Method for stem sample inspection in a charged particle beam instrument

Abstract

A method for sample examination in a dual-beam FIB calculates a first angle as a function of second, third and fourth angles defined by the geometry of the FIB and the tilt of the specimen stage. A fifth angle is calculated as a function of the stated angles, where the fifth angle is the angle between the long axis of an excised sample and the projection of the axis of the probe shaft onto the X-Y plane. The specimen stage is rotated by the calculated fifth angle, followed by attachment to the probe tip and lift-out. The sample may then be positioned perpendicular to the axis of the FIB electron beam for STEM analysis by rotation of the probe shaft through the first angle.

We claim: 
     
       1. A method for examination of an excised sample in a charged particle beam instrument, where the sample has a long axis, and where the charged particle beam instrument comprises:
 an ion-beam;   a specimen stage;
 the specimen stage having at least one tilt axis substantially perpendicular to the axis of the ion beam; 
   an electron beam;
 the electron beam having an axis; and, 
   an X-Y plane;   a nano-manipulator; the nano-manipulator having a probe shaft; the probe shaft having an axis;
 the probe shaft further having a probe tip; 
   where the method comprises:   calculating a first angle as a function of:
 a pre-determined second angle that is the angle of tilt of the specimen stage relative to the X-Y plane of the charged particle beam instrument; 
 a pre-determined third angle that is the angle between the tilt axis of the specimen stage and the projection onto the X-Y plane of the axis of the probe shaft; and, 
 a pre-determined fourth angle that is the inclination of the axis of the probe shaft relative to the X-Y plane of the charged particle beam instrument; 
   calculating a fifth angle as a function of the first, second, third, and fourth angles, where the fifth angle is the angle between the long axis of the sample and the projection of the axis of the probe shaft onto the X-Y plane;   rotating the specimen stage to the calculated fifth angle, whereby the projection of the axis of the probe shaft onto the X-Y plane is collinear with the long axis of the sample;   attaching the sample to the probe tip;   lifting out the sample with the probe tip; and,   rotating the probe shaft by the calculated first angle, whereby the sample is placed substantially perpendicular to the axis of the electron beam.   
     
     
       2. The method of  claim 1 , further comprising imaging the sample by a placing a transmitted electron detector beneath the sample. 
     
     
       3. The method of  claim 1 , further comprising:
 attaching the sample to a TEM grid;   separating the attached sample from the probe tip; and,   carrying out STEM analysis on the sample while it is attached to the TEM grid.   
     
     
       4. The method of  claim 3 , further comprising:
 transferring the TEM sample grid with TEM sample as attached to it, outside the charged particle beam instrument.   
     
     
       5. The method of  claim 1  where calculating the first angle and the fifth angle comprises transforming an angle-axis representation of the first, second, third, fourth and fifth angles to a rotation matrix representation. 
     
     
       6. A method for examination of an excised sample in a charged particle beam instrument, where the sample has a long axis, and where the charged particle beam instrument comprises:
 an ion-beam;   a specimen stage;
 the specimen stage having at least one tilt axis substantially perpendicular to the axis of the ion beam; 
   an electron beam;
 the electron beam having an axis; and, 
   an X-Y plane;   a nano-manipulator; the nano-manipulator having a probe shaft; the probe shaft having an axis;
 the probe shaft further having a probe tip; 
   where the method comprises:   firstly, rotating the specimen stage to establish the angle between the long axis of the sample and the projection of the axis of the probe shaft onto the X-Y plane to a fifth angle;   secondly, attaching the sample to the probe tip and lifting out the sample with the probe tip; and,   thirdly, rotating the probe shaft by a first angle, where the first angle is a function of:   a second angle that is the angle of tilt of the specimen stage relative to the X-Y plane;   a third angle that is the angle between the tilt axis of the specimen stage and the projection onto the X-Y plane of the axis of the probe shaft; and,
 a fourth angle that is the angle of the axis of the probe shaft relative to the X-Y plane; and, 
   whereby an area of interest in the sample is placed substantially perpendicular to the axis of the electron beam.   
     
     
       7. The method of claim 6, further comprising imaging the sample by placing a transmitted electron detector beneath the sample. 
     
     
       8. The method of claim 6, further comprising:
 attaching the sample to a TEM grid; and,   separating the attached sample from the probe tip.   
     
     
       9. The method of claim 8, further comprising:
 carrying out STEM analysis on the sample while it is attached to the TEM grid.   
     
     
       10. The method of claim 8, further comprising transferring the TEM sample grid with TEM sample attached to it, outside the charged particle beam instrument.