JP7494066B2 - Exposure apparatus and method for manufacturing article - Google Patents

Description

The present invention relates to an exposure apparatus and a method for manufacturing an article.

In an exposure apparatus, it is required to improve exposure performance by measuring the stage position with high accuracy.
When measuring the position of the stage using an interferometer, it is necessary to take care of changes in the wavelength of the measurement light emitted toward the stage.

In other words, when the environment, such as temperature, humidity, or air pressure, of the space through which the measurement light propagates changes, the refractive index of the space changes accordingly, causing a change in the wavelength of the measurement light, resulting in an error when measuring the position of the stage using an interferometer.
Patent Document 1 discloses an exposure apparatus that corrects changes in the measurement values by an interferometer due to the influence of sound waves from an air vibration source by correcting the wavelength of the measurement light from the interferometer based on the difference between the distance from the air vibration source to the optical path of the interferometer and to a wavelength detector.

JP 2008-145203 A

Furthermore, in an exposure apparatus in which a stage moves back and forth when exposing a substrate, the spatial environment through which the measurement light emitted from the interferometer to measure the position of the stage propagates, particularly the air pressure, changes over time, which causes the refractive index of the space and ultimately the wavelength of the measurement light to change over time.
On the other hand, in the exposure apparatus disclosed in Patent Document 1, the wavelength of the measurement light is corrected based on the distance from the air vibration source to the optical path of the interferometer, and no consideration is given to the change over time in the wavelength of the measurement light that accompanies such stage movement.
SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an exposure apparatus that can improve exposure performance by correcting the measurement results of the stage position taking into account the movement of the stage.

The exposure apparatus according to the present invention is an exposure apparatus that exposes a substrate to light so as to transfer a pattern formed on an original onto the substrate, and includes a first stage having a first reflecting surface perpendicular to a first direction and moving back and forth in the first direction at a predetermined frequency while holding either the substrate or the original, a first measuring unit that measures the position of the first stage in the first direction by emitting a first measuring light toward the first reflecting surface and then receiving the first measuring light reflected by the first reflecting surface, and a second reflecting surface perpendicular to the first direction. Both are characterized by comprising a second stage that holds the other of the substrate and the original, a second measurement unit that measures the position of the second stage in the first direction by emitting a second measurement light toward the second reflecting surface and then receiving the second measurement light reflected by the second reflecting surface, a third measurement unit that is disposed closer to the first stage than the second stage and measures the wavelength of a third measurement light propagating inside, and a control unit that corrects the measurement result of the second measurement unit based on the measurement result by the third measurement unit and a predetermined frequency.

The present invention provides an exposure apparatus that can improve exposure performance by correcting the measurement results of the stage position taking into account the movement of the stage.

FIG. 2 is a partially enlarged schematic cross-sectional view of the exposure apparatus according to the first embodiment. FIG. 4 is a diagram showing a schematic change over time in the wavelength of the measurement light in the exposure apparatus according to the first embodiment. 6 is a flowchart showing a process of acquiring components in a predetermined frequency range contained in the time change in the wavelength of the measurement light in the exposure apparatus according to the first embodiment. FIG. 11 is a partially enlarged schematic top view of an exposure apparatus according to a second embodiment.

Hereinafter, an exposure apparatus according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings shown below are drawn at a scale different from the actual scale in order to facilitate understanding of the present embodiment.
In the following description, the direction perpendicular to the substrate mounting surface of the substrate stage is defined as the z direction, and two directions perpendicular to each other (perpendicular) within the substrate mounting surface are defined as the x direction and the y direction, respectively.

[First embodiment]
Improvement in the positioning accuracy of a stage provided in an exposure apparatus is extremely important since it is directly linked to exposure performance.
In order to improve the positioning accuracy of the stage, it is necessary to improve the measurement accuracy of a means for measuring the position of the stage, such as an interferometer.

Furthermore, if the wavelength of the measurement light changes due to a change in the environment of the space through which the measurement light propagates, an error occurs in the measurement result of the interferometer.
Conventionally, a wavelength tracker has been used as a means for correcting such errors, which can detect the amount of change in the wavelength of the measurement light associated with changes in the environment of the specified space by comparing the wavelengths of the reference light propagated through a vacuum space and the measurement light propagated through a specified space.

In general, the size of a wavelength tracker is large, and therefore it may not be possible to place the wavelength tracker near the optical path along which the measurement light from the interferometer propagates.
Furthermore, the exposure apparatus is provided with a substrate stage that holds and moves the substrate, and an original stage that holds and moves the original.
Therefore, if a wavelength tracker is provided for each stage, the cost, the number of steps, and the size increase.

Therefore, the object of this embodiment is to provide an exposure apparatus that can improve the positioning accuracy of the stage by correcting measurement errors in the stage position with high precision while suppressing increases in costs, labor, and size.
Specifically, according to this embodiment, the changes in the environment of the space through which the measurement light for measuring the position of the original stage propagates are estimated using the measurement results from a wavelength tracker placed close to the space in which the substrate stage is located, as shown below.
Then, the amount of change in the wavelength of the measurement light is estimated, and the measurement result of the original stage position is corrected based on the estimated amount of change in wavelength, thereby improving the positioning accuracy of the stage.

More specifically, a length measurement system using an interferometer is employed to measure the positions of stages such as a substrate stage and an original stage provided in the exposure apparatus.
A length measurement system using an interferometer performs position measurement based on the wavelength of measurement light.

