Catadioptric projection objective with real intermediate images

The present invention relates to a reflection / refraction projection objective lens for projecting a pattern arranged on an object surface of the projection objective lens onto the image plane of the projection objective lens.

Such projection objectives are used in microlithographic projection exposure equipment to manufacture semiconductor components and other microstructure components. Their purpose is to project a photomask or wire drawing plate pattern, collectively referred to below as a mask or reticle, onto the photosensitive layer coated substrate at the highest resolution and reduced magnification.

To produce finer and finer structures, on the one hand, increase the numerical aperture (NA) on the image side of the projection objective, and on the other hand, use shorter wavelengths, preferably wavelengths less than about 260 nm, for example. It is necessary to use ultraviolet light at 248 nm, 193 nm or 157 nm.

In optical lithography, pure refraction projection objective lenses have been mainly used until now. They are characterized by a mechanically very simple alignment structure that has only a single optical axis. It is also possible to use an object-side field of view centered on the optical axis, which minimizes the spread to be corrected and simplifies the alignment of the objective lens.

However, the form of the refracted structure is largely constrained by two basic image errors: color correction and Petzvel sum (image-side visual field curvature) correction.

Only one refracting material (generally SiO for 193 nm)₂, CaF for 157 nm₂) Is used, which greatly limits the possibility of correcting color errors. Unable to perform full chromatic aberration correction. In that case, the best structural compromise is achieved by choosing a single waist structure with a small first convex portion and a large second convex portion.

Correction of the Petzval condition (flattening the field of view on the image side) imposes a waist structure characteristic of the objective lens and requires a very large maximum lens diameter, which is the material mass (lens material required for lens production). Increase the mass of the part). Once the waist structure is established, a mass-optimal structure is obtained by trying to match the maximum diameters of the first and second convex portions with each other. However, this conflicts with the correction of lateral chromatic aberration.

Easier correction of Petzval conditions and the possibility of color correction are achieved with a reflective refraction structure. In this case, the Petzval correction is achieved by the curvature of the concave mirror, and the color correction is achieved by the refractive power of the negative lens in front of the concave mirror (for CHL) and the aperture position with respect to the concave mirror (CHV).

However, the drawback of the reflective refraction structure is either an off-axis object-side field of view, i.e. an increased spread (with geometric beam splitting in the optics), or a physical beam splitter element that generally causes polarization problems. It is necessary to work with it.

In off-axis catadioptric systems, the requirements of the optics are (1) to minimize spread, and (2) the geometry of the fold back (beam deviation or deflection so that mounting techniques for it can be developed. ), And (3) Petzval sum and chromatic aberration are corrected together in the catadioptric mirror group.

In order to keep the spread small, structural wrapping must, in principle, be done within the low NA region (ie, eg near the object) and near the aperture (ie near the reticle or real intermediate image). ..

However, as the numerical aperture increases, so does the numerical aperture on the object side, and thus the distance from the reticle to the first turn, resulting in greater spread. The diameter of the concave mirror and the size of the folding mirror are also increased. This can cause space availability issues.

This can be addressed by first projecting the reticle onto the intermediate image with a first refraction relay system and forming a first fold in the vicinity of the intermediate image. Such a catadioptric system is disclosed in European Patent Application No. 1191378A1. It has a reflection-refractive objective lens portion with a concave mirror. Light travels from the object plane to a deflecting (folded) mirror located near the first intermediate image, from there to a concave mirror, and from the concave mirror to a refracting objective while generating a second real intermediate image near the second deflecting mirror. Proceeding to the lens portion, this refraction objective projectes a second intermediate image onto the image plane (wafer).

An optical system having a similar structure is disclosed in International Application No. 03/036361A1.

A long multi-lens relay objective to generate the first intermediate image, a polarizing beam splitter, a reflective refraction objective with a concave mirror to generate the second real intermediate image, and a second intermediate image on the image plane. A reflective refraction objective lens having a refraction objective lens portion for projection is disclosed in US Pat. No. 5,861,997.

However, the drawback of such optics is that the second refraction portion regenerates a color and Petzval deficiency correction component in the reflection refraction portion that requires correction.

Other catadioptric systems with two real intermediate images are disclosed in Japanese Patent Application No. 2002-372668 and US Pat. No. 5,636,066.

