Static information storage and retrieval – Floating gate – Particular connection
Patent
1994-12-19
1996-04-23
Nguyen, Viet Q.
Static information storage and retrieval
Floating gate
Particular connection
257316, H01L 2978
Patent
active
055110363
ABSTRACT:
Each unit cell (10) of a flash EEPROM array (50) includes a source (18), a drain (20) and a channel (22) formed in a substrate (12). A thin tunnel oxide layer (32) is formed over the substrate (12) and P-Well (14). A bifurcated floating gate (34) is formed on the tunnel oxide layer (32) overlying the channel (22) , and includes a program arm (34a) which overlaps the drain (20), an erase arm (34b) which overlaps the source (18) and a base (34c) which extends around an end of the channel (22) and interconnects the program and erase arms (34a,34b). A thick gate oxide layer (36,36a) is formed over the floating gate (34), and a control gate (38) is formed over the gate oxide layer (36,36a). A central section of the control gate (38) which overlies a gap (34d) between the program and erase arms (34a, 34b) provides threshold voltage control for erasure. The erase arm (34b) spans the entire width of the channel (22), enabling erasure with low applied voltages. The bifurcated floating gate design automatically compensates for alignment error during fabrication such that the relative areas of the channel (22) which underlie the program/erase arms (34a, 34b) and gap (34d) are independent of the location of the gap (34d).
REFERENCES:
patent: 4087795 (1978-05-01), Rossler
patent: 5343424 (1994-08-01), Chang et al.
patent: 5378909 (1995-01-01), Chang et al.
Authors: Gheorghe Samachisa, Chien-Sheng Su, Yu Sheng Kao, George Smarandoiu, Chen-Yuan Michae Wang, Ting Wong Chenming Hu "A 128K Flash EEPROM Using Double-Polysilicon Technology". Published in IEEE J. Solid-State Circuits vol. SC-22, No. 5, pp. 676-683; Oct., 1987.
Authors: H. Kume, H. Yamamoto, T. Adachi, T. Hagiwara, K. Komori, T. Nishimoto, A. Koike, S. Meguro, T. Hayashida, T. Tsukada "A Flash-Erase EEPROM Cell With a Asymmetric Source and Drain Structure". 1987 Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo 185 Japan.
Chang Chen-Chi P.
Farb Joseph E.
Li Mei F.
Denson-Low W. K.
Hughes Aircraft Company
Lachman M. E.
Nguyen Viet Q.
Sales M. W.
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