JP3214027B2 - Exposure apparatus and method of manufacturing semiconductor chip using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and a method for manufacturing a semiconductor chip using the same, and more particularly, to a projection lens system for forming a fine electronic circuit pattern such as an IC or LSI formed on a reticle (mask) surface. (Projection optical system) projects onto the wafer surface for exposure, and observes the state on the wafer surface through the projection lens system with light (detection light) having a wavelength different from the light for this exposure (exposure light). The present invention relates to an exposure apparatus having the function of performing a function and a semiconductor chip manufacturing method using the same.

[0002]

2. Description of the Related Art In an exposure apparatus for manufacturing a semiconductor, a circuit pattern of a reticle as a first object is projected and exposed on a wafer as a second object by a projection lens system. The alignment mark on the wafer is detected by observing the wafer surface by using the reticle, and based on the detection result, the position alignment 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. Therefore, the performance of the observation apparatus is an important factor in the exposure apparatus.

In a conventional reduction projection type exposure apparatus, a wafer alignment mark for obtaining positional information of a wafer is observed through a projection lens system of the exposure apparatus.
In an observation method using a projection lens system of this type, the effect of chromatic aberration generated in the projection lens system is reduced when observation is performed using monochromatic light having a wavelength equal to or close to the wavelength of light used for exposure. I do not receive.

Generally, the substrate surface of a wafer is covered with a resist layer having a predetermined thickness. The resist undergoes a chemical change when irradiated with exposure light, and its refractive index and transmittance change. For this reason, the appearance of the observation image changes over time during the observation, and is often not suitable for observation of the mark or position measurement using the observation image. Therefore, there has been proposed a method of performing image observation and position measurement using monochromatic light in a wavelength range that does not cause a chemical change in the resist, for example, light from a He-Ne laser.

[0006]

[0007]

[0008]

Generally, light whose resist is not photosensitive , such as light from a He--Ne laser, is light having a long wavelength different from the wavelength of the exposure light by at least 100 nm. Therefore, when observing the wafer surface through the projection lens system, many aberrations including chromatic aberration occur from the projection lens system with respect to the observation wavelength.

The present applicant has disclosed in Japanese Patent Application Laid-Open Nos. 62-281422 and 62-293718 a method of correcting aberration and aligning the position when the observation wavelength is different from the wavelength of the exposure light and is monochromatic light. is suggesting.

The present applicant discloses in Japanese Patent Application Laid-Open No. Hei 3-61802 that the observation light has a polychromatic light (a light having a continuous wavelength range of a certain area, a plurality of monochromatic lights, and a plurality of wavelengths having different center wavelengths). Correction) and a method of aligning the position when the light is the same.

Adjustment of the optical system in correcting these aberrations
, As coma aberration due to the individual manufacturing errors of the projection lens system and an observation system (microscope system), the color shift, also asymmetrical aberrations such as color image flow due to the magnification chromatic aberration of the projection lens system is corrected
These adjustments are generally complex because they need to be done.
Was.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an exposure apparatus which can easily adjust asymmetric aberration and a method for manufacturing a semiconductor chip using the same.

[0014]

