Plasma CVD of (BaSr)TiO3 Dielectrics for Gigabit DRAM Capacitors

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/TiSi _X /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/TiSi _X 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.