Plasma CVD of (BaSr)TiO3 dielectrics for gigabit DRAM capacitors

Abstract

Electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) of (BaSr)TiO3 dielectrics is reviewed. The oxygen plasma lowered the crystallization temperature and carbon contamination. (BaSr)TiO3 CVD process was developed under conditions of relatively low deposition rate of 1.1 nm/min and a relatively low deposition temperature of 550°C. Utilizing this process, we developed a gigabit dynamic random access memory (DRAM) capacitor technology involving the preparation of a thin (BaSr)TiO3 capacitor dielectric over a RuO2/Ru storage node contacting a TiN/TiSiX/poly-Si plug. The ECR plasma CVD enabled uniform deposition of gigabit-DRAM-quality (BaSr)TiO3 films on the electrode sidewalls. The storage node contact improved in endurance against oxidation, by fabricating the buried-in TiN/TiSiX plug (TiN-capped plug) under the RuO2/Ru storage node. (BaSr)TiO3 films with a small equivalent SiO2 thickness of 0.38 nm and a leakage current density of 8.5×10−7 A/cm2 at an applied voltage of 1.0 V, were obtained without any further annealing process. An equivalent SiO2 thickness of 0.40 nm on the RuO2 sidewall was also achieved. It is concluded that this technology has reached the requirements for gigabit DRAM capacitors.