According to an aspect of the present invention, there is provided an exposure apparatus for projecting a pattern of a first object illuminated with exposure light onto a second object, and detecting the exposure light having a different wavelength from the exposure light. An exposure apparatus having a detection unit that illuminates a mark formed on the second object with light, forms an image of the mark through the projection lens system and a detection optical system, and detects the mark. It is characterized in that it has a pair of wedge-shaped transparent members whose intervals are variable so as to correct coma aberration. The exposure apparatus according to the second aspect of the invention forms a projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and forms the exposure light on the second object with detection light having a wavelength different from that of the exposure light. Illuminating a mark, forming an image of the mark through the projection lens system and the detection optical system,
In an exposure apparatus having detection means for detecting, the detection optical system has a pair of wedge-shaped transparent members, and the interval between the pair of wedge-shaped transparent members is variable so as to correct coma aberration. . 4. The exposure apparatus according to claim 3, wherein the projection lens system projects the pattern of the first object illuminated with the exposure light onto the second object, and illuminates the mark formed on the second object with non-photosensitive light, and In an exposure apparatus having a detection means for forming an image of the mark through a lens system and a detection optical system and detecting the mark, the detection optical system has a variable interval between the two so as to correct coma aberration, It is characterized by having a pair of wedge-shaped transparent members whose wedge directions are opposite to each other. 5. An exposure apparatus according to claim 4, wherein the projection lens system projects a pattern of the first object illuminated with the exposure light onto a second object, and illuminates a mark formed on the second object with non-photosensitive light, and In an exposure apparatus having a detection unit for forming and detecting an image of the mark through a lens system and a detection optical system, the detection optical system corrects coma aberration on a meridional plane of the projection optical system. It is characterized by having a pair of wedge-shaped transparent members each having a variable wedge angle in the meridional plane, wherein the wedge directions are opposite to each other. 6. An exposure apparatus according to claim 5, wherein the projection lens system projects a pattern of the first object illuminated with the exposure light onto a second object, and illuminates a mark formed on the second object with non-photosensitive light, and Forming an image of the mark through a lens system and a detection optical system, in an exposure apparatus having a detection means for detecting, the detection optical system, the distance between the two was variable so as to correct asymmetric aberration, It has a pair of wedge-shaped transparent members whose wedge directions are opposite to each other, and an asymmetric aberration with respect to a meridional plane of the projection optical system is corrected through an operation of adjusting a distance between the pair of wedge-shaped transparent members. And 7. The exposure apparatus according to claim 6, wherein the projection lens system projects a pattern of the first object illuminated with the exposure light onto a second object, and illuminates a mark formed on the second object with non-photosensitive light, and In an exposure apparatus having a detection unit that forms and detects the image of the mark via a lens system and a detection optical system, the detection optical system corrects an asymmetric aberration with respect to a meridional plane of the projection optical system. The distance between both is variable, each has a wedge angle in the meridional plane, and has a pair of wedge-shaped transparent members whose wedge directions are opposite to each other, and adjusts the distance between the pair of wedge-shaped transparent members. The asymmetric aberration of the projection optical system with respect to the meridional plane is corrected. 8. An exposure apparatus according to claim 7, wherein a projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and illuminating a mark formed on the second object with non-photosensitive light, and In an exposure apparatus having a detection unit that forms and detects the image of the mark via a lens system and a detection optical system, the detection optical system corrects an asymmetric aberration with respect to a meridional plane of the projection optical system. A pair of wedge-shaped transparent members having a wedge angle in the meridional plane and wedge directions opposite to each other, wherein a distance between the pair of wedge-shaped transparent members is variable; It is characterized by.

According to a eighth aspect of the present invention, there is provided a method of manufacturing a semiconductor chip, comprising the step of transferring a circuit pattern of a reticle onto a wafer by using the exposure apparatus according to any one of the first to seventh aspects. I have.

An optical system according to a ninth aspect of the present invention is characterized in that the optical system has a pair of wedge-shaped transparent members for correcting coma aberration, and the interval between the pair of wedge-shaped transparent members is variable. According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the pair of wedge-shaped transparent members have wedge directions opposite to each other.

[0017]

FIG. 1 is a schematic view of a main part of an optical system according to a first embodiment when the present invention is applied to a reduction projection type exposure apparatus for manufacturing a semiconductor.

In FIG. 1, reference numeral 11 denotes a reticle as a first object, which is illuminated with exposure light from an illumination system 403.
The reticle 11 is placed on a reticle stage 30. Reference numeral 12 denotes a wafer as a second object, on which a resist is applied. Reference numeral 13 denotes a reduction-type projection lens system, which reduces and projects a circuit pattern drawn on the surface of the reticle 11 on the side of the projection lens system 13 onto the surface of the wafer 12.

In this embodiment, the projection lens system 13 is
The reticle 11 side is configured to be non-telecentric while the two side is telecentric. The projection lens system 13
Can be applied even if both sides are telecentric.