<p> An object of the present invention is to provide a reflection / refraction projection objective lens having a convenient structure and capable of satisfactorily correcting an image error. In particular, it must be possible to correct the Petzval sum and chromatic aberration under conditions that are favorable in terms of manufacturing technology.</p>

<p> An object of the present invention is to use a first objective lens portion for projecting an object-side field of view onto a first real intermediate image and a second real intermediate image with light rays arriving from the first objective lens portion according to one of the embodiments of the present invention. The second objective lens part for generating the second objective lens part, the third objective lens part for generating the third real intermediate image with the emitted light rays coming from the second objective lens part, and the third real intermediate image on the image plane. Achieved by a reflection-refractive objective lens with a fourth objective for projection.</p>

Mode for carrying out the invention

Therefore, such a reflection / refraction projection objective has at least three real intermediate images. In a suitable optical system, the third intermediate image is projected directly onto the image plane, i.e. without producing any other intermediate image. Therefore, an optical system having exactly three real intermediate images can be convenient.

The first objective lens portion can be used as a relay system for generating a first intermediate image in a correction state that can be determined in advance at an appropriate position by using a radiated ray arriving from an object surface.

Preferably, at least two of the objective lens portions are of the reflective refraction type, each having a concave mirror. In particular, it is possible to provide exactly two reflection / refraction objective lens portions.

In one improvement, the second objective lens portion and the third objective lens portion are configured as a catadioptric system having a concave mirror, respectively. A mirror surface can be assigned to each of the concave mirrors to either deflect the radiated rays toward the concave mirror or to deflect the radiated rays arriving from the concave mirror toward the subsequent objective lens portion. In some exemplary embodiments, for beam deflection, for example, use a fully specular surface (geometric beam division), a total internal reflection mirror surface (geometric beam division), or a polarization selective mirror surface (physical beam division). Can be done. Preferably, the fourth objective is purely refracted and can be optimized to produce a high numerical aperture (NA) on the image side.

There is a great advantage in providing at least two reflection / refraction sub-optical systems. In order to understand the essential disadvantages of optics with only one reflection-refraction sub-optic, it is necessary to consider how the Petzval sum and chromatic aberration corrections are made within the reflection-refraction portion. The contribution of the lens to the longitudinal chromatic aberration CHL is given by the equation: CHLh²Obtained by ψ · ν, that is, it is proportional to the peripheral beam height h (squared), the power ψ of the lens, and the variance ν of the material. On the other hand, the contribution of the surface to the Petzval sum is determined only by the curvature of the surface and the change in the index of refraction (-2 per mirror).

Therefore, in order to increase the contribution of the reflected refraction group to the color correction, it is necessary to have a large peripheral beam height (that is, a large diameter), and in order to increase the contribution to the Petzval correction, it is large. It is necessary to have a curvature (ie, a small radius, which is most conveniently achieved with a small diameter). These two requirements conflict with each other.

Competitive requirements for Petzval correction (ie, correction of image-side visual field curvature) and color correction can be resolved by introducing (at least) another reflection-refractive portion in the optics.

Here, the two catadioptric systems tend to have a large diameter with a flat radius for CHL correction and a small diameter with a sharp radius for Petzval correction. Can be configured.

In general, degrees of freedom are available to disperse the above and other image error corrections uniformly or non-uniformly between the two (or more) reflection-refraction sub-optics. This makes it possible to obtain a maximum aperture in the loosened structure with a significant correction.

The optical system according to the present invention is preferably used in the far ultraviolet wavelength range of, for example, 248 nm, 193 nm or 157 nm or less.

The above and other features are disclosed by the scope of claims together with description and drawings, and are realized in the embodiments of the present invention and other fields by forming small combinations of individual features individually or in combination with each other. It may also form a convenient and essentially protective form.

FIG. 1 shows a first embodiment of a projection objective lens according to the present invention. FIG. 2 shows a detailed view of the area of the beam deflection device (folded structure or folded device).

