JP2828090B2 - Exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a length measuring apparatus using a laser interferometer, and more particularly to a length measuring apparatus suitable for a case where high-precision position measurement is required, such as an exposure apparatus for manufacturing an integrated circuit. Things.

[0002]

2. Description of the Related Art An interferometer using a helium-neon (He-Ne) laser whose frequency is stabilized as a light source is used for precise length measurement and coordinate measurement. Conventionally, when using this type of interferometer, the interferometer can control the temperature and humidity of the air in order to prevent the wavelength from fluctuating due to the change in the density of the air (change in the refractive index) and the occurrence of measurement errors. The air conditioner is placed in a simple chamber and air-conditioned to a temperature of about ± 0.1 ° C. and a humidity of about ± 15%, and a change in atmospheric pressure is monitored by a sensor to correct the wavelength.

[0003]

However, even when the inside of the chamber in which the interferometer is arranged is air-conditioned as described above, the fluctuation of the air due to the temperature is reduced to such an extent that the required length measurement accuracy is not affected. The reason for this is that it is difficult to make the temperature in a chamber with a considerable volume completely uniform, so that there is a mass of air with locally different temperatures, which is To cross the measurement beam.

For example, when such an interferometer is used for positioning of a stage of an exposure apparatus required for manufacturing an integrated circuit, there are many heat sources such as a stage driving motor and an exposure light source other than the laser oscillator of the interferometer itself. , Causing air fluctuations. Further, the temperature around the measurement beam also fluctuates due to a change in the condition of how the wind from the chamber outlet contacts the measurement beam due to the movement of the stage, which causes air fluctuation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a length measuring apparatus capable of reducing fluctuations of air in a space through which a measuring beam passes and performing extremely accurate length measurement. It is the purpose.

[0006]

In the present invention, the above object is achieved by flowing an air flow substantially parallel to a measurement beam of a laser interferometer and adjusting the flow velocity of the air flow to an appropriate value. Have achieved. Further, in the present invention, the above object is achieved by flowing a temperature-uniform and laminarized air flow over almost the entire length of the measuring beam of the laser interferometer.

[0007]

According to the present invention, since the air flow is made to flow substantially parallel to the measurement beam, a lump of air passes through the optical path of the measurement beam for a long time. Therefore, not only the period of the air fluctuation becomes long, but also the influence of the air mass overlaps with each other over time, thereby averaging. In addition, since the speed of the air flow sent to the measurement beam is adjusted to an appropriate value, it is possible to suppress turbulence of the air flow and the occurrence of stage vibration due to the air flow. Further, according to the present invention, since the temperature uniformized and laminarized air flow is caused to flow over almost the entire length of the measuring beam, the space through which the measuring beam passes can be obtained without increasing the velocity of the air flow too much. Air fluctuation can be reduced.

Further, since the air flow is subdivided in parallel with the flow, the air flow is made laminar, and is sent out to the path of the measuring beam while keeping the temperature uniform without entraining the air around the periphery. It is. For this reason, there is almost no fluctuation of air in the space through which the measurement beam passes, and the error in the wavelength of the measurement beam becomes very small. That is, in this way, the present invention enables extremely accurate length measurement.

[0009]

FIG. 1 is a perspective view schematically showing a configuration in which a length measuring apparatus according to the present invention is used for detecting coordinates of a precision moving stage such as an exposure apparatus for manufacturing an integrated circuit.
Hereinafter, the configuration will be described with reference to FIG. First,
The XY stage 1 is provided in the main body of the exposure apparatus so as to hold the wafer 6 and move it by a predetermined amount in the X and Y directions. X and Y are provided on two orthogonal sides of the stage 1.
The reflecting mirrors 4 and 5 in the directions are mounted respectively, and the reflecting mirrors 4 and 5 move together with the X and Y stages 1.

