ILLUMINATION DEVICE OF A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS, AND MICROLITHOGRAPHIC PROJECTION EXPOSURE METHOD
Illumination devices of a microlithographic projection exposure apparatus, include a deflection device with which at least two light beams impinging on the deflection device can be variably deflected independently of one another by variation of the deflection angle in each case in such a way that each of the light beams can be directed onto at least one location in a pupil plane of the illumination device via at least two different beam paths; wherein, on the beam paths, at least one optical property of the respective light beam is influenced differently.
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This applications claims priority under 35 U.S.C. §119 to German Patent Application DE 10 2008 054 844.8, filed Dec. 17, 2008. The contents of DE 10 2008 054 844.8 are incorporated herein by reference in its entirety.
BACKGROUNDThe disclosure relates to an illumination device of a microlithographic projection exposure apparatus, and to a microlithographic projection exposure method. In particular, the disclosure relates to an illumination device and to a microlithographic projection exposure method which, in conjunction with comparatively little structural outlay, enable a light property such as, e.g., the polarization or the intensity to be flexibly and rapidly changed or adapted.
Microlithography is employed for producing microstructured components such as integrated circuits or LCDs, for example. The microlithography process is typically carried out in a so-called projection exposure apparatus, having an illumination device and a projection objective. In this case, the image of a mask (=reticle) illuminated by means of the illumination device is projected, by means of the projection objective, onto a substrate (e.g., a silicon wafer) coated with a light-sensitive layer (e.g., photoresist) and arranged in the image plane of the projection objective, in order to transfer the mask structure to the light-sensitive coating of the substrate. During operation of a microlithographic projection exposure apparatus there is a need to set defined illumination settings, that is to say intensity distributions in a pupil plane of the illumination device, in a targeted manner. In addition to the use of diffractive optical elements (so-called DOEs), the use of mirror arrangements is also known for this purpose, e.g., from WO 2005/026843 A2. Such mirror arrangements include a multiplicity of micromirrors that can be set independently of one another.
Various further approaches are known for setting specific polarization distributions in a targeted manner, for the purpose of optimizing the imaging contrast, in particular in the pupil plane of the illumination device or in the reticle plane.
There can be a need to be able to set further different distributions of the polarization and/or intensity in the illumination device (that is to say different illumination settings). One application example thereof is, for instance, the compensation of polarization-dependent reflection properties of the HR layers present on the mirrors or AR layers present on the lenses, which, without compensation measures, have the effect that, e.g., elliptically polarized light is generated from originally linearly polarized light.
Furthermore, there is increasingly also a need to produce further illumination settings, which are sometimes also referred to as “freeform illumination settings” and which can have, e.g., a plurality of illumination poles in such a way that in some of said illumination poles the polarization direction is oriented perpendicularly (that is to say tangentially) and in others of said illumination poles the polarization direction is oriented parallel (that is to say radially) with respect to the radius directed at the optical system axis. Such illumination settings are used, e.g., in so-called “source mask optimization” in conjunction with comparatively exotic mask structures in order to obtain the desired structure by suitable combination of the mask design with the illumination setting during imaging at the wafer level.
SUMMARYIllumination devices are disclosed that provide a microlithographic projection exposure apparatus and a microlithographic projection exposure method which, in conjunction with comparatively little structural outlay, enable a light property such as the polarization or the intensity, for example, to be flexibly and rapidly changed or adapted.
In a first aspect, the invention features an illumination device of a microlithographic projection exposure apparatus that has a deflection device, with which at least two light beams impinging on the deflection device can be variably deflected independently of one another by variation of the deflection angle in each case in such a way that each of said light beams can be directed onto at least one location in a pupil plane of the illumination device via at least two different beam paths, wherein, on said beam paths, at least one optical property of the respective light beam is influenced differently.
