Projection lens, projection exposure apparatus, and projection exposure method

Abstract

A refractive projection lens (PO) for imaging a pattern disposed on an object plane (OS) of a projection lens onto an image plane (IS) of the projection lens using electromagnetic radiation from the ultraviolet region longer than 280 nm includes a plurality of lens elements arranged between the object plane (OS) and the image plane (IS) along an optical axis (AX) and implemented such that a pattern disposed on the object plane can be imaged onto the image plane using the lens elements, a diaphragm position (BP) suitable for mounting an aperture diaphragm (AS) is positioned between the object plane and the image plane, a chief ray of imaging intersects with the optical axis at said diaphragm position, and the lens elements include at least one flint lens element made of a first material having a relatively low Abbe number and at least one crown lens element made of a second material having a higher Abbe number with respect to the first material. A crown lens element having a positive refractive power, at least one flint lens element having a negative refractive power, and two or less flint lens elements (L16) having a negative refractive power are arranged in an aperture region (BB) surrounding an aperture position (BP), and a condition |CRH / MRH|<1 is applied to the ray height ratio CRH / MRH between the chief ray height CRH of the image and the marginal ray height MRH.

Description

[Technical field]

[0001] The following disclosure is based on German patent application No. 102022201001.9, filed on January 31, 2022, which is incorporated herein by reference.

[0002] The present invention relates to a refractive projection lens for imaging a pattern arranged in the object plane of the projection lens onto an image plane of the projection lens using electromagnetic radiation with an operating wavelength in the ultraviolet range longer than 280 nm, a projection exposure apparatus equipped with the projection lens, and a projection exposure method which can be carried out using the projection lens. [Background technology]

[0003] Microlithographic projection exposure methods are currently mainly used for the production of semiconductor components and other finely structured components, for example masks for photolithography. In this case, a mask (reticle) or other pattern generating device is used, which carries or forms the pattern of the structures to be imaged, for example the wiring pattern of a layer of a semiconductor component. The pattern is positioned in the projection exposure apparatus between the illumination system and the projection lens in the region of the object plane of the projection lens and is illuminated by illumination radiation provided by the illumination system. The radiation modified by the pattern passes through the projection lens as projection radiation, which images the pattern onto a substrate to be exposed. The surface of the substrate is arranged in the image plane of the projection lens, which is optically conjugate with the object plane. The substrate is covered overall with a radiation-sensitive layer (resist, photoresist).

[0004] Typically, the requirements for semiconductor component manufacturing are different for the exposure of critical and non-critical structures. Currently, critical structures, i.e. fine structures, are mainly manufactured using refractive or catadioptric immersion systems working in the deep ultraviolet range (DUV), specifically at an operating wavelength of about 193 nm. Currently, the finest structures are exposed using EUV systems. These are projection exposure apparatuses built using only reflective components working in the extreme ultraviolet range (EUV) at an operating wavelength between about 5 nm and 20 nm, for example about 13.4 mm.

[0005] Non-critical structures, i.e. coarser structures, can be exposed using simpler and therefore more cost-effective systems.

[0006] To produce intermediate critical or non-critical layers with typical structure dimensions significantly exceeding 150 nm, work is conventionally carried out using projection exposure apparatus designed for operating wavelengths in the ultraviolet range from about 280 nm to about 400 nm, in which wavelength range refractive optical (refractive) projection lenses are usually used, whose manufacture is easily controllable due to their rotational symmetry around the optical axis.

[0007] For these applications, projection exposure apparatus for an operating wavelength of 365.5 nm ± 2 nm (so-called i-line systems) are particularly often used. These use the i-line of a mercury lamp, the inherent overall bandwidth of which is limited by means of filters or in any other way to a narrower usable bandwidth Δλ, for example of about 4 nm. During projection, in order to ensure aberration-free imaging with the required resolution even with broadband projection light, ultraviolet light of a relatively wide wavelength range is used, so that the projection lens necessarily provides a relatively strong correction of chromatic aberrations. In order to obtain a sufficient imaging quality, in particular the longitudinal chromatic aberration (CHL) has to be corrected.

[0008] For refractive projection lenses working in a broadband manner, different lens element materials are used that have sufficiently different dispersion characteristics for color correction (i.e. for correction of chromatic aberrations), and the lens element materials must be distributed in the projection lens in areas with different beam height ratios. Transparent materials used in typical i-line projection lenses include, in particular, synthetic fused silica (SiO2) and special glasses marketed by Schott, Mainz, Germany, under the names FK5, LF5 and LLF1. Among these optical glasses, synthetic fused silica and FK5 glass are representative of relatively low dispersion glasses (crown glasses), while LF5 and LLF1 glasses are representative of relatively high dispersion glasses (flint glasses). Other manufacturers provide different names for each type of glass.

[0009] Thus, within this application, lens elements made from crown glass will be referred to as "crown lens elements" and lens elements made from flint glass will be referred to as "flint lens elements."

[0010] As already mentioned, in these systems, at least the lowest order longitudinal chromatic aberration, called the "first spectrum", must be completely corrected. Specialized literature, for example Volker Witt, "Wie funktionieren Achromat und Apochromat", Sterne und Weltraum 10 / 2005, p. 72-75 (http: / / rohr.aiax.de / SUW_2005_10_S072.pdf), discloses how the lowest order longitudinal chromatic aberration can be corrected in optical imaging systems using crown and flint lens elements. From this article, it is clear that the use of at least diverging flint lens elements and converging crown lens elements is essential to correct the longitudinal chromatic aberration of an imaging system.

[0011] Applying this teaching to a projection lens, it can be deduced that the longitudinal chromatic aberration can be corrected using a combination of at least one crown lens element with positive refractive power and at least one flint lens element with negative refractive power. This lens element pair must be located in a region of the optical imaging system where the marginal rays of the image have as large a ray height (marginal ray height) as possible. Typically, this corresponds to the aperture region near the system aperture.

[0012] It is almost impossible to keep track of the number of different designs of refractive i-line projection lenses. References US Pat. No. 6,806,942 and US Pat. No. 5,930,049 provide examples.

[0013] What is common to many of the examples of i-line projection lenses found in these patent documents is that neither the type nor the dispersion of the glass is specified, and only the main refractive index of the glass is revealed from the design table. In some cases, a large number of different glasses with different refractive indices are used. The system was analyzed according to the refractive index of the materials used, and it was assumed that the glasses with high refractive index were flint-like glasses, while the glasses with lower refractive index were crown-like glasses. Under the assumption that this division between crown and flint glasses is valid, it seems to have been determined that the overwhelming majority of crown lens elements with a positive refractive index and at least one flint lens element with a larger negative refractive power are systematically used in the vicinity of the system stop for the purpose of correcting longitudinal chromatic aberration.

