JPH05283313A - Apparatus for measuring stage position - Google Patents

Abstract

PURPOSE:To increase the flow velocity of a gas in a vicinity of each beam even in a small amount of gas supply and to almost annihilate low frequency components which most cause fluctuation by covering the beam light path of an interferometer and simultaneously by flowing air conditioning air through the cover. CONSTITUTION:The respective light paths of reference beams B2x, B2y directing to fixed mirrors MRx, MRy and those of measuring beams B1x, B1y directing to movable mirrors MSx, MSy are provided with covers. A gas forcedly air- conditioned is flowed through these covers. This process almost uniform the flow velocity of a gas everywhere in proportion to blow air amounts from ducts 16x, 16y. Therefore, the beam light path of a photointerferometer can surely be air-conditioned, so that measuring errors due to air fluctuation is reduced. Further, the position of a stage can be measured stably with high reproducibility.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the position of a stage that moves one-dimensionally or two-dimensionally using an optical wave interferometer.

[0002]

2. Description of the Related Art Light wave interferometer (generally a laser interferometer)
It is a well-known technique to measure the position of a movable stage using. The intensity modulation type interferometer of the light wave interferometers is one in which a frequency-stabilized coherent laser beam (parallel light beam) is vertically incident on a moving mirror attached to a movable body and is fixed to the stage base. The laser beam (parallel light flux) is also vertically incident on the fixed mirror attached to the part connected to the, and the beams reflected by the moving mirror and the fixed mirror are interfered with each other, resulting in interference fringes (fringes).
Is detected photoelectrically. Therefore, when the stage moves, the brightness of the fringe repeatedly changes according to the wavelength of the laser beam and the amount of movement, and the photoelectric signal (sinusoidal) obtained at this time is converted into a digital pulse and measured by a counter Is required. A frequency modulation type interferometer is also known, in which a laser beam directed to each of the moving mirror and the fixed mirror has a certain frequency difference, and reflected beams from the moving mirror and the fixed mirror are interfered with each other to perform photoelectric detection. The amount of movement of the stage is measured from the phase transition of the beat signal (difference frequency) that is sometimes obtained.

An example of an exposure apparatus having a stage measured by a light wave interferometer will be described with reference to FIG. FIG. 1 shows a step-and-repeat type or step-and-scan type exposure apparatus, in which a reticle R on which an original image of a circuit pattern is drawn is a reticle stage RST.
The exposure light from the exposure illumination system ILS is uniformly illuminated while being held at. The pattern of the reticle R is image-projected via the projection optical system PL onto the wafer W coated with the photosensitive agent. The wafer W is placed on the wafer stage WST which moves two-dimensionally in a plane perpendicular to the optical axis AX of the projection optical system PL. In FIG. 1, wafer stage WST is assumed to move on the base in each of the left-right direction in the figure and the direction perpendicular to the paper surface. Although not shown in FIG. 1, the reticle stage RST and the projection optical system PL
Is attached to a column integrated with the base portion of wafer stage WST.

As shown in FIG. 1, one (or a plurality of) beams from a laser interference system (including a laser light source) IFM is projected onto a movable mirror MS fixed to a wafer stage WST, and an interferometer IFM is used. The other beam from is a fixed mirror (reference mirror) MR fixed to the lower part of the lens barrel of the projection optical system PL.
Projected on. The movable mirror MS is a mirror to be measured when the wafer stage WST moves in the left-right direction in FIG.
The reflecting surface of the movable mirror MS is formed elongated in a direction perpendicular to the paper surface of FIG.

