Simulation of a simplified design for a nanoscale metal-oxide field effect transistor
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Abstract We describe simulations on a simplified design for a metal-oxide nanoscale Field Effect Transistor (FET). The device features an oxide channel with a high dielectric constant ferroelectric as the gate insulator. In the present model, the gate and source/drain electrodes are unconventionally placed on opposite sides of the channel.
Simulations are quantum mechanical and are
based on a simplified transport model. Results on a 10 nm. channel device show adequate conductance and ON/OFF ratio, while simulation of a ring oscillator yields an estimated device switching time of 300 fs..
I. INTRODUCTION The imminent breakdown of scaling of device size (Moore's Law) in the conventional Si/SiO 2 MOSFET a.t the 50-60 nm. publications [1].
channel length scale has been well documented in technical
Hence in the present situation there is a need for intensive study of new
technology pathways leading to the possibility of continuing size shrinkage , especially those offering the possibility of considerable dynamic range of scaling and leading to increased device switching speed. In the present paper we shall present a simplified simulation study of a MOSFET design quite radically modified both as regards materials and physical design, which is predicted to operate clown to a relatively aggressive scale of 10 nm. channel length, with a very fast switching time of 300 fs. Key points in the design distinguishing it from the conventional
11 Mat. Res. Soc. Symp. Proc. Vol. 623 © 2000 Materials Research Society
MOSFET enable it to function at such a small scale.
The device operates via an oxide
channel material with only majority carriers, enabling the bulky pn junctions of the conventional MOSFET to be dispensed with. The concept of high dielectric constant gate oxide is extended to use of a ferroelectric material with a very high dielectric constant, thus enabling (i) reduction of the channel length into the nanoscopic regime, without intervention of unacceptable short channel effects, and (ii) a thick enough gate oxide to avoid tunneling. Following an early theoretical suggestion regarding the Mott Transition Field Effect Transistor (MTFET) [2], and early experimental work [3], the experimental approach to studying all-oxide transistors with ferroelectric gate oxide and cuprate channel materials has already made considerable progess [4]. Currents of 700 1zA have been switched, ON/OFF ratios of 10i observed, and progress made in enhancing mobility [5] [6], though bulk mobilities have not yet been reached. In concert with the first pass theoretical analysis derived in the present paper, the outlook for an all-oxide FET technology seems promising.
II. THE MODEL
A sketch of the 2D device model as simulated is illustrated in Fig. 1. The device, with a nominal 10 urn. channel length, has several features which, apart from scale, are quite different from a conventional FET. First of all, the geometry involves a back gate rather than the conventional front gate. The gate oxide is assumed to consist of a ferroelectric di
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