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

Abstract

The properties of oxides grown on p-type 4H-SiC in N 2 O by rapid thermal processing (RTP) have been investigated as a function of the growth conditions. The impact of the oxidation temperature and time has been evaluated first in terms of quantitative nitrogen profile analysis by TOF-SIMS measurements, and in terms of traps control at the SiO 2 /p-type 4H-SiC interface by C-V measurements. It has been found that the effect of the UV radiations induced by the halogen-lamps leads to an enhancement of the nitridation kinetics by one order of magnitude, and that the passivation of the interface traps varies in a similar way as oxynitridation proceeds and, therefore, is self-limiting. In addition, RTP has been evaluated for the gate oxide formation of lateral p-channel MOSFETs. It has been shown that this innovative oxidation method produces MOSFETs with promising electrical characteristics for a relatively low thermal budget.Metal-oxide-semiconductor field effect transistors (MOSFETs) in silicon carbide (SiC) have shown great potential for high-power and high-temperature applications. For the last two decades, SiC MOS technology has been focused mainly on n-channel MOS devices. However, due to the poor quality of the SiO 2 /SiC interface, and the low oxide reliability, SiC planar DMOSFETs have only been recently commercialized. 1 In view of realizing SiC-based complementary-MOS (CMOS) devices for future power integrated circuits (ICs), it is now imperative to develop SiC p-channel MOSFETs. 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. 5 In addition, MOS structures formed on the C face of n-or p-type 6H-and 4H-SiC were found to have a much higher density of interface states as compared to MOS structures formed on the Si face of identical samples. 5,6 This indicates that the formation of interface states is promoted by the presence of carbon atoms at the surface. 7,8 Chung et al. have demonstrated that the nitridation process by NO annealing has a clear positive effect on interface traps. 9 For n-type 4H-SiC, N incorporation leads to a significant decrease of the large density of interface states with energy levels in the upper half of the bandgap. Oxides grown in N 2 O have led to the same observations. 10 In contrast, near the valence band in p-type 4H-SiC, N incorporation causes a small increase in the density of interface defects. 9 Moreover, such nitridation processes have one main drawback when it is applied to SiC thermal oxidation. This technique requires a huge thermal budget in conventional furnaces (∼1100 -1300 • C for several hours). 11 ...

Irradiation impact on optimized 4H-SiC MOSFETs

“…Recently, it has been demonstrated the efficiency of the oxidation process under RTP furnace, which is a furnace that utilizes UV rays for reducing the carbon atom amount before oxidation [79]. Oxidation processes with this type of furnace allows obtaining excellent oxide qualities, with a low D it, increasing µ fe [80]. 42.5 nm of oxide can be grown in 20 minutes (including post-oxidation anneal) [Fig.…”