PROJECTION OBJECTIVE FOR A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to microlithographic projection exposure apparatuses as are used to manufacture large-scale integrated electrical circuits and other microstructured components. More particular, the invention relates to a projection objective of such an apparatus that is designed for immersion operation.

2. Description of Related Art

Integrated electrical circuits and other microstructured components are normally produced by applying a plurality of structured layers to a suitable substrate, which may be, for example, a silicon wafer. To structure the layers, they are first covered with a photoresist that is sensitive to light of a certain wavelength range. The wafer coated in this way is then exposed in a projection exposure apparatus. In this operation, a pattern of structures contained in a mask is imaged on the photoresist with the aid of a projection objective. Since the imaging scale is generally smaller than 1, such projection objectives are frequently also referred to as reduction objectives.

After the development of the photoresist, the wafer is subjected to an etching or deposition process, as a resuit of which the uppermost layer is structured in accordance with the pattern on the mask. The photoresist still remaining is then removed from the remaining parts of the layer. This process is repeated until all the layers have been applied to the wafer.

One of the most prominent objects in the design of projection exposure apparatuses is to be able to define lithographically structures having increasingly smaller dimensions on the wafer. Small structures result in high integration densities, which generally have a favorable effect on the performance of the microstructured components produced with the aid of such apparatuses.

One of the most important parameters that determine the minimum size of the structures to be lithographically defined is the resolution of the projection objective.

Since the resolution of the projection objectives decreases as the wavelength of the projection light becomes smaller, one approach to achieve smaller resolutions is to use projection light with ever-shorter wavelengths. The shortest currently used wavelengths are in the deep ultraviolet (DUV) spectral range and are 193 nm and 157 nm.

Another approach to decrease the resolution is to introduce an immersion liquid having high refractive index into the gap that remains between a final lens element on the image side of the projection objective and the photoresist or another photosensitive layer to be exposed. Projection objectives that are designed for immersion operation and are therefore also referred to as immersion objective may reach numerical apertures of more than 1, for example 1.3 or 1.4. The term “immersion liquid” shall, in the context of this application, relate also to what is commonly referrd to as “solid immersion”. In the case of solid immersion, the immersion liquid is in fact a solid medium that, however, does not get In direct contact with the photoresist but is spaced apart from it by a distance that is only a fraction of the wavelength used. This ensures that the laws of geometrical optics do not apply such that no total reflection occurs.

Immersion operation, however, does not only allow to achieve very high numerical apertures and, consequently, a smaller resolution, but it also has a favorable effect on the depth of focus. The higher the depth of focus is, the lower are the requirements imposed on an exact positioning of the wafer in the image plane of the projection objective. Apart from that, it has been found out that immersion operation considerably relaxes certain design constraints and simplifies the correction of aberrations if the numerical aperture is not increased.

In the meantime, immersion liquids have been developed whose refractive index is significantly above that of deionized water (n_H2O=1.43) and that are nevertheless also highly transparent and resistant to projection light of the wavelength 193 nm. When using immersion liquids with such high refractive indices, it may happen that the refractive index of the immersion liquid is greater than the refractive index of the material of which the last optical element on the image side is composed. In conventional projection objectives having a last optical element with a plane surface on the image side, the maximum numerical aperture is restricted by the refractive index of this last optical element. If this optical element is, for example, made of quartz glass, an increase in the numerical aperture beyond the refractive index of quartz glass (n_SiO2=1.56) is not possible although the refractive index of the immersion liquid is even higher.

Document JP 2000-058436 A discloses a projection exposure apparatus having a projection objective can be used both in dry and in immersion operation. When switching to immersion operation, an additional lens element having a concave surface on the image side is introduced into the gap between the last optical element of the projection objective and the wafer. The interspace between the additional lens element and the wafer may be filled with an immersion liquid, for example an oil. This document does not disclose the refractive indices of the immersion liquid and the additional lens element.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an immersion projection objective in which the refractive index of the last optical element on the image side is larger is smaller than the refractive index of the immersion liquid, but having a numerical aperture that is not restricted by the refractive index of the last optical element.

This object is achieved in that, during immersion operation, the immersion liquid is convexly curved towards the object plane.

As a result of the convex curvature of the immersion liquid towards the object plane, the angles of incidence at which projection light rays impinge on the interface between an adjoining medium, e.g. the last optical element on the image side, and the immersion liquid are reduced. Thus a light ray that would be totally reflected by a flat interface can now contribute to the image, and this, in turn, allows higher numerical apertures that can also be above the refractive index of the last optical element on the image side. In this way the numerical aperture is limited only by the refractive index of the immersion liquid, but not by the refractive index of the medium that adjoins the immersion liquid on the object side.

The simplest way of achieving an immersion liquid that is convexly curved towards the object plane is to allow the immersion liquid to adjoin directly a concavely curved image-side surface of the last optical element of the projection objective. The curvature of the immersion liquid is then unalterably fixed by the curvature of this surface.

In order to prevent an undesired drainage of the immersion liquid from the cavity that is formed by the concavely curved image-side surface of the last optical element, this surface may be surrounded circumferentially by a drainage barrier. This may, for example, be a ring that is joined to the last optical element and/or a housing of the projection objective. The ring, which may be composed, for example, of a standard lens material such as quartz glass or calcium fluoride (CaF₂), but also of a ceramic or of hardened steel, is preferably provided on the inside with a coating that prevents contamination of the immersion liquid by the ring. Such a ring is also advantageous if the refractive index of the immersion liquid is equal to or smaller than the refractive index of the medium that adjoins the immersion liquid on the object side.

The image-side surface of the last optical element may be spherical. Calculations have shown that the radius of curvature may advantageously be selected to be between 0.9 times and 1.5 times and preferably 1.3 times the axial distance (i.e. vertex distance) between the this surface and the image plane. Such a configuration, which is also advantageous if the refractive index of the immersion liquid is equal to or smaller than the refractive index of the medium that adjoins the immersion liquid on the object side, has the advantage the high angles of incidence at the object side interface of the immersion liquid are avoided. Such high angles usually result in a strong sensitivity of the interface to design and manufacturing deficiencies. From this point of view, the angles of incidence should be as small as possible. This generally requires a very large curvature (i.e. a small radius of curvature) of the object-side interface of the immersion liquid.

