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A site specific technique for cross-section transmission electron microscopy specimen preparation of difficult materials is presented. Focused ion beams are used to slice an electron transparent sliver of the specimen from a specific area of interest. Micromanipulation lift-out procedures are then used to transport the electron transparent specimen to a carbon coated copper grid for subsequent TEM analysis. The experimental procedures are described in detail and an example of the lift-out technique is presented.

Localized plan view TEM samples have been prepared from silicon semiconductor wafers using the focused ion beam lift-out technique. Two different methods of sample preparation before FIB machining were found to be successful: mounting cleaved samples sandwiched together or adding silver paint and cleaving through paint and samples. The plan view technique offers site specific TEM capability from a horizontal section rather than a vertical cross section. The sections can be taken from any layer and can be angled if desired. Results have been obtained from metal layers in a semiconductor device structure. TEM micrographs of tungsten plug arrays show non-uniform barrier layer coverage and tungsten grain size across the via. Hundreds of plugs have been cut through in one sample, thereby offering statistical as well as specific structural information. Metal and polysilicon lines have been examined for grain size and uniformity in a single micrograph. Plan view samples from continuous metal layers can also be made.

Stability of submicron contacts under high current density has been an outstanding reliability issue in advanced Si devices. Polarity effect of failure was observed in Ni and Ni2Si contacts on n+-Si and p+-Si. In this report, we studied the failure due to high current density in contacts to n+- and p+-silicon-on-insulator (SOI). We found similar polarity effects below certain current: the p+-SOI failed preferentially at the cathode, while the n+-SOI failed preferentially at the anode. At higher current, damage occurred at both contacts. The effect of current crowding was evident in both cases.

Titanium nitride (TiN) films are used as anti-reflection coatings (ARC) on aluminum (Al) films to facilitate lithography processes during multilevel metallization for the manufacture of integrated circuits on silicon-based (Si) semiconductor devices. It is generally accepted in the literature that the microstructure of multilevel metal stacks is influenced by the texture of the substrate. For the case of interconnect materials used in the semiconductor industry, a typical metal stack is as follows: Titanium/Titanium Nitride/Al-alloy/ARC-Titanium Nitride. The Ti/TiN layer underneath the Al-alloy film is used as a barrier stack to prevent junction spiking. The Ti/TiN underlayer also determines the growth conditions (crystallography and orientation relationships) of the subsequent Al-alloy film.This study focuses on the microstructural characterization of the ARC-TiN layer on Si-oxide and Ti/TiN/Al-alloy substrates that are fabricated under similar conditions using conventional physical vapor deposition (PVD - sputtering) techniques. The ARC-TiN microstructure was investigated by transmission electron microscopy (TEM) using a Philips EM430 operating at 300 kV.