The Potential of Ultrathin-Film SOI Devices for Low-Power and High-Speed Applications

Yuichi KADO  

IEICE TRANSACTIONS on Electronics   Vol.E80-C   No.3   pp.443-454
Publication Date: 1997/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on SOI Devices and Their Process Technologies)
Category: Circuit Technologies and Applications
CMOS,  SOI,  SIMOX,  low voltage,  low power,  

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For low-voltage, high-speed operation of LSIs, the most attractive features in fully-depleted (FD) SOI devices are their steep subthreshold slope and reduced drain junction capacitance. This paper discusses the impact of these features on circuit performance. FD SOI devices can have a threshold voltage of more than 100 mV lower than that of bulk devices within the limits of acceptable off-state leakage current. Thus they hold higher driving current even at supply voltages of less than 1 V. On the other hand, the reduced junction capacitance is effective to suppress the total parasitic capacitance especially in lightly loaded CMOS circuits. These attractive features improve the speed performance in FD SOI circuits remarkably at supply voltages of less than 1 V. For high-speed circuit applications, 0.25-µm-gate SIMOX circuits, such as frequency dividers, prescalers, MUX, and DEMUX, can operate at up to 1-2 GHz even at a supply voltage of 1 V. CMOS/SIMOX logic LSIs also exhibit better performance at very low supply voltages. At merely 1 V, a SIMOX logic LSI could be functional at up to 60-90 MHz using 0.26-0.34 µW/MHz/Gate of power dissipation. Furthermore, SIMOX logic LSIs will allow 20-30 MHz operation at 0.5 V of a solar cell with reasonable chip size. These investigations lead to the conclusion that FD CMOS/SIMOX technology will have a large impact on the development of low-voltage high-performance LSIs for portable digital equipment and telecommunication systems.