JP3089802B2 - Stage position measuring apparatus, projection exposure apparatus and projection exposure method - Google Patents

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 which moves one-dimensionally or two-dimensionally, a projection exposure apparatus using the apparatus, and a projection exposure method.

[0002]

2. Description of the Related Art Lightwave interferometers (generally, laser interferometers)
Measuring the position of the movable stage using is a well-known technique. An intensity-modulated interferometer is a type of light wave interferometer in which a frequency-stabilized coherent laser beam (parallel light beam) is vertically incident on a movable mirror attached to a movable body, and is fixed to the stage base. A laser beam (parallel light beam) is also vertically incident on the fixed mirror attached to the part connected to the mirror, causing the beams reflected by the moving mirror and the fixed mirror to interfere with each other, and their interference fringes (fringe)
This is to detect the change of the photoelectric conversion. Therefore, when the stage moves, the brightness of the fringe changes repeatedly according to the wavelength and the amount of movement of the laser beam. The photoelectric signal (sinusoidal shape) obtained at this time is converted into a digital pulse and measured by a counter, and the position of the stage is measured. Ask for. Also known is a frequency modulation type interferometer, in which a laser beam directed to each of a moving mirror and a fixed mirror has a certain frequency difference, and the reflected beams from the moving mirror and the fixed mirror interfere with each other to perform photoelectric detection. The movement amount of the stage is measured from the phase transition of the beat signal (difference frequency) obtained at the time.

Here, an example of an exposure apparatus having a stage measured by an optical 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 circuit pattern is drawn is a reticle stage RST.
Is uniformly illuminated with the exposure light from the exposure illumination system ILS. The pattern of the reticle R is image-formed and projected on the wafer W coated with the photosensitive agent via the projection optical system PL. Wafer W is placed on wafer stage WST which moves two-dimensionally in a plane perpendicular to optical axis AX of projection optical system PL. In FIG. 1, it is assumed that wafer stage WST moves on the base in each of the left-right direction and the direction perpendicular to the sheet of FIG. Although not shown in FIG. 1, reticle stage RST and projection optical system PL
Is attached to a column integrated with the base of the wafer stage WST.

As shown in FIG. 1, one (or a plurality of) beams from a laser interferometer (including a laser light source) IFM are projected onto a moving mirror MS fixed to a wafer stage WST, and interferometer IFM The other beam from the mirror is a fixed mirror (reference mirror) MR fixed below the lens barrel of the projection optical system PL.
Is projected to 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 to be elongated in a direction perpendicular to the paper surface of FIG.

The interferometer IFM combines a reflected beam from the fixed mirror MR and a reflected beam from the movable mirror MS with a beam splitter BS and causes them to interfere with each other, and a photoelectric detector for receiving the interference beam; And a pulse converter that outputs an up / down pulse based on the above.
The up / down pulse from the pulse converter is reversibly counted by an up / down counter in the stage control system STD, and the position of the wafer stage WST is measured. Further, stage control system STD appropriately controls an output signal to motor MT for driving wafer stage WST in accordance with a position measured by an up / down counter. When receiving the positioning target value (coordinate value) output from the main control system MCS, the stage control system STD detects the wafer stage WS detected by the interferometer IFM and counted by the up / down counter.
Stage WST is moved such that the current position of T matches its target value within a certain allowable range.

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

The wafer stage WST shown in FIG. 1 generally has a movement stroke of about 30 cm to 50 cm. However, in an exposure apparatus for a liquid crystal panel, a movement stroke may reach about 80 cm because of a large size of a plate as an object to be exposed. For this reason, the interferometer IFM fixed to the base unit and the beam optical path from the beam splitter BS to the movable mirror MS also need to have a distance corresponding to that. Accordingly, the distance of the beam optical path to the fixed mirror MR is determined. In the measurement using the interferometer IFM,
The wavelength of the laser beam is a reference 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 changes accordingly. Therefore, in this type of laser interferometer, an automatic wavelength compensation mechanism for detecting the change in the atmospheric pressure with a sensor is provided, and one wavelength of the beam is actually changed. The constant to be converted into the dimension value is corrected on the order of ppm.

