DETECTOR FOR REGISTERING A LIGHT INTENSITY, AND ILLUMINATION SYSTEM EQUIPPED WITH THE DETECTOR
The invention concerns a device for the detection of radiation with a wavelength λ<100 nm, preferably EUV radiation in a range of wavelengths 5 nm<λ EUV <30 nm, in an illumination system. The device encompasses: a conversion element ( 4 ) which contains a scintillator material ( 22 ) which converts radiation with wavelengths <100 nm falling on the conversion element, by interacting with said radiation with wavelengths <100 nm, into a radiation with a wavelength λ fluorescent >100 nm, and a detection element ( 5 ) for the detection of the radiation with a wavelength λ fluorescent >100 nm which is received by the light-conducting element.
1 . Device for detecting radiation with a wavelength λ<100 nm, preferably EUV radiation in a range of wavelengths of 5 nm<λ EUV <30 nm in a microlithography projection exposure apparatus, comprising:
a conversion element ( 4 ) which comprises a scintillator material ( 22 , 22 . 1 , 22 . 2 ) which converts radiation with wavelengths of λ<100 nm falling on the conversion element, through interaction with the radiation with wavelengths of λ<100 nm, into a radiation with a wavelength λ fluorescent >100 nm,
a detector element ( 5 ) serving to detect the radiation with a wavelength λ fluorescent >100 nm received by the light-conducting element.
2 . Device according to claim 1 , characterized in that the device further comprises a light conducting element ( 3 ) which receives the radiation with a wavelength λ fluorescent >100 nm.
3 . Device according to claim 1 or 2 , characterized in that the scintillator material is an inorganic material selected among the following:
quartz glass doped with cerium or other fluorescent atoms,
YAG- or YAP crystals doped with cerium,
calcium fluoride doped with europium,
barium fluoride doped with europium,
zinc selenide doped with tellurium,
CdWO 4 (cadmium tungsten oxide), and
Cesium Iodide doped with thallium.
4 . Device according to one of the claims 2 to 3 , characterized in that the light-conducting element ( 3 ) comprises a light-conducting fiber ( 11 ), in particular a glass- or quartz fiber, with a core ( 10 ) and a cladding ( 12 ), wherein the core ( 10 ) has a larger refractive index than the cladding ( 12 ).
5 . Device according to claim 4 , characterized in that the scintillator material ( 22 . 1 ) is arranged in the area of the cladding ( 12 ) of the light-conducting fiber ( 11 ) or constitutes a part of the cladding ( 12 ) itself.
6 . Device according to one of the claims 2 to 4 , characterized in that the light-conducting element is a light-conducting fiber ( 11 ) with an end surface ( 23 ) and wherein the scintillator material ( 22 ) is arranged on the end surface ( 23 )
7 . Device according to one of the claims 2 to 4 , characterized in that the light-conducting element is a light-conducting fiber ( 11 ), wherein said light-conducting fiber comprises an obliquely cut end surface ( 41 ) and the scintillator material is arranged in the area of said obliquely cut end surface ( 41 ).
8 . Device according to one of the claims 1 to 7 , characterized in that the light-conducting element comprises a reflector.
9 . Device according to claim 8 , characterized in that the reflector comprises a metallic material.
10 . Device according to one of the claims 1 to 9 , characterized in that the detector element comprises a photo detector or a thermal sensor.
11 . Device according to claim 10 , characterized in that the photo detector is a photodiode, a photomultiplier, or a photo resistor.
12 . Device according to one of the claims 1 to 11 , characterized in that the conversion element comprises as a scintillator material a scintillator layer with a layer thickness D 1 and wherein radiation with wavelengths <100 nm falls on the scintillator layer.
13 . Device according to claim 12 , wherein the layer thickness is D 1 <1 mm, preferably <0.1 mm, more preferably <0.01 mm, and with special preference <0.001 mm.
14 . Device according to one of the claims 12 or 13 ; wherein the conversion element comprises a filter coating ( 30 ), and wherein said filter coating is put on top of the scintillator layer.
15 . Device according to claim 14 , wherein the filter coating has a high transmissivity for radiation with a wavelength λ<100 nm, i.e. higher than 80% and preferably higher than 95%, and at the same time has a high reflectivity for radiation with a wavelength λ>100 nm, i.e. higher than 60% and preferably higher than 80%.
16 . Device according to one of the claims 14 to 15 , wherein the filter coating comprises zirconium.
17 . Illumination system for a microlithography projection exposure apparatus, wherein the illumination system comprises a light source which emits light with a wavelength λ, and a detector which receives the light of the light source with the wavelength λ, wherein the detector comprises a conversion element ( 4 ) with a scintillator material ( 22 ) which converts radiation with the wavelength λ falling on the conversion element into radiation with a wavelength λ fluorescent >λ.
