Glancing angle mill

Abstract

Embodiments are directed to a method and charged particle beam system for forming views for an electron microscope. Embodiments include milling a first surface at least in the local area of a feature of interest using an ion beam directed at a first angle to make the first surface at least in the local area of the feature of interest substantially planar, wherein the first angle between the ion beam and the first surface is equal to or less than ten degrees; subsequent to milling the first surface, milling the sample using the ion beam directed at a second angle to expose a second surface, the second surface comprising a cross-section of the feature of interest; and forming an image of the second surface by directing an electron beam to the second surface and detecting the interaction of the electron beam with the second surface.

We claim as follows: 
     
         1 . A method of forming a cross-section view for an electron microscope, the method comprising:
 milling a first surface at least in the local area of a feature of interest using an ion beam directed at a first angle to make the first surface at least in the local area of the feature of interest substantially planar, wherein the first angle between the ion beam and the first surface is equal to or less than ten degrees;   subsequent to milling the first surface, milling the sample using the ion beam directed at a second angle to expose a second surface, the second surface comprising a cross-section of the feature of interest; and   forming an image of the second surface by directing an electron beam to the second surface and detecting the interaction of the electron beam with the second surface.   
     
     
         2 . The method of  claim 1  in which a 45 degree stub is disposed between a sample stage and the sample, and the angle of the ion beam is changed from the first angle to the second angle by rotating the sample stage. 
     
     
         3 . The method of  claim 1  in which the tilt of a sample stage upon which the sample is mounted is changed between the milling steps and the image forming step. 
     
     
         4 . The method of  claim 1  further comprising analyzing the image of the second surface to determine whether a feature of the second surface includes a defect. 
     
     
         5 . The method of  claim 1  in which the first angle between the ion beam and the first surface is equal to or less than five degrees. 
     
     
         6 . The method of  claim 1  in which the first angle between the ion beam and the first surface is equal to or less than one degree. 
     
     
         7 . The method of  claim 1  in which the ion beam comprises a focused ion beam. 
     
     
         8 . A charged particle beam system for forming a cross-section view for an electron microscope, the system programmed to:
 mill a first surface at least in the local area of a feature of interest using an ion beam directed at a first angle to make the first surface at least in the local area of the feature of interest substantially planar, wherein the first angle between the ion beam and the first surface is equal to or less than ten degrees;   subsequent to milling the first surface, mill the sample using the ion beam directed at a second angle to expose a second surface, the second surface comprising a cross-section of the feature of interest; and   form an image of the second surface by directing an electron beam to the second surface and detecting the interaction of the electron beam with the second surface.   
     
     
         9 . The charged particle beam system of  claim 8  in which a 45 degree stub is disposed between a sample stage and the sample, and the angle of the ion beam is changed from the first angle to the second angle by rotating the sample stage. 
     
     
         10 . The charged particle beam system of  claim 8  in which the tilt of a sample stage upon which the sample is mounted is changed between the milling steps and the image forming step. 
     
     
         11 . The charged particle beam system of  claim 8  further comprising analyzing the image of the second surface to determine whether a feature of the second surface includes a defect. 
     
     
         12 . The charged particle beam system of  claim 8  in which the angle between the ion beam and the first surface is equal to or less than five degrees. 
     
     
         13 . The charged particle beam system of  claim 8  in which the angle between the ion beam and the first surface is equal to or less than one degree. 
     
     
         14 . The charged particle beam system of  claim 8  in which the ion beam comprises a focused ion beam. 
     
     
         15 . A charged particle beam system for forming a planar cross-section view for an electron microscope, the system programmed to:
 mill a first surface, using an ion beam directed at a milling angle, to expose a second surface in which the end of the second surface distal to the ion source is milled to a greater depth relative to a reference depth than the end of the first surface proximal to the ion source, the second surface including at least one feature of interest, wherein the first angle between the ion beam and the first surface is equal to or less than ten degrees;   form an image of the second surface by directing an electron beam from an electron source to the second surface and detecting the interaction of the electron beam with the second surface, the image including at least a portion of the feature of interest;   characterize the feature of interest in a plurality of locations along the image of the second surface; and   determine a depth of each of the plurality of locations based on the distance of the location from the end of the image proximal to the ion source and the milling angle between the ion beam and the first surface.   
     
     
         16 . The charged particle beam system of  claim 15  in which a 45 degree stub is disposed between the sample stage and the sample. 
     
     
         17 . The charged particle beam system of  claim 15  in which the tilt of the sample stage upon which the sample is mounted is changed between the milling step and the image forming step. 
     
     
         18 . The charged particle beam system of  claim 15  further programmed to analyze the image of the second surface to determine whether a feature of the second surface includes a defect. 
     
     
         19 . The charged particle beam system of  claim 15  in which the milling angle between the ion beam and the first surface is equal to or less than five degrees. 
     
     
         20 . The charged particle beam system of  claim 15  in which the milling angle between the ion beam and the first surface is equal to or less than one degree.