Aluminum Nitride Thin Films By Reactive Sputtering

"Aluminum nitride thin films ( -1000 A) have been deposited on silicon substrate by re active sputtering using Al target in 1 : 1 Ar:N2 environment. The atomic force microscopy examination revealed continuous microcrystalline film structure. The Auger electron spectroscopic analysis shows the presence of oxygen in the films. The annealing at 850 C in nitrogen is found to cause recrystallinization and, by FTIR analysis, further oxidation of the films. The films can be characterized as lossy dielectrics with relative permittivity ~ 10, higher than the bulk value of 8.9. Annealing the films is found to reduce anion vacancies and improve the dielectric strength within a range of a few MV/cm in these thin films. Optical constants, n & k, have been obtained from reflectance and transmittance spec tra (190-900 nm) of films on fused silica. The results indicate the presence of a low energy absorption tail, and exponential absorption that is proportional to degree of disorder in the film. The average defect density of the film as deposited was 1.1 x 10^20 cm"3. Annealing the film at 760 C increased the degree of disorder resulting in an average defect density of 3.4 x 10^20 cm^-3. Subsequent annealing at 800 C and 850 C systematically decreased the degree of disorder and the average defect density. The real part of permittivity (e1) of the annealed films over this frequency range varies approximately +-0.5 from the e(infinity) of 4.84"--Abstract.