Numeral 34 denotes a θ-Z stage on which the wafer 12 is attracted and mounted, and adjusts the rotation angle in the θ direction and the position in the Z direction of the wafer 12 based on a command from the stage driving device 401. . The θ-Z stage 34 is mounted on the wafer 12
XY stage 3 for performing high-precision step moving operation
2 above. The XY stage 32 moves in the XY plane, and is driven based on a command from the stage driving device 401 similarly to the θ-Z stage 34. X
An optical square 33 (mirror) serving as a reference for stage position measurement is placed on the Y stage 32, and the optical square 33 is monitored by a laser interferometer 35.

Reference numeral 14 denotes a folding mirror, and 31 denotes an auxiliary optical system (observation optical system). Two wedge-shaped transparent members which are arranged in the meridional plane of the projection lens system 13 with the directions of the wedges changed from one another are variable. 1, 2 and wedge-shaped transparent member 1,
2 are arranged at the same angle in a sagittal plane perpendicular to the plane in which the 2 is inclined, that is, the two wedge-shaped transparent members 1 and 2 are rotated by 90 degrees about the optical axis of the observation optical system 31 as a rotation axis. It has parallel plane plates 4A and 4B.

Reference numeral 40 denotes an objective lens, 41 denotes a beam splitter, 42 denotes a relay lens, and 43 denotes an image pickup device including a CCD. The wafer 12 is placed on (the light receiving surface of) the imaging device 43.
Are formed.

Reference numeral 46 denotes a light source. Light from a light source 46 passes through an illumination condenser lens 45 and a filter 44 that allows only non-photosensitive light to pass through, is directed to the auxiliary optical system 31 by a beam splitter 41, and passes through the projection lens system 13 to an alignment mark 37 on the wafer 12. Lighting. At this time, the illumination light of the alignment mark 37 is composed of several lights having different wavelengths. The light emitted from the light source 46 may be monochromatic light such as laser light or polychromatic light such as a halogen lamp.

Reference numeral 48 denotes the wafer 1 via the projection lens system 13.
Mark (hereinafter referred to as “reference mark 4”) serving as a reference for detecting the position of the alignment mark of the wafer 12 guided to the wafer 2
8 ").

The reference mark 48 is light from a light source 50 and is illuminated via a reference mark illumination condenser lens 49. The light from the reference mark 48 enters the beam splitter 41 via the objective lens 47, is combined with the optical path of the reflected light (multicolor image forming light beam) from the wafer 12 by the beam splitter 41, and is imaged by the relay lens 42 into the imaging device 43. To form an image of the reference mark 48 on the imaging device 43.

Next, the configuration of the reticle alignment optical system R for setting the reticle 11 in the exposure apparatus main body is as follows.

Illumination light having a non-exposure wavelength is emitted from the fiber 51, and enters the prism 52 to illuminate a reticle reference mark 53 and a reticle alignment mark of the reticle 11, which are fixed to the main body of the exposure apparatus. Light from these marks is redirected by a mirror 54 in the direction of an optical path, and directed to an image pickup device (CCD) 57 via an objective lens 55 and a relay lens 56. The reticle reference mark 53 and the reticle alignment mark are displayed on the image pickup device 57. Is imaged.

In order to supply light to the fiber 51, a part of the light emitted from an extra-high pressure mercury lamp for projecting and exposing the pattern of the reticle 11 may be introduced into the fiber 51.

Using the reticle alignment optical system R,
First, the reticle 11 is set on the exposure apparatus main body. The reticle 11 and the reticle reference mark 53 are illuminated with light from the fiber 51, images of both marks are formed on the image pickup device 57, and the positional shift amount of the reticle 11 with respect to the main body is determined by the positional relationship between the images of both marks. calculate. Based on the result, the reticle stage 30 is driven by a drive device (not shown), and the reticle alignment mark and the reticle reference mark 53 are aligned. When this alignment is performed, the center of the reticle 11 coincides with the optical axis AX of the projection lens system 13, and the alignment between the reticle 11 and the exposure apparatus body ends.

Next, the alignment of the wafer alignment mark 37 and the reference mark 48 will be described.

The reference mark 48 is illuminated by a light beam from a light source 50 via an illumination condenser lens 49 and forms an image on an image pickup device 43 via an optical system (47, 41, 42). Here, the reference mark 48 and the optical system (47, 4) are used.
1, 42) so as not to change over time.

