Gallium focused ion beam (FIB) milling is the method of choice to prepare cross sections of selected features from microelectronic devices for transmission electron microscope (TEM) imaging and analysis. The FIB milling technique is unsurpassed in producing an ultra-thin cross section accurately located through the feature of interest. While much effort has been invested in the development and refinement of Ga+ FIB techniques and instrumentation, there are problems due to the physics of the ion-solid interaction. The problem of surface amorphization limits the quality of the TEM samples and its significance increases as the feature size and the specimen thickness decrease.In Ga+ FIB milling of silicon, the amorphous damage layer consists of amorphous Si doped with implanted Ga. This damage layer is caused by ions that strike the surface of the silicon and are subsequently scattered laterally as a result of collisions with the Si atoms.

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TEM of semiconductors containing tungsten interconnects is hampered by the problem of tungsten being intrinsically opaque to the electron beam, and at the same time typically being much thicker than the rest of the specimen. This work describes a technique which can predictably and reproducibly thin tungsten to electron transparency using chemical mechanical polishing (CMP). Chemically-assisted ion beam etching (CAIBE) techniques were also investigated, but found to be of little benefit. The key to development and evaluation of these methods was the AFM.