This optical system has the following parts in the light propagation direction, that is, light propagates from the reticle (object surface) (left side of the drawing) through the first refraction part (R1) and onto the folding mirror (F1). , The folding mirror is located near the first intermediate image (ZB1). The first folding mirror F1 reflects light to the first (downward) reflective refraction part (HOA1). This part will be lined up almost horizontally during operation. Such an objective lens portion is also hereinafter referred to as a horizontal arm (HOA). This HOA1 projects light onto a second intermediate image (ZB2) near the folding mirrors (F1, F2). The light then passes through the other second reflective refraction portion (HOA2) at the top of the drawing, which produces an intermediate image (third intermediate image ZB3). ZB3 is projected onto the wafer directly, i.e., without another intermediate image, by the second refracted portion (R2).

The following features are given and can be seen from the drawings. This configuration has exactly three real intermediate images. Therefore, 3 + 1 = 4 possible aperture aperture positions (real pupil positions) are in the relay system R1, in the vicinity of the concave mirrors S1 and S2, and in the fourth sub-optical system R2. In this special exemplary embodiment, the aperture stop is within R1.

The fold mirror is located near the intermediate image, thereby minimizing spread (minimizing off-axis of the object). However, the intermediate image (ie, the entire region between the paraxial intermediate image and the peripheral beam intermediate image) is not on the mirror surface, so the defects expected on the mirror surface are not clearly projected onto the image surface. ..

In this particular exemplary embodiment, the fold angle is exactly 90 °, not more than 90 ° in particular. This is favorable for the performance of the mirror layer of the folded mirror (see below).

The reticle plane (the plane of the object-side field of view) is not affected by the mounting technique. A truncated lens is unnecessary. Full field of view (26 x 5.5 mm)²) And the NA is 1.3, the performance data of the optical system is about 7.5 mλ, and SiO₂The material mass of is about 90 kg. This is a value that has not yet been achieved in the refraction configuration or the h configuration. The lens diameter (optically free) is considerably smaller than 300 mm.

Each of the following features may be preferred alone or in combination with other features. This configuration includes four field lenses with positive power, each located in the immediate vicinity of the folded structure. There must be at least one negative lens in one of the two HOAs to ensure color correction. Within each reflective refraction portion, there will preferably be at least one negative lens in the immediate vicinity of the concave mirror. A convenient modification comprises at least three lenses that pass twice (in the illustrated exemplary embodiment, six lenses, namely the second and third field lenses, and one of the two mirrors for CHL correction. Pass at least one other negative lens in front of the lens twice).

The favorable modification involves little negative power in the refracted portion (in the exemplary embodiment, substantially the negative lens in R2).

This configuration has strong coma in the intermediate image, especially in the third intermediate image ZB3. This helps correct the sinusoidal condition in the image space without a surface with a large angle of incidence in R2.

Table 1 summarizes the structural details in tabular form. In this table, the first column shows the number of the refracting surface, reflective surface or other notable surface, the second column shows the radius r (in mm) of the surface, and the third column shows from that surface. The distance d (in mm), called thickness, to the next surface is shown, the fourth column shows the material of the part, and the fifth column shows the index of refraction of the material of the part following the designated plane of incidence. The sixth column shows half (in mm) of the optically effective free diameter of the optical component.

Table 2 shows the corresponding aspherical data, and the rising height (arrow) of the aspherical surface is based on the following rule: p (h) = [((1 / r) h).²/ (1 + SQRT (1- (1 + K) (1 / r))²h²)] + C1^*h⁴+ C2^*h⁶Calculated by + ...

However, the reciprocal of Earl (1 / r) represents the surface curvature at the surface vertex, and h represents the distance from the optic axis to the surface point. Therefore, p (h) indicates this rising height, in other words, the distance from the surface apex to the surface point in the z direction, that is, in the direction of the optic axis. The constants K, C1, C2 ... Are shown in Table 2.<tables num="1"><img file="JP2007508591A_D0001.tif" /></tables><tables num="2"><img file="JP2007508591A_D0002.tif" /></tables>

Many modifications are possible. FIG. 3 shows, as an example, a suitable modification with a suitable reflection-refraction sub-optic system (HOA) for a more convenient mirror layer. In this embodiment, the HOA is tilted by 20 ° from the horizontal. In this way, the angle of incidence on the folding mirror can be further reduced.

In principle, the order of the folding mirrors can be changed. As shown in this example, the optical path first crosses the beam from HOA1 to HOA2 before turnaround 1, then the beam is turned back by F2 and enters R2 without crossing. In this modified form, the total length of R2 can be shortened by the greatly protruding convex part.

