Effects of annealing time on the structural and magnetic properties of L10 FePt thin films

Thermal annealing of [Fe 1.65 nm/Pt 1.84 nm]₅₀ multilayers at 673 K for various annealing times between 60 and 12000 s leads to the direct formation of the fully ordered L1₀ FePt phase with (111) texture. The average grain sizes, determined from X-ray diffraction size-strain analysis, are smaller than the critical size for multi-domain FePt particles, suggesting the presence of single-domain (SD) grains. The coercivity increases with annealing time and increasing grain size and reaches values of about 955 kA/m. The remanence values are typical for randomly oriented weakly-interacting particles. A decrease of the remanence with annealing time suggests a decrease of the intergrain exchange interactions with annealing time. Analysis of minor loops and the initial magnetization curves shows the presence of a broad distribution of critical fields, which the individual SD particles have to overcome for the magnetization reversal.     

Lifetime of thin oxide and oxide-nitride-oxide dielectrics withintrench capacitors for DRAMs

An investigation of the field acceleration of the time-dependent dielectric breakdown behavior of a thermal oxide and an oxide-nitride-oxide (ONO) dielectric on planar- and trench-cell MIS capacitors under a constant field stress of 5-9 MV/cm at 150°C is discussed. Defect-related and intrinsic failures are distinguished by a statistical analysis of the breakdown distributions. Planar- and trench-cell capacitors with an ONO dielectric exhibit reduced early failures and a more favorable field-acceleration behavior than capacitors with a thermal-oxide layer. A method which determines the number of intrinsic failures by extrapolation of the accelerated constant field stress data to the device area and down to the operational electric field strength is proposed. The extrapolation predicts, for trench-capacitor arrays with a 5-mm² active device area and a 13.5-nm oxide dielectric operating at 3 MV/cm and 150°C, a mean intrinsic failure rate slightly below 100 Fit in the first year, whereas trench structures with an ONO-dielectric reach the same number of cumulative failures after 1 million years