New single-source precursors for the MOCVD of high-kappa dielectric zirconium silicates to replace SiO2 in semiconducting devices
Two new single-source zirconium silicate precursors Zr(acac)(2)(OSiMe3)(2) A, and Zr(acac)(2)((OSiBuMe2)-Bu-t)2 B, have been synthesized. The stability and vapor pressure of the two compounds were investigated. They have been used to deposit films of Zr1-xSixO2 by metal-organic (MO)CVD in the temperature range 400-700degreesC. Zirconium silicate films with very low carbon contamination and silicon content, x, in the range 0.05-0.25 have been obtained. The two precursors differ, by a factor of two, in activation energy for the MOCVD of films (63 kJ mol(-1) for A, and 145 kJ mol(-1) for B), and differential scanning calorimetry (DSC) shows they have quite different decomposition temperatures. The film composition was determined by X-ray photoelectron spectroscopy (XPS) and the crystallinity of the layers was studied by X-ray diffraction (XRD). Preliminary electrical characterizations of the zirconium silicate films were conducted on MOS capacitors with Al as gate electrodes. The experiments exhibit the generation of negative charges in the layers during the measurements, shown by a large hysteresis in the CV curves and a shift of the IV curves from the first to the following measurements. Low leakage current densities in the lower voltage regime are observed.