Properties Of Giant Dielectric Constant Material CaCu₃Ti₄O₁₂ Prepared In Sol-gel Way

The fast development of information technology requires integrated circuit to be greater integrated, faster functioned, and lower power-consumed, that lead to continuous shrinkage of MOS and DRAM feature size. And under this trend the thickness of MOS gate dielectrics would soon scale down to its physical limit. Substitution of SiO₂ gate and capacitor dielectrics with high-k dielectrics is a promising solution for the future development of CMOS technology. This work is based on the preparation, characterization, and processing of high-k materials.CaCu₃Ti₄O₁₂ (abbreviated to CCTO) is a kind of giant-dielectric material with perovskite-related structure (space group: Im3). It shows great dielectric constant normally above 10⁴ and low loss tangent less than 0.1 at 10 KHz, therefore it has many important and practical applications in electronic devices. It shows another more attractive property, its dielectric constant nearly does not change in a big temperature range such as 100 to 400 K, and this phenomenon is not observed on the other materials. Contrasted to other high-k materials such as Grain Boundry Layer ceramics (GBLC) material, it can be prepared in a simple way without being semiconducting in high temperature and being in low temperature. Contrasted to composite high-k materials with conductive and insulated phases, it is simple in structure and low in energy loss.In this article, CCTO powder and ceramics were first made by traditional sintering procedure for contrast. Next, CCTO powder was successfully produced by traditional sol-gel way and ceramics were obtained by following sintering.CaCu₃Ti₄O₁₂ ceramics were successfully prepared by sintering at 950—1 100 ℃ for 20h and using a powder prepared by sol-gel method and calcined at 700— 900℃ for 6—10h. The phase structures of CaCu₃Ti₄O₁₂ ceramics and precursor powders were measured by X-ray diffraction and the morphology of CaCu₃Ti₄O₁₂ ceramics was observed by scanning electron microscopy. The dielectric constant of was measured by LCR (Inductance-capacitance-resistance) meter at afrequency range from lOHz to 106Hz. The results show that the dielectric constant of the CaCu3Ti4Oi2 ceramics is dependent on the grain size of the perovskite-like phase. The calcination temperatures of the precursor powder prepared by sol-gel method and the sintering temperature of CaCu3Ti4Oi2 ceramics are at least 100°C lower than that by traditional solid phase reaction process. The CaCu3Ti4Oi2 ceramic with a dielectric constant of 194 753 was obtained by sintered at 1 100°C and using the precursor powder calcined at 800°C, which is much higher than that prepared by traditional solid phase reaction process...