Another way of obtaining an interface of the immersion liquid that is convexly curved toward the object plane is to introduce an intermediate liquid between the last optical element and the immersion liquid. This intermediate liquid is not miscible with the immersion liquid and forms a curved interface in an electric field during immersion operation. Such a configuration is also advantageous if the refractive index of the immersion liquid is equal to or smaller than the refractive index of the medium that adjoins the immersion liquid on the object side.

This approach makes use of an effect that is also known as “electrowetting”. If the magnitude of the electric field is altered, this is accompanied by an alteration in the curvature of the interface. This effect has hitherto been used, however, only for autofocus lenses for CCD or CMOS sensors on components that are produced by Varioptic, France.

The more the electrical conductivities of the two liquids differ from one another, the greater is the curvature of the interface. A large difference may be achieved if one of the two liquids, for example the intermediate liquid, is electrically conductive and the other liquid, for example the immersion liquid, is electrically insulating.

It is furthermore advantageous if the intermediate liquid has substantially the same density as the immersion liquid since no buoyancy forces can occur and, consequently, the shape of the interface is independent, of the position of the arrangement in space.

The refractive index of the intermediate liquid should be less than the refractive index of the immersion liquid, but it may be less or greater than the refractive index of the last optical element on the image side.

Preferably, the electric field that is necessary to form the curved interface is generated by an electrode. A symmetrical formation of the interface can be achieved, for example, by using an annular cone electrode that is disposed between the last optical element and the image plane. The curvature of the interface can be continuously varied in this way by varying a voltage applied to the electrode. This can be exploited in order to correct certain imaging properties of the projection objective.

Above it has been mentioned that it may be desirable to have a strongly curved interface between the immersion liquid and the medium adjoining to the object side, because this simplifies the correction, of imaging aberrations. However, it has also significant advantages if the curvature of this interface is small. This is because a large curvature generally leads to the formation of a cavity within the last optical element. Such a cavity has several drawbacks. For example, it favors the occurrence of undesired turbulences within the cavity if a flow of the immersion liquid has to maintained, for example for reasons of temperature stability and for purifying the liquid. Furthermore, highly refractive immersion liquids have a somewhat higher absorption than lens materials. For that reasons the maximum geometrical path lengths within the immersion liquid should be kept small. Finally, a small curvature simplifies the access to the image side surface of the last optical element for cleaning purposes.

Therefore it is generally preferred if the immersion liquid forms a convexly curved interface with a medium adjoining the immersion liquid towards the object plane such that light rays pass the interface with a maximum angle of incidence whose sine is between 0.98 and 0.5, more preferably between 0.95 and 0.85, and even more preferably between 0.94 and 0.87. The latter values correspond to angles of incidence of 60° and 70°, respectively. The angle of incidence here denotes the angle between the light ray and a surface normal at the point where the light ray impinges on the surface. These configurations are also advantageous if the refractive index of the immersion liquid is equal to, or smaller than the refractive index of the medium that adjoins the immersion liquid on the object side.

The very high numerical apertures possible according to the invention, which may be, for example, 1.6 and above, require, under some circumstances, a novel design of the projection objective. In this connection, a catadioptric projection objective comprising at least two imaging mirrors in which at least two intermediate images may be advantageous. Such a configuration is also advantageous if the refractive index of the immersion liquid is equal to or smaller than the refractive index of the medium that adjoins the immersion liquid on the object side.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawing in which:

FIG. 1 shows a meridian section through a microlithographic projection exposure apparatus having a projection objective according to the invention in a considerably simplified view that is not to scale;

FIG. 2 shows an enlarged view of the image-side end of the projection objective shown in FIG. 1;

FIG. 3 shows an enlarged view similar to FIG. 2 for an alternative embodiment with a drainage barrier;

FIG. 4 shows the image-side end of a projection objective in accordance with another exemplary embodiment in which an intermediate liquid has been introduced between the immersion liquid and the last optical element on the image side;

FIG. 5 shows details of the geometrical conditions at the image-side end of a projection objective according to the invention;

FIG. 6 shows a meridian section through a catadioptric projection objective in accordance, with an embodiment the present invention;

FIG. 7 shows a meridian section through a catadioptric projection objective in accordance with a further embodiment the present invention;

FIG. 8 shows a meridian section through a catadioptric projection objective in accordance with another embodiment the present invention;

FIG. 9 shows a meridian section through a complete catadioptric projection objective in accordance with still another embodiment the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a meridian section through a microlithographic projection exposure apparatus denoted in its entirety by 110 in a considerably simplified view that is not to scale. The projection exposure apparatus 110 comprises an illuminating system 112 for generating projection light 113 including a light source 114, illumination optics indicated by 116 and a diaphragm 118. In the exemplary embodiment shown, the projection light 113 has a wavelength of 193 nm.

The projection exposure apparatus 110 furthermore includes a projection objective 120 that comprises a multiplicity of lens elements, of which, for the sake of clarity, only a few are indicated by way of example in FIG. 1 and are denoted by L1 to L5. The projection objective 120 images a mask 124 disposed in an object plane 122 of the projection objective 120 on a reduced scale on a photosensitive layer 126. The layer 126, which may be composed of a photoresist, is disposed in an image plane 128 of the projection objective 120 and is applied to a substrate 130. The photosensitive layer 126 may itself be composed of a plurality of layers and may also comprise antireflection layers, as is known in the art as such.

An immersion liquid 134 has been introduced into a gap 132 that remains between the last lens element L5 on the image side and the photosensitive layer 126.

This can be seen more clearly in FIG. 2 that shows the image-side end of the projection objective 120 on an enlarged scale. The last lens element L5 on the image side has, on the image side, a surface 136 that is concavely curved. The gap 132 between the last lens element L5 on the image side and the photosensitive layer 126, which is usually flat at both ends, now transforms into a kind of cavity.

The surface 136 is approximately of spherical shell shape, the radius of curvature being denoted in FIG. 2 by R. In this arrangement, the radius of curvature R is about 1.3 times the axial distance s between, the last lens element L5 on the image side and the photosensitive layer 126.

The immersion liquid 134 has a refractive index n_Lthat is greater than the refractive index of the material n₁of which the last lens element L5 on the image side is composed. If, for example, quartz glass or calcium fluoride is used as material, a liquid should be chosen whose refractive index n_Lis above 1.56 or 1.5. This can be achieved, for example, by adding sulphates, alkalis such as caesium, or phosphates to water, as is described on Internet page www.eetimes.com/semi/news/OEG20040128S0017. These immersion liquids have sufficient transparency and stability even at wavelengths in the deep ultraviolet spectral range. If the projection exposure apparatus 110 is designed for longer wavelengths, for example for wavelengths in the visible spectral range, conventional immersion liquids having high refractive index, such as, for example, cedarwood oil, carbon disulphide or monobromonaphthalene may also be used as immersion liquid.

