sold by Hewlett-Packard Company. When this type of conventional device is used for highly accurate measurement, the temperature is stabilized by a special air conditioner of ± 0.1 ° C to prevent fluctuations in the refractive index of air.
The air temperature is stabilized within the range, and the atmospheric pressure is monitored and the wavelength is corrected to respond to changes in atmospheric pressure due to changes in the weather. As another example of a completely different method of correcting the refractive index of air, it may be considered to use a two-wavelength interferometer as disclosed in JP-A-58-87447 or JP-A-58-169004. However, it has not been commercialized because the device is complicated and the cost is high.

[0003]

Even in the conventional apparatus for stabilizing the temperature of air, the dispersion of the measured values due to the fluctuation of the refractive index of air cannot be ignored. For example, in the positioning of a stage of a stopper (projection exposure apparatus) in recent LSI manufacturing, the positioning reproducibility is 3σ =
The thickness is 0.08 to 0.15 μm, and it is considered that a considerable portion of this is due to fluctuations in the output of the laser interferometer having a frequency component of 1 Hz to 100 Hz. If the measurement time is set sufficiently long and the measured values are averaged, the influence of fluctuations of the interferometer will be reduced, but problems such as high speed stage positioning and measurement during high speed stage scanning cannot be achieved.

The present invention solves such conventional problems,
The objective is to reduce fluctuations in interferometer measurement values due to fluctuations in the refractive index of air by a simple method.

[0005]

In order to solve the above problems, according to the present invention, a wind is directed in a fixed direction at a portion where a laser beam (measuring beam and reflected beam) reciprocating to and from a moving mirror of a laser interferometer passes. Decided to run. Furthermore, it was decided to correct the variation in the measured values due to fluctuations by processing the value of the difference in the measured values of the laser beam on the leeward side and the leeward side.

[0006]

According to the present invention, since the temperature-controlled wind is individually supplied to the laser beam that reciprocates with respect to the moving mirror, fluctuations in measurement of the interferometer can be reduced. Further, in the present invention, the part on the lee side and the part on the lee side of the laser beam are
Since the relationship between the optical system and the wind direction is always the same, the time fluctuation of the output fluctuation of the interferometer always occurs in the order from the windward side to the leeward side, so the time change rate of the measured value can be immediately known. As long as the wind speed is almost constant, only the fluctuation component of the measurement value of the interferometer can be measured without causing a time delay. A change in fluctuation can be compensated by correcting the measured value obtained by the conventional measuring method by the magnitude of the fluctuation component of the measured value.

[0007]

FIG. 1 is a perspective view of a structure when a position detecting apparatus according to an embodiment of the present invention is applied to coordinate measurement of a precision moving stage. Reference numeral 1 denotes a frequency-stabilized laser light source, Zeeman effect. Is used to output a light beam 2 containing two components whose polarization characteristics are different from each other and whose frequencies are different from each other by about 2 MHz. Reference numeral 3 denotes a mirror, and the light beam 2 is divided into an X beam 4X for measuring the x direction of the stage and a Y beam 4Y for measuring the y direction of the stage by a beam splitter which is not visible in the figure, and is divided into an X interferometer unit 5X and a Y interferometer unit 5Y. Be guided. X
The interferometer unit 5X measures the amount of movement of the X mirror MX in the x direction, and 5Y measures the amount of movement of the Y mirror MY in the y direction. ST is an X mirror MX and a Y mirror MY which are orthogonal to each other.
Is a stage which is mounted and moves, and two-dimensionally moves in parallel to the X and Y directions. On the stage ST is an older WH on which a positioning object such as a wafer is installed.

FN is a fan, and winds the X duct DCX
And the Y duct DCY through the dust removal filter FL. The air outlets of the X duct DCX and the Y duct DCY are arranged so as not to spatially interfere with the movement loci of the X mirror MX and the Y mirror MY, and are located in the laser beam portion directed to the X mirror MX and the Y mirror MY for measurement. The temperature-stabilized wind blows from above at a constant speed. The air temperature of the wind should match the temperature of the air conditioner in the environment surrounding the device.

