JPH0235446B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an exposure apparatus, and in particular, to an exposure apparatus, in which fine electronic circuit patterns such as ICs and LSIs formed on a reticle surface are projected onto a wafer surface using a projection optical system. The present invention relates to an exposure apparatus having a function of projecting and exposing light and observing the state on a wafer surface via a projection optical system using light having a wavelength different from that of light for exposure.

(Prior Art) In a projection exposure apparatus for semiconductor manufacturing, a circuit pattern of a reticle as a first object is projected and exposed onto a wafer as a second object using a projection lens system. By observing the wafer surface using a wafer, an alignment mark on the wafer is detected, and based on the detection result, the positional matching between the reticle and the wafer, so-called alignment, is performed.

The alignment accuracy at this time largely depends on the optical performance of the observation device. For this reason, the performance of the observation device has become an important factor in the exposure device.

Various types of alignment devices using such observation devices have been proposed in the past.

For example, the present applicant has also proposed an alignment system using such an observation device in Japanese Patent Laid-Open No. 58-25638.

According to the publication, a projection lens system uses G-line (436 nm) light (exposure light) to project and expose the circuit pattern of a reticle onto a wafer, while an alignment system uses G-line (436 nm) light (exposure light) with a wavelength of 442 nm emitted from a He-Cd laser.
The alignment marks on the reticle and wafer are detected using this light (alignment light).

By constructing a so-called bi-telecentric optical system so that the projection lens system is telecentric on both the reticle side and the wafer side, the principal ray of the alignment light is always aligned when observing the wafer surface from the reticle side. It takes advantage of the fact that it is perpendicular to the reticle surface. Manufactured by this
Even if the type of IC changes, the pattern dimensions on the reticle surface change, and the observation position of the alignment system changes, the angle of the light incident on or reflected on the reticle surface can remain unchanged, and this property can be used. This creates a highly accurate TTL on Axis system.

Note that the TTL on Axis system aligns the reticle and wafer in the exposed state via a projection optical system for exposure.

A TTL on Axis alignment system using the wavelength of exposure light such as g-line or light of an equivalent wavelength as the alignment light, such as the apparatus disclosed in the above-mentioned publication, is a typical example of a preferable method in terms of alignment mark detection accuracy.

However, if the wavelength of the exposure light (exposure wavelength) and the wavelength of the alignment light (alignment wavelength) are made substantially the same, a resist layer such as a multilayer resist coated on the wafer absorbs the alignment light and forms an alignment mark on the wafer surface. By reducing the reflected light from the
This causes a decrease in the ratio and alignment accuracy. For this reason, it becomes necessary to make the alignment wavelength and the exposure wavelength different to improve the S/N ratio and improve the alignment accuracy.

By making the alignment wavelength and exposure wavelength different
When detecting alignment marks using the TTL method, the projection lens system has various aberrations well corrected only for the exposure wavelength, so light other than the exposure wavelength causes various chromatic aberrations, specifically axial chromatic aberration, magnification Chromatic aberration, comatic aberration of other colors, astigmatism, spherical aberration, etc. occur, making it impossible to detect an alignment mark properly and causing a decrease in alignment accuracy.

For this reason, various methods have been proposed in the past to allow good observation of the wafer surface through a projection lens system using light other than the exposure wavelength. For example, when observing the wafer surface through a reticle, the position of the wafer surface is shifted in the optical axis direction of the projection lens system by the amount of focus shift due to axial chromatic aberration caused by the projection lens system with respect to the alignment light used for observation. By establishing a mutual relationship between the reticle surface and the wafer surface, and by providing an auxiliary optical system that corrects longitudinal chromatic aberration between the reticle and the projection lens system, the reticle surface and the wafer surface are A method of establishing a mutually exclusive relationship with the government is being adopted.

However, none of these methods corrects other chromatic aberrations that occur in the projection lens system, so the alignment optical system is capable of forming a radial pattern image without causing asymmetric aberrations such as coma and lateral chromatic aberration. Alignment marks have been detected using only imaging in the sagittal direction.

However, detecting marks through a projection lens system using only images in the sagittal direction is not enough to achieve high precision in exposure equipment that needs to transfer submicron micropatterns onto wafers with high resolution. It is difficult to perform alignment and highly accurate magnification control.