Further, the interferometer IFM combines a reflected beam from the fixed mirror MR and a reflected beam from the movable mirror MS by a beam splitter BS to cause interference, and receives a photoelectric detector for receiving the interference beam and its photoelectric signal. It includes a pulse converter that outputs up-down pulses based on the above.
The up / down pulse from this pulse converter is reversibly counted by the up / down counter in the stage control system STD, and the position of wafer stage WST is measured. Further, the stage control system STD appropriately controls the output signal to the motor MT that drives the wafer stage WST according to the position measured by the up / down counter. When the stage control system STD receives the positioning target value (coordinate value) output from the main control system MCS, it is detected by the interferometer IFM and counted by the up / down counter.
The stage WST is moved so that the current position of T matches the target value within a certain allowable range.

In this type of exposure apparatus, the reticle R is aligned with the optical axis AX of the projection optical system PL,
A TTR (through-the-reticle) type alignment system AA1 for aligning the wafer W and the reticle R via the projection optical system PL, or for aligning the wafer W only via the projection optical system PL A TTL (through the lens) type alignment system AA2 is provided. Various kinds of alignment information from these alignment systems AA1 and AA2 are sent to the main control system MCS and used to calculate target values for accurate positioning of wafer stage WST.

Wafer stage WST shown in FIG. 1 generally has a moving stroke of about 30 cm to 50 cm. However, in the exposure apparatus for a liquid crystal panel, since the size of the plate as the exposed object is large, the moving stroke may reach about 80 cm. For this reason, the beam optical path from the interferometer IFM and the beam splitter BS fixed to the base unit side to the movable mirror MS also needs a distance corresponding thereto. Accordingly, the distance of the beam optical path to the fixed mirror MR is also determined. In the measurement using the interferometer IFM,
The wavelength of the laser beam is the standard for measurement. The actual length of one wavelength of the beam varies depending on the refractive index of the medium in which the beam propagates. Therefore, when the atmospheric pressure changes, the refractive index of the atmosphere also changes accordingly, so this type of laser interferometer is equipped with an automatic wavelength compensation mechanism that detects changes in atmospheric pressure with a sensor, and one wavelength of the beam is actually measured. The constants for conversion to dimensional values are corrected in the ppm order.

However, when the atmosphere in the beam optical path does not uniformly change the refractive index everywhere, but when the refractive index changes locally in the beam optical path, it appears as fluctuation of the measurement value by the interferometer. .. For example, when a gas having a temperature difference from the surroundings slowly crosses the beam optical path, the measured value (the value of the counter) changes unstable within a certain range even though the stage WST is correctly stationary. As an example,
If the minimum resolution of the interferometer is 0.01 μm, the amount of fluctuation due to the gas having a temperature difference that slowly traverses the beam optical path may reach ± 0.1 μm at worst. Since this has a fluctuation width of 0.2 μm, it is a value that cannot be practically used as an apparatus for exposing a pattern having a line width of about 0.5 μm. The effect of this fluctuation becomes a problem in two situations. One is that the random error included in the position measurement value at the time of various alignments using the laser interferometer becomes large and the reproducibility of the alignment is deteriorated.
The other is that when the wafer stage WST is kept stationary by servo control so that the measurement value of the interferometer becomes a constant value, the wafer stage WST follows a very small amount due to fluctuations and does not accurately settle. This appears as a thick line width and poor resolution when the reticle pattern is exposed on the wafer W. In other words, no matter how much the resolution is increased by the projection optical system and the illumination system, it will not be fully utilized.

Further, in the local change in the refractive index of gas in the beam optical path, a component having a relatively short period (10 Hz or more)
Components with a long cycle (less than 10 Hz) coexist, but of these, fluctuations of low frequency components of about 0.1 Hz to several Hz become a particular problem. Because the high fluctuation component of several Hz or more, the value of the counter of the interferometer is read several times by a computer etc. at an extremely short sampling interval (for example, about 1 mSec), and the fluctuation component of the high frequency is detected. This is because it can be practically ignored.

Therefore, it is considered that the fluctuation of the low frequency component is reduced by a method such as positively supplying gas (air) to the beam optical path, or covering the beam optical path with a cylindrical covering. ing.