FIG. 2 is a structural view of the laser interferometer on the X-axis, and a front view of the interferometer portion is shown. A top view of the interferometer is shown in FIG. The optical path of the laser interferometer is shown in FIG. The laser beam B1 emitted from the laser light source 1 is divided into two by the polarization beam splitter 10, and one polarization beam passing through the polarization beam splitter 10 passes through the λ / 4 plate 13 and becomes a beam B2 for length measurement. It is reflected by the mirror MX and returns. The beam passing through the λ / 4 plate in the opposite direction has its polarization state inverted, reflected by the polarization beam splitter 10, reflected by the prism 11, and then reflected by the polarization beam splitter 10, becoming a beam B3 again by the X mirror MX. Is reflected. The returned beam passes through the polarization beam splitter 10 toward the beam splitter 14. The beam splitter 14 has a prism-shaped reflecting surface for splitting the incident beam into two at the center of the beam diameter, and each of the split beams is a photoelectric detector DX.
1 and DX2 separately receive the light.

On the other hand, the other polarization component of the laser beam B1 is reflected by the polarization beam splitter 10 as the reference light and is reflected by the prism 12, and thereafter, in the polarization beam splitter 10, the return optical path of the measuring beam is obtained. The combined beam is incident on the beam splitter 14. In FIG. 2, the temperature-stabilized wind is sent from the X duct DCX to the path of the measuring beam at a substantially uniform velocity as indicated by an arrow 18. The returning laser beam is divided into two by the beam splitter 14 into the upper side and the lower side in the cross section, which are reflected by the photoelectric detector DX.
1, incident on DX2. The detectors DX1 and DX2 output a beat signal because there is a frequency difference between the reference light and the length measurement light,
This beat signal output is supplied with the reference difference frequency signal (about 2 MHz) from the laser light source 1 together with the signal processing systems CX1 and CX.
2 is input, and heterodyne detection is performed. Signal processing system C
A coordinate count output (for example, a resolution of 0.01 μm) is obtained from each of X1 and CX2.
5 is input to obtain a corrected interferometer output (measurement value) 16.

The beams B2 and B3 respond to the flow of the wind 18 by
The optical system is constructed so that the direction of the cross section does not reverse. Even if the temperature of the air to be blown is stabilized, there is some temperature unevenness, and air lumps whose temperature is slightly different from the surroundings are moving along with the wind. Therefore, when the upper part and the lower part of the beams B2 and B3 are independently measured with the X mirror MX stationary, the measured value of the lower part appears with a time delay with respect to the measured value of the upper part. If the X mirror MX is moving, the difference between the upper and lower measurement values, that is, the detectors DX1, DX
The difference between the measured values according to 2 indicates a time change value due to air fluctuation.

The measurement output from the signal processing system CX1 is x1.
(T), the measurement output from the signal processing system CX2 is x2 (t)
And It is assumed that these outputs x1 (t) and x2 (t) are simultaneously reset to zero at a determined position (for example, the origin of the stage ST). Output x1 here
The difference Δx (t) between (t) and x2 (t) is expressed by the equation (A).

[0013]

[Equation 1]

If the wind speed is constant,

[0015]

(Equation 2)

Since there is a relation of x1 (t), x2
The variation xa (t) of (t) due to the fluctuation of the refractive index of air is k, where k is a proportional constant.

[0017]

(Equation 3)

Is represented as k1 is xa (t) when there are no fluctuation factors other than fluctuations due to fluctuations in the refractive index of air.
Is determined to be zero. Equation (C) uses an appropriate time interval T

[0019]

(Equation 4)

It can also be expressed as The value of T may be at least the time when the wind crosses the laser beam. Further, the constant k2 is determined in the same manner as k1 in the equation (C). This formula (D) is generated in x1 (t) and x2 (t) generated within a fixed time T.
It is calculated by accumulating the difference and multiplying by a constant k2. Finally, the fluctuation-corrected output x0 (t) is

[0021]

(Equation 5)

Or

[0023]

(Equation 6)

Or

[0025]

(Equation 7)

It is calculated by one of the equations Therefore, the correction circuit 15 determines the interferometer output 16, that is, the output x0 (t) at each time interval T based on any one of the equations (D) and (E), (F), and (G). When there is a temperature fluctuation or a pressure fluctuation of the air, the temperature sensor or the pressure sensor output may be input to the correction circuit 15 to correct the wavelength of the laser light. This is possible by the conventionally known wavelength correction.