The magnification of the projection lens system changes as the atmospheric pressure changes, and the wafer becomes partially distorted as it undergoes processing such as development and etching. Therefore, the exposure apparatus is required to have a function of detecting such changes in magnification and distortion of the wafer and controlling the magnification of the projection lens system.

Therefore, one possible method for detecting magnification changes and wafer distortion is to form an image of the mark on the wafer through a projection lens system and detect changes in the imaging position in the meridional direction (radial direction). With the conventional method of forming a mark image using only radial pattern imaging, that is, imaging in the sagittal direction, it is not possible to accurately detect a change in the imaging position in the meridional direction.

In addition, conventional imaging only in the sagittal direction cannot
The mark position information obtained through one alignment optical system is one-dimensional, and two-dimensional mark position information cannot be accurately obtained using one alignment optical system.

(Summary of the Invention) The present invention has been made in view of the above-mentioned problems, and is aimed at determining the position of a mark image in the meridional direction when detecting a mark through a projection lens system using light having a wavelength different from the exposure light. An object of the present invention is to provide an exposure apparatus having an improved mark detection function.

In order to achieve this object, the exposure apparatus of the present invention includes a projection lens system that projects a pattern of a first object onto a second object using exposure light, and a projection lens system that projects a pattern of a first object onto a second object using exposure light, and a second object that uses detection light that has a wavelength different from that of the exposure light. and a detection means for illuminating an object and detecting a mark on the second object through the projection lens system, wherein the detection means transmits the detection light from the second object through the projection lens system. an image forming means for forming an image of the mark using the received detection light; the image forming means corrects astigmatism and coma that occur in the projection lens system due to a difference in wavelength between the exposure light and the detection light; It is characterized by being equipped with an optical system that makes it easier to use.

Other features of the invention are described in the Examples.

(Embodiment) FIG. 1 is a schematic diagram of an optical system of an embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing.
In the figure, reference numeral 1 denotes a reticle as a first object, which is placed on a reticle stage 28. 2 is the second
The wafer as an object, 3, is a projection optical system consisting of a projection lens system, which projects a circuit pattern etc. on one surface of the reticle onto the second surface of the wafer.

21 is a θ, Z stage on which the wafer 2 is placed, and the θ rotation of the wafer 2 and focus adjustment, that is, Z
Adjusting direction. The θ and Z stages 21 are XY stages 2 for performing step operations with high precision.
It is placed on 2. The XY stage 22 has an optical square 2 that serves as a reference for stage position measurement.
3 is placed, and this optical square 23 is monitored by a laser interferometer 24. A laser 25 irradiates the alignment mark 15 on the wafer surface 2 with a beam of light from the laser 25 via a mirror 26 and a projection lens 27.

Reference numeral 4 denotes a mirror, and reference numeral 100 denotes an observation optical system, which includes a plane parallel plate 6 arranged at an angle with respect to the meridional cross section of the projection optical system 3, and a plane parallel to each other in a plane orthogonal to the inclined plane of the plane parallel plate 6. In other words, two parallel plane plates 7 and 7' are arranged such that the parallel plane plate 6 is rotated by 90 degrees about the optical axis of the observation optical system 100 as a rotation axis.

In this embodiment, these parallel plates 6, 7, 7'
This constitutes an optical system that corrects chromatic astigmatism and coma that occur in the projection lens system.

10, 11, and 12 are mirrors, and 8 is a correction lens section. Reference numeral 16 denotes an alignment mark on the reticle 1 side, which is provided at a position where an image of the alignment mark 15 is formed by the projection optical system 3 and the observation optical system 100.

17 is a mirror, 18 is an alignment scope,
Reference numeral 19 is a CCD, which observes the conditions on one surface of the reticle and two surfaces of the wafer.

In this way, in this embodiment, elements 25, 26, 2
The alignment mark 15 on the wafer 2 is detected via the projection optical system 3 by a detecting means including 7, 4, 100, 12, 17, 18, and 19. This detection is performed by forming an image of the mark 15 on the CCD 1 by an image forming means having elements 4, 100, 12, 17, and 18.
The contrast of the image of the mark 15 is improved by the action of the optical system (6, 7, 7').