Since the immersion liquid forms, with respect to the object plane 122, a convexly curved interface 139 with the last lens element L5 on the image side, only relatively small beam incidence angles occur at said interface 139. This is shown in FIG. 2 by way of example for aperture rays 113a and 113b having a maximum aperture angles α. As a result, reflection losses at said interface are correspondingly small. Thus rays having large aperture angles with respect to an optical axis OA of the projection objective 120 may also contribute to forming an image of the mask 124, with the result that it is possible to achieve with the projection objective 120 numerical apertures that extend up to the refractive index n_Lof the immersion liquid 134. If, on the other hand, the interface 139 were plane, as is usual in the prior art, said rays would be totally reflected at the interface between the last lens element L5 and the immersion liquid.

FIG. 3 shows a projection objective 120 in accordance with another exemplary embodiment in a view along the lines of FIG. 2. Identical parts are characterized in the figure by identical reference numerals.

The projection objective 120′ differs from the projection objective 120 shown in FIGS. 1 and 2 only in that a ring 140 is tightly joined to the last lens element L5 and a housing 141 of the projection objective 120. The ring 140 functions as a drainage barrier for the immersion liquid 134. Such a drainage barrier may be particularly advantageous if the surface 136 of the last lens element L5 on the image side is strongly curved since then the gap 132 has a large maximum extension along the optical axis OA. Accordingly, the hydrostatic pressure of the immersion liquid 134 is relatively high. Without a drainage barrier, said pressure may ultimately have the result that the immersion liquid 134 is forced out of the cavity into the surrounding gap 132 between the projection objective 120 and the photosensitive layer 126 so that a surrounding gas may enter the cavity.

The ring 140 may be composed, for example, of a standard lens material such as quartz glass or calcium chloride, but also of other materials, such as Invar™ nickel alloy, stainless steel or (glass) ceramic.

FIG. 4 shows an image-side end of a projection objective 120″ in accordance with a further exemplary embodiment in which a curvature of the immersion liquid 134 is achieved in another way.

In the projection objective 120″, the immersion liquid 134 does not directly adjoin a last lens element L5″ on the image side. Instead, a further liquid, which is referred to in the following as intermediate liquid 142, is situated between the last lens element L5″ on the image side and the immersion liquid 134. The intermediate liquid 142 is, in the embodiment shown, water to which ions have been added. Due to the ions the water becomes electrically conductive. The immersion liquid 134, which also in this case has a greater refractive index than the last lens element L5″, is electrically insulating. For wavelengths of the projection light that are in the visible spectral range, the oils and naphthalenes already mentioned above are, for example, suitable as immersion liquid 134.

The intermediate liquid 142 completely fills the space that remains between an image-side surface 136″ of the last lens element L5″ on the image side and the immersion liquid 134. The surface 136″ is convexly curved in the exemplary embodiment shown, but the latter may also be a plane surface. Adjacent to a ring 140″ that, as in the exemplary embodiment described above, has the function of a drainage barrier, a likewise annular conical electrode 146 is provided that is connected to a controllable voltage source 147. Applied to the conical electrode 146 is an insulator layer 148 that, together with the photosensitive layer 126, ensures continuous insulation of the immersion liquid 134 with respect to the image plane. The voltage source 147 generates an alternating voltage whose frequency is between 100 kHz and 500 kHz. The voltage applied to the conical electrode 146 is in the order of magnitude of about 40 V.

When the alternating voltage is applied to the conical electrode 146, the electrowetting effect known as such has the result that the interface 139 between the immersion liquid 134 and the intermediate liquid 142 convexly curves towards the object plane 122. The cause of this curvature is capillary forces that, together with the unalterability of the total volume and the tendency to the formation of a minimum surface, generate, to a good approximation, a spherical interface 139 if a sufficiently high alternating voltage is applied to electrode 146.

If the alternating voltage is now reduced, the curvature of the interface 139 decreases. In FIG. 4 this is indicated by an interface 139′ shown as a broken line. The refractive index of the liquid lens formed by the immersion liquid 134 can consequently be continuously varied in a simple way, namely by altering the electrical alternating voltage applied to the conical electrode 146. For the sake of completeness, it may also be mentioned at this point that the curvature of the interface 139 does not necessarily require an alternating voltage, but may also be achieved with a direct voltage.

Also in this embodiment, the interface of the immersion liquid 134 that is convexly curved towards the object plane 122 has the effect that a numerical aperture can be achieved that is limited not by the refractive index of the last lens element L5″ but only by the refractive index of the immersion liquid 134.

The continuous variability of the refractive power of the liquid lens formed by the immersion liquid 134 can advantageously also be used at other locations in the projection objective. Advantageously, such a liquid lens can be used at positions inside the projection objective that are exposed to particularly high light intensities. Degradation phenomena, such as occur in the case of conventional solid lenses, can be suppressed in this way or at least be repaired by simply replacing the immersion liquid. Incidentally, corresponding remarks also apply to the embodiments shown in FIGS. 2 and 3.

FIG. 5 shows an image-side end of a projection objective according to a still further exemplary embodiment. Here the last lens element L205 has a spherical surface 236 facing towards the image plane that has a smaller concave curvature, i.e. a larger'radius R, than the lens element L5 in the embodiments shown in FIGS. 2 and 3. In the following the geometrical conditions at the interface between the last lens element L205 and the immersion liquid 134 will be discussed in further detail.

Reference numeral AR denotes an aperture ray having a maximum aperture angle φ. The aperture ray AR impinges on the photosensitive layer 126 at a peripheral point of the image field at a height h with respect to the optical axis OA. The aperture ray AR has an angle of incidence α and an angle of refraction β at the interface between the last lens element L205 and the immersion liquid 134. The distance between the vertex of the last surface 236 of the lens element L205 and the image plane in which the photosensitive layer 126 is positioned is denoted by s.

Projection objectives are basically characterized by two quantities, namely the image-side numerical aperture

NA=n·sin(φ)

and the quantity 2 h, i.e. the diameter of a circle around the optical axis OA on which an image can be formed.

