Interface traps

Water as an impurity accelerates the oxidation rate. Figure 4 compares growth curves for Si02 under dry and steam conditions. Halogens can also be introduced to the oxidation process, thereby reducing sodium ion contamination. This improves dielectric breakdown strength, and reduces interface trap density (15). 

Interface trapped charge, in silicon-based semiconductors, 22 240 Interfacial adhesion, in binary... 

Chung, G. Y., et al., Effect of Nitric Oxide Annealing on the Interface Trap Densities Near the Band Edges in the 4H Polytype of Silicon Carbide, Applied Physics Letters, Vol. 76, No. 13, March 27, 2000, p. 1713. 

O. Engstrom and A. Aim, Energy concepts of insulator-semiconductor interface traps, J. Appl. Phys., 54(9) (1983) 5240-5244. 

Good results have been reported [Saraswat et al.225, Deal et al.227, Trammel228, Metz228] for CVD-WSix-polycide MOS devices. Even in the case where there was no poly-Si and thus the silicide was in direct contact with the gate oxide, very low levels of fixed oxide charge and interface traps were present. It is interesting how the workfunction found for polycide MOS... 

Off-currents have also been measured at some organic field effect transistors using silicon dioxide as the gate dielectric. During the investigations it was not possible to detect the real reason for this sporadically occurring behaviour, which was only detectable after the pentacene deposition. One explanation could be the generation of interface traps as a consequence of the pentacene deposition. 

Capacitance/voltage (C/V) measurements of MOS-diodes fabricated by PECVD from AlMei showed interface trap densities comparable to those reported for thermal LPCVD films [90]. In addition, InP MOS diodes have been successfully fabricated with low trap densities (lO" cm eV ). However, the inability to fabricate MOS diodes on InP using AlMe3/02 PECVD is due to high conductivity of the AI2O3. Thus, it would appear that the incorporation of carbon is a symptom of the plasma deposition, and not the nature of the oxygen source. 

There have been a number of studies of n-type 3C-SiC MOS capacitors [5-7,21,26,31,32,37, 38,40,41], Fixed charge density in the low 10" cm 2 and interface trapped charge at midgap in the low 10llcm 2eV 1 are typical for n-type 3C-SiC MOS capacitors, although interface... 

It has been consistently observed that wet oxidation has produced less fixed charge and fewer interface traps than dry oxidation [5-7,31]. The presence of H20 molecules appears to be critical to the formation of high quality SiC MOS capacitors [5,7]. Dry oxide on 3C-SiC is not quite stoichiometric Si02 [27]. 

To reduce interface traps, the oxidation of SiC should be terminated in such a manner that no oxidation can take place during the time that the SiC is cooling to room... 

Oxidation temperature may influence the oxide charges. Wet oxidation of 3C-SiC at 1000°C has been reported to produce fewer interface traps than at higher temperatures because of reduced preferential oxidation at antiphase grain boundaries [7], Little or no effect on the oxide charges was seen in 3C-SiC oxidised between 1050 and 1200°C [37,40] and 1050 and 1150°C [41],... 

All highly conserved residues are located in the larger opening of the barrel. Both the extreme N- and C-termini remain disordered above the smaller opening on the opposite side of the barrel. The functional enzyme is a homodimer with two identical active sites. At the dimer interface, which takes up approximately 18% of each monomer s surface area, both ionic and hydrophobic interactions can be found. The interface traps a peculiar string of water molecules, which connect the two active sites (Fig. 2). 

---