Automatic sequencing of fib operations

Abstract

A method of processing a semiconductor device comprises: applying a focused ion beam to a structure of a semiconductor device to be processed; producing a live detector signal by detecting secondary electrons emitted as the focused ion beam is applied to the structure; comparing the live detector signal with a reference trace having a region indicative of an expected material boundary and a stop marker within said region; and terminating or altering a FIB operation when the live detector signal exhibits a characteristic corresponding to said region of the reference trace. The reference trace can be generated in accordance with the invention by applying a focused ion beam to a reference structure of a semiconductor device; producing a reference detector signal by detecting secondary electrons emitted as the focused ion beam is applied to the reference structure; and preparing from the reference signal a reference trace defining said region indicative of said expected material boundary and said stop marker within the region. The reference trace and the live detector signal are preferably normalized by compensating their average contrast levels, e.g., by applying automatic gain control. Normalized reference end-point traces are divided into distinct slope regions based upon the slope transitions of the trace. One of the slope regions as a 'stop region' on a reference end-point trace and a stop marker is assigned to the stop region. A FIB milling process can be automatically terminated or altered, such as by switching enhanced-etch gases, based upon run-time comparison of a live detector signal (live trace) against a reference end-point trace template for which slope regions and stop marker have been assigned. An end-point reference trace prepared while performing a FIB process on a semiconductor device structure can be used as a reference for automatic control of subsequent operations on similar semiconductor device structures.