From the image-side numerical aperture NA certain geometrical properties can be derived which ensure that the light can propagate through the last lens element and immersion liquid without being reflected at the interfaces. However, the design requirements applied to the last lens element are, in practice, somewhat stricter than those that can be derived solely from the image-side numerical aperture. For example, the angle of incidence α should not exceed a certain value that is, for example, about 75°, and more preferably 70°. This is because experience shows that projection objectives having larger angles of incidence α require very complex measures to achieve a good aberration correction and a reduced sensitivity to manufacturing tolerances and changing environmental conditions.

At present projection objectives for dry operation achieve an image-side NA close to about 0.95. This means that the numerical aperture NA does not exceed 95% of the refractive index of the medium (usually a gas or a mixture of gases such as air) that immediately precedes the image plane. In such dry projection objectives the maximum angles of incidence are in the order of about 70°, in particular at the last surfaces close to the image plane but also at other surfaces of lens elements.

Since these considerations also apply to immersion objectives, the angles of incidence should be kept below these values. From geometrical considerations it becomes clear that the stronger the curvature of the surface 236 is, the smaller are the angles of incidence. Thus a strong curvature ensures that the angles of incidence do not go beyond these values.

The surface 236 of the lens element L205 should, on the other hand, not be too severely curved. This is due to the fact that a too severely curvature may result in increased problems with respect to flow mechanics, contamination and temperature sensitivity of the immersion liquid 134. For example, it may be difficult to achieve a homogenous and constant temperature of the immersion liquid 134, and, the immersion liquid 134 may be enclosed in such a way within a strongly convex cavity that replacing the immersion liquid, for example for purging reasons, becomes a very complex task.

It has been found out that a good compromise is achieved if the following condition holds for the maximum angle of incidence α:

0.95>sin(α)>0.85.

In the following a formula is derived that specifies a suitable curvature ρ as a function of NA=n.sin(φ), distance s, image height h and the refractive indices n′, n of the last lens element L205 and the immersion liquid 134, respectively, so that the sine of the angle of incidence α does not exceed a certain advantageous and practicable value. Such a value was found to be sin(α)<κ, where κ=0.95. Using the law of refraction, it follows that

$\langle \frac{n}{n^{'}} \sin (β) \rangle > κ$

According to simple geometrical considerations, it can be deduced therefrom that

$\langle \frac{n}{n^{'}} (sp - 1) \sin (ϕ) \rangle > κ$

$Thus$

$ρ > \frac{(1 - \frac{n^{'} \cdot κ}{NA})}{s}$

is the condition for minimum surface curvature. For the radius R=1/ρ this gives

$R > \frac{s}{(1 - \frac{n^{'} \cdot κ}{NA})} .$

For an exemplary numerical aperture NA=1.5 and SiO₂as material for the last lens element L205 with n′=1.56, this results in

R>m·s

with m≈83. For s=2 mm, this leads to a radius R of about 167 mm for the maximum radius of curvature.

If, in addition, the aperture rays of the outermost image point are taken into account in the case of a finite image field, it is sufficient for this purpose to substitute the distance s by s′ according to

$s^{'} = s \frac{h}{\tan ϕ}$

in the above formulae. For a maximum field height h, it then follows for the minimum curvature ρ

$ρ > (1 - \frac{n^{'} \cdot κ}{NA}) / (s - \frac{h}{\tan ϕ})$

If one starts with a projection objective having the above mentioned parameters, i.e. NA=1.5 and n′=1.56, and if one further assumes that the maximum field height h is 15 mm, the maximum radius of curvature R should be below m=83 times (s−5.57 mm). For s=8 mm, this results in a maximum radius of curvature R of approximately 200 mm, and for s=10 mm R is approximately 375 mm.

If, for example, κ is selected to be'0.95 and an immersion liquid with a refractive index of n=1.43 is used, a numerical aperture NA=1.35 may be realized with a last lens element L205 that is made of SiO₂and which has a distance s=2 mm to the image plane and has a maximum radius of curvature below approximately 80 mm. The aforementioned detrimental effects that occur in the case of large curvatures can be minimized if the maximum radius of the surface is not only below the given values, but at least substantially identical to these values.

Apart from the fact that the maximum angle of incidence should not exceed certain upper and lower limits as is explained above, it should be ensured that the light rays rather quickly converge if one looks from a point on the image plane towards the object plane. Otherwise optical elements with very large diameters would be required.

This qualitative design rule can be mathematically expressed in the following way: If k, l, m are the three direction cosines of an aperture ray and n is the refractive within a medium with k²+l²+m²=n², there should be no volume in the objective (particularly in the vicinity of the image plane) in which (k²+l²)/n²>K₀. The limit K₀may be selected to be K₀=0.95 or even better K₀=0.85.

FIG. 6 shows a meridian section through a first exemplary embodiment of the projection objective 120 shown in FIGS. 1 and 2. The design data of the projection objective are listed in Table 1; radii and thicknesses are specified in millimeters. The numerals above the projection objective point to selected surfaces of optical elements. Surfaces that are characterized by groups of short bars are aspherically curved. The curvature of said surfaces is described by the aspherical formula below:

$z = \frac{c h^{2}}{1 + \sqrt{1 - (1 + k) c^{2} h^{2}}} + A h^{4} + B h^{6} + C h^{8} + D h^{10} + E h^{12} + F h^{14}$

In this equation, z is the saggita of the respective surface parallel to the optical axis, h is the radial distance from the optical axis, c=1/R is the curvature at the vertex of the respective surface where R is the radius of curvature, k is the conical constant and A, B, C, D, E and F are the aspherical constants listed in Table 2. In the exemplary embodiment, the spherical constant k equals zero.

The projection objective 120 contains two aspherical mirrors S1 and S2 between which two (not optimally corrected) intermediate images are produced. The projection objective 120 is designed for a wavelength of 193 nm and a refractive index n_Lof the immersion liquid of 1.60. The linear magnification of the projection objective 120 is β=−0.25 and the numerical aperture is NA=1.4. Some additional improvements, however, make it possible to achieve without difficulty also a numerical aperture NA that just reaches the refractive index of the immersion medium and is, consequently, only slightly less than 1.6.

FIGS. 7 to 9 show meridian sections through three furthey exemplary embodiments of the projection objective 120 shown in FIGS. 1 and 2. The design data and aspherical constants of the projection objective shown in FIG. 7 are listed in Tables 3 and 4; Tables 5, 6 and Tables 7, 8 list the design data and aspherical constants for the embodiments shown in FIGS. 8 and 9, respectively.

