Strain sensor using stress-magnetoresistance effect of Ni-Fe/Mn-Ir exchange-coupled magnetic filmExchange biasing properties of the NiFe/IrMn exchange couple were investigated by varying the IrMn composition and sputtering conditions. At a composition of Ir 20 Mn 80 an exchange field of ϳ60 Oe and a coercivity of 8 Oe were obtained for the structure Si/Ta-75 Å/NiFe-250 Å/IrMn-500 Å. The maximum exchange field obtained was similar for rf diode, rf magnetron, and dc magnetron sputtering of the IrMn. X-ray diffraction measurements showed that the crystalline texture was ͑111͒ for both the NiFe and IrMn, but a strong crystalline texture did not necessarily correspond to a large exchange field. The interfacial exchange energy, J k , was evaluated to be 0.145 erg/cm 2 and the minimum thickness of IrMn needed to support an exchange field was 75 Å. The blocking temperature was measured to be a function of the IrMn thickness and was in the range of 220-250°C for thicknesses Ͼ200 Å. Below this, the blocking temperature rapidly decreased to a value of 130°C at 75 Å of IrMn. Corrosion testing was done in a Battelle Class II type corrosive environment. Using the exchange field as a figure of merit, it was found that the IrMn corrosion properties were only slightly better than FeMn, and significantly worse than NiMn and CoNiO. We were also able to successfully fabricate NiFe based spin-valves pinned with IrMn and they show good magnetic properties. Our results show than IrMn is a good alternative to FeMn.

The blocking temperature was measured for several exchange biasing materials as a function of the antiferromagnet thickness and deposition conditions. For the oxide materials Co0.5Ni0.5O and NiO and for IrMn, the blocking temperature was found to decrease from the bulk values of 150, 190, and 250 °C, respectively, with decreasing thickness of the antiferromagnet. The minimum thickness needed in order to maintain a blocking temperature within 25% of the bulk value was 125, 145, and 140 Å for Co0.5Ni0.5O, NiO, and IrMn, respectively. The functional dependence with thickness was found to follow a power law relationship, which is consistent with the finite size scaling phenomenon. The shift exponent for scaling obtained by curve fitting the experimental data was 1.65, 1.40, and 1.52 for the three materials, respectively. These values were in good agreement with the theoretical values of 1.4–1.6, as calculated for idealized antiferromagnets. The corresponding values for the correlation length at 0 K were 22, 19, and 30 Å, respectively. For Co0.5Ni0.5O, the blocking temperature was also found to vary with deposition conditions, with high negative substrate biases and low pressures yielding the largest blocking temperatures. These trends were also found to follow a power-law relation.

Titanium nitride (TiN) has been widely used in the semiconductor industry for its diffusion barrier and seed layer properties. However, it has seen limited adoption in other industries in which low temperature (<200 °C) deposition is a requirement. Examples of applications which require low temperature deposition are seed layers for magnetic materials in the data storage (DS) industry and seed and diffusion barrier layers for through-silicon-vias (TSV) in the MEMS industry. This paper describes a low temperature TiN process with appropriate electrical, chemical, and structural properties based on plasma enhanced atomic layer deposition method that is suitable for the DS and MEMS industries. It uses tetrakis-(dimethylamino)-titanium as an organometallic precursor and hydrogen (H2) as co-reactant. This process was developed in a Veeco NEXUS™ chemical vapor deposition tool. The tool uses a substrate rf-biased configuration with a grounded gas shower head. In this paper, the complimentary and self-limiting character of this process is demonstrated. The effects of key processing parameters including temperature, pulse time, and plasma power are investigated in terms of growth rate, stress, crystal morphology, chemical, electrical, and optical properties. Stoichiometric thin films with growth rates of 0.4–0.5 Å/cycle were achieved. Low electrical resistivity (<300 μΩ cm), high mass density (>4 g/cm3), low stress (<250 MPa), and >85% step coverage for aspect ratio of 10:1 were realized. Wet chemical etch data show robust chemical stability of the film. The properties of the film have been optimized to satisfy industrial viability as a Ruthenium (Ru) preseed liner in potential data storage and TSV applications.

The effect of seed layers on the giant magnetoresistance (GMR) response of bottom spin-filter spin valves (SFSVs) of the structure (seed layer)/PtMn/CoFe/Cu/CoFe/NiFe/Cu/Ta have been studied in detail. Four types of seed layers, NiFeCr, Ta/NiFeCr, NiFeCr/NiFe, and Ta/NiFe were used. The GMR response has been found to be very sensitive to the type and the thickness of the seed layers, which determine the crystallographic quality of the films and the degree of the fcc to fct phase transformation of the PtMn crystals in the films. Among the four, Ta/NiFeCr and NiFeCr/NiFe seed layers give the optimal GMR performance at a NiFeCr layer thickness of about 40–45 Å.

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