[0014] Furthermore, it is possible to identify a tendency for many of the analyzed projection lenses to contain a number of additional lens elements with a high refractive index (i.e. assumed to be flint lens elements). For example, of the 31 lens elements in the projection lens of US Patent No. 5,930,049, only 8 lens elements were made of a lower refractive index material with a refractive index of 1.488 (possibly fused silica with n365=1.47455), while the remaining 23 lens elements were made of a higher refractive index material with n=1.613 (possibly LF5 with n365=1.619262). Summary of the Invention

[0015] It is an object of the invention to provide a projection lens, a projection exposure apparatus and a projection exposure method which function with UV radiation with an operating wavelength in the ultraviolet range longer than 280 nm, in particular with UV radiation of the mercury i-line, and which allow a high throughput rate.

[0016] To achieve this goal, the invention provides a refractive projection lens having the features of claim 1. Also provided is a projection exposure apparatus having the features of claim 11 and a projection exposure method having the features of claim 14. Advantageous developments are specified in the dependent claims. All claim language is incorporated by reference into the content of this description.

[0017] According to a representation of the claimed invention, a refractive projection lens is provided, which is implemented to image a pattern arranged on an object plane of the projection lens, on an image plane of the projection lens, using electromagnetic radiation with an operating wavelength in the ultraviolet region longer than 280 nm. All optical elements with refractive power are lens elements, i.e. refractive optical elements. In other words, the projection lens only includes lenses and does not include a diffractive optical element (DOE) with optical power. The lenses are arranged between the object plane and the image plane along the optical axis, and are implemented in such a way that the entirety of the lens provides this imaging. An aperture position suitable for mounting an aperture stop is located between the object plane and the image plane, at which the chief ray of the imaging intersects the optical axis. The lens elements include at least one flint lens element made of a first material having a relatively low Abbe number and at least one crown lens element made of a second material having a higher Abbe number with respect to the first material. At least one crown lens element having positive refractive power and at least one flint lens having negative refractive power, but not more than two flint lenses having negative refractive power, are disposed in an aperture region surrounding the aperture position.

[0018] The stop region is distinguished in that in the stop region, the ray height ratio CRH / MRH of the image's chief ray height CRH to its marginal ray height MRH satisfies the condition |CRH / MRH|<1. Thus, the stop region is a region in which the marginal ray height is greater than the chief ray height.

[0019] Thus, no more than two negative lens elements made of a first material are disposed in the aperture region in addition to at least one positive lens element made of a second material, and there must be at least one negative lens element made of the first material in the aperture region.

[0020] The invention is based in particular on the following consideration: in order to correct the chromatic aberration of a universal imaging optical system, for example a projection lens, in particular its longitudinal chromatic aberration, the individual lens elements of the lens must be manufactured from a flint material. However, flint materials have some disadvantageous properties. As an example, flint glass typically exhibits a reduced transmission of the light used, which is equivalent to an increased absorption. This can result in undesirable side effects such as lens heating and / or material compression. Furthermore, all current flint materials transparent in the wavelength range around 365 nm have a significant proportion of lead and further heavy metals, so that the use of these glasses is only permitted by special authorization. Comparable lead-free alternative glasses are not currently practically available. It would therefore be advantageous to develop a universal projection lens that uses fewer flint lens elements compared to the prior art.

[0021] Since to a first approximation the longitudinal chromatic aberration of a lens element is proportional to the square of the marginal ray height at the position of that lens element (and is proportional to the refractive power of the lens element and inversely proportional to the Abbe number), negative refractive power flint lens elements in regions of large marginal ray height can contribute particularly effectively to color correction, specifically to the correction of longitudinal chromatic aberration CHL. Nevertheless, the present invention teaches only the reduced use of these correction means.

[0022] By limiting the use of flint lens elements, the overall transmission can be improved compared to conventional systems that use many flint lens elements, thereby allowing for higher throughput rates, and the tendency for lens heating can be reduced.

[0023] According to one development, the projection lens has an imaging scale of more than 4:1, i.e. (|β|>0.25), which helps to obtain the above-mentioned sought advantages. By way of example, the imaging scale can be 2:1 (|β|=0.50) or less, optionally even 1:1 (|β|=1). The reduction of such lenses is not as large as in the case of conventional i-line projection lenses, which are often designed for a reduction of 4:1 or 5:1. This approach is based in particular on the following considerations: the throughput of the system can be increased compared to projection lenses with a larger reduction (for example |β|=0.25 or less). For a constant geometrical etendue LLW, there is a reduction in the image-side numerical aperture NA and in Rayleigh units, and therefore a greater depth of field range. As a result, the system becomes less sensitive to longitudinal aberrations such as defocus, astigmatism or field curvature. In some cases, this opens the possibility of significantly reducing or completely omitting the correction of chromatic changes in the Petzval sum. This further has a direct impact on the number of flint lens elements absolutely necessary in the lens, which can be kept relatively small.

[0024] The geometrical etendue LLW is the (dimensionless) objective numerical aperture NA O and the objective field size parameterized by the objective field height OBH (units in millimeters), i.e. LLW=|OBH*NA O | It can be defined as:

[0025] The object field height OBH corresponds to the object field radius, i.e. the radius of the smallest circle enclosing the object field points for which the optical correction meets the specifications, i.e. is sufficiently good. This circle must be large enough to enclose the effective object field.

[0026] In many embodiments, for an imaging scale with β = -0.5, the image-side numerical aperture NA is less than 0.4, and preferably the condition 0.1 < NA < 0.4 is applicable.

[0027] In many embodiments, the geometric étendue LLW is at least 7 mm, and preferably the condition 10 mm < LLW < 18 mm is applicable.

[0028] Some embodiments are distinguished in that they include only a single negative lens element made of flint material, i.e., only a single flint lens element having a negative refractive power. Thus, this correction means uses only the minimum necessary quantity.

[0029] In some embodiments, this negative lens element made of flint material is the only flint lens element within the projection lens, and thus the projection lens may contain exactly only one flint lens element. As a result, the use of flint material is minimized.

[0030] Preferably, the only flint lens element is a biconcave lens element. In the case of a biconcave lens element, a large refractive power (or curved surface) can be realized with a not-so-large incident angle.