Therefore, when measuring the position of the stage, if the refractive index of the gas in the space, i.e., air, changes in response to changes in the environment of the space through which the measurement light propagates, i.e., changes in temperature, humidity, air pressure, etc., the wavelength of the propagating measurement light changes.
In this case, an error occurs in the measurement result of the stage position, which reduces the positioning accuracy of the stage.
Therefore, in a length measurement system using an interferometer provided in an exposure apparatus, it is necessary to correct the measurement value in accordance with changes in the wavelength of the measurement light.

One method for correcting the wavelength of measurement light in an interferometer is to detect the environment of the path along which the measurement light propagates, such as the temperature, humidity, and air pressure, and then calculate the change in refractive index along the path along which the measurement light propagates from the detected results.
One example of such a method is to measure the position of the same measurement object using both a reference light propagating in a vacuum space and a measurement light propagating in a specified space, and to calculate the refractive index in the specified space by comparing the two measurement values.

Such a correction method is used in an apparatus called a wavelength tracker or a wavelength compensator, which is provided by a manufacturer of a length measurement system using an interferometer.
Here, if the wavelength of the measurement light propagating in the specified space is λ, the wavelength of the reference light propagating in the vacuum space is λ _v , and the refractive index of the specified space is n, the following equation (1) is satisfied.
λ=λ _v /n (1)

That is, the wavelength tracker can measure the refractive index n in a predetermined space, and by knowing the refractive index n in the predetermined space, the wavelength λ of the measurement light can be calculated.
As described above, since the interferometer is a sensor for measuring a position based on the wavelength and phase of the measurement light, a change in the wavelength of the measurement light causes an error in the position measurement result.
Therefore, if the wavelength of the measurement light can be calculated accurately, errors in the position measurement results obtained by the interferometer can be corrected.

Figures 1(a) and (b) show partially enlarged schematic cross-sectional views of the exposure apparatus 100 according to the first embodiment.

As shown in FIGS. 1A and 1B, an exposure apparatus 100 according to this embodiment includes a substrate stage 1 (first stage), an original stage 11 (second stage), and a projection optical system 13.
The exposure apparatus 100 according to this embodiment can perform exposure so as to transfer a pattern formed on an original (not shown) onto a substrate (not shown) using exposure light from a light source (not shown).
Here, the projection optical system 13 held by the holder 15 guides the exposure light that has passed through an original (not shown) onto a substrate (not shown).

In addition, in the exposure apparatus 100 according to this embodiment, the positions of the substrate stage 1 and the original stage 11 are measured using a length measurement system that uses an interferometer, as shown below.

The substrate stage 1 holds a substrate such as a wafer (not shown) and can perform scanning movement at least in the y direction (first direction) and step movement in the x direction.
A mirror 2 (first reflecting surface) is arranged on the substrate stage 1 for measuring the position of the substrate stage 1 in the y direction, and measurement light 30 (measurement beam, first measurement light) for position measurement propagates between an interferometer 3 (first measurement unit, first interferometer) and the mirror 2.

That is, the interferometer 3 emits measurement light 30 toward the mirror 2 and then receives the measurement light 30 reflected by the mirror 2 .
Then, the distance between the interferometer 3 and the mirror 2 is measured from the interference between the measurement light 30 reflected by the mirror 2 and a reference light (first reference light) (not shown).

Next, the interferometer 3 emits interference light 4 , which is obtained by causing the measurement light 30 reflected by the mirror 2 to interfere with a reference light (not shown), to an optical pickup 5 .
After receiving the interference light 4 , the optical pickup 5 outputs the interference light 4 to a signal processing board 8 via an optical fiber 6 .
The signal processing board 8 then performs photoelectric conversion on the input interference light 4 to calculate the position of the substrate stage 1 in the y direction.

Furthermore, measurement light output from a wavelength tracker 9 (third measurement unit) for detecting the refractive index of the space is input to the signal processing board 8 via an optical fiber 37 .
As described above, the wavelength tracker 9 measures the position of the same measurement object using both the measurement light (fourth measurement light) propagating in a vacuum space and the measurement light (third measurement light) propagating in a specified space, and calculates the refractive index in the specified space by comparing the two measurement values.
In other words, the wavelength tracker 9 is positioned closer to the substrate stage 1 than the original stage 11, and by measuring the wavelength of the measurement light propagating inside, the refractive index of the space in which the substrate stage 1 is located can be calculated.

The signal processing board 8 then transmits the measurement value of the refractive index of the space in which the substrate stage 1 is placed, acquired by the wavelength tracker 9, via a cable 21 to a wavelength correction means 20 (control unit).
Thereafter, the wavelength correction means 20 calculates in real time, from the value of the refractive index transmitted from the signal processing board 8, the amount of change in the wavelength of the measurement light 30 propagating within the space in which the substrate stage 1 is provided.
Then, the wavelength correction means 20 corrects the measurement result of the position of the substrate stage 1 in the y direction using the calculated amount of change in the wavelength of the measurement light 30 .

In addition, the exposure apparatus 100 according to this embodiment also uses a method similar to that described above to measure the position in the y direction of the original stage 11, which holds an original (not shown) and moves in a scanning manner in the y direction.

That is, as shown in Figures 1(a) and (b), measurement light 31 (length measurement beam, second measurement light) for position measurement propagates between a mirror 12 (second reflecting surface) provided on the original stage 11 and an interferometer 33 (second measurement unit, second interferometer).
In other words, the interferometer 33 measures the position of the original stage 11 in the y direction by emitting the measurement light 31 towards the mirror 12 and then receiving the measurement light 31 reflected by the mirror 12 .