[0011]

As one of the conventional techniques, an air duct for blowing out gas (clean air) perpendicular to or parallel to the beam optical path of a laser interferometer is used. It was proposed to provide. However, in the case of ejecting gas in parallel with the beam optical path, the ejection port of the air duct needs to be placed behind or in the vicinity of the laser interferometer and directed toward the moving mirror of the stage. In this case, when the stage is at the farthest position from the laser interferometer, the gas near the moving mirror is almost not parallel to the beam optical path and becomes a turbulent flow with a small flow velocity, and the laser light source for the laser interferometer is a heat source Convection may occur. The convection itself does not significantly affect the measurement of the laser interferometer. This is because this type of exposure apparatus is originally stored at a constant temperature (for example, 23 ± 0.1 ° C.) in the environmental chamber, and the influence of convection is reduced by controlling the temperature control of the chamber. ..

When the gas is made to flow obliquely from above in the direction perpendicular to the beam optical path, the gas ejection port must be arranged along the beam optical path. In this case as well, the problem of convection may similarly occur, but since the device itself is stored in the chamber as described above, its influence is small. However, at the position closest to the stage laser interferometer, the gas from the ejection port is directly sprayed on the wafer or the like on the stage.

As described above, when the gas is sprayed from the direction parallel to the beam optical path or the direction perpendicular to the beam optical path, since the jet port is simply provided in the free space, the gas flow cannot be accurately controlled. Dust generation caused by turbulence also became a problem. In particular, in this type of exposure apparatus, the storage space is controlled to about class 10 (less than 10 dust particles per 1 m ³ ). Therefore, the chamber that houses the exposure apparatus also cleans the internal air so as to ensure Class 10 (or Class 100). However, since the beam optical path of the laser interferometer is generally located at the lower part of the device, if the ejection port is simply directed toward the optical path, the dust generated in the movable part such as the stage or the friction part due to convection or (turbulent flow) will occur. (Micron-sized oil mist, metal powder, etc.) may fly up above the stage and eventually adhere to the wafer. Further, in order to blow air over the entire optical path, a large-capacity air conditioning mechanism is required, and a large-scale facility including a duct mechanism has to be used.

On the other hand, coating the beam optical path with an expandable pipe is also an effective method for fluctuations, but simply coating it may cause stagnant air in the pipe, or the pipe accompanying movement of the stage. Due to the expansion and contraction of, relatively large density and change of air in the pipe, that is, change of refractive index may occur. Therefore, an object of the present invention is to solve the above problems and to obtain an apparatus capable of stable measurement by an interferometer.

[0015]

Therefore, in the present invention,
The reference beam optical path toward the fixed mirror and / or the measurement beam optical path toward the movable mirror is covered by the covering means (the fixed cover 1).
No. 0, movable covers 12, 30, 31, 40, etc.), and temperature-controlled gas (temperature-controlled air) is supplied to the inside of these covering means.

[0016]

In the present invention, the beam optical path of the interferometer is covered with a cover and at the same time, temperature control air is made to flow into the cover, so that even if the gas supply flow rate is smaller than in the conventional case, the gas in the vicinity of each beam The flow velocity increases, and the low-frequency component that causes the largest fluctuation is almost eliminated.

[0017]

FIG. 2 shows the structure when the position measuring apparatus according to the first embodiment of the present invention is applied to an exposure apparatus similar to that shown in FIG. 2, members having the same functions as those in FIG. 1 are designated by the same reference numerals. Although not shown in FIG.
Since wafer stage WST translationally moves in a two-dimensional manner within a predetermined orthogonal coordinate system XY, a laser interferometer for position measurement is provided in each direction of movement axes X and Y. In FIG. 2, the Y-axis laser interferometer IFMg and its optical path are shown in detail, and the X-axis interferometer (IFMx) has the same configuration, so that the illustration is omitted. However, a beam B directed to each of the X-axis moving mirror MSx and the fixed mirror MRx.
Only 1x and B2x are shown. Here, as shown in FIG. 2, an orthogonal coordinate system XYZ is defined, the Z axis is parallel to the optical axis AX of the projection optical system PL, and the reflecting surfaces of the movable mirror MSx and the fixed mirror MRx are parallel to the YZ plane. Moving mirror MSy and fixed mirror MRy
It is assumed that each of the reflecting surfaces of is arranged so as to be parallel to the XZ plane. The beam from the laser light source for the interferometer is Bo, the beam from the interferometer IFMy to the moving mirror MSy, the beam reflected there is B1y, and the beam reflected to the fixed mirror MRy, and the beam reflected there is B2.
Let y.