[0031] Preferably, the single flint lens element having a negative refractive power is arranged in the aperture region, specifically in a region where the condition |CRH / MRH| < 0.5 or further |CRH / MRH| < 0.2 is applicable to the ray height ratio. Since the longitudinal chromatic aberration CHL of the lens element is proportional to the square of the marginal ray height at the position of the lens element (and proportional to the refractive power of the lens element and inversely proportional to the Abbe number), a flint lens element with a negative refractive power in a region with a large marginal ray height can contribute particularly effectively to color correction, specifically to the correction of the longitudinal chromatic aberration CHL. As a result, a large contribution to the correction of chromatic aberration, specifically longitudinal chromatic aberration, is possible.

[0032] In some embodiments, all lens elements made of flint material are negative lens elements, in other embodiments, there are no positive lens elements made of flint material, and in other embodiments, there are exactly two flint lens elements.

[0033] After the correction of the lowest order longitudinal chromatic aberration ("first order spectrum") by using at least one flint lens element with negative refractive power in the aperture area, the chromatic change of the field curvature remains as the limiting chromatic aberration. Therefore, it may be advantageous to use at least one positive lens element made of flint material, especially with a view to correcting the chromatic change of the field curvature.

[0034] Flattening the image field is an important requirement for the optical quality of projection lenses with a large image field. The requirement for this is that the Petzval sum of the projection lens is as small as possible, in particular zero. In the case of an optical system consisting mostly of a certain material (for example crown glass such as FK5 or synthetic fused silica) with a small number of lens elements consisting of a second material (in this case flint glass, for example LF5), the inventors have found that it is possible to derive the requirement that the Petzval sum must be corrected as much as possible within each material group. This cannot be met if only dispersion negative lenses consisting of flint glass are used. Some embodiments therefore provide the projection lens to include at least one lens element (converging lens) with a positive refractive power consisting of a first material, i.e. at least one positive flint lens element. This makes it possible to achieve a sufficiently small or zero chromaticity change of the Petzval sum.

[0035] The use of positive lens elements made of flint material is an obstacle to the correction of the longitudinal chromatic aberration CHL with negative lens elements made of flint material. Therefore, in order to make little contribution to the correction of the longitudinal chromatic aberration, the positive lens elements must be used at points in the beam path where the marginal ray height is small. This is the case in the optical vicinity of the field plane, i.e. in the vicinity of the object plane, in the vicinity of the image plane or, if an intermediate image is generated between the object plane and the image plane, in the optical vicinity of the intermediate image plane. Preferably, the positive lens elements made of flint material are arranged in areas where the ray height ratio |CRH / MRH| of the image formation is greater than 0.5, or greater than 0.7, or greater than 1, or greater than 2.

[0036] According to one development, the projection lens is implemented as a single-waist system. It comprises a first lens element group with a positive refractive power close to the object plane, a second lens element group with a negative refractive power following the first lens element group for generating a waist enclosing an area of ​​minimum ray height between the object plane and the image plane, a third lens element group with a positive refractive power following the second lens element group between the second lens element group and the diaphragm position, and a fourth lens element group with a positive refractive power between the diaphragm position and the image plane. Thus, a refractive power sequence PNPP is realizable, where "P" stands for a lens element group with an overall positive refractive power and "N" stands for a lens element group with an overall negative refractive power. The projection lens can be implemented such that there are no further lens element groups besides the above four lens element groups. In that case, the first lens element group immediately follows the object plane.

[0037] To obtain a higher numerical aperture, it may be advantageous if a front negative group with at least one lens element with negative refractive power is arranged between the object surface and the first lens element group. Thus, the refractive power sequence NPNPP can be realized. If the projection lens is designed as a single-waist system, it can make an important contribution to the Petzval correction in the case of a compact overall construction.

[0038] A class of projection lenses having particularly practical characteristics is implemented as a single constriction system in which the projection lens has a refractive power sequence of N-P-N-P-P, the image-side numerical aperture NA is in the range of 0.2 < NA < 4, the imaging scale is on the order of 2:1 (|β| = 0.50) or less, and the geometric étendue LLW is in the range of 10 mm < LLW < 18 mm, and it is characterized by including only a single flint lens having a negative refractive power.

[0039] Preferably, the projection exposure apparatus, and thus also the projection lens, is designed for the emission of the i-line of a mercury lamp (having a central operating wavelength of approximately 365.5 nm and an optionally limited bandwidth of several nm). The i-line system functions using a mercury lamp as the light source and uses only the i-line for imaging. Coatings and good-quality photoresists suitable for the lenses are well established, especially for these powerful light sources, and thus it is possible to build on prior developments in this regard. However, other light sources and / or UV operating wavelengths can also be used. As an example, when the projection lens is corrected in a corresponding broadband manner, two or three lines of a mercury lamp (the g, h, and i lines at approximately 436 nm, approximately 405 nm, and approximately 365 nm) can be used simultaneously. Alternatively, for example, a frequency-tripled Nd:YAG laser at approximately 355 nm can be used. There are also various LED light sources that emit wavelengths between 360 nm and 400 nm. Optionally, the emission range may be slightly adjusted.

[0040] Further advantages and aspects of the present invention will become apparent from the claims and the description of the exemplary embodiments of the present invention described below with reference to the drawings.

Brief Description of the Drawings

[0041] [Figure 1] It is a diagram showing a schematic view of a projection exposure apparatus according to an exemplary embodiment. [Diagram 2] It is a diagram showing a schematic meridional lens element cross-sectional view of a projection lens according to a first exemplary embodiment. [Diagram 3]FIG. 2 shows a schematic meridional lens element cross-section of a projection lens according to a second exemplary embodiment. [Figure 4] FIG. 13 shows a schematic meridional lens element cross-section of a projection lens according to a third exemplary embodiment. [Diagram 5] FIG. 13 shows a schematic meridional lens element cross-section of a projection lens according to a fourth exemplary embodiment. [Figure 6] FIG. 13 shows a schematic meridional lens element cross-section of a projection lens according to a fifth exemplary embodiment. [Figure 7] FIG. 13 shows a schematic meridional lens element cross-section of a projection lens according to a sixth exemplary embodiment. [Figure 8] FIG. 13 shows a schematic meridional lens element cross-section of a projection lens according to a seventh exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Figure 1 shows an example of a microlithography projection exposure apparatus WST that can be used in the manufacture of semiconductor components and other microstructured components and that works with light or electromagnetic radiation in the ultraviolet (UV) range to obtain a resolution down to a few parts per micrometer. A mercury lamp serves as the main radiation source or light source LS. The lamp emits a broad spectrum with emission lines of relatively high intensity I in wavelength ranges with central wavelengths of about 436 nm (visible light, blue, g-line), about 405 nm (visible light, violet, h-line) and about 365.5 nm (near ultraviolet, UV-A, i-line). This part of the spectrum is shown in the I(λ) schematic diagram.

