TW201421167A - Microlithographic projection exposure apparatus and method for varying an optical wavefront in a catoptric lens of such an apparatus - Google Patents

Abstract

A microlithographic projection exposure apparatus (10) for projecting a reflective mask (14) onto a light-sensitive layer (16) contains a catoptric lens (26) comprising a plurality of mutually adjusted mirrors (M1 to M6) configured to reflect projection light having a center wavelength of between 5 nm and 30 nm. The lens (26) is configured to direct projection light reflected from the mask (14) onto the light-sensitive layer (16). At least one of the plurality of mirrors (M2, M3) is a correction mirror for correcting wavefront deformations, which changes its form permanently when it is processed by a processing beam (65). Furthermore, a processing device (42) is provided, having a processing head (44), from which the processing beam (65) emerges during operation of the processing head. The processing head is arranged or can be arranged within the lens (26) such that the processing beam (65) impinges on none of the other plurality of mirrors before it processes the correction mirror (M2, M3).

Description

Micro-image projection exposure apparatus and method for changing optical wavefront in a reflective lens of such a device

The present invention relates to a lithographic EUV projection exposure apparatus and to a method of modifying the optical wavefront in a reflective lens of such apparatus.

The structure contained in the mask or formed on the mask is transferred to the photoresist or some other photosensitive layer using a lithographic projection exposure apparatus. The most important optical components of the projection exposure apparatus are: a light source; an illumination system that adjusts the projected light generated by the light source and directs the projected light onto the mask; and a lens that masks the section illuminated by the illumination system Imaged on the photosensitive layer.

The shorter the wavelength of the projected light, the smaller the structure defined by the projection exposure device on the photosensitive layer. The latest generation of projection exposure devices use projected light in the extreme ultraviolet spectral range (EUV) with a center wavelength of 13.5 nm. Such devices are often referred to as "EUV projection exposure devices."

However, for such a short wavelength, no optical material has a sufficiently high transmittance. Therefore, in the EUV projection exposure apparatus, the lens element and other refractive optical elements conventionally used at longer wavelengths are replaced by mirrors, and the mask also contains a pattern of the reflective structure. A lens specifically containing a mirror as an imaging optical element is named "reflective lens".

In order to ensure optimal imaging of the structure contained in the mask on the photosensitive layer, extremely stringent requirements are placed on the dimensional accuracy of the mirror in the lens. However, due to manufacturing and mounting tolerances, the minimum imaging aberration determined by the lens design can never be achieved. The imaging aberration of a lens is generally described as the deviation of the true optical wavefront from the ideal optical wavefront measured in general. Such deviations are also referred to as "wavefront distortions", which can be broken down into individual parts as a series expansion. In this case, in particular, since the decomposed individual items can be directly assigned to specific Seidel imaging aberrations, such as astigmatism or coma, it has been proved that decomposition according to Zernike coefficients is appropriate.

To correct for imaging aberrations, the mirrors contained in the lens can be finely adjusted by means of a manipulator, which covers both the displacement and deflection of the mirror. However, this method can only reduce the longer wave portion of the wavefront deformation.

Correction is also required after the projection exposure device is activated. This is because it has been determined that, for example, where the mirror substrate is subjected to a particularly high light intensity over a relatively long period of time, the high energy EUV projection light causes a tight effect, which is associated with a locally defined change in the shape of the mirror surface. Therefore, it is sometimes necessary to improve the imaging properties of the lens after the projection exposure apparatus is activated.

One approach to correcting short-wavefront distortion is to locally remove the surface of the appropriate mirror to alter the shape of the mirror and thereby reduce or affect the wavefront distortion, such that the wavefront can be corrected relatively easily using the previously mentioned manipulator. Deformation.

However, this post-processing by material removal, such as the post-processing successfully employed in lens elements, is problematic in EUV lenses for a number of reasons. First, although material removal changes the shape of the mirror, it also damages the sensitive reflective coating, resulting in a local reduction in the reflection coefficient. One solution to this problem consists in partial post-treatment of the mirror substrate (rather than the coating itself) as seen in US 2005/0134980 A1.

