DE102012203959A1 - Optical system for use in illuminating device of microlithographic projection exposure system for manufacturing LCDs, has facets trapping light from other respective facets during operating exposure system in switching positions - Google Patents

Abstract

The system has first facets (111-113) and second facets (121-123) associated to different polarization states of light, which is reflected at the facets during operating a microlithographic projection exposure system. Third facets (131-133) are arranged after the first and second facets in a light propagation direction. The third facets are switched between two switching positions. The third facets trap the light from one of the first facets during operating the system in one of the positions, and from one of the second facets during operating the system in the other position. An independent claim is also included for a method for microlithographic manufacturing of microstructured components.

Description

The invention relates to an optical system of a microlithographic projection exposure apparatus.

Microlithography is used to fabricate microstructured devices such as integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure apparatus which has an illumination device and a projection objective. The image of a mask (= reticle) illuminated by means of the illumination device is hereby projected onto a substrate (eg a silicon wafer) coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection objective in order to apply the mask structure to the photosensitive coating of the Transfer substrate.

In EUV projected projection lenses, i. at wavelengths of e.g. about 13 nm or about 7 nm, mirrors are used as optical components for the imaging process, due to the lack of availability of suitable translucent refractive materials.

In the operation of a projection exposure apparatus, there is a need to be able to set specific polarization distributions in the pupil plane and / or in the reticle in the illumination device to optimize the imaging contrast as well as to be able to change the polarization distribution during operation of the projection exposure apparatus.

The state of the art with regard to the change in the polarization distribution in projection exposure systems designed for the EUV range is merely an example DE 10 2008 002 749 A1 and US 2008/0192225 A1 directed.

It is an object of the present invention to provide an optical system of a microlithographic projection exposure apparatus, in particular for operation in the EUV, which allows increased flexibility with regard to the polarization distribution which can be set in the projection exposure apparatus.

This object is achieved according to the features of the independent claims.

• – eine Anordnung aus einer Mehrzahl erster Facetten und zumindest einer Mehrzahl zweiter Facetten, wobei den ersten Facetten und den zweiten Facetten unterschiedliche Polarisationszustände des im Betrieb der Projektionsbelichtungsanlage an den jeweiligen Facetten reflektierten Lichtes zugeordnet sind; und
• – eine Anordnung aus einer Mehrzahl dritter Facetten, wobei diese dritten Facetten in Lichtausbreitungsrichtung nach den ersten und den zweiten Facetten angeordnet sind;
• – wobei die dritten Facetten jeweils zwischen einer ersten Schaltstellung, in welcher sie im Betrieb der Projektionsbelichtungsanlage Licht von einer der ersten Facetten einfangen, und wenigstens einer zweiten Schaltstellung, in welcher sie im Betrieb der Projektionsbelichtungsanlage Licht von einer der zweiten Facetten einfangen, umschaltbar sind.

An optical system according to the invention of a microlithographic projection exposure apparatus, in particular for operation in the EUV, comprises:

• An arrangement of a plurality of first facets and at least one of a plurality of second facets, wherein the first facets and the second facets are assigned different polarization states of the light reflected at the respective facets during operation of the projection exposure apparatus; and
• An arrangement of a plurality of third facets, these third facets being arranged in the light propagation direction after the first and the second facets;
• - Wherein the third facets each between a first switching position, in which they capture the operation of the projection exposure system light from one of the first facets, and at least a second switching position in which they capture the operation of the projection exposure light from one of the second facets, are switchable.

The invention is based on the concept of providing a selection option with regard to the polarization state of the light beams reflected at the third facets (typically realized on a pupil facet mirror) in that these third facets are switchable between at least two switch positions and at least two in the light propagation direction These groups of first and second facets (which are typically realized on one or more field facet mirrors) arranged in these third facets may be designed in such a way that different light states of polarization are applied to the light reflected at these first and second facets.