[0043] Projection exposure tools are i-line systems that use only light from the i-line, i.e. UV light centered at a central operating wavelength of about 365.5 nm. The full intrinsic bandwidth of the i-line is limited by filters or any other method to a narrower usable bandwidth Δλ, for example about 5 nm.

[0044] At the exit surface ES, an illumination system ILL arranged downstream of the light source LS produces a wide, well-defined and substantially uniformly illuminated illumination field which is adapted to the telecentricity requirements of a projection lens PO arranged downstream in the optical path. The illumination system ILL has a device for setting different illumination modes (illumination settings) and is, for example, switchable between conventional on-axis illumination with different coherence degrees σ and off-axis illumination.

[0045] Those optical components that receive light from the light source LS and form from it an illumination radiation that is directed towards the reticle M are part of the illumination system ILL of the projection exposure apparatus.

[0046] Downstream of the illumination system is arranged a device RS for holding and manipulating a mask M (reticle) so that a pattern arranged on the reticle is located at an object plane OS of the projection lens PO, which coincides with the exit plane ES of the illumination system and is also referred to in this specification as the reticle plane OS.

[0047] Downstream of the reticle surface OS follows the projection lens PO, i.e. an imaging system which images the image of the pattern arranged on the mask M at a defined imaging scale, for example a reduction scale of 1:2 (|β|=0.50), onto a substrate W covered with a photoresist layer, whose photosensitive substrate surface SS is located in the area of ​​the image surface IS of the projection lens PO.

[0048] The substrate to be exposed, in this illustrative case a semiconductor wafer W, is held by a device WS, also called a "wafer stage."

[0049] The illumination field generated by the illumination system ILL defines the effective object field OF used during projection exposure. In this exemplary case, the effective object field is rectangular, has a height A* measured parallel to the y direction, and has a width B* < A* measured perpendicular thereto (x direction). The aspect ratio AR = B* / A* is approximately 104 / 132. The effective object field is centered on the optical axis (on-axis field). In a system with this field size, a typical 6-inch reticle can be imaged in a single exposure step.

[0050] However, scan systems are also often used, and their object fields are smaller than 104×132 mm 2 for example, only 104×28 mm 2 or less.

[0051] The effective image field on the image plane IS, which is optically conjugate to the effective object field, has the same shape and the same aspect ratio of height B and width A as the effective object field. However, in the case of a projection lens with a reduction effect (due to |β| < 1), the absolute field dimensions are reduced by the imaging scale β of the projection lens, i.e., A = |β|A* and B = |β|B*. In the case of a 1:1 system (imaging scale |β| = 1), the image field has the same size as the effective object field.

[0052] If the field size of the image field is 26×33 mm, a complete "die" can be exposed in a single exposure step without scanning. The term "die" refers to a single unpackaged piece of a semiconductor wafer in semiconductor and microsystem technology. Thus, the projection exposure apparatus can be designed as a wafer stepper for a step-and-repeat process. The device for performing the scanning operation for die exposure can be omitted. The projection exposure apparatus can also be designed as a wafer scanner for a step-and-scan process. In that case, a device for performing the scanning operation for die exposure needs to be provided.

[0053] In this rotationally symmetric system, a circle centered on the optical axis OA, enclosing the effective objective field OF and tangent to the corners of the effective objective field, defines the size of the objective field within which the optical corrections at all field points must meet the specifications. This also applies to all field points within the effective objective field. The more complex the correction of aberrations, the larger this objective field must be. In this case, the size of the circle is parameterized by the objective field radius OBH or half the objective field diameter OBH, which at the same time corresponds to the maximum field height of the objective field points.

[0054] In order to better understand important aspects of the exemplary embodiments described below, we first provide a brief description of chromatic aberration and its correction in dioptric (refractive) optical systems in order to clarify the terms and meanings used in this application.

[0055] Chromatic aberration is an imaging aberration in optical systems that arises due to the variation of the refractive index n of transparent optical materials as a function of wavelength λ. This dependence dn / dλ is called the dispersion of the optical material. In general, the refractive index of an optical material is larger for shorter wavelengths than for longer wavelengths.

[0056] Chromatic aberration can be subdivided into various categories. The first category of chromatic aberration considers that for each wavelength in the paraxial region (on the optical axis), a dedicated image is generated and that these images may vary in terms of their respective position along the optical axis, their respective shape and / or size. The first category of chromatic aberration includes longitudinal chromatic aberration CHL (axial chromatic aberration, axial color, AX) and lateral chromatic aberration or lateral chromatic aberration CHV (lateral chromatic aberration LAT).

[0057] Longitudinal chromatic aberration is the longitudinal aberration of the paraxial focal position as a function of wavelength. If the refractive index of shorter wavelengths is greater than that of longer wavelengths, then the shorter wavelengths will be refracted more strongly at each optical surface, such that, for example, in the case of a simple positive lens element, the relatively shorter wavelength rays will be focused at a focal position located closer to the lens element than the focal points of the relatively longer wavelengths. The paraxial distance along the optical axis of the lens element between these two focal points is the longitudinal chromatic aberration. If the shorter wavelength rays are focused closer to the imaging system than the longer wavelength rays, the longitudinal chromatic aberration is usually called "undercorrected" or "negative".

[0058] When an imaging system produces images of different sizes for different wavelengths, or when the image of an off-axis point produces color fringes, lateral chromatic aberration or lateral chromatic difference (CHV) exists. lateral chromatic difference can be quantified by the lateral distance between the paraxial image heights of different wavelengths.

[0059] Dispersion of the optical materials used, i.e., chromatic variation of the refractive index, can also give rise to variations in monochromatic aberrations, which can be subsumed under the second category of chromatic aberrations. For example, these include chromatic variation of spherical aberration, chromatic variation of field curvature, etc.

[0060] For further characterization of possible aberrations, imaging with light from a broadband source is considered, where the broadband source emits light of different wavelengths centered around a central wavelength λ, and the radiation distribution is characterized by a spectral bandwidth Δλ (full width at half maximum). Typically, the degree of chromatic aberration increases with increasing spectral bandwidth Δλ. Chromatic aberration can be characterized using the focal positions of different wavelengths along the optical axis for three wavelengths within the spectral bandwidth. The three wavelength components have wavelengths λ1, λ2 and λ3, where λ1<λ2<λ3.

[0061] In this case, the magnitude of the longitudinal chromatic aberration CHL corresponds to the maximum length of the focal range along the optical axis where the different wavelengths are focused. Typically, one of the wavelengths is focused closer to the imaging system than the other. The distance between the focal position of the nearest wavelength and the focal position of the furthest wavelength corresponds to the magnitude of the longitudinal chromatic aberration of the imaging system of the broadband light source. The focal position of the central wavelength λ along the optical axis can be considered as the image plane within the focal range.

