Layout overlay for FIB operations

A method of determining the site of a selected feature of a specimen, comprising the steps of:

• a. fixing a beam source (402) relative to a surface of a specimen (416) so that a beam (410) from the source can be directed at the surface over a region (506) which includes an expected site of a selected feature (504) of the specimen;
• b. scanning the beam over a first alignment area (514) of the surface to acquire a first contrast image having an X-Y aspect ratio of other than 1:1 and in which a first feature (518) is visible;
• c. displaying the first contrast image;
• d. generating from stored data describing features of the specimen a first overlay image which includes a representation of the first feature;
• e. displaying the first overlay image;
• f. registering the first overlay image with the first contrast image using as a first alignment point the representation of the first feature in the first overlay image and the first feature visible in the first contrast image;
• and
• g. determining the site of the selected feature from the stored data using the first alignment point as a reference.

Apparatus for positioning a beam relative to a selected feature of a specimen, comprising:

• a. a focused-particle beam column (402) responsive to deflection control signals for controllably scanning a beam (410) over a region of a surface of a specimen (416);
• b. a source (438) of an X-deflection control signal;
• c. a source (604) of an X-offset control signal;
• d. a first junction (608) for combining the X-deflection control signal with the X-deflection offset signal to produce a resultant X-axis signal and for supplying the resultant X-axis signal to the focused-particle beam column;
• e. a source (440) of a Y-deflection control signal;
• f. a source (606) of a Y-offset control signal;
• and
• g. a second junction (614) for combining the Y-deflection control signal with the Y-deflection offset signal to produce a resultant Y-axis signal and for supplying the resultant Y-axis signal to the focused-particle beam column.