The optical path of the reference beam B2y forming the interferometer IFMy is covered by a prismatic fixed cover 10y, and the optical path of the measurement beam B1y is formed by a prismatic movable cover (inner cylinder) 12y and a fixed cover. It is covered with the outer cover portion (outer cylinder) 11y for the interferometer 10y. The movable cover 12y is provided so that it can be inserted into and removed from the outer cover 11y in the beam optical path direction. However, since the movement of the movable cover 12y in the beam optical path direction needs to be interlocked with the movement of the wafer stage WST in the Y direction, the end of the movable cover 12y that faces the moving mirror MSy is moved to the wafer stage WST via the holding member 13y. It is attached to a part. However, since wafer stage WST also moves in the X direction, holding member 13y is provided movably in the X direction along guide portion 14y extending in the X direction on the side portion of stage WST.

More specifically, the fixed cover 10 will be described.
The length y is made so as to cover almost the entire optical path of the beam B2y traveling (or reflected) from the interferometer IFMy to the fixed mirror MRy via the beam splitter BSy and the mirror M. On the other hand, the movable cover 12y and the outer cover portion 11y
Is made to have a length so as to cover almost the entire optical path of the beam B1y traveling (or being reflected) from the beam splitter BSy to the movable mirror MSy. Movable cover 12y
The amount of movement between the most protruding position and the most retracted position is substantially equal to the movement stroke of wafer stage WST in the Y direction.

Thus, the reference optical path (beams B2y, B2x) and the measuring optical path (beams B1y, B1) of the laser interferometer are described.
x) and a cover is provided for each of them, and at the same time, a blower pipe 15y for supplying temperature-controlled clean air into each cover.
And the duct 16y are provided in a part of the fixed cover 10y.
The blower pipe 15y guides a part of the clean temperature control gas made in the environmental chamber that houses the exposure apparatus to the duct 16y. Also duct 16y
Supplies the temperature control gas into the outer cover portion 11y and the movable cover 12y through the fixed cover 10y. The temperature control gas is at both ends of the fixed cover 10y (the mirror M side and the fixed mirror M).
Ry side) flows out to the outside, and an end opening of the movable cover 12y on the moving mirror MSy side and the outer cover portion 11 are provided.
It also flows out from the respective end openings of y on the side of the beam splitter BSy. The flow rate can be remarkably reduced as compared with the conventional case where a jet port is provided in an open space and air is blown into the optical path. For this reason, dust rising by the gas flowing out from each cover is also reduced. For safety, the duct 16y contains HEPA (High Efficiency Pa of 0.1 μm class).
rticle Air) Filter may be put in.

FIG. 3 is a partial cross section of the structure of each cover shown in FIG. 2 as seen from the side, and here shows the cover structure of the interferometer optical path for the X axis, which is not shown in FIG. Further, the same members as those shown in FIG. 2 among the members in FIG. 3 are designated by the same reference numerals. Now, the wafer stage WS shown in FIG.
T is actually a Y stage 18Y that moves one-dimensionally on the base 20 in the Y direction (direction perpendicular to the paper surface of FIG. 3) and one-dimensional movement on the Y stage 18Y in the X direction as shown in FIG. The X stage 18X, the ZL stage 17 that slightly moves on the X stage 18 for leveling and autofocus, and the wafer holder WH that slightly moves the wafer W around the Z axis on the ZL stage 17.
Further, the X-axis moving mirror MSx is fixed around the ZL stage 17, and the measurement beam B1x is horizontally projected on the reflection surface thereof at substantially the same height as the surface of the wafer W.