In this example, a beam splitter cube (small cube) may be used instead of the beam splitting shown by the two plane mirrors. However, in this case, it should be kept in mind that if the beam splitter layer deviates from 100% reflection in the first reflection, the problem of light scattering on the wafer may occur. The problems that can be expected due to the birefringence of the beam splitter material can be minimized by appropriate compensating means.

The optical system shown in FIG. 1 is configured such that two planar folding mirrors are placed back to back at a small distance from each other. Under certain circumstances, this can be done using a single double mirror. In principle, it is also possible to perform beam deflection with a solid prism, as shown in FIG. In this case, the light first enters the folded prism, and the first folded reflection occurs on the hypotenuse of the prism. After passing through HOA1 and HOA2, the same hypotenuse surface, but the second fold reflection occurs on the posterior side.

CaF for this prism because of the heating of the lens₂Must be stated that must be selected. However, when the index of refraction n = 1.5 for 193 nm and the numerical aperture of about 0.3 are present in the intermediate image, total internal reflection over the entire beam cross section is not realistic, so a high-performance reflective layer must be applied to the hypotenuse. is there.

In terms of imaging magnification, in principle different imaging magnifications of the projection objective lens, especially 4x, 5x and 6x, are possible. Larger imaging magnifications (eg, 5x or 6x) may be advantageous as they reduce the aperture on the object side and thus loosen the folded morphology.

The relay system R1 (first sub-optical system) does not necessarily have to have an imaging magnification close to 1: 1 like HOA1 and HOA2. In this example, the magnified first objective lens portion R1 may be particularly convenient in order to loosen the folded form.

The optical system shown in FIG. 1 is configured as an immersion objective lens. For example, ultrapure water is suitable as an immersion medium for 193 nm, but the projection objective lens according to the present invention can be configured as a dry objective lens having a NA of 0.95 and a finite working distance on the wafer, for example. is there.

The above embodiment has two pure refraction optical groups, two catadioptric groups, and three intermediate images, and the two catadioptric sub-optical systems have different structures.

The sub-optical system is also referred to as a lens module below. The optics have four lens modules M1, M2, M3 and M4. The first lens module M1 having a positive refractive power has a reticle as its object and forms an intermediate image ZB1. This first intermediate image is an object of the second reflective refracting lens module M2 having a positive refractive power, which forms the intermediate image ZB2. This second intermediate image is an object of the reflective refraction lens module M3 having a positive refractive power, which forms the intermediate image ZB3. The lens module M4, which has a positive refractive power, forms ZB3 on a wafer (W).

The refraction front optical system (first sub-optical system, relay system) is asymmetrically configured. The distance between the two deflection plane mirrors (folding mirrors) is reduced so that the image shift (OIS), that is, the lateral shift between the optical axis on the object side and the optical axis on the image side, remains small. Should be.

There are embodiments that can provide these advantages. An example is shown in Figure 5.

The lens module M1 includes a first lens group LG1 having a positive refractive power and a second lens group LG2 having a positive refractive power. The main beam intersects the optical axis between these two lens groups. A suitable drawing surface B1 can be obtained there.

The first lens group LG1 preferably comprises at least two positive lenses, i.e. at least one lens L1 close to the field of view and at least one lens L2 close to the aperture.

The second lens group LG2 consists of at least two lenses, that is, at least one lens L3 close to the field of view and at least one lens L4 close to the aperture.

Preferably, the following conditions are not necessarily satisfied at the same time, but are preferably satisfied at the same time.

LG1 = LG2 L1 = L2 = L3 = L4 L1 = L4; L2 = L3 Here, it should be understood that two lenses are equal in their radius. Therefore, the thickness of the lenses will not be equal. The lens must be able to be made with the same tool. Equal groups means that those lenses are equal. Such optics provide an advantage in terms of production, as it simplifies lens fabrication and testing.

The arrangement of these lenses may be symmetrical or asymmetric with respect to the plane perpendicular to the optical axis. Here, a structure symmetrical with respect to the diaphragm surface B1 is preferable. The arrangement of the aperture diaphragm is preferably on this plane. This arrangement is advantageous because it does not cause any asymmetric image error in the intermediate image ZB1.

The imaging magnification β of the first lens module M1 is preferably β = 1.