However, if the refractive index does not change uniformly in the atmosphere in the beam optical path everywhere but locally changes in the refractive index in the beam optical path, it appears as a fluctuation of a value measured by an interferometer. . For example, when a gas having a temperature difference from the surroundings slowly crosses the beam optical path, the measured value (counter value) fluctuates unstable within a certain range even though the stage WST is correctly stopped. As an example,
Assuming that the minimum resolution of the interferometer is 0.01 μm, the amount of fluctuation due to a gas having a temperature difference that slowly crosses the beam optical path may be as large as ± 0.1 μm. Since the fluctuation width is 0.2 μm, this value is not practical for an apparatus for exposing a pattern having a line width of about 0.5 μm. The effect of this fluctuation is a problem in two situations. One is that random errors included in position measurement values at the time of various alignments using a laser interferometer increase, and the reproducibility of the alignment deteriorates.
The other is that when the wafer stage WST is kept stationary by servo control so that the measured value of the interferometer becomes a constant value, the fluctuation causes the wafer stage WST to follow only a very small amount and does not settle accurately. This appears as an increase in the line width and poor resolution when the reticle pattern is exposed on the wafer W. That is, no matter how much the resolving power is increased by the projection optical system and the illumination system, the resolution is not sufficiently utilized.

The local refractive index change of gas in the beam optical path includes a component having a relatively short period (10 Hz or more),
A component having a long cycle (less than 10 Hz) is mixed, and fluctuation of a low-frequency component of about 0.1 Hz to several Hz is particularly problematic. This is because high fluctuation components of several Hz or more can be obtained by reading the value of the counter of the interferometer several times at a very short sampling interval (for example, about 1 mSec) with a computer or the like and averaging the values. This is because it can be substantially ignored.

Therefore, it is conceivable to reduce the fluctuation of the low frequency component by a method such as actively supplying gas (air) to the beam optical path or covering the beam optical path with a cylindrical coating. ing.

[0011]

One approach that has been considered in the past is to provide an air duct that blows out gas (clean air) perpendicular to or parallel to the beam path of the laser interferometer. It was proposed to provide. However, when ejecting gas in parallel with the beam optical path, the ejection port of the air duct needs to be located behind or near the laser interferometer and point to the moving mirror of the stage. In this case, if the stage is located farthest from the laser interferometer, the gas near the moving mirror becomes turbulent with a small flow velocity and hardly parallel to the beam optical path. it may occur is a convection. 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 an environmental chamber, so that the influence of convection is reduced by controlling the temperature of the chamber. .

When the gas is caused 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, a problem of convection may occur, but the influence is small since the apparatus itself is stored in the chamber as described above. However, at the position closest to the stage laser interferometer, the gas from the ejection port is directly blown to the wafer or the like on the stage.

As described above, when gas is blown in a direction parallel to or perpendicular to the beam optical path, the gas flow cannot be accurately controlled because a jet port is simply provided in the free space. Dust generation due to turbulence also became a problem. In particular, in this type of exposure apparatus, the storage space is managed to a class 10 (less than 10 dusts in 1 m ³ ). Therefore, the air in the chamber accommodating the exposure apparatus is also cleaned so as to guarantee class 10 (or class 100). However, since the beam path of the laser interferometer is generally located at the lower part of the apparatus, if the ejection port is simply directed to the optical path, dust generated in a movable portion such as a stage or a friction portion due to convection or (turbulent flow). (Micron-sized oil mist, metal powder, etc.) may be raised above the stage and eventually adhere to the wafer. Further, in order to blow the entire optical path, a large-capacity air-conditioning mechanism was required, and large-scale equipment including a duct mechanism had to be provided.

On the other hand, covering the beam optical path with an extendable pipe or the like is also an effective technique against fluctuations. However, simply covering the beam path causes the air inside the pipe to stagnate, or the pipe accompanying the movement of the stage. Due to the expansion and contraction of the air, a relatively large air density and change, that is, a change in the refractive index may occur in the pipe. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and to obtain an apparatus capable of performing stable measurement by an interferometer.

[0015]

Means for Solving the Problems 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 are covered by the covering means (fixed cover 1).
0, movable covers 12, 30, 31, 40, etc.), and a temperature-controlled gas (temperature-controlled air) is supplied into the inside of these covering means.

[0016]

According to the present invention, the beam optical path of the interferometer is covered with the cover, and at the same time, the temperature-regulated air is flowed through the cover. The flow velocity increases, and there is almost no low frequency component that causes the largest fluctuation.

