Plan-view Preparation Research Articles

FIB Plan View Preparation and Electron Tomography of Ga-Containing Droplets Induced by Melt-Back Etching in Si.

Melt-back etching is an effect that can occur for gallium (Ga) containing III/V semiconductors grown on Si. Since this effect influences interfaces between the two compounds and therefore the physical characteristics of the material composition, it is desirable to understand its driving forces. Therefore, we investigated Ga grown on Si (001) via metal organic chemical vapor deposition using trimethyl Ga as a precursor. As a result of the melt-back etching, Ga-containing droplets formed on the Si surface which reach into the Si wafer. The shape of these structures was analyzed by plan view investigation and cross sectional tomography in a (scanning) transmission electron microscope. For plan view preparation a focused ion beam was used to avoid damage to the Ga-containing structures, which are sensitive to the chemicals normally used during conventional plan view preparation. Combining the results of both investigation methods confirms that the Ga-containing structure within the Si exhibits a pyramid shape with facets along the Si {111} lattice planes.

Plan-View Preparation of TEM Specimens from Thin Films Using Adhesive Tape

A simple plan-view sample preparation technique for transmission electron microscopy (TEM) specimens is proposed for thin films by tearing-off the film with adhesive tape. The demand for very thin samples is highest for nanostructured materials where the structure of 2-5 nm sized features (grains) needs to be resolved; therefore, overlapping of nanometer-sized features should be avoided. The method provides thin areas at the fracture edges of plan-view specimens with thickness in the range of the grain size in the film allowing for artifact free high-resolution TEM imaging. Nanostructured materials typically fracture between the grains providing areas with the thickness of the grain size. Besides the swiftness of the method, the samples are free of surface amorphization artifacts, which can occur in ion beam milling up to 1 nm depth even at low energy ion bombardment. The thin film tear-off technique is demonstrated on a CuMn alloy thin film with grain size of 2 nm.

Angled Plan View FIB Sample Preparation for Accurate via Sidewall Measurements

Abstract Critical dimensions in advanced semiconductor devices are now such that a significant fraction of some structures is contained within the thickness of a TEM foil. An important example is the vias used in multilevel metallization to interconnect transistors and other structures. Current generation vias have a diameter of 300 nm, and vias in devices under development are targeted at 180 nm. These dimensions are to be compared to the thickness of a TEM foil, which may be ∼50 nm. Vias are typically fabricated by etching holes in a dielectric layer, then depositing into these holes a barrier metal, such as Ta, followed by a Cu seed layer and finally Cu fill. Critical to via processing reliability are the thicknesses of barrier and seed layers. A TEM cross section of such a via will contain sharply curved layers which, when seen in projection, will lead to inaccurate measurement of layer thicknesses. Ordinary plan view preparation of these vias avoids this projection problem, but uncertainty is introduced in the height at which the via is sectioned. We have developed an angled plan view (APV) FIB preparation technique that allows accurate measurement of barrier and seed thicknesses at discrete heights from bottom to top of a via.

A fast preparation technique for high-quality plan view and cross-section TEM specimens of semiconducting materials

A reproducible and rapid preparation technique for high-quality TEM specimens of semiconducting materials is reported. The required equipment is available in most laboratories working on TEM in the field of solid state materials (Disc Grinder, Dimple Grinder, Ion-Miller and Chemical Thinning Equipment). Full cross-section preparation takes about 6 h. Plan view preparation takes between 2 and 5 h.