Title :
Leakage-current reduction in thin Ta2O5 films for high-density VLSI memories
Author :
Hashimoto, Chisato ; Oikawa, Hideo ; Honma, Nakahachiro
Author_Institution :
Electr. Commun. Lab., NTT, Atsugi, Japan
fDate :
1/1/1989 12:00:00 AM
Abstract :
Key techniques for applying Ta2O5 film to megabit-class MOS DRAMs are presented. A high-purity (4N and up) Ta sputtering target is developed to obtain high-purity Ta2 O5 film. The leakage current in Ta2O5 film that is deposited using a clean sputtering system with this high-purity target is far lower than that of film deposited with a conventional target. A previous drawback of Ta2O5, the decrease of effective dielectric constant as thickness decreases, is solved by using Mo as an electrode material. The leakage current increase that results from using metal as a bottom electrode is suppressed by reducing the electrode asperity. MOS DRAMs of up to 16-Mb capacity can be attained without trench technology by using these techniques
Keywords :
MOS integrated circuits; VLSI; dielectric thin films; integrated memory circuits; leakage currents; permittivity; random-access storage; sputtered coatings; tantalum compounds; 16 Mbit; MOS DRAMs; Mo; effective dielectric constant; electrode asperity; high-density VLSI memories; leakage current; sputtering target; thin Ta2O5 films; Dielectric constant; Dielectric materials; Electrodes; Laboratories; Leakage current; MOS capacitors; Purification; Semiconductor impurities; Sputtering; Very large scale integration;
Journal_Title :
Electron Devices, IEEE Transactions on