[0017]

FIG. 2 shows a structure in which 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. In FIG. 2, members having the same functions as those in FIG. 1 are denoted by the same reference numerals. Although not shown in FIG. 1,
Since wafer stage WST translates two-dimensionally in a predetermined orthogonal coordinate system XY, a laser interferometer for position measurement is provided in the directions of moving axes X and Y. FIG. 2 shows the Y-axis laser interferometer IFMg and its optical path in detail, and the X-axis interferometer (IFMx) is not shown because it has the same configuration. However, the beam B directed to each of the movable mirror MSx for X-axis 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 optical axis AX of the projection optical system PL is parallel to the Z axis, 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
Are arranged so as to be parallel to the XZ plane. The beam from the laser light source for the interferometer is Bo, and the beam from the interferometer IFMy goes to the moving mirror MSy, the beam reflected therefrom goes to B1y, and the beam reflected therefrom goes to the fixed mirror MRy, and the beam reflected therefrom becomes B2.
y.

The optical path of the reference beam B2y constituting the interferometer IFMy is covered with a prismatic fixed cover 10y, and the optical path of the measurement beam B1y is composed of a prismatic movable cover (inner cylinder) 12y and a fixed cover. An outer cover (outer cylinder) 11y for the interferometer 10y is covered. The movable cover 12y is provided so as to be freely 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 direction of the beam optical path needs to be linked with the movement of the wafer stage WST in the Y direction, the end of the movable cover 12y facing the movable mirror MSy is supported by the holding member 13y. Partly attached. However, since the wafer stage WST also moves in the X direction, the holding member 13y is provided movably in the X direction along a guide portion 14y extending in the X direction on the side of the stage WST.

More specifically, the fixed cover 10
y is made to have a length such that it covers almost the entire optical path of the beam B2y from the interferometer IFMy via the beam splitter BSy and the mirror M to (or reflected from) the fixed mirror MRy. On the other hand, the movable cover 12y and the outer cover portion 11y
Is formed so as to cover almost the entire optical path of the beam B1y from (or reflected from) the beam splitter BSy to the movable mirror MSy. In addition, the movable cover 12y
Is the same as the movement stroke of wafer stage WST in the Y direction between the most protruded position and the most retracted position.

As described above, the reference optical path (beams B2y and B2x) and the measurement optical path (beams B1y and B1) of the laser interferometer are used.
x), and a blower pipe 15y for supplying temperature-controlled clean air into each cover at the same time as providing a cover.
And the duct 16y are provided on a part of the fixed cover 10y.
The blower pipe 15y guides a part of the clean temperature-regulated gas produced in the environmental chamber accommodating the exposure apparatus to the duct 16y. Duct 16y
Supplies the temperature-controlled gas to the inside of the outer cover 11y and the inside of the movable cover 12y via the inside of the fixed cover 10y. The temperature control gas is supplied to both ends of the fixed cover 10y (the mirror M side and the fixed mirror M
Ry side) flows out to the outside from the opening, and the end opening of the movable cover 12y on the movable mirror MSy side and the outer cover portion 11
y also flows out from each of the end openings on the side of the beam splitter BSy. The flow rate can be significantly reduced as compared with a conventional case where an ejection port is provided in an open space and air is blown into an optical path. For this reason, soaring of dust by gas flowing out from each cover to the outside is also reduced. The duct 16y has a 0.1 μm class HEPA (High Efficiency Pa) for safety.
(rticle Air) A filter may be inserted.

FIG. 3 is a partial sectional view of the structure of each cover shown in FIG. 2 as viewed from the side. Here, the cover structure of the X-axis interferometer optical path not shown in FIG. 2 is shown. 3 that are the same as those shown in FIG. 2 are given the same reference numerals. Now, the wafer stage WS shown in FIG.
As shown in FIG. 3, T is a Y stage 18Y that moves one-dimensionally on the base 20 in the Y direction (a direction perpendicular to the plane of FIG. 3), and a one-dimensional movement that moves on the Y stage 18Y in the X direction. An X stage 18X, a ZL stage 17 that finely moves on the X stage 18 for leveling and autofocus, and a wafer holder WH that finely moves the wafer W about the Z axis on the ZL stage 17.
Further, the X-axis movable mirror MSx is fixed to the periphery of the ZL stage 17, and the measurement beam B1x is projected horizontally on the reflecting surface at substantially the same height as the surface of the wafer W.

Now, the fixed cover 10x is connected to the projection optical system PL.
The outer cover portion 11x integrated with the fixed cover 10x is fixed to a part of the column 22 for retaining
Fixed through. On the other hand, the movable cover 12x has its tip attached to the guide portion 14x on the side of the X stage 18X via the holding member 13x. 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 preventing vibration.

