Arrangement for inspecting objects, especially masks in microlithography
View Patent ↗Apparatus for inspecting objects especially masks in microlithography that are disposed in a vacuum chamber. The apparatus includes a converter for converting illuminating radiation emitted from the object into a radiation of a higher wavelength. A sensor for recording images is disposed outside the vacuum chamber and arranged as an optical interface from the vacuum chamber to the sensor of the converter or at least one part of an image lens is arranged as a window in the vacuum chamber.
1. Apparatus for inspecting a mask used in microlithography, the apparatus comprising:
a vacuum chamber;
illuminating means for illuminating a mask in the vacuum chamber with extreme ultraviolet light, the illuminating means being disposed inside the vacuum chamber;
converter means for converting an image in extreme ultraviolet radiation emitted by the mask into an image in radiation of a longer wavelength, the converter means being disposed inside the vacuum chamber;
sensor means for recording the image in the radiation of a longer wavelength, the sensor means being disposed outside the vacuum chamber; and
an optical interface from the vacuum chamber to the sensor means, the optical interface being arranged as a vacuum window in the vacuum chamber.
2. The apparatus of claim 1 , wherein the converter means comprises a scintillator.
3. The apparatus of claim 1 , wherein the converter means forms the optical interface from the vacuum chamber to the sensor means and is arranged as a window in the vacuum chamber.
4. The apparatus of claim 1 , further comprising imaging optic means disposed in front of the sensor means for reproducing the longer wavelength image on the sensor means, wherein:
at least a part of the imaging optic means is disposed inside the vacuum chamber, and
at least a part of the imaging optic means forms the optical interface from the vacuum chamber to the sensor means and is arranged as a window in the vacuum chamber.
5. The apparatus of claim 4 , wherein the imaging optic means is vacuum-tight and forms the optical interface.
6. The apparatus of claim 5 , where the imaging optic means includes a cement-free hybrid lens having at least one diffractive optical element.