Embodiments feature utilizing a deflection device present in an illumination device, which deflection device (for instance in the form of a mirror arrangement, referred to for short as MMA=“micro mirror array”) is present anyway in diverse designs for the variation of the illumination setting produced in the pupil plane, for offering the illumination light alternative beam paths within the illumination device in which in turn at least one further light property (e.g., the polarization state, the intensity and/or the wavelength of the light) is influenced in a different manner relative to the respective beam paths.
In this case—for instance in contrast to dividing the illumination device into mutually separate or parallel-connected modules—different beam paths are provided for at least two light beams of the illumination light (preferably for all the light beams) independently of one another, thereby creating increased (e.g., maximum) flexibility with regard to the obtainable manipulation of the relevant light property (e.g., polarization) or the illumination setting ultimately obtained in the pupil plane.
Among other advantages, the manipulation of the relevant light property (e.g. polarization) can be obtained solely by utilizing the degrees of freedom provided by the deflection device; in other words, no additional switchable components (such as, e.g., a Pockels cell) are required. The flexible setting or variation of the illumination setting that is made possible can therefore be realized with comparatively little structural outlay.
For realizing the different influencing of the light property (e.g., polarization) for the mutually different beam paths, all that may be necessary is to adapt the deflection angles that can be produced by the deflection device to the arrangement of optical elements used in the relevant beam paths for the manipulation of the relevant light property, that the relevant optical property of the beam bundle can be influenced differently for the beam paths.
In some embodiments, each location in the pupil plane (PP) is illuminated by a respective light beam impinging on the deflection device, via at least two different beam paths.
Different illumination settings can be set in the pupil plane by sole variation of deflection angles produced by the deflection device.
In certain embodiments, a polarization-manipulating optical element (e.g., an optical retarder or an optical rotator) is arranged in at least one of said beam paths.
An optical property that is influenced differently on said beam paths can be the polarization state of the respective light beam.
In some embodiments, an optical property that is influenced differently on said beam paths is the intensity of the respective light beam.
An optical property that is influenced differently on said beam paths can be the wavelength of the respective light beam.
In certain embodiments, the deflection device is embodied as a mirror arrangement having a plurality of mirror elements which can be adjusted independently of one another in order to alter an angle distribution of the light reflected by the mirror arrangement. The mirror elements can be adjusted in an angular range comprising at least the range of −2° to +2°, in particular at least the range of −5° to +5°, more particularly at least the range of −10° to +10°.
However, embodiments are not restricted to the configuration of the deflection device in the form of a mirror device or an MMA. In certain embodiments, instead of an MMA, by way of example, it is also possible to provide an exchangeable diffractive optical element (DOE) for producing alternative beam paths.
The illumination device furthermore can have a control device for driving the deflection device in a manner dependent on an operating state of the illumination device.
In another aspect, the invention features a mirror arrangement, in particular for use in an illumination device, including a plurality of mirror elements which can be adjusted independently of one another in order to alter an angle distribution of the light reflected by the mirror arrangement, wherein at least one of said mirror elements has a plurality of reflective surfaces which influence at least one optical property of the respectively reflected light in a different manner.
In some embodiments, at least two of said reflective surfaces are arranged at a finite angle with respect to one another. The optical property influenced in a different manner can be, in particular, the polarization state of the respectively reflected light.
In a further aspect, the invention features a microlithographic projection exposure method, wherein an object plane of a projection objective is illuminated by means of an illumination device, and wherein the object plane is imaged into an image plane of the projection objective using the projection objective, wherein light beams impinging on a deflection device provided in the illumination device are deflected by a deflection angle that can be set in variable fashion, and wherein different illumination settings are set in a pupil plane of the illumination device by sole variation of deflection angles produced by the deflection device.
In another aspect, the invention features a microlithographic projection exposure apparatus and a method for the microlithographic production of microstructured components.
Further configurations can be gathered from the description and also the claims.
Embodiments are described in greater detail below in conjunction with the accompanying figures.
