Electrical Characterization and Reliability of Nitrided-Gate Insulators for N- and P-Type 4H-SiC MIS Devices

Abstract

In this paper, nitrided insulators such as N2O-grown oxides, deposited SiO2 annealed in N2O, and deposited SiNx/SiO2 annealed in N2O on thin-thermal oxides have been investigated for realization of high performance n- and p-type 4H-SiC MIS devices. The MIS capacitors were utilized to evaluate MIS interface characteristics and the insulator reliability. The channel mobility was determined by using the characteristics of planar MISFETs. Although the N2O-grown oxides are superior to the dry O2-grown oxides, the deposited SiO2 and the deposited SiNx/SiO2 exhibited lower interface state density (n-MIS: below 7x1011 cm-2eV-1 at EC-0.2 eV, p-MIS: below 6x1011 cm-2eV-1 at EV+0.2 eV) and higher channel mobility (n-MIS: over 25 cm2/Vs, p-MIS: over 10 cm2/Vs). In terms of reliability, the deposited SiO2 annealed in N2O exhibits a high charge-to-breakdown over 50 C/cm2 at room temperature and 15 C/cm2 at 200°C. The nitrided-gate insulators formed by deposition method have superior characteristics than the thermal oxides grown in N2O.

Effect of the Growth Conditions on the Properties of Nitrided Oxides Grown by RTP for 4H-SiC p-Channel MOSFETs Fabrication

“…6 densities are obtained for interface states with energies higher than E−E v approximately 0.4 eV and do not significantly increase with oxidation time (for oxide thickness lower than the critical oxide thickness). Then, in contrast with nitrided oxides grown in a standard furnace, 3 we did not observe an increase in the density of interface defects by N incorporation at the SiO 2 /SiC interface. Indeed, performing rapid thermal oxidation in N 2 O, we obtained a reduction in the D it for the interface states located close to the valence band.…”

“…2 Despite the promising results achieved in 4H-SiC p-channel MOSFETs, oxides grown on p-type SiC suffer from a high density of interface states and charges. 3,4 It was proposed that Al dopants from the SiC are incorporated at the interface and in the oxide, causing degradation of their electrical properties. However, the lack of improvement in the electrical properties of p-type 6H-SiC MOS structures, when Al is replaced by B, which is known not to cause degradation of SiO 2 /Si interfaces, has already been reported.…”

Fowler-Nordheim tunneling at SiO2/4H-SiC interfaces in metal-oxide-semiconductor field effect transistors

“…[4][5][6][7] On the other hand, charge trapping at SiO 2 /SiC interfaces is in turn indicated as a possible reason for V th instabilities occurring under prolonged application of a gate bias. [8][9][10][11] In this context, Singh and Hefner 12 argued that the MOSFET reliability is essentially limited by the smaller band offset between SiC and SiO 2 (2.7 eV) as compared to silicon (3.2 eV), leading to higher tunnelling currents which can enhance electron trapping and oxide degradation. Furthermore, they pointed out that trap states at SiO 2 /SiC interface not only affect the channel mobility but also influence the barrier height for Fowler-Nordheim (FN) tunnelling.…”