When the output of the laser interferometer fluctuates due to the pressure wave of the sound wave, wavelength correction by the sound wave may be performed by using a high-speed response pressure sensor or an acoustic transducer 17 such as a microphone. In the above embodiments, the example of the two-dimensional coordinate measurement is given, but the same measurement can be performed in the one-dimensional or the three-dimensional. Further, the laser light source 1 is not limited to the Zeeman-stabilized laser, and may be a laser light source of another system such as a Lamb dip stable type frequency stabilized laser. In that case, although the signal processing of the laser interferometer is different, the present invention is basically applicable.

Further, in the above description of the embodiment, an example is shown in which, when air is blown across one laser beam, interference is detected separately on the leeward side and the leeward side of the beam. Two separate laser beams may be provided on the leeward side. That is, independent laser interferometers may be provided at predetermined intervals in the direction of wind flow to detect x1 (t) and x2 (t). In this case, the original laser light sources may be separate. Specifically, as shown in FIG. 4, two measurement beams (reflected beams) B2u, B parallel to the upper and lower sides of the reflection plane (parallel to the yz plane) MXr of the moving mirror MX.
Two independent laser interferometers 1 so that 2d is illuminated
FMu and 1FMd are provided. This interferometer 1FMu, 1F
Md independently measures the position and distance of the moving mirror MX in the x direction and outputs measured values CPu and CPd. The measured values CPu and CPd are the moving mirror MX (stage ST).
Are set in advance so that they have the same value when they are set to the reference position. Then, the correction circuit 15 outputs the interferometer measurement value 16 in which the variation amount due to the fluctuation of the refractive index of the air is corrected (or reduced) based on the input of the measurement values CPu and CPd as in the previous embodiment.

Also in such a structure, the temperature-stabilized wind 18 having a substantially constant velocity is made to flow from the top to the bottom, that is, from the measurement beams B2u to B2d, as in the previous embodiment. The measuring beams B2u, B2d
4 has been described as a so-called single-beam type interferometer having only one each, but as shown in FIG. 3 of the previous embodiment, one interferometer has two (or more) interferometers. A double beam type having a measuring beam (reflected beam) can be used as well.

By the way, the calculation of the correction circuit 15 is performed every fixed time interval T, but it may be performed every time the stage ST moves by a fixed distance. Further, the correction calculation may be performed at regular intervals while the stage ST is moving, and the correction calculation may be performed at regular intervals while the stage ST is stopped. Further, in the calculation formula (D) of the correction circuit 15, the value of the constant k2 may be sequentially changed according to the position (or moving speed) of the stage ST. This is to cope with the fact that the wind speed from the duct changes according to the stage position (speed) and the like.

Further, although the correction circuit 15 is always constituted so as to correct the fluctuation of the measured value due to the fluctuation of the refractive index of air, depending on the way of moving the stage ST (step and repeat system in case of stepper). It is not always necessary to correct. For example, in the step-and-repeat type exposure apparatus, fluctuations in the interferometer output value due to fluctuations occur during the exposure of one shot area on the wafer (0.2 to 0.5 seconds). Since the servo system responds, the stage ST may move slightly.
This causes blurring of the exposed pattern and poor resolution. When the exposure is performed by the step-and-repeat method only for the purpose of preventing the resolution defect, during the stepping movement to the next shot area of the stage ST, the above equation (E),
No correction is made by (F), (G), etc., and the time interval T is set between the time when the stepping is completed and the time when the exposure is completed.
It is better to perform correction by. Also, when photoelectrically detecting the alignment mark on the wafer with reference to the measurement value of the laser interferometer (or time-series count pulse), fluctuations in the signal waveform and position of the detected mark cause the alignment mark's effect. It is preferable that the correction circuit 15 also performs the correction operation at the time of detection.

In each of the embodiments of the present invention, only the temperature-stabilized air is sent from one direction, but the arrow 1 in FIG.
As shown in FIG. 9, wind may flow without stagnation by combining with an exhaust system (exhaust duct) not shown.

[0033]

As described above, according to the present invention, it is possible to obtain the effect that the fluctuation of the refractive index of air can be reduced, and
Since only the fluctuation component of the laser interferometer can be monitored,
It is effective because the measured value is corrected using this monitor amount, and a more accurate measured value that is not affected by the fluctuation of the refractive index can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the configuration of a measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an X interferometer of the present embodiment.

FIG. 3 is a plan view showing the configuration of an X interferometer of this embodiment.

FIG. 4 is a perspective view showing the configuration of a measuring apparatus according to another embodiment of the present invention.