The projection objectives shown in FIGS. 7 to 9 all have an image-side numerical aperture NA=1.40 and an immersion liquid with a refractive index of n_L=1.60. Thus this refractive index is always greater than the refractive index of the last lens element made of CaF₂, i.e. n_L>n_CaF2.

The projection objective shown in FIG. 7, which is designed for a wavelength λ=193 nm, is non-achromatized and has a last lens element LL7 with a strongly concavely curved image-side surface that forms a kind of cavity for the immersion liquid 134. The wavefront is corrected to about 2/100λ.

The projection objective shown in FIG. 8 is designed for a wavelength λ=157 nm and is achromatized. The image-side surface of the last lens element LL8 is even stronger concavely curved; apart from that, the radius of curvature is almost identical with the axial distance between the last lens element LL8 and the image plane, i.e. the center of curvature lies substantially within the image plane. As a result, the immersion liquid 134 has a large maximum thickness. Although the refractive index of CaF₂is about n_CaF2=1.56 at λ=157 nm, the refractive index of the immersion liquid is still assumed to be larger (n_L=1.60). The wavefront is corrected to about 4/100λ.

The projection objective shown in FIG. 9 is designed for a wavelength λ=193 nm and is non-achromatized. The image-side surface of the last lens element LL9 has only a small concave curvature so that the immersion liquid 934 forms almost a flat layer. The radius of curvature is significantly (about a factor 10) greater than the axial distance between the last lens element LL9 and the image plane, i.e. there is a substantial distance between the center of curvature and the image plane. The maximum angel of incidence at the interface between the last lens element LL9 and the immersion liquid 934 is about 67° (i.e. sin α=0.92). The wavefront is corrected to about 5/100λ.

When comparing the wavefront errors in the similar embodiments shown in FIGS. 7 and 9, it becomes clear that the design of FIG. 7 with its greater curvature of the image-side surface of the last lens element LL7 allows to achieve a much better wavefront correction (2/100λ vs. 5/100λ). However, although the projection objective shown in FIG. 9 is not as well corrected as the projection objective shown in FIG. 7, due to the comparatively large radius of curvature there is only a small cavity underneath the last lens element LL9 which is advantageous for the reasons that have been mentioned above.

It goes without saying that the present invention is not restricted to the use in catadioptric projection objectives as have been described above. The invention can also advantageously be used in projection objectives having a smaller or larger number of intermediate images than in the embodiments shown, and also in dioptric projection objectives with or without any intermediate images. In addition, the optical axis may also extend through the center of the image field. Examples of further suitable lens designs are to be found, for example, in US 2002/0196533 A1, WO 01/050171 A1, WO 02/093209 A2 and U.S. Pat. No. 6,496,306A.

