| Summary: | 碩士 === 國立交通大學 === 電子工程系 === 87 === As the dimensions of the charge storage node in high-density dynamic random access memory (DRAM) are scaled down. Silicon dioxide and silicon oxynitride which have been used as capacitor dielectric materials are no longer applicable because their thickness is already limited by direct tunneling. High dielectric constant materials are needed to keep a simpler cell structure. Potential dielectrics with high dielectric constant include Ta2O5, SrTiO3, Pb(Zr,Ti)O3 (PZT) and (Ba,Sr)TiO3 (BST)…etc. The BST is one of the most promising materials due to its high dielectric constant, low leakage current, a TDDB over 10 years and low dissipation factor for high density DRAM capacitor.
In this work, the electrical properties of BST film deposited on Ir and Pt bottom electrode and their correlation with various substrate temperatures are studied. In addition, the physical mechanism of the stress induced leakage current for BST thin film deposited with different film thickness and various oxygen to argon ratio (OAR) were investigated in details. Finally, the effect of various OAR on dielectric relaxation and defect quantity are discussed and an equivalent circuit model for (Ba0.65Sr0.35TiO3) thin film capacitors are proposed.
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