Analysis of the Silicon Film Thickness and the Ground Plane Influence on Ultra Thin Buried Oxide SOI nMOSFETs

Abstract

This paper presents an analysis of the Ground Plane (GP) implantation and silicon film thickness influences on Ultra Thin Buried Oxide (UTBOX) SOI MOSFETs. The results obtained experimentally and by simulations, considering the GP implantation, show that the device must have a GP implantation higher than 1x10 18 cm -3 in order to eliminate the substrate effect. In spite of the fact that the substrate influence on the drain current is negligible with a high GP concentration, the coupling between front and back interface increases for thinner silicon films.

Influence of High Temperature on UTBB SOI nMOSFETs with and without Ground Plane

“…It is possible to see that the simulated curves present a good agreement with experimental curves and that there is a back-gate voltage shift (kink) for devices without GP. This effect disappears for devices with GP substrate doping concentration higher than 10 18 cm -3 as already observed in reference (5).…”

Influence of High Temperature on UTBB SOI nMOSFETs with and without Ground Plane

“…This effect disappears for devices with GP substrate doping concentration higher than 10 18 cm -3 as observed in ref. (3). For high temperature, this effect occurs for almost the same back gate voltage, but the maximum amplitude (V GB MAX ) decreases as shown in figure 2 due to the Fermi level reduction.…”

Ground Plane Influence on Analog Parameters of Different UTBB nMOSFET Technologies

“…All devices have a silicon film concentration (Na) around 10 15 cm -3 since there is no channel doping, the substrate concentration (Na SUB ) is also around 10 15 cm -3 for the same reason. There are devices that have a GP implantation under the buried oxide, by a boron implantation at 25keV and a dose of 5x10 13 cm -2 , resulting in a substrate concentration around 1x10 18 cm -3 [17]. Two different channel lengths were studied: L= 70 nm and 1 µm.…”