In particular, the present invention thus includes the concept of not configuring the pupil facet mirror in a conventional manner with fixed facets, but to perform these facets on the pupil facet mirror independently adjustable in their tilt angle (this adjustability alternatively or continuously as a stepwise adjustability in two or more discrete switching positions or tilt angles can be realized). In other words, according to the invention, in addition to the field facet mirror, which is already conventionally provided with adjustable facets, the pupil facet mirror can also be made dynamically adjustable in order to be able to select different polarization states for the light spot ultimately generated by the individual facets of the pupil facet mirror.

As a result, the invention provides in particular the possibility of dynamically changing the polarization (such as the polarization distribution generated in a pupil plane) during the ongoing operation of the polarization Projection exposure to realize without this, for example, the exchange of polarization-influencing elements in the system is required.

According to one embodiment, the first facets and the second facets may each be provided as contiguous facet mirror regions. In this case, these contiguous facet mirror areas may alternatively be provided as spatially separated areas of the same facet mirror or on separate facet mirrors.

According to one embodiment, the first facets and the second facets may also be provided in an alternating arrangement on one and the same facet mirror. Such an embodiment has the advantage that two facets each assigned to one and the same facet of the pupil facet mirror with different associated polarization states, e.g. can also be arranged directly adjacent to each other and thus for a "switching" of the polarization state of the light spot in question require less switching paths or tilt angle of the respective associated facet of Pupillenfacettenspiegels.

According to one embodiment, the third facets are arranged on a pupil facet mirror. Furthermore, the first facets and the second facets can each be arranged on a field facet mirror.

According to one embodiment, the different polarization states are mutually orthogonal. However, the invention is not limited thereto, so that embodiments are also included in which the different polarization states generated by one and the same facet of the third facets differ from one another in another way, for example by an arbitrary angle between the respective polarization directions.

In particular, these different polarization states can each be generated by converting light from a light source, which generates unpolarized light.

According to one embodiment, the different polarization states are respectively generated by a beam-splitting optical element which effects splitting of a light beam impinging on this element during operation of the projection exposure apparatus into a first partial beam and a second partial beam, the first and second partial beams having mutually orthogonal polarization directions.

In this case, at least one beam deflecting optical element can be provided in the light propagation direction downstream of the beam splitting optical element.

According to a further embodiment, the different polarization states are respectively generated by a reflection taking place at the Brewster angle on a respective reflective element. In this case, the respective reflective elements can be formed by the first and the second facets. Alternatively, the respective reflective elements may also be provided in the light propagation direction in front of the first and second facets in addition to these.

According to one embodiment, at least one of the respective reflective elements may be adjustable in position for varying the direction of polarization of the light reflected on them.

In this case, the optical system may have an optical axis, wherein the adjustability of the reflective elements along a circular arc is given about this optical axis.

The invention further relates to a microlithographic projection exposure apparatus having an illumination device and a projection objective, the illumination device having an optical system with the features described above, and a method for microlithographic production of microstructured components.

Further embodiments of the invention are described in the description and the dependent claims.

The invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

Show it:

1 - 5 schematic representations for explaining different embodiments of the present invention; and

6 a schematic representation of a designed for operation in the EUV projection exposure equipment in which the present invention is feasible.

1 shows a schematic representation of an arrangement for explaining a first embodiment of the present invention.

According to 1 gets light from an EUV plasma light source 105 via a polarization-influencing optical arrangement of elements described in more detail below 106 . 107 to one of two arrays of first and second facets, respectively 111 . 112 . 113 respectively. 121 . 122 . 123 and from these in a direction of light propagation direction subsequent arrangement of third facets 131 . 132 . 133 , .... Of these facets 131 . 132 . 133 , .... the light - possibly via non-illustrated further beam deflecting elements - hits one in an object plane of a projection lens 150 arranged mask 140 , which has structures to be imaged, with the aid of the projection lens 150 on one in an image plane of the projection lens 150 arranged wafers 160 be imaged.

In addition, the first mentioned, in 1 between the EUV plasma light source 105 and the first and second facets, respectively 111 . 112 . 113 respectively. 121 . 122 . 123 used polarization-influencing optical arrangement explained in more detail.

