Title :
Promising storage capacitor structures with thin Ta2O 5 film for low-power high-density DRAMs
Author :
Shinriki, Hiroshi ; Kisu, Teruaki ; Kimura, Shin-Ichirou ; Nishioka, Yasushiro ; Kawamoto, Yoshifumi ; Mukai, Kiichirou
Author_Institution :
Hitachi Ltd., Tokyo, Japan
fDate :
9/1/1990 12:00:00 AM
Abstract :
To ensure the required capacitance for low-power DRAMs (dynamic RAMs) beyond 4 Mb, three kinds of capacitor structures are proposed: (a) poly-Si/SiO2/Ta2O5/SiO2 /poly-Si or poly-Si/Si3N4/Ta2O 5/SiO2/poly-Si (SIS), (b) W/Ta2O5 /SiO2/poly-Si (MIS), and (c) W/Ta2O5 W (MIM). The investigation of time-dependent dielectric breakdown and leakage current characteristics indicates that capacitor dielectrics that have equivalent SiO2 thicknesses of 5, 4, and 3 nm can be applied to 3.3-V operated 16-Mb DRAMs having stacked capacitor cells (STCs) by using SIS, MIS, and MIM structures, respectively, and that 3 and 1.5 nm can be applied to 1.5-V operated 64-Mb DRAMs having STCs by using MIS and MIM structures, respectively. This can be accomplished while maintaining a low enough leakage current for favorable refresh characteristics. In addition, all these capacitors show good heat endurance at 950°C for 30 min. Therefore, these capacitors allow the fabrication of low-power high-density DRAMs beyond 4 Mb using conventional fabrication processes at temperatures up to 950°C. Use of the SIS structure confirms the compatability of the fabrication process of a storage capacitor using Ta2O5 film and the conventional DRAM fabrication processes by successful application to the fabrication process of an experimental memory array with 1.5-μm×3.6-μm stacked-capacitor DRAM cells
Keywords :
capacitance; dielectric thin films; electric breakdown of solids; integrated memory circuits; leakage currents; metal-insulator-metal structures; metal-insulator-semiconductor structures; random-access storage; semiconductor-insulator-semiconductor structures; tantalum compounds; thin film capacitors; 1.5 V; 1.5 micron; 1.5 nm; 16 Mbit; 3 nm; 3.3 V; 3.6 micron; 4 nm; 5 nm; 64 Mbit; 950 degC; MIM structures; MIS structures; SIS structures; Si; Si-Si3N4-Ta2O5-SiO 2-Si; Si-SiO2-Ta2O5-SiO2-Si; W-Ta2O5-SiO2-Si; W-Ta2O5-W; capacitance; capacitor dielectrics; equivalent SiO2 thicknesses; experimental memory array; fabrication processes; heat endurance; leakage current characteristics; low-power DRAMs; refresh characteristics; stacked capacitor cells; stacked-capacitor DRAM cells; storage capacitor structures; thin film; time-dependent dielectric breakdown characteristics; Capacitance; Dielectric films; Dielectric thin films; Fabrication; Leakage current; MIM capacitors; MOS devices; Random access memory; Semiconductor films; Voltage;
Journal_Title :
Electron Devices, IEEE Transactions on