Another approach is not to remove the material from the surface of the mirror, but to make the mirror substrate under the reflective coating partially compact, as described in DE 10 2011 084 117 A1. For this purpose, a processing beam (eg, an electron beam or a high energy beam) is directed onto the mirror to be processed. The processing beam penetrates the reflective coating without significant interaction with the reflective coating and causes a tight effect in the underlying region of the mirror substrate. The associated local shrinkage of the substrate ultimately causes the desired mirror deformation.

However, in both approaches, the basic problem remains: in order to determine the need for calibration and the required post-processing, any type of post-processing needs to incorporate the mirror into the lens at the outset. If the mirrors are then removed from the lens, post-processed, and later merged, the conditions that exist when determining the calibration requirements may not fully reproduce. The removal and later merging of the mirror itself can be said to be an additional type of post-processing that is not required and cannot be controlled. In addition, the mirrors used to determine the calibration requirements are not post-processed, but the identical replicas of the mirrors are post-processed (as proposed in US 2005/0134980 A1) and cannot be avoided. .

DE 10 2004 046 542 A1 proposes to couple processing radiation from the light incident side or the light exit side of the lens to a projection exposure device designed for a projection light having a significantly longer central wavelength and thus mainly comprising a lens element as an optical element. In the lens. In this case, the optical properties of the lens elements are taken into account such that the intensity of the radiation required to shrink and/or increase the refractive index for the local material occurs only on the desired corrective lens element. As a result, the processing radiation does not process other lens elements that are skipped by the radiation.

However, because the coating of the mirror can reflect EUV projection light, but can not reflect the processing radiation, this method cannot be used in the EUV lens. As a result, the internal mirror cannot be processed in this way.

It is an object of the present invention to provide a lithographic projection exposure apparatus that can be used to effectively reduce even short wavefront distortion. Furthermore, it is an object of the present invention to provide a method for efficiently changing the optical wavefront in a reflective lens of such a device.

This object is achieved by a lithographic projection exposure apparatus that projects a reflective mask onto a photosensitive layer, the apparatus comprising a reflective lens comprising a plurality of mutually adjusted mirrors. The mirror is preferably configured to reflect projected light having a center wavelength between 5 nm and 30 nm. The lens is configured to direct the projected light reflected from the mask onto the photosensitive layer. At least one of the plurality of mirrors is a correcting mirror for correcting wavefront distortion that permanently changes its shape when processed by the processing beam. The projection exposure apparatus additionally includes a processing device that includes a processing head that appears from the processing head during operation of the processing head. The processing head is disposed or configurable within the lens such that the processing beam does not impinge on any of the other plurality of mirrors prior to processing the correcting mirror.

The invention is based on the consideration that an effective correction of the wavefront deformation is only carried out after the correction mirror to be processed remains in the lens after determining the correction requirement. On the other hand, since the processing beam suitable for processing is not reflected by the mirror, in order to process the internal mirror, the processing beam must appear from the processing head disposed in the lens. In this case, the processing head can be permanently disposed in the lens or only within the lens during actual processing. In this case, the processing head is introduced into the lens in a manner such that it is not necessary to disassemble the lens. As a result, imaging property impairments that are generally unavoidable in the case of unloading and later reintegration into the mirror will not occur.

As a result, even if it is an internal mirror (i.e., a mirror that is neither the first nor the last mirror in the beam path of the lens), the present invention can be post-processed for correction purposes without having to be detached from the lens. The mirror is post-processed.

The processing beam preferably has the property of only making the mirror substrate, rather than the reflective coating, compact (if it impinges on the reflective coating). In particular, an electron beam or beam of sufficient energy is suitable as the processing beam.

If the processing beam is a high energy beam, the high energy beam can be guided in a scanner-like manner by means of a tiltable mirror or the like in a targeted manner on the area to be processed by the correction mirror. However, particularly where the processing beam is an electron beam, it may be convenient to move the processing head across the area of the correction mirror by means of the moving device. A relatively short processing distance which is convenient in the case of using electron beam processing can be realized in this way without any problem, so that the electron beam diameter is kept small.

In particular, the mobile device can be configured to move the processing head across the area of the correcting mirror such that during processing of the correcting mirror with the processing beam, the distance between the processing head and the region does not exceed a maximum processing distance of 10 mm (preferably 5 mm, and more preferably 1 mm). In this way, even the local extreme narrow definition of compaction can be produced in the substrate material by means of the treatment beam.