In this embodiment, a circuit pattern on one surface of a reticle is projected onto two surfaces of a wafer by a projection optical system 3 using G-line (436 nm) exposure light. On the other hand, the alignment mark 15 on the second side of the wafer is marked by the He-Ne laser 2.
The projection optical system 3 and the observation optical system 100 form an alignment mark image on the surface of the reticle 1 near where the alignment mark is provided on the reticle side. The alignment scope 18 is used to simultaneously observe the relationship between both alignment marks. In this embodiment, it is not necessary to move and fix the observation optical system 100 along with the movement of the alignment image height, but for the sake of simplicity, the following description will be made assuming that the alignment image height is fixed.

Generally, the aberrations of the projection optical system 3 are well corrected at the projection wavelength of the g-line, but the aberrations are not sufficiently corrected at the alignment wavelength. In particular, many chromatic aberrations such as axial chromatic aberration, lateral chromatic aberration, chromatic spherical aberration, chromatic comatic aberration, and chromatic astigmatism remain.

Therefore, when the wafer 2 surface is considered as an object surface, the alignment mark 15 on the wafer 2 surface is often imaged above the reticle 1 surface due to various aberrations.

For example, if the projection magnification of the projection optical system 3 is 1/5 and the axial chromatic aberration on the wafer side is 300 μm, the image of the wafer 2 on the reticle side is 0.3×5 ² = 7.5
(mm) above the reticle 1.

This makes it difficult to observe the pattern on one side of the reticle and the pattern on two sides of the wafer at the same time.
Conventionally, various correction optical systems have been arranged between the reticle and the projection optical system to make the pattern images of the two coincide. However, it is difficult to completely correct aberrations with this correction optical system, and it is generally difficult to observe well.

In this embodiment, an observation optical system is used between the reticle 1 and the projection optical system 3, in which aberrations are well corrected in all directions including not only the sagittal direction but also the meridional direction, and in particular, various aberrations due to color are well corrected. By arranging the system 100, the pattern on the first side of the reticle and the pattern on the second side of the wafer are matched, and both patterns can be observed well.
This enables highly accurate alignment.

In the observation optical system in this embodiment, the projection optical system 3
In order to correct various chromatic aberrations that occur at the observation wavelength, that is, the alignment wavelength, the three
It is characterized in that coma aberration and astigmatism, in particular, are corrected by using an optical system comprising two parallel plane plates.

Of these, coma aberration with respect to the observation wavelength of the projection optical system 3 is corrected by a plane parallel plate 6 that is tilted with respect to the meridional cross section of the projection optical system, that is, disposed obliquely and asymmetrically with respect to the imaging light beam of the meridional cross section. . At this time, the tilt angle is determined depending on the amount of aberration generated by the projection optical system 3 and the thickness of the parallel plane plate 6. This single parallel plane plate 6 is effective against coma aberration, but on the other hand, it becomes a cause of astigmatism. The sum of the astigmatism at this time and the astigmatism at the observation wavelength of the projection optical system 3 becomes the astigmatism of the entire system. Therefore, in this embodiment, the astigmatism of the entire system is corrected by arranging the two plane-parallel plates 7, 7' so as to be inclined to each other in a plane orthogonal to the plane on which the plane-parallel plate 6 is inclined. That is, the two parallel plane plates 7 and 7' are arranged within a plane in which the plane parallel plate 6 is rotated by 90 degrees about the optical axis of the observation optical system 100.

When the parallel plane plates 7 and 7' have the same thickness, they may be arranged in a line-symmetrical relationship, and when they have different thicknesses, they may be arranged at different angles. And 2
The overall combination of the two parallel plane plates 7, 7' is designed to prevent comatic aberration from occurring. However, since the astigmatism of the parallel plane plates 7 and 7' is exerted as a synergistic effect, astigmatism occurs, but by arranging it in a plane twisted by 90 degrees with the parallel plane plate 6, the occurrence cancels each other out. It is adjusted as follows. For example, if the aberration occurring at the observation wavelength of the projection optical system 3 is only comatic aberration and no astigmatism, the thickness of the two plane parallel plates 7 and 7' should be approximately 1/2 that of the plane parallel plate 6.
Moreover, even though it is twisted, the angle made with the optical axis of the observation optical system 100 is adjusted by the three parallel plane plates 6, 7, 7'.
If all are made equal, it becomes possible to perform observation with the coma aberration and astigmatism of the projection optical system 3 corrected.

