Method for measuring registration

Abstract

A method and apparatus for measuring registration between two or more integrated circuit layers is disclosed. Images of actual operative circuitry of different layers of a semiconductor wafer, obtained by optical or scanning electron microscopy, are digitized and analyzed for the relative placement of pattern shapes of the corresponding layers. This relative placement is then compared to a predetermined database and the registration calculated.

1 - 39 . (canceled)  
   
   
       40 . A system for measuring the registration between at least two integrated circuit layers, one residing over the other, the system comprising: 
 an imaging system for generating a top-down field of the at least two integrated circuit layers, each of the layers having a respective visible feature in the image;    an image processor for digitizing the image;    a computer for processing the digitized image to determine a location of a first feature reference point in the visible feature of one of the layers, and allocation of a second feature reference point in the visible feature of the other of the layers, to indicate a relative location of the visible feature of one of the layers, relative to the visible feature of the other of the layers, wherein at least one of the visible features is a non-metrological structure on the one of the integrated circuit layers and for determining if the relative location is within acceptable design limits for the integrated circuit layers.    
   
   
       41 . The system of  claim 40 , wherein the computer further determines an x-axis value, X 1 , and a y-axis value, Y 1 .  
   
   
       42 . The system of  claim 40 , wherein the computer further determines an x-axis value, X 2 , and a y-axis value, Y 2 .  
   
   
       43 . The system of  claim 40 , wherein the computer further determines an x-axis value, Δx, and a y-axis value, Δy, wherein:  
       Δ x=X   1   −X   2 ; and    Δy=Y   1   −Y   2 .  
   
   
       44 . The system of  claim 40 , wherein the computer further compares said relative location to a stored data having reference locations and tolerable limits.  
   
   
       45 . The system of  claim 44 , wherein the computer further calculates an offset value.  
   
   
       46 . The system of  claim 45 , wherein the computer further compares the offset value to a predetermined tolerance.  
   
   
       47 . The system of  claim 40 , wherein the imaging system includes a scanning electron microscope.  
   
   
       48 . The system of  claim 40 , wherein the imaging system includes an optical system.