If, although the beam diameter is small, a relatively large area is to be processed continuously, the processing device can be configured to move the processing head across the area along the moving path such that after the moving path is finished, the processing beam has The amount of the area close to the two-dimensional area is progressively processed.

In general, the area treated with the processing beam will be the surface of the reflective coating carried by the mirror substrate. This ensures that the tight action of the mirror substrate occurs directly adjacent to the reflective coating and can therefore exert its maximum effect on the optical wavefront.

However, the processing beam can in principle also impinge on the area of the correction element which is not covered by the reflective coating. This region may for example be the area on the back side of the mirror substrate facing away from the reflective coating. Such processing regions are advantageous in certain circumstances with regard to the structural space required to configure the processing head in the lens.

If the processing head is not permanently disposed in the lens, the lens can have a support structure that supports a plurality of mirrors in which access channels are formed. The processing head can then be introduced into the lens through the access channel while the mirror is being corrected by the processing beam processing. Thus, with the aid of an always existing access channel, there is no need to make any structural changes to the lens in order to be able to perform the processing. This ensures that even after processing, all mirrors are exactly where they are located when determining the correction requirements. The access channel can be a light channel for passing the projected light. However, it is even more convenient to provide an access channel in addition to this optical channel.

There are many reasons why the processing head is introduced into the lens only during the actual processing time. First, the processing head can then be configured during processing to be in an optical channel that is actually designed to pass the projected light and preferably different from the access channel. Conversely, in the case where the processing head is permanently disposed in the lens, it must be ensured that the processing head is in a stationary position that does not interfere with the passage of the projected light, at least during the projection operation. This may be difficult from the point of view of the structural space depending on the lens design. Another advantage of the processing head being disposed in the lens as desired is that different correction mirrors can be processed with only one processing head.

With regard to the method, the object mentioned in the preamble is achieved by a method of changing the optical wavefront in the reflective lens of the lithographic projection exposure apparatus, wherein the method comprises the steps of: a) assembling a reflective lens from a plurality of mirrors, preferably the reflective lenses. Projected to reflect a projected light having a center wavelength between 5 nm and 30 nm, and wherein at least one of the plurality of mirrors is a correcting mirror for correcting wavefront distortion; b) adjusting the mirrors; c) Processing a region of the correcting mirror with a processing beam whereby the shape of the correcting mirror is permanently altered, and wherein the processing beam is processing The correcting mirror has not impinged on any of the other plurality of mirrors; wherein no mirrors have been removed from the lens between steps b) and c).

Reference is made to the above advantages and preferred embodiments.

In particular, the processing head that emits the processed beam may be moved across the area of the correcting mirror during step c) such that during processing of the correcting mirror with the processing beam, the distance between the processing head and the area is not More than the optimum treatment distance of 10 mm, preferably 5 mm, more preferably 1 mm.

During step c), the processing beam can be directed over the area such that after the moving path is completed, the processing beam has progressively processed the two-dimensional area on the area.

If the processing head is only in the lens during processing, the processing head can be introduced into the lens through the access channel prior to processing, the access channel being provided in a support structure configured to support the mirror, and the access The channel is different from the light channel designed to pass the projected light through the lens.

The invention further relates to a lens comprising: a mirror; a processing head configured to emit a processing beam; and a mobile device configured to configure the processing head on a region of the mirror At different locations, the processing beam causes a permanent change in the shape of the mirror.

In a specific embodiment, the distance between the processing head and the area of the mirror does not exceed a maximum processing distance of 10 mm in this case.

The invention further relates to a method of changing the optical wavefront in a lens, comprising the steps of: a) assembling a reflective lens from a plurality of mirrors; b) adjusting the mirrors; c) directing a processing beam to a mirror On one area, the mirror is taken The shape is permanently altered, wherein the mirror is neither the first nor the last mirror of the lens in the beam path of the lens.