TABLE 1

Design data

SURFACE
RADIUS
ASPHERICAL
THICKNESS
MATERIAL

Object plane
∞

37.648

1
210.931

21.995
SiO₂

2
909.02

1.605

3
673.572

22.728
SiO₂

4
−338.735
x
33.19

5
130.215
x
8.994
SiO₂

6
119.808

36.001

7
216

40.356
SiO₂

8
−210.59

0.939

9
97.24

49.504
SiO₂

10
216.208
x
8.164

12
−65.704

49.734
SiO₂

Diaphragm
∞

49.302

13
−113.325

55.26

14
−6210.149
x
70.31
SiO₂

15
−195.536

0.962

16
3980.16

65.997
SiO₂

17
−473.059

277.072

18
−225.942
x
246.731
Mirror

19
193.745
x
294.329
Mirror

20
−338.56
x
17.389
SiO₂

21
−206.244

8.884

22
−148.97

34.064
SiO₂

23
129.921
x
40.529

24
−2704.885

33.192
SiO₂

25
−195.599

0.946

26
−794.214
x
30.169
SiO₂

27
−479.39

24.236

28
−311.778
x
100.056
SiO₂

29
−159.333

28.806

30
309.839

43.609
SiO₂

31
836.077
x
0.951

32
225.096

55.667
SiO₂

33
687.556

0.945

34
154.575

64.278
SiO₂

35
911.8
x
0.932

36
89.986

44.143
SiO₂

37
199.475
x
0.878

38
61.984

9.635
SiO₂

39
35.475

34.43
Liquid

40
∞

Resist

TABLE 2

Aspherical constants

Surface 4
Surface 5
Surface10
Surface 14

A
5.36225288E−08
A
2.53854010E−08
A
4.51137087E−07
A
−8.48905023E−09

B
−5.17992581E−12
B
−1.22713179E−11
B
2.46833840E−11
B
1.45061822E−13

C
8.49599769E−16
C
1.21417341E−15
C
5.78496960E−15
C
−6.34351367E−18

D
−7.57832730E−20
D
−1.92474180E−19
D
−4.39101683E−18
D
2.84301572E−22

E
3.59228710E−24
E
2.08240691E−23
E
−5.64853356E−22
E
−8.24902650E−27

F
−9.16722201E−29
F
−9.29539601E−28
F
4.95744749E−26
F
1.27798308E−31

Surface 18
Surface 19
Surface 20

A
1.04673033E−08
A
−4.11099367E−09
A
1.14749646E−07

B
1.34351117E−13
B
−9.91828838E−14
B
−8.19248307E−12

C
1.03389626E−18
C
−7.93614779E−19
C
8.78420843E−16

D
5.16847878E−23
D
−1.66363646E−22
D
−1.39638210E−19

E
−1.23928686E−27
E
5.56486530E−27
E
2.09064504E−23

F
3.09904827E−32
F
−1.79683490E−31
F
−2.15981914E−27

Surface 23
Surface 26
Surface 28

A
−2.87603531E−08
A
−4.35420789E−08
A
−2.70754285E−08

B
−9.68432739E−12
B
−6.70429494E−13
B
−1.36708653E−12

C
6.88099059E−16
C
−4.05835225E−17
C
−2.46085956E−17

D
−8.70009838E−20
D
−1.10658303E−20
D
2.26651081E−21

E
9.59884320E−24
E
4.80978147E−25
E
−1.20009586E−25

F
−5.07639229E−28
F
−5.35014389E−29
F
9.28622501E−30

Surface 31
Surface 35
Surface 37

A
4.38707762E−09
A
1.73743303E−08
A
1.04975421E−07

B
−3.69893805E−13
B
1.60994523E−12
B
1.94141448E−11

C
−4.93747026E−18
C
−1.71036162E−16
C
−2.31145732E−15

D
4.05461849E−22
D
1.26964535E−20
D
4.57201996E−19

E
−7.59674606E−27
E
−5.77497378E−25
E
−3.92356845E−23

F
5.58403314E−32
F
1.55390733E−29
F
2.35233647E−27

G
−1.78430224E−34

TABLE 3

Design data

SUR-

THICK-
MATE-

FACE
RADIUS
NESS
RIAL
INDEX
SEMIDIAM

0
∞
32.0000

65.50

1
∞
0.0000

80.45

2
332.4480
18.9959
SiO₂
1.560318
84.22

3
27083.8930
17.5539

85.42

4
−253.5666
26.7129
SiO₂
1.560318
86.06

5
−179.3607
164.1318

90.72

6
1920.0084
34.5089
SiO₂
1.560318
111.13

7
−279.4103
0.9461

111.59

8
213.6767
34.3917
SiO₂
1.560318
103.48

9
17137.3629
26.7484

100.67

10
−208.9766
9.4997
SiO₂
1.560318
99.22

11
−609.1513
0.9500

97.67

12
734.0560
18.8742
SiO₂
1.560318
95.00

13
−1380.9253
24.2008

93.32

14
∞
231.0887

81.98

15
252.7510
74.6720
SiO₂
1.560318
126.43

16
1098.5274
0.9492

121.38

17
268.9906
50.1845
SiO₂
1.560318
119.28

18
−463.5300
1.0915

117.08

19
697.8278
30.0054
SiO₂
1.560318
106.59

20
292.0140
120.0163

94.90

21
∞
9.9914

82.23

22
∞
−100.0083
Mirror
1.560318
142.10

23
−178.0803
−45.0048
SiO₂
1.560318
115.52

24
−663.9291
−95.3149

113.38

25
−237.9404
−15.0000
SiO₂
1.560318
115.72

26
−166.3412
−152.4364

111.11

27
222.8026
−15.0000
SiO₂
1.560318
127.22

28
539.8416
−94.3687

138.91

29
364.8709
94.3687
Mirror

167.04

30
539.8416
15.0000
SiO₂
1.560318
138.91

31
222.8026
152.4364

127.22

32
−166.3412
15.0000
SiO₂
1.560318
111.11

33
−237.9404
95.3149

115.72

34
−663.9291
45.0048
SiO₂
1.560318
113.38

35
−178.0803
100.0083

115.52

36
∞
94.5942

122.31

37
∞
−23.8903

91.10

38
∞
20.0000

179.89

39
254.8239
29.5175
SiO₂
1.560318
96.82

40
−2985.0549
36.7407

96.62

41
200.4128
45.9683
SiO₂
1.560318
106.20

42
−666.1976
170.5500

105.01

43
−95.1516
15.0000
SiO₂
1.560318
77.96

44
−643.9252
55.6492

95.09

45
−175.8508
−55.6492
Mirror

109.51

46
−643.9252
−15.0000
SiO₂
1.560318
95.09

47
−95.1516
−170.5500

77.96

48
−666.1976
−45.9683
SiO₂
1.560318
105.01

49
200.4128
−12.1735

106.20

50
∞
−24.5646

90.83

51
−2985.0549
−29.5175
SiO₂
1.560318
96.62

52
254.8239
−20.0000

96.82

53
∞
180.1673
Mirror

134.73

54
−148.5117
25.7491
SiO₂
1.560318
95.86

55
327.9861
43.1843

116.84

56
−496.1113
30.0070
SiO₂
1.560318
124.28

57
−252.6773
19.1777

130.89

58
1365.3904
68.1411
SiO₂
1.560318
165.17

59
−284.3746
73.5313

172.58

60
754.4880
93.5313
SiO₂
1.560318
234.19

61
−588.1067
54.2510

235.10

62
357.9132
85.3268
SiO₂
1.560318
221.99

63
−762.8649
0.9929

220.72

64
304.8598
57.6484
SiO₂
1.560318
181.91

65
1098.9629
0.9340

177.48

66
143.0811
62.6047
SiO₂
1.560318
127.33

67
347.6273
0.9010

177.47

68
79.6669
50.1800
CaF₂
1.501403
73.25

69
36.1540
21.2194
Liquid
1.600000
31.82

70
∞

19.38

TABLE 4

Aspherical constants

SURFACE
3
19
24
28
30

K
0
0
0
0
0

A
4.047232E−09
−4.175853E−08
−3.889430E−08
