EP1483625A1

EP1483625A1 - High-aperture projection lens

Info

Publication number: EP1483625A1
Application number: EP02738025A
Authority: EP
Inventors: Karl-Heinz Schuster
Original assignee: Carl Zeiss SMT GmbH
Current assignee: Carl Zeiss SMT GmbH
Priority date: 2002-03-08
Filing date: 2002-05-03
Publication date: 2004-12-08
Also published as: EP1485760A1; CN100573222C; CN1639644A; AU2003221490A1; AU2002312872A1; US20050231814A1; US6891596B2; JP2005519348A; WO2003077037A1; US7495840B2; WO2003077036A1; US20030174408A1; DE10210899A1; US20070188880A1; US7312847B2; KR20040099307A; KR100991590B1; US7203008B2; JP2005519347A; US20050141098A1

Abstract

The invention relates to a purely refractive high aperture projection lens comprising a plurality of optical elements and a system shutter (5) arranged at a distance from the image plane. The optical element nearest to the image plane (3) of the projection lens is a plane-convex lens (34) having an incident surface which is essentially spherical and an exit surface which is essentially even. The size of the diameter of the plane-convex lens is at least 50 % of the size of the shutter diameter of the system shutter (5). Preferably, only positive lenses (32, 33, 34) are arranged between the system shutter (5) and the image plane (3). Said optical system enables high-aperture imaging at NA ≥ 0.85, optionally at NA ≥ 1.

Description

Description Projection lens with the highest aperture

The invention relates to a projection lens for imaging a pattern arranged in the object plane of the projection lens into the image plane of the projection lens with ultraviolet light of a predetermined working wavelength.

Photolithographic projection lenses have been used for the manufacture of semiconductor devices and other finely structured components for several decades. They serve to project patterns of photomasks or graticules, which are also referred to below as masks or reticles, onto an object coated with a light-sensitive layer with the highest resolution on a reduced scale.

Three parallel developments contribute to the generation of ever finer structures of the order of 100 nm or less. First, an attempt is made to increase the numerical aperture (NA) of the projection objective on the image side beyond the currently achievable values in the range of NA = 0.8 or above. Secondly, ever shorter working wavelengths of ultraviolet light are used, preferably wavelengths of less than 260 nm, for example 248 nm, 193 nm, 157 nm or less. Finally, other measures to increase the resolution are used, for example phase-shifting masks and / or oblique lighting. In particular, the use of phase-shifting masks requires obscuration-free systems, ie systems without shadowing in the image field. Systems without shadowing in the image field are in the Microlithography generally to be preferred, even if systems with obscuration with otherwise excellent optical properties are available (for example DE 196 39 586 corresponding to US 6,169,627 B1).

When the aperture is increased significantly above NA = 0.85, limits are placed on the angular capacity, especially of the near-image lenses. Larger apertures close to NA = 1 or above are considered impractical, since it must be assumed that with such high apertures, edge and coma rays cannot be coupled out of a lens or coupled into the light-sensitive layer of the substrate due to total reflection.

The object of the invention is to create a projection objective which has a very high numerical aperture on the image side, an image field which is sufficiently large for practical use in wafer steppers or wafer scanners, and a good correction state.

This object is achieved by a projection objective with the features of claim 1. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the content of the description.

According to one aspect of the invention, a projection lens for imaging a pattern arranged in the object plane of the projection lens into the image plane of the projection lens with ultraviolet light of a predetermined working wavelength has a multiplicity of optical elements which are arranged along an optical axis and one which is arranged at a distance in front of the image plane System cover with a cover diameter. The closest optical group with refractive power to the image plane is a plano-convex group with an essentially spherical entrance surface and an im substantially flat exit surface. The exit surface is the last optical surface of the system and should be arranged in the vicinity of a substrate to be exposed, but without touching it. If necessary, an optical contact can be imparted via an immersion medium, for example a liquid. The plano-convex group has a diameter that is at least 50% of the diaphragm diameter. The diameter of the plano-convex group can preferably even be more than 60% or more than 70% of the diaphragm diameter.

The system aperture in the sense of this application is the area near the image plane in which the main beam of the image intersects the optical axis. A diaphragm for limiting and possibly adjusting the aperture used can be arranged in the area of the system diaphragm. In systems with at least one intermediate image, there is at least one further aperture plane at a greater distance from the image plane.

The above-mentioned measures make it possible to implement the highest numerical apertures NA> 0.85 on the image side, the numerical aperture even being able to be NA = 1 or more, for example NA = 1.1. This means that at conventionally well manageable working wavelengths, for example at 193nm,

Show structure widths of the order of 50nm well. High apertures, in particular in the range of NA = 1 or above, require special measures in order to master the surface loading of the optical surfaces as a whole and in particular the surface loading in the region between the system aperture and the image plane. Component-related apertures must not be too high in this area, since in the case of very oblique light incidence, a large part of the incident light can no longer pass through the transparent optical elements and can therefore no longer contribute to the image formation. As the next picture If the refractive group uses a plano-convex group that is axially thick enough that its diameter reaches more than half the diaphragm diameter, the strongly curved entrance surface has an unusually large dimension compared to conventional lenses. If the lens surface is opened high, a long radius of the entrance surface should be aimed for, since this reduces the field load. The longer the radius of the last entry surface in front of the image plane, the smaller the relative field and the smaller the induced field aberrations. This makes it possible to transmit high beam apertures generated in a suitable manner in front of the plano-convex lens with low aberration and with reasonable light losses up to the point of action in the image plane.