10‧‧‧Projection exposure device

12‧‧‧Reflective structure

14‧‧‧ mask

16‧‧‧Photosensitive layer

18‧‧‧ Wafer

20‧‧‧ illumination system

22‧‧‧EUV light

24‧‧‧ illuminating field

24'‧‧‧Reduced image

26‧‧‧ lens

28‧‧‧ Beam

30‧‧‧ object plane

32‧‧‧Image plane

34‧‧‧First optical surface

36‧‧‧Main light

38‧‧‧Second optical surface

40‧‧‧Shielding light valve

42‧‧‧Processing device

44‧‧‧Processing head

46‧‧‧Mobile devices

47‧‧‧Support structure

48‧‧‧ telescopic arm

50‧‧‧ pivoting device

52‧‧‧Motor operated XY mobile platform

54‧‧‧Mirror substrate

56‧‧‧Optical area

58‧‧‧Reflective coating

60‧‧‧ thin layer

62‧‧‧ surrounding area

64‧‧‧Back area

65‧‧‧Electron beam

66‧‧‧ deformation

68‧‧‧Light channel

70‧‧‧Access channel

71‧‧‧External space

72‧‧‧ pivoting baffle

74‧‧‧Closed cover

78‧‧‧Base

80‧‧‧Guide elements

82‧‧‧ Guide hole

85‧‧‧ Position Detection Device

86‧‧‧Light emitting device

88a, 88b, 88c‧‧‧ light receiving unit

d‧‧‧Processing distance

M1-M6‧‧‧Mirror

OA‧‧‧ optical axis

Further features and advantages of the present invention will become apparent from the following description of the embodiments of the invention, wherein: FIG. 1 shows a schematic perspective view of an EUV projection exposure apparatus according to the present invention; FIG. 2 shows according to the first embodiment. Figure 1 shows a longitudinal section of the lens of the projection exposure apparatus, the processing head is in a non-enabled positioning; Figure 3 shows the longitudinal section of Figure 2, the processing head is in the activated position; Figures 4a to 4c show the correction mirror contained in the lens FIG. 5 shows a longitudinal section of a portion of the lens of the projection exposure apparatus of FIG. 1 according to the second embodiment, the processing head position is outside the lens; FIG. 6 shows the position of the processing head in FIG. In the longitudinal section, the processing head position is within the lens; Figure 7 shows a flow chart listing the important steps of the method according to the invention.

1. The basic structure of the projection exposure device

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a basic configuration of a lithographic projection exposure apparatus according to the present invention, which is designated as 10 in a highly schematic perspective view, not to scale. The projection exposure apparatus 10 is for projecting the reflective structure 12 disposed on the side of the mask 14 on the lower side in FIG. 1 to the photosensitive layer 16. Photosensitive layer 16 (specifically, a photoresist, also known as a resist) is carried by wafer 18 or some other substrate.

The projection exposure apparatus 10 includes an illumination system 20 that illuminates the side of the mask 14 with the structure 12 with EUV light 22. In particular, a range between 5 nm and 30 nm is suitable as the wavelength of the EUV light 22; in the illustrated embodiment, the EUV light 22 has a center wavelength of about 13.5 nm. The EUV light 22 illuminates the illumination field 24 on the downward facing side of the mask 14, which in the illustrated embodiment has the geometry of the annular segment.

The projection exposure apparatus 10 additionally includes a lens 26 that produces a reduced image 24' of the structure 12 in the region of the illumination field 24 on the photosensitive layer 16. The lens 26 has an optical axis OA which coincides with the axis of symmetry of the illumination field 24 of the annular segment shape and is therefore located outside the illumination field 24.

Lens 26 is designed for scanning operations in which mask 14 moves synchronously with wafer 18 during exposure of photosensitive layer 16. These movements of the mask 14 and the wafer 18 are indicated by arrows A1, A2 in FIG. Thus, during exposure of the photosensitive layer 16, the illumination field 24 is swept across the mask 14 in a scanner-like manner so that a relatively large continuous structural region can be projected onto the photosensitive layer 16. The speed at which the mask 14 and the wafer 18 move is greater than the imaging ratio β of the lens 26 in this case. In the illustrated embodiment, the image 24' produced by the lens 26 is reduced (|β|<1) and is a positive image (β>0), for which reason the wafer 18 moves slower than the mask 14. , but in the same direction.

