Position detecting method and apparatus

Abstract

A position detecting method includes the steps of forming an image of a mark on a sensor, performing a first process that processes a raw signal obtained from the sensor with plural parameters, performing a second process that determines an edge of a signal processed by the first process for each parameter, determining a parameter from a result of the second process obtained for each parameter, and calculating a position of the mark based on a determined parameter.

1 . A position detecting method of detecting a position of a mark formed on an object, said method comprising steps of: 
 forming an image of the mark on a sensor;    performing a first process that processes an image signal obtained by the sensor with respect to each of a plurality of values of a parameter of the first process;    performing a second process that processes a signal obtained by the first process to obtain a feature value with respect to each of the plurality of values of the parameter;    determining a value of the parameter based on feature values obtained by the second process and a reference value defined with respect to the mark; and    detecting a position of the mark based on a signal obtained by the first process using the value of the parameter determined in said determining step.    
   
   
       2 . A method according to  claim 1 , wherein the first process comprises zero phase filtering, and the parameter of the first process comprises an order of the filtering.  
   
   
       3 . A method according to  claim 1 , wherein the first process comprises approximation of the image signal using a polynimial, and the parameter of the first process comprises an order of the polynomial.  
   
   
       4 . A method according to  claim 1 , wherein the feature value corresponds to an interval between elements of the mark.  
   
   
       5 . A method according to  claim 1 , wherein said determining step determines the value of the parameter based on deviations of the feature values from the reference value.  
   
   
       6 . A method according to  claim 1 , wherein said determining step determines the value of the parameter based on a variation of a plurality of the feature value with respect to each of the plurality of values of the parameter.  
   
   
       7 . A position detecting apparatus for detecting a position of a mark on an object, said apparatus comprising: 
 a detecting system to detect an image of the mark; and    a processing system to perform a first process that processes an image signal obtained by said detecting system with respect to each of a plurality of values of a parameter of the first process, to perform a second process that processes a signal obtained by the first process to obtain a feature value with respect to each of the plurality of values of the parameter, to determine a value of the parameter based on feature values obtained by the second process and a reference value defined with respect to the mark, and to detect a position of the mark based on a signal obtained by the first process using the determined value of the parameter.    
   
   
       8 . An exposure apparatus for transferring a pattern to an object, said apparatus comprising: 
 a position detecting apparatus as defined in  claim 7  for detecting a position of a mark formed on the object.    
   
   
       9 . A method of fabricating a device, said method comprising steps of: 
 transferring a pattern to an object using an exposure apparatus as defined in  claim 8;     developing the object to which the pattern has been transferred; and    processing the developed object to fabricate the device.