In a preferred development, the plano-convex group is formed by a single, one-piece plano-convex lens. It is also possible to design the plano-convex group in the form of a divided plano-convex lens, the parts of which are preferably pressed against one another. The division can take place along a flat or curved division surface. A division in particular makes it possible to produce the part of the plano-convex group close to the image field, in which particularly high radiation energy densities occur, from a particularly radiation-resistant material, for example as calcium fluoride, while less radiation-exposed areas can be made from another material, for example synthetic quartz glass. A plane-parallel end plate can optionally be provided as the next element of the plano-convex group. This is preferably blown onto the preceding optical element. Within narrow limits it is also possible to split the plano-convex group into separate lens elements, between which there may be a small air gap at least in some areas, which should, however, be significantly less than one millimeter. The radii to the air gap should be curved this way be that there is no total reflection. Depending on the angular strength of the thin antireflection coating, the angular load preferably remains smaller than sin u ^' from 0.85 to 0.95.

According to another aspect of the invention, it is particularly advantageous if only lenses with a positive refractive power are arranged between the system diaphragm and the image plane, if appropriate plus one or more plane-parallel, transparent plates. For example, at least one biconvex positive lens can be arranged between the system diaphragm and the plano-convex group. At least two, in particular exactly two, biconvex positive lenses are more favorable. In a preferred embodiment, a plano-convex meniscus is preceded by two positive lenses, which provide the essential part of the system power. Because they sit close to the system panel and can work in large diameters, a very small relative field load can also be achieved here. This results in a very simple and efficient design of a projection lens with regard to the area behind the system aperture. It is therefore advantageous if the last lens group arranged between the system diaphragm and the image plane has a maximum of four optical elements with refractive power, ideally only three lenses, which are preferably positive lenses in each case. Lenses with a negative refractive power can be provided as long as their refractive power is low compared to the total refractive power of the lens group arranged between the system aperture and the image plane. Plane-parallel plates can also be provided.

A refractive power distribution that is favorable for a high numerical aperture on the image side is characterized in that the last lens group arranged between the system aperture and the image plane advantageously has a focal length that is less than 20% or 17%, in particular less than 15%, of the overall length of the projection lens is. The axial distance between the object plane and the optically conjugate image plane is referred to as the overall length. The distance between the system diaphragm and the image plane is preferably less than 25%, in particular less than 22% of the overall length and / or less than approximately 95%, 90% or 86% of the diaphragm diameter. Overall, a very close-to-image position of the system cover is favorable. The aperture can be real or equivalent to the conjugate location of the real aperture in the presence of an intermediate image.

Projection lenses according to the invention can be catadioptric or dioptric and should depict without obscuration. Purely refractive, ie dioptric projection lenses are preferred, in which all optical components with refractive power consist of transparent material. One example is a one-waist system with a stomach close to the object, a stomach close to the image and an intermediate waist, in the area of which the beam diameter is preferably less than approximately 50% of the maximum beam diameter in the area of one of the bellies.

The systems can be set up so that all transparent optical elements are made of the same material. In an embodiment designed for a working wavelength of 193 nm, synthetic quartz glass is used for all lenses. Embodiments for 157 nm, in which all lenses are made of calcium fluoride or another fluoride crystal material, are also possible. Combinations of several different materials are also possible, for example to make it easier to correct color errors or to reduce compaction. For example, at 193 nm, the synthetic quartz glass can be replaced by a crystal material, eg calcium fluoride. Within the scope of the invention, high-aperture projection objectives, in particular also purely refractive projection objectives, are possible, in which the numerical aperture NA> 0.85 on the image side. It is preferably at least 1 and, in an embodiment which will be explained in more detail later, has a value NA = 1.1. Despite these high numerical apertures, sufficient light energy can be coupled into the substrate to be exposed via a gas-filled gap if a sufficiently small working distance on both sides is maintained. In preferred embodiments, this is below four times the working wavelength used, in particular below the working wavelength. It is particularly favorable if the working distance is less than half the working wavelength, for example less than a third, a quarter or a fifth of the working wavelength. With these short working distances, imaging can take place in the near optical field, in which evanescent fields that existed in the immediate vicinity of the last optical surface of the imaging system are used for imaging. The projection objectives are also suitable for immersion lithography, in which the space between the exit surface of the objective and the substrate is filled with an immersion fluid with a suitable refractive index and sufficient transmission for the wavelength used. Suitable immersion liquids can, for example, mainly contain the elements H, F, C or S. Deionized water can also be used.

Despite these extreme values for numerical aperture and working distance, the invention makes it possible to use lenses with a very large image field diameter that is sufficient for practical lithography, which in preferred embodiments is larger than approx. 10 mm, in particular larger than approx. 20 mm and / or more than 1 %, in particular more than 1.5% of the overall length of the projection lens and / or more than 1%, in particular more than 5% of the largest lens diameter.

Preferred projection objectives are distinguished by a number of favorable constructive and optical features which, alone or in combination with one another, are conducive to the suitability of the objective for high-resolution microlithography, in particular in the optical near field and for immersion lithography.

At least one aspherical surface is preferably arranged in the area of the system cover. Preferably, several surfaces with aspheres come closely behind the diaphragm. In particular, at least one double-aspherical lens, which is preferably a biconvex lens, can be provided between the system aperture and the image plane. Thus, even in the area between the waist and image plane, i.e. in the last abdomen, at least one double-spherical biconvex lens should be cheap. It can also be advantageous if the last optical surface before the system diaphragm and the first optical surface after the system diaphragm are aspherical. In particular, opposite aspherical surfaces with curvature pointing away from the diaphragm can be provided here. The high number of aspherical surfaces in the area of the system diaphragm is favorable for the correction of the spherical aberration and has a favorable effect on the setting of the isoplanasia.