6.661869E−09
6.661869E−09

B
8.449241E−13
−5.621416E−13
2.260825E−13
2.899240E−13
2.899240E−13

C
5.603175E−17
−2.909466E−19
9.880822E−18
−1.932302E−17
−1.932302E−17

D
−4.004583E−21
3.690043E−22
−2.672567E−22
1.602360E−21
1.602360E−21

E
−8.168767E−25
2.119217E−26
4.717688E−26
−6.342246E−26
−6.342246E−26

F
2.123279E−29
−9.535588E−31
−3.817055E−30
1.183564E−30
1.183564E−30

SURFACE
34
39
44
46
52

K
0
0
0
0
0

A
−3.889430E−08
−2.037803E−08
−1.157857E−08
−1.157857E−08
−2.037803E−08

B
2.260825E−13
−6.612137E−13
1.455623E−12
1.455623E−12
−6.612137E−13

C
9.880822E−18
2.840028E−17
−5.746524E−17
−5.746524E−17
2.840028E−17

D
−2.672567E−22
−4.931922E−21
1.261354E−21
1.261354E−21
−4.931922E−21

E
4.717688E−26
4.142905E−25
4.054615E−25
4.054615E−25
4.142905E−25

F
−3.817055E−30
−1.562251E−29
−2.761361E−29
−2.761361E−29
−1.562251E−29

SURFACE
58
62
65
67

K
0
0
0
0

A
−1.679180E−08
−1.483428E−08
−9.489171E−09
−1.782977E−08

B
−5.846864E−14
−2.269457E−14
5.001612E−13
9.574096E−13

C
7.385649E−18
4.944523E−18
−1.283531E−17
7.878477E−17

D
−5.142028E−22
−1.410026E−22
−8.674473E−23
−7.167182E−21

E
1.479187E−26
1.643655E−27
7.103644E−27
2.682224E−25

F
−2.189903E−31
−7.668842E−33
−7.251904E−32
−3.423260E−30

TABLE 5

Design data

SUR-

THICK-
MATE-

FACE
RADIUS
NESS
RIAL
INDEX
SEMIDIAM

0
∞
32.0000

65.50

1
∞
0.0000

80.46

2
3568.5495
29.3610
CAF₂
1.555560
80.77

3
−306.4778
50.8080

84.99

4
−495.7015
32.5298
CAF₂
1.555560
97.37

5
−161.1181
81.4155

99.50

6
188.0753
36.2525
CAF₂
1.555560
93.00

7
−1013.7352
6.1886

90.93

8
288.3482
26.9703
CAF₂
1.555560
82.17

9
872.7887
32.5801

74.60

10
∞
47.8395

57.76

11
−76.3176
12.9591
CAF₂
1.555560
65.40

12
−82.8195
72.8834

71.21

13
494.0581
30.0025
CAF₂
1.555560
105.98

14
500.2689
0.9499

109.01

15
210.1705
55.9335
CAF₂
1.555560
115.54

16
−462.2471
0.9442

114.96

17
191.5029
28.1484
CAF₂
1.555560
104.19

18
469.5739
3.8083

100.65

19
313.4359
9.4935
CAF₂
1.555560
99.24

20
161.6230
115.1964

91.07

21
∞
14.7967

90.40

22
∞
−100.0183
Mirror

206.37

23
−247.2670
−56.5211
CAF₂
1.555560
148.25

24
1546.1350
−403.3917

147.84

25
500.0000
−25.0000
CAF₂
1.555560
142.88

26
−2059.5717
−87.3199

147.68

27
173.4701
−25.0000
CAF₂
1.555560
148.30

28
823.5657
−65.7941

193.66

29
295.8639
65.7941
Mirror

204.70

30
823.5657
25.0000
CAF₂
1.555560
193.66

31
173.4701
87.3199

148.30

32
−2059.5717
25.0000
CAF₂
1.555560
147.68

33
500.0000
403.3917

142.88

34
1546.1350
56.5211
CAF₂
1.555560
147.84

35
−247.2670
100.0183

148.25

36
∞
49.8789

125.86

37
∞
20.8278

89.12

38
∞
20.0000

149.02

39
215.5222
38.8898
CAF₂
1.555560
91.59

40
−548.9606
360.6137

90.02

41
−126.6780
15.0000
CAF₂
1.555560
120.92

42
−567.9480
48.8335

169.01

43
−224.2817
−48.8335
Mirror

171.87

44
−567.9480
−15.0000
CAF₂
1.555560
169.01

45
−126.6780
−314.8668

120.92

46
∞
−45.7487

81.94

47
−548.9606
−38.8898
CAF₂
1.555560
90.02

48
215.5222
−20.0000

91.59

49
∞
195.8787
Mirror

133.74

50
−121.2718
15.1499
CAF₂
1.555560
97.18

51
529.2614
24.3014

127.08

52
−8438.5548
64.5537
CAF₂
1.555560
137.42

53
−202.6253
25.2464

142.97

54
−1447.9251
63.0634
CAF₂
1.555560
168.91

55
−254.3816
80.5189

174.93

56
783.5550
57.0370
CAF₂
1.555560
203.06

57
−939.7625
70.4486

203.12

58
358.1334
55.4484
CAF₂
1.555560
186.96

59
5861.2627
0.9614

184.33

60
259.9889
36.5173
CAF₂
1.555560
161.62

61
371.5128
0.8975

156.47

62
134.7936
77.4909
CAF₂
1.555560
127.53

63
767.8631
0.7967

119.07

64
72.9080
48.3195
CAF₂
1.555560
70.97

65
29.7284
27.0563
IMMO16
1.600000
31.25

66
∞

19.39

TABLE 6

Aspherical constants

SURFACE
3
9
19
24
26

K
0
0
0
0
0

A
2.172737E−08
8.983641E−08
−5.825972E−08
−1.605889E−08
−2.779244E−10

B
1.718631E−12
−5.996759E−12
−6.306762E−13
4.504977E−16
−3.062909E−14

C
1.514127E−16
6.363808E−16
−2.783920E−17
3.596627E−21
1.861506E−18

D
−2.716770E−22
−3.998733E−20
−1.594705E−21
2.792862E−22
−2.425072E−22

E
−1.008203E−24
−5.130142E−24
2.956685E−25
−1.885291E−26
1.114443E−26

F
−1.157181E−28
1.266998E−28
−1.064251E−29
3.351694E−31
−2.553147E−31

SURFACE
28
30
32
34

K
0
0
0
0

A
4.632690E−09
4.632690E−09
−2.779244E−10
−1.605889E−08

B
−3.213384E−14
−3.213384E−14
−3.062909E−14
4.504977E−16

C
7.229632E−20
7.229632E−20
1.861506E−18
3.596627E−21

D
2.100335E−23
2.100335E−23
−2.425072E−22
2.792862E−22

E
−5.592560E−28
−5.592560E−28
1.114443E−26
−1.885291E−26

F
6.249291E−33
6.249291E−33
−2.553147E−31
3.351694E−31

SURFACE
39
42
44
48

K
0
0
0
0

A
−1.815667E−08
−9.514646E−09
−9.514646E−09
−1.815667E−08

B
−2.488991E−13
1.336864E−13
1.336864E−13
−2.488991E−13

C
2.824306E−17
−4.722253E−18
−4.722253E−18
2.824306E−17

D
−4.697303E−21
1.120165E−22
1.120165E−22
−4.697303E−21

E
3.415362E−25
−1.895395E−27
−1.895395E−27
3.415362E−25

F
−9.509214E−30
1.489410E−32
1.489410E−32
−9.509214E−30

SURFACE
54
59
61
63

K
0
0
0
0

A
−1.031964E−08
8.72E−09
−2.45E−08
4.37E−08

B
−1.081794E−13
−2.71E−13
6.62E−13
−8.96E−13

C
6.909628E−18
1.07E−17
−1.32E−17
4.21E−17

D
−3.648077E−22
−6.07E−22
6.68E−22
−3.88E−21

E
9.693996E−27
1.40E−26
−1.47E−26
2.01E−25

F
−1.380442E−31
−1.10E−31
1.14E−31
−3.84E−30

TABLE 7

Design data

SUR-

THICK-
MATE-

FACE
RADIUS
NESS
RIAL
INDEX
SEMIDIAM.

