Patent ID: 8170832

Claim:
A method for endpointing the thinning of a sample for Transmission Electron Microscope or Scanning Transmission Electron Microscope analysis comprising: (a) loading the sample into a dual beam focused ion beam and Transmission Electron Microscope or Scanning Transmission Electron Microscope apparatus, the Transmission Electron Microscope or Scanning Transmission Electron Microscope apparatus comprising an electron column and a signal detector; (b) imaging the sample using the electron column to direct an electron beam at the sample and using the signal detector to detect electrons passing through the sample; (c) normalizing the detected signal by assigning a low transmission value to a detected signal in which none or relatively few of the electrons of the beam are detected by the signal detector, and assigning a high transmission value to a detected signal in which substantially all of the electrons of the beam are detected by the signal detector, and normalizing image contrast values between the low transmission value and the high transmission value; (d) comparing the normalized image contrast values for at least a portion of the sample to stored contrast data; (e) determining, based upon the comparison between the stored contrast data and the image contrast values, a thickness value for the at least a portion of the sample; (f) if the determined thickness value is greater than a desired thickness value for the sample, thinning the sample using focused ion beam milling; (g) repeating steps (b) through (e) until the determined thickness value is equal to the desired thickness value, thereby determining the end point of the thinning process.