Unique problems, and possible solutions, in fully depleted SOI CMOS VLSI circuits

Author

Fossum, J.G. ; Choi, J.Y. ; Yeh, P.C.

Author_Institution

Dept. of Electr. Eng., Florida Univ., Gainesville, FL, USA

fYear

1991

fDate

1-3 Oct 1991

Firstpage

158

Lastpage

159

Abstract

The authors use a physical model for the fully depleted SOI (silicon-on-insulator) MOSFET, written into SPICE2 source code, to study floating-body problems in SOI CMOS circuits, and to suggest possible solutions. The model is seminumerical, accounting for all thin-film and short-channel effects, LDD (lightly doped drain) and LDS effects, subthreshold current at both the front and back surfaces, and the impact-ionization current and parasitic BJT (bipolar junction transistor). It is shown that optimally designed LDD and LDS regions can effectively suppress the BJT-induced problems. There is, however, a tradeoff involved because of the voltage drops across these regions and the concomitant reduced drive-current capability of the MOSFET. Also, SOISPICE-2 simulations of ring oscillators comprising SOI CMOS inverters show lengthened propagation delay (lower frequency of oscillation) when the LDD/LDS is used, because of the reduced MOSFET drive as well as the suppressed BJT current

Keywords

CMOS integrated circuits; VLSI; integrated circuit technology; semiconductor device models; semiconductor-insulator boundaries; CMOS; LDD effects; LDS effects; SOI; SOI CMOS inverters; SPICE2; VLSI; floating-body problems; fully depleted SOI MOSFET; impact-ionization current; lightly doped drain; lightly doped source; parasitic BJT; physical model; problems; propagation delay; reduced drive-current capability; ring oscillators; short-channel effects; solutions; subthreshold current; suppressed BJT current; tradeoff; voltage drops; Inverters; MOSFET circuits; Propagation delay; Ring oscillators; Semiconductor device modeling; Silicon on insulator technology; Subthreshold current; Thin film circuits; Thin film transistors; Voltage;

fLanguage

English

Publisher

ieee

Conference_Titel

SOI Conference, 1991. Proceedings, 1991., IEEE International

Conference_Location

Vail Valley, CO

Print_ISBN

0-7803-0184-6

Type

conf

DOI

10.1109/SOI.1991.162905

Filename

162905