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New applications for SEM specimen preparation by an ion beam etching/milling/coating system R. Alanil, R.J. Mitral, K. Ogura2 and H. Zhang 3 1 Gatan R&D, 5933 Coronado Lane, Pleasanton, CA 94588, USA. 2 JEOL Ltd. l-2 Musasino 3- Chome Akishima, Tokyo 196, Japan 3 Applied Materials, 4250 Burton Drive, Santa Clara, CA 95054, USA. The effectiveness of a broad ion-beam based etching and coating system for SEM specimen preparation of IC cross-sections (tungsten plugs) as well as metallographic specimens (stainless steel and aluminum bronze) has already been described [l]. As an update to that work, we report new application examples for the preparation of SEM specimens of ceramics and advanced materials/structures used in semiconductor industries. Furthermore, we report a new approach for preparing precision SEM crosssections from microcleaved semiconductor structures. Evaluating the system’s ability in handling ceramics, a mechanically polished yttria (Y203) specimen was etched at 10 KeV, coated with 208+ chromium and examined in a SEM. Fig.la,b show the yttria specimen before and after etching for 2 minutes. Note, the surface pores (see arrows), grain boundaries and the grain size variation (gradient), which increases from left to right in Fig lb. SEM cross-sections of semiconductors are routinely prepared for new process developments and fabrication problem solving. In this connection, we applied the combined etching/coating technique to study several advanced structures and materials. Fig.2 shows a typical cross-sectional SEM view of a tungsten layer grown on high aspect ratio “contacts” after etching at 6KeV and applying a 2OA tungsten coating. The uniform nucleation of tungsten layer can be seen. Fig. 3 is an SEM cross-section of new technology copper metallization layer/“contacts”, used in next generation IC devices, after etching (at. 4KeV) and coating ( 2OA tungsten). Well etched Cu grains and the Ta barrier layer are clearly observed. In this system, a major advancement for the preparation of precision SEM cross-sections is reported, which is based on perpendicular broad ion-beam milling technique. The controlled milling feature exposes any desired cross-section through a given feature of the specimen. As a typical example, Figs. 4a-b show SEM cross-sectional images of a Si based wafer before and after milling. Fig.4a is the as-cleaved wafer containing six tungsten “contacts” (labeled). Fig.4b shows all “contacts” are thinned after 15 minutes milling at lOKeV, e.g. “contacts” #4 and #5 are milled beyond their centerline, while “contacts” #2, #3 and #6 are cross-sectioned through the middle, exposing the tungsten grains and barrier layers. “Contact” #l is only partially niilled. This result provided an estimation on the milling rate of the tungsten layer ( = 3pm/hr, at 1OKeV and 300pA beam current). In conclusion, the integrated etching/milling/coating system used in this work, is capable of providing alternative/complementary techniques to traditional methods of SEM specimen preparation for a variety of applications. For example, it can provide an alternative approach to: i) “thermal etching” of ceramics, ii) “wet chemical” etching for new materials and structures in advanced semiconductors, e.g. copper metallization layers/contacts and iii) precision mechanical polishing, followed by “wet chemical” etching for IC cross-sections. In this regard, it can also provide a more economical substitute for FIB systems for the preparation of precision SEM cross sections. Reference 1) Alani, R, et al. Proc. 55th. Annual. Meeting of MSA, p 363, (1997) ,. .:: : liglal’ 19 la,b xx .., .. ‘. show an yttria arrows) ..: w, specimen before and the grain size change Figs. 4a.b are SEM images showng I and after Ar ion-beam across a cross-seci~onal etching Note the surface pores the specimen view of a cleaved SI based wafer before and after milling (see text).