In addition, if the projection optical system 3 has astigmatism at the observation wavelength, a parallel plane plate 6 and two parallel plane plates 7,
If the angle formed by 7' is made different depending on the amount of astigmatism, observation with the aberration corrected becomes possible. That is, in this embodiment, by adjusting the inclination of the parallel plane plate, it is possible to arbitrarily control the amount of correction.

In this embodiment, by properly correcting coma aberration and astigmatism with the above-described configuration, aberrations can be well corrected not only in the sagittal direction but also in all directions including the meridional direction.
This makes it possible to simultaneously observe alignment marks on both the reticle surface and the wafer surface as good images. This enables highly accurate alignment.

In this embodiment, if some spherical aberration remains, it is preferable to correct it using the correction lens section 8. In this case, if the occurrence of spherical aberration at the observation wavelength of the projection optical system 3 is small, it is preferable to generate an opposite spherical aberration in the correction lens section 8 to correct it.

In addition, the correction lens section 8 is arranged on the reticle side, and is relatively small, for example, with an NA of 0.1 or less.
For example, when there is a large aberration of several λ, an aspherical member 9 is disposed as part of the correction lens section 8 and at a position approximately coextensive with the pupil position of the projection optical system 3. It is better to correct it. For example, if spherical aberration occurs that is insufficiently corrected on the long wavelength side, an aspherical member having a shape in which the negative refractive power increases toward the periphery may be used.

Note that since the insertion of the observation optical system 100 in this embodiment does not satisfy the TTL on Axis condition, it is necessary to perform a certain amount of correction, which is treated as an adjustment of the optical system or an offset. Aberrations that can be treated by adjusting the optical system include color-based defocus (axial chromatic aberration) and field curvature, since the focus can be adjusted by adjusting the optical path length of the observation optical system. Further, the position of the image can be corrected if the amount of deviation is known in advance, and image deviation due to color (lateral chromatic aberration), distortion, etc. can be treated as offsets.

In short, in this example, refocusing,
If the position of the image is simply shifted, offset processing can be easily performed.

Therefore, when actually detecting an image, problems such as spherical aberration, coma aberration, and astigmatism that impair the contrast of the image arise. However, although these various aberrations are well corrected at the exposure wavelength, they are not necessarily well corrected at the observation wavelength. However, as a result of analysis, it has been found that the manner in which these various aberrations occur at the observation wavelength can be treated in the area of basic third-order aberrations as a simple deviation from good aberration correction at the exposure wavelength.

Therefore, in this embodiment, by using the optical system (6, 7, 7') equipped with three parallel plane plates having the above-mentioned configuration, an observation device that can perform good aberration correction and enable clear observation can be achieved. is possible.

With the above configuration, in this embodiment, the state on the surface of the wafer 2 can be observed well through the projection optical system 3. At this time, in this embodiment, the observation optical system 100
Since three mirrors 10, 11, and 12 are used, the pattern on the two wafer surfaces must be observed in an inverted state, but this can be observed without any problems by inverting the sign of both offsets through signal processing. can.

In addition, the correction lens unit 8 of this embodiment has an adjustment function to project the two wafer surfaces onto the reticle 1 at a predetermined magnification in addition to the function of forming an image of the pattern on the 2 wafer surfaces onto the 1 reticle. I have to. For example, when using a projection optical system with a projection magnification of 5 times, the projection magnification should be exactly 5 times (in this case, the imaging magnification of the correction lens section 8 itself is -1 times), thereby reducing the load on the subsequent processing device. I'm making it less.

Although the correction lens unit 8 forms an image of -1 times, a modified example of forming an image of 1 times is of course also applicable to this embodiment.

In this embodiment, coma, astigmatism, and spherical aberration among various color aberrations mainly generated by the projection optical system 3 are corrected by the observation optical system 100, and the deviation of the focus and image plane is determined by the optical path length. The magnification and distortion are generally corrected by offset processing. This allows reticle 1 and wafer 2 to
improves observation of both alignment marks,
This enables highly accurate alignment.