At least one meniscus lens with a concave surface on the object is preferably provided in the area immediately in front of the system diaphragm. With higher apertures, at least two such menisci, which follow one another, can be favorable, which can have positive or negative refractive power. At very high opening angles of NA> 1.0, a group of two menisci of this type is preferred, in which a meniscus with a negative refractive power and a meniscus with a positive one Refractive power follows. The negative refractive power is preferably so great that a slight cross-sectional narrowing (auxiliary waist) can occur in the beam.

A meniscus group with a positive meniscus and a negative meniscus behind it, in which the centers of curvature of all optical surfaces are on the object or reticle side, can also be advantageous for other projection lenses, in particular directly in front of a diaphragm in the area, regardless of the other features of the invention Large beam diameter, the aperture can be a physical aperture for changing the bundle cross-section or a conjugated aperture.

It has also proven to be advantageous if at least one meniscus lens with a negative refractive power and a concave surface directed toward the image is arranged between the waist and the system diaphragm. Often, at least two consecutive meniscus lenses of this type, whose centers of curvature lie on the image side, are often particularly favorable. It is advantageous if the refractive power of the first meniscus on the object side is at least 30% stronger than that of the subsequent meniscus on the image side of the meniscus group.

Furthermore, it can be favorable if at least one positive meniscus lens with a concave surface on the object side is arranged between the waist and the system diaphragm in the vicinity of the waist. Here too, several, for example two, successive lenses of this type can be provided instead of such a meniscus lens.

Embodiments are particularly advantageous in which at least one meniscus lens with a concave surface on the object side and behind at least one between the waist and the system diaphragm in this order a meniscus lens with a concave surface on the image side is arranged. Two consecutive menisci of the respective curvatures are preferably provided. The meniscus lenses facing the waist preferably have positive refractive powers, the menisci facing the image plane preferably have negative refractive powers. In the area between these lenses or lens groups, there is therefore a change in the position of the center of curvature of menisci.

A plurality of negative lenses are preferably arranged one after the other in the region of the waist, in preferred embodiments there are at least two, preferably three negative lenses. These bear the main burden of the Petzval correction.

At the object-side entrance of the system when entering the first belly, at least two negative lenses are advantageous in order to widen the beam coming from the object. Three or more such negative lenses are preferred. With high entrance apertures of more than 0.2, it is favorable if at least one aspherical surface is provided on at least one of the first lenses. Each of the input-side negative lenses preferably has at least one aspherical surface.

A lens group with a strong positive refractive power, which represents the first belly of the beam guidance, preferably follows behind this input group. In this group, at least one meniscus lens with positive refractive power and concave surfaces on the image side can be favorable in the area of large beam heights in the vicinity of the object plane. In the case of such a meniscus, the center of curvature of which lies on the image side, the exit side facing the image preferably has a relatively strong curvature, the radius of which can be, for example, less than 50% of the overall length of the projection objective. The foregoing and other features emerge from the claims and also from the description and the drawing, the individual features being implemented individually and in groups in the form of sub-combinations in one embodiment of the invention and in other fields, and advantageous as well protective designs can represent.

1 is a lens section through an embodiment of a refractive projection objective which is designed for a 193 nm working wavelength.

In the following description of the preferred embodiment, the term “optical axis” denotes a straight line through the centers of curvature of the spherical optical components or through the axes of symmetry of aspherical elements. Directions and distances are described as image-side, wafer-side or image-wise when they are in the direction of the If the image plane or the substrate to be exposed there is directed and as the object side, reticle side or object side, if they are directed towards the object in relation to the optical axis, the object is a mask (reticle) with the pattern of an integrated circuit in the examples The image is formed in the examples on a wafer serving as a substrate and serving with a photoresist layer, but other substrates are also possible, for example elements for liquid crystal displays or substrates for optical he grating The focal lengths given are focal lengths with respect to air.

1 shows a characteristic structure of a purely refractive reduction objective 1 according to the invention. It serves to insert a pattern of a reticle or the like into an object plane 2 image an image plane 3 conjugated to the object plane on a reduced scale without obscurations or shadowing in the image field, for example on a 5: 1 scale. It is a rotationally symmetrical one-waist system, the lenses of which are arranged along an optical axis 4 which is perpendicular to the object and image plane and form an abdomen 6 on the object side, an abdomen 8 on the image side and an intermediate waist 7. A small auxiliary waist 9 is formed within the second belly 8 close to the system cover 5. The system diaphragm 5 is in the near-image area of large beam diameters.

The lenses can be divided into several successive lens groups with specific properties and functions. A first lens group LG1 following the object plane 2 at the input of the projection lens has negative refractive power overall and serves to expand the beam coming from the object field. A subsequent second lens group LG2 with an overall positive refractive power forms the first belly 6 and brings the beam together again in front of the subsequent waist 7. In the area of the waist 7 there is a third lens group LG3 with negative refractive power. This is followed by a lens group 4 consisting of positive meniscus lenses with positive refractive power, followed by a fifth lens group LG5 consisting of negative meniscus lenses with negative refractive power. The subsequent lens group LG6 with positive refractive power leads the radiation to the system aperture 5. Behind this is the seventh and last lens group LG7, which consists of three individual lenses with positive refractive power and makes the main contribution to the generation of the very high image-side numerical aperture of NA = 1.1 , The following applies to these: NA = n * sin u ^' , where n is the refractive index of the last optical medium (for example an immersion fluid) and u ^{' is} half the aperture angle on the image side. The first lens group LG1 opens with three negative lenses 11, 12, 13 which, in this order, have a biconcave negative lens 11 with an aspherical entry side, a negative meniscus lens 12 with an image-side center of curvature and an aspherical entry side and a negative meniscus lens 13 with an object side

Center of curvature and aspherical exit side includes. With the present high entrance aperture of 0.2125, at least one aspherical surface should be provided on at least one of the first two lenses 11, 12 in order to limit the generation of aberrations in this area. Preferably, as in the present example, an aspherical surface (at least) is provided on each of the three negative lenses.