[0062] The variation of paraxial focal position with wavelength is usually expanded in a power series, where the linear part is called the "first order spectrum", the second order part is called the "second order spectrum", and one can further define the third order part as the "third order spectrum".

[0063] The primary spectrum can be corrected by combining converging and diverging lens elements made of different optical materials with different dispersions. Specifically, the longitudinal chromatic aberration can be corrected so that the paraxial focal planes of two different wavelengths, for example the minimum λ1 wavelength and the maximum λ3 wavelength of the spectral region, coincide on the optical axis. Such an optical imaging system is also referred to as "achromatized" or "achromat" in this application.

[0064] Typically, there remains longitudinal chromatic aberration remnant for other wavelengths that are not captured by the correction. This longitudinal chromatic aberration remnant is usually referred to as the "secondary spectrum."

[0065] In some cases, it is also possible to correct the secondary spectrum by appropriate selection of optical materials, lens element dimensions, distances, refractive powers, etc. The secondary spectrum can in some cases be corrected to the extent that the focal positions of all three wavelengths λ1, λ2 and λ3 of the wavelength range under consideration are located at the same axial position, resulting in only the "third order spectrum". In this application, an optical system in which the secondary spectrum is also corrected is also referred to as "apochromatically corrected" or "apochromatic".

[0066] In other words, for an achromatic imaging system, the longitudinal chromatic aberration for two spectrally separated wavelengths is very small (possibly even zero). For an apochromatic optical imaging system, the longitudinal chromatic aberration for three spectrally separated wavelengths is very small (possibly even zero).

[0067] In refractive projection lenses intended to work with spectrally broadband light sources, different lens element materials with Abbe numbers that differ as much as possible are used to correct chromatic aberrations. The Abbe number v facilitates the characterization of the dispersion properties of a material in the wavelength range of interest. As an example, the Abbe number of a material can be calculated using the following formula: v = (n2-1) / (n1-n3) where n1, n2, and n3 are the refractive indices of the material at wavelengths λ1, λ2, and λ3, with λ1<λ2<λ3. Generally, a low Abbe number represents a material with relatively strong dispersion, and a high Abbe number represents a material with relatively weak dispersion. Therefore, the Abbe number is sometimes called the "inverse relative dispersion."

[0068] In this case, the Abbe number v Hg must be related to the extent of the ultraviolet spectral region. For this purpose, the refractive indices n1, n2 and n3 of the mercury spectral lines at 365.0 (n1 i-line), 404.7 (n2 h-line) and 435.8 nm (n3 g-line) are used. The Abbe numbers of the glasses used are tabulated in Table 10.

[0069] Lens element materials for operating wavelengths in the emission lines of mercury lamps can be divided into three different groups according to their refractive index and their Abbe number. The first group includes materials whose Abbe number is in the range of 40-70. Here, the Abbe number is calculated for wavelengths λ1=365.01 nm, λ2=404.65 nm and λ3=435.84 nm, which correspond to the wavelengths of the i, h and g emission lines of a mercury lamp. Materials of the first group have typical refractive indices in the range of 1.46-1.56 at the mercury i line. Materials of the first group include, in particular, synthetic fused silica (SiO2) and various borosilicate glasses such as BK7 glass or K5, K7 or FK5 glass.

[0070] The second group includes materials that have an Abbe number greater than 70. Some materials in the second group, such as crystalline calcium fluoride (fluorspar or CaF2), have a refractive index less than 1.46.

[0071] The third group includes materials with an Abbe number less than 40. These materials have a refractive index greater than about 1.56. The third group of materials includes, in particular, typical flint glasses such as LLF-6, LLF-1 or LF-5 glasses.

[0072] In order to reduce chromatic aberration by refractive means, an optical system needs to have lens elements made of at least two materials with different dispersions or different Abbe numbers, thus combining a first optical element made of a first material with a relatively low Abbe number with a second optical element made of a second material with a higher Abbe number relative to the first material.

[0073] Typically, the second group of materials is used as the relative crown material. Typically, the third group of materials is used as the relative flint material. The first group of materials can act as the relative crown material in combination with the third group of materials and as the relative flint material in combination with the second group of materials. As an example, synthetic fused quartz (SiO2) acts as the relative crown material in combination with the third group of materials (e.g., LF5, LLF1, LLF6). In contrast, when synthetic fused quartz is combined with the second group of materials, e.g., CaF2, the fused quartz acts as the relative flint material.

[0074] Within the scope of this application, the first material having a relatively low Abbe number is also referred to as the "relative flint material" and the second material having a relatively higher Abbe number is also referred to as the "relative crown material". For ease of explanation, in more specific exemplary embodiments of this application, the lens element made of the relative crown material is also referred to as the "crown lens element" for short, and the lens made of the relative flint material is also referred to as the "flint lens element" for short. Typically, materials from the first and third material groups are used.

[0075] In the following description of preferred embodiments of the projection lens, the term "optical axis" refers to a straight line passing through the center of curvature of the curved lens element surface. In an embodiment, the object is a mask (reticle) with a pattern of an integrated circuit, which may for example be associated with different patterns of gratings. In an embodiment, the image is projected onto a wafer with a photoresist layer, said wafer serving as a substrate. Other substrates are also possible, for example substrates for elements for liquid crystal displays or optical gratings.

[0076] Some peculiarities can be revealed based on the profile and relationship of the imaging chief ray and marginal rays. In this case, the chief ray CR starts from the edge of the objective field and intersects with the optical axis in the area of ​​the pupil plane, i.e. in the area of ​​the stop position suitable for mounting the aperture stop (AS). The marginal ray MR within the meaning of this application runs from the center of the objective field to the edge of the aperture stop. The vertical distance of these rays from the optical axis results in the corresponding ray height. Insofar as the application speaks of "marginal ray height" (MRH) or "chief ray height" (CRH), this refers respectively to the paraxial marginal ray height and the paraxial chief ray height.

[0077] The term "aperture region" refers to the region surrounding the aperture position (i.e., upstream and downstream of the aperture position) in which the ray height ratio |CRH / MRH| between the image chief ray height CRH and the marginal ray height MRH is less than 1. Thus, a relatively large marginal ray height occurs in the aperture region.

[0078] In the figures of the drawings, crown lens elements, specifically fused silica lens elements or lens elements made of FK5, are represented by open lens elements, flint lens elements, specifically lens elements made of LF5 or LLF1, are represented by shaded lens elements, and aspheric surfaces are marked by short aspheric dashes.