The beams are emitted from points in the illumination field 24 (located in the object plane of the lens 26) that enter the lens 26. Lens 26 has the effect that the incoming beam converges in the image plane of lens 26 at each field point. The field points emitted by the beam from the plane of the object, and the field points at which the beams converge again in the image plane, in this case are in a relationship designated as optically conjugate.

For individual points at the center of the illumination field 24, the beam is schematically indicated and labeled at 28. In this case, the aperture angle of the beam 28 when entering the lens 26 is The unit of measure of the numerical aperture NA of the mirror. Due to the reduction in imaging, the image side numerical aperture NA of the lens 26 is magnified by the reciprocal of the imaging ratio β.

Figure 2 also shows important components of the lens 26 in a schematic and not to scale longitudinal section. A total of six mirrors M1 to M6 are arranged along the optical axis OA between the object plane shown at 30 and the image plane shown at 32. The light beam 28 emitted from a point in the object plane 30 first impinges on the concave first mirror M1, is reflected back onto the convex second mirror M2, impinges on the concave third mirror M3, and reflects backward to the concave fourth reflection. The mirror M4 and then the impact on the convex fifth mirror M5, the convex fifth mirror M5 leads the EUV light back to the concave sixth mirror M6. The concave sixth mirror M6 finally focuses the beam 28 into the conjugate image points in the image plane 32.

If the mirrors M1 to M6 are partially supplemented as indicated by the broken line in Fig. 2, the reflecting surface of the supplemental mirror will therefore be rotationally symmetric with respect to the optical axis OA of the lens 26. However, as can be readily seen, since the mirror will partially block the light path, the beam path cannot be achieved with this fully rotationally symmetric mirror. Therefore, the mirrors M1 to M6 have a shape indicated by a solid line.

The lens 26 has a first pupil surface 34 that is located in or directly adjacent to the surface of the second mirror M2. The pupil surface is identified by the fact that the chief ray of the light beam emitted from the point in the object plane 30 intersects the optical axis OA. This is shown in Figure 2 for the chief ray 36 of the beam 28, which is indicated in dashed lines.

The second pupil surface 38 is located in the beam path between the fifth mirror M5 and the sixth mirror M6, wherein the distance from the second pupil surface 38 to the two mirrors M5, M6 is relatively large. The shielded light valve 40 is disposed at a level of the second diaphragm surface 38.

2. Processing device

Processing device 42 is disposed in lens 26, which includes processing Head 44 and mobile device 46 for moving processing head 44. In the illustrated embodiment, the processing device 42 is permanently affixed to the support structure 47 of the lens 26. The support structure 47 carries, among other things, mirrors M1 to M6 and cooling means and adjustment manipulators, which are schematically indicated in Fig. 2 only by their outer contours.

The moving device 46 allows the processing head 44 to move relative to the support structure 47 and thus move relative to the mirrors Ml through M6 secured to the support structure. In the illustrated embodiment, the moving device 46 includes a telescoping arm 48 that supports the pivoting device 50 at its free end. With the pivoting device 50, the processing head 44 can be pivoted about two orthogonal axes in a motor operated manner. At the end of the telescoping arm 48 opposite the processing head 44, the telescoping arm 48 is secured to a motor operated XY moving platform 52, and the telescoping arm 48 and the fixed end processing head 44 are translatable in two orthogonal directions by means of the moving platform 52. mobile. The moving device 46 can guide the processing head 44 to different positions of the reflecting surfaces of the mirrors M2 and M3 in this manner, as shown in FIG. 3 with respect to the second mirror M2 in solid lines and with respect to the third mirror M3 in broken lines.

For reasons of structural space, it is convenient not to arrange the processing device 42 in the longitudinal plane of the lens 26 shown in Figures 2 and 3 but in the sagittal plane perpendicular thereto. Moreover, completely different designs are also suitable for use in mobile devices, as long as these designs are suitable for delivering the processing head to at least one of the mirrors Ml through M6 of the lens 26.

In the illustrated embodiment, the processing head 44 contains an electron gun that is a conventional one, such as an electron gun used in, for example, an X-ray source. Such electron guns typically include an electron source such as an incandescent cathode, a Wehnelt cylinder, and an accelerating anode to accelerate electrons released by the incandescent cathode. The energy of the electrons emitted by the processing head 44 is preferably between 5 keV and 80 keV, and especially between 40 keV and 50 keV. The energy that the emitted electrons should ideally have, among other things, also depend on the materials of the substrates that make up the mirrors M2, M3.