Further, a laser light source 10 having a stabilized frequency
From 0, a beam B1 including two components having polarization characteristics different from each other and having frequencies differing by about 2 MHz due to the Zeeman effect is emitted. The beam B1 is split by the beam splitter 7 into a beam B2 directed to the interferometer unit 2 for X-axis coordinate measurement and a beam B3 directed to the interferometer unit 3 for Y-axis coordinate measurement. Then, the interferometer unit 2 in the X-axis direction emits the measuring beam B4 to the reflecting mirror 4 attached to the XY stage 1, and receives the measuring beam B4 reflected by the reflecting mirror 4. Similarly, for the Y axis, the interferometer unit 3 emits the measuring beam B5 to the reflecting mirror 5 and receives the measuring beam B5 reflected by the reflecting mirror 5.

Next, the internal structure of the interferometer unit 2 (the same applies to the interferometer unit 3) will be described with reference to FIG. First,
The beam B2 is split by the polarizing beam splitter 21 into a reference beam B13 and a measurement beam B4 having different polarization directions. The measuring beam B4 transmitted through the polarizing beam splitter 21 is incident on the reflecting mirror 4 that can move at a predetermined speed together with the XY stage via the λ / 4 plate 24, is reflected there, and is reflected again by the λ / 4 plate 24. After that, the light enters the polarization beam splitter 21. Here, the measurement beam B4 is λ / 4.
Since the light has passed through the plate 24 twice, the polarization direction has changed by 90 °. This time, the light is reflected by the polarization beam splitter 21 and enters the right-angle prism 23. Here, measurement beam B
4 is reflected twice, returns to the incident direction, is reflected by the polarization beam splitter 21, and then enters the reflecting mirror 4 again and is reflected. Also in this case, the measurement beam B4 has passed through the λ / 4 plate 24 twice as before and the polarization direction 90 ° has changed, so that the measurement beam B4 reflected by the reflecting mirror 4 is now polarized beam splitter. Go straight through 21.

On the other hand, the other beam split by the polarizing beam splitter 21, ie, the reference beam B13
Enters a right-angle prism 22 as a reference mirror fixed at a predetermined position, where it is reflected twice and reenters the polarizing beam splitter 21 and is deflected by 90 degrees. In this way, the reference beam B13 and the measurement beam B4 again overlap and become the interference beam B6, and enter the photoelectric sensor 25.

Since the beam B2 has two components having different frequencies as described above, the beam B2 originally generates a beat (beat). However, the movement of the reflecting mirror 4 causes the reflecting mirror 4 to move. The frequency of the reflected measurement beam B4 changes due to the Doppler effect, and the beat period of the interference beam B6 changes. That is, the interference fringe generated by causing the measurement beam B4 and the reference beam B13 to interfere with each other changes. Therefore, the amount of movement of the reflecting mirror 4 (that is, the amount of movement of the XY stage) can be detected by detecting the change in the interference fringes with the photoelectric sensor 25.

Another possible configuration of the interferometer unit 2 other than the above is one in which the paths of the reference beam and the measurement beam are parallel. This configuration will be described with reference to FIG. The beam B2 emitted from the light source is divided into a measuring beam B4 and a reference beam B13 having different polarization directions by the polarizing beam splitter 31, and the measuring beam B4 is reflected by the reflecting mirror 4 moving together with the XY stage. Is the same as the case shown in FIG.

On the other hand, the reference beam B13 is separated from the measuring beam B4 by the polarizing beam splitter 31, then bent by the reflecting mirror 32, and passed through the λ / 4 plate 37 to a predetermined beam such as an exposure lens. The light enters a reflecting mirror 36 attached to an object fixed in position. Then, after being reflected by the reflecting mirror 36, the light is again incident on the reflecting mirror 32 through the λ / 4 plate 37, is bent by 90 °, and is polarized by the polarization beam splitter 31.
Incident on.

Here, the reference beam B21 has its polarization direction changed by 90 ° by passing through the λ / 4 plate 37 similarly to the measurement beam B4 described in FIG. 3, and this time passes through the polarization beam splitter 31. Then, the light enters the right-angle prism 33. Then, the reference beam B13 reflected by the two sides of the right-angle prism 33 passes through the polarizing beam splitter 31 again, is bent by the reflecting mirror 32, and is again λ
The light enters the reflecting mirror 36 via the / 4 plate 37. The reference beam B13 reflected here passes through the λ / 4 plate 37 and reaches the reflecting mirror 32, where it is bent by 90 ° and enters the polarizing beam splitter 31. Also in this case, the λ / 4 plate 3
7, the polarization direction of the reference beam B13 is changed by 90 °, and the reference beam B13 is deflected by 90 ° without transmitting through the polarization beam splitter 31, and overlaps with the measurement beam B4. Incident on the photoelectric sensor 35 as an interference beam B6.