Then, from the interferometer 33 , interference light 34 obtained by causing the measurement light 31 reflected by the mirror 12 and a reference light (second reference light) (not shown) to interfere with each other is emitted to an optical pickup 35 .
Next, the optical pickup 35 receives the interference light 34 and then outputs the interference light 34 to the signal processing board 8 via an optical fiber 36 .

The signal processing board 8 then performs photoelectric conversion on the input interference light 34 to calculate the position of the original stage 11 in the y direction.

Next, we will explain a method for correcting the measurement results of the position of the original stage 11 in the y direction in the exposure apparatus 100 according to this embodiment.

In an exposure apparatus, it is not preferable to provide a wavelength tracker in each of the space in which the original stage 11 is disposed and the space in which the substrate stage 1 is disposed, since this leads to an increase in the size of the apparatus.
Therefore, in a conventional exposure apparatus, it is assumed that the spatial environments in which the original stage 11 and the substrate stage 1 are disposed, that is, the temperature, humidity, and air pressure, are the same for both.
Based on this, the measurement result of the position of the original stage 11 is corrected using the value of the refractive index calculated by a wavelength tracker 9 provided in the space in which the substrate stage 1 is placed.

However, when exposure is performed using a scanning exposure apparatus, the substrate stage 1 and the original stage 11 generally perform scanning movements in opposite directions.
That is, as shown in FIG. 1B, for example, when the substrate stage 1 performs scanning movement in the +y direction, the original stage 11 performs scanning movement in the -y direction.
In other words, the original stage 11 reciprocates in the y direction at the same frequency f as the substrate stage 1 so that when the substrate stage moves in one direction in the y direction, it moves in the other direction.

The air pressure in a given space changes according to wind pressure caused by the movement of a stage provided within the space.
Therefore, while the air pressure in the space in which the substrate stage 1 is located changes as the substrate stage 1 moves in a scanning direction in the +y direction, the air pressure in the space in which the original stage 11 is located changes as the original stage 11 moves in a scanning direction in the -y direction.

Specifically, when the substrate stage 1 moves in a scanning manner in the +y direction, the air in the space through which the measurement light 30 for measuring the position of the substrate stage 1 in the y direction propagates expands, and the air pressure in the space decreases.
On the other hand, when the original stage 11 is scanned in the -y direction in synchronization with the scanning movement of the substrate stage in the +y direction, the air in the space through which the measurement light 31 for measuring the position of the original stage 11 in the y direction propagates is compressed, and the air pressure in the space increases.

Furthermore, in order to expose each of a plurality of shot areas formed on a substrate (not shown), the substrate stage 1 periodically repeats scanning movements in the +y direction and scanning movements in the −y direction.
On the other hand, the original stage 11 repeats scanning movements in the −y direction and the +y direction in the opposite phase to the substrate stage 1 .

Therefore, the air pressure in the space through which the measuring light 31 propagates and the air pressure in the space through which the measuring light 30 propagates vary periodically with time so as to be in opposite phase to each other.
In addition, since the original stage 11 generally moves in a scanning direction at a faster speed than the substrate stage 1, the amplitude of the change in air pressure over time in the space in which the original stage 11 is located and the amplitude of the change in air pressure over time in the space in which the substrate stage 1 is located are different from each other.

The exposure apparatus 100 according to this embodiment utilizes the above-mentioned characteristics to correct the measurement result of the position of the original stage 11 in the y direction using the refractive index value calculated by the wavelength tracker 9 provided in the space in which the substrate stage 1 is located, as follows:

FIG. 2A shows a schematic diagram of the change over time in the wavelength λ _w of the measurement light measured by the wavelength tracker 9 when a predetermined substrate is exposed in the exposure apparatus 100 according to this embodiment.
It should be noted that the change over time in the wavelength λ _w of the measurement light measured by the wavelength tracker 9 is equivalent to the change over time in the refractive index of the space in which the wavelength tracker 9 is installed, which changes with the environment of the space, i.e., the temperature, humidity, or air pressure.
In addition, since the wavelength tracker 9 is provided in the space where the substrate stage 1 is disposed, that is, the space through which the measurement light 30 propagates, the time change in the wavelength λ _w shown in FIG. 2A can be considered as the time change in the wavelength of the measurement light 30.

When the temperature of the space within the exposure apparatus is precisely controlled, as in the exposure apparatus 100 according to the present embodiment, the change in the refractive index of the space is dominated by the fluctuation in the air pressure of the space.
Then, the time change λ _w (t) of the wavelength of the measurement light measured by the wavelength tracker 9 when the substrate stage 1 moves in a scanning manner can be expressed by the following equation (2).
λ _w (t) = λ _w ^low (t) + λ _w ^high (t) ... (2)
Here, λ _w ^low (t) is a component due to the time change in atmospheric pressure, and λ _w ^high (t) is a component due to the time change in wind pressure generated when the substrate stage 1 moves in a scanning manner.

すなわち、時刻ｔがｔ_０からｔ_１までの間に基板ステージ１が複数回の走査移動を行うことに伴って、λ_ｗ ^ｈｉｇｈ（ｔ）は、振幅Ｍ及び周波数ｆで時間変化する正弦関数で表すことができる。 Here, λ _w ^high (t) is considered to change over time in accordance with the multiple scanning movements that the substrate stage 1 makes back and forth at a predetermined frequency when exposing multiple shot areas on the substrate.
That is, for example, if the frequency of the scanning movement of the substrate stage 1 is f [Hz], λ _w ^high (t) also changes at a frequency of f [Hz].
In this case, λ _w ^high (t) is expressed as in the following equation (3).