As an alternative to the electron gun, the processing head 44 may also preferably contain pulses A laser that operates in a manner, or a light exit window of an optical fiber to which the light from the laser is coupled. The laser should produce light with a center wavelength between 0.3 μm and 3 μm and a pulse energy between 0.01 μJ and 10 μJ; the repetition rate should be between 1 Hz and 100 MHz.

3. Function

The function of the lens 26 and the processing device 42 will be explained below with reference to Figs.

First, the lens 26 is assembled and adjusted. In the context of adjustment, the imaging properties of lens 26 are typically measured over. For example, this can be done in a manner known per se: the interferometer determines the optical wavefront in the image plane 32 of the lens 26. During the adjustment, changing the positioning of the mirrors M1 to M6 results in minimizing the imaging aberration. Alternatively, a manipulator (if present) can be used which deforms one or more of the mirrors M1 to M6 in a targeted manner to reduce wavefront distortion in this manner.

However, even after this relatively complicated adjustment procedure, residual imaging aberrations sometimes exist, which is unacceptable in the case where the imaging properties of the lens 26 are extremely strict. This residual imaging aberration is typically a short wave wavefront deformation, which is illustrated by the higher term in the decomposition of the wavefront deformation according to the Zernike coefficient. The target post-processing of the second mirror M2, which may be configured in the first pupil plane 34, reduces the effect of field positioning independent of residual imaging aberrations. The purpose of the post-processing is to deform the second mirror M2 such that the remaining residual imaging aberration is reduced or converted into a growing wave imaging aberration in which long-wave imaging aberrations can be corrected by means of other manipulators.

Fig. 4a shows an enlarged view of the second mirror M2 in a longitudinal section. Mirror M2 comprises a mirror substrate 54, which in the illustrated embodiment is composed of special glass, such as ULE® or Zerodur®. Such glasses have a coefficient of thermal expansion that is lower or equal to zero at the operating temperature of mirror M2, so that it does not deform under relatively small temperature changes. The mirror substrate 54 has an optical region that is accurately processed 56, the shape of which is the key to determining the optical properties of the second mirror M2. The optical region 56 carries a reflective coating 58 (not to scale) and the reflective coating 58 comprises a plurality of individual thin layers 60 having alternating refractive indices. Reflective coating 58 is designed to reflect short wave EUV projection light. The mirror substrate 54 additionally has a peripheral region 62 and a back region 64 which are not optically active but are important for heat dissipation of the second mirror M2.

Figure 4b shows the second mirror M2 during processing operations by means of the processing device 42. In the illustrated process positioning, the processing head 44 is at a processing distance d from the reflective coating 58, which is less than 10 mm. Such a short processing distance is required to cause the diverging electron beam 65 to produce a sufficiently small beam spot on the second mirror M2. The high energy electrons penetrate the reflective coating without significant interaction with the thin reflective coating 58. Conversely, in the mirror substrate 54, high-energy electrons are absorbed and locally cause a close interaction of the mirror substrate 54. This compaction is in turn associated with the optical region 56 and the deformation 66 of the supported reflective coating 58 as shown in Figure 4c. This local deformation 66 produces the desired wavefront correction and thus the imaging properties of the lens 26.

If a deformation 66 is to be produced at a plurality of positions of the second mirror M2, the processing head 44 is progressively moved to the corresponding position by means of the moving means 46. If the processing head 44 moves across the optical region 56 along the path of movement in a manner (in a meandering manner), the processing beam 65 has progressively processed the two-dimensional region on the optical region 56 after the moving path has been completed, A close effect of the relatively large area of the mirror substrate 54 may also occur.

If the field dependent wavefront deformation is also corrected, the near field configured mirror must be processed by the processing head 44 in the manner described above. Since the third mirror M3 is disposed at least outside the pupil plane 34, the correctable field dependence is small, as shown by the dashed line in FIG. More suitable for this is the fourth mirror M4, which is more configured. Close to the middle image.