[Description of Signs of Main Parts]

1 ... Laser light source, 15 ... Correction circuit, 18 ...
Wind, DX1, DX2 ... Detector, FN ... Fan,
FL ... filter, ST ... stage, DCX,
DCY ... duct, MX, MY ... moving mirror

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 13, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Title of exposure apparatus

[Claims]

[Question 5] The measuring means includes two signal processing circuits that individually detect the position and distance of the stage based on the output signals of the two photoelectric detectors, and the two signal processing circuits detect the two. 5. The exposure apparatus according to claim 4, further comprising a correction circuit that corrects an error amount due to fluctuation of a refractive index of the beam passing space based on the obtained information.

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly, to measurement of a stage position that can be precisely moved by using a laser interferometer.

[0002]

2. Description of the Related Art A laser interferometer using a frequency-stabilized helium-neon (He-Ne) laser as a light source is used for precise length measurement and coordinate measurement. A typical example is the system sold by Hewlett-Packard Company. When this type of conventional device is used for highly accurate measurement, the temperature is stabilized by a special air conditioner of ± 0.1 ° C to prevent fluctuations in the refractive index of air.
The air temperature is stabilized within the range, and the atmospheric pressure is monitored and the wavelength is corrected to respond to changes in atmospheric pressure due to changes in the weather. As another example of a completely different method of correcting the refractive index of air, it may be considered to use a two-wavelength interferometer as disclosed in JP-A-58-87447 or JP-A-58-169004. However, it has not been commercialized because the device is complicated and the cost is high.

[0003]

Even in the conventional apparatus for stabilizing the temperature of air, the dispersion of the measured values due to the fluctuation of the refractive index of air cannot be ignored. For example, in the positioning of a stage of a stopper (projection exposure apparatus) in recent LSI manufacturing, the positioning reproducibility is 3σ =
The thickness is 0.08 to 0.15 μm, and it is considered that a considerable portion of this is due to fluctuations in the output of the laser interferometer having a frequency component of 1 Hz to 100 Hz. If the measurement time is set sufficiently long and the measured values are averaged, the influence of fluctuations of the interferometer will be reduced, but problems such as high speed stage positioning and measurement during high speed stage scanning cannot be achieved.

The present invention solves such conventional problems,
An object of the present invention is to reduce fluctuations in interferometer measurement values due to fluctuations in the refractive index of air by a simple method and improve the accuracy of stage position measurement.

[0005]

In order to solve the above problems, according to the present invention, a wind is directed in a fixed direction at a portion where a laser beam (measuring beam and reflected beam) reciprocating to and from a moving mirror of a laser interferometer passes. Decided to run. Furthermore, it was decided to correct the variation in the measured values due to fluctuations by processing the value of the difference in the measured values of the laser beam on the leeward side and the leeward side.

[0006]

In the exposure apparatus of the present invention, the temperature-adjusted air is supplied to the laser beam that reciprocates with respect to the reflecting mirror, so that the measurement fluctuation of the interferometer can be reduced. Further, in the exposure apparatus of the present invention, the relationship between the optical system and the wind direction is such that the windward and leeward portions of the laser beam are always in the same direction with respect to the wind direction. Since the change always occurs from the windward side to the leeward side, the time change rate of the measured value can be immediately known, and if the wind speed is almost constant, only the fluctuation component of the measured value of the interferometer will not be delayed. Can be measured. By correcting the measured value obtained by the conventional measuring method by the magnitude of the fluctuation component of the measured value, the fluctuation of the fluctuation can be compensated and the predetermined pattern can be accurately exposed on the wafer or the like.

[0007]

FIG. 1 is a perspective view of a structure when a position detecting apparatus suitable for an exposure apparatus according to an embodiment of the present invention is applied to coordinate measurement of a precision moving stage, and 1 is a laser light source whose frequency is stabilized. Yes, about 2MHz using Zeeman effect
A light beam 2 including two components having different polarization characteristics but different frequencies is output. Reference numeral 3 denotes a mirror, and the light beam 2 is divided into an X beam 4X for measuring the x direction of the stage and a Y beam 4Y for measuring the y direction of the stage by a beam splitter (not shown), and an X interferometer unit 5X and a Y interferometer unit 5 are provided.
Guided by Y. The X interferometer unit 5X measures the amount of movement of the X mirror MX in the x direction, and 5Y measures the amount of movement of the Y mirror MY in the y direction. ST is an X mirror M orthogonal to each other
It is a stage that mounts and moves the X and Y mirrors MY,
It moves two-dimensionally parallel to the X and Y directions. A holder WH on which a positioning object such as a wafer is installed on the stage ST
There is.