According to 1 This is the EUV plasma light source 105 generated, unpolarized illumination light by means of a merely indicated Strahlaufspaltenden element 106 divided into two mutually orthogonally polarized light beams or partial beams S101, S102. The arrangement according to 1 further includes (without the invention being limited thereto) a beam deflecting element 107 in the form of a deflecting mirror, by means of which the partial beam S102 is again aligned parallel to the partial beam S101.

The above-described beam splitting element causing decomposition into the mutually orthogonal polarization states 106 can be realized in particular by a zirconium foil, wherein the thickness of the zirconium foil can be only about 50 microns by way of example. This zirconium foil is arranged in the beam path at an angle of 45 ° to the direction of light propagation (= z-direction in the drawn coordinate system). This angle corresponds to the Brewster angle, since the refractive index of zirconium in EUV is close to 1. The use of zirconium foils in EUV lithography is, for example EP 1 356 476 B1 and DE 10 2008 041 801 A1 for the realization of spectral filters for filtering out unwanted portions of the electromagnetic radiation, wherein, as in EP 1 356 476 B1 described zirconium foil may also be arranged between two silicon layers to prevent oxidation of the zirconium material.

The unpolarized state of the beam splitting element 106 incident input light is in 1 symbolizes that both polarization directions (s and p) are drawn for this light beam. By the zirconium foil used in the embodiment of the present invention, the s-polarized light is largely reflected, and the p-polarized light is largely transmitted. Specifically, by means of such, arranged at the Brewster angle zirconia - taking into account the attenuation due to absorption in the material - a transmission of about (70-80)% for the p-polarized light component and a reflection of about also (70-80) % for the s-polarized light component. According to 1 is thus the through the splitting element 106 transmitted sub-beam S101 p-polarized, and that at the beam splitting element 106 reflected sub-beam S102 is according to 1 s-polarized.

The through the splitting element 106 transmitted, p-polarized sub-beam S101 meets according to 1 on a first field facet mirror 110 with a plurality of first facets (of which, for the sake of simplicity, only three facets 111 . 112 . 113 are shown), whereas at the beam splitting element 106 reflected, s-polarized sub-beam S102 onto a second field facet mirror 120 with a plurality of second facets (of which also, for the sake of simplicity, only three facets 121 . 122 . 123 are shown). Typically, the number of first and second facets is substantially higher, and may be, for example, more than 10, in particular more than 100.

In the light propagation direction subsequent to the first and second field facet mirrors, respectively 110 . 120 is a pupil facet mirror 130 with a plurality of third facets (of which for simplicity only six facets 131 - 136 are shown) arranged. Also, the number of third facets is typically much higher, and may for example be more than 10, in particular more than 100.

Through the facets 131 - 136 of the pupil facet mirror 130 become in principle for themselves (eg from DE 10 2008 002 749 A1 ) in a known manner in conjunction with the first and second facets 111 . 112 . 113 respectively. 121 . 122 . 123 Defines light channels, which the illumination light channel by channel to the object field or in the object plane of the projection lens 150 arranged mask 140 to lead.

The third facets 131 - 136 are according to the invention by varying the tilt angle of each facet 131 - 136 switchable by at least one tilt axis such that with each of the third facets 131 - 136 between each one of the respective third facet associated facet of the first facets 111 - 113 and one of the facets of the second facets associated with the third facet in question 121 - 123 in the sense that either the light reflected at the relevant first facet or the light reflected at the respective second facet can optionally be captured or reflected by the third facet, in order thus to determine the polarization state of the relevant light source Select the light spots generated at the pupil level. In further embodiments, the tilt angle of each facet can also be 131 - 136 by more than one tilt axis, in particular by two tilt axes, be variable, which is particularly useful if three or more polarization directions are set and in this case the tilt angle should be kept as low as possible.

The in the embodiment of 1 realized generation of different polarization states of the light directed to the first and second facets light has the advantage that the according to 1 originally unpolarized light of the light source 105 can be converted into light with the respectively desired state of polarization particularly effectively or without loss of light. However, the invention is not limited to this embodiment, so that in further embodiments, for example as hereinafter with reference to 2 ff , explains that different polarization states of the light reflected at the first and second facets can also be generated in another way.