0
∞
32.0000

65.50

1
∞
0.0000

80.45

2
361.5503
30.0063
SiO₂
1.560318
83.87

3
3766.1854
29.9775

86.87

4
−313.0243
17.3177
SiO₂
1.560318
90.72

5
−211.2930
182.7697

93.19

6
−709.0001
29.1631
SiO₂
1.560318
120.83

7
−255.7121
13.1321

122.28

8
261.1325
45.4463
SiO₂
1.560318
118.65

9
−728.3260
29.9790

116.70

10
−209.1405
18.3161
SiO₂
1.560318
113.35

11
−2675.8307
4.7872

113.10

12
421.7508
25.2987
SiO₂
1.560318
112.42

13
−5576.5014
21.4392

111.29

14
∞
355.5491

103.93

15
249.8044
71.3667
SiO₂
1.560318
163.42

16
−4441.8089
32.5158

161.31

17
247.2422
37.4261
SiO₂
1.560318
135.08

18
797.4045
43.7199

130.81

19
665.9047
30.0078
SiO₂
1.560318
108.60

20
318.3673
120.0233

96.83

21
∞
9.9881

79.40

22
∞
−100.0079
Mirror

122.85

23
−145.3105
−45.0039
SiO₂
1.560318
107.21

24
−705.3999
−7.6524

104.90

25
−149.2286
−15.0000
SiO₂
1.560318
100.69

26
−107.5358
−125.6003

91.50

27
398.2665
−15.0000
SiO₂
1.560318
101.84

28
419.3212
−44.0802

104.16

29
398.6744
44.0802
Mirror

107.66

30
419.3212
15.0000
SiO₂
1.560318
104.16

31
398.2665
125.6003

101.84

32
−107.5358
15.0000
SiO₂
1.560318
91.50

33
−149.2286
7.6524

100.69

34
−705.3999
45.0039
SiO₂
1.560318
104.90

35
−145.3105
100.0079

107.21

36
∞
103.9571

130.84

37
∞
−33.2893

99.43

38
∞
20.0000

210.81

39
250.9147
31.5356
SiO₂
1.560318
101.23

40
−1057.0829
21.3930

102.52

41
202.0288
47.3927
SiO₂
1.560318
111.71

42
−941.7186
197.8094

110.48

43
−88.9067
15.0000
SiO₂
1.560318
72.67

44
−573.5619
23.1569

88.88

45
−142.4338
−23.1569
Mirror

89.38

46
−573.5619
−15.0000
SiO₂
1.560318
88.88

47
−88.9067
−197.8094

72.67

48
−941.7186
−47.3927
SiO₂
1.560318
110.48

49
202.0288
−11.3868

111.71

50
∞
−9.9896

92.32

51
−1057.0829
−31.5356
SiO₂
1.560318
102.52

52
250.9147
−20.0000

101.23

53
∞
209.4519
Mirror

135.07

54
−133.90811
9.4987
SiO₂
1.560318
97.71

55
406.9979
48.9711

119.82

56
−523.9173
41.1332
SiO₂
1.560318
135.89

57
−224.0541
29.8664

142.55

58
1367.6570
94.8234
SiO₂
1.560318
191.42

59
−271.7647
8.1788

198.87

60
667.9279
83.6854
SiO₂
1.560318
232.81

61
−808.5395
140.7841

233.01

62
286.6775
82.6895
SiO₂
1.560318
201.18

63
−1096.4782
0.9668

198.76

64
350.5350
35.6242
SiO₂
1.560318
164.87

65
884.2685
0.9173

159.58

66
115.9293
64.9068
SiO₂
1.560318
108.97

67
412.6826
0.8041

99.04

68
57.1792
41.0408
CaF₂
1.501403
55.06

69
99.9106
10.1713
Liquid
1.600000
30.68

70
∞

19.40

TABLE 8

Aspherical constants

SURFACE
3
19
24
28
30

K
0
0
0
0
0

A
−1.001534E−09
−4.128786E−08
−4.510495E−08
1.339665E−08
1.339665E−08

B
6.144615E−13
−4.980750E−13
6.742821E−13
1.482582E−12
1.482582E−12

C
1.247768E−16
2.649167E−18
3.004246E−17
−1.857530E−16
−1.857530E−16

D
−1.048854E−20
5.315992E−22
2.453737E−21
3.433994E−20
3.433994E−20

E
−4.463818E−25
−6.165935E−27
−3.687563E−25
−2.905941E−24
−2.905941E−24

F
6.154983E−30
1.945950E−32
−1.491146E−30
1.237374E−28
1.237374E−28

SURFACE
34
39
44
46
52

K
0
0
0
0
0

A
−4.510495E−08
−2.582589E−08
−1.589920E−08
−1.589920E−08
−2.582589E−08

B
6.742821E−13
−4.336537E−13
1.112204E−12
1.112204E−12
−4.336537E−13

C
3.004246E−17
5.153775E−17
−2.537422E−17
−2.537422E−17
5.153775E−17

D
2.453737E−21
−7.829187E−21
−5.148293E−21
−5.148293E−21
−7.829187E−21

E
−3.687563E−25
5.696031E−25
8.322199E−25
8.322199E−25
5.696031E−25

F
−1.491146E−30
−1.711252E−29
−2.485886E−29
−2.485886E−29
−1.711252E−29

SURFACE
58
62
65
67

K
0
0
0
0

A
−1.313863E−08
−1.809441E−08
−1.821041E−09
−4.599046E−10

B
1.817234E−14
−2.428724E−14
4.495016E−13
3.983791E−12

C
2.355838E−18
1.168088E−17
−7.637258E−18
−1.382332E−16

D
−1.447425E−22
−4.545469E−22
−1.610477E−21
−2.858839E−21

E
3.333235E−22
7.354258E−27
7.379400E−26
4.614539E−25

F
−4.355238E−32
−4.766510E−32
−9.483899E−31
−1.411510E−29

Number	Date	Country
60544967	Feb 2004	US
60591775	Jul 2004	US
60592208	Jul 2004	US

	Number	Date	Country
Parent	12194229	Aug 2008	US
Child	13115741		US
Parent	10597806	Aug 2006	US
Child	12194229		US

PROJECTION OBJECTIVE FOR A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Provisional Applications (3)

Continuations (2)