That is, as the substrate stage 1 performs multiple scanning movements during the time t from t ₀ to t ₁ , λ _w ^high (t) can be expressed as a sine function that changes with time with amplitude M and frequency f.

On the other hand, since the atmospheric pressure changes with time at a very low frequency, it is considered that λ _w ^low (t) changes with time at a frequency that is sufficiently lower than the frequency f of the scanning movement of the substrate stage 1 .

From the above, it can be considered that the wavelength λ _w of the measurement light measured by the wavelength tracker 9 changes with time as shown in FIG. 2( a ).
Of the time change λ _w (t) in the wavelength of the measurement light measured by the wavelength tracker 9, the component λ _w ^high (t) that fluctuates due to the scanning movement of the substrate stage 1 has a period _Ts of _Ts = 1/f = 0.2 seconds when the frequency f of the scanning movement is 5 Hz.

As described above, the substrate stage 1 and the original stage 11 perform scanning movements in the opposite directions.
Therefore, the time change in air pressure in the space through which the measurement light 31 propagates and the time change in air pressure in the space through which the measurement light 30 propagates are in opposite phase to each other.

Therefore, if a wavelength tracker is provided in the space in which the original stage 11 is located, it is considered that the time change in the wavelength of the measurement light measured by the wavelength tracker, i.e., the time change in the wavelength of the measurement light 31, will be in opposite phase to the time change in the wavelength of the measurement light 30.
Furthermore, since the scanning movement speed of the original stage 11 and the scanning movement speed of the substrate stage 1 differ from each other, it is considered that the amplitude of the time change in the wavelength of the measuring light 31 and the amplitude of the time change in the wavelength of the measuring light 30 also differ from each other.

であり、ａは基板ステージ１の走査移動における最大速度に対する原版ステージ１１の走査移動における最大速度の比に伴う係数（所定の係数）である。
一方、大気圧の時間変化は、原版ステージ１１が配置されている空間と基板ステージ１が配置されている空間とで互いに等しいと考えられるため、以下の式（５）が満たされると考えることができる。
λ_ｒ ^ｌｏｗ（ｔ）＝λ_ｗ ^ｌｏｗ（ｔ） ・・・（５） Considering the above, the time change λ _r (t) of the wavelength of the measurement light 31 can be expressed by the following equation (4).
_λr (t)= _λrlow ⁽ t)+ _λrhigh ⁽ t) (4)
Here, λ _r ^high (t) is

and a is a coefficient (a predetermined coefficient) associated with the ratio of the maximum speed in the scanning movement of the original stage 11 to the maximum speed in the scanning movement of the substrate stage 1 .
On the other hand, since the change in atmospheric pressure over time is considered to be equal in the space in which the original stage 11 is located and the space in which the substrate stage 1 is located, it can be considered that the following formula (5) is satisfied.
λ _r ^low ( t ) = λ _w ^low ( t ) (5)

From the above, the time change λ _r (t) of the wavelength of the measurement light 31 can be rewritten as the following equation (6).
λ _r (t) = λ _w ^low (t) - a λ _w ^high (t) ... (6)
FIG. 2B shows the change in wavelength of measurement light 31 over time λ _r (t) determined by the method described above in exposure apparatus 100 according to this embodiment.

As described above, the wavelengths of the measurement light 30 from the interferometer 3 and the measurement light in the wavelength tracker 9 change in accordance with the movement of the substrate stage 1, while the wavelength of the measurement light 31 from the interferometer 33 changes in accordance with the movement of the original stage 11.
Then, from the value measured by a wavelength tracker 9 installed in the space in which the substrate stage 1 is located, the change over time in air pressure in the space through which the measurement light 31 from an interferometer 33 for measuring the position of the original stage 11 in the y direction propagates is estimated.

Then, the change over time in the wavelength of the measuring light 31 is estimated, and the measurement result of the position of the original stage 11 in the y direction obtained by the interferometer 33 is corrected.
This makes it possible to improve the measurement accuracy of the position of the original stage 11 in the y direction by the interferometer 33 without providing a wavelength tracker in the space in which the original stage 11 is disposed.

Next, a method of separating λ _w ^low (t) and λ _w ^high (t) from each other from the time change λ _w (t) of the wavelength of the measurement light measured by the wavelength tracker 9 will be described.

FIG. 3 shows a flowchart of a process for separating λ _w ^low (t) and λ _w ^high (t) from each other from the time change λ _w (t) of the wavelength of the measurement light measured by the wavelength tracker 9 in the exposure apparatus 100 according to this embodiment.

First, in order to remove noise components from the time change λ _w (t) of the wavelength of the measurement light measured by the wavelength tracker 9, the output from the wavelength tracker 9 is input to a first low-pass filter (not shown) (step S1).
At this time, noise components that change over time at frequencies sufficiently higher than the frequency f of the scanning movement of the substrate stage 1 must be removed, while the component λ _w ^high (t) that changes over time according to the frequency f must be accurately extracted.