Here, when the interferometer unit has the configuration shown in FIG. 4, since the optical paths of the reference beam B13 and the measurement beam B4 are parallel, the situation of the air fluctuation is the same. Since the effects cancel each other out, if the optical path lengths are equal, the optical path length is not affected in principle by the air density change (dead bus error = 0), which is considered to be advantageous as compared with the case of FIG. . However, in reality, there is also a difference in air density between the reference beam B13 and the measurement beam B4 shown in FIG.
Regarding the configuration of the interferometer unit, it is not clear which is more advantageous.

Next, a description will be given of the air guiding means, which is a main component of the present invention, and a subdivided member for achieving uniform temperature and laminar air flow. In the embodiment shown in FIG. 1, the air outlets of the air guiding means 8 and 9 are installed in parallel with the paths of the measuring beams B4 and B5, respectively. That is, the air guide means 8 for the X axis sends an air flow so as to cross the measurement beam B4 vertically, and similarly, the wind guide means 9 for the Y axis sends the air flow so as to cross the measurement beam B5 vertically. It is arranged to send.
Subdivision members 10 and 11, which will be described later, are disposed in the vicinity of the air outlets of the air guide means 8 and 9, respectively, to make the temperature of the air flow passing through the inside uniform and laminar.

Since it is desirable to supply air having a stable temperature substantially equal to the air temperature near the measuring beams B4 and B5 to the wind guide means 8 and 9, respectively, a length measuring device according to the present invention is installed. It is desirable to take air directly into the air guide means 8 and 9 from the air outlet for air conditioning of the chamber in which it is located. In addition, because the airflow needs some speed,
It is necessary to provide a fan at the air intakes of the air guide means 8 and 9, or to increase the cross-section of the intakes and gradually narrow the cross-section.

The air outlets of the air guide means 8 and 9 need to be installed above or below the stage 1 so that they do not come into contact with each other even if the stage 1 moves within the XY plane. Since it is difficult to install the apparatus with a surface plate or the like on which it is mounted, it is appropriate to arrange the apparatus so that air is blown diagonally from above or directly above as shown in FIG. Also, in FIG.
Although the configuration of the interferometer units 2 and 3 is shown in FIG. 3, a configuration having the configuration shown in FIG. 4 can be similarly applied. In this case, an air flow is equally applied to the measurement beam B4 and the reference beam B13. It is good to determine the duct shape of the air outlet of the air guide means 8 and 9 so that it may be sent.

Next, the subdivided members 10 and 1 according to the present invention will be described.
1 will be described with reference to FIG. Such a subdivision member is configured to subdivide the air flow in parallel with the flow of the air flow in order to make the air flow a laminar flow. That is, as the shape of the subdivision member, for example, the shape shown in FIGS. 2A and 2B can be considered. (A) is obtained by alternately bending thin metal plates or the like, and (b) is a line in which pipes having a square cross section are arranged, and both are installed in the vicinity of the air outlet in parallel with the outer cylinder of the air guide means. The shape of the subdivision member is not limited to the shape shown in FIG. 2, but in order to make the air flow a laminar flow, the subdivision member is longer than a certain length in the flow direction of the air flow. It is desirable to have.

The subdivision members 10 and 11 are preferably made of a material having good heat conductivity and a large heat capacity, such as a metal, in order to promote uniform temperature of the air flow. In order to increase the contact area with the air flow, it is desirable to subdivide the cross section of the air flow as much as possible within a range where the resistance to the flow of the air flow does not become too large. Further, when the present invention is applied to an exposure apparatus for manufacturing an integrated circuit as in the present embodiment, since generation of dust is an important problem, if the air flow is not disturbed, air filtration for preventing dust is performed. It is also possible to attach a filter to the air outlet of the air guiding means.

