molybdenum and silicon targets; oxygen-contaminated films; polycrystalline silicon; amorphous phases; oxygen-free annealed films
Thin films of MoSix (with and without oxygen) were deposited by co-sputtering of molybdenum and silicon targets. As-deposited films were annealed in argon environment in the temperature range 700–1150 °C for 15–120 s. Rapid thermal annealing of oxygen-contaminated films at low temperature (700–800 °C) in an argon environment results in evolution of a mixture of MoSi2, Mo3Si3, polycrystalline silicon and amorphous phases. Subsequent annealing at higher temperature (above 800 °C) results in further growth of Mo5Si3, MoSi2 and polycrystalline silicon. At 1150 °C, a 15–120 s annealing time produces successive growth of tetragonal MoSi2 phase at the expense of Mo5Si3 and silicon. Auger electron spectroscopy depth profiles of annealed films indicate the accumulation of oxygen impurity at the MoSix---Si(crystalline) interface, which is initially distributed uniformly throughout the MoSix matrix. However, oxygen-free MoSix films do exhibit the growth of MoSi2 (both tetragonal and hexagonal) during rapid thermal annealing up to 1050 °C. At higher temperature (1150 °C) a single-phase MoSi2 (tetragonal) is observed. The surface morphology of oxygen-free annealed films reveals a uniform distribution of silicide grains as compared with oxygen-containing films. The sheet resistance of the finally annealed films (1150 °C and 120 s) was found to be 9.5 Ω/ for oxygen-contaminated films and 7.6 Ω/ for oxygen-free films.