In DRAM, maintaining the cell capacitance more than 25 fF/cell with shrinking cell capacitance area has been accomplished with the introduction of higher k oxides as the capacitor dielectric. Higher k materials include Al2O3, HfO2, ZrO2 or a combination of HfO2/Al2O3/HfO2 and ZrO2/Al2O3/ZrO2. These materials can satisfy DRAM device requirements down to the 50 nm node. However, for sub 40nm DRAM technology nodes, precursor delivery challenges are far greater and require unique precursor delivery methodology to ensure >90% conformality in high aspect ratio DRAM capacitor structures, while maintaining higher productivity. The precursor delivery problem is due to the very low vapor pressures of the precursors for advanced high k dielectrics.. This paper highlights the progress made in ALD equipment development offering solutions for critical problems facing sub 40nm DRAM technology nodes. Particularly, this paper describes a unique pulsed vaporization technology (TriJet®) coupled with a high performance ALD reactor that offers solution for next generation high k film deposition without compromising productivity.
Z. Karim, Senzaki, Y., Dr. Sasangan Ramanathan, Lindner, J., Silva, H., and Dauelsberg, M., “Advances in ALD Equipment for sub-40nm Memory Capacitor Dielectrics: Precursor delivery, Materials and Processes”, ECS Transactions, vol. 16. The Electrochemical Society, pp. 125–134, 2008.