Next, the angle of the airflow with respect to the beam will be described. In the example of FIG. 1, an example is shown in which the air outlets of the air guide means 8 and 9 are installed in parallel along the measuring beams B4 and B5. 5 near the measurement beams B4 and B5, and an air flow at an angle parallel or nearly parallel to the measurement beams B4 and B5.

Here, an advantage of the arrangement as shown in FIG. 1 is that the space between the air outlet of the baffle means and the beam is close, and a uniform air flow is sent over the entire length of the beam. There is no need for wind speed. On the other hand, the advantage of flowing the air stream parallel to the beam is that even if the air stream is not completely uniform in temperature, and there are remaining air masses with different air temperatures, the air In order to pass over, the fluctuation period becomes long enough, and the influence of each air mass overlaps with each other in time.
It is conceivable that the influence on the measurement is reduced. However, in this case, air beams having different temperatures may be mixed in from the surroundings because the air flow does not sufficiently reach the part of the beam separated from the air outlet. For this reason, the direction in which the air flow is sent out is generally difficult to determine, and air may be sent at an intermediate angle between the two. Next, a description will be given of a method of adjusting the flow velocity of the air flow sent from the air guide means.
If the air flow is too slow, the air will not be sent enough to the beam, and if it is too fast, the air flow will be disturbed by the reflection of the air flow and the measurement object will vibrate, so adjust the air flow speed to an appropriate value. It is desirable to do. For this reason, if the optimum flow velocity is not known in advance, a ventilation hole is provided in the air guide means to adjust the speed of the air flow, or the speed and area of the air intake fan are made variable. Is preferably provided. In order to adjust the flow velocity of the air flow optimally, for example, the XY stage 1 is fixed, the coordinate reading value in the interferometer unit is monitored, and the flow velocity is adjusted so that the fluctuation is minimized. , And a method of adjusting the flow velocity so as to obtain the highest accuracy. Also, since the state of the air flow around the beam is different between when the XY stage 1 is stopped and when it is moving,
It is more desirable to control the flow velocity of the air flow to the optimum flow velocity in each case.

In an ordinary interferometer system, the atmospheric pressure, temperature, etc. around the measurement beam are monitored and wavelength correction is performed. However, in the length measuring apparatus according to the present invention, the atmospheric pressure, air temperature around the beam is measured by a wind guide means. The atmospheric pressure of the air sent out of the
These sensors may be provided inside or near the air outlet of the air guide means because they match the air temperature. further,
The subdivided member according to the present invention not only aims to equalize the temperature of the air flow, but also controls the temperature of the subdivided member itself so as to send the air flow uniformized to a desired temperature. It is possible. As a method of controlling the temperature of the subdivision member, for example, a method of flowing a liquid or the like into the interior (inner wall) of the subdivision member and controlling the temperature thereof can be considered, and a signal from the temperature sensor provided near the air outlet described above is considered. It is desirable to perform feedback control so that the air flow is maintained at a desired temperature. In this way, even if the temperature of the air taken into the air guide is unstable to some extent, the temperature of the air flow sent out from the air outlet becomes substantially constant, and high measurement accuracy can be stably secured. In addition, since the air guide means is a hollow cylinder except for the portion where the subdivision member is installed,
It is highly probable that even small vibrations will resonate, and especially when a fan is used in the air intake, it is considered that such air guide means is always vibrating. Then, when this vibration is transmitted to the interferometer unit, a measurement error corresponding to the amplitude will occur, so it is desirable to insulate the vibration between the air guide means and the interferometer unit and the object to be measured. Examples of this method include a method of insulating with a vibration-proof rubber or the like, a method of arranging a duct and an interferometer unit, and a method of placing an object to be measured so as not to be in direct contact. In addition, vibration and air turbulence due to movement and stoppage of the XY stage 1 may occur. However, since it is difficult to prevent these, it is necessary to wait several seconds after stopping the stage if necessary. Exposure and the like may be started. In addition, when there is a heat source such as a motor and a laser oscillator, such as an exposure apparatus,
Needless to say, it is desirable to thermally insulate these heat sources and the length measuring device as well as against vibration.