Furthermore, the invention is not limited to the above-described realization of the different polarization states as mutually orthogonal polarization states. Rather, the invention also includes embodiments in which the different, of one and the same facet of the third facets 131 - 136 of the pupil facet mirror 130 polarization states generated in a different manner, for example by any angle between the respective polarization directions, from each other.

2 shows in a merely schematic representation of another embodiment of the invention, wherein compared to 1 analogous or substantially functionally identical components are designated with corresponding, increased by "100" reference numerals. The embodiment of 2 is different from the one 1 in that on the first facets 211 . 212 . 213 , ... or the second facets 221 . 222 . 223 , ... directed light from two light sources 205a . 205b coupled, which generate polarized light from the outset, such as a polarization-optical component such as US 2008/0192225 A1 is used known.

In further embodiments of the invention, more than two polarized light sources can also be used 205a . 205b , ... as well as more switching positions of the third facets 231 . 232 . 233 , ... of the pupil facet mirror.

The invention is not based on the realization of the first or second facets in two respectively spatially separated regions, and in particular also not on those in FIG 1 shown arrangement of the first and second facets on two separate field facet mirrors 110 . 120 limited.

In further embodiments, the first and second facets described above may also be provided in two spatially separated regions of the same facet mirror, in particular again a field facet mirror.

Furthermore, in further embodiments, eg as in 3 hinted, the first facets 311 . 312 . 313 , ... and the second facets 321 . 322 . 323 , ... also in an alternating arrangement on one and the same facet mirror 300 be provided. Such a refinement has the advantage that two facets assigned to one and the same facet of the pupil facet mirror can also be arranged directly adjacent to each other with different associated polarization states and thus lower switching paths or tilt angles of the relevant light source for a "changeover" of the polarization state of the relevant light spot require associated facet of the pupil facet mirror.

Both according to 1 as well as 2 As described above, the mutually orthogonally polarized partial beams S101, S102 and S201, S2022, respectively, are transmitted through the first and second facets of the facet mirrors 110 . 120 respectively. 210 . 220 in the light propagation direction, subsequently arranged third facets of the pupil facet mirror 130 respectively. 230 directed. The third facets of the pupil facet mirror 130 respectively. 230 can switch between at least two switching positions in which they capture the light from each one of the first facets (with a first polarization state) or one of the second facets (with a polarization state orthogonal to the first polarization state). As a result, by suitable choice of the switching positions of the third facets of the pupil facet mirror, different polarized illumination settings (ie different polarization distributions produced in the pupil plane) can be realized in this way. In embodiments of the invention, a continuous adjustability of the tilt angle of respective third facets of the pupil facet mirror 130 respectively. 230 be provided.

Further, with reference to 4 and 5 Embodiments of the invention are described in which the different polarization states that can be selected by the third facets of the pupil facet mirror are each produced by a Brewster-angle reflection on a reflective element.

These are initially with reference to 4 the first, second and third facets as well as the associated facet mirrors not shown, with respect to their construction, the above statements in connection with 1 - 3 apply analogously and wherein these components each part of the only schematically indicated lighting device 401 are.

According to 4 become reflective elements 408 . 409 in the light propagation direction in front of the first and second facets (which in 4 not shown or) in addition to these (for lighting device 401 belonging) first and second facets provided. These reflective elements 408 . 409 are arranged at an angle to the optical axis corresponding to the Brewster angle to subsequently obtain linearly polarized light in the reflection. At EUV, this corresponds to an angle of 45 ° for almost all materials in question.

It can be exploited that the polarization direction of the analog as in connection with 1 - 3 described depending on the respective first and second facet directed linearly polarized light is dependent on the angle at which the relevant light source and the associated reflective element 408 . 409 at which the reflection occurs at the Brewster angle to the yz plane in the in 4 are shown in the coordinate system.

While at (as in 4 Plotted) matching arrangement of the reflective elements 408 . 409 each perpendicular to the yz plane and the polarization directions of the elements 408 . 409 Matching the linearly polarized light reflected at the Brewster angle, these polarization directions can each be changed independently of one another and, in particular, adjusted orthogonally to one another by one or both light sources 405a . 405b together with the associated reflective element 408 respectively. 409 be tilted about the extending in the z-direction optical axis OA or rotated out of the yz plane, ie by the azimuthal orientation of the relevant light source 405a . 405b is varied in the plane perpendicular to the optical axis OA.