The wafer alignment mark 37 on the wafer 12 is a light beam from a light source 46 and is an optical system (45, 44, 4).
1, 31, 13), and the image is formed on the imaging device 43 in a state where the aberration is corrected by the auxiliary optical system 31.

The images of the reference mark 48 and the wafer alignment mark 37 formed on the image pickup device 43 are converted into video signals by the image pickup device 43, and the position of each image on the image pickup device 43 is determined by signal processing. Desired. Then, the position of the wafer 12 with respect to the virtual position of the reference mark 48 on the wafer 12 is detected from the positional relationship between the two.

In this embodiment, since the wafer alignment mark observation position and the exposure position of the wafer 12 are different, the position deviation amount of the wafer 12 detected at a distance (base line) from the known deviation amount observation position to the exposure position ( X and Y directions) are added by the stage driving device 401 to XY.
The stage 32 is driven to move the wafer 1 with respect to the reticle 11.
2, and the pattern is exposed by projection.

In this embodiment, two wafer alignment marks are provided at different positions on the wafer, and two reticle alignment marks are provided at different positions on the reticle, and a pair of reticle positioning optical systems R and a pair of reticle alignment optical systems R are provided for these alignment marks. By disposing the wafer positioning optical system W, it is possible to improve accuracy and processing speed in positioning between the reticle and the wafer.

In this embodiment, the amount of deviation of the wafer alignment mark from the reference position is measured by a wafer alignment marker.
This is done using the image of the click . For this reason, if the aberration remains in the optical system, the image is adversely affected, and it is difficult to obtain a correct measurement value. Further, when mass-producing the exposure apparatuses, it is very difficult to make uniform the various aberrations caused by the lot difference of the projection lens, the processing error of each part, and the assembly error between the exposure apparatuses.

Accordingly, in the present invention, as shown in FIG. 1, two wedge-shaped transparent members 1 and 2 (hereinafter, referred to as "wedges") are used in the auxiliary optical system 31 so that these various aberrations can be improved for each exposure apparatus. Has been corrected.

FIG. 2 is an enlarged explanatory view of the wedges 1 and 2 of FIG. The wedges 1 and 2 are opposed to each other so that their apical angles (wedge angles δ) are opposite to each other, and the distance D between them is variable.

In FIG. 2A, the interval between the wedges 1 and 2 is D1, and in FIG. 2B, the interval is D2 (D2> D1). When the detection light (light source 46) is monochromatic light, the aberrations depending on the interval D are coma and light beam shift. Therefore, first, coma will be described.

When comparing FIG. 2 (A) and FIG. 2 (B),
When the interval D between the wedges 1 and 2 is increased from the interval D1 to the interval D2, the amount CM of the coma generated at that time increases as the amount CM1 at the interval D1 and as CM2 at the interval D2. Table 1 shows the distance D and the amount of coma CM at this time.
The relationship is shown below.

In FIG. 1, when observation is performed from an off-axis image height using detection light having a wavelength different from the wavelength of the exposure light, light having a wavelength that has not been aberration-corrected is used. Aberrations occur. In order to correct the coma at this time, the interval between the wedges 1 and 2 is set to a predetermined amount (the position N in FIG. 3) determined by the design value.

When an exposure apparatus is actually assembled, the influence of aberration on an image differs between the exposure apparatuses due to an error in assembling or an error in processing of a part, and causes a difference in measurement values and alignment accuracy.

Therefore, in order to eliminate the machine difference at this time, the wedge 1,
The interval of 2 was adjusted and changed. This eliminates the influence of coma caused by errors in assembling and processing the projection lens system and the observation optical system. The optical axis changes by changing the distance between the two wedges. The change at this time is caused by moving a part or the whole of the observation optical system such as the mirror 14 and the optical axis of the observation optical system and the observation image of the projection lens system. What is necessary is just to adjust so that a high chief ray may be matched. In the case where the light source is monochromatic light, stable adjustment accuracy is always obtained in any of the exposure apparatuses in this embodiment by the above adjustment.

