Focused Ion Beam (FIB) Milling Damage Formed During Tem Sample Preparation of Silicon

Abstract The ongoing reduction of scale of semiconductor device structures places increasing demands on the sample preparation methods used for transmission electron microscopy (TEM). Much of the semiconductor industry's failure analysis and new process development effort requires specific transistor, metal or dielectric structures to be analyzed using TEM techniques. Focused ion beam (FIB) milling has emerged as a valuable technique for site-specific TEM sample preparation. FIB milling, typically with 25-50kV Ga+ ions, enables thin TEM samples to be prepared with submicron precision. However, Ga+ ion milling significantly modifies the surfaces of TEM samples by implantation and amorphization. Previous work using 90° milling angles has shown that Ga+ ion milling of Si produces a surface damage layer that is 280Å thick. This damage is problematical since the current generation of semiconductor devices requires TEM samples in the 500-1000Å thickness range.