Preferably, the first lens module is constructed substantially symmetrically but operates asymmetrically (β 1). The advantage of this quasi-symmetrical arrangement is the introduction of the color magnification difference value required for further correction and other asymmetric image errors (mainly coma).

In order to correct the telecentry in the object space, the lens L1 preferably has an aspherical surface.

In order to correct the spherical aberration in the first intermediate image, preferably one of the lenses L3 and / or L4 includes at least one aspherical surface. This loosens the folded morphology and allows for a small spread (geometric light induction value).

The first lens module M1 is preferably composed of a lens in the "low Petzval" format, i.e. with a reduced Petzval sum. A "low Petzval" structure can be made by using a lens with a low Petzval sum, especially a suitable meniscus. Telecentry, spherical aberration and astigmatism are corrected by the aspherical surface on lenses 1 and 2 or 3 and 4. The possible structure is shown in Figure 6. Table 3 shows the specifications of this first sub-optical system.<tables num="3"><img file="JP2007508591A_D0003.tif" /></tables>

In general, the distance between the mirror surface and the closest intermediate image must be between the finite minimum and maximum distances. The maximum distance may be, for example, 1/10 or 1/15 or 1/20 of the length of the optical system. The minimum distance should be smaller than that.

The first lens module M1 is preferably spherically overcorrected when the first folding mirror S1 is located after the paraxial intermediate image (ZB1) and when the paraxial intermediate image (ZB1) is located after the folding mirror S1. Must be corrected for lack of spherical surface. This makes it possible to prevent the intermediate image from being located on the mirror surface.

The Petzval sum is preferably adjusted so that the focal points of the outermost and innermost viewing points are located approximately the same distance from the first folding mirror. In that case, the intermediate image can be moved closer to the mirror surface, and the image-side field of view is curved in the direction away from the mirror surface. This loosens the folded form and allows for a small spread.

The lens modules M1 and M2 are preferably configured in a dual telecentric format. This makes it possible to correct astigmatism in the second and third intermediate images.

Preferably, the first lens module has no negative lens.

In another preferred embodiment, it is also beneficial to correct or significantly reduce the Petzval sum in the first lens module M1. For this purpose, a negative lens near the object or near the image may be used.

The two reflective and refracting lens modules M2 and M3 are preferably configured in an axisymmetric form (passing through all lenses twice).

They preferably consist of a positive lens group LG3 (LG5) near the corresponding intermediate image and a negative lens group LG4 (LG6) near the concave mirror. The main beam intersects the optical axis again on the two concave mirrors. This gives two other suitable aperture positions B2 and B3.

The lens groups LG3 and LG5 preferably consist of one or two positive lenses, and the lens groups LG4 and LG6 preferably consist of two or less, or at most three negative lenses.

The following conditions are preferably met individually or in combination.

LG3 = LG5 LG4 = LG6 S2 = S3 However, S2 and S3 are concave mirrors, and equal groups should be understood as equal lenses.

Therefore, the aberration loads (Petzval and CHL) are distributed across the two lens modules. This structure is very advantageous because the contribution of refractive power and thus aberrations is minimized.

The two lens modules M2 and M3 also preferably operate quasi-symmetrically (β is slightly different from 1). This makes it possible to easily correct CHV for the entire optical system.

In another suitable structure, each of the lens groups LG3 and LG5 consists of two positive lenses. Two equal lenses are preferred. This alleviates the aberration contribution of these lens groups.

It is also preferable that the structure of the lens modules M2 and M3 is such that the Petzval sums of the refracting lens elements of the lens groups LG3 and LG4 in the lens module M2 and the lens groups LG5 and LG6 in the lens module M3 cancel each other out. .. In particular, the following would be true:

(-PTZ (S2) / 8) &lt;PTZ (LG3 + LG4) &lt;(PTZ (S2) / 8) and (-PTZ (S3) / 8) &lt;PTZ (LG5 + LG6) &lt;(PTZ (S3) / 8) For this reason, the contribution of the Petzval of the concave mirrors S2 and S3 remains, mainly for the compensation of the Petzval curvature of the lens modules M1 and M4.

It is preferred that at least one of the lenses in groups LG4 and / or LG6, or mirrors S2 and / or S3, each have an aspheric surface. This makes it possible to correct spherical aberrations in the intermediate images ZB2 and ZB3 and thus loosen the folds, thereby reducing the spread.