For this reason, the cutoff frequency of the first low-pass filter is set to a value greater than the frequency f of the scanning movement of the substrate stage 1 .
That is, the change in wavelength λ _w (t) over time of the measurement light 30 for measuring the position of the substrate stage 1 in the y direction can be expressed by the following equation (7).
λ _w (t) = λ _w ^lpf_high (t) ... (7)

Furthermore, since the frequency f of the scanning movement of the substrate stage 1 depends on the speed and stroke of the scanning movement of the substrate stage 1, the cutoff frequency of the first low-pass filter can be changed in response to these.
In other words, the cutoff frequency of the first low-pass filter, ie, the predetermined frequency range selected by the first low-pass filter, is determined according to the frequency f of the scanning movement of the substrate stage 1 .
The output value of the first low-pass filter at this time is represented as λ _w ^{lpf — high} (t).

Next, as described above, λ _w ^low (t) is a component that changes with time at a frequency that is sufficiently lower than the frequency f of the scanning movement of the substrate stage 1 .
Therefore, in order to extract λ _w ^low (t) from the time change λ _w (t) of the wavelength of the measurement light measured by the wavelength tracker 9, the output from the wavelength tracker 9 is input to a second low-pass filter having a cutoff frequency sufficiently lower than the frequency f (step S2). Here, the cutoff frequency sufficiently lower than the frequency f is, for example, 0.1 Hz.
The output value of the second low-pass filter at this time is represented as λ _w ^{lpf — low} (t).

From the above, λ _w ^low (t) can be associated with the output value λ _w ^{lpf — low} (t) of the second low-pass filter as expressed by the following equation (8).
λ _w ^low ( t ) = λ _w ^lpf_low ( t ) (8)
Moreover, λ _w ^high (t) can be associated with the output values λ _w ^{lpf _ high} (t) and λ _w ^{lpf _ low} (t) of the first and second low-pass filters, respectively, as expressed by the following equation (9).
λ _w ^high (t) = λ _w ^{lpf _ high} (t) - λ _w ^{lpf _ low} (t) ... (9)
In this way, λ _w ^low (t) and λ _w ^high (t) can be obtained from λ w ^{lpf _} high (t) and λ _w lpf _{_} ^low (t) based on equations (8) and (9) (step S3).

Then, the time change λ _r (t) of the wavelength of the measurement light 31 can be expressed as the following formula (10) by substituting formulas (8) and (9) into formula (6).
λ _r (t) = λ _w ^lpf_low (t) - a ( λ _w ^lpf_high (t) - λ _w ^lpf_low (t)) ... (10)

The value of coefficient a in equation (10) is determined by the ratio between the maximum speeds of the scanning movements of the original stage 11 and the substrate stage 1, but it is not limited to this and may be determined to a predetermined value that improves the overlay accuracy.

As described above, in the exposure apparatus 100 according to this embodiment, the interferometer 3 measures the position of the substrate stage 1 in the y direction (first measurement step), and the interferometer 33 measures the position of the original stage 11 in the y direction (second measurement step).
Then, the wavelength of the measurement light is measured by the wavelength tracker 9 (third measurement step), and the time change in the wavelength of the measurement light measured by the wavelength tracker 9 is input to a low-pass filter to obtain components in a predetermined frequency range from the time change in the wavelength of the measurement light.
Specifically, the change over time in the wavelength of the measurement light measured by the wavelength tracker 9 is input to a first low-pass filter having a first cutoff frequency higher than the frequency f of the scanning movement, and a second low-pass filter having a second cutoff frequency lower than the frequency f. Thereby, a first frequency domain component and a second frequency domain component are obtained from the change over time in the wavelength of the measurement light measured by the wavelength tracker 9.
That is, in the exposure apparatus 100 according to this embodiment, predetermined frequency domain components λ _w ^{lpf _ high} (t) and λ _w ^{lpf _ low} (t) are extracted from the measurement value λ _w (t) of the wavelength tracker 9. In addition, the difference between them is multiplied by the gain a.

Then, the time change _λr (t) in the wavelength of the measurement light 31 of the interferometer 33 for measuring the position of the original stage 11 in the y direction is calculated, and the result is used to correct the measurement value of the position of the original stage 11 in the y direction (correction step).
That is, in the exposure apparatus 100 according to this embodiment, the wavelength correction means 20 corrects the measurement results of the position of the original stage 11 in the y direction by the interferometer 33 based on the measurement results by the wavelength tracker 9 and the frequency f of the scanning movement of the substrate stage 1.
This makes it possible to highly accurately correct the measurement value of the interferometer 33 for measuring the position of the original stage 11 in the y direction.

In the exposure apparatus 100 according to the present embodiment, the components λ _w ^{lpf _ high} (t) and λ _w ^{lpf _} low (t) in predetermined frequency regions are extracted from the measurement value λ _w (t) of the wavelength tracker 9 using a low-pass filter, but this is not limited to this.
For example, a component in a predetermined frequency range may be extracted from the measurement value λ _w (t) of the wavelength tracker 9 using a moving average filter, a band-pass filter, a high-pass filter, or the like.

[Second embodiment]
FIG. 4 shows a partially enlarged schematic top view of an exposure apparatus 200 according to the second embodiment.
As shown in FIG. 4, in the exposure apparatus 200 according to this embodiment, a mirror 2 (first reflecting surface) for measuring the position of the substrate stage 1 in the y direction (first direction) is disposed on the substrate stage 1.

Then, measurement light 30 (length measurement beam, first measurement light) for position measurement propagates between the interferometer 3 (first measurement unit, first interferometer) and the mirror 2 .
That is, the interferometer 3 measures the position of the substrate stage 1 in the y direction by emitting measuring light 30 towards the mirror 2 and then receiving the measuring light 30 reflected by the mirror 2 .

