Search

The proton irradiation effects on n-MuGFET devices with three different geometries (single fin, wide fin and multiple fin) are studied. Also, the effect of tensile strain in the fin on the radiation behavior is investigated. A fundamental difference in the radiation behavior between the non-strained and the strained devices is found. The degradation of the strained devices is most affected by the mobility decrease of the backside transistor. The non-strained devices show a much lesser back gate mobility degradation. For these devices the creation of positive oxide traps is dominant. This shifts the onset of the back channel to lower gate voltages, inducing a transconductance increase at intermediate gate voltages. This effect is less pronounced for single fin MuGFETs. At higher gate voltage, the transconductance decreases for the strained and increases for the non-strained transistors. Index Terms--Fully depleted, multiple gate transistors, proton irradiation effects, strain.

This paper reports on the radiation response of 90 nm CMOS transistors to a high fluence (3 x [10.sup.12] p/[cm.sup.2]) of ~60 MeV protons. A pronounced dependence on the gate bias [V.sub.GS] during the exposure has been noted for the n-channel devices: while no degradation of the input and output characteristics is found for [V.sub.GS] = 0 V and a modest degradation for floating gate conditions, a catastrophic failure can be observed when a positive gate bias of 1.2 V is applied. This behavior is found for devices with a physical gate oxide thickness of 1.5 and 2 nm and appears to be more pronounced for larger area transistors. As will be shown, the breakdown site is connected with either the source-to-gate or drain-to-gate junction, whereby the latter leads to a complete loss of functionality of the transistors. However, some of the biased nMOSFETs survive the high-energy proton exposure without degradation. A model will be proposed, explaining the gate oxide breakdown in terms of pre-existing defect sites at the source or drain junctions which develop into breakdown sites under biased irradiation. Index Terms--Biased irradiation, CMOS, gate oxide breakdown, proton irradiation, ultra-thin gate oxide.

The impact of an accumulation back-gate voltage on the linear kink effect (LKE) Lorentzians in thin-gate partially depleted silicon-on-insulator metal-oxide-semiconductor field-effect transistors (PD MOSFETs) is investigated. It is demonstrated that the front-back coupling effects can be explained by considering the increased body-source leakage currents.

The degradation of deep submicron (0.1 [micro]m) fully depleted (FD)-silicon-on-insulator (SOI) n-channel metal oxide semiconductor field effect transistors (MOSFETs) subjected to 7.5-MeV proton irradiation is reported. The radiation-induced damage is investigated by studying the static characteristics of devices with different geometries and bias conditions. Special attention is paid to the analysis of the front-back gate coupling effect by changing the back-gate bias [V.sub.BG]. The change of the front and back channel parameters, the impact of the gate coupling effect and the gate-induced floating body effect are clarified. A correction procedure is proposed for the extraction of the front- and back-interface and oxide trap charge contribution to the threshold voltage shift by accounting for the front-back gate coupling. Index Terms--Fully depleted (FD)-silicon-on-insulator (SOI), gate coupling, metal oxide semiconductor field effect transistor (MOSFET), proton irradiation, ultra thin gate.

The degradation of polycrystalline silicon (Poly-Si) films, subjected to 20-MeV alpha-ray irradiation, is studied. To investigate the radiation source dependence, 20-MeV proton and 1-MeV electron irradiation have been performed as well. The damage of alpha-rays is one and three orders of magnitude larger than for protons and electrons. The radiation source dependence of the performance degradation is attributed to the difference of mass and the probability of nuclear collisions for the formation of lattice defects. It is concluded that the combination of the induced lattice defects in the grain itself and the interface state density at its boundary are mainly responsible for the degradation of the Poly-Si films by high-energy particle irradiation. The degradation of the Poly-Si films can also be explained by a finite grain-bulk dynamic resistance [r.sub.c] and a large--barrier dynamic resistance [r.sub.SCR] based on the Schottky barrier diode degradation mechanism. Index Terms--Polycrystalline silicon, radiation effects.

It will be shown that an analysis of gated-diode (GD) structures enables to investigate the radiation damage in different parts of p-n junctions in a CMOS technology. This is important as the peripheral, especially corner, p-n junction leakage at reverse voltage sets the leakage and power consumption of state-of-the-art integrated circuits (ICs) and the DRAM retention time. One GD enables to extract the radiation-induced peripheral leakage-current defined by the isolation surrounding the active p-n junction, while two GDs with different dimensions--the corner leakage. The method is applied to junctions fabricated in different silicon substrate types and irradiated by 1-MeV equivalent neutrons with fluence ([PHI]) ranging from 5 x [10.sup.11] to 5 x [10.sup.13] n/[cm.sup.2]. While for low to moderate [PHI] the significance of the peripheral leakage-current decreases, a rebound occurs for the higher [PHI] investigated due to the increase of the bulk peripheral leakage and of the corner component. Index Terms--High-energy neutron irradiations, junction corner effects, p-n junction leakage, silicon diodes, silicon substrate hardening.