Development of a new focused ion beam preparation method of thin film for TEM with FIB - A method capable of re-thinning after TEM observation

Interface fine structure can be analyzed in detail by transmission electron microscope (TEM) observation. Sample is frequently prepared by focused ion beam (FIB) and pick-up method (lift-out method). However, it is difficult that thin film of interface, which consists of different materials with their own etching rates, is prepared in uniform thickness. Also, interfaces in a plate of a semiconductor device to be analyzed have various depth from less than 10 mum to more than 20 mum from the surface. In the case of preparing a thin film of these samples accurately, reprocessing is necessary, that is to say, FIB processing may be carried out again after observing secondary electron images and scanning transmission electron images. Also, sample pre-cutting methods are necessary taking into account its shape and observing direction (cross section and plan view). Here, we report a bulk-pick-up method where the conventional pick-up method is improved and reprocessing with FIB is possible. Eventually, it is found that interface characterization can be effectively carried out on a variety of samples prepared by FIB.