Next, the interferometer 3 emits interference light 4 , which is obtained by causing the measurement light 30 and a reference light (first reference light) (not shown) to interfere with each other, to the optical pickup 5 .
After receiving the interference light 4 , the optical pickup 5 outputs the interference light 4 to a signal processing board 8 via an optical fiber 6 .
The signal processing board 8 then performs photoelectric conversion on the input interference light 4 to calculate the position of the substrate stage 1 in the y direction.

Furthermore, measurement light output from a wavelength tracker 9 for detecting the refractive index of a predetermined space is input to the signal processing board 8 via an optical fiber 37 .
The signal processing board 8 then transmits the measurement value of the refractive index in the specified space acquired by the wavelength tracker 9 to the wavelength correction means 20 via the cable 21 .

Thereafter, the wavelength correction means 20 calculates in real time the amount of change in the wavelength of the measurement light 30 propagating within a specified space from the value of the refractive index transmitted from the signal processing board 8 .
Then, the wavelength correction means 20 corrects the measurement result of the position of the substrate stage 1 in the y direction using the calculated amount of change in the wavelength of the measurement light 30 .

At this time, the time change λ _y (t) of the wavelength of measurement light 30 measured by wavelength tracker 9 can be expressed as the following equation (11), similarly to exposure apparatus 100 according to the first embodiment.
_λy (t)= _λylow ⁽ t ^)+λyhigh ₍ t) (11)

すなわち、時刻ｔがｔ_０からｔ_１までの間に基板ステージ１が複数回の走査移動を行うことに伴って、λ_ｙ ^ｈｉｇｈ（ｔ）は、振幅Ｍ及び周波数ｆで時間変化する正弦関数で表すことができる。
そして、λ_ｙ ^ｌｏｗ（ｔ）は大気圧の時間変化による成分であり、基板ステージ１の走査移動の周波数ｆに比べて十分低い周波数で時間変化すると考える。 Here, λ _y ^high (t) is expressed as in the following equation (12).

That is, as the substrate stage 1 performs multiple scanning movements during the time t from t ₀ to t ₁ , λ _y ^high (t) can be expressed as a sine function that changes with time with amplitude M and frequency f.
It is considered that λ _y ^low (t) is a component due to the time change in atmospheric pressure, and changes with time at a frequency sufficiently lower than the frequency f of the scanning movement of the substrate stage 1 .

Furthermore, in the exposure apparatus 200 according to this embodiment, a mirror 12 (second reflecting surface) for measuring the position of the substrate stage 1 in the x direction (second direction) is also disposed on the substrate stage 1 .
Then, measurement light 31 (length measurement beam, second measurement light) for position measurement propagates between an interferometer 33 (second measurement unit, second interferometer) and the mirror 12 .
That is, the interferometer 33 measures the position of the substrate stage 1 in the x direction by emitting the measurement light 31 towards the mirror 12 and then receiving the measurement light 31 reflected by the mirror 12 .

Next, the interferometer 33 emits interference light 34 , which is obtained by causing the measurement light 31 and a reference light (second reference light) (not shown) to interfere with each other, to an optical pickup 35 .
After receiving the interference light 34 , the optical pickup 35 outputs the interference light 34 to the signal processing board 8 via an optical fiber 36 .

In addition, the wavelength tracker 9 (third measurement unit) is positioned closer to mirror 2 than mirror 12, and by measuring the wavelength of the measurement light (third measurement light) propagating inside, the refractive index of the space through which the measurement light 30 from the interferometer 3 propagates can be calculated.

In a conventional exposure apparatus, for example, the value of the refractive index calculated by a wavelength tracker 9 provided in the space in which the interferometer 3 is disposed is used as is to correct the measurement result by the interferometer 33 .
However, in a scanning exposure apparatus such as the exposure apparatus 200 according to this embodiment, the substrate stage 1 performs scanning movement in the y direction, while performing step movement in the x direction.
That is, in the substrate stage 1, the step movement in the x direction and the scanning movement in the y direction are not linked with each other but are performed independently.

Furthermore, in the substrate stage 1, the speed and acceleration during step movement in the x direction are different from the speed and acceleration during scanning movement in the y direction.
Therefore, the fluctuation in air pressure in the space through which the measurement light 30 propagates during scanning movement in the y direction and the fluctuation in air pressure in the space through which the measurement light 31 propagates during step movement in the x direction also differ from each other.

In other words, if the change over time in the wavelength of the measurement light measured by the wavelength tracker 9 provided in the space in which the interferometer 3 is placed is directly applied to the measurement light 31 from the interferometer 33 for correction, the measurement error regarding the position in the x direction will become large.
On the other hand, the change in atmospheric pressure over time can be considered to be equal between the space through which the measuring light 30 propagates and the space through which the measuring light 31 propagates.

Therefore, in exposure apparatus 200 according to this embodiment, the time change λ _x (t) in the wavelength of measurement light 31 is expressed as in equation (13) below, and the relationship expressed in equation (14) below is utilized.
λ _x (t) = λ _x ^low (t) (13)
λ _x ^low (t) = λ _y ^low (t) (14)

Then, λ _y ^{lpf _low} (t) is extracted from the time change λ _y (t) of the wavelength of the measurement light 30 using a low-pass filter having a cutoff frequency lower than the frequency f, and
λ _y ^low (t) = λ _y ^lpf_low (t)
Based on the relationship and equation (14), λ _y ^{lpf — low} (t) is used as λ _x ^low (t).