The fixed cover 10x is the projection optical system PL.
The outer cover portion 11x integrally fixed to the fixed cover 10x is fixed to a part of the base 20 by a mounting metal fitting 23.
Fixed through. On the other hand, the end of the movable cover 12x is attached to the guide portion 14x on the side of the X stage 18X via the holding member 13x. The movable cover 12
The other end of x is always housed inside the outer cover portion 11x, and is supported via a movable body 19 such as a roller for vibration prevention.

With such a structure, the temperature-controlled gas (air) flows to the outside through the duct 16x in the respective channels in the flow path as shown by the arrow in FIG. That is, part of the blown air flows toward the tip inside the fixed cover 10x, flows out to the outside in the vicinity of the fixed mirror MRx, and another part of the air flows to the movable cover 12x of the outer cover portion 11x.
While flowing out to the outside through a gap between the movable cover 12x and the movable cover 12x, it flows toward the tip in the movable cover 12x, and then to the outside in the vicinity of the movable mirror MSx. As shown in FIG. 2, the fixed cover 10x (10y) is provided on the mirror M side and the outer cover portion 11x.
A small opening for passing each of the beams B2x and B1x is formed on the beam splitter BSx (BSy) side of (11y), but a part of the blown air also flows out from the small opening. However, it is preferable to minimize the flow rate from this small opening.

As shown in FIGS. 2 and 3, the duct 16
Since the temperature-adjusting air jetted from the x and 16y into the fixed cover 10 and the outer cover 11 is set so as to proceed in a direction substantially perpendicular to the beams B1x and B2x, the inside of the cover in the vicinity of the blowing air outlet is blown. Then, the air is beam B
Fixed cover 1 while spiraling around 1x and B2x
0, or moveable cover 12.

As described above, as in the first embodiment, the fixed mirror MR
A cover is provided for each of the optical paths of the reference beams B2x and B2y directed to x and MRy and the optical paths of the measurement beams B1x and B1y directed to the movable mirrors MSx and MSy, respectively, and the covers are forcibly heated. When the adjusted gas is flowed, it is possible to obtain an effect that the flow velocity of the gas in each cover is almost uniform everywhere in proportion to the amount of air blown from the ducts 16x and 16y.

In this embodiment, the fixed mirrors MRx, MR
Since the temperature-controlled gas is constantly sprayed onto each of y and the movable mirrors MSx and MSy, the vicinity of the fixed mirror mounting portion of the projection optical system PL and the vicinity of the movable mirror mounting portion of the ZL stage 17 are actively air-cooled. This makes it possible to reduce thermal (temperature) instability factors of the projection optical system and the wafer stage. For this reason, the side effect that the deterioration of the imaging performance due to the transfer of the amount of heat generated by the absorption of part of the exposure light by the optical element in the projection optical system to the lens barrel can be suppressed is also obtained. Be done.

FIG. 4 shows the structure of the optical path cover according to the second embodiment of the present invention. The point that is largely different from the first embodiment is that
The movable cover has a multi-stage structure. That is, in the first embodiment described above, as is clear from FIG. 3, since the movable range of one movable cover 12x, 12y is the movement stroke of the wafer stage WST in the X and Y directions, the movable cover 12x, The size of 12y becomes long. Therefore, in the second embodiment, as shown in FIG. 4, the movable cover is a first movable cover 30x (30y) whose front end is fixed to the wafer stage WST, and the first movable cover 30x (3y).
0y) and a second movable cover (intermediate cover) 31x (31y) that connects the outer covers 11x and 11y. The second movable cover 31x (31y) is provided with each interferometer measurement value in the X direction or the Y direction of the wafer stage WST.
Alternatively, it is configured to be expandable / contractible based on ON / OFF of a limit switch provided on the stage, and its movement is driven by an air cylinder, a belt / pulley, etc. (not shown).