With such a structure, the temperature-controlled gas (air) flows through the ducts 16x through the insides of the covers in the flow paths shown by arrows in FIG. That is, a part of the blown air flows toward the tip inside the fixed cover 10x, flows out outside near the fixed mirror MRx, and another part of the air flows into the movable cover 12x of the outer cover part 11x.
Flows outside through a gap between the movable mirror 12x and the inside of the movable cover 12x toward the front end, and flows outside near the movable mirror MSx. In addition, as shown in FIG. 2, the mirror M side of the fixed cover 10x (10y) and the outer cover portion 11x
A small opening for passing each beam B2x, B1x is formed on the side of the beam splitter BSx (BSy) of (11y), but a part of the blowing air flows out from the small opening. However, it is preferable to reduce the flow rate from the small opening as much as possible.

As shown in FIG. 2 and FIG.
The temperature control air blown from the x and 16y into the fixed cover 10 and the outer cover 11 is set to proceed in a direction substantially perpendicular to the beams B1x and B2x. Then the air is beam B
Fixed cover 1 while spiraling around 1x, B2x
It proceeds inside 0 or inside the movable cover 12.

As described above, as in the first embodiment, the fixed mirror MR
Covers are provided for each of the optical paths of the reference beams B2x and B2y toward x and MRy and the respective optical paths of the measurement beams B1x and B1y toward the movable mirrors MSx and MSy. When the conditioned gas flows, the effect is obtained that the flow velocity of the gas in each cover becomes 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 jetted to each of the moving mirrors MSx and MSy, the vicinity of the fixed mirror mounting portion of the projection optical system PL and the vicinity of the moving mirror mounting portion of the ZL stage 17 are actively cooled. This makes it possible to reduce thermal (thermal) instability factors of the projection optical system and the wafer stage. For this reason, a secondary effect is obtained in that the deterioration of the imaging performance due to the heat generated by the optical element in the projection optical system absorbing a part of the exposure light being transmitted to the lens barrel is sufficiently small. Can be

FIG. 4 shows the structure of an optical path cover according to a second embodiment of the present invention.
That is, the movable cover has a multi-stage structure. That is, in the first embodiment, as is apparent from FIG. 3, 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 size of 12y becomes long. Therefore, in the second embodiment, as shown in FIG. 4, a movable cover is fixed to the wafer stage WST by a first movable cover 30x (30y), and the first movable cover 30x (30y).
0y) and a second movable cover (intermediate cover) 31x (31y) connecting the outer covers 11x and 11y. The second movable cover 31x (31y) measures the interferometer measurement values of the wafer stage WST in the X direction or the Y direction,
Alternatively, it is configured to be extendable and contractable based on ON / OFF of a limit switch provided on the stage, and the movement is driven by an air cylinder, a belt, a pulley, and the like (not shown).

In FIG. 4, the same members as those in FIG. 2 or 3 are denoted by the same reference numerals. As is clear from FIG. 4, the first movable cover 30x (30y) is
It can move in the movable cover 31x (31y) so that it can 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 1
The inside of 1x (11y) is supported via the movable body 33.

According to the second embodiment, since the optical paths of the measuring beams B1x and B1y are covered with the multistage telescopic cover, the space when the movable mirror of the wafer stage WST is closest to the beam splitter BS side. But at least
The telescopic cover can be easily arranged.
FIG. 5 shows the configuration of an optical path cover according to a third embodiment of the present invention. The difference from the first and second embodiments is that the dimension of the movable cover that is movable integrally with the wafer stage WST in the optical path direction is different. Is reduced while the telescopic structure of the optical path cover for measurement is changed.

In FIG. 5, a movable cover 40 having a short dimension is used.
y (40x for the 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 driving belt, and the like are provided on the lower surface of the fixed cover 10y (10x), and the movable cover 40y (4x) is provided.
0x) is a movable mirror M whose tip is
It is forcibly driven so as to keep a certain interval from Sy (MSx). Around the movable cover 40y, a plurality of opening / closing covers 41Y-1, 41Y-2,.
1Y-7 is provided. These open / close covers 41Y are shown in FIG.
Is defined to be above the upper surface of the movable mirror MSy when opened horizontally by 90 ° as in
In response to the movement of y in the direction of the optical path, that is, the movement of the movable cover 40y, the covers are sequentially opened like the covers 41Y-1 and 41Y-2 in FIG. Therefore, when the movable mirror MSy comes closest to the outer cover portion 11y side, all the opening / closing covers 41Y are opened.
-1 to 41Y-7 are opened horizontally. When the cover 41Y is closed, the movable cover 40y is closed.
However, a small space is provided so as not to slide on the inner wall.