As described above, in the exposure apparatus 200 according to the present embodiment, the change over time in the wavelength of the measurement light measured by the wavelength tracker 9 is input to a low-pass filter having a cutoff frequency lower than frequency f. Thereby, components in a predetermined frequency range are obtained from the change over time in the wavelength of the measurement light measured by the wavelength tracker 9.
That is, in the exposure apparatus 200 according to this embodiment, the component λ _y ^low (t) associated with the fluctuation in atmospheric pressure is extracted from the measurement value λ _y (t) of the wavelength tracker 9 .

Then, the change in wavelength λ _x (t) over time of the measurement light 31 from the interferometer 33 for measuring the position of the substrate stage 1 in the x direction is calculated, and the result is used to correct the measurement value of the position of the substrate stage 1 in the x direction.
That is, in the exposure apparatus 200 according to this embodiment, the wavelength correction means 20 corrects the measurement results of the position of the substrate stage 1 in the x direction by the interferometer 33 based on the measurement results by the wavelength tracker 9 and the frequency f of the scanning movement of the substrate stage 1 in the y direction.
This makes it possible to correct the measurement value of the position of the substrate stage 1 in the x direction with high accuracy.

It should be noted that the change over time in the wavelength of the measurement light from the wavelength tracker 9 may also contain a component corresponding to the change in air pressure in the space through which the measurement light 31 propagates during step movement in the x direction.
In this case, the output from the wavelength tracker 9 can be input to a bandpass filter corresponding to the frequency of the step movement, and the component associated with the step movement in the x direction can be extracted, thereby correcting the measurement value of the position of the substrate stage 1 in the x direction measured by the interferometer 33.

Furthermore, in the exposure apparatus 200 according to this embodiment, the measurement result of the position of the substrate stage 1 in the x direction is corrected based on the measurement result by the wavelength tracker 9 and the frequency f of the scanning movement of the substrate stage 1 in the y direction.
However, the present invention is not limited to this, and the measurement result of the position of the substrate stage 1 in the z direction may be corrected based on the measurement result by the wavelength tracker 9 and the frequency f of the scanning movement of the substrate stage 1 in the y direction.

[Production method of the article]
Next, a method for manufacturing an article using the exposure apparatus according to this embodiment will be described.
A method for manufacturing articles such as semiconductor IC elements, liquid crystal display elements, and MEMS includes a step of exposing a substrate, such as a wafer or a glass substrate, coated with a photosensitive agent, using the exposure apparatus according to this embodiment.
The method also includes steps of developing the exposed substrate (photosensitive material) and other well known steps of processing the developed substrate.

Other well-known processes mentioned here include etching, photoresist peeling, dicing, bonding, packaging, and the like.
According to the method for manufacturing an article according to this embodiment, it is possible to manufacture an article of higher quality than before.

The above describes preferred embodiments, but the invention is not limited to these embodiments and various modifications and variations are possible within the scope of the gist.

1. Substrate stage (first stage)
2 Mirror (first reflecting surface)
3. Interferometer (first measurement unit)
9 Wavelength tracker (third measurement unit)
11 Master Stage (Second Stage)
12 Mirror (second reflecting surface)
20 Wavelength correction means (control unit)
33 Interferometer (second measurement unit)
100 Exposure device

Claims (20)

