JP2001118768A - Mask alignment method and exposure apparatus - Google Patents

Abstract

(57) [Problem] To provide a mask alignment method and an exposure apparatus capable of improving productivity. SOLUTION: A reference plate alignment microscope 31Y measures a reference baseline amount,
The reference baseline amount and each of the other plate alignment microscopes 31T, 31X, and 31 with respect to the reference plate alignment microscope 31Y stored in advance.
Based on the relative positional relationship with A, the baseline amount in each of the plate alignment microscopes 31T, 31X, and 31A is determined, and the plate mounted on the substrate stage is reticled based on the baseline amount determined in this manner. Alignment with respect to.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display panel or the like, which is suitable for use in exposing a substrate while sequentially positioning a plurality of masks at predetermined positions. The present invention relates to a method and an exposure apparatus using the method.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a semiconductor integrated circuit or a liquid crystal display panel, a predetermined circuit pattern formed on a reticle (mask) is projected and exposed on a plate (substrate) by an exposure apparatus. . In particular, when manufacturing a liquid crystal display plate or the like, an exposure apparatus holds a plurality of reticles on a reticle changer and moves the reticle changer to sequentially expose a plurality of reticle patterns on a plate.

As shown in FIG. 5, an exposure apparatus 1 has a stage 2 movable in XY directions, and a plate P is held on the stage 2. A reticle changer (not shown) is provided above the projection optical system 3, and the reticle changer sucks and holds a plurality of reticles R and can move them in the horizontal direction. In such an exposure apparatus 1, the exposure light from a light source (not shown) is irradiated onto the plate P via the reticle R positioned on the optical path of the exposure light and the projection optical system 3, thereby forming the reticle R. The image of the formed pattern is exposed on the plate P. Then, with a reticle changer (not shown),
A plurality of reticles R are sequentially moved to a predetermined position, and pattern exposure on the plate P is performed on each reticle R in the same manner as described above.

In the exposure apparatus 1, the positioning of each reticle R to a predetermined position is performed as follows. The exposure apparatus 1 includes, for example, two sets of reticle microscopes 5a and 5b above the reticle R.
The reticle R is provided with alignment marks RMa and RMb at positions symmetrical with respect to the center of the reticle. On the other hand, the stage 2 is provided with a reference member having a fiducial mark FM as a reference.
The position of the stage 2 can be measured by a laser interferometer or the like. Further, an off-axis type substrate alignment system 7 is provided around the projection optical system 3. As the substrate alignment system 7, for example, a total of four sets of plate alignment microscopes are provided.

A so-called through-the-lens (TT)
L) In the reticle microscope 5a, the reticle R
The stage 2 is moved so that the alignment mark RMa and the fiducial mark FM on the stage 2 match, and the position X1 of the stage 2 at this time is measured by a laser interferometer or the like. Similarly, reticle microscope 5b
Then, the stage 2 is moved so that the alignment mark RMb of the reticle R coincides with the fiducial mark FM on the stage 2, and the position X2 of the stage 2 at this time is set.
Is measured by a laser interferometer or the like. Positions X1 and X2
Is set to X3, this position X3 is a position conjugate with the center of the reticle. Further, the fiducial mark FM on the stage 2 is matched with the index mark of the off-axis type substrate alignment system 7, and the position X4 of the stage 2 at this time is measured by a laser interferometer or the like.

From these measurement results, a relative position between the reticle R and the substrate alignment system 7, that is, a baseline amount is obtained. The baseline amount is obtained by calculating the difference (X3-X4). Based on the measured baseline amount, the plate P mounted on the stage 2 is moved by the substrate alignment system 7 to the reticle R
Are aligned with respect to.

[0007]

However, the conventional exposure apparatus as described above has the following problems. As described above, when manufacturing a liquid crystal display plate or the like, a plurality of reticles R are sequentially exposed to the plate P, and it is necessary to align each reticle R with the plate P. At this time, it is necessary to measure the baseline amount by the TTL method as described above not only for the first reticle R but also for each reticle R after the second reticle. Therefore, after the exposure of the previous lot is completed, the reticle R is replaced, and the amount of the baseline required when exposing the next lot is measured. At this time, as shown in the flowchart of FIG. 6, all of the plurality of plate alignment microscopes provided as the substrate alignment system 7 measure the respective baseline amounts.
However, if the measurement of the baseline amount was performed for all the plate alignment microscopes, it took time to set up the reticle R, which led to a decrease in productivity. The present invention has been made in consideration of the above points, and has as its object to provide a mask alignment method and an exposure apparatus capable of improving productivity.