Although not shown in FIG. 5, the same open / close cover is also provided on the opposite side of the fixed cover 10y, and the pair of open / close covers on the left and right are opened and closed almost simultaneously. Note that the movable cover 40y may be attached to some of the guide portions 14x and 14y of the wafer stage WST via the holding members 13x and 13y, as in FIGS. FIG. 6 shows the fixing covers 10x, 10x and 10x shown in FIGS.
y shows a partial cross section, and a pipe duct 50 for temperature-regulated gas distribution extending in the optical path direction is provided on the inner walls of the fixed covers 10x and 10y, and a flow path 51 inside the pipe duct 50 is provided.
A plurality of jet ports 52 are formed in a line on the side wall of the pipe duct 50. In the flow path 51 of the pipe duct 50, air from the ducts 16x and 16y shown in FIG. 2 or FIG. Therefore, the air from the ejection port 52 is ejected so as to cross 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 perpendicularly to the optical path of the beam, but is fixed to the fixed covers 10x, 10x.
It is desirable that the gas is ejected obliquely toward the tip (fixed mirror MRx, MRy) of y.

FIG. 7 shows the structure of an optical path cover according to a fourth embodiment of the present invention. This embodiment is different from the previous embodiments in that only the reference beam optical path for the fixed mirror MR is covered. And a special cover is not provided on the beam path for measurement with respect to the movable mirror MS. 7, the same members as those in FIGS. 2 and 3 are denoted by the same reference numerals.

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

In FIG. 7, a relatively large space is shown between the lower surface of the fixed cover 10x and the upper surface of the movable mirror MSx. However, this space can be several mm to 1 cm. For this reason, the distance between the small opening 60 and the beam B1x can also be set to about 1 cm, and air having a high flow velocity is blown in a direction substantially perpendicular to the optical path of the beam B1x.

In the present embodiment, the same concept as in the related art, in which air is blown in an open space with respect to the beam path for measurement, is applied. However, it has been confirmed by experiments and the like that it is significantly more effective than the conventional method. This is because the gas outlet (small opening 60) of the temperature-regulated gas is arranged along the optical path in the immediate vicinity of the beam optical path for measurement, so that gas in a state where the flow velocity near the outlet is large 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 near the small opening 60 can be increased by adopting a structure that effectively ejects the air 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 inside of the fixed cover 10x is formed in a two-layer structure, and air blown from the duct 16x is formed in the upper cover that covers the optical path of the reference beam B2x and a plurality of small openings 60 for blowing air. And 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 (brim) 61 for effectively guiding gas passing through the lower cover to the small opening 60.
Is provided. According to the embodiment shown in FIGS. 7 and 8, since there is no movable member that moves in conjunction with the movement position of the movable mirrors MSx and MSy, dust that cannot be avoided by using a movable structure is eliminated. Can be prevented.

Furthermore, since a part of the clean temperature-controlled gas blown into the fixed cover also air-conditions the beam path for measurement extremely efficiently, the measurement stability is the same as in the previous embodiments. improves. FIG. 9 shows a configuration of an optical path cover according to a fifth embodiment of the present invention, which is a slightly modified configuration 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 an outer cover part 11x, and air from the duct 16x is applied to the optical path of the beam B1x by the outer cover part 11x. Of these, the beam should be efficiently concentrated on the beam splitter side. The outer cover portion 11x is formed 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 far from the interferometer IFX, the beam splitter, and the like, the air from the plurality of small openings 60 formed on the lower surface of the fixed cover 10x generates the beam B1x for measurement. Actively control the light path. Therefore, the small opening 6
Nos. 0 are formed in a row at predetermined intervals in about half of the lower surface of the fixed cover 10x on the tip side.

Although the embodiments of the present invention have been described above, the present invention can be applied to other devices having a two-dimensional or one-dimensional stage using a laser interferometer as a length measuring device. Further, 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, the beam path of the light wave interferometer can be reliably air-conditioned, so that measurement errors due to air fluctuations are reduced, and the position of the stage is measured stably with good reproducibility. . According to the experiment, the measurement error due to fluctuation before providing the covering means (cover) is ± 0.04 μm
However, if a cover is provided and the inside is air-conditioned, the error due to fluctuation can be reduced to about ± 0.01 μm.

[Brief description of the drawings]

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

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

FIG. 3 is a partial cross-sectional view showing a structure of an optical path cover of the light wave interferometer of FIG. 2;

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 the 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 blowing out temperature-controlled air in a 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.