The second lens group LG2, with a small air gap behind the last lens 13 of the first lens group LG1, has a positive meniscus lens 14 with a center of curvature on the object side, a further positive meniscus lens 15 with an object side

The center of curvature, a positive meniscus lens 16 with the center of curvature on the image side, a further positive lens 17 with an almost flat exit side, a positive meniscus lens 18 with the center of curvature of the surfaces on the image side and a low-refractive power meniscus lens 20 of the same direction of curvature with almost parallel lens surfaces. The only slightly curved entry side of the lens 15, the likewise only slightly curved exit side of the lens 17 and the exit side of the last meniscus lens 20 are aspherical. This second lens group LG2 represents the first belly 6 of the objective. A special feature is the positive meniscus lens 16 arranged at the largest diameter, the centers of curvature of which lie on the image side. The radius of the exit surface of this lens 16 has a value that is less than half the object image distance. This lens group is used primarily for Petzval correction, distortion telecentricity correction and image field correction outside of the main sections. The third lens group LG3 consists of three negative meniscus lenses 20, 21, 22, the interfaces of which are each spherical. This lens group bears the main burden of correcting the curvature of the field of view and is designed in such a way that, despite the high system aperture of NA = 1.1, the maximum angle of incidence of the rays hitting the lens surfaces is below approx. 60 ° or the sine of the angle of incidence is respectively below 0.85 lies. The first negative lens 20 of the third group is preferably a strongly biconcave lens, so that the main waist 7 opens with strongly curved surfaces.

The fourth lens group LG4 following the waist 7 consists of two positive meniscus lenses 23, 24 with concave surfaces on the image side, the exit side of the meniscus lens 23 on the input side being aspherical, the other surfaces being spherical. In other embodiments, only a single positive meniscus of corresponding curvature can be provided at this point.

The subsequent fifth lens group LG5 also has two meniscus lenses 25, 26, but these each have negative refractive power and the concave surfaces are directed toward the image field 3. If necessary, only a negative meniscus can be provided at this point, the center of curvature of which lies on the wafer side. It has turned out to be favorable if the negative refractive power of the negative meniscus 25 on the object side is at least 30% stronger than that of the subsequent meniscus 26. Such a group with at least one negative meniscus is a central correction element for the function of the one-waist system, to elegantly correct off-axis image errors. In particular, this enables a compact design with relatively small lens diameters. It is particularly important that a change in the position of the centers of curvature between menisci of the fourth lens group LG4 and the fifth lens group LG5 takes place in the entrance region of the second abdomen 8 following the waist 7. It can thereby be achieved that oblique spherical aberration can be smoothed out with an extreme aperture.

The sixth lens group LG6 begins with a sequence of positive lenses 27, 28, 29, 30, it having turned out to be advantageous if at least two of these lenses are biconvex lenses, such as the lenses 27, 28 which follow one another immediately at the input of the sixth lens group each spherical lens surfaces. In the example, the biconvex lenses 27, 28 are followed by a weakly positive meniscus lens 29 with a concave surface on the image side.

At the exit of the sixth lens group LG6 immediately in front of the system diaphragm 5 there is a meniscus group with two meniscus lenses 30, 31, the centers of curvature of which are all on the reticle or object side. At this point, only a corresponding meniscus lens with positive or negative refractive power could also be provided, in particular in the case of lenses with lower apertures. In the very high aperture of NA> 1 shown, the group of two 30, 31 shown is preferred, the meniscus lens 30 on the input side preferably having positive refractive power and the subsequent meniscus lens 31 preferably having negative refractive power. Advantageously, their negative refractive power is so great that a slight constriction in the form of an auxiliary waist 9 occurs in the beam path. In this way it can be achieved that oblique spherical tangential to oblique spherical sagital can be balanced out favorably.

The seventh lens group LG7 arranged between system aperture 5 and image plane 3 represents a further special feature of the invention Projection lenses. Particularly in this area, special measures are required to master the surface loading of the optical surfaces overall in such a way that low-aberration imaging can be achieved with sufficient transmission of the overall lens. For this purpose, it should be ensured between the aperture 5 and the wafer 3 that no apertures are formed in the component that reach an aperture close to 1 as a component against air. A significant contribution to achieving this goal is made here in that a plano-convex lens 34 with a spherical entrance surface and a flat exit surface is arranged as the last optical element directly in front of the image plane 3. This is so thick that its diameter is more than half the diameter of the system diaphragm 5, ideally even more than 60% or 70% of this value. The aim should therefore be the longest possible radius with a high opening of this, preferably spherical, entry surface. This long radius is desirable because it reduces the field load on the entry surface. The longer the radius, the smaller the relative field and thus the induced field aberrations. The entrance surface can also be aspherical.