[0079] The specifications of the projection lenses shown in the figures of the drawings are given in the tables compiled at the end of this specification, the numbering of the tables corresponding respectively to the numbering of the corresponding figures in the drawings.

[0080] Tables 2 to 8 summarize the specifications of the respective designs in tabular form. In this case, the column "Surface" indicates the number of the refractive surface or surfaces distinguished in some other way, the column "Radius" indicates the radius r (in mm) of the surface, the column "Thickness" indicates the distance d between that surface and the subsequent surface, i.e. the distance expressed as thickness (in mm), and the column "Material" indicates the material of the optical component. The columns "Refractive Index 1", "Refractive Index 2" and "Refractive Index 3" indicate the refractive indices of the materials at wavelengths 365.5 nm (Refractive Index 1), 364.5 nm (Refractive Index 2) and 366.5 nm (Refractive Index 3). The column "Radius" indicates the usable free radius or free optical radius (in mm) of the lens element or of the optical element. The radius r=0 (column "Radius") corresponds to a plane. Some optical surfaces are aspheric. The tables marked with "A" indicate the corresponding aspheric data, the asphericity being calculated according to the following provisions: p(h)=[((1 / r)h 2 ) / (1+SQRT(1-(1+K)(1 / r) 2 h 2 ))]+C1*h 4 +C2*h 6 +....

[0081] In this case, the reciprocal of the radius (1 / r) denotes the surface curvature, and h denotes the distance between a surface point and the optical axis (i.e. the ray height). Thus, p(h) denotes the sagittal height, i.e. the distance between a surface point and the surface vertex in the z direction (direction of the optical axis). The coefficients K, C1, C2, ... are indicated in the table with the letter "A".

[0082] Table 9 summarizes important design parameters of the exemplary embodiment.

[0083] In the following description of the exemplary embodiments, the same reference numbers are used for identical or corresponding features in all figures. The lens elements are numbered in order from the object plane to the image plane, so for example, lens element L1 is the first lens element immediately following the object plane. For clarity, reference numbers have not been applied to all lenses.

[0084] FIG. 2 shows a schematic meridional lens element cross-section of a first exemplary embodiment of a refractive projection lens 200 with selected beams to reveal the imaging or projection beam paths of projection radiation passing through the projection lens during operation.

[0085] The projection lens is provided as an imaging system having a reduction effect for imaging the pattern of a mask arranged on its object plane OS directly onto its image plane IS aligned parallel to the object plane, i.e. without generating an intermediate image, at a reduced scale, specifically at a scale of -1:2 (imaging scale is -0.5).

[0086] Between the object plane and the image plane lies only the pupil plane PUP of the imaging system, where the chief ray CR of the optical imaging intersects with the optical axis OA. The aperture stop AS of the system is attached in the region of the pupil plane. A suitable position for attaching the aperture stop is therefore also referred to as the aperture position BP in this specification.

[0087] A stop area BB extends around the stop position, and the condition |CRH / MRH|<1 applies to the ray height ratio between the chief ray height CRH and the marginal ray height MRH of the image formed in said stop area. The marginal ray height is therefore higher than the chief ray height. This optical configuration can be characterized as follows:

[0088] The objective surface OS is immediately followed by a first lens element group LG1 having a positive refractive power and a total of four lens elements L1-L4, which collects light rays incident from field points of the objective surface and as a result forms at least approximately a bulge in the projection beam path.

[0089] The first lens element group LG1 is immediately followed by a second lens element group LG2 having a negative refractive power, which includes two lens elements L5 and L6 and creates a waist surrounding a local minimum in the marginal ray height between the object surface OS and the objective surface IS in the projection beam path.

[0090] The second lens element group LG2 is immediately followed by a third lens element group LG3 having a positive refractive power and a total of two lens elements L7-L8. The lens elements of the third lens element group are arranged between the second lens element group LG2 and a diaphragm position suitable for mounting an aperture diaphragm AS.

[0091] A fourth lens group LG4 having an overall positive refractive power is located between the aperture position and the image surface IS. The fourth lens element group LG4 includes six lens elements L9 to L14 having refractive power.

[0092] The projection lens is therefore characterized by a power sequence PNPP, where "P" stands for lens element groups with positive power and "N" stands for lens element groups with negative power. There is only a single pronounced waist in the region of the second negative lens element group LG2 between the object-proximity bulge (at LG1) and the image-proximity bulge (at LG3 and LG4). This single-waist system design contributes to Petzval correction.

[0093] With one exception (biconcave negative lens element L8), all lens elements are made of crown glass, specifically synthetic fused silica (SiO2, abbreviated as SILUV in Table 2), i.e., with an Abbe number v Hg The first group of materials, or lens element materials designated FK5, have an Abbe number v ≈60. Hg 52. The first group of lens element materials has a diameter of 0.5 mm.

[0094] On the other hand, the biconcave negative lens element L8 is a flint lens element made of flint glass named LF5, i.e. Hg A third group of lens materials has a relatively low Abbe number of ≈31.

[0095] The first exemplary embodiment includes a stepper field with OBH=84 mm for an image-side numerical aperture NA=0.18, with an imaging scale of −0.5×. The only flint lens element required is lens element L8, which is located directly adjacent to the aperture stop. The flint lens element is located at approximately the maximum ray height and, together with lens elements L7-L11, plays a decisive role in correcting the longitudinal chromatic aberration. As a result of the very small numerical aperture in the image field, it is possible to dispense with the correction of the chromaticity shift of the Petzval sum, and therefore the only flint lens element required is lens element L8, which is located directly adjacent to the aperture stop and approximately at the point of maximum peripheral ray height.

[0096] In the following exemplary embodiments, the same reference numerals are used for corresponding or similar features, which will not be separately mentioned again for the sake of clarity.

[0097] The second exemplary embodiment (FIG. 3, projection lens 300) is likewise a single waist system. However, in this case the refractive power sequence NPNPP is realized. For this purpose, a front negative group NV with two lens elements (a biconcave positive lens element L1 and a biconcave negative lens element L2) is arranged between the object surface OS and a first lens element group LG1 with an overall positive refractive power. Such a negative group directly adjacent to the object surface allows the formation of a subsequent bulge in a short axial length, thus resulting in a compact structural shape.

[0098] The etendue of the system in the second exemplary embodiment is slightly increased with respect to the first exemplary embodiment, but is mainly significantly differently distributed. Although the objective field radius is reduced to the scanner field (OBH=59 mm), the image-side numerical aperture of the system is more than doubled to NA=0.38. Nevertheless, in this case, it is also possible to realize a properly corrected optical design with the minimum required number of flint lens elements. Only a single lens element of the 22 lens elements L1-L22 is a flint lens element, specifically the biconcave negative lens element L16 in the region of the highest peripheral ray height near the aperture stop AS. Together with the adjacent positive lens elements L15, L17, L18, this negative lens element L16 again employs correction of longitudinal chromatic aberration.