[0008]

The invention according to claim 1 is
Illuminating the pattern formed on the mask (R) with exposure light,
When transferring onto the substrate (P) via the projection optical system (12), the relative position between the alignment sensor (31Y, 31T, 31X, 31A) for positioning the substrate (P) and the center of the mask (R). The relationship between the baseline amount and the alignment sensor (31Y, 31T, 3
1X, 31A), the alignment method for aligning the substrate (P) and the mask (R).
The alignment sensor (31Y, 31T, 31X, 3
1A) are provided, and a plurality of the alignment sensors (31Y, 31T, 3
1X, 31A), the relative positional relationship of each of the other alignment sensors (31T, 31X, 31A) with respect to the reference alignment sensor (31Y) is measured, and the center of the mask (R) is measured. And a reference baseline amount which is a relative position between the reference alignment sensor (31Y) and the reference alignment sensor (31Y), and a relative positional relationship between the other alignment sensors (31T, 31X, 31A) with respect to the reference alignment sensor (31Y). And a baseline amount of each of the other alignment sensors (31T, 31X, 31A) based on the reference baseline amount measurement result and the reference baseline amount and the other alignment sensor (31T, 31X, 31A). 31T, 31
X, 31A) based on the respective baseline amounts,
The mask (R) and the substrate (P) are positioned.

A plurality of alignment sensors (31
Y, 31T, 31X, 31A), by measuring the relative positional relationship of each of the other alignment sensors (31T, 31X, 31A) with respect to the reference alignment sensor (31Y), all the alignment sensors (31Y, 31T) are measured. , 31X, 31A), the substrate (P) and the mask (R) can be aligned without measuring the respective baseline amounts.

An exposure apparatus (10) for illuminating a pattern formed on a mask (R) with exposure light and transferring the pattern onto a substrate (P) via a projection optical system (12) according to claim 5,
Mask positioning means (14) for positioning the mask (R); and a plurality of substrate alignment marks (FM) provided around the projection optical system (12) and arranged on the substrate (P). A plurality of alignment sensors (31Y, 31T, 31X, 31A) to be detected and the alignment sensors (31Y, 31T, 31X, 31A);
A) baseline measurement means (30) for measuring a baseline amount which is a relative positional relationship between A) and a predetermined position of the mask (R), and the plurality of alignment sensors (31).
Y, 31T, 31X, 31A), and another alignment sensor (31T, 31X, 31A) with respect to the reference alignment sensor (31Y).
Storage means (32) for storing respective relative positional relationships
Mask exchange means for exchanging the mask (R) with a different mask (R); and when the mask is exchanged by the mask exchange means, the baseline amount and the storage means (3)
Based on the relative positional relationship stored in 2), the alignment sensors (31Y, 31T, 31X, 31X) are used.
Control means (32) for positioning the substrate (P) in A)
It is characterized by having.

In this manner, the relative positional relationship of the other alignment sensors (31T, 31X, 31A) with respect to the reference alignment sensor (31Y) stored in the storage means (32) and the baseline measurement means (30). The baseline amount of each of the other alignment sensors (31T, 31X, 31A) can be obtained by using the measured baseline amount of the reference alignment sensor (31Y) and the predetermined position of the mask (R). Thus, by positioning the mask (R) by the control means (32), the mask alignment method according to claim 1 can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a mask alignment method and an exposure apparatus according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the exposure apparatus 10 has an XY
A substrate stage 11 that is movable in the direction is provided, and a plate (substrate) P is held on the substrate stage 11. A reticle changer (mask changing means; not shown) is provided above the projection optical system 12, and this reticle changer (not shown) sucks and holds a plurality of reticles (masks) R and horizontally holds them. You can move in any direction.

In such an exposure apparatus 10, the reticle R is irradiated by irradiating the exposure light from the light source 13 onto the plate P via the reticle R positioned on the optical path of the exposure light and the projection optical system 12. The image of the pattern formed on the plate P is exposed on the plate P. Then, the reticle changer (not shown) moves the plurality of reticles R sequentially to a predetermined position, and the reticle R performs a pattern exposure on the plate P in the same manner as described above.

