The spin-transfer effect has been studied in magnetic tunnel junctions (PtMn/CoFe/Ru/CoFe/Al 2 O 3 /CoFe/NiFe) with dimensions down to 0.1x0.2 µm 2 and resistance-area product RA in the range of 0.5-10 Ωµm 2 (∆R/R=1-20%). Current-induced magnetization switching is observed with a critical current density of about 8x10 6 A/cm 2 . The attribution of the switching to the spintransfer effect is supported by a current-induced ∆R/R value identical to the one obtained from the R versus H measurements. Furthermore, the critical switching current density has clear dependence on the applied magnetic field, consistent with what has been observed previously in the case of spin-transfer induced switching in metallic multilayer systems.Magnetization switching induced by spin-polarized current has stimulated considerable interest in recent years due to its rich fundamental physics and potential for new magnetoelectronic applications. Low switching current density and high read signal are required for the application of the spin-transfer switching to non-volatile magnetic random access memory (MRAM). Most of the work to date, however, has focused on magnetic metallic multilayers, which require large currents applied in the currentperpendicular-to-plane direction but yield small resistance (R) and nominal magnetoresistance (∆R/R). 1 On the other hand, magnetic tunnel junctions (MTJ) have both high R and ∆R/R, resulting in high signal output. In order to utilize MTJs in spin transfer based MRAM, however, requires an understanding of the limits of both the spin transfer effect and the electron transport properties of tunnel barriers used in MTJs.We report the observation of the spin-transfer effect in low-resistance MTJs ( RA=0.5-10 Ωµm 2 ) with dimensions down to 0.1x 0.2 µm 2 . These deep submicron-sized MTJs minimize the Oersted (vortex) field contribution due to large vertical current through the MTJ pillars. 2,3 MTJ films Ta20/NiFeCr35/PtMn140/ CoFe20/Ru8 /CoFe22/ Al 2 O 3 / CoFe10/NiFe20/Ta50 (in Å) were deposited in a magnetron sputtering cluster system and annealed at 250-270 o C for 10 hours. A thin tunneling barrier was formed by two-step natural oxidation of the pre-deposited Al layer in a pure oxygen atmosphere. 4 The MTJ films were subsequently patterned into deep submicron ellipse-shaped pillars using DUV photolithography combined with resist trimming and ion milling. The pillar dimensions and microstructures have been characterized by high-resolution transmission electron microscope (TEM). The cross sectional TEM micrograph of an MTJ sample (0.12 x 0.23 µm 2 ellipse)

A patterning process for nanoscale current-perpendicular-to-plane magnetic devices was developed. Spin valve and magnetic tunnel junction (MTJ) pillars are patterned using electron-beam lithography and subsequent hard mask deposition and ion milling. Photoresist etch-back method is used to planarize the insulation layer, deposited on top of the spin valve/MTJ pillars, prior to top lead deposition. This method allows for a reduction of shadowing effect associated with the use of resist mask for ion milling. Critical switching current of ∼6×107A∕cm2 was observed for spin valve nanopillars with clear field dependence of the switching current, which is comparable to the reported value for metallic system.

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We present an enhanced smoothing algorithm in order to minimize the number of nodes in a surface triangulation while at the same time the wafer topography is maintained, and changes of geometry are limited to user-defined tolerances. Refined criteria for the protection of nodes and edges which have not to be removed because of topological reasons have been worked out. An algorithm has been implemented for the extraction of local smoothing tolerance. The use of local and material-dependent smoothing tolerance is mandatory for the optimization of surface triangulations. Our topologically correct smoothing algorithms with user-controlled tolerances provides large opportunities for increased efficiency of 3D simulation of various process steps. Some examples for this application are given.