PREPARATION OF ALN THIN-FILMS BY REACTIVE SPUTTERING AND OPTICAL-EMISSION SPECTROSCOPY DURING SPUTTERING

Aluminum Nitride (AlN) thin films were prepared by reactive rf-magnetron sputtering in a mixed gas atmosphere composing of argon and nitrogen. The deposition rate, electrical resistivity and crystal structure were studied as a function of partial pressure of nitrogen (P(N2)). Total pressure(P(N2+Ar)) was controlled to maintain a constant pressure of 6.0 x 10(-1) Pa. The structure of as-prepared films can be divided into three regions from X-ray diffraction analysis: (1) P(N2) less-than-or-equal-to 6.0 x 10(-3) Pa, Al, (2) P(N2) = 1.2 x 10(-2) Pa is similar to 2.4 x 10(-2) Pa, a mixed phase of Al and AlN, (3) P(N2) greater-than-or-equal-to 3.0 x 10(-2) Pa, AlN. With increase of P(N2), the deposition rate of the films decreased drastically around P(N2) = 2.4 x 10(-2) Pa, and finally approached to a constant value of 25 angstrom/min around P(N2) = 6.0 x 10(-1) Pa. This is proved from the measurement of optical emission spectroscopy to occur by the formation of nitride on the surface of aluminum target. AlN thin films deposited in higher P(N2) exhibited a higher crystallity and a higher refractive index because of less nitrogen deficiency.