The near-image plano-convex group, which is formed here by a single, one-piece lens element 34, has a refractive effect. This can be seen from the fact that the entrance surface is not arranged concentrically to the center of the image field because the radius differs from the lens thickness. Axially elongated lenses of this type are preferred, in which the center of curvature of the entrance surface lies within the lens. Plano-convex groups or plano-convex lenses of this type therefore differ significantly from hemispherical plano-convex lenses in which the radius corresponds essentially to their thickness and which are used, for example, in microscopy to improve the coupling of the light into the microscope objective and themselves may not have any refractive properties. In the embodiment shown, the plano-convex meniscus 34 is preceded by two very large positive lenses 32, 33, which provide the essential contribution to the system power. The fact that they sit close behind the diaphragm in the area of large beam diameters also minimizes the relative field load here. The example thus shows a very simple and efficient design of a lithographic lens suitable for the highest apertures with regard to the area behind the system aperture. The plano-convex meniscus 34 picks up the convergent tufts coming from the positive lenses 32, 33 in air or another suitable gaseous medium within the projection lens with a low refractive power in order to pass them on to the light-sensitive layer of the substrate. Embodiments are therefore favorable in which there are only positive lenses between the aperture 5 and the wafer, it also being possible for one or more plane-parallel plates to be provided in addition. The lowest possible number of optical surfaces in this area is also advantageous, since each surface causes reflection losses even with good anti-reflective coating. The number of lenses should be four or fewer here, and again plane-parallel plates can optionally be provided.

Further advantageous measures consist in the fact that surfaces with aspheres should be provided in the area of the diaphragm, particularly close behind it. These can face each other in a lens, as is the case with the biconvex, double-aspherical positive lens 32. It is also advantageous if an aspherical surface is provided both directly in front of the diaphragm plane and immediately behind it. In the example, these are the exit surface of the negative meniscus 31 and the entry surface of the biconvex positive lens 32. The high number of aspheres in the area around the system aperture 5 serves in the example above all to correct the spherical aberration (Zemike coefficients Z9, Z16, Z25, Z26, Z36, Z49) and the setting of the isoplanasia, i.e. the correction of the aperture-related imaging scale.

Table 1 summarizes the specification of the design in a known manner in tabular form. Column 1 gives the number of a refractive or otherwise distinguished surface, column 2 the radius r of the surface (in mm), column 3 the distance d of the surface from the following surface (in mm), which is referred to as thickness, column 4 the material of the optical components and column 5 the refractive index or the refractive index of the material of the component, which follows the entry surface. Column 6 shows the usable free radii or half the free diameter of the lenses (in mm).

In the embodiment, thirteen of the surfaces, namely surfaces 2, 4, 7, 10, 15, 19, 27, 32, 41, 43, 45, 46 and 48 are aspherical. Table 2 shows the corresponding aspherical data, whereby the aspherical surfaces are calculated according to the following rule:

p (h) = [((1 / r) h ² ) / (1 + SQRT (1 - (1-fK) (1 / r) ² h ² )] + C1 * h ⁴ + C2 * h ⁶ +. ...

The reciprocal (1 / r) of the radius indicates the surface curvature and h the distance of a surface point from the optical axis. Thus p (h) gives the so-called arrow height, i.e. the distance of the surface point from the surface vertex in the z direction, i.e. in the direction of the optical axis. The constants K, C1, C2, ... are shown in Table 2.

The optical system 1 which can be reproduced with the aid of this information is designed for a working wavelength of approximately 193 nm, at which the synthetic quartz glass used for all lenses has a refractive index n = 1,56029. The numerical aperture on the image side is 1.1. The lens has an overall length (distance between image plane and Object level) of 1297mm. With an image size of 22mm, a light guide value (product of numerical aperture and image size) of 24.1 mm is achieved. The image-side working distance, ie the distance between the flat exit surface of the last optical element 34 and the image plane 3 is not listed separately. For example, it can be 20 to 50nm. This makes the projection lens suitable for near-field lithography.

If one would like to use immersion lithography instead of near-field lithography, this is easily possible with minor modifications. If the immersion medium has essentially the same refractive index as the last optical element of the objective (which consists, for example, of glass or crystal), the solid is shortened to achieve a greater distance from the image plane and the resulting larger space is created by the immersion medium, e.g. deionized water filled. If the refractive index of the immersion medium deviates from that of the last optical component, both thicknesses are matched to one another as best as possible. A spherical post-correction is advantageous, which can be carried out, for example, with the aid of suitable manipulators on one or more lens elements, for example by adjusting the air gaps. It may also be favorable to easily modify the design shown here as an example.

This creates a projection lens that works at a working wavelength of 193nm, can be produced using conventional techniques for lens production and coatings and allows structures to be resolved well below 100nm. Many individually or in combination useful, constructive measures and the new structure of the area between the aperture 5 and image plane 3 allow a total aperture in the medium to be exposed of 1.1 with relatively small surface loads on the optical Areas within the projection lens. Structure widths in the range of 50nm can be displayed excellently despite the huge aperture of 1.1. This becomes clear from low transverse aberration values and a wavefront RMS value of 2.6mλ at 193nm over all image heights.

The example presented offers further development possibilities in the direction of a higher aperture and / or a smaller number of interfaces. For example, some lenses that are adjacent in pairs can be combined to form a single lens in order to reduce the number of interfaces by two. For example, the lenses 23 and 24, the lenses 18 and 19, the lenses 13 and 14, the lenses 26 and 27 and / or the lenses 11 and 12 can each be combined to form a lens. If necessary, aspherical surfaces must be installed or modified. A combination of lenses is especially useful for shorter wavelengths, e.g. 157nm cheap, where anti-reflective coating and surface roughness of lens surfaces can be problematic. If necessary, a further positive lens behind the diaphragm can be favorable at the highest apertures in order to introduce new aberrations with as few apertures as possible when the apertures are increased.