When the light source 46 is polychromatic light, color image flow due to chromatic aberration of magnification of the projection lens system 13 in addition to coma aberration and image shift causes image quality deterioration. This problem is solved by selecting the dispersion and refractive index of the glass material forming the wedges 1 and 2 so as to correct both the coma aberration and the color image flow.
Table 2 shows examples of actual numerical values for image shift. The angle of the wedge determines the adjustment sensitivity. When the wedge angle is large, the sensitivity of the coma aberration and the color image flow to the change in the interval increases. The wedge angle may be determined based on the correction resolution required for the exposure apparatus, the driving amount of the wedge, and the like.

If the function of rotating the wedges 1 and 2 around the optical axis is added, not only the meridional plane but also the eccentric coma aberration on the sagittal plane caused by an adjustment error or the like can be similarly corrected. it can.

In this embodiment, the case of observing an image at a certain off-axis image height of the projection lens of the exposure apparatus has been described. However, the mirror 14 and the objective lens 40 shown in FIG. The image height may be freely observed. At this time, the distance between the wedges 1 and 2 may be controlled so as to be proportional to the coma of the observation image height. The image shift may be performed by shifting the entire microscope, or the mirror 14 may be moved in the vertical direction.

When the image height changes, the projection lens system 13
Since the inclination of the principal ray changes, the mirror 14 should preferably be provided with an angle adjusting mechanism so that the ray always enters the microscope at the same angle.

Incidentally, in this embodiment, the design is made such that halo (spherical aberration) of the observation wavelength and axial chromatic aberration generated in the projection lens system are canceled by the observation optical system after the objective lens 40.

In this embodiment, the wedge angles δ of the opposed wedges 1 and 2 do not need to be the same, and the refractive index _ni and the wedge angle δ _i satisfying the following approximate expression may be selected. That is, when the wedge angles of the wedges ₁ and ₂ are δ ₁ and δ ₂ , and the refractive indices of the materials of the wedges 1 and 2 are n ₁ and n ₂ , (n ₁ −1) δ ₁ = (n ₂ −1) δ ₂ As long as ‥‥‥ (1) is satisfied, the wedge angles δ ₁ and δ ₂ may be any number.

FIG. 4 is an example of another embodiment of the wedge satisfying the expression (1). Even in this case, there is an interval D3 at which the coma aberration becomes zero. Therefore, as shown in FIG. 5, coma aberration can be zero-crossed.
Not TL scheme called off across the 0 like axis microscope minute coma aberration adjustment and comatic aberration colors in 0 most
This method is effective when it is desired to correct only the image flow of a color corresponding to coma .

In a TTL microscope , the coma aberration amount C
This is applicable when the value of M is 0 . The direction of the coma aberration (outer coma, inner coma) with respect to the color image flow can be determined by the magnitude of the dispersion of the material of the wedges 1a and 2a shown in FIG.

As described above, according to the present embodiment, a stable image can be always obtained for each of the exposure apparatuses, thereby achieving high-precision alignment for each of the exposure apparatuses.

[0053] Glass material BSL7 made by OHARA (Nd 1.51633, γd 6
4.1) Wavelength 632.8 nm Wedge angle 5 ° (Table 2) Image shift due to color, ΔD (deviation from position at wavelength 632.8 nm) Interval ΔDλ = 613 nm ΔDλ = 653 nm 0.0020.126-0. 117 4 0.252 -0.235 6 0.378 -0.352 8 0.504 -0.469 10 (mm) 0.630 (μm) -0.587 (μm) Glass material BSL7 OHARA (Nd 1.51633, γd 64.1) Wedge angle 5 °

[0054]

According to the present invention, as described above, by using two wedge-shaped light-transmitting members of a predetermined shape, detection light (alignment light) having a wavelength different from that of exposure light is projected onto a wafer through a projection lens system. When detecting a mark, the position of the mark image in the meridional direction has been improved so that various aberrations caused by assembling errors and processing errors of each exposure apparatus can be corrected satisfactorily and detected with high accuracy. An exposure apparatus having a mark detection function and a method for manufacturing a semiconductor chip using the same can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of an optical system according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a wedge-shaped light transmitting member of FIG. 1;

FIG. 3 is an explanatory diagram showing a relationship between a wedge interval and a coma aberration.

FIG. 4 is an explanatory view of another embodiment of the wedge according to the present invention.

