Title :
Novel multi-bit SONOS type flash memory using a high-k charge trapping layer
Author :
Sugizaki, T. ; Kobayashi, Masato ; Ishidao, M. ; Minakata, H. ; Yamaguchi, M. ; Tamura, Y. ; Sugiyama, Y. ; Nakanishi, T. ; Tanaka, H.
Author_Institution :
Fujitsu Labs. Ltd., Atsugi, Japan
Abstract :
We demonstrated SONOS flash memory with a SiO/sub 2//High-k/SiO/sub 2/ structure based on a 2-bit/cell scheme. We evaluated three kinds of high-k dielectric films which were Si/sub 3/N/sub 4/, Al/sub 2/O/sub 3/ and HfO/sub 2/. Among these films, Al/sub 2/O/sub 3/ showed superior retention characteristics. The charge loss amount of Al/sub 2/O/sub 3/ at 150/spl deg/C is almost the same as that of Si/sub 3/N/sub 4/ at 25/spl deg/C. HfO/sub 2/ showed poor retention characteristics. In addition, we have found that each film has a different charge loss mechanism. We speculate that Si/sub 3/N/sub 4/ causes vertical charge migration, Al/sub 2/O/sub 3/ causes scarcely any leakage, and HfO/sub 2/ causes lateral charge migration. As a consequence, Al/sub 2/O/sub 3/ is very suitable for a charge trapping layer in multi-bit SONOS memory.
Keywords :
alumina; dielectric losses; dielectric materials; dielectric thin films; flash memories; hafnium compounds; leakage currents; silicon compounds; 150 degC; 25 degC; SiO/sub 2/-Al/sub 2/O/sub 3/-SiO/sub 2/; SiO/sub 2/-SiO/sub 2/ structure; charge loss; charge migration; charge trapping layer; current leakage; dielectric films; multibit silicon-nitride-oxide-silicon flash memory; retention; Electron traps; Electronic mail; Flash memory; Flash memory cells; Hafnium oxide; High K dielectric materials; High-K gate dielectrics; Laboratories; SONOS devices; Semiconductor films;
Conference_Titel :
VLSI Technology, 2003. Digest of Technical Papers. 2003 Symposium on
Conference_Location :
Kyoto, Japan
Print_ISBN :
4-89114-033-X
DOI :
10.1109/VLSIT.2003.1221069