Since the processing device 42 is integrated in the lens 26, it is also possible to carry out the processing for the purpose of correction without problems after the projection exposure device 10 is activated. The reason for this correction requirement is that, for example, if a particular light intensity is exceeded for a relatively long period of time, the high energy EUV projection light will partially penetrate the reflective coating 48 of the mirrors M1 to M6 and may also result in a mirror substrate. The close function of 54. The deformation associated with the compaction of the optical region 56 can be compensated or at least modified by the processing device 42 with a post-processing of a suitable design, such that other manipulators can more easily correct the remaining residual imaging aberrations.

4. Second embodiment

The permanent configuration of the processing device 42 in the lens 26 can become difficult for a variety of reasons. First, because the beam path in the EUV lens 26 is complex, the available construction space is often limited, making it impossible to accommodate additional assemblies. Also, from a cost point of view, it may be advantageous for the processing device 42 to be disposed in the lens 26 only as needed, rather than permanently.

Referring to Figures 5 and 6, a second embodiment of a processing device 42 in accordance with the present invention is illustrated below in which the processing head 44 is incorporated into the lens 26 only as needed. Figure 5 shows a section of the lens 26 on top, forming a light channel 68 in its support structure 47 supporting the mirrors Ml to M6, which is provided for the passage of EUV projection light. In addition to the light tunnel 68, an access channel 70 is formed in the support structure 47 that connects the light tunnel 68 with the outer space 71 surrounding the lens 26. During normal projection operation, the pivoting shutter 72 can be separated from the optical channel 68 and the access channel 70; in addition, a closed outer cover 74 is provided that isolates the access channel 70 from the exterior space 71.

In this particular embodiment, the processing device 42 (or more specifically, its moving device 46) is secured to the base 78 that includes the guiding member 80. The guiding element 80 corresponds to a guiding hole 82 formed in the support structure 47 of the lens 26.

If the correction requirement for processing after the second mirror M2 is required after the initial adjustment or at the time point after the projection exposure apparatus 10 is activated, the closing outer cover 74 is removed and the pivoting shutter 72 is turned upward. Access channel 70 then provides a continuous connection between external space 71 and optical channel 68. Thereafter, the base 78 of the processing device 42 is secured to the support structure 47 from the outside, causing the guiding member 80 to engage into the guide hole 82, as shown in FIG.

In the next step, the processing head 44 is brought to the desired position relative to the second mirror M2 by means of the moving device 46, and the processing is performed by means of the processing beam 65.

In order to be able to accurately position the processing head above the optical region 56 of the second mirror M2, in this embodiment, the processing device 42 has an additional position detecting device 85 that can be used with a high accuracy The positioning of the processing head 44 relative to the support structure 47 and thus with respect to the second mirror M2 (ie, space and angular coordinates). For this purpose, the position detecting device 85 is designed as a μGPS system including a light emitting device 86 disposed on the processing head 44, and feeding light from the external light source to the light emitting device 86, and at least three lights The receiving units 88a, 88b, 88c are fixed to the support structure 47 at different locations. By superimposing the light received by the light receiving units 88a, 88b, 88c and the reference light generated by the external light source, the distance between the light receiving units 88a, 88b, 88c and the light emitting device 86 can be determined with high accuracy. In this way, the positioning of the processing head 44 relative to the second mirror M2 can be measured with an accuracy of a few microns. More details on the appropriate μGPS system can be found in DE 10 2008 003 282 A1. However, other measurement systems, such as the use of triangulation, are also suitable for position detection.

5. Important method steps

The important steps of the method according to the invention are outlined in the flow chart shown in FIG.

In a first step, the lens 26 is assembled from a plurality of mirrors M1 to M6, wherein at least one of the plurality of mirrors is a correcting mirror for correcting wavefront distortion.

Thereafter, in step S2, the mirrors are adjusted.

At a subsequent step S3, the area of the correction mirror is corrected by the processing beam, whereby the shape of the correction mirror is permanently changed. In this case, the processing beam does not impinge on any of the other plurality of mirrors before processing the correcting mirror. Furthermore, after step S2, no mirrors are removed from the lens.

