Interferometric measuring device and projection exposure installation comprising such measuring device

Abstract

A measuring device for interferometric measurement of an optical imaging system that is provided for projecting a useful pattern, provided on a mask, into the image plane of the imaging system, includes a wavefront source for generating at least one wavefront traversing the imaging system; a diffraction grating, arrangeable downstream of the imaging system, for interacting with the wavefront reshaped by the imaging system; and a spatially resolving detector, assigned to the diffraction grating, for acquiring interferometric information. The wavefront source has at least one measuring pattern that is formed on the mask in addition to the useful pattern. The useful pattern may represent the structure of a layer of a semiconductor component in a specific fabrication step. The measuring pattern may be formed as a coherence-forming structure periodic in one or two dimensions.

1 . A mask for use in a projection exposure installation for microlithography, having: 
 a carrier;    at least one useful pattern, formed on the carrier, for exposing a photosensitive substrate to be structured, and;    at least one measuring pattern that is provided in addition to the useful pattern and is formed as a coherence-forming structure of a wavefront source of an interferometric measuring device.    
   
   
       2 . The mask as claimed in  claim 1 , wherein the mask has ir at least one region a scattering structure for homogenizing the intensity of light in the light path downstream of the scattering structure.  
   
   
       3 . The mask as claimed in  claim 1 , wherein the mask has a transparent carrier with a light entrance side and a light exit side carrying the measuring pattern, the scattering structure being arranged on the light entrance side in the region of the measuring pattern.  
   
   
       4 . A mask for use in a projection exposure installation for microlithography, having: 
 a carrier and;    at least one useful pattern, formed on the carrier, for exposing a photosensitive substrate to be structured;    a scattering structure for homogenizing the intensity of light in the light path downstream of the scattering structure being provided in at least one region of the mask.    
   
   
       5 . A method for evaluating signals of a spatially resolving detector for forming a measuring signal provided for further processing, having the following step: 
 spatially selective evaluation of detector signals as a function of at least one evaluation threshold condition for determining areas of the detector with a signal-to-noise ratio sufficient for the further processing.    
   
   
       6 . The method as claimed in  claim 5 , wherein, in order to form the measuring signal intended for further processing, it is only temporally modulated signals from detector regions for which a signal intensity exceeds an intensity threshold value and a signal modulation exceeds a modulation threshold value that are selected.  
   
   
       7 . A mask for use in a projection exposure installation for microlithography, having: 
 a carrier;    at least one useful pattern, formed on the carrier, for exposing a photosensitive substrate to be structured, the useful pattern representing the structure of a layer of a semiconductor component in a specific fabrication step and;    at least one measuring pattern that is provided in addition to the useful pattern on the carrier, the measuring pattern being formed as a coherence-forming structure of a wavefront source of an interferometric measuring device.    
   
   
       8 . The mask as claimed in  claim 7 , wherein the mask has a transparent carrier with a light entrance side and a light exit side carrying the measuring pattern, the scattering structure being arranged on the light entrance side.  
   
   
       9 . The mask as claimed in  claim 8 , wherein the scattering structure is formed by a roughening of the light entry side of the carrier.  
   
   
       10 . The mask as claimed in  claim 8 , wherein the scattering structure has a statistical distribution of scattering centers.  
   
   
       11 . The mask as claimed in  claim 8 , wherein the scattering structure is a computer-generated hologram (CGH).