30 Prakt. Met. Sonderband 46 (2014) 
2.2.1 CROSS-SECTIONS Another possi 
by repeating t 
The simplest (and original) application is the perpendicular preparation of a material cross- recently elsew 
section at an edge. This would be challenging by electrochemical etching, since corners lamella, can s 
would always be rounded off by preferential attack. With the FIB, such cross-sections in the thin film 
could be prepared, but within reasonable time using broad beam ion milling, large 
dimensions of more than 10,000 pm? can be polished perpendicular to the material surface 
at a chosen position within few hours. To this purpose, shown in Fig. 2, the sample is 2.2.3 MASK-¢ 
partially covered by a thick mask (a), then the Ar" beam is used to sputter a cross-section 
into the material surface (b), thereby exposing the film microstructure and film/substrate Finally, once 
interface (c) for in depth analysis. broad beam i 
protecting ste 
performed (0), 
of micro-samr 
Fig. 2: Broad ion beam cross-section preparation of a thin film on substrate. 
2.2.2 FREE-STANDING FILMS OR LAMELLAS 
The inspection of a buried microstructure is one application for ion milling. However, when 
aiming towards micro-mechanical testing it is more important to prepare free standing 
lamellas out of bulk samples or thin films on substrates. For films on substrates this can in 
some cases be achieved by electrochemical removal of the substrate [24]. However, the 
broad beam ion milling approach shown in Fig. 3 works for any kind of film/substrate as 
well as for bulk materials. By covering the film (or any other area of interest) with the 
protecting mask, only the substrate is removed (b), creating a large free-standing lamella Fig. 4: Prep 
that can be used, for example, for subsequent FIB sample structuring (c, d). For very thin 
films also part of the substrate has to be covered to prevent damage of the film. 
Notably, this 
micrometer ri 
accessible by 
too large or v 
processes wit 
beam ion mil 
tolerates vac 
fabrication str 
2.3 FOCUSS 
In the followir 
well defined g 
many of thes 
will serve as r 
Fig. 3: Preparation of a free-standing thin film or lamella (a, b), that can subsequently be 
FIB structured.