[0026]

As described above, in the present invention, the air near the passage of the measuring beam is always kept at a substantially uniform temperature, so that the air density hardly changes due to the temperature difference. For this reason, the wavelength of the measurement beam is kept substantially constant, and extremely high measurement accuracy can be stably secured.

Therefore, alignment of a mask and a substrate performed by an exposure apparatus for manufacturing an integrated circuit can be performed very accurately, which is extremely useful for achieving high integration of an integrated circuit.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration example of a subdivision member.

FIG. 3 is a schematic diagram showing a configuration of an interferometer unit.

FIG. 4 is a schematic diagram showing a configuration of an interferometer unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 XY stage 2, 3 Interferometer unit 4, 5 Reflecting mirror 8, 9 Wind guide means 10, 11 Subdivision member B13 Reference beam B4, B5 Measurement beam

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G01B 9/00-9/10 G01B 11/00-11/30 G03F 9/00 H01L 21/30

Claims (17)

(57) [Claims] 1. An exposure apparatus comprising: a stage on which a substrate onto which a pattern of a mask is transferred is mounted and two-dimensionally moved; and a laser interferometer for measuring a position of the stage. An exposure apparatus, comprising: wind guide means for flowing an air flow substantially in parallel with the measurement beam; and adjusting means for adjusting the flow rate of the air flow from the wind guide means. 2. The apparatus according to claim 1, wherein said adjusting means includes a relief hole having a variable area provided in said air guiding means.
3. The exposure apparatus according to claim 1. 3. The exposure apparatus according to claim 1, wherein said adjusting means changes the speed and area of a fan at an air intake of said air guide means. 4. The exposure apparatus according to claim 1, wherein said adjusting means adjusts the flow velocity of said air flow so as to reduce the output fluctuation of said laser interferometer. 5. An exposure apparatus according to claim 1, wherein said adjusting means adjusts the air flow to a flow rate suitable for the operation accuracy of the apparatus itself. 6. An exposure apparatus according to claim 1, wherein said adjusting means adjusts the flow velocity of said air flow according to an operation state of said stage. 7. An exposure apparatus according to claim 1, wherein said air guide means flows an airflow having a temperature substantially equal to an air temperature near a measurement beam of said laser interferometer. 8. The apparatus according to claim 1, wherein said air guide means has a subdivision member for laminating said air flow.
The exposure apparatus according to any one of items 4 and 7. 9. An exposure apparatus according to claim 8, wherein said subdivision member is made of a material having high thermal conductivity and large heat capacity. 10. An exposure apparatus according to claim 1, wherein said air guide means has an air filtration filter. 11. The air guide means has a temperature sensor near an air outlet of the air flow, and performs feedback control based on a signal from the temperature sensor so that the temperature of the air flow is maintained at a desired temperature. 5. The method according to claim 1, wherein
The exposure apparatus according to any one of claims 7 and 8. 12. An exposure apparatus comprising: a stage on which a substrate on which a pattern of a mask is transferred is mounted and two-dimensionally moved; and a laser interferometer for measuring a position of the stage. For almost the entire length of the measuring beam
An exposure apparatus, further comprising: a wind guiding means for flowing a temperature uniform and laminarized air flow. 13. An exposure apparatus according to claim 12, wherein an air outlet of said air guide means is arranged so that said air flow crosses said measuring beam vertically. 14. An exposure apparatus according to claim 12, wherein said air guide means adjusts the air flow to an optimum flow velocity and flows the air flow with respect to the measurement beam. 15. The exposure apparatus according to claim 12, wherein said air guide means flows an airflow having a temperature substantially equal to an air temperature near a measurement beam of said laser interferometer. 16. The air guide means has a temperature sensor near the airflow opening of the airflow, and performs feedback control based on a signal from the temperature sensor so that the temperature of the airflow is maintained at a desired temperature. 12. The method according to claim 12, wherein
The exposure apparatus according to any one of items 4 and 15. 17. An exposure apparatus according to claim 12, wherein said air guiding means has an air filtration filter.