Comparative Electron Spin Resonance Study Of Epi-Lu2o3/(111)Si And A-Lu2o3/(100)Si Interfaces: Misfit Point Defects

An electron spin resonance study has been carried out on heteroepitaxial Si/insulator structures obtained through growth of epi-Lu2O3 films on (111)Si (similar to 4.5% mismatch) by molecular-beam epitaxy, with special attention to the inherent quality as well as the thermal stability of interfaces, monitored through occurring paramagnetic point defects. This indicates the presence, in the as-grown state, of P-b defects (similar to 5 x 10(11) cm(-2)) with the unpaired sp(3) Si dangling bond along the [111] interface normal, the archetypical defect (trap) of the standard thermal (111)Si/SiO2 interface, directly revealing, and identified as the result of, imperfect epitaxy. The occurrence of P-b defects, a major system of electrically detrimental interface traps, is ascribed to lattice mismatch with related introduction of misfit dislocations. This interface nature appears to persist for annealing in vacuum up to a temperature T-an similar to 420 degrees C. Yet, in the range T-an similar to 420-550 degrees C, the interface starts to "degrade" to standard Si/SiO2 properties, as indicated by the gradually increasing Pb density and attendant appearance of the EX center, an SiO2-associated defect. At T-an similar to 700 degrees C, [P-b] has increased to about 1.3 times the value for standard thermal (111)Si/SiO2, to remain constant up to T-an similar to 1000 degrees C, indicative of an unaltered interface structure. Annealing at T-an > 1000 degrees C results in disintegration altogether of the Si/SiO2-type interface. Passivation anneal in H-2 (405 degrees C) alarmingly fails to deactivate the P-b system to the device grade (sub) 1010 cm(-2) eV(-1) level, which would disfavor c-Lu2O3 as a suitable future high-kappa replacement for the a-SiO2 gate dielectric. Comparison of the thermal stability of the c-Lu2O3/(111)Si interface with that of molecular-beam deposited amorphous-Lu2O3/(100)Si shows the former to be superior, yet unlikely to meet technological thermal budget requirements. No Lu2O3-specific point defects could be observed. (c) 2010 American Institute of Physics. [doi:10.1063/1.3326516]