Also in FIG. 4, the same members as those in FIG. 2 or FIG. 3 are designated by the same reference numerals. As is apparent from FIG. 4, the first movable cover 30x (30y) is not
The movable cover 31x (31y) can be moved to expand and contract,
It is supported via a movable body (roller) 32 for preventing vibration.
The second movable cover 31x (31y) is the outer cover portion 1
The inside of 1x (11y) is supported via the movable body 33.

According to the second embodiment, since the optical paths of the measurement beams B1x and B1y are covered with the expandable cover of the multistage structure, the space when the movable mirror of the wafer stage WST is closest to the beam splitter BS side. It is possible to easily arrange the extendable cover even if the number is not small. FIG. 5 shows the structure of the optical path cover according to the third embodiment of the present invention. The difference from the first and second embodiments so far is that
This is to change the expansion / contraction structure of the measurement optical path cover while reducing the size of the movable cover that is movable integrally with the wafer stage WST in the optical path direction.

In FIG. 5, the movable cover 40 having a short dimension is used.
y (40x for X axis) is provided below the fixed cover 10y (10x) so as to be movable in the optical path direction. Therefore, a guide rail, a drive belt, etc. are provided on the lower surface of the fixed cover 10y (10x), and the movable cover 40y (4
0x) has the tip of the moving mirror M depending on the measurement value of the interferometer.
It is forcibly driven so as to keep a constant interval with Sy (MSx). Around the movable cover 40y, a plurality of open / close covers 41Y-1, 41Y-2, ...
1Y-7 is provided. These open / close covers 41Y are shown in FIG.
When it is opened horizontally by 90 °, the moving mirror MSy is positioned above the upper surface of the moving mirror MSy.
Interlocking with the movement of y in the optical path direction, that is, the movement of the movable cover 40y, the covers 41Y-1 and 41Y-2 are sequentially opened. Therefore, when the movable mirror MSy comes closest to the outer cover portion 11y side, all the opening / closing covers 41Y
-1 to 41Y-7 are opened horizontally. When the opening / closing cover 41Y is closed, the movable cover 40y is closed.
However, a small space is provided to prevent sliding on the inner wall.

Further, although not shown in FIG. 5, the same opening / closing cover is provided on the opposite side of the fixed cover 10y, and the opening / closing covers forming a pair on the left and right sides are opened and closed at substantially the same time. The movable cover 40y may be attached to a part of the guide portions 14x, 14y of the wafer stage WST via the holding members 13x, 13y as in FIGS. FIG. 6 shows the fixed covers 10x and 10 shown in FIGS.
A partial cross section of y is shown, and a pipe duct 50 for temperature control gas flow extending in the optical path direction is provided on the inner walls of the fixed covers 10x and 10y, and a flow passage 51 inside the pipe duct 50 is provided.
A temperature control gas is passed through the pipe duct 50, and a plurality of jet ports 52 are formed in a line on the side wall of the pipe duct 50. The air from the ducts 16x and 16y shown in FIG. 2 or FIG. 3 is guided to the flow path 51 of the pipe duct 50 so as to be concentrated. Therefore, the air from the ejection port 52 is ejected so as to traverse the entire beam optical path from a substantially vertical direction.
It should be noted that the air from each ejection port 52 is not ejected exactly perpendicular to the optical path of the beam, but the fixed covers 10x, 10
It is desirable to eject the light obliquely toward the tip (fixed mirrors MRx, MRy) side of y.

