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We studied the effect of post-deposition annealing (PDA) on the electrical property and the structure of aluminum oxide (AlOx) passivation films prepared by the atomic layer deposition with various temperatures. Surface recombination velocity (S max), interface trap density (D it), and fixed charge density (Q eff/q) before and after the PDA were evaluated employing lifetime and capacitance-voltage measurements. The structural change by the PDA was investigated by a Stokes ellipsometer and X-ray reflectivity measurements at SPring-8. The S max of all samples was improved by the PDA. The improvement of S max in the samples deposited at the temperature of 200 and 300 °C was due to the D it decrease, but that in the sample deposited at the temperature of 25 °C was due to both the D it decrease and the Q eff/q increase. From the XRR measurements, it revealed that the formation of the interfacial thin-layer is essential for the appearance of negative fixed charges.

Aluminum oxide (AlOx) films were deposited by mist chemical vapor deposition (MCVD) in air for p-type crystalline silicon, and the effects of the deposition temperature (Tdep) and AlOx film thickness on the maximum surface recombination velocities (Smax) were evaluated. It was found that Smax was improved with increasing Tdep. The AlOx film deposited at 400 °C exhibited the best Smax value of 2.8 cm/s, and the passivation quality was comparable to that of AlOx deposited by other vacuum-based techniques. Smax was also improved with increasing film thickness. When the film thickness was above 10 nm, Smax was approximately 10 cm/s. From the Fourier transform infrared spectra, it was found that the AlOx films deposited by MCVD consisted of an AlOx layer and a Si-diffused AlOx layer. In addition, it is important for the layers to be thick enough to obtain high-quality passivation.

Using pulsed-laser deposition, ferroelectric Bi4Ti3O12 (BiT) films were grown on Si(100) with and without an ultrathin buffer layer of silicon oxynitride (SiON), and the interface states were investigated using X-ray photoelectron spectroscopy. For both as-grown specimens, the additional oxidation of the interface Si was observed, and their thicknesses were almost identical. Due to the postannealing at 700°C in an oxygen ambient, on the other hand, a large difference in the Si oxidation was observed between the two specimens. The BiT films on Si(100) without the SiON buffer layer failed in preventing the significant development of the interfacial Si oxidation. On the contrary, it was clarified that the 1.3-nm-thick SiON buffer layers suppressed the additional oxidation to less than 3.5 nm.