Cross-sectional TEM sample preparation method using FIB etching for thin-film transistor

摘要

A rapid and precise sample preparation method using focused ion beam (FIB) etching was developed for cross-sectional transmission electron microscopy (X-TEM) analysis of a thin-film transistor (TFT) fabricated on a glass substrate. Gallium (Ga) ions accelerated at 30 kV and at various in cident beam angles were applied during FIB etching to create a uniform thin wall. We successfully prepared X-TEM specimens of long and fragile aluminum (Al) whiskers formed on thin Al films in TFT metallization, where a strong charge is built up during FIB etching. The effect of ion-beam-assisted tungest depisition prior to FIB etching is disuccsed. A whisker having a length not exceeding approximately 10 mu m can be successfully etched to a thickness of 200 nm while keeping its original shape. The performance of this technique is demonstrated in applications to etching at other fragile locations related to TFTs.