The advantages of the invention can be used not only with purely refractive projection lenses, but also with catadioptric projection lenses, in particular those that work with geometric or physical (polarization-selective) beam splitting. Special features are in the structure and function in the area of the near-system screen and between this and the picture plane. The upstream lens parts, which in the case of catadioptric projection lenses comprise at least one imaging mirror, should at least provide an overcorrection of the longitudinal color error in order to correct the corresponding undercorrection of the last lens group compensate. A Petzval overcorrection should preferably be provided in order to provide a lead for the Petzval undercorrection of the last lens group. Since this, like a single positive lens, is under-corrected for spherical aberration, the upstream part of the lens should have a spherically over-correcting effect. The measures for achieving these optical characteristics are known to the person skilled in the art and are therefore not explained in more detail here.

FRESH NUMBER 1/2 FREE

F AECHE RADIEN THICK GLASSES 193.304nm DIAMETER

0 0.000000000 27.200000000 L710 0.99998200 45.607

1 0.000000000 5.918415780 L710 0.99998200 53.333

2 -856.520151429AS 8.513391670 SI02HL 1.56028895 54.216

3 221.390186129 4.416825103 N2 1.00000320 58.807

4 388.002080060AS 7.500000000 SI02HL 1.56028895 62.597

5 145.662170604 35.066769313 N2 1.00000320 64.799

6 -156.528478897 13.825053459 SI02HL 1.56028895 68.237

7 -569.268909317AS 1.048245321 N2 1.00000320 84.737

8 -685.623617269 46.805975671 SI02HL 1.56028895 86.118

9 -204.957576367 0.709606715 N2 1.00000320 103.144

10 -880.911273998AS 54.777943597 SI02HL 1.56028895 125.013

11 -248.526945989 1.683182576 N2 1.00000320 131.423

12 224.822351709 54.871581452 SI02HL 1.56028895 156.309

13 512.337183722 33.734945339 N2 1.00000320 153.303

14 304.374483761 58.667551666 SI02HL 1.56028895 146.757

15 -6287.676161070AS 0.700000000 N2 1.00000320 140.984

16 129.979785804 69.743588545 SI02HL 1.56028895 112.463

17 138.594373293 2.395572054 N2 1.00000320 85.809

18 138.485177581 10.992090105 SI02HL 1.56028895 84.654

19 162.930027134AS 45.897552290 N2 1.00000320 78.232

20 -186.365747641 7.500000000 SI02HL 1.56028895 75.979

21 209.249850090 47.901412683 N2 1.00000320 70.469

22 -92.976145902 7.500000000 SI02HL 1.56028895 70.319

23 3940.003552383 22.698881573 N2 1.00000320 84.285

24 -210.566279065 13.458540900 SI02HL 1.56028895 86.301

25 -481.930608562 10.599713214 N2 1.00000320 98.309

26 -299.003037123 29.233512385 SI02H 1.56028895 100.896

27 -211.128540124AS 0.700000000 N2 1.00000320 111.974

28 -241.783293846 45.186608069 SI02HL 1.56028895 113.068

29 -142.093795869 0.700000000 N2 1.00000320 118.747

30 373.228657636 15.000000000 SI02HL 1.56028895 144.714

31 281.545559695 37.551434993 N2 1.00000320 144.973

32 2257.943358151AS 15.000000000 SI02HL 1.56028895 146.555

33 942.886809577 9.018344987 N2 1.00000320 151.237

34 1839.757565259 41.221307008 SI02HL 1.56028895 152.796

35 -572.892294825 0.700000000 N2 1.00000320 156.198

36 536.885209090 59.927790928 SI02HL 1.56028895 168.303

37 -588.394317091 0.700000003 N2 1.00000320 168.532

38 600.944472100 32.859055286 SI02HL 1.56028895 162.458

39 1435.651038119 39.540839130 N2 1.00000320 158.952

40 -542.595637794 21.000000000 SI02HL 1.56028895 157.309

41 -421.356226662AS 28.605920520 N2 1.00000320 156.999

42 -253.952587228 15.000000000 SI02HL 1.56028895 153.788

43 -804.677872363AS 32.000000000 N2 1.00000320 158.842

44 0.000000000 10.700000010 N2 1.00000320 162.250

45 439.828583479AS 60.615863511 SI02HL 1.56028895 169.169

46 -554.126799640AS 0.854609370 N2 1.00000320 169.058

47 251.288231110 66.707994802 SI02HL 1.56028895 152.022

48 -1261.158042833AS 0.700000000 N2 1.00000320 149.150

49 120.292681477 139.355322544 SI02HL 1.56028895 99.158

50 0.000000000 0.000000000 SI02HL 1.56028895 11.402

51 0.000000000 0.000000000 ^' ' 1.00000000 11.402

AREA NO. 2 AREA NO. 15

K 0.0000 K 0. .0000

Cl -2.94971307e-008 Cl 1., 77772008e-009

C2 -5.57984348e-011 C2 6,., 20555687e-014

C3 8.46982512e-015 C3 1., 17962639e-018

C4 5.00708078e-019 C4 -3, .75710986e-023

C5 -3.78477968e-022 C5 8. .23659263e-027

C6 4.94732324e-026 C6 -3, .78043433e-031

C7 -2.07498764e-030 C7 5. .28341681e-036

C8 0.00000000e + 000 C8 0. .00000000e + 000

C9 0.00000000e + 000 C9 0. .00000000e + 000

AREA NO. 4 AREA NO. 19

