Low-temperature processing of titanium nitride films by laser physical vapor deposition

Abstract

We have investigated the formation of polycrystalline TiN films on (100) Si substrates using a low-temperature laser processing method. The films were deposited by laser ablation of a TiN hot-pressed pellet in the presence of neutral or ionized nitrogen using a XeCl excimer laser (wavelength 308 nm, pulse duration 45×10−9 s, and energy density of 4–5 J cm−2). The substrate temperature ranged from 25 to 550 °C. Plan-view and cross-section transmission electron microscopy studies show that the films are polycrystalline (average grain size ∼100 Å) with face-centered-cubic structure and lattice constant of 4.25 Å. It is interesting to note that the average grain size remained approximately constant with substrate temperature up to 550 °C. Chemical composition was analyzed by Rutherford backscattering and Auger electron spectroscopy as a function of film depth. The results show that the films reproduced closely the chemical composition of the TiN target which contained some oxygen, and that the oxygen content decreased with increased substrate temperature. Four-point probe measurements and I-V characteristics show that the films are metallic with a typical resistivity of ∼150 μΩ cm. The microhardness values of these films were found to be as high as 17 GPa.