[0099] In the third exemplary embodiment (FIG. 4, projection lens 400), the second exemplary embodiment (FIG. 3) is supplemented with an additional flint lens element. This flint lens element is an image-side convex negative meniscus lens element L19. As a result, the correction of longitudinal chromatic aberration is distributed in a combination of two flint lens elements and a positive lens element made of crown material surrounding them. The individual refractive power of the two flint lens elements is smaller than the individual refractive power of the flint lens elements in FIG. 3, which leads to the relaxation of this exemplary embodiment.

[0100] The fourth exemplary embodiment (FIG. 5, projection lens 500) is again a symmetrical 1:1 system (imaging scale β=−1) in which only one flint lens element is used for one system part upstream and downstream of the diaphragm. In this case, it would be conceivable to use exactly one negative lens element made of flint material and with a large refractive power exactly halfway between the object and image planes. However, this would make access to the diaphragm at the same position impossible. Therefore, due to the symmetry of the design and the necessary accessibility to the diaphragm, two diverging flint lens elements are used here.

[0101] The projection lens of Fig. 5 has mirror symmetry with respect to the diaphragm plane. The diaphragm plane is located halfway between the object field (reticle) and the image field (wafer). This means that all lens elements in the first lens section upstream of the diaphragm (between the object plane and the diaphragm plane) have counterparts of identical design arranged in a mirror-symmetric manner in the second lens section downstream of the diaphragm.

[0102] This design is provided or designed for use with an optical wavelength of 365 mm and a bandwidth of a few nm. Thus, the longitudinal correction of the primary spectrum (longitudinal chromatic aberration) is sufficient. This is provided by the diverging flint lens elements in the vicinity of the aperture stop (i.e. when the marginal ray height is large). If a material with anomalous partial dispersion is not used as the flint material, the secondary spectrum is automatically set in the longitudinal direction. This is the case for available materials such as LF5 or LLF1.

[0103] Due to the extremely small NA of 0.18, the Rayleigh unit RU=λ / NA defines the scale of the depth of field. 2 is so large that residual secondary spectrum is nevertheless negligible. Due to the symmetry of the structure, transverse chromatic aberration is essentially corrected, as are distortion and coma aberrations and their chromatic variations. Separate correction means for this are therefore not required.

[0104] Up to now, only the main longitudinal chromatic aberration has been corrected by the flint material used. However, as a result of the extra negative refractive power in the flint material, the chromaticity change of the Petzval sum cannot be corrected at the same time. The following explanation will help to understand the possible correction measures.

[0105] For the design of a projection lens with a wide image field, flattening of the image field is an important requirement. The requirement in this regard is that the Petzval sum of the lens be zero. The Petzval sum PTZ is given by the following equation:

number

[0106] Where: i denotes the index of the surface in the optical system (the system is represented by k surfaces), r i denotes the radius of the i-th face, n i , n i ' denotes the refractive index upstream and downstream of the surface.

[0107] If the system consists of a sequence of K lens elements in air (n=1), then we can simply write

number

[0108] If we consider a monomaterial system, i.e., all lens elements are made of the same material, we can extract the refractive index n common to all lens elements from the sum, giving:

number

[0109] For the Petzval sum to be zero, the sum over the curvature differences of the lens elements must thus be zero.

number

[0110] Now we need to consider the variation of the Petzval sum with wavelength. A change in wavelength changes the refractive index of the material. Thus, for a lens element in air:

number

[0111] Therefore, the Petzval sum of the entire system changes as follows:

number

[0112] Here again the following applies: If this is a system consisting of only one material, we can extract the refractive index before the summation, giving:

number

[0113] The Petzval sum of a single material system becomes zero

number

[0114] If we have a two-material system with materials A and B, the Petzval sum and its chromaticity change are as follows:

number

[0115] However, in that case, the requirement that the Petzval sum and its chromatic change be simultaneously zero is equivalent to the sum of the radius differences of the lens elements in the individual materials being zero.

number

[0116] For an optical system consisting mainly of one material (crown glass, e.g. FK5) with a few lens elements of a second material (flint glass, e.g. LF5), this means that the Petzval sum must be corrected within each material group. This is not possible if only diverging negative lens elements made from flint are used. To be able to completely null the chromaticity change of the Petzval sum, the design must also use at least one converging lens element made from flint.

[0117] In the following exemplary embodiment, this method is implemented by additionally introducing an additional Flint lens element, specifically a Flint lens element with positive refractive power, into the design. However, this converging Flint lens element is an obstacle to the correction of longitudinal chromatic aberration. Therefore, in order to minimize this negative effect on the correction of longitudinal chromatic aberration, the converging Flint lens element should preferably be used at the point in the design where the marginal ray height is as small as possible. This is specifically the case in the vicinity of the reticle or wafer, i.e., in the optical field close position.

[0118] In a fifth exemplary embodiment (FIG. 6, projection lens 600), a flint lens element with positive refractive power is used near the wafer.

[0119] However, as a substantially equivalent alternative to the fifth exemplary embodiment, an additional flint lens element having a positive refractive power may be used in the vicinity of the reticle, for example as part of the front negative group NV, specifically as the first lens element L1 of the design. This is shown in the sixth exemplary embodiment (FIG. 7, projection lens 700). The remaining description is the same as that of FIG. 5.

[0120] The seventh embodiment (FIG. 8, projection lens 800) can be considered as a variant of the first exemplary embodiment. In this case, in addition to the first exemplary embodiment, an additional flint lens element is used in the vicinity of the reticle, which essentially serves to correct the chromaticity change of the Petzval sum, which is not necessary for a small numerical aperture of 0.18.

[0121] The use of this first flint lens element further significantly simplifies the first lens element group downstream of the reticle. As a result of this flint lens element, as compared to the first exemplary embodiment, an aspheric surface and two lens elements can be omitted. This occurs because, despite the increase in the individual refractive power, the flint lens elements with a higher refractive index significantly simplify the correction of aberrations.

[0122] The illustrated embodiment demonstrates, by way of example, that the inventors have succeeded in developing an i-line lens with reduced use of flint lens elements. Although the i-line of a mercury lamp is "only" a single emission line, its bandwidth is so large that even after bandwidth limitation of, for example, 5 nm, correction of the longitudinal chromatic aberration of the imaging system is unavoidable, at least for the correction of the lowest order, i.e., first order, spectrum.