In this example, aberrations are well corrected in all directions, not just the sagittal direction as in the past, so by observing the alignment mark at one point on the two surfaces of the wafer, two Signals can be detected. In order to perform two-dimensional alignment, it is necessary to observe at least one more point and thereby align the θ direction. This can be done using only one observation system, but as shown in Figure 2, it is possible to arrange two observation optical systems shown in Figure 1 and use the same alignment scope 18 as shown in Figure 1. If observed, it is possible to perform corrected alignment in x, y, and θ while maintaining throughput. In FIG. 2, the same elements as those shown in FIG. 1 are given the same reference numerals. Also, the system indicated by number 5 is the first
This is an optical system equipped with parallel flat plates 6, 7, and 7' shown in the figure.

In this embodiment, the alignment mark on the wafer surface of the target to be measured is always set to alignment mark 15.
It is necessary to bring it to the position and take measurements. For this reason, after measuring the alignment between the reticle 1 and the wafer 2, the wafer is moved to the exposure position by the XY stage 22 while being monitored by the laser interferometer 24 based on the measured value.

In order to perform two-dimensional alignment completely, it is necessary to measure at two points, and from this point on, it stops twice at the alignment position and takes measurements, and then it is fed to the exposure position based on the measured amount. Two alignment scopes shown in FIG. 2 may be used for the two measurements at this time, or one alignment scope may be used to measure two points by moving the stage.

Since changes in magnification can also be detected based on the results of measurement at two points, changes in magnification of the projection optical system can also be corrected by known means.

Alternatively, a method of measuring while moving the stage without necessarily stopping it may be used.

3, 5, and 6 are schematic diagrams of optical systems of other embodiments when the present invention is applied to an exposure apparatus for semiconductor manufacturing similarly to FIG. 1.

In FIGS. 3, 5, and 6, the same elements as those shown in FIG. 1 are given the same reference numerals.

The embodiment shown in FIG. 3 has the same structure as the embodiment shown in FIG. 1 from the top to the bottom of the reticle surface.

In this embodiment, a galvanometer mirror 33 is used instead of the CCD used in FIG. 1 to observe the alignment mark 16 on the surface of the reticle 1, and the alignment image is scanned, and the light is guided to the photomultiplier tube 35 via the slit 34. It is characterized by That is, an alignment mark image is scanned by a galvano mirror 33 by an erector 32 through a field lens 31 disposed near the imaging plane of the alignment mark 16 formed by the alignment scope 18, and the light is guided onto the slit 34 and passes through the slit 34. The photomultiplier tube 35 receives the light.

Note that the reflection point of the galvanometer mirror 33 is arranged so as to substantially match the pupil position of the projection optical system 3.

The scanning means in this embodiment may use a polygon mirror or the like instead of a galvano mirror, but since the scanning is one-dimensional, the opening of the slit 34 is provided in the ±45 degree direction, for example, as shown in FIG. If alignment marks are similarly provided in the ±45 degree direction, information in the x and y directions can be obtained by one-dimensional scanning.

The embodiment shown in FIG. 5 is a case where an observation optical system 100 correcting the chromatic aberration of the projection optical system 3 is arranged on the alignment scope 18 side with respect to the reticle 1. At this time, when observing the alignment mark 16 on the first surface of the reticle with the alignment scope 18, the alignment mark 15 on the second surface of the wafer is observed.
Due to chromatic aberration, the position of the alignment scope 18 is lower than the position of the alignment mark 16 on the first surface of the reticle.
Image is formed on the side. For example, this amount is 7.5mm as mentioned above.
Since the value becomes such a large value, the depth of focus of the objective lens in the alignment scope 18 is no longer included. Therefore, in this embodiment, a beam splitter 41 is provided between the alignment scope 18 and the CCD 19 to constitute a bifocal system in which the light beam is divided into two and combined again by the beam splitter 43.
Of the two optical paths divided by the beam splitter 41, a relay lens 42 is disposed in the optical path passing through the beam splitter 41 to image the alignment mark 16 on the reticle 1 surface on the CCD 19.

On the other hand, in the optical path of the beam reflected by the beam splitter 41, three parallel plane plates 6, 7, 7' corresponding to the observation optical system 100 shown in FIG. The upper alignment mark 15 is imaged onto the CCD 19 surface through these elements.

As a result, coma aberration, astigmatism, and spherical aberration are corrected similarly to the embodiment shown in FIG.

In this embodiment, in order to efficiently perform the processing after the CCD 19, it is preferable to make the imaging magnifications in the two divided optical paths the same.

