ZNO THIN-FILMS GROWTH BY APCVD USING ZINC ACETATE

ZnO thin films were prepared from zinc acetate using a horizontal tube hot-wall APCVD (Atmospheric Pressure Chemical Vapor Deposition) react or. Experimental temperature, flow rate and oxygen concentration in th e gas phase were in the range of 473 similar to 773K, 250 similar to 7 50 seem and 0 similar to 50mol%, respectively. The dependency of growt h rate, orientation and morphology of the films on growth conditions w as studied experimentally. The C-axis orientation is dominant in Alms grown at all temperatures, but C-axis orientation is thermally unstabl e when the film is prepared at low temperatures (T less than or equal to 673K). Conformal step coverage on micro trenches was obtained at lo w temperatures (T less than or equal to 673K). This indicates that the surface reaction is slow in the low temperature range. On the other h and, a much poorer step coverage was obtained at 723K, indicating that the surface reaction at this temperature proceeds much faster and pro bably via some different reaction mechanism from that at the low tempe rature range. Assuming that the growth rate at lower temperatures is g overned by the surface reaction, the surface reaction rate constant wa s chosen as a fitting parameter in a heat and mass transfer model to q uantitatively explain the experimental growth rate distributions. The activation energy was determined to be 63KJ/mol when CVD takes place w ithout oxygen in the gas phase and 23KJ/mol with 50 mol% of oxygen in the gas phase.