In the above exposure apparatus 10, the reticle R
Is held on a reticle stage (mask positioning means) 14, and a movable mirror (not shown) is fixed to the reticle stage 14, and is connected to a movable mirror (not shown) by a laser interferometer (not shown). By measuring the distance of
The position of the substrate stage 11 in the XY two-dimensional directions is measured.
The reticle alignment controller 15 controls the reticle stage 14 based on the output of a laser interferometer (not shown).
The reticle stage 14 is moved to a desired position by servo-controlling a driving means such as a motor while monitoring the position of the reticle.

On the other hand, the substrate stage 11 is provided so as to be movable in a two-dimensional direction. A movable mirror 21 is fixed to the substrate stage 11, and the distance between the movable stage 21 and the movable mirror 21 is measured by a laser interferometer 22. The position of the substrate stage 11 in the XY two-dimensional directions is measured. The stage controller 23 servo-controls the driving means 11D such as a motor while monitoring the position of the substrate stage 11 based on the output of the laser interferometer 22, and moves the substrate stage 11 to a desired position.

The exposure apparatus 10 has, for example, two sets of reticle microscopes 25a and 25b above the reticle R. An alignment mark (not shown) is provided on the reticle R at a position symmetrical with respect to the center of the reticle. On the other hand, the substrate stage 11 is provided with a reference member having a fiducial mark (substrate alignment mark) FM as a reference. Below the fiducial mark FM, the positional relationship between the two can be measured. A sensor (not shown) (e.g., a photomultiplier) is embedded.

Around the projection optical system 12,
An Axis type substrate alignment system (baseline measuring means) 30 is provided. As shown in FIG. 2, the substrate alignment system 30 includes, for example, a total of four plate alignment microscopes (alignment sensors) 31.
Y, 31T, 31X, and 31A are provided.

Further, a plate alignment controller (storage means, control means) 3 of the substrate alignment system 30
2, a plurality of plate alignment microscopes 31Y, 31
At least one of 1T, 31X, and 31A is used as a reference, and the plate alignment microscope 31Y serving as this reference is used.
Plate alignment microscopes 31T, 31 for
The relative positional relationship between X and 31A is stored.

In the exposure apparatus 10 as described above, the positioning of the reticle R is performed as follows. That is, the plate alignment microscopes 31Y, 31T, 31X, 31 constituting the substrate alignment system 30
Since the relative positional relationship of A is mechanically held by the main body, the relative positional relationship is not affected by the reticle setup operation or the like. Therefore, here, when positioning the reticle R at the time of lot switching, the baseline measurement is performed only with the reference plate alignment microscope 31Y, and the reference plate alignment microscope is used with the other plate alignment microscopes 31T, 31X, and 31A. Microscope 31Y
Is calculated and obtained based on the relative positional relationship with the base line.

More specifically, the processing is as shown in the flowchart of FIG. First, after the apparatus is started (step S1), 1
In the lot, each plate alignment microscope 31
Y, 31T, 31X, and 31A perform position measurement, and each plate alignment microscope 31Y, 31
The baseline amount at T, 31X, 31A is measured. The reticle microscopes 25a and 25a are formed by a so-called through-the-lens (TTL) method as in the related art.
b, alignment mark of reticle R (not shown)
And the fiducial mark FM on the substrate stage 11
The substrate stage 11 is moved so that the values coincide with each other, and the position of the substrate stage 11 at this time is measured by the laser interferometer 22 or the like, thereby obtaining a position conjugate with the center of the reticle. Furthermore, a plate alignment microscope 31Y, which constitutes an off-axis type substrate alignment system 30,
The fiducial marks FM on the substrate stage 11 are sequentially matched with the index marks 31T, 31X, and 31A, and the position of the substrate stage 11 at this time is measured by a laser interferometer or the like (steps S2 to S5). From these measurement results, the reticle R and the plate alignment microscopes 31Y and 31Y constituting the substrate alignment system 30 are used.
A relative position with respect to each of 1T, 31X, and 31A, that is, a baseline amount is obtained (step S6).

At this time, the plate alignment microscope 3
From the respective baseline amounts of 1Y, 31T, 31X, and 31A, a reference plate alignment microscope 31Y is used.
Plate alignment microscopes 31T, 31 for
The relative positional relationship (X and Y coordinates) between X and 31A is calculated and stored in the plate alignment controller 32 (step S7).