K 0.0000 K 0. 0000

Cl 2.26266925e-007 Cl 1. 12510953e-007

C2 4.12437333e-011 C2 5. 25382772e-012

C3 -8.13482251e-015 C3 3. 54985200e-016

C4 -9.73333957e-019 C4 2 .17219317e-020

C5 5.21683282e-022 C5 3. 35596515e-024

C6 -6.98262222e-026 C6 -1. 94149952e-028

C7 3.24713110e-030 C7 4. 47299373e-032

C8 0.00000000e + 000 C8 0. 00000000e + 000

C9 0.00000000e + 000 C9 0. 00000000e + 000

AREA NO. 7 AREA NO. 27

K 0.0000 K 0.0000

Cl 2.14406930e-008 Cl 2.75008177e-008

C2 4.01486796e-013 C2 -4.51696088e-013

C3 -1.15749689e-016 C3 -5.50353634e-018

C4 -2.17404465e-020 C4 -2.48871975e-022

C5 4.76039865e-024 C5 -4.84285060e-026

C6 -4.04274950e-028 C6 4.35721702e-030

C7 2.26352156e-032 C7 -1.70355795e-034

C8 0.00000000e + 000 C8 0.00000000e + 000

C9 0.00000000e + 000 C9 0.00000000e + 000

AREA NO. 10 AREA NO. 32

K 0. .0000 K 0.0000

Cl 4., 04801375e-008 Cl 4.61774725e-009

C2 3rd, 59502309e-013 C2 -1.45428945e-013

C3 -4, .82739756e-017 C3 5.33766031e-018

C4 -2. .12222071e-021 C4 -1.05172907e-022

C5 3, .16153319e-025 C5 1.13262775e-027

C6 -1. .24031349e-029 C6 2.90828821e-032

C7 1. .72585585e-034 C7 -9.47335184e-037

C8 0. .00000000e + 000 C8 0.00000000e + 000

C9 0 .00000000e + 000 C9 0.00000000e + 000

AREA NO. 41 AREA NO. 48

K 0.0000 K 0.0000

Cl -1.74774919e ~ 009 Cl 2.98238360e-010

C2 3.60065638e-015 C2 -6.63488568e-014

C3 -6.33371869e-019 C3 8.08884615e-018

C4 -2.58752868e-023 C4 -1.56791602e-022

C5 -1.29026764e-027 C5 -6.64400102e-029

C6 4.06422380e-032 C6 3.42882241e-032

C7 -2.03413277e-036 C7 -1.87278246e-037

C8 0.00000000e + 000 C8 0.00000000e + 000

C9 0.00000000e + 000 _C 9 0.00000000e + 000

AREA NO. 43

K 0. .0000

Cl -1,, 52776855e-009

C2 3rd, 99966157e-014

C3 -3. , 59152071e-019

C4 -2. .46490776e-023

C5 2. .62578515e-028

C6 9..94510225e-032

C7-1, .17559041e-036

C8 0, .00000000e + 000

C9 0, .00000000e + 000

AREA NO. 45

K 0.0000

Cl -6.79036688e-009

C2 -4.98113790e-014

C3 2.59739233e-018

C4 -5.22422066e-023

C5 1.38345858e-028

C6 -9.60600374e-033

C7 4.93449545e-037

C8 0.00000000e + 000

C9 0.00000000e + 000

AREA NO. 46

K 0.0000

Cl -1.23311338e-009

C2 9.47803783e-014

C3 -6.59387651e-020

C4 -4.20864177e-023

C5 -4.65343524e-028

C6 -7.27238546e-033

C7 5.62850375e-037

C8 0.00000000e + 000

C9 0.00000000e + 000

Claims

claims

1. projection lens for imaging a pattern arranged in the object plane of the projection lens into an image plane of the projection lens with ultraviolet light of a predetermined working wavelength, the projection lens with: a plurality of optical elements which are arranged along an optical axis; and a system aperture arranged at a distance from the image plane

(5) with an aperture diameter; the optical group closest to the image plane with refractive power being a plano-convex group (34) with an essentially spherical entrance surface and an essentially flat one

Exit surface is; and wherein the plano-convex group (34) has a diameter which is at least 50% of the diaphragm diameter.

2. Projection objective according to claim 1, in which the plano-convex group is formed by a single, preferably one-piece plano-convex lens (34).

3. Projection lens according to claim 1 or 2, in which only lenses (32, 33, 34) with positive refractive power are arranged between the system diaphragm (5) and the image plane (3), optionally in combination with at least one plane-parallel plate.

4. Projection lens according to one of the preceding claims, in which between the system diaphragm (5) and the image plane (3), in particular between the system diaphragm and plan-convex group (34), at least one biconvex positive lens is arranged, preferably two biconvex positive lenses (32, 33).

5. Projection objective according to one of the preceding claims, in which a last lens group (LG7) arranged between system aperture (5) and image plane (3) has a maximum of four optical lenses

Has elements with refractive power, preferably only three lenses

(32, 33, 34).

6. Projection objective according to one of the preceding claims, in which a last lens group arranged between the system aperture (5) and image plane (3) has a focal length which is less than 20%, in particular less than 15%, of the overall length of the projection objective.

7. Projection objective according to one of the preceding claims, in which a distance between the system diaphragm and the image plane (3) is less than 25% of the overall length and / or less than 95% of the diaphragm diameter.