18 . Illumination system according to claim 17 , characterized in that the wavelength λ is in the range from 5 nm to 200 nm, preferably in the range from 5 nm to 30 nm.
19 . Illumination system for a microlithography projection exposure apparatus, in particular for wavelengths <100 nm and preferably in the range of EUV wavelengths, wherein the illumination system comprises a light source serving to illuminate a field plane and further comprises at least one detector serving to detect light of the light source, wherein the detector is arranged in a light path from the light source to the field plane and is a device according to one of the claims 1 to 16 .
20 . Illumination system according to one of the claims 17 to 19 , characterized in that the detector is arranged in or near a field plane.
21 . Illumination system according to one of the claims 17 to 20 , characterized in that the detector ( 200 . 1 ) is arranged in or near an intermediate focus in the illumination system.
22 . Illumination system according to one of the claims 17 to 21 , characterized in that the detector ( 200 . 4 ) is arranged in or near a pupil plane.
23 . Illumination system according to one of the claims 17 to 22 , characterized in that the detector is arranged in or near a field plane.
24 . Illumination system according to one of the claims 17 to 23 , characterized in that the radiation that falls on the detector is uncoupled by means of a mirror.
25 . Illumination system according to claim 24 , characterized in that the mirror is a grazing-incidence mirror.
26 . Illumination system according to claim 24 , characterized in that the mirror is a multi-layered mirror.
27 . Illumination system according to one of the claims 17 to 26 , characterized in that the detector is arranged so that the light falls directly on the scintillator material.
28 . Illumination system according to one of the claims 17 to 27 , characterized in that the illumination system comprises a device which receives at least one light intensity signal of the detector and, dependent on at least the received light intensity signal, provides a control signal through which a scanning velocity of a light-sensitive object in an image plane of a microlithography projection exposure apparatus or the light intensity of the light source can be adjusted.
29 . Illumination system according to one of the claims 17 to 28 , characterized in that the device comprises a regulating unit with a memory storage unit in which at least one first calibration value is stored for an illumination of an area in a field plane.
30 . Illumination system according to one of the claims 17 to 29 , characterized in that a multitude of calibration values forming a calibration table are stored in the memory storage unit.
31 . Microlithography projection exposure apparatus, comprising an illumination system according to one of the claims 17 to 30 serving to illuminate an object plane, and also comprising a projection objective serving to project an image of an object arranged in an illuminated area of the object plane into an image plane.
32 . Microlithography projection exposure apparatus according to claim 31 , characterized in that the projection objective comprises a device according to one of the claims 1 to 16 .
33 . Microlithography projection exposure apparatus according to claim 32 , characterized in that the device is arranged in or near a pupil plane of the projection objective.
34 . Microlithography projection exposure apparatus according to one of the claims 32 to 33 , characterized in that the device is arranged in or near the image plane or in or near a plane that is conjugate to the image plane.
35 . Method of detecting radiation with wavelengths shorter than 100 nm, in particular EUV radiation in a range of wavelengths of 5 nm<λ EUV <30 nm in an illumination system, wherein the device comprises a conversion element which includes a scintillator material, and further comprises a detection element, said method comprising the following steps:
the EUV radiation falling on the conversion element is converted through interaction with the scintillation material into radiation with a wavelength longer than 100 nm,
the radiation with a wavelength longer than 100 nm is directed to the detection element,
the detection element detects a light intensity of the radiation with a wavelength longer than 100 nm.
36 . Method of detecting according to claim 35 , wherein the device comprises a light-conducting element and the radiation is directed by means of the light-conducting element to the detection element.
37 . Method according to claim 35 or 36 , wherein the scintillation material represents a scintillation layer with a layer thickness, and wherein the layer thickness is smaller than 1 μm and the radiation with a wavelength larger than 100 nm is produced through absorption of the incident EUV radiation in the scintillator material over a surface area.
38 . Method according to one of the claims 35 to 37 , characterized in that the light-conducting element is a light-conducting fiber and the light is being directed to the detector element by total reflection inside the light conductor.
39 . Method of setting an essentially invariable light intensity in a field plane of a microlithography projection exposure apparatus for radiation with wavelengths <100 nm, in particular EUV radiation in a range of wavelengths of 5 nm<λ EUV <30 nm, wherein the microlithography projection exposure apparatus comprises at least one detector according to one of the claims 1 to 16 arranged in the light path from a light source to a field, said method comprising the following steps:
a light energy is measured by means of a detector that is arranged in or in the proximity of the field plane, whereby a current actual value is obtained,
the light energy is compared to a target value,
a difference signal is established between the target value and the current actual value and, based on the difference signal, a scanning velocity of a light sensitive object in an image plane and/or a light intensity of a light source is adjusted.
40 . Method according to claim 39 , characterized in that a pulse frequency of the light source is adjusted.
41 . Method according to one of the claims 39 or 40 , characterized in that an energy quantity of a light pulse of the light source is adjusted.