Then, based on the baseline amount thus measured, the plate P mounted on the substrate stage 11 is aligned (aligned) with the reticle R by the substrate alignment system 30. (Step S8).

After that, when positioning different reticles R at the time of lot switching (step S9) after the second lot, the through-the-lens (TT) is used in the reference plate alignment microscope 31Y in the same manner as described above.
The relative position between the reticle R and the reference plate alignment microscope 31Y, that is, the baseline amount is measured by the L) method (steps S10 and S11).

The measured baseline amount and the reference plate alignment microscope 31Y stored in the plate alignment controller 32
Each other plate alignment microscope 31T, 3
From the relative positional relationship with 1X, 31A, the relative position with respect to the reticle R in each plate alignment microscope 31T, 31X, 31A, that is, the base line amount is calculated by the plate alignment controller 32 (step S).
12).

The plate P mounted on the stage is aligned with the reticle R by the substrate alignment system 30 based on the measured and calculated baseline amount.

As described above, the reference baseline amount is measured by the reference plate alignment microscope 31Y, and the reference baseline amount is stored in the plate alignment controller 32.
Each of the other plate alignment microscopes 31T, 31X, 3 with respect to the reference plate alignment microscope 31Y.
From the relative positional relationship with respect to 1A, the baseline amount in each of the plate alignment microscopes 31T, 31X, 31A is determined, and based on the baseline amount thus determined, the plate P mounted on the substrate stage 11 is determined. Are aligned with respect to the reticle R. Thereby, the plate alignment microscopes 31Y, 31T, 3
Alignment can be performed without measuring a baseline amount in all of 1X and 31A, and as a result, reticle setup at the time of lot switching can be performed efficiently, and productivity can be improved.

Incidentally, the above-described substrate alignment system 3
0 constituting a plate alignment microscope 31T, 31
The relative position measurement of X and 31A with respect to the reference plate alignment microscope 31Y and the update of the storage in the plate alignment controller 32 are preferably performed at predetermined intervals. For example, it may be performed every predetermined number of lots or every predetermined time such as 10 hours or 1 day. At this time, the relative position measurement and storage update of the plate alignment microscopes 31T, 31X, and 31A do not need to be performed at one time. For example, after the relative position measurement and storage update of the plate alignment microscope 31T are performed, a predetermined interval elapses. Then, the relative position measurement and storage update of the plate alignment microscope 31X may be performed, and the relative position measurement and storage update of the plate alignment microscope 31A may be performed after a predetermined interval has elapsed. Not limited to this, a plate alignment microscope 31Y serving as a reference,
Other plate alignment microscopes 31T, 31X, 31
A, that is, the plate alignment microscopes 31Y, 31T, 31X, and 31A in total.
Of these, at least two or more position measurements and storage updates may be sequentially performed.

The measurement of the relative positional relationship is not limited to the case of exchanging the mask, and the measurement of the baseline amount and the relative positional relationship are periodically performed while using the same mask. The line amount and the relative positional relationship may be updated. This is particularly effective when, for example, one lot has a large throughput.

Further, the plate alignment microscope 3
When measuring the relative positional relationship among 1Y, 31T, 31X, and 31A, it is preferable to perform the measurement a plurality of times, average the measurement results, and store the results in the plate alignment controller 32 in order to improve the accuracy.

In the above embodiment, the measurement interval of the relative positional relationship of the plate alignment microscope, or the measurement interval of the baseline amount and the relative positional relationship, does not matter at all. Further, the number and the configuration of the plate alignment microscopes constituting the substrate alignment system are merely examples, and the configurations other than the above can be similarly applied.

In the above embodiment, a photomultiplier is used as a sensor for the fiducial mark FM.
It is also possible to adopt a configuration using an image processing system using.

Further, the plate P of the present embodiment is not limited to a substrate for a liquid crystal display device, but also a semiconductor wafer for a semiconductor device, a ceramic wafer for a thin film magnetic head, or a mask or reticle used in an exposure apparatus. (Synthetic quartz, silicon wafer) and the like are applied.

