The critical current of Bi-2223/Ag superconducting samples after the last three thermo-mechanical treatments in the preparation of commercial tapes are measured at 77 K as a function of the magnitude and orientation of an applied field. We show how the zero-field critical current increases and the weak-link dominance is evolved to the strong-link dominance after each treatment. We also study the possibility of scaling the critical current as a function of an effective field, which is calculated from the magnitude and orientation of the applied field assuming a Gaussian distribution of the alignment of the c-axes of superconducting grains.
current and interpixel cross-talk on MIS devices without guard rings. However, the positive fixed charge is too large for MCT diode junction device passivation. Field plates would be required on diode devices with this passivation for surface potential control at the junction.These preliminary device data taken as a whole indicate the promise of ZnTe as a passivation candidate for MCT although further work and optimization would be required to translate these findings to routine applicability.
Long term stability of dry etched magnetoresistive random access memory elementsHigh density submicron magnetoresistive random access memory (invited)A typical magnetic random access memory stack consists of NiFe/Cu/NiFeCo multilayers, sandwiched by contact and antioxidation layers. For patterning of submicron features without redeposition on the sidewalls, it is desirable to develop plasma etch processes with a significant chlorinated etch component in addition to simple physical sputtering. Under conventional reactive ion etch conditions with Cl 2 -based plasmas, the magnetic layers do not etch because of the relatively involatile nature of the chlorinated reaction products. However, in high ion density plasmas, such as inductively coupled plasma, etch rates for NiFe and NiFeCo up to ϳ700 Å min Ϫ1 are achievable. The main disadvantage of the process is residual chlorine on the feature sidewalls, which can lead to corrosion. We have explored several options for avoiding this problem, including use of in situ and ex situ cleaning processes after the Cl 2 -etching, or by use of a noncorrosive plasma chemistry, namely CO/NH 3 . In the former case, removal of the chlorine residues with in situ H 2 plasma cleaning ͑to form volatile HCl that is pumped away͒, followed by ex situ solvent rinsing, appears effective in preventing corrosion. In the latter case, the CO/NH 3 plasma chemistry produces metal carbonyl etch products, that are desorbed in the simultaneous presence of an ion flux. The etch rates with CO/NH 3 are much lower than with Cl 2 over a broad range of source powers ͑0-1500 W͒, radio frequency chuck powers ͑50-450 W͒, pressures ͑1-30 mTorr͒ and plasma compositions. We have tried substitution of CO 2 for CO, and addition of Ar to produce faster etch rates, without success. Maximum rates of ϳ300 Å min Ϫ1 for NiFe and NiFeCo were obtained with CO/NH 3 under optimum conditions. The etched sidewalls tend to be sloped because of mask erosion during plasma exposure, in contrast to the case of Cl 2 -based chemistries where the sidewalls are vertical.
The barrier effect for oxygen diffusion is studied in TaSiN layers. The TaSiN is deposited by reactive sputtering employing Ta and Si targets. The composition of the layer ranges from Ta0 6Si027N057 to Ta055Si007N0 by varying the Ta target power from 100 to 400 watts (W). A resistivity of 210 pfl cm is obtained for the Ta055Si007N035 layer. The surface oxidation and in-diffusion of oxygen to a depth of 15 nm into the Ta030 17N053 'ayer are observed by annealing in 02 at 650° C. However, the oxygen diffusion is suppressed in the Ta0 55Si007N038 layer.No out-diffusion of oxygen occurs from the Ta205 dielectric layer to the amorphous barrier layer. This result shows that a low Si concentration layer for instance, Ta0 5551007N038 is a promising barrier layer for oxygen diffusion and is useful for charge storage capacitors for MOS memory devices.
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