1. An exposure apparatus that exposes a substrate to light so as to transfer a pattern formed on an original onto the substrate, comprising:
a first stage having a first reflecting surface perpendicular to a first direction and reciprocating at a predetermined frequency in the first direction while holding one of the substrate and the original;
a first measurement unit that measures a position of the first stage in the first direction by emitting a first measurement light toward the first reflecting surface and then receiving the first measurement light reflected by the first reflecting surface;
a second stage having a second reflecting surface perpendicular to the first direction and configured to hold the other of the substrate and the original;
a second measurement unit that measures a position of the second stage in the first direction by emitting a second measurement light toward the second reflecting surface and then receiving the second measurement light reflected by the second reflecting surface; and
a third measurement unit that is disposed closer to the first stage than the second stage and that measures a wavelength of a third measurement light propagating inside;
a control unit that corrects the measurement result of the second measurement unit based on the measurement result of the third measurement unit and the predetermined frequency;
An exposure apparatus comprising: The exposure apparatus according to claim 1, characterized in that the second stage moves back and forth in the first direction at the predetermined frequency so that when the first stage moves in one direction of the first direction, the second stage moves in the other direction. The exposure apparatus according to claim 2, characterized in that the wavelengths of the first measurement light and the third measurement light change in response to the movement of the first stage, and the wavelength of the second measurement light changes in response to the movement of the second stage. The exposure apparatus according to claim 2 or 3, characterized in that the control unit obtains components in a predetermined frequency range from the time change of the wavelength of the third measurement light by inputting the time change of the wavelength of the third measurement light measured by the third measurement unit to at least one of a low-pass filter, a band-pass filter, and a high-pass filter. the first stage and the second stage each perform a plurality of scanning movements so as to reciprocate in the first direction at the predetermined frequency when exposing the substrate;
5. An exposure apparatus according to claim 4, wherein the predetermined frequency range is determined in accordance with the predetermined frequency. a first low pass filter having a first cutoff frequency higher than the predetermined frequency;
a second low pass filter having a second cutoff frequency lower than the predetermined frequency;
Equipped with
6. The exposure apparatus according to claim 5, wherein the control unit acquires a first frequency domain component and a second frequency domain component of the time change in the wavelength of the third measurement light by inputting the time change in the wavelength of the third measurement light measured by the third measurement unit to the first low-pass filter and the second low-pass filter, respectively. When the first frequency domain component is λ _w ^{lpf _ high} (t), the second frequency domain component is λ _w ^{lpf _ low} (t), a predetermined coefficient is a, and the time change in the wavelength of the second measurement light is λ _r (t),
The control unit is
λ _r (t) = λ _w ^lpf_low (t) - a (λ _w ^lpf_high (t) - λ _w ^lpf_low (t))
7. The exposure apparatus according to claim 6, wherein the measurement result of the second measurement unit is corrected by correcting the wavelength of the second measurement light so that the following formula is satisfied: The exposure apparatus according to claim 7, characterized in that the value of a is determined from the ratio of the maximum speed of the scanning movement of the second stage to the maximum speed of the scanning movement of the first stage. When the change in wavelength of the first measurement light over time is denoted as λ _w (t),
The control unit is
λ _w (t) = λ _w ^lpf_high (t)
9. The exposure apparatus according to claim 7, wherein the measurement result of the first measurement unit is corrected by correcting a wavelength of the first measurement light so that the following formula is satisfied: 1. An exposure apparatus that exposes a substrate to light so as to transfer a pattern formed on an original onto the substrate, comprising:
a substrate stage having a first reflecting surface perpendicular to a first direction and a second reflecting surface perpendicular to a second direction perpendicular to the first direction, the substrate stage reciprocating in the first direction at a predetermined frequency while holding the substrate;
a first measurement unit that measures a position of the substrate stage in the first direction by emitting a first measurement light toward the first reflecting surface and then receiving the first measurement light reflected by the first reflecting surface;
a second measurement unit that measures a position of the substrate stage in the second direction by emitting a second measurement light toward the second reflecting surface and then receiving the second measurement light reflected by the second reflecting surface; and
a third measurement unit that is disposed closer to the first reflection surface than the second reflection surface and that measures a wavelength of a third measurement light propagating inside; and
a control unit that corrects the measurement result of the second measurement unit based on the measurement result of the third measurement unit and the predetermined frequency;
An exposure apparatus comprising: The exposure apparatus according to claim 10, characterized in that the substrate stage performs multiple scanning movements in the first direction so as to reciprocate at the predetermined frequency when exposing the substrate, and performs multiple step movements in the second direction. The exposure apparatus according to claim 11, characterized in that the wavelengths of the first measurement light and the third measurement light change according to the scanning movement of the substrate stage. The exposure apparatus according to any one of claims 10 to 12, characterized in that the control unit acquires components of a predetermined frequency range from the time change of the wavelength of the third measurement light by inputting the time change of the wavelength of the third measurement light measured by the third measurement unit to at least one of a low-pass filter, a band-pass filter, and a high-pass filter. The exposure apparatus according to claim 13, characterized in that the predetermined frequency range is a frequency range lower than the predetermined frequency. a low-pass filter having a cutoff frequency lower than the predetermined frequency,
The exposure apparatus according to claim 13 or 14, characterized in that the control unit acquires the components in the specified frequency range by inputting the time change of the wavelength of the third measurement light measured by the third measurement unit into the low-pass filter. When the component in the predetermined frequency region is denoted by λ _y ^{lpf — low} (t) and the change in wavelength of the second measurement light over time is denoted by λ _x (t),
The control unit is
λ _x (t) = λ _y ^lpf_low (t)
16. The exposure apparatus according to claim 15, wherein the measurement result of the second measurement unit is corrected by correcting a wavelength of the second measurement light so that the following formula is satisfied: the first measurement unit is a first interferometer that measures a distance between the first measurement unit and the first reflecting surface from interference between the first measurement light reflected by the first reflecting surface and a first reference light,
17. The exposure apparatus according to claim 1, wherein the second measurement unit is a second interferometer that measures the distance between the second measurement unit and the second reflecting surface from interference between the second measurement light reflected by the second reflecting surface and a second reference light. The exposure apparatus according to any one of claims 1 to 17, characterized in that the third measurement unit is a wavelength tracker that measures the wavelength of the third measurement light by comparing a measurement result of a predetermined object by the third measurement light propagating in a predetermined space with a measurement result of the predetermined object by a fourth measurement light propagating in a vacuum space. exposing the substrate using an exposure apparatus according to any one of claims 1 to 18;
developing the exposed substrate;
producing an article from the developed substrate;
A method for producing an article, comprising: A method for measuring positions of a first stage and a second stage in an exposure apparatus that exposes a substrate to light so as to transfer a pattern formed on the original to the substrate, the method comprising: a first stage having a first reflecting surface perpendicular to a first direction and reciprocating at a predetermined frequency in the first direction while holding one of a substrate or an original; and a second stage having a second reflecting surface perpendicular to the first direction and holding the other of the substrate or the original, the method comprising:
a first measurement step of measuring a position of the first stage in the first direction by emitting a first measurement light toward the first reflecting surface and then receiving the first measurement light reflected by the first reflecting surface;
a second measurement step of measuring a position of the second stage in the first direction by emitting a second measurement light toward the second reflecting surface and then receiving the second measurement light reflected by the second reflecting surface;
a third measurement step of measuring a wavelength of a third measurement light propagating through a space closer to the first stage than the second stage;
a correction step of correcting the measurement result in the second measurement step based on the measurement result in the third measurement step and the predetermined frequency;
The method according to claim 1, further comprising:

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