Flow for high resolution stereoscopic measurements

A method of determining a depth of a plurality holes milled into a sample at a plurality of different regions of interest spaced apart from each other at an upper surface of the sample, the method comprising:

• positioning the sample in a processing chamber having a focused ion beam column and a scanning electron microscope column and setting a tilt angle of the scanning electron microscope column at a first tilt angle;
• milling and imaging each region of interest in the plurality of regions of interest by:
• a) moving the sample within the processing chamber to position a region of interest within a field of view of the focused ion beam column;
• b) milling, with a charged particle beam generated by the focused ion beam column, a hole in the region of interest, a first registration mark at an upper level of the milled hole, and a second registration mark at a lower level of the milled hole;
• c) moving the sample withing the processing chamber to position the region of interest within a field of view of the scanning electron microscope;
• d) taking a first set of images at the first tilt angle, the first set of images including a first image taken with a field of view that captures the first registration mark but not the second registration mark, and a second image taken with a field of view that captures the second registration mark but not the first registration mark;
• and
• e) repeating steps (a) to (e) for a next region of interest in the plurality of regions of interest until all the regions of interest have been milled and imaged at the first tilt angle;
• changing the tilt angle of the scanning electron microscope column to a second tilt angle, different than the first tilt angle;
• and
• imaging each region of interest of interest in the plurality of region of interest at the second tilt angle by:
• f) moving the sample within the processing chamber to position a region of interest within the field of view of the scanning electron microscope;
• g) taking a second set of images at the second tilt angle, the second set of images including a third image taken with a field of view that captures the first registration mark but not the second registration mark, and a fourth image taken with a field of view that captures the second registration mark but not the first registration mark;
• and
• h) repeating steps (f) and (g) for a next region of interest in the plurality of regions of interest until all the regions of interest have been imaged at the second tilt angle;
• and
• using stereoscopic measurement techniques to calculate the depth of the hole based on the first and second sets of images.

A system for for determining a depth of a hole milled into a first region of a sample, the system comprising:

• a vacuum chamber;
• a sample support configured to hold a sample within the vacuum chamber during a milling process;
• a charged particle beam column configured to direct a charged particle beam into the vacuum chamber;
• a processor and a memory coupled to the processor, the memory including a plurality of computer-readable instructions that, when executed by the processor, cause the system to:
• position the sample in a processing chamber having a charged particle beam column;
• mill a hole in the first region of the sample using a charged particle beam generated by the charged particle beam column;
• identify a first registration mark at an upper level of the milled hole;
• identify a second registration mark at a lower level of the milled hole;
• take a first set of images at a first tilt angle, the first set of images including a first image taken with a field of view that captures the first registration mark but not the second registration mark, and a second image taken with a field of view that captures the second registration mark but not the first registration mark;
• take a second set of images at a second tilt angle, different than the first tilt angle, the second set of images including a third image taken with a field of view that captures the first registration mark but not the second registration mark, and a fourth image taken with a field of view that captures the second registration mark but not the first registration mark;
• use stereoscopic measurement techniques to determine the depth of the hole based on the first and second sets of images.