26‧‧‧ lens

44‧‧‧Processing head

47‧‧‧Support structure

48‧‧‧ telescopic arm

50‧‧‧ pivoting device

68‧‧‧Light channel

70‧‧‧Access channel

71‧‧‧External space

72‧‧‧ pivoting baffle

78‧‧‧Base

82‧‧‧ Guide hole

85‧‧‧ Position Detection Device

86‧‧‧Light emitting device

88a, 88b, 88c‧‧‧ light receiving unit

M1-M4‧‧‧Mirror

Claims (15)

A lithographic projection exposure apparatus (10) for projecting a reflective mask (14) onto a photosensitive layer (16), comprising a) a reflective lens (26) comprising a configuration for reflecting a center wavelength a plurality of mutually adjusted mirrors (M1 to M6) of projected light between 5 nm and 30 nm, wherein the lens (26) is configured to direct projected light reflected from the mask (14) to the photosensitive layer ( 16) above, and at least one of the plurality of mirrors (M2, M3) is a correcting mirror for correcting wavefront distortion, the correcting mirror being permanently processed by a processing beam (65) Changing its shape; b) a processing device (42) comprising a processing head (44) from which the processing beam (65) appears during operation of the processing head, wherein the processing head is configured or configurable Within the lens (26), the processing beam (65) is caused not to impinge on any of the other plurality of mirrors prior to processing the correction mirrors (M2, M3). The lithographic projection exposure apparatus of claim 1, wherein the correction mirrors (M2, M3) are neither the first nor the last mirror in the beam path of the lens (26). The lithographic projection exposure apparatus of claim 1 or 2, wherein the processing device comprises a moving device (46) configured to move the processing head (44) in the lens (26) An area of the correction mirror (M2, M3) is corrected. The lithographic projection exposure apparatus of claim 3, wherein the moving device (46) is configured to move the processing head (44) across the area of the correction mirror (M2, M3), such that Processing the correction mirror with the processing beam During this period, the distance (d) between the processing head (44) and the region does not exceed a maximum processing distance of 10 mm. A lithographic projection exposure apparatus according to any of the preceding claims, wherein the processing head (44) is permanently disposed in the lens (26). The lithographic projection exposure apparatus according to any one of claims 1 to 4, wherein the lens (26) has a support structure (47) for supporting the plurality of mirrors (M1 to M6), An access channel (70) is formed in the support structure, and wherein the processing head (44) is introduced into the lens (26) through the access channel (70). The lithographic projection exposure apparatus of claim 3, wherein the processing head (44) is held by the moving device (46) when introduced into the lens (26), and wherein At least a portion of the mobile device (46) extends through the access channel (70). The lithographic projection exposure apparatus of claim 6 or 7, wherein an optical channel (68) for passing the projection light is additionally formed in the support structure (47), the optical channel and the memory Take the channel (70) differently. The lithographic projection exposure apparatus of any of the preceding claims, wherein the processing beam (65) is an electron beam or a light beam. The lithographic projection exposure apparatus of any of the preceding claims, comprising a position detecting device (85) configured to detect the processing head (44) relative to the correcting mirror during processing ( Positioning of M2, M3). A method for changing a light wavefront in a reflective lens (26) of a lithographic projection exposure apparatus (10), wherein the method comprises the steps of: a) assembling the reflective lens (26) from a plurality of mirrors (M1 to M6), wherein at least one of the plurality of mirrors is a correcting mirror (M2, M3) for correcting wavefront distortion; b) Adjusting the mirrors (M1 to M6); c) processing a region of the correcting mirror with a processing beam (65), whereby the shape of the correcting mirror (M2, M3) is permanently changed, and The processing beam (65) does not impinge on any of the other plurality of mirrors prior to processing the correction mirror; wherein no mirrors are removed from the lens between steps b) and c). The method of claim 11, wherein a processing head (44) that emits the processing beam moves across the area of the correcting mirror (M2, M3) during step c), thereby causing the During processing of the correction beam, the distance (d) between the processing head and the region does not exceed a maximum processing distance of 10 mm. The method of claim 11 or 12, wherein the processing head (44) is located in the lens (26) only during a process. The method of claim 11 or 12, wherein the processing head (44) is introduced into the lens through an access channel (70) prior to processing, the access channel being provided to be configured to support the A support structure (47) of the mirrors (M1 to M6). The method of any of claims 12-14, wherein the positioning of the processing head (44) relative to the correction mirror (M2, M3) during processing is detected.