FN is a fan, and winds the X duct DCX
And the Y duct DCY through the dust removal filter FL. The air outlets of the X duct DCX and the Y duct DCY are arranged so as not to spatially interfere with the movement loci of the X mirror MX and the Y mirror MY, and are located in the laser beam portion directed to the X mirror MX and the Y mirror MY for measurement. The temperature-stabilized wind blows from above at a constant speed. The air temperature of the wind should match the temperature of the air conditioner in the environment surrounding the device.

FIG. 2 is a structural view of the laser interferometer on the X-axis, and a front view of the interferometer portion is shown. A top view of the interferometer is shown in FIG. The optical path of the laser interferometer is shown in FIG. The laser beam B1 emitted from the laser light source 1 is divided into two by the polarization beam splitter 10, and one polarization beam passing through the polarization beam splitter 10 passes through the λ / 4 plate 13 and becomes a beam B2 for length measurement. It is reflected by the mirror MX and returns. The beam passing through the λ / 4 plate in the opposite direction has its polarization state inverted, reflected by the polarization beam splitter 10, reflected by the prism 11, and then reflected by the polarization beam splitter 10, becoming a beam B3 again by the X mirror MX. Is reflected. The returned beam passes through the polarization beam splitter 10 toward the beam splitter 14. The beam splitter 14 has a prism-shaped reflecting surface for splitting the incident beam into two at the center of the beam diameter, and each of the split beams is a photoelectric detector DX.
1 and DX2 separately receive the light.

On the other hand, the other polarization component of the laser beam B1 is reflected by the polarization beam splitter 10 as the reference light and is reflected by the prism 12, and thereafter, in the polarization beam splitter 10, the return optical path of the measuring beam is obtained. The combined beam is incident on the beam splitter 14. In FIG. 2, the temperature-stabilized wind is sent from the X duct DCX to the path of the measuring beam at a substantially uniform velocity as indicated by an arrow 18. The returning laser beam is divided into two by the beam splitter 14 into the upper side and the lower side in the cross section, which are reflected by the photoelectric detector DX.
1, incident on DX2. The detectors DX1 and DX2 output a beat signal because there is a frequency difference between the reference light and the length measurement light,
This beat signal output is supplied with the reference difference frequency signal (about 2 MHz) from the laser light source 1 together with the signal processing systems CX1 and CX.
2 is input, and heterodyne detection is performed. Signal processing system C
A coordinate count output (for example, a resolution of 0.01 μm) is obtained from each of X1 and CX2.
5 is input to obtain a corrected interferometer output (measurement value) 16.

The beams B2 and B3 respond to the flow of the wind 18 by
The optical system is constructed so that the direction of the cross section does not reverse. Even if the temperature of the air to be blown is stabilized, there is some temperature unevenness, and air lumps whose temperature is slightly different from the surroundings are moving along with the wind. Therefore, when the upper part and the lower part of the beams B2 and B3 are independently measured with the X mirror MX stationary, the measured value of the lower part appears with a time delay with respect to the measured value of the upper part. If the X mirror MX is moving, the difference between the upper and lower measurement values, that is, the detectors DX1, DX
The difference between the measured values according to 2 indicates a time change value due to air fluctuation.

The measurement output from the signal processing system CX1 is x1.
(T), the measurement output from the signal processing system CX2 is x2 (t)
And It is assumed that these outputs x1 (t) and x2 (t) are simultaneously reset to zero at a determined position (for example, the origin of the stage ST). Output x1 here
The difference Δx (t) between (t) and x2 (t) is expressed by the equation (A).

[0013]

[Equation 1]

If the wind speed is constant,

[0015]

(Equation 2)

Since there is a relation of x1 (t), x2
The variation xa (t) of (t) due to the fluctuation of the refractive index of air is k, where k is a proportional constant.