The exposure apparatus 10 includes a step-and-scan type scanning exposure apparatus (scanning stepper; US Pat. No. 5,473,410) for scanning and exposing the pattern of the reticle R by synchronously moving the reticle R and the plate P. In addition, the present invention can be applied to a step-and-repeat type projection exposure apparatus (stepper) that exposes the pattern of the reticle R while the reticle R and the plate P are stationary and sequentially moves the plate P stepwise.

The type of the exposure apparatus 10 is not limited to an apparatus for manufacturing a liquid crystal display device that exposes a liquid crystal display device pattern to a substrate, but may be an exposure apparatus for manufacturing a semiconductor device that exposes a semiconductor device pattern to a wafer, or a thin film magnetic device. The present invention can be widely applied to an exposure apparatus for manufacturing a head, an image sensor (CCD), a reticle, and the like.

As the light source of the illumination light, bright lines (g-line (436 nm), h-line (4
04.7 nm), i-line (365 nm)), KrF excimer laser (248 nm), ArF excimer laser (19
3 nm), not only the F ₂ laser (157 nm) only, it is possible to use a charged particle beam such as X-ray or electron beam. For example, when an electron beam is used, a thermionic emission type lanthanum hexaborite (LaB ₆ ) or tantalum (Ta) can be used as an electron gun. Alternatively, a high frequency such as a YAG laser or a semiconductor laser may be used.

The magnification of the projection optical system 12 may be not only the same magnification system but also a reduction system or an enlargement system. Further, as the projection optical system 12, using a material which transmits far ultraviolet rays such as quartz and fluorite as the glass material when using a far ultraviolet ray such as an excimer laser, catadioptric system, or in the case of using the F ₂ laser or X-ray An optical system of a refraction system (a reticle R of a reflection type is also used). When an electron beam is used, an electron optical system including an electron lens and a deflector may be used as the optical system. It is needless to say that the optical path through which the electron beam passes is in a vacuum state.

Substrate stage 11 and reticle stage 14
When a linear motor (see US Pat. No. 5,623,853 or US Pat. No. 5,528,118) is used, any of an air levitation type using an air bearing and a magnetic levitation type using Lorentz force or reactance force may be used. Further, each of the substrate stage 11 and the reticle stage 14 may be a type that moves along a guide, or may be a guideless type in which a guide is not provided. As a drive mechanism of each substrate stage 11 and reticle stage 14, a magnet unit (permanent magnet) having a two-dimensionally arranged magnet and an armature unit having a two-dimensionally arranged coil are opposed to each other and each substrate stage 11 is driven by electromagnetic force. Alternatively, a flat motor for driving the reticle stage 14 may be used. In this case, one of the magnet unit and the armature unit is connected to the substrate stage 11 or the reticle stage 14, and the other of the magnet unit and the armature unit is connected to the moving surface side (base) of the substrate stage 11 or the reticle stage 14. May be provided. The reaction force generated by the movement of the substrate stage 11 is not transmitted to the projection optical system 12 so as to prevent the reaction force from being transmitted to the projection optical system 12 (US Pat.
As described in 18), it may be mechanically released to the floor (ground) using a frame member. The present invention is also applicable to an exposure apparatus having such a structure. To prevent the reaction force generated by the movement of the reticle stage 14 from being transmitted to the projection optical system 12, refer to Japanese Patent Laid-Open No. 8-33022.
As described in Japanese Patent Publication No. 4 (US S / N 08 / 416,558), a frame member may be used to mechanically escape to the floor (ground). The present invention is also applicable to an exposure apparatus having such a structure.

As described above, the exposure apparatus 1 of the present embodiment
No. 0 is manufactured by assembling various subsystems including each component recited in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. Before and after this assembly, adjustments to achieve optical accuracy for various optical systems, adjustments to achieve mechanical accuracy for various mechanical systems, and various electric systems to ensure these various accuracy Are adjusted to achieve electrical accuracy. The process of assembling the exposure apparatus 10 from the various subsystems includes mechanical connections, wiring connections of electric circuits, and piping connections of a pneumatic circuit between the various subsystems. It goes without saying that there is an assembling step for each subsystem before the assembling step from these various subsystems to the exposure apparatus 10. When the process of assembling the various subsystems into the exposure apparatus 10 is completed, comprehensive adjustment is performed, and various precisions of the entire exposure apparatus 10 are secured. The exposure apparatus 10 is desirably manufactured in a clean room in which temperature, cleanliness, and the like are controlled.