FIG. 7 shows the structure of an optical path cover according to a fourth embodiment of the present invention. The difference of this embodiment from the previous embodiments is that only the reference beam optical path for the fixed mirror MR is covered. Is provided, and no special cover is provided for the measurement beam optical path for the movable mirror MS. 7, the same members as those in FIGS. 2 and 3 are given the same reference numerals.

In FIG. 7, a fixed cover 10x (10y for the Y-axis) is fixed to the column 22 and the base 20 via mounting members 21 and 23, respectively. Fixed cover 1
The duct 16x is provided at 0x as in the previous embodiment,
Clean temperature control air flows through the fixed cover 10x to the outside from the fixed mirror MRx side. Fixed cover 10x
A plurality of small openings 60 for ejecting the temperature control air toward the optical path of the measurement beam B1x are formed in a line on the lower surface of the.

In FIG. 7, the lower surface of the fixed cover 10x and the upper surface of the movable mirror MSx are illustrated to have a relatively large distance, but this can be set to several mm to 1 cm. Therefore, the distance between the small opening 60 and the beam B1x can be set to about 1 cm, and the air having a large flow velocity is jetted almost vertically to the optical path of the beam B1x.

In the present embodiment, the same idea as in the prior art that air is blown in the open space is applied to the beam path for measurement. However, it has been confirmed by experiments that it is significantly more effective than the conventional method. This is because the temperature control gas ejection port (small opening 60) is arranged in the vicinity of the measurement beam optical path along the optical path, so that the gas in the state where the flow velocity near the ejection port is high can be used. Therefore, even if the flow rate of the air supplied from the ducts 16x and 16y per unit time is small, the flow velocity in the vicinity of the small opening 60 can be increased by adopting the structure in which the air is effectively ejected from the small opening 60. Become.

The structure of the fixed cover 10x shown in FIG. 7 and the structure shown in FIG. 6 may be combined to form a cover structure as shown in FIG. In FIG. 8, the fixed cover 10x has a two-layer structure, and the air blown from the duct 16x has an upper cover that covers the optical path of the reference beam B2x and a plurality of small openings 60 for ejecting air. It is diverted to the inside of the lower cover. On the leeward side of each small opening on the inner wall of the lower cover, a baffle plate (collar) 61 is provided to effectively guide the gas passing through the lower cover to the small opening 60.
Is provided. According to the embodiments shown in FIGS. 7 and 8, since there is no movable member that moves in conjunction with the moving positions of the movable mirrors MSx and MSy, dust is inevitably avoided due to the movable structure. It can be prevented.

Moreover, since a part of the clean temperature-controlled gas blown into the fixed cover also highly efficiently air-conditions the beam light path for measurement, the measurement stability is the same as in the previous embodiments. improves. FIG. 9 shows the structure of an optical path cover according to the fifth embodiment of the present invention, which is a slightly modified version of the structure shown in FIG. As shown in FIG. 9, in the present embodiment, a part of the measurement beam B1x (B1y) on the beam splitter side is covered with the outer cover portion 11x, and the air from the duct 16x is covered by the outer cover portion 11x in the optical path of the beam B1x. Efficiently concentrate on the beam splitter side. The outer cover portion 11x is made so as not to spatially interfere with the stage within the movement stroke of the wafer stage WST. Then, as shown in FIG. 9, at a position where the wafer stage WST is away from the interferometer IFX, the beam splitter, etc., the air from the plurality of small openings 60 formed on the lower surface of the fixed cover 10x causes the measurement beam B1x to move. Actively regulate the temperature of the optical path. Therefore, the small opening 6
Zeros are formed in a line at a predetermined interval on approximately half of the lower surface of the fixed cover 10x on the tip side.

Although the respective embodiments of the present invention have been described above, the present invention can also be applied to an apparatus having another two-dimensional or one-dimensional stage using a laser interferometer as a length measuring device. Furthermore, the present invention can be applied to a system in which the beam for the fixed mirror and the beam for the movable mirror are not parallel to each other.