[0017]

(Equation 3)

Is represented as k1 is xa (t) when there are no fluctuation factors other than fluctuations due to fluctuations in the refractive index of air.
Is determined to be zero. Equation (C) uses an appropriate time interval T

[0019]

(Equation 4)

It can also be expressed as The value of T may be at least the time when the wind crosses the laser beam. Further, the constant k2 is determined in the same manner as k1 in the equation (C). This equation (D) is obtained by x1 (t) and x2 occurring within the fixed time T.
It is calculated by integrating the difference of (t) and multiplying it by a constant k2. The final fluctuation-corrected output x0 (t)
Is

[0021]

(Equation 5)

Or

[0023]

(Equation 6)

Or

[0025]

(Equation 7)

It is calculated by one of the equations Therefore, the correction circuit 15 determines the interferometer output 16, that is, the output x0 (t) at each time interval T based on any one of the equations (D) and (E), (F), and (G). When there is a temperature fluctuation or a pressure fluctuation of the air, the temperature sensor or the pressure sensor output may be input to the correction circuit 15 to correct the wavelength of the laser light. This is possible by the conventionally known wavelength correction.

When the output of the laser interferometer fluctuates due to the pressure wave of the sound wave, wavelength correction by the sound wave may be performed by using a high-speed response pressure sensor or an acoustic transducer 17 such as a microphone. In the above embodiments, the example of the two-dimensional coordinate measurement is given, but the same measurement can be performed in the one-dimensional or the three-dimensional. Further, the laser light source 1 is not limited to the Zeeman-stabilized laser, and may be a laser light source of another system such as a Lamb dip stable type frequency stabilized laser. In that case, although the signal processing of the laser interferometer is different, the present invention is basically applicable.

Further, in the above description of the embodiment, an example is shown in which, when air is blown across one laser beam, interference is detected separately on the leeward side and the leeward side of the beam. Two separate laser beams may be provided on the leeward side. That is, independent laser interferometers may be provided at predetermined intervals in the direction of wind flow to detect x1 (t) and x2 (t). In this case, the original laser light sources may be separate. Specifically, as shown in FIG. 4, two measurement beams (reflected beams) B2u and B2d that are parallel to the upper and lower sides of the reflection plane (parallel to the yz plane) MXr of the reflection mirror MX.
Two independent laser interferometers 1FM
u, 1FMd is provided. This interferometer 1FMu, 1FMd
Respectively independently measure the position and distance of the reflecting mirror MX in the x direction, and output measured values CPu and CPd. Measured value CP
u and CPd are preset so that they have the same value when the reflecting mirror MX (stage ST) is at the reference position.
Then, the correction circuit 15 uses the measured value CP as in the previous embodiment.
Interferometer measurement value 1 that corrects (or reduces) the amount of fluctuation due to fluctuations in the refractive index of air based on the inputs of u and CPd
6 is output.

Also in such a structure, the temperature-stabilized wind 18 having a substantially constant velocity is made to flow from the top to the bottom, that is, from the measurement beams B2u to B2d, as in the previous embodiment. The measuring beams B2u, B2d
4 has been described as a so-called single-beam type interferometer having only one each, but as shown in FIG. 3 of the previous embodiment, one interferometer has two (or more) interferometers. A double beam type having a measuring beam (reflected beam) can be used as well.

By the way, the calculation of the correction circuit 15 is performed every fixed time interval T, but it may be performed every time the stage ST moves by a fixed distance. Further, the correction calculation may be performed at regular intervals while the stage ST is moving, and the correction calculation may be performed at regular intervals while the stage ST is stopped. Further, in the calculation formula (D) of the correction circuit 15, the value of the constant k2 may be sequentially changed according to the position (or moving speed) of the stage ST. This is to cope with the fact that the wind speed from the duct changes according to the stage position (speed) and the like.

Further, although the correction circuit 15 is always constituted so as to correct the fluctuation of the measured value due to the fluctuation of the refractive index of air, depending on the way of moving the stage ST (step and repeat system in case of stepper). It is not always necessary to correct. For example, in the step-and-repeat type exposure apparatus, fluctuations in the interferometer output value due to fluctuations occur during the exposure of one shot area on the wafer (0.2 to 0.5 seconds). Since the servo system responds, the stage ST may move slightly.
This causes blurring of the exposed pattern and poor resolution. When the exposure is performed by the step-and-repeat method only for the purpose of preventing the resolution defect, during the stepping movement to the next shot area of the stage ST, the above equation (E),
No correction is made by (F), (G), etc., and the time interval T is set between the time when the stepping is completed and the time when the exposure is completed.
It is better to perform correction by. Also, when photoelectrically detecting the alignment mark on the wafer using the measurement value of the laser interferometer (or time-series count pulse) as a reference, fluctuations in the signal waveform and position of the detected mark cause the alignment mark It is preferable that the correction circuit 15 also performs the correction operation at the time of detection.