The fourth lens module M4 preferably comprises three lens groups: a first lens group LG7, a second lens group LG8 and a third lens group LG9 near the field of view. The main beam intersects the optical axis between the lens groups LG8 and LG9 and thus forms a suitable fourth aperture surface B4.

The LG8 preferably comprises at least one surface with a large beam angle curved with respect to the image plane. As a lens surface on the image side, this will belong to a negative meniscus lens or a negative biconcave lens. This substantially contributes to the correction of the sinusoidal condition.

Preferably, the lens group LG9 has no negative lenses.

These three lens elements are preferably CaFs with different crystal orientations.₂Consists of.

The two reversing mirrors S1 and S3 are preferably configured as a single parallel plane plate that reflects on both sides. It should preferably be composed of a highly permeable material. This makes it easy to check the parallelism before applying the reflective layer. Suitable materials for folding mirrors are SiO₂Is.

Such a structure makes it possible to reduce the distance between the two mirrors and thus reduce the OIS (image shift).

Optical systems with four or more intermediate images are also possible within the scope of the present invention. These will provide even greater design freedom to optimize the required spatial and optical corrections. 7, 8 and 9 show embodiments of such an optical system as an example.

These optics consist of the following lens modules, namely, two pure refraction lens modules MR1 and MR2 with β1, two reflection refraction modules MK1 and MK2 with β1, and β [1/3, 1]. / 6] Refraction module MR3, and each module has a real object and gives a real image with an imaging magnification β.

By combining these four modules with each other, an imaging magnification of β [1/3, 1/6] can be obtained.

FIG. 7 shows an optical system structure in which all three refraction modules are arranged on one optical axis together with a reticle and a wafer. The reticle R is projected onto the first intermediate image ZB1 by the lens module MR1. The reflection / refraction module MK1 projects the first intermediate image onto the second intermediate image ZB2. The second refraction module MR2 projects the second intermediate image onto the third real intermediate image ZB3. This real intermediate image is used as an object for the second reflection / refraction module MK2, and the second reflection / refraction module MK2 gives the fourth intermediate image ZB4. This final intermediate image is projected onto the wafer by the folding optics MR3.

8 and 9 show two embodiments in which the axis of the reticle is located far away from the axis of the wafer.

Other structures are possible. However, what characterizes all of this type of optics is the order of the modules, namely MR1-MK1-MR2-MK2-MR3. The orientation of the axis can be arbitrarily determined by the folding mirrors FS1, FS2, FS3, and FS4.

The structure of the modules of these optics with four intermediate images corresponds to those of optics with three intermediate images as follows. Modules MR1 and MR2 correspond to module M1. Modules MK1 and MK2 correspond to modules M2 and M3. Module MR3 corresponds to module M4.

Aberration correction is performed in the same manner. The continuous line corresponds to the main beam in the outermost field of view.

In the optical systems presented so far, the optical axes of the mirror group, that is, the reflection / refraction sub-optical system, are aligned, so that if one of the optical axes is tilted, the other tilt is also required. This means that if one axis is tilted to create space, the other axis is also tilted, thus reducing the available space again.

Various exemplary embodiments of the optical imaging system that can avoid these problems are shown below. They will be used as independent optics or as sub-optics within more complex reflective refraction structures.

The (sub) optics shown in FIG. 9 have two real intermediate images and, among other things, the following features, that is, the optical axes of the reflective and refracting lens groups are separated from each other, so that they are not coaxial with each other. , It has the feature that it is laterally displaced from each other. The reflection / refraction sub-optical systems K1 and K2 are configured in an axisymmetric form. Each contains a positive lens group KL1 (KL1') near the object and a negative lens group KL2 (KL2') near the mirror.

For example, the illustrated optical system can be used as a sub-optical system that projects the first intermediate image of the field of view on the object side generated by the relay system of the above type onto the image plane of the projection objective lens. In that case, the entire optical system has three intermediate images.

According to another modification, in this optical system, both optical axes of the mirror group can be tilted toward the wafer plane. This increases the lost space between the concave mirror and the reticle plane.