[0039]

As described above, according to the present invention, since the beam optical path of the light wave interferometer can be reliably air-conditioned, the measurement error due to the fluctuation of air is reduced, and the position of the stage can be measured stably and with good reproducibility. .. According to the experiment, the measurement error due to the fluctuation before the covering means (cover) is provided is ± 0.04 μm.
Although there was a degree of occurrence, by providing a cover and air conditioning the inside, the error due to fluctuation can be reduced to about ± 0.01 μm.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a conventional projection exposure apparatus.

FIG. 2 is a perspective view showing the configuration of a stage with a light wave interferometer according to the first embodiment of the present invention.

3 is a partial cross-sectional view showing the structure of an optical path cover of the light wave interferometer of FIG.

FIG. 4 is a partial sectional view showing a structure of an optical path cover according to a second embodiment.

FIG. 5 is a perspective view showing a structure of an optical path cover according to a third embodiment.

FIG. 6 is a perspective view showing a modified example of a structure for ejecting temperature-controlled air in the fixed cover.

FIG. 7 is a partial sectional view showing the structure of an optical path cover according to a fourth embodiment of the present invention.

8 is a sectional view showing a modification of the optical path cover structure of FIG.

FIG. 9 is a partial sectional view showing the structure of an optical path cover according to a fifth embodiment of the present invention.

[Explanation of symbols]

 WST Wafer Stage MR, MRx, MRy Fixed Mirror MS, MSx, MRy Moving Mirror IFM, IFMy Interferometer 10x, 10y Fixed Cover 11x, 11y Outer Cover 12x, 12y, 30x, 31x, 40y Movable Cover 15y Blower Pipe 16x, 16y Blower duct B1x, B1y Measurement beam B2x, B2y Reference beam

Claims (3)

[Claims] 1. A stage movable in a predetermined direction, a movable mirror fixed to a part of the stage with a reflection surface perpendicular to the movement direction, and fixedly arranged with respect to a base portion of the stage. A fixed mirror, projecting a coherent light beam substantially perpendicular to each of the movable mirror and the fixed mirror, and receiving by interfering the light beam reflected by each of the movable mirror and the fixed mirror, In a position measuring device including a light wave interferometer that photoelectrically detects the interfered beam and outputs a measurement signal, and a position detection circuit that detects the position of the stage based on the measurement signal from the light wave interferometer, First coating means for covering a beam optical path from the light wave interferometer to the fixed mirror; a beam optical path from the light wave interferometer to the movable mirror, and a dimension of the stage in the direction of the beam optical path Changed with Second coating means for covering while; gas supply means for supplying a gas of a controlled temperature at a predetermined flow rate to each of the insides of the first coating means and the second coating means; Position measuring device characterized by. 2. A stage movable in a predetermined direction, a movable mirror fixed to a part of the stage with a reflection surface perpendicular to the movement direction, and fixedly arranged with respect to a base portion of the stage. A fixed mirror, projecting a coherent light beam substantially perpendicular to each of the movable mirror and the fixed mirror, and receiving by interfering the light beam reflected by each of the movable mirror and the fixed mirror, In a position measuring device including a light wave interferometer that photoelectrically detects the interfered beam and outputs a measurement signal, and a position detection circuit that detects the position of the stage based on the measurement signal from the light wave interferometer, Fixed coating means for covering the beam optical path from the light wave interferometer to the fixed mirror; and gas supply means for supplying a gas of a controlled temperature at a predetermined flow rate are provided inside the fixed coating means. Characteristic stage Position measuring device. 3. The apparatus according to claim 1, wherein the light beam directed to the fixed mirror and the light beam directed to the movable mirror are arranged in parallel to each other, and light directed to the fixed mirror is used. The first coating means or the fixed coating means for covering the optical path of the beam has an opening at a position close to the fixed mirror side, and allows the gas of the controlled temperature to flow out through the opening. Characteristic stage position measuring device.