In each of the embodiments of the present invention, only the temperature-stabilized air is sent from one direction, but the arrow 1 in FIG.
As shown in FIG. 9, wind may flow without stagnation by combining with an exhaust system (exhaust duct) not shown.

[0033]

As described above, according to the present invention, the effect that the fluctuation of the refractive index of the air in the exposure apparatus can be reduced and only the fluctuation component of the laser interferometer can be monitored. Since the measured value is corrected by using this to obtain a more accurate measured value that is not affected by the fluctuation of the refractive index, it is effective for measuring the position and distance of the stage that can be moved precisely.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the configuration of a measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an X interferometer of the present embodiment.

FIG. 3 is a plan view showing the configuration of an X interferometer of this embodiment.

FIG. 4 is a perspective view showing the configuration of a measuring apparatus according to another embodiment of the present invention.

[Explanation of Codes of Main Parts] 1 ... Laser light source, 15 ... Correction circuit, 18 ...
Wind, DX1, DX2 ... Detector, FN ... Fan,
FL ... filter, ST ... stage, DCX,
DCY ... Duct, MX, MY ... Reflector

Claims (8)

[Claims] 1. A beam from a laser light source is divided into a measuring beam and a reference beam, and a reflected beam from the object to be measured of the measuring beam and the reference beam are superposed to form an interference beam, In a device for measuring the position and distance of the object to be measured by photoelectrically detecting the interference beam, a gas supply source for generating a temperature-stabilized gas flow at a substantially constant velocity; the measurement beam and the reflected beam And a wind guide means for guiding a gas flow from the gas supply source across the beam in a space through which the measuring beam passes. 2. The air guide means is fixedly arranged in an axial direction of the beam so that a blower port to the passage space of the beam does not spatially interfere with a movement locus of the object to be measured. The device according to claim 1, characterized in that 3. The object to be measured has two reflecting surfaces that are orthogonal to each other, and the air guide means is provided in the space for passing the measuring beam and the reflected beam, which are respectively irradiated on the two reflecting surfaces. Device according to claim 1 or 2, characterized in that it respectively directs the gas flow. 4. The apparatus according to claim 1, wherein the air guide means sets the temperature of the gas flow substantially equal to the air conditioning temperature in the apparatus. 5. The apparatus according to any one of claims 1 to 4, wherein the air guide means sends the gas flow from above the measurement beam over the axial direction of the measurement beam. 6. A beam from a laser light source is divided into a measuring beam and a reference beam, and a reflected beam from the object to be measured of the measuring beam and the reference beam are superposed to form an interference beam, In a device for measuring the position and distance of the object to be measured by photoelectrically detecting the interference beam, a gas is supplied to a space where the measurement beam and the reflected beam pass so as to cross the beam from one direction. Gas supply means; splitting means for splitting the interference beam into two corresponding to the windward and leeward of the measuring beam and the reflected beam with respect to the gas, respectively; Two photoelectric detectors for photoelectrically detecting each of them; and a measuring means for measuring the position and distance of the object to be measured based on the output signals of the two photoelectric detectors. Apparatus. 7. The measuring means includes two signal processing circuits for individually detecting a position and a distance of the object to be measured based on respective output signals of the two photoelectric detectors, and the two signal processing circuits. 4. The apparatus according to claim 3, further comprising a correction circuit that corrects an error amount due to fluctuation of a refractive index of the beam passing space based on the detected information. 8. An object to be measured is irradiated with a measuring beam from a laser light source, the reflected beam interferes with another reference beam obtained from the laser light source to form an interference beam, and the interference beam is photoelectrically converted. In the device for measuring the position or distance of the object to be measured by detecting, the object to be measured is irradiated with a first measuring beam, and the reflected beam and the first reference beam are caused to interfere with each other to generate a first beam. First interference measuring means for making one interference beam to measure the position and distance of the object to be measured; and irradiating the object to be measured with a second beam for measurement in parallel with the first beam for measurement, A second interference beam is generated by causing the reflected beam and the second reference beam to interfere with each other, and a second position for measuring the position and distance of the object to be measured.
Interferometric measuring means; so that the first measuring beam is located upwind and the second measuring beam is located downwind,
A gas supply means for supplying a gas from a direction traversing the beam.