In an exemplary arrangement, for example, one of the two light sources 405a . 405b rotated by an angle of 90 ° from the yz plane, so that the light beam generated by this light source is emitted both perpendicular to the optical axis OA and perpendicular to the light beam generated by the other light source.

This tilting or twisting one of the light sources 405a . 405b together with the associated reflective element 408 respectively. 409 The optical axis OA or unscrewing from the yz plane can in particular take place variably along a circular arc (which lies in a plane perpendicular to the optical axis or xy plane), whereby the polarization direction of the corresponding sub-beam S401 or S402 is arbitrary can be adjusted.

Moreover, with regard to the arrangement of the first or second facets of the field facet mirror and of the third facets of the pupil facet mirror, the above statements apply in connection with FIG 1 - 3 analogously, so that the facets in question 4 as part of the lighting system 401 not shown again.

5 shows a further embodiment of the invention, which differs from that 4 merely differs in that the first and second facets of the field facet mirror itself are used as reflective elements, at which the reflection occurs at the Brewster angle. In other words, the functions of the facet mirror on the one hand and the function of generating a specific polarization state in each case in one and the same element (namely the facets 511 . 512 ) combined. In this way, as it were, a reflection can be saved and the light loss associated therewith due to the limited reflection can be avoided. In 5 are illustrative of the relevant facets producing the desired polarization state by reflection at the Brewster angle 511 . 512 before the subsequent optical system (containing the remaining components of the lighting device) 502 located. Incidentally, with regard to the adjustability for the purpose of varying the respectively set polarization state, the statements relating to FIG 4 analogous.

6 shows a schematic representation of an exemplary designed for operation in the EUV projection exposure equipment in which the present invention is feasible.

According to 6 points in a projection exposure system designed for EUV 675 a lighting device 680 a field facet mirror 681 (with facets 682 ) and a pupil facet mirror 683 (with facets 684 ) on. On the field facet mirror 681 becomes the light of a light source unit 685 , which is a plasma light source 686 and a collector mirror 687 includes, steered. In the light path after the pupil facet mirror 683 are a first telescope mirror 688 and a second telescope mirror 689 arranged. In the light path below is a deflection mirror 690 arranged, the radiation impinging on him on an object field 691 in the object plane OP of a six-mirror M1-M6 projection lens 695 directs. At the place of the object field 691 is a reflective structure-bearing mask M arranged using the projection lens 695 (which has six mirrors M1-M6) is imaged in an image plane IP.

For realization of the invention in the projection exposure apparatus 675 from 6 can now the field facet mirror 681 analogous to those previously based on 1 to 5 described embodiments having an arrangement of a plurality of first facets and at least a plurality of second facets are configured, wherein the first facets and the second facets are assigned different polarization states of the light reflected in the operation of the projection exposure system to the respective facets. Accordingly, the pupil facet mirror becomes 683 configured with an arrangement of a plurality of third facets such that these third facets respectively switchable between a first switching position in which they capture light from one of the first facets, and at least one second switching position in which they capture light from one of the second facets are.

As a result, the possibility is created of realizing a flexible change in the polarization or the polarization distribution generated in the pupil plane of the illumination device during operation of the projection exposure apparatus without, for example, requiring the replacement of polarization-influencing elements in the system.

While the invention has been described in terms of specific embodiments, numerous variations and alternative embodiments, e.g. by combination and / or exchange of features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are intended to be embraced by the present invention, and the scope of the invention is limited only in terms of the appended claims and their equivalents.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008002749 A1 [0005, 0036]
• US 2008/0192225 A1 [0005, 0040]
• EP 1356476 B1 [0032, 0032]
• DE 102008041801 A1 [0032]

Claims (16)