As shown in FIG. 4, for a device such as a liquid crystal display device or a semiconductor device, a step 201 for designing the function and performance of the liquid crystal display device and the like, and a step for manufacturing a reticle R (mask) based on this design step. 2
02, a step 203 of manufacturing a plate P from quartz or the like or a substrate such as a wafer from a silicon material, a step of exposing the pattern of the reticle R to the plate P (or wafer) as a substrate by the exposure apparatus 10 of the above-described embodiment. 204, steps for assembling a liquid crystal display device and the like (in the case of a wafer, a dicing process, a bonding process,
(Including a package process) 205, an inspection step 206, and the like.

Other than the above, any configuration may be adopted as long as it does not depart from the gist of the present invention, and it is needless to say that the above-described configurations may be appropriately selectively combined. No.

[0042]

As described above, according to the mask alignment method and the exposure apparatus of the present invention, the relative positional relationship of each of the other alignment sensors to the reference alignment sensor among the plurality of alignment sensors. Is measured, the substrate and the mask can be aligned without measuring the baseline amounts for all the alignment sensors. As a result, reticle setup at the time of lot switching can be performed efficiently, and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a mask alignment method and an exposure apparatus according to the present invention.

FIG. 2 is a view showing a substrate alignment system of the exposure apparatus.

FIG. 3 is a flowchart illustrating an alignment method of the mask.

FIG. 4 is a flowchart showing a manufacturing process of a device manufactured by applying the mask alignment method and the exposure apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a conventional mask alignment method and an exposure apparatus.

FIG. 6 is a flowchart showing a conventional mask alignment method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 12 Projection optical system 14 Reticle stage (mask positioning means) 30 Substrate alignment system (baseline measuring means) 31Y, 31T, 31X, 31A Plate alignment microscope (alignment sensor) 32 Plate alignment controller (storage means,
Control means) FM fiducial mark (substrate alignment mark) P plate (substrate) R reticle (mask)

Claims (6)

[Claims] 1. A relative positional relationship between an alignment sensor for positioning a substrate and a center of the mask when a pattern formed on the mask is illuminated with exposure light and transferred onto a substrate via a projection optical system. In an alignment method for determining a baseline amount and aligning the substrate and the mask using the alignment sensor, a plurality of the alignment sensors are provided, and a plurality of the alignment sensors are arranged at predetermined positions in advance. Using one of them as a reference, the relative positional relationship of each of the other alignment sensors with respect to the reference alignment sensor is measured, and a reference baseline amount that is a relative position between the center of the mask and the reference alignment sensor is determined. The other alignment sensor with respect to the measured alignment sensor The base amount of each of the other alignment sensors is obtained based on the relative positional relationship of and the measurement result of the reference baseline amount. The reference baseline amount and the base line of each of the other alignment sensors A method of aligning a mask, comprising: aligning the mask with the substrate based on an amount. 2. The mask alignment method according to claim 1, wherein the measurement of the relative positional relationship between the plurality of alignment sensors and the updating of the storage are performed at predetermined intervals. 3. The mask alignment method according to claim 2, wherein at least two of said plurality of alignment sensors measure relative positional relationship and update storage. 4. The method according to claim 1, wherein the measurement of the relative positional relationship between the plurality of alignment sensors is performed a plurality of times, and the measured data of the plurality of times is averaged and stored. The mask alignment method described in the above. 5. An exposure apparatus for illuminating a pattern formed on a mask with exposure light and transferring the pattern onto a substrate via a projection optical system, comprising: a mask positioning unit for positioning the mask; A plurality of alignment sensors provided around and each detecting a plurality of substrate alignment marks arranged on the substrate, and a baseline amount which is a relative positional relationship between the alignment sensor and a predetermined position of the mask. Baseline measuring means for measuring; storage means for storing, based on one of the plurality of alignment sensors, a relative positional relationship of each of the other alignment sensors with respect to the reference alignment sensor; different masks for the mask A mask exchange means for exchanging the mask, An exposure apparatus, comprising: control means for positioning the substrate with the alignment sensor based on a baseline amount and the relative positional relationship stored in the storage means. 6. The control unit periodically measures the baseline amount and the relative positional relationship other than when the mask is replaced by the mask replacing unit, and determines the baseline amount and the relative positional relationship. 6. The exposure apparatus according to claim 5, wherein the control is performed so as to update.