[0123] In order to increase the throughput of the system compared to the prior art, the imaging scale has been changed in all the illustrated examples from the previous 4× to 2× or less. Thus, for a constant geometrical etendue LLW, the image-side numerical aperture is reduced and the Rayleigh units and therefore the depth of the field range is increased. As a result, the system is less sensitive to longitudinal aberrations such as defocus, astigmatism or field curvature. The inventors have recognized that as a result, it is possible to significantly reduce or completely dispense with the correction of chromaticity changes of the Petzval sum. This further has a direct impact on the number of flint lens elements absolutely necessary in the projection lens. This number is kept as low as possible.

[0124] [Table 1]

[0125] [Table 2]

[0126] [Table 3]

[0127] [Table 4]

[0128] [Table 5]

[0129]

Table 6

[0130]

Table 7

[0131]

Table 8

[0132]

Table 9

[0133]

Table 10

[0134]

Table 11

[0135]

Table 12

[0136]

Table 13

[0137]

Table 14

[0138]

Table 15

[0139]

Table 16

Claims

1. A refractive projection lens (PO) for imaging a pattern arranged in an object plane (OS) of said projection lens (PO) into an image plane (IS) of said projection lens using electromagnetic radiation having an operating wavelength in the ultraviolet range longer than 280 nm, a plurality of lens elements and a non-dispersive optical element arranged between the object plane (OS) and the image plane (IS) along an optical axis (AX), the lens elements being implemented so that a pattern arranged on the object plane can be imaged on the image plane using the lens elements, a stop position (BP) suitable for mounting an aperture stop (AS) is positioned between the object plane and the image plane, and a chief ray of the image intersects with the optical axis at the stop position; the lens elements include at least one flint lens element made of a first material having a relatively low Abbe number and at least one crown lens element made of a second material having a higher Abbe number relative to the first material; A refractive projection lens, characterized in that at least one crown lens element having a positive refractive power, at least one flint lens element having a negative refractive power, and not more than two flint lens elements having a negative refractive power are arranged in an aperture region (BB) surrounding said aperture position (BP), and the condition |CRH / MRH|<1 is applied to the ray height ratio CRH / MRH of the chief ray height CRH of said image to the marginal ray height MRH.

2. 2. The projection lens according to claim 1, characterized in that the projection lens has an imaging scale of more than 1:4, preferably 1:2 (|β|=0.50) or 1:1 (|β|=1).

3. 3. Projection lens according to claim 1, characterized in that the image-side numerical aperture NA is less than 0.4, preferably the condition 0.1<NA<0.4 applies.

4. Projection lens according to any one of claims 1 to 3, characterized in that the projection lens (200, 300, 800) comprises only a single flint lens element (L16) having negative refractive power.

5. 5. The projection lens according to claim 4, characterized in that the single flint lens element having a negative refractive power is arranged in the aperture region, in particular in a region where the ray height ratio |CRH / MRH|<0.5, and / or the single flint lens element is a biconcave lens element (L16).

6. Projection lens according to any one of claims 1 to 5, characterized in that the projection lens (600, 700) comprises at least one flint lens element (L21, L1) having a positive refractive power.

7. 7. The projection lens according to claim 6, characterized in that the flint lens elements (L21, L1) having positive refractive power are arranged in the optical vicinity of a field surface in a region in which the ray height ratio of the image satisfies the condition CRH / MRH>0.

7.

8. The projection lens is a first lens element group (LG1) having a positive refractive power adjacent to the object surface (OS); a second lens element group (LG2) having a negative refractive power following the first lens element group (LG1) for creating a waist (TL) surrounding an area of ​​minimum peripheral ray height between the object surface (OS) and the image surface (INS); a third lens element group (LG3) having a positive refractive power subsequent to the second lens element group (LG2) between the aperture position (BP) and the second lens element group; a fourth lens element group (LG4) having a positive refractive power between said stop position (BP) and said image plane, Projection lens (200, 300, 400, 500, 600, 700, 800) according to any one of claims 1 to 7, characterized in that it comprises a front negative group (VN) with at least one lens element (L2) having negative refractive power, preferably arranged between the object surface (OS) and the first lens group (LG1).

9. 9. The projection lens according to claim 1 , characterized in that it is implemented as a single-waist system with refractive power sequence N-P-N-P-P, an image-side numerical aperture NA in the range 0.2<NA<4, an imaging scale of the order of 2:1 (|β|∼0.50) or less, and a geometrical etendue LLW in the range 10 mm<LLW<18 mm and comprises only a single flint lens element with negative refractive power.

10. Projection lens according to any one of the preceding claims, characterized in that the projection lens is designed for the radiation of the i-line of a mercury lamp (LS).

11. 1. A projection exposure apparatus (WST) for exposing a radiation-sensitive substrate arranged in the area of ​​an image plane (IS) of a projection lens (PO) using at least one image of a pattern arranged in the area of ​​an object plane (OS) of said projection lens, a light source (LS) emitting electromagnetic radiation with an operating wavelength in the ultraviolet region longer than 280 nm; an illumination system (ILL) for receiving light from the mercury lamp and for forming an illumination radiation that is directed towards the pattern; a projection lens (PO) for imaging the structure of the pattern onto a photosensitive substrate (W); Projection exposure apparatus, wherein the projection lens (PO) is embodied according to any one of claims 1 to 10.

12. 12. The projection exposure apparatus according to claim 11, wherein the projection exposure apparatus (WST) is designed as a wafer stepper for a step-and-repeat process.

13. 13. The projection exposure apparatus according to claim 11 or 12, wherein the light source comprises a mercury lamp (LS) emitting electromagnetic radiation in the i-line of the mercury lamp (LS).

14. 1. A projection exposure method for exposing a radiation-sensitive substrate using at least one image of a pattern of a mask, comprising the steps of: - providing said pattern between an illumination system of a projection exposure apparatus and a projection lens such that said pattern is located in the area of ​​an object plane of the projection lens; holding the substrate such that a radiation sensitive surface of the substrate is located in a region of an image plane of the projection lens that is optically conjugate with the object plane; illuminating an illumination area of ​​the mask with illumination radiation provided by the illumination system at an operating wavelength in the ultraviolet range longer than 280 nm; projecting, using the projection lens, a portion of the pattern located in the illumination area onto an image field on the substrate, whereby all rays of projection radiation contributing to the generation of an image in the image field form a projection beam path; A projection exposure method, in which a projection lens as claimed in any one of claims 1 to 10 is used.

15. 15. Projection exposure method according to claim 14, wherein individual dies of the substrate are exposed in a step-and-repeat process without scanning and / or illumination radiation of the i-line of a mercury lamp is used.

Images