8. Projection lens according to one of the preceding claims, which is a purely refractive projection lens (1).

9. Projection lens according to claim 7, wherein it is a one-waist system with a near-object belly (6), a near-image belly (8) and an intermediate waist (7).

10. Projection lens according to one of the preceding claims, which is designed for a working wavelength of 193nm.

11. Projection lens according to one of the preceding claims, in which all transparent optical elements are made of the same material, in particular of synthetic quartz glass.

12. Projection objective according to one of the preceding claims, which has an image-side numerical aperture NA> 0.85, preferably NA ≥ 1.

13. Projection lens according to one of the preceding claims, in which an image-side working distance is less than four times the working wavelength, the working distance preferably being less than the working wavelength and in particular being less than half the working wavelength.

14. Projection lens according to one of the preceding claims, in which the image field diameter is greater than 10 mm, in particular greater than 20 mm and / or in which the image field diameter is more than 1%, in particular more than 1.5% of the overall length of the

Projection lens and / or more than 1%, in particular more than 5% of the largest lens diameter.

15. Projection objective according to one of the preceding claims, in which at least one double-aspherical lens (32) is arranged between the system diaphragm (5) and image plane (3), which is preferably designed as a biconvex lens.

16. Projection lens according to one of the preceding claims, in which the last optical surface in front of the system diaphragm (5) and the first optical surface after the system diaphragm are aspherical, preferably with curvatures pointing away from the diaphragm.

17. Projection objective according to one of the preceding claims, in which at least one in the vicinity of the system diaphragm (5), in particular immediately in front of the system diaphragm

Meniscus lens (30, 31) is arranged with concave surfaces directed towards the object.

18. Projection objective according to one of the preceding claims, in which at least one meniscus group with at least two successive meniscus lenses (30, 31) with object-side concave surfaces is arranged in the vicinity of the system diaphragm (5), in particular immediately in front of the system diaphragm.

19. Projection objective according to one of the preceding claims, in which a positive-negative meniscus group with two meniscus lenses (30, 31) is arranged in the vicinity of the system diaphragm (5), the lens surfaces of which are concave on the object side.

20. Projection lens according to one of the preceding claims, in which an auxiliary waist (9) is present between the waist (7) and the image plane (3) by constriction of the beam diameter, which is preferably arranged in the vicinity of the system diaphragm (5).

21. Projection objective according to one of the preceding claims, in which at least one meniscus lens (25, 26) with a negative refractive power and image-oriented concave surfaces is arranged between the waist (7) and the system diaphragm (5).

22. Projection objective according to one of the preceding claims, in which a meniscus group with at least two meniscus lenses (25, 26) with negative refractive power and image-oriented concave surfaces is arranged between the waist (7) and the system diaphragm (5), the refractive power of the object-side meniscus preferably this meniscus group is at least 30% greater than the refractive power of a subsequent meniscus lens (26) of the meniscus group.

23. Projection objective according to one of the preceding claims, in which at least one positive meniscus lens (23, 24) with an object-side concave surface is arranged between the waist (7) and the system diaphragm (5) in the vicinity of the waist.

24. Projection objective according to one of the preceding claims, in which between the waist (7) and the system diaphragm (5) in this order at least one meniscus lens (23, 24) with an object-side concave surface and subsequently at least one meniscus lens (25, 26) with an image-side concave surface is arranged, wherein preferably the at least one meniscus lens with a concave surface on the object side has positive refractive power and the at least one meniscus lens with a concave surface on the image side has negative refractive power.

25. Projection objective according to one of the preceding claims, wherein a negative group with at least two negative lenses (20, 21, 22) is arranged in the region of the waist (7), the negative group preferably having at least three successive negative lenses.

26. Projection lens according to one of the preceding claims, in which one of the object plane (2) following the first lens group (LG1) has at least two, preferably three or more negative lenses (11, 12, 13).

27. The projection objective as claimed in claim 26, in which in the first lens group (LG1) at least one of the first four optical surfaces following the object plane is aspherical, preferably at least two optical surfaces in the first lens group being aspherical.

28. Projection objective according to one of the preceding claims, in which at least one meniscus lens (16) with positive refractive power and concave surface on the image side is arranged in the region of large beam diameters in the vicinity of the object plane (2).

29. The projection lens as claimed in claim 28, in which the convex surface of the meniscus lens (16) directed towards the image plane has a radius which is less than 50% of the overall length of the projection lens.

30. projection lens for the obscuration-free imaging of a pattern arranged in the object plane of the projection lens into an image plane of the projection lens with ultraviolet light of a predetermined working wavelength, the projection lens with: a multiplicity of optical elements which are arranged along an optical axis; and one arranged at a distance from the image plane (3)

System cover (5); wherein only lenses (32, 33, 34) with positive refractive power are arranged between the system diaphragm (5) and the image plane (3), optionally in addition to at least one plane-parallel plate.

31. Projection lens for imaging a pattern arranged in the object plane of the projection lens into an image plane of the projection lens with ultraviolet light of a predetermined working wavelength, the projection lens with: a multiplicity of optical elements which are arranged along an optical axis; and one arranged at a distance from the image plane (3)

System cover (5); with at least one meniscus group with at least two successive ones immediately before the system aperture

Meniscus lenses (30, 31) is arranged with concave surfaces on the object side.

32. Projection lens according to claim 31, wherein the meniscus group is a positive-negative meniscus group with two

Meniscus lenses (30, 31), the lens surfaces of which are concave on the object side.