FIG. 8 is a sectional view showing a modification of the optical path cover structure of FIG. 7;

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 part 12x, 12y, 30x, 31x, 40y Movable cover 15y Blast pipe 16x, 16y Ventilation duct B1x, B1y Measurement beam B2x, B2y Reference beam

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-20803 (JP, A) JP-A-2-1505 (JP, A) JP-A-64-18002 (JP, A) JP-A-63-1988 200090 (JP, A) JP-A-54-59883 (JP, A) JP-A-5-256611 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G01B 11 / 00

Claims (16)

(57) [Claims] A stage movable in a predetermined direction; and a light beam projected on a reflecting mirror provided on the stage;
A stage position measuring device comprising: a position detection unit configured to detect a position of the stage based on the light beam reflected by the reflecting mirror; a coating unit that covers a part of an optical path of the light beam; And a gas supply unit for supplying a temperature-controlled gas inside the stage. 2. The stage position measuring apparatus according to claim 1, wherein said coating means is configured to be expandable and contractible in the direction of an optical path of said beam with movement of said stage. 3. A light beam is projected onto a stage movably provided on a base, and a reflecting mirror provided on the stage and a reference mirror fixed on the base, respectively. In a stage position measuring device having a light wave interferometer for interfering a light beam reflected by each of the mirrors, a beam optical path between the reflecting mirror and the light wave interferometer, and a light path between the reference mirror and the light wave interferometer A coating means for covering at least one of the beam optical paths, and a gas supply means for supplying a temperature-controlled gas inside the coating means. 4. The coating means comprises: first coating means for covering a beam light path between the reference mirror and the light wave interferometer; and a beam light path between the reflection mirror and the light wave interferometer. 4. The stage position measuring device according to claim 3, further comprising a second covering unit configured to be expandable and contractable in a direction of the beam optical path as the stage moves. 5. 5. The covering means covers a beam path between the reference mirror and the light wave interferometer and supplies the gas to a beam path between the reflection mirror and the light wave interferometer. 4. The stage position measuring device according to claim 3, wherein the stage position measuring device has an opening. 6. A stage movable in a predetermined direction, and a light beam is projected onto each of a reflecting mirror provided on the stage and a reference mirror fixed at a predetermined position, and each of the reflecting mirror and the reference mirror is provided. In a projection exposure apparatus having a light wave interferometer that interferes with the light beam reflected by the light beam path between the reflecting mirror and the light wave interferometer, and a beam light path between the reference mirror and the light wave interferometer A projection exposure apparatus comprising: a coating unit that covers at least one of: a gas supply unit that supplies a temperature-controlled gas inside the coating unit. 7. A projection optical system for projecting an image of a pattern formed on a mask onto a photosensitive substrate, wherein the stage mounts the photosensitive substrate, and wherein the reference mirror has the predetermined position as the predetermined position. 7. The projection exposure apparatus according to claim 6, wherein the projection exposure apparatus is fixed to a base of the stage. 8. A column integrally formed with a base portion of the stage, to which the projection optical system is attached, wherein the reference mirror is fixed to the lens barrel of the projection optical system as the predetermined position. The projection exposure apparatus according to claim 7, wherein: 9. The projection exposure apparatus according to claim 7, wherein said coating means covers a beam optical path between said reference mirror and said light wave interferometer. 10. The apparatus according to claim 9, wherein the covering means has an opening at a position close to the reference mirror side, and allows the temperature-controlled gas to flow out through the opening. Projection exposure equipment. 11. The apparatus according to claim 9, wherein said coating means has an opening for supplying said gas to a beam optical path between said reflecting mirror and said light wave interferometer.
3. The projection exposure apparatus according to claim 1. 12. The projection exposure apparatus according to claim 6, wherein said covering means covers a beam optical path between said reflecting mirror and said light wave interferometer. 13. The projection exposure apparatus according to claim 12, wherein said coating means is configured to be able to expand and contract in the direction of said beam optical path with movement of said stage. 14. The projection exposure apparatus according to claim 6, wherein the gas is a gas in a chamber in which the stage is housed. 15. The projection exposure apparatus according to claim 6, wherein said gas is supplied into said coating means via a filter. 16. A stage position measuring apparatus according to claim 1, wherein the position of a stage on which a photosensitive substrate is mounted is measured, and the position of the stage is set to a target position. A projection exposure method for projecting an image of a mask pattern on the photosensitive substrate by positioning the mask pattern within a predetermined allowable range.