A complete catadioptric system having three intermediate images and a separation axis of the reflection / refraction portion will be described with reference to FIG. This optical system consists of four lens modules M1, M2, M3 and M4. The first lens module M1 having a positive refractive power has a reticle as its object and forms an intermediate image ZB1. This first intermediate image is an object for the second reflective refracting lens module M2 having a positive refractive power, and the second reflective refracting lens module M2 forms the intermediate image ZB2. This second intermediate image is an object for the reflection / refraction lens module M3 having a positive refractive power, and the reflection / refraction lens module M3 forms the intermediate image ZB3.

The reflection / refraction sub-optical systems M2 and M3 are configured in an axisymmetric form. Each contains a positive lens group KL1 (KL1') near the object and a negative lens group KL2 (KL2') near the mirror. The preferred structure of the sub-optics will correspond to the modifications described above.

A reflection-refraction-projection objective lens, which has a polarization beam splitter and three intermediate images and passes twice, but has only one reflection-refraction-objective lens portion, will be described with reference to FIG.

The reticle (or the first intermediate image of the object-side field of view) is projected onto the intermediate image ZB1 by the catadioptric module M2. Here, the circularly incident light is linearly polarized by the 1st λ / 4 plate, reflected by the polarization selective translucidum layer of the beam splitter, leaves the beam splitter, and is then circularly polarized by the 2nd λ / 4 plate. The circularly polarized light is reflected by the concave mirror, thereby changing its direction of rotation, reflected again by the first folding mirror FS1, and then changed its direction of rotation again, reflected again by the concave mirror, and changed its direction of rotation. As a result, before the light passes through the 2λ / 4 plate again, it has a direction of rotation opposite to the direction during the first passage. Therefore, the light is linearly polarized, but its vibration plane is perpendicular to the vibration plane of the light after the 1λ / 4 plate. This allows light to pass through the beam splitter to form the next intermediate image ZB2. This intermediate image is projected onto the wafer by the refraction lens module M3 at an imaging magnification of β [1/6, 1/3].

If the space between the reticle and the beam splitter is too narrow and therefore the reticle needs to be placed farther away from the beam splitter, which causes an increase in spread, project the reticle into the intermediate image ZB0. It is advantageous to place the first lens module M1 (relay system) between the reticle and the beam splitter.

The optical system modules M1 and M2 have an imaging magnification β1.

Since the reflection / refraction group corrects both image-side visual field curvature and longitudinal chromatic aberration, it is advantageous to pass through this optical group twice. Thereby, both the diameter and the refractive power of this group can be reduced. Therefore, the diameter of the concave mirror becomes smaller, thus leaving a space close to the reticle in the intermediate space.

A λ / 4 plate added near a suitable third aperture position in the lens module M3 ensures that the light is shining circularly on the wafer.

The folding mirror FS2 is arranged so that the reticle surface and the wafer surface extend in parallel.

Two other convenient aperture positions are in the first module M1 and in the vicinity of the concave mirror.

When the first lens module is not used, especially at a large numerical aperture (NA&gt; 0.8), refraction with a positive refractive power and an imaging magnification of β1 in order to bring the resulting intermediate image closer to the beam splitter. It is advantageous to place the anterior group between the reticle and the beam splitter. This reduces the size of the beam splitter.

<figref num="1">A first embodiment of a projection objective lens according to the present invention having an asymmetric structure is shown.</figref><figref num="2">A detailed view of the folding means of FIG. 1 is shown.</figref><figref num="3">A modified version of the optical system shown in Fig. 1 is shown.</figref><figref num="4">Another folding means having a prism is shown.</figref><figref num="5">Another embodiment of the projection objective lens according to the present invention having a substantially symmetrical structure is shown.</figref><figref num="6">Image field curvature small showing a again relay system.</figref><figref num="7">Another embodiment of the projection objective lens according to the present invention is shown.</figref><figref num="8">Another embodiment of the projection objective lens according to the present invention is shown.</figref><figref num="9">Another embodiment of the projection objective lens according to the present invention is shown.</figref><figref num="10">An embodiment of a projection objective lens according to the present invention having a catadioptric separation optical axis is shown.</figref><figref num="11">Another embodiment of a projection objective according to the present invention having a catadioptric separation optical axis is shown.</figref><figref num="12">Another embodiment of a projection objective according to the invention with a polarized beam split and a reflection / refraction objective that passes through twice is shown.</figref>