FIG. 5 is an explanatory diagram showing a relationship between an interval and a coma when the wedge of FIG. 4 is used.

[Explanation of symbols]

 1, 2 wedge-shaped translucent member 4A, 4B parallel plane plate 11 reticle (first object) 12 wafer (second object) 13 projection lens system 31 observation optical system 37 alignment mark 43 imaging device 46, 50 light source 48 reference mark 53 reticle Reference mark 403 Lighting system

Claims (10)

(57) [Claims] 1. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and illuminating a mark formed on the second object with detection light having a wavelength different from that of the exposure light. An exposure apparatus having a detection means for forming and detecting the image of the mark via the projection lens system and the detection optical system, wherein the detection optical system has a variable interval so as to correct coma. An exposure apparatus comprising a pair of wedge-shaped transparent members. 2. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and illuminating a mark formed on the second object with detection light having a wavelength different from that of the exposure light. Forming an image of the mark via the projection lens system and the detection optical system, and detecting means for detecting the mark, wherein the detection optical system has a pair of wedge-shaped transparent members, Wedge-shaped transparent member spacing corrects coma
An exposure apparatus characterized in that the exposure apparatus is variable. 3. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and a mark formed on the second object is illuminated with non-photosensitive light to detect the projection lens system. An exposure apparatus having a detection unit for forming and detecting the image of the mark via an optical system, wherein the detection optical system has a variable interval between the two so as to correct coma.
And, the exposure apparatus characterized by the orientation of the wedge has a pair of wedge-shaped transparent member are mutually opposite. 4. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and illuminating a mark formed on the second object with non-photosensitive light to detect the projection lens system An exposure apparatus having a detection unit for forming and detecting the image of the mark via an optical system, wherein the detection optical system sets a distance between the two so as to correct coma aberration on a meridional plane of the projection optical system. An exposure apparatus, comprising: a pair of wedge-shaped transparent members, each of which has a variable wedge angle on the meridional plane and wedge directions are opposite to each other. 5. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and a mark formed on the second object is illuminated with non-photosensitive light to detect the projection lens system. An exposure apparatus having a detection unit that forms and detects the image of the mark via an optical system, wherein the detection optical system has a variable distance between the two so as to correct asymmetric aberration.
A pair of wedge-shaped transparent members whose wedge directions are opposite to each other, and an asymmetric aberration with respect to a meridional plane of the projection optical system is corrected through an operation of adjusting a distance between the pair of wedge-shaped transparent members. Exposure apparatus characterized by the above-mentioned. 6. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and a mark formed on the second object is illuminated with non-photosensitive light to detect the projection lens system. An exposure apparatus having a detection unit for forming and detecting the image of the mark via an optical system, wherein the detection optical system is arranged so that an interval between the two is corrected so as to correct asymmetric aberration with respect to a meridional plane of the projection optical system. The projection optical system includes a pair of wedge-shaped transparent members having variable wedge angles in the meridional plane and having wedge directions opposite to each other, and adjusting a distance between the pair of wedge-shaped transparent members. An exposure apparatus, wherein an asymmetric aberration with respect to a meridional plane of a system is corrected. 7. A projection lens system for projecting a pattern of a first object illuminated with exposure light onto a second object, and illuminating a mark formed on the second object with non-photosensitive light to detect the projection lens system An exposure apparatus having a detection unit for forming and detecting the image of the mark via an optical system, wherein the detection optical system is arranged so that an interval between the two is corrected so as to correct asymmetric aberration with respect to a meridional plane of the projection optical system. A pair of wedge-shaped transparent members, each having a variable wedge angle in the meridional plane and having wedge directions opposite to each other, and a distance between the pair of wedge-shaped transparent members is variable. Exposure equipment. 8. A method for manufacturing a semiconductor chip, comprising a step of transferring a circuit pattern of a reticle onto a wafer using the exposure apparatus according to claim 1. Description: 9. An optical system comprising a pair of wedge-shaped transparent members for correcting coma aberration, wherein a distance between the pair of wedge-shaped transparent members is variable. 10. The optical system according to claim 9, wherein said pair of wedge-shaped transparent members have wedge directions opposite to each other.