Optical system of a microlithographic projection exposure apparatus, in particular for operation in the EUV, with an arrangement of a plurality of first facets ( 111 . 112 . 113 , ...; 211 . 212 . 213 , ...; 311 . 312 . 313 , ...) and at least a plurality of second facets ( 121 . 122 . 123 , ...; 221 . 222 . 223 , ...; 321 . 322 . 323 , ...), wherein the first facets and the second facets are assigned different polarization states of the light reflected at the respective facets during operation of the projection exposure apparatus; and an arrangement of a plurality of third facets ( 131 . 132 . 133 , ...; 231 . 232 . 233 , ...), these third facets being arranged in the light propagation direction after the first and the second facets; • where the third facets ( 131 . 132 . 133 , ...; 231 . 232 . 233 , ...) in each case between a first switching position, in which, during operation of the projection exposure apparatus, it receives light from one of the first facets ( 111 . 112 . 113 , ...; 211 . 212 . 213 , ...; 311 . 312 . 313 , ...) and at least one second switching position in which they capture light from one of the second facets during operation of the projection exposure apparatus ( 121 . 122 . 123 , ...; 221 . 222 . 223 , ...; 321 . 322 . 323 , ...), are switchable. Optical system according to claim 1, characterized in that the first facets ( 111 . 112 . 113 , ...; 211 . 212 . 213 , ...) and the second facets ( 121 . 122 . 123 , ...; 221 . 222 . 223 , ...) are each provided as contiguous facet mirror areas. Optical system according to claim 1, characterized in that the first facets ( 311 . 312 . 313 , ...) and the second facets ( 321 . 322 . 323 , ...) in an alternating arrangement on one and the same facet mirror ( 300 ) are provided. Optical system according to one of claims 1 to 3, characterized in that the first facets ( 111 . 112 . 113 , ...; 211 . 212 . 213 , ...; 311 . 312 . 313 , ...) and the second facets ( 121 . 122 . 123 , ...; 221 . 222 . 223 , ...; 321 . 322 . 323 , ...) are each arranged on a field facet mirror. Optical system according to one of the preceding claims, characterized in that the third facets ( 131 . 132 . 133 , ...; 231 . 232 . 233 , ...) are arranged on a pupil facet mirror. Optical system according to one of the preceding claims, characterized in that these different polarization states are mutually orthogonal. Optical system according to one of the preceding claims, characterized in that these different polarization states are respectively generated by conversion of light from a light source, which generates unpolarized light. Optical system according to one of the preceding claims, characterized in that the different polarization states in each case by a splitting optical element ( 106 ), which is a splitting of a in the operation of the projection exposure apparatus on this element ( 106 ) causing a light beam in a first partial beam (S101) and a second partial beam (S102), wherein the first and the second partial beam having mutually orthogonal polarization directions. Optical system according to one of Claims 8, characterized in that in the light propagation direction downstream of the beam splitting optical element ( 106 ) at least one beam deflecting optical element ( 107 ) is provided. Optical system according to one of the preceding claims, characterized in that the different polarization states in each case by a Brewster-angle reflection on a reflective element ( 408 . 409 . 511 . 512 ) be generated. Optical system according to claim 10, characterized in that the respective reflective elements ( 408 . 409 ) are provided in the light propagation direction in front of the first and second facets in addition to these. Optical system according to claim 10, characterized in that the respective reflective elements ( 511 . 512 ) are formed by the first facets and the second facets, respectively. Optical system according to one of claims 10 to 12, characterized in that at least one of the respective reflective elements ( 408 . 409 . 511 . 512 ) is adjustable in its position for varying the polarization direction of the light reflected at them. Optical system according to claim 13, characterized in that the system has an optical axis (OA), wherein the adjustability of the reflective elements ( 408 . 409 . 511 . 512 ) is given along a circular arc around this optical axis (OA). Microlithographic projection exposure apparatus with a lighting device and a projection lens, characterized in that the illumination device is an optical System according to one of the preceding claims. Method for the microlithographic production of microstructured components with the following steps: Providing a substrate on which at least partially a layer of a photosensitive material is applied; Providing a mask having structures to be imaged; Providing a microlithographic projection exposure apparatus according to claim 15; and Projecting at least a portion of the mask onto a portion of the layer using the projection exposure apparatus.

Images