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Abstract:
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Plasma enhanced deposition of amorphous aluminum nitride ~AlN! using trimethylaluminum,
hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temperature was
varied from 350 to 550 °C, and pressure dependence of the film structure was investigated. Films
were characterized by Fourier transform infrared, Rutherford backscattering ~RBS!, ellipsometry,
and x-ray diffraction ~XRD!. The films are amorphous in nature, as indicated by XRD. Variations in
the refractive index were observed in ellipsometric measurements, which is explained by the
incorporation of carbon in the films, and confirmed by RBS. Capacitance–voltage, conductance–
voltage (G–V), and current–voltage measurements were performed to reveal bulk and interface
electrical properties. The electrical properties showed marked dependence on processing conditions
of the AlN films. Clear peaks as observed in the G–V characteristics indicated that the losses are
predominantly due to interface states. The interface state density ranged between 1010 and
1011 eV21 cm22. Annealing in hydrogen resulted in lowering of interface state density values. |