The embodiment shown in FIG. 6 is an example of an alignment system using laser beam scanning disclosed in Japanese Patent Application Laid-open No. 53-135654 and Japanese Patent Application Laid-open No. 55-34490, etc. This is the case when applying

The projection optical system 3 of this embodiment is a telecentric system on both the reticle side and the wafer side.

The light beam from the laser 25 is passed through the lens 55,
The light is scanned by a polygon mirror 54 and an f-theta lens 53, and is guided onto the surface of the wafer 2 after passing through an alignment scope 18 and an optical system similar to the optical system shown in FIG. Then, the scattered light from the alignment mark 15 on the second surface of the wafer is reversed, returned to the alignment scope 18, reflected by the beam splitter 52, and then passed through the pupil imaging lens 56, the spatial frequency filter 57, and the condenser lens 58 for photoelectric conversion. The light is guided to an element 59.

The alignment method at this time is described in detail in the previous publication, so it will be omitted here.

Incidentally, in each of the above embodiments, when changing the position of the alignment mark 16 according to the chip size, a part of the observation optical system 100 may be finely adjusted.

Furthermore, the object of the present invention can also be achieved by dividing the three parallel plane plates into a plurality of parts and constructing three or more parallel plane plates, each of which is tilted.

In this way, among the various color aberrations generated by the projection lens system, the correction optical system removes astigmatism, coma, and spherical aberration, and the focus and image plane deviations are corrected by optical path length, magnification, and distortion by offset processing. By solving all these problems, it became possible to observe both the reticle and wafer as good images. As a result, two-dimensional positioning of the reticle and wafer, that is, x, y, and θ alignment became possible. Furthermore, by measuring the span at two points, changes in magnification can also be measured, making it possible to deal with changes in magnification of the lens system due to changes in atmospheric pressure or temperature, as well as local deformation of the wafer. Summer. When a change in magnification is detected, the magnification of the lens system can be changed using a known method to easily improve alignment accuracy.

Furthermore, in the above explanation, the correction optical system is assumed to be fixed at the formation position 16 of the alignment mark image. However, when the position of 16 is changed depending on the chip size, the change can be easily coped with by fine adjustment of the correction optical system. For example, the correction amount of a parallel plane plate that corrects astigmatism and coma at the alignment wavelength can be freely controlled by changing the tilt angle. Further, since changes in spherical aberration due to changes in image height can be ignored, there is no need to particularly correct the spherical aberration. Also TTL on
When implementing an Axis-like system as shown in FIG. 1, a part of the alignment scope (for example, the mirror 17) and the correction optical system may be retracted to the outside of the exposure area during exposure.

(Effects of the Invention) According to the present invention, by employing the above-described configuration, the projection optical system can project the pattern of the first object onto the second object using light of a different wavelength from that of the second object. It is possible to provide an exposure apparatus that satisfactorily corrects various chromatic aberrations occurring in the projection optical system when detecting a mark on an object via the projection optical system, and enables observation of a clear mark image.

In particular, if the present invention is applied to an exposure apparatus for semiconductor manufacturing, both the reticle surface and the wafer surface can be observed as clear images, and the two-dimensional alignment of the reticle and wafer in x, y, and θ can be improved. It is possible to achieve an alignment system that can be performed with precision.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system of one embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing, FIG. 2 is an explanatory diagram of another embodiment of a portion of FIG. 1, and FIG.
5 and 6 are schematic diagrams of an optical system of another embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing similarly to FIG. 1, and FIG. 4 shows a part of FIG. 3. It is an explanatory view of another example. 1 in the figure is the reticle,
2 is a wafer, 3 is a projection optical system, 100 is an observation optical system, 6, 7, and 7' are parallel plane plates, 8 is a correction lens section, 9 is an aspherical member, 15 and 16 are alignment marks, and 18 is a alignment scope,
19 is a CCD, and 25 is a laser.

Claims (1)

[Claims] 1. A projection lens system that projects a pattern of a first object onto a second object using exposure light; and a projection lens system that illuminates the second object with detection light having a wavelength different from that of the exposure light, and a detection means for detecting a mark on an object, wherein the detection means receives the detection light from the second object via the projection lens system and forms an image of the mark with the detection light. 1. An exposure apparatus, wherein the image forming means includes an optical system for correcting astigmatism and coma aberration caused in the projection lens system due to a difference in wavelength between the exposure light and the detection light.