A basic construction of a microlithographic projection exposure apparatus with an optical system is firstly explained below with reference to
The illumination device 10 has an optical unit 11, including, in particular, a deflection device in the form of a mirror arrangement (MMA) 200 for the variation of the illumination setting produced in a pupil plane of the illumination device, and also, in the example illustrated, a deflection mirror 12. Situated in the beam path in the light propagation direction downstream of the optical unit 11 are a light mixing device (not illustrated), which can have, for example, an arrangement of micro-optical elements that is suitable for achieving a light mixing, and also a lens group 14, behind which is situated a field plane with a reticle masking system (REMA), which is imaged by a REMA objective 15 disposed downstream in the light propagation direction onto the structure-bearing mask (reticle) 30, which is arranged in a further field plane, and thereby delimits the illuminated region on the reticle. The structure-bearing mask 30 is imaged by means of the projection objective 20 onto a substrate 40, or a wafer, provided with a light-sensitive layer.
The projection objective 20 can be designed for immersion operation, in particular. Furthermore, it can have a numerical aperture NA of greater than 0.85, in particular greater than 1.1.
In the construction illustrated schematically in
In accordance with
The flexibility provided by the mirror arrangement 200 with regard to the beam paths that can be set for the light beams passing through the illumination device is utilized then for changing over between different illumination settings, wherein said illumination settings can differ from one another in particular by virtue of the in the polarization states obtained at specific pupil locations or illumination poles.
Embodiments can be distinguished by the fact that for this variation of the illumination settings, no additional switchable components (such as, e.g., a Pockels cell) are utilized for changing over between different polarization states; rather the degrees of freedom already present in the system on account of a deflection device, such as a mirror arrangement for example, present for setting different illumination settings are utilized in order to manipulate at least one further light property solely by variation of the setting of the deflection device. For this purpose, as explained in greater detail below with reference to
In particular, the arrangement can be chosen such that each individual mirror element 200a, 200b, 200c, . . . of the mirror arrangement 200 can reach each location within the illuminable region of the pupil plane PP on a plurality of different and mutually separate beam paths, or paths. In some embodiments, an optical element is arranged in at least one of said paths, said optical element influencing at least one optical property of the light beam impinging on said optical element.
Even though said light property is the polarization state in the exemplary embodiments described below with reference to
The embodiment in
It becomes clear from
The optical elements or sections 350a, 350b and 350c can be embodied as retarders, for example, which, in transmission, set a retardation for light beams passing through and through which, depending on the position of the sections, the illumination light passes twice (in the case of arrangement directly on the mirror surface and suitable spacing of the sections) or alternatively just once (wherein in the latter case, e.g., the reflected beam no longer passes through the respective retarder). Retardation denotes the difference in the optical paths of two orthogonal (mutually perpendicular) polarization states.
The retarders can be produced in a known manner from optically uniaxial material such as, e.g., magnesium fluoride (MgF2) having a suitable thickness. In some embodiments, the optical elements 350a, 350b and 350c can also be embodied as rotators which, by means of circular birefringence, bring about a rotation of the polarization direction and can be produced from optically active material, such as, e.g., crystalline quartz having a thickness suitable for the desired rotation angle and having a crystal axis running parallel to the optical system axis.
It goes without saying that the number of, in total, three polarization-optical sections present in the example in
Consequently, analogously to the embodiment shown in
Situated between the mirror arrangement 410 and the pupil plane PP is a positive lens 420, the light proceeding from the mirror arrangement 410 being directed onto the pupil plane PP by virtue of the refractive power of said lens. In addition to the positive lens 420, further beam-deflecting elements, in the form of wedge-shaped prisms 430 and 440 in
The beam-deflecting elements 430 and 440, in the same way as the positive lens 420, can be produced from suitable lens material, for example quartz glass (SiO2). With regard to the possible configurations of the (polarization-) optical elements 450a, 450b and 450c in
Referring to
Specifically, in the embodiment shown in
It goes without saying that in the embodiment in
Analogously to the embodiments described above, an increased flexibility with regard to the setting of different polarization states is achieved by increasing the tilting angle range in the mirror arrangement. In contrast to the embodiments in
While several embodiments have been described, numerous variations and alternative embodiments are possible, for example through combination and/or exchange of features of individual embodiments. Accordingly, other embodiments are in the claims.
