Focused ion beam techniques

As a consequence one might expect that the future needs to rely on hybrid elements which arise from advanced UV-and electron-beam lithography, from imprint techniques or automated and parallelized nanomanipulation techniques, like dip-pen lithography or focused ion-beam techniques in combination with supramolecular approaches for the assembly of molecular inorganic/organic hybrid system. Nevertheless, it is evident for any kind of chemical approach that falling back onto the present-day... 

For the fabrication of stacked junctions we used focused ion beam technique. This technique has been developed for fabrication of both, the short [9] down to submicron scale [10] and the long junctions with a length of several tens microns [17]. For fabrication we used conventional FIB machine of Seiko Instr. Corp., SMI 9800 (SP) with Ga+-ion beam. The four leads were attached outside the junction area. The contact Ag pads were ablated and annealed before the FIB processing to avoid diffusion of Ga-ions into the junction body. The example of a short stack fabricated by FIB technique is shown in Fig. 1. Typically we had slightly overdoped stacked Bi2Sr2CaCu2C>8+8 structures with <5 0.25. They have Tc = 77K, pc(300K) = 10-12 Ohm cm, JC(4.2K) 1 kA/cm2. 

Langford, R. M. (2006). Focused ion beam techniques for nanomaterials characterization. Microsc. Res. Techn. 69, 538-549. 

In uniformly strained materials, deformation structures can be readily observed using transmission electron microscopy. However, it is much more difficult to prepare a similar sample where the deformation is more localized, as is the case of nanoindentation. Recently this situation has been revolutionized by the development of focused ion beam techniques for semiconductor processing, so that it is possible to select the region to be thinned to within 100 nm (Overwijk et al., 1993 Saka, 1998). 

Fig. 9.8 COgij-Pt ij patterned dots array fabricated by focused ion beam technique. Pitch of the dots is 200 nm and the dot size is 70 nm [38]...

Moghadam SH, Dinarvand R, Cartilier LH. The focused ion beam technique a useful tool for pharmaceutical characterization. Int J Pharm 2006 321 50-5. 

Special thin films are prepared, such as solution-cast films, or by the focused ion beam technique (EIB) with an additional staining agent, and then studied by TEM or AEM. 

Lugstein, A., E. Bertagnolli, C. Kranz, A. Kueng, and B. Mizaikoff, Integrating micro-and nanoelectrodes into atomic force microscopy cantilevers using focused ion beam techniques, Appl. Phys. Lett., Vol. 81, 2002 pp. 349-351. 

Deng, R, T. Ogasawara, and N. Takeda. 2007. Evaluating the orientation and dispersion of carbon nanotubes inside nanocomposites by a focused-ion-beam technique. Materials Letters 61 (29) (December) 5095-5097. doi 10.1016/j.matlet.2007.04.049. http // linkinghub.elsevier.eom/retrieve/pii/S0167577X0700376X. 

The first TEM studies of defects in minerals were mostly carried out on layer-structured crystals that could easily be cleaved to electron transparent thicknesses. These included mica [33], graphite [34], molybdenite [35,36], and talc [37]. The study of dislocation networks in talc [38] is an early milestone in dislocation analysis. Thereafter, the ion-rmllmg method (and, more recently, the FIB (focused ion beam) technique) made it possible to investigate dislocations and other defects in a wide range of minerals, crustal rocks, and extraterrestrial materials. 

Two newer areas of implantation have been receiving attention and development. Focused ion beams have been iavestigated to adow very fine control of implantation dimensions. The beams are focused to spot sizes down to 10 nm, and are used to create single lines of ion-implanted patterns without needing to create or use a mask. Although this method has many attractive features, it is hampered by the fact that the patterning is sequential rather than simultaneous, and only one wafer rather than many can be processed at any one time. This limits the production appHcations of the technique. 

Newer techniques that are responding to the need for atomic level imaging and chemical analysis include scanning tunneling microscopes (STMs), atomic force microscopes (AFMs) (52), and focused ion beams (FIBs). These are expected to quickly pass from laboratory-scale use to in-line monitoring apphcations for 200-mm wafers (32). 

In the early days of TEM, sample preparation was divided into two categories, one for thin films and one for bulk materials. Thin-films, particularly metal layers, were often deposited on substrates and later removed by some sort of technique involving dissolution of the substrate. Bulk materials were cut and polished into thin slabs, which were then either electropolished (metals) or ion-milled (ceramics). The latter technique uses a focused ion beam (typically Ar+) of high-energy, which sputters the surface of the thinned slab. These techniques produce so-called plan-view thin foils. 

The need to be able to thin complex microelectronic devices, and to select and thin specific regions within them has resulted in ever-more sophisticated specimen preparation methods involving precision ion polishing. This requirement culminated in the development of the focused ion beam (FIB) technique, which is able to slice out electron-transparent foils from any multilayer, multiphase material with extreme precision. Overwijk et al. (1993) have described such a technique for producing cross-section TEM specimens from (e.g.) integrated circuits. 

Focused ion beams can be used to expose resist, to write directly diffusion patterns into semiconductor substrates, and to repair masks. These techniques can potentially simplify semiconductor device production and perhaps reduce cost. Many of the technological challenges with ion beams are similar to those encountered with electron beams, but the development of ion sources and focusing/deflection systems are at a much earlier stage of development so application to manufacturing is several years away. 

High aspect ratio SFM probes can be also made by a focused-ion-beam (FIB) technique [209-211]. Microtips were reproducibly grown up to 1.0 pm in length and 0.1 pm in diameter. A tip radius as low as 5 nm could be achieved and was found to degrade only slightly after extensive SFM imaging. Conventional tips can be modified by etching techniques so that a sharper probe apex is provided [212]. 

A focused ion beam (FIB) can be used instead of a conventional ion mill to mill a sample. In such cases, especially targeted regions of a sample can be thinned for observation in the TEM. This technique requires expensive instrumentation but is becoming extremely popular in the age of VLSI devices and nanostructured components, where precise thinning of specific areas is necessary. 

One such approach has recently been developed and shown to enable high-resolution NSOM fluorescence and force measurements on viable cultured human arterial smooth muscle (HASM) cells under buffered conditions [28,29], This approach takes advantage of the nanofabrication capabilities of focused ion beam (FIB) milling to sculpt a light delivery structure into the end of a conventional AFM probe. The FIB technique, which utilizes a focused beam of gallium ions to mill samples with nanometer resolution, was first used by van Hulst and co-workers to modify conventional NSOM probes [30]. They demonstrated an improvement in single molecule fluorescence measurements using... 

In this mode of operation, ECMP leaves a uniform Cu film across pattern densities and allows conventional CMP to operate at low pressures less than 2 psi. The remaining Cu film after ECMP is measured by the focus ion beam (FIB) technique [25]. The film thickness is quite uniform across the wafer regardless of the pattern structures. For example, the thickness of the film over some representative structures (0.18-pm array, 0.25-pm array, 10-pm line, and 50-pm bond pad) is within a range of 200 A or less, as seen in Fig. 11.16. 

---