Claims
1. An illumination device of a microlithographic projection exposure apparatus, comprising:
- a deflection device configured to variably deflect at least two light beams impinging on the deflection device independently of one another by variation of the deflection angle in each case in such a way that each of said light beams are directed onto at least one location in a pupil plane of the illumination device via at least two different beam paths,
- wherein, on said beam paths, at least one optical property of the respective light beam is influenced differently relative to the beam paths.
2. The illumination device of claim 1, wherein each location in the pupil plane is illuminated by a respective light beam impinging on the deflection device, via at least two different beam paths.
3. The illumination device of claim 1, wherein different illumination settings are set in the pupil plane by sole variation of deflection angles produced by the deflection device.
4. The illumination device of claim 1, wherein a polarization-manipulating optical element is arranged in at least one of said beam paths.
5. The illumination device of claim 4, wherein at least one polarization-manipulating optical element is an optical retarder or an optical rotator.
6. The illumination device of claim 1, wherein the optical property that is influenced differently on said beam paths is the polarization state of the respective light beam.
7. The illumination device of claim 1, wherein the optical property that is influenced differently on said beam paths is the intensity of the respective light beam.
8. The illumination device of claim 1, wherein the optical property that is influenced differently on said beam paths is the wavelength of the respective light beam.
9. The illumination device of claim 1, wherein the deflection device is a mirror arrangement having a plurality of mirror elements which can be adjusted independently of one another in order to alter an angle distribution of the light reflected by the mirror arrangement.
10. The illumination device of claim 9, wherein the mirror elements can be adjusted in an angular range comprising at least the range of −2° to +2°.
11. The illumination device of claim 10, wherein the mirror elements can be adjusted in an angular range comprising at least the range of −5° to +5°.
12. The illumination device of claim 11, wherein the mirror elements can be adjusted in an angular range comprising at least the range of −10° to +10°.
13. The illumination device of claim 1, wherein the deflection device has an exchange device for exchanging a diffractive optical element.
14. The illumination device of claim 1, further comprising a control device for driving the deflection device in a manner dependent on an operating state of the illumination device.
15. The illumination device of claim 1, wherein each of the light beams are directed onto at least one location in a pupil plane of the illumination device via at least three different beam paths, wherein, on at least two of said beam paths, at least one optical property of the respective light beam is influenced differently relative to the beam paths.
16. The illumination device of claim 15, wherein on all of the beam paths at least one optical property of the respective light beam is influenced differently relative to the beam paths.
17. A microlithographic projection exposure apparatus comprising an illumination device and a projection objective, wherein the illumination device is the illumination device of claim 1.
18. A microlithographic projection exposure method, comprising:
- illuminating an object plane of a projection objective with an illumination device; and
- imaging the object plane into an image plane of the projection objective with the projection objective,
- wherein during the illuminating, light beams impinging on a deflection device provided in the illumination device are deflected by a deflection angle that can be set in variable fashion, and
- different illumination settings are set in a pupil plane of the illumination device by sole variation of deflection angles produced by the deflection device.
19. A method for the microlithographic production of microstructured components, comprising:
- providing a substrate, to which a layer composed of a light-sensitive material is applied at least in part;
- providing a mask having structures to be imaged;
- providing the microlithographic projection exposure apparatus of claim 17; and
- projecting at least one part of the mask onto a region of the layer with the aid of the projection exposure apparatus.
Type: Application
Filed: Dec 15, 2009
Publication Date: Jun 17, 2010
Applicant: CARL ZEISS SMT AG (Oberkochen)
Inventor: Markus Deguenther (Aalen)
Application Number: 12/637,889
International Classification: G03F 7/20 (20060101); G03B 27/54 (20060101); G03B 27/70 (20060101);